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Consider the simple three step pathway:
where and are fixed boundary species, the control equations for this pathway can be derived in a similar manner to the simple two step pathway although it is somewhat more tedious.
where D the denominator is given by
Note that every term in the numerator appears in the denominator, this ensures that the flux control coefficient summation theorem is satisfied.
Likewise the concentration control coefficients can also be derived, for
And for
Note that the denominators remain the same as before and behave as a normalizing factor. | 1 | Applied and Interdisciplinary Chemistry |
In the north-west of Germany, a series of closure works have been implemented. Initially, the primary aims of these closures were land reclamation and protection against flooding. Subsequently, the focus shifted towards safety and ecological conservation. Closures took place in Meldorf (1978), Nordstrander Bucht (Husum, 1987), and Leyhörn (Greetsiel, 1991).
Around 1975, evolving global perspectives on ecological significance led to a change in the approach to closures. As a result, in northern Germany, several closures were executed differently from their original designs. For instance, while there were plans to completely dam the Leybucht near Greetsiel, only a minor portion was ultimately closed—just enough to meet safety and water management requirements. This made the closure of the remaining area no longer a technical challenge. A discharge sluice and navigation lock were constructed, providing adequate capacity to mitigate currents in the closure gap of the dam. | 1 | Applied and Interdisciplinary Chemistry |
Radiofrequency Echographic Multi Spectrometry (REMS) is a non-ionizing technology for osteoporosis diagnosis and for fracture risk assessment. REMS processes the raw, unfiltered ultrasound signals acquired during an echographic scan of the axial sites, femur and spine. The analysis is performed in the frequency domain. Bone mineral density (BMD) is estimated by comparing the results against reference models.
The accuracy has been tested by comparing it against to DXA technology. | 0 | Theoretical and Fundamental Chemistry |
Stopped-flow is an experimental technique for studying chemical reactions with a half time of the order of 1 ms, introduced by Britton Chance and extended by Quentin Gibson (Other techniques, such as the temperature-jump method, are available for much faster processes.) | 0 | Theoretical and Fundamental Chemistry |
and , with constants and and rate equations ; and
The integrated rate equations are then ; and
One important relationship in this case is | 0 | Theoretical and Fundamental Chemistry |
In iron ore smelting, haematite gets reduced at the top of the furnace, where temperature is in the range 600 – 700 °C. The Ellingham diagram indicates that in this range carbon monoxide acts as a stronger reducing agent than carbon since the process
:2 CO + → 2
has a more-negative free energy change than the process:
:2 C + → 2 CO.
In the upper part of the blast furnace, haematite is reduced by CO (produced by oxidation of coke lower down at the bottom of blast furnace, at higher temperature) even in the presence of carbon – though this is mainly because the kinetics for gaseous CO reacting with the ore are better. | 1 | Applied and Interdisciplinary Chemistry |
A viruss host range determines which host it can acquire AMGs from. Additionally, the abundance of a host surrounding a virus will affect its likelihood to acquire genes from the host. Virus populations increasingly occupy lytic lifestyles as bacterial production increases. The strong evolutionary connection between viruses and their hosts makes AMG acquisition mirror the hosts own adaptation to its environment over time.
Synechococcus and Prochlorococcus are the most abundant picocyanobacteria, accounting for up to 50% of primary production in the marine environment. As such, many AMGs characterized have been discovered in phages of these host systems. | 1 | Applied and Interdisciplinary Chemistry |
Considering a plane wave the electron quantum parameter can be rewritten using this relation between electric and magnetic fields:where is the wavevector of the plane wave and the wavevector magnitude. Inserting this expression in the formula of :where the vectorial identity was used. Elaborating the expression:Since for a plane wave and the last two terms under the square root compensate each other, reduces to:
In the simplified configuration of a plane wave impinging on the electron, higher values of the electron quantum parameter are obtained when the plane wave is counter-propagating with respect to the electron velocity. | 0 | Theoretical and Fundamental Chemistry |
The notion of chromium as a potential regulator of glucose metabolism began in the 1950s when Walter Mertz and his co-workers performed a series of experiments controlling the diet of rats. The experimenters subjected the rats to a chromium deficient diet, and witnessed an inability of the organisms to respond effectively to increased levels of glucose within the blood. They then included "acid-hydrolyzed porcine kidney and Brewers yeast" in the diet of these rats, and found that the rats were now able to effectively metabolize glucose. Both the porcine kidney and Brewers yeast were rich in chromium, and so it was from these findings that began the study of chromium as a regulator of blood glucose.
The idea of chromium being used for the treatment of type II diabetes was first sparked in the 1970s. A patient receiving total parenteral nutrition (TPN) had developed "severe signs of diabetes", and was administered chromium supplements based on previous studies that proved the effectiveness of this metal in modulating blood glucose levels. The patient was administered chromium for a total of two weeks, and by the end of this time-period, their ability to metabolize glucose had increased significantly; they also now required less insulin ("exogenous insulin requirements decreased from 45 units/day to none"). It was these experiments that were performed in the 1950s and 1970s that paved the foundation for future studies on chromium and diabetes.
In 2005, the U.S. Food and Drug Administration approved a Qualified Health Claim for chromium picolinate with a requirement for very specific label wording: "One small study suggests that chromium picolinate may reduce the risk of insulin resistance, and therefore possibly may reduce the risk of type 2 diabetes. FDA concludes, however, that the existence of such a relationship between chromium picolinate and either insulin resistance or type 2 diabetes is highly uncertain." In 2010, chromium(III) picolinate was approved by Health Canada to be used in dietary supplements. Approved labeling statements included: "...provides support for healthy glucose metabolism." The European Food Safety Authority (EFSA) approved claims in 2010 that chromium contributed to normal macronutrient metabolism and maintenance of normal blood glucose concentration.
A 2016 review of meta-analyses concluded that whereas there may be modest decreases in fasting plasma glucose or glycosylated hemoglobin that achieve statistical significance, the changes were rarely large enough to be expected to be relevant to clinical outcome. | 1 | Applied and Interdisciplinary Chemistry |
Its name is derived from the word “pigment” (P) and the presence of a major bleaching band centered around 695-700 nm in the flash-induced absorbance difference spectra of P700/ P700+•. | 0 | Theoretical and Fundamental Chemistry |
Instrumentation of supercritical fluid chromatography SFC has a similar setup to an HPLC instrument. The stationary phases are similar, and are packed inside similar column types. However, there are special features in these systems, because of the need to keep the mobile phase at supercritical fluidic state over the entire system. Temperature is critical to keep the fluids in a supercritical state, so there should be a heat control tool in the system, similar to that of GC. Also, there should be a precise pressure control mechanism, a restrictor to keep the pressure above a certain point, because pressure is another essential parameter to keep the mobile phase in a supercritical fluid state, so it is kept at the required minimal level. A microprocessor mechanism is placed in the instrument for SFC. This unit collects data for pressure, oven temperature, and detector performance to control the related pieces of the instrument.
CO utilized in carbon dioxide dedicated pumps, which require that the incoming CO and pump heads be kept cold, in order to maintain the carbon dioxide at a temperature and pressure fit for supercritical fluidic state, where it can be effectively metered at a specified flow rate range. The CO subsequently becomes supercritical fluid throughout the injector and the column oven, when the temperature and pressure it is subjected to, are raised above the critical point of the liquid, thus the supercritical state is achieved.
Supercritical fluids combine useful properties of gas and liquid phases, as it can behave like both a gas and a liquid in various aspects. A supercritical fluid provides a gas-like characteristic when it fills a container and it takes the shape of the container. The motion and kinetics of the molecules are quite similar to gas molecules. On the other hand, a supercritical fluid behaves like a liquid because its density property is near liquid; thus, a supercritical fluid shows a similarity to the dissolving effect of a liquid. The result is that one can load masses, similar to those used in HPLC, on column per injection, and still maintain a high chromatographic efficiency similar to those attained in GC. Typically, gradient elution is employed in analytical SFC using a polar co-solvent such as methanol, possibly with a weak acid or base at low concentrations ~1%. The apparent plate count per analysis can be observed to exceed 500K plates per meter routinely with 5 um stationary phases. The operator uses software to set mobile phase flow rate, co-solvent composition, system back pressure and column oven temperature, which must exceed 40 °C for supercritical conditions needed to be achieved with CO. In addition, SFC provides an additional control parameter – pressure – by using an automated static and dynamic back pressure regulator. From an operational standpoint, SFC is as simple and robust as HPLC, but fraction collection is more convenient because the primary mobile phase evaporates leaving only the analyte and a small volume of polar co-solvent. If the outlet CO is captured, it can be re-compressed and recycled, allowing for >90% reuse of CO.
Similar to HPLC, SFC uses a variety of detection methods including UV/VIS, mass spectrometry, FID (unlike HPLC) and evaporative light scattering. | 0 | Theoretical and Fundamental Chemistry |
The Voitenko compressor is a shaped charge adapted from its original purpose of piercing thick steel armour to the task of accelerating shock waves. It was proposed by Anatoly Emelyanovich Voitenko (Анатолий Емельянович Войтенко), a Soviet scientist, in 1964. It slightly resembles a wind tunnel.
The Voitenko compressor initially separates a test gas from a shaped charge with a malleable steel plate. When the shaped charge detonates, most of its energy is focused on the steel plate, driving it forward and pushing the test gas ahead of it. Ames Research Center translated this idea into a self-destroying shock tube. A shaped charge accelerated the gas in a 3-cm glass-walled tube 2 meters in length. The velocity of the resulting shock wave was a phenomenal . The apparatus exposed to the detonation was, of course, completely destroyed, but not before useful data was extracted. In a typical Voitenko compressor, a shaped charge accelerates hydrogen gas, which in turn accelerates a thin disk up to about 40 km/s. A slight modification to the Voitenko compressor concept is a super-compressed detonation, a device that uses a compressible liquid or solid fuel in the steel compression chamber instead of a traditional gas mixture. A further extension of this technology is the explosive diamond anvil cell, utilizing multiple opposed shaped-charge jets projected at a single steel-encapsulated fuel, such as hydrogen. The fuels used in these devices, along with the secondary combustion reactions and long blast impulse, produce similar conditions to those encountered in fuel-air and thermobaric explosives.
This method of detonation produces energies over 100 keV (~10 K temperatures), suitable not only for nuclear fusion, but other higher-order quantum reactions as well. The UTIAS explosive-driven-implosion facility was used to produce stable, centered and focused hemispherical implosions to generate neutrons from D–D reactions. The simplest and most direct method proved to be in a predetonated stoichiometric mixture of deuterium and oxygen. The other successful method was using a miniature Voitenko-type compressor, where a plane diaphragm was driven by the implosion wave into a secondary small spherical cavity that contained pure deuterium gas at one atmosphere. In brief, PETN solid explosive is used to form a hemispherical shell (3–6 mm thick) in a 20-cm diameter hemispherical cavity milled in a massive steel chamber. The remaining volume is filled with a stoichiometric mixture of (H or D and O). This mixture is detonated by a very short, thin exploding wire located at the geometric center. The arrival of the detonation wave at the spherical surface instantly and simultaneously fires the explosive liner. The detonation wave in the explosive liner hits the metal cavity, reflects, and implodes on the preheated burnt gases, focuses at the center of the hemisphere (50 microseconds after the initiation of the exploding wire) and reflects, leaving behind a very small pocket (1 mm) of extremely high-temperature, high-pressure and high-density plasma. | 0 | Theoretical and Fundamental Chemistry |
Each endocytic pathway focuses on a particular component, and FEME is primarily involved in transporting receptors. These include receptors for acetylcholine and IL-2. | 1 | Applied and Interdisciplinary Chemistry |
A small fraction of electrons leave the electron transport chain before reaching complex IV. Premature electron leakage to oxygen results in the formation of superoxide. The relevance of this otherwise minor side reaction is that superoxide and other reactive oxygen species are highly toxic and are thought to play a role in several pathologies, as well as aging (the free radical theory of aging). Electron leakage occurs mainly at the Q site and is stimulated by antimycin A. Antimycin A locks the b hemes in the reduced state by preventing their re-oxidation at the Q site, which, in turn, causes the steady-state concentrations of the Q semiquinone to rise, the latter species reacting with oxygen to form superoxide. The effect of high membrane potential is thought to have a similar effect. Superoxide produced at the Qo site can be released both into the mitochondrial matrix and into the intermembrane space, where it can then reach the cytosol. This could be explained by the fact that Complex III might produce superoxide as membrane permeable HOO rather than as membrane impermeable O. | 1 | Applied and Interdisciplinary Chemistry |
In another case, the stereoelectronic effect can result in an increased contribution of one resonance structure over another, which leads to further consequences in reactivity. For 1,4-benzoquinone monoxime, there are significant differences in the physical properties and reactivities between C2-C3 double bond and C5-C6 double bond. For instance, in the H NMR, J higher than J The C2-C3 double bond also selectively undergoes Diels–Alder reaction with cyclopentadiene, despite the increased steric hindrance on that side of the molecule. These data illustrate an increased contribution of resonance structure B over structure A. The authors argue that the donation from n to σ* orbital lengthens the C4–C3 bond (C4 is the carbon bearing the nitrogen substituent), which reduces the p-p overlap between these two atoms. This in turn decreasing the relative importance of structure A which has a double bond between C4 and C3. | 0 | Theoretical and Fundamental Chemistry |
Since its introduction by Nicholas Bodor in the late 1970s, the soft drug concept generated considerable research both in academic and in industrial settings. Bodor defined soft drugs as biologically active, therapeutically useful chemical compounds characterized by a predictable and controllable in vivo metabolism to non-toxic moieties after they achieve their therapeutic role. There are several rationally designed soft drugs that have either already reached the market, such as
* esmolol (Breviblock)
* landiolol (Onoact)
* remifentanil (Ultiva)
* loteprednol etabonate (Lotemax, Alrex, Zylet)
* clevidipine (Cleviprex)
* remimazolam (Byfavo)
or are in late-stage development (budiodarone, celivarone, AZD3043, tecafarin). There are also compounds that can be considered as soft chemicals (e.g., malathion) or soft drugs (e.g., articaine, methylphenidate) even though they were not developed as such. | 1 | Applied and Interdisciplinary Chemistry |
Solid state NMR spectroscopy has been very useful in determining the structure of amorphous solids. Bioactive glasses have been studied by Si and P solid state MAS NMR spectroscopy. The chemical shift from MAS NMR is indicative of the type of chemical species present in the glass. The Si MAS NMR spectroscopy showed that Bioglass 45S5 was a Q2 type-structure with a small amount of Q3; i.e., silicate chains with a few crosslinks. The P MAS NMR revealed predominately Q0 species; i.e., PO; subsequent MAS NMR spectroscopy measurements have shown that Si-O-P bonds are below detectable levels | 0 | Theoretical and Fundamental Chemistry |
The chemistry of the subsurface ocean of Europa may be Earthlike. The subsurface ocean of Enceladus vents hydrogen and carbon dioxide to space. | 0 | Theoretical and Fundamental Chemistry |
Cryptophytes, or cryptomonads are a group of algae that contain a red-algal derived chloroplast. Cryptophyte chloroplasts contain a nucleomorph that superficially resembles that of the chlorarachniophytes. Cryptophyte chloroplasts have four membranes, the outermost of which is continuous with the rough endoplasmic reticulum. They synthesize ordinary starch, which is stored in granules found in the periplastid space—outside the original double membrane, in the place that corresponds to the red alga's cytoplasm. Inside cryptophyte chloroplasts is a pyrenoid and thylakoids in stacks of two.
Their chloroplasts do not have phycobilisomes, but they do have phycobilin pigments which they keep in their thylakoid space, rather than anchored on the outside of their thylakoid membranes.
Cryptophytes may have played a key role in the spreading of red algal based chloroplasts. | 0 | Theoretical and Fundamental Chemistry |
Subcooling may also be produced by superheating the gas leaving the evaporator and heading to the gas compressor. These systems withdraw heat from the liquid line and heat up the gas compressor's suction line. This is a very common solution to insure that gas reaches the compressor and liquid reaches the valve. It also allows maximum heat exchanger use as minimizes the portion of the heat exchangers used to change the temperature of the fluid, and maximizes the volume in which the refrigerant changes its phase (phenomena involving much more heat flow, the base principle of vapor-compression refrigeration).
An internal heat exchanger is simply a heat exchanger that uses the cold gas leaving the evaporator coil to cool the high-pressure liquid that is headed into the beginning of the evaporator coil via an expansion device. The gas is used to chill a chamber that normally has a series of pipes for the liquid running through it. The superheated gas then proceeds on to the compressor. The subcooling term refers to cooling the liquid below its boiling point. of subcooling means it is 10 °F colder than boiling at a given pressure. As it represents a difference of temperatures, the subcooling value is not measured on an absolute temperature scale, only on a relative scale as a temperature difference. | 0 | Theoretical and Fundamental Chemistry |
Titanium aluminide (chemical formula TiAl), commonly gamma titanium, is an intermetallic chemical compound. It is lightweight and resistant to oxidation and heat, but has low ductility. The density of γ-TiAl is about 4.0 g/cm. It finds use in several applications including aircraft, jet engines, sporting equipment and automobiles. The development of TiAl based alloys began circa 1970. The alloys have been used in these applications only since about 2000.
Titanium aluminide has three major intermetallic compounds: gamma titanium aluminide (gamma TiAl, γ-TiAl), alpha 2-TiAl and TiAl. Among the three, gamma TiAl has received the most interest and applications. | 1 | Applied and Interdisciplinary Chemistry |
Historically, sediments with the highest organic carbon contents were frequently found in areas with high surface water productivity or those with low bottom-water oxygen concentrations. 90% of organic carbon burial occurs in deposits of deltas and continental shelves and upper slopes; this is due partly to short exposure time because of a shorter distance to the seafloor and the composition of the organic matter that is already deposited in those environments. Organic carbon burial is also sensitive to climate patterns: the accumulation rate of organic carbon was 50% larger during the glacial maximum compared to interglacials. | 0 | Theoretical and Fundamental Chemistry |
Pyrohydrolysis based acid regeneration processes produce a considerable amount of stack emissions containing HCl, particles and chlorine, which has led to numerous violations of the U.S. clean air act in the past. | 0 | Theoretical and Fundamental Chemistry |
Precondition for repetitious manufacturing of porous glass is the knowledge about structure determining and structure controlling parameters. The composition of the initial glass is a structure controlling parameter. The manufacturing of the initial glass, mainly the cooling process, the temperature and time of thermal treatment, and the after treatment are structure determining parameters. The phase diagram for sodiumborosilica glass shows a miscibility gap for certain glass compositions.
The upper critical temperature lies at about 760 °C and the lower one at about 500 °C. O.S. Moltschanova was the first person who exactly described the definition of the exsolution. For a phase separation the initial glass composition must lie in the miscibility gap of the ternary -- glass system. By a thermal treatment, an interpenetration structure is generated, which results from a spinodal decomposition of the sodium-rich borate phase and the silica phase. This procedure is called primary decomposition. Using an initial glass composition, which lies on the line of anomaly, it is possible to attain a maximum decomposition, which is almost strainless.
As both phases have a different resistances to water, mineral acids, and inorganic salt solutions, the sodium-rich borate phase in these mediums can be removed by extraction. Optimal extraction is possible only if the initial glass composition and thermal treatment are chosen such that combine structures form, and not droplet structures. The texture is influenced by the composition of the initial glass, which directs size and type of decomposition areas. In the context of porous glasses, "texture" implies properties like specific pore volume, specific surface, pore size, and porosity. Furthermore, the texture of porous glasses is influenced by the concentration of the extraction medium and the ratio of fluid to solid. The emerging areas of decomposition depend on time and temperature of the thermal treatment.
Also, colloidal silica is solving in the sodium-rich borate phase, when time and temperature of thermal treatment are increased. This process is called secondary decomposition. The colloidal silica deposit in the macro pores during extraction and obscure the real pore structure. The solubility of colloidal silica in alkaline solutions is higher than network silica, and thus can be removed by an alkaline after-treatment. | 0 | Theoretical and Fundamental Chemistry |
Muon beams are classified into three types based on the energy of the muons being produced: high-energy, surface or "Arizona", and ultra-slow muon beams.
High-energy muon beams are formed by the pions escaping the production target at high energies. They are collected over a certain solid angle by quadrupole magnets and directed onto a decay section consisting of a long superconducting solenoid with a field of several tesla. If the pion momentum is not too high, a large fraction of the pions will have decayed before they reach the end of the solenoid. In the laboratory frame the polarization of a high-energy muon beam is limited to about 80% and its energy is of the order of ~40-50MeV. Although such a high energy beam requires the use of suitable moderators and samples with sufficient thickness, it guarantees a homogeneous implantation of the muons in the sample volume. Such beams are also used to study specimens inside of recipients, e.g. samples inside pressure cells. Such muon beams are available at PSI, TRIUMF, J-PARC and [https://web.archive.org/web/20110624051656/http://riken.nd.rl.ac.uk/ral.html RIKEN-RAL].
The second type of muon beam is often called the surface or Arizona beam (recalling the pioneering work of Pifer et al. from the University of Arizona). In these beams, muons arise from pions decaying at rest inside but near the surface of the production target. Such muons are 100% polarized, ideally monochromatic, and have a very low momentum of 29.8 MeV/c (corresponding to a kinetic energy of 4.1 MeV). They have a range width in matter of the order of 180 mg/cm. The paramount advantage of this type of beam is the ability to use relatively thin samples. Beams of this type are available at PSI (Swiss Muon Source SµS), TRIUMF, J-PARC, ISIS Neutron and Muon Source and RIKEN-RAL.
Positive muon beams of even lower energy (ultra-slow muons with energy down to the eV-keV range) can be obtained by further reducing the energy of an Arizona beam by utilizing the energy-loss characteristics of large band gap solid moderators. This technique was pioneered by researchers at the TRIUMF cyclotron facility in Vancouver, B.C., Canada. It was christened with the acronym μSOL (muon separator on-line) and initially employed LiF as the moderating solid. The same 1986 paper also reported the observation of negative muonium ions (i.e., Mu or μ e e) in vacuum. In 1987, the slow μ production rate was increased 100-fold using thin-film rare-gas solid moderators, producing a usable flux of low-energy positive muons. This production technique was subsequently adopted by PSI for their low-energy positive muon beam facility. The tunable energy range of such muon beams corresponds to implantation depths in solids of less than a nanometer up to several hundred nanometers. Therefore, the study of magnetic properties as a function of the distance from the surface of the sample is possible. At the present time, PSI is the only facility where such a low-energy muon beam is available on a regular basis. Technical developments have been also conducted at RIKEN-RAL, but with a strongly reduced low-energy muon rate. J-PARC is projecting the development of a high-intensity low-energy muon beam. | 0 | Theoretical and Fundamental Chemistry |
Usually, organometallic compounds are considered to contain the M-C-H group. The metal (M) in these species can either be a main group element or a transition metal. Operationally, the definition of an organometallic compound is more relaxed to include also highly lipophilic complexes such as metal carbonyls and even metal alkoxides.
Organometallic compounds are mainly considered a special category because organic ligands are often sensitive to hydrolysis or oxidation, necessitating that organometallic chemistry employs more specialized preparative methods than was traditional in Werner-type complexes. Synthetic methodology, especially the ability to manipulate complexes in solvents of low coordinating power, enabled the exploration of very weakly coordinating ligands such as hydrocarbons, H, and N. Because the ligands are petrochemicals in some sense, the area of organometallic chemistry has greatly benefited from its relevance to industry.
* Examples: Cyclopentadienyliron dicarbonyl dimer (CH)Fe(CO)CH, ferrocene Fe(CH), molybdenum hexacarbonyl Mo(CO), triethylborane EtB, Tris(dibenzylideneacetone)dipalladium(0) Pd(dba)) | 0 | Theoretical and Fundamental Chemistry |
Chemists have long been interested in mimicking chemical processes in nature. Coordination cages quickly became a hot topic as they can be made by self-assembly, a tool of chemistry in nature. The conceptualization of a closed-surface molecule capable of incorporating a guest was described by Donald Cram in 1985. Early cages were synthesized from bottom-up. Makoto Fujita introduced self-assembling cages, which are less tedious to prepare. These cages arise from the condensation of square planar complexes using polypodal ligands. | 0 | Theoretical and Fundamental Chemistry |
During his time at the University of Wisconsin, Stork kept a steak on his windowsill in the winter in order to keep it refrigerated. The steak began to degrade and to dispose of it Stork put it in a hot acid bath used to clean glassware which contained nitric and sulphuric acids. He was then concerned he would produce nitroglycerine due to the glycerine in the steak and the presence of nitric and sulphuric acids. However, due to the high temperature of the bath, the oxidation of glycerol was much faster than the nitration of glycerin thus preventing the formation of explosives. | 0 | Theoretical and Fundamental Chemistry |
It is possible to monosilylate a symmetrical diol, although this is known to be problematic occasionally. For example, the following monosilylation was reported:
However, it turns out that this reaction is hard to repeat. If the reaction were controlled solely by thermodynamics, and if the dianion is of similar reactivity to the monoanion, then a corresponding statistical mixture of 1:2:1 disilylated:monosilylated:unsilylated diol would be expected. However, the reaction in THF is made selective by two factors: 1. kinetic deprotonation of the first anion and 2. the insolubility of the monoanion. At the initial addition of TBSCl, there is only a minor amount of monoanion in solution with the rest being in suspension. This small portion reacts and shifts the equilibrium of the monoanion to draw more into solution, thereby allowing for high yields of the mono-TBS compound to be obtained. Superior results in some cases may be obtained with butyllithium:
A third method uses a mixture of DMF and DIPEA.
Alternatively, an excess (4 eq) of the diol can be used, forcing the reaction toward monoprotection. | 0 | Theoretical and Fundamental Chemistry |
Chloridometers are used to determine the concentration of chloride ions in biological fluids. For example, fish plasma chloride ion concentration is measured to gauge the effects of stress on osmoregulation in aquacultures. A small quantity of plasma (10 μL) combined with an acid reagent results in a chemical reaction that ultimately provides a concentration measure of chloride ions in meq/L.
Because they require alternating current, chloridometers are not portable and are better suited to a "bench-top location". This may necessitate freezing biological fluid specimens collected in the field for later analysis.
Chloridometers represent the most common use of coulometry in clinical biochemistry. | 0 | Theoretical and Fundamental Chemistry |
RNA-targeting small molecule drug discovery has greatly benefitted from the available cellular models for disease. The use of cell culture in early development has become a requirement for assessing the basic efficacy of a drug candidate. Thus, more research groups have implemented these techniques in their programs. In a leading example, Al-Hashimi and coworkers identified six small molecules with high affinity for TAR of HIV-1 through a computational approach. They docked a library of small molecules onto RNA dynamic structures generated by NMR and Molecular Dynamics (MD) simulations. The hit molecules inhibited the Tat—TAR interaction in vitro. They arrived at lead molecule, netilmicin, that had the best selectivity for HIV-1 TAR and inhibited HIV-1 replication in cells with a low IC50. The Disney group has studied aminoglycoside derivatives in 2009 for their ability to inhibit interactions between repeat RNA and proteins. Using their prediction database INFORNA, they discovered that a compound could bind to 1 x 1 UU internal loops on an N-methyl peptide backbone. They confirmed that like other compounds that target DM1 r(CUG), they could inhibit the complex between r(CUG)-MBNL1, disrupt nuclear foci, and increase nucleocytoplasmic transport of the gene in patient-derived DM1 fibroblasts. In that study the Disney group also described several approaches to validate the RNA targets of small molecules. In the first approach termed chemical cross-linking and isolation by pull down (Chem-CLIP) and chemical cross-linking and isolation by pull down to map binding sites (Chem-CLIP-Map).
These studies showed in cells that small molecules can direct target disease-causing r(CUG) repeats in DM1 and that impressively the compound can discriminate against other RNAs with shorter repeats and also between the mutant and wild type allele of the DMPK mRNA that contains r(CUG) disease-causing repeats. In an additional approach, dubbed small–molecule nucleic acid profiling by cleavage applied to RNA (Ribo-SNAP) showed that small molecules can be used to cleave RNA targets in cells and also importantly demonstrated that designer small molecules target precisely disease causing RNA repeats and discriminate against RNAs that are not disease causing but have short repeats of r(CUG). Thus, targeting RNA structure with small molecules can have important selectively discrimination implications in cells.
In 2014, Chenowith and colleagues reported a cationic triptycene scaffold that targets RNA and DNA three-way junctions. Subsequent studies showed that these molecules exhibited favorable cellular uptake and cytotoxicity in human ovarian cancer cell lines. In 2017, the Xodo group reported anthrafurandione and anthrathiophenedione small molecules with aminoethyl side chains could bind to RNA G-quadraplexes at the 5’-UTR of certain mRNAs. Further, these compounds were shown to suppress the KRAS oncogene in pancreatic cancer cells and induce apoptosis by reducing the metabolic activity of the cells. | 1 | Applied and Interdisciplinary Chemistry |
Particle tracking velocimetry (PTV) is a velocimetry method i.e. a technique to measure velocities and trajectories of moving objects. In fluid mechanics research these objects are neutrally buoyant particles that are suspended in fluid flow. As the name suggests, individual particles are tracked, so this technique is a Lagrangian approach, in contrast to particle image velocimetry (PIV), which is an Eulerian method that measures the velocity of the fluid as it passes the observation point, that is fixed in space. There are two experimental PTV methods:
* the two-dimensional (2-D) PTV. Measurements are made in a 2-D slice, illuminated by a thin laser sheet (a thin plane); a low density of seeded particles allows for tracking each of them individually for several frames.
* the three-dimensional particle tracking velocimetry (3-D PTV) is a distinctive experimental technique originally developed to study fully turbulent flows. It is now being used widely in various disciplines, ranging from structural mechanics research to medicine and industrial environments. It is based on a multiple camera-system in a stereoscopic arrangement, three-dimensional illumination of an observation volume, recording of the time sequence of stereoscopic images of optical targets (flow tracers illuminated particles), determining their instantaneous 3-D position in space by use of photogrammetric techniques and tracking their movement in time, thus obtaining a set of 3-D trajectories of the optical targets. Time-resolved three-dimensional particle tracking velocimetry is known as 4D-PTV. | 1 | Applied and Interdisciplinary Chemistry |
Pyridine has a conjugated system of six π electrons that are delocalized over the ring. The molecule is planar and, thus, follows the Hückel criteria for aromatic systems. In contrast to benzene, the electron density is not evenly distributed over the ring, reflecting the negative inductive effect of the nitrogen atom. For this reason, pyridine has a dipole moment and a weaker resonant stabilization than benzene (resonance energy 117 kJ·mol in pyridine vs. 150 kJ·mol in benzene).
The ring atoms in the pyridine molecule are sp-hybridized. The nitrogen is involved in the π-bonding aromatic system using its unhybridized p orbital. The lone pair is in an sp orbital, projecting outward from the ring in the same plane as the σ bonds. As a result, the lone pair does not contribute to the aromatic system but importantly influences the chemical properties of pyridine, as it easily supports bond formation via an electrophilic attack. However, because of the separation of the lone pair from the aromatic ring system, the nitrogen atom cannot exhibit a positive mesomeric effect.
Many analogues of pyridine are known where N is replaced by other heteroatoms from the same column of the Periodic Table of Elements (see figure below). Substitution of one C–H in pyridine with a second N gives rise to the diazine heterocycles (CHN), with the names pyridazine, pyrimidine, and pyrazine.
<div><ul> | 0 | Theoretical and Fundamental Chemistry |
*ANSYS Inc., 2007. Release 11 Documentation for ANSYS Workbench.
*Cermak, J.E., 2003. Wind-tunnel development and trends in applications to civil engineering. J. Wind Eng. Ind. Aerodyn. 91 (3), 355–370.
*Cermak, J.E., Cochran, L.S., 1992. Physical modeling of the atmospheric surface layer. J. Wind Eng. Ind. Aerodyn. 41–44, 935–946.
*Collar, A.R., 1939. The effect of a gauze on velocity distribution in a uniform duct. Aeronaut. Res. Counc. Rep. Memo No. 1867. Desai, S.S., 2003.
*Relative roles of computational fluid dynamics and wind tunnel testing in the development-of aircraft. Curr. Sci. 84 (1), 49–64.
*Derbunovich, G.I., Zemskaya, A.S., Repik, E.U., Sosedko, Y.P., 1993. Optimum Conditions of Turbulence Reduction with Screens, Mechanics of Nonuniform and Turbulent Flows. Nauka, Moscow, pp. 35.
*Dryden, H.I., Schubauer, G.B., 1947. The use of damping screens for the reduction of wind tunnel turbulence. J. Aeronautical Sci. 14, 221–228.
*Farell, C., Youssef, S., 1996. Experiments on turbulence management using screens and honeycombs. ASME J. Fluids Eng. 118, 26–32.
*Ghani, S.A.A.A., Aroussi, A., Rice, E., 2001. Simulation of road vehicle natural environment in a climatic wind tunnel. Simul. Pract. Theory 8 (6–7), 359–375.
*Gordon, R., Imbabi, M.S., 1998. CFD simulation and experimental validation of a new closed circuit wind/water tunnel design. J. Fluids Eng. Trans. ASME 120 (2), 311–318.
*Groth, J., Johansson, A., 1988. Turbulence reduction by screens. J. Fluids Mech. 197, 139–155.
*Hansen, S.O., Sorensen, E.G., 1985. A new boundary-layer wind tunnel at the Danish Maritime Institute. J. Wind Eng. Ind. Aerodyn. 18, 213–224. | 1 | Applied and Interdisciplinary Chemistry |
A major function of the thylakoid membrane and its integral photosystems is the establishment of chemiosmotic potential. The carriers in the electron transport chain use some of the electron's energy to actively transport protons from the stroma to the lumen. During photosynthesis, the lumen becomes acidic, as low as pH 4, compared to pH 8 in the stroma. This represents a 10,000 fold concentration gradient for protons across the thylakoid membrane. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, the Boussinesq approximation (, named for Joseph Valentin Boussinesq) is used in the field of buoyancy-driven flow (also known as natural convection). It ignores density differences except where they appear in terms multiplied by , the acceleration due to gravity. The essence of the Boussinesq approximation is that the difference in inertia is negligible but gravity is sufficiently strong to make the specific weight appreciably different between the two fluids. Sound waves are impossible/neglected when the Boussinesq approximation is used since sound waves move via density variations.
Boussinesq flows are common in nature (such as atmospheric fronts, oceanic circulation, katabatic winds), industry (dense gas dispersion, fume cupboard ventilation), and the built environment (natural ventilation, central heating). The approximation is extremely accurate for many such flows, and makes the mathematics and physics simpler. | 1 | Applied and Interdisciplinary Chemistry |
Thermodynamic heat pump cycles are the models for household heat pumps and refrigerators. There is no difference between the two except the purpose of the refrigerator is to cool a very small space while the household heat pump is intended to warm or cool a house. Both work by moving heat from a cold space to a warm space. The most common refrigeration cycle is the vapor compression cycle, which models systems using refrigerants that change phase. The absorption refrigeration cycle is an alternative that absorbs the refrigerant in a liquid solution rather than evaporating it. Gas refrigeration cycles include the reversed Brayton cycle and the Hampson–Linde cycle. Multiple compression and expansion cycles allow gas refrigeration systems to liquify gases. | 0 | Theoretical and Fundamental Chemistry |
A number of virus genera are transmitted, both persistently and non-persistently, by soil borne zoosporic protozoa. These protozoa are not phytopathogenic themselves, but parasitic. Transmission of the virus takes place when they become associated with the plant roots. Examples include Polymyxa graminis, which has been shown to transmit plant viral diseases in cereal crops and Polymyxa betae which transmits Beet necrotic yellow vein virus. Plasmodiophorids also create wounds in the plant's root through which other viruses can enter. | 1 | Applied and Interdisciplinary Chemistry |
The preferred scenario for good tilth is as the result of natural soil-building processes, provided by the activity of plant roots, microorganisms, earthworms and other beneficial organisms. Such stable aggregates break apart during tillage/planting and readily provide good tilth. Soil biota and organic matter work in unison to bind soil aggregates and establish a natural soil stability – a soil carbon sponge. Plant root exudates feed bacteria that emit extracellular polysaccharides (EPS), and feed the growth of fungal hyphae, to form a soil carbon sponge with the dispersed clay particles. These active tilth-forming processes contribute to the formation and stabilization of soil structure. The resulting soil structure reduces tensile strength and soil-bulk density while still forming soil aggregates through their abiotic/biotic binding mechanisms that resist breakdown during water saturation. The fungal hyphae networks can establish a role of enmeshment with EPS and rhizodeposition, thus improving aggregate stability. However, these organic materials are themselves subject to biological degradation, requiring active amendments with organic material, and minimal mechanical tillage. Tilth quality is heavily dependent on these naturally binding processes between biotic microorganisms and abiotic soil particles, as well as the necessary input of organic matter. All constituents in this naturally binding network must be supplied or managed in agriculture to ensure the sustainability of their presence through growing seasons. | 0 | Theoretical and Fundamental Chemistry |
Within the eye, it is difficult to achieve therapeutic concentrations through systemic administration. Often, other parts of the body will reach toxic levels of the medication before the eye reaches the treatment concentration. Consequently, direct administration through the fibrous tunic is common. This is made difficult due to the numerous defense mechanisms in place, such as blinking, tear production, and the tightness of the corneal epithelium. Estimates put tear turnover rates at 5 minutes, meaning most conventional drugs are not retained for long periods of time. Mucoadhesives increase retention rates, either by enhancing the viscosity or bonding directly to one of the mucosae surrounding the eye. | 1 | Applied and Interdisciplinary Chemistry |
There is an operational blacksmith shop with an operating line shaft setup powered by a 15-horsepower 1917 Mogul gasoline engine. During the show days, there are multiple forges lit, and multiple blacksmiths can be found working pieces of iron into many different things. | 1 | Applied and Interdisciplinary Chemistry |
Muscle tissue engineering is a subset of the general field of tissue engineering, which studies the combined use of cells and scaffolds to design therapeutic tissue implants. Within the clinical setting, muscle tissue engineering involves the culturing of cells from the patients own body or from a donor, development of muscle tissue with or without the use of scaffolds, then the insertion of functional muscle tissue into the patients body. Ideally, this implantation results in full regeneration of function and aesthetic within the patient's body. Outside the clinical setting, muscle tissue engineering is involved in drug screening, hybrid mechanical muscle actuators, robotic devices, and the development of engineered meat as a new food source.
Innovations within the field of muscle tissue engineering seek to repair and replace defective muscle tissue, thus returning normal function.The practice begins by harvesting and isolating muscle cells from a donor site, then culturing those cells in media. The cultured cells form cell sheets and finally muscle bundles which are implanted into the patient. | 1 | Applied and Interdisciplinary Chemistry |
Thionyl chloride is mainly used in the industrial production of organochlorine compounds, which are often intermediates in pharmaceuticals and agrichemicals. It usually is preferred over other reagents, such as phosphorus pentachloride, as its by-products (HCl and ) are gaseous, which simplifies purification of the product.
Many of the products of thionyl chloride are themselves highly reactive and as such it is involved in a wide range of reactions. | 0 | Theoretical and Fundamental Chemistry |
The ionization in the cathode dark space results in a high electron density, but slower electrons, making it easier for the electrons to recombine with positive ions, leading to intense light, through a process called bremsstrahlung radiation. | 0 | Theoretical and Fundamental Chemistry |
Eshelby was clear and amusing as a lecturer, and prepared his lectures with great care, but was not keen on doing experimental work. He was well versed in Sanskrit (among other classical languages) and was an avid second-hand book buyer.
Eshelby died on 10 December 1981. | 1 | Applied and Interdisciplinary Chemistry |
In general, vitamin D functions to activate the innate and dampen the adaptive immune systems with antibacterial, antiviral and anti-inflammatory effects. Low levels of vitamin D appear to be a risk factor for tuberculosis, and historically it was used as a treatment.
Vitamin D supplementation in low doses (400 to 1000 IU/day) may slightly decrease the overall risk of acute respiratory tract infections. The benefits were found in young children and adolescents (ages 1 up to 16 years) and were not confirmed with higher doses (>1000 IU per day or more). Vitamin D supplementation substantially reduces the rate of moderate or severe exacerbations of COPD in people with baseline 25(OH)D levels under 25nmol/L, but not in those with less severe deficiency. | 1 | Applied and Interdisciplinary Chemistry |
An mRNA molecule is said to be monocistronic when it contains the genetic information to translate only a single protein chain (polypeptide). This is the case for most of the eukaryotic mRNAs. On the other hand, polycistronic mRNA carries several open reading frames (ORFs), each of which is translated into a polypeptide. These polypeptides usually have a related function (they often are the subunits composing a final complex protein) and their coding sequence is grouped and regulated together in a regulatory region, containing a promoter and an operator. Most of the mRNA found in bacteria and archaea is polycistronic, as is the human mitochondrial genome. Dicistronic or bicistronic mRNA encodes only two proteins. | 1 | Applied and Interdisciplinary Chemistry |
Plasmids are double-stranded extra chromosomal and generally circular DNA sequences that are capable of replication using the host cells replication machinery. Plasmid vectors minimalistically consist of an origin of replication that allows for semi-independent replication of the plasmid in the host. Plasmids are found widely in many bacteria, for example in Escherichia coli, but may also be found in a few eukaryotes, for example in yeast such as Saccharomyces cerevisiae'. Bacterial plasmids may be conjugative/transmissible and non-conjugative:
* conjugative - mediate DNA transfer through conjugation and therefore spread rapidly among the bacterial cells of a population; e.g., F plasmid, many R and some col plasmids.
* nonconjugative - do not mediate DNA through conjugation, e.g., many R and col plasmids.
Plasmids with specially-constructed features are commonly used in laboratory for cloning purposes. These plasmid are generally non-conjugative but may have many more features, notably a "multiple cloning site" where multiple restriction enzyme cleavage sites allow for the insertion of a transgene insert. The bacteria containing the plasmids can generate millions of copies of the vector within the bacteria in hours, and the amplified vectors can be extracted from the bacteria for further manipulation. Plasmids may be used specifically as transcription vectors and such plasmids may lack crucial sequences for protein expression. Plasmids used for protein expression, called expression vectors, would include elements for translation of protein, such as a ribosome binding site, start and stop codons. | 1 | Applied and Interdisciplinary Chemistry |
The light harvesting materials employed in biological photovoltaic devices can be categorised by their complexity; more complex materials are typically less efficient but more robust. | 0 | Theoretical and Fundamental Chemistry |
In chaotic advection, a fluid particle travels within a large region, and encounters other particles that were initially far from it. One can then consider that a particle is mixed with particles that travel within the same region. However, the region covered by a trajectory does not always span the whole fluid domain. Poincaré sections are used to distinguish regions of good and bad mixing.
The Poincaré map is defined as the transformation
transforms a point-like particle into the position of the particle after a time-interval T. Especially, for a time-periodic flow with period T, applying the map several times to a particle gives the successive positions of the particle period after period. A Poincaré section is built by starting from a few different initial conditions and plotting the corresponding iterates. This comes down to plotting the trajectories stroboscoped every T.
As an example, the figure presented here (left part) depicts the Poincaré section obtained when one applies periodically a figure-eight-like movement to a circular mixing rod. Some trajectories span a large region: this is the chaotic or mixing region, where good mixing occurs. However, there are also two "holes": in these regions, the trajectories are closed. These are called elliptic islands, as the trajectories inside are elliptic-like curves. These regions are not mixed with the remainder of the fluid. For mixing applications, elliptic islands have to be avoided for two reasons :
* Fluid particles are unable to cross the boundaries of the islands (except by slow diffusion), resulting in segregation.
* Mixing inside these regions is not efficient because trajectories are closed and therefore not chaotic.
Avoiding non-chaotic islands requires understanding the physical origin of these regions. Generally speaking, changing the geometry of the flow can modify the presence or absence of islands. In the figure-eight flow for instance, for a very thin rod, the influence of the rod is not felt far from its location, and almost circular trajectories exist within the loops of the figure-eight. With a larger rod (right part of the figure), particles can escape from these loops and islands do not exist any more, resulting in better mixing.
With a Poincaré section, the mixing quality of a flow can be analyzed by distinguishing between chaotic and elliptic regions. This is a crude measure of the mixing process, however, since the stretching properties cannot be inferred from this mapping method. Nevertheless, this technique is very useful for studying the mixing of periodic flows and can be extended to a 3-D domain. | 1 | Applied and Interdisciplinary Chemistry |
* Cathodic arc deposition
* Electron beam physical vapor deposition (EBPVD)
* Ion plating
* Ion beam assisted deposition (IBAD)
* Magnetron sputtering
* Pulsed laser deposition
* Sputter deposition
* Vacuum deposition
* Vacuum evaporation, evaporation (deposition)
* Pulsed electron deposition (PED) | 1 | Applied and Interdisciplinary Chemistry |
The 18-electron rule is a chemical rule of thumb used primarily for predicting and rationalizing formulas for stable transition metal complexes, especially organometallic compounds. The rule is based on the fact that the valence orbitals in the electron configuration of transition metals consist of five (n−1)d orbitals, one ns orbital, and three np orbitals, where n is the principal quantum number. These orbitals can collectively accommodate 18 electrons as either bonding or non-bonding electron pairs. This means that the combination of these nine atomic orbitals with ligand orbitals creates nine molecular orbitals that are either metal-ligand bonding or non-bonding. When a metal complex has 18 valence electrons, it is said to have achieved the same electron configuration as the noble gas in the period, lending stability to the complex. Transition metal complexes that deviate from the rule are often interesting or useful because they tend to be more reactive. The rule is not helpful for complexes of metals that are not transition metals. The rule was first proposed by American chemist Irving Langmuir in 1921. | 0 | Theoretical and Fundamental Chemistry |
There are many other important measures of probability distance. Some of these are particularly connected with relative entropy. For example:
* The total-variation distance, . This is connected to the divergence through Pinskers inequality: Pinskers inequality is vacuous for any distributions where , since the total variation distance is at most . For such distributions, an alternative bound can be used, due to Bretagnolle and Huber (see, also, Tsybakov):
* The family of Rényi divergences generalize relative entropy. Depending on the value of a certain parameter, , various inequalities may be deduced.
Other notable measures of distance include the Hellinger distance, histogram intersection, Chi-squared statistic, quadratic form distance, match distance, Kolmogorov–Smirnov distance, and earth movers distance'. | 0 | Theoretical and Fundamental Chemistry |
Generating data on RNA transcripts can be achieved via either of two main principles: sequencing of individual transcripts (ESTs, or RNA-Seq) or hybridisation of transcripts to an ordered array of nucleotide probes (microarrays). | 1 | Applied and Interdisciplinary Chemistry |
The haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely used commercially. They are used as flame retardants, fire extinguishants, refrigerants, propellants, solvents, and pharmaceuticals. Subsequent to the widespread use in commerce, many halocarbons have also been shown to be serious pollutants and toxins. For example, the chlorofluorocarbons have been shown to lead to ozone depletion. Methyl bromide is a controversial fumigant. Only haloalkanes that contain chlorine, bromine, and iodine are a threat to the ozone layer, but fluorinated volatile haloalkanes in theory may have activity as greenhouse gases. Methyl iodide, a naturally occurring substance, however, does not have ozone-depleting properties and the United States Environmental Protection Agency has designated the compound a non-ozone layer depleter. For more information, see Halomethane. Haloalkane or alkyl halides are the compounds which have the general formula "RX" where R is an alkyl or substituted alkyl group and X is a halogen (F, Cl, Br, I).
Haloalkanes have been known for centuries. Chloroethane was produced in the 15th century. The systematic synthesis of such compounds developed in the 19th century in step with the development of organic chemistry and the understanding of the structure of alkanes. Methods were developed for the selective formation of C-halogen bonds. Especially versatile methods included the addition of halogens to alkenes, hydrohalogenation of alkenes, and the conversion of alcohols to alkyl halides. These methods are so reliable and so easily implemented that haloalkanes became cheaply available for use in industrial chemistry because the halide could be further replaced by other functional groups.
While many haloalkanes are human-produced, substantial amounts are biogenic. | 0 | Theoretical and Fundamental Chemistry |
* Enerkem from Canada produces renewable Methanol with a capacity of 100 000 t/a. The methanol is produced from municipal solid waste.
* Celanese announced in May 2021 the plan to produce methanol from CO at site Clear Lake, Texas. Herefore 180 000 tons of CO per year shall be used. | 1 | Applied and Interdisciplinary Chemistry |
Steel which utilizes the EPS process to remove surface scale shows few differences from steel which utilizes acid pickling to remove surface scale. "Downstream" industrial processes such as galvanizing, cold reducing and painting of EPS-processed steel strip show it to be interchangeable with acid-pickled steel strip. This also holds true for common sheet metal fabrication processes, such as laser cutting, plasma cutting, stamping, welding, bending, and roll forming – no meaningful difference between steel strip using the EPS process and steel strip using acid pickling.
An area where the difference between EPS-processed steel strip and acid-pickled steel strip is apparent is visual appearance. Steel which has undergone EPS processing exhibits a more uniform, lustrous appearance, as shown in Figure 4. In the EPS process, the impact of the abrasive particles on the steel surface serves to "smooth out" minor surface imperfections such as scratches, pits, roll marks and silicone streaks.
Another area of difference between EPS-treated steel strip and acid-pickled steel strip is rust resistance. Conventional acid-pickled steel strip is frequently coated with a thin film of oil to serve as a barrier to contact with oxygen so as to prevent rusting. EPS-processed steel is inherently rust-inhibitive and, therefore, needs no oil or other coating to prevent rusting. Many "downstream" processes and steel fabrication processes must have the steel's oil coating (or other surface contaminants) removed as a precursor step of the process. Use of EPS-treated steel in these processes precludes the need for any such "oil-stripping" precursor step, thereby simplifying the process. | 1 | Applied and Interdisciplinary Chemistry |
Various pharmaceutical and academic groups have conducted the synthesis of nonsteroidal compounds that inhibit human 5α-reductases due to the unwanted hormonal side effects of steroidal compounds. Nonsteroidal inhibitors can be categorized due to their structure. Many have been obtained from azasteroid inhibitors by taking away one or more rings from the steroid structure.
Four main categories of nonsteroidal 5-ARIs have been described:
* Benzo(c)quinolizinones
* Benzo(f)quinolonone
* Piperidones
* Carboxylic acids
Nonsteroidal inhibitors are thought to act as competitive inhibitors on the 5α-reductase isozymes, except for epristeride analogues (carboxylic acids), which are noncompetitive inhibitors.
Bexlosteride falls into the category of benzo(f)quinolonones, and is probably the derivative that has come closest to being marketed. It functions as a 5-ARI1 inhibitor which inhibits testosterone stimulated LNCaP cell growth but without testosterone the compound shows no effect and was therefore never marketed. | 1 | Applied and Interdisciplinary Chemistry |
Electroporation is a method that uses short pulses of high voltage to carry DNA across the cell membrane. This shock is thought to cause temporary formation of pores in the cell membrane, allowing DNA molecules to pass through. Electroporation is generally efficient and works across a broad range of cell types. However, a high rate of cell death following electroporation has limited its use, including clinical applications.
More recently a newer method of electroporation, termed electron-avalanche transfection, has been used in gene therapy experiments. By using a high-voltage plasma discharge, DNA was efficiently delivered following very short (microsecond) pulses. Compared to electroporation, the technique resulted in greatly increased efficiency and less cellular damage. | 1 | Applied and Interdisciplinary Chemistry |
*For the Canadian legal classification, see [https://laws-lois.justice.gc.ca/eng/acts/C-38.8/index.html Controlled Drugs and Substances Act]
* For the UK legal classification, see Drugs controlled by the UK Misuse of Drugs Act
* For the US legal classification, see
* Pregnancy category is defined using a variety of systems by different jurisdictions | 1 | Applied and Interdisciplinary Chemistry |
The Gauckler–Manning coefficient, often denoted as , is an empirically derived coefficient, which is dependent on many factors, including surface roughness and sinuosity. When field inspection is not possible, the best method to determine is to use photographs of river channels where has been determined using Gauckler–Manning's formula.
The friction coefficients across weirs and orifices are less subjective than along a natural (earthen, stone or vegetated) channel reach. Cross sectional area, as well as , will likely vary along a natural channel. Accordingly, more error is expected in estimating the average velocity by assuming a Manning's , than by direct sampling (i.e., with a current flowmeter), or measuring it across weirs, flumes or orifices.
In natural streams, values vary greatly along its reach, and will even vary in a given reach of channel with different stages of flow. Most research shows that will decrease with stage, at least up to bank-full. Overbank values for a given reach will vary greatly depending on the time of year and the velocity of flow. Summer vegetation will typically have a significantly higher value due to leaves and seasonal vegetation. Research has shown, however, that values are lower for individual shrubs with leaves than for the shrubs without leaves.
This is due to the ability of the plant's leaves to streamline and flex as the flow passes them thus lowering the resistance to flow. High velocity flows will cause some vegetation (such as grasses and forbs) to lay flat, where a lower velocity of flow through the same vegetation will not.
In open channels, the Darcy–Weisbach equation is valid using the hydraulic diameter as equivalent pipe diameter.
It is the only best and sound method to estimate the energy loss in human made open channels. For various reasons (mainly historical reasons), empirical resistance coefficients (e.g. Chézy, Gauckler–Manning–Strickler) were and are still used. The Chézy coefficient was introduced in 1768 while the Gauckler–Manning coefficient was first developed in 1865, well before the classical pipe flow resistance experiments in the 1920–1930s. Historically both the Chézy and the Gauckler–Manning coefficients were expected to be constant and functions of the roughness only. But it is now well recognised that these coefficients are only constant for a range of flow rates. Most friction coefficients (except perhaps the Darcy–Weisbach friction factor) are estimated 100% empirically and they apply only to fully rough turbulent water flows under steady flow conditions.
One of the most important applications of the Manning equation is its use in sewer design. Sewers are often constructed as circular pipes. It has long been accepted that the value of varies with the flow depth in partially filled circular pipes. A complete set of explicit equations that can be used to calculate the depth of flow and other unknown variables when applying the Manning equation to circular pipes is available. These equations account for the variation of with the depth of flow in accordance with the curves presented by Camp. | 1 | Applied and Interdisciplinary Chemistry |
Agricultural practices such as allowing livestock to graze near water bodies, spreading manure as fertilizer on fields during wet periods, using sewage sludge biosolids and allowing livestock watering in streams can all contribute to fecal coliform contamination. | 0 | Theoretical and Fundamental Chemistry |
The diamond cubic crystal structure occurs for example diamond (carbon), tin, and most semiconductors. There are 8 atoms in the cubic unit cell. We can consider the structure as a simple cubic with a basis of 8 atoms, at positions
But comparing this to the FCC above, we see that it is simpler to describe the structure as FCC with a basis of two atoms at (0, 0, 0) and (1/4, 1/4, 1/4). For this basis, Equation () becomes:
And then the structure factor for the diamond cubic structure is the product of this and the structure factor for FCC above, (only including the atomic form factor once)
with the result
* If h, k, ℓ are of mixed parity (odd and even values combined) the first (FCC) term is zero, so
* If h, k, ℓ are all even or all odd then the first (FCC) term is 4
** if h+k+ℓ is odd then
** if h+k+ℓ is even and exactly divisible by 4 () then
** if h+k+ℓ is even but not exactly divisible by 4 () the second term is zero and
These points are encapsulated by the following equations:
where is an integer. | 0 | Theoretical and Fundamental Chemistry |
The right-end hairpin of MVM contains 248 nucleotides organized into a cruciform shape. This region is almost perfectly basepaired, with just three unpaired bases at the axis and a mismatched region positioned 20 nucleotides from the axis. A three nucleotide insertion, AGA or TCT, on one strand separates opposing pairs of NS1 binding sites, creating a 36 basepair-length palindrome that can assume an alternate cruciform configuration. This configuration is expected to destabilize the duplex, which facilitates its ability to function as a hinge. The mismatch of the unpaired bases, rather than the three-nucleotide sequence itself, may help to promote instability of duplex DNA.
Fully-duplex linear forms of the right-end hairpin sequence also function as NS1-dependent origins. For many parvoviral telomeres, however, only an initiator binding site next to the nick site is required for the origin function so that the minimal sequences required for nicking are less than 40 basepairs in length. For MVM, the minimal right-end origin is around 125 basepairs in length and includes most of the hairpin sequence because at least three recognition elements are involved: the nick site 5′-CTWWTCA-3′ (element 1), positioned seven nucleotides upstream from a duplex NS1-binding site (element 2) that is oriented to have the attached NS1 complex extending over the nick site, and a second NS1-binding site (element 3), which is adjacent to the hairpin axis.
The second binding site is over 100 basepairs away from the nick site but is required for NS1-mediated cleavage. In vivo, there is slight variation in the position of the nick, plus or minus one nucleotide, with one position preferred. During nicking, this site is likely exposed as a single strand and is potentially stabilized as a minimal stem-loop by the tetranucleotide inverted repeats to the sides of the site. Optimal forms of the NS1-binding site contain at least three tandem copies of the 5′-ACCA-3′ sequence. Modest alterations to these motifs only have a small effect on affinity, which suggests that each tetranucleotide motif is recognized by different molecules in the NS1 complex. The NS1-binding site that positions NS1 over the nick site in the right-end origin is a high affinity site.
With ATP, NS1 binds asymmetrically over the aforementioned sequence, protecting a region 41 basepairs in length from digestion. This footprint extends just five nucleotides beyond the 3′-end of the ACCA repeat but 22 nucleotides beyond the 5′-end so that the footprint ends 15 nucleotides beyond the nick site, placing NS1 in position to nick the origin. Nicking only occurs if the second, distant NS1-binding site is also present in the origin and the entire complex is activated by addition of HMG1.
In the absence of NS1, HMG1 binds the hairpin sequence independently, causing it to bend, without protecting any region from digestion. HMG1 can also directly bind to NS1 and mediates interactions between NS1 molecules bound to their recognition elements in the origin, so it is essential for formation of the cleavage complex. The ability of the axis region to reconfigure into a cruciform does not appear to be important in this process. Cleavage is dependent on the correct spacing of the elements of the origin, so additions and deletions can be lethal, whereas substitutions can be tolerated. Addition of HMG1 appears to only slightly adjust the sequences protected by NS1, but the conformation of the intervening DNA changes, folding into a double helical loop that extends about 30 basepairs through a guanine-rich element in the hairpin stem. Between this element and the nick site there are five thymidine residues included in the loop, and the site has a region to its side containing many alternating adenine and thymine residues, which likely increases flexibility. The creation of the loop likely allows the terminus to assume a specific 3-dimensional structure required to activate the nickase since origins that fail to reconfigure into a double-helical loop once HMG1 is added are not nicked. | 1 | Applied and Interdisciplinary Chemistry |
Finding a suitable nanoscale motor capable of autonomous, unidirectional, linear motion is considered important to the development of DNA nanotechnology. The walkers have been shown to be capable of autonomous motion over linear, 2-dimensional and 3-dimensional DNA tracks through a large number of schemes. In July 2005, Bath et al. showed that another way to control DNA walker motion is to use restriction enzymes to strategically cleave the track, causing the forward motion of the walkers. In 2010, two different sets of researchers exhibited the walkers more complex abilities to selectively pick up and drop off molecular cargo and to perform DNA-templated synthesis as the walker moves along the track. In late 2015, Yehl et al. showed that three orders of magnitude higher than the speeds of motion seen previously were possible when using DNA-coated spherical particles that would "roll" on a surface modified with RNA complementary to the nanoparticles DNA. RNase H was used to hydrolyse the RNA, releasing the bound DNA and allowing the DNA to hybridize to RNA further downstream. In 2018, Valero et al. described a DNA walker based on two interlocked, catenated circular double-stranded DNAs (dsDNAs) and an engineered T7 RNA polymerase (T7RNAP) firmly attached to one of the DNA circles. This stator-ring unidirectionally rotated the interlocked rotor-ring by rolling circle transcription (RCT), driven by nucleotide triphosphate (NTP) hydrolysis, thereby constituting a catenated DNA wheel motor. The wheel motor produces long, repetitive RNA transcripts that remain attached to the DNA-catenane and are used to guide its directional walking along predefined ssDNA tracks arranged on a DNA nanotube. | 0 | Theoretical and Fundamental Chemistry |
The dyes are immobilized on the column matrix effectively, since usually the dyes link to a monochlorotriazine or dichlorotriazine ring (triazine dye). This type of dyes works especially well on a support matrix with hydroxyl group. The commonly used supporting matrix would be cross-linked agarose (sepharose), sephadex, polyacrylamide, and silica.
An example for triazine linkage immobilization is Blue Sepharose, resulting from Cibacron blue FG3-A with monochlorotriazine covalently coupled with OH group of sepharose. This reaction form an ether linkage and also hydrogen chloride.
CHClNOS + CHO → CHNOS + HCl
Cibacron Blue FG3-A + Sepharose → Blue Sepharose + HCl | 0 | Theoretical and Fundamental Chemistry |
The Student and Young Investigator Section of TERMIS (TERMIS-SYIS) brings together undergraduate and graduate students, post-doctoral researchers and young investigators in industry and academia related to tissue engineering and regenerative medicine. It follows the organizational and working pattern of TERMIS. | 1 | Applied and Interdisciplinary Chemistry |
It is conjectured that crystal nets may minimize entropy in the following sense. Suppose one is given an ensemble of uniformly discrete Euclidean graphs that fill space, with vertices representing atoms or molecular building blocks and with edges representing bonds or ligands, extending through all space to represent a solid. For some restrictions, there may be a unique Euclidean graph that minimizes a reasonably defined energy function, and the conjecture is that that Euclidean graph may necessarily be periodic. This question is still open, but some researchers observe crystal nets of high symmetry tending to predominate observed Euclidean graphs derived from some classes of materials.
Historically, crystals were developed by experimentation, currently formalized as combinatorial chemistry, but one contemporary desideratum is the synthesis of materials designed in advance, and one proposal is to design crystals (the designs being crystal nets, perhaps represented as one unit cell of a crystal net) and then synthesize them from the design. This effort, in what Omar Yaghi described as reticular chemistry is proceeding on several fronts, from the theoretical to synthesizing highly porous crystals.
One of the primary issues in annealing crystals is controlling the constituents, which can be difficult if the constituents are individual atoms, e.g., in zeolites, which are typically porous crystals primarily of silicon and oxygen and occasional impurities. Synthesis of a specific zeolite de novo from a novel crystal net design remains one of the major goals of contemporary research. There are similar efforts in sulfides and phosphates.
Control is more tractable if the constituents are molecular building blocks, i.e., stable molecules that can be readily induced to assemble in accordance with geometric restrictions. Typically, while there may be many species of constituents, there are two main classes: somewhat compact and often polyhedral secondary building units (SBUs), and linking or bridging building units. A popular class of examples are the Metal-Organic Frameworks (MOFs), in which (classically) the secondary building units are metal ions or clusters of ions and the linking building units are organic ligands. These SBUs and ligands are relatively controllable, and some new crystals have been synthesized using designs of novel nets. An organic variant are the Covalent Organic Frameworks (COFs), in which the SBUs might (but not necessarily) be themselves organic. The greater control over the SBUs and ligands can be seen in the fact that while no novel zeolites have been synthesized per design, several MOFs have been synthesized from crystal nets designed for zeolite synthesis, such as Zeolite-like Metal-Organic Frameworks (Z-MOFs) and zeolitic imidazolate framework (ZIFs). | 0 | Theoretical and Fundamental Chemistry |
Arsenic poisoning is caused by incidental ingestion or inhalation of arsenic, typically from drinking contaminated well water, eating food cooked in contaminated water, or being exposed to arsenic-containing pesticides, folk medicines, or industrial chemicals. The World Health Organization considers arsenic levels above 10 parts per billion (10 micrograms per liter) to be unsafe. | 1 | Applied and Interdisciplinary Chemistry |
A group of FeS ferredoxins, originally found in bacteria, has been termed "bacterial-type". Bacterial-type ferredoxins may in turn be subdivided into further groups, based on their sequence properties. Most contain at least one conserved domain, including four cysteine residues that bind to a [FeS] cluster. In Pyrococcus furiosus FeS ferredoxin, one of the conserved Cys residues is substituted with aspartic acid.
During the evolution of bacterial-type ferredoxins, intrasequence gene duplication, transposition and fusion events occurred, resulting in the appearance of proteins with multiple iron–sulfur centers. In some bacterial ferredoxins, one of the duplicated domains has lost one or more of the four conserved Cys residues. These domains have either lost their iron–sulfur binding property or bind to a [FeS] cluster instead of a [FeS] cluster and dicluster-type.
3-D structures are known for a number of monocluster and dicluster bacterial-type ferredoxins. The fold belongs to the α+β class, with 2-7 α-helices and four β-strands forming a barrel-like structure, and an extruded loop containing three "proximal" Cys ligands of the iron–sulfur cluster. | 0 | Theoretical and Fundamental Chemistry |
Even when working with ordinary eukaryotic sequences such as the Yeast genome, it is often desired to be able to use alternative translation tables—namely for translation of the mitochondrial genes. Currently the following translation tables are defined by the NCBI Taxonomy Group for the translation of the sequences in GenBank:
# The standard code
# The vertebrate mitochondrial code
# The yeast mitochondrial code
# The mold, protozoan, and coelenterate mitochondrial code and the mycoplasma/spiroplasma code
# The invertebrate mitochondrial code
# The ciliate, dasycladacean and hexamita nuclear code
# The kinetoplast code
# <li value="9"> The echinoderm and flatworm mitochondrial code
# The euplotid nuclear code
# The bacterial, archaeal and plant plastid code
# The alternative yeast nuclear code
# The ascidian mitochondrial code
# The alternative flatworm mitochondrial code
# The Blepharisma nuclear code
# The chlorophycean mitochondrial code
# <li value="21"> The trematode mitochondrial code
# The Scenedesmus obliquus mitochondrial code
# The Thraustochytrium mitochondrial code
# The Pterobranchia mitochondrial code
# The candidate division SR1 and gracilibacteria code
# The Pachysolen tannophilus nuclear code
# The karyorelict nuclear code
# The Condylostoma nuclear code
# The Mesodinium nuclear code
# The peritrich nuclear code
# The Blastocrithidia nuclear code
# <li value="33"> The Cephalodiscidae mitochondrial code | 1 | Applied and Interdisciplinary Chemistry |
Eurodoctorate is associated with the Chemistry Quality Eurolabels. As of 8 April 2013, 1 Eurodoctorate quality label was awarded. The label is intended for third cycle qualifications (i.e. doctoral degrees).
The Tuning Chemistry Subject Area Group (Tuning SAG) discussed with a working party of ECTN (European Chemistry Thematic Network Association) in a meeting held in February 2006 in Helsinki, Finland, taking into account the declarations of the Bergen Communiqué 2005. The EHEA Overarching Framework, which was approved by the Ministers of Education of European Union member states in Bergen uses the Dublin descriptors and Tuning SAG decided to use the Dublin descriptors to form a new set of descriptors, the Budapest descriptors for third cycle qualifications.
The Chemistry Eurodoctorate Framework version 1 was published in November 2006. | 1 | Applied and Interdisciplinary Chemistry |
The issues dealing with recovery of the often expensive catalyst after product formation poses a serious drawback for large-scale applications of homogeneous catalysis. Structures known as metallodendrimers combine the advantages of homogeneous and heterogeneous catalysts, as they are soluble and well defined on the molecular level, and yet they can be recovered by precipitation, ultrafiltration, or ultracentrifugation. Some recent examples can be found about the use of dendritic palladium complex catalysts for the copper-free Sonogashira reaction. Thus, several generations of bidentate phosphine palladium(II) polyamino dendritic catalysts have been used solubilized in triethylamine for the coupling of aryl iodides and bromides at 25-120 °C, and of aryl chlorides, but in very low yields.
The dendrimeric catalysts could usually be recovered by simple precipitation and filtration and reused up to five times, with diminished activity produced by dendrimer decomposition and not by palladium leaching being observed. These dendrimeric catalysts showed a negative dendritic effect; that is, the catalyst efficiency decreases as the dendrimer generation increases. A recyclable polymeric phosphine ligand is obtained from ring-opening metathesis polymerization of a norbornene derivative, and has been used in the copper co-catalyzed Sonogashira reaction of methyl p-iodobenzoate and phenylacetylene using as a palladium source. Despite recovery by filtration, polymer catalytic activity decreased by approximately 4-8% in each recycle experiment. | 0 | Theoretical and Fundamental Chemistry |
Once the oligonucleotide library has been incubated with target for sufficient time, unbound oligonucleotides are washed away from immobilized target, often using the incubation buffer so that specifically bound oligonucleotides are retained. With unbound sequences washed away, the specifically bound sequences are then eluted by creating denaturing conditions that promote oligonucleotide unfolding or loss of binding conformation including flowing in deionized water, using denaturing solutions containing urea and EDTA, or by applying high heat and physical force. Upon elution of bound sequences, the retained oligonucleotides are reverse-transcribed to DNA in the case of RNA or modified base selections, or simply collected for amplification in the case of DNA SELEX. These DNA templates from eluted sequences are then amplified via PCR and converted to single stranded DNA, RNA, or modified base oligonucleotides, which are used as the initial input for the next round of selection. | 1 | Applied and Interdisciplinary Chemistry |
fab immunoglobulin - facilitated diffusion - factor VIII - FADH - FADH2 - Fat - Fatty acid - fc immunoglobulin - fc receptor - feedback inhibition - fermentation - fetal protein - fibroblast growth factor - fibroblast growth factor receptor - fibronectin - Fick's law of diffusion - Filtration - fitness (biology) - fitness landscape - flagellum - flavin adenine dinucleotide - flavine - flavoprotein - fluid mosaic model - fms gene - Formaldehyde - fos gene - free energy - freezing point - FSH receptor - functional group - fungal protein - fungi - fusion oncogene protein | 1 | Applied and Interdisciplinary Chemistry |
Among the most fundamental characteristics of a protein are the N- and C-termini defining the start and end of the polypeptide chain. While genetically encoded, protein termini isoforms are also often generated during translation, following which, termini are highly dynamic, being frequently trimmed at their ends by a large array of exopeptidases. Neo-termini can also be generated by endopeptidases after precise and limited proteolysis, termed processing. Necessary for the maturation of many proteins, processing can also occur afterwards, often resulting in dramatic functional consequences. Aberrant proteolysis can cause wide range of diseases like arthritis or cancer. Hence, proteolytic generation of pleiotrophic stable forms of proteins, the universal susceptibility of proteins to proteolysis, and its irreversibility, distinguishes proteolysis from many highly studied posttranslational modifications. Proteases are tightly interconnected in the protease web and their aberrant activity in disease can lead to diagnostic fragment profiles with characteristic protein termini. Following proteolysis, the newly formed protein termini can be further modified, a process that affects protein function and stability. | 1 | Applied and Interdisciplinary Chemistry |
A possible mechanism for Leber's congenital amaurosis has been proposed as the deficiency of RPE65. Without the RPE65 protein, the RPE is unable to store retinyl esters, and the visual cycle is therefore interrupted. At the beginning stages of the disease, the cone cells are unaffected, as they can rely on the alternate Muller cell visual cycle. However, rods do not have access to this alternative and are rendered inert. LCA therefore manifests as nyctalopia (night blindness). In the later stages of the disease, general retinopathy is observed as the rod cells lose their ability to signal. As a result, the rods continually secrete glutamate, a neurotransmitter, at a rate the Muller cells are unable to absorb. The glutamate levels will build up within the retina, where they will reach neurotoxic levels. The RPE65 deficiency would be genetic in origin, and is only one of many proposed possible pathophysiologies of the disease. However, there is a retinal gene therapy to reintroduce normal RPE65 genes that has been approved by the FDA since 2017. | 1 | Applied and Interdisciplinary Chemistry |
The autocorrelations above assume that the fluctuations are not due to changes in the fluorescent properties of the particles. However, for the majority of (bio)organic fluorophores—e.g. green fluorescent protein, rhodamine, Cy3 and Alexa Fluor dyes—some fraction of illuminated particles are excited to a triplet state (or other non-radiative decaying states) and then do not emit photons for a characteristic relaxation time . Typically is on the order of microseconds, which is usually smaller than the dynamics of interest (e.g. ) but large enough to be measured. A multiplicative term is added to the autocorrelation to account for the triplet state. For normal diffusion:
where is the fraction of particles that have entered the triplet state and is the corresponding triplet state relaxation time. If the dynamics of interest are much slower than the triplet state relaxation, the short time component of the autocorrelation can simply be truncated and the triplet term is unnecessary. | 0 | Theoretical and Fundamental Chemistry |
*Data-retrieval: the HIVE is capable of retrieving data from a variety of sources such as local, cloud-based or network storage, sequencing instruments, and from http, ftp and sftp repositories. Additionally, HIVE implements the sophisticated handshake protocols with existing large scale data platforms such as NIH/NCBI to download large amounts of reference genomic or sequence read data on behalf of users in an easy and accurate manner.
*Data-warehousing: HIVE honeycomb data model was specifically created for adopting complex hierarchy of scientific datatypes, providing a platform for standardization and provenance of data within the framework of object-oriented data models. By using an integrated data-engine, honeycomb, HIVE contributes to the veracity of biomedical computations and helps ensure reproducibility, and harmonization of bio-computational processes.
*Security: HIVE-honeycomb employs a hierarchical security control system, allowing the determination of access privileges in an acutely granular manner without overwhelming the security subsystem with a multiplicity of rules. It provides on the fly encryption/decryption of PII and is compliant with the highest security protocols as requested for systems authorized to operate in regulatory FISMA moderate environments.
*Integration: HIVE provides unified Application Program Interface (API) to search, edit, view, secure, share and manipulate data and computations of all types. As an Integrator platform HIVE provides developers means to develop (C/C++, Python, Perl, JavaScript, R) and integrate existing almost any open source or commercial tools using generic adaptation framework to integrate command line tools. Additionally session controlled web-API provides means to drive HIVE to perform data quality control and complex computations on behalf of remote users. Currently there are tens of big data analytics tools in production HIVE and dozens more being developed; these include but are not limited to DNA-, RNA-, Transposon-, Chip-, Immune-sequencing), de novo assembly, population genomics metagenomic sequencing, differential profiling, statistical, classification and clusterization utilities to study bacteria, viruses, human germline and somatic profiles, quasispecies, infections, pathogens.
*Computations: Unlike many virtual computing environments, HIVE virtualizes services, not processes: it provides computations as a service by introducing agnostic abstraction layer between hardware, software and the computational tasks requested by users. The novel paradigm of relocating computations closer to the data, instead of moving data to computing cores has proven to be the key for optimal flow of tasks and data through network infrastructure.
*Visualization: HIVE provides number of scientific visualization components using technologies as HTML5, SVG, D3JS within its Data Driven Document context. The native data and metadata and computational results provided in JSON, CSV-based communication protocols, which are used to generate interactive, user driven, customizable tools allow bioinformaticians to manipulate terabytes of extra-large data using only an Internet browser. | 1 | Applied and Interdisciplinary Chemistry |
The influx of micrometeoroids also contributes to the composition of regolith (planetary/lunar soil) on other bodies in the Solar System. Mars has an estimated annual micrometeoroid influx of between 2,700 and 59,000 t/yr. This contributes to about 1 m of micrometeoritic content to the depth of the Martian regolith every billion years. Measurements from the Viking program indicate that the Martian regolith is composed of 60% basaltic rock and 40% rock of meteoritic origin. The lower-density Martian atmosphere allows much larger particles than on Earth to survive the passage through to the surface, largely unaltered until impact. While on Earth particles that survive entry typically have undergone significant transformation, a significant fraction of particles entering the Martian atmosphere throughout the 60 to 1200-μm diameter range probably survive unmelted. | 0 | Theoretical and Fundamental Chemistry |
AFM-IR enables nanoscale infrared spectroscopy, i.e. the ability to obtain infrared absorption spectra from nanoscale regions of a sample.
Chemical compositional mapping AFM-IR can also be used to perform chemical imaging or compositional mapping with spatial resolution down to ~10-20 nm, limited only by the radius of the AFM tip. In this case, the tuneable infrared source emits a single wavelength, corresponding to a specific molecular resonance, i.e. a specific infrared absorption band. By mapping the AFM cantilever oscillation amplitude as a function of position, it is possible to map out the distribution of specific chemical components. Compositional maps can be made at different absorption bands to reveal the distribution of difference chemical species. | 0 | Theoretical and Fundamental Chemistry |
The equation of state given here (PV = nRT) applies only to an ideal gas, or as an approximation to a real gas that behaves sufficiently like an ideal gas. There are in fact many different forms of the equation of state. Since the ideal gas law neglects both molecular size and intermolecular attractions, it is most accurate for monatomic gases at high temperatures and low pressures. The neglect of molecular size becomes less important for lower densities, i.e. for larger volumes at lower pressures, because the average distance between adjacent molecules becomes much larger than the molecular size. The relative importance of intermolecular attractions diminishes with increasing thermal kinetic energy, i.e., with increasing temperatures. More detailed equations of state, such as the van der Waals equation, account for deviations from ideality caused by molecular size and intermolecular forces. | 0 | Theoretical and Fundamental Chemistry |
Where land is in short supply sewage may be treated by injection of oxygen into a pressured return sludge stream which is injected into the base of a deep columnar tank buried in the ground. Such shafts may be up to deep and are filled with sewage liquor. As the sewage rises the oxygen forced into solution by the pressure at the base of the shaft breaks out as molecular oxygen providing a highly efficient source of oxygen for the activated sludge biota. The rising oxygen and injected return sludge provide the physical mechanism for mixing of the sewage and sludge. Mixed sludge and sewage is decanted at the surface and separated into supernatant and sludge components. The efficiency of deep shaft treatment can be high.
Surface aerators are commonly quoted as having an aeration efficiency of 0.5–1.5 kg O/kWh (1.1–3.3 lb O/kWh), diffused aeration as 1.5–2.5 kg O/kWh (3.3–5.5 lb O/kWh). Deep Shaft claims 5–8 kg O/kWh (11–18 lb O/kWh).
However, the costs of construction are high. Deep Shaft has seen the greatest uptake in Japan, because of the land area issues. Deep Shaft was developed by ICI, as a spin-off from their Pruteen process. In the UK it is found at three sites: Tilbury, Anglian water, treating a wastewater with a high industrial contribution; Southport, United Utilities, because of land space issues; and Billingham, ICI, again treating industrial effluent, and built (after the Tilbury shafts) by ICI to help the agent sell more.
DeepShaft is a patented, licensed, process. The licensee has changed several times and currently (2015) Noram Engineering sells it. | 1 | Applied and Interdisciplinary Chemistry |
The electrophoretic SCODA force is gentle enough to maintain the integrity of high molecular weight DNA as it is concentrated towards the center of the SCODA gel. Depending on the length of the DNA in the sample different protocols can be used to concentrate DNA over 1 Mb in length. | 1 | Applied and Interdisciplinary Chemistry |
Chemical libraries are usually designed by chemists and chemoinformatics scientists and synthesized by organic chemistry and medicinal chemistry. The method of chemical library generation usually depends on the project and there are many factors to consider when using rational methods to select screening compounds. Typically, a range of chemicals is screened against a particular drug target or disease model, and the preliminary "hits", or chemicals that show the desired activity, are re-screened to verify their activity. Once they are qualified as a "hit" by their repeatability and activity, these particular chemicals are registered and analysed. Chemoproteomics is a field of study that incorporates the use of chemical libraries to identify protein targets. Commonalities among the different chemical groups are studied as they are often reflective of a particular chemical subspace. Additional chemistry work may be needed to further optimize the chemical library in the active portion of the subspace. When it is needed, more synthesis is completed to extend out the chemical library in that particular subspace by generating more compounds that are very similar to the original hits. This new selection of compounds within this narrow range are further screened and then taken on to more sophisticated models for further validation in the Drug Discovery Hit to Lead process. | 1 | Applied and Interdisciplinary Chemistry |
A PLIF setup consists of a source of light (usually a laser), an arrangement of lenses to form a sheet, fluorescent medium, collection optics and a detector. The light from the source, illuminates the medium, which then fluoresces. This signal is captured by the detector and can be related to the various properties of the medium.
The typical lasers used as light sources are pulsed, which provide a higher peak power than the continuous-wave lasers. Also the short pulse time is useful for good temporal resolution. Some of the widely used laser sources are Nd:YAG laser, dye lasers, excimer lasers, and ion lasers. The light from the laser (usually a beam) is passed through a set of lenses and/or mirrors to form a sheet, which is then used to illuminate the medium. This medium is either made up of fluorescent material or can be seeded with a fluorescent substance. The signal is usually captured by a CCD or CMOS camera (sometimes intensified cameras are also used). Timing electronics are often used to synchronize pulsed light sources with intensified cameras. | 1 | Applied and Interdisciplinary Chemistry |
Agarose gel is a three-dimensional matrix formed of helical agarose molecules in supercoiled bundles that are aggregated into three-dimensional structures with channels and pores through which biomolecules can pass. The 3-D structure is held together with hydrogen bonds and can therefore be disrupted by heating back to a liquid state. The melting temperature is different from the gelling temperature, depending on the sources, agarose gel has a gelling temperature of 35–42 °C and a melting temperature of 85–95 °C. Low-melting and low-gelling agaroses made through chemical modifications are also available.
Agarose gel has large pore size and good gel strength, making it suitable as an anticonvection medium for the electrophoresis of DNA and large protein molecules. The pore size of a 1% gel has been estimated from 100 nm to 200–500 nm, and its gel strength allows gels as dilute as 0.15% to form a slab for gel electrophoresis. Low-concentration gels (0.1–0.2%) however are fragile and therefore hard to handle. Agarose gel has lower resolving power than polyacrylamide gel for DNA but has a greater range of separation, and is therefore used for DNA fragments of usually 50–20,000 bp in size. The limit of resolution for standard agarose gel electrophoresis is around 750 kb, but resolution of over 6 Mb is possible with pulsed field gel electrophoresis (PFGE). It can also be used to separate large proteins, and it is the preferred matrix for the gel electrophoresis of particles with effective radii larger than 5–10 nm. A 0.9% agarose gel has pores large enough for the entry of bacteriophage T4.
The agarose polymer contains charged groups, in particular pyruvate and sulphate. These negatively charged groups create a flow of water in the opposite direction to the movement of DNA in a process called electroendosmosis (EEO), and can therefore retard the movement of DNA and cause blurring of bands. Higher concentration gels would have higher electroendosmotic flow. Low EEO agarose is therefore generally preferred for use in agarose gel electrophoresis of nucleic acids, but high EEO agarose may be used for other purposes. The lower sulphate content of low EEO agarose, particularly low-melting point (LMP) agarose, is also beneficial in cases where the DNA extracted from gel is to be used for further manipulation as the presence of contaminating sulphates may affect some subsequent procedures, such as ligation and PCR. Zero EEO agaroses however are undesirable for some applications as they may be made by adding positively charged groups and such groups can affect subsequent enzyme reactions. Electroendosmosis is a reason agarose is used in preference to agar as the agaropectin component in agar contains a significant amount of negatively charged sulphate and carboxyl groups. The removal of agaropectin in agarose substantially reduces the EEO, as well as reducing the non-specific adsorption of biomolecules to the gel matrix. However, for some applications such as the electrophoresis of serum proteins, a high EEO may be desirable, and agaropectin may be added in the gel used. | 1 | Applied and Interdisciplinary Chemistry |
Polyimide foam is a foam originally designed for NASA by Inspec Foams Inc. under the brand name Solimide. Its primary purposes are as an insulator (such as for rocket fuels) and acoustic damper. NASA engineered the product to have relatively low outgassing (a problem in vacuum and aboard spacecraft), desirable thermal and acoustic performance, as well as uniformity during distribution and application. Typical uses of the foam include ducting, duct/piping insulation, structural components, and strengthening of hollow components while remaining lightweight. In addition to thermal and acoustic properties, polyimide foam is fire resistant, lightweight and non-toxic. | 0 | Theoretical and Fundamental Chemistry |
The simplest method to measure the electrical resistance of a sample of some material is to place it in an electrical circuit in series with a current source I and measure the resulting voltage V across the sample. The resistance of the sample is given by Ohms law as R = V / I'. If the voltage is zero, this means that the resistance is zero.
Superconductors are also able to maintain a current with no applied voltage whatsoever, a property exploited in superconducting electromagnets such as those found in MRI machines. Experiments have demonstrated that currents in superconducting coils can persist for years without any measurable degradation. Experimental evidence points to a lifetime of at least 100,000 years. Theoretical estimates for the lifetime of a persistent current can exceed the estimated lifetime of the universe, depending on the wire geometry and the temperature. In practice, currents injected in superconducting coils have persisted for more than 27 years (as of August 2022) in superconducting [http://www.astro.oma.be/en/world-record-in-the-underground-laboratory-of-membach/ gravimeters]. In such instruments, the measurement is based on the monitoring of the levitation of a superconducting niobium sphere with a mass of 4 grams.
In a normal conductor, an electric current may be visualized as a fluid of electrons moving across a heavy ionic lattice. The electrons are constantly colliding with the ions in the lattice, and during each collision some of the energy carried by the current is absorbed by the lattice and converted into heat, which is essentially the vibrational kinetic energy of the lattice ions. As a result, the energy carried by the current is constantly being dissipated. This is the phenomenon of electrical resistance and Joule heating.
The situation is different in a superconductor. In a conventional superconductor, the electronic fluid cannot be resolved into individual electrons. Instead, it consists of bound pairs of electrons known as Cooper pairs. This pairing is caused by an attractive force between electrons from the exchange of phonons. This pairing is very weak, and small thermal vibrations can fracture the bond. Due to quantum mechanics, the energy spectrum of this Cooper pair fluid possesses an energy gap, meaning there is a minimum amount of energy ΔE that must be supplied in order to excite the fluid. Therefore, if ΔE is larger than the thermal energy of the lattice, given by kT, where k is the Boltzmann constant and T is the temperature, the fluid will not be scattered by the lattice. The Cooper pair fluid is thus a superfluid, meaning it can flow without energy dissipation.
In the class of superconductors known as type II superconductors, including all known high-temperature superconductors, an extremely low but non-zero resistivity appears at temperatures not too far below the nominal superconducting transition when an electric current is applied in conjunction with a strong magnetic field, which may be caused by the electric current. This is due to the motion of magnetic vortices in the electronic superfluid, which dissipates some of the energy carried by the current. If the current is sufficiently small, the vortices are stationary, and the resistivity vanishes. The resistance due to this effect is minuscule compared with that of non-superconducting materials, but must be taken into account in sensitive experiments. However, as the temperature decreases far enough below the nominal superconducting transition, these vortices can become frozen into a disordered but stationary phase known as a "vortex glass". Below this vortex glass transition temperature, the resistance of the material becomes truly zero. | 0 | Theoretical and Fundamental Chemistry |
Tinning is the process of thinly coating sheets of wrought iron or steel with tin, and the resulting product is known as tinplate. The term is also widely used for the different process of coating a metal with solder before soldering.
It is most often used to prevent rust, but is also commonly applied to the ends of stranded wire used as electrical conductors to prevent oxidation (which increases electrical resistance), and to keep them from fraying or unraveling when used in various wire connectors like twist-ons, binding posts, or terminal blocks, where stray strands can cause a short circuit.
While once more widely used, the primary use of tinplate now is the manufacture of tin cans. Formerly, tinplate was used for cheap pots, pans, and other holloware. This kind of holloware was also known as tinware and the people who made it were tinplate workers.
The untinned sheets employed in the manufacture are known as black plates. They are now made of steel, either Bessemer steel or open-hearth. Formerly iron was used, and was of two grades, coke iron and charcoal iron; the latter, being the better, received a heavier coating of tin, and this circumstance is the origin of the terms coke plates and charcoal plates by which the quality of tinplate is still designated, although iron is no longer used. Tinplate was consumed in enormous quantities for the manufacture of the tin cans in which preserved meat, fish, fruit, biscuits, cigarettes, and numerous other products are packed, and also for the household utensils of various kinds made by the tinsmith. | 1 | Applied and Interdisciplinary Chemistry |
*Protection: Cushions the plasma membrane and protects it from chemical injury
*Immunity to infection: Enables the immune system to recognize and selectively attack foreign organisms
*Defense against cancer: Changes in the glycocalyx of cancerous cells enable the immune system to recognize and destroy them.
*Transplant compatibility: Forms the basis for compatibility of blood transfusions, tissue grafts, and organ transplants
*Cell adhesion: Binds cells together so that tissues do not fall apart
*Inflammation regulation: Glycocalyx coating on endothelial walls in blood vessels prevents leukocytes from rolling/binding in healthy states.
*Fertilization: Enables sperm to recognize and bind to eggs
*Embryonic development: Guides embryonic cells to their destinations in the body | 1 | Applied and Interdisciplinary Chemistry |
GABA is an inhibitory neurotransmitter that plays an important role in regulating dopamine and glutamate neurotransmission. It was found that patients with bipolar disorder had lower GABA levels, which results in excitotoxicity and can cause apoptosis (cell loss). Lithium has been shown to increase the level of GABA in plasma and cerebral spinal fluid. Lithium counteracts these degrading processes by decreasing pro-apoptotic proteins and stimulating release of neuroprotective proteins. Lithium's regulation of both excitatory dopaminergic and glutamatergic systems through GABA may play a role in its mood stabilizing effects. | 1 | Applied and Interdisciplinary Chemistry |
The radical-pair mechanism explains how a magnetic field can affect reaction kinetics by affecting electron spin dynamics. Most commonly demonstrated in reactions of organic compounds involving radical intermediates, a magnetic field can speed up a reaction by decreasing the frequency of reverse reactions. | 0 | Theoretical and Fundamental Chemistry |
Genetically Modified Organisms (GMOs) are plants or living things that have been altered at a genomic level by scientists to improve the organisms characteristics. These characteristics include providing new vaccines for humans, increasing nutrients supplies, and creating unique plastics. They may also be able to grow in climates that are typically not suitable for the original organism to grow in. Examples of GMOs include virus resistant tobacco and squash, delayed ripening tomatoes, and herbicide resistant soybeans.
GMO's came with an increased interest in using biotechnology to produce fertilizer and pesticides. Due to an increased market interest in biotechnology in the 1970s, there was more technology and infrastructure developed, a decreased cost, and an advance in research. Since the early 1980s, genetically-modified crops have been incorporated. Increased biotechnological work calls for the union of biology and chemistry to produce improved crops, a main reason behind this being the increasing amount of food needed to feed a growing population.
That being said, concerns with GMOs include potential antibiotic resistance from eating a GMO. There are also concerns about the long term effects on the human body since many GMOs were recently developed.
Much controversy surrounds GMOs. In the United States, all foods containing GMOs must be labeled as such. | 1 | Applied and Interdisciplinary Chemistry |
Ehrlich and Raven's paper was highly influential on a generation of biologists and contributed to the explosion of research on plant-insect interactions and chemical ecology. The theory of escape and radiate coevolution purports to explain why we see such vast biological diversity on earth. After the organism escapes, it then radiates into multiple species, and spreads geographically. Evidence of escape and radiate coevolution can be seen through the starburst effect in plant and herbivore clades. When analyzing clades of predator-prey associations, although it varies, the starburst effect is a good indicator that escape and radiate coevolution may be occurring. Eventually this cycle must come to an end because adaptations that entail costs (such as allocation of resources, or vulnerability to other predators) at some point outweigh their benefits.
Escape and radiate coevolution may support parallel cladogenesis, wherein plant and herbivore phylogenies might match with ancestral insects exploiting ancestral plants. This is significant because it allows researchers to hypothesize about the relationships between ancestral organisms. Unfortunately, there have not yet been any known examples specifically involving escape and radiate coevolution being used for hypothesizing ancestral relationships.
Many times the organism that has "escaped" continuously undergoes selective pressure because the predator it has escaped from evolves to create another adaptation in response, causing the process to continue. These "offensive" traits developed by predators range widely. For example, herbivores can develop an adaptation that allows for improved detoxification which allow to overcome plant defenses, thus causing escape and radiate coevolution to continue. Often the term "evolutionary arms race" is used to illustrate the idea that continuous evolution is needed to maintain the same relative fitness while the two species are coevolving. This idea also ties in with the Red Queen hypothesis. Counter adaptations among two organisms through escape and radiate coevolution is a major driving force behind diversity.
Escape and radiate coevolution produces much more biological variation than other evolutionary mechanisms. For instance, cospeciation is important for diversity amongst species that share a symbiotic relationship, however this does not create nearly as much diversity in comparison to reciprocal evolutionary change due to natural selection.
Evidence of rapid diversification following a novel adaptation is shown through the evolution of resin and latex canal tubes in 16 different lineages of plants. Plants with resin or latex canals can easily defend themselves against insect herbivores. When lineages of canal bearing plants are compared to the lineages of canal free plants, it is apparent that canal bearing plants are far more diverse, supporting escape and radiate coevolution. | 1 | Applied and Interdisciplinary Chemistry |
Since a variety of systems have been investigated, a study was done to investigate the individual adsorption of a mixed solution. This phenomenon is also called competitive adsorption because solutes tend to compete for the same adsorption sites. In the experiment conducted by Rosene and Manes, the competitive adsorption of glucose, urea, benzoic acid, phthalide, and p-nitrophenol. Using the Polanyi adsorption model, they were able to calculate the relative adsorption of each compound onto the surface of activated carbon. | 0 | Theoretical and Fundamental Chemistry |
The Bodenstein number (abbreviated Bo, named after Max Bodenstein) is a dimensionless parameter in chemical reaction engineering, which describes the ratio of the amount of substance introduced by convection to that introduced by diffusion. Hence, it characterises the backmixing in a system and allows statements whether and how much volume elements or substances within a chemical reactor mix due to the prevalent currents. It is defined as the ratio of the convection current to the dispersion current. The Bodenstein number is an element of the dispersion model of residence times and is therefore also called the dimensionless dispersion coefficient.
Mathematically, two idealized extreme cases exist for the Bodenstein number. These, however, cannot be fully reached in practice:
* corresponds to full backmixing, which is the ideal state to be reached in a continuous stirred-tank reactor.
* corresponds to no backmixing, but a continuous through flow as in an ideal flow channel.
Control of the flow velocity within a reactor allows to adjust the Bodenstein number to a pre-calculated desired value, so that the desired degree of backmixing of the substances in the reactor can be reached. | 1 | Applied and Interdisciplinary Chemistry |
Historically, there has not been any volume use for scrap tires other than burning that has been able to keep up with the volume of waste generated yearly. Tires produce the same energy as petroleum and approximately 25% more energy than coal. Burning tires is lower on the hierarchy of reducing waste than recycling, but it is better than placing the tire waste in a landfill or dump, where there is a possibility for uncontrolled tire fires or the harboring of disease vectors such as mosquitoes.
Tire Derived Fuel is an interim solution to the scrap tire waste problem. Advances in tire recycling technology might one day provide a solution other than burning by reusing tire derived material in high volume applications. | 1 | Applied and Interdisciplinary Chemistry |
In the late 1950s and early 1960s, the French molecular biologists François Jacob and Jacques Monod became the first to explain enzyme induction, in the context of the lac operon of Escherichia coli. In the absence of lactose, the constitutively expressed lac repressor protein binds to the operator region of the DNA and prevents the transcription of the operon genes. When present, lactose binds to the lac repressor, causing it to separate from the DNA and thereby enabling transcription to occur. Monod and Jacob generated this theory following 15 years of work by them and others (including Joshua Lederberg), partially as an explanation for Monod's observation of diauxie. Previously, Monod had hypothesized that enzymes could physically adapt themselves to new substrates; a series of experiments by him, Jacob, and Arthur Pardee eventually demonstrated this to be incorrect and led them to the modern theory, for which he and Jacob shared the 1965 Nobel Prize in Physiology or Medicine (together with André Lwoff).
* Aryl hydrocarbon receptor | 1 | Applied and Interdisciplinary Chemistry |
Liesegang rings () are a phenomenon seen in many, if not most, chemical systems undergoing a precipitation reaction under certain conditions of concentration and in the absence of convection. Rings are formed when weakly soluble salts are produced from reaction of two soluble substances, one of which is dissolved in a gel medium. The phenomenon is most commonly seen as rings in a Petri dish or bands in a test tube; however, more complex patterns have been observed, such as dislocations of the ring structure in a Petri dish, helices, and "Saturn rings" in a test tube. Despite continuous investigation since rediscovery of the rings in 1896, the mechanism for the formation of Liesegang rings is still unclear. | 0 | Theoretical and Fundamental Chemistry |
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