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There are many different approaches to transfer thermal energy to electricity, and the technologies to do so have existed for several decades.
An established approach is by using a thermoelectric device, where a change in temperature across a semiconductor material creates a voltage through a phenomenon known as the Seebeck effect.
A related approach is the use of thermogalvanic cells, where a temperature difference gives rise to an electric current in an electrochemical cell.
The organic Rankine cycle, offered by companies such as Ormat, is a very known approach, whereby an organic substance is used as working medium instead of water. The benefit is that this process can reject heat at lower temperatures for the production of electricity than the regular water steam cycle. An example of use of the steam Rankine cycle is the Cyclone Waste Heat Engine. | 7 | Physical Chemistry |
Unlike the proofreading mechanisms of DNA polymerase those of RNAP have only recently been investigated. Proofreading begins with separation of the mis-incorporated nucleotide from the DNA template. This pauses transcription. The polymerase then backtracks by one position and cleaves the dinucleotide that contains the mismatched nucleotide. In the RNA polymerase this occurs at the same active site used for polymerization and is therefore markedly different from the DNA polymerase where proofreading occurs at a distinct nuclease active site.
The overall error rate is around 10 to 10. | 1 | Biochemistry |
To prepare a cDNA library, the first step is to isolate the total mRNA from the cell type of interest. Then, the enzyme reverse transcriptase is used to generate cDNAs. Reverse transcriptase is a RNA-dependent DNA polymerase. It depends on the presence of a primer, usually a poly-dT oligonucleotide, to prime DNA synthesis. DNA polymerase can use these single–stranded primers to initiate second strand DNA synthesis on the mRNA templates. After the single-stranded DNA molecules are converted into double-stranded DNA molecules by DNA polymerase, they are inserted into vectors and cloned. To do this, the cDNA are frequently methylated with a specific methyl transferase. These synthetic oligonucleotides can either be “linkers”, the overhangs are generated by digestion with the appropriate restriction enzyme. | 1 | Biochemistry |
Entropic gravity, as proposed by Verlinde in his original article, reproduces the Einstein field equations and, in a Newtonian approximation, a potential for gravitational forces. Since its results do not differ from Newtonian gravity except in regions of extremely small gravitational fields, testing the theory with earth-based laboratory experiments does not appear feasible. Spacecraft-based experiments performed at Lagrangian points within our solar system would be expensive and challenging.
Even so, entropic gravity in its current form has been severely challenged on formal grounds. Matt Visser has shown that the attempt to model conservative forces in the general Newtonian case (i.e. for arbitrary potentials and an unlimited number of discrete masses) leads to unphysical requirements for the required entropy and involves an unnatural number of temperature baths of differing temperatures. Visser concludes:
For the derivation of Einsteins equations from an entropic gravity perspective, Tower Wang shows that the inclusion of energy-momentum conservation and cosmological homogeneity and isotropy requirements severely restricts a wide class of potential modifications of entropic gravity, some of which have been used to generalize entropic gravity beyond the singular case of an entropic model of Einsteins equations. Wang asserts that:
Cosmological observations using available technology can be used to test the theory. On the basis of lensing by the galaxy cluster Abell 1689, Nieuwenhuizen concludes that EG is strongly ruled out unless additional (dark) matter-like eV neutrinos is added. A team from Leiden Observatory statistically observing the lensing effect of gravitational fields at large distances from the centers of more than 33,000 galaxies found that those gravitational fields were consistent with Verlindes theory. Using conventional gravitational theory, the fields implied by these observations (as well as from measured galaxy rotation curves) could only be ascribed to a particular distribution of dark matter. In June 2017, a study by Princeton University researcher Kris Pardo asserted that Verlindes theory is inconsistent with the observed rotation velocities of dwarf galaxies. Another theory of entropy based on geometric considerations (Quantitative Geometrical Thermodynamics, QGT) provides an entropic basis for the holographic principle and also offers another explanation for galaxy rotation curves as being due to the entropic influence of the central supermassive blackhole found in the center of a spiral galaxy.
In 2018, Zhi-Wei Wang and Samuel L. Braunstein showed that, while spacetime surfaces near black holes (called stretched horizons) do obey an analog of the first law of thermodynamics, ordinary spacetime surfaces — including holographic screens — generally do not, thus undermining the key thermodynamic assumption of the emergent gravity program.
In his 1964 lecture on the Relation of Mathematics and Physics, Richard Feynman describes a related theory for gravity where the gravitational force is explained due to an entropic force due to unspecified microscopic degrees of freedom. However, he immediately points out that the resulting theory cannot be correct as the fluctuation-dissipation theorem would also lead to friction which would slow down the motion of the planets which contradicts observations. | 7 | Physical Chemistry |
Alcoholic fermentation is often used by plants in anaerobic conditions to produce ATP and regenerate NAD to allow for glycolysis to continue. For most plant tissues, fermentation only occurs in anaerobic conditions, but there are a few exceptions. In the pollen of maize (Zea mays) and tobacco (Nicotiana tabacum & Nicotiana plumbaginifolia), the fermentation enzyme ADH is abundant, regardless of the oxygen level. In tobacco pollen, PDC is also highly expressed in this tissue and transcript levels are not influenced by oxygen concentration. Tobacco pollen, similar to Crabtree-positive yeast, perform high levels of fermentation dependent on the sugar supply, and not oxygen availability. In these tissues, respiration and alcoholic fermentation occur simultaneously with high sugar availability. Fermentation produces the toxic acetaldehyde and ethanol, that can build up in large quantities during pollen development. It has been hypothesized that acetaldehyde is a pollen factor that causes cytoplasmic male sterility. Cytoplasmic male sterility is a trait observed in maize, tobacco and other plants in which there is an inability to produce viable pollen. It is believed that this trait might be due to the expression of the fermentation genes, ADH and PDC, a lot earlier on in pollen development than normal and the accumulation of toxic aldehyde. | 1 | Biochemistry |
Mitochondrial genes in some vertebrates (including humans) have incomplete stop codons ending in U or UA, which become complete termination codons (UAA) upon subsequent polyadenylation. | 1 | Biochemistry |
Köhler theory describes the process in which water vapor condenses and forms liquid cloud drops, and is based on equilibrium thermodynamics. It combines the Kelvin effect, which describes the change in saturation vapor pressure due to a curved surface, and Raoult's Law, which relates the saturation vapor pressure to the solute. It is an important process in the field of cloud physics. It was initially published in 1936 by Hilding Köhler, Professor of Meteorology in the Uppsala University.
Köhler equation:
where is the droplet water vapor pressure, is the corresponding saturation vapor pressure over a flat surface, is the droplet surface tension, is the density of pure water, is the moles of solute, is the molecular weight of water, and is the cloud drop diameter. | 7 | Physical Chemistry |
According to proponents of a classical double-well potential, the 2-norbornyl cation exists in dynamic equilibrium between two enantiomeric asymmetric structures. The delocalized species central to the non-classical picture is merely a transition state between the two structures. Wagner-Meerwein rearrangements are invoked as the mechanism that converts between the two enantiomers (see Figure 4).
Efforts to isolate the asymmetric species spectroscopically are typically unsuccessful. The major reason for this failure is reported to be extremely rapid forward and reverse reaction rates, which indicate a very low potential barrier for interconversion between the two enantiomers. | 7 | Physical Chemistry |
In the liver, bilirubin is conjugated with glucuronic acid by the enzyme glucuronyltransferase, first to bilirubin glucuronide and then to bilirubin diglucuronide, making it soluble in water: the conjugated version is the main form of bilirubin present in the "direct" bilirubin fraction. Much of it goes into the bile and thus out into the small intestine. Though most bile acid is reabsorbed in the terminal ileum to participate in enterohepatic circulation, conjugated bilirubin is not absorbed and instead passes into the colon.
There, colonic bacteria deconjugate and metabolize the bilirubin into colorless urobilinogen, which can be oxidized to form urobilin and stercobilin. Urobilin is excreted by the kidneys to give urine its yellow color and stercobilin is excreted in the feces giving stool its characteristic brown color. A trace (~1%) of the urobilinogen is reabsorbed into the enterohepatic circulation to be re-excreted in the bile.
Conjugated bilirubin's half-life is shorter than delta bilirubin. | 1 | Biochemistry |
*[http://pubs.acs.org/doi/pdf/10.1021/ac00053a012 Separation of amino acid homopolymers by capillary gel electrophoresis].
*[https://pubs.acs.org/doi/abs/10.1021/ac50042a043 Retention indices for programmed-temperature capillary-column gas chromatography of polycyclic aromatic hydrocarbons].
*[https://www.nature.com/articles/35015572 Ultrasensitive Pheromone Detection by mammalian vomeronasal neurons].
*[https://pubs.acs.org/doi/abs/10.1021/ac00221a013 Electrophoretic separations of proteins in capillaries with hydrolytically-stable surface structures].
*[https://academic.oup.com/glycob/article/17/4/411/602457 Comparison of the methods for profiling glycoprotein glycans—HUPO Human Disease Glycomics/Proteome Initiative multi-institutional study].
*[https://pubs.acs.org/doi/abs/10.1021/cr0103017 Structural Investigations of Glycoconjugates at High Sensitivity]. | 3 | Analytical Chemistry |
Dimethyl methylphosphonate is an organophosphorus compound with the chemical formula CHPO(OCH). It is a colourless liquid, which is primarily used as a flame retardant. | 1 | Biochemistry |
Under very oxidising or very reducing conditions, the steady-state catalytic current sometimes tends to a limiting value (a plateau) which (still provided there is no mass transport limitation) relates to the activity of the fully oxidised or fully reduced enzyme, respectively. If interfacial electron transfer is slow and if there is a distribution of electron transfer rates (resulting from a distribution of orientations of the enzymes molecules on the electrode), the current keeps increasing linearly with potential instead of reaching a plateau; in that case the limiting slope is proportional to the turnover rate of the fully oxidised or fully reduced enzyme.
The change in steady-state current against potential is often complex (e.g. not merely sigmoidal). | 7 | Physical Chemistry |
Physical lipolysis involves destruction of fat cells containing the fat droplets and can be used as part of cosmetic body contouring procedures. Currently there are four main non-invasive body contouring techniques in aesthetic medicine for reducing localized subcutaneous adipose tissue in addition to the standard minimally invasive liposuction: low-level laser therapy (LLLT), cryolipolysis, radio frequency (RF) and high-intensity focused ultrasound (HIFU). However, they are less effective with shorter lasting benefits and can remove significantly smaller amounts of fat compared to traditional surgical liposuction or lipectomy. However, future drug developments can be potentially combined with smaller procedures to augment the result. | 1 | Biochemistry |
The analysis of field effects on benthic organisms functions to assess the potential for community based effects resulting from the identified contaminants. This is done because benthic organisms are sessile and location specific, allowing them to be used as accurate markers of contaminant effect (Chapman, 1990). This is done through conducting field-based tests, which analyze changes in benthic community structures focusing on changes in number of species, abundance, and percentage of major taxonomic groups (Chapman, 1997). Changes in benthic communities are typically quantified using a principal component analysis and classification (Chapman, 1997). There is no one specifically defined method for conducting these field assessments, however the different multivariate analysis typically produces results identifying relationships between variables when a robust correlation exists.
Knowledge of the site-specific ecosystem and the ecological roles of dominant species within that ecosystem are critical to producing biological evidence of alteration in benthic community resultant of contaminant exposure. When possible, it is recommended to observe changes in community structure that directly relate to the test species used during the sediment toxicity portion of the triad approach in order to produce the most reliable evidence. | 2 | Environmental Chemistry |
Carbamate esters also arise via alcoholysis of carbamoyl chlorides:
:RNC(O)Cl + ROH → RNCOR + HCl
Alternatively, carbamates can be formed from chloroformates and amines:
:ROC(O)Cl + RNH → RNCOR + HCl
Carbamates may be formed from the Curtius rearrangement, where isocyanates formed are reacted with an alcohol.
:RCON → RNCO + N
:RNCO + R′OH → RNHCOR′ | 0 | Organic Chemistry |
PV work is path-dependent and is, therefore, a thermodynamic process function. In general, the term is not an exact differential. The statement that a process is quasi-static gives important information about the process but does not determine the P–V path uniquely, because the path can include several slow goings backwards and forward in volume, slowly enough to exclude friction within the system occasioned by departure from the quasi-static requirement. An adiabatic wall is one that does not permit passage of energy by conduction or radiation.
The first law of thermodynamics states that .
For a quasi-static adiabatic process, so that
Also so that
It follows that so that
Internal energy is a state function so its change depends only on the initial and final states of a process. For a quasi-static adiabatic process, the change in internal energy is equal to minus the integral amount of work done by the system, so the work also depends only on the initial and final states of the process and is one and the same for every intermediate path. As a result, the work done by the system also depends on the initial and final states.
If the process path is other than quasi-static and adiabatic, there are indefinitely many different paths, with significantly different work amounts, between the initial and final states. (Again the internal energy change depends only on the initial and final states as it is a state function).
In the current mathematical notation, the differential is an inexact differential.
In another notation, is written (with a horizontal line through the d). This notation indicates that is not an exact one-form. The line-through is merely a flag to warn us there is actually no function (0-form) which is the potential of . If there were, indeed, this function , we should be able to just use Stokes Theorem to evaluate this putative function, the potential of , at the boundary of the path, that is, the initial and final points, and therefore the work would be a state function. This impossibility is consistent with the fact that it does not make sense to refer to the work on a point in the PV diagram; work presupposes a path. | 7 | Physical Chemistry |
MFA is a convulsant poison. It causes severe convulsions in poisoned victims. Death results from respiratory failure.
For a variety of animals, the toxicity of methyl fluoroacetate has been determined orally and through subcutaneous injection. The dosage ranges from 0.1 mg/kg in dogs to 10–12 mg/kg in monkeys indicating considerable variation. An order of decreasing susceptibility has been determined within these animals which is: dog, guinea-pig, cat, rabbit, goat, and then likely horse, rat, mouse, and monkey. For the rat and mouse, the toxicity by inhalation has been investigated more fully than for other animals. The LD for the rat and mouse are 450 mg/m and above 1,000 mg/m for 5 minutes, respectively. In dogs, guinea-pigs, cats, rabbits, goats, horses, rats, mice, and monkeys, the pharmacological effects of this substance have been investigated by mouth and by injection. Methyl fluoroacetate causes progressive depression of respiration and is a convulsant poison in most animals. When applied to the skin it is not toxic, yet through inhalation, injection and by mouth it is. For the rat, cat and the rhesus monkey, the effects of methyl fluoroacetate have been determined similar to those of nicotine, strychnine, leptazol, picrotoxin, and electrically induced convulsions. The convulsive pattern is considered to be similar to that of leptazol. Little besides signs of asphyxia is found post-mortem in these animals. Estimations have been made for blood sugar, hemoglobin, plasma proteins, non-protein nitrogen, and serum potassium, calcium, chloride, and inorganic phosphate in a small number of rabbits, dogs, and goats. Blood changes include a rise of 20 to 60% in hemoglobin, a rise of up to 90% in blood sugar, a rise of 70 to 130% in inorganic phosphate, and a less significant rise in serum potassium with a terminal rise in non-protein nitrogen and potassium. The whole central nervous system is affected by methyl fluoroacetate just like with leptazol, with the higher centers being more sensitive than the lower ones. Small doses of methyl fluoroacetate have little effect on blood pressure yet in large doses it has an action similar to nicotine. It further stimulates the rate and volume of respiration and then causes failure of the respiration, probably central in origin as seen through graphic records. The knee jerk reaction appears to be accentuated through methyl fluoroacetate until convulsions occur due to the irradiation of the stimuli being so facilitated. Nervous conduction is increased and the threshold stimulus lessened in the reflex arc of a spinal cat. Methyl fluoroacetate reduces the electric convulsive threshold about 10 times in rats. The difficulties of treatments are stressed as methyl fluoroacetate is both a powerful convulsant and a respiratory depressant, yet suggestions for treatment in man are made. Methyl fluoroacetate presents a serious hazard as a food and water contaminant in the case that it is used as a poison against rodents and other vermin, as it is not easily detected or destroyed and is equally toxic by mouth and by injection. | 1 | Biochemistry |
The diagnosis and the study of the properties of quark–gluon plasma can be undertaken using quarks not present in matter seen around us. The experimental and theoretical work relies on the idea of strangeness enhancement. This was the first observable of quark–gluon plasma proposed in 1980 by Johann Rafelski and Rolf Hagedorn. Unlike the up and down quarks, strange quarks are not brought into the reaction by the colliding nuclei. Therefore, any strange quarks or antiquarks observed in experiments have been "freshly" made from the kinetic energy of colliding nuclei, with gluons being the catalyst. Conveniently, the mass of strange quarks and antiquarks is equivalent to the temperature or energy at which protons, neutrons and other hadrons dissolve into quarks. This means that the abundance of strange quarks is sensitive to the conditions, structure and dynamics of the deconfined matter phase, and if their number is large it can be assumed that deconfinement conditions were reached. An even stronger signature of strangeness enhancement is the highly enhanced production of strange antibaryons. An early comprehensive review of strangeness as a signature of QGP was presented by Koch, Müller and Rafelski, which was recently updated. The abundance of produced strange anti-baryons, and in particular anti-omega , allowed to distinguish fully deconfined large QGP domain from transient collective quark models such as the color rope model proposed by Biró, Nielsen and Knoll. The relative abundance of resolves questions raised by the canonical model of strangeness enhancement. | 7 | Physical Chemistry |
The Beer-Lambert law is commonly applied to chemical analysis measurements to determine the concentration of chemical species that absorb light. It is often referred to as Beer's law. In physics, the Bouguer–Lambert law is an empirical law which relates the extinction or attenuation of light to the properties of the material through which the light is travelling. It had its first use in astronomical extinction. The fundamental law of extinction (the process is linear in the intensity of radiation and amount of radiatively active matter, provided that the physical state is held constant) is sometimes called the Beer-Bouguer-Lambert law or the Bouguer-Beer-Lambert law or merely the extinction law. The extinction law is also used in understanding attenuation in physical optics, for photons, neutrons, or rarefied gases. In mathematical physics, this law arises as a solution of the BGK equation. | 7 | Physical Chemistry |
Phosphate is used in fertilisers. Immense quantities of phosphate rock or phosphorite occur in sedimentary shelf deposits, ranging in age from the Proterozoic to currently forming environments. Phosphate deposits are thought to be sourced from the skeletons of dead sea creatures which accumulated on the seafloor. Similar to iron ore deposits and oil, particular conditions in the ocean and environment are thought to have contributed to these deposits within the geological past.
Phosphate deposits are also formed from alkaline igneous rocks such as nepheline syenites, carbonatites, and associated rock types. The phosphate is, in this case, contained within magmatic apatite, monazite, or other rare-earth phosphates. | 9 | Geochemistry |
The mitochondria-associated ER membrane (MAM) is another structural element that is increasingly recognized for its critical role in cellular physiology and homeostasis. Once considered a technical snag in cell fractionation techniques, the alleged ER vesicle contaminants that invariably appeared in the mitochondrial fraction have been re-identified as membranous structures derived from the MAM—the interface between mitochondria and the ER. Physical coupling between these two organelles had previously been observed in electron micrographs and has more recently been probed with fluorescence microscopy. Such studies estimate that at the MAM, which may comprise up to 20% of the mitochondrial outer membrane, the ER and mitochondria are separated by a mere 10–25 nm and held together by protein tethering complexes.
Purified MAM from subcellular fractionation is enriched in enzymes involved in phospholipid exchange, in addition to channels associated with Ca signaling. These hints of a prominent role for the MAM in the regulation of cellular lipid stores and signal transduction have been borne out, with significant implications for mitochondrial-associated cellular phenomena, as discussed below. Not only has the MAM provided insight into the mechanistic basis underlying such physiological processes as intrinsic apoptosis and the propagation of calcium signaling, but it also favors a more refined view of the mitochondria. Though often seen as static, isolated powerhouses hijacked for cellular metabolism through an ancient endosymbiotic event, the evolution of the MAM underscores the extent to which mitochondria have been integrated into overall cellular physiology, with intimate physical and functional coupling to the endomembrane system. | 1 | Biochemistry |
Plants express the mechanistic target of rapamycin (mTOR) and have a TOR kinase complex. In plants, only the TORC1 complex is present unlike that of mammalian target of rapamycin which also contains the TORC2 complex. Plant species have TOR proteins in the protein kinase and FKBP-rapamycin binding (FRB) domains that share a similar amino acid sequence to mTOR in mammals.
Role of mTOR in plants
The TOR kinase complex has been known for having a role in the metabolism of plants. The TORC1 complex turns on when plants are living the proper environmental conditions to survive. Once activated, plant cells undergo particular anabolic reactions. These include plant development, translation of mRNA and the growth of cells within the plant. However, the TORC1 complex activation stops catabolic processes such as autophagy from occurring. TOR kinase signaling in plants has been found to aid in senescence, flowering, root and leaf growth, embryogenesis, and the meristem activation above the root cap of a plant. mTOR is also found to be highly involved in developing embryo tissue in plants. | 1 | Biochemistry |
A not often used definition of glaze is the highly sintered compacted oxide layer formed due to the sliding of either two metallic surfaces (or sometimes a metal surface and ceramic surface) at high temperatures (normally several hundred degrees Celsius) in oxidizing conditions. The sliding or tribological action generates oxide debris that can be compacted against one or both sliding surfaces and, under the correct conditions of load, sliding speed and oxide chemistry as well as (high) temperature, sinter together to form a glaze layer. The glaze formed in such cases is actually a crystalline oxide, with a very small crystal or grain size having been shown to approach nano-scale levels. Such glaze layers were originally thought to be amorphous oxides of the same form as ceramic glazes, hence the name glaze is still currently used.
Such glazes have attracted limited attention due to their ability to protect the metallic surfaces on which they may form, from wear under the high temperature conditions in which they are generated. This high temperature wear protection allows potential use at temperatures beyond the range of conventional hydrocarbon-based, silicone-based or even solid lubricants such as molybdenum disulfide (the latter useful up to about short term). Once they form, little further damage occurs unless there is a dramatic change in sliding conditions.
Such glazes work by providing a mechanically resistant layer, which prevents direct contact between the two sliding surfaces. For example, when two metals slide against each other, there can be a high degree of adhesion between the surfaces. The adhesion may be sufficient to result in metallic transfer from one surface to the other (or removal and ejection of such material) - effectively adhesive wear (also referred to as severe wear). With the glaze layer present, such severe adhesive interactions cannot occur and wear may be greatly reduced. The continued generation of oxidized debris during the more gradual wear that results (entitled mild wear) can sustain the glaze layer and maintain this low wear regime.
However, their potential application has been hampered as they have only successfully been formed under the very sliding conditions where they are meant to offer protection. A limited amount of sliding damage (referred to as run in wear - actually a brief period of adhesive or severe wear) needs to occur before the oxides are generated and such glaze layers can form. Efforts at encouraging their early formation have met with very limited success, and the damage inflicted during the run in period is one factor preventing this technique being used for practical applications.
As oxide generated is effectively the result of the tribochemical decay of one or both of the metallic (or ceramic) surfaces in contact, the study of compacted oxide layer glazes is sometimes referred to as part of the more general field of high temperature corrosion.
The generation of oxides during high temperature sliding wear does not automatically lead to the production of a compacted oxide layer glaze. Under certain conditions (potentially due to non-ideal conditions of sliding speed, load, temperature or oxide chemistry / composition), the oxide may not sinter together and instead the loose oxide debris may assist or enhance the removal of material by abrasive wear. A change in conditions may also see a switch from the formation of a loose, abrasive oxide to the formation of wear protective compacted oxide glaze layers and vice versa, or even the reappearance of adhesive or severe wear. Due to the complexities of the conditions controlling the types of wear observed, there have been a number of attempts to map types of wear with reference to sliding conditions in order to help better understand and predict them. | 8 | Metallurgy |
Amoxicillin is recommended by the World Health Organization for the treatment of infants with signs and symptoms of pneumonia in resource-limited situations when the parents are unable or unwilling to accept hospitalization of the child. Amoxicillin in combination with gentamicin is recommended for the treatment of infants with signs of other severe infections when hospitalization is not an option. | 4 | Stereochemistry |
While the sequence that constitutes the 3′-UTR contributes greatly to gene expression, the structural characteristics of the 3′-UTR also play a large role. In general, longer 3′-UTRs correspond to lower expression rates since they often contain more miRNA and protein binding sites that are involved in inhibiting translation. Human transcripts possess 3′-UTRs that are on average twice as long as other mammalian 3′-UTRs. This trend reflects the high level of complexity involved in human gene regulation. In addition to length, the secondary structure of the 3′-untranslated region also has regulatory functions. Protein factors can either aid or disrupt folding of the region into various secondary structures. The most common structure is a stem-loop, which provides a scaffold for RNA binding proteins and non-coding RNAs that influence expression of the transcript. | 1 | Biochemistry |
In order to achieve noticeable material strengthening via solution strengthening, one should alloy with solutes of higher shear modulus, hence increasing the local shear modulus in the material. In addition, one should alloy with elements of different equilibrium lattice constants. The greater the difference in lattice parameter, the higher the local stress fields introduced by alloying.
Alloying with elements of higher shear modulus or of very different lattice parameters will increase the stiffness and introduce local stress fields respectively. In either case, the dislocation propagation will be hindered at these sites, impeding plasticity and increasing yield strength proportionally with solute concentration.
Solid solution strengthening depends on:
* Concentration of solute atoms
* Shear modulus of solute atoms
* Size of solute atoms
* Valency of solute atoms (for ionic materials)
For many common alloys, rough experimental fits can be found for the addition in strengthening provided in the form of:
where is a solid solution strengthening coefficient and is the concentration of solute in atomic fractions.
Nevertheless, one should not add so much solute as to precipitate a new phase. This occurs if the concentration of the solute reaches a certain critical point given by the binary system phase diagram. This critical concentration therefore puts a limit to the amount of solid solution strengthening that can be achieved with a given material. | 8 | Metallurgy |
Wet storage stain, more commonly known as white rust or white corrosion, is a type of zinc corrosion. It is called wet storage stain because it occurs when a fresh zinc surface is stored in a wet environment with limited oxygen and carbon dioxide sources; the restriction in air is usually due to the items being stacked on one another or otherwise stored in close quarters. This type of corrosion does not usually occur to zinc surfaces that have had time to form their normal layers of corrosion protection. | 8 | Metallurgy |
As mining techniques and the price of minerals improve, it is not unusual for tailings to be reprocessed using new methods, or more thoroughly with old methods, to recover additional minerals. Extensive tailings dumps of Kalgoorlie / Boulder in Western Australia were re-processed profitably in the 1990s by KalTails Mining.
A machine called the PET4K Processing Plant has been used in a variety of countries for the past 20 years to remediate contaminated tailings. | 8 | Metallurgy |
The production of an amorphous metal can be achieved by rapidly cooling the liquid alloy to avoid forming a crystal structure. This is traditionally done using melt spinning, which produces a 0.5–125 mm wide strip with a thickness of 20–50 μm. After cooling, the metal can be made into parts or preforms by cutting, stamping, etching, or other methods. | 8 | Metallurgy |
A Web of Science search for the term multiferroic yields the year 2000 paper "Why are there so few magnetic ferroelectrics?" from N. A. Spaldin (then Hill) as the earliest result. This work explained the origin of the contraindication between magnetism and ferroelectricity and proposed practical routes to circumvent it, and is widely credited with starting the modern explosion of interest in multiferroic materials. The availability of practical routes to creating multiferroic materials from 2000 stimulated intense activity. Particularly key early works were the discovery of large ferroelectric polarization in epitaxially grown thin films of magnetic BiFeO, the observation that the non-collinear magnetic ordering in orthorhombic TbMnO and TbMnO causes ferroelectricity, and the identification of unusual improper ferroelectricity that is compatible with the coexistence of magnetism in hexagonal manganite YMnO. The graph to the right shows in red the number of papers on multiferroics from a Web of Science search until 2008; the exponential increase continues today. | 7 | Physical Chemistry |
* The log-normal distribution is often used to approximate the particle size distribution of aerosols, aquatic particles and pulverized material.
* The Weibull distribution or Rosin–Rammler distribution is a useful distribution for representing particle size distributions generated by grinding, milling and crushing operations.
* The log-hyperbolic distribution was proposed by Bagnold and Barndorff-Nielsen to model the particle-size distribution of naturally occurring sediments. This model suffers from having non-unique solutions for a range of probability coefficients.
* The skew log-Laplace model was proposed by Fieller, Gilbertson and Olbricht as a simpler alternative to the log-hyperbolic distribution. | 7 | Physical Chemistry |
A major bulk of work in the synthesis of lovastatin was done by M. Hirama in the 1980s.
Hirama synthesized compactin and used one of the intermediates to follow a different path to get to lovastatin. The synthetic sequence is shown in the schemes below. The γ-lactone was synthesized using Yamada methodology starting with glutamic acid. Lactone opening was done using lithium methoxide in methanol and then silylation to give a separable mixture of the starting lactone and the silyl ether. The silyl ether on hydrogenolysis followed by Collins oxidation gave the aldehyde. Stereoselective preparation of (E,E)-diene was accomplished by addition of trans-crotyl phenyl sulfone anion, followed by quenching with AcO and subsequent reductive elimination of sulfone acetate. Condensation of this with lithium anion of dimethyl methylphosphonate gave compound 1. Compound 2 was synthesized as shown in the scheme in the synthetic procedure. Compounds 1 and 2 were then combined using 1.3 eq sodium hydride in THF followed by reflux in chlorobenzene for 82 hr under nitrogen to get the enone 3.
Simple organic reactions were used to get to lovastatin as shown in the scheme. | 0 | Organic Chemistry |
In atmospheric radiation, Chandrasekhars H-function appears as the solutions of problems involving scattering, introduced by the Indian American astrophysicist Subrahmanyan Chandrasekhar. The Chandrasekhars H-function defined in the interval , satisfies the following nonlinear integral equation
where the characteristic function is an even polynomial in satisfying the following condition
If the equality is satisfied in the above condition, it is called conservative case, otherwise non-conservative. Albedo is given by . An alternate form which would be more useful in calculating the H function numerically by iteration was derived by Chandrasekhar as,
In conservative case, the above equation reduces to | 7 | Physical Chemistry |
* Acid value
* Bromine number
* Epoxy value
* Hydroxyl value
* Iodine value
* Peroxide value
* Saponification value | 3 | Analytical Chemistry |
Single photon detector used in time-domain diffuse optics require not only a high photon detection efficiency in the wavelength range of optical window, but also a large active area as well as large numerical aperture (N.A.) to maximize the overall light collection efficiency. They also require narrow timing response and a low noise background.
Traditionally, fiber coupled photomultiplier tubes (PMT) have been the detector of choice for diffuse optical measurements, thanks mainly due to the large active area, low dark count and excellent timing resolution. However, they are intrinsically bulky, prone to electromagnetic disturbances and they have a quite limited spectral sensitivity. Moreover, they require a high biasing voltage and they are quite expensive. Single photon avalanche diodes have emerged as an alternative to PMTS. They are low cost, compact and can be placed in contact, while needing a much lower biasing voltage. Also, they offer a wider spectral sensitivity and they are more robust to bursts of light. However, they have a much lower active area and hence a lower photon collection efficiency and a larger dark count. Silicon photomultipliers (SiPM) are an arrays of SPADs with a global anode and a global cathode and hence have a larger active area while maintaining all the advantages offered by SPADs. However, they suffer from a larger dark count and a broader timing response. | 7 | Physical Chemistry |
Acylsilanes can be synthesized by treating acyl anion equivalents with silyl halides (typically trimethylsilyl chloride, tmsCl). Silylation of 2-lithio-1,3-dithiane, followed by hydrolysis of the dithioacetal group with mercury(II) chloride. Analogous methods has also been used to produce acylgermanes.
Several approches to acylsilanes start with carboxylic acid derivatives. Esters undergo reductive silylation en route to acylsilanes:
Tertiary amides react with silyl lithium reagents:
Acid chlorides are converted using hexamethyldisilane:
Some acyl silanes are prepared by oxidation of a suitable silanes. | 0 | Organic Chemistry |
When absorption was measured against wavelength at various pH values, the changes at wavelength 408 nm and 470 nm yielded a sigmoidal line with a midpoint at 5.1. This indicated that the absorbance at these two wavelengths depends upon the ionization of the chromophoric portion of TNP-ATP and is unaffected by ionization of ATP. Although this ionization constant of 5.1 is not in physiological range, it has been shown that the absorbance of TNP-ATP is sensitive enough to detect changes due to slight shifts in neutral pH. Spectroscopic superposition indicated TNP-ATP’s isosbestic point to be 339 nm. | 7 | Physical Chemistry |
Currently the biosynthesis of rhodoquinone (RQ) is still being debated, but there are two main biosynthetic pathways that are being researched. The first pathway requires the organism to produce ubiquinone (UQ) before the amino group can be added onto the quinone ring. The second pathway allows RQ to be synthesized without any UQ being present by using tryptophan metabolites instead.
In the case of the prokaryotic organism R. rubrum, RQ has been shown to be synthesized by addition of an amino group to a pre-existing UQ; thus UQ needs to be present as a precursor before RQ can be made. Figure 1 shows the biosynthesis of UQ in yeast and E. coli where ‘n’ represents the number of isoprene units between various organisms. Dimethylallyl diphosphate A and isopentyl diphosphate B come together to form polyisoprenyl diphosphate C. With the addition of p-hydroxybenzoic acid, the product that arises is 3-polyprenyl-4-hydroxybenzoic acid D. The next three steps of synthesis varies between different organisms, but molecule E is made across all organisms and through oxidation, demethyldemethoxyubiquinone (DDMQ) is eventually formed. RQ has been theorized to be synthesized from DDMQn, DMQn, DMeQn, or UQn, as shown with the dashed arrows. Recent studies have shown that Path 4 - RQ biosynthesis via UQ, is the favored route. It has been further shown that the gene rquA is required for the biosynthesis of RQ in R. rubrum, and that RquA catalyzes the conversion of UQ to RQ. The RquA protein uses S-adenosyl-L-methionine as the amino donor to convert UQ to RQ in an unusual Mn(II)-catalyzed reaction.
Research in C. elegans has shown an alternative path for production of RQ. Even after knocking out all UQ production, RQ is still present within those mutant strains. Based on this data, RQ production is not solely based on UQ-like molecules and instead can be made via tryptophan metabolites. Therefore, the amino group that is added in late stages of RQ biosynthesis in rquA-containing species is instead present throughout intermediate stages of RQ biosynthesis in C. elegans. With this proposed biosynthesis, the kynurenine pathway still needs to be upregulated, and activity from certain genes like kynu-1 which encodes for the KYNU-1 enzyme that catalyzes production of 3-hydroxy-L-kynurenine to 3-hydroxyanthranilic acid, needs to be upheld. Recent work has revealed that alternative splicing of the coq-2 polyprenyltransferase gene controls the level of RQ in animals. Animals that produce RQ (e.g. C. elegans and helminth parasites) contain both COQ-2 protein isoforms (COQ-2a and COQ-2e), and COQ-2e catalyzes prenylation of 3-hydroxyanthranilic acid (instead of p-hydroxybenzoic acid) which leads to RQ. | 1 | Biochemistry |
The method combines the reactions of copper ions with the peptide bonds under alkaline conditions (the Biuret test) with the oxidation of aromatic protein residues. The Lowry method is based on the reaction of Cu, produced by the oxidation of peptide bonds, with Folin–Ciocalteu reagent (a mixture of phosphotungstic acid and phosphomolybdic acid in the Folin–Ciocalteu reaction). The reaction mechanism is not well understood, but involves reduction of the Folin–Ciocalteu reagent and oxidation of aromatic residues (mainly tryptophan, also tyrosine). Experiments have shown that cysteine is also reactive to the reagent. Therefore, cysteine residues in protein probably also contribute to the absorbance seen in the Lowry assay. The result of this reaction is an intense blue molecule known as heteropolymolybdenum Blue. The concentration of the reduced Folin reagent (heteropolymolybdenum Blue) is measured by absorbance at 660 nm. As a result, the total concentration of protein in the sample can be deduced from the concentration of tryptophan and tyrosine residues that reduce the Folin–Ciocalteu reagent.
The method was first proposed by Lowry in 1951. The bicinchoninic acid assay and the Hartree–Lowry assay are subsequent modifications of the original Lowry procedure. | 1 | Biochemistry |
In order to study gas phase interstellar chemistry, it is convenient to distinguish two types of interstellar clouds: diffuse clouds, with T=30-100 K, and n=10–1000 cm, and dense clouds with T=10-30K and density n=-. Ion chemical routes in both dense and diffuse clouds have been established for some works (Hartquist 1990). | 2 | Environmental Chemistry |
In proteomics, MALDI is used for the rapid identification of proteins isolated by using gel electrophoresis: SDS-PAGE, size exclusion chromatography, affinity chromatography, strong/weak ion exchange, isotope coded protein labeling (ICPL), and two-dimensional gel electrophoresis. Peptide mass fingerprinting is the most popular analytical application of MALDI-TOF mass spectrometers. MALDI TOF/TOF mass spectrometers are used to reveal amino acid sequence of peptides using post-source decay or high energy collision-induced dissociation (further use see mass spectrometry).
MALDI-TOF have been used to characterise post-translational modifications. For example, it has been widely applied to study protein methylation and demethylation. However, care must be taken when studying post-translational modifications by MALDI-TOF. For example, it has been reported that loss of sialic acid has been identified in papers when dihydroxybenzoic acid (DHB) has been used as a matrix for MALDI MS analysis of glycosylated peptides. Using sinapinic acid, 4-HCCA and DHB as matrices, S. Martin studied loss of sialic acid in glycosylated peptides by metastable decay in MALDI/TOF in linear mode and reflector mode. A group at Shimadzu Corporation derivatized the sialic acid by an amidation reaction as a way to improve detection sensitivity and also demonstrated that ionic liquid matrix reduces a loss of sialic acid during MALDI/TOF MS analysis of sialylated oligosaccharides. THAP, DHAP, and a mixture of 2-aza-2-thiothymine and phenylhydrazine have been identified as matrices that could be used to minimize loss of sialic acid during MALDI MS analysis of glycosylated peptides. It has been reported that a reduction in loss of some post-translational modifications can be accomplished if IR MALDI is used instead of UV MALDI.
Besides proteins, MALDI-TOF has also been applied to study lipids. For example, it has been applied to study the catalytic reactions of phospholipases. In addition to lipids, oligonucleotides have also been characterised by MALDI-TOF. For example, in molecular biology, a mixture of 5-methoxysalicylic acid and spermine can be used as a matrix for oligonucleotides analysis in MALDI mass spectrometry, for instance after oligonucleotide synthesis. | 1 | Biochemistry |
Vanillin has been used as a chemical intermediate in the production of pharmaceuticals, cosmetics, and other fine chemicals. In 1970, more than half the world's vanillin production was used in the synthesis of other chemicals. As of 2016, vanillin uses have expanded to include perfumes, flavoring and aromatic masking in medicines, various consumer and cleaning products, and livestock foods. | 0 | Organic Chemistry |
Aniline reacts with acyl chlorides or carboxylic anhydrides to give anilides. For example, reaction of aniline with acetyl chloride provides acetanilide (). At high temperatures, aniline and carboxylic acids react to give anilides. | 0 | Organic Chemistry |
mEH is widely expressed in virtually all mammalian cells as an endoplasmic reticulum-bound (i.e. microsomal-bound) enzyme with its C terminal catalytic domain facing the cytoplasm; in some tissues, however, mEH has been found bound to the cell surface plasma membrane with its catalytic domain facing the extracellular space. The primary function of mEH is to convert potentially toxic xenobiotics and other compounds that possess epoxide residues (which is often due to their initial metabolism by cytochrome P450 enzymes to epoxides) to diols. Epoxides are highly reactive electrophilic compounds that form adducts with DNA and proteins and also cause strand breaks in DHA; in consequence, epoxides can cause gene mutations, cancer, and the inactivation of critical proteins. The diols thereby formed are usually not toxic or far less toxic than their epoxide predecessors, are readily further metabolized, and ultimately excreted in the urine. mEH also metabolizes certain epoxides of polyunsaturated fatty acids such as the epoxyeicosatrienoic acids (EETs) but its activity in doing this is far less than that of sEH; mEH therefore may play a minor role, compared to sEH, in limiting the bioactivity of these cell signaling compounds (see microsomal epoxide hydrolase). | 1 | Biochemistry |
The stereochemical structure of a cyclic monosaccharide can be represented in a Haworth projection. In this diagram, the α-isomer for the pyranose form of a -aldohexose has the −OH of the anomeric carbon below the plane of the carbon atoms, while the β-isomer has the −OH of the anomeric carbon above the plane. Pyranoses typically adopt a chair conformation, similar to that of cyclohexane. In this conformation, the α-isomer has the −OH of the anomeric carbon in an axial position, whereas the β-isomer has the −OH of the anomeric carbon in equatorial position (considering -aldohexose sugars). | 0 | Organic Chemistry |
Metallacycles often arise by cyclization of arene-containing donor ligands, e.g. aryl phosphines and amines. An early example is the cyclization of IrCl(PPh) to give the corresponding Ir(III) hydride containing a four-membered IrPCC ring. Palladium(II) and platinum(II) have long been known to ortho-metalate aromatic ligands such as azobenzene, benzylamines, and 2-phenylpyridines. These reactions are strongly influenced by substituent effects, including the Thorpe-Ingold effect. Ligands that lack aryl substituents will sometimes cyclometalate via activation of methyl groups, an early example being the internal oxidative addition of methylphosphine ligands. Metallacycle formation interferes with intermolecular C-H activation processes. For this reason, specialized "pincer ligands" ligands have been developed that resist ortho-metalation. | 0 | Organic Chemistry |
The waste discharge can be sent into incineration plant, where the organic solid undergoes combustion process. The combustion process produces heat that can be used to generate electricity. | 3 | Analytical Chemistry |
Particulate pollution is pollution of an environment that consists of particles suspended in some medium. There are three primary forms: atmospheric particulate matter, marine debris, and space debris. Some particles are released directly from a specific source, while others form in chemical reactions in the atmosphere. Particulate pollution can be derived from either natural sources or anthropogenic processes. | 2 | Environmental Chemistry |
In organic chemistry, a hemiaminal (also carbinolamine) is a functional group or type of chemical compound that has a hydroxyl group and an amine attached to the same carbon atom: . R can be hydrogen or an alkyl group. Hemiaminals are intermediates in imine formation from an amine and a carbonyl by alkylimino-de-oxo-bisubstitution. Hemiaminals can be viewed as a blend of aminals and geminal diol. They are a special case of amino alcohols. | 0 | Organic Chemistry |
Continuous flow analysis (CFA) is a general term that encompasses both segmented flow analysis (SFA) and flow injection analysis (FIA). In segmented flow analysis, a continuous stream of material is divided by air bubbles into discrete segments in which chemical reactions occur. The continuous stream of liquid samples and reagents are combined and transported in tubing and mixing coils. The tubing passes the samples from one apparatus to the other with each apparatus performing different functions, such as distillation, dialysis, extraction, ion exchange, heating, incubation, and subsequent recording of a signal. An essential principle of SFA is the introduction of air bubbles. The air bubbles segment each sample into discrete packets and act as a barrier between packets to prevent cross contamination as they travel down the length of the glass tubing. The air bubbles also assist mixing by creating turbulent flow (bolus flow), and provide operators with a quick and easy check of the flow characteristics of the liquid. Samples and standards are treated in an exactly identical manner as they travel the length of the fluidic pathway, eliminating the necessity of a steady state signal, however, since the presence of bubbles create an almost square wave profile, bringing the system to steady state does not significantly decrease throughput ( third generation CFA analyzers average 90 or more samples per hour) and is desirable in that steady state signals (chemical equilibrium) are more accurate and reproducible. Reaching steady state enables lowest detection limits to be reached.
A continuous segmented flow analyzer (SFA) consists of different modules including a sampler, pump, mixing coils, optional sample treatments (dialysis, distillation, heating, etc.), a detector, and data generator. Most continuous flow analyzers depend on color reactions using a flow through photometer, however, also methods have been developed that use ISE, flame photometry, ICAP, fluorometry, and so forth. | 3 | Analytical Chemistry |
Myristoylation is a lipidation modification where a myristoyl group, derived from myristic acid, is covalently attached by an amide bond to the alpha-amino group of an N-terminal glycine residue. Myristic acid is a 14-carbon saturated fatty acid (14:0) with the systematic name of n-tetradecanoic acid. This modification can be added either co-translationally or post-translationally. N-myristoyltransferase (NMT) catalyzes the myristic acid addition reaction in the cytoplasm of cells. This lipidation event is the most common type of fatty acylation and is present in many organisms, including animals, plants, fungi, protozoans and viruses. Myristoylation allows for weak protein–protein and protein–lipid interactions and plays an essential role in membrane targeting, protein–protein interactions and functions widely in a variety of signal transduction pathways. | 1 | Biochemistry |
Also, alkaline lysis is sometimes used to extract plant genetic material. The plant cells are subjected to a strongly alkaline solution containing a detergent (usually a zwitterionic or nonionic detergent such as Tween 20), and the mixture is incubated at high temperature. This method is not used as often due to the sodium hydroxide's tendency to damage genetic material, reducing DNA fragment size. | 1 | Biochemistry |
In mammals, propionyl-CoA is converted to (S)-methylmalonyl-CoA by propionyl-CoA carboxylase, a biotin-dependent enzyme also requiring bicarbonate and ATP.
This product is converted to (R)-methylmalonyl-CoA by methylmalonyl-CoA racemase.
(R)-Methylmalonyl-CoA is converted to succinyl-CoA, an intermediate in the tricarboxylic acid cycle, by methylmalonyl-CoA mutase, an enzyme requiring
cobalamin to catalyze the carbon-carbon bond migration.
The methylmalonyl-CoA mutase mechanism begins with the cleavage of the bond between the 5 - of 5-deoxyadenosyl and the cobalt, which is in its 3+ oxidation state (III), which produces a 5'-deoxyadenosyl radical and cobalamin in the reduced Co(II) oxidation state.
Next, this radical abstracts a hydrogen atom from the methyl group of methylmalonyl-CoA, which generates a methylmalonyl-CoA radical. It is believed that this radical forms a carbon-cobalt bond to the coenzyme, which is then followed by the rearrangement of the substrates carbon skeleton, thus producing a succinyl-CoA radical. This radical then goes on to abstract a hydrogen from the previously produced 5-deoxyadenosine, again creating a deoxyadenosyl radical, which attacks the coenzyme to reform the initial complex.
A defect in methylmalonyl-CoA mutase enzyme results in methylmalonic aciduria, a dangerous disorder that causes a lowering of blood pH. | 1 | Biochemistry |
Some drug molecules are chiral, and the enantiomers have different effects on biological entities. They can be sold as one enantiomer or as a racemic mixture. Examples include thalidomide, ibuprofen, cetirizine and salbutamol. A well known drug that has different effects depending on its ratio of enantiomers is amphetamine. Adderall is an unequal mixture of both amphetamine enantiomers. A single Adderall dose combines the neutral sulfate salts of dextroamphetamine and amphetamine, with the dextro isomer of amphetamine saccharate and D/L-amphetamine aspartate monohydrate. The original Benzedrine was a racemic mixture, and isolated dextroamphetamine was later introduced to the market as Dexedrine. The prescription analgesic tramadol is also a racemate.
In some cases (e.g., ibuprofen and thalidomide), the enantiomers interconvert or racemize in vivo. This means that preparing a pure enantiomer for medication is largely pointless. However, sometimes samples containing pure enantiomers may be made and sold at a higher cost in cases where the use requires specifically one isomer (e.g., for a stereospecific reagent); compare omeprazole and esomeprazole. Moving from a racemic drug to a chiral specific drug may be done for a better safety profile or an improved therapeutic index. This process is called chiral switching and the resulting enantiopure drug is called a chiral switch. As examples, esomeprazole is a chiral switch of (±)-omeprazole and levocetirizine is a chiral switch of (±)-cetirizine.
While often only one enantiomer of the drug may be active, there are cases in which the other enantiomer is harmful, like salbutamol and thalidomide. The (R) enantiomer of thalidomide is effective against morning sickness, while the (S) enantiomer is teratogenic, causing birth defects. Since the drug racemizes, the drug cannot be considered safe for use by women of child-bearing age, and its use is tightly controlled when used for treating other illness.
Methamphetamine is available by prescription under the brand name Desoxyn. The active component of Desoxyn is dextromethamphetamine hydrochloride. This is the right-handed isomer of methamphetamine. The left-handed isomer of methamphetamine, levomethamphetamine, is an OTC drug that is less centrally-acting and more peripherally-acting. Methedrine during the 20th century was a 50:50 racemic mixture of both methamphetamine isomers (levo and dextro). | 4 | Stereochemistry |
* Siddiqui B.S., Afshan F., Rasheed M., Kardar N., Begum S., Faizi S. (2002) Medicinal Plants - A Source of Potential Chemicals of Diverse Structures and Biological Activity. In: Şener B. (eds) Biodiversity. Springer, Boston, MA. | 0 | Organic Chemistry |
The formulation of a coating depends primarily on the function required of the coating and also on aesthetics required such as color and gloss. The four primary ingredients are the resin (or binder), solvent which maybe water (or solventless), pigment(s) and additives. Research is ongoing to remove heavy metals from coating formulations completely.
For example on the basis of experimental and epidemiological evidence, it has been classified by the IARC (International Agency for Research on Cancer) as a human carcinogen by inhalation (class I) ([https://www.sicurezza.com/ispesl ISPESL], 2008). | 8 | Metallurgy |
Sequence reads are not perfect, so the accuracy of each base in the sequence needs to be estimated for downstream analyses. Raw data is examined to ensure: quality scores for base calls are high, the GC content matches the expected distribution, short sequence motifs (k-mers) are not over-represented, and the read duplication rate is acceptably low. Several software options exist for sequence quality analysis, including FastQC and FaQCs. Abnormalities may be removed (trimming) or tagged for special treatment during later processes. | 1 | Biochemistry |
As one of a range of ferric ferrocyanides, blue billy is a compound of iron, carbon and nitrogen. Processes producing ammonia or cyanides in the presence of iron may give rise to it.
Most commonly it is found around old gasworks. Part of the gas production process, producing town gas by the gasification of coal, involves a liquid bubbler scrubber to remove ammonia compounds, including ammonium cyanide compounds, from the raw gas. If left untreated, these could cause corrosion in gas pipework. A further process to make the gas less toxic by removing hydrogen sulphide and hydrogen cyanide, the purifier, passed the gas over trays of ferric oxide as bog iron ore, similar to red rust, which removed sulfur and cyanide compounds and became spent in this process. These could be arranged as either a wet or dry process, where the gas produced was bubbled through water or passed through a box of a dampened absorber material such as wood shavings. These cheap materials were consumed and discarded periodically. Waste tips where they were dumped, or even storage areas where they remained for a time and released leachates, are all common places to find billy deposits forming.
Early gasworks, from 1812, used Samuel Cleggs wet lime purification process which produced large quantities of blue billy. A later dry lime process was developed, using moist hydrated lime, in part to avoid the problem of disposing of the blue billy waste. This process produced a waste known as foul lime'. Later the bog iron process supplemented the dry lime. Although the overall compositions of both spent oxide and foul lime are similar, with 6% cyanides and 36-60% free sulfur, the foul lime is far easier to dispose of. It is broken down by being left in open piles and allowed to weather, leaving a lime-rich residue which could be sold and used as a fertiliser. Bog iron wastes were also weathered in open piles, which allowed them to be regenerated for use four or five times, until they reached a final sulfur content of 50–60%. This ferrous sulphate was commercially saleable for acid production, and although the economics of this were only marginally profitable, it avoided disposal costs.
Coke works, where a similar process is carried out primarily to manufacture coke, either for steelmaking or as a smokeless fuel, are also common sites for its occurrence. Coke plants were noted for their iron wastes being more prone to contain ferrocyanides, not merely sulphates. If sufficiently concentrated, >5%, these would be commercially saleable.
If wastes are preserved in anoxic environments, the Prussian blue colour may not yet have developed. Exposing these to the air and allowing them to become oxidised lets the colour develop. When looking for blue billy as a way to indicate the extent of contamination, this time should be allowed for. | 2 | Environmental Chemistry |
In chemistry, dioxirane (systematically named dioxacyclopropane, also known as methylene peroxide or peroxymethane) is an organic compound with formula . The molecule consists of a ring with one methylene and two oxygen atoms. It is of interest as the smallest cyclic organic peroxide, but otherwise it is of little practical value. | 0 | Organic Chemistry |
Conformational study on neuromuscular blocking drugs is relatively new and developing. Traditional SAR studies do not specify environmental factors on molecules. Computer-based conformational searches assume that the molecules are in vacuo, which is not the case in vivo. Solvation models take into account the effect of a solvent on the conformation of the molecule. However, no system of solvation can mimic the effect of the complex fluid composition of the body.
The division of muscle relaxants to rigid and non-rigid is at most qualitative. The energy required for conformational changes may give a more precise and quantitative picture. Energy required for reducing onium head distance in the longer muscle relaxant chains may quantify their ability to bend and fit its receptive sites. Using computers it is possible to calculate the lowest energy state conformer and thus most populated and best representing the molecule. This state is referred to as the global minimum. The global minimum for some simple molecules can be discovered quite easily with certainty. Such as for decamethonium the straight line conformer is clearly the lowest energy state. Some molecules, on the other hand, have many rotatable bonds and their global minimum can only be approximated. | 1 | Biochemistry |
The U.S. National Ambient Air Quality Standards (NAAQS, pronounced ) are limits on atmospheric concentration of six pollutants that cause smog, acid rain, and other health hazards. Established by the United States Environmental Protection Agency (EPA) under authority of the Clean Air Act (42 U.S.C. 7401 et seq.), NAAQS is applied for outdoor air throughout the country.
The six criteria air pollutants (CAP), or criteria pollutants, for which limits are set in the NAAQS are ozone (O), atmospheric particulate matter (PM/PM), lead (Pb), carbon monoxide (CO), sulfur oxides (SO), and nitrogen oxides (NO). These are typically emitted from many sources in industry, mining, transportation, electricity generation and agriculture. In many cases they are the products of the combustion of fossil fuels or industrial processes.
The National Emissions Standards for Hazardous Air Pollutants cover many other chemicals, and require the maximum achievable reduction that the EPA determines is feasible. | 2 | Environmental Chemistry |
Beweries, et al., developed a light-driven "closed cycle of water splitting using ansa-titanocene(III/IV) triflate complexes". | 5 | Photochemistry |
Epic-seq hypothesizes that cfDNA fragments originating from active promoters, which are less shielded by nucleosomes and thus more susceptible to endonuclease cleavage, will display more erratic cleavage patterns compared to fragments from inactive promoters, which are better protected by nucleosomes. PFE is a variation of the Shannon Index, which is a quantitative measure for estimating diversity. In the context of Epic-seq, PFE calculates the diversity of cfDNA fragment lengths where both ends of the fragment are situated within the 2 kb flanking region of each genes TSS. The higher the PFE of a genes TSS, the more likely the gene is highly expressed. | 1 | Biochemistry |
Electrons are often removed from the electron transport chains to charge NADP with electrons, reducing it to NADPH. Like ATP synthase, ferredoxin-NADP reductase, the enzyme that reduces NADP, releases the NADPH it makes into the stroma, right where it is needed for the dark reactions.
Because NADP reduction removes electrons from the electron transport chains, they must be replaced—the job of photosystem II, which splits water molecules (HO) to obtain the electrons from its hydrogen atoms. | 5 | Photochemistry |
Synthesis of diacylglycerol begins with glycerol-3-phosphate, which is derived primarily from dihydroxyacetone phosphate, a product of glycolysis (usually in the cytoplasm of liver or adipose tissue cells). Glycerol-3-phosphate is first acylated with acyl-coenzyme A (acyl-CoA) to form lysophosphatidic acid, which is then acylated with another molecule of acyl-CoA to yield phosphatidic acid. Phosphatidic acid is then de-phosphorylated to form diacylglycerol.
Dietary fat is mainly composed of triglycerides. Because triglycerides cannot be absorbed by the digestive system, triglycerides must first be enzymatically digested into monoacylglycerol, diacylglycerol, or free fatty acids. Diacylglycerol is a precursor to triacylglycerol (triglyceride), which is formed in the addition of a third fatty acid to the diacylglycerol under the catalysis of diglyceride acyltransferase.
Since diacylglycerol is synthesized via phosphatidic acid, it will usually contain a saturated fatty acid at the C-1 position on the glycerol moiety and an unsaturated fatty acid at the C-2 position.
Diacylglycerol can be phosphorylated to phosphatidic acid by diacylglycerol kinase. | 1 | Biochemistry |
Electric fans used for ventilation may be powered by solar panels instead of mains current. This is an attractive option because once the capital costs of the solar panel have been covered, the resulting electricity is free. Also, electricity is always available when the sun is shining and the fan needs to run.
During the absence of electric power solar powered fan is operate the air flowing and maintain environmental condition.
A typical example uses a detached 10-watt, solar panel and is supplied with appropriate brackets, cables, and connectors. It can be used to ventilate up to of area and can move air at up to . Because of the wide availability of 12 V brushless DC electric motors and the convenience of wiring such a low voltage, such fans usually operate on 12 volts.
The detached solar panel is typically installed in the spot which gets most of the sunlight and then connected to the fan mounted as far as away. Other permanently-mounted and small portable fans include an integrated (non-detachable) solar panel. | 7 | Physical Chemistry |
Combustion, Explosion, and Shock Waves (Russian: Fizika Goreniya i Vzryva, Физика горения и взрыва) is the English-language translated version of the Russian peer-reviewed scientific journal, Fizika Goreniya i Vzryva. It covers the combustion of gases and materials, detonation processes, dispersal and transformation of substances, and shock-wave propagation. The editor-in-chief is Anatoly A. Vasil'ev. | 7 | Physical Chemistry |
Protein–protein signalling interactions pose suitable therapeutic targets due to their specificity and pervasiveness. The random drug discovery approach uses compound banks that comprise random chemical structures, and requires a high-throughput method to test these structures in their intended target.
The cell chosen for the investigation can be specifically engineered to mirror the molecular aspect that the investigator intends to study and then used to identify new human or animal therapeutics or anti-pest agents. | 1 | Biochemistry |
The Ruhrchemie/Rhone–Poulenc process (RCRPP) relies on a rhodium catalyst with water-soluble TPPTS as ligand (Kuntz Cornils catalyst) for the hydroformylation of propene. The tri-sulfonation of triphenylphosphane ligand provides hydrophilic properties to the organometallic complex. The catalyst complex carries nine sulfonate-groups and is highly soluble in water (about 1 kg L), but not in the emerging product phase. The water-soluble TPPTS is used in about 50-fold excess, whereby the leaching of the catalyst is effectively suppressed. Reactants are propene and syngas consisting of hydrogen and carbon monoxide in a ratio of 1.1:1. A mixture of butyraldehyde and isobutyraldehyde in the ratio 96:4 is generated with few by-products such as alcohols, esters and higher boiling fractions. The Ruhrchemie/Rhone-Poulenc-process is the first commercially available two-phase system in which the catalyst is present in the aqueous phase.
In the progress of the reaction an organic product phase is formed which is separated continuously by means of phase separation, wherein the aqueous catalyst phase remains in the reactor.
The process is carried out in a stirred tank reactor where the olefin and the syngas are entained from the bottom of the reactor through the catalyst phase under intensive stirring. The resulting crude aldehyde phase is separated at the top from the aqueous phase. The aqueous catalyst-containing solution is re-heated via a heat exchanger and pumped back into the reactor. The excess olefin and syngas is separated from the aldehyde phase in a stripper and fed back to the reactor. The generated heat is used for the generation of process steam, which is used for subsequent distillation of the organic phase to separate into butyraldehyde and isobutyraldehyde. Potential catalyst poisons coming from the synthesis gas migrate into the organic phase and removed from the reaction with the aldehyde. Thus there is no accumulation of catalyst poisons, and the elaborate fine purification of the syngas can be omitted.
A plant was built in Oberhausen in 1984, which was debottlenecked in 1988 and again in 1998 up to a production capacity of 500,000 t/a butanal. The conversion rate of propene is 98% and the selectivity to n-butanal is high. During the life time of a catalyst batch in the process less than 1 ppb rhodium is lost. | 0 | Organic Chemistry |
Small activating Ribonucleic acids (saRNAs) are small double-stranded RNAs (dsRNAs) that target gene promoters to induce transcriptional gene activation in a process known as RNA activation (RNAa).
Small dsRNAs, such as small interfering RNAs (siRNAs) and microRNAs (miRNAs), are known to be the trigger of an evolutionarily conserved mechanism known as RNA interference (RNAi). RNAi invariably leads to gene silencing via remodeling of chromatin to thereby suppress transcription, degrading complementary mRNA, or blocking protein translation. Later it was found that dsRNAs can also act to activate transcription and was thus designated saRNA. By targeting selected sequences in gene promoters, saRNAs induce target gene expression at the transcriptional/epigenetic level.
saRNAs are typically 21 nucleotides in length with a 2 nucleotide overhang at the 3 end of each strand, the same structure as a typical siRNA. To identify an saRNA that can activate a gene of interest, several saRNAs need to be designed within a 1- to 2-kb promoter region by following a set of rules and tested in cultured cells. In some reports, saRNAs are designed in such a way to target non-coding transcripts that overlap the promoter sequence of a protein coding gene. Both chemically synthesized saRNAs and saRNAs expressed as short hairpin RNA (shRNA) have been used in in vitro and in vivo' experiments.
An online resource for saRNAs has been developed ([https://bioinfo.imtech.res.in/manojk/sarna/ https://bioinfo.imtech.res.in/manojk/sarna/]) and published.
Therapeutic use of saRNAs have been suggested. They have been tested in animal models to treat bladder tumors,
liver carcinogenesis,
pancreatic cancer,
and erectile dysfunction.
In 2016, a phase I clinical trial involving advanced liver cancer patients was launched for the saRNA drug MTL-CEBPA. It aimed to complete in 2021. | 1 | Biochemistry |
Loss of heterozygosity (LOH) is a technique that can only be used to compare two samples from the same individual. LOH analysis is often used when identifying cancer-causing oncogenes in that one sample consists of (mutant) tumor DNA and the other (control) sample consists of genomic DNA from non-cancerous cells from the same individual. RFLPs and microsatellite markers provide patterns of DNA polymorphisms, which can be interpreted as residing in a heterozygous region or a homozygous region of the genome. Provided that all individuals are affected with the same disease resulting from a manifestation of a deletion of a single copy of the same gene, all individuals will contain one region where their control sample is heterozygous but the mutant sample is homozygous - this region will contain the disease gene. | 1 | Biochemistry |
Eco pickled surface technology has been tested and approved for use as a replacement for acid pickled steel by automotive manufacturers General Motors and Chrysler. The Eco Pickled Surface process was a finalist in the 2013 American Metal Market (AMM) Awards for Steel Excellence. | 8 | Metallurgy |
The Lotka–Volterra equations describe dynamics of the predator-prey systems. The rate of predation upon the prey is assumed to be proportional to the rate at which the predators and the prey meet; this rate is evaluated as xy, where x is the number of prey, y is the number of predator. This is a typical example of the law of mass action. | 7 | Physical Chemistry |
As a hydrogen storage alloy, LaNi can absorb hydrogen to form the hydride LaNiH (x≈6) when the pressure is slightly high and the temperature is low, or when the pressure decreases or the temperature increases, hydrogen can be released to form repeated absorption and release of hydrogen. But for the dehydrogenation process, because it is an endothermic reaction, in order to enable the reaction to proceed, the necessary energy must be added, otherwise the reaction will stop due to the decrease in temperature. | 8 | Metallurgy |
Combustion of fuels produces sulfur dioxide and nitric oxides. They are converted into sulfuric acid and nitric acid. | 2 | Environmental Chemistry |
Some old studies suggested that the ingestion of large doses of thiamine (vitamin B) could be effective as an oral insect repellent against mosquito bites. However, there is now conclusive evidence that thiamin has no efficacy against mosquito bites. Some claim that plants such as wormwood or sagewort, lemon balm, lemon grass, lemon thyme, and the mosquito plant (Pelargonium) will act against mosquitoes. However, scientists have determined that these plants are "effective" for a limited time only when the leaves are crushed and applied directly to the skin.
There are several, widespread, unproven theories about mosquito control, such as the assertion that vitamin B, in particular B (thiamine), garlic, ultrasonic devices or incense can be used to repel or control mosquitoes. Moreover, manufacturers of "mosquito repelling" ultrasonic devices have been found to be fraudulent, and their devices were deemed "useless" according to a review of scientific studies. | 1 | Biochemistry |
The values below are standard apparent reduction potentials for electro-biochemical half-reactions measured at 25 °C, 1 atmosphere and a pH of 7 in aqueous solution.
The actual physiological potential depends on the ratio of the reduced () and oxidized () forms according to the Nernst equation and the thermal voltage.
When an oxidizer () accepts a number z of electrons () to be converted in its reduced form (), the half-reaction is expressed as:
: + z →
The reaction quotient () is the ratio of the chemical activity (a) of the reduced form (the reductant, a) to the activity of the oxidized form (the oxidant, a). It is equal to the ratio of their concentrations (C) only if the system is sufficiently diluted and the activity coefficients (γ) are close to unity (a = γ C):
The Nernst equation is a function of and can be written as follows:
At chemical equilibrium, the reaction quotient of the product activity (a) by the reagent activity (a) is equal to the equilibrium constant () of the half-reaction and in the absence of driving force () the potential () also becomes nul.
The numerically simplified form of the Nernst equation is expressed as:
Where is the standard reduction potential of the half-reaction expressed versus the standard reduction potential of hydrogen. For standard conditions in electrochemistry (T = 25 °C, P = 1 atm and all concentrations being fixed at 1 mol/L, or 1 M) the standard reduction potential of hydrogen is fixed at zero by convention as it serves of reference. The standard hydrogen electrode (SHE), with [] = 1 M works thus at a pH = 0.
At pH = 7, when [] = 10 M, the reduction potential of differs from zero because it depends on pH.
Solving the Nernst equation for the half-reaction of reduction of two protons into hydrogen gas gives:
In biochemistry and in biological fluids, at pH = 7, it is thus important to note that the reduction potential of the protons () into hydrogen gas is no longer zero as with the standard hydrogen electrode (SHE) at 1 M (pH = 0) in classical electrochemistry, but that versus the standard hydrogen electrode (SHE).
The same also applies for the reduction potential of oxygen:
For , = 1.229 V, so, applying the Nernst equation for pH = 7 gives:
For obtaining the values of the reduction potential at pH = 7 for the redox reactions relevant for biological systems, the same kind of conversion exercise is done using the corresponding Nernst equation expressed as a function of pH.
The conversion is simple, but care must be taken not to inadvertently mix reduction potential converted at pH = 7 with other data directly taken from tables referring to SHE (pH = 0). | 1 | Biochemistry |
It is usually recommended not to declare a person dead until their body is warmed to a near normal body temperature of greater than , since extreme hypothermia can suppress heart and brain function. This is summarized in the common saying "Youre not dead until youre warm and dead." Exceptions include if there are obvious fatal injuries or the chest is frozen so that it cannot be compressed. If a person was buried in an avalanche for more than 35 minutes and is found with a mouth packed full of snow without a pulse, stopping early may also be reasonable. This is also the case if a person's blood potassium is greater than 12 mmol/L.
Those who are stiff with pupils that do not move may survive if treated aggressively. Survival with good function also occasionally occurs even after the need for hours of CPR. Children who have near-drowning accidents in water near can occasionally be revived, even over an hour after losing consciousness. The cold water lowers the metabolism, allowing the brain to withstand a much longer period of hypoxia. While survival is possible, mortality from severe or profound hypothermia remains high despite optimal treatment. Studies estimate mortality at between 38% and 75%.
In those who have hypothermia due to another underlying health problem, when death occurs it is frequently from that underlying health problem. | 1 | Biochemistry |
The output is given for each season of any year during any number of years, as specified with the input data. The output data comprise hydrological and salinity aspects.<br>
As the soil salinity is very variable from place to place (figure left) SahysMod includes frequency distributions in the output. The figure was made with the CumFreq program.<br>
The output data are filed in the form of tables that can be inspected directly, through the user menu, that calls selected groups of data either for a certain polygon over time, or for a certain season over the polygons. <br />
The model includes mapping facilities of output data. Also, the program has the facility to store the selected data in a spreadsheet format for further analysis and for import into a GIS program. <br />
Different users may wish to establish different cause-effect relationships. The program offers only a limited number of standard graphics, as it is not possible to foresee all different uses that may be made. This is the reason why the possibility for further analysis through spreadsheet programs was created.<br>
Although the computations need many iterations, all the end results can be checked by hand using the equations presented in the manual. | 9 | Geochemistry |
Laser diffraction analysis has been questioned in validity in the following areas:
* assumptions including particles having random configurations and volume values. In some dispersion units, particles have been shown to align themselves together rather than have a turbulent flow, causing them to lead themselves in an orderly direction.
* algorithms used in laser diffraction analysis are not thoroughly validated. Different algorithms are used at times to have collected data match assumptions made by users as an attempt to avoid data that looks incorrect.
* measurement inaccuracies due to sharp edges on objects. Laser diffraction analysis has the chance of detecting imaginary particles at sharp edges because of the large angles the lasers make upon them.
* when compared to the data collecting of optical imaging, another particle-sizing technique, correlation between the two was poor for non-spherical particles. This is due to the fact that the underlying Fraunhofer and Mie theories only cover spherical particles. Non-spherical particles cause more diffuse scatter patterns and are more difficult to interpret. Some manufacturers have included algorithms in their software, which can partly compensate for non-spherical particles. | 7 | Physical Chemistry |
Antiferroelectricity is a physical property of certain materials. It is closely related to ferroelectricity; the relation between antiferroelectricity and ferroelectricity is analogous to the relation between antiferromagnetism and ferromagnetism.
An antiferroelectric material consists of an ordered (crystalline) array of electric dipoles (from the ions and electrons in the material), but with adjacent dipoles oriented in opposite (antiparallel) directions (the dipoles of each orientation form interpenetrating sublattices, loosely analogous to a checkerboard pattern). This can be contrasted with a ferroelectric, in which the dipoles all point in the same direction.
In an antiferroelectric, unlike a ferroelectric, the total, macroscopic spontaneous polarization is zero, since the adjacent dipoles cancel each other out.
Antiferroelectricity is a property of a material, and it can appear or disappear (more generally, strengthen or weaken) depending on temperature, pressure, external electric field, growth method, and other parameters. In particular, at a high enough temperature, antiferroelectricity disappears; this temperature is known as the Néel point or Curie point. | 7 | Physical Chemistry |
For cast iron the equivalent carbon content (CE) concept is used to understand how alloying elements will affect the heat treatment and casting behavior. It is used as a predictor of strength in cast irons because it gives an approximate balance of austenite and graphite in final structure. A number of formulas are available to determine the CE in cast irons, where an increasing number of elements are included:
This CE is then used to determine if the alloy is hypoeutectic, eutectic, or hypereutectic; for cast irons the eutectic is 4.3% carbon. When casting cast iron this is useful for determining the final grain structure; for example, a hypereutectic cast iron usually has a coarse grain structure and large kish graphite flakes are formed. Also, there is less shrinkage as the CE increases. When heat treating cast iron, various CE samples are tested to empirically determine the correlation between CE and hardness. The following is an example for induction hardened gray irons: | 8 | Metallurgy |
Colloidal phase separation is an important organising principle for compartmentalisation of both the cytoplasm and nucleus of cells into biomolecular condensates—similar in importance to compartmentalisation via lipid bilayer membranes, a type of liquid crystal. The term biomolecular condensate has been used to refer to clusters of macromolecules that arise via liquid-liquid or liquid-solid phase separation within cells. Macromolecular crowding strongly enhances colloidal phase separation and formation of biomolecular condensates. | 7 | Physical Chemistry |
The bead test is a traditional part of qualitative inorganic analysis to test for the presence of certain metals. The oldest one is the borax bead test or blister test. It was introduced by Berzelius in 1812. Since then other salts were used as fluxing agents, such as sodium carbonate or sodium fluoride. The most important one after borax is microcosmic salt, which is the basis of the microcosmic salt bead test. | 3 | Analytical Chemistry |
Aside from use as decorative or utilitarian objects, gold was used throughout the Philippine archipelago as currency, whether in the form of gold dust, small beads, or barter rings. | 8 | Metallurgy |
A SSATM instrument is typically designed in a time-domain spectroscopy configuration in which a high power infrared laser beam is divided into two optical paths by a beamsplitter.
The first optical path often receives a greater fraction of the optical power of the laser to maximize the output power of generated THz light. THz light is often generated with a voltage-pulsed photoconductive antenna, collected with a hyper-hemispherical silicon lens, collimated using an off-axis parabolic mirror that is then passed through a THz polarizer, made circular by a THz quarter waveplate constructed of two planar mirrors and a right-angled high-resistivity silicon prism to form circularly polarized light. A second THz polarizer selects from the circularly polarized THz light the angle at which each measurement is made once the light reaches a sample located at a focal point of the beam and mounted in direct contact with an electro-optic crystal often made of either ZnTe or GaP.
The second optical path includes a retroreflector mirror mounted on a delay stage that adjusts the time-of-flight of the NIR beam to match the delay time, , of the THz light at the sample. The NIR beam is linearly polarized and chopped at a frequency suitable for detection, directed to the EO crystal to measure the change in its birefringence due to the degree of THz absorption by the sample. The NIR beam is reflected by the sample/EO crystal interface and directed to the detection module that often consists of an NIR quarter waveplate, a Wollaston prism that spatially selects perpendicular polarization states of the light toward two detectors in a balanced detector. The detected signal is a measure of the difference of the magnitude of the two perpendicular polarization states and corresponds to the degree of birefringence induced in the EO crystal by the THz light as-perturbed by the sample. | 7 | Physical Chemistry |
A proposed mechanism of ultrasensitivity, called allovalency, suggests that activity "derives from a high local concentration of interaction sites moving independently of each other"
Allovalency was first proposed when it was believed to occur in the pathway in which Sic1, is degraded in order for Cdk1-Clb (B-type cyclins) to allow entry into mitosis. Sic1 must be phosphorylated multiple times in order to be recognized and degraded by Cdc4 of the SCF Complex. Since Cdc4 only has one recognition site for these phosphorylated residues it was suggested that as the amount of phosphorylation increases, it exponentially increases the likelihood that Sic1 is recognized and degraded by Cdc4. This type of interaction was thought to be relatively immune to loss of any one site and easily tuned to any given threshold by adjusting the properties of individual sites. Assumptions for the allovalency mechanism were based on a general mathematical model that describes the interaction between a polyvalent disordered ligand and a single receptor site
It was later found that the ultrasensitivity in Cdk1 levels by degradation of Sic1 is in fact due to a positive feedback loop. | 1 | Biochemistry |
The for thiourea is for rats (oral).
A goitrogenic effect (enlargement of the thyroid gland) has been reported for chronic exposure, reflecting the ability of thiourea to interfere with iodide uptake.
A cyclic derivative of thiourea called Thiamazole is used to treat overactive thyroid | 0 | Organic Chemistry |
A natural neuroactive substance (NAS) is a chemical synthesized by neurons that affects the actions of other neurons or muscle cells. Natural neuroactive substances include neurotransmitters, neurohormones, and neuromodulators. Neurotransmitters work only between adjacent neurons through synapses. Neurohormones are released into the blood and work at a distance. Some natural neuroactive substances act as both transmitters and as hormones. | 1 | Biochemistry |
Chlorosulfuric acid is a tetrahedral molecule. The formula is more descriptively written SO(OH)Cl, but HSOCl is traditional. It is an intermediate, chemically and conceptually, between sulfuryl chloride (SOCl) and sulfuric acid (HSO). The compound is rarely obtained pure. Upon standing with excess sulfur trioxide, it decomposes to pyrosulfuryl chlorides:
:2 ClSOH + SO → HSO + SOCl | 0 | Organic Chemistry |
In collaboration with Hopkins Marine Station and the Center for Ocean Solutions, Monterey Bay Aquarium Research Institute is developing a swFOCE system to examine the effects of ocean acidification on shallow subtidal communities in central California. swFOCE will use a shore side station for the control system and production of CO enriched seawater, and will also use and will use an existing cabled observational and research platform to connect the swFOCE node. Two swFOCE chambers will be installed initially at a depth of 15 m, approximately 250 m offshore. The nearby node of the cabled observatorynode, has instruments to monitor local currents, temperature, pH, and O2 in real-time, as a cabled observatory platform for scientific research. | 9 | Geochemistry |
There are several ways of measuring fluxes, however all of these are indirect. Due to this, these methods make one key assumption which is that all fluxes into a given intracellular metabolite pool balance all the fluxes out of the pool.
This assumption means that for a given metabolic network the balances around each metabolite impose a number of constraints on the system.
The techniques currently used mainly revolve around the use of either nuclear magnetic resonance (NMR) or gas chromatography–mass spectrometry (GC–MS).
In order to avoid the complexity of data analysis, a simpler method of estimating flux ratios has recently been developed which is based on cofeeding unlabelled and uniformly C labelled glucose. The metabolic intermediate patterns are then analysed using NMR spectroscopy.
This method can also be used to determine the metabolic network topologies. | 1 | Biochemistry |
Molecules synthesized in the cell bodies of neurons must be conveyed outward to the distal synapses. This is accomplished via fast anterograde transport. It has been found that APP can mediate interaction between cargo and kinesin and thus facilitate this transport. Specifically, a short peptide 15-amino-acid sequence from the cytoplasmic carboxy-terminus is necessary for interaction with the motor protein.
Additionally, it has been shown that the interaction between APP and kinesin is specific to the peptide sequence of APP. In a recent experiment involving transport of peptide-conjugated colored beads, controls were conjugated to a single amino acid, glycine, such that they display the same terminal carboxylic acid group as APP without the intervening 15-amino-acid sequence mentioned above. The control beads were not motile, which demonstrated that the terminal COOH moiety of peptides is not sufficient to mediate transport. | 1 | Biochemistry |
*Cannon, B., & Nedergaard, J. (2004). Brown adipose tissue: function and physiological significance. Physiological Reviews, 84, 277 - 359.
*Nedergaard, J., Bengtsson, T., & Cannon, B. (2007). Unexpected evidence for active brown adipose tissue in adult humans. American Journal of Physiology-Endocrinology and Metabolism, 293, E444- E452.
*Feldmann, H. M., Golozoubova, V., Cannon, B., & Nedergaard, J. (2009). UCP1 ablation induces obesity and abolishes diet-induced thermogenesis in mice exempt from thermal stress by living at thermoneutrality. Cell Metabolism, 9(2), 203–209.
*Whittle, A. J., Carobbio, S., Martins, L., Slawik, M., Hondares, E., Vázquez, M. J., ... & Vidal-Puig, A. (2012). BMP8B increases brown adipose tissue thermogenesis through both central and peripheral actions. Cell, 149(4), 871–885.
*Fischer, A. W., Cannon, B., & Nedergaard, J. (2018). Optimal housing temperatures for mice to mimic the thermal environment of humans: an experimental study. Molecular metabolism, 7, 161–170. | 1 | Biochemistry |
Circulation within local systems, such as bays, estuaries, and groundwater, may be examined with radium isotopes. Ra has a half-life of 11 days and can occur naturally at specific locations in rivers and groundwater sources. The isotopic ratio of radium will then decrease as the water from the source river enters a bay or estuary. By measuring the amount of Ra at a number of different locations, a circulation pattern can be deciphered. This same exact process can also be used to study the movement and discharge of groundwater.
Various isotopes of lead can be used to study circulation on a global scale. Different oceans (i.e. the Atlantic, Pacific, Indian, etc.) have different isotopic signatures. This results from differences in isotopic ratios of sediments and rocks within the different oceans. Because the different isotopes of lead have half-lives of 50–200 years, there is not enough time for the isotopic ratios to be homogenized throughout the whole ocean. Therefore, precise analysis of Pb isotopic ratios can be used to study the circulation of the different oceans. | 7 | Physical Chemistry |
In addition, there are 4 other mammalian enzymes named CPA-3 through CPA-6, and none of these are expressed in the pancreas. Instead, these other CPA-like enzymes have diverse functions.
* CPA3 (also known as mast-cell CPA) is involved in the digestion of proteins by mast cells.
* CPA4 (previously known as CPA-3, but renumbered when mast-cell CPA was designated CPA-3) may be involved in tumor progression, but this enzyme has not been well studied.
* CPA5 has not been well studied.
* CPA6 is expressed in many tissues during mouse development, and in adult shows a more limited distribution in brain and several other tissues. CPA6 is present in the extracellular matrix where it is enzymatically active. A human mutation of CPA-6 has been linked to Duane's syndrome (abnormal eye movement). Recently, mutations in CPA6 were found to be linked to epilepsy. CPA6 is also one of several enzymes which degrade enkephalins. | 1 | Biochemistry |
Discharge of red mud can be hazardous environmentally because of its alkalinity and species components.
Until 1972, Italian company Montedison was discharging red mud off the coast of Corsica. The case is important in international law governing the Mediterranean sea.
In October 2010, approximately one million cubic meters of red mud slurry from an alumina plant near Kolontár in Hungary was accidentally released into the surrounding countryside in the Ajka alumina plant accident, killing ten people and contaminating a large area. All life in the Marcal river was said to have been "extinguished" by the red mud, and within days the mud had reached the Danube. The long-term environmental effects of the spill have been minor after a remediation effort by the Hungarian government. | 2 | Environmental Chemistry |
Chiral auxiliaries are incorporated into synthetic routes to control the absolute configuration of stereogenic centers. David A. Evans' synthesis of the macrolide cytovaricin, considered a classic, utilizes oxazolidinone chiral auxiliaries for one asymmetric alkylation reaction and four asymmetric aldol reactions, setting the absolute stereochemistry of nine stereocenters.
A typical auxiliary-guided stereoselective transformation involves three steps: first, the auxiliary is covalently coupled to the substrate; second, the resulting compound undergoes one or more diastereoselective transformations; and finally, the auxiliary is removed under conditions that do not cause racemization of the desired products. The cost of employing stoichiometric auxiliary and the need to spend synthetic steps appending and removing the auxiliary make this approach appear inefficient. However, for many transformations, the only available stereoselective methodology relies on chiral auxiliaries. In addition, transformations with chiral auxiliaries tend to be versatile and very well-studied, allowing the most time-efficient access to enantiomerically pure products.
Furthermore, the products of auxiliary-directed reactions are diastereomers, which enables their facile separation by methods such as column chromatography or crystallization. | 4 | Stereochemistry |
The Simon–Glatzel equation is a monotonically increasing function. It can only describe the melting curves that rise indefinitely with increasing pressure. It may fail to describe the melting curves with a negative pressure dependence or local maximums. A damping term that asymptotically slopes down under pressure, (c is another component-specific parameter), is introduced by Vladimir V. Kechin to extend the Simon–Glatzel equation so that all melting curves, rising, falling, and flattening, as well as curves with a maximum, can be described by a unified equation:
where is the Simon–Glatzel equation (rising) and is the damping term (falling or flattening).
The unified equation may be rewritten as:
This form predicts that all solids have a maximum melting temperature at a positive or (fictitious) negative pressure. | 7 | Physical Chemistry |
A polytropic process is a thermodynamic process that obeys the relation:
where P is the pressure, V is volume, n is any real number (the "polytropic index"), and C is a constant. This equation can be used to accurately characterize processes of certain systems, notably the compression or expansion of a gas, but in some cases, liquids and solids. | 7 | Physical Chemistry |
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