It's possible they won't see ever see the radioactive decay.
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Our world's supply is created through the radioactive decay from uranium.
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Another technique uses the rate of uranium's radioactive decay as a clock.
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The light we see from the explosion is a result of radioactive decay.
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Such radioactive decay proved a source of yet more members of the periodic table.
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When an element undergoes radioactive decay, it creates radiation and turns into some other element.
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When an organism dies, radioactive decay gradually diminishes the concentration of 227C in its remains.
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They could have been produced in pairs by the radioactive decay of a new particle.
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By measuring the amount of radioactive decay, scientists can determine when a formerly living organism died.
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Scientists and codemakers rely on natural phenomena like radioactive decay and atmospheric noise to drive randomness.
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The arc reactor relies on radioactive decay, breaking down palladium into silver, which creates beta radiation.
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Radioactive decay causes uranium rock to disperse helium into natural gas chambers over millions of years.
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The scientists who operate GERDA are hoping to spot a very rare type of radioactive decay.
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Some elements lose alpha particles through radioactive decay, and your smoke detectors use them to detect smoke.
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My income, like the carbon-14 my dad was measuring, was in a state of radioactive decay.
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The other source of energy is the radioactive decay of some heavier elements like uranium, thorium, and potassium.
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Both spacecraft are powered by the radioactive decay of plutonium-238, which has a half-life of 88 years.
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Wu's breakthrough research revealed that during the process of radioactive decay, decaying identical nuclear particles didn't always behave symmetrically.
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Nor would heating from the radioactive decay of its elements help avoid a complete freeze, according to the new paper.
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The researchers were able to measure the radioactive decay of elements like uranium within the minerals to determine its age.
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Although some of this internal energy may arise from radioactive decay, even more energy is likely to come from tidal flexing.
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These atoms release neutrons, which in turn go through a radioactive decay process that turns them into protons, called beta decay.
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Another test is to measure the rate of radioactive decay of certain elements in the rocks, also known as carbon dating.
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The basic idea was that energy released by natural radioactive decay would be used to heat a gas, which would then expand.
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The detector measures how these elements lose subatomic particles to radioactive decay, creating a signature determining whether they've created something new or not.
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In the late 1950s, Gell-Mann co-authored a paper with the esteemed Caltech physicist Richard Feynman about the radioactive decay of neutrons.
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Iron-60, which has more neutrons making it unstable to radioactive decay, is present on Earth only from either cosmic explosions or nuclear weapons.
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These short-lived substances might, people worry, encounter bureaucratic obstacles that slowed down their delivery and thus increased the fraction lost to radioactive decay.
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The helium reserves we do have are mostly the result of uranium and other heavy elements undergoing radioactive decay, producing helium atoms in the process.
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Mølmer pointed out that by no means does this mean that any quantum process, like radioactive decay, be undone and returned to its initial state.
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Helium is a byproduct of the radioactive decay of heavy elements located in the Earth's crust, a process that takes hundreds of millions of years.
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A kind of radioactive decay known as beta decay is a result of weak nuclear force interactions inside of atoms that can turn neutrons into protons.
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They were followed by a kilonova—a burst of optical and ultraviolet radiation powered by the radioactive decay of heavy elements newly formed in the explosion.
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One class of hypothetical objects that might be dark matter do interact via the weak force, a phenomenon that also controls some sorts of radioactive decay.
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The events they detect are caused by background radiation, or the radioactive decay of atoms, which Baecker says is a complete non-deterministic and unpredictable process.
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The gas forms in nature through radioactive decay of uranium and thorium, but exceedingly slowly; in practical terms, all the helium we will ever have already exists.
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Heat radiating from within Pluto's interior—most likely the radioactive decay of elements left over from its formation over 4.5 billion years ago—is fueling thermal convection.
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The age was determined with a new technique that analyzes the radioactive decay of uranium in flowstone, a translucent mineral deposited by water trickling down cave walls.
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Argon can be measured from the lava flows as the radioactive decay of potassium occurs in the rocks, while beryllium can be measured in the ice cores.
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When I explained to the assembled company that radioactive decay does not really respond to this sort of intervention, I was offered an explanation based on quantum mechanics.
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Antimatter is rarer than matter, but it exists here on Earth most commonly in the form of positrons, or anti-electrons, produced by certain kinds of radioactive decay.
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Keeping with the Simpsons themed acronyms, the Demonstration Using Flattop Fissions (DUFF) used nuclear fission, rather than natural radioactive decay, as an energy source for a Stirling converter.
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Meanwhile, the SU(10353) symmetries associated with the weak force (which is responsible for many kinds of radioactive decay) include a symmetry between, for example, up quarks and down quarks.
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The other, known as an isotopic teletherapy machine, produces X-rays as silvery cobalt-60 chunks inside a small canister eject X-rays and transform into nickel through radioactive decay.
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Certain atoms spit out positrons during the natural process of radioactive decay, and the Earth often gets smacked by antiparticles from outside the solar system the form of cosmic rays.
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If indeed neutrinoless double beta decay exists, it's very hard to detect and it's important that scientists can discriminate between the many types of radioactive decay that mimic that of a neutrino.
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Douka's team used multiple techniques to indirectly and directly date thousands of bone fragments and artifacts, including radiocarbon dating and uranium-series dating, both of which take advantage of known rates of radioactive decay.
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Originally, uranium was formed by supernovas and its slow radioactive decay (Uranium-238, the most common uranium isotope, has a half-life of 4.5 billion years) is the main source of heat in Earth's core.
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In Pauli's case, he first posited the existence of an extremely light, chargeless particle as a "desperate remedy" to explain why the law of the conservation of energy appeared to be violated during radioactive decay.
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Future geologists, depending on precisely how much time has passed and therefore how much radioactive decay has occurred, will be able to see a layer of plutonium, or of uranium, or (eventually) of lead in the rocks.
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The KArlsruhe TRItium Neutrino (KATRIN) experiment in Germany is to attempting to measure the mass of a particle called the electron antineutrino by observing the radioactive decay of tritium, a hydrogen atom with two neutrons and a proton.
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Yet here we are, living lumps of regular matter reading blog posts on the internet, while antimatter only exists in some very specific cases, like in our experiments or as a product of some kinds of radioactive decay.
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So if you ever use zk-SNARKs on the next ZCash release, rest easy knowing that at least part of the network's security was generated on an airborne, air gapped computer and derived its entropy from the quantum mechanics of radioactive decay.
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Two theorists, Tsung-Dao Lee and Chen-Ning Yang (who shared the Nobel Prize that year), had speculated, amid widespread skepticism, that the weak nuclear force, which is involved in radioactive decay, might violate a law of physics called conservation of parity.
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These tritium atoms undergo a kind of radioactive decay called beta decay, where one of their neutrons turns into a proton, spitting out an electron and an electron-antineutrino in the process (which would have the same mass as the electron neutrino).
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The duo flew to 3,000 feet and used the Geiger counter to measure radioactive decay from the Chernobyl material—a piece of graphite moderator that was ejected from the core of the Chernobyl nuclear reactor during the 1986 meltdown—as the plane circled above southern Wisconsin.
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Though not definitive (which would require a full year's data) this analysis suggests that the average signal over the collection period, minus noise such as that caused by the radioactive decay of the surrounding rock, leaves little room for a dark-matter signal akin to that at DAMA.
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If some process determined by quantum mechanics, like radioactive decay, was in charge of whether a cat in a closed box was alive or dead, then our present understanding of physics implies the cat is both alive and dead simultaneously, until we open the box to take a look.
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Nature News reports that a team of physicists led by Attila Krasznahorkay of the Hungarian Academy of Sciences published a rather provocative paper late last year in Physical Review Letters (pre-print version available here) claiming that a strange radioactive decay anomaly is indicative of an unknown fundamental force.
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Working independently, they described how two of the four fundamental interactions of nature — electromagnetism and the so-called weak nuclear force, which is responsible for radioactive decay — could have emerged from what is known as the electroweak interaction, as the early universe expanded and cooled to lower energies.
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Hunting for that lower mass is important, as it might allow physicists to validate the 2016 measurement from a Hungarian team that seemed to indicate the presence of a fifth fundamental force, in addition to gravity, electromagnetism, the strong force (which holds together atomic nuclei), and the weak force (responsible for radioactive decay).
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What's called the Standard Model, one of the signature creations of quantum physics, is very good at explaining the workings of three of the four known forces in the universe: electromagnetism; the strong, or nuclear force, that binds together the nuclei of atoms; and the weak force, which is manifest in radioactive decay.
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The particles you deal with most often are the protons, neutrons, and electrons that make up atoms, which interact through gravity, electromagnetism, the strong nuclear force (which binds the components of atomic nuclei together), and the weak nuclear force (which also occurs over the tiny length scales inside the atomic nucleus and is partially responsible for some aspects of radioactive decay).
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Radiogenic Isotope Geology, Cambridge University Press. involves an isotope produced by radioactive decay, which is usually in a ratio with a non- radiogenic isotope (whose abundance in the earth does not vary due to radioactive decay).
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Radioisotope thermoelectric generators use the heat of radioactive decay to produce electricity.
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Models suggest that Rhea could be capable of sustaining an internal liquid-water ocean through heating by radioactive decay.
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Conventional definition places the boundary at a photon energy between 10 eV and 33 eV in the ultraviolet (see definition boundary section below). Typical ionizing subatomic particles found in radioactive decay include alpha particles, beta particles and neutrons. Almost all products of radioactive decay are ionizing because the energy of radioactive decay is typically far higher than that required to ionize. Other subatomic ionizing particles which occur naturally are muons, mesons, positrons, and other particles that constitute the secondary cosmic particles that are produced after primary cosmic rays interact with Earth's atmosphere.
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It utilizes the idea of radioactive decay of long-lived unstable isotopes in minerals to search for the age of events.
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Decay correction is a method of estimating the amount of radioactive decay at some set time before it was actually measured.
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The decay energy is the energy released by a radioactive decay. Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, called the daughter nuclide.
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Io, a moon of Jupiter, is a small terrestrial planet, its radius is 1821.6±0.5 km, with a size similar to the Moon's. Yet, Io produces a much higher heat flow, 60~160 terawatts (TW), which is 40 times larger than that on Earth. Radioactive decay cannot generate this large amount of heat. Radioactive decay supplies heating on other terrestrial planets.
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1025–26 These emissions are considered ionizing radiation because they are powerful enough to liberate an electron from another atom. The radioactive decay can produce a stable nuclide or will sometimes produce a new unstable radionuclide which may undergo further decay. Radioactive decay is a random process at the level of single atoms: it is impossible to predict when one particular atom will decay.
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The apparatus is configured so that when the Geiger counter detects radioactive decay, the flask will shatter, poisoning the cat. Unless and until the Geiger counter detects the radioactive decay of a single atom, the cat survives. The radioactive decay the Geiger counter detects is a quantum event; each decay corresponds to a quantum state transition of a single atom of the radioactive material. According to Schrödinger's wave equation, until they are observed, quantum particles, including the atoms of the radioactive material, are in quantum state superposition; each unmeasured atom in the radioactive material is in a quantum superposition of decayed and not decayed.
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A common example of a radioactive decay alteration is when a radioactive element bearing zircon or allanite crystal becomes metamict or amorphous due to structural damage.
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After the protoplanet formed, accumulation of heat from radioactive decay of short-lived elements melted the planet, allowing materials to differentiate (i.e. to separate according to their density).
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During his investigations of radioactivity, Ernest Rutherford coined the terms alpha rays, beta rays and gamma rays for the three types of emissions that occur during radioactive decay.
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Nuclear fission can occur without neutron bombardment as a type of radioactive decay. This type of fission (called spontaneous fission) is rare except in a few heavy isotopes.
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He went on to speculate in 1904: "If it were ever found possible to control at will the rate of disintegration of the radio-elements, an enormous amount of energy could be obtained from a small quantity of matter." Einstein's equation do not explain the large energies released in radioactive decay, but can be used to quantify it. The theoretical explanation for radioactive decay is given by the nuclear forces responsible for holding atoms together, though these forces were still unknown in 1905. The enormous energy released from radioactive decay (which had been measured by Rutherford) was much more easily measured than the small change in the gross mass of materials as a result.
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For radioactive decay measurements it must not be confused with disintegrations per unit time (dpm), which represents the rate of atomic disintegration events at the source of the radiation.
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It was most popular during the early 20th century, after the discovery in 1896 of radioactive decay. The practice has widely declined, but is still actively practiced by some.
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Though Tono-Bungay is not a science-fiction novel, radioactive decay plays a small but consequential role in it. Radioactive decay plays a much larger role in The World Set Free (1914). This book contains what is surely his biggest prophetic "hit", with the first description of a nuclear weapon. Scientists of the day were well aware that the natural decay of radium releases energy at a slow rate over thousands of years.
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Similarly, the bond-dissociation energy of a carbon–carbon bond is about 3.6 eV. Other chemical reactions typically involve similar amounts of energy. Even photons with far higher energy, gamma rays of the kind produced in radioactive decay, mostly have photon energy between and – still two orders of magnitude lower than the mass of a single proton. Radioactive decay gamma rays are considered as part of nuclear physics, rather than high energy physics.
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The geothermal energy of the Earth's crust originates from the original formation of the planet and from radioactive decay of materials (in currently uncertain but possibly roughly equal proportions). The adjective geothermal originates from the Greek roots (), meaning Earth, and (), meaning hot. Earth's internal heat is thermal energy generated from radioactive decay and continual heat loss from Earth's formation. Temperatures at the core–mantle boundary may reach over 4000 °C (7200 °F).
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Positrons can be created by positron emission radioactive decay (through weak interactions), or by pair production from a sufficiently energetic photon which is interacting with an atom in a material.
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A typical RTG is powered by radioactive decay and features electricity from thermoelectric conversion, but for the sake of knowledge, some systems with some variations on that concept are included here.
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Ionization can occur through radioactive decay by the internal conversion process, in which an excited nucleus transfers its energy to one of the inner-shell electrons causing it to be ejected.
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Unstable isotopes decay through various radioactive decay pathways, most commonly alpha decay, beta decay, or electron capture. Many rare types of decay, such as spontaneous fission or cluster decay, are known. (See Radioactive decay for details.) Isotope half-lives. The darker more stable isotope region departs from the line of protons (Z) = neutrons (N), as the element number Z becomes larger. Of the first 82 elements in the periodic table, 80 have isotopes considered to be stable.
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Alpha decay is observed only in heavier elements of atomic number 52 (tellurium) and greater, with the exception of beryllium-8 (which decays to two alpha particles). The other two types of decay are observed in all the elements. Lead, atomic number 82, is the heaviest element to have any isotopes stable (to the limit of measurement) to radioactive decay. Radioactive decay is seen in all isotopes of all elements of atomic number 83 (bismuth) or greater.
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The nuclear reaction theorised by Meitner and Frisch. Nuclear fission was discovered in December 1938 by physicists Lise Meitner and Otto Robert Frisch and chemists Otto Hahn and Fritz Strassmann. Fission is a nuclear reaction or radioactive decay process in which the nucleus of an atom splits into two or more smaller, lighter nuclei. The fission process often produces gamma rays and releases a very large amount of energy, even by the energetic standards of radioactive decay.
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Theoretical calculations indicate that the linear molecule is less stable than the van der Waals complex. Xenon tetrachloride is more unstable that can’t synthesized by chemical reaction.It was created by radioactive decay.
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This is the energy scale manifesting at the macroscopic level, such as in chemical reactions. Even photons with far higher energy, gamma rays of the kind produced in radioactive decay, have photon energy that is almost always between and – still two orders of magnitude lower than the mass-energy of a single proton. Radioactive decay gamma rays are considered as part of nuclear physics, rather than high energy physics. Finally, when reaching the quantum particle level, the high energy domain is revealed.
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The very heaviest elements (those beyond plutonium, element 94) undergo radioactive decay with half-lives so short that they are not found in nature and must be synthesized. There are now 118 known elements.
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Geitel and Elster published works on meteorology, nuclear physics, and the photoelectric effects. Geitel recognized the law of radioactive decay in 1899 and coined the term atomic energy. In 1893 he invented the photocell.
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Alpha decay is much more easily shielded against than other forms of radioactive decay. Static eliminators typically use polonium-210, an alpha emitter, to ionize the air, allowing the 'static cling' to dissipate more rapidly.
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Due to natural gamma ray exposure from radioactive decay of 40K in their granitic environment, gradual formation of Mn3+ ions occurs, which is responsible for the deepening of the pink to red color.Reinitz & Rossman, 1988.
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Radioactive decay has been put to use in the technique of radioisotopic labeling, which is used to track the passage of a chemical substance through a complex system (such as a living organism). A sample of the substance is synthesized with a high concentration of unstable atoms. The presence of the substance in one or another part of the system is determined by detecting the locations of decay events. On the premise that radioactive decay is truly random (rather than merely chaotic), it has been used in hardware random-number generators.
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Whole body monitor in use. If a gamma ray is emitted from a radioactive element within the human body due to radioactive decay, and its energy is sufficient to escape then it can be detected. This would be by means of either a scintillation detector or a semiconductor detector placed in close proximity to the body. Radioactive decay may give rise to gamma radiation which cannot escape the body due to being absorbed or other interaction whereby it can lose energy; so account must be taken of this in any measurement analysis.
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The (radioactive) tritium light source is an unstable isotope with a half-life of 12.32 years that gradually loses its brightness due to radioactive decay. It is to be replaced every 8–12 years to maintain adequate brightness.
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Volume 10. Naturally occurring xenon consists of nine stable isotopes. There are also over 40 unstable isotopes that undergo radioactive decay. The isotope ratios of xenon are an important tool for studying the early history of the Solar System.
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Several forms of radiation are used in APXS. They include alpha particles, protons, and X-rays. Alpha particles, protons, and X-rays are emitted during the radioactive decay of unstable atoms. A common source of alpha particles is curium-244.
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Tin also has four radioisotopes that occur as the result of the radioactive decay of uranium. These isotopes are tin-121, tin-123, tin-125, and tin-126. 38 isotopes of lead have been discovered. 9 of these are naturally occurring.
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It has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the Sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the Earth, the principal source of geothermal energy.
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Alfred Wegener, around 1925 In 1862, the physicist William Thomson, 1st Baron Kelvin, published calculations that fixed the age of Earth at between 20 million and 400 million years. He assumed that Earth had formed as a completely molten object, and determined the amount of time it would take for the near-surface to cool to its present temperature. With the discovery of radioactive decay the age of the Earth was pushed back even further. Arthur Holmes was among the pioneers in the use of radioactive decay as a mean to measure geological time, thus pioneering the discipline of geochronology.
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Free protons are emitted directly from atomic nuclei in some rare types of radioactive decay. Protons also result (along with electrons and antineutrinos) from the radioactive decay of free neutrons, which are unstable. The spontaneous decay of free protons has never been observed, and protons are therefore considered stable particles according to the Standard Model. However, some grand unified theories (GUTs) of particle physics predict that proton decay should take place with lifetimes between 1031 to 1036 years and experimental searches have established lower bounds on the mean lifetime of a proton for various assumed decay products.
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Gamma rays from radioactive decay are in the energy range from a few kiloelectronvolts (keV) to approximately 8 megaelectronvolts (~8 MeV), corresponding to the typical energy levels in nuclei with reasonably long lifetimes. The energy spectrum of gamma rays can be used to identify the decaying radionuclides using gamma spectroscopy. Very-high-energy gamma rays in the 100–1000 teraelectronvolt (TeV) range have been observed from sources such as the Cygnus X-3 microquasar. Natural sources of gamma rays originating on Earth are mostly as a result of radioactive decay and secondary radiation from atmospheric interactions with cosmic ray particles.
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Not all neutrons are emitted as a direct product of fission; some are instead due to the radioactive decay of some of the fission fragments. The neutrons that occur directly from fission are called "prompt neutrons," and the ones that are a result of radioactive decay of fission fragments are called "delayed neutrons". The fraction of neutrons that are delayed is called β, and this fraction is typically less than 1% of all the neutrons in the chain reaction. The delayed neutrons allow a nuclear reactor to respond several orders of magnitude more slowly than just prompt neutrons would alone.
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Ratios: 208Pb/207Pb, 207Pb/206Pb and 206Pb/204Pb are measured by mass spectrometry. Apart from 204Pb, the lead isotopes are all products of the radioactive decay of uranium and thorium. When ore is are deposited, uranium and thorium are separated from the ore.
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Thus, living plants and animals have the same ratio of 14C to 12C as the atmospheric CO2. Once organisms die they stop exchanging carbon with the atmosphere, and thus no longer take up new 14C. Radioactive decay then gradually depletes the 14C in the organism.
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Rhenium and osmium are siderophile elements which are present at very low abundances in the crust. Rhenium undergoes radioactive decay to produce osmium. The ratio of non-radiogenic osmium to radiogenic osmium throughout time varies. Rhenium prefers to enter sulfides more readily than osmium.
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Radio-luminescence uses the radioactive decay of tritium gas to illuminate the sign, while phosphorescence uses light-emitting phosphors to glow in the dark. While both of these signs meet California State Fire Marshal standards, electricity is used in the vast majority of signs.
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Alpha emission produced by some radioactive decay also produces neutrons by spallation knockout of neutron rich isotopes, such as the reaction of alpha particles with oxygen-18. Neutrons are also produced by neutron emission (a form of radioactive decay in some neutron-rich nuclides) and spontaneous fission of fissile isotopes on Earth (particularly uranium-235). Nucleogenesis (also known as nucleosynthesis) as a general phenomenon is a process usually associated with production of nuclides in the Big Bang or in stars, by nuclear reactions there. Some of these neutron reactions (such as the r-process and s-process) involve absorption by atomic nuclei of high-temperature (high energy) neutrons from the star.
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Radioactive decay is the process of emission of particles and energy from the unstable nucleus of an atom to form a stable product. This is done via the tunnelling of a particle out of the nucleus (an electron tunnelling into the nucleus is electron capture). This was the first application of quantum tunnelling and led to the first approximations. Radioactive decay is also a relevant issue for astrobiology as this consequence of quantum tunnelling is creating a constant source of energy over a large period of time for environments outside the circumstellar habitable zone where insolation would not be possible (subsurface oceans) or effective.
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Stars fuse hydrogen and helium into heavier and heavier elements in order to produce energy. For example, the observed light curves of supernova stars such as SN 1987A show them blasting large amounts (comparable to the mass of Earth) of radioactive nickel and cobalt into space. However, little of this material reaches Earth. Most natural transmutation on the Earth today is mediated by cosmic rays (such as production of carbon-14) and by the radioactive decay of radioactive primordial nuclides left over from the initial formation of the solar system (such as potassium-40, uranium and thorium), plus the radioactive decay of products of these nuclides (radium, radon, polonium, etc.).
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With irreversibility, the arrow of time is reintroduced to physics. Prigogine notes numerous examples of irreversibility, including diffusion, radioactive decay, solar radiation, weather and the emergence and evolution of life. Like weather systems, organisms are unstable systems existing far from thermodynamic equilibrium. Instability resists standard deterministic explanation.
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These had assumed that the original heat of the Earth and Sun had dissipated steadily into space, but radioactive decay meant that this heat had been continually replenished. George Darwin and John Joly were the first to point this out, in 1903. Reprinted by BookSurge Publishing (2004) .
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Of the actinides, primordial thorium and uranium occur naturally in substantial quantities. The radioactive decay of uranium produces transient amounts of actinium and protactinium, and atoms of neptunium and plutonium are occasionally produced from transmutation reactions in uranium ores. The other actinides are purely synthetic elements.Greenwood, p.
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Studies of the "radioactivity", that soon revealed the phenomenon of radioactive decay, provided another argument against considering chemical elements as fundamental nature's elements. Despite these discoveries, the term atom stuck to Dalton's (chemical) atoms and now denotes the smallest particle of a chemical element, not something really indivisible.
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"Quantitative Astronomy". Prentice Hall, 1992, Chapter 5, Section 1. Also note here that this equation does not take into account any effects from internal heating of the planet, which can arise directly from sources such as radioactive decay and also be produced from frictions resulting from tidal forces.
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One source of the lunar atmosphere is outgassing: the release of gases such as radon and helium resulting from radioactive decay within the crust and mantle. Another important source is the bombardment of the lunar surface by micrometeorites, the solar wind, and sunlight, in a process known as sputtering.
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The light emitted in the kilonova is believed to come from the radioactive decay of material ejected in the merger of the two neutron stars. This material may be responsible for the production of many of the chemical elements beyond iron, as opposed to the supernova nucleosynthesis theory.
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A microscope used to examine the behaviour of atomic nuclear produced, which are collected at the centre of 8pi where they undergo radioactive decay. The main component of the 8π spectrometer are the Hyper-pure Germanium detectors used to observe gamma rays emitted from excited states of daughter nuclei.
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Heating in Enceladus has occurred through various mechanisms ever since its formation. Radioactive decay in its core may have initially heated it, giving it a warm core and a subsurface ocean, which is now kept above freezing through an unidentified mechanism. Geophysical models indicate that tidal heating is a main heat source, perhaps aided by radioactive decay and some heat-producing chemical reactions. A 2007 study predicted the internal heat of Enceladus, if generated by tidal forces, could be no greater than 1.1 gigawatts, but data from Cassini's infrared spectrometer of the south polar terrain over 16 months, indicate that the internal heat generated power is about 4.7 gigawatts, and suggest that it is in thermal equilibrium.
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The remaining 6 transient elements (technetium, promethium, astatine, francium, neptunium, and plutonium) occur only rarely, as products of rare decay modes or nuclear reaction processes involving uranium or other heavy elements. No radioactive decay has been observed for elements with atomic numbers 1 through 82, except 43 (technetium) and 61 (promethium). Observationally stable isotopes of some elements (such as tungsten and lead), however, are predicted to be slightly radioactive with very long half-lives: for example, the half-lives predicted for the observationally stable lead isotopes range from 1035 to 10189 years. Elements with atomic numbers 43, 61, and 83 through 94 are unstable enough that their radioactive decay can readily be detected.
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These rearrangements and transformations may be hindered energetically, so that they do not occur immediately. In certain cases, random quantum vacuum fluctuations are theorized to promote relaxation to a lower energy state (the "decay") in a phenomenon known as quantum tunneling. Radioactive decay half-life of nuclides has been measured over timescales of 55 orders of magnitude, from 2.3 × 10−23 seconds (for hydrogen-7) to 6.9 × 1031 seconds (for tellurium-128).NUBASE evaluation of nuclear and decay properties The limits of these timescales are set by the sensitivity of instrumentation only, and there are no known natural limits to how brief or long a decay half-life for radioactive decay of a radionuclide may be.
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Despite being the favored daughter nuclide, it is rarely useful in dating because calcium is so common in the crust, with being the most abundant isotope. Thus, the amount of calcium originally present is not known and can vary enough to confound measurements of the small increases produced by radioactive decay.
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Electric power to the spacecraft and its scientific payload would be generated by three Advanced Stirling Radioisotope Generators (ASRG). ASRG is a radioisotope power system under development at NASA's Glenn Research Center. It uses a Stirling power conversion technology to convert radioactive-decay heat into electricity for use on spacecraft.
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Various imaginative ways of collecting this entropic information have been devised. One technique is to run a hash function against a frame of a video stream from an unpredictable source. Lavarand used this technique with images of a number of lava lamps. HotBits measures radioactive decay with Geiger–Muller tubes, while Random.
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Nuclear Physics in a Nutshell, C. A. Bertulani, Princeton University Press, Princeton, N.J., 2007, Chapter 1, . There may have been observations of . In 2000, physicists first observed a new type of radioactive decay in which a nucleus emits two protons at once—perhaps a nucleus.Physicists discover new kind of radioactivity, in physicsworld.
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For free protons, this process does not occur spontaneously but only when energy is supplied. The equation is: : + → + The process is reversible; neutrons can convert back to protons through beta decay, a common form of radioactive decay. In fact, a free neutron decays this way, with a mean lifetime of about 15 minutes.
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23 isotopes of silicon have been discovered. Five of these are naturally occurring. The most common is stable silicon-28, followed by stable silicon-29 and stable silicon-30. Silicon-32 is a radioactive isotope that occurs naturally as a result of radioactive decay of actinides, and via spallation in the upper atmosphere.
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Silicon-34 also occurs naturally as the result of radioactive decay of actinides. 32 isotopes of germanium have been discovered. Five of these are naturally occurring. The most common is the stable isotope germanium-74, followed by the stable isotope germanium-72, the stable isotope germanium-70, and the stable isotope germanium-73.
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A Lucas cell can be used to measure radon gas concentrations. Radon itself is an inert gas. Its danger lies in the fact that it undergoes radioactive decay. The radon decay products may lodge in the lungs and bombard them with alpha and beta particles, thus increasing the risk of lung cancer.
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For age dating, mass spectrometers with magnetic sectors have better precision than a quadrupole mass spectrometer or quadrupole mass analyzer. Inductively coupled plasma-quadrupole mass spectrometers allows for an even higher precision of detecting the change of isotopic ratios by radioactive decay. The more precision means the higher resolution in age dating.
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New atoms are also naturally produced on Earth as radiogenic daughter isotopes of ongoing radioactive decay processes such as alpha decay, beta decay, spontaneous fission, cluster decay, and other rarer modes of decay. Of the 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one stable isotope (except for technetium, element 43 and promethium, element 61, which have no stable isotopes). Isotopes considered stable are those for which no radioactive decay has yet been observed. Elements with atomic numbers 83 through 94 are unstable to the point that radioactive decay of all isotopes can be detected. Some of these elements, notably bismuth (atomic number 83), thorium (atomic number 90), and uranium (atomic number 92), have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy metals before the formation of our Solar System. At over 1.9 years, over a billion times longer than the current estimated age of the universe, bismuth-209 (atomic number 83) has the longest known alpha decay half-life of any naturally occurring element, and is almost always considered on par with the 80 stable elements.
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Another example is gamma-ray bursts, now known to be produced from processes too powerful to involve simple collections of atoms undergoing radioactive decay. This is part and parcel of the general realization that many gamma rays produced in astronomical processes result not from radioactive decay or particle annihilation, but rather in non-radioactive processes similar to X-rays. Although the gamma rays of astronomy often come from non- radioactive events, a few gamma rays in astronomy are specifically known to originate from gamma decay of nuclei (as demonstrated by their spectra and emission half life). A classic example is that of supernova SN 1987A, which emits an "afterglow" of gamma-ray photons from the decay of newly made radioactive nickel-56 and cobalt-56.
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The rutherford (symbol Rd) is a non-SI unit of radioactive decay. It is defined as the activity of a quantity of radioactive material in which one million nuclei decay per second. It is therefore equivalent to one megabecquerel, and one becquerel equals one microrutherford. One rutherford is equivalent to 2.703 × 10−5 curie.
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Internal conversion is a radioactive decay process wherein an excited nucleus interacts electromagnetically with one of the orbital electrons of the atom. This causes the electron to be emitted (ejected) from the atom.M.E. Rose: "Theory of Internal Conversion", in: Alpha-, Beta- and Gamma-Ray Spectroscopy, ed. by Kai Siegbahn, North-Holland Publishing, Amsterdam (1966), Vol.
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238PuO2 as used in the RTG for the Cassini and Galileo missions. This photo was taken after insulating the pellet under a graphite blanket for several minutes and then removing the blanket. The pellet is glowing red hot because of the heat generated by radioactive decay (primarily α). The initial output is 62 watts.
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He thought that the ionization from radon, which comes from radioactive decay of uranium and thorium in rocks, might account for the high frequency of lightning over land, which had been demonstrated on OSO. This research continued after his retirement in 1990, but did not reach a conclusion before he died on July 9, 1996.
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Maxwell's theory of electromagnetism and Einstein's theory of general relativity are also expressed in the language of differential calculus. Chemistry also uses calculus in determining reaction rates and radioactive decay. In biology, population dynamics starts with reproduction and death rates to model population changes. Calculus can be used in conjunction with other mathematical disciplines.
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Spontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements. The nuclear binding energy of the elements reaches its maximum at an atomic mass number of about 56; spontaneous breakdown into smaller nuclei and a few isolated nuclear particles becomes possible at greater atomic mass numbers.
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However, the planet is likely to maintain a massive atmosphere that would allow warmer temperatures at lower altitudes. It is even possible that interior heating by radioactive decay would be sufficient to make the surface as warm as the Earth, but theory suggests that the surface may be completely covered by a very deep ocean.
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However, very shortly thereafter, around twenty minutes after the Big Bang, the temperature and density became too low for any significant fusion to occur. At this point, the elemental abundances were nearly fixed, and the only changes were the result of the radioactive decay of the two major unstable products of BBN, tritium and beryllium-7.
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Uraninite, formerly pitchblende, is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2, but due to oxidation the mineral typically contains variable proportions of U3O8. Additionally, due to radioactive decay, the ore also contains oxides of lead and trace amounts of helium. It may also contain thorium and rare earth elements.
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This form of radioactive decay is accomplished through beta decay. Calcium is common in many minerals, with 40Ca being the most abundant naturally occurring isotope of calcium (96.94%),Potassium-calcium dating. A Dictionary of Earth Sciences, 2016. so use of this dating method to determine the ratio of daughter calcium produced from parent potassium is generally not practical.
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Ruth Pirret (24 July 1874 - 19 June 1939) was a Scottish scientist working in the field of radioactivity and the first woman to graduate from the University of Glasgow with a BSc. She was the second woman to register as a research student at the University after Louise McIlroy. Her research contributed to the understanding of radioactive decay.
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Earth's surface heat flux. Solid Earth, 1(1), 5–24. and comes from two main sources in roughly equal amounts: the radiogenic heat produced by the radioactive decay of isotopes in the mantle and crust, and the primordial heat left over from the formation of Earth. Earth's internal heat powers most geological processesBuffett, B. A. (2007).
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In nuclear physics and chemistry, the Q value for a reaction is the amount of energy absorbed or released during the nuclear reaction. The value relates to the enthalpy of a chemical reaction or the energy of radioactive decay products. It can be determined from the masses of reactants and products. Q values affect reaction rates.
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As of 2019, there are 118 known elements, about 80 of which are stable – that is, they do not change by radioactive decay into other elements. Some elements can occur as more than a single chemical substance (allotropes). For instance, oxygen exists as both diatomic oxygen (O2) and ozone (O3). The majority of elements are classified as metals.
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Another danger of actinium is that it undergoes radioactive decay faster than being excreted. Adsorption from the digestive tract is much smaller (~0.05%) for actinium than radium. Protactinium in the body tends to accumulate in the kidneys and bones. The maximum safe dose of protactinium in the human body is 0.03 µCi that corresponds to 0.5 micrograms of 231Pa.
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Comparison of fallout gamma dose and dose rate contours for a 1 Mt fission land surface burst, based on DELFIC calculations. Because of radioactive decay, the dose rate contours contract after fallout has arrived, but dose contours continue to grow. Meteorological conditions greatly influence fallout, particularly local fallout. Atmospheric winds are able to bring fallout over large areas.
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In 1952, helium concentrations were discovered in southwestern Saskatchewan. Production from four wells took place from 1963 to 1977, and resumed again in 2014. The Deadwood Formation, and other Lower Paleozoic formations, had the highest concentration. The helium originated through natural radioactive decay of uranium and thorium in Precambrian granitic basement rocks, or Lower Paleozoic shales.
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Pertechnetate is one of the most available forms of technetium. It is structurally related to permanganate. The most prevalent form of technetium that is easily accessible is sodium pertechnetate, Na[TcO4]. The majority of this material is produced by radioactive decay from [99MoO4]2−: :[99MoO4]2− → [99TcO4]− \+ γ Pertechnetate (tetroxidotechnetate) behaves analogously to perchlorate, both of which are tetrahedral.
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An alternative method is to use internal liquid scintillation counting, where the sample is mixed with a scintillation cocktail. When the light emissions are then counted, some machines will record the amount of light energy per radioactive decay event. Due to the imperfections of the liquid scintillation method (such as a failure for all the photons to be detected, cloudy or coloured samples can be difficult to count) and the fact that random quenching can reduce the number of photons generated per radioactive decay, it is possible to get a broadening of the alpha spectra obtained through liquid scintillation. It is likely that these liquid scintillation spectra will be subject to a Gaussian broadening, rather than the distortion exhibited when the layer of an active material on a disk is too thick.
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Horovitz was recruited by Otto Hönigschmid at the Institute for Radium Research, Vienna in 1913. At this time, the radioactive displacement law of Fajans and Soddy was a recent development in radiochemistry. It predicted that lead resulting from the radioactive decay of uranium or thorium would have different atomic weights than typical lead. Early experimental data was not considered authoritative by analytical chemists.
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Signs of past warming of the Kuiper belt object Quaoar. Reprint on Jewitt's site (pdf) have led scientists to speculate that it exhibited cryovolcanism in the past. Radioactive decay could provide the energy necessary for such activity, as cryovolcanoes can emit water mixed with ammonia, which would melt at and create an extremely cold liquid that would flow out of the volcano.
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However, there are trace amounts in nature of the radioactive isotope iodine-129, which occurs via spallation and from the radioactive decay of uranium in ores. Several other radioactive isotopes of iodine have also been created naturally via the decay of uranium. A total of 38 isotopes of iodine have been discovered, with atomic masses ranging from 108 to 145.
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The germanium was then chemically extracted and concentrated. Neutrinos were thus detected by measuring the radioactive decay of germanium. This latter method is nicknamed the "Alsace-Lorraine" technique because of the reaction sequence (gallium→germanium→gallium) involved. The SAGE experiment in Russia used about 50 tons, and the GALLEX / GNO experiments in Italy about 30 tons, of gallium as reaction mass.
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Derek Muller introduces uranium and its use throughout history. Uranium, originally sourced from pitchblende, became the subject of intense scientific study. Using computer-generated dragons as a metaphor for daughter isotopes, the episode shows how uranium turns into lead in the process of radioactive decay. The harmful effects of radiation from radium, which is produced during the decay of uranium, are discussed.
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For naturally occurring thorium-232, uranium-235, and uranium-238, spontaneous fission does occur rarely, but in the vast majority of the radioactive decay of these atoms, alpha decay or beta decay occurs instead. Hence, the spontaneous fission of these isotopes is usually negligible, except in using the exact branching ratios when finding the radioactivity of a sample of these elements.
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The radioactive decay impact of the 235U and 238U on its semiconducting properties was not measured . Due to the slow decay rate of these isotopes, it should not meaningfully influence the properties of uranium dioxide solar cells and thermoelectric devices, but it may become an important factor for VLSI chips. Use of depleted uranium oxide is necessary for this reason.
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Over extended time periods, thoriated glass may develop significant discoloration. This is due to induced F-centers forming in the glass as the radioactive decay of the thorium progresses. The formation of F-centers is due to the ionizing effect of the high energy thorium decay products. This process can potentially be reversed by annealing the glass or exposing it to light.
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For example, the extent to which we decide to use nuclear power to generate electricity is a sustainable design decision. The radioactive wastes may have half-lives of hundreds of thousands of years. That is, it will take all these years for half of the radioactive isotopes to decay. Radioactive decay is the spontaneous transformation of one element into another.
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Marie Curie, a physicist and chemist who conducted pioneering research on radioactive decay, was the first woman to receive a Nobel Prize in Physics and became the first person to receive a second Nobel Prize in Chemistry. Forty women have been awarded the Nobel Prize between 1901 and 2010. Seventeen women have been awarded the Nobel Prize in physics, chemistry, physiology or medicine.
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In 1898, Friedrich Ernst Dorn discovered a radioactive gas resulting from the radioactive decay of radium; Ramsay and Robert Whytlaw-Gray subsequently isolated radon in 1910. Astatine was synthesised in 1940 by Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè. They bombarded bismuth-209 with alpha particles in a cyclotron to produce, after emission of two neutrons, astatine-211.
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The principle behind the use of radioactive tracers is that an atom in a chemical compound is replaced by another atom, of the same chemical element. The substituting atom, however, is a radioactive isotope. This process is often called radioactive labeling. The power of the technique is due to the fact that radioactive decay is much more energetic than chemical reactions.
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Subsequent radiometric dating reduced the uncertainty. The concentration of decay products in impact glasses from the crater were used to derive an age of 65.04 ± 1.10 million years. Analysis of argon radioactive decay products yielded an age of 65.17 ± 0.64 million years. These ages are similar to that of Chicxulub Crater which argon dating yielded an age of 66.043 ± 0.011 million years.
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Helium-3 is a primordial isotope that formed in the Big Bang. Very little is produced, and little has been added to the Earth by other processes since then. Helium-4 includes a primordial component, but it is also produced by the natural radioactive decay of elements such as uranium and thorium. Over time, helium in the upper atmosphere is lost into space.
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The nuclides used in isotopic labeling may be stable nuclides or radionuclides. In the latter case, the labeling is called radiolabeling. In isotopic labeling, there are multiple ways to detect the presence of labeling isotopes; through their mass, vibrational mode, or radioactive decay. Mass spectrometry detects the difference in an isotope's mass, while infrared spectroscopy detects the difference in the isotope's vibrational modes.
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Radon is a chemical element with the symbol Rn and atomic number 86\. It is a radioactive, colorless, odorless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into lead and various other short-lived radioactive elements. Radon itself is the immediate decay product of radium.
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Since this isotope is generated by radioactive decay, the result may indicate that Mars lost most of its primordial atmosphere, possibly within the first 100 million years after the planet was formed. In another example, excess 129Xe found in carbon dioxide well gases from New Mexico is believed to be from the decay of mantle-derived gases from soon after Earth's formation.
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See Online version in German. A compromise between Earth-expansion and Earth-contraction is the "theory of thermal cycles" by Irish physicist John Joly. He assumed that heat flow from radioactive decay inside Earth surpasses the cooling of Earth's exterior. Together with British geologist Arthur Holmes, Joly proposed a hypothesis in which Earth loses its heat by cyclic periods of expansion.
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Working level (WL) is a historical unit of concentration of radioactive decay products of radon, applied to uranium mining environment. One working level refers to the concentration of short-lived decay products of radon in equilibrium with 3,700 Bq/m (100 pCi/L) in air. These decay products would emit 1.3 × 10 MeV in complete decay. The NRC uses this definition.
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Early protoplanets had more radioactive elements, the quantity of which has been reduced over time due to radioactive decay. Heating due to radioactivity, impact, and gravitational pressure melted parts of protoplanets as they grew toward being planets. In melted zones their heavier elements sank to the center, whereas lighter elements rose to the surface. Such a process is known as planetary differentiation.
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The chemical properties of the radioactive element will determine how mobile the substance is and how likely it is to spread into the environment and contaminate humans. This is further complicated by the fact that many radioisotopes do not decay immediately to a stable state but rather to radioactive decay products within a decay chain before ultimately reaching a stable state.
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Proton decay is a hypothetical form of radioactive decay, predicted by many grand unification theories. During proton decay, the common baryonic proton decays into lighter subatomic particles. However, proton decay has never been experimentally observed and is predicted to be mediated by hypothetical X and Y bosons. Many protonic decay modes have been predicted, one of which is shown below.
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Models of heat retention and heating via radioactive decay in smaller icy Solar System bodies suggest that Rhea, Titania, Oberon, Triton, Pluto, Eris, Sedna, and Orcus may have oceans underneath solid icy crusts approximately 100 km thick. Of particular interest in these cases is the fact that the models indicate that the liquid layers are in direct contact with the rocky core, which allows efficient mixing of minerals and salts into the water. This is in contrast with the oceans that may be inside larger icy satellites like Ganymede, Callisto, or Titan, where layers of high-pressure phases of ice are thought to underlie the liquid water layer. Models of radioactive decay suggest that MOA-2007-BLG-192Lb, a small planet orbiting a small star could be as warm as the Earth and completely covered by a very deep ocean.
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The heat causing the melting of a reactor may originate from the nuclear chain reaction, but more commonly decay heat of the fission products contained in the fuel rods is the primary heat source. The heat production from radioactive decay drops quickly, as the short half-life isotopes provide most of the heat and radioactive decay, with the curve of decay heat being a sum of the decay curves of numerous isotopes of elements decaying at different exponential half-life rates. A significant additional heat source can be the chemical reaction of hot metals with oxygen or steam. Hypothetically, the temperature of corium depends on its internal heat generation dynamics: the quantities and types of isotopes producing decay heat, dilution by other molten materials, heat losses modified by the corium physical configuration, and heat losses to the environment.
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There are two principal methods used to generate random numbers. The first method measures some physical phenomenon that is expected to be random and then compensates for possible biases in the measurement process. Example sources include measuring atmospheric noise, thermal noise, and other external electromagnetic and quantum phenomena. For example, cosmic background radiation or radioactive decay as measured over short timescales represent sources of natural entropy.
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Permissive Action Links are powered by low-maintenance radioisotope generators. Instead of a conventional battery, these generators produce electricity based on the heat evolved from the radioactive decay of plutonium-238. Although the half-life of 238Pu is 87.7 years, these generators have shorter lifespans. This is due to the pressurization of the generator from helium produced by the alpha decay of the plutonium fuel.
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Out of the six known chalcogens, one (oxygen) has an atomic number equal to a nuclear magic number, which means that their atomic nuclei tend to have increased stability towards radioactive decay. Oxygen has three stable isotopes, and 14 unstable ones. Sulfur has four stable isotopes, 20 radioactive ones, and one isomer. Selenium has six observationally stable or nearly stable isotopes, 26 radioactive isotopes, and 9 isomers.
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There are a few dozen tellurate minerals and telluride minerals, and tellurium occurs in some minerals with gold, such as sylvanite and calaverite. Tellurium makes up 9 parts per billion of the universe by weight. Polonium only occurs in trace amounts on earth, via radioactive decay of uranium and thorium. It is present in uranium ores in concentrations of 100 micrograms per metric ton.
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Simulation of many identical atoms undergoing radioactive decay, starting with either 4 atoms per box (left) or 400 (right). The number at the top is how many half-lives have elapsed. Note the consequence of the law of large numbers: with more atoms, the overall decay is more regular and more predictable. A half-life usually describes the decay of discrete entities, such as radioactive atoms.
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"Gamma Ray" is a song by American rock musician Beck. It was released as the second single from his eighth studio album, Modern Guilt, on August 11, 2008. It is seemingly inspired by the surf rock songs of the 1960s, but with ghostly moans and lyrics on the state of the world. The title refers to gamma rays, biologically hazardous energy emitted by radioactive decay.
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There are 252 known so-called stable nuclides. Many of these in theory could decay through spontaneous fission, alpha decay, double beta decay, etc. with a very long half-life, but no radioactive decay has yet been observed. Thus the number of stable nuclides is subject to change if some of these 252 are determined to be very long-lived radioactive nuclides in the future.
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The viscosity of the mantle ranges between 1021 and 1024 Pa·s, depending on depth. In comparison, the viscosity of water is approximately 10−3 Pa·s and that of pitch is 107 Pa·s. The source of heat that drives plate tectonics is the primordial heat left over from the planet's formation as well as the radioactive decay of uranium, thorium, and potassium in Earth's crust and mantle.
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Decays are mediated by one or several fundamental forces. The particles in the final state may themselves be unstable and subject to further decay. The term is typically distinct from radioactive decay, in which an unstable atomic nucleus is transformed into a lighter nucleus accompanied by the emission of particles or radiation, although the two are conceptually similar and are often described using the same terminology.
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Steam rising from the Nesjavellir Geothermal Power Station in Iceland Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. The geothermal energy of the Earth's crust originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%).How Geothermal energy works . Ucsusa.org. Retrieved on 2013-04-24.
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The ACOG is available in a variety of configurations from the manufacturer with different reticles, illumination, and other features. Most ACOGs do not use batteries for reticle illumination,thefirearmblog.com - Oct 2011, Trijicon came out with a conventional battery-powered illumination ACOG being designed to use internal phosphor illumination provided by the radioactive decay of tritium. The tritium illumination has a usable life of 10–15 years.
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A synonym for such neutron emission is "prompt neutron" production, of the type that is best known to occur simultaneously with induced nuclear fission. Induced fission happens only when a nucleus is bombarded with neutrons, gamma rays, or other carriers of energy. Many heavy isotopes, most notably californium-252, also emit prompt neutrons among the products of a similar spontaneous radioactive decay process, spontaneous fission.
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Most of the atoms that make up the Earth and its inhabitants were present in their current form in the nebula that collapsed out of a molecular cloud to form the Solar System. The rest are the result of radioactive decay, and their relative proportion can be used to determine the age of the Earth through radiometric dating.Manuel (2001). Origin of Elements in the Solar System, pp.
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Unstable isotopes decay at predictable rates, and the decay rates of different isotopes cover several orders of magnitude, so radioactive decay can be used to accurately date both recent events and events in past geologic eras. Radiometric mapping using ground and airborne gamma spectrometry can be used to map the concentration and distribution of radioisotopes near the Earth's surface, which is useful for mapping lithology and alteration.
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The most common isotope is lead-208, followed by lead-206, lead-207, and lead-204: all of these are stable. 4 isotopes of lead occur from the radioactive decay of uranium and thorium. These isotopes are lead-209, lead-210, lead-211, and lead-212. 6 isotopes of flerovium (flerovium-284, flerovium-285, flerovium-286, flerovium-287, flerovium-288, and flerovium-289) have been discovered.
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The neutron's magnetic moment has a negative value, because its orientation is opposite to the neutron's spin. A free neutron is unstable, decaying to a proton, electron and antineutrino with a mean lifetime of just under 15 minutes (). This radioactive decay, known as beta decay, is possible because the mass of the neutron is slightly greater than the proton. The free proton is stable.
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Confirming relevance to the r-process is that it is radiogenic power from radioactive decay of r-process nuclei that maintains the visibility of these spun off r-process fragments. Otherwise they would dim quickly. Such alternative sites were first seriously proposed in 1974 as decompressing neutron star matter. It was proposed such matter is ejected from neutron stars merging with black holes in compact binaries.
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Charged pions most often decay into muons and muon neutrinos, while neutral pions generally decay into gamma rays. The exchange of virtual pions, along with vector, rho and omega mesons, provides an explanation for the residual strong force between nucleons. Pions are not produced in radioactive decay, but commonly are in high energy collisions between hadrons. Pions also result from some matter-antimatter annihilation events.
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It has a low melting point (640 °C) and an unusually high boiling point (3,228 °C). Alpha decay, the release of a high-energy helium nucleus, is the most common form of radioactive decay for plutonium. A 5 kg mass of 239Pu contains about atoms. With a half-life of 24,100 years, about of its atoms decay each second by emitting a 5.157 MeV alpha particle.
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Geothermal energy is generated from heat that is stored in the Earth. The geothermal energy is that is generated from the Earth's crust is the original formation of the planet and from radioactive decay of material. Geothermal heat pumps tap into the ground to use this resource as a source of energy. The production of geothermal energy is a clean and sustainable form of energy.
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Einstein's equation, by theory, can give these energies by measuring mass differences before and after reactions, but in practice, these mass differences in 1905 were still too small to be measured in bulk. Prior to this, the ease of measuring radioactive decay energies with a calorimeter was thought possibly likely to allow measurement of changes in mass difference, as a check on Einstein's equation itself. Einstein mentions in his 1905 paper that mass–energy equivalence might perhaps be tested with radioactive decay, which releases enough energy (the quantitative amount known roughly by 1905) to possibly be "weighed," when missing from the system (having been given off as heat). However, radioactivity seemed to proceed at its own unalterable pace, and even when simple nuclear reactions became possible using proton bombardment, the idea that these great amounts of usable energy could be liberated at will with any practicality, proved difficult to substantiate.
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Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types. Plate tectonics is driven by convection cells in the mantle. Convection cells are the result of heat generated by radioactive decay of elements in the mantle escaping to the surface and the return of cool materials from the surface to the mantle.
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In in vivo systems it is often used to quantify the binding of a test molecule to the binding site of radioligand. The higher the affinity of the molecule the more radioligand is displaced from the binding site and the increasing radioactive decay can be measured by scintillography. This assay is commonly used to calculate binding constant of molecules to receptors. The transport of the radioligand is described by receptor kinetics.
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This obscures the target at long range and the foreground. The reticle is tritium-illuminated for low-light condition aiming. The radioactive tritium light source has to be replaced every 8–12 years, since it gradually loses its brightness due to radioactive decay. The L2A2 SUIT Sight uses a similar single post to the SUSAT, but protrudes from the top edge of the sight down to the middle of the field.
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At the time, solar panels were not practical at Jupiter's distance from the Sun; the spacecraft would have needed a minimum of of panels. Chemical batteries would likewise be prohibitively large due to technological limitations. The solution was two radioisotope thermoelectric generators (RTGs) which powered the spacecraft through the radioactive decay of plutonium-238. The heat emitted by this decay was converted into electricity through the solid-state Seebeck effect.
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However the methodology has been strongly criticised and these results discounted. Parapsychologist Helmut Schmidt presented quantum mechanical justifications for retrocausality, eventually claiming that experiments had demonstrated the ability to manipulate radioactive decay through retrocausal psychokinesis. These results and their underlying theory have been rejected by the mainstream scientific community, although they continue to have some support from fringe science sources. Efforts to associate retrocausality with prayer healing have been similarly discounted.
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Water, the most abundant volatile in the Solar System, comprises Triton's mantle, enveloping a core of rock and metal. There is enough rock in Triton's interior for radioactive decay to maintain a liquid subsurface ocean to this day, similar to what is thought to exist beneath the surface of Europa and a number of other icy outer Solar System worlds.Overlooked Ocean Worlds Fill the Outer Solar System. John Wenz, Scientific American.
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There are no stable isotopes of astatine. However, there are four naturally occurring radioactive isotopes of astatine produced via radioactive decay of uranium, neptunium, and plutonium. These isotopes are astatine-215, astatine-217, astatine-218, and astatine-219. A total of 31 isotopes of astatine have been discovered, with atomic masses ranging from 191 to 227. Tennessine has only two known synthetic radioisotopes, tennessine-293 and tennessine-294.
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IAEA(2015) p.1 This resulted in the total loss of AC power at Unit1 through 5. As nuclear reactor coolant systems stopped for a long time from cutting power, the reactors overheated due to the normal high radioactive decay heat producedsmaller amounts of this heat normally continue to be released for years, but are not enough to cause fuel melting. in the first few days after nuclear reactor shutdown.
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The radioactive decay of strontium-90 generates a significant amount of heat, 0.536 W/g in the form of pure strontium metal or approximately 0.256 W/g as strontium titanate and is cheaper than the alternative 238Pu. It is used as a heat source in many Russian/Soviet radioisotope thermoelectric generators, usually in the form of strontium titanate. It was also used in the US "Sentinel" series of RTGs.
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Hydrogen-1 (N/Z ratio = 0) and helium-3 (N/Z ratio = 0.5) are the only stable isotopes with neutron–proton ratio under one. Uranium-238 has the highest N/Z ratio of any primordial nuclide at 1.587, while lead-208 has the highest N/Z ratio of any known stable isotope at 1.537. Radioactive decay generally proceeds so as to change the N/Z ratio to increase stability.
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In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations. It is also known as a "radioactive cascade". Most radioisotopes do not decay directly to a stable state, but rather undergo a series of decays until eventually a stable isotope is reached. Decay stages are referred to by their relationship to previous or subsequent stages.
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Isolated proton emission was eventually observed in some elements. It was also found that some heavy elements may undergo spontaneous fission into products that vary in composition. In a phenomenon called cluster decay, specific combinations of neutrons and protons other than alpha particles (helium nuclei) were found to be spontaneously emitted from atoms. Other types of radioactive decay were found to emit previously-seen particles, but via different mechanisms.
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Young was part of the research team that developed the Atom Trap Trace Analysis (ATTA) methodology for counting atoms of rare isotopes whose isotopic abundances are less than one part in a trillion. ATTA is a tool that extends radiocarbon dating from 5000 yr to 200 kyr, operating on long-lived isotopes where radioactive decay counting is inefficient. ATTA has been used with 81Kr to date the groundwater of ancient aquifers.
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The ratio of to is approximately 1.25 parts of to 1012 parts of .Tsipenyuk (1997), p. 343. In addition, about 1% of the carbon atoms are of the stable isotope . The equation for the radioactive decay of is: : → + + By emitting a beta particle (an electron, e−) and an electron antineutrino (), one of the neutrons in the nucleus changes to a proton and the nucleus reverts to the stable (non-radioactive) isotope .
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De Pretto's paper discussed the radioactive decay of uranium and thorium and was the first to conclude that this decay was energy transformation from mass into energy. He also presented a hypothesis that the intense heat assumed to be in the center of the Earth (theory of central fire) was caused by the tremendous mass of the earth creating a massive radioactive core giving off heat and energy.
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Electrons (beta radiation) detected in an isopropanol cloud chamber Beta-minus (β−) radiation consists of an energetic electron. It is more penetrating than alpha radiation, but less than gamma. Beta radiation from radioactive decay can be stopped with a few centimeters of plastic or a few millimeters of metal. It occurs when a neutron decays into a proton in a nucleus, releasing the beta particle and an antineutrino.
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For these purposes, a particularly useful type of radioactive decay is positron emission. When a positron collides with an electron, it releases two high-energy photons traveling in diametrically opposite directions. If the positron is produced within a solid object, it is likely to do this before traveling more than a millimeter. If both of these photons can be detected, the location of the decay event can be determined very precisely.
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A planetary core acts as a heat source for the outer layers of a planet. In the Earth, the heat flux over the core mantle boundary is 12 terawatts. This value is calculated from a variety of factors: secular cooling, differentiation of light elements, Coriolis forces, radioactive decay, and latent heat of crystallization. All planetary bodies have a primordial heat value, or the amount of energy from accretion.
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Such an outcome is unlikely, to say the least, since Nibiru would spend over 99% of its time beyond Pluto. Sitchin's explanation that heat from radioactive decay and a thick atmosphere keep Nibiru warm is absurd and does not address the problem of darkness in deep space. Also unexplained is how the Nephilim, who evolved long after Nibiru arrived, knew what happened when Nibiru first entered the solar system.
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Naturally occurring xenon consists of seven stable isotopes and two long-lived radioactive isotopes. More than 40 unstable xenon isotopes undergo radioactive decay, and the isotope ratios of xenon are an important tool for studying the early history of the Solar System. Radioactive xenon-135 is produced by beta decay from iodine-135 (a product of nuclear fission), and is the most significant (and unwanted) neutron absorber in nuclear reactors.
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A uranium radionuclide is a radioactive isotope. Radioactivity is natural in the environment, however uranium radionuclides can lead to radioactive decay. In the case of uranium mines, these radionuclides can leach into the water and cause the radioactivity to be carried elsewhere, as well as form precipitates that can be harmful to the environment. The uranium radionuclides can eventually be carried to fruits and vegetables via contaminated waters.
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The dose rate from a single uptake decays over time due to both radioactive decay, and biological decay (i.e. excretion from the body). The combined radioactive and biological half-life, called the effective half-life of the material, may range from hours for medical radioisotopes to decades for transuranic waste. Committed dose is the integral of this decaying dose rate over the presumed remaining lifespan of the organism.
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The actions of mining, refining, purifying, using, and ultimately disposing of nuclear fuel together make up the nuclear fuel cycle. Not all types of nuclear fuels create power from nuclear fission. Plutonium-238 and some other elements are used to produce small amounts of nuclear power by radioactive decay in radioisotope thermoelectric generators and other types of atomic batteries. Also, light nuclides such as tritium (3H) can be used as fuel for nuclear fusion.
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The neutrinoless double beta decay (0νββ) is a commonly proposed and experimentally pursued theoretical radioactive decay process that would prove a Majorana nature of the neutrino particle. To this day, it has not been found. The discovery of the neutrinoless double beta decay could shed light on the absolute neutrino masses and on their mass hierarchy (Neutrino mass). It would mean the first ever signal of the violation of total lepton number conservation.
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The presence of 233U will affect the long-term radioactive decay of the spent fuel. If compared with MOX fuel, the activity around one million years in the cycles with thorium will be higher due to the presence of the not fully decayed 233U. For natural uranium fuel, fissile component starts at 0.7% 235U concentration in natural uranium. At discharge, total fissile component is still 0.5% (0.2% 235U, 0.3% fissile 239Pu, 241Pu).
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Depending on what a nuclear reactor is fueled with, the actinide composition in the SNF will be different. An example of this effect is the use of nuclear fuels with thorium. Th-232 is a fertile material that can undergo a neutron capture reaction and two beta minus decays, resulting in the production of fissile U-233. Its radioactive decay will strongly influence the long-term activity curve of the SNF around a million years.
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It would be possible in principle to capture and store this krypton gas as nuclear waste or for use. The cumulative global amount of krypton-85 released from reprocessing activity has been estimated as 10,600 PBq as of 2000. The global inventory noted above is smaller than this amount due to radioactive decay; a smaller fraction is dissolved into the deep oceans. Other man-made sources are small contributors to the total.
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Much of the heat is created by decay of naturally radioactive elements. An estimated 45 to 90 percent of the heat escaping from the Earth originates from radioactive decay of elements mainly located in the mantle. The major heat-producing isotopes in the Earth are potassium-40, uranium-238, uranium-235, and thorium-232. The radiogenic heat from the decay of 238U and 232Th are now the major contributors to the earth's internal heat budget.
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The design of an RTG is simple by the standards of nuclear technology: the main component is a sturdy container of a radioactive material (the fuel). Thermocouples are placed in the walls of the container, with the outer end of each thermocouple connected to a heat sink. Radioactive decay of the fuel produces heat. It is the temperature difference between the fuel and the heat sink that allows the thermocouples to generate electricity.
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Determining a nuclear material's age is critical to nuclear forensic investigations. Dating techniques can be utilized to identify a material's source as well as procedures performed on the material. This can aid in determining the information about the potential participant in the "age" of the material of interest. Nuclides, related through radioactive decay processes will have relative sample concentrations that can be predicted using parent-daughter in-growth equations and relevant half-lives.
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Lutetium is a rare-earth element, with one naturally-occurring stable isotope 175Lu and one naturally-occurring radioactive isotope 176Lu. When 176Lu atoms are incorporated into earth materials, such as rocks and minerals, they began to be "trapped" while starting to decay. Through radioactive decay, an unstable nucleus decays into another relatively stable one. Radiometric dating makes use of the decay relationship to calculate how long the atoms have been "trapped", i.e.
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Aperiodic frequency is the rate of incidence or occurrence of non-cyclic phenomena, including random processes such as radioactive decay. It is expressed in units of measurement of reciprocal seconds (s−1) or, in the case of radioactivity, becquerels. It is defined as a ratio, f = N/T, involving the number of times an event happened (N) during a given time duration (T); it is a physical quantity of type temporal rate.
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One of the most widely used and well- known absolute dating techniques is carbon-14 (or radiocarbon) dating, which is used to date organic remains. This is a radiometric technique since it is based on radioactive decay. Cosmic radiation entering the earth’s atmosphere produces carbon-14, and plants take in carbon-14 as they fix carbon dioxide. Carbon-14 moves up the food chain as animals eat plants and as predators eat other animals.
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Potassium is common in rocks and minerals, allowing many samples of geochronological or archeological interest to be dated. Argon, a noble gas, is not commonly incorporated into such samples except when produced in situ through radioactive decay. The date measured reveals the last time that the object was heated past the closure temperature at which the trapped argon can escape the lattice. K–Ar dating was used to calibrate the geomagnetic polarity time scale.
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"A new study into the identity of the [portfolio] of Van Meegeren". Chemical Magazine: 583–589. The white lead in the painting The Supper at Emmaus had polonium-210 values of 8.5±1.4 and radium-226 (part of the uranium-238 radioactive decay series) values of 0.8±0.3. In contrast, the white lead found in Dutch paintings from 1600 to 1660 had polonium-210 values of 0.23±0.27 and radium-226 values of 0.40±0.47.
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Due to its small size (and thus its small gravity), Mercury has no substantial atmosphere. Its extremely thin atmosphere mostly consists of a small amount of helium and traces of sodium, potassium, and oxygen. These gases derive from the solar wind, radioactive decay, meteor impacts, and breakdown of Mercury's crust. Mercury's atmosphere is not stable and is constantly being refreshed because of its atoms escaping into space as a result of the planet's heat.
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407-430, 511-519 Most of the helium in the crust of the Earth (about 99% of the helium from gas wells, as shown by its lower abundance of helium-3) is a product of alpha decay. There are a few trace atoms on Earth that were not present at the beginning (i.e., not "primordial"), nor are results of radioactive decay. Carbon-14 is continuously generated by cosmic rays in the atmosphere.
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The 83rd element, bismuth, was traditionally regarded as having the heaviest stable isotope, bismuth-209, but in 2003 researchers in Orsay, France, measured the half-life of to be . Technetium and promethium (atomic numbers 43 and 61, respectively) and all the elements with an atomic number over 82 only have isotopes that are known to decompose through radioactive decay. No undiscovered elements are expected to be stable; therefore, lead is considered the heaviest stable element.
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The first gamma ray source to be discovered was the radioactive decay process called gamma decay. In this type of decay, an excited nucleus emits a gamma ray almost immediately upon formation.It is now understood that a nuclear isomeric transition, however, can produce inhibited gamma decay with a measurable and much longer half-life. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from radium.
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Uranium–uranium dating is a radiometric dating technique which compares two isotopes of uranium (U) in a sample: uranium-234 (234U) and uranium-238 (238U). It is one of several radiometric dating techniques exploiting the uranium radioactive decay series, in which 238U undergoes 14 alpha and beta decay events on the way to the stable isotope 206Pb. Other dating techniques using this decay series include uranium–thorium dating and uranium–lead dating.
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Scientists of the time were well aware that the slow natural radioactive decay of elements like radium continues for thousands of years, and that while the rate of energy release is negligible, the total amount released is huge. Wells used this as the basis for his story. In his fiction, Wells's knowledge of atomic physics came from reading William Ramsay, Ernest Rutherford, and Frederick Soddy; the last discovered the disintegration of uranium.
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Neutrino telescope Neutrino astronomy is the branch of astronomy that observes astronomical objects with neutrino detectors in special observatories. Neutrinos are created as a result of certain types of radioactive decay, or nuclear reactions such as those that take place in the Sun, in nuclear reactors, or when cosmic rays hit atoms. Due to their weak interactions with matter, neutrinos offer a unique opportunity to observe processes that are inaccessible to optical telescopes.
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Because of the fossil fuel effect, this is not actually the activity level of wood from 1950; the activity would have been somewhat lower. The fossil fuel effect was eliminated from the standard value by measuring wood from 1890, and using the radioactive decay equations to determine what the activity would have been at the year of growth. The resulting standard value, Aabs, is 226 becquerels per kilogram of carbon.L'Annunziata, Radioactivity, p. 528.
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The power emitted in radioactive decay corresponding to one curie can be calculated by multiplying the decay energy by approximately 5.93 mW/MeV. A radiotherapy machine may have roughly 1000 Ci of a radioisotope such as caesium-137 or cobalt-60. This quantity of radioactivity can produce serious health effects with only a few minutes of close-range, unshielded exposure. Ingesting even a millicurie is usually fatal (unless it is a very short-lived isotope).
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The merger can also create a magnetic field that is trillions of times stronger than that of Earth in a matter of one or two milliseconds. These events are believed to create short gamma-ray bursts. The mergers are also believed to produce kilonovae, which are transient sources of fairly isotropic longer wave electromagnetic radiation due to the radioactive decay of heavy r-process nuclei that are produced and ejected during the merger process.
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The SPA technique is dependent on the energy conversion of radioactive decay, which releases light photons which can be detected via the use of some devices such as the photomultiplier tubes of scintillation counters or CCD imagers. This is a very popular technique in practices that require detecting and quantifying radioactivity.Homogeneous Proximity Tyrosine Kinase Assays: Scintillation Proximity Assay versus Homogeneous Time-Resolved Fluorescence. Analytical Biochemistry Volume 269, Issue 1, 10 April 1999, Pages 94-104.
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Important preliminary theoretical work was carried prior to the planetary missions launched starting in the 1970s. In particular, Lewis showed in 1971 that radioactive decay alone was likely sufficient to produce subsurface oceans in large moons, especially if ammonia () was present. Peale and Cassen figured out in 1979 the important role of tidal heating (aka: tidal flexing) on satellite evolution and structure. The first confirmed detection of an exoplanet was in 1992.
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Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar). Potassium is a common element found in many materials, such as micas, clay minerals, tephra, and evaporites. In these materials, the decay product is able to escape the liquid (molten) rock, but starts to accumulate when the rock solidifies (recrystallizes).
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On the far right we see the decay of Np-237 and U-233. The use of different fuels in nuclear reactors results in different SNF composition, with varying activity curves. Long-lived radioactive waste from the back end of the fuel cycle is especially relevant when designing a complete waste management plan for SNF. When looking at long- term radioactive decay, the actinides in the SNF have a significant influence due to their characteristically long half-lives.
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When the Sun ignited in the solar nebula, hydrogen, helium and other volatile materials were evaporated in the region around it. The solar wind and radiation pressure forced these low-density materials away from the Sun. Rocks, and the elements comprising them, were stripped of their early atmospheres, but themselves remained, to accumulate into protoplanets. Protoplanets had higher concentrations of radioactive elements early in their history, the quantity of which has reduced over time due to radioactive decay.
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Ria Novosti, November 11, 2009, retrieved January 2, 2011 of plutonium-238the heat from the material's radioactive decay was turned into electricity. Huygens was supported by Cassini during cruise, but used chemical batteries when independent. The probe contained a DVD with more than 616,400 signatures from citizens in 81 countries, collected in a public campaign. Until September 2017 the Cassini probe continued orbiting Saturn at a distance of between 8.2 and 10.2 astronomical units from the Earth.
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All uraninite minerals contain a small amount of radium as a radioactive decay product of uranium. Marie Curie used pitchblende, processing tons of it herself, as the source material for her isolation of radium in 1898. Uraninite also always contains small amounts of the lead isotopes 206Pb and 207Pb, the end products of the decay series of the uranium isotopes 238U and 235U respectively. Small amounts of helium are also present in uraninite as a result of alpha decay.
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The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundance of such stable isotopes can be measured experimentally (isotope analysis), yielding an isotope ratio that can be used as a research tool. Theoretically, such stable isotopes could include the radiogenic daughter products of radioactive decay, used in radiometric dating.
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Decay heat accidents are where the heat generated by the radioactive decay causes harm. In a large nuclear reactor, a loss of coolant accident can damage the core: for example, at Three Mile Island a recently shutdown (SCRAMed) PWR reactor was left for a length of time without cooling water. As a result, the nuclear fuel was damaged, and the core partially melted. The removal of the decay heat is a significant reactor safety concern, especially shortly after shutdown.
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The Brewer–Dobson circulation is a theory of large-scale ozone circulation. Concentrations of other trace gases are higher near natural and artificial sources. This includes pollution from human activity (especially agriculture, industry, and transportation), natural gas fields, radon produced by radioactive decay in certain minerals, volcanic gas, emissions from limnic eruptions. Oxygen is emitted and carbon dioxide is absorbed by plants and microorganisms performing photosynthesis, but CO2 levels are most strongly affected by wild fires and human activity.
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After ~100,000 years all the carbon-14 present in the original organic material will have undergone radioactive decay leaving only carbon-12. A product made from biomass will have a relatively high level of carbon-14, while a product made from petrochemicals will have no carbon-14. The percentage of renewable carbon in a material (solid or liquid) can be measured with an accelerator mass spectrometer. There is an important difference between biodegradability and biobased content.
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Incompatible trace elements become depleted when mantle melts and become enriched in oceanic or continental crust through volcanic activity. Other times, volcanism can produce enriched mantle melt onto the crust. These phenomena can be quantified by looking at radioactive decay records of isotopes in these basalts, which is a valuable tool for mantle geochemists. More specifically, the geochemistry of serpentinites along the ocean floor, specifically subduction zones, can be examined using compatibility of specific trace elements.
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He drives Batman out of Chinatown, leading Terry to find another one of the sabotaged aerial defense systems. Batman is attacked by the culprit behind the attacks, Freon of the Terrific Trio. She was resurrected thanks to Dr. Hodges using experimental molecular sieves to absorb and contain her radioactive decay, but the exposure to her kills him. Blaming Batman and Gotham for the deaths of her colleagues, she's rigged the city's defense systems to make Gotham destroy itself.
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Radiogenic heating occurs as a result of the release of heat energy from radioactive decay during the production of radiogenic nuclides. Along with heat from the outer core of the Earth, radiogenic heating occurring in the mantle make up the two main sources of heat in the Earth's interior. Most of the radiogenic heating in the Earth results from the decay of the daughter nuclei in the decay chains of uranium-238 and thorium-232, and potassium-40.
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Radioactive decay of naturally occurring uranium (238U and 235U), thorium (232Th), and potassium (40K) in seafloor sediments collectively bombard the interstitial water with α, β, and γ radiation. The irradiation ionizes and breaks apart water molecules, eventually yielding H2. The products of this reaction are aqueous electrons (e−aq), hydrogen radicals (H·), protons (H+), and hydroxyl radicals (OH·). The radicals are highly reactive, therefore short-lived, and recombine to produce hydrogen peroxide (H2 O2), and molecular hydrogen (H2).
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The quantum suicide thought experiment involves a similar apparatus to Schrödinger's cat – a box which kills the occupant in a given time frame with probability one-half due to quantum uncertainty.The simplest example of this is a weapon triggered by a two level system. Schrödinger described his as a radioactive decay detector while Moravec's was a device measuring the spin value of protons. The only difference is to have the experimenter recording observations be the one inside the box.
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Radio-Activity (German title: Radio-Aktivität) is the fifth studio album by German electronic band Kraftwerk, released in October 1975. The band's first entirely electronic album, it is a concept album organized around the themes of radioactive decay and radio communication. The album was accompanied by a single release of the title track, which was successful in France. To cater to the band's international audience, all releases of the album were bilingual, with lyrics in both English and German.
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While experimenting with the products of radioactive decay, in 1913 radiochemist Frederick Soddy discovered that there appeared to be more than one type of atom at each position on the periodic table. The term isotope was coined by Margaret Todd as a suitable name for different atoms that belong to the same element. J. J. Thomson created a technique for isotope separation through his work on ionized gases, which subsequently led to the discovery of stable isotopes.
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Of the actinides, thorium and uranium occur naturally in substantial, primordial, quantities. The radioactive decay of uranium produces transient amounts of actinium, protactinium and plutonium, and atoms of neptunium are occasionally produced from transmutation reactions in uranium ores. The other actinides are purely synthetic elements, although the first six actinides after plutonium would have been produced during the Oklo phenomenon (and long since decayed away), and curium almost certainly previously existed in nature as an extinct radionuclide.Greenwood, p.
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The sides of the valley correspond to increasing instability to beta decay (β− or β+). The decay of a nuclide becomes more energetically favorable the further it is from the line of beta stability. The boundaries of the valley correspond to the nuclear drip lines, where nuclides become so unstable they emit single protons or single neutrons. Regions of instability within the valley at high atomic number also include radioactive decay by alpha radiation or spontaneous fission.
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A neutron in free state is an unstable particle, with a half- life around ten minutes. It undergoes decay (a type of radioactive decay) by turning into a proton while emitting an electron and an electron antineutrino. (See the Neutron article for more discussion of neutron decay.) A proton by itself is thought to be stable, or at least its lifetime is too long to measure. This is an important discussion in particle physics, (see Proton decay).
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Hahn suggested a bursting of the nucleus, but he was unsure of what the physical basis for the results were. Barium had an atomic mass 40% less than uranium, and no previously known methods of radioactive decay could account for such a large difference in the mass of the nucleus. Frisch was skeptical, but Meitner trusted Hahn's ability as a chemist. Marie Curie had been separating barium from radium for many years, and the techniques were well-known.
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The radioactive emissions and radioactive decay paths for each element are well known. Using this information, it is possible to study spectra of the emissions of the radioactive sample, and determine the concentrations of the elements within it. A particular advantage of this technique is that it does not destroy the sample, and thus has been used for analysis of works of art and historical artifacts. NAA can also be used to determine the activity of a radioactive sample.
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Homemade Lucas cell A Lucas cell is a type of scintillation counter. It is used to acquire a gas sample, filter out the radioactive particulates through a special filter and then count the radioactive decay. The inside of the gas chamber is coated with ZnS(Ag) - a chemical that emits light when struck by alpha particles. A photomultiplier tube at the top of the chamber counts the photons and sends the count to a data logger.
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In the early 20th century, measurements of the atomic weight of lead showed significant variations depending on the origin of the sample. These differences were considered to be an exception attributed to lead isotopes being products of the natural radioactive decay chains of uranium. In 1930s, however, Malcolm Dole reported that the atomic weight of oxygen in air was slightly different from that in water. Soon thereafter, Alfred Nier reported natural variation in the isotopic composition of carbon.
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Earthquake chemistry II, collected papers, edn, Vol. II, Laboratory for Earthquake Chemistry, Faculty of Science, University of Tokyo, Japan. Radon has a half-life of approximately 3.8 days, which means that it can be found only shortly after it has been produced in the radioactive decay chain. For this reason, it has been hypothesized that increases in radon concentration is due to the generation of new cracks underground, which would allow increased groundwater circulation, flushing out radon.
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Barium found in the Earth's crust is a mixture of seven primordial nuclides, barium-130, 132, and 134 through 138. Barium-130 undergoes very slow radioactive decay to xenon-130 by double beta plus decay, with a half-life of (0.5–2.7)×1021 years (about 1011 times the age of the universe). Its abundance is ≈0.1% that of natural barium. Theoretically, barium-132 can similarly undergo double beta decay to xenon-132; this decay has not been detected.
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Chemistry uses calculus in determining reaction rates and radioactive decay (exponential decay). In biology, population dynamics starts with reproduction and death rates to model population changes (population modeling). In engineering, difference equations are used to plot a course of a spacecraft within zero gravity environments, to model heat transfer, diffusion, and wave propagation. Discrete Green's Theorem is applied in an instrument known as a planimeter, which is used to calculate the area of a flat surface on a drawing.
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Paralana geothermal springs are located on Wooltana, north of Arkaroola. Local granite rocks contain elevated levels of uranium that gives off heat during radioactive decay. Water percolating through fractures in the rock is heated and bubbles out at the surface as a hot spring, with gases such as carbon dioxide, nitrogen, radon and helium. Due to the presence of radon gas, which is heavier than air, staying near the springs for a prolonged period may constitute a health hazard.
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In natural environment, crystal lattices of quartz and/or feldspar are bombarded with radiation released from radiogenic source such as in -situ radioactive decay. As the crystals are irradiated, charges are stored up in their crystallographic defects. The charge trapping process involves atomic-scale ionic substitution of both electron and hole within the crystal lattices of quartz and feldspar. The electron diffusion happens in response to ionizing radiation as the minerals cools below their closure temperature.
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The second problem is that nuclear fission produces high levels of neutron and gamma rays, which require excessive shielding, that would result in a vehicle too large for use on public roads. However studies were made in this way by Ford Nucleon. A better way for a nuclear powered vehicle would be the use of power of radioactive decay in radioisotope thermoelectric generators, which are also very safe and reliable. The required shielding of these devices depends on the used radio nuclide.
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None of those experiments have produced positive results for the neutrinoless process, raising the half-life lower bound to approximately 1025 years. Geochemical experiments continued through the 1990s, producing positive results for several isotopes. Double beta decay is the rarest known kind of radioactive decay; as of 2019 it has been observed in only 14 isotopes (including double electron capture in observed in 2001, observed in 2013, and observed in 2019), and all have a mean lifetime over 1018 yr (table below).
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Hönigschmid had studied under leading expert Theodore Williams Richards at Harvard and his work in determining precise atomic weights was well respected. Horovitz isolated lead from uranium-rich pitchblende samples from the St. Joachmistal mine. Her gravimetric analysis to the thousandth of a gram proved that lead created from the radioactive decay of uranium had a lower atomic weight than typical lead. This was the first widely accepted experimental proof that elements could have different atomic weights depending on the source.
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In 1998 Clayton voiced a new idea for supernova chemistry by arguing that radioactive decay causes carbon to condense within oxygen-rich supernova gas. He reached that conclusion after Weihong Liu and Alexander DalgarnoW. Liu & A. Dalgarno, Astrophys. J. 454, 472–79 (1995) showed that radioactive decays of 56Co create fast Compton-scattered electrons that would dissociate the CO molecule [e+CO > e'+C+O], thereby preventing the complete oxidation of carbon atoms within young remnants of core-collapse supernovae.
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Deviations from this expected value are indicative of other processes that affect the delta ratio of radiocarbon, namely radioactive decay. This deviation can be converted to a time, giving the age of the water at that location. Doing this over the world's ocean can yield a circulation pattern of the ocean and the rate at which water flow through the deep ocean. Using this circulation in conjunction with the surface circulation allows scientists to understand the energy balance of the world.
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Many products come with some form of the statement "chemical free!" or "no chemicals!". As everything on Earth, save a few elementary particles formed by radioactive decay or present in minute quantities from solar wind and sunlight, is made of chemicals, it is impossible to have a chemical free product. The intention of this message is often to indicate the product contains no synthetic or exceptionally harmful chemicals, but as the word chemical itself has a stigma, it is often used without clarification.
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In the post-accident analysis of SL-1, scientists determined that the two shutdown mechanisms were almost equally matched (see below). Another relevant kinetics factor is the contribution of what are called delayed neutrons to the chain reaction in the core. Most neutrons (the prompt neutrons) are produced nearly instantaneously via fission. But a few—approximately 0.7 percent in a U-235-fueled reactor operating at steady- state—are produced through the relatively slow radioactive decay of certain fission products.
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They noted that positron emission continued after the neutron emissions ceased. Not only had they discovered a new form of radioactive decay, they had transmuted an element into a hitherto unknown radioactive isotope of another, thereby inducing radioactivity where there had been none before. Radiochemistry was now no longer confined to certain heavy elements, but extended to the entire periodic table. Chadwick noted that being electrically neutral, neutrons could penetrate the atomic nucleus more easily than protons or alpha particles.
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A radiogenic nuclide is a nuclide that is produced by a process of radioactive decay. It may itself be radioactive (a radionuclide) or stable (a stable nuclide). Radiogenic nuclides (more commonly referred to as radiogenic isotopes) form some of the most important tools in geology. They are used in two principal ways: #In comparison with the quantity of the radioactive 'parent isotope' in a system, the quantity of the radiogenic 'daughter product' is used as a radiometric dating tool (e.g.
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His scientific interests concentrate on new methods for the quantitative determination of radionuclides in environmental samples as well as the impact of technical activities on natural radioactive decay level and additional degree of radiation hazard. He is the author of over 80 scientific papers and 3 monographies, and is a fivefold doctoral advisor. He was from 1999 to 2005 the Deputy Dean for Education and in the years 2005-2008 the Dean of the Faculty of Chemistry at Lodz University of Technology.
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Glottochronology (from Attic Greek γλῶττα tongue, language and χρóνος time) is the part of lexicostatistics dealing with the chronological relationship between languages.Sheila Embleton (1992). Historical Linguistics: Mathematical concepts. In W. Bright (Ed.), International Encyclopedia of Linguistics The idea was developed by Morris Swadesh under two assumptions: there indeed exists a relatively stable basic vocabulary (referred to as Swadesh lists) in all languages of the world; and, any replacements happen in a way analogous to radioactive decay in a constant percentage per time elapsed.
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A volcanic eruption is the release of stored energy from below Earth's surface.Encyclopedia of Volcanoes, Academic Press, London, 2000 Plate tectonics, mountain ranges, volcanoes, and earthquakes are geological phenomena that can be explained in terms of physical and chemical processes in the Earth's crust. Beneath the Earth's crust lies the mantle which is heated by the radioactive decay of heavy elements. The mantle is not quite solid and consists of magma which is in a state of semi-perpetual convection.
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Spontaneous fission gives much the same result as induced nuclear fission. However, like other forms of radioactive decay, it occurs due to quantum tunneling, without the atom having been struck by a neutron or other particle as in induced nuclear fission. Spontaneous fissions release neutrons as all fissions do, so if a critical mass is present, a spontaneous fission can initiate a self-sustaining chain reaction. Radioisotopes for which spontaneous fission is not negligible can be used as neutron sources.
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Chain reactions do not occur inside RTGs, so a nuclear meltdown is impossible. In fact, some RTGs are designed so that fission does not occur at all; rather, forms of radioactive decay which cannot trigger other radioactive decays are used instead. As a result, the fuel in an RTG is consumed much more slowly and much less power is produced. RTGs are still a potential source of radioactive contamination: if the container holding the fuel leaks, the radioactive material will contaminate the environment.
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The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface. The adjective geothermal originates from the Greek roots γη (ge), meaning earth, and θερμος (thermos), meaning hot. Earth's internal heat is thermal energy generated from radioactive decay and continual heat loss from Earth's formation. Temperatures at the core-mantle boundary may reach over 4000 °C (7,200 °F).
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In the 1930s, isotopes would be shown to have nuclei with differing numbers of the neutral particles known as "neutrons". In that same year, other research was published establishing the rules for radioactive decay, allowing more precise identification of decay series. Many geologists felt these new discoveries made radiometric dating so complicated as to be worthless. Holmes felt that they gave him tools to improve his techniques, and he plodded ahead with his research, publishing before and after the First World War.
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The landmass of North and South America combined, to a depth of 16 kilometers (10 miles), contains only about one trillion astatine-215 atoms at any given time (around 3.5 × 10−10 grams). Astatine-217 is produced via the radioactive decay of neptunium-237. Primordial remnants of the latter isotope—due to its relatively short half-life of 2.14 million years—are no longer present on Earth. However, trace amounts occur naturally as a product of transmutation reactions in uranium ores.
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In a slower process, radioactive decay of atoms in the core of the Earth releases heat. This thermal energy drives plate tectonics and may lift mountains, via orogenesis. This slow lifting represents a kind of gravitational potential energy storage of the thermal energy, which may be later released to active kinetic energy in landslides, after a triggering event. Earthquakes also release stored elastic potential energy in rocks, a store that has been produced ultimately from the same radioactive heat sources.
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The mathematics of radioactive decay depend on a key assumption that a nucleus of a radionuclide has no "memory" or way of translating its history into its present behavior. A nucleus does not "age" with the passage of time. Thus, the probability of its breaking down does not increase with time but stays constant, no matter how long the nucleus has existed. This constant probability may differ greatly between one type of nuclei and another, leading to the many different observed decay rates.
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The Szilard–Chalmers effect is the breaking of a chemical bond as a result of a kinetic energy imparted from radioactive decay. It operates by the absorption of neutrons by an atom and subsequent emission of gamma rays, often with significant amounts of kinetic energy. This kinetic energy, by Newton's third law, pushes back on the decaying atom, which causes it to move with enough speed to break a chemical bond. This effect can be used to separate isotopes by chemical means.
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The Presence gained superhuman powers as a result of mutation through exposure to nuclear radiation. This granted him superhuman strength, stamina, and durability. He is capable of the generation of nuclear energy within his body and the ability to manipulate it for various effects, including force blasts, the creation of force fields, and the power of flight at near-warp speed through air or outer space. He subsists on radioactive decay, and hence does not require food, water, or oxygen.
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Olinto De Pretto (26 April 1857 – 16 March 1921) was an Italian industrialist and geologist from Schio, Vicenza. There is evidenceUmberto Bartocci, Albert Einstein e Olinto De Pretto—La vera storia della formula più famosa del mondo, editore Andromeda, Bologna, 1999. that De Pretto may have been the first person to derive the energy–mass-equivalence E=mc^2, generally attributed to Albert Einstein. De Pretto suggested that radioactive decay of uranium and thorium was an example of mass transforming into energy.
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The (radioactive) tritium light source has to be replaced every 8–12 years, since it gradually loses its brightness due to radioactive decay. With fiber optics ambient (day)light can be collected and directed to an illuminated daytime reticle. Fiber-optics reticles automatically interact with the ambient light level that dictates the brightness of the reticle. Trijicon uses fiber optics combined with other low-light conditions illumination methods in their AccuPoint telescopic sights and some of their ACOG sights models.
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The hydrocarbons in that environment do not come from living organisms. The source of the hydrogen needed for their respiration comes from the decomposition of water by radioactive decay of uranium, thorium, and potassium. The radiation allows for the production of sulphur compounds that these bacteria can use as a high-energy source of food. "Ca. D. audaxviator" not only survives in a complete absence of organic compounds, light, and oxygen, but also in temperatures as high as and a pH of 9.3.
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Curium metal is a radionuclide and emits alpa particles upon radioactive decay. Although it has a half life of 34 ms, many curium oxides, including curium sesquioxide, have half lives nearing thousands of years. Curium, in the form of curium sesquioxide, can be inhaled into the body, causing many biological defects. The LD50 of curium is 3 micro-Ci through ingestion and inhalation and 1 micro-Ci through absorption through the skin.“Radionuclide Data Sheet: Curium.” University of California, San Diego. n.d.1.
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The damage caused by free radicals is called indirect DNA damage. # Ionizing radiation such as that created by radioactive decay or in cosmic rays causes breaks in DNA strands. Intermediate-level ionizing radiation may induce irreparable DNA damage (leading to replicational and transcriptional errors needed for neoplasia or may trigger viral interactions) leading to pre-mature aging and cancer. # Thermal disruption at elevated temperature increases the rate of depurination (loss of purine bases from the DNA backbone) and single-strand breaks.
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In 1896, Henri Becquerel discovered radioactive decay in a variety of chemical elements. Subsequently, the beta radiation from these decays was discovered to be the emission of a negatively charged particle. Later these particles were identified with the electron, discovered in cathode ray experiments by J. J. Thomson in 1897. This was connected with the theoretical prediction of the electromagnetic mass by J. J. Thomson in 1881, who showed that the electromagnetic energy contributes to the mass of a moving charged body.
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On the far right we see the decay of Np-237 and U-233. The use of different fuels in nuclear reactors results in different spent nuclear fuel (SNF) composition, with varying activity curves. Long-lived radioactive waste from the back end of the fuel cycle is especially relevant when designing a complete waste management plan for SNF. When looking at long-term radioactive decay, the actinides in the SNF have a significant influence due to their characteristically long half-lives.
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The process of converting radioactivity to light requires a liquid medium of scintillation combination consisting soluble organic scintillators and organic solvents. During the process of radioactive decay, a beta particle will be released. While this particle travels in the medium, the energy it possesses is dissipated as it collides with the surrounding molecules in the solvent, exciting them while doing so. The excited molecules will transfer the energy they now possess to the scintillator molecules, where the energy will be emitted as light.
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Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes. The 80 elements with one or more stable isotopes comprise a total of 252 nuclides that have not been known to decay using current equipment (see list at the end of this article). Of these elements, 26 have only one stable isotope; they are thus termed monoisotopic.
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Some heavier elements are produced by less efficient processes such as the r-process and s-process. Elements with atomic numbers close to iron are produced in large quantities in supernova due to explosive oxygen and silicon fusion, followed by radioactive decay of nuclei such as Nickel-56. On average, heavier elements are less abundant in the universe, but some of those near iron are comparatively more abundant than would be expected from this trend. Abundances of the chemical elements in the Solar System.
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In nuclear physics, double beta decay is a type of radioactive decay in which two neutrons are simultaneously transformed into two protons, or vice versa, inside an atomic nucleus. As in single beta decay, this process allows the atom to move closer to the optimal ratio of protons and neutrons. As a result of this transformation, the nucleus emits two detectable beta particles, which are electrons or positrons. The literature distinguishes between two types of double beta decay: ordinary double beta decay and neutrinoless double beta decay.
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An absorption or release of nuclear energy occurs in nuclear reactions or radioactive decay; those that absorb energy are called endothermic reactions and those that release energy are exothermic reactions. Energy is consumed or liberated because of differences in the nuclear binding energy between the incoming and outgoing products of the nuclear transmutation. The best-known classes of exothermic nuclear transmutations are fission and fusion. Nuclear energy may be liberated by atomic fission, when heavy atomic nuclei (like uranium and plutonium) are broken apart into lighter nuclei.
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There are around 94 naturally occurring elements on earth. The atoms of each element have a nucleus containing a specific number of protons (always the same number for a given element), and some number of neutrons, which is often roughly a similar number. Two atoms of the same element having different numbers of neutrons are known as isotopes of the element. Different isotopes may have different properties - for example one might be stable and another might be unstable, and gradually undergo radioactive decay to become another element.
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By 1947, physicists believed that they had a good understanding of what the smallest bits of matter were. There were electrons, protons, neutrons, and photons (the components that make up the vast part of everyday experience such as atoms and light) along with a handful of unstable (i.e., they undergo radioactive decay) exotic particles needed to explain cosmic rays observations such as pions, muons and hypothesized neutrino. In addition, the discovery of the positron suggested there could be anti-particles for each of them.
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However, a small fraction (about 0.65%) of neutrons in a typical power reactor comes from the radioactive decay of a fission product. These delayed neutrons, which are emitted at lower velocities, will limit the rate at which a nuclear reactor will shut down. Due to flaws in its original control rod design, scramming an RBMK reactor could raise reactivity to dangerous levels before lowering it. This was noticed when it caused a power surge at the startup of Ignalina Nuclear Power Plant Unit number 1, in 1983.
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Three related terms are used in this context: ;Late-life mortality deceleration :Hazard rate increasing at a decreasing rate (rather than increasing log-linearly as in the Gompertz law). ; :More strongly, hazard rate eventually stops increasing (or rather, asymptotes towards a limit), and then proceeds at a constant rate (or rather, approaches a constant rate), yielding (slightly sub-) exponential decay, as in radioactive decay. ; This is used synonymously with "mortality leveling-off", or rather to refer to the region where hazard rate is approximately constant.
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The partial differentiation of Callisto (inferred e.g. from moment of inertia measurements) means that it has never been heated enough to melt its ice component. Therefore, the most favorable model of its formation is a slow accretion in the low-density Jovian subnebula—a disk of the gas and dust that existed around Jupiter after its formation. Such a prolonged accretion stage would allow cooling to largely keep up with the heat accumulation caused by impacts, radioactive decay and contraction, thereby preventing melting and fast differentiation.
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The open, V-shaped rear allows for faster acquisition and wider field of view, though less accurate for longer range precision type shooting. The dot on the front sight is aligned or set directly above the vertical bar on the rear sight, commonly referred to as "dotting the 'I'". ; Gold bead: Preferred by many competitors in IPSC and IDPA shooting. ; Night sights: On tactical firearms, the contrast enhancements can consist of small vials containing tritium gas whose radioactive decay causes a fluorescent material to glow.
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In chemistry, the decay technique is a method to generate chemical species such as radicals, carbocations, and other potentially unstable covalent structures by radioactive decay of other compounds. For example, decay of a tritium-labeled molecule yields an ionized helium atom, which might then break off to leave a cationic molecular fragment. The technique was developed in 1963 by the Italian chemist Fulvio Cacace at the University of Rome. It has allowed the study of a vast number of otherwise inaccessible compounds and reactions.
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"There goes a Nobel Prize", Hahn remarked. At the Kaiser Wilhelm Institute for Chemistry, Kurt Starke independently produced element 93, using only the weak neutron sources available there. Hahn and Strassmann then began researching its chemical properties. They knew that it should decay into the real element 94, which according to the latest version of the liquid drop model of the nucleus propounded by Bohr and John Archibald Wheeler, would be even more fissile than uranium-235, but were unable to detect its radioactive decay.
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The flooded generators failed, cutting power to the critical pumps that circulate coolant water to keep them from melting down. When the pumps stopped, the reactors overheated due to the high radioactive decay heat produced in the first few days after nuclear reactor shutdown. As the water boiled away in the reactors and the water levels in the fuel rod pools dropped, the reactor fuel rods began to overheat severely. In the hours and days that followed, Reactors 1, 2 and 3 experienced full meltdown.
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It was also believed that radioactive decay violated one of the central principles of the periodic table, namely that chemical elements could not undergo transmutations and always had unique identities. Frederick Soddy and Kazimierz Fajans found in 1913 that although these substances emitted different radiation, many of these substances were identical in their chemical characteristics, so shared the same place on the periodic table. They became known as isotopes, from the Greek ' ("same place").Soddy first used the word "isotope" in: See p. 400.
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Because radon is a product of the radioactive decay of uranium, underground uranium mines may have high concentrations of radon. Many uranium miners in the Four Corners region contracted lung cancer and other pathologies as a result of high levels of exposure to radon in the mid-1950s. The increased incidence of lung cancer was particularly pronounced among Native American and Mormon miners, because those groups normally have low rates of lung cancer. Safety standards requiring expensive ventilation were not widely implemented or policed during this period.
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Isotopes such as lithium-6, as well as some beryllium and boron are generated in space through cosmic ray spallation. This occurs when a high-energy proton strikes an atomic nucleus, causing large numbers of nucleons to be ejected. Elements heavier than iron were produced in supernovae and colliding neutron stars through the r-process, and in AGB stars through the s-process, both of which involve the capture of neutrons by atomic nuclei. Elements such as lead formed largely through the radioactive decay of heavier elements.
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While the electron has a negative electric charge, the positron has a positive electric charge, and is produced naturally in certain types of radioactive decay. The opposite is also true: the antiparticle of the positron is the electron. Some particles, such as the photon, are their own antiparticle. Otherwise, for each pair of antiparticle partners, one is designated as the normal particle (a kind of all particles usually interacted with is made of), and the other (usually given the prefix "anti-") as the antiparticle.
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Particle–antiparticle pairs can annihilate each other, producing photons; since the charges of the particle and antiparticle are opposite, total charge is conserved. For example, the positrons produced in natural radioactive decay quickly annihilate themselves with electrons, producing pairs of gamma rays, a process exploited in positron emission tomography. The laws of nature are very nearly symmetrical with respect to particles and antiparticles. For example, an antiproton and a positron can form an antihydrogen atom, which is believed to have the same properties as a hydrogen atom.
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The excited energy states resulting from these decays which fail to end in a ground energy state, also produce later internal conversion and gamma decay in almost 0.5% of the time. More common in heavy nuclides is competition between alpha and beta decay. The daughter nuclides will then normally decay through beta or alpha, respectively, to end up in the same place. Radioactive decay results in a reduction of summed rest mass, once the released energy (the disintegration energy) has escaped in some way.
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Either of those interactions will cause the ejection of an electron from an atom at relativistic speeds, turning that electron into a beta particle (secondary beta particle) that will ionize many other atoms. Since most of the affected atoms are ionized directly by the secondary beta particles, photons are called indirectly ionizing radiation. Photon radiation is called gamma rays if produced by a nuclear reaction, subatomic particle decay, or radioactive decay within the nucleus. It is otherwise called x-rays if produced outside the nucleus.
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Instead, nuclides are studied within nuclear physics, which studies nucleons and their interactions by approximations and models, such as the nuclear shell model. These models can successfully explain nuclide properties, as for example, whether or not a particular nuclide undergoes radioactive decay. The proton and neutron are in a scheme of categories being at once fermions, hadrons and baryons. The proton carries a positive net charge and the neutron carries a zero net charge; the proton's mass is only about 0.13% less than the neutron's.
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Bar chart depicting the natural abundance of 32S, 33S, 34S, and 36S on Earth. Sulfur has 24 known isotopes, 4 of which are stable (meaning that they do not undergo radioactive decay). 32S, the common isotope of sulfur, makes up 95.0% of the natural sulfur on Earth. In the atomic symbol of 32S, the number 32 refers to the mass of each sulfur atom in Daltons, the result of the 16 protons and 16 neutrons of 1 Dalton each that make up the sulfur nucleus.
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After the water evaporates, an invisible base surge of small radioactive particles may persist. For subsurface land bursts, the surge is made up of small solid particles, but it still behaves like a fluid. A soil earth medium favors base surge formation in an underground burst. Although the base surge typically contains only about 10% of the total bomb debris in a subsurface burst, it can create larger radiation doses than fallout near the detonation, because it arrives sooner than fallout, before much radioactive decay has occurred.
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Riazuddin postulated that radioactive decay in K mesons have almost vanished when chiral symmetry is introduced. After the introduction, the symmetries break the Standard Model of particle physics, even when the contribution from penguin diagrams is included. From 1972, Riazuddin made pioneering research on neutrinos— an elusive particle postulated by Wolfgang Pauli in 1930. In 1972, Riazuddin and Fayyazuddin were the first to post mathematical frameworks of Current-algebra in neutrino scattering to determine the Scale invariance of Chiral symmetry breaking the Hamiltonian Quantum Mechanics.
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Radioisotope Thermoelectric Generators (RTEG or RTG) are solid-state devices which have no moving parts. They generate heat from the radioactive decay of elements such as plutonium, and have a typical lifespan of more than 30 years. In the future, atomic sources of energy for spacecraft will hopefully be lighter and last longer than they do currently. They could be particularly useful for missions to the Outer Solar System which receives substantially less sunlight, meaning that producing a substantial power output with solar panels would be impractical.
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The radioactive decay rate of particles varies greatly, dependent upon the nuclear properties of a particular isotope. Radioactive Plutonium-244 has a half-life of 80.8 million years, which indicates the time duration required for half of a given sample to decay, though very little plutonium-244 is produced in the nuclear fuel cycle and lower half-life materials have lower activity thus giving off less dangerous radiation.Smith, G. (2012). Nuclear roulette: The truth about the most dangerous energy source on earth, Chelsea Green Publishing, .
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Temperature models predict melting of the disseminated iron alloy while silicate rocks soften at the upper level. The heat source is radioactive decay. Liquid iron migrated downward to levels where cooler temperatures kept silicates solidified, forming an iron layer on top of an undifferentiated material core, and below the primordial mantle in which impact-induced convection flow develops. From this stage on, iron aggregations triggered by Rayleigh-Taylor instabilities migrated through the primordial core in a long-term process (hundreds of million of years).
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Its radioactive decay will strongly influence the long-term activity curve of the SNF around a million years. A comparison of the activity associated to U-233 for three different SNF types can be seen in the figure on the top right. The burnt fuels are thorium with reactor-grade plutonium (RGPu), thorium with weapons-grade plutonium (WGPu) and Mixed Oxide fuel (MOX, no thorium). For RGPu and WGPu, the initial amount of U-233 and its decay around a million years can be seen.
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Geothermal power is considered to be renewable because any projected heat extraction is small compared to the Earth's heat content. The Earth has an internal heat content of 1031 joules (3·1015 TWh), approximately 100 billion times the 2010 worldwide annual energy consumption. About 20% of this is residual heat from planetary accretion; the remainder is attributed to higher radioactive decay rates that existed in the past. Natural heat flows are not in equilibrium, and the planet is slowly cooling down on geologic timescales.
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The feat was popularly known as "splitting the atom", but was not nuclear fission; as it was not the result of initiating an internal radioactive decay process. Just a few weeks before Cockcroft and Walton's feat, another scientist at the Cavendish Laboratory, James Chadwick, discovered the neutron, using an ingenious device made with sealing wax, through the reaction of beryllium with alpha particles:Chadwick announced his initial findings in: Subsequently he communicated his findings in more detail in: ; and : + → + n Irène Curie and Frédéric Joliot irradiated aluminium foil with alpha particles, they found that this results in a short-lived radioactive isotope of phosphorus with a half-life of around three minutes: : + → + n which then decays to a stable isotope of silicon : → + e+ They noted that radioactivity continued after the neutron emissions ceased. Not only had they discovered a new form of radioactive decay in the form of positron emission, they had transmuted an element into a hitherto unknown radioactive isotope of another, thereby inducing radioactivity where there had been none before. Radiochemistry was now no longer confined to certain heavy elements, but extended to the entire periodic table.
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Al Ghiorso at the University of California, Berkeley speculated that the filters might also contain atoms that had transformed, through radioactive decay, into the predicted but undiscovered elements 99 and 100. Ghiorso, Stanley Gerald Thompson and Glenn Seaborg obtained half a filter paper from the Ivy Mike test. They were able to detect the existence of the elements einsteinium and fermium, which had been produced by intensely concentrated neutron flux about the detonation site. The discovery was kept secret for several years, but the team was eventually given credit.
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A series of related techniques for determining the age at which a geomorphic surface was created (exposure dating), or at which formerly surficial materials were buried (burial dating). Exposure dating uses the concentration of exotic nuclides (e.g. 10Be, 26Al, 36Cl) produced by cosmic rays interacting with Earth materials as a proxy for the age at which a surface, such as an alluvial fan, was created. Burial dating uses the differential radioactive decay of 2 cosmogenic elements as a proxy for the age at which a sediment was screened by burial from further cosmic rays exposure.
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A modern reactor has many safety systems that are designed with a defence in depth philosophy, which is a design philosophy that is integrated throughout construction and commissioning. A BWR is similar to a pressurized water reactor (PWR) in that the reactor will continue to produce heat even after the fission reactions have stopped, which could make a core damage incident possible. This heat is produced by the radioactive decay of fission products and materials that have been activated by neutron absorption. BWRs contain multiple safety systems for cooling the core after emergency shut down.
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The KIWI A prime nuclear thermal rocket engine Curiosity rover powered by a RTG on Mars Nuclear power in space is the use of nuclear power in outer space, typically either small fission systems or radioactive decay for electricity or heat. Another use is for scientific observation, as in a Mössbauer spectrometer. The most common type is a radioisotope thermoelectric generator, which has been used on many space probes and on crewed lunar missions. Small fission reactors for Earth observation satellites, such as the TOPAZ nuclear reactor, have also been flown.
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In 1929, Rossi's first graduate student, Giuseppe Occhialini, was awarded the doctoral degree. In search of pioneering research, Rossi turned his attention to cosmic rays, which had been discovered by Victor Hess in manned balloon flights in 1911 and 1912. In 1929, Rossi read the paper of Walther Bothe and Werner Kolhörster, which described their discovery of charged cosmic ray particles that penetrated of gold. This was astonishing, for the most penetrating charged particles known at the time were electrons from radioactive decay, which could penetrate less than a millimetre of gold.
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Tc-99m's half-life of 6.0058 hours is considerably longer (by 14 orders of magnitude, at least) than most nuclear isomers, though not unique. This is still a short half-life relative to many other known modes of radioactive decay and it is in the middle of the range of half lives for radiopharmaceuticals used for medical imaging. After gamma emission or internal conversion, the resulting ground-state technetium-99 then decays with a half-life of 211,000 years to stable ruthenium-99. This process emits soft beta radiation without a gamma.
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Gmelin Handbook of Inorganic Chemistry, System No. 71, Volume 7a, transuranics, Part A2, p. 289 Therefore, curium can be used in its common oxide form in radioisotope thermoelectric generators like those in spacecraft. This application has been studied for the 244Cm isotope, while 242Cm was abandoned due to its prohibitive price of around 2000 USD/g. 243Cm with a ~30 year half-life and good energy yield of ~1.6 W/g could make a suitable fuel, but it produces significant amounts of harmful gamma and beta radiation from radioactive decay products.
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The shortest-lived isotope of lithium is 4Li, which decays through proton emission and has a half-life of 7.6 × 10−23 s. 7Li is one of the primordial elements (or, more properly, primordial nuclides) produced in Big Bang nucleosynthesis. A small amount of both 6Li and 7Li are produced in stars, but are thought to be "burned" as fast as produced. Additional small amounts of lithium of both 6Li and 7Li may be generated from solar wind, cosmic rays hitting heavier atoms, and from early solar system 7Be and 10Be radioactive decay.
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As radon decays, it produces radioactive decay products. If the contaminated dust of these "radon daughters" are inhaled, they can lodge in the lungs and increase the risk of developing lung cancer. Iodine in food is absorbed by the body and preferentially concentrated in the thyroid where it is needed for the functioning of that gland. When Iodine-131 is present in high levels in the environment from hydraulic fracturing flowback and blowouts, it can be absorbed through contaminated food and water, and will also accumulate in the thyroid.
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After Chadwick discovered the neutron in 1932, Irène Curie and Frédéric Joliot irradiated aluminium foil with alpha particles, and found that this results in a short- lived radioactive isotope of phosphorus. They noted that positron emission continued after the neutron emissions ceased. Not only had they discovered a new form of radioactive decay, they had transmuted an element into a hitherto unknown radioactive isotope of another, thereby inducing radioactivity where there had been none before. Radiochemistry was now no longer confined to certain heavy elements, but extended to the entire periodic table.
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Palladium-107 is the second-longest lived (half-life of 6.5 million years) and least radioactive (decay energy only 33 keV, specific activity 5 Ci/g) of the 7 long-lived fission products. It undergoes pure beta decay (without gamma radiation) to 107Ag, which is stable. Its yield from thermal neutron fission of uranium-235 is 0.1629% per fission, only 1/4 that of iodine-129, and only 1/40 those of 99Tc, 93Zr, and 135Cs. Yield from 233U is slightly lower, but yield from 239Pu is much higher, 3.3%.
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Xenon-135 is a radioactive isotope of xenon, produced as a fission product of uranium. It has a half-life of about 9.2 hours and is the most powerful known neutron- absorbing nuclear poison (having a neutron absorption cross-section of 2 million barnsChart of the Nuclides 13th Edition). The overall yield of xenon-135 from fission is 6.3%, though most of this results from the radioactive decay of fission-produced tellurium-135 and iodine-135. Xe-135 exerts a significant effect on nuclear reactor operation (xenon pit).
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There are 37 known isotopes of iodine (53I) from 108I to 144I; all undergo radioactive decay except 127I, which is stable. Iodine is thus a monoisotopic element. Its longest-lived radioactive isotope, 129I, has a half-life of 15.7 million years, which is far too short for it to exist as a primordial nuclide. Cosmogenic sources of 129I produce very tiny quantities of it that are too small to affect atomic weight measurements; iodine is thus also a mononuclidic element—one that is found in nature only as a single nuclide.
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Most helium on Earth is a result of radioactive decay. Helium is found in large amounts in minerals of uranium and thorium, including uraninite and its varieties cleveite and pitchblende, carnotite and monazite (a group name; "monazite" usually refers to monazite-(Ce)), because they emit alpha particles (helium nuclei, He2+) to which electrons immediately combine as soon as the particle is stopped by the rock. In this way an estimated 3000 metric tons of helium are generated per year throughout the lithosphere. In the Earth's crust, the concentration of helium is 8 parts per billion.
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In March 2006, Nature published a special report that called into question the validity of the results of the Purdue experiments. The report quotes Brian Naranjo of the University of California, Los Angeles to the effect that neutron energy spectrum reported in the 2006 paper by Taleyarkhan, et al. was statistically inconsistent with neutrons produced by the proposed fusion reaction and instead highly consistent with neutrons produced by the radioactive decay of Californium 252, an isotope commonly used as a laboratory neutron source . The response of Taleyarkhan et al.
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Some calculations indicate that cryovolcanism, which is considered one of the possible renewal mechanisms, may indeed be possible for trans-Neptunian objects larger than about . Orcus may have experienced at least one such episode in the past, which turned the amorphous water ice on its surface into crystalline. The preferred type of volcanism may have been explosive aqueous volcanism driven by an explosive dissolution of methane from water–ammonia melts. Models of internal heating via radioactive decay suggest that Orcus may be capable of sustaining an internal ocean of liquid water.
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From 1922 to 1925 he was a research student at the Cavendish Laboratory (in Lord Rutherford's group). He was Chief Physics Master at Repton School from 1926 until 1939, when Dr Fisher, later Archbishop of Canterbury, was headmaster. While at Repton he was awarded a doctorate from the University of London for a thesis in radioactive decay (the measurement of the half-period of Radium C). In 1939, he was appointed headmaster of King Edward VII School, Sheffield (photo). From 1950 to 1965 he was headmaster of the City of London School.
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Another major mode of heat loss is by conduction through the lithosphere, the majority of which occurs in the oceans due to the crust there being much thinner and younger than under the continents. The heat of Earth is replenished by radioactive decay at a rate of 30 TW. The global geothermal flow rates are more than twice the rate of human energy consumption from all primary sources. Global data on heat-flow density are collected and compiled by the International Heat Flow Commission (IHFC) of the IASPEI/IUGG. www.ihfc- iugg.
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Because they are identical to helium nuclei, they are also sometimes written as or indicating a helium ion with a +2 charge (missing its two electrons). If the ion gains electrons from its environment, the alpha particle becomes a normal (electrically neutral) helium atom . Alpha particles, like helium nuclei, have a net spin of zero. Due to the mechanism of their production in standard alpha radioactive decay, alpha particles generally have a kinetic energy of about 5 MeV, and a velocity in the vicinity of 4% the speed of light.
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After this discovery, J.J. Thomson's "plum pudding" model was abandoned, and Rutherford's experiment led to the Bohr model and later the modern wave-mechanical model of the atom. Energy-loss (Bragg curve) in air for typical alpha particle emitted through radioactive decay. The trace of a single alpha particle obtained by nuclear physicist Wolfhart Willimczik with his spark chamber specially made for alpha particles. In 1917, Rutherford went on to use alpha particles to accidentally produce what he later understood as a directed nuclear transmutation of one element to another.
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From an historical view, his major works in the field of atmospheric electricity should be mentioned. Schweidler's scientific work was recognized very early (1907) with the award of "Baumgartner Prize" of the Vienna Academy of Sciences for the study of the anomalies in the behavior of dielectrics. He pointed (in 1899) with Stefan Meyer, among others, the statistical nature of the radioactive decay or the magnetic deflection of beta radiation as fast electrons. His predicted variations (1905) of the ionization radiation formed in the end a large number of theoretical and experimental investigations.
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Diagram of a radioisotope heater unit Radioisotope heater units (RHU) are small devices that provide heat through radioactive decay. They are similar to tiny radioisotope thermoelectric generators (RTG) and normally provide about one watt of heat each, derived from the decay of a few grams of plutonium-238—although other radioactive isotopes could be used. The heat produced by these RHUs is given off continuously for several decades and, theoretically, for up to a century or more. In spacecraft, RHUs are necessary to heat critical components and subsystems.
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Click on image to enlarge. A nuclear reactor is a thermal power system—it generates heat, transports it and eventually converts it to mechanical energy in a heat engine, in this case a steam turbine. Such systems require that the heat is removed, transported and converted at the same rate it is generated. A fundamental issue for nuclear reactors is that even when the nuclear fission process is halted, heat continues to be generated at significant levels by the radioactive decay of the fission products for days and even months.
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The capture of alpha particles emitted during radioactive decay as helium atoms in the crystal lattice may also cause gradual long-term changes in its properties. The stoichiometry of the material dramatically influences its electrical properties. For example, the electrical conductivity of UO1.994 is orders of magnitude lower at higher temperatures than the conductivity of UO2.001. Uranium dioxide, like U3O8, is a ceramic material capable of withstanding high temperatures (about 2300 °C, in comparison with at most 200 °C for silicon or GaAs), making it suitable for high-temperature applications like thermophotovoltaic devices.
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The light atoms serve to slow down the neutrons by elastic scattering so they can then be absorbed by nuclear reactions. However, gamma radiation is often produced in such reactions, so additional shielding must be provided to absorb it. Care must be taken to avoid using nuclei that undergo fission or neutron capture that causes radioactive decay of nuclei, producing gamma rays. Neutrons readily pass through most material, and hence the absorbed dose (measured in Grays) from a given amount of radiation is low, but interact enough to cause biological damage.
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Helium production and storage in the United States, 1940–2014 (data from USGS) Almost all helium on Earth is a result of radioactive decay of uranium and thorium. Helium is extracted by fractional distillation from natural gas, which contains up to 7% helium. The world's largest helium-rich natural gas fields are found in the United States, especially in the Hugoton and nearby gas fields in Kansas, Oklahoma, and Texas. The extracted helium is stored underground in the National Helium Reserve near Amarillo, Texas, the self-proclaimed "Helium Capital of the World".
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Radon is formed as part of the normal radioactive decay chain of uranium into 206Pb. Uranium has been present since the earth was formed and its most common isotope has a very long half- life (4.5 billion years), which is the time required for one-half of uranium to break down. Thus, uranium and radon, will continue to occur for millions of years at about the same concentrations as they do now.Toxological profile for radon , Agency for Toxic Substances and Disease Registry, U.S. Public Health Service, In collaboration with U.S. Environmental Protection Agency, December 1990.
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For instance, it has been shown to accumulate in the air if there is a meteorological inversion and little wind. Because atmospheric radon concentrations are very low, radon-rich water exposed to air continually loses radon by volatilization. Hence, ground water generally has higher concentrations of 222Rn than surface water, because the radon is continuously produced by radioactive decay of 226Ra present in rocks. Likewise, the saturated zone of a soil frequently has a higher radon content than the unsaturated zone because of diffusional losses to the atmosphere.
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These particles as well as muons can be easily detected by many types of particle detectors, such as cloud chambers, bubble chambers, water-Cherenkov or scintillation detectors. The observation of a secondary shower of particles in multiple detectors at the same time is an indication that all of the particles came from that event. Cosmic rays impacting other planetary bodies in the Solar System are detected indirectly by observing high-energy gamma ray emissions by gamma-ray telescope. These are distinguished from radioactive decay processes by their higher energies above about 10 MeV.
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They have often quoted apparently inconsistent radiometric dates to cast doubt on the utility and accuracy of the method. Mainstream proponents who get involved in this debate point out that dating methods only rely on the assumptions that the physical laws governing radioactive decay have not been violated since the sample was formed (harking back to Lyell's doctrine of uniformitarianism). They also point out that the "problems" that creationists publicly mentioned can be shown to either not be problems at all, are issues with known contamination, or simply the result of incorrectly evaluating legitimate data.
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Rare Earth proponents argue that plate tectonics and a strong magnetic field are essential for biodiversity, global temperature regulation, and the carbon cycle. The lack of mountain chains elsewhere in the Solar System is direct evidence that Earth is the only body with plate tectonics, and thus the only nearby body capable of supporting life. Plate tectonics depend on the right chemical composition and a long- lasting source of heat from radioactive decay. Continents must be made of less dense felsic rocks that "float" on underlying denser mafic rock.
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Radioactivity, which had overthrown the old calculations, yielded a bonus by providing a basis for new calculations, in the form of radiometric dating. Ernest Rutherford in 1908 Ernest Rutherford and Frederick Soddy jointly had continued their work on radioactive materials and concluded that radioactivity was due to a spontaneous transmutation of atomic elements. In radioactive decay, an element breaks down into another, lighter element, releasing alpha, beta, or gamma radiation in the process. They also determined that a particular isotope of a radioactive element decays into another element at a distinctive rate.
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Neutron emission is a mode of radioactive decay in which one or more neutrons are ejected from a nucleus. It occurs in the most neutron-rich/proton- deficient nucleides, and also from excited states of other nucleides as in photoneutron emission and beta-delayed neutron emission. As only a neutron is lost by this process the number of protons remains unchanged, and an atom does not become an atom of a different element, but a different isotope of the same element. Neutrons are also produced in the spontaneous and induced fission of certain heavy nucleides.
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The importance of Harriet Brooks' contributions to physics became recognized in the 1980s as foundational work in the field of nuclear science. She was the first person to show that the radioactive substance emitted from thorium was a gas with molecular weight of 40-100, a discovery crucial to the determination that the elements undergo some transmutation in radioactive decay. Her research of radon and actinium was pioneering, and her brief research career was exceedingly accomplished. The Harriet Brooks Building, a nuclear research laboratory at Canadian Nuclear Laboratories was named for her.
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The Uranium Medical Research Centre (UMRC) is an independent non-profit organization founded in 1997 to provide objective and expert scientific and medical research into the effects of uranium, transuranium elements, and radionuclides produced by the process of radioactive decay and fission. UMRC is also a registered charity in the United States and Canada. The founder of UMRC, Asaf Durakovic, claimed on CNN CNN, broadcast 05/02/2007, American Morning special investigation by Greg Hunter: depleted uranium hidden health risks that: "Inhalation of uranium dust is harmful.... Even in the amount of one atom".
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The number of neutrons relative to the protons determines the stability of the nucleus, with certain isotopes undergoing radioactive decay. The proton, the electron, and the neutron are classified as fermions. Fermions obey the Pauli exclusion principle which prohibits identical fermions, such as multiple protons, from occupying the same quantum state at the same time. Thus, every proton in the nucleus must occupy a quantum state different from all other protons, and the same applies to all neutrons of the nucleus and to all electrons of the electron cloud.
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Visual representation of alpha decay Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atomic number that is reduced by two. An alpha particle is identical to the nucleus of a helium-4 atom, which consists of two protons and two neutrons. It has a charge of and a mass of . For example, uranium-238 decays to form thorium-234.
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Other natural energies exploited by human technology originate directly or indirectly with the Sun, including fossil fuel, conventional hydroelectric, wind, biofuel, wave and solar energy. Nuclear energy makes use of Earth's mineral deposits of fissionable elements, while geothermal power utilizes the Earth's internal heat, which comes from a combination of residual heat from planetary accretion (about 20%) and heat produced through radioactive decay (80%). A tidal generator converts the energy of tidal flows into electricity. Greater tidal variation and higher tidal current velocities can dramatically increase the potential of a site for tidal electricity generation.
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1250 Nuclear weapons tests have released at least six actinides heavier than plutonium into the environment; analysis of debris from a 1952 hydrogen bomb explosion showed the presence of americium, curium, berkelium, californium, einsteinium and fermium. All actinides are radioactive and release energy upon radioactive decay; naturally occurring uranium and thorium, and synthetically produced plutonium are the most abundant actinides on Earth. These are used in nuclear reactors and nuclear weapons. Uranium and thorium also have diverse current or historical uses, and americium is used in the ionization chambers of most modern smoke detectors.
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Non-divergent wind fields are produced by a procedure based on the variational principle and a finite-element discretization. The dispersion model, LODI, solves the 3-D advection-diffusion equation using a Lagrangian stochastic, Monte Carlo method.Ermak, D.L., and J.S. Nasstrom (2000), A Lagrangian Stochastic Diffusion Method for Inhomogeneous Turbulence, Atmospheric Environment, 34, 7, 1059-1068. LODI includes methods for simulating the processes of mean wind advection, turbulent diffusion, radioactive decay and production, bio-agent degradation, first-order chemical reactions, wet deposition, gravitational settling, dry deposition, and buoyant/momentum plume rise.
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Klein is credited for inventing the idea, part of Kaluza–Klein theory, that extra dimensions may be physically real but curled up and very small, an idea essential to string theory / M-theory. In 1938, he proposed a boson-exchange model for charge-charging weak interactions (radioactive decay), a few years after a similar proposal by Hideki Yukawa. His model was based on a local isotropic gauge symmetry and anticipated the later successful theory of Yang-Mills. The Oskar Klein Memorial Lecture, held annually at the University of Stockholm, has been named after him.
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While experimenting with the products of radioactive decay, in 1913 radiochemist Frederick Soddy discovered that there appeared to be more than one element at each position on the periodic table. The term isotope was coined by Margaret Todd as a suitable name for these elements. That same year, J. J. Thomson conducted an experiment in which he channeled a stream of neon ions through magnetic and electric fields, striking a photographic plate at the other end. He observed two glowing patches on the plate, which suggested two different deflection trajectories.
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Radioactive decay and nuclear particle reactions are two examples of such aggregate processes. The mathematics of Poisson processes reduce to the law of exponential decay, which describes the statistical behaviour of a large number of nuclei, rather than one individual nucleus. In the following formalism, the number of nuclei or the nuclei population N, is of course a discrete variable (a natural number)—but for any physical sample N is so large that it can be treated as a continuous variable. Differential calculus is used to model the behaviour of nuclear decay.
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For example, carbon-14, a radioactive nuclide with a half-life of only 5,730 years, is constantly produced in Earth's upper atmosphere due to interactions between cosmic rays and nitrogen. Nuclides that are produced by radioactive decay are called radiogenic nuclides, whether they themselves are stable or not. There exist stable radiogenic nuclides that were formed from short-lived extinct radionuclides in the early solar system. The extra presence of these stable radiogenic nuclides (such as xenon-129 from extinct iodine-129) against the background of primordial stable nuclides can be inferred by various means.
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Albert Stevens (1887–1966), also known as patient CAL-1, was a victim of a human radiation experiment, and survived the highest known accumulated radiation dose in any human. On May 14, 1945, he was injected with 131 kBq (3.55 µCi) of plutonium without his knowledge or informed consent. Plutonium remained present in his body for the remainder of his life, the amount decaying slowly through radioactive decay and biological elimination. Stevens died of heart disease some 20 years later, having accumulated an effective radiation dose of 64 Sv (6400 rem) over that period, i.e.
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Several heavy elements, such as uranium, thorium, and plutonium, undergo both spontaneous fission, a form of radioactive decay and induced fission, a form of nuclear reaction. Elemental isotopes that undergo induced fission when struck by a free neutron are called fissionable; isotopes that undergo fission when struck by a slow-moving thermal neutron are also called fissile. A few particularly fissile and readily obtainable isotopes (notably 233U, 235U and 239Pu) are called nuclear fuels because they can sustain a chain reaction and can be obtained in large enough quantities to be useful.
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The rate of fission reactions within a reactor core can be adjusted by controlling the quantity of neutrons that are able to induce further fission events. Nuclear reactors typically employ several methods of neutron control to adjust the reactor's power output. Some of these methods arise naturally from the physics of radioactive decay and are simply accounted for during the reactor's operation, while others are mechanisms engineered into the reactor design for a distinct purpose. The fastest method for adjusting levels of fission-inducing neutrons in a reactor is via movement of the control rods.
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The physics of radioactive decay also affects neutron populations in a reactor. One such process is delayed neutron emission by a number of neutron-rich fission isotopes. These delayed neutrons account for about 0.65% of the total neutrons produced in fission, with the remainder (termed "prompt neutrons") released immediately upon fission. The fission products which produce delayed neutrons have half-lives for their decay by neutron emission that range from milliseconds to as long as several minutes, and so considerable time is required to determine exactly when a reactor reaches the critical point.
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As seen from Earth, Betelgeuse as a type IIP supernova would have a peak apparent magnitude somewhere in the range −8 to −12. This would be easily visible in daylight, with a possible brightness up to a significant fraction of the full moon, though likely not exceeding it. This type of supernova would remain at roughly constant brightness for 2–3 months before rapidly dimming. The visible light is produced mainly by the radioactive decay of cobalt, and maintains its brightness due to the increasing transparency of the cooling hydrogen ejected by the supernova.
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Measuring is now most commonly done with an accelerator mass spectrometer For decades after Libby performed the first radiocarbon dating experiments, the only way to measure the in a sample was to detect the radioactive decay of individual carbon atoms. In this approach, what is measured is the activity, in number of decay events per unit mass per time period, of the sample. This method is also known as "beta counting", because it is the beta particles emitted by the decaying atoms that are detected.Walker (2005), p. 20.
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One of many power plants at The Geysers, a geothermal power field in northern California, with a total output of over 750 MW. Geothermal energy is produced by tapping into the thermal energy created and stored within the earth. It arises from the radioactive decay of an isotope of potassium and other elements found in the Earth's crust. Geothermal energy can be obtained by drilling into the ground, very similar to oil exploration, and then it is carried by a heat-transfer fluid (e.g. water, brine or steam).
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Nucleogenic isotopes, as noted, are the result of a more complicated nuclear reaction, although such reactions may begin with a radioactive decay event. Alpha particles that produce nucleogenic reactions come from natural alpha particle emitters in uranium and thorium decay chains. Neutrons to produce nucleogenic nuclides may be produced by a number of processes, but due to the short half- life of free neutrons, all of these reactions occur on Earth. Among the most common are cosmic ray spallation production of neutrons from elements near the surface of the Earth.
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Argon has a radiogenic isotope 40Ar, which is produced from the radioactive decay of 40K. In contrast, 36Ar is primordial and was incorporated into the atmosphere during the formation of Mars. Observations indicate that Mars is enriched in 40Ar relative to 36Ar, which cannot be attributed to mass-selective loss processes. A possible explanation for the enrichment is that a significant amount of primordial atmosphere, including 36Ar, was lost by impact erosion in the early history of Mars, while 40Ar was emitted to the atmosphere after the impact.
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It is the only bacterium found in water samples obtained underground in the Mponeng gold mine in South Africa. Approximately four micrometres in length, it has survived for millions of years on chemical food sources that derive from the radioactive decay of minerals in the surrounding rock. This makes it one of the few known organisms that does not depend on sunlight for nourishment, and the only species known to be alone in its ecosystem. Ca. D. audaxviator has genes for extracting carbon from dissolved carbon dioxide and for nitrogen fixation.
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Nuclear magnetic resonance detects atoms with different gyromagnetic ratios. The radioactive decay can be detected through an ionization chamber or autoradiographs of gels. An example of the use of isotopic labeling is the study of phenol (C6H5OH) in water by replacing common hydrogen (protium) with deuterium (deuterium labeling). Upon adding phenol to deuterated water (water containing D2O in addition to the usual H2O), the substitution of deuterium for the hydrogen is observed in phenol's hydroxyl group (resulting in C6H5OD), indicating that phenol readily undergoes hydrogen-exchange reactions with water.
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Iron meteorites have been linked to M-type asteroids because both have similar spectral characteristics in the visible and near-infrared. Iron meteorites are thought to be the fragments of the cores of larger ancient asteroids that have been shattered by impacts. The heat released from the radioactive decay of the short-lived nuclides 26Al and 60Fe is considered as a plausible cause for the melting and differentiation of their parent bodies in the early Solar System. Melting produced from the heat of impacts is another cause of melting and differentiation.
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If these features are volcanic in origin, it is "'literally going to make geologists rewrite the textbooks about the moon'". According to the current scientific theories, the Moon's small size means that its mantle should have fully solidified by about 1 billion years ago, which is backed up by seismic data. This would prevent any further geological action by the Moon's interior. A recent (in geological terms) eruption would indicate that the Moon has cooled much more slowly than thought, possibly due to heat released from radioactive decay of radioisotopes in the Moon.
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Highly massive progenitors may also eject sufficient nickel to cause a SLSN simply from the radioactive decay. The resulting remnant would be a black hole since it is highly unlikely such a massive star could ever lose sufficient mass for its core not to exceed the limit for a neutron star. The existence of a massive companion brings many other possibilities. If Eta Carinae A was rapidly stripped of its outer layers, it might be a less massive WC- or WO-type star when core collapse was reached.
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A device that uses radioisotopes is capable of producing electricity for up to 30 years without interruption using a process called radioactive decay. Another similar device was developed by researchers from MIT, which uses butane as a fuel source. It has the size of a button and is estimated to operate three times longer than a similarly sized lithium-ion battery and has the advantage of recharging immediately upon refuelling. Thermo-photovoltaics, which is a technology developed in the 1960s, is capable of converting heat energy into electricity.
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Thermocouples can be connected in series to form a thermopile, where all the hot junctions are exposed to a higher temperature and all the cold junctions to a lower temperature. The output is the sum of the voltages across the individual junctions, giving larger voltage and power output. In a radioisotope thermoelectric generator, the radioactive decay of transuranic elements as a heat source has been used to power spacecraft on missions too far from the Sun to use solar power. Thermopiles heated by kerosene lamps were used to run batteryless radio receivers in isolated areas.
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Hafnium–tungsten dating is a geochronological radiometric dating method utilizing the radioactive decay system of hafnium-182 to tungsten-182. The half-life of the system is 8.9 ± 0.1 million years. Today hafnium-182 is an extinct radionuclide, but the hafnium-tungsten radioactive system is useful in studies of the early Solar system since hafnium is lithophilic while tungsten is moderately siderophilic, which allows the system to be used to date the differentiation of a planet's core. It is also useful in determining the formation times of the parent bodies of iron meteorites.
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Fenton's post-doctoral work at the University of Tasmania resulted in the development of a technique to age fish based on the radioactive decay of radium-226 to lead-210. This revolutionized the understanding of the age of the important fishery species, orange roughy. Her work revealed that this species is extremely slow-growing, not maturing until between 20 and 25 years of age, with significant implications for sustainable management of catch limits for the species. Fenton joined the Tasmanian Government in marine environmental management and policy development in 1996.
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As the 99Mo continuously decays to 99mTc, the 99mTc can be removed periodically (usually daily) by flushing a saline solution (0.15 M NaCl in water) through the alumina column: the more highly charged 99MoO42− is retained on the column, where it continues to undergo radioactive decay, while the medically useful radioisotope 99mTcO4− is eluted in the saline. The eluate from the column must be sterile and pyrogen free, so that the Tc drug can be used directly, usually within 12 hours of elution. In a few cases, sublimation or solvent extraction may be used.
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Ceres Ceres appears to be differentiated into a rocky core and icy mantle and may harbour a liquid-water ocean under its surface. Not enough is known of the larger trans-Neptunian objects to determine whether they are differentiated bodies capable of supporting oceans, although models of radioactive decay suggest that Pluto, Eris, Sedna, and Orcus have oceans beneath solid icy crusts approximately thick. In June 2020, astronomers reported evidence that the dwarf planet Pluto may have had a subsurface ocean, and consequently may have been habitable, when it was first formed.
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Uranium ore emits radon gas. The health effects of high exposure to radon are a particular problem in the mining of uranium; significant excess lung cancer deaths have been identified in epidemiological studies of uranium miners employed in the 1940s and 1950s. The first major studies with radon and health occurred in the context of uranium mining, first in the Joachimsthal region of Bohemia and then in the Southwestern United States during the early Cold War. Because radon is a product of the radioactive decay of uranium, underground uranium mines may have high concentrations of radon.
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Mercury is too small and hot for its gravity to retain any significant atmosphere over long periods of time; it does have a tenuous surface-bounded exosphere containing hydrogen, helium, oxygen, sodium, calcium, potassium and others at a surface pressure of less than approximately 0.5 nPa (0.005 picobars). This exosphere is not stable—atoms are continuously lost and replenished from a variety of sources. Hydrogen atoms and helium atoms probably come from the solar wind, diffusing into Mercury's magnetosphere before later escaping back into space. Radioactive decay of elements within Mercury's crust is another source of helium, as well as sodium and potassium.
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The secondary radiation is also attenuated by absorption in the atmosphere, as well as by radioactive decay in flight of some particles, such as muons. Particles entering from a direction far from the zenith are especially attenuated. The world's population receives an average of 0.4 millisieverts (mSv) of cosmic radiation annually (separate from other sources of radiation exposure like inhaled radon) due to atmospheric shielding. At 12 km altitude, above most of the atmosphere's protection, radiation as an annual rate rises to 20 mSv at the equator to 50–120 mSv at the poles, varying between solar maximum and minimum conditions.
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The idea behind parity symmetry was that the equations of particle physics are invariant under mirror inversion. This led to the prediction that the mirror image of a reaction (such as a chemical reaction or radioactive decay) occurs at the same rate as the original reaction. However, in 1956 a careful critical review of the existing experimental data by theoretical physicists Tsung-Dao Lee and Chen-Ning Yang revealed that while parity conservation had been verified in decays by the strong or electromagnetic interactions, it was untested in the weak interaction. They proposed several possible direct experimental tests.
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Chain reactions do not occur in RTGs. Heat is produced through spontaneous radioactive decay at a non-adjustable and steadily decreasing rate that depends only on the amount of fuel isotope and its half-life. In an RTG, heat generation cannot be varied with demand or shut off when not needed and it is not possible to save more energy for later by reducing the power consumption. Therefore, auxiliary power supplies (such as rechargeable batteries) may be needed to meet peak demand, and adequate cooling must be provided at all times including the pre-launch and early flight phases of a space mission.
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For example, the image on the right is a simulation of many identical atoms undergoing radioactive decay. Note that after one half-life there are not exactly one-half of the atoms remaining, only approximately, because of the random variation in the process. Nevertheless, when there are many identical atoms decaying (right boxes), the law of large numbers suggests that it is a very good approximation to say that half of the atoms remain after one half-life. Various simple exercises can demonstrate probabilistic decay, for example involving flipping coins or running a statistical computer program.
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The Kuiper belt objects Varuna and are also moderately red in the spectral class. Larger Kuiper belt objects are often much brighter because they are covered in more fresh ice and have a higher albedo, and thus they present a neutral color. A 2006 model of internal heating via radioactive decay suggested that, unlike 90482 Orcus, Quaoar may not be capable of sustaining an internal ocean of liquid water at the mantle–core boundary. The presence of methane and other volatiles on Quaoar's surface suggest that it may support a tenuous atmosphere produced from the sublimation of volatiles.
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At 38 K, the N2 vapor pressure would be 14 microbar (1.4 Pa or 0.000014 atm). Its deep red spectral slope is indicative of high concentrations of organic material on its surface, and its weak methane absorption bands indicate that methane on Sedna's surface is ancient, rather than freshly deposited. This means that Sedna is too cold for methane to evaporate from its surface and then fall back as snow, which happens on Triton and probably on Pluto. Models of internal heating via radioactive decay suggest that Sedna might be capable of supporting a subsurface ocean of liquid water.
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AECL intends to leave potentially active or contaminated equipment on site for some decades yet to allow for further radioactive decay. The site was commemorated by a historical plaque detailing the operational history and highlights of the station. However, for reasons of security and public safety, the plaque is set three kilometres west of the site at a highway lookout, and the site itself cannot be seen from the plaque's location. Another bronze plaque and monument commemorating NPD, formerly located on the NPD site, was relocated to the Schoolhouse Museum about three kilometers to the east of the site.
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If the reaction will sustain itself, it is said to be critical, and the mass of 235U required to produce the critical condition is said to be a critical mass. A critical chain reaction can be achieved at low concentrations of 235U if the neutrons from fission are moderated to lower their speed, since the probability for fission with slow neutrons is greater. A fission chain reaction produces intermediate mass fragments which are highly radioactive and produce further energy by their radioactive decay. Some of them produce neutrons, called delayed neutrons, which contribute to the fission chain reaction.
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Familiar examples of other such processes transforming energy from the Big Bang include nuclear decay, which releases energy that was originally "stored" in heavy isotopes, such as uranium and thorium. This energy was stored at the time of the nucleosynthesis of these elements. This process uses the gravitational potential energy released from the collapse of Type II supernovae to create these heavy elements before they are incorporated into star systems such as the Solar System and the Earth. The energy locked into uranium is released spontaneously during most types of radioactive decay, and can be suddenly released in nuclear fission bombs.
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Thermal efficiency is high since no energy conversion is needed, but capacity factors tend to be low (around 20%) since the heat is mostly needed in the winter. Geothermal energy originates from the heat retained within the Earth since the original formation of the planet, from radioactive decay of minerals, and from solar energy absorbed at the surface. Most high temperature geothermal heat is harvested in regions close to tectonic plate boundaries where volcanic activity rises close to the surface of the Earth. In these areas, ground and groundwater can be found with temperatures higher than the target temperature of the application.
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The APS was designed to make a global examination of gas release events and polonium distribution with a surface resolution of and a precision of 10%. The APS was designed to detect radon outgassing events on the surface of the Moon. The APS recorded alpha particle signatures of radioactive decay of radon gas and its byproduct product, polonium. These putative outgassing events, in which radon, nitrogen, and carbon dioxide are vented, are hypothesized to be the source of the tenuous lunar atmosphere, and may be the result of the low-level volcanic/tectonic activity on the Moon.
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During World War II, he initially worked on radar in Suffolk, then with Cecil Powell in Bristol on a project that attempted to use photographic methods to detect fast particles from radioactive decay. James Chadwick recruited him to a Cambridge University team working on a possible heavy water reactor. The team was part of the British Tube Alloys directorate which was merged into the American Manhattan Project, the successful effort to create a nuclear weapon. In January 1943 the Cambridge team including Nunn May transferred to the Montreal Laboratory which was building a reactor at Chalk River near Ottawa, Ontario, Canada.
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Stars will eventually exhaust their supply of hydrogen fuel and burn out. Close encounters between astronomical objects gravitationally fling planets from their star systems, and star systems from galaxies. Physicists expect that matter itself will eventually come under the influence of radioactive decay, as even the most stable materials break apart into subatomic particles. Current data suggest that the universe has a flat geometry (or very close to flat), and thus will not collapse in on itself after a finite time, and the infinite future allows for the occurrence of a number of massively improbable events, such as the formation of Boltzmann brains.
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Another abnormal way of radionuclides migration are weak zones of crystalline rocks. The researches of Center of Radio-ecological Studies of the National Academy of Sciences of Ukraine showed that crustal surface has unconsolidated zones characterized by increased electric productivity, as well as higher moisture and emanation capacity. As to Cesium-137, this nuclide demonstrates lower migration potential in Chernobyl soils and aquifers. Its mobility is hampered by such factors as: clay minerals which fixate radionuclides in rock, absorption and neutralization of isotopes through ion- exchange with other chemical components of water; partial neutralization by vegetation metabolic cycles; overall radioactive decay.
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By their chemical nature, rock minerals contain certain elements and not others; but in rocks containing radioactive isotopes, the process of radioactive decay generates exotic elements over time. By measuring the concentration of the stable end product of the decay, coupled with knowledge of the half life and initial concentration of the decaying element, the age of the rock can be calculated. Typical radioactive end products are argon from decay of potassium-40, and lead from decay of uranium and thorium. If the rock becomes molten, as happens in Earth's mantle, such nonradioactive end products typically escape or are redistributed.
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Such a reaction as mX(γ,γ')X where mX is one of the five candidates listed above, is only different because there are lower energy states for the product nuclide to enter after the reaction than there were at the start. Practical difficulties arise from the need to ensure safety from the spontaneous radioactive decay of nuclear isomers in quantities sufficient for experimentation. Lifetimes must be long enough that doses from the spontaneous decay from the targets always remain within safe limits. In 1988 Collins and coworkers reported the first excitation of IGE from a nuclear isomer.
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The number of protons and neutrons in the atomic nucleus can be modified, although this can require very high energies because of the strong force. Nuclear fusion occurs when multiple atomic particles join to form a heavier nucleus, such as through the energetic collision of two nuclei. For example, at the core of the Sun protons require energies of 3 to 10 keV to overcome their mutual repulsion—the coulomb barrier—and fuse together into a single nucleus. Nuclear fission is the opposite process, causing a nucleus to split into two smaller nuclei—usually through radioactive decay.
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118 chemical elements are known to exist. All elements to element 94 are found in nature, and the remainder of the discovered elements are artificially produced, with isotopes all known to be highly radioactive with relatively short half-lives (see below). The elements in this list are ordered according to the lifetime of their most stable isotope. Of these, three elements (bismuth, thorium, and uranium) are primordial because they have half-lives long enough to still be found on the Earth, while all the others are produced either by radioactive decay or are synthesized in laboratories and nuclear reactors.
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The emission of a gamma ray from an excited nucleus typically requires only 10−12 seconds. Gamma decay may also follow nuclear reactions such as neutron capture, nuclear fission, or nuclear fusion. Gamma decay is also a mode of relaxation of many excited states of atomic nuclei following other types of radioactive decay, such as beta decay, so long as these states possess the necessary component of nuclear spin. When high-energy gamma rays, electrons, or protons bombard materials, the excited atoms emit characteristic "secondary" gamma rays, which are products of the creation of excited nuclear states in the bombarded atoms.
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Byproduct material can also be discrete sources of radium-226 or discretes sources of accelerator-produced isotopes or naturally occurring isotopes that pose a threat greater or equal to a discrete source of radium-226. Radium is also a regulated nuclear material that is found in nature and produced by the radioactive decay of uranium. Radiums half-life is approximately 1,600 years. Different countries may use different terminology: in the United States of America, "nuclear material" most commonly refers to "special nuclear materials" (SNM), with the potential to be made into nuclear weapons as defined in the Atomic Energy Act of 1954.
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Thus, gamma rays are now usually distinguished by their origin: X-rays are emitted by definition by electrons outside the nucleus, while gamma rays are emitted by the nucleus. Exceptions to this convention occur in astronomy, where gamma decay is seen in the afterglow of certain supernovas, but radiation from high energy processes known to involve other radiation sources than radioactive decay is still classed as gamma radiation. The Moon as seen by the Compton Gamma Ray Observatory, in gamma rays of greater than 20 MeV. These are produced by cosmic ray bombardment of its surface.
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In 1950, she began research work at the Oak Ridge Institute of Nuclear Studies as a chemist and senior scientist in nuclear studies. During this period, she collaborated with Texas A&M; University on the geochronology of seabed sediments, dating core samples by estimating their radioactive decay. She retired from Oak Ridge in 1965 and then went to work at the University of Miami, teaching at the Institute of Marine Sciences where she worked for a decade. Rona retired for a second time in 1976 and returned to Tennessee in the late 1970s, publishing a book in 1978 on her radioactive tracer methods.
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The discovery of hydrocarbon lakes on Saturn's moon Titan has begun to call into question the carbon chauvinism that underpins CHZ concept. Liquid-water environments have been found to exist in the absence of atmospheric pressure, and at temperatures outside the CHZ temperature range. For example, Saturn's moons Titan and Enceladus and Jupiter's moons Europa and Ganymede, all of which are outside the habitable zone, may hold large volumes of liquid water in subsurface oceans. Outside the CHZ, tidal heating and radioactive decay are two possible heat sources that could contribute to the existence of liquid water.
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While actinium and the late actinides (from americium onwards) behave similarly to the lanthanides, the elements thorium, protactinium, and uranium are much more similar to transition metals in their chemistry, with neptunium and plutonium occupying an intermediate position. All actinides are radioactive and release energy upon radioactive decay; naturally occurring uranium and thorium, and synthetically produced plutonium are the most abundant actinides on Earth. These are used in nuclear reactors and nuclear weapons. Uranium and thorium also have diverse current or historical uses, and americium is used in the ionization chambers of most modern smoke detectors.
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However, whatever the probability is, it does not change along time. This is in marked contrast to complex objects which do show aging, such as automobiles and humans. These aging systems do have a chance of breakdown per unit of time that increases from the moment they begin their existence. Aggregate processes, like the radioactive decay of a lump of atoms, for which the single event probability of realization is very small but in which the number of time-slices is so large that there is nevertheless a reasonable rate of events, are modelled by the Poisson distribution, which is discrete.
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The radioactive decay modes of electron capture and internal conversion are known to be slightly sensitive to chemical and environmental effects that change the electronic structure of the atom, which in turn affects the presence of 1s and 2s electrons that participate in the decay process. A small number of mostly light nuclides are affected. For example, chemical bonds can affect the rate of electron capture to a small degree (in general, less than 1%) depending on the proximity of electrons to the nucleus. In 7Be, a difference of 0.9% has been observed between half-lives in metallic and insulating environments.
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For a neutron-initiated chain reaction to occur, there must be a critical mass of the relevant isotope present in a certain space under certain conditions. The conditions for the smallest critical mass require the conservation of the emitted neutrons and also their slowing or moderation so that there is a greater cross-section or probability of them initiating another fission. In two regions of Oklo, Gabon, Africa, natural nuclear fission reactors were active over 1.5 billion years ago. Measurements of natural neutrino emission have demonstrated that around half of the heat emanating from the Earth's core results from radioactive decay.
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The Multi-mission radioisotope thermoelectric generator (MMRTG), used in several space missions such as the Curiosity Mars rover Both fission and fusion appear promising for space propulsion applications, generating higher mission velocities with less reaction mass. This is due to the much higher energy density of nuclear reactions: some 7 orders of magnitude (10,000,000 times) more energetic than the chemical reactions which power the current generation of rockets. Radioactive decay has been used on a relatively small scale (few kW), mostly to power space missions and experiments by using radioisotope thermoelectric generators such as those developed at Idaho National Laboratory.
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It featured modular construction so it could be assembled from smaller parts, and the suggested power source was radioisotope batteries. An example of RTG use is the Cassini-Huygens spacecraft, with a radioisotope power system that produced several hundred watts of electrical power. It produces this amount of power continuously with a slow decline over decades, with some of the heat given off by radioactive decay going to the production of electricity and a larger amount radiated as waste. In 2017, the Park Brother's Concepts debuted their Mars Rover design, which featured a six-wheel design, enclosed cab, and a mobile laboratory concept.
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Protoplanets that have avoided collisions may become natural satellites of planets through a process of gravitational capture, or remain in belts of other objects to become either dwarf planets or small bodies. The energetic impacts of the smaller planetesimals (as well as radioactive decay) will heat up the growing planet, causing it to at least partially melt. The interior of the planet begins to differentiate by mass, developing a denser core. Smaller terrestrial planets lose most of their atmospheres because of this accretion, but the lost gases can be replaced by outgassing from the mantle and from the subsequent impact of comets.
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If, instead, this person focused their attempts on a single safe, and "remembered" their previous attempts to open it, they would be guaranteed to open the safe after, at most, 500 attempts (and, in fact, at onset would only expect to need 250 attempts, not 500). Real-life examples of memorylessness include the universal law of radioactive decay, which describes the time until a given radioactive particle decays, and the time until the discovery of a new Bitcoin block. An often used (theoretical) example of memorylessness in queueing theory is the time a storekeeper must wait before the arrival of the next customer.
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Natural radon concentrations in the Earth's atmosphere are so low that radon- rich water in contact with the atmosphere will continually lose radon by volatilization. Hence, ground water has a higher concentration of 222Rn than surface water, because radon is continuously produced by radioactive decay of 226Ra present in rocks. Likewise, the saturated zone of a soil frequently has a higher radon content than the unsaturated zone because of diffusional losses to the atmosphere. In 1971, Apollo 15 passed above the Aristarchus plateau on the Moon, and detected a significant rise in alpha particles thought to be caused by the decay of 222Rn.
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Such duration of luminosity would not be possible without heating by internal radioactive decay, which is provided by r-process nuclei near their waiting points. Two distinct mass regions ( and ) for the r-process yields have been known since the first time dependent calculations of the r-process. Because of these spectroscopic features it has been argued that such nucleosynthesis in the Milky Way has been primarily ejecta from neutron-star mergers rather than from supernovae. These results offer a new possibility for clarifying six decades of uncertainty over the site of origin of r-process nuclei.
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The process is slow (hence the name) in the sense that there is sufficient time for this radioactive decay to occur before another neutron is captured. A series of these reactions produces stable isotopes by moving along the valley of beta-decay stable isobars in the table of nuclides. A range of elements and isotopes can be produced by the s-process, because of the intervention of alpha decay steps along the reaction chain. The relative abundances of elements and isotopes produced depends on the source of the neutrons and how their flux changes over time.
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The base surge is a cloud that rolls outward from the bottom of the subsiding column, which is caused by an excessive density of dust or water droplets in the air. This surge is made up of small solid particles, but it still behaves like a fluid. A soil earth medium favors base surge formation in an underground burst. Although the base surge typically contains only about 10% of the total bomb debris in a subsurface burst, it can create larger radiation doses than fallout near the detonation, because it arrives sooner than fallout, before much radioactive decay has occurred.
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If impurities are present or if physical conditions are created that prevent the establishment of a chemical equilibrium, the net production of hydrogen can be greatly enhanced. Another approach uses radioactive waste as an energy source for regeneration of spent fuel by converting sodium borate into sodium borohydride. By applying the proper combination of controls, stable borohydride compounds may be produced and used as hydrogen fuel storage medium. A study conducted in 1976 found an order-of- magnitude estimate can be made of the average hydrogen production rate that could be obtained by utilizing the energy liberated via radioactive decay.
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Swiss Military Watch Commander model with tritium- illuminated face The beta particles emitted by the radioactive decay of small amounts of tritium cause chemicals called phosphors to glow. This radioluminescence is used in self-powered lighting devices called betalights, which are used for night illumination of firearm sights, watches, exit signs, map lights, navigational compasses (such as current-use M-1950 U.S. military compasses), knives and a variety of other devices. Tritium has replaced radioluminescent paint containing radium in this application. The latter can cause bone cancer and has been banned in most countries for decades.
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Chang T M; Poznansky M J Journal of biomedical materials research (1968), 2(2), 187–99. Retrieved on December 11, 2008 While chair of physics at McGill, nuclear physicist Ernest Rutherford performed the experiment that led to the discovery of the alpha particle and its function in radioactive decay, which won him the Nobel Prize in Chemistry in 1908. Alumnus Jack W. Szostak was awarded the 2009 Nobel Prize in medicine for discovering a key mechanism in the genetic operations of cells, an insight that has inspired new lines of research into cancer. William Chalmers invented Plexiglas while a graduate student at McGill.
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Dzhelepov, Alikhanov and Alikhanian) was among the pioneers observing the phenomenon of radioactive decay. A method of determining the rest mass of the neutrino, using decay of the nuclei of Be7, was suggested by Alikhanov and Alikhanian in 1938. For their investigations both brothers (without being Communist party members) were awarded the USSR State Prize. In 1942 they initiated a scientific mission on Mt. Aragats in order to search for the third (proton) component of cosmic rays.Cosmic Ray Research in Armenia, by A. Chilingarian, R. Mirzoyan, M. Zazyan, Journal of Contemporary Physics, 2009, Vol. 44, No. 5, pp.
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Further research in atomic physics was interrupted by the outbreak of World War I. Moseley was killed in 1915 at the Battle of Gallipoli, while Rutherford's student James Chadwick was interned in Germany for the duration of the war, 1914-1918. In Berlin, Lise Meitner's and Otto Hahn's research work on determining the radioactive decay chains of radium and uranium by precise chemical separation was interrupted. Meitner spent much of the war working as a radiologist and medical X-ray technician near the Austrian front, while Hahn, a chemist, worked on research in poison gas warfare.
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Taylor has made contributions to quantum field theory and the physics of elementary particles. His contributions include: the discovery (also made independently by Lev Landau) of singularities in the analytical structure of the Feynman integrals for processes in quantum field theory, the PCAC nature of radioactive decay of the pion and the discovery in 1971 of the so-called Slavnov–Taylor identities, which control symmetry and renormalisation of gauge theories. With various collaborators, in 1980 he discovered that real and virtual infrared divergences do not cancel in QCD as they do in QED. They also showed how these infrared divergences exponentiate.
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Illustrations of dog and human embryos, looking almost identical at 4 weeks then differing at 6 weeks, shown above a 6-week turtle embryo and 8 day hen embryo, presented by Haeckel in 1868 as convincing proof of evolution. The pictures of the earliest embryonic stages are now considered inaccurate. Creationists claim that evolution relies on certain types of evidence that do not give reliable information about the past. For example, it is argued that radiometric dating technique of evaluating a material's age based on the radioactive decay rates of certain isotopes generates inconsistent and thus unreliable results.
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Since radioactive decay follows the half- life rule, the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like iodine-129 will be much less intense than that of a short-lived isotope like iodine-131. The two tables show some of the major radioisotopes, their half-lives, and their radiation yield as a proportion of the yield of fission of uranium-235. The energy and the type of the ionizing radiation emitted by a radioactive substance are also important factors in determining its threat to humans.
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Alpha radiation consists of helium nuclei and is readily stopped by a sheet of paper. Beta radiation, consisting of electrons or positrons, is stopped by a thin aluminum plate, but gamma radiation requires shielding by dense material such as lead, or concrete. A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay. There are two forms of beta decay, β− decay and β+ decay, which produce electrons and positrons respectively.
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Since water is highly soluble in magma, a large fraction of the planet's water content will initially be trapped in the mantle. As the planet cools and the mantle begins to solidify from the bottom up, large amounts of water (between 60% and 99% of the total amount in the mantle) are exsolved to form a steam atmosphere, which may eventually condense to form an ocean. Ocean formation requires differentiation, and a heat source, either radioactive decay, tidal heating, or the early luminosity of the parent body. Unfortunately, the initial conditions following accretion are theoretically incomplete.
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Cloud chambers played an important role as particle detectors in the early days of subatomic physics. Some particles including positron we even discovered by using this device By 1914, experiments by Ernest Rutherford, Henry Moseley, James Franck and Gustav Hertz had largely established the structure of an atom as a dense nucleus of positive charge surrounded by lower-mass electrons. These discoveries shed a light to the nature of radioactive decay and other forms of transmutation of elements, as well as of elements themselves. It appeared that atomic number is nothing else than (positive) electric charge of the atomic nucleus of a particular atom.
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In Doomsday Clock #3, the Alien Monster was seen in Reggie Long's nightmare. In the film, the Alien Monster was replaced with exploding energy reactors that generate a radioactive decay signature similar to Doctor Manhattan as a way to frame him for the retaliated attack in light of the cancer allegations against him. In the TV series, it is shown that "squidfalls", unexplained meteorological occurrences in which thousands of smaller alien monsters fall from the sky, occur around the world as late as 2019. These are revealed to be the continuing work of Adrian Veidt, believing them necessary to maintain fear of the "aliens" and thereby world peace.
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Transfers include the movement of a material within soil profile, and transformations are the change of composition and form of the materials within a soil. Soils can also be considered to be energy transformers in that they are physical structures of material that are modified by naturally occurring processes. The sun constitutes the primary energy source for soils, and significantly outweighs any heat generated by radioactive decay flowing up from deep within the Earth's crust. The deposition of sediment, or the addition of groundwater or rain, can also be considered an energy gain because new minerals and water can alter preexisting materials within the soil.
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It is now accepted that the plates carrying the continents do move across the Earth's surface, although not as fast as Wegener believed; ironically one of the chief outstanding questions is the one Wegener failed to resolve: what is the nature of the forces propelling the plates? The British geologist Arthur Holmes championed the theory of continental drift at a time when it was deeply unfashionable. He proposed in 1931 that the Earth's mantle contained convection cells which dissipated heat produced by radioactive decay and moved the crust at the surface. His Principles of Physical Geology, ending with a chapter on continental drift, was published in 1944.
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Some flashlights have slots for tritium vials so that the flashlight can be easily located in the dark. Tritium is used to illuminate the iron sights of some small arms. The reticle on the SA80's optical SUSAT sight as well as the LPS 4x6° TIP2 telescopic sight of a PSL rifle, contains a small amount of tritium for the same effect as an example of tritium use on a rifle sight. The electrons emitted by the radioactive decay of the tritium cause phosphor to glow, thus providing a long-lasting (several years) and non-battery-powered firearms sight that is visible in dim lighting conditions.
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In 1974, the TPG scientists engaged in the calculations for the implosion mechanism and completed the work on Fast neutron calculations. The work was submitted to the Office of Science and Technology (now known as Ministry of Science and Technology), and Abdus Salam review the work done by the TPG. Later, Abdus Salam led the work on simultaneity where the TPG finished the calculations on how weapon would be detonated from several points at same time. In 1977, the TPG scientists completed the theoretical work on the design of an atomic bomb. In 1978, the TPG took calculations on Neutron emission – a type of radioactive decay.
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This artist's impression video shows how two tiny but very dense neutron stars merge via gravitational wave radiation and then explode as a kilonova. Artist's impression of neutron stars merging, producing gravitational waves and resulting in a kilonova A kilonova (also called a macronova or r-process supernova) is a transient astronomical event that occurs in a compact binary system when two neutron stars or a neutron star and a black hole merge into each other. Kilonovae are thought to emit short gamma-ray bursts and strong electromagnetic radiation due to the radioactive decay of heavy r-process nuclei that are produced and ejected fairly isotropically during the merger process.
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Jacob Papish helped Hahn obtain several kilograms of the mineral. From 1,012 grams of the mineral, Strassmann and Ernst Walling extracted 253.4 milligrams of strontium carbonate, all of which was the strontium-87 isotope, indicating that it had all been produced from radioactive decay of rubidium-87. The age of the mineral had been estimated at 1,975 million years from uranium minerals in the same deposit, which implied that the half life of rubidium-87 was 2.3 x 1011 years: quite close to Hahn's original calculation. Rubidium–strontium dating became a widely used technique for dating rocks in the 1950s, when mass spectrometry became common.
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Neutrons may be emitted from nuclear fusion or nuclear fission, or from other nuclear reactions such as radioactive decay or particle interactions with cosmic rays or within particle accelerators. Large neutron sources are rare, and usually limited to large-sized devices such as nuclear reactors or particle accelerators, including the Spallation Neutron Source. Neutron radiation was discovered from observing an alpha particle colliding with a beryllium nucleus, which was transformed into a carbon nucleus while emitting a neutron, Be(α, n)C. The combination of an alpha particle emitter and an isotope with a large (α, n) nuclear reaction probability is still a common neutron source.
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Bertram Borden Boltwood (July 27, 1870 Amherst, Massachusetts – August 15, 1927, Hancock Point, Maine) was an American pioneer of radiochemistry. He graduated from Yale University, and taught there 1897-1900. He established that lead was the final decay product of uranium, noted that the lead-uranium ratio was greater in older rocks and, acting on a suggestion by Ernest Rutherford, was the first to measure the age of rocks by the decay of uranium to lead, in 1907. He got results of ages of 400 to 2200 million years, the first successful use of radioactive decay by Pb/U chemical dating (isotopes not discovered yet).
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In part because the reactor did not contain spent fuel, the fraction of biologically active isotopes was far smaller than in the case of the Chernobyl disaster. M. Takano et al. suggest that only 29 GBq of I-131 was released, but larger amounts (620 GBq of I-133 and 1840 GBq of I-135) of other isotopes. The same source suggests that the total release was about 259 PBq but due to radioactive decay this decreased to 43 TBq after 24 hours. The same source suggests that the fission yield was 5·1018 fissions which would deliver 156 MJ of heat into the reactor.
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Making the plasma from argon, instead of other gases, has several advantages. First, argon is abundant (in the atmosphere, as a result of the radioactive decay of potassium) and therefore cheaper than other noble gases. Argon also has a higher first ionization potential than all other elements except He, F, and Ne. Because of this high ionization energy, the reaction (Ar+ \+ e− → Ar) is more energetically favorable than the reaction (M+ \+ e− → M). This ensures that the sample remains ionized (as M+) so that the mass spectrometer can detect it. Argon can be purchased for use with the ICP-MS in either a refrigerated liquid or a gas form.
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Reactor 2 was shut down in October 1988, followed by Reactor 1 in March 1989. Berkeley was the first commercial Nuclear power station in the United Kingdom to be decommissioned following its closure in 1989. So far the nuclear decommissioning process has involved the removal of all fuel from the site in 1992, and the demolition of structures such as the turbine hall in 1995 and cooling ponds in 2001. The next step of decommissioning will be the care and maintenance stage of the nuclear reactor structures, scheduled to commence in 2026, until radioactive decay means that they can be demolished and the site completely cleared between 2070 and 2080.
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Boltwood was inspired to describe the relationships between elements in various decay series. Late in 1904, Rutherford took the first step toward radiometric dating by suggesting that the alpha particles released by radioactive decay could be trapped in a rocky material as helium atoms. At the time, Rutherford was only guessing at the relationship between alpha particles and helium atoms, but he would prove the connection four years later. Soddy and Sir William Ramsay had just determined the rate at which radium produces alpha particles, and Rutherford proposed that he could determine the age of a rock sample by measuring its concentration of helium.
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Positron emission or beta plus decay (β+ decay) is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino (νe). Positron emission is mediated by the weak force. The positron is a type of beta particle (β+), the other beta particle being the electron (β−) emitted from the β− decay of a nucleus. An example of positron emission (β+ decay) is shown with magnesium-23 decaying into sodium-23: : → + + Because positron emission decreases proton number relative to neutron number, positron decay happens typically in large "proton-rich" radionuclides.
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A nucleus that has a different number of protons than neutrons can potentially drop to a lower energy state through a radioactive decay that causes the number of protons and neutrons to more closely match. As a result, atoms with matching numbers of protons and neutrons are more stable against decay, but with increasing atomic number, the mutual repulsion of the protons requires an increasing proportion of neutrons to maintain the stability of the nucleus. Illustration of a nuclear fusion process that forms a deuterium nucleus, consisting of a proton and a neutron, from two protons. A positron (e+)—an antimatter electron—is emitted along with an electron neutrino.
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Nuclear potential energy is the potential energy of the particles inside an atomic nucleus. The nuclear particles are bound together by the strong nuclear force. Weak nuclear forces provide the potential energy for certain kinds of radioactive decay, such as beta decay. Nuclear particles like protons and neutrons are not destroyed in fission and fusion processes, but collections of them can have less mass than if they were individually free, in which case this mass difference can be liberated as heat and radiation in nuclear reactions (the heat and radiation have the missing mass, but it often escapes from the system, where it is not measured).
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This allows muons of a given energy to penetrate far deeper into matter because the deceleration of electrons and muons is primarily due to energy loss by the bremsstrahlung mechanism. For example, so- called "secondary muons", created by cosmic rays hitting the atmosphere, can penetrate the atmosphere and reach Earth's land surface and even into deep mines. Because muons have a greater mass and energy than the decay energy of radioactivity, they are not produced by radioactive decay. However they are produced in great amounts in high-energy interactions in normal matter, in certain particle accelerator experiments with hadrons, and in cosmic ray interactions with matter.
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The relative closeness of the supernova allowed astronomers to study it in much more detail than usual. Type Ia supernovae are especially important as standard candles in physical cosmology, and astronomers hope that SN 2014J will help them understand how these supernovae form and evolve. SN2014J was observed by the INTErnational Gamma- Ray Astrophysics Laboratory (INTEGRAL) which detected the gamma-ray spectral lines characteristic of the radioactive decay chain 56Ni→56Co→56Fe. This was the first time these lines were detected in a Type Ia supernova, providing support for the standard model that this class of supernova produces large quantities of 56Ni through nucleosynthesis.
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Nuclear power is any nuclear technology designed to extract usable energy from atomic nuclei via controlled nuclear reactions. The only controlled method now practical uses nuclear fission in a fissile fuel (with a small fraction of the power coming from subsequent radioactive decay). Use of the nuclear reaction nuclear fusion for controlled power generation is not yet practical, but is an active area of research. Nuclear power is usually used by using a nuclear reactor to heat a working fluid such as water, which is then used to create steam pressure, which is converted into mechanical work for the purpose of generating electricity or propulsion in water.
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The new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine (as had the discoveries of electricity and magnetism, earlier), and a number of patent medicines and treatments involving radioactivity were put forward. Gradually it was realized that the radiation produced by radioactive decay was ionizing radiation, and that even quantities too small to burn could pose a severe long-term hazard. Many of the scientists working on radioactivity died of cancer as a result of their exposure. Radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters.
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Miranda's surface may be mostly water ice, though it is far rockier than its corresponding satellites in the Saturn system, indicating that heat from radioactive decay may have led to internal differentiation, allowing silicate rock and organic compounds to settle in its interior. Miranda is too small for any internal heat to have been retained over the age of the Solar System. Miranda is the least spherical of Uranus's satellites, with an equatorial diameter 3% wider than its polar diameter. Only water has been detected so far on Miranda's surface, though it has been speculated that methane, ammonia, carbon monoxide or nitrogen may also exist at 3% concentrations.
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The melting and boiling points for a given noble gas are close together, differing by less than ; that is, they are liquids over only a small temperature range. Neon, argon, krypton, and xenon are obtained from air in an air separation unit using the methods of liquefaction of gases and fractional distillation. Helium is sourced from natural gas fields that have high concentrations of helium in the natural gas, using cryogenic gas separation techniques, and radon is usually isolated from the radioactive decay of dissolved radium, thorium, or uranium compounds. Noble gases have several important applications in industries such as lighting, welding, and space exploration.
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Abbot and Switzer (2011) put forward the possibility that subsurface water could exist on rogue planets as a result of radioactive decay-based heating and insulation by a thick surface layer of ice. With some theorising that life on Earth may have actually originated in stable, subsurface habitats, it has been suggested that it may be common for wet subsurface extraterrestrial habitats such as these to 'teem with life'. Indeed, on Earth itself living organisms may be found more than 6 kilometres below the surface. Another possibility is that outside the CHZ organisms may use alternative biochemistries that do not require water at all.
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This diagram illustrates the four decay chains discussed in the text: thorium (4n, in blue), neptunium (4n+1, in pink), radium (4n+2, in red) and actinium (4n+3, in green). The four most common modes of radioactive decay are: alpha decay, beta decay, inverse beta decay (considered as both positron emission and electron capture), and isomeric transition. Of these decay processes, only alpha decay changes the atomic mass number (A) of the nucleus, and always decreases it by four. Because of this, almost any decay will result in a nucleus whose atomic mass number has the same residue mod 4, dividing all nuclides into four chains.
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Cutaway diagram of the advanced Stirling radioisotope generator The advanced Stirling radioisotope generator (ASRG) was a radioisotope power system first developed at NASA's Glenn Research Center. It uses a Stirling power conversion technology to convert radioactive-decay heat into electricity for use on spacecraft. The energy conversion process used by an ASRG is about four times more efficient than in previous radioisotope systems to produce a similar amount of power, and allows it to use about one quarter of the plutonium-238 as other similar generators. Despite termination of the ASRG flight development contract in 2013, NASA continues a small investment testing by private companies.
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Potassium-Argon/Argon-Argon dating is applied in thermochronology in order to find the age of the minerals, such as apatite. Potassium-argon (K-Ar) dating is concerned with determining the amount of the product of radioactive decay of isotopic potassium (40K) into its decay product of isotopic argon (40Ar). Because the 40Ar is able to escape in liquids, such as molten rock, but accumulates when the rock solidifies, or recrystallizes, geologists are able to measure the time since recrystallization by looking at the ratio of the amount of 40Ar that has accumulated to the 40K remaining. The age can be found by knowing the half- life of potassium.
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Reticles may be illuminated, either by a plastic or fiber optic light pipe collecting ambient light or, in low light conditions, by a battery powered LED. Some sights also use the radioactive decay of tritium for illumination that can work for 11 years without using a battery, used in the British SUSAT sight for the SA80 (L85) assault rifle and in the American ACOG (Advanced Combat Optical Gunsight). Red is the most common color used, as it is the least destructive to the shooter's night vision, but some products use green or yellow illumination, either as a single colour or changeable via user selection.
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Such reactors can no longer form on Earth in its present geologic period. Radioactive decay of formerly more abundant uranium-235 over the time span of hundreds of millions of years has reduced the proportion of this naturally occurring fissile isotope to below the amount required to sustain a chain reaction with only plain water as a moderator. The natural nuclear reactors formed when a uranium-rich mineral deposit became inundated with groundwater that acted as a neutron moderator, and a strong chain reaction took place. The water moderator would boil away as the reaction increased, slowing it back down again and preventing a meltdown.
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The chirp mass, a directly observable parameter which may be very roughly equated to the geometric mean of the masses, is measured at . The neutron star merger event is thought to result in a kilonova, characterized by a short gamma-ray burst followed by a longer optical "afterglow" powered by the radioactive decay of heavy r-process nuclei. Kilonovae are candidates for the production of half the chemical elements heavier than iron in the Universe. A total of 16,000 times the mass of the Earth in heavy elements is believed to have formed, including approximately 10 Earth masses just of the two elements gold and platinum.
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The radioactive decay of 190Pt to 186Os has a half-life of 6.5(3)×1011 years (which is longer than the age of the universe, so it is essentially stable). However, in-situ 187Os / 188Os and 186Os / 188Os of modern plume related magmas show simultaneous enrichment which implies a source that is supra-chondritic in Pt/Os and Re/Os. Since both parental isotopes have extremely long half-lives, the Os-isotope rich reservoir must be very old to allow enough time for the daughter isotopes to form. These observations are interpreted to support the theory Archean subducted crust contributed Os-isotope rich melts back into the mantle.
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In about 10.72% of events, it decays to argon-40 (40Ar) by electron capture (EC), with the emission of a neutrino and then a 1.460 MeV gamma ray.This photon would be called an x-ray if emitted from an electron. In nuclear physics, it is common to name photons according to their origin rather than their energy, high energy photons produced by electrical transitions are called "x-rays" while those emitted from atomic nuclei are called "gamma rays" irrespective of their energy. The radioactive decay of this particular isotope explains the large abundance of argon (nearly 1%) in the Earth's atmosphere, as well as prevalence of 40Ar over other isotopes.
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Steam rising from the Nesjavellir Geothermal Power Station in Iceland At the end of 2019, global geothermal capacity was 14 GW. High temperature geothermal energy is from thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet and from radioactive decay of minerals (in currently uncertain but possibly roughly equal proportions). The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface.
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The r-process entails a succession of rapid neutron captures (hence the name) by one or more heavy seed nuclei, typically beginning with nuclei in the abundance peak centered on 56Fe. The captures must be rapid in the sense that the nuclei must not have time to undergo radioactive decay (typically via β− decay) before another neutron arrives to be captured. This sequence can continue up to the limit of stability of the increasingly neutron-rich nuclei (the neutron drip line) to physically retain neutrons as governed by the short range nuclear force. The r-process therefore must occur in locations where there exist a high density of free neutrons.
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For a maximum length sequence, where N = 2^k - 1, the duty cycle is 1/2. A PRBS is 'pseudorandom', because, although it is in fact deterministic, it seems to be random in a sense that the value of an a_j element is independent of the values of any of the other elements, similar to real random sequences. A PRBS can be stretched to infinity by repeating it after N elements, but it will then be cyclical and thus non- random. In contrast, truly random sequence sources, such as sequences generated by radioactive decay or by white noise, are infinite (no pre- determined end or cycle-period).
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The radioactive beta decay is due to the weak interaction, which transforms a neutron into a proton, an electron, and an electron antineutrino. In nuclear physics and particle physics, the weak interaction, which is also often called the weak force or weak nuclear force, is the mechanism of interaction between subatomic particles that is responsible for the radioactive decay of atoms. The weak interaction participates in nuclear fission, and the theory describing it in terms of both its behaviour and effects is sometimes called quantum flavourdynamics (QFD). However, the term QFD is rarely used, because the weak force is better understood in terms of electroweak theory (EWT).
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At the low doses of relevance to environmental radiation exposure, individual cells only rarely experience traversals by an ionizing particle and almost never experience more than one traversal. For example, in the case of domestic radon exposure, cancer risk estimation involves epidemiological studies of uranium miners. These miners inhale radon gas, which then undergoes radioactive decay, emitting an alpha particle This alpha particle traverses the cells of the bronchial epithelium, potentially causing cancer. The average lifetime radon exposure of these miners is high enough that cancer risk estimates are driven by data on individuals whose target bronchial cells are subjected to multiple alpha particle traversals.
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Definition of Weapons-Usable Uranium-233 ORNL/TM-13517 While U-233 would thus seem ideal for weaponization, a significant obstacle to that goal is the co-production of trace amounts of uranium-232 due to side-reactions. U-232 hazards, a result of its highly radioactive decay products such as thallium-208, are significant even at 5 parts per million. Implosion nuclear weapons require U-232 levels below 50 PPM (above which the U-233 is considered "low grade"; cf. "Standard weapon grade plutonium requires a Pu-240 content of no more than 6.5%." which is 65,000 PPM, and the analogous Pu-238 was produced in levels of 0.5% (5000 PPM) or less).
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Depending on which definition of "matter" is adopted, antimatter can be said to be a particular subclass of matter, or the opposite of matter. Antimatter is not found naturally on Earth, except very briefly and in vanishingly small quantities (as the result of radioactive decay, lightning or cosmic rays). This is because antimatter that came to exist on Earth outside the confines of a suitable physics laboratory would almost instantly meet the ordinary matter that Earth is made of, and be annihilated. Antiparticles and some stable antimatter (such as antihydrogen) can be made in tiny amounts, but not in enough quantity to do more than test a few of its theoretical properties.
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Its name derives from the fact that if a collection of random points in some space forms a Poisson process, then the number of points in a region of finite size is a random variable with a Poisson distribution. The process was discovered independently and repeatedly in several settings, including experiments on radioactive decay, telephone call arrivals and insurance mathematics. The Poisson point process is often defined on the real line, where it can be considered as a stochastic process. In this setting, it is used, for example, in queueing theory to model random events, such as the arrival of customers at a store, phone calls at an exchange or occurrence of earthquakes, distributed in time.
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These have modern equivalents such as kilohertz (kHz), megahertz (MHz), and gigahertz (GHz). Following the introduction of the SI standard, use of these terms began to fall off in favor of the new unit, with hertz becoming the dominant convention in both academic and colloquial speech by the 1970s. The rate at which aperiodic or stochastic events occur may be expressed in becquerels (as in the case of radioactive decay), not hertz, since although the two are mathematically similar, by convention hertz implies regularity where becquerels implies the requirement of a time averaging operation. Thus, one becquerel is one event per second on average, whereas one hertz is one event per second on a regular cycle.
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Electron capture is sometimes included as a type of beta decay, because the basic nuclear process, mediated by the weak force, is the same. In nuclear physics, beta decay is a type of radioactive decay in which a beta ray (fast energetic electron or positron) and a neutrino are emitted from an atomic nucleus. Electron capture is sometimes called inverse beta decay, though this term usually refers to the interaction of an electron antineutrino with a proton. If the energy difference between the parent atom and the daughter atom is less than 1.022 MeV, positron emission is forbidden as not enough decay energy is available to allow it, and thus electron capture is the sole decay mode.
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Barium had an atomic mass 40% less than uranium, and no previously known methods of radioactive decay could account for such a large difference in the mass of the nucleus. Nonetheless, she had immediately written back to Hahn to say: "At the moment the assumption of such a thoroughgoing breakup seems very difficult to me, but in nuclear physics we have experienced so many surprises, that one cannot unconditionally say: 'It is impossible.'" According to Frisch: Exhibition to mark the 75th anniversary of the discovery of nuclear fission, at the Vienna International Centre in 2013. The table (on loan from the Deutsches Museum Munich) is now described as a replica and images of Meitner and Strassmann are prominently displayed.
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Classical theory had also failed to explain successfully two other experimental results that appeared in the late 19th century. One of these was the demonstration by Albert A. Michelson and Edward W. Morley—known as the Michelson–Morley experiment—which showed there did not seem to be a preferred frame of reference, at rest with respect to the hypothetical luminiferous ether, for describing electromagnetic phenomena. Studies of radiation and radioactive decay continued to be a preeminent focus for physical and chemical research through the 1930s, when the discovery of nuclear fission by Lise Meitner and Otto Frisch opened the way to the practical exploitation of what came to be called "atomic" energy.
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For the isotopes with odd numbers of nucleons, this immediately rules out a stable isotope of technetium, since there can be only one stable nuclide with a fixed odd number of nucleons. For the isotopes with an even number of nucleons, since technetium has an odd number of protons, any isotope must also have an odd number of neutrons. In such a case, the presence of a stable nuclide having the same number of nucleons and an even number of protons rules out the possibility of a stable nucleus.Radiochemistry and Nuclear Chemistry The isotope technetium-97 decays only by electron capture, and could be inhibited from radioactive decay by fully ionizing it.
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All proxies included are useful in inferring the behavior of the meridional overturning circulation. For example, McManus et al. [2004] used protactinium/thorium isotopes (231Pa and 230Th) to show that the Atlantic Meridional Overturning Circulation had been nearly (or completely) shut off during the last glacial period. 231Pa and 230Th are both formed from the radioactive decay of dissolved uranium in seawater, with 231Pa able to remain supported in the water column longer than 230Th: 231Pa has a residence time ~100–200 years while 230Th has one ~20–40 years. In today's Atlantic Ocean and current overturning circulation, 230Th transport to the Southern Ocean is minimal due to its short residence time, and 231Pa transport is high.
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Terrestrial radiation, for the purpose of the table above, only includes sources that remain external to the body. The major radionuclides of concern are potassium, uranium and thorium and their decay products, some of which, like radium and radon are intensely radioactive but occur in low concentrations. Most of these sources have been decreasing, due to radioactive decay since the formation of the Earth, because there is no significant amount currently transported to the Earth. Thus, the present activity on earth from uranium-238 is only half as much as it originally was because of its 4.5 billion year half-life, and potassium-40 (half-life 1.25 billion years) is only at about 8% of original activity.
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Isotopes are different forms of elements; they have a different number of neutrons in the nucleus, meaning they have very similar chemical properties, but different mass. The weight difference means that some isotopes are discriminated against in chemical processes – for example, plants find it easier to incorporate the lighter 12C than heavy 13C. Other isotopes are only produced as a result of the radioactive decay of other elements, such as 87Sr, the daughter isotope of 87Rb. Rb, and therefore 87Sr, is common in the crust, so abundance of 87Sr in a sample of sediment (relative to 86Sr) is related to the amount of sediment which originated in the crust, as opposed to from the oceans.
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Three of these elements, bismuth (element 83), thorium (element 90), and uranium (element 92) have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy elements before the formation of the Solar System. For example, at over 1.9 years, over a billion times longer than the current estimated age of the universe, bismuth-209 has the longest known alpha decay half-life of any naturally occurring element. The very heaviest 24 elements (those beyond plutonium, element 94) undergo radioactive decay with short half-lives and cannot be produced as daughters of longer-lived elements, and thus are not known to occur in nature at all.
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The flooded generators failed, cutting power to the critical pumps that must continuously circulate coolant water through a Generation II nuclear reactor for several days in order to keep it from melting down after being shut down. As the pumps stopped, the reactors overheated due to the normal high radioactive decay heat produced in the first few days after nuclear reactor shutdown (smaller amounts of this heat normally continue to be released for years, but are not enough to cause fuel melting). At this point, only prompt flooding of the reactors with seawater could have cooled the reactors quickly enough to prevent meltdown. Salt water flooding was delayed because it would ruin the costly reactors permanently.
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The flooded generators failed, cutting power to the critical pumps that must continuously circulate coolant water through a nuclear reactor for several days in order to keep it from melting down after being shut down. As the pumps stopped, the reactors overheated due to the normal high radioactive decay heat produced in the first few days after nuclear reactor shutdown (smaller amounts of this heat normally continue to be released for years, but are not enough to cause fuel melting). At this point, only prompt flooding of the reactors with seawater could have cooled the reactors quickly enough to prevent meltdown. Salt water flooding was delayed because it would ruin the costly reactors permanently.
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In November 2011 TEPCO did not know the shape or porosity of the fuel mass, which is at the bottom of the containment vessel.TEPCO (30-11-2012)Handout 30 November 2011 As a result, it is impossible to know exactly how far the fuel mass would have eroded the concrete floor, but TEPCO estimate that no more than 70 cm of a 7.6 meter concrete slab was eroded away by the hot fuel. The production of heat and steam in unit 1 has decreased, as suggested by both radioactive decay calculations and photographic evidence (same source from TEPCO). TEPCO estimates the nuclear fuel was exposed to the air less than five hours after the earthquake struck.
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The major heat-producing isotopes in Earth are potassium-40, uranium-238, uranium-235, and thorium-232. At the center of the planet, the temperature may be up to and the pressure could reach 360 GPa (3.6 million atm). Because much of the heat is provided by radioactive decay, scientists believe that early in Earth history, before isotopes with short half-lives had been depleted, Earth's heat production would have been much higher. Heat production was twice that of present-day at approximately 3 billion years ago, resulting in larger temperature gradients within the Earth, larger rates of mantle convection and plate tectonics, allowing the production of igneous rocks such as komatiites that are no longer formed.
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In 1965–69, he was appointed as Vice-Chancellor of the University of Azad Kashmir, and later found employment with the Pakistani Ministry of Education as a consultant on education. He chaired the EducationUSA network in Pakistan through the Ministry of Education. In 1972, Hussain was delegated to provide consultation on the studies of mass–energy equivalence and radioactive decay by the Nuclear Physics Group studying under Dr. Ishfaq Ahmad, who was secretly working on the atomic bomb program. Throughout his career, Hussain remained on the teaching faculty at the Government College University, and wrote a college physics book, Fundamentals of Physics in 1970, which has been published in new editions since.
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George Gamow (March 4, 1904 – August 19, 1968), born Georgiy Antonovich Gamov, was a Soviet-American theoretical physicist and cosmologist. He was an early advocate and developer of Lemaître's Big Bang theory. He discovered a theoretical explanation of alpha decay by quantum tunneling, invented the liquid drop model and the first mathematical model of the atomic nucleus, and worked on radioactive decay, star formation, stellar nucleosynthesis and Big Bang nucleosynthesis (which he collectively called nucleocosmogenesis), and molecular genetics. In his middle and late career, Gamow directed much of his attention to teaching and wrote popular books on science, including One Two Three... Infinity and the Mr Tompkins series of books (1939–1967).
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Techniques include tree rings in timbers, radiocarbon dating of wood or bones, and trapped-charge dating methods such as thermoluminescence dating of glazed ceramics. Coins found in excavations may have their production date written on them, or there may be written records describing the coin and when it was used, allowing the site to be associated with a particular calendar year. In historical geology, the primary methods of absolute dating involve using the radioactive decay of elements trapped in rocks or minerals, including isotope systems from very young (radiocarbon dating with ) to systems such as uranium–lead dating that allow acquisition of absolute ages for some of the oldest rocks on Earth.
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Monju in 2007 On November 24, 2000, Japan Atomic Energy Agency announced their intention to restart the Monju reactor. This decision was met with resistance by the public, resulting in a series of court battles. On January 27, 2003, the Nagoya High Court's Kanazawa branch made a ruling reversing its earlier 1983 approval to build the reactor, but then on May 30, 2005, Japan's Supreme Court gave the green light to reopen the Monju reactor. The nuclear fuel was replaced for the restart. The original fuel loaded was mixed plutonium-uranium oxide with plutonium content of around 15–20%, but by 2009, due to natural radioactive decay, the fuel had only half of the original plutonium-241 content.
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Fanny Cook Gates (26 April 1872 – 24 February 1931) was an American physicist, an American Physical Society fellow and American Mathematical Society member. She made contributions to the research of radioactive materials, determining that radioactivity could not be destroyed by heat or ionization due to chemical reactions, and that radioactive materials differ from phosphorescent materials both qualitatively and quantitatively. More specifically, Gates showed that the emission of blue light from quinine was temperature dependent, providing evidence that the emitted light is produced from phosphorescence rather than radioactive decay. She also served as head of the Physics department at Goucher, Professor of Physics and Dean of Women at Grinnell College, and the Dean of Women at the University of Illinois.
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The potassium-argon method was utilized to determine the age of volcanism at Pilot Knob. This method is based upon the decay of the radioactive isotope of potassium (potassium 40) to argon 40, an isotope of argon, an inert gas. By knowing the concentration of potassium in a rock mineral and the amount of argon gas produced by radioactive decay trapped within the minerals, an age can be assigned to the rock because the decay rate of potassium 40 to argon 40 is known from experimental work. The age of Pilot Knob volcanism dated through the potassium-argon method is 79.5 +/- 3 million years, and agrees with the age derived by correlation with fossils to other radiometrically dated deposits.
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NASA guide to electromagnetic spectrum showing overlap of frequency between X-rays and gamma rays A gamma ray, or gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves and so imparts the highest photon energy. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays based on their relatively strong penetration of matter; in 1900 he had already named two less penetrating types of decay radiation (discovered by Henri Becquerel) alpha rays and beta rays in ascending order of penetrating power.
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The Nobel Prize in Chemistry 1908 was awarded to Ernest Rutherford "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances". In 1903, Rutherford considered a type of radiation discovered (but not named) by French chemist Paul Villard in 1900, as an emission from radium, and realised that this observation must represent something different from his own alpha and beta rays, due to its very much greater penetrating power. Rutherford therefore gave this third type of radiation the name of gamma ray. All three of Rutherford's terms are in standard use today – other types of radioactive decay have since been discovered, but Rutherford's three types are among the most common.
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Decay energy therefore remains associated with a certain measure of mass of the decay system, called invariant mass, which does not change during the decay, even though the energy of decay is distributed among decay particles. The energy of photons, the kinetic energy of emitted particles, and, later, the thermal energy of the surrounding matter, all contribute to the invariant mass of the system. Thus, while the sum of the rest masses of the particles is not conserved in radioactive decay, the system mass and system invariant mass (and also the system total energy) is conserved throughout any decay process. This is a restatement of the equivalent laws of conservation of energy and conservation of mass.
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The prompt neutron lifetime, l, is the average time between the emission of neutrons and either their absorption in the system or their escape from the system. The neutrons that occur directly from fission are called "prompt neutrons," and the ones that are a result of radioactive decay of fission fragments are called "delayed neutrons". The term lifetime is used because the emission of a neutron is often considered its "birth," and the subsequent absorption is considered its "death". For thermal (slow-neutron) fission reactors, the typical prompt neutron lifetime is on the order of 10−4 seconds, and for fast fission reactors, the prompt neutron lifetime is on the order of 10−7 seconds.
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A radioactive tracer, radiotracer, or radioactive label, is a chemical compound in which one or more atoms have been replaced by a radionuclide so by virtue of its radioactive decay it can be used to explore the mechanism of chemical reactions by tracing the path that the radioisotope follows from reactants to products. Radiolabeling or radiotracing is thus the radioactive form of isotopic labeling. Radioisotopes of hydrogen, carbon, phosphorus, sulfur, and iodine have been used extensively to trace the path of biochemical reactions. A radioactive tracer can also be used to track the distribution of a substance within a natural system such as a cell or tissue, or as a flow tracer to track fluid flow.
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The evolution of Earth's mantle radiogenic heat flow over time: contribution from 40K in yellow. The radioactive decay of 40K in the Earth's mantle ranks third, after 232Th and 238U, as the source of radiogenic heat. The core also likely contains radiogenic sources, although how much is uncertain. It has been proposed that significant core radioactivity (1–2 TW) may be caused by high levels of U, Th, and K. Potassium-40 is the largest source of natural radioactivity in animals including humans. A 70 kg human body contains about 140 grams of potassium, hence about 0.000117 × 140 = 0.0164 grams of 40K; whose decay produces about 4,300 disintegrations per second (becquerel) continuously throughout the life of the body.
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Radon concentration next to a uranium mine Radon is produced by the radioactive decay of radium-226, which is found in uranium ores, phosphate rock, shales, igneous and metamorphic rocks such as granite, gneiss, and schist, and to a lesser degree, in common rocks such as limestone. Every square mile of surface soil, to a depth of 6 inches (2.6 km2 to a depth of 15 cm), contains approximately 1 gram of radium, which releases radon in small amounts to the atmosphere. On a global scale, it is estimated that 2.4 billion curies (90 EBq) of radon are released from soil annually.Harley, J. H. in Radon concentration can differ widely from place to place.
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Radon is an invisible, radioactive atomic gas that results from the radioactive decay of radium, which may be found in rock formations beneath buildings or in certain building materials themselves. Radon is probably the most pervasive serious hazard for indoor air in the United States and Europe, and is probably responsible for tens of thousands of deaths from lung cancer each year. There are relatively simple test kits for do-it-yourself radon gas testing, but if a home is for sale the testing must be done by a licensed person in some U.S. states. Radon gas enters buildings as a soil gas and is a heavy gas and thus will tend to accumulate at the lowest level.
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Alpha decay is one type of radioactive decay, in which an atomic nucleus emits an alpha particle, and thereby transforms (or "decays") into an atom with a mass number decreased by 4 and atomic number decreased by 2. Nuclear chemistry is the sub-field of chemistry dealing with radioactivity, nuclear processes, and transformations in the nuclei of atoms, such as nuclear transmutation and nuclear properties. It is the chemistry of radioactive elements such as the actinides, radium and radon together with the chemistry associated with equipment (such as nuclear reactors) which are designed to perform nuclear processes. This includes the corrosion of surfaces and the behavior under conditions of both normal and abnormal operation (such as during an accident).
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Internal heat is the heat source from the interior of celestial objects, such as stars, brown dwarfs, planets, moons, dwarf planets, and (in the early history of the Solar System) even asteroids such as Vesta, resulting from contraction caused by gravity (the Kelvin–Helmholtz mechanism), nuclear fusion, tidal heating, core solidification (heat of fusion released as molten core material solidifies), and radioactive decay. The amount of internal heating depends on mass; the more massive the object, the more internal heat it has; also, for a given density, the more massive the object, the greater the ratio of mass to surface area, and thus the greater the retention of internal heat. The internal heating keeps celestial objects warm and active.
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The most troublesome transuranic elements in spent fuel are neptunium-237 (half-life two million years) and plutonium-239 (half-life 24,000 years). Consequently, high-level radioactive waste requires sophisticated treatment and management to successfully isolate it from the biosphere. This usually necessitates treatment, followed by a long-term management strategy involving permanent storage, disposal or transformation of the waste into a non-toxic form. Radioactive decay follows the half-life rule, which means that the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like iodine-129 will be much less intense than that of short-lived isotope like iodine-131.
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The earliest methods for generating random numbers, such as dice, coin flipping and roulette wheels, are still used today, mainly in games and gambling as they tend to be too slow for most applications in statistics and cryptography. A physical random number generator can be based on an essentially random atomic or subatomic physical phenomenon whose unpredictability can be traced to the laws of quantum mechanics. Sources of entropy include radioactive decay, thermal noise, shot noise, avalanche noise in Zener diodes, clock drift, the timing of actual movements of a hard disk read-write head, and radio noise. However, physical phenomena and tools used to measure them generally feature asymmetries and systematic biases that make their outcomes not uniformly random.
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Software rot, also known as bit rot, code rot, software erosion, software decay, or software entropy is either a slow deterioration of software quality over time or its diminishing responsiveness that will eventually lead to software becoming faulty, unusable, or in need of upgrade. This is not a physical phenomenon: the software does not actually decay, but rather suffers from a lack of being responsive and updated with respect to the changing environment in which it resides. The Jargon File, a compendium of hacker lore, defines "bit rot" as a jocular explanation for the degradation of a software program over time even if "nothing has changed"; the idea being this is almost as if the bits that make up the program were subject to radioactive decay.
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A paleoatmosphere (or palaeoatmosphere) is an atmosphere, particularly that of Earth, at some unspecified time in the geological past. The composition of Earth's paleoatmosphere can be inferred today from the study of the abundance of proxy materials such as iron oxides, charcoal and the stomatal density of fossil leaves in geological deposits. Although today's atmosphere is dominated by nitrogen (about 78%), oxygen (about 21%), and argon (about 1%), the pre- biological atmosphere is thought to have been a highly reducing atmosphere, having virtually no free oxygen, virtually no argon, which is generated by the radioactive decay of 40K, and to have been dominated by nitrogen, carbon dioxide and methane. Appreciable concentrations of free oxygen were probably not present until about 2,500 million years ago (Ma).
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One of the frequent uses of the technique is to date organic remains from archaeological sites. Plants fix atmospheric carbon during photosynthesis, so the level of 14C in plants and animals when they die approximately equals the level of 14C in the atmosphere at that time. However, it decreases thereafter from radioactive decay, allowing the date of death or fixation to be estimated. The initial 14C level for the calculation can either be estimated, or else directly compared with known year-by-year data from tree-ring data (dendrochronology) up to 10,000 years ago (using overlapping data from live and dead trees in a given area), or else from cave deposits (speleothems), back to about 45,000 years before the present.
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Its sources include outgassing and sputtering, a product of the bombardment of lunar soil by solar wind ions. Elements that have been detected include sodium and potassium, produced by sputtering (also found in the atmospheres of Mercury and Io); helium-4 and neon from the solar wind; and argon-40, radon-222, and polonium-210, outgassed after their creation by radioactive decay within the crust and mantle. The absence of such neutral species (atoms or molecules) as oxygen, nitrogen, carbon, hydrogen and magnesium, which are present in the regolith, is not understood. Water vapor has been detected by Chandrayaan-1 and found to vary with latitude, with a maximum at ~60–70 degrees; it is possibly generated from the sublimation of water ice in the regolith.
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A radioisotope heater unit is powered by radioactive decay and can keep components from becoming too cold to function, potentially over a span of decades. The United States tested the SNAP-10A nuclear reactor in space for 43 days in 1965, with the next test of a nuclear reactor power system intended for space use occurring on 13 September 2012 with the Demonstration Using Flattop Fission (DUFF) test of the Kilopower reactor. After a ground-based test of the experimental 1965 Romashka reactor, which used uranium and direct thermoelectric conversion to electricity, the USSR sent about 40 nuclear-electric satellites into space, mostly powered by the BES-5 reactor. The more powerful TOPAZ-II reactor produced 10 kilowatts of electricity.
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The most practical application of 244Cm—though rather limited in total volume—is as α-particle source in the alpha particle X-ray spectrometers (APXS). These instruments were installed on the Sojourner, Mars, Mars 96, Mars Exploration Rovers and Philae comet lander, as well as the Mars Science Laboratory to analyze the composition and structure of the rocks on the surface of planet Mars. APXS was also used in the Surveyor 5–7 moon probes but with a 242Cm source.Human Health Fact Sheet on Curium , Los Alamos National LaboratoryLeitenberger, Bernd Die Surveyor Raumsonden (in German) An elaborated APXS setup is equipped with a sensor head containing six curium sources having the total radioactive decay rate of several tens of millicuries (roughly a gigabecquerel).
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The alkaline earth metal strontium (38Sr) has four stable, naturally occurring isotopes: 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). Its standard atomic weight is 87.62(1). Only 87Sr is radiogenic; it is produced by decay from the radioactive alkali metal 87Rb, which has a half-life of 4.88 × 1010 years (i.e. more than three times longer than the current age of the universe). Thus, there are two sources of 87Sr in any material: primordial, formed during nucleosynthesis along with 84Sr, 86Sr and 88Sr; and that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic investigations; ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0 (see rubidium–strontium dating).
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The term "half-life" is almost exclusively used for decay processes that are exponential (such as radioactive decay or the other examples above), or approximately exponential (such as biological half-life discussed below). In a decay process that is not even close to exponential, the half-life will change dramatically while the decay is happening. In this situation it is generally uncommon to talk about half-life in the first place, but sometimes people will describe the decay in terms of its "first half-life", "second half-life", etc., where the first half-life is defined as the time required for decay from the initial value to 50%, the second half-life is from 50% to 25%, and so on.
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While Hahn was in North America, his attention was drawn to a mica-like mineral from Manitoba that contained rubidium. Some years before he had studied the radioactive decay of rubidium-87, and had estimated its half life at 2 x 1011 years. It occurred to Hahn that by comparing the quantity of strontium in the mineral (which had once been rubidium) with that of the remaining rubidium, he could measure the age of the mineral, assuming that his original calculation of the half life was reasonably accurate. This would be a superior dating method to studying the decay of uranium, because some of the uranium turns into helium, which then escapes, resulting in rocks appearing to be younger than they really were.
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Secular equilibrium can occur in a radioactive decay chain only if the half-life of the daughter radionuclide B is much shorter than the half- life of the parent radionuclide A. In such a case, the decay rate of A and hence the production rate of B is approximately constant, because the half- life of A is very long compared to the time scales considered. The quantity of radionuclide B builds up until the number of B atoms decaying per unit time becomes equal to the number being produced per unit time. The quantity of radionuclide B then reaches a constant, equilibrium value. Assuming the initial concentration of radionuclide B is zero, full equilibrium usually takes several half-lives of radionuclide B to establish.
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The r-process is responsible for our natural cohort of radioactive elements, such as uranium and thorium, as well as the most neutron-rich isotopes of each heavy element. The rp-process (rapid proton) involves the rapid absorption of free protons as well as neutrons, but its role and its existence are less certain. Explosive nucleosynthesis occurs too rapidly for radioactive decay to decrease the number of neutrons, so that many abundant isotopes with equal and even numbers of protons and neutrons are synthesized by the silicon quasi- equilibrium process. During this process, the burning of oxygen and silicon fuses nuclei that themselves have equal numbers of protons and neutrons to produce nuclides which consist of whole numbers of helium nuclei, up to 15 (representing 60Ni).
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George Wetherill (August 12, 1925 Philadelphia, PA – July 19, 2006 Washington, DC) was the Director Emeritus, Department of Terrestrial Magnetism, Carnegie Institution of Washington, DC, USA. George Wetherill benefited from the G.I. Bill to receive four degrees, the Ph.B. (1948), S.B. (1949), S.M. (1951), and Ph.D., in physics (1953), all from the University of Chicago. He did his thesis research, on the spontaneous fission of uranium, as well as nuclear processes in nature, as a U.S. Atomic Energy Commission Predoctoral Fellow. Upon receiving his Ph.D., Wetherill became a staff member at Carnegie's Department of Terrestrial Magnetism (DTM) in Washington, D.C. There, he joined an interdepartmental group of Carnegie scientists who were working to date the Earth's rocks by geochemical methods involving natural radioactive decay.
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A protection factor of at least 40 means that the radiation shielding provided by the shelter reduces the radiation dose experienced by at least 40 times that which would be experienced outside the shelter with no shielding. "Protection factor" is equivalent to the modern term "dose reduction factor". rads, this is a simplistic model (Gaussian) of a wind-blown fallout map, which depicts the unshielded ground level fallout gamma ray dose and dose rate contours expected to follow a 2 megaton land surface burst detonation, with 1 megaton of the yield coming from fission reactions. Because of radioactive decay, the dose rate contours (on the right) contract after fallout has arrived, but the total absorbed dose contours (left) continue to grow.
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Because of its scarcity, high radioactivity and high toxicity, there are currently no uses for protactinium outside scientific research, and for this purpose, protactinium is mostly extracted from spent nuclear fuel. Protactinium was first identified in 1913 by Kasimir Fajans and Oswald Helmuth Göhring and named brevium because of the short half-life of the specific isotope studied, i.e. protactinium-234. A more stable isotope of protactinium, 231Pa, was discovered in 1917/18 by Otto Hahn and Lise Meitner, and they chose the name proto-actinium, but the IUPAC finally named it "protactinium" in 1949 and confirmed Hahn and Meitner as discoverers. The new name meant "(nuclear) precursor of actinium" and reflected that actinium is a product of radioactive decay of protactinium.
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Nuclear weapons are a staple element in science fiction novels. The phrase "atomic bomb" predates their existence, and dates back to H. G. Wells' The World Set Free (1914) when scientists had discovered that radioactive decay implied potentially limitless energy locked inside of atomic particles (Wells' atomic bombs were only as powerful as conventional explosives, but would continue exploding for days on end). Cleve Cartmill predicted a chain-reaction-type nuclear bomb in his 1944 science-fiction story "Deadline", which led to the FBI investigating him, due to concern over a potential breach of security on the Manhattan Project."Reflections: The Cleve Cartmill Affair" by Robert Silverberg The use of radiological, biological and chemical weapons is another common theme in science fiction.
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J.J. Thomson The following year, Ramsay liberated another inert gas from a mineral called cleveite; this proved to be helium, previously known only in the solar spectrum. In his book The Gases of the Atmosphere (1896), Ramsay showed that the positions of helium and argon in the periodic table of elements indicated that at least three more noble gases might exist. In 1898 Ramsay and the British chemist Morris W. Travers isolated these elements—called neon, krypton, and xenon—from air brought to a liquid state at low temperature and high pressure. Sir William Ramsay worked with Frederick Soddy to demonstrate, in 1903, that alpha particles (helium nuclei) were continually produced during the radioactive decay of a sample of radium.
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In modern physics, antimatter is defined as matter which is composed of the antiparticles (or "partners") of the corresponding particles of "ordinary" matter. Minuscule numbers of antiparticles are generated daily at particle accelerators – total production has been only a few nanograms – and in natural processes like cosmic ray collisions and some types of radioactive decay, but only a tiny fraction of these have successfully been bound together in experiments to form anti-atoms. No macroscopic amount of antimatter has ever been assembled due to the extreme cost and difficulty of production and handling. In theory, a particle and its anti-particle (for example, a proton and an antiproton) have the same mass, but opposite electric charge and other differences in quantum numbers.
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In the case of raising the temperature, mantle melting will only occur if the mantle is heated past the normal geotherm. It is believed that heat flux from the core and lower mantle is responsible for increasing the temperature of the upper mantle. Local perturbations of the geothermal gradient, such as hotspots, are not well understood but are considered to be a likely heat source for the mantle.The decay of radioactive elements, though considered to be one of the simplest ways of generating heat in the mantle, is not realistically responsible for mantle melting, as it would take over 10 million years for the radioactive decay of K, U and Th to increase the temperature of peridotite by 1 degree Celsius.
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For protons, this corresponds to the elements helium, oxygen, calcium, nickel, tin, lead and the hypothetical unbihexium, although 126 is so far only known to be a magic number for neutrons. Atomic nuclei consisting of such a magic number of nucleons have a higher average binding energy per nucleon than one would expect based upon predictions such as the semi-empirical mass formula and are hence more stable against nuclear decay. The unusual stability of isotopes having magic numbers means that transuranium elements could theoretically be created with extremely large nuclei and yet not be subject to the extremely rapid radioactive decay normally associated with high atomic numbers. Large isotopes with magic numbers of nucleons are said to exist in an island of stability.
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See Ham 2006, , and It rejects one of the fundamental principles of modern geology (and of modern science generally), uniformitarianism, which applies the same physical and geological laws observed on the Earth today to interpret the Earth's geological history.NAS 1999 Sometimes creationists attack other scientific concepts, like the Big Bang cosmological model or methods of scientific dating based upon radioactive decay. Young Earth creationists also reject current estimates of the age of the universe and the age of the Earth, arguing for creationist cosmologies with timescales much shorter than those determined by modern physical cosmology and geological science, typically less than 10,000 years. The scientific community has overwhelmingly rejected the ideas put forth in creation science as lying outside the boundaries of a legitimate science.
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Halftime is also termed Half- life when linked to exponential processes such as radioactive decay. Haldane's five compartments (halftimes: 5, 10, 20, 40, 75 minutes) were used in decompression calculations and staged decompression procedures for fifty years. Previous theories to Haldane worked on "uniform compression", as Paul Bert pointed in 1878 that very slow decompression could avoid the caisson disease, then Hermann von Schrötter proposed in 1895 the safe "uniform decompression" rate to be of "one atmosphere per 20 minutes". Haldane in 1907 worked on "staged decompression" – decompression using a specified relatively rapid ascent rate, interrupted by specified periods at constant depth – and proved it to be safer than "uniform decompression" at the rates then in use, and produced his decompression tables on that basis.
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Fresh exposures of the pyriteiferous shale may develop the secondary mineralization of orange limonite (FeO(OH)·nH2O), and the pale yellow efflorescence or bloom of sulfur, associated with acid rock drainage. fissile Marcellus black shale at Marcellus, N.Y. Pyrite is especially abundant near the base, and the upper contacts of limestones, but framboidal microcrystals and euhedral crystals of pyrite occur throughout the organic-rich deposits. The Marcellus also contains uranium, and the radioactive decay of the uranium-238 (238U) makes it a source rock for radioactive radon gas (222Rn). Measured total organic content of the Marcellus ranges from less than 1% in eastern New York, to over 11% in the central part of the state, and the shale may contain enough carbon to support combustion.
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Since the intermediate state decays according to the laws of radioactive decay, one obtains an exponential curve with the lifetime of this intermediate state after plotting the frequency over time. Due to the non-spherically symmetric radiation of the second γ-quantum, the so-called anisotropy, which is an intrinsic property of the nucleus in this transition, it comes with the surrounding electrical and/or magnetic fields to a periodic disorder (hyperfine interaction). The illustration of the individual spectra on the right shows the effect of this disturbance as a wave pattern on the exponential decay of two detectors, one pair at 90° and one at 180° to each other. The waveforms to both detector pairs are shifted from each other.
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If the null hypothesis predicts (say) on average 9 counts per minute, then according to the Poisson distribution typical for radioactive decay there is about 41% chance of recording 10 or more counts. Thus we can say that the suitcase is compatible with the null hypothesis (this does not guarantee that there is no radioactive material, just that we don't have enough evidence to suggest there is). On the other hand, if the null hypothesis predicts 3 counts per minute (for which the Poisson distribution predicts only 0.1% chance of recording 10 or more counts) then the suitcase is not compatible with the null hypothesis, and there are likely other factors responsible to produce the measurements. The test does not directly assert the presence of radioactive material.
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Orbiting bodies can also be heated by tidal heating, geothermal energy which is driven by radioactive decay in the core of the planet, or accretional heating. These internal processes will cause the effective temperature (a blackbody temperature that produces the observed radiation from a planet) to be warmer than the equilibrium temperature (the blackbody temperature that one would expect from solar heating alone). For example, on Saturn, the effective temperature is approximately 95 K, compared to an equilibrium temperature of about 63 K. This corresponds to a ratio between power emitted and solar power received of ~2.4, indicating a significant internal energy source. Jupiter and Neptune have ratios of power emitted to solar power received of 2.5 and 2.7, respectively.
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Today, Sanford Lab operations are funded by the U.S. Department of Energy through Fermi National Accelerator Laboratory. The first two major physics experiments located on the 4850 Level were the Large Underground Xenon (LUX) experiment and the Majorana Demonstrator experiment. LUX is housed in the same cavern that was excavated for Ray Davis’s experiment in the 1960s. In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive dark matter detector in the world. The Majorana experiment is searching for a rare type of radioactive decay called “neutrinoless double-beta decay.” If this phenomenon were detected, it could confirm that neutrinos are their own antiparticles and provide clues as to why matter prevailed over antimatter.
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Temperatures of most magmas are in the range 700 °C to 1300 °C (or 1300 °F to 2400 °F), but very rare carbonatite magmas may be as cool as 490 °C, and komatiite magmas may have been as hot as 1600 °C. At any given pressure and for any given composition of rock, a rise in temperature past the solidus will cause melting. Within the solid earth, the temperature of a rock is controlled by the geothermal gradient and the radioactive decay within the rock. The geothermal gradient averages about 25 °C/km with a wide range from a low of 5–10 °C/km within oceanic trenches and subduction zones to 30–80 °C/km under mid-ocean ridges and volcanic arc environments.
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More recent results show that flerovium's reaction with gold is similar to that of copernicium, showing that it is a very volatile element that may even be gaseous at standard temperature and pressure, that it would show metallic properties, consistent with it being the heavier homologue of lead, and that it would be the least reactive metal in group 14. The question of whether flerovium behaves more like a metal or a noble gas is still unresolved as of 2018. About 90 atoms of flerovium have been observed: 58 were synthesized directly, and the rest were made from the radioactive decay of heavier elements. All of these flerovium atoms have been shown to have mass numbers from 284 to 290.
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After finishing his PhD, he spent two years as an assistant professor at the Iowa State College and worked at the Ames Laboratory at the university, which was run by the United States Atomic Energy Commission. There he taught nuclear physics and helped to increase the electron beam current in the facility's new 70-MeV synchrotron particle accelerator. While at the Ames lab, he read an article in Science News Letter magazine (now Science News), about the detection of the element technetium in the variable star R Andromedae and other red variable stars by the American astronomer Paul Merrill. Since this element has no stable isotopes, the observed technetium would experience radioactive decay with half-life of about 200,000 years, which was much shorter than the lifetime of the star.
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Naturally high in uranium, the Rincon Formation is a notorious source of radon gas emissions in Santa Barbara and Ventura Counties, making them the counties with the greatest radon hazard in California.Ron Churchill: "Radon Mapping: Santa Barbara and Ventura Counties." California Department of Conservation, Division of Mines and Geology, 1997. Available here Radon is a byproduct of radioactive decay of uranium, which is present in the Rincon at around 20 to 30 parts per million (ppm). A 1993 study found that approximately 74% of homes built on the Rincon Formation, or on alluvium or soils derived from the Rincon Formation, showed interior radon concentrations in excess of 4 picocuries per liter (pCi/l), the U.S. EPA action level, and 26% had measured levels of radon over 20 pCi/l.
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The United States has planned disposal in deep geological formations, such as the Yucca Mountain nuclear waste repository, where it has to be shielded and packaged to prevent its migration to humans' immediate environment for thousands of years.Large, John H: Radioactive Decay Characteristics of Irradiated Nuclear Fuels, January 2006.Testimony of Robert Meyers Principal deputy Assistant Administrator for the Office of Air and Radiation U.S. Environmental Protection Agency before the subcommittee on Energy and Air Quality Committee on Energy and Commerce U. S. House of Representatives, July 15, 2008 On March 5, 2009, however, Energy Secretary Steven Chu told a Senate hearing that "the Yucca Mountain site no longer was viewed as an option for storing reactor waste." Geological disposal has been approved in Finland, using the KBS-3 process.
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Chart of half-lives of known nuclides The composition of a nuclide (atomic nucleus) is defined by the number of protons Z and the number of neutrons N, which sum to mass number A. Proton number Z, also named the atomic number, determines the position of an element in the periodic table. The approximately 3300 known nuclides are commonly represented in a chart with Z and N for its axes and the half-life for radioactive decay indicated for each unstable nuclide (see figure). , 252 nuclides are observed to be stable (having never been observed to decay); generally, as the number of protons increases, stable nuclei have a higher neutron–proton ratio (more neutrons per proton). The last element in the periodic table that has a stable isotope is lead (Z = 82), with stability (i.e.
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The rate of release is too slow to have practical utility, but the total amount released is huge. Wells's novel revolves around an (unspecified) invention that accelerates the process of radioactive decay, producing bombs that explode with no more than the force of ordinary high explosives—but which "continue to explode" for days on end. "Nothing could have been more obvious to the people of the earlier twentieth century", he wrote, "than the rapidity with which war was becoming impossible ... [but] they did not see it until the atomic bombs burst in their fumbling hands". In 1932, the physicist and conceiver of nuclear chain reaction Leó Szilárd read The World Set Free (the same year Sir James Chadwick discovered the neutron), a book which he said made a great impression on him.
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Phillips, Cynthia (28 September 2006) Time for Europa, Space.com. Europa – possible effect of radiation on biosignature chemicals The energy provided by tidal forces drives active geological processes within Europa's interior, just as they do to a far more obvious degree on its sister moon Io. Although Europa, like the Earth, may possess an internal energy source from radioactive decay, the energy generated by tidal flexing would be several orders of magnitude greater than any radiological source. Life on Europa could exist clustered around hydrothermal vents on the ocean floor, or below the ocean floor, where endoliths are known to inhabit on Earth. Alternatively, it could exist clinging to the lower surface of Europa's ice layer, much like algae and bacteria in Earth's polar regions, or float freely in Europa's ocean.
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Zircon, a common target for Lu–Hf analysis Lutetium–hafnium dating is a geochronological dating method utilizing the radioactive decay system of lutetium–176 to hafnium–176. With a commonly accepted half-life of 37.1 billion years, the long-living Lu–Hf decay pair survives through geological time scales, thus is useful in geological studies. Due to chemical properties of the two elements, namely their valences and ionic radii, Lu is usually found in trace amount in rare-earth element loving minerals, such as garnet and phosphates, while Hf is usually found in trace amount in zirconium-rich minerals, such as zircon, baddeleyite and zirkelite. The trace concentration of the Lu and Hf in earth materials posed some technological difficulties in using Lu–Hf dating extensively in the 1980s.
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Transmutation of elements from one to another had been understood since 1901 as a result of natural radioactive decay, but when Rutherford projected alpha particles from alpha decay into air, he discovered this produced a new type of radiation which proved to be hydrogen nuclei (Rutherford named these protons). Further experimentation showed the protons to be coming from the nitrogen component of air, and the reaction was deduced to be a transmutation of nitrogen into oxygen in the reaction :14N + α → 17O + p This was the first discovered nuclear reaction. To the adjacent pictures: According to the energy-loss curve by Bragg, it is recognizable that the alpha particle indeed loses more energy on the end of the trace.Magazine "nuclear energy" (III/18 (203) special edition, Volume 10, Issue 2 /1967.
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Samarium–neodymium dating is a radiometric dating method useful for determining the ages of rocks and meteorites, based on the radioactive decay of a long-lived samarium isotope (147Sm) to a radiogenic neodymium isotope (143Nd). Neodymium isotope ratios together with samarium-neodymium ratios are used to provide information on age information and the source of igneous melts. It is sometimes assumed that at the moment when crustal material is formed from the mantle the neodymium isotope ratio depends only on the time when this event occurred, but thereafter it evolves in a way that depends on the new ratio of samarium to neodymium in the crustal material, which will be different from the ratio in the mantle material. Samarium–neodymium dating allows us to determine when the crustal material was formed.
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For example, the Lunar Prospector GRS identified several regions with high iron concentrations. Thorium concentrations on the Moon, as mapped by Lunar Prospector The fundamental purpose of the GRS experiment was to provide global maps of elemental abundances on the lunar surface. The GRS was designed to record the spectrum of gamma rays emitted by: # the radioactive decay of elements contained in the Moon's crust; and # elements in the crust bombarded by cosmic rays and solar wind particles. The most important elements detectable by the GRS were uranium (U), thorium (Th), and potassium (K), radioactive elements which generate gamma rays spontaneously, and iron (Fe), titanium (Ti), oxygen (O), silicon (Si), aluminum (Al), magnesium (Mg), and calcium (Ca), elements which emit gamma rays when hit by cosmic rays or solar wind particles.
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Radioactive contamination, also called radiological contamination, is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids or gases (including the human body), where their presence is unintended or undesirable (from the International Atomic Energy Agency (IAEA) definition). Such contamination presents a hazard because of the radioactive decay of the contaminants, which produces such harmful effects as ionizing radiation (namely α, β, and γ rays) and free neutrons. The degree of hazard is determined by the concentration of the contaminants, the energy of the radiation being emitted, the type of radiation, and the proximity of the contamination to organs of the body. It is important to be clear that the contamination gives rise to the radiation hazard, and the terms "radiation" and "contamination" are not interchangeable.
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Falsification and Research (1976) "Museum Folkwang, Essen and Staatliche Museen Preußischer Kulturbesitz, Berlin". Berlin. Language: German. . Forgeries in which modern lead or white lead pigment has been used can be recognized by using a technique called Pb(Lead)-210-Dating. Pb-210 is a naturally occurring radioactive isotope of lead that is part of the uranium-238 Radioactive decay series, and has a half-life of 22.3 years. To determine the amount of Pb-210, the alpha radiation emitted by another element, polonium-210 (Po-210), is measured.Flett, Robert (8 October 2003). Understanding the Pb-210 Method. Thus it is possible to estimate the age of a painting, within a few years' span, by extrapolating the Pb-210 content present in the paint used to create the painting.Froentjes, W., and R. Breek (1977).
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Iodine-131 (131I, I-131) is an important radioisotope of iodine discovered by Glenn Seaborg and John Livingood in 1938 at the University of California, Berkeley. It has a radioactive decay half-life of about eight days. It is associated with nuclear energy, medical diagnostic and treatment procedures, and natural gas production. It also plays a major role as a radioactive isotope present in nuclear fission products, and was a significant contributor to the health hazards from open-air atomic bomb testing in the 1950s, and from the Chernobyl disaster, as well as being a large fraction of the contamination hazard in the first weeks in the Fukushima nuclear crisis. This is because 131I is a major fission product of uranium and plutonium, comprising nearly 3% of the total products of fission (by weight).
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Since the probability of radioactive decay for a given radionuclide is a fixed physical quantity (with some slight exceptions, see changing decay rates), the number of decays that occur in a given time of a specific number of atoms of that radionuclide is also a fixed physical quantity (if there are large enough numbers of atoms to ignore statistical fluctuations). Thus, specific activity is defined as the activity per quantity of atoms of a particular radionuclide. It is usually given in units of Bq/g, but another commonly used unit of activity is the curie (Ci) allowing the definition of specific activity in Ci/g. The amount of specific activity should not be confused with level of exposure to ionizing radiation and thus the exposure or absorbed dose.
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Since the discovery of evidence for extraterrestrial liquid water, substantial quantities of it are now thought to occur outside the circumstellar habitable zone. The concept of deep biospheres, like Earth's, that exist independently of stellar energy, are now generally accepted in astrobiology given the large amount of liquid water known to exist within in lithospheres and asthenospheres of the Solar System. Sustained by other energy sources, such as tidal heating or radioactive decay or pressurized by non-atmospheric means, liquid water may be found even on rogue planets, or their moons. Liquid water can also exist at a wider range of temperatures and pressures as a solution, for example with sodium chlorides in seawater on Earth, chlorides and sulphates on equatorial Mars, or ammoniates, due to its different colligative properties.
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Bismuth-209, however, is only very slightly radioactive, with a half- life greater than the age of the universe; radioisotopes with extremely long half-lives are considered effectively stable for practical purposes. Transition diagram for decay modes of a radionuclide, with neutron number N and atomic number Z (shown are α, β±, p+, and n0 emissions, EC denotes electron capture). Types of radioactive decay related to neutron and proton numbers In analysing the nature of the decay products, it was obvious from the direction of the electromagnetic forces applied to the radiations by external magnetic and electric fields that alpha particles carried a positive charge, beta particles carried a negative charge, and gamma rays were neutral. From the magnitude of deflection, it was clear that alpha particles were much more massive than beta particles.
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Hahn and Meitner in 1912 The discovery of nuclear fission occurred in 1938 in the buildings of Kaiser Wilhelm Society for Chemistry, today part of the Free University of Berlin, following over four decades of work on the science of radioactivity and the elaboration of new nuclear physics that described the components of atoms. In 1911, Ernest Rutherford proposed a model of the atom in which a very small, dense and positively charged nucleus of protons was surrounded by orbiting, negatively charged electrons (the Rutherford model). Niels Bohr improved upon this in 1913 by reconciling the quantum behavior of electrons (the Bohr model). Work by Henri Becquerel, Marie Curie, Pierre Curie, and Rutherford further elaborated that the nucleus, though tightly bound, could undergo different forms of radioactive decay, and thereby transmute into other elements.
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But Hahn and Meitner had a sample from which they had regularly removed its mother isotope, mesothorium (), over a period of several years, allowing the radiothorium to decay away. Even then, it was still more difficult to work with because its induced decay products from neutron irradiation were isotopes of the same elements produced by thorium's own radioactive decay. What they found was three different decay series, all alpha emitters—a form of decay not found in any other heavy element, and for which Meitner once again had to postulate multiple isomers. They did find an interesting result: these (n, α) decay series occurred simultaneously when the energy of the incident neutrons was less than 2.5 MeV; when they had more, an (n, γ) reaction that formed was favoured.
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" Frisch normally celebrated Christmas with Meitner in Berlin, but in 1938 she accepted an invitation from Eva von Bahr to spend it with her family at Kungälv, and Meitner asked Frisch to join her there. Meitner received the letter from Hahn describing his chemical proof that some of the product of the bombardment of uranium with neutrons was barium. Barium had an atomic mass 40% less than uranium, and no previously known methods of radioactive decay could account for such a large difference in the mass of the nucleus. Nonetheless, she had immediately written back to Hahn to say: "At the moment the assumption of such a thoroughgoing breakup seems very difficult to me, but in nuclear physics we have experienced so many surprises, that one cannot unconditionally say: 'It is impossible.
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Discoveries of many SLSNe in the 21st century showed that not only were they more luminous by an order of magnitude than most supernovae, their remnants were also unlikely to be powered by the typical radioactive decay that is responsible for the observed energies of conventional supernovae. SLSNe events use a separate classification scheme to distinguish them from the conventional type Ia, type Ib/Ic, and type II supernovae, roughly distinguishing between the spectral signature of hydrogen- rich and hydrogen-poor events. Hydrogen-rich SLSNe are classified as Type SLSN-II, with observed radiation passing through the changing opacity of a thick expanding hydrogen envelope. Most hydrogen-poor events are classified as Type SLSN-I, with its visible radiation produced from a large expanding envelope of material powered by an unknown mechanism.
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Neon-21 production from absorption of neutrons from alpha- spallation on oxygen-18 Other nucleogenic reactions that produce heavy neon isotopes are (fast neutron capture, alpha emission) reactions, starting with magnesium-24 and magnesium-25, respectively. USGS explanation of the nucleogenic sources of Ne-21 and Ne-22 The source of the neutrons in these reactions is often secondary neutrons produced by alpha radiation from natural uranium and thorium in rock. Because nucleogenic isotopes have been produced later than the birth of the solar system (and the nucleosynthetic events that preceded it), nucleogenic isotopes, by definition, are not primordial nuclides. However, nucleogenic isotopes should not be confused with much more common radiogenic nuclides that are also younger than primordial nuclides, but which arise as simple daughter isotopes from radioactive decay.
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If it does decay via a positron, the proton's half- life is constrained to be at least years. According to the Standard Model, protons, a type of baryon, are stable because baryon number (quark number) is conserved (under normal circumstances; see chiral anomaly for exception). Therefore, protons will not decay into other particles on their own, because they are the lightest (and therefore least energetic) baryon. Positron emission - a form of radioactive decay which sees a proton become a neutron - is not proton decay, since the proton interacts with other particles within the atom. Some beyond-the-Standard Model grand unified theories (GUTs) explicitly break the baryon number symmetry, allowing protons to decay via the Higgs particle, magnetic monopoles, or new X bosons with a half-life of 1031 to 1036 years.
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Small amounts of fission products are naturally formed as the result of either spontaneous fission of natural uranium, which occurs at a low rate, or as a result of neutrons from radioactive decay or reactions with cosmic ray particles. The microscopic tracks left by these fission products in some natural minerals (mainly apatite and zircon) are used in fission track dating to provide the cooling (crystallization) ages of natural rocks. The technique has an effective dating range of 0.1 Ma to >1.0 Ga depending on the mineral used and the concentration of uranium in that mineral. About 1.5 billion years ago in a uranium ore body in Africa, a natural nuclear fission reactor operated for a few hundred thousand years and produced approximately 5 tonnes of fission products.
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In regular cold matter, quarks, fundamental particles of nuclear matter, are confined by the strong force into hadrons that consist of 2–4 quarks, such as protons and neutrons. Quark matter or quantum chromodynamical (QCD) matter is a group of phases where the strong force is overcome and quarks are deconfined and free to move. Quark matter phases occur at extremely high densities or temperatures, and there are no known ways to produce them in equilibrium in the laboratory; in ordinary conditions, any quark matter formed immediately undergoes radioactive decay. Strange matter is a type of quark matter that is suspected to exist inside some neutron stars close to the Tolman–Oppenheimer–Volkoff limit (approximately 2–3 solar masses), although there is no direct evidence of its existence.
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A strike- slip formation found by Whitham and Storey in 1989 proves the placement of this boundary as well as the spreading of the Weddell Sea Region, off the Antarctic Peninsula, and the change from fine anoxic to coarse clastic sedimentation. The Antarctic Peninsula was an active volcanic arc between the Late Jurassic and Tertiary period, created from the south-eastward subduction of the Panthalassa crust, the super ocean that surrounded the supercontinent of Pangaea. The finding from Potassium-argon or K-Ar dating, which measures the product of the radioactive decay of an isotope to determine the time period, from the Schists that line the Nordenskjöld Coast has found that a metamorphic event, a process of heating and cooling sediments which ultimately changes their composition, happened around the Permian times, estimating its peak at 245-250 Ma.
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Using Simon van der Meers technology of stochastic cooling, the Antiproton Accumulator was also built. The collider started running in 1981 and, in early 1983, an international team of more than 100 physicists headed by Rubbia and known as the UA1 Collaboration, detected the intermediate vector bosons, the W and Z bosons, which had become a cornerstone of modern theories of elementary particle physics long before this direct observation. They carry the weak force that causes radioactive decay in the atomic nucleus and controls the combustion of the Sun, just as photons, massless particles of light, carry the electromagnetic force which causes most physical and biochemical reactions. The weak force also plays a fundamental role in the nucleosynthesis of the elements, as studied in theories of stars evolution. These particles have a mass almost 100 times greater than the proton.
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Research has generated evidence that second-hand smoke causes the same problems as direct smoking, including lung cancer, cardiovascular disease, and lung ailments such as emphysema, bronchitis, and asthma. Specifically, meta- analyses show that lifelong non-smokers with partners who smoke in the home have a 20–30% greater risk of lung cancer than non-smokers who live with non- smokers. Non-smokers exposed to cigarette smoke in the workplace have an increased lung cancer risk of 16–19%. A study issued in 2002 by the International Agency for Research on Cancer of the World Health Organization concluded that non-smokers are exposed to the same carcinogens on account of tobacco smoke as active smokers. Sidestream smokeGlossary: Sidestream smoke contains 69 known carcinogens, particularly benzopyrene and other polynuclear aromatic hydrocarbons, and radioactive decay products, such as polonium-210.
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The project gets its name from the processing of uranium at Hanford, WA, in an open-loop water- cooled nuclear reactor for the sole purpose of irradiating the uranium-238, producing the fissile plutonium-239. Due to other unwanted highly radioactive decay products being formed, normal batch processing would take place 83 to 101 days after reactor extraction to allow the radioactive isotopes to decay before extracting the fissile plutonium-239 in a safe manner for the 30,000 nuclear weapons amassed and now MOX fuel during the cold war by the United States. For the Green Run test, a batch was fresh from the reactor with only a scheduled 16-day decay period and then was vented into the atmosphere prematurely. The unfiltered exhaust from the production facility was therefore much more radioactive than during a normal batch.
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Enhanced geothermal system 1:Reservoir 2:Pump house 3:Heat exchanger 4:Turbine hall 5:Production well 6:Injection well 7:Hot water to district heating 8:Porous sediments 9:Observation well 10:Crystalline bedrock The Earth's heat content is about . This heat naturally flows to the surface by conduction at a rate of 44.2 TW and is replenished by radioactive decay at a rate of 30 TW. These power rates are more than double humanity's current energy consumption from primary sources, but most of this power is too diffuse (approximately 0.1 W/m2 on average) to be recoverable. The Earth's crust effectively acts as a thick insulating blanket which must be pierced by fluid conduits (of magma, water or other) to release the heat underneath. Electricity generation requires high-temperature resources that can only come from deep underground.
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In August 1945 Wheeler and his family returned to Princeton, where he resumed his academic career. Working with Feynman, he explored the possibility of physics with particles, but not fields, and carried out theoretical studies of the muon with Jayme Tiomno, resulting in a series of papers on the topic, including a 1949 paper in which Tiomno and Wheeler introduced the "Tiomno Triangle", which related different forms of radioactive decay. He also suggested the use of muons as a nuclear probe. This paper, written and privately circulated in 1949 but not published until 1953, resulted in a series of measurements of the Chang radiation emitted by muons. Muons are a component of cosmic rays, and Wheeler became the founder and first director of Princeton's Cosmic Rays Laboratory, which received a substantial grant of $375,000 from the Office of Naval Research in 1948.
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Models of heat retention and heating via radioactive decay in smaller icy Solar System bodies suggest that Rhea, Titania, Oberon, Triton, Pluto, Eris, Sedna, and Orcus may have oceans underneath solid icy crusts approximately 100 km thick. Of particular interest in these cases is the fact that the models indicate that the liquid layers are in direct contact with the rocky core, which allows efficient mixing of minerals and salts into the water. This is in contrast with the oceans that may be inside larger icy satellites like Ganymede, Callisto, or Titan, where layers of high-pressure phases of ice are thought to underlie the liquid water layer. Hydrogen sulfide has been proposed as a hypothetical solvent for life and is quite plentiful on Jupiter's moon Io, and may be in liquid form a short distance below the surface.
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The young Earth creationist belief that the age of the Earth is 6,000 to 10,000 years old conflicts with the age of 4.54 billion years measured using independently cross-validated geochronological methods including radiometric dating. Creationists dispute these and all other methods which demonstrate the timescale of geologic history in spite of the lack of scientific evidence that there are any inconsistencies or errors in the measurement of the Earth's age. Between 1997 and 2005, a team of scientists at the Institute for Creation Research conducted an eight-year research project entitled RATE (Radioisotopes and the Age of The Earth) to assess the validity and accuracy of radiometric dating techniques. While they concluded that there was overwhelming evidence for over 500 million years' worth of radioactive decay, they claimed to have found other scientific evidence to prove a young earth.
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Thorium is the 41st most abundant element in the Earth's crust. Natural thorium is usually almost pure 232Th, which is the longest-lived and most stable isotope of thorium, having a half-life comparable to the age of the universe. Its radioactive decay is the largest single contributor to the Earth's internal heat; the other major contributors are the shorter-lived primordial radionuclides, which are 238U, 40K, and 235U in descending order of their contribution. (At the time of the Earth's formation, 40K and 235U contributed much more by virtue of their short half-lives, but they have decayed more quickly, leaving the contribution from 232Th and 238U predominant.) Its decay accounts for a gradual decrease of thorium content of the Earth: the planet currently has around 85% of the amount present at the formation of the Earth.
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3He is a primordial substance in the Earth's mantle, considered to have become entrapped within the Earth during planetary formation. The ratio of 3He to 4He within the Earth's crust and mantle is less than that for assumptions of solar disk composition as obtained from meteorite and lunar samples, with terrestrial materials generally containing lower 3He/4He ratios due to ingrowth of 4He from radioactive decay. 3He has a cosmological ratio of 300 atoms per million atoms of 4He (at. ppm),Wittenberg 1994 leading to the assumption that the original ratio of these primordial gases in the mantle was around 200-300 ppm when Earth was formed. A lot of 4He was generated by alpha-particle decay of uranium and thorium, and now the mantle has only around 7% primordial helium, lowering the total 3He/4He ratio to around 20 ppm.
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Elements in this region are likely to be highly unstable with respect to radioactive decay and undergo alpha decay or spontaneous fission with extremely short half-lives, though element 126 is hypothesized to be within an island of stability that is resistant to fission but not to alpha decay. Other islands of stability beyond the known elements may also be possible, including one theorised around element 164, though the extent of stabilizing effects from closed nuclear shells is uncertain. It is not clear how many elements beyond the expected island of stability are physically possible, whether period 8 is complete, or if there is a period 9. The International Union of Pure and Applied Chemistry (IUPAC) defines an element to exist if its lifetime is longer than 10−14 seconds (0.01 picoseconds, or 10 femtoseconds), which is the time it takes for the nucleus to form an electron cloud.
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Months after the explosion, when the outer layers have expanded to the point of transparency, the spectrum is dominated by light emitted by material near the core of the star, heavy elements synthesized during the explosion; most prominently isotopes close to the mass of iron (iron-peak elements). The radioactive decay of nickel-56 through cobalt-56 to iron-56 produces high-energy photons, which dominate the energy output of the ejecta at intermediate to late times. The use of Type Ia supernovae to measure precise distances was pioneered by a collaboration of Chilean and US astronomers, the Calán/Tololo Supernova Survey. In a series of papers in the 1990s the survey showed that while Type Ia supernovae do not all reach the same peak luminosity, a single parameter measured from the light curve can be used to correct unreddened Type Ia supernovae to standard candle values.
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Bismuth-209 is notable as the only naturally occurring isotope of an element long considered stable. A further 10 nuclides, platinum-190, samarium-147, lanthanum-138, rubidium-87, rhenium-187, lutetium-176, thorium-232, uranium-238, potassium-40, and uranium-235 have half-lives between 700 million and 1 trillion years, which means they have experienced significant depletion since the formation of the solar system about 4.6 billion years ago, but still exist on earth in significant quantities. They are the primary source of radiogenic heating and radioactive decay products. Together, there are a total of 286 primordial nuclides.Two further nuclides, plutonium-244 and samarium-146, have half-lives just long enough (80 and 68 million years) that they could have survived from the formation of the solar system and be present on earth in trace quantities (having survived 57 and 67 half-lives).
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In 2014, the United States Food and Drug Administration (FDA) released a report stating that radionuclides, traced from the Fukushima facility, were present in the United States food supply, but not to levels deemed to be a threat to public health – as well as any food and agricultural products imported from Japanese sources. It is commonly believed that, with the rate of the current radionuclide leakage, the dispersal into the water would prove beneficial as most of the isotopes would dilute into the water as well as become less effective over time, thanks to radioactive decay. Cesium (Cs-137) is the primary isotope released from the Fukushima Daiichi facility. Cs-137 has a long half-life, meaning it could potentially have long-term harmful effects, but as of now, its levels from 200 km outside of Fukushima show close to pre- accident levels with little spread to North American coasts.
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The stability of nuclei decreases greatly with the increase in atomic number after curium, element 96, whose half-life is four orders of magnitude longer than that of any currently known higher-numbered element. All isotopes with an atomic number above 101 undergo radioactive decay with half-lives of less than 30 hours. No elements with atomic numbers above 82 (after lead) have stable isotopes. Nevertheless, for reasons not yet well understood, there is a slight increase of nuclear stability around atomic numbers 110–114, which leads to the appearance of what is known in nuclear physics as the "island of stability". This concept, proposed by University of California professor Glenn Seaborg and stemming from the stabilizing effects of the closed nuclear shells around Z = 114 (or possibly 120, 122, 124, or 126) and N = 184 (and possibly also N = 228), explains why superheavy elements last longer than predicted.
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In the second type, subducting oceanic plates (which largely constitute the upper thermal boundary layer of the mantle) plunge back into the mantle and move downwards towards the core-mantle boundary. Mantle convection occurs at rates of centimeters per year, and it takes on the order of hundreds of millions of years to complete a cycle of convection. Neutrino flux measurements from the Earth's core (see kamLAND) show the source of about two- thirds of the heat in the inner core is the radioactive decay of 40K, uranium and thorium. This has allowed plate tectonics on Earth to continue far longer than it would have if it were simply driven by heat left over from Earth's formation; or with heat produced from gravitational potential energy, as a result of physical rearrangement of denser portions of the Earth's interior toward the center of the planet (i.e.
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The decay of a proton rich nucleus A populates excited states of a daughter nucleus B by β+ emission or electron capture (EC). Those excited states that lie below the separation energy for protons (Sp) decay by γ emission towards the groundstate of daughter B. For the higher excited states a competitive decay channel of proton emission to the granddaughter C exists, called β-delayed proton emission. Proton emission (also known as proton radioactivity) is a rare type of radioactive decay in which a proton is ejected from a nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay, in which case the process is known as beta-delayed proton emission, or can occur from the ground state (or a low- lying isomer) of very proton-rich nuclei, in which case the process is very similar to alpha decay.
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These creatures thrive despite having no access to sunlight, and it was soon discovered that they comprise an entirely independent ecosystem. Although most of these multicellular lifeforms need dissolved oxygen (produced by oxygenic photosynthesis) for their aerobic cellular respiration and thus are not completely independent from sunlight by themselves, the basis for their food chain is a form of bacterium that derives its energy from oxidization of reactive chemicals, such as hydrogen or hydrogen sulfide, that bubble up from the Earth's interior. Other lifeforms entirely decoupled from the energy from sunlight are green sulfur bacteria which are capturing geothermal light for anoxygenic photosynthesis or bacteria running chemolithoautotrophy based on the radioactive decay of uranium. This chemosynthesis revolutionized the study of biology and astrobiology by revealing that life need not be sun-dependent; it only requires water and an energy gradient in order to exist.
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Some neutrons will impact fuel nuclei and induce further fissions, releasing yet more neutrons. If enough nuclear fuel is assembled in one place, or if the escaping neutrons are sufficiently contained, then these freshly emitted neutrons outnumber the neutrons that escape from the assembly, and a sustained nuclear chain reaction will take place. An assembly that supports a sustained nuclear chain reaction is called a critical assembly or, if the assembly is almost entirely made of a nuclear fuel, a critical mass. The word "critical" refers to a cusp in the behavior of the differential equation that governs the number of free neutrons present in the fuel: if less than a critical mass is present, then the amount of neutrons is determined by radioactive decay, but if a critical mass or more is present, then the amount of neutrons is controlled instead by the physics of the chain reaction.
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The most important of these techniques would prove to be Brill's pioneering application of lead isotope analysis, hitherto used only in geology, to archaeological objects. Brill first presented this idea at the 1965 Seminar in Examination of Works of Art, held at the Museum of Fine Arts Boston, but the first widely published account of the method seems to be Brill and Wampler's 1967 article in the American Journal of Archaeology. Here, Brill and Wampler outlined how the technique could be used to provenance the lead contents of archaeological objects to lead ore sources around the world, based on the isotopic signature of various leads, which relates them to ‘ores occurring in different geographical areas’ (1967, 63). These different areas have different signatures because they are of varying geological age, something reflected by the individual lead isotopes which form only after the radioactive decay of uranium and thorium (Brill et al.
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Fortunately, the effective neutron lifetime is much longer than the average lifetime of a single neutron in the core. About 0.65% of the neutrons produced by 235U fission, and about 0.20% of the neutrons produced by 239Pu fission, are not produced immediately, but rather are emitted from an excited nucleus after a further decay step. In this step, further radioactive decay of some of the fission products (almost always negative beta decay), is followed by immediate neutron emission from the excited daughter product, with an average life time of the beta decay (and thus the neutron emission) of about 15 seconds. These so-called delayed neutrons increase the effective average lifetime of neutrons in the core, to nearly 0.1 seconds, so that a core with \alpha of 0.01 would increase in one second by only a factor of (1 + 0.01)10, or about 1.1: a 10% increase.
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Since tritium undergoes radioactive decay, and is also difficult to confine physically, the much larger secondary charge of heavy hydrogen isotopes needed in a true hydrogen bomb uses solid lithium deuteride as its source of deuterium and tritium, producing the tritium in situ during secondary ignition. During the detonation of the primary fission bomb stage in a thermonuclear weapon (Teller-Ullam staging), the sparkplug, a cylinder of 235U/239Pu at the center of the fusion stage(s), begins to fission in a chain reaction, from excess neutrons channeled from the primary. The neutrons released from the fission of the sparkplug split lithium-6 into tritium and helium-4, while lithium-7 is split into helium-4, tritium, and one neutron. As these reactions occur, the fusion stage is compressed by photons from the primary and fission of the 238U or 238U/235U jacket surrounding the fusion stage.
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The weak interaction is carried by particles called W and Z bosons, and also acts on the nucleus of atoms, mediating radioactive decay. The electromagnetic force, carried by the photon, creates electric and magnetic fields, which are responsible for the attraction between orbital electrons and atomic nuclei which holds atoms together, as well as chemical bonding and electromagnetic waves, including visible light, and forms the basis for electrical technology. Although the electromagnetic force is far stronger than gravity, it tends to cancel itself out within large objects, so over large (astronomical) distances gravity tends to be the dominant force, and is responsible for holding together the large scale structures in the universe, such as planets, stars, and galaxies. Many theoretical physicists believe these fundamental forces to be related and to become unified into a single force at very high energies on a minuscule scale, the Planck scale, but particle accelerators cannot produce the enormous energies required to experimentally probe this.
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The BBC reported that by coincidence another scientist, who had worked on Britain's early atomic bomb programme decades before, happened to overhear a discussion about the small spike and recognised it as the gamma ray signal from the radioactive decay of polonium-210, which was a critical component of early nuclear bombs. On the evening of 22 November, shortly before his death, his doctors were informed the poison was likely to be polonium-210. Further tests on a larger urine sample using spectroscopy designed to detect alpha particles confirmed the result the following day. Unlike most common radiation sources, polonium-210 emits very little gamma radiation (the low intensity gamma ray at an energy of 803 keV is the most prominent), but large amounts of alpha particles which do not penetrate even a sheet of paper or the epidermis of human skin, and is therefore relatively invisible to common radiation detectors such as Geiger counters.
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In 1862, the physicist William Thomson, 1st Baron Kelvin published calculations that fixed the age of Earth at between 20 million and 400 million years. Dalrymple (1994) pp. 14–17, 38 He assumed that Earth had formed as a completely molten object, and determined the amount of time it would take for the near-surface temperature gradient to decrease to its present value. His calculations did not account for heat produced via radioactive decay (a then unknown process) or, more significantly, convection inside the Earth, which allows the temperature in the upper mantle to remain high much longer, maintaining a high thermal gradient in the crust much longer. Even more constraining were Kelvin's estimates of the age of the Sun, which were based on estimates of its thermal output and a theory that the Sun obtains its energy from gravitational collapse; Kelvin estimated that the Sun is about 20 million years old.
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In 1943, astatine was found as a product of two naturally occurring decay chains by Berta Karlik and Traude Bernert, first in the so-called uranium series, and then in the actinium series. (Since then, astatine was also found in a third decay chain, the neptunium series.) Friedrich Paneth in 1946 called to finally recognize synthetic elements, quoting, among other reasons, recent confirmation of their natural occurrence, and proposed that the discoverers of the newly discovered unnamed elements name these elements. In early 1947, Nature published the discoverers' suggestions; a letter from Corson, MacKenzie, and Segrè suggested the name "astatine" coming from the Greek astatos (αστατος) meaning "unstable", because of its propensity for radioactive decay, with the ending "-ine", found in the names of the four previously discovered halogens. The name was also chosen to continue the tradition of the four stable halogens, where the name referred to a property of the element.
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When the animal or plant dies, it stops exchanging carbon with its environment, and thereafter the amount of it contains begins to decrease as the undergoes radioactive decay. Measuring the amount of in a sample from a dead plant or animal, such as a piece of wood or a fragment of bone, provides information that can be used to calculate when the animal or plant died. The older a sample is, the less there is to be detected, and because the half-life of (the period of time after which half of a given sample will have decayed) is about 5,730 years, the oldest dates that can be reliably measured by this process date to approximately 50,000 years ago, although special preparation methods occasionally make accurate analysis of older samples possible. Research has been ongoing since the 1960s to determine what the proportion of in the atmosphere has been over the past fifty thousand years.
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Best-fit models for these absorption features suggest that Huya's surface consists of a mixture of cometary ice tholins (ice tholin II), nitrogen-rich Titan tholins, as well as water ice. Spectrographic observations of Huya's spectrum with the Very Large Telescope in 2001 and 2002 have tentatively identified weak absorption features at near-infrared wavelengths around 0.6–0.82 μm, possibly indicating the presence of phyllosilicate materials on its surface. The 0.6 μm absorption feature in Huya's spectrum resembles those in the spectra of stony S-type asteroids, which may suggest the presence of spinel group minerals, albeit in trace amounts as such minerals are unlikely to be abundant in trans-Neptunian objects. Other absorption features near 0.7 μm in Huya's spectrum appear akin to those in the spectra of dark asteroids, indicating the presence of hydrous silicate minerals such as phyllosilicates, which may have been aqueously altered through heating induced by impact events or the radioactive decay of radionuclides in Huya's interior.
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As discussed above, deuterium and protium are stable isotopes which never undergo radioactive decay. Therefore, the D/H ratio of a pool containing hydrogen will remain constant as long as no hydrogen is added or removed from the system, a property known as conservation of mass. When two pools of hydrogen A and B mix with molar amounts of hydrogen m and m, each with their own starting fractional abundance of deuterium (F and F), then the fractional abundance of the resulting mixture is given by the following exact equation: :m_\Sigma F_\Sigma = m_AF_A+m_BF_B The terms with Σ represent the values for the combined pools. It is often common to find the following approximation used for calculations regarding the mixing of two pools with a known isotopic composition: :m_\Sigma \delta_\Sigma = m_A \delta_A+m_B \delta_B This approximation is convenient and applicable with little error in most applications having to deal with pools of hydrogen from natural processes.
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Even in a subcritical assembly such as a shut-down reactor core, any stray neutron that happens to be present in the core (for example from spontaneous fission of the fuel, from radioactive decay of fission products, or from a neutron source) will trigger an exponentially decaying chain reaction. Although the chain reaction is not self-sustaining, it acts as a multiplier that increases the equilibrium number of neutrons in the core. This subcritical multiplication effect can be used in two ways: as a probe of how close a core is to criticality, and as a way to generate fission power without the risks associated with a critical mass. If k is the neutron multiplication factor of a subcritical core and S_0 is the number of neutrons coming per generation in the reactor from an external source, then at the instant when the neutron source is switched on, number of neutrons in the core will be S_0.
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Enhanced geothermal system 1:Reservoir 2:Pump house 3:Heat exchanger 4:Turbine hall 5:Production well 6:Injection well 7:Hot water to district heating 8:Porous sediments 9:Observation well 10:Crystalline bedrock The Earth's internal thermal energy flows to the surface by conduction at a rate of 44.2 terawatts (TW), and is replenished by radioactive decay of minerals at a rate of 30 TW. These power rates are more than double humanity's current energy consumption from all primary sources, but most of this energy flow is not recoverable. In addition to the internal heat flows, the top layer of the surface to a depth of is heated by solar energy during the summer, and releases that energy and cools during the winter. Outside of the seasonal variations, the geothermal gradient of temperatures through the crust is 25–30 °C (77–86 °F) per km of depth in most of the world. The conductive heat flux averages 0.1 MW/km2.
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Time constants are a feature of the lumped system analysis (lumped capacity analysis method) for thermal systems, used when objects cool or warm uniformly under the influence of convective cooling or warming. Physically, the time constant represents the elapsed time required for the system response to decay to zero if the system had continued to decay at the initial rate, because of the progressive change in the rate of decay the response will have actually decreased in value to 1/e \approx 36.8\,\% in this time (say from a step decrease). In an increasing system, the time constant is the time for the system's step response to reach 1-1/e \approx 63.2\,\% of its final (asymptotic) value (say from a step increase). In radioactive decay the time constant is related to the decay constant (λ), and it represents both the mean lifetime of a decaying system (such as an atom) before it decays, or the time it takes for all but 36.8% of the atoms to decay.
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These rare objects, known as metal-poor stars, are the most chemically primitive stars known, and are among the first generations of stars born in our galaxy, the Milky Way. They provide crucial information on the astrophysical nucleosynthesis sites of the chemical elements, and are powerful tracers of the assembly and evolution of large spiral galaxies. Beers’ discoveries include: (1) The identification of the first metal-poor stars with measured abundances of Uranium, enabling the determination of a radioactive decay age limit on the Universe, (2) a class of stars known as carbon-enhanced metal- poor (CEMP) stars, a subset of which are thought to reflect the nucleosynthesis products of the very first stars in the Universe, and (3) The first large-scale chronographic (age) maps of the halo of the Milky Way, which astronomers can compare with simulations of the formation of the galaxy. In 2017, Beers and his graduate students were part of a team that identified the characteristic signature of the astrophysical r-process in the kilonova associated with a neutron star merger.
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A randomness extractor, often simply called an "extractor", is a function, which being applied to output from a weakly random entropy source, together with a short, uniformly random seed, generates a highly random output that appears independent from the source and uniformly distributed. Examples of weakly random sources include radioactive decay or thermal noise; the only restriction on possible sources is that there is no way they can be fully controlled, calculated or predicted, and that a lower bound on their entropy rate can be established. For a given source, a randomness extractor can even be considered to be a true random number generator (TRNG); but there is no single extractor that has been proven to produce truly random output from any type of weakly random source. Sometimes the term "bias" is used to denote a weakly random source's departure from uniformity, and in older literature, some extractors are called unbiasing algorithms,David K. Gifford, Natural Random Numbers, MIT/LCS/TM-371, Massachusetts Institute of Technology, August 1988.
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The tidal forces experienced by Io are about 20,000 times stronger than the tidal forces Earth experience due to the moon, and the vertical differences in its tidal bulge, between the times Io is at periapsis and apoapsis in its orbit, could be as much as .Interplanetary Low Tide - NASA Science Mission Directorate The friction or tidal dissipation produced in Io's interior due to this varying tidal pull, which, without the resonant orbit, would have gone into circularizing Io's orbit instead, creates significant tidal heating within Io's interior, melting a significant amount of Io's mantle and core. The amount of energy produced is up to 200 times greater than that produced solely from radioactive decay. This heat is released in the form of volcanic activity, generating its observed high heat flow (global total: 0.6 to 1.6×1014 W). Models of its orbit suggest that the amount of tidal heating within Io changes with time; however, the current amount of tidal dissipation is consistent with the observed heat flow.
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Boiling water reactor safety systems are nuclear safety systems constructed within boiling water reactors in order to prevent or mitigate environmental and health hazards in the event of accident or natural disaster. Like the pressurized water reactor, the BWR reactor core continues to produce heat from radioactive decay after the fission reactions have stopped, making a core damage incident possible in the event that all safety systems have failed and the core does not receive coolant. Also like the pressurized water reactor, a boiling water reactor has a negative void coefficient, that is, the neutron (and the thermal) output of the reactor decreases as the proportion of steam to liquid water increases inside the reactor. However, unlike a pressurized water reactor which contains no steam in the reactor core, a sudden increase in BWR steam pressure (caused, for example, by the actuation of the main steam isolation valve (MSIV) from the reactor) will result in a sudden decrease in the proportion of steam to liquid water inside the reactor.
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Henri Becquerel had carried a sample of radium in his pocket and as a result he suffered a highly localized dose which resulted in a radiation burn. This injury resulted in the biological properties of radiation being investigated, which in time resulted in the development of medical treatment Ernest Rutherford, working in Canada and England, showed that radioactive decay can be described by a simple equation (a linear first degree derivative equation, now called first order kinetics), implying that a given radioactive substance has a characteristic "half-life" (the time taken for the amount of radioactivity present in a source to diminish by half). He also coined the terms alpha, beta and gamma rays, he converted nitrogen into oxygen, and most importantly he supervised the students who did the Geiger–Marsden experiment (gold foil experiment) which showed that the 'plum pudding model' of the atom was wrong. In the plum pudding model, proposed by J. J. Thomson in 1904, the atom is composed of electrons surrounded by a 'cloud' of positive charge to balance the electrons' negative charge.
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Century Arms FN FAL rifle built from an L1A1 parts kit SLRs could be modified at unit level to take two additional sighting systems. The first was the "Hythe sight," formally known as the "Conversion Kit, 7.62mm Rifle Sight, Trilux, L5A1" (L5A2 and L5A3 variants with different foresight inserts also existed) and intended for use in close range and in poor lighting conditions. The sight incorporated two rear sight aperture leaves and a permanently glowing tritium foresight insert for improved night visibility, which had to be replaced after a period of time due to radioactive decay. The first rear sight leaf had a 7 mm aperture which could be used alone for night shooting or the second leaf could be raised in front of it, superimposing a 2 mm aperture for day shooting.Army Code No 12258 (Revised 1977): User Handbook for Rifle, 7.62mm, L1A1 and 0.22-inch caliber, L12A1 Conversion Kit, 7.62mm Rifle The second sight was the L2A2 "Sight Unit, Infantry, Trilux" (SUIT), a 4× optical sight which mounted on a rail welded to a top cover.
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It is likely that the fissile material of an old bomb which is due for refitting will contain decay products of the plutonium isotopes used in it, these are likely to include U-236 from Pu-240 impurities, plus some U-235 from decay of the Pu-239; due to the relatively long half-life of these Pu isotopes, these wastes from radioactive decay of bomb core material would be very small, and in any case, far less dangerous (even in terms of simple radioactivity) than the Pu-239 itself. The beta decay of Pu-241 forms Am-241; the in-growth of americium is likely to be a greater problem than the decay of Pu-239 and Pu-240 as the americium is a gamma emitter (increasing external-exposure to workers) and is an alpha emitter which can cause the generation of heat. The plutonium could be separated from the americium by several different processes; these would include pyrochemical processes and aqueous/organic solvent extraction. A truncated PUREX type extraction process would be one possible method of making the separation.
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The episode describes how science, in particular the work of Clair Patterson (voiced in animated sequences by Richard Gere) in the middle of the 20th century, has been able to determine the age of the Earth. Tyson first describes how the Earth was formed from the coalescence of matter some millions of years after the formation of the Sun, and while scientists can examine the formations in rock stratum to date some geological events, these can only trace back millions of years. Instead, scientists have used the debris from meteor impacts, such as the Meteor Crater in Arizona, knowing that the material from such meteors coming from the asteroid belt would have been made at the same time as the Earth. Tyson then outlines the work Patterson did as a graduate under his adviser Harrison Brown to provide an accurate count of lead in zircon particles from Meteor Crater, and to work with similar results being collected by George Tilton on uranium counts; with the established half-life of uranium's radioactive decay to lead, this would be used to estimate the age of the Earth.
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In addition to chemical, nonradioactive carcinogens, tobacco and tobacco smoke contain small amounts of lead-210(210Pb) and polonium-210 (210Po) both of which are radioactive carcinogens. The presence of polonium-210 in mainstream cigarette smoke has been experimentally measured at levels of 0.0263–0.036 pCi (0.97–1.33 mBq), which is equivalent to about 0.1 pCi per milligram of smoke (4 mBq/mg); or about 0.81 pCi of lead-210 per gram of dry condensed smoke (30 Bq/kg). Research by NCAR radiochemist Ed Martell suggested that radioactive compounds in cigarette smoke are deposited in "hot spots" where bronchial tubes branch, that tar from cigarette smoke is resistant to dissolving in lung fluid and that radioactive compounds have a great deal of time to undergo radioactive decay before being cleared by natural processes. Indoors, these radioactive compounds can linger in secondhand smoke, and greater exposure would occur when these radioactive compounds are inhaled during normal breathing, which is deeper and longer than when inhaling cigarettes. Damage to the protective epithelial tissue from smoking only increases the prolonged retention of insoluble polonium-210 compounds produced from burning tobacco.
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It is a two-dimensional graphical representation in the Segrè-arrangement with the neutron number N on the abscissa and the proton number Z on the ordinate. Each nuclide is represented at the intersection of its respective neutron and proton number by a small square box with the chemical symbol and the nucleon number A. By columnar subdivision of such a field, in addition to ground states also nuclear isomers can be shown. The coloring of a field (segmented if necessary) shows in addition to the existing text entries the observed types of radioactive decay of the nuclide and a rough classification of their relative shares: stable, nonradioactive nuclides completely black, primordial radionuclides partially black, proton emission orange, alpha decay yellow, beta plus decay/electron capture red, isomeric transition (gamma decay, internal conversion) white, beta minus decay blue, spontaneous fission green, cluster emission violet, neutron emission light blue. For each radionuclide its field includes (if known) information about its half-life and essential energies of the emitted radiation, for stable nuclides and primordial radionuclides there are data on mole fraction abundances in the natural isotope mixture of the corresponding chemical element.
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Some processes involving neutrons are notable for absorbing or finally yielding energy — for example neutron kinetic energy does not yield heat immediately if the neutron is captured by a uranium-238 atom to breed plutonium-239, but this energy is emitted if the plutonium-239 is later fissioned. On the other hand, so-called delayed neutrons emitted as radioactive decay products with half-lives up to several minutes, from fission-daughters, are very important to reactor control, because they give a characteristic "reaction" time for the total nuclear reaction to double in size, if the reaction is run in a "delayed-critical" zone which deliberately relies on these neutrons for a supercritical chain-reaction (one in which each fission cycle yields more neutrons than it absorbs). Without their existence, the nuclear chain-reaction would be prompt critical and increase in size faster than it could be controlled by human intervention. In this case, the first experimental atomic reactors would have run away to a dangerous and messy "prompt critical reaction" before their operators could have manually shut them down (for this reason, designer Enrico Fermi included radiation- counter-triggered control rods, suspended by electromagnets, which could automatically drop into the center of Chicago Pile-1).
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