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The word metabolome appears to be a blending of the words "metabolite" and "chromosome". It was constructed to imply that metabolites are indirectly encoded by genes or act on genes and gene products. The term "metabolome" was first used in 1998 and was likely coined to match with existing biological terms referring to the complete set of genes (the genome), the complete set of proteins (the proteome) and the complete set of transcripts (the transcriptome). The first book on metabolomics was published in 2003. The first journal dedicated to metabolomics (titled simply "Metabolomics") was launched in 2005 and is currently edited by Prof. Roy Goodacre. Some of the more significant early papers on metabolome analysis are listed in the references below. | 1 | Biochemistry |
The Mpemba effect is the name given to the observation that a liquid (typically water) which is initially hot can freeze faster than the same liquid which begins cold, under otherwise similar conditions. There is disagreement about its theoretical basis and the parameters required to produce the effect.
The Mpemba effect is named after Tanzanian scientist Erasto Bartholomeo Mpemba, who described it in 1963 as a secondary school student. The initial discovery and observations of the effect originate in ancient times; Aristotle said that it was common knowledge. | 7 | Physical Chemistry |
Cholesterol is a cell signaling molecule that is highly regulated in eukaryotic cell membranes. In human health, its effects are most notable in inflammation, metabolic syndrome, and neurodegeneration. At the molecular level, cholesterol primarily signals by regulating clustering of saturated lipids and proteins that depend on clustering for their regulation. | 1 | Biochemistry |
Transcription factor II E (TFE) is one of several general transcription factors that make up the RNA polymerase II preinitiation complex. It is a tetramer of two alpha and two beta chains and interacts with TAF6/TAFII80, ATF7IP, and varicella-zoster virus IE63 protein.
TFE recruits TFH to the initiation complex and stimulates the RNA polymerase II C-terminal domain kinase and DNA-dependent ATPase activities of TFH. Both TFH and TFE are required for promoter clearance by RNA polymerase. Transcription factor II E is encoded by the GTF2E1 and GTF2E2 genes. TFE is thought to be involved in DNA melting at the promoter: it contains a zinc ribbon motif that can bind single stranded DNA. | 1 | Biochemistry |
Mitochondrial phosphoenolpyruvate carboxykinase is thought to participate in the transfer of the phosphorylation potential from the matrix to the cytosol and vice versa. However, it is strongly favored towards GTP hydrolysis, thus it is not really considered as an important source of intra-mitochondrial substrate-level phosphorylation. | 1 | Biochemistry |
Non-Smad signaling proteins contribute to the responses of the TGF-β pathway in three ways. First, non-Smad signaling pathways phosphorylate the Smads. Second, Smads directly signal to other pathways by communicating directly with other signaling proteins, such as kinases. Finally, the TGF-β receptors directly phosphorylate non-Smad proteins. | 1 | Biochemistry |
The primary application of proton-exchange membranes is in PEM fuel cells. These fuel cells have a wide variety of commercial and military applications including in the aerospace, automotive, and energy industries.
Early PEM fuel cell applications were focused within the aerospace industry. The then-higher capacity of fuel cells compared to batteries made them ideal as NASA's Project Gemini began to target longer duration space missions than had previously been attempted.
, the automotive industry as well as personal and public power generation are the largest markets for proton-exchange membrane fuel cells. PEM fuel cells are popular in automotive applications due to their relatively low operating temperature and their ability to start up quickly even in below-freezing conditions. As of March 2019 there were 6,558 fuel cell vehicles on the road in the United States, with the Toyota Mirai being the most popular model. PEM fuel cells have seen successful implementation in other forms of heavy machinery as well, with Ballard Power Systems supplying forklifts based on the technology. The primary challenge facing automotive PEM technology is the safe and efficient storage of hydrogen, currently an area of high research activity.
Polymer electrolyte membrane electrolysis is a technique by which proton-exchange membranes are used to decompose water into hydrogen and oxygen gas. The proton-exchange membrane allows for the separation of produced hydrogen from oxygen, allowing either product to be exploited as needed. This process has been used variously to generate hydrogen fuel and oxygen for life-support systems in vessels such as US and Royal Navy submarines. A recent example is the construction of a 20 MW Air Liquide PEM electrolyzer plant in Québec. Similar PEM-based devices are available for the industrial production of ozone. | 7 | Physical Chemistry |
Apamin is a polypeptide possessing an amino acid sequence of H-Cys-Asn-Cys-Lys-Ala-Pro-Glu-Thr-Ala-Leu-Cys-Ala-Arg-Arg-Cys-Gln-Gln-His-NH (one-letter sequence CNCKAPETALCARRCQQH-NH, with disulfide bonds between Cys-Cys and Cys-Cys). Apamin is very rigid because of the two disulfide bridges and seven hydrogen bonds. The three-dimensional structure of apamin has been studied with several spectroscopical techniques: HNMR, Circular Dichroism, Raman spectroscopy, FT-IR. The structure is presumed to consist of an alpha-helix and beta-turns, but the exact structure is still unknown.
By local alterations it is possible to find the amino acids that are involved in toxicity of apamin. It was found by Vincent et al. that guanidination of the ε-amino group of lysine does not decrease toxicity. When the ε-amino group of lysine and the α-amino group of cysteine are acetylated or treated with fluorescamine, toxicity decreases with a factor of respectively 2.5 and 2.8. This is only a small decrease, which indicates that neither the ε-amino group of lysine nor the α-amino group of cysteine is essential for the toxicity of apamin. Glutamine was altered by formation of an amide bond with glycine ethyl ester, this resulted in a decrease in toxicity of a factor 2.0. Glutamine also doesn't appear to be essential for toxicity. When histidine is altered by carbethoxylation, toxicity decreases only by a factor 2.6. But when histidine, the ε-amino group of lysine and the α-amino group of cysteine all are carbethoxylated and acetylated toxicity decreases drastically. This means that these three amino acids are not essential for toxicity on their own, but the three of them combined are. Chemical alteration of arginine and arginine by treatment of 1,2-cyclohexanedione and cleavage by trypsin decreases toxicity by a factor greater than 10. The amino acids that cause toxicity of apamin are cysteine, lysine, arginine, arginine and histidine. | 1 | Biochemistry |
In the year 2000 Meat and Livestock Australia (MLA) initiated a pilot group of beef and cattle farmers to partake in an environmental management system that would be soon implemented into the cattle industry. The standard aimed for the pilot group was ISO 14001 which is the current system standard for principal management systems and particularises the requirements for the introduction and maintenance of an environmental management system. During this period of development, Commonwealth and state governments who had been promoting EMS models in the agricultural sector began to introduce these methods to the nation's red meat industry. | 2 | Environmental Chemistry |
Anaerobic oxidation of iron and steel commonly finds place in oxygen-depleted environments, such as in permanently water-saturated soils, peat bogs or wetlands in which archaeological iron artefacts are often found.
Anaerobic oxidation of carbon steel of canisters and overpacks is also expected to occur in deep geological formations in which high-level radioactive waste and spent fuels should be ultimately disposed. Nowadays, in the frame of the corrosion studies related to HLW disposal, anaerobic corrosion of steel is receiving a renewed and continued attention. Indeed, it is essential to understand this process to guarantee the total containment of HLW waste in an engineered barrier during the first centuries or millennia when the radiotoxicity of the waste is high and when it emits a significant quantity of heat.
The question is also relevant for the corrosion of the reinforcement bars (rebars) in concrete (Aligizaki et al., 2000). This deals then with the service life of concrete structures, amongst others the near-surface vaults intended for hosting low-level radioactive waste. | 8 | Metallurgy |
Heme O (or haem O) differs from the closely related heme A by having a methyl group at ring position 8 instead of the formyl group. The isoprenoid chain at position 2 is the same.
Heme O, found in the bacterium Escherichia coli, functions in a similar manner to heme A in mammalian oxygen reduction. | 1 | Biochemistry |
A kinetic and regional chemical study of the Evelyn effect has been described. The results, in the Journal of Chemical Education, made claims involving the mechanism by which the dehydrations occurred.
The article looks into the claim of having E1 and E2 mechanisms occur in the reaction.
The researchers measured the kinetics of the formation of a 3 degree carbocation’s and compared them to theoretical calculations that would occur if the experiment ran as an E2 reaction. Instead, the reaction showed a mechanism that initially formed a 2 degree carbocation, utilizing an E1 pathway. Their conclusion was that the mechanism is neither E1 or E2 but rather “E-2 like”, exhibiting first order kinetics. | 7 | Physical Chemistry |
The most important aliphatic compounds are:
* n-, iso- and cyclo-alkanes (saturated hydrocarbons)
* n-, iso- and cyclo-alkenes and -alkynes (unsaturated hydrocarbons).
Important examples of low-molecular aliphatic compounds can be found in the list below (sorted by the number of carbon-atoms): | 0 | Organic Chemistry |
Several molecular biology studies during the 1950s indicated that RNA played some kind of role in protein synthesis, but that role was not clearly understood. For instance, in one of the earliest reports, Jacques Monod and his team showed that RNA synthesis was necessary for protein synthesis, specifically during the production of the enzyme β-galactosidase in the bacterium E. coli. Arthur Pardee also found similar RNA accumulation in 1954. In 1953, Alfred Hershey, June Dixon, and Martha Chase described a certain cytosine-containing DNA (indicating it was RNA) that disappeared quickly after its synthesis in E. coli. In hindsight, this may have been one of the first observations of the existence of mRNA but it was not recognized at the time as such.
The idea of mRNA was first conceived by Sydney Brenner and Francis Crick on 15 April 1960 at Kings College, Cambridge, while François Jacob was telling them about a recent experiment conducted by Arthur Pardee, himself, and Monod (the so-called PaJaMo experiment, which did not prove mRNA existed but suggested the possibility of its existence). With Cricks encouragement, Brenner and Jacob immediately set out to test this new hypothesis, and they contacted Matthew Meselson at the California Institute of Technology for assistance. During the summer of 1960, Brenner, Jacob, and Meselson conducted an experiment in Meselson's laboratory at Caltech which was the first to prove the existence of mRNA. That fall, Jacob and Monod coined the name "messenger RNA" and developed the first theoretical framework to explain its function.
In February 1961, James Watson revealed that his Harvard-based research group had been right behind them with a series of experiments whose results pointed in roughly the same direction. Brenner and the others agreed to Watsons request to delay publication of their research findings. As a result, the Brenner and Watson articles were published simultaneously in the same issue of Nature in May 1961, while that same month, Jacob and Monod published their theoretical framework for mRNA in the Journal of Molecular Biology'. | 1 | Biochemistry |
In 1967, Akira Fujishima discovered the Honda-Fujishima effect, (the photocatalytic properties of titanium dioxide).
Titanium dioxide| and other metal oxides are still most prominent catalysts for efficiency reasons. Including Strontium titanate| and Barium titanate|, this kind of semiconducting titanates, the conduction band has mainly titanium 3d character and the valence band oxygen 2p character. The bands are separated by a wide band gap of at least 3 eV, so that these materials absorb only UV radiation.
Change of the microstructure has also been investigated to further improve the performance. In 2002, Guerra (Nanoptek Corporation) discovered that high localized strain could be induced in semiconductor films formed on micro to nano-structured templates, and that this strain shifted the bandgap of the semiconductor, in the case of titanium dioxide, into the visible blue. It was further found (Thulin and Guerra, 2008) that the strain also favorably shifted the band-edges to overlay the hydrogen evolution potential, and further still that the strain improved hole mobility, for lower charge recombination rate and high quantum efficiency. Chandekar developed a low-cost scalable manufacturing process to produce both the nano-structured template and the strained titanium dioxide coating. Other morphological investigations include nanowire arrays or porous nanocrystalline photoelectrochemical cells. | 5 | Photochemistry |
Cholesterol 7 alpha-hydroxylase also known as cholesterol 7-alpha-monooxygenase or cytochrome P450 7A1 (CYP7A1) is an enzyme that in humans is encoded by the gene which has an important role in cholesterol metabolism. It is a cytochrome P450 enzyme, which belongs to the oxidoreductase class, and converts cholesterol to 7-alpha-hydroxycholesterol, the first and rate limiting step in bile acid synthesis.
The inhibition of cholesterol 7-alpha-hydroxylase (CYP7A1) represses bile acid biosynthesis. | 1 | Biochemistry |
Trimethylsilyl chloride is used to prepare other trimethylsilyl halides and pseudohalides, including trimethylsilyl fluoride, trimethylsilyl bromide, trimethylsilyl iodide, trimethylsilyl cyanide, trimethylsilyl azide, and trimethylsilyl trifluoromethanesulfonate (TMSOTf). These compounds are produced by a salt metathesis reaction between trimethylsilyl chloride and a salt of the (pseudo)halide (MX):
TMSCl, lithium, and nitrogen molecule react to give tris(trimethylsilyl)amine, under catalysis by nichrome wire or chromium trichloride:
Using this approach, atmospheric nitrogen can be introduced into organic substrate. For example, tris(trimethylsilyl)amine reacts with α,δ,ω-triketones to give tricyclic pyrroles.
Reduction of trimethylsilyl chloride give hexamethyldisilane: | 0 | Organic Chemistry |
In molecular biology, a response regulator is a protein that mediates a cell's response to changes in its environment as part of a two-component regulatory system. Response regulators are coupled to specific histidine kinases which serve as sensors of environmental changes. Response regulators and histidine kinases are two of the most common gene families in bacteria, where two-component signaling systems are very common; they also appear much more rarely in the genomes of some archaea, yeasts, filamentous fungi, and plants. Two-component systems are not found in metazoans. | 1 | Biochemistry |
An event-specific detection searches for the presence of a DNA sequence unique to a certain GMO, usually the junction between the transgene and the organism's original DNA. This approach is ideal to precisely identify a GMO, yet highly similar GMOs will pass completely unnoticed. Event-specific detection is PCR-based. | 1 | Biochemistry |
Ring A synthesis (scheme 4) started with reduction of the C9 ketone group in 28 to diol 29 with alane in toluene followed by diol protection in 30 as a dimethyl carbonate. This allowed selective oxidation of the C1 alcohol with DDQ after deprotection to ketone 31. This compound was alkylated to 32 at the C1 ketone group with the Grignard homoallyl magnesium bromide (C4 fragment completing the carbon framework) and deprotected at C11 (TBAF) to diol 33. By reaction with cyclohexylmethylsilyldichloride both alcohol groups participated in a cyclic silyl ether (34) which was again cleaved by reaction with methyl lithium exposing the C11 alcohol in 35. The A ring closure required two ketone groups for a pinacol coupling which were realized by oxidation of the C11 alcohol (TPAP, NMO) to ketone 36 and Wacker oxidation of the allyl group to diketone 37. After formation of the pinacol product 38 the benzyl groups (sodium, ammonia) and the trialkylsilyl groups (TBAF) were removed to form pentaol 39.
The pentaol 39 was protected twice: two bottom hydroxyl groups as a carbonate ester (bis(trichloromethyl)carbonate, pyridine) and the C10 hydroxyl group as the acetate forming 40. The acetonide group was removed (HCl, THF), the C7 hydroxyl group protected as a TES silyl ether and the C11 OH group oxidized (TPAP, NMO) to ketone 41. The ring A diol group was next removed in a combined elimination reaction and Barton deoxygenation with 1,1-thiocarbonyldiimidazole' forming alkene 42. Finally the C15 hydroxyl group was introduced by oxidation at the allyl position with in two steps PPC and sodium acetate (to the enone) and with K-selectride to alcohol 43 which was protected as a TES ether in 44. | 0 | Organic Chemistry |
Here, the OAA produced by PEPC is transaminated by aspartate aminotransferase to aspartate (ASP) which is the metabolite diffusing to the bundle sheath. In the bundle sheath ASP is transaminated again to OAA and then undergoes a futile reduction and oxidative decarboxylation to release . The resulting Pyruvate is transaminated to alanine, diffusing to the mesophyll. Alanine is finally transaminated to pyruvate (PYR) which can be regenerated to PEP by PPDK in the mesophyll chloroplasts. This cycle bypasses the reaction of malate dehydrogenase in the mesophyll and therefore does not transfer reducing equivalents to the bundle sheath. | 5 | Photochemistry |
The optimal configurations of scanning helium microscopes are geometrical configurations that maximise the intensity of the imaging beam within a given lateral resolution and under certain technological constraints.
When designing a scanning helium microscope, scientists strive to maximise the intensity of the imaging beam while minimising its width. The reason behind this is that the beam's width gives the resolution of the microscope while its intensity is proportional to its signal to noise ratio. Due to their neutrality and high ionisation energy, neutral helium atoms are hard to detect. This makes high-intensity beams a crucial requirement for a viable scanning helium microscope.
In order to generate a high-intensity beam, scanning helium microscopes are designed to generate a supersonic expansion of the gas into vacuum, that accelerates neutral helium atoms to high velocities. Scanning helium microscopes exist in two different configurations: the pinhole configuration and the zone plate configuration. In the pinhole configuration, a small opening (the pinhole) selects a section of the supersonic expansion far away from its origin, which has previously been collimated by a skimmer (essentially, another small pinhole). This section then becomes the imaging beam. In the zone plate configuration a Fresnel zone plate focuses the atoms coming from a skimmer into a small focal spot.
Each of these configurations have different optimal designs, as they are defined by different optics equations. | 7 | Physical Chemistry |
There may be a general misconception between the term corrosion inspection and corrosion monitoring, but inspection means frequent checkpoints to check for changes or deviations from predicted results, while corrosion monitoring is a continuous check to control and act quickly against change. In inspection, the purpose is to evaluate or estimate the corrosion time in order to replace or correct the corrosion, while in corrosion monitoring, the purpose is to take care of the change in order to prevent corrosion and to improve the ways of prevention. | 8 | Metallurgy |
Based on their band structure, materials are characterised with a direct band gap or indirect band gap. In the free-electron model, k is the momentum of a free electron and assumes unique values within the Brillouin zone that outlines the periodicity of the crystal lattice. If the momentum of the lowest energy state in the conduction band and the highest energy state of the valence band of a material have the same value, then the material has a direct bandgap. If they are not the same, then the material has an indirect band gap and the electronic transition must undergo momentum transfer to satisfy conservation. Such indirect "forbidden" transitions still occur, however at very low probabilities and weaker energy. For materials with a direct band gap, valence electrons can be directly excited into the conduction band by a photon whose energy is larger than the bandgap. In contrast, for materials with an indirect band gap, a photon and phonon must both be involved in a transition from the valence band top to the conduction band bottom, involving a momentum change. Therefore, direct bandgap materials tend to have stronger light emission and absorption properties and tend to be better suited for photovoltaics (PVs), light-emitting diodes (LEDs), and laser diodes; however, indirect bandgap materials are frequently used in PVs and LEDs when the materials have other favorable properties. | 7 | Physical Chemistry |
The Integrated Carbon Observation System (ICOS) is a research infrastructure to quantify the greenhouse gas balance of Europe and adjacent regions. In November 2015 it received the international legal status of ERIC (European Research Infrastructure Consortium) by decision of the European Commission. It is recognized by The European Strategy Forum on Research Infrastructures (ESFRI) as a landmark European research infrastructure. It consists of a harmonized network of almost 150 long-term observation sites for the domains of atmosphere, ecosystems and ocean. The network is coordinated through its Head Office, the central data portal and central facilities including an atmosphere, ecosystem and ocean thematic center, and central analytical laboratories.
ICOS provides the essential long-term observations required to understand the present state and predict future behavior of the global carbon cycle and greenhouse gas emissions. It monitors and assesses the effectiveness of carbon sequestration and/or greenhouse gases emission reduction activities on global atmospheric composition levels, including attribution of sources and sinks by region and sector.
The highly standardized network offers improved access to data and enables the development of flux products for research and political application. ICOS is a state-of-the-art facility for the European research community. It contributes to the European share of global greenhouse gas observations under Group on Earth Observations (GEO), World Meteorological Organization GAW and GCOS programs. | 2 | Environmental Chemistry |
There is evidence from a phylogenetically diverse sample of tunicates (Urochordata) that AGA and AGG code for glycine. In other organisms, AGA/AGG code for either arginine or serine and in vertebrate mitochondria they code a STOP. Evidence for glycine translation of AGA/AGG was first found in 1993 in Pyura stolonifera and Halocynthia roretzi. It was then confirmed by tRNA sequencing and sequencing whole mitochondrial genomes. | 1 | Biochemistry |
The ICP-MS allows determination of elements with atomic mass ranges 7 to 250 (Li to U), and sometimes higher. Some masses are prohibited such as 40 due to the abundance of argon in the sample. Other blocked regions may include mass 80 (due to the argon dimer), and mass 56 (due to ArO), the latter of which greatly hinders Fe analysis unless the instrumentation is fitted with a reaction chamber. Such interferences can be reduced by using a high resolution ICP-MS (HR-ICP-MS) which uses two or more slits to constrict the beam and distinguish between nearby peaks. This comes at the cost of sensitivity. For example, distinguishing iron from argon requires a resolving power of about 10,000, which may reduce the iron sensitivity by around 99%. Another solution for some interfering species is the use of a collision chamber, as explained in collision reaction cell article.
A single collector ICP-MS may use a multiplier in pulse counting mode to amplify very low signals, an attenuation grid or a multiplier in analogue mode to detect medium signals, and a Faraday cup/bucket to detect larger signals. A multi-collector ICP-MS may have more than one of any of these, normally Faraday buckets which are much less expensive. With this combination, a dynamic range of 12 orders of magnitude, from 1 ppq to 100 ppm is possible.
ICP-MS is a method of choice for the determination of cadmium in biological samples.
Unlike atomic absorption spectroscopy, which can only measure a single element at a time, ICP-MS has the capability to scan for all elements simultaneously. This allows rapid sample processing. A simultaneous ICP-MS that can record the entire analytical spectrum from lithium to uranium in every analysis won the Silver Award at the 2010 Pittcon Editors' Awards. An ICP-MS may use multiple scan modes, each one striking a different balance between speed and precision. Using the magnet alone to scan is slow, due to hysteresis, but is precise. Electrostatic plates can be used in addition to the magnet to increase the speed, and this, combined with multiple collectors, can allow a scan of every element from Lithium 6 to Uranium Oxide 256 in less than a quarter of a second. For low detection limits, interfering species and high precision, the counting time can increase substantially. The rapid scanning, large dynamic range and large mass range is ideally suited to measuring multiple unknown concentrations and isotope ratios in samples that have had minimal preparation (an advantage over TIMS), for example seawater, urine, and digested whole rock samples. It also lends well to laser ablated rock samples, where the scanning rate is so quick that a real time plot of any number of isotopes is possible. This also allows easy spatial mapping of mineral grains. | 3 | Analytical Chemistry |
EA-3148 (Substance 100A) is a "V-series" nerve agent related to the better-known compounds VX and VR. It was studied by both the US and Soviet chemical weapons programmes during the Cold War, and is notable as the only V-series organophosphate nerve agent specifically identified in public domain sources as having a higher absolute potency as an acetylcholinesterase inhibitor than VX (around 50% more potent by weight). However, both the US and Soviet investigations of the compound concluded that despite its high potency, the physicochemical properties of the substance made it unsuitable for weaponisation, and further research was not conducted.
The chemical structure of EA-3148 falls within the scope of compounds designated "Toxic chemicals" under Schedule 1 of the Chemical Weapons Convention and so it is illegal throughout the world under international law and may only be used for certain types of scientific and medical research. | 1 | Biochemistry |
Chemical milling or industrial etching is the subtractive manufacturing process of using baths of temperature-regulated etching chemicals to remove material to create an object with the desired shape. Other names for chemical etching include photo etching, chemical etching, photo chemical etching and photochemical machining. It is mostly used on metals, though other materials are increasingly important. It was developed from armor-decorating and printing etching processes developed during the Renaissance as alternatives to engraving on metal. The process essentially involves bathing the cutting areas in a corrosive chemical known as an etchant, which reacts with the material in the area to be cut and causes the solid material to be dissolved; inert substances known as maskants are used to protect specific areas of the material as resists. | 8 | Metallurgy |
The biosynthesis of aspartate frequently involves the transamination of oxaloacetate.
The enzyme aspartokinase, which catalyzes the phosphorylation of aspartate and initiates its conversion into other amino acids, can be broken up into 3 isozymes, AK-I, II and III. AK-I is feed-back inhibited by threonine, while AK-II and III are inhibited by lysine. As a sidenote, AK-III catalyzes the phosphorylation of aspartic acid that is the committed step in this biosynthetic pathway. Aspartate kinase becomes downregulated by the presence of threonine or lysine. | 1 | Biochemistry |
In spatiospectral scanning, each 2-D sensor output represents a wavelength-coded (rainbow-colored, λ = λ(y)), spatial (x, y) map of the scene. A prototype for this technique, introduced in 2014, consists of a camera at some non-zero distance behind a basic slit spectroscope (slit + dispersive element). Advanced spatiospectral scanning systems can be obtained by placing a dispersive element before a spatial scanning system. Scanning can be achieved by moving the whole system relative to the scene, by moving the camera alone, or by moving the slit alone. Spatiospectral scanning unites some advantages of spatial and spectral scanning, thereby alleviating some of their disadvantages. | 7 | Physical Chemistry |
At first glance, using the fact that it would appear that two measurements of would suffice to be able to obtain an accurate value of :
where and are the equilibrium constant values obtained at temperatures and respectively. However, the precision of values obtained in this way is highly dependent on the precision of the measured equilibrium constant values.
The use of error propagation shows that the error in will be about 76 kJ/mol times the experimental uncertainty in , or about 110 kJ/mol times the uncertainty in the values. Similar considerations apply to the entropy of reaction obtained from .
Notably, when equilibrium constants are measured at three or more temperatures, values of and are often obtained by straight-line fitting. The expectation is that the error will be reduced by this procedure, although the assumption that the enthalpy and entropy of reaction are constant may or may not prove to be correct. If there is significant temperature dependence in either or both quantities, it should manifest itself in nonlinear behavior in the Van t'Hoff plot; however, more than three data points would presumably be needed in order to observe this. | 7 | Physical Chemistry |
* U.S. National Academy of Sciences, 1961
* American Academy of Arts and Sciences, 1962
* Foreign Member of the French Academy of Sciences, 1989
* American Philosophical Society, 1995
* The Royal Society, UK 1999 | 0 | Organic Chemistry |
GLV release is correlated with fruit ripeness. Although this may be of effect in attracting pollinators, it also can cause issues if these GLV’s attract predators. One such example of this is with boll weevils, as an increase of GLV release when the plants are ripe has been found to increase the predation rate of these beetles.
Another issue with GLV release and increasing predation is with populations that alter GLV emissions from the affected plants. In one case, it was noted that secretions from certain species of caterpillars significantly decrease the effect amount of GLV emissions. In order to determine what was being done to decrease GLV emissions, a study was run on four unique species of caterpillars to measure their effectiveness in decreasing GLV levels released from the predated plant. It’s been found that compounds in the gut and salivary glands, as well as modifications to those compounds in these various species, has been able to mute a large part of the effect of GLV released into the external environment. How this is done is though stopping the flow of pheromone molecules, so they can’t interact with receptors on the leaves of other plants. | 1 | Biochemistry |
Sex pheromones have evolved in many species. The many types of pheromones (i.e. alarm, aggregation, defense, sexual attraction) all have a common cause acting as chemical cues to trigger a response. However, sex pheromones are particularly associated with signaling mating behaviors or dominance. The odors released can be seen as a favorable trait selected by either the male or female leading to attraction and copulation. Chemical signaling is also used to find genetically different mates and thus avoid inbreeding. Females are often selective when deciding to mate, and chemical communication ensures that they find a high-quality mate that satisfies their reproductive needs. | 1 | Biochemistry |
The quantum yield of photosynthesis, which is also the photochemical quenching of fluorescence, is calculated through the following equation:
Φ = (F-F)/F = F/F
F is the low fluorescence intensity, which is measured by a short light flash that is not strong enough to cause photochemistry, and thus induces fluorescence. F is the maximum fluorescence that can be obtained from a sample by measuring the highest intensity of fluorescence after a saturating flash. The difference between the measured values is the variable fluorescence F. | 5 | Photochemistry |
While capillary sequencing was the first approach to successfully sequence a nearly full human genome, it is still too expensive and takes too long for commercial purposes. Since 2005 capillary sequencing has been progressively displaced by high-throughput (formerly "next-generation") sequencing technologies such as Illumina dye sequencing, pyrosequencing, and SMRT sequencing. All of these technologies continue to employ the basic shotgun strategy, namely, parallelization and template generation via genome fragmentation.
Other technologies have emerged, including Nanopore technology. Though the sequencing accuracy of Nanopore technology is lower than those above, its read length is on average much longer. This generation of long reads is valuable especially in de novo whole-genome sequencing applications. | 1 | Biochemistry |
The process was invented in Hanau, Germany in 1917. Heraeus Vacuumschmelze and Dr. Wilhelm Rohn applied for a patent on vacuum melting on 12 January 1918 and were granted a German patent DE 345161.
Edwin Fitch Northrup built the first prototype of a vacuum induction furnace in the United States of America in 1920.
Medium frequency furnaces were seen soon afterwards in England and Sweden in 1927.
The process was initially developed to refine certain special metals such as cobalt and nickel. As these metals and alloys became more common, the process of VIM became more widely used.
VIM now helps to melt a variety of metals for aircraft and nuclear applications. | 8 | Metallurgy |
The hydrolysis of ATP into ADP and inorganic phosphate
:ATP(aq) + (l) = ADP(aq) + HPO(aq) + H(aq)
releases of enthalpy. This may differ under physiological conditions if the reactant and products are not exactly in these ionization states. The values of the free energy released by cleaving either a phosphate (P) or a pyrophosphate (PP) unit from ATP at standard state concentrations of 1 mol/L at pH 7 are:
:ATP + → ADP + P ΔG°' = −30.5 kJ/mol (−7.3 kcal/mol)
:ATP + → AMP + PP ΔG°' = −45.6 kJ/mol (−10.9 kcal/mol)
These abbreviated equations at a pH near 7 can be written more explicitly (R = adenosyl):
:[RO-P(O)-O-P(O)-O-PO] + → [RO-P(O)-O-PO] + [HPO] + H
:[RO-P(O)-O-P(O)-O-PO] + → [RO-PO] + [HOP-O-PO] + H
At cytoplasmic conditions, where the ADP/ATP ratio is 10 orders of magnitude from equilibrium, the ΔG is around −57 kJ/mol.
Along with pH, the free energy change of ATP hydrolysis is also associated with Mg concentration, from ΔG° = −35.7 kJ/mol at a Mg concentration of zero, to ΔG° = −31 kJ/mol at [Mg] = 5 mM. Higher concentrations of Mg decrease free energy released in the reaction due to binding of Mg ions to negatively charged oxygen atoms of ATP at pH 7. | 1 | Biochemistry |
In the numerator we have the transition dipole moment for the transition, whose squared amplitude represents the strength of the interaction between the electromagnetic field and the atom, and is the vector electric field amplitude, which includes the polarization. The numerator has dimensions of energy, so dividing by gives an angular frequency.
By analogy with a classical dipole, it is clear that an atom with a large dipole moment will be more susceptible to perturbation by an electric field. The dot product includes a factor of , where is the angle between the polarization of the light and the transition dipole moment. When they are parallel the interaction is strongest, when they are perpendicular there is no interaction at all.
If we rewrite the differential equations found above:
and apply the rotating-wave approximation, which assumes that , such that we can discard the high frequency oscillating terms, we have
where is called the detuning between the laser and the atomic frequencies.
We can solve these equations, assuming at time the atom is in (i.e. ) to find
This is the probability as a function of detuning and time of the population of state . A plot as a function of detuning and ramping the time from 0 to gives:
We see that for the population will oscillate between the two states at the Rabi frequency. | 7 | Physical Chemistry |
The mission of EPA is to protect human health and the environment.
EPA works to ensure that:
* Americans have clean air, land and water;
* National efforts to reduce environmental risks are based on the best available scientific information;
* Federal laws protecting human health and the environment are administered and enforced fairly, effectively and as Congress intended;
* Environmental stewardship is integral to U.S. policies concerning natural resources, human health, economic growth, energy, transportation, agriculture, industry, and international trade, and these factors are similarly considered in establishing environmental policy;
* All parts of society--communities, individuals, businesses, and state, local and tribal governments--have access to accurate information sufficient to effectively participate in managing human health and environmental risks;
* Contaminated lands and toxic sites are cleaned up by potentially responsible parties and revitalized; and
* Chemicals in the marketplace are reviewed for safety. | 3 | Analytical Chemistry |
MAPseq or Multiplexed Analysis of Projections by Sequencing is a RNA-Seq based method for high-throughput mapping of neuronal projections. It was developed by Anthony M. Zador and his team at Cold Spring Harbor Laboratory and published in Neuron, a Cell Press magazine.
The method works by uniquely labeling neurons in a source region by injecting a viral library encoding a diverse collection of RNA sequences ("barcodes"). The barcode mRNA is expressed at high levels and transported into the axon terminals at distal target projection regions. Following this, the cells from source and putative target regions of interest are harvested, and their RNA is extracted and sequenced. By matching the presence of the unique "barcode" in the source and target tissue, one can map the projections of neuron in a one-to-many fashion. | 1 | Biochemistry |
Accelerated solvent extraction (ASE), also known as pressurized solvent extraction (PSE), is a method for extracting various chemicals from a complex solid or semisolid sample matrix. The process uses high temperature and pressure, which results in the extraction taking less time and requiring less solvent, and possibly also giving better analyte recovery, than traditional methods that use less extreme conditions. The elevated temperature is employed to increase extraction efficiency of the analyte of interest and the elevated pressure is used to keep the solvent in a liquid state as the temperature is increased above its boiling point. An automated system for the process was developed by Dionex, a company owned by Thermo Fisher Scientific. | 3 | Analytical Chemistry |
Another route to is the Raschig process: aqueous ammonium nitrite is reduced by Bisulfite| and Sulfur dioxide| at 0 °C to yield a hydroxylamido-N,N-disulfonate anion:
This anion is then hydrolyzed to give hydroxylammonium sulfate :
Solid can be collected by treatment with liquid ammonia. Ammonium sulfate, , a side-product insoluble in liquid ammonia, is removed by filtration; the liquid ammonia is evaporated to give the desired product.
The net reaction is:
A base then frees the hydroxylamine from the salt: | 0 | Organic Chemistry |
In most cases the fractionation of polymers on a preparative scale is based on chromatographic methods (e.g. preparative SEC or Baker-Williams fractionation). Therefore, the production is normally limited to few grams only. For large scales of several grams up to kg or even tons the “continuous spin fractionation” can be used. F. Francuskiewicz gives an overview about preparative polymer fractionation. | 7 | Physical Chemistry |
Researchers in structural geology are concerned with the orientations of planes and lines for a number of reasons. The foliation of a rock is a planar feature that often contains a linear feature called lineation. Similarly, a fault plane is a planar feature that may contain linear features such as slickensides.
These orientations of lines and planes at various scales can be plotted using the methods of the Visualization of lines and planes section above. As in crystallography, planes are typically plotted by their poles. Unlike crystallography, the southern hemisphere is used instead of the northern one (because the geological features in question lie below the Earth's surface). In this context the stereographic projection is often referred to as the equal-angle lower-hemisphere projection. The equal-area lower-hemisphere projection defined by the Lambert azimuthal equal-area projection is also used, especially when the plot is to be subjected to subsequent statistical analysis such as density contouring. | 3 | Analytical Chemistry |
Specific volume () is the volume occupied by a unit of mass of a material. In many cases, the specific volume is a useful quantity to determine because, as an intensive property, it can be used to determine the complete state of a system in conjunction with another independent intensive variable. The specific volume also allows systems to be studied without reference to an exact operating volume, which may not be known (nor significant) at some stages of analysis.
The specific volume of a substance is equal to the reciprocal of its mass density. Specific volume may be expressed in , , , or .
where, is the volume, is the mass and is the density of the material.
For an ideal gas,
where, is the specific gas constant, is the temperature and is the pressure of the gas.
Specific volume may also refer to molar volume. | 7 | Physical Chemistry |
For catalytic hydroboration, pinacolborane and catecholborane are widely used. They also exhibit higher reactivity toward alkynes. Pinacolborane is also widely used in a catalyst-free hydroborations. | 0 | Organic Chemistry |
This set of methods include number and brightness (N&B), photon counting histogram (PCH), fluorescence intensity distribution analysis (FIDA), and Cumulant Analysis. and Spatial Intensity Distribution Analysis. Combination of multiple methods is also reported.
Fluorescence cross correlation spectroscopy overcomes the weak dependence of diffusion rate on molecular mass by looking at multicolor coincidence. What about homo-interactions? The solution lies in brightness analysis. These methods use the heterogeneity in the intensity distribution of fluorescence to measure the molecular brightness of different species in a sample. Since dimers will contain twice the number of fluorescent labels as monomers, their molecular brightness will be approximately double that of monomers. As a result, the relative brightness is sensitive a measure of oligomerization. The average molecular brightness () is related to the variance () and the average intensity () as follows:
Here and are the fractional intensity and molecular brightness, respectively, of species . | 7 | Physical Chemistry |
F-ATPase gene linkage and gene order are widely conserved across ancient prokaryote lineages, implying that this system already existed at a date before the last universal common ancestor, the LUCA. | 5 | Photochemistry |
As magmatic gas travelling upward encounters meteoric water in an aquifer, steam is produced. Latent magmatic heat can also cause meteoric waters to ascend as a vapour phase. Extended fluid-rock interaction of this hot mixture can leach constituents out of the cooling magmatic rock and also the country rock, causing volume changes and phase transitions, reactions and thus an increase in ionic strength of the upward percolating fluid. This process also decreases the fluid's pH. Cooling can cause phase separation and mineral deposition, accompanied by a shift toward more reducing conditions. At the surface expression of such hydrothermal systems, low-temperature volcanic gases (<400 °C) are either emanating as steam-gas mixtures or in dissolved form in hot springs. At the ocean floor, such hot supersaturated hydrothermal fluids form gigantic chimney structures called black smokers, at the point of emission into the cold seawater.
Over geological time, this process of hydrothermal leaching, alteration, and/or redeposition of minerals in the country rock is an effective process of concentration that generates certain types of economically valuable ore deposits. | 2 | Environmental Chemistry |
Scottish chemist Thomas Graham (1805–1869) found experimentally that the rate of effusion of a gas is inversely proportional to the square root of the mass of its particles. In other words, the ratio of the rates of effusion of two gases at the same temperature and pressure is given by the inverse ratio of the square roots of the masses of the gas particles.
where and represent the molar masses of the gases.
This equation is known as Graham's law of effusion.
The effusion rate for a gas depends directly on the average velocity of its particles. Thus, the faster the gas particles are moving, the more likely they are to pass through the effusion orifice. | 7 | Physical Chemistry |
The Eschenmoser sulfide contraction method has been employed in a number of total synthesis efforts, like that of fuligocandin A and B, cocaine, diplodialide A and isoretronecanol
An example of general synthetic utility is the synthesis of novel carbapenems | 0 | Organic Chemistry |
In contrast to other gas components, water content in air, or humidity, to a higher degree depends on vaporization and condensation from or into water, which, in turn, mainly depends on temperature. Therefore, when applying more pressure to a gas saturated with water, all components will initially decrease in volume approximately according to the ideal gas law. However, some of the water will condense until returning to almost the same humidity as before, giving the resulting total volume deviating from what the ideal gas law predicted. Conversely, decreasing temperature would also make some water condense, again making the final volume deviating from predicted by the ideal gas law.
Therefore, gas volume may alternatively be expressed excluding the humidity content: V (volume dry). This fraction more accurately follows the ideal gas law. On the contrary, V (volume saturated) is the volume a gas mixture would have if humidity was added to it until saturation (or 100% relative humidity). | 7 | Physical Chemistry |
Ninhydrin was discovered in 1910 by the German-English chemist Siegfried Ruhemann (1859–1943). In the same year, Ruhemann observed ninhydrin's reaction with amino acids. In 1954, Swedish investigators Oden and von Hofsten proposed that ninhydrin could be used to develop latent fingerprints. | 0 | Organic Chemistry |
In the pharmaceutical industry, some amorphous drugs have been shown to offer higher bioavailability than their crystalline counterparts as a result of the higher solubility of the amorphous phase. However, certain compounds can undergo precipitation in their amorphous form in vivo, and can then decrease mutual bioavailability if administered together. | 7 | Physical Chemistry |
In New Zealand, pseudoephedrine is currently classified as a Class B Part II controlled drug in the Misuse of Drugs Act 1975, making it illegal to supply or possess except on prescription.
Pseudoephedrine, ephedrine, and any product containing these substances, e.g. cold and flu medicines, were first classified in October 2004 as Class C Part III (partially exempted) controlled drugs, due to being the principal ingredient in methamphetamine. New Zealand Customs and police officers continued to make large interceptions of precursor substances believed to be destined for methamphetamine production. On 9 October 2009, Prime Minister John Key announced pseudoephedrine-based cold and flu tablets would become prescription-only drugs and reclassified as a class B2 drug. The law was amended by The Misuse of Drugs Amendment Bill 2010, which passed in August 2011.
On 24 November 2023, the recently-formed National-led coalition government announced that the sale of cold medication containing pseudoephedrine would be allowed (as part of the coalition agreement between the National and ACT parties). | 4 | Stereochemistry |
In molecular biology, complementarity describes a relationship between two structures each following the lock-and-key principle. In nature complementarity is the base principle of DNA replication and transcription as it is a property shared between two DNA or RNA sequences, such that when they are aligned antiparallel to each other, the nucleotide bases at each position in the sequences will be complementary, much like looking in the mirror and seeing the reverse of things. This complementary base pairing allows cells to copy information from one generation to another and even find and repair damage to the information stored in the sequences.
The degree of complementarity between two nucleic acid strands may vary, from complete complementarity (each nucleotide is across from its opposite) to no complementarity (each nucleotide is not across from its opposite) and determines the stability of the sequences to be together. Furthermore, various DNA repair functions as well as regulatory functions are based on base pair complementarity. In biotechnology, the principle of base pair complementarity allows the generation of DNA hybrids between RNA and DNA, and opens the door to modern tools such as cDNA libraries.
While most complementarity is seen between two separate strings of DNA or RNA, it is also possible for a sequence to have internal complementarity resulting in the sequence binding to itself in a folded configuration. | 1 | Biochemistry |
Certain isotopes of trace metals are preferentially oxidized or reduced; thus, transitions between redox species of the metal ions (e.g., Fe → Fe) are fractionating, resulting in different isotopic compositions between the different redox pools in the environment. Additionally, at high temperatures, metals ions can evaporate (and subsequently condense upon cooling), and the relative differences in isotope masses of a given heavy metal leads to fractionation during these evaporation and condensation processes. Diffusion of isotopes through a solution or material can also result in fractionations, as the lighter mass isotopes are able to diffuse at a faster rate. Additionally, isotopes can have slight variations in their solubility and other chemical and physical properties, which can also drive fractionation. | 9 | Geochemistry |
The chemical composition of the Earth and other bodies is determined by two opposing processes: differentiation and mixing. In the Earth's mantle, differentiation occurs at mid-ocean ridges through partial melting, with more refractory materials remaining at the base of the lithosphere while the remainder rises to form basalt. After an oceanic plate descends into the mantle, convection eventually mixes the two parts together. Erosion differentiates granite, separating it into clay on the ocean floor, sandstone on the edge of the continent, and dissolved minerals in ocean waters. Metamorphism and anatexis (partial melting of crustal rocks) can mix these elements together again. In the ocean, biological organisms can cause chemical differentiation, while dissolution of the organisms and their wastes can mix the materials again. | 9 | Geochemistry |
Sizing of a UV system is affected by three variables: flow rate, lamp power, and UV transmittance in the water. Manufacturers typically developed sophisticated computational fluid dynamics (CFD) models validated with bioassay testing. This involves testing the UV reactor's disinfection performance with either MS2 or T1 bacteriophages at various flow rates, UV transmittance, and power levels in order to develop a regression model for system sizing. For example, this is a requirement for all public water systems in the United States per the EPA UV manual.
The flow profile is produced from the chamber geometry, flow rate, and particular turbulence model selected. The radiation profile is developed from inputs such as water quality, lamp type (power, germicidal efficiency, spectral output, arc length), and the transmittance and dimension of the quartz sleeve. Proprietary CFD software simulates both the flow and radiation profiles. Once the 3D model of the chamber is built, it is populated with a grid or mesh that comprises thousands of small cubes.
Points of interest—such as at a bend, on the quartz sleeve surface, or around the wiper mechanism—use a higher resolution mesh, whilst other areas within the reactor use a coarse mesh. Once the mesh is produced, hundreds of thousands of virtual particles are "fired" through the chamber. Each particle has several variables of interest associated with it, and the particles are "harvested" after the reactor. Discrete phase modeling produces delivered dose, head loss, and other chamber-specific parameters. | 5 | Photochemistry |
Linkage isomerism was first noted for nitropentaamminecobalt(III) chloride, . This cationic cobalt complex can be isolated as either of two linkage isomers. In the yellow-coloured isomer, the nitro ligand is bound through nitrogen. In the red linkage isomer, the nitrito is bound through one oxygen atom. The O-bonded isomer is often written as . Although the existence of the isomers had been known since the late 1800s, only in 1907 was the difference explained. It was later shown that the red isomer converted to the yellow isomer upon UV-irradiation. In this particular example, the formation of the nitro isomer () from the nitrito isomer () occurs by an intramolecular rearrangement. | 4 | Stereochemistry |
Soluble adenylyl cyclase (sAC) is a regulatory cytosolic enzyme present in almost every cell. sAC is a source of cyclic adenosine 3’,5’ monophosphate (cAMP) – a second messenger that mediates cell growth and differentiation in organisms from bacteria to higher eukaryotes. sAC differentiates from the transmembrane adenylyl cyclase (tmACs) – an important source of cAMP; in that sAC is regulated by bicarbonate anions and it is dispersed throughout the cell cytoplasm. sAC has been found to have various functions in physiological systems different from that of the tmACs. | 1 | Biochemistry |
Mini-bulk tests are conducted with 1-100t of samples on industrial scale sensor-based ore sorters. The size fraction intervals to be treated are prepared using screen classifications. Full capacity is established then with each fraction and multiple cut-points are programmed in the sorting software. After creating multiple sorting fractions in rougher, scavenger and cleaner steps these weighed are sent for assays. The resulting data delivers all input for flow-sheet development. Since the tests are conducted on industrial scale equipment, there is no scale-up factor involved when designing a flow-sheet and installation of sensor-based ore sorting. | 3 | Analytical Chemistry |
On metal, patina is a coating of various chemical compounds such as oxides, carbonates, sulfides, or sulfates formed on the surface during exposure to atmospheric elements (oxygen, rain, acid rain, carbon dioxide, sulfur-bearing compounds). In common parlance, weathering rust on steel is often mistakenly referred to as patina. Patina also refers to accumulated changes in surface texture and color that result from normal use of an object such as a coin or a piece of furniture over time.
Archaeologists also use the term patina to refer to a corticated layer that develops over time that is due to a range of complex factors on flint tools and ancient stone monuments. This has led stone tool analysts in recent times to generally prefer the term cortification as a better term to describe the process than patination.
In geology and geomorphology, the term patina is used to refer to discolored film or thin outer layer produced either on or within the surface of a rock or other material by either the development of a weathering rind within the surface of a rock, the formation of desert varnish on the surface of a rock, or combination of both. It also refers to development as the result of weathering of a case-hardened layer, called cortex by geologists, within the surface of either a flint or chert nodule. | 8 | Metallurgy |
* In quaternary structure denaturation, protein sub-units are dissociated and/or the spatial arrangement of protein subunits is disrupted.
* Tertiary structure denaturation involves the disruption of:
** Covalent interactions between amino acid side-chains (such as disulfide bridges between cysteine groups)
** Non-covalent dipole-dipole interactions between polar amino acid side-chains (and the surrounding solvent)
** Van der Waals (induced dipole) interactions between nonpolar amino acid side-chains.
* In secondary structure denaturation, proteins lose all regular repeating patterns such as alpha-helices and beta-pleated sheets, and adopt a random coil configuration.
* Primary structure, such as the sequence of amino acids held together by covalent peptide bonds, is not disrupted by denaturation. | 1 | Biochemistry |
The C-N distance in isocyanides is 115.8 pm in methyl isocyanide. The C-N-C angles are near 180°.
Akin to carbon monoxide, isocyanides are described by two resonance structures, one with a triple bond between the nitrogen and the carbon and one with a double bond between. The π lone pair of the nitrogen stabilizes the structure and is responsible of the linearity of isocyanides, although the reactivity of isocyanides reflects some carbene character, at least in a formal sense. Thus, both resonance structures are useful representations. They are susceptible to polymerization. | 0 | Organic Chemistry |
Partition chromatography theory and practice was introduced through the work and publications of Archer Martin and Richard Laurence Millington Synge during the 1940s. They would later receive the 1952 Nobel Prize in Chemistry "for their invention of partition chromatography". | 3 | Analytical Chemistry |
Operando spectroscopy is a class of methodology, rather than a specific spectroscopic technique such as FTIR or NMR. Operando spectroscopy is a logical technological progression in in situ studies. Catalyst scientists would ideally like to have a "motion picture" of each catalytic cycle, whereby the precise bond-making or bond-breaking events taking place at the active site are known; this would allow a visual model of the mechanism to be constructed. The ultimate goal is to determine the structure-activity relationship of the substrate-catalyst species of the same reaction. Having two experiments—the performing of a reaction plus the real-time spectral acquisition of the reaction mixture—on a single reaction facilitates a direct link between the structures of the catalyst and intermediates, and of the catalytic activity/selectivity. Although monitoring a catalytic process in situ can provide information relevant to catalytic function, it is difficult to establish a perfect correlation because of the current physical limitations of in situ reactor cells. Complications arise, for example, for gas phase reactions which require large void volumes, which make it difficult to homogenize heat and mass within the cell. The crux of a successful operando methodology, therefore, is related to the disparity between laboratory setups and industrial setups, i.e., the limitations of properly simulating the catalytic system as it proceeds in industry.
The purpose of operando spectroscopy is to measure the catalytic changes that occur within the reactor during operation using time-resolved (and sometimes spatially-resolved) spectroscopy. Time-resolved spectroscopy theoretically monitor the formation and disappearance of intermediate species at the active site of the catalyst as bond are made and broken in real time. However, current operando instrumentation often only works in the second or subsecond time scale and therefore, only relative concentrations of intermediates can be assessed. Spatially resolved spectroscopy combines spectroscopy with microscopy to determine active sites of the catalyst studied and spectator species present in the reaction. | 7 | Physical Chemistry |
Heinz Falk (born April 29, 1939, in Sankt Pölten, Lower Austria) is professor emeritus for organic chemistry at Johannes Kepler University of Linz and editor of "Progress in the Chemistry of Organic Natural Compounds".
His research is focused on structural analysis, synthesis, stereochemistry and photochemistry of plant and animal photosensitizing and photosensory pigments, such as hypericin. | 0 | Organic Chemistry |
In response to iron limitation in their environment, genes involved in microbe siderophore production and uptake are derepressed, leading to manufacture of siderophores and the appropriate uptake proteins. In bacteria, Fe-dependent repressors bind to DNA upstream to genes involved in siderophore production at high intracellular iron concentrations. At low concentrations, Fe dissociates from the repressor, which in turn dissociates from the DNA, leading to transcription of the genes. In gram-negative and AT-rich gram-positive bacteria, this is usually regulated by the Fur (ferric uptake regulator) repressor, whilst in GC-rich gram-positive bacteria (e.g. Actinomycetota) it is DtxR (diphtheria toxin repressor), so-called as the production of the dangerous diphtheria toxin by Corynebacterium diphtheriae is also regulated by this system.
This is followed by excretion of the siderophore into the extracellular environment, where the siderophore acts to sequester and solubilize the iron. Siderophores are then recognized by cell specific receptors on the outer membrane of the cell. In fungi and other eukaryotes, the Fe-siderophore complex may be extracellularly reduced to Fe, while in many cases the whole Fe-siderophore complex is actively transported across the cell membrane. In gram-negative bacteria, these are transported into the periplasm via TonB-dependent receptors, and are transferred into the cytoplasm by ABC transporters.
Once in the cytoplasm of the cell, the Fe-siderophore complex is usually reduced to Fe to release the iron, especially in the case of "weaker" siderophore ligands such as hydroxamates and carboxylates. Siderophore decomposition or other biological mechanisms can also release iron, especially in the case of catecholates such as ferric-enterobactin, whose reduction potential is too low for reducing agents such as flavin adenine dinucleotide, hence enzymatic degradation is needed to release the iron. | 1 | Biochemistry |
Since cells do not produce double-stranded RNA during normal nucleic acid metabolism, natural selection has favored the evolution of enzymes that destroy dsRNA on contact. The best known class of this type of enzymes is Dicer. It is hoped that broad-spectrum anti-virals could be synthesized that take advantage of this vulnerability of double-stranded RNA viruses. | 1 | Biochemistry |
Friction stir processing (FSP) is a method of changing the properties of a metal through intense, localized plastic deformation. This deformation is produced by forcibly inserting a non-consumable tool into the workpiece, and revolving the tool in a stirring motion as it is pushed laterally through the workpiece. The precursor of this technique, friction stir welding, is used to join multiple pieces of metal without creating the heat affected zone typical of fusion welding.
When ideally implemented, this process mixes the material without changing the phase (by melting or otherwise) and creates a microstructure with fine, equiaxed grains. This homogeneous grain structure, separated by high-angle boundaries, allows some aluminium alloys to take on superplastic properties. Friction stir processing also enhances the tensile strength and fatigue strength of the metal. In tests with actively cooled magnesium-alloy workpieces, the microhardness was almost tripled in the area of the friction stir processed seam (to 120–130 Vickers hardness). | 8 | Metallurgy |
The search for antifungal agents with acceptable toxicity profiles led first to the discovery of ketoconazole, the first azole-based oral treatment of systemic fungal infections, in the early 1980s. Later, triazoles fluconazole and itraconazole, with a broader spectrum of antifungal activity and improved safety profile were developed. In order to overcome limitations such as sub-optimal spectra of activity, drug-drug interactions, toxicity, development of resistance and unfavorable pharmacokinetics, analogues were developed. Second-generation triazoles, including voriconazole, posaconazole and ravuconazole, are more potent and more active against resistant pathogens. | 0 | Organic Chemistry |
Many very hydrophobic materials found in nature rely on Cassie's law and are biphasic on the submicrometer level. The fine hairs on some plants are hydrophobic, designed to exploit the solvent properties of water to attract and remove sunlight-blocking dirt from their photosynthetic surfaces. Inspired by this lotus effect, many functional superhydrophobic surfaces have been developed.
Water striders are insects that live on the surface film of water, and their bodies are effectively unwettable due to specialized hairpiles called hydrofuge; many of their body surfaces are covered with these specialized "hairpiles", composed of tiny hairs spaced so closely that there are more than one thousand microhairs per mm, which creates a hydrophobic surface. Similar hydrofuge surfaces are known in other insects, including aquatic insects that spend most of their lives submerged, with hydrophobic hairs preventing entry of water into their respiratory system. The skin surface of some species of lizards, such as geckos and anoles, has also been documented as highly hydrophobic, and may facilitate self-cleaning or underwater breathing.
Some birds are great swimmers, due to their hydrophobic feather coating. Penguins are coated in a layer of air and can release that trapped air to accelerate rapidly when needing to jump out of the water and land on higher ground. Wearing an air coat when swimming reduces the drag and also acts as a heat insulator. | 6 | Supramolecular Chemistry |
When hydrogen and steam are considered as reactants, the overall reaction takes this form:
where the forward reaction occurs during SOFC mode, and the backward reaction during SOEC mode. On the fuel electrode, hydrogen oxidation (forward reaction) takes in SOFC mode and water reduction (backward reaction) takes plain SOEC mode:
On the oxygen electrode, oxygen reduction (forward reaction) occurs in SOFC mode and oxide ions oxidation (backward reaction) occurs in SOEC mode:
The thermoneutral voltage for steam electrolysis is equal to 1.29 V. | 7 | Physical Chemistry |
Recent developments in heterogeneous catalysis enabled the use of metal oxide materials such as cuprous oxide nanocatalysts in flow processing technologies, which can enable the economical production of active pharmaceutical ingredients and various other fine chemicals. | 0 | Organic Chemistry |
*amp = ampicillin resistance
*azi = azide resistance
*bla = beta-lactam resistance
*cat = chloramphenicol resistance
*kan = kanamycin resistance
*rif = rifampicin resistance
*tonA = phage T1 resistance | 1 | Biochemistry |
To measure a PDRC surface's cooling power, the absorbed powers of atmospheric and solar radiations must be quantified. PDRC should not be measured when the surface is in a balanced or controlled state, but rather in a real-world setting. Standardized devices to measure PDRC effectiveness have been proposed.
Evaluating atmospheric downward longwave radiation based on "the use of ambient weather conditions such as the surface air temperature and humidity instead of the altitude-dependent atmospheric profiles," may be problematic since "downward longwave radiation comes from various altitudes of the atmosphere with different temperatures, pressures, and water vapor contents" and "does not have uniform density, composition, and temperature across its thickness." | 7 | Physical Chemistry |
For a given nonlinear optical process, the polarization which generates the output is given by
where is the th order nonlinear susceptibility, for .
It is worth noting that all the even order susceptibilities become zero in centrosymmetric media. A proof of this is as follows.
Let be the inversion operator, defined by for some arbitrary vector . Then applying to the left and right hand side of the polarization equation above gives
Adding together this equation with the original polarization equation then gives
which implies for in centrosymmetric media. Q.E.D.
[Note 1: The final equality can be proven by mathematical induction, by considering two cases in the inductive step; where is odd and is even.]
[Note 2: This proof holds for the case where is even. Setting gives the odd case and the remainder of the proof is the same.]
As a second-order nonlinear process, SFG is dependent on the 2nd order susceptibility , which is a third rank tensor. This limits what samples are accessible for SFG. Centrosymmetric media include the bulk of gases, liquids, and most solids under the assumption of the electric-dipole approximation, which neglects the signal generated by multipoles and magnetic moments. At an interface between two different materials or two centrosymmetric media, the inversion symmetry is broken and an SFG signal can be generated. This suggests that the resulting spectra represent a thin layer of molecules. A signal is found when there is a net polar orientation. | 7 | Physical Chemistry |
In Odessa, in the house in which Zelinsky lived while working at Novorossiysk University, the Department of Organic Chemistry, a descendant of the Odessa National University named after I.I.Mechnikov, now houses a memorial plaque. | 0 | Organic Chemistry |
Subfractions of LDL cholesterol that are implicated in causing atherosclerosis have reduced levels of sialic acid. These include small high density LDL particles and electronegative LDL. Reduced levels of sialic acid in small high density LDL particles increases the affinity of those particles for the proteoglycans in arterial walls. | 0 | Organic Chemistry |
Pdr1p is a main regulator of PDR genes and is known to target about 50 genes. Pdr1p binds to sequence 5-TCCGYGGR-3 of PDRE, which is located within the promoter sequences of its target genes. 218 genes are reported to possess PDRE. Pdr1p is observed to bind PDRE sites on DNA at basal level and also after simulation with toxins. This shows that Pdr1p-DNA interaction isnt dependent on toxic stimulation. This also suggests an involvement of activator(s) or co-activator(s) that induce PDR genes along with Pdr1p. Pdr1p has a functional homolog called Pdr3p encoded by gene called PDR3'. Pdr3p is known to be regulated by Pdr3p and Pdr1p. Pdr1p can form a homodimer with itself or heterodimer with Pdr3p.
Loss of function studies of both PDR1 and PDR3 revealed that Pdr1p mutant shows lower tolerance (grows less in culture) against organic toxins such as cycloheximide and oligomycin. This confirms the functions of Prf1p that confer stronger drug response phenotype than Pdr3p. However, Pdr3p is crucial for PDR responses since cells containing loss of function mutation in both PDR1 and PDR3 genes weren't able to grow at all in the presence of those two toxins.
Both Pdr1p and Pdr3p regulate Pdr5p, which is an ATP-binding cassette transporter. A single amino acid substitution mutation, which is a gain of function mutation of Pdr1p denoted as pdr1-3 (F815S, substitution mutation of Phenylalanine at 815th of the polypeptide by Serine) leads to an over-expression of mRNA of PDR5, which codes for Pdr5p. For cells treated with fluphenazine, Pdr1p was the only transcription factor necessary for PDR response genes induction. But at basal level, Pdr1p can be partially compensated by Pdr3p, a functional homolog of Pdr1p. | 1 | Biochemistry |
Ester exchange takes place between an ester carbonyl and an alcohol. Reverse esterification can take place via hydrolysis. This method has been used extensively in polymer synthesis. | 6 | Supramolecular Chemistry |
In size-exclusion chromatography, the residence time of a molecule is related to its volume, which is roughly proportional to its molecular weight. Residence times also affect the performance of continuous fermentors.
Biofuel cells utilize the metabolic processes of anodophiles (electronegative bacteria) to convert chemical energy from organic matter into electricity. A biofuel cell mechanism consists of an anode and a cathode that are separated by an internal proton exchange membrane (PEM) and connected in an external circuit with an external load. Anodophiles grow on the anode and consume biodegradable organic molecules to produce electrons, protons, and carbon dioxide gas, and as the electrons travel through the circuit they feed the external load. The HRT for this application is the rate at which the feed molecules are passed through the anodic chamber. This can be quantified by dividing the volume of the anodic chamber by the rate at which the feed solution is passed into the chamber. The hydraulic residence time (HRT) affects the substrate loading rate of the microorganisms that the anodophiles consume, which affects the electrical output. Longer HRTs reduce substrate loading in the anodic chamber which can lead to reduced anodophile population and performance when there is a deficiency of nutrients. Shorter HRTs support the development of non-exoelectrogenous bacteria which can reduce the Coulombic efficiency electrochemical performance of the fuel cell if the anodophiles must compete for resources or if they do not have ample time to effectively degrade nutrients. | 9 | Geochemistry |
Many organofluorine compounds are produced by electrofluorination. One manifestation of this technology is the Simons process, which can be described as:
:RC–H + HF → RC–F + H
In the course of a typical synthesis, this reaction occurs once for each C–H bond in the precursor. The cell potential is maintained near 5–6 V. The anode, the electrocatalyst, is nickel-plated. | 7 | Physical Chemistry |
About 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium. All 11 are necessary for life. The remaining elements are trace elements, of which more than a dozen are thought on the basis of good evidence to be necessary for life. All of the mass of the trace elements put together (less than 10 grams for a human body) do not add up to the body mass of magnesium, the least common of the 11 non-trace elements. | 1 | Biochemistry |
Converting is a type of metallurgical smelting that includes several processes; the most commercially important form is the treatment of molten metal sulfides to produce crude metal and slag, as in the case of copper and nickel converting. A now-uncommon form is batch treatment of pig iron to produce steel by the Bessemer process. The vessel used was called the Bessemer converter. Modern steel mills use basic oxygen process converters. | 8 | Metallurgy |
Pyridine has a flash point of 20 °C and is therefore highly flammable. Combustion produces toxic fumes which can include bipyridines, nitrogen oxides, and carbon monoxide. | 0 | Organic Chemistry |
Terpenes are a key component in chemotaxonomical classification of cannabis strains as terpene composition is a phenotypic trait. Majority of terpenes found in cannabis are hydrocarbons, which are a direct product of terpene synthase (TPS) enzymes. The molecular make up of terpenes in a cannabis plant involves the linking and elongation of chains in hydrocarbons and isoprene units, formed by isopentenyl pyrophosphate and dimethylallyl pyrophosphate. Terpenoids are basically terpenes with the addition of oxygen, among other structural additions. There are numerous types of unique functional terpenes in green plants and are formed via many differing pathways; methylerythritol phosphate (MEP), cytosolic mevalonate (MEV), or deoxyxylulose phosphate pathway (DOXP) to name a few. In addition, mevalonic acids (MVA) involvement in biosynthesis of complex terpenoids, such as steroids, was demonstrated in 1983. Once produced, specifically within the disk cells, terpenes are stored within the trichomes of the plant. There are several types of terpenes in cannabis composed of varying numbers of isoprene units. They contribute to the signature aroma and insecticidal properties via their emission as volatile organic compounds. Different cannabis strains synthesize different terpenes through their biochemical pathways, and diversity of the terpenes is dependent upon the diversity of the TPS enzymes present in the cannabis plants TPS gene pool. Though, causes of variations in the TPS enzymes are still unknown.
Monoterpenes myrcene and sesquiterpenes β-caryophyllene (binds to the human CB2 cannabinoids receptor) and α-humulene are the most common terpene compounds, and are present in most varieties of cannabis strains. The lack of exact standards makes it sometimes difficult for scientists to classify new terpenes. Terpene profiles are subject to change under different environmental conditions, which may lead to variation in TPS gene expression, ultimately leading to a variation in the synthesized terpenes. Terpenes have unique, distinct aromas, which is why each strain smells different. Cannabis plants, like many others, biochemically synthesize terpenes with intense aromas as a method of chemical defense in attempts to repel predators, and invite pollinators. Because terpenes and terpenoids are biologically active molecules, it is possible variations in terpenes may elicit different biological and psychoactive responses in humans. This is why people claim to have different psychological effects to different strains. | 1 | Biochemistry |
A salamander (or deadman's foot or furnace bear) in the metallurgy dialect means all liquid and solidified
materials in the hearth of a blast furnace below the tap hole.
The target of the salamander tapping is to remove the remaining hot metal and slag from the blast furnace to allow a safe and efficient intermediate repair and blow-in of the blast furnace.
During blowing down of the furnace the salamander is tapped by drilling a hole in the blast furnace hearth. | 8 | Metallurgy |
Newton's metal is a fusible alloy with a low melting point. Its composition by weight is 8 parts bismuth, 5 parts lead and 3 parts tin; its melting point is 97 °C.
Newton's metal is comparable to Cerrobend, but avoids its toxic cadmium content. This has encouraged its use for medical applications for easily shaped shielding during radiotherapy. | 8 | Metallurgy |
In the in situ method, protein synthesis is carried out on a protein array surface that is pre-coated with a protein-capturing reagent or antibody. Once the newly synthesized proteins are released from the ribosome, the tag sequence that is also synthesized at the N- or C-terminus of each nascent protein will be bound by the capture reagent or antibody, thus immobilizing the proteins to form an array. Commonly used tags include polyhistidine (His)6 and glutathione s-transferase (GST).
Various research groups have developed their own methods, each differing in their approach, but can be summarized into 3 main groups. | 1 | Biochemistry |
Lightweight textiles with porous surfaces are the most flammable fabrics. Wool is less flammable than cotton, linen, silk, or viscose (rayon). Polyester and nylon resist ignition, and melt rather than catch fire. Acrylic is the most flammable synthetic fiber. | 7 | Physical Chemistry |
Promoters reside at the beginning of the gene and serve as the site where the transcription machinery assembles and transcription of the gene begins. Enhancers turn on the promoters at specific locations, times, and levels and can be simply defined as the “promoters of the promoter.” Silencers are thought to turn off gene expression at specific time points and locations. Insulators, also called boundary elements, are DNA sequences that create cis-regulatory boundaries that prevent the regulatory elements of one gene from affecting neighboring genes. The general dogma is that these regulatory elements get activated by the binding of transcription factors, proteins that bind to specific DNA sequences, and control mRNA transcription. There could be several transcription factors that need to bind to one regulatory element in order to activate it. In addition, several other proteins, called transcription cofactors, bind to the transcription factors themselves to control transcription. | 1 | Biochemistry |
A-Values are measured using a mono-substituted cyclohexane ring, and are an indication of only the sterics a particular substituent imparts on the molecule. This leads to a problem when there are possible stabilizing electronic factors in a different system. The carboxylic acid substituent shown below is axial in the ground state, despite a positive A-value. From this observation, it is clear that there are other possible electronic interactions that stabilize the axial conformation. | 4 | Stereochemistry |
The 3-dimensional structure of micrococcal nuclease (then called Staphyloccal nuclease) was solved very early in the history of protein crystallography, in 1969, deposited as now-obsolete Protein Data Bank file 1SNS. Higher-resolution, more recent crystal structures are available for the apo form as Protein Data Bank file 1SNO: [http://www.rcsb.org/pdb/explore/explore.do?structureId=1SNO] and for the thymidine-diphosphate-inhibited form as Protein Data Bank file 3H6M: [http://www.rcsb.org/pdb/explore/explore.do?structureId=3H6M] or 1SNC: [http://www.rcsb.org/pdb/explore/explore.do?structureId=1SNC]. As seen in the ribbon diagram above, the nuclease molecule has 3 long alpha helices and a 5-stranded, barrel-shaped beta sheet, in an arrangement known as the OB-fold (for oligonucleotide-binding fold) as classified in the SCOP database. | 1 | Biochemistry |
Polymers come in a wide variety of compositions, and this diversity of chemistry results in wide-ranging embrittlement mechanisms. The most common sources of polymer embrittlement include oxygen in the air, water in liquid or vapor form, ultraviolet radiation from the sun, acids, and organic solvents.
One of the ways these sources alter the mechanical properties of polymers is through chain scission and chain cross-linking. Chain scission occurs when atomic bonds are broken in the main chain, so environments with elements such as solar radiation lead to this form of embrittlement. Chain scission reduces the length of the polymer chains in a material, resulting in a reduction of strength. Chain cross-linking has the opposite effect. An increase in the number of cross-links (due to an oxidative environment for example), results in stronger, less ductile material.
The thermal oxidation of polyethylene provides a quality example of chain scission embrittlement. The random chain scission induced a change from ductile to brittle behavior once the average molar mass of the chains dropped below a critical value. For the polyethylene system, embrittlement occurred when the weight average molar mass fell below 90 kg/mol. The reason for this change was hypothesized to be a reduction of entanglement and an increase in crystallinity. The ductility of polymers is typically a result of their amorphous structure, so an increase in crystallinity makes the polymer more brittle. In the case of polyethylene terephthalate, hydrolysis produces chain scission embrittlement. It has been demonstrated that the degradation of the mechanical properties correlates with the reduction of the mobile amorphous fraction (MAF), and that the ductile-to-brittle transition occurs when the minimum MAF is reached. This supports a micromechanical interpretation of the embrittlement mechanism rather than a molecular interpretation.
The embrittlement of silicone rubber is due to an increase in the amount of chain cross-linking. When silicone rubber is exposed to air at temperatures above oxidative cross-linking reactions occur at methyl side groups along the main chain. These cross-links make the rubber significantly less ductile.
Solvent stress cracking is a significant polymer embrittlement mechanism. It occurs when liquids or gasses are absorbed into the polymer, ultimately swelling the system. The polymer swelling results in less shear flow and an increase in crazing susceptibility. Solvent stress cracking from organic solvents typically results in static fatigue because of the low mobility of fluids. Solvent stress cracking from gasses is more likely to result in greater crazing susceptibility.
Polycarbonate provides a good example of solvent stress cracking. Numerous solvents have been shown to embrittle polycarbonate (i.e. benzene, toluene, acetone) through a similar mechanism. The solvent diffuses into the bulk, swells the polymer, induces crystallization, and ultimately produces interfaces between ordered and disordered regions. These interfaces produce voids and stress fields that can be propagated throughout the material at stresses much lower than the typical tensile strength of the polymer. | 8 | Metallurgy |
Ahrland, Chatt and Davies proposed that metal ions could be described as class A if they formed stronger complexes with ligands whose donor atoms are nitrogen, oxygen or fluorine than with ligands whose donor atoms are phosphorus, sulfur or chlorine and class B if the reverse is true. For example, Ni forms stronger complexes with amines than with phosphines, but Pd forms stronger complexes with phosphines than with amines. Later, Pearson proposed the theory of hard and soft acids and bases (HSAB theory). In this classification, class A metals are hard acids and class B metals are soft acids. Some ions, such as copper(I), are classed as borderline. Hard acids form stronger complexes with hard bases than with soft bases. In general terms hard–hard interactions are predominantly electrostatic in nature whereas soft–soft interactions are predominantly covalent in nature. The HSAB theory, though useful, is only semi-quantitative.
The hardness of a metal ion increases with oxidation state. An example of this effect is given by the fact that Fe tends to form stronger complexes with N-donor ligands than with O-donor ligands, but the opposite is true for Fe. | 7 | Physical Chemistry |
The Mountain Pass deposit was discovered in 1949 by Herbert S. Woodward, Clarence Watkins and P. A. Simon, who noticed anomalously high radioactivity. Molybdenum Corporation of America bought most of the mining claims, and began small-scale production in 1952.
Production expanded greatly in the 1960s, to supply demand for europium used in color television screens. Between 1965 and 1995, the mine supplied most of the worldwide rare-earth metals consumption.
Molybdenum Corporation of America changed its name to Molycorp in 1974. The corporation was acquired by Union Oil in 1977, which in turn became part of Chevron Corporation in 2005.
In 1998, the mine's separation plant ceased production of refined rare-earth compounds; it continued to produce bastnäsite concentrate.
The mine closed in 2002 after a toxic waste spill and wasn't reopened due to competition from Chinese suppliers, though processing of previously mined ore continued.
In 2008, Chevron sold the mine to privately-held Molycorp Minerals LLC, a company formed to revive the Mountain Pass mine. Molycorp announced plans to spend $500 million to reopen and expand the mine, and on July 29, 2010, it raised about $400 million through an initial public offering, selling 28,125,000 shares at $14 under the ticker symbol MCP on the New York Stock Exchange.
In December 2010, Molycorp announced that it had secured all the environmental permits needed to build a new ore processing plant at the mine; construction would begin in January 2011, and was expected to be completed by the end of 2012. On August 27, 2012, the company announced that mining had restarted.
The processing plant was in full production on June 25, 2015, when Molycorp filed for Chapter 11 bankruptcy with outstanding bonds in the amount of $US 1.4 billion. The company's shares were removed from the NYSE.
In August 2015, it was reported that the mine was to be shut down.
On August 31, 2016, Molycorp Inc. emerged from bankruptcy as Neo Performance Materials, leaving behind the mine as Molycorp Minerals LLC in its own separate Chapter 11 bankruptcy. As of January 2016, its shares were traded OTC under the symbol MCPIQ.
Mountain Pass was acquired out of bankruptcy in July 2017 with the goal of reviving America's rare-earth industry. MP Materials resumed mining and refining operations in January 2018. | 8 | Metallurgy |
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