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TPCK-treated trypsin is used to improve infection yield in laboratory tissue culture of some wild virus isolates that are not well-adapted to growth in vitro, such as some low-pathogenic avian influenza strains or fresh clinical isolates of SARS-CoV-2. The trypsin performs the maturation cleavage of the viral envelope proteins efficiently. | 1 | Biochemistry |
Metal alkene complexes are intermediates in many or most transition metal catalyzed reactions of alkenes: polymerization., hydrogenation, hydroformylation, and many other reactions. | 0 | Organic Chemistry |
Ordinary (non-time) crystals form through spontaneous symmetry breaking related to a spatial symmetry. Such processes can produce materials with interesting properties, such as diamonds, salt crystals, and ferromagnetic metals. By analogy, a time crystal arises through the spontaneous breaking of a time-translation symmetry. A time crystal can be informally defined as a time-periodic self-organizing structure. While an ordinary crystal is periodic (has a repeating structure) in space, a time crystal has a repeating structure in time. A time crystal is periodic in time in the same sense that the pendulum in a pendulum-driven clock is periodic in time. Unlike a pendulum, a time crystal "spontaneously" self-organizes into robust periodic motion (breaking a temporal symmetry). | 3 | Analytical Chemistry |
Like other β-lactam antibiotics, renal excretion of cefalexin is delayed by probenecid. It is also not recommended to take cefalexin with dofetilide, live Cholera vaccine, warfarin, and cholestyramine. Alcohol consumption reduces the rate at which it is absorbed. Cefalexin also interacts with metformin, an antidiabetic drug, and this can lead to higher concentrations of metformin in the body. Histamine H receptor antagonists like cimetidine and ranitidine may reduce the efficacy of cefalexin by delaying its absorption and altering its antimicrobial pharmacodynamics. Zinc and zinc supplements also interact with cefalexin and may reduce the amount of cefalexin in the body. | 4 | Stereochemistry |
The first step in failure analysis is investigating the failure to collect information. The sequence of steps for information gathering in a failure investigation are:
# Collection information about the circumstances surrounding the failure and selection of specimens
# Preliminary examination of the failed part (visual examination) and comparison with parts that have not failed
# Macroscopic examination and analysis and photographic documentation of specimens (fracture surfaces, secondary cracks, and other surface phenomena)
# Microscopic examination and analysis of specimens (fracture surfaces)
# Selection and preparation of metallographic sections
# Microscopic examination and analysis of prepared metallographic specimens
# Nondestructive testing
# Destructive/mechanical testing
# Determination of failure mechanism
# Chemical analysis (bulk, local, surface corrosion products, deposits or coatings)
# Identify all possible root causes
# Testing most likely possible root causes under simulated service conditions
# Analysis of all the evidence, formulation of conclusions, and writing the report including recommendations | 8 | Metallurgy |
In 1975, Mukaiyama reported that N-methyl-2-chloropyridinium iodide (also called 2-chloro-1-methylpyridinium iodide) allowed for a dehydration condensation between a carboxylic acid and an alcohol or similar functional groups to form an ester linkage. In the initial stage of the process, the carboxyl displaces the halogen atom on the reagent in the presence of a base. The resulting pyridyl ester is an activated electrophile and also serves as a good leaving group in a subsequent nucleophilic acyl substitution reaction with the alcohol reactant as nucleophile. Thus, the family of 2-halo-N-alkylpyridinium salts are named the Mukaiyama reagents. The reaction gives low yields if there are sterically large groups adjacent to the site of the reaction, such as tertiary carbons, but can be improved by using bromine as the halogen. In the years since its discovery, a number of different onium salts of aza-arenes have been used to catalyze a number of different dehydration reactions, including a macrolactonization. In 1994, Isamu Shiina developed his namesake macrolactonization in the Mukaiyama lab, making use of an aromatic carboxylic acid anhydride in the presence of a Lewis acid catalyst. | 0 | Organic Chemistry |
Newer developments of estimation methods have shown that the quality of the Joback method is limited. The original authors already stated themselves in the original article abstract: "High accuracy is not claimed, but the proposed methods are often as or more accurate than techniques in common use today."
The list of groups does not cover many common molecules sufficiently. Especially aromatic compounds are not differentiated from normal ring-containing components. This is a severe problem because aromatic and aliphatic components differ strongly.
The data base Joback and Reid used for obtaining the group parameters was rather small and covered only a limited number of different molecules. The best coverage has been achieved for normal boiling points (438 components), and the worst for heats of fusion (155 components). Current developments that can use data banks, like the Dortmund Data Bank or the DIPPR data base, have a much broader coverage.
The formula used for the prediction of the normal boiling point shows another problem. Joback assumed a constant contribution of added groups in homologous series like the alkanes. This doesn't describe the real behavior of the normal boiling points correctly. Instead of the constant contribution, a decrease of the contribution with increasing number of groups must be applied. The chosen formula of the Joback method leads to high deviations for large and small molecules and an acceptable good estimation only for mid-sized components. | 7 | Physical Chemistry |
Mono Lake ( ) is a saline soda lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in an endorheic basin. The lack of an outlet causes high levels of salts to accumulate in the lake which make its water alkaline.
The desert lake has an unusually productive ecosystem based on brine shrimp, which thrive in its waters, and provides critical habitat for two million annual migratory birds that feed on the shrimp and alkali flies (Ephydra hians). Historically, the native Kutzadikaa people ate the alkali flies pupae, which live in the shallow waters around the edge of the lake.
When the city of Los Angeles diverted water from the freshwater streams flowing into the lake, it lowered the lake level, which imperiled the migratory birds. The Mono Lake Committee formed in response and won a legal battle that forced Los Angeles to partially replenish the lake level. | 2 | Environmental Chemistry |
In order to confer to the pellets high resistance metallurgic mechanics and appropriate characteristics, the pellets are subjected to thermal processing, which involves stages of drying, preheating, firing, after-firing and cooling. The duration of each stage and the temperature that the pellets are subjected to have a strong influence on the final product quality. | 8 | Metallurgy |
Ocean acidification can also have effects on marine fish larvae. It internally affects their olfactory systems, which is a crucial part of their early development. Orange clownfish larvae mostly live on oceanic reefs that are surrounded by vegetative islands. Larvae are known to use their sense of smell to detect the differences between reefs surrounded by vegetative islands and reefs not surrounded by vegetative islands. Clownfish larvae need to be able to distinguish between these two destinations to be able to find a suitable area for their growth. Another use for marine fish olfactory systems is to distinguish between their parents and other adult fish, in order to avoid inbreeding.
In an experimental aquarium facility, clownfish were sustained in non-manipulated seawater with pH 8.15 ± 0.07, which is similar to our current ocean's pH. To test for effects of different pH levels, the seawater was modified to two other pH levels, which corresponded with climate change models that predict future atmospheric levels. In the year 2100 the model projects possible levels of 1,000 ppm, which correlates with the pH of 7.8 ± 0.05.
This experiment showed that when larvae are exposed to a pH of 7.8 ± 0.05 their reaction to environmental cues differs drastically from their reaction to cues at pH equal to current ocean levels. At pH 7.6 ± 0.05 larvae had no reaction to any type of cue. However, a meta-analysis published in 2022 found that the effect sizes of published studies testing for ocean acidification effects on fish behavior have declined by an order of magnitude over the past decade, and have been negligible for the past five years.
Eel embryos, a "critically endangered" species yet profound in aquaculture, are also being affected by ocean acidification, specifically the European eel. Although they spend most of their lives in fresh water, usually in rivers, streams, or estuaries, they go to spawn and die in the Sargasso Sea. Here is where European eels are experiencing the effects of acidification in one of their key life stages.
Fish embryos and larvae are usually more sensitive to pH changes than adults, as organs for pH regulation are not full developed. Because of this, European eel embryos are more vulnerable to changes in pH in the Sargasso Sea. A study of the European Eel in the Sargasso Sea was conducted in 2021 to analyze the specific effects of ocean acidification on embryos. The study found that exposure to predicted end-of-century ocean pCO conditions may affect normal development of this species in nature during sensitive early life history stages with limited physiological response capacities, while extreme acidification would negatively influence embryonic survival and development under hatchery conditions. | 9 | Geochemistry |
Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thylakoids frequently form stacks of disks referred to as grana (singular: granum). Grana are connected by intergranal or stromal thylakoids, which join granum stacks together as a single functional compartment.
In thylakoid membranes, chlorophyll pigments are found in packets called quantasomes. Each quantasome contains 230 to 250 chlorophyll molecules. | 5 | Photochemistry |
The ETS (Erythroblast Transformation Specific)family is divided into 12 subfamilies, which are listed below: | 1 | Biochemistry |
Multiferroic properties can appear in a large variety of materials. Therefore, several conventional material fabrication routes are used, including solid state synthesis, hydrothermal synthesis, sol-gel processing, vacuum based deposition, and floating zone.
Some types of multiferroics require more specialized processing techniques, such as
* Vacuum based deposition (for instance: MBE, PLD) for thin film deposition to exploit certain advantages that may come with 2-dimensional layered structures such as: strain mediated multiferroics, heterostructures, anisotropy.
* High pressure solid state synthesis to stabilize metastable or highly distorted structures, or in the case of the Bi-based multiferroics due to the high volatility of bismuth. | 7 | Physical Chemistry |
Journal of Photochemistry and Photobiology C: Photochemistry Reviews focusses on photochemistry literature reviews. It is the official journal of the Japanese Photochemistry Association and is published quarterly. The editor-in-chief is Noboru Kitamura. | 5 | Photochemistry |
In Vitis vinifera grape, trans-resveratrol is a phytoalexin produced against the growth of fungal pathogens such as Botrytis cinerea and delta-viniferin is another grapevine phytoalexin produced following fungal infection by Plasmopara viticola. Pinosylvin is a pre-infectious stilbenoid toxin (i.e. synthesized prior to infection), contrary to phytoalexins, which are synthesized during infection. It is present in the heartwood of Pinaceae. It is a fungitoxin protecting the wood from fungal infection.
Sakuranetin is a flavanone, a type of flavonoid. It can be found in Polymnia fruticosa and rice, where it acts as a phytoalexin against spore germination of Pyricularia oryzae. In Sorghum, the SbF3H2 H? --> gene, encoding a flavonoid 3-hydroxylase, seems to be expressed in pathogen-specific 3-deoxyanthocyanidin phytoalexins synthesis, for example in Sorghum-Colletotrichum' interactions.
6-Methoxymellein is a dihydroisocoumarin and a phytoalexin induced in carrot slices by UV-C, that allows resistance to Botrytis cinerea and other microorganisms.
Danielone is a phytoalexin found in the papaya fruit. This compound showed high antifungal activity against Colletotrichum gloesporioides, a pathogenic fungus of papaya.
Stilbenes are produced in Eucalyptus sideroxylon in case of pathogens attacks. Such compounds can be implied in the hypersensitive response of plants. High levels of phenolics in some woods can explain their natural preservation against rot.
In plants, VirA is a protein histidine kinase which senses certain sugars and phenolic compounds. These compounds are typically found from wounded plants, and as a result VirA is used by Agrobacterium tumefaciens to locate potential host organisms for infection. | 0 | Organic Chemistry |
Several computer applications attempt to relate the peaks in an electropherogram to specific bacteria in a database. Normally this type of analysis is done by simultaneously resolving several profiles of a single sample obtained with different restriction enzymes. The software then resolves the profile by attempting to maximize the matches between the peaks in the profiles and the entries in the database so that the number of peaks left without a matching sequence is minimal. The software withdraws from the database only those sequences which have their TRFs in all analyzed profiles. | 1 | Biochemistry |
Static fatigue tests can estimate a material’s lifetime and hardness to different environments. However, measuring a static fatigue limit can take a long time, and it is hard to measure a material’s true static fatigue limit with full certainty. | 8 | Metallurgy |
The oxidation of propionyl-CoA to form pyruvate is influenced by its necessity in Mycobacterium tuberculosis. Accumulation of propionyl-CoA can lead to toxic effects. In Mycobacterium tuberculosis, it has been suggested that the metabolism of propionyl-CoA is involved in cell wall biogenesis. A lack of such catabolism would therefore increase the susceptibility of the cell to various toxins, particularly to macrophage antimicrobial mechanisms. Another hypothesis regarding the fate of propionyl-CoA, in M. tuberculosisis, is that since propionyl-CoA is produced by beta odd chain fatty acid catabolism, the methylcitrate cycle is activated subsequently to negate any potential toxicity, acting as a buffering mechanism. | 1 | Biochemistry |
The raw material consumption and the conversion cost are the two elements that establish the manufacturing cost for a particular fine chemical. The former is determined primarily by the unit consumption and the purchasing cost of the materials used; the latter, by the throughput in kilograms per day in a given production bay. A precise calculation of the conversion cost is a demanding task. Different products with widely differing throughputs are produced in campaigns in multipurpose plants, occupying the equipment to different extents. Therefore, both the production capacity and the equipment utilization for a specific fine chemical are difficult to determine. Moreover, cost elements such as labor, capital, utilities, maintenance, waste disposal, and quality control cannot be allocated unambiguously.
An approximative calculation can be done by an experienced process development or pilot plant chemist on the basis of (1) the laboratory synthesis procedure and (2) by breaking down the process into unit operations, the standard costs of which have been determined previously Controlling has to be involved for a more in-depth costing.. The problems it has to address are how to fairly allocate costs for production capacity, which is not used. This can be due to the fact that part of a production bay is idle, because of lack of demand or because, e.g., a reactor is not required for a particular process.
Manufacturing costs usually are reported on a per kilogram product basis. For the purpose of benchmarking (both internal and external), the volume x time / output (VTO), as mentioned above, is a useful aid.
An indicative cost structure for a fine chemical company is shown in Table 10. Nowadays, a full 7-day/week operation, consisting of four or five shift teams, each working 8h per day, has become the standard. In terms of production costs, this is the most advantageous scheme. Higher salaries for night work are more than offset by better fixed cost absorption. As part of the budgeting process, standard costs for a production campaign of a particular fine chemical are determined on the basis of past experience. The actual results of the campaign are then compared with the standard. The capability of a fine chemical company to make dependable manufacturing cost forecasts is a distinct competitive advantage. | 0 | Organic Chemistry |
Vaporization (or vaporisation) of an element or compound is a phase transition from the liquid phase to vapor. There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, where as boiling is a bulk phenomenon. | 7 | Physical Chemistry |
*Go Down Old Hannah: the Living History of African American Texans Naomi Mitchell Carrier
*They Dance Alone Christine LeVeaux (2005)
*Harlem Renaissance by Ella O. Williams
*National Medical Association journal covers
**Summer 2007, Volume 99, Number 12
**December 2008, Volume 100, Number 12
**January 2010, Volume 102, Number 1
*National Directory of African American Organizations 2001–2003 Philip Morris Co. (Keep the Dream Alive)
*Worship in the House was commissioned by Integrity Music to be used as a CD cover.
*Beyond the Blues: Reflections of African America in the Fine Arts Collection of the Amistad Research Center (The Struggle Continues)
*2006 South Central Region Jack and Jill of America cookbook
*The Ensemble Theatre's 2008 production of Radio Golf playbill cover. | 3 | Analytical Chemistry |
The THz fields can be applied to accelerate electrons out of their equilibrium. If this is done fast enough, one can measure the elementary processes, such as how fast the screening of the Coulomb interaction is built up. This was experimentally explored in Ref. where it was shown that screening is complete within tens of femtoseconds in semiconductors. These insights are very important to understand how electronic plasma behaves in solids.
The Coulomb interaction can also pair electrons and holes into excitons, as discussed above. Due to their analog to the hydrogen atom, excitons have bound states that can be uniquely identified by the usual quantum numbers 1s, 2s, 2p, and so on. In particular, 1s-to-2p transition is dipole allowed and can be directly generated by E(t) if the photon energy matches the transition energy. In gallium arsenide-type systems, this transition energy is roughly 4 meV that corresponds to 1 THz photons. At resonance, the dipole d defines the Rabi energy Ω = d E(t) that determines the time scale at which the 1s-to-2p transition proceeds.
For example, one can excite the excitonic transition with an additional optical pulse which is synchronized with the THz pulse. This technique is called transient THz spectroscopy. Using this technique one can follow the formation dynamics of excitons or observe THz gain arising from intraexcitonic transitions.
Since a THz pulse can be intense and short, e.g., single-cycle, it is experimentally possible to realize situations where duration of the pulse, time scale related to Rabi- as well as the THz photon energy ħω are degenerate. In this situation, one enters the realm of extreme nonlinear optics where the usual approximations, such as the rotating-wave approximation (abbreviated as RWA) or the conditions for complete state transfer, break down. As a result, the Rabi oscillations become strongly distorted by the non-RWA contributions, the multiphoton absorption or emission processes, and the dynamic Franz–Keldysh effect, as measured in Refs.
By using a free-electron laser, one can generate longer THz pulses that are more suitable for detecting the Rabi oscillations directly. This technique could indeed demonstrate the Rabi oscillations, or actually the related Autler–Townes splitting, in experiments. The Rabi splitting has also been measured with a short THz pulse and also the onset to multi-THz-photon ionization has been detected, as the THz fields are made stronger. Recently, it has also been shown that the Coulomb interaction causes nominally dipole-forbidden intra-excitonic transitions to become partially allowed. | 7 | Physical Chemistry |
If the solubility, S, of an organic compound is known or predicted in both water and 1-octanol, then log P can be estimated as
There are a variety of approaches to predict solubilities, and so log S. | 7 | Physical Chemistry |
In aquatic toxicology multiple databases exist and each generally pertains to a single aspect of aquatic toxicology such as PCBs, tissue residues or sediment toxicity. Other informational and regulatory databases on toxicology in general are maintained by the U.S. EPA, USGS, United States Army Corps of Engineers and the National Oceanic and Atmospheric Administration. In the U.S. there are three major databases pertaining specifically to aquatic toxicology: the Toxicity/Residue Database, the Environmental Residue Effects Database and the ECOTOX database. | 1 | Biochemistry |
The role of electricity in the nervous systems of animals was first observed in dissected frogs by Luigi Galvani, who studied it from 1791 to 1797. Galvani's results inspired Alessandro Volta to develop the Voltaic pile—the earliest-known electric battery—with which he studied animal electricity (such as electric eels) and the physiological responses to applied direct-current voltages.
In the 19th century scientists studied the propagation of electrical signals in whole nerves (i.e., bundles of neurons) and demonstrated that nervous tissue was made up of cells, instead of an interconnected network of tubes (a reticulum). Carlo Matteucci followed up Galvanis studies and demonstrated that injured nerves and muscles in frogs could produce direct current. Matteuccis work inspired the German physiologist, Emil du Bois-Reymond, who discovered in 1843 that stimulating these muscle and nerve preparations produced a notable diminution in their resting currents, making him the first researcher to identify the electrical nature of the action potential. The conduction velocity of action potentials was then measured in 1850 by du Bois-Reymond's friend, Hermann von Helmholtz. Progress in electrophysiology stagnated thereafter due to the limitations of chemical theory and experimental practice. To establish that nervous tissue is made up of discrete cells, the Spanish physician Santiago Ramón y Cajal and his students used a stain developed by Camillo Golgi to reveal the myriad shapes of neurons, which they rendered painstakingly. For their discoveries, Golgi and Ramón y Cajal were awarded the 1906 Nobel Prize in Physiology. Their work resolved a long-standing controversy in the neuroanatomy of the 19th century; Golgi himself had argued for the network model of the nervous system.
The 20th century saw significant breakthroughs in electrophysiology. In 1902 and again in 1912, Julius Bernstein advanced the hypothesis that the action potential resulted from a change in the permeability of the axonal membrane to ions. Bernsteins hypothesis was confirmed by Ken Cole and Howard Curtis, who showed that membrane conductance increases during an action potential. In 1907, Louis Lapicque suggested that the action potential was generated as a threshold was crossed, what would be later shown as a product of the dynamical systems of ionic conductances. In 1949, Alan Hodgkin and Bernard Katz refined Bernsteins hypothesis by considering that the axonal membrane might have different permeabilities to different ions; in particular, they demonstrated the crucial role of the sodium permeability for the action potential. They made the first actual recording of the electrical changes across the neuronal membrane that mediate the action potential. This line of research culminated in the five 1952 papers of Hodgkin, Katz and Andrew Huxley, in which they applied the voltage clamp technique to determine the dependence of the axonal membrane's permeabilities to sodium and potassium ions on voltage and time, from which they were able to reconstruct the action potential quantitatively. Hodgkin and Huxley correlated the properties of their mathematical model with discrete ion channels that could exist in several different states, including "open", "closed", and "inactivated". Their hypotheses were confirmed in the mid-1970s and 1980s by Erwin Neher and Bert Sakmann, who developed the technique of patch clamping to examine the conductance states of individual ion channels. In the 21st century, researchers are beginning to understand the structural basis for these conductance states and for the selectivity of channels for their species of ion, through the atomic-resolution crystal structures, fluorescence distance measurements and cryo-electron microscopy studies.
Julius Bernstein was also the first to introduce the Nernst equation for resting potential across the membrane; this was generalized by David E. Goldman to the eponymous Goldman equation in 1943. The sodium–potassium pump was identified in 1957 and its properties gradually elucidated, culminating in the determination of its atomic-resolution structure by X-ray crystallography. The crystal structures of related ionic pumps have also been solved, giving a broader view of how these molecular machines work. | 7 | Physical Chemistry |
In sweetgum (Liquidambar styraciflua), sinapaldehyde arises in two steps from coniferyl aldehyde beginning with hydroxylation mediated by coniferyl aldehyde 5-hydroxylase. The diphenol is then methylated at the 5-OH by the action of caffeate O-methyltransferase.
Sinapaldehyde is reduced to the alcohol by the action of dehydrogenase enzymes. In Arabidopsis thaliana, the enzyme dihydroflavonol 4-reductase uses NADP to reduce sinapaldehyde to sinapyl alcohol.
It is found in Senra incana (Hibisceae). It is a low molecular weight phenol that is susceptible to extraction from cork stoppers into wine. | 1 | Biochemistry |
Alcohol consumption increases the risk of hypothermia in two ways: vasodilation and temperature controlling systems in the brain. Vasodilation increases blood flow to the skin, resulting in heat being lost to the environment. This produces the effect of feeling warm, when one is actually losing heat. Alcohol also affects the temperature-regulating system in the brain, decreasing the body's ability to shiver and use energy that would normally aid the body in generating heat. The overall effects of alcohol lead to a decrease in body temperature and a decreased ability to generate body heat in response to cold environments. Alcohol is a common risk factor for death due to hypothermia. Between 33% and 73% of hypothermia cases are complicated by alcohol. | 1 | Biochemistry |
*Justice: Collection of Artwork inspired by the Legal Profession – New Orleans City Hall, 1999
*Capturing Our Heritage – University of Texas Medical Branch Moody Medical Library, Galveston, 2001
*Born in the Spirit – Penn State Harrisburg Library, 2003
*Katrina: The Hope, Healing and Rebirth of New Orleans – National Bar Association, 2005
*Courage of Conviction: African Americans Serving in the Military from Colonial Time to the President of the U.S. – Stone Mountain Park, 2008/09
*American Slavery: The Reason Why We Are Here – The Beach Institute, Savannah, Georgia 2009
*Sumptin to See: Native Son Comes Home' – New Orleans African American Museum 2010
*Our History, Heritage and Culture: An American Story, the art of Ted Ellis – Rosa Parks Museum 2010
*Medicine and Art: Telling Our Story, Yale School of Medicine | 3 | Analytical Chemistry |
Pseudoephedrine is a diastereomer of ephedrine and is readily reduced into methamphetamine or oxidized into methcathinone. | 4 | Stereochemistry |
Bacterial artificial chromosomes (BACs) are circular DNA molecules, usually about 7kb in length, that are capable of holding inserts up to 300kb in size. BAC vectors contain a replicon derived from E. coli F factor, which ensures they are maintained at one copy per cell. Once an insert is ligated into a BAC, the BAC is introduced into recombination deficient strains of E. coli by electroporation. Most BAC vectors contain a gene for antibiotic resistance and also a positive selection marker. The figure to the right depicts a BAC vector being cut with a restriction enzyme, followed by the insertion of foreign DNA that is re-annealed by a ligase. Overall, this is a very stable vector, but they may be hard to prepare due to a single origin of replication just like PACs. | 1 | Biochemistry |
Whether or not a GMO is present in a sample can be tested by Q-PCR, but also by multiplex PCR. Multiplex PCR uses multiple, unique primer sets within a single PCR reaction to produce amplicons of varying sizes specific to different DNA sequences, i.e. different transgenes. By targeting multiple genes at once, additional information may be gained from a single test run that otherwise would require several times the reagents and more time to perform. Annealing temperatures for each of the primer sets must be optimized to work correctly within a single reaction, and amplicon sizes, i.e., their base pair length, should be different enough to form distinct bands when visualized by gel electrophoresis. | 1 | Biochemistry |
The Felspathic Highlands Terrane (alternatively Feldspathic), or FHT, is composed predominantly of ancient anorthositic materials. It has low iron oxide and thorium levels. The FHT can be split into an inner and outer felspathic highlands. The outer FHT has comparatively higher levels of iron oxide and thorium. It is thought to be part of the FHT, with the differences being due to modification by ejecta from impacts in other terranes. The FHT covers 65% of the lunar surface.
Overall, 6% of the lunar surface (and hence 9% of the FHT) consists of maria within the FHT, such as Mare Moscoviense. FHT maria have on average only 2.2 ppm of thorium, which is twice as much as the lunar average but significantly less than the levels seen in the PKT maria. Outer FHT non-maria regions contain 1 ppm of thorium, and only 0.3 ppm of thorium in the inner FHT.
The inner FHT lies exclusively in the far side of the Moon, whereas the outer FHT spans both sides and is the one of two terranes on the near side of the Moon, along with the PKT. No spacecraft have landed on the inner FHT, as the only lander to the far side touched down in the South Pole-Aitken Terrane. In contrast, the outer FHT has been the subject of human landings and sample return. | 9 | Geochemistry |
The Mukaiyama taxol total synthesis published by the group of Teruaki Mukaiyama of the Tokyo University of Science between 1997 and 1999 was the 6th successful taxol total synthesis. The total synthesis of Taxol is considered a hallmark in organic synthesis.
This version is a linear synthesis with ring formation taking place in the order C, B, A, D. Contrary to the other published methods, the tail synthesis is by an original design. Teruaki Mukaiyama is an expert on aldol reactions and not surprisingly his Taxol version contains no less than 5 of these reactions. Other key reactions encountered in this synthesis are a pinacol coupling and a Reformatskii reaction. In terms of raw materials the C20 framework is built up from L-serine (C3), isobutyric acid (C4), glycolic acid (C2), methyl bromide (C1), methyl iodide (C1), 2,3-dibromopropene (C3), acetic acid (C2) and homoallyl bromide (C4). | 0 | Organic Chemistry |
Protein phosphatases remove phosphates from proteins, usually on Serine, Threonine, and Tyrosine residues, reversing the action of protein kinases. The PTP family of protein phosphatases is tyrosine-specific, and several other families (PPPL, PPM, HAD) appear to be serine/threonine specific, while other families are unknown or have a variety of substrates (DSPs dephosphorylate any amino acid, while some protein phosphatases also have non-protein substrates). In the human genome, 20 different folds of protein are known to be phosphatases, of which 10 include protein phosphatases.
Protein phosphatomes have been cataloged for human and 8 other key eukaryotes, for Plasmodium and Trypanosomes
and phosphatomes have been used for functional analysis, by experimentally investing all known protein phosphatases, in the yeast Fusarium, in Plasmodium and in human cancer
Large scale databases exist for human and animal phosphatomes [http://phosphatome.net/wiki/index.php Phosphatome.net], parasitic protozoans [http://202.41.10.46/ProtozPhosDB/ ProtozPhosDB] and for the substrates of human phosphatases [http://www.koehn.embl.de/depod/ DEPOD]. | 1 | Biochemistry |
Records of bioluminescence due to bacteria have existed for thousands of years. They appear in the folklore of many regions, including Scandinavia and the Indian subcontinent. Both Aristotle and Charles Darwin have described the phenomenon of the oceans glowing. Since its discovery less than 30 years ago, the enzyme luciferase and its regulatory gene, lux, have led to major advances in molecular biology, through use as a reporter gene. Luciferase was first purified by McElroy and Green in 1955. It was later discovered that there were two subunits to luciferase, called subunits α and β. The genes encoding these enzymes, luxA and luxB, respectively, were first isolated in the lux operon of Aliivibrio fisheri. | 1 | Biochemistry |
In the cytoplasm, ferrous iron is found in a soluble, chelatable state which constitutes the labile iron pool (~0.001 mM). In this pool, iron is thought to be bound to low-mass compounds such as peptides, carboxylates and phosphates, although some might be in a free, hydrated form (aqua ions). Alternatively, iron ions might be bound to specialized proteins known as metallochaperones. Specifically, poly-r(C)-binding proteins PCBP1 and PCBP2 appear to mediate transfer of free iron to ferritin (for storage) and non-heme iron enzymes (for use in catalysis). The labile iron pool is potentially toxic due to iron's ability to generate reactive oxygen species. Iron from this pool can be taken up by mitochondria via mitoferrin to synthesize Fe-S clusters and heme groups. | 1 | Biochemistry |
In the coreless type, metal is placed in a crucible surrounded by a water-cooled alternating current solenoid coil. A channel-type induction furnace has a loop of molten metal, which forms a single-turn secondary winding through an iron core. | 8 | Metallurgy |
Inulin is a naturally occurring polysaccharide complex carbohydrate composed of fructose, a plant-derived food that human digestive enzymes cannot completely break down. The inulins belong to a class of dietary fibers known as fructans. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes. Most plants that synthesize and store inulin do not store other forms of carbohydrates such as starch. In the United States in 2018, the Food and Drug Administration approved inulin as a dietary fiber ingredient used to improve the nutritional value of manufactured food products. | 0 | Organic Chemistry |
Maharram Əli oğlu Mammadyarov (; 17 October 1924 – 2 January 2022) was an Azerbaijani scientist, doctor of chemistry, real member of Azerbaijan National Academy of Sciences. | 0 | Organic Chemistry |
Emma Schymanski (born Emma Craven) is chemist known for her work identifying unknown organic compounds, particularly pollutants, and is an advocate for open science. | 0 | Organic Chemistry |
In polymer chemistry, a structural unit is a building block of a polymer chain. It is the result of a monomer which has been polymerized into a long chain.
There may be more than one structural unit in the repeat unit. When different monomers are polymerized, a copolymer is formed. It is a routine way of developing new properties for new materials. | 7 | Physical Chemistry |
About a decade later, Jurkauskas and Buchwald also utilized dynamic kinetic resolution towards the hydrogenation of conjugated systems. 1,4 addition to cyclic enones is quite common in many reaction schemes, however asymmetric reductions in the presence of an easily epimerizable center adds to the complexity when trying to modify only one center. Through the use of a copper catalyzed reaction however, Buchwald was able to obtain 1,4 reduction in great enantiomeric excess (ee). In order to achieve a high rate of epimerization, a strong bulky base like sodium t-butoxide was used to ensure rapid equilibrium.
Copper proved to be an excellent metal in this reaction due to its ability to complex with the oxygen when the hydrogen was added. Being a soft metal, copper greatly prefers 1,4 addition over 1,2 addition, with the alkene being a softer more polarizable electrophile. Again, BINAP became the ligand of choice due to its steric selectivity, lowering the transition state energy of starting material in the left column. In addition, PMHS was used as a relatively less reactive silane. This prevented loss of ee before deprotection with tetra-n-butylammonium fluoride (TBAF). | 4 | Stereochemistry |
Thiamine triphosphate (ThTP) was chemically synthesized in 1948 at a time when the only organic triphosphate known was ATP. The first claim of the existence of ThTP in living organisms was made in rat liver, followed by baker’s yeast. Its presence was later confirmed in rat tissues and in plants germs, but not in seeds, where thiamine was essentially unphosphorylated. In all those studies, ThTP was separated from other thiamine derivatives using a paper chromatographic method, followed by oxidation in fluorescent thiochrome compounds with ferricyanide in alkaline solution. This method is at best semi-quantitative, and the development of liquid chromatographic methods suggested that ThTP represents far less than 10% of total thiamine in animal tissues. | 1 | Biochemistry |
Aqueous geochemistry studies the role of various elements in natural waters, including copper, sulfur, and mercury. Researchers in this field also study how elemental fluxes are exchanged through interactions between the atmosphere, the earth or soil (terrestrial interactions) and bodies of water (aquatic interactions).
Work in the field of aqueous geochemistry has also studied the prevalence of rare earth elements, nuclear waste products, and hydrocarbons. | 9 | Geochemistry |
The uhp system is composed of UhpA, UhpB, UhpC, and UhpT. UhpB and UhpC are both transmembrane proteins which form a complex with each other. UhpA is a signal protein found in the cytoplasm. UhpT is a transporter protein which facilitates the uptake of phosphorylated hexose molecules into the cell. | 1 | Biochemistry |
Malachite green is classified in the dyestuff industry as a triarylmethane dye and also using in pigment industry. Formally, malachite green refers to the chloride salt , although the term malachite green is used loosely and often just refers to the colored cation. The oxalate salt is also marketed. The anions have no effect on the color. The intense green color of the cation results from a strong absorption band at 621 nm (extinction coefficient of ).
Malachite green is prepared by the condensation of benzaldehyde and dimethylaniline to give leuco malachite green (LMG):
Second, this colorless leuco compound, a relative of triphenylmethane, is oxidized to the cation that is MG:
A typical oxidizing agent is manganese dioxide.
Hydrolysis of MG gives an alcohol:
This alcohol is important because it, not MG, traverses cell membranes. Once inside the cell, it is metabolized into LMG. Only the cation MG is deeply colored, whereas the leuco and alcohol derivatives are not. This difference arises because only the cationic form has extended pi-delocalization, which allows the molecule to absorb visible light. | 3 | Analytical Chemistry |
Distonic ions have been extensively examined due to their unique behavior and how commonly they can occur. It has been shown that in most cases distonic ions have a bonding arrangement corresponding to that of the original molecule before ionization occurred; but that distonic ions are less stable than before ionization occurred; even so, distonic ions are considered stable ions and have caught many scientists' attention because they possess more stability than its traditional isomer. It may be difficult to decipher the functions of the charge and radical site because distonic ions are limited to elementary reactions such as unimolecular reactions involving highly excited and short-lived species. | 7 | Physical Chemistry |
A large number of cloning vectors are available, and choosing the vector may depend upon a number of factors, such as the size of the insert, copy number and cloning method. Large insert may not be stably maintained in a general cloning vector, especially for those with a high copy number, therefore cloning large fragments may require more specialised cloning vector. | 1 | Biochemistry |
A monochromatic light source, usually a laser, is shot through a polarizer and into a sample. The scattered light then goes through a second polarizer where it is collected by a photomultiplier and the resulting image is projected onto a screen. This is known as a speckle pattern (Figure 1).
All of the molecules in the solution are being hit with the light and all of the molecules diffract the light in all directions. The diffracted light from all of the molecules can either interfere constructively (light regions) or destructively (dark regions). This process is repeated at short time intervals and the resulting set of speckle patterns is analyzed by an autocorrelator that compares the intensity of light at each spot over time.
The polarizers can be set up in two geometrical configurations. One is a vertical/vertical (VV) geometry, where the second polarizer allows light through that is in the same direction as the primary polarizer. In vertical/horizontal (VH) geometry the second polarizer allows light that is not in the same direction as the incident light. | 7 | Physical Chemistry |
In the area of solid state chemistry. graphite intercalation compounds are materials prepared by intercalation of diverse guests into graphite. The materials have the formula (guest)C where n can range from 8 to 40's. The distance between the carbon layers increases significantly upon insertion of the guests. Common guests are reducing agents such as alkali metals. Strong oxidants, such as arsenic pentafluoride also intercalate into graphite. Intercalation involves electron transfer into or out of the host. The properties of these materials differ from those of the parent graphite. | 6 | Supramolecular Chemistry |
Ružička was born in Vukovar (until 1920 in the Kingdom of Hungary, Austro-Hungarian Empire, today in Croatia). His family of craftsmen and farmers was mostly of Croat origin, with a Czech great-grandparent, Ružička, and a great-grandmother and a great-grandfather from Austria. He lost his father, Stjepan, at the age of four, and his mother, Amalija Sever, took him and his younger brother Stjepan, to live in Osijek.
Ružička attended the classics program secondary school in Osijek. He changed his original idea of becoming a priest and switched to studying technical disciplines. Chemistry was his choice, probably because he hoped to get a position at the newly opened sugar refinery built in Osijek.
Owing to the excessive hardship of everyday and political life, he left and chose the High Technical School in Karlsruhe in Germany. He was a good student in areas he liked and that he thought would be necessary and beneficial in the future, which was organic chemistry. That is why his physical chemistry professor, Fritz Haber (Nobel laureate in 1918), opposed his summa cum laude degree. However, in the course of his studies, Ružička set up excellent cooperation with Hermann Staudinger (a Nobel laureate in 1953). Studying within Staudingers department, he obtained his doctoral degree in 1910, then moving to Zürich as Staudingers assistant. | 0 | Organic Chemistry |
An experiment on oat plants by scientist Maria Quiles, revealed that extreme light intensity can inhibit photosynthesis and result in the lack of PS II activity. This reduction leads to an increase in NAD(P)H and PTOX levels which then causes the stimulation of chlororespiration.
Oat leaves were incubated and Chlorophyll fluorescence emission was used to examine the effect of extreme light intensity. As the emission of the Chlorophyll fluorescence increased the PQ pool decreased. This stimulated the cyclic electron flow, causing NAD(P)H and PTOX levels to ultimately incline and initiate the process of chlororespiration within the thylakoid membrane of oat plants.
The effect of adding n-propyl gallate to the incubated leaves was also observed. N-propyl gallate is a molecule that helps distinguish between PQ reduction and oxidation activities by inhibiting PTOX. Quiles noted an increase in chlorophyll fluorescence inside the thylakoid membrane of plant cells, after the addition of n-propyl gallate. The result led to the stimulation of the NAD(P)H enzyme and its cyclic pathway; causing a continuous increase in chlorophyll fluorescence levels within the oat. | 1 | Biochemistry |
* In 2013, six months prior to opening, the East Span of the Oakland Bay Bridge failed during testing. Catastrophic failures occurred in shear bolts in the span, after only two weeks of service, with the failure attributed to embrittlement (see details above).
* In the City of London, 122 Leadenhall Street, generally known as the Cheesegrater, suffered from hydrogen embrittlement in steel bolts, with three bolts failing in 2014 and 2015. Most of the 3,000 bolts were replaced at a cost of £6m. | 7 | Physical Chemistry |
Freeze–thaw weathering is caused by moisture freezing inside cracks in rock. Upon freezing its volume expands, causing large forces which cracks spall off the outer surface. As this cycle repeats the outer surface repeatedly undergoes spalling, resulting in weathering.
Some stone and masonry surfaces used as building surfaces will absorb moisture at their surface. If exposed to severe freezing conditions, the surface may flake off due to the expansion of the water. This effect can also be seen in terracotta surfaces (even if glazed) if there is an entrance for water at the edges. | 8 | Metallurgy |
The three-dimensional interior cavity of a cryptand provides a binding site – or host – for "guest" ions. The complex between the cationic guest and the cryptand is called a cryptate. Cryptands form complexes with many "hard cations" including , lanthanoids, alkali metals, and alkaline earth metals. In contrast to crown ethers, cryptands bind the guest ions using both nitrogen and oxygen donors. This three-dimensional encapsulation mode confers some size-selectivity, enabling discrimination among alkali metal cations (e.g. Na vs. K). Some cryptands are luminescent. | 6 | Supramolecular Chemistry |
Effusion from an equilibrated container into outside vacuum can be calculated based on kinetic theory. The number of atomic or molecular collisions with a wall of a container per unit area per unit time (impingement rate) is given by:
assuming mean free path is much greater than pinhole diameter and the gas can be treated as an ideal gas.
If a small area on the container is punched to become a small hole, the effusive flow rate will be
where is the molar mass, is the Avogadro constant, and is the gas constant.
The average velocity of effused particles is
Combined with the effusive flow rate, the recoil/thrust force on the system itself is
An example is the recoil force on a balloon with a small hole flying in vacuum. | 7 | Physical Chemistry |
Cubic materials are special orthotropic materials that are invariant with respect to 90° rotations with respect to the principal axes, i.e., the material is the same along its principal axes. Due to these additional symmetries the stiffness tensor can be written with just three different material properties like
The inverse of this matrix is commonly written as
where is the Youngs modulus, is the shear modulus, and is the Poissons ratio. Therefore, we can think of the ratio as the relation between the shear modulus for the cubic material and its (isotropic) equivalent: | 3 | Analytical Chemistry |
Exothermic and endothermic describe two types of chemical reactions or systems found in nature, as follows: | 7 | Physical Chemistry |
IUPAC defines chain propagation as a reaction of an active center on the growing polymer molecule, which adds one monomer molecule to form a new polymer molecule (RM°) one repeat unit longer.
For radical polymerization, the active center remains an atom with an unpaired electron. The addition of the second monomer and a typical later addition step are
* RM° + M → RM°
* RM° + M → RM°
For some polymers, chains of over 1000 monomer units can be formed in milliseconds. | 7 | Physical Chemistry |
In the early 1990s, the market was becoming more familiar with the potential of laser peening to increase fatigue life. In 1991, the U.S. Air Force introduced Battelle and Wagner engineers to GE Aviation to discuss the potential application of laser peening to address a foreign object damage (FOD) problem with fan blades in the General Electric F101 engine powering the Rockwell B-1B Lancer Bomber. The resulting tests showed that laser peened fan blades severely notched after laser peening had the same fatigue life as a new blade. After further development, GE Aviation licensed the laser shock peening technology from Battelle, and in 1995, GE Aviation and the U.S. Air Force made the decision to move forward with production development of the technology. GE Aviation began production laser peening of the F101 fan blades in 1998.
The demand for industrial laser systems required for GE Aviation to go into production attracted several of the laser shock peening team at Battelle to start LSP Technologies, Inc. in 1995 as the first commercial supplier of laser peening equipment. Led by founder Jeff Dulaney, LSP Technologies designed and built the laser systems for GE Aviation to perform production laser peening of the F101 fan blades. Through the late 1990s and early 2000s, the U.S. Air Force continued to work with LSP Technologies to mature the laser shock peening production capabilities and implement production manufacturing cells.
In the mid 1990s, independent of the laser peening developments ongoing in the United States and France, Yuji Sano of the Toshiba Corporation in Japan initiated the development of a laser peening system capable of laser peening welds in nuclear plant pressure vessels to mitigate stress corrosion cracking in these areas. The system used a low-energy pulsed laser operating at a higher pulse frequency than the higher powered lasers. The laser beam was introduced into the pressure vessels through articulated tubes. Because the pressure vessels were filled with water, the process did not require a water overlay over the irradiated surface. However, the beam had to travel some distance through the water, necessitating using a shorter wavelength beam, 532 nm, to minimize dielectric breakdown of the beam in the water, instead of the 1054 nm beam used in the United States and France. Also, it was impractical to consider using an opaque overlay. This process is now known as Laser Peening without Coating (LPwC). It began to be applied to Japanese boiling water and pressurized water reactors in 1999.
Also in the 1990s a significant laser peening research group was formed at the Madrid Polytechnic University by José Ocaña. Their work includes both experimental and theoretical studies using low-energy pulsed lasers both without and with an opaque overlay. | 8 | Metallurgy |
* 1.G.1 The Viral Pore-forming Membrane Fusion Protein-1 (VMFP1) Family
* 1.G.2 The Viral Pore-forming Membrane Fusion Protein-2 (VMFP2) Family
* 1.G.3 The Viral Pore-forming Membrane Fusion Protein-3 (VMFP3) Family
* 1.G.4 The Viral Pore-forming Membrane Fusion Protein-4 (VMFP4) Family
* 1.G.5 The Viral Pore-forming Membrane Fusion Protein-5 (VMFP5) Family
* 1.G.6 The Hepadnaviral S Fusion Protein (HBV-S Protein) Family
* 1.G.7 The Reovirus FAST Fusion Protein (R-FAST) Family
* 1.G.8 The Arenavirus Fusion Protein (AV-FP) Family
* 1.G.9 The Syncytin (Syncytin) Family
* 1.G.10 The Herpes Simplex Virus Membrane Fusion Complex (HSV-MFC) Family
* 1.G.11 Poxvirus Cell Entry Protein Complex (PEP-C) Family
* 1.G.12 The Avian Leukosis Virus gp95 Fusion Protein (ALV-gp95) Family
* 1.G.13 The Orthoreovirus Fusion-associated Small Transmembrane (FAST) Family
* 1.G.14 The Influenza Virus Hemagglutinin/Fusion Pore-forming Protein (Influenza-H/FPP) Family
* 1.G.15 The Autographa californica Nuclear Polyhedrosis Virus Major Envelope Glycoprotein GP64 (GP64) Family
* 1.G.16 The Human Immunodeficiency Virus Type 1 (HIV-1) Fusion Peptide (HIV-FP) Family
* 1.G.17 The Bovine Leukemia Virus Envelop Glycoprotein (BLV-Env) Family
* 1.G.18 The SARS-CoV Fusion Peptide in the Spike Glycoprotein Precursor (SARS-FP) Family
* 1.G.19 The Rotavirus Pore-forming Membrane Fusion Complex (Rotavirus MFC) Family
* 1.G.20 The Hantavirus Gc Envelope Fusion Glycoprotein (Gc-EFG) Family
* 1.G.21 The Epstein Barr Virus (Human Herpes Virus 4) Gp42 (Gp42) Family
* 1.G.22 The Cytomegalovirus (Human Herpesvirus 5) Glycoprotein gO (gO) Family | 1 | Biochemistry |
There may be side effects when changing over from glucose metabolism to fat metabolism. These may include headache, fatigue, dizziness, insomnia, difficulty in exercise tolerance, constipation, and nausea, especially in the first days and weeks after starting a ketogenic diet. Breath may develop a sweet, fruity flavor via production of acetone that is exhaled because of its high volatility.
Most adverse effects of long-term ketosis reported are in children because of its longstanding acceptance as a treatment for pediatric epilepsy. These include compromised bone health, stunted growth, hyperlipidemia, and kidney stones. | 1 | Biochemistry |
The Otto Cycle is an example of a reversible thermodynamic cycle.
*1→2: Isentropic / adiabatic expansion: Constant entropy (s), Decrease in pressure (P), Increase in volume (v), Decrease in temperature (T)
*2→3: Isochoric cooling: Constant volume(v), Decrease in pressure (P), Decrease in entropy (S), Decrease in temperature (T)
*3→4: Isentropic / adiabatic compression: Constant entropy (s), Increase in pressure (P), Decrease in volume (v), Increase in temperature (T)
*4→1: Isochoric heating: Constant volume (v), Increase in pressure (P), Increase in entropy (S), Increase in temperature (T) | 7 | Physical Chemistry |
Cos sequences are ~200 base pairs long and essential for packaging. They contain a cosN site where DNA is nicked at each strand, 12 bp apart, by terminase. This causes linearization of the circular cosmid with two "cohesive" or "sticky ends" of 12bp. (The DNA must be linear to fit into a phage head.) The cosB site holds the terminase while it is nicking and separating the strands. The cosQ site of next cosmid (as rolling circle replication often results in linear concatemers) is held by the terminase after the previous cosmid has been packaged, to prevent degradation by cellular DNases. | 1 | Biochemistry |
Natural bond orbital analysis has been carried out on the P-Ge p(π)-p(π) system, ((Dipp)P)Ge. Inspection of the molecular orbitals reveals that the HOMO-1 consists of a π orbital, resulting from donation from the planar P lone pair into the empty P orbital of the germylene center. Natural bond orbital analysis reveals that this bond is 77% P-based and 0.3 eV higher in energy than the P-Ge σ bond. In contrast, the lone pair of the pyramidal phosphorus center is essentially sp hybridized and directed away from the germanium center. The germanium lone pair is predominantly s-character. Wiberg bond indices for Ge-P1 and Ge-P2 bonds are 1.33 and 0.89, respectively, which is consistent with a double bond between Ge-P1 and a single bond between Ge-P2. | 0 | Organic Chemistry |
Bioaerosol transport and distribution is not consistent around the globe. While bioaerosols may travel thousands of kilometers before deposition, their ultimate distance of travel and direction is dependent on meteorological, physical, and chemical factors. The branch of biology that studies the dispersal of these particles is called Aerobiology. One study generated an airborne bacteria/fungi map of the United States from observational measurements, resulting community profiles of these bioaerosols were connected to soil pH, mean annual precipitation, net primary productivity, and mean annual temperature, among other factors. | 7 | Physical Chemistry |
Resnati was born in Monza, Italy. He obtained his PhD in Industrial Chemistry at the University of Milan in 1988 with Prof. Carlo Scolastico and a thesis on asymmetric synthesis via chiral sulfoxides. After a period of activity at the Italian National Research Council, in 2001 he became professor of chemistry for materials at the Politecnico di Milano. | 0 | Organic Chemistry |
* Khwarizmi International Award,
* Distinguished National Professor, 1997,
* The first-class Research Medal, University of Tehran, 2003,
* National Eminent Character 2003,
* First-rank basic science research medal in Annual Razi Medical Sciences Research Festival 2005,
*Iranian Science and Culture Hall of Fame, 2005
* Top Researcher Elsevier-Scopus International Award in the field of Biochemistry, Genetics & Molecular Biology, 2007,
* First Rank Avicenna Festival Award as Top Researcher 2008,
* Member of Academy of Sciences of Iran, 2009,
* National eminent researcher first- rank award conferred in National Research Festival by Ministry of Science, Research and Technology of Iran, 2009,
*Chosen as Eminent Professor of University of Tehran 2010,
* distinguished Professor appointed by Iran's National Elites Foundation 2012,
* Essential Science Indicators (ESI) 1% citation scientist in the field of Biology and Biochemistry since 2013,
* TWAS (The World Academy of Sciences) Fellow 2015,
* IAS (The Islamic Academy of Sciences) Fellow 2016
* COMSTECH Award for Lifetime Achievement Award in Chemistry 2021 | 7 | Physical Chemistry |
* Isolation of ephedrine from Ephedra vulgaris in 1885. Nagai recognized it to be the active component of the plant.
* Synthesis of methamphetamine from ephedrine in 1893. Methamphetamine was later synthesized in crystalline form in 1919 by Akira Ogata.
* Isolation of rotenone from Derris elliptica in 1902. Nagayoshi named the substance after the Japanese name for the plant, roten.
* Synthesis and structural elucidation of ephedrine in 1929. | 0 | Organic Chemistry |
Photoinduced electron transfer (PET) is an excited state electron transfer process by which an excited electron is transferred from donor to acceptor. Due to PET a charge separation is generated, i.e., redox reaction takes place in excited state (this phenomenon is not observed in Dexter electron transfer). | 5 | Photochemistry |
Before the 1860s and 1870s—when Pasteur published his work on this theory—it was believed that microorganisms and even some small animals such as frogs would spontaneously generate. Spontaneous generation was historically explained in a variety of ways. Aristotle, an ancient Greek philosopher, theorized that creatures appeared out of certain concoctions of earthly elements, such as clay or mud mixing with water and sunlight. Later on, Felix Pouchet argued for the existence of plastic forces within plant and animal debris capable of spontaneously generating eggs, and new organisms were born from these eggs. On top of this, a common piece of evidence that seemed to corroborate the theory was the appearance of maggots on raw meat after it was left exposed to open air.
In the 1860s and 1870s, Pasteurs interest in spontaneous generation led him to criticize Pouchets theories and conduct experiments of his own. In his first experiment, he took boiled sugared yeast-water and sealed it in an airtight contraption. Feeding hot, sterile air into the mixture left it unaltered, while introducing atmospheric dust resulted in microbes and mold appearing within the mixture. This result was also strengthened by the fact that Pasteur used asbestos, a form of totally inorganic matter, to carry the atmospheric dust. In a second experiment, Pasteur used the same flasks and sugar-yeast mixture, but left it idle in swan-neck flasks instead of introducing any extraneous matter. Some flasks were kept open to the common air as the control group, and these exhibited mold and microbial growths within a day or two. When the swan-neck flasks failed to show these same microbial growths, Pasteur concluded that the structure of the necks blocked the passage of atmospheric dust into the solution. From the two experiments, Pasteur concluded that the atmospheric dust carried germs responsible for the spontaneous generation in his broths. Thus, Pasteur's work provided proof that the emergent growth of bacteria in nutrient broths is caused by biogenesis rather than some form of spontaneous generation. | 1 | Biochemistry |
Its presence was identified by Nakabayashi and co-workers where the hybrid layer consists of demineralized intertubular dentin and infiltrated and polymerized adhesive resin.
The hybrid layer is hydrophobic, acid resistant and tough. The quality of hybrid layer formed decides the strength of resin dentin interface. When the hybrid layer becomes thicker and more uniform, the bond strength is better. | 7 | Physical Chemistry |
Pseudoproteases are catalytically-deficient pseudoenzyme variants of proteases that are represented across the kingdoms of life. | 1 | Biochemistry |
Recombinant antibodies (rAbs) are produced in vitro by the means of expression systems based on mammalian cells. Their monospecific binding to a specific epitope makes rAbs eligible not only for research purposes, but also as therapy options against certain cancer types, infections and autoimmune diseases. | 1 | Biochemistry |
Live vaccines, such as oral polio vaccine, can be stabilized by deuterium, either alone or in combination with other stabilizers such as MgCl. | 9 | Geochemistry |
Chemical bleaching is achieved by oxidation or reduction. Oxidation can destroy the dye completely, e.g. through the use of sodium hypochlorite (NaClO, common bleach) or hydrogen peroxide. Reduction of methyl violet occurs in microorganisms but can be attained chemically using sodium dithionite. | 3 | Analytical Chemistry |
In materials science, the Burgers vector, named after Dutch physicist Jan Burgers, is a vector, often denoted as , that represents the magnitude and direction of the lattice distortion resulting from a dislocation in a crystal lattice. | 3 | Analytical Chemistry |
Reciprocal space (also called -space) provides a way to visualize the results of the Fourier transform of a spatial function. It is similar in role to the frequency domain arising from the Fourier transform of a time dependent function; reciprocal space is a space over which the Fourier transform of a spatial function is represented at spatial frequencies or wavevectors of plane waves of the Fourier transform. The domain of the spatial function itself is often referred to as real space. In physical applications, such as crystallography, both real and reciprocal space will often each be two or three dimensional. Whereas the number of spatial dimensions of these two associated spaces will be the same, the spaces will differ in their quantity dimension, so that when the real space has the dimension length (L), its reciprocal space will of inverse length, so L (the reciprocal of length).
Reciprocal space comes into play regarding waves, both classical and quantum mechanical. Because a sinusoidal plane wave with unit amplitude can be written as an oscillatory term , with initial phase , angular wavenumber and angular frequency , it can be regarded as a function of both and (and the time-varying part as a function of both and ). This complementary role of and leads to their visualization within complementary spaces (the real space and the reciprocal space). The spatial periodicity of this wave is defined by its wavelength , where ; hence the corresponding wavenumber in reciprocal space will be .
In three dimensions, the corresponding plane wave term becomes , which simplifies to at a fixed time , where is the position vector of a point in real space and now is the wavevector in the three dimensional reciprocal space. (The magnitude of a wavevector is called wavenumber.) The constant is the phase of the wavefront (a plane of a constant phase) through the origin at time , and is a unit vector perpendicular to this wavefront. The wavefronts with phases , where represents any integer, comprise a set of parallel planes, equally spaced by the wavelength . | 3 | Analytical Chemistry |
The active vitamin D metabolite calcitriol mediates its biological effects by binding to the vitamin D receptor (VDR), which is principally located in the nuclei of target cells. The binding of calcitriol to the VDR allows the VDR to act as a transcription factor that modulates the gene expression of transport proteins (such as TRPV6 and calbindin), which are involved in calcium absorption in the intestine. The vitamin D receptor belongs to the nuclear receptor superfamily of steroid/thyroid hormone receptors, and VDRs are expressed by cells in most organs, including the brain, heart, skin, gonads, prostate and breast.
VDR activation in the intestine, bone, kidney, and parathyroid gland cells leads to the maintenance of calcium and phosphorus levels in the blood (with the assistance of parathyroid hormone and calcitonin) and to the maintenance of bone content.
One of the most important roles of vitamin D is to maintain skeletal calcium balance by promoting calcium absorption in the intestines, promoting bone resorption by increasing osteoclast number, maintaining calcium and phosphate levels for bone formation, and allowing proper functioning of parathyroid hormone to maintain serum calcium levels. Vitamin D deficiency can result in lower bone mineral density and an increased risk of reduced bone density (osteoporosis) or bone fracture because a lack of vitamin D alters mineral metabolism in the body. Thus, vitamin D is also critical for bone remodeling through its role as a potent stimulator of bone resorption.
The VDR regulates cell proliferation and differentiation. Vitamin D also affects the immune system, and VDRs are expressed in several white blood cells, including monocytes and activated T and B cells. In vitro, vitamin D increases expression of the tyrosine hydroxylase gene in adrenal medullary cells, and affects the synthesis of neurotrophic factors, nitric oxide synthase, and glutathione.
Vitamin D receptor expression decreases with age. | 1 | Biochemistry |
Quantitative measures of exposure are used: in risk assessment, together with inputs from toxicology, to determine risk from substances released to the environment, to establish protective standards, in epidemiology, to distinguish between exposed and control groups, and to protect workers from occupational hazards. | 2 | Environmental Chemistry |
It is a precursor to trifluoromethyltrimethylsilane, a popular trifluoromethylating reagent in organic synthesis. | 2 | Environmental Chemistry |
Saliva moistens and softens food, and along with the chewing action of the teeth, transforms the food into a smooth bolus. The bolus is further helped by the lubrication provided by the saliva in its passage from the mouth into the esophagus. Also of importance is the presence in saliva of the digestive enzymes amylase and lipase. Amylase starts to work on the starch in carbohydrates, breaking it down into the simple sugars of maltose and dextrose that can be further broken down in the small intestine. Saliva in the mouth can account for 30% of this initial starch digestion. Lipase starts to work on breaking down fats. Lipase is further produced in the pancreas where it is released to continue this digestion of fats. The presence of salivary lipase is of prime importance in young babies whose pancreatic lipase has yet to be developed.
As well as its role in supplying digestive enzymes, saliva has a cleansing action for the teeth and mouth. It also has an immunological role in supplying antibodies to the system, such as immunoglobulin A. This is seen to be key in preventing infections of the salivary glands, importantly that of parotitis.
Saliva also contains a glycoprotein called haptocorrin which is a binding protein to vitamin B. It binds with the vitamin in order to carry it safely through the acidic content of the stomach. When it reaches the duodenum, pancreatic enzymes break down the glycoprotein and free the vitamin which then binds with intrinsic factor. | 1 | Biochemistry |
Thermal radiation is one of the three principal mechanisms of heat transfer. It entails the emission of a spectrum of electromagnetic radiation due to an object's temperature. Other mechanisms are convection and conduction. | 7 | Physical Chemistry |
Since the time history of CFC concentrations in the atmosphere is relatively well known, they have provided an important constraint on ocean circulation. CFCs dissolve in seawater at the ocean surface and are subsequently transported into the ocean interior. Because CFCs are inert, their concentration in the ocean interior reflects simply the convolution of their atmospheric time evolution and ocean circulation and mixing. | 2 | Environmental Chemistry |
All bioluminescent bacteria share a common gene sequence: the lux operon characterized by the luxCDABE gene organization. LuxAB codes for luciferase while luxCDE codes for a fatty-acid reductase complex that is responsible for synthesizing aldehydes for the bioluminescent reaction. Despite this common gene organization, variations, such as the presence of other lux genes, can be observed among species. Based on similarities in gene content and organization, the lux operon can be organized into the following four distinct types: the Aliivibrio/Shewanella type, the Photobacterium type, theVibrio/Candidatus Photodesmus type, and the Photorhabdus type. While this organization follows the genera classification level for members of Vibrionaceae (Aliivibrio, Photobacterium, and Vibrio), its evolutionary history is not known.
With the exception of the Photorhabdus operon type, all variants of the lux operon contain the flavin reductase-encoding luxG gene. Most of the Aliivibrio/Shewanella type operons contain additional luxI/luxR regulatory genes that are used for autoinduction during quorum sensing. The Photobacterum operon type is characterized by the presence of rib genes that code for riboflavin, and forms the lux-rib operon. TheVibrio/Candidatus Photodesmus operon type differs from both the Aliivibrio/Shewanella and the Photobacterium operon types in that the operon has no regulatory genes directly associated with it. | 1 | Biochemistry |
In mammals, progesterone, like all other steroid hormones, is synthesized from pregnenolone, which itself is derived from cholesterol.
Cholesterol undergoes double oxidation to produce 22R-hydroxycholesterol and then 20α,22R-dihydroxycholesterol. This vicinal diol is then further oxidized with loss of the side chain starting at position C22 to produce pregnenolone. This reaction is catalyzed by cytochrome P450scc.
The conversion of pregnenolone to progesterone takes place in two steps. First, the 3β-hydroxyl group is oxidized to a keto group and second, the double bond is moved to C4, from C5 through a keto/enol tautomerization reaction. This reaction is catalyzed by 3β-hydroxysteroid dehydrogenase/δ-isomerase.
Progesterone in turn is the precursor of the mineralocorticoid aldosterone, and after conversion to 17α-hydroxyprogesterone, of cortisol and androstenedione. Androstenedione can be converted to testosterone, estrone, and estradiol, highlighting the critical role of progesterone in testosterone synthesis.
Pregnenolone and progesterone can also be synthesized by yeast.
Approximately 25 mg of progesterone is secreted from the ovaries per day in women, while the adrenal glands produce about 2 mg of progesterone per day. | 0 | Organic Chemistry |
The reagent Selectfluor is derived by alkylation of DABCO with dichloromethane following by treatment with fluorine. A colourless salt that tolerates air, Selectfluor has been commercialized for use for electrophilic fluorination.
As an unhindered amine, it is a strong ligand and Lewis base. It forms a crystalline 2:1 adduct with hydrogen peroxide and sulfur dioxide. | 0 | Organic Chemistry |
Leprecan, a proteoglycan, has demonstrated prolyl hydroxylase activity; prolyl hydroxylases hydroxylate proline residues. Prolyl 3-hydroxylase 1, P3H1, forms a larger complex with CRTAP and cyclophilin B, CyPB, in the endoplasimic reticulum. The complex hydroxylates a single proline residue, Pro986, on collagen chains. Recessive forms of Osteogenesis Imperfecta are partly caused by a mutation in the LEPRE1 gene. The mutation in the gene encodes prolyl 3-hydroxylase 1. The malfunctioning prolyl 3-hydroxylase in leprecan leads to inappropriate collagen folding. This is due to the instability caused by the absence of hydroxyproline. Hydroxyproline is the product of hydroxylating a proline residue. | 1 | Biochemistry |
The rate of reaction for the ionization reaction
:2 HO → HO + OH
depends on the activation energy, ΔE. According to the Boltzmann distribution the proportion of water molecules that have sufficient energy, due to thermal population, is given by
where k is the Boltzmann constant. Thus some dissociation can occur because sufficient thermal energy is available. The following sequence of events has been proposed on the basis of electric field fluctuations in liquid water. Random fluctuations in molecular motions occasionally (about once every 10 hours per water molecule) produce an electric field strong enough to break an oxygen–hydrogen bond, resulting in a hydroxide (OH) and hydronium ion (HO); the hydrogen nucleus of the hydronium ion travels along water molecules by the Grotthuss mechanism and a change in the hydrogen bond network in the solvent isolates the two ions, which are stabilized by solvation. Within 1 picosecond, however, a second reorganization of the hydrogen bond network allows rapid proton transfer down the electric potential difference and subsequent recombination of the ions. This timescale is consistent with the time it takes for hydrogen bonds to reorientate themselves in water.
The inverse recombination reaction
:HO + OH → 2 HO
is among the fastest chemical reactions known, with a reaction rate constant of at room temperature. Such a rapid rate is characteristic of a diffusion-controlled reaction, in which the rate is limited by the speed of molecular diffusion. | 7 | Physical Chemistry |
After Iraqi chemical attacks against Iranian soldiers and civilians, from 1983 to 1988, the number of people sustained injuries, including respiratory (42%), ocular (39%) and skin complications (25%) was more than 3,400 – a number which increased to at least 45,000 twenty years later, "due to the occurrence of late respiratory complications of mustard gas exposure." "The latency period can be as much as 40 years" and "So almost every day there are new cases — 30 years after the war," said Shahriar Khateri, the co-founder of the Society for Chemical Weapons Victims Support. According to Farhad Hashemnezhad in 2002, at least 20 percent of the patients were "civilians who didnt think they were close enough to be exposed." This large number of chemically affected veterans has made Iran the worlds largest laboratory for the study of the effects of chemical weapons. According to a declassified CIA report, as a result of Iraqs repeated use of nerve agents and toxic gases in the 1980s, Iran suffered more than 50,000 casualties mostly by mustard gas used in dusty, liquid and vapor forms packed into bombs and artillery shells which were then fired at the front lines and beyond, at targets such as hospitals. The number of registered chemically affected veterans was 70,000 by 2014, according to Shahriar Khateri, Irans leading expert on chemical weapons victims. "awareness could have saved lives," Khateri said. Doctors estimate that the final toll of Iraq's chemical weapons could be as high as 90,000, equal to the total deaths from all toxic gases in World War I.
During the Iran–Iraq War, mustard gas was used by Iraq against Iran, and it was the "first time ever that nerve agents such as sarin and tabun were employed." Experiencing the outcomes of the chemical weapons, chemical warfare veterans believe that the younger generations should be instructed that "war is not a computer game." "We want to show how painful the consequences are. We dont want revenge. We just want to show what happens so it wont happen again," said Saadi, injured by Iraqi mustard gas. | 1 | Biochemistry |
In rolling element bearings fretting may occur when the bearings are operating in an oscillating motion. Examples of applications are blade bearings in wind turbines, helicopter rotor pitch bearings, and bearings in robots. If the bearing movement is limited to small motions the damage caused may be called fretting or false brinelling depending on mechanism encountered. The main difference is that false brinelling occurs under lubricated and fretting under dry contact conditions. Between false brinelling and fretting corrosion, a time-dependent relation has been proposed. | 8 | Metallurgy |
Gestation can predispose for certain digestive disorders. Gestational diabetes can develop in the mother as a result of pregnancy and while this often presents with few symptoms it can lead to pre-eclampsia. | 1 | Biochemistry |
The genus Ancyronyx was established in 1847 by the German entomologist Wilhelm Ferdinand Erichson based on the type species Macronychus variegatus first described in 1824 by the German coleopterologist Ernst Friedrich Germar. It was regarded as a monotypic species until the French entomologist Antoine Henri Grouvelle described the second species, A. acaroides in 1896. It is the sole member of the tribe Ancyronychini, and is classified under the subfamily Elminae of the riffle beetle family, Elmidae. | 2 | Environmental Chemistry |
These responses require at least 1μmol/m to be initiated and become saturated at about 1000μmol/m. Unlike VLFRs, these responses are photoreversible. This was shown by exposing lettuce seed to a brief flash of red light causing germination. It was then shown if this red flash was followed by a flash of far red light, germination was again inhibited. LFRs also follow the law of reciprocity. Other examples of LFRs include leaf de-etiolation and enhancement of rate of chlorophyll production. | 5 | Photochemistry |
Off-axis parabolic mirrors are commonly used to collimate and focus THz radiation. Radiation from an effective point source, such as from a low-temperature gallium arsenide (LT-GaAs) antenna (active region ~5 μm) incident on an off-axis parabolic mirror becomes collimated, while collimated radiation incident on a parabolic mirror is focused to a point (see diagram). Terahertz radiation can thus be manipulated spatially using optical components such as metal-coated mirrors as well as lenses made from materials that are transparent at THz wavelengths. Samples for spectroscopy are commonly placed at a focus where the terahertz beam is most concentrated. | 7 | Physical Chemistry |
Antibody diversity is produced by genetic rearrangement after shuffling and rejoining one of each of the various gene segments for the heavy and light chains. Due to mixing and random recombination of the gene segments errors can occur at the sites where gene segments join with each other. These errors are one of the sources of the antibody diversity that is commonly observed in both the light and heavy chains. Moreover, when B cells continue to proliferate, mutations accumulate at the variable regions through a process called somatic hypermutation. The high concentrations of these mutations at the variable region also produce high antibody diversity. | 1 | Biochemistry |
Alastair Ian Scott (10 April 1928 in Glasgow – 18 April 2007) was a British-American organic chemist who achieved international renown for elucidating the biosynthetic pathway of vitamin B12.
He occupied successive chairs of organic chemistry at the universities of British Columbia, Sussex, and Yale before moving to Texas A&M University in 1977. In 1980 he occupied the [http://ourhistory.is.ed.ac.uk/index.php/Chemistry#Forbes_Chair_of_Organic_Chemistry Forbes chair of organic Chemistry] at the University of Edinburgh. He was named a distinguished professor of chemistry and biochemistry in 1981 at Texas A&M University, and remained there until the end of his career.
In 1964 he won the Corday-Morgan Medal of the Royal Society of Chemistry (RSC). He was awarded the 1975 Ernest Guenther Award and the 1994 Arthur C. Cope Scholar Award by the American Chemical Society (ACS). He gave the RSC Centenary Lecture in 1994 and the Royal Society Bakerian Lecture in 1996. He took the Tetrahedron Prize (1995), the RSC Natural Products Award (1996), the Welch Award in Chemistry (2000), the Royal Societys Davy Medal (2001), the Queens Royal Medal of the Royal Society of Edinburgh (2001), and the ACS Nakanishi Prize (2003). He was Texas Scientist of the Year in 2002.
He was a Fellow of the Royal Society and the Royal Society of Edinburgh, the American Association for the Advancement of Science and the European Academy of Sciences. In addition, he was an honorary member of the Japanese Pharmacological Society. | 0 | Organic Chemistry |
Equilibrium fractionation occurs between chemicals or phases that are in equilibrium with each other. In equilibrium fractionation between phases, heavier phases prefer the heavier isotopes. For two phases A and B, the effect can be represented by the factor
In the liquid-vapor phase transition for water, at 20 degrees Celsius is 1.0098 for O and 1.084 for H. In general, fractionation is greater at lower temperatures. At 0 °C, the factors are 1.0117 and 1.111. | 9 | Geochemistry |
CDs and DVDs have a polycarbonate surface and metal reflective layer which allow for storage and retrieval of information. The metal film is sometimes made of pure gold which is highly stable and has ideal optical properties. The metal can act as a substrate which allows compounds to bind to it. This alters the reflective and refractive properties of the disk. Disk reading is based on capturing analog signals with the disk drive. The signals are indicative of how much analyte is in a sample.
Because the disk spins, the platform has the ability to drive the sample through it through microfluidic channels and for multiple steps to be performed, allowing the possibility for sample preparation and more than one analysis to be conducted during a single run.
CD/DVD based assays could potentially be used for any immunoassay already in use and many assays used in analytical chemistry, as long as analytes have a corresponding probe, are soluble, and are large enough to alter the angle of incident. | 1 | Biochemistry |
Berberine bridge enzyme (BBE) is a central enzyme in the biosynthesis of berberine, a pharmaceutically important alkaloid. The enzyme itself hasn't had extensive research carried on, and has very limited, if any, specific medical application. On the other hand, berberine is highly regarded for its interactions with several diseases. Berberine has been known to influence weight loss, and this antiobesity effect may benefit all conditions related to increased body mass such as hypertension, dyslipidemia or pre-diabetes. This may reduce the likelihood of getting sedentary diseases such as heart failure or other problems related to this issue. By being an AMPK activator like Metformin, it acts similar, affecting metabolism in a way that may reveal useful applications to treat type-2 diabetes.
Overall, this alkaloid might be useful in the treatment and study of diseases like polycystic ovary syndrome (PCOS), some types of cancer, heart problems or dyslipidemia. | 1 | Biochemistry |
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