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Polyvinylidene difluoride (PVDF) is a fairly non-reactive, thermoplastic fluoropolymer with excellent chemical and thermal resistance for plastic pipework uses. PVDF resin is produced through polymerization of the vinylidene fluoride monomer. The PVDF resin is then used to make PVDF pipe as well as many other products.
Industries and applications select PVDF pipe due to its inert, durable qualities. PVDF piping is used most in the chemical process industry due to its ability to plumb aggressive, corrosive solutions. PVDF pipe also sees common use in high purity applications, semi-conductor fabrication, electronics / electricity, pharmaceutical developments, and nuclear waste processing.
PVDF piping specifications and performance characteristics approve PVDF pipe up to under pressurized system conditions. The pipe does not support fungus growth according to military test standard method 508, 81-0B. Dissimilar from other common thermoplastic pipes, (uPVC, CPVC, PE, PP), PVDF does not exhibit sensitivity to UV light or ozone oxidative damage, approving it for long term outdoor uses. | 1 | Applied and Interdisciplinary Chemistry |
Originally, the immune stimulation by drugs were exclusively explained by the hapten concept, which was investigated in the early 1930s: In these early studies it was found that drugs were too small to represent an antigen inherently. Only if they or their metabolites are haptens, thereby forming larger and stable drug-protein complexes, were they seen as new antigens. Such a formation of a complete antigen (drug-protein complexes, so-called adducts) were considered a necessary step to stimulate an immune response, since the drug alone remained unnoticed by the immune cells.
One classical clinical model for a hapten reaction is contact dermatitis. This is a skin disease based on a localized immune reaction in the skin to a chemically reactive, topical applied compound, which binds by covalent bonds to a carrier protein; many of the contact sensitizers also have a toxic effect, which may be important for the costimulation of the immune system. Extensive in vitro and in vivo data support the hapten concept in contact dermatitis.
It was tempting to use the hapten model to explain generalized DH as well: The drug class most often involved in generalized DHR are penicillins. When applied to the skin, they elicit contact dermatitis. Penicillins are classical haptens and penicillin modified proteins like albumin have been repeatedly found in patients after therapy. Thus it was assumed that the generalized DHR upon parenteral or oral application after penicillins is also due to the hapten-feature of this drug class.
The “hapten-concept” was soon extended to explain all immune mediated (adverse drug reactions): Only if the drug or a metabolite could act as hapten and bind covalently to proteins, then was the drug considered to be able to elicit immune reactions including generalized exanthema, drug induced hepatitis, DRESS, SJS/TEN etc. Consequently, during preclinical risk assessment of a new drug, the potential drug candidate may be screened carefully for hapten-features, and if the candidate drugs caused some adverse immune mediated reaction, it was linked to their hapten feature or, if the parent compound lacked hapten characteristics, a hapten feature of a drug metabolite as cause for the DHR was postulated. Importantly, the hapten theory as explanation for all generalized immune reactions was often disputed and hard to reconcile with many experimental or clinical findings. | 1 | Applied and Interdisciplinary Chemistry |
For example, consider the same problem from the previous section of a linear chain. The matrix is the unscaled elasticity matrix:
In this specific problem there are 3 species () and 4 reaction steps (), the elasticity matrix is therefore a matrix. However, a number of entries in the matrix will be zero. For example will be zero since has no effect on . The matrix, therefore, will contain the following entries:
The parameter matrix depends on which parameters are considered. In Metabolic control analysis, a common set of parameters are the enzyme activities. For the sake of argument, we can equate the rate constants with the enzyme activity parameters. We also assume that each enzyme, , only can affect its own step and no other. The matrix is the unscaled elasticity matrix with respect to the parameters. Since there are 4 reaction steps and 4 corresponding parameters, the matrix will be a 4 by 4 matrix. Since each parameter only affects one reaction, the matrix will be a diagonal matrix:
Since there are 3 species and 4 reactions, the resulting matrix will be a 3 by 4 matrix
Each expression in the matrix describes how a given parameter influences the steady-state concentration of a given species. Note that this is the unscaled derivative. It is often the case that the derivative is scaled by the parameter and concentration to eliminate units as well as turn the measure into a relative change. | 1 | Applied and Interdisciplinary Chemistry |
The geometry of TAP like all known geometries of tetraarylporphyrins is distorted to take a very characteristic “saddle” shape. | 1 | Applied and Interdisciplinary Chemistry |
There are 2 subgroups of NA inhibitors that have been approved by regulatory authorities in the US and Europe, Zanamivir and Oseltamivir. Both are for the treatment and prevention of influenza. Furthermore, Peramivir and Laninamivir have been approved by regulatory authorities in some parts of Asia. | 1 | Applied and Interdisciplinary Chemistry |
Topologically close pack (TCP) phases, also known as Frank-Kasper (FK) phases, are one of the largest groups of intermetallic compounds, known for their complex crystallographic structure and physical properties. Owing to their combination of periodic and aperiodic structure, some TCP phases belong to the class of quasicrystals. Applications of TCP phases as high-temperature structural and superconducting materials have been highlighted; however, they have not yet been sufficiently investigated for details of their physical properties. Also, their complex and often non-stoichiometric structure makes them good subjects for theoretical calculations. | 1 | Applied and Interdisciplinary Chemistry |
Elastin-like polypeptides (ELPs) are synthetic biopolymers with potential applications in the fields of cancer therapy, tissue scaffolding, metal recovery, and protein purification. For cancer therapy, the addition of functional groups to ELPs can enable them to conjugate with cytotoxic drugs. Also, ELPs may be able to function as polymeric scaffolds, which promote tissue regeneration. This capacity of ELPs has been studied particularly in the context of bone growth. ELPs can also be engineered to recognize specific proteins in solution. The ability of ELPs to undergo morphological changes at certain temperatures enables specific proteins that are bound to the ELPs to be separated out from the rest of the solution via experimental techniques such as centrifugation.
The general structure of polymeric ELPs is (VPGXG), where the monomeric unit is Val-Pro-Gly-X-Gly, and the "X" denotes a variable amino acid that can have consequences on the general properties of the ELP, such as the transition temperature (T). Specifically, the hydrophilicity or hydrophobicity and the presence or absence of a charge on the guest residue play a great role in determining the T Also, the solubilization of the guest residue can effect the T The "n" denotes the number of monomeric units that comprise the polymer. In general, these polymers are linear below the T, but aggregate into spherical clumps above the T. | 0 | Theoretical and Fundamental Chemistry |
A safety concern has been raised on the basis of several studies regarding the effect of toothpaste SDS on aphthous ulcers (more specifically, mouth ulcers or "canker sores"), commonly referred to as canker or white sores. According to the NHS, SLS is a cause for concern for mouth ulcers. As Lippert notes, of 2013, "very few... marketed toothpastes contain a surfactant other than SLS [SDS]," and leading manufacturers continue to formulate their produce with SDS. | 1 | Applied and Interdisciplinary Chemistry |
The ability to fine-tune pi stacking interactions would be useful in numerous synthetic efforts. One example would be to increase the binding affinity of a small-molecule inhibitor to an enzyme pocket containing aromatic residues. The effects of heteroatoms and substituents on pi stacking interactions is difficult to model and a matter of debate. | 0 | Theoretical and Fundamental Chemistry |
The chloralkali process is a large scale application that uses electrocatalysts. This technology supplies most of the chlorine and sodium hydroxide required by many industries. The cathode is a mixed metal oxide clad titanium anode (also called a dimensionally stable anode). | 0 | Theoretical and Fundamental Chemistry |
Flow cups are designed to accurately measure the viscosity of paints, inks, varnishes and similar products. The process of flow through an orifice can often be used as a relative measurement and classification of viscosity. This measured kinematic viscosity is generally expressed in seconds of flow time which can be converted into centistokes (cSt) using a viscosity calculator.
Flow cups are manufactured using high grade aluminium alloy with stainless steel orifices (where indicated), flow cups are available with a range of UKAS / ISO 17025 certified standard oils to confirm the flow cup is measuring within specification. | 1 | Applied and Interdisciplinary Chemistry |
* A birth–death process is a linear one-dimensional Markovian kinetic scheme.
* Michaelis–Menten kinetics are a type of a Markovian kinetic scheme when solved with the steady state assumption for the creation of intermediates in the reaction pathway. | 0 | Theoretical and Fundamental Chemistry |
Distribution law or the Nernst's distribution law gives a generalisation which governs the distribution of a solute between two immiscible solvents. This law was first given by Nernst who studied the distribution of several solutes between different appropriate pairs of solvents.
C/C = K
Where K is called the distribution coefficient or the partition coefficient.
Concentration of X in solvent A/concentration of X in solvent B=Kď
If C denotes the concentration of solute X in solvent A & C denotes the concentration of solute X in solvent B; Nernst's distribution law can be expressed as C/C = K. This law is only valid if the solute is in the same molecular form in both the solvents. Sometimes the solute dissociates or associates in the solvent.
In such cases the law is modified as,
D(Distribution factor)=concentration of solute in all forms in solvent 1/concentration of solute in all forms in solvent 2. | 0 | Theoretical and Fundamental Chemistry |
Unlike ultraviolet–visible spectroscopy which measures absorbance, charge modulation spectroscopy measures the charge introduced optical transmission variation. In other words, it reveals the new features in optical transmission introduced by charges. In this setup, there are mainly four components: lamp, monochromator, photodetector and lock-in amplifier. Lamp and monochromator are used for generating and selecting the wavelength. The selected wavelength passes through the transistor, and the transmitted light is recorded by the Photodiode. When the signal to noise ratio is very low, the signal can be modulated and recovered with a Lock-in amplifier.
In the experiment, a direct current plus an alternating current bias are applied to the organic field-effect transistor. Charge carries accumulate at the interface between the dielectric and the semiconductor (usually a few nanometers). With the appearance of the accumulation charge, the intensity of the transmitted light changes. The variation of the light intensity () is then collected though the photodetector and lock-in amplifier. The charge modulation frequency is given to Lock-in amplifier as the reference. | 0 | Theoretical and Fundamental Chemistry |
Some flying machines have been built which use the Magnus effect to create lift with a rotating cylinder at the front of a wing, allowing flight at lower horizontal speeds.
An early attempt to use the Magnus effect for a heavier-than-air aircraft was made in 1910 by a US member of Congress, Butler Ames of Massachusetts.
A later example was the Plymouth A-A-2004 in the early 1930s, built by three inventors in New York state.
French designer Jean de Chappedelaine developed his Aérogyre at much the same time. A prototype, based on a modified Caudron C.270 Luciole, was flown in 1934 with the wing rotor stationary. It crashed on its next flight, but whether the wing was rotating during that flight is unknown. | 1 | Applied and Interdisciplinary Chemistry |
Undamaged neighboring plants have been shown, in some cases, to respond to GLV signals. Both the plant emitting the GLVs and its neighboring plants can enter a primed state in which plants activate their defenses systems more quickly and in a stronger concentration.
The first study to clearly demonstrate anti-herbivore defense priming by GLVs focused on corn (Zea mays). Neighboring plants responded to the release of GLVs by priming against insect herbivore attack, reacting more rapidly and releasing greater levels of GLVs. Similar results have been shown in tomato plants. Neighboring plants reacted more strongly to GLVs from the plants exposed to the herbivore, by releasing more of the proteins related to the plants' defense mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
In the first part of the test, the patient is given radiolabeled vitamin B to drink or eat. The most commonly used radiolabels are Co and Co. An intramuscular injection of unlabeled vitamin B is given an hour later. This is not enough to replete or saturate body stores of B. The purpose of the single injection is to temporarily saturate B receptors in the liver with enough normal vitamin B to prevent radioactive vitamin B binding in body tissues (especially in the liver), so that if absorbed from the G.I. tract, it will pass into the urine. The patient's urine is then collected over the next 24 hours to assess the absorption.
Normally, the ingested radiolabeled vitamin B will be absorbed into the body. Since the body already has liver receptors for transcobalamin/vitamin B saturated by the injection, much of the ingested vitamin B will be excreted in the urine.
* A normal result shows at least 10% of the radiolabeled vitamin B in the urine over the first 24 hours.
* In patients with pernicious anemia or with deficiency due to impaired absorption, less than 10% of the radiolabeled vitamin B is detected.
The normal test will result in a higher amount of the radiolabeled cobalamin in the urine because it would have been absorbed by the intestinal epithelium, but passed into the urine because all hepatic B12 receptors were occupied. An abnormal result is caused by less of the labeled cobalamin to appear in the urine because it will remain in the intestine and be passed into the feces. | 1 | Applied and Interdisciplinary Chemistry |
DIDs are sensitive to a broad range of components.
In air separation plants, they are used to detect the components ; ; ; ; in argon product in ppm range.
DIDs are non-destructive detectors. They do not destroy or consume the components they detect. Therefore, they can be used before other detectors in multiple-detector configurations.
DIDs are an improvement over helium ionization detectors in that they contain no radioactive source. | 0 | Theoretical and Fundamental Chemistry |
Carboxypeptidase A usually refers to the pancreatic exopeptidase that hydrolyzes peptide bonds of C-terminal residues with aromatic or aliphatic side-chains. Most scientists in the field now refer to this enzyme as CPA1, and to a related pancreatic carboxypeptidase as CPA2. | 1 | Applied and Interdisciplinary Chemistry |
* Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine are widely used antidepressants that specifically block the reuptake of serotonin with less effect on other transmitters.
* Tricyclic antidepressants also block reuptake of biogenic amines from the synapse, but may primarily effect serotonin or norepinephrine or both. They typically take four to six weeks to alleviate any symptoms of depression. They are considered to have immediate and long-term effects.
* Monoamine oxidase inhibitors allow reuptake of biogenic amine neurotransmitters from the synapse, but inhibit an enzyme which normally destroys (metabolizes) some of the transmitters after their reuptake. More of the neurotransmitters (especially serotonin, noradrenaline and dopamine) are available for release into synapses. MAOIs take several weeks to alleviate the symptoms of depression.
Although changes in neurochemistry are found immediately after taking these antidepressants, symptoms may not begin to improve until several weeks after administration. Increased transmitter levels in the synapse alone does not relieve the depression or anxiety. | 1 | Applied and Interdisciplinary Chemistry |
In both the FCC and HCP arrangements each sphere has twelve neighbors. For every sphere there is one gap surrounded by six spheres (octahedral) and two smaller gaps surrounded by four spheres (tetrahedral). The distances to the centers of these gaps from the centers of the surrounding spheres is for the tetrahedral, and for the octahedral, when the sphere radius is 1.
Relative to a reference layer with positioning A, two more positionings B and C are possible. Every sequence of A, B, and C without immediate repetition of the same one is possible and gives an equally dense packing for spheres of a given radius.
The most regular ones are
*FCC = ABC ABC ABC... (every third layer is the same)
*HCP = AB AB AB AB... (every other layer is the same).
There is an uncountably infinite number of disordered arrangements of planes (e.g. ABCACBABABAC...) that are sometimes collectively referred to as "Barlow packings", after crystallographer William Barlow.
In close-packing, the center-to-center spacing of spheres in the xy plane is a simple honeycomb-like tessellation with a pitch (distance between sphere centers) of one sphere diameter. The distance between sphere centers, projected on the z (vertical) axis, is:
where d is the diameter of a sphere; this follows from the tetrahedral arrangement of close-packed spheres.
The coordination number of HCP and FCC is 12 and their atomic packing factors (APFs) are equal to the number mentioned above, 0.74. | 0 | Theoretical and Fundamental Chemistry |
Several factors influence the coordination number of an atom, but the most important of these is its size; larger atoms have larger coordination numbers. The coordination number depends on the surface area of the atom, and so is proportional to r. If V is the charge on the atomic core (which is the same as the valence of the atom when all the electrons in the valence shell are bonding), and N is the corresponding average coordination number, V/N is proportional to the electric field at the surface of the core, represented by S in Eq. 5:
: (Eq. 5)
Not surprisingly, S gives the same ordering of the main group elements as the electronegativity, though it differs in its numerical value from traditional electronegativity scales. Because it is defined in structural terms, S is the preferred measure of electronegativity in the bond valence model, | 0 | Theoretical and Fundamental Chemistry |
The trivial name carbyne is the preferred IUPAC name.
Following the substitutive nomenclature, the molecule is viewed as methane with three hydrogen atoms removed, yielding the systematic name "methylidyne".
Following the additive nomenclature, the molecule is viewed as a hydrogen atom bonded to a carbon atom, yielding the name "hydridocarbon".
By default, these names pay no regard to the excitation state of the molecule. When that attribute is considered, the states with one unpaired electron are named "methylylidene" or "hydridocarbon(•)", whereas the excited states with three unpaired electrons are named "methanetriyl" or "hydridocarbon(3•)". | 0 | Theoretical and Fundamental Chemistry |
As the deep waters sink into the ocean basins, they displace the older deep-water masses, which gradually become less dense due to continued ocean mixing. Thus, some water is rising, in what is known as upwelling. Its speeds are very slow even compared to the movement of the bottom water masses. It is therefore difficult to measure where upwelling occurs using current speeds, given all the other wind-driven processes going on in the surface ocean. Deep waters have their own chemical signature, formed from the breakdown of particulate matter falling into them over the course of their long journey at depth. A number of scientists have tried to use these tracers to infer where the upwelling occurs. Wallace Broecker, using box models, has asserted that the bulk of deep upwelling occurs in the North Pacific, using as evidence the high values of silicon found in these waters. Other investigators have not found such clear evidence.
Computer models of ocean circulation increasingly place most of the deep upwelling in the Southern Ocean, associated with the strong winds in the open latitudes between South America and Antarctica.
Direct estimates of the strength of the thermohaline circulation have also been madeat 26.5°N in the North Atlantic, by the UK-US RAPID programme. It combines direct estimates of ocean transport using current meters and subsea cable measurements with estimates of the geostrophic current from temperature and salinity measurements to provide continuous, full-depth, basin-wide estimates of the meridional overturning circulation. However, it has only been operating since 2004, which is too short when the timescale of the circulation is measured in centuries. | 0 | Theoretical and Fundamental Chemistry |
The principle of this method is based on the nucleic acid-binding properties of silica particles or diatoms in the presence of a chaotropic agent, which follows the chaotropic effect.
Put simply, the chaotropic effect is where a chaotropic anion in an aqueous solution disturbs the structure of water, and weakens the hydrophobic interaction.
According to the chaotropic effect,
in the presence of the chaotropic agent, hydration water of nucleic acids are taken from the phosphodiester bond of the phosphate group of the backbone of a nucleic acid. Thus, the phosphate group becomes "exposed" and hydrophobic interaction between silica and exposed phosphate group are formed. | 1 | Applied and Interdisciplinary Chemistry |
The advantage of using ketenyl anion molecule is to synthesize desired compound selectively without concerning dimerization before synthesizing a target product. In ylide-ketenyl anion, electrophile can be substituted in exchange of metal to functionalize the ketene moiety at high yield. Since the central carbon is negatively charged, this nucleophilicity enable substitution with a series of electrophilic compounds such as triphenylmethyl group. Some ketenyl anion can further react with other compounds to form a new functional group. For example, after electrophilic substitution of ketenyl anion with triphenylmethyl group, the treatment with water results in formation of carboxylic acid at C=O moiety. Reported compounds from Gessner et al. had more than 90% yield isolated as solid.
Not only at the central carbon where a cation can be coordinated, other carbon atom and terminal oxygen atom can also be functionalized upon electrophilic substitution. This reactivity allows activation of chemical bonds such as S-S and C=O bonds and new bonds C-S bond and C=C bond. These products requires CO and substrates of interests, which highlight new synthetic pathways of organic compounds at room temperature instead of extreme conditions such as pyrolysis.
A stabilized ketenyl anion also undergoes dimerization with disubstituted phosphine compound to form a heterocyclic product. In this reaction, an intermediate is proposed to be electrophilic substitution of a disubstituted phosphine compound followed by dimerization.
In different ketenyl anion compound, cleavage of C-H bond, C=N bond, and I bond at room temperature were also reported in phosphinidene-stabilized ketene. For I cleaving reaction, the mechanism is proposed to be cleavage of the bond at central carbon and migration of I to phosphorus atom. | 0 | Theoretical and Fundamental Chemistry |
Nanoparticle drug delivery focuses on maximizing drug efficacy and minimizing cytotoxicity. Fine-tuning nanoparticle properties for effective drug delivery involves addressing the following factors.
The surface-area-to-volume ratio of nanoparticles can be altered to allow for more ligand binding to the surface. Increasing ligand binding efficiency can decrease dosage and minimize nanoparticle toxicity. Minimizing dosage or dosage frequency also lowers the mass of nanoparticle per mass of drug, thus achieving greater efficiency.
Surface functionalization of nanoparticles is another important design aspect and is often accomplished by bioconjugation or passive adsorption of molecules onto the nanoparticle surface. By functionalizing nanoparticle surfaces with ligands that enhance drug binding, suppress immune response, or provide targeting/controlled release capabilities, both a greater efficacy and lower toxicity are achieved. Efficacy is increased as more drug is delivered to the target site, and toxic side effects are lowered by minimizing the total level of drug in the body.
The composition of the nanoparticle can be chosen according to the target environment or desired effect. For example, liposome-based nanoparticles can be biologically degraded after delivery, thus minimizing the risk of accumulation and toxicity after the therapeutic cargo has been released.
Metal nanoparticles, such as gold nanoparticles, have optical qualities(also described in nanomaterials) that allow for less invasive imaging techniques. Furthermore, the photothermal response of nanoparticles to optical stimulation can be directly utilized for tumor therapy. | 0 | Theoretical and Fundamental Chemistry |
Monosaccharides can be linked together by glycosidic bonds, which can be cleaved by hydrolysis. Two, three, several or many monosaccharides thus linked form disaccharides, trisaccharides, oligosaccharides, or polysaccharides, respectively. Enzymes that hydrolyze glycosidic bonds are called "glycoside hydrolases" or "glycosidases".
The best-known disaccharide is sucrose (table sugar). Hydrolysis of sucrose yields glucose and fructose. Invertase is a sucrase used industrially for the hydrolysis of sucrose to so-called invert sugar. Lactase is essential for digestive hydrolysis of lactose in milk; many adult humans do not produce lactase and cannot digest the lactose in milk.
The hydrolysis of polysaccharides to soluble sugars can be recognized as saccharification. Malt made from barley is used as a source of β-amylase to break down starch into the disaccharide maltose, which can be used by yeast to produce beer. Other amylase enzymes may convert starch to glucose or to oligosaccharides. Cellulose is first hydrolyzed to cellobiose by cellulase and then cellobiose is further hydrolyzed to glucose by beta-glucosidase. Ruminants such as cows are able to hydrolyze cellulose into cellobiose and then glucose because of symbiotic bacteria that produce cellulases. | 0 | Theoretical and Fundamental Chemistry |
Claude Auguste Lamy (; 15 June 1820 – 20 March 1878) was a French chemist who discovered the element thallium independently from William Crookes in 1862. | 1 | Applied and Interdisciplinary Chemistry |
It monitors background radiation in the UK. Workers exposed to radiation include workers in dental radiography and nuclear power stations; exposure to radiation for workers in the UK must be ALARP. It offers 3-day training courses around twice a month, at a national level, for workers exposed to radiation.
It produces reports on environmental background radiation in England. It works with the ICRP, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and the International Atomic Energy Agency (IAEA). Inside the UK, it works with the Scottish Environment Protection Agency (SEPA) and the Environment Agency (EA). | 1 | Applied and Interdisciplinary Chemistry |
The exchange current density depends critically on the nature of the electrode, not only its structure, but also physical parameters such as surface roughness. Of course, factors that change the composition of the electrode, including passivating oxides and adsorbed species on the surface, also influence the electron transfer. The nature of the electroactive species (the analyte) in the solution also critically affects the exchange current densities, both the reduced and oxidized form.
Less important but still relevant are the environment of the solution including the solvent, nature of other electrolytes, and temperature. For the concentration dependence of the exchange current density, the following expression is given for a one-electron reaction:
where:
* : the concentration of the oxidized species
*: the concentration of the reduced species
* : a symmetry factor
* : Faraday constant
* : reaction rate constant | 0 | Theoretical and Fundamental Chemistry |
All current methods of covalent organic framework (COF) synthesis use DCvC. Boronic acid dehydration, as demonstrated by Yaghi et al. is the most common type of reaction used. COFs have been used in gas storage, catalysis, . Possible morphologies include infinite covalent 3D frameworks, 2D polymers, or discrete molecular cages. | 0 | Theoretical and Fundamental Chemistry |
Several complexes are known with NS ligands. Like nitrosyls, thionitrosyls exist as both linear and bent geometries. | 0 | Theoretical and Fundamental Chemistry |
The second step of the RIC experimental process is to saturate the neighboring core sample with crude oil and subjected the sample to water imbibition. Applying the slope of the RIC curve , fluid properties of oil/brine system (ρ,μ,γ) and the ∁ value are determined from the neighboring core sample into Eq. 9 to calculate the contact angle, θ. | 1 | Applied and Interdisciplinary Chemistry |
Bowen lived for most of his working life in Park Town and is buried in Wolvercote Cemetery, north of Oxford. Bowen was married to Edith née Moule and they had a son (also a chemist) and a daughter. He died on 19 November 1980 after a short illness. | 0 | Theoretical and Fundamental Chemistry |
In order to force politics to take more responsibility in acting against ecological, economic and social problems related to water, the European Union implemented the Water Framework Directive. For each river basin district member, the states had to develop, implement and monitor measures to reach its prescribed goals. As a tool to accomplish this goal, so-called river basin management plans were required.
The implementation is an individual matter for the member states and must be reported regularly. In Germany, the German Council for Land Stewardship worked on a project financially supported by the North Rhine-Westphalia State Agency for Nature, Environment and Consumer Protection and Lennart-Bernadotte-Stiftung, in order to investigate how, in the sense of a beam effect, water biocoenoses in restricted areas can be developed and decoupled from a complete structural improvement in the area concerned. The applicability of stepping stones was thereby to be examined for the beam effect of interventions on running waters, as a parallel to wildlife corridors. | 1 | Applied and Interdisciplinary Chemistry |
The refrigeration industry has been seeking replacements for R-410A because of its high global warming potential. R-454B, formerly known as DL-5A, has been selected by several manufacturers, including Mitsubishi Electric, Carrier, Johnson Controls, and others.
R-454B was developed at and is manufactured by Chemours. Carrier first announced introduction of R-454B in ducted residential and light commercial packaged refrigeration and air conditioning products in 2018, with R-454B-based products launches starting in 2023. | 1 | Applied and Interdisciplinary Chemistry |
Volatile suspended solids (VSS) is an analytical parameter representing, loosely, the undissolved organic matter in a water sample. More technically, it a water quality parameter obtained from the loss on ignition of total suspended solids. This ignition generally takes place in an oven at a temperature of 550 °C to 600 °C. It represents the amount of volatile matter present in the undissolved solid fraction of the measured solution. | 0 | Theoretical and Fundamental Chemistry |
Some catalysts operate by "outer sphere mechanisms" such that the substrate never bonds directly to the metal but rather interacts with its ligands, which is often a metal hydride and a protic hydrogen on a ligand. As such, in most cases dihydrogen is split heterolytically, with the metal acting as a Lewis acid and either an external or internal base "deprotonating" the hydride.
For an example of this mechanism we can consider the BINAP-Ru-diamine system. The dihalide form of the catalyst is converted to the catalysts by reaction of H in the presence of base:
:RuCl(BINAP)(diamine) + 2 KOBu-t + 2 H → RuH(BINAP)(diamine) + 2 KCl + 2 HOBu-t
The resulting catalysts have three kinds of ligands:
*hydrides, which transfer to the unsaturated substrate
*diamines, which interact with substrate and with base activator by the second coordination sphere
*diphosphine, which confers asymmetry.
The "Noyori-class" of catalysts are often referred to as bifunctional catalysts to emphasize the fact that both the metal and the (amine) ligand are functional.
In the hydrogenation of C=O containing substates, the mechanism was long assumed to operate by a six membered pericyclic transition state/intermediate whereby the hydrido ruthenium hydride center (HRu-NH) interacts with the carbonyl substrate RC=O. More recent DFT and experimental studies have shown that this model is largely incorrect. Instead, the amine backbone interacts strongly with the base activator, which often is used in large excess. However in both cases, the substate does not bond directly with the metal centre, thus making it a great example of an outer sphere mechanism. | 0 | Theoretical and Fundamental Chemistry |
Dynamic kinetic resolution in chemistry is a type of kinetic resolution where 100% of a racemic compound can be converted into an enantiopure compound. It is applied in asymmetric synthesis. Asymmetric synthesis has become a much explored field due to the challenge of creating a compound with a single 3D structure. Even more challenging is the ability to take a racemic mixture and have only one chiral product left after a reaction. One method that has become an exceedingly useful tool is dynamic kinetic resolution (DKR). DKR utilizes a center of a particular molecule that can be easily epimerized so that the (R) and (S) enantiomers can interconvert throughout the reaction process. At this point the catalyst can selectively lower the transition state energy of a single enantiomer, leading to almost 100% yield of one reaction pathway over the other. The figure below is an example of an energy diagram for a compound with an (R) and (S) isomer.
If a catalyst is able to increase ΔΔG to a sufficient degree, then one pathway will dominate over the other, leading to a single chiral product. Manipulating kinetics therefore becomes a powerful way to achieve asymmetric products from racemic starting materials. There have been numerous uses of DKR in the literature that have provided new methods in pharmaceuticals as well as routes to natural products. | 0 | Theoretical and Fundamental Chemistry |
Exo-α-sialidase (, sialidase, neuraminidase; systematic name acetylneuraminyl hydrolase) is a glycoside hydrolase that cleaves the glycosidic linkages of neuraminic acids:
: Hydrolysis of α-(2→3)-, α-(2→6)-, α-(2→8)- glycosidic linkages of terminal sialic acid residues in oligosaccharides, glycoproteins, glycolipids, colominic acid and synthetic substrates
Neuraminidase enzymes are a large family, found in a range of organisms. The best-known neuraminidase is the viral neuraminidase, a drug target for the prevention of the spread of influenza infection. Viral neuraminidase was the first neuraminidase to be identified. It was discovered in 1957 by Alfred Gottschalk at the Walter and Eliza Hall Institute in Melbourne. The viral neuraminidases are frequently used as antigenic determinants found on the surface of the influenza virus. Some variants of the influenza neuraminidase confer more virulence to the virus than others. Other homologues are found in mammalian cells, which have a range of functions. At least four mammalian sialidase homologues have been described in the human genome (see NEU1, NEU2, NEU3, NEU4).
Sialidases may act as pathogenic factors in microbial infections. | 0 | Theoretical and Fundamental Chemistry |
It has been shown that PMCA is capable of detecting as little as a single molecule of oligomeric infectious PrP. PMCA possesses the ability to generate millions infectious units, starting with the equivalent to one PrP oligomer; well below the infectivity threshold. This data demonstrates that PMCA has a similar power of amplification as PCR techniques used to amplify DNA. It opens a great promise for development of a highly sensitive detection of PrP, and for understanding the molecular basis of prion replication. Indeed, PMCA has been used by various groups to PrP in blood of animals experimentally infected with prions during both the symptomatic and pre-symptomatic phases as well as in urine. | 1 | Applied and Interdisciplinary Chemistry |
The factors affecting V̇O may be separated into supply and demand. Supply is the transport of oxygen from the lungs to the mitochondria (combining pulmonary function, cardiac output, blood volume, and capillary density of the skeletal muscle) while demand is the rate at which the mitochondria can reduce oxygen in the process of oxidative phosphorylation. Of these, the supply factors may be more limiting. However, it has also been argued that while trained subjects are probably supply limited, untrained subjects can indeed have a demand limitation.
General characteristics that affect V̇O max include age, sex, fitness and training, and altitude. V̇O max can be a poor predictor of performance in runners due to variations in running economy and fatigue resistance during prolonged exercise. The body works as a system. If one of these factors is sub-par, then the whole system's normal capacity is reduced.
The drug erythropoietin (EPO) can boost V̇O max by a significant amount in both humans and other mammals. This makes EPO attractive to athletes in endurance sports, such as professional cycling. EPO has been banned since the 1990s as an illicit performance-enhancing substance. But by 1998 it had become widespread in cycling and led to the Festina affair as well as being mentioned ubiquitously in the USADA 2012 report on the U.S. Postal Service Pro Cycling Team. Greg LeMond has suggested establishing a baseline for riders' V̇O max (and other attributes) to detect abnormal performance increases. | 1 | Applied and Interdisciplinary Chemistry |
Variation in methylation states of DNA can alter gene expression levels significantly. Methylation variation usually occurs through the action of DNA methylases. When the change is heritable, it is considered epigenetic. When the change in information status is not heritable, it would be a somatic epitype. The effective information content has been changed by means of the actions of a protein or proteins on DNA, but the primary DNA sequence is not altered. | 1 | Applied and Interdisciplinary Chemistry |
MLST appears best in population genetic study but it is expensive. Due to the sequence conservation in housekeeping genes, MLST sometimes lacks the discriminatory power to differentiate bacterial strains, which limits its use in epidemiological investigations. To improve the discriminatory power of MLST, a multi-virulence-locus sequence typing (MVLST) approach has been developed using Listeria monocytogenes . MVLST broadens the benefits of MLST but targets virulence genes, which may be more polymorphic than housekeeping genes. Population genetics is not the only relevant factor in an epidemic. Virulence factors are also important in causing disease, and population genetic studies struggle to monitor these. This is because the genes involved are often highly recombining and mobile between strains in comparison with the population genetic framework. Thus, for example in Escherichia coli, identifying strains carrying toxin genes is more important than having a population genetics-based evaluation of prevalent strains.
The advent of second-generation sequencing technologies has made it possible to obtain sequence information across the entire bacterial genome at relatively modest cost and effort, and MLST can now be assigned from whole-genome sequence information, rather than sequencing each locus separately as was the practice when MLST was first developed. Whole-genome sequencing provides richer information for differentiating bacterial strains (MLST uses approximately 0.1% of the genomic sequence to assign type while disregarding the rest of the bacterial genome). For example, whole-genome sequencing of numerous isolates has revealed the single MLST lineage ST258 of Klebsiella pneumoniae comprises two distinct genetic clades, providing additional information about the evolution and spread of these multi-drug resistant organisms, and disproving the previous hypothesis of a single clonal origin for ST258. | 1 | Applied and Interdisciplinary Chemistry |
The desired activity of a drug is mainly due to successful targeting of one of the following:
*Cellular membrane disruption
*Chemical reaction with downstream effects
*Interaction with enzyme proteins
*Interaction with structural proteins
*Interaction with carrier proteins
*Interaction with ion channels
*Ligand binding to receptors:
**Hormone receptors
**Neuromodulator receptors
**Neurotransmitter receptors
General anesthetics were once thought to work by disordering the neural membranes, thereby altering the Na influx. Antacids and chelating agents combine chemically in the body. Enzyme-substrate binding is a way to alter the production or metabolism of key endogenous chemicals, for example aspirin irreversibly inhibits the enzyme prostaglandin synthetase (cyclooxygenase) thereby preventing inflammatory response. Colchicine, a drug for gout, interferes with the function of the structural protein tubulin, while digitalis, a drug still used in heart failure, inhibits the activity of the carrier molecule, Na-K-ATPase pump. The widest class of drugs act as ligands that bind to receptors that determine cellular effects. Upon drug binding, receptors can elicit their normal action (agonist), blocked action (antagonist), or even action opposite to normal (inverse agonist).
In principle, a pharmacologist would aim for a target plasma concentration of the drug for a desired level of response. In reality, there are many factors affecting this goal. Pharmacokinetic factors determine peak concentrations, and concentrations cannot be maintained with absolute consistency because of metabolic breakdown and excretory clearance. Genetic factors may exist which would alter metabolism or drug action itself, and a patient's immediate status may also affect indicated dosage. | 1 | Applied and Interdisciplinary Chemistry |
The downfall of the overall cyclol model generally led to a rejection of its elements; one notable exception was J. D. Bernal's short-lived acceptance of the Langmuir-Wrinch hypothesis that protein folding is driven by hydrophobic association. Nevertheless, cyclol bonds were identified in small, naturally occurring cyclic peptides in the 1950s.
Clarification of the modern terminology is appropriate. The classic cyclol reaction is the addition of the NH amine of a peptide group to the C=O carbonyl group of another; the resulting compound is now called an azacyclol. By analogy, an oxacyclol is formed when an OH hydroxyl group is added to a peptidyl carbonyl group. Likewise, a thiacyclol is formed by adding an SH thiol moiety to a peptidyl carbonyl group.
The oxacyclol alkaloid ergotamine from the fungus Claviceps purpurea was the first identified cyclol. The cyclic depsipeptide serratamolide is also formed by an oxacyclol reaction. Chemically analogous cyclic thiacyclols have also been obtained. Classic azacyclols have been observed in small molecules and tripeptides. Peptides are naturally produced from the reversion of azacylols, a key prediction of the cyclol model. Hundreds of cyclol molecules have now been identified, despite Linus Pauling's calculation that such molecules should not exist because of their unfavorably high energy.
After a long hiatus during which she worked mainly on the mathematics of X-ray crystallography, Wrinch responded to these discoveries with renewed enthusiasm for the cyclol model and its relevance in biochemistry. She also published two books describing the cyclol theory and small peptides in general. | 1 | Applied and Interdisciplinary Chemistry |
Molecular glue compounds have demonstrated significant potential in cancer treatment by influencing protein-protein interactions (PPIs) and subsequently modulating pathways promoting cancer growth. These compounds act as targeted protein degraders, contributing to the development of innovative cancer therapies. The high efficacy of small-molecule molecular glue compounds in cancer treatment is notable, as they can interact with and control multiple key protein targets involved in cancer etiology. This approach, with its wider range of action and ability to target "undruggable" proteins, holds promise for overcoming drug resistance and changing the landscape of drug development in cancer therapy. | 1 | Applied and Interdisciplinary Chemistry |
Although this term is also sometimes used interchangeably with exon, it is not the exact same thing: the exon is composed of the coding region as well as the 3 and 5 untranslated regions of the RNA, and so therefore, an exon would be partially made up of coding regions. The 3 and 5 untranslated regions of the RNA, which do not code for protein, are termed non-coding regions and are not discussed on this page.
There is often confusion between coding regions and exomes and there is a clear distinction between these terms. While the exome refers to all exons within a genome, the coding region refers to a singular section of the DNA or RNA which specifically codes for a certain kind of protein. | 1 | Applied and Interdisciplinary Chemistry |
Although the free-water method likely contains some benthic metabolic signal, isolating the benthic contribution to whole-lake metabolism requires benthic-specific methods. Analogous to the light and dark bottle methods described above, lake sediment cores can be collected and changes in dissolved oxygen or carbon fixation can be used to estimate rates of primary productivity and respiration. Relatively new methods describe isolating the sediment-water interface with transparent domes and measure changes in dissolved oxygen in-situ, which is a hybrid between the free-water method and light-dark bottle method. These in-situ benthic chamber methods allow for relatively easy multi-day estimate of benthic metabolism, which helps the researcher determine how benthic metabolism changes with varying weather patterns and lake characteristics. | 1 | Applied and Interdisciplinary Chemistry |
Following completion of his PhD degree, Oesper taught for a brief time at New York University and then at Smith College as a non-tenure track faculty member. He then in 1918 became a tenure track faculty member and later a full professor at the University of Cincinnati, where he remained until his retirement in 1951 as professor emeritus. In retirement, he remained active as an occasional lecturer, a journal editor, and a translator of scientific books and articles.
Oesper wrote approximately 300 scientific articles on analytical and organic chemistry, colloid chemistry and chemical history. He was fluent in the German language and translated about 20 chemistry books and numerous articles from German into English. He also translated chemistry articles from French and Dutch into English. | 1 | Applied and Interdisciplinary Chemistry |
Alkaliphiles maintain cytosolic acidification through both passive and active means. In passive acidification, it has been proposed that cell walls contain acidic polymers composed of residues such as galacturonic acid, gluconic acid, glutamic acid, aspartic acid, and phosphoric acid. Together, these residues form an acidic matrix that helps protect the plasma membrane from alkaline conditions by preventing the entry of hydroxide ions, and allowing for the uptake of sodium and hydronium ions. In addition, the peptidoglycan in alkaliphilic B. subtilis has been observed to contain higher levels of hexosamines and amino acids as compared to its neutrophilic counterpart. When alkaliphiles lose these acidic residues in the form of induced mutations, it has been shown that their ability to grow in alkaline conditions is severely hindered. However, it is generally agreed upon that passive methods of cytosolic acidification are not sufficient to maintain an internal pH 2-2.3 levels below that of external pH; there must also be active forms of acidification. The most characterized method of active acidification is in the form of Na/H antiporters. In this model, H ions are first extruded through the electron transport chain in respiring cells and to some extent through an ATPase in fermentative cells. This proton extrusion establishes a proton gradient that drives electrogenic antiporters—which drive intracellular Na out of the cell in exchange for a greater number of H ions, leading to the net accumulation of internal protons. This proton accumulation leads to a lowering of cytosolic pH. The expelled Na can be used for solute symport, which are necessary for cellular processes. It has been noted that Na/H antiport is required for alkaliphilic growth, whereas either K/H antiporters or Na/H antiporters can be utilized by neutrophilic bacteria. If Na/H antiporters are disabled through mutation or another means, the bacteria are rendered neutrophilic. The sodium required for this antiport system is the reason some alkaliphiles can only grow in saline environments. | 1 | Applied and Interdisciplinary Chemistry |
* Nematoda: Ascaris, Caenorhabditis ;
* Mollusca: Bivalvia); Polyplacophora;
* Arthropoda/Crustacea: Artemia;
* Arthropoda/Insecta: Drosophila [<nowiki />Locusta migratoria (migratory locust), Apis mellifera (honeybee)]. | 1 | Applied and Interdisciplinary Chemistry |
In carbohydrate chemistry carbohydrate acetalisation is an organic reaction and a very effective means of providing a protecting group. The example below depicts the acetalisation reaction of D-ribose 1. With acetone or 2,2-dimethoxypropane as the acetalisation reagent the reaction is under thermodynamic reaction control and results in the pentose 2. The latter reagent in itself is an acetal and therefore the reaction is actually a cross-acetalisation.
Kinetic reaction control results from 2-methoxypropene as the reagent. D-ribose in itself is a hemiacetal and in equilibrium with the pyranose 3. In aqueous solution ribose is 75% pyranose and 25% furanose and a different acetal 4 is formed.
Selective acetalization of carbohydrate and formation of acetals possessing atypical properties is achieved by using arylsulfonyl acetals. An example of arylsulfonyl acetals as carbohydrate-protective groups are phenylsulfonylethylidene acetals. These acetals are resistant to the acid hydrolysis and can be deprotected easily by classical reductive conditions. | 0 | Theoretical and Fundamental Chemistry |
A large number of cloning vectors are available, and choosing the vector may depend upon a number of factors, such as the size of the insert, copy number and cloning method. Large insert may not be stably maintained in a general cloning vector, especially for those with a high copy number, therefore cloning large fragments may require more specialised cloning vector. | 1 | Applied and Interdisciplinary Chemistry |
Though nitrogen fixation is the primary source of plant-available nitrogen in most ecosystems, in areas with nitrogen-rich bedrock, the breakdown of this rock also serves as a nitrogen source. Nitrate reduction is also part of the iron cycle, under anoxic conditions Fe(II) can donate an electron to and is oxidized to Fe(III) while is reduced to , and depending on the conditions and microbial species involved. The fecal plumes of cetaceans also act as a junction in the marine nitrogen cycle, concentrating nitrogen in the epipelagic zones of ocean environments before its dispersion through various marine layers, ultimately enhancing oceanic primary productivity. | 1 | Applied and Interdisciplinary Chemistry |
Plasmid vectors are circular strands of DNA, found in virions, that are used in genetic engineering to integrate new genes into a host cell genome.
The small T intron is an intron, that is used in some plasmid vectors, in order to induce gene expression in mammalian cells. | 1 | Applied and Interdisciplinary Chemistry |
Spent nuclear fuel contains abundant fertile uranium and traces of fissile materials. Methods such as the PUREX process can be used to remove useful actinides for the production of active nuclear fuel.
Another option is to find applications for the isotopes in nuclear waste so as to re-use them. Already, caesium-137, strontium-90 and a few other isotopes are extracted for certain industrial applications such as food irradiation and radioisotope thermoelectric generators. While re-use does not eliminate the need to manage radioisotopes, it can reduce the quantity of waste produced.
The Nuclear Assisted Hydrocarbon Production Method, Canadian patent application 2,659,302, is a method for the temporary or permanent storage of nuclear waste materials comprising the placing of waste materials into one or more repositories or boreholes constructed into an unconventional oil formation. The thermal flux of the waste materials fractures the formation and alters the chemical and/or physical properties of hydrocarbon material within the subterranean formation to allow removal of the altered material. A mixture of hydrocarbons, hydrogen, and/or other formation fluids is produced from the formation. The radioactivity of high-level radioactive waste affords proliferation resistance to plutonium placed in the periphery of the repository or the deepest portion of a borehole.
Breeder reactors can run on U-238 and transuranic elements, which comprise the majority of spent fuel radioactivity in the 1,000–100,000-year time span. | 0 | Theoretical and Fundamental Chemistry |
Mixed alkyl/aryl-halide compounds, which contain a single C-M bond and a C-X bond, are typically prepared by oxidative addition. Magnesium-containing compounds of this configuration are known as the Grignard reagents, though some calcium Grignards are known and more reactive and sensitive to decomposition. Calcium grignards must be pre-activated prior to synthesis.
There are three key reaction pathways for dialkyl and diaryl group 2 metal compounds.
*metathesis:
:MX + R-Y → MR + Y-X'
*transmetallation:
:MR + M → MR + M
*via the Schlenk equilibrium:
:2 RMX → MR + MX | 0 | Theoretical and Fundamental Chemistry |
The field has expanded significantly since the publication in 1973 with biochemists Stanley N. Cohen and Herbert W. Boyer by using E. coli bacteria to learn how to cut fragments, rejoin different fragments, and insert the new genes. The field has expanded tremendously in terms of precision and accuracy since then. Computers and technology have made it technologically easier to achieve narrowing of error and expand understanding in this field. Computers having a high capacity for data and calculations which made processing the large volume of information tangible, i.e., the use of ChIP and gene sequence. | 1 | Applied and Interdisciplinary Chemistry |
*Nucleobase analogues
**Thiopurines such as thioguanine are used to treat acute leukemias and remissions in acute granulocytic leukemias.
***Azathioprine is the main immunosuppressive cytotoxic substance. A prodrug, it is widely used in transplantation to control rejection reactions. It is nonenzymatically cleaved to mercaptopurine, a purine analogue that inhibits DNA synthesis. By preventing the clonal expansion of lymphocytes in the induction phase of the immune response, it affects both cell immunity and humoral immunity. It also successfully suppresses autoimmunity.
***Mercaptopurine
***Thioguanine
*Nucleoside analogues
**Clofarabine
**Pentostatin and cladribine are adenosine analogs that are used primarily to treat hairy cell leukemia.
*Nucleotide analogues
**Fludarabine inhibits multiple DNA polymerases, DNA primase, and DNA ligase I, and is S phase-specific (since these enzymes are highly active during DNA replication). | 1 | Applied and Interdisciplinary Chemistry |
Storms has published more than a hundred journal articles and several books. He has spoken on his work at conferences of the ACS, APS, and ICCF | 0 | Theoretical and Fundamental Chemistry |
Crystallography has 230 space groups to distinguish, far more than the 17 wallpaper groups, but many of the symmetries in the groups are the same. Thus one can use a similar notation for both kinds of groups, that of Carl Hermann and Charles-Victor Mauguin. An example of a full wallpaper name in Hermann-Mauguin style (also called IUCr notation) is p31m, with four letters or digits; more usual is a shortened name like cmm or pg.
For wallpaper groups the full notation begins with either p or c, for a primitive cell or a face-centred cell; these are explained below. This is followed by a digit, n, indicating the highest order of rotational symmetry: 1-fold (none), 2-fold, 3-fold, 4-fold, or 6-fold. The next two symbols indicate symmetries relative to one translation axis of the pattern, referred to as the "main" one; if there is a mirror perpendicular to a translation axis that is the main one (or if there are two, one of them). The symbols are either m, g, or 1, for mirror, glide reflection, or none. The axis of the mirror or glide reflection is perpendicular to the main axis for the first letter, and either parallel or tilted 180°/n (when n > 2) for the second letter. Many groups include other symmetries implied by the given ones. The short notation drops digits or an m that can be deduced, so long as that leaves no confusion with another group.
A primitive cell is a minimal region repeated by lattice translations. All but two wallpaper symmetry groups are described with respect to primitive cell axes, a coordinate basis using the translation vectors of the lattice. In the remaining two cases symmetry description is with respect to centred cells that are larger than the primitive cell, and hence have internal repetition; the directions of their sides is different from those of the translation vectors spanning a primitive cell. Hermann-Mauguin notation for crystal space groups uses additional cell types.
;Examples
* p2 (p2): Primitive cell, 2-fold rotation symmetry, no mirrors or glide reflections.
* p4gm (p4gm): Primitive cell, 4-fold rotation, glide reflection perpendicular to main axis, mirror axis at 45°.
* c2mm (c2mm): Centred cell, 2-fold rotation, mirror axes both perpendicular and parallel to main axis.
* p31m (p31m): Primitive cell, 3-fold rotation, mirror axis at 60°.
Here are all the names that differ in short and full notation.
The remaining names are p1, p2, p3, p3m1, p31m, p4, and p6. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, Sauter mean diameter (SMD) is an average measure of particle size. It was originally developed by German scientist Josef Sauter in the late 1920s. It is defined as the diameter of a sphere that has the same volume/surface area ratio as a particle of interest.
Several methods have been devised to obtain a good estimate of the SMD. | 1 | Applied and Interdisciplinary Chemistry |
In particle therapy (proton therapy being one example), energetic ionizing particles (protons or carbon ions) are directed at the target tumor. The dose increases while the particle penetrates the tissue, up to a maximum (the Bragg peak) that occurs near the end of the particle's range, and it then drops to (almost) zero. The advantage of this energy deposition profile is that less energy is deposited into the healthy tissue surrounding the target tissue. | 0 | Theoretical and Fundamental Chemistry |
The sigma-2 receptor is located in the lipid raft. The sigma-2 receptor is found in several areas of the brain, including high densities in the cerebellum, motor cortex, hippocampus, and substantia nigra. It is also highly expressed in the lungs, liver, and kidneys. | 1 | Applied and Interdisciplinary Chemistry |
The fastest World War II fighters were the first aircraft to experience Mach tuck. Their wings were not designed to counter Mach tuck because research on supersonic airfoils was just beginning; areas of supersonic flow, together with shock waves and flow separation, were present on the wing. This condition was known at the time as compressibility burble and was known to exist on propeller tips at high aircraft speeds.
The P-38 was one of the first 400 mph fighters, and it suffered more than the usual teething troubles. It had a thick, high-lift wing, distinctive twin booms and a single, central nacelle containing the cockpit and armament. It quickly accelerated to terminal velocity in a dive. The short stubby fuselage had a detrimental effect in reducing the critical Mach number of the 15% thick wing center section with high velocities over the canopy adding to those on the upper surface of the wing. Mach tuck occurred at speeds above Mach 0.65; the air flow over the wing center section became transonic, causing a loss of lift. The resultant change in downwash at the tail caused a nose-down pitching moment and the dive to steepen (Mach tuck). The aircraft was very stable in this condition making recovery from the dive very difficult.
Dive recovery (auxiliary) flaps were added to the underside of the wing (P-38J-LO) to increase the wing lift and downwash at the tail to allow recovery from transonic dives. | 1 | Applied and Interdisciplinary Chemistry |
The plant sorghum is well established model organism and can adapt in hot and dry environments. For this reason, it is used as a model to study calmodulins role in plants. Sorghum contains seedlings that express a glycine-rich RNA-binding protein, SbGRBP. This particular protein can be modulated by using heat as a stressor. Its unique location in the cell nucleus and cytosol demonstrates interaction with calmodulin that requires the use of Ca. By exposing the plant to versatile stress conditions, it can cause different proteins that enable the plant cells to tolerate environmental changes to become repressed. These modulated stress proteins are shown to interact with CaM. The CaMBP' genes expressed in the sorghum are depicted as a “model crop” for researching the tolerance to heat and drought stress. | 1 | Applied and Interdisciplinary Chemistry |
Metals in Earths inner core could possibly be in the chain-melted state, as suggested by several simulations, where metals such as titanium and iron displayed partially molten states, or quasi-solid properties. It is also possible that Earths mantle may contain metals like potassium in the chain-melted state; however, potassium is usually not found in pure form.
These suggestions may also possibly be proven by the Kola superdeep borehole, where according to declassified documents, the rock at the bottom of the borehole was found to be in a texture between solid and liquid. | 0 | Theoretical and Fundamental Chemistry |
Inhibition of fatty acid oxidation requires that ACC is active. Both AMPK and MCD are inactive and glucose uptake is stimulated. The LCFAs are then rerouted to esterification. These conditions exist in tissues rich in oxygen, in which AMPK is inactive and glucose inactivates the AMPK (researched in skeletal muscle).
The inhibition of MCD suppresses the oxidation of fatty acids and stimulates glucose oxidation. In a study on MCD deficient mice there was no difference in the oxidation of fatty acids and glucose in the heart under aerobic conditions. It is theorized that the overexpression of fatty acids being used makes up for the lack of MCD. | 1 | Applied and Interdisciplinary Chemistry |
Selecting an oocyte for in vitro fertilization involves assessing the quality of the oocyte which is usually done by accessing the morphological features of the oocyte. The major parts of the oocyte that are accessed for quality in terms of morphological characteristics are the cumulus cells, zona pellucida, polar body, perivitelline space, and cytoplasm; These are the main parts of the oocyte and are usually assessed by conventional microscopy. The size of an oocyte is another factor of the quality of the oocyte; Larger oocyte are usually more quality than smaller ones. Chromosomal evaluation may be performed. Embryos from rescued in vitro-matured metaphase II (IVM-MII) oocytes show significantly higher fertilization rates and more blastomeres per embryo compared with those from arrested metaphase I (MI) oocytes (58.5% vs. 43.9% and 5.7 vs. 5.0, respectively).
Also, morphological features of the oocyte that can be obtained by standard light or polarized light microscopy. However, there is no clear tendency in recent publications to a general increase in predictive value of morphological features. Suggested techniques include zona pellucida imaging, which can detect differences in birefringence between eggs, which is a predictor of compaction, blastulation and pregnancy.
Potentially, polar body biopsy may be used for molecular analysis, and can be used for preimplantation genetic screening. | 1 | Applied and Interdisciplinary Chemistry |
Nasonov's gland produces a pheromone used in recruitment in worker honeybees. The pheromone can serve the purposes of attracting workers to a settled swarm and draw bees who have lost their way back to the hive. It is used to recruit workers to food that lacks a characteristic scent and lead bees to water sources. The gland is located on the dorsal side of the abdomen. Its opening is located at the base of the last tergite at the tip of the abdomen.
The gland was first described in 1882 by the Russian zoologist Nikolai Viktorovich Nasonov (February 14, 1855 – February 11, 1939). Nasonov thought that the gland performed perspiration; it was Frederick William Lambert Sladen (May 30, 1876 - 1921) of England who in 1901 first proposed that the gland produced a pheromone. | 1 | Applied and Interdisciplinary Chemistry |
The systematic names sulfanediide and sulfide(2−), valid IUPAC names, are determined according to the substitutive and additive nomenclatures, respectively. However, the name sulfide is also used in compositional IUPAC nomenclature which does not take the nature of bonding involved. Examples of such naming include selenium disulfide and titanium sulfide, which contain no sulfide ions. | 0 | Theoretical and Fundamental Chemistry |
River engineering, a branch of civil engineering, deals with the process of planned human intervention to improve and restore rivers for human and environmental needs. With modern technologies, data collection and modelling, navigation can be improved, dredging reduced and new habitats can be created. River engineering also handles sediment and erosion control, which can be a threat to humankind by destroying infrastructure, hindering water supply and causing major river cutoffs. River training structures will help to modify the hydraulic flow and the sediment response of a river.
Humans have modified the natural behavior of rivers for longer than history is recorded. The management of water resources, protection against floods and hydropower are not new concepts. Regardless, river engineering has changed in the past century because of environmental concerns. The available amount and type of data about rivers has increased which provides more useful information about the behaviour of rivers and their ecosystems. Engineering experts are able to analyse and adapt in a more environmentally conscious way. Renaturalisation projects raise more awareness for the environment, however, rapidly growing and urbanizing population needs to be supplied with enough water resources and hydropower energy, which calls for more sustainable solutions. | 1 | Applied and Interdisciplinary Chemistry |
While the halogens are not nucleophilic in their diatomic form (e.g. I is not a nucleophile), their anions are good nucleophiles. In polar, protic solvents, F is the weakest nucleophile, and I the strongest; this order is reversed in polar, aprotic solvents. | 0 | Theoretical and Fundamental Chemistry |
For substances to be regulated and handled appropriately they must be properly classified and labelled. Classification is determined by approved testing measures or calculations and has determined cut-off levels set by governments and scientists (for example, no-observed-adverse-effect levels, threshold limit values, and tolerable daily intake levels). Pesticides provide the example of well-established toxicity class systems and toxicity labels. While currently many countries have different regulations regarding the types of tests, numbers of tests and cut-off levels, the implementation of the Globally Harmonized System has begun unifying these countries.
Global classification looks at three areas: Physical Hazards (explosions and pyrotechnics), Health Hazards and environmental hazards. | 1 | Applied and Interdisciplinary Chemistry |
The RFU measurements are used, for DNA profiling, in a real-time polymerase chain reaction (PCR). Two common methods for detection of products in real-time PCR are: (1) non-specific fluorescent dyes that intercalate with any double-stranded DNA, and (2) sequence-specific DNA probes consisting of oligonucleotides that are labeled with a fluorescent reporter which permits detection only after hybridization of the probe with its complementary DNA target. Frequently, real-time PCR is combined with reverse transcription to quantify messenger RNA and Non-coding RNA in cells or tissues. | 1 | Applied and Interdisciplinary Chemistry |
Fluoroalkenes polymerize more exothermically than normal alkenes. Unsaturated fluorocarbons have a driving force towards sp hybridization due to the electronegative fluorine atoms seeking a greater share of bonding electrons with reduced s character in orbitals. The most famous member of this class is tetrafluoroethylene, which is used to manufacture polytetrafluoroethylene (PTFE), better known under the trade name Teflon. | 1 | Applied and Interdisciplinary Chemistry |
Esters derived from carboxylic acids and alcohols contain a carbonyl group C=O, which is a divalent group at C atom, which gives rise to C–C–O and O–C–O angles. Unlike amides, carboxylic acid esters are structurally flexible functional groups because rotation about the C–O–C bonds has a low barrier. Their flexibility and low polarity is manifested in their physical properties; they tend to be less rigid (lower melting point) and more volatile (lower boiling point) than the corresponding amides. The pK of the alpha-hydrogens on esters of carboxylic acids is around 25 (alpha-hydrogen is a hydrogen bound to the carbon adjacent to the carbonyl group (C=O) of carboxylate esters).
Many carboxylic acid esters have the potential for conformational isomerism, but they tend to adopt an S-cis (or Z) conformation rather than the S-trans (or E) alternative, due to a combination of hyperconjugation and dipole minimization effects. The preference for the Z conformation is influenced by the nature of the substituents and solvent, if present. Lactones with small rings are restricted to the s-trans (i.e. E) conformation due to their cyclic structure. | 0 | Theoretical and Fundamental Chemistry |
In the early 1900s, Werner Spalteholz developed a technique that allowed the clarification of large tissues, using Wintergrünöl (methyl salicylate) and benzyl benzoate. Over the next hundred years, various scientists introduced their own variations on Spalteholzs technique. Tuchin et al. introduced TOC in 1997, adding a new branch of tissue clearing that was hydrophilic instead of hydrophobic like Spalteholzs technique. In 2007, Dodt et al. developed a two step process, wherein tissues were first dehydrated with ethanol and hexane and subsequently made transparent by immersion in benzyl alcohol and benzyl benzoate (BABB), a technique they coupled with light sheet fluorescence microscopy. Hama et al. developed another hydrophilic approach, Scale, in 2011. The following year, Ertürk et al. developed a hydrophobic approach called 3DISCO, in which they pretreated tissue with tetrahydrofuran and dichloromethane before clearing it in dibenzyl ether. A year later, in 2013, Chung et al. developed CLARITY, the first approach to use hydrogel monomers to clear tissue. | 1 | Applied and Interdisciplinary Chemistry |
A polar molecule has a net dipole as a result of the opposing charges (i.e. having partial positive and partial negative charges) from polar bonds arranged asymmetrically. Water (HO) is an example of a polar molecule since it has a slight positive charge on one side and a slight negative charge on the other. The dipoles do not cancel out, resulting in a net dipole. The dipole moment of water depends on its state. In the gas phase the dipole moment is ≈ 1.86 debye (D), whereas liquid water (≈ 2.95 D) and ice (≈ 3.09 D) are higher due to differing hydrogen-bonded environments. Other examples include sugars (like sucrose), which have many polar oxygen–hydrogen (−OH) groups and are overall highly polar.
If the bond dipole moments of the molecule do not cancel, the molecule is polar. For example, the water molecule (HO) contains two polar O−H bonds in a bent (nonlinear) geometry. The bond dipole moments do not cancel, so that the molecule forms a molecular dipole with its negative pole at the oxygen and its positive pole midway between the two hydrogen atoms. In the figure each bond joins the central O atom with a negative charge (red) to an H atom with a positive charge (blue).
The hydrogen fluoride, HF, molecule is polar by virtue of polar covalent bondsin the covalent bond electrons are displaced toward the more electronegative fluorine atom.
Ammonia, NH, is a molecule whose three N−H bonds have only a slight polarity (toward the more electronegative nitrogen atom). The molecule has two lone electrons in an orbital that points towards the fourth apex of an approximately regular tetrahedron, as predicted by the VSEPR theory. This orbital is not participating in covalent bonding; it is electron-rich, which results in a powerful dipole across the whole ammonia molecule.
In ozone (O) molecules, the two O−O bonds are nonpolar (there is no electronegativity difference between atoms of the same element). However, the distribution of other electrons is unevensince the central atom has to share electrons with two other atoms, but each of the outer atoms has to share electrons with only one other atom, the central atom is more deprived of electrons than the others (the central atom has a formal charge of +1, while the outer atoms each have a formal charge of −). Since the molecule has a bent geometry, the result is a dipole across the whole ozone molecule. | 0 | Theoretical and Fundamental Chemistry |
In physical chemistry and chemical engineering, extent of reaction is a quantity that measures the extent to which the reaction has proceeded. Often, it refers specifically to the value of the extent of reaction when equilibrium has been reached. It is usually denoted by the Greek letter ξ. The extent of reaction is usually defined so that it has units of amount (moles). It was introduced by the Belgian scientist Théophile de Donder. | 0 | Theoretical and Fundamental Chemistry |
All five families of luminescent beetle, Phengodidae, Rhagophthalidae, Elateridae, Sinopyrophoridae, and Lampyridae are categorized into the Lampyroid clade. It has been determined that the luciferases and luciferin protein expressed in the photocytes of all species of firefly is homologous with that expressed in beetle species within the families Phengodidae, Rhagophthalidae, and Elateridae. In fact, every bioluminescent beetle species studied has been shown to use very similar mechanisms for light production in the photocyte. The beetle genus, Sinopyrophoridae, has been shown to exhibit biolumiescence although the exact mechanism is not known. It is believed that it shares homology with other genera of beetles however. The first time the entire genome of a bioluminescent beetle was determined was in 2017 with Pyrocoelia pectoralis, a species of firefly, and in 2018, three more species of bioluminescent beetle had their genomes sequenced. Biolumiescence in beetles has been shown to serve multiple purposes including the deterrence of predators and the attraction of mates.
The variation in coloring among different species of firefly has been determined to be due to differences in the amino acid sequences of the luciferases expressed in their photocytes. Two luciferace genes have been identified in the genomes of fireflies. They are luc1-type and luc2-type. There is evidence that suggests that Luc1-type evolved from a gene duplication of the gene that encodes for acyl-CoA synthetase. It is hypothesized that the luciferase of click beetles evolved separately from that in fireflies being the result of two gene duplications of the acyl-CoA synthetase gene suggesting analogy instead of homology between the groups. Additional genes have been found to be related to the storage of luciferin. | 1 | Applied and Interdisciplinary Chemistry |
Portal site mediated adsorption is a model for site-selective activated gas adsorption in metallic catalytic systems that contain a variety of different adsorption sites. In such systems, low-coordination "edge and corner" defect-like sites can exhibit significantly lower adsorption enthalpies than high-coordination (basal plane) sites. As a result, these sites can serve as "portals" for very rapid adsorption to the rest of the surface. The phenomenon relies on the common "spillover" effect (described below), where certain adsorbed species exhibit high mobility on some surfaces. The model explains seemingly inconsistent observations of gas adsorption thermodynamics and kinetics in catalytic systems where surfaces can exist in a range of coordination structures, and it has been successfully applied to bimetallic catalytic systems where synergistic activity is observed.
In contrast to pure spillover, portal site adsorption refers to surface diffusion to adjacent adsorption sites, not to non-adsorptive support surfaces.
The model appears to have been first proposed for carbon monoxide on silica-supported platinum by Brandt et al. (1993). A similar, but independent model was developed by King and co-workers to describe hydrogen adsorption on silica-supported alkali promoted ruthenium, silver-ruthenium and copper-ruthenium bimetallic catalysts. The same group applied the model to CO hydrogenation (Fischer–Tropsch synthesis). Zupanc et al. (2002) subsequently confirmed the same model for hydrogen adsorption on magnesia-supported caesium-ruthenium bimetallic catalysts. Trens et al. (2009) have similarly described CO surface diffusion on carbon-supported Pt particles of varying morphology. | 0 | Theoretical and Fundamental Chemistry |
In anti-tank warfare, spalling through mechanical stress is an intended effect of high-explosive squash head (HESH) anti-tank shells and many other munitions, which may not be powerful enough to pierce the armour of a target. The relatively soft warhead, containing or made of plastic explosive, flattens against the armour plating on tanks and other armoured fighting vehicles (AFVs) and explodes, creating a shock wave that travels through the armour as a compression wave and is reflected at the free surface as a tensile wave breaking (tensile stress/strain fracture) the metal on the inside. The resulting spall is dangerous to crew and equipment, and may result in a partial or complete disablement of a vehicle and/or its crew. Many AFVs are equipped with spall liners inside their armour for protection.
A kinetic energy penetrator, if it can defeat the armour, generally causes spalling within the target as well, which helps to destroy or disable the vehicle and its crew.
An early example of anti-tank weapon intentionally designed to cause spallation instead of penetration is the wz. 35 anti-tank rifle. | 1 | Applied and Interdisciplinary Chemistry |
The unique relationship between the compressibility factor and the reduced temperature, , and the reduced pressure, , was first recognized by Johannes Diderik van der Waals in 1873 and is known as the two-parameter principle of corresponding states. The principle of corresponding states expresses the generalization that the properties of a gas which are dependent on intermolecular forces are related to the critical properties of the gas in a universal way. That provides a most important basis for developing correlations of molecular properties.
As for the compressibility of gases, the principle of corresponding states indicates that any pure gas at the same reduced temperature, , and reduced pressure, , should have the same compressibility factor.
The reduced temperature and pressure are defined by
: and
Here and are known as the critical temperature and critical pressure of a gas. They are characteristics of each specific gas with being the temperature above which it is not possible to liquify a given gas and is the minimum pressure required to liquify a given gas at its critical temperature. Together they define the critical point of a fluid above which distinct liquid and gas phases of a given fluid do not exist.
The pressure-volume-temperature (PVT) data for real gases varies from one pure gas to another. However, when the compressibility factors of various single-component gases are graphed versus pressure along with temperature isotherms many of the graphs exhibit similar isotherm shapes.
In order to obtain a generalized graph that can be used for many different gases, the reduced pressure and temperature, and , are used to normalize the compressibility factor data. Figure 2 is an example of a generalized compressibility factor graph derived from hundreds of experimental PVT data points of 10 pure gases, namely methane, ethane, ethylene, propane, n-butane, i-pentane, n-hexane, nitrogen, carbon dioxide and steam.
There are more detailed generalized compressibility factor graphs based on as many as 25 or more different pure gases, such as the Nelson-Obert graphs. Such graphs are said to have an accuracy within 1–2 percent for values greater than 0.6 and within 4–6 percent for values of 0.3–0.6.
The generalized compressibility factor graphs may be considerably in error for strongly polar gases which are gases for which the centers of positive and negative charge do not coincide. In such cases the estimate for may be in error by as much as 15–20 percent.
The quantum gases hydrogen, helium, and neon do not conform to the corresponding-states behavior and the reduced pressure and temperature for those three gases should be redefined in the following manner to improve the accuracy of predicting their compressibility factors when using the generalized graphs:
: and
where the temperatures are in kelvins and the pressures are in atmospheres. | 0 | Theoretical and Fundamental Chemistry |
German engineers have also devoted special attention to the measurement of the flow in rivers; the Beiträge zur Hydrographie des Königreiches Böhmen (Prague, 1872–1875) of Andreas Rudolf Harlacher contained valuable measurements of this kind, together with a comparison of the experimental results with the formulae of flow that had been proposed up to the date of its publication, and important data were yielded by the gaugings of the Mississippi made for the United States government by Andrew Atkinson Humphreys and Henry Larcom Abbot, by Robert Gordons gaugings of the Irrawaddy River, and by Allen J. C. Cunninghams experiments on the Ganges canal. The friction of water, investigated for slow speeds by Coulomb, was measured for higher speeds by William Froude (1810–1879), whose work is of great value in the theory of ship resistance (Brit. Assoc. Report., 1869), and stream line motion was studied by Professor Osborne Reynolds and by Professor Henry S. Hele-Shaw. | 1 | Applied and Interdisciplinary Chemistry |
The Eastern Analytical Symposium and Exposition is sponsored by the following organizations: the Analytical Division of the American Chemical Society, the American Chemical Society New York and New Jersey Sections, the American Microchemical Society, the Chromatography Forum of Delaware Valley, the Coblentz Society, the New York Microscopical Society, the Society for Applied Spectroscopy's Delaware Valley, New York, and New England Sections, the Association of Laboratory Managers (ALMA), and the New Jersey Association of Forensic Scientists. | 0 | Theoretical and Fundamental Chemistry |
Denatured proteins can exhibit a wide range of characteristics, from loss of solubility to protein aggregation. | 1 | Applied and Interdisciplinary Chemistry |
CoQ is not approved by the U.S. Food and Drug Administration (FDA) for the treatment of any medical condition. However, it is sold as a dietary supplement not subject to the same regulations as medicinal drugs, and is an ingredient in some cosmetics. The manufacture of CoQ is not regulated, and different batches and brands may vary significantly. | 1 | Applied and Interdisciplinary Chemistry |
* 2003: Norman J. Zabusky
* 2002: Andrea Prosperetti
* 2001: John Kim
* 2000: Hassan Aref
* 1999: Eli Reshotko
* 1998: David G. Crighton
* 1997: Marvin Emanuel Goldstein
* 1996: Donald Coles
* 1995: Katepalli R. Sreenivasan
* 1994: Philip G. Saffman
* 1993: Robert Kraichnan
* 1992: William C. Reynolds
* 1991: Steven A. Orszag
* 1990: Tony Maxworthy
* 1989: Chia-Shun Yih
* 1988: Akiva Yaglom
* 1987: John Trevor Stuart
* 1986: Milton Van Dyke
* 1985: Hans W. Liepmann
* 1984: Sir James Lighthill
* 1983: John W. Miles
* 1982: Peter Wegener
* 1981: H. W. Emmons
* 1980: R. Byron Bird
* 1979: Stanley Corrsin
* 1978: Cecil E. Leith, Jr.
* 1977: Y. C. Fung
* 1976: George F. Carrier
* 1975: Russell J. Donnelly
* 1974: J. M. Burgers
* 1973: Chia C. Lin
* 1972: Richard G. Fowler | 1 | Applied and Interdisciplinary Chemistry |
When choosing between inducing transient or stable expression in cells, time frame and experimental goal must be taken into consideration. Transiently transfected cells are often used to study the effects of short-term gene expression, perform RNA interference (RNAi)‑mediated gene silencing, or quickly generate small-scale recombinant proteins. This rapid generation small quantities of recombinant proteins can be applied towards evaluating their potential as drug candidates or examining their integrity of constructs during stages of vector development. Additionally, transient expression can be a useful tool when aiming to optimize selected parameters before undergoing the time-consuming process of scale-up in stably transfected cells. Typically, the cells are harvested within 1-4 days after successful transfection. For even quicker results, replacing DNA with mRNA can result in transient expression within minutes after successful transfection in some systems; this process bypasses translocation to the nucleus and transcription.
If stable, long-term gene expression is desired, stable transfection of cells is more useful. However, since successful integration of a DNA vector into the chromosome is a rare occurrence, this process is more difficult and time-consuming, and is reserved for large-scale protein production, gene therapies, and long-term pharmacology studies. | 1 | Applied and Interdisciplinary Chemistry |
Insertion of a SINE upstream of a coding region may result in exon shuffling or changes to the regulatory region of the gene. Insertion of a SINE into the coding sequence of a gene can have deleterious effects and unregulated transposition can cause genetic disease. The transposition and recombination of SINEs and other active nuclear elements is thought to be one of the major contributions of genetic diversity between lineages during speciation. | 1 | Applied and Interdisciplinary Chemistry |
A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.
In contrast, hydrophobes are not attracted to water and may seem to be repelled by it. Hygroscopics are attracted to water, but are not dissolved by water. | 0 | Theoretical and Fundamental Chemistry |
Masri is the former Palestinian Chapter Chairman of the Young Presidents' Organization (YPO). He was named as a "Global Leader of Tomorrow" by the World Economic Forum. Masri serves on the Board of Trustees of An-Najah National University. Masri is a member of the Deans’ Council of the John F. Kennedy School of Government at Harvard University.
Fortune Magazine ranked Masri #38 on its list of "The World's 50 Greatest Leaders". | 1 | Applied and Interdisciplinary Chemistry |
Eudistomin C is a naturally occurring β-carboline derivative which has been found in the Ascidian, Eudistoma Olivaseum. Eudistomin C is a cytotoxic molecule; this cytotoxicity is achieved by the Eudistomin C binds onto the 40S or 80S Ribosomal subunits, which inhibits the process of protein translation, leading to cell death. There are cells that are resistance to Eudistomin Cs cytotoxicity, and these cells are called Yeast EudiC Resistance mutants (YER). YER mutants have a RPS14A mutation on the cells uS11 gene, which encodes for the cell's 40S ribosomal subunit. This produces the RPS14A 40S Ribosomal subunit which confers a resistance against Eudistomin C, preventing protein translation inhibition. Eudistomin C has also shown antitumor and antiviral properties. The exact mechanism of these properties are unknown, however it is believed that its ability to inhibit protein translation is responsible for its antitumor and antiviral properties. | 1 | Applied and Interdisciplinary Chemistry |
Missiles typically do not have a preferred plane or direction of maneuver and thus have symmetric airfoils. Since the center of pressure for symmetric airfoils is relatively constant for small angle of attack, missile engineers typically speak of the complete center of pressure of the entire vehicle for stability and control analysis. In missile analysis, the center of pressure is typically defined as the center of the additional pressure field due to a change in the angle of attack off of the trim angle of attack.
For unguided rockets the trim position is typically zero angle of attack and the center of pressure is defined to be the center of pressure of the resultant flow field on the entire vehicle resulting from a very small angle of attack (that is, the center of pressure is the limit as angle of attack goes to zero). For positive stability in missiles, the total vehicle center of pressure defined as given above must be further from the nose of the vehicle than the center of gravity. In missiles at lower angles of attack, the contributions to the center of pressure are dominated by the nose, wings, and fins. The normalized normal force coefficient derivative with respect to the angle of attack of each component multiplied by the location of the center of pressure can be used to compute a centroid representing the total center of pressure. The center of pressure of the added flow field is behind the center of gravity and the additional force "points" in the direction of the added angle of attack; this produces a moment that pushes the vehicle back to the trim position.
In guided missiles where the fins can be moved to trim the vehicles in different angles of attack, the center of pressure is the center of pressure of the flow field at that angle of attack for the undeflected fin position. This is the center of pressure of any small change in the angle of attack (as defined above). Once again for positive static stability, this definition of center of pressure requires that the center of pressure be further from the nose than the center of gravity. This ensures that any increased forces resulting from increased angle of attack results in increased restoring moment to drive the missile back to the trimmed position. In missile analysis, positive static margin implies that the complete vehicle makes a restoring moment for any angle of attack from the trim position. | 1 | Applied and Interdisciplinary Chemistry |
Prokaryotic ribosomes begin translation of the mRNA transcript while DNA is still being transcribed. Thus translation and transcription are parallel processes. Bacterial mRNA are usually polycistronic and contain multiple ribosome binding sites. Translation initiation is the most highly regulated step of protein synthesis in prokaryotes.
The rate of translation depends on two factors:
* the rate at which a ribosome is recruited to the RBS
* the rate at which a recruited ribosome is able to initiate translation (i.e. the translation initiation efficiency)
The RBS sequence affects both of these factors. | 1 | Applied and Interdisciplinary Chemistry |
Because the net variation in state properties during a thermodynamic cycle is zero, it forms a closed loop on a PV diagram. A PV diagrams Y axis shows pressure (P) and X axis shows volume (V). The area enclosed by the loop is the work (W') done by the process:
This work is equal to the balance of heat (Q) transferred into the system:
Equation (2) is consistent with the First Law; even though the internal energy changes during the course of the cyclic process, when the cyclic process finishes the system's internal energy is the same as the energy it had when the process began.
If the cyclic process moves clockwise around the loop, then W will be positive, and it represents a heat engine. If it moves counterclockwise, then W will be negative, and it represents a heat pump. | 0 | Theoretical and Fundamental Chemistry |
The KRAB domain had initially been identified in 1988 as a periodic array of leucine residues separated by six amino acids 5’ to the zinc finger region of KOX1/ZNF10 coined heptad repeat of leucines (also known as a leucine zipper). Later, this domain was named in association with the C2H2-Zinc finger proteins Krüppel associated box (KRAB). The KRAB domain is confined to genomes from tetrapod organisms. The KRAB containing C2H2-ZNF genes constitute the largest sub-family of zinc finger genes. More than half of the C2H2-ZNF genes are associated with a KRAB domain in the human genome. They are more prone to clustering and are found in large clusters on the human genome.
The KRAB domain presents one of the strongest repressors in the human genome. Once the KRAB domain was fused to the tetracycline repressor (TetR), the TetR-KRAB fusion proteins were the first engineered drug-inducible repressor that worked in mammalian cells. Two distinct types of KRAB A domains can be structurally and functionally distinguished. Ancestral KRAB A domains present in human PDRM9 proteins are even evolutionary conserved in mussel genomes. Modern KRAB A domain sequences are found in coelacanth latimeria chalumnae and in Lungfish genomes. | 1 | Applied and Interdisciplinary Chemistry |
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