text
stringlengths 105
4.44k
| label
int64 0
9
| label_text
stringclasses 10
values |
|---|---|---|
2,4,6-Trichlorobenzoyl chloride or Yamaguchi's reagent is an chlorinated aromatic compound that is commonly used in a variety of organic syntheses. | 0 | Organic Chemistry |
CID has been used for a number of applications in biomedical research. In most applications each dimerizing protein is expressed as part of a fusion construct with other proteins of interest. Adding the chemical dimerizing agent brings both constructs into proximity with each other and induces interactions between the proteins of interest. CID has been used to regulate and monitor gene transcription, signal transduction and post translational modifications in proteins.
Recently, CID has also been used to create a basic component of biocomputers, logic gates, from genetically manipulated cells. In this application, two independent CID systems, one based on plant proteins and one based on bacterial proteins are expressed in the same cell. Each set of proteins can be induced to dimerize by the addition of a separate chemical. By creating fusion proteins with the dimerizing proteins, membrane bound proteins and proteins that activate cell ruffling an AND gate and OR gate can be created that take chemical dimerizing agents as inputs and returns a ruffled or unruffled state as output. | 1 | Biochemistry |
Rudd serves as an associate of the Anglican Church at the Community of St Mary the Virgin in Wantage, Oxfordshire. She took a fifteen-year career break to raise her four children. | 1 | Biochemistry |
Photosystem II is the photosystem that generates the two electrons that will eventually reduce NADP in ferredoxin-NADP-reductase. Photosystem II is present on the thylakoid membranes inside chloroplasts, the site of photosynthesis in green plants. The structure of Photosystem II is remarkably similar to the bacterial reaction center, and it is theorized that they share a common ancestor.
The core of Photosystem II consists of two subunits referred to as D1 and D2. These two subunits are similar to the L and M subunits present in the bacterial reaction center. Photosystem II differs from the bacterial reaction center in that it has many additional subunits that bind additional chlorophylls to increase efficiency. The overall reaction catalyzed by Photosystem II is:
:2Q + 2HO + hν → O + 2QH
Q represents the oxidized form of plastoquinone while QH represents its reduced form. This process of reducing quinone is comparable to that which takes place in the bacterial reaction center. Photosystem II obtains electrons by oxidizing water in a process called photolysis. Molecular oxygen is a byproduct of this process, and it is this reaction that supplies the atmosphere with oxygen. The fact that the oxygen from green plants originated from water was first deduced by the Canadian-born American biochemist Martin David Kamen. He used a stable isotope of oxygen, O, to trace the path of the oxygen from water to gaseous molecular oxygen. This reaction is catalyzed by a reactive center in Photosystem II containing four manganese ions.
The reaction begins with the excitation of a pair of chlorophyll molecules similar to those in the bacterial reaction center. Due to the presence of chlorophyll a, as opposed to bacteriochlorophyll, Photosystem II absorbs light at a shorter wavelength. The pair of chlorophyll molecules at the reaction center are often referred to as P680. When the photon has been absorbed, the resulting high-energy electron is transferred to a nearby pheophytin molecule. This is above and to the right of the pair on the diagram and is coloured grey. The electron travels from the pheophytin molecule through two plastoquinone molecules, the first tightly bound, the second loosely bound. The tightly bound molecule is shown above the pheophytin molecule and is colored red. The loosely bound molecule is to the left of this and is also colored red. This flow of electrons is similar to that of the bacterial reaction center. Two electrons are required to fully reduce the loosely bound plastoquinone molecule to QH as well as the uptake of two protons.
The difference between Photosystem II and the bacterial reaction center is the source of the electron that neutralizes the pair of chlorophyll a molecules. In the bacterial reaction center, the electron is obtained from a reduced compound haem group in a cytochrome subunit or from a water-soluble cytochrome-c protein.
Every time the P680 absorbs a photon, it gives off an electron to pheophytin, gaining a positive charge. After this photoinduced charge separation, P680 is a very strong oxidant of high energy. It passes its energy to water molecules that are bound at the manganese center directly below the pair and extracts an electron from them. This center, below and to the left of the pair in the diagram, contains four manganese ions, a calcium ion, a chloride ion, and a tyrosine residue. Manganese is adept at these reactions because it is capable of existing in four oxidation states: Mn, Mn, Mn and Mn. Manganese also forms strong bonds with oxygen-containing molecules such as water. The process of oxidizing two molecules of water to form an oxygen molecule requires four electrons. The water molecules that are oxidized in the manganese center are the source of the electrons that reduce the two molecules of Q to QH. To date, this water splitting catalytic center has not been reproduced by any man-made catalyst. | 5 | Photochemistry |
The procedure involves heating a sample of genomic DNA until it denatures into the single stranded-form, and then slowly cooling it, so the strands can pair back together. While the sample is cooling, measurements are taken of how much of the DNA is base paired at each temperature.
The amount of single and double-stranded DNA is measured by rapidly diluting the sample, which slows reassociation, and then binding the DNA to a hydroxyapatite column. The column is first washed with a low concentration of sodium phosphate buffer, which elutes the single-stranded DNA, and then with high concentrations of phosphate, which elutes the double stranded DNA. The amount of DNA in these two solutions is then measured using a spectrophotometer. | 1 | Biochemistry |
The technique operates on the principle that a positron or positronium will annihilate through interaction with electrons. This annihilation releases gamma rays that can be detected; the time between emission of positrons from a radioactive source and detection of gamma rays due to annihilation corresponds to the lifetime of positron or positronium.
When positrons are injected into a solid body, they interact in some manner with the electrons in that species. For solids containing free electrons (such as metals or semiconductors), the implanted positrons annihilate rapidly unless voids such as vacancy defects are present. If voids are available, positrons will reside in them and annihilate less rapidly than in the bulk of the material, on time scales up to ~1 ns. For insulators such as polymers or zeolites, implanted positrons interact with electrons in the material to form positronium.
Positronium is a metastable hydrogen-like bound state of an electron and a positron which can exist in two spin states. Para-positronium, p-Ps, is a singlet state (the positron and electron spins are anti-parallel) with a characteristic self-annihilation lifetime of 125 ps in vacuum. Ortho-positronium, o-Ps, is a triplet state (the positron and electron spins are parallel) with a characteristic self-annihilation lifetime of 142 ns in vacuum. In molecular materials, the lifetime of o-Ps is environment dependent and it delivers information pertaining to the size of the void in which it resides. Ps can pick up a molecular electron with an opposite spin to that of the positron, leading to a reduction of the o-Ps lifetime from 142 ns to 1-4 ns (depending on the size of the free volume in which it resides). The size of the molecular free volume can be derived from the o-Ps lifetime via the semi-empirical Tao-Eldrup model.
While the PALS is successful in examining local free volumes, it still needs to employ data from combined methods in order to yield free volume fractions. Even approaches to obtain fractional free volume from the PALS data that claim to be independent on other experiments, such as PVT measurements, they still do employ theoretical considerations, such as iso-free-volume amount from Simha-Boyer theory. A convenient emerging method for obtaining free volume amounts in an independent manner are computer simulations; these can be combined with the PALS measurements and help to interpret the PALS measurements.
Pore structure in insulators can be determined using the quantum mechanical Tao-Eldrup model and extensions thereof. By changing the temperature at which a sample is analyzed, the pore structure can be fit to a model where positronium is confined in one, two, or three dimensions. However, interconnected pores result in averaged lifetimes that cannot distinguish between smooth channels or channels having smaller, open, peripheral pores due to energetically favored positronium diffusion from small to larger pores.
The behavior of positrons in molecules or condensed matter is nontrivial due
to the strong correlation between electrons and positrons. Even the simplest
case, that of a single positron immersed in a homogeneous gas of electrons,
has proved to be a significant challenge for theory. The positron attracts
electrons to it, increasing the contact density and hence enhancing the
annihilation rate. Furthermore, the momentum density of annihilating
electron-positron pairs is enhanced near the Fermi surface. Theoretical
approaches used to study this problem have included the Tamm-Dancoff
approximation, Fermi and perturbed hypernetted chain approximations, density functional theory methods and quantum Monte Carlo. | 7 | Physical Chemistry |
Multi-junction cells consist of multiple thin films, each essentially a solar cell grown on top of another, typically using metalorganic vapour phase epitaxy. Each layer has a different band gap energy to allow it to absorb electromagnetic radiation over a different portion of the spectrum. Multi-junction cells were originally developed for special applications such as satellites and space exploration, but are now used increasingly in terrestrial concentrator photovoltaics (CPV), an emerging technology that uses lenses and curved mirrors to concentrate sunlight onto small, highly efficient multi-junction solar cells. By concentrating sunlight up to a thousand times, High concentration photovoltaics (HCPV) has the potential to outcompete conventional solar PV in the future.
Tandem solar cells based on monolithic, series connected, gallium indium phosphide (GaInP), gallium arsenide (GaAs), and germanium (Ge) p–n junctions, are increasing sales, despite cost pressures. Between December 2006 and December 2007, the cost of 4N gallium metal rose from about $350 per kg to $680 per kg. Additionally, germanium metal prices have risen substantially to $1000–1200 per kg this year. Those materials include gallium (4N, 6N and 7N Ga), arsenic (4N, 6N and 7N) and germanium, pyrolitic boron nitride (pBN) crucibles for growing crystals, and boron oxide, these products are critical to the entire substrate manufacturing industry.
A triple-junction cell, for example, may consist of the semiconductors: GaAs, Ge, and Indium gallium phosphide|. Triple-junction GaAs solar cells were used as the power source of the Dutch four-time World Solar Challenge winners Nuna in 2003, 2005 and 2007 and by the Dutch solar cars Solutra (2005), Twente One (2007) and 21Revolution (2009). GaAs based multi-junction devices are the most efficient solar cells to date. On 15 October 2012, triple junction metamorphic cells reached a record high of 44%. | 7 | Physical Chemistry |
Carbaminohemoglobin interacts with carbon dioxide in a process known as respiratory gas exchange. The interaction involves the binding of carbon dioxide to hemoglobin. Carbon dioxide binds to the protein chains of hemoglobin. The ability of hemoglobin to bind to both oxygen and carbon dioxide molecules is what makes it an important protein to the respiratory system in respiratory gas exchange.
The interactions between carbon dioxide and hemoglobin helps in the transport of carbon dioxide from the tissues to the lungs for eliminations. When carbon dioxide is transported from the tissues, it is produced as a waste product of a set of reactions known as cellular metabolism. Most importantly, the binding of carbon dioxide to hemoglobin plays a part in the buffering of blood pH by preventing the drop of pH due to the production of carbonic acid.
Although, the carbaminohemoglobin protein interacts with another protein (like hemoglobin) found in red blood cells, this interaction only takes place in the bloodstream and its products can be expelled. Carbaminohemoglobin does not interact with DNA since DNA is a molecule that is found in cell nucleus and its function is to carry genetic information. | 1 | Biochemistry |
UPS has seen a considerable revival with the increasing availability of synchrotron light sources which provide a wide range of monochromatic photon energies. | 7 | Physical Chemistry |
The eluate contains the analyte material that emerges from the chromatograph. It specifically includes both the analytes and coeluting solutes passing through the column, while the eluent is only the carrier. | 3 | Analytical Chemistry |
Certain types of venom, such as those produced by venomous snakes, can also cause proteolysis. These venoms are, in fact, complex digestive fluids that begin their work outside of the body. Proteolytic venoms cause a wide range of toxic effects, including effects that are:
* cytotoxic (cell-destroying)
* hemotoxic (blood-destroying)
* myotoxic (muscle-destroying)
* hemorrhagic (bleeding) | 1 | Biochemistry |
Anti-Ro/SSA can target Ro52 and Ro60 proteins. Most Anti-Ro/SSA activity occurs on the cell surface, wherein Ro proteins are expressed on the cell membrane and extracellular Anti-Ro/SSAs bind to Ro. There is some evidence that the IgG isotype of anti-Ro/SSA antibody can enter the cell.
* Anti-Ro autoantibodies are typically IgA, IgM, and IgG isotypes, though most is known about the five IgG subclasses. The antibody is inducible via immunization using Ro peptide.
The mechanism that induces Anti-Ro/SSA production in autoimmune disorders remains under study. Some proposed factors that may stimulate production are viral infection, treatment of cells with TNF-α, cellular apoptosis, and exposure to UV irradiation.
* Anti-Ro/SSA is produced in the cytoplasm of cells in the epidermal layer of the skin following UV irradiation. Ro antigens are simultaneously upregulated on the cell surface, resulting in the Anti-Ro/SSA antibody marking cells for destruction. Anti-Ro52 antibodies in particular have been tied to elevated photosensitivity.
Certain alleles of the human major histocompatibility complex (MHC II, called HLA II in humans) have been associated with the presence of Anti-Ro antibodies and the spread of the immune response. Anti-Ro/SSA associates with the HLA II alleles HLA-DR3 and HLA-DR2, as well as some HLA-DQ alleles. The T-cell response plays a role in the formation of Anti-Ro/SSA antibodies due to T-cell affinity for MHC class II. | 1 | Biochemistry |
The movement of ions across the membrane depends on a combination of two factors:
# Diffusion force caused by a concentration gradient - all particles tend to diffuse from higher concentration to lower.
# Electrostatic force caused by electrical potential gradient - cations like protons H tend to diffuse down the electrical potential, from the positive (P) side of the membrane to the negative (N) side. Anions diffuse spontaneously in the opposite direction.
These two gradients taken together can be expressed as an electrochemical gradient.
Lipid bilayers of biological membranes, however, are barriers for ions. This is why energy can be stored as a combination of these two gradients across the membrane. Only special membrane proteins like ion channels can sometimes allow ions to move across the membrane (see also: Membrane transport). In the chemiosmotic hypothesis a transmembrane ATP synthases is central to convert energy of spontaneous flow of protons through them into chemical energy of ATP bonds.
Hence researchers created the term proton-motive force (PMF), derived from the electrochemical gradient mentioned earlier. It can be described as the measure of the potential energy stored (chemiosmotic potential) as a combination of proton and voltage (electrical potential) gradients across a membrane. The electrical gradient is a consequence of the charge separation across the membrane (when the protons H move without a counterion, such as chloride Cl).
In most cases the proton-motive force is generated by an electron transport chain which acts as a proton pump, using the Gibbs free energy of redox reactions to pump protons (hydrogen ions) out across the membrane, separating the charge across the membrane. In mitochondria, energy released by the electron transport chain is used to move protons from the mitochondrial matrix (N side) to the intermembrane space (P side). Moving the protons out of the mitochondrion creates a lower concentration of positively charged protons inside it, resulting in excess negative charge on the inside of the membrane. The electrical potential gradient is about -170 mV , negative inside (N). These gradients - charge difference and the proton concentration difference both create a combined electrochemical gradient across the membrane, often expressed as the proton-motive force (PMF). In mitochondria, the PMF is almost entirely made up of the electrical component but in chloroplasts the PMF is made up mostly of the pH gradient because the charge of protons H is neutralized by the movement of Cl and other anions. In either case, the PMF needs to be greater than about 460 mV (45 kJ/mol) for the ATP synthase to be able to make ATP. | 1 | Biochemistry |
A membrane osmometer is a device used to indirectly measure the number average molecular weight () of a polymer sample. One chamber contains pure solvent and the other chamber contains a solution in which the solute is a polymer with an unknown . The osmotic pressure of the solvent across the semipermeable membrane is measured by the membrane osmometer. This osmotic pressure measurement is used to calculate for the sample. | 7 | Physical Chemistry |
DEB theory has been extended into many directions, such as
*effects of changes in shape during growth (e.g. V1-morphs and V0-morphs)
*non-standard embryo->juvenile->adult transitions, for example in holometabolic insects
*inclusion of more types of food (substrate), which requires synthesizing units to model
*inclusion of more reserves (which is necessary for organisms that do not feed on other organisms) and more structures (which is necessary to deal with plants), or a simplified version of the model (DEBkiss) applicable in ecotoxicology
*the formation and excretion of metabolic products (which is a basis for syntrophic relationships, and useful in biotechnology)
*the production of free radicals (linked to size and nutritional status) and their effect on survival (aging)
*the growth of body parts (including tumours)
*effects of chemical compounds (toxicants) on parameter values and the hazard rate (which is useful to establish no effect concentrations for environmental risk assessment): the DEBtox method
*processes of adaptation (gene expression) to the availability of substrates (important in biodegradation)
A list and description of most common typified models can be found [http://www.debtheory.org/wiki/index.php?title=Typified_models here] . | 1 | Biochemistry |
Paleosalinity (or palaeosalinity) is the salinity of the global ocean or of an ocean basin at a point in geological history. | 9 | Geochemistry |
Artificial introduction of long dsRNAs or siRNAs has been adopted as a tool to inactivate gene expression, both in cultured cells and in living organisms. Structural and functional resolution of small RNAs as the effectors of RNA silencing has had a direct impact on experimental biology. For example, dsRNA may be synthesized to have a specific sequence complementary to a gene of interest. Once introduced into a cell or biological system, it is recognized as exogenous genetic material and activates the corresponding RNA silencing pathway. This mechanism can be used to effect decreases in gene expression with respect to the target, useful for investigating loss of function for genes relative to a phenotype. That is, studying the phenotypic and/or physiologic effects of expression decreases can reveal the role of a gene product. The observable effects can be nuanced, such that some methods can distinguish between “knockdown” (decrease expression) and “knockout” (eliminate expression) of a gene. RNA interference technologies have been noted recently as one of the most widely utilized techniques in functional genomics. Screens developed using small RNAs have been used to identify genes involved in fundamental processes such as cell division, apoptosis and fat regulation. | 1 | Biochemistry |
Meta-analyses found that increased perceived psychological stress was associated with a small decrease in telomere length—but that these associations attenuate to no significant association when accounting for publication bias. The literature concerning telomeres as integrative biomarkers of exposure to stress and adversity is dominated by cross-sectional and correlational studies, which makes causal interpretation problematic. A 2020 review argued that the relationship between psychosocial stress and telomere length appears strongest for stress experienced in utero or early life. | 1 | Biochemistry |
In dynamic covalent chemistry covalent bonds are broken and formed in a reversible reaction under thermodynamic control. While covalent bonds are key to the process, the system is directed by non-covalent forces to form the lowest energy structures. | 6 | Supramolecular Chemistry |
A transcript is an RNA molecule that is copied or transcribed from a DNA template. A transcript can be further processed by alternative splicing, which is the retention of different combinations of exons. These unique combinations of exons are termed RNA transcript isoforms. The transcriptome is a set of all RNA, including rRNA, mRNA, tRNA, and non-coding RNA. Specifically mRNA transcripts can be used to investigate differences in gene expression patterns. Transcriptome profiling is determining the composition of transcripts and their relative expression levels in a given reference set of cells. This analysis involves characterization of all functional genomic elements, coding and non-coding.
The current RNA capture methods involve sorting cells in suspension from acutely dissociated tissue, and thus can lose information about cell morphology and microenvironment. Transcript abundance and isoforms are significantly different across tissues and are continually changing throughout an individual’s life. Gene expression is highly tissue specific, therefore with traditional RNA capture methods one must be cautious in the interpretation of gene expression patterns, as they often reflect expression of a heterogeneous mix of cell populations. Even in the same cell type, tissue measurements, where a population of cells is obtained, mask both low-level mRNA expression in single cells and variation in expression between cells. The photoactivatable TIVA tag is engineered to capture the mRNA of a single cell in complex tissues. | 1 | Biochemistry |
The smelting of gold began sometime around 6000 – 3000 BC. According to one source the technique began to be in use in Mesopotamia or Syria. In ancient Greece, Heraclitus wrote on the subject.
According to de Lecerda and Salomons (1997) mercury was first in use for extraction at about 1000 BC, according to Meech and others (1998), mercury was used in obtaining gold until the latter period of the first millennia.
A technique known to Pliny the Elder was extraction by way of crushing, washing, and then applying heat, with the resultant material powdered. | 8 | Metallurgy |
In their largest application, an oxime is an intermediate in the industrial production of caprolactam, a precursor to Nylon 6. About half of the world's supply of cyclohexanone, more than a million tonnes annually, is converted to the oxime. In the presence of sulfuric acid catalyst, the oxime undergoes the Beckmann rearrangement to give the cyclic amide caprolactam: | 0 | Organic Chemistry |
Anammox, an abbreviation for "anaerobic ammonium oxidation", is a globally important microbial process of the nitrogen cycle that takes place in many natural environments. The bacteria mediating this process were identified in 1999, and were a great surprise for the scientific community. In the anammox reaction, nitrite and ammonium ions are converted directly into diatomic nitrogen and water.
The bacteria that perform the anammox process are genera that belong to the bacterial phylum Planctomycetota. The anammox bacteria all possess one anammoxosome, a lipid bilayer membrane-bound compartment inside the cytoplasm in which the anammox process takes place. The anammoxosome membranes are rich in ladderane lipids; the presence of these lipids is so far unique in biology.
"Anammox" is also the trademarked name for an anammox-based ammonium removal technology developed by the Delft University of Technology. | 1 | Biochemistry |
Hydroxylamine reacts with electrophiles, such as alkylating agents, which can attach to either the oxygen or the nitrogen atoms:
The reaction of with an aldehyde or ketone produces an oxime.
: (in NaOH solution)
This reaction is useful in the purification of ketones and aldehydes: if hydroxylamine is added to an aldehyde or ketone in solution, an oxime forms, which generally precipitates from solution; heating the precipitate with an inorganic acid then restores the original aldehyde or ketone.
Oximes such as dimethylglyoxime are also employed as ligands.
reacts with chlorosulfonic acid to give hydroxylamine-O-sulfonic acid:
When heated, hydroxylamine explodes. A detonator can easily explode aqueous solutions concentrated above 80% by weight, and even 50% solution might prove detonable if tested in bulk. In air, the combustion is rapid and complete:
Absent air, pure hydroxylamine requires stronger heating and the detonation does not complete combustion:
Partial isomerisation to the amine oxide contributes to the high reactivity. | 0 | Organic Chemistry |
In the Hooker reaction (1936) an alkyl chain in a certain naphthoquinone (phenomenon first observed in the compound lapachol) is reduced by one methylene unit as carbon dioxide in each potassium permanganate oxidation.
:Mechanistically oxidation causes ring-cleavage at the alkene group, extrusion of carbon dioxide in decarboxylation with subsequent ring-closure. | 0 | Organic Chemistry |
Quantum dots are fluorescent semiconductor nanoparticles that typically brighter than conventional stains. They are generally more expensive, toxic, do not permeate cell membranes, and cannot be manufactured by the cell. | 1 | Biochemistry |
When the temperature of concrete exceeds 65 °C for too long a time at an early age, the crystallization of ettringite (AFt) does not occur because of its higher solubility at elevated temperature and the then less soluble mono-sulfate (AFm) is formed. After dissipation of the cement hydration heat, temperature goes back to ambient and the temperature curves of the solubilities of AFt and AFm phases cross over. The mono-sulfate (AFm) now more soluble at low temperature slowly dissolves to recrystallize as the less soluble ettringite (AFt). AFt crystal structure hosts more water molecules than AFm. So, AFt has a higher molar volume than AFm because of its 32 HO molecules. During months, or years, after young concrete cooling, AFt crystallizes very slowly as small acicular needles and can exert a considerable crystallization pressure on the surrounding hardened cement paste (HCP). This leads to the expansion of concrete, to its cracking, and it can ultimately lead to the ruin of the affected structure. The characteristic feature of delayed ettringite formation (DEF) is a random honeycomb cracking pattern similar to this of the alkali-silica reaction (ASR). In fact, this typical crack pattern is common to all expansive internal reactions and also to restrained shrinkage where a rigid substrate or a dense rebar network prevents the movements of a superficial concrete layer. DEF is also known as internal sulfate attack (ISA). External sulfate attack (ESA) also involves ettringite (AFt) formation and deleterious expansion with the same harmful symptoms but requires an external source of sulfate anions in the surrounding terrains or environment. To avoid DEF or ISA reactions, the best way is to use a low CA (tri-calcium aluminate) cement precluding the formation of ettringite (AFt). Sulfate resisting (SR) cements have also a low content in AlO. DEF, or ISA, only affects the hardened cement paste (HCP) and leaves intact the aggregates.
DEF is exacerbated at high pH in cement with a too high content in alkalis and therefore in hydroxides. This is caused by the transformation of ettringite (AFt) into aluminoferrite monosulfate (AFm) under the action of the hydroxyl anions (OH) as schematized as follows:
: AFt + OH → AFm
The complete reaction can be derived from the molecular formulas of the reagents and products involved in the reaction. This reaction favors the dissolution of AFt and the formation of AFm. When combined, it is an aggravating factor of the harmful effect of too high temperatures. To minimize DEF, the use of low-alkali cements is also recommended. The detrimental crystallization of ettringite (AFt) preferentially occurs when concrete is exposed to water infiltrations and that the pH decreases due to the leaching of the (OH) ions: the reaction is reversed as when temperature decreases. | 8 | Metallurgy |
The compressibility of water is a function of pressure and temperature. At 0 °C, at the limit of zero pressure, the compressibility is . At the zero-pressure limit, the compressibility reaches a minimum of around 45 °C before increasing again with increasing temperature. As the pressure is increased, the compressibility decreases, being at 0 °C and .
The bulk modulus of water is about 2.2 GPa. The low compressibility of non-gasses, and of water in particular, leads to their often being assumed as incompressible. The low compressibility of water means that even in the deep oceans at 4 km depth, where pressures are 40 MPa, there is only a 1.8% decrease in volume.
The bulk modulus of water ice ranges from 11.3 GPa at 0 K up to 8.6 GPa at 273 K. The large change in the compressibility of ice as a function of temperature is the result of its relatively large thermal expansion coefficient compared to other common solids. | 2 | Environmental Chemistry |
Perfluorohexane (), or tetradecafluorohexane, is a fluorocarbon. It is a derivative of hexane in which all the hydrogen atoms are replaced by fluorine atoms. It is used in one formulation of the electronic cooling liquid/insulator Fluorinert for low-temperature applications due to its low boiling point of 56 °C and freezing point of −90 °C. It is odorless and colorless. Unlike typical hydrocarbons, the structure features a helical carbon backbone. | 2 | Environmental Chemistry |
Purines are biologically synthesized as nucleotides and in particular as ribotides, i.e. bases attached to ribose 5-phosphate. Both adenine and guanine are derived from the nucleotide inosine monophosphate (IMP), which is the first compound in the pathway to have a completely formed purine ring system. | 1 | Biochemistry |
It is manufactured by the reaction of methane and sulfuryl chloride in a radical reaction:
Another method of manufacture entails chlorination of methanesulfonic acid with thionyl chloride or phosgene: | 0 | Organic Chemistry |
Plasmas are studied by the vast academic field of plasma science or plasma physics, including several sub-disciplines such as space plasma physics.
Plasmas can appear in nature in various forms and locations, with a few examples given in the following table: | 7 | Physical Chemistry |
The Faraday paradox was a once inexplicable aspect of the reaction between nitric acid and steel. Around 1830, the English scientist Michael Faraday found that diluted nitric acid would attack steel, but concentrated nitric acid would not. The attempt to explain this discovery led to advances in electrochemistry. | 7 | Physical Chemistry |
Christoph Weder is the former director of the Adolphe Merkle Institute (AMI) at the University of Fribourg, Switzerland, and a professor of polymer chemistry and materials. He is best known for his work on stimuli-responsive polymers, polymeric materials that change one or more of their properties when exposed to external cues. His research is focused on the development, investigation, and application of functional materials, in particular stimuli-responsive and bio-inspired polymers. | 7 | Physical Chemistry |
Many routes for the synthesis of TMP have been reported. One method starts with a conjugate addition reaction of ammonia to phorone. The intermediate triacetone amine is then reduced in a Wolff-Kishner reaction. | 0 | Organic Chemistry |
In many binary semiconducting systems, the band gap in semiconductors is approximately a linear function of the lattice parameter. Therefore, if the lattice parameter of a semiconducting system follows Vegard's law, one can also write a linear relationship between the band gap and composition. Using as before, the band gap energy, , can be written as:
Sometimes, the linear interpolation between the band gap energies is not accurate enough, and a second term to account for the curvature of the band gap energies as a function of composition is added. This curvature correction is characterized by the bowing parameter, : | 8 | Metallurgy |
The active transport of monoamines from the cytosol into storage vesicles operates against a large (>10) concentration gradient. Secondary active transport is the type of active transport used, meaning that VMAT1 is an antiporter. This transport is facilitated via proton gradient generated by the protein proton ATPase. The inward transport of the monoamine is coupled with the efflux of two protons per monoamine. The first proton is thought to cause a change in VMAT1's conformation, which pushes a high affinity amine binding site, to which the monoamine attaches. The second proton then causes a second change in the conformation which pulls the monoamine into the vesicle and greatly reduces the affinity of the binding site for amines. A series of tests suggest that His419, located between TMDs X and XI, plays the key role in the first of these conformational changes, and that Asp431, located on TMD XI, does likewise during the second change. | 1 | Biochemistry |
In the field of biochemistry, the specificity constant (also called kinetic efficiency or ), is a measure of how efficiently an enzyme converts substrates into products. A comparison of specificity constants can also be used as a measure of the preference of an enzyme for different substrates (i.e., substrate specificity). The higher the specificity constant, the more the enzyme "prefers" that substrate.
The following equation, known as the Michaelis–Menten model, is used to describe the kinetics of enzymes:
where E, S, ES, and P represent nzyme, ubstrate, nzyme–ubstrate complex, and roduct, respectively. The symbols , , and denote the rate constants for the "forward" binding and "reverse" unbinding of substrate, and for the "catalytic" conversion of substrate into product, respectively.
The Michaelis constant in turn is defined as follows:
The Michaelis constant is equal to the substrate concentration at which the enzyme converts substrates into products at half its maximal rate and hence is related to the affinity of the substrate for the enzyme. The catalytic constant () is the rate of product formation when the enzyme is saturated with substrate and therefore reflects the enzyme's maximum rate. The rate of product formation is dependent on both how well the enzyme binds substrate and how fast the enzyme converts substrate into product once substrate is bound. For a kinetically perfect enzyme, every encounter between enzyme and substrate leads to product and hence the reaction velocity is only limited by the rate the enzyme encounters substrate in solution. Hence the upper limit for is equal to rate of substrate diffusion which is between 10 and 10 sM. | 1 | Biochemistry |
This syndrome is associated with increased susceptibility to tumors and growth abnormalities in children. A common cause of this syndrome is a mutation in an imprint control region <nowiki/>near the Igf2 gene. This imprint control region is normally bound by an insulator on the maternal allele, which represses an enhancer from acting on the Igf2 gene. This insulator is absent on the paternal allele and allows it access to the gene. Mutations in this imprint control region inhibit the insulator from binding, which derepresses enhancer activity on the maternal Igf2 gene. This abnormal derepression and increase in gene expression can result in Beckwith-Wiedemann syndrome. | 1 | Biochemistry |
Alkaline hydrolysis usually refers to types of nucleophilic substitution reactions in which the attacking nucleophile is a hydroxide ion. The best known type is saponification: cleaving esters into carboxylate salts and alcohols. In ester hydrolysis and amide hydrolysis the hydroxide ion nucleophile attacks the carbonyl carbon in a nucleophilic acyl substitution reaction. This mechanism is supported by isotope labeling experiments. For example, when ethyl propionate with an oxygen-18 labeled ethoxy group is treated with sodium hydroxide (NaOH), the oxygen-18 is completely absent from the sodium propionate product and is found exclusively in the ethanol formed.
The reaction is often used to solubilize solid organic matter. Chemical drain cleaners take advantage of this method to dissolve hair and fat in pipes. The reaction is also used to dispose of human and other animal remains as an alternative to traditional burial or cremation. | 7 | Physical Chemistry |
High-temperature corrosion is a mechanism of corrosion that takes place when gas turbines, diesel engines, furnaces or other machinery come in contact with hot gas containing certain contaminants. Fuel sometimes contains vanadium compounds or sulfates, which can form low melting point compounds during combustion. These liquid melted salts are strongly corrosive to stainless steel and other alloys normally resistant with respect to corrosion at high temperatures. Other types of high-temperature corrosion include high-temperature oxidation, sulfidation, and carbonization. High temperature oxidation and other corrosion types are commonly modeled using the Deal-Grove model to account for diffusion and reaction dynamics. | 8 | Metallurgy |
The rule can be used to understand the stability of completely conjugated monocyclic hydrocarbons (known as annulenes) as well as their cations and anions.
The best-known example is benzene (CH) with a conjugated system of six π electrons, which equals 4n + 2 for n = 1. The molecule undergoes substitution reactions which preserve the six π electron system rather than addition reactions which would destroy it. The stability of this π electron system is referred to as aromaticity. Still, in most cases, catalysts are necessary for substitution reactions to occur.
The cyclopentadienyl anion () with six π electrons is planar and readily generated from the unusually acidic cyclopentadiene (pK 16), while the corresponding cation with four π electrons is destabilized, being harder to generate than a typical acyclic pentadienyl cations and is thought to be antiaromatic. Similarly, the tropylium cation (), also with six π electrons, is so stable compared to a typical carbocation that its salts can be crystallized from ethanol. On the other hand, in contrast to cyclopentadiene, cycloheptatriene is not particularly acidic (pK 37) and the anion is considered nonaromatic. The cyclopropenyl cation () and the triboracyclopropenyl dianion () are considered examples of a two π electron system, which are stabilized relative to the open system, despite the angle strain imposed by the 60° bond angles.
Planar ring molecules with 4n π electrons do not obey Hückels rule, and theory predicts that they are less stable and have triplet ground states with two unpaired electrons. In practice such molecules distort from planar regular polygons. Cyclobutadiene (CH) with four π electrons is stable only at temperatures below 35 K and is rectangular rather than square. Cyclooctatetraene (CH) with eight π electrons has a nonplanar "tub" structure. However the dianion (cyclooctatetraenide anion), with ten π electrons obeys the 4n + 2 rule for n = 2 and is planar, while the 1,4-dimethyl derivative of the dication, with six π electrons, is also believed to be planar and aromatic. The Cyclononatetraenide anion () is the largest all-cis monocyclic annulene/annulenyl system that is planar and aromatic. These bond angles (140°) differ significantly from the ideal angles of 120°. Larger rings possess trans bonds to avoid the increased angle strain. However, 10 to 14-membered systems all experience considerable transannular strain. Thus, these systems are either nonaromatic or experience modest aromaticity. This changes when we get to [[Cyclooctadecanonaene|[18]annulene]], with (4×4) + 2 = 18 π electrons, which is large enough to accommodate six interior hydrogen atoms in a planar configuration (3 cis double bonds and 6 trans' double bonds). Thermodynamic stabilization, NMR chemical shifts, and nearly equal bond lengths all point to considerable aromaticity for [18]annulene.
The (4n+2) rule is a consequence of the degeneracy of the π orbitals in cyclic conjugated hydrocarbon molecules. As predicted by Hückel molecular orbital theory, the lowest π orbital in such molecules is non-degenerate and the higher orbitals form degenerate pairs. For benzene the lowest π orbital is non-degenerate and can hold 2 electrons, and the next 2 π orbitals form a degenerate pair which can hold 4 electrons. The 6 π electrons in benzene therefore form a stable closed shell in a regular hexagonal molecule.
However for cyclobutadiene or cyclooctatrene with regular geometries, the highest molecular orbital pair is occupied by only 2 π electrons forming a less stable open shell. The molecules therefore stabilize by geometrical distortions which separate the degenerate orbital energies so that the last two electrons occupy the same orbital, but the molecule as a whole is less stable in the presence of such a distortion. | 7 | Physical Chemistry |
The Sepro Leach Reactor is a high concentration leach reactor developed to treat the gold concentrate produced by the Falcon Concentrator. The unit consists of a concentrate holding tank and a leach tank and impeller which are linked by a Sepro vertical bowl pump. The SLR uses either peroxide or oxygen gas to achieve elevated levels of dissolved oxygen required to accelerate the leaching process with no reagents required. The pregnant leach solution produced can be directly electrowon. With the addition of an electrowinning unit the final product becomes a gold plated carbon that can be directly refined to produce gold bullion. Extensive test work of the SLR on site has shown over 99% of the target mineral is recovered through a simple, fully automated process that is easily incorporated into recovery operations. Sepro Mineral Systems Corp. supplies SLR units with capacities ranging from . | 8 | Metallurgy |
In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organyl substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands. Alkoxides, although generally not stable in protic solvents such as water, occur widely as intermediates in various reactions, including the Williamson ether synthesis. Transition metal alkoxides are widely used for coatings and as catalysts.
Enolates are unsaturated alkoxides derived by deprotonation of a bond adjacent to a ketone or aldehyde. The nucleophilic center for simple alkoxides is located on the oxygen, whereas the nucleophilic site on enolates is delocalized onto both carbon and oxygen sites. Ynolates are also unsaturated alkoxides derived from acetylenic alcohols.
Phenoxides are close relatives of the alkoxides, in which the alkyl group is replaced by a phenyl group. Phenol is more acidic than a typical alcohol; thus, phenoxides are correspondingly less basic and less nucleophilic than alkoxides. They are, however, often easier to handle, and yield derivatives that are more crystalline than those of the alkoxides. | 0 | Organic Chemistry |
Nearly two billion people in the developing world are deficient in zinc. Groups at risk include children in developing countries and the elderly with chronic illnesses. In children, it causes an increase in infection and diarrhea and contributes to the death of about 800,000 children worldwide per year. The World Health Organization advocates zinc supplementation for severe malnutrition and diarrhea. Zinc supplements help prevent disease and reduce mortality, especially among children with low birth weight or stunted growth. However, zinc supplements should not be administered alone, because many in the developing world have several deficiencies, and zinc interacts with other micronutrients. While zinc deficiency is usually due to insufficient dietary intake, it can be associated with malabsorption, acrodermatitis enteropathica, chronic liver disease, chronic renal disease, sickle cell disease, diabetes, malignancy, and other chronic illnesses.
In the United States, a federal survey of food consumption determined that for women and men over the age of 19, average consumption was 9.7 and 14.2 mg/day, respectively. For women, 17% consumed less than the EAR, for men 11%. The percentages below EAR increased with age. The most recent published update of the survey (NHANES 2013–2014) reported lower averages – 9.3 and 13.2 mg/day – again with intake decreasing with age.
Symptoms of mild zinc deficiency are diverse. Clinical outcomes include depressed growth, diarrhea, impotence and delayed sexual maturation, alopecia, eye and skin lesions, impaired appetite, altered cognition, impaired immune functions, defects in carbohydrate utilization, and reproductive teratogenesis. Zinc deficiency depresses immunity, but excessive zinc does also.
Despite some concerns, western vegetarians and vegans do not suffer any more from overt zinc deficiency than meat-eaters. Major plant sources of zinc include cooked dried beans, sea vegetables, fortified cereals, soy foods, nuts, peas, and seeds. However, phytates in many whole-grains and fibers may interfere with zinc absorption and marginal zinc intake has poorly understood effects. The zinc chelator phytate, found in seeds and cereal bran, can contribute to zinc malabsorption. Some evidence suggests that more than the US RDA (8 mg/day for adult women; 11 mg/day for adult men) may be needed in those whose diet is high in phytates, such as some vegetarians. The European Food Safety Authority (EFSA) guidelines attempt to compensate for this by recommending higher zinc intake when dietary phytate intake is greater. These considerations must be balanced against the paucity of adequate zinc biomarkers, and the most widely used indicator, plasma zinc, has poor sensitivity and specificity. | 1 | Biochemistry |
Nanoelectrodes are tiny electrodes made of metals or semiconducting materials having typical dimensions of 1-100 nm.
Various forms of nanoelectrodes have been developed taking advantage of the different possible fabrication techniques: among the most studied are the nanoband, disk, hemispherical, nanopore geometries as well as the different forms of carbon nanostructures.
It is necessary to characterize each produced electrode: size and shape determine its behavior. The most used characterization techniques are:
* Electron microscopy
* Steady-state voltammetry
* Atomic force microscopy (AFM)
* scanning electrochemical microscopy (SECM)
There are mainly two properties that distinguish nanoelectrodes from electrodes: smaller RC constant and faster mass transfer. The former allows measurements to be made in high-resistance solutions because they offer less resistance, the latter, due to radial diffusion, allows much faster voltammetry responses. Due to these and other properties, nanoelectrodes are used in various applications:
* Studying the kinetics of fast reactions
* Electrochemical reactions
* Studying small volumes, such as cells or single molecules
* As probes for obtaining high-resolution images with scanning electrochemical microscopy (SECM) | 7 | Physical Chemistry |
The majority of eukaryotic genes are transcribed by RNA polymerase II, proceeding in the 5 to 3 direction. In eukaryotes, specific subunits within the RNA polymerase II complex allow it to carry out multiple functions. General transcription factors help binding RNA polymerase II to DNA. Promoters are cites where RNA polymerase II binds to start transcription and, in eukaryotes, transcription starting point is positioned at +1 nucleotide. Like all RNA polymerases, it travels along the template DNA, in the 3 to 5 direction and synthesizes a new RNA strand in the 5 to 3 direction, by adding new bases to the 3' end of the new RNA. A transcription bubble occurs as a result of the double stranded DNA unwinding. After about 25 base pairs of the DNA double strand are unwound, RNA synthesis takes place within the transcription bubble region. Supercoiling is also part of this process since DNA regions in front of the RNA polymerase II are unwinding, while DNA regions behind it are rewinding, forming a double helix again.
The RNA polymerase carries out the majority of the steps during the transcription cycle, especially in maintaining the transcription bubble open for the complementary base pairing. There are some steps of the transcription cycle that require more proteins, such as the Rpb4/7 complex and the RNA polymerase attached to the elongation factor transcription factor IIS (TFIIS). | 1 | Biochemistry |
Pyrimidine biosynthesis creates derivatives —like orotate, thymine, cytosine, and uracil— de novo from carbamoyl phosphate and aspartate.
As is often the case with parent heterocyclic ring systems, the synthesis of pyrimidine is not that common and is usually performed by removing functional groups from derivatives. Primary syntheses in quantity involving formamide have been reported.
As a class, pyrimidines are typically synthesized by the principal synthesis involving cyclization of β-dicarbonyl compounds with N–C–N compounds. Reaction of the former with amidines to give 2-substituted pyrimidines, with urea to give 2-pyrimidinones, and guanidines to give 2-aminopyrimidines are typical.
Pyrimidines can be prepared via the Biginelli reaction and other multicomponent reactions. Many other methods rely on condensation of carbonyls with diamines for instance the synthesis of 2-thio-6-methyluracil from thiourea and ethyl acetoacetate or the synthesis of 4-methylpyrimidine with 4,4-dimethoxy-2-butanone and formamide.
A novel method is by reaction of N-vinyl and N-aryl amides with carbonitriles under electrophilic activation of the amide with 2-chloro-pyridine and trifluoromethanesulfonic anhydride: | 1 | Biochemistry |
Studies have shown that the binding of TFIIB to TBP is affected by the length of the polyglutamine tract in TBP. Extended polyglutamine tracts such as those found in neurodegenerative diseases cause increased interaction with TFIIB. This is thought to affect transcription in these diseases as it reduces the availability of TFIIB to other promoters in the brain as the TFIIB is instead interacting with the expanded polyglutamine tracts. | 1 | Biochemistry |
Polarized liquid interfaces have been used to examine the thermodynamics and kinetics of the transfer of charged species from one phase to another. Two main methods exist. The first is ITIES, "interfaces between two immiscible electrolyte solutions". The second is droplet experiments. Here a reaction at a triple interface between a conductive solid, droplets of a redox active liquid phase and an electrolyte solution have been used to determine the energy required to transfer a charged species across the interface. | 7 | Physical Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2012 impact factor of 1.435, ranking it 12th out of 75 journals in the category "Metallurgy & Metallurgical Engineering". | 8 | Metallurgy |
Thalidomide is provided as a racemic mixture of two enantiomers; while there are reports that only one of the enantiomers may cause birth defects, the body converts each enantiomer into the other through mechanisms that are not well understood. The (R)-enantiomer has the desired sedative effect while the (S)-enantiomer harbors embryo-toxic and teratogenic effect. Attempting to extract solely R-thalidomide does not remove the risk of birth defects, as it was demonstrated that the "safe" R-thalidomide undergoes an in vivo chiral inversion to the "teratogenic" S-thalidomide. Under biological conditions, the enantiomers interconvert (bidirectional chiral inversion – (R)- to (S)- and vice versa). | 4 | Stereochemistry |
Molecular intermixing tends to broaden the glass transition regions of some IPN materials compared to their component polymers. This unique characteristic provides excellent mechanical damping properties over a wide range of temperatures and frequencies due to a relatively constant and high phase angle. In IPNs composed of both rubbery and glassy polymers, considerable toughening is observed compared to the constituent polymers. When the glassy component forms a discrete, discontinuous phase, the elastomeric nature of the continuous rubbery phase can be preserved while increasing the overall toughness of the material and its elongation at break. On the other hand, when the glassy polymer forms a bicontinuous phase within the rubbery network, the IPN material can behave like an impact-resistant plastic. | 7 | Physical Chemistry |
Ariconium was a road station of Roman Britain mentioned in Iter XIII of the Iter Britanniarum of the Antonine Itineraries. It was located at Bury Hill in the parish of Weston under Penyard, about east of Ross on Wye, Herefordshire, and about southeast of Hereford. The site existed prior to the Roman era, and then came under Roman control. It was abandoned, perhaps shortly after 360, but precisely when and under what circumstances is unknown.
Discovered as a result of efforts to map the stations of the Antonine Itineraries, research and excavation have provided the only information on its history, to date showing it to have been a place of bloom furnaces, forges, and iron working throughout its existence. | 8 | Metallurgy |
The mechanism of its actions is thought to be related to the selective inhibition of viral RNA-dependent RNA polymerase. Favipiravir is a prodrug that is metabolized to its active form, favipiravir-ribofuranosyl-5'-triphosphate (favipiravir-RTP), available in both oral and intravenous formulations. In 2014, favipiravir was approved in Japan for stockpiling against influenza pandemics. However, favipiravir has not been shown to be effective in primary human airway cells, casting doubt on its efficacy in influenza treatment.
Favipiravir-RTP is a nucleoside analogue. It mimics both guanosine and adenosine for the viral RdRP. Incorporating two such bases in a row stops primer extension, although it is unclear how as of 2013. | 4 | Stereochemistry |
Instrumental analysis is a field of analytical chemistry that investigates analytes using scientific instruments. | 3 | Analytical Chemistry |
The historical background is divided into several subsections. The first is the general background to electrons in vacuum and the technological developments that led to cathode-ray tubes as well as vacuum tubes that dominated early television and electronics; the second is how these led to the development of electron microscopes; the last is work on the nature of electron beams and the fundamentals of how electrons behave, a key component of quantum mechanics and the explanation of electron diffraction. | 7 | Physical Chemistry |
Internal oxidation, in corrosion of metals, is the process of formation of corrosion products (e.g. a metal oxide) within the metal bulk. In other words, the corrosion products are created away from the metal surface, and they are isolated from the surface.
Internal oxidation occurs when some components of the alloy are oxidized in preference to the balance of the bulk. The oxidizer is often oxygen diffusing through the metal bulk from the interface, but it can be also another element (for example sulfur or nitrogen).
Internal oxidation is a well-known corrosion mechanism of nickel-based alloys in the temperature range of 500 to 1200 °C.
Internal oxidation is distinct from selective leaching. | 8 | Metallurgy |
An ISASMELT furnace is an upright-cylindrical shaped steel vessel that is lined with refractory bricks. There is a molten bath of slag, matte or metal (depending on the application) at the bottom of the furnace. A steel lance is lowered into the bath through a hole in the roof of the furnace, and air or oxygen-enriched air that is injected through the lance into the bath causes vigorous agitation of the bath.
Mineral concentrates or materials for recycling are dropped into the bath through another hole in the furnace roof or, in some cases, injected down the lance. These feed materials react with the oxygen in the injected gas, resulting in an intensive reaction in a small volume (relative to other smelting technologies).
ISASMELT lances contain one or more devices called "swirlers" that cause the injected gas to spin within the lance, forcing it against the lance wall, cooling it. The swirler consists of curved vanes around a central pipe forming an annular flow. They are designed to minimize pressure losses changing the angle from axial to tangential thus creating a strong vortex. The vortex helps mix liquids and solids with oxygen in the bath. The cooling effect results in a layer of slag "freezing" on the outside of the lance. This layer of solid slag protects the lance from the high temperatures inside the furnace. The tip of the lance that is submerged in the bath eventually wears out, and the worn lance is easily replaced with a new one when necessary. The worn tips are subsequently cut off and a new tip welded onto the lance body before it is returned to the furnace.
ISASMELT furnaces typically operate in the range of 1000–1200 °C, depending on the application. The refractory bricks that form the internal lining of the furnace protect the steel shell from the heat inside the furnace.
The products are removed from the furnace through one or more "tap holes" in a process called "tapping". This can be either continuous removal or in batches, with the tap holes being blocked with clay at the end of a tap, and then reopened by drilling or with a thermic lance when it is time for the next tap.
The products are allowed to separate in a settling vessel, such as a rotary holding furnace or an electric furnace.
While smelting sulfide concentrates, most of the energy needed to heat and melt the feed materials is derived from the reaction of oxygen with the sulfur and iron in the concentrate. However, a small amount of supplemental energy is required. ISASMELT furnaces can use a variety of fuels, including coal, coke, petroleum coke, oil and natural gas. The solid fuel can be added through the top of the furnace with the other feed materials, or it can be injected down the lance. Liquid and gaseous fuels are injected down the lance. | 8 | Metallurgy |
The ability of pitch to contaminate those in contact with it is mentioned by Dogberry, a character in Shakespeares Much Ado About Nothing', and the same point is made in a speech by Falstaff in Henry IV, Part 1, who refers to "ancient writers" who have made this observation. The Jewish deuterocanonical Book of Sirach states that "whoever touches pitch gets dirty, and whoever associates with a proud person becomes like him". | 7 | Physical Chemistry |
Arsenic biochemistry refers to biochemical processes that can use arsenic or its compounds, such as arsenate. Arsenic is a moderately abundant element in Earth's crust, and although many arsenic compounds are often considered highly toxic to most life, a wide variety of organoarsenic compounds are produced biologically and various organic and inorganic arsenic compounds are metabolized by numerous organisms. This pattern is general for other related elements, including selenium, which can exhibit both beneficial and deleterious effects. Arsenic biochemistry has become topical since many toxic arsenic compounds are found in some aquifers, potentially affecting many millions of people via biochemical processes. | 1 | Biochemistry |
Sedimentation is a long-term sink for carbon in the ocean, as well as the largest loss of carbon from the oceanic system. Deep marine sediments and geologic formations are important since they provide a thorough record of life on Earth and an important source of fossil fuel. Oceanic carbon can exit the system in the form of detritus that sinks and is buried in the seafloor without being fully decomposed or dissolved. Ocean floor surface sediments account for 1.75x10 kg of carbon in the global carbon cycle At most, 4% of the particulate organic carbon from the euphotic zone in the Pacific Ocean, where light-powered primary production occurs, is buried in marine sediments. It is then implied that since there is a higher input of organic matter to the ocean than what is being buried, a large portion of it is used up or consumed within. | 9 | Geochemistry |
The RFamide peptide family, or the RFamide-related peptides (RFRPs), are a family of neuropeptides. They are characterized by the possession of an Arg-Phe-NH motif at their C-terminal extremities.
Members of the family include:
* Neuropeptide FF group
** Neuropeptide AF
** Neuropeptide FF
** Neuropeptide SF (RFRP-1)
** Neuropeptide VF (RFRP-3) (GnIH - avian species)
* Prolactin-releasing peptide (PrRP)
* Pyroglutamylated RFamide peptide (QRFP)
* Kisspeptin (disputed) | 1 | Biochemistry |
Diffusing-wave spectroscopy (DWS) is an optical technique derived from dynamic light scattering (DLS) that studies the dynamics of scattered light in the limit of strong multiple scattering. It has been widely used in the past to study colloidal suspensions, emulsions, foams, gels, biological media and other forms of soft matter. If carefully calibrated, DWS allows the quantitative measurement of microscopic motion in a soft material, from which the rheological properties of the complex medium can be extracted via the microrheology approach. | 7 | Physical Chemistry |
In chemistry, a selone (also known as a selenoketone) is the structural analog of a ketone where selenium replaces oxygen. Selenium-77 is one of the isotopes of selenium that is stable and naturally occurring, so selenoketone-containing chemicals can be analyzed by nuclear magnetic resonance spectroscopy (NMR). Selones can be used as chiral derivatizing agents for Se-NMR. Chiral oxazolidineselones can be used for stereoselective control of aldol reactions, analogous to the Evans aldol reaction that uses oxazolidinones, which allows Se-NMR to be used to determine the diastereomeric ratio of the aldol product.
Selenobenzophenone reversibly dimerizes. It is known to undergo cycloaddition with 1,3-dienes in a reaction similar to the Diels-Alder reaction. | 0 | Organic Chemistry |
A future nanocar with a synthetic molecular motor has been developed by Jean-Francois Morin et al. It is fitted with carborane wheels and a light-powered helicene synthetic molecular motor. Although the motor moiety displayed unidirectional rotation in solution, light-driven motion on a surface has yet to be observed. Mobility in water and other liquids can be also realized by a molecular propeller in the future. | 6 | Supramolecular Chemistry |
Gerhard Ertl (; born 10 October 1936) is a German physicist and a Professor emeritus at the Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft in Berlin, Germany. Ertl's research laid the foundation of modern surface chemistry, which has helped explain how fuel cells produce energy without pollution, how catalytic converters clean up car exhausts and even why iron rusts, the Royal Swedish Academy of Sciences said.
His work has paved the way for development of cleaner energy sources and will guide the development of fuel cells, said Astrid Graslund, secretary of the Nobel Committee for Chemistry.
He was awarded the 2007 Nobel Prize in Chemistry for his studies of chemical processes on solid surfaces. The Nobel academy said Ertl provided a detailed description of how chemical reactions take place on surfaces. His findings applied in both academic studies and industrial development, the academy said. “Surface chemistry can even explain the destruction of the ozone layer, as vital steps in the reaction actually take place on the surfaces of small crystals of ice in the stratosphere,” the award citation reads.
In 2015, Ertl signed the Mainau Declaration 2015 on Climate Change on the final day of the 65th Lindau Nobel Laureate Meeting. The declaration was signed by a total of 76 Nobel Laureates and handed to then-President of the French Republic, François Hollande, as part of the COP21 climate summit in Paris. | 7 | Physical Chemistry |
In chemistry, deposition occurs when molecules settle out of a solution.
Deposition can be viewed as a reverse process to dissolution or particle re-entrainment. | 7 | Physical Chemistry |
This salt is prepared by treating an aqueous solution of ruthenium trichloride with 2,2'-bipyridine. In this conversion, Ru(III) is reduced to Ru(II), and hypophosphorous acid is typically added as a reducing agent. [Ru(bpy)] is octahedral, containing a central low spin d Ru(II) ion and three bidentate bpy ligands. The Ru-N distances are 2.053(2), shorter than the Ru-N distances for [Ru(bpy)]. The complex is chiral, with D symmetry. It has been resolved into its enantiomers. In its lowest lying triplet excited state the molecule is thought to attain lower C symmetry, as the excited electron is localized primarily on a single bipyridyl ligand. | 5 | Photochemistry |
Memory metal has been utilized in orthopedic surgery as a fixation-compression device for osteotomies, typically for lower extremity procedures. The device, usually in the form of a large staple, is stored in a refrigerator in its malleable form and is implanted into pre-drilled holes in the bone across an osteotomy. As the staple warms it returns to its non-malleable state and compresses the bony surfaces together to promote bone union. | 8 | Metallurgy |
Esters () are named as alkyl derivatives of carboxylic acids. The alkyl (R') group is named first. The part is then named as a separate word based on the carboxylic acid name, with the ending changed from "-oic acid" to "-oate" or "-carboxylate" For example, is methyl pentanoate, and is ethyl 4-methylpentanoate. For esters such as ethyl acetate (), ethyl formate () or dimethyl phthalate that are based on common acids, IUPAC recommends use of these established names, called [http://www.acdlabs.com/iupac/nomenclature/93/r93_511.htm retained names]. The "-oate" changes to "-ate." Some simple examples, named both ways, are shown in the figure above.
If the alkyl group is not attached at the end of the chain, the bond position to the ester group is suffixed before "-yl": may be called butan-2-yl propanoate or butan-2-yl propionate.. The prefix form is "oxycabonyl-" with the (R') group preceding. | 0 | Organic Chemistry |
* Handling of small quantities is not always simple.
* Higher accuracy of weighing is necessary (e.g. use of accurate balance).
* Sample surface preparation can have a major impact on measurement results. | 3 | Analytical Chemistry |
The electrolysis process, also known as the hydrometallurgical process, Roast-Leach-Electrowin (RLE) process, or electrolytic process, is more widely used than the pyrometallurgical processes.
The electrolysis process consists of 4 steps: leaching, purification, electrolysis, and melting and casting. | 8 | Metallurgy |
Because of the complementary nature of base-pairing between nucleic acid polymers, a double-stranded DNA molecule will be composed of two strands with sequences that are reverse complements of each other. To help molecular biologists specifically identify each strand individually, the two strands are usually differentiated as the "sense" strand and the "antisense" strand. An individual strand of DNA is referred to as positive-sense (also positive (+) or simply sense) if its nucleotide sequence corresponds directly to the sequence of an RNA transcript which is translated or translatable into a sequence of amino acids (provided that any thymine bases in the DNA sequence are replaced with uracil bases in the RNA sequence). The other strand of the double-stranded DNA molecule is referred to as negative-sense (also negative (−) or antisense), and is reverse complementary to both the positive-sense strand and the RNA transcript. It is actually the antisense strand that is used as the template from which RNA polymerases construct the RNA transcript, but the complementary base-pairing by which nucleic acid polymerization occurs means that the sequence of the RNA transcript will look identical to the positive-sense strand, apart from the RNA transcript's use of uracil instead of thymine.
Sometimes the phrases coding strand and template strand are encountered in place of sense and antisense, respectively, and in the context of a double-stranded DNA molecule the usage of these terms is essentially equivalent. However, the coding/sense strand need not always contain a code that is used to make a protein; both protein-coding and non-coding RNAs may be transcribed.
The terms "sense" and "antisense" are relative only to the particular RNA transcript in question, and not to the DNA strand as a whole. In other words, either DNA strand can serve as the sense or antisense strand. Most organisms with sufficiently large genomes make use of both strands, with each strand functioning as the template strand for different RNA transcripts in different places along the same DNA molecule. In some cases, RNA transcripts can be transcribed in both directions (i.e. on either strand) from a common promoter region, or be transcribed from within introns on either strand (see "ambisense" below). | 1 | Biochemistry |
RNA polymerase III performs "intrinsic-like" termination. The majority of genes transcribed by RNAP III have a poly(dT) region. However, although poly(dT) pauses every RNA polymerase, it alone cannot be insufficient; some other mechanism must destablize the clamp. In RNAP III, some poly(dT) sites are indeed occationally read-thorugh: some genes have multiple such regions, allowing transcripts of different lengths to be produced.
The instability of rU:dA hybrids likely is essential to termination by RNAP III. Parts of core subunits C1 and C2, as well as "subcomplexes" C53/37 and C11 are functionally important. A number of extraneous factors can modify the termination behavior. | 1 | Biochemistry |
Essential genes are the set of genes thought to be critical for an organisms survival. This definition assumes the abundant availability of all relevant nutrients and the absence of environmental stress. Only a small portion of an organisms genes are essential. In bacteria, an estimated 250–400 genes are essential for Escherichia coli and Bacillus subtilis, which is less than 10% of their genes. Half of these genes are orthologs in both organisms and are largely involved in protein synthesis. In the budding yeast Saccharomyces cerevisiae the number of essential genes is slightly higher, at 1000 genes (~20% of their genes). Although the number is more difficult to measure in higher eukaryotes, mice and humans are estimated to have around 2000 essential genes (~10% of their genes). The synthetic organism, Syn 3, has a minimal genome of 473 essential genes and quasi-essential genes (necessary for fast growth), although 149 have unknown function.
Essential genes include housekeeping genes (critical for basic cell functions) as well as genes that are expressed at different times in the organisms development or life cycle. Housekeeping genes are used as experimental controls when analysing gene expression, since they are constitutively expressed at a relatively constant level. | 1 | Biochemistry |
In 2018 road transport used 49% of petroleum, aviation 8%, and uses other than energy 17%. Electric vehicles are the main alternative for road transport and biojet for aviation. Single-use plastics have a high carbon footprint and may pollute the sea, but as of 2022 the best alternatives are unclear. | 7 | Physical Chemistry |
A homogeneous electrocatalyst is one that is present in the same phase of matter as the reactants, for example, a water-soluble coordination complex catalyzing an electrochemical conversion in solution. This technology is not practiced commercially, but is of research interest. | 7 | Physical Chemistry |
Embryo transfer refers to a step in the process of assisted reproduction in which embryos are placed into the uterus of a female with the intent to establish a pregnancy. This technique - which is often used in connection with in vitro fertilization (IVF) - may be used in humans or in other animals, in which situations and goals may vary.
Embryo transfer can be done at day two or day three, or later in the blastocyst stage, which was first performed in 1984.
Factors that can affect the success of embryo transfer include the endometrial receptivity, embryo quality, and embryo transfer technique. | 1 | Biochemistry |
Many definitions that describe a specific conformer (IUPAC Gold Book) exist, developed by William Klyne and Vladimir Prelog, constituting their Klyne–Prelog system of nomenclature:
* a torsion angle of ±60° is called gauche
* a torsion angle between 0° and ±90° is called syn (s)
* a torsion angle between ±90° and 180° is called anti (a)
* a torsion angle between 30° and 150° or between –30° and –150° is called clinal
* a torsion angle between 0° and 30° or 150° and 180° is called periplanar (p)
* a torsion angle between 0° to 30° is called synperiplanar or syn- or cis-conformation (sp)
* a torsion angle between 30° to 90° and –30° to –90° is called synclinal or gauche or skew (sc)
* a torsion angle between 90° to 150°, and –90° to –150° is called anticlinal (ac)
* a torsion angle between ±150° to 180° is called antiperiplanar or anti or trans (ap).
Torsional strain results from resistance to twisting about a bond. | 4 | Stereochemistry |
AOAC Research Institute (AOAC RI) Performance Tested Methods program develops, improves, and validates proprietary kit-based food safety testing methods. | 3 | Analytical Chemistry |
Metabolic pathways require tight regulation so that the proper compounds get produced in the proper amounts. Often, the first committed step is regulated by processes such as feedback inhibition and activation. Such regulation ensures that pathway intermediates do not accumulate, a situation that can be wasteful or even harmful to the cell. | 1 | Biochemistry |
The term calcareous can be applied to a sediment, sedimentary rock, or soil type which is formed from, or contains a high proportion of, calcium carbonate in the form of calcite or aragonite. | 9 | Geochemistry |
A chemical glycosylation reaction involves the coupling of a glycosyl donor, to a glycosyl acceptor forming a glycoside. If both the donor and acceptor are sugars, then the product is an oligosaccharide. The reaction requires activation with a suitable activating reagent. The reactions often result in a mixture of products due to the creation of a new stereogenic centre at the anomeric position of the glycosyl donor. The formation of a glycosidic linkage allows for the synthesis of complex polysaccharides which may play important roles in biological processes and pathogenesis and therefore having synthetic analogs of these molecules allows for further studies with respect to their biological importance. | 0 | Organic Chemistry |
According to the Agency for Toxic Substances and Disease Registry (ATSDR), eating food or drinking water contaminated with high levels of coal-tar creosote may cause a burning in the mouth and throat, and stomach pains. ATSDR also states that brief direct contact with large amounts of coal-tar creosote may result in a rash or severe irritation of the skin, chemical burns of the surfaces of the eyes, convulsions and mental confusion, kidney or liver problems, unconsciousness, and even death. Longer direct skin contact with low levels of creosote mixtures or their vapours can result in increased light sensitivity, damage to the cornea, and skin damage. Longer exposure to creosote vapours can cause irritation of the respiratory tract.
The International Agency for Research on Cancer (IARC) has determined that coal-tar creosote is probably carcinogenic to humans, based on adequate animal evidence and limited human evidence. The animal testing relied upon by IARC involved the continuous application of creosote to the shaved skin of rodents. After weeks of creosote application, the animals developed cancerous skin lesions and in one test, lesions of the lung. The United States Environmental Protection Agency has stated that coal-tar creosote is a probable human carcinogen based on both human and animal studies. As a result, the Federal Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit of 0.2 milligrams of coal-tar creosote per cubic meter of air (0.2 mg/m3) in the workplace during an 8-hour day, and the Environmental Protection Agency (EPA) requires that spills or accidental releases into the environment of one pound (0.454 kg) or more of creosote be reported to them.
There is no unique exposure pathway of children to creosote. Children exposed to creosote probably experience the same health effects seen in adults exposed to creosote. It is unknown whether children differ from adults in their susceptibility to health effects from creosote.
A 2005 mortality study of creosote workers found no evidence supporting an increased risk of cancer death, as a result of exposure to creosote. Based on the findings of the largest mortality study to date of workers employed in creosote wood treating plants, there is no evidence that employment at creosote wood-treating plants or exposure to creosote-based preservatives was associated with any significant mortality increase from either site-specific cancers or non-malignant diseases. The study consisted of 2,179 employees at eleven plants in the United States where wood was treated with creosote preservatives. Some workers began work in the 1940s to 1950s. The observation period of the study covered 1979–2001. The average length of employment was 12.5 years. One third of the study subjects were employed for over 15 years.
The largest health effect of creosote is deaths caused by residential chimney fires due to chimney tar (creosote) build-up. This is entirely unconnected with its industrial production or use. | 7 | Physical Chemistry |
Retinal (also known as retinaldehyde) is a polyene chromophore. Retinal, bound to proteins called opsins, is the chemical basis of visual phototransduction, the light-detection stage of visual perception (vision).
Some microorganisms use retinal to convert light into metabolic energy. In fact, a recent study suggests most living organisms on our planet ~3 billion years ago used retinal to convert sunlight into energy rather than chlorophyll. Since retinal absorbs mostly green light and transmits purple light, this gave rise to the Purple Earth Hypothesis.
Retinal itself is considered to be a form of vitamin A when eaten by an animal. There are many forms of vitamin A, all of which are converted to retinal, which cannot be made without them. The number of different molecules that can be converted to retinal varies from species to species. Retinal was originally called retinene, and was renamed after it was discovered to be vitamin A aldehyde.
Vertebrate animals ingest retinal directly from meat, or they produce retinal from carotenoids — either from α-carotene or β-carotene — both of which are carotenes. They also produce it from β-cryptoxanthin, a type of xanthophyll. These carotenoids must be obtained from plants or other photosynthetic organisms. No other carotenoids can be converted by animals to retinal. Some carnivores cannot convert any carotenoids at all. The other main forms of vitamin A — retinol and a partially active form, retinoic acid — may both be produced from retinal.
Invertebrates such as insects and squid use hydroxylated forms of retinal in their visual systems, which derive from conversion from other xanthophylls. | 1 | Biochemistry |
The phosphatome of an organism is the set of phosphatase genes in its genome. Phosphatases are enzymes that catalyze the removal of phosphate from biomolecules. Over half of all cellular proteins are modified by phosphorylation which typically controls their functions. Protein phosphorylation is controlled by the opposing actions of protein phosphatases and protein kinases.
Most phosphorylation sites are not linked to a specific phosphatase, so the phosphatome approach allows a global analysis of dephosphorylation, screening to find the phosphatase responsible for a given reaction, and comparative studies between different phosphatases, similar to how protein kinase research has been impacted by the kinome approach. | 1 | Biochemistry |
*BAT1 aka DDX39B
*HNRPD Homo sapiens heterogeneous nuclear ribonucleoprotein D (AU-rich element RNA
*HNRPK Homo sapiens heterogeneous nuclear ribonucleoprotein K (HNRPK), transcript
*PABPN1 poly(A) binding protein, nuclear 1
*SRSF3 splicing factor, arginine/serine-rich | 1 | Biochemistry |
Christopher Bruce Murray is the Richard Perry University Professor of Chemistry and Materials Science and Engineering at the University of Pennsylvania. He is a member of the National Academy of Engineering and a Fellow of the Materials Research Society. He was a Clarivate Citation Laureate in 2020. He is known for his contributions to quantum dots and other nanoscale materials. | 7 | Physical Chemistry |
Many cells produce specific carbohydrate-binding proteins known as lectins, which mediate cell adhesion with oligosaccharides. Selectins, a family of lectins, mediate certain cell–cell adhesion processes, including those of leukocytes to endothelial cells. In an immune response, endothelial cells can express certain selectins transiently in response to damage or injury to the cells. In response, a reciprocal selectin–oligosaccharide interaction will occur between the two molecules which allows the white blood cell to help eliminate the infection or damage. Protein-Carbohydrate bonding is often mediated by hydrogen bonding and van der Waals forces. | 0 | Organic Chemistry |
Phenol extraction is a laboratory technique that purifies nucleic acid samples using a phenol solution. Phenol is common reagent in extraction because its properties allow for effective nucleic acid extraction, particularly as it strongly denatures proteins, it is a nucleic acid preservative, and it is immiscible in water.
It may also refer to the process of extracting and isolating phenols from raw materials such as coal tar. These purified phenols are used in many industrial and medical compounds and are used as precursors in some synthesis reactions. | 1 | Biochemistry |
Chemical analysis typically involves sampling some part of the environment and using lab equipment to figure out how much of a certain target compound exists. Chemical analysis may be used to assess pollution levels for remediation, or to make sure groundwater is safe for drinking.
Biological surveys typically includes a measurement of the abundance of a certain species within a certain area to confirm information about the ecosystem for specific reasons. Analysis like this could be used in efforts to understand species abundance, or to look at how external effects from the environment are affecting an ecosystem.
Soil tests may involve chemical analysis, but most often soil tests involve removing a section of soil to understand what each layer of soil is composed of for specific reasons. Soil samples might be needed when determining whether they can build on a certain site, or just to produce a model of an area, or to determine possible crop production considering nutrient levels.
Vegetation surveys are quite similar to a biosurvey, it's the process of measuring the abundance of plant species and trees within a specific area to understand more about the ecosystem for specific reasons. Sometimes these are done to understand ecological effects from outside factors, or to just determine overall ecosystem health.
Remote sensing can be used for environmental analysis by taking imagery shot by satellites in multiple wavelengths to assess areas of different scales for a certain objective. Remote sensing can be used to identify land use, it can be used to determine damages from forest fires, it can be used for weather systems and meteorology, and also for atmospheric composition. Recent advances in remote sensing field has also led to the development of autonomous devices for the analysis of physical and chemical parameters of the environment using the sensors. | 3 | Analytical Chemistry |
LEAPER (Leveraging endogenous ADAR for programmable editing of RNA) is a genetic engineering technique in molecular biology by which RNA can be edited. The technique relies on engineered strands of RNA to recruit native ADAR enzymes to swap out different compounds in RNA. Developed by researchers at Peking University in 2019, the technique, some have claimed, is more efficient than the CRISPR gene editing technique. Initial studies have claimed that editing efficiencies of up to 80%. | 1 | Biochemistry |
The transduction of the signal through the membrane by the receptor is not completely understood. It is known that in the inactive state, the GPCR is bound to a heterotrimeric G protein complex. Binding of an agonist to the GPCR results in a conformational change in the receptor that is transmitted to the bound G subunit of the heterotrimeric G protein via protein domain dynamics. The activated G subunit exchanges GTP in place of GDP which in turn triggers the dissociation of G subunit from the G dimer and from the receptor. The dissociated G and G subunits interact with other intracellular proteins to continue the signal transduction cascade while the freed GPCR is able to rebind to another heterotrimeric G protein to form a new complex that is ready to initiate another round of signal transduction.
It is believed that a receptor molecule exists in a conformational equilibrium between active and inactive biophysical states. The binding of ligands to the receptor may shift the equilibrium toward the active receptor states. Three types of ligands exist: Agonists are ligands that shift the equilibrium in favour of active states; inverse agonists are ligands that shift the equilibrium in favour of inactive states; and neutral antagonists are ligands that do not affect the equilibrium. It is not yet known how exactly the active and inactive states differ from each other. | 1 | Biochemistry |
Fluoroalkenes polymerize more exothermically than normal alkenes. Unsaturated fluorocarbons have a driving force towards sp hybridization due to the electronegative fluorine atoms seeking a greater share of bonding electrons with reduced s character in orbitals. The most famous member of this class is tetrafluoroethylene, which is used to manufacture polytetrafluoroethylene (PTFE), better known under the trade name Teflon. | 2 | Environmental Chemistry |
Compared to seagrass beds and coral reefs, hypoxia is more common on a regular basis in mangrove ecosystems, though ocean deoxygenation is compounding the negative effects by anthropogenic nutrient inputs and land use modification.
Like seagrass, mangrove trees transport oxygen to roots of rhizomes, reduce sulfide concentrations, and alter microbial communities. Dissolved oxygen is more readily consumed in the interior of the mangrove forest. Anthropogenic inputs may push the limits of survival in many mangrove microhabitats. For example, shrimp ponds constructed in mangrove forests are considered the greatest anthropogenic threat to mangrove ecosystems. These shrimp ponds reduce estuary circulation and water quality which leads to the promotion of diel-cycling hypoxia. When the quality of the water degrades, the shrimp ponds are quickly abandoned leaving massive amounts of wastewater. This is a major source of water pollution that promotes ocean deoxygenation in the adjacent habitats.
Due to these frequent hypoxic conditions, the water does not provide habitats to fish. When exposed to extreme hypoxia, ecosystem function can completely collapse. Extreme deoxygenation will affect the local fish populations, which are an essential food source. The environmental costs of shrimp farms in the mangrove forests grossly outweigh their economic benefits. Cessation of shrimp production and restoration of these areas and reduce eutrophication and anthropogenic hypoxia. | 9 | Geochemistry |
Lacking any other plausible explanation, the anomalous excess heat produced during such electrolysis was attributed by Pons and Fleischmann to cold fusion. Later, it was discovered that such excess heat can easily be the product of conventional chemistry, i.e. internal recombination of hydrogen and oxygen. Such recombination leads to a reduction in the Faraday efficiency of the electrolysis. The Faraday-efficiency effect is the observation of anomalous excess heat due to a reduction in the Faraday efficiency. | 7 | Physical Chemistry |
According to the analysis by electron paramagnetic resonance spectroscopy, the resting state of the FeMo cofactor has a spin state of S=3/2. Upon one-electron reduction, the cofactor becomes EPR silent. Understanding the process in which an electron is transferred in the protein adduct shows a more precise kinetic model of the FeMo cofactor. Density functional theory calculations as well as spatially resolved anomalous dispersion refinement have suggested that the formal oxidation state is Mo-2Fe-5Fe-C-H, but the "true" oxidation states have not been confirmed experimentally. | 7 | Physical Chemistry |
TopFIND is the Termini oriented protein Function Inferred Database (TopFIND) is an integrated knowledgebase focused on protein termini, their formation by proteases and functional implications. It contains information about the processing and the processing state of proteins and functional implications thereof derived from research literature, contributions by the scientific community and biological databases. | 1 | Biochemistry |
Spatiotemporal gene expression is the activation of genes within specific tissues of an organism at specific times during development. Gene activation patterns vary widely in complexity. Some are straightforward and static, such as the pattern of tubulin, which is expressed in all cells at all times in life. Some, on the other hand, are extraordinarily intricate and difficult to predict and model, with expression fluctuating wildly from minute to minute or from cell to cell. Spatiotemporal variation plays a key role in generating the diversity of cell types found in developed organisms; since the identity of a cell is specified by the collection of genes actively expressed within that cell, if gene expression was uniform spatially and temporally, there could be at most one kind of cell.
Consider the gene wingless, a member of the wnt family of genes. In the early embryonic development of the model organism Drosophila melanogaster, or fruit fly, wingless is expressed across almost the entire embryo in alternating stripes three cells separated. This pattern is lost by the time the organism develops into a larva, but wingless is still expressed in a variety of tissues such as the wing imaginal discs, patches of tissue that will develop into the adult wings. The spatiotemporal pattern of wingless gene expression is determined by a network of regulatory interactions consisting of the effects of many different genes such as even-skipped and Krüppel.
What causes spatial and temporal differences in the expression of a single gene? Because current expression patterns depend strictly on previous expression patterns, there is a regressive problem of explaining what caused the first differences in gene expression. The process by which uniform gene expression becomes spatially and temporally differential is known as symmetry breaking. For example, in the case of embryonic Drosophila development, the genes nanos and bicoid are asymmetrically expressed in the oocyte because maternal cells deposit messenger RNA (mRNA) for these genes in the poles of the egg before it is laid. | 1 | Biochemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.