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Medications that contain more than 10% pseudoephedrine are prohibited under the Stimulants Control Law in Japan. | 0 | Theoretical and Fundamental Chemistry |
While the carbamate acetylcholinesterase inhibitors are commonly referred to as "carbamate insecticides" due to their generally high selectivity for insect acetylcholinesterase enzymes over the mammalian versions, the most potent compounds such as aldicarb and carbofuran are still capable of inhibiting mammalian acetylcholinesterase enzymes at low enough concentrations that they pose a significant risk of poisoning to humans, especially when used in large amounts for agricultural applications. Other carbamate based acetylcholinesterase inhibitors are known with even higher toxicity to humans, and some such as T-1123 and EA-3990 were investigated for potential military use as nerve agents. However, since all compounds of this type have a quaternary ammonium group with a permanent positive charge, they have poor blood–brain barrier penetration, and also are only stable as crystalline salts or aqueous solutions, and so were not considered to have suitable properties for weaponisation. | 0 | Theoretical and Fundamental Chemistry |
The inductive effect also plays a vital role in deciding the acidity and basicity of a molecule. Groups having +I effect (Inductive effect) attached to a molecule increases the overall electron density on the molecule and the molecule is able to donate electrons, making it basic. Similarly, groups having -I effect attached to a molecule decreases the overall electron density on the molecule making it electron deficient which results in its acidity. As the number of -I groups attached to a molecule increases, its acidity increases; as the number of +I groups on a molecule increases, its basicity increases. | 0 | Theoretical and Fundamental Chemistry |
A settling chamber where the two phases separate by static decantation. Coalescence plates facilitate the separation of the emulsion into two phases (heavy and light). The two phases then pass to continuous stages by overflowing the light phase and heavy phase weirs. The height of the heavy phase weir can be adjusted in order to position the heavy/light interphase in the settling chamber based on the density of each one of the phases.
The settler is a calm pool downstream of the mixer where the liquids are allowed to separate by gravity. The liquids are then removed separately from the end of the mixer. | 0 | Theoretical and Fundamental Chemistry |
Recently, there has been an interest in magnetic surface plasmons. These require materials with large negative magnetic permeability, a property that has only recently been made available with the construction of metamaterials. | 0 | Theoretical and Fundamental Chemistry |
The nonribosomal code refers to key amino acid residues and their positions within the primary sequence of an adenylation domain of a nonribosomal peptide synthetase used to predict substrate specificity and thus (partially) the final product. Analogous to the nonribosomal code is prediction of peptide composition by DNA/RNA codon reading, which is well supported by the central dogma of molecular biology and accomplished using the genetic code simply by following the DNA codon table or RNA codon table. However, prediction of natural product/secondary metabolites by the nonribosomal code is not as concrete as DNA/RNA codon-to-amino acid and much research is still needed to have a broad-use code. The increasing number of sequenced genomes and high-throughput prediction software has allowed for better elucidation of predicted substrate specificity and thus natural products/secondary metabolites. Enzyme characterization by, for example, ATP-pyrophosphate exchange assays for substrate specificity, in silico substrate-binding pocket modelling and structure-function mutagenesis (in vitro tests or in silico modelling) helps support predictive algorithms. Much research has been done on bacteria and fungi, with prokaryotic bacteria having easier-to-predict products.
The nonribosomal peptide synthetase (NRPS), a multi-modular enzyme complex, minimally contains repeating, tri-domains (adenylation (A), peptidyl carrier protein (PCP) and lastly condensation(C)). The adenylation domain (A) is the focus for substrate specificity since it is the initiating and substrate recognition domain. In one example, adenylation substrate-binding pocket (defined by 10 residue within) alignments led to clusters giving rise to defined specificity (i.e. the residues of the enzyme pocket can predict nonribosomal peptide sequence). In silico mutations of substrate-determining residues also led to varying or relaxed specificity. Additionally, the NRPS collinearity principle/rule dictates that given the order of adenylation domains (and substrate-specificity code) throughout the NRPS one can predict the amino acid sequence of the produced small peptide. NRPS, NRPS-like or NRPS-PKS complexes also exist and have domain variations, additions and/or exclusions. | 1 | Applied and Interdisciplinary Chemistry |
According to the main source, Ibn Hayyan, Ziryab had eight sons and two daughters. Five of the sons and both daughters became musicians of some prominence. These children kept their father's music school alive, but the female slave singers he trained also were regarded as reliable sources for his repertoire in the following generation. | 1 | Applied and Interdisciplinary Chemistry |
Since 1978, the institute has operated a nationwide air quality monitoring network. Sponsored by the Central Pollution Control Board (CPCB) since 1990. Receptor modelling techniques are used. CSIR-NEERI is involved in the design and development of air pollution control systems.
The institute has also developed a water purification system called NEERI ZAR. In the 1960s and 1970s, the Institute developed guidelines for deflouridation techniques. They have sometimes formed a departure point for the development of other techniques. The Institute tests samples for research on deflouridation and the measurement of particulate matter in air.
The institute has been entrusted by the courts to provide an inspection of the current environmental and legal framework. | 1 | Applied and Interdisciplinary Chemistry |
Deoxycytidine monophosphate (dCMP), also known as deoxycytidylic acid or deoxycytidylate in its conjugate acid and conjugate base forms, respectively, is a deoxynucleotide, and one of the four monomers that make up DNA. In a DNA double helix, it will base pair with deoxyguanosine monophosphate. | 1 | Applied and Interdisciplinary Chemistry |
Fibrous proteins, such as proteins involved in Alzheimer's disease and prion proteins fulfil the requirements for UV LD in that they are a class of long, thin molecules. In addition, cytoskeletal proteins can also be measured using LD. | 0 | Theoretical and Fundamental Chemistry |
A primordial element is a chemical element with at least one primordial nuclide. There are 251 stable primordial nuclides and 35 radioactive primordial nuclides, but only 80 primordial stable elements—hydrogen through lead, atomic numbers 1 to 82, with the exceptions of technetium (43) and promethium (61)—and three radioactive primordial elements—bismuth (83), thorium (90), and uranium (92). If plutonium (94) turns out to be primordial (specifically, the long-lived isotope Pu), then it would be a fourth radioactive primordial, though practically speaking it would still be more convenient to produce synthetically. Bismuth's half-life is so long that it is often classed with the 80 primordial stable elements instead, since its radioactivity is not a cause for serious concern. The number of elements is smaller than the number of nuclides, because many of the primordial elements are represented by multiple isotopes. See chemical element for more information. | 0 | Theoretical and Fundamental Chemistry |
Ketones containing alkene and alkyne units are often called unsaturated ketones. The most widely used member of this class of compounds is methyl vinyl ketone, , which is useful in the Robinson annulation reaction. Lest there be confusion, a ketone itself is a site of unsaturation; that is, it can be hydrogenated. | 0 | Theoretical and Fundamental Chemistry |
Dexmethylphenidate, sold under the brand name Focalin among others, is a potent central nervous system (CNS) stimulant used to treat attention deficit hyperactivity disorder (ADHD) in those over the age of five years. It is taken by mouth. The immediate release formulation lasts up to five hours while the extended release formulation lasts up to twelve hours. It is the more active enantiomer of methylphenidate.
Common side effects include abdominal pain, loss of appetite, and fever. Serious side effects may include abuse, psychosis, sudden cardiac death, mania, anaphylaxis, seizures, and dangerously prolonged erection. Safety during pregnancy and breastfeeding is unclear. Dexmethylphenidate is a central nervous system (CNS) stimulant. How it works in ADHD is unclear.
Dexmethylphenidate was approved for medical use in the United States in 2001. It is available as a generic medication. In 2021, it was the 121st most commonly prescribed medication in the United States, with more than 4million prescriptions. | 0 | Theoretical and Fundamental Chemistry |
In the seventh chapter discusses qualities such as color and taste as a function of heat, time, object and subject. Kanada dedicates a significant number of Sutras to his theory and importance of measurement. | 1 | Applied and Interdisciplinary Chemistry |
Approximately 95% of hydroxylamine is used in the synthesis of cyclohexanone oxime, a precursor to Nylon 6. The treatment of this oxime with acid induces the Beckmann rearrangement to give caprolactam (3). The latter can then undergo a ring-opening polymerization to yield Nylon 6. | 0 | Theoretical and Fundamental Chemistry |
* Budget analyses
*Parameter estimation
* Scaling in time and space
* Data assimilation
* Quality control of data – see for example Double mass analysis | 1 | Applied and Interdisciplinary Chemistry |
Higher temperatures can also affect the chemical stability of the polymer and thus its use properties. If a polymer's ceiling temperature is exceeded, it will partially revert to its monomers, destroying its usability. More generally, polymer degradation also occurs during devolatilization, limiting the temperature and residence time available for the process. | 1 | Applied and Interdisciplinary Chemistry |
The boiling point is an important property because it determines the speed of evaporation. Small amounts of low-boiling-point solvents like diethyl ether, dichloromethane, or acetone will evaporate in seconds at room temperature, while high-boiling-point solvents like water or dimethyl sulfoxide need higher temperatures, an air flow, or the application of vacuum for fast evaporation.
*Low boilers: boiling point below 100 °C (boiling point of water)
*Medium boilers: between 100 °C and 150 °C
*High boilers: above 150 °C | 1 | Applied and Interdisciplinary Chemistry |
After serious opposition about plans and negotiations between Mongolia with Japan and the United States of America to build nuclear-waste facilities in Mongolia, Mongolia stopped all negotiations in September 2011. These negotiations had started after U.S. Deputy Secretary of Energy Daniel Poneman visited Mongolia in September 2010. Talks took place in Washington, D.C. between officials of Japan, the United States, and Mongolia in February 2011. After this the United Arab Emirates (UAE), which wanted to buy nuclear fuel from Mongolia, joined in the negotiations. The talks were kept secret and, although the Mainichi Daily News reported on them in May, Mongolia officially denied the existence of these negotiations. However, alarmed by this news, Mongolian citizens protested against the plans and demanded the government withdraw the plans and disclose information. The Mongolian President Tsakhiagiin Elbegdorj issued a presidential order on September 13 banning all negotiations with foreign governments or international organizations on nuclear-waste storage plans in Mongolia. The Mongolian government has accused the newspaper of distributing false claims around the world. After the presidential order, the Mongolian president fired the individual who was supposedly involved in these conversations. | 0 | Theoretical and Fundamental Chemistry |
As mentioned, negative resists are photopolymers that become insoluble upon exposure to radiation. They have found a variety of commercial applications, especially in the area of designing and printing small chips for electronics. A characteristic found in most negative tone resists is the presence of multifunctional branches on the polymers used. Radiation of the polymers in the presence of an initiator results in the formation of a chemically resistant network polymer. A common functional group used in negative resists is epoxy functional groups. An example of a widely used polymer of this class is SU-8. SU-8 was one of the first polymers used in this field, and found applications in wire board printing. In the presence of a cationic photoinitiator photopolymer, SU-8 forms networks with other polymers in solution. Basic scheme shown below.
SU-8 is an example of an intramolecular photopolymerization forming a matrix of cross-linked material. Negative resists can also be made using co-polymerization. In the event that two different monomers, or oligomers, are in solution with multiple functionalities, it is possible for the two to polymerize and form a less soluble polymer.
Manufacturers also use light curing systems in OEM assembly applications such as specialty electronics or medical device applications. | 0 | Theoretical and Fundamental Chemistry |
Many definitions that describe a specific conformer (IUPAC Gold Book) exist, developed by William Klyne and Vladimir Prelog, constituting their Klyne–Prelog system of nomenclature:
* a torsion angle of ±60° is called gauche
* a torsion angle between 0° and ±90° is called syn (s)
* a torsion angle between ±90° and 180° is called anti (a)
* a torsion angle between 30° and 150° or between –30° and –150° is called clinal
* a torsion angle between 0° and 30° or 150° and 180° is called periplanar (p)
* a torsion angle between 0° to 30° is called synperiplanar or syn- or cis-conformation (sp)
* a torsion angle between 30° to 90° and –30° to –90° is called synclinal or gauche or skew (sc)
* a torsion angle between 90° to 150°, and –90° to –150° is called anticlinal (ac)
* a torsion angle between ±150° to 180° is called antiperiplanar or anti or trans (ap).
Torsional strain results from resistance to twisting about a bond. | 0 | Theoretical and Fundamental Chemistry |
An enzyme inducer is a type of drug that increases the metabolic activity of an enzyme either by binding to the enzyme and activating it, or by increasing the expression of the gene coding for the enzyme. It is the opposite of an enzyme repressor. There are specific types of enzyme inducers that create cytoprotective pathways that play a role in prevention and treatment of cancer and other diseases including cardiovascular disease and neurodegenerative diseases. Enzyme inducers can be either naturally occurring or synthetically made. | 1 | Applied and Interdisciplinary Chemistry |
RapiGest SF, the brand-name for sodium 3-[(2-methyl-2-undecyl-1,3-dioxolan-4-yl)methoxy]-1-propanesulfonate, is an acid-cleavable anionic detergent marketed by Waters Corporation and AOBIOUS INC. | 0 | Theoretical and Fundamental Chemistry |
There are two types of overlayers: commensurate and incommensurate. In the former the substrate-adsorbate interaction tends to dominate over any lateral adsorbate-adsorbate interaction, while in the latter the adsorbate-adsorbate interactions are of similar magnitude to those between adsorbate and substrate. | 0 | Theoretical and Fundamental Chemistry |
:V09FX01 Technetium (Tc) pertechnetate
:V09FX02 Sodium iodide (I)
:V09FX03 Sodium iodide (I)
:V09FX04 Sodium iodide (I) | 1 | Applied and Interdisciplinary Chemistry |
Ammonium perrhenate may be prepared from virtually all common sources of rhenium. The metal, oxides, and sulfides can be oxidized with nitric acid and the resulting solution treated with aqueous ammonia. Alternatively an aqueous solution of ReO can be treated with ammonia followed by crystallisation. | 0 | Theoretical and Fundamental Chemistry |
Pourbaix diagrams have many applications in different fields dealing with e.g., corrosion problems, geochemistry, and environmental sciences. Using the Pourbaix diagram correctly will help shedding light not only on the nature of the species present in aqueous solution, or in the solid phases, but may also help to understand the reaction mechanism. | 0 | Theoretical and Fundamental Chemistry |
In addition to the method of proton extrusion discussed above, it is believed that the general method of cellular respiration is different in obligate alkaliphiles as compared to neutrophiles. Generally, ATP production operates by establishing a proton gradient (greater H+ concentration outside the membrane) and a transmembrane electrical potential (with a positive charge outside the membrane). However, since alkaliphiles have a reversed pH gradient, it would seem that ATP production—which is based on a strong proton-motive force – would be severely reduced. However, the opposite is true. It has been proposed that while the pH gradient has been reversed, the transmembrane electrical potential is greatly increased. This increase in charge causes the production of greater amounts of ATP by each translocated proton when driven through an ATPase. Research in this area is ongoing. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, an acyl group is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. It contains a double-bonded oxygen atom and an organyl group () or hydrogen in the case of formyl group (). In organic chemistry, the acyl group (IUPAC name alkanoyl if the organyl group is alkyl) is usually derived from a carboxylic acid, in which case it has the formula , where R represents an organyl group or hydrogen. Although the term is almost always applied to organic compounds, acyl groups can in principle be derived from other types of acids such as sulfonic acids and phosphonic acids. In the most common arrangement, acyl groups are attached to a larger molecular fragment, in which case the carbon and oxygen atoms are linked by a double bond. | 0 | Theoretical and Fundamental Chemistry |
Hydrostatic tests are conducted under the constraints of either the industrys or the customers specifications, or may be required by law. The vessel is filled with a nearly incompressible liquid – usually water or oil – pressurised to test pressure, and examined for leaks or permanent changes in shape. Red or fluorescent dyes may be added to the water to make leaks easier to see. The test pressure is always considerably higher than the operating pressure to give a factor of safety. This factor of safety is typically 166.66%, 143% or 150% of the designed working pressure, depending on the regulations that apply. For example, if a cylinder was rated to DOT-2015 PSI (approximately 139 bar), it would be tested at around 3360 PSI (approximately 232 bar).
Water is commonly used because it is cheap and easily available, and is usually harmless to the system to be tested. Hydraulic fluids and oils may be specified where contamination with water could cause problems. These fluids are nearly incompressible, therefore requiring relatively little work to develop a high pressure, and is therefore also only able to release a small amount of energy in case of a failure - only a small volume will escape under high pressure if the container fails. If high pressure gas were used, then the gas would expand to V=(nRT)/p with its compressed volume resulting in an explosion, with the attendant risk of damage or injury.
Small pressure vessels are normally tested using a water jacket test. The vessel is visually examined for defects and then placed in a container filled with water, and in which the change in volume of the vessel can be measured, usually by monitoring the water level in a calibrated tube. The vessel is then pressurised for a specified period, usually 30 or more seconds, and if specified, the expansion will be measured by reading off the amount of liquid that has been forced into the measuring tube by the volume increase of the pressurised vessel. The vessel is then depressurised, and the permanent volume increase due to plastic deformation while under pressure () is measured by comparing the final volume in the measuring tube with the volume before pressurisation.
A leak will give a similar result to permanent set, but will be detectable by holding the volume in the pressurised vessel by closing the inlet valve for a period before depressurising, as the pressure will drop steadily during this period if there is a leak. In most cases a permanent set that exceeds the specified maximum will indicate failure. A leak may also be a failure criterion, but it may be that the leak is due to poor sealing of the test equipment. If the vessel fails, it will normally go through a condemning process marking the cylinder as unsafe.
The information needed to specify the test is stamped onto the cylinder. This includes the design standard, serial number, manufacturer, and manufacture date. After testing, the vessel or its nameplate will usually be stamp marked with the date of the successful test, and the test facility's identification mark.
A simpler test, that is also considered a hydrostatic test but can be performed by anyone who has a garden hose, is to pressurise the vessel by filling it with water and to physically examine the outside for leaks. This type of test is suitable for containers such as boat fuel tanks, which are not pressure vessels but must work under the hydrostatic pressure of the contents. A hydrostatic test head is usually specified as a height above the tank top. The tank is pressurised by filling water to the specified height through a temporary standpipe if necessary. It may be necessary to seal vents and other outlets during the test. | 1 | Applied and Interdisciplinary Chemistry |
The Rayleigh–Taylor instability is another application of hydrodynamic stability and also occurs between two fluids but this time the densities of the fluids are different. Due to the difference in densities, the two fluids will try to reduce their combined potential energy. The less dense fluid will do this by trying to force its way upwards, and the more dense fluid will try to force its way downwards. Therefore, there are two possibilities: if the lighter fluid is on top the interface is said to be stable, but if the heavier fluid is on top, then the equilibrium of the system is unstable to any disturbances of the interface. If this is the case then both fluids will begin to mix. Once a small amount of heavier fluid is displaced downwards with an equal volume of lighter fluid upwards, the potential energy is now lower than the initial state, therefore the disturbance will grow and lead to the turbulent flow associated with Rayleigh–Taylor instabilities.
This phenomenon can be seen in interstellar gas, such as the Crab Nebula. It is pushed out of the Galactic plane by magnetic fields and cosmic rays and then becomes Rayleigh–Taylor unstable if it is pushed past its normal scale height. This instability also explains the mushroom cloud which forms in processes such as volcanic eruptions and atomic bombs.
Rayleigh–Taylor instability has a big effect on the Earth's climate. Winds that come from the coast of Greenland and Iceland cause evaporation of the ocean surface over which they pass, increasing the salinity of the ocean water near the surface, and making the water near the surface denser. This then generates plumes which drive the ocean currents. This process acts as a heat pump, transporting warm equatorial water North. Without the ocean overturning, Northern Europe would likely face drastic drops in temperature. | 1 | Applied and Interdisciplinary Chemistry |
Persephin has been found to be less potent than other members of the GDNF family. It has been found to support the survival and morphological differentiation of tyrosine hydroxylase immunoreactive neurons, although less so than both GDNF and neurturin. The mRNA levels of persephin in developing neurons has been low compared to other neurotrophic factors, but relatively higher levels of persephin mRNA have been found in embryonic neurons.
Similarly to the other members of the GDNF family of ligands, persephin uses a receptor that consists of the tyrosine kinase signaling component Ret and a unit of glycosylphosphatidylinsitol (GPI)-anchored receptor (GFRα). Persephin specifically binds to GFRα4.
Persephin acts on both neurons in the CNS and PNS, but also has the ability to act as a renal ramogen. | 1 | Applied and Interdisciplinary Chemistry |
Westinghouse continued its manufacturing and research at the plant after the war. In 1964, Westinghouse was issued a permit from United States Atomic Energy Commission to conduct research using thorium and uranium to produce thorium-tungsten wire. In 1983, Westinghouse sold its lamp manufacturing operation to North American Phillips Lighting Corporation. The manufacturing of thorium-tungsten wire was continued at the plant until 1984. In 1986, North American Phillips Lighting Corporation returned the control of the plant back to Westinghouse. | 1 | Applied and Interdisciplinary Chemistry |
The nano guitar is a microscopically small carved guitar. It was developed by Dustin W. Carr in 1997, under the direction of Professor Harold G. Craighead, in the Cornell Nanofabrication Facility. The idea came about as a fun way to illustrate nanotechnology, and captured popular attention. It is disputed as to whether the nano guitar should be classified as a guitar, but it is the common opinion that it is in fact a guitar. | 0 | Theoretical and Fundamental Chemistry |
An increased plasma transferrin level is often seen in patients with iron deficiency anemia, during pregnancy, and with the use of oral contraceptives, reflecting an increase in transferrin protein expression. When plasma transferrin levels rise, there is a reciprocal decrease in percent transferrin iron saturation, and a corresponding increase in total iron binding capacity in iron deficient states
A decreased plasma transferrin level can occur in iron overload diseases and protein malnutrition. An absence of transferrin results from a rare genetic disorder known as atransferrinemia, a condition characterized by anemia and hemosiderosis in the heart and liver that leads to heart failure and many other complications as well as to H63D syndrome.
Studies reveal that a transferrin saturation (serum iron concentration ÷ total iron binding capacity) over 60 percent in men and over 50 percent in women identified the presence of an abnormality in iron metabolism (Hereditary hemochromatosis, heterozygotes and homozygotes) with approximately 95 percent accuracy. This finding helps in the early diagnosis of Hereditary hemochromatosis, especially while serum ferritin still remains low. The retained iron in Hereditary hemochromatosis is primarily deposited in parenchymal cells, with reticuloendothelial cell accumulation occurring very late in the disease. This is in contrast to transfusional iron overload in which iron deposition occurs first in the reticuloendothelial cells and then in parenchymal cells. This explains why ferritin levels remain relative low in Hereditary hemochromatosis, while transferrin saturation is high.
Transferrin and its receptor have been shown to diminish tumour cells when the receptor is used to attract antibodies. | 1 | Applied and Interdisciplinary Chemistry |
Differences in the abundance of stable isotopes among natural materials are usually very small (natural differences in the ratio of rare to common isotope are almost always below 0.1%, and sometimes much smaller). Nevertheless, these very small differences can record meaningful biological and geological processes. To facilitate comparison of these small but meaningful differences, isotope abundances in natural materials are often reported relative to isotope abundances in designated standards. The convention for reporting the measured difference between a sample and a standard is called "delta notation." For example, imagine an element X for which we wish to compare the rare, heavy stable isotope with atomic mass A (X) to the light, common isotope with atomic mass B (X). The abundance of X and X in any given material is reported with the notation δX. δX for the sample material is calculated as follows:
:R = (total amount of X)/(total amount of X)
:δX = (R − R)/R
δ values are most commonly reported in parts per thousand, commonly referred to in isotope chemistry as per mille and represented by the symbol ‰. To report δ values in per mille, the δ value as calculated above should be multiplied by 1000:
:δX (‰) = ((R − R)/R) * 1000 | 0 | Theoretical and Fundamental Chemistry |
If the β phase is replaced by a flat rigid surface, as shown in Figure 5, then β = π, and the second net force equation simplifies to the Young equation,
which relates the surface tensions between the three phases: solid, liquid and gas. Subsequently, this predicts the contact angle of a liquid droplet on a solid surface from knowledge of the three surface energies involved. This equation also applies if the "gas" phase is another liquid, immiscible with the droplet of the first "liquid" phase. | 0 | Theoretical and Fundamental Chemistry |
In hydrodynamics, the Perrin friction factors are multiplicative adjustments to the translational and rotational friction of a rigid spheroid, relative to the corresponding frictions in spheres of the same volume. These friction factors were first calculated by Jean-Baptiste Perrin.
These factors pertain to spheroids (i.e., to ellipsoids of revolution), which are characterized by the axial ratio p = (a/b), defined here as the axial semiaxis a
(i.e., the semiaxis along the axis of revolution) divided by the equatorial semiaxis b. In prolate spheroids, the axial ratio p > 1 since the axial semiaxis is longer than the equatorial semiaxes. Conversely, in oblate spheroids, the axial ratio p < 1 since the axial semiaxis is shorter than the equatorial semiaxes. Finally, in spheres, the axial ratio p = 1, since all three semiaxes are equal in length.
The formulae presented below assume "stick" (not "slip") boundary conditions, i.e., it is assumed that the velocity of the fluid is zero at the surface of the spheroid. | 1 | Applied and Interdisciplinary Chemistry |
Friction stir processing can also be used to improve the microstructural properties of powder metal objects. In particular, when dealing with aluminium powder metal alloys, the aluminium oxide film on the surface of each granule is detrimental to the ductility, fatigue properties and fracture toughness of the workpiece. While conventional techniques for removing this film include forging and extrusion, friction stir processing is suited for situations where localized treatment is desired. | 1 | Applied and Interdisciplinary Chemistry |
Consider the two equilibria, in aqueous solution, between the copper(II) ion, Cu and ethylenediamine (en) on the one hand and methylamine, MeNH on the other.
In the first reaction the bidentate ligand ethylene diamine forms a chelate complex with the copper ion. Chelation results in the formation of a five-membered ring. In the second reaction the bidentate ligand is replaced by two monodentate methylamine ligands of approximately the same donor power, meaning that the enthalpy of formation of Cu–N bonds is approximately the same in the two reactions. Under conditions of equal copper concentrations and when the concentration of methylamine is twice the concentration of ethylenediamine, the concentration of the bidentate complex will be greater than the concentration of the complex with 2 monodentate ligands. The effect increases with the number of chelate rings so the concentration of the EDTA complex, which has six chelate rings, is much higher than a corresponding complex with two monodentate nitrogen donor ligands and four monodentate carboxylate ligands. Thus, the phenomenon of the chelate effect is a firmly established empirical fact: under comparable conditions, the concentration of a chelate complex will be higher than the concentration of an analogous complex with monodentate ligands.
The thermodynamic approach to explaining the chelate effect considers the equilibrium constant for the reaction: the larger the equilibrium constant, the higher the concentration of the complex.
When the analytical concentration of methylamine is twice that of ethylenediamine and the concentration of copper is the same in both reactions, the concentration [Cu(en)] is much higher than the concentration [Cu(MeNH)] because
The difference between the two stability constants is mainly due to the difference in the standard entropy change, ΔS. In the reaction with the chelating ligand there are two particles on the left and one on the right, whereas in equation with the monodentate ligand there are three particles on the left and one on the right. This means that less entropy of disorder is lost when the chelate complex is formed than when the complex with monodentate ligands is formed. This is one of the factors contributing to the entropy difference. Other factors include solvation changes and ring formation. Some experimental data to illustrate the effect are shown in the following table.
These data show that the standard enthalpy changes are indeed approximately equal for the two reactions and that the main reason why the chelate complex is so much more stable is that the standard entropy term is much less unfavourable, indeed, it is favourable in this instance. In general it is difficult to account precisely for thermodynamic values in terms of changes in solution at the molecular level, but it is clear that the chelate effect is predominantly an effect of entropy. Other explanations, including that of Schwarzenbach, are discussed in Greenwood and Earnshaw.
The chelate effect increases as the number of chelate rings increases. For example, the complex [Ni(dien))] is more stable than the complex [Ni(en))]; both complexes are octahedral with six nitrogen atoms around the nickel ion, but dien (diethylenetriamine, 1,4,7-triazaheptane) is a tridentate ligand and en is bidentate. The number of chelate rings is one less than the number of donor atoms in the ligand. EDTA (ethylenediaminetetracetic acid) has six donor atoms so it forms very strong complexes with five chelate rings. Ligands such as DTPA, which have eight donor atoms are used to form complexes with large metal ions such as lanthanide or actinide ions which usually form 8- or 9-coordinate complexes.
5-membered and 6-membered chelate rings give the most stable complexes. 4-membered rings are subject to internal strain because of the small inter-bond angle is the ring. The chelate effect is also reduced with 7- and 8- membered rings, because the larger rings are less rigid, so less entropy is lost in forming them. | 0 | Theoretical and Fundamental Chemistry |
Ion pairs are formed when a cation and anion, which are present in a solution of an ionizable substance, come together to form a discrete chemical species. There are three distinct types of ion pairs, depending on the extent of solvation of the two ions. For example, magnesium sulfate exists as both contact and solvent-shared ion-pairs in seawater.
In the schematic representation above, the circles represent spheres. The sizes are arbitrary and not necessarily similar as illustrated. The cation is coloured red and the anion is coloured blue. The green area represents solvent molecules in a primary solvation shell; secondary solvation is ignored. When both ions have a complete primary solvation sphere, the ion pair may be termed fully solvated (separated ion pair, SIP). When there is about one solvent molecule between cation and anion, the ion pair may be termed solvent-shared. Lastly, when the ions are in contact with each other, the ion pair is termed a contact ion pair (CIP). Even in a contact ion pair, however, the ions retain most of their solvation shell. The nature of this solvation shell is generally not known with any certainty. In aqueous solution and in other donor solvents, metal cations are surrounded by between 4 and 9 solvent molecules in the primary solvation shell,
An alternative name for a solvent-shared ion pair is an outer-sphere complex. This usage is common in coordination chemistry and denotes a complex between a solvated metal cation and an anion. Similarly, a contact ion pair may be termed an inner-sphere complex. The essential difference between the three types is the closeness with which the ions approach each other: fully solvated > solvent-shared > contact. With fully solvated and solvent-shared ion pairs the interaction is primarily electrostatic, but in a contact ion pair some covalent character in the bond between cation and anion is also present.
An ion triplet may be formed from one cation and two anions or from one anion and two cations. Higher aggregates, such as a tetramer , may be formed.
Ternary ion associates involve the association of three species. Another type, named intrusion ion pair, has also been characterized. | 0 | Theoretical and Fundamental Chemistry |
In steady state, the third order virial equation becomes
If the axis of rotation is chosen in direction, the equation becomes | 1 | Applied and Interdisciplinary Chemistry |
To understand the how the MRI works, we must first understand the conditions inside a perfectly conducting fluid in motion. This is often a good approximation to astrophysical gases. In the presence of a magnetic field a moving conductor responds by trying to eliminate the Lorentz force on the free charges. The magnetic force acts in such a way as to locally rearrange these charges to produce an internal electric field of In this way, the direct Lorentz force on the charges vanishes. (Alternatively, the electric field in the local rest frame of the moving charges vanishes.) This induced electric field can now itself induce further changes in the magnetic field according to Faraday's law,
Another way to write this equation is that if in time the fluid makes a displacement then the magnetic field changes by
The equation of a magnetic field in a perfect conductor in motion has a special property: the combination of Faraday induction and zero Lorentz force makes the field lines behave as though they were painted, or "frozen," into the fluid. In particular, if is initially nearly constant and is a divergence-free displacement, then our equation reduces to
because of the vector calculus identity
Out of these 4 terms, is one of Maxwell's equations. By the divergence-free assumption, . because B is assumed to be nearly constant. Equation shows that changes only when there is a shearing displacement along the field line.
To understand the MRI, it is sufficient to consider the case in which is uniform in vertical direction, and varies as Then
where it is understood that the real part of this equation expresses its physical content. (If is proportional to for example, then is proportional to )
A magnetic field exerts a force per unit volume on an electrically neutral, conducting fluid equal to Amperes circuital law gives because Maxwells correction is neglected in the MHD approximation. The force per unit volume becomes
where we have used the same vector calculus identity. This equation is fully general, and makes no assumptions about the strength or direction of the magnetic field.
The first term on the right is analogous to a pressure gradient. In our problem it may be neglected because it exerts no force in the plane of the disk, perpendicular to The second term acts like a magnetic tension force, analogous to a taut string. For a small disturbance it exerts an acceleration given by force divided by mass, or equivalently, force per unit volume divided by mass per unit volume:
Thus, a magnetic tension force gives rise to a return force which is directly proportional to the displacement. This means that the oscillation frequency for small displacements in the plane of rotation of a disk with a uniform magnetic field in the vertical direction satisfies an equation ("dispersion relation") exactly analogous to equation , with the "spring constant"
As before, if there is an exponentially growing root of this equation for wavenumbers satisfying
This corresponds to the MRI.
Notice that the magnetic field appears in equation only as the product Thus, even if is very small, for very large wavenumbers this magnetic tension can be important. This is why the MRI is so sensitive to even very weak magnetic fields: their effect is amplified by multiplication by Moreover, it can be shown that MRI is present regardless of the magnetic field geometry, as long as the field is not too strong.
In astrophysics, one is generally interested in the case for which the disk is supported by rotation against the gravitational attraction of a central mass. A balance between the Newtonian gravitational force and the radial centripetal force immediately gives
where is the Newtonian gravitational constant, is the central mass, and is radial location in the disk. Since this so-called Keplerian disk is unstable to the MRI . Without a weak magnetic field, the flow would be stable.
For a Keplerian disk, the maximum growth rate is which occurs at a wavenumber satisfying
is very rapid, corresponding to an amplification factor of more than 100 per rotation period.
The nonlinear development of the MRI into fully developed turbulence may be followed via large scale numerical computation. | 1 | Applied and Interdisciplinary Chemistry |
One way to visualize the internal standard method is to create one calibration curve that doesn't use the method and one calibration curve that does. Suppose there are known concentrations of nickel in a set of calibration solutions: 0 ppm, 1.6 ppm, 3.2 ppm, 4.8 ppm, 6.4 ppm, and 8 ppm. Each solution also has 5 ppm yttrium to act as an internal standard. If these solutions are measured using ICP-OES, the intensity of the yttrium signal should be consistent across all solutions. If not, the intensity of the nickel signal is likely imprecise as well.
The calibration curve that does not use the internal standard method ignores the uncertainty between measurements. The coefficient of determination (R) for this plot is 0.9985.
In the calibration curve that uses the internal standard, the y-axis is the ratio of the nickel signal to the yttrium signal. This ratio is unaffected by uncertainty in the nickel measurements, as it should affect the yttrium measurements in the same way. This results in a higher R, 0.9993. | 0 | Theoretical and Fundamental Chemistry |
The Greek Ministry of Finance has now installed a green roof on the Treasury in Constitution Square in Athens. The so-called "oikostegi" (Greek – oiko, , meaning building-ecological, and stegi, pronounced staygee, meaning roof-abode-shelter) was inaugurated in September 2008. Studies of the thermodynamics of the roof in September 2008 concluded that the thermal performance of the building was significantly affected by the installation. In further studies, in August 2009, energy savings of 50% were observed for air conditioning in the floor directly below the installation. The ten-floor building has a total floor space of . The oikostegi covers , equalling 52% of the roof space and 8% of the total floor space. Despite this, energy savings totalling €5,630 per annum were recorded, which translates to a 9% saving in air conditioning and a 4% saving in heating bills for the whole building. An additional observation and conclusion of the study was that the thermodynamic performance of the oikostegi had improved as biomass was added over the 12 months between the first and second study. This suggests that further improvements will be observed as the biomass increases still further. The study also stated that while measurements were being made by thermal cameras, a plethora of beneficial insects were observed on the roof, such as butterflies, honey bees and ladybirds. Obviously this was not the case before installation. Finally, the study suggested that both the micro-climate and biodiversity of Constitution Square, in Athens, Greece had been improved by the oikostegi. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, racemization is a conversion, by heat or by chemical reaction, of an optically active compound into a racemic (optically inactive) form. This creates a 1:1 molar ratio of enantiomers and is referred to as a racemic mixture (i.e. contain equal amount of (+) and (−) forms). Plus and minus forms are called Dextrorotation and levorotation. The D and L enantiomers are present in equal quantities, the resulting sample is described as a racemic mixture or a racemate. Racemization can proceed through a number of different mechanisms, and it has particular significance in pharmacology as different enantiomers may have different pharmaceutical effects. | 0 | Theoretical and Fundamental Chemistry |
Okano’s group expanded on their success by using different modifiers to enhance hydrophobicity through the attachment of butyl methacrylate (BMA), a hydrophobic comonomer. For simplification the resultant polymer has been labeled as IBc (isopropylacrylamide butyl methacrylate copolymer). The polymers were synthesized using radical telomerization with varying BMA content. Where pure PNIPAAm was unable to resolve hydrophobic steroids at any temperature, IBc-grafted silica stationary phases were able to resolve steroid peaks with increasingly retarded retention times in correlation to both increased BMA content and increased temperature. They went on to develop a method to separate phenylthiohydantoin(PTH)-amino acids using their IBc stationary phase with a stronger emphasis of implementing environmentally friendly conditions using a purely aqueous phase in HPLC. Another group separated catechins using PNIPAAm. | 0 | Theoretical and Fundamental Chemistry |
Unlike conventional composites, which typically fail catastrophically, RCCM fail incrementally because of the non-linear deformation phase and the multiplicity of joints and links. These results matched finite-element simulations with finely-meshed rigid body models. In addition to convergence to the observed coordinated buckling mode, these simulations accurately predict the relative strength scaling observed in load test experiments. These results are consistent with the observation that open-cell lattice materials fail through micro-structural strut bending failures with σmax ∝. The simulations also suggest that the coordinated buckling phenomenon as well as the modulus measurements are not dominated by edge effects, with minimal influence on overall results beyond characteristic lengths exceeding several units.
Varying the locations of more and less rigid elements can trigger pure axial compression, simple uni-directional Euler buckling and complex buckling. | 0 | Theoretical and Fundamental Chemistry |
Aggregate exposures to consumers (direct and indirect dermal contact, ingestion, and inhalation) have been estimated to be 1.42 ug/Kg bw/day.
Calcium xylene sulfonate and sodium cumene sulfonate have been shown to cause temporary, slight eye irritation in animals. Studies have not found hydrotropes to be mutagenic, carcinogenic or have reproductive toxicity. | 0 | Theoretical and Fundamental Chemistry |
Gamma rays detected in a spectroscopic system produce peaks in the spectrum. These peaks can also be called lines by analogy to optical spectroscopy. The width of the peaks is determined by the resolution of the detector, a very important characteristic of gamma spectroscopic detectors, and high resolution enables the spectroscopist to separate two gamma lines that are close to each other. Gamma spectroscopy systems are designed and adjusted to produce symmetrical peaks of the best possible resolution. The peak shape is usually a Gaussian distribution. In most spectra the horizontal position of the peak is determined by the gamma ray's energy, and the area of the peak is determined by the intensity of the gamma ray and the efficiency of the detector.
The most common figure used to express detector resolution is full width at half maximum (FWHM). This is the width of the gamma ray peak at half of the highest point on the peak distribution. Resolution figures are given with reference to specified gamma ray energies. Resolution can be expressed in absolute (i.e., eV or MeV) or relative terms. For example, a sodium iodide (NaI) detector may have a FWHM of 9.15 keV at 122 keV, and 82.75 keV at 662 keV. These resolution values are expressed in absolute terms. To express the resolution in relative terms, the FWHM in eV or MeV is divided by the energy of the gamma ray and usually shown as percentage. Using the preceding example, the resolution of the detector is 7.5% at 122 keV, and 12.5% at 662 keV. A germanium detector may give resolution of 560 eV at 122 keV, yielding a relative resolution of 0.46%. | 0 | Theoretical and Fundamental Chemistry |
Rigid polyurethane foam has many desirable properties which has enabled increased use in various applications, some of which are quite demanding. These properties include low thermal conduction making it useful as an insulator. It also has low density compared to metals and other materials and also good dimensional stability. A metal will expand on heating whereas rigid PU foam does not. They have excellent strength to weight ratios. Like many applications, there has been a trend to make rigid PU foam from renewable raw materials in place of the usual polyols.
They are used in vehicles, planes and buildings in structural applications. They have also been used in fire-retardant applications. | 0 | Theoretical and Fundamental Chemistry |
DAA developers face foreseeable challenges in the years to come. Therapeutic gaps for individuals with complicating conditioned such as chronic kidney disease and cirrhosis will need to be bridged. Shorter therapies with milder side effects would yield greater adherence, and the ever present spectre of drug resistance is looming. The highly adaptive HCV has evolved into a number of different genomes that all need to be adequately treated, preferably with pan-genotypic regimens.
Some of these challenges already have possible solutions in sight. The protease inhibitor ABT-493 and the next-generation NS5A inhibitor ABT-530 are considered active against all HCV genotypes, including the hard to treat genotype 3. In vitro, ABT-530 showed potency against the resistance associated variants which are immune to the first generations of NS5A inhibitors, including ledipasvir, daclatasvir and ombitasvir. Because this drug combination has the additional quality of being hepatically cleared, it holds the promise that patients with chronic kidney disease and HCV could receive a safe, non-sofosbuvir-based treatment in the near future.
At least three drug combinations for the treatment of HCV are in the pipeline to be approved in 2016-2017: Sofosbuvir in combination with velpatasvir, ABT-493 in combination with ABT-530, and grazoprevir in combination with elbasvir, of which velpatasvir, ABT-530 and elbasvir are NS5A inhibitors. | 1 | Applied and Interdisciplinary Chemistry |
The two main tasks of transcription initiation are to provide RNA polymerase with an access to the promoter and to assemble general transcription factors with polymerase into a transcription initiation complex. Diverse mechanisms of initiating transcription by overriding inhibitory signals at the gene promoter have been identified. Eukaryotic genes have acquired extensive regulatory sequences that encompass a large number of regulator-binding sites and spread overall kilobases (sometimes hundreds of kilobases) from the promoter–-both upstream and downstream. The regulator binding sites are often clustered together into units called enhancers. Enhancers can facilitate highly cooperative action of several transcription factors (which constitute enhanceosomes). Remote enhancers allow transcription regulation at a distance. Insulators situated between enhancers and promoters help define the genes that an enhancer can or cannot influence.
Eukaryotic transcriptional activators have separate DNA-binding and activating functions. Upon binding to its cis-element, an activator can recruit polymerase directly or recruit other factors needed by the transcriptional machinery. An activator can also recruit nucleosome modifiers that alter chromatin in the vicinity of the promoter and thereby help initiation. Multiple activators can work together, either by recruiting a common or two mutually dependent components of the transcriptional machinery, or by helping each other bind to their DNA sites. These interactions can synergize multiple signaling inputs and produce intricate transcriptional responses to address cellular needs. | 1 | Applied and Interdisciplinary Chemistry |
In contradistinction with electrophoresis, motion of particle in homogeneous electric field only, electrodiffusiophoresis occurs in the areas of the dispersion that experience concentration polarization due to, for instance, electrochemical reactions, see electrochemistry. There are concentration gradients in such areas that affect particles motion strongly. First of all they create inhomogeneity in the electric field. Secondly, they cause diffusiophoresis. This peculiarities of the particles motion in the areas subjected to the concentration polarization justifies introduction of the special term for this electrokinetic effect - electrodiffusiophoresis.
One of the most important differences of the electrodiffusioporesis from the electrophoresis is that exists as directed particles drift in the alternating electric field. Electrophoresis, in contrary, causes only particles oscillation on the same spot. This difference opens opportunities for important applications.
Electrodiffusiophoresis was theoretically predicted in 1980 - 82.
It was experimentally observed microscopically in 1982.
The first application of this effect was explanation of particles depositing at some distance from the surface of the ion selective membrane.
These earlier experiments and theory were described in the review published in 1990. This review presents also application of electrodiffusiophoresis for making bactericidal coatings.
This effect has attracted new attention in 2010 with regard to microfluidics. | 0 | Theoretical and Fundamental Chemistry |
Albert believed that all natural things were compositions of matter and form, he referred to it as quod est and quo est. Albert also believed that God alone is the absolute ruling entity. Albert's version of hylomorphism is very similar to the Aristotelian doctrine. | 1 | Applied and Interdisciplinary Chemistry |
The predominant form of lining for water applications is cement mortar centrifugally applied during manufacturing. The cement mortar comprises a mixture of cement and sand to a ratio of between 1:2 and 1:3.5. For potable water, portland cement is used; for sewage it is common to use sulfate resisting or high alumina cement.
Cement mortar linings have been found to dramatically reduce internal corrosion. A DIPRA survey has demonstrated that the Hazen-Williams factor of cement lining remains between 130 and 151 with only slight reduction with age. | 1 | Applied and Interdisciplinary Chemistry |
Creation of canals would need large areas of land resulting in large scale deforestation in certain areas. | 1 | Applied and Interdisciplinary Chemistry |
The K factor or characterization factor is defined from Rankine boiling temperature °R=1.8Tb[k] and relative to water density ρ at 60°F:
K(UOP) =
The K factor is a systematic way of classifying a crude oil according to its paraffinic, naphthenic, intermediate or aromatic nature. 12.5 or higher indicate a crude oil of predominantly paraffinic constituents, while 10 or lower indicate a crude of more aromatic nature. The K(UOP) is also referred to as the UOP K factor or just UOPK. | 0 | Theoretical and Fundamental Chemistry |
Yuri Andreyevich Zhdanov (; 20 August 1919 – 19 December 2006) was a Soviet and Russian chemistry professor and rector of the University of Rostov. He was the son of Soviet politician Andrei Zhdanov and a former husband of Joseph Stalin's daughter, Svetlana Alliluyeva. | 0 | Theoretical and Fundamental Chemistry |
Hazards posed by titanium tetrachloride generally arise from its reaction with water that releases hydrochloric acid, which is severely corrosive itself and whose vapors are also extremely irritating. is a strong Lewis acid, which exothermically forms adducts with even weak bases such as THF and water. | 0 | Theoretical and Fundamental Chemistry |
The erythromycin breath test (ERMBT) is a method used to measure metabolism (oxidation and elimination from the system) by a part of the cytochrome P450 system. Erythromycin produces CO and this CO can be measured to study drugs that interact with the cytochrome P450 system. Erythromycin is tagged with carbon-14 and given as an intravenous injection; after 20 minutes the subject blows up a balloon and the carbon dioxide exhaled that is tagged with carbon-14 shows the activity of the CYP3A4 isoenzyme on the erythromycin. ERMBT can be used to determine how drugs that the CYP3A4 isoenzyme metabolizes will function in a given individual.
Erythromycin is a drug that treats bacterial infections like bronchitis, sexually transmitted diseases, and pneumonia. The medication is in a capsule form and takes on a "delayed-release," to ensure it is only broken down once it reaches the intestine and not by stomach acids.
The test allows doctors to determine or predict an individual’s drug treatment outcome. Will a patient develop serious or fatal side effects from a certain drug? Which foods and drugs should not be taken together? With this and other tests a physician may determine treatment outcomes in advance or study the effects of new drugs.
Some patients have a congenital inability to synthesize certain enzymes, so drugs may build up to toxic levels in their system or other drugs and foods a patient is taking may consume all of their ability to metabolize certain foods and drugs. An example is: when a person taking a cholesterol-lowering statin drug then drinking grapefruit juice, they may have a poor treatment outcome (adverse drug reaction) and sustain liver damage or kidney failure due to drug induced rhabdomyolysis (the breaking up of muscle tissue). | 1 | Applied and Interdisciplinary Chemistry |
In molecular biology, linker DNA is double-stranded DNA (38-53 base pairs long) in between two nucleosome cores that, in association with histone H1, holds the cores together. Linker DNA is seen as the string in the "beads and string model", which is made by using an ionic solution on the chromatin. Linker DNA connects to histone H1 and histone H1 sits on the nucleosome core. Nucleosome is technically the consolidation of a nucleosome core and one adjacent linker DNA; however, the term nucleosome is used freely for solely the core. Linker DNA may be degraded by endonucleases.
The linkers are short double stranded DNA segments which are formed of oligonucleotides. These contain target sites for the action of one or more restriction enzymes. The linkers can be synthesized chemically and can be ligated to the blunt end of foreign DNA or vector DNA. These are then treated with restriction endonuclease enzyme to produce cohesive ends of DNA fragments. The commonly used linkers are EcoRI-linkers and sal-I linkers. | 0 | Theoretical and Fundamental Chemistry |
Miglustat is an iminosugar in which the ring oxygen is replaced by nitrogen. Miglustat a drug used to treat some rare lysosomal storage disorder diseases. | 1 | Applied and Interdisciplinary Chemistry |
The Campaign to Electrify Britain's Railway (CEBR) is an internet-based campaign group formed in 2018 whose aim is to convince the government to completely electrify the British Railway network. Its slogan is "Down with Dirty Diesel." The campaign promotes a rolling programme of electrification, which it considers essential to improve UK railways and help to decarbonise transport. It collaborates with groups such as the Railway Industry Association, Rail Delivery Group, Birmingham Centre for Railway Research and Education, Campaign for Better Transport, Institute of Electrical Engineers and the Permanent Way Institution. The group has given evidence to the Transport Select Committee. Huw Merriman the committee chair at the time, put it writing he agreed with their view. Merriman was appointed as Minister of State for Rail and HS2 in October 2022. The desire to achieve net zero carbon in transport has increased calls for electrification. | 1 | Applied and Interdisciplinary Chemistry |
Atmospheric Methane Removal is a category of potential approaches being researched to accelerate the breakdown of methane once in the atmosphere to mitigate some of the impacts of climate change.
Different methods to remove methane from the atmosphere include thermal-catalytic oxidation, photocatalytic oxidation, biological methanotrophic methane removal, concentration with zeolites or other porous solids, and separation by membranes. | 1 | Applied and Interdisciplinary Chemistry |
The yield of a system can be measured by either its value or its net benefit. For a water supply system, the true value or the net benefit is a reliable water supply service having adequate quantity and good quality of the product. For example, if the existing water supply of a city needs to be extended to supply a new municipality, the impact of the new branch of the system must be designed to supply the new needs, while maintaining supply to the old system. | 1 | Applied and Interdisciplinary Chemistry |
FEBS publishes four scientific journals: The FEBS Journal, FEBS Letters, Molecular Oncology and FEBS Open Bio. The FEBS Journal was previously entitled the European Journal of Biochemistry. Molecular Oncology and FEBS Open Bio are open-access journals. | 1 | Applied and Interdisciplinary Chemistry |
Two very similar expressions for are in wide use in hydrology. Both have the form ‰ (‰ = permil or parts per thousand) where s and a are the relative abundances of N in respectively the sample and the atmosphere. The difference is whether the relative abundance is with respect to all the nitrogen, i.e. N plus N, or just to N. Since the atmosphere is 99.6337% N and 0.3663% N, a is 0.003663 in the former case and 0.003663/0.996337 = 0.003676 in the latter. However s varies similarly; for example if in the sample N is 0.385% and N is 99.615%, s is 0.003850 in the former case and 0.00385/0.99615 = 0.003865 in the latter. The value of is then 51.05‰ in the former case and 51.38‰ in the latter, an insignificant difference in practice given the typical range of -20 to 80 for . | 0 | Theoretical and Fundamental Chemistry |
Archaea have a single type of RNAP, responsible for the synthesis of all RNA. Archaeal RNAP is structurally and mechanistically similar to bacterial RNAP and eukaryotic nuclear RNAP I-V, and is especially closely structurally and mechanistically related to eukaryotic nuclear RNAP II.
The history of the discovery of the archaeal RNA polymerase is quite recent. The first analysis of the RNAP of an archaeon was performed in 1971, when the RNAP from the extreme halophile Halobacterium cutirubrum was isolated and purified. Crystal structures of RNAPs from Sulfolobus solfataricus and Sulfolobus shibatae set the total number of identified archaeal subunits at thirteen.
Archaea has the subunit corresponding to Eukaryotic Rpb1 split into two. There is no homolog to eukaryotic Rpb9 (POLR2I) in the S. shibatae complex, although TFS (TFIIS homolog) has been proposed as one based on similarity. There is an additional subunit dubbed Rpo13; together with Rpo5 it occupies a space filled by an insertion found in bacterial β′ subunits (1,377–1,420 in Taq). An earlier, lower-resolution study on S. solfataricus structure did not find Rpo13 and only assigned the space to Rpo5/Rpb5. Rpo3 is notable in that it's an iron–sulfur protein. RNAP I/III subunit AC40 found in some eukaryotes share similar sequences, but does not bind iron. This domain, in either case, serves a structural function.
Archaeal RNAP subunit previously used an "RpoX" nomenclature where each subunit is assigned a letter in a way unrelated to any other systems. In 2009, a new nomenclature based on Eukaryotic Pol II subunit "Rpb" numbering was proposed. | 1 | Applied and Interdisciplinary Chemistry |
A cooling curve is a line graph that represents the change of phase of matter, typically from a gas to a solid or a liquid to a solid. The independent variable (X-axis) is time and the dependent variable (Y-axis) is temperature. Below is an example of a cooling curve used in castings.
The initial point of the graph is the starting temperature of the matter, here noted as the "pouring temperature". When the phase change occurs, there is a "thermal arrest"; that is, the temperature stays constant. This is because the matter has more internal energy as a liquid or gas than in the state that it is cooling to. The amount of energy required for a phase change is known as latent heat. The "cooling rate" is the slope of the cooling curve at any point.
Alloy have range of melting point. It solidifies as above. First, molten alloy reaches to liquidus temperature and then freezing range starts. At solidus temperature, molten alloys becomes solid. | 0 | Theoretical and Fundamental Chemistry |
The overwhelming majority of aromatic compounds are compounds of carbon, but they need not be hydrocarbons. | 0 | Theoretical and Fundamental Chemistry |
In the analysis of sediments, C/N ratios are a proxy for paleoclimate research, having different uses whether the sediment cores are terrestrial-based or marine-based. Carbon-to-nitrogen ratios are an indicator for nitrogen limitation of plants and other organisms and can identify whether molecules found in the sediment under study come from land-based or algal plants. Further, they can distinguish between different land-based plants, depending on the type of photosynthesis they undergo. Therefore, the C/N ratio serves as a tool for understanding the sources of sedimentary organic matter, which can lead to information about the ecology, climate, and ocean circulation at different times in Earth's history. | 0 | Theoretical and Fundamental Chemistry |
Possibly the most exciting potential use for PECO is producing hydrogen to be used as a source of renewable energy. Photoelectrochemical oxidation reactions that take place within PEC cells are the key to water splitting for hydrogen production. While the main concern with this technology is stability, systems that use PECO technology to create hydrogen from vapor rather than liquid water has demonstrated potential for greater stability. Early researchers working on vapor fed systems developed modules with 14% solar to hydrogen (STH) efficiency, while remaining stable for 1000+ hours. More recently, further technological developments have been made, demonstrated by the direct air electrolysis (DAE) module developed by Jining Guo and his team, which produces 99% pure hydrogen from the air and has demonstrated stability of 8 months thus far.
Promising research and technological advancement using PECO for different applications like water and air treatment and hydrogen production suggests that it is a valuable tool that can be utilized in a variety of ways. | 0 | Theoretical and Fundamental Chemistry |
Static fatigue describes how prolonged and constant cyclic stress weakens a material until it breaks apart, which is called failure. Static fatigue is sometimes called "delayed fracture". The damage occurs at a lower stress level than the stress level needed to create a normal tensile fracture. Static fatigue can involve plastic deformation or crack growth. For example, repeated stress can create small cracks that grow and eventually break apart plastic, glass, or ceramic materials. The material reaches failure faster by increasing cyclic stress. Static fatigue varies with material type and environmental factors, such as moisture presence and temperature. | 1 | Applied and Interdisciplinary Chemistry |
Oxyhydrogen is a mixture of hydrogen (H) and oxygen (O) gases. This gaseous mixture is used for torches to process refractory materials and was the first
gaseous mixture used for welding. Theoretically, a ratio of 2:1 hydrogen:oxygen is enough to achieve maximum efficiency; in practice a ratio 4:1 or 5:1 is needed to avoid an oxidizing flame.
This mixture may also be referred to as (Scandinavian and German ; ), although some authors define knallgas to be a generic term for the mixture of fuel with the precise amount of oxygen required for complete combustion, thus 2:1 oxyhydrogen would be called "hydrogen-knallgas".
"Brown's gas" and HHO are terms for oxyhydrogen originating in pseudoscience, although is preferred due to meaning . | 0 | Theoretical and Fundamental Chemistry |
Although enol ethers can be considered the ether of the corresponding enolates, they are not prepared by alkylation of enolates. Some enol ethers are prepared from saturated ethers by elimination reactions.
Alternatively, vinyl ethers can be prepared from alcohols by iridium-catalyzed transesterification of vinyl esters, especially the widely available vinyl acetate:
:ROH + CH=CHOAc → ROCH=CH + HOAc
Vinyl ethers can be prepared by reaction of acetylene and alcohols in presence of a base. | 0 | Theoretical and Fundamental Chemistry |
There are 3 types of tumor suppressor genes:
* Genes that affect cell growth
* Genes that limit the cell cycle and induce apoptosis
* Genes that repair damaged DNA
SFRP1 appears to fall in the first category of genes, those that affect cell growth.
The role of SFRP1 as a tumor suppressor has been proposed in many cancers, based on its loss in patient tumors. Its frequent inactivation by methylation-induced silencing is consistent with it behaving as a tumor suppressor. Also, the SFRP1 gene is located in a region on chromosome 8 that is frequently lost in many cancer types. Expression levels of several targets of the Wnt signaling pathways are increased in tumor tissue compared with normal, and the expression of SFRP1 is lost in patient tumor samples. The role for the Wnt/β-catenin signaling in cancer has been well defined: β-catenin drives transcription of genes that contribute to the tumor phenotype by regulating processes such as proliferation, survival and invasion.
Gumz et al. showed that SFRP1 expression in UMRC3 cells (clear cell renal cell carcinoma cell line) resulted in a growth-inhibited phenotype. SFRP1 expression not only reduced the expression of Wnt target genes, but also markedly inhibited tumor cell growth in culture, soft agar and xenografts in athymic nude mice. Growth in culture and anchorage-independent growth were inhibited in SFRP1-expressing UMRC3 cells. The growth-inhibitory effects of SFRP1 were due primarily to decreased cell proliferation rather than an increase in apoptosis. This was consistent with the effect of SFRP1 on cellular proliferation as seen in prostate cancer, where retroviral-mediated expression of SFRP1 resulted in inhibited cellular proliferation but had no effect on apoptosis. Also, restoration of SFRP1 expression attenuated the malignant phenotype of cRCC; moreover, other studies showed reexpression of SFRP1 resulted in decreased colony formation in colon and lung cancer models. | 1 | Applied and Interdisciplinary Chemistry |
Large thermal reactors with low flux coupling between regions may experience spatial power oscillations because of the non-uniform presence of xenon-135. Xenon-induced spatial power oscillations occur as a result of rapid perturbations to power distribution that cause the xenon and iodine distribution to be out of phase with the perturbed power distribution. This results in a shift in xenon and iodine distributions that causes the power distribution to change in an opposite direction from the initial perturbation.
The instantaneous production rate of xenon-135 is dependent on the iodine-135 concentration and therefore on the local neutron flux history. On the other hand, the destruction rate of xenon-135 is dependent on the instantaneous local neutron flux.
The combination of delayed generation and high neutron-capture cross section produces a diversity of impacts on nuclear reactor operation. The mechanism is described in the following four steps.
# An initial lack of symmetry (for example, axial symmetry, in the case of axial oscillations) in the core power distribution (for example as a result of significant control rods movement) causes an imbalance in fission rates within the reactor core, and therefore, in the iodine-135 buildup and the xenon-135 absorption.
# In the high-flux region, xenon-135 burnout allows the flux to increase further, while in the low-flux region, the increase in xenon-135 causes a further reduction in flux. The iodine concentration increases where the flux is high and decreases where the flux is low. This shift in the xenon distribution is such as to increase (decrease) the multiplication properties of the region in which the flux has increased (decreased), thus enhancing the flux tilt.
# As soon as the iodine-135 levels build up sufficiently, decay to xenon reverses the initial situation. Flux decreases in this area, and the former low-flux region increases in power.
# Repetition of these patterns can lead to xenon oscillations moving about the core with periods on the order of about 24 hours.
With little change in overall power level, these oscillations can significantly change the local power levels. This oscillation may go unnoticed and reach dangerous local flux levels if only the total power of the core is monitored. Therefore, most PWRs use tandem power range excore neutron detectors to monitor upper and lower halves of the core separately. | 0 | Theoretical and Fundamental Chemistry |
Generally, in progression to cancer, hundreds of genes are silenced or activated. Although silencing of some genes in cancers occurs by mutation, a large proportion of carcinogenic gene silencing is a result of altered DNA methylation (see DNA methylation in cancer). DNA methylation causing silencing in cancer typically occurs at multiple CpG sites in the CpG islands that are present in the promoters of protein coding genes.
Altered expressions of microRNAs also silence or activate many genes in progression to cancer (see microRNAs in cancer). Altered microRNA expression occurs through hyper/hypo-methylation of CpG sites in CpG islands in promoters controlling transcription of the microRNAs.
Silencing of DNA repair genes through methylation of CpG islands in their promoters appears to be especially important in progression to cancer (see methylation of DNA repair genes in cancer). | 1 | Applied and Interdisciplinary Chemistry |
The Henry adsorption constant is the constant appearing in the linear adsorption isotherm, which formally resembles Henrys law; therefore, it is also called Henrys adsorption isotherm. It is named after British chemist William Henry. This is the simplest adsorption isotherm in that the amount of the surface adsorbate is represented to be proportional to the partial pressure of the adsorptive gas:
where:
* X - surface coverage,
* P - partial pressure,
* K - Henry's adsorption constant.
For solutions, concentrations, or activities, are used instead of the partial pressures.
The linear isotherm can be used to describe the initial part of many practical isotherms. It is typically taken as valid for low surface coverages, and the adsorption energy being independent of the coverage (lack of inhomogeneities on the surface).
The Henry adsorption constant can be defined as:
where:
* is the number density at free phase,
* is the surface number density, | 0 | Theoretical and Fundamental Chemistry |
Transannular strain can be eliminated by the simple addition of a carbon bridge. E,Z,E,Z,Z-[10]-annulene is quite unstable; while it has the requisite number of π-electrons to be aromatic, they are for the most part isolated. Ultimately, the molecule itself is very difficult to observe. However, by the simple addition of a methylene bridge between the 1 and 6 positions, a stable, flat, aromatic molecule can be made and observed. | 0 | Theoretical and Fundamental Chemistry |
An overlayer is a layer of adatoms adsorbed onto a surface, for instance onto the surface of a single crystal. | 0 | Theoretical and Fundamental Chemistry |
Although RNA polymerase holoenzyme shows high affinity to non-specific sites of the DNA, this characteristic does not allow us to clarify the process of promoter location. This process of promoter location has been attributed to the structure of the holoenzyme to DNA and sigma 4 to DNA complexes. | 1 | Applied and Interdisciplinary Chemistry |
A centisome is a unit of length defined as one percent of the length of a particular chromosome. This course unit of physical DNA length began to be used in the early exploration of genomes through molecular biology before the resolution of the nucleic acid sequences of chromosomes was possible.
One of the main uses for this unit was for describing the locus of a gene by giving a distance in centisomes from a reference point on the chromosome. For instance, when the complete genome of the bacterium Escherichia coli was finally completed in 1997, it was presented with a scale given in centisomes (as well as one in kilobases). Since bacterial chromosomes are circular, the reference point cannot be an end of the DNA molecule, but must be some point that has some easily determinable unique characteristic. Often this point is the origin of replication, although for E. coli it is the origin of transfer during conjugation. Hence, the reference point for centisome positions is simply a convention established for each individual species of organism.
For the most part, modern scientific literature uses "centisome" as part of a shorthand way of referring to a particular region of interest on the chromosome of particular organisms. For instance, much research has been done on the "Centisome 63" area of the chromosomes of Salmonella species. | 1 | Applied and Interdisciplinary Chemistry |
The average wholesale price (AWP) for oxacillin products are provided as follows. The prices listed below are intended to serve as reference values and do not represent the pricing determined by any single manufacturer or entity.
*Bactocill in Dextrose Intravenous
**1 g/50 mL: $20.37
**2 g/50 mL: $32.48
*Oxacillin Sodium Injection
**1 g: $17.52
**2 g: $33.99
**10 g: $138.77 | 0 | Theoretical and Fundamental Chemistry |
The calcium cycle links ionic and non ionic calcium together in both marine and terrestrial environments and is essential for the functioning of all living organisms. In animals, calcium enables neurons to transmit signals by opening voltage gated channels that allow neurotransmitters to reach the next cell, bone formation and development and kidney function, whilst being maintained by hormones that ensure calcium homeostasis is reached. In plants, calcium promotes enzyme activity and ensures cell wall function, providing stability to plants. It also enables crustaceans to form shells and corals to exist, as calcium provides structure, rigidity and strength to structures when complexed (combined) to other atoms. Without its presence in the environment, many life-preserving processes would not exist. In the modern context, calcium also enables many industrial processes to occur, promoting further technological developments.
With its close relation to the carbon cycle and the effects of greenhouse gasses, both calcium and carbon cycles are predicted to change in the coming years. Tracking calcium isotopes enables the prediction of environmental changes, with many sources suggesting increasing temperatures in both the atmosphere and marine environment. As a result, this will drastically alter the breakdown of rock, the pH of oceans and waterways and thus calcium sedimentation, hosting an array of implications on the calcium cycle.
Due to the complex interactions of calcium with many facets of life, the effects of altered environmental conditions are unlikely to be known until they occur. Predictions can however be tentatively made, based upon evidence-based research. Increasing carbon dioxide levels and decreasing ocean pH will alter calcium solubility, preventing corals and shelled organisms from developing their calcium-based exoskeletons, thus making them vulnerable or unable to survive. | 1 | Applied and Interdisciplinary Chemistry |
A siphon rain gauge is a rain gauge that can record rainfall over an extended period. A siphon is used to automatically empty the gauge. It is often simply called a "siphon gauge" and is not to be confused with a siphon pressure gauge. | 1 | Applied and Interdisciplinary Chemistry |
Enhancers or cis-regulatory modules/elements (CRM/CRE) are non-coding DNA sequences containing multiple activator and repressor binding sites. Enhancers range from 200 bp to 1 kb in length and can be either proximal, 5’ upstream to the promoter or within the first intron of the regulated gene, or distal, in introns of neighboring genes or intergenic regions far away from the locus. Through DNA looping, active enhancers contact the promoter dependently of the core DNA binding motif promoter specificity. Promoter-enhancer dichotomy provides the basis for the functional interaction between transcription factors and transcriptional core machinery to trigger RNA Pol II escape from the promoter. Whereas one could think that there is a 1:1 enhancer-promoter ratio, studies of the human genome predict that an active promoter interacts with 4 to 5 enhancers. Similarly, enhancers can regulate more than one gene without linkage restriction and are said to “skip” neighboring genes to regulate more distant ones. Even though infrequent, transcriptional regulation can involve elements located in a chromosome different from one where the promoter resides. Proximal enhancers or promoters of neighboring genes can serve as platforms to recruit more distal elements. | 1 | Applied and Interdisciplinary Chemistry |
# Multimedia filters use multiple layers of different filter media to achieve more effective and efficient filtration than single-media filters like sand filters.
# They can remove a wider range of particle sizes and types than single-media filters, resulting in more efficient filtration and longer filter life.
# They are effective at removing suspended solids, turbidity, and other contaminants from water.
# They can be used for a wide range of flow rates and particle sizes. They can be easily backwashed to clean the filter media and restore filtration efficiency.
# They require little to no electricity to operate. | 1 | Applied and Interdisciplinary Chemistry |
* Alfred P. Sloan Fellow, 1961-65
* NSF Senior Postdoctoral Fellow, 1968-69
* Heinrich Hertz Fellow (West Germany)
* Meyerhoff Fellow (Israel)
* Fellow of the American Physical Society, citation: For his many contributions to the statistical mechanics of transport processes, especially to the understanding of Brownian motion and the couplings of moving molecules, 1983. | 0 | Theoretical and Fundamental Chemistry |
Transferrins are glycoproteins that are often found in biological fluids of vertebrates. When a transferrin protein loaded with iron encounters a transferrin receptor on the surface of a cell, e.g., erythroid precursors in the bone marrow, it binds to it and is transported into the cell in a vesicle by receptor-mediated endocytosis. The pH of the vesicle is reduced by hydrogen ion pumps ( ATPases) to about 5.5, causing transferrin to release its iron ions. Iron release rate is dependent on several factors including pH levels, interactions between lobes, temperature, salt, and chelator. The receptor with its ligand bound transferrin is then transported through the endocytic cycle back to the cell surface, ready for another round of iron uptake.
Each transferrin molecule has the ability to carry two iron ions in the ferric form (). | 1 | Applied and Interdisciplinary Chemistry |
The Boltzmann equation is valid only under several assumptions. For instance, the particles are assumed to be pointlike, i.e. without having a finite size. There exists a generalization of the Boltzmann equation that is called the Enskog equation. The collision term is modified in Enskog equations such that particles have a finite size, for example they can be modelled as spheres having a fixed radius.
No further degrees of freedom besides translational motion are assumed for the particles. If there are internal degrees of freedom, the Boltzmann equation has to be generalized and might possess inelastic collisions.
Many real fluids like liquids or dense gases have besides the features mentioned above more complex forms of collisions, there will be not only binary, but also ternary and higher order collisions. These must be derived by using the BBGKY hierarchy.
Boltzmann-like equations are also used for the movement of cells. Since cells are composite particles that carry internal degrees of freedom, the corresponding generalized Boltzmann equations must have inelastic collision integrals. Such equations can describe invasions of cancer cells in tissue, morphogenesis, and chemotaxis-related effects. | 1 | Applied and Interdisciplinary Chemistry |
Organostannane addition reactions comprise the nucleophilic addition of an allyl-, allenyl-, or propargylstannane to an aldehyde, imine, or, in rare cases, a ketone. The reaction is widely used for carbonyl allylation.
Organostannane addition to carbonyl groups constitutes one of the most common and efficient methods for the construction of contiguous, oxygen-containing stereocenters in organic molecules. As many molecules containing this motif—polypropionates and polyacetates, for instance—are desired by natural products chemists, the title reaction has become important synthetically and has been heavily studied over the years. Substituted allylstannanes may create one or two new stereocenters, often with a very high degree of stereocontrol.
Organostannanes are known for their stability, ease of handling, and selective reactivity. Chiral allylstannanes often react with good stereoselectivity to give single diastereomers. Models explaining the sense of selectivity are reliable. In terms of disadvantages, stoichiometric amounts of metal-containing byproducts are generated. Additions to sterically encumbered pi bonds, such as those of ketones, are uncommon. | 0 | Theoretical and Fundamental Chemistry |
The continuous process of applying up to three separate coating layers onto one or both sides of a metal strip substrate occurs on a coil coating line. These lines vary greatly in size, with widths from and speeds from ; however, all coil-coating lines share the same basic process steps.
A typical organic coil coating line consists of decoilers, entry strip accumulator, cleaning, chemical pretreatment, primer coat application, curing, final coat application, curing, exit accumulator and recoilers.
The following steps take place on a modern coating line:
* Mechanical stitching of the strip to its predecessor
* Cleaning the strip
* Power brushing
* Surface treatment by chemical conversion
* Drying the strip
* Application of primer on one or both sides
* Passage through the first curing oven (between 15 and 60 seconds)
* Cooling the strip
* Coating the finish on one or both sides
* Passage through the second curing oven (between 15 and 60 seconds)
* Cooling down to room temperature
* Rewinding of the coated coil | 1 | Applied and Interdisciplinary Chemistry |
An example of a short-lived fission product is iodine-131, this can also be formed as an activation product by the neutron activation of tellurium.
In both bomb fallout and a release from a power reactor accident, the short-lived isotopes cause the dose rate on day one to be much higher than that which will be experienced at the same site many days later. This holds true even if no attempts at decontamination are made. In the graphs below, the total gamma dose rate and the share of the dose due to each main isotope released by the Chernobyl accident are shown. | 0 | Theoretical and Fundamental Chemistry |
Druglikeness is a qualitative concept used in drug design for how "druglike" a substance is with respect to factors like bioavailability. It is estimated from the molecular structure before the substance is even synthesized and tested. A druglike molecule has properties such as:
*Solubility in both water and fat, as an orally administered drug needs to pass through the intestinal lining after it is consumed, be carried in aqueous blood and penetrate the lipid-based cell membrane to reach the inside of a cell. A model compound for the lipophilic cellular membrane is 1-octanol (a lipophilic medium-chain fatty alcohol), so the logarithm of the octanol-water partition coefficient, known as LogP, is used to predict the solubility of a potential oral drug. This coefficient can be experimentally measured or predicted computationally, in which case it is sometimes called "cLogP". As the lipophilicity of ionizable compounds is strongly dependent of pH, the distribution coefficient logD, or a logP vs pH curve may be used instead.
*Potency at the biological target. High potency (high value of pIC) is a desirable attribute in drug candidates, as it reduces the risk of non-specific, off-target pharmacology at a given concentration. When associated with low clearance, high potency also allows for low total dose, which lowers the risk of idiosyncratic drug reactions.
*Ligand efficiency and lipophilic efficiency.
*Molecular weight: The smaller the better, because diffusion is directly affected. The great majority of drugs on the market have molecular weights between 200 and 600 daltons, and particularly <500; they belong to the group of small molecules.
A traditional method to evaluate druglikeness is to check compliance of Lipinski's Rule of Five, which covers the numbers of hydrophilic groups, molecular weight and hydrophobicity.
Since the drug is transported in aqueous media like blood and intracellular fluid, it has to be sufficiently water-soluble in the absolute sense (i.e. must have a minimum chemical solubility in order to be effective). Solubility in water can be estimated from the number of hydrogen bond donors vs. alkyl sidechains in the molecule. Low water solubility translates to slow absorption and action. Too many hydrogen bond donors, on the other hand, lead to low fat solubility, so that the drug cannot penetrate the cell membrane to reach the inside of the cell.
Based on one definition, a drug-like molecule has a logarithm of partition coefficient (log P) between -0.4 and 5.6, molecular weight 160-480 g/mol, molar refractivity of 40–130, which is related to the volume and molecular weight of the molecule and has 20-70 atoms.
Substructures with known toxic, mutagenic or teratogenic properties affect the usefulness of a designed molecule. However, several poisons have a good druglikeness. Natural toxins are used in pharmacological research to find out their mechanism of action, and if it could be exploited for beneficial purposes. Alkylnitro compounds tend to be irritants, and Michael acceptors, such as enones, are alkylating agents and thus potentially mutagenic and carcinogenic.
Druglikeness indices are inherently limited tools. Druglikeness can be estimated for any molecule, and does not evaluate the actual specific effect that the drug achieves (biological activity). Simple rules are not always accurate and may unnecessarily limit the chemical space to search: many best-selling drugs have features that cause them to score low on various druglikeness indices. Furthermore, first-pass metabolism, which is biochemically selective, can destroy the pharmacological activity of a compound despite good druglikeness.
Druglikeness is not relevant for most biologics, since they are usually proteins that need to be injected, because proteins are digested if eaten. | 1 | Applied and Interdisciplinary Chemistry |
# Magnetic materials e.g. alnico, sendust, Permendur, FeCo, Terfenol-D
# Superconductors e.g. A15 phases, niobium-tin
# Hydrogen storage e.g. AB compounds (nickel metal hydride batteries)
# Shape memory alloys e.g. Cu-Al-Ni (alloys of CuAl and nickel), Nitinol (NiTi)
# Coating materials e.g. NiAl
# High-temperature structural materials e.g. nickel aluminide, NiAl
# Dental amalgams, which are alloys of intermetallics AgSn and CuSn
# Gate contact/ barrier layer for microelectronics e.g. TiSi
# Laves phases (AB), e.g., MgCu, MgZn and MgNi.
The formation of intermetallics can cause problems. For example, intermetallics of gold and aluminium can be a significant cause of wire bond failures in semiconductor devices and other microelectronics devices. The management of intermetallics is a major issue in the reliability of solder joints between electronic components. | 1 | Applied and Interdisciplinary Chemistry |
Contact angle, or wetting angle, is a very important parameter in real systems where perfect wetting ( = 0) is hardly ever achieved. The Young equation provides reasoning for contact angle involvement in capillary condensation. The Young Equation explains that the surface tension between the liquid and vapor phases is scaled to the cosine of the contact angle. As shown in the figure to the right, the contact angle between a condensed liquid and the inner wall of a capillary can affect the radius of curvature a great deal. For this reason, contact angle is coupled inherently to the curvature term of the Kelvin equation. As the contact angle increases, the radius of curvature will increase as well. This is to say that a system with perfect wetting will exhibit a larger amount of liquid in its pores than a system with non-perfect wetting ( > 0). Also, in systems where = 0 the radius of curvature is equal to the capillary radius. Due to these complications caused by contact angle, scientific studies are often designed to assume = 0. | 1 | Applied and Interdisciplinary Chemistry |
Nilson was professor of analytical chemistry at Uppsala from 1878 until 1883, when he became professor of chemistry of the Royal Swedish Academy of Agriculture and Forestry in Stockholm. As an agricultural chemist and Director of the Agricultural Chemical Experiment Station, he published nearly sixty papers concerning topics such as soils and manures. As a result of his inquiries many of the swamps of Gothland were drained and cultivated. The sugar beet was introduced and became a major crop, as chalky moors were treated with potash fertilizers.
He also conducted studies of cow's milk and various plants for cattle fodder.
Nilson was elected a foreign member of the Chemical Society of Great Britain on February 2, 1888.
Nilson was a member of several other academies as well. He received several awards, including the Order of the Polar Star. | 1 | Applied and Interdisciplinary Chemistry |
In 1908, Lawrence Joseph Henderson derived an equation to calculate the hydrogen ion concentration of a bicarbonate buffer solution, which rearranged looks like this:
In 1909 Søren Peter Lauritz Sørensen introduced the pH terminology, which allowed Karl Albert Hasselbalch to re-express Henderson's equation in logarithmic terms, resulting in the Henderson–Hasselbalch equation. | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits