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Coal comes in four main types or ranks: lignite or brown coal, bituminous coal or black coal, anthracite and graphite. Each type of coal has a certain set of physical parameters which are mostly controlled by moisture, volatile content (in terms of aliphatic or aromatic hydrocarbons) and carbon content. | 0 | Theoretical and Fundamental Chemistry |
There are a number of effects which control spectral line shape. A spectral line extends over a tiny spectral band with a nonzero range of frequencies, not a single frequency (i.e., a nonzero spectral width). In addition, its center may be shifted from its nominal central wavelength. There are several reasons for this broadening and shift. These reasons may be divided into two general categories – broadening due to local conditions and broadening due to extended conditions. Broadening due to local conditions is due to effects which hold in a small region around the emitting element, usually small enough to assure local thermodynamic equilibrium. Broadening due to extended conditions may result from changes to the spectral distribution of the radiation as it traverses its path to the observer. It also may result from the combining of radiation from a number of regions which are far from each other. | 0 | Theoretical and Fundamental Chemistry |
Bromophenol blue (3′,3″,5′,5″-tetrabromophenolsulfonphthalein, BPB), albutest is used as a pH indicator, an electrophoretic color marker, and a dye. It can be prepared by slowly adding excess bromine to a hot solution of phenolsulfonphthalein in glacial acetic acid. | 0 | Theoretical and Fundamental Chemistry |
In pharmacology, is often written as , where is the ligand, equivalent to L, and is the receptor. can be expressed in terms of the total amount of receptor and ligand-bound receptor concentrations: . is equal to the ratio of the dissociation rate of the ligand-receptor complex to its association rate (). Kd is the equilibrium constant for dissociation. is defined so that , this is also known as the microscopic dissociation constant and is the ligand concentration occupying half of the binding sites. In recent literature, this constant is sometimes referred to as . | 1 | Applied and Interdisciplinary Chemistry |
Organic photochemical reactions are explained in the context of the relevant excited states.
Parallel to the structural studies described above, the role of spin multiplicity – singlet vs triplet – on reactivity was evaluated. The importance of triplet excited species was emphasized. Triplets tend to be longer-lived than singlets and of lower energy than the singlet of the same configuration. Triplets may arise from (A) conversion of the initially formed singlets or by (B) interaction with a higher energy triplet (sensitization).
It is possible to quench triplet reactions.
Common organic photochemical reactions include: Norrish Type I, the Norrish Type II, the racemization of optically active biphenyls, the type A cyclohexadienone rearrangement, the type B cyclohexenone rearrangement, the di--methane rearrangement, the type B bicyclo[3.1.0]hexanone rearrangement to phenols, photochemical electrocyclic processes, the rearrangement of epoxyketones to beta-diketones, ring opening of cyclopropyl ketones, heterolysis of 3,5-dimethoxylbenzylic derivatives, and photochemical cyclizations of dienes. | 0 | Theoretical and Fundamental Chemistry |
Romanian surgeon Nicolae Racoviceanu-Pitești (1860–1942) was the first to use opioids for intrathecal analgesia; he presented his experience in Paris in 1901.
In 1921, Spanish military surgeon Fidel Pagés (18861923) developed the modern technique of lumbar epidural anesthesia, which was popularized in the 1930s by Italian surgery professor (18971966). Dogliotti is known for describing a "loss-of-resistance" technique, involving constant application of pressure to the plunger of a syringe to identify the epidural space whilst advancing the Tuohy needle – a technique sometimes referred to as Dogliotti's principle. Eugen Bogdan Aburel (18991975) was a Romanian surgeon and obstetrician who in 1931 was the first to describe blocking the lumbar plexus during early labor, followed by a caudal epidural injection for the expulsion phase.
Beginning in October 1941, Robert Andrew Hingson (19131996), Waldo B. Edwards and James L. Southworth, working at the United States Marine Hospital at Stapleton, on Staten Island in New York, developed the technique of continuous caudal anesthesia. Hingson and Southworth first used this technique in an operation to remove the varicose veins of a Scottish merchant seaman. Rather than removing the caudal needle after the injection as was customary, the two surgeons experimented with a continuous caudal infusion of local anesthetic. Hingson then collaborated with Edwards, the chief obstetrician at the Marine Hospital, to study the use of continuous caudal anesthesia for analgesia during childbirth. Hingson and Edwards studied the caudal region to determine where a needle could be placed to deliver anesthetic agents safely to the spinal nerves without injecting them into the cerebrospinal fluid.
The first use of continuous caudal anesthesia in a laboring woman was on January 6, 1942, when the wife of a United States Coast Guard sailor was brought into the Marine Hospital for an emergency Caesarean section. Because the woman had rheumatic heart disease (heart failure following an episode of rheumatic fever during childhood), her doctors believed that she would not survive the stress of labor but they also felt that she would not tolerate general anesthesia due to her heart failure. With the use of continuous caudal anesthesia, the woman and her baby survived.
The first described placement of a lumbar epidural catheter was performed by Manuel Martínez Curbelo (5 June 19061 May 1962) on January 13, 1947. Curbelo, a Cuban anesthesiologist, introduced a 16 gauge Tuohy needle into the left flank of a 40-year-old woman with a large ovarian cyst. Through this needle, he introduced a 3.5 French ureteral catheter made of elastic silk into the lumbar epidural space. He then removed the needle, leaving the catheter in place and repeatedly injected 0.5% percaine (cinchocaine, also known as dibucaine) to achieve anesthesia. Curbelo presented his work on September 9, 1947, at the 22nd Joint Congress of the International Anesthesia Research Society and the International College of Anesthetists, in New York City. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, Rayleigh's equation or Rayleigh stability equation is a linear ordinary differential equation to study the hydrodynamic stability of a parallel, incompressible and inviscid shear flow. The equation is:
with the flow velocity of the steady base flow whose stability is to be studied and is the cross-stream direction (i.e. perpendicular to the flow direction). Further is the complex valued amplitude of the infinitesimal streamfunction perturbations applied to the base flow, is the wavenumber of the perturbations and is the phase speed with which the perturbations propagate in the flow direction. The prime denotes differentiation with respect to | 1 | Applied and Interdisciplinary Chemistry |
In many engineering applications the local flow velocity vector field is not known in every point and the only accessible velocity is the bulk velocity or average flow velocity (with the usual dimension of length per time), defined as the quotient between the volume flow rate (with dimension of cubed length per time) and the cross sectional area (with dimension of square length): | 1 | Applied and Interdisciplinary Chemistry |
PI-3K is one of the important components in the regulation of the insulin signaling pathway. It maintains the insulin sensitivity in the liver. PI-3K is composed of a regulatory subunit (P85) and a catalytic subunit (P110). P85 regulates the activation of PI-3K enzyme. In the PI-3K heterodimer (P85-p110), P85 is responsible for the PI-3K activity, by binding to the binding site on the insulin receptor substrates (IRS). It was noted that an increase of P85 a (isoform of P85) results in a competition between the later and the P85-P110 complex to the IRS binding site, reducing the PI-3k activity and leading to insulin resistance. Insulin resistance refers also to Type 2 diabetes.
It was also noted that increased serine phosphorylation of IRS is involved in the insulin resistance by reducing their ability to attract PI3K. The serine phosphorylation can also lead to degradation of IRS-1. | 1 | Applied and Interdisciplinary Chemistry |
The Henderson–Hasselbalch equation, when applied to the carbonic acid-bicarbonate buffer system in the extracellular fluids, states that:
where:
* is the negative logarithm (or cologarithm) of molar concentration of hydrogen ions in the extracellular fluid.
* is the cologarithm of the acid dissociation constant of carbonic acid. It is equal to 6.1.
* is the molar concentration of bicarbonate in the blood plasma.
* is the molar concentration of carbonic acid in the extracellular fluid.
However, since the carbonic acid concentration is directly proportional to the partial pressure of carbon dioxide () in the extracellular fluid, the equation can be rewritten as follows:
where:
* is the negative logarithm of molar concentration of hydrogen ions in the extracellular fluid.
* is the molar concentration of bicarbonate in the plasma.
* is the partial pressure of carbon dioxide in the blood plasma.
The pH of the extracellular fluids can thus be controlled by the regulation of and the other metabolic acids. | 0 | Theoretical and Fundamental Chemistry |
Ketenes were first studied as a class by Hermann Staudinger before 1905.
Ketenes were systematically investigated by Hermann Staudinger in 1905 in the form of diphenylketene (conversion of -chlorodiphenyl acetyl chloride with zinc). Staudinger was inspired by the first examples of reactive organic intermediates and stable radicals discovered by Moses Gomberg in 1900 (compounds with triphenylmethyl group). | 0 | Theoretical and Fundamental Chemistry |
Numerous chemical targets have distinct stereochemical demands. Stereochemical transformations (such as the Claisen rearrangement and Mitsunobu reaction) can remove or transfer the desired chirality thus simplifying the target. | 0 | Theoretical and Fundamental Chemistry |
The presence of humic acid in water intended for potable or industrial use can have a significant impact on the treatability of that water and the success of chemical disinfection processes. For instance, humic and fulvic acids can react with the chemicals used in the chlorination process to form disinfection byproducts such as dihaloacetonitriles, which are toxic to humans. Accurate methods of establishing humic acid concentrations are therefore essential in maintaining water supplies, especially from upland peaty catchments in temperate climates.
As a lot of different bio-organic molecules in very diverse physical associations are mixed together in natural environments, it is cumbersome to measure their exact concentrations in the humic superstructure. For this reason, concentrations of humic acid are traditionally estimated out of concentrations of organic matter, typically from concentrations of total organic carbon (TOC) or dissolved organic carbon (DOC).
Extraction procedures are bound to alter some of the chemical linkages present in the soil humic substances (mainly ester bonds in biopolyesters such as cutins and suberins). The humic extracts are composed of large numbers of different bio-organic molecules that have not yet been totally separated and identified. However, single classes of residual biomolecules have been identified by selective extractions and chemical fractionation, and are represented by alkanoic and hydroxy alkanoic acids, resins, waxes, lignin residues, sugars, and peptides. | 0 | Theoretical and Fundamental Chemistry |
The theoretical model that was first conceived for superconductivity was completely classical: it is summarized by London constitutive equations.
It was put forward by the brothers Fritz and Heinz London in 1935, shortly after the discovery that magnetic fields are expelled from superconductors. A major triumph of the equations of this theory is their ability to explain the Meissner effect, wherein a material exponentially expels all internal magnetic fields as it crosses the superconducting threshold. By using the London equation, one can obtain the dependence of the magnetic field inside the superconductor on the distance to the surface.
The two constitutive equations for a superconductor by London are:
The first equation follows from Newton's second law for superconducting electrons. | 0 | Theoretical and Fundamental Chemistry |
Hemorphin-4 is an endogenous opioid peptide of the hemorphin family which possesses antinociceptive properties and is derived from the β-chain of hemoglobin in the bloodstream. It is a tetrapeptide with the amino acid sequence Tyr-Pro-Trp-Thr. Hemorphin-4 has affinities for the μ-, δ-, and κ-opioid receptors that are in the same range as the structurally related β-casomorphins, although affinity to the κ-opioid receptor is markedly higher in comparison. It acts as an agonist at these sites. Hemorphin-4 also has inhibitory effects on angiotensin-converting enzyme (ACE), and as a result, may play a role in the regulation of blood pressure. Notably, inhibition of ACE also reduces enkephalin catabolism. | 1 | Applied and Interdisciplinary Chemistry |
The pH of a solution containing a buffering agent can only vary within a narrow range, regardless of what else may be present in the solution. In biological systems this is an essential condition for enzymes to function correctly. For example, in human blood a mixture of carbonic acid (HCO) and bicarbonate (HCO) is present in the plasma fraction; this constitutes the major mechanism for maintaining the pH of blood between 7.35 and 7.45. Outside this narrow range (7.40 ± 0.05 pH unit), acidosis and alkalosis metabolic conditions rapidly develop, ultimately leading to death if the correct buffering capacity is not rapidly restored.
If the pH value of a solution rises or falls too much, the effectiveness of an enzyme decreases in a process, known as denaturation, which is usually irreversible. The majority of biological samples that are used in research are kept in a buffer solution, often phosphate buffered saline (PBS) at pH 7.4.
In industry, buffering agents are used in fermentation processes and in setting the correct conditions for dyes used in colouring fabrics. They are also used in chemical analysis and calibration of pH meters. | 0 | Theoretical and Fundamental Chemistry |
Zenobi-Wong works in the area of tissue engineering, in particular for cartilage regeneration. She develops functional biomaterials which mimic the extracellular matrix. The biofabrication techniques used to develop these materials include electrospinning, casting, two-photon polymerization and bioprinting.
Zenobi-Wong holds four licensed patents in the fields of tissue engineering, tissue engineering techniques, and gene expression assays. She was one of the originators of the MSc Biomedical Engineering program at ETH Zürich, and developed several graduate level courses in tissue engineering and biomedical engineering. Zenobi-Wong currently serves as President of the Swiss Society for Biomaterials and Regenerative Medicine, and as secretary general of the International Society of Biofabrication. | 1 | Applied and Interdisciplinary Chemistry |
Wallach's rule (first proposed by Otto Wallach) states that racemic crystals tend to be denser than their chiral counterparts. This rule has been substantiated by crystallographic database analysis. | 0 | Theoretical and Fundamental Chemistry |
In 2009 the Chesapeake Bay Foundation (CBF) filed suit against EPA for its failure to finalize a total maximum daily load (TMDL) ruling for the bay, pursuant to the Clean Water Act. The TMDL would restrict water pollution from farms, land development, power plants and sewage treatment plants. EPA, which had been working with the states on various components of the TMDL since the 1980s (e.g. water quality criteria, standards for individual tributaries, improvements in data gathering and modeling techniques), agreed to settle the lawsuit and issued its TMDL for nitrogen, phosphorus and sediment pollution on December 29, 2010. This was the largest, most complex TMDL document that EPA had issued to date. The TMDL was challenged in litigation by the agriculture and construction industries, but EPA's document was upheld by the courts.
In 2020 the CBF filed another lawsuit against EPA for its failure to require the states of New York and Pennsylvania to comply with their TMDL goals and reduce pollution in the bay.
EPAs 2010 TMDL document requires all states in the bay watershed region to develop detailed implementation plans for pollutant reduction. The states have been developing their plans for years, in many cases building upon restoration projects that they had initiated before EPAs TMDL was finalized. These plans are long and complex, involving regular consultation with many stakeholders (i.e. governments, industry, agriculture, citizen groups). The plans include multiple milestone goals for project initiation or continued progress in water quality, through the use of pollution control upgrades (such as at sewage treatment plants) and more widespread utilization of various best management practices (BMPs). The BMPs are designed for specific sites to control pollution from nonpoint sources, principally agriculture, land development and urban runoff. For example, a farmer may install vegetated stream buffers along a stream bank to reduce runoff of sediment, nutrients and other pollutants. A land developer may install stormwater management facilities such as infiltration basins or constructed wetlands during the construction of housing or commercial buildings.
In 2011 both Maryland and Virginia enacted laws to reduce the effects of lawn fertilizer use, by restricting nitrogen and phosphorus content. The Virginia law also banned deicers containing urea, nitrogen or phosphorus.
Installation of stormwater management facilities is already a requirement for most new construction projects in the bay region, under various state and local government requirements. These facilities reduce erosion and keep sediment and other pollutants from entering tributaries and the bay. However retrofitting such facilities into existing developed areas is often expensive due to high land costs, or difficult to install among existing structures. As a result, the extent of such retrofit projects in the bay region has been limited. | 1 | Applied and Interdisciplinary Chemistry |
The excess volume is another important property in the characterization of grain boundaries. Excess volume was first proposed by Bishop in a private communication to Aaron and Bolling in 1972. It describes how much expansion is induced by the presence of a GB and is thought that the degree and susceptibility of segregation is directly proportional to this. Despite the name the excess volume is actually a change in length, this is because of the 2D nature of GBs the length of interest is the expansion normal to the GB plane. The excess volume () is defined in the following way,
at constant temperature , pressure and number of atoms . Although a rough linear relationship between GB energy and excess volume exists the orientations where this relationship is violated can behave significantly differently affecting mechanical and electrical properties.
Experimental techniques have been developed which directly probe the excess volume and have been used to explore the properties of nanocrystalline copper and nickel. Theoretical methods have also been developed and are in good agreement. A key observation is that there is an inverse relationship with the bulk modulus meaning that the larger the bulk modulus (the ability to compress a material) the smaller the excess volume will be, there is also direct relationship with the lattice constant, this provides methodology to find materials with a desirable excess volume for a specific application. | 1 | Applied and Interdisciplinary Chemistry |
The notion of isomer also appears in other fields such as chemistry and meteorology. Therefore, in the first publications devoted to this effect the name nuclear isomeric shift on spectral lines was used. Before the discovery of the Mössbauer effect, the isomeric shift referred exclusively to atomic spectra; this explains the absence of the word atomic in the initial definition of the effect. Subsequently, the isomeric shift was also observed in gamma spectroscopy through the Mössbauer effect and was called Mössbauer isomeric shift. For further details on the history of the isomeric shift and the terminology used, see. | 0 | Theoretical and Fundamental Chemistry |
Canada is one of the largest owners of fresh water and has for years been engaged in a legal dispute over its possession of the resource. In 1990 an American company named Sunbelt was invited by the government of British Columbia to invest in a water exporting operation. Due to setbacks, the contract never matured and Sunbelt sued the government of British Columbia for failing to meet its obligations. After years of battle the Canadian government declared in 1999 that water in its fresh state as those found in rivers and lakes contains no economic value, and is therefore outside the obligations of its trade agreement. In addition, the government cited article XI of GATT (G). This article allows for the conservation of a natural resource as long as the action taken by the government is done in a non-discriminatory manner. Sunbelt however, disagreed with the applicability of this clause and claimed that Canada’s actions are in direct violation of several international trade agreements. Particularly, Sunbelt addressed Article XI of GATT which forbids a member nation from imposing measures other than taxes, levies and other charges on the export of its good. Likewise, Sunbelt argued that the water located in British Columbia belonged to US companies just as much as it belongs to Canadian companies. This argument is based on Article 11 of NAFTA known as the investment chapter. Once water is extracted from its natural state for whatever reason that same right must be given to foreign investors. Sunbelt argues that Canadian companies had such extractions in the past and therefore opened the door for foreign investors to come in and do likewise. | 1 | Applied and Interdisciplinary Chemistry |
Early examples of different solutions to alleviate rotating stall in the front stages include the Rolls-Royce Avon with variable inlet guide vanes and interstage bleed, the General Electric J79 with variable inlet guide vanes and variable stators, the Bristol Olympus with split compressor and the Pratt & Whitney J57 with split compressor and intercompressor bleed. Compressor bleed up to this point had been only necessary for starting and accelerating beyond low corrected speeds where its loss to thrust production, from dumping overboard, was not important.
A further development was permanent compressor bleed routed back into the engine where it contributed to thrust. The Rolls-Royce Conway had a split compressor with intercompressor bleed to the jetpipe. A split compressor with this bypass arrangement allowed the highest pressure ratio of any Rolls-Royce engine, at that time, without the need for variable inlet guide vanes or interstage bleed. It was better known as an arrangement for better propulsive efficiency, a bypass engine. The Pratt & Whitney J58 used interstage overboard bleed for starting and accelerating through low corrected speeds but since it returned to these speeds at high mach numbers the bleed was opened again but this time routed to the jetpipe where it cooled the afterburner and nozzle. This cooling contributed indirectly to thrust in allowing more fuel to be burned in the afterburner. A similar arrangement, but using a split compressor with intercompressor bleed to the jetpipe, was later known as a leaky turbojet, a bypass engine with only enough bypass for cooling the afterburner and nozzle. | 0 | Theoretical and Fundamental Chemistry |
If enough mass is used it can create a seasonal advantage. That is, it can heat in the winter and cool in the summer. This is sometimes called passive annual heat storage or PAHS. The PAHS system has been successfully used at 7000 ft. in Colorado and in a number of homes in Montana. The Earthships of New Mexico utilize passive heating and cooling as well as using recycled tires for foundation wall yielding a maximum PAHS/STES. It has also been used successfully in the UK at Hockerton Housing Project. | 0 | Theoretical and Fundamental Chemistry |
Polymerase chain reaction (PCR) is an extremely versatile technique for copying DNA. In brief, PCR allows a specific DNA sequence to be copied or modified in predetermined ways. The reaction is extremely powerful and under perfect conditions could amplify one DNA molecule to become 1.07 billion molecules in less than two hours. PCR has many applications, including the study of gene expression, the detection of pathogenic microorganisms, the detection of genetic mutations, and the introduction of mutations to DNA. The PCR technique can be used to introduce restriction enzyme sites to ends of DNA molecules, or to mutate particular bases of DNA, the latter is a method referred to as site-directed mutagenesis. PCR can also be used to determine whether a particular DNA fragment is found in a cDNA library. PCR has many variations, like reverse transcription PCR (RT-PCR) for amplification of RNA, and, more recently, quantitative PCR which allow for quantitative measurement of DNA or RNA molecules. | 1 | Applied and Interdisciplinary Chemistry |
Cyclamin has not been thoroughly investigated in terms of its effects on animals, given it is not a widely known compound. However, the effects of Cyclamin on the snail Biomphalaria glabrata (Say) in terms of molluscicidal activity were researched. The lowest concentration showing 100% mortality to snails was 21 mg/l. Beside cyclamin its effect on these snails, no further data is known about its effect on animals. | 0 | Theoretical and Fundamental Chemistry |
Dispersive soils are more common in older landscapes where leaching and illuviation processes have had more time to work. A source of sodium is also required. Possible sources can include weathering from soil parent materials or wind-blown salt deposition. Sodium ions are highly mobile in the soil solution and so they accumulate in the lower parts of the landscape.
The dispersive portion of a soil profile is generally confined to the subsoil, where soil-forming processes concentrate clay minerals and sodium. This means that dispersive soils may not be identified until they are disturbed in a way that exposes the subsoil to running water.
When observed in situ, dispersive soil textures may feel soapy, and in many cases the physical structure of subsoil layers will be prismatic or columnar. A simplified version of the Emerson soil dispersion test can be completed in the field on a 20-minute to two-hour timescale.
Laboratory tests used to diagnose a soil as dispersive focus on the cation exchange capacity of a soil sample and its cation breakdown. Soil cations are dominated by Ca, Mg, K, and Na, as well as H in acidic soils. The exchangeable sodium percentage ( "ESP", (sodium / (total cations)) * 100 ) is a key indicator derived from these measurements. Where ESP exceeds 5%, dispersive behaviour becomes possible, and is highly likely where ESP exceeds 15%. | 0 | Theoretical and Fundamental Chemistry |
Binding sites can be characterized also by their structural features. Single-chain sites (of “monodesmic” ligands, μόνος: single, δεσμός: binding) are formed by a single protein chain, while multi-chain sites (of "polydesmic” ligands, πολοί: many) are frequent in protein complexes, and are formed by ligands that bind more than one protein chain, typically in or near protein interfaces. Recent research shows that binding site structure has profound consequences for the biology of protein complexes (evolution of function, allostery). | 1 | Applied and Interdisciplinary Chemistry |
From left to right the peaks are due to Po, Pu, Po and Am. The fact that isotopes such as Pu and Am have more than one alpha line indicates that the (daughter) nucleus can be in different discrete energy levels.
Calibration:
MCA does not work on energy, it works on voltage. To relate the energy to voltage one must calibrate the detection system. Here different alpha emitting sources of known energy were placed under the detector and the full energy peak is recorded.
Measurement of thickness of thin foils:
Energies of alpha particles from radioactive sources are measured before and after passing through the thin films. By measuring difference and using SRIM we can measure the thickness of thin foils. | 0 | Theoretical and Fundamental Chemistry |
Unlike crystalline materials which exhibit strong Bragg diffraction, the diffraction patterns of amorphous materials are characterized by broad and diffuse peaks. As a result, detailed analysis and complementary techniques are required to extract real space structural information from the diffraction patterns of amorphous materials. It is useful to obtain diffraction data from both X-ray and neutron sources as they have different scattering properties and provide complementary data. Pair distribution function analysis can be performed on diffraction data to determine the probability of finding a pair of atoms separated by a certain distance. Another type of analysis that is done with diffraction data of amorphous materials is radial distribution function analysis, which measures the number of atoms found at varying radial distances away from an arbitrary reference atom. From these techniques, the local order of an amorphous material can be elucidated. | 0 | Theoretical and Fundamental Chemistry |
During the rule of Peter I the Great, Fedor I. Soimonov was a pioneering explorer of the sea. He was a hydrographer who charted and greatly expanded knowledge of the sea. He drew a set of four maps and wrote Pilot of the Caspian Sea, the first lengthy report and modern maps. These were published in 1720 by the Russian Academy of Sciences. | 1 | Applied and Interdisciplinary Chemistry |
They were the first set of nonsense mutations to be discovered, isolated by Richard H. Epstein and Charles Steinberg and named after their friend and graduate Caltech student Harris Bernstein, whose last name means "amber" in German (cf. Bernstein).
Viruses with amber mutations are characterized by their ability to infect only certain strains of bacteria, known as amber suppressors. These bacteria carry their own mutation that allows a recovery of function in the mutant viruses. For example, a mutation in the tRNA that recognizes the amber stop codon allows translation to "read through" the codon and produce a full-length protein, thereby recovering the normal form of the protein and "suppressing" the amber mutation.
Thus, amber mutants are an entire class of virus mutants that can grow in bacteria that contain amber suppressor mutations. Similar suppressors are known for ochre and opal stop codons as well.
tRNA molecules carrying unnatural aminoacids have been designed to recognize the amber stop codon in bacterial RNA. This technology allows for incorporation of orthogonal aminoacids (such as p-azidophenylalanine) at specific locations of the target protein. | 1 | Applied and Interdisciplinary Chemistry |
ASO analysis is only one of the methods used to detect genetic polymorphisms. Direct DNA sequencing is used to initially characterize the mutation, but is too laborious for routine screening. An earlier method, Restriction Fragment Length Polymorphism (RFLP) didn't need to know the sequence change beforehand, but required that the mutation affect the cleavage site of a Restriction Enzyme. The RFLP assay was briefly adapted to the use of oligonucleotide probes, but this technique was quickly supplanted by ASO analysis of polymerase chain reaction (PCR) amplified DNA. The PCR technique itself has been adapted to detect polymorphisms, as allele-specific PCR. However, the simplicity and versatility of the combined PCR/ASO method has led to its continued use, including with non-radioactive labels, and in a "reverse dot blot" format where the ASO probes are bound to the membrane and the amplified sample DNA is used for hybridization. | 1 | Applied and Interdisciplinary Chemistry |
In October 1885, it was announced that the authorities were in favour of the creation of an institute of chemistry in Nancy. This pulled together a variety of chemical activities in the University of Nancy, with the specific aim of instructing young men in the practical application of chemistry to industry and agriculture. The decree authorizing the creation of the Institute was made on 8 September 1887 and construction began in 1888. The first 6 students joined in 1889 and Albin Haller was appointed as director on 30 July 1890. on 6 June 1892 it was formally inaugurated by the President of the Republic, Marie François Sadi Carnot. | 1 | Applied and Interdisciplinary Chemistry |
Artemether was more promising for clinical drug than its parent molecule artemisinin. In 1981, the National Steering Committee for Development of Qinghaosu (artemisinin) and its Derivatives authorised Zhou Yiqing, who was working at the Institute of Microbiology and Epidemiology of the Chinese Academy of Military Medical Sciences, to work on artemether. Zhou showed that artemether combined with another antimalarial lumefantrine was the most potent of all antimalarial drugs. He worked alone for four years, and Ning Dianxi and his team joined Zhou in 1985. They found that in clinical trials the combined tablet had cure rate of severe malaria of more than 95%, including in areas where multi-drug resistance is experienced. They applied for patent in 1991 but received it only in 2002. In 1992, they registered it as a new drug in China. Noticing this, Novartis signed a pact for mass production. In 1999, Novartis obtained the international licensing rights and gave the brand name Coartem. The US Food and Drug Administration approved the drug in 2009. | 1 | Applied and Interdisciplinary Chemistry |
Apoptosis triggered by FasR-Fas ligand binding plays a fundamental role in the regulation of the immune system. Its functions include:
*T-cell homeostasis: the activation of T-cells leads to their expression of the Fas ligand. T cells are initially resistant to Fas-mediated apoptosis during clonal expansion, but become progressively more sensitive the longer they are activated, ultimately resulting in activation-induced cell death (AICD). This process is needed to prevent an excessive immune response and eliminate autoreactive T-cells. Humans and mice with deleterious mutations of Fas or Fas ligand develop an accumulation of aberrant T-cells, leading to lymphadenopathy, splenomegaly, and lupus erythematosus.
*Cytotoxic T-cell activity: Fas-induced apoptosis and the perforin pathway are the two main mechanisms by which cytotoxic T lymphocytes induce cell death in cells expressing foreign antigens.
*Immune privilege: Cells in immune privileged areas such as the cornea or testes express Fas ligand and induce the apoptosis of infiltrating lymphocytes. It is one of many mechanisms the body employs in the establishment and maintenance of immune privilege.
*Maternal tolerance: Fas ligand may be instrumental in the prevention of leukocyte trafficking between the mother and the fetus, although no pregnancy defects have yet been attributed to a faulty Fas-Fas ligand system.
*Tumor counterattack: Tumors may over-express Fas ligand and induce the apoptosis of infiltrating lymphocytes, allowing the tumor to escape the effects of an immune response. The up-regulation of Fas ligand often occurs following chemotherapy, from which the tumor cells have attained apoptosis resistance. | 1 | Applied and Interdisciplinary Chemistry |
Many reaction exists which make use of an intermediate nitroso compound, such as the Barton reaction and Davis–Beirut reaction, as well as in the synthesis of indoles, for example: Baeyer–Emmerling indole synthesis, Bartoli indole synthesis. In the Saville reaction, mercury is used to replace a nitrosyl from a thiol group.
C-nitroso compounds are used in organic synthesis as synthons in some well-documented chemical reactions such as hetero Diels-Alder (HDA), nitroso-ene and nitroso-aldol reactions. | 0 | Theoretical and Fundamental Chemistry |
Paz-Pujalt was born August 9, 1954, in Arequipa, Peru. He is of Galician and Welsh descent on his fathers side and Catalan and Basque on his mothers. He graduated from San Andrés (Colegio), an Anglo Peruvian college preparatory school in Lima, Peru. He graduated with honors and received the Miller Prize for accomplishments in English. Paz-Pujalt did his undergraduate work at the University of Wisconsin-Eau Claire and completed his Ph.D. in physical chemistry at the University of Wisconsin–Milwaukee. His doctoral adviser was George Keulks. He was also mentored by the distinguished professor W. Keith Hall. During this time he studied surface science under Gert Ertl, winner of the Nobel Prize in Chemistry. Additionally, Paz-Pujalt has received numerous executive level diplomas from MIT and Wharton. | 0 | Theoretical and Fundamental Chemistry |
This describes the preparation of what Agricola calls "juices": salt, soda, nitre, alum, vitriol, saltpetre, sulphur and bitumen. Finally glass making is covered. Agricola seems less secure about this process. He is not clear about making glass from the raw ingredients but clearer about remelting glass to make objects.
Prof. Philippus Bechius (1521–1560), a friend of Agricola, translated De re metallica libri XII into German. It was published with the German title Vom Bergkwerck XII Bücher in 1557. The Hoovers describe the translation as "a wretched work, by one who knew nothing of the science," but it, like the Latin original, saw further editions. In 1563 Agricola's publisher, Froben and Bischoff ("Hieronimo Frobenio et Nicolao Episcopio") in Basel, published an Italian translation by Michelangelo Florio as well. | 1 | Applied and Interdisciplinary Chemistry |
The main source of atmospheric free oxygen is photosynthesis, which produces sugars and free oxygen from carbon dioxide and water:
Photosynthesizing organisms include the plant life of the land areas, as well as the phytoplankton of the oceans. The tiny marine cyanobacterium Prochlorococcus was discovered in 1986 and accounts for up to half of the photosynthesis of the open oceans. | 0 | Theoretical and Fundamental Chemistry |
An amorphous brazing foil (ABF) is a form of eutectic amorphous metal that serves as a filler metal in brazing operations. ABFs are composed of various transition metals, including nickel, iron, and copper, blended with metalloids like silicon, boron, and phosphorus. By precisely managing the concentration of these metalloids to achieve or approach the eutectic point, these alloys can undergo rapid solidification to form a ductile, amorphous foil. This process allows the ABF to effectively bond materials in the brazing process, providing a strong and seamless joint. | 1 | Applied and Interdisciplinary Chemistry |
This reaction shows the oxidation of p-cresol in a sulfate-enriched environment. P-cresol was seen to be the easiest to degrade through the sulfate-enriched environment, while m-cresol and o-cresol where inhibited. In the chart above, p-cresol was oxidized under an anaerobic sulfate reducing condition and formed four different intermediates. After the formation of the intermediates, the study reported further degradation of the intermediates leading to the production of carbon dioxide and methane. The p-hydroxylbenzyl alcohol, p-hydroxylbenzaldehye, p-hyrdoxylbenzoate, and benzoate intermediates all are produced from this oxidation and released into the sediments. Similar results were also produced by different studies using other forms of oxidation such as: iron-reducing organisms, Copper/Manganese Oxide catalyst, and nitrate- reducing conditions. | 0 | Theoretical and Fundamental Chemistry |
He graduated from the Chinese University of Hong Kong with a B.Sc. in 1977, and obtained his Ph.D. in biochemistry and cell biology at the University of Newcastle, Australia, in 1981. He came to New York as a Population Council post-doctoral trainee in 1981, studying in the laboratory of Drs. Wayne Bardin, Neal Musto, and Glen Gunsalus and was appointed as a research investigator in December 1982.
Cheng's research focuses on the development of a novel contraceptive for human males. These studies currently are supported by grants from the National Institutes of Health, the CONRAD Program, and the Andrew Mellon Foundation. | 1 | Applied and Interdisciplinary Chemistry |
LTR retrotransposons are class I transposable element characterized by the presence of long terminal repeats (LTRs) directly flanking an internal coding region. As retrotransposons, they mobilize through reverse transcription of their mRNA and integration of the newly created cDNA into another location. Their mechanism of retrotransposition is shared with retroviruses, with the difference that most LTR-retrotransposons do not form infectious particles that leave the cells and therefore only replicate inside their genome of origin. | 1 | Applied and Interdisciplinary Chemistry |
Signal transducer and activator of transcription 1 (STAT1) is a transcription factor which in humans is encoded by the STAT1 gene. It is a member of the STAT protein family. | 1 | Applied and Interdisciplinary Chemistry |
When a pressurized gas is released, the velocity of the flow will heavily depend on the pressure difference between stagnant pressure and downstream pressure. By assuming an isentropic expansion of an ideal gas from its stagnant conditions (P , meaning the velocity of the gas is zero) to downstream conditions (P, positioned at the exit plane of the nozzle or orifice), the subsonic flow rate of the source term is given by Ramskill's formulation:
As the ratio between downstream condition pressure and stagnant condition pressure decreases, the flow rate of the ideal gas will increase. This behavior will continue until a critical value is reached (in air, P/P is roughly 0.528, dependent on the heat capacity ratio, γ), changing the condition of the jet from a non-choked flow to a choked flow. This will lead to the a newly defined expression for the aforementioned pressure ratio and, sub-sequentially, the flow rate equation.
The critical value for the pressure ratio is defined as:
This newly defined ratio can then be used to determine the flow rate for a sonic choked flow:
The flow rate equation for a choked flow will have a fixed velocity, which is the speed of sound of the medium, where the Mach number is equals to 1:
It is important to note that if P keeps on decreasing, no flow rate change will occur if the ratio is already below the critical value, unless P also changes (also assuming that the orifice/nozzle exit area and upstream temperature stay the same). | 1 | Applied and Interdisciplinary Chemistry |
When an atom or molecule interacts with an electromagnetic wave of frequency , it can undergo a transition from an initial to a final state of energy difference through the coupling of the electromagnetic field to the transition dipole moment. When this transition is from a lower energy state to a higher energy state, this results in the absorption of a photon. A transition from a higher energy state to a lower energy state results in the emission of a photon. If the charge, , is omitted from the electric dipole operator during this calculation, one obtains as used in oscillator strength. | 0 | Theoretical and Fundamental Chemistry |
Generally, oral CoQ supplementation is well tolerated. The most common side effects are gastrointestinal symptoms (nausea, vomiting, appetite suppression, and abdominal pain), rashes, and headaches. Some adverse effects, largely gastrointestinal, are reported with intakes. Doses of 100-300 mg per day may induce insomnia or elevate liver enzymes. The observed safe level risk assessment method indicated that the evidence of safety is acceptable at intakes up to 1200 mg per day.
Use of CoQ supplementation is not recommended in people with liver or kidney disease, during pregnancy or breastfeeding, or in the elderly. | 1 | Applied and Interdisciplinary Chemistry |
Tap water may be added to a paper bag which then is put on a stove to boil. The paper bag can absorb water, which cools down the system and prevents the paper bag from being burnt. | 1 | Applied and Interdisciplinary Chemistry |
In addition to treating copper concentrates, ISASMELT furnaces have also been built to treat secondary (scrap) copper materials. | 1 | Applied and Interdisciplinary Chemistry |
NRA can also be used non-resonantly (of course, RBS is non-resonant). For example, deuterium can easily be profiled with a He beam without changing the incident energy by using the
:He + D = α + p + 18.353 MeV
reaction, usually written H(He,p)α. The energy of the fast proton detected depends on the depth of the deuterium atom in the sample. | 0 | Theoretical and Fundamental Chemistry |
Photoproteins are a type of enzyme produced by bioluminescent organisms. They add to the function of the luciferins whose usual light-producing reaction is catalyzed by the enzyme luciferase. | 1 | Applied and Interdisciplinary Chemistry |
Polycyclic aromatic hydrocarbons are molecules containing two or more simple aromatic rings fused together by sharing two neighboring carbon atoms (see also simple aromatic rings). Examples are naphthalene, anthracene, and phenanthrene. | 0 | Theoretical and Fundamental Chemistry |
A thermodynamic operation is an externally imposed manipulation that affects a thermodynamic system. The change can be either in the connection or wall between a thermodynamic system and its surroundings, or in the value of some variable in the surroundings that is in contact with a wall of the system that allows transfer of the extensive quantity belonging that variable. It is assumed in thermodynamics that the operation is conducted in ignorance of any pertinent microscopic information.
A thermodynamic operation requires a contribution from an independent external agency, that does not come from the passive properties of the systems. Perhaps the first expression of the distinction between a thermodynamic operation and a thermodynamic process is in Kelvins statement of the second law of thermodynamics: "It is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the surrounding objects." A sequence of events that occurred other than "by means of inanimate material agency" would entail an action by an animate agency, or at least an independent external agency. Such an agency could impose some thermodynamic operations. For example, those operations might create a heat pump, which of course would comply with the second law. A Maxwells demon conducts an extremely idealized and naturally unrealizable kind of thermodynamic operation.
Another commonly used term that indicates a thermodynamic operation is change of constraint, for example referring to the removal of a wall between two otherwise isolated compartments.
An ordinary language expression for a thermodynamic operation is used by Edward A. Guggenheim: "tampering" with the bodies. | 0 | Theoretical and Fundamental Chemistry |
Unlike the Environmental Protection Agency (EPA), ATSDR is an advisory, nonregulatory agency. ATSDR conducts research on the health impacts of hazardous waste sites and provides information and recommendations to federal and state agencies, community members, and other interested parties. However, ATSDR is not involved in cleanup of those sites, nor can ATSDR provide or fund medical treatment for people who have been exposed to hazardous substances. | 1 | Applied and Interdisciplinary Chemistry |
Small RNA sequencing can be useful for:
* studying the expression profile of miRNA and other small RNAs
* increasing the understanding of how cells are regulated or misregulated under pathological conditions
* small RNA clustering
* novel small RNA discovery
* small RNA prediction
* differential expression of all small RNAs in any sample | 1 | Applied and Interdisciplinary Chemistry |
Olson received her bachelor's degree in chemistry at the University of Delaware in 1967, with honors and distinction. During her studies, she received the A.C.S. (Delaware Section) Student Award. Olson obtained her Ph.D. in 1971 at Stanford University, where she studied the configurational statistics of polynucleotide chains. Her advisor was polymer scientist Paul J. Flory, who would win the Nobel Prize in chemistry in 1974. | 1 | Applied and Interdisciplinary Chemistry |
Mono Lake ( ) is a saline soda lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in an endorheic basin. The lack of an outlet causes high levels of salts to accumulate in the lake which make its water alkaline.
The desert lake has an unusually productive ecosystem based on brine shrimp, which thrive in its waters, and provides critical habitat for two million annual migratory birds that feed on the shrimp and alkali flies (Ephydra hians). Historically, the native Kutzadikaa people ate the alkali flies pupae, which live in the shallow waters around the edge of the lake.
When the city of Los Angeles diverted water from the freshwater streams flowing into the lake, it lowered the lake level, which imperiled the migratory birds. The Mono Lake Committee formed in response and won a legal battle that forced Los Angeles to partially replenish the lake level. | 1 | Applied and Interdisciplinary Chemistry |
Heterochromatin in S. cerevisiae is composed of a wide array of proteins and plays several roles. The first stage of heterochromatin formation requires DNA binding proteins, which interact with specific cis DNA sequences at the telomeres, rDNA and HM loci. These proteins, including Rap1p and the origin recognition complex (ORC), serve as a platform for other proteins to bind, condense the DNA, and modify neighboring histones. Some of these proteins, notably Rap1p, also play other roles, including initiation of transcription. The first known step in the formation of dedicated heterochromatin is the binding of Sir4p to Rap1p (Luo, Vega-Palas et al. 2002). Sir4p is one of four ‘Silent Information Regulator’ proteins that also include Sir1p, Sir2p and Sir3p. Of these, Sir2p, Sir3p and Sir4p form the core of heterochromatin. Sir4p serves as a binding site for Sir2p, which is the next to bind. Sir2p deacetylates adjacent histones, which is thought to further condense the chromatin and prevent the binding of other transcription promoting histone modification enzymes. Sir3p binding follows, further condensing the heterochromatin. Sir1p plays a role in the initiation of silencing at the HM loci. A large number of other proteins act in both a synergistic and antagonistic manner.
Early work characterizing Ty5 targeted transposition focused on two fronts: identifying the component of Ty5 responsible for targeting and identifying the factor with which it interacted. Due to the central role of the Sir proteins in heterochromatin formation, they were initially considered as potential targeting signals. Because integration is mediated by the retrotransposon integrase enzyme, it was speculated to contain a component that would recognize heterochromatin.
The C-terminus of the Ty retrotransposon’s integrase contains an extension not seen in the retroviruses. This region is also not conserved between Ty1 and Ty5, whereas the rest of the integrase is, suggesting that this divergence could be responsible for the different targeting of the yeast Ty elements. A mutation was identified in the integrase C-terminus that randomized Ty5 integration, suggesting that this region of integrase was in fact involved in targeted transposition. | 1 | Applied and Interdisciplinary Chemistry |
Fluciclovine (F), also known as anti-1-amino-3-18F-fluorocyclobutane-1-carboxylic acid (anti-3[18F] FACBC), or as Axumin (brand name), is a diagnostic agent indicated for positron emission tomography (PET) imaging in men with suspected prostate cancer recurrence based on elevated prostate specific antigen (PSA) levels. | 1 | Applied and Interdisciplinary Chemistry |
Petite mutants show extranuclear inheritance.The inheritance pattern varying with the type of petite involved.
Segregational petites (pet–): mutants are created by nuclear mutations and exhibit Mendelian 1:1 segregation.
Neutral petites (rho–N): Neutral petite when crossed to wild-type, all offspring are wild-type. It has inherited normal mitochondrial DNA from wild-type parent, which is replicated in the offspring.
Suppressive petites (rho–S): crosses between petite and wild-type, all offspring are petite, showing "dominant" behavior to suppress wild-type mitochondrial function.
Most petite mutants of S. cerevisiae are of a suppressive type, and they differ from neutral petite by affecting the wild-type, although both are a mutation in mitochondrial DNA. Mitochondrial genome of yeast will be the first eukaryotic genome to be understood in terms of both structure and function and this should smooth the way to understand the evolution of organelle genomes and its relationship with nuclear genomes.It is evident that Ephrussi's work not only opened the field of extrachromosomal genetics, but also provide a fantastic incentive for the investigations which followed up to this day.
Though S. cerevisiae has been extensively studied in this and other areas, it is difficult to say if the molecular mechanisms of this process in the mitochondrial DNA are conserved across other yeast species. Other yeast species, such as Kluyveromyces lactis, Saccharomyces castellii, and Candida albicans have all shown to produce petite negative mutants. Potentially, these yeasts have a different inheritance system in place for their mitochondrial genome than S. cerevisiae does.
The frequency at which S. castellii spontaneously produces petites is similar to that of S. cerevisiae, with the mitochondrial DNA of those petites being highly altered via deletion and rearrangement. Suppressive petites of S. cerevisiae are the most commonly observed spontaneously created mutants, whereas in S. castellii, the most commonly observed spontaneous mutant is the neutral petite, further leading to speculation that the transference of this mutation differs between species. | 1 | Applied and Interdisciplinary Chemistry |
Combined with the energy needed to produce hydrogen and purified atmospheric nitrogen, ammonia production is energy-intensive, accounting for 1% to 2% of global energy consumption, 3% of global carbon emissions, and 3% to 5% of natural gas consumption. Hydrogen required for ammonia synthesis is most often produced through gasification of carbon-containing material, mostly natural gas, but other potential carbon sources include coal, petroleum, peat, biomass, or waste. As of 2012, the global production of ammonia produced from natural gas using the steam reforming process was 72%. Hydrogen can also be produced from water and electricity using electrolysis: at one time, most of Europe's ammonia was produced from the Hydro plant at Vemork. Other possibilities include biological hydrogen production or photolysis, but at present, steam reforming of natural gas is the most economical means of mass-producing hydrogen.
The choice of catalyst is important for synthesizing ammonia. In 2012, Hideo Hosonos group found that Ru-loaded calcium-aluminum oxide C12A7: electride works well as a catalyst and pursued more efficient formation. This method is implemented in a small plant for ammonia synthesis in Japan. In 2019, Hosonos group found another catalyst, a novel perovskite oxynitride-hydride , that works at lower temperature and without costly ruthenium. | 0 | Theoretical and Fundamental Chemistry |
A carbon–carbon bond is a covalent bond between two carbon atoms. The most common form is the single bond: a bond composed of two electrons, one from each of the two atoms. The carbon–carbon single bond is a sigma bond and is formed between one hybridized orbital from each of the carbon atoms. In ethane, the orbitals are sp-hybridized orbitals, but single bonds formed between carbon atoms with other hybridizations do occur (e.g. sp to sp). In fact, the carbon atoms in the single bond need not be of the same hybridization. Carbon atoms can also form double bonds in compounds called alkenes or triple bonds in compounds called alkynes. A double bond is formed with an sp-hybridized orbital and a p-orbital that is not involved in the hybridization. A triple bond is formed with an sp-hybridized orbital and two p-orbitals from each atom. The use of the p-orbitals forms a pi bond. | 0 | Theoretical and Fundamental Chemistry |
Unlike most epidermal cells, the guard cells of plant stomata contain relatively well-developed chloroplasts. However, exactly what they do is controversial. | 0 | Theoretical and Fundamental Chemistry |
The basis of catalytic resonance theory utilizes the transient behavior of adsorption, surface reactions, and desorption as surface binding energy and surface transition states oscillate with time. The binding energy of a single species, i, is described via a temporal functional including square or sinusoidal waves of frequency, f, and amplitude, dU:
Other surface chemical species, j, are related to the oscillating species, i, by the constant linear parameter, gamma γ:
The two surface species also share the common enthalpy of adsorption, delta δ. Specification of the oscillation frequency and amplitude of species i and relating γ and δ for all other surface species j permits determination of all chemical surface species adsorption enthalpy with time.
The transition state energy of a surface reaction between any two species i and j is predicted by the linear scaling relationship of the Bell–Evans–Polanyi principle which relates to the surface reaction enthalpy, ΔH, to the transition state energy, E, by parameters α and β with the following relationship:
The oscillating surface and transition state energies of chemical species alter the kinetic rate constants associated with surface reaction, adsorption, and desorption. The surface reaction rate constant of species i converting to surface species j includes the dynamic activation energy:
The resulting surface chemistry kinetics are then described via a surface reaction rate expression containing dynamic kinetic parameters responding to the oscillation in surface binding energy:
with k reactions with dynamic activation energy. The desorption rate constant also varies with oscillating surface binding energy by:
Implementation of dynamic surface binding energy of a reversible A-to-B reaction on a heterogeneous catalyst in a continuous flow stirred tank reactor operating at 1% conversion of A produces a sinusoidal binding energy in species B as shown. In the transition between surface binding energy amplitude endpoints, the instantaneous reaction rate (i.e., turnover frequency) oscillates over an order of magnitude as a limit cycle solution. | 0 | Theoretical and Fundamental Chemistry |
Enolate activation is the simplest Conia-ene activation mode. In this mode, the carbonyl starting material is treated with a strong base, such as nBuLi, NaH, or tBuOK, to form a metal-stabilized enolate, which then attacks the tethered alkyne and transfers the metal cation. An early example of enolate activation was reported by Taguchi and coworkers in 1999. The authors found that in the presence of catalytic base, alkynyl-substituted malonate esters undergo facile cyclization to the corresponding cyclopentanes. High yields were also obtained with substituted cyanoacetate, sulfonylacetate, and phosphonoacetate analogs. | 0 | Theoretical and Fundamental Chemistry |
In some snails, the protein component of the egg yolk is primarily ferritin. This is a different ferritin, with a different genetic sequence, from the somatic ferritin. It is produced in the midgut glands and secreted into the haemolymph, whence it is transported to the eggs. | 1 | Applied and Interdisciplinary Chemistry |
Ingram's research areas are analytical chemistry and environmental chemistry. She specializes on environmental uranium and arsenic contamination and how they effect the food chain and water supplies of the Navajo nation. She also researches traditional Navajo food ingredients and their health benefits, for example juniper ash as a calcium source. In light of the COVID-19 pandemic, her research laboratory repurposed their facilities to produce hand sanitizer which was donated to the Navajo Nation. | 0 | Theoretical and Fundamental Chemistry |
In 1999 the New Zealand Association of Scientists established the Shorland Medal in Shorland's honour. It is awarded annually in recognition of a "major and continued contribution to basic or applied research that has added significantly to scientific understanding or resulted in significant benefits to society." | 0 | Theoretical and Fundamental Chemistry |
Reverse transcriptase is commonly used in research to apply the polymerase chain reaction technique to RNA in a technique called reverse transcription polymerase chain reaction (RT-PCR). The classical PCR technique can be applied only to DNA strands, but, with the help of reverse transcriptase, RNA can be transcribed into DNA, thus making PCR analysis of RNA molecules possible. Reverse transcriptase is used also to create cDNA libraries from mRNA. The commercial availability of reverse transcriptase greatly improved knowledge in the area of molecular biology, as, along with other enzymes, it allowed scientists to clone, sequence, and characterise RNA. | 1 | Applied and Interdisciplinary Chemistry |
Fumagillin is a complex biomolecule and used as an antimicrobial agent. It was isolated in 1949 from the microbial organism Aspergillus fumigatus. | 0 | Theoretical and Fundamental Chemistry |
Power steering fluid is a sub type of hydraulic fluid. Most are mineral oil or silicone based fluids, while some use automatic transmission fluid, made from synthetic base oil. Automatic transmissions use fluids for their lubrication, cooling and hydraulic properties for viscous couplings.
Use of the wrong type of fluid can lead to failure of the power steering pump. | 1 | Applied and Interdisciplinary Chemistry |
Sulfur is intimately involved in production of fossil fuels and a majority of metal deposits because of its ability to act as an oxidizing or reducing agent. The vast majority of the major mineral deposits on Earth contain a substantial amount of sulfur including, but not limited to: sedimentary exhalative deposits (SEDEX), Carbonate-hosted lead-zinc ore deposits (Mississippi Valley-Type MVT) and porphyry copper deposits. Iron sulfides, galena and sphalerite will form as by-products of hydrogen sulfide generation, as long as the respective transition or base metals are present or transported to a sulfate reduction site. If the system runs out of reactive hydrocarbons economically viable elemental sulfur deposits may form. Sulfur also acts as a reducing agent in many natural gas reservoirs and generally ore forming fluids have a close relationship with ancient hydrocarbon seeps or vents.
Important sources of sulfur in ore deposits are generally deep-seated, but they can also come from local country rocks, sea water, or marine evaporites. The presence or absence of sulfur is one of the limiting factors on both the concentration of precious metals and its precipitation from solution. pH, temperature and especially redox states determine whether sulfides will precipitate. Most sulfide brines will remain in concentration until they reach reducing conditions, a higher pH or lower temperatures.
Ore fluids are generally linked to metal rich waters that have been heated within a sedimentary basin under the elevated thermal conditions typically in extensional tectonic settings. The redox conditions of the basin lithologies exert an important control on the redox state of the metal-transporting fluids and deposits can form from both oxidizing and reducing fluids. Metal-rich ore fluids tend to be by necessity comparatively sulfide deficient, so a substantial portion of the sulfide must be supplied from another source at the site of mineralization. Bacterial reduction of seawater sulfate or a euxinic (anoxic and HS-containing) water column is a necessary source of that sulfide. When present, the δS values of barite are generally consistent with a seawater sulfate source, suggesting baryte formation by reaction between hydrothermal barium and sulfate in ambient seawater.
Once fossil fuels or precious metals are discovered and either burned or milled, the sulfur become a waste product which must be dealt with properly or it can become a pollutant. There has been a great increase in the amount of sulfur in our present day atmosphere because of the burning of fossil fuels. Sulfur acts as a pollutant and an economic resource at the same time. | 0 | Theoretical and Fundamental Chemistry |
The simplest polymetallic system, the [FeS] cluster, is constituted by two iron ions bridged by two sulfide ions and coordinated by four cysteinyl ligands (in FeS ferredoxins) or by two cysteines and two histidines (in Rieske proteins). The oxidized proteins contain two Fe ions, whereas the reduced proteins contain one Fe and one Fe ion. These species exist in two oxidation states, (Fe) and FeFe. CDGSH iron sulfur domain is also associated with 2Fe-2S clusters.
The Rieske proteins contain Fe–S clusters that coordinate as a 2Fe–2S structure and can be found in the membrane bound cytochrome bc1 complex III in the mitochondria of eukaryotes and bacteria. They are also a part of the proteins of the chloroplast such as the cytochrome bf complex in photosynthetic organisms. These photosynthetic organisms include plants, green algae, and cyanobacteria, the bacterial precursor to chloroplasts. Both are part of the electron transport chain of their respective organisms which is a crucial step in the energy harvesting for many organisms. | 0 | Theoretical and Fundamental Chemistry |
Cubic materials are special orthotropic materials that are invariant with respect to 90° rotations with respect to the principal axes, i.e., the material is the same along its principal axes. Due to these additional symmetries the stiffness tensor can be written with just three different material properties like
The inverse of this matrix is commonly written as
where is the Youngs modulus, is the shear modulus, and is the Poissons ratio. Therefore, we can think of the ratio as the relation between the shear modulus for the cubic material and its (isotropic) equivalent: | 0 | Theoretical and Fundamental Chemistry |
In vitro, thienamycin employs a similar mode of action as penicillins through disrupting the cell wall synthesis (peptidoglycan biosynthesis) of various Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa to name a few). Although thienamycin binds to all of the penicillin-binding proteins (PBPs) in Escherichia coli, it preferentially binds to PBP-1 and PBP-2, which are both associated with the elongation of the cell wall.
Unlike penicillins, which are rendered ineffective through rapid hydrolysis by the β-lactamase enzyme present in some strains of bacteria, thienamycin remains antimicrobially active. Thienamycin displayed high activity against bacteria that were resistant to other β-lactamase-stable compounds (cephalosporins), highlighting the superiority of thienamycin as an antibiotic among β-lactams. | 0 | Theoretical and Fundamental Chemistry |
Internal corrosion is occasioned by the combined effects and severity of four modes of material deterioration, namely: general corrosion, pitting corrosion, microbial corrosion, and fluid corrosivity. The same principals of external corrosion control can be applied to internal corrosion but due to accessibility, the approaches can be different. Thus special instruments for internal corrosion control and inspection are used that are not used in external corrosion control. Video scoping of pipes and high tech smart pigs are used for internal inspections. The smart pigs can be inserted into a pipe system at one point and "caught" far down the line. The use of corrosion inhibitors, material selection, and internal coatings are mainly used to control corrosion in piping while anodes along with coatings are used to control corrosion in tanks.
Internal corrosion challenges apply to the following amongst others: Water pipes; Gas pipes; Oil pipes and Water tank reservoirs. | 1 | Applied and Interdisciplinary Chemistry |
Condensation of long double-helical DNAs is a sharp phase transition, which takes place within a narrow interval of condensing agent concentrations.[ref] Since the double helices come very closely to each other in the condensed phase, this leads to the restructuring of water molecules, which gives rise to the so-called hydration forces.[ref] To understand attraction between negatively charged DNA molecules, one also must account for correlations between counterions in the solution.[ref] DNA condensation by proteins can exhibit hysteresis, which can be explained using a modified Ising model. | 1 | Applied and Interdisciplinary Chemistry |
Carboxypeptidase B (, protaminase, pancreatic carboxypeptidase B, tissue carboxypeptidase B, peptidyl-L-lysine [L-arginine]hydrolase) is a carboxypeptidase that preferentially cleaves off basic amino acids arginine and lysine from the C-terminus of a peptide. This enzyme is secreted by the pancreas, and it travels to the small intestine, where it aids in protein digestion. Plasma carboxypeptidase B (carboxypeptidase B2) is responsible for converting the C5a protein into C5a des-Arg, with one less amino acid. | 1 | Applied and Interdisciplinary Chemistry |
Airborne sawdust and sawdust accumulations present a number of health and safety hazards. Wood dust becomes a potential health problem when, for example, the wood particles, from processes such as sanding, become airborne and are inhaled. Wood dust is a known human carcinogen. Certain woods and their dust contain toxins that can produce severe allergic reactions. The composition of sawdust depends on the material it comes from; sawdust produced from natural wood is different from that of sawdust produced from processed wood or wood veneer.
Breathing airborne wood dust may cause allergic respiratory symptoms, mucosal and non-allergic respiratory symptoms, and cancer. In the US, lists of carcinogenic factors are published by the American Conference of Governmental Industrial Hygienists (ACGIH), the Occupational Safety and Health Administration (OSHA), and the National Institute for Occupational Safety and Health (NIOSH). All these organisations recognize wood dust as carcinogenic in relation to the nasal cavities and paranasal sinuses.
People can be exposed to wood dust in the workplace by breathing it in, skin contact, or eye contact. The OSHA has set the legal limit (permissible exposure limit) for wood dust exposure in the workplace as 15 mg/m total exposure and 5 mg/m respiratory exposure over an 8-hour workday. The NIOSH has set a recommended exposure limit (REL) of 1 mg/m over an 8-hour workday.
Water-borne bacteria digest organic material in leachate, but use up much of the available oxygen. This high biochemical oxygen demand can suffocate fish and other organisms. There is an equally detrimental effect on beneficial bacteria, so it is not at all advisable to use sawdust within home aquariums, as was once done by hobbyists seeking to save some expense on activated carbon. | 1 | Applied and Interdisciplinary Chemistry |
The convection–diffusion equation can be derived in a straightforward way from the continuity equation, which states that the rate of change for a scalar quantity in a differential control volume is given by flow and diffusion into and out of that part of the system along with any generation or consumption inside the control volume:
where is the total flux and is a net volumetric source for . There are two sources of flux in this situation. First, diffusive flux arises due to diffusion. This is typically approximated by Fick's first law:
i.e., the flux of the diffusing material (relative to the bulk motion) in any part of the system is proportional to the local concentration gradient. Second, when there is overall convection or flow, there is an associated flux called advective flux:
The total flux (in a stationary coordinate system) is given by the sum of these two:
Plugging into the continuity equation: | 1 | Applied and Interdisciplinary Chemistry |
β-carotene can be extracted from fungus Blakeslea trispora, marine algae Dunaliella salina or genetically modified yeast Saccharomyces cerevisiae, starting with xylose as a substrate. Chemical synthesis uses either a method developed by BASF or a Grignard reaction utilized by Hoffman-La Roche.
The world market for synthetic retinol is primarily for animal feed, leaving approximately 13% for a combination of food, prescription medication and dietary supplement use. Industrial methods for the production of retinol rely on chemical synthesis. The first industrialized synthesis of retinol was achieved by the company Hoffmann-La Roche in 1947. In the following decades, eight other companies developed their own processes. β-ionone, synthesized from acetone, is the essential starting point for all industrial syntheses. Each process involves elongating the unsaturated carbon chain. Pure retinol is extremely sensitive to oxidization and is prepared and transported at low temperatures and oxygen-free atmospheres. When prepared as a dietary supplement or food additive, retinol is stabilized as the ester derivatives retinyl acetate or retinyl palmitate. Prior to 1999, three companies, Roche, BASF and Rhone-Poulenc controlled 96% of global vitamin A sales. In 2001, the European Commission imposed total fines of 855.22 million euros on these and five other companies for their participation in eight distinct market-sharing and price-fixing cartels that dated back to 1989. Roche sold its vitamin division to DSM in 2003. DSM and BASF have the major share of industrial production. A biosynthesis alternative utilizes genetically engineered yeast species Saccharomyces cerevisiae to synthesize retinal and retinol, using xylose as a starting substrate. This was accompished by having the yeast first synthesize β-carotene and then the cleaving enzyme β-carotene 15,15'-dioxygenase to yield retinal. | 1 | Applied and Interdisciplinary Chemistry |
Transitions between scales are always fluent. There is no sharp cut that defines the end of small- and the beginning of medium/pilot scale. However, chromatography columns with an inner diameter (ID) of up to 5 cm are generally considered small scale or laboratory scale columns.
Small scale chromatography columns are mostly intended for design of experiments (DoE); proof of concept; validation (drug manufacture) or research and development experiments. Columns of this scale category are distinguished by their small dimensions in comparison to chromatography columns intended for larger scales as well as relatively high pressure tolerance and selection of materials in contact with the liquid phase. This is especially important for applications in the biopharmaceutical industry which underlie close scrutiny by regulatory agencies (U.S. Food and Drug Administration; European Medicines Agency). | 0 | Theoretical and Fundamental Chemistry |
In lactic acid fermentation, each pyruvate molecule is directly reduced by NADH. The only byproduct from this type of fermentation is lactate. Lactic acid fermentation is used by human muscle cells as a means of generating ATP during strenuous exercise where oxygen consumption is higher than the supplied oxygen. As this process progresses, the surplus of lactate is brought to the liver, which converts it back to pyruvate. | 1 | Applied and Interdisciplinary Chemistry |
The phrase -ate ion or ate ion can refer generically to many negatively charged anions. -ate compound or ate compound can refer to salts of the anions or esters of the functional groups.
Chemical terms ending in -ate (and -ite) generally refer to the negatively charged anions, neutral radicals, and covalently bonded functional groups that share the same chemical formulas (with different charges). For example, the nitrate anion, ; the nitrate functional group that forms nitrate esters, or ; and the nitrate radical or nitrogen trioxide, .
Most numerous are oxyanions (oxyacids that have lost one or more protons to deprotonation) and the radicals and functional groups that share their names.
Oxyanions derived from inorganic acids include:
* Fully deprotonated oxyanions, such as borate, carbonate, nitrate, cyanate, isocyanate, thiocyanate, fulminate, aluminate, zincate, silicate, phosphate, sulfate and other sulfur oxoanions, chlorate, titanate, vanadate, chromate, manganate, ferrate, percobaltate, nickelate, germanate, arsenate, selenate, bromate, molybdate, pertechnate, perruthenate, stannate, antimonate, tellurate, iodate, perxenate, tungstate, plumbate, and bismuthate.
* Partially deprotonated oxyanions, such as hydrogensulfate, hydrogenphosphate, and dihydrogenphosphate.
Oxyanions derived from organic acids include:
* Carboxylate ions such as formate, acetate, propionate, butyrate, isobutyrate, and oxalate, along with their sulfur analogs, the thiocarboxylate ions, such as thioacetate.
* Phosphonate and sulfonate ions.
* Deprotonated alcohols such as methanolate (methoxide) and ethanolate (ethoxide), along with their sulfur analogs, the thiolates.
A lyate ion is a generic solvent molecule that has become a negative ion by loss of one or more protons.
The -ate suffix also applies to negative fluoroanions, fluorides which have gained one or more protons and twice as many electrons. Tetrafluoroborate, , is boron trifluoride, , which has gained one fluoride and two electrons. | 0 | Theoretical and Fundamental Chemistry |
LA-ICP-MS can determine major and trace elements, however, with LA-ICPMS, the melt inclusion and any accompanying materials within the melt inclusion are ionized, thus destroying the melt inclusion, and then analyzed with a mass spectrometer. | 0 | Theoretical and Fundamental Chemistry |
While there are multitudes of molecules in existence which would appear to be antiaromatic on paper, the number of molecules that are antiaromatic in actuality is considerably less. This is compounded by the fact that one cannot typically make derivatives of antiaromatic molecules by adding more antiaromatic hydrocarbon rings, etc. because the molecule typically loses either its planar nature or its conjugated system of π-electrons and becomes nonaromatic. In this section, only examples of antiaromatic compounds which are non-disputable are included.
Pentalene is an antiaromatic compound which has been well-studied both experimentally and computationally for decades. It is dicyclic, planar and has eight π-electrons, fulfilling the IUPAC definition of antiaromaticity. Pentalene’s dianionic and dicationic states are aromatic, as they follow Hückel’s 4n +2 π-electron rule. | 0 | Theoretical and Fundamental Chemistry |
Hot particles, radioactive particles of nuclear fallout and radioactive waste, also exhibit distinct isotopic signatures. Their radionuclide composition (and thus their age and origin) can be determined by mass spectrometry or by gamma spectrometry. For example, particles generated by a nuclear blast contain detectable amounts of Co and Eu. The Chernobyl accident did not release these particles but did release Sb and Ce. Particles from underwater bursts will consist mostly of irradiated sea salts. Ratios of Eu/Eu, Eu/Eu, and Pu/Pu are also different for fusion and fission nuclear weapons, which allows identification of hot particles of unknown origin.
Uranium has a relatively constant isotope ratio in all natural samples with ~0.72% some 55 ppm (in secular equilibrium with its parent nuclide ) and the balance made up by . Isotopic compositions that diverge significantly from those values are evidence for the uranium having been subject to depletion or enrichment in some fashion or of (part of it) having participated in a nuclear fission reaction. While the latter is almost as universally due to human influence as the former two, the natural nuclear fission reactor at Oklo, Gabon was detected through a significant diversion of concentration in samples from Oklo compared to those of all other known deposits on earth. Given that is a material of proliferation concern then as now every IAEA-approved supplier of Uranium fuel keeps track of the isotopic composition of uranium to ensure none is diverted for nefarious purposes. It would thus become apparent quickly if another Uranium deposit besides Oklo proves to have once been a natural nuclear fission reactor. | 0 | Theoretical and Fundamental Chemistry |
Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". Alternatively, for samples which scatter light, absorbance may be defined as "the negative logarithm of one minus absorptance, as measured on a uniform sample". The term is used in many technical areas to quantify the results of an experimental measurement. While the term has its origin in quantifying the absorption of light, it is often entangled with quantification of light which is “lost” to a detector system through other mechanisms. What these uses of the term tend to have in common is that they refer to a logarithm of the ratio of a quantity of light incident on a sample or material to that which is detected after the light has interacted with the sample.
The term absorption refers to the physical process of absorbing light, while absorbance does not always measure only absorption; it may measure attenuation (of transmitted radiant power) caused by absorption, as well as reflection, scattering, and other physical processes. Sometimes the term "attenuance" or "experimental absorbance" is used to emphasize that radiation is lost from the beam by processes other than absorption, with the term "internal absorbance" used to emphasize that the necessary corrections have been made to eliminate the effects of phenomena other than absorption. | 0 | Theoretical and Fundamental Chemistry |
The saddle coil shows the most complex geometry of these three coil types.
The B field is generated primarily by the four vertical wire segments. Because of this coil geometry, the B field of a saddle coil is more homogeneous in z direction than that of a planar coil. The saddle coil can be formed from wire, but it is also often etched from thin copper foil, which is then adhered to glass or PTFE tubing. The latter procedure leads to a high geometric precision, resulting in better B homogeneity. The saddle coil is easily accessible and provides a good ‘filling factor’ of the usable area in the magnet bore. For these reasons it is widely used in NMR microscopy. However, these advantages are achieved at the price of decreased sensitivity. Compared to a saddle coil, the sensitivity performance of a solenoidal coil of the same dimensions is approximately three times better. | 0 | Theoretical and Fundamental Chemistry |
Ribosome profiling is a method that can reveal pausing sites through sequencing the ribosome protected fragments (RPFs or footprints) to map ribosome occupancy on the mRNA. Ribosome profiling has the ability to reveal the ribosome pause sites in the whole transcriptome. When the kinetics layer is added, it discloses the time of the pause, and the translation takes place. Ribosome profiling is however still in early stages and has biases that need to be explored further. Ribosome profiling allows for translation to be measured more accurately and precisely. During this process, translation needs to be stopped in order for ribosome profiling to be performed. This may cause a problem with ribosome profiling because the methods that are used to stop translation in an experiment can impact the outcome, which causes incorrect results. Ribosome profiling is useful for getting specific information on translation and the process of protein synthesis. | 1 | Applied and Interdisciplinary Chemistry |
The similarity-based virtual screening (a kind of ligand-based virtual screening) assumes that all compounds in a database that are similar to a query compound have similar biological activity. Although this hypothesis is not always valid, quite often the set of retrieved compounds is considerably enriched with actives. To achieve high efficacy of similarity-based screening of databases containing millions of compounds, molecular structures are usually represented by molecular screens (structural keys) or by fixed-size or variable-size molecular fingerprints. Molecular screens and fingerprints can contain both 2D- and 3D-information. However, the 2D-fingerprints, which are a kind of binary fragment descriptors, dominate in this area. Fragment-based structural keys, like MDL keys, are sufficiently good for handling small and medium-sized chemical databases, whereas processing of large databases is performed with fingerprints having much higher information density. Fragment-based Daylight, BCI, and UNITY 2D (Tripos) fingerprints are the best known examples. The most popular similarity measure for comparing chemical structures represented by means of fingerprints is the Tanimoto (or Jaccard) coefficient T. Two structures are usually considered similar if T > 0.85 (for Daylight fingerprints). However, it is a common misunderstanding that a similarity of T > 0.85 reflects similar bioactivities in general ("the 0.85 myth"). | 1 | Applied and Interdisciplinary Chemistry |
In an oscillatory flow with flow velocity , the Morison equation gives the inline force parallel to the flow direction:
where
* is the total inline force on the object,
* is the flow acceleration, i.e. the time derivative of the flow velocity
* the inertia force , is the sum of the Froude–Krylov force and the hydrodynamic mass force
* the drag force according to the drag equation,
* is the inertia coefficient, and the added mass coefficient,
* A is a reference area, e.g. the cross-sectional area of the body perpendicular to the flow direction,
* V is volume of the body.
For instance for a circular cylinder of diameter D in oscillatory flow, the reference area per unit cylinder length is and the cylinder volume per unit cylinder length is . As a result, is the total force per unit cylinder length:
Besides the inline force, there are also oscillatory lift forces perpendicular to the flow direction, due to vortex shedding. These are not covered by the Morison equation, which is only for the inline forces. | 1 | Applied and Interdisciplinary Chemistry |
Nuclear DNA is normally tightly wrapped around histones rendering the DNA inaccessible to the general transcription machinery and hence this tight association prevents transcription of DNA. At physiological pH, the phosphate component of the DNA backbone is deprotonated which gives DNA a net negative charge. Histones are rich in lysine residues which at physiological pH are protonated and therefore positively charged. The electrostatic attraction between these opposite charges is largely responsible for the tight binding of DNA to histones.
Many coactivator proteins have intrinsic histone acetyltransferase (HAT) catalytic activity or recruit other proteins with this activity to promoters. These HAT proteins are able to acetylate the amine group in the sidechain of histone lysine residues which makes lysine much less basic, not protonated at physiological pH, and therefore neutralizes the positive charges in the histone proteins. This charge neutralization weakens the binding of DNA to histones causing the DNA to unwind from the histone proteins and thereby significantly increases the rate of transcription of this DNA.
Many corepressors can recruit histone deacetylase (HDAC) enzymes to promoters. These enzymes catalyze the hydrolysis of acetylated lysine residues restoring the positive charge to histone proteins and hence the tie between histone and DNA. PELP-1 can act as a transcriptional corepressor for transcription factors in the nuclear receptor family such as glucocorticoid receptors. | 1 | Applied and Interdisciplinary Chemistry |
Fractional crystallization is the removal and segregation from a melt of mineral precipitates, which changes the composition of the melt. This is one of the most important geochemical and physical processes operating within the Earth's crust and mantle.
Fractional crystallization in silicate melts (magmas) is a very complex process compared to chemical systems in the laboratory because it is affected by a wide variety of phenomena. Prime amongst these are the composition, temperature, and pressure of a magma during its cooling.
The composition of a magma is the primary control on which mineral is crystallized as the melt cools down past the liquidus. For instance in mafic and ultramafic melts, the MgO and SiO contents determine whether forsterite olivine is precipitated or whether enstatite pyroxene is precipitated.
Two magmas of similar composition and temperature at different pressure may crystallize different minerals. An example is high-pressure and high-temperature fractional crystallization of granites to produce single-feldspar granite, and low-pressure low-temperature conditions which produce two-feldspar granites.
The partial pressure of volatile phases in silicate melts is also of prime importance, especially in near-solidus crystallization of granites. | 0 | Theoretical and Fundamental Chemistry |
Sweat diagnostics is an emerging non-invasive technique used to provide insights to the health of the human body. Common sweat diagnostic tests include testing for cystic fibrosis and illicit drugs. Most testing of human sweat is in reference to the eccrine sweat gland which in contrast to the apocrine sweat gland, has a lower composition of oils.
Although sweat is mostly water, there are many solutes which are found in sweat that have at least some relation to biomarkers found in blood. These include: sodium (Na), chloride (Cl), potassium (K), ammonium (NH), alcohols, lactate, peptides & proteins. Development of devices, sensing techniques and biomarker identification in sweat continues to be an expanding field for medical diagnostics and athletics applications.
The use of smart biosensors for on-skin sweat analysis has been described as internet-enabled Sudorology (iSudorology) by Brasier et al. in 2019. It describes the lab-independent detection of molecular, next-generation digital biomarkers in sweat. | 1 | Applied and Interdisciplinary Chemistry |
Different solvents can affect the equilibrium constant of a reaction by differential stabilization of the reactant or product. The equilibrium is shifted in the direction of the substance that is preferentially stabilized.
Stabilization of the reactant or product can occur through any of the different non-covalent interactions with the solvent such as H-bonding, dipole-dipole interactions, van der Waals interactions etc. | 0 | Theoretical and Fundamental Chemistry |
Couette flow is frequently used in undergraduate physics and engineering courses to illustrate shear-driven fluid motion. A simple configuration corresponds to two infinite, parallel plates separated by a distance ; one plate translates with a constant relative velocity in its own plane. Neglecting pressure gradients, the Navier–Stokes equations simplify to
where is the spatial coordinate normal to the plates and is the velocity field. This equation reflects the assumption that the flow is unidirectional — that is, only one of the three velocity components is non-trivial. If the lower plate corresponds to , the boundary conditions are and . The exact solution
can be found by integrating twice and solving for the constants using the boundary conditions.
A notable aspect of the flow is that shear stress is constant throughout the domain. In particular, the first derivative of the velocity, , is constant. According to Newton's Law of Viscosity (Newtonian fluid), the shear stress is the product of this expression and the (constant) fluid viscosity. | 1 | Applied and Interdisciplinary Chemistry |
In some cases, rates of reaction decrease with increasing temperature. When following an approximately exponential relationship so the rate constant can still be fit to an Arrhenius expression, this results in a negative value of E.
Elementary reactions exhibiting negative activation energies are typically barrierless reactions, in which the reaction proceeding relies on the capture of the molecules in a potential well. Increasing the temperature leads to a reduced probability of the colliding molecules capturing one another (with more glancing collisions not leading to reaction as the higher momentum carries the colliding particles out of the potential well), expressed as a reaction cross section that decreases with increasing temperature. Such a situation no longer leads itself to direct interpretations as the height of a potential barrier.
Some multistep reactions can also have apparent negative activation energies. For example, the overall rate constant k for a two-step reaction A B, B → C is given by k = kK, where k is the rate constant of the rate-limiting slow second step and K is the equilibrium constant of the rapid first step. In some reactions, K decreases with temperature more rapidly than k increases, so that k actually decreases with temperature corresponding to a negative observed activation energy.
An example is the oxidation of nitric oxide which is a termolecular reaction . The rate law is with a negative activation energy. This is explained by the two-step mechanism: and .
Certain cationic polymerization reactions have negative activation energies so that the rate decreases with temperature. For chain-growth polymerization, the overall activation energy is , where i, p and t refer respectively to initiation, propagation and termination steps. The propagation step normally has a very small activation energy, so that the overall value is negative if the activation energy for termination is larger than that for initiation. The normal range of overall activation energies for cationic polymerization varies from . | 0 | Theoretical and Fundamental Chemistry |
Strong Acids
* Perchloric acid HClO
* Hydriodic acid HI
* Hydrobromic acid HBr
* Hydrochloric acid HCl
* Sulfuric acid HSO
* Nitric acid HNO
* Chloric acid HClO
* Bromic acid HBrO
* Perbromic acid HBrO
* Periodic acid HIO
* Fluoroantimonic acid HSbF
* Magic acid FSOHSbF
* Carborane superacid H(CHBCl)
* Fluorosulfuric acid FSOH
* Triflic acid CFSOH
Strong Bases
* Lithium hydroxide LiOH
* Sodium hydroxide NaOH
* Potassium hydroxide KOH
* Rubidium hydroxide RbOH
* Caesium hydroxide CsOH
* Calcium hydroxide Ca(OH)
* Strontium hydroxide Sr(OH)
* Barium hydroxide Ba(OH)
* Lithium diisopropylamide (LDA) CHLiN
* Lithium diethylamide (LDEA)
* Sodium amide NaNH
* Sodium hydride NaH
* Lithium bis(trimethylsilyl)amide ((CH)Si)NLi
Salts
* Sodium chloride NaCl
* Potassium nitrate KNO
* Magnesium chloride MgCl
* Sodium acetate CHCOONa | 0 | Theoretical and Fundamental Chemistry |
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