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Polarized liquid interfaces have been used to examine the thermodynamics and kinetics of the transfer of charged species from one phase to another. Two main methods exist. The first is ITIES, "interfaces between two immiscible electrolyte solutions". The second is droplet experiments. Here a reaction at a triple interface between a conductive solid, droplets of a redox active liquid phase and an electrolyte solution have been used to determine the energy required to transfer a charged species across the interface. | 0 | Theoretical and Fundamental Chemistry |
Giuliana Tesoro (née Cavaglieri) (June 1, 1921 – September 29, 2002) was an Italian-born American chemist who earned more than 125 patents, with her most notable consisting of improvements in fabric comfort, practicality, and flame resistance. | 0 | Theoretical and Fundamental Chemistry |
During the 1960s cruising at speeds between Mach 2 to 3 was pursued for commercial and military aircraft. Concorde, North American XB-70 and Lockheed SR-71 used ejector-type supersonic nozzles which had a secondary flow obtained from the inlet upstream of the engine compressor. The secondary flow was used to purge the engine compartment, cool the engine case, cool the ejector nozzle and cushion the primary expansion. The secondary flow was ejected by the pumping action of the primary gas flow through the engine nozzle and the ram pressure in the inlet. | 1 | Applied and Interdisciplinary Chemistry |
Telomerization is a reaction that produces a particular kind of oligomer with two distinct end groups. The oligomer is called a telomer. Some telomerizations proceed by radical pathways, many do not. A generic equation is:
where M is the monomer, and A and B are the end groups, and n is the degree of polymerization.
One example is the coupled dimerization and hydroesterification of 1,3-butadiene. This step produces a doubly unsaturated C9-ester:
:2CH=CH-CH=CH + CO + CHOH → CH=CH(CH)CH=CHCHCOCH
The monomer in this reaction is butadiene, the degree of polymerization is 2, and the end groups are vinyl and the carboxy methyl (COCH). This and several related reactions proceed with palladium catalysts. Many telomerizations are used in industrial chemistry. | 0 | Theoretical and Fundamental Chemistry |
Eukaryotic messages are subject to surveillance by nonsense-mediated decay (NMD), which checks for the presence of premature stop codons (nonsense codons) in the message. These can arise via incomplete splicing, V(D)J recombination in the adaptive immune system, mutations in DNA, transcription errors, leaky scanning by the ribosome causing a frame shift, and other causes. Detection of a premature stop codon triggers mRNA degradation by 5 decapping, 3 poly(A) tail removal, or endonucleolytic cleavage. | 1 | Applied and Interdisciplinary Chemistry |
CO stripping is one of the methods used to determine the electrochemically active surface area of electrodes and catalysts that irreversibly adsorb carbon monoxide, most notably ones containing platinum and other transition metals. | 0 | Theoretical and Fundamental Chemistry |
Another property of nanoparticles that is heavily influenced by the surfactants is the solubility of the nanoparticle. One can imagine that a metallic nanoparticle would not dissolve well in organic solvents. By adding the surfactants the nanoparticles will stay more evenly dispersed throughout the solvent. This is due to the, often, amphiphilic nature of the surfactants. The interfacial layer can be used to essentially tune the solubility of nanoparticles in different media, which can range from extremely hydrophilic to hydrophobic. | 0 | Theoretical and Fundamental Chemistry |
Later medieval Latin had alchimia / alchymia "alchemy", alchimicus "alchemical", and alchimista "alchemist". The mineralogist and humanist Georg Agricola (died 1555) was the first to drop the Arabic definite article al-. In his Latin works from 1530 on he exclusively wrote chymia and chymista in describing activity that we today would characterize as chemical or alchemical. As a humanist, Agricola was intent on purifying words and returning them to their classical roots. He had no intent to make a semantic distinction between chymia and alchymia.
During the later sixteenth century Agricolas new coinage slowly propagated. It seems to have been adopted in most of the vernacular European languages following Conrad Gessners adoption of it in his extremely popular pseudonymous work, Thesaurus Euonymi Philiatri De remediis secretis: Liber physicus, medicus, et partim etiam chymicus (Zurich 1552). Gessners work was frequently re-published in the second half of the 16th century in Latin and was also published in a number of vernacular European languages, with the word spelled without the al-'.
In the 16th and 17th centuries in Europe the forms alchimia and chimia (and chymia) were synonymous and interchangeable. The semantic distinction between a rational and practical science of chimia and an occult alchimia arose only in the early eighteenth century.
In 16th, 17th and early 18th century English the spellings — both with and without the "al" — were usually with an i or y as in chimic / chymic / alchimic / alchymic. During the later 18th century the spelling was re-fashioned to use a letter e, as in chemic in English. In English after the spelling shifted from chimical to chemical, there was corresponding shift from alchimical to alchemical, which occurred in the early 19th century. In French, Italian, Spanish and Russian today it continues to be spelled with an i as in for example Italian chimica. | 1 | Applied and Interdisciplinary Chemistry |
Some guest molecules are charged compounds, which might be oxidized or reduced by certain chemicals. This type of guest molecule can present redox responsiveness. Some host molecules (i.e., α-CD) or guest molecules (i.e., tetra ammonium ion) are pH-sensitive, different pH can result in different species, which significantly influences the binding behavior, giving the material pH responsive properties. Some guest molecules may change their configurations under different lights, which makes the material photo-responsive. Cai et al employed a halogen bond to prepare a host-guest system, and the materials are heat- and mechano-responsive with long persistent emission. | 0 | Theoretical and Fundamental Chemistry |
Elizabeth Joy New AM SFHEA FRSC FRACI FRSN (born 1984) is an Australian chemist and Professor of the School of Chemistry, University of Sydney. She won the 2018 Australian Museum 3M Eureka Prize. | 0 | Theoretical and Fundamental Chemistry |
Methyl vinyl ketone and ethyl acetoacetate undergo aldol cyclization in the presence of catalytic pyrrolidinum acetate or Triton B or sodium ethoxide to produce Hagemann's ester. This variant is a type of Robinson annulation. | 0 | Theoretical and Fundamental Chemistry |
François Stanislas Cloez (24 June 1817 – 12 October 1883) was a French chemist, who authored both as "F. S. Cloez" and "S. Cloez", and is known for his pioneering role in analytical chemistry during the 19th century. He was a founder and later president of the Chemistry Society of France.
In 1851, Cloez and Italian chemist Stanislao Cannizzaro, working on collaborative research, prepared cyanamide by the action of ammonia on cyanogen chloride in ethereal solution.
In the 1870s, he commenced the identification of the constituents of individual essential oils and their classification into groups according to their suitability for medicinal, industrial and perfumery purposes. He identified the major constituent of eucalyptus oil, which he called "eucalyptol" (now generally known as cineole). In honour of his work on eucalyptus oil Eucalyptus cloeziana (Gympie messmate) is named after him.
Cloez also played a role in developing a theory on the origin of life elsewhere in the Solar System.
In 1864, Cloez was the first scientist to examine a carbonaceous chondrite, the Orgueil meteorite, after it had fallen in France. Cloez said that its content "would seem to indicate the existence of organized substances in celestial bodies."
The Orgueil meteorite was subject to a hoax, when a sample of the meteorite was contaminated with a rush seed. The hoax was discovered in the 1960s when the meteorite was being examined for evidence of extraterrestrial biological material. There is no suggestion in literature that Cloez was party to this hoax. | 0 | Theoretical and Fundamental Chemistry |
The observed intrinsic KIEs of RuBisCO have been correlated with two aspects of its enzyme kinetics: 1) Its "specificity" for CO over O, and 2) Its rate of carboxylation. | 0 | Theoretical and Fundamental Chemistry |
Quality scores are normally stored together with the nucleotide sequence in the widely accepted FASTQ format. They account for about half of the required disk space in the FASTQ format (before compression), and therefore the compression of the quality values can significantly reduce storage requirements and speed up analysis and transmission of sequencing data. Both lossless and lossy compression are recently being considered in the literature. For example, the algorithm QualComp performs lossy compression with a rate (number of bits per quality value) specified by the user. Based on rate-distortion theory results, it allocates the number of bits so as to minimize the MSE (mean squared error) between the original (uncompressed) and the reconstructed (after compression) quality values. Other algorithms for compression of quality values include SCALCE, Fastqz and more recently QVZ, AQUa and the MPEG-G standard, that is currently under development by the MPEG standardisation working group. Both are lossless compression algorithms that provide an optional controlled lossy transformation approach. For example, SCALCE reduces the alphabet size based on the observation that “neighboring” quality values are similar in general. | 1 | Applied and Interdisciplinary Chemistry |
As noted above, human cells do not express TLR11, but mice cells do. Mouse-specific TLR11 recognizes uropathogenic E.coli and the apicomplexan parasite Toxoplasma gondii. With Toxoplasma its ligand is the protein profilin and the ligand for E. coli is flagellin. The flagellin from the enteropathogen Salmonella is also recognized by TLR11.
As mouse TLR11 is able to recognize Salmonella effectively, normal mice do not get infected by oral Salmonella Typhi, which causes food- and waterborne gastroenteritis and typhoid fever in humans. TLR11 deficient knockout mice, on the other hand, are efficiently infected. As a result, this knockout mouse can act as a disease model of human typhoid fever. | 1 | Applied and Interdisciplinary Chemistry |
One strand of the DNA, the template strand (or noncoding strand), is used as a template for RNA synthesis. As transcription proceeds, RNA polymerase traverses the template strand and uses base pairing complementarity with the DNA template to create an RNA copy (which elongates during the traversal). Although RNA polymerase traverses the template strand from 3 → 5, the coding (non-template) strand and newly formed RNA can also be used as reference points, so transcription can be described as occurring 5 → 3. This produces an RNA molecule from 5 → 3, an exact copy of the coding strand (except that thymines are replaced with uracils, and the nucleotides are composed of a ribose (5-carbon) sugar where DNA has deoxyribose (one fewer oxygen atom) in its sugar-phosphate backbone).
mRNA transcription can involve multiple RNA polymerases on a single DNA template and multiple rounds of transcription (amplification of particular mRNA), so many mRNA molecules can be rapidly produced from a single copy of a gene. The characteristic elongation rates in prokaryotes and eukaryotes are about 10–100 nts/sec. In eukaryotes, however, nucleosomes act as major barriers to transcribing polymerases during transcription elongation. In these organisms, the pausing induced by nucleosomes can be regulated by transcription elongation factors such as TFIIS.
Elongation also involves a proofreading mechanism that can replace incorrectly incorporated bases. In eukaryotes, this may correspond with short pauses during transcription that allow appropriate RNA editing factors to bind. These pauses may be intrinsic to the RNA polymerase or due to chromatin structure.
Double-strand breaks in actively transcribed regions of DNA are repaired by homologous recombination during the S and G2 phases of the cell cycle. Since transcription enhances the accessibility of DNA to exogenous chemicals and internal metabolites that can cause recombinogenic lesions, homologous recombination of a particular DNA sequence may be strongly stimulated by transcription. | 1 | Applied and Interdisciplinary Chemistry |
A maltoside is a glycoside with maltose as the glycone (sugar) functional group. Among the most common are alkyl maltosides, which contain hydrophobic alkyl chains as the aglycone. Given their amphiphilic properties, these comprise a class of detergents, where variation in the alkyl chain confers a range of detergent properties including CMC and solubility. Maltosides are most often used for the solubilization and purification of membrane proteins. | 1 | Applied and Interdisciplinary Chemistry |
Second generation proton sponges are known with even higher basicity. 1,8-bis(hexamethyltriaminophosphazenyl)naphthalene or HMPN is prepared from 1,8-diaminonaphthalene by reaction with tris(dimethylamino)bromophosphonium bromide in the presence of triethylamine. HMPN has a pK of 29.9 in acetonitrile which is more than 11 orders of magnitude higher than Proton Sponge.
The aromatization of an additional ring in 4,12-Dihydrogen-4,8,12-triazatriangulene is utilized by Al-Yassiri and Puchta to get a representative for a new class of Δ-shaped proton sponges. This compound has a calculated proton affinity of 254 kcal/mol (B3LYP/6-311+G**) and is therefore between 1,8-Bis(dimethylamino)naphthalene and HMPN. | 0 | Theoretical and Fundamental Chemistry |
This compound is prepared by oxidation of 4-aminodimethylaniline in the presence of sodium thiosulfate to give the quinonediiminothiosulfonic acid, reaction with dimethylaniline, oxidation to the indamine, and cyclization to give the thiazine:
A green electrochemical procedure, using only dimethyl-4-phenylenediamine and sulfide ions has been proposed. | 0 | Theoretical and Fundamental Chemistry |
CRISPR-associated transposons have been harnessed for in vitro and in vivo gene editing at different targets, in different hosts, and with different payloads. All CAST components of the Tn6677 system from Vibrio cholerae have been combined into a single plasmid and confirmed to deliver up to 10kb transposons at near 100% efficiency. This has also been shown in a community context with conjugative delivery of suicide vectors to provide antibiotic resistance or enhanced metabolic function to only a single microbe. Much of the initial characterization of these systems has been done in E. coli, but functionality has been confirmed in beta- and gammaproteobacteria with high efficiency, and in alphaproteobacteria at somewhat lower efficiency. A single plasmid Tn677 has also been shown to function in human HEK293T cells showing potential therapeutic use in the future. | 1 | Applied and Interdisciplinary Chemistry |
Zinc (Zn) was incorporated into living cells in two waves. Four to three Ga, anaerobic prokaryotes arose, and the atmosphere was full of HS and highly reductive. Thus most zinc was in the form of insoluble ZnS. However, because seawater at the time was slightly acidic, some Zn(II) was available in its ionic form and became part of early anaerobic prokaryotes' external proteases, external nucleases, internal synthetases and dehydrogenases.
During the second wave, once the Great Oxygenation Event occurred, more Zn(II) ions were available in the seawater. This allowed its incorporation in the single-cell eukaryotes as they arose at this time. It is believed that the later addition of ions such as zinc and copper allowed them to displace iron and manganese from the enzyme superoxide dismutase (SOD). Fe and Mn complexes dissociate readily (Irving–Williams series) while Zn and Cu do not. This is why eukaryotic SOD contains Cu or Zn and its prokaryotic counterpart contains Fe or Mn.
Zn (II) doesn't pose an oxidation threat to the cytoplasm. This allowed it to become a major cytoplasmic element in the eukaryotes. It became associated with a new group of transcription proteins, zinc fingers. This could only have occurred due to the long life of eukaryotes, which allowed time for zinc to exchange and hence become an internal messenger coordinating the action of other transcription factors during growth. | 0 | Theoretical and Fundamental Chemistry |
Butyric acid is an inhibitor that is selective for class I HDACs in humans. HDACs are histone-modifying enzymes that can cause histone deacetylation and repression of gene expression. HDACs are important regulators of synaptic formation, synaptic plasticity, and long-term memory formation. Class I HDACs are known to be involved in mediating the development of an addiction. Butyric acid and other HDAC inhibitors have been used in preclinical research to assess the transcriptional, neural, and behavioral effects of HDAC inhibition in animals addicted to drugs. | 1 | Applied and Interdisciplinary Chemistry |
In research, whole-genome sequencing can be used in a Genome-Wide Association Study (GWAS) – a project aiming to determine the genetic variant or variants associated with a disease or some other phenotype. | 1 | Applied and Interdisciplinary Chemistry |
Surfactants can destabilize toxic organic compounds in paint which can enter the environment and have negative effects. Water-soluble surfactants can wash out of dried paints and enter the environment. Some of these surfactants are directly toxic to animals and the environment as well as increase the ability of other toxic contaminants present to enter the environment. | 0 | Theoretical and Fundamental Chemistry |
Jehle pointed out that, when immersed in a liquid and intermingled with other molecules, charge fluctuation forces favor the association of identical molecules as nearest neighbors. In accord with this principle, the multiple copies of a polypeptide encoded by a gene often undergo molecular recognition with each other to form an ordered multi-polypeptide protein structure. When such a protein is formed from polypeptides produced by two different mutant alleles of a particular gene, the protein composed of a mixture of polypeptides may exhibit greater functional activity than the multi-polypeptide protein formed by each of the mutants alone. In such a case, the phenomenon is referred to as intragenic complementation.
Intragenic complementation (also called inter-allelic complementation) has been demonstrated in many different genes in a variety of organisms. Crick and Orgel analyzed of the results of such studies and came to the conclusion that intragenic complementation, in general, arises from the interaction of differently defective polypeptide monomers when they form an ordered aggregate they called a “multimer.” | 0 | Theoretical and Fundamental Chemistry |
The rate of change of momentum of a particle is given by the Lorentz equation:
By using this equation and the Vlasov Equation, the momentum equation for each fluid becomes
where is the pressure tensor. The material derivative is
The pressure tensor is defined as the particle mass times the covariance matrix of the velocity: | 1 | Applied and Interdisciplinary Chemistry |
The precise mechanism of action of modafinil for narcolepsy and other sleep disorders remains unclear. Although modafinil may have interactions with neurotransmitter systems, its exact mode of action is not fully understood.
From laboratory research, modafinil has little to no affinity for serotonin or norepinephrine transporters and does not directly interact with these systems. However, studies have shown that elevated concentrations of norepinephrine and serotonin can occur as an indirect effect following modafinil administration due to increased extracellular dopamine activity. Unlike traditional psychostimulant drugs, such as cocaine or amphetamine, modafinil shows low potential for causing euphoria due to differences in how it interacts with dopamine transporters at a cellular level.
In addition to its influence on dopaminergic pathways, modafinil may impact other neurotransmitter systems, such as orexin or hypocretin. Orexin neurons play a crucial role in promoting wakefulness and regulating arousal states. Modafinil may increase signaling within hypothalamic orexin pathways, potentially contributing to its wake-promoting effects. | 0 | Theoretical and Fundamental Chemistry |
By linking the rivers, vast amount of land areas which will not otherwise be irrigated and are unusable for agriculture become fertile. | 1 | Applied and Interdisciplinary Chemistry |
This unusual triad occurs only in one superfamily of amidases. In this case, the lysine acts to polarise the middle serine. The middle serine then forms two strong hydrogen bonds to the nucleophilic serine to activate it (one with the side chain hydroxyl and the other with the backbone amide). The middle serine is held in an unusual cis orientation to facilitate precise contacts with the other two triad residues. The triad is further unusual in that the lysine and cis-serine both act as the base in activating the catalytic serine, but the same lysine also performs the role of the acid member as well as making key structural contacts. | 1 | Applied and Interdisciplinary Chemistry |
Xenon isotope geochemistry uses the abundance of xenon (Xe) isotopes and total xenon to investigate how Xe has been generated, transported, fractionated, and distributed in planetary systems. Xe has nine stable or very long-lived isotopes. Radiogenic Xe and fissiogenic Xe isotopes are of special interest in geochemical research. The radiogenic and fissiogenic properties can be used in deciphering the early chronology of Earth. Elemental Xe in the atmosphere is depleted and isotopically enriched in heavier isotopes relative to estimated solar abundances. The depletion and heavy isotopic enrichment can be explained by hydrodynamic escape to space that occurred in Earths early atmosphere. Differences in the Xe isotope distribution between the deep mantle (from Ocean Island Basalts, or OIBs), shallower Mid-ocean Ridge Basalts (MORBs), and the atmosphere can be used to deduce Earths history of formation and differentiation of the solid Earth into layers. | 0 | Theoretical and Fundamental Chemistry |
Carbon monoxide-releasing molecules are metal carbonyl complexes that are being developed as potential drugs to release CO. At low concentrations, CO functions as a vasodilatory and an anti-inflammatory agent. CO-RMs have been conceived as a pharmacological strategic approach to carry and deliver controlled amounts of CO to tissues and organs. | 0 | Theoretical and Fundamental Chemistry |
Depending on the source material, product quality varies. High quality oxidized lignite (brown coal), usually referred to as leonardite, is the best source material for extraction of large quantities of potassium humate. The less oxidized the coal, the less potassium humate extracted. Sources low in ash produce the best quality. Less oxidized brown coal contains a higher proportion of the insoluble humin fraction and along with peat which is lower in humic acid content and usually high in ash content requires separation by filtration or centrifugation to remove ash and humin. Peat is also high in non-humified organic matter that needs to be reduced to produce a high quality product. The benefit of peat is that it is usually 2-3 times higher in fulvic acid content, which are the low molecular weight fractions of humic acid that are high in oxygen containing functional groups and soluble at a low pH of <1. Fulvic acids have a higher cation exchange capacity and therefore have a higher chemical interaction with fertilizers and are able to form soluble chelates of trace metals. | 0 | Theoretical and Fundamental Chemistry |
Ethanol precipitation is a widely used method for purifying and concentrating nucleic acids, including plasmid DNA. The basic principle of this method is that nucleic acids are insoluble in ethanol or isopropanol but soluble in water. Therefore, it works by using ethanol as an antisolvent of DNA, causing it to precipitate out of solution and then it can be collected by centrifugation. The soluble fraction is discarded to remove other biomolecules. | 1 | Applied and Interdisciplinary Chemistry |
The Ritchie equation, derived in 1972, is another free-energy relationship:
where N is the nucleophile dependent parameter and k the reaction rate constant for water. In this equation, a substrate-dependent parameter like s in the Swain–Scott equation is absent. The equation states that two nucleophiles react with the same relative reactivity regardless of the nature of the electrophile, which is in violation of the reactivity–selectivity principle. For this reason, this equation is also called the constant selectivity relationship.
In the original publication the data were obtained by reactions of selected nucleophiles with selected electrophilic carbocations such as tropylium or diazonium cations:
or (not displayed) ions based on malachite green. Many other reaction types have since been described.
Typical Ritchie N values (in methanol) are: 0.5 for methanol, 5.9 for the cyanide anion, 7.5 for the methoxide anion, 8.5 for the azide anion, and 10.7 for the thiophenol anion. The values for the relative cation reactivities are −0.4 for the malachite green cation, +2.6 for the benzenediazonium cation, and +4.5 for the tropylium cation. | 0 | Theoretical and Fundamental Chemistry |
Unlike a classical ideal gas, whose pressure is proportional to its temperature
where P is pressure, k is Boltzmanns constant, N is the number of particles—typically atoms or molecules—, T is temperature, and V' is the volume, the pressure exerted by degenerate matter depends only weakly on its temperature. In particular, the pressure remains nonzero even at absolute zero temperature. At relatively low densities, the pressure of a fully degenerate gas can be derived by treating the system as an ideal Fermi gas, in this way
where m is the mass of the individual particles making up the gas. At very high densities, where most of the particles are forced into quantum states with relativistic energies, the pressure is given by
where K is another proportionality constant depending on the properties of the particles making up the gas.
All matter experiences both normal thermal pressure and degeneracy pressure, but in commonly encountered gases, thermal pressure dominates so much that degeneracy pressure can be ignored. Likewise, degenerate matter still has normal thermal pressure; the degeneracy pressure dominates to the point that temperature has a negligible effect on the total pressure. The adjacent figure shows the thermal pressure (red line) and total pressure (blue line) in a Fermi gas, with the difference between the two being the degeneracy pressure. As the temperature falls, the density and the degeneracy pressure increase, until the degeneracy pressure contributes most of the total pressure.
While degeneracy pressure usually dominates at extremely high densities, it is the ratio between degenerate pressure and thermal pressure which determines degeneracy. Given a sufficiently drastic increase in temperature (such as during a red giant star's helium flash), matter can become non-degenerate without reducing its density.
Degeneracy pressure contributes to the pressure of conventional solids, but these are not usually considered to be degenerate matter because a significant contribution to their pressure is provided by electrical repulsion of atomic nuclei and the screening of nuclei from each other by electrons. The free electron model of metals derives their physical properties by considering the conduction electrons alone as a degenerate gas, while the majority of the electrons are regarded as occupying bound quantum states. This solid state contrasts with degenerate matter that forms the body of a white dwarf, where most of the electrons would be treated as occupying free particle momentum states.
Exotic examples of degenerate matter include neutron degenerate matter, strange matter, metallic hydrogen and white dwarf matter. | 0 | Theoretical and Fundamental Chemistry |
Sugar alcohols, a class of low molecular weight polyols, are commonly obtained by hydrogenation of sugars. They have the formula (CHOH)H, where n = 4–6.
Sugar alcohols are added to foods because of their lower caloric content than sugars; however, they are also, in general, less sweet, and are often combined with high-intensity sweeteners. They are also added to chewing gum because they are not broken down by bacteria in the mouth or metabolized to acids, and thus do not contribute to tooth decay. Maltitol, sorbitol, xylitol, erythritol, and isomalt are common sugar alcohols. | 0 | Theoretical and Fundamental Chemistry |
Kirchhoff showed in 1858 that, in thermochemistry, the variation of the heat of a chemical reaction is given by the difference in heat capacity between products and reactants:
Integration of this equation permits the evaluation of the heat of reaction at one temperature from measurements at another temperature. | 1 | Applied and Interdisciplinary Chemistry |
The first to mention premelting might have been Michael Faraday in 1842 for ice surfaces. He compared the effect which holds a snowball together to that which makes buildings from moistured sand stable. Another interesting thing he mentioned is that two blocks of ice can freeze together. Later Tammann (1910) and Stranski (1942) suggested that all crystals might, due to the reduction of surface energy, start melting at their surfaces. Frenkel strengthened this by noting that, in contrast to liquids, no overheating can be found for solids. After extensive studies on many materials, it can be concluded that it is a common attribute of the solid state that the melting process begins at the surface. | 0 | Theoretical and Fundamental Chemistry |
The Science History Institutes magazine, Distillations, appeared in print three times a year until 2019, when content became digital-only. As an online resource, it continues to present stories about the history of science for a popular readership. Distillations first appeared in spring 2015, as a publication of the Chemical Heritage Foundation. It was predated by the Chemical Heritage Magazine', published as a quarterly by the Chemical Heritage Foundation. | 1 | Applied and Interdisciplinary Chemistry |
The main exposure to UFPs is through inhalation. Owing to their size, UFPs are considered to be respirable particles. Contrary to the behaviour of inhaled PM and PM, ultrafine particles are deposited in the lungs, where they have the ability to penetrate tissue and undergo interstitialization, or to be absorbed directly into the bloodstream—and therefore are not easily removed from the body and may have immediate effect. Exposure to UFPs, even if components are not very toxic, may cause oxidative stress, inflammatory mediator release, and could induce heart disease, lung disease, and other systemic effects.
The exact mechanism through which UFP exposure leads to health effects remains to be elucidated, but effects on Blood pressure may play a role. It has recently been reported that UFP is associated with an increase in blood pressure in schoolchildren with the smallest particles inducing the largest effect. According to research, infants whose mothers were exposed to higher levels of UFPs during pregnancy are much more likely to develop asthma.
There is a range of potential human exposures that include occupational, due to the direct manufacturing process or a byproduct from an industrial or office environment, as well as incidental, from contaminated outdoor air and other byproduct emissions. In order to quantify exposure and risk, both in vivo and in vitro studies of various UFP species are currently being done using a variety of animal models including mouse, rat, and fish. These studies aim to establish toxicological profiles necessary for risk assessment, risk management, and potential regulation and legislation.
Some sizes of UFPs may be filtered from the air using ULPA filters. | 0 | Theoretical and Fundamental Chemistry |
The orthoborate ion is known in the solid state, for example, in calcium orthoborate , where it adopts a nearly trigonal planar structure. It is a structural analogue of the carbonate anion , with which it is isoelectronic. Simple bonding theories point to the trigonal planar structure. In terms of valence bond theory, the bonds are formed by using sp hybrid orbitals on boron.
Some compounds termed orthoborates do not necessarily contain the trigonal planar ion. For example, gadolinium orthoborate contains the planar ion only a high temperatures; otherwise it contains the polyborate anion . | 0 | Theoretical and Fundamental Chemistry |
The Leray projection has the following properties:
# The Leray projection is a projection: for all .
# The Leray projection is a divergence-free operator: for all .
# The Leray projection is simply the identity for the divergence-free vector fields: for all such that .
# The Leray projection vanishes for the vector fields coming from a potential: for all . | 1 | Applied and Interdisciplinary Chemistry |
The MAPK/ERK pathway (also known as the Ras-Raf-MEK-ERK pathway) is a chain of proteins in the cell that communicates a signal from a receptor on the surface of the cell to the DNA in the nucleus of the cell.
The signal starts when a signaling molecule binds to the receptor on the cell surface and ends when the DNA in the nucleus expresses a protein and produces some change in the cell, such as cell division. The pathway includes many proteins, such as mitogen-activated protein kinases (MAPKs), originally called extracellular signal-regulated kinases (ERKs), which communicate by adding phosphate groups to a neighboring protein (phosphorylating it), thereby acting as an "on" or "off" switch.
When one of the proteins in the pathway is mutated, it can become stuck in the "on" or "off" position, a necessary step in the development of many cancers. In fact, components of the MAPK/ERK pathway were first discovered in cancer cells, and drugs that reverse the "on" or "off" switch are being investigated as cancer treatments. | 1 | Applied and Interdisciplinary Chemistry |
*Kurchatov Medal (1989)
*Lise Meitner Prize of the European Physical Society (2000)
*Lomonosov Gold Medal (2018) "for fundamental research in the fields of interaction of complex nuclei and experimental evidence of existence of an island of stability for superheavy elements"
*Demidov Prize (2019)
*UNESCO-Russia Mendeleev International Prize in the Basic Sciences (2021) | 1 | Applied and Interdisciplinary Chemistry |
Most biological oxidation processes for treating industrial wastewaters have in common the use of oxygen (or air) and microbial action. Surface-aerated basins achieve 80 to 90% removal of BOD with retention times of 1 to 10 days. The basins may range in depth from and utilize motor-driven aerators floating on the surface of the wastewater.
In an aerated basin system, the aerators provide two functions: they transfer air into the basins required by the biological oxidation reactions, and they provide the mixing required for dispersing the air and for contacting the reactants (that is, oxygen, wastewater and microbes). Typically, the floating surface aerators are rated to deliver the amount of air equivalent to 1.8 to 2.7 kilograms O/kWh (4.0 to 6.0 lb O/kWh). However, they do not provide as good mixing as is normally achieved in activated sludge systems and therefore aerated basins do not achieve the same performance level as activated sludge units.
Biological oxidation processes are sensitive to temperature and, between , the rate of biological reactions increase with temperature. Most surface aerated vessels operate at between . | 1 | Applied and Interdisciplinary Chemistry |
A good ion source should provide a strong ion beam without consuming much of the gas. For hydrogen isotopes, production of atomic ions is favored over molecular ions, as atomic ions have higher neutron yield on collision. The ions generated in the ion source are then extracted by an electric field into the accelerator region, and accelerated towards the target. The gas consumption is chiefly caused by the pressure difference between the ion generating and ion accelerating spaces that has to be maintained. Ion currents of 10 mA at gas consumptions of 40 cm/hour are achievable.
For a sealed neutron tube, the ideal ion source should use low gas pressure, give high ion current with large proportion of atomic ions, have low gas clean-up, use low power, have high reliability and high lifetime, its construction has to be simple and robust and its maintenance requirements have to be low.
Gas can be efficiently stored in a replenisher, an electrically heated coil of zirconium wire. Its temperature determines the rate of absorption/desorption of hydrogen by the metal, which regulates the pressure in the enclosure. | 0 | Theoretical and Fundamental Chemistry |
The reactions involving charged transition metal complexes (cationic or anionic) are dramatically influenced by solvation, especially in the polar media. As high as 30-50 kcal/mol changes in the potential energy surface (activation energies and relative stability) were calculated if the charge of the metal species was changed during the chemical transformation. | 0 | Theoretical and Fundamental Chemistry |
Landau and Levich split the entire flow regime into two regimes, a lower regime and an upper regime. In the lower regime closer to the liquid surface, the flow is assumed to be static, leading to the problem of the Young–Laplace equation (a static meniscus). In the upper region far away from the liquid surface, the thickness of the liquid layer attaching to the plate is very small and also the since the velocity of the plate is small, this regime comes under the approximation of lubrication theory. The solution of these two problems are then matched using method of matched asymptotic expansions. | 1 | Applied and Interdisciplinary Chemistry |
*Mobile Phone Based Remote Monitoring and Control system For Individualized Healthcare. First AMA-IEEE Medical Technology on Individualized Healthcare, Washington DC, US.2010
*Connected Healthcare Solution Using Cell phone. ASME's 5th Frontiers in Biomedical Devices Conference & Exhibition, California, US.2010
*Automated Wireless System for Individuals Requiring Continuous Remote Care 6th World Congress on Biomechanics, in conjunction with 14th International Conference on Biomedical Engineering (ICBME), Singapore .2010
*Ankabut Users Meeting January 2012. | 0 | Theoretical and Fundamental Chemistry |
In the European Union (EU), the European Medicines Agency (EMA) defines a drug as "orphan" if it is intended for the diagnosis, prevention or treatment of a life-threatening or chronically and seriously debilitating condition affecting not more than 5 in 10,000 EU people. EMA also qualifies a drug as orphan if – without incentives – it would be unlikely that marketing the drug in the EU would generate sufficient benefit for the affected people and for the drug manufacturer to justify the investment. | 1 | Applied and Interdisciplinary Chemistry |
Historically, the three main divisions of radiation therapy are:
* external beam radiation therapy (EBRT or XRT) or teletherapy;
* brachytherapy or sealed source radiation therapy; and
* systemic radioisotope therapy or unsealed source radiotherapy.
The differences relate to the position of the radiation source; external is outside the body, brachytherapy uses sealed radioactive sources placed precisely in the area under treatment, and systemic radioisotopes are given by infusion or oral ingestion. Brachytherapy can use temporary or permanent placement of radioactive sources. The temporary sources are usually placed by a technique called afterloading. In afterloading a hollow tube or applicator is placed surgically in the organ to be treated, and the sources are loaded into the applicator after the applicator is implanted. This minimizes radiation exposure to health care personnel.
Particle therapy is a special case of external beam radiation therapy where the particles are protons or heavier ions.
A review of radiation therapy randomised clinical trials from 2018 to 2021 found many practice-changing data and new concepts that emerge from RCTs, identifying techniques that improve the therapeutic ratio, techniques that lead to more tailored treatments, stressing the importance of patient satisfaction, and identifying areas that require further study. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, the carbon number of a compound is the number of carbon atoms in each molecule.
The properties of hydrocarbons can be correlated with the carbon number, although the carbon number alone does not give an indication of the saturation of the organic compound. When describing a particular molecule, the "carbon number" is also the ordinal position of a particular carbon atom in a chain. | 0 | Theoretical and Fundamental Chemistry |
The rearrangements of heavy-chains are different from the light chains because DNA undergoes rearrangements of V-D-J gene segments in the heavy chains. These reorganizations of gene segments produce gene sequence from 5 prime to 3 prime ends such as a short leader exon, an intron, a joined VDJ segment, a second intron and several gene segments. The final product of the rearrangement is transcribed when RNA polymerase | 1 | Applied and Interdisciplinary Chemistry |
Vilma Espín Guillois was born on 7 April 1930, in Santiago de Cuba. She was the daughter of a wealthy Cuban lawyer, Jose Espín and wife Margarita Guillois. She had four siblings, Nilsa, Iván, Sonia and José. Espín attended Academia Pérez-Peña for primary school and studied ballet and singing at the Asociación Pro-Arte Cubano during the 1940s. In the 1950s, she studied chemical engineering at Universidad de Oriente, Santiago de Cuba (one of the first women in Cuba to study this subject). While attending Universidad de Oriente, Santiago de Cuba, she played volleyball, tennis, and was a soprano in the University Choir. In university, Espin met her mentor Frank Pais in a university group called Oriente Revolutionary Action (ARO), which was responsible for the assault on the Moncada barracks. After graduating, her father encouraged her to attend MIT in Cambridge, Massachusetts to complete her post-graduate studies in the hopes that visiting America would dissuade her from becoming involved in socialist activity. When she finally acquiesced, her brief academic career at MIT left her with even more animosity toward the United States, as she officially joined the 26th of July Movement on her way back to Cuba through Mexico. Espin only completed one semester at MIT. | 1 | Applied and Interdisciplinary Chemistry |
Barium chlorate is used to produce chloric acid, the formal precursor to all chlorate salts, through its reaction with dilute sulfuric acid, which results in a solution of chloric acid and insoluble barium sulfate precipitate:
:Ba(ClO) + HSO → 2 HClO + BaSO
Both the chlorate and the acid should be prepared as dilute solutions before mixing, such that the chloric acid produced is dilute, as concentrated solutions of chloric acid (above 30%) are unstable and prone to decompose, sometimes explosively. | 0 | Theoretical and Fundamental Chemistry |
Several estimations of the reaeration rate exist, which generally follow the equation
where
* is a constant.
* is the flow velocity [m/s].
* is the depth [m].
* is a constant.
* is a constant.
The constants depend on the system to which the equation is applied, i.e. the flow velocity and the size of the stream or river. Different values are available in the literature.
The software "International Hydrological Programme" applies the following equation derived on the basis of values used in published literature
where
* is the average flow velocity [m/s].
* is the average depth of flow in the river [m]. | 1 | Applied and Interdisciplinary Chemistry |
PT clearly plays a central role in the pathogenesis of pertussis although this was discovered only in the early 1980s. The appearance of pertussis is quite recent, compared with other epidemic infectious diseases. The earliest mention of pertussis, or whooping cough, is of an outbreak in Paris in 1414. This was published in Moultons The Mirror of Health, in 1640. Another epidemic of pertussis took place in Paris in 1578 and was described by a contemporary observer, Guillaume de Baillou. Pertussis was well known throughout Europe by the middle of the 18th century. Jules Bordet and Octave Gengou described in 1900 the finding of a new “ovoid bacillus” in the sputum of a 6-month-old infant with whooping cough. They were also the first to cultivate Bordetella pertussis' at the Pasteur Institute in Brussels in 1906.
One difference between the different species of Bordetella is that B. pertussis produces PT and the other species do not. Bordetella parapertussis shows the most similarity to B. pertussis and was therefore used for research determining the role of PT in causing the typical symptoms of whooping cough. Rat studies showed the development of paroxysmal coughing, a characteristic for whooping cough, occurred in rats infected with B. pertussis. Rats infected with B. parapertussis or a PT-deficient mutant of B. pertussis did not show this symptom; neither of these two strains produced PT. | 1 | Applied and Interdisciplinary Chemistry |
The worm-like chain model (WLC) takes the energy required to bend a molecule into account. The variables are the same except that , the persistence length, replaces . Then, the force follows this equation:
Therefore, when there is no distance between chain ends (r=0), the force required to do so is zero, and to fully extend the polymer chain (), an infinite force is required, which is intuitive. Graphically, the force begins at the origin and initially increases linearly with . The force then plateaus but eventually increases again and approaches infinity as the chain length approaches . | 0 | Theoretical and Fundamental Chemistry |
An alternative model has been developed by S. Gronert based not on breaking molecules into fragments but based on 1,2 and 1,3 interactions
The Gronert equation reads:
The pentanes are now calculated as:
* n-pentane = 4CC + 12CH + 9HCH + 18HCC + 3CCC + (5C + 12H) = - 35.1 kcal/mol
* isopentane = 4CC + 12CH + 10HCH + 16HCC + 4CCC + (5C + 12H) = - 36.7 kcal/mol
* neopentane = 4CC + 12CH + 12HCH + 12HCC + 6CCC + (5C + 12H) = -40.1 kcal/mol
Key in this treatment is the introduction of 1,3-repulsive and destabilizing interactions and this type of steric hindrance should exist considering the molecular geometry of simple alkanes. In methane the distance between the hydrogen atoms is 1.8 angstrom but the combined van der Waals radii of hydrogen are 2.4 angstrom implying steric hindrance. Also in propane the methyl to methyl distance is 2.5 angstrom whereas the combined van der Waals radii are much larger (4 angstrom).
In the Gronert model these repulsive 1,3 interactions account for trends in bond dissociation energies which for example decrease going from methane to ethane to isopropane to neopentane. In this model the homolysis of a C-H bond releases strain energy in the alkane. In traditional bonding models the driving force is the ability of alkyl groups to donate electrons to the newly formed free radical carbon. | 0 | Theoretical and Fundamental Chemistry |
Anhydrous zinc chloride or its hydrates is not known in nature. However, the related zinc chloride hydroxide monohydrate is known as simonkolleite in nature. | 0 | Theoretical and Fundamental Chemistry |
In case the body moves as well, with velocity , the Morison equation becomes:
where the total force contributions are:
* a: Froude–Krylov force,
* b: hydrodynamic mass force,
* c: drag force.
Note that the added mass coefficient is related to the inertia coefficient as . | 1 | Applied and Interdisciplinary Chemistry |
For humans, porcine endogenous retroviruses (PERVs) pose a concern when using porcine tissues and organs in xenotransplantion, the transplanting of living cells, tissues, and organs from an organism of one species to an organism of different species. Although pigs are generally the most suitable donors to treat human organ diseases due to practical, financial, safety, and ethical reasons, PERVs previously could not be removed from pigs, due to their viral ability to integrate into the host genome and to be passed into offspring, until the year 2017, when one lab, using CRISPR-Cas9, removed all 62 retroviruses from the pig genome. The consequences of cross-species transmission remain unexplored and have dangerous potential.
Researchers have indicated that infection of human tissues by PERVs is very possible, especially in immunosuppressed individuals. An immunosuppressed condition could potentially permit a more rapid and tenacious replication of viral DNA, and would later have less difficulty adapting to human-to-human transmission. Although known infectious pathogens present in the donor organ/tissue can be eliminated by breeding pathogen-free herds, unknown retroviruses can be present in the donor. These retroviruses are often latent and asymptomatic in the donor, but can become active in the recipient. Some examples of endogenous viruses that can infect and multiply in human cells are from baboons (BaEV), cats (RD114), and mice.
There are three different classes of PERVs, PERV-A, PERV-B, and PERV-C. PERV-A and PERV-B are polytropic and can infect human cells in vitro, while PERV-C is ecotropic and does not replicate on human cells. The major differences between the classes is in the receptor binding domain of the env protein and the long terminal repeats (LTRs) that influence the replication of each class. PERV-A and PERV-B display LTRs that have repeats in the U3 region. However, PERV-A and PERV-C show repeatless LTRs. Researchers found that PERVs in culture actively adapted to the repeat structure of their LTR in order to match the best replication performance a host cell could perform. At the end of their study, researchers concluded that repeatless PERV LTR evolved from the repeat-harboring LTR. This was likely to have occurred from insertional mutation and was proven through use of data on LTR and env/Env. It is thought that the generation of repeatless LTRs could be reflective of an adaptation process of the virus, changing from an exogenous to an endogenous lifestyle.
A clinical trial study performed in 1999 sampled 160 patients who were treated with different living pig tissues and observed no evidence of a persistent PERV infection in 97% of the patients for whom a sufficient amount of DNA was available to PCR for amplification of PERV sequences. This study stated that retrospective studies are limited to find the true incidence of infection or associated clinical symptoms, however. It suggested using closely monitored prospective trials, which would provide a more complete and detailed evaluation of the possible cross-species PERV transmission and a comparison of the PERV. | 1 | Applied and Interdisciplinary Chemistry |
Another aspect is the similarity of arsenic effects to the heat shock response. Short-term arsenic exposure has effects on signal transduction inducing heat shock proteins with masses of 27, 60, 70, 72, 90, and 110 kDa as well as metallothionein, ubiquitin, mitogen-activated [MAP] kinases, extracellular regulated kinase [ERK], c-jun terminal kinases [JNK] and p38.
Via JNK and p38 it activates c-fos, c-jun and egr-1 which are usually activated by growth factors and cytokines. The effects are largely dependent on the dosing regime and may be as well inversed.
As shown by some experiments reviewed by Del Razo (2001), reactive oxygen species induced by low levels of inorganic arsenic increase the transcription and the activity of the activator protein 1 (AP-1) and the nuclear factor-κB (NF-κB) (maybe enhanced by elevated MAPK levels), which results in c-fos/c-jun activation, over-secretion of pro-inflammatory and growth promoting cytokines stimulating cell proliferation. Germolec et al. (1996) found an increased cytokine expression and cell proliferation in skin biopsies from individuals chronically exposed to arsenic-contaminated drinking water.
Increased AP-1 and NF-κB obviously also result in an up-regulation of mdm2 protein, which decreases p53 protein levels. Thus, taking into account p53's function, a lack of it could cause a faster accumulation of mutations contributing to carcinogenesis. However, high levels of inorganic arsenic inhibit NF-κB activation and cell proliferation. An experiment of Hu et al. (2002) demonstrated increased binding activity of AP-1 and NF-κB after acute (24 h) exposure to +3 sodium arsenite, whereas long-term exposure (10–12 weeks) yielded the opposite result. The authors conclude that the former may be interpreted as a defense response while the latter could lead to carcinogenesis. As the contradicting findings and connected mechanistic hypotheses indicate, there is a difference in acute and chronic effects of arsenic on signal transduction which is not clearly understood yet. | 1 | Applied and Interdisciplinary Chemistry |
Agmatine has been shown to enhance glomerular filtration rate (GFR) and to exert nephroprotective effects. | 1 | Applied and Interdisciplinary Chemistry |
The Wyckoff positions are named after Ralph Walter Graystone Wyckoff, an American X-ray crystallographer who authored several books in the field. His 1922 book, The Analytical Expression of the Results of the Theory of Space Groups, contained tables with the positional coordinates, both general and special, permitted by the symmetry elements. This book was the forerunner of International Tables for X-ray Crystallography, which first appeared in 1935. | 0 | Theoretical and Fundamental Chemistry |
A scaffold or matrix serves as a temporary supporting structure (extracellular matrix), the initial architecture, on which the cells can grow three-dimensionally into the desired tissue. A scaffold must provide the environment needed for cellular growth and differentiation; it must provide the strength to withstand mechanical stress and guide their growth. Moreover, scaffolds should be biodegradable and degrade at the same rate as the tissue regenerates to be optimally replaced by the host tissue. There are numerous scaffolds to choose from and when choosing a scaffold biocompatibility, porosity and stability should also be held into account. Available scaffolds for oral mucosa tissue engineering are: | 1 | Applied and Interdisciplinary Chemistry |
A flow tracer is any fluid property used to track the flow velocity (i.e., flow magnitude and direction) and circulation patterns. Tracers can be chemical properties, such as radioactive material, or chemical compounds, physical properties, such as density, temperature, salinity, or dyes, and can be natural or artificially induced. Flow tracers are used in many fields, such as physics, hydrology, limnology, oceanography, environmental studies and atmospheric studies.
Conservative tracers remain constant following fluid parcels, whereas reactive tracers (such as compounds undergoing a mutual chemical reaction) grow or decay with time. Active tracers dynamically alter the flow of the fluid by changing fluid properties which appear in the equation of motion such as density or viscosity, while passive tracers have no influence on flow. | 1 | Applied and Interdisciplinary Chemistry |
When pullulan is modified with a hydrophobic functionality, such as cholesterol, the pullulan derivative forms self-assembled vesicles that can encapsulate a hydrophobic drug. With the hydrophobic functional group, the pullulan derivative is an amphiphilic molecule, which when in an aqueous environment forms a micelle. This micelle has a hydrophilic exterior with the pullulan backbone and a hydrophobic core due to the functional group added to the pullulan. The nanoparticles formed are spherical, have an average size of 20-30 nanometers according to dynamic light scattering measurements, and are able to be maintained in physiological conditions. Cholesteryl-pullulan (CHP) is an example of a pullulan derivative that is capable of forming self-assembled mechanisms and has been used to anticancer drugs. The size of the self-assembled nanoparticle can be adjusted by changing the amount of cholesterol attached to the pullulan. The higher the number of cholesterol substitutions, the smaller the nanoparticle created. PA and folated PA (FPA) have been created and form self-assembled nanoparticles, which have been used to deliver epirubicin. Pullulan derivatives have been combined with gold to form self-assembled nanoparticles that were capable of loading doxorubicin. Pullulan-dexamethasone bioconjugates have been created which also exhibit self-assembling nanoparticles that have an approximate size of 400 nanometers and have shown to extend the release of the dexamethasone. | 1 | Applied and Interdisciplinary Chemistry |
These are directly measurable physical quantities in which no allowance has been made for biological effects. Radiation fluence is the number of radiation particles impinging per unit area per unit time, kerma is the ionising effect on air of gamma rays and X-rays and is used for instrument calibration, and absorbed dose is the amount of radiation energy deposited per unit mass in the matter or tissue under consideration. | 0 | Theoretical and Fundamental Chemistry |
In genetics, DNase I hypersensitive sites (DHSs) are regions of chromatin that are sensitive to cleavage by the DNase I enzyme. In these specific regions of the genome, chromatin has lost its condensed structure, exposing the DNA and making it accessible. This raises the availability of DNA to degradation by enzymes, such as DNase I. These accessible chromatin zones are functionally related to transcriptional activity, since this remodeled state is necessary for the binding of proteins such as transcription factors.
Since the discovery of DHSs 30 years ago, they have been used as markers of regulatory DNA regions. These regions have been shown to map many types of cis-regulatory elements including promoters, enhancers, insulators, silencers and locus control regions. A high-throughput measure of these regions is available through DNase-Seq. | 1 | Applied and Interdisciplinary Chemistry |
In course of his research and scholastic endeavors, Achinewhu has visited many universities and has received a number of international as well as local awards. | 1 | Applied and Interdisciplinary Chemistry |
Organocatalysis refers to a form of catalysis, where the rate of a chemical reaction is increased by an organic compound consisting of carbon, hydrogen, sulfur and other non-metal elements.
When the organocatalyst is chiral, then enantioselective synthesis can be achieved;
for example a number of carbon–carbon bond forming reactions become enantioselective in the presence of proline with the aldol reaction being a prime example.
Organocatalysis often employs natural compounds and secondary amines as chiral catalysts; these are inexpensive and environmentally friendly, as no metals are involved. | 0 | Theoretical and Fundamental Chemistry |
In 2009, Gaunts group reported a copper catalyzed meta-selective C–H arylation reaction on anilide derivatives. Despite the intrinsic ortho-/para- selectivity of the amido group, the arylation occurs exclusively on the meta position on a variety of anilide substrates. Remarkably, the regioselectivity is totally different from the earlier reported Pd catalyzed C-H functionalizations, where the amido group serve as a powerful ortho-directing group. The method is robust under mild reaction conditions. It is compatible with a spectrum of substituted anilide as well as different bisaryliodonium salts. However, the meta-selectivity is lost when highly ortho/para-directing methoxy group substitutes one of the meta'-hydrogen of the anilide, which marks the limitation of this method. Despite the limitation, the paper was of high impact. It has been highlighted in a number of journals and news and was voted as one of the top 12 papers of 2009 by Chemical and Engineering News.
In a more recent report from the same group, α-arylcarbonyl compounds were found to be good substrates for the copper catalyzed meta-selective C-H arylation. The power of the meta-selectivity overrides the electronic effect of different substituents, including the strong ortho/para-directing m-methoxy group.
Although the copper catalyzed meta-selective C–H arylation is quite successful, the mechanism behind the meta-selectivity is not completely understood. There are generally two proposed mechanisms both involving a Cu(I)/Cu(III) catalyst cycle.
In Gaunts original paper, he proposed a mechanism involving an anti-oxy-cupration step as the key to the meta-selectivity. First, the Cu(II) salt generates the active Cu(I) species through either disproportionation or reduction by nucleophile. The active Cu(I) species undergoes oxidative addition with diphenyliodonium salt to generate a highly electrophilic Cu(III) species. While the Cu(III) species activates the aromatic ring, the amide oxygen attacks the ortho position, breaking the aromaticity and allowing cupration at the meta position. The intermediate then rearomatizes with base and undergoes reductive elimination to afford the meta'-arylated product and regenerate the active Cu(I) catalyst.
Alternatively, Li and Wu, based on DFT calculations, proposed a mechanism involving a "Heck-like four-membered-ring transition state". The amide oxygen first coordinates to the Cu(III) species generated from oxidative addition of Cu(I) triflate and diphenyliodonium triflate. Then, the phenyl group bonded to copper interacts with the aromatic ring at the meta-position, forming a four-membered-ring transition state. According to their calculations, the aromaticity is not completely lost during the transformation. In the last step, the Cu(III)-C bond breaks to regenerate the Cu(I) catalyst while the triflate ion abstract the meta-hydrogen to recover the aromaticity and gives the product. | 0 | Theoretical and Fundamental Chemistry |
Di(2-ethylhexyl)phosphoric acid (DEHPA or HDEHP) is an organophosphorus compound with the formula (CHO)POH. The colorless liquid is a diester of phosphoric acid and 2-ethylhexanol. It is used in the solvent extraction of uranium, vanadium and the rare-earth metals. | 0 | Theoretical and Fundamental Chemistry |
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. This process differs from absorption, in which a fluid (the absorbate) is dissolved by or permeates a liquid or solid (the absorbent). While adsorption does often precede absorption, which involves the transfer of the absorbate into the volume of the absorbent material, alternatively, adsorption is distinctly a surface phenomenon, wherein the adsorbate does not penetrate through the material surface and into the bulk of the adsorbent. The term sorption encompasses both adsorption and absorption, and desorption is the reverse of sorption.
Like surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent or metallic) of the constituent atoms of the material are fulfilled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates. The exact nature of the bonding depends on the details of the species involved, but the adsorption process is generally classified as physisorption (characteristic of weak van der Waals forces) or chemisorption (characteristic of covalent bonding). It may also occur due to electrostatic attraction. The nature of the adsorption can affect the structure of the adsorbed species. For example, polymer physisorption from solution can result in squashed structures on a surface.
Adsorption is present in many natural, physical, biological and chemical systems and is widely used in industrial applications such as heterogeneous catalysts, activated charcoal, capturing and using waste heat to provide cold water for air conditioning and other process requirements (adsorption chillers), synthetic resins, increasing storage capacity of carbide-derived carbons and water purification. Adsorption, ion exchange and chromatography are sorption processes in which certain adsorbates are selectively transferred from the fluid phase to the surface of insoluble, rigid particles suspended in a vessel or packed in a column. Pharmaceutical industry applications, which use adsorption as a means to prolong neurological exposure to specific drugs or parts thereof, are lesser known.
The word "adsorption" was coined in 1881 by German physicist Heinrich Kayser (1853–1940). | 0 | Theoretical and Fundamental Chemistry |
Degeneracy is the redundancy of the genetic code. This term was given by Bernfield and Nirenberg. The genetic code has redundancy but no ambiguity (see the codon tables below for the full correlation). For example, although codons GAA and GAG both specify glutamic acid (redundancy), neither specifies another amino acid (no ambiguity). The codons encoding one amino acid may differ in any of their three positions. For example, the amino acid leucine is specified by YUR or CUN (UUA, UUG, CUU, CUC, CUA, or CUG) codons (difference in the first or third position indicated using IUPAC notation), while the amino acid serine is specified by UCN or AGY (UCA, UCG, UCC, UCU, AGU, or AGC) codons (difference in the first, second, or third position). A practical consequence of redundancy is that errors in the third position of the triplet codon cause only a silent mutation or an error that would not affect the protein because the hydrophilicity or hydrophobicity is maintained by equivalent substitution of amino acids; for example, a codon of NUN (where N = any nucleotide) tends to code for hydrophobic amino acids. NCN yields amino acid residues that are small in size and moderate in hydropathicity; NAN encodes average size hydrophilic residues. The genetic code is so well-structured for hydropathicity that a mathematical analysis (Singular Value Decomposition) of 12 variables (4 nucleotides x 3 positions) yields a remarkable correlation (C = 0.95) for predicting the hydropathicity of the encoded amino acid directly from the triplet nucleotide sequence, without translation. Note in the table, below, eight amino acids are not affected at all by mutations at the third position of the codon, whereas in the figure above, a mutation at the second position is likely to cause a radical change in the physicochemical properties of the encoded amino acid.
Nevertheless, changes in the first position of the codons are more important than changes in the second position on a global scale. The reason may be that charge reversal (from a positive to a negative charge or vice versa) can only occur upon mutations in the first position of certain codons, but not upon changes in the second position of any codon. Such charge reversal may have dramatic consequences for the structure or function of a protein. This aspect may have been largely underestimated by previous studies. | 1 | Applied and Interdisciplinary Chemistry |
Wittig's contributions also include the preparation of phenyllithium and the discovery of the 1,2-Wittig rearrangement and the 2,3-Wittig rearrangement.
Wittig was well known in the chemistry community for being a consummate experimenter and observer of chemical transformations, while caring very little for the theoretical and mechanistic underpinnings of the work he produced.
Georg also has his name on a literature work titled on a compound labelled Colopidalol. | 0 | Theoretical and Fundamental Chemistry |
* CRC atlas of spectral data and physical constants for organic compounds, Volume 3 (1975)
* Infrared and Raman Spectroscopy, Part 1 (1976)
* Chemical applications of Raman spectroscopy (1981)
* The Analytical approach (1983)
* 1985 International Conference on Fourier and Computerized Infrared Spectroscopy (1985)
* Handbook of data on organic compounds, Volume 11 (1992) | 0 | Theoretical and Fundamental Chemistry |
The practice of tin mining likely began circa 3000 B.C. in Western Asia, British Isles and Europe. Tin was an essential ingredient of bronze production during the Bronze Age.
The practice of tinning ironware to protect it against rust is an ancient one. This may have been the work of the whitesmith. This was done after the article was fabricated, whereas tinplate was tinned before fabrication. Tinplate was apparently produced in the 1620s at a mill of (or under the patronage of) the Earl of Southampton, but it is not clear how long this continued.
The first production of tinplate was probably in Bohemia, from where the trade spread to Saxony, and was well-established there by the 1660s. Andrew Yarranton and Ambrose Crowley (a Stourbridge blacksmith and father of the more famous Sir Ambrose) visited Dresden in 1667 and learned how it was made. In doing so, they were sponsored by various local ironmasters and people connected with the project to make the river Stour navigable. In Saxony, the plates were forged, but when they conducted experiments on their return to England, they tried rolling the iron. This led to the ironmasters Philip Foley and Joshua Newborough (two of the sponsors) in 1670 erecting a new mill, Wolverley Lower Mill (or forge) in Worcestershire. This contained three shops, one being a slitting mill (which would serve as a rolling mill), and the others were forges. In 1678 one of these was making frying pans and the other drawing out blooms made in finery forges elsewhere. It is likely that the intention was to roll the plates and then finish them under a hammer, but the plan was frustrated by William Chamberlaine renewing a patent granted to him and Dud Dudley in 1662.
The slitter at Wolverley was Thomas Cooke. Another Thomas Cooke, perhaps his son, moved to Pontypool and worked there for John Hanbury. He had a slitting mill there and was also producing iron plates called Pontpoole plates. Edward Lhuyd reported the existence of this mill in 1697. This has been claimed as a tinplate works, but it was almost certainly only producing (untinned) blackplate.
Tinplate first begins to appear in the Gloucester Port Books (which record trade passing through Gloucester), mostly from ports in the Bristol Channel in 1725. The tinplate was shipped from Newport, Monmouthshire. This immediately follows the first appearance (in French) of Reamurs Principes de lart de fer-blanc, and prior to a report of it being published in England.
Further mills followed a few years later, initially in many iron-making regions in England and Wales, but later mainly in south Wales, most notably the Melingriffith Tin Plate Works, Whitchurch, Cardiff, which was founded some time before 1750. In 1805, 80,000 boxes were made and 50,000 exported. The industry continued to grow until 1891. One of the greatest markets was the United States, but that market was cut off in 1891 when the McKinley tariff was enacted. This caused a great retrenchment in the British industry and the emigration to America of many of those were no longer employed in the surviving tinplate works.
Despite this blow, the industry continued, but on a smaller scale. There were 518 mills in operation in 1937, including 224 belonging to Richard Thomas & Co. The traditional pack mill had been overtaken by the improved strip mill, of which the first in Great Britain was built by Richard Thomas & Co. in the late 1930s. Strip mills rendered the old pack mills obsolete and the last of them closed circa the 1960s. | 1 | Applied and Interdisciplinary Chemistry |
Integration was the watchword as the various processes were brought together by large corporations, from mining the iron ore to shipping the finished product to wholesalers. The typical steelworks was a giant operation, including blast furnaces, Bessemer converters, open-hearth furnaces, rolling mills, coke ovens and foundries, as well as supported transportation facilities. The largest ones were operated in the region from Chicago to St. Louis to Baltimore, Philadelphia and Buffalo. Smaller operations appeared in Birmingham, Alabama, and in California.
The industry grew slowly but other industries grew even faster, so that by 1967, as the downward spiral began, steel accounted for 4.4% of manufacturing employment and 4.9% of manufacturing output. After 1970 American steel producers could no longer compete effectively with low-wage producers elsewhere. Imports and local mini-mills undercut sales.
Per-capita steel consumption in the U.S. peaked in 1977, then fell by half before staging a modest recovery to levels well below the peak.
Most mills were closed. Bethlehem went bankrupt in 2001. In 1984, Republic merged with Jones and Laughlin Steel Company; the new firm went bankrupt in 2001. US Steel diversified into oil (Marathon Oil was spun off in 2001). Finally US Steel reemerged in 2002 with plants in three American locations (plus one in Europe) that employed fewer than one-tenth the 168,000 workers of 1902. By 2001 steel accounted for only 0.8% of manufacturing employment and 0.8% of manufacturing output.
The world steel industry peaked in 2007. That year, ThyssenKrupp spent $12 billion to build the two most modern mills in the world, in Alabama and Brazil. The worldwide great recession starting in 2008, however, with its heavy cutbacks in construction, sharply lowered demand and prices fell 40%. ThyssenKrupp lost $11 billion on its two new plants, which sold steel below the cost of production. Finally in 2013, ThyssenKrupp offered the plants for sale at under $4 billion. | 1 | Applied and Interdisciplinary Chemistry |
In crystallography, interstitial sites, holes or voids are the empty space that exists between the packing of atoms (spheres) in the crystal structure.
The holes are easy to see if you try to pack circles together; no matter how close you get them or how you arrange them, you will have empty space in between. The same is true in a unit cell; no matter how the atoms are arranged, there will be interstitial sites present between the atoms. These sites or holes can be filled with other atoms (interstitial defect). The picture with packed circles is only a 2D representation. In a crystal lattice, the atoms (spheres) would be packed in a 3D arrangement. This results in different shaped interstitial sites depending on the arrangement of the atoms in the lattice. | 0 | Theoretical and Fundamental Chemistry |
ζ-Carotene (zeta-carotene) is a carotenoid. It is different from α-carotene and β-carotene because it is acyclic. ζ-Carotene is similar in structure to lycopene, but has an additional 4 hydrogen atoms. ζ-carotene can be used as an intermediate in forming β-carotene. A dehydrogenation reaction converts ζ-carotene into lycopene, which then can be transformed into β-carotene through the action of lycopene beta-cyclase. ζ-Carotene is a natural product found in Lonicera japonica and Rhodospirillum rubrum. | 1 | Applied and Interdisciplinary Chemistry |
Although engineered and modified in a laboratory setting, ELPs share structural characteristics with intrinsically disordered proteins (IDPs) naturally found in the body, such as tropoelastin, from which ELPs were given their name. The repeat sequences found in the biopolymer give each ELP a distinct structure, as well as influence the lower critical solution temperature (LCST), also referred to commonly as the T. It is at this temperature that the ELPs move from a linear, relatively disordered state to a more densely aggregated, partially ordered state Although given as a single temperature, T the ELP phase change process generally begins and ends within a temperature range of approximately 2 °C. Also, T is altered by the addition of unique proteins to the free ELPs. | 0 | Theoretical and Fundamental Chemistry |
Epothilone D, with the generic drug name utidelone, was approved in China in 2021 for the treatment of metastatic breast cancer. Utidelone has shown benefits in a phase III breast cancer trial when added to capecitabine.
One synthetic analog, ixabepilone, was approved in October 2007 by the United States Food and Drug Administration for use in the treatment of aggressive metastatic or locally advanced breast cancer that no longer responds to currently available chemotherapies. In November 2008, the EMEA refused a marketing authorization for ixabepilone.
Epothilone B, with the generic drug name patupilone, was proven to contain potent in vivo anticancer activities at tolerated dose levels in several human xenograft models. As a result, patupilone and various analogs underwent various clinical phases.
Patupilone and the fully synthetic sagopilone were tested in phase II trials and BMS-310705 was tested in phase I trials). Patupilone failed a phase III trial for ovarian cancer in 2010.
Results of a phase III trial with ixabepilone (BMS-247550) in combination with capecitabine in metastatic breast cancer have been announced (2007 – leading to FDA approval). | 0 | Theoretical and Fundamental Chemistry |
Triethyloxonium tetrafluoroborate is a very strong alkylating agent, although the hazards are diminished because it is non-volatile. It releases strong acid upon contact with water. The properties of the methyl derivative are similar. | 0 | Theoretical and Fundamental Chemistry |
Scientists at the CSIRO conducted small-scale test work on copper sulfide concentrate in 1979, using the CSIRO's 50 kg Sirosmelt test rig. These trials included producing copper matte containing 40–52% copper and, in some cases, converting the matte to produce blister copper.
The results of this work were sufficiently encouraging that MIM in 1983 undertook its own copper smelting test work program using its 120 kg/h test rig, which had by then been rerated to 250 kg/h. It was found that the process was easy to control and that copper loss to slag was low. It was also learned that the process could easily recover copper from copper converter slag concentrate, of which there was a large stockpile at Mount Isa. | 1 | Applied and Interdisciplinary Chemistry |
Neopeltolide was originally isolated from sponges near the Jamaican coast and exhibits nanomolar cytoxic activity against several lines of cancer cells. The synthesis of the neopeltolide macrocyclic core displays a hydrogenation controlled by the ground state conformation of the macrocycle. | 0 | Theoretical and Fundamental Chemistry |
The meteorite fell to Earth after the retreat of glaciers from the area. All fragments recovered were found at the surface, partly buried, some on unstable terrain. The largest fragment was recovered in an area where the landscape consists of "flowing" gravel or clay-like sediments on permafrost, indicating that it had been in place for no more than a few thousand years. Other estimates have put the date of the fall as 10,000 years ago.
The iron masses were known to Inuit as Saviksoah (Great Iron, later renamed Ahnighito by Robert Edwin Peary) weighing ; the Woman, weighing ; and the Dog, weighing . For centuries, Inuit living near the meteorites used them as a source of metal for tools and harpoons. The Inuit would work the metal using cold forging—that is, by hammering the metal with stones. Excavations of a Norse farm in 1976 located an arrowhead made of iron from the meteorite, dating from the 11th to 14th century AD; its presence is evidence of Norse journeys to northern Greenland. Other pieces of Cape York meteoritic iron dating prior to 1450 (i.e. before the Little Ice Age) have been found throughout the Arctic Archipelago and on the North American mainland, and are evidence of an extensive Thule culture trade network which supplied iron to First Nations peoples prior to European contact.
In 1818, the British First Ross Expedition (led by Captain John Ross) made contact with Inuit on the northern shore of Melville Bay, who stated they had settled in the area to exploit a nearby source of iron. The Inuit described the location of this iron, but poor weather and sea ice prevented Ross from investigating further. Ross correctly surmised that the large iron rocks described by the Inuit were meteorites, and purchased several tools with blades made of the meteoritic iron.
Between 1818 and 1883, five further expeditions to the area were mounted by Britain, Sweden, and Denmark, which all failed to find the source of the iron. Only in 1894 did a Western explorer reach the meteorite: Robert E. Peary, of the US Navy. Peary enlisted the help of a local Inuit guide, who brought him to Saviksoah Island, just off northern Greenlands Cape York. Peary dedicated three years to planning and executing the removal of the meteorite, a process which required the building of a short railroad. Peary sold the pieces for $40,000 (equivalent to $ in ) to the American Museum of Natural History in New York City, where they are still on display. The piece named Ahnighito is on display in the Arthur Ross Hall of the American Museum of Natural History. Ahnighito' is the second-heaviest meteorite to have been relocated. It is so heavy that it was necessary to build its display stand so that the supports reached directly to the bedrock below the museum.
Peary has received significant criticism for his removal of the meteorite and treatment of the Inuit (including Minik Wallace). During his expedition to retrieve the meteorite, Peary convinced six Inughuit Greenlandic Inuit people ("three men, one woman, a boy, and a girl") to travel with him for study at the American Museum of Natural History in the United States, where four died within a few months.
In 1963, a fourth major piece of the Cape York meteorite was discovered by on Agpalilik peninsula. The , also known as the Man, weighs about , and it is currently on display in the Geological Museum of the University of Copenhagen, Denmark. Other smaller pieces have also been found, such as the Savik I meteorite found in 1911 and the Tunorput fragment found in 1984. Surveys of the area with a magnetometer in 2012 and georadar in 2014 found no evidence of further large iron fragments, either buried or on the surface. | 1 | Applied and Interdisciplinary Chemistry |
The set of all lines through the origin in three-dimensional space forms a space called the real projective plane. This plane is difficult to visualize, because it cannot be embedded in three-dimensional space.
However, one can visualize it as a disk, as follows. Any line through the origin intersects the southern hemisphere ≤ 0 in a point, which can then be stereographically projected to a point on a disk in the XY plane. Horizontal lines through the origin intersect the southern hemisphere in two antipodal points along the equator, which project to the boundary of the disk. Either of the two projected points can be considered part of the disk; it is understood that antipodal points on the equator represent a single line in 3 space and a single point on the boundary of the projected disk (see quotient topology). So any set of lines through the origin can be pictured as a set of points in the projected disk. But the boundary points behave differently from the boundary points of an ordinary 2-dimensional disk, in that any one of them is simultaneously close to interior points on opposite sides of the disk (just as two nearly horizontal lines through the origin can project to points on opposite sides of the disk).
Also, every plane through the origin intersects the unit sphere in a great circle, called the trace of the plane. This circle maps to a circle under stereographic projection. So the projection lets us visualize planes as circular arcs in the disk. Prior to the availability of computers, stereographic projections with great circles often involved drawing large-radius arcs that required use of a beam compass. Computers now make this task much easier.
Further associated with each plane is a unique line, called the planes pole', that passes through the origin and is perpendicular to the plane. This line can be plotted as a point on the disk just as any line through the origin can. So the stereographic projection also lets us visualize planes as points in the disk. For plots involving many planes, plotting their poles produces a less-cluttered picture than plotting their traces.
This construction is used to visualize directional data in crystallography and geology, as described below. | 0 | Theoretical and Fundamental Chemistry |
Klein-Seetharaman was born in Germany. She completed her undergraduate training at the University of Cologne, where she earned dual honours in biology and chemistry. After earning her doctorate, she moved to the United States, where she worked in the laboratory of Har Gobind Khorana at the Massachusetts Institute of Technology. Her research considered conformational changes in rhodopsin, the G protein coupled receptor. She was a postdoctoral researcher at MIT with Harald Schwalbe, focusing on nuclear magnetic resonance spectroscopy. After eight months as a postdoc, Klein-Seetharaman moved Carnegie Mellon University where she worked with Raj Reddy in biology. She was eventually appointed to the faculty at Carnegie Mellon. | 1 | Applied and Interdisciplinary Chemistry |
1,4-dioxane is a recently-identified contaminant of concern. The regulatory criteria for 1,4-dioxane is constantly changing as more is learned about this contaminant. 1,4-dioxane has a high solubility in water and a low Henry's Law constant which combine to present complex challenges associated with remediation. At ambient conditions, the physical properties of 1,4-dioxane indicate air stripping is not an efficient treatment mechanism. Recent ERH remediation results indicate that ERH creates conditions favorable for treatment. ERH remediation involves steam stripping, which historically had not been investigated for 1,4-dioxane. At ERH sites, steam stripping was observed to effectively transfer 1,4-dioxane to the vapor phase for subsequent treatment. 99.8% reductions (or greater) in 1,4-dioxane concentrations in groundwater have been documented on recent ERH remediation. Monitoring of the above grade treatment streams indicates that 95% of 1,4-dioxane remained in the vapor stream after removal from the subsurface. Furthermore, granular activated carbon has proven to be an effective 1,4-dioxane vapor treatment method. | 1 | Applied and Interdisciplinary Chemistry |
The purpose of the refractory lining is to insulate the steel shell from the high temperatures inside the kiln, and to protect it from the corrosive properties of the process material. It may consist of refractory bricks or cast refractory concrete, or may be absent in zones of the kiln that are below approximately 250 °C. The refractory selected depends upon the temperature inside the kiln and the chemical nature of the material being processed. In some processes, such as cement, the refractory life is prolonged by maintaining a coating of the processed material on the refractory surface. The thickness of the lining is generally in the range 80 to 300 mm. A typical refractory will be capable of maintaining a temperature drop of 1000 °C or more between its hot and cold faces. The shell temperature needs to be maintained below around 350 °C to protect the steel from damage, and continuous infrared scanners are used to give early warning of "hot-spots" indicative of refractory failure. | 1 | Applied and Interdisciplinary Chemistry |
While if both ends of a siphon are at atmospheric pressure, liquid flows from high to low, if the bottom end of a siphon is pressurized, liquid can flow from low to high. If pressure is removed from the bottom end, the liquid flow will reverse, illustrating that it is pressure driving the siphon. An everyday illustration of this is the siphon coffee brewer, which works as follows (designs vary; this is a standard design, omitting coffee grounds):
* a glass vessel is filled with water, then corked (so air-tight) with a siphon sticking vertically upwards
* another glass vessel is placed on top, open to the atmosphere – the top vessel is empty, the bottom is filled with water
* the bottom vessel is then heated; as the temperature increases, the vapor pressure of the water increases (it increasingly evaporates); when the water boils the vapor pressure equals atmospheric pressure, and as the temperature increases above boiling the pressure in the bottom vessel then exceeds atmospheric pressure, and pushes the water up the siphon tube into the upper vessel.
* a small amount of still hot water and steam remain in the bottom vessel and are kept heated, with this pressure keeping the water in the upper vessel
* when the heat is removed from the bottom vessel, the vapor pressure decreases, and can no longer support the column of water – gravity (acting on the water) and atmospheric pressure then push the water back into the bottom vessel.
In practice, the top vessel is filled with coffee grounds, and the heat is removed from the bottom vessel when the coffee has finished brewing. What vapor pressure means concretely is that the boiling water converts high-density water (a liquid) into low-density steam (a gas), which thus expands to take up more volume (in other words, the pressure increases). This pressure from the expanding steam then forces the liquid up the siphon; when the steam then condenses down to water the pressure decreases and the liquid flows back down. | 1 | Applied and Interdisciplinary Chemistry |
Methyl tert-butyl ether (MTBE), also known as tert-butyl methyl ether, is an organic compound with a structural formula (CH)COCH. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble in water. Primarily used as a fuel additive, MTBE is blended into gasoline to increase its octane rating and knock resistance, and reduce unwanted emissions. | 1 | Applied and Interdisciplinary Chemistry |
By 1971, solid-state cells and batteries based on rubidium silver iodide (RbAgI) have been designed and tested in a wide range of temperatures and discharge currents. Despite the relatively high conductivity of RbAgI, they have never been commercialized due to a low overall energy content per unit weight (ca. 5 W·h/kg).
On the contrary, LiI, which had a conductivity of only ca. 1 S/cm at room temperature, found a wide-scale application in batteries for artificial pacemakers. The first such device, based on undoped LiI, was implanted into a human in March 1972 in Ferrara, Italy. Later models used as electrolyte a film of LiI, which was doped with alumina nanoparticles to increase its conductivity. LiI was formed in an in situ chemical reaction between the Li anode and iodine-poly(2-vinylpyridine) cathode, and therefore was self-healed from erosion and cracks during the operation.
Sodium-sulfur cells, based on ceramic β-AlO electrolyte sandwiched between molten-sodium anode and molten-sulfur cathode showed high energy densities and were considered for car batteries in the 1990s, but disregarded due to the brittleness of alumina, which resulted in cracks and critical failure due to reaction between molten sodium and sulfur. Replacement of β-AlO with NASICON did not save this application because it did not solve the cracking problem, and because NASICON reacted with the molten sodium.
Yttria-stabilized zirconia is used as a solid electrolyte in oxygen sensors in cars, generating voltage that depends on the ratio of oxygen and exhaust gas and providing electronic feedback to the fuel injector. Such sensors are also installed at many metallurgical and glass-making factories. Similar sensors of CO, chlorine and other gases based on solid silver halide electrolytes have been proposed in the 1980s–1990s.
Since mid-1980s, a Li-based solid electrolyte is used to separate the electrochromic film (typically WO) and ion-storing film (typically LiCoO) in the smart glass, a window whose transparency is controlled by external voltage.
Solid-state ionic conductors are essential components of lithium-ion batteries, proton exchange membrane fuel cells (PEMFCs), supercapacitors, a novel class of electrochemical energy storage devices, and solid oxide fuel cells, devices that produces electricity from oxidizing a fuel. Nafion, a flexible fluoropolymer-copolymer discovered in the late 1960s, is widely used as a polymer electrolyte in PEMFCs. | 0 | Theoretical and Fundamental Chemistry |
The metal reagents used in this reaction include lithium bromide and silver acetate. In this method, the metal coordinates to the nitrogen in order to activate the substrate for deprotonation. Another way to form azomethine ylides from imines is by prototropy and by alkylation. | 0 | Theoretical and Fundamental Chemistry |
The rms charge radius is a measure of the size of an atomic nucleus, particularly the proton distribution. The proton radius is about one femtometre = . It can be measured by the scattering of electrons by the nucleus. Relative changes in the mean squared nuclear charge distribution can be precisely measured with atomic spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
If R and R (note equation at top of page) are different substituents, there is a new stereocenter formed at the alpha position when an enol converts to its keto form. Depending on the nature of the three R groups, the resulting products in this situation would be diastereomers or enantiomers. | 0 | Theoretical and Fundamental Chemistry |
The chemical composition for fats differs from that of carbohydrates in that fats contain considerably fewer oxygen atoms in proportion to atoms of carbon and hydrogen. When listed on nutritional information tables, fats are generally divided into six categories: total fats, saturated fatty acid, polyunsaturated fatty acid, monounsaturated fatty acid, dietary cholesterol, and trans fatty acid. From a basal metabolic or resting metabolic perspective, more energy is needed to burn a saturated fatty acid than an unsaturated fatty acid. The fatty acid molecule is broken down and categorized based on the number of carbon atoms in its molecular structure. The chemical equation for metabolism of the twelve to sixteen carbon atoms in a saturated fatty acid molecule shows the difference between metabolism of carbohydrates and fatty acids. Palmitic acid is a commonly studied example of the saturated fatty acid molecule.
The overall equation for the substrate utilization of palmitic acid is
(106 ATP molecules produced, 4.61 ATP molecules per molecule of oxygen.)
Thus the R.Q. for palmitic acid is 0.696: | 1 | Applied and Interdisciplinary Chemistry |
Exclusion chromatography.
Fractionation Range of Globular Proteins and Dextrans (Da).
Ion-exchange chromatography. | 1 | Applied and Interdisciplinary Chemistry |
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