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Propionyl-CoA is a coenzyme A derivative of propionic acid. It is composed of a 24 total carbon chain (without the coenzyme, it is a 3 carbon structure) and its production and metabolic fate depend on which organism it is present in. Several different pathways can lead to its production, such as through the catabolism of specific amino acids or the oxidation of odd-chain fatty acids. It later can be broken down by propionyl-CoA carboxylase or through the methylcitrate cycle. In different organisms, however, propionyl-CoA can be sequestered into controlled regions, to alleviate its potential toxicity through accumulation. Genetic deficiencies regarding the production and breakdown of propionyl-CoA also have great clinical and human significance. | 1 | Applied and Interdisciplinary Chemistry |
Spectral lines are associated with atomic electronic transitions and polyatomic gases have their own absorption band system. | 0 | Theoretical and Fundamental Chemistry |
The elasticity for an enzyme catalyzed reaction with respect to the enzyme concentration has special significance. The Michaelis model of enzyme action means that the reaction rate for an enzyme catalyzed reaction is a linear function of enzyme concentration. For example, the irreversible Michaelis rate law is given below there the maximal velocity, is explicitly given by the product of the and total enzyme concentration, :
In general we can expresion this relationship as the product of the enzyme concentration and a saturation function, :
This form is applicable to many enzyme mechanisms. The elasticity coefficient can be derived as follows:
It is this result that gives rise to the control coefficient summation theorems. | 0 | Theoretical and Fundamental Chemistry |
In addition to undergoing S2-type reactions, alkyl halides and similar substrates can add to a metal center via a radical mechanism, although some details remain controversial. Reactions which are generally accepted to proceed by a radical mechanism are known however. One example was proposed by Lednor and co-workers.
;Initiation
:[[Azobisisobutyronitrile|[(CH)C(CN)N]]] → 2 (CH)(CN)C + N
:(CH)(CN)C + PhBr → (CH)(CN)CBr + Ph
;Propagation
:Ph + [Pt(PPh)] → [Pt(PPh)Ph]
:[Pt(PPh)Ph] + PhBr → [Pt(PPh)PhBr] + Ph | 0 | Theoretical and Fundamental Chemistry |
See: Partition chromatography, Gas chromatography
Partition equilibrium chromatography is a type of chromatography that is typically used in gas chromatography (GC) and high performance liquid chromatography (HPLC). The stationary phase in GC is a high boiling liquid bonded to solid surface and the mobile phase is a gas. In gas-liquid chromatography, analyte from the mobile gas phase equilibrates with the liquid phase. Molecules more soluble in the liquid phase will remain longer in the column, allowing for separation using partition equilibriums. | 0 | Theoretical and Fundamental Chemistry |
Henrys law has been shown to apply to a wide range of solutes in the limit of infinite dilution (x' → 0), including non-volatile substances such as sucrose. In these cases, it is necessary to state the law in terms of chemical potentials. For a solute in an ideal dilute solution, the chemical potential depends only on the concentration. For non-ideal solutions, the activity coefficients of the components must be taken into account:
where for a volatile solute; c° = 1 mol/L.
For non-ideal solutions, the infinite dilution activity coefficient γ depends on the concentration and must be determined at the concentration of interest. The activity coefficient can also be obtained for non-volatile solutes, where the vapor pressure of the pure substance is negligible, by using the Gibbs-Duhem relation:
By measuring the change in vapor pressure (and hence chemical potential) of the solvent, the chemical potential of the solute can be deduced.
The standard state for a dilute solution is also defined in terms of infinite-dilution behavior. Although the standard concentration c° is taken to be 1 mol/L by convention, the standard state is a hypothetical solution of 1 mol/L in which the solute has its limiting infinite-dilution properties. This has the effect that all non-ideal behavior is described by the activity coefficient: the activity coefficient at 1 mol/L is not necessarily unity (and is frequently quite different from unity).
All the relations above can also be expressed in terms of molalities b rather than concentrations, e.g.:
where for a volatile solute; b° = 1 mol/kg.
The standard chemical potential μ°, the activity coefficient γ and the Henrys law constant H' all have different numerical values when molalities are used in place of concentrations. | 0 | Theoretical and Fundamental Chemistry |
The human vomeronasal organ has epithelia that may be able to serve as a chemical sensory organ; however, the genes that encode the VNO receptors are nonfunctional pseudogenes in humans. Also, while there are sensory neurons in the human VNO there seem to be no connections between the VNO and the central nervous system. The associated olfactory bulb is present in the fetus, but regresses and vanishes in the adult brain. There have been some reports that the human VNO does function, but only responds to hormones in a "sex-specific manner". There also have been pheromone receptor genes found in olfactory mucosa. There have been no experiments that compare people lacking the VNO, and people that have it. It is disputed on whether the chemicals are reaching the brain through the VNO or other tissues.
In 2006, it was shown that a second mouse receptor sub-class is found in the olfactory epithelium. Called the trace amine-associated receptors (TAAR), some are activated by volatile amines found in mouse urine, including one putative mouse pheromone. Orthologous receptors exist in humans providing, the authors propose, evidence for a mechanism of human pheromone detection.
Although there are disputes about the mechanisms by which pheromones function, there is evidence that pheromones do affect humans. Despite this evidence, it has not been conclusively shown that humans have functional pheromones. Those experiments suggesting that certain pheromones have a positive effect on humans are countered by others indicating they have no effect whatsoever.
A possible theory being studied now is that these axillary odors are being used to provide information about the immune system. Milinski and colleagues found that the artificial odors that people chose are determined in part by their major histocompatibility complexes (MHC) combination. Information about an individual's immune system could be used as a way of "sexual selection" so that the female could obtain good genes for her offspring. Claus Wedekind and colleagues found that both men and women prefer the axillary odors of people whose MHC is different from their own.
Some body spray advertisers claim that their products contain human sexual pheromones that act as an aphrodisiac. Despite these claims, no pheromonal substance has ever been demonstrated to directly influence human behavior in a peer reviewed study. Thus, the role of pheromones in human behavior remains speculative and controversial. | 1 | Applied and Interdisciplinary Chemistry |
The cold-vapor technique is an atomization method limited only for the determination of mercury, due to it being the only metallic element to have a large vapor pressure at ambient temperature. Because of this, it has an important use in determining organic mercury compounds in samples and their distribution in the environment. The method initiates by converting mercury into Hg by oxidation from nitric and sulfuric acids, followed by a reduction of Hg with tin(II) chloride. The mercury, is then swept into a long-pass absorption tube by bubbling a stream of inert gas through the reaction mixture. The concentration is determined by measuring the absorbance of this gas at 253.7 nm. Detection limits for this technique are in the parts-per-billion range making it an excellent mercury detection atomization method. | 0 | Theoretical and Fundamental Chemistry |
In the US, onshore and offshore pipelines used to transport oil and gas are regulated by the Pipeline and Hazardous Materials Safety Administration (PHMSA). Certain offshore pipelines used to produce oil and gas are regulated by the Minerals Management Service (MMS). In Canada, pipelines are regulated by either the provincial regulators or, if they cross provincial boundaries or the Canada–US border, by the National Energy Board (NEB). Government regulations in Canada and the United States require that buried fuel pipelines must be protected from corrosion. Often, the most economical method of corrosion control is by use of pipeline coating in conjunction with cathodic protection and technology to monitor the pipeline. Above ground, cathodic protection is not an option. The coating is the only external protection. | 1 | Applied and Interdisciplinary Chemistry |
A novel myokine osteonectin, or SPARC (secreted protein acidic and rich in cysteine), plays a vital role in bone mineralization, cell-matrix interactions, and collagen binding. Osteonectin inhibits tumorigenesis in mice. Osteonectin can be classed as a myokine, as it was found that even a single bout of exercise increased its expression and secretion in skeletal muscle in both mice and humans. | 1 | Applied and Interdisciplinary Chemistry |
In the RHEED setup, only atoms at the sample surface contribute to the RHEED pattern. The glancing angle of incident electrons allows them to escape the bulk of the sample and to reach the detector. Atoms at the sample surface diffract (scatter) the incident electrons due to the wavelike properties of electrons.
The diffracted electrons interfere constructively at specific angles according to the crystal structure and spacing of the atoms at the sample surface and the wavelength of the incident electrons. Some of the electron waves created by constructive interference collide with the detector, creating specific diffraction patterns according to the surface features of the sample. Users characterize the crystallography of the sample surface through analysis of the diffraction patterns. Figure 2 shows a RHEED pattern. Video 1 depicts a metrology instrument recording the RHEED intensity oscillations and deposition rate for process control and analysis.
Two types of diffraction contribute to RHEED patterns. Some incident electrons undergo a single, elastic scattering event at the crystal surface, a process termed kinematic scattering. Dynamic scattering occurs when electrons undergo multiple diffraction events in the crystal and lose some of their energy due to interactions with the sample. Users extract non-qualitative data from the kinematically diffracted electrons. These electrons account for the high intensity spots or rings common to RHEED patterns. RHEED users also analyze dynamically scattered electrons with complex techniques and models to gather quantitative information from RHEED patterns. | 0 | Theoretical and Fundamental Chemistry |
Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmons Polygraphice' (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum. By the fifth edition in 1685, he had included more asphaltum recipes from other sources.
The first British patent for the use of asphalt was "Cassell's patent asphalte or bitumen" in 1834. Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement, having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain. Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also "instrumental in introducing the asphalte pavement (in 1836)".
Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge. Claridges Patent Asphalte Companyformed in 1838 for the purpose of introducing to Britain "Asphalte in its natural state from the mine at Pyrimont Seysell in France","laid one of the first asphalt pavements in Whitehall". Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks, "and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park". "The formation in 1838 of Claridges Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry". "By the end of 1838, at least two other companies, Robinsons and the Bastenne company, were in production", with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridges Whitehall paving "continue(d) in good order". The Bonnington Chemical Works manufactured asphalt using coal tar and by 1839 had installed it in Bonnington.
In 1838, there was a flurry of entrepreneurial activity involving bitumen, which had uses beyond paving. For example, bitumen could also be used for flooring, damp proofing in buildings, and for waterproofing of various types of pools and baths, both of which were also proliferating in the 19th century. One of the earliest surviving examples of its use can be seen at Highgate Cemetery where it was used in 1839 to seal the roof of the terrace catacombs. On the London stockmarket, there were various claims as to the exclusivity of bitumen quality from France, Germany and England. And numerous patents were granted in France, with similar numbers of patent applications being denied in England due to their similarity to each other. In England, "Claridge's was the type most used in the 1840s and 50s".
In 1914, Claridges Company entered into a joint venture to produce tar-bound macadam, with materials manufactured through a subsidiary company called Clarmac Roads Ltd. Two products resulted, namely Clarmac, and Clarphalte, with the former being manufactured by Clarmac Roads and the latter by Claridges Patent Asphalte Co., although Clarmac was more widely used. However, the First World War ruined the Clarmac Company, which entered into liquidation in 1915. The failure of Clarmac Roads Ltd had a flow-on effect to Claridge's Company, which was itself compulsorily wound up, ceasing operations in 1917, having invested a substantial amount of funds into the new venture, both at the outset and in a subsequent attempt to save the Clarmac Company.
Bitumen was thought in 19th century Britain to contain chemicals with medicinal properties. Extracts from bitumen were used to treat catarrh and some forms of asthma and as a remedy against worms, especially the tapeworm. | 0 | Theoretical and Fundamental Chemistry |
Coulomb crystals of various ionic species have applications across much of physics, for example, in high precision spectroscopy, quantum information processing and cavity QED. | 0 | Theoretical and Fundamental Chemistry |
In 2000, Steglich et al. reported an intramolecular Pd(II)-mediated decarboxylative cross-coupling reaction in their synthesis of lamellarin L.
Myers et al. reported decarboxylative olefination of ortho-substituted arene carboxylates in the presence of an oxidant (Ag2CO3) in 2002.
Subsequent studies showed that homogeneous Pd catalysts were able to decarboxylate acids at lower temperatures than their Cu and Ag counterparts, but were limited to electron rich ortho-substituted aromatic carboxylic acids.
Despite this, palladium catalysts are able to promote a wide variety of cross-coupling reactions including biaryl formation and aryl alkyne formation, along with a variety of cross-coupling reactions in which the carboxylic acid is not bonded to an aromatic.
Other Pd-catalyzed decarboxylation cross-coupling reactions include conjugated diene preparation (see dienes and trienes below) and dehydrogenative reactions (with a variety of substrate and catalyst combinations).
Contrarily to Cu-only systems, decarboxylative palladation is the rate-limiting step in the palladium catalytic cycle. | 0 | Theoretical and Fundamental Chemistry |
The insertion of membrane proteins into a lipid membrane has been monitored using LD, supplying the experimentalist with information about the orientation of the protein relative to the lipid membrane at different time points.
In addition, other types of molecule have been analysed by UV LD, including carbon nanotubes and their associated ligand complexes. | 0 | Theoretical and Fundamental Chemistry |
MAP1a (MAP1A) and MAP1b (MAP1B) are the two major members of the MAP1 family. These two proteins are high molecular weight. They bind to microtubules through charge interactions, a different mechanism to many other MAPs. While the C termini of these MAPs bind the microtubules, the N termini bind other parts of the cytoskeleton or the plasma membrane to control spacing of the microtubule within the cell. Members of the MAP1 family are found in the axons and dendrites of nerve cells.
Another member of this family is MAP1S, which has a low molecular-weight. MAP1S has been found to regulate cell division and cell death | 1 | Applied and Interdisciplinary Chemistry |
Knockout mice that completely lack the RIP140 molecule are lean and stay lean, even on a rich diet.
Knockout mice (females) are also infertile because they fail to ovulate. Failure of ovulation in these mice is caused by lack of cumulus expansion and altered expression of various genes, including amphiregulin, in ovarian follicles. | 1 | Applied and Interdisciplinary Chemistry |
Hieronymus Theodor Richter (21 November 1824 – 25 September 1898) was a German chemist.
He was born in Dresden. In 1863, while working at the Freiberg University of Mining and Technology, he co-discovered indium with Ferdinand Reich. He was also a member of the student fraternity "Corps Saxo-Borussia Freiberg". In 1875, he became the director of the Mining Academy in Freiberg.
He died September 25, 1898, in Freiberg, Saxony, at the age of 73. | 1 | Applied and Interdisciplinary Chemistry |
Selection of an appropriate DNA polymerase is critical to the efficiency of the base addition step and must meet several criteria:
* Ability to efficiently incorporate FdNTP at consecutive positions
* Lack of 3–5 exonuclease and proofreading activity to prevent the removal newly incorporated FdNTP
* High fidelity to minimize mis-incorporations
* Good activity on templates which are mounted to surfaces (e.g. optical mapping surface)
In addition, different polymerase preference for different fluorochromes, linker length on fluorochrome-nucleotides, and buffer compositions are also important factors to be considered to optimize the base addition process and maximize number of consecutive FdNTP incorporations. | 1 | Applied and Interdisciplinary Chemistry |
PTT utilizes photothermal transduction agents (PTAs) which can transform light energy to heat through photothermal effect to raise the temperature of tumor area and thus cause the ablation of tumor cells. Specifically, ideal PTAs should have high photothermal conversion efficiency (PCE), excellent optical stability and biocompatibility, and strong light adsorption in the near-infrared (NIR) region (650-1350 nm) due to the deep-tissue penetration and minimal absorption of NIR light in the biological tissues. PTAs mainly include inorganic materials and organic materials. Inorganic PTAs, such as noble metal materials, carbon-based nanomaterials, and other 2D materials, have high PCE and excellent photostability, but they are not biodegradable and thus have potential long-term toxicity in vivo. Organic PTAs including small molecule dyes and conjugated polymers (CPs) have good biocompatibility and biodegradability, but poor photostability. Among them, small molecule dyes, such as cyanine, porphyrin, phthalocyanine, are limited in the field of cancer treatment because of their susceptibility to photobleaching and poor tumor enrichment ability. Conjugated polymers with large π−π conjugated skeleton and a high electron delocalization structure show potential for PTT due to their strong NIR absorption, excellent photostability, low cytotoxicity, outstanding PCE, good dispersibility in aqueous medium, increased accumulation at tumor site, and long blood circulation time. Moreover, conjugated polymers can be easily combined with other imaging agents and drugs to construct multifunctional nanomaterials for selective and synergistic cancer therapy.
The CPs used for tumor PTT mainly include polyaniline (PANI), polypyrrole (PPy), polythiophene (PTh), polydopamine (PDA), donor−acceptor (D-A) conjugated polymers, and poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS). | 0 | Theoretical and Fundamental Chemistry |
Hard water is water that has a high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum, which are largely made up of calcium and magnesium carbonates, bicarbonates and sulfates.
Drinking hard water may have moderate health benefits. It can pose critical problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment that handles water. In domestic settings, hard water is often indicated by a lack of foam formation when soap is agitated in water, and by the formation of limescale in kettles and water heaters. Wherever water hardness is a concern, water softening is commonly used to reduce hard water's adverse effects. | 0 | Theoretical and Fundamental Chemistry |
Molecular rotational transitions can also be observed by Raman spectroscopy. Rotational transitions are Raman-allowed for any molecule with an anisotropic polarizability which includes all molecules except for spherical tops. This means that rotational transitions of molecules with no permanent dipole moment, which cannot be observed in absorption or emission, can be observed, by scattering, in Raman spectroscopy. Very high resolution Raman spectra can be obtained by adapting a Fourier Transform Infrared Spectrometer. An example is the spectrum of . It shows the effect of nuclear spin, resulting in intensities variation of 3:1 in adjacent lines. A bond length of 109.9985 ± 0.0010 pm was deduced from the data. | 0 | Theoretical and Fundamental Chemistry |
Besides anchoring cells to the ECM, laminins are also involved in the signalling of cells and other components of the ECM. Even though there is not a general mechanism that applies to all laminins in signalling, there are some common pathways that can be seen in more than one isoform of laminin. For example, the PI3K/AKT pathway is used by laminin-111 (promotes cell-survival), 511 (prevents apoptosis with laminin 521), and 521 (stabilizes pluripotency of human embryonic stem cells). The pathway begins with the adhesion of the cell to the ECM for activation of the lipid-associated PI3K. Once PI3K is activated, it will localize AKT that is in the cytoplasm to the cell membrane where AKT is then phosphorylated to promote cell survival. | 0 | Theoretical and Fundamental Chemistry |
The effects on animals occur very rapidly and strongly, all resulting in death. Exposure to a high concentration of MFA vapor does not show any symptoms in animals until 30–60 minutes. Then violent reactions and death took place in a few hours, according to studies. From intravenous injection mice, rats, and guinea pigs show symptoms after 15 min to 2 hours. The animals become quiet and limp. Rabbits show a similar latent time period and muscle weakness. Dogs show symptoms of hyperactivity. They are more sensitive because of higher rates of metabolism and, eventually, they also fail to respirate. Fish are more resistant because of slow metabolism and therefore it is not expected that the substance will build up in fish. Also, Australian herbivores (e.g. possum and seed-eating birds) that live in a habitat consisting of plants with traces of fluoroacetate, have some tolerance. This can happen by detoxifying fluoroacetate or more resistivity of aconitase to fluorocitrate in the presence of GSH. Some insects can store the toxin in vacuoles and use it later. The highly hazardous MFA cannot be used for poisoning animals without risking human life. | 1 | Applied and Interdisciplinary Chemistry |
Some of the best-known examples of quorum sensing come from studies of bacteria. Bacteria use quorum sensing to regulate certain phenotype expressions, which in turn, coordinate their behavio rs. Some common phenotypes include biofilm formation, virulence factor expression, and motility. Certain bacteria are able to use quorum sensing to regulate bioluminescence, nitrogen fixation and sporulation.
The quorum-sensing function is based on the local density of the bacterial population in the immediate environment. It can occur within a single bacterial species, as well as between diverse species. Both gram-positive and gram-negative bacteria use quorum sensing, but there are some major differences in their mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
The names "caffeine" and "3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione" both signify the same chemical compound. The systematic name encodes the structure and composition of the caffeine molecule in some detail, and provides an unambiguous reference to this compound, whereas the name "caffeine" just names it. These advantages make the systematic name far superior to the common name when absolute clarity and precision are required. However, for the sake of brevity, even professional chemists will use the non-systematic name almost all of the time, because caffeine is a well-known common chemical with a unique structure. Similarly, HO is most often simply called water in English, though other chemical names do exist.
# Single atom anions are named with an -ide suffix: for example, H is hydride.
# Compounds with a positive ion (cation): The name of the compound is simply the cations name (usually the same as the elements), followed by the anion. For example, NaCl is sodium chloride, and CaF is calcium fluoride.
# Cations of transition metals able to take multiple charges are labeled with Roman numerals in parentheses to indicate their charge. For example, Cu is copper(I), Cu is copper(II). An older, deprecated notation is to append -ous or -ic to the root of the Latin name to name ions with a lesser or greater charge. Under this naming convention, Cu is cuprous and Cu is cupric. For naming metal complexes see the page on complex (chemistry).
# Oxyanions (polyatomic anions containing oxygen) are named with -ite or -ate, for a lesser or greater quantity of oxygen, respectively. For example, is nitrite, while is nitrate. If four oxyanions are possible, the prefixes hypo- and per- are used: hypochlorite is ClO, perchlorate is .
# The prefix bi- is a deprecated way of indicating the presence of a single hydrogen ion, as in "sodium bicarbonate" (NaHCO). The modern method specifically names the hydrogen atom. Thus, NaHCO would be pronounced sodium hydrogen carbonate.
Positively charged ions are called cations and negatively charged ions are called anions. The cation is always named first. Ions can be metals, non-metals or polyatomic ions. Therefore, the name of the metal or positive polyatomic ion is followed by the name of the non-metal or negative polyatomic ion. The positive ion retains its element name whereas for a single non-metal anion the ending is changed to -ide.
:Example: sodium chloride, potassium oxide, or calcium carbonate.
When the metal has more than one possible ionic charge or oxidation number the name becomes ambiguous. In these cases the oxidation number (the same as the charge) of the metal ion is represented by a Roman numeral in parentheses immediately following the metal ion name. For example, in uranium(VI) fluoride the oxidation number of uranium is 6. Another example is the iron oxides. FeO is iron(II) oxide and FeO is iron(III) oxide.
An older system used prefixes and suffixes to indicate the oxidation number, according to the following scheme:
Thus the four oxyacids of chlorine are called hypochlorous acid (HOCl),
chlorous acid (HOClO), chloric acid (HOClO) and perchloric acid (HOClO), and their respective conjugate bases are hypochlorite, chlorite, chlorate and perchlorate ions. This system has partially fallen out of use, but survives in the common names of many chemical compounds: the modern literature contains few references to "ferric chloride" (instead calling it "iron(III) chloride"), but names like "potassium permanganate" (instead of "potassium manganate(VII)") and "sulfuric acid" abound. | 0 | Theoretical and Fundamental Chemistry |
Many structures have been characterized by single-crystal X-ray crystallography. Metallacrowns typically contain fused chelate rings in their structure, which imparts them with substantial stability. Metallacrowns have been synthesized with substantial variety. Mixed ligand and mixed ring-metal, and mixed-oxidation state metallacrowns are known. Inverse metallacrowns have been reported that contain metal ions oriented towards the center of the ring. Metallacryptates, metallahelicates, and fused metallacrowns are known. Among the interesting features of metallacrowns are the similarities between certain structures and the corresponding crown ether. For example, in the 12-C-4, the cavity size is 2.79 Å and the bite distance is 0.6 Å. In the 12-MC-4, the cavity size is 2.67 Å and the bite distance is 0.5 Å. | 0 | Theoretical and Fundamental Chemistry |
Similar to d metal complexes, d octahedral metal complexes have D spectral term. The transition is from the (t)(e) configuration (E state) to the (t)(e) configuration (T state). This could also be described as a positive "hole" that moves from the e to the t orbital set. The sign of Dq is opposite that for d, with a E ground state and a T excited state. Like the d case, d octahedral complexes do not require the Tanabe–Sugano diagram to predict their absorption spectra. | 0 | Theoretical and Fundamental Chemistry |
The emerging understanding of the role of eNSCs in the adult mammalian brain suggested the relevance of these cells to disease. To address this issue, experiments were performed where the activation of eNSCs was induced in models of disease. This allowed the study of the consequences of activating eNSCs in the diseased brain. Several lines of evidence implicate the STAT3-Ser/Hes3 signaling axis in various diseases:
:* Activation of the signaling pathway by Delta4 in combination with basic fibroblast growth factor (bFGF) induces motor and sensory skill improvements in adult rat models of ischemic stroke (PMCAO model).
:* This signaling pathway may mediate pro-survival functions of macrophage migration inhibitory factor on neural stem cells.
:* Activation of the signaling pathway by Delta4, Angiopoietin 2, insulin, or a combination of the three and a JAK inhibitor induces motor skill improvements in adult rat models of Parkinson's disease (6-hydroxydopamine model).
:* RNA interference (“knockdown”) of Hes3 in cultures of cells with cancer stem cell properties from patients with glioblastoma multiforme reduces cell number.
:* Mice lacking Hes3 exhibit increased sensitivity to particular paradigms of pancreatic islet damage, suggesting roles in diabetes. | 1 | Applied and Interdisciplinary Chemistry |
In 1837, Draper accepted an appointment to be head of chemistry in a proposed medical school at New York University, but sufficient funds were not available to go ahead with the project. In 1839, Draper was elected undergraduate professor of chemistry and botany at the university, and moved with his family to New York City . Once there he helped to found the New York University Medical School, acting as a professor there from 1840 to 1850, president of the school from 1850 to 1873, and as a professor of chemistry until 1881. | 0 | Theoretical and Fundamental Chemistry |
The creator of LEXO, Hongbin "Bill" Ma, is a professor of mechanical and aerospace engineering and director of the Center for Thermal Management at the University of Missouri. After noticing how often he forgot coffee while waiting for it to cool, Ma began working on a “cup with constant temperature” in the summer of 2015. The LEXO was released to the general public in December 2016. | 0 | Theoretical and Fundamental Chemistry |
Self-assembled monolayers (SAM) of organic molecules are molecular assemblies formed spontaneously on surfaces by adsorption and are organized into more or less large ordered domains. In some cases molecules that form the monolayer do not interact strongly with the substrate. This is the case for instance of the two-dimensional supramolecular networks of e.g. perylenetetracarboxylic dianhydride (PTCDA) on gold or of e.g. porphyrins on highly oriented pyrolitic graphite (HOPG). In other cases the molecules possess a head group that has a strong affinity to the substrate and anchors the molecule to it. Such a SAM consisting of a head group, tail and functional end group is depicted in Figure 1. Common head groups include thiols, silanes, phosphonates, etc.
SAMs are created by the chemisorption of "head groups" onto a substrate from either the vapor or liquid phase followed by a slow organization of "tail groups". Initially, at small molecular density on the surface, adsorbate molecules form either a disordered mass of molecules or form an ordered two-dimensional "lying down phase", and at higher molecular coverage, over a period of minutes to hours, begin to form three-dimensional crystalline or semicrystalline structures on the substrate surface. The "head groups" assemble together on the substrate, while the tail groups assemble far from the substrate. Areas of close-packed molecules nucleate and grow until the surface of the substrate is covered in a single monolayer.
Adsorbate molecules adsorb readily because they lower the surface free-energy of the substrate and are stable due to the strong chemisorption of the "head groups." These bonds create monolayers that are more stable than the physisorbed bonds of Langmuir–Blodgett films. A trichlorosilane based "head group", for example in a FDTS molecule, reacts with a hydroxyl group on a substrate, and forms very stable, covalent bond [R-Si-O-substrate] with an energy of 452 kJ/mol. Thiol-metal bonds are on the order of 100 kJ/mol, making them fairly stable in a variety of temperatures, solvents, and potentials. The monolayer packs tightly due to van der Waals interactions, thereby reducing its own free energy. The adsorption can be described by the Langmuir adsorption isotherm if lateral interactions are neglected. If they cannot be neglected, the adsorption is better described by the Frumkin isotherm. | 0 | Theoretical and Fundamental Chemistry |
As an example camphor tosylhydrazone is synthesised from camphor and tosylhydrazine in ethanol with hydrochloric acid catalysis. | 0 | Theoretical and Fundamental Chemistry |
The binding of glycan-binding proteins (GBPs) to glycans could be modeled with simple equilibrium. Denoting glycans as and proteins as :
With an associated equilibrium constant of
Which is rearranged to give dissociation constant following biochemical conventions:
Given that many GBPs exhibit multivalency, this model may be expanded to account for multiple equilibria:
Denoting cumulative equilibrium of binding with ligands as
With corresponding equilibrium constant:
And writing material balance for protein ( denotes the total concentration of protein):
Expressing the terms through an equilibrium constant, a final result is found:
The concentration of free protein is, thus:
If , i.e. there is only one carbohydrate receptor domain, the equation reduces to
With increasing the concentration of free protein decreases; hence, the apparent decreases too. | 1 | Applied and Interdisciplinary Chemistry |
The International Tables for Crystallography is an eight-book series that outlines the standard notations for formatting, describing and testing crystals. The series contains books that covers analysis methods and the mathematical procedures for determining organic structure through x-ray crystallography, electron diffraction, and neutron diffraction. The International tables are focused on procedures, techniques and descriptions and do not list the physical properties of individual crystals themselves. Each book is about 1000 pages and the titles of the books are:
:Vol A - Space Group Symmetry,
:Vol A1 - Symmetry Relations Between Space Groups,
:Vol B - Reciprocal Space,
:Vol C - Mathematical, Physical, and Chemical Tables,
:Vol D - Physical Properties of Crystals,
:Vol E - Subperiodic Groups,
:Vol F - Crystallography of Biological Macromolecules, and
:Vol G - Definition and Exchange of Crystallographic Data. | 0 | Theoretical and Fundamental Chemistry |
Most metal alkyl complexes contain other, non-alkyl ligands. Great interest, mainly theoretical, has focused on the homoleptic complexes. Indeed, the first reported example of a complex containing a metal-sp carbon bond was the homoleptic complex diethylzinc. Other examples include hexamethyltungsten, tetramethyltitanium, and tetranorbornylcobalt.
Mixed ligand, or heteroleptic, complexes containing alkyls are numerous. In nature, vitamin B12 and its many derivatives contain reactive Co-alkyl bonds. | 0 | Theoretical and Fundamental Chemistry |
According to the Agency for Toxic Substances and Disease Registry (ATSDR), eating food or drinking water contaminated with high levels of coal-tar creosote may cause a burning in the mouth and throat, and stomach pains. ATSDR also states that brief direct contact with large amounts of coal-tar creosote may result in a rash or severe irritation of the skin, chemical burns of the surfaces of the eyes, convulsions and mental confusion, kidney or liver problems, unconsciousness, and even death. Longer direct skin contact with low levels of creosote mixtures or their vapours can result in increased light sensitivity, damage to the cornea, and skin damage. Longer exposure to creosote vapours can cause irritation of the respiratory tract.
The International Agency for Research on Cancer (IARC) has determined that coal-tar creosote is probably carcinogenic to humans, based on adequate animal evidence and limited human evidence. The animal testing relied upon by IARC involved the continuous application of creosote to the shaved skin of rodents. After weeks of creosote application, the animals developed cancerous skin lesions and in one test, lesions of the lung. The United States Environmental Protection Agency has stated that coal-tar creosote is a probable human carcinogen based on both human and animal studies. As a result, the Federal Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit of 0.2 milligrams of coal-tar creosote per cubic meter of air (0.2 mg/m3) in the workplace during an 8-hour day, and the Environmental Protection Agency (EPA) requires that spills or accidental releases into the environment of one pound (0.454 kg) or more of creosote be reported to them.
There is no unique exposure pathway of children to creosote. Children exposed to creosote probably experience the same health effects seen in adults exposed to creosote. It is unknown whether children differ from adults in their susceptibility to health effects from creosote.
A 2005 mortality study of creosote workers found no evidence supporting an increased risk of cancer death, as a result of exposure to creosote. Based on the findings of the largest mortality study to date of workers employed in creosote wood treating plants, there is no evidence that employment at creosote wood-treating plants or exposure to creosote-based preservatives was associated with any significant mortality increase from either site-specific cancers or non-malignant diseases. The study consisted of 2,179 employees at eleven plants in the United States where wood was treated with creosote preservatives. Some workers began work in the 1940s to 1950s. The observation period of the study covered 1979–2001. The average length of employment was 12.5 years. One third of the study subjects were employed for over 15 years.
The largest health effect of creosote is deaths caused by residential chimney fires due to chimney tar (creosote) build-up. This is entirely unconnected with its industrial production or use. | 0 | Theoretical and Fundamental Chemistry |
In horizontal sieve shaker the sieve stack moves in horizontal circles in a plane. Horizontal sieve shakers are preferably used for needle-shaped, flat, long or fibrous samples, as their horizontal orientation means that only a few disoriented particles enter the mesh and the sieve is not blocked so quickly. The large sieving area enables the sieving of large amounts of sample, for example as encountered in the particle-size analysis of construction materials and aggregates. | 1 | Applied and Interdisciplinary Chemistry |
Pharmaceutical formulation, in pharmaceutics, is the process in which different chemical substances, including the active drug, are combined to produce a final medicinal product. The word formulation is often used in a way that includes dosage form. | 1 | Applied and Interdisciplinary Chemistry |
On Curtius rearrangement, acyl azides yield isocyanates.
Acyl azides are also formed in Darapsky degradation, | 0 | Theoretical and Fundamental Chemistry |
In an infrared spectrum the intensity of an absorption band is proportional to the derivative of the molecular dipole moment with respect to the normal coordinate. Likewise, the intensity of Raman bands depends on the derivative of polarizability with respect to the normal coordinate. There is also a dependence on the fourth-power of the wavelength of the laser used. | 0 | Theoretical and Fundamental Chemistry |
Jeremy Munday writes that although "unexpected effects will likely occur" with global PDRC implementation, that "these structures can be removed immediately if needed, unlike methods that involve dispersing particulate matter into the atmosphere, which can last for decades." Wang et al. state that stratospheric aerosol injection "might cause potentially dangerous threats to the Earth’s basic climate operations" that may not be reversible, preferring PDRC. Zevenhoven et al. state that "instead of stratospheric aerosol injection (SAI), cloud brightening or a large number of mirrors in the sky (“sunshade geoengineering”) to block out or reflect incoming (short-wave, SW) solar irradiation, long-wavelength (LW) thermal radiation can be selectively emitted and transferred through the atmosphere into space". | 0 | Theoretical and Fundamental Chemistry |
1,3-Dienes such as butadiene and isoprene dimerize in the coordination spheres of some metals, giving chelating bis(allyl) complexes. Such complexes also arise from ring-opening of divinylcyclobutane. Chelating bis(allyl) complexes are intermediates in the metal-catalyzed dimerization of butadiene to give vinylcyclohexene and cycloocta-1,5-diene. | 0 | Theoretical and Fundamental Chemistry |
The initial condition is not required because of periodicity. Since both the equation and the boundary conditions are linear, the velocity can be written as the real part of some complex function
because .
Substituting this into the partial differential equation reduces it to ordinary differential equation
with boundary conditions
The solution to the above problem is
The disturbance created by the oscillating plate travels as the transverse wave through the fluid, but it is highly damped by the exponential factor. The depth of penetration of this wave decreases with the frequency of the oscillation, but increases with the kinematic viscosity of the fluid.
The force per unit area exerted on the plate by the fluid is
There is a phase shift between the oscillation of the plate and the force created. | 1 | Applied and Interdisciplinary Chemistry |
*[http://www-ssrl.slac.stanford.edu/absorb.html The SSRL Absorption Package] —
*[https://web.archive.org/web/20081223025616/http://www.gwyndafevans.co.uk/chooch.html CHOOCH] —
*[https://web.archive.org/web/20090909133542/http://www.hwi.buffalo.edu/snb/ Shake-and-Bake] (SnB) —
*[http://shelx.uni-ac.gwdg.de/SHELX/ SHELX] — | 0 | Theoretical and Fundamental Chemistry |
Newton's Second Law can be written as follows if only the pressure gradient, gravity, and friction act on an air parcel, where bold symbols are vectors:
Here U is the velocity field of the air, Ω is the angular velocity vector of the planet, ρ is the density of the air, P is the air pressure, F is the friction, g is the acceleration vector due to gravity and is the material derivative.
Locally this can be expanded in Cartesian coordinates, with a positive u representing an eastward direction and a positive v representing a northward direction. Neglecting friction and vertical motion, as justified by the Taylor–Proudman theorem, we have:
With the Coriolis parameter (approximately , varying with latitude).
Assuming geostrophic balance, the system is stationary and the first two equations become:
By substituting using the third equation above, we have:
with Z the height of the constant pressure surface (geopotential height), satisfying
This leads us to the following result for the geostrophic wind components (u, v):
The validity of this approximation depends on the local Rossby number. It is invalid at the equator, because f is equal to zero there, and therefore generally not used in the tropics.
Other variants of the equation are possible; for example, the geostrophic wind vector can be expressed in terms of the gradient of the geopotential Φ on a surface of constant pressure: | 1 | Applied and Interdisciplinary Chemistry |
Ultraviolet lamps are used to sterilize workspaces and tools used in biology laboratories and medical facilities. Commercially available low-pressure mercury-vapor lamps emit about 86% of their radiation at 254 nanometers (nm), with 265 nm being the peak germicidal effectiveness curve. UV at these germicidal wavelengths damage a microorganism's DNA/RNA so that it cannot reproduce, making it harmless, (even though the organism may not be killed). Since microorganisms can be shielded from ultraviolet rays in small cracks and other shaded areas, these lamps are used only as a supplement to other sterilization techniques.
UV-C LEDs are relatively new to the commercial market and are gaining in popularity. Due to their monochromatic nature (±5 nm) these LEDs can target a specific wavelength needed for disinfection. This is especially important knowing that pathogens vary in their sensitivity to specific UV wavelengths. LEDs are mercury free, instant on/off, and have unlimited cycling throughout the day.
Disinfection using UV radiation is commonly used in wastewater treatment applications and is finding an increased usage in municipal drinking water treatment. Many bottlers of spring water use UV disinfection equipment to sterilize their water. Solar water disinfection has been researched for cheaply treating contaminated water using natural sunlight. The UV-A irradiation and increased water temperature kill organisms in the water.
Ultraviolet radiation is used in several food processes to kill unwanted microorganisms. UV can be used to pasteurize fruit juices by flowing the juice over a high-intensity ultraviolet source. The effectiveness of such a process depends on the UV absorbance of the juice.
Pulsed light (PL) is a technique of killing microorganisms on surfaces using pulses of an intense broad spectrum, rich in UV-C between 200 and 280 nm. Pulsed light works with xenon flash lamps that can produce flashes several times per second. Disinfection robots use pulsed UV.
The antimicrobial effectiveness of filtered far-UVC (222 nm) light on a range of pathogens, including bacteria and fungi showed inhibition of pathogen growth, and since it has lesser harmful effects, it provides essential insights for reliable disinfection in healthcare settings, such as hospitals and long-term care homes. UVC has also been shown to be effective at degrading SARS-CoV-2 virus. | 0 | Theoretical and Fundamental Chemistry |
A lime kiln is a kiln used for the calcination of limestone (calcium carbonate) to produce the form of lime called quicklime (calcium oxide). The chemical equation for this reaction is
:CaCO + heat → CaO + CO
This reaction can take place at anywhere above , but is generally considered to occur at (at which temperature the partial pressure of CO is 1 atmosphere), but a temperature around (at which temperature the partial pressure of CO is 3.8 atmospheres) is usually used to make the reaction proceed quickly. Excessive temperature is avoided because it produces unreactive, "dead-burned" lime.
Slaked lime (calcium hydroxide) can be formed by mixing quicklime with water. | 1 | Applied and Interdisciplinary Chemistry |
The first named alkyl radical was ethyl, named so by Liebig in 1833 from the German word "Äther" (which in turn had been derived from the Greek word "aither" meaning "air", for the substance now known as diethyl ether) and the Greek word ύλη (hyle), meaning "matter". This was followed by methyl (Dumas and Peligot in 1834, meaning "spirit of wood") and amyl (Auguste Cahours in 1840). The word alkyl was introduced by Johannes Wislicenus in or before 1882, based on the German word "Alkoholradikale" and then-common suffix -yl. | 0 | Theoretical and Fundamental Chemistry |
RNA polymerase III uses a very similar factor to TFIIB called Brf (TFIIB-related factor) which also contains a conserved zinc ribbon and C terminal core. However, the structure diverges in the more flexible linker region although Brf still contains highly conserved sequences in the same positions that the B reader and B linker are found. These conserved regions probably carry out similar functions as the domains in TFIIB. RNA polymerase I does not use a factor that is similar to TFIIB; however, it is thought that another unknown factor fulfils the same function.
There is no direct homologue for TFIIB in bacterial systems but there are proteins that bind the bacterial polymerase in a similar manner with no sequence similarity. In particular the bacterial protein σ70 contains domains that bind the polymerase at the same points as the B-linker, B-ribbon and B-core. This is especially apparent in the σ 3 region and the region 4 linker which might stabilise the DNA in the polymerase active site. | 1 | Applied and Interdisciplinary Chemistry |
The transcriptome is the set of all RNA transcripts, including coding and non-coding, in an individual or a population of cells. The term can also sometimes be used to refer to all RNAs, or just mRNA, depending on the particular experiment. The term transcriptome is a portmanteau of the words transcript and genome; it is associated with the process of transcript production during the biological process of transcription.
The early stages of transcriptome annotations began with cDNA libraries published in the 1980s. Subsequently, the advent of high-throughput technology led to faster and more efficient ways of obtaining data about the transcriptome. Two biological techniques are used to study the transcriptome, namely DNA microarray, a hybridization-based technique and RNA-seq, a sequence-based approach. RNA-seq is the preferred method and has been the dominant transcriptomics technique since the 2010s. Single-cell transcriptomics allows tracking of transcript changes over time within individual cells.
Data obtained from the transcriptome is used in research to gain insight into processes such as cellular differentiation, carcinogenesis, transcription regulation and biomarker discovery among others. Transcriptome-obtained data also finds applications in establishing phylogenetic relationships during the process of evolution and in in vitro fertilization. The transcriptome is closely related to other -ome based biological fields of study; it is complementary to the proteome and the metabolome and encompasses the translatome, exome, meiome and thanatotranscriptome which can be seen as ome fields studying specific types of RNA transcripts. There are quantifiable and conserved relationships between the Transcriptome and other -omes, and Transcriptomics data can be used effectively to predict other molecular species, such as metabolites. There are numerous publicly available transcriptome databases. | 1 | Applied and Interdisciplinary Chemistry |
ITPP is a membrane-permeant allosteric regulator of hemoglobin that mildly reduces its oxygen-binding affinity, which shifts the oxygen-hemoglobin dissociation curve to the right and thereby increases oxygen release from the blood into tissue. Phytic acid, in contrast, is not membrane-permeant due to its charge distribution.
Rodent studies in vivo demonstrated increased tissue oxygenation and dose-dependent increases in endurance during physical exercise, in both healthy mice and transgenic mice expressing a heart failure phenotype.
The substance is believed to have a high potential for use in athletic doping, and liquid chromatography–mass spectrometry tests have been developed to detect ITPP in urine tests. Its use as a performance-enhancing substance in horse racing has also been suspected and similar tests have been developed for horses
ITPP has been studied for potential adjuvant use in the treatment of cancer in conjunction with chemotherapy, due to its effects in reducing tissue hypoxia. Human clinical trials were registered in 2014 under the compound number OXY111A. The substance has also been examined in the context of other illnesses involving hypoxia, such as cardiovascular disease and dementia | 1 | Applied and Interdisciplinary Chemistry |
Protein backbones are very stable in water at neutral pH and room temperature, although the rate of hydrolysis of different peptide bonds can vary. The half life of a peptide bond under normal conditions can range from 7 years to 350 years, even higher for peptides protected by modified terminus or within the protein interior. The rate of hydrolysis however can be significantly increased by extremes of pH and heat. Spontaneous cleavage of proteins may also involve catalysis by zinc on serine and threonine.
Strong mineral acids can readily hydrolyse the peptide bonds in a protein (acid hydrolysis). The standard way to hydrolyze a protein or peptide into its constituent amino acids for analysis is to heat it to 105 °C for around 24 hours in 6M hydrochloric acid. However, some proteins are resistant to acid hydrolysis. One well-known example is ribonuclease A, which can be purified by treating crude extracts with hot sulfuric acid so that other proteins become degraded while ribonuclease A is left intact.
Certain chemicals cause proteolysis only after specific residues, and these can be used to selectively break down a protein into smaller polypeptides for laboratory analysis. For example, cyanogen bromide cleaves the peptide bond after a methionine. Similar methods may be used to specifically cleave tryptophanyl, aspartyl, cysteinyl, and asparaginyl peptide bonds. Acids such as trifluoroacetic acid and formic acid may be used for cleavage.
Like other biomolecules, proteins can also be broken down by high heat alone. At 250 °C, the peptide bond may be easily hydrolyzed, with its half-life dropping to about a minute. Protein may also be broken down without hydrolysis through pyrolysis; small heterocyclic compounds may start to form upon degradation. Above 500 °C, polycyclic aromatic hydrocarbons may also form, which is of interest in the study of generation of carcinogens in tobacco smoke and cooking at high heat. | 1 | Applied and Interdisciplinary Chemistry |
HOSA reacts under basic conditions as an electrophile and under neutral and acid conditions as a nucleophile. | 0 | Theoretical and Fundamental Chemistry |
The functionality of a monomeric structural unit is defined as the number of covalent bonds which it forms with other reactants. A structural unit in a linear polymer chain segment forms two bonds and is therefore bifunctional, as for the PET structural units above.
Other values of functionality exist. Unless the macromolecule is cyclic, it will have monovalent structural units at each end of the polymer chain. In branched polymers, there are trifunctional units at each branch point. For example, in the synthesis of PET, a small fraction of the ethylene glycol can be replaced by glycerol which has three alcohol groups. This trifunctional molecule inserts itself in the polymeric chain and bonds to three carboxylic acid groups forming a branch point.
Finally, the formation of cross-linked polymers involves tetrafunctional structural units. For example, in the synthesis of cross-linked polystyrene, a small fraction of monomeric styrene (or vinylbenzene) is remplaced by 1,4-divinylbenzene (or para-divinylbenzene). Each of the two vinyl groups is inserted into a polymeric chain, so that the tetravalent unit is inserted into both chains, linking them together. | 0 | Theoretical and Fundamental Chemistry |
In experiments in animals favipiravir has shown activity against West Nile virus, yellow fever virus, foot-and-mouth disease virus as well as other flaviviruses, arenaviruses, bunyaviruses and alphaviruses. Activity against enteroviruses and Rift Valley fever virus has also been demonstrated. Favipiravir has showed limited efficacy against Zika virus in animal studies, but was less effective than other antivirals such as MK-608. The agent has also shown some efficacy against rabies, and has been used experimentally in some humans infected with the virus. | 0 | Theoretical and Fundamental Chemistry |
The main finding of Haber and Weiss was that hydrogen peroxide (HO) is decomposed by a chain reaction.
The Haber–Weiss reaction chain proceeds by successive steps: (i) initiation, (ii) propagation and (iii) termination.
The chain is initiated by the Fenton reaction:
:Fe + HO → Fe + HO + HO (step 1: initiation)
Then, the reaction chain propagates by means of two successive steps:
:HO + HO → HO + O + H (step 2: propagation)
:O + H + HO → O + HO + HO (step 3: propagation)
Finally, the chain is terminated when the hydroxyl radical is scavenged by a ferrous ion:
:Fe + HO + H → Fe + HO (step 4: termination)
George showed in 1947 that, in water, step 3 cannot compete with the spontaneous disproportionation of superoxide, and proposed an improved mechanism for the disappearance of hydrogen peroxide. See for a summary. The reactions proposed therein are:
:Fe + HO → Fe + HO + HO (initiation)
:Fe + HO → Fe + HO (termination)
:HO + HO → HO + HO (propagation)
:Fe + HO → Fe + HO (termination)
:Fe + HO → Fe + HO + H (termination) | 1 | Applied and Interdisciplinary Chemistry |
Three-roll push bending (TRPB) is the most commonly used freeform-bending process to manufacture bending geometries consisting of several plane bending curves. Nevertheless, 3D-shaping is possible. The profile is guided between bending-roll and supporting-roll(s), while being pushed through the tools. The position of the forming-roll defines the bending radius. The bending point is the tangent-point between tube and bending-roll. To change the bending plane, the pusher rotates the tube around its longitudinal axis. Generally, a TRPB tool kit can be applied on a conventional rotary draw bending machine. The process is very flexible since with a unique tool set, several bending radii values Rm can be obtained, although the geometrical precision of the process is not comparable to rotary draw bending.
Bending contours defined as spline- or polynomial-functions can be manufactured. | 1 | Applied and Interdisciplinary Chemistry |
Values for log K typically range between -3 (very hydrophilic) and +10 (extremely lipophilic/hydrophobic).
The values listed here are sorted by the partition coefficient. Acetamide is hydrophilic, and 2,2′,4,4′,5-Pentachlorobiphenyl is lipophilic. | 0 | Theoretical and Fundamental Chemistry |
Together with benzyltrimethylammonium hydroxide, salts of benzyltriethylammonium are common phase-transfer catalysts. | 0 | Theoretical and Fundamental Chemistry |
Penicillin patents became a matter of concern and conflict. Chain had wanted to apply for a patent but Florey had objected, arguing that penicillin should benefit all. Florey sought the advice of Sir Henry Dale, the chairman of the Wellcome Trust and a member of the Scientific Advisory Panel to the British Cabinet, and John William Trevan, the director of the Wellcome Trust Research Laboratory. On 26 and 27 March 1941, Dale and Trevan met at Oxford Universitys Sir William Dunn School of Pathology to discuss the issue. Dale advised that patenting penicillin would be unethical. Undeterred, Chain approached Sir Edward Mellanby, then Secretary of the Medical Research Council, who also objected on ethical grounds. As Chain later admitted, he had "many bitter fights" with Mellanby, but Mellanbys decision was accepted as final.
In 1945, Moyer patented the methods for production and isolation of penicillin. He could not obtain patents in the US as an employee of the NRRL, but filed for patents with the British Patent Office. He gave the license to a US company, Commercial Solvents Corporation. When Fleming learnt of the American patents on penicillin production, he was incensed and commented:
The patenting of penicillin-related technologies by US companies gave rise to a myth in the UK that British scientists had done the work but American ones garnered the rewards. When the Rockefeller Foundation published its annual report in 1944, The Evening News contrasted the foundations generous support of the Oxford teams work with that of the parsimonious MRC. In April 1945, the British firm Glaxo signed agreements with Squibb and Merck under which it paid 5 per cent royalties on its sales of penicillin for five years in return for the use of their deep submergence fermentation techniques. Glaxo paid almost £500,000 () in royalties between 1946 and 1956. The controversy over patents led to the establishment of the UK National Research Development Corporation (NRDC) in June 1948. This organisation collected government patents and charged royalties on them. | 1 | Applied and Interdisciplinary Chemistry |
Joseph Priestley (1733–1804) was an English polymath who discovered nitrous oxide, nitric oxide, ammonia, hydrogen chloride, and (along with Carl Wilhelm Scheele and Antoine Lavoisier) oxygen. Beginning in 1775, Priestley published his research in Experiments and Observations on Different Kinds of Air, a six-volume work. The recent discoveries about these and other gases stimulated a great deal of interest in the European scientific community. Thomas Beddoes (1760–1808) was an English philosopher, physician and teacher of medicine, and like his older colleague Priestley, was also a member of the Lunar Society of Birmingham. With an eye toward making further advances in this new science as well as offering treatment for diseases previously thought to be untreatable (such as asthma and tuberculosis), Beddoes founded the Pneumatic Institution for inhalation gas therapy in 1798 at Dowry Square in Clifton, Bristol. Beddoes employed chemist and physicist Humphry Davy (1778–1829) as superintendent of the institute, and engineer James Watt (1736–1819) to help manufacture the gases. Other members of the Lunar Society such as Erasmus Darwin and Josiah Wedgwood were also actively involved with the institute.
During the course of his research at the Pneumatic Institution, Davy discovered the anesthetic properties of nitrous oxide. Davy, who coined the term "laughing gas" for nitrous oxide, published his findings the following year in the now-classic treatise, Researches, chemical and philosophical–chiefly concerning nitrous oxide or dephlogisticated nitrous air, and its respiration. Davy was not a physician, and he never administered nitrous oxide during a surgical procedure. He was, however, the first to document the analgesic effects of nitrous oxide, as well as its potential benefits in relieving pain during surgery: | 1 | Applied and Interdisciplinary Chemistry |
*Iran:
**Ali Abad
**Astane-ye Ashrafiye
**Astara
**Babolsar
**Bandar-e Anzali
**Bandar-e-Gaz
**Bandar Torkaman
**Behshahr
**Chalus
**Fenderesk
**Gomishan
**Gonbad-e Kavus
**Gorgan
**Juybar
**Kordkuy
**Lahijan
**Langarud
**Mahmudabad
**Neka
**Nowshahr
**Nur
**Ramsar
**Rasht
**Rudbar
**Rudsar
**Sari
**Sorkhrud
**Talesh
**Tonekabon
*Azerbaijan:
**Astara
**Baku
**Gobustan
**Khudat
**Khachmaz
**Lankaran
**Masallı
**Nabran
**Neftchala
**Shabran
**Siyazan
**Oil Rocks
**Sumqayit
*Kazakhstan:
**Atyrau
**Aktau
*Russia:
**Astrakhan
**Dagestanskiye Ogni
**Derbent
**Izberbash
**Kaspiysk
**Makhachkala
*Turkmenistan:
**Türkmenbaşy (formerly Krasnovodsk)
**Hazar (formerly Çeleken)
**Esenguly
**Garabogaz (formerly Bekdaş) | 1 | Applied and Interdisciplinary Chemistry |
Bilirubin consists of an open-chain tetrapyrrole. It is formed by oxidative cleavage of a porphyrin in heme, which affords biliverdin. Biliverdin is reduced to bilirubin. After conjugation with glucuronic acid, bilirubin is water-soluble and can be excreted.
Bilirubin is structurally similar to the pigment phycobilin used by certain algae to capture light energy, and to the pigment phytochrome used by plants to sense light. All of these contain an open chain of four pyrrolic rings.
Like these other pigments, some of the double-bonds in bilirubin isomerize when exposed to light. This isomerization is relevant to the phototherapy of jaundiced newborns: the E,Z-isomers of bilirubin formed upon light exposure are more soluble than the unilluminated Z,Z-isomer, as the possibility of intramolecular hydrogen bonding is removed. Increased solubility allows the excretion of unconjugated bilirubin in bile.
Some textbooks and research articles show the incorrect geometric isomer of bilirubin. The naturally occurring isomer is the Z,Z-isomer. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, resonance, also called mesomerism, is a way of describing bonding in certain molecules or polyatomic ions by the combination of several contributing structures (or forms, also variously known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bond theory. It has particular value for analyzing delocalized electrons where the bonding cannot be expressed by one single Lewis structure. The resonance hybrid is the accurate structure for a molecule or ion; it is an average of the theoretical contributing structures. | 0 | Theoretical and Fundamental Chemistry |
Magnetometric surveys can be useful in defining magnetic anomalies which represent ore (direct detection), or in some cases gangue minerals associated with ore deposits (indirect or inferential detection). This includes iron ore, magnetite, hematite, and often pyrrhotite.
Developed countries such as Australia, Canada and USA invest heavily in systematic airborne magnetic surveys of their respective continents and surrounding oceans, to assist with map geology and in the discovery of mineral deposits. Such aeromag surveys are typically undertaken with 400 m line spacing at 100 m elevation, with readings every 10 meters or more. To overcome the asymmetry in the data density, data is interpolated between lines (usually 5 times) and data along the line is then averaged. Such data is gridded to an 80 m × 80 m pixel size and image processed using a program like ERMapper. At an exploration lease scale, the survey may be followed by a more detailed helimag or crop duster style fixed wing at 50 m line spacing and 50 m elevation (terrain permitting). Such an image is gridded on a 10 x 10 m pixel, offering 64 times the resolution.
Where targets are shallow (<200 m), aeromag anomalies may be followed up with ground magnetic surveys on 10 m to 50 m line spacing with 1 m station spacing to provide the best detail (2 to 10 m pixel grid) (or 25 times the resolution prior to drilling).
Magnetic fields from magnetic bodies of ore fall off with the inverse distance cubed (dipole target), or at best inverse distance squared (magnetic monopole target). One analogy to the resolution-with-distance is a car driving at night with lights on. At a distance of 400 m one sees one glowing haze, but as it approaches, two headlights, and then the left blinker, are visible.
There are many challenges interpreting magnetic data for mineral exploration. Multiple targets mix together like multiple heat sources and, unlike light, there is no magnetic telescope to focus fields. The combination of multiple sources is measured at the surface. The geometry, depth, or magnetisation direction (remanence) of the targets are also generally not known, and so multiple models can explain the data.
Potent by Geophysical Software Solutions [https://web.archive.org/web/20131213095908/http://www.geoss.com.au/] is a leading magnetic (and gravity) interpretation package used extensively in the Australian exploration industry.
Magnetometers assist mineral explorers both directly (i.e., gold mineralisation associated with magnetite, diamonds in kimberlite pipes) and, more commonly, indirectly, such as by mapping geological structures conducive to mineralisation (i.e., shear zones and alteration haloes around granites).
Airborne Magnetometers detect the change in the Earth's magnetic field using sensors attached to the aircraft in the form of a "stinger" or by towing a magnetometer on the end of a cable. The magnetometer on a cable is often referred to as a "bomb" because of its shape. Others call it a "bird".
Because hills and valleys under the aircraft make the magnetic readings rise and fall, a radar altimeter keeps track of the transducer's deviation from the nominal altitude above ground. There may also be a camera that takes photos of the ground. The location of the measurement is determined by also recording a GPS. | 0 | Theoretical and Fundamental Chemistry |
In addition to chip cooling, thermal bumps can also be applied to high heat-flux interconnects to provide a constant, steady source of power for energy scavenging applications. Such a source of power, typically in the mW range, can trickle charge batteries for wireless sensor networks and other battery operated systems. | 0 | Theoretical and Fundamental Chemistry |
In physics and chemistry, effusion is the process in which a gas escapes from a container through a hole of diameter considerably smaller than the mean free path of the molecules. Such a hole is often described as a pinhole and the escape of the gas is due to the pressure difference between the container and the exterior. Under these conditions, essentially all molecules which arrive at the hole continue and pass through the hole, since collisions between molecules in the region of the hole are negligible. Conversely, when the diameter is larger than the mean free path of the gas, flow obeys the Sampson flow law.
In medical terminology, an effusion refers to accumulation of fluid in an anatomic space, usually without loculation. Specific examples include subdural, mastoid, pericardial and pleural effusions. | 0 | Theoretical and Fundamental Chemistry |
In some forms of photosynthetic bacteria, a chromatophore is a pigmented(coloured), membrane-associated vesicle used to perform photosynthesis. They contain different coloured pigments.
Chromatophores contain bacteriochlorophyll pigments and carotenoids. In purple bacteria, such as Rhodospirillum rubrum, the light-harvesting proteins are intrinsic to the chromatophore membranes. However, in green sulfur bacteria, they are arranged in specialised antenna complexes called chlorosomes. | 0 | Theoretical and Fundamental Chemistry |
"Uranium and Thorium contents were measured inside various tobacco samples by using a method based on determining detection efficiencies of the CR-39 and LR-115 II solid state nuclear track detectors (SSNTD) for the emitted alpha particles. Alpha and beta activities per unit volume, due to radon, thoron and their decay products, were evaluated inside cigarette smokes of tobacco samples studied. Annual committed equivalent doses due to short-lived radon decay products from the inhalation of various cigarette smokes were determined in the thoracic and extrathoracic regions of the respiratory tract. Three types of cigarettes made in Morocco of black tobacco show higher annual committed equivalent doses in the extrathoracic and thoracic regions of the respiratory tract than the other studied cigarettes (except one type of cigarettes made in France of yellow tobacco); their corresponding annual committed equivalent dose ratios are larger than 1.8. Measured annual committed equivalent doses ranged from 1.8×10 Sv/yr to in the extrathoracic region and from 1.3×10 Sv/yr to in the thoracic region of the respiratory tract for a smoker consuming 20 cigarettes a day." | 0 | Theoretical and Fundamental Chemistry |
Most transcription factors function in cooperation with other factors by protein–protein interactions. Association of MITF with other proteins is a critical step in the regulation of MITF-mediated transcriptional activity. Some commonly studied MITF interactions include those with MAZR, PIAS3, Tfe3, hUBC9, PKC1, and LEF1. Looking at the variety of structures gives insight into MITF's varied roles in the cell.
The Myc-associated zinc-finger protein related factor (MAZR) interacts with the Zip domain of MITF. When expressed together, both MAZR and MITF increase promoter activity of the mMCP-6 gene. MAZR and MITF together transactivate the mMCP-6 gene. MAZR also plays a role in the phenotypic expression of mast cells in association with MITF.
PIAS3 is a transcriptional inhibiter that acts by inhibiting STAT3's DNA binding activity. PIAS3 directly interacts with MITF, and STAT3 does not interfere with the interaction between PIAS3 and MITF. PIAS3 functions as a key molecule in suppressing the transcriptional activity of MITF. This is important when considering mast cell and melanocyte development.
MITF, TFE3 and TFEB are part of the basic helix-loop-helix-leucine zipper family of transcription factors. Each protein encoded by the family of transcription factors can bind DNA. MITF is necessary for melanocyte and eye development and new research suggests that TFE3 is also required for osteoclast development, a function redundant of MITF. The combined loss of both genes results in severe osteopetrosis, pointing to an interaction between MITF and other members of its transcription factor family. In turn, TFEB has been termed as the master regulator of lysosome biogenesis and autophagy. Interestingly, MITF, TFEB and TFE3 separate roles in modulating starvation-induced autophagy have been described in melanoma. Moreover, MITF and TFEB proteins, directly regulate each other’s mRNA and protein expression while their subcellular localization and transcriptional activity are subject to similar modulation, such as the mTOR signaling pathway.
UBC9 is a ubiquitin conjugating enzyme whose proteins associates with MITF. Although hUBC9 is known to act preferentially with SENTRIN/SUMO1, an in vitro analysis demonstrated greater actual association with MITF. hUBC9 is a critical regulator of melanocyte differentiation. To do this, it targets MITF for proteasome degradation.
Protein kinase C-interacting protein 1 (PKC1) associates with MITF. Their association is reduced upon cell activation. When this happens MITF disengages from PKC1. PKC1 by itself, found in the cytosol and nucleus, has no known physiological function. It does, however, have the ability to suppress MITF transcriptional activity and can function as an in vivo negative regulator of MITF induced transcriptional activity.
The functional cooperation between MITF and the lymphoid enhancing factor (LEF-1) results in a synergistic transactivation of the dopachrome tautomerase gene promoter, which is an early melanoblast marker. LEF-1 is involved in the process of regulation by Wnt signaling. LEF-1 also cooperates with MITF-related proteins like TFE3. MITF is a modulator of LEF-1, and this regulation ensures efficient propagation of Wnt signals in many cells. | 1 | Applied and Interdisciplinary Chemistry |
Poly(A)polymerase was first identified in 1960 as an enzymatic activity in extracts made from cell nuclei that could polymerise ATP, but not ADP, into polyadenine. Although identified in many types of cells, this activity had no known function until 1971, when poly(A) sequences were found in mRNAs. The only function of these sequences was thought at first to be protection of the 3′ end of the RNA from nucleases, but later the specific roles of polyadenylation in nuclear export and translation were identified. The polymerases responsible for polyadenylation were first purified and characterized in the 1960s and 1970s, but the large number of accessory proteins that control this process were discovered only in the early 1990s. | 1 | Applied and Interdisciplinary Chemistry |
Prior to the final of Phantom Singer 2, Kang was grouped together with Bae Doo-hoon, Cho Min-kyu and Ko Woo-rim to form Forestella. He had never been grouped with any of the other members up until the random quartet stage. They eventually won the competition and debuted on March 14, 2018.
Kang signed as a solo artist with Arts & Artists, which had also managed Forestella as a group until June 2021. In October 2020, he made his debut release with the digital single "Universe" under the stage name PITTA. It was the name of the band had been part of from his amateur days and he chose to use it as a homage to his members. In November 2021, he released the self-composed extended play ID: PITTA, his first non-single release as a solo artist.
He participated in various televised music competitions, like King of Mask Singer, where he was eliminated in the first round, but showcased a wide vocal range. He finished 5th overall in the celebrity singing competition Lotto Singer, despite receiving the highest score from judges. | 1 | Applied and Interdisciplinary Chemistry |
Amorphous brazing foils are typically used for brazing, a metallurgy process by which two pieces of metal are joined by melting and cooling a third "fill metal" at their joint. The use of preforms increases the capability of ABFs for use on an industrial scale, even being able to be assembled by machine. | 1 | Applied and Interdisciplinary Chemistry |
Pourbaix diagrams are widely used to describe the behaviour of chemical species in the hydrosphere. In this context, reduction potential is often used instead of . The main advantage is to directly work with a logarithm scale.
is a dimensionless number and can easily be related to by the equation:
Where, is the thermal voltage, with , the gas constant (), , the absolute temperature in Kelvin (298.15 K = 25 °C = 77 °F), and , the Faraday constant (96 485 coulomb/mol of ). Lambda, λ = ln(10) ≈ 2.3026.
Moreover,
: , an expression with a similar form to that of pH.
values in environmental chemistry ranges from −12 to +25, since at low or high potentials water will be respectively reduced or oxidized. In environmental applications, the concentration of dissolved species is usually set to a value between 10 M and 10 M for the determination of the equilibrium lines. | 0 | Theoretical and Fundamental Chemistry |
The most common anodizing processes, for example, sulphuric acid on aluminium, produce a porous surface which can accept dyes easily. The number of dye colours is almost endless; however, the colours produced tend to vary according to the base alloy. The most common colours in the industry, due to them being relatively cheap, are yellow, green, blue, black, orange, purple and red. Though some may prefer lighter colours, in practice they may be difficult to produce on certain alloys such as high-silicon casting grades and 2000-series aluminium-copper alloys. Another concern is the "lightfastness" of organic dyestuffs—some colours (reds and blues) are particularly prone to fading. Black dyes and gold produced by inorganic means (ferric ammonium oxalate) are more lightfast. Dyed anodizing is usually sealed to reduce or eliminate dye bleed out. White color cannot be applied due to the larger molecule size than the pore size of the oxide layer.
Alternatively, metal (usually tin) can be electrolytically deposited in the pores of the anodic coating to provide more lightfast colours. Metal dye colors range from pale champagne to black. Bronze shades are commonly used for architectural metals. Alternatively, the colour may be produced integral to the film. This is done during the anodizing process using organic acids mixed with the sulfuric electrolyte and a pulsed current.
Splash effects are created by dying the unsealed porous surface in lighter colours and then splashing darker colour dyes onto the surface. Aqueous and solvent-based dye mixtures may also be alternately applied since the coloured dyes will resist each other and leave spotted effects.
Another interesting coloring method is anodizing interference coloring. The thin oil film resting on the waters surface displays a rainbow hue due to the interference between light reflected from the water-oil interface and the oil films surface. Because the oil films thickness isnt regulated, the resulting rainbow color appears random.
In the anodizing coloring of aluminum, desired colors are achieved by depositing a controllably thick metal layer (typically tin) at the base of the porous structure. This involves reflections on the aluminum substrate and the upper metal surface. The color resulting from interference shifts from blue, green, and yellow to red as the deposited metal layer thickens. Beyond a specific thickness, the optical interference vanishes, and the color turns bronze. Interference-colored anodized aluminum parts exhibit a distinctive quality: their color varies when viewed from different angles. The interference coloring involves a 3-step process: sulfuric acid anodizing, electrochemical modification of the anodic pore, and metal (tin) deposition. | 1 | Applied and Interdisciplinary Chemistry |
The Overlapping distribution method was introduced by Charles H. Bennett for estimating chemical potential. | 0 | Theoretical and Fundamental Chemistry |
The concept of a transition state has been important in many theories of the rates at which chemical reactions occur. This started with the transition state theory (also referred to as the activated complex theory), which was first developed around 1935 by Eyring, Evans and Polanyi, and introduced basic concepts in chemical kinetics that are still used today. | 0 | Theoretical and Fundamental Chemistry |
Provided a vertex unit is isolobal with BH then it can, in principle at least, be substituted for a BH unit, even though BH and CH are not isoelectronic. The CH unit is isolobal, hence the rules are applicable to carboranes. This can be explained due to a frontier orbital treatment. Additionally there are isolobal transition-metal units. For example, Fe(CO) provides 2 electrons. The derivation of this is briefly as follows:
*Fe has 8 valence electrons.
*Each carbonyl group is a net 2 electron donor after the internal σ- and π-bonding are taken into account making 14 electrons.
*3 pairs are considered to be involved in Fe–CO σ-bonding and 3 pairs are involved in π-backbonding from Fe to CO reducing the 14 to 2. | 0 | Theoretical and Fundamental Chemistry |
The following illustrate the principles.
The 1:1:1:1 quaternary compound between bromine, chlorine, iodine and phosphorus:
* phosphorus bromide chloride iodide (phosphorus is the most electropositive, the others are all designated as electronegative and are sequenced alphabetically)
The ternary 2:1:5 compound of antimony, copper and potassium can be named in two ways depending on which are designated as electronegative.
*CuKSb copper pentapotassium diantimonide, (both copper and potassium are designated as electropositive and are sequenced alphabetically)
*KCuSb pentapotassium diantimonide cupride (only potassium is designated as electropositive and the two electronegative elements are sequenced alphabetically) (Note the red book shows this example incorrectly) | 0 | Theoretical and Fundamental Chemistry |
The Bessel function at its upper limit becomes
which converges to
This is highly reminiscent of the Stokes layer on an oscillating flat plate, or the skin-depth penetration of an alternating magnetic field into an electrical conductor.
On the surface , but the exponential term becomes negligible once becomes large, the velocity profile becomes almost constant and independent of the viscosity. Thus, the flow simply oscillates as a plug profile in time according to the pressure gradient,
However, close to the walls, in a layer of thickness , the velocity adjusts rapidly to zero. Furthermore, the phase of the time oscillation varies quickly with position across the layer. The exponential decay of the higher frequencies is faster. | 1 | Applied and Interdisciplinary Chemistry |
In 2007 Houser et al. developed the analogous parameter to distinguish whether the geometry of the coordination center is square planar or tetrahedral. The formula is:
where: and are the two greatest valence angles of coordination center; is a tetrahedral angle.
When is close to 0 the geometry is similar to square planar, while if is close to 1 then the geometry is similar to tetrahedral. However, in contrast to the parameter, this does not distinguish and angles, so structures of significantly different geometries can have similar values. To overcome this issue, in 2015 Okuniewski et al. developed parameter that adopts values similar to but better differentiates the examined structures:
where: are the two greatest valence angles of coordination center; is a tetrahedral angle.
Extreme values of and denote exactly the same geometries, however is always less or equal to so the deviation from ideal tetrahedral geometry is more visible. If for tetrahedral complex the value of parameter is low, then one should check if there are some additional interactions within coordination sphere. For example, in complexes of mercury(II), the Hg···π interactions were found this way. | 0 | Theoretical and Fundamental Chemistry |
Due to their relatively weak bond dissociation energy (in comparison to C−C bonds and the like), disulfides have been employed in covalent adaptable network (CAN) systems in order to allow for dynamic breakage and reformation of crosslinks. By incorporating disulfide functional groups as crosslinks between polymer chains, materials can be produced which are stable at room temperature while also allowing for reversible crosslink dissociation upon application of elevated temperature. The mechanism behind this reaction can be attributed to the cleavage of disulfide linkages (RS−SR) into thiyl radicals (2 RS•) which can subsequently reassociate into new bonds, resulting in reprocessability and self-healing characteristics for the bulk material. However, since the bond dissociation energy of the disulfide bond is still fairly high, it is typically necessary to augment the bond with adjacent chemistry that can stabilize the unpaired electron of the intermediate state. As such, studies usually employ aromatic disulfides or disulfidediamine (RNS−SNR) functional groups to encourage the dynamic dissociation of the S−S bond; these chemistries can result in the bond dissociation energy being reduced to half (or even less) of its prior magnitude.
In practical terms, disulfide-containing CANs can be used to impart recyclability to polymeric materials while still exhibiting physical properties similar to that of thermosets. Typically, recyclability is restricted to thermoplastic materials, as said materials consist of polymer chains which are not bonded to each other at the molecular level; as a result, they can be melted down and reformed (as the addition of thermal energy allows the chains to untangle, move past each other, and adopt new configurations), but this comes at the expense of their physical robustness. Meanwhile, conventional thermosets contain permanent crosslinks which bolster their strength, toughness, creep resistance, and the like (as the bonding between chains provides resistance to deformation at the macroscopic level), but due to the permanence of said crosslinks, these materials cannot be reprocessed akin to thermoplastics. However, due to the dynamic nature of the crosslinks in disulfide CANs, they can be designed to exhibit the best attributes of both of the aforementioned material types. Studies have shown that disulfide CANs can be reprocessed multiple times with negligible degradation in performance while also exhibiting creep resistance, glass transition, and dynamic modulus values comparable to those observed in similar conventional thermoset systems. | 0 | Theoretical and Fundamental Chemistry |
Pathways utilizing nutrients found in low concentrations in the local environment are generally found in higher abundance in the virus. In marine environments, AMGs can confer fitness advantages for both host and viruses under relatively nutrient-limited conditions compared to sediment and strong ultraviolet stress of water. In sunlit versus dark ocean waters, AMGs in distinct pathways are unequally distributed to reprogram host energy production and viral replication based on available nutrients. In sedimentary environments, carbon and sulfur metabolism AMGs are typically more prevalent to outcompete other organisms for the abundant resources. | 1 | Applied and Interdisciplinary Chemistry |
Bryoamaride is a chemical compound isolated from certain plants, notably Bryonia dioica. It can be seen as a derivative of the triterpene hydrocarbon cucurbitane (), more specifically from cucurbitacin L or 23,24-dihydrocucurbitacin I.
The derivative 25-O-acetylbryoamaride is found in Trichosanthes tricuspidata. | 1 | Applied and Interdisciplinary Chemistry |
In the Fermi transition, the electron and neutrino emitted from the β-decay parent nucleus have spin vectors which are anti-parallel to one another.
This means
: no change in the total angular momentum of the nucleus
;Examples:
also parity is conserved: .
: = excited state of N | 0 | Theoretical and Fundamental Chemistry |
Memory metal has been utilized in orthopedic surgery as a fixation-compression device for osteotomies, typically for lower extremity procedures. The device, usually in the form of a large staple, is stored in a refrigerator in its malleable form and is implanted into pre-drilled holes in the bone across an osteotomy. As the staple warms it returns to its non-malleable state and compresses the bony surfaces together to promote bone union. | 1 | Applied and Interdisciplinary Chemistry |
Iron export occurs in a variety of cell types, including neurons, red blood cells, macrophages and enterocytes. The latter two are especially important since systemic iron levels depend upon them. There is only one known iron exporter, ferroportin. It transports ferrous iron out of the cell, generally aided by ceruloplasmin and/or hephaestin (mostly in enterocytes), which oxidize iron to its ferric state so it can bind ferritin in the extracellular medium. Hepcidin causes the internalization of ferroportin, decreasing iron export. Besides, hepcidin seems to downregulate both TFR1 and DMT1 through an unknown mechanism. Another player assisting ferroportin in effecting cellular iron export is GAPDH. A specific post translationally modified isoform of GAPDH is recruited to the surface of iron loaded cells where it recruits apo-transferrin in close proximity to ferroportin so as to rapidly chelate the iron extruded.
The expression of hepcidin, which only occurs in certain cell types such as hepatocytes, is tightly controlled at the transcriptional level and it represents the link between cellular and systemic iron homeostasis due to hepcidin's role as "gatekeeper" of iron release from enterocytes into the rest of the body. Erythroblasts produce erythroferrone, a hormone which inhibits hepcidin and so increases the availability of iron needed for hemoglobin synthesis. | 1 | Applied and Interdisciplinary Chemistry |
Annealing of the 3 end of one primer to itself or the second primer may cause primer extension, resulting in the formation of so-called primer dimers, visible as low-molecular-weight bands on PCR gels. Primer dimer formation often competes with formation of the DNA fragment of interest, and may be avoided using primers that are designed such that they lack complementarity—especially at the 3 ends—to itself or the other primer used in the reaction. If primer design is constrained by other factors and if primer-dimers do occur, methods to limit their formation may include optimisation of the MgCl concentration or increasing the annealing temperature in the PCR. | 1 | Applied and Interdisciplinary Chemistry |
Particular advantages of the powder technology include:
# Very high levels of purity and uniformity in starting materials
# Preservation of purity, due to the simpler subsequent fabrication process (fewer steps) that it makes possible
# Stabilization of the details of repetitive operations, by control of grain size during the input stages
# Absence of binding contact between segregated powder particles – or "inclusions" (called stringering) – as often occurs in melting processes
# No deformation needed to produce directional elongation of grains
# Capability to produce materials of controlled, uniform porosity.
# Capability to produce nearly net-shaped objects.
# Capability to produce materials which cannot be produced by any other technology.
# Capability to fabricate high-strength material like turbine blades.
# After sintering the mechanical strength to handling becomes higher.
The literature contains many references on sintering dissimilar materials to produce solid/solid-phase compounds or solid/melt mixtures at the processing stage. Almost any substance can be obtained in powder form, through either chemical, mechanical or physical processes, so basically any material can be obtained through sintering. When pure elements are sintered, the leftover powder is still pure, so it can be recycled. | 1 | Applied and Interdisciplinary Chemistry |
Control of the wetting contact angle can often be achieved through the deposition or incorporation of various organic and inorganic molecules onto the surface. This is often achieved through the use of specialty silane chemicals which can form a SAM (self-assembled monolayers) layer. With the proper selection of the organic molecules with varying molecular structures and amounts of hydrocarbon and/or perfluorinated terminations, the contact angle of the surface can tune. The deposition of these specialty silanes can be achieved in the gas phase through the use of a specialized vacuum ovens or liquid-phase process. Molecules that can bind more perfluorinated terminations to the surface can results in lowering the surface energy (high water contact angle). | 0 | Theoretical and Fundamental Chemistry |
For many years scientists in drug development have been blind to the three-dimensional consequences of stereochemistry, chiefly due to the lack of technology for making enantioselective investigations. Besides the thalidomide tragedy, another event that raised the importance of issues of stereochemistry in drug research and development was the publication of a manuscript in 1984 entitled, "Stereochemistry, a basis of sophisticated nonsense in pharmacokinetics and clinical pharmacology" by Ariëns. This article, and the series of articles that followed, criticized the practice of conducting pharmacokinetic and pharmacodynamic studies on racemic drugs and ignoring the separate contributions of the individual enantiomers. These papers have served to crystallize some of the important issues surrounding racemic drugs and stimulated much discussion in industry, government and academia. | 0 | Theoretical and Fundamental Chemistry |
An illustrative example: There are two types of Zintl ions in KSi; 2x (pseudo P,
or according to Wades rules, 12 = 2n + 4 skeletal-electrons corresponding to a nido'-form of a trigonal-bipyramid) and 1x
(according to Wades rules, 22 = 2n + 4 skeletal-electrons corresponding to a nido'-form of a bicapped square antiprism)
Examples from Müller's 1973 review paper with known structures are listed in the table below. | 0 | Theoretical and Fundamental Chemistry |
Several numerical studies of small lattice systems appear to tentatively confirm the predictions of the eigenstate thermalization hypothesis in interacting systems which would be expected to thermalize. Likewise, systems which are integrable tend not to obey the eigenstate thermalization hypothesis.
Some analytical results can also be obtained if one makes certain assumptions about the nature of highly excited energy eigenstates. The original 1994 paper on the ETH by Mark Srednicki studied, in particular, the example of a quantum hard sphere gas in an insulated box. This is a system which is known to exhibit chaos classically. For states of sufficiently high energy, Berrys conjecture states that energy eigenfunctions in this many-body system of hard sphere particles will appear to behave as superpositions of plane waves, with the plane waves entering the superposition with random' phases and Gaussian-distributed amplitudes (the precise notion of this random superposition is clarified in the paper). Under this assumption, one can show that, up to corrections which are negligibly small in the thermodynamic limit, the momentum distribution function for each individual, distinguishable particle is equal to the Maxwell–Boltzmann distribution
where is the particle's momentum, m is the mass of the particles, k is the Boltzmann constant, and the "temperature" is related to the energy of the eigenstate according to the usual equation of state for an ideal gas,
where N is the number of particles in the gas. This result is a specific manifestation of the ETH, in that it results in a prediction for the value of an observable in one energy eigenstate which is in agreement with the prediction derived from a microcanonical (or canonical) ensemble. Note that no averaging over initial states whatsoever has been performed, nor has anything resembling the H-theorem been invoked. Additionally, one can also derive the appropriate Bose–Einstein or Fermi–Dirac distributions, if one imposes the appropriate commutation relations for the particles comprising the gas.
Currently, it is not well understood how high the energy of an eigenstate of the hard sphere gas must be in order for it to obey the ETH. A rough criterion is that the average thermal wavelength of each particle be sufficiently smaller than the radius of the hard sphere particles, so that the system can probe the features which result in chaos classically (namely, the fact that the particles have a finite size ). However, it is conceivable that this condition may be able to be relaxed, and perhaps in the thermodynamic limit, energy eigenstates of arbitrarily low energies will satisfy the ETH (aside from the ground state itself, which is required to have certain special properties, for example, the lack of any nodes ). | 0 | Theoretical and Fundamental Chemistry |
Chemical potential is the partial molar free energy. The potential, μ, of the ith species in a chemical reaction is the partial derivative of the free energy with respect to the number of moles of that species, N:
A general chemical equilibrium can be written as
n are the stoichiometric coefficients of the reactants in the equilibrium equation, and m are the coefficients of the products. The value of δG for these reactions is a function of the chemical potentials of all the species.
The chemical potential, μ, of the ith species can be calculated in terms of its activity, a.
μ is the standard chemical potential of the species, R is the gas constant and T is the temperature. Setting the sum for the reactants j to be equal to the sum for the products, k, so that δG(Eq) = 0:
Rearranging the terms,
This relates the standard Gibbs free energy change, ΔG</sup> to an equilibrium constant, K, the reaction quotient of activity values at equilibrium.
It follows that any equilibrium of this kind can be characterized either by the standard free energy change or by the equilibrium constant. In practice concentrations are more useful than activities. Activities can be calculated from concentrations if the activity coefficient are known, but this is rarely the case. Sometimes activity coefficients can be calculated using, for example, Pitzer equations or Specific ion interaction theory. Otherwise conditions must be adjusted so that activity coefficients do not vary much. For ionic solutions this is achieved by using a background ionic medium at a high concentration relative to the concentrations of the species in equilibrium.
If activity coefficients are unknown they may be subsumed into the equilibrium constant, which becomes a concentration quotient. Each activity a is assumed to be the product of a concentration, [A], and an activity coefficient, γ:
This expression for activity is placed in the expression defining the equilibrium constant.
By setting the quotient of activity coefficients, Γ, equal to one, the equilibrium constant is defined as a quotient of concentrations.
In more familiar notation, for a general equilibrium
:α A + β B ... σ S + τ T ...
This definition is much more practical, but an equilibrium constant defined in terms of concentrations is dependent on conditions. In particular, equilibrium constants for species in aqueous solution are dependent on ionic strength, as the quotient of activity coefficients varies with the ionic strength of the solution.
The values of the standard free energy change and of the equilibrium constant are temperature dependent. To a first approximation, the van 't Hoff equation may be used.
This shows that when the reaction is exothermic (ΔH</sup>, is independent of temperature, which is a good approximation only over a small temperature range. Thermodynamic arguments can be used to show that
where C is the heat capacity at constant pressure. | 0 | Theoretical and Fundamental Chemistry |
Predicted or estimated protein chemical shifts can be used to assist with the chemical shift assignment process. This is especially true if a similar (or identical) protein structure has been solved by X-ray crystallography. In this case, the three-dimensional structure can be used to estimate what the NMR chemical shifts should be and thereby simplify the process of assigning the experimentally observed chemical shifts. Predicted/estimated protein chemical shifts can also be used to identify incorrect or mis-assignments, to correct mis-referenced or incorrectly referenced chemical shifts, to optimize protein structures via chemical shift refinement and to identify the relative contributions of different electronic or geometric effects to nucleus-specific shifts. Protein chemical shifts can also be used to identify secondary structures, to estimate backbone torsion angles, to determine the location of aromatic rings, to assess cysteine oxidation states, to estimate solvent exposure and to measure backbone flexibility. | 0 | Theoretical and Fundamental Chemistry |
The Buckingham π theorem describes how every physically meaningful equation involving variables can be equivalently rewritten as an equation of dimensionless parameters, where m is the rank of the dimensional matrix. Furthermore, and most importantly, it provides a method for computing these dimensionless parameters from the given variables.
A dimensional equation can have the dimensions reduced or eliminated through nondimensionalization, which begins with dimensional analysis, and involves scaling quantities by characteristic units of a system or physical constants of nature. This may give insight into the fundamental properties of the system, as illustrated in the examples below.
The dimension of a physical quantity can be expressed as a product of the base physical dimensions such as length, mass and time, each raised to an integer (and occasionally rational) power. The dimension of a physical quantity is more fundamental than some scale or unit used to express the amount of that physical quantity. For example, mass is a dimension, while the kilogram is a particular reference quantity chosen to express a quantity of mass. The choice of unit is arbitrary, and its choice is often based on historical precedent. Natural units, being based on only universal constants, may be thought of as being "less arbitrary".
There are many possible choices of base physical dimensions. The SI standard selects the following dimensions and corresponding dimension symbols:
: time (T), length (L), mass (M), electric current (I), absolute temperature (Θ), amount of substance (N) and luminous intensity (J).
The symbols are by convention usually written in roman sans serif typeface. Mathematically, the dimension of the quantity is given by
where , , , , , , are the dimensional exponents. Other physical quantities could be defined as the base quantities, as long as they form a linearly independent basis – for instance, one could replace the dimension (I) of electric current of the SI basis with a dimension (Q) of electric charge, since .
A quantity that has only (with all other exponents zero) is known as a geometric quantity. A quantity that has only both and is known as a kinematic quantity. A quantity that has only all of , , and is known as a dynamic quantity.
A quantity that has all exponents null is said to have dimension one.
The unit chosen to express a physical quantity and its dimension are related, but not identical concepts. The units of a physical quantity are defined by convention and related to some standard; e.g., length may have units of metres, feet, inches, miles or micrometres; but any length always has a dimension of L, no matter what units of length are chosen to express it. Two different units of the same physical quantity have conversion factors that relate them. For example, ; in this case 2.54 cm/in is the conversion factor, which is itself dimensionless. Therefore, multiplying by that conversion factor does not change the dimensions of a physical quantity.
There are also physicists who have cast doubt on the very existence of incompatible fundamental dimensions of physical quantity, although this does not invalidate the usefulness of dimensional analysis. | 1 | Applied and Interdisciplinary Chemistry |
The basic oxygen process developed outside of traditional "big steel" environment. It was developed and refined by a single man, Swiss engineer Robert Durrer, and commercialized by two small steel companies in allied-occupied Austria, which had not yet recovered from the destruction of World War II.
In 1856, Henry Bessemer had patented a steelmaking process involving oxygen blowing for decarbonizing molten iron (UK Patent No. 2207). For nearly 100 years commercial quantities of oxygen were not available or were too expensive, and the invention remained unused. During WWII German (Karl Valerian Schwarz), Belgian (John Miles) and Swiss (Durrer and Heinrich Heilbrugge) engineers proposed their versions of oxygen-blown steelmaking, but only Durrer and Heilbrugge brought it to mass-scale production.
In 1943, Durrer, formerly a professor at the Berlin Institute of Technology, returned to Switzerland and accepted a seat on the board of Roll AG, the country's largest steel mill. In 1947 he purchased the first small 2.5-ton experimental converter from the US, and on April 3, 1948 the new converter produced its first steel. The new process could conveniently process large amounts of scrap metal with only a small proportion of primary metal necessary. In the summer of 1948, Roll AG and two Austrian state-owned companies, VÖEST and ÖAMG, agreed to commercialize the Durrer process.
By June 1949, VÖEST developed an adaptation of Durrers process, known as the LD (Linz-Donawitz) process. In December 1949, VÖEST and ÖAMG committed to building their first 30-ton oxygen converters. They were put into operation in November 1952 (VÖEST in Linz) and May 1953 (ÖAMG, Donawitz) and temporarily became the leading edge of the worlds steelmaking, causing a surge in steel-related research. Thirty-four thousand businesspeople and engineers visited the VÖEST converter by 1963. The LD process reduced processing time and capital costs per ton of steel, contributing to the competitive advantage of Austrian steel. VÖEST eventually acquired the rights to market the new technology. Errors by the VÖEST and the ÖAMG management in licensing their technology made control over its adoption in Japan impossible. By the end of the 1950s, the Austrians lost their competitive edge.
In the original LD process, oxygen was blown over the top of the molten iron through the water-cooled nozzle of a vertical lance. In the 1960s, steelmakers introduced bottom-blown converters and developed inert gas blowing for stirring the molten metal and removing phosphorus impurities.
In the Soviet Union, some experimental production of steel using the process was done in 1934, but industrial use was hampered by lack of efficient technology to produce liquid oxygen. In 1939, the Russian physicist Pyotr Kapitsa perfected the design of the centrifugal turboexpander. The process was put to use in 1942–1944. Most turboexpanders in industrial use since then have been based on Kapitsa's design and centrifugal turboexpanders have taken over almost 100% of industrial gas liquefaction, and in particular the production of liquid oxygen for steelmaking.
Big American steelmakers were late adopters of the new technology. The first oxygen converters in the US were launched at the end of 1954 by McLouth Steel in Trenton, Michigan, which accounted for less than 1% of the national steel market. U.S. Steel and Bethlehem Steel introduced the oxygen process in 1964. By 1970, half of the worlds and 80% of Japans steel output was produced in oxygen converters.
In the last quarter of the 20th century, use of basic oxygen converters for steel production was gradually, partially replaced by the electric arc furnace using scrap steel and iron. In Japan the share of LD process decreased from 80% in 1970 to 70% in 2000; worldwide share of the basic oxygen process stabilized at 60%. | 1 | Applied and Interdisciplinary Chemistry |
Once particles have aggregated to several micrometers in diameter, they begin to accumulate bacteria, since there is sufficient site space for feeding and reproduction. At this size, it is large enough to undergo sinking. It also has the components necessary to fit the "aggregate spinning wheel hypothesis". Evidence for this has been found by Alldredge and Cohen (1987) who found evidence of both respiration and photosynthesis within aggregates, suggesting the presence of both autotrophic and heterotrophic organisms. During zooplankton's vertical migration, the abundances of aggregates increased while size distributions decreased. Aggregates were found in the abdomen in zooplankton indicating their grazing will fragment larger aggregates. | 0 | Theoretical and Fundamental Chemistry |
Species community assemblages and changes therein can help researchers to infer changes in the health of an ecosystem. In typical unpolluted temperate streams of Europe and North America, certain insect taxa predominate. Mayflies (Ephemeroptera), caddisflies (Trichoptera), and stoneflies (Plecoptera) are the most common insects in these undisturbed streams. In contrast, in rivers disturbed by urbanization, agriculture, forestry, and other perturbations, flies (Diptera), and especially midges (family Chironomidae) predominate. | 1 | Applied and Interdisciplinary Chemistry |
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