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2 FeCl + 3 HO → 6 HCl + FeO
Today hydrothermal hydrolysis, which operates at very low temperatures, consumes only a fraction of the energy other processes demand and produces virtually no emissions, is considered the most effective way to regenerate any given quantity of spent pickle liquor. | 0 | Theoretical and Fundamental Chemistry |
Crystallography of large biological macromolecules can be achieved while maintaining their solution state. The best known example is the ribosome.
Today, liquid nitrogen cryo cooling is used for protein crystallography at every synchrotron around the world. Radiation damaged is reduced by more than 70 fold at cryo temperatures. A recent review paper explains the development of reduced radiation damage in macromolecular crystals at Synchrotrons and describes how more than 90% of all structures deposited in the Protein Data Bank used cryo cooling in their determination.
2020 Haas, DJ. The early history of cryo-cooling for macromolecular crystallography (2020)
IUCrJ (2020). 7, 148–157. https://journals.iucr.org/m/issues/2020/02/00/be5283/be5283.pdf
1970 Haas, D.J., and Rossmann, M.G.
Crystallographic Studies on Lactate Dehydrogenase at -75 C. Acta Crystallogr. (1970), B26, 998. | 0 | Theoretical and Fundamental Chemistry |
Molecular cloning is used to isolate and then transfer a DNA sequence of interest into a plasmid vector. This recombinant DNA technology was first developed in the 1960s. In this technique, a DNA sequence coding for a protein of interest is cloned using polymerase chain reaction (PCR), and/or restriction enzymes, into a plasmid (expression vector). The plasmid vector usually has at least 3 distinctive features: an origin of replication, a multiple cloning site (MCS), and a selective marker (usually antibiotic resistance). Additionally, upstream of the MCS are the promoter regions and the transcription start site, which regulate the expression of cloned gene.
This plasmid can be inserted into either bacterial or animal cells. Introducing DNA into bacterial cells can be done by transformation via uptake of naked DNA, conjugation via cell-cell contact or by transduction via viral vector. Introducing DNA into eukaryotic cells, such as animal cells, by physical or chemical means is called transfection. Several different transfection techniques are available, such as calcium phosphate transfection, electroporation, microinjection and liposome transfection. The plasmid may be integrated into the genome, resulting in a stable transfection, or may remain independent of the genome and expressed temporarily, called a transient transfection.
DNA coding for a protein of interest is now inside a cell, and the protein can now be expressed. A variety of systems, such as inducible promoters and specific cell-signaling factors, are available to help express the protein of interest at high levels. Large quantities of a protein can then be extracted from the bacterial or eukaryotic cell. The protein can be tested for enzymatic activity under a variety of situations, the protein may be crystallized so its tertiary structure can be studied, or, in the pharmaceutical industry, the activity of new drugs against the protein can be studied. | 1 | Applied and Interdisciplinary Chemistry |
Chemically, levorphanol belongs to the morphinan class and is (−)-3-hydroxy-N-methyl-morphinan. It is the "left-handed" (levorotatory) stereoisomer of racemorphan, the racemic mixture of the two stereoisomers with differing pharmacology. The "right-handed" (dextrorotatory) enantiomer of racemorphan is dextrorphan (DXO), an antitussive, potent dissociative hallucinogen (NMDA receptor antagonist), and weakly active opioid. DXO is an active metabolite of the pharmaceutical drug dextromethorphan (DXM), which, analogously to DXO, is an enantiomer of the racemic mixture racemethorphan along with levomethorphan, the latter of which has similar properties to those of levorphanol. | 0 | Theoretical and Fundamental Chemistry |
Fosdevirine (also known as IDX899 and GSK-2248761) is another next generation NNRTI developed by Idenix Pharmaceuticals and ViiV Healthcare. It belongs to the family of 3-phosphoindoles. In vitro studies have shown comparable resistance profile to that of the other next generation NNRTIs. In November 2009 the candidate entered phase II clinical trials, but the trial and all further development was halted when 5 of 35 subjects receiving fosdevirine experienced delayed-onset seizures. | 1 | Applied and Interdisciplinary Chemistry |
The Zeeman effect can be demonstrated by placing a sodium vapor source in a powerful electromagnet and viewing a sodium vapor lamp through the magnet opening (see diagram). With magnet off, the sodium vapor source will block the lamp light; when the magnet is turned on the lamp light will be visible through the vapor.
The sodium vapor can be created by sealing sodium metal in an evacuated glass tube and heating it while the tube is in the magnet.
Alternatively, salt (sodium chloride) on a ceramic stick can be placed in the flame of Bunsen burner as the sodium vapor source. When the magnetic field is energized, the lamp image will be brighter. However, the magnetic field also affects the flame, making the observation depend upon more than just the Zeeman effect. These issues also plagued Zeeman's original work; he devoted considerable effort to ensure his observations were truly an effect of magnetism on light emission.
When salt is added to the Bunsen burner, it dissociates to give sodium and chloride. The sodium atoms get excited due to photons from the sodium vapour lamp, with electrons excited from 3s to 3p states, absorbing light in the process. The sodium vapour lamp emits light at 589nm, which has precisely the energy to excite an electron of a sodium atom. If it was an atom of another element, like chlorine, shadow will not be formed. When a magnetic field is applied, due to the Zeeman effect the spectral line of sodium gets split into several components. This means the energy difference between the 3s and 3p atomic orbitals will change. As the sodium vapour lamp dont precisely deliver the right frequency any more, light doesnt get absorbed and passes through, resulting in the shadow dimming. As the magnetic field strength is increased, the shift in the spectral lines increases and lamp light is transmitted. | 0 | Theoretical and Fundamental Chemistry |
Nine different candidates of nuclei are being considered in experiments to confirm neutrinoless double beta-decay: . They all have arguments for and against their use in an experiment. Factors to be included and revised are natural abundance, reasonably priced enrichment, and a well understood and controlled experimental technique. The higher the -value, the better are the chances of a discovery, in principle. The phase-space factor , and thus the decay rate, grows with .
Experimentally of interest and thus measured is the sum of the kinetic energies of the two emitted electrons. It should equal the -value of the respective nucleus for neutrinoless double beta emission.
The table shows a summary of the currently best limits on the lifetime of 0νββ. From this, it can be deduced that neutrinoless double beta decay is an extremely rare process, if it occurs at all. | 0 | Theoretical and Fundamental Chemistry |
* Berton, Alain Edgard : Montre-bracelet-réveil tactile. 5 décembre 1949 : FR953313-A
* Berton Alain Edgard : Photomètre infrarouge utilisable en analyse physique et chimique. 24 janvier 1955 : FR1084823-A
* Berton Alain: Photomètre simple ultraviolet, avec enregistreur photographique à lecture instantanée, utilisable en analyse physique et chimique. 27 juin 1958 : FR1159401-A
* Berton Alain : Apparatus for detecting and measuring traces of impurities in a gas. 16 juin 1960 : FR1223277-A; idem, 27 juin 1960 : FR1224831-A
* Berton Alain : Dispositif chimique denregistrement sans contact'. 14 octobre 1960 : FR1234235-A
* Berton Alain : Analyseur colorimétrique de vapeurs, portatif. 17 mars 1961 : FR1255988-A
* Berton Alain : Dispositif électrochimique de détection dimpuretés dans les gaz'. 10 août 1962 : FR1300917-A | 0 | Theoretical and Fundamental Chemistry |
In ancient China, the method was improved by mechanization with the development of the rotary winnowing fan, which used a cranked fan to produce the airstream. This was featured in Wang Zhens book the Nong Shu' of 1313 AD. | 0 | Theoretical and Fundamental Chemistry |
Within the field of microbial ecology, oligonucleotide probes are used in order to determine the presence of microbial species, genera, or microorganisms classified on a more broad level, such as bacteria, archaea, and eukaryotes via fluorescence in situ hybridization (FISH). rRNA probes have enabled scientists to visualize microorganisms, yet to be cultured in laboratory settings, by retrieval of rRNA sequences directly from the environment. Examples of these types of microorganisms include:
*Nevskia ramosa: N. ramosa is a neuston bacterium that forms typical, dichotomically-branching rosettes on the surface of shallow freshwater habitats.
*Achromatium oxaliferum: This huge bacterium (cell length up to >100 µm, diameter up to 50 µm) contains sulfur globules and massive calcite inclusions and inhabits the upper layers of freshwater sediments. It is visible to the naked eye and has, by its resistance to cultivation, puzzled generations of microbiologists. | 1 | Applied and Interdisciplinary Chemistry |
The key elements of tholins are carbon, nitrogen, and hydrogen. Laboratory infrared spectroscopy analysis of experimentally synthesized tholins has confirmed earlier identifications of chemical groups present, including primary amines, nitriles, and alkyl portions such as / forming complex disordered macromolecular solids. Laboratory tests generated complex solids formed from exposure of : gaseous mixtures to electrical discharge in cold plasma conditions, reminiscent of the famous Miller–Urey experiment conducted in 1952. | 0 | Theoretical and Fundamental Chemistry |
The article concerns the total synthesis of galanthamine, a drug used for the treatment of mild to moderate Alzheimer's disease.
The natural source of galantamine are certain species of daffodil and because these species are scarce and because the isolation of galanthamine from daffodil is expensive (a 1996 figure specifies 50,000 US dollar per kilogram, the yield from daffodil is 0.1–0.2% dry weight) alternative synthetic sources are under development by means of total synthesis. | 0 | Theoretical and Fundamental Chemistry |
Acyl chloride are reactive, versatile reagents. Acyl chlorides have a greater reactivity than other carboxylic acid derivatives like acid anhydrides, esters or amides: | 0 | Theoretical and Fundamental Chemistry |
The Trolox equivalent antioxidant capacity (TEAC) assay measures the antioxidant capacity of a given substance, as compared to the standard, Trolox. Most commonly, antioxidant capacity is measured using the ABTS Decolorization Assay. Other antioxidant capacity assays which use Trolox as a standard include the diphenylpicrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC) and ferric reducing ability of plasma (FRAP) assays. The TEAC assay is often used to measure the antioxidant capacity of foods, beverages and nutritional supplements. | 1 | Applied and Interdisciplinary Chemistry |
If oxygen is present, then following glycolysis, the two pyruvate molecules are brought into the mitochondrion itself to go through the Krebs cycle. In this cycle, the pyruvate molecules from glycolysis are further broken down to harness the remaining energy. Each pyruvate goes through a series of reactions that converts it to acetyl coenzyme A. From here, only the acetyl group participates in the Krebs cycle—in which it goes through a series of redox reactions, catalyzed by enzymes, to further harness the energy from the acetyl group. The energy from the acetyl group, in the form of electrons, is used to reduce NAD+ and FAD to NADH and FADH, respectively. NADH and FADH contain the stored energy harnessed from the initial glucose molecule and is used in the electron transport chain where the bulk of the ATP is produced. | 1 | Applied and Interdisciplinary Chemistry |
The Robinson synthesis is an example of a so-called relay synthesis. As many of the chemical intermediates (all steroids) were already known and available from natural resources all that was needed for a formal synthesis was proof that these intermediates could be linked to each other via chemical synthesis. Starting point for the Robinson synthesis was 1,6-dihydroxynaphthalene 1 that was converted in about 20 steps into the then already known androsterone 4. Ruzicka had already demonstrated in 1938 that androsterone could be converted into androstenedione 5 and Robinson demonstrated its conversion to dehydroepiandrosterone 6 (note the epimerized hydroxyl group) also already a known compound. Conversion of 6 to pregnenolone 7 and then to allopregnanolone 8 allowed the addition of the tail group as the acetate in 9 and then conversion to cholestanol 10.
The conversion of cholestanol to cholesterol was already demonstrated by oxidation of the ketone, bromination to the bromoketone and elimination to the enone.
The conversion of cholestenone into cholesterol by the method of Dauben and Eastham (1950) consisted of reduction of the enol acetate (lithium aluminium hydride) and fractionation with digitonin for the isolation of the correct isomer. | 0 | Theoretical and Fundamental Chemistry |
Gaseous mediators are chemicals that are produced in small amounts by some cells of the mammalian body and have a number of biological signalling functions. There are three so-far-identified gaseous mediator molecules: nitric oxide (NO), hydrogen sulfide (HS), and carbon monoxide (CO). | 1 | Applied and Interdisciplinary Chemistry |
The synthesis of hexachlorophosphazene was first reported by von Liebig in 1834. In that report he describes experiments conducted with Wöhler. They found that phosphorus pentachloride and ammonia react exothermically to yield a new substance that could be washed with cold water to remove the ammonium chloride coproduct. The new compound contained P, N, and Cl, on the basis of elemental analysis. It was sensitive toward hydrolysis by hot water.
Modern syntheses are based on the developments by Schenk and Römer who used ammonium chloride in place of ammonia and inert chlorinated solvents. By replacing ammonia with ammonium chloride allows the reaction to proceed without a strong exotherm associated with the / reaction. Typical chlorocarbon solvents are 1,1,2,2-tetrachloroethane or chlorobenzene, which tolerate the hydrogen chloride side product. Since ammonium chloride is insoluble in chlorinated solvents, workup is facilitated. For the reaction under such conditions, the following stoichiometry applies:
where n can usually take values of 2 (the dimer tetrachlorodiphosphazene), 3 (the trimer hexachlorotriphosphazene), and 4 (the tetramer octachlorotetraphosphazene).
Purification by sublimation gives mainly the trimer and tetramer. Slow vacuum sublimation at approximately 60 °C affords the pure trimer free of the tetramer. Reaction conditions such as temperature may also be tuned to maximise the yield of the trimer at the expense of the other possible products; nonetheless, commercial samples of hexachlorophosphazene usually contain appreciable amounts of octachlorotetraphosphazene, even up to 40%. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, flow can be decomposed into primary flow plus secondary flow, a relatively weaker flow pattern superimposed on the stronger primary flow pattern. The primary flow is often chosen to be an exact solution to simplified or approximated governing equations, such as potential flow around a wing or geostrophic current or wind on the rotating Earth. In that case, the secondary flow usefully spotlights the effects of complicated real-world terms neglected in those approximated equations. For instance, the consequences of viscosity are spotlighted by secondary flow in the viscous boundary layer, resolving the tea leaf paradox. As another example, if the primary flow is taken to be a balanced flow approximation with net force equated to zero, then the secondary circulation helps spotlight acceleration due to the mild imbalance of forces. A smallness assumption about secondary flow also facilitates linearization.
In engineering secondary flow also identifies an additional flow path. | 1 | Applied and Interdisciplinary Chemistry |
Bis(trimethylsilyl)mercury (CH)Si-Hg-Si(CH) reacts with chloro-iminium and chloro-amidinium salts to give a metal-free carbene and elemental mercury. For example:
:(CH)Si−Hg−Si(CH) + RN=C(Cl)−Cl → RN−C−NR + Hg + 2(CH)SiCl | 0 | Theoretical and Fundamental Chemistry |
Fungi, thanks to their non-specific enzymes, are able to break down many kinds of substances including pharmaceuticals and fragrances that are normally recalcitrant to bacteria degradation, such as paracetamol (also known as acetaminophen). For example, using Mucor hiemalis, the breakdown of products which are toxic in traditional water treatment, such as phenols and pigments of wine distillery wastewater, X-ray contrast agents, and ingredients of personal care products, can be broken down in a non-toxic way.
Mycoremediation is a cheaper method of remediation, and it doesn't usually require expensive equipment. For this reason, it is often used in small scale applications, such as mycofiltration of domestic wastewater, and industrial effluent filtration.
According to a 2015 study, mycoremediation can even help with the polycyclic aromatic hydrocarbons (PAH) soil biodegradation. Soils soaked with creosote contain high concentrations of PAH and in order to stop the spread, mycoremediation has proven to be the most successful strategy. | 1 | Applied and Interdisciplinary Chemistry |
The outer thermal protection layer of NASA's LOFTID inflatable heat shield incorporates a woven ceramic made from silicon carbide, with fiber of such small diameter that it can be bundled and spun into a yarn. | 1 | Applied and Interdisciplinary Chemistry |
In host–guest chemistry the bistable states of molecular switches differ in their affinity for guests. Many early examples of such systems are based on crown ether chemistry. The first switchable host is described in 1978 by Desvergne & Bouas-Laurent who create a crown ether via photochemical anthracene dimerization. Although not strictly speaking switchable the compound is able to take up cations after a photochemical trigger and exposure to acetonitrile gives back the open form.
In 1980 Yamashita et al. construct a crown ether already incorporating the anthracene units (an anthracenophane) and also study ion uptake vs photochemistry.
Also in 1980 Shinkai throws out the anthracene unit as photoantenna in favor of an azobenzene moiety and for the first time envisions the existence of molecules with an on-off switch. In this molecule light triggers a trans-cis isomerization of the azo group which results in ring expansion. Thus in the trans form the crown binds preferentially to ammonium, lithium and sodium ions while in the cis form the preference is for potassium and rubidium (both larger ions in same alkali metal group). In the dark the reverse isomerization takes place.
Shinkai employs this devices in actual ion transport mimicking the biochemical action of monensin and nigericin: in a biphasic system ions are taken up triggered by light in one phase and deposited in the other phase in absence of light. | 0 | Theoretical and Fundamental Chemistry |
In a normal bearing the surfaces are separated by a layer of oil, this is known as elastohydrodynamic (EHD) lubrication. If the thickness of the EHD film is of the same order of magnitude as the surface roughness, the surface topography is able to interact and cause micro pitting. A thin EHD film may be caused by excess load or temperature, a lower oil viscosity than is required, low speed or water in the oil. Water in the oil can make micro pitting worse by causing hydrogen embrittlement of the surface. Micro pitting occurs only under poor EHD lubrication conditions.
A surface with a deep scratch might break exactly at the scratch if stress is applied. One can imagine that the surface roughness is a composite of many very small scratches. So high surface roughness decreases the stability on heavy stressed parts. To get a good overview of the surface an areal scan (Surface metrology) gives more information that a measurement along a single profile (profileometer). To quantify the surface roughness the ISO 25178 can be used. | 1 | Applied and Interdisciplinary Chemistry |
Cations, often carbocations, serve as intermediates in various types of reactions to synthesize new compounds. | 0 | Theoretical and Fundamental Chemistry |
Compounds elute in the carrier gas phase only. Compounds solved in the stationary phase stay put. The ratio of gas time and residence time in the stationary liquid polymer phase is called the capacity factor :
where the variables used are:
* gas constant (8.314J/mole/k)
* temperature [k]
* solubility of compound i in polymer stationary phase [mole/m]
* vapor pressure of pure liquid i [Pa]
Capillary tubes with uniform coatings have this phase ratio β:
Capillary inner diameter is well defined but film thickness reduces by bleed and thermal breakdown that occur after column heating over time, depending on chemical bonding to the silica glass wall and polymer cross-linking of the stationary phase.
Above capacity factor can be expressed explicit for retention time:
Retention time is shorter by reduced over column life time. Column length is introduced with average gas velocity :
and temperature have a direct relation with . However, warmer columns ↑ do not have longer but shorter, following temperature programming experience. Pure liquid vapor pressure rises exponentially with so that we do get shorter warming the column ↑. Solubility of compounds in the stationary phase may rise or fall with , but not exponentially. is referred to as selectivity or polarity by gas chromatographers today.
Isothermal Kovats index in terms of the physical properties becomes:
Isothermal Kovats index is independent of , any GC dimension or ß or carrier gas velocity , which compares favorable to retention time . Isothermal Kovats index is based on solubility and vapor pressure of compound i and n-Alkanes (). dependence depends on the compound compared to the n-alkanes. Kovats index of n-alkanes is independent of .
Isothermal Kovats indices of hydrocarbon were measured by Axel Lubeck and Donald Sutton. | 0 | Theoretical and Fundamental Chemistry |
In pharmacology, a dirty drug is an informal term for drugs that may bind to many different molecular targets or receptors in the body, and so tend to have a wide range of effects and possibly adverse drug reactions. Today, pharmaceutical companies try to make new drugs as selective as possible to minimise binding to antitargets and hence reduce the occurrence of side effects and risk of adverse reactions.
Examples of compounds often cited as "dirty drugs" include tramadol, chlorpromazine, olanzapine, dextromethorphan, ibogaine, and ethanol, all of which bind to multiple receptors or influence multiple receptor systems. There may be instances of advantages to drugs that exhibit multi-receptor activity such as the anti-addictive drug ibogaine that acts within a broad range of neurohormonal systems where activity is also exhibited by drugs commonly associated with addiction including opioids, nicotine, and alcohol. Similarly chlorpromazine is primarily used as an antipsychotic, but its strong serotonin receptor blocking effects make it useful for treating serotonergic crisis such as serotonin syndrome. Dextromethorphan for its part is widely used as a cough medication, but its other actions have led to trials for several conditions such as its use as an adjunct to analgesia, and a potential anti-addictive drug, as well as its occasional recreational use as a dissociative.
Kanamycin is an aminoglycoside antibiotic which induces deafness through blockage of the outer hair cells of the cochlea; yet it has many other effects, weakening for instance the collagen and DNA biosynthesis. It acts by inhibiting the synthesis of proteins in susceptible organisms. Kanamycin requires close clinical supervision because of its potential toxicity and adverse side effects to the auditory and vestibular branches of the eighth cranial nerve and to the renal tubules.
Clozapine and latrepirdine are examples of drugs used in the treatment of CNS disorders that have a superior efficacy precisely because of their "multifarious" broadspectrum mode of activity. Likewise, in cancer chemotherapeutics, it has been recognized that drugs active at more than one target have a higher probability of being efficacious.
The anti-histamine and anti-cholinergic effects of atypical and low potency typical antipsychotics, such as the aforementioned clozapine and chlorpromazine, can also mediate against potentially distressing movement disorders such as extrapyramidal symptoms and akathisia associated with dopamine antagonism. In fact, clozapine may even help treat movement problems associated with Parkinson's disease.
Examples of "promiscuous" cancer drugs include: Sutent, Sorafenib, Zactima, and AG-013736.
In the field of drugs used to treat depression, the nonselective MAOIs and the TCAs are sometimes believed to have an efficacy that is superior to the SSRIs. SSRIs are usually nevertheless picked as the first-line choice of agent and not the (less-selective) MAOIs and TCAs for several reasons. Firstly, SSRIs are safer in overdose than TCAs. Secondly, MAOIs can cause serious side effects when mixed with certain foods, including life-threatening hypertensive crisis. MAOIs and TCAs generally have more side effects than SSRIs. TCAs in particular have anticholinergic side effects such as constipation and blurred vision, whereas SSRIs have fewer anticholinergic side effects. | 1 | Applied and Interdisciplinary Chemistry |
Experimentally it was determined that extent of gas adsorption varies directly with pressure, and then it directly varies with pressure raised to the power until saturation pressure is reached. Beyond that point, the rate of adsorption saturates even after applying higher pressure. Thus, the Freundlich adsorption isotherm fails at higher pressure. | 0 | Theoretical and Fundamental Chemistry |
Rotational Echo DOuble Resonance (REDOR) experiment, are a type of heteronuclear dipolar recoupling experiment which enable one to re-introduce heteronuclear dipolar couplings averaged by MAS. The reintroduction of such dipolar coupling reduce the intensity of the NMR signal intensity compared to a reference spectrum where no dephasing pulse is used. REDOR can be used to measure heteronuclear distances, and are the basis of NMR crystallographic studies. | 0 | Theoretical and Fundamental Chemistry |
The Arc system is a two-component system found in some bacteria that regulates gene expression in faculatative anaerobes such as Escheria coli. Two-component system means that it has a sensor molecule and a response regulator. Arc is an abbreviation for Anoxic Redox Control system. Arc systems are instrumental in maintaining energy metabolism during transcription of bacteria. The ArcA response regulator looks at growth conditions and expresses genes to best suit the bacteria. The Arc B sensor kinase, which is a tripartite protein, is membrane bound and can autophosphorylate.
The Arc System was first reported in E. coli strains and subsequently many followed. ArcA/ArcB were first identified as playing an important role in regulation of aerobic and anaerobic pathways by Shiro Iuchi and E. C. Lin. These two scientists designed a genetic screen using the sdh-lacZ operon in a Δlac strain of E. coli. It was shown that mutations in arcA and arcB resulted in elevated levels of enzymes involved in anaerobic fermentation pathways. These two scientists are responsible for the name arc, which originally stood for aerobic respiration control. | 1 | Applied and Interdisciplinary Chemistry |
MALDI matrix compounds such as α-cyano-4-hydroxycinnamic acid have been linked through a linker consisting of an unsymmetric formaldehyde acetals to dodecanol. This type of cleavable detergent is inherently compatible with MALDI and does not have to be removed prior to analysis.
UV light- or fluoride-cleavable surfactants have also been developed but are not in current use. | 0 | Theoretical and Fundamental Chemistry |
Artificial introduction of long dsRNAs or siRNAs has been adopted as a tool to inactivate gene expression, both in cultured cells and in living organisms. Structural and functional resolution of small RNAs as the effectors of RNA silencing has had a direct impact on experimental biology. For example, dsRNA may be synthesized to have a specific sequence complementary to a gene of interest. Once introduced into a cell or biological system, it is recognized as exogenous genetic material and activates the corresponding RNA silencing pathway. This mechanism can be used to effect decreases in gene expression with respect to the target, useful for investigating loss of function for genes relative to a phenotype. That is, studying the phenotypic and/or physiologic effects of expression decreases can reveal the role of a gene product. The observable effects can be nuanced, such that some methods can distinguish between “knockdown” (decrease expression) and “knockout” (eliminate expression) of a gene. RNA interference technologies have been noted recently as one of the most widely utilized techniques in functional genomics. Screens developed using small RNAs have been used to identify genes involved in fundamental processes such as cell division, apoptosis and fat regulation. | 1 | Applied and Interdisciplinary Chemistry |
Eastern meadow voles eat most available species of grasses, sedges, and forbs, including many agricultural plant species. In summer and fall, grasses are cut into match-length sections to reach the succulent portions of the leaves and seedheads. Leaves, flowers, and fruits of forbs are also typical components of the summer diet. Fungi, primarily endogones (Endogone spp.), have been reported in eastern meadow vole diets. They occasionally consume insects and snails, and occasionally scavenge on animal remains; cannibalism is frequent in periods of high population density. Eastern meadow voles may damage woody vegetation by girdling when population density is high.
In winter, eastern meadow voles consume green basal portions of grass plants, often hidden under snow. Other winter diet components include seeds, roots, and bulbs. They occasionally strip the bark from woody plants. Seeds and tubers are stored in nests and burrows. Evidence of coprophagy is sparse, but thought to occur.
In an old-field community in Quebec, plants preferred by eastern meadow voles included quackgrass (Elytrigia repens), sedges, fescues (Festuca spp.), wild strawberry (Fragaria virginiana), timothy (Phleum pratense), bluegrasses (Poa spp.), and bird vetch (Vicia cracca). | 1 | Applied and Interdisciplinary Chemistry |
ATSDR maintains registries of people who were exposed to certain toxic substances or have certain diseases. Participation in these registries is voluntary, and individual data and personal information is kept private. The information collected is used by epidemiologists and other researchers to examine long-term health outcomes or risk factors for illness. It can also help doctors diagnose those health conditions in other individuals and treat them earlier. The agency also uses registries to contact registered individuals with important health information. | 1 | Applied and Interdisciplinary Chemistry |
Gel permeation chromatography (GPC) has become the most widely used technique for analyzing polymer samples in order to determine their molecular weights and weight distributions. Examples of GPC chromatograms of polystyrene samples with their molecular weights and dispersities are shown on the left.
Benoit and co-workers proposed that the hydrodynamic volume, V, which is proportional to the product of [η] and M, where [η] is the intrinsic viscosity of the polymer in the SEC eluent, may be used as the universal calibration parameter. If the Mark–Houwink–Sakurada constants K and α are known (see Mark–Houwink equation), a plot of log [η]M versus elution volume (or elution time) for a particular solvent, column and instrument provides a universal calibration curve which can be used for any polymer in that solvent. By determining the retention volumes (or times) of monodisperse polymer standards (e.g. solutions of monodispersed polystyrene in THF), a calibration curve can be obtained by plotting the logarithm of the molecular weight versus the retention time or volume. Once the calibration curve is obtained, the gel permeation chromatogram of any other polymer can be obtained in the same solvent and the molecular weights (usually M and M) and the complete molecular weight distribution for the polymer can be determined. A typical calibration curve is shown to the right and the molecular weight from an unknown sample can be obtained from the calibration curve. | 0 | Theoretical and Fundamental Chemistry |
The transport of electrons from redox pair NAD/ NADH to the final redox pair 1/2 O/ HO can be summarized as
1/2 O + NADH + H → HO + NAD
The potential difference between these two redox pairs is 1.14 volt, which is equivalent to -52 kcal/mol or -2600 kJ per 6 mol of O.
When one NADH is oxidized through the electron transfer chain, three ATPs are produced, which is equivalent to 7.3 kcal/mol x 3 = 21.9 kcal/mol.
The conservation of the energy can be calculated by the following formula
Efficiency = (21.9 x 100%) / 52 = 42%
So we can conclude that when NADH is oxidized, about 42% of energy is conserved in the form of three ATPs and the remaining (58%) energy is lost as heat (unless the chemical energy of ATP under physiological conditions was underestimated). | 1 | Applied and Interdisciplinary Chemistry |
Williams joined the University of Cambridge as a postdoctoral research associate working with Andrew Bruce Holmes and Richard Friend. Here she focused on the synthesis of electroactive polymers. She then moved to the University of Minnesota, working in the group of Marc Hillymer and William Tollman on zinc catalysis.
In 2003 Williams was appointed to Imperial College London as a lecturer. She was appointed a Senior Lecturer in 2007, a Reader in 2009 and a Professor in 2012. Here she developed sugar-based biodegradable polymers that were produced from lignocellulosic biomass. During her time at Imperial she was an inventor of several granted patents.
She joined Trinity College, Oxford, in 2016. Her research focuses on metal complexes for use in homogeneous polymerisation catalysis. She identified catalysts that could use of carbon dioxide as a raw material for polymers, which prompted Williams to start Econic Technologies. Econic Technologies has received more than £13 million in funding. She also identified transition metal complex catalysts, biorenewable polymers and liquid fuel production. She has developed switchable catalysts that allow the combination of monomers into block copolymers. Working with Milo Shaffer at Imperial College London, Williams uses nanoparticles in polymer composites. She is a member of the London Centre for Nanotechnology.
She appears regularly in the media, including on BBC Radio 4s In Our Time' and at museums and festivals. In 2015 she won the WISE Campaign research award for her eco-plastics start-up. | 0 | Theoretical and Fundamental Chemistry |
Each metabolic pathway consists of a series of biochemical reactions that are connected by their intermediates: the products of one reaction are the substrates for subsequent reactions, and so on. Metabolic pathways are often considered to flow in one direction. Although all chemical reactions are technically reversible, conditions in the cell are often such that it is thermodynamically more favorable for flux to proceed in one direction of a reaction. For example, one pathway may be responsible for the synthesis of a particular amino acid, but the breakdown of that amino acid may occur via a separate and distinct pathway. One example of an exception to this "rule" is the metabolism of glucose. Glycolysis results in the breakdown of glucose, but several reactions in the glycolysis pathway are reversible and participate in the re-synthesis of glucose (gluconeogenesis).
* Glycolysis was the first metabolic pathway discovered:
# As glucose enters a cell, it is immediately phosphorylated by ATP to glucose 6-phosphate in the irreversible first step.
# In times of excess lipid or protein energy sources, certain reactions in the glycolysis pathway may run in reverse to produce glucose 6-phosphate, which is then used for storage as glycogen or starch.
* Metabolic pathways are often regulated by feedback inhibition.
* Some metabolic pathways flow in a cycle wherein each component of the cycle is a substrate for the subsequent reaction in the cycle, such as in the Krebs Cycle (see below).
* Anabolic and catabolic pathways in eukaryotes often occur independently of each other, separated either physically by compartmentalization within organelles or separated biochemically by the requirement of different enzymes and co-factors. | 1 | Applied and Interdisciplinary Chemistry |
The second type of browning, non-enzymatic browning, is a process that also produces the brown pigmentation in foods but without the activity of enzymes. The two main forms of non-enzymatic browning are caramelization and the Maillard reaction. Both vary in the reaction rate as a function of water activity (in food chemistry, the standard state of water activity is most often defined as the partial vapor pressure of pure water at the same temperature).
Caramelization is a process involving the pyrolysis of sugar. It is used extensively in cooking for the desired nutty flavor and brown color. As the process occurs, volatile chemicals are released, producing the characteristic caramel flavor.
The other non-enzymatic reaction is the Maillard reaction. This reaction is responsible for the production of the flavor when foods are cooked. Examples of foods that undergo Maillard reaction include breads, steaks, and potatoes. It is a chemical reaction that takes place between the amine group of a free amino acid and the carbonyl group of a reducing sugar, usually with the addition of heat. The sugar interacts with the amino acid, producing a variety of odors and flavors. The Maillard reaction is the basis for producing artificial flavors for processed foods in the flavoring industry since the type of amino acid involved determines the resulting flavor.
Melanoidins are brown, high molecular weight heterogeneous polymers that are formed when sugars and amino acids combine through the Maillard reaction at high temperatures and low water activity. Melanoidins are commonly present in foods that have undergone some form of non-enzymatic browning, such as barley malts (Vienna and Munich), bread crust, bakery products and coffee. They are also present in the wastewater of sugar refineries, necessitating treatment in order to avoid contamination around the outflow of these refineries. | 1 | Applied and Interdisciplinary Chemistry |
Förster resonance energy transfer is named after the German scientist Theodor Förster. When both chromophores are fluorescent, the term "fluorescence resonance energy transfer" is often used instead, although the energy is not actually transferred by fluorescence. In order to avoid an erroneous interpretation of the phenomenon that is always a nonradiative transfer of energy (even when occurring between two fluorescent chromophores), the name "Förster resonance energy transfer" is preferred to "fluorescence resonance energy transfer"; however, the latter enjoys common usage in scientific literature. FRET is not restricted to fluorescence and occurs in connection with phosphorescence as well. | 1 | Applied and Interdisciplinary Chemistry |
Hai-Lung Dai is a Taiwanese-born American physical chemist and university administrator. He currently is the Laura H. Carnell Professor of Chemistry and Vice President for International Affairs at Temple University in Philadelphia, Pennsylvania, in the United States. | 0 | Theoretical and Fundamental Chemistry |
Phorbol is a natural product found in many plants, especially those of the Euphorbiaceae and Thymelaeaceae families. Phorbol is the active constituent of the highly toxic New World tropical manchineel or beach apple, Hippomane mancinella. It is very soluble in most polar organic solvents, as well as in water. In the manchineel, this leads to an additional exposure risk during rain, where liquid splashing from an undamaged tree may also be injurious. Contact with the tree or consumption of its fruit can lead to symptoms such as severe pain and swelling.
The purging croton, Croton tiglium, is the source of croton oil from which phorbol was initially isolated. Its seeds and oil have been used for hundreds of years in traditional medicine, generally as a purgative, and the seeds were mentioned in Chinese herbal texts 2000 years ago. The purgative effects of the oil are largely attributed to the high percentage of phorbol esters contained in the oil. Phorbol was isolated from C. tiglium seeds in 1934. The structure of the compound was determined in 1967, and a total synthesis was described in 2015. | 0 | Theoretical and Fundamental Chemistry |
The vector lattice (lattice) is defined as the infinite set consisting of all of the translation vectors of a crystal pattern. Each of the vectors in the vector lattice are called lattice vectors. From the vector lattice it is possible to construct a point lattice. This is done by selecting an origin with position vector . The endpoints of each of the vectors make up the point lattice of and . Each point in a point lattice has periodicity i.e., each point is identical and has the same surroundings. There exist an infinite number of point lattices for a given vector lattice as any arbitrary origin can be chosen and paired with the lattice vectors of the vector lattice. The points or particles that are made coincident with one another through a translation are called translation equivalent. | 0 | Theoretical and Fundamental Chemistry |
Residence time distributions are measured by introducing a non-reactive tracer into the system at the inlet. Its input concentration is changed according to a known function and the output concentration measured. The tracer should not modify the physical characteristics of the fluid (equal density, equal viscosity) or the hydrodynamic conditions and it should be easily detectable.
In general, the change in tracer concentration will either be a pulse or a step. Other functions are possible, but they require more calculations to deconvolute the RTD curve. | 0 | Theoretical and Fundamental Chemistry |
Deer have seven types of external scent glands distributed across their bodies. These are the forehead glands (on the forehead), the preorbital glands (below the eyes), the nasal glands (inside the nostrils), the interdigital glands (between the toes), the preputial gland (inside the foreskin of the deer's penis), the metatarsal glands (outside of the hind legs), and the tarsal glands (located inside of the hind legs). Although it is not their primary function, the salivary glands also function as scent glands. Deer rely heavily on the scent glands to communicate with other members of their species, and possibly even with members of other species. A deer may rub its preorbital gland (e.g., on a branch) purely for pleasure. | 1 | Applied and Interdisciplinary Chemistry |
In contrast to the use of mercury (which relies on amalgamation of the gold to coalesce it and separate it from impurities) this method relies on boraxs ability to lower all the minerals melting points. Since the gold is usually the heaviest of these minerals, it allows for concentrating the gold on the bottom of the crucible. The process requires considerably less heat than conventional refining methods, which can be obtainable even in remote locations (using charcoal).
After the ore is crushed into a fine powder, its lightly panned to leave only the heaviest minerals in the pan. Its then thoroughly mixed by three times (by volume) as much of borax and a few drops of water. This mixture is then heated until the whole mixture is molten, after which molten droplets of gold collect on the bottom of the crucible. | 1 | Applied and Interdisciplinary Chemistry |
Wootz steel has been reproduced and studied in depth by the Royal School of Mines. Dr. Pearson was the first to chemically examine wootz in 1795 and he published his contributions to the Philosophical Transactions of the Royal Society.
Russian metallurgist Pavel Petrovich Anosov (see Bulat steel) was almost able to reproduce ancient Wootz steel with nearly all of its properties and the steel he created was very similar to traditional Wootz. He documented four different methods of producing Wootz steel that exhibited traditional patterns. He died before he could fully document and publish his research. Oleg Sherby and Jeff Wadsworth and Lawrence Livermore National Laboratory have all done research, attempting to create steels with characteristics similar to Wootz, but without success. J.D Verhoeven and Alfred Pendray reconstructed methods of production, proved the role of impurities of ore in the pattern creation, and reproduced Wootz steel with patterns microscopically and visually identical to one of the ancient blade patterns. Reibold et al.'s analyses spoke of the presence of carbon nanotubes enclosing nanowires of cementite, with the trace elements/impurities of vanadium, molybdenum, chromium etc. contributing to their creation, in cycles of heating/cooling/forging. This resulted in a hard high carbon steel that remained malleable
There are smiths who are now consistently producing Wootz steel blades visually identical to the old patterns. Steel manufactured in Kutch particularly enjoyed a widespread reputation, similar to those manufactured at Glasgow and Sheffield.
Wootz was made over nearly a 2,000-year period (the oldest sword samples date to around 200 AD) and the methods of production of ingots, the ingredients, and the methods of forging varied from one area to the next. Some Wootz blades displayed a pattern, while some did not. Heat treating was quite different from forging, and there were many different patterns which were created by the various smiths who spanned from China to Scandinavia. | 1 | Applied and Interdisciplinary Chemistry |
The mixed reactants pass an observation cell that allows the reaction to be followed spectrophotometrically, typically by ultraviolet spectroscopy, fluorescence spectroscopy, circular dichroism or light scattering, and it is now common to combine several of these.
Observation cuvette with a short light path (0.75 to 1.5mm) are usually preferred for fluorescence measurements to reduce self-absorption effects. Observation cuvette with longer light path (0.5 cm to 1 cm) are preferred for absorbance measurements. Modern stopped-flow can accommodate different models of cells and it is possible to change the cuvette between two experiments.
For stopped-flow X-ray measurements, a quartz capillary with thin wall is used to minimize quartz absorption. Simultaneous x-ray and absorbance measurements are possible in the same capillary. | 0 | Theoretical and Fundamental Chemistry |
This technology is currently being incorporated into a variety of industries for applications in effluent treatment areas such as:
* Groundwater remediation
* Volatile Organic Compound Removal
* Dye-house Effluent De-Colourisation
* Electrochemical Disinfection | 0 | Theoretical and Fundamental Chemistry |
Camphorsultam is synthesized by reduction of camphorsulfonylimine. This reaction was originally performed as a catalytic hydrogenation using Raney Nickel, but the modern preparation instead uses lithium aluminium hydride for the reduction. These reductive methods are stereoselective: although both the endo and exo diastereomeric forms are theoretically possible, only the exo isomer is actually produced due to steric effects of one of the methyl groups. Camphorsultam is often referred to as Oppolzers sultam' in reference to Wolfgang Oppolzer and colleagues, who developed the lithium aluminium hydride approach to this compound and pioneered its use in asymmetric synthesis. | 0 | Theoretical and Fundamental Chemistry |
Let and be the numerical values of the concentrations of a given contaminant, respectively before and after treatment, following a defined process.
It is irrelevant in what units these concentrations are given, provided that both use the same units.
Then an and -log reduction is achieved, where
For the purpose of presentation, the value of is rounded down to a desired precision, usually to a whole number.
;Example:
Let the concentration of some contaminant be 580 ppm before and 0.725 ppm after treatment. Then
Rounded down, is 2, so a 2-log reduction is achieved.
Conversely, an -log reduction means that a reduction by a factor of has been achieved. | 0 | Theoretical and Fundamental Chemistry |
Plants are under horticulture care, but the environment is managed to near natural conditions. This occurs with either restored or semi-natural environments. This technique is primarily used for taxa that are rare or in areas where habitat has been severely degraded. | 1 | Applied and Interdisciplinary Chemistry |
The lacUV5 promoter is a mutated promoter from the Escherichia coli lac operon which is used in molecular biology to drive gene expression on a plasmid. lacUV5 is very similar to the classical lac promoter, containing just 2 base pair mutations in the -10 hexamer region, compared to the lac promoter. LacUV5 is among the most commonly used promoters in molecular biology because it requires no additional activators and it drives high levels of gene expression.
The lacUV5 promoter sequence conforms more closely to the consensus sequence recognized by bacterial sigma factors than the traditional lac promoter does. Due to this, lacUV5 recruits RNA Polymerase more effectively, thus leading to higher transcription of target genes. Additionally, unlike the lac promoter, lacUV5 works independently of activator proteins or other cis regulatory elements (apart from the -10 and -35 promoter regions). While no activators are required, lacUV5 promoter expression can be regulated by the LacI repressor and can be induced with IPTG, which is an effective inducer of protein expression when used in the concentration range of 100 μM to 1.5 mM. Due to this control, the lacUV5 promoter is commonly found on expression plasmids and is used when controllable but high levels of a product are desired.
The lacUV5 mutation was first identified in 1970 in a study of lac promoter mutants that produce higher yields. Some of them, including UV5, has lost catabolite repression at the CAP site. Development into cloning vectors is known since 1982, when a UV5-carrying phage known as "λ h80 lacUV5 cI857" has its genome spliced with the HaeIII restriction enzyme to make plasmids carrying the fragment with UV5. | 1 | Applied and Interdisciplinary Chemistry |
The process was based on the oxidation of hydrogen chloride:
:4 HCl + O → 2 Cl + 2HO
The reaction takes place at about 400 to 450 °C in the presence of a variety of catalysts, including copper chloride (CuCl). Three companies developed commercial processes for producing chlorine based on the Deacon reaction:
*The Kel-Chlor process developed by the M. W. Kellogg Company, which utilizes nitrosylsulfuric acid.
*The Shell-Chlor process developed by the Shell Oil Company, which utilizes copper catalysts.
*The MT-Chlor process developed by the Mitsui Toatsu Company, which utilizes chromium-based catalysts.
The Deacon process is now outdated technology. Most chlorine today is produced by using electrolytic processes. New catalysts based on ruthenium(IV) oxide have been developed by Sumitomo. | 0 | Theoretical and Fundamental Chemistry |
Currently, there is ongoing research in developing new ways of utilizing the knowledge already associated with affinity electrophoresis to improve its functionality and speed, as well as attempts to improve already established methods and tailor them towards performing specific tasks. | 1 | Applied and Interdisciplinary Chemistry |
Sulfuric acid created by John Roebuck's process approached a 65% concentration. Later refinements to the lead chamber process by French chemist Joseph Louis Gay-Lussac and British chemist John Glover improved concentration to 78%. However, the manufacture of some dyes and other chemical processes require a more concentrated product. Throughout the 18th century, this could only be made by dry distilling minerals in a technique similar to the original alchemical processes. Pyrite (iron disulfide, ) was heated in air to yield iron(II) sulfate, , which was oxidized by further heating in air to form iron(III) sulfate, , which, when heated to 480 °C, decomposed to iron(III) oxide and sulfur trioxide, which could be passed through water to yield sulfuric acid in any concentration. However, the expense of this process prevented the large-scale use of concentrated sulfuric acid. | 0 | Theoretical and Fundamental Chemistry |
The starting material for this route is a norbornane derivative with a good leaving group in position 2. If the leaving group is on the exo- face, electron density from the σ bond between carbons 1 and 6 is donated into the σ* antibond between carbon 2 and the leaving group (see Figure 8b).
If the leaving group is on the endo- face, the leaving group first leaves on its own. Then electron density from the σ bond between carbons 1 and 6 is donated into the resulting empty atomic orbital on carbon 2. However, this formation route is much slower than that of the exo- isomer because the σ bond cannot provide anchimeric assistance for the first step, making the activation energy to the first transition state much higher. Additionally, if there is a high concentration of reactive electrophiles in the reaction mixture, formation of a newly substituted norbornane derivative may preclude non-classical ion formation.
An example of this formation route is the reaction that led Winstein and Trifan to propose the delocalized structure of the 2-norbornyl cation. 2-norbornyl tosylates and brosylates form the 2-norbornyl cation through this route as an intermediate towards solvolysis. | 0 | Theoretical and Fundamental Chemistry |
One of the most important features of chemical synapses is that they are the site of action for the majority of psychoactive drugs. Synapses are affected by drugs, such as curare, strychnine, cocaine, morphine, alcohol, LSD, and countless others. These drugs have different effects on synaptic function, and often are restricted to synapses that use a specific neurotransmitter. For example, curare is a poison that stops acetylcholine from depolarizing the postsynaptic membrane, causing paralysis. Strychnine blocks the inhibitory effects of the neurotransmitter glycine, which causes the body to pick up and react to weaker and previously ignored stimuli, resulting in uncontrollable muscle spasms. Morphine acts on synapses that use endorphin neurotransmitters, and alcohol increases the inhibitory effects of the neurotransmitter GABA. LSD interferes with synapses that use the neurotransmitter serotonin. Cocaine blocks reuptake of dopamine and therefore increases its effects. | 1 | Applied and Interdisciplinary Chemistry |
Cloning has been used in fiction as a way of recreating historical figures. In the 1976 Ira Levin novel The Boys from Brazil and its 1978 film adaptation, Josef Mengele uses cloning to create copies of Adolf Hitler.
In Michael Crichtons 1990 novel Jurassic Park, which spawned a series of Jurassic Park' feature films, the bioengineering company InGen develops a technique to resurrect extinct species of dinosaurs by creating cloned creatures using DNA extracted from fossils. The cloned dinosaurs are used to populate the Jurassic Park wildlife park for the entertainment of visitors. The scheme goes disastrously wrong when the dinosaurs escape their enclosures. Despite being selectively cloned as females to prevent them from breeding, the dinosaurs develop the ability to reproduce through parthenogenesis. | 1 | Applied and Interdisciplinary Chemistry |
Self-healing hydrogels encompass a wide range of applications. With a high biocompatibility, hydrogels are useful for a number of medical applications. Areas where active research is currently being conducted include:
*Absorbable sutures
*Tissue engineering and regeneration
*Drug delivery | 0 | Theoretical and Fundamental Chemistry |
RNA-Seq has the potential to identify new disease biology, profile biomarkers for clinical indications, infer druggable pathways, and make genetic diagnoses. These results could be further personalized for subgroups or even individual patients, potentially highlighting more effective prevention, diagnostics, and therapy. The feasibility of this approach is in part dictated by costs in money and time; a related limitation is the required team of specialists (bioinformaticians, physicians/clinicians, basic researchers, technicians) to fully interpret the huge amount of data generated by this analysis. | 1 | Applied and Interdisciplinary Chemistry |
A common assumption is that the Casimir force is of little practical use; the argument is made that the only way to actually gain energy from the two plates is to allow them to come together (getting them apart again would then require more energy), and therefore it is a one-use-only tiny force in nature. In 1984 Robert Forward published work showing how a "vacuum-fluctuation battery" could be constructed; the battery can be recharged by making the electrical forces slightly stronger than the Casimir force to reexpand the plates.
In 1999, Pinto, a former scientist at NASAs Jet Propulsion Laboratory at Caltech in Pasadena, published in Physical Review' his thought experiment (Gedankenexperiment) for a "Casimir engine". The paper showed that continuous positive net exchange of energy from the Casimir effect was possible, even stating in the abstract "In the event of no other alternative explanations, one should conclude that major technological advances in the area of endless, by-product free-energy production could be achieved."
Garret Moddel at University of Colorado has highlighted that he believes such devices hinge on the assumption that the Casimir force is a nonconservative force, he argues that there is sufficient evidence (e.g. analysis by Scandurra (2001)) to say that the Casimir effect is a conservative force and therefore even though such an engine can exploit the Casimir force for useful work it cannot produce more output energy than has been input into the system.
In 2008, DARPA solicited research proposals in the area of Casimir Effect Enhancement (CEE). The goal of the program is to develop new methods to control and manipulate attractive and repulsive forces at surfaces based on engineering of the Casimir force.
A 2008 patent by Haisch and Moddel details a device that is able to extract power from zero-point fluctuations using a gas that circulates through a Casimir cavity. A published test of this concept by Moddel was performed in 2012 and seemed to give excess energy that could not be attributed to another source. However it has not been conclusively shown to be from zero-point energy and the theory requires further investigation. | 0 | Theoretical and Fundamental Chemistry |
The oxygen effect has particular importance in external beam radiation therapy where the killing of tumour cells with photon and electron beams in well oxygenated regions can be up to three times greater than in a poorly vasculated portion of the tumour.
Besides tumour hypoxia, the oxygen effect is also relevant to hypoxia conditions present in the normal physiology of stem cell niches such as the endosteum adjacent to bone in bone marrow and the epithelium layer of the intestine. In addition, there are non-malignant diseases where oxygenated tissues can become hypoxic such as in stenosed coronary arteries associated with cardiovascular disease. | 1 | Applied and Interdisciplinary Chemistry |
Nitrite produced in the first step of autotrophic nitrification is oxidized to nitrate by nitrite oxidoreductase (NXR) (). It is a membrane-associated iron-sulfur molybdo protein and is part of an electron transfer chain which channels electrons from nitrite to molecular oxygen. The enzymatic mechanisms involved in nitrite-oxidizing bacteria are less described than that of ammonium oxidation. Recent research (e.g. Woźnica A. et al., 2013) proposes a new hypothetical model of NOB electron transport chain and NXR mechanisms. Here, in contrast to earlier models, the NXR would act on the outside of the plasma membrane and directly contribute to a mechanism of proton gradient generation as postulated by Spieck and coworkers. Nevertheless, the molecular mechanism of nitrite oxidation is an open question. | 1 | Applied and Interdisciplinary Chemistry |
Triatomic molecules are molecules composed of three atoms, of either the same or different chemical elements. Examples include HO, CO (pictured), HCN, O (ozone) and NO. | 0 | Theoretical and Fundamental Chemistry |
The hydrogen requirement of Arrhenius and Brønsted–Lowry was removed by the Lewis definition of acid–base reactions, devised by Gilbert N. Lewis in 1923, in the same year as Brønsted–Lowry, but it was not elaborated by him until 1938. Instead of defining acid–base reactions in terms of protons or other bonded substances, the Lewis definition defines a base (referred to as a Lewis base) to be a compound that can donate an electron pair, and an acid (a Lewis acid) to be a compound that can receive this electron pair.
For example, boron trifluoride, is a typical Lewis acid. It can accept a pair of electrons as it has a vacancy in its octet. The fluoride ion has a full octet and can donate a pair of electrons. Thus
is a typical Lewis acid, Lewis base reaction. All compounds of group 13 elements with a formula can behave as Lewis acids. Similarly, compounds of group 15 elements with a formula , such as amines, , and phosphines, , can behave as Lewis bases. Adducts between them have the formula with a dative covalent bond, shown symbolically as ←, between the atoms A (acceptor) and D (donor). Compounds of group 16 with a formula may also act as Lewis bases; in this way, a compound like an ether, , or a thioether, , can act as a Lewis base. The Lewis definition is not limited to these examples. For instance, carbon monoxide acts as a Lewis base when it forms an adduct with boron trifluoride, of formula .
Adducts involving metal ions are referred to as co-ordination compounds; each ligand donates a pair of electrons to the metal ion. The reaction
can be seen as an acid–base reaction in which a stronger base (ammonia) replaces a weaker one (water).
The Lewis and Brønsted–Lowry definitions are consistent with each other since the reaction
is an acid–base reaction in both theories. | 0 | Theoretical and Fundamental Chemistry |
Potassium is the major cation (K, a positive ion) inside animal cells, while sodium (Na) is the major cation outside animal cells. The difference between the concentrations of these charged particles causes a difference in electric potential between the inside and outside of cells, known as the membrane potential. The balance between potassium and sodium is maintained by ion transporters in the cell membrane. All potassium ion channels are tetramers with several conserved secondary structural elements. A number of potassium channel structures have been solved including voltage gated, ligand gated, tandem-pore, and inwardly rectifying channels, from prokaryotes and eukaryotes. The cell membrane potential created by potassium and sodium ions allows the cell to generate an action potential—a "spike" of electrical discharge. The ability of cells to produce electrical discharge is critical for body functions such as neurotransmission, muscle contraction, and heart function. | 1 | Applied and Interdisciplinary Chemistry |
With the restoration of democracy in 1974, Zervas was able to contribute once more to research and educational policy. As previously, refusing to take a salary for these positions, he served a second time as the President of the Greek Atomic Energy Commission (1974–1975) and then as the President of the National Hellenic Research Foundation (1975–1979).
Zervas had suffered from periodic issues with respiratory health throughout his adult life, but in his final years the situation deteriorated. The extended use of phosgene in his research has been implicated as the cause of this chronic pulmonary disease. He showed perseverance and a pleasant attitude despite his health issues, continuing to attend meetings of the Academy of Athens until the very end of his life. This came in the summer of 1980 after an acute pulmonary episode, which lasted three weeks before he died at the age of 78. | 0 | Theoretical and Fundamental Chemistry |
Dr. Diana Fleischman, of the University of Portsmouth, and colleagues looked for a relationship between progesterone and sexual attitudes in 92 women. Their research, published in the Archives of Sexual Behavior found that women who had higher levels of progesterone scored higher on a questionnaire measuring homoerotic motivation. They also found that men who had high levels of progesterone were more likely to have higher homoerotic motivation scores after affiliative priming compared to men with low levels of progesterone. | 0 | Theoretical and Fundamental Chemistry |
Foam, entrained and dissolved air that are present in coolants and processing liquids, may cause various kinds of problems, including:
* Reduction of pump efficiency (cavitation)
* Reduced capacity of pumps and storage tanks
* Bacterial growth
* Dirt flotation / deposit formation
* Reduced effectiveness of the fluid solution(s)
* Eventual downtime to clean tanks
* Drainage problems in sieves and filters
* Formation problems (i.e. in a paper mill it may cause the fibers to form an inhomogeneous sheet)
* Cost of replenishing the liquid
* Cost of entire material rejection due to imperfections | 0 | Theoretical and Fundamental Chemistry |
The ICP-MS allows determination of elements with atomic mass ranges 7 to 250 (Li to U), and sometimes higher. Some masses are prohibited such as 40 due to the abundance of argon in the sample. Other blocked regions may include mass 80 (due to the argon dimer), and mass 56 (due to ArO), the latter of which greatly hinders Fe analysis unless the instrumentation is fitted with a reaction chamber. Such interferences can be reduced by using a high resolution ICP-MS (HR-ICP-MS) which uses two or more slits to constrict the beam and distinguish between nearby peaks. This comes at the cost of sensitivity. For example, distinguishing iron from argon requires a resolving power of about 10,000, which may reduce the iron sensitivity by around 99%. Another solution for some interfering species is the use of a collision chamber, as explained in collision reaction cell article.
A single collector ICP-MS may use a multiplier in pulse counting mode to amplify very low signals, an attenuation grid or a multiplier in analogue mode to detect medium signals, and a Faraday cup/bucket to detect larger signals. A multi-collector ICP-MS may have more than one of any of these, normally Faraday buckets which are much less expensive. With this combination, a dynamic range of 12 orders of magnitude, from 1 ppq to 100 ppm is possible.
ICP-MS is a method of choice for the determination of cadmium in biological samples.
Unlike atomic absorption spectroscopy, which can only measure a single element at a time, ICP-MS has the capability to scan for all elements simultaneously. This allows rapid sample processing. A simultaneous ICP-MS that can record the entire analytical spectrum from lithium to uranium in every analysis won the Silver Award at the 2010 Pittcon Editors' Awards. An ICP-MS may use multiple scan modes, each one striking a different balance between speed and precision. Using the magnet alone to scan is slow, due to hysteresis, but is precise. Electrostatic plates can be used in addition to the magnet to increase the speed, and this, combined with multiple collectors, can allow a scan of every element from Lithium 6 to Uranium Oxide 256 in less than a quarter of a second. For low detection limits, interfering species and high precision, the counting time can increase substantially. The rapid scanning, large dynamic range and large mass range is ideally suited to measuring multiple unknown concentrations and isotope ratios in samples that have had minimal preparation (an advantage over TIMS), for example seawater, urine, and digested whole rock samples. It also lends well to laser ablated rock samples, where the scanning rate is so quick that a real time plot of any number of isotopes is possible. This also allows easy spatial mapping of mineral grains. | 0 | Theoretical and Fundamental Chemistry |
The process of DNA replication inherently places cells at risk of acquiring mutations. Thus, caretaker genes are vitally important to cellular health. Rounds of cell replication allow fixation of mutated genes into the genome. Caretaker genes provide genome stability by preventing the accumulation of these mutations.
Factors that contribute to genome stabilization include proper cell-cycle checkpoints, DNA repair pathways, and other actions that ensure cell survival following DNA damage. Specific DNA maintenance operations encoded by caretaker genes include nucleotide excision repair, base excision repair, non-homologous end joining recombination pathways, mismatch repair pathways, and telomere metabolism.
Loss of function mutations in caretaker genes allow mutations in other genes to survive that can result in increased conversion of a normal cell to a neoplastic cell, a cell that; (1) divides more often than it should or (2) does not die when conditions warrant cell death. Thus, caretaker genes do not directly regulate cell proliferation. Instead, they prevent other mutations from surviving for example by slowing the cell division process to enable DNA repair to complete, or by initiating apoptosis of the cell. In genetic knock-out and rescue experiments, restoration of a caretaker gene from the mutated form to the wildtype version does not limit tumorigenesis. This is because caretaker genes only indirectly contribute to the pathway to cancer.
Cells deficient in a DNA repair process tend to accumulate unrepaired DNA damages. Cells defective in apoptosis tend to survive even with excessive DNA damage, thus permitting replication of the damaged DNA and consequently carcinogenic mutations. Some key caretaker proteins that contribute to cell survival by acting in DNA repair processes when the level of damage is manageable, become executioners by inducing apoptosis when there is excess DNA damage.
Inactivation of caretaker genes is environmentally equivalent to exposing the cell to mutagens incessantly. For example, a mutation in a caretaker gene coding for a DNA repair pathway that leads to the inability to properly repair DNA damage could allow uncontrolled cell growth. This is the result of mutations of other genes that accumulate unchecked as a result of faulty gene products encoded by the caretakers.
In addition to providing genomic stability, caretakers also provide chromosomal stability. Chromosomal instability resulting from dysfunctional caretaker genes is the most common form of genetic instability that leads to cancer in humans. In fact, it has been proposed that these caretaker genes are responsible for many hereditary predispositions to cancers.
In individuals predisposed to cancer via mutations in caretaker genes, a total of three subsequent somatic mutations are required to acquire the cancerous phenotype. Mutations must occur in the remaining normal caretaker allele in addition to both alleles of gatekeeper genes within that cell for the said cell to turn to neoplasia. Thus, the risk of cancer in these affected populations is much less when compared to cancer risk in families predisposed to cancer via the gatekeeper pathway. | 1 | Applied and Interdisciplinary Chemistry |
One recent, successful business endeavor has been the introduction of AFPs into ice cream and yogurt products. This ingredient, labelled ice-structuring protein, has been approved by the Food and Drug Administration. The proteins are isolated from fish and replicated, on a larger scale, in genetically modified yeast.
There is concern from organizations opposed to genetically modified organisms (GMOs) who believe that antifreeze proteins may cause inflammation. Intake of AFPs in diet is likely substantial in most northerly and temperate regions already. Given the known historic consumption of AFPs, it is safe to conclude their functional properties do not impart any toxicologic or allergenic effects in humans.
As well, the transgenic process of ice structuring proteins production is widely used in society. Insulin and rennet are produced using this technology. The process does not impact the product; it merely makes production more efficient and prevents the death of fish that would otherwise be killed to extract the protein.
Currently, Unilever incorporates AFPs into some of its American products, including some Popsicle ice pops and a new line of Breyers Light Double Churned ice cream bars. In ice cream, AFPs allow the production of very creamy, dense, reduced fat ice cream with fewer additives. They control ice crystal growth brought on by thawing on the loading dock or kitchen table, which reduces texture quality.
In November 2009, the Proceedings of the National Academy of Sciences published the discovery of a molecule in an Alaskan beetle that behaves like AFPs, but is composed of saccharides and fatty acids.
A 2010 study demonstrated the stability of superheated water ice crystals in an AFP solution, showing that while the proteins can inhibit freezing, they can also inhibit melting.
In 2021, EPFL and Warwick scientists have found an artificial imitation of antifreeze proteins. | 1 | Applied and Interdisciplinary Chemistry |
Levonorgestrel is used in emergency contraceptive pills (ECPs), both in a combined Yuzpe regimen which includes estrogen, and as a levonorgestrel-only method. The levonorgestrel-only method uses levonorgestrel 1.5 mg (as a single dose or as two 0.75 mg doses 12 hours apart) taken within three days of unprotected sex. With one study indicating that beginning as late as 120 hours (5 days) after intercourse could be effective. However, taking more than one dose of emergency contraception does not increase the chance of pregnancy not happening. Planned Parenthood asserts "Taking the morning-after pill (also known as emergency contraception) multiple times doesnt change its effectiveness, and wont cause any long-term side effects." There is no age, I.D., or prescription required to purchase emergency contraception. Plan B hit the market in 1999 where it could be bought by anyone older than 18. However, in 2013, the rules were changed so that Plan B could be purchased at any age without ID or prescription.
The primary mechanism of action of levonorgestrel as a progestogen-only emergency contraceptive pill is, according to International Federation of Gynecology and Obstetrics (FIGO), to prevent fertilization by inhibition of ovulation and thickening of cervical mucus. FIGO has stated that: "review of the evidence suggests that LNG [levonorgestreol] ECPs cannot prevent implantation of a fertilized egg. Language on implantation should not be included in LNG ECP product labeling." In November 2013, the European Medicines Agency (EMA) approved a change to the label saying it cannot prevent implantation of a fertilized egg.
Other studies still find the evidence to be unclear. While it is unlikely that emergency contraception affects implantation it is impossible to completely exclude the possibility of post-fertilization effect.
In November 2013, the EMA also approved a change to the label for HRA Pharmas NorLevo' saying: "In clinical trials, contraceptive efficacy was reduced in women weighing 75 kg [165 pounds] or more, and levonorgestrel was not effective in women who weighed more than 80 kg [176 pounds]." In November 2013 and January 2014, the FDA and the EMA said they were reviewing whether increased weight and body mass index (BMI) reduce the efficacy of emergency contraceptives.
An analysis of four WHO randomised clinical trials, published in January 2017, showed pregnancy rates of 1.25% (68/5428) in women with BMI under 25, 0.61% (7/1140) in women with BMI between 25 and 30, and 2.03% (6/295) in women with BMI over 30. These values yield an eight-fold reduction in efficacy for women with BMI over 30 compared to women with BMI under 25. However, emergency contraceptives remain effective regardless of BMI. | 0 | Theoretical and Fundamental Chemistry |
The process by which a photon initiates a chemical reaction directly is known as photolysis; if this process is aided by a catalyst, it is called photocatalysis. If a photon has more energy than a material's characteristic band gap, it can free an electron upon absorption by the material. The remaining, positively charged hole and the free electron may recombine, generating heat, or they can take part in photoreactions with nearby species. If the photoreactions with these species result in regeneration of the electron-donating material—i.e., if the material acts as a catalyst for the reactions—then the reactions are deemed photocatalytic. PECO represents a type of photocatalysis whereby semiconductor-based electrochemistry catalyzes an oxidation reaction—for example, the oxidative degradation of an airborne contaminant in air purification systems.
The principal objective of photoelectrocatalysis is to provide low-energy activation pathways for the passage of electronic charge carriers through the electrode electrolyte interface and, in particular, for the photoelectrochemical generation of chemical products. With regard to photoelectrochemical oxidation, we may consider, for example, the following system of reactions, which constitute TiO-catalyzed oxidation.
:TiO (hv) → TiO (e + h)
:TiO(h) +RX → TiO + RX
:TiO(h) + HO → TiO + HO + H
:TiO(h) + OH → TiO + HO
:TiO(e) + O → TiO + O
This system shows a number of pathways for the production of oxidative species that facilitate the oxidation of the species, RX, in addition to its direct oxidation by the excited TiO itself. PECO concerns such a process where the electronic charge carriers are able to readily move through the reaction medium, thereby to some extent mitigating recombination reactions that would limit the oxidative process. The “photoelectrochemical cell” in this case could be as simple as a very small particle of the semiconductor catalyst. Here, on the “light” side a species is oxidized, while on the “dark” side a separate species is reduced. | 0 | Theoretical and Fundamental Chemistry |
The Redlich–Kwong equation is formulated as:
where:
*p is the gas pressure
*R is the gas constant,
*T is temperature,
*V is the molar volume (V/n),
*a is a constant that corrects for attractive potential of molecules, and
*b is a constant that corrects for volume.
The constants are different depending on which gas is being analyzed. The constants can be calculated from the critical point data of the gas:
where:
*T is the temperature at the critical point, and
*P is the pressure at the critical point.
The Redlich–Kwong equation can also be represented as an equation for the compressibility factor of gas, as a function of temperature and pressure:
where:
Or more simply:
This equation only implicitly gives Z as a function of pressure and temperature, but is easily solved numerically, originally by graphical interpolation, and now more easily by computer. Moreover, analytic solutions to cubic functions have been known for centuries and are even faster for computers. The Redlich-Kwong equation of state may also be expressed as a cubic function of the molar volume.
For all Redlich–Kwong gases:
where:
*Z is the compressibility factor at the critical point
Using the equation of state can be written in the reduced form:
And since it follows: with
From the Redlich–Kwong equation, the fugacity coefficient of a gas can be estimated: | 0 | Theoretical and Fundamental Chemistry |
Volatile thiols are easily and almost unerringly detected by their distinctive odor. Sulfur-specific analyzers for gas chromatographs are useful. Spectroscopic indicators are the DO-exchangeable SH signal in the H NMR spectrum (S is NMR-active but signals for divalent sulfur are very broad and of little utility). The ν band appears near 2400 cm in the IR spectrum. In the nitroprusside reaction, free thiol groups react with sodium nitroprusside and ammonium hydroxide to give a red colour. | 0 | Theoretical and Fundamental Chemistry |
Isocyanides have a very disagreeable odour. To quote from Lieke, "Es besitzt einen penetranten, höchst unangenehmen Geruch; das Oeffnen eines Gefässes mit Cyanallyl reicht hin, die Luft eines Zimmers mehrere Tage lang zu verpesten, ..." (It has a penetrating, extremely unpleasant odour; the opening of a flask of allyl [iso]cyanide is enough to foul up the air in a room for several days). Note that in Lieke's day, the difference between isocyanide and nitrile was not fully appreciated.
Ivar Karl Ugi states that "The development of the chemistry of isocyanides has probably suffered only little delay through the characteristic odor of volatile isonitriles, which has been described by Hofmann and Gautier as highly specific, almost overpowering, horrible, and extremely distressing. It is true that many potential workers in this field have been turned away by the odour, but this is heavily outweighed by the fact that isonitriles can be detected even in traces, and that most of the routes leading to the formation of isonitriles were discovered through the odor of these compounds." Isocyanides have been investigated as potential non-lethal weapons.
Some isocyanides convey less offensive odours such as malt, natural rubber, creosote, cherry or old wood. Non-volatile derivatives such as tosylmethyl isocyanide do not have an odor. | 0 | Theoretical and Fundamental Chemistry |
Dose-dependent changes of heart rate and cardiac output are observed within the first hour after administration of ractopamine and gradually return to baseline values. The systolic blood pressure will also increase in a dose-dependent manner, while the diastolic pressure remains unchanged. | 0 | Theoretical and Fundamental Chemistry |
The plot is occasionally attributed to Augustinsson and referred to the Woolf–Augustinsson–Hofstee plot or simply the Augustinsson plot. However, although Haldane, Woolf or Eadie were not explicitly cited when Augustinsson introduced the versus equation, both the work of Haldane and of Eadie are cited at other places of his work and are listed in his bibliography. | 1 | Applied and Interdisciplinary Chemistry |
Massively parallel single molecule direct RNA-Seq has been explored as an alternative to traditional RNA-Seq, in which RNA-to-cDNA conversion, ligation, amplification, and other sample manipulation steps may introduce biases and artifacts. Technology platforms that perform single-molecule real-time RNA-Seq include Oxford Nanopore Technologies (ONT) Nanopore sequencing, PacBio IsoSeq, and Helicos (bankrupt). Sequencing RNA in its native form preserves modifications like methylation, allowing them to be investigated directly and simultaneously. Another benefit of single-molecule RNA-Seq is that transcripts can be covered in full length, allowing for higher confidence isoform detection and quantification compared to short-read sequencing. Traditionally, single-molecule RNA-Seq methods have higher error rates compared to short-read sequencing, but newer methods like ONT direct RNA-Seq limit errors by avoiding fragmentation and cDNA conversion. Recent uses of ONT direct RNA-Seq for differential expression in human cell populations have demonstrated that this technology can overcome many limitations of short and long cDNA sequencing. | 1 | Applied and Interdisciplinary Chemistry |
* [http://aeesociety.org/ American Ecological Engineering Society], homepage.
* [http://groups.engr.oregonstate.edu/eess/ Ecological Engineering Student Society] Website, EESS, Oregon State University, 2011.
* [https://web.archive.org/web/20170919162604/http://aspwe.org/ American Society of Professional Wetland Engineers], homepage, wiki.
* [http://www.ecological-engineering.com/ Ecological Engineering Group], homepage.
* [http://www.iees.ch/ International Ecological Engineering Society] homepage. | 1 | Applied and Interdisciplinary Chemistry |
Like the preceding method, the most popular method for synthesizing phosphaalkynes is reliant upon the expulsion of products containing strong silicon-element bonds. Specifically, it is possible to synthesize phosphaalkynes via the elimination of hexamethyldisiloxane (HMDSO) from certain silylated phosphaalkenes with the general structure RO(SiMe)C=PSiMe. These phosphaalkenes are formed rapidly following the synthesis of the appropriate acyl bis-trimethylsilylphosphine, which undergoes a rapid [1,3]-silyl shift to produce the relevant phosphaalkene. This synthetic strategy is particularly appealing because the precursors (an acyl chloride and tris-trimethylsilylphosphine or bis-trimethylsilylphosphide) are either readily available or simple to synthesize.
This method has been utilized to produce a variety of kinetically stable phosphaalkynes, including aryl, tertiary alkyl, secondary alkyl, and even primary alkyl phosphaalkynes in good yields. | 0 | Theoretical and Fundamental Chemistry |
Minerals are the exogenous chemical elements indispensable for life. Although the four elements: carbon, hydrogen, oxygen, and nitrogen (CHON) are essential for life, they are so plentiful in food and drink that these are not considered nutrients and there are no recommended intakes for these as minerals. The need for nitrogen is addressed by requirements set for protein, which is composed of nitrogen-containing amino acids. Sulfur is essential, but again does not have a recommended intake. Instead, recommended intakes are identified for the sulfur-containing amino acids methionine and cysteine.
The essential nutrient trace elements for humans, listed in order of Recommended Dietary Allowance (expressed as a mass), are potassium, chloride, sodium, calcium, phosphorus, magnesium, iron, zinc, manganese, copper, iodine, chromium, molybdenum, selenium. Additionally, cobalt is a component of Vitamin B which is essential. There are other minerals which are essential for some plants and animals, but may or may not be essential for humans, such as boron and silicon. | 0 | Theoretical and Fundamental Chemistry |
Although the liquid is static and the sphere is moving with a certain velocity, with respect to the frame of sphere, the sphere is at rest and liquid is flowing in the opposite direction to the motion of the sphere. | 1 | Applied and Interdisciplinary Chemistry |
Data recording in a 3D optical storage medium requires that a change take place in the medium upon excitation. This change is generally a photochemical reaction of some sort, although other possibilities exist. Chemical reactions that have been investigated include photoisomerizations, photodecompositions and photobleaching, and polymerization initiation. Most investigated have been photochromic compounds, which include azobenzenes, spiropyrans, stilbenes, fulgides, and diarylethenes. If the photochemical change is reversible, then rewritable data storage may be achieved, at least in principle. Also, MultiLevel Recording, where data is written in "grayscale" rather than as "on" and "off" signals, is technically feasible. | 0 | Theoretical and Fundamental Chemistry |
Solenopsins are described as toxic against vertebrates and invertebrates. For example, the compound known as isosolenopsin A has been demonstrated to have strong insecticidal effects which may play a central role in the biology of fire ants.
In addition to its toxicity, solenopsis has a number of other biological activities. It inhibits angiogenesis in vitro via the phosphoinositide 3-kinase (PI3K) signaling pathway, inhibits neuronal nitric oxide synthase (nNOS) in a manner that appears to be non-competitive with -arginine, and inhibits quorum-sensing signaling in some bacteria. The biological activities of solenopsins have led researchers to propose a number of biotechnological and biomedical applications for these compounds. For instance, mentioned anti-bacterial and interference in quorum-sensing signalling apparently provide solenopsins with considerable anti-biofilm activity, which suggests the potential of analogs as new disinfectants and surface-conditioning agents. Also, solenopsins have been demonstrated to inhibit cell division and viability of Trypanosoma cruzi, the cause of Chagas disease, which suggests these alkaloids as potential chemotherapeutic drugs.
Solenopsin and analogs share structural and biological properties with the sphingolipid ceramide, a major endogenous regulator of cell signaling, inducing mitophagy and anti-proliferative effects in different tumor cell lines.
Synthetic analogs of solenopsin are being studied for the potential treatment of psoriasis. | 0 | Theoretical and Fundamental Chemistry |
Dimetcote is commonly used for steel corrosion resistance. It is generally reliable under humid or corrosive conditions. Because of this, Dimetcote is widely used in ships, power generation facilities, and marine, oil, and offshore structures. | 1 | Applied and Interdisciplinary Chemistry |
The process of extracting and reducing gold from pyrite in gold ores using chlorine gas was initially introduced by Karl Friedrich Plattner around 1848. | 1 | Applied and Interdisciplinary Chemistry |
Quantum dot solar cells (QDSCs) are based on the Gratzel cell, or dye-sensitized solar cell architecture, but employ low band gap semiconductor nanoparticles, fabricated with crystallite sizes small enough to form quantum dots (such as CdS, CdSe, Stibnite|, PbS, etc.), instead of organic or organometallic dyes as light absorbers. Due to the toxicity associated with Cd and Pb based compounds there are also a series of "green" QD sensitizing materials in development (such as CuInS CuInSe and CuInSeS). QD's size quantization allows for the band gap to be tuned by simply changing particle size. They also have high extinction coefficients and have shown the possibility of multiple exciton generation.
In a QDSC, a mesoporous layer of titanium dioxide nanoparticles forms the backbone of the cell, much like in a DSSC. This layer can then be made photoactive by coating with semiconductor quantum dots using chemical bath deposition, electrophoretic deposition or successive ionic layer adsorption and reaction. The electrical circuit is then completed through the use of a liquid or solid redox couple. The efficiency of QDSCs has increased to over 5% shown for both liquid-junction and solid state cells, with a reported peak efficiency of 11.91%. In an effort to decrease production costs, the Prashant Kamat research group demonstrated a solar paint made with and CdSe that can be applied using a one-step method to any conductive surface with efficiencies over 1%. However, the absorption of quantum dots (QDs) in QDSCs is weak at room temperature. The plasmonic nanoparticles can be utilized to address the weak absorption of QDs (e.g., nanostars). Adding an external infrared pumping source to excite intraband and interband transition of QDs is another solution. | 0 | Theoretical and Fundamental Chemistry |
While the idea of non-synaptic interactions between neurons has existed since the 19th century, there has historically been considerable skepticism in the field of neuroscience. Many people believed that the micro electrical fields produced by the neurons themselves were so small that they were negligible. While many supporters of the ephaptic coupling theory have been trying to prove its existence through experiments that block both chemical and electrical synapses, still some opponents in the field express caution. For example, in 2014, one scientist published a review that presents his skepticism on the idea of ephaptic coupling, saying “The agreement between their simulations and Poelzing’s data is impressive, but I will need a more definitive experimental confirmation before I can embrace the ephaptic hypothesis.” He bases his caution in wanting more distinction between gap junctions' propagation of charge and true ephaptic coupling. Whether it is a true lack of evidence or simply obstinance in the face of change, many in the field are still not entirely convinced there is unambiguous evidence of ephaptic coupling.
Research continues and in 2018 what appears to be a definitive experiment was published. A process of slow wave propagation in the brain of about 0.1m per second has been shown in vivo. Slow wave propagation was also recorded by inserting two electrodes into two ends of a piece of mouse brain taken from a freshly killed mouse. The tissue was then cut between the two electrode positions, severing any possible link by neurons or gap junctions between the two electrodes. The slow wave continued to propagate and could only be stopped by separating the two pieces of tissue with a 400-micron gap. Assuming the reproducibility of this experiment skeptics of ephaptic coupling should be satisfied it is a real phenomenon and investigations will focus now on its mechanisms and role rather than its existence. | 1 | Applied and Interdisciplinary Chemistry |
The modern RREMS system is operated by CGI following a successful contract bid in 2018. The system is run within cloud computing servers.
The network of monitoring stations includes 93 fixed and an unknown number of mobile stations located strategically across the country. These are operated by Ultra Electronics. | 0 | Theoretical and Fundamental Chemistry |
After the end of the Hittite empire, from the 12th to 7th century BC, the city became the center of an independent Luwian Neo-Hittite state of Kammanu, also known as Malizi. A palace was built and monumental stone sculptures of lions and the ruler erected.
In the 12th century, Melid was probably dependent on Karkemiš, where king Kuzi-Tešub ruled. His two grandsons, Runtyas (Runtiya) and Arnuwantis, were at first appointed as “Country Lords” of Melid, but later they also became kings of Melid.
The encounter with the Assyrian king Tiglath-Pileser I (1115–1077 BC) resulted in the kingdom of Melid being forced to pay tribute to Assyria. Melid remained able to prosper until the Assyrian king Sargon II (722–705 BC) sacked the city in 712 BC. At the same time, the Cimmerians and Scythians invaded Anatolia and the city declined.
According to Igor Diakonoff and John Greppin, there was likely an Armenian presence in Melid by 1200 BCE. | 1 | Applied and Interdisciplinary Chemistry |
Single nucleotide variant can also affect the cis-acting regulatory elements in mRNA’s to inhibit/promote the translation initiation. Change in the synonymous codons region due to mutation may affect the translation efficiency because of codon usage biases. The translation elongation can also be retarded by mutations along the ramp of ribosomal movement. In the post-translational level, genetic variants can contribute to proteostasis and amino acid modifications. However, mechanisms of variant effect in this field are complicated and there are only a few tools available to predict variant’s effect on translation related modifications. | 1 | Applied and Interdisciplinary Chemistry |
The following scheme describes the interconversion between an aldose and a ketose, where R is any organic residue.
The equilibrium or the reactant to product ratio depends on concentration, solvent, pH and temperature. At equilibrium the aldose and ketose form a mixture which in the case of the glyceraldehyde and dihydroxyacetone is also called glycerose.
A related reaction is the alpha-ketol rearrangement. | 0 | Theoretical and Fundamental Chemistry |
In January 1942, Okamoto started out as a research assistant at Tokyo Women's Medical University researching the cerebellum under a neurophysiologist who "created many more opportunities for [women] than were otherwise available at the time."
After World War II and the Second Sino-Japanese War respectively in 1945, she moved to Keio University in Shinanomachi in Tokyo. As resources were scarce, she and her husband Shosuke Okamoto changed to research on blood: "If there was not enough we could simply use our own". They hoped to find a treatment for post-partum haemorrhage, a potent drug to stop bleeding after childbirth. They began by studying epsilon-amino-caproic acid (EACA). They then studied a related chemical, 1-(aminomethyl)-cyclohexane-4-carboxylic acid (AMCHA), also known as tranexamic acid. The Okamotos found it was 27 times as powerful and thus a promising hemostatic agent and published their findings in the Keio Journal of Medicine in 1962.
In 1966, Okamoto was granted a chair at Kobe Gakuin University. In 1980, she founded a local Committee for Projects on Thrombosis and Haemostasis with Shosuke, who also worked at Kobe. She retired from the University in 1990. After her husband died in 2004, she led the committee until 2014. She could never persuade obstetricians to trial the drug in post-partum hemorrhage. | 1 | Applied and Interdisciplinary Chemistry |
In aqueous solutions (solutions of water), water gradually (over the course of hours) hydrolyzes polyphosphates into smaller phosphates and finally into ortho-phosphate, given enough water. Higher temperature or acidic conditions can speed up the hydrolysis reactions considerably.
Conversely, polyphosphoric acids or polyphosphates are often formed by dehydrating a phosphoric acid solution; in other words, removing water from it often by heating and evaporating the water off. | 0 | Theoretical and Fundamental Chemistry |
Sodium orthovanadate is produced by dissolving vanadium(V) oxide in a solution of sodium hydroxide:
The salt features tetrahedral anion centers linked to octahedral cation sites. | 0 | Theoretical and Fundamental Chemistry |
In covalent bond classification, a Z-type ligand refers to a ligand that accepts two electrons from the metal center. This is in contrast to X-type ligands, which form a bond with the ligand and metal center each donating one electron, and L-type ligands, which form a bond with the ligand donating two electrons. Typically, these Z-type ligands are Lewis acids, or electron acceptors. They are also known as zero-electron reagents. | 0 | Theoretical and Fundamental Chemistry |
Demethylation is relevant to epigenetics. Demethylation of DNA is catalyzed by demethylases. These enzymes oxidize N-methyl groups, which occur in histones, in lysine derivatives, and in some forms of DNA.
:RN-CH + O → RN-H + CHO
One family of such oxidative enzymes is the cytochrome P450. Alpha-ketoglutarate-dependent hydroxylases are also active for demethylation of DNA, operating by a similar stoichiometry. These reactions, which proceed via hydroxylation, exploit the slightly weakened C-H bonds of methylamines and methyl ethers.
Demethylation of some sterols are steps in the biosynthesis of testosterone and cholesterol. Methyl groups are lost as formate. | 0 | Theoretical and Fundamental Chemistry |
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