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When orthoborate salts are dissolved in water, the anion converts mostly to boric acid and other hydrogen-containing borate anions, mainly tetrahydroxyborate . The reactions of orthoborate in solution are therefore mostly those of these compounds.
In particular, these reactions include the condensation of tetrahydroxoborate with cis-vicinal diols such as mannitol, sorbitol, glucose and glycerol, to form relatively stable anion esters. This reaction is used in analytic chemistry to determine the concentration of borate anions. | 0 | Theoretical and Fundamental Chemistry |
When stars in the 0.8–2.0 solar mass range exhaust the hydrogen in their cores and become red giants, the helium accumulating in their cores reaches degeneracy before it ignites. When the degenerate core reaches a critical mass of about 0.45 solar masses, helium fusion is ignited and takes off in a runaway fashion, called the helium flash, briefly increasing the star's energy production to a rate 100 billion times normal. About 6% of the core is quickly converted into carbon. While the release is sufficient to convert the core back into normal plasma after a few seconds, it does not disrupt the star, nor immediately change its luminosity. The star then contracts, leaving the red giant phase and continuing its evolution into a stable helium-burning phase. | 1 | Applied and Interdisciplinary Chemistry |
Quantification of sequence alignments may be performed at the gene, exon, or transcript level. Typical outputs include a table of read counts for each feature supplied to the software; for example, for genes in a general feature format file. Gene and exon read counts may be calculated quite easily using HTSeq, for example. Quantitation at the transcript level is more complicated and requires probabilistic methods to estimate transcript isoform abundance from short read information; for example, using cufflinks software. Reads that align equally well to multiple locations must be identified and either removed, aligned to one of the possible locations, or aligned to the most probable location.
Some quantification methods can circumvent the need for an exact alignment of a read to a reference sequence altogether. The kallisto software method combines pseudoalignment and quantification into a single step that runs 2 orders of magnitude faster than contemporary methods such as those used by tophat/cufflinks software, with less computational burden. | 1 | Applied and Interdisciplinary Chemistry |
Early reactions to the tailings spill expressed grave concern, but no fines or charges against Imperial Metals have been assessed.
On August 6, two days after the breach, the British Columbia Ministry of Environment issued a Pollution Abatement Order to Mount Polley Mining Corporation. The company submitted an action plan for the Preliminary Environmental Impact Assessment, environmental monitoring. The company was required and did report weekly on the implementation of action plan measures.
A local state of emergency in nearby communities was initially declared in the interest of public safety with widespread water restrictions implemented and local equitable water distribution set up as a precautionary measure. Days later, some water use restrictions were removed for non-local residents, leaving a boiling water advisory, and narrowing the "Do Not Use" order to Polley Lake, Hazeltine Creek, and an area within of the shoreline sediment deposit, where Hazeltine Creek runs into Quesnel Lake. Initial tests at five testing sites of the second water test run indicated zinc levels above chronic exposure limits for aquatic life,although rainbow trout toxicity test results from water collected at Quesnel Lake near the mouth of Hazeltine Creek on August 5 and 6 showed water was not toxic to rainbow trout.
Some tourism businesses in the adjacent surrounding areas remained open. Because the affected water system is salmon-bearing, there was a temporary closure of part of the Chinook salmon fishery by Fisheries and Oceans Canada. Complaints were filed with B.C.'s privacy commissioner regarding the release of environmental assessments and dam inspection reports after journalists found a report from 2010 and assessments from 1992 and 1997 in the public domain, the B.C. government has withheld subsequent reports. Following the event, some First Nations activists held protests and set up blockades. Several local landowners and business operators affected by the spill have launched legal challenges to seek compensation for damages. | 1 | Applied and Interdisciplinary Chemistry |
Willard and his wife Margaret had two daughters, Ann and Nancy. Willard was a photography enthusiast and hobbyist who occasionally sold his work. He died in Ann Arbor, Michigan, on May 7, 1974. Michigan holds a named professorship in his honor; the current Willard Professor of Chemistry is Robert T. Kennedy. | 0 | Theoretical and Fundamental Chemistry |
A lipokine is a lipid-controlling hormone. The term was coined by [https://www.hsph.harvard.edu/gsh-lab/ Hotamisligil Lab] in 2008 to classify fatty acids which modulate lipid metabolism by what he called a "chaperone effect".
The lipokine palmitoleic acid (C16:1n7-palmitoleate) travels to the muscles and liver, where it improves cell sensitivity to insulin and blocks fat accumulation in the liver. In addition, researchers observed that palmitoleate suppresses inflammation, which is considered by many to be a primary factor leading to metabolic disease.
Palmitoleic acid also serves as a biomarker for metabolic status. More specifically, a low concentration in the free acid component of the serum indicates a risk of metabolic disease, and that de novo lipogenesis should be stimulated. Additionally, administering palmitoleic acid to a subject (via nutraceutical or other means), positively impacts lipid metabolism.
FAHFAs (fatty acid esters of hydroxy fatty acids) are lipokines formed in adipose tissue. FAHFAs improve glucose tolerance and also reduce adipose tissue inflammation. Palmitic acid esters of hydroxy-stearic acids (PAHSAs) are among the most bioactive members able to activate G-protein coupled receptors 120. Docosahexaenoic acid ester of hydroxy-linoleic acid (DHAHLA) exert anti-inflammatory and pro-resolving properties. | 1 | Applied and Interdisciplinary Chemistry |
The forms of sulfur available in aquatic environments depends on whether it is a marine or freshwater environment. Freshwater environments are more varied and subject to a multitude of sulfur inputs and outputs, including atmospheric deposition, runoff, diagenesis of bedrock and the presence of microbial sulfate reducers (MSR). Overall, the main species of sulfur in freshwater environments are hydrogen sulfide and sulfate. In estuaries, plant roots extend into sulfide-rich, S-depleted sediments created by MSR, and incorporate that sulfide into their biomass. However, levels of sulfide produced by MSR can be toxic, and it has been proposed that these plants pump oxygen into their roots to oxidize sulfide into the less toxic sulfate. In these environments algae will preferentially acquire sulfur from HS if present, rather than the more abundant sulfate, as sulfide can be readily incorporated into the direct formation of cysteine. This is consistent with cyanobacteria being able to carry out anoxygenic photosynthesis using sulfide.
In marine environments, the main forms of sulfur available is in sulfate at ~29 mM and a δS of 21‰ in seawater. At the surface of the sea, this excess in sulfur is subsequently converted into dimethylsulfoniopropionate (DMSP) by algae as an osmolyte and a repellent against grazing. DMSP also accounts for 50–100% of bacterial sulfur demand, making it the most important source of reduced sulfur for marine bacteria. DMSP's cleavage product dimethyl sulfide (DMS) is highly volatile, escaping the ocean into the atmosphere with emissions ranging between 15 and 33 Tg S year and accounting for 50–60% of the total natural reduced sulfur flux to the atmosphere. In seafloor sediments, microbial sulfate reduction is a major biogeochemical process that consumes organic carbon. Microbial sulfate reduction can completely use up sulfate from the seawater and accumulate hydrogen sulfide in the sediment. Sulfide reoxidation and disproportionation are also thought to be major processes affecting the sulfur isotopic compositions of marine minerals and sediment porewater. | 0 | Theoretical and Fundamental Chemistry |
When the activities () can be considered as equal to the molar, or the molal, concentrations () at sufficiently diluted concentrations when the activity coefficients () tend to one, the term regrouping all the activity coefficients is equal to one, and the Nernst equation can be written simply with the concentrations () denoted here with square braces [ ]:
There are three types of line boundaries in a Pourbaix diagram: Vertical, horizontal, and sloped. | 0 | Theoretical and Fundamental Chemistry |
The output of CAGE is a set of short nucleotide sequences (often called tags in analogy to expressed sequence tags) with their observed counts. Copy numbers of CAGE tags provide a digital quantification of the RNA transcript abundances in biological samples. Using a reference genome, a researcher can usually determine, with some confidence, the original mRNA (and therefore which gene) the tag was extracted from.
Unlike a similar technique serial analysis of gene expression (SAGE) in which tags come from other parts of transcripts, CAGE is primarily used to locate exact transcription start sites in the genome. This knowledge in turn allows a researcher to investigate promoter structure necessary for gene expression.
CAGE tags tend to start with an extra guanine (G) that is not encoded in the genome, which is attributed to the template-free 5′-extension during the first-strand cDNA synthesis or reverse-transcription of the cap itself. When not corrected, this can induce erroneous mapping of CAGE tags, for instance to nontranscribed pseudogenes. On the other hand, this addition of Gs was also utilised as a signal to filter more reliable TSS peaks. | 1 | Applied and Interdisciplinary Chemistry |
For dilute systems (e.g. gases), the correlations in the positions of the particles that accounts for are only due to the potential engendered by the reference particle, neglecting indirect effects. In the first approximation, it is thus simply given by the Boltzmann distribution law:
If were zero for all – i.e., if the particles did not exert any influence on each other, then for all and the mean local density would be equal to the mean density : the presence of a particle at O would not influence the particle distribution around it and the gas would be ideal. For distances such that is significant, the mean local density will differ from the mean density , depending on the sign of (higher for negative interaction energy and lower for positive ).
As the density of the gas increases, the low-density limit becomes less and less accurate since a particle situated in experiences not only the interaction with the particle in O but also with the other neighbours, themselves influenced by the reference particle. This mediated interaction increases with the density, since there are more neighbours to interact with: it makes physical sense to write a density expansion of , which resembles the virial equation:
This similarity is not accidental; indeed, substituting () in the relations above for the thermodynamic parameters (Equations , and ) yields the corresponding virial expansions. The auxiliary function is known as the cavity distribution function. It has been shown that for classical fluids at a fixed density and a fixed positive temperature, the effective pair potential that generates a given under equilibrium is unique up to an additive constant, if it exists.
In recent years, some attention has been given to develop pair correlation functions for spatially-discrete data such as lattices or networks. | 0 | Theoretical and Fundamental Chemistry |
NSOM combined with FTIR/Raman techniques can provide local chemical information together with topographical details. This technique is non-destructive and can work in a variety of environments (liquids), for example, when detecting single biomolecules. The illuminated area of sample is relatively big at around 1 μm. However, the sampling area is only ~10 nm. This means that a strong background from an unclean tip contributes to the overall signal, hindering the signal analysis.
The Raman spectroscopy in general could be time-consuming due to the low scattering efficiency (<1 in 107 photons). It usually takes several minutes to accumulate a conventional Raman spectrum, and this time could be much longer in Raman-NSOM; for example, 9 hours for a 32×32-pixel image. As to near-field IR/AFM, high optical losses in aqueous environments (water is strongly absorbing in the IR range) reduces the signal-to-noise ratio. | 0 | Theoretical and Fundamental Chemistry |
Although the sequence of atomic weights suggested that inert gases should be located between halogens and alkali metals, and there were suggestions to put them into group VIII coming from as early as 1895, such placement contradicted one of Mendeleev's basic considerations, that of the highest oxides. Inert gases did not form any oxides, and no other compounds at all, and as such, their placement in a group where elements should form tetroxides was seen as merely auxiliary and not natural; Mendeleev doubted inclusion of those elements in group VIII. Later developments, particularly by British scientists, focused on correspondence of inert gases with halogens to their left and alkali metals to their right. In 1898, when only helium, argon, and krypton were definitively known, Crookes suggested these elements be placed in a single column between the hydrogen group and the fluorine group. In 1900, at the Prussian Academy of Sciences, Ramsay and Mendeleev discussed the new inert gases and their location in the periodic table; Ramsay proposed that these elements be put in a new group between halogens and alkali metals, to which Mendeleev agreed. Ramsay published an article after his discussions with Mendeleev; the tables in it featured halogens to the left of inert gases and alkali metals to the right. Two weeks before that discussion, Belgian botanist Léo Errera had proposed to the Royal Academy of Science, Letters and Fine Arts of Belgium to put those elements in a new group 0. In 1902, Mendeleev wrote that those elements should be put in a new group 0; he said this idea was consistent with what Ramsay suggested to him and referred to Errera as to the first person to suggest the idea. Mendeleev himself added these elements to the table as group 0 in 1902, without disturbing the basic concept of the periodic table.
In 1905, Swiss chemist Alfred Werner resolved the dead zone of Mendeleev's table. He determined that the rare-earth elements (lanthanides), 13 of which were known, lay within that gap. Although Mendeleev knew of lanthanum, cerium, and erbium, they were previously unaccounted for in the table because their total number and exact order were not known; Mendeleev still could not fit them in his table by 1901. This was in part a consequence of their similar chemistry and the imprecise determination of their atomic masses. Combined with the lack of a known group of similar elements, this rendered the placement of the lanthanides in the periodic table difficult. This discovery led to a restructuring of the table and the first appearance of the 32-column form. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, a 1,3-dipolar compound or 1,3-dipole is a dipolar compound with delocalized electrons and a separation of charge over three atoms. They are reactants in 1,3-dipolar cycloadditions.
The dipole has at least one resonance structure with positive and negative charges having a 1,3 relationship which can generally be denoted as , where a may be a carbon, oxygen or nitrogen, b may be nitrogen or oxygen, and c may be a carbon, oxygen or nitrogen.
Known 1,3-dipoles are:
* Azides ()
* Ozone ()
* Nitro compounds ()
* Diazo compounds ()
* Some oxides
** Azoxide compounds (RN(O)NR)
** Carbonyl oxides (Criegee zwitterions)
** Nitrile oxides ()
** Nitrous oxide ()
** Nitrones ()
* Some imines:
** Azomethine imine
** Nitrilimines (, analogous to nitrile oxide)
** Carbonyl imines
* Some ylides
** Azomethine ylide
** Nitrile ylide ()
** Carbonyl ylide
** Thiosulfines () | 0 | Theoretical and Fundamental Chemistry |
Nitinol is exceedingly difficult to make, due to the exceptionally tight compositional control required, and the tremendous reactivity of titanium. Every atom of titanium that combines with oxygen or carbon is an atom that is robbed from the NiTi lattice, thus shifting the composition and making the transformation temperature lower.
There are two primary melting methods used today. Vacuum arc remelting (VAR) is done by striking an electrical arc between the raw material and a water-cooled copper strike plate. Melting is done in a high vacuum, and the mold itself is water-cooled copper. Vacuum induction melting (VIM) is done by using alternating magnetic fields to heat the raw materials in a crucible (generally carbon). This is also done in a high vacuum. While both methods have advantages, it has been demonstrated that an industrial state-of-the-art VIM melted material has smaller inclusions than an industrial state-of-the-art VAR one, leading to a higher fatigue resistance. Other research report that VAR employing extreme high-purity raw materials may lead to a reduced number of inclusions and thus to an improved fatigue behavior. Other methods are also used on a boutique scale, including plasma arc melting, induction skull melting, and e-beam melting. Physical vapour deposition is also used on a laboratory scale.
Heat treating nitinol is delicate and critical. It is a knowledge intensive process to fine-tune the transformation temperatures. Aging time and temperature controls the precipitation of various Ni-rich phases, and thus controls how much nickel resides in the NiTi lattice; by depleting the matrix of nickel, aging increases the transformation temperature. The combination of heat treatment and cold working is essential in controlling the properties of nitinol products. | 1 | Applied and Interdisciplinary Chemistry |
In mammals there are several structures that have been implicated as oxygen sensing structures; however, all of these structures are situated to detect aortic or internal hypoxia since mammals rarely run into environmental hypoxia. These structures include the type I cells of the carotid body, the neuroepithelial bodies of the lungs as well as some central and peripheral neurons and vascular smooth muscle cells.
In fish, the neuroepithelial cells (NEC) have been implicated as the major oxygen sensing cells. NEC have been found in all teleost fish studied to date, and are likely a highly conserved structure within many taxa of fish. NEC are also found in all four gill arches within several different structures, such as along the filaments, at the ends of the gill rakers and throughout the lamellae. Two separate neural pathways have been identified within the zebrafish gill arches both the motor and sensory nerve fibre pathways. Since neuroepithelial cells are distributed throughout the gills, they are often ideally situated to detect both arterial as well as environmental oxygen. | 0 | Theoretical and Fundamental Chemistry |
RuBP can be measured isotopically via the conversion of and RuBP into glyceraldehyde 3-phosphate. G3P can then be measured using an enzymatic optical assay. Given the abundance of RuBP in biological samples, an added difficulty is distinguishing particular reservoirs of the substrate, such as the RuBP internal to a chloroplast vs external. One approach to resolving this is by subtractive inference, or measuring the total RuBP of a system, removing a reservoir (e.g. by centrifugation), re-measuring the total RuBP, and using the difference to infer the concentration in the given repository. | 0 | Theoretical and Fundamental Chemistry |
Heat retention can be a disadvantage when used in mattresses and pillows, so in second-generation memory foam, companies began using open cell structure to improve breathability.
In 2006, the third generation of memory foam was introduced. Gel visco or gel memory foam consists of gel particles fused with visco foam to reduce trapped body heat, speed up spring back time and help the mattress feel softer. This technology was originally developed and patented by Peterson Chemical Technology, and gel mattresses became popular with the release of Sertas iComfort line and Simmons Beautyrest line in 2011. Gel-infused memory foam was next developed with what were described as "beads" containing the gel which, as a phase-change material, achieved the desired temperature stabilization or cooling effect by changing from a solid to a liquid "state" within the capsule. Changing physical states can significantly alter an element's heat absorption properties.
Since the development of gel memory foam, other materials have been added. Aloe vera, green tea extract and activated charcoal have been combined with it to reduce odors and even provide aromatherapy while sleeping. Rayon has been used in woven mattress covers over memory foam beds to wick moisture away from the body to increase comfort. Phase-change materials (PCMs) have also been used in covers on memory foam pillows, beds, and mattress pads. Materials other than polyurethane also have the properties necessary to make memory foam. Polyethylene terephthalate, one such polymeric material, provides certain benefits over polyurethane, such as recyclability, lightness, and thermal insulation. | 0 | Theoretical and Fundamental Chemistry |
Newton's metal is a fusible alloy with a low melting point. Its composition by weight is 8 parts bismuth, 5 parts lead and 3 parts tin; its melting point is 97 °C.
Newton's metal is comparable to Cerrobend, but avoids its toxic cadmium content. This has encouraged its use for medical applications for easily shaped shielding during radiotherapy. | 1 | Applied and Interdisciplinary Chemistry |
Ramipril is a pro-drug. The molecule must be hydrolyzed by the esterase at the OCH2CH3 and form a carboxylate. This carboxylate then interacts with the positive Zn+2 to inhibit the ACE enzyme. The COOH helps orient it with the enzyme. Ramipril is similar in structure to another ACE Inhibitor, trandolapril, but it has a second cyclopentane ring instead of a cyclohexane ring. | 0 | Theoretical and Fundamental Chemistry |
The actual formula seems to be somewhat of a secret. However, they are likely based on a nitrated pitch composition. Additionally, they are often marketed in the form of small black pellets and are nondeliquescent and shelf-stable. There are very few retailers of this product in Europe, and there is possibly only one large-scale manufacturer in the world. | 1 | Applied and Interdisciplinary Chemistry |
The ground state of methylene has an ionisation energy of 10.396 eV. It has a bent configuration, with H-C-H angle of 133.84°, and is thus paramagnetic. (The correct prediction of this angle was an early success of ab initio quantum chemistry.) However conversion to a linear configuration requires only 5.5 kcal/mol.
The singlet state has a slightly higher energy (by about 9 kcal/mol) than the triplet state, and its H-C-H angle is smaller, about 102°. In dilute mixtures with an inert gas, the two states will convert to each other until reaching an equilibrium. | 0 | Theoretical and Fundamental Chemistry |
Extruded pipes consisting of one layer of a homogeneous matrix of thermoplastic material which is ready for use in a pipeline. | 1 | Applied and Interdisciplinary Chemistry |
The Carnot cycle is a cycle composed of the totally reversible processes of isentropic compression and expansion and isothermal heat addition and rejection. The thermal efficiency of a Carnot cycle depends only on the absolute temperatures of the two reservoirs in which heat transfer takes place, and for a power cycle is:
where is the lowest cycle temperature and the highest. For Carnot power cycles the coefficient of performance for a heat pump is:
and for a refrigerator the coefficient of performance is:
The second law of thermodynamics limits the efficiency and COP for all cyclic devices to levels at or below the Carnot efficiency. The Stirling cycle and Ericsson cycle are two other reversible cycles that use regeneration to obtain isothermal heat transfer. | 0 | Theoretical and Fundamental Chemistry |
The crystal structure was solved to 3.0 Å resolution in 2000, as shown in the figure in the reference. In (A), notice that the separate subunits appear to be anchored through interactions between an alpha helix and an adjacent subunit. In (B), there are six sets of three loops. The red loop, known as loop II, contains three lysine residues and is thought to be involved in binding the ssDNA that is fed through the center of the enzyme. | 1 | Applied and Interdisciplinary Chemistry |
The Geneva Rules are the rules established by the International Chemistry Committee in 1892. These rules were the beginning of international cooperation for organic chemistry nomenclature. They were decided upon by a group of 34 of leading chemists from 9 different European nations. Their goal was to provide rules for the naming of aliphatic compounds, some of which are still in place today such as the longest chain provides the parent name and a functional group is indicated by a suffix. They also intended to extend the rules to include naming schemes for cyclic compounds however this did not occur. | 0 | Theoretical and Fundamental Chemistry |
MLPA facilitates the amplification and detection of multiple targets with a single primer pair. In a standard multiplex PCR reaction, each fragment needs a unique amplifying primer pair. These primers being present in a large quantity result in various problems such as dimerization and false priming. With MLPA, amplification of probes can be achieved. Thus, many sequences (up to 40) can be amplified and quantified using just a single primer pair. MLPA reaction is fast, inexpensive and very simple to perform.
MLPA has a variety of applications including detection of mutations and single nucleotide polymorphisms, analysis of DNA methylation, relative mRNA quantification, chromosomal characterisation of cell lines and tissue samples, detection of gene copy number, detection of duplications and deletions in human cancer predisposition genes such as BRCA1, BRCA2, hMLH1 and hMSH2 and aneuploidy determination. MLPA has potential application in prenatal diagnosis both invasive and noninvasive.
Recent studies have shown that MLPA (as well as another variants such as iMLPA) is a robust technique for inversion characterisation. | 1 | Applied and Interdisciplinary Chemistry |
Lyso- is a prefix applied to the various phospholipids to indicate the removal of one of the two fatty acids. For example, lysophosphatidylcholines are phosphatidylcholines with a single acyl group in either the 1- or 2-position. | 1 | Applied and Interdisciplinary Chemistry |
In thermodynamics, the saturation vapor curve is the curve separating the two-phase state and the superheated vapor state in the T–s diagram (temperature–entropy diagram).
The saturated liquid curve is the curve separating the subcooled liquid state and the two-phase state in the T–s diagram.
When used in a power cycle, the fluid expansion depends strongly on the nature of this saturation curve:
*A "wet" fluid shows a negative saturation vapor curve. If overheating before the expansion is limited, a two-phase state is obtained at the end of the expansion.
*An "isentropic" fluid shows a vertical saturation vapor curve. It remains very close to the saturated vapor state after an hypothetical isentropic expansion.
*A "dry" fluid shows a positive saturation vapor curve. It is in dry vapor state at the end of the expansion, and strongly overheated. | 0 | Theoretical and Fundamental Chemistry |
The physical properties of solids have been common subjects of scientific inquiry for centuries, but a separate field going by the name of solid-state physics did not emerge until the 1940s, in particular with the establishment of the Division of Solid State Physics (DSSP) within the American Physical Society. The DSSP catered to industrial physicists, and solid-state physics became associated with the technological applications made possible by research on solids. By the early 1960s, the DSSP was the largest division of the American Physical Society.
Large communities of solid state physicists also emerged in Europe after World War II, in particular in England, Germany, and the Soviet Union. In the United States and Europe, solid state became a prominent field through its investigations into semiconductors, superconductivity, nuclear magnetic resonance, and diverse other phenomena. During the early Cold War, research in solid state physics was often not restricted to solids, which led some physicists in the 1970s and 1980s to found the field of condensed matter physics, which organized around common techniques used to investigate solids, liquids, plasmas, and other complex matter. Today, solid-state physics is broadly considered to be the subfield of condensed matter physics, often referred to as hard condensed matter, that focuses on the properties of solids with regular crystal lattices. | 1 | Applied and Interdisciplinary Chemistry |
Ryōji Noyori and colleagues have developed a methodology for the kinetic resolution of benzylic and allylic secondary alcohols via transfer hydrogenation. The ruthenium complex catalyzes oxidation of the more reactive enantiomer from acetone, yielding an unreacted enantiopure alcohol, an oxidized ketone, and isopropanol. In the example illustrated below, exposure of 1-phenylethanol to the (S,S) enantiomer of the catalyst in the presence of acetone results in a 51% yield of 94% ee (R)-1-phenylethanol, along with 49% acetophenone and isopropanol as a byproduct.
This methodology is essentially the reverse of Noyori's asymmetric transfer hydrogenation of ketones, which yield enantioenriched alcohols via reduction. This limits the attractiveness of the kinetic resolution method, since there is a similar method to achieve the same products without the loss of half the material. Thus, the kinetic resolution would only be carried out in an instance for which the racemic alcohol was at least one half the price of the ketone or significantly easier to access.
In addition, Uemura and Hidai have developed a ruthenium catalyst for the kinetic resolution oxidation of benzylic alcohols, yielding highly enantioenriched alcohols in good yields.
The complex can, like Noyori's catalyst, affect transfer hydrogenation between a ketone and isopropanol to give an enantioenriched alcohol as well as affect kinetic resolution of a racemic alcohol, giving enantiopure alcohol (>99% ee) and oxidized ketone, with acetone as the byproduct. It is highly effective at reducing ketones enantioselectively, giving most benzylic alcohols in >99% ee and can resolve a number of racemic benzylic alcohols to give high yields (up to 49%) of single enantiomers, as shown below. This method has the same disadvantages as the Noyori kinetic resolution, namely that the alcohols can also be accessed via reduction of the ketones enantioselectively. Additionally, only one enantiomer of the catalyst has been reported. | 0 | Theoretical and Fundamental Chemistry |
Mutants are viable, but may be distinguished from normal plants by FeCl staining: plants able to synthesize benzoxinoids have pale blue color when crushed and treated with FeCl solutions (Hamilton 1964, Simcox 1993 ). Mutations in the bx1 gene reduce the resistance to first generation European corn borer (Ostrinia nubilalis) that is conferred by benzoxazinoids (Klun et al. 1970 ). Bx1 mutant maize deposited less callose in response to chitosan elicitation than isogenic wildtype plants (Ahmad et al. 2011 ). Genetic mapping using recombinant inbred lines derived from maize inbred lines B73 and Mo17 showed that a 3.9 kb cis-regulatory element that is located approximately 140 kb upstream of Bx1 causes higher 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) accumulation in Mo17 than in B73 seedlings (Zheng et al. 2015 ). This genetic variation is also associated with higher corn leaf aphid (Rhopalosiphum maidis) reproduction on B73 compared to Mo17 maize seedlings (Betsiashvili et al. 2014 ). Relative to maize inbred line W22, Bx1::Ds mutant maize plants are more sensitive to corn leaf aphids (Rhopalosiphum maidis) (Betsiashvili et al. 2014) and beet armyworms (Spodoptera exigua) (Tzin et al. 2017 ). Highly localized induction of benzoxazinoid accumulation in response to Egyptian cotton leafworm (Spodoptera littoralis) feeding is abolished in a maize bx1 mutant (Maag et al. 2016 ). | 1 | Applied and Interdisciplinary Chemistry |
High-temperature corrosion is a mechanism of corrosion that takes place when gas turbines, diesel engines, furnaces or other machinery come in contact with hot gas containing certain contaminants. Fuel sometimes contains vanadium compounds or sulfates, which can form low melting point compounds during combustion. These liquid melted salts are strongly corrosive to stainless steel and other alloys normally resistant with respect to corrosion at high temperatures. Other types of high-temperature corrosion include high-temperature oxidation, sulfidation, and carbonization. High temperature oxidation and other corrosion types are commonly modeled using the Deal-Grove model to account for diffusion and reaction dynamics. | 1 | Applied and Interdisciplinary Chemistry |
Selegiline is also delivered via a transdermal patch used as a treatment for major depressive disorder.
Administration of transdermal selegiline bypasses hepatic first pass metabolism. This avoids inhibition of gastrointestinal and hepatic MAO-A activity, which would result in an increase of food-borne tyramine in the blood and possible related adverse effects, while allowing for a sufficient amount of selegiline to reach the brain for an antidepressant effect.
A quantitative review published in 2015 found that for the pooled results of the pivotal trials, the number needed to treat (a sign of effect size, so a low number is better) for the patch for symptom reduction was 11, and for remission, was 9. The number needed to harm (inverse of the NNT, a high number here is better) ranged from 387 for sexual side effects to 7 for application site reaction. With regard to the likelihood to be helped or harmed (LHH), the analysis showed that the selegiline patch was 3.6 times as likely to lead to a remission vs. a discontinuation due to side effects; the LHH for remission vs. incidence of insomnia was 2.1; the LHH for remission vs. discontinuation due to insomnia was 32.7. The LHH for remission vs. insomnia and sexual dysfunction were both very low. | 0 | Theoretical and Fundamental Chemistry |
The L-type amino acid transporter (LAT1) is a uniporter that mediates the transport of neutral amino acids like L-tryptophan, leucine, histidine, proline, alanine, etc. LAT1 favors the transport of amino acids with large branched or aromatic side chains. The amino acid transporter functions to move essential amino acids into the intestinal epithelium, placenta, and blood-brain barrier for cellular processes such as metabolism and cell signaling. The transporter is of particular significance in the central nervous system as it provides the necessary amino acids for protein synthesis and neurotransmitter production in brain cells. Aromatic amino acids like phenylalanine and tryptophan are precursors for neurotransmitters like dopamine, serotonin, and norepinephrine.
LAT1 is a membrane protein of the SLC7 family of transporters and works in conjunction with the SLC3 family member 4F2hc to form a heterodimeric complex known as the 4F2hc complex. The heterodimer consists of a light chain and a heavy chain covalently bonded by a disulfide bond. The light chain is the one that carries out transport, while the heavy chain is needed to stabilize the dimer.
There is some controversy over whether LAT1 is an uniporter or an antiporter. The transporter has uniporter characteristics of transporting amino acids into cells in a unidirectional manner down the concentration gradient. However, recently it has been found that the transporter has antiporter characteristics of exchanging neutral amino acids for abundant intracellular amino acids. Over-expression of LAT1 has been found in human cancer and is associated with playing a role in cancer metabolism. | 1 | Applied and Interdisciplinary Chemistry |
The above descriptions ignore the effects of Gβγ–signalling, which can also be important, in particular in the case of activated G-coupled GPCRs. The primary effectors of Gβγ are various ion channels, such as G-protein-regulated inwardly rectifying K channels (GIRKs), P/Q- and N-type voltage-gated Ca channels, as well as some isoforms of AC and PLC, along with some phosphoinositide-3-kinase (PI3K) isoforms. | 1 | Applied and Interdisciplinary Chemistry |
The recommendations give a full list of acceptable names for common acids and related anions. A selection from this list is shown below. | 0 | Theoretical and Fundamental Chemistry |
The sample suspended in a suitable medium is placed in a hermetically closed metabolic chamber. The mitochondria are brought into defined “states” by the sequential addition of substrates or inhibitors. Since the mitochondria consume oxygen, the oxygen concentration drops. This change of oxygen concentration is recorded by an oxygen sensor in the chamber. From the rate of the oxygen decline (taking into account correction for oxygen diffusion) the respiratory rate of the mitochondria can be computed. | 1 | Applied and Interdisciplinary Chemistry |
Polymer chemistry is a sub-discipline of chemistry that focuses on the structures of chemicals, chemical synthesis, and chemical and physical properties of polymers and macromolecules. The principles and methods used within polymer chemistry are also applicable through a wide range of other chemistry sub-disciplines like organic chemistry, analytical chemistry, and physical chemistry. Many materials have polymeric structures, from fully inorganic metals and ceramics to DNA and other biological molecules. However, polymer chemistry is typically related to synthetic and organic compositions. Synthetic polymers are ubiquitous in commercial materials and products in everyday use, such as plastics, and rubbers, and are major components of composite materials. Polymer chemistry can also be included in the broader fields of polymer science or even nanotechnology, both of which can be described as encompassing polymer physics and polymer engineering. | 0 | Theoretical and Fundamental Chemistry |
Facets () are flat faces on geometric shapes. The organization of naturally occurring facets was key to early developments in crystallography, since they reflect the underlying symmetry of the crystal structure. Gemstones commonly have facets cut into them in order to improve their appearance by allowing them to reflect light. | 0 | Theoretical and Fundamental Chemistry |
Certain aspects of the lipid pump such as the diapause depth and duration of zooplankton can vary among regions that have different overwintering temperatures and resident community characteristics. There are other subarctic regions that have shown similar carbon export rates to those found in the temperate North Atlantic (1–4 g C m y) via seasonally-migrating zooplankton. For instance, C. glacialis and C. hyperboreus are the most dominant zooplankton species found in the Arctic Ocean at similar latitudes, and they contribute to a 3.1 g C m y flux of lipid carbon below 100 m during overwintering. A slightly higher maximum flux in lipid carbon (2–4.3 g C m y) below 150 m was observed in the subarctic North Pacific and was primarily attributed to the Neocalanus genus of copepods. In these areas, N. flemingeri, N. cristatus, and N. plumchrus are the primary contributors to the lipid pump, whereas, the subantarctic Southern Ocean consists primarily of N. tonsus contributing to a lipid carbon flux of 1.7–9.3 g C m y out of the euphotic zone. The rates or magnitude of these processes may slightly vary due to characteristic differences between these subpolar regions, which have largely been under-studied relative to their contributions to the lipid pump. | 0 | Theoretical and Fundamental Chemistry |
Termites use trail pheromones primarily as a means of foraging. They can lay pheromones along a trail as their abdomens touch the ground, specifically through their abdominal sternal glands. As the other termites follow, they will continue to add to the trail.
The basal termite Mastotermes darwiniensis produces trail pheromones from at least two sternal glands despite every other species producing theirs from only one. This pheromone, composed soley of a norsesquiterpene alcohol, elicits trail-following from other termites. As aforementioned, these successive termites can add to the trail, depending if it is used for foraging or recruiting workers to complete tasks. In the case of Reticulitermes santonensis, foraging trails have spotted markings throughout the path, whereas recruitment trails are more continuous from the termites dragging their bodies along the path. | 1 | Applied and Interdisciplinary Chemistry |
* acetan (Acetobacter xylinum)
* alginate (Azotobacter vinelandii, Pseudomonas spp.)
* cellulose (Acetobacter xylinum)
* chitosan (Mucorales spp.)
* curdlan (Alcaligenes faecalis var. myxogenes)
* cyclosophorans (Agrobacterium spp., Rhizobium spp. and Xanthomonas spp.)
* dextran (Leuconostoc mesenteroides, Leuconostoc dextranicum and Lactobacillus hilgardii)
* emulsan (Acinetobacter calcoaceticus)
* galactoglucopolysaccharides (Achromobacter spp., Agrobacterium radiobacter, Pseudomonas marginalis, Rhizobium spp. and Zooglea spp.)
* galactosaminogalactan (Aspergillus spp.)
* gellan (Aureomonas elodea and Sphingomonas paucimobilis)
* glucuronan (Sinorhizobium meliloti)
* N-acetylglucosamine (Staphylococcus epidermidis)
* N-acetyl-heparosan (Escherichia coli)
* hyaluronic acid (Streptococcus equi)
* indican (Beijerinckia indica)
* kefiran (Lactobacillus hilgardii)
* lentinan (Lentinus elodes)
* levan (Alcaligenes viscosus, Zymomonas mobilis, Bacillus subtilis)
* pullulan (Aureobasidium pullulans)
* scleroglucan (Sclerotium rolfsii, Sclerotium delfinii and Sclerotium glucanicum)
* schizophyllan (Schizophylum commune)
* stewartan (Pantoea stewartii subsp. stewartii)
* succinoglycan (Alcaligenes faecalis var. myxogenes, Sinorhizobium meliloti)
* xanthan (Xanthomonas campestris)
* welan (Alcaligenes spp.) | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, nitroso refers to a functional group in which the nitric oxide () group is attached to an organic moiety. As such, various nitroso groups can be categorized as C-nitroso compounds (e.g., nitrosoalkanes; ), S-nitroso compounds (nitrosothiols; ), N-nitroso compounds (e.g., nitrosamines, ), and O-nitroso compounds (alkyl nitrites; ). | 0 | Theoretical and Fundamental Chemistry |
Cut sections of roadway or rail are areas where the roadway has a lower elevation than the surrounding terrain. Fill sections are elevated sections of a roadway or trackbed. Cut and fill takes material from cut excavations and uses this to make fill sections. It costs resources to excavate material, relocate it, and to compact and otherwise prepare the filled sections. The technique aims to minimise the effort of relocating excavated material while also taking into account other constraints such as maintaining a specified grade over the route. | 1 | Applied and Interdisciplinary Chemistry |
While the formation of a sigma hole pair interaction is associated with energetic stabilization, this process is often thermodynamically disfavored as the energetic stabilization is often offset by a decrease in the entropy of the system. It has been shown that an enthalpy-entropy compensation relationship exists between the energetic and entropic changes associated with interactions, with more stabilizing interactions tending to result in larger entropy decreases. However, the decrease in entropy associated with the formation of a sigma hole interaction has been shown to approach a limiting value as the energetic favorability of the process is increased, and as such very energetically stabilizing interactions tend to be thermodynamically favored. There are additional factors that contribute to thermodynamic stability in the liquid and solid phases, which cannot be as easily modeled as gas phase interactions. As such, the favorability of a given sigma hole interaction in the liquid or solid phase may not necessarily match that of the gas phase equivalent. | 0 | Theoretical and Fundamental Chemistry |
Through literature discussing the fabrication of a completely porous nanofoam biopolymer is scarce, recent endeavors have resulted in the formation of nanofoam surfaces on biopolymers. In these instances, biopolymers such as collagen and gelatine, chitosan, and pure curcumin have been used to varying degrees. | 0 | Theoretical and Fundamental Chemistry |
The El Segundo Trisonic Wind Tunnel or North American Trisonic Wind Tunnel (NATWT) was a wind tunnel that was located in El Segundo, California. It was built by North American Aviation in the 1950s. The tunnel had a maximum testing speed of Mach 3.5.
The NATWT was a blow-down type tunnel. In contrast to a continuous wind tunnel, a blow-down wind tunnel only provides air for short period. A continuous wind tunnel is driven by large fans and typically is only capable of subsonic speeds. Because a blow-down tunnel can build up pressure over a long period time, it can release air at faster speeds.
The NATWT used two Westinghouse motors, totaling 10,000 hp and consuming 8 megawatts of electricity, that drove two compressors. NATWT had its own substation to supply its high electrical demand. During the hot summer season, NATWT ran on a night schedule to balance its load with public air conditioning.
The compressors pressurized eight large spheres totaling . These spheres were connected to a single manifold that connected to a valve mechanism. When the valve was opened, the compressed air passed through the settling chamber, nozzle, and the test section, where instrumented aerodynamic models were mounted. A diffusing area that expanded in size slowed the air before it was exhausted vertically into the atmosphere. The diffuser area included a colander-like sieve made of steel to catch debris in the event of a catastrophic model failure.
The speed of the air was determined by the pressure of the spheres and the cross sectional area of the wind tunnel nozzle and diffuser. A smaller cross section in the nozzle caused the air to move faster. The NATWT could change the shape of the nozzle by operating a series of hydraulic pistons that would bend one-inch thick steel plates into the desired contour.
A distinguishing feature of the NATWT was the size of its test section []. Unlike most blow-down wind tunnels, the NATWT test section had a so-called "walk in" test section that could accommodate very large aerodynamic models. Large models have several advantages:
* ability to model relatively small features, such as vortex generators
* ability to instrument the model with more pressure probes and sensors
* more surface area enabling more pressure sensors
* more interior space for instrumentation
Because of the "walk in" nature of NATWT, the tunnel was designed with the possibility that someone could accidentally be locked in the tunnel. Two large emergency safety switches were provided. One was located at the test section, the other at the diffuser area. When either of these safety switches were activated, the valve could not be opened.
Another feature of NATWT was the ability to visualize airflow over a model surface. By using optics built into the test section, an engineer could view air disturbance patterns as they were occurring during a test. | 1 | Applied and Interdisciplinary Chemistry |
Ammonium perrhenate (APR) is the ammonium salt of perrhenic acid, NHReO. It is the most common form in which rhenium is traded. It is a white salt; soluble in ethanol and water, and mildly soluble in NHCl. It was first described soon after the discovery of rhenium. | 0 | Theoretical and Fundamental Chemistry |
The most famous cold fusion claims were made by Stanley Pons and Martin Fleischmann in 1989. After a brief period of interest by the wider scientific community, their reports were called into question by nuclear physicists. Pons and Fleischmann never retracted their claims, but moved their research program from the US to France after the controversy erupted. | 0 | Theoretical and Fundamental Chemistry |
Guido Bargellini (1879–1963) was an Italian organic chemist. He specialized in natural product chemistry, in particular, flavonoid dyes and coumarins, and the compound santonin. He was admitted to the Accademia dei Lincei in 1946. The Bargellini reaction is named for him. | 0 | Theoretical and Fundamental Chemistry |
The total synthesis of Aflatoxin B2 is a multistep sequence that begins with a [2+3]cycloaddition between the quinone 1 and the 2,3-Dihydrofuran. This reaction is catalyzed by a CBS catalyst and is enantioselective. The next step is the orthoformylation of reaction product 2 in a Duff reaction. The hydroxyl group in 3 is esterified with triflic anhydride which adds a triflate protecting group. This step enables a Grignard reaction of the aldehyde group in 4 with methylmagnesiumbromide to the alcohol 5 which is then oxidized with the Dess-Martin periodinane to the ketone 6. A Baeyer-Villiger oxidation converts the ketone to an ester (7) and a reduction with Raney nickel converts the ester into an alcohol and removes the triflic acid group. In the final step the coumarin skeleton is added to 9 by a combined coupling reaction with zinc carbonate of the vinyl bromide in 8 and a transesterification step between the phenol group and the ethyl ester group. | 0 | Theoretical and Fundamental Chemistry |
Sodium hydroxide is frequently used as an industrial cleaning agent where it is often called "caustic". It is added to water, heated, and then used to clean process equipment, storage tanks, etc. It can dissolve grease, oils, fats and protein-based deposits. It is also used for cleaning waste discharge pipes under sinks and drains in domestic properties. Surfactants can be added to the sodium hydroxide solution in order to stabilize dissolved substances and thus prevent redeposition. A sodium hydroxide soak solution is used as a powerful degreaser on stainless steel and glass bakeware. It is also a common ingredient in oven cleaners.
A common use of sodium hydroxide is in the production of parts washer detergents. Parts washer detergents based on sodium hydroxide are some of the most aggressive parts washer cleaning chemicals. The sodium hydroxide-based detergents include surfactants, rust inhibitors and defoamers. A parts washer heats water and the detergent in a closed cabinet and then sprays the heated sodium hydroxide and hot water at pressure against dirty parts for degreasing applications. Sodium hydroxide used in this manner replaced many solvent-based systems in the early 1990s when trichloroethane was outlawed by the Montreal Protocol. Water and sodium hydroxide detergent-based parts washers are considered to be an environmental improvement over the solvent-based cleaning methods.
Sodium hydroxide is used in the home as a type of drain openers to unblock clogged drains, usually in the form of a dry crystal or as a thick liquid gel. The alkali dissolves greases to produce water soluble products. It also hydrolyzes proteins, such as those found in hair, which may block water pipes. These reactions are sped by the heat generated when sodium hydroxide and the other chemical components of the cleaner dissolve in water. Such alkaline drain cleaners and their acidic versions are highly corrosive and should be handled with great caution. | 0 | Theoretical and Fundamental Chemistry |
The types of RNAs transcribed from RNA polymerase III include:
*Transfer RNAs
*5S ribosomal RNA
*U6 spliceosomal RNA
*RNase P and RNase MRP RNA
*7SL RNA (the RNA component of the signal recognition particle)
*Vault RNAs
*Y RNA
*SINEs (short interspersed repetitive elements)
*7SK RNA
*Several microRNAs
*Several small nucleolar RNAs
*Several gene regulatory antisense RNAs | 1 | Applied and Interdisciplinary Chemistry |
Stripping is commonly used in industrial applications to remove harmful contaminants from waste streams. One example would be the removal of TBT and PAH contaminants from harbor soils. The soils are dredged from the bottom of contaminated harbors, mixed with water to make a slurry and then stripped with steam. The cleaned soil and contaminant rich steam mixture are then separated. This process is able to decontaminate soils almost completely.
Steam is also frequently used as a stripping agent for water treatment. Volatile organic compounds are partially soluble in water and because of environmental considerations and regulations, must be removed from groundwater, surface water, and wastewater. These compounds can be present because of industrial, agricultural, and commercial activity. | 0 | Theoretical and Fundamental Chemistry |
Some azeotropes fit into neither the positive nor negative categories. The best known of these is the ternary azeotrope formed by 30% acetone, 47% chloroform, and 23% methanol, which boils at 57.5 °C. Each pair of these constituents forms a binary azeotrope, but chloroform/methanol and acetone/methanol both form positive azeotropes while chloroform/acetone forms a negative azeotrope. The resulting ternary azeotrope is neither positive nor negative. Its boiling point falls between the boiling points of acetone and chloroform, so it is neither a maximum nor a minimum boiling point. This type of system is called a saddle azeotrope. Only systems of three or more constituents can form saddle azeotropes. | 1 | Applied and Interdisciplinary Chemistry |
Caesium-137 has a number of practical uses. In small amounts, it is used to calibrate radiation-detection equipment. In medicine, it is used in radiation therapy. In industry, it is used in flow meters, thickness gauges, moisture-density gauges (for density readings, with americium-241/beryllium providing the moisture reading), and in gamma ray well logging devices.
Caesium-137 is not widely used for industrial radiography because it is hard to obtain a very high specific activity material with a well defined (and small) shape as caesium from used nuclear fuel contains stable caesium-133 and also long-lived caesium-135. Isotope separation is too costly compared to cheaper alternatives. Also the higher specific activity caesium sources tend to be made from very soluble caesium chloride (CsCl), as a result if a radiography source was damaged it would increase the spread of the contamination. It is possible to make water insoluble caesium sources (with various ferrocyanide compounds such as , and ammonium ferric hexacyano ferrate (AFCF), Giese salt, ferric ammonium ferrocyanide but their specific activity will be much lower. Other chemically inert caesium compounds include caesium-aluminosilicate-glasses akin to the natural mineral pollucite. The latter has been used in demonstration of chemically stable water-insoluble forms of nuclear waste for disposal in deep geological repositories. A large emitting volume will harm the image quality in radiography. and , are preferred for radiography, since these are chemically non-reactive metals and can be obtained with much higher specific activities by the activation of stable cobalt or iridium in high flux reactors. However, while is a waste product produced in great quantities in nuclear fission reactors, and are specifically produced in commercial and research reactors and their life cycle entails the destruction of the involved high-value elements. Cobalt-60 decays to stable nickel, whereas iridium-192 can decay to either stable osmium or platinum. Due to the residual radioactivity and legal hurdles, the resulting material is not commonly recovered even from "spent" radioactive sources, meaning in essence that the entire mass is "lost" for non-radioactive uses.
As an almost purely human-made isotope, caesium-137 has been used to date wine and detect counterfeits and as a relative-dating material for assessing the age of sedimentation occurring after 1945.
Caesium-137 is also used as a radioactive tracer in geologic research to measure soil erosion and deposition; its affinity for fine sediments is useful in this application. | 0 | Theoretical and Fundamental Chemistry |
Various composite coatings were analyzed on filter paper in an experiment done by Wang et al. The ability to separate homogenous liquid solutions based on varying surface tensions has great practical use. Creating superhydrophobic and superoleophilic filter paper was achieved by treating the surface of commercially available filter paper with hydrophobic silica nanoparticles and polystyrene solution in toluene. Oil and water were successfully separated through the use of the filter paper created with an efficiency greater than 96%. In a homogenous solution the filter paper was also successful in separating the liquids through differentiating for surface tensions. Although with a lower efficiency, aqueous ethanol was also extracted from the solution when tested on the filter paper. | 0 | Theoretical and Fundamental Chemistry |
Copper came into use in the Aegean area near the end of the predynastic age of Egypt about 3500 BC. The earliest known implement is a flat celt, which was found on a Neolithic house-floor in the central court of the palace of Knossos in Crete, and is regarded as an Egyptian product. Bronze was not generally used until a thousand years or more later. Its first appearance is probably in the celts and dagger-blades of the Second City of Troy, where it is already the standard alloy of 10% tin. It was not established in Crete until the beginning of the Middle Minoan age (MMI, c. 2000 BC). The Copper Age began in northern Greece and Italy c. 2500 BC, much later than in Crete and Anatolia, and the mature Italian Bronze Age of Terremare culture coincided in time with the Late Aegean (Mycenaean) civilisation (1600–1000 BC). The original sources both of tin and copper in these regions are unknown. | 1 | Applied and Interdisciplinary Chemistry |
In Japan, geisha wore lipstick made of crushed safflower petals to paint the eyebrows and edges of the eyes as well as the lips, and sticks of bintsuke wax, a softer version of the sumo wrestlers hair wax, were used by geisha as a makeup base. Rice powder colors the face and back; rouge contours the eye socket and defines the nose. Ohaguro (black paint) colours the teeth for the ceremony, called Erikae, when maiko' (apprentice geisha) graduate and become independent. The geisha would also sometimes use bird droppings to compile a lighter color. The beginning of the modern Japanese cosmetic industry began after the Meiji Restoration in 1868. New products began appearing in the markets for skin care and dermatology due to new ingredients and technologies. | 1 | Applied and Interdisciplinary Chemistry |
Sediment toxicity is evaluated based on bioassay analysis. Standard bioassay toxicity tests are utilized and are not organism restricted (Chapman, 1997). Differences in mechanisms of exposure and organism physiology must be taken into account when selecting your test organisms, and you must be able to adequately justify the use of that organism. These bioassay tests evaluate effects based on different toxicological endpoints. The toxicity tests are conducted with respect to the chemicals of concern at environmentally relevant concentrations identified by the sediment chemistry portion of the triad approach. Chapman (1990) lists typically used endpoints, which include lethal endpoints such as mortality, and sublethal endpoints such as growth, behavior, reproduction, cytotoxicity and optionally bioaccumulation. Often pilot studies are utilized to assist in the selection of the appropriate test organism and end points. Multiple endpoints are recommended and each of the selected endpoints must adequately complement each of the others (Chapman, 1997). Effects are evaluated using statistical methods that allow for the distinction between responses that are significantly different than negative controls. If sufficient data is generated, minimum significant differences (MSDs) are calculated using power analyses and applied to toxicity tests to determine the difference between statistical difference and ecological relevance.
The function of the toxicity portion of the triad approach is to allow you to estimate the effects in the field. While laboratory based experiments simplify a complex and dynamic environment, toxicity results allow the potential for field extrapolation. This creates a link of exposure and effect and allows the determination of an exposure-response relationship. When combined with the other two components of the Sediment Quality Triad it allows for a holistic understanding between cause and effect. | 1 | Applied and Interdisciplinary Chemistry |
It catalyzes the reduction of cytochrome c by
oxidation of coenzyme Q (CoQ) and the concomitant pumping of 4 protons from the mitochondrial matrix to the intermembrane space:
: QH + 2 cytochrome c (Fe) + 2 H → Q + 2 cytochrome c (Fe) + 4 H
In the process called Q cycle, two protons are consumed from the matrix (M), four protons are released into the inter membrane space (IM) and two electrons are passed to cytochrome c. | 1 | Applied and Interdisciplinary Chemistry |
The standard biochemistry and molecular biology textbooks describe non-coding nucleotides in mRNA located between the 5 end of the gene and the translation initiation codon. These regions are called 5-untranslated regions or 5-UTRs. Similar regions called 3-untranslated regions (3-UTRs) are found at the end of the gene. The 5-UTRs and 3UTRs are very short in bacteria but they can be several hundred nucleotides in length in eukaryotes. They contain short elements that control the initiation of translation (5-UTRs) and transcription termination (3'-UTRs) as well as regulatory elements that may control mRNA stability, processing, and targeting to different regions of the cell. | 1 | Applied and Interdisciplinary Chemistry |
Lentiviral vectors have certain general limitations. For one, it is impossible to control where the viral genome integrates into the host genome, and this may affect important functions of the cell. Vannucci et al. provide an excellent review of viral vectors along with their general advantages and disadvantages. In the specific context of genome-wide CRISPR screens, producing and transducing the lentiviral particles is relatively laborious and time-consuming, taking about two weeks in total. Additionally, because the DNA integrates into the host genome, lentiviral delivery leads to long-term expression of Cas9, potentially leading to off-target effects. | 1 | Applied and Interdisciplinary Chemistry |
In addition to its role in synaptic plasticity described above, PI3K-AKT signaling pathway also has an important role in brain growth, which is altered when PI3K signaling is disturbed. For example, intracranial volume is also associated with this pathway, in particular with AKT3 intronic variants. Thyroid hormone was originally identified as the primary regulator of brain growth and cognition, and recent evidence has demonstrated that thyroid hormone produces some of its effects on the maturation and plasticity of synapses through PI3K. | 1 | Applied and Interdisciplinary Chemistry |
SPEARpesticides estimates pesticide effects and contamination. The calculation is based on monitoring data of invertebrate communities as ascertained for the EU Water Framework Directive (WFD). A simplified version of SPEARpesticides is included in the [http://www.fliessgewaesserbewertung.de ASTERICS] software for assessing the ecological quality of rivers. A detailed analysis is enabled by the free [http://www.systemecology.eu/spearcalc/ SPEAR Calculator]. The [http://www.systemecology.eu/spearcalc/ SPEAR Calculator] provides most recent information on species traits and allows specific user settings.
The SPEARpesticides index is computed as relative abundance of vulnerable SPecies At Risk (SPEAR) to be affected by pesticides. Relevant species traits comprises the physiological sensitivity towards pesticides, generation time, migration ability and exposure probability. The indicator value of SPEARpesticides at a sampling site is calculated as follows:
with n = number of taxa; x = abundance of taxon i; y = 1 if taxon i is classified as SPEAR-sensitive; y = 0 if taxon i is classified as SPEAR-insensitive.
An application is available as download for PC. [http://www.systemecology.eu/indicate/ Web address to download the SPEAR calculator] | 1 | Applied and Interdisciplinary Chemistry |
He was born in Bratislava, then Czechoslovakia in a family of Slovak actor Juraj Kukura. In 1984 the family emigrated to Germany. In 2002 he graduated with a Master of Chemistry from the University of Oxford and competed in the 2001 and 2002 Rugby League Varsity matches. In 2006 he completed his PhD in Chemistry from the University of California, Berkeley College of Chemistry. | 0 | Theoretical and Fundamental Chemistry |
A common form of refrigeration economizer is a "walk-in cooler economizer" or "outside air refrigeration system". In such a system outside air that is cooler than the air inside a refrigerated space is brought into that space and the same amount of warmer inside air is ducted outside. The resulting cooling supplements or replaces the operation of a compressor-based refrigeration system. If the air inside a cooled space is only about 5 °F warmer than the outside air that replaces it (that is, the ∆T>5 °F) this cooling effect is accomplished more efficiently than the same amount of cooling resulting from a compressor based system. If the outside air is not cold enough to overcome the refrigeration load of the space the compressor system will need to also operate, or the temperature inside the space will rise. | 0 | Theoretical and Fundamental Chemistry |
One of the most common triggers for drug delivery systems is pH. This stimulus is abundantly used in cancer therapies due to the fact that the tumor microenvironment is acidic. The development of pH triggered systems meant that drug could be introduced to the body but not be deployed until encountering the tumor microenvironment. Hence a possible and probable reason that pH triggered systems are so common. There are a few approaches to making these systems. One method is using linkages that dissolve at certain pH levels. As the system enters an acidic environment, the linkages that hold that gates onto the porous scaffold are hydrolyzed and the cargo can be released. Examples of pH linkages are imine, amides, esters, and acetals. Another method that can be used is protonation. This method relies on electrostatic interactions between the gate molecule and the porous scaffold. The two will be linked together with a certain molecule, for example, acetylated carboxymethyl. When the system reaches an acidic environment, protonation of the molecule is initiated. The protonation causes a disruption in the linkage and the cargo can be released. | 1 | Applied and Interdisciplinary Chemistry |
Kanada opens his Sutra with definitions of Dharma, the importance of the Vedas and his goals. The text, states Matilal, then defines and describes three categories and their causal aspects: substance, quality and action. He explains their differences, similarities and relationships between these three. The second part of first chapter defines and explains a universal, a particular (viśeṣa,) and their hierarchical relationship. Kanada states that it is from combination of particulars that some universals emerge. | 1 | Applied and Interdisciplinary Chemistry |
Phenol red was used by Leonard Rowntree and John Geraghty in the phenolsulfonphthalein test to estimate the overall blood flow through the kidney in 1911. It was the first test of kidney function and was used for almost a century but is now obsolete.
The test is based on the fact that phenol red is excreted almost entirely in the urine. Phenol red solution is administered intravenously; the urine produced is collected. By measuring the amount of phenol red excreted colorimetrically, kidney function can be determined. | 0 | Theoretical and Fundamental Chemistry |
The Boltzmann constant provides a mapping from the characteristic microscopic energy to the macroscopic temperature scale . In fundamental physics, this mapping is often simplified by using the natural units of setting to unity. This convention means that temperature and energy quantities have the same dimensions. In particular, the SI unit kelvin becomes superfluous, being defined in terms of joules as . With this convention, temperature is always given in units of energy, and the Boltzmann constant is not explicitly needed in formulas.
This convention simplifies many physical relationships and formulas. For example, the equipartition formula for the energy associated with each classical degree of freedom ( above) becomes
As another example, the definition of thermodynamic entropy coincides with the form of information entropy:
where is the probability of each microstate. | 0 | Theoretical and Fundamental Chemistry |
Aerobic respiration, in which oxygen is used as the terminal electron acceptor, is crucial to all water-breathing fish. When fish are deprived of oxygen, they require other ways to produce ATP. Thus, a switch from aerobic metabolism to anaerobic metabolism occurs at the onset of hypoxia. Glycolysis and substrate-level phosphorylation are used as alternative pathways for ATP production. However, these pathways are much less efficient than aerobic metabolism. For example, when using the same substrate, the total yield of ATP in anaerobic metabolism is 15 times lower than in aerobic metabolism. This level of ATP production is not sufficient to maintain a high metabolic rate, therefore, the only survival strategy for fish is to alter their metabolic demands. | 0 | Theoretical and Fundamental Chemistry |
This group includes modified peptides that are mainly composed of proteogenic amino acids thereby closely resembling a natural peptide binding epitope. Introduced modifications usually aim to increase the stability of the peptide, its affintiy for a desired binding partner, oral availablity or cell permeability. The design of class A peptidomimetics often involves macrocyclization strategies as for example in stapled peptides. | 0 | Theoretical and Fundamental Chemistry |
Patlak method is based on the assumption that the backflow of tracer from bone mineral to bone ECF is zero (i.e., k=0). The calculation of K using Patlak method is simpler than using non-linear regression (NLR) fitting the arterial input function and the tissue time-activity curve data to the Hawkins model. It is crucial to note that Patlak method can only measure bone plasma clearance (K), and cannot measure the individual kinetic parameters, K, k, k, or k.
The concentration of tracer in tissue region-of-interest can be represented as a sum of concentration in bone ECF and the bone mineral. It can be mathematically represented as
where, within the tissue region-of-interest from the PET image, C(T) is the bone tissue activity concentration of tracer (in units: MBq/ml) at any time T, C(T) is the plasma concentration of tracer (in units: MBq/ml) at time T, V is the fraction of the ROI occupied by the ECF compartment, and is the area under the plasma curve is the net tracer delivery to the tissue region of interest (in units: MBq.Sec/ml) over time T. The Patlak equation is a linear equation of the form
Therefore, linear regression is fitted to the data plotted on Y- and X-axis between 4–60 minutes to obtain m and c values, where m is the slope of the regression line representing K and c is the Y-intercept of the regression line representing V. | 1 | Applied and Interdisciplinary Chemistry |
Copepods are assigned to the class Copepoda within the superclass Multicrustacea in the subphylum Crustacea. An alternative treatment is as a subclass belonging to class Hexanauplia. They are divided into 10 orders. Some 13,000 species of copepods are known, and 2,800 of them live in fresh water. | 1 | Applied and Interdisciplinary Chemistry |
Meibom currently leads the laboratory for biological geochemistry at EPFL. Research performed in his laboratory is interdisciplinary in nature, at the interface between isotope geochemistry and biology. Active themes in the laboratory include the use of NanoSIMS to visualize and characterize the diagenesis of biogenic substrates, as well as the study of metabolic processes in symbiotic organisms (notably corals) and how these processes may be influenced by environmental stress, in particular climate change. | 0 | Theoretical and Fundamental Chemistry |
ASBMB hosts and sponsors numerous meetings each year. The annual meeting is held each April in conjunction with the Experimental Biology meeting. Additionally, themed special symposia are organized throughout the year. The society also produces webinars throughout the year focused on topics related to scientific research, professional development and education. | 1 | Applied and Interdisciplinary Chemistry |
Peter D. Mitchell proposed the chemiosmotic hypothesis in 1961. In brief, the hypothesis was that most adenosine triphosphate (ATP) synthesis in respiring cells comes from the electrochemical gradient across the inner membranes of mitochondria by using the energy of NADH and FADH formed during the oxidative breakdown of energy-rich molecules such as glucose.
Molecules such as glucose are metabolized to produce acetyl CoA as a fairly energy-rich intermediate. The oxidation of acetyl coenzyme A (acetyl-CoA) in the mitochondrial matrix is coupled to the reduction of a carrier molecule such as nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD).
The carriers pass electrons to the electron transport chain (ETC) in the inner mitochondrial membrane, which in turn pass them to other proteins in the ETC. The energy at every redox transfer step is used to pump protons from the matrix into the intermembrane space, storing energy in the form of a transmembrane electrochemical gradient. The protons move back across the inner membrane through the enzyme ATP synthase. The flow of protons back into the matrix of the mitochondrion via ATP synthase provides enough energy for ADP to combine with inorganic phosphate to form ATP.
This was a radical proposal at the time, and was not well accepted. The prevailing view was that the energy of electron transfer was stored as a stable high potential intermediate, a chemically more conservative concept. The problem with the older paradigm is that no high energy intermediate was ever found, and the evidence for proton pumping by the complexes of the electron transfer chain grew too great to be ignored. Eventually the weight of evidence began to favor the chemiosmotic hypothesis, and in 1978 Peter D. Mitchell was awarded the Nobel Prize in Chemistry.
Chemiosmotic coupling is important for ATP production in mitochondria, chloroplasts
and many bacteria and archaea. | 1 | Applied and Interdisciplinary Chemistry |
A physician may order many laboratory tests on one specimen, referred to as a test panel, when a single test cannot provide sufficient information to make a swift and accurate diagnosis and treatment plan. A test panel is a group of many tests a clinical chemists do on one sample to look for changes in many analytes that may be indicative of specific medical concerns or the health status of an organ system. Thus, panel tests provide a more extensive evaluation of a patient's health, have higher predictive values for confirming or disproving a disease, and are quick and cost-effective. | 1 | Applied and Interdisciplinary Chemistry |
The RM system was first discovered by Salvatore Luria and Mary Human in 1952 and 1953. They found that a bacteriophage growing within an infected bacterium could be modified, so that upon their release and re-infection of a related bacterium the bacteriophages growth is restricted (inhibited; also described by Luria in his autobiography on pages 45 and 99 in 1984). In 1953, Jean Weigle and Giuseppe Bertani reported similar examples of host-controlled modification using different bacteriophage system. Later work by Daisy Roulland-Dussoix and Werner Arber in 1962 and many other subsequent workers led to the understanding that restriction was due to attack and breakdown of the modified bacteriophages DNA by specific enzymes of the recipient bacteria. Further work by Hamilton O. Smith isolated HinDII, the first of the class of enzymes now known as restriction enzymes, while Daniel Nathans showed that it can be used for restriction mapping. When these enzymes were isolated in the laboratory they could be used for controlled manipulation of DNA, thus providing the foundation for the development of genetic engineering. Werner Arber, Daniel Nathans, and Hamilton Smith were awarded the Nobel Prize in Physiology or Medicine in 1978 for their work on restriction-modification. | 1 | Applied and Interdisciplinary Chemistry |
Tetrakis(triphenylphosphine)palladium(0) was first prepared by Lamberto Malatesta et al. in the 1950s by reduction of sodium chloropalladate with hydrazine in the presence of the phosphine. It is commercially available, but can be prepared in two steps from Pd(II) precursors:
:PdCl + 2 PPh → PdCl(PPh)
:PdCl(PPh) + 2 PPh + NH → Pd(PPh) + N + 2 NHCl
Both steps may be carried out in a one-pot reaction, without isolating and purifying the PdCl(PPh) intermediate. Reductants other than hydrazine can be employed, including ascorbic acid. The compound is sensitive to air, but can be purified by washing with methanol to give the desired yellow powder. It is usually stored cold under argon. | 0 | Theoretical and Fundamental Chemistry |
Standard addition involves adding known amounts of analyte to an unknown sample, a process known as spiking. By increasing the number of spikes, the analyst can extrapolate for the analyte concentration in the unknown that has not been spiked. There are multiple approaches to the standard addition. The following section summarize each approach. | 0 | Theoretical and Fundamental Chemistry |
Radiative cooling is one of the few ways an object in space can give off energy. In particular, white dwarf stars are no longer generating energy by fusion or gravitational contraction, and have no solar wind. So the only way their temperature changes is by radiative cooling. This makes their temperature as a function of age very predictable, so by observing the temperature, astronomers can deduce the age of the star. | 0 | Theoretical and Fundamental Chemistry |
Stars known as white dwarfs have mass comparable to the Sun, but have about a hundredth of its radius. The high densities mean that the electrons are no longer bound to single nuclei and instead form a degenerate electron gas. The number density of electrons in a white dwarf is of the order of 10 electrons/m. This means their Fermi energy is: | 0 | Theoretical and Fundamental Chemistry |
In 1900 Moses Gomberg unexpectedly discovered true trivalent carbon and the first radical in the modern sense of the word in his (unsuccessful) attempt to make hexaphenylethane. In current organic chemistry concepts such as benzoyl and acetyl persist in chemical nomenclature but only to identify a functional group having the same fragment. | 0 | Theoretical and Fundamental Chemistry |
Alternatively, the general statement can be formulated in terms of the total number of electrons using simple rules of divisibility by a straightforward analysis of two cases.
First, consider the case where the total number of electrons is 4n + 2:
:4n + 2 = a(4q + 2) + b(4p + 2) + c(4t) + d(4r),
where a, b, c, and d are coefficients indicating the number of each type of component. This equation implies that one of, but not both, a or b is odd, for if a and b are both even or both odd, then the sum of the four terms is 0 (mod 4).
The generalized statement of the Woodward–Hoffmann rules states that a + d is odd if the reaction is allowed. Now, if a is even, then this implies that d is odd. Since b is odd in this case, the number of antarafacial components, b + d, is even. Likewise, if a is odd, then d is even. Since b even in this case, the number of antarafacial components, b + d, is again even. Thus, regardless of the initial assumption of parity for a and b, the number of antarafacial components is even when the electron count is 4n + 2. Contrariwise,, b + d is odd.
In the case where the total number of electrons is 4n, similar arguments (omitted here) lead to the conclusion that the number of antarafacial components b + d must be odd in the allowed case and even in the forbidden case.
Finally, to complete the argument, and show that this new criterion is truly equivalent to the original criterion, one needs to argue the converse statements as well, namely, that the number of antarafacial components b + d and the electron count (4n + 2 or 4n) implies the parity of a + d that is given by the Woodward–Hoffmann rules (odd for allowed, even for forbidden). Another round of (somewhat tedious) case analyses will easily show this to be the case. The pericyclic selection rule states:
In this formulation, the electron count refers to the entire reacting system, rather than to individual components, as enumerated in Woodward and Hoffmann's original statement. In practice, an even or odd number of antarafacial components usually means zero or one antarafacial components, respectively, as transition states involving two or more antarafacial components are typically disfavored by strain. As exceptions, certain intramolecular reactions may be geometrically constrained in such a way that enforces an antarafacial trajectory for multiple components. In addition, in some cases, e.g., the Cope rearrangement, the same (not necessarily strained) transition state geometry can be considered to contain two supra or two antara π components, depending on how one draws the connections between orbital lobes. (This ambiguity is a consequence of the convention that overlap of either both interior or both exterior lobes of a σ component can be considered to be suprafacial.)
This alternative formulation makes the equivalence of the Woodward–Hoffmann rules to the Dewar–Zimmerman analysis (see below) clear. An even total number of phase inversions is equivalent to an even number of antarafacial components and corresponds to Hückel topology, requiring 4n + 2 electrons for aromaticity, while an odd total number of phase inversions is equivalent to an odd number of antarafacial components and corresponds to Möbius topology, requiring 4n electrons for aromaticity. To summarize aromatic transition state theory: Thermal pericyclic reactions proceed via (4n + 2)-electron Hückel or (4n)-electron Möbius transition states.
As a mnemonic, the above formulation can be further restated as the following: | 0 | Theoretical and Fundamental Chemistry |
In a multicomponent system, where the vapor and liquid consist of more than one type of compounds, describing the equilibrium state is more complicated. For all components in the system, the equilibrium state between the two phases is described by the following equations:
:; and
where and are the temperature and pressure for each phase, and and are the partial molar Gibbs free energy also called chemical potential (units of energy per amount of substance) within the liquid and vapor, respectively, for each phase. The partial molar Gibbs free energy is defined by:
where is the (extensive) Gibbs free energy, and is the amount of substance of component . | 0 | Theoretical and Fundamental Chemistry |
Consider the nuclear fission of U into Kr, Ba, and three neutrons.
:U → Kr + Ba + 3 n
The mass number of the reactant, U, is 236. Because the actual mass is , its mass excess is +. Calculated in the same manner, the respective mass excesses for the products, Kr, Ba, and three neutrons, are , and , respectively, for a total mass excess of . The difference between the mass excess of the reactants and that of the products is , which shows that the mass excess of the products is less than that of the reactants, and so the fission can occur – a calculation which could have also been done with only the masses of the reactants.
The mass excess can be converted into energy using = , and , yielding . | 0 | Theoretical and Fundamental Chemistry |
Burks became an assistant professor of chemistry at St. Edward's University in Austin, Texas, in 2016, where she taught and conducted research until 2020. She then moved to Washington, D.C., to join the faculty at American University as an associate professor of chemistry.
Her current research centers on developing low-cost colorimetric sensors for detecting chemicals of forensic interest including explosives and illicit drugs. To maximize portability in the field, her group focuses on transforming smartphones into detection devices. Her research interests lie in the applied science domain, which she believes is well-suited to capturing and holding students' attention because they are working to solve real-world problems. She has spoken about her intersectional research approach to equipping students with the technical knowledge they need to work on these real-world challenges with the United States Department of Defense Science, Technology, and Innovation Exchange. | 0 | Theoretical and Fundamental Chemistry |
The upper critical magnetic field H of the superconducting state of CeCoIn is anisotropic, in accordance with the crystal structure and other physical properties. For magnetic fields applied along the [100] direction, H amounts to approximately 11.6 T, and H for fields along the [001] directions to 4.95 T.
The superconducting order parameter has d-wave symmetry, as established by several experiments, such as scanning tunneling microscopy (STM) and spectroscopy (STS).
Detailed studies close to the critical field have been performed on CeCoIn, and indications were found that certain regimes in the phase diagram of this material should be interpreted in terms of the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) phase.
Subsequently, the neutron-diffraction experiments showed that this regime features a more complex phase that also exhibits incommensurate antiferromagnetic order, a so-called Q phase.
Evidence for a delocalization quantum phase transition without symmetry breaking is presented. | 1 | Applied and Interdisciplinary Chemistry |
Due to the high potency and clinical need for cancer treatments, epothilones have been the target of many total syntheses. The first group to publish the total synthesis of epothilones was S. J. Danishefsky et al. in 1996. This total synthesis of epothilone A was achieved via an intramolecular ester enolate-aldehyde condensation. Other syntheses of epothilones have been published by Nicolaou, Schinzer, Mulzer, and Carreira. In this approach, key building blocks aldehyde, glycidols, and ketoacid were constructed and coupled to the olefin metathesis precursor via an aldol reaction and then an esterification coupling. Grubbs' catalyst was employed to close the bis terminal olefin of the precursor compound. The resulting compounds were cis- and trans-macrocyclic isomers with distinct stereocenters. Epoxidation of cis- and trans-olefins yield epothilone A and its analogs.
One of the total syntheses of epothilone B is outlined below and was described by the laboratory of K. C. Nicolaou. The retrosynthetic analysis revealed 1, 2, and 3 as the building blocks (Figure 1).
As seen in Figure 2, keto acid 1 was generated from the keto aldehyde that was converted to the silyl ether via asymmetric allylboration and silylation of the resulting alcohol. Ozonolysis of the silyl ether and Lindgren–Pinnick oxidation of the aldehyde afforded the keto acid. Ketone 2 was constructed via Enders alkylation starting from the hydrazone. Ozonolysis, the last step of the Enders alkylation, was followed by reduction of the aldehyde and silylation of the resulting alcohol. Hydrogenolysis of the benzyl ether gave the alcohol, which was oxidized under Swern condition and alkylated with the Grignard reagent to yield the secondary alcohol. Oxidation of this alcohol with the Ley–Griffith reagent gave the desired ketone. Thiazole 3 was synthesized from the ester, which was reduced with diisobutylaluminium hydride, and the aldehyde was reacted with the stabilized ylide in the Wittig reaction. Asymmetric allylboration of the α,β-unsaturated aldehyde and protection of the hydroxy group gave the silyl ether, whose terminal olefin was reacted with osmium tetroxide to a diol that was cleaved with lead tetraacetate to furnish the aldehyde. Reduction, iodination, and treatment with triphenylphosphine led to phosphonium salt.
Fragments 1, 2, and 3 were reacted with each other to deliver epothilone B in an approach including Wittig reaction, aldol reaction, and Yamaguchi esterification (Figure 3). Preparative thin-layer chromatography was used to separate the diastereomers. | 0 | Theoretical and Fundamental Chemistry |
Ninhydrin was discovered in 1910 by the German-English chemist Siegfried Ruhemann (1859–1943). In the same year, Ruhemann observed ninhydrin's reaction with amino acids. In 1954, Swedish investigators Oden and von Hofsten proposed that ninhydrin could be used to develop latent fingerprints. | 0 | Theoretical and Fundamental Chemistry |
Fluorogenic describes a property of chemical compounds which are initially not fluorescent, but become fluorescent through a chemical reaction, typically through an intermolecular covalent reaction which binds the now fluorescent compound to a target molecule. IUPAC uses a broader definition of fluorogenic, wherein a enhancement of fluorescence via a chemical reaction is not required, however in contrast to the IUPAC definition common use of fluorogenic does not refer to non-reaction effects like the enhancement of fluorescence from a fluorophore being in different solvents. Fluorogenic labeling reagents are often used in analytical chemistry procedures, particularly in HPLC or CE to derivative target compounds (e.g. labeling the primary amines of polypeptides), thereby allowing enhanced sensitivity through fluorescence based detection. | 0 | Theoretical and Fundamental Chemistry |
In this approach, a narrow pulse of light (and respectively.
Multiple scattering events broaden the DTOF and the attenuation of a result of both absorption and scattering as they divert photons from the direction of the detector. Higher scattering leads to a more delayed and a broader DTOF and higher absorption reduces the amplitude and changes the slope of the tail of the DTOF. Since absorption and scattering have different effects on the DTOF, they can be extracted independently while using a single source-detector separation. Moreover, the penetration depth in TD depends solely on the photon arrival times and is independent of the source-detector separation unlike in CW approach.
The theory of light propagation in diffusive media is usually dealt with using the framework of radiative transfer theory under the multiple scattering regime. It has been demonstrated that radiative transfer equation under the diffusion approximation yields sufficiently accurate solutions for practical applications. For example, it can be applied for the semi-infinite geometry or the infinite slab geometry, using proper boundary conditions. The system is considered as a homogeneous background and an inclusion is considered as an absorption or scattering perturbation.
The time-resolved reflectance curve at a point from the source for a semi-infinite geometry is given by
where is the diffusion coefficient, is the reduced scattering coefficient and is asymmetry factor, is the photon velocity in the medium, takes into account the boundary conditions and is a constant.
The final DTOF is a convolution of the instrument response function (IRF) of the system with the theoretical reflectance curve.
When applied to biological tissues estimation of <math>\mu_a
allows us to then estimate the concentration of the various tissue constituents as well as provides information about blood oxygenation (oxy and deoxy-hemoglobin) as well as saturation and total blood volume. These can then be used as biomarkers for detecting various pathologies. | 0 | Theoretical and Fundamental Chemistry |
Age at time of death: Stillborn fetuses and infants putrefy slowly due to their sterility. Otherwise, however, younger people generally putrefy more quickly than older people.
Condition of the body: A body with a greater fat percentage and less lean body mass will have a faster rate of putrefaction, as fat retains more heat and it carries a larger amount of fluid in the tissues.
Cause of death: The cause of death has a direct relationship to putrefaction speed, with bodies that died from acute violence or accident generally putrefying slower than those that died from infectious diseases. Certain poisons, such as potassium cyanide or strychnine, may also delay putrefaction, while chronic alcoholism and cocaine use will speed it.
External injuries: Antemortem or postmortem injuries can speed putrefaction as injured areas can be more susceptible to invasion by bacteria. | 1 | Applied and Interdisciplinary Chemistry |
Conventional air conditioning systems are a source of waste heat by releasing waste heat into the outdoor ambient air whilst cooling indoor spaces. This expelling of waste heat from air conditioning can worsen the urban heat island effect. Waste heat from air conditioning can be reduced through the use of passive cooling building design and zero-energy methods like evaporative cooling and passive daytime radiative cooling, the latter of which sends waste heat directly to outer space through the infrared window. | 0 | Theoretical and Fundamental Chemistry |
Experimental archaeometallurgy is a subset of experimental archaeology that specifically involves past metallurgical processes most commonly involving the replication of copper and iron objects as well as testing the methodology behind the production of ancient metals and metal objects. Metals and elements used primarily as alloying materials, such as tin, lead, and arsenic, are also a part of experimental research. | 1 | Applied and Interdisciplinary Chemistry |
Sulfate reduction in the seabed is strongly focused toward near-surface sediments with high depositional rates along the ocean margins. The benthic marine sulfur cycle is therefore sensitive to anthropogenic influence, such as ocean warming and increased nutrient loading of coastal seas. This stimulates photosynthetic productivity and results in enhanced export of organic matter to the seafloor, often combined with low oxygen concentration in the bottom water (Rabalais et al., 2014; Breitburg et al., 2018). The biogeochemical zonation is thereby compressed toward the sediment surface, and the balance of organic matter mineralization is shifted from oxic and suboxic processes toward sulfate reduction and methanogenesis (Middelburg and Levin, 2009).
* cable bacteria
The sulfur cycle in marine environments has been well-studied via the tool of sulfur isotope systematics expressed as δS. The modern global oceans have sulfur storage of 1.3 × 10 g, mainly occurring as sulfate with the δS value of +21‰. The overall input flux is 1.0 × 10 g/year with the sulfur isotope composition of ~3‰. Riverine sulfate derived from the terrestrial weathering of sulfide minerals (δS = +6‰) is the primary input of sulfur to the oceans. Other sources are metamorphic and volcanic degassing and hydrothermal activity (δS = 0‰), which release reduced sulfur species (e.g., HS and S). There are two major outputs of sulfur from the oceans. The first sink is the burial of sulfate either as marine evaporites (e.g., gypsum) or carbonate-associated sulfate (CAS), which accounts for 6 × 10 g/year (δS = +21‰). The second sulfur sink is pyrite burial in shelf sediments or deep seafloor sediments (4 × 10 g/year; δS = -20‰). The total marine sulfur output flux is 1.0 × 10 g/year which matches the input fluxes, implying the modern marine sulfur budget is at steady state. The residence time of sulfur in modern global oceans is 13,000,000 years.
In modern oceans, Hydrogenovibrio crunogenus, Halothiobacillus, and Beggiatoa are primary sulfur oxidizing bacteria, and form chemosynthetic symbioses with animal hosts. The host provides metabolic substrates (e.g., CO, O, HO) to the symbiont while the symbiont generates organic carbon for sustaining the metabolic activities of the host. The produced sulfate usually combines with the leached calcium ions to form gypsum, which can form widespread deposits on near mid-ocean spreading centers.
Hydrothermal vents emit hydrogen sulfide that support the carbon fixation of chemolithotrophic bacteria that oxidize hydrogen sulfide with oxygen to produce elemental sulfur or sulfate. | 0 | Theoretical and Fundamental Chemistry |
Miraculin, unlike curculin (another taste-modifying agent), is not sweet by itself, but it can change the perception of sourness to sweetness, even for a long period after consumption. The duration and intensity of the sweetness-modifying effect depends on various factors, such as miraculin concentration, duration of contact of the miraculin with the tongue, and acid concentration. Miraculin reaches its maximum sweetness with a solution containing at least 4*10 mol/L miraculin, which is held in the mouth for about 3 minutes. Maximum is equivalent in sweetness to a 0.4 mol/L solution of sucrose. Miraculin degrades permanently via denaturation at high temperatures, at pH below 3 or above 12.
Although the detailed mechanism of the taste-inducing behavior is unknown, it appears the sweet receptors are activated by acids which are related to sourness, an effect remaining until the taste buds perceive a neutral pH. Sweeteners are perceived by the human sweet taste receptor, hT1R2-hT1R3, which belongs to G protein-coupled receptors, modified by the two histidine residues (i.e. His30 and His60) which participate in the taste-modifying behavior. One site maintains the attachment of the protein to the membranes while the other (with attached xylose or arabinose) activates the sweet receptor membrane in acid solutions. | 1 | Applied and Interdisciplinary Chemistry |
Examples of chain reactions in living organisms include excitation of neurons in epilepsy and lipid peroxidation. In peroxidation, a lipid radical reacts with oxygen to form a peroxyl radical (L• + O → LOO•). The peroxyl radical then oxidises another lipid, thus forming another lipid radical (LOO• + L–H → LOOH + L•). A chain reaction in glutamatergic synapses is the cause of synchronous discharge in some epileptic seizures. | 0 | Theoretical and Fundamental Chemistry |
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