text
stringlengths 105
4.44k
| label
int64 0
9
| label_text
stringclasses 10
values |
|---|---|---|
Cloxacillin is an antibiotic useful for the treatment of a number of bacterial infections. This includes impetigo, cellulitis, pneumonia, septic arthritis, and otitis externa. It is not effective for methicillin-resistant Staphylococcus aureus (MRSA). It can be used by mouth and by injection.
Side effects include nausea, diarrhea, and allergic reactions including anaphylaxis. Clostridium difficile diarrhea may also occur. It is not recommended in people who have previously had a penicillin allergy. Use during pregnancy appears to be relatively safe. Cloxacillin is in the penicillin family of medications.
Cloxacillin was patented in 1960 and approved for medical use in 1965. It is on the World Health Organization's List of Essential Medicines. It is not commercially available in the United States. | 4 | Stereochemistry |
In many cases, the Benesi–Hildebrand method provides excellent linear plots, and reasonable values for K and ε. However, various problems arising from experimental data have been noted from time to time. Some of these issues include: different values of ε with different concentration scales, lack of consistency between the Benesi–Hildebrand values and those obtained from other methods (e.g. equilibrium constants from partition measurements), and zero and negative intercepts. Concerns have also surfaced over the accuracy of the Benesi–Hildebrand method as certain conditions cause these calculations to become invalid. For instance, the reactant concentrations must always obey the assumption that the initial concentration of the guest ([G]) is much larger than the initial concentration of the host ([H]). In the case when this breaks down, the Benesi–Hildebrand plot deviates from its linear nature and exhibits scatter plot characteristics. Also, in the case of determining the equilibrium constants for weakly bound complexes, it is common for the formation of 2:1 complexes to occur in solution. It has been observed that the existence of these 2:1 complexes generate inappropriate parameters that significantly interfere with the accurate determination of association constants. Due to this fact, one of the criticisms of this method is the inflexibility of only being able to study reactions with 1:1 product complexes.
These limitations can be overcome by using a computational method which is more generally applicable, a non-linear least-squares minimization method. The two parameters, K or ε are determined by using the Solver module a spreadsheet, by minimizing a sum of squared differences between observed and calculated quantities with respect to the equilibrium constant and molar absorbance or chemical shift values of the individual chemical species involved. The use of this and more sophisticated methods have the additional advantage that they are not limited to systems where a single complex is formed. | 7 | Physical Chemistry |
Thermometric titrations of silver nitrate with halides and cyanide are all possible. The reaction of silver nitrate with chloride is strongly exothermic. For instance, the reaction enthalpy of Ag with Cl is a high −61.2 kJ/mol. This permits convenient determination of chloride with commonly available standard 0.1 mol/L AgNO. Endpoints are very sharp, and with care, chloride concentrations down to 15 mg/L can be analyzed. Bromide and chloride may be determined in admixture. | 3 | Analytical Chemistry |
__FORCETOC__
Formamide-based prebiotic chemistry is a reconstruction of the beginnings of life on Earth, assuming that formamide could accumulate in sufficiently high amounts to serve as the building block and reaction medium for the synthesis of the first biogenic molecules.
Formamide (NHCHO), the simplest naturally occurring amide, contains all the elements (hydrogen, carbon, oxygen, and nitrogen), which are required for the synthesis of biomolecules, and is a ubiquitous molecule in the universe. Formamide has been detected in galactic centers, star-forming regions of dense molecular clouds, high-mass young stellar objects, the interstellar medium, comets, and satellites. In particular, dense clouds containing formamide, with sizes on the order of kiloparsecs, have been observed in the vicinity of the Solar System.
Formamide forms under a variety of conditions, corresponding to both terrestrial environments and interstellar media: e.g., on high-energy particle irradiation of binary mixtures of ammonia (NH) and carbon monoxide (CO), or from the reaction between formic acid (HCOOH) with NH. It has been suggested that in hydrothermal pores formamide may accumulate in sufficiently high concentrations to enable synthesis of biogenic molecules. Ab initio molecular dynamics simulations suggest that formamide could be a key intermediate of the Miller–Urey experiment as well.
The combinatorial power of carbon is manifested in the composition of the molecular populations detected in circum- and interstellar media (see the Astrochemistry.net web site). The number and the complexity of carbon-containing molecules are significantly higher than those of inorganic compounds, presumably all over the universe. One of the most abundant C-containing three-atoms molecule observed in space is hydrogen cyanide (HCN). The chemistry of HCN has thus attracted attention in origin of life studies since the earliest times, and the laboratory synthesis of adenine from HCN under presumptive prebiotic conditions was reported as early as 1961. The intrinsic limit of HCN stems from its high reactivity, which leads in turn, to instability and the difficulty associated with its concentration and accumulation in unreacted form. The “Warm Little Pond” in which life is supposed to have started, as imagined by Charles Darwin and re-elaborated by Alexander Oparin, had most likely to reach sufficiently high concentrations to start creating the next levels of complexity. Hence the necessity of a derivative of HCN that is sufficiently stable to survive for time periods extended enough to allow its concentration in the actual physico-chemical settings, but that is sufficiently reactive to originate new compounds in prebiotically plausible environments. Ideally, this derivative should be able to undergo reactions in various directions, without prohibitively high energy barriers, thus allowing the production of different classes of potentially prebiotic compounds. Formamide fulfils all these requirements and, due to its significantly higher boiling point (210 °C), enables chemical synthesis in a much broader temperature range than water. | 9 | Geochemistry |
Source:
The measurement of contact angles with the captive bubble method could also be useful in the surface analysis of the reverse osmosis membrane in the study of membrane performances. Through the analysis of contact angles, properties of membranes, such as roughness, can be determined. The roughness of membranes, which indicates the effective surface area, can further lead to the investigation in the hydrophilic and hydrophobic properties of the surface. Through studies, a higher contact angle may correspond to a more hydrophobic surface in membrane analysis. In the performance of the captive bubble method in membrane analysis, several factors can have influence on the contact angle, including the bubble volume, liquid types and tensions.
In the apparatus of the captive bubble method in membrane analysis, the membrane sample is attached to a piece of glass, while a J-shaped needle is inserted from below the glass in the liquid to release air bubbles. In this case, the contact angle between the air bubble and the glass surface is recorded as a function of time to investigate the effect of measurement time. | 7 | Physical Chemistry |
In physics, absorption of electromagnetic radiation is how matter (typically electrons bound in atoms) takes up a photon's energy — and so transforms electromagnetic energy into internal energy of the absorber (for example, thermal energy).
A notable effect of the absorption of electromagnetic radiation is attenuation of the radiation; attenuation is the gradual reduction of the intensity of light waves as they propagate through the medium.
Although the absorption of waves does not usually depend on their intensity (linear absorption), in certain conditions (optics) the medium's transparency changes by a factor that varies as a function of wave intensity, and saturable absorption (or nonlinear absorption) occurs. | 7 | Physical Chemistry |
The van Oss theory separates the surface energy of solids and liquids into three components. It includes the dispersive surface energy, as before, and subdivides the polar component as being the sum of two more specific components: the surface energy due to acidic interactions () and due to basic interactions (). The acid component theoretically describes a surface's propensity to have polar interactions with a second surface that has the ability to act basic by donating electrons. Conversely, the base component of the surface energy describes the propensity of a surface to have polar interactions with another surface that acts acidic by accepting electrons. The principle equation for this theory is
Again, the best way to deal with this theory, much like the two-component theories, is to use at least three liquids (more can be used to get more results for statistical purposes) one with only a dispersive component in its surface energy (), one with only a dispersive and an acidic or basic component (), and finally either a liquid with a dispersive and a basic or acidic component (whichever the second probe liquid did not have ()), or a liquid with all three components () and linearizing the results.
It is naturally more robust than other theories, particularly in cases where there is a great imbalance between the acid and base components of the polar surface energy. The van Oss theory is most suitable for testing the surface energies of inorganics, organometallics, and surface containing ions.
The most significant difficulty of applying the van Oss theory is the fact that there is not much of an agreement in regards to a set of reference solids that can be used to characterize the acid and base components of potential probe liquids. There are however some liquids that are generally agreed to have known dispersive/acid/base components to their surface energies. Two of them are listed in table 1. | 7 | Physical Chemistry |
In molecular cloning and biology, a gene knock-in (abbreviation: KI) refers to a genetic engineering method that involves the one-for-one substitution of DNA sequence information in a genetic locus or the insertion of sequence information not found within the locus. Typically, this is done in mice since the technology for this process is more refined and there is a high degree of shared sequence complexity between mice and humans. The difference between knock-in technology and traditional transgenic techniques is that a knock-in involves a gene inserted into a specific locus, and is thus a "targeted" insertion. It is the opposite of gene knockout.
A common use of knock-in technology is for the creation of disease models. It is a technique by which scientific investigators may study the function of the regulatory machinery (e.g. promoters) that governs the expression of the natural gene being replaced. This is accomplished by observing the new phenotype of the organism in question. The BACs and YACs are used in this case so that large fragments can be transferred. | 1 | Biochemistry |
Hydrogen bonding significantly influences the properties of primary and secondary amines. For example, methyl and ethyl amines are gases under standard conditions, whereas the corresponding methyl and ethyl alcohols are liquids. Amines possess a characteristic ammonia smell, liquid amines have a distinctive "fishy" and foul smell.
The nitrogen atom features a lone electron pair that can bind H to form an ammonium ion RNH. The lone electron pair is represented in this article by two dots above or next to the N. The water solubility of simple amines is enhanced by hydrogen bonding involving these lone electron pairs. Typically salts of ammonium compounds exhibit the following order of solubility in water: primary ammonium () > secondary ammonium () > tertiary ammonium (RNH). Small aliphatic amines display significant solubility in many solvents, whereas those with large substituents are lipophilic. Aromatic amines, such as aniline, have their lone pair electrons conjugated into the benzene ring, thus their tendency to engage in hydrogen bonding is diminished. Their boiling points are high and their solubility in water is low. | 0 | Organic Chemistry |
As there are a number of different electron donors (organic matter in organotrophs, inorganic matter in lithotrophs), there are a number of different electron acceptors, both organic and inorganic. As with other steps of the ETC, an enzyme is required to help with the process.
If oxygen is available, it is most often used as the terminal electron acceptor in aerobic bacteria and facultative anaerobes. An oxidase reduces the O to water while oxidizing something else. In mitochondria, the terminal membrane complex (Complex IV) is cytochrome oxidase, which oxidizes the cytochrome. Aerobic bacteria use a number of differet terminal oxidases. For example, E. coli (a facultative anaerobe) does not have a cytochrome oxidase or a bc complex. Under aerobic conditions, it uses two different terminal quinol oxidases (both proton pumps) to reduce oxygen to water.
Bacterial terminal oxidases can be split into classes according to the molecules act as terminal electron acceptors. Class I oxidases are cytochrome oxidases and use oxygen as the terminal electron acceptor. Class II oxidases are quinol oxidases and can use a variety of terminal electron acceptors. Both of these classes can be subdivided into categories based on what redox-active components they contain. E.g. Heme aa3 Class 1 terminal oxidases are much more efficient than Class 2 terminal oxidases.
Mostly in anaerobic environments different electron acceptors are used, including nitrate, nitrite, ferric iron, sulfate, carbon dioxide, and small organic molecules such as fumarate. When bacteria grow in anaerobic environments, the terminal electron acceptor is reduced by an enzyme called a reductase. E. coli can use fumarate reductase, nitrate reductase, nitrite reductase, DMSO reductase, or trimethylamine-N-oxide reductase, depending on the availability of these acceptors in the environment.
Most terminal oxidases and reductases are inducible. They are synthesized by the organism as needed, in response to specific environmental conditions. | 1 | Biochemistry |
By having more than one anion, many more compounds can be made, and properties tuned to desirable values.
In terms of optics, properties include phosphorescence, photocatalysis, laser damage threshold, refractive index, birefringence, absorption particularly in the ultraviolet or near infrared, non-linearity.
Mechanical properties can include ability to grow a large crystal, ability to form a thin layer, strength, or brittleness.
Thermal properties can include melting point, thermal stability, phase transition temperatures, thermal expansion coefficient.
For electrical properties, electric conductivity, band gap, superconducting transition temperature piezoelectricity, pyroelectricity, ferromagnetism, dielectric constant, charge-density wave transition can be adjusted. | 7 | Physical Chemistry |
* Distinguished Service Award of the Society for Applied Spectroscopy (1985)
* Garvan Medal from the American Chemical Society (1986)
* Fisher Award in Analytical Chemistry from the American Chemical Society (1993)
* Wilfred R. and Ann Lee Konneker Award from Ohio University (2003)
* Founder's Citation Award from Ohio University (2003–2004)
* Great American Award from the Stan Hywet Foundation (2004)
* In Tribute to Public Service Award (2006)
* Leona Hughes Inspiration Award by the Women in Philanthropy of Ohio University (2010)
* President's Medal of Merit from the Republic of Hungary (2012)
* Lifetime Ambassador's Award from OneCommunity (2014)
* Alumni Association's Medal of Merit from Ohio University
* Alumna of the Year Award from Ohio University
* John C. Baker Founders Award from Ohio University | 3 | Analytical Chemistry |
The Eli Lilly Award in Biological Chemistry was established in 1934. Consisting of a bronze medal and honorarium, its purpose is to stimulate fundamental research in biological chemistry by scientists not over thirty-eight years of age. The Award is administered by the Division of Biological Chemistry of the American Chemical Society. | 1 | Biochemistry |
The family also contains L-lactate dehydrogenases that catalyse the conversion of pyruvate to L-lactate, the last step in anaerobic glycolysis. Malate dehydrogenases that catalyse the interconversion of malate to oxaloacetate and participate in the citric acid cycle, and L-2-hydroxyisocaproate dehydrogenases are also members of the family. The N-terminus is a Rossmann NAD-binding fold and the C-terminus is an unusual alpha+beta fold. | 1 | Biochemistry |
Paul Benjamin Ferrara (November 2, 1942 – May 30, 2011) was a scientist and administrator who pioneered the use of DNA profiling in America. | 0 | Organic Chemistry |
The two ends of an actin filament differ in their dynamics of subunit addition and removal. They are thus referred to as the plus end (with faster dynamics, also called barbed end) and the minus end (with slower dynamics, also called pointed end). This difference results from the fact that subunit addition at the minus end requires a conformational change of the subunits. Note that each subunit is structurally polar and has to attach to the filament in a particular orientation. As a consequence, the actin filaments are also structurally polar.
Elongating the actin filament occurs when free-actin (G-actin) bound to ATP associates with the filament. Under physiological conditions, it is easier for G-actin to associate at the positive end of the filament, and harder at the negative end. However, it is possible to elongate the filament at either end. Association of G-actin into F-actin is regulated by the critical concentration outlined below. Actin polymerization can further be regulated by profilin and cofilin. Cofilin functions by binding to ADP-actin on the negative end of the filament, destabilizing it, and inducing depolymerization. Profilin induces ATP binding to G-actin so that it can be incorporated onto the positive end of the filament. | 1 | Biochemistry |
A quantitative method to determine the amount of phosphate present in samples, such as boiler feedwater, is as follows. A measured amount of boiler water is poured into a mixing tube and ammonium heptamolybdate reagent is added. The tube is then stoppered and vigorously shaken. The next step is to add dilute stannous chloride reagent, which has been freshly prepared from concentrated stannous chloride reagent and distilled water, to the mixture in the tube. This will produce a blue colour (due to the formation of molybdenum blue) and the depth of the blue colour indicates the amount of phosphate in the boiler water. The absorbance of the blue solution can be measured with a colorimeter and the concentration of phosphate in the original solution can be calculated. Alternatively, a direct (but approximate) reading of phosphate concentration can be obtained by using a Lovibond comparator. This method for phosphate determination is known as Denigés' method. | 3 | Analytical Chemistry |
The carbon–fluorine bond stretching appears in the infrared spectrum between 1000 and 1360 cm. The wide range is due to the sensitivity of the stretching frequency to other substituents in the molecule. Monofluorinated compounds have a strong band between 1000 and 1110 cm; with more than one fluorine atoms, the band splits into two bands, one for the symmetric mode and one for the asymmetric. The carbon–fluorine bands are so strong that they may obscure any carbon–hydrogen bands that might be present.
Organofluorine compounds can also be characterized using NMR spectroscopy, using carbon-13, fluorine-19 (the only natural fluorine isotope), or hydrogen-1 (if present). The chemical shifts in F NMR appear over a very wide range, depending on the degree of substitution and functional group. The table below shows the ranges for some of the major classes. | 0 | Organic Chemistry |
* C. Michael Hogan, Leda C. Patmore and Harry Seidman (1973) Statistical Prediction of Dynamic Thermal Equilibrium Temperatures using Standard Meteorological Data Bases, Second Edition (EPA-660/2-73-003 2006) United States Environmental Protection Agency Office of Research and Development, Washington, D.C. [http://library.wur.nl/WebQuery/catalog/lang/1851848]
* Cesare Barbieri (2007) Fundamentals of Astronomy. First Edition (QB43.3.B37 2006) CRC Press ,
* F. Mandl (1988) Statistical Physics, Second Edition, John Wiley & Sons
* Hans R. Griem (2005) Principles of Plasma Spectroscopy (Cambridge Monographs on Plasma Physics), Cambridge University Press, New York | 7 | Physical Chemistry |
The Zeldovich number is a dimensionless number which provides a quantitative measure for the activation energy of a chemical reaction which appears in the Arrhenius exponent, named after the Russian scientist Yakov Borisovich Zeldovich, who along with David A. Frank-Kamenetskii, first introduced in their paper in 1938. In 1983 ICDERS meeting at Poitiers, it was decided to name after Zel'dovich.
It is defined as
where
* is the activation energy of the reaction
* is the universal gas constant
* is the burnt gas temperature
* is the unburnt mixture temperature.
In terms of heat release parameter , it is given by
For typical combustion phenomena, the value for Zel'dovich number lies in the range . Activation energy asymptotics uses this number as the large parameter of expansion. | 7 | Physical Chemistry |
In plants, light-dependent reactions occur in the thylakoid membranes of the chloroplasts where they drive the synthesis of ATP and NADPH. The light-dependent reactions are of two forms: cyclic and non-cyclic.
In the non-cyclic reaction, the photons are captured in the light-harvesting antenna complexes of photosystem II by chlorophyll and other accessory pigments (see diagram at right). The absorption of a photon by the antenna complex loosens an electron by a process called photoinduced charge separation. The antenna system is at the core of the chlorophyll molecule of the photosystem II reaction center. That loosened electron is taken up by the primary electron-acceptor molecule, pheophytin. As the electrons are shuttled through an electron transport chain (the so-called Z-scheme shown in the diagram), a chemiosmotic potential is generated by pumping proton cations (H) across the membrane and into the thylakoid space. An ATP synthase enzyme uses that chemiosmotic potential to make ATP during photophosphorylation, whereas NADPH is a product of the terminal redox reaction in the Z-scheme. The electron enters a chlorophyll molecule in Photosystem I. There it is further excited by the light absorbed by that photosystem. The electron is then passed along a chain of electron acceptors to which it transfers some of its energy. The energy delivered to the electron acceptors is used to move hydrogen ions across the thylakoid membrane into the lumen. The electron is eventually used to reduce the coenzyme NADP with an H to NADPH (which has functions in the light-independent reaction); at that point, the path of that electron ends.
The cyclic reaction is similar to that of the non-cyclic but differs in that it generates only ATP, and no reduced NADP (NADPH) is created. The cyclic reaction takes place only at photosystem I. Once the electron is displaced from the photosystem, the electron is passed down the electron acceptor molecules and returns to photosystem I, from where it was emitted, hence the name cyclic reaction. | 5 | Photochemistry |
EFF-AFF are the identifiers for type 1 glycoproteins that makeup cell–cell fusogens. They were first identified when EFF-1 mutants were found to "block cell fusion in all epidermal and vulval epithelia" in the roundworm, Caenorhabditis elegans. EFF-AFF is a family of type I membrane glycoproteins that act as cell–cell fusogens, named from Anchor cell fusion failure. Because it was known that EFF-1 mutants successfully fused the anchor cell and (uterine seam) utse syncytium to produce a continuous uterine-vulval tube, where these connections failed, AFF-1 mutants were discovered. AFF-1 was deemed necessary for this process in addition to the fusion of heterologous cells in C. elegans. The transmembrane forms of these proteins, like most viral fusogens, possess an N-terminal signal sequence followed by a long extracellular portion, a predicted transmembrane domain, and a short intracellular tail. " A striking conservation in the position and number of all 16 cysteines in the extracellular portion" of EFF-AFF proteins from different nematode species suggests that these proteins are folded in a similar 3D structure that is
essential for their fusogenic activity. C. elegans AFF-1 and EFF-1 proteins are essential for developmental cell-to-cell fusion and can merge insect cells. "Thus FFs comprise an ancient
family of cellular fusogens that can promote fusion when expressed on a viral particle." | 1 | Biochemistry |
El-Sayed's research interests include the use of steady-state and ultra fast laser spectroscopy to understand relaxation, transport and conversion of energy in molecules, in solids, in photosynthetic systems, semiconductor quantum dots and metal nanostructures. The El-Sayed group has also been involved in the development of new techniques such as magnetophotonic selection, picosecond Raman spectroscopy and phosphorescence microwave double resonance spectroscopy. A major focus of his lab is currently on the optical and chemical properties of noble metal nanoparticles and their applications in nanocatalysis, nanophotonics and nanomedicine. His lab is known for the development of the gold nanorod technology. As of 2021, El-Sayed has produced over 1200 publications in refereed journals in the areas of spectroscopy, molecular dynamics and nanoscience, with over 130,000 citations. | 1 | Biochemistry |
There are three basic methodologies: gel-clot, turbidimetric, and chromogenic. The primary application for LAL is the testing of parenteral pharmaceuticals and medical devices that contact blood or cerebrospinal fluid. In the United States, the FDA has published a guideline for validation of the LAL test as an endotoxin test for such products.
The LAL cascade is also triggered by (1,3)-β-D-glucan, via a different Factor G. Both bacterial endotoxins and (1,3)-β-D-glucan are considered pathogen-associated molecular patterns, or PAMPs, substances which elicit inflammatory responses in mammals. | 3 | Analytical Chemistry |
Isotopomers or isotopic isomers are isomers which differ by isotopic substitution, and which have the same number of atoms of each isotope but in a different arrangement. For example, CHOD and CHDOH are two isotopomers of monodeuterated methanol.
The molecules may be either structural isomers (constitutional isomers) or stereoisomers depending on the location of the isotopes. Isotopomers have applications in areas including nuclear magnetic resonance spectroscopy, reaction kinetics, and biochemistry. | 4 | Stereochemistry |
Different 2A peptides have different efficiencies of self-cleaving, T2A and P2A being the most and F2A the least efficient. Therefore, up to 50% of F2A-linked proteins can remain in the cell as a fusion protein, which might cause some unpredictable outcomes, including a gain of function. One study reported that 2A sites cause the ribosome to fall off approximately 60% of the time, and that, together with ribosome read-through of about 10% for P2A and T2A, this results in reducing expression of the downstream peptide chain by about 70%. However, the level of drop-off detected in this study varied widely depending on the exact construct used, with some constructs showing little evidence of drop-off; furthermore, within a tri-cistronic transcript it reported a higher level of ribosome drop-off after one 2A sequence than after two 2As combined, which is at odds with a linear model of translation. | 1 | Biochemistry |
In Cartesian coordinates the 2 basis vectors are represented by a cell tensor :
The area of the unit cell, , is given by the determinant of the cell matrix:
For the special case of a square or rectangular unit cell, the matrix is diagonal, and we have that: | 3 | Analytical Chemistry |
The most general formula for radiated power as a function of angle is:
where is a unit vector pointing from the particle towards the observer, and is an infinitesimal bit of solid angle.
In the case where velocity is parallel to acceleration (for example, linear motion), this simplifies to
where is the angle between and the direction of observation . | 7 | Physical Chemistry |
In some cases it is desirable to soften hard water. Most detergents contain ingredients that counteract the effects of hard water on the surfactants. For this reason, water softening is often unnecessary. Where softening is practised, it is often recommended to soften only the water sent to domestic hot water systems to prevent or delay inefficiencies and damage due to scale formation in water heaters. A common method for water softening involves the use of ion-exchange resins, which replace ions like Ca by twice the number of mono cations such as sodium or potassium ions.
Washing soda (sodium carbonate, NaCO) is easily obtained and has long been used as a water softener for domestic laundry, in conjunction with the usual soap or detergent.
Water that has been treated by a water softening may be termed softened water. In these cases, the water may also contain elevated levels of sodium or potassium and bicarbonate or chloride ions. | 3 | Analytical Chemistry |
NBS electrophilically brominates the amine, which is followed by decarboxylation and release of an imine. Further hydrolysis will yield an aldehyde and ammonia. (cf. non-oxidative PLP dependent decarboxylation) | 0 | Organic Chemistry |
Like many of the lakes in the Northwest Territories (NWT), Frame is glacial in origin. During the Wisconsin Glaciation, the last ice age, glaciers covered almost all of today's Western Canada. As they retreated about 20,000 years ago, they left large lakes of meltwater behind. One, known today as Lake McConnell, covered almost all of the western NWT as well as adjacent regions of what is now Alberta and Saskatchewan. By 8,000 years ago, it had drained and evaporated to the point that only small remnants were left, such as Athabasca, Great Bear and Great Slave Lakes. Along with those larger lakes were smaller lakes like Frame, where fine sand that accumulated in depressions formed the lake bed.
Human use of the lake began with the Dene, the First Nations in the region, whose ancestors settled there around 7,500 years ago. The Yellowknife band, who would later give their name to the city, found the lake abundant with pike, suckers and whitefish. While they did not settle on its shores, they established a fishing camp there. | 2 | Environmental Chemistry |
The salt balances are calculated for each reservoir separately. They are based on their water balances, using the salt concentrations of the incoming and outgoing water. Some concentrations must be given as input data, like the initial salt concentrations of the water in the different soil reservoirs, of the irrigation water and of the incoming ground water in the aquifer.
The concentrations are expressed in terms of electric conductivity (EC in dS/m). When the concentrations are known in terms of g salt/L water, the rule of thumb: 1 g/L -> 1.7 dS/m can be used. Usually, salt concentrations of the soil are expressed in ECe, the electric conductivity of an extract of a saturated soil paste (saturation extract). In Saltmod, the salt concentration is expressed as the EC of the soil moisture when saturated under field conditions. As a rule, one can use the conversion rate EC : ECe = 2 : 1.<br>
Salt concentrations of outgoing water (either from one reservoir into the other or by subsurface drainage) are computed on the basis of salt balances, using different leaching or salt mixing efficiencies to be given with the input data. The effects of different leaching efficiencies can be simulated by varying their input value.
If drain or well water is used for irrigation, the method computes the salt concentration of the mixed irrigation water in the course of the time and the subsequent effect on the soil and ground water salinities, which again influences the salt concentration of the drain and well water. By varying the fraction of used drain or well water (to be given in the input data), the long-term effect of different fractions can be simulated.
The dissolution of solid soil minerals or the chemical precipitation of poorly soluble salts is not included in the computation method, but to some extent it can be accounted for through the input data, e.g. by increasing or decreasing the salt concentration of the irrigation water or of the incoming water in the aquifer. | 9 | Geochemistry |
Each country adopts their own agricultural policies and Maximum Residue Limits (MRL) and Acceptable Daily Intake (ADI). The level of food additive usage varies by country because forms of agriculture are different in regions according to their geographical or climatical factors.
Pre-harvest intervals are also set to require a crop or livestock product not be harvested before a certain period after application in order to allow the pesticide residue to decrease below maximum residue limits or other tolerance levels. Likewise, restricted entry intervals are the amount of time to allow residue concentrations to decrease before a worker can reenter without protective equipment an area where pesticides have been applied. | 2 | Environmental Chemistry |
As the name suggests, the prerequisite of a successful RDRP is fast and reversible activation/deactivation of propagating chains. There are three types of RDRP; namely deactivation by catalyzed reversible coupling, deactivation by spontaneous reversible coupling and deactivation by degenerative transfer (DT). A mixture of different mechanisms is possible; e.g. a transition metal mediated RDRP could switch among ATRP, OMRP and DT mechanisms depending on the reaction conditions and reagents used.
In any RDRP processes, the radicals can propagate with the rate coefficient k by addition of a few monomer units before the deactivation reaction occurs to regenerate the dormant species. Concurrently, two radicals may react with each other to form dead chains with the rate coefficient k. The rates of propagation and termination between two radicals are not influenced by the mechanism of deactivation or the catalyst used in the system. Thus it is possible to estimate how fast a RDRP can be conducted with preserved chain end functionality?
In addition, other chain breaking reactions such as irreversible chain transfer/termination reactions of the propagating radicals with solvent, monomer, polymer, catalyst, additives, etc. would introduce additional loss of chain end functionality (CEF). The overall rate coefficient of chain breaking reactions besides the direct termination between two radicals is represented as k.
In all RDRP methods, the theoretical number average molecular weight of obtained polymers, M, can be defined by following equation:
where M is the molecular weight of monomer; [M] and [M] are the monomer concentrations at time 0 and time t; [R-X] is the initial concentration of the initiator.
Besides the designed molecular weight, a well controlled RDRP should give polymers with narrow molecular distributions, which can be quantified by M/M values, and well preserved chain end functionalities.
A well controlled RDRP process requires: 1) the reversible deactivation process should be sufficiently fast; 2) the chain breaking reactions which cause the loss of chain end functionalities should be limited; 3) properly maintained radical concentration; 4) the initiator should have proper activity. | 7 | Physical Chemistry |
SMA is subject to structural fatigue – a failure mode by which cyclic loading results in the initiation and propagation of a crack that eventually results in catastrophic loss of function by fracture. The physics behind this fatigue mode is accumulation of microstructural damage during cyclic loading. This failure mode is observed in most engineering materials, not just SMAs.
SMAs are also subject to functional fatigue, a failure mode not typical of most engineering materials, whereby the SMA does not fail structurally but loses its shape-memory/superelastic characteristics over time. As a result of cyclic loading (both mechanical and thermal), the material loses its ability to undergo a reversible phase transformation. For example, the working displacement in an actuator decreases with increasing cycle numbers. The physics behind this is gradual change in microstructure—more specifically, the buildup of accommodation slip dislocations. This is often accompanied by a significant change in transformation temperatures. Design of SMA actuators may also influence both structural and functional fatigue of SMA, such as the pulley configurations in SMA-Pulley system. | 8 | Metallurgy |
Fast hole drilling EDM was designed for producing fast, accurate, small, deep holes. It is conceptually akin to sinker EDM but the electrode is a rotating tube conveying a pressurized jet of dielectric fluid. It can make a hole an inch deep in about a minute and is a good way to machine holes in materials too hard for twist-drill machining. This EDM drilling type is used largely in the aerospace industry, producing cooling holes into aero blades and other components. It is also used to drill holes in industrial gas turbine blades, in molds and dies, and in bearings. | 8 | Metallurgy |
An apparent self-protective behaviour, known as "terminal burrowing", or "hide-and-die syndrome", occurs in the final stages of hypothermia. Those affected will enter small, enclosed spaces, such as underneath beds or behind wardrobes. It is often associated with paradoxical undressing. Researchers in Germany claim this is "obviously an autonomous process of the brain stem, which is triggered in the final state of hypothermia and produces a primitive and burrowing-like behavior of protection, as seen in hibernating mammals". This happens mostly in cases where temperature drops slowly. | 1 | Biochemistry |
*MCM3AP possibly a primase
*XRCC5 NM_021141 Ku80
*XRCC6 NM_001469 Homo sapiens thyroid autoantigen: Single-stranded DNA-dependent ATP-dependent helicase. Has a role in chromosome translocation. | 1 | Biochemistry |
Earths natural greenhouse effect makes life as we know it possible and carbon dioxide plays a significant role in providing for the relatively high temperature on Earth. The greenhouse effect is a process by which thermal radiation from a planetary atmosphere warms the planets surface beyond the temperature it would have in the absence of its atmosphere. Without the greenhouse effect, the Earths average surface temperature would be about compared to Earths actual average surface temperature of approximately 14 °C (57.2 °F).
Water is responsible for most (about 36–70%) of the total greenhouse effect, and the role of water vapor as a greenhouse gas depends on temperature. On Earth, carbon dioxide is the most relevant, direct anthropologically influenced greenhouse gas. Carbon dioxide is often mentioned in the context of its increased influence as a greenhouse gas since the pre-industrial (1750) era. In 2013, the increase in CO was estimated to be responsible for 1.82 W m of the 2.63 W m change in radiative forcing on Earth (about 70%).
The concept of atmospheric CO increasing ground temperature was first published by Svante Arrhenius in 1896. The increased radiative forcing due to increased CO in the Earths atmosphere is based on the physical properties of CO and the non-saturated absorption windows where CO absorbs outgoing long-wave energy. The increased forcing drives further changes in Earths energy balance and, over the longer term, in Earth's climate. | 2 | Environmental Chemistry |
The type of growth factor signaling can effect whether or not NSCs differentiate into motor neurons or not. Priming a media with FGF2 lowers the activity of the PI3K/AKT pathway, which activates GSK3β. This increases expression of HB9. Directly inhibiting PI3K in NSCs leads to a population of cells that are purely HB9+ and differentiate at an elevated efficiency into motor neurons. Grafting these cells into different parts of rats generates motor neurons regardless of the transplanted cells' microenvironment. Following injury, neural stem cells enter a repair phase and express high levels of PI3K to enhance proliferation. This is better for survival of the neurons as a whole but is at the expense of generating motor neurons. Therefore, it can be difficult for injured motor neurons to recover their ability. It is the purpose of modern research to generate neural stem cells that can proliferate but still differentiate into motor neurons. Lowering the effect of the PI3K pathway and increasing the effect of GSK3β and HB9 in NSCs is a potential way of generating these cells. | 1 | Biochemistry |
The NTN has over 250 sites that focus on wet deposition chemistry by collecting weekly precipitation samples nationwide. The samples are sent to the Central Analytical Laboratory (The Wisconsin State Lab of Hygiene) for analysis and are then used to determine geographic distribution and annual trends. The sample collection and handling methods follow strict clean-handling procedures in order to ensure accurate results. The analytes monitored are: Free acidity (H as pH), conductance, calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), sulfate (SO), nitrate (NO), chloride (Cl), and ammonium (NH). The CAL also measures orthophosphate, but only for quality assurance as an indicator of sample contamination. | 2 | Environmental Chemistry |
In the body, stores of fat are referred to as adipose tissue. In these areas, intracellular triglycerides are stored in cytoplasmic lipid droplets. When lipase enzymes are phosphorylated, they can access lipid droplets and through multiple steps of hydrolysis, breakdown triglycerides into fatty acids and glycerol. Each step of hydrolysis leads to the removal of one fatty acid. The first step and the rate-limiting step of lipolysis is carried out by adipose triglyceride lipase (ATGL). This enzyme catalyzes the hydrolysis of triacylglycerol to diacylglycerol. Subsequently, hormone-sensitive lipase (HSL) catalyzes the hydrolysis of diacylglycerol to monoacylglycerol and monoacylglycerol lipase (MGL) catalyzes the hydrolysis of monoacylglycerol to glycerol.
Perilipin 1A is a key protein regulator of lipolysis in adipose tissue. This lipid droplet-associated protein, when deactivated, will prevent the interaction of lipases with triglycerides in the lipid droplet and grasp the ATGL co-activator, comparative gene identification 58 (CGI-58) (a.k.a. ABHD5). When perilipin 1A is phosphorylated by PKA, it releases CGI-58 and it expedites the docking of phosphorylated lipases to the lipid droplet. CGI-58 can be further phosphorylated by PKA to assist in its dispersal to the cytoplasm. In the cytoplasm, CGI-58 can co-activate ATGL. ATGL activity is also impacted by the negative regulator of lipolysis, G0/G1 switch gene 2 (G0S2). When expressed, G0S2 acts as a competitive inhibitor in the binding of CGI-58. Fat-specific protein 27 (FSP-27) (a.k.a. CIDEC) is also a negative regulator of lipolysis. FSP-27 expression is negatively correlated with ATGL mRNA levels. | 1 | Biochemistry |
Other photoinitiated free radical polymerization reactions can also be used for fiber production. In this case, the shealth fluid was only used to separate the core fluid from the tube wall. Also, to achieve the solidification rapid enough, a more concentrated monomer solution was usually used.
An example would be the production of 4-hydroxybutyl acrylate fiber reported by Beebe et al. The microfluid device they used was built with ethylvinyl acetate caplliary and PDMS rubber. The core fluid was a mixture of [https://pubchem.ncbi.nlm.nih.gov/compound/75588 4-hydroxybutyl acrylate], acrylic acid, ethyleneglycol dimethacrylate (crosslinker), [https://www.chemicalbook.com/ChemicalProductProperty_EN_CB0439891.htm 2,2′-dimethoxy-2-phenyl-acetonephenone] (photoinitiator). The sheath fluid was only for separation. The crosslinked network was formed by free radical polymerization when the UV light met the core fluid. | 7 | Physical Chemistry |
Unichiral indicates configurationally homogeneous substance (i.e. made up of chiral molecules of one and the same configuration). Other commonly used synonyms are enantiopure drugs and enantiomerically pure drugs. Monochiral drugs has also been suggested as another synonym. Professor Eliel, Wilen, and Gal expressed their deep concern over the misuse of the term "homochiral" in articles to denote enantiomerically pure drugs, which is incorrect. Homochiral means objects or molecules of the same handedness. Hence should be used only for comparison of two or more objects of like "chirality". For instance, left hands of different individuals, or say R-naproxen and R-ibuprofen.
Globally drug companies and regulatory agencies have an inclination towards the development of unichiral drugs as a consequence of the increased understanding of the differing biological properties of individual enantiomers of a racemic therapeutics. Most of these unichiral drugs are the consequence of chiral switch approach. The table below list selected unichiral drugs used in drug therapy.
A company may go in for developing a racemic drug against an enantiomer by providing adequate reasoning. The rationale why a company might pursue developing racemic drugs could include expensive separation of enantiomers, eutomer racemizes in solution (e.g. oxazepam), activities of the enantiomeric pair are different but supplementary, distomer is inactive, but separation is exorbitant. Insignificant/low toxicity of the distomer, high therapeutic index, mutually beneficial, pharmacological activities of both the enantiomers, and if the development of an enantiomer takes huge amount of time for a drug of emergency need e.g., cancer, AIDS, etc. | 4 | Stereochemistry |
Transcriptomic strategies have seen broad application across diverse areas of biomedical research, including disease diagnosis and profiling. RNA-Seq approaches have allowed for the large-scale identification of transcriptional start sites, uncovered alternative promoter usage, and novel splicing alterations. These regulatory elements are important in human disease and, therefore, defining such variants is crucial to the interpretation of disease-association studies. RNA-Seq can also identify disease-associated single nucleotide polymorphisms (SNPs), allele-specific expression, and gene fusions, which contributes to the understanding of disease causal variants.
Retrotransposons are transposable elements which proliferate within eukaryotic genomes through a process involving reverse transcription. RNA-Seq can provide information about the transcription of endogenous retrotransposons that may influence the transcription of neighboring genes by various epigenetic mechanisms that lead to disease. Similarly, the potential for using RNA-Seq to understand immune-related disease is expanding rapidly due to the ability to dissect immune cell populations and to sequence T cell and B cell receptor repertoires from patients. | 1 | Biochemistry |
RNA Pol II elongation promoters can be summarised in three classes:
# Drug/sequence-dependent arrest affected factors, e.g., SII (TFIIS) and P-TEFb protein families.
# Chromatin structure oriented factors. Based on histone post translational modifications – phosphorylation, acetylation, methylation and ubiquination.
#: See: chromatin, histone, and nucleosome
# RNA Pol II catalysis improving factors. Improve the Vmax or Km of RNA Pol II, so improving the catalytic quality of the polymerase enzyme. E.g. TFIIF, Elongin and ELL families.
#: See: Enzyme kinetics, Henri–Michaelis–Menten kinetics, Michaelis constant, and Lineweaver–Burk plot
As for initiation, protein interference, seen as the "drug/sequence-dependent arrest affected factors" and "RNA Pol II catalysis improving factors" provide a very rapid response and is used for fine level individual gene control. Elongation downregulation is also possible, in this case usually by blocking polymerase progress or by deactivating the polymerase.
Chromatin structure-oriented factors are more complex than for initiation control. Often the chromatin-altering factor becomes bound to the polymerase complex, altering the histones as they are encountered and providing a semi-permanent memory of previous promotion and transcription. | 1 | Biochemistry |
In most laboratory situations, the difference in behaviour between a real gas and an ideal gas is dependent only on the pressure and the temperature, not on the presence of any other gases. At a given temperature, the "effective" pressure of a gas is given by its fugacity : this may be higher or lower than its mechanical pressure. By historical convention, fugacities have the dimension of pressure, so the dimensionless activity is given by:
where is the dimensionless fugacity coefficient of the species, is its mole fraction in the gaseous mixture ( for a pure gas) and is the total pressure. The value is the standard pressure: it may be equal to 1 atm (101.325 kPa) or 1 bar (100 kPa) depending on the source of data, and should always be quoted. | 7 | Physical Chemistry |
For strong gradients the transport equation typically has to be modified with higher order terms (and higher order Transport coefficients). | 7 | Physical Chemistry |
* Cross-linkage: another irreversible method that does not require a support material for the attachment of enzyme molecules. In this technique, the molecules of enzymes are covalently bonded to each other to create a matrix consisting of almost only enzyme. The reaction ensures that the binding site does not cover the enzyme's active site, the activity of the enzyme is only affected by immobility. However, the inflexibility of the covalent bonds precludes the self-healing properties exhibited by chemo-adsorbed self-assembled monolayers. Use of a spacer molecule like poly(ethylene glycol) helps in the reduction of steric hindrance by the substrate in this case. | 4 | Stereochemistry |
All of these forms of crack development are the result of the cylinder being subject to high pressure for prolonged periods. The cracks are intergranular and occur at grain boundaries. There is no evidence of stress corrosion or fatigue.
The presence of a relatively high lead content has been identified as a contributory factor. Cracking at the grain boundaries is accelerated in the presence of lead. The presence of bismuth is also suspected to be contributory.
Alloy composition has also been found to be a factor. Alloy 6061 has shown good resistance to SLC, as have alloys 5283 and 7060.
Manufacturing defects such as folds on the inside surface have been shown to be harmful, particularly for parallel-threaded cylinders.
Grain size has been shown to be of relatively minor importance. | 8 | Metallurgy |
The pyrosequencing method is based on the detection of the pyrophosphate release on nucleotide incorporation. Before performing pyrosequencing, the DNA strand to sequence has to be amplified by PCR. Then the order in which the nucleotides have to be added in the sequencer is chosen (i.e. G-A-T-C). When a specific nucleotide is added, if the DNA polymerase incorporates it in the growing chain, the pyrophosphate is released and converted into ATP by ATP sulfurylase. ATP powers the oxidation of luciferase through the luciferase; this reaction generates a light signal recorded as a pyrogram peak. In this way, the nucleotide incorporation is correlated to a signal. The light signal is proportional to the amount of nucleotides incorporated during the synthesis of the DNA strand (i.e. two nucleotides incorporated correspond to two pyrogram peaks). When the added nucleotides aren't incorporated in the DNA molecule, no signal is recorded; the enzyme apyrase removes any unincorporated nucleotide remaining in the reaction.
This method requires neither fluorescently-labelled nucleotides nor gel electrophoresis.
Pyrosequencing, which was developed by Pål Nyrén and Mostafa Ronaghi DNA, has been commercialized by Biotage (for low-throughput sequencing) and 454 Life Sciences (for high-throughput sequencing). The latter platform sequences roughly 100 megabases [now up to 400 megabases] in a seven-hour run with a single machine. In the array-based method (commercialized by 454 Life Sciences), single-stranded DNA is annealed to beads and amplified via EmPCR. These DNA-bound beads are then placed into wells on a fiber-optic chip along with enzymes which produce light in the presence of ATP. When free nucleotides are washed over this chip, light is produced as ATP is generated when nucleotides join with their complementary base pairs. Addition of one (or more) nucleotide(s) results in a reaction that generates a light signal that is recorded by the CCD camera in the instrument. The signal strength is proportional to the number of nucleotides, for example, homopolymer stretches, incorporated in a single nucleotide flow. [https://web.archive.org/web/20080318163514/http://www.454.com/] | 1 | Biochemistry |
Each action potential is followed by a refractory period, which can be divided into an absolute refractory period, during which it is impossible to evoke another action potential, and then a relative refractory period, during which a stronger-than-usual stimulus is required. These two refractory periods are caused by changes in the state of sodium and potassium channel molecules. When closing after an action potential, sodium channels enter an "inactivated" state, in which they cannot be made to open regardless of the membrane potential—this gives rise to the absolute refractory period. Even after a sufficient number of sodium channels have transitioned back to their resting state, it frequently happens that a fraction of potassium channels remains open, making it difficult for the membrane potential to depolarize, and thereby giving rise to the relative refractory period. Because the density and subtypes of potassium channels may differ greatly between different types of neurons, the duration of the relative refractory period is highly variable.
The absolute refractory period is largely responsible for the unidirectional propagation of action potentials along axons. At any given moment, the patch of axon behind the actively spiking part is refractory, but the patch in front, not having been activated recently, is capable of being stimulated by the depolarization from the action potential. | 7 | Physical Chemistry |
* Organic Synthesis Directed Toward Life Science, (Japanese), Kodansha, 1985.
* Organic Chemistry for Graduate Students, (Japanese), Tokyo Kagaku Dojin, 1998.
* Asymmetric Reaction for the Basis of Medicinal Chemistry, （Japanese, Hirokawa Shoten
* Stimulating Concepts in Chemistry, (English), VCH Verlagsgesellschaft mbH, 2000.
* Multimetallic Catalysts In Organic Synthesis, (English), John Wiley & Sons Inc., 2004.
* New Development of Organocatalyst, (Japanese), CMC publishing Co., Ltd., 2006.
* Shibasaki M, Yoshikawa N: Lanthanide complexes in multifunctional asymmetric catalysis, Chemical Reviews 102 (2002) 2187–2209.
* Sasai H, Suzuki T, Arai S, Arai T, Shibasaki M: Basic Character of Rare-Earth-Metal Alkoxides – Utilization in Catalytic C-C Bond-Forming Reactions and Catalytic Asymmetric Nitroaldol Reactions, Journal of the American Chemical Society 114 (1992) 4418–4420.
* Yoshikawa N, Yamada YMA, Das J, Sasai H, Shibasaki M: Direct catalytic asymmetric aldol reaction, Journal of the American Chemical Society 121 (1999) 4168–4178.
* Yamada YMA, Yoshikawa N, Sasai H, Shibasaki M: Direct catalytic asymmetric aldol reactions of aldehydes with unmodified ketones, Angewandte Chemie International Edition in English 36 (1997) 1871–1873.
* Sasai H, Arai T, Satow Y, Houk KN, Shibasaki M: The first Heterobimetallic Multifunctional Asymmetric Catalyst, Journal of the American Chemical Society 117 (1995) 6194–6198.
* Shibasaki M, Boden CDJ, Kojima A: The asymmetric Heck reaction, Tetrahedron 53 (1997) 7371–7395.
* Gröger H, Vogl EM, Shibasaki M: New catalytic concepts for the asymmetric aldol reaction, Chemistry – a European Journal 4 (1998) 1137–1141.
* Hamashima Y, Sawada D, Kanai M, Shibasaki M: A new bifunctional asymmetric catalysis: An efficient catalytic asymmetric cyanosilylation of aldehydes, Journal of the American Chemical Society 121 (1999) 2641–2642.
* Bougauchi M, Watanabe S, Arai T, Sasai H, Shibasaki M: Catalytic asymmetric epoxidation of alpha,beta-unsaturated ketones promoted by lanthanoid complexes, Journal of the American Chemical Society 119 (1997) 2329–2330.
* Arai T, Sasai H, Aoe K, Okamura K, Date T, Shibasaki M: A new multifunctional heterobimetallic asymmetric catalyst for Michael additions and tandem Michael-Aldol reactions, Angewandte Chemie-International Edition in English 35 (1996) 104–106.
His research interests are focussed on the development of new synthetic methods, the design of biologically significant compounds and synthetic studies of such compounds. | 0 | Organic Chemistry |
Christian Alfred Elie Janot (January 4, 1936 – February 23, 2022) was a French physicist and materials scientist known for his work on materials characterization using Mössbauer spectroscopy and his physical metallurgy studies of quasicrystals and noncrystalline materials using neutron scattering techniques. | 8 | Metallurgy |
The magnetic moment of a gyrating particle is
which respects special relativity. is the relativistic Lorentz factor, is the rest mass, is the velocity perpendicular to the magnetic field, and is the magnitude of the magnetic field.
is a constant of the motion to all orders in an expansion in , where is the rate of any changes experienced by the particle, e.g., due to collisions or due to temporal or spatial variations in the magnetic field. Consequently, the magnetic moment remains nearly constant even for changes at rates approaching the gyrofrequency. When is constant, the perpendicular particle energy is proportional to , so the particles can be heated by increasing , but this is a "one-shot" deal because the field cannot be increased indefinitely. It finds applications in magnetic mirrors and magnetic bottles.
There are some important situations in which the magnetic moment is not invariant:
; Magnetic pumping: If the collision frequency is larger than the pump frequency, μ is no longer conserved. In particular, collisions allow net heating by transferring some of the perpendicular energy to parallel energy.
; Cyclotron heating: If B is oscillated at the cyclotron frequency, the condition for adiabatic invariance is violated, and heating is possible. In particular, the induced electric field rotates in phase with some of the particles and continuously accelerates them.
; Magnetic cusps: The magnetic field at the center of a cusp vanishes, so the cyclotron frequency is automatically smaller than the rate of any changes. Thus the magnetic moment is not conserved, and particles are scattered relatively easily into the loss cone. | 7 | Physical Chemistry |
Photocytes are found distributed unevenly near the plate cilia cells. Gastric cells form a barrier that keep the photocytes away from the opening of the radially canal which they are found to exist along. | 1 | Biochemistry |
In general the product distribution of hydrocarbons formed during the Fischer–Tropsch process follows an Anderson–Schulz–Flory distribution, which can be expressed as:
: = (1 − α)α
where W is the weight fraction of hydrocarbons containing n carbon atoms, and α is the chain growth probability or the probability that a molecule will continue reacting to form a longer chain. In general, α is largely determined by the catalyst and the specific process conditions.
Examination of the above equation reveals that methane will always be the largest single product so long as α is less than 0.5; however, by increasing α close to one, the total amount of methane formed can be minimized compared to the sum of all of the various long-chained products. Increasing α increases the formation of long-chained hydrocarbons. The very long-chained hydrocarbons are waxes, which are solid at room temperature. Therefore, for production of liquid transportation fuels it may be necessary to crack some of the FT products. In order to avoid this, some researchers have proposed using zeolites or other catalyst substrates with fixed sized pores that can restrict the formation of hydrocarbons longer than some characteristic size (usually n < 10). This way they can drive the reaction so as to minimize methane formation without producing many long-chained hydrocarbons. Such efforts have had only limited success. | 0 | Organic Chemistry |
Other methods available for the preparation of 2,3-epoxy alcohols have the advantage that they do not begin with an existing 2,3-epoxy alcohol; however, they tend to involve more steps than epoxide migration. Asymmetric dihydroxylation may be used to synthesize epoxy alcohols with high stereoselectivity, and some of the methods relying on dihydroxylation avoid the use of strongly basic conditions.
An alternative method that leads to retention of configuration at C-2 involves mesylation of an epoxy alcohol, epoxide opening, and re-closing by displacement of the mesylate. | 0 | Organic Chemistry |
Unlike thermally initiated phosphaalkyne oligomerization reactions, transition metals and main group metals are capable of oligomerizing phosphaalkynes in a controlled manner, and have led to the isolation of phosphaalkyne dimers, trimers, tetramers, pentamers, and even hexamers. A nickel complex is capable of catalytically homocoupling Bu-C≡P to yield a diphosphatetrahedrane. | 0 | Organic Chemistry |
The Gilchrist–Thomas process or Thomas process is a historical process for refining pig iron, derived from the Bessemer converter. It is named after its inventors who patented it in 1877: Percy Carlyle Gilchrist and his cousin Sidney Gilchrist Thomas. By allowing the exploitation of phosphorous iron ore, the most abundant, this process allowed the rapid expansion of the steel industry outside the United Kingdom and the United States.
The process differs essentially from the Bessemer process in the refractory lining of the converter. The latter, being made of dolomite fired with tar, is basic, whereas the Bessemer lining, made of packed sand, is acidic. Phosphorus, by migrating from iron to slag, allows both the production of a metal of satisfactory quality, and of phosphates sought after as fertilizer, known as "Thomas meal". The disadvantages of the basic process includes larger iron loss and more frequent relining.
After having favored the spectacular growth of the Lorraine iron and steel industry, the process progressively faded away in front of the Siemens-Martin open hearth, which also used the benefit of basic refractory lining, before disappearing in the mid-1960s: with the development of gas liquefaction, the use of pure oxygen became economically viable. Even if modern pure oxygen converters all operate with a basic medium, their performance and operation have little to do with their ancestor. | 8 | Metallurgy |
It is often useful to group processes into pairs, in which each variable held constant is one member of a conjugate pair. | 7 | Physical Chemistry |
Places significantly impacted by acid rain around the globe include most of eastern Europe from Poland northward into Scandinavia, the eastern third of the United States, and southeastern Canada. Other affected areas include the southeastern coast of China and Taiwan. | 2 | Environmental Chemistry |
The major ARCHER subsystem components include:
* advanced hyperspectral imaging (HSI) system with a resolution of one square meter per pixel.
* panchromatic high-resolution imaging (HRI) camera with a resolution of per pixel.
* global positioning system (GPS) integrated with an inertial navigation system (INS) | 7 | Physical Chemistry |
HSP have been criticized for lacking the formal theoretical derivation of Hildebrand solubility parameters. All practical correlations of phase equilibrium involve certain assumptions that may or may not apply to a given system. In particular, all solubility parameter-based theories have a fundamental limitation that they apply only to associated solutions (i.e., they can only predict positive deviations from Raoults law): they cannot account for negative deviations from Raoults law that result from effects such as solvation (often important in water-soluble polymers) or the formation of electron donor acceptor complexes. Like any simple predictive theory, HSP are best used for screening with data used to validate the predictions. Hansen parameters have been used to estimate Flory-Huggins Chi parameters, often with reasonable accuracy.
The factor of 4 in front of the dispersion term in the calculation of Ra has been the subject of debate. There is some theoretical basis for the factor of four (see Ch 2 of Ref 1 and also. However, there are clearly systems (e.g. Bottino et al., "Solubility parameters of poly(vinylidene fluoride)" J. Polym. Sci. Part B: Polymer Physics 26(4), 785-79, 1988) where the regions of solubility are far more eccentric than predicted by the standard Hansen theory.
HSP effects can be over-ridden by size effects (small molecules such as methanol can give "anomalous results").
It has been shown that it is possible to calculate HSP via molecular dynamics techniques, though currently the polar and hydrogen bonding parameters cannot reliably be partitioned in a manner that is compatible with Hansen's values. | 7 | Physical Chemistry |
In thiol–disulfide exchange, a thiolate group displaces one sulfur atom in a disulfide bond . The original disulfide bond is broken, and its other sulfur atom is released as a new thiolate, carrying away the negative charge. Meanwhile, a new disulfide bond forms between the attacking thiolate and the original sulfur atom.
Thiolates, not thiols, attack disulfide bonds. Hence, thiol–disulfide exchange is inhibited at low pH (typically, below 8) where the protonated thiol form is favored relative to the deprotonated thiolate form. (The pK of a typical thiol group is roughly 8.3, but can vary due to its environment.)
Thiol–disulfide exchange is the principal reaction by which disulfide bonds are formed and rearranged in a protein. The rearrangement of disulfide bonds within a protein generally occurs via intra-protein thiol–disulfide exchange reactions; a thiolate group of a cysteine residue attacks one of the proteins own disulfide bonds. This process of disulfide rearrangement (known as disulfide shuffling) does not change the number of disulfide bonds within a protein, merely their location (i.e., which cysteines are bonded). Disulfide reshuffling is generally much faster than oxidation/reduction reactions, which change the number of disulfide bonds within a protein. The oxidation and reduction of protein disulfide bonds in vitro also generally occurs via thiol–disulfide exchange reactions. Typically, the thiolate of a redox reagent such as glutathione, dithiothreitol attacks the disulfide bond on a protein forming a mixed disulfide bond' between the protein and the reagent. This mixed disulfide bond when attacked by another thiolate from the reagent, leaves the cysteine oxidized. In effect, the disulfide bond is transferred from the protein to the reagent in two steps, both thiol–disulfide exchange reactions.
The in vivo oxidation and reduction of protein disulfide bonds by thiol–disulfide exchange is facilitated by a protein called thioredoxin. This small protein, essential in all known organisms, contains two cysteine amino acid residues in a vicinal arrangement (i.e., next to each other), which allows it to form an internal disulfide bond, or disulfide bonds with other proteins. As such, it can be used as a repository of reduced or oxidized disulfide bond moieties. | 0 | Organic Chemistry |
Yoon is openly gay and has been a vocal advocate for greater inclusion of and support for diverse members of the STEM community throughout his career. Yoon is a long time member of the UW-Madison Committee on LGBT Issues, which he chaired between 2013 and 2014. He has also given numerous invited lectures on topics relating to being LGBTQIA+ in STEM. Yoon lives in Madison, Wisconsin with his husband, Michael Velliquette, who is an artist. | 0 | Organic Chemistry |
Indicator bacteria are types of bacteria used to detect and estimate the level of fecal contamination of water. They are not dangerous to human health but are used to indicate the presence of a health risk.
Each gram of human feces contains approximately ~100 billion () bacteria. These bacteria may include species of pathogenic bacteria, such as Salmonella or Campylobacter, associated with gastroenteritis. In addition, feces may contain pathogenic viruses, protozoa and parasites. Fecal material can enter the environment from many sources including waste water treatment plants, livestock or poultry manure, sanitary landfills, septic systems, sewage sludge, pets and wildlife. If sufficient quantities are ingested, fecal pathogens can cause disease. The variety and often low concentrations of pathogens in environmental waters makes them difficult to test for individually. Public agencies therefore use the presence of other more abundant and more easily detected fecal bacteria as indicators of the presence of fecal contamination. Aside from bacteria being found in fecal matter, it can also be found in oral and gut contents. | 3 | Analytical Chemistry |
Protein arginine N-methyltransferase-4 (PRMT4/CARM1) methylation of arginine residues within proteins plays a critical key role in transcriptional regulation (see the PRMT4 pathway on the left). PRMT4 binds to the classes of transcriptional activators known as p160 and CBP/p300. The modified forms of these proteins are involved in stimulation of gene expression via steroid hormone receptors. Significantly, PRMT4 methylates core histones H3 and H4, which are also targets of the histone acetylase activity of CBP/p300 coactivators. PRMT4 recruitment of chromatin by binding to coactivators increases histone methylation and enhances the accessibility of promoter regions for transcription. Methylation of the transcriptional coactivator CBP by PRMT4 inhibits binding to CREB and thereby partitions the limited cellular pool of CBP for steroid hormone receptor interaction. | 1 | Biochemistry |
Some kinds of cheese also, kefir, kumis (mare milk), shubat (camel milk), ayran, cultured milk products such as quark, filmjölk, crème fraîche, smetana, skyr, and yogurt | 1 | Biochemistry |
Gamma rays are the highest-energy form of electromagnetic radiation, being physically the same as all other forms (e.g., X-rays, visible light, infrared, radio) but having (in general) higher photon energy due to their shorter wavelength. Because of this, the energy of gamma-ray photons can be resolved individually, and a gamma-ray spectrometer can measure and display the energies of the gamma-ray photons detected.
Radioactive nuclei (radionuclides) commonly emit gamma rays in the energy range from a few keV to ~10 MeV, corresponding to the typical energy levels in nuclei with reasonably long lifetimes. Such sources typically produce gamma-ray "line spectra" (i.e., many photons emitted at discrete energies), whereas much higher energies (upwards of 1 TeV) may occur in the continuum spectra observed in astrophysics and elementary particle physics. The difference between gamma rays and X-rays is somewhat blurred. Gamma rays are always from nuclear energy level transitions of atoms and are mono energetic, whereas X-rays are electrically generated (X-ray tube, linear accelerator) and have a broad energy range. | 7 | Physical Chemistry |
Prelog wanted to work in an academic environment, so he accepted the position of lecturer at the University of Zagreb in 1935. At the Technical Faculty in Zagreb, he lectured on organic chemistry and chemical engineering.
With the help of collaborators and students, Prelog started researching quinine and its related compounds. He was financially supported by the pharmaceutical factory "Kaštel", currently Pliva. He developed a financially successful method of producing Streptazol, one of the first commercial sulfonamides. In 1941, while at Zagreb, Prelog developed the first synthesis of adamantane, a hydrocarbon with an unusual structure that was isolated from Moravian oil fields. | 4 | Stereochemistry |
Butyric acid is metabolized by various human XM-ligases (ACSM1, ACSM2B, ASCM3, ACSM4, ACSM5, and ACSM6), also known as butyrate–CoA ligase. The metabolite produced by this reaction is butyryl–CoA, and is produced as follows:
:Adenosine triphosphate + butyric acid + coenzyme A → adenosine monophosphate + pyrophosphate + butyryl-CoA
As a short-chain fatty acid, butyrate is metabolized by mitochondria as an energy (i.e., adenosine triphosphate or ATP) source through fatty acid metabolism. In particular, it is an important energy source for cells lining the mammalian colon (colonocytes). Without butyrates, colon cells undergo autophagy (i.e., self-digestion) and die.
In humans, the butyrate precursor tributyrin, which is naturally present in butter, is metabolized by triacylglycerol lipase into dibutyrin and butyrate through the reaction:
:Tributyrin + dibutyrin + butyric acid | 1 | Biochemistry |
An exopolymer is a biopolymer that is secreted by an organism into the environment (i.e. external to the organism). These exopolymers include the biofilms produced by bacteria to anchor them and protect them from environmental conditions. One type of expolymer, Transparent Exopolymers (TEP), found in both marine and aquatic ecosystems, are planktonic acidic polysaccharides of a gel-like consistency, originally defined by their ability to be stained visible by acidic Alcian Blue. Their free-floating characteristic sets TEPs aside from other extracellular polymeric substance subgroups where exopolymers exists as cell coating, dissolved slime or as part of biofilm matrices.
The formation of Transparent Exopolymer Particles(TEP) is mainly due to the abiotic coagulation of dissolved carbohydrates, which is secreted by the phytoplankton communities. Transparent Exopolymer Particles (TEP) have the ability to form larger aggregates because of their strong surface active properties or “stickiness”. This particular property of TEP allows them to perform as a glue matrix for other solid particles including detritus.
Transparent Exopolymer Particles (TEP) is also a carbon source for bacteria, which plays a significant role in affecting the food web structure and the carbon cycle in the ocean. Additionally, the conversion of dissolved organic carbon (DOC) to particulate organic carbon (POC) is an aggregation process that is due to TEP formation. | 1 | Biochemistry |
ASBMB hosts and sponsors numerous meetings each year. The annual meeting is held each April in conjunction with the Experimental Biology meeting. Additionally, themed special symposia are organized throughout the year. The society also produces webinars throughout the year focused on topics related to scientific research, professional development and education. | 1 | Biochemistry |
Both up and downregulation of miR-324-5p is shown to contribute to various types of cancer.
miR-324-5p plays a role in inflammation and tumorigenesis in colorectal cancer through regulation of CUEDC2, which regulates inflammation via interaction with NF-kB signaling. miR-324-5p can inhibit glioma proliferation, suppress hepatocellular carcinoma and nasopharyngeal carcinoma cell invasion, and regulate growth and pathology in multiple myeloma. Additionally, chromosome 17 deletions, which include deletion of miR-324-5p, are present in 10% of multiple myeloma patients and are associated with poorer prognosis.
In contrast, overexpression of miR-324-5p in gastric cancer cells reduces cell death and promotes growth and proliferation. miR-324-5p has also been shown to reduce the viability of gastric cancer cells via downregulation of TSPAN8, and miR-324-5p expression increased apoptosis in these same gastric cancer cells. | 1 | Biochemistry |
From 1907 onward, Charles Moureu was a professor of chemical pharmacy at the École supérieure de Pharmacie in Paris. In 1913 he was named director of the laboratory of hydrological physical chemistry at the École pratique des hautes études.
He became a member of the Académie Nationale de Médecine (from 1907), Académie des sciences (from 1911) and Académie nationale de pharmacie (president 1913).
After the use of poison gas against French troops in the Second Battle of Ypres on April 22, 1915, Charles Moureu was appointed vice-chairman of France's Committee for Gas Warfare. Moreu headed the Section des produits agressifs (Aggressive Products Section). In this role, he was responsible for 16 chemistry laboratories in Paris, supervising and coordinating their work until 1918. He was also involved in conferences of the allied powers in September 1917, March
1918, and October 1918.
In 1917 Charles Moureu was appointed professor of organic chemistry at the Collège de France. Succeeding Émile Jungfleisch, Moureu was the only professor to be appointed to the college during the first world war.
Moureu supported initiatives for international cooperation and standardization among chemists. He served as a vice-president of the Société chimique de France (SCF) in 1910.
Moureu was active in the restructuring of chemical organizations in 1918–1919. The Allied Conference of Academies formally dissolved the International Association of Chemical Societies (IACS), as of July 22, 1919. Moureu was the founding President of the International Union of Pure and Applied Chemistry (IUPAC), holding the position from 1920 to 1922. He also supported the establishment of the Maison de la chimie in Paris as an international center for chemists.
In 1921 and 1922, Moureu visited the United States as a scientific expert. In 1921 he was part of a French Mission on Disarmament.
In 1922, he visited Washington, D.C. for discussions on the use of gas in warfare. He visited a number of universities in the United States and Canada, and was given an honorary degree by the University of Montreal.
Moureu became chairman of the French Committee of National Defence when it was established in 1925, leading it until his death in 1929. | 0 | Organic Chemistry |
Of sulfur nucleophiles, hydrogen sulfide and its salts, thiols (RSH), thiolate anions (RS), anions of thiolcarboxylic acids (RC(O)-S), and anions of dithiocarbonates (RO-C(S)-S) and dithiocarbamates (RN-C(S)-S) are used most often.
In general, sulfur is very nucleophilic because of its large size, which makes it readily polarizable, and its lone pairs of electrons are readily accessible. | 7 | Physical Chemistry |
The aza-Payne rearrangement may be effected in either the "forward" (epoxide to aziridine) or "reverse" (aziridine to epoxide) direction depending on the conditions employed. Electron-poor aziridines undergo the reverse rearrangement in the presence of hydride base, while the corresponding epoxy amines undergo the forward rearrangement in the presence of boron trifluoride etherate.
The thia-Payne rearrangement has only been observed in the forward direction (epoxide to thiiranium) with in situ opening of the thiiranium. Invertive nucleophilic opening at C-2 is possible through the use of trialkylaluminum reagents. | 0 | Organic Chemistry |
Histones are composed of mostly positively charged amino acid residues such as lysine and arginine. The positive charges allow them to closely associate with the negatively charged DNA through electrostatic interactions. Neutralizing the charges in the DNA allows it to become more tightly packed. | 1 | Biochemistry |
The development of various methods of cryopreservation of bovine embryos improved embryo transfer technique considerably efficient technology, no longer depending on the immediate readiness of suitable recipients. Pregnancy rates are just slightly less than those achieved with fresh embryos. Recently, the use of cryoprotectants such as ethylene glycol has permitted the direct transfer of bovine embryos. The world's first live crossbred bovine calf produced under tropical conditions by Direct Transfer (DT) of embryo frozen in ethylene glycol freeze media was born on 23 June 1996. Dr. Binoy Sebastian Vettical of Kerala Livestock Development Board Ltd has produced the embryo stored frozen in Ethylene Glycol freeze media by slow programmable freezing (SPF) technique and transferred directly to recipient cattle immediately after thawing the frozen straw in water for the birth of this calf. In a study, in vivo produced crossbred bovine embryos stored frozen in ethylene glycol freeze media were transferred directly to recipients under tropical conditions and achieved a pregnancy rate of 50 percent. In a survey of the North American embryo transfer industry, embryo transfer success rates from direct transfer of embryos were as good as to those achieved with glycerol. Moreover, in 2011, more than 95% of frozen-thawed embryos were transferred by Direct Transfer. | 1 | Biochemistry |
Many metabolic pathways are of commercial interest. For instance, the production of many antibiotics or other drugs requires complex pathways. The pathways to produce such compounds can be transplanted into microbes or other more suitable organism for production purposes. For example, the worlds supply of the anti-cancer drug vinblastine is produced by relatively ineffient extraction and purification of the precursors vindoline and catharanthine from the plant Catharanthus roseus', which are then chemically converted into vinblastine. The biosynthetic pathway to produce vinblastine, including 30 enzymatic steps, has been transferred into yeast cells which is a convenient system to grow in large amounts. With these genetic modifications yeast can use its own metabolites geranyl pyrophosphate and tryptophan to produce the precursors of catharanthine and vindoline. This process required 56 genetic edits, including expression of 34 heterologous genes from plants in yeast cells. | 1 | Biochemistry |
Haloalkanes undergo free-radical reactions with elemental magnesium to give alkyl-magnesium compound: Grignard reagent. Haloalkanes also react with lithium metal to give organolithium compounds. Both Grignard reagents and organolithium compounds behave as the R synthon. Alkali metals such as sodium and lithium are able to cause haloalkanes to couple in Wurtz reaction, giving symmetrical alkanes. Haloalkanes, especially iodoalkanes, also undergo oxidative addition reactions to give organometallic compounds. | 0 | Organic Chemistry |
One of the ways cell apoptosis is activated is by release of cytochrome c from the mitochondria into cytosol. A study has shown that cells are able to protect themselves from apoptosis by blocking the release of cytochrome c using Bcl-x. Another way that cells can control apoptosis is by phosphorylation of Tyr48, which would turn cytochrome c into an anti-apoptotic switch. | 1 | Biochemistry |
Bioaerosols impact a variety of biogeochemical systems on earth including, but not limited to atmospheric, terrestrial, and marine ecosystems. As long-standing as these relationships are, the topic of bioaerosols is not very well-known. Bioaerosols can affect organisms in a multitude of ways including influencing the health of living organisms through allergies, disorders, and disease. Additionally, the distribution of pollen and spore bioaerosols contribute to the genetic diversity of organisms across multiple habitats. | 7 | Physical Chemistry |
Latvian Academy of Sciences named a biannual prize for advances in chemistry in Gustavs Vanags' name.
A commemorative plaque with bas-relief of G. Vanags is installed in the hall of Riga Technical University Faculty of Chemistry. A commemorative stone is erected at the place where his native house of "Rungas" once stood. | 0 | Organic Chemistry |
An Alkali-metal thermal to electric converter works by pumping something, usually sodium, though any Alkali metal will do, through, around, and over, a circuit. The heat evaporates the sodium at one end. This puts it at high pressure. It then passes through/over the Anode, releasing electrons, thus, charge. It then passes through an electrolyte to conduct it to the other side. This works because the electrolyte chosen can conduct Ions, but not electrons so well. At the Cathode, the Alkali metal gets its electrons back, effectively pumping electrons through the external circuit. The pressure from the electrolyte pushes it to a low-pressure vapor chamber, where it “cools off” to a liquid again. An electromagnetic pump, or a wick, takes this liquid sodium back to the hot side.
This device accepts a heat input in a range 900–1300 K and produces direct current with predicted device efficiencies of 15–40%. In the AMTEC, sodium is driven around a closed thermodynamic cycle between a high-temperature heat reservoir and a cooler reservoir at the heat rejection temperature. The unique feature of the AMTEC cycle is that sodium ion conduction between a high-pressure or -activity region and a low-pressure or -activity region on either side of a highly ionically conducting refractory solid electrolyte is thermodynamically nearly equivalent to an isothermal expansion of sodium vapor between the same high and low pressures. Electrochemical oxidation of neutral sodium at the anode leads to sodium ions, which traverse the solid electrolyte, and electrons, which travel from the anode through an external circuit, where they perform electrical work, to the low-pressure cathode, where they recombine with the ions to produce low-pressure sodium gas. The sodium gas generated at the cathode then travels to a condenser at the heat-rejection temperature of perhaps 400–700 K, where liquid sodium reforms. The AMTEC thus is an electrochemical concentration cell, which converts the work generated by expansion of sodium vapor directly into electric power.
The converter is based on the electrolyte used in the sodium–sulfur battery, sodium beta″-alumina, a crystalline phase of somewhat variable composition containing aluminum oxide, AlO, and sodium oxide, NaO, in a nominal ratio of 5:1, and a small amount of the oxide of a small-cation metal, usually lithium or magnesium, which stabilizes the beta″ crystal structure. The sodium beta″-alumina solid electrolyte (BASE) ceramic is nearly insulating with respect to transport of electrons and is a thermodynamically stable phase in contact with both liquid sodium and sodium at low pressure. | 7 | Physical Chemistry |
The Pulvermacher chain, especially in the form of one being worn on the body, was very familiar in the late 19th and early 20th century and would not have needed to be explained to an audience. For instance, there are references to it in the novel Madame Bovary when the character Homais wearing a number of Pulvermacher chains is described as "more bandaged than a Scythian". | 7 | Physical Chemistry |
The glyoxylate cycle may serve an entirely different purpose in some species of pathogenic fungi. The levels of the main enzymes of the glyoxylate cycle, ICL and MS, are greatly increased upon contact with a human host. Mutants of a particular species of fungi that lacked ICL were also significantly less virulent in studies with mice compared to the wild type. The exact link between these two observations is still being explored, but it can be concluded that the glyoxylate cycle is a significant factor in the pathogenesis of these microbes. | 1 | Biochemistry |
Using a glass pipette, the photolysed cell is isolated by aspiration. Cells are lysed and affinity purification is performed using streptavidin-coated beads that bind, immobilize and purify the biotinylated TIVA tag. | 1 | Biochemistry |
Copper tubes have been used to distribute potable water within building for many years and hundreds of miles are installed throughout Europe every year. The long life of copper when exposed to natural waters is a result of its thermodynamic stability, its high resistance to reacting with the environment, and the formation of insoluble corrosion products that insulate the metal from the environment. The corrosion rate of copper in most potable waters is less than 2.5 µm/year, at this rate a 15 mm tube with a wall thickness of 0.7 mm would last for about 280 years. In some soft waters the general corrosion rate may increase to 12.5 µm/year, but even at this rate it would take over 50 years to perforate the same tube. Despite the reliability of copper and copper alloys, in some cold hard waters pits may form in the bore of a tube. If these pits form, failure times can be expected between 6 months and 2 years from initiation. The mechanism that leads to the pitting of copper in cold hard waters is complex, it requires a water with a specific chemistry that is capable of supporting pit growth and a mechanism for the initiation of the pits. | 8 | Metallurgy |
Hybridization probes can be used to detect base flipping. This technique uses a molecule that has a complementary sequence to the sequence you would like to detect such that it binds to a single-strand of the DNA or RNA. Several hybridization probes have been used to detect base flipping. Potassium permanganate is used to detect thymine residues that have been flipped out by cytosine-C5 and adenine-N6 methyltransferases. Chloroacetaldehyde is used to detect cytosine residues flipped out by the HhaI DNA cytosine-5 methyltransferase (M. HhaI). | 1 | Biochemistry |
Romans used many methods to create metal objects. Like Samian ware, moulds were created by making a model of the desired shape (whether through wood, wax, or metal), which would then be pressed into a clay mould. In the case of a metal or wax model, once dry, the ceramic could be heated and the wax or metal melted until it could be poured from the mould (this process utilising wax is called the “lost wax“ technique). By pouring metal into the aperture, exact copies of an object could be cast. This process made the creation of a line of objects quite uniform. This is not to suggest that the creativity of individual artisans did not continue; rather, unique handcrafted pieces were normally the work of small, rural metalworkers on the peripheries of Rome using local techniques (Tylecote 1962).
There is archaeological evidence throughout the Empire demonstrating the large scale excavations, smelting, and trade routes concerning metals. With the Romans came the concept of mass production; this is arguably the most important aspect of Roman influence in the study of metallurgy. Three particular objects produced en masse and seen in the archaeological record throughout the Roman Empire are brooches called fibulae, worn by both men and women (Bayley 2004), coins, and ingots (Hughes 1980). These cast objects can allow archaeologists to trace years of communication, trade, and even historic/stylistic changes throughout the centuries of Roman power. | 8 | Metallurgy |
Different factors have been proposed to be related to codon usage bias, including gene expression level (reflecting selection for optimizing the translation process by tRNA abundance), guanine-cytosine content (GC content, reflecting horizontal gene transfer or mutational bias), guanine-cytosine skew (GC skew, reflecting strand-specific mutational bias), amino acid conservation, protein hydropathy, transcriptional selection, RNA stability, optimal growth temperature, hypersaline adaptation, and dietary nitrogen. | 1 | Biochemistry |
Biocompatibility is related to the behavior of biomaterials in various environments under various chemical and physical conditions. The term may refer to specific properties of a material without specifying where or how the material is to be used. For example, a material may elicit little or no immune response in a given organism, and may or may not able to integrate with a particular cell type or tissue. Immuno-informed biomaterials that direct the immune response rather than attempting to circumvent the process is one approach that shows promise. The ambiguity of the term reflects the ongoing development of insights into "how biomaterials interact with the human body" and eventually "how those interactions determine the clinical success of a medical device (such as pacemaker or hip replacement)". Modern medical devices and prostheses are often made of more than one material, so it might not always be sufficient to talk about the biocompatibility of a specific material. Surgical implantation of a biomaterial into the body triggers an organism-inflammatory reaction with the associated healing of the damaged tissue. Depending upon the composition of the implanted material, the surface of the implant, the mechanism of fatigue, and chemical decomposition there are several other reactions possible. These can be local as well as systemic. These include immune response, foreign body reaction with the isolation of the implant with a vascular connective tissue, possible infection, and impact on the lifespan of the implant. Graft-versus-host disease is an auto- and alloimmune disorder, exhibiting a variable clinical course. It can manifest in either acute or chronic form, affecting multiple organs and tissues and causing serious complications in clinical practice, both during transplantation and implementation of biocompatible materials. | 1 | Biochemistry |
The refrigerant naming system is mainly used for fluorinated and chlorinated short alkanes used as refrigerants. In the United States, the standard is specified in ANSI/ASHRAE Standard 34–1992, with additional annual supplements. The specified ANSI/ASHRAE prefixes were FC (fluorocarbon) or R (refrigerant), but today most are prefixed by a more specific classification:
*CFC—list of chlorofluorocarbons
*HCFC—list of hydrochlorofluorocarbons
*HFC—list of hydrofluorocarbons
*FC—list of fluorocarbons
*PFC—list of perfluorocarbons (completely fluorinated)
The decoding system for CFC-01234a is:
*0 = Number of double bonds (omitted if zero)
*1 = Carbon atoms -1 (omitted if zero)
*2 = Hydrogen atoms +1
*3 = Fluorine atoms
*4 = Replaced by Bromine ("B" prefix added)
*a = Letter added to identify isomers, the "normal" isomer in any number has the smallest mass difference on each carbon, and a, b, or c are added as the masses diverge from normal.
Other coding systems are in use as well. | 2 | Environmental Chemistry |
Helium-3 surface spin echo (HeSE) is an inelastic scattering technique in surface science that has been used to measure microscopic dynamics at well-defined surfaces in ultra-high vacuum. The information available from HeSE complements and extends that available from other inelastic scattering techniques such as neutron spin echo and traditional helium-4 atom scattering (HAS). | 7 | Physical Chemistry |
Poroma is a benign, relatively common skin tumor that has the cellular features similar to those of a sweat gland duct. This tumor typically occurs as a solitary stalkless nodule on the soles and palms but may occur in any area where there are sweat glands. Porocarcinoma (also termed eccrine porocarcinoma and malignant eccrine poroma) is an extremely rare malignant counterpart of poromas. It may arise from a longstanding poroma but more commonly appears to develop independently of any precursor poroma. Porocarcinoma tumors predominantly afflict elderly individuals. A study of 104 poroma tumors detected the YAP1-NUTM1 and WWTR1-NUTM1 fusion genes in 21 cases and 1 case, respectively, while the same study of 11 porocarcinoma tumors detected the YAP1-NUTM1 fusion gene in 6 cases. Expression of the NUTM1 (fusion) protein was observed in 25 poroma and 6 porocarcinoma cases but not in a wide range of other skin tumor types. Studies on cultured immortalized human dermal keratinocyte (i.e. HDK) and mouse embryonic fibroblast NIH-3T3 cell lines found that the YAP1-NUTM1 and WWTR1-NUTM1 fusion genes stimulated the anchorage-independent growth of NIH-3T3 cells and activated a transcriptional enhancer factor family member (i.e. TEAD family) reporter gene. The TEAD family in mammals includes four members, TEAD1, TEAD2, TEAD3, and TEAD4 that are transcription factors, i.e. proteins that regulate the expression of various genes. TEAD family proteins have been found to promote the development, progression, and/or metastasis of various cancer types and, based on the studies just cited, are thought to do so in poromas and porocarcinomas. However, further studies are needed to confirm this association and determine if TEAD family transcription factors may be useful targets for treating the porocarcinomas. | 1 | Biochemistry |
Class I TEs are copied in two stages: first, they are transcribed from DNA to RNA, and the RNA produced is then reverse transcribed to DNA. This copied DNA is then inserted back into the genome at a new position. The reverse transcription step is catalyzed by a reverse transcriptase, which is often encoded by the TE itself. The characteristics of retrotransposons are similar to retroviruses, such as HIV.
Retrotransposons are commonly grouped into three main orders:
* Retrotransposons, with long terminal repeats (LTRs), which encode reverse transcriptase, similar to retroviruses
* Retroposons, long interspersed nuclear elements (LINEs, LINE-1s, or L1s), which encode reverse transcriptase but lack LTRs, and are transcribed by RNA polymerase II
* Short interspersed nuclear elements (SINEs) do not encode reverse transcriptase and are transcribed by RNA polymerase III
Retroviruses can also be considered TEs. For example, after the conversion of retroviral RNA into DNA inside a host cell, the newly produced retroviral DNA is integrated into the genome of the host cell. These integrated DNAs are termed proviruses. The provirus is a specialized form of eukaryotic retrotransposon, which can produce RNA intermediates that may leave the host cell and infect other cells. The transposition cycle of retroviruses has similarities to that of prokaryotic TEs, suggesting a distant relationship between the two. | 1 | Biochemistry |
In spite of the usefulness in cell tracking and cell visualization of Kaede, there are some limitations.
Although Kaede will shift to red upon the exposure of UV or violet light and display a 2,000-fold increase in red-to-green fluorescence ratio, using both the red and green fluorescence bands can cause problems in multilabel experiments. The tetramerization of Kaede may disturb the localization and trafficking of fusion proteins. This limits the usefulness of Kaede as a fusion protein tag. | 1 | Biochemistry |
More recently Yamago et al. reported stibine-mediated polymerization, using an organostibine transfer agent with the general structure Z(Z')-Sb-R (where Z= activating group and R= free radical leaving group). A wide range of monomers (styrenics, (meth)acrylics and vinylics) can be controlled, giving narrow molecular weight distributions and predictable molecular weights under thermally initiated conditions. Yamago has also published a patent indicating that bismuth alkyls can also control radical polymerizations via a similar mechanism. | 7 | Physical Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.