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Bonnoris noted, “The environmental justice movement posits that the distribution of environmental harms and benefits should be fairly apportioned among all communities”. As Bonnoris argued, the burden of air pollution is disproportionally distributed among communities based on their racial, social or economic status. Disproportion distribution of air pollution among communities can be a violation of the Equal Protection Clause of the Constitution because it violates equal protection of residents’ public health.
Los Angeles is known for the nation's worst air quality and its “sharp inequalities in environmental exposures”. Wilmington, Los Angeles is a neighborhood located on the southern part of Los Angeles, California. 54,512 people live in Wilmington, the median household income is $40,627, about 86 percentage of them are Latino and only 5.1% of Wilmington residents 25 or older have a four-year degree.
Wilmington, most of its residents are ethnic minorities, is possible to bear more environmental burden than other communities in Los Angeles because it is located next to several sources of air pollution. For example, Wilmington has "the highest concentration of refineries in the State". Emissions from refineries in Wilmington include carbon dioxide, sulfur dioxide and benzene. Wilmington has higher concentration of diesel particulate matter due to emissions from diesel trucks from the ports of Los Angeles and Long Beach. The risks associated with diesel are often underestimated since existing epidemiological studies cannot isolate exposure to diesel PM. However, exposure to diesel particulate matter can cause “irritation to the eyes, nose, throat and lungs”, asthma, “exhaust immunological effects”, and cancer.
Several NGOs have worked to improve the accuracy of Wilmington air quality data and air quality in order to protect approximately 1400 children who live or visit schools or childcare facilities at Wilmington. The environmental group “Coalition For a Safe Environment” installed an air pollution monitoring devices on the residential buildings in Wilmington in order to prove that emissions from local oil refineries and diesel trucks to the ports pollute the air in Wilmington, disproportionately affecting Wilmington residents to suffer from health problems including lung diseases and respiratory diseases. | 2 | Environmental Chemistry |
Molecular self-assembly is an important aspect of bottom-up approaches to nanotechnology. Using molecular self-assembly, the final (desired) structure is programmed in the shape and functional groups of the molecules. Self-assembly is referred to as a bottom-up manufacturing technique in contrast to a top-down technique such as lithography where the desired final structure is carved from a larger block of matter. In the speculative vision of molecular nanotechnology, microchips of the future might be made by molecular self-assembly. An advantage to constructing nanostructure using molecular self-assembly for biological materials is that they will degrade back into individual molecules that can be broken down by the body. | 6 | Supramolecular Chemistry |
SELDI can be seen as a combination of solid-phase chromatography and TOF-MS. The sample is applied to a modified chip surface, which allows for the specific binding of proteins from the sample to the surface. Contaminants and unbound proteins are then washed away. After washing the sample, an energy absorbing matrix, such as sinapinic acid (SPA) or α-Cyano-4-hydroxycinnamic acid (CHCA), is applied to the surface and allowed to crystallize with the sample. Alternatively, the matrix can be attached to the sample surface by covalent modification or adsorption before the sample is applied. The sample is then irradiated by a pulsed laser, causing ablation and desorption of the sample and matrix. | 1 | Biochemistry |
In 2020, conservationists raised concerns about the potential slaughter of sharks to obtain squalene for a COVID-19 vaccine.
Environmental and other concerns over shark hunting have motivated its extraction from other sources. Biosynthetic processes use genetically engineered yeast or bacteria. | 1 | Biochemistry |
The concept of homoaromaticity has its origins in the debate over the non-classical carbonium ions that occurred in the 1950s. Saul Winstein, a famous proponent of the non-classical ion model, first described homoaromaticity while studying the 3-bicyclo[3.1.0]hexyl cation.
In a series of acetolysis experiments, Winstein et al. observed that the solvolysis reaction occurred empirically faster when the tosyl leaving group was in the equatorial position. The group ascribed this difference in reaction rates to the anchimeric assistance invoked by the "cis" isomer. This result thus supported a non-classical structure for the cation.
Winstein subsequently observed that this non-classical model of the 3-bicyclo[3.1.0]hexyl cation is analogous to the previously well-studied aromatic cyclopropenyl cation. Like the cyclopropenyl cation, positive charge is delocalized over three equivalent carbons containing two π electrons. This electronic configuration thus satisfies Huckel's rule (requiring 4n+2 π electrons) for aromaticity. Indeed, Winstein noticed that the only fundamental difference between this aromatic propenyl cation and his non-classical hexyl cation was the fact that, in the latter ion, conjugation is interrupted by three -- units. The group thus proposed the name "tris-homocyclopropenyl"—the tris-homo counterpart to the cyclopropenyl cation. | 7 | Physical Chemistry |
Vacuum deoxidation is a method which involves using a vacuum to remove impurities. A portion of the carbon and oxygen in steel will react, forming carbon monoxide. CO gas will float up to the top of the liquid steel and be removed by a vacuum system.
As the chemical reaction involved in vacuum deoxidation is:
the reaction between carbon and oxygen is represented by the following chemical equilibrium equation:
where P is the partial pressure of the carbon monoxide formed.
Decreasing the oxygen activity(a) will result in a higher equilibrium constant, thus more product, CO. To achieve this, subjecting the pool of steel to vacuum treatment decreases the value of P, allowing for more CO gas to be produced. | 8 | Metallurgy |
While the first observation of Bose-Einstein condensation was made in a magnetic atom trap using RF driven evaporative cooling, optical dipole traps are now much more common platforms for achieving condensation. Beginning in a MOT, cold, trapped atoms are transferred to the focal point of a high power, tightly focused, off-resonant laser beam. The electric field of the laser at its focus is sufficiently strong to induce dipole moments in the atoms, which are then attracted to the electric field maximum at the laser focus, effectively creating a trapping potential to hold them at the beam focus.
The depth of the optical trapping potential in an optical dipole trap (ODT) is proportional to the intensity of the trapping laser light. Decreasing the power in the trapping laser beam therefore decreases the depth of the trapping potential. In the case of RF-driven evaporation, the actual height of the potential barrier confining the atoms is fixed during the evaporation sequence, but the RF knife effectively decreases the depth of this barrier, as previously discussed. For an optical trap, however, evaporation is facilitated by decreasing the laser power and thus lowering the depth of the trapping potential. As a result, the warmest atoms in the trap will have sufficient kinetic energy to be able to make it over the barrier walls and escape the trap, reducing the average energy of the remaining atoms as previously described. While trap depths for ODTs can be shallow (on the order of mK, in terms of temperature), the simplicity of this optical evaporation procedure has helped to make it increasingly popular for BEC experiments since its first demonstrations shortly after magnetic BEC production. | 7 | Physical Chemistry |
Isocyanates are electrophiles, and as such they are reactive toward a variety of nucleophiles including alcohols, amines, and even water having a higher reactivity compared to structurally analogous isothiocyanates.
Upon treatment with an alcohol, an isocyanate forms a urethane linkage:
where R and R' are alkyl or aryl groups.
If a diisocyanate is treated with a compound containing two or more hydroxyl groups, such as a diol or a polyol, polymer chains are formed, which are known as polyurethanes.
Isocyanates react with water to form carbon dioxide:
This reaction is exploited in tandem with the production of polyurethane to give polyurethane foams. The carbon dioxide functions as a blowing agent.
Isocyanates also react with amines to give ureas:
The addition of an isocyanate to a urea gives a biuret:
Reaction between a di-isocyanate and a compound containing two or more amine groups produces long polymer chains known as polyureas.
Carbodiimides are produced by the decarboxylation of alkyl and aryl isocyanate using phosphine oxides as a catalyst: | 0 | Organic Chemistry |
* [http://www.chemicalland21.com/arokorhi/industrialchem/inorganic/HYPOPHOSPHOROUS%20ACID.htm ChemicalLand21 Listing] | 0 | Organic Chemistry |
Two basic forms of leaves can be described considering the way the blade (lamina) is divided. A simple leaf has an undivided blade. However, the leaf may be dissected to form lobes, but the gaps between lobes do not reach to the main vein. A compound leaf has a fully subdivided blade, each leaflet of the blade being separated along a main or secondary vein. The leaflets may have petiolules and stipels, the equivalents of the petioles and stipules of leaves. Because each leaflet can appear to be a simple leaf, it is important to recognize where the petiole occurs to identify a compound leaf. Compound leaves are a characteristic of some families of higher plants, such as the Fabaceae. The middle vein of a compound leaf or a frond, when it is present, is called a rachis.
;Palmately compound: The leaflets all have a common point of attachment at the end of the petiole, radiating like fingers of a hand; for example, Cannabis (hemp) and Aesculus (buckeyes).
;Pinnately compound: Leaflets are arranged either side of the main axis, or rachis.
;Bipinnately compound: Leaves are twice divided: the leaflets (technically "subleaflets") are arranged along a secondary axis that is one of several branching off the rachis. Each leaflet is called a pinnule. The group of pinnules on each secondary vein forms a pinna; for example, Albizia (silk tree).
;Trifoliate (or trifoliolate): A pinnate leaf with just three leaflets; for example, Trifolium (clover), Laburnum (laburnum), and some species of Toxicodendron (for instance, poison ivy).
;Pinnatifid: Pinnately dissected to the central vein, but with the leaflets not entirely separate; for example, Polypodium, some Sorbus (whitebeams). In pinnately veined leaves the central vein is known as the midrib. | 5 | Photochemistry |
The Science Based Targets initiative was established in 2015 to help companies to set emission reduction targets in line with climate sciences and Paris Agreement goals. It is funded by IKEA Foundation, Amazon, Bezos Earth Fund, We Mean Business coalition, Rockefeller Brothers Fund and UPS Foundation. In October 2021, SBTi developed and launched the worlds first net zero standard, providing the framework and tools for companies to set science-based net zero targets and limit global temperature rise above pre-industrial levels to 1.5 °C. Best practice as identified by SBTi is for companies to adopt transition plans covering scope 1, 2 and 3 emissions, set out short-term milestones, ensure effective board-level governance and link executive compensation to the companys adopted milestones. | 2 | Environmental Chemistry |
Euxinia most frequently occurred in the Earth's ancient oceans, but its distribution and frequency of occurrence are still under debate. The original model was that it was quite constant for approximately a billion years. Some meta-analyses have questioned how persistent euxinic conditions were based on relatively small black shale deposits in a period when the ocean should have theoretically been preserving more organic matter.
Before the Great Oxygenation Event happened approximately 2.3 billion years ago, there was little free oxygen in either the atmosphere or the ocean. It was originally thought that the ocean accumulated oxygen soon after the atmosphere did, but this idea was challenged by Canfield in 1998 when he proposed that instead of the deep ocean becoming oxidizing, it became sulfidic. This hypothesis is partially based on the disappearance of banded iron formations from the geological records 1.8 billion years ago. Canfield argued that although enough oxygen entered the atmosphere to erode sulfides in continental rocks, there was not enough oxygen to mix into the deep ocean. This would result in an anoxic deep ocean with an increased flux of sulfur from the continents. The sulfur would strip iron ions from the sea water, resulting in iron sulfide (pyrite), a portion of which was eventually buried. When sulfide became the major oceanic reductant instead of iron, the deep water became euxinic. This has become what is known as the Canfield ocean, a model backed by the increase in presence of δS in sedimentary pyrite and the discovery of evidence of the first sulfate evaporites.
Anoxia and sulfidic conditions often occur together. In anoxic conditions anaerobic, sulfate reducing bacteria convert sulfate into sulfide, creating sulfidic conditions. The emergence of this metabolic pathway was very important in the pre-oxygenated oceans because adaptations to otherwise inhabitable or "toxic" environments like this may have played a role in the diversification of early eukaryotes and protozoa in the pre-Phanerozoic.
Euxinia still occurs occasionally today, mostly in meromictic lakes and silled basins such as the Black Sea and some fjords. It is rare in modern times; less than 0.5% of today's sea floor is euxinic. | 9 | Geochemistry |
The oldest and best known quantized force field is the electromagnetic field. Maxwell's equations have been superseded by quantum electrodynamics (QED). By considering the zero-point energy that arises from QED it is possible to gain a characteristic understanding of zero-point energy that arises not just through electromagnetic interactions but in all quantum field theories. | 7 | Physical Chemistry |
Her awards and honors include;
* 2019 AAAS IF/THEN Ambassador
* 2019 Young Observer Award at the 50th IUPAC General Assembly and 47th World Chemistry Congress in Paris, France
* 2020 American Chemical Society Grady-Stack award for her public engagement excellence
*BBC Science Focus named her one of six women changing chemistry in February 2021
*2023 Research Corporation for Science Advancement’s Robert Holland Jr. Award for Research Excellence and Contributions to Diversity, Equity, and Inclusion | 3 | Analytical Chemistry |
On an industrial scale, the reaction of acetic anhydride with hydrogen chloride produces a mixture of acetyl chloride and acetic acid:
Common syntheses of acyl chlorides also entail the reaction of carboxylic acids with phosgene, thionyl chloride, and phosphorus trichloride Phosphorus pentabromide is used for acyl bromides, which are rarely of value. | 0 | Organic Chemistry |
The Cativa process is a method for the production of acetic acid by the carbonylation of methanol. The technology, which is similar to the Monsanto process, was developed by BP Chemicals and is under license by BP Plc. The process is based on an iridium-containing catalyst, such as the complex [Ir(CO)I] (1).
The Cativa and Monsanto processes are sufficiently similar that they can use the same chemical plant. Initial studies by Monsanto had shown iridium to be less active than rhodium for the carbonylation of methanol. Subsequent research, however, showed that the iridium catalyst could be promoted by ruthenium, and this combination leads to a catalyst that is superior to the rhodium-based systems. The switch from rhodium to iridium also allows the use of less water in the reaction mixture. This change reduces the number of drying columns necessary, decreases formation of by-products, such as propionic acid, and suppresses the water gas shift reaction.
The catalytic cycle for the Cativa process, shown above, begins with the reaction of methyl iodide with the square planar active catalyst species (1) to form the octahedral iridium(III) species (2), the fac-isomer of [Ir(CO)(CH)I]. This oxidative addition reaction involves the formal insertion of the iridium(I) centre into the carbon-iodine bond of methyl iodide. After ligand exchange (iodide for carbon monoxide), the migratory insertion of carbon monoxide into the iridium-carbon bond, step (3) to (4), results in the formation of a square pyramidal species with a bound acetyl ligand. The active catalyst species (1) is regenerated by the reductive elimination of acetyl iodide from (4), a de-insertion reaction. The acetyl iodide is hydrolysed to produce the acetic acid product, in the process generating hydroiodic acid which is in turn used to convert the starting material (methanol) to the methyl iodide used in the first step. | 0 | Organic Chemistry |
All the graphical symbols used in the SBGN languages are associated with an SBO term. This permits, for instance, to help generate SBGN maps from SBML models. | 1 | Biochemistry |
Fatty acyl-CoA esters are fatty acid derivatives formed of one fatty acid, a 3'-phospho-AMP linked to phosphorylated pantothenic acid (vitamin B) and cysteamine.
Long-chain acyl-CoA esters are substrates for a number of important enzymatic reactions and play a central role in the regulation of metabolism as allosteric regulators of several enzymes. To participate in specific metabolic processes, fatty acids must first be activated by being joined in thioester linkage (R-CO-SCoA) to the -SH group of coenzyme A, where R is a fatty carbon chain. The thioester bond is a high energy bond.
The activation reaction normally occurs in the endoplasmic reticulum or the outer mitochondrial membrane. This is an ATP-requiring reaction (fatty acyl-CoA synthase), yielding AMP and pyrophosphate (PPi). Different enzymes are specific for fatty acids of different chain length.
Then, the acyl CoA esters are transported in mitochondria. They are converted to fatty acyl carnitine by carnitine acyltransferase I, an enzyme of the inner leaflet of the outer mitochondrial membrane. Fatty acyl carnitine is then transported by an antiport in exchange for free carnitine to the inner surface of the inner mitochondrial membrane. There carnitine acyltransferase II reverses the process, producing fatty acyl-CoA and carnitine. This shuttle mechanism is required only for longer chain fatty acids.
Once inside the mitochondrial matrix, the fatty acyl-CoA derivatives are degraded by a series of reactions that release acetyl-CoA and leads to the production of NADH and FADH2. There are four steps in fatty acid oxidation pathway; oxidation, hydration, oxidation, and thiolysis. It requires 7 rounds of this pathway to degrade palmitate (a C16 fatty acid). | 1 | Biochemistry |
Antibodies coating paramagnetic beads will bind to antigens present on the surface of cells thus capturing the cells and facilitate the concentration of these bead-attached cells. The concentration process is created by a magnet placed on the side of the test tube bringing the beads to it.
MACS systems (Magnetic Cell Separation system):
Through the usage of smaller super paramagnetic beads (<100 nm), which requires a stronger magnetic field to separate cells. Cells are labeled with primary antibodies and then MACS beads are coated with specific- specific antibodies. These labeled cell suspension is then put into a separation column in a strong magnetic field. The labeled cells are contained, magnetized, while in the magnetic field and the unlabeled cells are suspended, un-magnetized, to be collected. Once removed from magnetic field positive cells are eluted. These MACS beads are then incorporated by the cells allowing them to remain in the column because they do not intrude with the cell attachment to the culture surface to cell-cell interactions. A bead removal reagent is then applied to have an enzymatically release of the MACS beads allowing those cells to become relabeled with some other marker, which then is sorted. | 1 | Biochemistry |
In this oxidation scheme, ultraviolet light alone oxidizes the carbon within the sample to produce CO. The UV oxidation method offers the most reliable, low maintenance method of analyzing TOC in ultra-pure waters. | 3 | Analytical Chemistry |
SMAs display a phenomenon sometimes called superelasticity, but is more accurately described as pseudoelasticity. “Superelasticity” implies that the atomic bonds between atoms stretch to an extreme length without incurring plastic deformation. Pseudoelasticity still achieves large, recoverable strains with little to no permanent deformation, but it relies on more complex mechanisms.
SMAs exhibit at least 3 kinds of pseudoelasticty. The two less-studied kinds of pseudoelasticity are pseudo-twin formation and rubber-like behavior due to short range order.
The main pseudoelastic effect comes from a stress-induced phase transformation. The figure on the right exhibits how this process occurs.
Here a load is isothermally applied to a SMA above the austenite finish temperature, A, but below the martensite deformation temperature, M. The figure above illustrates how this is possible, by relating the pseudoelastic stress-induced phase transformation to the shape memory effect temperature induced phase transformation. For a particular point on A it is possible to choose a point on the M line with a higher temperature, as long as that point M also has a higher stress. The material initially exhibits typical elastic-plastic behavior for metals. However, once the material reaches the martensitic stress, the austenite will transform to martensite and detwin. As previously discussed, this detwinning is reversible when transforming back from martensite to austenite. If large stresses are applied, plastic behavior such as detwinning and slip of the martensite will initiate at sites such as grain boundaries or inclusions. If the material is unloaded before plastic deformation occurs, it will revert to austenite once a critical stress for austenite is reached (σ). The material will recover nearly all strain that was induced from the structural change, and for some SMAs this can be strains greater than 10 percent. This hysteresis loop shows the work done for each cycle of the material between states of small and large deformations, which is important for many applications.
In a plot of strain versus temperature, the austenite and martensite start and finish lines run parallel. The SME and pseudoelasticity are actually different parts of the same phenomenon, as shown on the left.
The key to the large strain deformations is the difference in crystal structure between the two phases. Austenite generally has a cubic structure while martensite can be monoclinic or another structure different from the parent phase, typically with lower symmetry. For a monoclinic martensitic material such as Nitinol, the monoclinic phase has lower symmetry which is important as certain crystallographic orientations will accommodate higher strains compared to other orientations when under an applied stress. Thus it follows that the material will tend to form orientations that maximize the overall strain prior to any increase in applied stress. One mechanism that aids in this process is the twinning of the martensite phase. In crystallography, a twin boundary is a two-dimensional defect in which the stacking of atomic planes of the lattice are mirrored across the plane of the boundary. Depending on stress and temperature, these deformation processes will compete with permanent deformation such as slip.
It is important to note that σ is dependent on parameters such as temperature and the number of nucleation sites for phase nucleation. Interfaces and inclusions will provide general sites for the transformation to begin, and if these are great in number, it will increase the driving force for nucleation. A smaller σ will be needed than for homogeneous nucleation. Likewise, increasing temperature will reduce the driving force for the phase transformation, so a larger σ will be necessary. One can see that as you increase the operational temperature of the SMA, σ will be greater than the yield strength, σ, and superelasticity will no longer be observable. | 8 | Metallurgy |
Chromosome jumping library is different from chromosome walking due to the manipulations executed before the cloning step. In order to construct the library of chromosome jumping, individual clones originate from random points in the genome (general jumping libraries first basic protocol) or from the termini of specific restriction fragments (specific jumping libraries alternate protocol) should be identified. | 1 | Biochemistry |
As evidenced by a decreased fluorescence, OCP in its red form is capable of dissipating absorbed light energy from the phycobilisome antenna complex. According to Rakhimberdieva and coworkers, about 30-40% of the energy absorbed by phycobilisomes does not reach the reaction centers when the carotenoid-induced NPQ is active.
The exact mechanism and quenching site in both the carotenoid as well as the phycobilisome still remain uncertain. The linker polypeptide ApcE in the allophycocyanin (APC) core of the phycobilisomes is known to be important, but is not the site of quenching. Several lines of evidence suggest that it is the 660 nm fluorescence emission band of the APC core which is quenched by OCP.
The temperature dependence of the rate of fluorescence quenching is similar to that of soluble protein folding, supporting the hypothesis that OCP slightly unfolds when it converts to OCP. | 5 | Photochemistry |
TFA interacts with the TBP subunit of TFD and aids in the binding of TBP to TATA-box containing promoter DNA. Interaction of TFA with TBP facilitates formation of and stabilizes the preinitiation complex. Interaction of TFA with TBP also results in the exclusion of negative (repressive) factors that might otherwise bind to TBP and interfere with PIC formation. TFA also acts as a coactivator for some transcriptional activators, assisting with their ability to increase, or activate, transcription. The requirement for TFA in vitro transcription systems has been variable, and it can be considered either as a GTF and/or a loosely associated TAF-like coactivator. Genetic analysis in yeast has shown that TFA is essential for viability. | 1 | Biochemistry |
This is another factor which slows the motion of ions within a solution. It is the tendency of the applied potential to move the ionic atmosphere itself. This drags the solvent molecules along because of the attractive forces between ions and solvent molecules. As a result, the central ion at the centre of the ionic atmosphere is influenced to move towards the pole opposite its ionic atmosphere. This inclination retards its motion. | 7 | Physical Chemistry |
Superfluidity in an ultracold fermionic gas was experimentally proven by Wolfgang Ketterle and his team who observed quantum vortices in lithium-6 at a temperature of 50 nK at MIT in April 2005. Such vortices had previously been observed in an ultracold bosonic gas using rubidium-87 in 2000, and more recently in two-dimensional gases. As early as 1999, Lene Hau created such a condensate using sodium atoms for the purpose of slowing light, and later stopping it completely. Her team subsequently used this system of compressed light to generate the superfluid analogue of shock waves and tornadoes: | 7 | Physical Chemistry |
Macrocycles can access a number of stable conformations, with preferences to reside in those that minimize the number of transannular nonbonded interactions within the ring. Medium rings (8-11 atoms) are the most strained with between 9-13 (kcal/mol) strain energy; analysis of the factors important in considering larger macrocyclic conformations can thus be modeled by looking at medium ring conformations. Conformational analysis of odd-membered rings suggests they tend to reside in less symmetrical forms with smaller energy differences between stable conformations. | 0 | Organic Chemistry |
The VAR process is used on many different materials. Certain applications almost always use a material that has been VAR treated. A list of materials that may be VAR treated include:
*Stainless Steel
*Alloy Steel
**4340 & 4330+V
**300M
**AF1410
**Aermet 100
**M50
**BG42
**Nitralloy
**16NCD13
**35NCD16
**HY-100
**HY-180
**HY-TUF
**D6AC
**Maraging steels
**UT-18
**HP 9-4-30
*Titanium
**Ti-6Al-4V
**Ti-10V-2Al-3Fe
**Ti-5Al-5V-5Mo-3Cr
*Invar
*Nitinol
*Nickel superalloys
**Inconel alloys
**Hastelloy alloys
**Rene alloys
**RR1000
*Zirconium
*Niobium
*Platinum
*Tantalum
*Rhodium
Note that pure titanium and most titanium alloys are double or triple VAR processed. Nickel-based super alloys for aerospace applications are usually VAR processed. Zirconium and niobium alloys used in the nuclear industry are routinely VAR processed. Pure platinum, tantalum, and rhodium may be VAR processed. | 8 | Metallurgy |
A reaction step of a chemical reaction is defined as: "An elementary reaction, constituting one of the stages of a stepwise reaction in which a reaction intermediate (or, for the first step, the reactants) is converted into the next reaction intermediate (or, for the last step, the products) in the sequence of intermediates between reactants and products". To put it simply, it is an elementary reaction which goes from one reaction intermediate to another or to the final product. | 7 | Physical Chemistry |
The outgassing of volatile silicones on low Earth orbit devices leads to presence of a cloud of contaminants around the spacecraft. Together with atomic oxygen bombardment, this may lead to gradual deposition of thin layers of carbon-containing silicon dioxide. Their poor transparency is a concern in case of optical systems and solar panels. Deposits of up to several micrometers were observed after 10 years of service on the solar panels of the Mir space station.
Other sources of problems for structures subjected to outer space are erosion and redeposition of the materials by sputtering caused by fast atoms and micrometeoroids. Another major concern, though of non-corrosive kind, is material fatigue caused by cyclical heating and cooling and associated thermal expansion mechanical stresses. | 8 | Metallurgy |
; In vitro measurements
Other tests measure the antioxidant capacity of a fraction. Some make use of the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical cation, which is reactive towards most antioxidants including phenolics, thiols and vitamin C. During this reaction, the blue ABTS radical cation is converted back to its colorless neutral form. The reaction may be monitored spectrophotometrically. This assay is often referred to as the Trolox equivalent antioxidant capacity (TEAC) assay. The reactivity of the various antioxidants tested are compared to that of Trolox, which is a vitamin E analog.
Other antioxidant capacity assays that use Trolox as a standard include the diphenylpicrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC), ferric reducing ability of plasma (FRAP) assays or inhibition of copper-catalyzed in vitro human low-density lipoprotein oxidation.
A cellular antioxidant activity (CAA) assay also exists. Dichlorofluorescin is a probe that is trapped within cells and is easily oxidized to fluorescent dichlorofluorescein (DCF). The method measures the ability of compounds to prevent the formation of DCF by 2,2'-Azobis(2-amidinopropane) dihydrochloride (ABAP)-generated peroxyl radicals in human hepatocarcinoma HepG2 cells.
Other methods include butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), Rancimat method (rancidification assessment of fat).
; In vivo models
Larvae of the model animal Galleria mellonella, also called waxworms, can be used to test the antioxidant effect of individual molecules using boric acid in food to induce an oxidative stress. The content of malondialdehyde, an oxidative stress indicator, and activities of the antioxidant enzymes superoxide dismutase, catalase, glutathione S-transferase and glutathione peroxidase can be monitored. A prophenoloxidase can also be recovered from the insect. | 0 | Organic Chemistry |
K and U move together during geochemical processes and have long-lived radioisotopes that emit gamma rays. It is calculated as a ratio of one to the other on an equal mass basis which is often .
This creates a compelling explanation for the evolution of the solar system.
This result is consistent with an increasing temperature toward the sun during its early protoplanetary nebula phase.
The temperature at the early stage of solar system formation was in excess of 1,000K at the distance of Earth from the sun, and as low as 200–100K at the distances of Jupiter and Saturn. | 9 | Geochemistry |
Phage λ is a double-stranded DNA virus that infects E. coli. The λ chromosome is 48.5kb long and can carry inserts up to 25kb. These inserts replace non-essential viral sequences in the λ chromosome, while the genes required for formation of viral particles and infection remain intact. The insert DNA is replicated with the viral DNA; thus, together they are packaged into viral particles. These particles are very efficient at infection and multiplication leading to a higher production of the recombinant λ chromosomes. However, due to the smaller insert size, libraries made with λ phage may require many clones for full genome coverage. | 1 | Biochemistry |
The company Evolva has developed a genetically modified microorganism which can produce vanillin. Because the microbe is a processing aid, the resulting vanillin would not fall under U.S. GMO labeling requirements, and because the production is nonpetrochemical, food using the ingredient can claim to contain "no artificial ingredients".
Using ferulic acid as an input and a specific non GMO species of Amycolatopsis bacteria, natural vanillin can be produced. | 0 | Organic Chemistry |
Bimetallic materials are materials that are made out of two different metals or alloys that are tightly bonded together. A good example of a bimetallic material would be a bimetallic strip which is used in some kinds of thermometers. In ISCR, bimetallic materials are small pieces of metals that are coated lightly with a catalyst such as palladium, silver, or platinum. The catalyst drives a faster reaction and the small size of the particles allows them to effectively move into and remain in the target zone. | 2 | Environmental Chemistry |
Gilbert Stork was born in the Ixelles municipality of Brussels, Belgium on December 31, 1921. The oldest of 3 children, his middle brother, Michel, died in infancy, but he remained close with his younger sister Monique his whole life. His family had Jewish origins, although Gilbert himself didnt recall them being religiously active. The family moved to Nice when Gilbert was about 14 (circa. 1935) and remained there until 1939. During this period, Gilbert completed his lycée studies, distinguishing himself in French literature and writing. Characterizing himself during those years as "not terribly self-confident," and uncertain whether he could find employment in a profession he enjoyed, Gilbert considered applying for a colonial civil service job in French Indochina. However, the outbreak of World War II that year led the family to flee to New York, where his fathers older brother, Sylvain, had already emigrated. | 0 | Organic Chemistry |
There are several sources for single strand nucleases. The first widely used enzyme was mung bean nuclease, but this nuclease has been shown to have high non-specific activity, and only works at low pH, which can degrade PCR products and dye-labeled primers. The original source for single strand nuclease was from CEL1, or CJE (celery juice extract), but other products have entered the market including Frontier Genomics’ SNiPerase enzymes, which have been optimized for use on platforms that use labeled and unlabeled PCR products (see next section). Transgenomic isolated the single strand nuclease protein and sells it as a recombinant form. The advantage of the recombinant form is that unlike the enzyme mixtures, it does not contain non-specific nuclease activity, which can degrade the dyes on the PCR primers. The disadvantage is a substantially higher cost. | 1 | Biochemistry |
Some plants mimic the presence of insect eggs on their leaves, dissuading insect species from laying their eggs there. Because female butterflies are less likely to lay their eggs on plants that already have butterfly eggs, some species of neotropical vines of the genus Passiflora (Passion flowers) contain physical structures resembling the yellow eggs of Heliconius butterflies on their leaves, which discourage oviposition by butterflies. | 1 | Biochemistry |
Total synthesis is the complete chemical synthesis of a complex molecule, often a natural product, from simple, commercially-available precursors. It usually refers to a process not involving the aid of biological processes, which distinguishes it from semisynthesis. Syntheses may sometimes conclude at a precursor with further known synthetic pathways to a target molecule, in which case it is known as a formal synthesis. Total synthesis target molecules can be natural products, medicinally-important active ingredients, known intermediates, or molecules of theoretical interest. Total synthesis targets can also be organometallic or inorganic, though these are rarely encountered. Total synthesis projects often require a wide diversity of reactions and reagents, and subsequently requires broad chemical knowledge and training to be successful.
Often, the aim is to discover a new route of synthesis for a target molecule for which there already exist known routes. Sometimes, however, no route exists, and chemists wish to find a viable route for the first time. Total synthesis is particularly important for the discovery of new chemical reactions and new chemical reagents, as well as establishing synthetic routes for medicinally important compounds. | 0 | Organic Chemistry |
Rust is associated with the degradation of iron-based tools and structures. As rust has a much higher volume than the originating mass of iron, its buildup can also cause failure by forcing apart adjacent parts — a phenomenon sometimes known as "rust packing". It was the cause of the collapse of the Mianus river bridge in 1983, when the bearings rusted internally and pushed one corner of the road slab off its support.
Rust was an important factor in the Silver Bridge disaster of 1967 in West Virginia, when a steel suspension bridge collapsed in less than a minute, killing 46 drivers and passengers on the bridge at the time. The Kinzua Bridge in Pennsylvania was blown down by a tornado in 2003, largely because the central base bolts holding the structure to the ground had rusted away, leaving the bridge anchored by gravity alone.
Reinforced concrete is also vulnerable to rust damage. Internal pressure caused by expanding corrosion of concrete-covered steel and iron can cause the concrete to spall, creating severe structural problems. It is one of the most common failure modes of reinforced concrete bridges and buildings. | 8 | Metallurgy |
Flutamide has also been associated with interstitial pneumonitis (which can progress to pulmonary fibrosis). The incidence of interstitial pneumonitis with flutamide was found to be 0.04% (4 per 10,000) in a large clinical cohort of 41,700 prostate cancer patients. A variety of case reports have associated flutamide with photosensitivity. Flutamide has been associated with several case reports of methemoglobinemia. Bicalutamide does not appear to share this risk with flutamide. Flutamide has also been associated with reports of sulfhemoglobinemia and neutropenia. | 4 | Stereochemistry |
A benzoporphyrin is a porphyrin with a benzene ring fused to one of the pyrrole units. e.g. verteporfin is a benzoporphyrin derivative. | 1 | Biochemistry |
Kinetic models describe the particle velocity distribution function at each point in the plasma and therefore do not need to assume a Maxwell–Boltzmann distribution. A kinetic description is often necessary for collisionless plasmas. There are two common approaches to kinetic description of a plasma. One is based on representing the smoothed distribution function on a grid in velocity and position. The other, known as the particle-in-cell (PIC) technique, includes kinetic information by following the trajectories of a large number of individual particles. Kinetic models are generally more computationally intensive than fluid models. The Vlasov equation may be used to describe the dynamics of a system of charged particles interacting with an electromagnetic field.
In magnetized plasmas, a gyrokinetic approach can substantially reduce the computational expense of a fully kinetic simulation. | 7 | Physical Chemistry |
In a normal bearing the surfaces are separated by a layer of oil, this is known as elastohydrodynamic (EHD) lubrication. If the thickness of the EHD film is of the same order of magnitude as the surface roughness, the surface topography is able to interact and cause micro pitting. A thin EHD film may be caused by excess load or temperature, a lower oil viscosity than is required, low speed or water in the oil. Water in the oil can make micro pitting worse by causing hydrogen embrittlement of the surface. Micro pitting occurs only under poor EHD lubrication conditions.
A surface with a deep scratch might break exactly at the scratch if stress is applied. One can imagine that the surface roughness is a composite of many very small scratches. So high surface roughness decreases the stability on heavy stressed parts. To get a good overview of the surface an areal scan (Surface metrology) gives more information that a measurement along a single profile (profileometer). To quantify the surface roughness the ISO 25178 can be used. | 8 | Metallurgy |
Herman Thompson Briscoe (November 6, 1893 – October 8, 1960) was an American chemist and professor of chemistry. The Herman T. Briscoe Professorship in Chemistry at Indiana University was established in 1961, and the Herman T. Briscoe Quadrangle Dormitory was dedicated in 1966. | 3 | Analytical Chemistry |
A thermodynamic cycle consists of linked sequences of thermodynamic processes that involve transfer of heat and work into and out of the system, while varying pressure, temperature, and other state variables within the system, and that eventually returns the system to its initial state. In the process of passing through a cycle, the working fluid (system) may convert heat from a warm source into useful work, and dispose of the remaining heat to a cold sink, thereby acting as a heat engine. Conversely, the cycle may be reversed and use work to move heat from a cold source and transfer it to a warm sink thereby acting as a heat pump. If at every point in the cycle the system is in thermodynamic equilibrium, the cycle is reversible. Whether carried out reversible or irreversibly, the net entropy change of the system is zero, as entropy is a state function.
During a closed cycle, the system returns to its original thermodynamic state of temperature and pressure. Process quantities (or path quantities), such as heat and work are process dependent. For a cycle for which the system returns to its initial state the first law of thermodynamics applies:
The above states that there is no change of the internal energy () of the system over the cycle. represents the total work and heat input during the cycle and would be the total work and heat output during the cycle. The repeating nature of the process path allows for continuous operation, making the cycle an important concept in thermodynamics. Thermodynamic cycles are often represented mathematically as quasistatic processes in the modeling of the workings of an actual device. | 7 | Physical Chemistry |
Twenty-two DNA repair genes with hypermethylated promoters, and reduced or absent expression, were found to occur among 17 types of cancer, as listed in two review articles. Promoter hypermethylation of MGMT occurs frequently in a number of cancers including 93% of bladder cancers, 88% of stomach cancers, 74% of thyroid cancers, 40%-90% of colorectal cancers and 50% of brain cancers. That review also indicated promoter hypermethylation of LIG4, NEIL1, ATM, MLH1 or FANCB occurs at frequencies between 33% and 82% in one or more of head and neck cancers, non-small-cell lung cancers or non-small-cell lung cancer squamous cell carcinomas. The article Epigenetic inactivation of the premature aging Werner syndrome gene in human cancer indicates the DNA repair gene WRN has a promoter that is frequently hypermethylated in a number of cancers, with hypermethylation occurring in 11% to 38% of colorectal, head and neck, stomach, prostate, breast, thyroid, non-Hodgkin lymphoma, chondrosarcoma and osteosarcoma cancers (see WRN). | 1 | Biochemistry |
Methyl orange has mutagenic properties. When methyl orange is put under oxidative stress, one of the double-bonded nitrogen atoms that connects the aromatic rings gets radicalized and can further break down into reactive oxygen species or anilines, which are carcinogenic and can mutate DNA. Various bacteria and enzymes can also cause this breakdown to occur. | 3 | Analytical Chemistry |
This acid–base theory was a revival of the oxygen theory of acids and bases proposed by German chemist Hermann Lux in 1939, further improved by Håkon Flood and is still used in modern geochemistry and electrochemistry of molten salts. This definition describes an acid as an oxide ion () acceptor and a base as an oxide ion donor. For example:
This theory is also useful in the systematisation of the reactions of noble gas compounds, especially the xenon oxides, fluorides, and oxofluorides. | 7 | Physical Chemistry |
Industrially, hydrocyanation is commonly performed on alkenes catalyzed by nickel complexes of phosphite () ligands. A general reaction is shown: | 0 | Organic Chemistry |
Soil amendments such as fertilizers and manures can cause soil acidification. Sulfur based fertilizers can be highly acidifying, examples include elemental sulfur and iron sulfate while others like potassium sulfate have no significant effect on soil pH. While most nitrogen fertilizers have an acidifying effect, ammonium-based nitrogen fertilizers are more acidifying than other nitrogen sources. Ammonia-based nitrogen fertilizers include ammonium sulfate, diammonium phosphate, monoammonium phosphate, and ammonium nitrate. Organic nitrogen sources, such as urea and compost, are less acidifying. Nitrate sources which have little or no ammonium, such as calcium nitrate, magnesium nitrate, potassium nitrate, and sodium nitrate, are not acidifying. | 9 | Geochemistry |
Some SELEX reactions can generate probes that are dependent on primer binding regions for secondary structure formation. There are aptamer applications for which a short sequence, and thus primer truncation, is desirable. An advancement on the original method allows an RNA library to omit the constant primer regions, which can be difficult to remove after the selection process because they stabilize secondary structures that are unstable when formed by the random region alone. | 1 | Biochemistry |
In organic and physical organic chemistry, Clars rule is an empirical rule that relates the chemical stability of a molecule with its aromaticity. It was introduced in 1972 by the Austrian organic chemist Erich Clar in his book The Aromatic Sextet'. The rule states that given a polycyclic aromatic hydrocarbon, the resonance structure most important to characterize its properties is that with the largest number of aromatic π-sextets i.e. benzene-like moieties. | 7 | Physical Chemistry |
Indirect DNA damage occurs when a UV-photon is absorbed in the human skin by a chromophore that does not have the ability to convert the energy into harmless heat very quickly. Molecules that do not have this ability have a long-lived excited state. This long lifetime leads to a high probability for reactions with other molecules—so-called bimolecular reactions. Melanin and DNA have extremely short excited state lifetimes in the range of a few femtoseconds (10s). The excited state lifetime of compounds used in sunscreens such as menthyl anthranilate, avobenzone or padimate O is 1,000 to 1,000,000 times longer than that of melanin, and therefore they may cause damage to living cells that come in contact with them.
The molecule that originally absorbs the UV-photon is called a "chromophore". Bimolecular reactions can occur either between the excited chromophore and DNA or between the excited chromophore and another species, to produce free radicals and reactive oxygen species. These reactive chemical species can reach DNA by diffusion and the bimolecular reaction damages the DNA (oxidative stress). It is important to note that, unlike direct DNA damage which causes sunburn, indirect DNA damage does not result in any warning signal or pain in the human body.
The bimolecular reactions that cause the indirect DNA damage are illustrated in the figure:
O is reactive harmful singlet oxygen: | 5 | Photochemistry |
When block copolymer micelles do not display the characteristic relaxation processes of surfactant micelles, these are called kinetically frozen micelles. These can be achieved in two ways: when the unimers forming the micelles are not soluble in the solvent of the micelle solution, or if the core forming blocks are glassy at the temperature in which the micelles are found. Kinetically frozen micelles are formed when either of these conditions is met. A special example in which both of these conditions are valid is that of polystyrene-b-poly(ethylene oxide). This block copolymer is characterized by the high hydrophobicity of the core forming block, PS, which causes the unimers to be insoluble in water. Moreover, PS has a high glass transition temperature which is, depending on the molecular weight, higher than room temperature. Thanks to these two characteristics, a water solution of PS-PEO micelles of sufficiently high molecular weight can be considered kinetically frozen. This means that none of the relaxation processes, which would drive the micelle solution towards thermodynamic equilibrium, are possible. Pioneering work on these micelles was done by Adi Eisenberg. It was also shown how the lack of relaxation processes allowed great freedom in the possible morphologies formed. Moreover, the stability against dilution and vast range of morphologies of kinetically frozen micelles make them particularly interesting, for example, for the development of long circulating drug delivery nanoparticles. | 6 | Supramolecular Chemistry |
Amides undergo many chemical reactions, although they are less reactive than esters. Amides hydrolyse in hot alkali as well as in strong acidic conditions. Acidic conditions yield the carboxylic acid and the ammonium ion while basic hydrolysis yield the carboxylate ion and ammonia. The protonation of the initially generated amine under acidic conditions and the deprotonation of the initially generated carboxylic acid under basic conditions render these processes non-catalytic and irreversible. Amides are also versatile precursors to many other functional groups. Electrophiles react with the carbonyl oxygen. This step often precedes hydrolysis, which is catalyzed by both Brønsted acids and Lewis acids. Enzymes, e.g. peptidases and artificial catalysts, are known to accelerate the hydrolysis reactions. | 0 | Organic Chemistry |
A ribosome binding site, or ribosomal binding site (RBS), is a sequence of nucleotides upstream of the start codon of an mRNA transcript that is responsible for the recruitment of a ribosome during the initiation of translation. Mostly, RBS refers to bacterial sequences, although internal ribosome entry sites (IRES) have been described in mRNAs of eukaryotic cells or viruses that infect eukaryotes. Ribosome recruitment in eukaryotes is generally mediated by the 5' cap present on eukaryotic mRNAs. | 1 | Biochemistry |
Cytokeratin 5/6 antibodies are antibodies that target both cytokeratin 5 and cytokeratin 6. These are used in immunohistochemistry, often called CK 5/6 staining, including the following applications:
*Identifying basal cells or myoepithelial cells in the breast and prostate.
*For breast pathology, also in distinguishing usual ductal hyperplasia (UDH) and papillary lesions (having a mosaic-like pattern) from ductal carcinoma in situ, which is usually negative. Cyclin D1 and CK5/6 staining could be used in concert to distinguish between the diagnosis of papilloma (Cyclin D1 < 4.20%, CK 5/6 positive) or papillary carcinoma (Cyclin D1 > 37.00%, CK 5/6 negative).
*In the lung, distinguishing epithelioid mesothelioma (CK5/6 positive in 83%) from lung adenocarcinoma (CK5/6 negative in 85%). | 1 | Biochemistry |
An important application of Z-HIT is the examination of experimental impedance spectra for artifacts. The examination of EIS series measurements is often difficult due to the tendency of examined objects to undergo changes during the measurement. This may occur in many standard EIS applications such as the evaluation of fuel cells or batteries during discharge. Further examples include the investigation of light-sensitive systems under illumination (e.g. Photoelectrochemistry) or the analysis of water uptake of lacquers on metal surfaces (e.g. corrosion-protection).
A descriptive example for an unsteady system is a Lithium-ion battery. Under cyclization or discharging, the amount of charge in the battery changes over time. The change in charge is coupled with a chemical redox reaction, transferring to a change in concentrations of the involved substances. This violates the principles of stationarity and causality which are prerequisites for proper EIS measurements. In theory, this would exclude drift-affected samples from valid evaluation. Using the ZHIT-algorithm, these and similar artifacts can be recognized and spectra following causality can even be reconstructed, which are consistent with the Kramers–Kronig relations and thereby valid for analysis. | 7 | Physical Chemistry |
In contrast to selenonic and seleninic acids, selenenic acids are unstable with respect to a self-condensation reaction to form the corresponding selenoseleninates or disproportionation into corresponding seleninic acids and diselenides:
:2 RSeOH → RSe(O)SeR + HO
:2 RSeOH → RSeOH + 1/2 RSeSeR
Even the very bulky 2,4,6-tri-tert-butylbenzeneselenenic acid disproportionates readily. A stable selenenic acid was synthesized by burying the SeOH functional group within the cavity of a [[Calixarene|p-tert-butyl[calix[6]arene macrocycle]]]. X-ray crystallographic analysis revealed the Se-O bond length to be 1.763 Å. The Se-O absorbs in the IR spectrum at 680–700 cm. In a stable selenenic acid prepared by oxidizing a highly hindered selenol, BmtSeH, the Se-O bond length was found to be 1.808 Å while the O-Se-C angle was 96.90°. Oxidation of BmtSeOH gave BmtSeOH.
Selenenic acids are believed to be transient intermediates in a number of redox reactions involving organoselenium compounds. One notable example is the syn-elimination of selenoxides. Selenenic acids are also transient intermediates in the reduction of seleninic acids as well as the oxidation of diselenides. The reasoning for postulating selenenic acids as reactive intermediates is based in part on analogy with their more extensively studied sulfenic acid analogs. | 0 | Organic Chemistry |
Over-activation of mTOR signaling significantly contributes to the initiation and development of tumors and mTOR activity was found to be deregulated in many types of cancer including breast, prostate, lung, melanoma, bladder, brain, and renal carcinomas. Reasons for constitutive activation are several. Among the most common are mutations in tumor suppressor PTEN gene. PTEN phosphatase negatively affects mTOR signalling through interfering with the effect of PI3K, an upstream effector of mTOR. Additionally, mTOR activity is deregulated in many cancers as a result of increased activity of PI3K or Akt. Similarly, overexpression of downstream mTOR effectors 4E-BP1, S6K1, S6K2 and eIF4E leads to poor cancer prognosis. Also, mutations in TSC proteins that inhibit the activity of mTOR may lead to a condition named tuberous sclerosis complex, which exhibits as benign lesions and increases the risk of renal cell carcinoma.
Increasing mTOR activity was shown to drive cell cycle progression and increase cell proliferation mainly due to its effect on protein synthesis. Moreover, active mTOR supports tumor growth also indirectly by inhibiting autophagy. Constitutively activated mTOR functions in supplying carcinoma cells with oxygen and nutrients by increasing the translation of HIF1A and supporting angiogenesis. mTOR also aids in another metabolic adaptation of cancerous cells to support their increased growth rate—activation of glycolytic metabolism. Akt2, a substrate of mTOR, specifically of mTORC2, upregulates expression of the glycolytic enzyme PKM2 thus contributing to the Warburg effect. | 1 | Biochemistry |
The first law gives rise to the following formula:
in which
* is the permeability, an experimentally determined membrane "conductance" for a given gas at a given temperature.
* is the difference in concentration of the gas across the membrane for the direction of flow (from to ).
Fick's first law is also important in radiation transfer equations. However, in this context, it becomes inaccurate when the diffusion constant is low and the radiation becomes limited by the speed of light rather than by the resistance of the material the radiation is flowing through. In this situation, one can use a flux limiter.
The exchange rate of a gas across a fluid membrane can be determined by using this law together with Graham's law.
Under the condition of a diluted solution when diffusion takes control, the membrane permeability mentioned in the above section can be theoretically calculated for the solute using the equation mentioned in the last section (use with particular care because the equation is derived for dense solutes, while biological molecules are not denser than water):
where
* is the total area of the pores on the membrane (unit m).
* transmembrane efficiency (unitless), which can be calculated from the stochastic theory of chromatography.
* D is the diffusion constant of the solute unit m⋅s.
* t is time unit s.
* c, c concentration should use unit mol m, so flux unit becomes mol s.
The flux is decay over the square root of time because a concentration gradient builds up near the membrane over time under ideal conditions. When there is flow and convection, the flux can be significantly different than the equation predicts and show an effective time t with a fixed value, which makes the flux stable instead of decay over time. A critical time has been estimated under idealized flow conditions when there is no gradient formed. This strategy is adopted in biology such as blood circulation. | 7 | Physical Chemistry |
Mice with truncated EpoR are viable, which suggests Jak2 activity is sufficient to support basal erythropoiesis by activating the necessary pathways without phosphotyrosine docking sites being needed. EpoR-H form of EpoR truncation contains the first, and, what can be argued, the most important tyrosine 343 that serves as a docking site for the Stat5 molecule, but lacks the rest of the cytoplasmic tail. These mice exhibit elevated erythropoiesis consistent with the idea that phosphatase recruitment (and therefore the shutting down of signaling) is aberrant in these mice.
The EpoR-HM receptor also lacks the majority of the cytoplasmic domain, and contains the tyrosine 343 that was mutated to phenylalanine, making it unsuitable for efficient Stat5 docking and activation. These mice are anemic and show poor response to hypoxic stress, such as phenylhydrazine treatment or erythropoietin injection.
EpoR knockout mice have defects in heart, brain and the vasculature. These defects may be due to blocks in RBC formation and thus insufficient oxygen delivery to developing tissues because mice engineered to express Epo receptors only in erythroid cells develop normally. | 1 | Biochemistry |
Organotantalum compounds are invoked as intermediates in C-alkylation of secondary amines with 1-alkenes using Ta(NMe). The chemistry developed by Maspero was later brought to fruition when Hartwig and Herzon reported the hydroaminoalkylation of olefins to form alkylamines:
The catalytic cycle may proceed by β-hydrogen abstraction of the bisamide, which forms the metallaaziridine. Subsequent olefin insertion, protonolysis of the tantalum-carbon bond, and β-hydrogen abstraction affords the alkylamine product. | 0 | Organic Chemistry |
Triphosgene is used as a reagent in organic synthesis as a source of CO. It behaves like phosgene, to which it cracks thermally:
Alcohols are converted to carbonates. Primary and secondary amines are converted to ureas and isocyanates.
Triphosgene has been used to synthesize chlorides. Some Alkyl chlorides are prepared by treating alcohols with a mixture of triphosgene and pyridine. Alkyl dichlorides and trichlorides can similarly be synthesized using triphosgene. Vinyl chlorides are synthesized from ketones using triphosgene and DMF to form a Vilsmeier reagent, followed by a ring opening by chloride ions. Aryl chlorides can also be produced using a Vilsmeier reagent from triphosgene and DMF. | 0 | Organic Chemistry |
Explosophores are functional groups in organic chemistry that give organic compounds explosive properties. | 0 | Organic Chemistry |
2-Phenylpyridine is an organic compound with the formula CHCHN (or CHN). It is a colourless viscous liquid. The compound and related derivatives have attracted interest as precursors to highly fluorescent metal complexes of possible value as organic light emitting diodes (OLEDs).
The compound is prepared by the reaction of phenyl lithium with pyridine:
:CHLi + CHN → CH-CHN + LiH
The reaction of iridium trichloride with 2-phenylpyridine proceeds via cyclometallation to give the chloride-bridged complex:
:4 CH-CHN + 2 IrCl(HO) → IrCl(CH-CHN) + 4 HCl
This complex can be converted to the pictured tris(cyclometallated) derivative tris(2-phenylpyridine)iridium. | 5 | Photochemistry |
In rare cases, a mutation in the genes controlling the production of lactate dehydrogenase will lead to a medical condition known as lactate dehydrogenase deficiency. Depending on which gene carries the mutation, one of two types will occur: either lactate dehydrogenase-A deficiency (also known as glycogen storage disease XI) or lactate dehydrogenase-B deficiency. Both of these conditions affect how the body breaks down sugars, primarily in certain muscle cells. Lactate dehydrogenase-A deficiency is caused by a mutation to the LDHA gene, while lactate dehydrogenase-B deficiency is caused by a mutation to the LDHB gene.
This condition is inherited in an autosomal recessive pattern, meaning that both parents must contribute a mutated gene in order for this condition to be expressed.
A complete lactate dehydrogenase enzyme consists of four protein subunits. Since the two most common subunits found in lactate dehydrogenase are encoded by the LDHA and LDHB genes, either variation of this disease causes abnormalities in many of the lactate dehydrogenase enzymes found in the body. In the case of lactate dehydrogenase-A deficiency, mutations to the LDHA gene result in the production of an abnormal lactate dehydrogenase-A subunit that cannot bind to the other subunits to form the complete enzyme. This lack of a functional subunit reduces the amount of enzyme formed, leading to an overall decrease in activity. During the anaerobic phase of glycolysis (the Cori cycle), the mutated enzyme is unable to convert pyruvate into lactate to produce the extra energy the cells need. Since this subunit has the highest concentration in the LDH enzymes found in the skeletal muscles (which are the primary muscles responsible for movement), high-intensity physical activity will lead to an insufficient amount of energy being produced during this anaerobic phase. This in turn will cause the muscle tissue to weaken and eventually break down, a condition known as rhabdomyolysis. The process of rhabdomyolysis also releases myoglobin into the blood, which will eventually end up in the urine and cause it to become red or brown: another condition known as myoglobinuria. Some other common symptoms are exercise intolerance, which consists of fatigue, muscle pain, and cramps during exercise, and skin rashes. In severe cases, myoglobinuria can damage the kidneys and lead to life-threatening kidney failure. In order to obtain a definitive diagnosis, a muscle biopsy may be performed to confirm low or absent LDH activity. There is currently no specific treatment for this condition.
In the case of lactate dehydrogenase-B deficiency, mutations to the LDHB gene result in the production of an abnormal lactate dehydrogenase-B subunit that cannot bind to the other subunits to form the complete enzyme. As with lactate dehydrogenase-A deficiency, this mutation reduces the overall effectiveness in the enzyme. However, there are some major differences between these two cases. The first is the location where the condition manifests itself. With lactate dehydrogenase-B deficiency, the highest concentration of B subunits can be found within the cardiac muscle, or the heart. Within the heart, lactate dehydrogenase plays the role of converting lactate back into pyruvate so that the pyruvate can be used again to create more energy. With the mutated enzyme, the overall rate of this conversion is decreased. However, unlike lactate dehydrogenase-A deficiency, this mutation does not appear to cause any symptoms or health problems linked to this condition. At the present moment, it is unclear why this is the case. Affected individuals are usually discovered only when routine blood tests indicate low LDH levels present within the blood. | 1 | Biochemistry |
Protein adsorption refers to the adhesion of proteins to solid surfaces. This phenomenon is an important issue in the food processing industry, particularly in milk processing and wine and beer making. Excessive adsorption, or protein fouling, can lead to health and sanitation issues, as the adsorbed protein is very difficult to clean and can harbor bacteria, as is the case in biofilms. Product quality can be adversely affected if the adsorbed material interferes with processing steps, like pasteurization. However, in some cases protein adsorption is used to improve food quality, as is the case in fining of wines. | 1 | Biochemistry |
Certain gases, when mixed with dry water, combine with the water, which then traps them in a solid clathrate hydrate cage. This presents the possibility that explosive gases could be transported in dry water with a reduced risk of detonation. Dry water is currently being considered for use as a carbon sequestration agent to capture and seal away greenhouse gases from the atmosphere. It can trap four times more carbon dioxide than ordinary water over a similar length of time. Dry water also has applications for the transportation and storage of many dangerous materials. It can be used as a medium for volatile compounds, as materials stored within the dry water can be reduced to powder and stabilized – reducing not only the volatility of the substance, but also its weight for transport. It has also been theorized that dry water could have potential uses in the construction of fuel cells for automobiles due to its ability to store and stabilize very large amounts of volatile gases and materials without permanently binding them. Due to its nature, dry water is classified as an adsorbent material. It has many potential uses in fields where emulsions are used. Recent studies have also found dry water can act as a catalyst. | 7 | Physical Chemistry |
Catherine E. Costello attended the Emmanuel College in Boston for her undergraduate studies in chemistry, and minors in mathematics and physics. She received a Master of Science (1967) and a PhD from Georgetown University (1971). After graduation, she did post-doctoral research with Klaus Biemann at Massachusetts Institute of Technology. | 1 | Biochemistry |
Compressible flows in non-ideal conditions are encountered in several industrial and aerospace applications. They are employed for example in Organic Rankine Cycles (ORC) and supercritical carbon dioxide (sCO) systems for power production. In the aerospace field, fluids in conditions close to saturation can be used as oxiders in hybrid rocket motors or for surface cooling of rocket nozzles. Gases made of molecules of high molecular mass can be used in supersonic wind tunnels instead of air to obtain higher Reynolds numbers. Finally, non-ideal flows find application in fuels transportation at high-speed and in Rapid Expansion of Supercritical Solutions (RESS) of CO for particles generation or extraction of chemicals. | 7 | Physical Chemistry |
Sulfites and hydrogensulfites reduce iodine readily in acidic medium to iodide. Thus when a diluted but excess amount of standard iodine solution is added to known volume of sample, the sulfurous acid and sulfites present reduces iodine quantitatively:
(This application is used for iodimetry titration because here Iodine is directly used) | 3 | Analytical Chemistry |
[Ru(bpy)] absorbs ultraviolet and visible light. Aqueous solutions of [Ru(bpy)]Cl are orange due to a strong MLCT absorption at 452 ± 3 nm (extinction coefficient of 14,600 Mcm). Further absorption bands are found at 285 nm corresponding to ligand centered π← π transitions and a weak transition around 350 nm (d-d transition). Light absorption results in formation of an excited state have a relatively long lifetime of 890 ns in acetonitrile and 650 ns in water. The excited state relaxes to the ground state by emission of a photon or non-radiative relaxation. The quantum yield is 2.8% in air-saturated water at 298 K and the emission maximum wavelength is 620 nm. The long lifetime of the excited state is attributed to the fact that it is triplet, whereas the ground state is a singlet state and in part due to the fact that the structure of the molecule allows for charge separation. Singlet-triplet transitions are forbidden and therefore often slow.
Like all molecular excited states, the triplet excited state of [Ru(bpy)] has both stronger oxidizing and reducing properties than its ground state. This situation arises because the excited state can be described as an Ru complex containing a bpy radical anion as a ligand. Thus, the photochemical properties of [Ru(bpy)] are reminiscent of the photosynthetic assembly, which also involves separation of an electron and a hole.
[Ru(bpy)] has been examined as a photosensitizer for both the oxidation and reduction of water. Upon absorbing a photon, [Ru(bpy)] converts to the aforementioned triplet state, denoted [Ru(bpy)]*. This species transfers an electron, located on one bpy ligand, to a sacrificial oxidant such as peroxodisulfate (SO). The resulting [Ru(bpy)] is a powerful oxidant and oxidizes water into O and protons via a catalyst. Alternatively, the reducing power of [Ru(bpy)]* can be harnessed to reduce methylviologen, a recyclable carrier of electrons, which in turn reduces protons at a platinum catalyst. For this process to be catalytic, a sacrificial reductant, such as EDTA or triethanolamine is provided to return the Ru(III) back to Ru(II).
Derivatives of [Ru(bpy)] are numerous. Such complexes are widely discussed for applications in biodiagnostics, photovoltaics and organic light-emitting diode, but no derivative has been commercialized. Application of [Ru(bpy)] and its derivatives to fabrication of optical chemical sensors is arguably one of the most successful areas so far. | 5 | Photochemistry |
Wades rules are successful in describing the geometry of the anionic sublattice of Zintl phases and of Zintl ions but not the electronic structure. Other spherical shell models with spherical harmonic wave functions for molecular orbitals—analogous to atomic orbitals—that describe the clusters as pseduo elements. The Jellium model uses a spherical potential from the nuclei to give orbitals with global nodal properties. Again, this formulates the cluster as a super atom' with an electron configuration comparable to a single atom. The model is best applied to spherically symmetric systems, and two examples for which it works well are the icosahedral Al and [Sn@Cu@Sn] clusters. DFT or ab initio molecular orbital calculations similarly treat the clusters with atomic, and correspondingly label them S, P, D etc. These closed shell configurations have prompted some investigation of 3D aromaticity. This concept was first suggested for fullerenes and corresponds to a 2(N+1) rule in the spherical shell model. An indicator of this phenomenon is a negative Nucleus Independent Chemical Shift (NICS) values of the center of the cluster or of certain additional high symmetry points. | 7 | Physical Chemistry |
MAO inhibitors within 14 days. MAO inhibitors include isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, and tranylcypromine.
Drinking alcohol can increase side effects of dexbrompheniramine. | 4 | Stereochemistry |
ROP proteins are a type of monomeric G proteins found in plants belonging to the Rho family. ROP binding to GTP or GDP determines its activity due to conformational changes within its structure. Within the G-domain of the structure are the G-box motifs G1-5. These motifs are formed during protein folding and are composed of conserved sequences that are responsible for nucleotide and magnesium binding as well as hydrolysis of GTP. Motifs G2 (switch I loop) and G3 (switch II loop) possess distinct conformations depending on GTP binding state. In addition, the G-domain contains a unique and conserved helical domain commonly found in Rho family proteins called αi.
Specific locations within the 3D ROP protein structure, including the amino acids 13-20, 60-64, and 118-121, act as binding sites during protein activity. The serine residue at amino acid 74 has been shown to be a potential protein activity regulation site through phosphorylation. | 1 | Biochemistry |
If V is the molar volume and T the critical temperature of a liquid the surface tension γ is given by
where k is a constant valid for all liquids, with a value of 2.1×10 J/(K·mol).
More precise values can be gained when considering that the line normally passes the temperature axis 6 K before the critical point:
The molar volume V is given by the molar mass M and the density ρ
The term is also referred to as the "molar surface tension" γ :
A useful representation that prevents the use of the unit mol is given by the Avogadro constant N :
As John Lennard-Jones and Corner showed in 1940 by means of the statistical mechanics the constant k′ is nearly equal to the Boltzmann constant. | 7 | Physical Chemistry |
Owing to the importance of butyrate as an inflammatory regulator and immune system contributor, butyrate depletions could be a key factor influencing the pathogenesis of many vasculitic conditions. It is thus essential to maintain healthy levels of butyrate in the gut. Fecal microbiota transplants (to restore BPB and symbiosis in the gut) could be effective by replenishing butyrate levels. In this treatment, a healthy individual donates their stool to be transplanted into an individual with dysbiosis. A less-invasive treatment option is the administration of butyrate—as oral supplements or enemas—which has been shown to be very effective in terminating symptoms of inflammation with minimal-to-no side-effects. In a study where patients with ulcerative colitis were treated with butyrate enemas, inflammation decreased significantly, and bleeding ceased completely after butyrate provision. | 1 | Biochemistry |
The location of spliceosomal activity for the minor class spliceosome is regarded by most experts to be in the nucleus. However, a single paper has claimed that the minor spliceosome is active in the cytosol. The data presented within this paper are not fully accepted within the field and directly contradict numerous other papers. | 1 | Biochemistry |
Total suspended solids (TSS) concentration is the concentration (dry weight mass per unit volume of water) of all the material in water that is caught on a filter, usually a filter with about a 0.7 micrometer pore size. This includes all the particles suspended in water, such as mineral particles (silt, clay), organic detritus, and phytoplankton cells. Clear water bodies have low TSS concentrations. Other names for TSS include total suspended matter (TSM) and suspended particulate matter (SPM). The term suspended sediment concentration (SSC) refers to the mineral component of TSS but is sometimes used interchangeably with TSS. If desired, the concentrations of volatile (organic) and fixed (inorganic) suspended solids can be separated out using the loss-on-ignition method by burning the filter in a muffle furnace to burn off organic matter, leaving behind ash including mineral particles and inorganic components of phytoplankton cells, with TSS = volatile suspended solids + fixed suspended solids. | 3 | Analytical Chemistry |
* pnictochalcogenides
** oxypnictides, including oxynitrides, oxyphosphides, oxyarsenides, oxyantimonides, oxybismuthides
* chalcohalides or chalcogenide halides
** oxohalides, including oxyfluorides, oxychlorides, oxybromides, oxyiodides
** fluorosulfides
** sulfide chlorides, selenide chlorides, telluride chlorides
** sulfide bromides, selenide bromides, telluride bromides
** sulfide iodides, selenide iodides, telluride iodides
* oxysulfides, oxyselenides
* oxyhydrides
* halopnictides
** fluoropnictides, including fluorophosphides, fluoroarsenides, fluoroantimonides, fluorobismuthides, arsenide chlorides | 7 | Physical Chemistry |
As with Cu, the field of Zn isotope biogeochemistry is still in a relatively early stage, so the Zn isotope compositions of materials in the environment are not well-documented. However, based on a compilation of some reported measurements, it appears that Zn isotope ratios do not vary widely among environmental materials (e.g., plants, minerals, seawater, etc.), as δZn values of materials typically fall within a range of -1 to +1‰. | 9 | Geochemistry |
This consists of a refrigeration cycle, where heat is removed from a low-temperature space or source and rejected to a high-temperature sink with the help of external work, and its inverse, the thermodynamic power cycle. In the power cycle, heat is supplied from a high-temperature source to the engine, part of the heat being used to produce work and the rest being rejected to a low-temperature sink. This satisfies the second law of thermodynamics.
A refrigeration cycle describes the changes that take place in the refrigerant as it alternately absorbs and rejects heat as it circulates through a refrigerator. It is also applied to heating, ventilation, and air conditioning HVACR work, when describing the "process" of refrigerant flow through an HVACR unit, whether it is a packaged or split system.
Heat naturally flows from hot to cold. Work is applied to cool a living space or storage volume by pumping heat from a lower temperature heat source into a higher temperature heat sink. Insulation is used to reduce the work and energy needed to achieve and maintain a lower temperature in the cooled space. The operating principle of the refrigeration cycle was described mathematically by Sadi Carnot in 1824 as a heat engine.
The most common types of refrigeration systems use the reverse-Rankine vapor-compression refrigeration cycle, although absorption heat pumps are used in a minority of applications.
Cyclic refrigeration can be classified as:
#Vapor cycle, and
#Gas cycle
Vapor cycle refrigeration can further be classified as:
#Vapor-compression refrigeration
#Sorption Refrigeration
##Vapor-absorption refrigeration
##Adsorption refrigeration | 7 | Physical Chemistry |
An unspliced form of SFRP1 is the dominant form in the lung and liver, leading to an extended protein. This extended sequence contains a hydrophobic region that may act as a transmembrane anchor, modifying the localization of the protein. This may then influence the function of SFRP1 in different tissues because an untethered protein may be more effective in antagonizing Wnt signaling to tumor cells than would a membrane-bound form. | 1 | Biochemistry |
Nickel–metal hydride batteries (Ni-MH) largely replaced Ni-Cd batteries in the early 1990s. They replaced the metallic cadmium electrode with a hydrogen-absorbing alloy, allowing it to have over two times the capacity of Ni-Cd batteries while being easier to recycle. Their heyday in computer equipment was in the early- to mid-1990s. By 1995, most motherboard manufacturers switched to non-rechargeable lithium button cells to keep the BIOS chip powered. Lithium-based battery packs replaced Ni-MH packs in all but the lowest-end laptops by the early 2000s.
The practical shelf life of a Ni-MH is roughly five years. Cylindrical jelly-roll Ni-MH cells, like the ones used in 1990s laptop battery packs, discharge at a rate of up to 2% per day, while button cells like the ones used in motherboard batteries discharge at a rate of less than 20% per month. They are said to leak less frequently than alkaline batteries but have a similar failure mode.
Ni-MH leakage can be effectively neutralized with lemon juice or distilled white vinegar. | 8 | Metallurgy |
A reaction mixture
containing 1 ml of 0.05% O-Phenanthroline in methanol, 2 ml ferric chloride (200 M) and 2 ml of various concentrations ranging from 10 to 1000 g was incubated at room temperature for 10 min and the absorbance of the same was measured at 510 nm. EDTA was used as a classical metal chelator. The experiment was performed in triplicates. The ferric reducing activity of date seed extract was estimated based on the method of Benzie and Strain (1999). The FRAP reagent was prepared by mixing 50 ml of acetate buffer (0.3 M) at pH 3.6, 5 ml of tripyridyltriazine (TPTZ) solution 10 mM prepared in HCl (40 mM) and 5 ml of ferric chloride solution (FeCl) (20 mM). 2 ml of the freshly prepared FRAP reagent was added to 10 lL of the extract. Then the absorbance was measured at 593 nm against the blank after 10 min at room temperature. The standard curve was constructed using Trolox. The result was expressed as Trolox equivalent in mg/100 g of dry weight (DW) date seed. | 1 | Biochemistry |
An improvement on vibration, vibratory, and linear screeners, a tumbler screener uses elliptical action which aids in screening of even very fine material. As like panning for gold, the fine particles tend to stay towards the center and the larger go to the outside. It allows for segregation and unloads the screen surface so that it can effectively do its job. With the addition of multiple decks and ball cleaning decks, even difficult products can be screened at high capacity to very fine separations. | 8 | Metallurgy |
In multi-exponential fitting, the time-resolved curves are fitted with an exponential decay model to determine the decay constants. While this method is straightforward, it has low accuracy. | 7 | Physical Chemistry |
Galvanic corrosion is the electrochemical erosion of metals. Corrosion occurs when two dissimilar metals are in contact with each other in the presence of an electrolyte, such as salt water. This forms a galvanic cell, with hydrogen gas forming on the more noble (less active) metal. The resulting electrochemical potential then develops an electric current that electrolytically dissolves the less noble material. A concentration cell can be formed if the same metal is exposed to two different concentrations of electrolyte. | 8 | Metallurgy |
There are several methods for cell lysis, including alkaline lysis, mechanical lysis, and enzymatic lysis. | 1 | Biochemistry |
The use of anti-graffiti barrier coatings to protect graffiti-prone historic buildings, monuments, and other culturally-sensitive surfaces may seem to be an easy solution to a persistent problem. Research suggests that the application of such coatings can cause physical or aesthetic changes or otherwise damage historic substrates. Both the National Park Service and English Heritage advise against the use of anti-graffiti coatings and promote the exercise of caution when they are applied to historic buildings and monuments.
In the United States, many state and local historic district commissions and review boards have regulations that require approval for both graffiti removal work and the application of coatings applied to the facades on designated landmarks or properties located in local historic districts. Alternatives to anti-graffiti barrier coatings include security measures such as night lighting and surveillance cameras, design strategies such as barrier plantings and fences, improved maintenance of the general area and rapid graffiti removal, as well as community awareness raising programs like a neighborhood watch. | 7 | Physical Chemistry |
A typical humic substance is a mixture of many molecules, some of which are based on a motif of aromatic nuclei with phenolic and carboxylic substituents, linked together; the illustration shows a typical structure.
The functional groups that contribute most to surface charge and reactivity of humic substances are phenolic and carboxylic groups. Humic acids behave as mixtures of dibasic acids, with a pK value around 4 for protonation of carboxyl groups and around 8 for protonation of phenolate groups. There is considerable overall similarity among individual humic acids. For this reason, measured pK values for a given sample are average values relating to the constituent species. The other important characteristic is charge density. The molecules may form a supramolecular structure held together by non-covalent forces, such as van der Waals force, π-π, and CH-π bonds.
The presence of carboxylate and phenolate groups gives the humic acids the ability to form complexes with ions such as Mg, Ca, Fe, and Fe. Many humic acids have two or more of these groups arranged so as to enable the formation of chelate complexes. The formation of (chelate) complexes is an important aspect of the biological role of humic acids in regulating bioavailability of metal ions. | 9 | Geochemistry |
Herbert Charles Brown (May 22, 1912 – December 19, 2004) was an American chemist and recipient of the 1979 Nobel Prize in Chemistry for his work with organoboranes. | 4 | Stereochemistry |
SOCl adopts a trigonal pyramidal molecular geometry with C molecular symmetry. This geometry is attributed to the effects of the lone pair on the central sulfur(IV) center.
In the solid state SOCl forms monoclinic crystals with the space group P2/c. | 0 | Organic Chemistry |
Cyclization of an azomethine ylide with a carbonyl affords a spirocyclic oxazolidine, which loses CO to form a seven-membered ring. These high-utility decarboxylative multi-step reactions are common in azomethine ylide chemistry. | 0 | Organic Chemistry |
A number of implanted ceramics have not actually been designed for specific biomedical applications. However, they manage to find their way into different implantable systems because of their properties and their good biocompatibility. Among these ceramics, we can cite silicon carbide, titanium nitrides and carbides, and boron nitride. TiN has been suggested as the friction surface in hip prostheses. While cell culture tests show a good biocompatibility, the analysis of implants shows significant wear, related to a delaminating of the TiN layer. Silicon carbide is another modern-day ceramic which seems to provide good biocompatibility and can be used in bone implants. | 7 | Physical Chemistry |
Methylated DNA immunoprecipitation (MeDIP or mDIP) is a large-scale (chromosome- or genome-wide) purification technique in molecular biology that is used to enrich for methylated DNA sequences. It consists of isolating methylated DNA fragments via an antibody raised against 5-methylcytosine (5mC). This technique was first described by Weber M. et al. in 2005 and has helped pave the way for viable methylome-level assessment efforts, as the purified fraction of methylated DNA can be input to high-throughput DNA detection methods such as high-resolution DNA microarrays (MeDIP-chip) or next-generation sequencing (MeDIP-seq). Nonetheless, understanding of the methylome remains rudimentary; its study is complicated by the fact that, like other epigenetic properties, patterns vary from cell-type to cell-type. | 1 | Biochemistry |
Virilization in females can manifest as clitoral enlargement, increased muscle strength, acne, hirsutism, frontal hair thinning, deepening of the voice, menstrual disruption due to anovulation, and a strengthened libido. Some of the possible causes of virilization in females are:
* Androgen-producing tumors of the
** ovaries
** adrenal glands (see adrenal tumor)
** pituitary gland (see pituitary adenoma)
* Hyperthecosis
* Hypothyroidism
* Anabolic steroid exposure
* Congenital adrenal hyperplasia due to 21-hydroxylase deficiency (late-onset)
* Conn's syndrome | 1 | Biochemistry |
The objectives of the European Coil Coating Association are described in the association's statutes and rules of procedure:
* Setting quality performance standards and developing test methods
* Spreading the benefits of coil and/or sheet coated metal with particular emphasis on environmental, cost and quality benefits
* Stimulating product, process, application and market developments
* Increasing the awareness of coil and/or sheet-coated metal through professional marketing and by organising educational training programmes for non-users
* Creating an industry network and forum for the development and exchange of ideas
* Representation of the Industry in its contacts with Public Officials and Public Authorities
* Providing liaison with other Trade Associations and Professional Bodies. | 8 | Metallurgy |
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