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Antiporters and symporters both transport two or more different types of molecules at the same time in a coupled movement. An energetically unfavored movement of one molecule is combined with an energetically favorable movement of another molecule(s) or ion(s) to provide the power needed for transport. This type of transport is known as secondary active transport and is powered by the energy derived from the concentration gradient of the ions/molecules across the membrane the cotransporter protein is integrated within.
Cotransporters undergo a cycle of conformational changes by linking the movement of an ion with its concentration gradient (downhill movement) to the movement of a cotransported solute against its concentration gradient (uphill movement). In one conformation the protein will have the binding site (or sites in the case of symporters) exposed to one side of the membrane. Upon binding of both the molecule which is to be transported uphill and the molecule to be transported downhill a conformational change will occur. This conformational change will expose the bound substrates to the opposite side of the membrane, where the substrates will disassociate. Both the molecule and the cation must be bound in order for the conformational change to occur. This mechanism was first introduced by Oleg Jardetzky in 1966. This cycle of conformational changes only transports one substrate ion at a time, which results in a fairly slow transport rate (10 to 10 ions or molecules per second) when compared to other transport proteins like ion channels. The rate at which this cycle of conformational changes occurs is called the turnover rate (TOR) and is expressed as the average number of complete cycles per second performed by a single cotransporter molecule. | 1 | Applied and Interdisciplinary Chemistry |
Butyrate that is produced in the colon through microbial fermentation of dietary fiber is primarily absorbed and metabolized by colonocytes and the liver for the generation of ATP during energy metabolism; however, some butyrate is absorbed in the distal colon, which is not connected to the portal vein, thereby allowing for the systemic distribution of butyrate to multiple organ systems through the circulatory system. Butyrate that has reached systemic circulation can readily cross the blood–brain barrier via monocarboxylate transporters (i.e., certain members of the SLC16A group of transporters). Other transporters that mediate the passage of butyrate across lipid membranes include SLC5A8 (SMCT1), SLC27A1 (FATP1), and SLC27A4 (FATP4). | 1 | Applied and Interdisciplinary Chemistry |
In the area of organometallic chemistry, a bulky cyclopentadienyl ligand is jargon for a ligand of the type where R is a branched alkyl and n = 3 or 4. Representative examples are the tetraisopropyl derivative and the tris(tert-butyl) derivative . These ligands are so large that their complexes behave differently from the pentamethylcyclopentadienyl analogues. Because they cannot closely approach the metal, these bulky ligands stabilize high spin complexes, such as (CHBu)FeI. These large ligands stabilize highly unsaturated derivatives such as (CHBu)FeN. | 0 | Theoretical and Fundamental Chemistry |
A flame test is relatively quick test for the presence of some elements in a sample. The technique is archaic and of questionable reliability, but once was a component of qualitative inorganic analysis. The phenomenon is related to pyrotechnics and atomic emission spectroscopy. The color of the flames is understood through the principles of atomic electron transition and photoemission, where varying elements require distinct energy levels (photons) for electron transitions. | 1 | Applied and Interdisciplinary Chemistry |
Several methods for detecting the RB1 gene mutations have been developed including a method that can detect large deletions that correlate with advanced stage retinoblastoma. | 1 | Applied and Interdisciplinary Chemistry |
* Good convergence characteristics of loop method are maintained.
* No need to define and optimize the loops. | 1 | Applied and Interdisciplinary Chemistry |
Unsaturated esters may be epoxidized using either electrophilic or nucleophilic methods. Lanthanide-mediated epoxidation has been successfully applied to cinnamates and β-heteroaryl unsaturated esters. Amides are also epoxidized under lanthanide-mediated conditions.
Epoxidations of other electron-deficient double bonds (substituted by electron-withdrawing groups other than carbonyls) are limited in scope, although a few examples have been reported. The ability of the carbonyl group to coordinate Lewis acidic functionality is critical for most existing methods. | 0 | Theoretical and Fundamental Chemistry |
Focusing on crystallographic data and applications of the group theory in solid state physics, the server is built on a core of databases and contains different shells. | 0 | Theoretical and Fundamental Chemistry |
A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At the lowest range, metal particles smaller than 1 nm are usually called atom clusters instead.
Nanoparticles are distinguished from microparticles (1-1000 µm), "fine particles" (sized between 100 and 2500 nm), and "coarse particles" (ranging from 2500 to 10,000 nm), because their smaller size drives very different physical or chemical properties, like colloidal properties and ultrafast optical effects or electric properties.
Being more subject to the Brownian motion, they usually do not sediment, like colloidal particles that conversely are usually understood to range from 1 to 1000 nm.
Being much smaller than the wavelengths of visible light (400-700 nm), nanoparticles cannot be seen with ordinary optical microscopes, requiring the use of electron microscopes or microscopes with laser. For the same reason, dispersions of nanoparticles in transparent media can be transparent, whereas suspensions of larger particles usually scatter some or all visible light incident on them. Nanoparticles also easily pass through common filters, such as common ceramic candles, so that separation from liquids requires special nanofiltration techniques.
The properties of nanoparticles often differ markedly from those of larger particles of the same substance. Since the typical diameter of an atom is between 0.15 and 0.6 nm, a large fraction of the nanoparticle's material lies within a few atomic diameters of its surface. Therefore, the properties of that surface layer may dominate over those of the bulk material. This effect is particularly strong for nanoparticles dispersed in a medium of different composition since the interactions between the two materials at their interface also becomes significant.
Nanoparticles occur widely in nature and are objects of study in many sciences such as chemistry, physics, geology, and biology. Being at the transition between bulk materials and atomic or molecular structures, they often exhibit phenomena that are not observed at either scale. They are an important component of atmospheric pollution, and key ingredients in many industrialized products such as paints, plastics, metals, ceramics, and magnetic products. The production of nanoparticles with specific properties is a branch of nanotechnology.
In general, the small size of nanoparticles leads to a lower concentration of point defects compared to their bulk counterparts, but they do support a variety of dislocations that can be visualized using high-resolution electron microscopes. However, nanoparticles exhibit different dislocation mechanics, which, together with their unique surface structures, results in mechanical properties that are different from the bulk material.
Non-spherical nanoparticles (e.g., prisms, cubes, rods etc.) exhibit shape-dependent and size-dependent (both chemical and physical) properties (anisotropy). Non-spherical nanoparticles of gold (Au), silver (Ag), and platinum (Pt) due to their fascinating optical properties are finding diverse applications. Non-spherical geometries of nanoprisms give rise to high effective cross-sections and deeper colors of the colloidal solutions. The possibility of shifting the resonance wavelengths by tuning the particle geometry allows using them in the fields of molecular labeling, biomolecular assays, trace metal detection, or nanotechnical applications. Anisotropic nanoparticles display a specific absorption behavior and stochastic particle orientation under unpolarized light, showing a distinct resonance mode for each excitable axis. | 0 | Theoretical and Fundamental Chemistry |
* co-culture with stromal cells or feeder cells, and on specific culture substrates:
support cells and matrices provide developmental-like environmental signals.
* 3D cell aggregate formation, termed embryoid bodies (EBs): the aggregate aim at mimicking early embryonic development and instructing the cell differentiation.
* culture in presence of fetal bovine serum, removal of pluripotency factors. | 1 | Applied and Interdisciplinary Chemistry |
Modafinil and/or its major metabolite, modafinil acid, may be quantified in plasma, serum, or urine to monitor dosage in those receiving the drug therapeutically, to confirm a diagnosis of poisoning in hospitalized patients, or to assist in the forensic investigation of a vehicular traffic violation. Instrumental techniques involving gas or liquid chromatography are usually employed for these purposes. In 2011, modafinil was not tested for by common drug screens (except for anti-doping screens) and is unlikely to cause false positives for other chemically unrelated drugs such as substituted amphetamines.
Reagent testing can screen for the presence of modafinil in samples. | 0 | Theoretical and Fundamental Chemistry |
*Group 2 elements calcium, strontium, and barium can all form octacarbonyl complexes M(CO) (M = Ca, Sr, Ba). The compounds were characterized in cryogenic matrices by vibrational spectroscopy and in gas phase by mass spectrometry.
*Group 4 elements with 4 valence electrons are expected to form heptacarbonyls; while these are extremely rare, substituted derivatives of Ti(CO) are known.
*Group 5 elements with 5 valence electrons, again are subject to steric effects that prevent the formation of M–M bonded species such as V(CO), which is unknown. The 17-VE V(CO) is however well known.
*Group 6 elements with 6 valence electrons form hexacarbonyls Cr(CO), Mo(CO), W(CO), and Sg(CO). Group 6 elements (as well as group 7) are also well known for exhibiting the cis effect (the labilization of CO in the cis position) in organometallic synthesis.
*Group 7 elements with 7 valence electrons form pentacarbonyl dimers Mn(CO), Tc(CO), and Re(CO).
*Group 8 elements with 8 valence electrons form pentacarbonyls Fe(CO), Ru(CO) and Os(CO). The heavier two members are unstable, tending to decarbonylate to give Ru(CO), and Os(CO). The two other principal iron carbonyls are Fe(CO) and Fe(CO).
*Group 9 elements with 9 valence electrons and are expected to form tetracarbonyl dimers M(CO). In fact the cobalt derivative of this octacarbonyl is the only stable member, but all three tetramers are well known: Co(CO), Rh(CO), Rh(CO), and Ir(CO). Co(CO) unlike the majority of the other 18 VE transition metal carbonyls is sensitive to oxygen.
*Group 10 elements with 10 valence electrons form tetracarbonyls such as Ni(CO). Curiously Pd(CO) and Pt(CO) are not stable. | 0 | Theoretical and Fundamental Chemistry |
Genetic evidence suggesting that RNAP was the target of ppGpp came from the discovery that M+ mutants (also called stringent RNAP mutants) display in vitro and in vivo mimicry of physiology and transcription regulation conferred by (p)ppGpp, even in its absence. Cross-linking ppGpp to RNAP reinforced this notion. Structural details of an association between ppGpp and RNAP came from the analysis of cocrystals that positioned ppGpp in the secondary channel of RNAP near the catalytic center. | 1 | Applied and Interdisciplinary Chemistry |
A stepping stone is a morphological element that allows organisms to either migrate and settle or drift though the river section. It does not necessarily have to be a stone or a group of stones; large woody debris (LWD), roots or aquatic plants can also have a supporting effect. | 1 | Applied and Interdisciplinary Chemistry |
Moreover, in constrained reaction environments such as in enzyme and nanomaterial binding sites, early evidence suggests that BD angles for reactivity can be quite distinct, since reactivity concepts assuming orbital overlaps during random collision are not directly applicable.
For instance, the BD value determined for enzymatic cleavage of an amide by a serine protease (subtilisin) was 88°, quite distinct from the hydride-formaldehyde value of 107°; moreover, compilation of literature crystallographic BD angle values for the same reaction mediated by different protein catalysts clustered at 89 ± 7° (i.e., only slightly offset from directly above or below the carbonyl carbon). At the same time, the subtilisin FL value was 8°, and FL angle values from the careful compilation clustered at 4 ± 6° (i.e., only slightly offset from directly behind the carbonyl; see the Flippin–Lodge angle article). | 0 | Theoretical and Fundamental 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. | 0 | Theoretical and Fundamental Chemistry |
* Contrast in Ramsey fringes
** The coherence time is the time at which the contrast in Ramsey fringes drops to 1/e.
* Damping of Rabi oscillations
** The coherence time is the time at which the amplitude of the Rabi oscillation has dropped to 1/e. | 0 | Theoretical and Fundamental Chemistry |
Ultraviolet-sensitive beads (UV beads) are beads that are colorful in the presence of ultraviolet radiation. Ultraviolet rays are present in sunlight and light from various artificial sources and can cause sunburn or skin cancer. The color change in the beads alerts the wearer to the presence of the radiation.
When changing colour they undergo photochromism.
When the beads are not exposed to ultraviolet rays, they are colorless and either translucent or opaque. However, when sunlight falls onto the beads, they instantly turn into red, orange, yellow, blue, purple, or pink. | 0 | Theoretical and Fundamental Chemistry |
The AutoAnalyzer is an automated analyzer using a flow technique called continuous flow analysis (CFA), or more correctly segmented flow analysis (SFA) first made by the Technicon Corporation. The instrument was invented in 1957 by Leonard Skeggs, PhD and commercialized by Jack Whitehead's Technicon Corporation. The first applications were for clinical analysis, but methods for industrial and environmental analysis soon followed. The design is based on segmenting a continuously flowing stream with air bubbles. | 0 | Theoretical and Fundamental Chemistry |
The word methemoglobin derives from the Ancient Greek prefix μετα- (meta-: behind, later, subsequent) and the word hemoglobin.
The name hemoglobin is itself derived from the words heme and globin, each subunit of hemoglobin being a globular protein with an embedded heme group. | 1 | Applied and Interdisciplinary Chemistry |
Metal carbonyl hydrides are used as catalysts in the hydroformylation of olefins. The catalyst is usually formed in situ in a reaction of a metal salt precursor with the syngas. The hydroformylation starts with the generation of a coordinatively unsaturated 16-electron metal carbonyl hydride complex like HCo(CO) or HRh(CO)(PPh) by dissociation of a ligand. Such complexes bind olefins in a first step via π-complexation, thus beginning the transformation of the alkene to the aldehyde.
Iron carbonyl hydrides occur in nature at the active sites of hydrogenase enzymes. | 0 | Theoretical and Fundamental Chemistry |
Crosslinking is the process of joining two or more polymer chains. Both chemical and physical crosslinking exists. In addition, both natural polymers such as proteins or synthetic polymers with a high affinity for water may be used as starting materials when selecting a hydrogel. Different crosslinking methods can be implemented for the design of a hydrogel. By definition, a crosslinked polymer gel is a macromolecule that solvent will not dissolve. Due to the polymeric domains created by crosslinking in the gel microstructure, hydrogels are not homogenous within the selected solvent system. The following sections summarize the chemical and physical methods by which hydrogels are crosslinked. | 0 | Theoretical and Fundamental Chemistry |
The vast majority of organisms encode their genes in long strands of DNA (deoxyribonucleic acid). DNA consists of a chain made from four types of nucleotide subunits, each composed of: a five-carbon sugar (2-deoxyribose), a phosphate group, and one of the four bases adenine, cytosine, guanine, and thymine.
Two chains of DNA twist around each other to form a DNA double helix with the phosphate-sugar backbone spiraling around the outside, and the bases pointing inwards with adenine base pairing to thymine and guanine to cytosine. The specificity of base pairing occurs because adenine and thymine align to form two hydrogen bonds, whereas cytosine and guanine form three hydrogen bonds. The two strands in a double helix must, therefore, be complementary, with their sequence of bases matching such that the adenines of one strand are paired with the thymines of the other strand, and so on.
Due to the chemical composition of the pentose residues of the bases, DNA strands have directionality. One end of a DNA polymer contains an exposed hydroxyl group on the deoxyribose; this is known as the 3 end of the molecule. The other end contains an exposed phosphate group; this is the 5 end. The two strands of a double-helix run in opposite directions. Nucleic acid synthesis, including DNA replication and transcription occurs in the 5→3 direction, because new nucleotides are added via a dehydration reaction that uses the exposed 3' hydroxyl as a nucleophile.
The expression of genes encoded in DNA begins by transcribing the gene into RNA, a second type of nucleic acid that is very similar to DNA, but whose monomers contain the sugar ribose rather than deoxyribose. RNA also contains the base uracil in place of thymine. RNA molecules are less stable than DNA and are typically single-stranded. Genes that encode proteins are composed of a series of three-nucleotide sequences called codons, which serve as the "words" in the genetic "language". The genetic code specifies the correspondence during protein translation between codons and amino acids. The genetic code is nearly the same for all known organisms. | 1 | Applied and Interdisciplinary Chemistry |
A primary standard in metrology is a standard that is sufficiently accurate such that it is not calibrated by or subordinate to other standards. Primary standards are defined via other quantities like length, mass and time. Primary standards are used to calibrate other standards referred to as working standards. See Hierarchy of Standards. | 0 | Theoretical and Fundamental Chemistry |
Bartolomé de Medina was a successful Spanish merchant who became fascinated with the problem of decreasing silver yields from ores mined in Spanish America. By the mid-sixteenth century, it was well known in Spain that American silver production was in decline due to the depletion of high-grade ores and increasing production costs. The New Laws, prohibiting the enslavement of Indians, had resulted in higher labor costs as miners turned to wage labor and expensive African slaves. These higher production costs made mining and smelting anything but the highest grade silver ores prohibitively expensive, just as the availability of high grade ores was in decline. Bartolomé de Medina initially focused his attentions on learning about new smelting methods from smelters in Spain. He was approached during his research by an unknown German man, known only as "Maestro Lorenzo," who told him that silver could be extracted from ground ores using mercury and a salt-water brine. With this knowledge, Medina left Spain for New Spain (Mexico) in 1554 and established a model patio refinery in order to prove the effectiveness of the new technology. Medina is generally credited with adding "magistral" (a type of copper sulfate CuSO derived from pyrites) to the mercury and salt-water (HO · NaCl) solution in order to catalyze the amalgamation reaction. Some historians assert that there were already sufficient copper sulfates in the local ores and that no additional magistral was needed, though others argue that while naturally occurring copper sulfates allowed for potential amalgamation sans magistral, the erratic results of this method made magistral a key component of the effective refinement of ore on a large scale. Regardless of whether or not Medina's contribution was entirely original, he promoted his process to local miners and was able to obtain a patent from the Viceroy of New Spain. As a result, he is generally credited with the invention of silver amalgamation in the form of the patio process.
The effectiveness of this method was such that when German experts arrived in America in the late 1700s to teach the newest amalgamation technology, they admitted they did not believe they could improve upon the American method in its context. Friedrich Sonneschmidt, a German refiner, stated: "It is not to be expected that there will ever be found a method by which all varieties of ore can be refined, having expenses lower than or even equal to those required by the patio beneficiation." The amalgamation was so efficient that a refiner could turn a profit even if the ores were poor enough to yield only 1.5 oz of silver per 100 lbs of original material. | 1 | Applied and Interdisciplinary Chemistry |
Dithiocarbamates are readily S-alkylated. Thus, methyl dimethyldithiocarbamate can be prepared by methylation of the dithiocarbamate:
:(CH)NCSNa + (CHO)SO → (CH)NC(S)SCH + Na[CHOSO]
Oxidation of dithiocarbamates gives the thiuram disulfide:
:2 RNCS → [RNC(S)S] + 2e
Thiuram disulfides react with Grignard reagents to give esters of dithiocarbamic acid:
:[RNC(S)S] + RMgX → RNC(S)SR + RNCSMgX
Dithiocarbamates react with transition metal salts to give a wide variety of transition metal dithiocarbamate complexes. | 0 | Theoretical and Fundamental Chemistry |
Radical theory is an obsolete scientific theory in chemistry describing the structure of organic compounds. The theory was pioneered by Justus von Liebig, Friedrich Wöhler and Auguste Laurent around 1830 and is not related to the modern understanding of free radicals. In this theory, organic compounds were thought to exist as combinations of radicals that could be exchanged in chemical reactions just as chemical elements could be interchanged in inorganic compounds. | 0 | Theoretical and Fundamental Chemistry |
The major benefits of ion semiconductor sequencing are rapid sequencing speed and low upfront and operating costs. This has been enabled by the avoidance of modified nucleotides and optical measurements.
Because the system records natural polymerase-mediated nucleotide incorporation events, sequencing can occur in real-time. In reality, the sequencing rate is limited by the cycling of substrate nucleotides through the system. Ion Torrent Systems Inc., the developer of the technology, claims that each incorporation measurement takes 4 seconds and each run takes about one hour, during which 100-200 nucleotides are sequenced. If the semiconductor chips are improved (as predicted by Moore’s law), the number of reads per chip (and therefore per run) should increase.
The cost of acquiring a pH-mediated sequencer from Ion Torrent Systems Inc. at time of launch was priced at around $50,000 USD, excluding sample preparation equipment and a server for data analysis. The cost per run is also significantly lower than that of alternative automated sequencing methods, at roughly $1,000. | 1 | Applied and Interdisciplinary Chemistry |
The Miller process is an industrial-scale chemical procedure used to refine gold to a high degree of purity (99.5%). It was patented by Francis Bowyer Miller in 1867. This chemical process involves blowing chlorine gas through molten, but (slightly) impure, gold. Nearly all metal contaminants react to form chlorides but gold does not at these high temperatures. The other metals volatilize or form a low density slag on top of the molten gold.
When all impurities have been removed from the gold (observable by a change in flame color) the gold is removed and processed in the manner required for sale or use. The resulting gold is 99.5% pure, but of lower purity than gold produced by the other common refining method, the Wohlwill process, which produces gold of up to 99.999% purity.
The Wohlwill process is commonly used for producing high-purity gold, such as in electronics work, where exacting standards of purity are required. When highest purity gold is not required, refiners use the Miller process due to its relative ease, quicker turnaround times, and because it does not tie up the large amount of gold in the form of chloroauric acid which the Wohlwill process permanently requires for the electrolyte. | 1 | Applied and Interdisciplinary Chemistry |
TOC is the first chemical analysis to be carried out on potential petroleum source rock in oil exploration. It is very important in detecting contaminants in drinking water, cooling water, water used in semiconductor manufacturing, and water for pharmaceutical use. Analysis may be made either as an online continuous measurement or a lab-based measurement.
TOC detection is an important measurement because of the effects it may have on the environment, human health, and manufacturing processes. TOC is a highly sensitive, non-specific measurement of all organics present in a sample. It, therefore, can be used to regulate the organic chemical discharge to the environment in a manufacturing plant. In addition, low TOC can confirm the absence of potentially harmful organic chemicals in water used to manufacture pharmaceutical products. TOC is also of interest in the field of potable water purification due to byproducts of disinfection. Inorganic carbon poses little to no threat. | 0 | Theoretical and Fundamental Chemistry |
Absinthin is a naturally produced triterpene lactone from the plant Artemisia absinthium (Wormwood). It constitutes one of the most bitter chemical agents responsible for absinthes distinct taste. The compound shows biological activity and has shown promise as an anti-inflammatory agent, and should not be confused with thujone, a neurotoxin also found in Artemisia absinthium'. | 0 | Theoretical and Fundamental Chemistry |
Party and play, or chemsex, is the consumption of drugs to facilitate sexual activity. Sociologically, both terms refer to a subculture of recreational drug users who engage in high-risk sexual activities under the influence of drugs within groups. The term PnP is commonly used by gay men and other men who have sex with men (MSM) in North America, while chemsex is more associated with the gay scene in Europe. The drug of choice is typically methamphetamine, known as tina or T, but other drugs are also used, such as mephedrone, GHB, GBL and alkyl nitrites (known as poppers). | 1 | Applied and Interdisciplinary Chemistry |
Originally developed for cleaning closed systems as described above, CIP has more recently been applied to groundwater source boreholes used for high end-uses such as natural mineral/spring waters, food production and carbonated soft drinks (CSD).
Boreholes that are open to the atmosphere are prone to a number of chemical and microbiological problems, so sources for high end-use are often sealed at the surface (headworks). An air filter is built into the headworks to permit the borehole to inhale and exhale when the water level rises and falls quickly (usually due to the pump being turned on and off) without drawing in airborne particles or contaminants (spores, molds, fungi, bacteria, etc.).
In addition, CIP systems can be built into the borehole headworks to permit the injection of cleaning solutions (such as sodium hypochlorite or other sanitizers) and the subsequent recirculation of the mix of these chemicals and the groundwater. This process cleans the borehole interior and equipment without any invasive maintenance being required. | 1 | Applied and Interdisciplinary Chemistry |
The presence of conserved moieties can affect how computer simulation models are constructed. Moiety-conserved cycles will reduce the number of differential equations required to solve a system. For example, a simple cycle has only one independent variable. The other variable can be computed using the difference between the total mass and the independent variable. The set of differential equations for the two-cycle is given by:
These can be reduced to one differential equation and one linear algebraic equation: | 1 | Applied and Interdisciplinary Chemistry |
Chemisorption is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate. New chemical bonds are generated at the adsorbent surface. Examples include macroscopic phenomena that can be very obvious, like corrosion, and subtler effects associated with heterogeneous catalysis, where the catalyst and reactants are in different phases. The strong interaction between the adsorbate and the substrate surface creates new types of electronic bonds.
In contrast with chemisorption is physisorption, which leaves the chemical species of the adsorbate and surface intact. It is conventionally accepted that the energetic threshold separating the binding energy of "physisorption" from that of "chemisorption" is about 0.5 eV per adsorbed species.
Due to specificity, the nature of chemisorption can greatly differ, depending on the chemical identity and the surface structural properties.
The bond between the adsorbate and adsorbent in chemisorption is either ionic or covalent. | 0 | Theoretical and Fundamental Chemistry |
With the excellent nature in biodegradation and biocompatibility, supramolecular polymers show great potential in the development of drug delivery, gene transfection and other biomedical applications.
: Multiple cellular stimuli could induce responses in supramolecular polymers. The dynamic molecular skeletons of supramolecular polymers can be depolymerized when exposing to the external stimuli like pH in vivo. On the basis of this property, supramolecular polymers are capable of being a drug carrier. Making use of hydrogen bonding between nucleobases to induce self-assemble into pH-sensitive spherical micelles.
: Effective and low-toxic nonviral cationic vectors are highly desired in the field of gene therapy. On account of the dynamic and stimuli-responsive properties, supramolecular polymers offer a cogent platform to construct vectors for gene transfection. By combining ferrocene dimer with β-cyclodextrin dimer, a redox-control supramolecular polymers system has been proposed as a vector. In COS-7 cells, this supramolecular polymersic vector can release enclosed DNA upon exposing to hydrogen peroxide and achieve gene transfection. | 0 | Theoretical and Fundamental Chemistry |
Pirkle's alcohol is an off-white, crystalline solid that is stable at room temperature when protected from light and oxygen. This chiral molecule is typically used, in nonracemic form, as a chiral shift reagent in nuclear magnetic resonance spectroscopy, in order to simultaneously determine absolute configuration and enantiomeric purity of other chiral molecules. The molecule is named after William H. Pirkle, Professor of Chemistry at the University of Illinois whose group reported its synthesis and its application as a chiral shift reagent. | 0 | Theoretical and Fundamental Chemistry |
Suppose that the reactions between carbon dioxide, hydrogen ions, bicarbonate and carbonate ions, all dissolved in water, are as follows:
Note that reaction is actually the combination of two elementary reactions:
: + H +
Assuming the mass action law applies to these two reactions, that water is abundant, and that the different chemical species are always well-mixed, their rate equations are
where denotes concentration, t is time, and K and k are appropriate proportionality constants for reaction , called respectively the forwards and reverse rate constants for this reaction. (Similarly K and k for reaction .)
, the concentrations are unchanging, hence the left hand sides of these equations are zero. Then, from the first of these four equations, the ratio of reaction s rate constants equals the ratio of its equilibrium concentrations, and this ratio, called K', is called the equilibrium constant for reaction , i.e.
where the subscript eq denotes that these are equilibrium concentrations.
Similarly, from the fourth equation for the equilibrium constant K for reaction ,
Rearranging gives
and rearranging , then substituting in , gives
The total concentration of dissolved inorganic carbon in the system is given by substituting in and :
Re-arranging this gives the equation for :
The equations for and are obtained by substituting this into and . | 0 | Theoretical and Fundamental Chemistry |
The second generation of mTOR inhibitors is known as ATP-competitive mTOR kinase inhibitors. mTORC1/mTORC2 dual inhibitors such as torin-1, torin-2 and vistusertib, are designed to compete with ATP in the catalytic site of mTOR. They inhibit all of the kinase-dependent functions of mTORC1 and mTORC2 and block the feedback activation of PI3K/AKT signaling, unlike rapalogs, which only target mTORC1. Development of these drugs has reached clinical trials, although some, such as vistusertib, have been discontinued. Like rapalogs, they decrease protein translation, attenuate cell cycle progression, and inhibit angiogenesis in many cancer cell lines and also in human cancer. In fact, they have been proven to be more potent than rapalogs.
Theoretically, the most important advantages of these mTOR inhibitors is the considerable decrease of AKT phosphorylation on mTORC2 blockade and in addition to a better inhibition on mTORC1. However, some drawbacks exist. Even though these compounds have been effective in rapamycin-insensitive cell lines, they have only shown limited success in KRAS driven tumors. This suggests that combinational therapy may be necessary for the treatment of these cancers. Another drawback is also their potential toxicity. These facts have raised concerns about the long term efficacy of these types of inhibitors.
The close interaction of mTOR with the PI3K pathway has also led to the development of mTOR/PI3K dual inhibitors. Compared with drugs that inhibit either mTORC1 or PI3K, these drugs have the benefit of inhibiting mTORC1, mTORC2, and all the catalytic isoforms of PI3K. Targeting both kinases at the same time reduces the upregulation of PI3K, which is typically produced with an inhibition on mTORC1. The inhibition of the PI3K/mTOR pathway has been shown to potently block proliferation by inducing G1 arrest in different tumor cell lines. Strong induction of apoptosis and autophagy has also been seen. Despite good promising results, there are preclinical evidence that some types of cancers may be insensitive to this dual inhibition. The dual PI3K/mTOR inhibitors are also likely to have increased toxicity. | 1 | Applied and Interdisciplinary Chemistry |
Biomolecular Adsorption Database (BAD) is a freely available online database with experimental protein adsorption data collected from the literature.
The database can be used for the selection of materials for microfluidic device fabrication and for the selection of optimum operating conditions of lab-on-a-chip devices. The amount of protein adsorbed to the surface can be predicted using neural networks-based prediction available at BAD. This prediction has been validated to be below 5% error for the overall data available in the BAD. Other parameters, such as the thickness of protein layers and the surface tension of protein-covered surfaces, can also be estimated. | 1 | Applied and Interdisciplinary Chemistry |
With the advance of nanoscale electrodes, the resolution of SEE has advanced from being able to detect single cells to detecting single molecules within cells. Nanoscale electrodes are small enough they can be inserted into the synapses between neurons, which can be used to detect neurotransmitter concentrations. If the electrode is thin enough, it can be inserted directly into a cell and used to detect concentrations of intracellular molecules, such as metabolites or even DNA. | 0 | Theoretical and Fundamental Chemistry |
For non-linear surface waves there is, in general, ambiguity in splitting the total motion into a wave part and a mean part. As a consequence, there is some freedom in choosing the phase speed (celerity) of the wave. identified two logical definitions of phase speed, known as Stokes's first and second definition of wave celerity:
#Stokess first definition of wave celerity has, for a pure wave motion, the mean value of the horizontal Eulerian flow-velocity Ū at any location below trough level equal to zero. Due to the irrotationality of potential flow, together with the horizontal sea bed and periodicity the mean horizontal velocity, the mean horizontal velocity is a constant between bed and trough level. So in Stokes first definition the wave is considered from a frame of reference moving with the mean horizontal velocity Ū. This is an advantageous approach when the mean Eulerian flow velocity Ū' is known, e.g. from measurements.
#Stokess second definition of wave celerity is for a frame of reference where the mean horizontal mass transport of the wave motion equal to zero. This is different from the first definition due to the mass transport in the splash zone, i.e. between the trough and crest level, in the wave propagation direction. This wave-induced mass transport is caused by the positive correlation between surface elevation and horizontal velocity. In the reference frame for Stokess second definition, the wave-induced mass transport is compensated by an opposing undertow (so Ū < 0 for waves propagating in the positive x-direction). This is the logical definition for waves generated in a wave flume in the laboratory, or waves moving perpendicular towards a beach.
As pointed out by Michael E. McIntyre, the mean horizontal mass transport will be (near) zero for a wave group approaching into still water, with also in deep water the mass transport caused by the waves balanced by an opposite mass transport in a return flow (undertow). This is due to the fact that otherwise a large mean force will be needed to accelerate the body of water into which the wave group is propagating. | 1 | Applied and Interdisciplinary Chemistry |
Magnesium alloys. A putative flux for soldering these alloys at low temperature is molten acetamide. Acetamide dissolves surface oxides on both aluminium and magnesium; promising experiments were done with its use as a flux for a tin-indium solder on magnesium. | 1 | Applied and Interdisciplinary Chemistry |
Previously, protein markers had been developed using a variety of whole proteins. The development of a kit including a molecular-weight size marker based on protein fragments began in 1993. This protein marker, composed of 49 different amino acid sequences, included multidomain proteins, and allowed for the analysis of proteins cleaved at different sites.
Current technique improvements in protein markers involve the use of auto-development. The first auto-developed regularly-weight protein marker was invented in 2012. | 1 | Applied and Interdisciplinary Chemistry |
Commonly aircraft are propelled by airbreathing jet engines. Most airbreathing jet engines that are in use are turbofan jet engines, which give good efficiency at speeds just below the speed of sound. | 1 | Applied and Interdisciplinary Chemistry |
The implementation differintegral calculation using fast fourier transform has certain benefits because it is easily combined with low pass quadratic filtering methods. This is very useful when cyclic voltammograms are recorded in high resistivity solvents like tetrahydrofuran or toluene, where feedback oscillations are a frequent problem. | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, p represents the partial pressure of a gas required to achieve 50% saturation of a particular proteins binding sites. Values of p are negatively correlated with substrate affinity; lower values correspond to higher affinity and vice versa. The term is analogous to the Michaelis–Menten constant (K'), which identifies the concentration of substrate required for an enzyme to achieve 50% of its maximum reaction velocity.
The concept of p is derived from considering the fractional saturation of a protein by a gas. Imagine myoglobin, a protein which is able to bind a single molecule of oxygen, as per the reversible reaction below, whose equilibrium constant K (which is also a dissociation constant, since it describes a reversible association-dissociation event) is equal to the product of the concentrations (at equilibrium) of free myoglobin and free oxygen, divided by the concentration of myoglobin-oxygen complex.
The fractional saturation Y of the myoglobin is what proportion of the total myoglobin concentration is made up of oxygen-bound myoglobin, which can be rearranged as the concentration of free oxygen over the sum of that concentration and the dissociation constant K. Since diatomic oxygen is a gas, its concentration in solution can be thought of as a partial pressure.
From defining the p as the partial pressure at which the fractional saturation is 50%, we can deduce that it is in fact equal to the dissociation constant K.
For example, myoglobins p for O is 130 pascals while the P for adult hemoglobin is 3.5 kPa. Thus, when O partial pressure is low, hemoglobin-bound O is more readily transferred to myoglobin. Myoglobin, found in high concentrations in muscle tissue, can then transfer the oxygen to muscle tissue muscle fibers, where it will be used in the generation of energy to fuel muscle contraction. Another example is that of human fetal hemoglobin, which has a higher affinity (lower P') than adult hemoglobin, and therefore allows uptake of oxygen across the placental diffusion barrier. | 1 | Applied and Interdisciplinary Chemistry |
Another criticism of entropic gravity is that entropic processes should, as critics argue, break quantum coherence. There is no theoretical framework quantitatively describing the strength of such decoherence effects, though. The temperature of the gravitational field in earth gravity well is very small (on the order of 10K).
Experiments with ultra-cold neutrons in the gravitational field of Earth are claimed to show that neutrons lie on discrete levels exactly as predicted by the Schrödinger equation considering the gravitation to be a conservative potential field without any decoherent factors. Archil Kobakhidze argues that this result disproves entropic gravity, while Chaichian et al. suggest a potential loophole in the argument in weak gravitational fields such as those affecting Earth-bound experiments. | 0 | Theoretical and Fundamental Chemistry |
Left-hand traffic (LHT) and right-hand traffic (RHT) are the practices, in bidirectional traffic, of keeping to the left side and to the right side of the road, respectively. They are fundamental to traffic flow, and are sometimes called the rule of the road. The terms right- and left-hand drive refer to the position of the driver and the steering wheel in the vehicle and are, in automobiles, the reverse of the terms right- and left-hand traffic. The rule also includes where on the road a vehicle is to be driven, if there is room for more than one vehicle in the one direction, and the side on which the vehicle in the rear overtakes the one in the front. For example, a driver in an LHT country would typically overtake on the right of the vehicle being overtaken.
RHT is used in 165 countries and territories, mainly in the Americas, Continental Europe, northern Africa and mainland Asia (except South Asia), while 75 countries use LHT, which account for about a sixth of the worlds land area, a quarter of its roads, and about a third of its population. In 1919, 104 of the worlds territories were LHT and an equal number were RHT. Between 1919 and 1986, 34 of the LHT territories switched to RHT.
Many of the countries using LHT were part of the British Empire, while others, including Indonesia, Japan, Nepal, Bhutan, Macao, Thailand, Mozambique, Suriname, United States Virgin Islands, Sweden and Iceland (which use RHT since September 1967 and late May 1968 respectively), were not. Most of the countries that were part of the French colonial empire adopted RHT.
Historical switches of traffic handedness have often been motivated by factors such as changes in political administration, a desire for uniformity within a country or with neighboring states, or availability and affordability of vehicles.
In LHT, traffic keeps left and cars usually have the steering wheel on the right (RHD: right-hand drive) and roundabouts circulate clockwise. RHT is the opposite: traffic keeps right, the driver usually sits on the left side of the car (LHD: left-hand drive), and roundabouts circulate counterclockwise.
In most countries, rail traffic follows the handedness of the roads; but many of the countries that switched road traffic from LHT to RHT did not switch their trains. Boat traffic on rivers is RHT, regardless of location. Boats are traditionally piloted from the starboard side to facilitate priority to the right. | 0 | Theoretical and Fundamental Chemistry |
In general terms, different plant species are adapted to soils of different pH ranges. For many species, the suitable soil pH range is fairly well known. Online databases of plant characteristics, such as USDA PLANTS and Plants for a Future can be used to look up the suitable soil pH range of a wide range of plants. Documents like Ellenbergs indicator values for British plants' can also be consulted.
However, a plant may be intolerant of a particular pH in some soils as a result of a particular mechanism, and that mechanism may not apply in other soils. For example, a soil low in molybdenum may not be suitable for soybean plants at pH 5.5, but soils with sufficient molybdenum allow optimal growth at that pH. Similarly, some calcifuges (plants intolerant of high-pH soils) can tolerate calcareous soils if sufficient phosphorus is supplied. Another confounding factor is that different varieties of the same species often have different suitable soil pH ranges. Plant breeders can use this to breed varieties that can tolerate conditions that are otherwise considered unsuitable for that species – examples are projects to breed aluminium-tolerant and manganese-tolerant varieties of cereal crops for food production in strongly acidic soils.
The table below gives suitable soil pH ranges for some widely cultivated plants as found in the USDA PLANTS Database. Some species (like Pinus radiata and Opuntia ficus-indica) tolerate only a narrow range in soil pH, whereas others (such as Vetiveria zizanioides) tolerate a very wide pH range.
In natural or near-natural plant communities, the various pH preferences of plant species (or ecotypes) at least partly determine the composition and biodiversity of vegetation. While both very low and very high pH values are detrimental to plant growth, there is an increasing trend of plant biodiversity along the range from extremely acidic (pH 3.5) to strongly alkaline (pH 9) soils, i.e. there are more calcicole than calcifuge species, at least in terrestrial environments. Although widely reported and supported by experimental results, the observed increase of plant species richness with pH is still in need of a clearcut explanation. Competitive exclusion between plant species with overlapping pH ranges most probably contributes to the observed shifts of vegetation composition along pH gradients. | 0 | Theoretical and Fundamental Chemistry |
Cardiovascular medical devices are implanted in cases where the heart, its valves, and the rest of the circulatory system is in disorder. They are used to treat conditions such as heart failure, cardiac arrhythmia, ventricular tachycardia, valvular heart disease, angina pectoris, and atherosclerosis. Examples include the artificial heart, artificial heart valve, implantable cardioverter-defibrillator, artificial cardiac pacemaker, and coronary stent. | 1 | Applied and Interdisciplinary Chemistry |
P42 MAP kinase -p53 - pancreatic polypeptide - parathyroid hormone receptor - partial pressure - passive transport - Pauling scale - PCR - peptide - peptide bond - peptide elongation factor - peptide elongation factor tu - peptide fragment - peptide initiation factor - peptide receptor - peptide termination factor - peripheral membrane protein - pesticide - pH - phage display - pharmaceutical - pharmacist - pharmacology - phenol - phenotype - phenyl group - phenylalanine - Philadelphia chromosome - phospholipid - phospholipid bilayer - phosphopeptide - phosphoprotein - phosphorus - phosphorylation - phosphoserine - phosphothreonine - phosphotyrosine - photobiology - photolysis - photophosphorylation - photoreceptor - photorespiration - photosynthesis - photosystem I - photosystem II - phototransduction - phylogenetics - phylogeny - physical chemistry - physiology - phytohaemagglutinin - pituitary hormone receptor - pituitary hormone-regulating hormone receptor - plant protein - plasma membrane - plasmid - plasmin - plasminogen - platelet glycoprotein GPIb-IX complex - platelet membrane glycoprotein - platelet-derived growth factor - platelet-derived growth factor receptor - polymer - polymerase chain reaction - polymerization - polymyxin - polymyxin B - polyomavirus transforming antigen - polypeptide - polysaccharide - porphyrin - Posttranslational modification - potassium - potassium channel - potential energy - pregnancy proteins - primary nutritional groups - primary structure - primer - prion - progesterone receptor - prokaryote - prolactin - prolactin receptor - proline - promoter - prostaglandin e receptor - prostaglandin receptor - protein - protein biosynthesis - Protein Data Bank - protein design - protein expression - protein folding - protein isoform - protein nuclear magnetic resonance spectroscopy - protein P16 - protein P34cdc2 - protein precursor - protein structure prediction - protein subunit - protein synthesis - protein targeting - protein translocation - protein-tyrosine kinase - protein-tyrosine-phosphatase - proteinoid - proteomics - protirelin - proto-oncogene - proto-oncogene proteins - proto-oncogene protein C-kit - proto-oncogene proteins c-abl - proto-oncogene proteins c-bcl-2 - Proto-oncogene proteins c-fos - proto-oncogene proteins c-jun - proto-oncogene proteins c-mo - proto-oncogene proteins c-myc - proto-oncogene proteins c-raf - proton - proton pump - protozoan proteins - purine - purinergic P1 receptor - purinergic P2 receptor - purinergic receptor - pyridine - pyrimidine - pyruvate - pyruvate oxidation | 1 | Applied and Interdisciplinary Chemistry |
Gating also includes activation and inactivation by second messengers from the inside of the cell membrane – rather than from outside the cell, as in the case for ligands.
*Some potassium channels:
**Inward-rectifier potassium channels: These channels allow potassium ions to flow into the cell in an "inwardly rectifying" manner: potassium flows more efficiently into than out of the cell. This family is composed of 15 official and 1 unofficial member and is further subdivided into 7 subfamilies based on homology. These channels are affected by intracellular ATP, PIP, and G-protein βγ subunits. They are involved in important physiological processes such as pacemaker activity in the heart, insulin release, and potassium uptake in glial cells. They contain only two transmembrane segments, corresponding to the core pore-forming segments of the K and K channels. Their α subunits form tetramers.
**Calcium-activated potassium channels: This family of channels is activated by intracellular Ca and contains 8 members.
**Tandem pore domain potassium channel: This family of 15 members form what are known as leak channels, and they display Goldman-Hodgkin-Katz (open) rectification. Contrary to their common name of Two-pore-domain potassium channels, these channels have only one pore but two pore domains per subunit.
*Two-pore channels include ligand-gated and voltage-gated cation channels, so-named because they contain two pore-forming subunits. As their name suggests, they have two pores.
*Light-gated channels like channelrhodopsin are directly opened by photons.
*Mechanosensitive ion channels open under the influence of stretch, pressure, shear, and displacement.
*Cyclic nucleotide-gated channels: This superfamily of channels contains two families: the cyclic nucleotide-gated (CNG) channels and the hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels. This grouping is functional rather than evolutionary.
**Cyclic nucleotide-gated channels: This family of channels is characterized by activation by either intracellular cAMP or cGMP. These channels are primarily permeable to monovalent cations such as K and Na. They are also permeable to Ca, though it acts to close them. There are 6 members of this family, which is divided into 2 subfamilies.
**Hyperpolarization-activated cyclic nucleotide-gated channels
*Temperature-gated channels: Members of the transient receptor potential ion channel superfamily, such as TRPV1 or TRPM8, are opened either by hot or cold temperatures. | 1 | Applied and Interdisciplinary Chemistry |
Photografting is a technique used in the study of polymers and more in specific polymeric biomaterials. Technically speaking it is the covalent incorporation of functional additives to a polymer matrix or polymer surface using a light-induced mechanism. It is an important technique for the modification of biomaterial surfaces. For example, by graft with polar monomers, the inert polymer surface can become more biocompatible. | 0 | Theoretical and Fundamental Chemistry |
The electrochemical regeneration of activated carbon based adsorbents involves the removal of molecules adsorbed onto the surface of the adsorbent with the use of an electric current in an electrochemical cell restoring the carbon's adsorptive capacity. Electrochemical regeneration represents an alternative to thermal regeneration commonly used in waste water treatment applications. Common adsorbents include powdered activated carbon (PAC), granular activated carbon (GAC) and activated carbon fibre. | 0 | Theoretical and Fundamental Chemistry |
Presence of un-phosphorylated pRb drives cell cycle exit and maintains senescence. At the end of mitosis, PP1 dephosphorylates hyper-phosphorylated pRb directly to its un-phosphorylated state. Furthermore, when cycling C2C12 myoblast cells differentiated (by being placed into a differentiation medium), only un-phosphorylated pRb was present. Additionally, these cells had a markedly decreased growth rate and concentration of DNA replication factors (suggesting G0 arrest).
This function of un-phosphorylated pRb gives rise to a hypothesis for the lack of cell cycle control in cancerous cells: Deregulation of Cyclin D - Cdk 4/6 phosphorylates un-phosphorylated pRb in senescent cells to mono-phosphorylated pRb, causing them to enter G1. The mechanism of the switch for Cyclin E activation is not known, but one hypothesis is that it is a metabolic sensor. Mono-phosphorylated pRb induces an increase in metabolism, so the accumulation of mono-phosphorylated pRb in previously G0 cells then causes hyper-phosphorylation and mitotic entry. Since any un-phosphorylated pRb is immediately phosphorylated, the cell is then unable to exit the cell cycle, resulting in continuous division.
DNA damage to G0 cells activates Cyclin D - Cdk 4/6, resulting in mono-phosphorylation of un-phosphorylated pRb. Then, active mono-phosphorylated pRb causes repression of E2F-targeted genes specifically. Therefore, mono-phosphorylated pRb is thought to play an active role in DNA damage response, so that E2F gene repression occurs until the damage is fixed and the cell can pass the restriction point. As a side note, the discovery that damages causes Cyclin D - Cdk 4/6 activation even in G0 cells should be kept in mind when patients are treated with both DNA damaging chemotherapy and Cyclin D - Cdk 4/6 inhibitors. | 1 | Applied and Interdisciplinary Chemistry |
Bioavailability, or the amount of a substance that is physiochemically accessible to microorganisms is a key factor in the efficient biodegradation of pollutants. OLoughlin et al. (2000) showed that, with the exception of kaolinite clay, most soil clays and cation exchange resins attenuated biodegradation of 2-picoline by Arthrobacter' sp. strain R1, as a result of adsorption of the substrate to the clays. Chemotaxis, or the directed movement of motile organisms towards or away from chemicals in the environment is an important physiological response that may contribute to effective catabolism of molecules in the environment. In addition, mechanisms for the intracellular accumulation of aromatic molecules via various transport mechanisms are also important. | 1 | Applied and Interdisciplinary Chemistry |
Either copper powder or copper salts can be used very generally for intramolecular reactions of diazocarbonyl compounds. This section describes the different types of diazocarbonyl compounds that may undergo intramolecular reactions in the presence of copper. Note that for intermolecular reactions of diazocarbonyl compounds, the use of rhodium catalysts is preferred.
Diazoketones containing pendant double bonds undergo cyclopropanation in the presence of copper. The key step in one synthesis of barbaralone is the selective intramolecular cyclopropanation of a cycloheptatriene.
α,β-Cyclopropyl ketones may act as masked α,β-unsaturated ketones. In one example, intramolecular participation of an aryl group leads to the formation of a polycyclic ring system with complete diastereoselectivity.
α-Diazoesters are not as efficient as diazoketones at intramolecular cyclizations in some cases because of the propensity of esters to exist in the trans conformation about the carbon–oxygen single bond. However, intramolecular reactions of diazoesters do take place—in the example in equation (5), copper(II) sulfate is used to effect the formation of the cyclopropyl ester shown.
In the presence of a catalytic amount of acid, diazomethyl ketone substrates containing a pendant double bond or aryl group undergo cyclization. The mechanism of this process most likely involves protonation of the diazocarbonyl group to form a diazonium salt, followed by displacement of nitrogen by the unsaturated functionality and deprotonation. In the example below, demethylation affords a quinone.
When no unsaturated functionality is present in the substrate, C-H insertion may occur. C-H Insertion is particularly facile in conformationally restricted substrates in which a C-H bond is held in close proximity to the diazo group.
Transannular insertions, which form fused carbocyclic products, have also been observed. Yields are often low for these reactions, however.
Insertion into carbon–carbon bonds has been observed. In the example in equation (9), the methyl group is held in close proximity to the diazo group, facilitating C-C insertion. | 0 | Theoretical and Fundamental Chemistry |
Paired receptors are pairs or clusters of receptor proteins that bind to extracellular ligands but have opposing activating and inhibitory signaling effects. Traditionally, paired receptors are defined as homologous pairs with similar extracellular domains and different cytoplasmic regions, whose genes are located together in the genome as part of the same gene cluster and which evolved through gene duplication. Homologous paired receptors often, but not always, have a shared ligand in common. More broadly, pairs of receptors have been identified that exhibit paired functional behavior - responding to a shared ligand with opposing intracellular signals - but are not closely homologous or co-located in the genome. Paired receptors are highly expressed in the cells of the immune system, especially natural killer (NK) and myeloid cells, and are involved in immune regulation. | 1 | Applied and Interdisciplinary Chemistry |
Hafnium or zirconium added to niobium–tin increases the maximum current density in a magnetic field. This may allow it to be used at 16 tesla for CERN's planned Future Circular Collider. | 1 | Applied and Interdisciplinary Chemistry |
Aside from the aforementioned published results of his analytical round robin and his lead and oxygen isotope studies in the early 1970s, the 1970s saw Brill publish comparatively little, perhaps due to his post as director at The Corning Museum of Glass. Those publications he did pen are largely concerned with the development of lead isotope analysis and are listed in the further reading section. Alas, before Brill could be named Director, however, the museum was to be blighted by an enormous flood, ‘possibly the greatest single catastrophe borne by an American museum’ according to Buechner, Brill's successor in 1976 (1977, 7). | 0 | Theoretical and Fundamental Chemistry |
Lipids are a diverse and ubiquitous group of compounds which have many key biological functions, such as acting as structural components of cell membranes, serving as energy storage sources and participating in signaling pathways. Lipids may be broadly defined as hydrophobic or amphipathic small molecules that originate entirely or in part from two distinct types of biochemical subunits or "building blocks": ketoacyl and isoprene groups. The
huge structural diversity found in lipids arises from the biosynthesis of various combinations of these building blocks. For example, glycerophospholipids are composed of a glycerol backbone linked to one of approximately 10 possible headgroups and also to 2 fatty acyl/alkyl chains, which in turn may have 30 or more different molecular structures. In practice, not all possible permutations are detected experimentally, due to chain preferences depending on the cell type and also to detection limits - nevertheless several hundred distinct glycerophospholipid molecular species have been detected in mammalian cells.
Plant chloroplast thylakoid membranes however, have unique lipid composition as they are deficient in phospholipids. Also, their largest constituent, monogalactosyl diglyceride or MGDG, does not form aqueous bilayers. Nevertheless, dynamic studies reveal a normal lipid bilayer organisation in thylakoid membranes. | 1 | Applied and Interdisciplinary Chemistry |
Local exhaust ventilation addresses the issue of avoiding the contamination of indoor air by specific high-emission sources by capturing airborne contaminants before they are spread into the environment. This can include water vapor control, lavatory effluent control, solvent vapors from industrial processes, and dust from wood- and metal-working machinery. Air can be exhausted through pressurized hoods or the use of fans and pressurizing a specific area.<br />A local exhaust system is composed of 5 basic parts
# A hood that captures the contaminant at its source
# Ducts for transporting the air
# An air-cleaning device that removes/minimizes the contaminant
# A fan that moves the air through the system
# An exhaust stack through which the contaminated air is discharged
In the UK, the use of LEV systems has regulations set out by the Health and Safety Executive (HSE) which are referred to as the Control of Substances Hazardous to Health (CoSHH). Under CoSHH, legislation is set to protect users of LEV systems by ensuring that all equipment is tested at least every fourteen months to ensure the LEV systems are performing adequately. All parts of the system must be visually inspected and thoroughly tested and where any parts are found to be defective, the inspector must issue a red label to identify the defective part and the issue.
The owner of the LEV system must then have the defective parts repaired or replaced before the system can be used. | 1 | Applied and Interdisciplinary Chemistry |
Nanocomposite hydrogels that are enforced with carbon-based nanomaterials are mechanically tough and electrically conducive, which make them suitable for use in biomedicine, tissue engineering, drug delivery, biosensing, etc. The electrical conducting property of these hydrogels allow them to mimic the characteristic of nerve, muscle, and cardiac tissues. However, even though these nanocomposite hydrogels demonstrate some functions of human tissue in lab environments, more research is needed to ensure their utility as tissue replacement. | 0 | Theoretical and Fundamental Chemistry |
Along with other NSAIDs, ibuprofen has been associated with the onset of bullous pemphigoid or pemphigoid-like blistering. As with other NSAIDs, ibuprofen has been reported to be a photosensitising agent, but it is considered a weak photosensitising agent compared to other members of the 2-arylpropionic acid class. Like other NSAIDs, ibuprofen is an extremely rare cause of the autoimmune disease Stevens–Johnson syndrome (SJS). Ibuprofen is also an extremely rare cause of toxic epidermal necrolysis. | 0 | Theoretical and Fundamental Chemistry |
* Cabaniss, Steve, Greg Madey, Patricia Maurice, Yingping Zhou, Laura Leff, Ola Olapade, Bob Wetzel, Jerry Leenheer, and Bob Wershaw, comps. Stochastic Synthesis of Natural Organic Matter. UNM, ND, KSU, UNC, USGS. 22 Apr. 2007.
* Cho, Min, Hyenmi Chung, and Jeyong Yoon. "Disinfection of Water Containing Natural Organic Matter by Using Ozone-Initiated Radical Reactions." Abstract. Applied and Environmental Microbiology Vol. 69 No.4 (2003): 2284–2291.
* Fortner, John D., Joseph B. Hughes, Jae-Hong Kim, and Hoon Hyung. "Natural Organic Matter Stabilizes Carbon Nanotubes in the Aqueous Phase." Abstract. Environmental Science & Technology Vol. 41 No. 1 (2007): 179–184.
* "Researchers Study Role of Natural Organic Matter in Environment." Science Daily 20 Dec. 2006. 22 Apr. 2007 <https://www.sciencedaily.com/releases/2006/12/061211221222.htm>.
* Senesi, Nicola, Baoshan Xing, and P.m. Huang. Biophysico-Chemical Processes Involving Natural Nonliving Organic Matter in Environmental Systems. New York: IUPAC, 2006.
* "Table 1: Surface Area, Volume, and Average Depth of Oceans and Seas." Encyclopædia Britannica.
* "Topic Snapshot: Natural Organic Material." American Water Works Association Research Foundation. 2007. 22 Apr. 2007 <https://web.archive.org/web/20070928102105/http://www.awwarf.org/research/TopicsAndProjects/topicSnapShot.aspx?Topic=Organic>.
* United States of America. United States Geological Survey. Earth's Water Distribution. 10 May 2007. <http://ga.water.usgs.gov/edu/waterdistribution.html>
* Water Sheds: Organic Matter. North Carolina State University. 1 May 2007 <http://www.water.ncsu.edu/watershedss/info/norganics.html >. | 0 | Theoretical and Fundamental Chemistry |
The genes provided in this section are only a small number of the vast amount of oscillating genes found in the world. These genes were selected because they were determined to be the some of most important genes in regulating the circadian rhythm of their respective classification. | 1 | Applied and Interdisciplinary Chemistry |
Salting out (also known as salt-induced precipitation, salt fractionation, anti-solvent crystallization, precipitation crystallization, or drowning out) is a purification technique that utilizes the reduced solubility of certain molecules in a solution of very high ionic strength. Salting out is typically used to precipitate large biomolecules, such as proteins or DNA. Because the salt concentration needed for a given protein to precipitate out of the solution differs from protein to protein, a specific salt concentration can be used to precipitate a target protein. This process is also used to concentrate dilute solutions of proteins. Dialysis can be used to remove the salt if needed. | 0 | Theoretical and Fundamental Chemistry |
Butyrates effects on the immune system are mediated through the inhibition of class I histone deacetylases and activation of its G-protein coupled receptor targets: Hydroxycarboxylic acid receptor 2| (GPR109A), FFAR2 (GPR43), and FFAR3 (GPR41). Among the short-chain fatty acids, butyrate is the most potent promoter of intestinal regulatory T cells in vitro' and the only one among the group that is an ligand. It has been shown to be a critical mediator of the colonic inflammatory response. It possesses both preventive and therapeutic potential to counteract inflammation-mediated ulcerative colitis and colorectal cancer.
Butyrate has established antimicrobial properties in humans that are mediated through the antimicrobial peptide LL-37, which it induces via HDAC inhibition on histone H3. In vitro, butyrate increases gene expression of FOXP3 (the transcription regulator for ) and promotes colonic regulatory T cells (Tregs) through the inhibition of class I histone deacetylases; through these actions, it increases the expression of interleukin 10, an anti-inflammatory cytokine. Butyrate also suppresses colonic inflammation by inhibiting the IFN-γ–STAT1 signaling pathways, which is mediated partially through histone deacetylase inhibition. While transient IFN-γ signaling is generally associated with normal host immune response, chronic IFN-γ signaling is often associated with chronic inflammation. It has been shown that butyrate inhibits activity of HDAC1 that is bound to the Fas gene promoter in T cells, resulting in hyperacetylation of the Fas promoter and up-regulation of Fas receptor on the T-cell surface.
Similar to other agonists studied, butyrate also produces marked anti-inflammatory effects in a variety of tissues, including the brain, gastrointestinal tract, skin, and vascular tissue. Butyrate binding at FFAR3 induces neuropeptide Y release and promotes the functional homeostasis of colonic mucosa and the enteric immune system. | 1 | Applied and Interdisciplinary Chemistry |
In July 2012, the US Food and Drug Administration (FDA) approved ethyl eicosapentaenoic acid (E-EPA) for severe hypertriglyceridemia as an adjunct to dietary measures; Amarin Corporation had developed the drug. Amarin Corporation challenged the FDA's authority to limit its ability to market the drug for off-label use and won its case on appeal in 2012, changing the way the FDA regulates the marketing of medication.
Ethyl eicosapentaenoic acid (E-EPA) was the second fish-oil drug to be approved, after omega-3-acid ethyl esters (GlaxoSmithKline's Lovaza, which was approved in 2004.) Initial sales were not as robust as Amarin had hoped. The labels for the two drugs were similar, but doctors prescribed Lovaza for people who had triglycerides lower than 500 mg/dL based on some clinical evidence. Amarin wanted to actively market E-EPA for that population as well which would have greatly expanded its revenue and applied to the FDA for permission to do so in 2013, which the FDA denied. In response, in May 2015 Amarin sued the FDA for infringing its First Amendment rights, and in August 2015, a judge ruled that the FDA could not "prohibit the truthful promotion of a drug for unapproved uses because doing so would violate the protection of free speech." The ruling left open the question of what the FDA would allow Amarin to say about E-EPA, and in March 2016 the FDA and Amarin agreed that Amarin would submit specific marketing material to the FDA for the FDA to review (as is usual for prescription medications). If the parties disagreed on whether the material was truthful, they would seek a judge to mediate.
In December 2019, the FDA approved the use of icosapent ethyl as an adjunctive (secondary) therapy to reduce the risk of cardiovascular events among adults with elevated triglyceride levels (a type of fat in the blood) of 150 milligrams per deciliter or higher. People must also have either established cardiovascular disease alone or diabetes along with two or more additional risk factors for cardiovascular disease.
Icosapent ethyl is the first FDA approved drug to reduce cardiovascular risk among people with elevated triglyceride levels as an add-on to maximally tolerated statin therapy.
The efficacy and safety of icosapent ethyl were established in a study with 8,179 participants who were either 45 years and older with a documented history of coronary artery, cerebrovascular, carotid artery and peripheral artery disease or 50 years and older with diabetes and additional risk factors for cardiovascular disease. Participants who received icosapent ethyl were significantly less likely to experience a cardiovascular event, such as a stroke or heart attack.
In clinical trials, icosapent ethyl was associated with an increased risk of atrial fibrillation or atrial flutter (irregular heart rhythms) requiring hospitalization. The incidence of atrial fibrillation was greater among participants with a history of atrial fibrillation or atrial flutter. Icosapent ethyl was also associated with an increased risk of bleeding events. The incidence of bleeding was higher among participants who were also taking other medications that increase the risk of bleeding, such as aspirin, clopidogrel or warfarin at the same time. | 1 | Applied and Interdisciplinary Chemistry |
An V1-morph is an organism that changes in shape during growth such that its surface area is proportional to its volume. In most cases both volume and surface area are proportional to length
The reason the concept is important in the context of the Dynamic Energy Budget theory is that food (substrate) uptake is proportional to surface area, and maintenance to volume. The surface area that is of importance is that part that is involved in substrate uptake. Since uptake is proportional to maintenance for V1-morphs, there is no size control, and an organism grows exponentially at constant food (substrate) availability.
Filaments, such as fungi that form hyphae growing in length, but not in diameter, are examples of V1-morphs. Sheets that extend, but do not change in thickness, like some colonial bacteria and algae, are another example.
An important property of V1-morphs is that the distinction between the individual and the population level disappears; a single long filament grows as fast as many small ones of the same diameter and the same total length. | 1 | Applied and Interdisciplinary Chemistry |
In the first step, the protein of interest (POI) is cross-linked with the DNA site it binds to in an in vitro environment. Usually this is done by a gentle formaldehyde fixation that is reversible with heat.
Then, the cells are lysed and the DNA is sheared by sonication or using micrococcal nuclease. This results in double-stranded chunks of DNA fragments, normally 1 kb or less in length. Those that were cross-linked to the POI form a POI-DNA complex.
In the next step, only these complexes are filtered out of the set of DNA fragments, using an antibody specific to the POI. The antibodies may be attached to a solid surface, may have a magnetic bead, or some other physical property that allows separation of cross-linked complexes and unbound fragments. This procedure is essentially an immunoprecipitation (IP) of the protein. This can be done either by using a tagged protein with an antibody against the tag (ex. FLAG, HA, c-myc) or with an antibody to the native protein.
The cross-linking of POI-DNA complexes is reversed (usually by heating) and the DNA strands are purified. For the rest of the workflow, the POI is no longer necessary.
After an amplification and denaturation step, the single-stranded DNA fragments are labeled with a fluorescent tag such as Cy5 or Alexa 647.
Finally, the fragments are poured over the surface of the DNA microarray, which is spotted with short, single-stranded sequences that cover the genomic portion of interest. Whenever a labeled fragment "finds" a complementary fragment on the array, they will hybridize and form again a double-stranded DNA fragment. | 1 | Applied and Interdisciplinary Chemistry |
Aerated lagoons are a low technology suspended-growth method of secondary treatment using motor-driven aerators floating on the water surface to increase atmospheric oxygen transfer to the lagoon and to mix the lagoon contents. The floating surface aerators are typically rated to deliver the amount of air equivalent to 1.8 to 2.7 kg O/kW·h. Aerated lagoons provide less effective mixing than conventional activated sludge systems and do not achieve the same performance level. The basins may range in depth from 1.5 to 5.0 metres. Surface-aerated basins achieve 80 to 90 percent removal of BOD with retention times of 1 to 10 days. Many small municipal sewage systems in the United States (1 million gal./day or less) use aerated lagoons. | 1 | Applied and Interdisciplinary Chemistry |
Three of Davys paintings from around 1796 have been donated to the Penlee House museum at Penzance. One is of the view from above Gulval showing the church, Mounts Bay and the Mount, while the other two depict Loch Lomond in Scotland. | 1 | Applied and Interdisciplinary Chemistry |
There are two types of carbon monoxide dehydrogenase: one contains iron and molybdenum, the other contains iron and nickel. Parallels and differences in catalytic strategies have been reviewed.
Pb (lead) can replace Ca (calcium) as, for example, with calmodulin or Zn (zinc) as with metallocarboxypeptidases
Some other metalloenzymes are given in the following table, according to the metal involved. | 1 | Applied and Interdisciplinary Chemistry |
At higher temperatures RuBisCO is less able to discriminate between and . This is because the enediol intermediate is less stable. Increasing temperatures also lower the solubility of , thus lowering the concentration of relative to in the chloroplast. | 0 | Theoretical and Fundamental Chemistry |
One DNA or RNA molecule differs from another primarily in the sequence of nucleotides. Nucleotide sequences are of great importance in biology since they carry the ultimate instructions that encode all biological molecules, molecular assemblies, subcellular and cellular structures, organs, and organisms, and directly enable cognition, memory, and behavior. Enormous efforts have gone into the development of experimental methods to determine the nucleotide sequence of biological DNA and RNA molecules, and today hundreds of millions of nucleotides are sequenced daily at genome centers and smaller laboratories worldwide. In addition to maintaining the GenBank nucleic acid sequence database, the National Center for Biotechnology Information (NCBI) provides analysis and retrieval resources for the data in GenBank and other biological data made available through the NCBI web site. | 1 | Applied and Interdisciplinary Chemistry |
Usually unstable nuclides are clearly either "neutron rich" or "proton rich", with the former undergoing beta decay and the latter undergoing electron capture (or more rarely, due to the higher energy requirements, positron decay). However, in a few cases of odd-proton, odd-neutron radionuclides, it may be energetically favorable for the radionuclide to decay to an even-proton, even-neutron isobar either by undergoing beta-positive or beta-negative decay. An often-cited example is the single isotope (29 protons, 35 neutrons), which illustrates three types of beta decay in competition. Copper-64 has a half-life of about 12.7 hours. This isotope has one unpaired proton and one unpaired neutron, so either the proton or the neutron can decay. This particular nuclide (though not all nuclides in this situation) is almost equally likely to decay through proton decay by positron emission () or electron capture () to , as it is through neutron decay by electron emission () to . | 0 | Theoretical and Fundamental Chemistry |
Paradoxically, dimensional analysis can be a useful tool even if all the parameters in the underlying theory are dimensionless, e.g., lattice models such as the Ising model can be used to study phase transitions and critical phenomena. Such models can be formulated in a purely dimensionless way. As we approach the critical point closer and closer, the distance over which the variables in the lattice model are correlated (the so-called correlation length, ) becomes larger and larger. Now, the correlation length is the relevant length scale related to critical phenomena, so one can, e.g., surmise on "dimensional grounds" that the non-analytical part of the free energy per lattice site should be , where is the dimension of the lattice.
It has been argued by some physicists, e.g., Michael J. Duff, that the laws of physics are inherently dimensionless. The fact that we have assigned incompatible dimensions to Length, Time and Mass is, according to this point of view, just a matter of convention, borne out of the fact that before the advent of modern physics, there was no way to relate mass, length, and time to each other. The three independent dimensionful constants: Speed of light|, Planck constant|, and Gravitational constant|, in the fundamental equations of physics must then be seen as mere conversion factors to convert Mass, Time and Length into each other.
Just as in the case of critical properties of lattice models, one can recover the results of dimensional analysis in the appropriate scaling limit; e.g., dimensional analysis in mechanics can be derived by reinserting the constants , , and (but we can now consider them to be dimensionless) and demanding that a nonsingular relation between quantities exists in the limit , and . In problems involving a gravitational field the latter limit should be taken such that the field stays finite. | 1 | Applied and Interdisciplinary Chemistry |
In this method, the glycosyl donor is protected at the C-2 position by an OAc group. The C-2-OAc protecting group is transformed into an enol ether by the Tebbe reagent (CpTi=CH), and then the glycosyl acceptor is tethered to the enol ether under acid-catalysed conditions to generate a mixed acetal. In a subsequent step, the β-mannoside is formed upon activation of the anomeric leaving group (Y), followed by work up. | 0 | Theoretical and Fundamental Chemistry |
The key labware or testing vessel of HTS is the microtiter plate, which is a small container, usually disposable and made of plastic, that features a grid of small, open divots called wells. In general, microplates for HTS have either 96, 192, 384, 1536, 3456 or 6144 wells. These are all multiples of 96, reflecting the original 96-well microplate with spaced wells of 8 x 12 with 9 mm spacing. Most of the wells contain test items, depending on the nature of the experiment. These could be different chemical compounds dissolved e.g. in an aqueous solution of dimethyl sulfoxide (DMSO). The wells could also contain cells or enzymes of some type. (The other wells may be empty or contain pure solvent or untreated samples, intended for use as experimental controls.)
A screening facility typically holds a library of stock plates, whose contents are carefully catalogued, and each of which may have been created by the lab or obtained from a commercial source. These stock plates themselves are not directly used in experiments; instead, separate assay plates are created as needed. An assay plate is simply a copy of a stock plate, created by pipetting a small amount of liquid (often measured in nanoliters) from the wells of a stock plate to the corresponding wells of a completely empty plate. | 1 | Applied and Interdisciplinary Chemistry |
The steam engine was applied to power blast air, overcoming a shortage of water power in areas where coal and iron ore were located. This was first done at Coalbrookdale where a steam engine replaced a horse-powered pump in 1742. Such engines were used to pump water to a reservoir above the furnace. The first engines used to blow cylinders directly was supplied by Boulton and Watt to John Wilkinson's New Willey Furnace. This powered a cast iron blowing cylinder, which had been invented by his father Isaac Wilkinson. He patented such cylinders in 1736, to replace the leather bellows, which wore out quickly. Isaac was granted a second patent, also for blowing cylinders, in 1757. The steam engine and cast iron blowing cylinder led to a large increase in British iron production in the late 18th century. | 1 | Applied and Interdisciplinary Chemistry |
A number of experimental methods of spacecraft propulsion are based on magnetohydrodynamics. As this kind of MHD propulsion involves compressible fluids in the form of plasmas (ionized gases) it is also referred to as magnetogasdynamics or magnetoplasmadynamics.
In such electromagnetic thrusters, the working fluid is most of the time ionized hydrazine, xenon or lithium. Depending on the propellant used, it can be seeded with alkali such as potassium or caesium to improve its electrical conductivity. All charged species within the plasma, from positive and negative ions to free electrons, as well as neutral atoms by the effect of collisions, are accelerated in the same direction by the Lorentz "body" force, which results from the combination of a magnetic field with an orthogonal electric field (hence the name of "cross-field accelerator"), these fields not being in the direction of the acceleration. This is a fundamental difference with ion thrusters which rely on electrostatics to accelerate only positive ions using the Coulomb force along a high voltage electric field.
First experimental studies involving cross-field plasma accelerators (square channels and rocket nozzles) date back to the late 1950s. Such systems provide greater thrust and higher specific impulse than conventional chemical rockets and even modern ion drives, at the cost of a higher required energy density.
Some devices also studied nowadays besides cross-field accelerators include the magnetoplasmadynamic thruster sometimes referred to as the Lorentz force accelerator (LFA), and the electrodeless pulsed inductive thruster (PIT).
Even today, these systems are not ready to be launched in space as they still lack a suitable compact power source offering enough energy density (such as hypothetical fusion reactors) to feed the power-greedy electromagnets, especially pulsed inductive ones. The rapid ablation of electrodes under the intense thermal flow is also a concern. For these reasons, studies remain largely theoretical and experiments are still conducted in the laboratory, although over 60 years have passed since the first research in this kind of thrusters. | 1 | Applied and Interdisciplinary Chemistry |
Mukaiyama studied chemistry at the Tokyo Institute of Technology, earning his BSc in synthetic organic chemistry in 1948. He became assistant professor at Gakushuin University in 1953, where he stayed until he received his Ph.D. in synthetic organic chemistry from the University of Tokyo in 1957. | 0 | Theoretical and Fundamental Chemistry |
While mold and related microbial agents can be found both inside and outside, specific factors can lead to significantly higher levels of these microbes, creating a potential health hazard. Several notable factors are water damage in buildings, the use of building materials which provide a suitable substrate and source of food to amplify mold growth, relative humidity, and energy-efficient building designs, which can prevent proper circulation of outside air and create a unique ecology in the built environment. A common issue with mold hazards in the household can be the placement of furniture, resulting in a lack of ventilation of the nearby wall. The simplest method of avoiding mold in a home so affected is to move the furniture in question.
More than half of adult workers in moldy/humid buildings suffer from nasal or sinus symptoms due to mold exposure.
Prevention of mold exposure and its ensuing health issues begins with the prevention of mold growth in the first place by avoiding a mold-supporting environment. Extensive flooding and water damage can support extensive mold growth. Following hurricanes, homes with greater flood damage, especially those with more than of indoor flooding, demonstrated far higher levels of mold growth compared with homes with little or no flooding.
It is useful to perform an assessment of the location and extent of the mold hazard in a structure. Various practices of remediation can be followed to mitigate mold issues in buildings, the most important of which is to reduce moisture levels. Removal of affected materials after the source of moisture has been reduced and/or eliminated may be necessary, as some materials cannot be remediated. Thus, the concept of mold growth, assessment, and remediation is essential in preventing health issues arising due to the presence of dampness and mold.
Molds may excrete liquids or low-volatility gases, but the concentrations are so low that frequently they cannot be detected even with sensitive analytical sampling techniques. Sometimes, these by-products are detectable by odor, in which case they are referred to as "ergonomic odors", meaning the odors are noticeable but do not indicate toxicologically significant exposures. | 1 | Applied and Interdisciplinary Chemistry |
Relies on the operation of either a lever arm, tightening screws, or pneumatic or hydraulic pressure applied to a membrane. In all cases the force is uniaxial and is applied to the tables (bases) of the two anvils. | 0 | Theoretical and Fundamental Chemistry |
The process is commonly used in control of the morphology of polymer blends, for applications in thermoelectrics, solid-state lighting, polymer electrolytes, composites, membrane formation, and surface pattern formations. | 0 | Theoretical and Fundamental Chemistry |
The adverse effect profile of mecillinam is similar to that of other penicillins. Its most common side effects are rash and gastrointestinal upset, including nausea and vomiting. | 0 | Theoretical and Fundamental Chemistry |
CDs and DVDs have a polycarbonate surface and metal reflective layer which allow for storage and retrieval of information. The metal film is sometimes made of pure gold which is highly stable and has ideal optical properties. The metal can act as a substrate which allows compounds to bind to it. This alters the reflective and refractive properties of the disk. Disk reading is based on capturing analog signals with the disk drive. The signals are indicative of how much analyte is in a sample.
Because the disk spins, the platform has the ability to drive the sample through it through microfluidic channels and for multiple steps to be performed, allowing the possibility for sample preparation and more than one analysis to be conducted during a single run.
CD/DVD based assays could potentially be used for any immunoassay already in use and many assays used in analytical chemistry, as long as analytes have a corresponding probe, are soluble, and are large enough to alter the angle of incident. | 1 | Applied and Interdisciplinary Chemistry |
The Ergun equation, derived by the Turkish chemical engineer Sabri Ergun in 1952, expresses the friction factor in a packed column as a function of the modified Reynolds number. | 1 | Applied and Interdisciplinary Chemistry |
Quantitation by indirect calorimetry, as opposed to the Harris-Benedict equation, is needed to accurately measure REE in cancer patients. | 1 | Applied and Interdisciplinary Chemistry |
Vectorette PCR can develop a strategy to bring about PCR amplification that is unidirectional. Vectorette PCR comprises three main steps. The first step includes utilizing a restriction enzyme in order to accomplish digestion of the sample DNA. The DNA that is to be utilized for the purpose of investigation has to be capable of being digested by restriction enzymes that are appropriate for that gene otherwise the DNA fragments that form the general population cannot be created. After that is completed, a Vectorette library is brought together by ligating the Vectorette units to the appropriate DNA fragments which were previously digested. Ligation is the act of binding two things together. A Vectorette unit is only partially not completely double stranded with a mismatched section located in the center of the unit. The reason it is mismatched is to help it avoid Vectorette primers’ attempts at causing it to undergo first strand synthesis. By doing this any priming that is nonspecific is also avoided. This ligation brings together the vectorette which is double stranded and the ends of the restriction fragments which were previously made in the first step. By doing this, the known sequence which is used to prime the PCR reaction at one side is introduced while the other is primed on the genomic sequence which is already known to the user. The third and last step has two parts to it. This is due to there being two primers, the initiating primer (IP) and the Vectorette primer (VP), that act in different stages. During the first part, the IP works on amplifying the primer extension while the VP remains hybridized with the product; thus, any background amplification is not carried out at this stage. However, this changes during the last and following part of PCR as the priming that is performed comes from both the IP and the VP. | 1 | Applied and Interdisciplinary Chemistry |
Chlorprothixene, sold under the brand name Truxal among others, is a typical antipsychotic of the thioxanthene group. | 0 | Theoretical and Fundamental Chemistry |
In addition to providing static information on molecules by determining their 3D structures, one of the remarkable advantages of NMR over X-ray crystallography is that it can be used to obtain important dynamic information. This is due to the orientation dependence of the chemical-shift, dipole-coupling, or electric-quadrupole-coupling contributions to the instantaneous NMR frequency in an anisotropic molecular environment. When the molecule or segment containing the NMR-observed nucleus changes its orientation relative to the external field, the NMR frequency changes, which can result in changes in one- or two-dimensional spectra or in the relaxation times, depending on the correlation time and amplitude of the motion. | 0 | Theoretical and Fundamental Chemistry |
The term macromolecule (macro- + molecule) was coined by Nobel laureate Hermann Staudinger in the 1920s, although his first relevant publication on this field only mentions high molecular compounds (in excess of 1,000 atoms). At that time the term polymer, as introduced by Berzelius in 1832, had a different meaning from that of today: it simply was another form of isomerism for example with benzene and acetylene and had little to do with size.
Usage of the term to describe large molecules varies among the disciplines. For example, while biology refers to macromolecules as the four large molecules comprising living things, in chemistry, the term may refer to aggregates of two or more molecules held together by intermolecular forces rather than covalent bonds but which do not readily dissociate.
According to the standard IUPAC definition, the term macromolecule as used in polymer science refers only to a single molecule. For example, a single polymeric molecule is appropriately described as a "macromolecule" or "polymer molecule" rather than a "polymer," which suggests a substance composed of macromolecules.
Because of their size, macromolecules are not conveniently described in terms of stoichiometry alone. The structure of simple macromolecules, such as homopolymers, may be described in terms of the individual monomer subunit and total molecular mass. Complicated biomacromolecules, on the other hand, require multi-faceted structural description such as the hierarchy of structures used to describe proteins. In British English, the word "macromolecule" tends to be called "high polymer". | 0 | Theoretical and Fundamental Chemistry |
Electron-transferring-flavoprotein dehydrogenase (ETF dehydrogenase or electron transfer flavoprotein-ubiquinone oxidoreductase, ) is an enzyme that transfers electrons from electron-transferring flavoprotein in the mitochondrial matrix, to the ubiquinone pool in the inner mitochondrial membrane. It is part of the electron transport chain. The enzyme is found in both prokaryotes and eukaryotes and contains a flavin and FE-S cluster. In humans, it is encoded by the ETFDH gene. Deficiency in ETF dehydrogenase causes the human genetic disease multiple acyl-CoA dehydrogenase deficiency. | 1 | Applied and Interdisciplinary Chemistry |
The IUPAC recommended name for phosphorous acid is phosphonic acid. Correspondingly, the IUPAC-recommended name for the ion is phosphonate. In the US the IUPAC naming conventions for inorganic compounds are taught at high school, but not as a required part of the curriculum. A well-known university-level textbook follows the IUPAC recommendations. In practice any reference to "phosphite" should be investigated to determine the naming convention being employed. | 0 | Theoretical and Fundamental Chemistry |
The common factor in nonsteroidal 5-ARI discovery is that the first compounds were all selective inhibitors to 5α-reductase type 1 only, but were then developed in order to get dual inhibition on both type 1 and 2, since inhibition of the type 2 isozyme is a more important factor in treating the disease of BPH.
Benzo(c)quinolizinones are tricyclic derivatives of 10-azasteroids. The D-ring has been removed and the C-ring substituted for an aromatic one. The first compounds developed were selective 5-alpha reductase type 1 inhibitors, but the most potent one inhibits both type 1 and 2. The fluorine atom is an important part of the structure.
Benzo(f)quinolonone are also tricyclic compounds, but derivatives of the 4-azasteroid structure. The compounds that have been designed can be divided into two categories, hexahydro derivatives and octahydro derivatives. The octahydro derivatives have been proven to be more potent. Compound LY 191704, later named bexlosteride, is the most potent octahydro derivative designed. It is a selective inhibitor to the type 1 isozyme, especially because of the chlorine atom and the amino-methyl group.
Piperidones are also 4-azasteroid derivatives but both B- and D-ring have been removed. The original compounds designed were type 1 selective, especially the ones containing a chlorine atom connected to the aromatic ring. By inserting a styryl group to the piperidones type 2 inhibitory activity increased.
Nonsteroidal carboxylic acids are tricyclic compounds designed to resemble steroidal carboxylic acids such as episteride. As with the other nonsteroidal inhibitors, they have been designed by removing steroid ring systems. As with the piperidones, addition of a styryl group provides good dual inhibition on isozyme 1 and 2, but the nonsteroidal carboxylic acids are mostly type 1 selective. | 1 | Applied and Interdisciplinary Chemistry |
A phosphodiesterase (PDE) is an enzyme that breaks a phosphodiester bond. Usually, phosphodiesterase refers to cyclic nucleotide phosphodiesterases, which have great clinical significance and are described below. However, there are many other families of phosphodiesterases, including phospholipases C and D, autotaxin, sphingomyelin phosphodiesterase, DNases, RNases, and restriction endonucleases (which all break the phosphodiester backbone of DNA or RNA), as well as numerous less-well-characterized small-molecule phosphodiesterases.
The cyclic nucleotide phosphodiesterases comprise a group of enzymes that degrade the phosphodiester bond in the second messenger molecules cAMP and cGMP. They regulate the localization, duration, and amplitude of cyclic nucleotide signaling within subcellular domains. PDEs are therefore important regulators of signal transduction mediated by these second messenger molecules. | 1 | Applied and Interdisciplinary Chemistry |
An Alfvén resonator or Ionosphere Alfvén resonator is a spectral resonance structure found within geomagnetic fields in the frequency range of 0.1–10 Hz. First reported in 1989, they are ionospheric short-period geomagnetic variations primarily seen as nighttime phenomena and rarely observed during the day. The nighttime preference is due to lower electrical conductivity in the ionospheric dynamo region, which enables the feedback instability. | 0 | Theoretical and Fundamental Chemistry |
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