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Aluminum hydrides (AlH) such as lithium aluminum hydride can reduce diphosphene to give stable diphosphanes: (with Ar=2,4,6-BuCH) | 0 | Organic Chemistry |
Pesticides may exhibit toxic effects on humans and other non-target species, the severity of which depends on the frequency and magnitude of exposure. Toxicity also depends on the rate of absorption, distribution within the body, metabolism, and elimination of compounds from the body. Commonly used pesticides like organophosphates and carbamates act by inhibiting acetylcholinesterase activity, which prevents the breakdown of acetylcholine at the neural synapse. Excess acetylcholine can lead to symptoms like muscle cramps or tremors, confusion, dizziness and nausea. Studies show that farm workers in Ethiopia, Kenya, and Zimbabwe have decreased concentrations of plasma acetylcholinesterase, the enzyme responsible for breaking down acetylcholine acting on synapses throughout the nervous system. Other studies in Ethiopia have observed reduced respiratory function among farm workers who spray crops with pesticides. Numerous exposure pathways for farm workers increase the risk of pesticide poisoning, including dermal absorption walking through fields and applying products, as well as inhalation exposure. | 2 | Environmental Chemistry |
hnRNP C is a key regulator of the BRCA1 and BRCA2 genes. In response to ionizing radiation, hnRNP C partially localizes to the site of DNA damage, and when depleted, S-phase progression of the cell is impaired. Additionally, BRCA1 and BRCA2 levels fall when hnRNP C is lost. BRCA1 and BRCA2 are crucial tumor-suppressor genes which are strongly implicated in breast cancers when mutated. BRCA1 in particular causes G2/M cell cycle arrest in response to DNA damage via the CHEK1 signaling cascade. hnRNP C is important for the proper expression of other tumor suppressor genes including RAD51 and BRIP1 as well. Through these genes, hnRNP is necessary to induce cell-cycle arrest in response to DNA damage by ionizing radiation. | 1 | Biochemistry |
Tellus Series B: Chemical and Physical Meteorology is a scientific journal that was published by Blackwell Publishing for the International Meteorological Institute in Stockholm, Sweden until December 2011. From January 2012 the issues are published online by Co-action Publishing as an open access journal. The journal publishes original articles, short contributions, and correspondence on atmospheric chemistry, surface exchange processes, long-range and global transport, aerosol science, and cloud physics including related radiation transfer. Biogeochemical cycles including related aspects of marine chemistry and geochemistry also represent a central theme.
Tellus B is the companion to Tellus Series A: Dynamic Meteorology and Oceanography. | 9 | Geochemistry |
The relationship between fractional and Cartesian coordinates can be described by the matrix transformation :
Similarly, the Cartesian coordinates can be converted back to fractional coordinates using the matrix transformation : | 3 | Analytical Chemistry |
Though often placed at the top of the alkali metal column in the periodic table, hydrogen does not, under ordinary conditions, exhibit the properties of an alkali metal. Instead, it forms diatomic molecules, similar to halogens and some nonmetals in the second period of the periodic table, such as nitrogen and oxygen. Diatomic hydrogen is a gas that, at atmospheric pressure, liquefies and solidifies only at very low temperature (20 K and 14 K respectively).
In 1935, physicists Eugene Wigner and Hillard Bell Huntington predicted that under an immense pressure of around , hydrogen would display metallic properties: instead of discrete molecules (which consist of two electrons bound between two protons), a bulk phase would form with a solid lattice of protons and the electrons delocalized throughout. Since then, producing metallic hydrogen in the laboratory has been described as "the holy grail of high-pressure physics".
The initial prediction about the amount of pressure needed was eventually shown to be too low. Since the first work by Wigner and Huntington, the more modern theoretical calculations point toward higher but potentially achievable metalization pressures of around . | 7 | Physical Chemistry |
Yields can also be calculated by measuring the amount of product formed (typically in the crude, unpurified reaction mixture) relative to a known amount of an added internal standard, using techniques like Gas chromatography (GC), High-performance liquid chromatography, or Nuclear magnetic resonance spectroscopy (NMR spectroscopy) or magnetic resonance spectroscopy (MRS). A yield determined using this approach is known as an internal standard yield. Yields are typically obtained in this manner to accurately determine the quantity of product produced by a reaction, irrespective of potential isolation problems. Additionally, they can be useful when isolation of the product is challenging or tedious, or when the rapid determination of an approximate yield is desired. Unless otherwise indicated, yields reported in the synthetic organic and inorganic chemistry literature refer to isolated yields, which better reflect the amount of pure product one is likely to obtain under the reported conditions, upon repeating the experimental procedure. | 0 | Organic Chemistry |
With the determination of the first structure of the complex between a G-protein coupled receptor (GPCR) and a G-protein trimer (Gαβγ) in 2011 a new chapter of GPCR research was opened for structural investigations of global switches with more than one protein being investigated. The previous breakthroughs involved determination of the crystal structure of the first GPCR, rhodopsin, in 2000 and the crystal structure of the first GPCR with a diffusible ligand (βAR) in 2007. The way in which the seven transmembrane helices of a GPCR are arranged into a bundle was suspected based on the low-resolution model of frog rhodopsin from cryogenic electron microscopy studies of the two-dimensional crystals. The crystal structure of rhodopsin, that came up three years later, was not a surprise apart from the presence of an additional cytoplasmic helix H8 and a precise location of a loop covering retinal binding site. However, it provided a scaffold which was hoped to be a universal template for homology modeling and drug design for other GPCRs – a notion that proved to be too optimistic.
Seven years later, the crystallization of β-adrenergic receptor (βAR) with a diffusible ligand brought surprising results because it revealed quite a different shape of the receptor extracellular side than that of rhodopsin. This area is important because it is responsible for the ligand binding and is targeted by many drugs. Moreover, the ligand binding site was much more spacious than in the rhodopsin structure and was open to the exterior. In the other receptors crystallized shortly afterwards the binding side was even more easily accessible to the ligand. New structures complemented with biochemical investigations uncovered mechanisms of action of molecular switches which modulate the structure of the receptor leading to activation states for agonists or to complete or partial inactivation states for inverse agonists.
The 2012 Nobel Prize in Chemistry was awarded to Brian Kobilka and Robert Lefkowitz for their work that was "crucial for understanding how G protein-coupled receptors function". There have been at least seven other Nobel Prizes awarded for some aspect of G protein–mediated signaling. As of 2012, two of the top ten global best-selling drugs (Advair Diskus and Abilify) act by targeting G protein-coupled receptors. | 1 | Biochemistry |
The Jameson Cell has been adopted by Shell Canada and Syncrude for floating bitumen in the oil sands industry (see Bitumen flotation). Syncrude bought an additional eight 500 mm downcomers for its plant in 2012. | 8 | Metallurgy |
Activated carbon is a highly porous, amorphous solid consisting of microcrystallites with a graphite lattice, usually prepared in small pellets or a powder. It is non-polar and cheap. One of its main drawbacks is that it reacts with oxygen at moderate temperatures (over 300 °C).
Activated carbon can be manufactured from carbonaceous material, including coal (bituminous, subbituminous, and lignite), peat, wood, or nutshells (e.g., coconut). The manufacturing process consists of two phases, carbonization and activation. The carbonization process includes drying and then heating to separate by-products, including tars and other hydrocarbons from the raw material, as well as to drive off any gases generated. The process is completed by heating the material over in an oxygen-free atmosphere that cannot support combustion. The carbonized particles are then "activated" by exposing them to an oxidizing agent, usually steam or carbon dioxide at high temperature. This agent burns off the pore blocking structures created during the carbonization phase and so, they develop a porous, three-dimensional graphite lattice structure. The size of the pores developed during activation is a function of the time that they spend in this stage. Longer exposure times result in larger pore sizes. The most popular aqueous phase carbons are bituminous based because of their hardness, abrasion resistance, pore size distribution, and low cost, but their effectiveness needs to be tested in each application to determine the optimal product.
Activated carbon is used for adsorption of organic substances and non-polar adsorbates and it is also usually used for waste gas (and waste water) treatment. It is the most widely used adsorbent since most of its chemical (e.g. surface groups) and physical properties (e.g. pore size distribution and surface area) can be tuned according to what is needed. Its usefulness also derives from its large micropore (and sometimes mesopore) volume and the resulting high surface area. Recent research works reported activated carbon as an effective agent to adsorb cationic species of toxic metals from multi-pollutant systems and also proposed possible adsorption mechanisms with supporting evidences. | 7 | Physical Chemistry |
Depending on the type of substrates to which the phytobenthos is attached, they would be considered as epilithic (growing on rocks and other manmade, artificial substances), epipelic (growing on silt), episammic (growing on sand), epiphytic (growing on other plants), or epizoic (growing on animals). Epizoic phytobenthos such as Ostreobium and Symbiodinium have also been found to grow on skeletons or within corals to which they have established symbiotic relationships by exchanging nutrients.
The phytobenthos' habitats can range from freshwater systems such as rivers and lakes to coastal regions. In the marine environment, phytobenthos can be found as far back from the shore as the subtidal zones where they are consistently submerged in water. Their productivity does not extend beyond the outer boundary of the littoral zones, the region to which sunlight can still penetrate to the bottom.
With increasing depth, there is a decline in algal cover due in part to light availability. In addition to depth, turbidity can restrict the extent of light availability, which would also impact the extent of phytobenthic growth. However, phytobenthos such as Ostreobium have demonstrated capability to adapt to low-light conditions as grow in areas as deep as 200 meters. Some diatoms also demonstrated mobility and rise to the surface during the earlier part of the year.
Other physical and chemical conditions that also determine phytobenthos distributions include flow, acidity, nutrient, temperature, and the community's composition. Water flow can determine the types and distributions of phytobenthos, especially in the stream communities where the water is constantly moving. Rivers with more steady flow contribute to the stable environment that can promote the growth of phytobenthos communities. | 5 | Photochemistry |
Under 0.3 GPa pressure, carbon dioxide is stable at room temperature in the same form as dry ice. Over 0.5 GPa carbon dioxide forms a number of different solid forms containing molecules. At pressures over 40 GPa and high temperatures, carbon dioxide forms a covalent solid that contains CO tetrahedra, and has the same structure as β-cristobalite. This is called phase V or CO-V. When CO-V is subjected to high temperatures, or higher pressures, experiments show it breaks down to form diamond and oxygen. In the mantle the geotherm would mean that carbon dioxide would be a liquid till a pressure of 33 GPa, then it would adopt the solid CO-V form till 43 GPa, and deeper than that would make diamond and fluid oxygen. | 9 | Geochemistry |
Cannulas are typically implanted in healthy cows to research cow digestion in a university setting, to analyze the nutritional quality of feed in an agricultural setting, or to improve the microbiome of a cow with digestive disturbance in a veterinary or agricultural setting. | 1 | Biochemistry |
Major families of biopolymers are polysaccharides (carbohydrates), peptides, and polynucleotides. Many variants of each are known. | 0 | Organic Chemistry |
Chemi-excitation via oxidative stress by reactive oxygen species or catalysis by enzymes (i.e., peroxidase, lipoxygenase) is a common event in the biomolecular milieu. Such reactions can lead to the formation of triplet excited species, which release photons upon returning to a lower energy level in a process analogous to phosphorescence. That this process is a contributing factor to spontaneous biophoton emission has been indicated by studies demonstrating that biophoton emission can be increased by depleting assayed tissue of antioxidants or by addition of carbonyl derivatizing agents. Further support is provided by studies indicating that emission can be increased by addition of reactive oxygen species. | 1 | Biochemistry |
Steric effects are critical to chemistry, biochemistry, and pharmacology. In organic chemistry, steric effects are nearly universal and affect the rates and activation energies of most chemical reactions to varying degrees.
In biochemistry, steric effects are often exploited in naturally occurring molecules such as enzymes, where the catalytic site may be buried within a large protein structure. In pharmacology, steric effects determine how and at what rate a drug will interact with its target bio-molecules. | 4 | Stereochemistry |
The term agmatine stems from A- (for amino-) + g- (from guanidine) + -ma- (from ptomaine) + -in (German)/-ine (English) suffix with insertion of -t- apparently for euphony. A year after its discovery, it was found that Agmatine could increase blood flow in rabbits; however, the physiological relevance of these findings were questioned given the high concentrations (high μM range) required. In the 1920s, researchers in the diabetes clinic of Oskar Minkowski have shown that agmatine can exert mild hypoglycemic effects. In 1994, endogenous agmatine synthesis in mammals was discovered. | 1 | Biochemistry |
In 1985, the United States Congress passed legislation requiring the disposal of the stockpile chemical agents and munitions consisting of over 3 million chemical weapons, adding up to 31,000 tons of chemical weapons needing to be disposed of. This was ordered because a timely and safe disposal of chemical weapons is far safer than chemical weapon storage. Between the years of 1982 and 1992, the United States army reported approximately 1,500 leaking chemical weapons munitions, and in 1993 a 100-gallon chemical spill was reported at the Tooele Army Depot in Utah consisting of mustard agents. When chemical weapons are leaked or spilled into the ground, an insidious process follows where the condition of the agent is unknown. This occurs because the process of chemical agents degrading in soil is a complex process that is affected by many factors such as temperature, acidity, alkalinity, meteorological conditions, and the types of organisms present in the soil. This complexity causes persistent agents such as sulfur mustards to be harmful for decades. | 1 | Biochemistry |
ILs can aid the recycling of synthetic goods, plastics, and metals. They offer the specificity required to separate similar compounds from each other, such as separating polymers in plastic waste streams. This has been achieved using lower temperature extraction processes than current approaches and could help avoid incinerating plastics or dumping them in landfill. | 7 | Physical Chemistry |
Because of the success of gene knock-in methods thus far, many clinical applications can be envisioned. Knock-in of sections of the human immunoglobulin gene into mice has already been shown to allow them to produce humanized antibodies that are therapeutically useful. It should be possible to modify stem cells in humans to restore targeted gene function in certain tissues, for example possibly correcting the mutant gamma-chain gene of the IL-2 receptor in hematopoietic stem cells to restore lymphocyte development in people with X-linked severe combined immunodeficiency. | 1 | Biochemistry |
Thermodynamic diagrams usually show a net of five different lines:
* isobars = lines of constant pressure
* isotherms = lines of constant temperature
* dry adiabats = lines of constant potential temperature representing the temperature of a rising parcel of dry air
* saturated adiabats or pseudoadiabats = lines representing the temperature of a rising parcel saturated with water vapor
* mixing ratio = lines representing the dewpoint of a rising parcel
The lapse rate, dry adiabatic lapse rate (DALR) and moist adiabatic lapse rate (MALR), are obtained. With the help of these lines, parameters such as cloud condensation level, level of free convection, onset of cloud formation. etc. can be derived from the soundings. | 7 | Physical Chemistry |
For over 150 years, scientists from all around the world have known about the crystallization of protein molecules.
In 1840, Friedrich Ludwig Hünefeld accidentally discovered the formation of crystalline material in samples of earthworm blood held under two glass slides and occasionally observed small plate-like crystals in desiccated swine or human blood samples. These crystals were named as haemoglobin, by Felix Hoppe-Seyler in 1864. The seminal findings of Hünefeld inspired many scientists in the future.
In 1851, Otto Funke described the process of producing human haemoglobin crystals by diluting red blood cells with solvents, such as pure water, alcohol or ether, followed by slow evaporation of the solvent from the protein solution. In 1871, William T. Preyer, Professor at University of Jena, published a book entitled Die Blutkrystalle (The Crystals of Blood), reviewing the features of haemoglobin crystals from around 50 species of mammals, birds, reptiles and fishes.
In 1909, the physiologist Edward T. Reichert, together with the mineralogist Amos P. Brown, published a treatise on the preparation, physiology and geometrical characterization of haemoglobin crystals from several hundreds animals, including extinct species such as the Tasmanian wolf. Increasing protein crystals were found.
In 1934, John Desmond Bernal and his student Dorothy Hodgkin discovered that protein crystals surrounded by their mother liquor gave better diffraction patterns than dried crystals. Using pepsin, they were the first to discern the diffraction pattern of a wet, globular protein. Prior to Bernal and Hodgkin, protein crystallography had only been performed in dry conditions with inconsistent and unreliable results. This is the first X‐ray diffraction pattern of a protein crystal.
In 1958, the structure of myoglobin (a red protein containing heme), determined by X-ray crystallography, was first reported by John Kendrew. Kendrew shared the 1962 Nobel Prize in Chemistry with Max Perutz for this discovery.
Now, based on the protein crystals, the structures of them play a significant role in biochemistry and translational medicine. | 3 | Analytical Chemistry |
Chronic solvent exposures are often caused by the inhalation of solvent vapors, or the ingestion of diluted solvents, repeated over the course of an extended period.
Some solvents can damage internal organs like the liver, the kidneys, the nervous system, or the brain. The cumulative brain effects of long-term or repeated exposure to some solvents is called chronic solvent-induced encephalopathy (CSE).
Chronic exposure to organic solvents in the work environment can produce a range of adverse neuropsychiatric effects. For example, occupational exposure to organic solvents has been associated with higher numbers of painters suffering from alcoholism. Ethanol has a synergistic effect when taken in combination with many solvents; for instance, a combination of toluene/benzene and ethanol causes greater nausea/vomiting than either substance alone.
Some organic solvents are known or suspected to be cataractogenic. A mixture of aromatic hydrocarbons, aliphatic hydrocarbons, alcohols, esters, ketones, and terpenes were found to greatly increase the risk of developing cataracts in the lens of the eye. | 2 | Environmental Chemistry |
Historically, the theory of rotational energy levels was developed to account for observations of vibration-rotation spectra of gases in infrared spectroscopy, which was used before microwave spectroscopy had become practical. To a first approximation, the rotation and vibration can be treated as separable, so the energy of rotation is added to the energy of vibration. For example, the rotational energy levels for linear molecules (in the rigid-rotor approximation) are
In this approximation, the vibration-rotation wavenumbers of transitions are
where and are rotational constants for the upper and lower vibrational state respectively, while and are the rotational quantum numbers of the upper and lower levels. In reality, this expression has to be modified for the effects of anharmonicity of the vibrations, for centrifugal distortion and for Coriolis coupling.
For the so-called R branch of the spectrum, so that there is simultaneous excitation of both vibration and rotation. For the P branch, so that a quantum of rotational energy is lost while a quantum of vibrational energy is gained. The purely vibrational transition, , gives rise to the Q branch of the spectrum. Because of the thermal population of the rotational states the P branch is slightly less intense than the R branch.
Rotational constants obtained from infrared measurements are in good accord with those obtained by microwave spectroscopy, while the latter usually offers greater precision. | 7 | Physical Chemistry |
Ding was born in March 1966 in Yongcheng, Henan, China. He earned his bachelor's degree from Zhengzhou University in 1985 and his Ph.D. from the Department of Chemistry of Nanjing University in 1990. His doctoral advisor was Wu Yangjie.
Ding became a faculty member of Zhengzhou University in 1990. He conducted postdoctoral research at Ryukoku University in Japan from 1993 to 1994, and was promoted to full professor of Zhengzhou University in 1995. From 1997 to 1998, he was a UNESCO fellow at Tokyo Institute of Technology.
In December 1998, he became a research professor at the Shanghai Institute of Organic Chemistry. He served as President of the institute from 2009 to 2018. In October 2018, he was appointed Executive Vice President of Shanghai Jiao Tong University.
Ding's research interests are asymmetric catalysis and organometallics. He developed multiple chiral phosphine ligands that have been produced by chemical companies. He has received many awards, including the State Natural Science Award (Second Class), the Eli Lilly Scientific Excellence Award, the Yoshida Prize, and the Humboldt Prize. He serves as an editor of more than ten international chemistry journals. He was elected an academician of the Chinese Academy of Sciences in 2013. | 0 | Organic Chemistry |
Trimethylamine N-oxide reductase (TOR or TMAO reductase, EC 1.7.2.3) is a microbial enzyme that can reduce trimethylamine N-oxide (TMAO) into trimethylamine (TMA), as part of the electron transport chain. The enzyme has been purified from E. coli and the photosynthetic bacteria Roseobacter denitrificans.
Trimethylamine oxide is found at high concentrations in the tissues of fish, and the bacterial reduction of this compound to foul-smelling trimethylamine is a major process in the spoilage of fish. | 1 | Biochemistry |
Radiocarbon ages from hyraceum are not subject to reservoir effects or the inclusion of new carbon. This is primarily a function of middens being isolated systems, and that through respiration the hyraceum is brought into equilibrium with atmospheric C at the time of deposition. Published data show that hyrax middens can be of considerable antiquity, and middens from the Groenfontein site in the Cederberg Mountains of South Africa are considered to have begun accumulating ~70,000 years ago
It has been commonly observed that many middens are no longer actively accumulating. Often this is controlled by the shelters in which they are found, with accumulation ceasing when the middens grow to such an extent that the hyraxes can no longer physically enter the shelters. Until recently, field sampling was limited to the collection of middens that were most accessible and easiest to sample. In many cases this meant that the individual sampled middens were relatively thin (<5 cm) with aggregate records subsequently constructed from fragments of as many as 25 separate middens. (Scott and Woodborne, 2007a, b). With recent developments in sampling tools and techniques, larger, more stratigraphically coherent middens are more regularly sampled, which better represent the full period of accumulation at a given site | 9 | Geochemistry |
The Castner process is a process for manufacturing sodium metal by electrolysis of molten sodium hydroxide at approximately 330 °C. Below that temperature, the melt would solidify; above that temperature, the molten sodium would start to dissolve in the melt. | 8 | Metallurgy |
CKLF1 is the first member of the CKLF-like MARVEL transmembrane domain-containing family of proteins to be defined and the most investigated of its four isoforms. Studies conducted in freshly isolated cells, cultured cells, animals, and tissue samples indicate that CKLF1 is a chemokine-like chemotactic factor that acts through the CCR4 receptors on human CD4+ Th2 lymphocytes, neutrophils, monocytes, macrophages, dendritic cells, and perhaps other CCR4-receptor bearing cells. Preliminary findings suggest that the actions of CKLF1 on these CCR4-bearing cells may contribute to the maturation of various tissues such as blood cells and skeletal muscle from their precursor cells and the regulation of allergic (e.g. asthma), autoimmune (e.g. rheumatoid arthritis and the antiphospholipid syndrome), and inflammatory (e.g. acute respiratory distress syndrome) disorders. Other studies have found that: 1) the benign fibrous skin tumor, keloids, had higher levels of CKLF1 and CKLF1 mRNA than nearby normal skin tissues; 2) CKLF1 levels were higher in ovarian carcinoma tissues than nearby normal ovary tissues and patients with higher levels of CKLF1 in their ovarian cancer tissues had a more aggressive cancer than patients with lover levels of the protein in their ovarian cancer tissues; and 3) the levels of CKLF1 protein were higher in cancerous than nearby normal liver tissues in patients with hepatocellular carcinoma (HCC) and patients with higher HCC tissue levels of CKLF1 had poorer overall survival times than patients with lower levels of this protein in their HCC tissues. These results suggest that high levels of CKLF1 promote the development and/or progression of these three neoplasms although further studies are required to further define these relationships and to determine if CKLF1 can be used as a marker for their severity and/or a therapeutic target for treating them. | 1 | Biochemistry |
The physics and chemistry of mantle largely depend on pressure. As mantle minerals are compressed, they are transformed into other minerals at certain depths. Seismic observations of velocity discontinuities and experimental simulations on phase boundaries both verified the structure transformations within the mantle. As such, the mantle can be further divided into three layers with distinct mineral compositions.
Since mantle mineral composition changes, the mineral hosting environment for polyvalent elements also alters. For each layer, the mineral combination governing the redox reactions is unique and will be discussed in detailed below. | 9 | Geochemistry |
In partnership with Sunfire, Audi produces E-diesel in small scale with two steps, the second one being FT. | 0 | Organic Chemistry |
In physiology, base excess and base deficit refer to an excess or deficit, respectively, in the amount of base present in the blood. The value is usually reported as a concentration in units of mEq/L (mmol/L), with positive numbers indicating an excess of base and negative a deficit. A typical reference range for base excess is −2 to +2 mEq/L.
Comparison of the base excess with the reference range assists in determining whether an acid/base disturbance is caused by a respiratory, metabolic, or mixed metabolic/respiratory problem. While carbon dioxide defines the respiratory component of acid–base balance, base excess defines the metabolic component. Accordingly, measurement of base excess is defined, under a standardized pressure of carbon dioxide, by titrating back to a standardized blood pH of 7.40.
The predominant base contributing to base excess is bicarbonate. Thus, a deviation of serum bicarbonate from the reference range is ordinarily mirrored by a deviation in base excess. However, base excess is a more comprehensive measurement, encompassing all metabolic contributions. | 1 | Biochemistry |
The alarm photosynthesis process was first evidenced in pigweed Amaranthus hybridus plant in 2016 when A. hybridus leaves were exposed to drought conditions or exogenous application of abscisic acid. The same study showed similar results in Dianthus chinensis, Pelargonium peltatum, and Portulacaria afra plants under drought stress. In 2018, the alarm photosynthesis process was exhibited in A. hybridus plants under controlled CO starvation conditions. In 2020, evidence of this process was shown in the Antarctic extremophile plant Colobanthus quitensis under CO limiting conditions. | 5 | Photochemistry |
Trichloroethyl chloroformate is used in organic synthesis for the introduction of the trichloroethyl chloroformate (Troc) protecting group for amines, thiols and alcohols. It readily cleaves vs other carbamates and can be used in an overall protecting group strategy.
The troc group is traditionally removed via Zn insertion in the presence of acetic acid, resulting in elimination and decarboxylation. | 0 | Organic Chemistry |
A maltoside is a glycoside with maltose as the glycone (sugar) functional group. Among the most common are alkyl maltosides, which contain hydrophobic alkyl chains as the aglycone. Given their amphiphilic properties, these comprise a class of detergents, where variation in the alkyl chain confers a range of detergent properties including CMC and solubility. Maltosides are most often used for the solubilization and purification of membrane proteins. | 1 | Biochemistry |
A double-blind comparator-controlled Phase I/II clinical trial for Friedreichs ataxia, sponsored by Retrotope and Friedreichs Ataxia Research Alliance, was conducted to determine the safety profile and appropriate dosing for consequent trials. Deulinoleate ethyl was promptly absorbed and was found to be safe and tolerable over 28 days at the maximal dose of 9 g/day. It improved peak workload and peak oxygen consumption in the test group compared to the control group who received the equal doses of normal, non-deuterated ethyl linoleate. Another randomized, double-blind, placebo-controlled clinical study began in 2019. | 1 | Biochemistry |
Copper and copper-based metals continued to be the major metal in use during the first part of the Iron Age (end of 2nd–beginning of 1st millennium BCE). Bronze scrap re-melting continued (mainly v-shaped clay crucibles, slags, clay tuyères) and structures of open campfires full of metal production remains were found in several sites in Israel associated mainly with the Philistines and the Sea People settlements on the northern Sharon coast between modern Tel Aviv and Haifa, e.g., Tel Qasile, Tel Gerisa, Tel Dor, and Tel Dan, in northern Israel. Only later in the Iron Age did metallic iron start to play a major role as a base metal for tools and weapons.
XRF analyses of metals, metallurgical remains, and FTIR + XRF analyses of archaeological sediments
from the open industrial area G in Tel Dor enabled the identification of the exact locations of metal working during the end of the Late Bronze Age and the Iron Age. It was also possible to partially reconstruct the pyrotechnological events that probably involved re-melting bronze in an open fireplace. Even after thousands of years the ash, charcoal, calcite, and burnt ground in the immediate vicinity of the metal work area retained significantly higher values of copper (circa 0.05 wt% Cu) than the surrounding archaeological layers.
During Iron Age II and III and the Persian Period (the first half of the first millennium BCE), copper-based objects continued to be present beside growing numbers of iron products. Silver hoards containing small tongueshaped bar chunks or scrapped jewellery became more and more common in the archaeological context in Israel as well as all over the Mediterranean. A similar phenomenon was evident during the Persian Period on the coast of Israel, where copper and copper-based objects were found in relatively large quantities and with parallels in other sites all around the Mediterranean Sea. What could be defined as a basic Phoenician metal “kit” is composed mainly of the “Irano–Scythian” shape of three winged and socketed arrowheads made mainly of tin bronze, sometimes with arsenic and/or lead and left as-cast, and “hand”-like decorated fibulae made of good quality (7 wt%–12 wt% Sn) tin bronze and lead (up to 17 wt% Pb). They underwent mechanical treatment after casting and an extensive final cold working in the area where the needle spring was fastened into the fibulae body. Long unalloyed copper nails that were found in coastal sites as well as part of the structure of ships were found in the shipwreck from Ma’agan Mikhael. | 8 | Metallurgy |
Many reaction exists which make use of an intermediate nitroso compound, such as the Barton reaction and Davis–Beirut reaction, as well as in the synthesis of indoles, for example: Baeyer–Emmerling indole synthesis, Bartoli indole synthesis. In the Saville reaction, mercury is used to replace a nitrosyl from a thiol group.
C-nitroso compounds are used in organic synthesis as synthons in some well-documented chemical reactions such as hetero Diels-Alder (HDA), nitroso-ene and nitroso-aldol reactions. | 0 | Organic Chemistry |
Phosphoinositide phospholipase C performs its catalytic function at the plasma membrane where the substrate PIP is present. This membrane docking is mediated mostly by lipid-binding domains (e.g. PH domain and C2 domain) that display affinity for different phospholipid components of the plasma membrane. It is important to note that research has also discovered that, in addition to the plasma membrane, phosphoinositide phospholipase C also exists within other sub-cellular regions such as the cytoplasm and nucleus of the cell. At present, it is unclear exactly what the definitive roles for these enzymes in these cellular compartments are, particularly the nucleus. | 1 | Biochemistry |
Chloropentafluoroethane is a chlorofluorocarbon (CFC) once used as a refrigerant and also known as R-115 and CFC-115. Its production and consumption has been banned since 1 January 1996 under the Montreal Protocol because of its high ozone depletion potential and very long lifetime when released into the environment. CFC-115 is also a potent greenhouse gas. | 2 | Environmental Chemistry |
m6A-CLIP (crosslinking immunoprecipitation) and miCLIP (m6A individual-nucleotide-resolution crosslinking and immunoprecipitation) are UV-based sequencing techniques. These two methods activate crosslinking at 254 nm, fragments RNA molecules before immunoprecipitation with antibody, and do not depend on the incorporation of photoactivatable ribonucleosides - the antibody directly crosslinks with a base close (very predictable location) to the m6A site. These UV-based strategies uses antibodies that induces consistent and predictable mutational and truncation patterns in the cDNA strand during reverse-transcription that could be leveraged to more precisely locate the m6A site. Though both m6A-CLIP and miCLIP reply on UV induced mutations, m6A-CLIP is distinct by taking advantage that m6A alone can induce cDNA truncation during reverse transcription and generate single-nucleotide mapping for over ten folds more precise m6A sites (MITS, m6A-induced truncation sites), permitting comprehensive and unbiased precise m6A mapping. In contrast, UV-mapped m6A sites by miCLIP is only a small subset of total precise m6A sites. The precise location of tens of thousands of m6A sites in human and mouse mRNAs by m6A-CLIP reveals that m6A is enriched at last exon but not around stop codon.
In m6A-CLIP and miCLIP, RNA is fragmented to ~20-80nt first, then the 254 nm UV-induced covalent RNA/m6A antibody complex was formed in the fragments containing m6A. The antibody was removed with proteinase K before reverse-transcription, library construction and sequencing. Remnants of peptides at the crosslinking site on the RNA after antibody removal, leads to insertions, truncations, and C to T mutations during reverse transcription to cDNA, especially at the +1 position to the m6A site (5’ to the m6A site) in the sequence reads.
Positive sites seen using m6A-CLIP and miCLIP had high percent of matches with those detected using SCARLET, which has higher local resolution around a specific site, (see below), implicating m6A-CLIP and miCLIP has high spatial resolution and low false discovery rate.
miCLIP has been used to detect m6Am by looking at crosslinking-induced truncation sites at the 5’UTR. | 1 | Biochemistry |
In thermodynamics, heat engines are often modeled using a standard engineering model such as the Otto cycle. The theoretical model can be refined and augmented with actual data from an operating engine, using tools such as an indicator diagram. Since very few actual implementations of heat engines exactly match their underlying thermodynamic cycles, one could say that a thermodynamic cycle is an ideal case of a mechanical engine. In any case, fully understanding an engine and its efficiency requires a good understanding of the (possibly simplified or idealised) theoretical model, the practical nuances of an actual mechanical engine and the discrepancies between the two.
In general terms, the larger the difference in temperature between the hot source and the cold sink, the larger is the potential thermal efficiency of the cycle. On Earth, the cold side of any heat engine is limited to being close to the ambient temperature of the environment, or not much lower than 300 kelvin, so most efforts to improve the thermodynamic efficiencies of various heat engines focus on increasing the temperature of the source, within material limits. The maximum theoretical efficiency of a heat engine (which no engine ever attains) is equal to the temperature difference between the hot and cold ends divided by the temperature at the hot end, each expressed in absolute temperature.
The efficiency of various heat engines proposed or used today has a large range:
*3% (97 percent waste heat using low quality heat) for the ocean thermal energy conversion (OTEC) ocean power proposal
*25% for most automotive gasoline engines
*49% for a supercritical coal-fired power station such as the Avedøre Power Station
*60% for a combined cycle gas turbine
The efficiency of these processes is roughly proportional to the temperature drop across them. Significant energy may be consumed by auxiliary equipment, such as pumps, which effectively reduces efficiency. | 7 | Physical Chemistry |
Levobetaxolol should not be used by people who have sinus bradycardia, atrioventricular block, cardiogenic shock, or overt cardiac failure. The drug has been associated with bradycardia and hypertension. | 4 | Stereochemistry |
According to empirical calibrations, the difference in δSi (denoted as ΔSi) between sponges and their hosting water is correlated with the Si concentration of the hosting solution. Therefore, it has been suggested that the Si concentrations in bottom waters of ancient oceans can be interpreted from the δSi of coexisting sponge spicules, which are preserved in the rock record. It has been proposed that this relation is determined by the growth rate and the Si uptake kinetics of sponges, but the current understanding of sponge biomineralization pathways is limited. Although the mechanism behind this relation is yet to be clear, it appears consistent among various laboratory experiments, modern environments, and core top sediments. However, there is also evidence that the δSi of carnivorous sponges may differ significantly from the expected correlation. | 9 | Geochemistry |
The main processes that remove DOC from the ocean water column are: (1) Thermal degradation in e.g., submarine hydrothermal systems; (2) bubble coagulation and abiotic flocculation into microparticles or sorption to particles; (3) abiotic degradation via photochemical reactions; and (4) biotic degradation by heterotrophic marine prokaryotes. It has been suggested that the combined effects of photochemical and microbial degradation represent the major sinks of DOC. | 2 | Environmental Chemistry |
The compound has two commercial uses.
It is used as an ingredient in Fluosol, artificial blood. This application exploits the high solubility of oxygen and carbon dioxide in the solvent, as well as the low viscosity and toxicity. It is also a component of Fluorinert coolant liquids. CPUs of some computers are immersed in this liquid to facilitate cooling. | 2 | Environmental Chemistry |
Fusion of Armstrong's acid in NaOH gives the disodium salt of 1,5-dihydroxynaphthalene, which can be acidified to give the diol. The intermediate in this hydrolysis, 1-hydroxynaphthalene-5-sulfonic acid, is also useful. Nitration gives nitrodisulfonic acids, which are precursors to amino derivatives.
The disodium salt is sometimes used as a divalent counterion for forming salts of basic drug compounds, as an alternative to the related mesylate or tosylate salts. When used in this way such a salt is called a naphthalenedisulfonate salt, as seen with the most common salt form of the stimulant drug CFT. The disodium salt is also used as an electrolyte in certain kinds of chromatography. | 0 | Organic Chemistry |
* A. Marquet, De l’arme chimique à l’agent thérapeutique. L’Actualité Chimique, 2014 ,N°391, XIII-XVIII.
* A. Marquet et Y. Jacquot. Faut-il avoir peur du Bisphenol A ? L’Actualité Chimique, 2013, N°378-379,11-19.
* A. Marquet et B.Sillion, coordinateurs. Chimie et Société : Quel dialogue ? L’Actualité Chimique, 2011, N°355.
* A. Marquet, B. Tse Sum Bui, AG. Smith, MJ. Warren. Iron-sulfur proteins as initiators of radical chemistry. Nat. Prod. Rep., 2007 ; 24 : 1027-1040.
* M. Lotierzo, B. Tse Sum Bui, D. Florentin, F. Escalettes, A. Marquet. Biotin synthase mechanism: An overview. Biochemical Society Transactions, 2005, 33, 820 – 823.
* B. Rüdiger, B. Tse Sum Bui, V. Schünemann, D. Florentin, A. Marquet, A..S. Trautwein. Iron-sulfur clusters of biotin synthase in vivo: a Mössbauer study. Biochemistry, 2002, 41, 15000-15006.
* E. Davioud, A. Piffeteau, C. Delorme, S. Coustal, A. Marquet.18-Vinyldeoxycorticosterone: a potent inhibitor of the bovine cytochrome P-450. Bioorganic and Medicinal Chemistry, 1998, 6, 1781-1788.
* A. Vidal-Cros, M. Gaudry, A. Marquet. Vitamin K dependent carboxylation. Mechanistic studies with 3-fluoroglutamate containing substrates. Biochemical Journal, 1990, 266, 749-755.
* G. Chassaing and A. Marquet. A C NMR study of the structure of sulfur-stabilized carbanions. Tetrahedron, 1978, 34, 1399.
* S. Lavielle, S. Bory, B. Moreau, M.J. Luche and A. Marquet. A total synthesis of biotin based on the stereoselective alkylation of sulfoxides. J. Am. Chem. Soc., 1978, 100, 1558. | 0 | Organic Chemistry |
Compounds containing the tetrathionate anion include sodium tetrathionate, NaSO, potassium tetrathionate, KSO, and barium tetrathionate dihydrate, BaSO·2HO. | 8 | Metallurgy |
The nucleosome core particle is the most basic form of DNA compaction in eukaryotes. Nucleosomes consist of a histone octamer surrounded by 146 base pairs of DNA wrapped in a superhelical manner. In addition to compacting the DNA, the histone octamer plays a key role in the transcription of the DNA surrounding it. The histone octamer interacts with the DNA through both its core histone folds and N-terminal tails. The histone fold interacts chemically and physically with the DNA's minor groove. Studies have found that the histones interact more favorably with A:T enriched regions than G:C enriched regions in the minor grooves. The N-terminal tails do not interact with a specific region of DNA but rather stabilize and guide the DNA wrapped around the octamer. The interactions between the histone octamer and DNA, however, are not permanent. The two can be separated quite easily and often are during replication and transcription. Specific remodeling proteins are constantly altering the chromatin structure by breaking the bonds between the DNA and nucleosome. | 1 | Biochemistry |
This book is extensively illustrated and describes the tools and machinery associated with mining. Handtools and different sorts of buckets, wheelbarrows and trucks on wooded plankways are described. Packs for horses and sledges are used to carry loads above ground. Agricola then provides details of various kinds of machines for lifting weights. Some of these are man-powered and some powered by up to four horses or by waterwheels. Horizontal drive shafts along tunnels allow lifting in shafts not directly connected to the surface. If this is not possible, treadmills will be installed underground. Instead of lifting weights, similar machines use chains of buckets to lift water. Agricola also describes several designs of piston force pumps, which are either man or animal-powered, or powered by water wheels. Because these pumps can only lift water about 24 feet, batteries of pumps are required for the deepest mines. Water pipe designs are also covered in this section. Designs of wind scoop for ventilating shafts or forced air using fans or bellows are also described. Finally, ladders and lifts using wicker cages are used to get miners up and down shafts. | 8 | Metallurgy |
Corby became a steelmaking centre through the establishment of the Stewarts & Lloyds production site in the 1930s, and by 1960 had grown to become one of the most heavily industrialised areas in the Midlands. In 1981 however the plant had become unprofitable and owners British Steel Corporation closed the site. By then it was one of the largest steelmaking operations in Western Europe, covering , with four blast furnaces, two coke oven complexes and associated facilities. During its operation a huge quantity of industrial waste, including toxic waste, had been deposited there.
Between 1984 and 1999 Corby Borough Council undertook the demolition, excavation and redevelopment of the site as part of a program of urban regeneration. This involved transporting the waste through populated areas to a quarry north of the site, utilising up to 200 vehicle movements daily. The toxic waste was carried in open lorries, spilling sludge over the roads and releasing huge amounts of dust into the air.
Subsequently, in the late 1980s and 1990s, the rates of upper-limb defects in babies born in Corby were found to be almost three times higher than those of children born in the surrounding area and ten times higher than a town with a population of 60,000 should expect. In all cases initially referred to the court there were no previous family histories of limb defect. | 2 | Environmental Chemistry |
Zirconia exists in the monoclinic, tetragonal or cubic crystal system depending on the temperature. The surface acidity and basicity of the oxide depends on the crystal structure and surface orientation. The surfaces of zirconia have hydroxyl groups, which can act as Brønsted acids or bases, and coordination-unsaturated ZrO acid base pairs which contribute to its overall acid–base properties. Adsorption studies have shown that monoclinic zirconia is more basic than tetragonal, as it forms stronger bonds with CO. Adsorption of CO shows that the tetragonal phase has more acidic Lewis acid sites than the monoclinic phase, but that it has a lower concentration of Lewis acid sites. | 7 | Physical Chemistry |
The CFIIm complex is responsible for transcription termination and triggering the disassembly of the elongation complex. It is composed of only two proteins:
*PCF11
*CLP1 | 1 | Biochemistry |
The absorption of dietary iron is a variable and dynamic process. The amount of iron absorbed compared to the amount ingested is typically low, but may range from 5% to as much as 35% depending on circumstances and type of iron. The efficiency with which iron is absorbed varies depending on the source. Generally, the best-absorbed forms of iron come from animal products. Absorption of dietary iron in iron salt form (as in most supplements) varies somewhat according to the body's need for iron, and is usually between 10% and 20% of iron intake. Absorption of iron from animal products, and some plant products, is in the form of heme iron, and is more efficient, allowing absorption of from 15% to 35% of intake. Heme iron in animals is from blood and heme-containing proteins in meat and mitochondria, whereas in plants, heme iron is present in mitochondria in all cells that use oxygen for respiration.
Like most mineral nutrients, the majority of the iron absorbed from digested food or supplements is absorbed in the duodenum by enterocytes of the duodenal lining. These cells have special molecules that allow them to move iron into the body. To be absorbed, dietary iron can be absorbed as part of a protein such as heme protein or iron must be in its ferrous Fe form. A ferric reductase enzyme on the enterocytes brush border, duodenal cytochrome B (Dcytb), reduces ferric Fe to Fe. A protein called divalent metal transporter 1 (DMT1), which can transport several divalent metals across the plasma membrane, then transports iron across the enterocytes cell membrane into the cell. If the iron is bound to heme, it is instead transported across the apical membrane by heme carrier protein 1 (HCP1). Heme is then catabolized by microsomal heme oxygenase into biliverdin, releasing Fe.
These intestinal lining cells can then either store the iron as ferritin, which is accomplished by Fe binding to apoferritin (in which case the iron will leave the body when the cell dies and is sloughed off into feces), or the cell can release it into the body via the only known iron exporter in mammals, ferroportin. Hephaestin, a ferroxidase that can oxidize Fe to Fe and is found mainly in the small intestine, helps ferroportin transfer iron across the basolateral end of the intestine cells. Upon release into the bloodstream, Fe binds transferrin and circulates to tissues. In contrast, ferroportin is post-translationally repressed by hepcidin, a 25-amino acid peptide hormone. The body regulates iron levels by regulating each of these steps. For instance, enterocytes synthesize more Dcytb, DMT1 and ferroportin in response to iron deficiency anemia. Iron absorption from diet is enhanced in the presence of vitamin C and diminished by excess calcium, zinc, or manganese.
The human body's rate of iron absorption appears to respond to a variety of interdependent factors, including total iron stores, the extent to which the bone marrow is producing new red blood cells, the concentration of hemoglobin in the blood, and the oxygen content of the blood. The body also absorbs less iron during times of inflammation, in order to deprive bacteria of iron. Recent discoveries demonstrate that hepcidin regulation of ferroportin is responsible for the syndrome of anemia of chronic disease. | 1 | Biochemistry |
Amines are often used as epoxy resin curing agents. These include dimethylethylamine, cyclohexylamine, and a variety of diamines such as 4,4-diaminodicyclohexylmethane. Multifunctional amines such as tetraethylenepentamine and triethylenetetramine are also widely used in this capacity. The reaction proceeds by the lone pair of electrons on the amine nitrogen attacking the outermost carbon on the oxirane ring of the epoxy resin. This relieves ring strain on the epoxide and is the driving force of the reaction. | 0 | Organic Chemistry |
Seeding implants with growth factors, such as neural progenitor cells (NPCs), improves the brain-implant interface. NPCs are progenitor cells that have the ability to differentiate into neurons or cells found in the brain. By coating the implant with NPCs, it can reduce the foreign body reaction and improve biocompatibility. To attach the NPCs, prior surface modification of the implant is required; these modifications can be done via the immobilization of laminin (an extracellular matrix derived protein) on an implant, such as silicon. To verify the success of surface immobilization, Fourier transform infrared spectroscopy (FTIR) and an analysis of hydrophobicity can be used. The Fourier transform infrared spectroscopy can be used to characterize the chemical composition of the surface or a contact angle goniometer can be used to determine the contact angle of water to determine the hydrophobicity. A higher contact angle indicates higher hydrophobicity, showing successful modification of the surface via the laminin protein. The laminin immobilized surface promotes the attachment and growth of the NPCs and also allows for their differentiation, thereby reducing the glial response and foreign body response to the implant. | 7 | Physical Chemistry |
Atomic force microscopy (AFM), a type of scanning force microscopy, was developed for mapping three-dimensional topographical variations in atomic surfaces with high resolution (on the order of fraction of nanometers). AFM was developed to overcome the material conduction limitations of electron transmission and scanning microscopy methods (SEM & STM). Invented by Binnig, Quate, and Gerbe in 1985, atomic force microscopy uses laser beam deflection to measure the variations in atomic surfaces. The method does not rely on the variation in electron conduction through the material, as the scanning tunneling microscope (STM) does, and therefore allow microscopy on nearly all materials, including polymers.
The application of AFM on polymeric surfaces is especially favorable because polymer general lack of crystallinity leads to large variations in surface topography. Surface functionalization techniques such as grafting, corona treatment, and plasma processing increase the surface roughness greatly (compared to the unprocessed substrate surface) and are therefore accurately measured by AFM. | 7 | Physical Chemistry |
Many phenols of commercial interest are prepared by elaboration of phenol or cresols. They are typically produced by the alkylation of benzene/toluene with propylene to form cumene then is added with to form phenol (Hock process). In addition to the reactions above, many other more specialized reactions produce phenols:
* rearrangement of esters in the Fries rearrangement
* rearrangement of N-phenylhydroxylamines in the Bamberger rearrangement
* dealkylation of phenolic ethers
* reduction of quinones
* replacement of an aromatic amine by an hydroxyl group with water and sodium bisulfide in the Bucherer reaction
*thermal decomposition of aryl diazonium salts, the salts are converted to phenol
* by the oxidation of aryl silanes—an aromatic variation of the Fleming-Tamao oxidation
*catalytic synthesis from aryl bromides and iodides using nitrous oxide | 0 | Organic Chemistry |
Unlike most epidermal cells, the guard cells of plant stomata contain relatively well-developed chloroplasts. However, exactly what they do is controversial. | 5 | Photochemistry |
Nucleotide sugars are the activated forms of monosaccharides. Nucleotide sugars act as glycosyl donors in glycosylation reactions. Those reactions are catalyzed by a group of enzymes called glycosyltransferases. | 0 | Organic Chemistry |
Once a suitable genomic fragment is chosen (Step 1), the exons and introns of the fragment can be inserted and amplified, along with the flanking constitutive exons and introns of the original gene, by PCR. The primers for PCR can be chosen so that they leave "sticky ends" at 3' sense and anti-sense strands (Step 2). These "sticky-ends" can be easily incorporated into a TOPO Vector by ligation into a commercially available source which has ligase already attached to it at the sight of incorporation (Step 3). The subsequent TOPO Vectors can be transfected into E.coli cells (Step 4). After incubation, total RNA can be extracted from the bacterial colonies and analyzed using RT-PCR to quantify ratios of exon inclusion/exclusion (step 5). The minigene can be transfected into different cell types with various splicing factors to test trans-acting elements (Step 6). The expressed genes or the proteins they encode can be analyzed to evaluate splicing components and their effects via a variety of methods including hybridization or size-exclusion chromatography. | 1 | Biochemistry |
Charge recombination reactions of PSII cause the production of triplet P and, as a consequence, singlet oxygen. Charge recombination is more probable under dim light than under higher light intensities. | 5 | Photochemistry |
__NOTOC__
A trace element is a chemical element of a minute quantity, a trace amount, especially used in referring to a micronutrient, but is also used to refer to minor elements in the composition of a rock, or other chemical substance.
In nutrition, trace elements are classified into two groups: essential trace elements, and non-essential trace elements. Essential trace elements are needed for many physiological and biochemical processes in both plants and animals. Not only do trace elements play a role in biological processes but they also serve as catalysts to engage in redox – oxidation and reduction mechanisms. Trace elements of some heavy metals have a biological role as essential micronutrients. | 9 | Geochemistry |
Interfacial energy affects the mechanisms of grain boundary sliding and dislocation transmission. Higher interfacial energy promotes greater resistance to grain boundary sliding, as the higher energy barriers inhibit the relative movement of adjacent grains. Additionally, dislocations that encounter grain boundaries can either transmit across the boundary or be reflected back into the same grain. The interfacial energy influences the likelihood of dislocation transmission, with higher interfacial energy barriers impeding dislocation motion and enhancing grain boundary strengthening. | 8 | Metallurgy |
CMD begins with a high valent, late transition metal like Pd that may or may not be bound to a carboxylate anion. The computed transition state involves concerted partial formation of a carbon–metal bond and partial protonation of the carboxylate. At the same time, any anionic metal–carboxylate bond begins to break, as does the carbon–hydrogen bond that is being activated. Compared to other possible processes such as oxidative addition of the C–H bond to the metal, CMD is lower in energy in many cases. A transition state in which the carboxylate is bound to the metal can be referred to as either CMD or AMLA, which stands for "ambiphilic metal–ligand assistance," but the latter emphasizes that the carboxylate acts as a ligand during the transition state. | 0 | Organic Chemistry |
Historically, bacteria were first classified as plants constituting the class Schizomycetes, which along with the Schizophyceae (blue-green algae/Cyanobacteria) formed the phylum Schizophyta, then in the phylum Monera in the kingdom Protista by Haeckel in 1866, comprising Protogens, Protamaeba, Vampyrella, Protomonae, and Vibrio, but not Nostoc and other cyanobacteria, which were classified with algae, later reclassified as the Prokaryotes by Chatton.
The cyanobacteria were traditionally classified by morphology into five sections, referred to by the numerals I–V. The first three – Chroococcales, Pleurocapsales, and Oscillatoriales – are not supported by phylogenetic studies. The latter two – Nostocales and Stigonematales – are monophyletic as a unit, and make up the heterocystous cyanobacteria.
The members of Chroococales are unicellular and usually aggregate in colonies. The classic taxonomic criterion has been the cell morphology and the plane of cell division. In Pleurocapsales, the cells have the ability to form internal spores (baeocytes). The rest of the sections include filamentous species. In Oscillatoriales, the cells are uniseriately arranged and do not form specialized cells (akinetes and heterocysts). In Nostocales and Stigonematales, the cells have the ability to develop heterocysts in certain conditions. Stigonematales, unlike Nostocales, include species with truly branched trichomes.
Most taxa included in the phylum or division Cyanobacteria have not yet been validly published under The International Code of Nomenclature of Prokaryotes (ICNP) except:
*The classes Chroobacteria, Hormogoneae, and Gloeobacteria
*The orders Chroococcales, Gloeobacterales, Nostocales, Oscillatoriales, Pleurocapsales, and Stigonematales
*The families Prochloraceae and Prochlorotrichaceae
*The genera Halospirulina, Planktothricoides, Prochlorococcus, Prochloron, and Prochlorothrix
The remainder are validly published under the International Code of Nomenclature for algae, fungi, and plants.
Formerly, some bacteria, like Beggiatoa, were thought to be colorless Cyanobacteria.
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI).
Class "Cyanobacteriia"
* Subclass "Gloeobacteria"
** Gloeobacterales
* Subclass "Phycobacteria"
** Acaryochloridales [incl. Thermosynechococcales]
** Aegeococcales
** "Elainellales"
** "Eurycoccales"
** Geitlerinematales
** Gloeoemargaritales
** "Leptolyngbyales"
** Nodosilineales
** Oculatellales
** "Phormidesmiales"
** Prochlorococcaceae {"PCC-6307"}
** Pseudanabaenales
** "Pseudophormidiales"
** Thermostichales
** Synechococcophycidae
*** "Limnotrichales"
*** Prochlorotrichales (PCC-9006)
*** Synechococcales
** Nostocophycidae
*** Cyanobacteriales (Chamaesiphonales, Chroococcales, Chroococcidiopsidales, Nostocales, Oscillatoriales, Pleurocapsales, Spirulinales, Stigonematales) | 5 | Photochemistry |
In LS AAS the high resolution that is required for the measurement of atomic absorption is provided by the narrow line emission of the radiation source, and the monochromator simply has to resolve the analytical line from other radiation emitted by the lamp. This can usually be accomplished with a band pass between 0.2 and 2 nm, i.e., a medium-resolution monochromator. Another feature to make LS AAS element-specific is modulation of the primary radiation and the use of a selective amplifier that is tuned to the same modulation frequency, as already postulated by Alan Walsh. This way any (unmodulated) radiation emitted for example by the atomizer can be excluded, which is imperative for LS AAS. Simple monochromators of the Littrow or (better) the Czerny-Turner design are typically used for LS AAS. Photomultiplier tubes are the most frequently used detectors in LS AAS, although solid state detectors might be preferred because of their better signal-to-noise ratio. | 3 | Analytical Chemistry |
Soil bacteria and archaea account for approximately 5% of the natural methane sink. Early research is going into how the activity of these bacteria may be able to be enhanced, either through the use of soil amendments, or introduction of selected or engineered methane-oxidizing bacteria. | 2 | Environmental Chemistry |
Olson's studies DNA as polymers, with atoms and chemical bonds. She studies the interaction between DNA and structural proteins which do not bind to the nuclear bases, but to the phosphorus-sugar backbone, e.g.histones. Also, the energy needed to form circular DNA is investigated Olson aims to clarify the role of local structure on the overall folding of RNA, for instance the helices and loops in the ribosome. A second goal is to uncover structural details of nucleic acid structural transitions, such as those involving different DNA duplexes. This information helps to design new drugs and materials. | 1 | Biochemistry |
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and sometimes broadened to include metalloids like boron, silicon, and selenium, as well. Aside from bonds to organyl fragments or molecules, bonds to inorganic carbon, like carbon monoxide (metal carbonyls), cyanide, or carbide, are generally considered to be organometallic as well. Some related compounds such as transition metal hydrides and metal phosphine complexes are often included in discussions of organometallic compounds, though strictly speaking, they are not necessarily organometallic. The related but distinct term "metalorganic compound" refers to metal-containing compounds lacking direct metal-carbon bonds but which contain organic ligands. Metal β-diketonates, alkoxides, dialkylamides, and metal phosphine complexes are representative members of this class. The field of organometallic chemistry combines aspects of traditional inorganic and organic chemistry.
Organometallic compounds are widely used both stoichiometrically in research and industrial chemical reactions, as well as in the role of catalysts to increase the rates of such reactions (e.g., as in uses of homogeneous catalysis), where target molecules include polymers, pharmaceuticals, and many other types of practical products. | 0 | Organic Chemistry |
The origin of nitrogenase has been of interest to paleobiologists and is an area of active research. Nitrogenase is thought to have evolved sometime between 1.5-2.2 billion years ago (Ga) although some isotopic support showing nitrogenase evolution as early as around 3.2 Ga. Nitrogenase appears to have evolved from maturase-like proteins, although the function of the preceding protein is currently unknown.
Nitrogenase has three different forms (Nif, Anf, and Vnf) that correspond with the metal found in the active site of the protein (Molybdenum, Iron, and Vanadium respectively). Marine metal abundances over Earth’s geologic timeline are thought to have driven the relative abundance of which form of nitrogenase was most common. Currently, there is no conclusive agreement on which form of nitrogenase arose first. | 1 | Biochemistry |
Understanding the mechanical properties of Heusler compounds is paramount for temperature-sensitive applications (e.g. thermoelectrics) for which some sub-classes of Heusler compounds are used. However, experimental studies are rarely encountered in literature. In fact, the commercialization of these compounds is limited by the materials ability to undergo intense, repetitive thermal cycling and resist cracking from vibrations. An appropriate measure for crack resistance is the materials toughness, which typically scales inversely with another important mechanical property: the mechanical strength. In this section, we highlight existing experimental and computational studies on the mechanical properties of Heusler alloys. Note that the mechanical properties of such a compositionally-diverse class of materials is expectedly dependent on the chemical composition of the alloys themselves, and therefore trends in mechanical properties are difficult to identify without a case-by-case study.
The elastic modulus values of half-Heusler alloys range from 83 to 207 GPa, whereas the bulk modulus spans a tighter range from 100 GPa in HfNiSn to 130 GPa in TiCoSb. A collection of various density functional theory (DFT) calculations show that half-Heusler compounds are predicted to have a lower elastic, shear, and bulk modulus than in quaternary-, full-, and inverse-Hausler alloys. DFT also predicts a decrease in elastic modulus with temperature in NiXAl (X=Sc, Ti, V), as well as an increase in stiffness with pressure. The decrease in modulus with respect to temperature is also observed in TiNiSn, ZrNiSn, and HfNiSn, where ZrNiSn has the highest modulus and Hf has the lowest. This phenomenon can be explained by the fact that the elastic modulus decreases with increasing interatomic separation: as temperature increases, the atomic vibrations also increase, resulting in a larger equilibrium interatomic separation.
The mechanical strength is also rarely studied in Heusler compounds. One study has shown that, in off-stoichiometric NiMnIn, the material reaches a peak strength of 475 MPa at 773 K, which drastically reduces to below 200 MPa at 973 K. In another study, a polycrystalline Heusler alloy composed of the Ni-Mn-Sn ternary composition space was found to possess a peak compressive strength of about 2000 MPa with plastic deformation up to 5%. However, the addition of Indium to the Ni-Mn-Sn ternary alloy not only increases the porosity of the samples, but it also reduces the compressive strength to 500 MPa. It is unclear from the study what percentage of the porosity increase from the indium addition reduces the strength. Note that this is opposite to the outcome expected from solid solution strengthening, where adding indium to the ternary system slows dislocation movement through dislocation-solute interaction and subsequently increases the material's strength.
The fracture toughness can also be tuned with composition modifications. For example, the average toughness of Ti(Zr, Hf)NiSn ranges from 1.86 MPa m to 2.16 MPa m, increasing with Zr/Hf content. The preparation of samples may affect the measured fracture toughness however, as elaborated by O’Connor et al. In their study, samples of TiHfCoIrSbSn were prepared using three different methods: a high-temperature solid state reaction, high-energy ball milling, and a combination of both. The study found higher fracture toughness in samples prepared without a high-energy ball milling step of 2.7 MPa m to 4.1 MPa m, as opposed to samples that were prepared with ball milling of 2.2 MPa m to 3.0 MPa m. Fracture toughness is sensitive to inclusions and existing cracks in the material, so it is as expected dependent on the sample preparation. | 8 | Metallurgy |
Another application is in radiochemistry, where this may refer to isotopic ratios or isotopic abundances. Mathematically, the isotopic abundance is
where N are the number of atoms of the isotope of interest and N is the total number of atoms, while the atomic ratio is
For example, the isotopic ratio of deuterium (D) to hydrogen (H) in heavy water is roughly (corresponding to an isotopic abundance of 0.00014%). | 7 | Physical Chemistry |
In an conventional CCC experiment the biphasic solvent system is pre-equilibrated before the instrument is filled with the stationary phase and equilibrated with the mobile phase. An ion-exchange mode has been created by modifying both of the phases after pre-equilibration. Generally, an ionic displacer (or eluter) is added to mobile phase and an ionic retainer is added to the stationary phase. For example, the aqueous mobile phase may contain NaI as a displacer and the organic stationary phase may be modified with the quaternary ammonium salt called Aliquat 336 as a retainer. The mode known a pH-zone-refining is a type of ion-exchange mode that utilizes acids and/or bases as solvent modifiers. Typically, the analytes are eluted in an order determined by their pKa values. For example, 6 oxindole alkaloids were isolated from a 4.5g sample of Gelsemium elegans stem extract with a biphasic solvent system composed of hexane–ethyl acetate–methanol–water (3:7:1:9, v/v) where 10 mM triethylamine (TEA) was added to the upper organic stationary phase as a retainer and 10 mM hydrochloric acid (HCl) to the aqueous mobile phase as an eluter. Ion-exchange modes such as pH-zone-refining have tremendous potential because high sample loads can be achieved without sacrificing separation power. It works best with ionizable compounds such as nitrogen containing alkaloids or carboxylic acid containing fatty acids. | 3 | Analytical Chemistry |
Tin-lead (Sn-Pb) solders, also called soft solders, are commercially available with tin concentrations between 5% and 70% by weight. The greater the tin concentration, the greater the solder's tensile and shear strengths. Lead mitigates the formation of tin whiskers, though the precise mechanism for this is unknown. Today, many techniques are used to mitigate the problem, including changes to the annealing process (heating and cooling), addition of elements like copper and nickel, and the application of conformal coatings. Alloys commonly used for electrical soldering are 60/40 Sn-Pb, which melts at , and 63/37 Sn-Pb used principally in electrical/electronic work. The latter mixture is a eutectic alloy of these metals, which:
# has the lowest melting point () of all the tin-lead alloys; and
# the melting point is truly a point — not a range.
In the United States, since 1974, lead is prohibited in solder and flux in plumbing applications for drinking water use, per the Safe Drinking Water Act. Historically, a higher proportion of lead was used, commonly 50/50. This had the advantage of making the alloy solidify more slowly. With the pipes being physically fitted together before soldering, the solder could be wiped over the joint to ensure water tightness. Although lead water pipes were displaced by copper when the significance of lead poisoning began to be fully appreciated, lead solder was still used until the 1980s because it was thought that the amount of lead that could leach into water from the solder was negligible from a properly soldered joint. The electrochemical couple of copper and lead promotes corrosion of the lead and tin. Tin, however, is protected by insoluble oxide. Since even small amounts of lead have been found detrimental to health as a potent neurotoxin, lead in plumbing solder was replaced by silver (food-grade applications) or antimony, with copper often added, and the proportion of tin was increased (see lead-free solder).
The addition of tin—more expensive than lead—improves wetting properties of the alloy; lead itself has poor wetting characteristics. High-tin tin-lead alloys have limited use as the workability range can be provided by a cheaper high-lead alloy.
Lead-tin solders readily dissolve gold plating and form brittle intermetallics.
60/40 Sn-Pb solder oxidizes on the surface, forming a complex 4-layer structure: tin(IV) oxide on the surface, below it a layer of tin(II) oxide with finely dispersed lead, followed by a layer of tin(II) oxide with finely dispersed tin and lead, and the solder alloy itself underneath.
Lead, and to some degree tin, as used in solder contains small but significant amounts of radioisotope impurities. Radioisotopes undergoing alpha decay are a concern due to their tendency to cause soft errors. Polonium-210 is especially troublesome; lead-210 beta decays to bismuth-210 which then beta decays to polonium-210, an intense emitter of alpha particles. Uranium-238 and thorium-232 are other significant contaminants of alloys of lead. | 8 | Metallurgy |
Mary Shelleys Frankenstein, wherein a man stitches together a human body from corpses and brings it to life, was inspired in part by the theory and demonstrations of Galvanism which may have been conducted by James Lind. Although the Creature was described in later works as a composite of whole body parts grafted together from cadavers and reanimated by the use of electricity, this description is not consistent with Shelleys work; both the use of electricity and the cobbled-together image of Frankensteins monster were more the result of James Whales popular 1931 film adaptation of the story. | 7 | Physical Chemistry |
It occurs in tree fern fronds, a specialty called fiddlehead (furled fronds of a young tree fern in the order Cyatheales, harvested for use as a vegetable). These fronds are edible, but can be roasted to remove shikimic acid.
Shikimic acid is also the glycoside part of some hydrolysable tannins. The acid is highly soluble in water and insoluble in nonpolar solvents, and this is why shikimic acid is active only against Gram-positive bacteria, due to outer cell membrane impermeability of Gram-negatives. | 1 | Biochemistry |
Since microsphere beads are easily suspended in solution and each microsphere retains its identity when hybridized to the test sample, a typical suspension array experiment can analyze a wide range of biological analysis in a single reaction, called "multiplexing". In general, each type of microsphere used in an array is individually prepared in bulk. For example, the commercially available microsphere arrays from Luminex xMAP technology uses a 10X10 element array. This array involves beads with red and infrared dyes, each with ten different intensities, to give a 100-element array. Thus, the array size would increase exponentially if multiple dyes are used. For example, five different dyes with 10 different intensities per dye will give rise to 100,000 different array elements. | 1 | Biochemistry |
Neptunes internal heat and convection drives cycles of methane, carbon, and a combination of other volatiles within Tritons lithosphere.
Models predicted the presence of seasonal nitrogen cycles on the moon Triton, however this has not been supported by observations to date. | 9 | Geochemistry |
Born to Instructor Commodore M. G. S. Perera (1 June 1917 – 10 August 1999), Founder and the First Commandant Naval & Maritime Academy Trincomalee, the First and Foremost Director of Naval Training, Royal Ceylon Navy, and former Senior Staff Captain / Nautical Instructor (Training of Deck Officer Cadets) Ceylon Shipping Corporation (1977–1983) and Maureen Johanna Perera (19 February 1924 - 22 October 2019), he has one sister, Deepthi C. J. Guneratne BSc (Botany), MSc (Soil Chemistry). | 3 | Analytical Chemistry |
The problem can be prevented by adding antiozonants to the rubber before vulcanization. Ozone cracks were commonly seen in automobile tire sidewalls, but are now seen rarely thanks to the use of these additives. A common and low cost antiozonant is a wax which bleeds to the surface and forms a protective layer, but other specialist chemicals are also widely used.
On the other hand, the problem does recur in unprotected products such as rubber tubing and seals, where ozone attack is thought to be impossible. Unfortunately, traces of ozone can turn up in the most unexpected situations. Using ozone-resistant rubbers is another way of inhibiting cracking. EPDM rubber and butyl rubber are ozone resistant, for example.
For high value equipment where loss of function can cause serious problems, low cost seals may be replaced at frequent intervals so as to preclude failure.
Ozone gas is produced during electric discharge by sparking or corona discharge for example. Static electricity can build up within machines like compressors with moving parts constructed from insulating materials. If those compressors feed pressurised air into a closed pneumatic system, then all seals in the system may be at risk from ozone cracking.
Ozone is also produced by the action of sunlight on volatile organic compounds or VOCs, such as gasoline vapour present in the air of towns and cities, in a problem known as photochemical smog. The ozone formed can drift many miles before it is destroyed by further reactions. | 7 | Physical Chemistry |
WeNMR aims at bringing together complementary research teams in the structural biology and life science area into a virtual research community at a worldwide level and provide them with a platform integrating and streamlining the computational approaches necessary for NMR and SAXS data analysis and structural modelling. Access to the infrastructure is provided through a portal integrating commonly used software and GRID technology. | 1 | Biochemistry |
Ibuprofen is used primarily to treat fever (including postvaccination fever), mild to moderate pain (including pain relief after surgery), painful menstruation, osteoarthritis, dental pain, headaches, and pain from kidney stones. About 60% of people respond to any NSAID; those who do not respond well to a particular one may respond to another. A Cochrane medical review of 51 trials of NSAIDS for the treatment of lower back pain found that "NSAIDs are effective for short-term symptomatic relief in patients with acute low back pain".
It is used for inflammatory diseases such as juvenile idiopathic arthritis and rheumatoid arthritis. It is also used for pericarditis and patent ductus arteriosus. | 4 | Stereochemistry |
Although the Pho regulon system is most widely studied in Escherichia coli it is found in other bacterial species such as Pseudomonas fluorescens and Bacillus subtilis. In Pseudomonas fluorescens, the transcriptional response regulator (PhoB/PhoR) retain the same function they play in E. coli. Bacillus subtilis also shares some similarities when encountering low intracellular phosphate concentrations. Under phosphate-starved conditions B. subtilis binds its transcription regulator, PhoP and the histidine kinase, PhoR to the Pho-regulon gene which induces a production of teichuronic acid. Furthermore, recent studies have suggested the critical role that techoic acid plays in the cell wall of B. subtilis, by acting as a phosphate reservoir and storing the necessary amount of inorganic phosphate in phosphate-starved conditions. | 1 | Biochemistry |
A common quantity used to describe the collection efficiency of a froth flotation process is flotation recovery (). This quantity incorporates the probabilities of collision and attachment of particles to gas flotation bubbles.
where:
* , which is the product of the probability of the particle being collected () and the number of possible particle collisions ()
* is particle diameter
* is bubble diameter
* is a specified height within the flotation which the recovery was calculated
* is the particle concentration
The following are several additional mathematical methods often used to evaluate the effectiveness of froth flotation processes. These equations are more simple than the calculation for flotation recovery, as they are based solely on the amounts of inputs and outputs of the processes.
For the following equations:
* is the weight percent of feed
* is the weight percent concentrate
* is the weight percent of tailings
* , , and are the metallurgical assays of the concentrate, tailings, and feed, respectively
Ratio of feed weight to concentrate weight (unitless)
Percent of metal recovered () in wt%
Percent of metal lost () in wt%
Percent of weight recovered in wt%
This can be calculated using weights and assays, as . Or, since , the percent of metal recovered () can be calculated from assays alone using .
Percent of metal lost is the opposite of the percent of metal recovered, and represents the material lost to the tailings. | 8 | Metallurgy |
Many coastal mosses were initiated by the process of glaciation, which sheared rock formations to a generally level terrain, while also gouging moderate sized craters that would pond. This description fits the fundamental situation of Portlethen Moss, where sphagnum would have flourished over millennia of evaporation, further intensifying the soil acidity, fueled by organic matter decaying, with little drainage outlet. A layer of sphagnum moss would have developed at the benthic level of the bog, and additional sphagnum layers floated in mats atop the bog.
At an intermediate level of evolution, thick peat layers formed from decay and carbonisation of the rotting sphagnum. Generations of Carex and Juncus flourished, leading to further decay of these materials and eventual heightening of the organic mass. Finally, secondary vegetation took root in the spongy sphagnum mats adding greater biomass to the bog. In some cases the heavy saturated organic layers could actually rupture, spilling large volumes of mud and organic debris to surrounding fields, thus enabling a bed for further spatial expansion of the entire bog. Ultimately the colour of the moss waters became blood red, from the successive organic decay and stagnation. Only in times associated with cattle grazing and significant human presence (probably the late Iron Age), would this process reverse and the bog reduce in size. | 2 | Environmental Chemistry |
The Lucas test in alcohols is a test to differentiate between primary, secondary, and tertiary alcohols. It is based on the difference in reactivity of the three classes of alcohols with hydrogen halides via an S1 reaction:
: tert-BuOH + HCl → tert-BuCl + HO
The differing reactivity reflects the differing ease of formation of the corresponding carbocations. Tertiary carbocations are far more stable than secondary carbocations, and primary carbocations are the least stable(due to hyperconjugation).
An equimolar mixture of ZnCl and concentrated HCl is the reagent. The alcohol is protonated, the HO group formed leaves, forming a carbocation, and the nucleophile Cl (which is present in excess) readily attacks the carbocation, forming the chloroalkane. Tertiary alcohols react immediately with Lucas reagent as evidenced by turbidity owing to the low solubility of the organic chloride in the aqueous mixture. Secondary alcohols react within five or so minutes (depending on their solubility). Primary alcohols do not react appreciably with Lucas reagent at room temperature. Hence, the time taken for turbidity to appear is a measure of the reactivity of the class of alcohol, and this time difference is used to differentiate among the three classes of alcohols:
* no visible reaction at room temperature and forming an oily layer only on heating: primary, such as 1-pentanol
* solution forms oily layer in 3–5 minutes: secondary, such as 2-pentanol
* solution forms an oily layer immediately: tertiary, such as 2-methyl-2-butanol
The Lucas test is usually an alternative to the oxidation test - which is used to identify primary and secondary alcohols. | 3 | Analytical Chemistry |
Carly Stevens is a professor of plant ecology and soil biogeochemistry at University of Lancaster, UK. Her work focuses on how changes in the atmospheric nitrogen cycle affect plant communities, particularly grasslands. | 9 | Geochemistry |
FAIRE uses the biochemical properties of protein-bound DNA to separate nucleosome-depleted regions in the genome. Cells will be subjected to cross-linking, ensuring that the interaction between the nucleosomes and DNA are fixed. After sonication, the fragmented and fixed DNA is separated using a phenol-chloroform extraction. This method creates two phases, an organic and an aqueous phase. Due to their biochemical properties, the DNA fragments cross-linked to nucleosomes will preferentially sit in the organic phase. Nucleosome depleted or ‘open’ regions on the other hand will be found in the aqueous phase. By specifically extracting the aqueous phase, only nucleosome-depleted regions will be purified and enriched. | 1 | Biochemistry |
An antideuteron is the antimatter counterpart of the nucleus of deuterium, consisting of an antiproton and an antineutron. The antideuteron was first produced in 1965 at the Proton Synchrotron at CERN and the Alternating Gradient Synchrotron at Brookhaven National Laboratory. A complete atom, with a positron orbiting the nucleus, would be called antideuterium, but antideuterium has not yet been created. The proposed symbol for antideuterium is , that is, D with an overbar. | 9 | Geochemistry |
There have been very few commercial uses for blue billy, either as a by-product of production or as a means of disposal when unintended deposits are discovered.
It has been offered for sale as an ingredient in sulfuric acid production, although with little commercial acceptance.
In the past, blue billy has been sold as a weedkiller. | 2 | Environmental Chemistry |
The enzyme first catalyzes nucleophilic attack on the α-phosphate of ATP to form pyrophosphate and an acyl chain linked to AMP. The next step is formation of an activated thioester bond between the fatty acyl chain and Coenzyme A.
The balanced equation for the above is:
RCOO + CoASH + ATP → RCO-SCoA + AMP + PP <br />
This two-step reaction is freely reversible and its equilibrium lies near 1. To drive the reaction forward, the reaction is coupled to a strongly exergonic hydrolysis reaction: the enzyme inorganic pyrophosphatase cleaves the pyrophosphate liberated from ATP to two phosphate ions, consuming one water molecule in the process. Thus the net reaction becomes:
RCOO + CoASH + ATP → RCO-SCoA+ AMP + 2P | 1 | Biochemistry |
An overdose of ouabain can be detected by the presence of the following symptoms: rapid twitching of the neck and chest musculature, respiratory distress, increased and irregular heartbeat, rise in blood pressure, convulsions, wheezing, clicking, and gasping rattling. Death is caused by cardiac arrest. | 0 | Organic Chemistry |
Electron donating groups are typically divided into three levels of activating ability (The "extreme" category can be seen as "strong".) Electron withdrawing groups are assigned to similar groupings. Activating substituents favour electrophilic substitution about the ortho and para positions. Weakly deactivating groups direct electrophiles to attack the benzene molecule at the ortho- and para- positions, while strongly and moderately deactivating groups direct attacks to the meta- position. This is not a case of favoring the meta- position like para- and ortho- directing functional groups, but rather disfavouring the ortho- and para-positions more than they disfavour the meta- position. | 0 | Organic Chemistry |
Mass spectrometry measures mass-to-charge ratio of molecules using electric and magnetic fields. There are several ionization methods: electron ionization, chemical ionization, electrospray, fast atom bombardment, matrix-assisted laser desorption/ionization, and others. Also, mass spectrometry is categorized by approaches of mass analyzers: magnetic-sector, quadrupole mass analyzer, quadrupole ion trap, time-of-flight, Fourier transform ion cyclotron resonance, and so on. | 3 | Analytical Chemistry |
Prior to entering politics, Jones was a high pressure liquid chromatographer. She worked at the Washington University School of Medicine and KV Pharmaceutical before becoming a sales director with Mary Kay. In April 2015, Jones was the first African-American elected to the Ferguson City Council, where she represented the city's first ward. In February 2020, Jones was selected to serve on the United States Environmental Protection Agency Local Government Advisory Committee.
In the 2017 municipal election, Jones ran for mayor, receiving 42.77% of the vote. It was the city's first election after the shooting of Michael Brown and subsequent Ferguson unrest.
In the June 2, 2020 mayoral election, Jones defeated fellow council member Heather Robinett. Jones succeeded incumbent James Knowles III, a Republican who was unable to seek re-election due to term limits. On June 17, 2020, Jones was sworn in as the first black and female mayor of Ferguson.
She is also a pastor in the African Methodist Episcopal Church. | 3 | Analytical Chemistry |
While arsenic was most likely originally mixed with copper as a result of the ores already containing it, its use probably continued for a number of reasons. First, it acts as a deoxidizer, reacting with oxygen in the hot metal to form arsenous oxides which vaporize from the liquid metal. If a great deal of oxygen is dissolved in liquid copper, when the metal cools the copper oxide separates out at grain boundaries, and greatly reduces the ductility of the resulting object. However, its use can lead to a greater risk of porous castings, owing to the solution of hydrogen in the molten metal and its subsequent loss as a bubble (although any bubbles could be forge-welded and still leave the mass of the metal ready to be work-hardened).
Second, the alloy is capable of greater work-hardening than is the case with pure copper, so that it performs better when used for cutting or chopping. An increase in work-hardening capability arises with an increasing percentage of arsenic, and the bronze can be work-hardened over a wide range of temperatures without fear of embrittlement. Its improved properties over pure copper can be seen with as little as 0.5 to 2 wt% As, giving a 10-to-30% improvement in hardness and tensile strength.
Third, in the correct percentages, it can contribute a silvery sheen to the article being manufactured. There is evidence of arsenical bronze daggers from the Caucasus and other artifacts from different locations having an arsenic-rich surface layer which may well have been produced deliberately by ancient craftsmen, and Mexican bells were made of copper with sufficient arsenic to color them silver. | 8 | Metallurgy |
The process produces a quantity of fluoride waste: perfluorocarbons and hydrogen fluoride as gases, and sodium and aluminium fluorides and unused cryolite as particulates. This can be as small as 0.5 kg per tonne of aluminium in the best plants in 2007, up to 4 kg per tonne of aluminium in older designs in 1974. Unless carefully controlled, hydrogen fluorides tend to be very toxic to vegetation around the plants.
The Soderberg process which bakes the Anthracite/pitch mix as the anode is consumed, produces significant emissions of polycyclic aromatic hydrocarbons as the pitch is consumed in the smelter.
The linings of the pots end up contaminated with cyanide-forming materials; Alcoa has a process for converting spent linings into aluminium fluoride for reuse and synthetic sand usable for building purposes and inert waste. | 8 | Metallurgy |
Grignard reactions and reagents were discovered by and are named after the French chemist François Auguste Victor Grignard (University of Nancy, France), who described them in 1900. He was awarded the 1912 Nobel Prize in Chemistry for this work.
The reaction of an organic halide with magnesium is not a Grignard reaction, but provides a Grignard reagent.
Classically, the Grignard reaction refers to the reaction between a ketone or aldehyde group with a Grignard reagent to form a primary or tertiary alcohol. However, some chemists understand the definition to mean all reactions of any electrophiles with Grignard reagents. Therefore, there is some dispute about the modern definition of the Grignard reaction. In the Merck Index, published online by the Royal Society of Chemistry, the classical definition is acknowledged, followed by "A more modern interpretation extends the scope of the reaction to include the addition of Grignard reagents to a wide variety of electrophilic substrates." This variety of definitions illustrates that there is some dispute within the chemistry community about the definition of a Grignard reaction.
Shown below are some reactions involving Grignard reagents, but they themselves are not classically understood as Grignard reactions. | 0 | Organic Chemistry |
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