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Phosphoramidites derived from protected nucleosides are referred to as nucleoside phosphoramidites and are widely used in chemical synthesis of DNA, RNA, and other nucleic acids and their analogs. | 0 | Organic Chemistry |
The determination of enantiomeric purity and absolute configuration is frequently necessary in organic synthesis. Pirkles alcohol is applied to obtain this information by NMR spectroscopy. When Pirkles alcohol is in solution with an ensemble of chiral molecules, short-lived diastereomeric solvates may be formed from Pirkles alcohol and the enantiomers of the analyte. Enantiomorphic protons of the analyte enantiomers, which without Pirkles alcohol are indistinguishable by NMR, become diastereomorphic when the analyte interacts with Pirkle's alcohol, and appear as different signals in an NMR spectrum. The relative magnitude of the signals quantitatively reveals the enantiomeric purity of the analyte. Also, a model of the solvated complex may be used to deduce absolute configuration of an enantioenriched analyte. | 4 | Stereochemistry |
The following outline is provided as an overview of and topical guide to biochemistry:
Biochemistry – study of chemical processes in living organisms, including living matter. Biochemistry governs all living organisms and living processes. | 1 | Biochemistry |
Multimedia fugacity model is a model in environmental chemistry that summarizes the processes controlling chemical behavior in environmental media by developing and applying of mathematical statements or "models" of chemical fate.
Most chemicals have the potential to migrate from the medium to medium. Multimedia fugacity models are utilized to study and predict the behavior of chemicals in different environmental compartments.
The models are formulated using the concept of fugacity, which was introduced by Gilbert N. Lewis in 1901 as a criterion of equilibrium and convenient method of calculating multimedia equilibrium partitioning.
The fugacity of chemicals is a mathematical expression that describes the rates at which chemicals diffuse, or are transported between phases. The transfer rate is proportional to the fugacity difference that exists between the source and destination phases.
For building the model, the initial step is to set up a mass balance equation for each phase in question that includes fugacities, concentrations, fluxes and amounts. The important values are the proportionality constant, called fugacity capacity expressed as Z-values (SI unit: mol/m Pa) for a variety of media, and transport parameters expressed as D-values (SI unit: mol/Pa h) for processes such as advection, reaction and intermedia transport. The Z-values are calculated using the equilibrium partitioning coefficients of the chemicals, Henry's law constant and other related physical-chemical properties. | 7 | Physical Chemistry |
N-methylhistamine (NMH), also known as 1-methylhistamine, is a product of N-methylation of histamine in a reaction catalyzed by the HNMT enzyme.
NMH is considered a biologically inactive metabolite of histamine. NMH is excreted in the urine and can be measured to estimate the amounts of active histamine in the body. While NMH has some biological activity on its own, it is much weaker than histamine. NMH can bind to histamine receptors but has a lower affinity and efficacy than histamine for these receptors, meaning that it binds less strongly and activates them less effectively. Depending on the receptor subtype and the tissue context, NMH may act as a partial agonist or an antagonist for some histamine receptors. NMH may have some modulatory effects on histamine signaling, but it is unlikely to cause significant allergic or inflammatory reactions by itself. NMH may also serve as a feedback mechanism to regulate histamine levels and prevent excessive histamine release. Still, NMT, being a product in a reaction catalyzed by HNMT, may inhibit expression of HNMT in a negative feedback loop.
Urinary NMH can be measured in clinical settings when systemic mastocytosis is suspected. Systemic mastocytosis and anaphylaxis are typically associated with at least a two-fold increase in urinary NMH levels, which are also increased in patients taking monoamine oxidase inhibitors and in patients on histamine-rich diets. | 1 | Biochemistry |
*Bacterial meningitis; an aminoglycoside can be added to increase efficacy against gram-negative meningitis bacteria
*Endocarditis by enterococcal strains (off-label use); often given with an aminoglycoside
*Gastrointestinal infections caused by contaminated water or food (for example, by Salmonella)
*Genito-urinary tract infections
*Healthcare-associated infections that are related to infections from using urinary catheters and that are unresponsive to other medications
*Otitis media (middle ear infection)
*Prophylaxis (i.e. to prevent infection) in those who previously had rheumatic heart disease or are undergoing dental procedures, vaginal hysterectomies, or C-sections. It is also used in pregnant woman who are carriers of group B streptococci to prevent early-onset neonatal infections.
*Respiratory infections, including bronchitis, pharyngitis
*Sinusitis
*Sepsis
*Whooping cough, to prevent and treat secondary infections
Ampicillin used to also be used to treat gonorrhea, but there are now too many strains resistant to penicillins. | 4 | Stereochemistry |
Mid-FTIR spectroscopy can be used to rapidly and quantitatively determine the BN of hydrocarbon lubricating oils by spectroscopically measuring the carboxylate (COO-) functional group of the salt produced when trifluoroacetic acid (TFA) reacts with basic constituents present in an oil sample. | 3 | Analytical Chemistry |
Fatty acid synthesis is an anabolic process that starts from the conversion of acetyl-CoA to malonyl-CoA by acetyl-CoA carboxylase. Malonyl CoA leads to fatty acid synthesis (FAS) and is involved in the elongation of fatty acids through Fatty acid synthase (FASN). Although aerobic glycolysis is the best documented metabolic phenotype of tumor cells, it is not a universal feature of all human cancers. Amino acids and fatty acids have been shown to function as fuels for tumor cells to proliferate. The carnitine palmitoyltransferase enzymes that regulate the β-oxidation of fatty acids may have a key role in determining some of these phenotypes. Enhanced fatty acid synthesis provides lipids for membrane biogenesis to tumor cells and hence, it gives advantage in both growth and survival of the cell. | 1 | Biochemistry |
In chemistry, the Bates–Guggenheim Convention refers to a conventional method based on the Debye–Hückel theory to determine pH standard values. | 7 | Physical Chemistry |
The Thraustochytrium mitochondrial code (translation table 23) is a genetic code found in the mitochondria of the labyrinthulid protist Thraustochytrium aureum. The mitochondrial genome was sequenced by the Organelle Genome Megasequencing Program. | 1 | Biochemistry |
An essential trace element is a dietary element, a mineral that is only needed in minute quantities for the proper growth, development, and physiology of the organism. The essential trace elements are those that are required to perform vital metabolic activities in organisms. Essential trace elements in human nutrition, and other animals include iron (Fe) (hemoglobin), copper (Cu) (respiratory pigments), cobalt (Co) (Vitamin B12), iodine (I), manganese (Mn), chlorine (Cl), molybdenum (Mo), selenium (Se) and zinc (Zn) (enzymes). Although they are essential, they become toxic at high concentrations. | 9 | Geochemistry |
The Shilov system is a classic example of catalytic C-H bond activation and oxidation which preferentially activates stronger C-H bonds over weaker C-H bonds for an overall partial oxidation. | 0 | Organic Chemistry |
Bachrach has written a textbook about computational organic chemistry, the second edition of which was published by John Wiley and Sons in 2014. Bachrach maintains a blog to provide supplementary materials for the textbook. For example, following the publication of the structure of the dication of hexamethylbenzene, , in Angewandte Chemie International Edition, Bachrach discussed its pyramidal geometry and six-coordinate carbon moiety in a blog post, demonstrating it is not hypervalent and explaining its three-dimensional aromaticity. | 0 | Organic Chemistry |
Nanoelectrochemistry is a branch of electrochemistry that investigates the electrical and electrochemical properties of materials at the nanometer size regime. Nanoelectrochemistry plays significant role in the fabrication of various sensors, and devices for detecting molecules at very low concentrations. | 7 | Physical Chemistry |
o-Cresolphthalein is a phthalein dye used as a pH indicator in titrations. It is insoluble in water but soluble in ethanol. Its solution is colourless below pH 8.2, and purple above 9.8. Its molecular formula is CHO. It is used medically to determine calcium levels in the human body, or to synthesize polyamides or polyimides. | 3 | Analytical Chemistry |
In a scanning electron microscope the region near the surface can be mapped using an electron beam that is scanned in a grid across the sample. A diffraction pattern can be recorded using electron backscatter diffraction (EBSD), as illustrated in Figure 25, captured with a camera inside the microscope. A depth from a few nanometers to a few microns, depending upon the electron energy used, is penetrated by the electrons, some of which are diffracted backwards and out of the sample. As result of combined inelastic and elastic scattering, typical features in an EBSD image are Kikuchi lines. Since the position of Kikuchi bands is highly sensitive to the crystal orientation, EBSD data can be used to determine the crystal orientation at particular locations of the sample. The data are processed by software yielding two-dimensional orientation maps. As the Kikuchi lines carry information about the interplanar angles and distances and, therefore, about the crystal structure, they can also be used for phase identification or strain analysis. | 7 | Physical Chemistry |
Lipid droplets are composed of a neutral lipid core consisting mainly of triacylglycerols (TAGs) and cholesteryl esters surrounded by a phospholipid monolayer. The surface of lipid droplets is decorated by a number of proteins which are involved in the regulation of lipid metabolism. The first and best-characterized family of lipid droplet coat proteins is the perilipin protein family, consisting of five proteins. These include perilipin 1 (PLIN1), perilipin 2 (PLIN2/ ADRP), perilipin 3 (PLIN3/ TIP47), perilipin 4 (PLIN4/ S3-12) and perilipin 5 (PLIN5/ OXPAT/ LSDP5/ MLDP). Proteomics studies have elucidated the association of many other families of proteins to the lipid surface including proteins involved in membrane trafficking, vesicle docking, endocytosis and exocytosis. Analysis of the lipid composition of lipid droplets has revealed the presence of a diverse set of phospholipid species; phosphatidylcholine and phosphatidylethanolamine are the most abundant, followed by phosphatidylinositol.
Lipid droplets vary greatly in size, ranging from 20 to 40 nm to 100 um. In adipocytes, lipid bodies tend to be larger and they may compose the majority of the cell, while in other cells they may only be induced under certain conditions and are considerably smaller in size. | 1 | Biochemistry |
The nitrogen–phosphorus detector (NPD) is also known as thermionic specific detector (TSD) is a detector commonly used with gas chromatography, in which thermal energy is used to ionize an analyte. It is a type of flame thermionic detector (FTD), the other being the alkali flame-ionization detector (AFID also known as AFD).
With this method, nitrogen and phosphorus can be selectively detected with a sensitivity that is 10 times greater than that for carbon. | 3 | Analytical Chemistry |
Magnetic nanoparticle synthesis can sometimes lead to a wide range of differently sized particles. The size of particles can influence their usefulness. Specifically, nanoparticles that are less than 10 nm or greater than 200 nm in size tend to be cleared from the body more quickly. | 1 | Biochemistry |
Response elements are short sequences of DNA within a gene promoter or enhancer region that are able to bind specific transcription factors and regulate transcription of genes.
Under conditions of stress, a transcription activator protein binds to the response element and stimulates transcription. If the same response element sequence is located in the control regions of different genes, then these genes will be activated by the same stimuli, thus producing a coordinated response. | 1 | Biochemistry |
The sugar derivatives used for SHJ reactions should be purified, dried, and powdered before use. Intramolecular Friedel-Crafts reaction of the aromatic ring of a benzoate ester at the 2-position of 1-acetoxy ribose in the presence of a Lewis acid has been observed, and represents a potential side reaction. Heterocycles must not be too basic in order to avoid excessive complexation with the Lewis acid; amino-substituted heterocycles such as cytosine, adenine, and guanine react slowly or not at all under SHJ conditions (although their N-acetylated derivatives react more rapidly).
Silylation is most commonly accomplished using HMDS, which evolves ammonia as the only byproduct of silylation. Catalytic or stoichiometric amounts of acidic additives such as trimethylsilyl chloride accelerate silylation; when such an additive is used, ammonium salts will appear in the reaction as a turbid impurity.
Lewis acids should be distilled immediately before use for best results. More than about 1.2-1.4 equivalents of Lewis acid are rarely needed. Acetonitrile is the most common solvent employed for these reactions, although other polar solvents are also common. Workup of reactions employing TMSOTf involves treatment with an ice-cold solution of sodium bicarbonate and extraction of the resulting sodium salts. When tin(IV) chloride is used in 1,2-dichloroethane, workup involves the addition of pyridine and filtering of the resulting pyridine-tin complex, followed by extraction with aqueous sodium bicarbonate. | 0 | Organic Chemistry |
Though characterization of 2-norbornyl cation crystals may have significantly precluded further debates about its electronic structure, it does not crystallize under any standard conditions. Recently, the crystal structure has been obtained and reported through a creative means: addition of aluminium tribromide to 2-norbornyl bromide in dibromomethane at low temperatures afforded crystals of [][]·. By examining the resulting crystal structure, researchers were able to confirm that the crystalline geometry best supports the case for delocalized bonding in the stable 2-norbornyl cation. Bond lengths between the "bridging" carbon 6 and each of carbons 1 and 2 were found to be slightly longer than typical alkane bonds. According to the nonclassical picture, one would expect a bond order between 0 and 1 for these bonds, signifying that this explains the crystal structure well. The bond length between carbons 1 and 2 was reported as being between typical single and double carbon-carbon bond lengths, which agrees with nonclassical predictions of a bond order slightly above 1. Investigators who crystallized the 2-norbornyl cation commented that the cation proved impossible to crystallize unless provided a chemical environment that locked it into one definite orientation. | 7 | Physical Chemistry |
A Fermi gas is an idealized model, an ensemble of many non-interacting fermions. Fermions are particles that obey Fermi–Dirac statistics, like electrons, protons, and neutrons, and, in general, particles with half-integer spin. These statistics determine the energy distribution of fermions in a Fermi gas in thermal equilibrium, and is characterized by their number density, temperature, and the set of available energy states. The model is named after the Italian physicist Enrico Fermi.
This physical model is useful for certain systems with many fermions. Some key examples are the behaviour of charge carriers in a metal, nucleons in an atomic nucleus, neutrons in a neutron star, and electrons in a white dwarf. | 7 | Physical Chemistry |
The earliest steps of a touchdown polymerase chain reaction cycle have high annealing temperatures. The annealing temperature is decreased in increments for every subsequent set of cycles. The primer will anneal at the highest temperature which is least-permissive of nonspecific binding that it is able to tolerate. Thus, the first sequence amplified is the one between the regions of greatest primer specificity; it is most likely that this is the sequence of interest. These fragments will be further amplified during subsequent rounds at lower temperatures, and will outcompete the nonspecific sequences to which the primers may bind at those lower temperatures. If the primer initially (during the higher-temperature phases) binds to the sequence of interest, subsequent rounds of polymerase chain reaction can be performed upon the product to further amplify those fragments. Touchdown increases specificity of the reaction at higher temperatures and increases the efficiency towards the end by lowering the annealing temperature.
From a mathematical point of view products of annealing at smaller temperatures are disadvantaged by for the first annealing in cycle and the second one in cycle for . | 1 | Biochemistry |
The hallmark difference of elongation in eukaryotes in comparison to prokaryotes is its separation from transcription. While prokaryotes are able to undergo both cellular processes simultaneously, the spatial separation that is provided by the nuclear membrane prevents this coupling in eukaryotes. Eukaryotic elongation factor 2 (eEF2) is a regulateable GTP-dependent translocase that moves nascent polypeptide chains from the A-site to the P-site in the ribosome. Phosphorylation of threonine 56 is inhibitory to the binding of eEF2 to the ribosome. Cellular stressors, such as anoxia have proven to induce translational inhibition through this biochemical interaction. | 1 | Biochemistry |
The Payne rearrangement is the isomerization, under basic conditions, of 2,3-epoxy alcohols to isomeric 1,2-epoxy alcohols with inversion of configuration. Aza- and thia-Payne rearrangements of aziridines and thiiraniums, respectively, are also known. | 0 | Organic Chemistry |
Temperate climates have a high radiative cooling potential and higher average population densities when compared to desert climates, which may increase willingness to apply PDRCs in these zones. This is because these climatic zones tend to be "transitional" zones between dry and humid climates. High population areas in temperate climatic zones may be susceptible to an "overcooling" effect from PDRCs (see: overcooling section below) due to temperature shifts from hot summers to mild winters, which can be overcome with the modification of PDRCs to adjust for temperature shifts. | 7 | Physical Chemistry |
To maximize the purity of product water, EDI feedwater needs pre-treatment, usually done via reverse osmosis. When fed with feedwater that is low in total dissolved solids (e.g., purified by RO), the product can reach very high purity levels. The contents of the feedwater must be kept within certain parameters to prevent damage to the EDI instrument.
Common feedwater quality concerns are:
* Hardness, which is often limited to 1 part per million (ppm) of CaCO or corresponding molecule, with limited exceptions up to 2 ppm.
* Silica content (SiO), which generally must be no more than 1 ppm in most EDI cells or 2 ppm in thin-cell modules.
* CO, which must be monitored to prevent excessive loading of anion exchange resin.
* TOC, which can foul resins and membranes, must be minimized.
* Chlorine, ozone, and other oxidizers can oxidize resins and membranes and create permanent damage, and must be minimized. | 7 | Physical Chemistry |
We can recognize which of these isometries we have according to whether it preserves hands or swaps them, and whether it has at least one fixed point or not, as shown in the following table (omitting the identity). | 3 | Analytical Chemistry |
Robert John Ferrier FRSNZ, FNZIC, (7 August 1932 – 11 July 2013) was an organic chemist who discovered two chemical reactions, the Ferrier rearrangement and the Ferrier carbocyclization. Originally from Edinburgh, he moved to Wellington, New Zealand, in 1970. | 0 | Organic Chemistry |
Grantham's distance depends on three properties: composition, polarity and molecular volume.
Distance difference D for each pair of amino acid i and j is calculated as:
where c = composition, p = polarity, and v = molecular volume; and are constants of squares of the inverses of the mean distance for each property, respectively equal to 1.833, 0.1018, 0.000399. According to Grantham's distance, most similar amino acids are leucine and isoleucine and the most distant are cysteine and tryptophan. | 1 | Biochemistry |
Electromigration is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applications where high direct current densities are used, such as in microelectronics and related structures. As the structure size in electronics such as integrated circuits (ICs) decreases, the practical significance of this effect increases. | 7 | Physical Chemistry |
Hicks earned her bachelor's degree at Marshall University in 2001, and went on to earn her doctorate at the University of Illinois Urbana-Champaign in 2005. She was an Assistant Member and Principal Investigator at the Donald Danforth Plant Science Center from 2006 to 2013, and an adjunct professor in the Department of Biology at Washington University in St. Louis before beginning her current position as a professor at UNC. She was named Sherman Fairchild Foundation Chancellor’s Science Scholars Term Associate Professor in 2022. | 3 | Analytical Chemistry |
* Allinger, Cava, de Jongh, Johnson, Lebel, Stevens: Organische Chemie, 1. Auflage, Walter de Gruyter, Berlin 1980, , p. 749.
* Beyer / Walter: Lehrbuch der Organischen Chemie, 19. Auflage, S. Hirzel Verlag, Stuttgart 1981, , pp. 98–99, 122.
* K. Peter C. Vollhardt, Neil E. Schore: Organische Chemie, 4. Auflage, Wiley-VCH, Weinheim 2005, , p. 632. | 0 | Organic Chemistry |
Temperature gradient gel electrophoresis (TGGE) and denaturing gradient gel electrophoresis (DGGE) are forms of electrophoresis which use either a temperature or chemical gradient to denature the sample as it moves across an acrylamide gel. TGGE and DGGE can be applied to nucleic acids such as DNA and RNA, and (less commonly) proteins. TGGE relies on temperature dependent changes in structure to separate nucleic acids. DGGE separates genes of the same size based on their different denaturing ability which is determined by their base pair sequence. DGGE was the original technique, and TGGE a refinement of it. | 1 | Biochemistry |
Neurophysins are acidic proteins with a molecular weight of approximately 10,000 Da that are rich in cysteine, glycine, and proline residues . The protein is double domain with a polypeptide chain of 93-95 residues with 14 cysteine residues forming 7 disulfide bridges . Domain I contains a COOH terminal with a disulfide loop; domain II lacks this COOH terminal disulfide loop . Based on the resemblance of the disulfide loop present on vasopressin and oxytocin, it is suggested that the hormones form covalent linkages to this disulfide loop present on the COOH terminal of domain I. | 1 | Biochemistry |
Slip bands or stretcher-strain marks are localized bands of plastic deformation in metals experiencing stresses. Formation of slip bands indicates a concentrated unidirectional slip on certain planes causing a stress concentration. Typically, slip bands induce surface steps (e.g., roughness due persistent slip bands during fatigue) and a stress concentration which can be a crack nucleation site. Slip bands extend until impinged by a boundary, and the generated stress from dislocations pile-up against that boundary will either stop or transmit the operating slip depending on its (mis)orientation.
Formation of slip bands under cyclic conditions is addressed as persistent slip bands (PSBs) where formation under monotonic condition is addressed as dislocation planar arrays (or simply slip-bands, see Slip bands in the absence of cyclic loading section). Slip-bands can be simply viewed as boundary sliding due to dislocation glide that lacks (the complexity of ) PSBs high plastic deformation localisation manifested by tongue- and ribbon-like extrusion. And, where PSBs normally studied with (effective) Burgers vector aligned with the extrusion plane because a PSB extends across the grain and exacerbates during fatigue; a monotonic slip-band has a Burger’s vector for propagation and another for plane extrusions both controlled by the conditions at the tip. | 8 | Metallurgy |
One accepted scientific hypothesis is that the Earth was formed by accretion of material with a chondritic composition through impacts with differentiated planetesimals. During this accretionary phase, planetary differentiation separated the Earth's core, where heavy metallic siderophile elements accumulated, from the surrounding undifferentiated primitive mantle. Further differentiation would take place later, creating the different chemical reservoirs of crust and mantle material, with incompatible elements accumulating in the crust.
Today, differentiation still continues in the upper mantle, resulting in two types of mantle reservoirs: those depleted in lithophile elements (depleted reservoirs), and those composed of "fresh" undifferentiated mantle material (enriched or primitive reservoirs). Volcanic rocks from hotspot areas often have a primitive composition, and because the magma at hotspots is supposed to have been taken to the surface from the deepest regions of the mantle by mantle plumes, geochemists assume there must be a relatively closed and very undifferentiated primitive reservoir somewhere in the lower mantle. One hypothesis to describe this assumption is the existence of the D"-layer at the core-mantle boundary. | 9 | Geochemistry |
Phosphohydroxypyruvic acid is an organic acid most widely known as an intermediate in the synthesis of serine. | 1 | Biochemistry |
The plate height given as:
with the column length and the number of theoretical plates can be estimated from a chromatogram by analysis of the retention time for each component and its standard deviation as a measure for peak width, provided that the elution curve represents a Gaussian curve.
In this case the plate count is given by:
By using the more practical peak width at half height the equation is:
or with the width at the base of the peak: | 3 | Analytical Chemistry |
MMC can be classified into physical MMC and chemical MMC. In the former method, the stationary phase is constructed of two or more types of packing materials. In the chemical method, just one type of packing material containing two or more functionalities is used. | 3 | Analytical Chemistry |
Thermal desorption fundamentally involves collecting volatile organic compounds onto a sorbent, and then heating this sorbent in a flow of gas to release the compounds and concentrate them into a smaller volume.
Early thermal desorbers used just single-stage operation, whereby the volatiles collected on a sorbent tube were released by heating the tube in a flow of gas, from where they passed directly into the GC.
Modern thermal desorbers can also accommodate two-stage operation, whereby the gas stream from the sorbent tube (typically 100–200 mL) is collected on a narrower tube integral to the thermal desorber, called the focusing trap or cold trap. Heating this trap releases the analytes once again, but this time in an even smaller volume of gas (typically 100–200 μL), resulting in improved sensitivity and better GC peak shape.
Modern thermal desorbers can accommodate both single-stage and two-stage operation, although single-stage operation is now usually carried out using the focusing trap to collect the analytes, rather than a sorbent tube.
It is normal for the focusing trap to be held at or below room temperature, although a temperature no lower than 0 °C is sufficient for all but the most volatile analytes. Higher trap temperatures also reduce the amount of water condensing inside the trap (when transferred to the GC column, water can reduce the quality of the chromatography). | 3 | Analytical Chemistry |
Other than the accumulation of toxins in human liver and organs, Bolesatine poisoning causes agglutination in human red blood cells and platelets at threshold concentrations. The following symptoms of hypertension and dizziness would be expected when affected. In severe cases, death may result. | 1 | Biochemistry |
Tar is a dark brown or black viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat.
Mineral products resembling tar can be produced from fossil hydrocarbons, such as petroleum. Coal tar is produced from coal as a byproduct of coke production. | 7 | Physical Chemistry |
The Suess effect is a change in the ratio of the atmospheric concentrations of heavy isotopes of carbon (C and C) by the admixture of large amounts of fossil-fuel derived CO, which contains no CO and is depleted in CO relative to CO in the atmosphere and carbon in the upper ocean and the terrestrial biosphere . It was discovered by and is named for the Austrian chemist Hans Suess, who noted the influence of this effect on the accuracy of radiocarbon dating. More recently, the Suess effect has been used in studies of climate change. The term originally referred only to dilution of atmospheric CO relative to CO. The concept was later extended to dilution of CO and to other reservoirs of carbon such as the oceans and soils, again relative to C.
Although the ratio of atmospheric CO to CO decreased over the industrial era (prior to atmospheric testing of nuclear weapons, commencing about 1950), because of the increase, due to fossil fuel emissions, in the amount of atmospheric CO over this period, roughly 1850 to 1950, the amount of atmospheric CO actually increased over this period. | 9 | Geochemistry |
A crista (; : cristae) is a fold in the inner membrane of a mitochondrion. The name is from the Latin for crest or plume, and it gives the inner membrane its characteristic wrinkled shape, providing a large amount of surface area for chemical reactions to occur on. This aids aerobic cellular respiration, because the mitochondrion requires oxygen. Cristae are studded with proteins, including ATP synthase and a variety of cytochromes. | 1 | Biochemistry |
One group of researchers applied the field of neuroproteomics to examine how different proteins affect the initial growth of neuritis. The experiment compared the protein activity of control neurons with the activity of neurons treated with nerve growth factor (NGF) and JNJ460, an “immunophilin ligand.” JNJ460 is an offspring of another drug that is used to prevent immune attack when organs are transplanted. It is not an immunosuppressant, however, but rather it acts as a shield against microglia. NGF promotes neuron viability and differentiation by binding to TrkA, a tyrosine receptor kinase. This receptor is important in initiating intracellular metabolic pathways, including Ras, Rak, and MAP kinase.
Protein differentiation was measured in each cell sample with and without treatment by NGF and JNJ460. A peptide mixture was made by washing off unbound portions of the amino acid sequence in a reverse column. The resulting mixture was then suspended a peptide mixture in a bath of cation exchange fluid. The proteins were identified by splicing them with trypsin and then searching through the results of passing the product through a mass spectrometer. This applies a form of liquid chromatography mass spectrometry to identify proteins in the mixture
JNJ460 treatment resulted in an increase in “signal transduction” proteins, while NGF resulted in an increase in proteins associated with the ribosome and synthesis of other proteins. JNJ460 also resulted in more structural proteins associated with intercellular growth, such as actin, myosin, and troponin. With NGF treatment, cells increased protein synthesis and creation of ribosomes. This method allows the analysis of all of the protein patterns overall, rather than a single change in an amino acid. Western blots confirmed the results, according to the researchers, though the changes in proteins were not as obvious in their protocol.
The main significance to these findings are that JNJ460 are NGF are distinct processes that both control the protein output of the cell. JNJ460 resulted in increased neuronal size and stability while NGF resulted in increased membrane proteins. When combined, they significantly increase a neuron’s chance of growth. While JNJ460 may “prime” some parts of the cell for NGF treatment, they do not work together. JNJ460 is thought to interact with Schwann cells in regenerating actin and myosin, which are key players in axonal growth. NGF helps the neuron grow as a whole. These two proteins do not play a part in communication with other neurons, however. They merely increase the size of the membrane down which a signal can be sent. Other neurotrophic factor proteomes are needed to guide neurons to each other to create synapses. | 1 | Biochemistry |
The amount of time required to destroy residual chloromethyl methyl ether using various standard aqueous quench solutions (ammonium chloride solution, water, and sodium carbonate solution) has been measured. In all cases, a solution of chloromethyl methyl ether in toluene/methyl acetate was destroyed (to within detection limit) after vigorous stirring with the quench solution for 15 minutes.
CMME is a known human carcinogen. Chronic exposure can increase the incidence of respiratory cancers, including small cell carcinoma. It is one of 13 chemicals regulated by the Occupational Safety and Health Administration despite not having an established permissible exposure limit.
It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities. It listed in Schedule 1 Part 1 of Canada's Prohibition of Certain Toxic Substances Regulations. | 0 | Organic Chemistry |
Vital effects are relevant to study because of their influence on paleoclimatic interpretations. Scientists study the isotopic composition of marine organisms’ shells that have been preserved in marine sediment in order to reconstruct past environmental conditions. The earliest example of this work is using oxygen isotopes from the calcium carbonate (CaCO) in belemnites to reconstruct paleotemperatures. It is important to understand vital effects because they affect how paleoclimatic data are interpreted, which influences how scientists predict future impacts of climate change. | 9 | Geochemistry |
In chemistry, the electrochemical equivalent (Eq or Z) of a chemical element is the mass of that element (in grams) transported by a specific quantity of electricity, usually expressed in grams per coulomb of electric charge. The electrochemical equivalent of an element is measured with a voltameter. | 7 | Physical Chemistry |
There are three main metals used as galvanic anodes: magnesium, aluminum and zinc. They are all available as blocks, rods, plates or extruded ribbon. Each material has advantages and disadvantages.
Magnesium has the most negative electropotential of the three (see galvanic series) and is more suitable for areas where the electrolyte (soil or water) resistivity is higher. This is usually on-shore pipelines and other buried structures, although it is also used on boats in fresh water and in water heaters. In some cases, the negative potential of magnesium can be a disadvantage: if the potential of the protected metal becomes too negative, reduction of water or solvated protons may evolve hydrogen atoms on the cathode surface, for instance according to
leading to hydrogen embrittlement or to disbonding of the coating. Where this is a concern, zinc anodes may be used. An aluminum-zinc-tin alloy called KA90 is commonly used in marine and water heater applications.
Zinc and aluminium are generally used in salt water, where the resistivity is generally lower and magnesium dissolves relatively quickly by reaction with water under hydrogen evolution (self-corrosion). Typical uses are for the hulls of ships and boats, offshore pipelines and production platforms, in salt-water-cooled marine engines, on small boat propellers and rudders, and for the internal surface of storage tanks.
Zinc is considered a reliable material, but is not suitable for use at higher temperatures, as it tends to passivate (the oxide layer formed shields from further oxidation); if this happens, current may cease to flow and the anode stops working. Zinc has a relatively low driving voltage, which means in higher-resistivity soils or water it may not be able to provide sufficient current. However, in some circumstances — where there is a risk of hydrogen embrittlement, for example — this lower voltage is advantageous, as overprotection is avoided.
Aluminium anodes have several advantages, such as a lighter weight, and much higher capacity than zinc. However, their electrochemical behavior is not considered as reliable as zinc, and greater care must be taken in how they are used. Aluminium anodes will passivate where chloride concentration is below 1,446 parts per million.
One disadvantage of aluminium is that if it strikes a rusty surface, a large thermite spark may be generated, so its use is restricted in tanks where there may be explosive atmospheres and there is a risk of the anode falling.
Since the operation of a galvanic anode relies on the difference in electropotential between the anode and the cathode, practically any metal can be used to protect some other, providing there is a sufficient difference in potential. For example, iron anodes can be used to protect copper. | 7 | Physical Chemistry |
Agricultural chemistry encompases the science and technology of producing not only edible crops, but feedstocks for fuels ("biofuels") and materials. Ethanol fuel obtained by fermentation of sugars. Biodiesel is derived from fats, both animal- and plant-derived. Methane can be recovered from manure and other ag wastes by microbial action. Lignocellulose is a promising precursor to new materials. | 1 | Biochemistry |
The PDE3 family in mammals consists of two members, PDE3A and PDE3B. The PDE3 isoforms are structurally similar, containing an N-terminal domain important for the localization and a C-terminus end. The 44-amino acid insertion in the catalytic domain differs in the PDE3 isoforms, and the N-terminal portions of the isoforms are quite divergent. PDE3A and PDE3B have strikingly similar pharmacological and kinetic properties, but the distinction is in expression profiles and affinity for cGMP.
The PDE3 family is composed of two genes, PDE3A and PDE3B. In cells expressing both genes, PDE3A is usually dominant. Three different variants of PDE3A (PDE3A1-3) are products of alternate startcodon usage of the PDE3A gene. The PDE3B encodes a single isoform only.
In their full-length both PDE3A and PDE3B contain two N-terminal hydrophobic membrane association regions, NHR1 and NHR2 (figure 2). The difference of the PDE3A1-3 variants lies in whether they include:
*both NHR1 and NHR2
*only NHR2
*neither NHR1 nor the NHR2.
The last can be predicted to be exclusively on soluble/cytosolic form. | 1 | Biochemistry |
Several tests can determine exposure to benzene. Benzene itself can be measured in breath, blood or urine, but such testing is usually limited to the first 24 hours post-exposure due to the relatively rapid removal of the chemical by exhalation or biotransformation. Most people in developed countries have measureable baseline levels of benzene and other aromatic petroleum hydrocarbons in their blood. In the body, benzene is enzymatically converted to a series of oxidation products including muconic acid, phenylmercapturic acid, phenol, catechol, hydroquinone and 1,2,4-trihydroxybenzene. Most of these metabolites have some value as biomarkers of human exposure, since they accumulate in the urine in proportion to the extent and duration of exposure, and they may still be present for some days after exposure has ceased. The current ACGIH biological exposure limits for occupational exposure are 500 μg/g creatinine for muconic acid and 25 μg/g creatinine for phenylmercapturic acid in an end-of-shift urine specimen. | 2 | Environmental Chemistry |
The metallotranscriptome can be defined as the map of the entire transcriptome in the presence of biologically or environmentally relevant concentrations of an essential or toxic metal, respectively. The metallometabolome constitutes the complete pool of small metabolites in a cell at any given time. This gives rise to the whole metallointeractome and knowledge of this is important in comparative metallomics dealing with toxicity and drug discovery. | 1 | Biochemistry |
Bexxar, a radioligand therapy using the radioisotope I-131+Tositumomab (a murine monoclonal antibody) and binding/targeting the ligand CD20 on human B-cells. CD20 is a membrane spanning protein found on B-cell lymphocytes that is a tumor marker as it is in higher concentration in cancer patients - specifically leukemias or lymphomas (like non-hodgkin's lymphoma).
I-131 is produced by nuclear fission or through neutron irradiation of Te-130 to convert it to Te-131 which decays to I-131 (produced in the University of Missouri Research Reactor). I-131 is stored in lead-shielding vials.
24 hours before and 14 days after administration, thyroid protective drugs and KI tablets are administered. I-131 and Tositumomab are administered separately over the course of 14 days intravenously by dosimetric and therapeutic doses. Side-effects include anemia, fever, rigors or chills, sweating, hypotension, dyspnea, bronchospasm, and nausea. There is a risk of radiation exposure to other individuals (women/children/fetus), anaphylaxis, neutropenia (low neutrophils), and thrombocytopenia (low platelet).
Zevalin, another radioligand therapy that targets non-Hodgkin lymphoma CD20 ligand but using Yttrium-90 as the radioisotope, was FDA approved in 2002. | 1 | Biochemistry |
When a second phase of mass fragmentation is added, for example using a second quadrupole in a quadrupole instrument, it is called tandem MS (MS/MS). MS/MS can sometimes be used to quantitate low levels of target compounds in the presence of a high sample matrix background.
The first quadrupole (Q1) is connected with a collision cell (Q2) and another quadrupole (Q3). Both quadrupoles can be used in scanning or static mode, depending on the type of MS/MS analysis being performed. Types of analysis include product ion scan, precursor ion scan, selected reaction monitoring (SRM) (sometimes referred to as multiple reaction monitoring (MRM)) and neutral loss scan. For example: When Q1 is in static mode (looking at one mass only as in SIM), and Q3 is in scanning mode, one obtains a so-called product ion spectrum (also called "daughter spectrum"). From this spectrum, one can select a prominent product ion which can be the product ion for the chosen precursor ion. The pair is called a "transition" and forms the basis for SRM. SRM is highly specific and virtually eliminates matrix background. | 3 | Analytical Chemistry |
There are a variety of approaches to identifying large-scale genomic variations (such as indels, duplications, inversions, translocations) between genomes. Other categories of methods include using microarrays, pulsed-field gel electrophoresis, cytogenetics and paired-end tags. | 1 | Biochemistry |
Aldehydes participate in many reactions. From the industrial perspective, important reactions are:
* condensations, e.g., to prepare plasticizers and polyols, and
* reduction to produce alcohols, especially "oxo-alcohols". From the biological perspective, the key reactions involve addition of nucleophiles to the formyl carbon in the formation of imines (oxidative deamination) and hemiacetals (structures of aldose sugars). | 0 | Organic Chemistry |
Since plasmas are very good electrical conductors, electric potentials play an important role. The average potential in the space between charged particles, independent of how it can be measured, is called the "plasma potential", or the "space potential". If an electrode is inserted into a plasma, its potential will generally lie considerably below the plasma potential due to what is termed a Debye sheath. The good electrical conductivity of plasmas makes their electric fields very small. This results in the important concept of "quasineutrality", which says the density of negative charges is approximately equal to the density of positive charges over large volumes of the plasma (), but on the scale of the Debye length, there can be charge imbalance. In the special case that double layers are formed, the charge separation can extend some tens of Debye lengths.
The magnitude of the potentials and electric fields must be determined by means other than simply finding the net charge density. A common example is to assume that the electrons satisfy the Boltzmann relation:
Differentiating this relation provides a means to calculate the electric field from the density:
It is possible to produce a plasma that is not quasineutral. An electron beam, for example, has only negative charges. The density of a non-neutral plasma must generally be very low, or it must be very small, otherwise, it will be dissipated by the repulsive electrostatic force. | 7 | Physical Chemistry |
Escitalopram was developed in cooperation between Lundbeck and Forest Laboratories. Its development was initiated in 1997, and the resulting new drug application was submitted to the US FDA in March 2001. The short time (3.5 years) it took to develop escitalopram can be attributed to the previous experience of Lundbeck and Forest with citalopram, which has similar pharmacology. | 4 | Stereochemistry |
The earliest research showing that yeast takes up Mg appears to be done by Schmidt et al. (1949). However, these authors only showed altered yeast Mg content in a table within the paper, and the report's conclusions dealt entirely with the metabolism of phosphate. A series of experiments by Rothstein shifted the focus more towards the uptake of the metal cations, showing that yeast take up cations with the following affinity series; Mg, Co, Zn > Mn > Ni > Ca > Sr. Additionally, it was suggested that the transport of the different cations is mediated by the same transport system — a situation very much like that in bacteria.
In 1998, MacDiarmid and Gardner finally identified the proteins responsible for the observed cation transport phenotype in Saccharomyces cerevisiae. The genes involved in this system and a second mitochondrial Mg transport system, functionally identified significantly after the gene was cloned, are described in the sections below. | 1 | Biochemistry |
There are two common measures of photosynthetically active radiation: photosynthetic photon flux (PPF) and yield photon flux (YPF). PPF values all photons from 400 to 700 nm equally, while YPF weights photons in the range from 360 to 760 nm based on a plant's photosynthetic response.
PAR as described with PPF does not distinguish between different wavelengths between 400 and 700 nm, and assumes that wavelengths outside this range have zero photosynthetic action. If the exact spectrum of the light is known, the photosynthetic photon flux density (PPFD) values in μmol⋅s⋅m) can be modified by applying different weighting factors to different wavelengths. This results in a quantity called the yield photon flux (YPF). The red curve in the graph shows that photons around 610 nm (orange-red) have the highest amount of photosynthesis per photon. However, because short-wavelength photons carry more energy per photon, the maximum amount of photosynthesis per incident unit of energy is at a longer wavelength, around 650 nm (deep red).
It has been noted that there is considerable misunderstanding over the effect of light quality on plant growth. Many manufacturers claim significantly increased plant growth due to light quality (high YPF). The YPF curve indicates that orange and red photons between 600 and 630 nm can result in 20 to 30% more photosynthesis than blue or cyan photons between 400 and 540 nm.
But the YPF curve was developed from short-term measurements made on single leaves in low light. More recent longer-term studies with whole plants in higher light indicate that light quality may have a smaller effect on plant growth rate than light quantity. Blue light, while not delivering as many photons per joule, encourages leaf growth and affects other outcomes.
The conversion between energy-based PAR and photon-based PAR depends on the spectrum of the light source (see Photosynthetic efficiency). The following table shows the conversion factors from watts for black-body spectra that are truncated to the range 400–700 nm. It also shows the luminous efficacy for these light sources and the fraction of a real black-body radiator that is emitted as PAR.
For example, a light source of 1000 lm at a color temperature of 5800 K would emit approximately 1000/265 = 3.8 W of PAR, which is equivalent to 3.8 × 4.56 = 17.3 μmol/s. For a black-body light source at 5800 K, such as the sun is approximately, a fraction 0.368 of its total emitted radiation is emitted as PAR. For artificial light sources, that usually do not have a black-body spectrum, these conversion factors are only approximate.
The quantities in the table are calculated as
where is the black-body spectrum according to Planck's law, is the standard luminosity function, represent the wavelength range (400–700 nm) of PAR, and is the Avogadro constant. | 5 | Photochemistry |
* Alcan Lynemouth Aluminium Smelter, powered by the coal-fired Lynemouth Power Station in North East England, ceased production in 2012, demolished in 2018.
* Anglesey Aluminium, powered by Wylfa nuclear power station in north-west Wales, closed in 2013, with redevelopment of the site announced in 2022.
* The Valco aluminium smelter in Ghana, powered by the Akosombo Hydroelectric Project
* Fjarðaál in Iceland, powered by the Kárahnjúkar Hydropower Plant
* Jharsuguda in Orissa, India, to be powered by its own coal-fired power station.
* Aluminerie Alouette in Sept-Îles, Québec, powered by the Churchill Falls Hydro Electric project.
* Alba Smelter in Bahrain, powered by its own four power stations with a total generating capacity of . | 8 | Metallurgy |
Commercial varieties of important agricultural crops (including soy, maize/corn, sorghum, canola, alfalfa and cotton) have been developed that incorporate a recombinant gene that results in resistance to the herbicide glyphosate (trade name Roundup), and simplifies weed control by glyphosate application. These crops are in common commercial use in several countries. | 1 | Biochemistry |
Viel is a co-author of the book Biology: How Life Works. It is published by Macmillan Education and is the first project to develop three pillars: the text, the visual program, and the assessment at the same time. | 1 | Biochemistry |
The biological monitoring working party (BMWP) is a procedure for measuring water quality using families of macroinvertebrates as biological indicators.
The method is based on the principle that different aquatic invertebrates have different tolerances to pollutants. In the case of BMWP, this is based on the sensitivity/tolerance to organic pollution (i.e. nutrient enrichment that can affect the availability of dissolved oxygen). It is important to recognise that the ranking of sensitivity/tolerance will vary for different kinds of pollution. In the case of BMWP/Organic pollution rankings, the presence of mayflies or stoneflies for instance indicate the cleanest waterways and are given a tolerance score of 10. The lowest scoring invertebrates are worms (Oligochaeta) which score 1. The number of different macroinvertebrates is also an important factor, because a better quality water is assumed to contain fewer pollutants that would exclude "sensitive" species - resulting in a higher diversity.
Kick sampling, where a net is placed downstream from the sampler and the river bed is agitated with the foot for a given period of time (the standard is 3 minutes), is employed. Any macroinvertebrates caught in the net are stored and preserved with an alcohol solution, and identified to the family level, this can be done with the live organisms as well.
The BMWP score equals the sum of the tolerance scores of all macroinvertebrate families in the sample. A higher BMWP score is considered to reflect a better water quality. Alternatively, also the Average Score Per Taxon (ASPT) score is calculated. The ASPT equals the average of the tolerance scores of all macroinvertebrate families found, and ranges from 0 to 10. The main difference between both indices is that ASPT does not depend on the family richness. Once BMWP and ASPT are calculated, the Lincoln Quality Index (LQI) is used to assess the water quality in the Anglian Water Authority area.
Other indices that can be used to assess water quality are the Chandler Score, the Trent Biotic Index and the Rapid Bioassessment Protocols. | 3 | Analytical Chemistry |
In organic chemistry, a thial or thioaldehyde is a functional group which is similar to an aldehyde, , in which a sulfur (S) atom replaces the oxygen (O) atom of the aldehyde (R represents an alkyl or aryl group). Thioaldehydes are even more reactive than thioketones. Unhindered thioaldehydes are generally too reactive to be isolated — for example, thioformaldehyde, , condenses to the cyclic trimer 1,3,5-trithiane. Thioacrolein, , formed by decomposition of allicin from garlic, undergoes a self Diels-Alder reaction giving isomeric vinyldithiins. While thioformaldehyde is highly reactive, it is found in interstellar space along with its mono- and di-deuterated isotopologues. With sufficient steric bulk, however, stable thioaldehydes can be isolated.
In early work, the existence of thioaldehydes was inferred by trapping processes. For instance the reaction of with benzaldehyde was proposed to form thiobenzaldehyde, which forms a cycloadduct with the dithiophosphine ylides to form a ring. | 0 | Organic Chemistry |
Optical contact bonding is a glueless process whereby two closely conformal surfaces are joined, being held purely by intermolecular forces. | 6 | Supramolecular Chemistry |
Afterhyperpolarization, or AHP, is the hyperpolarizing phase of a neurons action potential where the cells membrane potential falls below the normal resting potential. This is also commonly referred to as an action potential's undershoot phase. AHPs have been segregated into "fast", "medium", and "slow" components that appear to have distinct ionic mechanisms and durations. While fast and medium AHPs can be generated by single action potentials, slow AHPs generally develop only during trains of multiple action potentials.
During single action potentials, transient depolarization of the membrane opens more voltage-gated K channels than are open in the resting state, many of which do not close immediately when the membrane returns to its normal resting voltage. This can lead to an "undershoot" of the membrane potential to values that are more polarized ("hyperpolarized") than was the original resting membrane potential. Ca-activated K channels that open in response to the influx of Ca during the action potential carry much of the K current as the membrane potential becomes more negative. The K permeability of the membrane is transiently unusually high, driving the membrane voltage V even closer to the K equilibrium voltage E. Hence, hyperpolarization persists until the membrane K permeability returns to its usual value.
Medium and slow AHP currents also occur in neurons. The ionic mechanisms underlying medium and slow AHPs are not yet well understood, but may also involve M current and HCN channels for medium AHPs, and ion-dependent currents and/or ionic pumps for slow AHPs.
The afterhyperpolarized (sAHP) state can be followed by an afterdepolarized state (which is not to be confused with the cardiac afterdepolarization) and can thus set the phase of the subthreshold oscillation of the membrane potential, as reported for the stellate cells of the entorhinal cortex. This mechanism is proposed to be functionally important to maintain the spiking of these neurons at a defined phase of the theta cycle, that, in turn, is thought to contribute to encoding of new memories by the medial temporal lobe of the brain | 7 | Physical Chemistry |
He was born in Nafplio, the first capital of Greece and his paternal family home. During World War II, he accompanied his parents to Egypt, South Africa, and finally the United States (U.S.), where his father held ministerial posts in the Greek Government in exile. The family stayed in the U.S. until 1944, when, following the liberation of Greece after the defeat of Nazi Germany, they returned permanently to Greece.
After his secondary education at the 8th Gymnasium of Athens, he graduated from the Medical School of the National and Kapodistrian University of Athens in 1956. After completion of Army service he joined the team of Prof. Peter Karlson at the Institut für Physiologische Chemie of the Ludwig Maximilian University of Munich. He completed his doctoral degree in biochemistry in 1962 from the Medical School of the Ludwig Maximilian University of Munich. | 1 | Biochemistry |
The fundamental way to prevent fretting is to design for no relative motion of the surfaces at the contact. Surface roughness plays an important role as fretting normally occurs by the contact of the asperities of the mating surfaces. Lubricants are often employed to mitigate fretting because they reduce friction and inhibit oxidation. This may however, also cause the opposite effect as a lower coefficient of friction may lead to more movement. Thus, a solution must be carefully considered and tested.
In the aviation industry, coatings are applied to cause a harder surface and/or influence the friction coefficient.
Soft materials often exhibit higher susceptibility to fretting than hard materials of a similar type. The hardness ratio of the two sliding materials also has an effect on fretting wear. However, softer materials such as polymers can show the opposite effect when they capture hard debris which becomes embedded in their bearing surfaces. They then act as a very effective abrasive agent, wearing down the harder metal with which they are in contact. | 8 | Metallurgy |
The law was named after scientist Jacques Charles, who formulated the original law in his unpublished work from the 1780s.
In two of a series of four essays presented between 2 and 30 October 1801, John Dalton demonstrated by experiment that all the gases and vapours that he studied expanded by the same amount between two fixed points of temperature. The French natural philosopher Joseph Louis Gay-Lussac confirmed the discovery in a presentation to the French National Institute on 31 Jan 1802, although he credited the discovery to unpublished work from the 1780s by Jacques Charles. The basic principles had already been described by Guillaume Amontons and Francis Hauksbee a century earlier.
Dalton was the first to demonstrate that the law applied generally to all gases, and to the vapours of volatile liquids if the temperature was well above the boiling point. Gay-Lussac concurred. With measurements only at the two thermometric fixed points of water (0°C and 100°C), Gay-Lussac was unable to show that the equation relating volume to temperature was a linear function. On mathematical grounds alone, Gay-Lussacs paper does not permit the assignment of any law stating the linear relation. Both Daltons and Gay-Lussac's main conclusions can be expressed mathematically as:
where is the volume occupied by a given sample of gas at 100 °C; is the volume occupied by the same sample of gas at 0 °C; and is a constant which is the same for all gases at constant pressure. This equation does not contain the temperature and so is not what became known as Charles Law. Gay-Lussacs value for (), was identical to Dalton's earlier value for vapours and remarkably close to the present-day value of . Gay-Lussac gave credit for this equation to unpublished statements by his fellow Republican citizen J. Charles in 1787. In the absence of a firm record, the gas law relating volume to temperature cannot be attributed to Charles.
Dalton's measurements had much more scope regarding temperature than Gay-Lussac, not only measuring the volume at the fixed points of water but also at two intermediate points. Unaware of the inaccuracies of mercury thermometers at the time, which were divided into equal portions between the fixed points, Dalton, after concluding in Essay II that in the case of vapours, “any elastic fluid expands nearly in a uniform manner into 1370 or 1380 parts by 180 degrees (Fahrenheit) of heat”, was unable to confirm it for gases. | 7 | Physical Chemistry |
E. coli produces a second protein responsible for degradation of (p)ppGpp, SpoT. When the amino acid balance in the cell is restored, (p)ppGpp is hydrolyzed by SpoT and returned to a more energetically favorable state. This protein also has the capacity to synthesize (p)ppGpp, and seems to be the primary synthase under certain conditions of stress. Most other bacteria encode a single protein that is responsible for both synthesis and degradation of (p)ppGpp, generally homologs of SpoT. | 1 | Biochemistry |
Achinewhu has analyzed more than fifty homegrown foodstuffs, which include seeds, nuts, tubers, spices, and herbs. These indigenous food items where examined and explored for their nutrient compositions and quality of protein content. Details of his findings are being used along with others in the compendium of Nigeria's food composition table.
He evolved the processing and production of coffee from coffee seed grown in Bayelsa State, Nigeria.
He did research on cassava processing, which identified upgrade cassava cultivars with superior quality food values with regards to product output and other physico-chemical properties. He identified new cultivars with high starch yield and therefore high export potentials.
He developed a baby food (weaning) supplement employing the use of a combination of fermented plant food products. This was used to nourish children who were undernourished, in the days of Better Life Programme for Rural Women. | 1 | Biochemistry |
In sensory neurons, an external signal such as pressure, temperature, light, or sound is coupled with the opening and closing of ion channels, which in turn alter the ionic permeabilities of the membrane and its voltage. These voltage changes can again be excitatory (depolarizing) or inhibitory (hyperpolarizing) and, in some sensory neurons, their combined effects can depolarize the axon hillock enough to provoke action potentials. Some examples in humans include the olfactory receptor neuron and Meissner's corpuscle, which are critical for the sense of smell and touch, respectively. However, not all sensory neurons convert their external signals into action potentials; some do not even have an axon. Instead, they may convert the signal into the release of a neurotransmitter, or into continuous graded potentials, either of which may stimulate subsequent neuron(s) into firing an action potential. For illustration, in the human ear, hair cells convert the incoming sound into the opening and closing of mechanically gated ion channels, which may cause neurotransmitter molecules to be released. In similar manner, in the human retina, the initial photoreceptor cells and the next layer of cells (comprising bipolar cells and horizontal cells) do not produce action potentials; only some amacrine cells and the third layer, the ganglion cells, produce action potentials, which then travel up the optic nerve. | 7 | Physical Chemistry |
A typical dialysis procedure for protein samples is as follows:
# Prepare the membrane according to instructions
# Load the sample into dialysis tubing, cassette or device
# Place sample into an external chamber of dialysis buffer (with gentle stirring of the buffer)
# Dialyze for 2 hours (at room temperature or 4 °C)
# Change the dialysis buffer and dialyze for another 2 hours
# Change the dialysis buffer and dialyze for 2 hours or overnight
The total volume of sample and dialysate determine the final equilibrium concentration of the small molecules on both sides of the membrane. By using the appropriate volume of dialysate and multiple exchanges of the buffer, the concentration of small contaminants within the sample can be decreased to acceptable or negligible levels.
For example, when dialyzing 1mL of sample against 200mL of dialysate, the concentration of unwanted dialyzable substances will be decreased 200-fold when equilibrium is attained. Following two additional buffer changes of 200mL each, the contaminant level in the sample will be reduced by a factor of 8 x 10 (200 x 200 x 200). | 1 | Biochemistry |
The Seebeck effect refers to the development of an electromotive force across two points of an electrically conducting material when there is a temperature difference between those two points.
Under open-circuit conditions where there is no internal current flow, the gradient of voltage () is directly proportional to the gradient in temperature ():
where is a temperature-dependent material property known as the Seebeck coefficient.
The standard measurement configuration shown in the figure shows four temperature regions and thus four voltage contributions:
# Change from to , in the lower copper wire.
# Change from to , in the alumel wire.
# Change from to , in the chromel wire.
# Change from to , in the upper copper wire.
The first and fourth contributions cancel out exactly, because these regions involve the same temperature change and an identical material.
As a result, does not influence the measured voltage.
The second and third contributions do not cancel, as they involve different materials.
The measured voltage turns out to be
where and are the Seebeck coefficients of the conductors attached to the positive and negative terminals of the voltmeter, respectively (chromel and alumel in the figure). | 8 | Metallurgy |
Atomic spectroscopy was the first application of spectroscopy. Atomic absorption spectroscopy and atomic emission spectroscopy involve visible and ultraviolet light. These absorptions and emissions, often referred to as atomic spectral lines, are due to electronic transitions of outer shell electrons as they rise and fall from one electron orbit to another. Atoms also have distinct x-ray spectra that are attributable to the excitation of inner shell electrons to excited states.
Atoms of different elements have distinct spectra and therefore atomic spectroscopy allows for the identification and quantitation of a sample's elemental composition. After inventing the spectroscope, Robert Bunsen and Gustav Kirchhoff discovered new elements by observing their emission spectra. Atomic absorption lines are observed in the solar spectrum and referred to as Fraunhofer lines after their discoverer. A comprehensive explanation of the hydrogen spectrum was an early success of quantum mechanics and explained the Lamb shift observed in the hydrogen spectrum, which further led to the development of quantum electrodynamics.
Modern implementations of atomic spectroscopy for studying visible and ultraviolet transitions include flame emission spectroscopy, inductively coupled plasma atomic emission spectroscopy, glow discharge spectroscopy, microwave induced plasma spectroscopy, and spark or arc emission spectroscopy. Techniques for studying x-ray spectra include X-ray spectroscopy and X-ray fluorescence. | 7 | Physical Chemistry |
When mutations occur in the genes responsible for the biological mechanisms that herbicides interfere with, these mutations may cause the herbicide mode of action to work less effectively. This is called target-site resistance. Specific mutations that have the most helpful effect for the plant have been shown to occur in separate instances and dominate throughout resistant weed populations. This is an example of convergent evolution. Some mutations conferring herbicide resistance may have fitness costs, reducing the plant's ability to survive in other ways, but over time, the least costly mutations tend to dominate in weed populations.
Recently, incidences of non-target site resistance have increasingly emerged, such as examples where plants are capable of producing enzymes that neutralize herbicides before they can enter the plant's cells – metabolic resistance. This form of resistance is particularly challenging, since plants can develop non-target-site resistance to herbicides their ancestors were never directly exposed to. | 2 | Environmental Chemistry |
Diisopinocampheylborane is an organoborane that is useful for asymmetric synthesis. This colourless solid is the precursor to a range of related reagents. The compound was reported in 1961 by Zweifel and Brown in a pioneering demonstration of asymmetric synthesis using boranes. The reagent is mainly used for the synthesis of chiral secondary alcohols. The reagent is often depicted as a monomer but like most hydroboranes, it is dimeric with B-H-B bridges. | 0 | Organic Chemistry |
Colored dissolved organic matter (CDOM) is the optically measurable component of dissolved organic matter in water. Also known as chromophoric dissolved organic matter, yellow substance, and gelbstoff, CDOM occurs naturally in aquatic environments and is a complex mixture of many hundreds to thousands of individual, unique organic matter molecules, which are primarily leached from decaying detritus and organic matter. CDOM most strongly absorbs short wavelength light ranging from blue to ultraviolet, whereas pure water absorbs longer wavelength red light. Therefore, water with little or no CDOM, such as the open ocean, appears blue. Waters containing high amounts of CDOM can range from brown, as in many rivers, to yellow and yellow-brown in coastal waters. In general, CDOM concentrations are much higher in fresh waters and estuaries than in the open ocean, though concentrations are highly variable, as is the estimated contribution of CDOM to the total dissolved organic matter pool. | 0 | Organic Chemistry |
Many different fusion proteins have been created using EosFP and its engineered variants. These fusion proteins allow for the tracking of proteins within living cells while retaining complex biological functions like protein-protein interactions and protein-DNA interactions. Eos fusion constructs include those with recombination signal-binding protein (RBP) and cytokeratin. Studies have shown that it is favourable to attach the protein of interest to the N-terminal side of the EosFP label. These fusion constructs have been used to visualize nuclear translocation with androgen receptors, dynamics of the cytoskeleton with actin and vinculin and intranuclear protein movement with RBP. | 1 | Biochemistry |
As EPIC-seq studies epigenetic markers to infer gene expression, one can study epigenetic sequencing methods like ChIP-seq, ATAC-seq, MeDIP-seq, and Bisulfite-Free DNA Methylation sequencing in combination with methods for profiling RNA expression such as RNA-seq and scRNA-seq.
Considering the method is mainly developed for early cancer detection or subgrouping, liquid biopsy methods, such as [https://www.twistbioscience.com/resources/technical-document/twist-cfdna-pan-cancer-reference-standard-variant-list Twist cfDNA Pan-Cancer Reference Standard], can be used as an alternative. Different liquid biopsy methods focus on cell-free tumour markers, tumour methylation markers, exomes, proteins, lipids, carbohydrates, electrolytes, metabolites, RNA, extracellular vesicles, circulating tumour cells, and tumour-educated platelets for early identification of cancer non-invasively. Some of the proposed liquid biopsy methods provide a comprehensive detection of cancer types, such as ATR-FTIR spectroscopy and CancerSEEK, while others, like Dxcover and SelectMdx operate on more specific (even single) cancer targets.
EPIC-seq utilizes fragmentomic features to infer expression levels of genes. Several studies also employ fragmentomic features to infer cancer existence, infer cell death, and detect other clinical conditions such as transplant failure. | 1 | Biochemistry |
The indexing results are used to generate a map of the crystallographic orientation at each point on the surface being studied. Thus, scanning the electron beam in a prescribed fashion (typically in a square or hexagonal grid, correcting for the image foreshortening due to the sample tilt) results in many rich microstructural maps. These maps can spatially describe the crystal orientation of the material being interrogated and can be used to examine microtexture and sample morphology. Some maps describe grain orientation, boundary, and diffraction pattern (image) quality. Various statistical tools can measure the average misorientation, grain size, and crystallographic texture. From this dataset, numerous maps, charts and plots can be generated. The orientation data can be visualised using a variety of techniques, including colour-coding, contour lines, and pole figures.
Microscope misalignment, image shift, scan distortion that increases with decreasing magnification, roughness and contamination of the specimen surface, boundary indexing failure and detector quality can lead to uncertainties in determining the crystal orientation. The EBSD signal-to-noise ratio depends on the material and decreases at excessive acquisition speed and beam current, thereby affecting the angular resolution of the measurement. | 7 | Physical Chemistry |
In order of net imports in 2011, 2009 and 2006 in thousand bbl/d and thousand m/d:
Source: [http://www.eia.gov/countries/index.cfm?topL=imp US Energy Information Administration] | 7 | Physical Chemistry |
The Bottom-blown Oxygen Converter or BBOC is a smelting furnace developed by the staff at Britannia Refined Metals Limited (“BRM”), a British subsidiary of MIM Holdings Limited (which is now part of the Glencore group of companies). The furnace is currently marketed by Glencore Technology. It is a sealed, flat-bottomed furnace mounted on a tilting frame that is used in the recovery of precious metals. A key feature is the use of a shrouded lance to inject oxygen through the bottom of the furnace, directly into the precious metals contained in the furnace, to oxidize base metals or other impurities as part of their removal as slag. | 8 | Metallurgy |
The species used in Germany to measure saprobic water quality tend to group around s = 2, while other countries like Austria and the Czech Republic use a more diverse list of organisms. | 2 | Environmental Chemistry |
Energy recovery can reduce energy consumption by 50% or more. Much of the input energy can be recovered from the concentrate flow, and the increasing efficiency of energy recovery devices greatly reduces energy requirements. Devices used, in order of invention, are:
* Turbine or Pelton wheel: a water turbine driven by the concentrate flow, connected to the pump drive shaft provides part of the input power. Positive displacement axial piston motors have been used in place of turbines on smaller systems.
* Turbocharger: a water turbine driven by concentrate flow, directly connected to a centrifugal pump that boosts the output pressure, reducing the pressure needed from the pump and thereby its energy input, similar in construction principle to car engine turbochargers.
* Pressure exchanger: using the pressurized concentrate flow, via direct contact or a piston, to pressurize part of the membrane feed flow to near concentrate flow pressure. A boost pump then raises this pressure by typically 3 bar / 50 psi to the membrane feed pressure. This reduces flow needed from the high-pressure pump by an amount equal to the concentrate flow, typically 60%, and thereby its energy input. These are widely used on larger low-energy systems. They are capable of 3 kWh/m or less energy consumption.
* Energy-recovery pump: a reciprocating piston pump. The pressurized concentrate flow is applied to one side of each piston to help drive the membrane feed flow from the opposite side. These are the simplest energy recovery devices to apply, combining the high pressure pump and energy recovery in a single self-regulating unit. These are widely used on smaller low-energy systems. They are capable of 3 kWh/m or less energy consumption.
* Batch operation: RO systems run with a fixed volume of fluid (thermodynamically a closed system) do not suffer from wasted energy in the brine stream, as the energy to pressurize a virtually incompressible fluid (water) is negligible. Such systems have the potential to reach second-law efficiencies of 60%. | 3 | Analytical Chemistry |
Imidazol-2-ylidenes, triazol-5-ylidenes (and less so, diaminocarbenes) have been shown to coordinate to a plethora of elements, from alkali metals, main group elements, transition metals and even lanthanides and actinides. A periodic table of elements gives some idea of the complexes which have been prepared, and in many cases these have been identified by single crystal X-ray crystallography.
Stable carbenes are believed to behave in a similar fashion to organophosphines in their coordination properties to metals. These ligands are said to be good σ-donors through the carbenic lone pair, but poor π-acceptors due to internal ligand back-donation from the nitrogen atoms adjacent to the carbene centre, and so are able to coordinate to even relatively electron deficient metals. Enders and Hermann have shown that these carbenes are suitable replacements for phosphine ligands in several catalytic cycles. Whilst they have found that these ligands do not activate the metal catalyst as much as phosphine ligands they often result in more robust catalysts. Several catalytic systems have been looked into by Hermann and Enders, using catalysts containing imidazole and triazole carbene ligands, with moderate success. Grubbs has reported replacing a phosphine ligand (PCy) with an imidazol-2-ylidene in the olefin metathesis catalyst RuCl(PCy)CHPh, and noted increased ring closing metathesis as well as exhibiting "a remarkable air and water stability". Molecules containing two and three carbene moieties have been prepared as potential bidentate and tridentate carbene ligands. | 0 | Organic Chemistry |
Standard addition involves adding known amounts of analyte to an unknown sample, a process known as spiking. By increasing the number of spikes, the analyst can extrapolate for the analyte concentration in the unknown that has not been spiked. There are multiple approaches to the standard addition. The following section summarize each approach. | 3 | Analytical Chemistry |
In quantum mechanics, a repulsive state is an electronic state of a molecule for which there is no minimum in the potential energy. This means that the state is unstable and unbound since the potential energy smoothly decreases with the interatomic distance and the atoms repel one another. In such a state there are no discrete vibrational energy levels; instead, these levels form a continuum. This should not be confused with an excited state, which is a metastable electronic state containing a minimum in the potential energy, and may be short or long-lived.
When a molecule is excited by means such as UV/VIS spectroscopy it can undergo a molecular electronic transition: if such a transition brings the molecule into a repulsive state, it will spontaneously dissociate. This condition is also known as predissociation since the chemical bond is broken at an energy which is lower than what might be expected. In electronic spectroscopy, this often appears as a strong, continuous feature in the absorption or emission spectrum, making repulsive states easy to detect.
For example, triatomic hydrogen has a repulsive ground state, which means it can only exist in an excited state: if it drops down to the ground state, it will immediately break up into one of the several possible dissociation products. | 7 | Physical Chemistry |
Historically, this approach was seen through the New England colonies. Virtually every old home is a clapboard structure fitted with shutters applied in this manner. They were likely hung on the casing to allow for the frost heaves and movement of the structures in the harsh New England winters. The shutters simply allowed the house to heave and settle behind them.
A strap hinge with a zero offset and an angle pintle matched to the thickness of the shutter will serve in every case. The shutter is removed from the face of the casing by the thickness of the shutter plus the diameter of the pintle pin leaving the shutter to clear the corner of the casing. | 8 | Metallurgy |
Methanedithiol is an organosulfur compound with the formula HC(SH). It forms when formaldehyde is treated with hydrogen sulfide under pressure. The reaction competes with formation of trithiane. The compound forms a solid dibenzoate upon treatment with benzoic anhydride. | 0 | Organic Chemistry |
Work, i.e. "weight lifted through a height", was originally defined in 1824 by Sadi Carnot in his famous paper Reflections on the Motive Power of Fire, where he used the term motive power for work. Specifically, according to Carnot: | 7 | Physical Chemistry |
The use of cross-linked enzyme crystals (CLECs) as industrial biocatalysts was pioneered by Altus Biologics in the 1990s. CLECs proved to be significantly more stable to denaturation by heat, organic solvents and proteolysis than the corresponding soluble enzyme or lyophilized (freeze-dried) powder. CLECs are robust, highly active immobilized enzymes of controllable particle size, varying from 1 to 100 micrometer. Their operational stability and ease of recycling, coupled with their high catalyst and volumetric productivities, renders them ideally suited for industrial biotransformations.
However, CLECs have an inherent disadvantage: enzyme crystallization is a laborious procedure requiring enzyme of high purity, which translates to prohibitively high costs. The more recently developed cross-linked enzyme aggregates (CLEAs), on the other hand, are produced by simple precipitation of the enzyme from aqueous solution, as physical aggregates of protein molecules, by the addition of salts, or water miscible organic solvents or non-ionic polymers. The physical aggregates are held together by covalent bonding without perturbation of their tertiary structure, that is without denaturation. Subsequent cross-linking of these physical aggregates renders them permanently insoluble while maintaining their pre-organized superstructure, and, hence their catalytic activity. This discovery led to the development of a new family of immobilized enzymes: cross-linked enzyme aggregates (CLEAs). Since precipitation from an aqueous medium, by addition of ammonium sulfate or polyethylene glycol, is often used to purify enzymes, the CLEA methodology essentially combines purification and immobilization into a single unit operation that does not require a highly pure enzyme. It could be used, for example, for the direct isolation of an enzyme, in a purified and immobilized form suitable for performing biotransformations, from a crude fermentation broth.
CLEAs are very attractive biocatalysts, owing to their facile, inexpensive and effective production method. They can readily be reused and exhibit improved stability and performance. The methodology is applicable to essentially any enzyme, including cofactor dependent oxidoreductases. Application to penicillin acylase used in antibiotic synthesis showed large improvements over other type of biocatalysts.
The potential applications of CLEAs are numerous and include:
# Synthesis of pharmaceuticals, flavors and fragrances, agrochemicals, nutraceuticals, fine chemicals, bulk monomers and biofuels.
# Animal feed, e.g. phytase for utilization of organically bound phosphate by pigs and poultry.
# Food and beverage processing, e.g. lipases in cheese manufacture and laccase in wine clarification.
# Cosmetics, e.g. in skin care products
# Oils and fats processing, e.g. in biolubricants, bioemulsifiers, bio-derived emollients.
# Carbohydrate processing, e.g. laccase in carbohydrate oxidations.
# Pulp and paper, e.g. in pulp bleaching.
# Detergents, e.g. proteases, amylases and lipases for removal of protein, carbohydrate and fat stains.
# Waste water treatment, e.g. for removal of phenols, dyes, and endocrine disrupters.
# Biosensors/diagnostics, e.g. glucose oxidase and cholesterol oxidase biosensors.
# Delivery of proteins as therapeutic agents or nutritional/digestive supplements e.g. beta-galactosidase for digestive hydrolysis of lactose in dairy products to alleviate the symptoms of lactose intolerance. | 4 | Stereochemistry |
In chain-growth polymerization, the degree of polymerization depends not only on the kinetic chain length but also on the type of termination step and the possibility of chain transfer. | 7 | Physical Chemistry |
Molybdenum blue is a term applied to:
*reduced heteropolymolybdate complexes, polyoxometalates containing Mo(V), Mo(VI), and a hetero atom such as phosphorus or silicon
*reduced isopolymolybdate complexes, polyoxometalates containing Mo(V), Mo(VI) formed when solutions of Mo(VI) are reduced
*a blue pigment containing molybdenum(VI) oxide
The "heteropoly-molybdenum blues", are used extensively in analytical chemistry and as catalysts. The formation of "isopoly-molybdenum blues" which are intense blue has been used as a sensitive test for reducing reagents. They have recently been shown to contain very large anionic species based on the so-called "big wheel" containing 154 Mo atoms, with a formula [MoOH(HO)].
The molybdenum blue pigment is historically documented but may not be in use today. | 7 | Physical Chemistry |
RPA is one of several isothermal nucleic acid amplification techniques to be developed as a molecular diagnostic technique, frequently with the objective of simplifying the laboratory instrumentation required relative to PCR. A partial list of other isothermal amplification techniques include LAMP, NASBA, helicase-dependent amplification (HDA), and nicking enzyme amplification reaction (NEAR). The techniques differ in the specifics of primer design and reaction mechanism, and in some cases (like RPA) make use of cocktails of two or more enzymes. Like RPA, many of these techniques offer rapid amplification times with the potential for simplified instrumentation, and reported resistance to substances in unpurified samples that are known to inhibit PCR. With respect to amplification time, modern thermocyclers with rapid temperature ramps can reduce PCR amplification times to less than 30 minutes, particularly for short amplicons using dual-temperature cycling rather than the conventional three-temperature protocols. In addition, the demands of sample prep (including lysis and extraction of DNA or RNA, if necessary) should be considered as part of the overall time and complexity inherent to the technique. These requirements vary according to the technique as well as to the specific target and sample type.
Compared to PCR, the guidelines for primer and probe design for RPA are less established, and may take a certain degree of trial and error, although recent results indicate that standard PCR primers can work as well. The general principle of a discrete amplicon bounded by a forward and reverse primer with an (optional) internal fluorogenic probe is similar to PCR. PCR primers may be used directly in RPA, but their short length means that recombination rates are low and RPA will not be especially sensitive or fast. Typically 30–38 base primers are needed for efficient recombinase filament formation and RPA performance. This is in contrast to some other techniques such as LAMP which use a larger number of primers subject to additional design constraints. Although the original 2006 report of RPA describes a functional set of reaction components, the current (proprietary) formulation of the TwistAmp kit is "substantially different" and is available only from the TwistDx supplier. This is in comparison to reaction mixtures for PCR which are available from many suppliers, or LAMP or NASBA for which the composition of the reaction mixture is freely published, allowing researchers to create their own customized "kits" from inexpensive ingredients.
Published scientific literature generally lacks detailed comparison of the performance of isothermal amplification techniques such as RPA, HDA, and LAMP relative to each other, often rather comparing a single isothermal technique to a "gold standard" PCR assay. This makes it difficult to judge the merits of these techniques independently from the claims of the manufacturers, inventors, or proponents. Furthermore, performance characteristics of any amplification technique are difficult to decouple from primer design: a "good" primer set for one target for RPA may give faster amplification or more sensitive detection than a "poor" LAMP primer set for the same target, but the converse may be true for different primer sets for a different target. An exception is a recent study comparing RT-qPCR, RT-LAMP, and RPA for detection of Schmallenberg virus and bovine viral diarrhea virus, which effectively makes the point that each amplification technique has strengths and weaknesses, which may vary by the target, and that the properties of the available amplification techniques need to be evaluated in combination with the requirements for each application. As with PCR and any other amplification technique, there is obviously a publication bias, with poorly performing primer sets rarely deemed worthy of reporting. | 1 | Biochemistry |
Distal promoter elements are regulatory DNA sequences that can be many kilobases distant from the gene that they regulate.
They can either be enhancers (increasing expression) or silencers (decreasing expression). They act by binding activator or repressor proteins (transcription factors) and the intervening DNA bends such that the bound proteins contact the core promoter and RNA polymerase. | 1 | Biochemistry |
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