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The first chemical compounds of the cephalosporin group were isolated from Cephalosporium acremonium, a cephalosporin-producing fungus first discovered by Giuseppe Brotzu in 1948 from a sewage outfall off the Sardinian coast. From crude filtrates of the Cephalosporium acremonium culture scientists got new antibacterial activity. It was noted that the crude filtrate could inhibit the growth of Staphylococcus aureus. | 1 | Applied and Interdisciplinary Chemistry |
One technique for detecting indicator organisms is the use of chromogenic compounds, which are added to conventional or newly devised media used for isolation of the indicator bacteria. These chromogenic compounds are modified to change color or fluorescence by the addition of either enzymes or specific bacterial metabolites. This enables for easy detection and avoids the need for isolation of pure cultures and confirmatory tests. | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, the metallome is the distribution of metal ions in a cellular compartment. The term was coined in analogy with proteome as metallomics is the study of metallome: the "comprehensive analysis of the entirety of metal and metalloid species within a cell or tissue type". Therefore, metallomics can be considered a branch of metabolomics, even though the metals are not typically considered as metabolites.
An alternative definition of "metallomes" as metalloproteins or any other metal-containing biomolecules, and "metallomics" as a study of such biomolecules. | 1 | Applied and Interdisciplinary Chemistry |
The society has an extensive awards and honours programme.
The Honours programme was established in 1996 and is designed to raise awareness of the benefits of the practical application of chemistry and related sciences across scientific disciplines and industrial sectors and to celebrate accomplished scientists, inventors and entrepreneurs through a number of international awards, medals, and lectureships.
The most prestigious honours are the Society Medals, of which there are around 12, and these recognise those who exhibit leadership in promoting the objectives and values of the society. The Society Medals are awarded to persons who have made significant contributions in the field of chemical sciences, innovation and entrepreneurship. | 1 | Applied and Interdisciplinary Chemistry |
In 1937, Xing returned to China. He moved to Kunming since eastern China was occupied by Japanese invaders. There, he spent some efforts on the refining of Quinine. Then Xing joined the New Fourth Army as a teacher in its military medical school. Moreover, he assisted the army to product medicine.
In 1946, Xing went back to Beijing and accepted an appointment as a professor at Peking University.
In 1950s, Xing designed a new method to synthesize the chloramphenicol.
During 1964–65, Xing participated in the total synthesis of bovine insulin project, co-operating with Shanghai Institutes for Biological Sciences.
In 1980, Xing was elected as an academician of the Chinese Academy of Sciences.
During 1981–87, Xing focused on the activation methods for the carboxyl group in the peptide synthesis, and developed related chemical reagents. | 0 | Theoretical and Fundamental Chemistry |
Knock out of AK1 disrupts the synchrony between inorganic phosphate and turnover at ATP-consuming sites and ATP synthesis sites. This reduces the energetic signal communication in the post-ischemic heart and precipitates inadequate coronary reflow following ischemia-reperfusion. | 1 | Applied and Interdisciplinary Chemistry |
The evolution of Mg transport appears to have been rather complicated. Proteins apparently based on MgtE are present in bacteria and metazoa, but are missing in fungi and plants, whilst proteins apparently related to CorA are present in all of these groups. The two active transport transporters present in bacteria, MgtA and MgtB, do not appear to have any homologies in higher organisms. There are also Mg transport systems that are found only in the higher organisms. | 1 | Applied and Interdisciplinary Chemistry |
Naturally, it is produced in the human placenta by the syncytiotrophoblast.
Like any other gonadotropins, it can be extracted from the urine of pregnant women or produced from cultures of genetically modified cells using recombinant DNA technology.
In Pubergen, Pregnyl, Follutein, Profasi, Choragon and Novarel, it is extracted from the urine of pregnant women. In Ovidrel, it is produced with recombinant DNA technology. | 1 | Applied and Interdisciplinary Chemistry |
This type of categorisation of drugs is from a medical perspective and categorises them by the pathology they are used to treat. Drug classes that are defined by their therapeutic use (the pathology they are intended to treat) include:
* Analgesics
* Antibiotic
* Anticancer
* Anticoagulant
* Antidepressant
* Antidiabetic
* Antiepileptic
* Antipsychotic
* Antispasmodic
* Antiviral
* Cardiovascular
* Depressant
* Sedative
* Stimulant | 1 | Applied and Interdisciplinary Chemistry |
As the no-slip condition was an empirical observation, there are physical scenarios in which it fails. For sufficiently rarefied flows, including flows of high altitude atmospheric gases and for microscale flows, the no-slip condition is inaccurate. For such examples, this change is driven by an increasing Knudsen number, which implies increasing rarefaction, and gradual failure of the continuum approximation. The first-order expression, which is often used to model fluid slip, is expressed as
where is the coordinate normal to the wall, is the mean free path and is some constant known as the slip coefficient, which is approximately of order 1. Alternatively, one may introduce as the slip length. Some highly hydrophobic surfaces, such as carbon nanotubes with added radicals, have also been observed to have a nonzero but nanoscale slip length.
Similarly, some researchers have investigated this slip condition, modelling the cause as due to the high smoothness of highly-ordered nanoscale surfaces.
While the no-slip condition is used almost universally in modeling of viscous flows, it is sometimes neglected in favor of the no-penetration condition (where the fluid velocity normal to the wall is set to the wall velocity in this direction, but the fluid velocity parallel to the wall is unrestricted) in elementary analyses of inviscid flow, where the effect of boundary layers is neglected.
The no-slip condition poses a problem in viscous flow theory at contact lines: places where an interface between two fluids meets a solid boundary. Here, the no-slip boundary condition implies that the position of the contact line does not move, which is not observed in reality. Analysis of a moving contact line with the no slip condition results in infinite stresses that can't be integrated over. The rate of movement of the contact line is believed to be dependent on the angle the contact line makes with the solid boundary, but the mechanism behind this is not yet fully understood. | 1 | Applied and Interdisciplinary Chemistry |
In contrast to DCC, DIC (N,N-diisopropylcarbodiimide) is a liquid. Its hydrolysis product, N,N'-diisopropylurea, is soluble in organic solvents. | 0 | Theoretical and Fundamental Chemistry |
pH-dependent primary, secondary, or tertiary amines; primary and secondary amines become positively charged at pH < 10: octenidine dihydrochloride.
Permanently charged quaternary ammonium salts: cetrimonium bromide (CTAB), cetylpyridinium chloride (CPC), benzalkonium chloride (BAC), benzethonium chloride (BZT), dimethyldioctadecylammonium chloride, and dioctadecyldimethylammonium bromide (DODAB). | 0 | Theoretical and Fundamental Chemistry |
The Wong–Sandler mixing rule is a thermodynamic mixing rule used for vapor–liquid equilibrium and liquid-liquid equilibrium calculations.
__TOC__ | 0 | Theoretical and Fundamental Chemistry |
A discussion of all mediator subunits is beyond the scope of this article, but details of one of the subunits are illustrative of the types of information that may be gathered for other subunits. | 1 | Applied and Interdisciplinary Chemistry |
Since its first inception in 1967, many synthesis techniques have been developed and employed for the polymerization of o-phthalaldehyde. Most notably, living polymerization methods are among the most common and promising techniques used, as can be seen in the high number of publications in the literature depicting their usage in poly(phthalaldehyde) preparation. | 0 | Theoretical and Fundamental Chemistry |
The erythropoietin receptor (EpoR) is a protein that in humans is encoded by the EPOR gene. EpoR is a 52kDa peptide with a single carbohydrate chain resulting in an approximately 56-57 kDa protein found on the surface of EPO responding cells. It is a member of the cytokine receptor family. EpoR pre-exists as dimers. These dimers were originally thought to be formed by extracellular domain interactions, however, it is now assumed that it is formed by interactions of the transmembrane domain and that the original structure of the extracellular interaction site was due to crystallisation conditions and does not depict the native conformation. Binding of a 30 kDa ligand erythropoietin (Epo), changes the receptor's conformational change, resulting in the autophosphorylation of Jak2 kinases that are pre-associated with the receptor (i.e., EpoR does not possess intrinsic kinase activity and depends on Jak2 activity). At present, the best-established function of EpoR is to promote proliferation and rescue of erythroid (red blood cell) progenitors from apoptosis. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, regioselectivity is the preference of chemical bonding or breaking in one direction over all other possible directions. It can often apply to which of many possible positions a reagent will affect, such as which proton a strong base will abstract from an organic molecule, or where on a substituted benzene ring a further substituent will be added.
A specific example is a halohydrin formation reaction with 2-propenylbenzene:
Because of the preference for the formation of one product over another, the reaction is selective. This reaction is regioselective because it selectively generates one constitutional isomer rather than the other.
Various examples of regioselectivity have been formulated as rules for certain classes of compounds under certain conditions, many of which are named. Among the first introduced to chemistry students are Markovnikov's rule for the addition of protic acids to alkenes, and the Fürst-Plattner rule for the addition of nucleophiles to derivatives of cyclohexene, especially epoxide derivatives.
Regioselectivity in ring-closure reactions is subject to Baldwin's rules. If there are two or more orientations that can be generated during a reaction, one of them is dominant (e.g., Markovnikov/anti-Markovnikov addition across a double bond)
Regioselectivity can also be applied to specific reactions such as addition to pi ligands.
Selectivity also occurs in carbene insertions, for example in the Baeyer-Villiger reaction. In this reaction, an oxygen is regioselectively inserted near an adjacent carbonyl group. In ketones, this insertion is directed toward the carbon which is more highly substituted (i.e. according to Markovnikov's rule). For example, in a study involving acetophenones, this oxygen was preferentially inserted between the carbonyl and the aromatic ring to give acetyl aromatic esters instead of methyl benzoates. | 0 | Theoretical and Fundamental Chemistry |
The Mountain Pass deposit was discovered in 1949 by Herbert S. Woodward, Clarence Watkins and P. A. Simon, who noticed anomalously high radioactivity. Molybdenum Corporation of America bought most of the mining claims, and began small-scale production in 1952.
Production expanded greatly in the 1960s, to supply demand for europium used in color television screens. Between 1965 and 1995, the mine supplied most of the worldwide rare-earth metals consumption.
Molybdenum Corporation of America changed its name to Molycorp in 1974. The corporation was acquired by Union Oil in 1977, which in turn became part of Chevron Corporation in 2005.
In 1998, the mine's separation plant ceased production of refined rare-earth compounds; it continued to produce bastnäsite concentrate.
The mine closed in 2002 after a toxic waste spill and wasn't reopened due to competition from Chinese suppliers, though processing of previously mined ore continued.
In 2008, Chevron sold the mine to privately-held Molycorp Minerals LLC, a company formed to revive the Mountain Pass mine. Molycorp announced plans to spend $500 million to reopen and expand the mine, and on July 29, 2010, it raised about $400 million through an initial public offering, selling 28,125,000 shares at $14 under the ticker symbol MCP on the New York Stock Exchange.
In December 2010, Molycorp announced that it had secured all the environmental permits needed to build a new ore processing plant at the mine; construction would begin in January 2011, and was expected to be completed by the end of 2012. On August 27, 2012, the company announced that mining had restarted.
The processing plant was in full production on June 25, 2015, when Molycorp filed for Chapter 11 bankruptcy with outstanding bonds in the amount of $US 1.4 billion. The company's shares were removed from the NYSE.
In August 2015, it was reported that the mine was to be shut down.
On August 31, 2016, Molycorp Inc. emerged from bankruptcy as Neo Performance Materials, leaving behind the mine as Molycorp Minerals LLC in its own separate Chapter 11 bankruptcy. As of January 2016, its shares were traded OTC under the symbol MCPIQ.
Mountain Pass was acquired out of bankruptcy in July 2017 with the goal of reviving America's rare-earth industry. MP Materials resumed mining and refining operations in January 2018. | 1 | Applied and Interdisciplinary Chemistry |
Some phase change materials are suspended in water, and are relatively nontoxic. Others are hydrocarbons or other flammable materials, or are toxic. As such, PCMs must be selected and applied very carefully, in accordance with fire and building codes and sound engineering practices. Because of the increased fire risk, flamespread, smoke, potential for explosion when held in containers, and liability, it may be wise not to use flammable PCMs within residential or other regularly occupied buildings. Phase change materials are also being used in thermal regulation of electronics. | 0 | Theoretical and Fundamental Chemistry |
A variety of cleavage agents can be chosen. a desirable agent is one that is sequence neutral, easy to use, and is easy to control. Unfortunately no available agents meet all of these standards, so an appropriate agent can be chosen, depending on your DNA sequence and ligand of interest. The following cleavage agents are described in detail:
DNase I is a large protein that functions as a double-strand endonuclease. It binds the minor groove of DNA and cleaves the phosphodiester backbone. It is a good cleavage agent for footprinting because its size makes it easily physically hindered. Thus is more likely to have its action blocked by a bound protein on a DNA sequence. In addition, the DNase I enzyme is easily controlled by adding EDTA to stop the reaction. There are however some limitations in using DNase I. The enzyme does not cut DNA randomly; its activity is affected by local DNA structure and sequence and therefore results in an uneven ladder. This can limit the precision of predicting a protein’s binding site on the DNA molecule.
Hydroxyl radicals are created from the Fenton reaction, which involves reducing Fe with HO to form free hydroxyl molecules. These hydroxyl molecules react with the DNA backbone, resulting in a break. Due to their small size, the resulting DNA footprint has high resolution. Unlike DNase I they have no sequence dependence and result in a much more evenly distributed ladder. The negative aspect of using hydroxyl radicals is that they are more time consuming to use, due to a slower reaction and digestion time.
Ultraviolet irradiation can be used to excite nucleic acids and create photoreactions, which results in damaged bases in the DNA strand. Photoreactions can include: single strand breaks, interactions between or within DNA strands, reactions with solvents, or crosslinks with proteins. The workflow for this method has an additional step, once both your protected and unprotected DNA have been treated, there is subsequent primer extension of the cleaved products. The extension will terminate upon reaching a damaged base, and thus when the PCR products are run side-by-side on a gel; the protected sample will show an additional band where the DNA was crosslinked with a bound protein. Advantages of using UV are that it reacts very quickly and can therefore capture interactions that are only momentary. Additionally it can be applied to in vivo experiments, because UV can penetrate cell membranes. A disadvantage is that the gel can be difficult to interpret, as the bound protein does not protect the DNA, it merely alters the photoreactions in the vicinity. | 1 | Applied and Interdisciplinary Chemistry |
Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which increases the substance's temperature to the melting point. At the melting point, the ordering of ions or molecules in the solid breaks down to a less ordered state, and the solid melts to become a liquid.
Substances in the molten state generally have reduced viscosity as the temperature increases. An exception to this principle is elemental sulfur, whose viscosity increases in the range of 160 °C to 180 °C due to polymerization.
Some organic compounds melt through mesophases, states of partial order between solid and liquid. | 0 | Theoretical and Fundamental Chemistry |
Combustion of fuels produces sulfur dioxide and nitric oxides. They are converted into sulfuric acid and nitric acid. | 1 | Applied and Interdisciplinary Chemistry |
Ribulose 5-phosphate is one of the end-products of the pentose phosphate pathway. It is also an intermediate in the Calvin cycle.
It is formed by phosphogluconate dehydrogenase, and it can be acted upon by phosphopentose isomerase and phosphopentose epimerase.
In plants, Ribulose 5-phosphate produced from the pentose-phosphate pathway is converted into Ribulose-1-5-bisphosphate by the enzyme phosphoribokinase. | 1 | Applied and Interdisciplinary Chemistry |
Surficial processes are the physical and chemical phenomena which cause concentration of ore material within the regolith, generally by the action of the environment. This includes placer deposits, laterite deposits, and residual or eluvial deposits. Superficial deposits processes of ore formation include;
* Erosion of non-ore material.
* Deposition by sedimentary processes, including winnowing, density separation (e.g.; gold placers).
* Weathering via oxidation or chemical attack of a rock, either liberating rock fragments or creating chemically deposited clays, laterites, or supergene enrichment.
* Deposition in low-energy environments in beach environments.
* Sedimentary Exhalative Deposits (SEDEX), formed on the sea floor from metal-bearing brines. | 0 | Theoretical and Fundamental Chemistry |
ArcB consists of 778 amino acids. It is a multipass transmembrane protein that passes through the inner membrane twice. The majority of the secondary structure of ArcB is alpha helices; five alpha helices and one beta sheet. The two transmembrane portions of the protein are 20 amino acid long alpha helices that are both rich in hydrophobic amino acids. Amino acids 79-778 are cytoplasmic, 93% of the protein is cytoplasmic. Both the sensory and regulator regions of ArcB are present in this cytoplasmic domain.
ArcA consists of 238 amino acids. This is an oligomeric protein with two identical subunits; each subunit composed of 119 amino acids, five alpha helices, and six beta sheets. Amino acids 134-234 have the DNA binding domain which can activate or suppress gene expression. There are 76 DNA binding sites in the E. coli genome, however, ArcA directly regulates approximately 30 different operons. | 1 | Applied and Interdisciplinary Chemistry |
A still is an apparatus used to distill liquid mixtures by heating to selectively boil and then cooling to condense the vapor. A still uses the same concepts as a basic distillation apparatus, but on a much larger scale. Stills have been used to produce perfume and medicine, water for injection (WFI) for pharmaceutical use, generally to separate and purify different chemicals, and to produce distilled beverages containing ethanol. | 0 | Theoretical and Fundamental Chemistry |
In spark plasma sintering (SPS), external pressure and an electric field are applied simultaneously to enhance the densification of the metallic/ceramic powder compacts. However, after commercialization it was determined there is no plasma, so the proper name is spark sintering as coined by Lenel. The electric field driven densification supplements sintering with a form of hot pressing, to enable lower temperatures and taking less time than typical sintering. For a number of years, it was speculated that the existence of sparks or plasma between particles could aid sintering; however, Hulbert and coworkers systematically proved that the electric parameters used during spark plasma sintering make it (highly) unlikely. In light of this, the name "spark plasma sintering" has been rendered obsolete. Terms such as field assisted sintering technique (FAST), electric field assisted sintering (EFAS), and direct current sintering (DCS) have been implemented by the sintering community. Using a direct current (DC) pulse as the electric current, spark plasma, spark impact pressure, joule heating, and an electrical field diffusion effect would be created. By modifying the graphite die design and its assembly, it is possible to perform pressureless sintering in spark plasma sintering facility. This modified die design setup is reported to synergize the advantages of both conventional pressureless sintering and spark plasma sintering techniques. | 1 | Applied and Interdisciplinary Chemistry |
Several, so-called mTOR/PI3K dual inhibitors (TPdIs), have been developed and are in early-stage preclinical trials and show promising results. Their development has been benefited from previous studies with PI3K-selective inhibitors. The activity of these small molecules from rapalog activity differs in the way by blocking both mTORC1-dependent phospholylation of S6K1 and mTORC2-dependent phosphorylation of AKT Ser473 residue.
Dual mTOR/PI3K inhibitors include dactolisib, voxtalisib, BGT226, SF1126, PKI-587 and many more. For example, Novartis has developed the compound NVPBE235 that was reported to inhibit tumor growth in various preclinical models. It enhances antitumor activity of some other drugs such as vincristine. Dactolisib seems to inhibit effectively both wild-type and mutant form of PI3KCA, which suggests its use towards wide types of tumors. Studies have shown superior antiproliferative activity to rapalogs and in vivo models have confirmed these potent antineoplastic effects of dual mTOR/PI3K inhibitors. These inhibitors target isoforms of PI3K (p110α, β and γ) along with ATP-binding sites of mTORC1 and mTORC2 by blocking PI3K/AKT signaling, even in cancer types with mutations in this pathway. | 1 | Applied and Interdisciplinary Chemistry |
Published books by Moureu include:
* (doctoral thesis, Contribution to the study of acrylic acid and its derivatives)
* (The azoles, lecture delivered at the laboratory of Charles Friedel)
* (Theoretical study of pyridine compounds and hydropyridines)
* Translated into English as
* (Chemistry and war: science and the future)
* (Speeches and lectures on science and its applications)
Published papers include: | 0 | Theoretical and Fundamental Chemistry |
Pre-mRNAs from the D. melanogaster gene dsx contain 6 exons. In males, exons 1,2,3,5,and 6 are joined to form the mRNA, which encodes a transcriptional regulatory protein required for male development. In females, exons 1,2,3, and 4 are joined, and a polyadenylation signal in exon 4 causes cleavage of the mRNA at that point. The resulting mRNA is a transcriptional regulatory protein required for female development.
This is an example of exon skipping. The intron upstream from exon 4 has a polypyrimidine tract that doesnt match the consensus sequence well, so that U2AF proteins bind poorly to it without assistance from splicing activators. This 3 splice acceptor site is therefore not used in males. Females, however, produce the splicing activator Transformer (Tra) (see below). The SR protein Tra2 is produced in both sexes and binds to an ESE in exon 4; if Tra is present, it binds to Tra2 and, along with another SR protein, forms a complex that assists U2AF proteins in binding to the weak polypyrimidine tract. U2 is recruited to the associated branchpoint, and this leads to inclusion of exon 4 in the mRNA. | 1 | Applied and Interdisciplinary Chemistry |
1st generation ATP tests are derived from hygiene monitoring uses where samples are relatively free of interferences. 2nd Generation tests are specifically designed for water, wastewater and industrial applications where, for the most part, samples contain a variety of components that can interfere with the ATP assay. | 1 | Applied and Interdisciplinary Chemistry |
Oxygen evolution is the process of generating molecular oxygen (O) by a chemical reaction, usually from water. Oxygen evolution from water is effected by oxygenic photosynthesis, electrolysis of water, and thermal decomposition of various oxides. The biological process supports aerobic life. When relatively pure oxygen is required industrially, it is isolated by distilling liquefied air. | 0 | Theoretical and Fundamental Chemistry |
In general terms, the Maxwell Garnett EMA is expected to be valid at low volume fractions , since it is assumed that the domains are spatially separated and electrostatic interaction between the chosen inclusions and all other neighbouring inclusions is neglected. The Maxwell Garnett formula, in contrast to Bruggeman formula, ceases to be correct when the inclusions become resonant. In the case of plasmon resonance, the Maxwell Garnett formula is correct only at volume fraction of the inclusions . The applicability of effective medium approximation for dielectric multilayers and metal-dielectric multilayers have been studied, showing that there are certain cases where the effective medium approximation does not hold and one needs to be cautious in application of the theory. | 0 | Theoretical and Fundamental Chemistry |
In the pinacol rearrangement, a methyl group is found anti-periplanar to an activated alcohol functional group. This places the σ orbital of the methyl group parallel with the σ* orbital of the activated alcohol. Before the activated alcohol leaves as HO the methyl bonding orbital donates into the C–O antibonding orbital, weakening both bonds. This hyperconjugation facilitates the 1,2-methyl shift that occurs to remove water. See Figure 11 for the mechanism. | 0 | Theoretical and Fundamental Chemistry |
This article focuses on homoleptic complexes, which are simpler to describe and analyze. Most complexes of SCN, however are mixed ligand species. Mentioned above is one example, [Co(NH)(NCS)]. Another example is [OsCl(SCN)(NCS)]. Reinecke's salt, a precipitating agent, is a derivative of [Cr(NCS)(NH)]. | 0 | Theoretical and Fundamental Chemistry |
Hügelkultur is a German word meaning mound culture or hill culture. Though the technique is alleged to have been practiced in German and Eastern European societies for hundreds of years, the term was first published in a 1962 German gardening booklet by Herrman Andrä. Inspired by the diversity of plants growing in a pile of woody debris in his grandmothers garden, Andrä promoted "mound culture" as opposed to "flatland culture". This was also posited as an easy way to utilise woody debris without burning, which was illegal. Andrä appears to have been influenced by Rudolf Steiners biodynamic agriculture. Steiner explained his biodynamic philosophy as developed through meditation and clairvoyance, on the grounds that his methods were “true and correct unto themselves.” Andrä quotes a 1924 lecture on biodynamics by Steiner, which describes mixing of soil with composting or decaying material in earthen hillocks. Joined by author Hans Beba, another German gardener, "Hill Culture - the horticultural method of the future" was revised and republished several times in the 1970s and 1980s.
The technique was later adopted and developed by Sepp Holzer, an Austrian permaculture advocate. More recent permaculture advocates such as Paul Wheaton strongly promote Hügelkultur beds as a perfect permaculture design. | 1 | Applied and Interdisciplinary Chemistry |
A variety of ion channel blockers (inorganic and organic molecules) can modulate ion channel activity and conductance.
Some commonly used blockers include:
* Tetrodotoxin (TTX), used by puffer fish and some types of newts for defense. It blocks sodium channels.
* Saxitoxin is produced by a dinoflagellate also known as "red tide". It blocks voltage-dependent sodium channels.
* Conotoxin is used by cone snails to hunt prey.
* Lidocaine and novocaine belong to a class of local anesthetics which block sodium ion channels.
* Dendrotoxin is produced by mamba snakes, and blocks potassium channels.
* Iberiotoxin is produced by the Hottentotta tamulus (Eastern Indian scorpion) and blocks potassium channels.
* Heteropodatoxin is produced by Heteropoda venatoria (brown huntsman spider or laya) and blocks potassium channels. | 1 | Applied and Interdisciplinary Chemistry |
Electric sonic amplitude or electroacoustic sonic amplitude is an electroacoustic phenomenon that is the reverse to colloid vibration current. It occurs in colloids, emulsions and other heterogeneous fluids under the influence of an oscillating electric field. This field moves particles relative to the liquid, which generates ultrasound.
Electric sonic amplitude was experimentally discovered by Oja and co-authors in the early 1980s. It is also widely used for characterizing zeta potential in dispersions and emulsions. There is review of the theory of this effect, its experimental verification, and multiple applications published by Hunter. | 0 | Theoretical and Fundamental Chemistry |
Lithium is primarily used as a maintenance drug in the treatment of bipolar disorder to stabilize mood and prevent manic episodes, but it may also be helpful in the acute treatment of manic episodes. Although recommended by treatment guidelines for the treatment of depression in bipolar disorder, the evidence that lithium is superior to placebo for acute depression is low-quality; atypical antipsychotics are considered more effective for treating acute depressive episodes. Lithium carbonate treatment was previously considered to be unsuitable for children; however, more recent studies show its effectiveness for treatment of early-onset bipolar disorder in children as young as eight. The required dosage is slightly less than the toxic level (representing a low therapeutic index), requiring close monitoring of blood levels of lithium carbonate during treatment. Within the therapeutic range there is a dose response relationship. A limited amount of evidence suggests lithium carbonate may contribute to treatment of substance use disorders for some people with bipolar disorder. Although it is believed that lithium prevents suicide in people with bipolar disorder, a 2022 systematic review found that "Evidence from randomised trials is inconclusive and does not support the idea that lithium prevents suicide or suicidal behaviour." | 1 | Applied and Interdisciplinary Chemistry |
The LaMer model for the kinetics of the formation of hydrosols is widely applicable for production of monodisperse systems, and it was originally hypothesized that the Stöber process followed this monomer addition model. This model includes a rapid burst of nucleation forming all of the particle growth sites, then proceeds with hydrolysis as the rate-limiting step for condensation of triethylsilanol monomers to the nucleation sites. The production of monodisperse particle sizes is attributed to monomer addition happening at a slower rate on larger particles as a consequence of diffusion-limited mass transfer of TEOS. However, experimental evidence demonstrates that the concentration of hydrolyzed TEOS stays above that required for nucleation until late into the reaction, and the introduction of seeded growth nuclei does not match the kinetics of a monomer addition process. Consequently, the LaMer model has been rejected in favour of a kinetic model based around growth via particle aggregation.
Under an aggregation-based model, nucleation sites are continually being generated and absorbed where the merging leads to particle growth. The generation of the nucleation sites and the interaction energy between merging particles dictates the overall kinetics of the reaction. The generation of the nucleation sites follows the equation below:
Where J is the nucleation rate, k and k are rate constants based on the concentrations of HO and NH and g is the normalization factor based on the amount of silica precursor. Adjusting the concentration ratios of these compounds directly influences the rate at which nucleation sites are produced.
Merging of nucleation sites between particles is influenced by their interaction energies. The total interaction energy is dependent on three forces: electrostatic repulsion of like charges, vanderWaals attraction between particles, and the effects of solvation. These interaction energies (equations below) describe the particle aggregation process and demonstrate why the Stöber process produces particles that are uniform in size.
The van der Waals attraction forces are governed by the following equation:
Where A is the Hamaker constant, R is the distance between the centers of the two particles and a, a are the radii of the two particles. For electrostatic repulsion force the equation is as follows:
: where
Where ε is the dielectric constant of the medium, k is Boltzmanns constant, e is the elementary charge, T is the absolute temperature, κ is the inverse Debye length for a 1:1 electrolyte, x is the (variable) distance between the particles, and φ' is the surface potential. The final component of the total interaction energy is the solvation repulsion which is as follows:
Where A is the pre-exponential factor (1.5 × 10 J m) and L is the decay length (1 × 10 m).
This model for controlled growth aggregation fits with experimental observations from small-angle X-ray scattering techniques and accurately predicts particle sizing based on initial conditions. In addition, experimental data from techniques including microgravity analysis and variable pH analysis agree with predictions from the aggregate growth model. | 0 | Theoretical and Fundamental Chemistry |
Dissolved organic matter can be classified as labile or as recalcitrant, depending on its reactivity. Recalcitrant DOC is also called refractory DOC, and these terms seem to be used interchangeably in the context of DOC. Depending on the origin and composition of DOC, its behavior and cycling are different; the labile fraction of DOC decomposes rapidly through microbially or photochemically mediated processes, whereas refractory DOC is resistant to degradation and can persist in the ocean for millennia. In the coastal ocean, organic matter from terrestrial plant litter or soils appears to be more refractory and thus often behaves conservatively. In addition, refractory DOC is produced in the ocean by the bacterial transformation of labile DOC, which reshapes its composition.
Due to the continuous production and degradation in natural systems, the DOC pool contains a spectrum of reactive compounds each with their own reactivity, that have been divided into fractions from labile to recalcitrant, depending on the turnover times, as shown in the following table...
This wide range in turnover or degradation times has been linked with the chemical composition, structure and molecular size, but degradation also depends on the environmental conditions (e.g., nutrients), prokaryote diversity, redox state, iron availability, mineral-particle associations, temperature, sun-light exposure, biological production of recalcitrant compounds, and the effect of priming or dilution of individual molecules. For example, lignin can be degraded in aerobic soils but is relatively recalcitrant in anoxic marine sediments. This example shows bioavailability varies as a function of the ecosystem's properties. Accordingly, even normally ancient and recalcitrant compounds, such as petroleum, carboxyl-rich alicyclic molecules, can be degraded in the appropriate environmental setting. | 1 | Applied and Interdisciplinary Chemistry |
The worlds largest scale implementation of Fischer–Tropsch technology is a series of plants operated by Sasol in South Africa, a country with large coal reserves, but little oil. With a capacity of 165000 Bpd at its Secunda plant. The first commercial plant opened in 1952. Sasol uses coal and natural gas as feedstocks and produces a variety of synthetic petroleum products, including most of the countrys diesel fuel. | 0 | Theoretical and Fundamental Chemistry |
Surprisal analysis was extended to better characterize and understand cellular processes, see figure, biological phenomena and human disease with reference to personalized diagnostics. Surprisal analysis was first utilized to identify genes implicated in the balance state of cells in vitro; the genes mostly present in the balance state were genes directly responsible for the maintenance of cellular homeostasis. Similarly, it has been used to discern two distinct phenotypes during the EMT of cancer cells. | 0 | Theoretical and Fundamental Chemistry |
While the original effort failed to produce useful products, follow-on work in Europe did produce usable astronomical detectors
but without apparent use of this technology. In other areas, however, the approach seems to be competitive, with prior art for making various end-products, since it has been used as a fabrication step for experimental devices and structures. Many groups have used the approach to grow homoepitaxial diamond and subsequently release the thin-films with a variety of "lift-off" processes.
It has also been considered in contexts such as carbon microelectromechanical systems production and different materials applications, for example with non-contacted palladium deposition and extensions. While not citing Marchywka et al.'s original paper, these continue to cite non-contactedness as a feature,
"The electrode assembly and the conductive surface may be positioned in close proximity to, but without contacting, one another". references a much earlier patent covering related attempts to achieve non-contacted electro-etching, "The present invention relates to a method of and apparatus for electrochemically processing metallic surfaces of workpieces arranged in a contact-free manner with regard to the cathode and anode[...]."
The effect has been mentioned in passing with regard to novel devices such
as quantum coherent devices while patents on emerging uses for amorphous carbon
and
diamond thermal conductors by manufacturers of high density electronic chips reference the related lift-off technology. | 0 | Theoretical and Fundamental Chemistry |
After his Berlin, Dresden and New York years, Zervas decided to return to Greece in 1937. He was immediately appointed full Professor of Organic Chemistry and Biochemistry at the Aristotle University of Thessaloniki in recognition of his distinguished international work. He stayed in this position until 1939, when he was invited to the Professorship of Organic Chemistry at the University of Athens and also appointed director of the Laboratory of Organic Chemistry of the same institution. He continued conducting research, despite the severe limitations he often faced from the lack of equipment and funding. Concurrent to research, Zervas taught organic chemistry, oversaw the laboratory and guided many generations of young chemists as doctoral advisor for the 29 years he held the post at the University of Athens.
During the Axis occupation of Greece Zervas played an active part in the Greek Resistance as a member of EDES; he was imprisoned twice, first by the Italian and then by the German occupying forces, and his laboratory was destroyed. Following the liberation of Greece, Zervas managed to secure a small part of the American postwar aid for repairs in the University of Athens and the Athens Polytechnic, and thus rebuilt his laboratory in 1948–1951.
In the following years, guided by a sense of personal and professional duty, Zervas voluntarily took on a variety of responsibilities within the Greek state. At his own insistence, he never got paid for these posts and kept receiving only his professorial salary. Some notable positions he held in chronological order until 1968 include:
*Member of the State Committee on Vocational Education (1948–1951)
*Member of numerous committees for the foundation of new industries in postwar Greece (throughout the 1950s)
*First Vice-President of the National Hellenic Research Foundation (1958–1968), of which he was a key founder
*Minister of Industry in the Paraskevopoulos technocratic caretaker government (1963–1964)
*President of the Greek Atomic Energy Commission (1964–1965)
The democratic ideals of Zervas made him a target of the military junta established in 1967, which removed him from his position in the University of Athens in 1968 after almost three decades of dedicated research and teaching. In response, the Academy of Athens of which Zervas had been a member since 1956 elected him as its president in 1970. After his term as President of the Academy, Zervas retired in 1971. | 0 | Theoretical and Fundamental Chemistry |
Water, oil and gas from a well often contain radon. The radon decays to form solid radioisotopes which form coatings on the inside of pipework. In an oil processing plant the area of the plant where propane is processed is often one of the more contaminated areas of the plant as radon has a similar boiling point to propane. | 0 | Theoretical and Fundamental Chemistry |
The Condylostoma nuclear code (translation table 28) is a genetic code used by the nuclear genome of the heterotrich ciliate Condylostoma magnum. This code, along with translation tables 27 and 31, is remarkable in that every one of the 64 possible codons can be a sense codon. Experimetnal evidence suggests that translation termination relies on context, specifically proximity to the poly(A) tail. Near such a tail, PABP could help terminate the protein by recruiting eRF1 and eRF3 to prevent the cognate tRNA from binding. | 1 | Applied and Interdisciplinary Chemistry |
The Woltman meter (invented by Reinhard Woltman in the 19th century) comprises a rotor with helical blades inserted axially in the flow, much like a ducted fan; it can be considered a type of turbine flowmeter. They are commonly referred to as helix meters, and are popular at larger sizes. | 1 | Applied and Interdisciplinary Chemistry |
Barley yellow dwarf virus 5' UTR is a non-coding RNA element containing structural elements required for translation of the genome of the plant disease pathogen Barley yellow dwarf virus.
Unlike eukaryotic mRNA, this virus lacks a 5 cap and a poly(A) tail but still circularises its mRNA through base pairing between two stem loops, one located in the 5 untranslated region (UTR) and the other within the 3 UTR. The structure within the 3 UTR has been previously characterised as the 3 cap-independent translation element (3 TE element) and the 5 UTR of barley yellow dwarf virus has been predicted to contain 4 stem loop structures. Mutagenesis showed that stem loop 4 is essential for base pairing with 3TE and only 5 bases are needed to base pair for mRNA circularization to occur. | 1 | Applied and Interdisciplinary Chemistry |
Lise Meitner ( , ; born Elise Meitner, 7 November 1878 – 27 October 1968) was an Austrian-Swedish physicist who was one of those responsible for the discovery of the element protactinium and nuclear fission. While working on radioactivity at the Kaiser Wilhelm Institute of Chemistry in Berlin, she discovered the radioactive isotope protactinium-231 in 1917. In 1938, Meitner and her nephew, the physicist Otto Robert Frisch, discovered nuclear fission. She was praised by Albert Einstein as the "German Marie Curie".
Completing her doctoral research in 1905, Meitner became the second woman from the University of Vienna to earn a doctorate in physics. She spent most of her scientific career in Berlin, Germany, where she was a physics professor and a department head at the Kaiser Wilhelm Institute; she was the first woman to become a full professor of physics in Germany. She lost these positions in the 1930s because of the anti-Jewish Nuremberg Laws of Nazi Germany, and in 1938 she fled to Sweden, where she lived for many years, ultimately becoming a Swedish citizen.
In mid-1938, Meitner with chemists Otto Hahn and Fritz Strassmann at the Kaiser Wilhelm Institute found that bombarding thorium with neutrons produced different isotopes. Hahn and Strassmann later in the year showed that isotopes of barium could be formed by bombardment of uranium. In late December, Meitner and Frisch worked out the physics of such a splitting process. In their report in February issue of Nature in 1939, they gave it the name "fission". This principle led to the development of the first atomic bomb during World War II, and subsequently other nuclear weapons and nuclear reactors.
Meitner did not share the 1944 Nobel Prize in Chemistry for nuclear fission, which was awarded exclusively to her long-time collaborator Otto Hahn. Several scientists and journalists have called her exclusion "unjust". According to the Nobel Prize archive, she was nominated 19 times for the Nobel Prize in Chemistry between 1924 and 1948, and 30 times for the Nobel Prize in Physics between 1937 and 1967. Despite not having been awarded the Nobel Prize, Meitner was invited to attend the Lindau Nobel Laureate Meeting in 1962. She received many other honours, including the naming of chemical element 109 meitnerium in 1997 after her death. | 1 | Applied and Interdisciplinary Chemistry |
The Mg(I) dimer formula, LMgMgL, has undergone multiple theoretical investigations regarding the bonds. Furthermore, L, a monoanionic ligand, can also include halides, hydrogen, small alkyl groups, aryl groups, cyclopentadienyl with respective derivatives and chelating monoanionic nitrogen ligands. Mg—Mg bonded molecules underwent the primary investigation, with the bond length found to be 2.76-2.89 Å. Additionally, the bond dissociation energy was found to be between 45 and 48 kcal mol. Specifically, for ClMgMgCl, it was found to be 47.1 kcal mol. | 0 | Theoretical and Fundamental Chemistry |
CHNOPS and CHON are mnemonic acronyms for the most common elements in living organisms. "CHON" stands for carbon, hydrogen, oxygen, and nitrogen, which together make up more than 95 percent of the mass of biological systems. "CHNOPS" adds phosphorus and sulfur. | 1 | Applied and Interdisciplinary Chemistry |
Turbidity currents are often triggered by tectonic disturbances of the sea floor. The displacement of continental crust in the form of fluidization and physical shaking both contribute to their formation. Earthquakes have been linked to turbidity current deposition in many settings, particularly where physiography favors preservation of the deposits and limits the other sources of turbidity current deposition. Since the famous case of breakage of submarine cables by a turbidity current following the 1929 Grand Banks earthquake, earthquake triggered turbidites have been investigated and verified along the Cascadia subduction Zone, the Northern San Andreas Fault, a number of European, Chilean and North American lakes, Japanese lacustrine and offshore regions and a variety of other settings. | 1 | Applied and Interdisciplinary Chemistry |
Certain amphiphilic block copolymer micelles display a similar behavior as surfactant micelles. These are generally called dynamic micelles and are characterized by the same relaxation processes assigned to surfactant exchange and micelle scission/recombination. Although the relaxation processes are the same between the two types of micelles, the kinetics of unimer exchange are very different. While in surfactant systems the unimers leave and join the micelles through a diffusion-controlled process, for copolymers the entry rate constant is slower than a diffusion controlled process. The rate of this process was found to be a decreasing power-law of the degree of polymerization of the hydrophobic block to the power 2/3. This difference is due to the coiling of the hydrophobic block of a copolymer exiting the core of a micelle.
Block copolymers which form dynamic micelles are some of the tri-block poloxamers under the right conditions. | 0 | Theoretical and Fundamental Chemistry |
Many of the byproducts produced in the processing of microalgae can be used in various applications, many of which have a longer history of production than algal biofuel. Some of the products not used in the production of biofuel include natural dyes and pigments, antioxidants, and other high-value bio-active compounds. These chemicals and excess biomass have found numerous use in other industries. For example, the dyes and oils have found a place in cosmetics, commonly as thickening and water-binding agents. Discoveries within the pharmaceutical industry include antibiotics and antifungals derived from microalgae, as well as natural health products, which have been growing in popularity over the past few decades. For instance Spirulina contains numerous polyunsaturated fats (Omega 3 and 6), amino acids, and vitamins, as well as pigments that may be beneficial, such as beta-carotene and chlorophyll. | 1 | Applied and Interdisciplinary Chemistry |
Cobalt chloride is fairly soluble in water. Under atmospheric pressure, the mass concentration of a saturated solution of in water is about 54% at the boiling point, 120.2 °C; 48% at 51.25 °C; 35% at 25 °C; 33% at 0 °C; and 29% at −27.8 °C.
Diluted aqueous solutions of contain the species , besides chloride ions. Concentrated solutions are red at room temperature but become blue at higher temperatures. | 0 | Theoretical and Fundamental Chemistry |
* Kai genes – Found in the Synechococcus elongatus, these genes are essential components of the cyanobacterium clock, the leading example of bacterial circadian rhythms. Kai proteins regulate genome wide gene expression. The oscillation of phosphorylation and dephosphorylation of KaiC acts as the pacemaker of the circadian clock. | 1 | Applied and Interdisciplinary Chemistry |
A mixing chamber where a mechanical agitator brings in intimate contact the feed solution and the solvent to carry out the transfer of solute(s). The mechanical agitator is equipped with a motor which drives a mixing and pumping turbine. This turbine draws the two phases from the settlers of the adjacent stages, mixes them, and transfers this emulsion to the associated settler.
The mixer may consists of one or multiple stages of mixing tanks. Common laboratory mixers consist of a single mixing stage, whereas industrial scale copper mixers may consist of up to three mixer stages where each stage performs a combined pumping and mixing action. Use of multiple stages allows a longer reaction time and also minimizes the short circuiting of unreacted material through the mixers. | 0 | Theoretical and Fundamental Chemistry |
The crystal structures of the THF complexes of the Reformatsky reagents tert-butyl bromozincacetate and ethyl bromozincacetate have been determined. Both form cyclic eight-membered dimers in the solid state, but differ in stereochemistry: the eight-membered ring in the ethyl derivative adopts a tub-shaped conformation and has cis bromo groups and cis THF ligands, whereas in the tert-butyl derivative, the ring is in a chair form and the bromo groups and THF ligands are trans. Note that, in contrast to lithium and boron enolates, which have the metal(loid)s exclusively bond to oxygen, the zinc enolate moiety in the Reformatsky reagents have zinc atoms that are simultaneously O- and C-bound and can therefore be described as "organometallic". | 0 | Theoretical and Fundamental Chemistry |
Rhizofiltration is the adsorption and precipitation of radionuclides in plant roots or absorption thereof if soluble in effluents. It has great efficiency in the treatment of cesium-137 and strontium-90, particularly by algae and aquatic plants, such as Cladophora and Elodea genera, respectively. It is the most efficient strategy for bioremediation technologies in wetlands, but must have a continuous and rigorous control of pH to make it an optimal process.
From this process, some strategies have been designed based on sequences of ponds with a slow flow of water to clean polluted water with radionuclides. The results of these facilities, for flows of 1000 liters of effluent are about 95% retention of radiation in the first pond (by plants and sludge), and over 99% in three-base systems.
The most promising plants for rhizofiltration are sunflowers. They are able to remove up to 95% of uranium of contaminated water in 24 hours, and experiments in Chernobyl have demonstrated that they can concentrate on 55 kg of plant dry weight all the cesium and strontium radioactivity from an area of 75 m (stabilized material suitable for transfer to a nuclear waste repository). | 1 | Applied and Interdisciplinary Chemistry |
Ochir has been a professor at the Mongolian University of Science and Technology since 1965. She held the positions of assistant professor, associate professor and professor, teaching courses in petrology and petrography. She served as the head of the universitys Department of Geology and Mineralogy from 1978 to 2009. She has also served as Director of the universitys Geoscience Center since 2001.
Ochir has carried out field and basic research work through joint expeditions of the Russian and Mongolian Academies of Sciences. She is the author of over 350 scientific publications and was the lead editor of the book Mineral Resources of Mongolia.
Ochir served as vice president of the International Union of Geological Sciences for four years. She is an adjunct professor at the Institute of Mineral Resources of the Chinese Academy of Geological Sciences and a foreign member of the Russian Academy of Natural Sciences.
Ochir is an Honoured Scientist of Mongolia. She was presented with the Jan Masaryk Medal by the Czech Ambassador in 2021. | 0 | Theoretical and Fundamental Chemistry |
A detailed mechanism for the Murai reaction has not been elucidated. Experimental and computational studies give evidence for at least two different mechanisms, depending on the catalyst. For catalysts such as [Ru(H)(CO)(PR)] which are active as Ru, a combination of computational density functional studies and experimental evidence has resulted in the following proposed mechanism:
It is proposed that at high temperatures RuH(CO)(PPh) converts to an unsaturated Ru(CO)(PPh) species. The catalytic cycle is proposed to begins with coordination of the ketone followed by oxidative addition of a C-H bond. The resulting five-coordinated metallocycle is stabilized by an agostic interaction. The C-C bond formation is the rate limiting step. | 0 | Theoretical and Fundamental Chemistry |
Surfactant production in humans begins in type II cells during the alveolar sac stage of lung development. Lamellar bodies appear in the cytoplasm at about 20 weeks gestation. These lamellar bodies are secreted by exocytosis into the alveolar lining fluid, where the surfactant forms a meshwork of tubular myelin Full term infants are estimated to have an alveolar storage pool of approximately 100 mg/kg of surfactant, while preterm infants have an estimated 4–5 mg/kg at birth.
Club cells also produce a component of lung surfactant.
Alveolar surfactant has a half-life of 5 to 10 hours once secreted. It can be both broken down by macrophages and/or reabsorbed into the lamellar structures of type II pneumocytes. Up to 90% of surfactant DPPC (dipalmitoylphosphatidylcholine) is recycled from the alveolar space back into the type II pneumocyte. This process is believed to occur through SP-A stimulating receptor-mediated, clathrin dependent endocytosis. The other 10% is taken up by alveolar macrophages and digested. | 0 | Theoretical and Fundamental Chemistry |
Scientists have developed air pollution dispersion models to evaluate the concentration of a pollutant at a receptor or the impact on overall air quality from vehicle exhausts and industrial flue gas stack emissions. To some extent, this field overlaps the desire to decrease carbon dioxide and other greenhouse gas emissions from combustion processes. | 1 | Applied and Interdisciplinary Chemistry |
CK1δ and CK1ε have been shown to be relevant in human disease. Recent findings indicate that pharmaceutical inhibition of CK1 may be a promising therapeutic for aberrant circadian rhythm. Mutations and variants of the CK1ε phosphorylation site of PER2 are associated with cases of Familial Advanced Sleep Phase Syndrome (FASPS). Similarly, length variations in the CK1ε phosphorylation site of PER3 have been found to correlate with morningness and eveningness; longer alleles are associated with early risers while shorter alleles are associated with late risers. Additionally, 75% of patients with Delayed sleep phase syndrome are homozygous for the shorter allele.
Mutations in CK1 have been shown to alter circadian behavior in other mammals, as well. In 1988, the golden hamster tau mutant, which has a freerunning period of 22hrs, was the first mammalian circadian mutant discovered. Twelve years later in 2000, the tau mutation was mapped to CK1ε. Since its discovery, the tau mutant has proven to be a valuable research tool in circadian biology. CK1ɛ, a T178C substitution, is a gain-of function mutation that causes an increase in degradation of PER, but not CRY. This creates a disruption in the PER-regulated feedback loop and consequently an acceleration of molecular oscillations. Homozygous mutants (CK1ε(tau/tau)) show a significant decrease in period, both in vivo (behaviorally) and in vitro (measured by firing rates of the suprachiasmatic nucleus). Recent research has also identified a link between mutations in the CK1δ gene and familial migraine and advanced sleep phase, a finding that was replicated in mice migraine models. | 1 | Applied and Interdisciplinary Chemistry |
On Mars, Xe isotopes in the present atmosphere are mass fractionated relative to their primordial composition from in situ measurement of the Curiosity Rover at Gale Crater, Mars. Paleo-atmospheric Xe trapped in the Martian regolith breccia NWA 11220 is mass-dependently fractionated relative to solar Xe by ~16.2‰. The extent of fractionation is comparable for Mars and Earth, which may be compelling evidence that hydrodynamic escape also occurred in the Mars history. The regolith breccia NWA7084 and the >4 Ga orthopyroxene ALH84001 Martian meteorites trap ancient Martian atmospheric gases with little if any Xe isotopic fractionation relative to modern Martian atmospheric Xe. Alternative models for Mars consider that the isotopic fractionation and escape of Mars atmospheric Xe occurred very early in the planet's history and ceased around a few hundred million years after planetary formation rather than continuing during its evolutionary history | 0 | Theoretical and Fundamental Chemistry |
In situ thermal desorption (ISTD) is an intensive thermally enhanced environmental remediation technology that uses thermal conductive heating (TCH) elements to directly transfer heat to environmental media. The ISTD/TCH process can be applied at low (<100 °C), moderate (~100 °C) and higher (>100 °C) temperature levels to accomplish the remediation of a wide variety of contaminants, both above and below the water table. ISTD/TCH is the only major in situ thermal remediation (ISTR) technology capable of achieving subsurface target treatment temperatures above the boiling point of water and is effective at virtually any depth in almost any media. TCH works in tight soils, clay layers, and soils with wide heterogeneity in permeability or moisture content that are impacted by a broad range of volatile and semi-volatile organic contaminants. | 1 | Applied and Interdisciplinary Chemistry |
NMR spectroscopy has been utilized for the analysis of biological samples since the 1980s, and can be used as an effective technique for the identification and quantification of both known and unknown metabolites. For details on the principles of this technique, see NMR spectroscopy. In pharmacometabolomics analyses, NMR is advantageous because minimal sample preparation is required. Isolated patient samples typically include blood or urine due to their minimally-invasive acquisition, however, other fluid types and solid tissue samples have also been studied with this approach. Due to the minimal preparation of samples before analysis, samples can be potentially fully recovered following NMR analysis (If samples are kept refrigerated to avoid degradation). This permits samples to be repeatedly analysed with extremely high levels of reproducibility, as well as maintaining precious patient samples for an alternative analysis. The high reproducibility and precision of NMR, coupled with relatively fast processing time (greater than 100 samples per day), makes this process a relatively high-throughput form of sample analysis. One disadvantage of this technique is the relatively poor metabolite detection sensitivity compared to MS-based analysis, leading to a requirement for greater initial sample volume. Furthermore, the initial instrument costs are extremely high, for both NMR and MS equipment. | 1 | Applied and Interdisciplinary Chemistry |
A solution of sulfur tetrafluoride in hydrogen fluoride converts hydroxy-containing amino acids to the fluoro amino acids:
When vicinal diols are combined with SF, difluorination occurs with inversion of configuration at only one of the alcohols. This was demonstrated in the synthesis of meso-difluorosuccinate from (L)-tartrate and the synthesis of (D)- and (L)-difluorosuccinate from meso-tartrate.
Carbonyl compounds generally react with SF to yield geminal difluorides. Reaction times tend to be on the order of hours and yields are moderate. Fluorination of lactones can provide heterocyclic fluorides, although ring opening has been observed for γ-butyrolactone. The six-membered lactide does not experience ring opening.
Fluorination opens epoxides to give either geminal or vicinal difluorides in most cases. Monoarylepoxides give geminal products with migration of the aryl group. Yields are low for sterically hindered di- and trisubstituted epoxides. Epoxides substituted with an ester group give vicinal difluorides via an alkoxysulfur trifluoride intermediate.
Carboxylic acids react with SF to afford trifluoromethyl compounds:
The formation of the trifluoromethyl derivative sometimes competes with formation of tetrafluoroalkyl ethers, which arise from the reaction between difluoromethyl cation and acyl fluoride.
Sulfur tetrafluoride can be used to fluorinate polymers efficiently. This often has a profound effect on polymer properties—fluorination of polyvinyl alcohol, for instance, improves its resistance to strong acids and bases.
A prostaglandin bearing a trifluoromethyl group at C-16 is prepared using sulfur tetrafluoride. | 0 | Theoretical and Fundamental Chemistry |
There are many advantages to using a proton beam over an electron beam. There is less crystal charging from Bremsstrahlung radiation, although there is some from the emission of Auger electrons, and there is significantly less than if the primary beam was itself an electron beam.
Because of the higher mass of protons relative to electrons, there is less lateral deflection of the beam; this is important for proton beam writing applications. | 0 | Theoretical and Fundamental Chemistry |
Carbon in pulp (CIP) is an extraction technique for recovery of gold which has been liberated into a cyanide solution as part of the gold cyanidation process.
Introduced in the early 1980s, Carbon in Pulp is regarded as a simple and cheap process. As such it is used in most industrial applications where the presence of competing silver or copper does not prohibit its use. In the case of high (i.e., 1%) copper content, froth flotation is more typical.
Activated carbon acts like a sponge to dicyanoaurate, the main soluble gold species in gold extraction technologies. Hard carbon particles (much larger than the ore particle sizes) can be mixed with the solution. The gold cyanide complex adsorb onto the carbon and is proposed to be reduced back to the metal. Because the carbon particles are much larger than the ore particles, the coarse carbon can then be separated from the slurry by screening using a wire mesh. | 1 | Applied and Interdisciplinary Chemistry |
Mitogen-activated protein kinase (MAPK) networks are the pathways and signaling of MAPK, which is a protein kinase that consists of amino acids serine and threonine. MAPK pathways have both a positive and negative regulation in plants. A positive regulation of MAPK networks is to help in assisting with stresses from the environment. A negative regulation of MAPK networks is pertaining to a high quantity of reactive oxygen species (ROS) in the plant. | 1 | Applied and Interdisciplinary Chemistry |
By the time he was a teenager, Scheele had learned the dominant theory of gases which in the 1770s was the phlogiston theory. Phlogiston, classified as "matter of fire", was supposed to be released from any burning material, and when it was exhausted, combustion would stop. When Scheele discovered oxygen he called it "fire air" as it supported combustion. Scheele explained oxygen using phlogistical terms because he did not believe that his discovery disproved the phlogiston theory.
Before Scheele made his discovery of oxygen, he studied air. Air was thought to be an element that made up the environment in which chemical reactions took place but did not interfere with the reactions. Scheele's investigation of air enabled him to conclude that air was a mixture of "fire air" and "foul air;" in other words, a mixture of two gases. Scheele performed numerous experiments in which he heated substances such as saltpetre (potassium nitrate), manganese dioxide, heavy metal nitrates, silver carbonate and mercuric oxide. In all of these experiments, he isolated the same gas: his "fire air," which he believed combined with phlogiston in materials to be released during heat-releasing reactions.
However, his first publication, Chemische Abhandlung von der Luft und dem Feuer, was delivered to the printer Swederus in 1775, but not published until 1777, at which time both Joseph Priestley and Antoine Lavoisier had already published their experimental data and conclusions concerning oxygen and the phlogiston theory. Carl was credited for finding oxygen with two other people, Joseph Priestley and Antoine Lavoisier. The first English edition, Chemical Observation and Experiments on Air and Fire was published in 1780, with an introduction "Chemical Treatise on Air and Fire". | 1 | Applied and Interdisciplinary Chemistry |
Spectrophotometry is a tool that hinges on the quantitative analysis of molecules depending on how much light is absorbed by colored compounds. Important features of spectrophotometers are spectral bandwidth (the range of colors it can transmit through the test sample), the percentage of sample transmission, the logarithmic range of sample absorption, and sometimes a percentage of reflectance measurement.
A spectrophotometer is commonly used for the measurement of transmittance or reflectance of solutions, transparent or opaque solids, such as polished glass, or gases. Although many biochemicals are colored, as in, they absorb visible light and therefore can be measured by colorimetric procedures, even colorless biochemicals can often be converted to colored compounds suitable for chromogenic color-forming reactions to yield compounds suitable for colorimetric analysis. However, they can also be designed to measure the diffusivity on any of the listed light ranges that usually cover around 200–2500 nm using different controls and calibrations. Within these ranges of light, calibrations are needed on the machine using standards that vary in type depending on the wavelength of the photometric determination.
An example of an experiment in which spectrophotometry is used is the determination of the equilibrium constant of a solution. A certain chemical reaction within a solution may occur in a forward and reverse direction, where reactants form products and products break down into reactants. At some point, this chemical reaction will reach a point of balance called an equilibrium point. To determine the respective concentrations of reactants and products at this point, the light transmittance of the solution can be tested using spectrophotometry. The amount of light that passes through the solution is indicative of the concentration of certain chemicals that do not allow light to pass through.
The absorption of light is due to the interaction of light with the electronic and vibrational modes of molecules. Each type of molecule has an individual set of energy levels associated with the makeup of its chemical bonds and nuclei and thus will absorb light of specific wavelengths, or energies, resulting in unique spectral properties. This is based upon its specific and distinct makeup.
The use of spectrophotometers spans various scientific fields, such as physics, materials science, chemistry, biochemistry, chemical engineering, and molecular biology. They are widely used in many industries including semiconductors, laser and optical manufacturing, printing and forensic examination, as well as in laboratories for the study of chemical substances. Spectrophotometry is often used in measurements of enzyme activities, determinations of protein concentrations, determinations of enzymatic kinetic constants, and measurements of ligand binding reactions. Ultimately, a spectrophotometer is able to determine, depending on the control or calibration, what substances are present in a target and exactly how much through calculations of observed wavelengths.
In astronomy, the term spectrophotometry refers to the measurement of the spectrum of a celestial object in which the flux scale of the spectrum is calibrated as a function of wavelength, usually by comparison with an observation of a spectrophotometric standard star, and corrected for the absorption of light by the Earth's atmosphere. | 0 | Theoretical and Fundamental Chemistry |
Solar cells are electrical devices that convert sunlight to electricity. However, due to the properties of the materials composing solar cells, many solar cells do not harvest low energy (with wavelength above 800 nm) photons efficiently. Thus, the ability for TTA-UC materials to combine the energy of two low energy photons into one high energy photon is desirable to capture more of the energy from sunlight. | 0 | Theoretical and Fundamental Chemistry |
In physics and mathematics, the Clebsch representation of an arbitrary three-dimensional vector field is:
where the scalar fields and are known as Clebsch potentials or Monge potentials, named after Alfred Clebsch (1833–1872) and Gaspard Monge (1746–1818), and is the gradient operator. | 1 | Applied and Interdisciplinary Chemistry |
Laboratory magnetometers measure the magnetization, also known as the magnetic moment of a sample material. Unlike survey magnetometers, laboratory magnetometers require the sample to be placed inside the magnetometer, and often the temperature, magnetic field, and other parameters of the sample can be controlled. A sample's magnetization, is primarily dependent on the ordering of unpaired electrons within its atoms, with smaller contributions from nuclear magnetic moments, Larmor diamagnetism, among others. Ordering of magnetic moments are primarily classified as diamagnetic, paramagnetic, ferromagnetic, or antiferromagnetic (although the zoology of magnetic ordering also includes ferrimagnetic, helimagnetic, toroidal, spin glass, etc.). Measuring the magnetization as a function of temperature and magnetic field can give clues as to the type of magnetic ordering, as well as any phase transitions between different types of magnetic orders that occur at critical temperatures or magnetic fields. This type of magnetometry measurement is very important to understand the magnetic properties of materials in physics, chemistry, geophysics and geology, as well as sometimes biology. | 0 | Theoretical and Fundamental Chemistry |
These planar defects are similar to stacking faults in that they are often created through slip of atomic planes and dislocation motion, but the degree of translation varies. In stacking faults, the region of stacking mismatch is bounded by two partial dislocations, and an extended dislocation is formed. For anti-phase domains which only exhibit chemical disorder, the region is bounded by two complex stacking faults, which exhibit both stacking and chemical disorder. Thus, it takes 4 partial dislocations to fully restore the order of the crystal. These can be seen in Figure 1 and 2 below. The width of these regions is determined by the force balance between the like-signed partial dislocations’ repulsion and the regions surface energy. As the anti-phase boundary surface energy increases, the degree of separation between the partial dislocations will decrease to compensate.
Figure 1: This figure depicts two layers of atoms in a Ni3Al crystal, a binary alloy that often exhibits anti-phase boundaries. For visualization purposes, the atoms in the bottom layer are shown as larger than the top layer, but this is not actually the case. The translation of the top layer can be broken down into two steps, indicated by the small arrows 1 and 2. (b) The partial sliding of the top layer by the short vector 1 leads to the formation of a complex stacking fault. (c) The complete sliding of the top layer with the translation magnitude given by a unit lattice translation (1+2), resulting in the formation of an anti-phase boundary. If the top plane slips by two complete lattice spacings (1, 2, 3, and 4), a superdislocation is formed, and this is required for the perfect crystal structure to be restored. It is expected that this superdislocation, consisting of two perfect lattice translations, dissociates into four different partial dislocations with two on each side.
Figure 2: An antiphase boundary created by four partial dislocations (1,2,3,4), surrounded by complex stacking faults. Outside of these shaded regions, the crystal is perfect. | 0 | Theoretical and Fundamental Chemistry |
Heparin cofactor II (HCII), a protein encoded by the SERPIND1 gene, is a coagulation factor that inhibits IIa, and is a cofactor for heparin and dermatan sulfate ("minor antithrombin").
The product encoded by this gene is a serine protease inhibitor which rapidly inhibits thrombin in the presence of dermatan sulfate or heparin. The gene contains five exons and four introns. This protein shares homology with antithrombin III and other members of the alpha-1 antitrypsin superfamily. Mutations in this gene are associated with heparin cofactor II deficiency. Heparin cofactor II deficiency can lead to increased thrombin generation and a hypercoagulable state.
A purification experiment of heparin cofactor II was performed in 1981, in which it was discovered that the purified version of the protein consists of a single polypeptide chain. Further experimentation demonstrated that whether β-Mercaptoethanol is present does not affect HCII's activity in gel electrophoresis. β-Mercaptoethanol is typically used for the reduction of disulfide bonds within a molecule, but the gel electrophoresis revealed that HCII does not have any of these bonds. The structure is similar to antithrombin III (ATIII), which was known to effectively inhibit thrombin as well as coagulation factor X. This experiment suggested that HCII has strong thrombin inhibition, yet weak inhibition of coagulation factor X.
Heparin cofactor II may play a role in the immune response, as it has been associated with leukocyte-mediated protein degradation, which releases cytokines in the inflammatory response with neutrophils and monocytes. Its role has been questioned because although it is a thrombin inhibitor, an absence of HCII does not result in significantly higher levels of thrombosis. This does not negate the results of the 1981 study, but novel discoveries create more questions of the biological mechanism and function of the protein. However, this cofactor shows stronger capability in inhibiting thrombin in pregnant women, protecting them from thrombosis. Pregnant women have shown increased levels of heparin cofactor II as well as dermatan sulfate, which is a polysaccharide that is expected to be involved in wound repair, coagulation, and overall maintenance throughout the body. Pregnant women who had thrombosis are likely to also have low levels of heparin cofactor II, but whether this is a causation is still unknown. | 1 | Applied and Interdisciplinary Chemistry |
For a network consisting of a high density of random resistors, an exact solution for each individual element may be impractical or impossible. In such case, a random resistor network can be considered as a two-dimensional graph and the effective resistance can be modelled in terms of graph measures and geometrical properties of networks.
Assuming, edge length is much less than electrode spacing and edges to be uniformly distributed, the potential can be considered to drop uniformly from one electrode to another.
Sheet resistance of such a random network () can be written in terms of edge (wire) density (), resistivity (), width () and thickness () of edges (wires) as: | 0 | Theoretical and Fundamental Chemistry |
Mass cytometry is a mass spectrometry technique based on inductively coupled plasma mass spectrometry and time of flight mass spectrometry used for the determination of the properties of cells (cytometry). In this approach, antibodies are conjugated with isotopically pure elements, and these antibodies are used to label cellular proteins. Cells are nebulized and sent through an argon plasma, which ionizes the metal-conjugated antibodies. The metal signals are then analyzed by a time-of-flight mass spectrometer. The approach overcomes limitations of spectral overlap in flow cytometry by utilizing discrete isotopes as a reporter system instead of traditional fluorophores which have broad emission spectra. | 0 | Theoretical and Fundamental Chemistry |
Methylphenidate is a catecholamine reuptake inhibitor that indirectly increases catecholaminergic neurotransmission by inhibiting the dopamine transporter (DAT) and norepinephrine transporter (NET), which are responsible for clearing catecholamines from the synapse, particularly in the striatum and meso-limbic system. Moreover, it is thought to "increase the release of these monoamines into the extraneuronal space."
Although four stereoisomers of methylphenidate (MPH) are possible, only the threo diastereoisomers are used in modern practice. There is a high eudysmic ratio between the SS and RR enantiomers of MPH. Dexmethylphenidate (d-threo-methylphenidate) is a preparation of the RR enantiomer of methylphenidate. In theory, D-TMP (d-threo-methylphenidate) can be anticipated to be twice the strength of the racemic product. | 0 | Theoretical and Fundamental Chemistry |
In functional analysis a Reynolds operator is a linear operator R acting on some algebra of functions φ, satisfying the Reynolds identity
The operator R is called an averaging operator if it is linear and satisfies
If R(R(φ)) = R(φ) for all φ then R is an averaging operator if and only if it is a Reynolds operator. Sometimes the R(R(φ)) = R(φ) condition is added to the definition of Reynolds operators. | 1 | Applied and Interdisciplinary Chemistry |
Phred quality scores are used for assessment of sequence quality, recognition and removal of low-quality sequence (end clipping), and determination of accurate consensus sequences.
Originally, Phred quality scores were primarily used by the sequence assembly program Phrap. Phrap was routinely used in some of the largest sequencing projects in the Human Genome Sequencing Project and is currently one of the most widely used DNA sequence assembly programs in the biotech industry. Phrap uses Phred quality scores to determine highly accurate consensus sequences and to estimate the quality of the consensus sequences. Phrap also uses Phred quality scores to estimate whether discrepancies between two overlapping sequences are more likely to arise from random errors, or from different copies of a repeated sequence.
Within the Human Genome Project, the most important use of Phred quality scores was for automatic determination of consensus sequences. Before Phred and Phrap, scientists had to carefully look at discrepancies between overlapping DNA fragments; often, this involved manual determination of the highest-quality sequence, and manual editing of any errors. Phrap's use of Phred quality scores effectively automated finding the highest-quality consensus sequence; in most cases, this completely circumvents the need for any manual editing. As a result, the estimated error rate in assemblies that were created automatically with Phred and Phrap is typically substantially lower than the error rate of manually edited sequence.
In 2009, many commonly used software packages make use of Phred quality scores, albeit to a different extent. Programs like Sequencher use quality scores for display, end clipping, and consensus determination; other programs like CodonCode Aligner also implement quality-based consensus methods. | 1 | Applied and Interdisciplinary Chemistry |
In addition to the reconstruction of the impedance from the phase shift, the reverse approach is also possible. However, the herein presented procedure possesses several advantages:
* When calculating the phase shift from the impedance, a function of the angular frequency ω comes into play which is more difficult to determine compared to the constant C in equation (3).
* Generally, the phase shift is more stable than the impedance. This is based on the fact that for impedance elements (more precisely: Constant phase element, CPE ) the property "phase shift" remains constant even if the value of the impedance drastically changes. Such Constant Phase-elements are the typical electronic elements, among others such as the electrical resistor, capacitor and coil. For illustration, Figure 2 shows the impedance spectrum of an NTC resistor heated during the measurement (starting between 1 kHz and 10 kHz down to lower frequencies). It can clearly be seen that the value of the impedance (red curve) changes with temperature, while the phase shift (blue curve) remains constant. In other words, "a resistor remains a resistor".
* The reconstruction of the impedance from the phase shift further restores the "inner (= complex)" relationship between these two quantities. This relationship is lost by the independent construction of the supporting point splines for impedance and phase (Figure 1). Depending on the system under investigation, this restored correlation - even in the absence of artifacts - can lead to an improved evaluation of the spectra. In such cases, the gain in accuracy due to the reconstruction of the complex impedance outweighs the approximation error according to equation (3), which results from the neglection of the higher derivatives. | 0 | Theoretical and Fundamental Chemistry |
*Materials, instrumentation, and measurement classes specific to biological systems
*Systems optimization
*Modeling and management of biological and physical systems
*Soil, water, conservation, and nutrient management engineering | 1 | Applied and Interdisciplinary Chemistry |
The process of converting pig iron into wrought iron (also known as bar iron) was at that time carried out in a finery forge, which was fuelled by charcoal. Charcoal was a limited resource, but coal, more widely available, could not be used because the sulphur in coal would adversely affect the quality of the wrought iron.
George Cranege worked in Coalbrookdale in Shropshire, at the ironworks established by Abraham Darby I, and his brother Thomas worked at a forge in Bridgnorth in Shropshire. They suggested to Richard Reynolds, manager of the works at Coalbrookdale, that the conversion process could be done in a reverbatory furnace, where the iron did not mix with the coal. Reynolds was sceptical, but authorized the brothers to try out the idea.
Richard Reynolds, in a letter dated 25 April 1766 to his colleague Thomas Goldney III, described his conversation with the Craneges and the experiment:
A patent for the process, dated 17 June 1766, in the name of the brothers Cranege, was secured. It apparently made little difference to the lives of the brothers. The process was improved soon afterwards, by Peter Onions who received a patent in 1783, and by Henry Cort who received patents in 1783 and 1784 for his improvements. | 1 | Applied and Interdisciplinary Chemistry |
Urban residents in many parts of the world rely on on-site sanitation systems without sewers, such as septic tanks and pit latrines, and fecal sludge management in these cities is an enormous challenge.
For sewage treatment the use of septic tanks and other on-site sewage facilities (OSSF) is widespread in some rural areas, for example serving up to 20 percent of the homes in the U.S. | 1 | Applied and Interdisciplinary Chemistry |
The deterministic (acute tissue damage) effects that can lead to acute radiation syndrome only occur in the case of acute high doses (≳ 0.1 Gy) and high dose rates (≳ 0.1 Gy/h) and are conventionally not measured using the unit sievert, but use the unit gray (Gy).
A model of deterministic risk would require different weighting factors (not yet established) than are used in the calculation of equivalent and effective dose. | 0 | Theoretical and Fundamental Chemistry |
Perovskites may be structured in layers, with the structure separated by thin sheets of intrusive material. Different forms of intrusions, based on the chemical makeup of the intrusion, are defined as:
* Aurivillius phase: the intruding layer is composed of a [] ion, occurring every n layers, leading to an overall chemical formula of []-. Their oxide ion-conducting properties were first discovered in the 1970s by Takahashi et al., and they have been used for this purpose ever since.
* Dion−Jacobson phase: the intruding layer is composed of an alkali metal (M) every n layers, giving the overall formula as
* Ruddlesden-Popper phase: the simplest of the phases, the intruding layer occurs between every one (n = 1) or multiple (n > 1) layers of the lattice. Ruddlesden−Popper phases have a similar relationship to perovskites in terms of atomic radii of elements with A typically being large (such as La or Sr) with the B ion being much smaller typically a transition metal (such as Mn, Co or Ni). Recently, hybrid organic-inorganic layered perovskites have been developed, where the structure is constituted of one or more layers of MX-octahedra, where M is a +2 metal (such as Pb or Sn) and X and halide ion (such as ), separated by layers of organic cations (such as butylammonium- or phenylethylammonium-cation). | 0 | Theoretical and Fundamental Chemistry |
An optical isomer can be named by the spatial configuration of its atoms. The system (named after Latin dexter and laevus, right and left), not to be confused with the d- and l-system, see above, does this by relating the molecule to glyceraldehyde. Glyceraldehyde is chiral itself and its two isomers are labeled and (typically typeset in small caps in published work). Certain chemical manipulations can be performed on glyceraldehyde without affecting its configuration, and its historical use for this purpose (possibly combined with its convenience as one of the smallest commonly used chiral molecules) has resulted in its use for nomenclature. In this system, compounds are named by analogy to glyceraldehyde, which, in general, produces unambiguous designations, but is easiest to see in the small biomolecules similar to glyceraldehyde. One example is the chiral amino acid alanine, which has two optical isomers, and they are labeled according to which isomer of glyceraldehyde they come from. On the other hand, glycine, the amino acid derived from glyceraldehyde, has no optical activity, as it is not chiral (it's achiral).
The labeling is unrelated to (+)/(−) it does not indicate which enantiomer is dextrorotatory and which is levorotatory. Rather, it indicates the compound's stereochemistry relative to that of the dextrorotatory or levorotatory enantiomer of glyceraldehyde. The dextrorotatory isomer of glyceraldehyde is, in fact, the isomer. Nine of the nineteen -amino acids commonly found in proteins are dextrorotatory (at a wavelength of 589 nm), and -fructose is also referred to as levulose because it is levorotatory. A rule of thumb for determining the isomeric form of an amino acid is the "CORN" rule. The groups
:COOH, R, NH and H (where R is the side-chain)
are arranged around the chiral center carbon atom. With the hydrogen atom away from the viewer, if the arrangement of the CO→R→N groups around the carbon atom as center is counter-clockwise, then it is the form. If the arrangement is clockwise, it is the form. As usual, if the molecule itself is oriented differently, for example, with H towards the viewer, the pattern may be reversed. The form is the usual one found in natural proteins. For most amino acids, the form corresponds to an S absolute stereochemistry, but is R instead for certain side-chains. | 0 | Theoretical and Fundamental Chemistry |
Ca currents through cardiomyocyte gap junctions mediate synchronized contraction of cardiac tissue. As a result, GCaMP expression in cardiomyocytes, both in vitro and in vivo, has been used to study Ca-influx-dependent excitation and contraction in zebrafish and mice. For instance, Tallini et al. (2006) expressed GCaMP2 in mouse embryos to show that, at embryonic day 10.5, electrical conduction was rapid in the atria and ventricles but slow in the atrioventricular canal. Chi et al. (2008) used a transgenic cardiac-specific GCaMP zebrafish line to image cardiomyocyte activation throughout the cardiac cycle; from their results, they characterized four developmental stages of the zebrafish cardiac conduction system and identified 17 novel mutations affecting cardiac conduction. However, uncontrolled expression of GCaMP leads to cardiac hypertrophy due to overexpression of the calmodulin motif, which interferes with intracellular calcium signaling. As a result, experiments using cardiac tissue should carefully control the level of GCaMP expression. | 1 | Applied and Interdisciplinary Chemistry |
The Reynolds number can be obtained when one uses the nondimensional form of the incompressible Navier–Stokes equations for a newtonian fluid expressed in terms of the Lagrangian derivative:
Each term in the above equation has the units of a "body force" (force per unit volume) with the same dimensions of a density times an acceleration. Each term is thus dependent on the exact measurements of a flow. When one renders the equation nondimensional, that is when we multiply it by a factor with inverse units of the base equation, we obtain a form that does not depend directly on the physical sizes. One possible way to obtain a nondimensional equation is to multiply the whole equation by the factor
where
* is the mean velocity, or , relative to the fluid (m/s),
* is the characteristic length (m),
* is the fluid density (kg/m).
If we now set
we can rewrite the Navier–Stokes equation without dimensions:
where the term .
Finally, dropping the primes for ease of reading:
This is why mathematically all Newtonian, incompressible flows with the same Reynolds number are comparable. Notice also that in the above equation, the viscous terms vanish for . Thus flows with high Reynolds numbers are approximately inviscid in the free stream. | 1 | Applied and Interdisciplinary Chemistry |
Phosphonium ylides are used in the Wittig reaction, a method used to convert ketones and especially aldehydes to alkenes. The positive charge in these Wittig reagents is carried by a phosphorus atom with three phenyl substituents and a bond to a carbanion. Ylides can be stabilised or non-stabilised. A phosphonium ylide can be prepared rather straightforwardly. Typically, triphenylphosphine is allowed to react with an alkyl halide in a mechanism analogous to that of an S2 reaction. This quaternization forms an alkyltriphenylphosphonium salt, which can be isolated or treated in situ with a strong base (in this case, butyllithium) to form the ylide.
Due to the S2 mechanism, a less sterically hindered alkyl halide reacts more favorably with triphenylphosphine than an alkyl halide with significant steric hindrance (such as tert-butyl bromide). Because of this, there will typically be one synthetic route in a synthesis involving such compounds that is more favorable than another.
Phosphorus ylides are important reagents in organic chemistry, especially in the synthesis of naturally occurring products with
biological and pharmacological activities. Much of the interest in the coordination properties of a-keto stabilized phosphorus
ylides stems from their coordination versatility due to the presence of different functional groups in their molecular structure. | 0 | Theoretical and Fundamental Chemistry |
Thalidomide and its analogs help with the co-stimulation of T-cells through the B7-CD28 complex by phosphorylating tyrosine on the CD28 receptor. In vitro data suggests this co-stimulation leads to increased Th1 type cytokine release of IFN-γ and IL-2 that further stimulates clonal T cell proliferation and natural killer cell proliferation and activity. This enhances natural and antibody dependent cellular cytotoxicity. Lenalidomide and pomalidomide are about 100-1000 times more potent in stimulating T-cell clonal proliferation than thalidomide. In addition, in vitro data suggests pomalidomide reverts Th2 cells into Th1 by enhancing transcription factor T-bet. | 1 | Applied and Interdisciplinary Chemistry |
Changes in the imidoylthiourea complexes led to the synthesis of a new class of compounds, diaryltriazine (DATA). In these compounds, the thiourea part of the ITU compounds was replaced by a triazine ring. The DATA compounds were more potent than the ITU compounds against common NNRTI resistant mutant strains. R106168, a prototype DATA compound, was rather easy to synthesize. Multiple substitutions were made at different positions on all of the three rings and on the linkers connecting the rings. In the pocket, most of the DATA derivatives conformed a horseshoe conformation. The two wings in R106168 (2,6-dichlorobenzyl and 4-cyanoanilino) occupied positions in the pocket similar to that of the two wings of the derivatives of ITU. The central part of the DATA compounds, in which the triazine ring replaced the thiourea group of ITU derivatives, is positioned between the side chains of L100 and V179. This removed a number of torsional degrees of freedom in the central part while keeping the flexibility between the triazine ring and the wings.
Chemical substitution or modification in the three-aromatic-ring backbone of the DATA compounds had substantial effect on the activity. R120393, a DATA analog, was designed with a chloroindole part in wing I to expand interactions with the side chain of conserved W229 of the polymerase primer grip loop. R120393 had similar effect as R106168 against most of the NNRTI-resistant mutants. The cloroindole part interacted with the hydrophobic core of the pocket and influenced the binding mode of the R120393 so it went deeper into the pocket compared to the wing I position of other DATA analogs. Crystal structures showed that the DATA compounds could bind the NNIBP in different conformations. The capability to bind in multiple modes made the NNRTIs stronger against drug-resistance mutations. Variability between the inhibitors could be seen when the chemical composition, size of wing I and the two linker groups connecting the rings were altered. The potency of the NNRTIs changed when the triazine nitrogen atoms were substituted with carbons. | 1 | Applied and Interdisciplinary Chemistry |
France 24 documentary "Nicola Spaldin: The pioneer behind multiferroics" (12 minutes) [https://www.youtube.com/watch?v=bfVKtIcl2Nk&t=10s Nicola Spaldin: The pioneer behind multiferroics]
Seminar "Electric field control of magnetism" by R. Ramesh at U Michigan (1 hour) [https://www.youtube.com/watch?v=dTpr9CEYP6M Ramamoorthy Ramesh | Electric Field Control of Magnetism]
Max Roessler prize for multiferroics at ETH Zürich (5 minutes): [https://www.youtube.com/watch?v=Nq0j6xrNcLk Nicola Spaldin, Professor of Materials Theory at ETH Zurich]
ICTP Colloquium "From materials to cosmology; Studying the early universe under the microscope" by Nicola Spaldin (1 hour) [https://www.youtube.com/watch?v=CYHB0BZQU-U From Materials to Cosmology: Studying the early universe under the microscope - ICTP COLLOQUIUM]
Tsuyoshi Kimura's research on "Toward highly functional devices using mulitferroics" (4 minutes): [https://www.youtube.com/watch?v=_KfySbeVO4M Toward highly functional devices using multi-ferroics]
"Strong correlation between electricity and magnetism in materials" by Yoshi Tokura (45 minutes): [https://www.youtube.com/watch?v=i6tcSXbEELE 4th Kyoto Prize Symposium [Materials Science and Engineering] Yoshinori Tokura, July 2, 2017]
"Breaking the wall to the next material age", Falling Walls, Berlin (15 minutes): [https://www.youtube.com/watch?v=pirXBfwni-w How Materials Science Heralds a New Class of Technologies | NICOLA SPALDIN] | 0 | Theoretical and Fundamental Chemistry |
Thalidomide has been approved by the FDA for ENL and MM in combination with dexamethasone. EMA has also approved it to treat MM in combination with prednisone and/or melphalan. Orphan indications by the FDA include graft-versus-host disease, mycobacterial infection, recurrent aphthous ulcers, severe recurrent aphthous stomatitis, primary brain malignancies, AIDS-associated wasting syndrome, Crohns disease, Kaposis sarcoma, myelodysplastic syndrome and hematopoietic stem cell transplantation. | 1 | Applied and Interdisciplinary Chemistry |
The induced vortices have many applications in various aspects of electrokinetic microfluidics. There are many micro-mixers that are designed and fabricated based on the existence of their induced vortices in the microfluidics devices. Such micro-mixers which are used for biochemical, medicine, biology applications has no mechanical parts and only use conducting surfaces to generate induced vortices to mix the different fluid streams.
This phenomenon even is used to trap the micron and submicron particles floating in flow inside a micro-channel. This method can be used to manipulate, detect, handle, and concentrate cells and virus in biomedical field; or, for colloidal particle assembly.
In addition the induced vortices around the conducting surfaces in a microfluidic system can be used as a micro-valve, micro-actuator, micro-motor and micro-regulator to control the direction and manipulation. | 0 | Theoretical and Fundamental Chemistry |
The difference between substituents R1-R5 is described below. All marketed β-agonists have hydroxyl group in position R3 and most often in position R5.
R: This group determines α- or β-receptor selectivity. The larger the substituent, the greater the selectivity for the β-receptor. If t-butyl is positioned at R it shows high affinity for the β-receptor. A long phenylbutoxyhexyl substituent in this position gives high β-selectivity and also high lipophilicity and therefore a longer duration of action.
R: Substituents other than hydrogen would give increased duration of action. An ethyl group would increase the selectivity for the β-receptor. However, an ethyl group seems to cause increased adverse effects and low β-receptor potency compared to other β-selective agonists.
R: A hydroxyl group gives direct action to the β-receptor. As noted earlier, all marketed β-agonists have a hydroxyl group in this position which makes the compound chiral, and is active when it has the (R)-configuration.
R or R: Hydroxyl group placed on carbon number 5 or 3 (meta position) gives direct action to the β-adrenergic receptor.
R: Either hydroxyl group or hydrogen group in this position gives direct action to the β-receptor.
Summarizing a few β-adrenoceptor agonists and their structure activity shows how they act differently referred to potency, selectivity, affinity and duration of action (see table 1): | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits