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Photocurable adhesives are also used in the production of catheters, hearing aids, surgical masks, medical filters, and blood analysis sensors. Photopolymers have also been explored for uses in drug delivery, tissue engineering and cell encapsulation systems. Photopolymerization processes for these applications are being developed to be carried out in vivo or ex vivo. In vivo photopolymerization would provide the advantages of production and implantation with minimal invasive surgery. Ex vivo photopolymerization would allow for fabrication of complex matrices and versatility of formulation. Although photopolymers show promise for a wide range of new biomedical applications, biocompatibility with photopolymeric materials must still be addressed and developed. | 5 | Photochemistry |
*Steric effects strain – Increasing the steric strain of the chelate backbone in square planar complexes pushes the carbonyl and methyl groups closer together, increasing the reactivity of insertion reactions.
*Oxidation state – Oxidation of the metal tends to increase insertion reaction rates. The main rate-limiting step in the mechanism is the migration of the methyl group onto a carbonyl ligand, oxidizing the metal by imparting a greater partial positive charge on the acetyl carbon, and thus increasing the rate of reaction.
*Lewis acids – Lewis acids also increase the reaction rates, for reasons similar to metal oxidation increasing the positive charge on the carbon. Lewis acids bind to the CO oxygen and remove charge, increasing the electrophilicity of the carbon. This can increase the reaction rate by a factor of up to 10, and the complex formed is stable enough that the reaction proceeds even without additional CO to bind to the metal.
*Electronegativity of the leaving group - Increasing the electronegativity of the leaving alkyl group stabilizes the metal-carbon bond interaction and thus increases the activation energy required for migration, decreasing the reaction rate.
*Trans-effect – Ligands in an octahedral or square planar complex are known to influence the reactivity of the group to which they are trans. This ligand influence is often referred to as the trans-influence, and it varies in intensity between ligands. A partial list of trans-influencing ligands is as follows, from highest trans-effect to lowest: aryl, alkyl > NR > PR > AsR > CO > Cl. Ligands with a greater trans-influence impart greater electrophilicity to the active site. Increasing the electrophilicity of the CO group has been shown experimentally to greatly increase the reaction rate, while decreasing the electrophilicity of the methyl group slightly increases the reaction rate. This can be demonstrated by reacting a square planar [(PN)M(CO)(CH)] complex with CO, where PN is a bidentate phosphorus- or nitrogen-bound ligand. This reaction proceeds in much greater yield when the methyl group is trans-P and the CO trans-N, owing to the higher trans-influence of the more electronegative nitrogen. | 0 | Organic Chemistry |
There are many variations to the general phycobilisome structure. Their shape can be hemidiscoidal (in cyanobacteria) or hemiellipsoidal (in red algae). Species lacking phycoerythrin have at least two disks of phycocyanin per rod, which is sufficient for maximum photosynthesis.
The phycobiliproteins themselves show little sequence evolution due to their highly constrained function (absorption and transfer of specific wavelengths).
In some species of cyanobacteria, when both phycocyanin and phycoerythrin is present, the phycobilisome can undergo significant restructuring as response to light color. In green light the distal portions of the rods are made of red colored phycoerythrin, which absorbs green light better. In red light, this is replaced by blue colored phycocyanin, which absorbs red light better. This reversible process is known as complementary chromatic adaptation. It is the component of photosynthetic system of cyanobacteria, as a particle with which various structures are linked (i.e. thylakoid membrane, etc). | 5 | Photochemistry |
In polymer chemistry, chain walking (CW) or chain running or chain migration is a mechanism that operates during some alkene polymerization reactions. CW can be also considered as a specific case of intermolecular chain transfer (analogous to radical ethene polymerization). This reaction gives rise to branched and hyperbranched/dendritic hydrocarbon polymers. This process is also characterized by accurate control of polymer architecture and topology. The extent of CW, displayed in the number of branches formed and positions of branches on the polymers are controlled by the choice of a catalyst. The potential applications of polymers formed by this reaction are diverse, from drug delivery to phase transfer agents, nanomaterials, and catalysis. | 7 | Physical Chemistry |
The following issues are commonly observed during acid-base extraction and typically have simple solutions
* Only one layer is observed in the separatory funnel.
** This is due to using an organic solvent with significant miscibility with water (e.g. acetonitrile). The organic solvent used must be water-insoluble to observe phase separation and perform an acid-base extraction.
* Three layers form in the separatory funnel.
** Often this is a result of insufficient mixing, and light stirring will solve the issue.
* The boundary between the organic layer and aqueous layer is not observed.
** Ice can be used to identify the boundary as it will float between the two layers.
* An emulsion forms and one layer is suspended in the other as tiny droplets.
** This can be solved by using a glass stirring rod to gently "push" the tiny droplets into each other, eventually resulting in separation and causing the two layers to appear. Adding a small amount of brine solution can also be used to break up the emulsion; this process is termed "salting out". Emulsions can be prevented by mixing the solutions gently rather than vigorously.
* The relative positions of the aqueous/organic layers are unknown.
** A small amount of water can be added to the separatory funnel. Whichever layer these droplets go into is identified as the aqueous layer. | 7 | Physical Chemistry |
Quartz dolerite or quartz diabase is an intrusive rock similar to dolerite (also called diabase), but with an excess of quartz. Dolerite is similar in composition to basalt, which is volcanic, and gabbro, which is plutonic. The differing crystal sizes are due to the different rate of cooling, basalt cools quickly and has a very fine structure, while gabbro cools very slowly, at great depth, and large crystals develop. Dolerite is intermediate.
Quartz dolerite is very common in central Scotland, in intrusive formations, sills and dykes, and is widely quarried for roadstone. It was used with some success for making millstones at one time, the Millstone Grit part of the carboniferous strata not being present in Scotland, but it is no longer used for this purpose, and would probably be illegal now due to the formation of small quartz and other silicate particles, which could cause the serious respiratory disease silicosis.
In Scotland, quartz dolerite is commonly known as whin or whinstone.
Quartz dolerite contains many cooling fractures and weathers readily, becoming unstable. It is not uncommon for large boulders to break loose, and significant rockfalls are not uncommon. It is regarded as dangerous as far as climbing is concerned. | 9 | Geochemistry |
The inductive effect also plays a vital role in deciding the acidity and basicity of a molecule. Groups having +I effect (Inductive effect) attached to a molecule increases the overall electron density on the molecule and the molecule is able to donate electrons, making it basic. Similarly, groups having -I effect attached to a molecule decreases the overall electron density on the molecule making it electron deficient which results in its acidity. As the number of -I groups attached to a molecule increases, its acidity increases; as the number of +I groups on a molecule increases, its basicity increases. | 7 | Physical Chemistry |
The Caspian has characteristics common to both seas and lakes. It is often listed as the world's largest lake, although it is not freshwater: the 1.2% salinity classes it with brackish water bodies.
It contains about 3.5 times as much water, by volume, as all five of North Americas Great Lakes combined. The Volga River (about 80% of the inflow) and the Ural River discharge into the Caspian Sea, but it has no natural outflow other than by evaporation. Thus the Caspian ecosystem is a closed basin, with its own sea level history that is independent of the eustatic level of the worlds oceans.
The sea level of the Caspian has fallen and risen, often rapidly, many times over the centuries. Some Russian historians claim that a medieval rising of the Caspian, perhaps caused by the Amu Darya changing its inflow to the Caspian from the 13th century to the 16th century, caused the coastal towns of Khazaria, such as Atil, to flood. In 2004, the water level was below sea level.
Over the centuries, Caspian Sea levels have changed in synchrony with the estimated discharge of the Volga, which in turn depends on rainfall levels in its vast catchment basin. Precipitation is related to variations in the amount of North Atlantic depressions that reach the interior, and they in turn are affected by cycles of the North Atlantic oscillation. Thus levels in the Caspian Sea relate to atmospheric conditions in the North Atlantic, thousands of kilometres to the northwest.
The last short-term sea-level cycle started with a sea-level fall of from 1929 to 1977, followed by a rise of from 1977 until 1995. Since then smaller oscillations have taken place.
A study by the Azerbaijan Academy of Sciences estimated that the level of the sea was dropping by more than six centimetres per year due to increased evaporation due to rising temperatures caused by climate change. | 2 | Environmental Chemistry |
The adaptor protein Grb2 forms a complex with Sos by the Grb2 SH3 domain. Grb2 (or the Grb2/Sos complex) is recruited to the membrane by the Grb2 SH2 domain binding to activated PDGFR-bound SHP2 (also known as PTPN11, a cytosolic PTP), thereby allowing interaction with Ras and the exchange of GDP for GTP on Ras. Whereas the interaction between Grb2 and PDGFR occurs through interaction with the SHP2 protein, Grb2 instead binds to activated EGFR through Shc, another adaptor protein that forms a complex with many receptors via its PTB domain. Once activated, Ras interacts with several proteins, namely Raf. Activated Raf stimulates MAPK-kinase (MAPKK or MEK) by phosphorylating a serine residue in its activation loop. MAPKK then phosphorylates MAPK (ERK1/2) on T and Y residues at the activation-loop leading to its activation. Activated MAPK phosphorylates a variety of cytoplasmic substrates, as well as transcription factors, when translocated into the nucleus. MAPK family members have been found to regulate various biological functions by phosphorylation of particular target molecules (such as transcription factors, other kinases etc.) located in cell membrane, cytoplasm and nucleus, and thus contribute to the regulation of different cellular processes such as cell proliferation, differentiation, apoptosis and immunoresponses. | 1 | Biochemistry |
When a photon is absorbed, the electromagnetic field of the photon disappears as it initiates a change in the state of the system that absorbs the photon. Energy, momentum, angular momentum, magnetic dipole moment and electric dipole moment are transported from the photon to the system. Because there are conservation laws, that have to be satisfied, the transition has to meet a series of constraints. This results in a series of selection rules. It is not possible to make any transition that lies within the energy or frequency range that is observed.
The strength of an electromagnetic absorption process is mainly determined by two factors. First, transitions that only change the magnetic dipole moment of the system are much weaker than transitions that change the electric dipole moment and that transitions to higher order moments, like quadrupole transitions, are weaker than dipole transitions. Second, not all transitions have the same transition matrix element, absorption coefficient or oscillator strength.
For some types of bands or spectroscopic disciplines temperature and statistical mechanics plays an important role. For (far) infrared, microwave and radio frequency ranges the temperature dependent occupation numbers of states and the difference between Bose-Einstein statistics and Fermi-Dirac statistics determines the intensity of observed absorptions. For other energy ranges thermal motion effects, like Doppler broadening may determine the linewidth. | 7 | Physical Chemistry |
With the advent of modern laboratory techniques such as High-throughput sequencing and software capable of genome-wide analysis, sequence acquisition has become increasingly less expensive and time-consuming, thus providing significant benefits to science in the form of more efficient disease gene identification techniques. | 1 | Biochemistry |
The Dutch (the Netherlands), who are members of the International Hallmarking Convention, have been striking hallmarks since at least 1814, and boast a 600-year history of hallmarking in Dutch territories. Like many other nations, the Dutch require the registration and use of Responsibility Marks since 1797. The Dutch also use a date letter code.
After the French defeat at Leipzig 1813 the Kingdom of the Netherlands was established. William VI, prince of Orange (known in Dutch as Willem Frederik), was proclaimed the sovereign. On March 15, 1815, with the support of the powers gathered at the Congress of Vienna, William proclaimed himself King William I of the Netherlands. He was also made grand duke of Luxembourg. The two countries remained separate despite sharing a common monarch. For our purposes, he retained much of the French legislation, including the precious metal guarantee law of November 9, 1787. On December 26, 1813, the precious metal laws were however, modified and the French hallmarks, the Gaul cockerels were replaced with Dutch lions. The existing guarantee offices were reopened after re-staffing and the production of the new hallmark dies. Willem abdicated in 1840. As of January 1, 1853, the out-of-date French guarantee law was replaced by a new Dutch law. This law of September 18, 1852, in a modified form (last modified in 1986 as the "Dutch Assay Law of 1986") is in still effective. As a result of the Benelux treaty the guarantee tax was abolished in 1953. At the same time gold and silver fineness standards were adapted to conform to international standards. Also the assaying of platinum was introduced in 1953.
In 1987, the assay system was privatized and since 1988 has been located in only an office at Gouda. The system is overseen by the Dutch Ministry of Economic Affairs which appointed Edelmetaal Waarborg Nederland B.V. as of March 11, 2002. In 1999, the Netherlands ratified the Vienna Convention on the Control of the Fineness and the Hallmarking of Precious Metal Objects.
Dutch hallmarks are recognized in Austria, France, Ireland, Portugal, Spain and the United Kingdom without further testing and have also been recognized in Belgium, Denmark, Finland and Sweden, which have voluntary hallmarking systems. All jewelry produced in the Netherlands or imported for the Dutch market must carry hallmarks. | 3 | Analytical Chemistry |
Mathematically, a wallpaper group or plane crystallographic group is a type of topologically discrete group of isometries of the Euclidean plane that contains two linearly independent translations.
Two such isometry groups are of the same type (of the same wallpaper group) if they are the same up to an affine transformation of the plane. Thus e.g. a translation of the plane (hence a translation of the mirrors and centres of rotation) does not affect the wallpaper group. The same applies for a change of angle between translation vectors, provided that it does not add or remove any symmetry (this is only the case if there are no mirrors and no glide reflections, and rotational symmetry is at most of order 2).
Unlike in the three-dimensional case, one can equivalently restrict the affine transformations to those that preserve orientation.
It follows from the Bieberbach theorem that all wallpaper groups are different even as abstract groups (as opposed to e.g. frieze groups, of which two are isomorphic with Z).
2D patterns with double translational symmetry can be categorized according to their symmetry group type. | 3 | Analytical Chemistry |
Oxaziridine derivatives were first reported in the mid-1950s by Emmons and subsequently by Krimm and Horner and Jürgens. Whereas oxygen and nitrogen typically act as nucleophiles due to their high electronegativity, oxaziridines allow for electrophilic transfer of both heteroatoms. This unusual reactivity is due to the presence of the highly strained three membered ring and the relatively weak N-O bond. Nucleophiles tend to attack at the aziridine nitrogen when the nitrogen substituent is small (R= H), and at the oxygen atom when the nitrogen substituent has greater steric bulk. The unusual electronics of the oxaziridine system may be exploited to perform a number of oxygen and nitrogen transfer reactions including, but not limited to: α-hydroxylation of enolates, epoxidation of alkenes, selective oxidation of sulfides and selenides, amination of N-nucleophiles and N-acylamidation.
The peroxide process for the industrial production of hydrazine through the oxidation of ammonia with hydrogen peroxide in the presence of ketones was developed in the early 1970s.
Chiral camphorsulfonyloxaziridines proved useful in the syntheses of complex products, such as taxol which is marketed as a chemotherapy agent. Both the Holton Taxol total synthesis and the Wender Taxol total synthesis feature asymmetric α-hydroxylation with camphorsulfonyloxaziridine. | 0 | Organic Chemistry |
NF-kB is a transcription factor that can be activated by p75NTR. Nerve growth factor (NGF) is a neurotrophin that promotes neuronal growth, and, in the absence of NGF, neurons die. Neuronal death in the absence of NGF can be prevented by NF-kB activation. Phosphorylated IκB kinase binds to and activates NF-kB before separating from NF-kB. After separation, IκB degrades and NF-kB continues to the nucleus to initiate pro-survival transcription. NF-kB also promotes neuronal survival in conjunction with NGF.
NF-kB activity is activated by p75NTR, and is not activated via Trk receptors. NF-kB activity does not effect Brain-derived neurotrophic factor promotion of neuronal survival. | 1 | Biochemistry |
A photochromic complex is a kind of chemical compound that has photoresponsive parts on its ligand. These complexes have a specific structure: photoswitchable organic compounds are attached to metal complexes. For the photocontrollable parts, thermally and photochemically stable chromophores (azobenzene, diarylethene, spiropyran, etc.) are usually used. And for the metal complexes, a wide variety of compounds that have various functions (redox response, luminescence, magnetism, etc.) are applied.
The photochromic parts and metal parts are so close that they can affect each other's molecular orbitals. The physical properties of these compounds shown by parts of them (i.e., chromophores or metals) thus can be controlled by switching their other sites by external stimuli. For example, photoisomerization behaviors of some complexes can be switched by oxidation and reduction of their metal parts. Some other compounds can be changed in their luminescence behavior, magnetic interaction of metal sites, or stability of metal-to-ligand coordination by photoisomerization of their photochromic parts. | 5 | Photochemistry |
Diphenylchlorarsine was used as a chemical weapon on the Western front during the trench warfare of World War I. It belongs to the class of chemicals classified as vomiting agents. Other such agents are diphenylcyanoarsine (DC) and diphenylaminechlorarsine (DM, Adamsite). Diphenylchlorarsine was sometimes believed to penetrate the gas masks of the time and to cause violent sneezing, forcing removal of the protecting device. The Germans called it (mask breaker), together with other substances with similar effects, such as Adamsite, diphenylarsincyanide, and diphenylaminarsincyanide. This gas did not actually penetrate masks any better than other gases.
DA (military code and acronym for diphenylchloroarsine) is a precursor to DC (diphenylcyanoarsine), generated by the reaction of an aqueous solution of sodium cyanide and DA (DC process, NaCN method), with cyanide being used in excess of 5%, for military purposes. | 1 | Biochemistry |
Ishikawas reagent is a fluorinating reagent used in organic chemistry. It is used to convert alcohols into alkyl fluorides and carboxylic acids into acyl fluorides. Aldehydes and ketones do not react with it. The reagent consists of a mixture of N,N-diethyl-(1,1,2,3,3,3-hexafluoropropyl)amine and N,N-diethyl-(E')-pentafluoropropenylamine in varying proportions. The active species is the hexafluoropropylamine; any enamine is converted into this by the hydrogen fluoride byproduct as the reaction proceeds.
Ishikawas reagent is a popular alternative to the DAST reagent, since it is shelf-stable and easily prepared from inexpensive and innocuous reagents. It is an improvement on Yarovenkos reagent, the adduct of chlorotrifluoroethylene and diethylamine, which must be prepared in a sealed vessel and once prepared keeps only for a few days, even in the refrigerator.
The reagent is mostly used to convert primary alcohols to alkyl fluorides under mild conditions with high yield. However, secondary and tertiary alcohols give a substantial amount of alkenes and ethers as side products. | 0 | Organic Chemistry |
Excess heme is converted in macrophages to Biliverdin and ferrous ions by the enzyme HO-1. Biliverdin formed further gets converted to Bilirubin and carbon monoxide. Biliverdin and Bilirubin are potent anti oxidants and regulate important biological processes like inflammation, apoptosis, cell proliferation, fibrosis and angiogenesis. | 1 | Biochemistry |
The Ewald sphere is a geometric construction used in electron, neutron, and x-ray diffraction which shows the relationship between:
* the wavevector of the incident and diffracted beams,
* the diffraction angle for a given reflection,
* the reciprocal lattice of the crystal.
It was conceived by Paul Peter Ewald, a German physicist and crystallographer. Ewald himself spoke of the sphere of reflection. It is often simplified to the two-dimensional "Ewald's circle" model or may be referred to as the Ewald sphere. | 3 | Analytical Chemistry |
The Volga River, the longest river in Europe, drains 20% of the European land area and is the source of 80% of the Caspian's inflow. Heavy development in its lower reaches has caused numerous unregulated releases of chemical and biological pollutants. The UN Environment Programme warns that the Caspian "suffers from an enormous burden of pollution from oil extraction and refining, offshore oil fields, radioactive wastes from nuclear power plants and huge volumes of untreated sewage and industrial waste introduced mainly by the Volga River".
The magnitude of fossil fuel extraction and transport activity in the Caspian also poses a risk to the environment. The island of Vulf off Baku, for example, has suffered ecological damage as a result of the petrochemical industry; this has significantly decreased the number of species of marine birds in the area. Existing and planned oil and gas pipelines under the sea further increase the potential threat to the environment.
The high concentration of mud volcanoes under the Caspian Sea were thought to be the cause of a fire that broke out 75 kilometers from Baku on July 5, 2021. The State oil company of Azerbaijan SOCAR said preliminary information indicated it was a mud volcano which spewed both mud and flammable gas.
It is calculated that during the 21st century, the water level of the Caspian Sea will decrease by 9–18 m (30–60 ft) due to the acceleration of evaporation due to global warming and the process of desertification, causing an ecocide.
On October 23, 2021, Kazakhstan President Kassym-Jomart Tokayev signed the Protocol for the Protection of the Caspian Sea against Pollution from Land-based Sources in order to ensure better protection for the biodiversity of the Caspian Sea. | 2 | Environmental Chemistry |
Large quantities of fecal coliform bacteria in water are not harmful according to some authorities, but may indicate a higher risk of pathogens being present in the water. Some waterborne pathogenic diseases that may coincide with fecal coliform contamination include ear infections, dysentery, typhoid fever, viral and bacterial gastroenteritis, and hepatitis A. | 3 | Analytical Chemistry |
Macromolecular structures can be determined from protein crystal using a variety of methods, including X-Ray Diffraction/X-ray crystallography, Cryogenic Electron Microscopy (CryoEM) (including Electron Crystallography and Microcrystal Electron Diffraction (MicroED)), Small-angle X-ray scattering, and Neutron diffraction. See also Structural biology.
Crystallization of proteins can also be useful in the formulation of proteins for pharmaceutical purposes. | 3 | Analytical Chemistry |
In a crystal containing different cations, those of high valency and small coordination number tend not to share polyhedron elements with one another. This rule tends to increase the distance between highly charged cations, so as to reduce the electrostatic repulsion between them.
One of Pauling's examples is olivine, , where M is a mixture of at some sites and at others. The structure contains distinct tetrahedra which do not share any oxygens (at corners, edges or faces) with each other. The lower-valence and cations are surrounded by polyhedra which do share oxygens. | 4 | Stereochemistry |
A combustion train is an analytical tool for the determination of elemental composition of a chemical compound. With knowledge of elemental composition a chemical formula can be derived. The combustion train allows the determination of carbon and hydrogen in a succession of steps:
* combustion of the sample at high temperatures with Copper(II) oxide as the oxidizing agent,
* collection of the resulting gas in a hygroscopic agent (magnesium perchlorate or calcium chloride) to trap generated water,
* collection of the remainder gas in a strong base (for instance potassium hydroxide) to trap generated carbon dioxide.
Analytical determination of the amounts of water and carbon dioxide produced from a known amount of sample gives the empirical formula. For every hydrogen atom in the compound 1/2 equivalent of water is produced, and for every carbon atom in the compound 1 equivalent of carbon dioxide is produced.
Nowadays, modern instruments are sufficiently automated to be able to do these analyses routinely. Samples required are also extremely small — 0.5 mg of sample can be sufficient to give satisfactory CHN analysis. | 0 | Organic Chemistry |
Historically, one distinguishes between the normal and an anomalous Zeeman effect (discovered by Thomas Preston in Dublin, Ireland). The anomalous effect appears on transitions where the net spin of the electrons is non-zero. It was called "anomalous" because the electron spin had not yet been discovered, and so there was no good explanation for it at the time that Zeeman observed the effect. Wolfgang Pauli recalled that when asked by a colleague as to why he looked unhappy, he replied, "How can one look happy when he is thinking about the anomalous Zeeman effect?"
At higher magnetic field strength the effect ceases to be linear. At even higher field strengths, comparable to the strength of the atom's internal field, the electron coupling is disturbed and the spectral lines rearrange. This is called the Paschen–Back effect.
In the modern scientific literature, these terms are rarely used, with a tendency to use just the "Zeeman effect".
Another rarely used obscure term is inverse Zeeman effect, referring to the Zeeman effect in an absorption spectral line.
A similar effect, splitting of the nuclear energy levels in the presence of a magnetic field, is referred to as the nuclear Zeeman effect. | 7 | Physical Chemistry |
An analytical calculation of the VIPA was first performed by Vega and Weiner in 2003 based on the theory of plane waves and an improved model based on the Fresnel diffraction theory was developed by Xiao and Weiner in 2004. | 7 | Physical Chemistry |
The antibody based methods use designed antibodies to bind to proteins of interest, allowing the relative abundance of multiple individual targets to be identified by one of several different techniques.
Imaging: Antibodies can be bound to fluorescent molecules such as quantum dots or tagged with organic fluorophores for detection by fluorescence microscopy. Since different colored quantum dots or unique fluorophores are attached to each antibody it is possible to identify multiple different proteins in a single cell. Quantum dots can be washed off of the antibodies without damaging the sample, making it possible to do multiple rounds of protein quantification using this method on the same sample. For the methods based on organic fluorophores, the fluorescent tags are attached by a reversible linkage such as a DNA-hybrid (that can be melted/dissociated under low-salt conditions) or chemically inactivated, allowing multiple cycles of analysis, with 3-5 targets quantified per cycle. These approaches have been used for quantifying protein abundance in patient biopsy samples (e.g. cancer) to map variable protein expression in tissues and/or tumors, and to measure changes in protein expression and cell signaling in response to cancer treatment.
Mass Cytometry: rare metal isotopes, not normally found in cells or tissues, can be attached to the individual antibodies and detected by mass spectrometry for simultaneous and sensitive identification of proteins. These techniques can be highly multiplexed for simultaneous quantification of many targets (panels of up to 38 markers) in single cells.
Antibody-DNA quantification: another antibody-based method converts protein levels to DNA levels. The conversion to DNA makes it possible to amplify protein levels and use NGS to quantify proteins. In one such approach, two antibodies are selected for each protein needed to be quantified. The two antibodies are then modified to have single stranded DNA connected to them that are complementary. When the two antibodies bind to a protein the complementary strands will anneal and produce a double stranded segment of DNA that can then be amplified using PCR. Each pair of antibodies designed for one protein is tagged with a different DNA sequence. The DNA amplified from PCR can then be sequenced, and the protein levels quantified. | 1 | Biochemistry |
Besides the classic MAP groups, novel MAPs have been identified that bind the length of the microtubules. These include STOP (also known as MAP6), and ensconsin (also known as MAP7).
In addition, plus end tracking proteins, which bind to the very tip of growing microtubules, have also been identified. These include EB1, EB2, EB3, p150Glued, Dynamitin, Lis1, CLIP170, CLIP115, CLASP1, and CLASP2.
Another MAP whose function has been investigated during cell division is known as XMAP215 (the "X" stands for Xenopus). XMAP215 has generally been linked to microtubule stabilization. During mitosis the dynamic instability of microtubules has been observed to rise approximately tenfold. This is partly due to phosphorylation of XMAP215, which makes catastrophes (rapid depolymerization of microtubules) more likely. In this way the phosphorylation of MAPs plays a role in mitosis.
There are many other proteins which affect microtubule behavior, such as catastrophin, which destabilizes microtubules, katanin, which severs them, and a number of motor proteins that transport vesicles along them. Certain motor proteins were originally designated as MAPs before it was found that they utilized ATP hydrolysis to transport cargo. In general, all these proteins are not considered "MAPs" because they do not bind directly to tubulin monomers, a defining characteristic of MAPs. MAPs bind directly to microtubules to stabilize or destabilize them and link them to various cellular components including other microtubules. | 1 | Biochemistry |
Britain led the worlds Industrial Revolution with its early commitment to coal mining, steam power, textile mills, machinery, railways, and shipbuilding. Britains demand for iron and steel, combined with ample capital and energetic entrepreneurs, made it the world leader in the first half of the 19th century. Steel has a vital role during the industrial revolution.
In 1875, Britain accounted for 47% of world production of pig iron, a third of which came from the Middlesbrough area and almost 40% of steel. 40% of British output was exported to the U.S., which was rapidly building its rail and industrial infrastructure. Two decades later in 1896, however, the British share of world production had plunged to 29% for pig iron and 22.5% for steel, and little was sent to the U.S. The U.S. was now the world leader and Germany was catching up to Britain. Britain had lost its American market, and was losing its role elsewhere; indeed American products were now underselling British steel in Britain.
The growth of pig iron output was dramatic. Britain went from 1.3 million tons in 1840 to 6.7 million in 1870 and 10.4 in 1913. The US started from a lower base, but grew faster; from 0.3 million tons in 1840, to 1.7 million in 1870, and 31.5 million in 1913. Germany went from 0.2 million tons in 1859 to 1.6 in 1871 and 19.3 in 1913. France, Belgium, Austria-Hungary, and Russia, combined, went from 2.2 million tons in 1870 to 14.1 million tons in 1913, on the eve of the First World War. During the war the demand for artillery shells and other supplies caused a spurt in output and a diversion to military uses. | 8 | Metallurgy |
Pseudokinases are catalytically-deficient pseudoenzyme variants of protein kinases that are represented in all kinomes across the kingdoms of life. Pseudokinases have both physiological (signal transduction) and pathophysiological functions. | 1 | Biochemistry |
It is a possible carcinogen. As "butter yellow", the agent had been used as a food additive in butter and margarine before its toxicity was recognized. | 3 | Analytical Chemistry |
The method has been in use since World War I. Prior to this, the process and purity of hydrogen generation relying on steam passing over hot iron was difficult to control. The chemical reaction uses sodium hydroxide (NaOH), ferrosilicon, and water (HO). While in the "silicol" process, a heavy steel pressure vessel is filled with sodium hydroxide and ferrosilicon, and upon closing, a controlled amount of water is added; the dissolving of the hydroxide heats the mixture to about and starts the reaction; sodium silicate, hydrogen and steam are produced. The overall reaction of the process is believed to be:
: 2NaOH + Si + HO → NaSiO + 2H
Ferrosilicon is used by the military to quickly produce hydrogen for balloons by the ferrosilicon method. The generator may be small enough to fit in a truck and requires only a small amount of electric power, the materials are stable and not combustible, and they do not generate hydrogen until mixed.
One report notes that this method of hydrogen production wasn't thoroughly investigated for about century despite being reported by the US military in the beginning of 20th century. | 8 | Metallurgy |
The most famous case of polyamorphism is amorphous ice. Pressurizing conventional hexagonal ice crystals to about 1.6 GPa at liquid nitrogen temperature (77 K) converts them to the high-density amorphous ice. Upon releasing the pressure, this phase is stable and has density of 1.17 g/cm at 77 K and 1 bar. Consequent warming to 127 K at ambient pressure transforms this phase to a low-density amorphous ice (0.94 g/cm at 1 bar). Yet, if the high-density amorphous ice is warmed up to 165 K not at low pressures but keeping the 1.6 GPa compression, and then cooled back to 77 K, then another amorphous ice is produced, which has even higher density of 1.25 g/cm at 1 bar. All those amorphous forms have very different vibrational lattice spectra and intermolecular distances.
A similar abrupt liquid-amorphous phase transition is predicted in liquid silicon when cooled under high pressures. This observation is based on first principles molecular dynamics computer simulations, and might be expected intuitively since tetrahedral amorphous carbon, silicon, and germanium are known to be structurally analogous to water. | 7 | Physical Chemistry |
Leakage of Nr (reactive nitrogen) from human activities can cause nitrate accumulation in the natural water environment, which can create harmful impacts on human health. Excessive use of N-fertilizer in agriculture has been one of the major sources of nitrate pollution in groundwater and surface water. Due to its high solubility and low retention by soil, nitrate can easily escape from the subsoil layer to the groundwater, causing nitrate pollution. Some other non-point sources for nitrate pollution in groundwater are originated from livestock feeding, animal and human contamination and municipal and industrial waste. Since groundwater often serves as the primary domestic water supply, nitrate pollution can be extended from groundwater to surface and drinking water in the process of potable water production, especially for small community water supplies, where poorly regulated and unsanitary waters are used.
The WHO standard for drinking water is 50 mg L for short-term exposure, and for 3 mg L chronic effects. Once it enters the human body, nitrate can react with organic compounds through nitrosation reactions in the stomach to form nitrosamines and nitrosamides, which are involved in some types of cancers (e.g., oral cancer and gastric cancer). | 1 | Biochemistry |
Robinson was awarded the 2010 Geological Society of London President's Award for her contributions to geosciences. In 2011 Robinson moved back to the United Kingdom, where she was appointed to the faculty of the University of Bristol. She was awarded a European Research Council Starting Grant studying changes in chemistry and circulation of the Atlantic Ocean. She makes use of an Agassiz Trawl to collect samples from the floor of the ocean, with a particular focus on deep-sea corals. Robinson was involved with a British Antarctic Survey mission to the South Orkney Islands. The mission took place on the RRS James Clark Ross and investigated the biodiversity in and outside of the South Orkney Islands. For this work she was awarded the Antarctic Service Medal.
In 2016 she delivered a Ted Talk on the secrets she discovers on the ocean floor. | 9 | Geochemistry |
The Hall-Héroult electrolysis process is the major production route for primary aluminium. An electrolytic cell is made of a steel shell with a series of insulating linings of refractory materials. The cell consists of a brick-lined outer steel shell as a container and support. Inside the shell, cathode blocks are cemented together by ramming paste. The top lining is in contact with the molten metal and acts as the cathode. The molten electrolyte is maintained at high temperature inside the cell. The prebaked anode is also made of carbon in the form of large sintered blocks suspended in the electrolyte. A single Soderberg electrode or a number of prebaked carbon blocks are used as anode, while the principal formulation and the fundamental reactions occurring on their surface are the same.
An aluminium smelter consists of a large number of cells (pots) in which the electrolysis takes place. A typical smelter contains anywhere from 300 to 720 pots, each of which produces about a ton of aluminium a day, though the largest proposed smelters are up to five times that capacity. Smelting is run as a batch process, with the aluminium deposited at the bottom of the pots and periodically siphoned off. Particularly in Australia these smelters are used to control electrical network demand, and as a result power is supplied to the smelter at a very low price. However power must not be interrupted for more than 4–5 hours, since the pots have to be repaired at significant cost if the liquid metal solidifies. | 8 | Metallurgy |
Gallamine triethiodide is originally developed for preventing muscle contractions during surgical procedures. However, it is no longer marketed in the United States according to the FDA orange book. | 1 | Biochemistry |
The Henry solubility can also be expressed as the dimensionless ratio between the aqueous-phase concentration of a species and its gas-phase concentration :
For an ideal gas, the conversion is:
where is the gas constant, and is the temperature.
Sometimes, this dimensionless constant is called the water–air partitioning coefficient . It is closely related to the various, slightly different definitions of the Ostwald coefficient , as discussed by Battino (1984). | 7 | Physical Chemistry |
All cells in animal body tissues are electrically polarized – in other words, they maintain a voltage difference across the cell's plasma membrane, known as the membrane potential. This electrical polarization results from a complex interplay between protein structures embedded in the membrane called ion pumps and ion channels. In neurons, the types of ion channels in the membrane usually vary across different parts of the cell, giving the dendrites, axon, and cell body different electrical properties. As a result, some parts of the membrane of a neuron may be excitable (capable of generating action potentials), whereas others are not. Recent studies have shown that the most excitable part of a neuron is the part after the axon hillock (the point where the axon leaves the cell body), which is called the axonal initial segment, but the axon and cell body are also excitable in most cases.
Each excitable patch of membrane has two important levels of membrane potential: the resting potential, which is the value the membrane potential maintains as long as nothing perturbs the cell, and a higher value called the threshold potential. At the axon hillock of a typical neuron, the resting potential is around –70 millivolts (mV) and the threshold potential is around –55 mV. Synaptic inputs to a neuron cause the membrane to depolarize or hyperpolarize; that is, they cause the membrane potential to rise or fall. Action potentials are triggered when enough depolarization accumulates to bring the membrane potential up to threshold. When an action potential is triggered, the membrane potential abruptly shoots upward and then equally abruptly shoots back downward, often ending below the resting level, where it remains for some period of time. The shape of the action potential is stereotyped; this means that the rise and fall usually have approximately the same amplitude and time course for all action potentials in a given cell. (Exceptions are discussed later in the article). In most neurons, the entire process takes place in about a thousandth of a second. Many types of neurons emit action potentials constantly at rates of up to 10–100 per second. However, some types are much quieter, and may go for minutes or longer without emitting any action potentials. | 7 | Physical Chemistry |
The IF2 initiation factor is a crucial component in the process of protein synthesis. The largest among the three indispensable translation initiation factors is IF-2, which possesses a molecular mass of 97 kDa. The protein has many domains, including an N-terminal domain, a GTPase domain, a linker region, C1, C2, and C-terminal domains. The GTPase domain encompasses the G1-G5 motif, which is responsible for the binding and hydrolysis of GTP. The activity of IF2 is regulated by conformational changes induced by the binding and hydrolysis of GTP. The primary function of IF-2 is to transport the initiator fMet-tRNA to the P-site of the 30S ribosomal subunit. The C2 domain of IF2 has a unique recognition and binding affinity towards the initiator tRNA. The IF-2 protein has been observed to form a ternary complex when interacting with GTP and fMet-tRNA. This complex has been found to interact with the 30S subunit. The initiation of mRNA translation involves the placement of the start codon in the P-site through the codon-anticodon base matching with the tRNA anti-codon. IF2 regulates start codon selection accuracy and inhibits elongator tRNAs' binding by selectively binding to fMet-tRNA. Additionally, it relocates the initiator tRNA on the 30S subunit to enhance the optimum contact with the P-site. Furthermore, IF2 exhibits RNA chaperone activity, which enables it to rectify misfolded RNA structures. In general, the IF2 protein plays a crucial role in coordinating many steps of translation initiation, including the binding of mRNA and fMet-tRNA to the start codon, the joining of sub-units, and the activation of GTPase. | 1 | Biochemistry |
Sulfur has four stable isotopes, with the following abundances: S (0.9502), S (0.0075), S (0.0421) and S (0.0002). These abundances are compared to those found in Cañon Diablo troilite. Variations in sulfur isotope ratios are used to study the origin of sulfur in an orebody and the temperature of formation of sulfur–bearing minerals as well as a biosignature that can reveal presence of sulfate reducing microbes. | 9 | Geochemistry |
Ultraviolet illumination can be produced from longer wavelengths using non-linear optical materials. These can be a second harmonic generator. They must have a suitable birefringence in order to phase match the output frequency doubled UV light. One compound commercially used is L-arginine phosphate monohydrate known as LAP. Research is underway for substances that are very non-linear, have a suitable birefringence, are transparent in the spectrum and have a high degree of resistance to damage from lasers. | 5 | Photochemistry |
Chemical WorkBench can be used by researchers and engineers working in the following fields:
*General chemical kinetics and thermodynamics
*Kinetic mechanisms development
*Thin films growth for microelectronics
*Nanotechnology
*Catalysis and chemical engineering
*Combustion, detonation and pollution control
*Waste treatment and recovering
*Plasma light sources and plasma chemistry
*High-temperature chemistry
*Education
*Combustion and detonation, clean power-generation technologies, safety analysis, CVD, heterogeneous and catalytic reactions and processes, and processes in non-equilibrium plasmas are the main areas of interest. | 7 | Physical Chemistry |
The World Trade Center Health Registry was established in 2002 by ATSDR and the New York City Department of Health and Mental Hygiene to track the long-term physical and mental health effects of the September 11 attacks. The registry contains more than 71,000 people who lived, worked, or went to school near the World Trade Center site, as well as emergency response personnel who were involved in rescue and recovery efforts. It is the largest post-disaster health registry in the United States. Researchers use the registry to study the health effects of the disaster and to develop public health recommendations for future disasters. A 2009 study based on registry data found that posttraumatic stress disorder and asthma were the two most commonly reported conditions among registry participants 5 to 6 years after the disaster. The study found that 19% of adult participants reported new posttraumatic stress symptoms, and 10% of adult participants reported developing new asthma. | 1 | Biochemistry |
Although known primarily for his work on the Theory of Evolution, Charles Darwin was also keenly interested in plants. Through the 1870s, he and his son Francis studied the movement of plants towards light. They were able to show that light is perceived at the tip of a young stem (the coleoptile), whereas the bending occurs lower down the stem. They proposed that a transmissible substance communicated the direction of light from the tip down to the stem. The idea of a transmissible substance was initially dismissed by other plant biologists, but their work later led to the discovery of the first plant hormone. In the 1920s Dutch scientist Frits Warmolt Went and Russian scientist Nikolai Cholodny (working independently of each other) conclusively showed that asymmetric accumulation of a growth hormone was responsible for this bending. In 1933 this hormone was finally isolated by Kögl, Haagen-Smit and Erxleben and given the name auxin. | 1 | Biochemistry |
Oxoguanine glycosylase (OGG1) catalyses the first step in base excision repair of the oxidatively damaged base 8-OHdG. OGG1 finds 8-OHdG by sliding along the linear DNA at 1,000 base pairs of DNA in 0.1 seconds. OGG1 very rapidly finds 8-OHdG. OGG1 proteins bind to oxidatively damaged DNA with a half maximum time of about 6 seconds. When OGG1 finds 8-OHdG it changes conformation and complexes with 8-OHdG in its binding pocket. OGG1 does not immediately act to remove the 8-OHdG. Half maximum removal of 8-OHdG takes about 30 minutes in HeLa cells in vitro, or about 11 minutes in the livers of irradiated mice. DNA oxidation by reactive oxygen species preferentially occurs at a guanine in a methylated CpG site, because of a lowered ionization potential of guanine bases adjacent to 5-methylcytosine. TET1 binds (is recruited to) the OGG1 bound to 8-OHdG (see figure). This likely allows TET1 to demethylate an adjacent methylated cytosine. When human mammary epithelial cells (MCF-10A) were treated with HO, 8-OHdG increased in DNA by 3.5-fold and this caused about 80% demethylation of the 5-methylcytosines in the MCF-10A genome. | 1 | Biochemistry |
Perhaps one of the most studied materials to exhibit negative thermal expansion is zirconium tungstate (). This compound contracts continuously over a temperature range of 0.3 to 1050 K (at higher temperatures the material decomposes). Other materials that exhibit NTE behaviour include other members of the family of materials (where A = or , M = or ) and and , though and only in their high temperature phase starting at 350 to 400 K. also is an example of controllable negative thermal expansion. Cubic materials like and also and are especially precious for applications in engineering because they exhibit isotropic NTE i.e. the NTE is the same in all three dimensions making it easier to apply them as thermal expansion compensators.
Ordinary ice shows NTE in its hexagonal and cubic phases at very low temperatures (below –200 °C). In its liquid form, pure water also displays negative thermal expansivity below 3.984 °C.
ALLVAR Alloy 30, a titanium-based alloy, shows NTE over a wide temperature range, with a -30 ppm/°C instantaneous coefficient of thermal expansion at 20 °C. ALLVAR Alloy 30's negative thermal expansion is anisotropic. This commercially available material is used in the optics, aerospace, and cryogenics industries in the form of optical spacers that prevent thermal defocus, ultra-stable struts, and washers for thermally-stable bolted joints.
Carbon fibers shows NTE between 20°C and 500°C. This property is utilized in tight-tolerance aerospace applications to tailor the CTE of carbon fiber reinforced plastic components for specific applications/conditions, by adjusting the ratio of carbon fiber to plastic and by adjusting the orientation of the carbon fibers within the part.
Quartz () and a number of zeolites also show NTE over certain temperature ranges. Fairly pure silicon (Si) has a negative coefficient of thermal expansion for temperatures between about 18 K and 120 K.
Cubic Scandium trifluoride has this property which is explained by the quartic oscillation of the fluoride ions. The energy stored in the bending strain of the fluoride ion is proportional to the fourth power of the displacement angle, unlike most other materials where it is proportional to the square of the displacement. A fluorine atom is bound to two scandium atoms, and as temperature increases the fluorine oscillates more perpendicularly to its bonds. This draws the scandium atoms together throughout the material and it contracts. exhibits this property from 10 to 1100 K above which it shows the normal positive thermal expansion. Shape memory alloys such as NiTi are a nascent class of materials that exhibit zero and negative thermal expansion. | 7 | Physical Chemistry |
Cyclohexylthiophthalimide (abbreviated CTP) is an organosulfur compound that is used in production of rubber. It is a white solid, although commercial samples often appear yellow. It features the sulfenamide functional group, being a derivative of phthalimide and cyclohexanethiol. In the production of synthetic rubber, CTP impedes the onset of sulfur vulcanization. | 0 | Organic Chemistry |
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and for many other biological effects. In humans, the most important compounds in this group are vitamin D (cholecalciferol) and vitamin D (ergocalciferol).
The major natural source of vitamin D is synthesis of cholecalciferol in the lower layers of the epidermis of the skin, through a photochemical reaction with Ultraviolet B (UV-B) radiation from sun exposure or UV-B lamps. Cholecalciferol and ergocalciferol can be ingested from the diet and supplements. Only a few foods, such as the flesh of fatty fish, naturally contain significant amounts of vitamin D. In the U.S. and other countries, cows milk and plant-derived milk substitutes are fortified with vitamin D, as are many breakfast cereals. Mushrooms exposed to ultraviolet light contribute useful amounts of vitamin D. Dietary recommendations typically assume that all of a persons vitamin D is taken by mouth, because sun exposure in the population is variable and recommendations about the amount of sun exposure that is safe are uncertain in view of the associated risks of skin cancer.
Vitamin D from the diet, or from skin synthesis, is biologically inactive. It is activated by two protein enzyme hydroxylation steps, the first in the liver and the second in the kidneys. Because vitamin D can be synthesized in adequate amounts by most mammals if they get enough sunlight, it is not essential and therefore is technically not a vitamin. Instead it can be considered a hormone, with activation of the vitamin D pro-hormone resulting in the active form, calcitriol, which then produces effects via a nuclear receptor in multiple locations.
Cholecalciferol is converted in the liver to calcifediol (25-hydroxycholecalciferol); ergocalciferol is converted to 25-hydroxyergocalciferol. These two vitamin D metabolites (called 25-hydroxyvitamin D or 25(OH)D) are measured in serum to determine a person's vitamin D status. Calcifediol is further hydroxylated by the kidneys and some of the immune system cells to form calcitriol (1,25-dihydroxycholecalciferol), the biologically active form of vitamin D. Calcitriol circulates as a hormone in the blood, having a major role regulating the concentration of calcium and phosphate, and promoting the healthy growth and remodeling of bone. Calcitriol also has other effects, including some on cell growth, neuromuscular and immune functions, and reduction of inflammation.
Vitamin D has a significant role in calcium homeostasis and metabolism. Its discovery was due to effort to find the dietary substance lacking in children with rickets (the childhood form of osteomalacia). Vitamin D supplements are given to treat or to prevent osteomalacia and rickets. The evidence for other health effects of vitamin D supplementation in vitamin D–replete individuals is inconsistent. The effect of vitamin D supplementation on mortality is not clear, with one meta-analysis finding a small decrease in mortality in elderly people. Except for the prevention of rickets and osteomalacia in high-risk groups, any benefit of vitamin D supplements to musculoskeletal or general health may be small. | 1 | Biochemistry |
Thiosulfate ion extensively forms diverse complexes with transition metals. In the era of silver-based photography, thiosulfate ion was consumed on a large scale as a "fixer" reagent. This application exploits thiosulfate ion's ability to dissolve silver halides. Thiosulfate ion (as sodium thiosulfate) is also used to extract or leach gold and silver from their ores as a less toxic alternative to cyanide ion.
Also reflecting its affinity for metals, thiosulfate ion rapidly corrodes metals in acidic conditions. Steel and stainless steel are particularly sensitive to pitting corrosion induced by thiosulfate ions. Molybdenum improves the resistance of stainless steel toward pitting (AISI 316L hMo). In alkaline aqueous conditions and medium temperature (60 °C), carbon steel and stainless steel (AISI 304L, 316L) are not attacked, even at high concentration of base (30%w KOH), thiosulfate ion (10%w) and in presence of fluoride ion (5%w KF). | 8 | Metallurgy |
Alternative Splicing Annotation Project (ASAP) in computational biology was a database for alternative splicing data maintained by the University of California from 2003 to 2013. The purpose of ASAP was to provide a source for data mining projects by consolidating the information generated by genomics and proteomics researchers. | 1 | Biochemistry |
Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:
Errors in compilations concerning equilibrium and/or data elaboration. Data not recommended. It is strongly suggested to refer to the original papers. | 7 | Physical Chemistry |
Advanced glycation end products (AGEs) are proteins or lipids that become glycated as a result of exposure to sugars. They are a bio-marker implicated in aging and the development, or worsening, of many degenerative diseases, such as diabetes, atherosclerosis, chronic kidney disease, and Alzheimer's disease. | 1 | Biochemistry |
When the soil is saturated and the depression storage filled, and rain continues to fall, the rainfall will immediately produce surface runoff. The level of antecedent soil moisture is one factor affecting the time until soil becomes saturated. This runoff is called saturation excess overland flow, saturated overland flow, or Dunne runoff. | 2 | Environmental Chemistry |
Schwab was born in 1899 in Berlin as the second son of famed journalist and his wife, the writer Marie Köglmayr. Both his parents originated from Bavaria; Josef Schwab was a Franconian Jew and his wife a Catholic from Upper Bavaria. Georg-Maria finished his secondary education at the Friedrich Wilhelm Gymnasium in Berlin, and upon turning 18 was conscripted for WWI and served for a year with the Bavarian Army in Flanders.
Following WWI, Schwab studied Chemistry and Physics in the University of Berlin. He continued his postgraduate studies there under the supervision of Ernst Hermann Riesenfeld and in 1923 received his doctorate with his thesis "Über Ozon" (On Ozone), which was awarded the rare distinction eximium opus. For the following two years, until 1925, Schwab worked as a research assistant to Max Bodenstein, the successor of Walther Nernst in the Institute of Physical Chemistry that Nernst founded in Berlin. Under Bodenstein, Schwab was initiated and trained in the field of chemical kinetics, in which he contributed much for the rest of his career.
In 1925, he accepted a position in the University of Würzburg, initially as the assistant of Otto Dimroth. He was eventually habilitated in 1927 as a Privatdozent in Würzburg with his habilitation thesis on the thermal decomposition of methane and ammonia. In 1928, after the invitation of Heinrich Otto Wieland, Schwab began working in the inorganic laboratory at the University of Munich and was promoted to extraordinary professor in 1933.
It was during this period that he met his future wife Elly Agallidis (), a Greek physicist who was doing her PhD in the University of Munich.
Schwab remained at his position in Munich until 1938, when he was expelled and barred from teaching by Nazi authorities on account of "racial grounds" i.e. his half-Jewish origin. Raised a Catholic, he had been previously unaware of his father's origin until questioned about it under the provisions of the 1933 anti-Semitic Civil Service Law. | 7 | Physical Chemistry |
Due to the difficulty of C-C activation, a driving force is required to facilitate the reaction. One common strategy is to form stable metal complexes. One example is reported by Milstein and coworkers, in which the C(sp)–C(sp) bond of bisphosphine ligands was selectively cleaved by a number of metals to afford stable pincer complexes under mild conditions.
Aromatization is another driving force that is utilized for C–C bond activation. For example, Chaudret group reported that the C–C bond of steroid compounds can be cleaved through the Ru-promoted aromatization of the B ring. At the same time, a methane molecule is released, which is possibly another driving force for this reaction.
In addition, the metalloradical has also been proven to have the ability to cleave the C–C single bond. Chan group reported the C–C bond scission of cyclooctane via 1,2-addition with Rh(III) porphyrin hydride, which involved [Rh(ttp)]· radical as the key intermediate. | 0 | Organic Chemistry |
Fentons reagent is a solution of hydrogen peroxide (HO) and an iron catalyst (typically iron(II) sulfate, FeSO). It is used to oxidize contaminants or waste water as part of an advanced oxidation process. Fentons reagent can be used to destroy organic compounds such as trichloroethylene and tetrachloroethylene (perchloroethylene). It was developed in the 1890s by Henry John Horstman Fenton as an analytical reagent. | 2 | Environmental Chemistry |
Transient liquid phase diffusion bonding is a process that differs from diffusion bonding. In transient liquid phase diffusion bonding, an element or alloy with a lower melting point in an interlayer diffuses into the lattice and grain boundaries of the substrates at the bonding temperature. Solid state diffusional processes lead to a change of composition at the bond interface and the dissimilar interlayer melts at a lower temperature than the parent materials. Thus, a thin layer of liquid spreads along the interface to form a joint at a lower temperature than the melting point of either of the parent materials. This method differs from brazing in that it is "isothermally solidifying". While holding the temperature above the filler metal melting point, interdiffusion shifts the composition away from eutectic, so solidification occurs at the process temperature. If sufficient interdiffusion occurs, the joint will remain solid and strong well above the original melt process temperature. This is why it is termed "transient liquid phase." The liquid solidifies before cooling. | 8 | Metallurgy |
Commercial tanning services are banned in all states, except the Northern Territory where no salons are in operation. Private ownership of tanning beds is permitted. | 5 | Photochemistry |
Two proteins are crucial for interacting ethylene with the receptors, namely constitutive triple response 1 (CTR1) and ethylene insensitive 2 (EIN2). CTR1 is a serine/threonine protein kinase that functions as a negative regulator of ethylene signalling. It is a member of the signaling protein mitogen-activated protein kinase (MAPK) kinase kinase. EIN2 is required for ethylene signalling and is part of the NRAMP (natural resistance-associated macrophage protein) family of metal transporters; it comprises a large, N-terminal portion containing multiple transmembrane domains (EIN2-N) in the ER membrane and a cytosolic C-terminal portion (EIN2-C). Other proteins such as reversion to ethylene sensitivity 1 (RTE1), cytochrome b5 and tetratricopeptide repeat protein 1 (TRP1) also play important roles in ethylene signaling. RTE1 is a highly conserved proteins in plants and protists but absent in fungi and prokaryotes. TRP1 is genetically related to transmembrane and coiled-coil protein 1 (TCC1) in animals that is involved F actin function and competes with Raf-1 for Ras binding.
Unlike in most signal transductions where the ligands activate their receptors to relay their signals, ethylene acts as the suppressor of its receptor, and the receptor being the negative regulator in ethylene responses. Ethylene receptor is active in the absence of ethylene. Without ethylene, the receptor binds to CTR1 at its C-terminal kinase domain. The kinase activity of CTR1 becomes activated and phosphorylates the neighbouring EIN2. As long as EIN2 remains highly phosphorylated, it remains inactive and there never is an ethylene signal relay. In ETR1, the receptor histidine kinase is required for binding with EIN2. RTE1 can bind to and activate ETR1 independent of CTR1. There is evidence that cytochrome b5 aids or acts similar to RTE1.
Ethylene binding to the receptor disrupts the EIN2 phosphorylation. It does not cause any particular change in the structural feature of the receptor-CTR1-EIN2 complex or stop the phosphorylation. In fact, at low level of ethylene there is increased receptor-CTR1-EIN2 complexes, which is then reduced as ethylene level rises. The turnover process is not yet fully understood. The only consequence of ethylene binding is reduced phosphorylation of EIN2. Under such condition EIN2 is activated and is cleaved to release EIN2-C from the membrane-bound EIN2-N portion. The enzyme that causes the cleavage is yet unknown. The role of EIN2-N is also unknown in A. thaliana. But in rice, its homologue OsEIN2-N (Os for Oryza sativa, the scientific name for rice) interacts with another protein, mao huzi 3 (MHZ3), a mutation of which gives rise to insensitivity to ethylene.
EIN2-C is the main component that mediates ethylene signal in the cell. It acts in two ways. In one, it binds the mRNAs that encode for EIN3-binding F-box proteins, EBF1 and EBF2 to cause their degradation. In another, it enters the nucleus to bind with EIN2 nuclear associated protein 1 (ENAP1) to regulate transcriptional and translational activities of EIN3 and the related EIL1 transcription factor to cause most of the ethylene responses. | 1 | Biochemistry |
Examples of chain reactions in living organisms include excitation of neurons in epilepsy and lipid peroxidation. In peroxidation, a lipid radical reacts with oxygen to form a peroxyl radical (L• + O → LOO•). The peroxyl radical then oxidises another lipid, thus forming another lipid radical (LOO• + L–H → LOOH + L•). A chain reaction in glutamatergic synapses is the cause of synchronous discharge in some epileptic seizures. | 7 | Physical Chemistry |
Pressureless sintering is the sintering of a powder compact (sometimes at very high temperatures, depending on the powder) without applied pressure. This avoids density variations in the final component, which occurs with more traditional hot pressing methods.
The powder compact (if a ceramic) can be created by slip casting, injection moulding, and cold isostatic pressing. After presintering, the final green compact can be machined to its final shape before being sintered.
Three different heating schedules can be performed with pressureless sintering: constant-rate of heating (CRH), rate-controlled sintering (RCS), and two-step sintering (TSS). The microstructure and grain size of the ceramics may vary depending on the material and method used.
Constant-rate of heating (CRH), also known as temperature-controlled sintering, consists of heating the green compact at a constant rate up to the sintering temperature. Experiments with zirconia have been performed to optimize the sintering temperature and sintering rate for CRH method. Results showed that the grain sizes were identical when the samples were sintered to the same density, proving that grain size is a function of specimen density rather than CRH temperature mode.
In rate-controlled sintering (RCS), the densification rate in the open-porosity phase is lower than in the CRH method. By definition, the relative density, ρ, in the open-porosity phase is lower than 90%. Although this should prevent separation of pores from grain boundaries, it has been proven statistically that RCS did not produce smaller grain sizes than CRH for alumina, zirconia, and ceria samples.
Two-step sintering (TSS) uses two different sintering temperatures. The first sintering temperature should guarantee a relative density higher than 75% of theoretical sample density. This will remove supercritical pores from the body. The sample will then be cooled down and held at the second sintering temperature until densification is completed. Grains of cubic zirconia and cubic strontium titanate were significantly refined by TSS compared to CRH. However, the grain size changes in other ceramic materials, like tetragonal zirconia and hexagonal alumina, were not statistically significant. | 8 | Metallurgy |
Block copolymers comprise two or more homopolymer subunits linked by covalent bonds. The union of the homopolymer subunits may require an intermediate non-repeating subunit, known as a junction block. Diblock copolymers have two distinct blocks; triblock copolymers have three. Technically, a block is a portion of a macromolecule, comprising many units, that has at least one feature which is not present in the adjacent portions. A possible sequence of repeat units A and B in a triblock copolymer might be ~A-A-A-A-A-A-A-B-B-B-B-B-B-B-A-A-A-A-A~.
Block copolymers are made up of blocks of different polymerized monomers. For example, polystyrene-b-poly(methyl methacrylate) or PS-b-PMMA (where b = block) is usually made by first polymerizing styrene, and then subsequently polymerizing methyl methacrylate (MMA) from the reactive end of the polystyrene chains. This polymer is a "diblock copolymer" because it contains two different chemical blocks. Triblocks, tetrablocks, multiblocks, etc. can also be made. Diblock copolymers are made using living polymerization techniques, such as atom transfer free radical polymerization (ATRP), reversible addition fragmentation chain transfer (RAFT), ring-opening metathesis polymerization (ROMP), and living cationic or living anionic polymerizations. An emerging technique is chain shuttling polymerization.
The synthesis of block copolymers requires that both reactivity ratios are much larger than unity (r >> 1, r >> 1) under the reaction conditions, so that the terminal monomer unit of a growing chain tends to add a similar unit most of the time.
The "blockiness" of a copolymer is a measure of the adjacency of comonomers vs their statistical distribution. Many or even most synthetic polymers are in fact copolymers, containing about 1-20% of a minority monomer. In such cases, blockiness is undesirable. A block index has been proposed as a quantitative measure of blockiness or deviation from random monomer composition. | 7 | Physical Chemistry |
Bacteria are inoculated on a medium containing sodium citrate and a pH indicator such as bromothymol blue. The medium also contains inorganic ammonium salts, which are utilized as sole source of nitrogen. Use of citrate involves the enzyme citrate lyase, which breaks down citrate to oxaloacetate and acetate. Oxaloacetate is further broken down to pyruvate and carbon dioxide (CO). Production of sodium bicarbonate (NaHCO) as well as ammonia (NH) from the use of sodium citrate and ammonium salts results in alkaline pH. This results in a change of the medium's color from green (neutral) to blue (alkaline).
Bacterial colonies are picked up from a straight wire and inoculated into slope of Simmons citrate agar and incubated overnight at 37 °C. Inoculating from a broth culture is not recommended because the inoculum would be too heavy. If the organism has the ability to use citrate, the medium usually changes its color from green to blue, though growth on the medium even without colour change is considered a positive result. An observation of no growth is a negative result.
Examples:
* Escherichia coli: Negative
* Klebsiella pneumoniae: Positive
* Frateuria aurantia: Positive | 3 | Analytical Chemistry |
Following the 120 kg/h test work, MIM decided to proceed to install a 5 t/h lead ISASMELT pilot plant in its Mount Isa lead smelter. It bought Aberfoyle's matte fuming furnace and transported it from Kalgoorlie to Mount Isa, where it was rebuilt and commissioned in 1983 to demonstrate the first stage of the process in continuous operation and for testing the reduction step using batches of high-lead slag.
One of the key features of the pilot plant was that it was run by operations’ personnel in the lead smelter as though it was an operations’ plant. The high lead slag produced by the continuous smelting of the lead concentrate was subsequently treated in the sinter plant, thus increasing the production of the lead smelter by up to 17%. This gave the operations’ people ownership of the plant and an incentive to make it work, thus ensuring management and maintenance priority. It also gave MIM assurance that the process simple enough to be operable in a production environment, with normal staff and supervision, and that it was robust enough to withstand normal control excursions. In addition to the continuous operation of lead concentrate to produce high-lead slag, the pilot plant was used to produce lead metal from batches of the slag, investigate the wear rates of the furnace's refractory lining and lances, and initial work aimed at developing a low-pressure version of the Sirosmelt lance. The result was a lance design that allowed operation at significantly lower pressure than the initial values of about 250 kilopascal (gauge) ("kPag"), thus reducing operating costs.
MIM built a second, identical furnace next to the first, and commissioned it in August 1985. This combination of furnaces was used to demonstrate the two-stage process in continuous operation in mid-1987. However, for most of the time the two furnaces were not able to operate simultaneously due to a constraint in the capacity of the baghouse used to filter the lead dust from the waste gas.
A series of process improvements, particularly in the waste gas handling system, resulted in increasing the throughput of the plant from the initial design of 5 t/h to 10 t/h. The pilot plant had treated more than 125,000 t of lead concentrate by April 1989.
The two furnaces were also used to develop a process to recover lead from the Mount Isa lead smelter's drossing operations. | 8 | Metallurgy |
Many organisms are capable of using hydrogen () as a source of energy. While several mechanisms of anaerobic hydrogen oxidation have been mentioned previously (e.g. sulfate reducing- and acetogenic bacteria), the chemical energy of hydrogen can be used in the aerobic Knallgas reaction:
:2 H + O → 2 HO + energy
In these organisms, hydrogen is oxidized by a membrane-bound hydrogenase causing proton pumping via electron transfer to various quinones and cytochromes. In many organisms, a second cytoplasmic hydrogenase is used to generate reducing power in the form of NADH, which is subsequently used to fix carbon dioxide via the Calvin cycle. Hydrogen-oxidizing organisms, such as Cupriavidus necator (formerly Ralstonia eutropha), often inhabit oxic-anoxic interfaces in nature to take advantage of the hydrogen produced by anaerobic fermentative organisms while still maintaining a supply of oxygen. | 1 | Biochemistry |
In order to measure Cu isotope ratios of various materials, several steps must be taken prior to the isotopic measurement in order to extract and purify copper. The first step in the analytical pipeline to measure Cu isotopes is to liberate Cu from its host material. Liberation should be quantitative, otherwise fractionation may be introduced at this step. Cu-containing rocks are generally dissolved with HF; biological materials are commonly digested with HNO. Seawater samples must be concentrated due to the low (nM) concentrations of Cu in the ocean. The sample material is subsequently run through an anion-exchange column to isolated and purify Cu. This step can also introduce Cu isotope fractionation if Cu is not quantitatively recovered from the column. If samples are from seawater, other ions (e.g., Na, Mg, Ca) must be removed in order to eliminate isobaric interferences during the isotope measurement. Prior to 1992, Cu/Cu ratios were measured via thermal ionization mass spectrometry (TIMS). Today, Cu isotopic compositions are measured via multi-conductor inductively coupled plasma mass spectrometry (MC-ICP-MS), which ionizes samples using inductively coupled plasma and introduces smaller errors than TIMS. | 9 | Geochemistry |
Pseudin-2 is the most abundant version of the pseudins found on the skin of the paradoxical frog. The primary sequence reads as GLNALKKVFQGIHEAIKLINNHVQ. Its secondary/tertiary structure consists of one cationic amphipathic α-helix. | 1 | Biochemistry |
Electromagnets are placed above the sample slide, and an inverted microscope is placed below. The image is captured via a CCD camera and transferred to a computer, where the three-dimensional positions of the magnetic beads are determined. The position of the bead within the horizontal plane of the glass slide, x and y, are determined by real-time correlation of the bead images. The vertical length of the hairpin, measured by the vertical position of the attached magnetic bead, is measured by the bead’s diffraction ring diameter, which increases with distance. | 1 | Biochemistry |
Within nature carbon dioxide can bind with neutral amine groups to form a carbamate, this post-translational modification is known as carbamylation. This modification is known to occur on several important proteins; see examples below. | 0 | Organic Chemistry |
Circle-Throw Vibrating Equipment is a shaker or a series of shakers as to where the drive causes the whole structure to move. The structure extends to a maximum throw or length and then contracts to a base state. A pattern of springs are situated below the structure to where there is vibration and shock absorption as the structure returns to the base state.
This type of equipment is used for very large particles, sizes that range from pebble size on up to boulder size material. It is also designed for high volume output. As a scalper, this shaker will allow oversize material to pass over and fall into a crusher such a cone crusher, jaw crusher, or hammer mill. The material that passes the screen by-passes the crusher and is conveyed and combined with the crush material.
Also this equipment is used in washing processes, as material passes under spray bars, finer material and foreign material is washed through the screen. This is one example of wet screening. | 8 | Metallurgy |
The common trend in all examples of protein adsorption in the food industry is that of adsorption to minerals adsorbed to the surface first. This phenomenon has been studied but it is not well understood. Spectroscopy of proteins adsorbed onto clay-like minerals show variations in the C=O and N-H bond stretches, meaning that these bonds are involved in the protein binding. | 1 | Biochemistry |
In electronic spectroscopy, constructing a Deslandres table is a useful method to assign vibronic transitions. In such a table, the frequencies of the lines seen in an electronic spectrum of a molecule are collected so that the differences in energy between adjacent columns or rows are all the same (within experimental error). Every line seen in the spectrum corresponds to a transition from the lower-lying electronic energy state to an excited electronic state (molecular electronic transition): associated with this, there are corresponding transitions between the vibrational levels of the two states, that give rise to many closely spaced lines. The intensity of the lines is governed by the Franck–Condon principle.
When a Deslandres table is filled correctly, the columns represent the vibrational energy levels of the lower electronic state (v), while the rows represent those for the upper electronic state (v). Clearly, the difference in energy between two successive rows (columns) must remain constant for any column (row) in the table because this represents the energy difference of two given vibrational levels within the same electronic state. Thus, by completing a Deslandres table it is easy to assign the correct vibrational quantum numbers v and v for the transition, allowing important molecular properties to be calculated, such as the dissociation energy. | 7 | Physical Chemistry |
Orange carotenoid protein (OCP) is a water-soluble protein which plays a role in photoprotection in diverse cyanobacteria. It is the only photoactive protein known to use a carotenoid as the photoresponsive chromophore. The protein consists of two domains, with a single keto-carotenoid molecule non-covalently bound between the two domains. It is a very efficient quencher of excitation energy absorbed by the primary light-harvesting antenna complexes of cyanobacteria, the phycobilisomes. The quenching is induced by blue-green light. It is also capable of preventing oxidative damage by directly scavenging singlet oxygen (O). | 5 | Photochemistry |
Sulfenamides have been characterized by X-ray crystallography. The S-N bond in sulfenamides is a chiral axis that leads to formation of diastereomeric compounds. The existence of these distinct stereoisomers is due to the formation of a partial double bond between either sulfur or nitrogen’s lone pair and the other atom's antibonding orbitals. Additionally bulky substituent groups and lone pair repulsion can contribute resistance to interconversion. The resulting torsional barriers can be quite large and vary from 12-20 kcal/mol. The interactions are thought to be dependent on the torsional preferences (also known as the gauche effect). The nitrogen atom is usually pyramidal, but cyclic and strongly steric hindered acyclic sulfenamides can display a planar arrangement of bonds around the nitrogen atom. | 0 | Organic Chemistry |
Stimuli-responsive hydrogel fibers can be used as actuators and soft robots. By braiding the hydrogel fiber together, the force of the single fiber can be magnified. Also, due to the slipping between hydrogel fibers, the stain of the bending can be reduced to further enhance the performance. | 7 | Physical Chemistry |
Tinning is the process of thinly coating sheets of wrought iron or steel with tin, and the resulting product is known as tinplate. The term is also widely used for the different process of coating a metal with solder before soldering.
It is most often used to prevent rust, but is also commonly applied to the ends of stranded wire used as electrical conductors to prevent oxidation (which increases electrical resistance), and to keep them from fraying or unraveling when used in various wire connectors like twist-ons, binding posts, or terminal blocks, where stray strands can cause a short circuit.
While once more widely used, the primary use of tinplate now is the manufacture of tin cans. Formerly, tinplate was used for cheap pots, pans, and other holloware. This kind of holloware was also known as tinware and the people who made it were tinplate workers.
The untinned sheets employed in the manufacture are known as black plates. They are now made of steel, either Bessemer steel or open-hearth. Formerly iron was used, and was of two grades, coke iron and charcoal iron; the latter, being the better, received a heavier coating of tin, and this circumstance is the origin of the terms coke plates and charcoal plates by which the quality of tinplate is still designated, although iron is no longer used. Tinplate was consumed in enormous quantities for the manufacture of the tin cans in which preserved meat, fish, fruit, biscuits, cigarettes, and numerous other products are packed, and also for the household utensils of various kinds made by the tinsmith. | 8 | Metallurgy |
The second major application of pharmacometabolomics is the analysis of a patient's metabolic profile following the administration of a specific therapy. This process is often secondary to a pre-treatment metabolic analysis, allowing for the comparison of pre- and post-treatment metabolite concentrations. This allows for the identification of the metabolic processes and pathways that are being altered by the treatment either intentionally as a designated target of the compound, or unintentionally as a side effect. Furthermore, the concentration and variety of metabolites produced from the compound itself can also be identified, providing information on the rate of metabolism and potentially leading to development of a related compound with increased efficacy or decreased side effects. An example of this approach was used to investigate the effect of several antipsychotic drugs on lipid metabolism in patients treated for schizophrenia. It was hypothesized that these antipsychotic drugs may be altering lipid metabolism in treated patients with schizophrenia, contributing to the weight gain and hypertriglyceridemia. The study monitored lipid metabolites in patients both before and after treatment with antipsychotics. The compiled pre- and post-treatment profiles were then compared to examine the effect of these compounds on lipid metabolism. The researchers found correlations between treatment with antipsychotic drugs and lipid metabolism, in both a lipid-class-specific and drug-specific manner, establishing new foundations around the concept that pharmacometabolomics provides powerful tools for enabling detailed mapping of drug effects. Additional studies by the Pharmacometabolomics Research Network enabled mapping in ways not possible before effects of statins, atenolol and aspirin. Totally new insights were gained about effect of these drugs on metabolism and they highlighted pathways implicated in response and side effects. | 1 | Biochemistry |
In economic geology, the term humate refers to geological materials, such as weathered coal beds (leonardite), mudrock, or pore material in sandstones, that are rich in humic acids. Humate has been mined from the Fruitland Formation of New Mexico for use as a soil amendment since the 1970s, with nearly 60,000 metric tons produced by 2016. Humate deposits may also play an important role in the genesis of uranium ore bodies. | 9 | Geochemistry |
Solid-state processes do not involve melting or evaporating the material and are typically done at relatively low temperatures. Examples of solid state processes include mechanical alloying using a high-energy ball mill and certain types of severe plastic deformation processes. | 8 | Metallurgy |
Until now, ten anammox species have been described, including seven that are available in laboratory enrichment cultures. All have the taxonomical status of Candidatus, as none were obtained as classical pure cultures. Known species are divided over five genera:
# Kuenenia, one species: Kuenenia stuttgartiensis.
# Brocadia, three species: B. anammoxidans, B. fulgida, and B. sinica.
# Anammoxoglobus, one species: A. propionicus.
# Jettenia, one species: J. asiatica.
# Scalindua, four species: S. brodae, S. sorokinii, S. wagneri, and S. profunda.
Representatives of the first four genera were enriched from sludge from wastewater treatment plants; K. stuttgartiensis, B. anammoxidans, B. fulgida, and A. propionicus were even obtained from the same inoculum. Scalindua dominates the marine environment, but is also found in some freshwater ecosystems and wastewater treatment plants.
Together, these 10 species likely only represent a minute fraction of anammox biodiversity. For instance, there are currently over 2000 16S rRNA gene sequences affiliated with anammox bacteria that have been deposited to the Genbank (https://www.ncbi.nlm.nih.gov/genbank/), representing an overlooked continuum of species, subspecies, and strains, each apparently having found its specific niche in the wide variety of habitats where anammox bacteria are encountered. Species microdiversity is particularly impressive for the marine representative Scalindua. A question that remains to be investigated is which environmental factors determine species differentiation among anammox bacteria.
The sequence identities of the anammox 16S rRNA genes range from 87 to 99%, and phylogenetic analysis places them all within the phylum Planctomycetota, which form the PVC superphylum together with Verrucomicrobia and Chlamydiae. Within the Planctomycetota, anammox bacteria deeply branch as a monophyletic clade. Their phylogenetic position together with a broad range of specific physiological, cellular, and molecular traits give anammox bacteria their own order Brocadiales. | 1 | Biochemistry |
In nucleophilic trifluoromethylation the active species is the CF anion. It was, however, widely believed that the trifluoromethyl anion is a transient species and thus cannot be isolated or observed in the condensed phase. Contrary to the popular belief, the CF anion, with [K(18-crown-6)] as a countercation, was produced and characterized by Prakash and coworkers. The challenges associated with observation of CF anion are alluded to its strong basic nature and its tendency to form pentacoordinated silicon species, such as [MeSi(CF)] or [MeSi(F)(CF)].
The reactivity of fluoroform in combination with a strong base such as t-BuOK with carbonyl compounds in DMF is an example. Here CF and DMF form an hemiaminolate adduct ([MeNCH(O)CF]K). | 0 | Organic Chemistry |
Evidence suggests that mitochondrial dysfunction is present in patients with bipolar disorder.
Oxidative stress and reduced levels of anti-oxidants (such as glutathione) lead to cell death. Lithium may protect against oxidative stress by up-regulating complex I and II of the mitochondrial electron transport chain. | 1 | Biochemistry |
The rusticle consists of up to 35% iron compounds including iron oxides, iron carbonates, and iron hydroxides. Rusticles are found in a tube shapes of iron oxides which are vertical to one another. Rusticles are found to grow at approximately a year and are most often found in areas of sunken hulls underwater.
The remainder of the structure is a complex community of symbiotic or mutualistic microbes including bacteria Halomonas titanicae and fungi that use the rusting metal as a source of food, causing microbial corrosion and collectively producing the mineral compounds that form the rusticle as waste products.
Rusticles have been found to most often be composed of iron, calcium, chloride, magnesium, silica, sodium, and sulfate while there are other chemical compositions of rusticles but in much smaller quantities. | 8 | Metallurgy |
Variations in iron isotopic composition have been observed in meteorite samples from other planetary bodies. The Moon has variations in iron isotopes of 0.4‰ per atomic mass unit. Mars has very small isotope fractionation of 0.001 ± 0.006‰ per atomic mass unit. Vesta has iron fractionations of 0.010 ± 0.010‰ per atomic mass unit. The chondritic reservoir exhibits fractionations of 0.069 ± 0.010‰ per atomic mass unit. Isotopic variations observed on planetary bodies can help to constrain and better understand their formation and processes occurring in the early Solar System. | 9 | Geochemistry |
ILAC describes the following five types of reference material:
# Pure substances; essentially pure chemicals, characterised for chemical purity and/or trace impurities.
# Standard solutions and gas mixtures, often prepared gravimetrically from pure substances.
# Matrix reference materials, characterised for the composition of specified major, minor or trace chemical constituents. Such materials may be prepared from matrices containing the components of interest, or by preparing synthetic mixtures.
# Physico-chemical reference materials, characterised for properties such as melting point, viscosity, or optical density.
# Reference objects or artifacts, characterised for functional properties such as taste, odour, octane number, flash point and hardness. This type also includes microscopy specimens characterised for properties ranging from fibre type to microbiological specimens. | 3 | Analytical Chemistry |
Human activities have a major effect on the global sulfur cycle. The burning of coal, natural gas, and other fossil fuels has greatly increased the amount of sulfur in the atmosphere and ocean and depleted the sedimentary rock sink. Without human impact sulfur would stay tied up in rocks for millions of years until it was uplifted through tectonic events and then released through erosion and weathering processes. Instead it is being drilled, pumped and burned at a steadily increasing rate. Over the most polluted areas there has been a 30-fold increase in sulfate deposition.
Although the sulfur curve shows shifts between net sulfur oxidation and net sulfur reduction in the geologic past, the magnitude of the current human impact is probably unprecedented in the geologic record. Human activities greatly increase the flux of sulfur to the atmosphere, some of which is transported globally. Humans are mining coal and extracting petroleum from the Earths crust at a rate that mobilizes 150 x 10 gS/yr, which is more than double the rate of 100 years ago. The result of human impact on these processes is to increase the pool of oxidized sulfur (SO) in the global cycle, at the expense of the storage of reduced sulfur in the Earths crust. Therefore, human activities do not cause a major change in the global pools of sulfur, but they do produce massive changes in the annual flux of sulfur through the atmosphere.
When SO is emitted as an air pollutant, it forms sulfuric acid through reactions with water in the atmosphere. Once the acid is completely dissociated in water the pH can drop to 4.3 or lower causing damage to both man-made and natural systems. According to the EPA, acid rain is a broad term referring to a mixture of wet and dry deposition (deposited material) from the atmosphere containing higher than normal amounts of nitric and sulfuric acids. Distilled water (water without any dissolved constituents), which contains no carbon dioxide, has a neutral pH of 7. Rain naturally has a slightly acidic pH of 5.6, because carbon dioxide and water in the air react together to form carbonic acid, a very weak acid. Around Washington, D.C., however, the average rain pH is between 4.2 and 4.4. Since pH is on a log scale dropping by 1 (the difference between normal rain water and acid rain) has a dramatic effect on the strength of the acid. In the United States, roughly two thirds of all SO and one fourth of all NO come from electric power generation that relies on burning fossil fuels, like coal.
As it is an important nutrient for plants, sulfur is increasingly used as a component of fertilizers. Recently sulfur deficiency has become widespread in many countries in Europe. Because of actions taken to limit acid rains atmospheric inputs of sulfur continue to decrease, As a result, the deficit in the sulfur input is likely to increase unless sulfur fertilizers are used. | 9 | Geochemistry |
The expansion of the corrosion products (iron oxides) of carbon steel reinforcement structures may induce internal mechanical stress (tensile stress) that cause the formation of cracks and disrupt the concrete structure. If rebars have been improperly installed or have inadequate concrete cover at surfaces exposed to the elements, oxide jacking and spalling can occur during the structures lifetime: flat fragments of concrete are detached from the concrete mass as a result of the rebars corrosion.
Concrete, like most consolidated hard rocks, is a material very resistant to compression but which cannot withstand tension, especially internal tensions. Its tensile strength is about 10 times lower than its compressive strength. In itself carbonated concrete is a very solid material because its compressive strength increases due to its porosity decrease by the precipitation of calcium carbonate (calcite, ). In the absence of steel reinforcement bars and without the formation of expansive reaction products inducing tensile stress inside the concrete matrix, pure concrete is most often a long-lasting material. An illustration of the concrete intrinsic durability is the dome of the Pantheon building in Rome made with Roman concrete more than 2000 years ago.
When atmospheric carbon dioxide (), or carbonate ions (, dissolved in water) diffuse into concrete from its external surface, they react with calcium hydroxide (portlandite, ) and the pH of the concrete pore water progressively decreases from 13.5 – 12.5 to 8.5 (pH of water in equilibrium with calcite). Below a pH value of about 9.5 – 10, the solubility of iron oxides present at the surface of carbon steel increases and they start to dissolve. As a consequence, they no longer protect the underlying metallic iron against oxidation by atmospheric oxygen and the reinforcement bars are no longer passivated against corrosion. It is the considerable forces internally created by the expansion of the iron corrosion products (about 6 – 7 times less dense than metallic iron, so 6 – 7 times more voluminous) that cause the cracks in the concrete matrix and destroy reinforced concrete. In the absence of iron (and without some harmful chemical degradation reactions also producing expansive products) concrete would probably be one of the most durable materials. However, steel reinforcement bars are necessary to take over the tensile efforts to which concrete is submitted in most engineering structures and stainless steel would be too costly a metal to replace carbon steel. Zinc-galvanization or epoxy-coating can improve the corrosion resistance of rebar, but have also other disadvantages such as their lower surface adhesion to concrete (risk of slip), the possible formation of cathodic and anodic zones conducive to galvanic corrosion if the protective coating is locally punctured or damaged, and their higher costs. | 8 | Metallurgy |
Chlorosulfonyl isocyanate is the chemical compound ClSONCO, known as CSI. This compound is a versatile reagent in organic synthesis. | 0 | Organic Chemistry |
Sigma-2 receptors are highly expressed in breast, ovarian, lung cancers, brain, bladder, colon cancers, and melanoma. This novelty makes them a valuable biomarker for identifying cancerous tissues. Furthermore, studies have shown that they are more highly expressed in malignant tumors than dormant tumors.
Exogenous sigma-2 receptor ligands have been altered to be neuronal-tracers, used to map cells and their connections. These tracers have high selectivity and affinity for sigma-2 receptors, and high lipophilicity, making them ideal for usage in the brain. Because sigma-2 receptors are highly expressed in tumor cells and are part of the cell proliferation mechanism, PET scans using sigma-2 targeted tracers can reveal if a tumor is proliferating and what its growth rate is. | 1 | Biochemistry |
Acid rain does not directly affect human health. The acid in the rainwater is too dilute to have direct adverse effects. The particulates responsible for acid rain (sulfur dioxide and nitrogen oxides) do have an adverse effect. These particulates come together and react in the atmosphere, forming nitrate particles and fine sulfate. Exposure to high amounts of these particles, particularly over a long period of time, can cause irritation to the eyes and skin, increased fluid in the lungs, and dental damage and erosion. Increased amounts of fine particulate matter in the air contribute to heart and lung problems, including asthma and bronchitis. These particular effects on the heart and lungs can alter their function, including heart attack caused death for those with an increased risk of heart disease and other heart conditions. | 2 | Environmental Chemistry |
Mechanically created wounds in the plasma membrane have been observed as a result of sonoporation-produced shear forces. The nature of these wounds may vary based on the degree of acoustic cavitation leading to a spectrum of cell behavior, from membrane blebbing to instant cell lysis. Multiple studies examining membrane wounds note observing resealing behavior, a process dependent on recruitment of ATP and intracellular vesicles. | 1 | Biochemistry |
In metallurgy, refining consists of purifying an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical change to the raw material, whereas in refining, the final material is usually identical chemically to the original one, only it is purer. The processes used are of many types, including pyrometallurgical and hydrometallurgical techniques. | 8 | Metallurgy |
Calcium disilicide (CaSi) is an inorganic compound, a silicide of calcium. It is a whitish or dark grey to black solid matter with melting point 1033 °C. It is insoluble in water, but may decompose when subjected to moisture, evolving hydrogen and producing calcium hydroxide. It decomposes in hot water, and is flammable and may ignite spontaneously in air.
Industrial calcium silicide usually contains iron and aluminium as the primary contaminants, and low amounts of carbon and sulfur. | 8 | Metallurgy |
Consider two coupled ultrasensitive modules, disregarding effects of sequestration of molecular components between layers. In this case, the expression for the system's dose-response curve, , results from the mathematical composition of the functions, , which describe the input/output relationship of isolated modules :
Brown et al. (1997) have shown that the local ultrasensitivity of the different layers combines multiplicatively:
In connection with this result, Ferrell et al. (1997) showed, for Hill-type modules, that the overall cascade global ultrasensitivity had to be less than or equal to the product of the global ultrasensitivity estimations of each cascade's layer,
where and are the Hill coefficient of modules 1 and 2 respectively.
Altszyler et al. (2017) have shown that the cascade's global ultrasensitivity can be analytically calculated:
where and delimited the Hill inputs working range of the composite system, i.e. the input values for the i-layer so that the last layer (corresponding to in this case) reached the 10% and 90% of it maximal output level. It followed this equation that the systems Hill coefficient could be written as the product of two factors, and , which characterized local average sensitivities over the relevant input region for each layer: , with in this case.
For the more general case of a cascade of modules, the Hill coefficient can be expressed as: | 1 | Biochemistry |
Wide band gap semiconductors like tin oxide generally possess a high chemical stability and mobility, are cheap to fabricate and have a suitable band alignment, making these semiconductors often used in various electronics as thin film transistors, anodes in lithium ion batteries and as electron transport layer in solar cells. The large band gap of () and large binding energy () make it useful in ultraviolet based devices.
But a fundamental problem arises with its dipole forbidden band structure in bulk form: the transition from the valence to the conduction band is dipole forbidden since both types of states exist with even parity with the effect that band edge emission of is forbidden in nature. This can be offset by employing its reduced dimensional structure, partially destroying the crystal symmetry, turning the forbidden dipole transition into allowed ones. Observing optical transitions in at room temperature, however, is challenging due to the light absorbing efficiency in the UV region of the reduced structures being very weak and background scattering of electrons with lower energies. Using electroreflectance the optical transitions of thin films can be recovered: by placing a thin film in an electric field, the critical points of the optical transition will be enhanced while, due to a change in reflectivity, low energy background scattering is reduced. | 7 | Physical Chemistry |
The Mandelin reagent is used as a simple spot-test to presumptively identify alkaloids as well as other compounds. It is composed of a mixture of ammonium metavanadate and concentrated sulfuric acid. Its primary use is for the detection of ketamine and PMA Unlike the most common reagent test chemicals, it has a deep red colour that changes to yellow if there is no alkaloid, which occurs within about 48 hours of mixing.
The United States Department of Justice method for producing the reagent is the addition of 100 mL of concentrated (95–98%) sulfuric acid to 0.5-1 g of Ammonium metavanadate.
This reagent was invented by the German pharmacologist, Karl Friedrich Mandelin (1854–1906) at the University of Dorpat. | 3 | Analytical Chemistry |
This reaction accounts for around half of the transformation of wustite FeO into iron, and removes 30% of the total oxygen supplied, mainly in the form of iron oxide FeO. This mode of wustite reduction is highly endothermic, whereas the reduction of iron oxides by CO is slightly exothermic (+155.15 kJ/mol vs. -17.45 kJ/mol), so it is essential to keep it to a minimum.
This reaction concerns all the iron oxides present in a blast furnace, but also manganese(II) oxides (Mno), silica (SiO), chromium, vanadium and titanium, which are partially reduced in blast furnaces. These chemical reactions are described below:
MnO + C → Mn + CO consuming 282,4 kJ/mol à 1 400 °C (begins above 1,000°C and involves half of the manganese present in the charge)
SiO + 2 C → Si + 2 CO consuming 655,5 kJ/mol (begins above 1 500 °C)
Chromium and vanadium behave like manganese, titanium like silicon. As for the other iron oxides, their direct reduction is of negligible importance. This can be written as:
3 FeO + C → 2 FeO + CO consuming 118,821 kJ/mol
FeO + C → 3 FeO + CO consuming 209,256 kJ/mol
In non-steel blast furnaces, dedicated to the production of ferroalloys, direct reduction is fundamental. For example, for ferronickel production, both direct reduction reactions are used:
NiO + C → Ni + CO above 445 °C
FeO + C → Fe + CO above 800 °C
So, although nickel reduces slightly more easily than iron, it cannot be reduced and cast independently of iron. | 8 | Metallurgy |
As sedimentation field flow fractionation (SFFF) is one of field flow fractionation separation techniques, it is appropriate for fractionation and characterization of particulate materials and soluble samples in the colloid size range. Differences in interaction between a centrifugal force field and particles with different masses or sizes lead to the separation. An exponential distribution of particles of a certain size or weight is results due to the Brownian motion. Some of the assumptions to develop the theoretical equations include that there is no interaction between individual particles and equilibrium can occur anywhere in separation channels. | 7 | Physical Chemistry |
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