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In Combustion, G equation is a scalar field equation which describes the instantaneous flame position, introduced by Forman A. Williams in 1985 in the study of premixed turbulent combustion. The equation is derived based on the Level-set method. The equation was first studied by George H. Markstein, in a restrictive form for the burning velocity. | 1 | Applied and Interdisciplinary Chemistry |
Crystalline structure is the composition of ions, atoms, and molecules that are held together and ordered in a 3D shape. The main difference between a crystalline structure and an amorphous structure is the order of the components. Crystalline has the highest level of order possible in the material where amorphous structure consists of irregularities in the ordering pattern. One way to describe crystalline structures is through the crystal lattice, which is a three-dimensional representation of the location of a repeating factor (unit cell) in the structure denoted with lattices. There are 14 different configurations of atom arrangement in a crystalline structure, and are all represented under Bravais lattices. | 1 | Applied and Interdisciplinary Chemistry |
Very high densities are required to thermalize the rotational transitions of HO, so it is difficult to detect far-infrared emission lines from a quiescent molecular cloud. Even at H densities of 10 cm, dust must be optically thick at infrared wavelengths. But the passage of a shock wave through a molecular cloud is precisely the process which can bring the molecular gas out of equilibrium with the dust, making observations of far-infrared emission lines possible. A moderately fast shock may produce a transient raise in the HO abundance relative to hydrogen. So, it is possible that far-infrared emission lines of HO can be a good diagnostic of shock conditions. | 1 | Applied and Interdisciplinary Chemistry |
Vanadyl ribonucleoside is produced by combining vanadyl sulphate with various ribonucleosides (such as guanosine) in a 1:10 molar ratio. | 1 | Applied and Interdisciplinary Chemistry |
Inside protons and neutrons, there are fundamental particles called quarks. The two most common types of quarks are up quarks, which have a charge of +, and down quarks, with a − charge. Quarks arrange themselves in sets of three such that they make protons and neutrons. In a proton, whose charge is +1, there are two up quarks and one down quark ( + − = 1). Neutrons, with no charge, have one up quark and two down quarks ( − − = 0). Via the weak interaction, quarks can change flavor from down to up, resulting in electron emission. Positron emission happens when an up quark changes into a down quark, effectively converting a proton to a neutron.
Nuclei which decay by positron emission may also decay by electron capture. For low-energy decays, electron capture is energetically favored by 2mc = , since the final state has an electron removed rather than a positron added. As the energy of the decay goes up, so does the branching fraction of positron emission. However, if the energy difference is less than 2mc, then positron emission cannot occur and electron capture is the sole decay mode. Certain otherwise electron-capturing isotopes (for instance, ) are stable in galactic cosmic rays, because the electrons are stripped away and the decay energy is too small for positron emission. | 0 | Theoretical and Fundamental Chemistry |
The very high breakdown voltages, high electron mobility, and high saturation velocity of GaN has made it an ideal candidate for high-power and high-temperature microwave applications, as evidenced by its high Johnson's figure of merit. Potential markets for high-power/high-frequency devices based on GaN include microwave radio-frequency power amplifiers (e.g., those used in high-speed wireless data transmission) and high-voltage switching devices for power grids. A potential mass-market application for GaN-based RF transistors is as the microwave source for microwave ovens, replacing the magnetrons currently used. The large band gap means that the performance of GaN transistors is maintained up to higher temperatures (~400 °C) than silicon transistors (~150 °C) because it lessens the effects of thermal generation of charge carriers that are inherent to any semiconductor. The first gallium nitride metal semiconductor field-effect transistors (GaN MESFET) were experimentally demonstrated in 1993 and they are being actively developed.
In 2010, the first enhancement-mode GaN transistors became generally available. Only n-channel transistors were available. These devices were designed to replace power MOSFETs in applications where switching speed or power conversion efficiency is critical. These transistors are built by growing a thin layer of GaN on top of a standard silicon wafer, often referred to as GaN-on-Si by manufacturers. This allows the FETs to maintain costs similar to silicon power MOSFETs but with the superior electrical performance of GaN. Another seemingly viable solution for realizing enhancement-mode GaN-channel HFETs is to employ a lattice-matched quaternary AlInGaN layer of acceptably low spontaneous polarization mismatch to GaN.
GaN power ICs monolithically integrate a GaN FET, GaN-based drive circuitry and circuit protection into a single surface-mount device. Integration means that the gate-drive loop has essentially zero impedance, which further improves efficiency by virtually eliminating FET turn-off losses. Academic studies into creating low-voltage GaN power ICs began at the Hong Kong University of Science and Technology (HKUST) and the first devices were demonstrated in 2015. Commercial GaN power IC production began in 2018. | 0 | Theoretical and Fundamental Chemistry |
Movement joints are designed to absorb the movement of the subfloor and the tiles themselves due to thermal expansion and contraction, moisture variations, and structural shifts. These joints are essentially gaps, typically filled with a flexible material like silicone or rubber, that separate tiles and allow for movement without causing the tiles to crack, buckle, or become disjointed. | 1 | Applied and Interdisciplinary Chemistry |
The rule states that with the addition of a protic acid HX or other polar reagent to an asymmetric alkene, the acid hydrogen (H) or electropositive part gets attached to the carbon with more hydrogen substituents, and the halide (X) group or electronegative part gets attached to the carbon with more alkyl substituents. This is in contrast to Markovnikov's original definition, in which the rule is stated that the X component is added to the carbon with the fewest hydrogen atoms while the hydrogen atom is added to the carbon with the greatest number of hydrogen atoms.
The same is true when an alkene reacts with water in an addition reaction to form an alcohol which involve formation of carbocations. The hydroxyl group (OH) bonds to the carbon that has the greater number of carbon–carbon bonds, while the hydrogen bonds to the carbon on the other end of the double bond, that has more carbon–hydrogen bonds.
The chemical basis for Markovnikov's Rule is the formation of the most stable carbocation during the addition process. The addition of the hydrogen ion to one carbon atom in the alkene creates a positive charge on the other carbon, forming a carbocation intermediate. The more substituted the carbocation, the more stable it is, due to induction and hyperconjugation. The major product of the addition reaction will be the one formed from the more stable intermediate. Therefore, the major product of the addition of HX (where X is some atom more electronegative than H) to an alkene has the hydrogen atom in the less substituted position and X in the more substituted position. But the other less substituted, less stable carbocation will still be formed at some concentration, and will proceed to be the minor product with the opposite, conjugate attachment of X. | 0 | Theoretical and Fundamental Chemistry |
Hydrocarbon chains are long chains which consist of a carbon backbone hydrogen substituents, making them very hydrophobic. Hydrocarbon chains alone form waxes and oils and retain these characteristics when they are incorporated into surfactant. A good example of surfactants containing a hydrocarbon chain are lipids, which form cell membranes.
Alkyl ether chains are similar to hydrocarbon chains, except with oxygens incorporated within the backbone as well as carbons. There are two alkyl chains commonly used in surfactants: polyethylene oxide and polypropylene oxide. Polyethylene oxide chains have an oxygen and two carbon (-O-CH-CH-) repeating unit and has an increased hydrophilic character compared to hydrocarbons. Polypropylene oxide has the same backbone structure as polyethylene oxide but with a methyl group substituent of one of the carbons, and this structure has hydrophobicity between hydrocarbons and polyethylene oxides.
Fluorocarbon chain tails consist of a carbon backbone that has fluorine substituents instead of hydrogens. Fluorocarbons help to lower the surface tension of water and other solvents because of their lipophobic nature even in harsh conditions such as low pH. When fluorocarbons are incorporated into surfactants they are used as stain repellents and incorporated into coatings in order to decrease surface defects.
Siloxane chains consist of a backbone which contains alternating oxygen and silicon atoms. Surfactants with siloxane tails have been found to resist hydrolysis and prevent breakdown polymer chains which can cause cracking in the paint and are thus used in products such as cosmetics, deodorants, defoamer, and soap. | 0 | Theoretical and Fundamental Chemistry |
Enzymes, which are composed of chiral amino acids, catalyze chemical reactions with high stereoselectivity. Specifically, esterase enzymes catalyze the hydrolysis of esters to carboxylic acids. This transformation may be rendered asymmetric if two enantiotopic ester groups exist in the substrate or if a racemic mixture of chiral esters is used. In the former case (desymmetrization), the chiral environment of the enzyme active site leads to selective hydrolysis of the ester that is closer to the catalytically active serine residue when the substrate is bound to the enzyme. In the latter case (kinetic resolution), one of the enantiomers is hydrolyzed faster than the other, leading to an excess of hydrolyzed product from one enantiomer. Both strategies rely on the fact that the transition states for hydrolysis of enantiotopic or enantiomorphic ester groups by the chiral enzyme are diastereomeric.
Pig liver esterase (PLE) is a widely used enzyme for asymmetric ester hydrolysis. Although it was originally used for the desymmetrizing hydrolysis of glutarate esters, PLE also hydrolyzes malonates, cyclic diesters, monoesters, and other substrates. Active site models have been advanced to explain the selectivity of PLE. | 0 | Theoretical and Fundamental Chemistry |
A few stable nitronium salts with anions of weak nucleophilicity can be isolated. These include nitronium perchlorate , nitronium tetrafluoroborate , nitronium hexafluorophosphate , nitronium hexafluoroarsenate , and nitronium hexafluoroantimonate . These are all very hygroscopic compounds.
The solid form of dinitrogen pentoxide, , actually consists of nitronium and nitrate ions, so it is an ionic compound, nitronium nitrate , not a molecular solid. However, dinitrogen pentoxide in liquid or gaseous state is molecular and does not contain nitronium ions. | 0 | Theoretical and Fundamental Chemistry |
Double diffusive convection is a fluid dynamics phenomenon that describes a form of convection driven by two different density gradients, which have different rates of diffusion.
Convection in fluids is driven by density variations within them under the influence of gravity. These density variations may be caused by gradients in the composition of the fluid, or by differences in temperature (through thermal expansion). Thermal and compositional gradients can often diffuse with time, reducing their ability to drive the convection, and requiring that gradients in other regions of the flow exist in order for convection to continue. A common example of double diffusive convection is in oceanography, where heat and salt concentrations exist with different gradients and diffuse at differing rates. An effect that affects both of these variables is the input of cold freshwater from an iceberg. Another example of double diffusion is the formation of false bottoms at the interface of sea ice and under-ice meltwater layers. A good discussion of many of these processes is in Stewart Turner's monograph "Buoyancy effects in fluids".
Double diffusive convection is important in understanding the evolution of a number of systems that have multiple causes for density variations. These include convection in the Earth's oceans (as mentioned above), in magma chambers, and in the sun (where heat and helium diffuse at differing rates). Sediment can also be thought as having a slow Brownian diffusion rate compared to salt or heat, so double diffusive convection is thought to be important below sediment laden rivers in lakes and the ocean.
Two quite different types of fluid motion exist—and therefore are classified accordingly—depending on whether the stable stratification is provided by the density-affecting component with the lowest or the highest molecular diffusivity. If the stratification is provided by the component with the lower molecular diffusivity (for example in case of a stable salt-stratified ocean perturbed by a thermal gradient due to an iceberg—a density ratio between 0 and 1), the stratification is called to be of "diffusive"
type (see external link below), otherwise it is of "finger" type, occurring frequently in oceanographic studies as salt-fingers. These long fingers of rising and sinking water occur when hot saline water lies over cold fresh water of a higher density. A perturbation to the surface of hot salty water results in an element of hot salty water surrounded by cold fresh water. This element loses its heat more rapidly than its salinity because the diffusion of heat is faster than of salt; this is analogous to the way in which just unstirred coffee goes cold before the sugar has diffused to the top. Because the water becomes cooler but remains salty, it becomes denser than the fluid layer beneath it. This makes the perturbation grow and causes the downward extension of a salt finger. As this finger grows, additional thermal diffusion accelerates this effect. | 1 | Applied and Interdisciplinary Chemistry |
:Heat removal is done by internal cooling coils. The synthesis gas is bubbled through the waxy products and finely-divided catalyst which is suspended in the liquid medium. This also provides agitation of the contents of the reactor. The catalyst particle size reduces diffusional heat and mass transfer limitations. A lower temperature in the reactor leads to a more viscous product and a higher temperature (> 297 °C, 570 K) gives an undesirable product spectrum. Also, separation of the product from the catalyst is a problem. | 0 | Theoretical and Fundamental Chemistry |
Expanded nucleotides and their oligomeric helices share many properties with their natural B-DNA counterparts, including their pairing preference: A with T, C with G. The various differences in chemical properties between xDNA and B-DNA support the hypothesis that the benzene ring which expands x-nucleobases is not, in fact, chemically inert. xDNA is more hydrophobic than B-DNA, and also has a smaller HOMO-LUMO gap (distance between the highest occupied molecular orbital and lowest unoccupied molecular orbital) as a result of modified saturation. xDNA has higher melting temperatures than B-DNA (a mixed decamer of xA and T has a melting temperature of 55.6 °C, 34.3 °C higher than the same decamer of A and T), and exhibits an "all-or-nothing" melting behaviour. | 1 | Applied and Interdisciplinary Chemistry |
In order for proteins to adsorb, they must first come into contact with the surface through one or more of these major transport mechanisms: diffusion, thermal convection, bulk flow, or a combination thereof. When considering the transport of proteins, it is clear how concentration gradients, temperature, protein size and flow velocity will influence the arrival of proteins to a solid surface. Under conditions of low flow and minimal temperature gradients, the adsorption rate can be modeled after the diffusion rate equation. | 1 | Applied and Interdisciplinary Chemistry |
Proteolysis is also involved in the regulation of many cellular processes by activating or deactivating enzymes, transcription factors, and receptors, for example in the biosynthesis of cholesterol, or the mediation of thrombin signalling through protease-activated receptors.
Some enzymes at important metabolic control points such as ornithine decarboxylase is regulated entirely by its rate of synthesis and its rate of degradation. Other rapidly degraded proteins include the protein products of proto-oncogenes, which play central roles in the regulation of cell growth. | 1 | Applied and Interdisciplinary Chemistry |
Some neutron-rich isotopes decay by the emission of two or more neutrons. For example, hydrogen-5 and helium-10 decay by the emission of two neutrons, hydrogen-6 by the emission of 3 or 4 neutrons, and hydrogen-7 by emission of 4 neutrons. | 0 | Theoretical and Fundamental Chemistry |
The estrogen receptor, as well as the progesterone receptor, have been detected in the skin, including in keratinocytes and fibroblasts. At menopause and thereafter, decreased levels of female sex hormones result in atrophy, thinning, and increased wrinkling of the skin and a reduction in skin elasticity, firmness, and strength. These skin changes constitute an acceleration in skin aging and are the result of decreased collagen content, irregularities in the morphology of epidermal skin cells, decreased ground substance between skin fibers, and reduced capillaries and blood flow. The skin also becomes more dry during menopause, which is due to reduced skin hydration and surface lipids (sebum production). Along with chronological aging and photoaging, estrogen deficiency in menopause is one of the three main factors that predominantly influences skin aging.
Hormone replacement therapy, consisting of systemic treatment with estrogen alone or in combination with a progestogen, has well-documented and considerable beneficial effects on the skin of postmenopausal women. These benefits include increased skin collagen content, skin thickness and elasticity, and skin hydration and surface lipids. Topical estrogen has been found to have similar beneficial effects on the skin. In addition, a study has found that topical 2% progesterone cream significantly increases skin elasticity and firmness and observably decreases wrinkles in peri- and postmenopausal women. Skin hydration and surface lipids, on the other hand, did not significantly change with topical progesterone.
These findings suggest that progesterone, like estrogen, also has beneficial effects on the skin, and may be independently protective against skin aging. | 0 | Theoretical and Fundamental Chemistry |
Difluoroethane is an extremely flammable gas, which decomposes rapidly on heating or burning, producing toxic and irritating fumes, including hydrogen fluoride and carbon monoxide.
In a DuPont study, rats were exposed to up to 25,000 ppm (67,485 mg/m) for six hours daily, five days a week for two years. This has become the no-observed-adverse-effect level for this substance. Prolonged exposure to 1,1-difluoroethane has been linked in humans to the development of coronary disease and angina. Repeated or sufficiently high levels of exposure, particularly purposeful inhalation, can precipitate fatal cardiac arrhythmia. | 1 | Applied and Interdisciplinary Chemistry |
The extrusion of stationary phase from the column at the end of a separation experiment by stopping rotation and pumping solvent or gas through the column was used by CCC practitioners before the term EECCC was suggested. In elution-extrusion mode (EECCC), The mobile phase is extruded after a certain point by switching the phase being pumped into the system whilst maintaining rotation. For example, if the separation has been initiated with the aqueous phase as the mobile phase at a certain point the organic phase is pumped through the column which effectively pushes out both phases that are present in the column at the time of switching. The complete sample is eluted in the order of polarity (either normal or reversed) without loss of resolution by diffusion. It requires only one column volume of solvent phase and leaves the column full of fresh stationary phase for the subsequent separation. | 0 | Theoretical and Fundamental Chemistry |
Bicalutamide is an arylpropionamide analog, seen in figure 6. It has replaced flutamide and nilutamide as the first choice antiandrogen for prostate cancer treatment. Bicalutamide is not as hepatotoxic as flutamide and nilutamide and has a longer half-life, of 6 days in humans, that allows once a day administration at lower dosage. Bicalutamide shares the amide bond structure with flutamide. Even so, the amide bond hydrolysis was discovered in rats, not in humans, which could explain the prolonged half life of bicalutamide in humans.
Bicalutamide has a cyano group at the para position instead of a nitro group like flutamide and nilutamide. This change in groups avoids the nitro reduction observed in nilutamide. Bicalutamide has a chiral carbon in its structure (labeled with an asterisk in figure 6), which is connected to the hydroxyl and methyl groups . It is therefore administered as a racemate. Post-approval investigation revealed that its antiandrogenic activity resides almost entirely in the (R)-enantiomer. (R)-bicalutamide has an almost fourfold higher affinity for the prostate AR than hydroxyflutamide and has a better side-effect profile compared to other antiandrogens. | 1 | Applied and Interdisciplinary Chemistry |
In April the Committee for Medicinal Products for Human Use of the European Medicines Agency endorsed a gene therapy treatment called Strimvelis and the European Commission approved it in June. This treats children born with adenosine deaminase deficiency and who have no functioning immune system. This was the second gene therapy treatment to be approved in Europe.
In October, Chinese scientists reported they had started a trial to genetically modify T cells from 10 adult patients with lung cancer and reinject the modified T cells back into their bodies to attack the cancer cells. The T cells had the PD-1 protein (which stops or slows the immune response) removed using CRISPR-Cas9.
A 2016 Cochrane systematic review looking at data from four trials on topical cystic fibrosis transmembrane conductance regulator (CFTR) gene therapy does not support its clinical use as a mist inhaled into the lungs to treat cystic fibrosis patients with lung infections. One of the four trials did find weak evidence that liposome-based CFTR gene transfer therapy may lead to a small respiratory improvement for people with CF. This weak evidence is not enough to make a clinical recommendation for routine CFTR gene therapy. | 1 | Applied and Interdisciplinary Chemistry |
Pesticide residue refers to the pesticides that may remain on or in food after they are applied to food crops. The maximum residue limits (MRL) of pesticides in food are carefully set by the regulatory authorities to ensure, to their best judgement, no health impacts. Regulations such as pre-harvest intervals also often prevent harvest of crop or livestock products if recently treated in order to allow residue concentrations to decrease over time to safe levels before harvest. Exposure of the general population to these residues most commonly occurs through consumption of treated food sources, or being in close contact to areas treated with pesticides such as farms or lawns.
Persistent pesticides are no longer used for agriculture, and will not be approved by the authorities. Because the half life in soil is long (for DDT 2–15 years) residues can still be detected in humans at levels 5 to 10 times lower than found in the 1970s.
Residues are monitored by the authorities. In 2016, over 99% of samples of US produce had no pesticide residue or had residue levels well below the EPA tolerance levels for each pesticide. | 1 | Applied and Interdisciplinary Chemistry |
Water, alcohols, carboxylic acids, and many other hydroxy-containing compounds can be readily deprotonated due to a large difference between the electronegativity of oxygen (3.5) and that of hydrogen (2.1). Hydroxy-containing compounds engage in intermolecular hydrogen bonding increasing the electrostatic attraction between molecules and thus to higher boiling and melting points than found for compounds that lack this functional group. Organic compounds, which are often poorly soluble in water, become water-soluble when they contain two or more hydroxy groups, as illustrated by sugars and amino acid. | 0 | Theoretical and Fundamental Chemistry |
Ct filtration is a technique that uses the principles of DNA renaturation kinetics to separate the repetitive DNA sequences that dominate many eukaryotic genomes from "gene-rich" single/low-copy sequences. This allows DNA sequencing to concentrate on the parts of the genome that are most informative and interesting, which will speed up the discovery of new genes and make the process more efficient. | 1 | Applied and Interdisciplinary Chemistry |
Following, the IMFP is employed to calculate the effective attenuation length (EAL), the mean escape depth (MED) and the information depth (ID). Besides, one can utilize the IMFP to make matrix corrections for the relative sensitivity factor in quantitative surface analysis. Moreover, the IMFP is an important parameter in Monte Carlo simulations of photoelectron transport in matter. | 0 | Theoretical and Fundamental Chemistry |
A new development of the activated sludge process is the Nereda process which produces a granular sludge that settles very well (the sludge volume index is reduced from ). A new process reactor system is created to take advantage of this quick settling sludge and is integrated into the aeration tank instead of having a separate unit outside. About 30 Nereda wastewater treatment plants worldwide are operational, under construction or under design, varying in size from 5,000 up to 858,000 person equivalent. | 1 | Applied and Interdisciplinary Chemistry |
ESI interface for LC–MS systems was developed by Fenn and collaborators in 1988. This ion source/ interface can be used for the analysis of moderately polar and even very polar molecules (e.g., metabolites, xenobiotics, peptides, nucleotides, polysaccharides). The liquid eluate coming out of the LC column is directed into a metal capillary kept at 3 to 5 kV and is nebulized by a high-velocity coaxial flow of gas at the tip of the capillary, creating a fine spray of charged droplets in front of the entrance to the vacuum chamber. To avoid contamination of the vacuum system by buffers and salts, this capillary is usually perpendicularly located at the inlet of the MS system, in some cases with a counter-current of dry nitrogen in front of the entrance through which ions are directed by the electric field. In some sources, rapid droplet evaporation and thus maximum ion emission is achieved by mixing an additional stream of hot gas with the spray plume in front of the vacuum entrance. In other sources, the droplets are drawn through a heated capillary tube as they enter the vacuum, promoting droplet evaporation and ion emission. These methods of increasing droplet evaporation now allow the use of liquid flow rates of 1 - 2 mL/min to be used while still achieving efficient ionisation and high sensitivity. Thus while the use of 1 – 3 mm microbore columns and lower flow rates of 50 - 200 μl/min was commonly considered necessary for optimum operation, this limitation is no longer as important, and the higher column capacity of larger bore columns can now be advantageously employed with ESI LC–MS systems. Positively and negatively charged ions can be created by switching polarities, and it is possible to acquire alternate positive and negative mode spectra rapidly within the same LC run . While most large molecules (greater than MW 1500–2000) produce multiply charged ions in the ESI source, the majority of smaller molecules produce singly charged ions. | 0 | Theoretical and Fundamental Chemistry |
Photorespiration can occur when the oxygen concentration is too high. RuBisCO cannot distinguish between oxygen and carbon dioxide very well, so it can accidentally add O instead of CO to RuBP. This process reduces the efficiency of photosynthesis—it consumes ATP and oxygen, releases CO, and produces no sugar. It can waste up to half the carbon fixed by the Calvin cycle. Several mechanisms have evolved in different lineages that raise the carbon dioxide concentration relative to oxygen within the chloroplast, increasing the efficiency of photosynthesis. These mechanisms are called carbon dioxide concentrating mechanisms, or CCMs. These include Crassulacean acid metabolism, carbon fixation, and pyrenoids. Chloroplasts in plants are notable as they exhibit a distinct chloroplast dimorphism. | 0 | Theoretical and Fundamental Chemistry |
Due to the thermal constraints faced by using polypropylene as base material, applications where high sensitivity is needed, long-term temperatures should be below 70 °C, which limits its scope in terms of some potential applications such as the automotive industry.
The air voids present in the structure become smaller and higher in pressure as force is applied to the film. This means that the film becomes harder to compress as it goes under more load, meaning that in the sensor mode, the charge output is non-linear, which can make calibrating the sensor difficult. | 1 | Applied and Interdisciplinary Chemistry |
Factors influencing habit include: a combination of two or more crystal forms; trace impurities present during growth; crystal twinning and growth conditions (i.e., heat, pressure, space); and specific growth tendencies such as growth striations. Minerals belonging to the same crystal system do not necessarily exhibit the same habit. Some habits of a mineral are unique to its variety and locality: For example, while most sapphires form elongate barrel-shaped crystals, those found in Montana form stout tabular crystals. Ordinarily, the latter habit is seen only in ruby. Sapphire and ruby are both varieties of the same mineral: corundum.
Some minerals may replace other existing minerals while preserving the originals habit, i.e. pseudomorphous replacement. A classic example is tigers eye quartz, crocidolite asbestos replaced by silica. While quartz typically forms prismatic (elongate, prism-like) crystals, in tigers eye the original fibrous' habit of crocidolite is preserved. | 0 | Theoretical and Fundamental Chemistry |
Fumarate, produced from the purine nucleotide cycle, is an intermediate of TCA cycle and enters the mitochondria by converting into malate and utilizing the malate shuttle where it is converted into oxaloacetic acid (OAA). During exercise, OAA either enters into TCA cycle or converts into aspartate in the mitochondria.
As the purine nucleotide cycle produces ammonia (see below in ammonia synthesis), skeletal muscle needs to synthesize glutamate in a way that does not further increase ammonia, and as such the use of glutaminase to produce glutamate from glutamine would not be ideal. Also, plasma glutamine (released from the kidneys) requires active transport into the muscle cell (consuming ATP). Consequently, during exercise when the ATP reservoir is low (ADP>ATP), glutamate is produced from branch-chained amino acids (BCAAs) and α-ketoglutarate, as well as from alanine and α-ketoglutarate. Glutamate is then used to produce aspartate. The aspartate enters the purine nucleotide cycle, where it is used to convert IMP into S-AMP.
:BCAAs + α-Ketoglutarate ⇌ Glutamate + Branch-chain keto acids (BCKAs) (catalyzed by Branched-chain aminotransferases (BCAT))
:Alanine + α-Ketoglutarate ⇌ Pyruvate + Glutamate (catalyzed by alanine transaminase)
:Oxaloacetic acid + Glutamate ⇌ α-Ketoglutarate + Aspartate (catalyzed by aspartate aminotransferase)
When skeletal muscle is at rest (ADP | 1 | Applied and Interdisciplinary Chemistry |
Carbonate ions (CO) are essential in marine calcifying organisms, like plankton and shellfish, as they are required to produce their calcium carbonate () shells and skeletons. As the ocean acidifies, the increased uptake of CO by seawater increases the concentration of hydrogen ions, which lowers the pH of the water. This change in the chemical equilibrium of the inorganic carbon system reduces the concentration of these carbonate ions. This reduces the ability of these organisms to create their shells and skeletons.
The two polymorphs of calcium carbonate that are produced by marine organisms are aragonite and calcite. These are the materials that makes up most of the shells and skeletons of these calcifying organisms. Aragonite, for example, makes up nearly all mollusc shells, as well as the exoskeleton of corals. The formation of these materials is dependent on the saturation state of CaCO in ocean water. Waters which are saturated in are favorable to precipitation and formation of shells and skeletons, but waters which are undersaturated are corrosive to shells. In the absence of protective mechanisms, dissolution of calcium carbonate will occur. As colder arctic water absorbs more , the concentration of CO is reduced, therefore the saturation of calcium carbonate is lower in high-latitude oceans than it is in tropical or temperate oceans.
The undersaturation of CaCO causes the shells of calcifying organisms to dissolve, which can have devastating consequences to the ecosystem. As the shells dissolve, the organisms struggle to maintain proper health, which can lead to mass mortality. The loss of many of these species can lead to intense consequences on the marine food web in the Arctic Ocean, as many of these marine calcifying organisms are keystone species. Laboratory experiments on various marine biota in an elevated environment show that changes in aragonite saturation cause substantial changes in overall calcification rates for many species of marine organisms, including coccolithophore, foraminifera, pteropods, mussels, and clams.
Although the undersaturation of arctic water has been proven to have an effect on the ability of organisms to precipitate their shells, recent studies have shown that the calcification rate of calcifiers, such as corals, coccolithophores, foraminiferans and bivalves, decrease with increasing p, even in seawater supersaturated with respect to . Additionally, increased p has been found to have complex effects on the physiology, growth and reproductive success of various marine calcifiers. | 0 | Theoretical and Fundamental Chemistry |
The reactivity series is sometimes quoted in the strict reverse order of standard electrode potentials, when it is also known as the "electrochemical series".
The following list includes the metallic elements of the first six periods. It is mostly based on tables provided by NIST. However, not all sources give the same values: there are some differences between the precise values given by NIST and the CRC Handbook of Chemistry and Physics. In the first six periods this does not make a difference to the relative order, but in the seventh period it does, so the seventh-period elements have been excluded. (In any case, the typical oxidation states for the most accessible seventh-period elements thorium and uranium are too high to allow a direct comparison.)
Hydrogen has been included as a benchmark, although it is not a metal. Borderline germanium, antimony, and astatine have been included. Some other elements in the middle of the 4d and 5d rows have been omitted (Zr–Tc, Hf–Os) when their simple cations are too highly charged or of rather doubtful existence. Greyed-out rows indicate values based on estimation rather than experiment.
The positions of lithium, sodium and gold are changed on such a series.
Standard electrode potentials offer a quantitative measure of the power of a reducing agent, rather than the qualitative considerations of other reactive series. However, they are only valid for standard conditions: in particular, they only apply to reactions in aqueous solution. Even with this proviso, the electrode potentials of lithium, sodium and gold – and hence their positions in the electrochemical series – appear anomalous. The order of reactivity, as shown by the vigour of the reaction with water or the speed at which the metal surface tarnishes in air, appears to be
:caesium>potassium > sodium > lithium > alkaline earth metals,
i.e., alkali metals>alkaline earth metals
the same as the reverse order of the (gas-phase) ionization energies. This is borne out by the extraction of metallic lithium by the electrolysis of a eutectic mixture of lithium chloride and potassium chloride: lithium metal is formed at the cathode, not potassium. | 0 | Theoretical and Fundamental Chemistry |
In this example, a gene from mammalian gene library will be subcloned into a bacterial plasmid (destination platform). The bacterial plasmid is a piece of circular DNA which contains regulatory elements allowing for the bacteria to produce a gene product (gene expression) if it is placed in the correct place in the plasmid. The production site is flanked by two restriction enzyme cutting sites "A" and "B" with incompatible sticky ends.
The mammalian DNA does not come with these restriction sites, so they are built in by overlap extension PCR. The primers are designed to put the restriction sites carefully, so that the coding of the protein is in-frame, and a minimum of extra amino acids is implanted on either side of the protein.
Both the PCR product containing the mammalian gene with the new restriction sites and the destination plasmid are subjected to restriction digestion, and the digest products are purified by gel electrophoresis.
The digest products, now containing compatible sticky ends with each other (but incompatible sticky ends with themselves) are subjected to ligation, creating a new plasmid which contains the background elements of the original plasmid with a different insert.
The plasmid is transformed into bacteria and the identity of the insert is confirmed by DNA sequencing. | 1 | Applied and Interdisciplinary Chemistry |
The primary limitations of photofermentation as a sustainable energy source stem from the precise requirements of maintaining the bacteria in the bioreactor. Researchers have found it difficult to maintain a constant temperature for the bacteria within the bioreactor. Furthermore, the growth media for the bacteria must be rotated and refreshed without introducing air to the bioreactor system, complicating the already expensive bioreactor set up. | 1 | Applied and Interdisciplinary Chemistry |
These models based on data are black box systems, using mathematical and statistical concepts to link a certain input (for instance rainfall) to the model output (for instance runoff). Commonly used techniques are regression, transfer functions, neural networks and system identification. These models are known as stochastic hydrology models. Data based models have been used within hydrology to simulate the rainfall-runoff relationship, represent the impacts of antecedent moisture and perform real-time control on systems. | 1 | Applied and Interdisciplinary Chemistry |
Ethers have boiling points similar to those of the analogous alkanes. Simple ethers are generally colorless. | 0 | Theoretical and Fundamental Chemistry |
Hunter was born on 19 February 1965 in Dunedin, New Zealand. He is the son of John Alexander Hunter and his wife Alice Mary Hunter. He and his family moved to Northern Ireland in 1969. He was educated at Portstewart Primary School and the Coleraine Academical Institution, an all-boys grammar school in Coleraine, County Londonderry. He studied Natural Sciences and then chemistry at the University of Cambridge. He graduated with a Bachelor of Arts (BA) degree in 1986, this was later promoted to Master of Arts (MA Cantab) as per tradition, and with a Doctor of Philosophy (PhD) degree in 1989. | 0 | Theoretical and Fundamental Chemistry |
This syndrome is associated with increased susceptibility to tumors and growth abnormalities in children. A common cause of this syndrome is a mutation in an imprint control region <nowiki/>near the Igf2 gene. This imprint control region is normally bound by an insulator on the maternal allele, which represses an enhancer from acting on the Igf2 gene. This insulator is absent on the paternal allele and allows it access to the gene. Mutations in this imprint control region inhibit the insulator from binding, which derepresses enhancer activity on the maternal Igf2 gene. This abnormal derepression and increase in gene expression can result in Beckwith-Wiedemann syndrome. | 1 | Applied and Interdisciplinary Chemistry |
Estradiol with levonorgestrel in the form of a skin patch is used under the brand name Climara Pro for hormone replacement therapy in postmenstrual women, treating symptoms such as hot flashes or osteoporosis. The simultaneous delivery of a progestogen such as levonorgestrel is necessary for the protection of the endometrium. | 0 | Theoretical and Fundamental Chemistry |
Woodward and Hoffmann developed the pericyclic selection rules after performing extensive orbital-overlap calculations. At the time, Woodward wanted to know whether certain electrocyclic reactions might help synthesize vitamin B. Chemists knew that such reactions exhibited striking stereospecificity, but could not predict which stereoisomer a reaction might select. In 1965, Woodward–Hoffmann realized that a simple set of rules explained the observed stereospecificity at the ends of open-chain conjugated polyenes when heated or irradiated. In their original publication, they summarized the experimental evidence and molecular orbital analysis as follows:
*In an open-chain system containing 4n π electrons, the orbital symmetry of the highest occupied molecule orbital is such that a bonding interaction between the ends must involve overlap between orbital envelopes on opposite faces of the system and this can only be achieved in a conrotatory process.
*In open systems containing (4n + 2) π electrons, terminal bonding interaction within ground-state molecules requires overlap of orbital envelopes on the same face of the system, attainable only by disrotatory displacements.
*In a photochemical reaction an electron in the HOMO of the reactant is promoted to an excited state leading to a reversal of terminal symmetry relationships and stereospecificity.
In 1969, they would use correlation diagrams to state a generalized pericyclic selection rule equivalent to that now attached to their name: a pericyclic reaction is allowed if the sum of the number of suprafacial 4q + 2 components and number of antarafacial 4r components is odd. .
In the intervening four years, Howard Zimmerman and Michael J. S. Dewar proposed an equally general conceptual framework: the Möbius-Hückel concept, or aromatic transition state theory. In the Dewar-Zimmerman approach the orbital overlap topology (Hückel or Möbius) and electron count (4n + 2 or 4n) results in either an aromatic or antiaromatic transition state.
Meanwhile, Kenichi Fukui analyzed the frontier orbitals of such systems. A process in which the HOMO-LUMO interaction is constructive (results in a net bonding interaction) is favorable and considered symmetry-allowed, while a process in which the HOMO-LUMO interaction is non-constructive (results in bonding and antibonding interactions that cancel) is disfavorable and considered symmetry-forbidden.
Though conceptually distinct, aromatic transition state theory (Zimmerman and Dewar), frontier molecular orbital theory (Fukui), and orbital symmetry conservation (Woodward and Hoffmann) all make identical predictions. The Woodward–Hoffmann rules exemplify molecular orbital theory's power, and indeed helped demonstate that useful chemical results could arise from orbital analysis. The discovery would earn Hoffmann and Fukui the 1981 Nobel Prize in Chemistry. By that time, Woodward had died, and so was ineligible for the prize. | 0 | Theoretical and Fundamental Chemistry |
Transcription factors are proteins that bind to specific DNA sequences in order to regulate the expression of a given gene. There are approximately 1,400 transcription factors in the human genome and they constitute about 6% of all human protein coding genes. The power of transcription factors resides in their ability to activate and/or repress wide repertoires of downstream target genes. The fact that these transcription factors work in a combinatorial fashion means that only a small subset of an organism's genome encodes transcription factors.
Transcription factors function through a wide variety of mechanisms. In one mechanism, CpG methylation influences binding of most transcription factors to DNA—in some cases negatively and in others positively. In addition, often they are at the end of a signal transduction pathway that functions to change something about the factor, like its subcellular localization or its activity. Post-translational modifications to transcription factors located in the cytosol can cause them to translocate to the nucleus where they can interact with their corresponding enhancers. Other transcription factors are already in the nucleus, and are modified to enable the interaction with partner transcription factors. Some post-translational modifications known to regulate the functional state of transcription factors are phosphorylation, acetylation, SUMOylation and ubiquitylation.
Transcription factors can be divided in two main categories: activators and repressors. While activators can interact directly or indirectly with the core machinery of transcription through enhancer binding, repressors predominantly recruit co-repressor complexes leading to transcriptional repression by chromatin condensation of enhancer regions. It may also happen that a repressor may function by allosteric competition against a determined activator to repress gene expression: overlapping DNA-binding motifs for both activators and repressors induce a physical competition to occupy the site of binding. If the repressor has a higher affinity for its motif than the activator, transcription would be effectively blocked in the presence of the repressor.
Tight regulatory control is achieved by the highly dynamic nature of transcription factors. Again, many different mechanisms exist to control whether a transcription factor is active. These mechanisms include control over protein localization or control over whether the protein can bind DNA. An example of this is the protein HSF1, which remains bound to Hsp70 in the cytosol and is only translocated into the nucleus upon cellular stress such as heat shock. Thus the genes under the control of this transcription factor will remain untranscribed unless the cell is subjected to stress. | 1 | Applied and Interdisciplinary Chemistry |
Potential Sulfidic Acidity (PSA) is a function of the concentration of Reduced Inorganic Sulfur (RIS) in a soil sample. If RIS were the only pool of sulfur present in a sample, PSA could be directly estimated from the total concentration of sulfur. In some cases this may possible. However, sulfate minerals (e.g., gypsum, epsomite, and jarosite) and organic matter typically constitute additional sources of sulfur in most sulfidic and sulfuric soils. Chromium Reducible Sulfur (S or CRS) accurately measures RIS without significant interference from these other sources of sulfur. The chromium reduction method is summarized in Soil Chemical Methods:S by a hot acidic CrCl solution; the evolved gas is trapped quantitatively in a Zn acetate solution as solid ZnS. The ZnS is then treated with HCl to release HS into solution, which must then be quickly titrated with I solution to the blue-coloured end point indicated by the reaction of I with starch.) - is calculated as the difference between the sulfur determined via peroxide digestion (S) and sulfur extracted with a 1 M KCl solution (S).
S is a measure of sulfur associated with relativity soluble sulfates (e.g., gyspum and epsomite). S is a measure of sulfur associated with both RIS and organic matter. As such, S may overestimate PSA where samples contain even relatively small amounts of organic matter. Therefore, S is recommended for samples containing > 0.06% organic carbon.
Neither S nor S provide a measure of sulfur associated with sparingly soluble sulfate minerals such as jarosite. | 0 | Theoretical and Fundamental Chemistry |
In response to specific cases in which unfavorable data from pharmaceutical company-sponsored research were not published, the Pharmaceutical Research and Manufacturers of America published new guidelines urging companies to report all findings and limit the financial involvement in drug companies by researchers. The US Congress signed into law a bill which requires PhaseII and PhaseIII clinical trials to be registered by the sponsor on the clinicaltrials.gov website compiled by the National Institutes of Health.
Drug researchers not directly employed by pharmaceutical companies often seek grants from manufacturers, and manufacturers often look to academic researchers to conduct studies within networks of universities and their hospitals, e.g., for translational cancer research. Similarly, competition for tenured academic positions, government grants and prestige create conflicts of interest among academic scientists. According to one study, approximately 75% of articles retracted for misconduct-related reasons have no declared industry financial support. Seeding trials are particularly controversial.
In the United States, all clinical trials submitted to the FDA as part of a drug approval process are independently assessed by clinical experts within the Food and Drug Administration, including inspections of primary data collection at selected clinical trial sites.
In 2001, the editors of 12 major journals issued a joint editorial, published in each journal, on the control over clinical trials exerted by sponsors, particularly targeting the use of contracts which allow sponsors to review the studies prior to publication and withhold publication. They strengthened editorial restrictions to counter the effect. The editorial noted that contract research organizations had, by 2000, received 60% of the grants from pharmaceutical companies in the US. Researchers may be restricted from contributing to the trial design, accessing the raw data, and interpreting the results.
Despite explicit recommendations by stakeholders of measures to improve the standards of industry-sponsored medical research, in 2013, Tohen warned of the persistence of a gap in the credibility of conclusions arising from industry-funded clinical trials, and called for ensuring strict adherence to ethical standards in industrial collaborations with academia, in order to avoid further erosion of the public's trust. Issues referred for attention in this respect include potential observation bias, duration of the observation time for maintenance studies, the selection of the patient populations, factors that affect placebo response, and funding sources. | 1 | Applied and Interdisciplinary Chemistry |
The Newbery-Vautin chlorination process is a method for extracting gold from its ore through the use of chlorination. This process was jointly developed by James Cosmo Newbery and Claude Vautin. | 1 | Applied and Interdisciplinary Chemistry |
The absorbed dose also plays an important role in radiation protection, as it is the starting point for calculating the stochastic health risk of low levels of radiation, which is defined as the probability of cancer induction and genetic damage. The gray measures the total absorbed energy of radiation, but the probability of stochastic damage also depends on the type and energy of the radiation and the types of tissues involved. This probability is related to the equivalent dose in sieverts (Sv), which has the same dimensions as the gray. It is related to the gray by weighting factors described in the articles on equivalent dose and effective dose.
The International Committee for Weights and Measures states: "In order to avoid any risk of confusion between the absorbed dose D and the dose equivalent H, the special names for the respective units should be used, that is, the name gray should be used instead of joules per kilogram for the unit of absorbed dose D and the name sievert instead of joules per kilogram for the unit of dose equivalent H."
The accompanying diagrams show how absorbed dose (in grays) is first obtained by computational techniques, and from this value the equivalent doses are derived. For X-rays and gamma rays the gray is numerically the same value when expressed in sieverts, but for alpha particles one gray is equivalent to 20 sieverts, and a radiation weighting factor is applied accordingly. | 0 | Theoretical and Fundamental Chemistry |
One problem with the SBSP concept is the cost of space launches and the amount of material that would need to be launched.
Much of the material launched need not be delivered to its eventual orbit immediately, which raises the possibility that high efficiency (but slower) engines could move SPS material from LEO to GEO at an acceptable cost. Examples include ion thrusters or nuclear propulsion.
To give an idea of the scale of the problem, assuming a solar panel mass of 20 kg per kilowatt (without considering the mass of the supporting structure, antenna, or any significant mass reduction of any focusing mirrors) a 4 GW power station would weigh about 80,000 metric tons, all of which would, in current circumstances, be launched from the Earth. This is, however, far from the state of the art for flown spacecraft, which as of 2015 was 150 W/kg (6.7 kg/kW), and improving rapidly. Very lightweight designs could likely achieve 1 kg/kW, meaning 4,000 metric tons for the solar panels for the same 4 GW capacity station. Beyond the mass of the panels, overhead (including boosting to the desired orbit and stationkeeping) must be added.
To these costs must be added the environmental impact of heavy space launch missions, if such costs are to be used in comparison to earth-based energy production. For comparison, the direct cost of a new coal or nuclear power plant ranges from $3 billion to $6 billion per GW (not including the full cost to the environment from emissions or storage of spent nuclear fuel, respectively). | 0 | Theoretical and Fundamental Chemistry |
Isoenzymes, or isozymes, are multiple forms of an enzyme, with slightly different protein sequence and closely similar but usually not identical functions. They are either products of different genes, or else different products of alternative splicing. They may either be produced in different organs or cell types to perform the same function, or several isoenzymes may be produced in the same cell type under differential regulation to suit the needs of changing development or environment. LDH (lactate dehydrogenase) has multiple isozymes, while fetal hemoglobin is an example of a developmentally regulated isoform of a non-enzymatic protein. The relative levels of isoenzymes in blood can be used to diagnose problems in the organ of secretion . | 0 | Theoretical and Fundamental Chemistry |
Alanine is produced by the transamination of one molecule of pyruvate using two alternate steps: 1) conversion of glutamate to α-ketoglutarate using a glutamate-alanine transaminase, and 2) conversion of valine to α-ketoisovalerate via Transaminase C.
Not much is known about the regulation of alanine synthesis. The only definite method is the bacteriums ability to repress Transaminase C activity by either valine or leucine (see ilvEDA' operon). Other than that, alanine biosynthesis does not seem to be regulated. | 1 | Applied and Interdisciplinary Chemistry |
The ε-amino groups of the lysine residues in urease and phosphotriesterase also feature carbamate. The carbamate derived from aminoimidazole is an intermediate in the biosynthesis of inosine. Carbamoyl phosphate is generated from carboxyphosphate
rather than CO. | 0 | Theoretical and Fundamental Chemistry |
In 2016, microcystin had been found in San Francisco Bay Area shellfish in seawater, apparently from freshwater runoff, exacerbated by drought. | 1 | Applied and Interdisciplinary Chemistry |
Alpha-acceptor-substituted primary aliphatic amines R-CH-NH (R = COOR, CN, CHO, COR) react with nitrous acid to generate the diazo compound. | 0 | Theoretical and Fundamental Chemistry |
Biological nitrogen fixation was discovered by Jean-Baptiste Boussingault in 1838. Later, in 1880, the process by which it happens was discovered by German agronomist Hermann Hellriegel and and was fully described by Dutch microbiologist Martinus Beijerinck.
"The protracted investigations of the relation of plants to the acquisition of nitrogen begun by de Saussure, Ville, Lawes, Gilbert and others, and culminated in the discovery of symbiotic fixation by Hellriegel and Wilfarth in 1887."
"Experiments by Bossingault in 1855 and Pugh, Gilbert & Lawes in 1887 had shown that nitrogen did not enter the plant directly. The discovery of the role of nitrogen fixing bacteria by Herman Hellriegel and Herman Wilfarth in 1886-1888 would open a new era of soil science."
In 1901, Beijerinck showed that Azotobacter chroococcum was able to fix atmospheric nitrogen. This was the first species of the azotobacter genus, so-named by him. It is also the first known diazotroph, species that use diatomic nitrogen as a step in the complete nitrogen cycle. | 1 | Applied and Interdisciplinary Chemistry |
Scientists use a number of methods to study the complex structures and functions of the 3′ UTR. Even if a given 3′-UTR in an mRNA is shown to be present in a tissue, the effects of localization, functional half-life, translational efficiency, and trans-acting elements must be determined to understand the 3′-UTR's full functionality. Computational approaches, primarily by sequence analysis, have shown the existence of AREs in approximately 5 to 8% of human 3′-UTRs and the presence of one or more miRNA targets in as many as 60% or more of human 3′-UTRs. Software can rapidly compare millions of sequences at once to find similarities between various 3′ UTRs within the genome. Experimental approaches have been used to define sequences that associate with specific RNA-binding proteins; specifically, recent improvements in sequencing and cross-linking techniques have enabled fine mapping of protein binding sites within the transcript. Induced site-specific mutations, for example those that affect the termination codon, polyadenylation signal, or secondary structure of the 3′-UTR, can show how mutated regions can cause translation deregulation and disease. These types of transcript-wide methods should help our understanding of known cis elements and trans-regulatory factors within 3′-UTRs. | 1 | Applied and Interdisciplinary Chemistry |
Biodiesel production is the process of producing the biofuel, biodiesel, through the chemical reactions of transesterification and esterification. This process renders a product (chemistry) and by-products.
The fats and oils react with short-chain alcohols (typically methanol or ethanol). The alcohols used should be of low molecular weight. Ethanol is the most used because of its low cost, however, greater conversions into biodiesel can be reached using methanol. Although the transesterification reaction can be catalyzed by either acids or bases, the base-catalyzed reaction is more common. This path has lower reaction times and catalyst cost than those acid catalysis. However, alkaline catalysis has the disadvantage of high sensitivity to both water and free fatty acids present in the oils. | 0 | Theoretical and Fundamental Chemistry |
In 1776, Laplace formulated a single set of linear partial differential equations for tidal flow described as a barotropic two-dimensional sheet flow. Coriolis effects are introduced as well as lateral forcing by gravity. Laplace obtained these equations by simplifying the fluid dynamics equations, but they can also be derived from energy integrals via Lagrange's equation.
For a fluid sheet of average thickness D, the vertical tidal elevation ζ, as well as the horizontal velocity components u and v (in the latitude φ and longitude λ directions, respectively) satisfy Laplace's tidal equations:
where Ω is the angular frequency of the planets rotation, g is the planets gravitational acceleration at the mean ocean surface, a is the planetary radius, and U is the external gravitational tidal-forcing potential.
William Thomson (Lord Kelvin) rewrote Laplace's momentum terms using the curl to find an equation for vorticity. Under certain conditions this can be further rewritten as a conservation of vorticity. | 1 | Applied and Interdisciplinary Chemistry |
Ureas in the more general sense can be accessed in the laboratory by reaction of phosgene with primary or secondary amines:
These reactions proceed through an isocyanate intermediate. Non-symmetric ureas can be accessed by the reaction of primary or secondary amines with an isocyanate.
Urea can also be produced by heating ammonium cyanate to 60 °C. | 0 | Theoretical and Fundamental Chemistry |
The substitution of CO ligands can be induced thermally or photochemically by donor ligands. The range of ligands is large, and includes phosphines, cyanide (CN), nitrogen donors, and even ethers, especially chelating ones. Alkenes, especially dienes, are effective ligands that afford synthetically useful derivatives. Substitution of 18-electron complexes generally follows a dissociative mechanism, involving 16-electron intermediates.
Substitution proceeds via a dissociative mechanism:
:M(CO) → M(CO) + CO
:M(CO) + L → M(CO)L
The dissociation energy is for nickel tetracarbonyl and for chromium hexacarbonyl.
Substitution in 17-electron complexes, which are rare, proceeds via associative mechanisms with a 19-electron intermediates.
:M(CO) + L → M(CO)L
:M(CO)L → M(CO)L + CO
The rate of substitution in 18-electron complexes is sometimes catalysed by catalytic amounts of oxidants, via electron transfer. | 0 | Theoretical and Fundamental Chemistry |
The importance of the mathematical methods' efficiency arises from the large scale of simulated network. It is required that the computation costs of the simulation method be low, this is related to the computation time and computer storage. At the same time the accuracy of the computed values must acceptable for the particular model. | 1 | Applied and Interdisciplinary Chemistry |
The areas are saturated with unexploded shells (including many gas shells), grenades, and rusting ammunition. Soils were heavily polluted by lead, mercury, chlorine, arsenic, various dangerous gases, acids, and human and animal remains. The area was also littered with ammunition depots and chemical plants. The land of the Western Front is covered in old trenches and shell holes.
Each year, numerous unexploded shells are recovered from former WWI battlefields in what is known as the iron harvest. According to the Sécurité Civile, the French agency in charge of the land management of Zone Rouge, 300 to 700 more years at this current rate will be needed to clean the area completely. Some experiments conducted in 2005–06 discovered up to 300 shells per hectare (120 per acre) in the top of soil in the worst areas.
Areas where 99% of all plants still die remain off limits (for example, two small pieces of land close to Ypres and the Woëvre), as arsenic constitutes up to 175,907 mg (175.9 g) per kilogramme of soil samples because arsenical shells were destroyed in the 1920s. | 1 | Applied and Interdisciplinary Chemistry |
In biochemistry and molecular biology, SDD-AGE is short for Semi-Denaturating Detergent Agarose Gel Electrophoresis. This is a method for detecting and characterizing large protein polymers which are stable in 2% SDS at room temperature, unlike most large protein complexes. This method is very useful for studying prions and amyloids, which are characterized by the formation of proteinaceous polymers. Agarose is used for the gel since the SDS-resistant polymers are large (in the 200-4000+ kDa range) and cannot enter a conventional polyacrylamide gel, which has small pores. Agarose on the other hand has large pores, which allows for the separation of polymers.
Use of this method allowed researchers to understand that at least some types of prion aggregates existed in a two-level structure - protein molecules grouped into polymers, which are very stable and withstand treatment with 2% SDS at room temperature, and aggregates, which are bundles of polymers, that dissociate under these conditions.
Differences in the size of polymers can indicate the efficiency of polymer fragmentation in vivo. | 1 | Applied and Interdisciplinary Chemistry |
Celecoxib was the first specific inhibitor of COX-2 approved to treat patients with rheumatism and osteoarthritis. A study showed that the absorption rate, when given orally, is moderate, and peak plasma concentration occurs after about 2–4 hours. However, the extent of absorption is not well known. Celecoxib has the affinity to bind extensively to plasma proteins, especially to plasma albumin. It has an apparent volume of distribution (V) of 455 +/- 166 L in humans and the area under the plasma concentration-time curve (AUC) increases proportionally to increased oral doses, between 100 and 800 mg. Celecoxib is metabolized primarily by CYP2C9 isoenzyme to carboxylic acid and also by non-CYP-dependent glucuronidation to glucuronide metabolites. The metabolites are excreted in urine and feces, with a small proportion of unchanged drug (2%) in the urine. Its elimination half-life is about 11 hours (6–12 hours) in healthy individuals, but racial differences in drug disposition and pharmacokinetic changes in the elderly have been reported. People with chronic kidney disease appear to have 43% lower plasma concentration compared to healthy individuals, with a 47% increase in apparent clearance, and it can be expected that patients with mild to moderate hepatic impairment have increased steady-state AUC. | 1 | Applied and Interdisciplinary Chemistry |
Inorganic fluxes contain components playing the same role as in organic fluxes. They are more often used in brazing and other high-temperature applications, where organic fluxes have insufficient thermal stability. The chemicals used often simultaneously act as both vehicles and activators; typical examples are borax, borates, fluoroborates, fluorides and chlorides. Halogenides are active at lower temperatures than borates, and are therefore used for brazing of aluminium and magnesium alloys; they are however highly corrosive. | 1 | Applied and Interdisciplinary Chemistry |
Crystallite size in monodisperse microstructures is usually approximated from X-ray diffraction patterns and grain size by other experimental techniques like transmission electron microscopy. Solid objects large enough to see and handle are rarely composed of a single crystal, except for a few cases (gems, silicon single crystals for the electronics industry, certain types of fiber, single crystals of a nickel-based superalloy for turbojet engines, and some ice crystals which can exceed 0.5 meters in diameter). The crystallite size can vary from a few nanometers to several millimeters. | 1 | Applied and Interdisciplinary Chemistry |
The background noise caused by single nucleotide polymorphisms (SNPs), somatic mutations, pseudogenes and sequencing errors reduce the reliability of the signal, especially in a single-cell context. | 1 | Applied and Interdisciplinary Chemistry |
In chromatography, endcapping refers to the replacement of accessible silanol groups in a bonded stationary phase by trimethylsilyl groups. End-capped columns have much lower residual silanol group activity compared to non-endcapped columns. Endcapped columns show decreased retention for hydrogen bond acceptors, such as ionized bases, and increased retention for protonated bases. | 0 | Theoretical and Fundamental Chemistry |
A radical is a molecule with an odd number of electrons, and is induced in a variety of ways, including ultra-violet radiation. A sun burn is largely due to radical formation from this radiation. The radical-pair, however, is not simply two radicals. This is because radical-pairs (specifically singlets) are quantum entangled, even as separate molecules. More fundamental to the radical-pair mechanism, however, is the fact that radical-pair electrons both have spin, short for spin angular momentum, which gives each separate radical a magnetic moment. Therefore, spin states can be altered by magnetic fields. | 0 | Theoretical and Fundamental Chemistry |
The following are some of the more important of his works:
* 1660 – New Experiments Physico-Mechanical: Touching the Spring of the Air and their Effects
* 1661 – The Sceptical Chymist
* 1662 – Whereunto is Added a Defence of the Authors Explication of the Experiments, Against the Obiections of Franciscus Linus and Thomas Hobbes (a book-length addendum to the second edition of New Experiments Physico-Mechanical)
* 1663 – Considerations touching the Usefulness of Experimental Natural Philosophy (followed by a second part in 1671)
* 1664 – Experiments and Considerations Touching Colours, with Observations on a Diamond that Shines in the Dark
* 1665 – New Experiments and Observations upon Cold
* 1666 – Hydrostatical Paradoxes
* 1666 – Origin of Forms and Qualities according to the Corpuscular Philosophy. (A continuation of his work on the spring of air demonstrated that a reduction in ambient pressure could lead to bubble formation in living tissue. This description of a viper in a vacuum was the first recorded description of decompression sickness.)
* 1669 – A Continuation of New Experiments Physico-mechanical, Touching the Spring and Weight of the Air, and Their Effects
* 1670 – Tracts about the Cosmical Qualities of Things, the Temperature of the Subterraneal and Submarine Regions, the Bottom of the Sea, &tc. with an Introduction to the History of Particular Qualities
* 1672 – Origin and Virtues of Gems
* 1673 – Essays of the Strange Subtilty, Great Efficacy, Determinate Nature of Effluviums
* 1674 – Two volumes of tracts on the Saltiness of the Sea, Suspicions about the Hidden Realities of the Air, Cold, Celestial Magnets
* 1674 – Animadversions upon Mr. Hobbess Problemata de Vacuo'
* 1676 – Experiments and Notes about the Mechanical Origin or Production of Particular Qualities, including some notes on electricity and magnetism
* 1678 – Observations upon an artificial Substance that Shines without any Preceding Illustration
* 1680 – The Aerial Noctiluca
* 1682 – New Experiments and Observations upon the Icy Noctiluca (a further continuation of his work on the air)
* 1684 – Memoirs for the Natural History of the Human Blood
* 1685 – Short Memoirs for the Natural Experimental History of Mineral Waters
* 1686 – A Free Enquiry into the Vulgarly Received Notion of Nature
* 1690 – Medicina Hydrostatica
* 1691 – Experimenta et Observationes Physicae
Among his religious and philosophical writings were:
* 1648 (1659) – Some Motives and Incentives to the Love of God, often known by its running head Seraphic Love, written in 1648, but not published until 1659
* 1663 – Some Considerations Touching the Style of the H[oly] Scriptures
* 1664 – Excellence of Theology compared with Natural Philosophy
* 1665 – Occasional Reflections upon Several Subjects, which was ridiculed by Swift in Meditation Upon a Broomstick, and by Butler in An Occasional Reflection on Dr Charltons Feeling a Dogs Pulse at Gresham College
* 1675 – Some Considerations about the Reconcileableness of Reason and Religion, with a Discourse about the Possibility of the Resurrection
* 1687 – The Martyrdom of Theodora, and of Didymus
* 1690 – The Christian Virtuoso | 1 | Applied and Interdisciplinary Chemistry |
The theorem is also useful on a more microscopic scale, in biology. Living systems, such as cells, can be analyzed thermodynamically. They are rather complex systems, where many energy transformations occur, and they often waste heat. Hence, the Gouy-Stodola theorem may be useful, in certain situations, to perform exergy analysis on such systems. In particular, it may help to highlight differences between healthy and diseased cells.
Generally, the theorem may find applications in fields of biomedicine, or where biology and physics cross over, such as biochemical engineering thermodynamics. | 0 | Theoretical and Fundamental Chemistry |
Dorn was born in Guttstadt (Dobre Miasto), Province of Prussia (nowadays Warmia in Poland), and died in Halle, Province of Saxony. He was educated at Königsberg and went on to teach at the university level. In 1885, at Halle University, Dorn took over the position of personal ordinarius professor for theoretical physics from Anton Oberbeck. Since Dorn was already an ordinarius professor, he was allowed to assume the title so as to not appear as having been demoted. In 1895, Dorn succeeded Hermann Knoblauch at Halle as the ordinarius professor for experimental physics and director of the physics institute. Dorns previous duties were assumed by Carl Schmidt, who had been a Privatdozent and was called as an extraordinarius' professor for theoretical physics.
In 1900, Dorn published a paper in which he described experiments that repeated and extended some earlier work on thorium by Ernest Rutherford. Dorn verified Rutherford's observation that a radioactive material was emitted by thorium, and discovered that a similar emission arose from the element radium. Additional work by Rutherford and Soddy showed that the same emission came from both thorium and radium, that it was a gas, and that it was actually a new element.
Dorn called the radioactive gaseous product from radium simply "emanation", but in 1904 Rutherford introduced the name "radium emanation" for the same material. Ramsay later suggested "niton", from the Latin word "nitens" meaning "shining". In 1923 the name was again changed, this time to radon by an international body of scientists.
Marshall and Marshall have examined the original papers leading to radons discovery and their work should be consulted for a full treatment and extensive references. They conclude that it is actually Rutherford who should be awarded credit for radons discovery since he was the first to detect the element being emitted from any radioisotope (thorium) and the first to demonstrate radons gaseous nature. Rutherford was also the first to integrate his own work on radon with that of others on radons atomic mass, its spectrum, and its position on the periodic table. | 1 | Applied and Interdisciplinary Chemistry |
Type B (70%Pt/30%Rh–94%Pt/6%Rh, by weight) thermocouples are suited for use at up to 1800 °C. Type-B thermocouples produce the same output at 0 °C and 42 °C, limiting their use below about 50 °C. The emf function has a minimum around 21 °C, meaning that cold-junction compensation is easily performed, since the compensation voltage is essentially a constant for a reference at typical room temperatures. | 1 | Applied and Interdisciplinary Chemistry |
Molecular distillation is a type of short-path vacuum distillation, characterized by an extremely low vacuum pressure, 0.01 torr or below, which is performed using a molecular still. It is a process of separation, purification and concentration of natural products, complex and thermally sensitive molecules for example vitamins and polyunsaturated fatty acids. This process is characterized by short term exposure of the distillate liquid to high temperatures in high vacuum (around mmHg) in the distillation column and a small distance between the evaporator and the condenser around 2 cm. In molecular distillation, fluids are in the free molecular flow regime, i.e. the mean free path of molecules is comparable to the size of the equipment. The gaseous phase no longer exerts significant pressure on the substance to be evaporated, and consequently, rate of evaporation no longer depends on pressure. The motion of molecules is in the line of sight, because they do not form a continuous gas anymore. Thus, a short path between the hot surface and the cold surface is necessary, typically by suspending a hot plate covered with a film of feed next to a cold plate with a line of sight in between.
This process has the advantages of avoiding the problem of toxicity that occurs in techniques that use solvents as the separating agent, and also of minimizing losses due to thermal decomposition. and can be used in a continuous feed process to harvest distillate without having to break vacuum.
Molecular distillation is used industrially for purification of oils. It is also used to enrich borage oil in γ-linolenic acid (GLA) and also to recover tocopherols from deodorizer distillate of soybean oil (DDSO). Molecular stills were historically used by Wallace Carothers in the synthesis of larger polymers, as a reaction product, water, interfered with polymerization by undoing the reaction via hydrolysis, but the water could be removed by the molecular still. | 0 | Theoretical and Fundamental Chemistry |
In 1845, George Gabriel Stokes published another important set of equations, today known as the Navier-Stokes equations. Claude-Louis Navier developed the equations first using molecular theory, which was further confirmed by Stokes using continuum theory. The Navier-Stokes equations describe the motion of fluids:
When the fluid is inviscid, or the viscosity can be assumed to be negligible, the Navier-Stokes equation simplifies to the Euler equation: This simplification is much easier to solve, and can apply to many types of flow in which viscosity is negligible. Some examples include flow around an airplane wing, upstream flow around bridge supports in a river, and ocean currents.
The Navier-Stokes equation reduces to the Euler equation when . Another condition that leads to the elimination of viscous force is , and this results in an "inviscid flow arrangement". Such flows are found to be vortex-like. | 1 | Applied and Interdisciplinary Chemistry |
The Vlasov–Poisson equations are an approximation of the Vlasov–Maxwell equations in the non-relativistic zero-magnetic field limit:
and Poisson's equation for self-consistent electric field:
Here is the particles electric charge, is the particles mass, is the self-consistent electric field, the self-consistent electric potential, is the electric charge density, and is the electric permitivity.
Vlasov–Poisson equations are used to describe various phenomena in plasma, in particular Landau damping and the distributions in a double layer plasma, where they are necessarily strongly non-Maxwellian, and therefore inaccessible to fluid models. | 1 | Applied and Interdisciplinary Chemistry |
In instances where the biomass and enzyme concentrations are not appreciably changing in time, we can assume that biomass dynamics is negligible and that the total enzyme concentration is constant, and the GEBIK equations become
Eqs. () for isotopic compositions, Eq. () for the fractionation factor and Eq. () for the enrichment factor equally applies to the GEBIK equations under the BFEI hypothesis. | 0 | Theoretical and Fundamental Chemistry |
Unlike ground state oxygen, singlet oxygen participates in Diels–Alder [4+2]- and [2+2]-cycloaddition reactions and formal concerted ene reactions. It oxidizes thioethers to sulfoxides. Organometallic complexes are often degraded by singlet oxygen. With some substrates 1,2-dioxetanes are formed; cyclic dienes such as 1,3-cyclohexadiene form [4+2] cycloaddition adducts.
The [4+2]-cycloaddition between singlet oxygen and furans is widely used in organic synthesis.
In singlet oxygen reactions with alkenic allyl groups, e.g., citronella, shown, by abstraction of the allylic proton, in an ene-like reaction, yielding the allyl hydroperoxide, R–O–OH (R = alkyl), which can then be reduced to the corresponding allylic alcohol.
In reactions with water trioxidane, an unusual molecule with three consecutive linked oxygen atoms, is formed. | 0 | Theoretical and Fundamental Chemistry |
Britannia metal (also called britannium or Britannia ware) is a specific type of pewter alloy, favoured for its silvery appearance and smooth surface. The composition by weight is typically about 92% tin, 6% antimony, and 2% copper.
Britannia metal is usually spun rather than cast, and melts at 255 degrees Celsius. | 1 | Applied and Interdisciplinary Chemistry |
was a Japanese chemist who was best known for his discovery of the Negishi coupling. He spent most of his career at Purdue University in the United States, where he was the Herbert C. Brown Distinguished Professor and the director of the Negishi-Brown Institute. He was awarded the 2010 Nobel Prize in Chemistry "for palladium catalyzed cross couplings in organic synthesis" jointly with Richard F. Heck and Akira Suzuki. | 0 | Theoretical and Fundamental Chemistry |
The initial concept of an attainable region for chemical processes was proposed by Fritz Horn in 1964, where he believed in geometric methods to improve process design. These ideas were later refined and made specific to chemical reactors by co-developers David Glasser, Diane Hildebrandt, and Martin Feinberg. | 1 | Applied and Interdisciplinary Chemistry |
The College of Engineering at UC Berkeley defines Environmental Engineering Science, including the following: | 1 | Applied and Interdisciplinary Chemistry |
Sodium hydroxide also reacts with acidic oxides, such as sulfur dioxide. Such reactions are often used to "scrub" harmful acidic gases (like and ) produced in the burning of coal and thus prevent their release into the atmosphere. For example, | 0 | Theoretical and Fundamental Chemistry |
Kodevirions are FSL modified viruses. Several FSL Kode constructs have been used to label viruses to assist in their flow-cytometric visualisation and to track them real time distribution in animal models. They have also been used to modify the surface of viruses with the intention of targeting them to be used to attach tumors (oncolytic). | 1 | Applied and Interdisciplinary Chemistry |
The presynaptic bouton has an efficiently orchestrated process to fuse vesicles to the presynaptic membrane to release neurotransmitters and regenerate neurotransmitter vesicles. This process called the synaptic vesicle cycle maintains the number of vesicles in the presynaptic bouton and allows the synaptic terminal to be an autonomous unit. The cycle begins with (1) a region of the golgi apparatus is pinched off to form the synaptic vesicle and this vesicle is transported to the synaptic terminal. At the terminal (2) the vesicle is filled with neurotransmitter. (3) The vesicle is transported to the active zone and docked in close proximity to the plasma membrane. (4) During an action potential the vesicle is fused with the membrane, releases the neurotransmitter and allows the membrane proteins previously on the vesicle to diffuse to the periactive zone. (5) In the periactive zone the membrane proteins are sequestered and are endocytosed forming a clathrin coated vesicle. (6) The vesicle is then filled with neurotransmitter and is then transported back to the active zone.
The endocytosis mechanism is slower than the exocytosis mechanism. This means that in intense activity the vesicle in the terminal can become depleted and no longer available to be released. To help prevent the depletion of synaptic vesicles the increase in calcium during intense activity can activate calcineurin which dephosphorylate proteins involved in clathrin-mediated endocytosis. | 1 | Applied and Interdisciplinary Chemistry |
Chiral drugs with stereo-labile configuration are likely to undergo interconversion of the enantiomers that may be enzymatic (biological) or non-enzymatic. Enzyme-mediated conversion is the process of chiral inversion that happens in a living organism. Non-enzymatic inversion of drugs is important and relevant in the pharmaceutical manufacturing process. This may have impact on the shelf-life of a drug and the economic feasibility of the resolution. Inversion can also happen without enzymes when precolumn derivatization is used in enantioselective chromatographic separation techniques. Racemization can also happen in the acidic environment of the stomach and other bodily fluids. | 0 | Theoretical and Fundamental Chemistry |
Berlin is a member of the New York Academy of Science, the American Chemical Society, and the Royal Society of Chemistry. He is a member of the International Society for the Study of the Origin of Life, an honor Member of the European Molecular Liquids Group, a fellow of the Mendeleev Chemical Society and the Russian Physical Society. His work has earned him many awards, including EU Erasmus Mundus Professorship Award (2009) and Scientific Award of Hans Veilberth Foundation, Germany (2007). Most recently, Yuri Berlin was awarded the Maria Sklodowska-Curie Medal (2019) in recognition of his distinguished achievements in radiation research as well as the long-lasting and productive cooperation with Polish scientists. | 0 | Theoretical and Fundamental Chemistry |
Mercury(II) oxide, also called mercuric oxide or simply mercury oxide, is the inorganic compound with the formula HgO. It has a red or orange color. Mercury(II) oxide is a solid at room temperature and pressure. The mineral form montroydite is very rarely found. | 0 | Theoretical and Fundamental Chemistry |
In February 2020 the FDA published the Table of Pharmacogenetic Associations. For the gene-drug pairs included in the table, "the FDA has evaluated and believes there is sufficient scientific evidence to suggest that subgroups of patients with certain genetic variants, or genetic variant-inferred phenotypes (such as affected subgroup in the table below), are likely to have altered drug metabolism, and in certain cases, differential therapeutic effects, including differences in risks of adverse events."
"The information in this Table is intended primarily for prescribers, and patients should not adjust their medications without consulting their prescriber. This version of the table is limited to pharmacogenetic associations that are related to drug metabolizing enzyme gene variants, drug transporter gene variants, and gene variants that have been related to a predisposition for certain adverse events. The FDA recognizes that various other pharmacogenetic associations exist that are not listed here, and this table will be updated periodically with additional pharmacogenetic associations supported by sufficient scientific evidence." | 1 | Applied and Interdisciplinary Chemistry |
Cnoidal waves can be derived directly from the inviscid, irrotational and incompressible flow equations, and expressed in terms of three invariants of the flow, as shown by in their research on undular bores. In a frame of reference moving with the phase speed, in which reference frame the flow becomes a steady flow, the cnoidal wave solutions can directly be related to the mass flux, momentum flux and energy head of the flow. Following —using a stream function description of this incompressible flow—the horizontal and vertical components of the flow velocity are the spatial derivatives of the stream function Ψ(ξ,z): +∂Ψ and −∂Ψ, in the ξ and z direction respectively (ξ = x−ct). The vertical coordinate z is positive in the upward direction, opposite to the direction of the gravitational acceleration, and the zero level of z is at the impermeable lower boundary of the fluid domain. While the free surface is at z = ζ(ξ); note that ζ is the local water depth, related to the surface elevation η(ξ) as ζ = h + η with h the mean water depth.
In this steady flow, the discharge Q through each vertical cross section is a constant independent of ξ, and because of the horizontal bed also the horizontal momentum flux S, divided by the density ρ, through each vertical cross section is conserved. Further, for this inviscid and irrotational flow, Bernoullis principle can be applied and has the same Bernoulli constant R' everywhere in the flow domain. They are defined as:
For fairly long waves, assuming the water depth ζ is small compared to the wavelength λ, the following relation is obtained between the water depth ζ(ξ) and the three invariants Q, R and S:
This nonlinear and first-order ordinary differential equation has cnoidal wave solutions.
For very long waves of infinitesimal amplitude on a fluid of depth h and with a uniform flow velocity v, the flow constants are according to the shallow water equations:
: and
Equation () can be brought into non-dimensional form by use of the discharge Q and gravitational acceleration g, and defining the critical depth h:
related to the critical flow demarcation between subcritical flow and supercritical flow (see also Froude number). Consequently, the non-dimensional form of the equation is
with
: and | 1 | Applied and Interdisciplinary Chemistry |
Cleavage is a physical property traditionally used in mineral identification, both in hand-sized specimen and microscopic examination of rock and mineral studies. As an example, the angles between the prismatic cleavage planes for the pyroxenes (88–92°) and the amphiboles (56–124°) are diagnostic.
Crystal cleavage is of technical importance in the electronics industry and in the cutting of gemstones.
Precious stones are generally cleaved by impact, as in diamond cutting.
Synthetic single crystals of semiconductor materials are generally sold as thin wafers which are much easier to cleave. Simply pressing a silicon wafer against a soft surface and scratching its edge with a diamond scribe is usually enough to cause cleavage; however, when dicing a wafer to form chips, a procedure of scoring and breaking is often followed for greater control. Elemental semiconductors (silicon, germanium, and diamond) are diamond cubic, a space group for which octahedral cleavage is observed. This means that some orientations of wafer allow near-perfect rectangles to be cleaved. Most other commercial semiconductors (GaAs, InSb, etc.) can be made in the related zinc blende structure, with similar cleavage planes. | 0 | Theoretical and Fundamental Chemistry |
George Oliver was a physician practicing in the spa town of Harrogate in North Yorkshire while Edward Albert Schäfer was Professor of Physiology at University College London. In 1918, he prefixed the surname of his physiology teacher, William Sharpey, to his own to become Edward Albert Sharpey Schafer. The canonical story, told by Henry Hallett Dale, who worked at University College London from 1902 to 1904, runs as follows:
Despite this tale being reiterated many times, it is not beyond doubt. Dale himself said that it was handed down at University College and showed some surprise that the constriction of the radial artery was measurable. Of Olivers descendants, none recalled experiments on his son. Dales report of subcutaneous injections contradicts the concerned parties. Oliver: “During the winter of 1893–4, while prosecuting an inquiry as to … agents that vary the caliber of … arteries … I found that the administration by the mouth of a glycerin extract of the adrenals of the sheep and calf produced a marked constrictive action on the arteries.” Schafer: “In the autumn of 1893 there called upon me in my laboratory at University College a gentleman who was personally unknown to me. … I found that my visitor was Dr. George Oliver, <who> was desirous of discussing with me the results which he had been obtaining from the exhibition by the mouth of extracts from certain animal tissues, and the effects which these had in his hands produced upon the blood vessels of man.” Systemic effects of orally given adrenaline are highly unlikely, so details of the canonical text may be legend.
On March 10, 1894, Oliver and Schafer presented their findings to the Physiological Society in London. A 47-page account followed a year later, in the style of the time without statistics, but with precise description of many individual experiments and 25 recordings on kymograph smoked drums, showing, besides the blood pressure increase, reflex bradycardia and contraction of the spleen. ″It appears to be established as the result of these investigations that the suprarenal capsules are to be regarded although ductless, as strictly secreting glands. The material which they form and which is found, at least in its fully active condition, only in the medulla of the gland, produces striking physiological effects upon the muscular tissue generally, and especially upon that of the heart and arteries. Its action is produced mainly if not entirely by direct action.″
The reports created a sensation. Oliver was fast to try adrenal extracts in patients, orally again and rather indiscriminately, from Addisons disease, hypotension (″loss of vasomotor tone″), Diabetes mellitus and Diabetes insipidus to Graves disease (″exophthalmic goiter″). It seems he adhered to contemporary ideas of organotherapy, believing that powerful substances existed in tissues and ought to be discovered for medicinal use. He immediately went on to extract the pituitary gland and, again with Schafer, discovered vasopressin. In 1903 adrenaline, meanwhile purified, was first used in asthma. The use was based, not on the bronchodilator effect, which was discovered later, but on the vasoconstrictor effect, which was hoped to alleviate the “turgidity of the bronchial mucosa” – presumably vascular congestion and edema. Also as of 1903, adrenaline was added to local anesthetic solutions. The surgeon Heinrich Braun in Leipzig showed that it prolonged the anesthesia at the injection site and simultaneously reduced ″systemic″ effects elsewhere in the body. | 1 | Applied and Interdisciplinary Chemistry |
The Delhi Jal Board (DJB) is currently operating on the construction of the largest sewage treatment plant in India. It [https://www.thehindu.com/news/cities/Delhi/stp-at-okhla-to-be-completed-by-2022-end/article36528044.ece will be operational by the end of 2022] with an estimated capacity of 564 MLD. It is supposed to solve the existing situation wherein untreated sewage water is being discharged directly into the river Yamuna. | 1 | Applied and Interdisciplinary Chemistry |
In terms of genomic coverage and accuracy, whole genome sequencing can broadly be classified into either of the following:
*A draft sequence, covering approximately 90% of the genome at approximately 99.9% accuracy
*A finished sequence, covering more than 95% of the genome at approximately 99.99% accuracy
Producing a truly high-quality finished sequence by this definition is very expensive. Thus, most human "whole genome sequencing" results are draft sequences (sometimes above and sometimes below the accuracy defined above). | 1 | Applied and Interdisciplinary Chemistry |
Anaerobic corrosion (also known as hydrogen corrosion) is a form of metal corrosion occurring in anoxic water. Typically following aerobic corrosion, anaerobic corrosion involves a redox reaction that reduces hydrogen ions and oxidizes a solid metal. This process can occur in either abiotic conditions through a thermodynamically spontaneous reaction or biotic conditions through a process known as bacterial anaerobic corrosion. Along with other forms of corrosion, anaerobic corrosion is significant when considering the safe, permanent storage of chemical waste. | 1 | Applied and Interdisciplinary Chemistry |
Zn isotopes may be useful as a tracer for breast cancer. Relative to non-cancerous patients, breast cancer patients are known to have significantly higher concentrations of Zn in their breast tissue, but lower concentrations in their blood serum and erythrocytes, due to overexpression of Zn transporters in breast cancer cells. Consistent with these body-wide shifts in Zn homeostasis, δZn values in breast cancer tumors of 5 patients were found to be anomalously light (varying from -0.9 to -0.6‰) relative to healthy tissue in 3 breast cancer patients and 1 healthy control (δZn = -0.5 to -0.3‰). In this study, δZn values of blood and serum were not found to be significantly different between cancerous and non-cancerous patients, suggesting an unknown isotopically heavy pool of Zn must exist in cancer patients. Though results from this study are promising regarding the use of Zn isotope ratios as a biomarker for breast cancer, a mechanistic understanding of how Zn isotopes fractionate during tumor formation in breast cancer is still lacking. Fortunately, increasing attention is being devoted to the use of stable metal isotopes as tracers of cancer and other diseases, and the usefulness of these isotope systems in medical applications will become more apparent in the next few decades. | 0 | Theoretical and Fundamental Chemistry |
Co-administration of quinidine, a potent CYP2D6 enzyme inhibitor, with tramadol, a combination which results in markedly reduced levels of desmetramadol, was found not to significantly affect the analgesic effects of tramadol in human volunteers. However, other studies have found that the analgesic effects of tramadol are significantly decreased or even absent in CYP2D6 poor metabolizers. The analgesic effects of tramadol are only partially reversed by naloxone in human volunteers, hence indicating that its opioid action is unlikely the sole factor; tramadol's analgesic effects are also partially reversed by α-adrenergic receptor antagonists such as yohimbine, the 5-HT receptor antagonist ondansetron, and the 5-HT receptor antagonists SB-269970 and SB-258719. Pharmacologically, tramadol is similar to tapentadol and methadone in that it not only binds to the MOR, but also inhibits the reuptake of serotonin and norepinephrine due to its action on the noradrenergic and serotonergic systems, such as its "atypical" opioid activity.
Tramadol has inhibitory actions on the 5-HT receptor. Antagonism of 5-HT could be partially responsible for tramadols reducing effect on depressive and obsessive–compulsive symptoms in patients with pain and co-morbid neurological illnesses. 5-HT blockade may also account for its lowering of the seizure threshold, as 5-HT knockout mice display significantly increased vulnerability to epileptic seizures, sometimes resulting in spontaneous death. However, the reduction of seizure threshold could be attributed to tramadols putative inhibition of GABA receptors at high doses (significant inhibition at 100 μM). In addition, desmetramadol is a high-affinity ligand of the DOR, and activation of this receptor could be involved in tramadol's ability to provoke seizures in some individuals, as DOR agonists are well known for inducing seizures.
Nausea and vomiting caused by tramadol are thought to be due to activation of the 5-HT receptor via increased serotonin levels. In accordance, the 5-HT receptor antagonist ondansetron can be used to treat tramadol-associated nausea and vomiting. Tramadol and desmetramadol themselves do not bind to the 5-HT receptor. | 0 | Theoretical and Fundamental Chemistry |
The katal (symbol: kat) is that catalytic activity that will raise the rate of conversion by one mole per second in a specified assay system. It is a unit of the International System of Units (SI) used for quantifying the catalytic activity of enzymes (that is, measuring the enzymatic activity level in enzyme catalysis) and other catalysts.
The unit katal is not attached to a specified measurement procedure or assay condition, but any given catalytic activity is: the value measured depends on experimental conditions that must be specified. Therefore, to define the quantity of a catalyst in katals, the catalysed rate of conversion (the rate of conversion in presence of the catalyst minus the rate of spontaneous conversion) of a defined chemical reaction is measured in moles per second. One katal of trypsin, for example, is that amount of trypsin which breaks one mole of peptide bonds in one second under the associated specified conditions. | 0 | Theoretical and Fundamental Chemistry |
He received bachelors and doctoral degrees from the Imperial University of Tokyo. He studied under Professor Kenjiro Kimura.
His first paper was published in 1935. He focused mostly on radio and cosmochemistry, and most of his 40 papers published prior to 1944 are about the chemistry of hot springs. In 1944, he became the youngest faculty member of the Imperial University of Tokyo, and after World War II, despite the ban on radiochemistry in Japan, he continued to study radiochemistry until 1949.
On arrival to the United States in 1949, he met with nuclear chemist, Glenn Seaborg. He became an assistant professor of chemistry at the University of Arkansas in 1952, becoming a US citizen in 1955.
In 1956, Kuroda was the first to propose that natural self-sustaining nuclear chain reactions were possible. Such a reactor was discovered in September 1972 in the Oklo Mines of Gabon.
He became the first Edgar Wertheim Distinguished Professor of Chemistry in 1979, he officially retired from the University of Arkansas in 1987. | 0 | Theoretical and Fundamental Chemistry |
Glass batch calculation or glass batching is used to determine the correct mix of raw materials (batch) for a glass melt. | 0 | Theoretical and Fundamental Chemistry |
Is the most common geometry used, based on a spiral design with the center winding contacted to the outside using a connection to another layer which is electrically isolated with a thin oxide layer. In this configuration the axis of the RF coil will be oriented perpendicular to the external static field B. | 0 | Theoretical and Fundamental Chemistry |
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