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In geology, a deformation mechanism is a process occurring at a microscopic scale that is responsible for changes in a material's internal structure, shape and volume. The process involves planar discontinuity and/or displacement of atoms from their original position within a crystal lattice structure. These small changes are preserved in various microstructures of materials such as rocks, metals and plastics, and can be studied in depth using optical or digital microscopy. | 8 | Metallurgy |
Originally, n was held to have an integer value between 1 and 4, which reflected the nature of the transformation in question. In the derivation above, for example, the value of 4 can be said to have contributions from three dimensions of growth and one representing a constant nucleation rate. Alternative derivations exist, where n has a different value.
If the nuclei are preformed, and so all present from the beginning, the transformation is only due to the 3-dimensional growth of the nuclei, and n has a value of 3.
An interesting condition occurs when nucleation occurs on specific sites (such as grain boundaries or impurities) that rapidly saturate soon after the transformation begins. Initially, nucleation may be random, and growth unhindered, leading to high values for n (3 or 4). Once the nucleation sites are consumed, the formation of new particles will cease.
Furthermore, if the distribution of nucleation sites is non-random, then the growth may be restricted to 1 or 2 dimensions. Site saturation may lead to n values of 1, 2 or 3 for surface, edge and point sites respectively. | 3 | Analytical Chemistry |
Viruses in the sea surface microlayer, the so-called virioneuston, have recently become of interest to researchers as enigmatic biological entities in the boundary surface layers with potentially important ecological impacts. Given this vast air–water interface sits at the intersection of major air–water exchange processes spanning more than 70% of the global surface area, it is likely to have profound implications for marine biogeochemical cycles, on the microbial loop and gas exchange, as well as the marine food web structure, the global dispersal of airborne viruses originating from the sea surface microlayer, and human health.
Viruses are the most abundant biological entities in the water column of the world's oceans. In the free water column, the virioplankton typically outnumbers the bacterioplankton by one order of magnitude reaching typical bulk water concentrations of 10 viruses mL. Moreover, they are known as integral parts of global biogeochemical cycles to shape and drive microbial diversity and to structure trophic networks. Like other neuston members, the virioneuston likely originates from the bulk seawater. For instance, in 1977 Baylor et al. postulated adsorption of viruses onto air bubbles as they rise to the surface, or viruses can stick to organic particles also being transported to the SML via bubble scavenging.
Within the SML, viruses interacting with the bacterioneuston will probably induce the viral shunt, a phenomenon that is well known for marine pelagic systems. The term viral shunt describes the release of organic carbon and other nutritious compounds from the virus-mediated lysis of host cells, and its addition to the local dissolved organic matter (DOM) pool. The enriched and densely packed bacterioneuston forms an excellent target for viruses compared to the bacterioplankton populating the subsurface. This is because high host-cell numbers will increase the probability of host–virus encounters. The viral shunt might effectively contribute to the SML's already high DOM content enhancing bacterial production as previously suggested for pelagic ecosystems and in turn replenishing host cells for viral infections. By affecting the DOM pool, viruses in the SML might directly interfere with the microbial loop being initiated when DOM is microbially recycled, converted into biomass, and passed along the food web. In addition, the release of DOM from lysed host cells by viruses contributes to organic particle generation. However, the role of the virioneuston for the microbial loop has never been investigated. | 7 | Physical Chemistry |
Cis–trans isomerism, also known as geometric isomerism, describes certain arrangements of atoms within molecules. The prefixes "cis" and "trans" are from Latin: "this side of" and "the other side of", respectively. In the context of chemistry, cis indicates that the functional groups (substituents) are on the same side of some plane, while trans conveys that they are on opposing (transverse) sides. Cis–trans isomers are stereoisomers, that is, pairs of molecules which have the same formula but whose functional groups are in different orientations in three-dimensional space. Cis and trans isomers occur both in organic molecules and in inorganic coordination complexes. Cis and trans descriptors are not used for cases of conformational isomerism where the two geometric forms easily interconvert, such as most open-chain single-bonded structures; instead, the terms "syn" and "anti" are used.
According to IUPAC, "geometric isomerism" is an obsolete synonym of "cis–trans isomerism".
Cis–trans or geometric isomerism is classified as one type of configurational isomerism. | 4 | Stereochemistry |
Prelog was elected to the American Academy of Arts and Sciences in 1960 and the United States National Academy of Sciences in 1961.
Prelog was elected a Foreign Member of the Royal Society (ForMemRS) in 1962 for his contribution to the development of modern stereochemistry.
Prelog received the 1975 Nobel Prize in Chemistry for his research into the stereochemistry of organic molecules and reaction, sharing it with the Australian/British research chemist John Cornforth. He was elected to the American Philosophical Society the following year.
In 1986, he became an honorary member of the Yugoslav Academy of Sciences and Arts. Prelog was also a member of Serbian Academy of Sciences and Arts. | 4 | Stereochemistry |
RNA interference (RNAi) is a natural process used by cells to regulate gene expression. It was discovered in 1998 by Andrew Fire and Craig Mello, who won the Nobel Prize for their discovery in 2006. The process to silence genes first begins with the entrance of a double-stranded RNA (dsRNA) molecule into the cell, which triggers the RNAi pathway. The double-stranded molecule is then cut into small double-stranded fragments by an enzyme called Dicer. These small fragments, which include small interfering RNAs (siRNA) and microRNA (miRNA), are approximately 21–23 nucleotides in length. The fragments integrate into a multi-subunit protein called the RNA-induced silencing complex, which contains Argonaute proteins that are essential components of the RNAi pathway. One strand of the molecule, called the "guide" strand, binds to RISC, while the other strand, known as the "passenger" strand is degraded. The guide or antisense strand of the fragment that remains bound to RISC directs the sequence-specific silencing of the target mRNA molecule. The genes can be silenced by siRNA molecules that cause the endonucleatic cleavage of the target mRNA molecules or by miRNA molecules that suppress translation of the mRNA molecule. With the cleavage or translational repression of the mRNA molecules, the genes that form them are rendered essentially inactive. RNAi is thought to have evolved as a cellular defense mechanism against invaders, such as RNA viruses, or to combat the proliferation of transposons within a cell's DNA. Both RNA viruses and transposons can exist as double-stranded RNA and lead to the activation of RNAi. Currently, siRNAs are being widely used to suppress specific gene expression and to assess the function of genes. Companies utilizing this approach include Alnylam, Sanofi, Arrowhead, Discerna, and Persomics, among others. | 1 | Biochemistry |
Ligand-gated ion channels are likely to be the major site at which anaesthetic agents and ethanol have their effects, although unequivocal evidence of this is yet to be established. In particular, the GABA and NMDA receptors are affected by anaesthetic agents at concentrations similar to those used in clinical anaesthesia.
By understanding the mechanism and exploring the chemical/biological/physical component that could function on those receptors, more and more clinical applications are proven by preliminary experiments or FDA. Memantine is approved by the U.S. F.D.A and the European Medicines Agency for the treatment of moderate-to-severe Alzheimers disease, and has now received a limited recommendation by the UKs National Institute for Health and Care Excellence for patients who fail other treatment options. Agomelatine, is a type of drug that acts on a dual melatonergic-serotonergic pathway, which have shown its efficacy in the treatment of anxious depression during clinical trials, study also suggests the efficacy in the treatment of atypical and melancholic depression. | 1 | Biochemistry |
There are four different general schemes in which diffusion may take place. Tracer diffusion and chemical diffusion differ in the level of adsorbate coverage at the surface, while intrinsic diffusion and mass transfer diffusion differ in the nature of the diffusion environment. Tracer diffusion and intrinsic diffusion both refer to systems where adparticles experience a relatively homogeneous environment, whereas in chemical and mass transfer diffusion adparticles are more strongly affected by their surroundings.
*Tracer diffusion describes the motion of individual adparticles on a surface at relatively low coverage levels. At these low levels (< 0.01 monolayer), particle interaction is low and each particle can be considered to move independently of the others. The single atom diffusing in figure 1 is a nice example of tracer diffusion.
*Chemical diffusion describes the process at higher level of coverage where the effects of attraction or repulsion between adatoms becomes important. These interactions serve to alter the mobility of adatoms. In a crude way, figure 3 serves to show how adatoms may interact at higher coverage levels. The adatoms have no "choice" but to move to the right at first, and adjacent adatoms may block adsorption sites from one another.
*Intrinsic diffusion occurs on a uniform surface (e.g. lacking steps or vacancies) such as a single terrace, where no adatom traps or sources are present. This regime is often studied using field ion microscopy, wherein the terrace is a sharp sample tip on which an adparticle diffuses. Even in the case of a clean terrace the process may be influenced by non-uniformity near the edges of the terrace.
*Mass transfer diffusion takes place in the case where adparticle sources and traps such as kinks, steps, and vacancies are present. Instead of being dependent only on the jump potential barrier E, diffusion in this regime is now also dependent on the formation energy of mobile adparticles. The exact nature of the diffusion environment therefore plays a role in dictating the diffusion rate, since the formation energy of an adparticle is different for each type of surface feature as is described in the Terrace Ledge Kink model. | 7 | Physical Chemistry |
Isoserine is a non-proteinogenic α-hydroxy-β-amino acid, and an isomer of serine. Non-proteinogenic amino acids do not form proteins, and are not part of the genetic code of any known organism. Isoserine has only been produced synthetically.
The first documented synthesis of isoserine in a laboratory setting was by Miyazawa et al., who published their results in 1976. | 1 | Biochemistry |
The mathematical equation for Boyle's law is:
where denotes the pressure of the system, denotes the volume of the gas, is a constant value representative of the temperature and volume of the system.
So long as temperature remains constant the same amount of energy given to the system persists throughout its operation and therefore, theoretically, the value of will remain constant. However, due to the derivation of pressure as perpendicular applied force and the probabilistic likelihood of collisions with other particles through collision theory, the application of force to a surface may not be infinitely constant for such values of , but will have a limit when differentiating such values over a given time. Forcing the volume of the fixed quantity of gas to increase, keeping the gas at the initially measured temperature, the pressure must decrease proportionally. Conversely, reducing the volume of the gas increases the pressure. Boyle's law is used to predict the result of introducing a change, in volume and pressure only, to the initial state of a fixed quantity of gas.
The initial and final volumes and pressures of the fixed amount of gas, where the initial and final temperatures are the same (heating or cooling will be required to meet this condition), are related by the equation:
Here and represent the original pressure and volume, respectively, and and represent the second pressure and volume.
Boyles law, Charless law, and Gay-Lussacs law form the combined gas law. The three gas laws in combination with Avogadros law can be generalized by the ideal gas law. | 7 | Physical Chemistry |
Georg Jacob Tysland (13 February 1890 – 14 February 1932) was a Norwegian engineer and metallurgist. Tysland is known as the originator of a successful electric smelting furnace for the production of pig iron, a semi-finished product for the production of steel. | 8 | Metallurgy |
The root alk- is used in organic chemistry to form classification names for classes of organic compounds which contain a carbon skeleton but no aromatic rings. It was extracted from the word alcohol by removing the -ol suffix. See e.g. alkyl, alkane.
The International Union of Pure and Applied Chemistry [https://iupac.org/ (IUPAC)] nomenclature system is used to systematically identify organic compounds. Prefixes, suffixes, and infixes are known as organic chemistry affixes. These affixes provide details about the molecule's structure, such as the quantity of carbon atoms, the kind of carbon-to-carbon bonds, and the existence of functional groups.
The following are a few typical additions in organic chemistry:
Prefixes
Hydrocarbon prefixes: These prefixes indicate the number of carbon atoms in a straight-chain alkane. Some examples include:
meth- (1 carbon)
eth- (2 carbons)
prop- (3 carbons)
but- (4 carbons)
pent- (5 carbons)
hex- (6 carbons)
Alkyl group prefixes: These prefixes are used to name alkyl groups (chains of carbon atoms) that are attached to another molecule. They are formed by adding the suffix "-yl" to the hydrocarbon prefix. For example, a methyl group (CH3) is an alkyl group derived from methane (CH4).
Halo prefixes: These prefixes are used to indicate the presence of a halogen atom (F, Cl, Br, or I) in a molecule. Some examples include:
fluoro- (F)
chloro- (Cl)
bromo- (Br)
iodo- (I)
Suffixes
Hydrocarbon suffixes: These suffixes indicate the type of bonds between the carbon atoms in a molecule. Some examples include:
-ane (all single bonds)
-ene (at least one double bond)
-yne (at least one triple bond)
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Hydrocarbon suffixes organic chemistry
Functional group suffixes: These suffixes indicate the presence of a particular functional group in a molecule. Some examples include:
-ol (alcohol)
-al (aldehyde)
-one (ketone)
-oic acid (carboxylic acid)
-amine (amine)
-amide (amide)
-ester (ester)
Infixes
Cycloinfix: The prefix "cyclo-" is used to indicate that the carbon chain is cyclic (ring-shaped).
Other infixes: There are a few other infixes used in IUPAC nomenclature to indicate more complex structures, such as "spiro-" and "bicyclo-".
By understanding these affixes, you can learn to name and interpret the names of a wide variety of organic compounds. | 0 | Organic Chemistry |
*Epinephrine induces platelet aggregation, and so does hepatocyte growth factor (HGF). Thus, they are physiological agonists to each other. | 1 | Biochemistry |
Ynols can interconvert with ketenes, much like enols can with aldehydes and ketones. The ynol tautomer is usually unstable, does not survive long, and changes into the ketene. This is because oxygen is more electronegative than carbon and thus forms stronger bonds. For instance, ethynol quickly interconverts with ethenone: | 0 | Organic Chemistry |
* Phi Beta Kappa
* Sigma Xi
* 1950 The Chittenden Award given to the top B.S. graduate in the Yale class of 1950
*1971 The first Northeast ACS Award for Photochemistry
*1976 The ACS James Flack Norris Award in Physical Organic Chemistry
*1980 The Halpern Award of the New York Academy of Sciences
*1980 Election to the National Academy of Sciences
*1986 Recipient of the American Institute of Chemists Chemical Pioneer Award
*1988 A Senior Alexander von Humboldt Award
*1990 Hilldale Award in the Physical Sciences from the University of Wisconsin
* 1991 Arthur C. Cope Scholar Award of the ACS
* 2006 IUPAC Porter Medal for Photochemical Research | 5 | Photochemistry |
Ružička was the recipient of eight honorary doctorates and the 1938 Marcel Benoist Prize. He was listed as author on 583 scientific papers. In 1965, he became an honorary member of the Polish Chemical Society, and he was an honorary member of the American Academy of Arts and Sciences. After the war he acquired a taste for Dutch masterpieces, which he later lodged in the Kunsthaus Zürich as the Ružička collection. He militated against nuclear weapons.
In 1970, Ružička delivered to the Nobel Laureate Conferences in Lindau a lecture entitled "Nobel Prizes and the chemistry of life".
In later years, he served as consultant to Sandoz A. G. of Basel.
Ružička dedicated significant efforts to the problems of education. He insisted on a better organization of academic education and scientific work in the new Yugoslavia, and established the Swiss-Yugoslav Society. Ružička became an honorary academician at the then Yugoslav Academy of Sciences and Arts in Zagreb.
In 1974 he was awarded the Order of the Yugoslav Flag with Golden Wreath.
At ETH Zurich, the Ružička Award was established in 1957 on the occasion of his retirement, for young chemists working in Switzerland.
In his native Vukovar, a museum was opened in his honour in 1977.
Ružička's archives are kept at ETH Zurich.
The Ružička reaction is named after him. | 0 | Organic Chemistry |
After the last solute has been eluted, it is necessary to strip the displacer from the column. Since the displacer was chosen for high affinity, this can pose a challenge. On reverse-phase materials, a wash with a high percentage of organic solvent may suffice. Large pH shifts are also often employed. One effective strategy is to remove the displacer by chemical reaction; for instance if hydrogen ion was used as displacer it can be removed by reaction with hydroxide, or a polyvalent metal ion can be removed by reaction with a chelating agent. For some matrices, reactive groups on the stationary phase can be titrated to temporarily eliminate the binding sites, for instance weak-acid ion exchangers or chelating resins can be converted to the protonated form. For gel-type ion exchangers, selectivity reversal at very high ionic strength can also provide a solution. Sometimes the displacer is specifically designed with a titratable functional group to shift its affinity. After the displacer is washed out, the column is washed as needed to restore it to its initial state for the next run. | 3 | Analytical Chemistry |
In case (c), the spin-orbit coupling is stronger than the coupling to the internuclear axis, and and from case (a) cannot be defined. Instead and combine to form , which has a projection along the internuclear axis of magnitude . Then , as in case (a).
The good quantum numbers in case (c) are , , and . Since is undefined for this case, the states cannot be described as , or . An example of Hund's case (c) is the lowest Π state of diiodine (I), which approximates more closely to case (c) than to case (a).
The selection rules for , and parity are valid as for cases (a) and (b), but there are no rules for and since these are not good quantum numbers for case (c). | 7 | Physical Chemistry |
Flutamide has been found to be effective in the treatment of female pattern hair loss in a number of studies. In one study of 101 pre- and postmenopausal women, flutamide alone or in combination with an oral contraceptive produced a marked decrease in hair loss scores after 1 year of treatment, with maximum effect after 2 years of treatment and benefits maintained for another 2 years. In a small study of flutamide with an oral contraceptive, the medication caused an increase in cosmetically acceptance hair density in 6 of 7 women with diffuse scalp hair loss. In a comparative study, flutamide significantly improved scalp hair growth (21% reduction in Ludwig scores) in hyperandrogenic women after 1 year of treatment, whereas cyproterone acetate and finasteride were ineffective. | 4 | Stereochemistry |
The boat conformations have higher energy than the chair conformations. The interaction between the two flagpole hydrogens, in particular, generates steric strain. Torsional strain also exists between the C2–C3 and C5–C6 bonds (carbon number 1 is one of the two on a mirror plane), which are eclipsed — that is, these two bonds are parallel one to the other across a mirror plane. Because of this strain, the boat configuration is unstable (i.e. is not a local energy minimum).
The molecular symmetry is C.
The boat conformations spontaneously distorts to twist-boat conformations. Here the symmetry is D, a purely rotational point group with three twofold axes. This conformation can be derived from the boat conformation by applying a slight twist to the molecule so as to remove eclipsing of two pairs of methylene groups. The twist-boat conformation is chiral, existing in right-handed and left-handed versions.
The concentration of the twist-boat conformation at room temperature is less than 0.1%, but at it can reach 30%. Rapid cooling of a sample of cyclohexane from to will freeze in a large concentration of twist-boat conformation, which will then slowly convert to the chair conformation upon heating. | 4 | Stereochemistry |
Ali Akbar Moosavi-Movahedi was born in Shiraz, Iran, in 1953. He attended Alborz High School in 1968, graduated from the National University of Iran (now known as Shahid Beheshti University) with a BSc in chemistry in 1975, earned his MSc in Bioanalytical Chemistry at the Eastern Michigan University in 1979, and obtained his Ph.D. in Biophysical Chemistry at the University of Manchester in 1986. | 7 | Physical Chemistry |
From 1963 until 1965, Suzuki worked as a postdoctoral student with Herbert C. Brown at Purdue University and after returning to the Hokudai he became a full professor there. The postdoctoral experience was utilized in the study of the coupling reaction with his assistant Norio Miyaura and led to the discovery of Suzuki reaction announced in 1979. Its organic boronic acids with aryl and vinyl group are stable to water and air, easy to handle, and because the conditions required for use are also relatively mild, even among the several cross-coupling techniques, it is said to be easy to use. Its full mechanism is shown in the image below.
With his retirement from Hokudai in 1994 he took several positions in other universities: 1994–1995 Okayama University of Science and 1995–2002 Kurashiki University of Science and the Arts. In addition, he was an invited professor at Purdue University (2001), Academic Sinica and the National Taiwan University (2002).
In 2010, Suzuki was jointly awarded the Nobel Prize for Chemistry together with Richard F. Heck and Ei-ichi Negishi.
To celebrate International Year of Chemistry (IYC 2011), Suzuki was interviewed by the UNESCO Courier magazine, he said：
In 2014, a Canadian-Chinese student asked for Suzuki's advice: "how can I become a great chemist like you?", Suzuki answered him: "... above all else, you must learn to see through the appearance to perceive the essence." | 0 | Organic Chemistry |
In 2018, Alnylam Pharmaceuticals became the first company to have a siRNA therapy approved by the FDA. Onpattro (patisiran) was approved for the treatment of polyneuropathy of hereditary transthyretin-mediated (hATTR) amyloidosis in adults. hATTR is a rare, progressively debilitating condition. During hATTR amyloidosis, misfolded transthyretin (TTR) protein is deposited in the extracellular space. Under typical folding conditions, TTR tetramers are made up of four monomers. Hereditary ATTR amyloidosis is caused by a fault or mutation in the transthyretin (TTR) gene which is inherited. Changing just one amino-acid changes the tetrameric transthyretin proteins, resulting in unstable tetrameric transthyretin protein that aggregates in monomers and forms insoluble extracellular amyloid deposits. Amyloid buildup in various organ systems causes cardiomyopathy, polyneuropathy, gastrointestinal dysfunction. It affects 50,000 people worldwide. To deliver the drug directly to the liver, siRNA is encased in a lipid nanoparticle. The siRNA molecule halts the production of amyloid proteins by interfering with the RNA production of abnormal TTR proteins. This prevents the accumulation of these proteins in different organs of the body and helps the patients manage this disease.
Traditionally, liver transplantation has been the standard treatment for hereditary transthyretin amyloidosis, however its effectiveness may be limited by the persistent deposition of wild-type transthyretin amyloid after transplantation. There are also small molecule medications that provide temporary relief. Before Onpattro was released, the treatment options for hATTR were limited. After the approval of Onpattro, FDA awarded Alnylam with the Breakthrough Therapy Designation, which is given to drugs that are intended to treat a serious condition and are a substantial improvement over any available therapy. It was also awarded Orphan Drug Designations given to those treatments that are intended to safely treat conditions affecting less than 200,000 people.
Along with Onpattro, another RNA interference therapeutic drug has also been discovered (Partisiran) which has property of inhibiting hepatic synthesis of transthyretin. Target messenger RNA (mRNA) is cleaved as a result by tiny interfering RNAs coupled to the RNA-induced silencing complex. Patisiran, an investigational RNAi therapeutic drug, uses this process to decrease the production of mutant and wild-type transthyretin by cleaving on 3-untranslated region of transthyretin mRNA.
In 2019, FDA approved the second RNAi therapy, Givlaari (givosiran) used to treat acute hepatic porphyria (AHP). The disease is caused due to the accumulation of toxic porphobilinogen (PBG) molecules which are formed during the production of heme. These molecules accumulate in different organs and this can lead to the symptoms or attacks of AHP.
Givlaari is an siRNA drug that downregulates the expression of aminolevulinic acid synthase 1 (ALAS1), a liver enzyme involved in an early step in heme production. The downregulation of ALAS1 lowers the levels of neurotoxic intermediates that cause AHP symptoms.
Years of research has led to a greater understanding of siRNA therapies beyond those affecting the liver. As of 2019, Alnylam Pharmaceuticals was involved in therapies that may treat amyloidosis and CNS disorders like Huntingtons disease and Alzheimers disease. They have also partnered with Regeneron Pharmaceuticals to develop therapies for CNS, eye and liver diseases.
As of 2020, ONPATTRO and GIVLAARI, were available for commercial application, and two siRNAs, lumasiran (ALN-GO1) and inclisiran, have been submitted for new drug application to the FDA. Several siRNAs are undergoing phase 3 clinical studies, and more candidates are in the early developmental stage. In 2020, Alnylam and Vir pharmaceuticals announced a partnership and have started working on a RNAi therapy that would treat severe cases of COVID-19.
Other companies that have had success in developing a pipeline of siRNA therapies are Dicerna Pharmaceuticals, partnered Eli Lilly and Company and Arrowhead Pharmaceuticals partnered with Johnson and Johnson. Several other big pharmaceutical companies such as Amgen and AstraZeneca have also invested heavily in siRNA therapies as they see the potential success of this area of biological drugs. | 1 | Biochemistry |
Serine is the first amino acid in this family to be produced; it is then modified to produce both glycine and cysteine (and many other biologically important molecules). Serine is formed from 3-phosphoglycerate in the following pathway:
3-phosphoglycerate → phosphohydroxyl-pyruvate → phosphoserine → serine
The conversion from 3-phosphoglycerate to phosphohydroxyl-pyruvate is achieved by the enzyme phosphoglycerate dehydrogenase. This enzyme is the key regulatory step in this pathway. Phosphoglycerate dehydrogenase is regulated by the concentration of serine in the cell. At high concentrations this enzyme will be inactive and serine will not be produced. At low concentrations of serine the enzyme will be fully active and serine will be produced by the bacterium. Since serine is the first amino acid produced in this family both glycine and cysteine will be regulated by the available concentration of serine in the cell. | 1 | Biochemistry |
In science, and most specifically chemistry, the accepted value denotes a value of a substance accepted by almost all scientists and the experimental value denotes the value of a substance's properties found in a localized lab. | 7 | Physical Chemistry |
Suzuki was born on September 12, 1930, in Mukawa, Hokkaidō, his father died when he was in high school. He studied chemistry at Hokkaido University (Hokudai) and after receiving his PhD while he worked there as assistant professor. He initially wanted to major in mathematics, as his favorite subject in childhood was arithmetic. It was an encounter with two books that became an opportunity to advance to the path of organic synthesis, one is Textbook of Organic Chemistry written by Louis Fieser of Harvard University, and another is Hydroboration written by Herbert C. Brown of Purdue University. | 0 | Organic Chemistry |
Parkeol is a relatively uncommon sterol secondary metabolite found mostly in plants, particularly noted in Butyrospermum parkii (now called Vitellaria paradoxa, or the shea tree). It can be synthesized as a minor product by several oxidosqualene cyclase enzymes, and is the sole product of the enzyme parkeol synthase.
Parkeol is the dominant sterol found in the planctomycete Gemmata obscuriglobus, a rare example of a sterol-synthesizing prokaryote. The only other sterol identified in this organism is lanosterol, a key component of the sterol biosynthetic pathway in animals and fungi; this relatively limited sterol repertoire may resemble the early evolution of sterol synthesis, which is ubiquitous in eukaryotes. | 0 | Organic Chemistry |
With the sequencing of the genomes of a diverse array or model organisms, it became clear that the number of genes does not correlate with the human perception of relative organism complexity – the human proteome contains some 20 000 genes, which is smaller than some species such as corn. A statistical approach to calculating the number of interactions in humans gives an estimate of around 650 000, one order of magnitude bigger than Drosophila and 3 times larger than C. Elegans. As of 2008, only about <0.3% of all estimated interactions among human proteins has been identified, although in recent years there has been exponential growth in discovery – as of 2015, over 210 000 unique human positive protein–protein interactions are currently catalogued, and bioGRID database contains almost 750 000 literature-curated PPI's for 30 model organisms, 300 000 of which are verified or predicted human physical or genetic protein–protein interactions, a 50% increase from 2013. The currently available information on the human interactome network originates from either literature-curated interactions, high-throughput experiments, or from potential interactions predicted from interactome data, whether through phylogenetic profiling (evolutionary similarity), statistical network inference, or text/literature mining methods.
Protein–protein interactions are only the raw material for networks. To form useful interactome databases and create integrated networks, other types of data that can be combined with protein–protein interactions include information on gene expression and co-expression, cellular co-localization of proteins (based on microscopy), genetic information, metabolic and signalling pathways, and more. The end goal of unravelling human protein interactomes is ultimately to understand mechanisms of disease and uncover previously unknown disease genes. It has been found that proteins with a high number of interactions (outward edges) are significantly more likely to be hubs in modules that correlate with disease, probably because proteins with more interactions are involved in more biological functions. By mapping disease alterations to the human interactome, we can gain a much better understanding of the pathways and biological processes of disease. | 1 | Biochemistry |
A 2006 meta analysis concluded that compared to other proton pump inhibitors, esomeprazole confers a modest overall benefit in esophageal healing and symptom relief. When broken down by disease severity, the benefit of esomeprazole relative to other proton pump inhibitors was negligible in people with mild disease (number needed to treat 50), but appeared more in those with severe disease (number needed to treat 8). A second meta analysis also found increases in erosive esophageal healing (>95% healing rate) when compared to standardized doses in broadly selected patient populations. A 2017 study found esomeprazole to be among a number of effective PPIs. | 4 | Stereochemistry |
The cosmic microwave background contains a small linearly-polarized component attributed to Thomson scattering. That polarized component mapping out the so-called E-modes was first detected by DASI in 2002.
The solar K-corona is the result of the Thomson scattering of solar radiation from solar coronal electrons. The ESA and NASA SOHO mission and the NASA STEREO mission generate three-dimensional images of the electron density around the Sun by measuring this K-corona from three separate satellites.
In tokamaks, corona of ICF targets and other experimental fusion devices, the electron temperatures and densities in the plasma can be measured with high accuracy by detecting the effect of Thomson scattering of a high-intensity laser beam. An upgraded Thomson scattering system in the Wendelstein 7-X stellarator uses Nd:YAG lasers to emit multiple pulses in quick succession. The intervals within each burst can range from 2 ms to 33.3 ms, permitting up to twelve consecutive measurements. Synchronization with plasma events is made possible by a newly added trigger system that facilitates real-time analysis of transient plasma events.
In the Sunyaev–Zeldovich effect, where the photon energy is much less than the electron rest mass, the inverse-Compton scattering can be approximated as Thomson scattering in the rest frame of the electron.
Models for X-ray crystallography are based on Thomson scattering. | 7 | Physical Chemistry |
Between 2007 and 2008, the waste commissioner Guido Bertolaso, (the head of the civil protection department), planned to open a landfill but this was opposed by residents of Chiaiano. There was similar resistance in Pianosa to reopening a closed landfill proposed by government commissioner Giovanni De Gennaro. Some of the protests turned violent, and in May 2008, it became a penal felony to protest in the vicinity of landfills, incinerators or any plant related to waste management. It is alleged that there was collusion between local political interests and organised crime over building interests.
By July 17, 2008, Berlusconi declared that the emergency had ended.
The incinerator of Acerra has also received backlash in the local area. In 2009, the Acerra incineration facility was completed at a cost of over €350 million. The incinerator burns 600,000 tons of waste per year to produce refuse-derived fuel. The energy produced from the facility is enough to power 200,000 households per year. | 2 | Environmental Chemistry |
Nitrates are used as oxidizing agents, most notably in explosives, where the rapid oxidation of carbon compounds liberates large volumes of gases (see gunpowder for an example). | 0 | Organic Chemistry |
In liquid crystals, homeotropic alignment is one of the ways of alignment of liquid crystalline molecules. Homeotropic alignment is the state in which a rod-like liquid crystalline molecule aligns perpendicularly to the substrate. In the polydomain state, the parts also are called homeotropic domains. In contrast, the state in which the molecule aligns to a substance in parallel is called homogeneous alignment.
There are various other ways of alignment in liquid crystals. Because homeotropic alignment is not anisotropic optically, a dark field is observed between crossed polarizers in polarizing optical microscopy.
By conoscope observation, however, a cross image is observed in the homeotropic alignments. Homeotropic alignment often appears in the smectic A phase (S).
In discotic liquid crystals homeotropic alignment is defined as the state in which an axis of the column structure, which is formed by disc-like liquid crystalline molecules, aligns perpendicularly to a substance. In other words, this alignment looks like a state in which columns formed by piled-up coins are arranged in an orderly way on a table.
In practice, the homeotropic alignment is usually achieved by surfactants and detergent for example lecithin, some esilanes or some special polyimide (PI 1211). Generally liquid crystals align homeotropically at an air or glass interface. | 3 | Analytical Chemistry |
Her early research included the development of a process to remove sulfur and phosphorus from acetylene. Her first article on the derivatives of benzophenone, coauthored by German chemist Fritz Ullmann, was published in 1897. She also researched and wrote a paper (published in 1904) on using copper as a catalyst for the preparation of a phenyl derivative of thiosalicylic acid, a process known as the Ullmann reaction; Goldberg is the only woman scientist unambiguously recognized for her own named reaction: the amidation (Goldberg) reaction. This modification to previous forms of the method was a great improvement, and was extremely helpful for laboratory-scale preparations. She coordinated on other forms of chemistry research with her husband, Fritz Ullmann, in what they called the Ullmann-Goldberg collaborative. | 0 | Organic Chemistry |
The term vertical resistance, used commonly in context of plant selection, was first used by J.E. Vanderplank to describe single-gene resistance. This contrasted the term horizontal resistance which was used to describe many-gene resistance. Raoul A. Robinson further refined the definition of vertical resistance, emphasizing that in vertical resistance there are single genes for resistance in the host plant, and there are also single genes for parasitic ability in the parasite. This phenomenon is known as the gene-for-gene relationship, and it is the defining character of vertical resistance. | 1 | Biochemistry |
In linear elasticity, the stress and strain are related by Hooke's law, i.e.,
or, using Voigt notation,
The condition for material symmetry in linear elastic materials is.
where | 3 | Analytical Chemistry |
Levofloxacin is a third-generation fluoroquinolone, being one of the isomers of ofloxacin, which was a broader-spectrum conformationally locked analog of norfloxacin; both ofloxacin and levofloxaxin were synthesized and developed by scientists at Daiichi Seiyaku. The Daiichi scientists knew that ofloxacin was racemic, but tried unsuccessfully to separate the two isomers; in 1985 they succeeded in separately synthesizing the pure levo form and showed that it was less toxic and more potent than the other form.
It was first approved for marketing in Japan in 1993, for oral administration, and Daiichi marketed it there under the brand name Cravit. Daiichi, working with Johnson & Johnson as it had with ofloxacin, obtained FDA approval in 1996 under the brand name Levaquin to treat bacterial sinusitus, bacterial exacerbations of bronchitis, community-acquired pneumonia, uncomplicated skin infections, complicated urinary tract infections, and acute pyelonephritis.
Levofloxacin is marketed by Sanofi-Aventis under a license agreement signed with Daiichi in 1993, under the brand name "Tavanic".
Levofloxacin had reached blockbuster status by this time; combined worldwide sales of levofloxacin and ofloxacin for J&J alone were in 2009.
The term of the levofloxacin United States patent was extended by the U.S. Patent and Trademark Office 810 days under the provisions of the Hatch Waxman Amendment so that the patent would expire in 2010 instead of 2008. This extension was challenged by generic drug manufacturer Lupin Pharmaceuticals, which did not challenge the validity of the patent, but only the validity of the patent extension, arguing that the patent did not cover a "product" and so Hatch-Waxman was not available for extensions. The federal patent court ruled in favor of J&J and Daiichi, and generic versions of levofloxacin did not enter the U.S. market until 2009. | 4 | Stereochemistry |
Antanas Purėnas (16 February 1881 – 5 November 1962) was a famous Lithuanian organic chemist and politician. | 0 | Organic Chemistry |
In the thermodynamic limit, the total number of particles N are so large that the quantum number n may be treated as a continuous variable. In this case, the overall number density profile in the box is indeed uniform.
The number of quantum states in the range is:
Without loss of generality, the zero-point energy is chosen to be zero, with the following result:
Therefore, in the range:
the number of quantum states is:
Here, the degree of degeneracy is:
And the density of states is:
In modern literature, the above is sometimes also called the "density of states". However, differs from by a factor of the system's volume (which is in this 1D case).
Based on the following formula:
the Fermi energy in the thermodynamic limit can be calculated to be: | 7 | Physical Chemistry |
In an ordinary fermion gas in which thermal effects dominate, most of the available electron energy levels are unfilled and the electrons are free to move to these states. As particle density is increased, electrons progressively fill the lower energy states and additional electrons are forced to occupy states of higher energy even at low temperatures. Degenerate gases strongly resist further compression because the electrons cannot move to already filled lower energy levels due to the Pauli exclusion principle. Since electrons cannot give up energy by moving to lower energy states, no thermal energy can be extracted. The momentum of the fermions in the fermion gas nevertheless generates pressure, termed "degeneracy pressure".
Under high densities matter becomes a degenerate gas when all electrons are stripped from their parent atoms. The core of a star, once hydrogen burning nuclear fusion reactions stops, becomes a collection of positively charged ions, largely helium and carbon nuclei, floating in a sea of electrons, which have been stripped from the nuclei. Degenerate gas is an almost perfect conductor of heat and does not obey ordinary gas laws. White dwarfs are luminous not because they are generating energy but rather because they have trapped a large amount of heat which is gradually radiated away. Normal gas exerts higher pressure when it is heated and expands, but the pressure in a degenerate gas does not depend on the temperature. When gas becomes super-compressed, particles position right up against each other to produce degenerate gas that behaves more like a solid. In degenerate gases the kinetic energies of electrons are quite high and the rate of collision between electrons and other particles is quite low, therefore degenerate electrons can travel great distances at velocities that approach the speed of light. Instead of temperature, the pressure in a degenerate gas depends only on the speed of the degenerate particles; however, adding heat does not increase the speed of most of the electrons, because they are stuck in fully occupied quantum states. Pressure is increased only by the mass of the particles, which increases the gravitational force pulling the particles closer together. Therefore, the phenomenon is the opposite of that normally found in matter where if the mass of the matter is increased, the object becomes bigger. In degenerate gas, when the mass is increased, the particles become spaced closer together due to gravity (and the pressure is increased), so the object becomes smaller. Degenerate gas can be compressed to very high densities, typical values being in the range of 10,000 kilograms per cubic centimeter.
There is an upper limit to the mass of an electron-degenerate object, the Chandrasekhar limit, beyond which electron degeneracy pressure cannot support the object against collapse. The limit is approximately 1.44 solar masses for objects with typical compositions expected for white dwarf stars (carbon and oxygen with two baryons per electron). This mass cut-off is appropriate only for a star supported by ideal electron degeneracy pressure under Newtonian gravity; in general relativity and with realistic Coulomb corrections, the corresponding mass limit is around 1.38 solar masses. The limit may also change with the chemical composition of the object, as it affects the ratio of mass to number of electrons present. The object's rotation, which counteracts the gravitational force, also changes the limit for any particular object. Celestial objects below this limit are white dwarf stars, formed by the gradual shrinking of the cores of stars that run out of fuel. During this shrinking, an electron-degenerate gas forms in the core, providing sufficient degeneracy pressure as it is compressed to resist further collapse. Above this mass limit, a neutron star (primarily supported by neutron degeneracy pressure) or a black hole may be formed instead. | 7 | Physical Chemistry |
The most common method is alkaline lysis, which involves the use of a high concentration of a basic solution, such as sodium hydroxide, to lyse the bacterial cells. When bacteria are lysed under alkaline conditions (pH 12.0–12.5) both chromosomal DNA and protein are denatured; the plasmid DNA however, remains stable. Some scientists reduce the concentration of NaOH used to 0.1M in order to reduce the occurrence of ssDNA. After the addition of acetate-containing neutralization buffer to lower the pH to around 7, the large and less supercoiled chromosomal DNA and proteins form large complexes and precipitate; but the small bacterial DNA plasmids stay in solution. | 1 | Biochemistry |
Expression is quantified to study cellular changes in response to external stimuli, differences between healthy and diseased states, and other research questions. Transcript levels are often used as a proxy for protein abundance, but these are often not equivalent due to post transcriptional events such as RNA interference and nonsense-mediated decay.
Expression is quantified by counting the number of reads that mapped to each locus in the transcriptome assembly step. Expression can be quantified for exons or genes using contigs or reference transcript annotations. These observed RNA-Seq read counts have been robustly validated against older technologies, including expression microarrays and qPCR. Tools that quantify counts are HTSeq, FeatureCounts, Rcount, maxcounts, FIXSEQ, and Cuffquant. These tools determine read counts from aligned RNA-Seq data, but alignment-free counts can also be obtained with Sailfish and Kallisto. The read counts are then converted into appropriate metrics for hypothesis testing, regressions, and other analyses. Parameters for this conversion are:
* Sequencing depth/coverage: Although depth is pre-specified when conducting multiple RNA-Seq experiments, it will still vary widely between experiments. Therefore, the total number of reads generated in a single experiment is typically normalized by converting counts to fragments, reads, or counts per million mapped reads (FPM, RPM, or CPM). The difference between RPM and FPM was historically derived during the evolution from single-end sequencing of fragments to paired-end sequencing. In single-end sequencing, there is only one read per fragment (i.e., RPM = FPM). In paired-end sequencing, there are two reads per fragment (i.e., RPM = 2 x FPM). Sequencing depth is sometimes referred to as library size, the number of intermediary cDNA molecules in the experiment.
* Gene length: Longer genes will have more fragments/reads/counts than shorter genes if transcript expression is the same. This is adjusted by dividing the FPM by the length of a feature (which can be a gene, transcript, or exon), resulting in the metric fragments per kilobase of feature per million mapped reads (FPKM). When looking at groups of features across samples, FPKM is converted to transcripts per million (TPM) by dividing each FPKM by the sum of FPKMs within a sample.
* Total sample RNA output: Because the same amount of RNA is extracted from each sample, samples with more total RNA will have less RNA per gene. These genes appear to have decreased expression, resulting in false positives in downstream analyses. Normalization strategies including quantile, DESeq2, TMM and Median Ratio attempt to account for this difference by comparing a set of non-differentially expressed genes between samples and scaling accordingly.
* Variance for each genes expression:' is modeled to account for sampling error (important for genes with low read counts), increase power, and decrease false positives. Variance can be estimated as a normal, Poisson, or negative binomial distribution and is frequently decomposed into technical and biological variance. | 1 | Biochemistry |
Hemozoin formation is an excellent drug target, since it is essential to malaria parasite survival and absent from the human host. The drug target hematin is host-derived and largely outside the genetic control of the parasite, which makes the development of drug resistance more difficult. Many clinically used drugs are thought to act by inhibiting the formation of hemozoin in the food vacuole. This prevents the detoxification of the heme released in this compartment, and kills the parasite.
The best-understood examples of such hematin biocrystallization inhibitors are quinoline drugs such as chloroquine and mefloquine. These drugs bind to both free heme and hemozoin crystals, and therefore block the addition of new heme units onto the growing crystals. The small, most rapidly growing face is the face to which inhibitors are believed to bind. | 1 | Biochemistry |
This method starts with a solution of hydrogen peroxide and sulfuric acid. To this a solution containing potassium iodide, sodium thiosulfate, and starch is added. There are two reactions occurring simultaneously in the solution.
In the first, slow reaction, iodine is produced:
In the second, fast reaction, iodine is reconverted to two iodide ions by the thiosulfate:
After some time the solution always changes color to a very dark blue, almost black.
When the solutions are mixed, the second reaction causes the iodine to be consumed much faster than it is generated, and only a small amount of iodine is present in the dynamic equilibrium. Once the thiosulfate ion has been exhausted, this reaction stops and the blue colour caused by the iodine – starch complex appears.
Anything that accelerates the first reaction will shorten the time until the solution changes color. Decreasing the pH (increasing concentration), or increasing the concentration of iodide or hydrogen peroxide will shorten the time. Adding more thiosulfate will have the opposite effect; it will take longer for the blue colour to appear.
Aside from using sodium thiosulfate as a substrate, cysteine can also be used.
Iodide from potassium iodide is converted to iodine in the first reaction:
2 + 2 H + HO → I + 2 HO
The iodine produced in the first reaction is reduced back to iodide by the reducing agent, cysteine. At the same time, cysteine is oxidized into cystine.
2 CHNOS + I → CHNOS + 2 + 2 H
Similar to thiosulfate case, when cysteine is exhausted, the blue color appears. | 7 | Physical Chemistry |
ESI-MS was initially developed by Fenn and colleagues for analysis of biomolecules. It depends on the formation of gaseous ions from polar, thermally labile and mostly non-volatile molecules and thus is completely suitable for a variety of lipids. It is a soft-ionization method that rarely disrupts the chemical nature of the analyte prior to mass analysis. Various ESI-MS methods have been developed for analysis of different classes, subclasses, and individual lipid species from biological extracts. Comprehensive reviews of the methods and their application have recently been published. The major advantages of ESI-MS are high accuracy, sensitivity, reproducibility, and the applicability of the technique to complex solutions without prior derivatization. Han and coworkers have developed a method known as"shotgun lipidomics" which involves direct infusion of a crude lipid extract into an ESI source optimized for intrasource separation of lipids based on their intrinsic electrical properties. | 1 | Biochemistry |
Horizontal plate filter paper is commonly utilized in industrial processing. Filter paper typically is designed to fit the manufacturers specifications. Absolute micron retention can range from 1–100 microns but Diatomaceous earth is commonly used with filter paper to obtain sub-micron filtration. Activated carbon or other filter aids can be used with the filter paper to form a filter cake to achieve specific results. Filter paper can be impregnated with DE or activated carbon. | 3 | Analytical Chemistry |
Orbiting bodies can also be heated by tidal heating, geothermal energy which is driven by radioactive decay in the core of the planet, or accretional heating. These internal processes will cause the effective temperature (a blackbody temperature that produces the observed radiation from a planet) to be warmer than the equilibrium temperature (the blackbody temperature that one would expect from solar heating alone).
For example, on Saturn, the effective temperature is approximately 95 K, compared to an equilibrium temperature of about 63 K. This corresponds to a ratio between power emitted and solar power received of ~2.4, indicating a significant internal energy source. Jupiter and Neptune have ratios of power emitted to solar power received of 2.5 and 2.7, respectively.
Close correlation between the effective temperature and equilibrium temperature of Uranus can be taken as evidence that processes producing an internal flux are negligible on Uranus compared to the other giant planets.
Earth has insufficient geothermal heating to significantly affect its global temperature, with geothermal heating supplying only 0.03% of Earth's total energy budget. | 7 | Physical Chemistry |
For aircraft the US Federal Aviation Regulations suggest RHT principles, both in the air and on water, and in aircraft with side-by-side cockpit seating, the pilot-in-command (or more senior flight officer) traditionally occupies the left seat. However, helicopter practice tends to favour the right hand seat for the pilot-in-command, particularly when flying solo. | 4 | Stereochemistry |
The American Society for Biochemistry and Molecular Biology publishes three research journals and a monthly magazine covering society news and activity updates. ASBMB journals are peer-reviewed and cover research in the fields of microbiology, molecular genetics, RNA-related research, proteomics, genomics, transcription, peptides, cell signaling, lipidomics, and systems biology. All articles are published online as "Papers in Press" upon acceptance. As of January 2021, all three ASBMB journals are fully open access.
* The Journal of Biological Chemistry publishes research in any area of biochemistry or molecular biology in one online-only issue per week.
* Molecular & Cellular Proteomics is a monthly online only publication. Articles appearing in MCP "...describe the structural and functional properties of proteins and their expression, particularly with respect to the developmental time courses of the organism of which they are a part." The journal also publishes other content such as "HUPO views" (reports from the Human Proteome Organization), proceedings from HUPO meetings, and the proceedings of the International Symposium On Mass Spectrometry In The Life Sciences.
* The Journal of Lipid Research covers "...the science of lipids in health and disease. The Journal emphasizes lipid function and the biochemical and genetic regulation of lipid metabolism. In addition, JLR publishes manuscripts on patient-oriented and epidemiological research relating to altered lipid metabolism, including modification of dietary lipids."
* ASBMB Today is the societys monthly news magazine. It contains extensive coverage of awards, meetings, research highlights, job placement advertising and human interest articles. All ASBMB members receive a complimentary subscription to ASBMB Today'. The online version of the magazine features daily publishing. | 1 | Biochemistry |
Researching jelly-falls relies on direct observational data such as video, photography, or benthic trawls. A complication with trawling for jelly-falls is the gelatinous carcass easily falls apart and as a result, opportunistic photography, videography, and chemical analysis have been primary methods of monitoring. This means that jelly-falls are not always observed in the time period in which they exist. Because jelly-falls can be fully processed and degraded within a number of hours by scavengers and the fact that some jelly-falls will not sink below 500 m in tropical and subtropical waters, the importance and prevalence of jelly-falls may be underestimated. | 9 | Geochemistry |
The chemical reaction that is responsible for bio-luminescence is catalyzed by the enzyme luciferase. In the presence of oxygen, luciferase catalyzes the oxidation of an organic molecule called luciferin. Though bio-luminescence across a diverse range of organisms such as bacteria, insects, and dinoflagellates function in this general manner (utilizing luciferase and luciferin), there are different types of luciferin-luciferase systems. For bacterial bio-luminescence specifically, the biochemical reaction involves the oxidation of an aliphatic aldehyde by a reduced flavin mononucleotide. The products of this oxidation reaction include an oxidized flavin mononucleotide, a fatty acid chain, and energy in the form of a blue-green visible light.
Reaction: FMNH + O + RCHO → FMN + RCOOH + HO + light | 1 | Biochemistry |
Some crops are grown under the protective shelter of different kinds of plant, whether as wind breaks or for shade. For example, shade-grown coffee, especially Coffea arabica, has traditionally been grown in light shade created by scattered trees with a thin canopy, allowing light through to the coffee bushes but protecting them from overheating. Suitable Asian trees include Erythrina subumbrans (tton tong or dadap), Gliricidia sepium (khae falang), Cassia siamea (khi lek), Melia azedarach (khao dao sang), and Paulownia tomentosa, a useful timber tree. | 1 | Biochemistry |
Pharmacometabolomics is thought to provide information that complements that gained from other omics, namely genomics, transcriptomics, and proteomics. Looking at the characteristics of an individual down through these different levels of detail, there is an increasingly more accurate prediction of a person's ability to respond to a pharmaceutical compound. The genome, made up of 25 000 genes, can indicate possible errors in drug metabolism; the transcriptome, made up of 85,000 transcripts, can provide information about which genes important in metabolism are being actively transcribed; and the proteome, >10,000,000 members, depicts which proteins are active in the body to carry out these functions. Pharmacometabolomics complements the omics with direct measurement of the products of all of these reactions, but with perhaps a relatively smaller number of members: that was initially projected to be approximately 2200 metabolites, but could be a larger number when gut derived metabolites and xenobiotics are added to the list. Overall, the goal of pharmacometabolomics is to more closely predict or assess the response of an individual to a pharmaceutical compound, permitting continued treatment with the right drug or dosage depending on the variations in their metabolism and ability to respond to treatment.
Pharmacometabolomic analyses, through the use of a metabolomics approach, can provide a comprehensive and detailed metabolic profile or “metabolic fingerprint” for an individual patient. Such metabolic profiles can provide a complete overview of individual metabolite or pathway alterations, providing a more realistic depiction of disease phenotypes. This approach can then be applied to the prediction of response to a pharmaceutical compound by patients with a particular metabolic profile. Pharmacometabolomic analyses of drug response are often coupled or followed up with pharmacogenetics studies. Pharmacogenetics focuses on the identification of genetic variations (e.g. single-nucleotide polymorphisms) within patients that may contribute to altered drug responses and overall outcome of a certain treatment. The results of pharmacometabolomics analyses can act to “inform” or “direct” pharmacogenetic analyses by correlating aberrant metabolite concentrations or metabolic pathways to potential alterations at the genetic level. This concept has been established with two seminal publications from studies of antidepressants serotonin reuptake inhibitors where metabolic signatures were able to define pathway implicated in response to the antidepressant and that lead to identification of genetic variants within a key gene within highlighted pathway as being implicated in variation in response. These genetic variants were not identified through genetic analysis alone and hence illustrated how metabolomics can guide and inform genetic data. | 1 | Biochemistry |
Phycobiliproteins are found in cyanobacteria (also known as blue-green algae) and algae groups such as rhodophyta (red algae) and cryptophytes. Major phycobiliproteins include variations of phycocyanin (blue-pigment), variations of phycoerythrin (red pigment), and allophycocyanin (light-blue pigment); each of them possessing different spectral properties. These water-soluble biliproteins are not essential for the functioning of cells. Some special qualities of phycobiliproteins include antioxidant properties and high fluorescence, and it is their chromophores that give these proteins their strong pigment. Phycobiliproteins are classified into two categories based on their amino-terminal sequences: "α-type" and "β-type" sequences. In biliproteins where the number of bilins on the two subunits is unequal, the subunit with more bilins has a β-type amino sequence. | 1 | Biochemistry |
Woods metal, also known as Lipowitzs alloy or by the commercial names Cerrobend, Bendalloy, Pewtalloy and MCP 158, is a metal alloy that is useful for soldering and making custom metal parts, but its vapor is toxic to touch or breathe. The alloy is named for Barnabas Wood, who invented and patented the alloy in 1860. It is a eutectic, fusible alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by mass. It has a melting point of approximately . | 8 | Metallurgy |
George Warren Hammond (April 4, 1833 – January 6, 1908) was an American businessman. Camp Hammond, in Yarmouth, Maine, is named for him. He was also one of its architects. Built in , it was placed on the National Register of Historic Places in 1979.
Hammond was also co-owner of Forest Paper Company, which was the largest paper mill in the world at the time of his death. The mill was also known as a pioneer in the processing of soda pulp. | 8 | Metallurgy |
Cryolite (NaAlF) is the least abundant of the three major fluorine-containing minerals, but is a concentrated source of fluorine. It was formerly used directly in aluminium production. However, the main commercial mine, on the west coast of Greenland, closed in 1987. | 9 | Geochemistry |
Viel is co-author of The Inner Life of the Cell, an 8.5-minute 3D computer graphics animation illustrating the molecular mechanisms that occur when a white blood cell in the blood vessels of the human body is activated by inflammation (Leukocyte extravasation). It shows how a white blood cell rolls along the inner surface of the capillary, flattens out, and squeezes through the cells of the capillary wall to the site of inflammation where it contributes to the immune reaction. | 1 | Biochemistry |
Ring A was synthesised starting from geraniol 1 and involved acylation (acetic anhydride, DMAP, EtN) to 2, epoxidation (N-bromosuccinimide, tBuOH/HO then triethylamine) to 3, radical cyclisation (titanocene dichloride, manganese, triethylborane, 2,6-lutidine) to 4, alcohol protection (ethyl vinyl ether, camphorsulfonic acid) to 5, alcohol deprotection (NaOH, MeOH/THF/HO) to alcohol 6, Parikh-Doering oxidation to aldehyde 7, isomerization (DBU) to enone 8, organic reduction (sodium borohydride) to alcohol 9, alcohol protection (TBSCl, EtN) to TBS ether 10, hydrazone formation (HNNHTs) to 11 and finally vinyl bromide formation (tBuLi, 1,2-Dibromoethane) in 12. | 0 | Organic Chemistry |
Claudine Helen Stirling is a New Zealand isotope geochemistry academic. As of 2018, she is a full professor at the University of Otago. In 2024 she was elected as a Fellow of the Royal Society Te Apārangi. | 9 | Geochemistry |
The proposed pathway for electron transport prior to ubiquinone reduction is as follows: NADH – FMN – N3 – N1b – N4 – N5 – N6a – N6b – N2 – Q, where Nx is a labelling convention for iron sulfur clusters. The high reduction potential of the N2 cluster and the relative proximity of the other clusters in the chain enable efficient electron transfer over long distance in the protein (with transfer rates from NADH to N2 iron-sulfur cluster of about 100 μs).
The equilibrium dynamics of Complex I are primarily driven by the quinone redox cycle. In conditions of high proton motive force (and accordingly, a ubiquinol-concentrated pool), the enzyme runs in the reverse direction. Ubiquinol is oxidized to ubiquinone, and the resulting released protons reduce the proton motive force. | 1 | Biochemistry |
The scale of a chemical process refers to the rough ranges in mass or volume of a chemical reaction or process that define the appropriate category of chemical apparatus and equipment required to accomplish it, and the concepts, priorities, and economies that operate at each. While the specific terms used—and limits of mass or volume that apply to them—can vary between specific industries, the concepts are used broadly across industry and the fundamental scientific fields that support them. Use of the term "scale" is unrelated to the concept of weighing; rather it is related to cognate terms in mathematics (e.g., geometric scaling, the linear transformation that enlarges or shrinks objects, and scale parameters in probability theory), and in applied areas (e.g., in the scaling of images in architecture, engineering, cartography, etc.).
Practically speaking, the scale of chemical operations also relates to the training required to carry them out, and can be broken out roughly as follows:
* procedures performed at the laboratory scale, which involve the sorts of procedures used in academic teaching and research laboratories in the training of chemists and in discovery chemistry venues in industry,
* operations at the pilot plant scale, e.g., carried out by process chemists, which, though at the lowest extreme of manufacturing operations, are on the order of 200- to 1000-fold larger than laboratory scale, and used to generate information on the behavior of each chemical step in the process that might be useful to design the actual chemical production facility;
* intermediate bench scale sets of procedures, 10- to 200-fold larger than the discovery laboratory, sometimes inserted between the preceding two;
* operations at demonstration scale and full-scale production, whose sizes are determined by the nature of the chemical product, available chemical technologies, the market for the product, and manufacturing requirements, where the aim of the first of these is literally to demonstrate operational stability of developed manufacturing procedures over extended periods (by operating the suite of manufacturing equipment at the feed rates anticipated for commercial production).
For instance, the production of the streptomycin-class of antibiotics, which combined biotechnologic and chemical operations, involved use of a 130,000 liter fermenter, an operational scale approximately one million-fold larger than the microbial shake flasks used in the early laboratory scale studies.
As noted, nomenclature can vary between manufacturing sectors; some industries use the scale terms pilot plant and demonstration plant interchangeably.
Apart from defining the category of chemical apparatus and equipment required at each scale, the concepts, priorities and economies that obtain, and the skill-sets needed by the practicing scientists at each, defining scale allows for theoretical work prior to actual plant operations (e.g., defining relevant process parameters used in the numerical simulation of large-scale production processes), and allows economic analyses that ultimately define how manufacturing will proceed.
Besides the chemistry and biology expertises involved in scaling designs and decisions, varied aspects of process engineering and mathematical modeling, simulations, and operations research are involved. | 0 | Organic Chemistry |
Water quality models have different information, but generally have the same purpose, which is to provide evidentiary support of water issues. Models can be either deterministic or statistical depending on the scale with the base model, which is dependent on if the area is on a local, regional, or a global scale. Another aspect to consider for a model is what needs to be understood or predicted about that research area along with setting up any parameters to define the research. Another aspect of building a water quality model is knowing the audience and the exact purpose for presenting data like to enhance water quality management for water quality law makers for the best possible outcomes. | 9 | Geochemistry |
There are two main assaying techniques: heterogeneous and homogeneous. If two lanthanide chelates are used in the analysis one after the other—it is called heterogeneous assaying. The first analyte is linked to a specific binding agent on a solid support such as a polymer and then another reaction couples the first poorly luminescent lanthanide complex with a new better one. This tedious method is used because the second more luminescent compound would not bind without the first analyte already present. Subsequent time resolved detection of the metal-centered luminescent probe yields the desired signal. Antigens, steroids and hormones are routinely assayed with heterogeneous techniques. Homogeneous assays rely on direct coupling of the lanthanide label with an organic acceptor.
The relaxation of excited molecules states often occurs by the emission of light which is called fluorescence. There are two ways of measuring this emitted radiation: as a function of frequency (inverse to wavelength) or time. Conventionally the fluorescence spectrum shows the intensity of fluorescence at different wavelengths, but since lanthanides have relatively long fluorescence decay times (ranging from one microsecond to one millisecond), it is possible to record the fluorescence emission at different decay times from the given excitation energy at time zero. This is called time resolved fluorescence spectroscopy. | 1 | Biochemistry |
Microarrays use hybridization probes to test the prevalence of known DNA sequences, thus they cannot be used to identify unexpected genetic changes. In contrast, the high-throughput sequencing technologies used in exome sequencing directly provide the nucleotide sequences of DNA at the thousands of exonic loci tested. Hence, WES addresses some of the present limitations of hybridization genotyping arrays.
Although exome sequencing is more expensive than hybridization-based technologies on a per-sample basis, its cost has been decreasing due to the falling cost and increased throughput of whole genome sequencing. | 1 | Biochemistry |
The strength of an electrofusion joint is measured using tensile and peel tests on coupons taken from the fusion zone of the joint. Two methods have been developed to assess the effect of fusion time on joint strength:
# Simulating an electrofusion joint solely for testing purposes
# Removing test coupons from standard electrofusion welded joints
The strength of the joint develops throughout the welding process, and this development is affected by the fusion time, joint gap, and pipe material. These are detailed below. | 7 | Physical Chemistry |
In December 2004 plans were submitted, in partnership with Countryside Properties, to build an urban village over two-thirds of the site, comprising residential and business developments, a retail site and doctors surgery. MMC director Mark Russell stated that the plans were in everyones interests and would be carried out without harming the environment or causing problems with old asbestos: "At the end of the day this is a contaminated site with lots of old, ugly, dilapidated buildings on and it needs something doing with it. It is in everyone's interests that this happens." The planning application summary claimed: "of particular note is the absence of any asbestos contamination". A report submitted by the developers said only one out of the 86 soil tests they carried out showed any traces of asbestos dust, and that traces of lead and copper were more prevalent on the site. A working party of six councillors expressed concern that many areas on the site might have been unchecked, however, and Councillor Elwyn Watkins said that he had personally observed asbestos containing materials hanging on trees when he joined campaigners on the north side of the site. Heavy winds in January 2005 felled several trees, revealing asbestos-like fibres on the exposed roots. Residents eventually had the waste tested themselves at an independent laboratory where it was confirmed to be Amosite ("brown asbestos"), the most hazardous of the asbestos minerals because of its long persistence in the lungs of exposed people. | 2 | Environmental Chemistry |
EDM is often compared to electrochemical machining.
Advantages of EDM include:
*Ability to machine complex shapes that would otherwise be difficult to produce with conventional cutting tools.
*Machining of extremely hard material to very close tolerances.
*Very small work pieces can be machined where conventional cutting tools may damage the part from excess cutting tool pressure.
*There is no direct contact between tool and work piece. Therefore, delicate sections and weak materials can be machined without perceivable distortion.
*A good surface finish can be obtained; a very good surface may be obtained by redundant finishing paths.
*Very fine holes can be attained.
*Tapered holes may be produced.
*Pipe or container internal contours and internal corners down to R 0.001".
Disadvantages of EDM include:
*Difficulty finding expert machinists.
*The slow rate of material removal.
*Potential fire hazard associated with use of combustible oil based dielectrics.
*The additional time and cost used for creating electrodes for ram/sinker EDM.
*Reproducing sharp corners on the workpiece is difficult due to electrode wear.
*Specific power consumption is very high.
*Power consumption is high.
*"Overcut" is formed.
*Excessive tool wear occurs during machining.
*Electrically non-conductive materials can be machined only with specific set-up of the process. | 8 | Metallurgy |
The formose reaction, discovered by Aleksandr Butlerov in 1861, and hence also known as the Butlerov reaction, involves the formation of sugars from formaldehyde. The term formose is a portmanteau of formaldehyde and aldose. | 0 | Organic Chemistry |
For blast furnaces, direct reduction corresponds to the reduction of oxides by the carbon in the coke. However, in practice, direct reduction only plays a significant role in the final stage of iron reduction in a blast furnace, by helping to reduce wustite (FeO) to iron. In this case, the chemical reaction can be trivially described as follows:
FeO + C → Fe + CO consuming 155,15 kJ/mol
However, "in the solid state, there is virtually no reaction in the absence of gases, even between finely ground iron ore and coal powders. In other words, it seems certain that the reaction takes place via gases". This means that direct reduction most probably corresponds to the following chain of reactions:
FeO + CO → Fe + CO producing 17,45 kJ/mol (reduction by CO)
CO + C ⇌ 2 CO consuming 172,45 kJ/mol (Boudouard reaction) | 8 | Metallurgy |
The slow but continuous production of hydrogen in deep low-permeability argillaceous formations could represent a problem for the long-term disposal of radioactive waste (Ortiz et al., 2001; Nagra, 2008; recent Nagra NTB reports). Indeed, a gas pressure build-up could occur if the rate of hydrogen production by the anaerobic corrosion of carbon-steel and by the subsequent transformation of green rust into magnetite should exceed the rate of diffusion of dissolved H in the pore water of the formation. The question is presently the object of many studies (King, 2008; King and Kolar, 2009; Nagra Technical Reports 2000–2009) in the countries (Belgium, Switzerland, France, Canada) envisaging the option of disposal in clay formation. | 8 | Metallurgy |
The structure of cyclopropyl cyanide has been determined by a variety of experiments, including microwave spectroscopy, rotational spectroscopy and photodissociation. In 1958, cyclopropyl cyanide was first studied for its rotational spectra, by Friend and Dailey. An additional experiment involving cyclopropyl cyanide was the determination of the molecular dipole moment through spectroscopy experiments, by Carvalho in 1967. | 7 | Physical Chemistry |
The DNA formed after reverse transcription (the provirus) is longer than the RNA genome because each of the terminals have the U3 - R - U5 sequences called long terminal repeat (LTR). Thus, 5' terminal has the extra U3 sequence, while the other terminal has the U5 sequence. LTRs are able to send signals for vital tasks to be carried out such as initiation of RNA production or management of the rate of transcription. This way, LTRs can control replication, hence, the entire progress of the viral cycle. Although located in the nucleus, the non-integrated retroviral cDNA is a very weak substrate for transcription. For this reason, an integrated provirus is a necessary for permanent and an effective expression of retroviral genes.
This DNA can be incorporated into host genome as a provirus that can be passed on to progeny cells. The retrovirus DNA is inserted at random into the host genome. Because of this, it can be inserted into oncogenes. In this way some retroviruses can convert normal cells into cancer cells. Some provirus remains latent in the cell for a long period of time before it is activated by the change in cell environment. | 1 | Biochemistry |
Dehydrogenation of amine-boranes or dehydrocoupling of amine-boranes is a chemical process in main group and organometallic chemistry wherein dihydrogen is released by the coupling of two or more amine-borane adducts. This process is of due to the potential of using amine-boranes for hydrogen storage. | 0 | Organic Chemistry |
A typical laboratory FPLC consist of one or two high-precision pumps, a control unit, a column, a detection system and a fraction collector. Although it is possible to operate the system manually, the components are normally linked to a personal computer or, in older units, a microcontroller. | 3 | Analytical Chemistry |
The SUPERFAMILY annotation is based on a collection of hidden Markov models (HMM), which represent structural protein domains at the SCOP superfamily level.
A superfamily groups together domains which have an evolutionary relationship. The annotation is produced by scanning protein sequences from completely sequenced genomes against the hidden Markov models.
For each protein you can:
* Submit sequences for SCOP classification
* View domain organisation, sequence alignments and protein sequence details
For each genome you can:
* Examine superfamily assignments, phylogenetic trees, domain organisation lists and networks
* Check for over- and under-represented superfamilies within a genome
For each superfamily you can:
* Inspect SCOP classification, functional annotation, Gene Ontology annotation, InterPro abstract and genome assignments
* Explore taxonomic distribution of a superfamily across the tree of life
All annotation, models and the database dump are freely available for download to everyone. | 1 | Biochemistry |
PDE3a expression has been described as a biomarker for sensitivity for PDE3-inhibitor Zardaverine in different types of cancer. | 1 | Biochemistry |
Most natural waters contain small quantities of organic compounds. Aquatic microorganisms have evolved to use some of these compounds as food. Microorganisms living in oxygenated waters use dissolved oxygen to oxidatively degrade the organic compounds, releasing energy which is used for growth and reproduction. Populations of these microorganisms tend to increase in proportion to the amount of food available. This microbial metabolism creates an oxygen demand proportional to the amount of organic compounds useful as food. Under some circumstances, microbial metabolism can consume dissolved oxygen faster than atmospheric oxygen can dissolve into the water or the autotrophic community (algae, cyanobacteria and macrophytes) can produce. Fish and aquatic insects may die when oxygen is depleted by microbial metabolism.
Biochemical oxygen demand is the amount of oxygen required for microbial metabolism of organic compounds in water. This demand occurs over some variable period of time depending on temperature, nutrient concentrations, and the enzymes available to indigenous microbial populations. The amount of oxygen required to completely oxidize the organic compounds to carbon dioxide and water through generations of microbial growth, death, decay, and cannibalism is total biochemical oxygen demand (total BOD). Total BOD is of more significance to food webs than to water quality. Dissolved oxygen depletion is most likely to become evident during the initial aquatic microbial population explosion in response to a large amount of organic material. If the microbial population deoxygenates the water, however, that lack of oxygen imposes a limit on population growth of aerobic aquatic microbial organisms resulting in a longer term food surplus and oxygen deficit.
A standard temperature at which BOD testing should be carried out was first proposed by the Royal Commission on Sewage Disposal in its eighth report in 1912:
This was later standardised at 68 °F and then 20 °C. This temperature may be significantly different from the temperature of the natural environment of the water being tested.
Although the Royal Commission on Sewage Disposal proposed 5 days as an adequate test period for rivers of the United Kingdom of Great Britain and Ireland, longer periods were investigated for North American rivers. Incubation periods of 1, 2, 5, 10 and 20 days were being used into the mid-20th century. Keeping dissolved oxygen available at their chosen temperature, investigators found up to 99 percent of total BOD was exerted within 20 days, 90 percent within 10 days, and approximately 68 percent within 5 days. Variable microbial population shifts to nitrifying bacteria limit test reproducibility for periods greater than 5 days. The 5-day test protocol with acceptably reproducible results emphasizing carbonaceous BOD has been endorsed by the United States Environmental Protection Agency (EPA). This 5-day BOD test result may be described as the amount of oxygen required for aquatic microorganisms to stabilize decomposable organic matter under aerobic conditions. Stabilization, in this context, may be perceived in general terms as the conversion of food to living aquatic fauna. Although these fauna will continue to exert biochemical oxygen demand as they die, that tends to occur within a more stable evolved ecosystem including higher trophic levels. | 3 | Analytical Chemistry |
Dexlansoprazole was approved by the U.S. Food and Drug Administration (FDA) in 2009, and was approved in Canada in 2010 and in Mexico in 2011.
Since Kapidex was approved in 2009, there have been reports of dispensing errors because of confusion with the drugs Casodex (bicalutamide) and Kadian (morphine), which have very different uses from Kapidex and from each other. In 2010, the FDA approved a name change for Kapidex to avoid confusion with the two other medications and Takeda began marketing it under the new name Dexilant. It is also available in Bangladesh for the first time as Dexlan by IBN SINA Pharmaceuticals Ltd. in April 2014 and after them DEXILEND by Ziska Pharmaceuticals Ltd., Desopra by Alco Pharma, Delanix by Incepta Pharmaceuticals, Dexogut by Popular Pharmaceuticals Ltd. also introduced it in BD market. In 2020 many other Pharmaceuticals have launched Dexlansoprazole. | 4 | Stereochemistry |
Shamoo currently resides in Columbia, MD with his wife and occasional co-author, Bonnie Bricker; his daughter, and stepdaughter. He has two sons and another stepdaughter who also all reside in the Washington Metropolitan Area. | 1 | Biochemistry |
For example, in a two electrons couple like : the reduction potential becomes ~ 30 mV (or more exactly, 59.16 mV/2 = 29.6 mV) more positive for every power of ten increase in the ratio of the oxidised to the reduced form. | 1 | Biochemistry |
The string-net model is claimed to show the derivation of photons, electrons, and U(1) gauge charge, small (relative to the Planck mass) but nonzero masses, and suggestions that the leptons, quarks, and gluons can be modeled in the same way. In other words, string-net condensation provides a unified origin for photons and electrons (or gauge bosons and fermions). It can be viewed as an origin of light and electron (or gauge interactions and Fermi statistics).
However, their model does not account for the chiral coupling between the fermions and the SU(2) gauge bosons in the standard model.
For strings labeled by the positive integers, string-nets are the spin networks studied in loop quantum gravity. This has led to the proposal by Levin and Wen, and Smolin, Markopoulou and Konopka that loop quantum gravitys spin networks can give rise to the standard model of particle physics through this mechanism, along with fermi statistics and gauge interactions. To date, a rigorous derivation from LQGs spin networks to Levin and Wen's spin lattice has yet to be done, but the project to do so is called quantum graphity, and in a more recent paper, Tomasz Konopka, Fotini Markopoulou, Simone Severini argued that there are some similarities to spin networks (but not necessarily an exact equivalence) that gives rise to U(1) gauge charge and electrons in the string net mechanism.
Herbertsmithite may be an example of string-net matter. | 7 | Physical Chemistry |
The following packages calculate the state of the carbonate system in seawater (including pH):
* [http://cdiac.ornl.gov/oceans/co2rprt.html CO2SYS] , available as a stand-alone executable, Excel spreadsheet, or MATLAB script.
* [http://cran.at.r-project.org/web/packages/seacarb/index.html seacarb], a R package for Windows, Mac OS X and Linux (also available [https://web.archive.org/web/20060212225505/http://www.obs-vlfr.fr/%7Egattuso/seacarb.php here])
* [http://www.soest.hawaii.edu/oceanography/faculty/zeebe_files/CO2_System_in_Seawater/csys.html CSYS], a Matlab script | 9 | Geochemistry |
Substantial decreases in extracellular Ca ion concentrations may result in a condition known as hypocalcemic tetany, which is marked by spontaneous motor neuron discharge. In addition, severe hypocalcaemia will begin to affect aspects of blood coagulation and signal transduction.
Ca ions can damage cells if they enter in excessive numbers (for example, in the case of excitotoxicity, or over-excitation of neural circuits, which can occur in neurodegenerative diseases, or after insults such as brain trauma or stroke). Excessive entry of calcium into a cell may damage it or even cause it to undergo apoptosis, or death by necrosis. Calcium also acts as one of the primary regulators of osmotic stress (osmotic shock). Chronically elevated plasma calcium (hypercalcemia) is associated with cardiac arrhythmias and decreased neuromuscular excitability. One cause of hypercalcemia is a condition known as hyperparathyroidism. | 1 | Biochemistry |
Physalaemin (PHY) is known to take on both a linear and helical three dimensional structure. Grace et al. (2010) have shown that in aqueous environments, PHY preferentially takes on the linear conformation whereas in an environment that simulates a cellular membrane, PHY takes on a helical confirmation from the Pro residue to the C-Terminus. This helical conformation is essential to allow the binding of PHY to neurokinin-1 (NK1) receptors. Consensus sequences between Substance P (a mammalian tachykinin and agonist of NK1) and PHY have been used to confirm that the helical confirmation is necessary for PHY to bind to NK1. | 1 | Biochemistry |
Tin is an essential metal in the creation of tin-bronzes, and its acquisition was an important part of ancient cultures from the Bronze Age onward. Its use began in the Middle East and the Balkans around 3000 BC. Tin is a relatively rare element in the Earth's crust, with about two parts per million (ppm), compared to iron with 50,000 ppm, copper with 70 ppm, lead with 16 ppm, arsenic with 5 ppm, silver with 0.1 ppm, and gold with 0.005 ppm. Ancient sources of tin were therefore rare, and the metal usually had to be traded over very long distances to meet demand in areas which lacked tin deposits.
Known sources of tin in ancient times include the southeastern tin belt that runs from Yunnan in China to the Malay Peninsula; Cornwall and Devon in Britain; Brittany in France; the border between Germany and the Czech Republic; Spain; Portugal; Italy; and central and South Africa. Syria and Egypt have been suggested as minor sources of tin, but the archaeological evidence is inconclusive. | 8 | Metallurgy |
*The G complexes sometimes also have active functions. Examples include coupling to and activating G protein-coupled inwardly-rectifying potassium channels. | 1 | Biochemistry |
There are numerous reasons that each of the four processes can occur (detailed in each article). Generally speaking, sources of acid gain include:
# Retention of carbon dioxide
# Production of nonvolatile acids from the metabolism of proteins and other organic molecules
# Loss of bicarbonate in feces or urine
# Intake of acids or acid precursors
Sources of acid loss include:
# Use of hydrogen ions in the metabolism of various organic anions
# Loss of acid in the vomitus or urine
# Gastric aspiration in hospital
# Severe diarrhea
# Carbon dioxide loss through hyperventilation | 7 | Physical Chemistry |
Certain lithium compounds, also known as lithium salts, are used as psychiatric medication, primarily for bipolar disorder and for major depressive disorder. In lower doses, other salts such as lithium citrate are known as nutritional lithium and have occasionally been used to treat ADHD. Lithium is taken orally (by mouth).
Common side effects include increased urination, shakiness of the hands, and increased thirst. Serious side effects include hypothyroidism, diabetes insipidus, and lithium toxicity. Blood level monitoring is recommended to decrease the risk of potential toxicity. If levels become too high, diarrhea, vomiting, poor coordination, sleepiness, and ringing in the ears may occur. Lithium is teratogenic at high doses, especially during the first trimester of pregnancy. The use of lithium while breastfeeding is controversial; however, many international health authorities advise against it, and the long-term outcomes of perinatal lithium exposure have not been studied. The American Academy of Pediatrics lists lithium as contraindicated for pregnancy and lactation. The United States Food and Drug Administration categorizes lithium as having positive evidence of risk for pregnancy and possible hazardous risk for lactation.
Lithium salts are classified as mood stabilizers. Lithium's mechanism of action is not known.
In the nineteenth century, lithium was used in people who had gout, epilepsy, and cancer. Its use in the treatment of mental disorders began with Carl Lange in Denmark and William Alexander Hammond in New York City, who used lithium to treat mania from the 1870s onwards, based on now-discredited theories involving its effect on uric acid. Use of lithium for mental disorders was re-established (on a different theoretical basis) in 1948 by John Cade in Australia. Lithium carbonate is on the World Health Organization's List of Essential Medicines, and is available as a generic medication. In 2020, it was the 197th most commonly prescribed medication in the United States, with more than 2million prescriptions. It appears to be under-utilised in older people, though the reason for that is unclear. | 1 | Biochemistry |
It can be seen in some studies that biodegradation accounts for the absence of creosote preservatives on the initial surface of the sediment. In a study from Pensacola, Florida, PAHs were not detected on the surface on the aquatic sediment, but the highest concentrations were detected at a depth of 8-13 centimeters. A form an anaerobic biodegradation of m-cresol was seen in a study using sulfate-reducing and nitrate-reducing enriched environments. The reduction of m-cresol in this study was seen in under 144 hours, while additional chemical intermediates were being formed. The chemical intermediates were formed in the presence of bicarbonate. The products included 4-hydroxy-2-methylbenzoic acid and acetate compounds. Although the conditions were enriched with the reducing anaerobic compounds, sulfate and nitrate reducing bacteria are commonly found in the environment. For further information, see sulfate-reducing bacteria. The type of anaerobic bacteria ultimately determines the reduction of the creosote preservative compounds, while each individual compound may only go through reduction under certain conditions. BTEX is a mixture of benzene, toluene, ethylbenzene, and xylene, that was studied in the presence of four different anaerobic-enriched sediments. Though the compound, BTEX, is not found in creosote preservatives, the products of creosote preservatives' oxidation-reduction reactions include some of these compounds. For oxidation-reduction reactions, see the following section. In this study, it was seen that certain compounds such as benzene were only reduced under sulfate-enriched environments, while toluene was reduced under a variety of bacteria-enriched environments, not just sulfate. The biodegradation of a creosote preservative in an anaerobic enrichment depends not only on the type of bacteria enriching the environment, but also the compound that has been released from the preservative. In aerobic environments, preservative compounds are limited in the biodegradation process by the presence of free oxygen. In an aerobic environment, free oxygen comes from oxygen saturated sediments, sources of precipitation, and plume edges. The free oxygen allows for the compounds to be oxidized and decomposed into new intermediate compounds. Studies have shown that when BTEX and PAH compounds were placed in aerobic environments, the oxidation of the ring structures caused cleavage in the aromatic ring and allowed for other functional groups to attach. When an aromatic hydrocarbon was introduced to the molecular oxygen in experimental conditions, a dihydrodiol intermediate was formed, and then oxidation occurred transforming the aromatic into a catechol compound. Catechol allows for cleavage of the aromatic ring to occur, where functional groups can then add in an ortho- or meta- position. | 7 | Physical Chemistry |
Hard water is water that has a high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum, which are largely made up of calcium and magnesium carbonates, bicarbonates and sulfates.
Drinking hard water may have moderate health benefits. It can pose critical problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment that handles water. In domestic settings, hard water is often indicated by a lack of foam formation when soap is agitated in water, and by the formation of limescale in kettles and water heaters. Wherever water hardness is a concern, water softening is commonly used to reduce hard water's adverse effects. | 3 | Analytical Chemistry |
People with disabilities who wish to have children are equally or more likely than the non-disabled population to experience infertility, yet disabled individuals are much less likely to have access to fertility treatment such as IVF. There are many extraneous factors that hinder disabled individuals access to IVF, such as assumptions about decision-making capacity, sexual interests and abilities, heritability of a disability, and beliefs about parenting ability. These same misconceptions about people with disabilities that once led health care providers to sterilise thousands of women with disabilities now lead them to provide or deny reproductive care on the basis of stereotypes concerning people with disabilities and their sexuality.
Not only do misconceptions about disabled individuals parenting ability, sexuality, and health restrict and hinder access to fertility treatment such as IVF, structural barriers such as providers uneducated in disability healthcare and inaccessible clinics severely hinder disabled individuals access to receiving IVF. | 1 | Biochemistry |
The [4+2] cycloaddition of singlet oxygen to cyclopentadiene to create cis-2-cyclopentene-1,4-diol is a common step involved in the synthesis of prostaglandins. The initial addition singlet oxygen, through the concerted [4+2] cycloaddition, forms an unstable endoperoxide. Subsequent reduction of the peroxide bound produces the two alcohol groups. | 5 | Photochemistry |
Similar to natural bases, x-nucleotides selectively assemble into a duplex-structure resembling B-DNA. xDNA was originally synthesized by incorporating a benzene ring into the nitrogenous base. However, other expanded bases have been able to incorporate thiophene and [[Benzothiophene|benzo[b]thiophene]] as well. xDNA and yDNA use benzene rings to widen the bases and are thus termed "benzo-homologated". Another form of expanded nucleobases known as yyDNA incorporate naphthalene into the base and are "naptho-homologated". xDNA has a rise of 3.2Å and a twist of 32°, significantly smaller than B-DNA, which has a rise of 3.3Å and a twist of 34.2° xDNA nucleotides can occur on both strands—either alone (known as "doubly expanded DNA") or mixed with natural bases—or exclusively on one strand or the other. Similar to B-DNA, xDNA can recognize and bind complementary single-stranded DNA or RNA sequences.
Duplexes formed from xDNA are similar to natural duplexes aside from the distance between the two sugar-phosphate backbones. xDNA helices have a greater number of base pairs per turn of the helix as a result of a reduced distance between neighbour nucleotides. NMR spectra report that xDNA helices are anti-parallel, right-handed and take an anti conformation around the glycosidic bond, with a C2-endo sugar pucker. Helices created from xDNA are more likely to take a B-helix over an A-helix conformation, and have an increased major groove width by 6.5Å (where the backbones are farthest apart) and decreased minor groove width by 5.5Å (where the backbones are closest together) compared to B-DNA. Altering groove width affects the xDNAs ability to associate with DNA-binding proteins, but as long as the expanded nucleotides are exclusive to one strand, recognition sites are sufficiently similar to B-DNA to allow bonding of transcription factors and small polyamide molecules. Mixed helices present the possibility of recognizing the four expanded bases using other DNA-binding molecules. | 1 | Biochemistry |
In general, most ingestions in children involve exploratory ingestions of small amounts of caustic substances, with the rare exception being cases of child abuse where larger amounts are often ingested. Caustic ingestions in adults usually involve larger amounts of ingested material during attempts of self harm. Due to the greater amount of material usually ingested; injuries are often more severe in the intentional ingestions of adolescents and adults as compared to those of children. Commonly ingested substances include ammonium hydroxide (found in general cleaner and grease remover), sodium hydroxide or potassium hydroxide (found in drain opener or oven cleaner), sodium hypochlorite (bleach), oxalic acid (metal polish) and hydrochloric acid (toilet bowl cleaner). Storage of caustic substances in water or drink containers is a risk factor for accidental ingestion of these materials, particularly in children. Boys of preschool age are at the greatest risk of accidental caustic ingestion. | 8 | Metallurgy |
Schiff bases can be synthesized from an aliphatic or aromatic amine and a carbonyl compound by nucleophilic addition forming a hemiaminal, followed by a dehydration to generate an imine. In a typical reaction, 4,4-oxydianiline reacts with o'-vanillin: | 0 | Organic Chemistry |
DPVweb is a central web-based source of information about viruses, viroids and satellites of plants, fungi and protozoa.
It provides comprehensive taxonomic information, including brief descriptions of each family and genus, and classified lists of virus sequences. It makes use of a large database that also holds detailed, curated, information for all sequences of viruses, viroids and satellites of plants, fungi and protozoa that are complete or that contain at least one complete gene. There are currently about 10,000 such sequences. For comparative purposes, DPVweb also contains a representative sequence of all other fully sequenced virus species with an RNA or single-stranded DNA genome. For each curated sequence the database contains the start and end positions of each feature (gene, non-translated region, etc.), and these have been checked for accuracy. As far as possible, the nomenclature for genes and proteins are standardized within genera and families. Sequences of features (either as DNA or amino acid sequences) can be directly downloaded from the website in FASTA format.
The sequence information can also be accessed via client software for personal computers. | 1 | Biochemistry |
Sedimentation potential occurs when dispersed particles move under the influence of either gravity or centrifugation or electricity in a medium. This motion disrupts the equilibrium symmetry of the particles double layer. While the particle moves, the ions in the electric double layer lag behind due to the liquid flow. This causes a slight displacement between the surface charge and the electric charge of the diffuse layer. As a result, the moving particle creates a dipole moment. The sum of all of the dipoles generates an electric field which is called sedimentation potential'. It can be measured with an open electrical circuit, which is also called sedimentation current.
There are detailed descriptions of this effect in many books on colloid and interface science. | 7 | Physical Chemistry |
Fluxes have several important properties:
* Activity – the ability to dissolve existing oxides on the metal surface and promote wetting with solder. Highly active fluxes are often acidic or corrosive in nature.
* Corrosivity – the promotion of corrosion by the flux and its residues. Most active fluxes tend to be corrosive at room temperatures and require careful removal. As activity and corrosivity are linked, the preparation of surfaces to be joined should allow use of milder fluxes. Some water-soluble flux residues are hygroscopic, which causes problems with electrical resistance and contributes to corrosion. Fluxes containing halides and mineral acids are highly corrosive and require thorough removal. Some fluxes, especially those based on borax used for brazing, form very hard glass-like coatings that are difficult to remove.
* Cleanability – the difficulty of removal of flux and its residues after the soldering operation. Fluxes with higher content of solids tend to leave larger amount of residues; thermal decomposition of some vehicles also leads to formation of difficult-to-clean, polymerized and possibly even charred deposits (a problem especially for hand soldering). Some flux residues are soluble in organic solvents, others in water, some in both. Some fluxes are no-clean, as they are sufficiently volatile or undergo thermal decomposition to volatile products, that they do not require the cleaning step. Other fluxes leave non-corrosive residues that can be left in place. However, flux residues can interfere with subsequent operations; they can impair adhesion of conformal coatings, or act as undesired insulation on connectors and contact pads for test equipment.
* Residue tack – the stickiness of the surface of the flux residue. When not removed, the flux residue should have smooth, hard surface. Tacky surfaces tend to accumulate dust and particulates, which causes issues with electrical resistance; the particles themselves can be conductive or they can be hygroscopic or corrosive.
* Volatility – this property has to be balanced to facilitate easy removal of solvents during the preheating phase but to not require too frequent replenishing of solvent in the process equipment.
* Viscosity – especially important for solder pastes, which have to be easy to apply but also thick enough to stay in place without spreading to undesired locations. Solder pastes may also function as a temporary adhesive for keeping electronic parts in place before and during soldering. Fluxes applied by e.g. foam require low viscosity.
* Flammability – relevant especially for glycol-based vehicles and for organic solvents. Flux vapors tend to have low autoignition temperature and present a risk of a flash fire when the flux comes in contact with a hot surface.
* Solids – the percentage of solid material in the flux. Fluxes with low solids, sometimes as little as 1–2%, are called low solids flux, low-residue flux, or no clean flux. They are often composed of weak organic acids, with addition of small amount of rosin or other resins.
* Conductivity – some fluxes remain conductive after soldering if not cleaned properly, leading to random malfunctions on circuits with high impedances. Different types of fluxes are differently prone to cause these issues. | 8 | Metallurgy |
Ehrlich reagent can be used to detect urobilinogen, which can indicate jaundice or other liver-related issues.
A very common Ehrlich test is a simple spot test to identify possible psychoactive compounds such as tryptamines (e.g. DMT) and lysergamides (e.g. LSD). It gives a negative test-result for 25I-NBOMe and many other non-indole-related psychoactives. The reagent will also give a positive result for opium, because of the presence of tryptophan in natural opium.
Pyridoxine, present in vitamin supplements, can give positive results to the Ehrlich test, showing a pink colour change. | 3 | Analytical Chemistry |
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