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Proteolysis is also used in research and diagnostic applications:
* Cleavage of fusion protein so that the fusion partner and protein tag used in protein expression and purification may be removed. The proteases used have high degree of specificity, such as thrombin, enterokinase, and TEV protease, so that only the targeted sequence may be cleaved.
* Complete inactivation of undesirable enzymatic activity or removal of unwanted proteins. For example, proteinase K, a broad-spectrum proteinase stable in urea and SDS, is often used in the preparation of nucleic acids to remove unwanted nuclease contaminants that may otherwise degrade the DNA or RNA.
* Partial inactivation, or changing the functionality, of specific protein. For example, treatment of DNA polymerase I with subtilisin yields the Klenow fragment, which retains its polymerase function but lacks 5'-exonuclease activity.
* Digestion of proteins in solution for proteome analysis by liquid chromatography-mass spectrometry (LC-MS). This may also be done by in-gel digestion of proteins after separation by gel electrophoresis for the identification by mass spectrometry.
* Analysis of the stability of folded domain under a wide range of conditions.
* Increasing success rate of crystallisation projects
* Production of digested protein used in growth media to culture bacteria and other organisms, e.g. tryptone in Lysogeny Broth. | 1 | Biochemistry |
The three cinnamyl alcohol-vicianosides of rhodiola rosea commonly referred to as "rosavins" are rosin and the structurally related disaccharide Rosavin which is the arabinose ester of rosin, and Rosarin, the arabinofuranose ester of rosin. Salidroside, common in rhodiola spp. and occurring in Rhodiola rosea is not a cinnamyl alcohol glycoside, but a glycoside of tyrosol. | 0 | Organic Chemistry |
Similar to chirality planes, chirality axes arise from an axis about which the spatial arrangement of substituents creates chirality. This can be seen in helical molecules (see section 3a) as well as some alkenes. | 4 | Stereochemistry |
Chowdhury made pioneering contributions to the development of physical chemistry in the country, publishing more than 20 articles. He focused on cellulose fibers (of jute in particular), polyelectrolytes, and proteins. He also guided a number of PhD theses. | 7 | Physical Chemistry |
Notable sources of natural phenols in human nutrition include berries, tea, beer, olive oil, chocolate or cocoa, coffee, pomegranates, popcorn, yerba maté, fruits and fruit based drinks (including cider, wine and vinegar) and vegetables. Herbs and spices, nuts (walnuts, peanut) and algae are also potentially significant for supplying certain natural phenols.
Natural phenols can also be found in fatty matrices like olive oil. Unfiltered olive oil has the higher levels of phenols, or polar phenols that form a complex phenol-protein complex.
Phenolic compounds, when used in beverages, such as prune juice, have been shown to be helpful in the color and sensory components, such as alleviating bitterness.
Some advocates for organic farming claim that organically grown potatoes, oranges, and leaf vegetables have more phenolic compounds and these may provide antioxidant protection against heart disease and cancer. However, evidence on substantial differences between organic food and conventional food is insufficient to support claims that organic food is safer or healthier than conventional food. | 0 | Organic Chemistry |
The subgroups discussed so far are not only infinite, they are also continuous (Lie groups). Any subgroup containing at least one non-zero translation must be infinite, but subgroups of the orthogonal group can be finite. For example, the symmetries of a regular pentagon consist of rotations by integer multiples of 72° (360° / 5), along with reflections in the five mirrors which perpendicularly bisect the edges. This is a group, D, with 10 elements. It has a subgroup, C, of half the size, omitting the reflections. These two groups are members of two families, D and C, for any n > 1. Together, these families constitute the rosette groups.
Translations do not fold back on themselves, but we can take integer multiples of any finite translation, or sums of multiples of two such independent translations, as a subgroup. These generate the lattice of a periodic tiling of the plane.
We can also combine these two kinds of discrete groups — the discrete rotations and reflections around a fixed point and the discrete translations — to generate the frieze groups and wallpaper groups. Curiously, only a few of the fixed-point groups are found to be compatible with discrete translations. In fact, lattice compatibility imposes such a severe restriction that, up to isomorphism, we have only 7 distinct frieze groups and 17 distinct wallpaper groups. For example, the pentagon symmetries, D, are incompatible with a discrete lattice of translations. (Each higher dimension also has only a finite number of such crystallographic groups, but the number grows rapidly; for example, 3D has 230 groups and 4D has 4783.) | 3 | Analytical Chemistry |
Chemical milling is normally performed in a series of five steps: cleaning, masking, scribing, etching, and demasking. [https://www.youtube.com/watch?v=YtnUZanxtLs Video of chemical milling process] [https://www.fotofab.com/photo-etching-process/ Learn more about the video] | 8 | Metallurgy |
The earliest electrical application of SiC was as a surge protection in lightning arresters in electric power systems. These devices must exhibit high resistance until the voltage across them reaches a certain threshold V at which point their resistance must drop to a lower level and maintain this level until the applied voltage drops below V flushing current into the ground.
It was recognized early on that SiC had such a voltage-dependent resistance, and so columns of SiC pellets were connected between high-voltage power lines and the earth. When a lightning strike to the line raises the line voltage sufficiently, the SiC column will conduct, allowing strike current to pass harmlessly to the earth instead of along the power line. The SiC columns proved to conduct significantly at normal power-line operating voltages and thus had to be placed in series with a spark gap. This spark gap is ionized and rendered conductive when lightning raises the voltage of the power line conductor, thus effectively connecting the SiC column between the power conductor and the earth. Spark gaps used in lightning arresters are unreliable, either failing to strike an arc when needed or failing to turn off afterwards, in the latter case due to material failure or contamination by dust or salt. Usage of SiC columns was originally intended to eliminate the need for the spark gap in lightning arresters. Gapped SiC arresters were used for lightning-protection and sold under the GE and Westinghouse brand names, among others. The gapped SiC arrester has been largely displaced by no-gap varistors that use columns of zinc oxide pellets. | 8 | Metallurgy |
In the seminar paper on the total synthesis of (+)-monensin, Kishi and co-workers utilized the allylic strain to induce asymmetric induction in the hydroboration oxidation reaction. The reaction is regioselective and stereoselective. The regioselectivity of the reaction is due to the significant positive character developed at the tertiary carbon. The stereoselectivity of the reaction is due to the attack by the borane from the least hindered side to which is where the methyl group lies at. | 4 | Stereochemistry |
A cloning vector is a small piece of DNA that can be stably maintained in an organism, and into which a foreign DNA fragment can be inserted for cloning purposes. The cloning vector may be DNA taken from a virus, the cell of a higher organism, or it may be the plasmid of a bacterium. The vector contains features that allow for the convenient insertion of a DNA fragment into the vector or its removal from the vector, for example through the presence of restriction sites. The vector and the foreign DNA may be treated with a restriction enzyme that cuts the DNA, and DNA fragments thus generated contain either blunt ends or overhangs known as sticky ends, and vector DNA and foreign DNA with compatible ends can then be joined by molecular ligation. After a DNA fragment has been cloned into a cloning vector, it may be further subcloned into another vector designed for more specific use.
There are many types of cloning vectors, but the most commonly used ones are genetically engineered plasmids. Cloning is generally first performed using Escherichia coli, and cloning vectors in E. coli include plasmids, bacteriophages (such as phage λ), cosmids, and bacterial artificial chromosomes (BACs). Some DNA, however, cannot be stably maintained in E. coli, for example very large DNA fragments, and other organisms such as yeast may be used. Cloning vectors in yeast include yeast artificial chromosomes (YACs). | 1 | Biochemistry |
Various degrees of hypothermia may be deliberately induced in medicine for purposes of treatment of brain injury, or lowering metabolism so that total brain ischemia can be tolerated for a short time. Deep hypothermic circulatory arrest is a medical technique in which the brain is cooled as low as 10 °C, which allows the heart to be stopped and blood pressure to be lowered to zero, for the treatment of aneurysms and other circulatory problems that do not tolerate arterial pressure or blood flow. The time limit for this technique, as also for accidental arrest in ice water (which internal temperatures may drop to as low as 15 °C), is about one hour. | 1 | Biochemistry |
G protein-coupled receptors (GPCRs) are a large family of integral membrane proteins that respond to a variety of extracellular stimuli. Each GPCR binds to and is activated by a specific ligand stimulus that ranges in size from small molecule catecholamines, lipids, or neurotransmitters to large protein hormones. When a GPCR is activated by its extracellular ligand, a conformational change is induced in the receptor that is transmitted to an attached intracellular heterotrimeric G protein complex. The G alpha subunit of the stimulated G protein complex exchanges GDP for GTP and is released from the complex.
In a cAMP-dependent pathway, the activated G alpha subunit binds to and activates an enzyme called adenylyl cyclase, which, in turn, catalyzes the conversion of ATP into cyclic adenosine monophosphate (cAMP).
Increases in concentration of the second messenger cAMP may lead to the activation of
* cyclic nucleotide-gated ion channels
* exchange proteins activated by cAMP (EPAC) such as RAPGEF3
* popeye domain containing proteins (Popdc)
* an enzyme called protein kinase A (PKA).
The PKA enzyme is also known as cAMP-dependent enzyme because it gets activated only if cAMP is present. Once PKA is activated, it phosphorylates a number of other proteins including:
* enzymes that convert glycogen into glucose
* enzymes that promote muscle contraction in the heart leading to an increase in heart rate
* transcription factors, which regulate gene expression
* also phosphorylate AMPA receptors
Specificity of signaling between a GPCR and its ultimate molecular target through a cAMP-dependent pathway may be achieved through formation of a multiprotein complex that includes the GPCR, adenylyl cyclase, and the effector protein. | 1 | Biochemistry |
Solomon received an Associate of Sydney Technical College, (equivalent to a Diploma of Chemistry) in 1950 and went on to complete a Bachelor of Science (BSc (Hons)) in 1952 from the New South Wales University of Technology (now the University of New South Wales), a Master of Science (MSc) from the same university in 1955, and a PhD from the University of New South Wales in 1959 with a thesis entitled Studies on the Chemistry of Carbonyl Compounds. In 1968 he was awarded a DSc from the University of New South Wales for his thesis Studies on the Chemistry of Coating Compounds. He also received an Honorary Doctorate in Applied Science from the University of Melbourne in 2005, one of only seven awarded in the university's history. | 7 | Physical Chemistry |
When there is a stimulus, the CRP level can increase 10,000-fold from less than 50 μg/L to more than 500 mg/L. Its concentration can increase to 5 mg/L by 6 hours and peak at 48 hours. The plasma half-life of CRP is 19 hours, and is constant in all medical conditions. Therefore, the only factor that affects the blood CRP concentration is its production rate, which increases with inflammation, infection, trauma, necrosis, malignancy, and allergic reactions. Other inflammatory mediators that can increase CRP are TGF beta 1, and tumor necrosis factor alpha. In acute inflammation, CRP can increase as much as 50 to 100 mg/L within 4 to 6 hours in mild to moderate inflammation or an insult such as skin infection, cystitis, or bronchitis. It can double every 8 hours and reaches its peak at 36 to 50 hours following injury or inflammation. CRP between 100 and 500 mg/L is considered highly predictive of inflammation due to bacterial infection. Once inflammation subsides, CRP level falls quickly because of its relatively short half-life. | 1 | Biochemistry |
Specialized proteins can unzip small segments of the DNA molecule when it is replicated or transcribed into RNA. But work published in 2015 illustrates how DNA opens on its own.
Simply twisting DNA can expose internal bases to the outside, without the aid of any proteins. Also, transcription itself contorts DNA in living human cells, tightening some parts of the coil and loosening it in others. That stress triggers changes in shape, most notably opening up the helix to be read. Unfortunately, these interactions are very difficult to study because biological molecules morph shapes so easily. In 2008 it was noted that transcription twists DNA, leaving a trail of undercoiled (or negatively supercoiled) DNA in its wake. Moreover, they discovered that the DNA sequence itself affects how the molecule responds to supercoiling.
For example, the researchers identified a specific sequence of DNA that regulates transcription speed; as the amount of supercoil rises and falls, it slows or speeds the pace at which molecular machinery reads DNA. It is hypothesized that these structural changes might trigger stress elsewhere along its length, which in turn might provide trigger points for replication or gene expression. This implies that it is a very dynamic process in which both DNA and proteins each influences how the other acts and reacts. | 1 | Biochemistry |
The population of vibrationally excited states follows a Boltzmann distribution, so low-frequency vibrational states are appreciably populated even at room temperatures. As the moment of inertia is higher when a vibration is excited, the rotational constants (B) decrease. Consequently, the rotation frequencies in each vibration state are different from each other. This can give rise to "satellite" lines in the rotational spectrum. An example is provided by cyanodiacetylene, H−C≡C−C≡C−C≡N.
Further, there is a fictitious force, Coriolis coupling, between the vibrational motion of the nuclei in the rotating (non-inertial) frame. However, as long as the vibrational quantum number does not change (i.e., the molecule is in only one state of vibration), the effect of vibration on rotation is not important, because the time for vibration is much shorter than the time required for rotation. The Coriolis coupling is often negligible, too, if one is interested in low vibrational and rotational quantum numbers only. | 7 | Physical Chemistry |
Endogenous template-independent primer-primer interaction is due to the random design of hexamer primers. One possible solution is to design constrained-randomized hexanucleotide primers that do not cross-hybridize. | 1 | Biochemistry |
In the context of pharmacokinetics (how the body absorbs, metabolizes, and excretes a drug), the distribution coefficient has a strong influence on ADME properties of the drug. Hence the hydrophobicity of a compound (as measured by its distribution coefficient) is a major determinant of how drug-like it is. More specifically, for a drug to be orally absorbed, it normally must first pass through lipid bilayers in the intestinal epithelium (a process known as transcellular transport). For efficient transport, the drug must be hydrophobic enough to partition into the lipid bilayer, but not so hydrophobic, that once it is in the bilayer, it will not partition out again. Likewise, hydrophobicity plays a major role in determining where drugs are distributed within the body after absorption and, as a consequence, in how rapidly they are metabolized and excreted. | 7 | Physical Chemistry |
Certain diagnostic tests are available for the quantification of the end-products of lipid peroxidation, to be specific, malondialdehyde (MDA). The most commonly used test is called a TBARS Assay (thiobarbituric acid reactive substances assay). Thiobarbituric acid reacts with malondialdehyde to yield a fluorescent product. However, there are other sources of malondialdehyde, so this test is not completely specific for lipid peroxidation. | 1 | Biochemistry |
Duplex sequencing tagged adapters can be used in combination with the majority of NGS adapters. In the figures and workflow section of this article, Illumina sequencing adapters are used as an example following the original published protocol. | 1 | Biochemistry |
Thermal bumps can be evenly distributed across the surface of a chip to provide a uniform cooling effect. In this case, the thermal bumps may be interspersed with standard bumps that are used for signal, power and ground. This allows the thermal bumps to be placed directly under the active circuitry of the chip for maximum effectiveness. The number and density of thermal bumps are based on the heat load from the chip. Each P/N couple can provide a specific heat pumping (Q) at a specific temperature differential (ΔT) at a given electric current. Temperature sensors on the chip (“on board” sensors) can provide direct measurement of the thermal bump performance and provide feedback to the driver circuit. | 7 | Physical Chemistry |
The Vroman effect, named after Leo Vroman, describes the process of competitive protein adsorption to a surface by blood serum proteins. The highest mobility proteins generally arrive first and are later replaced by less mobile proteins that have a higher affinity for the surface. The order of protein adsorption also depends on the molecular weight of the species adsorbing. Typically, low molecular weight proteins are displaced by high molecular weight protein while the opposite, high molecular weight being displaced by low molecular weight, does not occur. A typical example of this occurs when fibrinogen displaces earlier adsorbed proteins on a biopolymer surface and is later replaced by high molecular weight kininogen. The process is delayed in narrow spaces and on hydrophobic surfaces, fibrinogen is usually not displaced. Under stagnant conditions initial protein deposition takes place in the sequence: albumin; globulin; fibrinogen; fibronectin; factor XII, and HMWK. | 7 | Physical Chemistry |
In laboratory experiments, activation of cannabinoid receptors had an effect on the activation of GTPases in macrophages, neutrophils, and bone marrow cells. These receptors have also been implicated in the migration of B cells into the marginal zone and the regulation of IgM levels. | 1 | Biochemistry |
Initially written off as a non-essential process due to the ATE1 knockout in yeast, later studies have shown arginylation plays a significant role in several biological processes. The knockout of ATE1 in mice and Drosophila resulted in embryonic lethality for both species. Further studies using the mouse model to observe the effects of ATE1 knockout in the development of the organism revealed that the gene loss resulted in abnormal cardiac and craniofacial morphogenesis, impaired angiogenesis, and the ability of cells to undergo meiosis. Postnatally, ATE1 knockout resulted in weight loss, infertility, and mental retardation. Additionally, observing the effects of ATE1 deletion in Arabidopsis thaliana, a model plant organism, revealed defective shoot and leaf development, abnormal seed germination, and delayed leaf senescence. The dysfunctions resulting from the knockout of the ATE1 enzyme therefore suggest that arginylation is necessary for many physiological pathways within eukaryotes. | 1 | Biochemistry |
A dusty plasma contains tiny charged particles of dust (typically found in space). The dust particles acquire high charges and interact with each other. A plasma that contains larger particles is called grain plasma. Under laboratory conditions, dusty plasmas are also called complex plasmas. | 7 | Physical Chemistry |
Heteroboranes are classes of boranes in which at least one boron atom is replaced by another elements. Like many of the related boranes, these clusters are polyhedra and are similarly classified as closo-, nido-, arachno-, and hypho-, according to the so-called electron count. Closo- represents a complete polyhedron, while nido-, arachno- and hypho- stand for polyhedrons that are missing one, two and three vertices.
Besides carbon (carboranes or carbaboranes), other elements can also be included in the heteroborane molecules as well, such as Si (silaboranes), N (azaboranes, including borazine), P (phosphaboranes), As (arsaboranes), Sb (stibaboranes), O (oxaboranes), S (thiaboranes), Se (selenaboranes) and Te (telluraboranes), either alone or in combination.
Structurally, some heteroboranes can be derived from the icosahedral (I) Dodecaborate| anion via formal replacement of its BH fragments with isoelectronic , or fragments, e.g., closo-1- and closo-1,2- (two of the carboranes), closo-1,2- (one of the phosphaboranes) or closo-1- (one of the thiaboranes).
Heteroboranes are used in various fields, such as drug discovery, imaging, and nanotechnology. | 7 | Physical Chemistry |
Flucloxacillin is a narrow-spectrum antibiotic belonging to the penicillin group of antibiotics. It works by breaking down the bacterial cell wall.
Like other β-lactam antibiotics, flucloxacillin acts by inhibiting the synthesis of bacterial cell walls. It inhibits cross-linkage between the linear peptidoglycan polymer chains that make up a major component of the cell wall of Gram-positive bacteria.
Flucloxacillin is more acid-stable than many other penicillins and can be given orally, in addition to parenteral routes. However, like methicillin, it is less potent than benzylpenicillin against non-β-lactamase-producing Gram-positive bacteria.
Flucloxacillin has similar pharmacokinetics, antibacterial activity, and indications to dicloxacillin, and the two agents are considered interchangeable. It is reported to have higher, though rare, incidence of severe hepatic adverse effects than dicloxacillin, but a lower incidence of renal adverse effects. | 4 | Stereochemistry |
Because so many chloroplast genes have been moved to the nucleus, many proteins that would originally have been translated in the chloroplast are now synthesized in the cytoplasm of the plant cell. These proteins must be directed back to the chloroplast, and imported through at least two chloroplast membranes.
Curiously, around half of the protein products of transferred genes arent even targeted back to the chloroplast. Many became exaptations, taking on new functions like participating in cell division, protein routing, and even disease resistance. A few chloroplast genes found new homes in the mitochondrial genome—most became nonfunctional pseudogenes, though a few tRNA genes still work in the mitochondrion. Some transferred chloroplast DNA protein products get directed to the secretory pathway, though many secondary plastids are bounded by an outermost membrane derived from the hosts cell membrane, and therefore topologically outside of the cell because to reach the chloroplast from the cytosol, the cell membrane must be crossed, which signifies entrance into the extracellular space. In those cases, chloroplast-targeted proteins do initially travel along the secretory pathway.
Because the cell acquiring a chloroplast already had mitochondria (and peroxisomes, and a cell membrane for secretion), the new chloroplast host had to develop a unique protein targeting system to avoid having chloroplast proteins being sent to the wrong organelle.
In most, but not all cases, nuclear-encoded chloroplast proteins are translated with a cleavable transit peptide that's added to the N-terminus of the protein precursor. Sometimes the transit sequence is found on the C-terminus of the protein, or within the functional part of the protein. | 5 | Photochemistry |
Even if it is not a common substrate for metabolism, benzene can be oxidized by both bacteria and eukaryotes. In bacteria, dioxygenase enzyme can add an oxygen to the ring, and the unstable product is immediately reduced (by NADH) to a cyclic diol with two double bonds, breaking the aromaticity. Next, the diol is newly reduced by NADH to catechol. The catechol is then metabolized to acetyl CoA and succinyl CoA, used by organisms mainly in the citric acid cycle for energy production.
The pathway for the metabolism of benzene is complex and begins in the liver. Several enzymes are involved. These include cytochrome P450 2E1 (CYP2E1), quinine oxidoreductase (NQ01 or DT-diaphorase or NAD(P)H dehydrogenase (quinone 1)), GSH, and myeloperoxidase (MPO). CYP2E1 is involved at multiple steps: converting benzene to oxepin (benzene oxide), phenol to hydroquinone, and hydroquinone to both benzenetriol and catechol. Hydroquinone, benzenetriol and catechol are converted to polyphenols. In the bone marrow, MPO converts these polyphenols to benzoquinones. These intermediates and metabolites induce genotoxicity by multiple mechanisms including inhibition of topoisomerase II (which maintains chromosome structure), disruption of microtubules (which maintains cellular structure and organization), generation of oxygen free radicals (unstable species) that may lead to point mutations, increasing oxidative stress, inducing DNA strand breaks, and altering DNA methylation (which can affect gene expression). NQ01 and GSH shift metabolism away from toxicity. NQ01 metabolizes benzoquinone toward polyphenols (counteracting the effect of MPO). GSH is involved with the formation of phenylmercapturic acid.
Genetic polymorphisms in these enzymes may induce loss of function or gain of function. For example, mutations in CYP2E1 increase activity and result in increased generation of toxic metabolites. NQ01 mutations result in loss of function and may result in decreased detoxification. Myeloperoxidase mutations result in loss of function and may result in decreased generation of toxic metabolites. GSH mutations or deletions result in loss of function and result in decreased detoxification. These genes may be targets for genetic screening for susceptibility to benzene toxicity. | 2 | Environmental Chemistry |
Automated mineralogy is a generic term describing a range of analytical solutions, areas of commercial enterprise, and a growing field of scientific research and engineering applications involving largely automated and quantitative analysis of minerals, rocks and man-made materials. | 7 | Physical Chemistry |
Paul Ehrlich coined the term antibody () in his side-chain theory at the end of the 19th century. In 1899, Ladislas Deutsch (László Detre) named the hypothetical substances halfway between bacterial constituents and antibodies "antigenic or immunogenic substances" (). He originally believed those substances to be precursors of antibodies, just as a zymogen is a precursor of an enzyme. But, by 1903, he understood that an antigen induces the production of immune bodies (antibodies) and wrote that the word antigen is a contraction of antisomatogen (). The Oxford English Dictionary indicates that the logical construction should be "anti(body)-gen".
The term originally referred to a substance that acts as an antibody generator. | 1 | Biochemistry |
A molecular probe is a group of atoms or molecules used in molecular biology or chemistry to study the properties of other molecules or structures. If some measurable property of the molecular probe used changes when it interacts with the analyte (such as a change in absorbance), the interactions between the probe and the analyte can be studied. This makes it possible to indirectly study the properties of compounds and structures which may be hard to study directly.
The choice of molecular probe will depend on which compound or structure is being studied as well as on what property is of interest. Radioactive DNA or RNA sequences are used in molecular genetics to detect the presence of a complementary sequence by molecular hybridization. | 1 | Biochemistry |
In their 2010 Synlett article, Martina Wernerova and organic chemist, Tomáš Hudlický, raised concerns about inaccurate reporting of yields, and offered solutions—including the proper characterization of compounds. After performing careful control experiments, Wernerova and Hudlický said that each physical manipulation (including extraction/washing, drying over desiccant, filtration, and column chromatography) results in a loss of yield of about 2%. Thus, isolated yields measured after standard aqueous workup and chromatographic purification should seldom exceed 94%. They called this phenomenon "yield inflation" and said that yield inflation had gradually crept upward in recent decades in chemistry literature. They attributed yield inflation to careless measurement of yield on reactions conducted on small scale, wishful thinking and a desire to report higher numbers for publication purposes. Hudlickýs 2020 article published in Angewandte Chemie—since retracted—honored and echoed Dieter Seebachs often-cited 1990 thirty-year review of organic synthesis, which had also been published in Angewandte Chemie. In his 2020 Angewandte Chemie 30-year review, Hudlický said that the suggestions that he and Wernerova had made in their 2010 Synlett article, were "ignored by the editorial boards of organic journals, and by most referees." | 0 | Organic Chemistry |
In organic chemistry, a dithiocarbamate is a functional group with the general formula and structure . It is the analog of a carbamate in which both oxygen atoms are replaced by sulfur atoms (when only 1 oxygen is replaced the result is thiocarbamate).
Dithiocarbamate also refers to the dithiocarbamate ion and its salts. A common example is sodium diethyldithiocarbamate. Dithiocarbamates and their derivatives are widely used in the vulcanization of rubber. | 0 | Organic Chemistry |
In spectroscopy, the term "plane parallel layers" may be employed as a mathematical construct in discussing theory. The layers are considered to be semi-infinite. (In mathematics, semi-infinite objects are objects which are infinite or unbounded in some, but not all, possible ways.) Generally, a semi-infinite layer is envisioned as a being bounded by two flat parallel planes, each extending indefinitely, and normal (perpendicular) to the direction of a collimated (or directed) incident beam. The planes are not necessarily physical surfaces which refract and reflect light, but may just describe a mathematical plane, suspended in space. When the plane parallel layers have surfaces, they have been variously called plates, sheets, or slabs. | 7 | Physical Chemistry |
The phenomenon is known as mareel in Shetland. This term is derived from the Norn word *mareld, which is itself derived from the Old Norse word mǫrueldr, which is a compound of marr (mere, sea) and eldr (fire).
In the Somali language it is called “Kaluunka Iftiima”. The term translates to glowing sea creatures or glowing fish as the word Kaluun refers to any bio organism that lives in the sea. It is most commonly used to refer to fish. | 1 | Biochemistry |
Wilma K. Olson (born ) is the Mary I. Bunting professor at the Rutgers Center for Quantitative Biology (CQB) (formerly known as BioMaPS institute for Quantitative Biology) at Rutgers University. Olson has her own research group on the New Brunswick campus. Although she is a polymer chemist by training, her research aims to understand the influence of chemical architecture on the conformation, properties, and interactions of nucleic acids. | 1 | Biochemistry |
Nickel-cobalt lateritic ores can be treated by either hydrometallurgical processes or pyrometallurgical processes, such as matte or ferronickel smelting, which require the entire ore to be melted and the metal values to be separated from the residual components of the ore. The hydrometallurgical process for laterite ore can use sulfuric acid or ammonia leach solutions. | 8 | Metallurgy |
Oceanographers and limnologists use pCO to measure the amount of carbon dioxide dissolved in water, as well as to parameterize its flux into (influx) and out of (efflux) the atmosphere. Carbon dioxide reacts with water to form bicarbonate and carbonate ions, such that the relative solubility of carbon dioxide in water is greater than that of other unreactive gasses (e.g. Helium). As more carbon dioxide dissolves in water, its pCO rises until it equals the pCO of the overlying atmosphere. Conversely, a body of water with a pCO greater than that of the atmosphere effluxes carbon dioxide.
pCO is additionally affected by water temperature and salinity. Carbon dioxide is less soluble in warmer water than cooler water, so hot water will exhibit a larger pCO than cold water with the same concentration of carbon dioxide. pCO can be used to describe the inorganic carbon system of a body of water, together with other parameters such as pH, dissolved inorganic carbon, and alkalinity. Together, these parameters describe the concentration and speciation of inorganic carbon species (CO, HCO, CO) in water.
Biological processes such as respiration and photosynthesis affect and can be affected by aquatic pCO. Respiration degrades organic matter, releasing CO into the water column and increasing pCO. Photosynthesis assimilates inorganic carbon, thereby decreasing aquatic pCO. | 7 | Physical Chemistry |
Autoreceptor inhibition leads to increase respective neurotransmitter release. Major autoreceptor which clinically important are alpha 2(adrenergic receptor subtype 2), H 3(histamine receptor subtype 3), 5 HT 1(serotonin receptor subtype 1). In which respective drugs act are Clonidine on alpha 2 as Agonist used in hypertension which reduce release of norepinephrine and epinephrine from presynaptic neurons. Tizanidine used as centrally acting skeletal muscle relaxant is also act on alpha 2. 5 HT 1A is target of Buspirone which act as a partial Agonist and used as Atypical non sedative anxiolytic.5HT 1B/1D receptor Agonist are Triptans and Ergot alkaloids which used in treatment of migraine. 5 HT 1F receptor subtype Agonist drug lesmiditan also used in treatment of migraine. H 3 receptor antagonist Pitolisant used in narcolepsy. As an example, norepinephrine released from sympathetic neurons may interact with the alpha-2A and alpha-2C adrenoreceptors to inhibit further release of norepinephrine. Similarly, acetylcholine released from parasympathetic neurons may interact with M and M receptors to inhibit further release of acetylcholine. An atypical example is given by the β-adrenergic autoreceptor in the sympathetic peripheral nervous system, which acts to increase transmitter release.
The D2sh autoreceptor has been shown recently to interact with the trace amine-assorted receptor 1 (TAAR1), a G-Coupled Protein Receptor GPCR, to regulate monoaminergic systems in the brain. Active TAAR1 opposes the autoreceptor's activity by inactivating the dopamine transporter (DAT). In their review of TAAR1 in monoaminergic systems, Xie and Miller proposed this schematic: synaptic dopamine binds to the dopamine autoreceptor, which activates the DAT. Dopamine enters the presynaptic cells and binds to TAAR1, which increases adenylyl cyclase activity. This eventually allows for the translation of trace amines in the cytoplasm and activation of cyclic nucleotide-gated ion channels, which further activate TAAR1 and dump dopamine into the synapse. Through a series of phosphorylation events related to PKA and PKC, active TAAR1 inactivates DAT, preventing uptake of dopamine from the synapse. The presence of two Postsynaptic receptors with opposite abilities to regulate monoamine transporter function allows for regulation of the monoaminergic system.
Autoreceptor activity may also decrease paired-pulse facilitation (PPF). A feedback cell is activated by the (partially) depolarized post-synaptic neuron. The feedback cell releases a neurotransmitter to which the autoreceptor of the presynaptic neuron is receptive. The autoreceptor causes the inhibition of calcium channels (slowing calcium ion influx) and the opening of potassium channels (increasing potassium ion efflux) in the presynaptic membrane. These changes in ion concentration effectively diminish the amount of the original neurotransmitter released by the presynaptic terminal into the synaptic cleft. This causes a final depression on the activity of the postsynaptic neuron. Thus the feedback cycle is complete. | 1 | Biochemistry |
A sub-plot shows the variation of isentropic (i.e. adiabatic) efficiency with flow, at constant speed. Some maps use polytropic efficiency. Alternatively, for illustrative purposes, efficiency contours are sometimes cross-plotted onto the main map.
Note that the locus of peak efficiency exhibits a slight kink in its upward trend. This is due to the choking-up of the compressor as speed increases, with the variable stators closed-off. The trend line resumes once the variables start to move open. | 7 | Physical Chemistry |
The column used for GPC is filled with a microporous packing material. The column is filled with the gel. Since the total penetration volume is the maximum volume permeated by the analytes, and there is no retention on the surface of the stationary phase, the total column volume is usually large, relatively to the sample volume. | 3 | Analytical Chemistry |
Internal coordinates are of the following types, illustrated with reference to the planar molecule ethylene,
* Stretching: a change in the length of a bond, such as C–H or C–C
* Bending: a change in the angle between two bonds, such as the HCH angle in a methylene group
* Rocking: a change in angle between a group of atoms, such as a methylene group and the rest of the molecule.
* Wagging: a change in angle between the plane of a group of atoms, such as a methylene group and a plane through the rest of the molecule,
* Twisting: a change in the angle between the planes of two groups of atoms, such as a change in the angle between the two methylene groups.
* Out-of-plane: a change in the angle between any one of the C–H bonds and the plane defined by the remaining atoms of the ethylene molecule. Another example is in BF when the boron atom moves in and out of the plane of the three fluorine atoms.
In a rocking, wagging or twisting coordinate the bond lengths within the groups involved do not change. The angles do. Rocking is distinguished from wagging by the fact that the atoms in the group stay in the same plane.
In ethylene there are 12 internal coordinates: 4 C–H stretching, 1 C–C stretching, 2 H–C–H bending, 2 CH rocking, 2 CH wagging, 1 twisting. Note that the H–C–C angles cannot be used as internal coordinates as well as the H-C-H angle because the angles at each carbon atom cannot all increase at the same time.
Note that these coordinates do not correspond to normal modes (see #Normal coordinates). In other words, they do not correspond to particular frequencies or vibrational transitions. | 7 | Physical Chemistry |
Hattori began her academic career as a postdoctoral researcher at the University of Alberta in Edmonton in 1977 and participated in the International Drilling project as a Canadian delegate to study volcanic rocks and thermal alteration in Iceland. In 1980, she moved to the University of Calgary as a Research Associate jointly affiliated with the Department of Physics and the Department of Geology and Geophysics. Three years later, she joined the University of Ottawa as an Assistant Professor and was promoted to Associate Professor in the Department of Geology in 1987.
She was the first female Professor in earth science departments within the national capital region as well as the first female Professor of mineral deposits in Canada. In 1994 she became Full Professor in the Department of Earth and Environmental Sciences at the University of Ottawa. She was awarded the title of Distinguished University Professor in 2023 for her contributions to scientific research and education.
Hattori has held numerous administrative appointments throughout her career. From July 1991 to June 1994, she served as the Director of the Ottawa-Carleton Geoscience Centre. In 2004, she was appointed as the department chair for Earth Sciences at the University of Ottawa, a position she held for four years.
Apart from the administrative work related to universities, she has been engaged in the activities of several scientific organizations including Mineralogical Society of America, Society of Economic Geologists, and Royal Society of Canada. She is Director of Earth, Ocean and Atmosphere Science Division of Royal Society of Canada (2021-2024).
Hattori was an appraiser of graduate-research programs at various Ontario Universities (1999-2002) and geoscience program reviewers of American University of Beirut in Lebanon (2016-17), Western University (2012) and Hiroshima University (2009).
Hattori has been appointed as Visiting Professor at Université de Lyon (1999) and l’Universiteé Grenoble (2016), Visiting Scientist at Japan Marine Science and Technology (2003-2004), Visiting Professor at Nagoya Institute, Guest Research Scientists at Woods Hole Oceanographic Institution (1995-1996), Visiting Research Scientist at Massachusetts Institute of Technology (1989-1990). | 9 | Geochemistry |
During transcription, RNA polymerase unwinds a short section of the DNA double helix near the start of the gene (the transcription start site). This unwound section is known as the transcription bubble. The RNA polymerase, and with it the transcription bubble, travels along the noncoding strand in the opposite, 3 to 5, direction, as well as polymerizing a newly synthesized strand in 5 to 3 or downstream direction. The DNA double helix is rewound by RNA polymerase at the rear of the transcription bubble. Like how two adjacent zippers work, when pulled together, they unzip and rezip as they proceed in a particular direction. Various factors can cause double-stranded DNA to break; thus, reorder genes or cause cell death. | 1 | Biochemistry |
ECS sections introduce and support activities in electrochemistry and solid state science in Asia, Europe, Latin America, the Middle East, and North America. Involvement in a section provides networking opportunities for those both new to the field or advanced in their careers. For those not able to attend ECS biannual meetings, sections bring technical news and activities within reach. Sections participate in ECS affairs, work to build Society membership, and help create awareness for the science.
ECS Arizona Section
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In the Chan–Lam coupling the alkyl, alkenyl or aryl boronic acid reacts with a N–H or O–H containing compound with Cu(II) such as copper(II) acetate and oxygen and a base such as pyridine forming a new carbon–nitrogen bond or carbon–oxygen bond for example in this reaction of 2-pyridone with trans-1-hexenylboronic acid:
The reaction mechanism sequence is deprotonation of the amine, coordination of the amine to the copper(II), transmetallation (transferring the alkyl boron group to copper and the copper acetate group to boron), oxidation of Cu(II) to Cu(III) by oxygen and finally reductive elimination of Cu(III) to Cu(I) with formation of the product. Direct reductive elimination of Cu(II) to Cu(0) also takes place but is very slow. In catalytic systems oxygen also regenerates the Cu(II) catalyst. | 0 | Organic Chemistry |
The influence of dead zones on fisheries and other marine commercial activities varies by the length of occurrence and location. Dead zones are often accompanied by a decrease in biodiversity and collapse in benthic populations, lowering the diversity of yield in commercial fishing operations, but in cases of eutrophication-related dead zone formations, the increase in nutrient availability can lead to temporary rises in select yields among pelagic populations, such as anchovies. However, studies estimate that the increased production in the surrounding areas do not offset the net decrease in productivity resulting from the dead zone. For instance, an estimated 17,000 MT of carbon in the form of prey for fisheries has been lost as a result of dead zones in the Gulf of Mexico. Additionally, many stressors in fisheries are worsened by hypoxic conditions. Indirect factors such as increased success by invasive species and increased pandemic intensity in stressed species such as oysters both lead to losses in revenue and ecological stability in affected regions. | 9 | Geochemistry |
Application/process uses and methods for thermosets include protective coating, seamless flooring, civil engineering construction grouts for jointing and injection, mortars, foundry sands, adhesives, sealants, castings, potting, electrical insulation, encapsulation, solid foams, wet lay-up laminating, pultrusion, gelcoats, filament winding, pre-pregs, and molding.
Specific methods of molding thermosets are:
* Reactive injection moulding (used for objects such as milk bottle crates)
* Extrusion molding (used for making pipes, threads of fabric and insulation for electrical cables)
* Compression molding (used to shape SMC and BMC thermosetting plastics)
* Spin casting (used for producing fishing lures and jigs, gaming miniatures, figurines, emblems as well as production and replacement parts) | 7 | Physical Chemistry |
In chemistry, oxychlorination is a process for generating the equivalent of chlorine gas (Cl) from hydrogen chloride and oxygen. This process is attractive industrially because hydrogen chloride is less expensive than chlorine. | 0 | Organic Chemistry |
The proof only relies on the Schrödinger equation and the assumption that partial derivatives with respect to λ and t can be interchanged. | 6 | Supramolecular Chemistry |
In epigenetics, a paramutation is an interaction between two alleles at a single locus, whereby one allele induces a heritable change in the other allele. The change may be in the pattern of DNA methylation or histone modifications. The allele inducing the change is said to be paramutagenic, while the allele that has been epigenetically altered is termed paramutable. A paramutable allele may have altered levels of gene expression, which may continue in offspring which inherit that allele, even though the paramutagenic allele may no longer be present. Through proper breeding, paramutation can result in siblings that have the same genetic sequence, but with drastically different phenotypes.
Though studied primarily in maize, paramutation has been described in a number of other systems, including animal systems like Drosophila melanogaster and mice. Despite its broad distribution, examples of this phenomenon are scarce and its mechanism is not fully understood. | 1 | Biochemistry |
Photodegradation is the alteration of materials by light. Commonly, the term is used loosely to refer to the combined action of sunlight and air, which cause oxidation and hydrolysis. Often photodegradation is intentionally avoided, since it destroys paintings and other artifacts. It is, however, partly responsible for remineralization of biomass and is used intentionally in some disinfection technologies. Photodegradation does not apply to how materials may be aged or degraded via infrared light or heat, but does include degradation in all of the ultraviolet light wavebands. | 5 | Photochemistry |
As electrons from the cathode gain more energy, they tend to ionize, rather than excite atoms. Excited atoms quickly fall back to ground level emitting light, however, when atoms are ionized, the opposite charges are separated, and do not immediately recombine. This results in more ions and electrons, but no light. This region is sometimes called Crookes dark space, and sometimes referred to as the cathode fall, because the largest voltage drop in the tube occurs in this region. | 3 | Analytical Chemistry |
Devices made from aluminum and its alloys, such as aircraft, must be carefully designed to minimize or evenly distribute flexure, which can lead to work hardening and, in turn, stress cracking, possibly causing catastrophic failure. For this reason modern aluminum aircraft will have an imposed working lifetime (dependent upon the type of loads encountered), after which the aircraft must be retired. | 8 | Metallurgy |
Cyanidin is a natural organic compound. It is a particular type of anthocyanidin (glycoside version called anthocyanins). It is a pigment found in many red berries including grapes, bilberry, blackberry, blueberry, cherry, chokeberry, cranberry, elderberry, hawthorn, loganberry, açai berry and raspberry. It can also be found in other fruits such as apples and plums, and in red cabbage and red onion. It has a characteristic reddish-purple color, though this can change with pH; solutions of the compound are red at pH < 3, violet at pH 7-8, and blue at pH > 11. In certain fruits, the highest concentrations of cyanidin are found in the seeds and skin. Cyanidin has been found to be a potent sirtuin 6 (SIRT6) activator. | 3 | Analytical Chemistry |
Whilst calculation of thermal transmittance can readily be carried out with the help of software which is compliant with ISO 6946, a thermal transmittance calculation does not fully take workmanship into account and it does not allow for adventitious circulation of air between, through and around sections of insulation. To take the effects of workmanship-related factors fully into account it is necessary to carry out a thermal transmittance measurement.
ISO 9869 describes how to measure the thermal transmittance of a roof or a wall by using heat flux sensor. These heat flux meters usually consist of thermopiles which provide an electrical signal which is in direct proportion to the heat flux. Typically they might be about in diameter and perhaps about thick and they need to be fixed firmly to the roof or wall which is under test in order to ensure good thermal contact. When the heat flux is monitored over a sufficiently long time, the thermal transmittance can be calculated by dividing the average heat flux by the average difference in temperature between the inside and outside of the building. For most wall and roof constructions the heat flux meter needs to monitor heat flows (and internal and external temperatures) continuously for a period of 72 hours to be conform the ISO 9869 standards.
Generally, thermal transmittance measurements are most accurate when:
*The difference in temperature between the inside and outside of the building is at least .
*The weather is cloudy rather than sunny (this makes accurate measurement of temperature easier).
*There is good thermal contact between the heat flux meter and the wall or roof being tested.
*The monitoring of heat flow and temperatures is carried out over at least 72 hours.
*Different spots on a building element are measured or a thermographic camera is used to secure the homogeneity of the building element.
When convection currents play a part in transmitting heat across a building component, then thermal transmittance increases as the temperature difference increases. For example, for an internal temperature of and an external temperature of , the optimum gap between panes in a double glazed window will be smaller than the optimum gap for an external temperature of .
The inherent thermal transmittance of materials can also vary with temperaturethe mechanisms involved are complex, and the transmittance may increase or decrease as the temperature increases. | 7 | Physical Chemistry |
Many types of arrays exist and the broadest distinction is whether they are spatially arranged on a surface or on coded beads:
* The traditional solid-phase array is a collection of orderly microscopic "spots", called features, each with thousands of identical and specific probes attached to a solid surface, such as glass, plastic or silicon biochip (commonly known as a genome chip, DNA chip or gene array). Thousands of these features can be placed in known locations on a single DNA microarray.
* The alternative bead array is a collection of microscopic polystyrene beads, each with a specific probe and a ratio of two or more dyes, which do not interfere with the fluorescent dyes used on the target sequence.
DNA microarrays can be used to detect DNA (as in comparative genomic hybridization), or detect RNA (most commonly as cDNA after reverse transcription) that may or may not be translated into proteins. The process of measuring gene expression via cDNA is called expression analysis or expression profiling.
Applications include:
Specialised arrays tailored to particular crops are becoming increasingly popular in molecular breeding applications. In the future they could be used to screen seedlings at early stages to lower the number of unneeded seedlings tried out in breeding operations. | 1 | Biochemistry |
In 1833, Adam August Krantz (who studied pharmacy and later "Geognosie" at the Bergakademie Freiberg) founded the Krantz company in Bonn. Four years later, Krantz moved to Berlin and sold minerals, fossils, rocks and basically acquired a monopoly in the production of crystal models made of pear wood or walnut. Ever since its foundation, the firm was always in contact with renowned scientists and important collectors. Hence in 1880, Krantz proposed a series of 743 pear wood models compiled for teaching purposes by the crystallographer Paul Groth. Seven years later, a supplementary collection of 213 models was available.
At the onset of the 20th century, Friedrich Krantz (a nephew of August Krantz, with a degree in mineralogy) supported by his teacher the crystallographer Carl Hintze, offered a collection of 928 models including most of the Groth models. Later, and along with many other productions, a Dana collection of 282 models was manufactured. Krantz offered a choice of collections of wooden models in different sizes (5, 10, 15–25 cm). In addition, he sold a variety of glass models having the crystallographic axes illustrated by colored silk threads or with the holohedral form made of cardboard inside. Also available were models in massive cut and polished glass (colored and uncolored), cardboard models, wire crystal models, crystal lattice models, models with rotating parts, etc.
Over the years, Krantz published numerous detailed catalogues of the collections he offered; they constitute a precious documentation. | 3 | Analytical Chemistry |
In 1961, Peter Mitchell proposed chemiosmosis as a cell's primary system of energy conversion. The mechanism, now ubiquitous in living cells, powers energy conversion in micro-organisms and in the mitochondria of eukaryotes, making it a likely candidate for early life. Mitochondria produce adenosine triphosphate (ATP), the energy currency of the cell used to drive cellular processes such as chemical syntheses. The mechanism of ATP synthesis involves a closed membrane in which the ATP synthase enzyme is embedded. The energy required to release strongly bound ATP has its origin in protons that move across the membrane. In modern cells, those proton movements are caused by the pumping of ions across the membrane, maintaining an electrochemical gradient. In the first organisms, the gradient could have been provided by the difference in chemical composition between the flow from a hydrothermal vent and the surrounding seawater, or perhaps meteoric quinones that were conducive to the development of chemiosmotic energy across lipid membranes if at a terrestrial origin. | 9 | Geochemistry |
Changes in N-linked glycosylation has been associated with different diseases including rheumatoid arthritis, type 1 diabetes, Crohn's disease, and cancers.
Mutations in eighteen genes involved in N-linked glycosylation result in a variety of diseases, most of which involve the nervous system. | 0 | Organic Chemistry |
Decreased TOR activity has been found to increase life span in S. cerevisiae, C. elegans, and D. melanogaster. The mTOR inhibitor rapamycin has been confirmed to increase lifespan in mice.
It is hypothesized that some dietary regimes, like caloric restriction and methionine restriction, cause lifespan extension by decreasing mTOR activity. Some studies have suggested that mTOR signaling may increase during aging, at least in specific tissues like adipose tissue, and rapamycin may act in part by blocking this increase. An alternative theory is mTOR signaling is an example of antagonistic pleiotropy, and while high mTOR signaling is good during early life, it is maintained at an inappropriately high level in old age. Calorie restriction and methionine restriction may act in part by limiting levels of essential amino acids including leucine and methionine, which are potent activators of mTOR. The administration of leucine into the rat brain has been shown to decrease food intake and body weight via activation of the mTOR pathway in the hypothalamus.
According to the free radical theory of aging, reactive oxygen species cause damage to mitochondrial proteins and decrease ATP production. Subsequently, via ATP sensitive AMPK, the mTOR pathway is inhibited and ATP-consuming protein synthesis is downregulated, since mTORC1 initiates a phosphorylation cascade activating the ribosome. Hence, the proportion of damaged proteins is enhanced. Moreover, disruption of mTORC1 directly inhibits mitochondrial respiration. These positive feedbacks on the aging process are counteracted by protective mechanisms: Decreased mTOR activity (among other factors) upregulates removal of dysfunctional cellular components via autophagy.
mTOR is a key initiator of the senescence-associated secretory phenotype (SASP). Interleukin 1 alpha (IL1A) is found on the surface of senescent cells where it contributes to the production of SASP factors due to a positive feedback loop with NF-κB. Translation of mRNA for IL1A is highly dependent upon mTOR activity. mTOR activity increases levels of IL1A, mediated by MAPKAPK2. mTOR inhibition of ZFP36L1 prevents this protein from degrading transcripts of numerous components of SASP factors. | 1 | Biochemistry |
Beyond domatia and nutritional rewards, other plant characteristics influence the colonization of plants by natural enemies. These can include the physical size, shape, density, maturity, colour, and texture of a given plant species. Specific plant features such as the hairiness or glossiness of vegetation can have mixed effects on different natural enemies. For example, trichomes decrease hunting efficiency of many natural enemies, as trichomes tend to slow or prevent movement due to the physical obstacles they present or the adhesive secretions they produce. However, sometimes the prey species may be more impeded than the predator. For example, when the whitefly prey of the parasitoid Encarsia formosa is slowed by plant hairs, the parasitoid can detect and parasitize a higher number of juvenile whiteflies.
Many predatory coccinelid beetles have a preference for the type of leaf surface they frequent. Presented with the opportunity to land on glossy or hairy Brassica oleracea foliage, the beetles prefer the glossy foliage as they are better able to cling to these leaves. Studies are evaluating the effect of various plant genotypes on natural enemies. | 1 | Biochemistry |
The most widely used anodizing specification in the US is a U.S. military spec, MIL-A-8625, which defines three types of aluminium anodizing. Type I is chromic acid anodizing, Type II is sulphuric acid anodizing, and Type III is sulphuric acid hard anodizing. Other anodizing specifications include more MIL-SPECs (e.g., MIL-A-63576), aerospace industry specs by organizations such as SAE, ASTM, and ISO (e.g., AMS 2469, AMS 2470, AMS 2471, AMS 2472, AMS 2482, ASTM B580, ASTM D3933, ISO 10074, and BS 5599), and corporation-specific specs (such as those of Boeing, Lockheed Martin, Airbus and other large contractors). AMS 2468 is obsolete. None of these specifications define a detailed process or chemistry, but rather a set of tests and quality assurance measures which the anodized product must meet. BS 1615 guides the selection of alloys for anodizing. For British defense work, a detailed chromic and sulfuric anodizing processes are described by DEF STAN 03-24/3 and DEF STAN 03-25/3 respectively. | 8 | Metallurgy |
The term "RuBisCO" was coined humorously in 1979, by David Eisenberg at a seminar honouring the retirement of the early, prominent RuBisCO researcher, Sam Wildman, and also alluded to the snack food trade name "Nabisco" in reference to Wildman's attempts to create an edible protein supplement from tobacco leaves.
The capitalization of the name has been long debated. It can be capitalized for each letter of the full name (Ribulose-1,5 bisphosphate carboxylase/oxygenase), but it has also been argued that is should all be in lower case (rubisco), similar to other terms like scuba or laser. | 5 | Photochemistry |
Potassium is the major cation (K, a positive ion) inside animal cells, while sodium (Na) is the major cation outside animal cells. The difference between the concentrations of these charged particles causes a difference in electric potential between the inside and outside of cells, known as the membrane potential. The balance between potassium and sodium is maintained by ion transporters in the cell membrane. All potassium ion channels are tetramers with several conserved secondary structural elements. A number of potassium channel structures have been solved including voltage gated, ligand gated, tandem-pore, and inwardly rectifying channels, from prokaryotes and eukaryotes. The cell membrane potential created by potassium and sodium ions allows the cell to generate an action potential—a "spike" of electrical discharge. The ability of cells to produce electrical discharge is critical for body functions such as neurotransmission, muscle contraction, and heart function. | 1 | Biochemistry |
Covalent bonds can be polarized depending on the relative electronegativity of the two atoms forming the bond. The electron cloud in a σ-bond between two unlike atoms is not uniform and is slightly displaced towards the more electronegative of the two atoms. This causes a permanent state of bond polarization, where the more electronegative atoms has a fractional negative charge (δ) and the less electronegative atom has a fractional positive charge (δ).
For example, the water molecule has an electronegative oxygen atom that attracts a negative charge. This is indicated by δ in the water molecule in the vicinity of the O atom, as well as by a δ next to each of the two H atoms. The vector addition of the individual bond dipole moments results in a net dipole moment for the molecule. A polar bond is a covalent bond in which there is a separation of charge between one end and the other - in other words in which one end is slightly positive and the other slightly negative. Examples include most covalent bonds. The hydrogen-chlorine bond in HCl or the hydrogen-oxygen bonds in water are typical. | 7 | Physical Chemistry |
The metabolism of drospirenone is extensive. It is metabolized into the acid form of drospirenone by opening of its lactone ring. The medication is also metabolized by reduction of its double bond between the C4 and C5 positions and subsequent sulfation. The two major metabolites of drospirenone are drospirenone acid and 4,5-dihydrodrospirenone 3-sulfate, and are both formed independently of the cytochrome P450 system. Neither of these metabolites are known to be pharmacologically active. Drospirenone also undergoes oxidative metabolism by CYP3A4. | 4 | Stereochemistry |
Outside of his scientific, teaching and administrative pursuits, Gemperline enjoys cycling, sailing, kayaking, photography and watching Dancing with the Stars on TV. | 3 | Analytical Chemistry |
Resin acids are protectants and wood preservatives that are produced by parenchymatous epithelial cells that surround the resin ducts in trees from temperate coniferous forests. The resin acids are formed when two-carbon and three-carbon molecules couple with isoprene building units to form monoterpenes (volatile), sesquiterpenes (volatile), and diterpenes (nonvolatile) structures.
Pines contain numerous vertical and radial resin ducts scattered throughout the entire wood. The accumulation of resin in the heartwood and resin ducts causes a maximum concentration in the base of the older trees. Resin in the sapwood, however, is less at the base of the tree and increases with height.
In 2005, as an infestation of the Mountain pine beetle (Dendroctonus ponderosae) and blue stain fungus devastated the Lodgepole Pine forests of northern interior British Columbia, Canada, resin acid levels three to four times greater than normal were detected in infected trees, prior to death. These increased levels show that a tree uses the resins as a defense. Resins are both toxic to the beetle and the fungus and also can entomb the beetle in diterpene remains from secretions. Increasing resin production has been proposed as a way to slow the spread of the beetle in the "Red Zone" or the wildlife urban interface. | 1 | Biochemistry |
The US Government uses the Hazardous Materials Identification System (HMIS) standard for flammability ratings, as do many US regulatory agencies, and also the US National Fire Protection Association (NFPA).
The ratings are as follows: | 7 | Physical Chemistry |
From the contamination of the sediment, more of the ecosystem is affected. Organisms in the sediment are now exposed to the new chemicals. Organisms are then ingested by fish and other aquatic animals. These animals now contain concentrations of hazardous chemicals which were secreted from the creosote. Other issues with ecosystems include bioaccumulation. Bioaccumulation occurs when high levels of chemicals are passed to aquatic life near the creosote pilings. Mollusks and other smaller crustaceans are at higher risk because they are directly attached to the surface of wood pilings that are filled with creosote preservative. Studies show that mollusks in these environments take on high concentrations of chemical compounds which will then be transferred through the ecosystem's food chain. Bioaccumulation contributes to the higher concentrations of chemicals within the organisms in the aquatic ecosystems. | 7 | Physical Chemistry |
Embryonic biomarkers are very important to fetuses, as each cell's role is decided through the use of biomarkers. Research has been conducted concerning the use of embryonic stem cells (ESCs) in regenerative medicine. This is because certain biomarkers within a cell could be altered (most likely in the tertiary stage of their formation) to change the future role of the cell, thereby creating new ones. One example of an embryonic biomarker is the protein Oct-4. | 1 | Biochemistry |
One study conducted by investigators at the University of North Carolina Chapel Hill looked into donated sperm utilization within the United States from 1995 to 2017. Cross-sectional studies recorded that an estimated 170,701 individuals during 1995 used donated sperm, while the 2011 to 2013 cohort had a decreased amount of donated sperm use of 37,385. Most recently, in the 2015 to 2017 cohort, 440,986 individuals were reported to use donated sperm. When looking at 200,197 individuals across 2011–2017, 76% had a 4-year college degree or further while 24% had high school or 2-year college degree. In terms of household percent of poverty, 71% of the sperm bank users were at or above 400% of the household poverty level while only 11% were between 200 and 399% of the household poverty levels. Although the household income levels were not explicit, there seems to be an obvious trend that higher education level attainment (such as finishing college or higher) and being at much higher income level above the household poverty levels were the common tendencies in the sperm bank users. | 1 | Biochemistry |
Improper maintenance would cause potential sources of fracture to go untreated and lead to premature failure of a component in the future. The reason for improper maintenance could be either intentional, such as skipping a yearly maintenance to avoid the cost, or unintentional, such as using the wrong engine oil. | 8 | Metallurgy |
A secondary kinetic isotope effect is observed when no bond to the isotopically labeled atom in the reactant is broken or formed. Secondary kinetic isotope effects tend to be much smaller than primary kinetic isotope effects; however, secondary deuterium isotope effects can be as large as 1.4 per deuterium atom, and techniques have been developed to measure heavy-element isotope effects to very high precision, so secondary kinetic isotope effects are still very useful for elucidating reaction mechanisms.
For the aforementioned nucleophilic substitution reactions, secondary hydrogen kinetic isotope effects at the α-carbon provide a direct means to distinguish between S1 and S2 reactions. It has been found that S1 reactions typically lead to large secondary kinetic isotope effects, approaching to their theoretical maximum at about 1.22, while S2 reactions typically yield secondary kinetic isotope effects that are very close to or less than unity. Kinetic isotope effects that are greater than 1 are referred to as normal kinetic isotope effects, while kinetic isotope effects that are less than one are referred to as inverse kinetic isotope effects. In general, smaller force constants in the transition state are expected to yield a normal kinetic isotope effect, and larger force constants in the transition state are expected to yield an inverse kinetic isotope effect when stretching vibrational contributions dominate the kinetic isotope effect.
The magnitudes of such secondary isotope effects at the α-carbon atom are largely determined by the C-H(D) vibrations. For an S1 reaction, since the carbon atom is converted into an sp hybridized carbenium ion during the transition state for the rate-determining step with an increase in C-H(D) bond order, an inverse kinetic isotope effect would be expected if only the stretching vibrations were important. The observed large normal kinetic isotope effects are found to be caused by significant out-of-plane bending vibrational contributions when going from the reactants to the transition state of carbenium ion formation. For S2 reactions, bending vibrations still play an important role for the kinetic isotope effect, but stretching vibrational contributions are of more comparable magnitude, and the resulting kinetic isotope effect may be normal or inverse depending on the specific contributions of the respective vibrations. | 7 | Physical Chemistry |
In some cases, simply changing the way the material is processed can influence the microstructure. An example is the titanium alloy TiAl6V4. Its microstructure and mechanical properties are enhanced using SLM (selective laser melting) which is a 3D printing technique using powder and melting the particles together using high powered laser. Other conventional techniques for improving the microstructure are thermal processes. Those processes rely in the principle that an increase in temperature will induce the reduction or annihilation of pores. Hot isostatic pressing (HIP) is a manufacturing process, used to reduce the porosity of metals and increase the density of many ceramic materials. This improves the material's mechanical properties and workability.
The HIP process exposes the desired material to an isostatic gas pressure as well as high temperature in a sealed vessel (high pressure). The gas used during this process is mostly Argon. The gas needs to be chemically inert so that no reaction occurs between it and the sample. The pressure is achieved by simply applying heat to the hermetically sealed vessel. However, some systems also associate gas pumping to the process to achieve the required pressure level. The pressure applied on the materials is equal and comes from all directions (hence the term “isostatic”). When castings are treated with HIP, the simultaneous application of heat and pressure eliminates internal voids and microporosity through a combination of plastic deformation, creep, and diffusion bonding; this process improves fatigue resistance of the component. | 8 | Metallurgy |
The second step of fatty acid degradation is beta oxidation. Beta oxidation occurs in mitochondria. After formation in the cytosol, acyl-CoA is transported into the mitochondria, the locus of beta oxidation. Transport of acyl-CoA into the mitochondria requires carnitine palmitoyltransferase 1 (CPT1), which converts acyl-CoA into acylcarnitine, which gets transported into the mitochondrial matrix. Once in the matrix, acylcarnitine is converted back to acyl-CoA by CPT2. Beta oxidation may begin now that Acyl-CoA is in the mitochondria.
Beta oxidation of acyl-CoA occurs in four steps.
1. Acyl-CoA dehydrogenase catalyzes dehydrogenation of the acyl-CoA, creating a double bond between the alpha and beta carbons. FAD is the hydrogen acceptor, yielding FADH2.
2. Enoyl-CoA hydrase catalyzes the addition of water across the newly formed double bond to make an alcohol.
3. 3-hydroxyacyl-CoA dehydrogenase oxidizes the alcohol group to a ketone. NADH is produced from NAD+.
4. Thiolase cleaves between the alpha carbon and ketone to release one molecule of Acetyl-CoA and the Acyl-CoA which is now 2 carbons shorter.
This four step process repeats until acyl-CoA has removed all carbons from the chain, leaving only Acetyl-CoA. During one cycle of beta oxidation, Acyl-CoA creates one molecule of Acetyl-CoA, FADH2, and NADH. Acetyl-CoA is then used in the citric acid cycle while FADH2 and NADH are sent to the electron transport chain. These intermediates all end up providing energy for the body as they are ultimately converted to ATP.
Beta oxidation, as well as alpha-oxidation, also occurs in the peroxisome. The peroxisome handles beta oxidation of fatty acids that have more than 20 carbons in their chain because the peroxisome contains very-long-chain Acyl-CoA synthetases. These enzymes are better equipped to oxidize Acyl-CoA with long chains that the mitochondria cannot handle. | 1 | Biochemistry |
Orosomucoid (ORM) or alpha-1-acid glycoprotein (αAGp, AGP or AAG) is an acute phase protein found in plasma. It is an alpha-globulin glycoprotein and is modulated by two polymorphic genes. It is synthesized primarily in hepatocytes and has a normal plasma concentration between 0.6–1.2 mg/mL (1–3% plasma protein). Plasma levels are affected by pregnancy, burns, certain drugs, and certain diseases, particularly HIV.
The only established function of ORM is to act as a carrier of basic and neutrally charged lipophilic compounds. In medicine, it is known as the primary carrier of basic (negatively charged) drugs (whereas albumin carries acidic (positively charged) and neutral drugs), steroids, and protease inhibitors. Aging causes a small decrease in plasma albumin levels; if anything, there is a small increase in alpha-1-acid glycoprotein. The effect of these changes on drug protein binding and drug delivery, however, appear to be minimal. AGP shows a complex interaction with thyroid homeostasis: AGP in low concentrations was observed to stimulate the thyrotropin (TSH) receptor and intracellular accumulation of cyclic AMP. High AGP concentrations, however, inhibited TSH signalling.
Alpha-1-acid glycoprotein has been identified as one of four potentially useful circulating biomarkers for estimating the five-year risk of all-cause mortality (the other three are albumin, very low-density lipoprotein particle size, and citrate).
Orosomucoid increases in amount in obstructive jaundice while it diminishes in hepatocellular jaundice and in intestinal infections. | 1 | Biochemistry |
Pathway building has been performed by individual groups studying a network of interest (e.g., immune signaling pathway) as well as by large bioinformatics consortia (e.g., the Reactome Project) and commercial entities (e.g., Ingenuity Systems). Pathway building is the process of identifying and integrating the entities, interactions, and associated annotations, and populating the knowledge base. Pathway construction can have either a data-driven objective (DDO) or a knowledge-driven objective (KDO). Data-driven pathway construction is used to generate relationship information of genes or proteins identified in a specific experiment such as a microarray study. Knowledge-driven pathway construction entails development of a detailed pathway knowledge base for particular domains of interest, such as a cell type, disease, or system. The curation process of a biological pathway entails identifying and structuring content, mining information manually and/or computationally, and assembling a knowledgebase using appropriate software tools. A schematic illustrating the major steps involved in the data-driven and knowledge-driven construction processes.
For either DDO or KDO pathway construction, the first step is to mine pertinent information from relevant information sources about the entities and interactions. The information retrieved is assembled using appropriate formats, information standards, and pathway building tools to obtain a pathway prototype. The pathway is further refined to include context-specific annotations such as species, cell/tissue type, or disease type. The pathway can then be verified by the domain experts and updated by the curators based on appropriate feedback. Recent attempts to improve knowledge integration have led to refined classifications of cellular entities, such as GO, and to the assembly of structured knowledge repositories. Data repositories, which contain information regarding sequence data, metabolism, signaling, reactions, and interactions are a major source of information for pathway building. A few useful databases are described in the following table.
Legend: Y – Yes, N – No; BIND – Biomolecular Interaction Network Database, DIP – Database of Interacting Proteins, GNPV – Genome Network Platform Viewer, HPRD = Human Protein Reference Database, MINT – Molecular Interaction database, MIPS – Munich Information center for Protein Sequences, UNIHI – Unified Human Interactome, OPHID – Online Predicted Human Interaction Database, EcoCyc – Encyclopaedia of E. Coli Genes and Metabolism, MetaCyc – aMetabolic Pathway database, KEGG – Kyoto Encyclopedia of Genes and Genomes, PANTHER – Protein Analysis Through Evolutionary Relationship database, STKE – Signal Transduction Knowledge Environment, PID – The Pathway Interaction Database, BioPP – Biological Pathway Publisher. A comprehensive list of resources can be found at http://www.pathguide.org. | 7 | Physical Chemistry |
If the drip rate is quicker than one drop per minute, most of the CaCO will be carried to the ground, still in solution. The leachate solution then has a chance to absorb CO from the atmosphere (or degas CO depending on reaction) and deposit the CaCO on the ground as a stalagmite.
In most locations within manmade concrete structures, calthemite stalagmites only grow to a maximum of a few centimetres high, and look like low rounded lumps. This is because of the limited supply of CaCO from the leachate seepage path through the concrete and the amount which reaches the ground. Their location may also inhibit their growth due to abrasion from vehicle tires and pedestrian traffic. | 8 | Metallurgy |
Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ions across the cell membrane, controlling the flow of ions across secretory and epithelial cells, and regulating cell volume. Ion channels are present in the membranes of all cells. Ion channels are one of the two classes of ionophoric proteins, the other being ion transporters.
The study of ion channels often involves biophysics, electrophysiology, and pharmacology, while using techniques including voltage clamp, patch clamp, immunohistochemistry, X-ray crystallography, fluoroscopy, and RT-PCR. Their classification as molecules is referred to as channelomics. | 1 | Biochemistry |
* AsP
* [GeSn]
* [SnBi]
* [SnBi]
* [PbSb]
* SnSb
* [InBi]
* BiGe
* [GaBi]
* [InBi]
* [TlSn]
* [TlSn]
* [Sb@InSb]
* [Sb@InSb] | 7 | Physical Chemistry |
The term forensic stems from the Latin word, forēnsis (3rd declension, adjective), meaning "of a forum, place of assembly". The history of the term originates in Roman times, when a criminal charge meant presenting the case before a group of public individuals in the forum. Both the person accused of the crime and the accuser would give speeches based on their sides of the story. The case would be decided in favor of the individual with the best argument and delivery. This origin is the source of the two modern usages of the word forensic—as a form of legal evidence; and as a category of public presentation.
In modern use, the term forensics is often used in place of "forensic science."
The word "science", is derived from the Latin word for knowledge and is today closely tied to the scientific method, a systematic way of acquiring knowledge. Taken together, forensic science means the use of scientific methods and processes for crime solving. | 3 | Analytical Chemistry |
Avogadros law provides a way to calculate the quantity of gas in a receptacle. Thanks to this discovery, Johann Josef Loschmidt, in 1865, was able for the first time to estimate the size of a molecule. His calculation gave rise to the concept of the Loschmidt constant, a ratio between macroscopic and atomic quantities. In 1910, Millikans oil drop experiment determined the charge of the electron; using it with the Faraday constant (derived by Michael Faraday in 1834), one is able to determine the number of particles in a mole of substance. At the same time, precision experiments by Jean Baptiste Perrin led to the definition of the Avogadro number as the number of molecules in one gram-molecule of oxygen. Perrin named the number to honor Avogadro for his discovery of the namesake law. Later standardization of the International System of Units led to the modern definition of the Avogadro constant. | 7 | Physical Chemistry |
As a material cools, the relative motion of its component molecules/atoms decreases - its temperature decreases. Cooling can continue until all motion ceases, and its kinetic energy, or energy of motion, disappears. This condition is known as absolute zero and it forms the basis for the Kelvin temperature scale, which measures the temperature above absolute zero. Zero degrees Celsius (°C) coincides with 273 Kelvin.
At absolute zero most elements become a solid, but not all behave as predictably as this; for instance, helium becomes a highly unusual liquid. The chemistry between substances, however, does not disappear, even near absolute zero temperatures, since separated molecules/atom can always combine to lower their total energy. Almost every molecule or element will show different properties at different temperatures; if cold enough, some functions are lost entirely. Cryogenic chemistry can lead to very different results compared with standard chemistry, and new chemical routes to substances may be available at cryogenic temperatures, such as the formation of argon fluorohydride, which is only a stable compound at or below . | 7 | Physical Chemistry |
One of the first common applications of surface plasmon resonance spectroscopy was the measurement of the thickness (and refractive index) of adsorbed self-assembled nanofilms on gold substrates. The resonance curves shift to higher angles as the thickness of the adsorbed film increases. This example is a static SPR measurement.
When higher speed observation is desired, one can select an angle right below
the resonance point (the angle of minimum reflectance), and measure the reflectivity changes at that point.
This is the so-called dynamic SPR measurement. The interpretation of the data assumes that the structure of the film does not change significantly during the measurement. | 7 | Physical Chemistry |
Prostaglandins are derived from the parent molecule arachidonic acid. The synthesis of prostaglandins can be blocked by anti-inflammatory drugs such as ibuprofen. Anti-inflammatory drugs block the synthesis of cyclooxygenases which in turn produce prostaglandins. Prostaglandins (PG) are the result of an enzyme cascade pathway that includes two enzymes cyclooxygenase and PG synthase. Prostaglandin E2 is produced by PGE synthase via the activation of EP1-4 receptors. Prostaglandin E2s (PGEs) are associated with the development of vascular diseases that lead to inflammation in the body. In the human body, PGEs are involved in the control of the vascular smooth muscle, cell migration and the division of a cell into two daughter cells. The process of producing two daughter cells via cell division is called cell proliferation. | 1 | Biochemistry |
The stream is exposed to ozone and ozone is unstable at atmospheric condition. The ozone (O3) decomposes into oxygen (O2) and more oxygen is dissolved into the stream. The pathogen is oxidised to form carbon dioxide. This process eliminates the odour of the stream but result in slightly acidic product due to the effect of carbon dioxide present. | 3 | Analytical Chemistry |
Sulfones with a good leaving group in the β position may undergo reductive elimination under desulfonylation conditions to afford alkenes. This process is a key step of the Julia olefination, which yields alkenes via addition of an α-sulfonyl carbanion to an aldehyde followed by reductive elimination. Sodium amalgam or samarium(II) iodide/HMPA may be used to convert β-sulfonyloxy or β-acyloxy sulfones to the corresponding alkenes. The key mechanistic step of this process is elimination of an anionic or organometallic intermediate to generate the alkene.
The use of sodium amalgam, which promotes the formation of essentially free alkyl anions, leads to (E) alkenes with extremely high selectivity. Samarium(II) iodide also produces the (E) alkene predominantly, but with lower selectivity. | 0 | Organic Chemistry |
Patch-Clamp Electrophysiology was developed by Neher and Sakmann in 1976. This technique allowed measurements of individual proteins through ion channels. A glass pipette was fixed to the cell membrane, and the ion currents though the ion channels were measured. The Patch-Clamp method increased the sensitivity of detection by three orders of magnitude over previous methods, and the time resolution for the measurements was decreased to nearly 10 microseconds. The success of this method was a result of the ability to create a high resistance seal between the glass micropipette and the cell membrane; isolating the system chemically and electrically. | 7 | Physical Chemistry |
A common concept in materials science is that, at ambient conditions, smaller features (like grain size or absolute size) generally lead to stronger materials (see Hall-Petch strengthening, Weibull statistics). However, due to the high-level of porosity in the dealloyed materials, their strengths and stiffnesses are relatively low compared to the bulk counterparts. The decrease in strength due to porosity can be described with the Gibson-Ashby (GA) relations, which give the yield strength and Young's modulus of a foam according to the following equations:
where and <math>C_E
and <math>n_E
is the relative density of the foam.
The GA relations can be used to estimate the strength and stiffness of a given dealloyed, porous material, but more extensive study has revealed an additional factor: ligament size. When the ligament diameter is greater than 100 nm, increasing ligament size leads to greater agreement between GA predictions and experimental measurements of yield stress and Young's modulus. However, when the ligament size is under 100 nm, which is very common in many dealloying processes, there is an addition to the GA strength that looks similar to Hall-Petch strengthening of bulk polycrystalline metals (i.e., the yield stress increases with the inverse square root of grain size). Combining this relationship with the GA relation from before, an expression for the yield stress of dealloyed materials with ligaments smaller than 100 nm can be determined:
where A and m are empirically determined constants, and is the ligament size. The represents the Hall-Petch-like contribution.
There are two theories for why this increase in strength occurs: 1) dislocations are less common in smaller sample volumes, so deformation requires activation of sources (which is a more difficult process), or 2) dislocations pile-up, which strengthens the material. Either way, there would be significant surface and small volume effects in the ligaments <100 nm, which lead to this increase in yield stress. A relationship between ligament size and Young's modulus has not been studied past the GA relation.
Occasionally, the metastable nature of these materials means that ligaments in the structure may "pinch off" due to surface diffusion, which decreases the connectivity of the structure, and reduces the strength of the dealloyed material past what would be expected from simply porosity (as predicted by the Gibson-Ashby relations). | 8 | Metallurgy |
Waste heat can be forced to heat incoming fluids and objects before being highly heated. For instance outgoing water can give its waste heat to incoming water in a heat exchanger before heating in homes or power plants. | 7 | Physical Chemistry |
Paschen's law is an equation that gives the breakdown voltage, that is, the voltage necessary to start a discharge or electric arc, between two electrodes in a gas as a function of pressure and gap length. It is named after Friedrich Paschen who discovered it empirically in 1889.
Paschen studied the breakdown voltage of various gases between parallel metal plates as the gas pressure and gap distance were varied:
* With a constant gap length, the voltage necessary to arc across the gap decreased as the pressure was reduced and then increased gradually, exceeding its original value.
* With a constant pressure, the voltage needed to cause an arc reduced as the gap size was reduced but only to a point. As the gap was reduced further, the voltage required to cause an arc began to rise and again exceeded its original value.
For a given gas, the voltage is a function only of the product of the pressure and gap length. The curve he found of voltage versus the pressure-gap length product (right) is called Paschens curve. He found an equation that fit these curves, which is now called Paschens law.
At higher pressures and gap lengths, the breakdown voltage is approximately proportional to the product of pressure and gap length, and the term Paschen's law is sometimes used to refer to this simpler relation. However, this is only roughly true, over a limited range of the curve. | 7 | Physical Chemistry |
In many documented cases, dextromethorphan has produced psychological dependence in people who used it recreationally. It is considered less addictive than other common cough suppressants, such as the weak opiate codeine. Since dextromethorphan also acts as a serotonin reuptake inhibitor, users report that regular recreational use over a long period of time can cause withdrawal symptoms similar to those of antidepressant discontinuation syndrome. Additionally, disturbances have been reported in sleep, senses, movement, mood, and thinking. | 4 | Stereochemistry |
Oxyntomodulin (often abbreviated OXM) is a naturally occurring 37-amino acid peptide hormone found in the colon, produced by the oxyntic (fundic) cells of the oxyntic (fundic) mucosa. It has been found to suppress appetite.
The mechanism of action of oxyntomodulin is not well understood. It is known to bind both the GLP-1 receptor and the glucagon receptor, but it is not known whether the effects of the hormone are mediated through these receptors or through an unidentified receptor.
Oxyntomodulin has been linked to entrainment of the liver's circadian clock.
Oxyntomodulin has been investigated as a blood-glucose regulation agent in connection with diabetes. | 1 | Biochemistry |
The design of a galvanic anode CP system should consider many factors, including the type of structure, the resistivity of the electrolyte (soil or water) it will operate in, the type of coating and the service life.
The primary calculation is how much anode material will be required to protect the structure for the required time. Too little material may provide protection for a while, but need to be replaced regularly. Too much material would provide protection at an unnecessary cost. The mass in kg is given by equation ().
* The design life is in years (1 year = 8760 hours).
* The utilisation factor (UF) of the anode is a constant value, depending on the shape of the anode and how it is attached, which signifies how much of the anode can be consumed before it ceases to be effective. A value of 0.8 indicates that 80% of the anode can be consumed, before it should be replaced. A long slender stand off anode (installed on legs to keep the anode away from the structure) has a UF value of 0.9, whereas the UF of a short, flush mounted anode is 0.8.
* Anode capacity is an indication of how much material is consumed as current flows over time. The value for zinc in seawater is 780 Ah/kg but aluminium is 2000 Ah/kg, which reflects the lower atomic mass of aluminium and means that, in theory, aluminium can produce much more current per weight than zinc before being depleted and this is one of the factors to consider when choosing a particular material.
The amount of current required corresponds directly to the surface area of the metal exposed to the soil or water, so the application of a coating drastically reduces the mass of anode material required. The better the coating, the less anode material is needed.
Once the required mass of material is known, the particular type of anode is chosen. Differently shaped anodes will have a different resistance to earth, which governs how much current can be produced, so the resistance of the anode is calculated to ensure that sufficient current will be available. If the resistance of the anode is too high, either a differently shaped or sized anode is chosen, or a greater quantity of anodes must be used.
The arrangement of the anodes is then planned so as to provide an even distribution of current over the whole structure. For example, if a particular design shows that a pipeline long needs 10 anodes, then approximately one anode per kilometre would be more effective than putting all 10 anodes at one end or in the centre. | 7 | Physical Chemistry |
ASF/SF2 is an SR protein, and as such, contains two functional modules: an arginine-serine rich region (RS domain), where the bulk of ASF/SF2 regulation takes place, and two RNA recognition motifs (RRMs), through which ASF/SF2 interacts with RNA and other splicing factors. These modules have different functions within general splicing factor function. | 1 | Biochemistry |
Hydrofluoric acid, the water solution of hydrogen fluoride (HF), is a contact poison. Even though it is from a chemical perspective a relatively weak acid, it is far more dangerous than conventional strong mineral acids, such as nitric acid, sulfuric acid, or hydrochloric acid. Owing to its lesser chemical dissociation in water (remaining a neutral molecule), hydrogen fluoride penetrates tissue more quickly than typical acids. Poisoning can occur readily through the skin or eyes or when inhaled or swallowed. From 1984 to 1994, at least nine workers died in the United States from accidents with HF.
Once in the blood, hydrogen fluoride reacts with calcium and magnesium, resulting in electrolyte imbalances, potentially including hypocalcemia. The consequent effect on the heart (cardiac arrhythmia) may be fatal. Formation of insoluble calcium fluoride also causes severe pain. Burns with areas larger than 160 cm, about the size of a man's hand, can cause serious systemic toxicity.
Symptoms of exposure to hydrofluoric acid may not be immediately evident, with an eight-hour delay for 50% HF and up to 24 hours for lower concentrations. Hydrogen fluoride interferes with nerve function, meaning that burns may not initially be painful. If the burn has been initially noticed, then HF should be washed off with a forceful stream of water for ten to fifteen minutes to prevent its further penetration into the body. Clothing used by the person burned may also present a danger. Hydrofluoric acid exposure is often treated with calcium gluconate, a source of Ca that binds with the fluoride ions. Skin burns can be treated with a water wash and 2.5 percent calcium gluconate gel or special rinsing solutions. Because HF is absorbed, further medical treatment is necessary. Calcium gluconate may be injected or administered intravenously. Use of calcium chloride is contraindicated and may lead to severe complications. Sometimes surgical excision of tissue or amputation is required. | 1 | Biochemistry |
Design parameters include type of mill, milling container, milling speed, milling time, type, size, and size distribution of the grinding medium, ball-to-powder weight ratio, extent of filling the vial, milling atmosphere, process control agent, temperature of milling, and the reactivity of the species. | 8 | Metallurgy |
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