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Mikhail Shneider and Richard Miles first described the phenomenon mathematically in their 2005 work on microwave diagnostics of small plasma objects. The scattering regime was experimentally demonstrated and formally named by Adam R. Patel and Alexey Shashurin and has been applied in the coherent microwave scattering diagnosis of small laser-induced plasma objects. | 7 | Physical Chemistry |
Sorbent tubes are the most widely used collection media for sampling hazardous gases and vapors in air, mostly as it relates to Industrial hygiene. They were developed by the US National Institute for Occupational Safety and Health (NIOSH) for air quality testing of workers. Sorbent Tubes are available from CARO Analytical Services, SKC Inc., 7Solutions BV, Uniphos Ltd., SKC Ltd, Zefon International, Sigma-Aldrich/Supelco and Markes International. SKC Inc. manufactured the first commercially available sorbent tubes. XAD2 Tubes.
Sorbent tubes are typically made of glass and contain various types of solid adsorbent material (sorbents). Commonly used sorbents include activated charcoal, silica gel, and organic porous polymers such as Tenax and Amberlite XAD resins. Solid sorbents are selected for sampling specific compounds in air because they:
# Trap and retain the compound(s) of interest even in the presence of other compounds
# Do not alter the compound(s) of interest
# Allow collected compounds to be easily desorbed or extracted for analysis
Sorbent tubes are attached to air sampling pumps for sample collection. A pump with a calibrated flow rate in ml/min is normally placed on a worker’s belt and it draws a known volume of air through the sorbent tube. Alternatively, pumps and sorbent tubes are placed in areas for fixed-point sampling. Chemicals are trapped onto the sorbent material throughout the sampling period.
Occasionally, when desorbing the air sample from the sorbent tube, a large portion of the analyte will fail to go into the solution. In these cases, the sorbent tubes will have to be adjusted for desorption efficiency (DE). | 3 | Analytical Chemistry |
As of 2015 hypothermia had shown no improvements in neurological outcomes or in mortality in neurosurgery. | 1 | Biochemistry |
In 1960, Atalla and Kahng fabricated the first MOSFET with a gate oxide thickness of 100 nm, along with a gate length of 20µm. In 1962, Atalla and Kahng fabricated a nanolayer-base metal–semiconductor junction (M–S junction) transistor. This device has a metallic layer with nanometric thickness sandwiched between two semiconducting layers, with the metal forming the base and the semiconductors forming the emitter and collector. With its low resistance and short transit times in the thin metallic nanolayer base, the device was capable of high operation frequency compared to bipolar transistors. Their pioneering work involved depositing metal layers (the base) on top of single crystal semiconductor substrates (the collector), with the emitter being a crystalline semiconductor piece with a top or a blunt corner pressed against the metallic layer (the point contact). They deposited gold (Au) thin films with a thickness of 10 nm on n-type germanium (n-Ge), while the point contact was n-type silicon (n-Si). Atalla resigned from BTL in 1962. | 7 | Physical Chemistry |
The interface between a crystal and its vapor can be molecularly sharp at temperatures well below the melting point. An ideal crystalline surface grows by the spreading of single layers, or equivalently, by the lateral advance of the growth steps bounding the layers. For perceptible growth rates, this mechanism requires a finite driving force (or degree of supercooling) in order to lower the nucleation barrier sufficiently for nucleation to occur by means of thermal fluctuations. In the theory of crystal growth from the melt, Burton and Cabrera have distinguished between two major mechanisms: | 3 | Analytical Chemistry |
EPIC-seq may exhibit enhanced performance in detecting late-stage cancer due to higher levels of ctDNA and more pronounced genetic alterations. For example, EPIC-seq's sensitivity for detecting NSCLC diminishes significantly in patients with low tumor-DNA burden (below 1%), resulting in decreased detection rates by approximately 34%. | 1 | Biochemistry |
It was long considered that the best examples of neutral homoaromatics are bishomoaromatics such as barrelene and semibullvalene. First synthesized in 1966, semibullvalene has a structure that should lend itself well to homoaromaticity although there has been much debate whether semibullvalene derivatives can provide a true delocalized, ground state neutral homoaromatic compound or not. In an effort to further stabilize the delocalized transition structure by substituting semibullvalene with electron donating and accepting groups, it has been found that the activation barrier to this rearrangement can be lowered, but not eliminated. However, with the introduction of ring strain into the molecule, aimed at destabilizing the localized ground state structure's through the strategic addition of cyclic annulations, a delocalized homoaromatic ground-state structure can indeed be achieved.
Of the neutral homoaromatics, the compounds best believed to exhibit neutral homoaromaticity are boron containing compounds of 1,2-diboretane and its derivatives. Substituted diboretanes are shown to have a much greater stabilization in the delocalized state over the localized one, giving strong indications of homoaromaticity. When electron-donating groups are attached to the two boron atoms, the compound favors a classical model with localized bonds. Homoaromatic character is best seen when electron-withdrawing groups are bonded to the boron atoms, causing the compound to adopt a nonclassical, delocalized structure. | 7 | Physical Chemistry |
For an adsorption column, the column resin (the stationary phase) is composed of microbeads. Even smaller particles such as proteins, carbohydrates, metal ions, or other chemical compounds are conjugated onto the microbeads. Each binding particle that is attached to the microbead can be assumed to bind in a 1:1 ratio with the solute sample sent through the column that needs to be purified or separated.
Binding between the target molecule to be separated and the binding molecule on the column beads can be modeled using a simple equilibrium reaction K = [CS]/([C][S]) where K is the equilibrium constant, [C] and [S] are the concentrations of the target molecule and the binding molecule on the column resin, respectively. [CS] is the concentration of the complex of the target molecule bound to the column resin.
Using this as a basis, three different isotherms can be used to describe the binding dynamics of a column chromatography: linear, Langmuir, and Freundlich.
The linear isotherm occurs when the solute concentration needed to be purified is very small relative to the binding molecule. Thus, the equilibrium can be defined as:
:[CS] = K[C].
For industrial scale uses, the total binding molecules on the column resin beads must be factored in because unoccupied sites must be taken into account. The Langmuir isotherm and Freundlich isotherm are useful in describing this equilibrium. The Langmuir isotherm is given by:
:[CS] = (KS[C])/(1 + K[C]), where S is the total binding molecules on the beads.
The Freundlich isotherm is given by:
:[CS] = K[C]
The Freundlich isotherm is used when the column can bind to many different samples in the solution that needs to be purified. Because the many different samples have different binding constants to the beads, there are many different Ks. Therefore, the Langmuir isotherm is not a good model for binding in this case. | 3 | Analytical Chemistry |
Cefazaflur stands out among this group of analogues because it lacks an arylamide C-7 side chain (see cephacetrile for another example).
Cefazaflur is synthesized by reaction of 3-(1-methyl-1-tetrazol-5-ylthiomethylene)-7-amino-cephem-4-carboxylic acid (1) with trifluoromethylthioacetyl chloride (2). | 4 | Stereochemistry |
Supercritical angle fluorescence microscopy (SAF) is a technique to detect and characterize fluorescent species (proteins, biomolecules, pharmaceuticals, etc.) and their behaviour close or even adsorbed or linked at surfaces. The method is able to observe molecules in a distance of less than 100 to 0 nanometer from the surface even in presence of high concentrations of fluorescent species around. Using an aspheric lens for excitation of a sample with laser light, fluorescence emitted by the specimen is collected above the critical angle of total internal reflection selectively and directed by a parabolic optics onto a detector. The method was invented in 1998 in the laboratories of Stefan Seeger at University of Regensburg/Germany and later at University of Zurich/Switzerland. | 3 | Analytical Chemistry |
There are no d-d electron transitions in d metal complexes because the d orbitals are completely filled. Thus, UV-vis absorption bands are not observed and a Tanabe–Sugano diagram does not exist. | 7 | Physical Chemistry |
Restriction landmark genomic scanning (RLGS) is a genome analysis method for rapid simultaneous visualization of thousands of landmarks, or restriction sites. Using a combination of restriction enzymes some of which are specific to DNA modifications, the technique can be used to visualize differences in methylation levels across the genome of a given organism. RLGS employs direct labeling of DNA, which is first cut by a specific series of restriction enzymes, and then labeled by a radioactive isotope (usually phosphorus-32). A two-dimensional electrophoresis process is then employed, yielding high-resolution results. The radioactive second-dimension gel is then allowed to expose a large sheet of film. The radiation produced by the radioactive labeling will cause the film to be exposed wherever the restriction fragments have migrated during electrophoresis. The film is then developed, yielding a visual representation of the results in the form of an autoradiograph. The same combination of restriction enzymes will produce the same pattern of spots from samples from the same organisms, but different patterns for different types of organism. For example, human and mouse DNA will produce distinctly different patterns when treated with the same combination of enzymes. These finished auto-rads can be examined against each other, revealing any changes in gene expression that lead to visual differences in the film. Each autoradiograph contains thousands of spots, each corresponding to a labeled DNA restriction landmark.
RLGS becomes useful when doing whole-genome scans, and can effectively do the work of thousands of polymerase chain reactions at once. It readily detects alterations deviating from normal, and thus is exceptionally effective in identifying hyper/hypomethylation in tumors, deletions or amplifications of genes, or simply changes in gene expression throughout the development of an organism. | 1 | Biochemistry |
The exact temperatures at which iron will transition from one crystal structure to another depends on how much and what type of other elements are dissolved in the iron. The phase boundary between the different solid phases is drawn on a binary phase diagram, usually plotted as temperature versus percent iron. Adding some elements, such as Chromium, narrows the temperature range for the gamma phase, while others increase the temperature range of the gamma phase. In elements that reduce the gamma phase range, the alpha-gamma phase boundary connects with the gamma-delta phase boundary, forming what is usually called the Gamma loop. Adding Gamma loop additives keeps the iron in a body-centered cubic structure and prevents the steel from suffering phase transition to other solid states. | 8 | Metallurgy |
Operando spectroscopy requires measurement of the catalyst under (ideally) real working conditions, involving comparable temperature and pressure environments to those of industrially catalyzed reactions, but with a spectroscopic device inserted into the reaction vessel. The parameters of the reaction are then measured continuously during the reaction using the appropriate instrumentation, i.e., online mass spectrometry, gas chromatography or IR/NMR spectroscopy.
Operando instruments (in situ cells) must ideally allow for spectroscopic measurement under optimal reaction conditions. Most industrial catalysis reactions require excessive pressure and temperature conditions which subsequently degrades the quality of the spectra by lowering the resolution of signals. Currently many complications of this technique arise due to the reaction parameters and the cell design. The catalyst may interact with the components of the operando apparatus; open space in the cell can have an effect on the absorption spectra, and the presence of spectator species in the reaction may complicate analysis of the spectra. Continuing development of operando reaction-cell design is in line with working towards minimizing the need for compromise between optimal catalysis conditions and spectroscopy. These reactors must handle specific temperature and pressure requirements while still providing access for spectrometry.
Other requirements considered when designing operando experiments include reagent and product flow rates, catalyst position, beam paths, and window positions and sizes. All of these factors must also be accounted for while designing operando experiments, as the spectroscopic techniques used may alter the reaction conditions. An example of this was reported by Tinnemans et al., which noted that local heating by a Raman laser can give spot temperatures exceeding 100 °C. Also, Meunier reports that when using DRIFTS, there is a noticeable temperature difference (on the order of hundreds of degrees) between the crucible core and the exposed surface of the catalyst due to losses caused by the IR-transparent windows necessary for analysis. | 7 | Physical Chemistry |
Most asymmetric Heck reactions employing chiral phosphines proceed by the cationic pathway, which does not require the dissociation of a phosphine ligand. Oxidative addition of an aryl perfluorosulfonate generates a cationic palladium aryl complex V. The mechanism then proceeds as in the neutral case, with the difference that an extra site of coordinative unsaturation exists on palladium throughout the process.
Thus, coordination of the alkene does not require ligand dissociation. Stoichiometric amounts of base are still required to reduce the palladium(II)-hydrido complex VIII back to palladium(0). Silver salts may be used to initiate the cationic pathway in reactions of aryl halides. | 0 | Organic Chemistry |
GFP can be used to analyse the colocalization of proteins. This is achieved by "splitting" the protein into two fragments which are able to self-assemble, and then fusing each of these to the two proteins of interest. Alone, these incomplete GFP fragments are unable to fluoresce. However, if the two proteins of interest colocalize, then the two GFP fragments assemble together to form a GFP-like structure which is able to fluoresce. Therefore, by measuring the level of fluorescence it is possible to determine whether the two proteins of interest colocalize. | 1 | Biochemistry |
Limulus amebocyte lysate (LAL) is an aqueous extract of motile blood cells (amebocytes) from the Atlantic horseshoe crab Limulus polyphemus. LAL reacts with bacterial endotoxins such as lipopolysaccharides (LPS), which are components of the bacterial capsule, the outermost membrane of cell envelope of gram-negative bacteria. This reaction is the basis of the LAL test, which is widely used for the detection and quantification of bacterial endotoxins.
In Asia, a similar Tachypleus amebocyte lysate (TAL) test based on the local horseshoe crabs Tachypleus gigas or Tachypleus tridentatus is occasionally used instead. The recombinant factor C (rFC) assay is a replacement of LAL and TAL based on a similar reaction. | 3 | Analytical Chemistry |
An additional source of atmospheric free oxygen comes from photolysis, whereby high-energy ultraviolet radiation breaks down atmospheric water and nitrous oxide into component atoms. The free hydrogen and nitrogen atoms escape into space, leaving O in the atmosphere: | 5 | Photochemistry |
Free thyroxine (fT or free T4) is generally elevated in hyperthyroidism and decreased in hypothyroidism.
Reference ranges depend on the method of analysis. Results should always be interpreted using the range from the laboratory that performed the test. Example values are: | 1 | Biochemistry |
It is known that aluminum improves the sulfidation resistance of iron alloys.
The sulfidation of tungsten is a multiple step process. The first step is an oxidation reaction, converting the tungsten to a tungsten bronze on the surface of the object. The tungsten bronze coating is then converted to a sulfide.
One commonly encountered occurrence of sulfidation in manufacturing environments involves the sulfidic corrosion of metal piping. The increased resistance to corrosion found in stainless steel is attributed to a layer of chromium oxide that forms due to oxidation of the chromium found in the alloy.
The process of liquid sulfidation has also been used in the manufacturing of diamond-like carbon films. These films are generally used to coat surfaces to reduce the wear due to friction. The inclusion of sulfidation in the process has been shown to reduce the friction coefficient of the diamond-like carbon film. | 7 | Physical Chemistry |
The sun bombards the earth with billions of charged nanoparticles with an immense amount of energy stored in them. This energy can be used for water heating, space heating, space cooling and process heat generation. Many steam generation systems have adapted to using sunlight as a primary source for heating feed water, a development that has greatly increased the overall efficiency of boilers and many other types of waste heat recovery systems. Solar cookers use sunlight for cooking, drying and pasteurization. Solar distillation is used for water treatment processes to create potable drinking water, which has been an extremely powerful player in providing countries in need with relief efforts through the use of advancing technology. | 7 | Physical Chemistry |
Hydraulic residence time (HRT) is an important factor in the transport of environmental toxins or other chemicals through groundwater. The amount of time that a pollutant spends traveling through a delineated subsurface space is related to the saturation and the hydraulic conductivity of the soil or rock. Porosity is another significant contributing factor to the mobility of water through the ground (e.g. toward the water table). The intersection between pore density and size determines the degree or magnitude of the flow rate through the media. This idea can be illustrated by a comparison of the ways water moves through clay versus gravel. The retention time through a specified vertical distance in clay will be longer than through the same distance in gravel, even though they are both characterized as high porosity materials. This is because the pore sizes are much larger in gravel media than in clay, and so there is less hydrostatic tension working against the subsurface pressure gradient and gravity.
Groundwater flow is important parameter for consideration in the design of waste rock basins for mining operations. Waste rock is heterogeneous material with particles varying from boulders to clay-sized particles, and it contains sulfidic pollutants which must be controlled such that they do not compromise the quality of the water table and also so the runoff does not create environmental problems in the surrounding areas. Aquitards are clay zones that can have such a degree of impermeability that they partially or completely retard water flow. These clay lenses can slow or stop seepage into the water table, although if an aquitard is fractured and contaminated then it can become a long-term source of groundwater contamination due to its low permeability and high HRT. | 9 | Geochemistry |
Strange quarks are naturally radioactive and decay by weak interactions into lighter quarks on a timescale that is extremely long compared with the nuclear-collision times. This makes it relatively easy to detect strange particles through the tracks left by their decay products. Consider as an example the decay of a negatively charged baryon (green in figure, dss), into a negative pion (d) and a neutral (uds) baryon. Subsequently, the decays into a proton and another negative pion. In general this is the signature of the decay of a . Although the negative (sss) baryon has a similar final state decay topology, it can be clearly distinguished from the because its decay products are different.
Measurement of abundant formation of (uss/dss), (sss) and especially their antiparticles is an important cornerstone of the claim that quark–gluon plasma has been formed. This abundant formation is often presented in comparison with the scaled expectation from normal proton–proton collisions; however, such a comparison is not a necessary step in view of the large absolute yields which defy conventional model expectations. The overall yield of strangeness is also larger than expected if the new form of matter has been achieved. However, considering that the light quarks are also produced in gluon fusion processes, one expects increased production of all hadrons. The study of the relative yields of strange and non strange particles provides information about the competition of these processes and thus the reaction mechanism of particle production. | 7 | Physical Chemistry |
PIT1 is part of the POU family of transcription factors. It is expressed by somatotrophic cells, as well as thyrotrophs and lactotrophs of the anterior pituitary gland. It contains a C-terminal domain for transactivation. Another domain is DNA binding—its C-terminal portion is homologous to the homeodomain consensus, common to many genes involved in development, while the other portion is POU specific, affords PIT1 specificity in its transcriptional activation of the prolactin and growth hormone genes and is involved in protein-protein interactions. Activity on thyroid stimulating hormone-beta expression is also known for PIT1. | 1 | Biochemistry |
SBPase and FBPase (fructose-1,6-bisphosphatase, EC 3.1.3.11) are both phosphatases that catalyze similar during the Calvin cycle. The genes for SBPase and FBPase are related. Both genes are found in the nucleus in plants, and have bacterial ancestry. SBPase is found across many species. In addition to being universally present in photosynthetic organism, SBPase is found in a number of evolutionarily-related, non-photosynthetic microorganisms. SBPase likely originated in red algae. | 5 | Photochemistry |
Low molecular weight acyl chlorides are often lachrymators, and they react violently with water, alcohols, and amines. | 0 | Organic Chemistry |
The structure of chitin was determined by Albert Hofmann in 1929. Hofmann hydrolyzed chitin using a crude preparation of the enzyme chitinase, which he obtained from the snail Helix pomatia.
Chitin is a modified polysaccharide that contains nitrogen; it is synthesized from units of N-acetyl--glucosamine (to be precise, 2-(acetylamino)-2-deoxy--glucose). These units form covalent β-(1→4)-linkages (like the linkages between glucose units forming cellulose). Therefore, chitin may be described as cellulose with one hydroxyl group on each monomer replaced with an acetyl amine group. This allows for increased hydrogen bonding between adjacent polymers, giving the chitin-polymer matrix increased strength.
In its pure, unmodified form, chitin is translucent, pliable, resilient, and quite tough. In most arthropods, however, it is often modified, occurring largely as a component of composite materials, such as in sclerotin, a tanned proteinaceous matrix, which forms much of the exoskeleton of insects. Combined with calcium carbonate, as in the shells of crustaceans and molluscs, chitin produces a much stronger composite. This composite material is much harder and stiffer than pure chitin, and is tougher and less brittle than pure calcium carbonate. Another difference between pure and composite forms can be seen by comparing the flexible body wall of a caterpillar (mainly chitin) to the stiff, light elytron of a beetle (containing a large proportion of sclerotin).
In butterfly wing scales, chitin is organized into stacks of gyroids constructed of chitin photonic crystals that produce various iridescent colors serving phenotypic signaling and communication for mating and foraging. The elaborate chitin gyroid construction in butterfly wings creates a model of optical devices having potential for innovations in biomimicry. Scarab beetles in the genus Cyphochilus also utilize chitin to form extremely thin scales (five to fifteen micrometres thick) that diffusely reflect white light. These scales are networks of randomly ordered filaments of chitin with diameters on the scale of hundreds of nanometres, which serve to scatter light. The multiple scattering of light is thought to play a role in the unusual whiteness of the scales. In addition, some social wasps, such as Protopolybia chartergoides, orally secrete material containing predominantly chitin to reinforce the outer nest envelopes, composed of paper.
Chitosan is produced commercially by deacetylation of chitin by treatment with sodium hydroxide. Chitosan has a wide range of biomedical applications including wound healing, drug delivery and tissue engineering. Due to its specific intermolecular hydrogen bonding network, dissolving chitin in water is very difficult.Chitosan (with a degree of deacetylation of more than ~28%), on the other hand, can be dissolved in dilute acidic aqueous solutions below a pH of 6.0 such as acetic, formic and lactic acids. Chitosan with a degree of deacetylation greater than ~49% is soluble in water | 1 | Biochemistry |
A trap crop is a plant that attracts agricultural pests, usually insects, away from nearby target crops. This form of companion planting can save a target crop from decimation by pests without the use of artificial pesticides. A trap crop is used for attracting the insect and pests away from a target crop field. Many trap crops have successfully diverted pests from focal crops in small scale greenhouse, garden and field experiments; a small portion of these plants have been shown to reduce pest damage at larger commercial scales. A common explanation for reported trap cropping failures, is that attractive trap plants only protect nearby plants if the insects do not move back into the target crop. In a review of 100 trap cropping examples in 2006, only 10 trap crops were classified as successful at a commercial scale, and in all successful cases, trap cropping was supplemented with management practices that specifically limited insect dispersal from the trap crop back into the target crop. | 1 | Biochemistry |
RSC is expressed in meq/L units. RSC should not be higher than 1 and preferably less than +0.5 for considering the water use for irrigation. The formula for calculating RSC index is:
* RSC index = [HCO + CO] − [Ca + Mg]
* RSC index = HCO/61 + CO/30 – Ca/20 – Mg/12 (in case the ionic concentrations are measured in mg/L or ppm as salts)
While calculating RSC index, the water quality present at the root zone of the crop should be considered which would take into account the leaching factor in the field. Calcium present in dissolved form is also influenced by the partial pressure of dissolved at the plants root zone in the field water. | 9 | Geochemistry |
A pepper-spray projectile may be a sphere, hence the name pepper-ball, but it may also come in other shapes. The irritant payload may differ from product to product but is usually a powder, less frequently a liquid, gas or aerosol. Some companies offer different substances as payload for their projectiles and launcher systems, so potential sellers can choose a substance that is certified for use in their country. Also, projectiles with an inert dummy payload are often offered, for training and testing purposes.
A powder called PAVA (capsaicin II) pepper is often used. PAVA is a capsaicinoid that can be synthesized for cheaper than grown peppers, although it is also found in nature.
Pepper-spray weapons systems are used by law enforcement, military and other organizations, and individuals. The weapon is used generally in the role of stand-off weapons, where physical proximity to a suspect is deemed dangerous but deadly force is not warranted. The systems are not limited to classic standoff situations and allow agents to apply as many rounds as required to bring individual suspects, multiple suspects, or crowds into compliance. | 1 | Biochemistry |
After short stays at NRC and Acadia University, Yu was appointed to the Department of Chemistry at Simon Fraser University in 2001 as an assistant professor and promoted to a tenured full professor in 2009. He is now a principal investigator of the CFI-funded Centre for Nanomaterials and Microstructures (4D LABS) and an associate member of the Department of Molecular Biology and Biochemistry, both at SFU. Yu has been perusing his cutting-edge research on solving fundamental problems that have direct impact on applied analytical science and technology. His innovation of adapting mobile electronics (office scanners, disc players, and now smartphones) for portable molecular analysis and his contribution to the de novo construction of ultrasensitive electronic biosensors for disease markers, lead to the possibility of performing many quantitative chemical analysis on-site and biomedical diagnostic tests at point-of-care settings. He has published more than 160 peer-reviewed articles and holds/filed 14 national/international patents. | 3 | Analytical Chemistry |
An alternative mechanism to the one described above was proposed by Russian scientists in the mid-1850s, the hypothesis of abiogenic petroleum origin (petroleum formed by inorganic means), but this is contradicted by geological and geochemical evidence. Abiogenic sources of oil have been found, but never in commercially profitable amounts. "The controversy isnt over whether abiogenic oil reserves exist," said Larry Nation of the American Association of Petroleum Geologists. "The controversy is over how much they contribute to Earths overall reserves and how much time and effort geologists should devote to seeking them out." | 7 | Physical Chemistry |
Heinz Falk was born April 29, 1939, in Sankt Pölten, Austria, went to elementary school in Statzendorf and completed middle school in Krems an der Donau. After moving to Vienna in 1953 he completed a three-year program at HBLVA for Chemical Industry, Rosensteingasse and completed his high-school diploma in 1959 through classes at an evening school, where he met his future wife, Rotraud Falk (née Strohbach). | 0 | Organic Chemistry |
This fjord was born as a glacial lake that was separated from the open ocean (the North Sea) when it was lifted during glacial rebound. A shallow channel (2m deep) was dug in 1850, providing a marginal connection to the North Sea. A strong pycnocline separates fresh surface water from dense, saline bottom water, and this pycnocline reduces mixing between the layers. Anoxic conditions persist below the chemocline at 20m, and the fjord has the highest levels of hydrogen sulfide in the anoxic marine world. Like the Black Sea, vertical overlap of oxygen and sulfur is limited, but the decline of HS approaching the chemocline from below is indicative of oxidation of HS, which has been attributed to manganese and iron oxides, photo-autotrophic bacteria, and entrainment of oxygen horizontally from the boundaries of the fjord. These oxidation processes are similar to those present in the Black Sea.
Two strong seawater intrusion events have occurred through the channel in recent history (1902 and 1942). Seawater intrusions to fjords force dense, salty, oxygen-rich water into the typically anoxic, sulfidic bottom waters of euxinic fjords. These events result in a temporary disturbance to the chemocline, raising the depth at which HS is detected. The breakdown of the chemocline causes HS to react with dissolved oxygen in a redox reaction. This decreases the concentration of dissolved oxygen in the biologically active photic zone which can result in basin-scale fish die-offs. The 1942 event, in particular, was strong enough to chemically reduce the vast majority of oxygen and elevate the chemocline to the air-water interface. This caused a temporary state of total anoxia in the fjord, and resulted in dramatic fish mortality. | 9 | Geochemistry |
The measurement approaches of end-point RT-PCR requires the detection of gene expression levels by the use of fluorescent dyes like ethidium bromide, P32 labeling of PCR products using phosphorimager, or by scintillation counting. End-point RT-PCR is commonly achieved using three different methods: relative, competitive and comparative.
; Relative RT-PCR: Relative quantifications of RT-PCR involves the co-amplification of an internal control simultaneously with the gene of interest. The internal control is used to normalize the samples. Once normalized, a direct comparison of relative transcript abundances across multiple samples of mRNA can be made. One precaution to note is that the internal control must be chosen so that it is not affected by the experimental treatment. The expression level should be constant across all samples and with the mRNA of interest for the results to be accurate and meaningful. Because the quantification of the results are analyzed by comparing the linear range of the target and control amplification, it is crucial to take into consideration the starting target molecules concentration and their amplification rate prior to starting the analysis. The results of the analysis are expressed as the ratios of gene signal to internal control signal, which the values can then be used for the comparison between the samples in the estimation of relative target RNA expression.
; Competitive RT-PCR: Competitive RT-PCR technique is used for absolute quantification. It involves the use of a synthetic “competitor” RNA that can be distinguished from the target RNA by a small difference in size or sequence. It is important for the design of the synthetic RNA be identical in sequence but slightly shorter than the target RNA for accurate results. Once designed and synthesized, a known amount of the competitor RNA is added to experimental samples and is co-amplified with the target using RT-PCR. Then, a concentration curve of the competitor RNA is produced and it is used to compare the RT-PCR signals produced from the endogenous transcripts to determine the amount of target present in the sample.
; Comparative RT-PCR: Comparative RT-PCR is similar to the competitive RT-PCR in that the target RNA competes for amplification reagents within a single reaction with an internal standard of unrelated sequence. Once the reaction is complete, the results are compared to an external standard curve to determine the target RNA concentration. In comparison to the relative and competitive quantification methods, comparative RT-PCR is considered to be the more convenient method to use since it does not require the investigator to perform a pilot experiment; in relative RT-PCR, the exponential amplification range of the mRNA must be predetermined and in competitive RT-PCR, a synthetic competitor RNA must be synthesized. | 1 | Biochemistry |
Defective Fas-mediated apoptosis may lead to oncogenesis as well as drug resistance in existing tumors. Germline mutation of Fas is associated with autoimmune lymphoproliferative syndrome (ALPS), a childhood disorder of apoptosis.
Increases in Fas-mediated signaling have been implicated in the pathology of low-risk myelodysplastic syndromes (MDS) and glioblastoma.
More recently, FasL-mediated apoptosis of T cells has also been suggested as an immune-evasive mechanism by which tumors can suppress T cell infiltration similar to inhibitory immune checkpoints such as PD-1 and CTLA-4. | 1 | Biochemistry |
Acetone cyanohydrin, (CH)C(OH)CN is the cyanohydrin of acetone. It is generated as an intermediate in the industrial production of methyl methacrylate. In the laboratory, this liquid serves as a source of HCN, which is inconveniently volatile. Thus, acetone cyanohydrin can be used for the preparation of other cyanohydrins, for the transformation of HCN to Michael acceptors, and for the formylation of arenes. Treatment of this cyanohydrin with lithium hydride affords anhydrous lithium cyanide: | 0 | Organic Chemistry |
Ketones are pervasive in nature. The formation of organic compounds in photosynthesis occurs via the ketone ribulose-1,5-bisphosphate. Many sugars are ketones, known collectively as ketoses. The best known ketose is fructose; it mostly exists as a cyclic hemiketal, which masks the ketone functional group. Fatty acid synthesis proceeds via ketones. Acetoacetate is an intermediate in the Krebs cycle which releases energy from sugars and carbohydrates.
In medicine, acetone, acetoacetate, and beta-hydroxybutyrate are collectively called ketone bodies, generated from carbohydrates, fatty acids, and amino acids in most vertebrates, including humans. Ketone bodies are elevated in the blood (ketosis) after fasting, including a night of sleep; in both blood and urine in starvation; in hypoglycemia, due to causes other than hyperinsulinism; in various inborn errors of metabolism, and intentionally induced via a ketogenic diet, and in ketoacidosis (usually due to diabetes mellitus). Although ketoacidosis is characteristic of decompensated or untreated type 1 diabetes, ketosis or even ketoacidosis can occur in type 2 diabetes in some circumstances as well. | 0 | Organic Chemistry |
Potassium tert-butoxide (or potassium t-butoxide) is a chemical compound with the formula [(CH)COK] (abbr. KOtBu). This colourless solid is a strong base (pKa of conjugate acid around 17), which is useful in organic synthesis. The compound is often depicted as a salt, and it often behaves as such, but its ionization depends on the solvent. | 0 | Organic Chemistry |
N-linked glycans have intrinsic and extrinsic functions.
Within the immune system, the N-linked glycans on an immune cell's surface will help dictate that migration pattern of the cell, e.g. immune cells that migrate to the skin have specific glycosylations that favor homing to that site. The glycosylation patterns on the various immunoglobulins including IgE, IgM, IgD, IgA, and IgG bestow them with unique effector functions by altering their affinities for Fc and other immune receptors. Glycans may also be involved in "self" and "non self" discrimination, which may be relevant to the pathophysiology of various autoimmune diseases.
In some cases, interaction between the N-glycan and the protein stabilizes the protein through complex electronic effects. | 0 | Organic Chemistry |
Charge modulation spectroscopy is an electro-optical spectroscopy technique tool. It is used to study the charge carrier behavior of organic field-effect transistors. It measures the charge introduced optical transmission variation by directly probing the accumulation charge at the burning interface of semiconductor and dielectric layer where the conduction channel forms. | 7 | Physical Chemistry |
Maxwell’s thermodynamic surface is an 1874 sculpture made by Scottish physicist James Clerk Maxwell (1831–1879). This model provides a three-dimensional space of the various states of a fictitious substance with water-like properties. This plot has coordinates volume (x), entropy (y), and energy (z). It was based on the American scientist Josiah Willard Gibbs’ graphical thermodynamics papers of 1873. The model, in Maxwell's words, allowed "the principal features of known substances [to] be represented on a convenient scale." | 7 | Physical Chemistry |
Measuring LDH in fluid aspirated from a pleural effusion (or pericardial effusion) can help in the distinction between exudates (actively secreted fluid, e.g., due to inflammation) or transudates (passively secreted fluid, due to a high hydrostatic pressure or a low oncotic pressure). The usual criterion (included in Light's criteria) is that a ratio of pleural LDH to serum LDH greater than 0.6 or the upper limit of the normal laboratory value for serum LDH indicates an exudate, while a ratio of less indicates a transudate. Different laboratories have different values for the upper limit of serum LDH, but examples include 200 and 300 IU/L. In empyema, the LDH levels, in general, will exceed 1000 IU/L. | 1 | Biochemistry |
Lynch-Stieglitz's research links the ocean and climate over the past 100,000 years. She has used carbon isotopes in benthic foraminifera to reconstruct air-sea exchange in carbon isotopes, changes in the movement of deep water masses, and Antarctic Intermediate Water in the transitions between glacial and interglacial periods. In the Atlantic Ocean, she has examined movement of the Gulf Stream during the Last Glacial Maximum and linked changes in the Atlantic meridional overturning circulation and to rapid changes in climate. Her research also extends to regions where ice alters the exchange of carbon dioxide between atmosphere and ocean in glacial periods, and work in the Pacific Ocean where she has examined sea surface temperatures from the Last Glacial Maximum to the present. | 9 | Geochemistry |
Bertram Oliver "Bert" Fraser-Reid (23 February 1934 – 25 May 2020) was a Jamaican synthetic organic chemist who has been widely recognised for his work using carbohydrates as starting materials for chiral materials and on the role of oligosaccharides in immune response. | 0 | Organic Chemistry |
Phosphinous acid (or Phosphinol) is the inorganic compound with the formula HPOH. It exists, fleetingly, as a mixture with its less stable tautomer HPO (phosphine oxide). This mixture has been generated by low temperature oxidation of phosphine with ozone. HPOH is mainly of pedagogical interest. Organophosphinous acids are more prevalent than the parent HPOH. | 0 | Organic Chemistry |
Most processes begin with phosphorous acid (aka phosphonic acid, HPO), exploiting its reactive P−H bond.
Phosphonic acid can be alkylated via the Kabachnik–Fields reaction or Pudovik reaction to give aminophosphonate, which are useful as chelating agents. One example is the industrial preparation of nitrilotris(methylenephosphonic acid):
:NH + 3 HPO + 3 CHO → N(CHPOH) + 3 HO
Phosphonic acid also can be alkylated with acrylic acid derivatives to afford carboxyl functionalized phosphonic acids. This reaction is a variant of the Michael addition:
:CH=CHCOR + 3 HPO → (HO)P(O)CHCHCOR
In the Hirao coupling dialkyl phosphites (which can also be viewed as di-esters of phosphonic acid: (O=PH(OR)) undergo a palladium-catalyzed coupling reaction with an aryl halide to form a phosphonate. | 0 | Organic Chemistry |
B. subtilis is a soil-dwelling microbe that uses quorum sensing to regulate two different biological processes: competence and sporulation. During stationary growth phase when B. subtilis are at high cell density, approximately 10% of the cells in a population are induced to become competent. It is believed that this subpopulation becomes competent to take up DNA that could potentially be used for the repair of damaged (mutated) chromosomes. ComX (also known as competence factor) is a 10-amino acid peptide that is processed from a 55-amino acid peptide precursor. Like most autoinducers, ComX is secreted and accumulates as a function of cell density. Once a threshold extracellular level is achieved, ComX is detected by a two-component ComP/ComA sensor kinase/response regulator pair. Phosphorylation of ComA activates the expression of comS gene, ComS inhibits the degradation of ComK, and finally ComK activates the expression of a number of genes required for competence.
Sporulation, on the other hand, is a physiological response of B. subtilis to depletion of nutrients within a particular environment. It is also regulated by extracellular signaling. When B. subtilis populations sense waning conditions, they respond by undergoing asymmetric cell division. This ultimately produces spores that are adapted for dispersal and survival in unfavorable conditions. Sporulation in B. subtilis is mediated by CSF (sporulation factor), a pentapeptide cleaved from the precursor peptide PhrC. CSF is secreted into the extracellular environment and is taken back up into cells via the ABC transporter Opp where it acts intracellularly. While low internal concentrations of CSF contribute to competence, high concentrations induce sporulation. CSF inhibits a phosphatase, RabB, which increases the activity of Spo0A, favoring a switch in commitment from competence to the sporulation pathway | 1 | Biochemistry |
In chemistry, a hydride is formally the anion of hydrogen (H), a hydrogen atom with two electrons. The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are also called hydrides: water (HO) is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. For inorganic chemists, hydrides refer to compounds and ions in which hydrogen is covalently attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed.
Almost all of the elements form binary compounds with hydrogen, the exceptions being He, Ne, Ar, Kr, Pm, Os, Ir, Rn, Fr, and Ra. Exotic molecules such as positronium hydride have also been made. | 0 | Organic Chemistry |
Alkaline lysis or alkaline extraction is a method used in molecular biology to isolate plasmid DNA from bacteria. | 1 | Biochemistry |
The fundamental aminophosphines have the formulae PH(NH) (n = 1, 2, 3). These species cannot be isolated in a practical quantities, although they have been examined theoretically. HNPH is predicted to be more stable than the P(V) tautomer HN=PH.
With secondary amines, the chemistry is more straightforward. Trisaminophosphines are prepared by treatment of phosphorus trichloride with secondary amines:
:PCl + 6 HNMe → (MeN)P + 3 [HNMe]Cl | 0 | Organic Chemistry |
A single, broad singlet is observed at 3.2 ppm at room temperature in the solution state phosphorus nuclear magnetic resonance (PNMR) of ((Dipp)P)Ge. This signal is consistent with rapid exchange between the planar and pyramidal phosphorus centers. As the temperature is reduced to -80 C, the signal becomes two broad, equal intensity singlets at -42.0 ppm and 8.0.
Two peaks with isotropic chemical shifts of 81.9 and -61.6 ppm, in a 1:1 ratio are observed in the solid state PNMR. No other signals are observed in the PNMR. In general diphosphagermylenes with pyramidal phosphorus centers exhibit a chemical shift close to those of free phosphine. In addition, planar phosphorus centers of Ge=P compounds generally have a downfield PNMR shift. Consequently, peaks at 81.9 and -61.6 ppm have been assigned as planar and pyramidal phosphorus centers of ((Dipp)P)Ge, respectively. This has been supported by DFT calculations that predict PNMR shifts of planar and pyramidal phosphorus centers of ((Dipp)P)Ge are at 100 and -61 ppm. | 0 | Organic Chemistry |
Since there is a frequent large pharmacokinetic and pharmacodynamic differences between enantiomers of a chiral drug it is not surprising that enantiomers may result in stereoselective toxicity. They can reside in the pharmacologically active enantiomer (eutomer) or in the inactive one (distomer). The toxicologic differences between enantiomers of have also been demonstrated. The following are examples of some of the chiral drugs where their toxic/undesirable side-effects dwell almost in the distomer. This would seem to be a clear cut case of going for a chiral switch. | 4 | Stereochemistry |
In certain enzymatic processes, redox non-innocent cofactors provide redox equivalents to complement the redox properties of metalloenzymes. Of course, most redox reactions in nature involve innocent systems, e.g. [[ferrodoxin|[4Fe-4S] clusters]]. The additional redox equivalents provided by redox non-innocent ligands are also used as controlling factors to steer homogeneous catalysis. | 0 | Organic Chemistry |
Two materials may form a compound at the joint. The strongest joints are where atoms of the two materials share or swap electrons (known respectively as covalent bonding or ionic bonding). A weaker bond is formed if a hydrogen atom in one molecule is attracted to an atom of nitrogen, oxygen, or fluorine in another molecule, a phenomenon called hydrogen bonding.
Chemical adhesion occurs when the surface atoms of two separate surfaces form ionic, covalent, or hydrogen bonds. The engineering principle behind chemical adhesion in this sense is fairly straightforward: if surface molecules can bond, then the surfaces will be bonded together by a network of these bonds. It bears mentioning that these attractive ionic and covalent forces are effective over only very small distances – less than a nanometer. This means in general not only that surfaces with the potential for chemical bonding need to be brought very close together, but also that these bonds are fairly brittle, since the surfaces then need to be kept close together. | 6 | Supramolecular Chemistry |
For the parallel-plate capacitor we have , where is the applied voltage. As a single ionization was assumed is the elementary charge . We can now put () and () into () and get
Putting this into (5) and transforming to we get the Paschen law for the breakdown voltage that was first investigated by Paschen in
and whose formula was first derived by Townsend in | 7 | Physical Chemistry |
Mouza Sulaiman Mohamed Al-Wardi (Arabic: موزة سليمان محمد الوردي) is a curator and historian from Oman, who is Director of the Collections Department at the National Museum. She specialises in the history of silverworking in the Oman region. | 8 | Metallurgy |
Mesocrystal is an abbreviation for mesoscopically structured crystal, where individual subunits often form a perfect 3D order, as in a traditional crystal where the subunits are individual atoms. | 7 | Physical Chemistry |
The experimental determination of pK values is commonly performed by means of titrations, in a medium of high ionic strength and at constant temperature. A typical procedure would be as follows. A solution of the compound in the medium is acidified with a strong acid to the point where the compound is fully protonated. The solution is then titrated with a strong base until all the protons have been removed. At each point in the titration pH is measured using a glass electrode and a pH meter. The equilibrium constants are found by fitting calculated pH values to the observed values, using the method of least squares.
The total volume of added strong base should be small compared to the initial volume of titrand solution in order to keep the ionic strength nearly constant. This will ensure that pK remains invariant during the titration.
A calculated titration curve for oxalic acid is shown at the right. Oxalic acid has pK values of 1.27 and 4.27. Therefore, the buffer regions will be centered at about pH 1.3 and pH 4.3. The buffer regions carry the information necessary to get the pK values as the concentrations of acid and conjugate base change along a buffer region.
Between the two buffer regions there is an end-point, or equivalence point, at about pH 3. This end-point is not sharp and is typical of a diprotic acid whose buffer regions overlap by a small amount: pK − pK is about three in this example. (If the difference in pK values were about two or less, the end-point would not be noticeable.) The second end-point begins at about pH 6.3 and is sharp. This indicates that all the protons have been removed. When this is so, the solution is not buffered and the pH rises steeply on addition of a small amount of strong base. However, the pH does not continue to rise indefinitely. A new buffer region begins at about pH 11 (pK − 3), which is where self-ionization of water becomes important.
It is very difficult to measure pH values of less than two in aqueous solution with a glass electrode, because the Nernst equation breaks down at such low pH values. To determine pK values of less than about 2 or more than about 11 spectrophotometric or NMR measurements may be used instead of, or combined with, pH measurements.
When the glass electrode cannot be employed, as with non-aqueous solutions, spectrophotometric methods are frequently used. These may involve absorbance or fluorescence measurements. In both cases the measured quantity is assumed to be proportional to the sum of contributions from each photo-active species; with absorbance measurements the Beer–Lambert law is assumed to apply.
Isothermal titration calorimetry (ITC) may be used to determine both a pK value and the corresponding standard enthalpy for acid dissociation. Software to perform the calculations is supplied by the instrument manufacturers for simple systems.
Aqueous solutions with normal water cannot be used for H NMR measurements but heavy water, , must be used instead. C NMR data, however, can be used with normal water and H NMR spectra can be used with non-aqueous media. The quantities measured with NMR are time-averaged chemical shifts, as proton exchange is fast on the NMR time-scale. Other chemical shifts, such as those of P can be measured. | 7 | Physical Chemistry |
Retinoic acids tretinoin (all-trans-retinoic acid) and isotretinoin (13-cis-retinoic acid) are prescription topical medications used to treat moderate to severe cystic acne and acne not responsive to other treatments. These are usually applied as a skin cream to the face after cleansing to remove make-up and skin oils. Tretinoin and isotretinoin act by binding to two nuclear receptor families within keratinocytes: the retinoic acid receptors (RAR) and the retinoid X receptors (RXR). These events contribute to the normalization of follicular keratinization and decreased cohesiveness of keratinocytes, resulting in reduced follicular occlusion and microcomedone formation. The retinoid-receptor complex competes for coactivator proteins of AP-1, a key transcription factor involved in inflammation. Retinoic acid products also reduce sebum secretion, a nutrient source for bacteria, from facial pores.
These drugs are US-designated Pregnancy Category C (animal reproduction studies have shown an adverse effect on the fetus), and should not be used by pregnant women or women who are anticipating becoming pregnant. Many countries established a physician- and patient- education pregnancy prevention policy.
Trifarotene is a prescription retinoid for the topical treatment acne vulgaris. It functions as a retinoic acid receptor (RAR)-γ agonist.
Non-prescription topical products that have health claims for reducing facial acne, combating skin dark spots and reducing wrinkles and lines associated with aging often contain retinyl palmitate. The hypothesis is that this is absorbed and desterified to free retinol, then converted to retinaldehyde and further metabolized to all-trans-retinoic acid, whence it will have the same effects as prescription products with fewer side effects. There is some ex vivo evidence with human skin that esterified retinol is absorbed and then converted to retinol. In addition to esterified retinol, some of these products contain hydroxypinacolone retinoate, identified as esterified 9-cis-retinoic acid. | 1 | Biochemistry |
Self-assembly is the most common term in use in the modern scientific community to describe the spontaneous aggregation of particles (atoms, molecules, colloids, micelles, etc.) without the influence of any external forces. Large groups of such particles are known to assemble themselves into thermodynamically stable, structurally well-defined arrays, quite reminiscent of one of the seven crystal systems found in metallurgy and mineralogy (e.g., face-centered cubic, body-centered cubic, etc.). The fundamental difference in equilibrium structure is in the spatial scale of the unit cell (lattice parameter) in each particular case.
Molecular self assembly is found widely in biological systems and provides the basis of a wide variety of complex biological structures. This includes an emerging class of mechanically superior biomaterials based on microstructural features and designs found in nature. Thus, self-assembly is also emerging as a new strategy in chemical synthesis and nanotechnology. Molecular crystals, liquid crystals, colloids, micelles, emulsions, phase-separated polymers, thin films and self-assembled monolayers all represent examples of the types of highly ordered structures, which are obtained using these techniques. The distinguishing feature of these methods is self-organization. | 1 | Biochemistry |
In a system with two spin-1/2 particlesfor example the proton and electron in the ground state of hydrogenmeasured on a given axis, each particle can be either spin up or spin down so the system has four basis states in all
using the single particle spins to label the basis states, where the first arrow and second arrow in each combination indicate the spin direction of the first particle and second particle respectively.
More rigorously
where and are the spins of the two particles, and and are their projections onto the z axis. Since for spin-1/2 particles, the basis states span a 2-dimensional space, the basis states span a 4-dimensional space.
Now the total spin and its projection onto the previously defined axis can be computed using the rules for adding angular momentum in quantum mechanics using the Clebsch–Gordan coefficients. In general
substituting in the four basis states
returns the possible values for total spin given along with their representation in the basis. There are three states with total spin angular momentum 1:
which are symmetric and a fourth state with total spin angular momentum 0:
which is antisymmetric. The result is that a combination of two spin-1/2 particles can carry a total spin of 1 or 0, depending on whether they occupy a triplet or singlet state. | 7 | Physical Chemistry |
The expression for Z is dependent on the media/phase/compartment. The following list gives the fugacity capacities for common medias:
* Air (under ideal gas assumptions): Z = 1/RT
* Water: Z = 1/H
* Octanol: Z = K/H
* Pure phase of target chemical: Z = 1/Pv
Where: R is the Ideal gas constant (8.314 Pa·m/mol·K); T is the absolute temperature (K); H is the Henry's law constant for the target chemical (Pa/mmol); K is the octanol-water partition coefficient for the target chemical (dimensionless ratio); P is the vapor pressure of the target chemical (Pa); and v is the molar volume of the target chemical (m/mol).
Notice that the ratio between Z-values for different media (e.g. octanol and water) is the same as the ratio between the concentrations of the target chemical in each media at equilibrium.
When using a fugacity capacity approach to calculate the concentrations of a chemical in each of several medias/phases/compartments, it is often convenient to calculate the prevailing fugacity of the system using the following equation if the total mass of target chemical (M) and the volume of each compartment (V) are known:
Alternatively, if the target chemical is present as a pure phase at equilibrium, its vapor pressure will be the prevailing fugacity of the system. | 7 | Physical Chemistry |
Carbon tetrachloride was briefly used as a volatile inhalation anaesthetic and analgesic for intense menstruation pains and headaches in the mid-19th century. Its anaesthetic effects were known as early as 1847 or 1848.
It was introduced as a safer alternative to Chloroform by Doctor Protheroe Smith in 1864. In December 1865, the Scottish obstetrician who discovered the anaesthetic effects of chloroform on humans, James Young Simpson, had experimented with carbon tetrachloride as an anaesthetic. Simpson named the compound "Chlorocarbon" for its similarity to chloroform. His experiments involved injecting carbon tetrachloride into two women's vaginas. Simpson orally consumed carbon tetrachloride and described it as having "the same effect as swallowing a capsule of chloroform".
Because of the higher amount of chlorine atoms (compared to chloroform) in its molecule, carbon tetrachloride has a stronger anaesthetic effect than chloroform and required a smaller amount. Its anaesthetic action was likened to ether, rather than the related chloroform. It is less volatile than chloroform, therefore it was more difficult to apply and needed warm water to evaporate. Its smell has been described as "fruity", quince-like and "more pleasant than chloroform", and had a "pleasant taste". Carbon tetrachloride for anaesthetic use was made by the chlorination of carbon disulfide. It was used on at least 50 patients, of which most were women in labour. During anaesthesia, carbon tetrachloride has caused violent muscular contractions and negative effects on the heart in some patients that it had to be substituted with chloroform or ether. Such use was experimental and the anaesthetic use of carbon tetrachloride never gained popularity due to its potential toxicity. | 2 | Environmental Chemistry |
* 1.C.3 α-Hemolysin (αHL) family
* 1.C.4 Aerolysin family
* 1.C.5 ε-toxin family
* 1.C.11 RTX-toxin superfamily
* 1.C.12 Membrane attack complex/perforin superfamily
* 1.C.13 Leukocidin family
* 1.C.14 Cytohemolysin (CHL) family
* 1.C.39 Thiol-activated cholesterol-dependent cytolysin family
* 1.C.43 Lysenin family
* 1.C.56 Pseudomonas syringae HrpZ cation channel family
* 1.C.57 Clostridial cytotoxin family
*1.C.58 The Microcin E492/C24 (Microcin E492) Family
* 1.C.74 Snake cytotoxin (SCT) family
* 1.C.97 Pleurotolysin pore-forming family | 1 | Biochemistry |
William M. Williams (25 February 1927 – 28 January 2011) was a Welsh-born metallurgical engineer and Birks professor of metallurgy at McGill University. | 8 | Metallurgy |
Predators may identify their prey by sound as well as sight; mimics have accordingly evolved to deceive the hearing of their predators. Bats are nocturnal predators that rely on echolocation to detect their prey. Some potential prey are unpalatable to bats, and produce an ultrasonic aposematic signal, the auditory equivalent of warning coloration. In response to echolocating red bats and big brown bats, tiger moths such as Cycnia tenera produce warning sounds. Bats learn to avoid the harmful moths, but similarly avoid other species such as some pyralid moths that produce such warning sounds as well. Acoustic mimicry complexes, both Batesian and Müllerian, may be widespread in the auditory world. | 1 | Biochemistry |
Myogenic hyperuricemia, as a result of the purine nucleotide cycle running when ATP reservoirs in muscle cells are low (ADP > ATP), is a common pathophysiologic feature of glycogenoses such as GSD-III, GSD-V and GSD-VII, as they are metabolic myopathies which impair the ability of ATP (energy) production within muscle cells. In these metabolic myopathies, myogenic hyperuricemia is exercise-induced; inosine, hypoxanthine and uric acid increase in plasma after exercise and decrease over hours with rest. Excess AMP (adenosine monophosphate) is converted into uric acid.
:AMP → IMP → Inosine → Hypoxanthine → Xanthine → Uric acid
Hyperammonemia is also seen post-exercise in McArdle disease (GSD-V) and phosphoglucomutase deficiency (PGM1-CDG, formerly GSD-XIV), due to the purine nucleotide cycle running when the ATP reservoir is low due to the glycolytic block.O + H → IMP + NH </blockquote> | 1 | Biochemistry |
Quinone methides are often prepared by oxidation of the corresponding ortho or para cresol.
Quinone methides can be produced in aqueous solution by photochemical dehydration of o-hydroxybenzyl alcohols (i.e. salicyl alcohol). | 0 | Organic Chemistry |
MERMOZ (also, MERMOZ project and Monitoring planEtary suRfaces with Modern pOlarimetric characteriZation) is an astrobiology project designed to remotely detect biosignatures of life. Detection is based on molecular homochirality, a characteristic property of the biochemicals of life. The aim of the project is to remotely identify and characterize life on the planet Earth from space, and to extend this technology to other solar system bodies and exoplanets. The project began in 2018, and is a collaboration of the University of Bern, University of Leiden and Delft University of Technology.
According to a member of the research team, “When light is reflected by biological matter, a part of the light’s electromagnetic waves will travel in either clockwise or counterclockwise spirals ... This phenomenon is called circular polarization and is caused by the biological matter’s homochirality.” These unique spirals of light indicate living materials; whereas, non-living materials do not reflect such unique spirals of light, according to the researchers.
The research team conducted feasibility studies, using a newly designed detection instrument, based on circular spectropolarimetry, and named FlyPol+ (an upgrade from the original FlyPol), by flying in a helicopter at an altitude of and velocity of for 25 minutes. The results were successful in remotely detecting living material, and quickly (within seconds) distinguishing living material from non-living material. The researchers concluded: "Circular spectropolarimetry can be a powerful technique to detect life beyond Earth, and we emphasize the potential of utilizing circular spectropolarimetry as a remote sensing tool to characterize and monitor in detail the vegetation physiology and terrain features of Earth itself."
The researchers next expect to scan the Earth from the International Space Station (ISS) with their detection instruments. One consequence of further successful studies is a possible pathfinder space mission, scheduled to launch in 2024. | 2 | Environmental Chemistry |
When grown in glucose-rich media, trypanosomatid parasites degrade glucose via aerobic fermentation. In this group, this phenomenon is not a pre-adaptation to/or remnant of anaerobic life, shown through their inability to survive in anaerobic conditions. It is believed that this phenomenon developed due to the capacity for a high glycolytic flux and the high glucose concentrations of their natural environment. The mechanism for repression of respiration in these conditions is not yet known. | 1 | Biochemistry |
One of the primary causes of WECs is the passage of electrical current through the bearings. Both Alternating Current (AC) and Direct Current (DC) can lead to the formation of WECs, albeit through slightly different mechanisms. In general, hydrogen generation from lubricants can be accelerated by electric current, potentially accelerating WEC formation. Under certain conditions, when the current densities are low (less than 1 mA/mm2), electrical discharges can significantly shorten the lifespan of bearings by causing WECs. These WECs can develop in under 50 hours due to electrical discharges. Electrostatic sensors prove to be useful in detecting these critical discharges early on, which are associated with failures induced by WECs. The analysis revealed that different reaction layers form in the examined areas, depending on the electrical polarity.
In the case of AC, the rapid change in polarity involves the creation of a plasma channel through the lubricant film in the bearing, leading to a momentary, intense discharge of energy. The localised heating and rapid cooling associated with these discharges can cause changes in the microstructure of the steel, leading to the formation of WEAs and WECs.
On the other hand, DC can cause a steady flow of electrons through the bearing. This can lead to the electrochemical dissolution of the metal, a process known as fretting corrosion. The constant flow of current can also cause local heating, leading to thermal gradients within the bearing material. These gradients can cause stresses that lead to the formation of WECs. | 8 | Metallurgy |
In most organisms, malate dehydrogenase (MDH) exists as a homodimeric molecule and is closely related to lactate dehydrogenase (LDH) in structure. It is a large protein molecule with subunits weighing between 30 and 35 kDa. Based on the amino acid sequences, it seems that MDH has diverged into two main phylogenetic groups that closely resemble either mitochondrial isozymes or cytoplasmic/chloroplast isozymes. Because the sequence identity of malate dehydrogenase in the mitochondria is more closely related to its prokaryotic ancestors in comparison to the cytoplasmic isozyme, the theory that mitochondria and chloroplasts were developed through endosymbiosis is plausible. The amino acid sequences of archaeal MDH are more similar to that of LDH than that of MDH of other organisms. This indicates that there is a possible evolutionary linkage between lactate dehydrogenase and malate dehydrogenase.
Each subunit of the malate dehydrogenase dimer has two distinct domains that vary in structure and functionality. A parallel β-sheet structure makes up the NAD+ binding domain, while four β-sheets and one α-helix comprise the central NAD binding site. The subunits are held together through extensive hydrogen-bonding and hydrophobic interactions.
Malate dehydrogenase has also been shown to have a mobile loop region that plays a crucial role in the enzyme's catalytic activity. Studies have shown that conformational change of this loop region from the open conformation to the closed conformation after binding of substrate enhances MDH catalysis through shielding of substrate and catalytic amino acids from solvent. Studies have also indicated that this loop region is highly conserved in malate dehydrogenase. | 1 | Biochemistry |
In biochemistry, a metabolite is an intermediate or end product of metabolism.
The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, catalytic activity of their own (usually as a cofactor to an enzyme), defense, and interactions with other organisms (e.g. pigments, odorants, and pheromones).
A primary metabolite is directly involved in normal "growth", development, and reproduction. Ethylene exemplifies a primary metabolite produced large-scale by industrial microbiology.
A secondary metabolite is not directly involved in those processes, but usually has an important ecological function. Examples include antibiotics and pigments such as resins and terpenes etc.
Some antibiotics use primary metabolites as precursors, such as actinomycin, which is created from the primary metabolite tryptophan. Some sugars are metabolites, such as fructose or glucose, which are both present in the metabolic pathways.
Examples of primary metabolites produced by industrial microbiology include:
The metabolome forms a large network of metabolic reactions, where outputs from one enzymatic chemical reaction are inputs to other chemical reactions.
Metabolites from chemical compounds, whether inherent or pharmaceutical, form as part of the natural biochemical process of degrading and eliminating the compounds.
The rate of degradation of a compound is an important determinant of the duration and intensity of its action. Understanding how pharmaceutical compounds are metabolized and the potential side effects of their metabolites is an important part of drug discovery. | 1 | Biochemistry |
Flame atomic absorption spectroscopy (AAS) determines the total magnesium content of a biological sample. This method is destructive; biological samples must be broken down in concentrated acids to avoid clogging the fine nebulising apparatus. Beyond this, the only limitation is that samples must be in a volume of approximately 2 mL and at a concentration range of 0.1 – 0.4 μmol/L for optimum accuracy. As this technique cannot distinguish between Mg already present in the cell and that taken up during the experiment, only content not uptaken can be quantified.
Inductively coupled plasma (ICP) using either the mass spectrometry (MS) or atomic emission spectroscopy (AES) modifications also allows the determination of the total ion content of biological samples. These techniques are more sensitive than flame AAS and are capable of measuring the quantities of multiple ions simultaneously. However, they are also significantly more expensive. | 1 | Biochemistry |
Hemoglobin concentration measurement is among the most commonly performed blood tests, usually as part of a complete blood count. For example, it is typically tested before or after blood donation. Results are reported in g/L, g/dL or mol/L. 1 g/dL equals about 0.6206 mmol/L, although the latter units are not used as often due to uncertainty regarding the polymeric state of the molecule. This conversion factor, using the single globin unit molecular weight of 16,000 Da, is more common for hemoglobin concentration in blood. For MCHC (mean corpuscular hemoglobin concentration) the conversion factor 0.155, which uses the tetramer weight of 64,500 Da, is more common. Normal levels are:
* Men: 13.8 to 18.0 g/dL (138 to 180 g/L, or 8.56 to 11.17 mmol/L)
* Women: 12.1 to 15.1 g/dL (121 to 151 g/L, or 7.51 to 9.37 mmol/L)
* Children: 11 to 16 g/dL (110 to 160 g/L, or 6.83 to 9.93 mmol/L)
* Pregnant women: 11 to 14 g/dL (110 to 140 g/L, or 6.83 to 8.69 mmol/L) (9.5 to 15 usual value during pregnancy)
Normal values of hemoglobin in the 1st and 3rd trimesters of pregnant women must be at least 11 g/dL and at least 10.5 g/dL during the 2nd trimester.
Dehydration or hyperhydration can greatly influence measured hemoglobin levels. Albumin can indicate hydration status.
If the concentration is below normal, this is called anemia. Anemias are classified by the size of red blood cells, the cells that contain hemoglobin in vertebrates. The anemia is called "microcytic" if red cells are small, "macrocytic" if they are large, and "normocytic" otherwise.
Hematocrit, the proportion of blood volume occupied by red blood cells, is typically about three times the hemoglobin concentration measured in g/dL. For example, if the hemoglobin is measured at 17 g/dL, that compares with a hematocrit of 51%.
Laboratory hemoglobin test methods require a blood sample (arterial, venous, or capillary) and analysis on hematology analyzer and CO-oximeter. Additionally, a new noninvasive hemoglobin (SpHb) test method called Pulse CO-Oximetry is also available with comparable accuracy to invasive methods.
Concentrations of oxy- and deoxyhemoglobin can be measured continuously, regionally and noninvasively using NIRS. NIRS can be used both on the head and on muscles. This technique is often used for research in e.g. elite sports training, ergonomics, rehabilitation, patient monitoring, neonatal research, functional brain monitoring, brain–computer interface, urology (bladder contraction), neurology (Neurovascular coupling) and more.
Hemoglobin mass can be measured in humans using the non-radioactive, carbon monoxide (CO) rebreathing technique that has been used for more than 100 years. With this technique, a small volume of pure CO gas is inhaled and rebreathed for a few minutes. During rebreathing, CO binds to hemoglobin present in red blood cells. Based on the increase in blood CO after the rebreathing period, the hemoglobin mass can be determined through the dilution principle. Although CO gas in large volumes is toxic to humans, the volume of CO used to assess blood volumes corresponds to what would be inhaled when smoking a cigarette. While researchers typically use custom-made rebreathing circuits, the Detalo Performance from Detalo Health has automated the procedure and made the measurement available to a larger group of users.
Long-term control of blood sugar concentration can be measured by the concentration of Hb A. Measuring it directly would require many samples because blood sugar levels vary widely through the day. Hb A is the product of the irreversible reaction of hemoglobin A with glucose. A higher glucose concentration results in more Hb A. Because the reaction is slow, the Hb A proportion represents glucose level in blood averaged over the half-life of red blood cells, is typically ~120 days. An Hb A proportion of 6.0% or less show good long-term glucose control, while values above 7.0% are elevated. This test is especially useful for diabetics.
The functional magnetic resonance imaging (fMRI) machine uses the signal from deoxyhemoglobin, which is sensitive to magnetic fields since it is paramagnetic. Combined measurement with NIRS shows good correlation with both the oxy- and deoxyhemoglobin signal compared to the BOLD signal. | 7 | Physical Chemistry |
Reid vapor pressure (RVP) is a common measure of the volatility of gasoline and other petroleum products. It is defined as the
absolute vapor pressure exerted by the vapor of the liquid and any dissolved gases/moisture at 37.8 °C (100 °F) as determined by the test method ASTM-D-323, which was first developed in 1930 and has been revised several times (the latest version is ASTM D323-15a). The test method measures the vapor pressure of gasoline, volatile crude oil, jet fuels, naphtha, and other volatile petroleum products but is not applicable for liquefied petroleum gases. ASTM D323-15a requires that the sample be chilled to 0 to 1 degrees Celsius and then poured into the apparatus; for any material that solidifies at this temperature, this step cannot be performed. RVP is commonly reported in kilopascals (kPa) or pounds per square inch (psi) and represents volatization at atmospheric pressure because ASTM-D-323 measures the gauge pressure of the sample in a non-evacuated chamber.
The matter of vapor pressure is important relating to the function and operation of gasoline-powered, especially carbureted, vehicles and is also important for many other reasons. High levels of vaporization are desirable for winter starting and operation and lower levels are desirable in avoiding vapor lock during summer heat. Fuel cannot be pumped when there is vapor in the fuel line (summer) and winter starting will be more difficult when liquid gasoline in the combustion chambers has not vaporized. Thus, oil refineries manipulate the Reid vapor pressure seasonally specifically to maintain gasoline engine reliability.
The Reid vapor pressure (RVP) can differ substantially from the true vapor pressure (TVP) of a liquid mixture, since (1) RVP is the vapor pressure measured at 37.8 °C (100 °F) and the TVP is a function of the temperature; (2) RVP is defined as being measured at a vapor-to-liquid ratio of 4:1, whereas the TVP of mixtures can depend on the actual vapor-to-liquid ratio; (3) RVP will include the pressure associated with the presence of dissolved water and air in the sample (which is excluded by some but not all definitions of TVP); and (4) the RVP method is applied to a sample which has had the opportunity to volatilize somewhat prior to measurement: i.e., the sample container is required to be only 70-80% full of liquid (so that whatever volatilizes into the container headspace is lost prior to analysis); the sample then again volatilizes into the headspace of the D323 test chamber before it is heated to 37.8 degrees Celsius. | 7 | Physical Chemistry |
Dexmedetomidine was approved in 1999 by the US Food and Drug Administration (FDA) as a short-term sedative and analgesic (<24 hours) for critically ill or injured people on mechanical ventilation in the intensive care unit (ICU). The rationale for its short-term use was due to concerns over withdrawal side effects such as rebound high blood pressure. These effects have not been consistently observed in research studies, however. | 4 | Stereochemistry |
Glycopeptide antibiotics are a class of drugs of microbial origin that are composed of glycosylated cyclic or polycyclic nonribosomal peptides. Significant glycopeptide antibiotics include the anti-infective antibiotics vancomycin, teicoplanin, telavancin, ramoplanin and decaplanin, corbomycin, complestatin and the antitumor antibiotic bleomycin. Vancomycin is used if infection with methicillin-resistant Staphylococcus aureus (MRSA) is suspected. | 0 | Organic Chemistry |
*4-Nitrophenol is an intermediate in the synthesis of paracetamol. It is reduced to 4-aminophenol, then acetylated with acetic anhydride.
* 4-Nitrophenol is used as the precursor for the preparation of phenetidine and acetophenetidine, indicators, and raw materials for fungicides. Bioaccumulation of this compound rarely occurs.
* In peptide synthesis, carboxylate ester derivatives of 4-nitrophenol may serve as activated components for construction of amide moieties. | 3 | Analytical Chemistry |
Glycoproteins have distinct Oligosaccharide structures which have significant effects on many of their properties, affecting critical functions such as antigenicity, solubility, and resistance to proteases. Glycoproteins are relevant as cell-surface receptors, cell-adhesion molecules, immunoglobulins, and tumor antigens. | 0 | Organic Chemistry |
DAST is prepared by the reaction of diethylaminotrimethylsilane and sulfur tetrafluoride:
:EtNSiMe + SF → EtNSF + MeSiF
The original paper calls for trichlorofluoromethane (Freon-11) as a solvent. Diethyl ether is a green alternative that can be used with no decrease in yield. Because of the dangers involved in the preparation of DAST (glass etching, possibility of exothermic events), it is often purchased from a commercial source. At one time Carbolabs was one of the few suppliers of the chemical but a number of companies now sell DAST. Carbolabs was acquired by Sigma-Aldrich in 1998. | 0 | Organic Chemistry |
Molecular motion in condensed matter can be represented by a Fourier series whose physical interpretation consists of a superposition of longitudinal and transverse waves of atomic displacement with varying directions and wavelengths. In monatomic systems, these waves are called density fluctuations. (In polyatomic systems, they may also include compositional fluctuations.)
Thus, thermal motion in liquids can be decomposed into elementary longitudinal vibrations (or acoustic phonons) while transverse vibrations (or shear waves) were originally described only in elastic solids exhibiting the highly ordered crystalline state of matter. In other words, simple liquids cannot support an applied force in the form of a shearing stress, and will yield mechanically via macroscopic plastic deformation (or viscous flow). Furthermore, the fact that a solid deforms locally while retaining its rigidity – while a liquid yields to macroscopic viscous flow in response to the application of an applied shearing force – is accepted by many as the mechanical distinction between the two.
The inadequacies of this conclusion, however, were pointed out by Frenkel in his revision of the kinetic theory of solids and the theory of elasticity in liquids. This revision follows directly from the continuous characteristic of the viscoelastic crossover from the liquid state into the solid one when the transition is not accompanied by crystallization—ergo the supercooled viscous liquid. Thus we see the intimate correlation between transverse acoustic phonons (or shear waves) and the onset of rigidity upon vitrification, as described by Bartenev in his mechanical description of the vitrification process.
The velocities of longitudinal acoustic phonons in condensed matter are directly responsible for the thermal conductivity that levels out temperature differentials between compressed and expanded volume elements. Kittel proposed that the behavior of glasses is interpreted in terms of an approximately constant "mean free path" for lattice phonons, and that the value of the mean free path is of the order of magnitude of the scale of disorder in the molecular structure of a liquid or solid. The thermal phonon mean free paths or relaxation lengths of a number of glass formers have been plotted versus the glass transition temperature, indicating a linear relationship between the two. This has suggested a new criterion for glass formation based on the value of the phonon mean free path.
It has often been suggested that heat transport in dielectric solids occurs through elastic vibrations of the lattice, and that this transport is limited by elastic scattering of acoustic phonons by lattice defects (e.g. randomly spaced vacancies).
These predictions were confirmed by experiments on commercial glasses and glass ceramics, where mean free paths were apparently limited by "internal boundary scattering" to length scales of . The relationship between these transverse waves and the mechanism of vitrification has been described by several authors who proposed that the onset of correlations between such phonons results in an orientational ordering or "freezing" of local shear stresses in glass-forming liquids, thus yielding the glass transition. | 7 | Physical Chemistry |
The kinetic theory of gases deals not only with gases in thermodynamic equilibrium, but also very importantly with gases not in thermodynamic equilibrium. This means using Kinetic Theory to consider what are known as "transport properties", such as viscosity, thermal conductivity, mass diffusivity and thermal diffusion.
In its most basic form, Kinetic gas theory is only applicable to dilute gases. The extension of Kinetic gas theory to dense gas mixtures, Revised Enskog Theory, was developed in 1983-1987 by E. G. D. Cohen, J. M. Kincaid and M. Lòpez de Haro, building on work by H. van Beijeren and M. H. Ernst. | 7 | Physical Chemistry |
If Albert Einstein's photoelectric law is applied to a free molecule, the kinetic energy () of an emitted photoelectron is given by
where h is Plancks constant, ν is the frequency of the ionizing light, and I is an ionization energy for the formation of a singly charged ion in either the ground state or an excited state. According to Koopmans theorem, each such ionization energy may be identified with the energy of an occupied molecular orbital. The ground-state ion is formed by removal of an electron from the highest occupied molecular orbital, while excited ions are formed by removal of an electron from a lower occupied orbital. | 7 | Physical Chemistry |
Qualitatively, guanine (G) and cytosine (C) undergo a specific hydrogen bonding with each other, whereas adenine (A) bonds specifically with thymine (T) in DNA and with uracil (U) in RNA. Quantitatively, each GC base pair is held together by three hydrogen bonds, while AT and AU base pairs are held together by two hydrogen bonds. To emphasize this difference, the base pairings are often represented as "G≡C" versus "A=T" or "A=U".
DNA with low GC-content is less stable than DNA with high GC-content; however, the hydrogen bonds themselves do not have a particularly significant impact on molecular stability, which is instead caused mainly by molecular interactions of base stacking. In spite of the higher thermostability conferred to a nucleic acid with high GC-content, it has been observed that at least some species of bacteria with DNA of high GC-content undergo autolysis more readily, thereby reducing the longevity of the cell per se. Because of the thermostability of GC pairs, it was once presumed that high GC-content was a necessary adaptation to high temperatures, but this hypothesis was refuted in 2001. Even so, it has been shown that there is a strong correlation between the optimal growth of prokaryotes at higher temperatures and the GC-content of structural RNAs such as ribosomal RNA, transfer RNA, and many other non-coding RNAs. The AU base pairs are less stable than the GC base pairs, making high-GC-content RNA structures more resistant to the effects of high temperatures.
More recently, it has been demonstrated that the most important factor contributing to the thermal stability of double-stranded nucleic acids is actually due to the base stackings of adjacent bases rather than the number of hydrogen bonds between the bases. There is more favorable stacking energy for GC pairs than for AT or AU pairs because of the relative positions of exocyclic groups. Additionally, there is a correlation between the order in which the bases stack and the thermal stability of the molecule as a whole. | 1 | Biochemistry |
Injury in plants is damage caused by other organisms or by the non-living (abiotic) environment to plants. Animals that commonly cause injury to plants include insects, mites, nematodes, and herbivorous mammals; damage may also be caused by plant pathogens including fungi, bacteria, and viruses. Abiotic factors that can damage plants include heat, freezing, flooding, lightning, ozone gas, and pollutant chemicals.
Plants respond to injury by signalling that damage has occurred, by secreting materials to seal off the damaged area, by producing antimicrobial chemicals, and in woody plants by regrowing over wounds. | 1 | Biochemistry |
Kode Technology has been used for the in vitro modification of murine embryos, spermatozoa, zebra fish, epithelial/endometrial cells and red blood cells to create cellular quality controls systems, serologic kits (teaching), rare antigen expression, add infectious markers onto cells, modified cell adhesion/interaction/separation/immobilisation, and labelling. It has also been intravascularly infused for in vivo modification of blood cells and neutralisation of circulating antibodies and in in vivo imaging of circulating bone marrow kodecytes in zebrafish. Kode FSL constructs have also been applied to non-biological surfaces such as modified cellulose, paper, silica, polymers, natural fibers, glass and metals and has been shown to be ultra-fast in labelling these surfaces. | 1 | Biochemistry |
The water molecule, in the gaseous state, has three types of transition that can give rise to absorption of electromagnetic radiation:
* Rotational transitions, in which the molecule gains a quantum of rotational energy. Atmospheric water vapour at ambient temperature and pressure gives rise to absorption in the far-infrared region of the spectrum, from about 200 cm (50 μm) to longer wavelengths towards the microwave region.
* Vibrational transitions in which a molecule gains a quantum of vibrational energy. The fundamental transitions give rise to absorption in the mid-infrared in the regions around 1650 cm (μ band, 6 μm) and 3500 cm (so-called X band, 2.9 μm)
*Electronic transitions in which a molecule is promoted to an excited electronic state. The lowest energy transition of this type is in the vacuum ultraviolet region.
In reality, vibrations of molecules in the gaseous state are accompanied by rotational transitions, giving rise to a vibration-rotation spectrum. Furthermore, vibrational overtones and combination bands occur in the near-infrared region. The HITRAN spectroscopy database lists more than 37,000 spectral lines for gaseous HO, ranging from the microwave region to the visible spectrum.
In liquid water the rotational transitions are effectively quenched, but absorption bands are affected by hydrogen bonding. In crystalline ice the vibrational spectrum is also affected by hydrogen bonding and there are lattice vibrations causing absorption in the far-infrared. Electronic transitions of gaseous molecules will show both vibrational and rotational fine structure. | 7 | Physical Chemistry |
RiPPs constitute one of the major superfamilies of natural products, like alkaloids, terpenoids, and nonribosomal peptides, although they tend to be large, with molecular weights commonly in excess of 1000 Da. The advent of next-generation sequencing methods has made genome mining of RiPPs a common strategy. In part due to their increased discovery and hypothesized ease of engineering, the use of RiPPs as drugs is increasing. Although they are ribosomal peptides in origin, RiPPs are typically categorized as small molecules rather than biologics due to their chemical properties, such as moderate molecular weight and relatively high hydrophobicity.
The uses and biological activities of RiPPs are diverse.
RiPPs in commercial use include nisin, a food preservative, thiostrepton, a veterinary topical antibiotic, and nosiheptide and duramycin, which are animal feed additives. Phalloidin functionalized with a fluorophore is used in microscopy as a stain due to its high affinity for actin. Anantin is a RiPP used in cell biology as an atrial natriuretic peptide receptor inhibitor.
In 2012-2013, a derivatized RiPP in clinical trials was LFF571. Phase II clinical trials of LFF571, a derivative of the thiopeptide GE2270-A, for the treatment of Clostridium difficile infections, with comparable safety and efficacy to vancomycin, was terminated early as the results were unfavorable. Also recently in clinical trials was the NVB302 (a derivative of the lantibiotic actagardine) which is used for the treatment of Clostridium difficile infection. Duramycin has completed phase II clinical trials for the treatment of cystic fibrosis.
Other bioactive RiPPs include the antibiotics cyclothiazomycin and bottromycin, the ultra-narrow spectrum antibiotic plantazolicin, and the cytotoxin patellamide A. Streptolysin S, the toxic virulence factor of Streptococcus pyogenes, is also a RiPP. Additionally, human thyroid hormone itself is a RiPP due to its biosynthetic origin as thyroglobulin. | 1 | Biochemistry |
The oxyallyl diradical (OXA) is a trimethylenemethane molecule with one methylene group replaced by oxygen. This reactive intermediate is postulated to occur in ring opening of cyclopropanones, allene oxides and in the Favorskii rearrangement. The intermediate has been produced by reaction of oxygen radical anions with acetone and studied by photoelectron spectroscopy. The experimental electron affinity of OXA is 1.94 eV. | 0 | Organic Chemistry |
After the processed antigen (peptide) is complexed to the MHC molecule, they both migrate together to the cell membrane, where they are exhibited (elaborated) as a complex that can be recognized by the CD 4+ (T helper cell) – a type of white blood cell. This is known as antigen presentation. However, the epitopes (conformational epitopes) that are recognized by the B cell prior to their digestion may not be the same as that presented to the T helper cell. Additionally, a B cell may present different peptides complexed to different MHC-II molecules. | 1 | Biochemistry |
Through studying the transport of biogenic substances in the Tatar Strait in the Sea of Japan, a Russian team noted that biogenic substances can enter the marine environment due to input from either external sources, transport inside the water masses, or development by metabolic processes within the water. They can likewise be expended due to biotransformation processes, or biomass formation by microorganisms. In this study the biogenic substance concentrations, transformation frequency, and turnover were all highest in the upper layer of the water. Additionally, in different regions of the strait the biogenic substances with the highest annual transfer were constant. These were O, DOC, and DISi, which are normally found in large concentrations in natural water. The biogenic substances that tend to have lower input through the external boundaries of the strait and therefore least transfer were mineral and detrital components of N and P. These same substances take active part in biotransformation processes in the marine environment and have lower annual output as well. | 0 | Organic Chemistry |
A classical event is the retroposition of a spliced pre-mRNA molecule of the c-Src gene into the proviral ancestor of the Rous sarcoma virus (RSV). The retroposed c-src pre-mRNA still contained a single intron and within RSV is now referred to as v-Src gene. | 1 | Biochemistry |
The term archaerhodopsin is a portmanteau of archaea (the domain in which the proteins are found) and rhodopsin (a photoreceptor responsible for vision in the mammalian eye).
:archaea from Ancient Greek [https://en.wiktionary.org/wiki/%E1%BC%80%CF%81%CF%87%CE%B1%E1%BF%96%CE%BF%CF%82#Ancient_Greek ἀρχαῖα] (arkhaîa, "ancient"), the plural and neuter form of [https://en.wiktionary.org/wiki/%E1%BC%80%CF%81%CF%87%CE%B1%E1%BF%96%CE%BF%CF%82#Ancient_Greek ἀρχαῖος] (arkhaîos, "ancient").
:rhodopsin from Ancient Greek [https://en.wiktionary.org/wiki/%E1%BF%A5%CF%8C%CE%B4%CE%BF%CE%BD#Ancient_Greek ῥόδον] (rhódon, "rose"), because of its pinkish color, and [https://en.wiktionary.org/wiki/%E1%BD%84%CF%88%CE%B9%CF%82#Ancient_Greek ὄψις] (ópsis, "sight"). | 5 | Photochemistry |
Some such phenomena resisting the tendency to thermalize include (see, e.g., a quantum scar):
* Conventional quantum scars, which refer to eigenstates with enhanced probability density along unstable periodic orbits much higher than one would intuitively predict from classical mechanics.
* Perturbation-induced quantum scarring: despite the similarity in appearance to conventional scarring, these scars have a novel underlying mechanism stemming from the combined effect of nearly-degenerate states and spatially localized perturbations, and they can be employed to propagate quantum wave packets in a disordered quantum dot with high fidelity.
* Many-body quantum scars.
*Many-body localisation (MBL), quantum many-body systems retaining memory of their initial condition in local observables for arbitrary amounts of time.
Other systems that resist thermalisation and are better understood are quantum integrable systems and systems with dynamical symmetries. | 7 | Physical Chemistry |
* Loupe (sidérurgie)
* Krupp-Renn Process
* Direct reduced iron.
* Direct reduction (blast furnace)
* Histoire de la production de l'acier. | 8 | Metallurgy |
Excimer lamps emit narrow-band UVC and vacuum-ultraviolet radiation at a variety of wavelengths depending on the medium. They are mercury-free and reach full output quicker than a mercury lamp, and generate less heat. Excimer emission at 207 and 222 nm appears to be safer than traditional 254 nm germicidal radiation, due to greatly reduced penetration of these wavelengths in human skin. | 5 | Photochemistry |
Life and particulate organic matter in the ocean have fundamentally shaped the planet. On the most basic level, particulate organic matter can be defined as both living and non-living matter of biological origin with a size of ≥0.2 μm in diameter, including anything from a small bacterium (0.2 μm in size) to blue whales (20 m in size). Organic matter plays a crucial role in regulating global marine biogeochemical cycles and events, from the Great Oxidation Event in Earth's early history to the sequestration of atmospheric carbon dioxide in the deep ocean. Understanding the distribution, characteristics, dynamics, and changes over time of particulate matter in the ocean is hence fundamental in understanding and predicting the marine ecosystem, from food web dynamics to global biogeochemical cycles. | 9 | Geochemistry |
Wood flour is finely pulverized wood that has a consistency fairly equal to sand or sawdust, but can vary considerably, with particles ranging in dimensions from a fine powder to roughly that of a grain of rice. Most wood flour manufacturers are able to create batches of wood flour that have the same consistency throughout. All high quality wood flour is made from hardwoods because of its durability and strength. Very low grade wood flour is occasionally made from sapless softwoods such as pine or fir. | 2 | Environmental Chemistry |
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