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Transfer RNAs, which are RNAs that participate in translation, contain the greatest number of modifications of any type of RNA, with up to one-fourth of the nucleosides in these molecules containing some sort of modification in eukaryotes. There are several known reasons for the wide variety of modifications found in tRNA. First of all, such modifications allow for easier differentiation between different tRNA molecules, such as separating the initiator tRNA from elongator tRNA. Moreover, they increase overall tRNA stability. Some studies have shown that the modifications of tRNA can be dynamic and adaptive to the changes of the environment. Examples include methylation of cytosine groups by tRNA methyltransferase (Trm4) in response to the depletion of nutrients in the body. The tRNA's cruciform structure is incredibly important to its overall function and such a complicated structure is maintained by post-transcriptional modifications. A primary example of this is the methylation of guanosine at junctions within the tRNA structure. These methylguanosine impact the overall tertiary structure by disrupting any potential canonical hydrogen bonding (hydrogen bonds that are conventional Watson-Crick base pairs), thus creating a loop at the core of the tRNA. Other modifications are integral for creating and maintaining the extreme bends in the structure. | 1 | Applied and Interdisciplinary Chemistry |
The state of an amount of gas is determined by its pressure, volume, and temperature. The modern form of the equation relates these simply in two main forms. The temperature used in the equation of state is an absolute temperature: the appropriate SI unit is the kelvin. | 0 | Theoretical and Fundamental Chemistry |
Hydrazine, organohydrazines, and 1,1-diorganohydrazines react with aldehydes and ketones to give hydrazones.
Phenylhydrazine reacts with reducing sugars to form hydrazones known as osazones, which was developed by German chemist Emil Fischer as a test to differentiate monosaccharides. | 0 | Theoretical and Fundamental Chemistry |
The structures of acceptors play a critical role in the rate and stereoselectivity of glycosylations. Generally, the unprotected hydroxyl groups are less reactive when they are between bulky protecting groups. That is the reason why the hydroxyl group at OH-4 in pyranosides is unreactive. Hyperconjugation is involved when OH-4 is anti-periplanar to the ring oxygen, which can also reduce its reactivity. (Scheme 3) Furthermore, acyl protecting groups can reduce the reactivity of the acceptors compared with alkyl protecting groups because of their electron-withdrawing ability. Hydroxyl group at OH-4 of N-acetylglucosamine derivatives is particularly unreactive.
The glycosidic bond is formed from a glycosyl donor and a glycosyl acceptor. There are four types of glycosidic linkages: 1, 2-trans-α, 1, 2-trans-beta, 1, 2-cis-α, and 1, 2-cis-beta linkages. 1, 2-trans glycosidic linkages can be easily achieved by using 2-O-acylated glycosyl donors (neighboring group participation). To prevent the accumulation of the orthoester intermediates, the glycosylation condition should be slightly acidic. | 0 | Theoretical and Fundamental Chemistry |
In oxidizing environment, green rust generally turns into oxyhydroxides, namely α- (goethite) and γ- (lepidocrocite).
Oxidation of the carbonate variety can be retarded by wetting the material with hydroxyl-containing compounds such as glycerol or glucose, even though they do not penetrate the structure. Some variety of green rust is stabilized also by an atmosphere with high partial pressure.
Sulfate green rust has been shown to reduce nitrate and nitrite in solution to ammonium , with concurrent oxidation of to . Depending on the cations in the solution, the nitrate anions replaced the sulfate in the intercalation layer, before the reduction. It was conjectured that green rust may be formed in the reducing alkaline conditions below the surface of marine sediments and may be connected to the disappearance of oxidized species like nitrate in that environment.
Suspensions of carbonate green rust and orange γ- in water will react over a few days produce a black precipitate of magnetite . | 1 | Applied and Interdisciplinary Chemistry |
This reagent can be synthesized quickly and in near-quantitative yield by reacting phenyl thioacetate with tert-butyldichloroamine in hot benzene. After the reaction is complete, the product can be isolated as a yellow, moisture-sensitive solid by vacuum distillation. | 0 | Theoretical and Fundamental Chemistry |
The photoelectric effect will cause spacecraft exposed to sunlight to develop a positive charge. This can be a major problem, as other parts of the spacecraft are in shadow which will result in the spacecraft developing a negative charge from nearby plasmas. The imbalance can discharge through delicate electrical components. The static charge created by the photoelectric effect is self-limiting, because a higher charged object does not give up its electrons as easily as a lower charged object does. | 0 | Theoretical and Fundamental Chemistry |
Michael Philip Hartshorn (10 September 1936 – 15 December 2017) was a British-born New Zealand organic chemist. He was awarded the Hector Memorial Medal by the Royal Society of New Zealand in 1973. | 0 | Theoretical and Fundamental Chemistry |
The mycotoxin phomoxanthone A, or PXA for short, is a toxic natural product that affects the mitochondria. It is the most toxic and the best studied of the naturally occurring phomoxanthones. PXA has recently been shown to induce rapid, non-canonical mitochondrial fission by causing the mitochondrial matrix to fragment while the outer mitochondrial membrane can remain intact. This process was shown to be independent from the mitochondrial fission and fusion regulators DRP1 and OPA1. | 1 | Applied and Interdisciplinary Chemistry |
Slack was born on 22 April 1937 in Ashton-under-Lyne, Lancashire, England; the first and only child of Albert and Eva Slack. He studied biochemistry at the University of Nottingham, where he graduated with a Bachelor of Science (Honours) in 1958, and a PhD in 1962. He married Pam Shaw in March 1963, and had two children.
From 1962, Slack worked as a biochemist at the David North Plant Research Centre in Brisbane, Queensland, Australia (funded by the Colonial Sugar Refining Co. Ltd). In 1970, he joined the Department of Scientific and Industrial Research in New Zealand. From 1989 until his retirement in 2000, Slack was a senior scientist at the newly formed Crown Research Institute for Crop & Food Research in Palmerston North.
Slack died in Palmerston North in 2016. | 1 | Applied and Interdisciplinary Chemistry |
In complexation catalysis, the term passive binding refers to any stabilizing interaction that is equally strong at the transition state level and in the reactant-catalyst complex.
Having the same effect on the stability of the transition state and the reactant-catalyst complex, passive binding contributes to acceleration only if the equilibrium between the unassociated reactant and catalyst and their complex is not completely shifted to the right. It was defined by A.J. Kirby in 1996 as opposed to the dynamic binding, i.e. the whole of interactions that are stronger at the transition state level than in the reactant-catalyst complex. | 0 | Theoretical and Fundamental Chemistry |
An injector is a system of ducting and nozzles used to direct the flow of a high-pressure fluid in such a way that a lower pressure fluid is entrained in the jet and carried through a duct to a region of higher pressure. It is a fluid-dynamic pump with no moving parts except a valve to control inlet flow.
Depending on the application, an injector can also take the form of an eductor-jet pump, a water eductor or an aspirator. An ejector operates on similar principles to create a vacuum feed connection for braking systems etc.
The motive fluid may be a liquid, steam or any other gas. The entrained suction fluid may be a gas, a liquid, a slurry, or a dust-laden gas stream. | 1 | Applied and Interdisciplinary Chemistry |
Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state. The verb form of sublimation is sublime, or less preferably, sublimate. Sublimate also refers to the product obtained by sublimation. The point at which sublimation occurs rapidly (for further details, see below) is called critical sublimation point, or simply sublimation point. Notable examples include sublimation of dry ice at room temperature and atmospheric pressure, and that of solid iodine with heating.
The reverse process of sublimation is deposition (also called desublimation), in which a substance passes directly from a gas to a solid phase, without passing through the liquid state.
All solids sublime, though most sublime at extremely low rates that are hardly detectable. At normal pressures, most chemical compounds and elements possess three different states at different temperatures. In these cases, the transition from the solid to the gas state requires an intermediate liquid state. The pressure referred to is the partial pressure of the substance, not the total (e.g. atmospheric) pressure of the entire system. Thus, any solid can sublime if its vapour pressure is higher than the surrounding partial pressure of the same substance, and in some cases, sublimes at an appreciable rate (e.g. water ice just below 0 °C).
For some substances, such as carbon and arsenic, sublimation from solid state is much more achievable than evaporation from liquid state and it is difficult to obtain them as liquids. This is because the pressure of their triple point in its phase diagram (which corresponds to the lowest pressure at which the substance can exist as a liquid) is very high.
Sublimation is caused by the absorption of heat which provides enough energy for some molecules to overcome the attractive forces of their neighbors and escape into the vapor phase. Since the process requires additional energy, sublimation is an endothermic change. The enthalpy of sublimation (also called heat of sublimation) can be calculated by adding the enthalpy of fusion and the enthalpy of vaporization. | 0 | Theoretical and Fundamental Chemistry |
Magnetic trapping is created by adding a spatially varying magnetic quadrupole field to the red detuned optical field needed for laser cooling. This causes a Zeeman shift in the magnetic-sensitive m levels, which increases with the radial distance from the center of the trap. Because of this, as an atom moves away from the center of the trap, the atomic resonance is shifted closer to the frequency of the laser light, and the atom becomes more likely to get a photon kick towards the center of the trap.
The direction of the kick is given by the polarization of the light, which is either left or right handed circular, giving different interactions with the different m levels. The correct polarizations are used so that photons moving towards the center of the trap will be on resonance with the correct shifted atomic energy level, always driving the atom towards the center. | 0 | Theoretical and Fundamental Chemistry |
Mixed-valence compounds are subdivided into three groups, according to the Robin–Day classification:
*Class I, where the valences are trapped—localized on a single site—such as PbO and antimony tetroxide. There are distinct sites with different specific valences in the complex that cannot easily interconvert.
*Class II, which are intermediate in character. There is some localization of distinct valences, but there is a low activation energy for their interconversion. Some thermal activation is required to induce electron transfer from one site to another via the bridge. These species exhibit an intense Intervalence charge transfer (IT or IVCT) band, a broad intense absorption in the infrared or visible part of the spectrum, and also exhibit magnetic exchange coupling at low temperatures. The degree of interaction between the metal sites can be estimated from the absorption profile of the IVCT band and the spacing between the sites. This type of complex is common when metals are in different ligand fields. For example, Prussian blue is an iron(II,III)–cyanide complex in which there is an iron(II) atom surrounded by six carbon atoms of six cyanide ligands bridged to an iron(III) atom by their nitrogen ends. In the Turnbull's blue preparation, an iron(II) solution is mixed with an iron(III) cyanide (c-linked) complex. An electron-transfer reaction occurs via the cyanide ligands to give iron(III) associated with an iron(II)-cyanide complex.
*Class III, wherein mixed valence is not distinguishable by spectroscopic methods as the valence is completely delocalized. The Creutz–Taube complex is an example of this class of complexes. These species also exhibit an IT band. Each site exhibits an intermediate oxidation state, which can be half-integer in value. This class is possible when the ligand environment is similar or identical for each of the two metal sites in the complex. In fact, Robson type dianionic tetraimino-diphenolate ligands which provide equivalent N2O2 environments for two metal centres have stabilized the mixed valence diiron complexes of class III. The bridging ligand needs to be very good at electron transfer, be highly conjugated, and be easily reduced. | 0 | Theoretical and Fundamental Chemistry |
Viruses can be used to deliver genes for genetic engineering or gene therapy. Commonly used viruses include adenoviruses, retroviruses, and various bacteriophages. The surface of the viral particle can also be modified with ligands to increase targeting capabilities. While viral vectors can be used to great efficacy, one concern is that may cause off-target effects due to its natural tropism. This usually requires replacing the proteins causing virus-cell interactions with chimeric proteins.
In addition to using viruses, drug molecules can also be encapsulated in protein particles derived from the viral capsid, or virus-like particles (VLPs). VLPs are easier to manufacture than viruses, and their structural uniformity allows VLPs to be produced precisely in large amounts. VLPs also have easy-to-modify surfaces, allowing the possibility for targeted delivery. There are various methods of packaging the molecule into the capsid; most take advantage of the capsid's ability to self-assemble. One strategy is to alter the pH gradient outside the capsid to create pores on the capsid surface and trap the desired molecule. Other methods use aggregators such as leucine zippers or polymer-DNA amphiphiles to induce capsid formation and capture drug molecules. It is also possible to chemically conjugate of drugs directly onto the reactive sites on the capsid surface, often involving the formation of amide bonds.
After being introduced to the organism, VLPs often have broad tissue distribution, rapid clearance, and are generally non-toxic. It may, however, like viruses, invoke an immune response, so immune-masking agents may be necessary. | 0 | Theoretical and Fundamental Chemistry |
Benzyltrimethylammonium hydroxide, also known as Triton B or trimethylbenzylammonium hydroxide, is a quaternary ammonium salt that functions as an organic base. It is usually handled as a solution in water or methanol. The compound is colourless, although the solutions often appear yellowish. Commercial samples often have a distinctive fish-like odour, presumably due to the presence of trimethylamine via hydrolysis. | 0 | Theoretical and Fundamental Chemistry |
This stage is useful for identifying patients with bacterial overgrowth syndrome. The physician will provide a course of 2 weeks of antibiotics to eliminate any possible bacterial overgrowth and repeat the test to check whether radio-labeled Vitamin B12 would be found in urine or not. | 1 | Applied and Interdisciplinary Chemistry |
Some elements of the cholinergic crisis can be reversed with antimuscarinic drugs like atropine or diphenhydramine, but the most dangerous effect - respiratory depression, cannot.
The neuromuscular junction, where the brain communicates with muscles (like the diaphragm, the main breathing muscle), works by acetylcholine activating nicotinic acetylcholine receptors and leading to muscle contraction. Atropine only blocks muscarinic acetylcholine receptors (a different receptor class than the nicotinic receptors at the neuromuscular junction), so atropine will not improve the muscle strength and ability to breathe in someone with cholinergic crisis. Such a patient will require neuromuscular blocking drugs and mechanical ventilation until the crisis resolves on its own. | 1 | Applied and Interdisciplinary Chemistry |
TLE uses continuous-wave lasers (typically with a wavelength of around 1000 nm) located outside the vacuum chamber to heat sources of material in order to generate a flux of vapor via evaporation or sublimation. Owing to the localized nature of the heat induced by the laser, a portion of the source may be transformed into a liquid state while the rest remains solid, such that the source acts as its own crucible. The strong absorption of light causes the laser-induced heat to be highly localized via the small diameter of the laser beam, which can also have the effect of confining the heat to the axis of the source. The resulting absorption corresponds to a typical photon penetration depth on the order of 2 nm due to the high absorption coefficients of α ~ 10 cm of many materials. Heat loss via conduction and radiation further localizes the high-temperature region close to the irradiated surface of the source. The localized character of the heating enables many materials to be grown by TLE from freestanding sources without a crucible. Owing to the direct transfer of energy from the laser to the source, TLE is more efficient than other evaporation techniques such as evaporation and molecular beam epitaxy, which typically rely on wire-based Joule heaters to reach high temperatures.
By heating the source, a flux of vapor is produced, the pressure of which frequently has an approximately exponential relation to temperature. The vapor is then deposited onto a substrate, which is heated via a laser. This laser-heated substrate allows the use of adsorption-controlled growth modes, similar to molecular beam epitaxy, ensuring precise control of the stoichiometry and temperature of the deposited film. This precise control is valuable for growing thin-film heterostructures of complex materials, such as high-T superconductors. By positioning all lasers outside of the evaporation chamber, contamination can be reduced compared to using in situ heaters, resulting in highly pure deposited films.
The deposition rate of the vapor impinging upon the substrate is controlled by adjusting the power of the incident source laser. The deposition rate frequently increases exponentially with source temperature, which in turn increases linearly with incident laser power.
The gas in the chamber can be incorporated in the deposition film. With the addition of an oxygen or ozone atmosphere, oxide films can readily be grown with TLE at pressures up to 10 hPa. | 0 | Theoretical and Fundamental Chemistry |
In fluid mechanics, the Reynolds number is the ratio of inertial forces (vρ) to viscous forces (μ/L). It is one of the most important dimensionless numbers in fluid dynamics and is used, usually along with other dimensionless numbers, to provide a criterion for determining dynamic similitude. As such, the Reynolds number provides the link between modeling results (design) and the full-scale actual conditions. It can also be used to characterize the flow. | 0 | Theoretical and Fundamental Chemistry |
The third description of the flow field's state is swirl. Swirl is the tangential flow component of the velocity vector. The velocity profile should be referred to as the axial velocity profile. As the velocity vector can be resolved into three mutually orthogonal components, the velocity profile only represents the axial component of velocity. fig.(2) showing the Swirl Angle which explains the definition of flow swirl and swirl angle. Note that swirl is usually referenced to full body rotation (that which the full pipeline flow follows one axis of swirl). In real pipeline conditions, such as downstream of elbows two or more mechanisms of swirl may be present. | 1 | Applied and Interdisciplinary Chemistry |
2-(Dicyanomethylene)croconate is a divalent anion with chemical formula or ((N≡C−)C=)(CO). It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the croconate oxocarbon anion through the replacement of one oxygen atom by a dicyanomethylene group =C(−C≡N).
The anion was synthesized and characterized by A. Fatiadi in 1980, by hydrolysis of croconate violet treated with potassium hydroxide. It gives an orange solution in water. | 0 | Theoretical and Fundamental Chemistry |
The dynamic energy budget (DEB) theory is a formal metabolic theory which provides a single quantitative framework to dynamically describe the aspects of metabolism (energy and mass budgets) of all living organisms at the individual level, based on assumptions about energy uptake, storage, and utilization of various substances. The DEB theory adheres to stringent thermodynamic principles, is motivated by universally observed patterns, is non-species specific, and links different levels of biological organization (cells, organisms, and populations) as prescribed by the implications of energetics. Models based on the DEB theory have been successfully applied to over a 1000 species with real-life applications ranging from conservation, aquaculture, general ecology, and ecotoxicology (see also the [https://www.bio.vu.nl/thb/deb/deblab/add_my_pet/species_list.html Add-my-pet collection]). The theory is contributing to the theoretical underpinning of the emerging field of metabolic ecology.
The explicitness of the assumptions and the resulting predictions enable testing against a wide variety of experimental results at the various levels of biological organization. The theory explains many general observations, such as the body size scaling relationships of certain physiological traits, and provides a theoretical underpinning to the widely used method of indirect calorimetry. Several popular empirical models are special cases of the DEB model, or very close numerical approximations. | 1 | Applied and Interdisciplinary Chemistry |
At the beginning of the twentieth century, a relationship between the pituitary, testes and prostate gland had been established.
American physician Charles Brenton Huggins found out that castration or estrogen administration led to glandular atrophy in men, which could be reversed by re-administration of androgen. In 1941 Huggins treated prostate cancer patients by androgen ablation with either castration or estrogen therapy; the beneficial effect of androgen ablation on metastatic prostate cancer was realised, for which he was awarded the Nobel Prize in Physiology or Medicine in 1966.
It became evident that androgen ablation alone was insuffient to cure patients with advanced prostate cancer. In the late 1960s, the androgen receptor (AR) was discovered and characterized. Screening of chemical libraries for AR blockers led to the discovery of the first antiandrogen, cyproterone. An acetate group was then added to cyproterone and created cyproterone acetate. In the 1970s, the antiandrogen flutamide was discovered.
In 1989 the United States Food and Drug Administration (FDA) approved it for use the treatment of prostate cancer.
In 1995, bicalutamide was approved, and nilutamide followed a year later. | 1 | Applied and Interdisciplinary Chemistry |
The detection efficiency for electrons is essentially 100% for most scintillators. But because electrons can make large angle scatterings (sometimes backscatterings), they can exit the detector without depositing their full energy in it. The back-scattering is a rapidly increasing function of the atomic number Z of the scintillator material. Organic scintillators, having a lower Z than inorganic crystals, are therefore best suited for the detection of low-energy (< 10 MeV) beta particles. The situation is different for high energy electrons: since they mostly lose their energy by bremsstrahlung at the higher energies, a higher-Z material is better suited for the detection of the bremsstrahlung photon and the production of the electromagnetic shower which it can induce. | 0 | Theoretical and Fundamental Chemistry |
When mechanical strain is applied to a PECT material it changes the chemical potential, and therefore the electric potential of that material. Since current flows from more negative materials to more positive materials, it is possible to induce a current flow between two ionically connected materials by simply applying a mechanical strain. It is therefore possible to harness and convert mechanical energy into electrical energy.
A number of materials have been demonstrated to be capable of PECT-based energy harvesting, including: carbon fibers inserted with lithium, sodiated black phosphorus; lithiated aluminium; and lithiated silicon. A structural carbon fibre composite has also been shown to be capable of harvesting energy using the PECT effect. Conventional lithium-ion batteries have also been shown to be capable of PECT-based energy harvesting.
This effect has most often been demonstrated using a two-electrode bending setup:
# Two electrodes of the same material are connected ionically through an electrolyte, and electrically via an outer circuit.
# A bending deformation is applied causing tension in one electrode and compression in the other.
# The resulting change in chemical potential results in current flow in the outer circuit, which can be used to power an external device.
PECT energy harvesting is limited by the rate of ionic diffusion, and therefore is only efficient at low frequency (typically below around 1 Hz).
Figures of merit for comparing different PECT-based energy harvesters were formulated by Preimesberger et al. | 0 | Theoretical and Fundamental Chemistry |
Although some inorganic species can be obtained in pure form from nature, most are synthesized in chemical plants and in the laboratory.
Inorganic synthetic methods can be classified roughly according to the volatility or solubility of the component reactants. Soluble inorganic compounds are prepared using methods of organic synthesis. For metal-containing compounds that are reactive toward air, Schlenk line and glove box techniques are followed. Volatile compounds and gases are manipulated in "vacuum manifolds" consisting of glass piping interconnected through valves, the entirety of which can be evacuated to 0.001 mm Hg or less. Compounds are condensed using liquid nitrogen (b.p. 78K) or other cryogens. Solids are typically prepared using tube furnaces, the reactants and products being sealed in containers, often made of fused silica (amorphous SiO) but sometimes more specialized materials such as welded Ta tubes or Pt "boats". Products and reactants are transported between temperature zones to drive reactions. | 0 | Theoretical and Fundamental Chemistry |
Sulfoxides are typically prepared by oxidation of sulfides, sometimes referred to as sulfoxidation. hydrogen peroxide is a typical oxidant, but periodate has also been used. In these oxidations, care is required to avoid over oxidation to form the sulfone. For example, dimethyl sulfide is oxidized to dimethyl sulfoxide and then further to dimethyl sulfone. Unsymmetrical sulfides are prochiral, thus their oxidation gives chiral sulfoxides. This process can be performed enantioselectively. | 0 | Theoretical and Fundamental Chemistry |
In nuclear engineering, fissile material is material that can undergo nuclear fission when struck by a neutron of low energy. A self-sustaining thermal chain reaction can only be achieved with fissile material. The predominant neutron energy in a system may be typified by either slow neutrons (i.e., a thermal system) or fast neutrons. Fissile material can be used to fuel thermal-neutron reactors, fast-neutron reactors and nuclear explosives. | 0 | Theoretical and Fundamental Chemistry |
A number bioplastic classes have been synthesized from plant and animal derived fats and oils. Polyurethanes, polyesters, epoxy resins and a number of other types of polymers have been developed with comparable properties to crude oil based materials. The recent development of olefin metathesis has opened a wide variety of feedstocks to economical conversion into biomonomers and polymers. With the growing production of traditional vegetable oils as well as low cost microalgae derived oils, there is huge potential for growth in this area. | 0 | Theoretical and Fundamental Chemistry |
The great interest in the study of the two-dimensional electron gas (2DEG) has also resulted in many investigations on the properties of polarons in two dimensions. A simple model for the 2D polaron system consists of an electron confined to a plane, interacting via the Fröhlich interaction with the LO phonons of a 3D surrounding medium. The self-energy and the mass of such a 2D polaron are no longer described by the expressions valid in 3D; for weak coupling they can be approximated as:
It has been shown that simple scaling relations exist, connecting the physical properties of polarons in 2D with those in 3D. An example of such a scaling relation is:
where () and () are, respectively, the polaron and the electron-band masses in 2D (3D).
The effect of the confinement of a Fröhlich polaron is to enhance the effective polaron coupling. However, many-particle effects tend to counterbalance this effect because of screening.
Also in 2D systems cyclotron resonance is a convenient tool to study polaron effects. Although several other effects have to be taken into account (nonparabolicity of the electron bands, many-body effects, the nature of the confining potential, etc.), the polaron effect is clearly revealed in the cyclotron mass. An interesting 2D system consists of electrons on films of liquid He. In this system the electrons couple to the ripplons of the liquid He, forming "ripplopolarons". The effective coupling can be relatively large and, for some values of the parameters, self-trapping can result. The acoustic nature of the ripplon dispersion at long wavelengths is a key aspect of the trapping.
For GaAs/AlGaAs quantum wells and superlattices, the polaron effect is found to decrease the energy of the shallow donor states at low magnetic fields and leads to a resonant splitting of the energies at high magnetic fields. The energy spectra of such polaronic systems as shallow donors ("bound polarons"), e. g., the D and D centres, constitute the most complete and detailed polaron spectroscopy realised in the literature.
In GaAs/AlAs quantum wells with sufficiently high electron density, anticrossing of the cyclotron-resonance spectra has been observed near the GaAs transverse optical (TO) phonon frequency rather than near the GaAs LO-phonon frequency. This anticrossing near the TO-phonon frequency was explained in the framework of the polaron theory.
Besides optical properties, many other physical properties of polarons have been studied, including the possibility of self-trapping, polaron transport, magnetophonon resonance, etc. | 0 | Theoretical and Fundamental Chemistry |
Simmons-Smith cyclopropanation, which employs carbenes derived from diiodomethane, is a popular alternative to rhodium-catalyzed cyclopropanation. In the presence of a chiral diamine, Simmons-Smith cyclopropanation is enantioselective; however, selectivities are not as high as the corresponding rhodium-catalyzed reactions.
Substituted zinc carbenoids can be prepared from the corresponding ketones or aldehydes through a sequence analogous to the mechanism of the Clemmensen reduction. Cyclopropanation of olefins with these intermediates occurs with moderate diastereoselectivity and yield.
Other diazo compounds besides diazocarbonyl compounds have been used for rhodium-catalyzed cyclopropanations; however, these substrates are much more difficult to handle and unstable than diazocarbonyl compounds. Thus, they have not been extensively adopted for organic synthesis. | 0 | Theoretical and Fundamental Chemistry |
Assays have been developed to identify regions of the genome that are accessible. These regions of accessible chromatin are candidate regulatory regions. These assays include ATAC-seq, DNase-Seq and FAIRE-Seq. | 1 | Applied and Interdisciplinary Chemistry |
The Antica Farmacia Sant'Anna (Italian for “Ancient Pharmacy of Saint Anne”) is a pharmacy and herbal medicine dispensary in Genoa, Italy, located in the quarter of Castelletto. Founded by the Discalced Carmelites friars of the annex Convent of Sant’Anna in 1650, it is the oldest commercial establishment still operating in Genoa and the only instance in Italy of a fully licensed pharmacy owned and operated by a religious institution. While its ancient furniture and instruments are listed and protected as cultural heritage, its modern laboratories are equipped with state-of-the-art technology for the preparation of medicines, Galenic formulations, herbal medicine products, lotions, cosmetics and dietary supplements under the supervision of legally qualified personnel. | 1 | Applied and Interdisciplinary Chemistry |
A group of researchers at Georgia Tech made dye-sensitized solar cells with a higher effective surface area by wrapping the cells around a quartz optical fiber. The researchers removed the cladding from optical fibers, grew zinc oxide nanowires along the surface, treated them with dye molecules, surrounded the fibers by an electrolyte and a metal film that carries electrons off the fiber. The cells are six times more efficient than a zinc oxide cell with the same surface area. Photons bounce inside the fiber as they travel, so there are more chances to interact with the solar cell and produce more current. These devices only collect light at the tips, but future fiber cells could be made to absorb light along the entire length of the fiber, which would require a coating that is conductive as well as transparent. Max Shtein of the University of Michigan said a sun-tracking system would not be necessary for such cells, and would work on cloudy days when light is diffuse. | 0 | Theoretical and Fundamental Chemistry |
The Castner Gold Medal on Industrial Electrochemistry is an biennial award given by the Electrochemical Technology Group of Society of Chemical Industry (SCI) to an authority on applied electrochemistry or electrochemical engineering connected to industrial research. The award is named in honor of Hamilton Castner, a pioneer in the field of industrial electrochemistry, who patented in 1892 the mercury cell for the chloralkali process. Castner was an early member of SCI.
The medal is presented in a public lecture, usually at the annual Electrochem conference, which is organised by the Royal Society of Chemistry (RSC) Electrochemistry Interest Group and the SCI Electrochemical Technology Group. When this is not possible, the medal presentation and lecture takes place at SCI's headquarters.
The medal's design was conceived by Humphrey Paget by commission of SCI. At least until 1958, the award was called Castner Gold Medal. | 1 | Applied and Interdisciplinary Chemistry |
There is a number of external triggers that can be used to release cargo on gated delivery systems. Examples of some triggers include pH, redox, enzyme, light, temperature, magnetic, ultrasound, and small molecule responsive gated systems. | 1 | Applied and Interdisciplinary Chemistry |
There are relatively simple tests for radon gas. Radon test kits are commercially available. The short-term radon test kits used for screening purposes are inexpensive, in many cases free. In the United States, discounted test kits can be purchased online through The National Radon Program Services at Kansas State University or through state radon offices. Information about local radon zones and specific state contact information can be accessed through the Environmental Protection Agency (EPA) Map. The kit includes a collector that the user hangs in the lowest livable floor of the dwelling for 2 to 7 days. Charcoal canisters are another type of short-term radon test, and are designed to be used for 2 to 4 days. The user then sends the collector to a laboratory for analysis. Both devices are passive, meaning that they do not need power to function.
The accuracy of the residential radon test depends upon the lack of ventilation in the house when the sample is being obtained. Thus, the occupants will be instructed not to open windows, etc., for ventilation during the pendency of test, usually two days or more.
Long-term kits, taking collections for 3 months up to one year, are also available. An open-land test kit can test radon emissions from the land before construction begins. A Lucas cell is one type of long-term device. A Lucas cell is also an active device, or one that requires power to function. Active devices provide continuous monitoring, and some can report on the variation of radon and interference within the testing period. These tests usually require operation by trained testers and are often more expensive than passive testing. The National Radon Proficiency Program (NRPP) provides a list of radon measurement professionals.
Radon levels fluctuate naturally. An initial test might not be an accurate assessment of a home's average radon level. Transient weather can affect short term measurements. Therefore, a high result (over 4 pCi/L) justifies repeating the test before undertaking more expensive abatement projects. Measurements between 4 and 10 pCi/L warrant a long-term radon test. Measurements over 10 pCi/L warrant only another short-term test so that abatement measures are not unduly delayed. Purchasers of real estate are advised to delay or decline a purchase if the seller has not successfully abated radon to 4 pCi/L or less.
Since radon concentrations vary substantially from day to day, single grab-type measurements are generally not very useful, except as a means of identifying a potential problem area, and indicating a need for more sophisticated testing. The EPA recommends that an initial short-term test be performed in a closed building. An initial short-term test of 2 to 90 days allows residents to be informed quickly in case a home contains high levels of radon. Long-term tests provide a better estimate of the average annual radon level. | 1 | Applied and Interdisciplinary Chemistry |
A review in 2013 came to the result that infants resulting from IVF (with or without ICSI) have a relative risk of birth defects of 1.32 (95% confidence interval 1.24–1.42) compared to naturally conceived infants. In 2008, an analysis of the data of the National Birth Defects Study in the US found that certain birth defects were significantly more common in infants conceived through IVF, notably septal heart defects, cleft lip with or without cleft palate, esophageal atresia, and anorectal atresia; the mechanism of causality is unclear. However, in a population-wide cohort study of 308,974 births (with 6,163 using assisted reproductive technology and following children from birth to age five) researchers found: "The increased risk of birth defects associated with IVF was no longer significant after adjustment for parental factors." Parental factors included known independent risks for birth defects such as maternal age, smoking status, etc. Multivariate correction did not remove the significance of the association of birth defects and ICSI (corrected odds ratio 1.57), although the authors speculate that underlying male infertility factors (which would be associated with the use of ICSI) may contribute to this observation and were not able to correct for these confounders. The authors also found that a history of infertility elevated risk itself in the absence of any treatment (odds ratio 1.29), consistent with a Danish national registry study and "implicates patient factors in this increased risk." The authors of the Danish national registry study speculate: "our results suggest that the reported increased prevalence of congenital malformations seen in singletons born after assisted reproductive technology is partly due to the underlying infertility or its determinants." | 1 | Applied and Interdisciplinary Chemistry |
Similar to the issue of a point of reference is the issue of orientation: a displacement in 2 or 3 dimensions is not just a length, but is a length together with a direction. (In 1 dimension, this issue is equivalent to the distinction between positive and negative.) Thus, to compare or combine two dimensional quantities in multi-dimensional Euclidean space, one also needs a bearing: they need to be compared to a frame of reference.
This leads to the extensions discussed below, namely Huntleys directed dimensions and Sianos orientational analysis. | 1 | Applied and Interdisciplinary Chemistry |
The United States Department of Agriculture (USDA) web site has a very complete searchable table of calcium content (in milligrams) in foods, per common measures such as per 100 grams or per a normal serving. | 1 | Applied and Interdisciplinary Chemistry |
The journal is abstracted and indexed in:
* Chemical Abstracts Service
* Index Medicus/MEDLINE/PubMed
* Science Citation Index Expanded
* Current Contents/Life Sciences
* BIOSIS Previews
* Scopus
According to the Journal Citation Reports, the journal has a 2019 impact factor of 2.014. 5 year Impact Factor 2.063 | 0 | Theoretical and Fundamental Chemistry |
Esters can also be derived from inorganic acids.
*Perchloric acid forms perchlorate esters, e.g., methyl perchlorate ()
*Sulfuric acid forms sulfate esters, e.g., dimethyl sulfate () and methyl bisulfate ()
*Nitric acid forms nitrate esters, e.g. methyl nitrate () and nitroglycerin ()
*Phosphoric acid forms phosphate esters, e.g. triphenyl phosphate () and methyl dihydrogen phosphate ()
*Carbonic acid forms carbonate esters, e.g. dimethyl carbonate () and 5-membered cyclic ethylene carbonate () (if one classifies carbonic acid as an inorganic compound)
*Trithiocarbonic acid forms trithiocarbonate esters, e.g. dimethyl trithiocarbonate () (if one classifies trithiocarbonic acid as an inorganic compound)
*Chloroformic acid forms chloroformate esters, e.g. methyl chloroformate () (if one classifies chloroformic acid as an inorganic compound)
*Boric acid forms borate esters , e.g. trimethyl borate ()
*Chromic acid forms di-tert-butyl chromate ()
Inorganic acids that exist as tautomers form two or more types of esters.
*Thiosulfuric acid forms two types of thiosulfate esters, e.g. O,O-dimethyl thiosulfate () and O,S-dimethyl thiosulfate ()
*Thiocyanic acid forms thiocyanate esters, e.g. methyl thiocyanate () (if one classifies thiocyanic acid as an inorganic compound), but forms isothiocyanate "esters" as well, e.g. methyl isothiocyanate (), although organyl isothiocyanates are not clasified as esters by the IUPAC
*Phosphorous acid forms two types of esters: phosphite esters, e.g. triethyl phosphite (), and phosphonate esters, e.g. diethyl phosphonate ()
Some inorganic acids that are unstable or elusive form stable esters.
*Sulfurous acid, which is unstable, forms stable dimethyl sulfite ()
In principle, a part of metal and metalloid alkoxides, of which many hundreds are known, could be classified as esters of the corresponding acids (e.g. aluminium triethoxide () could be classified as an ester of aluminic acid which is aluminium hydroxide, tetraethyl orthosilicate () could be classified as an ester of orthosilicic acid, and titanium ethoxide () could be classified as an ester of orthotitanic acid). | 0 | Theoretical and Fundamental Chemistry |
Reactions of conjugated double-bond systems can be synthesized into cycloalkenes through electrocyclic reactions. Addition of heat or photolysis causes a reversible reaction that causes one pi bond to become a sigma bond, which closes the ring and creates a cycloalkene. | 0 | Theoretical and Fundamental Chemistry |
As a pseudohalide, azide generally displaces many leaving group, e.g. , , , sulfonate, and others to give the azido compound. The azide source is most often sodium azide (), although lithium azide () has been demonstrated. | 0 | Theoretical and Fundamental Chemistry |
Spontaneous absolute asymmetric synthesis is a chemical phenomenon that stochastically generates chirality based on autocatalysis and small fluctuations in the ratio of enantiomers present in a racemic mixture. In certain reactions which initially do not contain chiral information, stochastically distributed enantiomeric excess can be observed. The phenomenon is different from chiral amplification, where enantiomeric excess is present from the beginning and not stochastically distributed. Hence, when the experiment is repeated many times, the average enantiomeric excess approaches 0%. The phenomenon has important implications concerning the origin of homochirality in nature. | 0 | Theoretical and Fundamental Chemistry |
Pd-mediated Sonogashira, Heck, and Suzuki-Miyaura cross-coupling reactions have been applied widely to modify peptides and proteins, where diverse Pd reagents have been developed for the application in aqueous solutions. Those reactions require the protein or peptide substrate bearing unnatural functional groups such as alkyne, aryl halides, and aryl boronic acids, which can be achieved through genetic code expansion or post-translational modifications. | 1 | Applied and Interdisciplinary Chemistry |
Galvanic corrosion (also called bimetallic corrosion or dissimilar metal corrosion) is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte. A similar galvanic reaction is exploited in primary cells to generate a useful electrical voltage to power portable devices. This phenomenon is named after Italian physician Luigi Galvani (1737–1798). | 1 | Applied and Interdisciplinary Chemistry |
Phosphite esters are Lewis bases and hence can form coordination complexes with various metal ions. Representative phosphite ligands include trimethylphosphite ((MeO)P), triethylphosphite ((EtO)P), trimethylolpropane phosphite, and triphenylphosphite ((PhO)P). Phosphites exhibit a smaller ligand cone angles than the structurally related phosphine ligand family. Phosphite ligands are components of industrial catalysts for hydroformylation and hydrocyanation. | 0 | Theoretical and Fundamental Chemistry |
The rate of cell growth is directly dependent on the rate of protein synthesis, which is itself intricately linked to ribosome synthesis and rRNA transcription. Thus, intracellular signals must coordinate the synthesis of rRNA with that of other components of protein translation. Myc is known to bind to human ribosomal DNA in order to stimulate rRNA transcription by RNA polymerase I. Two specific mechanisms have been identified, ensuring proper control of rRNA synthesis and Pol I-mediated transcription.
Given the large numbers of rDNA genes (several hundreds) available for transcription, the first mechanism involves adjustments in the number of genes being transcribed at a specific time. In mammalian cells, the number of active rDNA genes varies between cell types and level of differentiation. In general, as a cell becomes more differentiated, it requires less growth and, therefore, will have a decrease in rRNA synthesis and a decrease in rDNA genes being transcribed. When rRNA synthesis is stimulated, SL1 (selectivity factor 1) will bind to the promoters of rDNA genes that were previously silent, and recruit a pre-initiation complex to which Pol I will bind and start transcription of rRNA.
Changes in rRNA transcription can also occur via changes in the rate of transcription. While the exact mechanism through which Pol I increases its rate of transcription is as yet unknown, evidence has shown that rRNA synthesis can increase or decrease without changes in the number of actively transcribed rDNA. | 1 | Applied and Interdisciplinary Chemistry |
All magneto-optical traps require at least one trapping laser plus any necessary repumper lasers (see above). These lasers need stability, rather than high power, requiring no more than the saturation intensity, but a linewidth much less than the Doppler width, usually several megahertz. Because of their low cost, compact size and ease of use, laser diodes are used for many of the standard MOT species while the linewidth and stability of these lasers is controlled using servo systems, which stabilises the lasers to an atomic frequency reference by using, for example, saturated absorption spectroscopy and the Pound-Drever-Hall technique to generate a locking signal.
By employing a 2-dimensional diffraction grating it is possible to generate the configuration of laser beams required for a magneto-optical trap from a single laser beam and thus have a very compact magneto-optical trap. | 0 | Theoretical and Fundamental Chemistry |
Polyhedron is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2020 impact factor of 3.052. | 0 | Theoretical and Fundamental Chemistry |
RNA-Binding Proteins (RBPs) are dynamic assemblages between mRNAs and different proteins that form messenger ribonucleoprotein complexes (mRNPs). These complexes are essential for the regulation of gene expression to ensure that all the steps are performed correctly throughout the whole process. Therefore, they are important control factors for protein levels and cell phenotypes. Moreover, they affect mRNA stability by regulating its conformation due to the environment, stress or extracellular signals. However, their ability to bind and control such a wide variety of RNA targets allows them to form complex regulatory networks (PTRNs).These networks represent a challenge to study each RNA-binding protein individually. Thankfully, due to new methodological advances, the identification of RBPs is slowly expanding, which demonstrates that they are contained in broad families of proteins. RBPs can significantly impact multiple biological processes, and have to be very accurately expressed. Overexpression can change the mRNA target rate, binding to low-affinity RNA sites and causing deleterious results on cellular fitness. Not being able to synthesize at the right level is also problematic because it can lead to cell death. Therefore, RBPs are regulated via auto-regulation, so they are in control of their own actions. Furthermore, they use both negative feedback, to maintain homeostasis, and positive feedback, to create binary genetic changes in the cell.
In metazoans and bacteria, many genes involved in post-post transcriptional regulation are regulated post transcriptionally. For Drosophila RBPs associated with splicing or nonsense mediated decay, analyses of protein-protein and protein-RNA interaction profiles have revealed ubiquitous interactions with RNA and protein products of the same gene. It remains unclear whether these observations are driven by ribosome proximal or ribosome mediated contacts, or if some protein complexes, particularly RNPs, undergo co-translational assembly. | 1 | Applied and Interdisciplinary Chemistry |
The fluxgate magnetometer was invented by H. Aschenbrenner and G. Goubau in 1936. A team at Gulf Research Laboratories led by Victor Vacquier developed airborne fluxgate magnetometers to detect submarines during World War II and after the war confirmed the theory of plate tectonics by using them to measure shifts in the magnetic patterns on the sea floor.
A fluxgate magnetometer consists of a small magnetically susceptible core wrapped by two coils of wire. An alternating electric current is passed through one coil, driving the core through an alternating cycle of magnetic saturation; i.e., magnetised, unmagnetised, inversely magnetised, unmagnetised, magnetised, and so forth. This constantly changing field induces a voltage in the second coil which is measured by a detector. In a magnetically neutral background, the input and output signals match. However, when the core is exposed to a background field, it is more easily saturated in alignment with that field and less easily saturated in opposition to it. Hence the alternating magnetic field and the induced output voltage, are out of step with the input current. The extent to which this is the case depends on the strength of the background magnetic field. Often, the signal in the output coil is integrated, yielding an output analog voltage proportional to the magnetic field.
A wide variety of sensors are currently available and used to measure magnetic fields. Fluxgate compasses and gradiometers measure the direction and magnitude of magnetic fields. Fluxgates are affordable, rugged and compact with miniaturization recently advancing to the point of complete sensor solutions in the form of IC chips, including examples from both academia and industry. This, plus their typically low power consumption makes them ideal for a variety of sensing applications. Gradiometers are commonly used for archaeological prospecting and unexploded ordnance (UXO) detection such as the German militarys popular Foerster'.
The typical fluxgate magnetometer consists of a "sense" (secondary) coil surrounding an inner "drive" (primary) coil that is closely wound around a highly permeable core material, such as mu-metal or permalloy. An alternating current is applied to the drive winding, which drives the core in a continuous repeating cycle of saturation and unsaturation. To an external field, the core is alternately weakly permeable and highly permeable. The core is often a toroidally wrapped ring or a pair of linear elements whose drive windings are each wound in opposing directions. Such closed flux paths minimise coupling between the drive and sense windings. In the presence of an external magnetic field, with the core in a highly permeable state, such a field is locally attracted or gated (hence the name fluxgate) through the sense winding. When the core is weakly permeable, the external field is less attracted. This continuous gating of the external field in and out of the sense winding induces a signal in the sense winding, whose principal frequency is twice that of the drive frequency, and whose strength and phase orientation vary directly with the external-field magnitude and polarity.
There are additional factors that affect the size of the resultant signal. These factors include the number of turns in the sense winding, magnetic permeability of the core, sensor geometry, and the gated flux rate of change with respect to time.
Phase synchronous detection is used to extract these harmonic signals from the sense winding and convert them into a DC voltage proportional to the external magnetic field. Active current feedback may also be employed, such that the sense winding is driven to counteract the external field. In such cases, the feedback current varies linearly with the external magnetic field and is used as the basis for measurement. This helps to counter inherent non-linearity between the applied external field strength and the flux gated through the sense winding. | 0 | Theoretical and Fundamental Chemistry |
The law of combining volumes states that when gases chemically react together, they do so in amounts by volume which bear small whole-number ratios (the volumes calculated at the same temperature and pressure).
The ratio between the volumes of the reactant gases and the gaseous products can be expressed in simple whole numbers.
For example, Gay-Lussac found that two volumes of hydrogen react with one volume of oxygen to form two volumes of gaseous water. Expressed concretely, 100 mL of hydrogen combine with 50 mL of oxygen to give 100 mL of water vapor: Hydrogen(100 mL) + Oxygen(50 mL) = Water(100 mL). Thus, the volumes of hydrogen and oxygen which combine (i.e., 100mL and 50mL) bear a simple ratio of 2:1, as also is the case for the ratio of product water vapor to reactant oxygen.
Based on Gay-Lussacs results, Amedeo Avogadro hypothesized in 1811 that, at the same temperature and pressure, equal volumes of gases (of whatever kind) contain equal numbers of molecules (Avogadros law). He pointed out that if this hypothesis is true, then the previously stated result
:2 volumes of hydrogen + 1 volume of oxygen = 2 volume of gaseous water
could also be expressed as
:2 molecules of hydrogen + 1 molecule of oxygen = 2 molecule of water.
The law of combining volumes of gases was announced publicly by Joseph Louis Gay-Lussac on the last day of 1808, and published in 1809. Since there was no direct evidence for Avogadros molecular theory, very few chemists adopted Avogadros hypothesis as generally valid until the Italian chemist Stanislao Cannizzaro argued convincingly for it during the First International Chemical Congress in 1860. | 0 | Theoretical and Fundamental Chemistry |
Step-growth polymerization involves two monomers with bi- or multifunctionality to form polymer chains. Many polymers are synthesized via step-growth polymerization and include polyesters, polyamides, and polyurethanes. A sub-class of step-growth polymerization is condensation polymerization. | 0 | Theoretical and Fundamental Chemistry |
Nayak advocates that more people should be taught to perform the so-called miracles of godmen. He also advocates that people should be trained to recognize pseudoscience and demand scientific evidence. He holds the opinion that well-known scientists should be convinced to join the cause and form pressure groups against pseudoscience. He is also lobbying for a bill for the separation of state and religion to be introduced in the Indian parliament. After the murder of anti-superstition activist Narendra Dabholkar and enactment of the anti-superstition ordinance in Maharashtra state, Nayak expressed the need of a similar law in Karnataka. Regarding fellow Mangalorean George Fernandes, Nayak said the "You can hate George Fernandes, You can love Fernandes, but you cannot ignore him". Nayak was the guest of honour during the launch event of the book Bandh Samrat - Tales of Eternal Rebel written on George Fernandes's early trade union activities in Mangalore and Bombay | 1 | Applied and Interdisciplinary Chemistry |
Sulfur oxidation involves the oxidation of reduced sulfur compounds (such as sulfide ), inorganic sulfur (S), and thiosulfate () to form sulfuric acid (). A classic example of a sulfur-oxidizing bacterium is Beggiatoa, a microbe originally described by Sergei Winogradsky, one of the founders of environmental microbiology. Another example is Paracoccus. Generally, the oxidation of sulfide occurs in stages, with inorganic sulfur being stored either inside or outside of the cell until needed. This two step process occurs because energetically sulfide is a better electron donor than inorganic sulfur or thiosulfate, allowing for a greater number of protons to be translocated across the membrane. Sulfur-oxidizing organisms generate reducing power for carbon dioxide fixation via the Calvin cycle using reverse electron flow, an energy-requiring process that pushes the electrons against their thermodynamic gradient to produce NADH. Biochemically, reduced sulfur compounds are converted to sulfite () and subsequently converted to sulfate () by the enzyme sulfite oxidase. Some organisms, however, accomplish the same oxidation using a reversal of the APS reductase system used by sulfate-reducing bacteria (see above). In all cases the energy liberated is transferred to the electron transport chain for ATP and NADH production. In addition to aerobic sulfur oxidation, some organisms (e.g. Thiobacillus denitrificans) use nitrate () as a terminal electron acceptor and therefore grow anaerobically. | 1 | Applied and Interdisciplinary Chemistry |
* Guerneri Rolfincii, Phil. Ac Med. Doctoris Et Professoris Publici Chimia In Artis Formam Redacta : Sex Libris comprehensa .... Genevae, 1671 [http://nbn-resolving.de/urn:nbn:de:hbz:061:2-170303 Digital edition] of the University and State Library Düsseldorf. | 1 | Applied and Interdisciplinary Chemistry |
Vacuum deoxidation is a method which involves using a vacuum to remove impurities. A portion of the carbon and oxygen in steel will react, forming carbon monoxide. CO gas will float up to the top of the liquid steel and be removed by a vacuum system.
As the chemical reaction involved in vacuum deoxidation is:
the reaction between carbon and oxygen is represented by the following chemical equilibrium equation:
where P is the partial pressure of the carbon monoxide formed.
Decreasing the oxygen activity(a) will result in a higher equilibrium constant, thus more product, CO. To achieve this, subjecting the pool of steel to vacuum treatment decreases the value of P, allowing for more CO gas to be produced. | 1 | Applied and Interdisciplinary Chemistry |
Most countries require continuous monitoring of emissions produced by coal and oil-fired power plants, municipal and hazardous waste incinerators, cement plants, as well as many other types of industrial sources. This monitoring is usually performed using extractive sampling systems coupled with infrared spectroscopy techniques. Some recent standoff measurements performed allowed the evaluation of the air quality but not many remote independent methods allow for low uncertainty measurements. | 0 | Theoretical and Fundamental Chemistry |
The set of monoisotopic elements overlap but are not the same as the set of 21 mononuclidic elements, which are characterized as having essentially only one isotope (nuclide) found in nature. The reason for this is the occurrence of certain long-lived radioactive primordial nuclides in nature, which may form admixtures with the monoisotopics, and thus prevent them from being naturally mononuclidic. This happens in the cases of 7 of the monoisotopic elements. These isotopes are monoisotopic, but due to the presence of the long-lived radioactive primordial nuclide, are not mononuclidic. These elements are vanadium, rubidium, indium, lanthanum, europium, lutetium and rhenium. For indium and rhenium, the long-lived radionuclide is actually the most abundant isotope in nature, and the stable isotope is less abundant.
In 2 additional cases (bismuth and protactinium), mononuclidic elements occur primordially which are not monoisotopic because the naturally occurring nuclide is radioactive, and thus the element has no stable isotopes at all. For an element to be monoisotopic, it must have one stable nuclide. | 0 | Theoretical and Fundamental Chemistry |
Krafft temperature is defined as the minimum temperature from which the micelle formation takes place. It is named after German chemist Friedrich Krafft. It has been found that solubility at the Krafft point is nearly equal to critical micelle concentration (CMC). Below the Krafft temperature, the maximum solubility of the surfactant will be lower than the critical micelle concentration, meaning micelles will not form. The Krafft temperature is a point of phase change below which the surfactant remains in crystalline form, even in an aqueous solution. Visually the effect of going below the Krafft point is similar to that of going above the cloud point, with the solution becoming cloudy or opaque due to the surfactant molecules undergoing flocculation.
Surfactants in such a crystalline state will only solubilize and form micelles if another surfactant assists it in overcoming the forces that keep it crystallized, or if the temperature increases, thus causing entropy to increase and encouraging the crystalline structure to break apart. | 0 | Theoretical and Fundamental Chemistry |
Conjugation is a convenient means for transferring genetic material to a variety of targets. In laboratories, successful transfers have been reported from bacteria to yeast, plants, mammalian cells, diatoms and isolated mammalian mitochondria. Conjugation has advantages over other forms of genetic transfer including minimal disruption of the targets cellular envelope and the ability to transfer relatively large amounts of genetic material (see the above discussion of E. coli chromosome transfer). In plant engineering, Agrobacterium-like conjugation complements other standard vehicles such as tobacco mosaic virus (TMV). While TMV is capable of infecting many plant families these are primarily herbaceous dicots. Agrobacterium'-like conjugation is also primarily used for dicots, but monocot recipients are not uncommon. | 1 | Applied and Interdisciplinary Chemistry |
When there is excess glucose, coenzyme A is used in the cytosol for synthesis of fatty acids. This process is implemented by regulation of acetyl-CoA carboxylase, which catalyzes the committed step in fatty acid synthesis. Insulin stimulates acetyl-CoA carboxylase, while epinephrine and glucagon inhibit its activity.
During cell starvation, coenzyme A is synthesized and transports fatty acids in the cytosol to the mitochondria. Here, acetyl-CoA is generated for oxidation and energy production. In the citric acid cycle, coenzyme A works as an allosteric regulator in the stimulation of the enzyme pyruvate dehydrogenase. | 1 | Applied and Interdisciplinary Chemistry |
Alarm photosynthesis is a variation of photosynthesis where calcium oxalate crystals function as dynamic carbon pools, supplying carbon dioxide (CO) to photosynthetic cells when stomata are partially or totally closed. This biochemical appendance of the photosynthetic machinery is a means to alleviate the perpetual plant dilemma of using atmospheric CO for photosynthesis and losing water vapor, or saving water and reducing photosynthesis. The function of alarm photosynthesis seems to be rather auxiliary to the overall photosynthetic performance. It supports a low photosynthetic rate, aiming at the maintenance and photoprotection of the photosynthetic apparatus rather than a substantial carbon gain. | 0 | Theoretical and Fundamental Chemistry |
The particle size distribution can also be obtained using the autocorrelation function. However, polydisperse samples are not well resolved by the cumulant fit analysis. Thus, the combination of non-negative least squares (NNLS) algorithms with regularization methods, such as the Tikhonov regularization, can be used to resolve multimodal samples. An important feature of the NNLS optimization is the regularization term used to identify specific solutions and minimize the deviation between the measure data and the fit. There is no ideal regularization term that is suitable for all samples. The shape of this term can determine if the solution will represent a general broad distribution with small number of peaks or if narrow and discrete populations will be fit. Alternatively, the calculation of the particle size distribution is performed using the CONTIN algorithm. | 0 | Theoretical and Fundamental Chemistry |
Globo-Hs TACA character allows for its utilization as an anticancer vaccine, inducing antibody response against the epitope. The resulting humoral immunity could enable the selective eradication of Globo H-presenting tumors. The Taiwanese biopharma company OBI Pharma, Inc., was first to develop Adagloxad Simolenin (OBI-822), a Globo H hexasaccharide conjugated with the immunostimulatory carrier protein KLH. The Phase III GLORIA study is underway evaluating the carbohydrate-based immunogens effects in high risk triple-negative breast cancer (TNBC) patients with an estimated completion date in 2027.
Alternative vaccine conjugates have been developed which avoid issues associated with the protein carrier KLH by substituting it with a lipid or carbohydrate-based carrier. Examples include the use of lipid A derivatives or entirely carbohydrate vaccine conjugates such as Globo H-PS A1 | 1 | Applied and Interdisciplinary Chemistry |
Polychorinated biphenyls, or PCBs, are a type of chemical that was widely used in the 1960s and 1970s, and which are a contamination source of soil and water. They are fairly stable and therefore persistent in the environment. Bioremediation of PCBs is the use of microorganisms to degrade PCBs from contaminated sites, relying on multiple microorganisms' co-metabolism. Anaerobic microorganisms dechlorinate PCBs first, and other microorganisms that are capable of doing BH pathway can break down the dechlorinated PCBs to usable intermediates like acyl-CoA or carbon dioxide. If no BH pathway-capable microorganisms are present, dechlorinated PCBs can be mineralized with help of fungi and plants. However, there are multiple limiting factors for this co-metabolism. | 1 | Applied and Interdisciplinary Chemistry |
Fossils of what are thought to be filamentous photosynthetic organisms have been dated at 3.4 billion years old. More recent studies also suggest that photosynthesis may have begun about 3.4 billion years ago, though the first direct evidence of photosynthesis comes from thylakoid membranes preserved in 1.75-billion-year-old cherts.
Oxygenic photosynthesis is the main source of oxygen in the Earth's atmosphere, and its earliest appearance is sometimes referred to as the oxygen catastrophe. Geological evidence suggests that oxygenic photosynthesis, such as that in cyanobacteria, became important during the Paleoproterozoic era around two billion years ago. Modern photosynthesis in plants and most photosynthetic prokaryotes is oxygenic, using water as an electron donor, which is oxidized to molecular oxygen in the photosynthetic reaction center. | 0 | Theoretical and Fundamental Chemistry |
Amoxicillin is also sometimes used as an antibiotic for animals. The use of amoxicillin for animals intended for human consumption (chickens, cattle, and swine for example) has been approved. | 0 | Theoretical and Fundamental Chemistry |
The presence of harmful algae blooms can lead to hypoxia or anoxia in a body of water. The depletion of oxygen within a body of water can lead to the creation of a dead zone. Dead zones occur when a body of water has become unsuitable for organism survival in that location. HABs cause dead zones by consuming oxygen in these bodies of water - leaving minimal oxygen available to other marine organisms. When the HABs die, their bodies will sink to the bottom of the body of water - as the decaying of their bodies (through bacteria) is what causes the consumption of oxygen. Once oxygen levels get so low, the HABs have placed the body of water in hypoxia - and these low oxygen levels will cause marine organisms to seek out better suited locations for their survival.
Blooms can harm the environment even without producing toxins by depleting oxygen from the water when growing and while decaying after they die. Blooms can also block sunlight to organisms living beneath it. A record-breaking number and size of blooms have formed in the Pacific coast, in Lake Erie, in the Chesapeake Bay and in the Gulf of Mexico, where a number of dead zones were created as a result. In the 1960s the number of dead zones worldwide was 49; the number rose to over 400 by 2008.
Among the largest dead zones were those in northern Europe's Baltic Sea and the Gulf of Mexico, which affects a $2.8 billion U.S. fish industry. Unfortunately, dead zones rarely recover and usually grow in size. One of the few dead zones to ever recover was in the Black Sea, which returned to normal fairly quickly after the collapse of the Soviet Union in the 1990s due to a resulting reduction in fertilizer use. | 0 | Theoretical and Fundamental Chemistry |
As in the standard code, initiation is most efficient at AUG. In addition, GUG and UUG starts are documented in archaea and bacteria. In Escherichia coli, UUG is estimated to serve as initiator for about 3% of the bacteriums proteins. CUG is known to function as an initiator for one plasmid-encoded protein (RepA) in E. coli. In addition to the NUG initiations, in rare cases bacteria can initiate translation from an AUU codon as e.g. in the case of poly(A) polymerase PcnB and the InfC gene that codes for translation initiation factor IF3. The internal assignments are the same as in the standard code though UGA codes at low efficiency for tryptophan in Bacillus subtilis and, presumably, in Escherichia coli'.
The NCBI raw format is as follows, with UUG, CUG, AUU, AUC, AUA, AUG, and GUG marked as possible initiators:
AAs = FFLLSSSSYY**CC*WLLLLPPPPHHQQRRRRIIIMTTTTNNKKSSRRVVVVAAAADDEEGGGG
Starts = ---M------**--*----M------------MMMM---------------M------------
Base1 = TTTTTTTTTTTTTTTTCCCCCCCCCCCCCCCCAAAAAAAAAAAAAAAAGGGGGGGGGGGGGGGG
Base2 = TTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGG
Base3 = TCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAG
Initiation at AUC and AUA is not addressed in the NCBI description text, but both are indeed known to occur in E. coli. | 1 | Applied and Interdisciplinary Chemistry |
Tagging technology and instrument development occurred at the University of Toronto and DVS Sciences, Inc. CyTOF (cytometry by time of flight) was initially commercialized by DVS Sciences in 2009. In 2014, Fluidigm acquired DVS Sciences to become a reference company in single cell technology. In 2022 Fluidigm received a capitol infusion and changed its name to Standard BioTools. The CyTOF, CyTOF2, Helios (CyTOF3) and CyTOF XT(4th generation) have been commercialized up to now. Fluidigm sells a variety of commonly used metal-antibody conjugates, and an antibody conjugation kit. | 0 | Theoretical and Fundamental Chemistry |
In fluid mechanics, pressure head is the height of a liquid column that corresponds to a particular pressure exerted by the liquid column on the base of its container. It may also be called static pressure head or simply static head (but not static head pressure).
Mathematically this is expressed as:
where
: is pressure head (which is actually a length, typically in units of meters or centimetres of water)
: is fluid pressure (i.e. force per unit area, typically expressed in pascals)
: is the specific weight (i.e. force per unit volume, typically expressed in N/m units)
: is the density of the fluid (i.e. mass per unit volume, typically expressed in kg/m)
: is acceleration due to gravity (i.e. rate of change of velocity, expressed in m/s).
Note that in this equation, the pressure term may be gauge pressure or absolute pressure, depending on the design of the container and whether it is open to the ambient air or sealed without air. | 1 | Applied and Interdisciplinary Chemistry |
Phenol red (also known as phenolsulfonphthalein or PSP) is a pH indicator frequently used in cell biology laboratories. | 0 | Theoretical and Fundamental Chemistry |
CataCXium F sulf is a water-soluble organophosphorus compound derived from fluorene. The palladium complexes of the respective phosphine show an excellent activity in various palladium-catalyzed coupling reactions, including Suzuki reactions, Sonogashira couplings and Buchwald–Hartwig reactions. | 0 | Theoretical and Fundamental Chemistry |
Micelles are composed of surfactant, or detergent, monomers with a hydrophobic moiety, or tail, on one end, and a hydrophilic moiety, or head group, on the other. The polar head group may be anionic, cationic, zwitterionic, or non-ionic. When the concentration of a surfactant in solution reaches its critical micelle concentration (CMC), it forms micelles which are aggregates of the monomers. The CMC is different for each surfactant, as is the number of monomers which make up the micelle, termed the aggregation number (AN). Table 1 lists some common detergents used to form micelles along with their CMC and AN where available.
Many of the characteristics of micelles differ from those of bulk solvents. For example, the micelles are, by nature, spatially heterogeneous with a hydrocarbon, nearly anhydrous core and a highly solvated, polar head group. They have a high surface-to-volume ratio due to their small size and generally spherical shape. Their surrounding environment (pH, ionic strength, buffer ion, presence of a co-solvent, and temperature) has an influence on their size, shape, critical micelle concentration, aggregation number and other properties.
Another important property of micelles is the Kraft point, the temperature at which the solubility of the surfactant is equal to its CMC. For HPLC applications involving micelles, it is best to choose a surfactant with a low Kraft point and CMC. A high CMC would require a high concentration of surfactant which would increase the viscosity of the mobile phase, an undesirable condition. Additionally, a Kraft point should be well below room temperature to avoid having to apply heat to the mobile phase. To avoid potential interference with absorption detectors, a surfactant should also have a small molar absorptivity at the chosen wavelength of analysis. Light scattering should not be a concern due to the small size, a few nanometers, of the micelle.
The effect of organic additives on micellar properties is another important consideration. A small amount of organic solvent is often added to the mobile phase to help improve efficiency and to improve separations of compounds. Care needs to be taken when determining how much organic to add. Too high a concentration of the organic may cause the micelle to disperse, as it relies on hydrophobic effects for its formation. The maximum concentration of organic depends on the organic solvent itself, and on the micelle. This information is generally not known precisely, but a generally accepted practice is to keep the volume percentage of organic below 15–20%. | 0 | Theoretical and Fundamental Chemistry |
The design was first reported by McCarthy (1934).
As shown in the diagram, a stoppered reservoir is supplied with an air inlet and a siphon. The pressure at the bottom of the air inlet is always the same as the pressure outside the reservoir, i.e. the atmospheric pressure. If it were greater, air would not enter. If the entrance to the siphon is at the same depth, then it will always supply the water at atmospheric pressure and will deliver a flow under constant head height, regardless of the changing water level within the reservoir.
This apparatus has many variations in design and has been used extensively when a constant water pressure is needed, e.g. supplying water at constant head for measuring water infiltration into soil or supplying the mobile phase in chromatography.
The drawback of the design is that it is sensitive for gas inlet leakage and that during operation liquid cannot be added, since it would change the pressure control. Accurate control is nowadays provided by electronic devices. | 1 | Applied and Interdisciplinary Chemistry |
At slow scan rates there should be no separation between the oxidative and reductive peaks.
* A one-electron site (e.g. a heme or FeS cluster) gives a broad peak (fig 1A). The equation that gives the shape and intensity of the peak is:
: Ideally, the peak position is in both directions. The peak current is (it is proportional to scan rate, , and to the amount of redox sites on the electrode, ). The ideal half width at half height (HWHH) equates mV at 20 °C. Non-ideal behaviour may result in the peak being broader than the ideal limit.
* The peak shape for a two-electron redox site (e.g. a flavin) depends on the stability of the half-reduced state (fig 1B). If the half-reduced state is stable over a large range of electrode potential, the signal is the sum of two one-electron peaks (purple line in fig 1B). If the half reduced state is unstable, the signal is a single peak (red line in fig 1B), which may have up to four times the height and half the width of a one-electron peak.
* A protein that contains multiple redox centers should give multiple peaks which all have the same area (scaled by ). | 0 | Theoretical and Fundamental Chemistry |
* Bimal Matilal, The Navya-nyāya doctrine of negation: the semantics and ontology of negative statements, Harvard University Press,
* Daniel H.H. Ingalls, Materials for the study of Navya-nyāya logic, Harvard University Press, | 1 | Applied and Interdisciplinary Chemistry |
A carbyne can occur as a short-lived reactive intermediate. For instance, fluoromethylidyne (CF) can be detected in the gas phase by spectroscopy as an intermediate in the flash photolysis of CHFBr.
Carbynes can act as trivalent ligands in complexes with transition metals, in which they are connected to a metal by the three non-bonded electrons in the –C group. Examples of such coordination compounds are , WBr(CO)(2,2'-bipyridine)≡C-aryl and WBr(CO)(PPh)≡C-NR. Such a compound can be obtained by the reaction of tungsten hexacarbonyl W(CO) with lithium diisopropylamide to form (PrN)(OLi)C=W(CO). This salt is then oxidized with either oxalyl bromide or triphenylphosphine dibromide, followed by addition of triphenylphosphine. Another method is to treat a methoxy metal carbene with a Lewis acid. | 0 | Theoretical and Fundamental Chemistry |
According to the IsoRes hypothesis, there are certain resonance isotopic compositions at which terrestrial organisms thrive best. Curiously, average terrestrial isotopic compositions are very close to a resonance affecting a large class of amino acids and polypeptides, the molecules of outmost importance for life. Thus, the IsoRes hypothesis suggests that early life on Earth was aided, perhaps critically, by the proximity to an IsoRes. In contrast, there is no strong resonance for then atmosphere of Mars, which led to a prediction that life could not have originated on Mars and that the planet is probably sterile. | 0 | Theoretical and Fundamental Chemistry |
Cantilever enhanced photoacoustic spectroscopy enables the detection of small amount of trace gases which is vital in many applications. Photoacoustic spectroscopy is one of the most sensitive optical detection schemes. It is based on detecting a gas specific acoustic wave generated that originates from the absorption of light in the medium. The sensitivity of the traditional membrane microphones is limited by electrical noise and the nonlinearity of the displacement of the mechanical sensor at high optical power levels. Conventional membrane microphones can be replaced with optically measured micromechanical cantilevers to enhance sensitivity.
__TOC__ | 0 | Theoretical and Fundamental Chemistry |
Woollins' reagent is commercially available. It can also be conveniently prepared in the laboratory by heating a mixture of dichlorophenylphosphine and sodium selenide (NaSe), (itself prepared from reacting elementary selenium with sodium in liquid ammonia). An alternative synthesis is the reaction of the pentamer (PPh) (pentaphenylcyclopentaphosphine) with elemental selenium. | 0 | Theoretical and Fundamental Chemistry |
The banteng was the second endangered species to be successfully cloned, and the first clone to survive beyond infancy. Scientists at Advanced Cell Technology in Worcester, Massachusetts, extracted DNA from skin cells of a dead male banteng, that were preserved in San Diego 's Frozen Zoo facility, and transferred it into eggs from domestic banteng cows, a process called somatic cell nuclear transfer. Thirty embryos were created and implanted in domestic banteng cows. Two were carried to term and delivered by Caesarian section. The first was born on 1 April 2003, and the second two days later. The second was euthanized, apparently suffering from large offspring syndrome (an overgrowth disorder), but the first survived and lived for seven years at the San Diego Zoo, where it died in April 2010 after it broke a leg and was euthanized. | 1 | Applied and Interdisciplinary Chemistry |
Electrodeless discharge lamps (EDL) contain a small quantity of the analyte as a metal or a salt in a quartz bulb together with an inert gas, typically argon gas, at low pressure. The bulb is inserted into a coil that is generating an electromagnetic radio frequency field, resulting in a low-pressure inductively coupled discharge in the lamp. The emission from an EDL is higher than that from an HCL, and the line width is generally narrower, but EDLs need a separate power supply and might need a longer time to stabilize. | 0 | Theoretical and Fundamental Chemistry |
The different sets of transcriptional repression and activation which characterize a and α cells are caused by the presence of one of two alleles of a mating-type locus called MAT: MATa or MATα located on chromosome III. The MAT locus is usually divided into five regions (W, X, Y, Z1, and Z2) based on the sequences shared among the two mating types. The difference lies in the Y region (Ya and Yα), which contains most of the genes and promoters.
The MATa allele of MAT encodes a gene called a1, which in haploids direct the transcription of the a-specific transcriptional program (such as expressing STE2 and repressing STE3) that defines an a cell. The MATα allele of MAT encodes the α1 and α2 genes, which in haploids direct the transcription of the α-specific transcriptional program (such as expressing STE3, repressing STE2, producing prepro-α-factor) which causes the cell to be an α cell. S. cerevisiae has an a2 gene with no apparent function that shares much of its sequence with α2; however, other yeasts like Candida albicans do have a functional and distinct MATa2 gene. | 1 | Applied and Interdisciplinary Chemistry |
The Journal of Chemical & Engineering Data is a peer-reviewed scientific journal, published since 1956 by the American Chemical Society. JCED is currently indexed in: Chemical Abstracts Service (CAS), SCOPUS, EBSCOhost, ProQuest, British Library, PubMed, Ovid, Web of Science, and SwetsWise.
The current Editor is J. Ilja Siepmann. According to the Journal Citation Reports, the journal has a 2022 impact factor of 2.6. | 1 | Applied and Interdisciplinary Chemistry |
The formation of a disaccharide molecule from two monosaccharide molecules proceeds by displacing a hydroxy group from one molecule and a hydrogen nucleus (a proton) from the other, so that the new vacant bonds on the monosaccharides join the two monomers together. Because of the removal of the water molecule from the product, the term of convenience for such a process is "dehydration reaction" (also "condensation reaction" or "dehydration synthesis"). For example, milk sugar (lactose) is a disaccharide made by condensation of one molecule of each of the monosaccharides glucose and galactose, whereas the disaccharide sucrose in sugar cane and sugar beet, is a condensation product of glucose and fructose. Maltose, another common disaccharide, is condensed from two glucose molecules.
The dehydration reaction that bonds monosaccharides into disaccharides (and also bonds monosaccharides into more complex polysaccharides) forms what are called glycosidic bonds. | 0 | Theoretical and Fundamental Chemistry |
The office of Public Analyst was established by the Adulteration of Food and Drink Act 1860 (23 & 24 Vict. c. 84), the first three appointments being in London, Birmingham and Dublin. The first Scottish analyst was Henry Littlejohn in Edinburgh in 1862, who, with a strong medicinal background and brilliant mind, established many of the critical foundations of public analysis. The Sale of Food and Drugs Act 1875 (38 & 39 Vict. c. 63) made food analysis compulsory and the Sale of Food and Drugs Act 1899 (62 & 63 Vict. c. 51) extended its scope. Sampling officers generally operated through local public health or sanitary committees. By 1894 there were 99 public analysts overseeing 237 English and Welsh districts. The City of London Corporation had three food inspectors and a wharf and warehouse inspector in 1908. Bradford employed an inspector who made 756 visits to fish and chip shops in 1915. In the 1930s the staff in Birmingham comprised three qualified assistants, a clerk and a laboratory attendant.
The Nuisances Removal Act for England 1855 (18 & 19 Vict. c. 121) and the Public Health Act 1875 (38 & 39 Vict. c. 55) gave authority for taking food samples "at all reasonable times". Inspectors, police constables and samplers were responsible for taking food samples, which were divided into three parts, for the vendors, the inspectors and the analysts and sealed into bottles. Food systems were engineered to allow inspection through portals, manholes and windows. Prosecution was not common though fines and prison sentences were not unknown. Adulteration rates fell from 13.8% of samples in 1879 to 4.8% in 1930. Inspectors were empowered to follow milk to sources outside their formal jurisdiction in checking for infection with tuberculosis. Sanitary authorities were required to register all dairies and enforce cleanliness regulations.
The Manchester Corporation (General Powers) Act 1899 (62 & 63 Vict. c. clxxxviii), as amended in 1904, contained what were known as `milk clauses', which empowered officials to prosecute anyone who knowingly sold milk from cows with tuberculosis of the udder, to demand the isolation of infected cows and notification of any cow exhibiting signs of tuberculosis of the udder and to inspect the cows and take samples from herds which supplied milk to the city. By 1910 these provisions had been copied by 67 boroughs and 24 urban districts .
The Society of Public Analysts was established in 1874, later becoming the Society for Analytical Chemistry and joining with other societies to form the Royal Society of Chemistry in 1980.
Since the separation of the UK and Ireland, the function of the Public Analyst operates under different legislation, but the term and general duties are the same. The original work was chemical testing, and this is still a major part, but nowadays microbiological examination of food is an important activity, particularly in Scotland, where Public Analyst laboratories also carry out a statutory Food Examiner role. | 1 | Applied and Interdisciplinary Chemistry |
Electrochemical regeneration of activated carbon adsorbents such as granular activated carbon present an alternative to thermal regeneration or land filling at the end of useful adsorbent life. Continuous adsorption-electrochemical regeneration encompasses the adsorption and regeneration steps, typically separated in the bulk of industrial processes due to long adsorption equilibrium times (ranging from hours to months), into one continuous system. This is possible using a non-porous, electrically conducting carbon derivative called Nyex. The non-porosity of Nyex allows it to achieve its full adsorptive capacity within a few minutes and its electrical conductivity allows it to form part of the electrode in an electrochemical cell. As a result of its properties Nyex can undergo quick adsorption and fast electrochemical regeneration in a combined adsorption-electrochemical regeneration cell achieving 100% regeneration efficiency. | 0 | Theoretical and Fundamental Chemistry |
Viscimation is the turbulence when liquids of different viscosities mix,
particularly the formation of vortices (also known as "viscimetric whorls") and visible separate threads of the different liquids.
The term viscimation is archaic and idiosyncratic to whisky tasting; their study (or appreciation) is called viscimetry, and the capacity of a whisky to sustain viscimation (which is predominantly its alcohol percentage) is viscimetric potential or viscimetric index.
Causing viscometric whorls by adding water to liquor is colloquially called "awakening the serpent". | 1 | Applied and Interdisciplinary Chemistry |
According to Spanish scholar González Echeverría in several communications in the ISHM, the John M. Riddle Anonymous B (De Materia Medica of 1543) would be Michael Servetus, and that the Anonymous D (De Materia Medica of 1554 of Mattioli plus non-signed commentaries) is two commentarians, Servetus and Mattioi, being the last one hired for editing the "Lyons printers Tribute to Michel de Villeneuve'" edition.
Michael Servetus, using the name "Michel de Villeneuve", who already had his first death sentence from the University of Paris, anonymously published a Dioscorides-De Materia Medica in 1543, printed by Jean & Francois Frellon in Lyon. It has 277 marginalia and 20 commentaries on a De Materia Medica of Jean Ruel. According to Gonzalez Echeverría, to be associated to an anonymous Pharmacopeia that "Michel de Villeneuve" published the same year, meant to be a single unit, which is typical when it comes to De Materia Medica-Pharmacopeia. This work had six later editions, in 1546 and 1547 by Jean Frellon, who considered Michael de Villeneuve "his friend and brother", another in 1547 by Thibaut Payen, etc.
There is another Materia Medica with commentaries on a Ruel edition of 1537, printed by Simon de Colines. This work contains hundreds of manuscript marginaia, all along 420 out of 480 pages. The scholar Gonzalez Echeverria demonstrated in the ISHM with a graphological, historical and linguistic study that this task was carried out by Michel de Villeneuve. It also demonstrated that this document was written by the same hand that wrote the famous "Manuscript of Paris", a work also by Michel de Villeneuve, consisting of a draft for his Christianismo Restitutio. "The manuscript of the Complutense" is not just a union of the ideas of the previous works by Michel de Villeneuve, Syropum Ratio, etc., but also of the later works, Enquiridion, De Materia Medica of 1543, sharing with this last many of its 20 big commentaries, for instance.
According to this theory, in 1554, after the immolation of Michael de Villeneuve/Servetus, the editors and printers that had worked with him would have decided to make a new De Materia Medica as a tribute to their colleague and friend. All the commentaries that could identify Michel de Villeneuve as the author disappeared, but the rest are copied from his work of 1543. It is a very strange edition because there exist four different kinds of copies with different covers, one per editor: Jean Frellon, Guillaume Rouillé, Antoine Vicent and Balthazar Arnoullet, who was also the printer of this unique edition, in Lyons. For developing a bigger work and to blur the mark of Michel de Villeneuve, they hired the expert on De Materia Medica, Pietro Andrea Mattioli. | 1 | Applied and Interdisciplinary Chemistry |
In case (b), the spin-orbit coupling is weak or non-existent (in the case ). In this case, we take and and assume precesses quickly around the internuclear axis.
The good quantum numbers in case (b) are , , , and . We express the rotational energy operator as , where is a rotational constant. The rotational levels therefore have relative energies starting with . For example, a Σ state has rotational levels = 0, 1, 2, 3, 4, ..., and each level is divided by spin-orbit coupling into two levels = ± 1/2 (except for = 0 which corresponds only to = 1/2 because cannot be negative).
Another example is the Σ ground state of dioxygen, which has two unpaired electrons with parallel spins. The coupling type is Hund's case b), and each rotational level N is divided into three levels = , , .
For case b) the selection rules for quantum numbers , , and and for parity are the same as for case a). However for the rotational levels, the rule for quantum number does not apply and is replaced by the rule . | 0 | Theoretical and Fundamental Chemistry |
Laminins are non-collagenous proteins found in basement membranes and form networks through non-covalent self-interactions. Nidogens (also known as entactins) are sulfated monomeric glycoproteins that are ubiquitously present in basement membranes of higher organisms. Nidogens help with the formation of the basement. With both laminins and nidogens present, both interact with each other to have a stoichiometry relationship of 1:1 in a complex. In order to study the short arm of laminin γ1, photo methionine introduced both to nidogen-1, laminin γ1 LEb2-4, and laminin γ1 short arm to see if this photo-cross linking method could map out the structure. MS/MS analysis was done before cross-linking to find only 13-25% of methionines had been incorporated, but once UV-A-induced or another cross-linker, BSG-mediated cross-linked (a homobifunctional cross-linker), the percentage of photo-methionine's had increased to 35%. Both cross-linkers had shown extra structural insight both computationally and experimentally to help with understanding the functions. | 0 | Theoretical and Fundamental Chemistry |
To calculate the breakthrough voltage, a homogeneous electrical field is assumed. This is the case in a parallel-plate capacitor setup. The electrodes may have the distance . The cathode is located at the point .
To get impact ionization, the electron energy must become greater than the ionization energy of the gas atoms between the plates. Per length of path a number of ionizations will occur. is known as the first Townsend coefficient as it was introduced by Townsend.
The increase of the electron current , can be described for the assumed setup as
(So the number of free electrons at the anode is equal to the number of free electrons at the cathode that were multiplied by impact ionization. The larger and/or , the more free electrons are created.)
The number of created electrons is
Neglecting possible multiple ionizations of the same atom, the number of created ions is the same as the number of created electrons:
is the ion current. To keep the discharge going on, free electrons must be created at the cathode surface. This is possible because the ions hitting the cathode release secondary electrons at the impact. (For very large applied voltages also field electron emission can occur.) Without field emission, we can write
where is the mean number of generated secondary electrons per ion. This is also known as the second Townsend coefficient. Assuming that , one gets the relation between the Townsend coefficients by putting () into () and transforming: | 0 | Theoretical and Fundamental Chemistry |
Heavy water, DO, self-ionizes less than normal water, HO;
:DO + DO DO + OD
This is due to the equilibrium isotope effect, a quantum mechanical effect attributed to oxygen forming a slightly stronger bond to deuterium because the larger mass of deuterium results in a lower zero-point energy.
Expressed with activities a, instead of concentrations, the thermodynamic equilibrium constant for the heavy water ionization reaction is:
Assuming the activity of the DO to be 1, and assuming that the activities of the DO and OD are closely approximated by their concentrations
The following table compares the values of pK for HO and DO. | 0 | Theoretical and Fundamental Chemistry |
Another possible model for fusion pore formation is the protein-lined pore theory. In this model, after activation of synaptotagmin by calcium, several SNARE complexes come together to form a ring structure, with synaptobrevin forming the pore in the vesicle membrane and Syntaxin forming the pore in the cell membrane. As the initial pore expands it incorporates lipids from both bilayers, eventually resulting in complete fusion of the two membranes. The SNARE complex has a much more active role in the protein-lined pore theory; because the pore consists initially entirely of SNARE proteins, the pore is easily able to undergo intercellular regulation, making fluctuation and "kiss-and-run" mechanisms easily attainable.
A protein-lined pore perfectly meets all the observed requirements of the early fusion pore, and while some data does support this theory, sufficient data does not exist to pronounce it the primary method of fusion. A protein-lined pore requires at least five copies of the SNARE complex while fusion has been observed with as few as two.
In both theories the function of the SNARE complex remains largely unchanged, and the entire SNARE complex is necessary to initiate fusion. It has, however, been proven that in vitro Syntaxin per se is sufficient to drive spontaneous calcium independent fusion of synaptic vesicles containing v-SNAREs. This suggests that in Ca-dependent neuronal exocytosis synaptotagmin is a dual regulator, in absence of Ca ions to inhibit SNARE dynamics, while in presence of Ca ions to act as agonist in the membrane fusion process. | 1 | Applied and Interdisciplinary Chemistry |
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