Certain metallic atoms, like silver and copper, diffuse through certain dielectric materials in a very similar way.
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Signaling molecules called morphogens then diffuse through the embryonic tissues, eventually defining the formation of body parts.
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That most likely means its quinones, although still involved in receiving electrons, are mobile and able to diffuse through the membrane.
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The drugs would then diffuse through a membrane into the inner ear—the same technique is used to treat ear infections.
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They found that by adding a bit of electric stimulation, the atoms diffuse through the electrode gap, like calcium ions between two neurons.
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But instead, Juno's measurements showed that heavy elements were diffuse through Jupiter's center, in an area up to half of the planet's radius.
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Word of the Day : allowing fluids or gases to pass or diffuse through _________ The word permeable has appeared in 21 articles on nytimes.
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The researchers found that these beetles have markedly thin cuticles compared with their surface-dwelling brethren, which would make it easier for oxygen to diffuse through it.
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Expensive consumer durables such as washing machines or passenger cars tend to diffuse through a population following an S-curve – slowly at first, then more rapidly, before tapering off as market saturation nears.
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Cucumbers and apples are both covered by a natural protective layer of wax, but once pesticides diffuse through that layer, rinsing them off becomes harder, said Dr. Jeffrey Jenkins, director of the National Pesticide Information Center.
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The PCT is highly permeable meaning it is easy for molecules to diffuse through it.
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Neurotransmitter released by pre-synaptic axons diffuse through the synaptic clef to bind to and open ion channels in post-synaptic axons.
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Testosterone is a steroid hormone; therefore it has the ability to diffuse through the amniotic fluid between fetuses. In addition, hormones can transfer among fetuses through the mother's bloodstream.
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As with many aquatic animals, most fish release their nitrogenous wastes as ammonia. Some of the wastes diffuse through the gills. Blood wastes are filtered by the kidneys. Saltwater fish tend to lose water because of osmosis.
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The intestine is lined by phagocytic cells which capture food particles that have already been partially digested by enzymes in the gut. Digestion is then completed within the phagocytic cells and the nutrients diffuse through the body.
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The wasps detect the hosts' prepupae by detecting volatile chemicals which diffuse through the prepupal integument and the cocoon. When the wasp detects these chemicals it drums its antennae, a sign that it has recognised a potential host.
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Pressure solution is a metamorphic process that requires a rock to be under strong pressure from one direction and in the presence of hot water. During this process mineral of the protolith partially dissolve, diffuse through the water and precipitate elsewhere.
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This gene encodes a member of the nucleoporin family. The protein is localized to the nuclear rim and is part of the nuclear pore complex (NPC). All molecules entering or leaving the nucleus either diffuse through or are actively transported by the NPC.
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The outer membrane is more permeable to hydrophilic substances, due to the presence of porins. Porins have threshold sizes of transportable molecules that depend on the type of bacteria and porin. Generally, only substances less than 600 Daltons in size can diffuse through.
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6th ed. New York: W.H. Freeman, 2013. 908. The cholesterol backbone consists of four hydrocarbon rings, three cyclohexane rings and one cyclopentane, that contribute to its insolubility in aqueous environments. However, the hydrophobic nature allows them to readily diffuse through the plasma membrane of cells.
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What happens is that the chemical process (diffusion) responsible for transporting active chemicals around the battery progresses at a finite rate, so draining the battery quickly causes the voltage to reach the cutoff level prematurely before all the active material in the battery is used up. Given time, the active material will diffuse through the cell (for example, sulfuric acid in a lead-acid battery will diffuse through the porous lead plates and separators) and be available for further reaction. For example, consider a battery with a capacity of 200Ah at the C20 rate (C20 means the 20-hour rate - i.e. the rate that will fully discharge the battery in 20 hours - which in this case is 10 Amps).
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The absorption of hydrogen is reversible and is highly selective. Industrially, a palladium-based diffuser separator is used. Impure gas is passed through tubes of thin walled silver-palladium alloy as protium and deuterium readily diffuse through the alloy membrane. The gas that comes through is pure and ready for use.
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Drugs diffuse through capillary walls in the same manner as endogenous molecules. One of the most important examples of this is drug diffusion across the blood brain barrier. The blood brain barrier consists of a bed of continuous capillaries. Typically only small hydrophobic molecules are able to diffuse across the blood brain barrier.
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Lycoperdon perlatum Enzymes are manufactured close to the hyphal tip. Some are packaged in vesicles associated with the Golgi and then delivered to the hyphal tip. The contents are released at the tip. Some enzymes are actively excreted through the plasma membrane, where they diffuse through or act in the cell wall.
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In sharks, this includes a rectal gland that secretes salt to help the animal maintain osmotic balance with the seawater. The gland somewhat resembles a caecum in structure, but is not a homologous structure. As with many aquatic animals, most fish release their nitrogenous wastes as ammonia. Some of the wastes diffuse through the gills.
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Yuri Gamalei first described the different types of phloem-loading mechanisms in 1989, correlating loading strategy with the leaf's anatomy. He found that plasmodesmatal abundance in the minor veins of leaves was correlated with a plant's loading strategy. Plasmodesmata allow solutes to diffuse through the symplast. Thus, plants with a lot of plasmodesmata are generally passive loaders.
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The molecular weight of FAM76A is 38.4 kDa, making it possible for this protein to diffuse through nuclear pores. The isoelectric point is 9.28. FAM76A does not have any significant positive, negative, or mixed charge clusters. In addition, FAM76A does not have any predicted hydrophobic or transmembrane segments, suggesting that this protein is not found within the cell membrane.
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Penetrating solutes can diffuse through the cell membrane, causing momentary changes in cell volume as the solutes "pull" water molecules with them. Non-penetrating solutes cannot cross the cell membrane; therefore, the movement of water across the cell membrane (i.e., osmosis) must occur for the solutions to reach equilibrium. A solution can be both hyperosmotic and isotonic.
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These vacant sites are subsequently filled by atoms from the lead excess and the valence electrons of these vacant atoms will diffuse through crystal. Common p-type doping agents are Na2Te, K2Te and Ag2Te. They substitute for Te and create vacant uncharged Te sites. These sites are filled by Te atoms which are ionized to create additional positive holes.
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The initial members were Richard Ehrich, and Frederick Reines. joined it in the early spring of 1944. The group's main task was to estimate the rate at which neutrons would diffuse through the explosive core of the bomb during nuclear fission. Somewhat facetiously Feynman later claimed that the work done at Los Alamos was mostly engineering, not science.
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Pre-urine is formed in the tubules, when nitrogenous waste and electrolytes are transported through the tubule walls. Wastes such as urea and amino acids are thought to diffuse through the walls, while ions such as sodium and potassium are transported by active pump mechanisms. Water follows thereafter. The pre-urine, along with digested food, merge in the hindgut.
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This study was later expanded to demonstrate that several salts (for example KCl, MgCl2) diffuse through the graphene oxide membrane if it is immersed in water solution. Graphene oxide membranes are actively being studied for their applications to water desalination. Retention rates over 90% were reported in a 1960 study for NaCl solutions using stabilized graphene oxide membranes in reverse osmosis setup.
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Olfactory transduction begins with the movement of odorants from the air phase to the aqueous phase in the olfactory mucus. Odorants are transported by odorant binding proteins or diffuse through the mucus and reach the cilia on the dendritic ends of bipolar receptor neurons. Stimulation causes action potentials to be initiated and the signals are sent to the brain via the olfactory fila.
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Once palytoxin is bound to the pump, it flips constantly between open and normal conformations. The open conformation is more likely (over 90% probability). If palytoxin detaches, the pump will return to closed conformation. In open conformation, millions of ions diffuse through the pump per second, whereas only about one hundred ions per second are transported through a normally functioning transporter.
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A simplified depiction of the gradients of nodal and lefty in the mouse embryo. Lefty proteins function as an antagonist of the Nodal Signaling pathway. Nodal is another signaling protein which is responsible for gastrulation, left-right patterning and induction of the primitive node. As NODAL protein diffuse through an embryo, it triggers Nodal Signaling within tissues with the required receptors and coreceptors.
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At initial condition, the nodes carry a label that denotes the community they belong to. Membership in a community changes based on the labels that the neighboring nodes possess. This change is subject to the maximum number of labels within one degree of the nodes. Every node is initialized with a unique label, then the labels diffuse through the network.
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Water-soluble hormones include glycoproteins, catecholamines, and peptide hormones composed of polypeptides, e.g. thyroid-stimulating hormone, follicle- stimulating hormone, luteinizing hormone and insulin. These molecules are not lipid-soluble and therefore cannot diffuse through cell membranes. Consequently, receptors for peptide hormones are located on the plasma membrane because they have bound to a receptor protein located on the plasma membrane.
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The average distance an exciton can diffuse through a material before annihilation by recombination is the exciton diffusion length. This is short in polymers, on the order of 5–10 nanometers. The time scale for radiative and non-radiative decay is from 1 picosecond to 1 nanosecond. Excitons generated within this length close to an acceptor would contribute to the photocurrent.
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Seelig, A., Gottschlich, R., & Devant, R. M. (1994). A Method to Determine the Ability of Drugs to Diffuse through the Blood- Brain Barrier. Proceedings of the National Academy of Sciences of the United States of America, 91(1), 68-72. They then set out to analyze the above factors to determine what is necessary to transverse the blood–brain barrier.
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The finding suggests that the AAV-mediated expression of angiostatic factors can be implemented to treat NV. This approach could be useful as an alternative to frequent injections of recombinant protein into the eye. In addition, PEDF and sFlt-1 may be able to diffuse through sclera tissue, allowing for the potential to be relatively independent of the intraocular site of administration.
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This allows trainee surgeons to track their progress objectively. The pig eyes are infused with diluted fluorescein to trace outflow. Fluorescein can diffuse through the trabecular meshwork, which allows flow speeds to be estimated in non-treated parts of the eye. A disadvantage of this method is that over time, diffusion also takes place through intact vascular endothelium, staining the extravascular space.
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This gene encodes a member of the nucleoporin family. The protein is localized to the nuclear rim and is an essential component of the nuclear pore complex (NPC). All molecules entering or leaving the nucleus either diffuse through or are actively transported by the NPC. Alternate transcriptional splice variants of this gene have been observed but have not been thoroughly characterized.
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Highly crosslinked resins typically swell much less than the latter. The property that allows these types of resins to work efficiently lies in their porous properties. The reacting compound can diffuse through the porous layer of the resin to converge with the scavenger's functional group. These types of resins are utilized in situations where swelling of the resins may cause a physical barrier to reaction purification.
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Hydrolysis follows first order kinetic, with t1/2 = 7.5 hours at 25 °C and 3.1 hours at 40 °C. TEPP and most of the other organophosphates are detoxified by hydrolysis. Due to this oxidation and hydrolysis the compound gets more polar, which makes it much easier to excrete via the urine. Note that TEPP is a lipophilic compound, so it can diffuse through tissues easily.
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A continuous, tightly spaced endothelial cell lining only permits the diffusion of small molecules. Larger molecules and blood cells require adequate space between cells or holes in the lining. The high resistivity of a cellular membrane prevents the diffusion of ions without a membrane transport protein. The hydrophobicity of an endothelial cell surface determines whether water or lipophilic molecules will diffuse through the capillary lining.
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The other isotopes have half-lives from a few days to fractions of a second. Almost all caesium produced from nuclear fission comes from beta decay of originally more neutron-rich fission products, passing through isotopes of iodine then isotopes of xenon. Because these elements are volatile and can diffuse through nuclear fuel or air, caesium is often created far from the original site of fission.
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Dissolved materials are transported in the blood much faster than they would be distributed by diffusion alone. From the systemic capillaries the dissolved gases diffuse through the cell membranes and into the tissues, where it may eventually reach equilibrium. The greater the blood supply to a tissue, the faster it will reach equilibrium with gas at the new partial pressure. This equilibrium is called saturation.
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Nanoparticles 40 nm in diameter and smaller have been successful in penetrating the skin. Research confirms that nanoparticles larger than 40 nm do not penetrate the skin past the stratum corneum. Most particles that do penetrate will diffuse through skin cells, but some will travel down hair follicles and reach the dermis layer. The permeability of skin relative to different shapes of nanoparticles has also been studied.
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For steel, the first step will be the volatilization of the inhibitor into the airspace. This may entail simple evolution of the molecule or the chemical may disassociate first and then volatilize. (15) The molecules will then diffuse through the enclosed airspace until some of the molecules will reach the metallic surface to be protected. There are two likely paths once the molecules reach the metallic surface.
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For highway electric vehicles, rapid charging is necessary for charging in a reasonable time. A rechargeable battery cannot be recharged at an arbitrarily high rate. The internal resistance of the battery will produce heat, and excessive temperature rise will damage or destroy a battery. For some types, the maximum charging rate will be limited by the speed at which active material can diffuse through a liquid electrolyte.
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Normally, copper contains small inclusions of copper(I) oxide. Hydrogen diffuses through the metal and reacts with the oxide, reducing it to copper and yielding water. The water molecules however can not diffuse through the metal, are trapped in the location of the inclusion, and cause embrittlement. As copper(I) oxide bonds well to the glass, it is often used for combined glass-metal devices.
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After neurotransmitters are synthesized, they are packaged and stored in vesicles. These vesicles are pooled together in terminal boutons of the presynaptic neuron. When there is a change in voltage in the terminal bouton, voltage-gated calcium channels embedded in the membranes of these boutons become activated. These allow Ca2+ ions to diffuse through these channels and bind with synaptic vesicles within the terminal boutons.
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Nucleoporin p58/p45 is a protein that in humans is encoded by the NUPL1 gene. This gene encodes a member of the nucleoporin family that shares 87% sequence identity with rat nucleoporin p58. The protein is localized to the nuclear rim and is a component of the nuclear pore complex (NPC). All molecules entering or leaving the nucleus either diffuse through or are actively transported by the NPC.
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An alternative to using a glovebox for air sensitive work is to employ Schlenk methods using a Schlenk line. One disadvantage of working in a glovebox is that organic solvents will attack the plastic seals. As a result, the box will start to leak and water and oxygen can then enter the box. Another disadvantage of a glovebox is that oxygen and water can diffuse through the plastic gloves.
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Steroid hormones such as cortisol and aldosterone, as well as other small lipid-soluble molecules involved in intercellular signaling, can diffuse through the cell membrane and into the cytoplasm, where they bind nuclear receptor proteins that are trafficked into the nucleus. There they serve as transcription factors when bound to their ligand; in the absence of a ligand, many such receptors function as histone deacetylases that repress gene expression.
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When these two cells interact, it allows calcium to diffuse through the TRPV2 channel. TRPV2 mRNA has been detected in CD4+ and CD8+ T cells as well as in human B lymphocytes. TRPV2 is one type of ion channel that directs T cell activation, proliferation, and defense mechanisms. If the TRPV2 channel were absent or not functioning properly in T cells, T cell receptor signaling would not be optimal.
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The electrolyte must be dense enough that the steam and hydrogen gas cannot diffuse through and lead to the recombination of the H2 and O2−. At the electrolyte-anode interface, the oxygen ions are oxidized to form pure oxygen gas, which is collected at the surface of the anode.Ni, M., Leung, M. K. H., & Leung, D. Y. C. (2008). Technological development of hydrogen production by solid oxide electrolyzer cell (SOEC).
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Karyopherins release of their cargo is driven by Ran, a G protein. Ran is small enough that it can diffuse through nuclear pores down its concentration gradient without interacting with nucleoporins. Ran will bind to either GTP or GDP and has the ability to change a karyopherin's affinity for its cargo. Inside the nucleus, RanGTP causes an importin karyopherin to change conformation, allowing its cargo to be released.
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In some fish, a rete mirabile fills the swim bladder with oxygen. A countercurrent exchange system is utilized between the venous and arterial capillaries. By lowering the pH levels in the venous capillaries, oxygen unbinds from blood hemoglobin. This causes an increase in venous blood oxygen concentration, allowing the oxygen to diffuse through the capillary membrane and into the arterial capillaries, where oxygen is still sequestered to hemoglobin.
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Coatings allow the retention and improvement of bulk properties of a material. They can provide protection for a substrate from environmental exposure. Thus, when damage occurs (often in the form of microcracks), environmental elements like water and oxygen can diffuse through the coating and may cause material damage or failure. Microcracking in coatings can result in mechanical degradation or delamination of the coating, or in electrical failure in fibre-reinforced composites and microelectronics, respectively.
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In some fish, a rete mirabile fills the swim bladder with oxygen, increasing the fish's buoyancy. A countercurrent exchange system is utilized between the venous and arterial capillaries. Lowering the pH levels in the venous capillaries causes oxygen to unbind from blood hemoglobin. This causes an increase in venous blood oxygen partial pressure, allowing the oxygen to diffuse through the capillary membrane and into the arterial capillaries, where oxygen is still sequestered to hemoglobin.
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Poisoning often involves compounds that chemically bond to a catalyst's active sites. Poisoning decreases the number of active sites, and the average distance that a reactant molecule must diffuse through the pore structure before undergoing reaction increases as a result.Charles G. Hill, An Introduction To Chemical Engine Design, John Wiley & Sons Inc., 1977 , page 464 As a result, poisoned sites can no longer accelerate the reaction with which the catalyst was supposed to catalyze.
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John Northrup Shive (February 22, 1913 - June 1, 1984) was an American physicist and inventor. He made notable contributions in electronic engineering and solid-state physics during the early days of transistor development at Bell Laboratories. In particular, he produced experimental evidence that holes could diffuse through bulk germanium, and not just along the surface as previously thought. This paved the way from Bardeen and Brattain's point-contact transistor to Shockley's more-robust junction transistor.
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Human skin has a low permeability; that is, most foreign substances are unable to penetrate and diffuse through the skin. Skin's outermost layer, the stratum corneum, is an effective barrier to most inorganic nanosized particles. This protects the body from external particles such as toxins by not allowing them to come into contact with internal tissues. However, in some cases it is desirable to allow particles entry to the body through the skin.
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Nabarro–Herring creep is a mode of deformation of crystalline materials (and amorphous materials) that occurs at low stresses and held at elevated temperatures in fine-grained materials. In Nabarro–Herring creep (NH creep), atoms diffuse through the crystals, and the creep rate varies inversely with the square of the grain size so fine-grained materials creep faster than coarser-grained ones.Goldsby, D. (2009). Superplastic flow of ice relevant to glacier and ice-sheet mechanics.
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When the extracellular environment is more acidic than the neutral pH within the cell, certain acids will exist in their neutral form and will be membrane soluble, allowing them to cross the phospholipid bilayer. Acids that lose a proton at the intracellular pH will exist in their soluble, charged form and are thus able to diffuse through the cytosol to their target. Ibuprofen, aspirin and penicillin are examples of drugs that are weak acids.
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Reuptake is necessary for normal synaptic physiology because it allows for the recycling of neurotransmitters and regulates the level of neurotransmitter present in the synapse, thereby controlling how long a signal resulting from neurotransmitter release lasts. Because neurotransmitters are too large and hydrophilic to diffuse through the membrane, specific transport proteins are necessary for the reabsorption of neurotransmitters. Much research, both biochemical and structural, has been performed to obtain clues about the mechanism of reuptake.
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H+ ions diffusing in an O2- lattice of superionic ice Atomic diffusion is a diffusion process whereby the random thermally-activated movement of atoms in a solid results in the net transport of atoms. For example, helium atoms inside a balloon can diffuse through the wall of the balloon and escape, resulting in the balloon slowly deflating. Other air molecules (e.g. oxygen, nitrogen) have lower mobilities and thus diffuse more slowly through the balloon wall.
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Fogponics is a derivation of aeroponics wherein the nutrient solution is aerosolized by a diaphragm vibrating at ultrasonic frequencies. Solution droplets produced by this method tend to be 5–10 µm in diameter, smaller than those produced by forcing a nutrient solution through pressurized nozzles, as in aeroponics. The smaller size of the droplets allows them to diffuse through the air more easily, and deliver nutrients to the roots without limiting their access to oxygen.
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In contrast, paracrine transmission (volume transmission) involves neurotransmitters released by synaptic boutons, which then diffuse through the extra-cellular medium until they reach their receptors, which may be distant. Nicotinic receptors can also be found in different synaptic locations; for example the muscle nicotinic receptor always functions post-synaptically. The neuronal forms of the receptor can be found both post-synaptically (involved in classical neurotransmission) and pre-synaptically where they can influence the release of multiple neurotransmitters.
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The formation of L-dopa from L-tyrosine is catalyzed by the enzyme tyrosine hydroxylase. The third stage is the formation of dopamine by removing the carboxylic acid group from L-dopa, catalysed by the enzyme dopa decarboxylase. Levodopa is also too polar to cross the blood brain barrier but it happens to be an amino acid so it has a specialized transporter called L-type amino acid transporter or LAT-1 that helps it diffuse through the barrier.
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The high abundance of ladderane lipids in the anammoxosome results in an exceptionally dense membrane with reduced permeability. The reduced permeability may decrease the passive diffusion of protons across the membrane that would dissipate the electrochemical gradient. This would be especially detrimental to anammox bacteria, due to the relatively slow anammox metabolism. The decreased permeability has also been hypothesized to sequester the highly toxic and mutagenic intermediates, hydrazine and hydroxylamine, which can readily diffuse through biomembranes.
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Hemorrhagic infarcts are infarcts commonly caused by occlusion of veins, with red blood cells entering the area of the infarct, or an artery occlusion of an organ with collaterals or dual circulation. This is commonly seen in brain, lungs, and the GI tract, areas referred to as having "loose tissue," or dual circulation. Loose-textured tissue allows red blood cells released from damaged vessels to diffuse through the necrotic tissue. White infarcts can become hemorrhagic with reperfusion.
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Ions cannot passively diffuse through the gastrointestinal tract because the epithelial cell membrane is made up of a phospholipid bilayer. The bilayer is made up of two layers of phospholipids in which the charged hydrophilic heads face outwards and the non-charged hydrophobic fatty acid chains are in the middle of the layer. The uncharged fatty acid chains repel ionized, charged molecules. This means that the ionized molecules cannot pass through the intestinal membrane and be absorbed.
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These flexible parts form unfolded, or disordered segments without a fixed structure. They form a mass of chains which allow smaller molecules to diffuse through, but exclude large hydrophilic macromolecules. These large molecules are only able to cross a nuclear pore if they are accompanied by a signaling molecule that temporarily interacts with a nucleoporin's FG-repeat segment. FG-nucleoporins also contain a globular portion that serves as an anchor for attachment to the nuclear pore complex.
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The membrane potential alters the conformation of the channel proteins, regulating their opening and closing. Cell membranes are generally impermeable to ions, thus they must diffuse through the membrane through transmembrane protein channels. They have a crucial role in excitable cells such as neuronal and muscle tissues, allowing a rapid and co-ordinated depolarization in response to triggering voltage change. Found along the axon and at the synapse, voltage-gated ion channels directionally propagate electrical signals.
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The apoplast is also a site for cell-to-cell communication. During local oxidative stress, hydrogen peroxide and superoxide anions can diffuse through the apoplast and transport a warning signal to neighbouring cells. In addition, a local alkalinization of the apoplast due to such a stress can travel within minutes to the rest of the plant body via the xylem and trigger systemic acquired resistance. The apoplast also plays an important role in resistance to aluminium toxicity and resistance.
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This can be accomplished via dechlorination towers with acid and sodium bisulfite addition. Failure to remove chlorine can result in damage to the ion exchange units. Brine should be monitored for accumulation of both chlorate anions and sulfate anions, and either have a treatment system in place, or purging of the brine loop to maintain safe levels, since chlorate anions can diffuse through the membranes and contaminate the caustic, while sulfate anions can damage the anode surface coating.
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The theory of the Brownian motion and the atomistic backgrounds of diffusion were developed by Albert Einstein. The concept of diffusion is typically applied to any subject matter involving random walks in ensembles of individuals. Biologists often use the terms "net movement" or "net diffusion" to describe the movement of ions or molecules by diffusion. For example, oxygen can diffuse through cell membranes so long as there is a higher concentration of oxygen outside the cell.
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The ceramics used in SOFCs do not become electrically and ionically active until they reach very high temperature and as a consequence, the stacks have to run at temperatures ranging from 500 to 1,000 °C. Reduction of oxygen into oxygen ions occurs at the cathode. These ions can then diffuse through the solid oxide electrolyte to the anode where they can electrochemically oxidize the fuel. In this reaction, a water byproduct is given off as well as two electrons.
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When steel is heated to an austenizing temperature, the carbon begins to diffuse through the iron. The higher the temperature; the greater the rate of diffusion. At such high temperatures, carbon readily combines with oxygen to form carbon dioxide, so the carbon can easily diffuse out of the steel and into the surrounding air. By the end of a blacksmithing job, the steel will be of a lower carbon content than it was prior to heating.
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The laboratories at the University of Liverpool and the University of Oxford experimented with different types of isotope separation. Chadwick's group at Liverpool dealt with thermal diffusion, which worked based on the principle that different isotopes of uranium diffuse at different speeds because of the equipartition theorem. Franz Simon's group at Oxford investigated the gaseous diffusion of isotopes. This method works on the principle that at differing pressures uranium 235 would diffuse through a barrier faster than uranium 238.
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Pellistors measure essentially all combustible gases, but they are more sensitive to smaller molecules that diffuse through the sinter more quickly. The measureable concentration ranges are typically from a few hundred ppm to a few volume percent. Such sensors are inexpensive and robust, but require a minimum of a few percent oxygen in the atmosphere to be tested and they can be poisoned or inhibited by compounds such as silicones, mineral acids, chlorinated organic compounds, and sulfur compounds.
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Water molecules freely diffuse through the plasma membrane in both directions, and as the rate of water diffusion is the same in each direction, the cell will neither gain nor lose water. An iso-osmolar solution can be hypotonic if the solute is able to penetrate the cell membrane. For example, an iso-osmolar urea solution is hypotonic to red blood cells, causing their lysis. This is due to urea entering the cell down its concentration gradient, followed by water.
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Ranirestat is aldose reductase inhibitor that acts by reducing sorbitol accumulation in cells. Aldose reductase is an enzyme that catalyzes one of the steps in sorbitol (polyol) pathway which is responsible for formation of fructose from glucose. Aldose reductase activity is increased, parallel to glucose blood levels, in tissues that are not insulin sensitive, including lenses, peripheral nerves and renal glomeruli. Sorbitol does not diffuse through cell membranes easily and therefore accumulates in these tissues, causing osmotic damage, leading to retinopathy and neuropathy.
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The presumptive test to detect saliva is the alpha-amylase test also known as the Phadebas Test. This detection technique is based on the activity of the enzyme alpha-amylase which breaks down starches from food into smaller oligosaccharide molecules, starting digestion in the mouth. Using a petri dish gel, the saliva sample is added and allowed to diffuse through the gel overnight. Visualization is accomplished by adding iodine to the gel which stains the starch in the gel blue.
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Alpha particles emitted by polonium will damage organic tissue easily if polonium is ingested, inhaled, or absorbed, although they do not penetrate the epidermis and hence are not hazardous as long as the alpha particles remain outside the body. Wearing chemically resistant and intact gloves is a mandatory precaution to avoid transcutaneous diffusion of polonium directly through the skin. Polonium delivered in concentrated nitric acid can easily diffuse through inadequate gloves (e.g., latex gloves) or the acid may damage the gloves.
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T3 and T4 bind to nuclear receptors (thyroid hormone receptors). T3 and T4, although being lipophilic, are not able to passively diffuse through the phospholipid bilayers of target cells, instead relying on transmembrane iodothyronine transporters. The lipophilicity of T3 and T4 requires their binding to the protein carrier thyroid-binding protein (TBG) (thyroxine-binding globulins, thyroxine binding prealbumins, and albumins) for transport in the blood. The thyroid receptors bind to response elements in gene promoters, thus enabling them to activate or inhibit transcription.
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The fourth generation cephalosporins have greater activity against gram-negative bacteria than the second and third generation. This difference is attributed to them being dipolar ionic zwitterion compounds. The C-7 side chain is similar to third generation cephalosporins usually containing iminomethoxy-aminothiazole group or in the case of Cefclidine an aminothiadiazole. Because of the positively charged quaternary nitrogen in the C-3 side chain fourth generation cephalosporins can diffuse through the gram-negative bacterial membrane more readily than earlier cephalosporins.
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Not only did this ensure a higher salary, but also greater social prestige, visibly distinguished by dress. This institutionalized distinction of scholar- officials by dress included the type and even color of traditional silken robes, hats, and girdles, demarcating that scholar-official's level of administrative authority.Gernet, 127–128. This rigid code of dress was especially enforced during the beginning of the dynasty, although the prestigious clothing color of purple slowly began to diffuse through the ranks of middle and low grade officials.Gernet, 128.
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Most toolkit genes are parts of signalling pathways: they encode transcription factors, cell adhesion proteins, cell surface receptor proteins and signalling ligands that bind to them, and secreted morphogens that diffuse through the embryo. All of these help to define the fate of undifferentiated cells in the embryo. Together, they generate the patterns in time and space which shape the embryo, and ultimately form the body plan of the organism. Among the most important toolkit genes are the Hox genes.
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From The Absolute proceeds the Supreme Being, at the dawn of manifestation: this is The One, the "Great Architect of the Universe". The first aspect of the Supreme Being may be characterized as Power, from this proceeds the second aspect, the Word, and from both of these proceeds the third, aspect, Motion. From the threefold Supreme Being proceed the "seven Great Logoi". They contain within Themselves all the great Hierarchies which differentiate more and more as they diffuse through the various Cosmic Planes.
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When the condenser is located above the evaporator in a gravitational field, gravity can return the liquid. In this case, the heat pipe is a thermosiphon. Finally, rotating heat pipes use centrifugal forces to return liquid from the condenser to the evaporator. Heat pipes contain no mechanical moving parts and typically require no maintenance, though non- condensable gases that diffuse through the pipe's walls, resulting from breakdown of the working fluid or as impurities extant in the material, may eventually reduce the pipe's effectiveness at transferring heat.
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These diffuse through a stagnant boundary layer that exists over the heated substrate, after which they dissociate into the atomic group III elements. These atoms then migrate to the appropriate lattice site and deposit epitaxially by associating with a group V atom that was derived from the thermal decomposition of the hydrides. The growth rate here is usually limited by the diffusion rate of the group III alkyls through the boundary layer. Gas phase reactions between the reactants have also been observed in this process.
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Corrosion protection is supplied via a system of dispensers that have been attached to ports that have been installed on the tank roof. (Ports and shut-off valves are installed when the tank is out of service). Bottles containing the VCI are placed in the dispenser and the shut off valves are opened. The VCI has a high vapor pressure such that the inhibitor will saturate the airspace within the dispenser and then will diffuse through the open port into the storage tank headspace.
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Heat fixation cannot be used in the capsular stain method as heat fixation will shrink or destroy the capsule (glycocalyx) and cannot be seen in stains. Immersion: The sample of tissue is immersed in fixative solution of volume at a minimum of 20 times greater than the volume of the tissue to be fixed. The fixative must diffuse through the tissue to fix, so tissue size and density, as well as type of fixative must be considered. This is a common technique for cellular applications.
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Increasing gas pressure improves the energy density by volume making for smaller container tanks. Tanks made of carbon and glass fibres reinforcing plastic as fitted in Toyota Marai and Kenworth trucks are required to meet safety standards. Few materials are suitable for tanks as hydrogen being a small molecule tends to diffuse through many liner materials and hydrogen embrittlement causes weakening in some types of metal containers. The most common on board hydrogen storage in today's 2020 vehicles is hydrogen at pressure 700bar = 70MPa.
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This combined with the microbubbles allows for a very specific area of diffusion for the microbubbles, because they can only diffuse where the ultrasound is disrupting the barrier. The hypothesis and usefulness of these is the possibility of loading a microbubble with an active drug to diffuse through the barrier and target a specific area. There are several important factors in making this a viable solution for drug delivery. The first is that the loaded microbubble must not be substantially greater than the unloaded bubble.
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Their target, aldose reductase, is an enzyme that is normally present in many other parts of the body, and catalyzes one of the steps in the sorbitol(polyol) pathway that is responsible for fructose formation from glucose. Aldose reductase activity increases as the glucose concentration rises in diabetes in those tissues that are not insulin sensitive, which include the lenses, peripheral nerves and glomerulus. Sorbitol does not diffuse through cell membranes easily and therefore accumulates, causing osmotic damage which leads to retinopathy and neuropathy.
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Even larger crystals can be obtained by slowing down the common reaction. A simple setup is to submerge two beakers containing the concentrated reactants in a larger container of water, taking care to avoid currents. As the two substances diffuse through the water and meet, they slowly react and deposit the iodide in the space between the beakers. Another similar method is to react the two substances in a gel medium, that slows down the diffusion and supports the growing crystal away from the container's walls.
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Continuous capillaries are continuous in the sense that the endothelial cells provide an uninterrupted lining, and they only allow smaller molecules, such as water and ions, to pass through their intercellular clefts. Lipid-soluble molecules can passively diffuse through the endothelial cell membranes along concentration gradients. Continuous capillaries can be further divided into two subtypes: :# Those with numerous transport vesicles, which are found primarily in skeletal muscles, fingers, gonads, and skin. :# Those with few vesicles, which are primarily found in the central nervous system.
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Some ion channels are voltage gated, meaning that they can be switched between open and closed states by altering the voltage difference across the membrane. Others are chemically gated, meaning that they can be switched between open and closed states by interactions with chemicals that diffuse through the extracellular fluid. The ion materials include sodium, potassium, chloride, and calcium. The interactions between ion channels and ion pumps produce a voltage difference across the membrane, typically a bit less than 1/10 of a volt at baseline.
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As IAAH is lipophilic, it can easily cross the lipid bilayer. ::`IAAH` `IAA− + H+`, where `IAAH` = indole-3-acetic acid; `IAA−` = its conjugate base The inside of cells (pH ~ 7) is less acidic than the outside (the apoplast; pH ~ 5.5). So outside the cell a significant portion (17%) of the IAA molecules remain un-dissociated (proton-associated). This portion of auxin molecules is charge-neutral and therefore it is able to diffuse through the lipophilic lipid bilayer (lipid bilayer being constituent of cell membrane) into the cells.
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These tightly packed, rigid structures decrease the gas permeability of the polymers by restricting the rate at which the gas can diffuse through the membrane. However, this effect is much stronger on large gas molecules such as oxygen and nitrogen compared to small gas molecules. This effect results in an increased permselectivity where the membrane will restrict the transport of large gas molecule, favoring that of small gas molecules. These gas transport membranes must be ultra-thin and are most commonly obtained via a phase inversion process.
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When a cell or vesicle with a high interior salt concentration is placed in a solution with a low salt concentration it will swell and eventually burst. Such a result would not be observed unless water was able to pass through the bilayer with relative ease. The anomalously large permeability of water through bilayers is still not completely understood and continues to be the subject of active debate. Small uncharged apolar molecules diffuse through lipid bilayers many orders of magnitude faster than ions or water.
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The committee consulted with Peierls and Simon over the separation method and concluded that "ordinary" gaseous diffusion was the best method to pursue. This relies on Graham's Law, the fact that the gases diffuse through porous materials at rates determined by their molecular weight. Francis William Aston applied this method in 1913 when he separated two isotopes of neon by diffusing a sample thousands of times through a pipe clay. Thick materials like pipe clay proved too slow to be efficient on an industry scale.
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Thus, if the molecular weight of one gas is four times that of another, it would diffuse through a porous plug or escape through a small pinhole in a vessel at half the rate of the other (heavier gases diffuse more slowly). A complete theoretical explanation of Graham's law was provided years later by the kinetic theory of gases. Graham's law provides a basis for separating isotopes by diffusion--a method that came to play a crucial role in the development of the atomic bomb.R.H. Petrucci, W.S. Harwood and F.G. Herring, General Chemistry (8th ed.
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In these cases the movement of molecules is best described by pressure-driven convective flow through capillaries, which is quantified by Darcy's law. However, the more general model in gas applications is the solution-diffusion (d) where particles are first dissolved onto the membrane and then diffuse through it both at different rates. This model is employed when the pores in the polymer membrane appear and disappear faster relative to the movement of the particles. In a typical membrane system the incoming feed stream is separated into two components: permeant and retentate.
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Dissolved phase models are of two main groups. Parallel compartment models, where several compartments with varying rates of gas absorption (half time), are considered to exist independently of each other, and the limiting condition is controlled by the compartment which shows the worst case for a specific exposure profile. These compartments represent conceptual tissues and are not intended to represent specific organic tissues, merely to represent the range of possibilities for the organic tissues. The second group uses serial compartments, where gas is assumed to diffuse through one compartment before it reaches the next.
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A typical dive computer has an 8–12 tissue model, with half times varying from 5 minutes to 400 minutes. The Bühlmann tables use an algorithm with 16 tissues, with half times varying from 4 minutes to 640 minutes. Tissues may be assumed to be in series, where dissolved gas must diffuse through one tissue to reach the next, which has different solubility properties, in parallel, where diffusion into and out of each tissue is considered to be independent of the others, and as combinations of series and parallel tissues, which becomes computationally complex.
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Gold-plated electrical connectors Gold plating is often used in electronics, to provide a corrosion-resistant electrically conductive layer on copper, typically in electrical connectors and printed circuit boards. With direct gold-on-copper plating, the copper atoms tend to diffuse through the gold layer, causing tarnishing of its surface and formation of an oxide and/or sulphide layer. A layer of a suitable barrier metal, usually nickel, is often deposited on the copper substrate before the gold plating. The layer of nickel provides mechanical backing for the gold layer, improving its wear resistance.
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After that, the silicon is thermally oxidized, so the oxide grows in regions where there is no Si3N4 and the growth is between 0.5 and 1.0 μm thick. Since the oxidizing species such as water or oxygen are unable to diffuse through the mask, the nitride prevents the oxidation. Next, the etching process is used to etch the wafer and leave a small amount of oxide in the active areas. In the end, CMP is used to polish the SiO2 overburden with an oxide on the active area.
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As a result, the presence of superoxide in surface waters has been known to result in an increase of reduced iron. This, in turn, serves to enhance the availability of iron to phytoplankton whose growth is often limited by this key nutrient. As a charged radical species, superoxide is unlikely to significantly affect an organism's cellular function since it is not able to easily diffuse through the cell membrane. Instead, its potential toxicity lies in its ability to react with extracellular surface proteins or carbohydrates to inactivate their functions.
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Ideally, this should be high enough to keep the biofilm in the sand layer wet and allow oxygen to diffuse through the standing water to the biolayer. The pause period allows microorganisms in the biolayer to consume the pathogens and nutrients in the water. The rate of flow through the filter is restored as they are consumed. If the pause period is too long, the biolayer will consume all of the pathogens and nutrients and will die, reducing the efficiency of the filter when it is used again.
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By application of P11-4 on the tooth surface, the peptide diffuse through the intact hypomineralized plate into the early caries lesion body and start, due to the low pH in such a lesion, to self-assemble generating a peptide scaffold mimicking the enamel matrix. Around the newly formed matrix de-novo enamel-crystals are formed from calcium phosphate present in saliva. Through the remineralization caries activity is significantly reduced in comparison with a fluoride treatment alone. In aqueous oral care gels the peptide is present as matrix.
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BPA is an endocrine disruptor, meaning BPA has a similar structure to oestrogen (ligand) and can bind to the oestrogen receptor ERα and ERβ and activate it. Oestrogen is hydrophobic and is able to diffuse through the plasma membrane and into the target cell. Oestradiol binding to the oestrogen receptor releases the heat shock protein from the ligand binding domain of the receptor causing dimerization. The nuclear localisation signal targets the ligand-receptor complex to the nucleus where it can bind oestrogen response elements within the promoter of target genes on DNA.
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The pattern of fluoride release from glass ionomer cement is characterised by an initial rapid release of appreciable amounts of fluoride, followed by a taper in the release rate over time. An initial fluoride “burst” effect is desirable to reduce the viability of remaining bacteria in the inner carious dentin, hence, inducing enamel or dentin remineralization. The constant fluoride release during the following days are attributed to the fluoride ability to diffuse through cement pores and fractures. Thus, continuous small amounts of fluoride surrounding the teeth reduces demineralization of the tooth tissues.
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During hydrogen embrittlement, hydrogen is introduced to the surface of a metal and individual hydrogen atoms diffuse through the metal structure. Because the solubility of hydrogen increases at higher temperatures, raising the temperature can increase the diffusion of hydrogen. When assisted by a concentration gradient where there is significantly more hydrogen outside the metal than inside, hydrogen diffusion can occur even at lower temperatures. There are a variety of mechanisms that have been proposed: Internal pressure: Adsorbed hydrogen species recombine to form hydrogen molecules, creating pressure from within the metal.
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Self assembling properties of P11-4 are used to regenerate early caries lesions. By application of P11-4 on the tooth surface, the peptide diffuse through the intact hypomineralized plate into the early caries lesion body and start, due to the low pH in such a lesion, to self-assemble generating a peptide scaffold mimicking the enamel matrix. Around the newly formed matrix de-novo enamel-crystals are formed from calcium phosphate present in saliva. Through the remineralization caries activity is significantly reduced in comparison with a fluoride treatment alone.
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Until the early 20th century, blow-by gases escaped from the crankcase by leaking through seals and gaskets. It was considered normal for oil to leak from an engine and drip onto the ground, as this had also been the case for steam engines in the decades before. Gaskets and shaft seals were intended to limit the leakage of oil, but they were usually not expected to entirely prevent it. The blow-by gases would diffuse through the oil and then leak through the seals and gaskets into the atmosphere, causing air pollution and odours.
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To deliver the molecules to a site of action, the lipid bilayer can fuse with other bilayers such as the cell membrane, thus delivering the liposome contents; this is a complex and non-spontaneous event, however. By preparing liposomes in a solution of DNA or drugs (which would normally be unable to diffuse through the membrane) they can be (indiscriminately) delivered past the lipid bilayer, but are then typically distributed non-homogeneously. Liposomes are used as models for artificial cells. Liposomes can also be designed to deliver drugs in other ways.
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Larger grains of nickel would reduce the contact area that ions can be conducted through, which would lower the cells efficiency. The anode is commonly the thickest and strongest layer in each individual cell, because it has the smallest polarization losses, and is often the layer that provides the mechanical support. Electrochemically speaking, the anode’s job is to use the oxygen ions that diffuse through the electrolyte to oxidize the hydrogen fuel. The oxidation reaction between the oxygen ions and the hydrogen produces heat as well as water and electricity.
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The thermoacoustic effect inside the stack takes place mainly in the region that is close to the solid walls of the stack. The layers of gas too far away from the stack walls experience adiabatic oscillations in temperature that result in no heat transfer to or from the walls, which is undesirable. Therefore, an important characteristic for any thermoacoustic element is the value of the thermal and viscous penetration depths. The thermal penetration depth δκ is the thickness of the layer of the gas where heat can diffuse through during half a cycle of oscillations.
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Non-polar compounds would not be influenced by the hydroxyls on the surface of the paper, but because of their hydrophobic nature may not diffuse through the aqueous medium resulting in false negatives. Large molecules also often diffuse poorly. Thus, some antimicrobial compounds may not be identified using a disc diffusion assay. On the other hand, the accuracy of the MTT microdilution assay can be compromised by samples that are coloured (such as plant extracts), redox active and/or samples that are not soluble in the medium, which is predominantly aqueous.
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Pt nanoparticles can be introduced to the SiC/C interface during chlorine treatment (in the form of Pt3Cl3). The particles diffuse through the material to form Pt particle surfaces, which may serve as catalyst support layers. In particular, in addition to Pt, other noble elements such as gold can be deposited into the pores, with the resulting nanoparticle size controlled by the pore size and overall pore size distribution of the CDC substrate. Such gold or platinum nanoparticles can be smaller than 1 nm even without employing surface coatings.
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Since the CTZ is located in the area postrema, a sensory circumventricular organ, it does not have a blood–brain barrier. This means that large polar molecules, such as emetic toxins, can diffuse through to and reach the CTZ quite easily. This is because the medulla oblongata is located in the area of the brain, the most inferior portion, which does not have a robust and highly developed blood-brain barrier. Without this barrier, emetic drugs and toxins are free to interact with a receptor (biochemistry), or multiple receptors located in the CTZ.
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The mechanism of uptake of MPP+ is important to its toxicity. MPP+ injected as an aqueous solution into the bloodstream causes no symptoms of Parkinsonism in test subjects, since the highly charged molecule is unable to diffuse through the blood-brain barrier. Furthermore, MPP+ shows little toxicity to cells other than dopaminergic neurons, suggesting that these neurons have a unique process by which they can uptake the molecule, since, being charged, MPP+ cannot readily diffuse across the lipid bilayer that composes cellular membranes. Unlike MPP+, its common biological precursor MPTP is a lipid-soluble molecule that diffuses readily across the blood-brain barrier.
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Almost all caesium produced from nuclear fission comes from the beta decay of originally more neutron-rich fission products, passing through various isotopes of iodine and xenon. Because iodine and xenon are volatile and can diffuse through nuclear fuel or air, radioactive caesium is often created far from the original site of fission. With nuclear weapons testing in the 1950s through the 1980s, 137Cs was released into the atmosphere and returned to the surface of the earth as a component of radioactive fallout. It is a ready marker of the movement of soil and sediment from those times.
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Gold plating is a method of depositing a thin layer of gold on the surface of glass or metal, most often copper or silver. Gold plating is often used in electronics, to provide a corrosion-resistant electrically conductive layer on copper, typically in electrical connectors and printed circuit boards. With direct gold-on-copper plating, the copper atoms have the tendency to diffuse through the gold layer, causing tarnishing of its surface and formation of an oxide/sulfide layer. Therefore, a layer of a suitable barrier metal, usually nickel, has to be deposited on the copper substrate, forming a copper-nickel-gold sandwich.
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7-Nitroindazole, or 7-NI, is a heterocyclic small molecule containing an indazole ring that has been nitrated at the 7 position. Nitroindazole acts as a selective inhibitor for neuronal nitric oxide synthase, a hemoprotein enzyme that, in neuronal tissue, converts arginine to citrulline and nitric oxide (NO). Nitric oxide can diffuse through the plasma membrane into neighbouring cells, allowing cell signalling, so nitroindazole indirectly inhibits this signalling process. Other inhibitors exist such as 3-bromo-7-nitroindazole, which is more potent but less specific, or NPA (N-propyl-L-arginine), which acts on a different site.
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Gallium tends to segregate in plutonium, causing "coring"—gallium-rich centers of grains and gallium-poor grain boundaries. To stabilize the lattice and reverse and prevent segregation of gallium, annealing is required at the temperature just below the δ–ε phase transition, so gallium atoms can diffuse through the grains and create homogeneous structure. The time to achieve homogenization of gallium increases with increasing grain size of the alloy and decreases with increasing temperature. The structure of stabilized plutonium at room temperature is the same as unstabilized at δ-phase temperature, with the difference of gallium atoms substituting plutonium in the fcc lattice.
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The common way to assess differences in tissue patterning in the fly wing is to look at the pattern of veins in the wing. In flies where the ability of Dpp to diffuse through the tissue is impaired, the positioning of the veins is shifted from that in normal flies, and the wing is generally smaller. Dpp has also been proposed as a regulator of tissue growth and size, a classic problem in development. A problem common to organisms with multicellular organs that must grow from an initial size is how to know when to stop growing after the appropriate size is reached.
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Smell is the process of absorbing molecules through olfactory organs, which are absorbed by humans through the nose. These molecules diffuse through a thick layer of mucus; come into contact with one of thousands of cilia that are projected from sensory neurons; and are then absorbed into a receptor (one of 347 or so). It is this process that causes humans to understand the concept of smell from a physical standpoint. Smell is also a very interactive sense as scientists have begun to observe that olfaction comes into contact with the other sense in unexpected ways.
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In modern construction, the shōji often do not form the exterior surface of the building; they sit inside a sliding glass door or window. Shōji are valued for not setting a sharp barrier between the interior and the exterior; outside influences such as the swaying silhouettes of trees, or the chorus of frogs, can be appreciated from inside the house. As exterior walls, shōji diffuse sunlight into the house; as interior partitions between rooms, they allow natural light deep into the interior. While shōji block wind, they do allow air to diffuse through, important when buildings were heated with charcoal.
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The lamellar separation only occurs in plagioclases of a certain composition; those of calcic labradorite and bytownite (anorthite content of ~60 to 90%) particularly exemplify this. Another requirement for the lamellar separation is very slow cooling of the rock that contains the plagioclase. Slow cooling is required to allow the Ca, Na, Si, and Al ions to diffuse through the plagioclase and produce the lamellar separation. Therefore, not all labradorites exhibit labradorescence (they might not be the correct composition and/or they cooled too quickly), and not all plagioclases that exhibit labradorescence are labradorites (they may be bytownite).
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As the proteins are continuously broken down to smaller components, the bacteria excrete gases and organic compounds, such as the functional-group amines putrescine (from ornithine) and cadaverine (from lysine), which carry the noxious odor of rotten flesh. Initially, the gases of putrefaction are constrained within the body cavities, but eventually diffuse through the adjacent tissues, and then into the circulatory system. Once in the blood vessels, the putrid gases infiltrate and diffuse to other parts of the body and the limbs. The visual result of gaseous tissue-infiltration is notable bloating of the torso and limbs.
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Methanol on the anodic side is usually in a weak solution (from 1M to 3M), because methanol in high concentrations has the tendency to diffuse through the membrane to the cathode, where its concentration is about zero because it is rapidly consumed by oxygen. Low concentrations help in reducing the cross-over, but also limit the maximum attainable current. The practical realization is usually that a solution loop enters the anode, exits, is refilled with methanol, and returns to the anode again. Alternatively, fuel cells with optimized structures can be directly fed with high concentration methanol solutions or even pure methanol.
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Nuclear receptors (NRs) may be classified into two broad classes according to their mechanism of action and subcellular distribution in the absence of ligand. Small lipophilic substances such as natural hormones diffuse through the cell membrane and bind to nuclear receptors located in the cytosol (type I NR) or nucleus (type II NR) of the cell. Binding causes a conformational change in the receptor which, depending on the class of receptor, triggers a cascade of downstream events that direct the NRs to DNA transcription regulation sites which result in up or down-regulation of gene expression. They generally function as homo/heterodimers.
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Factors which influence this include the atmospheric abundance of the two gases, the supply of the gases to the site of fixation (i.e. in land plants: whether the stomata are open or closed), the length of the liquid phase (how far these gases have to diffuse through water in order to reach the reaction site). For example, when the stomata are closed to prevent water loss during drought: this limits the supply, while production within the leaf will continue. In algae (and plants which photosynthesise underwater); gases have to diffuse significant distances through water, which results in a decrease in the availability of relative to .
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When the cluster reaches a certain size, known as the critical radius, it becomes energetically favorable, and thus stable enough to continue to grow. This nucleus then remains in the system and grows as more silver atoms diffuse through the solution and attach to the surface When the dissolved concentration of atomic silver decreases enough, it is no longer possible for enough atoms to bind together to form a stable nucleus. At this nucleation threshold, new nanoparticles stop being formed, and the remaining dissolved silver is absorbed by diffusion into the growing nanoparticles in the solution. As the particles grow, other molecules in the solution diffuse and attach to the surface.
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The outer membrane, plasma membrane, and thylakoid membranes each have specialized roles in the cyanobacterial cell. Understanding the organization, functionality, protein composition and dynamics of the membrane systems remains a great challenge in cyanobacterial cell biology. In contrast to the thylakoid network of higher plants, which is differentiated into grana and stroma lamellae, the thylakoids in cyanobacteria are organized into multiple concentric shells that split and fuse to parallel layers forming a highly connected network. This results in a continuous network that encloses a single lumen (as in higher‐plant chloroplasts) and allows water‐soluble and lipid‐soluble molecules to diffuse through the entire membrane network.
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This model denotes that before antigen stimulation, receptors diffuse through the membrane coming into contact with Lck and CD45 in equal frequency, rendering a net equilibrium of phosphorylation and non-phosphorylation. It is only when the cell comes in contact with an antigen presenting cell that the larger CD45 is displaced due to the close distance between the two membranes. This allows for net phosphorylation of the BCR and the initiation of the signal transduction pathway. Of the three B cell subsets, FO B cells preferentially undergo T cell-dependent activation while MZ B cells and B1 B cells preferentially undergo T cell-independent activation.
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Oxytocin neurons themselves express oxytocin receptors, and vasopressin neurons express vasopressin receptors, so dendritically-released peptides "autoregulate" the supraoptic neurons. Francoise Moos and Phillipe Richard first showed that the autoregulatory action of oxytocin is important for the milk-ejection reflex. These peptides have relatively long half-lives in the brain (about 20 minutes in the CSF), and they are released in large amounts in the supraoptic nucleus, and so they are available to diffuse through the extracellular spaces of the brain to act at distant targets. Oxytocin and vasopressin receptors are present in many other brain regions, including the amygdala, brainstem, and septum, as well as most nuclei in the hypothalamus.
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In order to understand how blood is delivered to cranial tissues, it is important to understand the vascular anatomy of the space itself. Large cerebral arteries in the brain split into smaller arterioles, also known as pial arteries. These consist of endothelial cells and smooth muscle cells, and as these pial arteries further branch and run deeper into the brain, they associate with glial cells, namely astrocytes. The intracerebral arterioles and capillaries are unlike systemic arterioles and capillaries in that they do not readily allow substances to diffuse through them; they are connected by tight junctions in order to form the blood brain barrier (BBB).
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A window layer is used in order to reduce the surface recombination velocity S. Similarly, a back-surface field (BSF) layer reduces the scattering of carriers towards the tunnel junction. The structure of these two layers is the same: it is a heterojunction which catches electrons (holes). Indeed, despite the electric field Ed, these cannot jump above the barrier formed by the heterojunction because they don't have enough energy, as illustrated in figure E. Hence, electrons (holes) cannot recombine with holes (electrons) and cannot diffuse through the barrier. By the way, window and BSF layers must be transparent to wavelengths absorbed by the next pn junction i.e.
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The impact of Product Space's structure can be evaluated through simulations in which a country repeatedly moves to new products with proximities above a given threshold. At a threshold of proximity equal to 0.55, countries are able to diffuse through the core of the Product Space but the speed at which they do so is determined by the set of initial products. By raising the threshold to 0.65, some countries, whose initial products occupy periphery industries, become trapped and cannot find any near- enough products. This implies that a country's orientation within the space can in fact dictate whether the country achieves economic growth.
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Another method is to correlate radionuclides or trace atmospheric gases with other timescales such as periodicities in the earth's orbital parameters. A difficulty in ice core dating is that gases can diffuse through firn, so the ice at a given depth may be substantially older than the gases trapped in it. As a result, there are two chronologies for a given ice core: one for the ice, and one for the trapped gases. To determine the relationship between the two, models have been developed for the depth at which gases are trapped for a given location, but their predictions have not always proved reliable., pp. 2530–2531.
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Pirenzepine (Gastrozepin), an M1 selective antagonist, is used in the treatment of peptic ulcers, as it reduces gastric acid secretion and reduces muscle spasm. It is in a class of drugs known as muscarinic receptor antagonists - acetylcholine being the neurotransmitter of the parasympathetic nervous system which initiates the rest-and-digest state (as opposed to fight- or-flight), resulting in an increase in gastric motility and digestion; whereas pirenzepine would inhibit these actions and cause decreased gastric motility leading to delayed gastric emptying and constipation. It has no effects on the brain and spinal cord as it cannot diffuse through the blood–brain barrier. Pirenzepine has been investigated for use in myopia control.
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At moderate rates of discharge, the lead sulfate crystals grow throughout the cross section of the electrode plate (which has a sponge-like consistency) since the electrolyte (dilute sulfuric acid) is drawn diffused through the body of the electrode to allow the reaction can take place throughout the plate. But at very fast rates of discharge, the acid already inside the body of the plate is used up quickly and fresh acid cannot diffuse through the electrode in time to continue the reaction. Hence the reaction is favored toward the outer wall of the electrode, where crystals may form in a dense mat, rather than in dispersed clumps throughout the plate. This mat of crystals further impedes electrolyte transfer.
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Positively charged sodium ions can enter the axon through these voltage-gated channels, leading to depolarisation of the membrane potential at the node of Ranvier. The resting membrane potential is then rapidly restored due to positively charged potassium ions leaving the axon through potassium channels. The sodium ions inside the axon then diffuse rapidly through the axoplasm (axonal cytoplasm), to the adjacent myelinated internode and ultimately to the next (distal) node of Ranvier, triggering the opening of the voltage gated sodium channels and entry of sodium ions at this site. Although the sodium ions diffuse through the axoplasm rapidly, diffusion is decremental by nature, thus nodes of Ranvier have to be (relatively) closely spaced, to secure action potential propagation.
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Thus, as a country develops, it will diffuse through the product space from one product to the next, reaching more and more complex products as it goes. In a recent publication titled "Structural Transformation and Patterns of Comparative Advantage in the Product Space", Hausmann and co-author Bailey Klinger explain the idea of the Product Space using the following analogy: > Our metaphor is that products are like trees, and any two trees can be close > together or far apart, depending on the similarity of the needed > capabilities. Firms are like monkeys, who derive their livelihood from > exploiting the tree they occupy. We take the forest – the product space – as > given and identical for all countries.
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Food vacuoles are formed through phagocytosis and typically follow a particular path through the cell as their contents are digested and broken down by lysosomes so the substances the vacuole contains are then small enough to diffuse through the membrane of the food vacuole into the cell. Anything left in the food vacuole by the time it reaches the cytoproct (anal pore) is discharged by exocytosis. Most ciliates also have one or more prominent contractile vacuoles, which collect water and expel it from the cell to maintain osmotic pressure, or in some function to maintain ionic balance. In some genera, such as Paramecium, these have a distinctive star shape, with each point being a collecting tube.
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The Western Wisdom Teachings present the conception of The Absolute (unmanifested and unlimited "Boundless Being" or "Root of Existence", beyond the whole universe and beyond comprehension) from whom proceeds the Supreme Being at the dawn of manifestation: The One, the "Great Architect of the Universe". From the threefold Supreme Being proceed the "seven Great Logoi" who contain within themselves all the great hierarchies that differentiate more and more as they diffuse through the six lower Cosmic Planes. In the Highest World of the seventh (lowest) Cosmic Plane dwells the god of the solar systems in the universe. These great beings are also threefold in manifestation, like the Supreme Being; their three aspects are Will, Wisdom and Activity.
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In typical operation, the base–emitter junction is forward-biased, which means that the p-doped side of the junction is at a more positive potential than the n-doped side, and the base–collector junction is reverse-biased. When forward bias is applied to the base–emitter junction, the equilibrium between the thermally generated carriers and the repelling electric field of the n-doped emitter depletion region is disturbed. This allows thermally excited electrons (in an NPN; holes in a PNP) to inject from the emitter into the base region. These electrons diffuse through the base from the region of high concentration near the emitter toward the region of low concentration near the collector.
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Hyperbaric oxygen therapy increases oxygen transport via dissolved oxygen in serum, and is most efficacious where the haemoglobin is compromised (e.g. carbon monoxide poisoning) or where the extra oxygen in solution can diffuse through tissues past embolisms that are blocking the blood supply as in decompression illness. Hyperbaric chambers capable of admitting more than one patient (multiplace) and an inside attendant have advantages for the treatment of decompression sickness (DCS) if the patient requires other treatment for serious complications or injury while in the chamber, but in most cases monoplace chambers can be successfully used for treating decompression sickness. Rigid chambers are capable of greater depth of recompression than soft chambers that are unsuitable for treating DCS.
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Gaseous diffusion uses semi-permeable membranes to separate enriched uranium Often done with gases, but also with liquids, the diffusion method relies on the fact that in thermal equilibrium, two isotopes with the same energy will have different average velocities. The lighter atoms (or the molecules containing them) will travel more quickly and be more likely to diffuse through a membrane. The difference in speeds is proportional to the square root of the mass ratio, so the amount of separation is small and many cascaded stages are needed to obtain high purity. This method is expensive due to the work needed to push gas through a membrane and the many stages necessary.
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Larger gas molecules have a lower diffusion coefficient. The polymer chain flexibility and free volume in the polymer of the membrane material influence the diffusion coefficient, as the space within the permeable membrane must be large enough for the gas molecules to diffuse across. The solubility is expressed as the ratio of the concentration of the gas in the polymer to the pressure of the gas in contact with it. Permeability is the ability of the membrane to allow the permeating gas to diffuse through the material of the membrane as a consequence of the pressure difference over the membrane, and can be measured in terms of the permeate flow rate, membrane thickness and area and the pressure difference across the membrane.
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Morphogenesis of Drosophila fruit flies is intensively studied in the laboratory A morphogen is a substance whose non-uniform distribution governs the pattern of tissue development in the process of morphogenesis or pattern formation, one of the core processes of developmental biology, establishing positions of the various specialized cell types within a tissue. More specifically, a morphogen is a signaling molecule that acts directly on cells to produce specific cellular responses depending on its local concentration. Typically, morphogens are produced by source cells and diffuse through surrounding tissues in an embryo during early development, such that concentration gradients are set up. These gradients drive the process of differentiation of unspecialised stem cells into different cell types, ultimately forming all the tissues and organs of the body.
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On January 30, 1948 Shive discovered that gold-plated tungsten point contacts on a p-type layer of germanium grown on an n-type substrate gave "a terrific triode effect". On February 13, he also discovered that a transistor consisting of bronze contacts on the surface of an n-type substrate without a p-layer gave "gains up to 40× in power!" He leveraged this discovery to build a point contact transistor with bronze contacts on the front and back of thin wedge of germanium, proving that holes could diffuse through bulk germanium and not just along the surface as previously thought. This confirmed William Shockley's idea that it should be possible to build a junction transistor, an idea that hitherto he had kept secret from the rest of the team.
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Common lipid signaling molecules: lysophosphatidic acid (LPA) sphingosine-1-phosphate (S1P) platelet activating factor (PAF) anandamide or arachidonoyl ethanolamine (AEA) Lipid signaling, broadly defined, refers to any biological signaling event involving a lipid messenger that binds a protein target, such as a receptor, kinase or phosphatase, which in turn mediate the effects of these lipids on specific cellular responses. Lipid signaling is thought to be qualitatively different from other classical signaling paradigms (such as monoamine neurotransmission) because lipids can freely diffuse through membranes (see osmosis.) One consequence of this is that lipid messengers cannot be stored in vesicles prior to release and so are often biosynthesized "on demand" at their intended site of action. As such, many lipid signaling molecules cannot circulate freely in solution but, rather, exist bound to special carrier proteins in serum.
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Genes, embryos and development together determine the form of an adult organism's body, through the complex switching processes involved in morphogenesis. Developmental biologists seek to understand how genes control the development of structural features through a cascade of processes in which key genes produce morphogens, chemicals that diffuse through the body to produce a gradient that acts as a position indicator for cells, turning on other genes, some of which in turn produce other morphogens. A key discovery was the existence of groups of homeobox genes, which function as switches responsible for laying down the basic body plan in animals. The homeobox genes are remarkably conserved between species as diverse as the fruit fly and humans, the basic segmented pattern of the worm or fruit fly being the origin of the segmented spine in humans.
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These organic vapours, especially the more volatile ones, may desorb from the filter and diffuse through the cartridge while it is not in use, such that they may be breathed by the wearer when they begin to use the cartridge again. For this reason, cartridges used against organic vapours are single-use, unless experimental evidence shows that desorbtion-caused breakthrough after a storage period is not a problem for the specific organic vapours in question. Chemical cartridges must be replaced when they no longer have the ability to absorb the toxic chemicals, a point which is determined by a qualified industrial hygienist. Cartridge service life is dependent on many factors, including contaminant type and concentrations, interference from other chemicals, breathing rates, whether respirator use is continuous or intermittent, sorption capacity of the cartridges, and environmental factors like humidity and temperature.
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The coronal and solar wind plasmas are highly electrically conductive, meaning the magnetic field lines and the plasma flows are effectively "frozen" together and the magnetic field cannot diffuse through the plasma on time scales of interest. In the solar corona, the magnetic pressure greatly exceeds the plasma pressure and thus the plasma is primarily structured and confined by the magnetic field. With increasing altitude through the corona, solar wind acceleration results in the flow momentum exceeding the restraining magnetic tension force and the coronal magnetic field is dragged out by the solar wind to form the HMF. The dynamic pressure of the wind dominates over the magnetic pressure through most of the Solar System (or heliosphere), so that the magnetic field is pulled into an Archimedean spiral pattern (the Parker spiralParker, E. N., "Dynamics of the Interplanetary Gas and Magnetic Fields", (1958) Astrophysical Journal, vol.
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He even made efforts to have the patent written only in his name, and told Bardeen and Brattain of his intentions. Shockley, angered by not being included on the patent applications, secretly continued his own work to build a different sort of transistor based on junctions instead of point contacts; he expected this kind of design would be more likely to be commercially viable. The point contact transistor, he believed, would prove to be fragile and difficult to manufacture. Shockley was also dissatisfied with certain parts of the explanation for how the point contact transistor worked and conceived of the possibility of minority carrier injection. On February 13, 1948 another team member, John N. Shive, built a point contact transistor with bronze contacts on the front and back of thin wedge of germanium, proving that holes could diffuse through bulk germanium and not just along the surface as previously thought.
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Buccal administration is a topical route of administration by which drugs held or applied in the buccal () area (in the cheek) diffuse through the oral mucosa (tissues which line the mouth) and enter directly into the bloodstream. Buccal administration may provide better bioavailability of some drugs and a more rapid onset of action compared to oral administration because the medication does not pass through the digestive system and thereby avoids first pass metabolism. As of May 2014, the psychiatric drug asenapine; the opioid drugs buprenorphine, naloxone, and fentanyl; the cardiovascular drug nitroglycerin; the nausea medication Prochlorperazine; the hormone replacement therapy testosterone; and nicotine as a smoking cessation aid were commercially available in buccal forms, as was midazolam, an anticonvulsant, used to treat acute epileptic seizures. Buccal administration of vaccines has been studied, but there are challenges to this approach due to immune tolerance mechanisms that prevent the body from over-reacting to immunogens encountered in the course of daily life.
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Anna Jane Grossman Ahh, Minty Clean, but Lacking a Jolt New York Times July 12, 2007, Accessed 15 July 2008 Showershock is peppermint scented glycerine soap that comes in a "normal" size, weighing 4 ounces (113 grams), estimated to provide 12 washes with 200 milligrams of caffeine per wash.ThinkGeek :: Shower Shock Caffeinated Soap The soap is also sold in a "Travel" size, estimated to provide 4.5 showers and 200 milligrams of caffeine per wash, weighing 1.5 ounces.ThinkGeek :: Shower Shock Caffeine Soap Travel In addition to the soap bars, there is also a Showershock Caffeinated showergel, with the same amount of caffeine per wash (if someone uses the "normal" amount of gel) with each bottle weighing 6.76 ounces.ThinkGeek :: Shower Shock Caffeinated Body Wash The addition of peppermint oil to the body soap is widely considered to help to stimulate the user's senses to effect an alert state in the user, as caffeine's ability to meaningfully diffuse through human skin is extremely limited and, as a result, users will generally not receive a meaningful dose of the drug through the soap itself.
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In NMOS and CMOS technologies, over time and elevated temperatures, the positive voltages employed by the gate structure can cause any existing positively charged sodium impurities directly under the positively charged gate to diffuse through the gate dielectric and migrate to the less-positively-charged channel surface, where the positive sodium charge has a higher effect on the channel creation thus lowering the threshold voltage of an N-channel transistor and potentially causing failures over time. Earlier PMOS technologies were not sensitive to this effect because the positively charged sodium was naturally attracted towards the negatively charged gate, and away from the channel, minimizing threshold voltage shifts. N-channel, metal gate processes (in the 1970s) imposed a very high standard of cleanliness (absence of sodium) difficult to achieve in that timeframe, resulting in high manufacturing costs. Polysilicon gates while sensitive to the same phenomenon, could be exposed to small amounts of HCl gas during subsequent high-temperature processing (commonly called "gettering") to react with any sodium, binding with it to form NaCl and carrying it away in the gas stream, leaving an essentially sodium-free gate structure greatly enhancing reliability.
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