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A paper coauthored by Tomlin won the 1992 Sugden Award of The Combustion Institute. Tomlin was elected to the inaugural 2018 class of Fellows of The Combustion Institute, "for innovative research on the development and application of mechanism reduction, sensitivity analysis and uncertainty quantification in combustion models". | 7 | Physical Chemistry |
Alkyl or aryl acyl chlorides react with sodium azide in aqueous solution to give acyl azides, which give isocyanates in the Curtius rearrangement. | 0 | Organic Chemistry |
On March 28, 2013, a team of bioengineers from Stanford University led by Drew Endy announced that they had created the biological equivalent of a transistor, which they named a "transcriptor". That is, they created a three-terminal device with a logic system that can control other components. The transcriptor regulates the flow of RNA polymerase across a strand of DNA using special combinations of enzymes to control movement. According to project member Jerome Bonnet, "The choice of enzymes is important. We have been careful to select enzymes that function in bacteria, fungi, plants and animals, so that bio-computers can be engineered within a variety of organisms."
Transcriptors can replicate traditional AND, OR, NOR, NAND, XOR, and XNOR gates with equivalents, which Endy dubbed "Boolean Integrase Logic (BIL) gates", in a single-layer process (i.e., without requiring multiple instances of the simpler gates to build up more complex ones). Like a traditional transistor, a transcriptor can amplify an input signal. A group of transcriptors can do almost any type of computing, including counting and comparison. | 1 | Biochemistry |
Double-stranded RNA viruses (dsRNA viruses) are a polyphyletic group of viruses that have double-stranded genomes made of ribonucleic acid. The double-stranded genome is used as a template by the viral RNA-dependent RNA polymerase (RdRp) to transcribe a positive-strand RNA functioning as messenger RNA (mRNA) for the host cell's ribosomes, which translate it into viral proteins. The positive-strand RNA can also be replicated by the RdRp to create a new double-stranded viral genome.
A distinguishing feature of the dsRNA viruses is their ability to carry out transcription of the dsRNA segments within the capsid, and the required enzymes are part of the virion structure.
Double-stranded RNA viruses are classified into two phyla, Duplornaviricota and Pisuviricota (specifically class Duplopiviricetes), in the kingdom Orthornavirae and realm Riboviria. The two phyla do not share a common dsRNA virus ancestor, but evolved their double strands two separate times from positive-strand RNA viruses. In the Baltimore classification system, dsRNA viruses belong to Group III.
Virus group members vary widely in host range (animals, plants, fungi, and bacteria), genome segment number (one to twelve), and virion organization (T-number, capsid layers, or turrets). Double-stranded RNA viruses include the rotaviruses, known globally as a common cause of gastroenteritis in young children, and bluetongue virus, an economically significant pathogen of cattle and sheep. The family Reoviridae is the largest and most diverse dsRNA virus family in terms of host range. | 1 | Biochemistry |
The standard Isa Process cathodes have slightly higher electrical resistance than solid-copper hanger bar systems used by the Kidd Process, meaning that there is a higher power cost. However, this cost is offset by greater reliability and predictability in the increase in resistance over time, allowing for maintenance planning.
The solid-copper hanger bars, on the other hand, lose electrical performance over a shorter period of time due to corrosive attack on the joint and sudden failure is possible. The maintenance costs of such systems are greater and less predictable. A trial of approximately 3000 solid-copper hanger bars, found over time a lower current efficiency in the solid-copper hanger bars of about 2.4%.
The MIM development team looked for other ways to reduce the resistance of the cathode plates and developed a new low-resistance cathode, which it called ISA Cathode BR. This new design extended the copper plating from 15–17 mm down the blade to approximately 55 mm, and it increased the thickness of the copper to 3.0 mm from the 2.5 mm used on the standard cathode.
The new cathode plate design was tested in the CRL refinery in Townsville and at Compania Minera Zaldivar in Chile. The Chilean results indicated the new cathode design had the potential to reduce power costs by approximately US$100,000 in 2003 for the plant, compared to using conventional Isa Process cathode designs. | 8 | Metallurgy |
The ocean naturally sequesters carbon through different processes. The solubility pump moves carbon dioxide from the atmosphere into the surface ocean where it reacts with water molecules to form carbonic acid. The solubility of carbon dioxide increases with decreasing water temperatures. Thermohaline circulation moves dissolved carbon dioxide to cooler waters where it is more soluble, increasing carbon concentrations in the ocean interior. The biological pump moves dissolved carbon dioxide from the surface ocean to the ocean's interior through the conversion of inorganic carbon to organic carbon by photosynthesis. Organic matter that survives respiration and remineralization can be transported through sinking particles and organism migration to the deep ocean.
The low temperatures, high pressure, and reduced oxygen levels in the deep sea slow down decomposition processes, preventing the rapid release of carbon back into the atmosphere and acting as a long-term storage reservoir. | 5 | Photochemistry |
Trimethylsilyl azide is incompatible with moisture, strong oxidizing agents, and strong acids. Azides are often explosive, as illustrated by their use in air bags. | 0 | Organic Chemistry |
Thyroid function tests (TFTs) is a collective term for blood tests used to check the function of the thyroid.
TFTs may be requested if a patient is thought to suffer from hyperthyroidism (overactive thyroid) or hypothyroidism (underactive thyroid), or to monitor the effectiveness of either thyroid-suppression or hormone replacement therapy. It is also requested routinely in conditions linked to thyroid disease, such as atrial fibrillation and anxiety disorder.
A TFT panel typically includes thyroid hormones such as thyroid-stimulating hormone (TSH, thyrotropin) and thyroxine (T4), and triiodothyronine (T3) depending on local laboratory policy. | 1 | Biochemistry |
Hydrolysis of GTP bound to an (active) G domain-GTPase leads to deactivation of the signaling/timer function of the enzyme. The hydrolysis of the third (γ) phosphate of GTP to create guanosine diphosphate (GDP) and P, inorganic phosphate, occurs by the S2 mechanism (see nucleophilic substitution) via a pentacoordinate transition state and is dependent on the presence of a magnesium ion Mg.
GTPase activity serves as the shutoff mechanism for the signaling roles of GTPases by returning the active, GTP-bound protein to the inactive, GDP-bound state. Most "GTPases" have functional GTPase activity, allowing them to remain active (that is, bound to GTP) only for a short time before deactivating themselves by converting bound GTP to bound GDP. However, many GTPases also use accessory proteins named GTPase-activating proteins or GAPs to accelerate their GTPase activity. This further limits the active lifetime of signaling GTPases. Some GTPases have little to no intrinsic GTPase activity, and are entirely dependent on GAP proteins for deactivation (such as the ADP-ribosylation factor or ARF family of small GTP-binding proteins that are involved in vesicle-mediated transport within cells).
To become activated, GTPases must bind to GTP. Since mechanisms to convert bound GDP directly into GTP are unknown, the inactive GTPases are induced to release bound GDP by the action of distinct regulatory proteins called guanine nucleotide exchange factors or GEFs. The nucleotide-free GTPase protein quickly rebinds GTP, which is in far excess in healthy cells over GDP, allowing the GTPase to enter the active conformation state and promote its effects on the cell. For many GTPases, activation of GEFs is the primary control mechanism in the stimulation of the GTPase signaling functions, although GAPs also play an important role. For heterotrimeric G proteins and many small GTP-binding proteins, GEF activity is stimulated by cell surface receptors in response to signals outside the cell (for heterotrimeric G proteins, the G protein-coupled receptors are themselves GEFs, while for receptor-activated small GTPases their GEFs are distinct from cell surface receptors).
Some GTPases also bind to accessory proteins called guanine nucleotide dissociation inhibitors or GDIs that stabilize the inactive, GDP-bound state.
The amount of active GTPase can be changed in several ways:
# Acceleration of GDP dissociation by GEFs speeds up the accumulation of active GTPase.
# Inhibition of GDP dissociation by guanine nucleotide dissociation inhibitors (GDIs) slows down accumulation of active GTPase.
# Acceleration of GTP hydrolysis by GAPs reduces the amount of active GTPase.
# Artificial GTP analogues like GTP-γ-S, β,γ-methylene-GTP, and β,γ-imino-GTP that cannot be hydrolyzed can lock the GTPase in its active state.
# Mutations (such as those that reduce the intrinsic GTP hydrolysis rate) can lock the GTPase in the active state, and such mutations in the small GTPase Ras are particularly common in some forms of cancer. | 1 | Biochemistry |
Work hardening is a consequence of plastic deformation, a permanent change in shape. This is distinct from elastic deformation, which is reversible. Most materials do not exhibit only one or the other, but rather a combination of the two. The following discussion mostly applies to metals, especially steels, which are well studied. Work hardening occurs most notably for ductile materials such as metals. Ductility is the ability of a material to undergo plastic deformations before fracture (for example, bending a steel rod until it finally breaks).
The tensile test is widely used to study deformation mechanisms. This is because under compression, most materials will experience trivial (lattice mismatch) and non-trivial (buckling) events before plastic deformation or fracture occur. Hence the intermediate processes that occur to the material under uniaxial compression before the incidence of plastic deformation make the compressive test fraught with difficulties.
A material generally deforms elastically under the influence of small forces; the material returns quickly to its original shape when the deforming force is removed. This phenomenon is called elastic deformation. This behavior in materials is described by Hookes Law. Materials behave elastically until the deforming force increases beyond the elastic limit, which is also known as the yield stress. At that point, the material is permanently deformed and fails to return to its original shape when the force is removed. This phenomenon is called plastic deformation. For example, if one stretches a coil spring up to a certain point, it will return to its original shape, but once it is stretched beyond the elastic limit, it will remain deformed and wont return to its original state.
Elastic deformation stretches the bonds between atoms away from their equilibrium radius of separation, without applying enough energy to break the inter-atomic bonds. Plastic deformation, on the other hand, breaks inter-atomic bonds, and therefore involves the rearrangement of atoms in a solid material. | 8 | Metallurgy |
In chemistry, racemization is a conversion, by heat or by chemical reaction, of an optically active compound into a racemic (optically inactive) form. This creates a 1:1 molar ratio of enantiomers and is referred to as a racemic mixture (i.e. contain equal amount of (+) and (−) forms). Plus and minus forms are called Dextrorotation and levorotation. The D and L enantiomers are present in equal quantities, the resulting sample is described as a racemic mixture or a racemate. Racemization can proceed through a number of different mechanisms, and it has particular significance in pharmacology as different enantiomers may have different pharmaceutical effects. | 4 | Stereochemistry |
Even though many studies conduct testing under experimental or enriched conditions, oxidation-reduction reactions occur naturally and allow for chemicals to go through processes such as biodegradation, outlined above. Oxidation is defined as the loss of an electron to another species, while reduction is the gaining of an electron from another species. As compounds go through oxidation and reduction in sediments, the preservative compounds are altered to form new chemicals, leading to decomposition. An example of the oxidation of p-cresol and phenol can be seen in the figures below: | 7 | Physical Chemistry |
The Mars 2020 rover, which launched in 2020, is intended to investigate an astrobiologically relevant ancient environment on Mars, investigate its surface geological processes and history, including the assessment of its past habitability, the possibility of past life on Mars, and potential for preservation of biosignatures within accessible geological materials. In addition, it will cache the most interesting samples for possible future transport to Earth. | 2 | Environmental Chemistry |
Complexes with η-allyl ligands (classified as X-type ligands) are also known. One example is CpFe(CO)(η-CH), in which only the methylene group is attached to the Fe centre (i.e., it has the connectivity [Fe]–CH–CH=CH). As is the case for many other η-allyl complexes, the monohapticity of the allyl ligand in this species is enforced by the 18-electron rule, since CpFe(CO)(η-CH) is already an 18-electron complex, while an η-allyl ligand would result in an electron count of 20 and violate the 18-electron rule. Such complexes can convert to the η-allyl derivatives by dissociation of a neutral (two-electron) ligand L. For CpFe(CO)(η-CH), dissociation of L = CO occurs under photochemical conditions:
: CpFe(CO)(η-CH) → CpFe(CO)(η-CH) + CO | 0 | Organic Chemistry |
Recently the phylogenetic relationship of the group Thermotogota was characterized based on the CSI approach. Previously no biochemical or molecular markers were known that could clearly distinguish the species of this phylum from all other bacteria. More than 60 CSIs that were specific for the entire Thermotogota phylum or its different subgroups were discovered. 18 CSIs are uniquely present in various Thermotogota species and provide molecular markers for the phylum. Additionally there were many CSIs that were specific for various Thermotogota subgroups. 12 CSIs were specific for a clade consisting of various Thermotogota species except Tt. Lettingae. 14CSIs were specific for a clade consisting of the Fervidobacterium and Thermosipho genera and 18 CSIs were specific for the genus Thermosiphon.
Lastly 16 CSIs were reported that were shared by either some or all Thermotogota species or some species from other taxa such as Archaea, Aquificota, Bacillota, Pseudomonadota, Deinococcota, Fusobacteriota, Dictyoglomota, Chloroflexota, and eukaryotes. The shared presence of some of these CSIs could be due to lateral gene transfer (LGT) between these groups. However the number of CSIs that are commonly shared with other taxa is much smaller than those that are specific for Thermotogota and they do not exhibit any specific pattern. Hence they have no significant effect on the distinction of Thermotogota. | 1 | Biochemistry |
Zinc serves a purely structural role in zinc fingers, twists and clusters. Zinc fingers form parts of some transcription factors, which are proteins that recognize DNA base sequences during the replication and transcription of DNA. Each of the nine or ten ions in a zinc finger helps maintain the finger's structure by coordinately binding to four amino acids in the transcription factor.
In blood plasma, zinc is bound to and transported by albumin (60%, low-affinity) and transferrin (10%). Because transferrin also transports iron, excessive iron reduces zinc absorption, and vice versa. A similar antagonism exists with copper. The concentration of zinc in blood plasma stays relatively constant regardless of zinc intake. Cells in the salivary gland, prostate, immune system, and intestine use zinc signaling to communicate with other cells.
Zinc may be held in metallothionein reserves within microorganisms or in the intestines or liver of animals. Metallothionein in intestinal cells is capable of adjusting absorption of zinc by 15–40%. However, inadequate or excessive zinc intake can be harmful; excess zinc particularly impairs copper absorption because metallothionein absorbs both metals.
The human dopamine transporter contains a high affinity extracellular zinc binding site which, upon zinc binding, inhibits dopamine reuptake and amplifies amphetamine-induced dopamine efflux in vitro. The human serotonin transporter and norepinephrine transporter do not contain zinc binding sites. Some EF-hand calcium binding proteins such as S100 or NCS-1 are also able to bind zinc ions. | 1 | Biochemistry |
Eslicarbazepine acetate is absorbed to at least 90% from the gut, independently of food intake. It is quickly metabolised to eslicarbazepine, so that the original substance cannot be detected in the bloodstream. Peak plasma levels of eslicarbazepine are reached after 2–3 (1–4) hours, and plasma protein binding is somewhat less than 40%. Biological half-life is 10 to 20 hours, and steady-state concentrations are reached after four to five days after start of the treatment. Oxcarbazepine, for comparison, is also nearly completely absorbed from the gut, and peak plasma concentrations of licarbazepine are reached after 4.5 hours on average after oxcarbazepine intake. Plasma protein binding and half-life are of course the same.
Other metabolites of ESL are the less active (R)-(−)-licarbazepine (5%; the stereoisomer of eslicarbazepine), the pharmacologically active oxcarbazepine (1%), and inactive glucuronides of all of these substances. The drug is excreted mainly via the urine, of which two thirds are in the form of eslicarbazepine and one third in the form of eslicarbazepine glucuronide. The other metabolites only account for a few percent of the excreted drug. | 4 | Stereochemistry |
In psychiatry research, the accepted criteria which a biomarker must fulfill to be called an endophenotype include:
# An endophenotype must segregate with illness in the population.
# An endophenotype must be heritable.
# An endophenotype must not be state-dependent (i.e., manifests whether illness is active or in remission).
# An endophenotype must co-segregate with illness within families.
# An endophenotype must be present at a higher rate within affected families than in the population.
# An endophenotype must be amenable to reliable measurement, and be specific to the illness of interest. | 2 | Environmental Chemistry |
The commercial production of amino acids usually relies on mutant bacteria that overproduce individual amino acids using glucose as a carbon source. Some amino acids are produced by enzymatic conversions of synthetic intermediates. 2-Aminothiazoline-4-carboxylic acid is an intermediate in the industrial synthesis of L-cysteine for example. Aspartic acid is produced by the addition of ammonia to fumarate using a lyase. | 1 | Biochemistry |
BSA is prepared by treating acetamide with trimethylsilyl chloride in the presence of a base (Me = CH, Et = CH):
The reaction of BSA with alcohols gives the corresponding trimethylsilyl ether, together with acetamide as a byproduct (Me = CH): | 0 | Organic Chemistry |
Chloroplasts are considered endosymbiotic Cyanobacteria. Cyanobacteria are sometimes called blue-green algae even though they are prokaryotes. They are a diverse phylum of gram-negative bacteria capable of carrying out photosynthesis. Cyanobacteria also contain a peptidoglycan cell wall, which is thicker than in other gram-negative bacteria, and which is located between their two cell membranes. Like chloroplasts, they have thylakoids within them. On the thylakoid membranes are photosynthetic pigments, including chlorophyll a. Phycobilins are also common cyanobacterial pigments, usually organized into hemispherical phycobilisomes attached to the outside of the thylakoid membranes (phycobilins are not shared with all chloroplasts though). | 5 | Photochemistry |
In the addition of a nucleophile (Nu) attack to a carbonyl, the BD angle is defined as the Nu-C-O bond angle. The BD angle adopted during an approach by a nucleophile to a trigonal unsaturated electrophile depends primarily on the molecular orbital (MO) shapes and occupancies of the unsaturated carbon center (e.g., carbonyl center), and only secondarily on the molecular orbitals of the nucleophile.
Of the two angles which define the geometry of nucleophilic "attack", the second describes the "offset" of the nucleophile's approach toward one of the two substituents attached to the carbonyl carbon or other electrophilic center, and was named the Flippin–Lodge angle (FL angle) by Clayton Heathcock after his contributing collaborators Lee A. Flippin and Eric P. Lodge.
These angles are generally construed to mean the angle measured or calculated for a given system, and not the historically observed value range for the original Bürgi–Dunitz aminoketones, or an idealized value computed for a particular system (such as hydride addition to formaldehyde, image at left). That is, the BD and FL angles of the hydride-formadehyde system produce a given pair of values, while the angles observed for other systems may vary relative to this simplest of chemical systems. | 7 | Physical Chemistry |
Plant biochemistry encompasses the chemical reactions that occur within plants. In principle, knowledge at a molecular level informs technologies for providing food. Particular focus is on the biochemical differences between plants and other organisms as well as the differences within the plant kingdom, such as dicotyledons vs monocotyledons, gymnosperms vs angiosperms, C2- vs C4-fixers, etc. | 1 | Biochemistry |
An example of how glycolipids function within the body is the interaction between leukocytes and endothelial cells during inflammation. Selectins, a class of lectins found on the surface of leukocytes and endothelial cells bind to the carbohydrates attached to glycolipids to initiate the immune response. This binding causes leukocytes to leave circulation and congregate near the site of inflammation. This is the initial binding mechanism, which is followed by the expression of integrins which form stronger bonds and allow leukocytes to migrate toward the site of inflammation. Glycolipids are also responsible for other responses, notably the recognition of host cells by viruses. | 0 | Organic Chemistry |
Ethanol is obtained by fermentation of glucose (which is often obtained from starch) in the presence of yeast. Carbon dioxide is cogenerated. Like ethanol, butanol can be produced by fermentation processes. Saccharomyces yeast are known to produce these higher alcohols at temperatures above . The bacterium Clostridium acetobutylicum can feed on cellulose (also an alcohol) to produce butanol on an industrial scale. | 0 | Organic Chemistry |
Shikimic acid, more commonly known as its anionic form shikimate, is a cyclohexene, a cyclitol and a cyclohexanecarboxylic acid. It is an important biochemical metabolite in plants and microorganisms. Its name comes from the Japanese flower shikimi (, the Japanese star anise, Illicium anisatum), from which it was first isolated in 1885 by Johan Fredrik Eykman. The elucidation of its structure was made nearly 50 years later. | 1 | Biochemistry |
Chemokine (C-C motif) ligand 7 (CCL7) is a small cytokine that was previously called monocyte-chemotactic protein 3 (MCP3). CCL7 is a small protein that belongs to the CC chemokine family and is most closely related to CCL2 (previously called MCP1). | 1 | Biochemistry |
Generally, synthetic schemes that begin with ketones () involve conversion of the ketone with the desired substituents to diaziridines (). These diaziridenes are then subsequently oxidized to form the desired diazirines.
Diaziridines can be prepared from ketones by oximation, followed by tosylation (or mesylation), and then finally by treatment with ammonia (). Generally, oximation reactions are performed by reacting the ketone with hydroxylammonium chloride () under heat in the presence of a base such as pyridine. Subsequent tosylation or mesylation of the alpha-substituted oxygen with tosyl or mesyl chloride in the presence of base yields the tosyl or mesyl oxime. The final treatment of the tosyl or mesyl oxime with ammonia produces the diaziridine.
Diaziridines can be also produced directly by the reaction of ketones with ammonia in the presence of an aminating agent such as a monochloramine or hydroxyl amine O-sulfonic acid.
Diaziridines can be oxidized to diazirines by a number of methods. These include oxidation by chromium-based reagents such as the Jones oxidation, oxidation by iodine and triethylamine, oxidation by silver oxide, oxidation by oxalyl chloride, or even electrochemical oxidation on a platinum-titanium anode. | 5 | Photochemistry |
There are two major applications to studying the genome at the single cell level. One application is to track the changes that occur in bacterial populations, where phenotypic differences are often seen. These differences are missed by bulk sequencing of a population, but can be observed in single cell sequencing. The second major application is to study the genetic evolution of cancer. Since cancer cells are constantly mutating it is of great interest to see how cancers evolve at the genetic level. These patterns of somatic mutations and copy number aberration can be observed using single cell sequencing. | 1 | Biochemistry |
Trinitroethylorthoformate also known as TNEOF is an explosive with excellent chemical stability. It does not have hygroscopicity, does not dissolve in water, and does not react with acids. It decomposes in aqueous sodium hydroxide solution to release formaldehyde odor. The explosion point of TNEOF is 229 °C, though it begins to decompose at 190 °C. Its explosion heat is 6.3076 J/g and specific volume is 682 L/kg. Its structure is closely related to that of trinitroethylorthocarbonate (TNEOC). Both are highly explosive and very shock-sensitive, and may be dissolved in nitroalkanes to reduce their shock-sensitivity. | 0 | Organic Chemistry |
Multiple labs identified the PRR genes as parts of the circadian clock in the 1990s. In 2000, Akinori Matsushika, Seiya Makino, Masaya Kojima, and Takeshi Mizuno were the first to understand PRR genes as pseudo-response repressor genes rather than as response regulator (ARR) genes. The factor that distinguishes PRR from ARR genes is the lack of a phospho-accepting aspartate site that characterizes ARR proteins. Though their research that discovered PRR genes was primarily hailed during the early 2000s as informing the scientific community about the function of TOC1 (named APRR1 by the Mizuno lab), an additional pseudo-response regulator in the Arabidopsis thaliana biological clock, the information about PRR genes that Matsushika and his team found deepened scientific understanding of circadian clocks in plants and led other researchers to hypothesize about the purpose of the PRR genes. Though current research has identified TOC1, PRR3, PRR5, PRR7, and PRR9 as of importance to the A. thaliana circadian clock mechanism, Matsushika et al. first categorized PRR genes into two subgroups (APRR1 and APRR2, the A stands for Arabidopsis) due to two differing amino acid structures. The negative feedback loops including PRR genes, proposed by Mizuno, were incorporated into a complex repressilator circuit by Andrew Millar’s lab in 2012. The conception of the plant biological clock as made up of interacting negative feedback loops is unique in comparison to mammal and fungal circadian clocks which contain autoregulatory negative feedback loops with positive and negative elements (see "Transcriptional and non-transcriptional control on the Circadian clock page). | 1 | Biochemistry |
For steelmaking, direct current (DC) arc furnaces are used, with a single electrode in the roof and the current return through a conductive bottom lining or conductive pins in the base. The advantage of DC is lower electrode consumption per ton of steel produced, since only one electrode is used, as well as less electrical harmonics and other similar problems. The size of DC arc furnaces is limited by the current carrying capacity of available electrodes, and the maximum allowable voltage. Maintenance of the conductive furnace hearth is a bottleneck in extended operation of a DC arc furnace.
In a steel plant, a ladle furnace (LF) is used to maintain the temperature of liquid steel during processing after tapping from EAF or to change the alloy composition. The ladle is used for the first purpose when there is a delay later in the steelmaking process. The ladle furnace consists of a refractory roof, a heating system, and, when applicable, a provision for injecting argon gas into the bottom of the melt for stirring. Unlike a scrap melting furnace, a ladle furnace does not have a tilting or scrap-charging mechanism.
Electric arc furnaces are also used for production of calcium carbide, ferroalloys, and other non-ferrous alloys, and for production of phosphorus. Furnaces for these services are physically different from steel-making furnaces and may operate on a continuous, rather than batch, basis. Continuous-process furnaces may also use paste-type, Søderberg electrodes to prevent interruptions from electrode changes.
Such a furnace is known as a submerged arc furnace, because the electrode tips are buried in the slag/charge, and arcing occurs through the slag, between the matte and the electrode. The casing and casing fins of the electrode melt the electrode paste through electrical current passing through the electrode casing and heat from the furnace. A steelmaking arc furnace, by comparison, arcs in the open. The key is the electrical resistance, which is what generates the heat required: the resistance in a steelmaking furnace is the atmosphere, while in a submerged-arc furnace, the slag (or charge) supplies the resistance. The liquid metal formed in either furnace is too conductive to form an effective heat-generating resistance.
Amateurs have constructed a variety of arc furnaces, often based on electric arc welding kits contained by silica blocks or flower pots. Though crude, these simple furnaces can melt a wide range of materials, create calcium carbide, and more. | 8 | Metallurgy |
Total RNA is purified from the specimen of interest. Poly A messenger RNA is then purified from total RNA and subsequently translated into cDNA using a reverse transcription reaction. The cDNA produced from the mRNA is labeled using primers homologous to the spliced leader sequences of the organism. In a nine step PCR reaction the cDNAs are concurrently embedded with the BpmI restriction endonuclease site (though any class IIs restriction endonuclease may work) and a biotin label which are present in the primers. These tagged cDNAs are then cleaved 14 bp downstream from the recognition site using BpmI restriction endonuclease and blunt ended with T4 DNA polymerase. The fragments are further purified away from extraneous DNA material by using the biotin labels to bind them to a strepdavidin matrix. They are then ligated to adapter DNA, in six separate reactions, containing six different restriction endonuclease recognition sites. These tags are then amplified by PCR with primers containing a mismatch changing the Bpm1 site to a Xho1 site. The amplicons are concatenated and ligated into a plasmid vector. The clonal vectors are then sequenced and mapped to the genome. | 1 | Biochemistry |
While slight variations on the standard genetic code had been predicted earlier, none was discovered until 1979, when researchers studying human mitochondrial genes determined that they used an alternative code. Nonetheless, the mitochondria of many other eukaryotes, including most plants, use the standard code. Many slight variants have been discovered since, including various alternative mitochondrial codes. Further, the AUA, AUC, and AUU codons are all allowable start codons.
Some of these differences should be regarded as pseudo-changes in the genetic code due to the phenomenon of RNA editing, which is common in mitochondria. In higher plants, it was thought that CGG encoded for tryptophan and not arginine; however, the codon in the processed RNA was discovered to be the UGG codon, consistent with the standard genetic code for tryptophan. Of note, the arthropod mitochondrial genetic code has undergone parallel evolution within a phylum, with some organisms uniquely translating AGG to lysine. | 1 | Biochemistry |
There are two methods for the production of spiropyrans. The first one can be by condensation of methylene bases with o-hydroxy aromatic aldehydes (or the condensation of the precursor of methylene bases). Spiropyrans generally could be obtained by boiling the aldehyde and the respective benzazolium salts in presence of pyridine or piperidine. The general formula of the synthesis of spiropyrans is shown in the Figure 1.
The second way is by condensation of o-hydroxy aromatic aldehydes with the salts of heterocyclic cations which contains active methylene groups and isolation of the intermediate styryl salts. This second procedure is followed by the removal of the elements of the acid from the obtained styryl salt, such as perchloric acid, with organic bases (gaseous ammonia or amines). | 5 | Photochemistry |
Since all the A functional groups are from the trifunctional monomer, ρ = 1 and
Therefore, gelation occurs when
or when,
Similarly, gelation occurs when | 7 | Physical Chemistry |
In chemistry, the square planar molecular geometry describes the stereochemistry (spatial arrangement of atoms) that is adopted by certain chemical compounds. As the name suggests, molecules of this geometry have their atoms positioned at the corners. | 4 | Stereochemistry |
Solvated electrons are involved in the reaction of alkali metals with water, even though the solvated electron has only a fleeting existence. Below pH = 9.6 the hydrated electron reacts with the hydronium ion giving atomic hydrogen, which in turn can react with the hydrated electron giving hydroxide ion and usual molecular hydrogen H.
Solvated electrons can be found even in the gas phase. This implies their possible existence in the upper atmosphere of Earth and involvement in nucleation and aerosol formation.
Its standard electrode potential value is -2.77 V. The equivalent conductivity of 177 Mho cm is similar to that of hydroxide ion. This value of equivalent conductivity corresponds to a diffusivity of 4.75 cms. | 0 | Organic Chemistry |
A naturally occurring predator to coral reefs in the Great Barrier Reef is the Crown of Thorns sea star (Acanthaster planci). Population outbreaks of the Crown of Thorns sea star are one of the major causes of coral decline across the Great Barrier Reef, as an adult crown-of-thorns starfish is capable of consuming up to 10 m2 of reef building coral a year. However, each species of coral is not equally impacted, as the sea star has been observed to favor branching species of coral, Acropora, followed by a sub branching species. This results in a sequential and ordered eradication of coral reef species.
Crown of Thorns Sea Star outbreaks on the Great Barrier Reef have become more frequent in recent years, which scientists predict could be linked to human activities. Any increase in nutrients, possibly from river run-off, can positively affect starfish populations, leading to detrimental outbreaks. As pressures from climate change increase, the time between reef disturbances is becoming shorter, leaving less time for reef recovery. | 9 | Geochemistry |
Pronounced intensity minima were first observed in 1930 by Theodor Estermann, Otto Frisch, and Otto Stern, during a series of gas-surface interaction experiments attempting to demonstrate the wave nature of atoms and molecules. The phenomenon has been explained in 1936 by John Lennard-Jones and Devonshire in terms of resonant transitions to bound surface states. | 7 | Physical Chemistry |
The slip-line theory was co-developed by Hilda Geiringer in the early 1930s. She developed the Geiringer equations, which simplify the process of calculating the deformation. | 8 | Metallurgy |
If with , , as integers represents the reciprocal lattice for a crystal lattice (defined by ) in real space, we know that with an integer due to the known orthogonality between primitive vectors for the reciprocal lattice and those for the crystal lattice. (We use the physical, not crystallographers, definition for reciprocal lattice vectors which gives the factor of .) But notice that this is nothing but the Laue equations. Hence we identify , means that allowed scattering vectors are those equal to reciprocal lattice vectors for a crystal in diffraction, and this is the meaning of the Laue equations. This fact is sometimes called the Laue condition. In this sense, diffraction patterns are a way to experimentally measure the reciprocal lattice for a crystal lattice.'
The Laue condition can be rewritten as the following.
Applying the elastic scattering condition (In other words, the incoming and diffracted waves are at the same (temporal) frequency. We can also say that the energy per photon does not change.)
To the above equation, we obtain
The second equation is obtained from the first equation by using .
The result (also ) is an equation for a plane (as the set of all points indicated by satisfying this equation) as its equivalent equation is a plane equation in geometry. Another equivalent equation, that may be easier to understand, is (also ). This indicates the plane that is perpendicular to the straight line between the reciprocal lattice origin and and located at the middle of the line. Such a plane is called Bragg plane. This plane can be understood since for scattering to occur. (It is the Laue condition, equivalent to the Laue equations.) And, the elastic scattering has been assumed so , , and form a rhombus. Each is by definition the wavevector of a plane wave in the Fourier series of a spatial function which periodicity follows the crystal lattice (e.g., the function representing the electronic density of the crystal), wavefronts of each plane wave in the Fourier series is perpendicular to the plane waves wavevector , and these wavefronts are coincident with parallel crystal lattice planes. This means that X-rays are seemingly "reflected" off parallel crystal lattice planes perpendicular at the same angle as their angle of approach to the crystal with respect to the lattice planes; in the elastic light (typically X-ray)-crystal scattering, parallel crystal lattice planes perpendicular to a reciprocal lattice vector for the crystal lattice play as parallel mirrors for light which, together with , incoming (to the crystal) and outgoing (from the crystal by scattering) wavevectors forms a rhombus.'
Since the angle between and is , (Due to the mirror-like scattering, the angle between and is also .) . Recall, with as the light (typically X-ray) wavelength, and with as the distance between adjacent parallel crystal lattice planes and as an integer. With these, we now derive Bragg's law that is equivalent to the Laue equations (also called the Laue condition): | 3 | Analytical Chemistry |
Nod factors structurally are lipochitooligosaccharides (LCOs) that consist of an N-acetyl--glucosamine chain linked through β-1,4 linkage with a fatty acid of variable identity attached to a non reducing nitrogen in the backbone with various functional group substitutions at the terminal or non-terminal residues.
Nod factors are produced in complex mixtures differing in the following characteristics:
* Length of the chain can vary from three to six units of N-acetyl--glucosamine with the exception of M. loti which can produce Nod factors with two unit only.
* Presence or absence of strain-specific substitutions along the chain
* Identity of the fatty acid component
* Presence or absence of unsaturated fatty acids
Nod gene expression is induced by the presence of certain flavonoids in the soil, which are secreted by the plant and act as an attractant to bacteria and induce Nod factor production. Flavonoids activate NodD, a LysR family transcription factor, which binds to the nod box and initiates the transcription of the nod genes which encode the proteins necessary for the production of a wide range of LCOs. | 1 | Biochemistry |
Compared to the number of drug candidates that have successfully made it to the clinical trial phase, there are many more lead compounds which have been tested in vivo using various animal models. Much of the current work that has progressed to in vivo testing has been directed to the RNA repeat expansions implicated in genetic neuromuscular diseases. In myotonic dystrophy type 1 (DM1), r(CUG)exp mRNAs sequester proteins including the alternative splicing regulator MBNL1 into the nucleus causing missplicing. Several groups have developed compounds which bind the toxic RNA and dissolve nuclear foci. In 2011, Artero and coworkers discovered that a peptide could reduce the toxicity associated with r(CUG) repeats in Drosophila and mouse models. [https://scholar.google.com/citations?user=sYLAwlMAAAAJ&hl=en Disney] and colleagues provided the first small molecules that targeted r(CUG) repeats in animals models by using rational designing to identify many small molecules directly targeting this toxic RNA and the compounds improved disease defects in a DM1 mouse model.
Other works by the Disney group has shown that in cellular models of various RNA-mediated diseases that are causes by RNA repeats such as r(CAG) in Huntingtons disease and r(CCUG) repeats in Myotonic Dystrophy Types 2 could also be targeted with small molecules. Nakamori and colleagues also reported in 2012 that erythromycin could be orally dosed in DM1 mouse models to restore missplicing defects and inhibit the complex formed between r(CUG) and MBNL1. In that same year, Miller and coworkers screened a library of compounds to find a small molecule drug that could improve splicing defects in a mouse model. The Zimmerman group has taken a rational design approach to discovering small molecule drugs that target r(CUG). One such compound contains a selective triaminotriazine recognition motif which binds to the UU mismatches in r(CUG) selectively most likely in a base triplet combined with an amidinium RNA groove binding unit. Studies using a Drosophila' model for DM1 showed an influence on related phenotypic outcomes such as eye morphology and climbing distance.
Aside from studies involved r(CUG) repeats, other complex RNA structures have also been targeted. Pearson and coworkers discovered that a cationic porphyrin (TMPyP4) bound a G-quadruplex r(GC) and inhibited the binding of proteins to r(GC). Work by Disney and Petrucelli rationally identified small molecules that can target this repeat and affect disease biology in model cellular systems and also in patient-derive iNeurons. Further studies by Rothstein and colleagues determined that TMPyP4 could suppress r(GC)-mediated neurodegeneration in a Drosophila model. Additionally targets have been rationally identified by using a powerful seqecune-based design approach termed informal to identify dozens of bioactive small molecules that target disease causing non-coding RNA termed INFORNA. This study important showed for the first time that small molecules appear to have selectivities that are competitive with oligonucleotides with cell-permeable and medicinally optimizable small molecules. Additionally, compounds have been shown to be bioactive in diverse disease settings that ranged from breast cancer. and hepatocellular carcinoma. More recently, the Disney group further used their prediction database INFORNA to design Targaprimir-96 to target miRNA precursors in animal models of cancer, the first small molecules to do so. This compound has a nanomolar affinity for the miRNA hairpin precursor selectively over other sequences. Targaprimir-96 was further tested in cells and in mice, inhibiting tumor growth in a xenograft mouse model of triple negative breast cancer upon i.p. injection. | 1 | Biochemistry |
The laws of gravity seem to be time reversal invariant in classical mechanics; however, specific solutions need not be.
An object can cross through the event horizon of a black hole from the outside, and then fall rapidly to the central region where our understanding of physics breaks down. Since within a black hole the forward light-cone is directed towards the center and the backward light-cone is directed outward, it is not even possible to define time-reversal in the usual manner. The only way anything can escape from a black hole is as Hawking radiation.
The time reversal of a black hole would be a hypothetical object known as a white hole. From the outside they appear similar. While a black hole has a beginning and is inescapable, a white hole has an ending and cannot be entered. The forward light-cones of a white hole are directed outward; and its backward light-cones are directed towards the center.
The event horizon of a black hole may be thought of as a surface moving outward at the local speed of light and is just on the edge between escaping and falling back. The event horizon of a white hole is a surface moving inward at the local speed of light and is just on the edge between being swept outward and succeeding in reaching the center. They are two different kinds of horizons—the horizon of a white hole is like the horizon of a black hole turned inside-out.
The modern view of black hole irreversibility is to relate it to the second law of thermodynamics, since black holes are viewed as thermodynamic objects. For example, according to the gauge–gravity duality conjecture, all microscopic processes in a black hole are reversible, and only the collective behavior is irreversible, as in any other macroscopic, thermal system. | 7 | Physical Chemistry |
Wet storage stain is a white, crumbly, and porous substance that is a mixture of three chemical compounds: 2ZnCO·3Zn(OH), ZnO, and β-Zn(OH). Underneath the white coating is usually a dark gray surface. The corrosion product is very voluminous; it is approximately 100 times greater in volume than the zinc consumed. Because of this the corrosion is not usually detrimental to the usability of the item, unless the zinc surface is only a thin coating, such as zinc electroplating.
Wet storage stain only occurs in situations where there is a lack of oxygen or carbon dioxide, because it usually forms zinc oxide and zinc hydroxide in open air environments. These oxides are usually present on zinc surfaces, but do not protect them from wet storage stain because they are only loosely adherent to the surface and any moisture can attack the oxides from underneath. Also, chlorides and sulfates accelerate the formation of corrosion. | 8 | Metallurgy |
As early as the 1920s, the concept of using hot water and alkali catalysts to produce oil out of biomass was proposed. In 1939, U.S. patent 2,177,557, described a two-stage process in which a mixture of water, wood chips, and calcium hydroxide is heated in the first stage at temperatures in a range of , with the pressure "higher than that of saturated steam at the temperature used." This produces "oils and alcohols" which are collected. The materials are then subjected in a second stage to what is called "dry distillation", which produces "oils and ketones". Temperatures and pressures for this second stage are not disclosed.
These processes were the foundation of later HTL technologies that attracted research interest especially during the 1970s oil embargo. It was around that time that a high-pressure (hydrothermal) liquefaction process was developed at the Pittsburgh Energy Research Center (PERC) and later demonstrated (at the 100 kg/h scale) at the Albany Biomass Liquefaction Experimental Facility at Albany, Oregon, US. In 1982, Shell Oil developed the HTU™ process in the Netherlands. Other organizations that have previously demonstrated HTL of biomass include Hochschule für Angewandte Wissenschaften Hamburg, Germany, SCF Technologies in Copenhagen, Denmark, EPA’s Water Engineering Research Laboratory, Cincinnati, Ohio, USA, and Changing World Technology Inc. (CWT), Philadelphia, Pennsylvania, USA. Today, technology companies such as [http://www.licella.com.au Licella/Ignite Energy Resources] (Australia), [https://arbiosbiotech.com Arbios Biotech], a Licella/Canfor joint venture, [http://altacaenergy.com Altaca Energy] (Turkey), [https://circlianordic.com/ Circlia Nordic] (Denmark), [http://steeperenergy.com/ Steeper Energy] (Denmark, Canada) continue to explore the commercialization of HTL. Construction has begun in Teesside, UK, for a catalytic hydrothermal liquefaction plant that aims to process 80,000 tonnes per year of mixed plastic waste by 2022. | 0 | Organic Chemistry |
Most importantly, with the sequential order rules, also referred to as Nodas rules', the sequence of the intensity changes can be determined. By carefully interpreting the signs of the 2D synchronous and asynchronous cross peaks with the following rules, the sequence of spectral events during the experiment can be determined:
#if the intensities of the bands at x and y in the dataset are changing in the same direction, the synchronous 2D cross peak at (x,y) is positive
#if the intensities of the bands at x and y in the dataset are changing in the opposite direction, the synchronous 2D cross peak at (x,y) is negative
#if the change at x mainly precedes the change in the band at y, the asynchronous 2D cross peak at (x,y) is positive
#if the change at x mainly follows the change in the band at y, the asynchronous 2D cross peak at (x,y) is negative
#if the synchronous 2D cross peak at (x,y) is negative, the interpretation of rule 3 and 4 for the asynchronous 2D peak at (x,y) has to be reversed
:where x and y are the positions on the x-xaxis of two bands in the original data that are subject to intensity changes.
Following the rules above. It can be derived that the changes at 10 and 30 occur simultaneously and the changes in intensity at 20 and 40 occur simultaneously as well. Because of the positive asynchronous cross-peak at (10, 20), the changes at 10 and 30 (predominantly) occur before the intensity changes at 20 and 40.
In some cases the Noda rules cannot be so readily implied, predominately when spectral features are not caused by simple intensity variations. This may occur when band shifts occur, or when a very erratic intensity variation is present in a given frequency range. | 7 | Physical Chemistry |
Plastic deformation happens when stresses flatten, bend, or twist a material until it cannot return to its original shape. This can create cracks in the material and decrease its lifetime. | 8 | Metallurgy |
A mesocrystal is a material structure composed of numerous small crystals of similar size and shape, which are arranged in a regular
periodic pattern. It is a form of oriented aggregation, where the small crystals have parallel crystallographic alignment but are spatially separated.
When the sizes of individual components are at the nanoscale, mesocrystals represent a new class of nanostructured solids made from crystiallographically oriented nanoparticles. The sole criterion for determining whether a material is mesocrystal is the unique crystallographically hierarchical structure, not its formation mechanism. | 7 | Physical Chemistry |
Tip-enhanced Raman spectroscopy requires a confocal microscope, and a scanning probe microscope. The optical microscope is used to align the laser focal point with the tip coated with a SERS active metal. The three typical experimental configurations are bottom illumination, side illumination, and top illumination, depending on which direction the incident laser propagates towards the sample, with respect to the substrate. In the case of STM-TERS, only side and top illumination configurations can be applied, since the substrate is required to be conductive, therefore typically being non-transparent. In this case, the incident laser is usually linearly polarized and aligned parallel to the tip, in order to generate confined surface plasmon at the tip apex. The sample is moved rather than the tip so that the laser remains focused on the tip. The sample can be moved systematically to build up a series of tip enhanced Raman spectra from which a Raman map of the surface can be built allowing for surface heterogeneity to be assessed with up to 1.7 nm resolution. Subnanometer resolution has been demonstrated in certain cases allowing for submolecular features to be resolved.
In 2019, Yan group and Liu group at University of California, Riverside developed a lens-free nanofocusing technique, which concentrates the incident light from a tapered optical fiber to the tip apex of a metallic nanowire and collects the Raman signal through the same optical fiber. Fiber-in-fiber-out NSOM-TERS has been developed. | 7 | Physical Chemistry |
JAKs range from 120-140 kDa in size and have seven defined regions of homology called Janus homology domains 1 to 7 (JH1-7). JH1 is the kinase domain important for the enzymatic activity of the JAK and contains typical features of a tyrosine kinase such as conserved tyrosines necessary for JAK activation (e.g., Y1038/Y1039 in JAK1, Y1007/Y1008 in JAK2, Y980/Y981 in JAK3, and Y1054/Y1055 in Tyk2). Phosphorylation of these dual tyrosines leads to the conformational changes in the JAK protein to facilitate binding of substrate. JH2 is a "pseudokinase domain", a domain structurally similar to a tyrosine kinase and essential for a normal kinase activity, yet lacks enzymatic activity. This domain may be involved in regulating the activity of JH1, and was likely a duplication of the JH1 domain which has undergone mutation post-duplication. The JH3-JH4 domains of JAKs share homology with Src-homology-2 (SH2) domains. The amino terminal (NH) end (JH4-JH7) of Jaks is called a FERM domain (short for band 4.1, ezrin, radixin and moesin); this domain is also found in the focal adhesion kinase (FAK) family and is involved in association of JAKs with cytokine receptors and/or other kinases. | 1 | Biochemistry |
Arene oxides are intermediates in the oxidation of arenes by cytochrome P450. For prochiral arenes (naphthalene, toluene, benzoates, benzopyrene), the epoxides are often obtained in high enantioselectivity.
Chiral epoxides can often be derived enantioselectively from prochiral alkenes. Many metal complexes give active catalysts, but the most important involve titanium, vanadium, and molybdenum.
The Sharpless epoxidation reaction is one of the premier enantioselective chemical reactions. It is used to prepare 2,3-epoxyalcohols from primary and secondary allylic alcohols. | 0 | Organic Chemistry |
In 1780, Luigi Galvani discovered that when two different metals (e.g., copper and zinc) are in contact and then both are touched at the same time to two different parts of a muscle of a frog leg, to close the circuit, the frogs leg contracts. He called this "animal electricity". The frogs leg, as well as being a detector of electrical current, was also the electrolyte (to use the language of modern chemistry).
A year after Galvani published his work (1790), Alessandro Volta showed that the frog was not necessary, using instead a force-based detector and brine-soaked paper (as electrolyte). (Earlier Volta had established the law of capacitance with force-based detectors). In 1799 Volta invented the voltaic pile, which is a stack of galvanic cells each consisting of a metal disk, an electrolyte layer, and a disk of a different metal. He built it entirely out of non-biological material to challenge Galvanis (and the later experimenter Leopoldo Nobili)s animal electricity theory in favor of his own metal-metal contact electricity theory. Carlo Matteucci in his turn constructed a battery entirely out of biological material in answer to Volta. Voltas contact electricity view characterized each electrode with a number that we would now call the work function of the electrode. This view ignored the chemical reactions at the electrode-electrolyte interfaces, which include H formation on the more noble metal in Voltas pile.
Although Volta did not understand the operation of the battery or the galvanic cell, these discoveries paved the way for electrical batteries; Volta's cell was named an IEEE Milestone in 1999.
Some forty years later, Faraday (see Faraday's laws of electrolysis) showed that the galvanic cell—now often called a voltaic cell—was chemical in nature. Faraday introduced new terminology to the language of chemistry: electrode (cathode and anode), electrolyte, and ion (cation and anion). Thus Galvani incorrectly thought the source of electricity (or source of electromotive force (emf), or seat of emf) was in the animal, Volta incorrectly thought it was in the physical properties of the isolated electrodes, but Faraday correctly identified the source of emf as the chemical reactions at the two electrode-electrolyte interfaces. The authoritative work on the intellectual history of the voltaic cell remains that by Ostwald.
It was suggested by Wilhelm König in 1940 that the object known as the Baghdad battery might represent galvanic cell technology from ancient Parthia. Replicas filled with citric acid or grape juice have been shown to produce a voltage. However, it is far from certain that this was its purpose—other scholars have pointed out that it is very similar to vessels known to have been used for storing parchment scrolls. | 8 | Metallurgy |
Bacterial two hybrid methods (B2H or BTH) are usually carried out in E. coli and have some advantages over yeast-based systems. For instance, the higher transformation efficiency and faster rate of growth lends E. coli to the use of larger libraries (in excess of 10). The absence of requirements for a nuclear localisation signal to be included in the protein sequence and the ability to study proteins that would be toxic to yeast may also be major factors to consider when choosing an experimental background organism.
The methylation activity of certain E. coli DNA methyltransferase proteins may interfere with some DNA-binding protein selections. If this is anticipated, the use of an E. coli strain that is defective for a particular methyltransferase may be an obvious solution. The B2H may not be ideal when studying eukaryotic protein-protein interactions (e.g. human proteins) as proteins may not fold as in eukaryotic cells or may lack other processing. | 1 | Biochemistry |
Knockdown of Alms1 by short interfering RNA in mouse inner medullary collecting duct cells caused defective ciliogenesis. Cilia were stunted and treated cells lacked the ability to increase calcium influx in response to mechanical stimuli. | 1 | Biochemistry |
Tartaric acid and its derivatives have a plethora of uses in the field of pharmaceuticals. For example, it has been used in the production of effervescent salts, in combination with citric acid, to improve the taste of oral medications. The potassium antimonyl derivative of the acid known as tartar emetic is included, in small doses, in cough syrup as an expectorant.
Tartaric acid also has several applications for industrial use. The acid has been observed to chelate metal ions such as calcium and magnesium. Therefore, the acid has served in the farming and metal industries as a chelating agent for complexing micronutrients in soil fertilizer and for cleaning metal surfaces consisting of aluminium, copper, iron, and alloys of these metals, respectively. | 4 | Stereochemistry |
Manganese is an essential human dietary element. It is present as a coenzyme in several biological processes, which include macronutrient metabolism, bone formation, and free radical defense systems. It is a critical component in dozens of proteins and enzymes. The human body contains about 12 mg of manganese, mostly in the bones. The soft tissue remainder is concentrated in the liver and kidneys. In the human brain, the manganese is bound to manganese metalloproteins, most notably glutamine synthetase in astrocytes. | 1 | Biochemistry |
In blood vessels Endothelium-Derived Hyperpolarizing Factor or EDHF is proposed to be a substance and/or electrical signal that is generated or synthesized in and released from the endothelium; its action is to hyperpolarize vascular smooth muscle cells, causing these cells to relax, thus allowing the blood vessel to expand in diameter. | 1 | Biochemistry |
Chambers isolated by filters are proper tools for accurate determination of chemotactic behavior. The pioneer type of these chambers was constructed by Boyden. The motile cells are placed into the upper chamber, while fluid containing the test substance is filled into the lower one. The size of the motile cells to be investigated determines the pore size of the filter; it is essential to choose a diameter which allows active transmigration. For modelling in vivo conditions, several protocols prefer coverage of filter with molecules of extracellular matrix (collagen, elastin etc.) Efficiency of the measurements was increased by development of multiwell chambers (e.g. NeuroProbe), where 24, 96, 384 samples are evaluated in parallel. Advantage of this variant is that several parallels are assayed in identical conditions. | 1 | Biochemistry |
Transcription fidelity is achieved through multiple mechanisms. RNA polymerases select correct nucleoside triphosphate (NTP) substrate to prevent transcription errors. Only the NTP which correctly base pairs with the coding base in the DNA is admitted to the active center. RNA polymerase performs two known proof reading functions to detect and remove misincorporated nucleotides: pyrophosphorylytic editing and hydrolytic editing. The former removes the incorrectly inserted ribonucleotide by a simple reversal of the polymerization reaction, while the latter involves backtracking of the polymerase and cleaving of a segment of error-containing RNA product. Elongation factor TFIIS (; TCEA1, TCEA2, TCEA3) stimulates an inherent ribonuclease activity in the polymerase, allowing the removal of misincorporated bases through limited local RNA degradation. Note that all reactions (phosphodiester bond synthesis, pyrophosphorolysis, phosphodiester bond hydrolysis) are performed by RNA polymerase by using a single active center. | 1 | Biochemistry |
There are various protein targets of PCAF's acetyltransferase activity including transcription factors such as Fli1, p53 and numerous histone residues. Hdm2, itself a ubiquitin ligase that targets p53, has also been demonstrated to be a target of the ubiquitin-ligase activity of PCAF. | 1 | Biochemistry |
Wood's notation takes the form
where M is the chemical symbol of the substrate, A is the chemical symbol of the overlayer, are the Miller indices of the surface plane, R and correspond to the rotational difference between the substrate and overlayer vectors, and the vector magnitudes shown are those of the substrate ( subscripts) and of the overlayer ( subscripts). This notation can only describe commensurate overlayers however, while matrix notation can describe both. | 7 | Physical Chemistry |
A transcription unit is a set of one or more genes transcribed from a single promoter. A TU may also include regulatory protein binding sites affecting this promoter and a terminator. A complex operon with several promoters contains, therefore, several transcription units. A transcription unit must include all the genes in an operon. | 1 | Biochemistry |
The word aldehyde was coined by Justus von Liebig as a contraction of the Latin (dehydrogenated alcohol). In the past, aldehydes were sometimes named after the corresponding alcohols, for example, vinous aldehyde for acetaldehyde. (Vinous is from Latin "wine", the traditional source of ethanol, cognate with vinyl.)
The term formyl group is derived from the Latin word "ant". This word can be recognized in the simplest aldehyde, formaldehyde, and in the simplest carboxylic acid, formic acid. | 0 | Organic Chemistry |
The pipette itself is an apparatus comprising following members (see Fig. 2).
: pipette tip configured to be able to access and aspirate/discharge liquid from/into each of vessels, having
::a front end portion,
::a reservoir portion,
::a liquid passage
:::connecting the front end portion and the reservoir portion,
::a separation region
:::in the liquid passage subjected to an action of a magnetic field, and
::a mechanism
:::for applying a negative or positive pressure to the interior of the pipette portion to draw or discharge a magnetic substance suspended liquid into or from the pipette portion
:magnetic field Source
::arranged on the outside of and adjacent to pipette tip; and
:magnetic field source driving device
::for driving the magnetic field source to apply or remove a magnetic field to or from the separation region from outside the liquid passage. When the magnet is brought close to the pipette tip, a magnetic field is applied; when retracted away from the pipette tip, that magnetic field is removed.
A nucleic acid extraction apparatus incorporating Tajima pipettes typically consists of:
:Above mentioned Tajima pipette,
:Plurality of tubes.
: Plurality of tube holder for above mentioned tubes,
:Transport mean
::to transport Tajima pipette among that plurality of tubes (tubes are supported by tube holder), and
:Control device
::for controlling abovementioned devices. | 1 | Biochemistry |
In chemical reactors, the goal is to make components react with a high yield. In a homogeneous, first-order reaction, the probability that an atom or molecule will react depends only on its residence time:
for a rate constant . Given a RTD, the average probability is equal to the ratio of the concentration of the component before and after:
If the reaction is more complicated, then the output is not uniquely determined by the RTD. It also depends on the degree of micromixing, the mixing between molecules that entered at different times. If there is no mixing, the system is said to be completely segregated, and the output can be given in the form
For given RTD, there is an upper limit on the amount of mixing that can occur, called the maximum mixedness, and this determines the achievable yield. A continuous stirred-tank reactor can be anywhere in the spectrum between completely segregated and perfect mixing.
The RTD of chemical reactors can be obtained by CFD simulations. The very same procedure that is performed in experiments can be followed. A pulse of inert tracer particles (during a very short time) is injected into the reactor. The linear motion of tracer particles is governed by Newton's second law of motion and a one-way coupling is stablished between fluid and tracers. In one-way coupling, fluid affects tracer motion by drag force while tracer does not affect fluid. The size and density of tracers are chosen so small that the time constant of tracers becomes very small. In this way, tracer particles exactly follow the same path as the fluid does. | 9 | Geochemistry |
Electrodeless discharge lamps (EDL) contain a small quantity of the analyte as a metal or a salt in a quartz bulb together with an inert gas, typically argon gas, at low pressure. The bulb is inserted into a coil that is generating an electromagnetic radio frequency field, resulting in a low-pressure inductively coupled discharge in the lamp. The emission from an EDL is higher than that from an HCL, and the line width is generally narrower, but EDLs need a separate power supply and might need a longer time to stabilize. | 3 | Analytical Chemistry |
Databases and computational tools for mimotopes have been an important part of phage display study. Databases, programs and web servers have been widely used to exclude target-unrelated peptides, characterize small molecules-protein interactions and map protein-protein interactions. Users can use three dimensional structure of a protein and the peptides selected from phage display experiment to map conformational epitopes. Some of the fast and efficient computational methods are available online. | 1 | Biochemistry |
In organic chemistry, a carbonyl group characterizes the following types of compounds:
Other organic carbonyls are urea and the carbamates, the derivatives of acyl chlorides chloroformates and phosgene, carbonate esters, thioesters, lactones, lactams, hydroxamates, and isocyanates. Examples of inorganic carbonyl compounds are carbon dioxide and carbonyl sulfide.
A special group of carbonyl compounds are dicarbonyl compounds, which can exhibit special properties. | 0 | Organic Chemistry |
Regarding biological membranes, the liquid ordered phase is a liquid crystalline phase of a lipid bilayer, and is of significant biological importance. It occurs in many lipid mixtures combining cholesterol with a phospholipid and/or sphingolipids e.g. sphingomyelin. This phase has been related to lipid rafts that may exist in plasma membranes. | 1 | Biochemistry |
Ingold married Dr. Edith Hilda Ingold (Usherwood) in 1923. She was a fellow chemist with whom he collaborated. They had two daughters and a son, the chemist Keith Ingold. | 4 | Stereochemistry |
AMGs are not randomly distributed throughout genomes. Current research is being done to determine the genes that most commonly surround specific AMGs. Hyperplastic regions including the region between genes g15-g18 has been classified as locales where multiple AMGs have been inserted. Possible AMG contexts can be divided into locally collinear blocks (LCBs), or homologous regions shared by multiple viruses without rearrangements. AMGs have been found in just one or up to 14 LCBs. Those found in more diverse contexts have also shown up in variable locales within the LCB. | 1 | Biochemistry |
Watt's Expansion Engine is generally considered as of historic interest only. There are however some recent developments which may lead to a renaissance of the technology. Today, there is an enormous amount of waste steam and waste heat with temperatures between 100 and 150 °C generated by industry. In addition, solarthermal collectors, geothermal energy sources and biomass reactors produce heat in this temperature range. There are technologies to utilise this energy, in particular the Organic Rankine Cycle. In principle, these are steam turbines which do not use water but a fluid (a refrigerant) which evaporates at temperatures below 100 °C. Such systems are however fairly complex. They work with pressures of 6 to 20 bars, so that the whole system has to be completely sealed.
The Expansion Engine can offer significant advantages here, in particular for lower power ratings of 2 to 100 kW: with expansion ratios of 1:5, the theoretical efficiency reaches 15%, which is in the range of ORC systems. The Expansion Engine uses water as working fluid which is simple, cheap, non-toxic, non-flammable and non-corrosive. It works at pressure near and below atmospheric, so that sealing is not a problem. And it is a simple machine, implying cost effectiveness. Researchers from the University of Southampton / UK are currently developing a modern version of Watt's engine in order to generate energy from waste steam and waste heat. They improved the theory, demonstrating that theoretical efficiencies of up to 17.4% (and actual efficiencies of 11%) are possible.
In order to demonstrate the principle, a 25 watt experimental model engine was built and tested. The engine incorporates steam expansion as well as new features such as electronic control. The picture shows the model built and tested in 2016. Currently, a project to build and test a scaled-up 2 kW engine is under preparation. | 7 | Physical Chemistry |
Scattering-based DDM belongs to the so-called near-field (or deep Fresnel) scattering family, a recently introduced family of imaging-based scattering methods. Near field is used here in a similar way to what is used for near field speckles i.e. as a particular case of Fresnel region as opposed to the far field or Fraunhofer region. The near field scattering family includes also quantitative shadowgraphy and Schlieren. | 7 | Physical Chemistry |
In chemical ionization (CI) a reagent gas, typically methane or ammonia is introduced into the mass spectrometer. Depending on the technique (positive CI or negative CI) chosen, this reagent gas will interact with the electrons and analyte and cause a soft ionization of the molecule of interest. A softer ionization fragments the molecule to a lower degree than the hard ionization of EI. One of the main benefits of using chemical ionization is that a mass fragment closely corresponding to the molecular weight of the analyte of interest is produced.
In positive chemical ionization (PCI) the reagent gas interacts with the target molecule, most often with a proton exchange. This produces the species in relatively high amounts.
In negative chemical ionization (NCI) the reagent gas decreases the impact of the free electrons on the target analyte. This decreased energy typically leaves the fragment in great supply. | 3 | Analytical Chemistry |
Endomorphin-1 (EM-1) (amino acid sequence Tyr-Pro-Trp-Phe-NH) is an endogenous opioid peptide and one of the two endomorphins. It is a high affinity, highly selective agonist of the μ-opioid receptor, and along with endomorphin-2 (EM-2), has been proposed to be the actual endogenous ligand of the μ-receptor. EM-1 produces analgesia in animals and is equipotent with morphine in this regard. The gene encoding for EM-1 has not yet been identified, and it has been suggested that endomorphins could be synthesized by an enzymatic, non-ribosomal mechanism.
By combining N-terminal guadino modifications, a new class of endonmorphin-1 was synthesized, the range of their bioactivities were measured by radioligand binding assay in order to conclude its potency as an opioid. Endomorphin-1 has high affinity and specificity for opioid receptors for behavioral, physiological and pharmacological assays, it is also a potent analgesic agent which brings effects on cardiovascular, respiratory and gastrointestinal functions as well as in immune system responses. This endogenous opioid peptide can help with neuropathic pain without having the common side effects many neuropathic drugs caused which produces constipation. To make this drug side effect-free, a modification at the N-terminus by 2-aminodecainoic acid is made which in term showed an improve in the drug's metabolic stability along with improving its membrane permeability, while holding its high receptor binding affinity, helping the drug act as a potent agonist | 1 | Biochemistry |
Mutations in complex III-related genes typically manifest as exercise intolerance. Other mutations have been reported to cause septo-optic dysplasia and multisystem disorders. However, mutations in BCS1L, a gene responsible for proper maturation of complex III, can result in Björnstad syndrome and the GRACILE syndrome, which in neonates are lethal conditions that have multisystem and neurologic manifestations typifying severe mitochondrial disorders. The pathogenicity of several mutations has been verified in model systems such as yeast.
The extent to which these various pathologies are due to bioenergetic deficits or overproduction of superoxide is presently unknown. | 1 | Biochemistry |
The sulfur cycle in marine environments has been well-studied via the tool of sulfur isotope systematics expressed as δS. The modern global oceans have sulfur storage of , mainly occurring as sulfate with the δS value of +21‰. The overall input flux is with the sulfur isotope composition of ~3‰. Riverine sulfate derived from the terrestrial weathering of sulfide minerals (δS = +6‰) is the primary input of sulfur to the oceans. Other sources are metamorphic and volcanic degassing and hydrothermal activity (δS = 0‰), which release reduced sulfur species (such as HS and S). There are two major outputs of sulfur from the oceans. The first sink is the burial of sulfate either as marine evaporites (such as gypsum) or carbonate-associated sulfate (CAS), which accounts for (δS = +21‰). The second sulfur sink is pyrite burial in shelf sediments or deep seafloor sediments (; δS = −20‰). The total marine sulfur output flux is which matches the input fluxes, implying the modern marine sulfur budget is at steady state. The residence time of sulfur in modern global oceans is 13,000,000 years. | 9 | Geochemistry |
The Bolzano process is a means to reduce magnesium to metallic form. "Dolomite-ferrosilicon briquettes are stacked on a special charge support system through which internal electric heating is conducted to the charge. A complete reaction takes 20 to 24 hours at 1,200 °C."
In 2014, Brazilian operations produced 10-15 kilotons of Mg by this process.
Also in 2014, Nevada Clean Magnesium announced its Tami-Mosi plan to create a ASTM B-92 pilot plant. The mineral resource is estimated at 412 billion tons of 12.3% grade Mg. The company produced its first ingot from a pilot plant in December 2018. | 8 | Metallurgy |
Hydrogen embrittlement is a complex process involving a number of distinct contributing micro-mechanisms, not all of which need to be present. The mechanisms include the formation of brittle hydrides, the creation of voids that can lead to high-pressure bubbles, enhanced decohesion at internal surfaces and localised plasticity at crack tips that assist in the propagation of cracks. There is a great variety of mechanisms that have been proposed and investigated as to the cause of brittleness once diffusible hydrogen has been dissolved into the metal. In recent years, it has become widely accepted that HE is a complex, material and environmental dependent process, so that no single mechanism applies exclusively.
* Internal pressure: At high hydrogen concentrations, absorbed hydrogen species recombine in voids to form hydrogen molecules (H), creating pressure from within the metal. This pressure can increase to levels where cracks form, commonly designated hydrogen-induced cracking (HIC), as well as blisters forming on the specimen surface, designated hydrogen-induced blistering. These effects can reduce ductility and tensile strength.
* Hydrogen enhanced localised plasticity (HELP): Hydrogen increases the nucleation and movement of dislocations at a crack tip. HELP results in crack propagation by localised ductile failure at the crack tip with less deformation occurring in the surrounding material, which gives a brittle appearance to the fracture.
* Hydrogen decreased dislocation emission: Molecular dynamics simulations reveal a ductile-to-brittle transition caused by the suppression of dislocation emission at the crack tip by dissolved hydrogen. This prevents the crack tip rounding-off, so the sharp crack then leads to brittle-cleavage failure.
* Hydrogen enhanced decohesion (HEDE): Interstitial hydrogen lowers the stress required for metal atoms to fracture apart. HEDE can only occur when the local concentration of hydrogen is high, such as due to the increased hydrogen solubility in the tensile stress field at a crack tip, at stress concentrators, or in the tension field of edge dislocations.
* Metal hydride formation: The formation of brittle hydrides with the parent material allows cracks to propagate in a brittle fashion. This is particularly a problem with vanadium alloys, but most structural alloys do not easily form hydrides.
* Phase transformations: Hydrogen can induce phase transformations in some materials, and the new phase may be less ductile. | 7 | Physical Chemistry |
In biochemistry, several important enzymatic cascades and signal transduction cascades participate in metabolic pathways or signaling networks, in which enzymes are usually involved to catalyze the reactions. For example, the tissue factor pathway in the coagulation cascade of secondary hemostasis is the primary pathway leading to fibrin formation, and thus, the initiation of blood coagulation. The pathways are a series of reactions, in which a zymogen (inactive enzyme precursor) of a serine protease and its glycoprotein co-factors are activated to become active components that then catalyze the next reaction in the cascade, ultimately resulting in cross-linked fibrin.
Another example, sonic hedgehog signaling pathway, is one of the key regulators of embryonic development and is present in all bilaterians. Different parts of the embryo have different concentrations of hedgehog signaling proteins, which give cells information to make the embryo develop properly and correctly into a head or a tail. When the pathway malfunctions, it can result in diseases like basal cell carcinoma. Recent studies point to the role of hedgehog signaling in regulating adult stem cells involved in maintenance and regeneration of adult tissues. The pathway has also been implicated in the development of some cancers. Drugs that specifically target hedgehog signaling to fight diseases are being actively developed by a number of pharmaceutical companies. Most biochemical cascades are series of events, in which one event triggers the next, in a linear fashion.
Biochemical cascades include:
*The Complement system
*The Insulin Signaling Pathway
*The Sonic hedgehog Signaling Pathway
*The Wnt signaling pathway
*The JAK-STAT signaling pathway
*The Adrenergic receptor Pathways
*The Acetylcholine receptor Pathways
*The Mitogen-activated protein kinase cascade
Conversely, negative cascades include events that are in a circular fashion, or can cause or be caused by multiple events. Negative cascades include:
*Ischemic cascade | 7 | Physical Chemistry |
Disulfide bonds play an important protective role for bacteria as a reversible switch that turns a protein on or off when bacterial cells are exposed to oxidation reactions. Hydrogen peroxide (HO) in particular could severely damage DNA and kill the bacterium at low concentrations if not for the protective action of the SS-bond. Archaea typically have fewer disulfides than higher organisms. | 0 | Organic Chemistry |
It may sometimes be useful to perform other diagnostic measures in addition to spot tests. For example, some lichen metabolites fluoresce under ultraviolet radiation such that exposing certain parts of the lichen to a UV light source can reveal the presence or absence of those metabolites similarly to spot tests. Examples of lichen substances that give a bright fluorescence in UV are alectoronic, lobaric, and divaricatic acids, and lichexanthone. In some cases, the UV light test can be used to help distinguish between closely related species, such as Cladonia deformis (UV−) and Cladonia sulphurina (UV+, due to presence of squamatic acid). Only long-wavelength UV is useful for observing lichens directly.
More advanced analytical techniques, such as thin-layer chromatography, high-performance liquid chromatography, and mass spectrometry may also be useful in initially characterising the chemical composition of lichens or when spot tests are unrevealing. | 3 | Analytical Chemistry |
Prp24 has a human homolog, SART3. SART3 is a tumor rejection antigen (SART3 stands for "squamous cell carcinoma antigen recognized by T cells, gene 3). The RRMs 1 and 2 in yeast are similar to RRMs in human SART3. The C-terminal domain is also highly conserved from yeast to humans. This protein, like Prp24, interacts with the LSm proteins for the recycling of U6 into the U4/U6 snRNP. It has been proposed that SART3 target U6 to a Cajal body or a nuclear inclusion as the site of assembly of the U4/U6 snRNP. SART3 is located on chromosome 12, and a mutation is likely the cause of disseminated superficial actinic porokeratosis. | 1 | Biochemistry |
Biuret was first prepared and studied by Gustav Heinrich Wiedemann (1826–1899) for his doctoral dissertation, which was submitted in 1847. His findings were reported in several articles. | 0 | Organic Chemistry |
Boronic esters are esters formed between a boronic acid and an alcohol.
The compounds can be obtained from borate esters by condensation with alcohols and diols. Phenylboronic acid can be selfcondensed to the cyclic trimer called triphenyl anhydride or triphenylboroxin.
Compounds with 5-membered cyclic structures containing the C–O–B–O–C linkage are called dioxaborolanes and those with 6-membered rings dioxaborinanes. | 0 | Organic Chemistry |
Because the energy of an X-ray with particular wavelength is known (for Al K X-rays, E = 1486.7 eV), and because the emitted electrons' kinetic energies are measured, the electron binding energy of each of the emitted electrons can be determined by using the photoelectric effect equation,
where E is the binding energy (BE) of the electron measured relative to the chemical potential, E is the energy of the X-ray photons being used, E is the kinetic energy of the electron as measured by the instrument and is a work function-like term for the specific surface of the material, which in real measurements includes a small correction by the instrument's work function because of the contact potential. This equation is essentially a conservation of energy equation. The work function-like term can be thought of as an adjustable instrumental correction factor that accounts for the few eV of kinetic energy given up by the photoelectron as it gets emitted from the bulk and absorbed by the detector. It is a constant that rarely needs to be adjusted in practice. | 7 | Physical Chemistry |
Iterons have an important role in plasmid replication. An iteron-containing plasmid origin of replication can be found containing about five iterons about 20 base pairs in length total. These iterons provide a saturation site for initiator receptor proteins and promote replication thus increasing plasmid copy number in a given cell. | 1 | Biochemistry |
Modafinil is a racemic mixture of two enantiomers, armodafinil ((R)-modafinil) and esmodafinil ((S)-modafinil). | 4 | Stereochemistry |
In colloidal chemistry, an aggregation number is a description of the number of molecules present in a micelle once the critical micelle concentration (CMC) has been reached. In more detail, it has been defined as the average number of surfactant monomers in a spherical micelle.
The aggregation number of micelles can be determined by isothermal titration calorimetry when the aggregation number is not too high.
Another classical experiment to determine the mean aggregation number would involve the use of a luminescent probe, a quencher and a known concentration of surfactant. If the concentration of the quencher is varied, and the CMC of the surfactant known, the mean aggregation number can be calculated. | 7 | Physical Chemistry |
Culcheth is just over one mile north of junction 11 of the M62 motorway on the A574.
It was administered by the Research and Development Branch of the United Kingdom Atomic Energy Authority (UKAEA). | 8 | Metallurgy |
In the study of metallomes the transcriptome, proteome and the metabolome constitutes the whole metallome. A study of the metallome is done to arrive at the metallointeractome. | 1 | Biochemistry |
Triuret is an organic compound with the formula (HNC(O)NH)CO. It is a product from the pyrolysis of urea. Triuret is a colorless, crystalline, hygroscopic solid, slightly soluble in cold water or ether, and more soluble in hot water. It is a planar molecule. The central carbonyl is hydrogen-bonded to both terminal amino groups. | 0 | Organic Chemistry |
Ethyl cyanohydroxyiminoacetate is a white solid which is soluble in many solvents common in the synthesis of peptides, such as dichloromethane or dimethylformamide (DMF). In crystalline form, the compound is present as an oxime, whereas it exists as a salt or in a strongly basic solution predominantly as a tautomeric nitrosoisomer in anionic form. | 0 | Organic Chemistry |
Victor Moritz Goldschmidt (27 January 1888 – 20 March 1947) was a Norwegian mineralogist considered (together with Vladimir Vernadsky) to be the founder of modern geochemistry and crystal chemistry, developer of the Goldschmidt Classification of elements. | 9 | Geochemistry |
Hydrazides in organic chemistry are a class of organic compounds with the formula where R is acyl (), sulfonyl (), phosphoryl (), phosphonyl () and similar groups (chalcogen analogs are included, for example sulfur analogs called thiohydrazides), and R' are any groups (typically hydrogen or organyl). Unlike hydrazine and alkylhydrazines, hydrazides are nonbasic owing to the inductive influence of the acyl, sulfonyl, or phosphoryl substituent. | 0 | Organic Chemistry |
Because their double bonds are electron rich, enols behave as nucleophiles and react with electrophiles in much the same way that alkenes do. But because of resonance electron donation of a lone pair of electrons on the neighboring oxygen, enols are more electron- rich and correspondingly more reactive than alkenes. Notice in the following electrostatic potential map of ethenol (HC=CHOH) how there is a substantial amount of electron density on the α carbon.
When an alkene reacts with an electrophile, such as HCl, initial addition of H gives an intermediate cation and subsequent reaction with Cl yields an addition product. When an enol reacts with an electrophile, however, only the initial addition step is the same. Instead of reacting with CI to give an addition product, the intermediate cation loses the OH proton to give an α-substituted carbonyl compound. | 0 | Organic Chemistry |
Since the 1970s and the well-publicized advocacy of Benjamin Feingold, there has been public concern that food colorings may cause ADHD-like behavior in children. These concerns have led the FDA and other food safety authorities to regularly review the scientific literature, and led the UK FSA to commission a study by researchers at Southampton University of the effect of a mixture of the "Southampton 6" and sodium benzoate (a preservative) on children in the general population who consumed them in beverages; the study published in 2007. The study found "a possible link between the consumption of these artificial colours and a sodium benzoate preservative and increased hyperactivity" in the children; the advisory committee to the FSA that evaluated the study also determined that because of study limitations, the results could not be extrapolated to the general population, and further testing was recommended".
The European regulatory community, with a stronger emphasis on the precautionary principle, required labelling and temporarily reduced the acceptable daily intake (ADI) for the food colorings; the UK FSA called for voluntary withdrawal of the colorings by food manufacturers. However, in 2009 the EFSA re-evaluated the data at hand and determined that "the available scientific evidence does not substantiate a link between the color additives and behavioral effects" and in 2014 after further review of the data, the EFSA restored the prior ADI levels.
The US FDA did not make changes following the publication of the Southampton study, but following a citizen petition filed by the Center for Science in the Public Interest in 2008, requesting the FDA to ban several food additives, the FDA commenced a review of the available evidence, and still made no changes. | 3 | Analytical Chemistry |
Radiosynthesis is the theorized capture and metabolism, by living organisms, of energy from ionizing radiation, analogously to photosynthesis. Metabolism of ionizing radiation was theorized as early as 1956 by the Russian microbiologist S. I. Kuznetsov.
Beginning in the 1990s, researchers at the Chernobyl Nuclear Power Plant uncovered some 200 species of apparently radiotrophic fungi containing the pigment melanin on the walls of the reactor room and in the surrounding soil. Such "melanized" fungi have also been discovered in nutrient-poor, high-altitude areas which are exposed to high levels of ultraviolet radiation.
Following the Russian results, an American team at the Albert Einstein College of Medicine of Yeshiva University in New York began experimenting with radiation exposure of melanin and melanized fungi. They found that ionizing radiation increased the ability of melanin to support an important metabolic reaction, and that Cryptococcus neoformans fungi grew three times faster than normal. Microbiologist Ekaterina Dadachova suggested such fungi could serve as a food supply and source of radiation protection for interplanetary astronauts, who would be exposed to cosmic rays.
In 2014, the American research group was awarded a patent for a method of enhancing the growth of microorganisms through increasing melanin content. The inventors of this process claimed their fungi were employing radiosynthesis, and hypothesized that radiosynthesis may have played a role in early life on Earth, by allowing melanized fungi to act as autotrophs.
From October 2018 through March 2019, NASA conducted an experiment aboard the International Space Station to study radiotrophic fungi as a potential radiation barrier to the harmful radiation in space. Radiotrophic fungi have many possible applications on Earth as well, potentially including a disposal method for nuclear waste or use as high-altitude biofuel or a nutrition source. | 5 | Photochemistry |
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