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For narrow ridges with large period , the ridges just blocks the part of the wavefront. Then, it can be interpreted in terms of the Fresnel diffraction of the de Broglie wave, or the Zeno effect; such interpretation leads to the estimate the reflectivity
is wavenumber, is period (distance between ridges) and
where the grazing angle is supposed to be small. This estimate predicts enhancement of the reflectivity at the reduction of period . This estimate requires that . | 0 | Theoretical and Fundamental Chemistry |
A liquid metal is a metal or a metal alloy which is liquid at or near room temperature.
The only stable liquid elemental metal at room temperature is mercury (Hg), which is molten above −38.8 °C (234.3 K, −37.9 °F). Three more stable elemental metals melt just above room temperature: caesium (Cs), which has a melting point of 28.5 °C (83.3 °F); gallium (Ga) (30 °C [86 °F]); and rubidium (Rb) (39 °C [102 °F]). The radioactive metal francium (Fr) is probably liquid close to room temperature as well. Calculations predict that the radioactive metals copernicium (Cn) and flerovium (Fl) should also be liquid at room temperature.
Alloys can be liquid if they form a eutectic, meaning that the alloys melting point is lower than any of the alloys constituent metals. The standard metal for creating liquid alloys used to be mercury, but gallium-based alloys, which are lower both in their vapor pressure at room temperature and toxicity, are being used as a replacement in various applications. | 1 | Applied and Interdisciplinary Chemistry |
Hash rosin has recently become a top quality, highly prized product in the cannabis market. For dabbing, it is considered to be the cleanest form of concentrating cannabis, as it requires only ice, water (instead of organic solvents like butane), heat, pressure, and collection tools. Cannabis flower material is washed with ice water, and strained using filters in sequential micron size to isolate intact trichomes and their heads into ice water hash. The microns that are held in highest regards are the 73u and 90u, as this is where the resin heads reside. These are sometimes isolated and sold as one of the highest quality, most expensive cannabis products in the market today, known as "full melt" because it will dab fine without having to be pressed. "Full spectrum" hash rosin will normally come from 45u-159u, as smaller and larger particles are likely to be too unrefined or broken stalks of the trichomes.
This hash is then pressed at the appropriate temperature and pressure to squeeze the oils out of the hash, and is collected with metal tools and parchment paper. Just like hydrocarbon extraction, the quality of the final product depends greatly on the quality of the starting material. This is emphasized even more so with hash rosin due to its lower yield percentages compared to solvent-derived concentrates (.3-8% rosin vs 10-20% hydrocarbon). Hash rosin producers often touch on how growing cannabis for hash production is different than growing for flower production, as some strains will be deceptive with their looks regarding yields. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, one usually ignores distinctions between isotopes of the same element. However, in some situations (for instance in Raman, NMR, or microwave spectroscopy) one may treat different isotopes of the same element as different elements. In the second case, two molecules with the same number of atoms of each isotope but distinct bonding schemes are said to be structural isotopomers.
Thus, for example, ethene would have no structural isomers under the first interpretation; but replacing two of the hydrogen atoms (H) by deuterium atoms (H) may yield any of two structural isotopomers (1,1-dideuteroethene and 1,2-dideuteroethene), if both carbon atoms are the same isotope. If, in addition, the two carbons are different isotopes (say, C and C), there would be three distinct structural isotopomers, since 1-C-1,1-dideuteroethene would be different from 1-C-2,2-dideuteroethene.) And, in both cases, the 1,2-dideutero structural isotopomer would occur as two stereo isotopomers, cis and trans. | 0 | Theoretical and Fundamental Chemistry |
Here are some different [https://collegedunia.com/exams/photochemical-reactions-science-articleid-653 types of photochemical reactions]-
* Photo-dissociation: AB + hν → A* + B*
* Photo induced rearrangements, isomerization: A + hν → B
* Photo-addition: A + B + hν → AB + C
* Photo-substitution: A + BC + hν → AB + C
* Photo-redox reaction: A + B + hν → A− + B+ | 0 | Theoretical and Fundamental Chemistry |
Glycoprotein hormones may be removed by the liver from the bloodstream when the passage of time causes the breaking-off of carbohydrates from the glycoproteins. | 0 | Theoretical and Fundamental Chemistry |
* Preplant: Preplant herbicides are nonselective herbicides applied to the soil before planting. Some preplant herbicides may be mechanically incorporated into the soil. The objective for incorporation is to prevent dissipation through photodecomposition and/or volatility. The herbicides kill weeds as they grow through the herbicide-treated zone. Volatile herbicides have to be incorporated into the soil before planting the pasture. Crops grown in soil treated with a preplant herbicide include tomatoes, corn, soybeans, and strawberries. Soil fumigants like metam-sodium and dazomet are in use as preplant herbicides.
* Preemergence: Preemergence herbicides are applied before the weed seedlings emerge through the soil surface. Herbicides do not prevent weeds from germinating but they kill weeds as they grow through the herbicide-treated zone by affecting the cell division in the emerging seedling. Dithiopyr and pendimethalin are preemergence herbicides. Weeds that have already emerged before application or activation are not affected by pre-herbicides as their primary growing point escapes the treatment.
* Postemergence: These herbicides are applied after weed seedlings have emerged through the soil surface. They can be foliar or root absorbed, selective or nonselective, and contact or systemic. Application of these herbicides is avoided during rain since being washed off the soil makes it ineffective. 2,4-D is a selective, systemic, foliar-absorbed postemergence herbicide. | 1 | Applied and Interdisciplinary Chemistry |
Transition state analogs (transition state analogues), are chemical compounds with a chemical structure that resembles the transition state of a substrate molecule in an enzyme-catalyzed chemical reaction. Enzymes interact with a substrate by means of strain or distortions, moving the substrate towards the transition state. Transition state analogs can be used as inhibitors in enzyme-catalyzed reactions by blocking the active site of the enzyme. Theory suggests that enzyme inhibitors which resembled the transition state structure would bind more tightly to the enzyme than the actual substrate. Examples of drugs that are transition state analog inhibitors include flu medications such as the neuraminidase inhibitor oseltamivir and the HIV protease inhibitors saquinavir in the treatment of AIDS. | 1 | Applied and Interdisciplinary Chemistry |
Currently there are a very limited number of commercially available carbon based adsorption- electrochemical regeneration systems. One system that does exist uses a carbon adsorbent called Nyex in a continuous adsorption-regeneration system that uses electrochemical regeneration to adsorb and destroy organic pollutants. | 0 | Theoretical and Fundamental Chemistry |
Chain reactions naturally give rise to reaction rates that grow (or shrink) exponentially, whereas a nuclear power reactor needs to be able to hold the reaction rate reasonably constant. To maintain this control, the chain reaction criticality must have a slow enough time scale to permit intervention by additional effects (e.g., mechanical control rods or thermal expansion). Consequently, all nuclear power reactors (even fast-neutron reactors) rely on delayed neutrons for their criticality. An operating nuclear power reactor fluctuates between being slightly subcritical and slightly delayed-supercritical, but must always remain below prompt-critical.
It is impossible for a nuclear power plant to undergo a nuclear chain reaction that results in an explosion of power comparable with a nuclear weapon, but even low-powered explosions due to uncontrolled chain reactions (that would be considered "fizzles" in a bomb) may still cause considerable damage and meltdown in a reactor. For example, the Chernobyl disaster involved a runaway chain reaction but the result was a low-powered steam explosion from the relatively small release of heat, as compared with a bomb. However, the reactor complex was destroyed by the heat, as well as by ordinary burning of the graphite exposed to air. Such steam explosions would be typical of the very diffuse assembly of materials in a nuclear reactor, even under the worst conditions.
In addition, other steps can be taken for safety. For example, power plants licensed in the United States require a negative void coefficient of reactivity (this means that if coolant is removed from the reactor core, the nuclear reaction will tend to shut down, not increase). This eliminates the possibility of the type of accident that occurred at Chernobyl (which was due to a positive void coefficient). However, nuclear reactors are still capable of causing smaller chemical explosions even after complete shutdown, such as was the case of the Fukushima Daiichi nuclear disaster. In such cases, residual decay heat from the core may cause high temperatures if there is loss of coolant flow, even a day after the chain reaction has been shut down (see SCRAM). This may cause a chemical reaction between water and fuel that produces hydrogen gas, which can explode after mixing with air, with severe contamination consequences, since fuel rod material may still be exposed to the atmosphere from this process. However, such explosions do not happen during a chain reaction, but rather as a result of energy from radioactive beta decay, after the fission chain reaction has been stopped. | 0 | Theoretical and Fundamental Chemistry |
The flow is completely unidirectional for low Dean numbers (De < 40~60). As the Dean number increases between 40~60 to 64~75, some wavy perturbations can be observed in the cross-section, which evidences some secondary flow. At higher Dean numbers than that (De > 64~75) the pair of Dean vortices becomes stable, indicating a primary dynamic instability. A secondary instability appears for De > 75~200, where the vortices present undulations, twisting, and eventually merging and pair splitting. Fully turbulent flow forms for De > 400. Transition from laminar to turbulent flow has also been examined in a number of studies, even though no universal solution exists since the parameter is highly dependent on the curvature ratio. Somewhat unexpectedly, laminar flow can be maintained for larger Reynolds numbers (even by a factor of two for the highest curvature ratios studied) than for straight pipes, even though curvature is known to cause instability. | 1 | Applied and Interdisciplinary Chemistry |
Between 1962 and 1983, the Iskra Kondenzatorji company in Semič (White Carniola, Southeast Slovenia) manufactured capacitors using PCBs. Due to the wastewater and improperly disposed waste products, the area (including the Krupa and Lahinja rivers) became highly contaminated with PCBs. The pollution was discovered in 1983, when the Krupa river was meant to become a water supply source. The area was sanitized then, but the soil and water are still highly polluted. Traces of PCBs were found in food (eggs, cow milk, walnuts) and Krupa is still the most PCB-polluted river in the world. | 1 | Applied and Interdisciplinary Chemistry |
Whiting event clouds consist of calcium carbonate polymorphs; aragonite tends to be the dominant precipitate, but some studies in oligotrophic and mesotrophic lakes show calcite is favored. Whiting events have been observed in tropical and temperate waters, and they can potentially cover hundreds of meters. They tend to occur more often in summer months, as warmer waters promote calcium carbonate precipitation, and in hard waters. Whitings are typically characterized by cloudy, white patches of water, but they can also be tanner in hue in very shallow waters (less than 5m deep). In some cases, the whiting might be cryptic (not visible at the surface), but still generate calcium carbonate. These shallow water whiting events also tend to last less than a day in comparison to deeper water events that can last for several days up to several months. Regardless of the event's lifespan, the clouds it produces increase turbidity and hamper light penetration. | 0 | Theoretical and Fundamental Chemistry |
In genomics, DNA–DNA hybridization is a molecular biology technique that measures the degree of genetic similarity between DNA sequences. It is used to determine the genetic distance between two organisms and has been used extensively in phylogeny and taxonomy. | 1 | Applied and Interdisciplinary Chemistry |
Light-activated resins have found a place in floor refinishing applications, offering an instant return to service not available with any other chemical due to the need to cure at ambient temperatures. Because of application constraints, these coatings are exclusively UV cured with portable equipment containing high intensity discharge lamps. Such UV coatings are now commercially available for a variety of substrates, such as wood, vinyl composition tile and concrete, replacing traditional polyurethanes for wood refinishing and low durability acrylics for VCT. | 0 | Theoretical and Fundamental Chemistry |
The Standard Model of physics, in particular the work of Murray Gell-Mann in the 1960s, had been successful in uniting much of the previously disparate concepts in particle physics into one, relatively straightforward, scheme. In essence, there were three types of particles:
* The leptons, which were low-mass particles such as electrons, neutrinos and their antiparticles. They have integer electric charge.
* The gauge bosons, which were particles that exchange forces. These ranged from the massless, easy-to-detect photon (the carrier of the electro-magnetic force) to the exotic (though still massless) gluons that carry the strong nuclear force.
*The quarks, which were massive particles that carried fractional electric charges. They are the "building blocks" of the hadrons. They are also the only particles to be affected by the strong interaction.
The leptons had been detected since 1897, when J. J. Thomson had shown that electric current is a flow of electrons. Some bosons were being routinely detected, although the W, W and Z particles of the electroweak force were only categorically seen in the early 1980s, and gluons were only firmly pinned down at DESY in Hamburg at about the same time. Quarks, however, were still elusive.
Drawing on Rutherford's groundbreaking experiments in the early years of the 20th century, ideas for detecting quarks were formulated. Rutherford had proven that atoms had a small, massive, charged nucleus at their centre by firing alpha particles at atoms of gold. Most had gone through with little or no deviation, but a few were deflected through large angles or came right back. This suggested that atoms had internal structure and a lot of empty space.
In order to probe the interiors of baryons, a small, penetrating and easily produced particle needed to be used. Electrons were ideal for the role, as they are abundant and easily accelerated to high energies due to their electric charge. In 1968, at the Stanford Linear Accelerator Center (SLAC), electrons were fired at protons and neutrons in atomic nuclei. Later experiments were conducted with muons and neutrinos, but the same principles apply.
The collision absorbs some kinetic energy, and as such it is inelastic. This is a contrast to Rutherford scattering, which is elastic: no loss of kinetic energy. The electron emerges from the nucleus, and its trajectory and velocity can be detected. Analysis of the results led to the conclusion that hadrons do indeed have internal structure. The experiments were important because not only did they confirm the physical reality of quarks, but also proved again that the Standard Model was the correct avenue of research for particle physicists to pursue. | 0 | Theoretical and Fundamental Chemistry |
In April 2005, a UCLA team headed by chemistry professor James K. Gimzewski and physics professor Seth Putterman utilized a tungsten probe attached to a pyroelectric crystal to increase the electric field strength. Brian Naranjo, a graduate student working under Putterman, conducted the experiment demonstrating the use of a pyroelectric power source for producing fusion on a laboratory bench top device. The device used a lithium tantalate () pyroelectric crystal to ionize deuterium atoms and to accelerate the deuterons towards a stationary erbium dideuteride (ErD) target. Around 1000 fusion reactions per second took place, each resulting in the production of an 820 keV helium-3 nucleus and a 2.45 MeV neutron. The team anticipates applications of the device as a neutron generator or possibly in microthrusters for space propulsion.
A team at Rensselaer Polytechnic Institute, led by Yaron Danon and his graduate student Jeffrey Geuther, improved upon the UCLA experiments using a device with two pyroelectric crystals and capable of operating at non-cryogenic temperatures.
Pyroelectric fusion has been hyped in the news media, which overlooked the work of Dougar Jabon, Fedorovich and Samsonenko. Pyroelectric fusion is not related to the earlier claims of fusion reactions, having been observed during sonoluminescence (bubble fusion) experiments conducted under the direction of Rusi Taleyarkhan of Purdue University. Naranjo of the UCLA team was one of the main critics of these earlier prospective fusion claims from Taleyarkhan. | 0 | Theoretical and Fundamental Chemistry |
Vancomycin targets bacterial cell wall synthesis by binding to the basic building block of the bacterial cell wall of Gram-positive bacteria, whether it is of aerobic or anaerobic class. Specifically, vancomycin forms hydrogen bonds with the -alanyl--alanine (-Ala--Ala) peptide motif of the peptidoglycan precursor, a crucial component of the bacterial cell wall.
Peptidoglycan is a polymer that provides structural support to the bacterial cell wall. The peptidoglycan precursor is synthesized in the cytoplasm and then transported across the cytoplasmic membrane to the periplasmic space, where it is assembled into the cell wall. The assembly process involves two enzymatic activities: transglycosylation and transpeptidation. Transglycosylation involves the polymerization of the peptidoglycan precursor into long chains, while transpeptidation involves the cross-linking of these chains to form a three-dimensional mesh-like structure.
Vancomycin inhibits bacterial cell wall synthesis by binding to the -Ala--Ala peptide motif of the peptidoglycan precursor, thereby preventing its processing by the transglycosylase; as such vancomycin disrupts the transglycosylation activity of the cell wall synthesis process. The disruption leads to an incomplete and corrupted cell wall, which makes the replicating bacteria vulnerable to external forces such as osmotic pressure, so that the bacteria cannot survive and are eliminated by the immune system.
Gram-negative bacteria are insensitive to vancomycin due to their different cell wall morphology. The outer membrane of Gram-negative bacteria contains lipopolysaccharide, which acts as a barrier to vancomycin penetration. That is why vancomycin is mainly used to treat infections caused by Gram-positive bacteria (except some nongonococcal species of Neisseria).
The large hydrophilic molecule of vancomycin is able to form hydrogen bond interactions with the terminal -alanyl--alanine moieties of the NAM/NAG-peptides. Under normal circumstances, this is a five-point interaction. This binding of vancomycin to the -Ala--Ala prevents cell wall synthesis of the long polymers of N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) that form the backbone strands of the bacterial cell wall, and prevents the backbone polymers from cross-linking with each other. | 0 | Theoretical and Fundamental Chemistry |
The ndhF fragment has been a very useful tool in phylogenetic reconstruction at a number of taxonomic levels. | 0 | Theoretical and Fundamental Chemistry |
In 1802, Humphry Davy had what was then the most powerful electrical battery in the world at the Royal Institution. With it, Davy created the first incandescent light by passing electric current through a thin strip of platinum, chosen because the metal had an extremely high melting point. It was neither sufficiently bright nor long lasting enough to be of practical use, but demonstrated the principle. By 1806 he was able to demonstrate a much more powerful form of electric lighting to the Royal Society in London. It was an early form of arc light which produced its illumination from an electric arc created between two charcoal rods. | 1 | Applied and Interdisciplinary Chemistry |
Algal oil is used as a source of fatty acid supplementation in food products, as it contains mono- and polyunsaturated fats, in particular EPA and DHA. Its DHA content is roughly equivalent to that of salmon based fish oil. | 1 | Applied and Interdisciplinary Chemistry |
The retroviruses include T-cell Leukemia virus type I, HIV, and Rous Sarcoma Virus (RSV). The viral gene tax is expressed when the T-cell Leukemia virus transforms a cell altering the expression of cellular growth control genes and causing the transformed cells to become cancerous. HIV works differently by not directly causing cells to become cancerous but by instead making those infected more susceptible to lymphoma and Kaposi's sarcoma. Many other retroviruses contain the three genes, gag, pol, and env, which do not directly cause transformation or tumor formation. | 1 | Applied and Interdisciplinary Chemistry |
Water quality models have different information, but generally have the same purpose, which is to provide evidentiary support of water issues. Models can be either deterministic or statistical depending on the scale with the base model, which is dependent on if the area is on a local, regional, or a global scale. Another aspect to consider for a model is what needs to be understood or predicted about that research area along with setting up any parameters to define the research. Another aspect of building a water quality model is knowing the audience and the exact purpose for presenting data like to enhance water quality management for water quality law makers for the best possible outcomes. | 0 | Theoretical and Fundamental Chemistry |
When molten, the salt sodium chloride can be electrolyzed to yield metallic sodium and gaseous chlorine. Industrially this process takes place in a special cell named Downs cell. The cell is connected to an electrical power supply, allowing electrons to migrate from the power supply to the electrolytic cell.
Reactions that take place in a Downs cell are the following:
:Anode (oxidation): 2 Cl → Cl + 2 e
:Cathode (reduction): 2 Na + 2 e → 2 Na
:Overall reaction: 2 Na + 2 Cl → 2 Na + Cl
This process can yield large amounts of metallic sodium and gaseous chlorine, and is widely used in mineral dressing and metallurgy industries.
The emf for this process is approximately −4 V indicating a (very) non-spontaneous process. In order for this reaction to occur the power supply should provide at least a potential difference of 4 V. However, larger voltages must be used for this reaction to occur at a high rate. | 0 | Theoretical and Fundamental Chemistry |
*1973 J W Menter
*1972 M Morgan
*1971 A G Quarrell
*1970 P Coheur
*1969 Queen Elizabeth II
*1968 F D Richardson
*1967 E T Judge
*1966 John Hugh Chesters
*1965 T Sendzimir
*1965 N P Allen
*1964 H Malcor
*1963 F H Saniter
*1962 Sir Charles Goodeve
*1961 W Barr
*1960 Hermann Schenck
*1959 B M S Kalling
*1958 W F Cartwright
*1957 R Durrer
*1956 C Sykes
*1955 J Chipman
*1954 T P Colclough
*1953 R Mather
*1952 H H Burton
*1951 B F Fairless
*1950 J Mitchell
*1948 W J Dawson
*1947 K M Tigerchiold
*1947 Sir William J Larke
*1946 J S Hollings
*1945 Harold Wright
*1944 E Lewis
*1943 J H Whiteley
*1942 E G Grace
*1941 T Swinden
*1940 Sir Andrew McCance
*1939 J Henderson
*1938 C H Desch
*1937 Colonel N. T. Belaiew
*1937 A Mayer
*1936 F Clements
*1935 A M Portevin
*1934 King George V
*1933 W H Hatfield
*1932 H Louis
*1931 Sir Harold Carpenter
*1930 W Rosenhain
*1930 E Schneider
*1929 Sir Charles A Parsons
*1928 C M Schwab
*1927 Axel Wahlberg
*1926 Sir Hugh Bel
*1925 T Turner
*1924 A Sauveur
*1923 W H Maw
*1922 K Honda
*1921 C Freemont
*1920 H Brearley
*1919 Federico Giolitti
*1918 The Rt Hon Lord Invernairn of Strathnairn
*1917 A Lamberton
*1916 F W Harbord
*1915 P Martin
*1914 Edward Riley
*1913 A Greiner
*1912 J H Darby
*1911 H L Le Chatelier
*1910 E H Saniter
*1909 A Pourcel
*1908 B Talbot
*1907 J A Brinell
*1906 F Osmond
*1906 King Edward VII
*1905 J O Arnold
*1904 A Carnegie
*1904 Sir R Hadfield
*1903 The Rt Hon Lord Airedale of Gledhow
*1902 F A Krupp
*1901 J E Stead
*1900 Henri de Wendel
*1899 H M Queen Victoria
*1898 R Prince-Williams
*1897 Sir Frederick Abel
*1896 H Wedding
*1895 H M Howe
*1894 John Gjers
*1893 J Fritz
*1892 A Cooper
*1891 The Rt Hon Lord Armstrong
*1890 W D Allen
*1890 Hon A S Hewitt
*1889 J D Ellis
*1889 H Schneider
*1888 D Adamson
*1887 James Riley
*1886 Edward Williams
*1885 R Akerman
*1884 E P Martin
*1884 E W Richards
*1883 G J Snelus
*1883 Sidney Gilchrist Thomas
*1882 A L Holley
*1881 W Menelaus
*1880 Sir J Whitworth
*1879 P Cooper
*1878 P R von Tunner
*1877 J Percy
*1876 R F Mushet
*1875 Sir C W Siemens
*1874 Sir Lowthian Bell | 1 | Applied and Interdisciplinary Chemistry |
As an example, consider the gas-phase reaction + CO → NO + . If this reaction occurred in a single step, its reaction rate (r) would be proportional to the rate of collisions between and CO molecules: r = k[][CO], where k is the reaction rate constant, and square brackets indicate a molar concentration. Another typical example is the Zel'dovich mechanism. | 0 | Theoretical and Fundamental Chemistry |
The electric eel, Electrophorus, is capable of delivering a powerful electric shock that can stun or kill its prey. Bluntnose knifefishes, Brachyhypopomus, create an electric discharge pattern similar to the low voltage electrolocation discharge of the electric eel. This is thought to be Batesian mimicry of the powerfully protected electric eel. | 1 | Applied and Interdisciplinary Chemistry |
The cluster cation has the Keggin structure with a tetrahedral Al atom in the centre of the cluster coordinated to 4 oxygen atoms. The formula can be expressed as . This ion is generally called the ion. A analogue is known an unusual ionic compound with an cation and a Keggin polyoxoanion has been characterised. | 0 | Theoretical and Fundamental Chemistry |
Radiological dispersal devices (RDDs) are weapons of mass disruption rather than weapons of mass destruction. "Dirty bombs" are examples of RDDs. As the name suggests, an RDD aims at dispersing radioactive material over an area, causing high cleanup costs, psychological, and economic damage. Nevertheless, direct human losses caused by RDDs are low and not attributed to the radiological aspect. RDDs are easily fabricated and components readily obtainable. RDDs are comparatively easy to detect with RPMs due to their high level of radioactivity. RDDs emit gamma radiation as well as sometimes, depending on what isotopes are used, neutrons. | 0 | Theoretical and Fundamental Chemistry |
Localized electronic effects are a combination of inductive and field effects. Due to the similarity in these effects, it is difficult to separate their contributions to the electronic structure of a molecule. There is, however, a large body of literature devoted to developing an understanding of the relative significance of induction and field effects by analyzing related compounds in an attempt to quantify each effect based on the present substituents and molecular geometry. For example, the three compounds to the right, all octanes, differ only in the number of linkers between the electron withdrawing group X and an acidic functional group, which are approximately the same spatial distance apart in each compound. It is known that an electron-withdrawing substituent will decrease the pKa of a given proton (i.e. increase the acidity) inductively. If induction was the dominant effect in these compounds, acidity should increase linearly with the number of available inductive pathways (linkers). However, the experimental data shows that effect on acidity in related octanes and cubanes is very similar, and therefore the dominant effect must be through space.
In the cis-11,12-dichloro-9,10-dihydro-9,10-ethano-2-anthroic acid syn and anti isomers seen below and to the left, the chlorines provide a field effect. The concentration of negative charge on each chlorine has a through space effect which can be seen in the relative pKa values. When the chlorines are pointed over the carboxylic acid group, the pKa is higher because loss of a proton is less favorable due to the increase in negative charge in the area. Loss of a proton results in a negative charge which is less stable if there is already an inherent concentration of electrons. This can be attributed to a field effect because in the same compound with the chlorines pointed away from the acidic group the pKa is lower, and if the effect were inductive the conformational position would not matter. | 0 | Theoretical and Fundamental Chemistry |
The Monsanto process is an industrial method for the manufacture of acetic acid by catalytic carbonylation of methanol. The Monsanto process has largely been supplanted by the Cativa process, a similar iridium-based process developed by BP Chemicals Ltd which is more economical and environmentally friendly.
This process operates at a pressure of 30–60 atm and a temperature of 150–200 °C and gives a selectivity greater than 99%. It was developed in 1960 by the German chemical company, BASF, and improved by the Monsanto Company in 1966, which introduced a new catalyst system. | 0 | Theoretical and Fundamental Chemistry |
Particles and small organisms floating through the water column can become trapped within aggregates. Marine snow aggregates are porous, however, and some particles are able to pass through them. | 0 | Theoretical and Fundamental Chemistry |
A pill was originally defined as a small, round, solid pharmaceutical oral dosage form of medication. The words etymology reflects the historical concepts of grinding the ingredients with a mortar and pestle and rolling the resultant paste or dough into lumps to be dried. Today, in its strict sense, the word pill still refers specifically to tablets (including caplets) rather than capsules (which were invented much later), but because a simple hypernym is needed to intuitively cover all such oral dosage forms, the broad sense of the word pill is also widely used and includes both tablets and capsules — colloquially, any solid oral form of medication falls into the "pill" category (see pill § Usage notes').
An early example of a pill comes from ancient Rome. They were made of zinc carbonates, hydrozincite and smithsonite. The pills were used for sore eyes and were found aboard a Roman ship that wrecked in 140 BC. However, these tablets were meant to be pressed on the eyes, not swallowed.
;Defects/imperfections arising during tablet manufacturing
*Formulation related: sticking, picking, binding
*Processing: capping, lamination, cracking, chipping
*Machine: double impression | 1 | Applied and Interdisciplinary Chemistry |
π bonding in octahedral complexes occurs in two ways: via any ligand p-orbitals that are not being used in σ bonding, and via any π or π molecular orbitals present on the ligand.
In the usual analysis, the p-orbitals of the metal are used for σ bonding (and have the wrong symmetry to overlap with the ligand p or π or π orbitals anyway), so the π interactions take place with the appropriate metal d-orbitals, i.e. d, d and d. These are the orbitals that are non-bonding when only σ bonding takes place.
One important π bonding in coordination complexes is metal-to-ligand π bonding, also called π backbonding. It occurs when the LUMOs (lowest unoccupied molecular orbitals) of the ligand are anti-bonding π orbitals. These orbitals are close in energy to the d, d and d orbitals, with which they combine to form bonding orbitals (i.e. orbitals of lower energy than the aforementioned set of d-orbitals). The corresponding anti-bonding orbitals are higher in energy than the anti-bonding orbitals from σ bonding so, after the new π bonding orbitals are filled with electrons from the metal d-orbitals, Δ has increased and the bond between the ligand and the metal strengthens. The ligands end up with electrons in their π molecular orbital, so the corresponding π bond within the ligand weakens.
The other form of coordination π bonding is ligand-to-metal bonding. This situation arises when the π-symmetry p or π orbitals on the ligands are filled. They combine with the d, d and d orbitals on the metal and donate electrons to the resulting π-symmetry bonding orbital between them and the metal. The metal-ligand bond is somewhat strengthened by this interaction, but the complementary anti-bonding molecular orbital from ligand-to-metal bonding is not higher in energy than the anti-bonding molecular orbital from the σ bonding. It is filled with electrons from the metal d-orbitals, however, becoming the HOMO (highest occupied molecular orbital) of the complex. For that reason, Δ decreases when ligand-to-metal bonding occurs.
The greater stabilization that results from metal-to-ligand bonding is caused by the donation of negative charge away from the metal ion, towards the ligands. This allows the metal to accept the σ bonds more easily. The combination of ligand-to-metal σ-bonding and metal-to-ligand
π-bonding is a synergic effect, as each enhances the other.
As each of the six ligands has two orbitals of π-symmetry, there are twelve in total. The symmetry adapted linear combinations of these fall into four triply degenerate irreducible representations, one of which is of t symmetry. The d, d and d orbitals on the metal also have this symmetry, and so the π-bonds formed between a central metal and six ligands also have it (as these π-bonds are just formed by the overlap of two sets of orbitals with t symmetry.) | 0 | Theoretical and Fundamental Chemistry |
Ground waters by their very nature are often very difficult to access to take a sample. As a consequence the majority of ground-water data comes from samples taken from springs, wells, water supply bore-holes and in natural caves. In recent decades as the need to understand ground water dynamics has increased, an increasing number or monitoring bore-holes have been drilled into aquifers. | 1 | Applied and Interdisciplinary Chemistry |
* 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 | Applied and Interdisciplinary 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 | Applied and Interdisciplinary Chemistry |
Photosynthetic oxygen evolution is the fundamental process by which oxygen is generated in the earth's biosphere. The reaction is part of the light-dependent reactions of photosynthesis in cyanobacteria and the chloroplasts of green algae and plants. It utilizes the energy of light to split a water molecule into its protons and electrons for photosynthesis. Free oxygen, generated as a by-product of this reaction, is released into the atmosphere.
Water oxidation is catalyzed by a manganese-containing cofactor contained in photosystem II, known as the oxygen-evolving complex (OEC) or the water-splitting complex. Manganese is an important cofactor, and calcium and chloride are also required for the reaction to occur. The stoichiometry of this reaction is as follows:
: 2HO ⟶ 4e + 4H + O
The protons are released into the thylakoid lumen, thus contributing to the generation of a proton gradient across the thylakoid membrane. This proton gradient is the driving force for adenosine triphosphate (ATP) synthesis via photophosphorylation and the coupling of the absorption of light energy and the oxidation of water for the creation of chemical energy during photosynthesis. | 0 | Theoretical and Fundamental Chemistry |
The genome of the P1 phage is moderately large, around 93Kbp in length (compared to the genomes of e.g. T4 - 169Kbp, lambda - 48Kbp and Ff - 6.4Kbp). In the viral particle it is in the form of a linear double stranded DNA molecule. Once inserted into the host it circularizes and replicates as a plasmid.
In the viral particle the DNA molecule is longer (110Kbp) than the actual length of the genome. It is created by cutting an appropriately sized fragment from a concatemeric DNA chain having multiple copies of the genome (see the section below on lysis for how this is made). Due to this the ends of the DNA molecule are identical. This is referred to as being terminally redundant. This is important for the DNA to be circularized in the host. Another consequence of the DNA being cut out of a concatemer is that a given linear molecule can start at any location on the circular genome. This is called a cyclic permutation.
The genome is especially rich in Chi sequences recognized by the bacterial recombinase RecBCD. The genome contains two origins of replication: oriR which replicates it during the lysogenic cycle and oriL which replicates it during the lytic stage. The genome of P1 encodes three tRNAs which are expressed in the lytic stage.
Proteome. The genome of P1 encodes 112 proteins and 5 untranslated genes and is this about twice the size of bacteriophage lambda. | 1 | Applied and Interdisciplinary Chemistry |
Natural and contaminant organometallic compounds are found in the environment. Some that are remnants of human use, such as organolead and organomercury compounds, are toxicity hazards. Tetraethyllead was prepared for use as a gasoline additive but has fallen into disuse because of lead's toxicity. Its replacements are other organometallic compounds, such as ferrocene and methylcyclopentadienyl manganese tricarbonyl (MMT). The organoarsenic compound roxarsone is a controversial animal feed additive. In 2006, approximately one million kilograms of it were produced in the U.S alone. Organotin compounds were once widely used in anti-fouling paints but have since been banned due to environmental concerns. | 0 | Theoretical and Fundamental Chemistry |
Contrary to popular misconception, the electrical deflection of a stream of water from a charged object is not based on polarity. The deflection occurs because of electrically charged droplets in the stream, which the charged object induces. A stream of water can also be deflected in a uniform electrical field, which cannot exert force on polar molecules. Additionally, after a stream of water is grounded, it can no longer be deflected. Weak deflection is even possible for nonpolar liquids. | 0 | Theoretical and Fundamental Chemistry |
Chromids are elements that exist at the boundary between a chromosome and a plasmid, found in about 10% of bacterial species sequenced by 2009. These elements carry core genes and have codon usage similar to the chromosome, yet use a plasmid-type replication mechanism such as the low copy number RepABC. As a result, they have been variously classified as minichromosomes or megaplasmids in the past. In Vibrio, the bacterium synchronizes the replication of the chromosome and chromid by a conserved genome size ratio. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics and plasma physics, the Clebsch representation provides a means to overcome the difficulties to describe an inviscid flow with non-zero vorticity – in the Eulerian reference frame – using Lagrangian mechanics and Hamiltonian mechanics. At the critical point of such functionals the result is the Euler equations, a set of equations describing the fluid flow. Note that the mentioned difficulties do not arise when describing the flow through a variational principle in the Lagrangian reference frame. In case of surface gravity waves, the Clebsch representation leads to a rotational-flow form of Luke's variational principle.
For the Clebsch representation to be possible, the vector field has (locally) to be bounded, continuous and sufficiently smooth. For global applicability has to decay fast enough towards infinity. The Clebsch decomposition is not unique, and (two) additional constraints are necessary to uniquely define the Clebsch potentials. Since is in general not solenoidal, the Clebsch representation does not in general satisfy the Helmholtz decomposition. | 1 | Applied and Interdisciplinary Chemistry |
Bis(trimethylsilyl)peroxide (sometimes abbreviated as BTSP) is an organosilicon compound with the formula ((CH)SiO). It is a colorless liquid that is soluble in organic solvents so long as they lack acidic groups. The compound represents an aprotic analogue of hydrogen peroxide and as such it is used for certain sensitive organic oxidations. Upon treatment with organolithium compounds, it affords the silyl ether. | 0 | Theoretical and Fundamental Chemistry |
Surfactants are in demand for a wide range of industrial applications as they increase solubility, foaming capacity and lower surface tensions. In particular, rhamnolipids have been used broadly in the cosmetic industry for products such as moisturisers, condom lubricant and shampoo. Rhamnolipids are efficacious in bioremediation of organic and heavy metal polluted sites. They also facilitate degradation of waste hydrocarbons such as crude oil and vegetable oil by Pseudomonas aeruginosa. The rhamnolipid surfactant itself is valuable in the cosmetic industry, and rhamnolipids are a source of rhamnose, which is an expensive sugar in itself.
Other bio-based surfactants include sophorolipids and mannose-erythritol lipids. | 0 | Theoretical and Fundamental Chemistry |
A fluid flowing along a flat plate will stick to it at the point of contact and this is known as the no-slip condition. This is an outcome of the adhesive forces between the flat plate and the fluid. The presence of the wall has an effect up to a certain distance
in the fluid (in the direction perpendicular to the wall area and flow ) and this is known as the boundary layer.
Any layer of fluid that is not in contact with the wall will be flowing with a certain velocity and will be sandwiched between two layers of fluid. Now the layer just above it (flowing with a greater velocity) will try to drag it in the direction of flow, whereas the layer just below it (flowing with a lesser velocity) will try to slow it down. The attraction between the layers of the fluid is the result of cohesive forces, and viscosity is the property that explains the nature and strength of cohesive forces within a fluid.
It is common to experience the fact that the flowing fluid will exert a certain amount of force on the plate, trying to pull it in its flow direction. The flat plate exerts an equal amount of force on the fluid. (Newton's third law)
Experiments on the fluid flow parallel to a flat plate reveal that the force, known as shear stress can be expressed mathematically as
Note this is valid only for one dimensional fluid flow in rectangular coordinates. The is the shear stress at any layer of the fluid where (i.e. the gradient of velocity in a direction perpendicular to the flow and the area of the flat plate), is the local gradient and is the viscosity.
The units of shear stress are Force/Unit Area. This is in M.K.S system. This can also be interpreted as . However, these are also the units of momentum flux. This is the precise reason why shear stress in a fluid can also be interpreted as the flux of momentum. The diffusion of momentum is in the direction of decreasing velocity. This means that momentum is being transferred from the fluid in the upper layers (which has greater momentum) towards the fluid that is close to the wall (which has lesser momentum due to its lower velocity).
The phrase "momentum diffusion" can also refer to the diffusion of the probability for a single particle to have a particular momentum. In this case, it is the probability distribution function that diffuses in momentum space, rather than the (conserved) quantity of momentum that diffuses among many particles. | 1 | Applied and Interdisciplinary Chemistry |
The susceptibility to crevice corrosion varies widely from one material-environment system to another. In general, crevice corrosion is of greatest concern for materials which are normally passive metals, like stainless steel or aluminum. Crevice corrosion tends to be of greatest significance to components built of highly corrosion-resistant superalloys and operating with the purest-available water chemistry. For example, steam generators in nuclear power plants degrade largely by crevice corrosion.
Crevice corrosion is extremely dangerous because it is localized and can lead to component failure while the overall material loss is minimal. The initiation and progress of crevice corrosion can be difficult to detect. | 1 | Applied and Interdisciplinary Chemistry |
There has been a reluctance for modern drug discovery programs to consider covalent inhibitors due to toxicity concerns. An important contributor has been the drug toxicities of several high-profile drugs believed to be caused by metabolic activation of reversible drugs. For example, high dose acetaminophen can lead to the formation of the reactive metabolite N-acetyl-p-benzoquinone imine. Also, covalent inhibitors such as beta lactam antibiotics which contain weak electrophiles can lead to idiosyncratic toxicities (IDT) in some patients. It has been noted that many approved covalent inhibitors have been used safely for decades with no observed idiosyncratic toxicity. Also, that IDTs are not limited to proteins with a covalent mechanism of action. A recent analysis has noted that the risk of idiosyncratic toxicities may be mitigated through lower doses of administered drug. Doses of less than 10 mg per day rarely lead to IDT irrespective of the drug mechanism. | 1 | Applied and Interdisciplinary Chemistry |
Transient kinetic isotope effects (or fractionation) occur when the reaction leading to isotope fractionation does not follow pure first-order kinetics and therefore isotopic effects cannot be described with the classical equilibrium fractionation equations or with steady-state kinetic fractionation equations (also known as the Rayleigh equation). In these instances, the general equations for biochemical isotope kinetics (GEBIK) and the general equations for biochemical isotope fractionation (GEBIF) can be used.
The GEBIK and GEBIF equations are the most generalized approach to describe isotopic effects in any chemical, catalytic reaction and biochemical reactions because they can describe isotopic effects in equilibrium reactions, kinetic chemical reactions and kinetic biochemical reactions. In the latter two cases, they can describe both stationary and non-stationary fractionation (i.e., variable and inverse fractionation). In general, isotopic effects depend on the number of reactants and on the number of combinations resulting from the number of substitutions in all reactants and products. Describing with accuracy isotopic effects, however, depends also on the specific rate law used to describe the chemical or biochemical reaction that produces isotopic effects. Normally, regardless of whether a reaction is purely chemical or whether it involves some enzyme of biological nature, the equations used to describe isotopic effects base on first-order kinetics. This approach systematically leads to isotopic effects that can be described by means of the Rayleigh equation. In this case, isotopic effects will always be expressed as a constant, hence will not be able to describe isotopic effects in reactions where fractionation and enrichment are variable or inverse during the course of a reaction. Most chemical reactions do not follow first-order kinetics; neither biochemical reactions can normally be described with first-order kinetics. To properly describe isotopic effects in chemical or biochemical reactions, different approaches must be employed such as the use of Michaelis–Menten reaction order (for chemical reactions) or coupled Michaelis–Menten and Monod reaction orders (for biochemical reactions). However, conversely to Michaelis–Menten kinetics, GEBIK and GEBIF equations are solved under the hypothesis of non-steady state. This characteristic allows GEBIK and GEBIF to capture transient isotopic effects. | 0 | Theoretical and Fundamental Chemistry |
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 | Applied and Interdisciplinary Chemistry |
FK phase materials have been pointed out for their high-temperature structure and as superconducting materials. Their complex and often non-stoichiometric structure makes them good subjects for theoretical calculations.
A15, Laves and σ are the most applicable FK structures with interesting fundamental properties.
The A15 compounds include important intermetallic superconductors such as: NbSn, NbAl, and VGa with applications including wires for high-field superconducting magnets. NbSn is also being investigated as a potential material for fabricating superconducting radio frequency cavities.
Small extents of σ phase considerably decreases the flexibility and impairment in erosion resistance. While addition of refractory elements like W, Mo, or Re to FK phases helps to enhance the thermal properties in such alloys as steels or nickel-based superalloys, it increases the risk of unwanted precipitation in intermetallic compounds. | 1 | Applied and Interdisciplinary Chemistry |
The Reynolds number and the Womersley number are the only two physical parameters necessary to solve an incompressible fluid flow problem. The Reynolds number is given by:
The terms of the equation itself represent the following:
When the Reynolds number is large, it shows that the flow is dominated by convective inertial effects; When the Reynolds Number is small, it shows that the flow is dominated by shear effects.
The Womersley number is given by:
which is simply the square-root of the Stokes Number; the terms of the equation itself represent the following:
When the Womersley number is large (around 10 or greater), it shows that the flow is dominated by oscillatory inertial forces and that the velocity profile is flat. When the Womersley parameter is low, viscous forces tend to
dominate the flow, velocity profiles are parabolic in shape, and the center-line velocity oscillates in phase with the driving pressure gradient.
Starting with Navier–Stokes equation for Cartesian flow:
The terms of the equation itself represent the following:
Ignoring gravitational forces and dividing the equation by density () yields:
where is the kinematic viscosity. Since both the Reynolds and Womersley numbers are dimensionless, Navier-Stokes must be represented as a dimensionless expression as well. Choosing , , and as a characteristic velocity, frequency, and length respectively yields dimensionless variables:
Dimensionless Length Term (same for y and z):,
Dimensionless Velocity Term (same for v and w): ,
Dimensionless Pressure Term: ,
Dimensionless Time Term: .
Dividing the Navier-Stokes equation by (Convective Inertial Force term) gives:
With the addition of the dimensionless continuity equation (seen below) in any incompressible fluid flow problem the Reynolds and Womersley numbers are the only two physical parameters that are in the two equations: | 1 | Applied and Interdisciplinary Chemistry |
AutoChem is NASA release software that constitutes an automatic computer code generator and documenter for chemically reactive systems written by David Lary between 1993 and the present. It was designed primarily for modeling atmospheric chemistry, and in particular, for chemical data assimilation.
The user selects a set of chemical species. AutoChem then searches chemical reaction databases for these species and automatically constructs the ordinary differential equations (ODE) that describe the chemical system. AutoChem symbolically differentiates the time derivatives to give the Jacobian matrix, and symbolically differentiates the Jacobian matrix to give the Hessian matrix and the adjoint. The Jacobian matrix is required by many algorithms that solve the ordinary differential equations numerically, particular when the ODEs are stiff. The Hessian matrix and the adjoint are required for four-dimensional variational data assimilation (4D-Var). AutoChem documents the whole process in a set of LaTeX and PDF files.
The reactions involving the user specified constituents are extracted by the first AutoChem preprocessor program called Pick. This subset of reactions is then used by the second AutoChem preprocessor program RoC (rate of change) to generate the time derivatives, Jacobian, and Hessian. Once the two preprocessor programs have run to completion all the Fortran 90 code has been generated that is necessary for modeling and assimilating the kinetic processes.
A huge observational database of many different atmospheric constituents from a host of platforms are available from the AutoChem site.
AutoChem has been used to perform long term chemical data assimilation of atmospheric chemistry. This assimilation was automatically documented by the AutoChem software and is available on line at CDACentral. Data quality is always an issue for chemical data assimilation, in particular the presence of biases. To identify and understand the biases it is useful to compare observations using probability distribution functions. Such an analysis is available on line at PDFCentral which was designed for the validation of observations from the NASA Aura satellite. | 0 | Theoretical and Fundamental Chemistry |
Mefloquine was formulated at Walter Reed Army Institute of Research (WRAIR) in the 1970s shortly after the end of the Vietnam war. Mefloquine was number 142,490 of a total of 250,000 antimalarial compounds screened during the study.
Mefloquine was the first Public-Private Venture (PPV) between the US Department of Defense and a pharmaceutical company. WRAIR transferred all its phase I and phase II clinical trial data to Hoffman-LaRoche and Smith Kline. FDA approval as a treatment for malaria was swift. Most notably, phase III safety and tolerability trials were skipped.
The drug was first approved in Switzerland in 1984 by Hoffmann-LaRoche, who brought it to market with the name Lariam.
However, mefloquine was not approved by the FDA for prophylactic use until 1989. This approval was based primarily on compliance, while safety and tolerability were overlooked. Because of the drug's very long half-life, the Centers for Disease Control originally recommended a mefloquine dosage of 250 mg every two weeks; however, this caused an unacceptably high malaria rate in the Peace Corps volunteers who participated in the approval study, so the drug regimen was switched to once a week.
By 1991, Hoffman was marketing the drug on a worldwide basis.
By the 1992 UNITAF, Canadian soldiers were being prescribed the drug en masse.
By 1994, medical professionals were noting "severe psychiatric side effects observed during prophylaxis and treatment with mefloquine", and recommending that "the absence of contraindications and minor side effects during an initial course of mefloquine should be confirmed before another course is prescribed." Other doctors at the University Hospital of Zurich noted in a case of "a 47-year-old, previously healthy Japanese tourist" who had severe neuropsychiatric side-effects from the drug that
The first randomized, controlled trial on a mixed population was performed in 2001. Prophylaxis with mefloquine was compared to prophylaxis with atovaquone-proguanil. Roughly 67% of participants in the mefloquine arm reported greater than or equal to one adverse event, versus 71% in the atovaquone-proguanil arm. In the mefloquine arm, 5% of the users reported severe events requiring medical attention, versus 1.2% in the atovaquone-proguanil arm.
In August 2009, Roche stopped marketing Lariam in the United States.
Retired soldier Johnny Mercer, who was later appointed Minister for Veterans Affairs by Boris Johnson, told in 2015 that he had received "a letter about once or twice a week" about ill-effects from the drug. In July 2016, Roche took this brand off the market in Ireland. | 0 | Theoretical and Fundamental Chemistry |
Inorganic chemistry is a highly practical area of science. Traditionally, the scale of a nation's economy could be evaluated by their productivity of sulfuric acid.
An important man-made inorganic compound is ammonium nitrate, used for fertilization. The ammonia is produced through the Haber process. Nitric acid is prepared from the ammonia by oxidation. Another large-scale inorganic material is portland cement. Inorganic compounds are used as catalysts such as vanadium(V) oxide for the oxidation of sulfur dioxide and titanium(III) chloride for the polymerization of alkenes. Many inorganic compounds are used as reagents in organic chemistry such as lithium aluminium hydride. | 0 | Theoretical and Fundamental Chemistry |
Ex-situ bonding is achieved by gluing face sheets with an aluminium foam by adhesive bonding, brazing or diffusion bonding. Foams used in this method are either closed-cell or open-cell. When a closed-cell foam is used then it is produced from aluminium alloys either by liquid metal route (e.g. Alporas, Cymat) or by powder metallurgy route. Open-cell foam core is made of aluminium and other metals as well. Face sheets are chosen from a variety of aluminium alloy, and other metals such as steel. | 0 | Theoretical and Fundamental Chemistry |
By the 1960s solar power was the standard for powering space-bound satellites. In the early 1970s, solar cell technology became cheaper and more available ($20/watt). Between 1970 and 1990, solar power became more commercially operated. Railroad crossings, oil rigs, space stations, microwave towers, aircraft, etc. Now, houses and businesses all over the world use solar cells to power electrical devices with a wide variety of uses. Solar power is the dominant technology in the renewable energy field, primarily due to its high efficiency and cost-effectiveness. By the early 1990s, photovoltaic conversion had reached an unprecedented new height. Scientists used solar cells constructed of highly conductive photovoltaic materials such as gallium, indium, phosphide and gallium arsenide that increased total efficiency by over 30%. By the end of the century, scientists created a special type of solar cells that converted upwards of 36% of the sunlight it collected into usable energy. These developments built tremendous momentum for not only solar power, but for renewable energy technologies around the world. | 0 | Theoretical and Fundamental Chemistry |
The above derivation uses the first and second laws of thermodynamics. The first law of thermodynamics is essentially a definition of heat, i.e. heat is the change in the internal energy of a system that is not caused by a change of the external parameters of the system.
However, the second law of thermodynamics is not a defining relation for the entropy. The fundamental definition of entropy of an isolated system containing an amount of energy is:
where is the number of quantum states in a small interval between and . Here is a macroscopically small energy interval that is kept fixed. Strictly speaking this means that the entropy depends on the choice of . However, in the thermodynamic limit (i.e. in the limit of infinitely large system size), the specific entropy (entropy per unit volume or per unit mass) does not depend on . The entropy is thus a measure of the uncertainty about exactly which quantum state the system is in, given that we know its energy to be in some interval of size .
Deriving the fundamental thermodynamic relation from first principles thus amounts to proving that the above definition of entropy implies that for reversible processes we have:
The fundamental assumption of statistical mechanics is that all the states at a particular energy are equally likely. This allows us to extract all the thermodynamical quantities of interest. The temperature is defined as:
This definition can be derived from the microcanonical ensemble, which is a system of a constant number of particles, a constant volume and that does not exchange energy with its environment. Suppose that the system has some external parameter, x, that can be changed. In general, the energy eigenstates of the system will depend on x. According to the adiabatic theorem of quantum mechanics, in the limit of an infinitely slow change of the system's Hamiltonian, the system will stay in the same energy eigenstate and thus change its energy according to the change in energy of the energy eigenstate it is in.
The generalized force, X, corresponding to the external parameter x is defined such that is the work performed by the system if x is increased by an amount dx. E.g., if x is the volume, then X is the pressure. The generalized force for a system known to be in energy eigenstate is given by:
Since the system can be in any energy eigenstate within an interval of , we define the generalized force for the system as the expectation value of the above expression:
To evaluate the average, we partition the energy eigenstates by counting how many of them have a value for within a range between and . Calling this number , we have:
The average defining the generalized force can now be written:
We can relate this to the derivative of the entropy with respect to x at constant energy E as follows. Suppose we change x to x + dx. Then will change because the energy eigenstates depend on x, causing energy eigenstates to move into or out of the range between and . Lets focus again on the energy eigenstates for which lies within the range between and . Since these energy eigenstates increase in energy by Y dx, all such energy eigenstates that are in the interval ranging from E − Y dx to E move from below E to above E'. There are
such energy eigenstates. If , all these energy eigenstates will move into the range between and and contribute to an increase in . The number of energy eigenstates that move from below to above is, of course, given by . The difference
is thus the net contribution to the increase in . Note that if Y dx is larger than there will be energy eigenstates that move from below to above . They are counted in both and , therefore the above expression is also valid in that case.
Expressing the above expression as a derivative with respect to E and summing over Y yields the expression:
The logarithmic derivative of with respect to x is thus given by:
The first term is intensive, i.e. it does not scale with system size. In contrast, the last term scales as the inverse system size and thus vanishes in the thermodynamic limit. We have thus found that:
Combining this with
Gives:
which we can write as: | 0 | Theoretical and Fundamental Chemistry |
Transcriptomics is the quantitative science that encompasses the assignment of a list of strings ("reads") to the object ("transcripts" in the genome). To calculate the expression strength, the density of reads corresponding to each object is counted. Initially, transcriptomes were analyzed and studied using expressed sequence tags libraries and serial and cap analysis of gene expression (SAGE).
Currently, the two main transcriptomics techniques include DNA microarrays and RNA-Seq. Both techniques require RNA isolation through RNA extraction techniques, followed by its separation from other cellular components and enrichment of mRNA.
There are two general methods of inferring transcriptome sequences. One approach maps sequence reads onto a reference genome, either of the organism itself (whose transcriptome is being studied) or of a closely related species. The other approach, de novo transcriptome assembly, uses software to infer transcripts directly from short sequence reads and is used in organisms with genomes that are not sequenced. | 1 | Applied and Interdisciplinary Chemistry |
Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. Photosystems are found in the thylakoid membranes of plants, algae, and cyanobacteria. These membranes are located inside the chloroplasts of plants and algae, and in the cytoplasmic membrane of photosynthetic bacteria. There are two kinds of photosystems: PSI and PSII.
PSII will absorb red light, and PSI will absorb far-red light. Although photosynthetic activity will be detected when the photosystems are exposed to either red or far-red light, the photosynthetic activity will be the greatest when plants are exposed to both wavelengths of light. Studies have actually demonstrated that the two wavelengths together have a synergistic effect on the photosynthetic activity, rather than an additive one.
Each photosystem has two parts: a reaction center, where the photochemistry occurs, and an antenna complex, which surrounds the reaction center. The antenna complex contains hundreds of chlorophyll molecules which funnel the excitation energy to the center of the photosystem. At the reaction center, the energy will be trapped and transferred to produce a high energy molecule.
The main function of PSII is to efficiently split water into oxygen molecules and protons. PSII will provide a steady stream of electrons to PSI, which will boost these in energy and transfer them to NADP and H to make NADPH. The hydrogen from this NADPH can then be used in a number of different processes within the plant. | 0 | Theoretical and Fundamental Chemistry |
The rule usefully predicts the formulas for low-spin complexes of the Cr, Mn, Fe, and Co triads. Well-known examples include ferrocene, iron pentacarbonyl, chromium carbonyl, and nickel carbonyl.
Ligands in a complex determine the applicability of the 18-electron rule. In general, complexes that obey the rule are composed at least partly of π-acceptor ligands (also known as π-acids). This kind of ligand exerts a very strong ligand field, which lowers the energies of the resultant molecular orbitals so that they are favorably occupied. Typical ligands include olefins, phosphines, and CO. Complexes of π-acids typically feature metal in a low-oxidation state. The relationship between oxidation state and the nature of the ligands is rationalized within the framework of π backbonding. | 0 | Theoretical and Fundamental Chemistry |
Contrary to prevailing thought at the time, Lavoisier theorized that common air, or one of its components, combines with substances when they are burned. He demonstrated this through experiment.
During late 1772 Lavoisier turned his attention to the phenomenon of combustion, the topic on which he was to make his most significant contribution to science. He reported the results of his first experiments on combustion in a note to the Academy on 20 October, in which he reported that when phosphorus burned, it combined with a large quantity of air to produce acid spirit of phosphorus, and that the phosphorus increased in weight on burning. In a second sealed note deposited with the Academy a few weeks later (1 November) Lavoisier extended his observations and conclusions to the burning of sulfur and went on to add that "what is observed in the combustion of sulfur and phosphorus may well take place in the case of all substances that gain in weight by combustion and calcination: and I am persuaded that the increase in weight of metallic calces is due to the same cause." | 1 | Applied and Interdisciplinary Chemistry |
The European green infrastructure is an important part of the new (post-2010) EU strategy for biodiversity and biodiversity policy.
It is one of the main tools to tackle threats on biodiversity resulting from habitat fragmentation, land use change and loss of habitats.
Green Infrastructure will play a decisive role in integrating biodiversity into other policies, such as agriculture, forestry, water, marine and fisheries, regional and cohesion policy, climate change mitigation and adaptation, transport, energy and land use policy. It is also an important tool for existing Directives such as the Water Framework Directive, the Marine Framework Directive, Environmental Impact Assessment and Strategic Environment Assessment Directives.
In addition, particular attention will be given to strengthening the integration of green infrastructure aspects in the EU’s various funding programmes (e.g. structural and cohesion funds, CAP, LIFE) over the current and future financial programming period starting in 2013 and to improving the ecological coherence of the Natura 2000 Network. | 1 | Applied and Interdisciplinary Chemistry |
Broadband acoustic resonance dissolution spectroscopy (BARDS) is a technique in analytical chemistry. Developed in the late 2000s, it involves the analysis of the changes in sound frequency generated when a solute dissolves in a solvent, by harnessing the hot chocolate effect.
The technique is partly based on the solubility difference of gas in pure solvents and in solutions. The dissolution of a compound in a pure solvent results in the generation of gas bubbles in the solvent, due to the lowering of gas solubility in the resulting solution, as well as the introduction of gases with the solute. The presence of these gas bubbles increases the compressibility of the solution, thereby lowering the velocity of sound in the solution. This effect can be monitored by means of the frequency change of acoustic resonances that are mechanically produced in the solvent. | 0 | Theoretical and Fundamental Chemistry |
The existence of intermolecular forces was first postulated by Johannes Diderik van der Waals in 1873. However, Nobel laureate Hermann Emil Fischer developed supramolecular chemistry's philosophical roots. In 1894, Fischer suggested that enzyme–substrate interactions take the form of a "lock and key", the fundamental principles of molecular recognition and host–guest chemistry. In the early twentieth century non-covalent bonds were understood in gradually more detail, with the hydrogen bond being described by Latimer and Rodebush in 1920.
The use of these principles led to an increasing understanding of protein structure and other biological processes. For instance, the important breakthrough that allowed the elucidation of the double helical structure of DNA occurred when it was realized that there are two separate strands of nucleotides connected through hydrogen bonds. The use of non-covalent bonds is essential to replication because they allow the strands to be separated and used to template new double stranded DNA. Concomitantly, chemists began to recognize and study synthetic structures based on non-covalent interactions, such as micelles and microemulsions.
Eventually, chemists were able to take these concepts and apply them to synthetic systems. The breakthrough came in the 1960s with the synthesis of the crown ethers by Charles J. Pedersen. Following this work, other researchers such as Donald J. Cram, Jean-Marie Lehn and Fritz Vögtle became active in synthesizing shape- and ion-selective receptors, and throughout the 1980s research in the area gathered a rapid pace with concepts such as mechanically interlocked molecular architectures emerging.
The importance of supramolecular chemistry was established by the 1987 Nobel Prize for Chemistry which was awarded to Donald J. Cram, Jean-Marie Lehn, and Charles J. Pedersen in recognition of their work in this area. The development of selective "host–guest" complexes in particular, in which a host molecule recognizes and selectively binds a certain guest, was cited as an important contribution.
In the 1990s, supramolecular chemistry became even more sophisticated, with researchers such as James Fraser Stoddart developing molecular machinery and highly complex self-assembled structures, and Itamar Willner developing sensors and methods of electronic and biological interfacing. During this period, electrochemical and photochemical motifs became integrated into supramolecular systems in order to increase functionality, research into synthetic self-replicating system began, and work on molecular information processing devices began. The emerging science of nanotechnology also had a strong influence on the subject, with building blocks such as fullerenes, nanoparticles, and dendrimers becoming involved in synthetic systems. | 0 | Theoretical and Fundamental Chemistry |
Gas turbine engines have a power-producing primary airflow passing through the compressor. They also have a substantial (25% of core flow in a Pratt & Whitney PW2000) secondary flow obtained from the primary flow and which is pumped from the compressor and used by the secondary air system. Like the secondary flow in turbomachinery this secondary flow is also a loss to the power-producing capability of the engine. | 1 | Applied and Interdisciplinary Chemistry |
Antoine Lavoisier, in a collaborative effort with Louis Bernard Guyton de Morveau, Claude Louis Berthollet, and Antoine François de Fourcroy, published Méthode de nomenclature chimique in 1787. This work established a terminology for the "new chemistry" which Lavoisier was creating, which focused on a standardized set of terms, establishment of new elements, and experimental work. Méthode established 55 elements which were substances that could not be broken down into simpler composite parts at the time of publishing. By introducing new terminology into the field, Lavoisier encouraged other chemists to adopt his theories and practices in order to use his terms and stay current in chemistry. | 1 | Applied and Interdisciplinary Chemistry |
The absence of long-range order in liquids is mirrored by the absence of Bragg peaks in X-ray and neutron diffraction. Under normal conditions, the diffraction pattern has circular symmetry, expressing the isotropy of the liquid. Radially, the diffraction intensity smoothly oscillates. This can be described by the static structure factor , with wavenumber given by the wavelength of the probe (photon or neutron) and the Bragg angle . The oscillations of express the short-range order of the liquid, i.e., the correlations between a molecule and "shells" of nearest neighbors, next-nearest neighbors, and so on.
An equivalent representation of these correlations is the radial distribution function , which is related to the Fourier transform of . It represents a spatial average of a temporal snapshot of pair correlations in the liquid. | 0 | Theoretical and Fundamental Chemistry |
In 1949, Glendenin earned his Ph.D. from the Massachusetts Institute of Technology. That same year he joined Argonne National Laboratory, where he worked until his retirement in 1985.
He published extensively on the properties of fission products. He served as Scientific Secretary for the U.S. delegation to the Atoms for Peace Conference and received the American Chemical Society's Glenn T. Seaborg Award for Nuclear Chemistry in 1974. | 1 | Applied and Interdisciplinary Chemistry |
Flow-FISH was first published in 1998 by Rufer et al. as a modification of another technique for analyzing telomere length, Q-FISH, that employs peptide nucleic acid probes of a 3-CCCTAACCCTAACCCTAA-5 sequence labeled with a fluorescin fluorophore to stain telomeric repeats on prepared metaphase spreads of cells that have been treated with colcemid, hypotonic shock, and fixation to slides via methanol/acetic acid treatment Images of the resultant fluorescent spots could then be analyzed via a specialized computer program to yield quantitative fluorescence values that can then be used to estimate actual telomere length. The fluorescence yielded by probe staining is considered to be quantitative because PNA binds preferentially to DNA at low ionic salt concentrations and in the presence of formamide, thus the DNA duplex may not reform once it has been melted and annealed to PNA probe, allowing the probe to saturate its target repeat sequence (as it is not displaced from the target DNA by competing anti sense DNA on the complementary strand), thus yielding a reliable and quantifiable readout of the frequency of PNA probe target at a given chromosomal site after washing away of unbound probe. | 1 | Applied and Interdisciplinary Chemistry |
The term self-neutralising acid sulfate soils has been used to refer to sulfidic material which does not become acidic upon oxidation due to the presence of alkaline materials (e.g., marine carbonates) - which neutralise acidity generated by the oxidation of sulfidic material.
The use of this term is discouraged as it can give the impression that the soil is not hazardous. Although the aerobic weathering of hyposulfidic material does not produce excess acidity, it typically generates a saline solution containing environmentally hazardous concentrations of metals and metalloids.Therefore, hyposulfidic material should be used instead of self-neutralising acid sulfate soil. | 0 | Theoretical and Fundamental Chemistry |
MFA was first synthesized in 1896 by the Belgian chemist Frédéric Swarts by reacting methyl iodoacetate with silver fluoride. It can also be synthesized by reacting methyl chloroacetate with potassium fluoride
Because of its toxicity, MFA was studied for potential use as a chemical weapon during World War II. It was considered a good water poison since it is colorless and odorless and therefore it can toxify the water supply and kill a big part of the population. By the end of the war, several countries began to make methyl fluoroacetate to debilitate or kill the enemy. | 1 | Applied and Interdisciplinary Chemistry |
The human genome contains at least 21 genes involved in determining the intracellular levels of cAMP and cGMP by the expression of phosphodiesterase proteins or PDEs. These PDEs are grouped into at least 11 functional subfamilies, named PDE1-PDE11. PDEs are enzymes that hydrolyze cyclic adenosine 3,5-monophosphate (cAMP) and cyclic guanosine 3,5-monophospahate (cGMP), which are intracellular second messengers, into AMP and GMP. These second messengers control many physiological processes.
The cAMP is formed from ATP by the enzyme adenylyl cyclase and cGMP is formed from GTP by the enzyme guanylyl cyclase which are either membrane bound or soluble in the cytosol. When soluble it functions as a receptor for nitric oxide (NO) (see figure 1).
Formation of cGMP initiates several reactions in the body including influence on cGMP ion channels, cGMP binding proteins and protein kinase G (PKG). The effect on PKG reduces levels of calcium leading to relaxation of smooth muscles (see figure 2).
The PDE5 enzyme is specific for cGMP which means it only hydrolyzes cGMP but not cAMP. The selectivity is mediated through an intricate network of hydrogen bonding which is favorable for cGMP but unfavorable for cAMP in PDE5.
By inhibition of PDE5 enzyme the cGMP concentration will be raised and can therefore increase the relaxation of smooth muscles. PDE5 has only one subtype, PDE5A, of which there are 4 isoforms in humans called PDE5A1-4. The difference in PDE5A1-3 isoforms is only in the 5´ end of the mRNA and corresponding N-terminal of the protein. | 1 | Applied and Interdisciplinary Chemistry |
In its simplest and most presently used form, laser Doppler velocimetry crosses two beams of collimated, monochromatic, and coherent laser light in the flow of the fluid being measured. The two beams are usually obtained by splitting a single beam, thus ensuring coherence between the two. Lasers with wavelengths in the visible spectrum (390–750 nm) are commonly used; these are typically He-Ne, Argon ion, or laser diode, allowing the beam path to be observed. A transmitting optics system focuses the beams to intersect at their waists (the focal point of a laser beam), where they interfere and generate a set of straight fringes. As particles (either naturally occurring or induced) entrained in the fluid pass through the fringes, they scatter light that is then collected by a receiving optics and focused on a photodetector (typically an avalanche photodiode).
The scattered light fluctuates in intensity, the frequency of which is equivalent to the Doppler shift between the incident and scattered light, and is thus proportional to the component of particle velocity which lies in the plane of two laser beams. If the sensor is aligned to the flow such that the fringes are perpendicular to the flow direction, the electrical signal from the photodetector will then be proportional to the full particle velocity. By combining three devices (e.g., He-Ne, Argon ion, and laser diode) with different wavelengths, all three flow velocity components can be simultaneously measured.
Another form of laser Doppler velocimetry, particularly used in early device developments, has a completely different approach akin to an interferometer. The sensor also splits the laser beam into two parts; one (the measurement beam) is focused into the flow and the second (the reference beam) passes outside the flow. A receiving optics provides a path that intersects the measurement beam, forming a small volume. Particles passing through this volume will scatter light from the measurement beam with a Doppler shift; a portion of this light is collected by the receiving optics and transferred to the photodetector. The reference beam is also sent to the photodetector where optical heterodyne detection produces an electrical signal proportional to the Doppler shift, by which the particle velocity component perpendicular to the plane of the beams can be determined.
The signal detection scheme of the instrument is using the principle of optical heterodyne detection. This principle is similar to other laser Doppler-based instruments such as laser Doppler vibrometer, or laser surface velocimeter. It is possible to apply digital techniques to the signal to obtain the velocity as a measured fraction of the speed-of-light, and therefore in one sense Laser Doppler velocimetry is a particularly fundamental measurement traceable to the S.I. system of measurement. | 1 | Applied and Interdisciplinary Chemistry |
Glycosynthase have been useful for the preparation of oligosaccharides; however, their use suffers from certain limitations. First, glycosynthase can only be used to synthesize glycosidic linkages for which there is a known glycosidase. That glycosidase must also be first converted into a glycosynthase, which is not always possible. Second, the product of the glycosynthase reaction is often a better substrate for the glycosynthase then the starting material, resulting in the formation of multiple products of varying lengths. Finally, glycosynthase are specific for the donor sugar but often have loose specificity for the acceptor sugar. This can result in different regioselectivity depending on the acceptor resulting in products with different glycosidic linkages. One example is the Agrobacterium sp. β-glucosynthase, which forms a β-1,4-glycoside with glucose as the acceptor, but forms a β-1,3-glycoside with xylose as the acceptor. | 0 | Theoretical and Fundamental Chemistry |
ECOTOX is considered to be more comprehensive in that it holds results from toxicity tests of single chemicals on aquatic and terrestrial plants and animals. Data can be found on both freshwater and marine taxa. ECOTOX collects data from previously EPA established databases , TERRATOX, and PHYTOTOX which individually provide aquatic, terrestrial species and plant data respectively. Data large is collected from peer-reviewed literature however some amount of data is sourced from grey literature. Using the Quick Database Query function enables searches by chemical, taxonomic name, effect, and publication year. Data from ECOTOX is used to provide reference parameters to current toxicity studies and serves as a regulatory guideline. | 1 | Applied and Interdisciplinary Chemistry |
Methionine sulfoxide (MetO), the oxidized form of the amino acid methionine (Met), increases with age in body tissues, which is believed by some to contribute to biological ageing. Oxidation of methionine residues in tissue proteins can cause them to misfold or otherwise render them dysfunctional. Uniquely, the methionine sulfoxide reductase (Msr) group of enzymes act with thioredoxin to catalyze the enzymatic reduction and repair of oxidized methionine residues. Moreover, levels of methionine sulfoxide reductase A (MsrA) decline in aging tissues in mice and in association with age-related disease in humans. There is thus a rationale for thinking that by maintaining the structure, increased levels or activity of MsrA might retard the rate of aging.
Indeed, transgenic Drosophila (fruit flies) that overexpress methionine sulfoxide reductase show extended lifespan. However, the effects of MsrA overexpression in mice were ambiguous. MsrA is found in both the cytosol and the energy-producing mitochondria, where most of the bodys endogenous free radicals are produced. Transgenically increasing the levels of MsrA in either the cytosol or the mitochondria had no significant effect on lifespan assessed by most standard statistical tests, and may possibly have led to early deaths in the cytosol-specific mice, although the survival curves appeared to suggest a slight increase in maximum (90%) survivorship, as did analysis using Boschloos Exact test, a binomial test designed to test greater extreme variation.
The oxidation of methionine serves as a switch that deactivates certain protein activities such as E.coli ribosomal protein, L12. Proteins with great amount of methionine residues tend to exist within the lipid bilayer as methionine is one of the most hydrophobic amino acids. Those methionine residues that are exposed to the aqueous exterior thus are vulnerable to oxidation. The oxidized residues tend to be arrayed around the active site and may guard access to this site by reactive oxygen species. Once oxidized, the MetO residues are reduced back to methionine by the enzyme methionine sulfoxide reductase. Thus, an oxidation–reduction cycle occurs in which exposed methionine residues are oxidized (e.g., by HO) to methionine sulfoxide residues, which are subsequently reduced.
Methionine(protein)+ HO→ Methionine Sulfoxide(protein)+ HO
Methionine Sulfoxide(protein)+ NADPH+H→ Methionine(protein)+ NADP+HO | 1 | Applied and Interdisciplinary Chemistry |
In three dimensions, every figure that possesses a mirror plane of symmetry S, an inversion center of symmetry S, or a higher improper rotation (rotoreflection) S axis of symmetry is achiral. (A plane of symmetry of a figure is a plane , such that is invariant under the mapping , when is chosen to be the --plane of the coordinate system. A center of symmetry of a figure is a point , such that is invariant under the mapping , when is chosen to be the origin of the coordinate system.) Note, however, that there are achiral figures lacking both plane and center of symmetry. An example is the figure
which is invariant under the orientation reversing isometry and thus achiral, but it has neither plane nor center of symmetry. The figure
also is achiral as the origin is a center of symmetry, but it lacks a plane of symmetry.
Achiral figures can have a center axis. | 0 | Theoretical and Fundamental Chemistry |
The Leverett J-function serves to provide a relationship between the capillary pressure and the pore structure (see Leverett J-function). | 1 | Applied and Interdisciplinary Chemistry |
Anti-sp100 antibodies are found in approximately 20–30% of primary biliary cirrhosis (PBC). They are found in few individuals without PBC, and therefore are a very specific marker of the disease. The sp100 antigen is found within nuclear bodies; large protein complexes in the nucleus that may have a role in cell growth and differentiation. | 1 | Applied and Interdisciplinary Chemistry |
A subtropical climate vegetated roof (SCV roof) is a type of green building practice that employs a planted soil media installed above a waterproof roof deck to obtain environmental benefits and address sustainability concerns, similar to traditional green roofs located in northern continental United States. Soil media, plant palettes, and green roof systems that can adapt to the adverse weather conditions and physical characteristics of the humid, subtropical regions of the United States are utilized in the construction and design of subtropical climate vegetated roofs.
Green roofs are used for various reasons including: urban oasis, storm water mitigation, carbon reduction, energy conservation, aesthetics, and therapeutic values depending on the geographic location and the intended specific goals of the project. Most of the current green roof research pertains to northern parts of the continental United States, whereas, very limited research has been conducted in humid, subtropical regions.
Although similar characteristics and principles exist, there are several differences between the two types of environmentally sound roofing systems. These differences are comparable to the differences found between regions of the United States in conventional landscaping and gardening or the variations found in forms of landscaping. Plant species and landscaping methods utilized in northern parts of the United States are not suitable for humid, subtropical regions of United States due to the extreme temperatures and rain events that occur. This accounts for the most significant difference between a green roof in northern United States and a subtropical climate vegetated roof (SCV roof).
A subtropical climate vegetated roof that is well designed according to the specific geographic locations climate can lower roof surface temperatures by as much 38° and depending on the amount of the event retain up to 88% of rainfall. An improperly designed subtropical climate vegetated (SCV roof) using incorrect soil media and plant species can fail by not achieving the intended goals. This roofing method also contributes towards growing the green economy, clean energy technology policies, and qualifies for Federal and local tax incentives, set in place by the United States government. | 1 | Applied and Interdisciplinary Chemistry |
The hydrostatic analysis shows that , combining this with the Laplace pressure calculation we have:solving for returns Jurin's law. | 1 | Applied and Interdisciplinary Chemistry |
Russia has the largest area of peatlands of all the northern circumpolar countries with the world's largest peatland being the West Siberian mire massif and the largest in Europe the Polistovo-Lovatsky mire in northern Russia. An estimate derived from the digital soil database of Russia at a geographical scale of 1:5 million, indicates that the area of soils with a peat depth of more than 30 cm is nearly 2210×10 km. Approximately 28% occurs in the zone of seasonally frozen soils, nearly 30% in the zone of sporadic and discontinuous permafrost, and 42% in the zone of continuous permafrost. Peat with a depth of more than 50 cm tends to be dominant in the Northern and Middle Taiga zones, but is uncommon in the Tundra zone.
Ongoing restoration does not seem to include paludiculture. The Wetland International together with the Institute of Forest Science of the Russian Academy of Sciences and the Michael Succow Foundation, implemented a major peatland restoration project in response to the extensive peat fires in the summer of 2010 in the Moscow region. The project was initiated within the framework of co-operation between the Russian Federation and the Federal Republic of Germany to the spearhead the ecological rewetting of peatlands and represents one of the largest peatland ecosystem restoration projects in the world. To date, over 35,000 ha of drained peatlands have been restored using ecological methods with another 10,000 ha currently underway. | 1 | Applied and Interdisciplinary Chemistry |
Many protein-coding genes have more than one polyadenylation site, so a gene can code for several mRNAs that differ in their 3′ end. The 3’ region of a transcript contains many polyadenylation signals (PAS). When more proximal (closer towards 5’ end) PAS sites are utilized, this shortens the length of the 3’ untranslated region (3 UTR) of a transcript. Studies in both humans and flies have shown tissue specific APA. With neuronal tissues preferring distal PAS usage, leading to longer 3’ UTRs and testis tissues preferring proximal PAS leading to shorter 3’ UTRs. Studies have shown there is a correlation between a genes conservation level and its tendency to do alternative polyadenylation, with highly conserved genes exhibiting more APA. Similarly, highly expressed genes follow this same pattern. Ribo-sequencing data (sequencing of only mRNAs inside ribosomes) has shown that mRNA isoforms with shorter 3’ UTRs are more likely to be translated.
Since alternative polyadenylation changes the length of the 3' UTR, it can also change which binding sites are available for microRNAs in the 3′ UTR. MicroRNAs tend to repress translation and promote degradation of the mRNAs they bind to, although there are examples of microRNAs that stabilise transcripts. Alternative polyadenylation can also shorten the coding region, thus making the mRNA code for a different protein, but this is much less common than just shortening the 3′ untranslated region.
The choice of poly(A) site can be influenced by extracellular stimuli and depends on the expression of the proteins that take part in polyadenylation. For example, the expression of CstF-64, a subunit of cleavage stimulatory factor (CstF), increases in macrophages in response to lipopolysaccharides (a group of bacterial compounds that trigger an immune response). This results in the selection of weak poly(A) sites and thus shorter transcripts. This removes regulatory elements in the 3′ untranslated regions of mRNAs for defense-related products like lysozyme and TNF-α. These mRNAs then have longer half-lives and produce more of these proteins. RNA-binding proteins other than those in the polyadenylation machinery can also affect whether a polyadenylation site is used, as can DNA methylation near the polyadenylation signal. In addition, numerous other components involved in transcription, splicing or other mechanisms regulating RNA biology can affect APA. | 1 | Applied and Interdisciplinary Chemistry |
Polymers have been essential components of commodities since the early days of humankind. The use of wool (keratin), cotton and linen fibres (cellulose) for garments, paper reed (cellulose) for paper are just a few examples of how ancient societies exploited polymer-containing raw materials to obtain artefacts. The latex sap of "caoutchouc" trees (natural rubber) reached Europe in the 16th century from South America long after the Olmec, Maya and Aztec had started using it as a material to make balls, waterproof textiles and containers.
The chemical manipulation of polymers dates back to the 19th century, although at the time the nature of these species was not understood. The behaviour of polymers was initially rationalised according to the theory proposed by Thomas Graham which considered them as colloidal aggregates of small molecules held together by unknown forces.
Notwithstanding the lack of theoretical knowledge, the potential of polymers to provide innovative, accessible and cheap materials was immediately grasped. The work carried out by Braconnot, Parkes, Ludersdorf, Hayward and many others on the modification of natural polymers determined many significant advances in the field. Their contributions led to the discovery of materials such as celluloid, galalith, parkesine, rayon, vulcanised rubber and, later, Bakelite: all materials that quickly entered industrial manufacturing processes and reached households as garments components (e.g., fabrics, buttons), crockery and decorative items.
In 1920, Hermann Staudinger published his seminal work "Über Polymerisation", in which he proposed that polymers were in fact long chains of atoms linked by covalent bonds. His work was debated at length, but eventually it was accepted by the scientific community. Because of this work, Staudinger was awarded the Nobel Prize in 1953.
After the 1930s polymers entered a golden age during which new types were discovered and quickly given commercial applications, replacing naturally-sourced materials. This development was fuelled by an industrial sector with a strong economic drive and it was supported by a broad academic community that contributed innovative syntheses of monomers from cheaper raw material, more efficient polymerisation processes, improved techniques for polymer characterisation and advanced, theoretical understanding of polymers.
Since 1953, six Nobel prizes have been awarded in the area of polymer science, excluding those for research on biological macromolecules. This further testifies to its impact on modern science and technology. As Lord Todd summarised in 1980, "I am inclined to think that the development of polymerization is perhaps the biggest thing that chemistry has done, where it has had the biggest effect on everyday life". | 0 | Theoretical and Fundamental Chemistry |
Thermodynamic scale differs from empirical scales in that it is absolute. It is based on the fundamental laws of thermodynamics or statistical mechanics instead of some arbitrary chosen working material. Besides it covers full range of temperature and has simple relation with microscopic quantities like the average kinetic energy of particles (see equipartition theorem). In experiments ITS-90 is used to approximate thermodynamic scale due to simpler realization. | 0 | Theoretical and Fundamental Chemistry |
Among others, ISMP maintains and disseminates a list of "do not crush" medications, as well as clinical best practices. The ISMP's Medication Safety Self-Assessment tool has been used in surveys of medication safety in hospitals in the United States and elsewhere.
The ISMP frequently investigates and reports on medication errors that have occurred in practice. These investigations are often published in the peer-reviewed journal Hospital Pharmacy. | 1 | Applied and Interdisciplinary Chemistry |
When insulator sequences are located in close proximity to the promoter of a gene, it has been suggested that they might serve to stabilize enhancer-promoter interactions. When they are located farther away from the promoter, insulator elements would compete with the enhancer and interfere with activation of transcription. Loop formation is common in eukaryotes to bring distal elements (enhancers, promoters, locus control regions) into closer proximity for interaction during transcription. The mechanism of enhancer-blocking insulators then, if in the correct position, could play a role in regulating transcription activation. | 1 | Applied and Interdisciplinary Chemistry |
The GTEx project is a human genetics project aimed at understanding the role of genetic variation in shaping variation in the transcriptome across tissues. The project has collected a variety of tissue samples (> 50 different tissues) from more than 700 post-mortem donors. This has resulted in the collection of >11,000 samples. GTEx has helped understand the tissue-sharing and tissue-specificity of eQTLs. The genomic resource was developed to "enrich our understanding of how differences in our DNA sequence contribute to health and disease." | 1 | Applied and Interdisciplinary Chemistry |
Hypothyroidism is the most common thyroid abnormality associated with PFAS exposure. PFASs have been shown to decrease thyroid peroxidase, resulting in decreased production and activation of thyroid hormones in vivo. Other proposed mechanisms include alterations in thyroid hormone signaling, metabolism and excretion as well as function of nuclear hormone receptor. | 0 | Theoretical and Fundamental Chemistry |
ATP2A2 also known as sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2) is an ATPase associated with Darier's disease and Acrokeratosis verruciformis.
This gene encodes one of the SERCA Ca(2+)-ATPases, which are intracellular pumps located in the sarcoplasmic or endoplasmic reticula of muscle cells. This enzyme catalyzes the hydrolysis of ATP coupled with the translocation of calcium from the cytosol to the sarcoplasmic reticulum lumen, and is involved in calcium sequestration associated with muscular excitation and contraction. Alternative splicing results in multiple transcript variants encoding different isoforms. | 1 | Applied and Interdisciplinary Chemistry |
The Bessel function at its lower limit becomes
which converges to the Hagen-Poiseuille flow profile for steady flow for
or to a quasi-static pulse with parabolic profile when
In this case, the function is real, because the pressure and velocity waves are in phase. | 1 | Applied and Interdisciplinary Chemistry |
Side effects of the tablet form in conjunction with levodopa include, in decreasing order of frequency, nausea, hallucinations, confusion, depression, loss of balance, insomnia, increased involuntary movements, agitation, slow or irregular heart rate, delusions, hypertension, new or increased angina pectoris, and syncope. Most of the side effects are due to a high dopamine signaling, and can be alleviated by reducing the dose of levodopa.
The main side effects of the patch form for depression include application-site reactions, insomnia, diarrhea, and sore throat. The selegiline patch carries a black box warning about a possible increased risk of suicide, especially for young people, as do all antidepressants since 2007. | 0 | Theoretical and Fundamental Chemistry |
Trimyristin is a saturated fat and the triglyceride of myristic acid with the chemical formula CHO. Trimyristin is a white to yellowish-gray solid that is insoluble in water, but soluble in ethanol, acetone, benzene, chloroform, dichloromethane, ether, and TBME. | 1 | Applied and Interdisciplinary Chemistry |
SINEs are characterized by their different modules, which are essentially a sectioning of their sequence. SINEs can, but do not necessarily have to possess a head, a body, and a tail. The head, is at the 5 end of short-interspersed nuclear elements and is an evolutionarily derived from an RNA synthesized by RNA Polymerase III such as ribosomal RNAs and tRNAs; the 5 head is indicative of which endogenous element that SINE was derived from and was able to parasitically utilize its transcriptional machinery. For example, the 5' of the Alu sine is derived from 7SL RNA, a sequence transcribed by RNA Polymerase III which codes for the RNA element of SRP, an abundant ribonucleoprotein. The body of SINEs possess an unknown origin but often share much homology with a corresponding LINE which thus allows SINEs to parasitically co-opt endonucleases coded by LINEs (which recognize certain sequence motifs). Lastly, the 3′ tail of SINEs is composed of short simple repeats of varying lengths; these simple repeats are sites where two (or more) short-interspersed nuclear elements can combine to form a dimeric SINE. Short-interspersed nuclear elements which only possess a head and tail are called simple SINEs whereas short-interspersed nuclear elements which also possess a body or are a combination of two or more SINEs are complex SINEs. | 1 | Applied and Interdisciplinary Chemistry |
Erythropoietin receptor has been shown to interact with:
* CRKL,
* Erythropoietin,
* Grb2,
* Janus kinase 2,
* LYN,
* PIK3R1,
* PTPN6,
* SOCS2,
* SOCS3, and
* STAT5A. | 1 | Applied and Interdisciplinary Chemistry |
In a baroclinic fluid, the thermal-wind balance holds, which is a combination of the geostrophic balance and the hydrostatic balance. This implies that isopycnals can slope with respect to the isobars. Furthermore, this also results in changing horizontal velocities with height as a result of horizontal temperature and therefore density gradients.
Under the thermal-wind balance, geostrophic balance and hydrostatic balance, a flow is in equilibrium. However, this is not the equilibrium of least energy. A reduction in slope of the isopycnals would lower the center of gravity and therefore also the potential energy. It would also reduce the pressure gradient, leading to an increase in the kinetic energy. However, under the thermal-wind balance, a decrease in slope of the isopycnals cannot occur spontaneously. It requires a change of potential vorticity. Under certain conditions, slight perturbations of the equilibrium under the thermal-wind balance may increase, leading to larger perturbations from the initial state and thus the growth of an instability.
It is often considered that baroclinic instability is the mechanism which extracts potential energy stored in horizontal density gradients and uses this "eddy potential energy" to drive eddies. | 1 | Applied and Interdisciplinary Chemistry |
Metal-induced embrittlement (MIE) is the embrittlement caused by diffusion of metal, either solid or liquid, into the base material. Metal induced embrittlement occurs when metals are in contact with low-melting point metals while under tensile stress. The embrittler can be either solid (SMIE) or liquid (liquid metal embrittlement). Under sufficient tensile stress, MIE failure occurs instantaneously at temperatures just above melting point. For temperatures below the melting temperature of the embrittler, solid-state diffusion is the main transport mechanism. This occurs in the following ways:
* Diffusion through grain boundaries near the crack of matrix
* Diffusion of first monolayer heterogeneous surface embrittler atoms
* Second monolayer heterogenous surface diffusion of embrittler
* Surface diffusion of the embrittler over a layer of embrittler
The main mechanism of transport for SMIE is surface self-diffusion of the embrittler over a layer of embrittler that’s thick enough to be characterized as self-diffusion at the crack tip. In comparison, LMIE dominant mechanism is bulk liquid flow that penetrates at the tips of cracks. | 1 | Applied and Interdisciplinary Chemistry |
Metallography is the study of the physical structure and components of metals, by using microscopy.
Ceramic and polymeric materials may also be prepared using metallographic techniques, hence the terms ceramography, plastography and, collectively, materialography. | 1 | Applied and Interdisciplinary Chemistry |
RT can be used to synthesize actinide complexes. RT has been used to synthesize uranium halides using uranium metal and mercury halides as shown:
:U + HgX → UX + Hg (X = Cl, Br, I)
This actinide RT reaction can be done with multiple mercury compounds to coordinate ligands other than halogens to the metal:
:2 U + 3 (CH)Hg + HgCl → 2 (CH)UCl + 4 Hg | 0 | Theoretical and Fundamental Chemistry |
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