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In forensic science, hybridization probes are used, for example, for detection of short tandem repeats (microsatellite) regions and in restriction fragment length polymorphism (RFLP) methods, all of which are widely used as part of DNA profiling analysis. | 1 | Applied and Interdisciplinary Chemistry |
In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect. A mechanism of action usually includes mention of the specific molecular targets to which the drug binds, such as an enzyme or receptor. Receptor sites have specific affinities for drugs based on the chemical structure of the drug, as well as the specific action that occurs there.
Drugs that do not bind to receptors produce their corresponding therapeutic effect by simply interacting with chemical or physical properties in the body. Common examples of drugs that work in this way are antacids and laxatives.
In contrast, a mode of action (MoA) describes functional or anatomical changes, at the cellular level, resulting from the exposure of a living organism to a substance. | 1 | Applied and Interdisciplinary Chemistry |
Source:
* Mil-PRF-5606 (originally Mil-H-5606): Mineral base, flammable, fairly low flashpoint, usable from to , red color, developed in the 1940s
* MIL-PRF-6083: Usable from −54 °C to 135 °C "where corrosion protection is required and a determination has been made that MIL-PRF-46170 (FRH) hydraulic fluid cannot be used. This includes use in recoil mechanisms and hydraulic systems for rotating weapons or aiming devices of tactical and support ordnance equipment, except combat armored vehicles/equipment which require FRH. The hydraulic fluid is also used as a preservative fluid for aircraft hydraulic systems and components where MIL-H-5606 (OHA) or MIL-PRF-87257 is used as an operational fluid."
Synthetic hydrocarbon base:
These synthetic fluids are compatible with mineral-base hydraulic fluids and were developed to address the low flash point draw back of mineral based hydraulic fluids.
* Mil-H-83282: Synthetic hydrocarbon base, higher flashpoint, self-extinguishing, backward compatible to -5606, red color, rated to degrees.
* Mil-H-87257: A development of -83282 fluid to improve its low temperature viscosity. | 1 | Applied and Interdisciplinary Chemistry |
The sublimation sandwich method (also called the sublimation sandwich process and the sublimation sandwich technique) is a kind of physical vapor deposition used for creating man-made crystals. Silicon carbide is the most common crystal grown this way, though others crystals may also be created with it (notably gallium nitride).
In this method, the environment around a single crystal or a polycrystalline plate is filled with vapor heated to between 1600°C and 2100°C-- changes to this environment can affect the gas phase stoichiometry. The source-to-crystal distance is kept between 0.02-0.03mm (very low). Parameters that can affect crystal growth include source-to-substrate distance, temperature gradient, and the presence of tantalum for gathering excess carbon. High growth rates are the result of small source-to-seed distances combined with a large heat flux onto a small amount of source material with no more than a moderate temperature difference between the substrate and the source (0.5-10°C). The growth of large boules, however, remains quite difficult using this method, and it is better suited to the creation of epitaxial films with uniform polytype structures. Ultimately, samples with a thickness of up to 500µm can be produced using this method. | 0 | Theoretical and Fundamental Chemistry |
*Ar for any aromatic substituent (Ar is also the symbol for the element argon. However, argon is inert under all usual conditions encountered in organic chemistry, so the use of Ar to represent an aryl substituent never causes confusion.)
*Het for any heteroaromatic substituent
*Bn or Bzl for the benzyl group (not to be confused with Bz for benzoyl group; However, old literature may use Bz for benzyl group.)
*Dipp for the 2,6-diisopropylphenyl group
*Mes for the mesityl group
*Ph, Φ, or φ for the phenyl group (the use of phi for phenyl has been in decline)
*Tol for the tolyl group, usually the para isomer
*Is or Tipp for the 2,4,6-triisopropylphenyl group (the former symbol is derived from the synonym isityl)
*An for the anisyl group, usually the para isomer (An is also the symbol for a generic actinoid element. However, since the anisyl group is monovalent, while the actinides are usually divalent, trivalent, or even higher valency, ambiguity rarely, if ever, arises in practice.)
*Cp for the cyclopentadienyl group (Cp was the symbol for cassiopeium, a former name for lutetium)
*Cp* for the pentamethylcyclopentadienyl group
*Vi for the vinyl group (uncommon) | 0 | Theoretical and Fundamental Chemistry |
Configurational electronic entropy is usually observed in mixed-valence transition metal oxides, as the charges in these systems are both localized (the system is ionic), and capable of changing (due to the mixed valency). To a first approximation (i.e. assuming that the charges are distributed randomly), the molar configurational electronic entropy is given by:
where is the fraction of sites on which a localized electron/hole could reside (typically a transition metal site), and is the concentration of localized electrons/holes. Of course, the localized charges are not distributed randomly, as the charges will interact electrostatically with one another, and so the above formula should only be regarded as an approximation to the configurational atomic entropy. More sophisticated approximations have been made in the literature. | 0 | Theoretical and Fundamental Chemistry |
Membraneless organelles (MLOs), also known as biomolecular condensates, are a form of cell compartmentalization. Unlike classic membrane-bound organelles (e.g. mitochondrion, nucleus or lysosome), MLOs are not separated from their surroundings by a lipid bilayer. MLOs are mostly composed of proteins and nucleic acids, held together by weak intermolecular forces.
MLOs are present in the cytoplasm (e.g. stress granules, processing bodies) and in the nucleus (e.g. nucleolus, nuclear speckles). They have been shown to serve various functions: they can store and protect cellular material during stress conditions, they participate in gene expression and they are involved in the control of signal transduction.
It is now widely believed that MLOs form through LLPS. This was first proposed after observing that Cajal bodies and P granules show liquid-like properties, and was later confirmed by showing that liquid condensates can be reconstituted from purified protein and RNA in vitro. However, whether MLOs should be referred to as liquids, remains disputable. Even if initially they are liquid-like, over time some of them maturate into solids (gel-like or even crystalline, depending on the extent of spatial ordering within the condensate).
Many proteins participating in the formation of MLO contain so-called intrinsically disordered regions (IDRs), parts of the polypeptide chain that can adopt multiple secondary structures and form random coils in solution. IDRs can provide interactions responsible for LLPS, but over time conformational changes (sometimes promoted by mutations or post-translational modifications) may lead to the formation of higher ordered structures and solidification of MLOs. Some MLOs serve their biological role as solid particles (e.g. Balbiani body stabilised by β-sheet structure), but in many cases transformation from liquid to solid results in the formation of pathological aggregates. Examples of both liquid-liquid phase separating and aggregation-prone proteins include FUS, TDP-43 and hnRNPA1. Aggregates of these proteins are associated with neurodegenerative diseases (e.g. amyotrophic lateral sclerosis, or frontotemporal dementia). | 0 | Theoretical and Fundamental Chemistry |
Methylene blue is a formal derivative of phenothiazine. It is a dark green powder that yields a blue solution in water. The hydrated form has 3 molecules of water per unit of methylene blue. | 0 | Theoretical and Fundamental Chemistry |
"Radon therapy" is an intentional exposure to radon via inhalation or ingestion. Nevertheless, epidemiological evidence shows a clear link between breathing high concentrations of radon and incidence of lung cancer. | 1 | Applied and Interdisciplinary Chemistry |
The effect of solvent on elimination and nucleophillic substitution reactions was originally studied by British chemists Edward D. Hughes and Christopher Kelk Ingold. Using a simple solvation model that considered only pure electrostatic interactions between ions or dipolar molecules and solvents in initial and transition states, all nucleophilic and elimination reactions were organized into different charge types (neutral, positively charged, or negatively charged).
Hughes and Ingold then made certain assumptions about the extent of solvation to be expected in these situations:
* increasing magnitude of charge will increase solvation
* increasing delocalization will decrease solvation
* loss of charge will decrease solvation more than the dispersal of charge
The applicable effect of these general assumptions are shown in the following examples:
* An increase in solvent polarity accelerates the rates of reactions where a charge is developed in the activated complex from neutral or slightly charged reactant
* An increase in solvent polarity decreases the rates of reactions where there is less charge in the activated complex in comparison to the starting materials
* A change in solvent polarity will have little or no effect on the rates of reaction when there is little or no difference in charge between the reactants and the activated complex. | 0 | Theoretical and Fundamental Chemistry |
Thioureas are building blocks to pyrimidine derivatives. Thus thioureas condense with β-dicarbonyl compounds. The amino group on the thiourea initially condenses with a carbonyl, followed by cyclization and tautomerization. Desulfurization delivers the pyrimidine.
Similarly, aminothiazoles can be synthesized by the reaction of α-haloketones and thiourea.
The pharmaceuticals thiobarbituric acid and sulfathiazole are prepared using thiourea. 4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole is prepared by the reaction of thiourea and hydrazine. | 0 | Theoretical and Fundamental Chemistry |
Cold fusion researchers (McKubre since 1994, ENEA in 2011) have speculated that a cell that is loaded with a deuterium/palladium ratio lower than 100% (or 1:1) will not produce excess heat. Since most of the negative replications from 1989 to 1990 did not report their ratios, this has been proposed as an explanation for failed reproducibility. This loading ratio is hard to obtain, and some batches of palladium never reach it because the pressure causes cracks in the palladium, allowing the deuterium to escape. Fleischmann and Pons never disclosed the deuterium/palladium ratio achieved in their cells; there are no longer any batches of the palladium used by Fleischmann and Pons (because the supplier now uses a different manufacturing process), and researchers still have problems finding batches of palladium that achieve heat production reliably. | 0 | Theoretical and Fundamental Chemistry |
Ca ion flow regulates several secondary messenger systems in neural adaptation for visual, auditory, and the olfactory system. It may often be bound to calmodulin such as in the olfactory system to either enhance or repress cation channels. Other times the calcium level change can actually release guanylyl cyclase from inhibition, like in the photoreception system. Ca ion can also determine the speed of adaptation in a neural system depending on the receptors and proteins that have varied affinity for detecting levels of calcium to open or close channels at high concentration and low concentration of calcium in the cell at that time. | 1 | Applied and Interdisciplinary Chemistry |
Dissimilatory nitrate reduction to ammonium is a two step process, reducing NO to NO then NO to NH, though the reaction may begin with NO directly. Each step is mediated by a different enzyme, the first step of dissimilatory nitrate reduction to ammonium is usually mediated by a periplasmic nitrate reductase. The second step (respiratory NO reduction to NH) is mediated by cytochrome c nitrite reductase, occurring at the periplasmic membrane surface. Despite DNRA not producing nitrous oxide (NO) as an intermediate during nitrate reduction (as denitrification does), NO may still be released as a byproduct, thus DNRA may also act as a sink of fixed, bioavailable nitrogen. DNRA's production of NO may be enhanced at higher pH levels. | 1 | Applied and Interdisciplinary Chemistry |
The Baylis–Hillman reaction is a route for C-C bond formation between an alpha, beta-unsaturated carbonyl and an aldehyde, which requires a nucleophilic catalyst, usually a tertiary amine, for a Michael-type addition and elimination. The stereoselectivity of these reactions is usually poor. Lanthanum(III)-containing CLAs have been demonstrated to improve stereoselectivity. Similarly, a chiral amine may also be used to achieve stereoselectivity.
The product obtained by the reaction using the chiral catalyst was obtained in good yield with excellent enantioselectivity. | 0 | Theoretical and Fundamental Chemistry |
Phosphorylation and dephosphorylation of hydroxyl groups belonging to neutral but polar amino acids such as serine, threonine, and tyrosine within specific target proteins is a fundamental part of the regulation of every physiologic process. Phosphorylation involves the covalent modification of the hydroxyl with a phosphate group through the nucleophilic attack of the alpha phosphate in ATP by the oxygen in the hydroxyl. Dephosphorylation involves removal of the phosphate group through a hydration reaction by addition of a molecule of water and release of the original phosphate group, regenerating the hydroxyl. Both processes are reversible and either mechanism can be used to activate or deactivate a protein. Phosphorylation of a protein produces many biochemical effects, such as changing its conformation to alter its binding to a specific ligand to increase or reduce its activity. Phosphorylation and dephosphorylation can be used on all types of substrates, such as structural proteins, enzymes, membrane channels, signaling molecules, and other kinases and phosphatases. The sum of these processes is referred to as phosphoregulation. The deregulation of phosphorylation can lead to disease. | 1 | Applied and Interdisciplinary Chemistry |
A Riemann problem, named after Bernhard Riemann, is a specific initial value problem composed of a conservation equation together with piecewise constant initial data which has a single discontinuity in the domain of interest. The Riemann problem is very useful for the understanding of equations like Euler conservation equations because all properties, such as shocks and rarefaction waves, appear as characteristics in the solution. It also gives an exact solution to some complex nonlinear equations, such as the Euler equations.
In numerical analysis, Riemann problems appear in a natural way in finite volume methods for the solution of conservation law equations due to the discreteness of the grid. For that it is widely used in computational fluid dynamics and in computational magnetohydrodynamics simulations. In these fields, Riemann problems are calculated using Riemann solvers. | 1 | Applied and Interdisciplinary Chemistry |
There are several applications of spectroscopy in the fields of medicine, physics, chemistry, and astronomy. Taking advantage of the properties of absorbance and with astronomy emission, spectroscopy can be used to identify certain states of nature. The uses of spectroscopy in so many different fields and for so many different applications has caused specialty scientific subfields. Such examples include:
* Determining the atomic structure of a sample
* Studying spectral emission lines of the sun and distant galaxies
* Space exploration
* Cure monitoring of composites using optical fibers.
* Estimating weathered wood exposure times using near infrared spectroscopy.
* Measurement of different compounds in food samples by absorption spectroscopy both in visible and infrared spectrum.
* Measurement of toxic compounds in blood samples
* Non-destructive elemental analysis by X-ray fluorescence.
* Electronic structure research with various spectroscopes.
* Redshift to determine the speed and velocity of a distant object
* Determining the metabolic structure of a muscle
* Monitoring dissolved oxygen content in freshwater and marine ecosystems
* Altering the structure of drugs to improve effectiveness
* Characterization of proteins
* Respiratory gas analysis in hospitals
* Finding the physical properties of a distant star or nearby exoplanet using the Relativistic Doppler effect.
* In-ovo sexing: spectroscopy allows to determine the sex of the egg while it is hatching. Developed by French and German companies, both countries decided to ban chick culling, mostly done through a macerator, in 2022.
* Process monitoring in Industrial process control | 0 | Theoretical and Fundamental Chemistry |
* Highly parallel identification of active, tissue-specific transcriptional enhancers in whole embryos
* Candidate enhancers activity assayed in a genomic context
* High specificity of detected enhancers | 1 | Applied and Interdisciplinary Chemistry |
Bawendi was granted the Sloan Research Fellowship in 1994. He won the 1997 Nobel Signature Award for Graduate Education in Chemistry of American Chemical Society (ACS). In 2001, he received the Sackler Prize in Physical Chemistry of Advanced Materials. In 2006, he was awarded the Ernest Orlando Lawrence Award.
He was elected member of the American Association for the Advancement of Science in 2003, of the American Academy of Arts and Sciences in 2004, and of the National Academy of Sciences in 2007.
In 2010 during the National Meeting on March 23, 2010, Bawendi received the ACS Award in Colloid and Surface Chemistry. He also received the 2011 SEMI Award for North America for quantum dot research.
Bawendi was selected as a Clarivate Citation Laureate in Chemistry in 2020, jointly with Christopher B. Murray and Hyeon Taeghwan, "for synthesis of nanocrystals with precise attributes for a wide range of applications in physical, biological, and medical systems."
In 2023, Bawendi was awarded the Nobel Prize in Chemistry jointly with Louis E. Brus and Alexey Ekimov "for the discovery and synthesis of quantum dots". | 0 | Theoretical and Fundamental Chemistry |
The tetrathionate anion, , is a sulfur oxyanion derived from the compound tetrathionic acid, HSO. Two of the sulfur atoms present in the ion are in oxidation state 0 and two are in oxidation state +5. Alternatively, the compound can be viewed as the adduct resulting from the binding of disulfide| to SO. Tetrathionate is one of the polythionates, a family of anions with the formula [S(SO)]. Its IUPAC name is 2-(dithioperoxy)disulfate, and the name of its corresponding acid is 2-(dithioperoxy)disulfuric acid. The Chemical Abstracts Service identifies tetrathionate by the CAS Number 15536-54-6. | 1 | Applied and Interdisciplinary Chemistry |
The exclusion zone is a large stratum (typically on the order of a few microns to a millimeter) observed in pure liquid water, from which particles of other materials in suspension are repelled. It is observed next to the surface of solid materials, e.g. the walls of the container in which the liquid water is held, or solid specimens immersed in it, and also at the water/air interface. Several independent research groups have reported observations of the exclusion zone next to hydrophilic surfaces. Some research groups have reported the observation of the exclusion zone next to metal surfaces. The Exclusion zone has been observed using different techniques, e.g. birefringence, neutron radiography, nuclear magnetic resonance, and others, and it has potentially high importance in biology, and in engineering applications such as filtration and microfluidics. | 1 | Applied and Interdisciplinary Chemistry |
In diffusioosmosis, for a surface at rest the velocity increases from zero at the surface to the diffusioosmotic velocity, over the width of the interface between the surface and the solution. Beyond this distance, the diffusioosmotic velocity does not vary with distance from the surface. The driving force for diffusioosmosis is thermodynamic, i.e., it acts to reduce the free energy if the system, and so the direction of flow is away from surface regions of low surface free energy, and towards regions of high surface free energy. For a solute that adsorbs at surface, diffusioosmotic flow is away from regions of high solute concentration, while for solutes that are repelled by the surface, flow is away from regions of low solute concentration.
For gradients that are not-too-large, the diffusioosmotic slip velocity, i.e., the relative flow velocity far from the surface will be proportional to the gradient in the concentration gradient
where is a diffusioosmotic coefficient, and is the solute concentration. When the solute is ideal and interacts with a surface in the plane at via a potential , the coefficient is given by
where is Boltzmann's constant, is the absolute temperature, and is the viscosity in the interfacial region, assumed to be constant in the interface. This expression assumes that the fluid velocity for fluid in contact with the surface is forced to be zero, by interaction between the fluid and the wall. This is called the no-slip condition.
To understand these expressions better, we can consider a very simple model, where the surface simply excludes an ideal solute from an interface of width , this is would be the Asakura-Oosawa model of an ideal polymer against a hard wall. Then the integral is simply and the diffusioosmotic slip velocity
Note that the slip velocity is directed towards increasing solute concentrations.
A particle much larger than moves with a diffusiophoretic velocity relative to the surrounding solution. So diffusiophoresis moves particles towards lower solute concentrations, in this case. | 0 | Theoretical and Fundamental Chemistry |
Polydentate ligands are chelating agents and classified by their denticity. Some atoms cannot form the maximum possible number of bonds a ligand could make. In that case one or more binding sites of the ligand are unused. Such sites can be used to form a bond with another chemical species.
* Bidentate (also called didentate) ligands bind with two atoms, an example being ethylenediamine.
* Tridentate ligands bind with three atoms, an example being terpyridine. Tridentate ligands usually bind via two kinds of connectivity, called "mer" and "fac." "fac" stands for facial, the donor atoms are arranged on a triangle around one face of the octahedron. "mer" stands for meridian, where the donor atoms are stretched out around one half of the octahedron. Cyclic tridentate ligands such as TACN and 9-ane-S3 bind in a facial manner.
* Tetradentate ligands bind with four donor atoms, an example being triethylenetetramine (abbreviated trien). For different central metal geometries there can be different numbers of isomers depending on the ligand's topology and the geometry of the metal center. For octahedral metals, the linear tetradentate trien can bind via three geometries. Tripodal tetradentate ligands, e.g. tris(2-aminoethyl)amine, are more constrained, and on octahedra leave two cis sites (adjacent to each other). Many naturally occurring macrocyclic ligands are tetradentative, an example being the porphyrin in heme. On an octahedral metal these leave two vacant sites opposite each other.
* Pentadentate ligands bind with five atoms, an example being ethylenediaminetriacetic acid.
* Hexadentate ligands bind with six atoms, an example being EDTA (although it can bind in a tetradentate manner).
* Ligands of denticity greater than 6 are well known. The ligands 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA) and diethylene triamine pentaacetate (DTPA) are octadentate. They are particularly useful for binding lanthanide ions, which typically have coordination numbers greater than 6. | 0 | Theoretical and Fundamental Chemistry |
Microwaves are used for heating of various materials in cooking and various industrial processes. The rate of heating of the material depends on the energy absorption, which depends on the dielectric constant of the material. The dependence of dielectric constant on temperature varies for different materials; some materials display significant increase with increasing temperature. This behavior, when the material gets exposed to microwaves, leads to selective local overheating, as the warmer areas are better able to accept further energy than the colder areas—potentially dangerous especially for thermal insulators, where the heat exchange between the hot spots and the rest of the material is slow. These materials are called thermal runaway materials. This phenomenon occurs in some ceramics. | 1 | Applied and Interdisciplinary Chemistry |
The hydrophobicity scales developed by physical property methods are based on the measurement of different physical properties. Examples include, partial molar heat capacity, transition temperature and surface tension. Physical methods are easy to use and flexible in terms of solute. The most popular hydrophobicity scale was developed by measuring surface tension values for the naturally occurring 20 amino acids in NaCl solution. The main drawbacks of surface tension measurements is that the broken hydrogen bonds and the neutralized charged groups remain at the solution air interface. Another physical property method involve measuring the solvation free energy. The solvation free energy is estimated as a product of an accessibility of an atom to the solvent and an atomic solvation parameter. Results indicate the solvation free energy lowers by an average of 1 Kcal/residue upon folding. | 0 | Theoretical and Fundamental Chemistry |
Tetrakis(hexahydropyrimidinopyrimidine)ditungsten(II), known as ditungsten tetra(hpp), is the name of the coordination compound with the formula W(hpp). This material consists of a pair of tungsten centers linked by the conjugate base of four hexahydropyrimidopyrimidine (hpp) ligands. It adopts a structure sometimes called a Chinese lantern structure or paddlewheel compound, the prototype being copper(II) acetate.
The molecule is of research interest because it has the lowest ionization energy (3.51 eV) of all stable chemical elements or chemical compounds as of the year 2005. This value is even lower than of caesium with 3.89 eV (or 375 kJ/mol) located at the extreme left lower corner of the periodic table (although francium is at a lower position in the periodic table compared to caesium, it has a higher ionization energy and is radioactive) or known metallocene reducing agents such as decamethylcobaltocene with 4.71 eV. | 0 | Theoretical and Fundamental Chemistry |
The enzyme first catalyzes nucleophilic attack on the α-phosphate of ATP to form pyrophosphate and an acyl chain linked to AMP. The next step is formation of an activated thioester bond between the fatty acyl chain and Coenzyme A.
The balanced equation for the above is:
RCOO + CoASH + ATP → RCO-SCoA + AMP + PP <br />
This two-step reaction is freely reversible and its equilibrium lies near 1. To drive the reaction forward, the reaction is coupled to a strongly exergonic hydrolysis reaction: the enzyme inorganic pyrophosphatase cleaves the pyrophosphate liberated from ATP to two phosphate ions, consuming one water molecule in the process. Thus the net reaction becomes:
RCOO + CoASH + ATP → RCO-SCoA+ AMP + 2P | 1 | Applied and Interdisciplinary Chemistry |
A few incidents have occurred when radioactive material was disposed of improperly, shielding during transport was defective, or when it was simply abandoned or even stolen from a waste store. In the Soviet Union, waste stored in Lake Karachay was blown over the area during a dust storm after the lake had partly dried out. In Italy, several radioactive waste deposits let material flow into river water, thus contaminating water for domestic use. In France in the summer of 2008, numerous incidents happened: in one, at the Areva plant in Tricastin, it was reported that, during a draining operation, liquid containing untreated uranium overflowed out of a faulty tank and about 75 kg of the radioactive material seeped into the ground and, from there, into two rivers nearby; in another case, over 100 staff were contaminated with low doses of radiation. There are ongoing concerns around the deterioration of the nuclear waste site on the Enewetak Atoll of the Marshall Islands and a potential radioactive spill.
Scavenging of abandoned radioactive material has been the cause of several other cases of radiation exposure, mostly in developing nations, which may have less regulation of dangerous substances (and sometimes less general education about radioactivity and its hazards) and a market for scavenged goods and scrap metal. The scavengers and those who buy the material are almost always unaware that the material is radioactive and it is selected for its aesthetics or scrap value. Irresponsibility on the part of the radioactive material's owners, usually a hospital, university, or military, and the absence of regulation concerning radioactive waste, or a lack of enforcement of such regulations, have been significant factors in radiation exposures. For an example of an accident involving radioactive scrap originating from a hospital see the Goiânia accident.
Transportation accidents involving spent nuclear fuel from power plants are unlikely to have serious consequences due to the strength of the spent nuclear fuel shipping casks.
On 15 December 2011, top government spokesman Osamu Fujimura of the Japanese government admitted that nuclear substances were found in the waste of Japanese nuclear facilities. Although Japan did commit itself in 1977 to these inspections in the safeguard agreement with the IAEA, the reports were kept secret for the inspectors of the International Atomic Energy Agency. Japan did start discussions with the IAEA about the large quantities of enriched uranium and plutonium that were discovered in nuclear waste cleared away by Japanese nuclear operators. At the press conference Fujimura said: "Based on investigations so far, most nuclear substances have been properly managed as waste, and from that perspective, there is no problem in safety management," but according to him, the matter was at that moment still being investigated. | 0 | Theoretical and Fundamental Chemistry |
A bole hill (also spelt bail hill) was a place where lead was formerly smelted in the open air. The bole was usually situated at or near the top of a hill where the wind was strong.
Totley Bole Hill on the western fringes of Sheffield consisted of a long low wall with two shorter walls at right angles to it at each end. At the base of a bole long were laid great trees called blocks. On these were laid blackwork, partly smelted ore about half a yard thick. Then came ten or twelve trees called shankards. On top of these three or four courses of fire trees were laid with fresh ore. This was ignited and burnt for about 48 hours. This smelted lead, which ran down channels provided for the purpose and was cast into sows of about 11 hundredweight. A single firing produced 16 fothers of lead (about 18 tons) from 160 loads of ore (about 40 tons) and 30 tons of wood. Much of the ore was left incompletely smelted having become blackwork. Some of this was smelted in a foot-pump blown furnace, but some was left to be used when the bole was next fired. Bole smelting was replaced by smelting in smeltmills in the late 16th century. That was in turn replaced by smelting in cupolas, a variety of reverberatory furnace in the 18th century. | 1 | Applied and Interdisciplinary Chemistry |
Hydroxycorticosteroids (OHCSs) are corticosteroids that have an additional hydroxy (-OH) group.
There are two main positions where the hydroxy group may be added: at carbon atom 11, and at carbon atom 17. | 0 | Theoretical and Fundamental Chemistry |
The preinitiation complex (PIC) assembles in a stepwise fashion on the promoter of genes to initiate transcription. The TFIID binds to the TATA box in order to begin the assembly of the TFIIA, recruiting other transcription factors and components needed in the PIC. Data suggests that pRb is able to repress transcription by both pRb being recruited to the promoter as well as having a target present in TFIID.
The presence of pRb may change the conformation of the TFIIA/IID complex into a less active version with a decreased binding affinity. pRb can also directly interfere with their association as proteins, preventing TFIIA/IID from forming an active complex. | 1 | Applied and Interdisciplinary Chemistry |
Photolithotrophs such as plants obtain energy from light and therefore use inorganic electron donors such as water only to fuel biosynthetic reactions (e. g., carbon dioxide fixation in lithoautotrophs). | 1 | Applied and Interdisciplinary Chemistry |
Monoaminergic means "working on monoamine neurotransmitters", which include serotonin, dopamine, norepinephrine, epinephrine, and histamine.
A monoaminergic, or monoaminergic drug, is a chemical, which functions to directly modulate the serotonin, dopamine, norepinephrine, epinephrine, and/or histamine neurotransmitter systems in the brain. Monoaminergics include catecholaminergics (which can be further divided into adrenergics and dopaminergics), serotonergics, and histaminergics.
Examples of monoaminergic drugs include monoamine precursors, monoamine receptor modulators, monoamine reuptake inhibitors, monoamine releasing agents, and monoamine metabolism modulators such as monoamine oxidase inhibitors. | 1 | Applied and Interdisciplinary Chemistry |
A core-excited shape resonance is a shape resonance in a system with more than one degree of freedom where, after fragmentation, one of the fragments is in an excited state. It is sometimes very difficult to distinguish a core-excited shape resonance from a Feshbach resonance. | 0 | Theoretical and Fundamental Chemistry |
Comprehensive two-dimensional gas chromatography is an analytical technique that separates and analyzes complex mixtures. It has been utilized in fields such as: flavor, fragrance, environmental studies, pharmaceuticals, petroleum products and forensic science. GCxGC provides a high range of sensitivity and produces a greater separation power due to the increased peak capacity. | 0 | Theoretical and Fundamental Chemistry |
The calorimeter constants are used in constant pressure calorimetry to calculate the amount of heat required to achieve a certain raise in the temperature of the calorimeter's contents. | 0 | Theoretical and Fundamental Chemistry |
*The Ki Database is a public domain database of published binding affinities (Ki) of drugs and chemical compounds for receptors, neurotransmitter transporters, ion channels, and enzymes.
*BindingDB is a public domain database of measured binding affinities, focusing chiefly on the interactions of protein considered to be drug-targets with small, drug-like molecules | 0 | Theoretical and Fundamental Chemistry |
The Deal–Grove model mathematically describes the growth of an oxide layer on the surface of a material. In particular, it is used to predict and interpret thermal oxidation of silicon in semiconductor device fabrication. The model was first published in 1965 by Bruce Deal and Andrew Grove of Fairchild Semiconductor, building on Mohamed M. Atalla's work on silicon surface passivation by thermal oxidation at Bell Labs in the late 1950s. This served as a step in the development of CMOS devices and the fabrication of integrated circuits. | 1 | Applied and Interdisciplinary Chemistry |
JNK can directly phosphorylate Bim-EL, a splicing isoform of Bcl-2 interacting mediator of cell death (Bim), which activates Bim-EL apoptotic activity. JNK activation is required for apoptosis but c-jun, a protein in the JNK signaling pathway, is not always required. | 1 | Applied and Interdisciplinary Chemistry |
Pepper spray is banned for use in war by Article I.5 of the Chemical Weapons Convention, which bans the use of all riot control agents in warfare whether lethal or less-than-lethal. Depending on the location, it may be legal to use for self-defense. | 1 | Applied and Interdisciplinary Chemistry |
Detailed sample preparation depends on the type of material. Pure standards are most likely to be prepared by chemical synthesis and purification and characterized by determination of remaining impurities. This is often done by commercial producers. Natural matrix CRMs (often shortened to matrix CRMs) contain an analyte or analytes in a natural sample (for, example, lead in fish tissue). These are typically produced by homogenization of a naturally occurring material followed by measurement of each analyte. Due to the difficulty in production and value assignment, these are usually produced by national or transnational metrology institutes like NIST (USA), BAM (Germany), KRISS (Korea) and EC JRC ( European Commission Joint Research Centre).
For natural materials, homogenization is often critical; natural materials are rarely homogeneous on the scale of grams so production of a solid natural matrix reference material typically involves processing to a fine powder or paste. Homogenization can have adverse effects, for example on proteins, so producers must take care not to over-process materials. Stability of a certified reference material is also important, so a range of strategies may be used to prepare a reference material that is more stable than the natural material it is prepared from. For example, stabilizing agents such as antioxidants or antimicrobial agents may be added to prevent degradation, liquids containing certified concentrations of trace metals may have pH adjusted to keep metals in solution, and clinical reference materials may be freeze-dried for long term storage if they can be reconstituted successfully. | 0 | Theoretical and Fundamental Chemistry |
The pressure transmitting medium is an important component in any high-pressure experiment. The medium fills the space within the sample chamber and applies the pressure being transmitted to the medium onto the sample. In a good high-pressure experiment, the medium should maintain a homogeneous distribution of pressure on the sample. In other words, the medium must stay hydrostatic to ensure uniform compressibility of the sample. Once a pressure transmitting medium has lost its hydrostaticity, a pressure gradient forms in the chamber that increases with increasing pressure. This gradient can greatly affect the sample, compromising results. The medium must also be inert, as to not interact with the sample, and stable under high pressures. For experiments with laser heating, the medium should have low thermal conductivity. If an optical technique is being employed, the medium should be optically transparent and for x-ray diffraction, the medium should be a poor x-ray scatterer – as to not contribute to the signal.
Some of the most commonly used pressure transmitting media have been sodium chloride, silicone oil, and a 4:1 methanol-ethanol mixture. Sodium chloride is easy to load and is used for high-temperature experiments because it acts as a good thermal insulator. The methanol-ethanol mixture displays good hydrostaticity to about 10 GPa and with the addition of a small amount of water can be extended to about 15 GPa.
For pressure experiments that exceed 10 GPa, noble gases are preferred. The extended hydrostaticity greatly reduces the pressure gradient in samples at high pressure. Noble gases, such as helium, neon, and argon are optically transparent, thermally insulating, have small X-ray scattering factors, and have good hydrostaticity at high pressures. Even after solidification, noble gases provide quasihydrostatic environments.
Argon is used for experiments involving laser heating because it is chemically insulating. Since it condenses at a temperature above that of liquid nitrogen, it can be loaded cryogenically. Helium and neon have low X-ray scattering factors and are thus used for collecting X-ray diffraction data. Helium and neon also have low shear moduli; minimizing strain on the sample. These two noble gases do not condense above that of liquid nitrogen and cannot be loaded cryogenically. Instead, a high-pressure gas loading system has been developed that employs a gas compression method. | 0 | Theoretical and Fundamental Chemistry |
Bian Que (Chinese: 扁鵲, Wade–Giles: Pien Chiao, ) was a legendary Chinese internist and surgeon who reportedly used general anesthesia for surgical procedures. It is recorded in the Book of Master Han Fei (), the Records of the Grand Historian (), and the Book of Master Lie' () that Bian Que gave two men, named "Lu" and "Chao", a toxic drink which rendered them unconscious for three days, during which time he performed a gastrostomy upon them.
Hua Tuo (Chinese:華佗， ) was a Chinese surgeon of the 2nd century AD. According to the Records of Three Kingdoms () and the Book of the Later Han (), Hua Tuo performed surgery under general anesthesia using a formula he had developed by mixing wine with a mixture of herbal extracts he called mafeisan (麻沸散). Hua Tuo reportedly used mafeisan to perform even major operations such as resection of gangrenous intestines. Before the surgery, he administered an oral anesthetic potion, probably dissolved in wine, in order to induce a state of unconsciousness and partial neuromuscular blockade.
The exact composition of mafeisan, similar to all of Hua Tuos clinical knowledge, was lost when he burned his manuscripts, just before his death. The composition of the anesthetic powder was not mentioned in either the Records of Three Kingdoms or the Book of the Later Han. Because Confucian teachings regarded the body as sacred and surgery was considered a form of body mutilation, surgery was strongly discouraged in ancient China. Because of this, despite Hua Tuos reported success with general anesthesia, the practice of surgery in ancient China ended with his death.
The name mafeisan combines ma (麻, meaning "cannabis, hemp, numbed or tingling"), fei (沸, meaning "boiling or bubbling"), and san (散, meaning "to break up or scatter", or "medicine in powder form"). Therefore, the word mafeisan probably means something like "cannabis boil powder". Many sinologists and scholars of traditional Chinese medicine have guessed at the composition of Hua Tuo's mafeisan powder, but the exact components still remain unclear. His formula is believed to have contained some combination of:
* bai zhi (Chinese:白芷，Angelica dahurica),
* cao wu (Chinese:草烏, Aconitum kusnezoffii, Aconitum kusnezoffii, Kusnezoff's monkshood, or wolfsbane root),
* chuān xiōng (Chinese:川芎，Ligusticum wallichii, or Szechuan lovage),
* dong quai (Chinese:当归, Angelica sinensis, or "female ginseng"),
* wu tou (烏頭, Aconitum carmichaelii, rhizome of Aconitum, or "Chinese monkshood"),
* yang jin hua (洋金花, Flos Daturae metelis, or Datura stramonium, jimson weed, devil's trumpet, thorn apple, locoweed, moonflower),
* ya pu lu (押不芦, Mandragora officinarum),
* rhododendron flower, and
* jasmine root.
Others have suggested the potion may have also contained hashish, bhang, shang-luh, or opium. Victor H. Mair wrote that mafei "appears to be a transcription of some Indo-European word related to "morphine"." Some authors believe that Hua Tuo may have discovered surgical analgesia by acupuncture, and that mafeisan either had nothing to do with or was simply an adjunct to his strategy for anesthesia. Many physicians have attempted to re-create the same formulation based on historical records but none have achieved the same clinical efficacy as Hua Tuos. In any event, Hua Tuos formula did not appear to be effective for major operations.
Other substances used from antiquity for anesthetic purposes include extracts of juniper and coca. | 1 | Applied and Interdisciplinary Chemistry |
The following outline is provided as an overview of and topical guide to biochemistry:
Biochemistry – study of chemical processes in living organisms, including living matter. Biochemistry governs all living organisms and living processes. | 1 | Applied and Interdisciplinary Chemistry |
The phenacyl PPG is the archetypal example of a carbonyl-based PPG. Under this motif, the PPG is attached to the protected substrate at the αβ-carbon, and can exhibit varied photodeprotection mechanisms based on the phenacyl skeleton, substrate identify and reaction conditions. Overall, phenacyl PPGs can be used to protect sulfonates, phosphates, carboxylates and carbamates.
As with nitrobenzyl-based PPGs, several modifications are known. For example, the 3’,5’-dimethoxybenzoin PPG (DMB) contains a 3,5-dimethoxyphenyl substituent on the carbonyls α-carbon. Under certain conditions, DMB has exhibited quantum yields as high as 0.64. Additionally, the p-hydroxyphenacyl PPG (pHP) has been designed to react through a photo-Favorskii rearrangement. This mechanism yields the carboxylic acid as the exclusive photoproduct; the key benefit of the pHP PPG is the lack of secondary photoreactions and the significantly different UV absorption profiles of the products and reactants. While the quantum yield of the p-hydroxyphenacyl PPG is generally in the 0.1-0.4 range, it can increase to near unity when releasing a good leaving group such as a tosylate. The photoextrusion of the leaving group from the pHP PPG is so effective, that it also releases even poor nucleofuges such as amines (with the quantum yield in the 0.01-0.5 range, and dependent on solution pH). The Additionally, photorelease occurs on the nanosecond timeframe, with k' > 10 s.
The o-hydroxyphenacyl PPG has been introduced as an alternative with absorption band shifted closer towards the visible region, however it has slightly lower quantum yields of deprotection (generally 0.1-0.3) due to excited state proton transfer available as an alternative deactivation pathway.
The phenacyl moiety itself contains one chiral carbon atom in the backbone. The protected group (leaving group) is not directly attached to this chiral carbon atom, however has been shown to be able to work as a chiral auxiliary directing approach of a diene to a dienophile in a stereoselective thermal Diels–Alder reaction. The auxiliary is then removed simply upon irradiation with UV light. | 0 | Theoretical and Fundamental Chemistry |
CdS is used as pigment in plastics, showing good thermal stability, light and weather fastness, chemical resistance and high opacity. As a pigment, CdS is known as cadmium yellow (CI pigment yellow 37). About 2000 tons are produced annually as of 1982, representing about 25% of the cadmium processed commercially. | 0 | Theoretical and Fundamental Chemistry |
Ten communes border the Étang de Berre: Istres, Miramas, Saint-Chamas, Berre-l'Étang, Rognac, Vitrolles, Marignane, Châteauneuf-les-Martigues, Martigues and Saint-Mitre-les-Remparts. | 1 | Applied and Interdisciplinary Chemistry |
Lignin is a complex polyphenolic macromolecule composed mainly of beta-O4-aryl linkages. After cellulose, lignin is the second most abundant biopolymer and is one of the primary structural components of most plants. It contains subunits derived from p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol and is unusual among biomolecules in that it is racemic. The lack of optical activity is due to the polymerization of lignin which occurs via free radical coupling reactions in which there is no preference for either configuration at a chiral center. | 0 | Theoretical and Fundamental Chemistry |
The key concept is that larger cells tend to stay within the flowing buffer solution while smaller cells will be washed away follow the buffer solution (different sedimentation property within the buffer solution), and cells will have different sedimentation properties in different cell cycle stages.
The basic principle of separating the cells inside CCE is the balance between centripetal and the counter flow drag force. When the cells enter the elutriation chamber, all the cells will stay at the outer edge of the chamber due to centrifugal force. Then when the flow rate of the buffer solution increases, the solution tends to push the cells towards the middle of the CCE. When the counter flow drag force outweighs the centripetal force, particles will be driven by the net force and leave the chamber. Smaller particles are able to leave the chamber at lower flow rates. In contrast, larger particles will stay within the elutriation chamber. Therefore, buffer flow rate can be used to control size sorting within the elutriation chamber. | 0 | Theoretical and Fundamental Chemistry |
In photosynthesis, state transitions are rearrangements of the photosynthetic apparatus which occur on short time-scales (seconds to minutes). The effect is prominent in cyanobacteria, whereby the phycobilisome light-harvesting antenna complexes alter their preference for transfer of excitation energy between the two reaction centers, PS I and PS II. This shift helps to minimize photodamage caused by reactive oxygen species (ROS) under stressful conditions such as high light, but may also be used to offset imbalances between the rates of generating reductant and ATP.
The phenomenon was first discovered in unicellular green algae, and may also occur in plants. However, in these organisms it occurs by a different mechanism, which is not as well understood. The plant/algal mechanism is considered functionally analogous to the cyanobacterial mechanism but involves completely different components. The foremost difference is the presence of fundamentally different types of light-harvesting antenna complexes: plants and green algae use an intrinsically-bound membrane complex of chlorophyll a/b binding proteins for their antenna, instead of the soluble phycobilisome complexes used by cyanobacteria (and certain algae). | 1 | Applied and Interdisciplinary Chemistry |
When sound spreads out evenly in all directions in three dimensions, the intensity drops in proportion to the inverse square of the distance. However, in the ocean, there is a layer called the deep sound channel or SOFAR channel which can confine sound waves at a particular depth.
In the SOFAR channel, the speed of sound is lower than that in the layers above and below. Just as light waves will refract towards a region of higher refractive index, sound waves will refract towards a region where their speed is reduced. The result is that sound gets confined in the layer, much the way light can be confined to a sheet of glass or optical fiber. Thus, the sound is confined in essentially two dimensions. In two dimensions the intensity drops in proportion to only the inverse of the distance. This allows waves to travel much further before being undetectably faint.
A similar effect occurs in the atmosphere. Project Mogul successfully used this effect to detect a nuclear explosion at a considerable distance. | 1 | Applied and Interdisciplinary Chemistry |
The Volga River, the longest river in Europe, drains 20% of the European land area and is the source of 80% of the Caspian's inflow. Heavy development in its lower reaches has caused numerous unregulated releases of chemical and biological pollutants. The UN Environment Programme warns that the Caspian "suffers from an enormous burden of pollution from oil extraction and refining, offshore oil fields, radioactive wastes from nuclear power plants and huge volumes of untreated sewage and industrial waste introduced mainly by the Volga River".
The magnitude of fossil fuel extraction and transport activity in the Caspian also poses a risk to the environment. The island of Vulf off Baku, for example, has suffered ecological damage as a result of the petrochemical industry; this has significantly decreased the number of species of marine birds in the area. Existing and planned oil and gas pipelines under the sea further increase the potential threat to the environment.
The high concentration of mud volcanoes under the Caspian Sea were thought to be the cause of a fire that broke out 75 kilometers from Baku on July 5, 2021. The State oil company of Azerbaijan SOCAR said preliminary information indicated it was a mud volcano which spewed both mud and flammable gas.
It is calculated that during the 21st century, the water level of the Caspian Sea will decrease by 9–18 m (30–60 ft) due to the acceleration of evaporation due to global warming and the process of desertification, causing an ecocide.
On October 23, 2021, Kazakhstan President Kassym-Jomart Tokayev signed the Protocol for the Protection of the Caspian Sea against Pollution from Land-based Sources in order to ensure better protection for the biodiversity of the Caspian Sea. | 1 | Applied and Interdisciplinary Chemistry |
Fluorine-18 (F) is a fluorine radioisotope which is an important source of positrons. It has a mass of 18.0009380(6) u and its half-life is 109.771(20) minutes. It decays by positron emission 96.7% of the time and electron capture 3.3% of the time. Both modes of decay yield stable oxygen-18. | 1 | Applied and Interdisciplinary Chemistry |
Trimethylsilyldiazomethane can be prepared by treating (trimethylsilyl)methylmagnesium chloride with diphenyl phosphorazidate. The C-labeled reagent is also known. | 0 | Theoretical and Fundamental Chemistry |
Dissociative photoionization processes can be generalized as:
If the enthalpies of formation of two of the three species are known, the third can be calculated with the help of the dissociative photoionization energy, E, using Hess's law. This approach was used, for instance, to determine the enthalpy of formation of the methyl ion, , which in turn was used to obtain the enthalpy of formation of iodomethane, as 15.23 kJ mol, with an uncertainty of only 0.3 kJ mol.
If different sample molecules produce shared fragment ions, a complete thermochemical chain can be constructed, as was shown for some methyl trihalides, where the uncertainty in e.g. the , (Halon-1021) heat of formation was reduced from 20 to 2 kJ mol. Furthermore, dissociative photoionization energies can be combined with calculated isodesmic reaction energies to build thermochemical networks. Such an approach was used to revise primary alkylamine enthalpies of formation. | 0 | Theoretical and Fundamental Chemistry |
Named after its inventor, biologist Edwin Southern, the Southern blot is a method for probing for the presence of a specific DNA sequence within a DNA sample. DNA samples before or after restriction enzyme (restriction endonuclease) digestion are separated by gel electrophoresis and then transferred to a membrane by blotting via capillary action. The membrane is then exposed to a labeled DNA probe that has a complement base sequence to the sequence on the DNA of interest. Southern blotting is less commonly used in laboratory science due to the capacity of other techniques, such as PCR, to detect specific DNA sequences from DNA samples. These blots are still used for some applications, however, such as measuring transgene copy number in transgenic mice or in the engineering of gene knockout embryonic stem cell lines. | 1 | Applied and Interdisciplinary Chemistry |
Sulfinic acids are oxoacids of sulfur with the structure RSO(OH). In these organosulfur compounds, sulfur is pyramidal. | 0 | Theoretical and Fundamental Chemistry |
Uranium in the environment is a global health concern, and comes from both natural and man-made sources. Mining, phosphates in agriculture, weapons manufacturing, and nuclear power are sources of uranium in the environment.
In the natural environment, radioactivity of uranium is generally low, but uranium is a toxic metal that can disrupt normal functioning of the kidney, brain, liver, heart, and numerous other systems. Chemical toxicity can cause public health issues when uranium is present in groundwater, especially if concentrations in food and water are increased by mining activity. The biological half-life (the average time it takes for the human body to eliminate half the amount in the body) for uranium is about 15 days.
Uranium's radioactivity can present health and environmental issues in the case of nuclear waste produced by nuclear power plants or weapons manufacturing.
Uranium is weakly radioactive and remains so because of its long physical half-life (4.468 billion years for uranium-238). The use of depleted uranium (DU) in munitions is controversial because of questions about potential long-term health effects. | 0 | Theoretical and Fundamental Chemistry |
Double Helix (2004), a novel by Nancy Werlin, is about 18-year-old Eli Samuels, who works for a famous molecular biologist named Dr. Quincy Wyatt. There is a mysterious connection between Dr. Wyatt and Elis parents, and all Eli knows about the connection is that it has something to do with his mother, who has Huntingtons disease. Because of the connection between Dr. Wyatt and the Samuels family, Elis father is strongly against Eli working there. The job is perfect, and the wages are great, but Eli cant help but notice that Dr. Wyatt seems to be a little too interested in him. Later on, as Eli continues to work in the lab, he discovers with the help of Kayla Matheson, Dr. Wyatt's supposed "niece," that he and Kayla are the product of a highly unethical eugenics experiment. | 1 | Applied and Interdisciplinary Chemistry |
In 1972, Corbett was elected a Fellow of the Royal Society of New Zealand. He was also a Fellow of the New Zealand Institute of Chemistry. | 0 | Theoretical and Fundamental Chemistry |
Ethyl eicosapentaenoic acid (E-EPA, icosapent ethyl), sold under the brand name Vascepa among others, is a medication used to treat dyslipidemia and hypertriglyceridemia. It is used in combination with changes in diet in adults with hypertriglyceridemia ≥ 150 mg/dL. Further, it is often required to be used with a statin (maximally-tolerated dose).
The most common side effects are musculoskeletal pain, peripheral edema (swelling of legs and hands), atrial fibrillation, and arthralgia (joint pain). Other common side effects include bleeding, constipation, gout, and rash.
It is made from the omega-3 fatty acid eicosapentaenoic acid (EPA). The US Food and Drug Administration (FDA) granted the approval of icosapent ethyl in 2012 to Amarin Corporation, and it became the second fish oil-based medication after omega-3-acid ethyl esters (brand named Lovaza, itself approved in 2004). On 13 December 2019, the FDA also approved Vascepa as the first drug specifically "to reduce cardiovascular risk among people with elevated triglyceride levels". It is available as a generic medication. In 2020, it was the 285th most commonly prescribed medication in the United States, with more than 1million prescriptions. | 1 | Applied and Interdisciplinary Chemistry |
A Stöber-like process has been used to produce monodisperse carbon spheres using resorcinol-formaldehyde resin in place of a silica precursor. The modified process allows production of carbon spheres with smooth surfaces and a diameter ranging from 200 to 1000 nm. Unlike the silica-based Stöber process, this reaction is completed at neutral pH and ammonia has a role in stabilizing the individual carbon particles by preventing self-adhesion and aggregation, as well as acting as a catalyst. | 0 | Theoretical and Fundamental Chemistry |
The regulation of drugs varies by jurisdiction. In some countries, such as the United States, they are regulated at the national level by a single agency. In other jurisdictions, they are regulated at the state level, or at both state and national levels by various bodies, as is the case in Australia. The role of therapeutic goods regulation is designed mainly to protect the health and safety of the population. Regulation is aimed at ensuring the safety, quality, and efficacy of the therapeutic goods which are covered under the scope of the regulation. In most jurisdictions, therapeutic goods must be registered before they are allowed to be marketed. There is usually some degree of restriction on the availability of certain therapeutic goods depending on their risk to consumers.
Depending upon the jurisdiction, drugs may be divided into over-the-counter drugs (OTC) which may be available without special restrictions, and prescription drugs, which must be prescribed by a licensed medical practitioner in accordance with medical guidelines due to the risk of adverse effects and contraindications. The precise distinction between OTC and prescription depends on the legal jurisdiction. A third category, "behind-the-counter" drugs, is implemented in some jurisdictions. These do not require a prescription, but must be kept in the dispensary, not visible to the public, and be sold only by a pharmacist or pharmacy technician. Doctors may also prescribe prescription drugs for off-label use – purposes which the drugs were not originally approved for by the regulatory agency. The Classification of Pharmaco-Therapeutic Referrals helps guide the referral process between pharmacists and doctors.
The International Narcotics Control Board of the United Nations imposes a world law of prohibition of certain drugs. They publish a lengthy list of chemicals and plants whose trade and consumption (where applicable) are forbidden. OTC drugs are sold without restriction as they are considered safe enough that most people will not hurt themselves accidentally by taking it as instructed. Many countries, such as the United Kingdom have a third category of "pharmacy medicines", which can be sold only in registered pharmacies by or under the supervision of a pharmacist.
Medical errors include over-prescription and polypharmacy, mis-prescription, contraindication and lack of detail in dosage and administration instructions. In 2000 the definition of a prescription error was studied using a Delphi method conference; the conference was motivated by ambiguity in what a prescription error is and a need to use a uniform definition in studies. | 1 | Applied and Interdisciplinary Chemistry |
DMAP has a relatively high toxicity and is particularly dangerous because of its ability to be absorbed through the skin. It is also corrosive. | 0 | Theoretical and Fundamental Chemistry |
The start of the Cambrian period is marked by "fluctuations" in a number of geochemical records, including Strontium, Sulfur and Carbon isotopic excursions. While these anomalies are difficult to interpret, a number of possibilities have been put forward. They probably represent changes on a global scale, and as such may help to constrain possible causes of the Cambrian explosion.
The chemical signature may be related to continental break-up, the end of a "global glaciation", or a catastrophic drop in productivity caused by a mass extinction just before the beginning of the Cambrian. | 0 | Theoretical and Fundamental Chemistry |
Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. What distinguishes them from other gases is that they absorb the wavelengths of radiation that a planet emits, resulting in the greenhouse effect. The Earth is warmed by sunlight, causing its surface to radiate heat, which is then mostly absorbed by greenhouse gases. Without greenhouse gases in the atmosphere, the average temperature of Earth's surface would be about , rather than the present average of .
The five most abundant greenhouse gases in Earth's atmosphere, listed in decreasing order of average global mole fraction, are: water vapor, carbon dioxide, methane, nitrous oxide, ozone. Other greenhouse gases of concern include chlorofluorocarbons (CFCs and HCFCs), hydrofluorocarbons (HFCs), perfluorocarbons, sulfur hexafluoride|, and nitrogen trifluoride|. Water vapor causes about half of the greenhouse effect, but humans are not directly adding to its amount, so it is not a driver of climate change.
Carbon dioxide is causing about three-quarters of global warming and can take thousands of years to be fully absorbed by the carbon cycle. Methane causes most of the remaining warming and lasts in the atmosphere for an average of 12 years. Human activities since the beginning of the Industrial Revolution (around 1750) have increased carbon dioxide by over 50%, up to a level not seen in over 3 million years. The atmospheric methane concentrations have increased by over 150% during the same time period.
Without human influence, the natural flows of carbon between the atmosphere, terrestrial ecosystems, the ocean, and sediments would be fairly balanced. The vast majority of carbon dioxide emissions by humans come from the burning of fossil fuels. Further contributions come for example from cement manufacturing and deforestation. Methane emissions originate from agriculture, fossil fuel production, waste, and other sources. If current emission rates continue then temperature rises will surpass sometime between 2040 and 2070. This is a level which the Intergovernmental Panel on Climate Change (IPCC) says is "dangerous". | 1 | Applied and Interdisciplinary Chemistry |
Le Fevre was an able chemist and a lucid, learned, and accurate author. He wrote:
*Traité de la Chymie: A Compendious Body of Chymistry: Wherein is contained whatsoever is necessary for the attaining to the curious knowledge of this Art; Comprehending in general the whole practice thereof: and teaching the most exact preparation of Animals, Vegetables and Minerals, so as to preserve their essential Vertues. Laid open in two Books, and dedicated to the use of all Apothecaries, &c. (2 volumes, 1664 - English translation).
*Disputatio de Myrrhata Potione (in volume ix. of John Pearsons Critici Sacri' (1660).
*A Discourse upon Sr. Walter Rawleigh’s Great Cordial (1664). | 1 | Applied and Interdisciplinary Chemistry |
Ballentine has shown that by measuring noble gas isotopes, he can identify and quantify the processes controlling the origin, migration, and interaction of subsurface water, hydrocarbons, and fluids.
He has applied noble gas tools and principles to understand how natural gas fields form inside Earth, the role of groundwater in forming hydrocarbon reservoirs, and the origins of different gases on the planet. Ballentine also has developed quantitative techniques to understand how carbon dioxide behaves in the subsurface, including its role in the crustal carbon cycle, and how carbon-rich fluids have supported subsurface life over geological timescales. | 0 | Theoretical and Fundamental Chemistry |
Water is miscible with many liquids, including ethanol in all proportions. Water and most oils are immiscible, usually forming layers according to increasing density from the top. This can be predicted by comparing the polarity. Water being a relatively polar compound will tend to be miscible with liquids of high polarity such as ethanol and acetone, whereas compounds with low polarity will tend to be immiscible and poorly soluble such as with hydrocarbons.
As a gas, water vapor is completely miscible with air. On the other hand, the maximum water vapor pressure that is thermodynamically stable with the liquid (or solid) at a given temperature is relatively low compared with total atmospheric pressure. For example, if the vapor's partial pressure is 2% of atmospheric pressure and the air is cooled from 25 °C, starting at about 22 °C, water will start to condense, defining the dew point, and creating fog or dew. The reverse process accounts for the fog burning off in the morning. If the humidity is increased at room temperature, for example, by running a hot shower or a bath, and the temperature stays about the same, the vapor soon reaches the pressure for phase change and then condenses out as minute water droplets, commonly referred to as steam.
A saturated gas or one with 100% relative humidity is when the vapor pressure of water in the air is at equilibrium with vapor pressure due to (liquid) water; water (or ice, if cool enough) will fail to lose mass through evaporation when exposed to saturated air. Because the amount of water vapor in the air is small, relative humidity, the ratio of the partial pressure due to the water vapor to the saturated partial vapor pressure, is much more useful. Vapor pressure above 100% relative humidity is called supersaturated and can occur if the air is rapidly cooled, for example, by rising suddenly in an updraft. | 1 | Applied and Interdisciplinary Chemistry |
Properties of materials such as electrical conduction and heat capacity are investigated by solid state physics. An early model of electrical conduction was the Drude model, which applied kinetic theory to the electrons in a solid. By assuming that the material contains immobile positive ions and an "electron gas" of classical, non-interacting electrons, the Drude model was able to explain electrical and thermal conductivity and the Hall effect in metals, although it greatly overestimated the electronic heat capacity.
Arnold Sommerfeld combined the classical Drude model with quantum mechanics in the free electron model (or Drude-Sommerfeld model). Here, the electrons are modelled as a Fermi gas, a gas of particles which obey the quantum mechanical Fermi–Dirac statistics. The free electron model gave improved predictions for the heat capacity of metals, however, it was unable to explain the existence of insulators.
The nearly free electron model is a modification of the free electron model which includes a weak periodic perturbation meant to model the interaction between the conduction electrons and the ions in a crystalline solid. By introducing the idea of electronic bands, the theory explains the existence of conductors, semiconductors and insulators.
The nearly free electron model rewrites the Schrödinger equation for the case of a periodic potential. The solutions in this case are known as Bloch states. Since Blochs theorem applies only to periodic potentials, and since unceasing random movements of atoms in a crystal disrupt periodicity, this use of Blochs theorem is only an approximation, but it has proven to be a tremendously valuable approximation, without which most solid-state physics analysis would be intractable. Deviations from periodicity are treated by quantum mechanical perturbation theory. | 1 | Applied and Interdisciplinary Chemistry |
Donald James Cram (April 22, 1919 – June 17, 2001) was an American chemist who shared the 1987 Nobel Prize in Chemistry with Jean-Marie Lehn and Charles J. Pedersen "for their development and use of molecules with structure-specific interactions of high selectivity." They were the founders of the field of host–guest chemistry. | 0 | Theoretical and Fundamental Chemistry |
Every polyhedron has a dihedral angle at every edge describing the relationship of the two faces that share that edge. This dihedral angle, also called the face angle, is measured as the internal angle with respect to the polyhedron. An angle of 0° means the face normal vectors are antiparallel and the faces overlap each other, which implies that it is part of a degenerate polyhedron. An angle of 180° means the faces are parallel, as in a tiling. An angle greater than 180° exists on concave portions of a polyhedron.
Every dihedral angle in an edge-transitive polyhedron has the same value. This includes the 5 Platonic solids, the 13 Catalan solids, the 4 Kepler–Poinsot polyhedra, the two quasiregular solids, and two quasiregular dual solids. | 0 | Theoretical and Fundamental Chemistry |
Gay-Lussacs law usually refers to Joseph-Louis Gay-Lussacs law of combining volumes of gases, discovered in 1808 and published in 1809. However, it sometimes refers to the proportionality of the volume of a gas to its absolute temperature at constant pressure. The latter law was published by Gay-Lussac in 1802, but in the article in which he described his work, he cited earlier unpublished work from the 1780s by Jacques Charles. Consequently, the volume-temperature proportionality is usually known as Charles's Law. | 0 | Theoretical and Fundamental Chemistry |
Since 1975 ion chromatography has been widely used in many branches of industry. The main beneficial advantages are reliability, very good accuracy and precision, high selectivity, high speed, high separation efficiency, and low cost of consumables. The most significant development related to ion chromatography are new sample preparation methods; improving the speed and selectivity of analytes separation; lowering of limits of detection and limits of quantification; extending the scope of applications; development of new standard methods; miniaturization and extending the scope of the analysis of a new group of substances. Allows for quantitative testing of electrolyte and proprietary additives of electroplating baths. It is an advancement of qualitative hull cell testing or less accurate UV testing. Ions, catalysts, brighteners and accelerators can be measured. Ion exchange chromatography has gradually become a widely known, universal technique for the detection of both anionic and cationic species. Applications for such purposes have been developed, or are under development, for a variety of fields of interest, and in particular, the pharmaceutical industry. The usage of ion exchange chromatography in pharmaceuticals has increased in recent years, and in 2006, a chapter on ion exchange chromatography was officially added to the United States Pharmacopia-National Formulary (USP-NF). Furthermore, in 2009 release of the USP-NF, the United States Pharmacopia made several analyses of ion chromatography available using two techniques: conductivity detection, as well as pulse amperometric detection. Majority of these applications are primarily used for measuring and analyzing residual limits in pharmaceuticals, including detecting the limits of oxalate, iodide, sulfate, sulfamate, phosphate, as well as various electrolytes including potassium, and sodium. In total, the 2009 edition of the USP-NF officially released twenty eight methods of detection for the analysis of active compounds, or components of active compounds, using either conductivity detection or pulse amperometric detection. | 0 | Theoretical and Fundamental Chemistry |
Hydrophobic forces are the attractive entropic forces between any two hydrophobic groups in aqueous media, e.g. the forces between two long hydrocarbon chains in aqueous solutions. The magnitude of these forces depends on the hydrophobicity of the interacting groups as well as the distance separating them (they are found to decrease roughly exponentially with the distance). The physical origin of these forces is a debated issue but they have been found to be long-ranged and are the strongest among all the physical interaction forces operating between biological surfaces and molecules. Due to their long range nature, they are responsible for rapid coagulation of hydrophobic particles in water and play important roles in various biological phenomena including folding and stabilization of macromolecules such as proteins and fusion of cell membranes.
The potential V is given by
where C ( is a characteristic length scale of hydrophobic attraction and z is the distance of separation. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, charge-transfer (CT) complex, or electron donor-acceptor complex, describes a type of supramolecular assembly of two or more molecules or ions. The assembly consists of two molecules that self-attract through electrostatic forces, i.e., one has at least partial negative charge and the partner has partial positive charge, referred to respectively as the electron acceptor and electron donor. In some cases, the degree of charge transfer is "complete", such that the CT complex can be classified as a salt. In other cases, the charge-transfer association is weak, and the interaction can be disrupted easily by polar solvents. | 0 | Theoretical and Fundamental Chemistry |
Adverse effects are similar to oxcarbazepine. The most common ones (more than 10% of patients) are tiredness and dizziness. Other fairly common side effects (1 to 10%) include impaired coordination, gastrointestinal disorders such as diarrhoea, nausea and vomiting, rash (1.1%), and hyponatremia (low sodium blood levels, 1.2%). There may also be an increased risk of suicidal thoughts. | 0 | Theoretical and Fundamental Chemistry |
In isochromat mode, the incident electron energy is ramped and the emitted photons are detected at a fixed energy that is determined by the photon detector. Typically, an I gas filled Geiger-Müller tube with an entrance window of either SrF or CaF is used as the photon detector. The combination of window and filling gas determines the detected photon energy, and for I gas and either a SrF or CaF window, the photons energies are ~ 9.5 eV and ~ 9.7 eV, respectively. | 0 | Theoretical and Fundamental Chemistry |
In contrast to other gas components, water content in air, or humidity, to a higher degree depends on vaporization and condensation from or into water, which, in turn, mainly depends on temperature. Therefore, when applying more pressure to a gas saturated with water, all components will initially decrease in volume approximately according to the ideal gas law. However, some of the water will condense until returning to almost the same humidity as before, giving the resulting total volume deviating from what the ideal gas law predicted. Conversely, decreasing temperature would also make some water condense, again making the final volume deviating from predicted by the ideal gas law.
Therefore, gas volume may alternatively be expressed excluding the humidity content: V (volume dry). This fraction more accurately follows the ideal gas law. On the contrary, V (volume saturated) is the volume a gas mixture would have if humidity was added to it until saturation (or 100% relative humidity). | 0 | Theoretical and Fundamental Chemistry |
para-Dimethylaminobenzaldehyde is an organic compound containing amine and aldehyde moieties which is used in Ehrlichs reagent and Kovacs reagent to test for indoles. The carbonyl group typically reacts with the electron rich 2-position of the indole but may also react at the C-3 or N-1 positions. It may also be used for determination of hydrazine. | 0 | Theoretical and Fundamental Chemistry |
The Emerson Cavitation Tunnel consists of a water circuit which flows in the vertical plane, within which propellers and other propulsion devices can be tested. The system is powered by a pump, with a four-bladed impeller and can produce a maximum water velocity of . The test area has a cross sectional area of allowing model propellers of up to in diameter to be tested. The pressure range of the tunnel can vary from a minimum of 7.6 kN/m to a maximum of 106 kN/m. Cavitation numbers of 0.5 (minimum) to 23 (maximum) can be accommodated for. Measurements can be taken using a 3 Watt, water-cooled, Argon-ion laser, a hydrophone, and two dynamometers. A high-speed video camera is also attached with an imaging frequency of 1–10,000 frames per second.
Funding for the tunnel's equipment is raised by numerous organisations, including the Engineering and Physical Sciences Research Council (EPSRC) and the Scottish Universities of Glasgow and Strathclyde. | 1 | Applied and Interdisciplinary Chemistry |
Databases and computational tools for mimotopes have been an important part of phage display study. Databases, programs and web servers have been widely used to exclude target-unrelated peptides, characterize small molecules-protein interactions and map protein-protein interactions. Users can use three dimensional structure of a protein and the peptides selected from phage display experiment to map conformational epitopes. Some of the fast and efficient computational methods are available online. | 1 | Applied and Interdisciplinary Chemistry |
The most common F-gases are hydrofluorocarbons (HFCs), which contain hydrogen, fluorine, and carbon. They are used in a multitude of applications including commercial refrigeration, industrial refrigeration, air-conditioning systems, heat pump equipment, and as blowing agents for foams, fire extinguishants, aerosol propellants, and solvents. HFC-134a (1,1,1,2-Tetrafluoroethane) has grown to become the most abundant HFC in Earth's atmosphere as of year 2015.
Perfluorocarbons (PFCs) are the compounds consisting of fluorine and carbon. They are widely used in the electronics, cosmetics, and pharmaceutical industries, as well as in refrigeration when combined with other gases. PFCs were commonly used as fire extinguishants in the past and are still found in older fire protection systems. They are also a by-product of the aluminium smelting process. PFC-14 (Carbon tetrafluoride - CF) has grown to become the most abundant PFC in earth's atmosphere as of year 2015.
Sulphur hexafluoride (SF) is used primarily as an arc suppression and insulation gas. It can be found in high-voltage switchgear and is used in the production of magnesium.
Nitrogen trifluoride (NF) is used primarily as an etchant for microelectronics fabrication. | 1 | Applied and Interdisciplinary Chemistry |
* Co-rotating twin screw extruders: The polymer solution is brought into a co-rotating twin screw extruders, where it is subjected to shear and mechanical energy input and where vapors are drawn off. This type of machine allows different pressures in different zones. An advantage is the self-cleaning action of those extruders.
* Single-screw extruders: In principle similar to co-rotating twin screw extruders, without the self-cleaning action.
* Wiped-film evaporators: Polymer solution is brought into a single large vessel, where a rotor agitates the product and creates surface renewal. Only a single pressure level is possible in these machines.
* Large-volume kneaders: A polymer solution is brought into a large-volume kneader and subjected to shear at longer residence times than in an extruder. | 1 | Applied and Interdisciplinary Chemistry |
Bulk carbon-13 for commercial use, e.g. in chemical synthesis, is enriched from its natural 1% abundance. Although carbon-13 can be separated from the major carbon-12 isotope via techniques such as thermal diffusion, chemical exchange, gas diffusion, and laser and cryogenic distillation, currently only cryogenic distillation of methane or carbon monoxide is an economically feasible industrial production technique. Industrial carbon-13 production plants represent a substantial investment, greater than 100 meter tall cryogenic distillation columns are needed to separate the carbon-12 or carbon-13 containing compounds. The largest reported commercial carbon-13 production plant in the world as of 2014 has a production capability of ~400 kg of carbon-13 annually. In contrast, a 1969 carbon monoxide cryogenic distillation pilot plant at Los Alamos Scientific Laboratories could produce 4 kg of carbon-13 annually. | 0 | Theoretical and Fundamental Chemistry |
*1802 Éleuthère Irénée du Pont, who had emigrated from France after the French Revolution, founded a company to produce gunpowder called E. I. du Pont de Nemours and Company (commonly referred to as DuPont) in Brandywine Creek, near Wilmington, Delaware. | 1 | Applied and Interdisciplinary Chemistry |
The alchemical tradition sought to turn the "base metal", lead, into gold. As a nuclear transmutation, it requires far less energy to turn gold into lead; for example, this would occur via neutron capture and beta decay if gold were left in a nuclear reactor for a sufficiently long period of time. Glenn Seaborg succeeded in producing a minuscule amount of gold from bismuth, at a net energy loss. | 0 | Theoretical and Fundamental Chemistry |
One particular metallofullerene with gadolinium at its core is up to 40 times better as a contrast agent in magnetic resonance imaging scans for diagnostic imaging. Metallofullerenes may also provide ways to carry therapeutic radioactive ions to cancerous tissue. | 0 | Theoretical and Fundamental Chemistry |
The origin of the stereographic projection is not known, but it is believed to have been discovered by Ancient Greek astronomers and used for projecting the celestial sphere to the plane so that the motions of stars and planets could be analyzed using plane geometry. Its earliest extant description is found in Ptolemys Planisphere (2nd century AD), but it was ambiguously attributed to Hipparchus (2nd century BC) by Synesius (), and Apolloniuss Conics () contains a theorem which is crucial in proving the property that the stereographic projection maps circles to circles. Hipparchus, Apollonius, Archimedes, and even Eudoxus (4th century BC) have sometimes been speculatively credited with inventing or knowing of the stereographic projection, but some experts consider these attributions unjustified. Ptolemy refers to the use of the stereographic projection in a "horoscopic instrument", perhaps the described by Vitruvius (1st century BC).
By the time of Theon of Alexandria (4th century), the planisphere had been combined with a dioptra to form the planispheric astrolabe ("star taker"), a capable portable device which could be used for measuring star positions and performing a wide variety of astronomical calculations. The astrolabe was in continuous use by Byzantine astronomers, and was significantly further developed by medieval Islamic astronomers. It was transmitted to Western Europe during the 11th–12th century, with Arabic texts translated into Latin.
In the 16th and 17th century, the equatorial aspect of the stereographic projection was commonly used for maps of the Eastern and Western Hemispheres. It is believed that already the map created in 1507 by Gualterius Lud was in stereographic projection, as were later the maps of Jean Roze (1542), Rumold Mercator (1595), and many others. In star charts, even this equatorial aspect had been utilised already by the ancient astronomers like Ptolemy.
François dAguilon gave the stereographic projection its current name in his 1613 work Opticorum libri sex philosophis juxta ac mathematicis utiles' (Six Books of Optics, useful for philosophers and mathematicians alike).
In the late 16th century, Thomas Harriot proved that the stereographic projection is conformal; however, this proof was never published and sat among his papers in a box for more than three centuries. In 1695, Edmond Halley, motivated by his interest in star charts, was the first to publish a proof. He used the recently established tools of calculus, invented by his friend Isaac Newton. | 0 | Theoretical and Fundamental Chemistry |
Aluminium alloys are anodized to increase corrosion resistance and to allow dyeing (colouring), improved lubrication, or improved adhesion. However, anodizing does not increase the strength of the aluminium object. The anodic layer is insulative.
When exposed to air at room temperature, or any other gas containing oxygen, pure aluminium self-passivates by forming a surface layer of amorphous aluminium oxide 2 to 3 nm thick, which provides very effective protection against corrosion. Aluminium alloys typically form a thicker oxide layer, 5–15 nm thick, but tend to be more susceptible to corrosion. Aluminium alloy parts are anodized to greatly increase the thickness of this layer for corrosion resistance. The corrosion resistance of aluminium alloys is significantly decreased by certain alloying elements or impurities: copper, iron, and silicon, so 2000-, 4000-, 6000 and 7000-series Al alloys tend to be most susceptible.
Although anodizing produces a very regular and uniform coating, microscopic fissures in the coating can lead to corrosion. Further, the coating is susceptible to chemical dissolution in the presence of high- and low-pH chemistry, which results in stripping the coating and corrosion of the substrate. To combat this, various techniques have been developed either to reduce the number of fissures, to insert more chemically stable compounds into the oxide, or both. For instance, sulphuric-anodized articles are normally sealed, either through hydro-thermal sealing or precipitating sealing, to reduce porosity and interstitial pathways that allow corrosive ion exchange between the surface and the substrate. Precipitating seals enhance chemical stability but are less effective in eliminating ionic exchange pathways. Most recently, new techniques to partially convert the amorphous oxide coating into more stable micro-crystalline compounds have been developed that have shown significant improvement based on shorter bond lengths.
Some aluminium aircraft parts, architectural materials, and consumer products are anodized. Anodized aluminium can be found on MP3 players, smartphones, multi-tools, flashlights, cookware, cameras, sporting goods, firearms, window frames, roofs, in electrolytic capacitors, and on many other products both for corrosion resistance and the ability to retain dye. Although anodizing only has moderate wear resistance, the deeper pores can better retain a lubricating film than a smooth surface would.
Anodized coatings have a much lower thermal conductivity and coefficient of linear expansion than aluminium. As a result, the coating will crack from thermal stress if exposed to temperatures above 80 °C (353 K). The coating can crack, but it will not peel. The melting point of aluminium oxide is 2050°C (2323K), much higher than pure aluminium's 658°C (931K). This and the insulativity of aluminium oxide can make welding more difficult.
In typical commercial aluminium anodizing processes, the aluminium oxide is grown down into the surface and out from the surface by equal amounts. Therefore, anodizing will increase the part dimensions on each surface by half the oxide thickness. For example, a coating that is 2 μm thick will increase the part dimensions by 1 μm per surface. If the part is anodized on all sides, then all linear dimensions will increase by the oxide thickness. Anodized aluminium surfaces are harder than aluminium but have low to moderate wear resistance, although this can be improved with thickness and sealing. | 1 | Applied and Interdisciplinary Chemistry |
Collision theory is a principle of chemistry used to predict the rates of chemical reactions. It states that when suitable particles of the reactant hit each other with the correct orientation, only a certain amount of collisions result in a perceptible or notable change; these successful changes are called successful collisions. The successful collisions must have enough energy, also known as activation energy, at the moment of impact to break the pre-existing bonds and form all new bonds. This results in the products of the reaction. The activation energy is often predicted using the Transition state theory. Increasing the concentration of the reactant brings about more collisions and hence more successful collisions. Increasing the temperature increases the average kinetic energy of the molecules in a solution, increasing the number of collisions that have enough energy. Collision theory was proposed independently by Max Trautz in 1916 and William Lewis in 1918.
When a catalyst is involved in the collision between the reactant molecules, less energy is required for the chemical change to take place, and hence more collisions have sufficient energy for the reaction to occur. The reaction rate therefore increases.
Collision theory is closely related to chemical kinetics.
Collision theory was initially developed for the gas reaction system with no dilution. But most reactions involve solutions, for example, gas reactions in a carrying inert gas, and almost all reactions in solutions. The collision frequency of the solute molecules in these solutions is now controlled by diffusion or Brownian motion of individual molecules. The flux of the diffusive molecules follows Ficks laws of diffusion. For particles in a solution, an example model to calculate the collision frequency and associated coagulation rate is the Smoluchowski coagulation equation proposed by Marian Smoluchowski in a seminal 1916 publication. In this model, Ficks flux at the infinite time limit is used to mimic the particle speed of the collision theory. Jixin Chen proposed a finite-time solution to the diffusion flux in 2022 which significantly changes the estimated collision frequency of two particles in a solution. | 0 | Theoretical and Fundamental Chemistry |
Based on the sequencing approach used, the 5’ and 3’ adaptor sequences used to tag the cDNA library can be altered as needed. Previously, dual adapter-tagged cDNA libraries have been characterized using Illumina NGS. Low-cycle PCR can also be used to index universal adaptor cDNA libraries following the RT reaction. Alternatively, full-length adaptor sequences of choice can be included in the 5’ and 3’ adaptors used in the initial RT reaction. | 1 | Applied and Interdisciplinary Chemistry |
Biological sequestration of carbon causes enrichment of carbon-12, so that substances that originate from living organisms have a higher carbon-12 content. Due to the kinetic isotope effect, chemical reactions can happen faster with lighter isotopes, so that photosynthesis fixes lighter carbon-12 faster than carbon-13. Also lighter isotopes diffuse across a biological membrane faster. Enrichment in carbon 13 is measured by delta C(o/oo) = [(C/C)sample/(C/C)standard - 1] * 1000.
The common standard for carbon is Cretaceous Peedee formation belemnite. | 0 | Theoretical and Fundamental Chemistry |
The Department of Pharmacology at the University College London, the first of its kind in England, was founded in 1905 and remained in existence until 2007. | 1 | Applied and Interdisciplinary Chemistry |
MIKE 21 is a computer program that simulates flows, waves, sediments and ecology in rivers, lakes, estuaries, bays, coastal areas and seas in two dimensions. It was developed by DHI. | 1 | Applied and Interdisciplinary Chemistry |
Some aldehydes are substrates for aldehyde dehydrogenase enzymes which metabolize aldehydes in the body. There are toxicities associated with some aldehydes that are related to neurodegenerative disease, heart disease, and some types of cancer. | 0 | Theoretical and Fundamental Chemistry |
Pseudoephedrine (PSE) is a sympathomimetic drug of the phenethylamine and amphetamine chemical classes. It may be used as a nasal/sinus decongestant, as a stimulant, or as a wakefulness-promoting agent in higher doses.
It was first characterized in 1889 by the German chemists Ladenburg and Oelschlägel, who used a sample that had been isolated from Ephedra vulgaris by the Merck pharmaceutical corporation of Darmstadt, Germany. The salts pseudoephedrine hydrochloride and pseudoephedrine sulfate are found in over-the-counter preparations, either as a single ingredient or (more commonly) in a fixed-dose combination with one or more additional active ingredients such as antihistamines, guaifenesin, dextromethorphan, paracetamol (acetaminophen), or an NSAID (such as aspirin or ibuprofen). | 0 | Theoretical and Fundamental Chemistry |
Except for some refinements, little has changed since Jacksons 1957 assessment of the feasibility of muon-catalyzed fusion other than Vesmans 1967 prediction of the hyperfine resonant formation of the muonic (d–μ–t) molecular ion which was subsequently experimentally observed. This helped spark renewed interest in the whole field of muon-catalyzed fusion, which remains an active area of research worldwide. However, as Jackson observed in his paper, muon-catalyzed fusion is "unlikely" to provide "useful power production ... unless an energetically cheaper way of producing μ-mesons can be found."
One practical problem with the muon-catalyzed fusion process is that muons are unstable, decaying in (in their rest frame). Hence, there needs to be some cheap means of producing muons, and the muons must be arranged to catalyze as many nuclear fusion reactions as possible before decaying.
Another, and in many ways more serious, problem is the "alpha-sticking" problem, which was recognized by Jackson in his 1957 paper. The α-sticking problem is the approximately 1% probability of the muon "sticking" to the alpha particle that results from deuteron-triton nuclear fusion, thereby effectively removing the muon from the muon-catalysis process altogether. Even if muons were absolutely stable, each muon could catalyze, on average, only about 100 d-t fusions before sticking to an alpha particle, which is only about one-fifth the number of muon catalyzed d–t fusions needed for break-even, where as much thermal energy is generated as electrical energy is consumed to produce the muons in the first place, according to Jackson's rough estimate.
More recent measurements seem to point to more encouraging values for the α-sticking probability, finding the α-sticking probability to be around 0.3% to 0.5%, which could mean as many as about 200 (even up to 350) muon-catalyzed d–t fusions per muon. Indeed, the team led by Steven E. Jones achieved 150 d–t fusions per muon (average) at the Los Alamos Meson Physics Facility. The results were promising and almost enough to reach theoretical break-even. Unfortunately, these measurements for the number of muon-catalyzed d–t fusions per muon are still not enough to reach industrial break-even. Even with break-even, the conversion efficiency from thermal energy to electrical energy is only about 40% or so, further limiting viability. The best recent estimates of the electrical "energy cost" per muon is about with accelerators that are (coincidentally) about 40% efficient at transforming electrical energy from the power grid into acceleration of the deuterons.
As of 2012, no practical method of producing energy through this means has been published, although some discoveries using the Hall effect show promise. | 0 | Theoretical and Fundamental Chemistry |
Recent research suggests that patients with elevated basal levels of CRP are at an increased risk of diabetes, hypertension and cardiovascular disease. A study of over 700 nurses showed that those in the highest quartile of trans fat consumption had blood levels of CRP that were 73% higher than those in the lowest quartile. Although one group of researchers indicated that CRP may be only a moderate risk factor for cardiovascular disease, this study (known as the Reykjavik Study) was found to have some problems for this type of analysis related to the characteristics of the population studied, and there was an extremely long follow-up time, which may have attenuated the association between CRP and future outcomes. Others have shown that CRP can exacerbate ischemic necrosis in a complement-dependent fashion and that CRP inhibition can be a safe and effective therapy for myocardial and cerebral infarcts; this has been demonstrated in animal models and humans.
It has been hypothesized that patients with high CRP levels might benefit from use of statins. This is based on the JUPITER trial that found that elevated CRP levels without hyperlipidemia benefited. Statins were selected because they have been proven to reduce levels of CRP. Studies comparing effect of various statins in hs-CRP revealed similar effects of different statins. A subsequent trial however failed to find that CRP was useful for determining statin benefit.
In a meta-analysis of 20 studies involving 1,466 patients with coronary artery disease, CRP levels were found to be reduced after exercise interventions. Among those studies, higher CRP concentrations or poorer lipid profiles before beginning exercise were associated with greater reductions in CRP.
To clarify whether CRP is a bystander or active participant in atherogenesis, a 2008 study compared people with various genetic CRP variants. Those with a high CRP due to genetic variation had no increased risk of cardiovascular disease compared to those with a normal or low CRP. A study published in 2011 shows that CRP is associated with lipid responses to low-fat and high-polyunsaturated fat diets. | 1 | Applied and Interdisciplinary Chemistry |
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