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In protein structures determined by X-ray crystallography, poor peptide-plane geometry has been described as a common problem; many structures need correction by peptide-plane flips or peptide bond flips. | 1 | Applied and Interdisciplinary Chemistry |
A subgenomic promoter is a promoter added to a virus for a specific heterologous gene, resulting in the formation of mRNA for that gene alone. Many positive-sense RNA viruses produce these subgenomic mRNAs (sgRNA) as one of the common infection techniques used by these viruses and generally transcribe late viral genes. Subgenomic promoters range from 24 nucleotide (Sindbis virus) to over 100 nucleotides (Beet necrotic yellow vein virus) and are usually found upstream of the transcription start. | 1 | Applied and Interdisciplinary Chemistry |
In any form of chromatography, the rate at which the solute moves down the column is a direct reflection of the percentage of time the solute spends in the mobile phase. To achieve separation in either elution or displacement chromatography, there must be appreciable differences in the affinity of the respective solutes for the stationary phase. Both methods rely on movement down the column to amplify the effect of small differences in distribution between the two phases. Distribution between the mobile and stationary phases is described by the binding isotherm, a plot of solute bound to (or partitioned into) the stationary phase as a function of concentration in the mobile phase. The isotherm is often linear, or approximately so, at low concentrations, but commonly curves (concave-downward) at higher concentrations as the stationary phase becomes saturated. | 0 | Theoretical and Fundamental Chemistry |
A Euclidean graph in three-dimensional space is a pair (V, E), where V is a set of vertices (sometimes called points or nodes) and E is a set of edges (sometimes called bonds or spacers) where each edge joins two vertices. There is a tendency in the polyhedral and chemical literature to refer to geometric graphs as nets (contrast with polyhedral nets), and the nomenclature in the chemical literature differs from that of graph theory. | 0 | Theoretical and Fundamental Chemistry |
Similar to bromocresol green, the structure of bromocresol purple changes with pH. Changing the level of acidity causes a shift in the equilibrium between two different structures that have different colors. In near-neutral or alkaline solution, the chemical has a sulfonate structure that gives the solution a purple color. As the pH decreases, it converts to a sultone (cyclic sulfonic ester) that colors the solution yellow. In some microbiology tests, this change is used as an indicator of bacterial growth. | 0 | Theoretical and Fundamental Chemistry |
During the separation, the cell only needs to be suspended in a buffer solution and enter a centrifuge, the whole processes does not involve any chemical (e.g. staining) and physical (e.g. attachment of antibody, lyses of cell membrane) effect on the cells, so the cell will remain unchanged before and after the separation. Because of this, the collected cells can be used for further experiment or further separation by other techniques. Finally the CCE rely on centrifugal force and the counter flow drag force to separate the cells, so the speed of separation is fast. In summary:
*Minimum effect on the cells
*High recovery viability
*Separated cells can be used further
*Rapid | 0 | Theoretical and Fundamental Chemistry |
MIKE 21 comprises three simulation engines:
Single Grid: the -dependent non-linear equations of continuity and conservation of momentum are solved by implicit finite difference techniques with the variables defined on a space-staggered rectangular grid.
Multiple Grids: the Multiple Grids version uses the same simulation engine and numerical approach as the single grid version. However, it provides the possibility of refining areas of special interest within the model area (nesting). All domains within the model area are dynamically linked.
Flexible Mesh: is an unstructured mesh and uses a cell-centred finite volume solution technique. The mesh is based on linear triangular elements. | 1 | Applied and Interdisciplinary Chemistry |
It has been proposed that mutations in gatekeeper genes could, to an extent, offer a sort of selective advantage to the individual in which the change occurs. This is because cells with these mutations are able to replicate at a faster rate than nearby cells. This is known as "increased somatic fitness". Caretaker genes, on the other hand, confer selective disadvantage because the result is inherently decreased cellular success. However, increased somatic fitness could also arise from a mutation in a caretaker gene if mutations in tumor suppressor genes increase the net reproductive rate of the cell.
Although mutations in gatekeeper genes may lead to the same result as those of caretaker genes, namely cancer, the transcripts that gatekeeper genes encode are significantly different from those encoded by caretaker genes.
In many cases, gatekeeper genes encode a system of checks and balances that monitor cell division and death. In cases of tissue damage, for example, gatekeeper genes would ensure that balance of cell growth over cellular death remains in check. In the presence of competent gatekeeper genes, mutations of other genes would not lead to on-going growth imbalances.
Whether or not mutations in these genes confer beneficial or deleterious effects to the animal depends partially on the environmental context in which these changes occur, a context encoded by the landscaper genes. For example, tissues of the skin and colon reside in compartments of cells that rarely mix with one another. These tissues are replenished by stem cells. Mutations that occur within these cell lineages remain confined to the compartment in which they reside, increasing the future risk of cancer. This is also protective, however, because the cancer will remain confined to that specific area, rather than invading the rest of the body, a phenomenon known as metastasis.
In areas of the body compartmentalized into small subsets of cells, mutations that lead to cancer most often begin with caretaker genes. On the other hand, cancer progression in non-compartmentalized or large cell populations may be a result of initial mutations in gatekeepers.
These delineations offer a suggestion why different types of tissue within the body progress to cancer by differing mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
Devices that integrate multiple laboratory functions on a single chip of only a few square millimeters or centimeters in size and that are capable of handling extremely small fluid volumes down to less than picoliters. | 0 | Theoretical and Fundamental Chemistry |
The formation of amide is promoted by CDI. Although the reactivity of CDI is less than acid chlorides, it is more easily handled and avoids the use of thionyl chloride in acid chloride formation, which can cause side reactions. An early application of this type of reaction was noted in the formation of peptide bonds (with CO formation as a driving force). The proposed mechanism for the reaction between a carboxylic acid and CDI is presented below.
In the realm of peptide synthesis, this product may be treated with an amine such as that found on an amino acid to release the imidazole group and couple the peptides. The side products, carbon dioxide and imidazole, are relatively innocuous. Racemization of the amino acids also tends to be minimal, reflecting the mild reaction conditions.
CDI can also be used for esterification, although alcoholysis requires heat or the presence of a potent nucleophiles as sodium ethoxide, or other strong bases like NaH. This reaction has generally good yield and wide scope, although forming the ester from tertiary alcohols when the acid reagent has a relatively acidic α-proton is troublesome, since C-C condensations can occur, though this itself may be a desirable reaction. A similar reaction involving thiols and selenols can yield the corresponding esters. The alcohol reaction can also be used to form glycosidic bonds.
Similarly, an acid can be used in the place of an alcohol to form the anhydride, although dicyclohexylcarbodiimide is a more typical reagent. The equilibrium can be shifted in the favor of the anhydride by utilizing an acid in a 2:1 ratio that forms an insoluble salt with the imidazole. Typical acids are trifluoro- and trichloroacetic acids. Symmetric anhydrides can thus be formed by replacing this trifluoro- or trichloroacetyl group with the acid that was used to form the original reagent.
Another related reaction is the reaction of formic acid with CDI to form the formylized imidazole. This reagent is a good formylating agent and can regenerate the unsubstituted imidazole (with formation of carbon monoxide) upon heating.
Yet another reaction involves the acylation of triphenylalkelynephosphoranes.
::(CH)P=CHR + R-CO-Im → (CH)P-CHR-COR + ImH)P-CHR-COR + (CH)P=CHR → (CH)P=CR-COR + (CH)P-CHR
These can undergo the Wittig reaction to form α,β unsaturated ketones or aldehydes.
The reagent can even undergo reaction with peroxide to form the peroxycarboxylic acid, which can react further to form diacyl peroxides. The imidazole group is also reduced by LiAlH to form aldehydes from the carboxylic acid (rather than amines or alcohols). The reagent can also be reacted with Grignard reagents to form ketones.
A C-C acylation reaction can occur with a malonic ester-type compound, in the following scheme useful for syntheses of macrolide antibiotics. | 0 | Theoretical and Fundamental Chemistry |
Reduction by alkoxyaluminium hydrides is thought in most cases to proceed by a polar mechanism. Hydride transfer to the organic substrate generates an organic anion, which is neutralized either by protic solvent or upon acidic workup.
Reductions of α,β-unsaturated carbonyl compounds may occur in a 1,2 sense (direct addition) or a 1,4 sense (conjugate addition). The tendency to add in a 1,4 sense is correlated with the softness of the hydride reagent according to Pearson's hard-soft acid-base theory. Experimental results agree with the theory—softer hydride reagents afford higher yields of the conjugate reduction product.
A few substrates, including diaryl ketones, diarylalkenes, and anthracene, are known to undergo reduction by single-electron transfer pathways with lithium aluminium hydride.
Metal alkoxylaluminium hydride reagents are well characterized in a limited number of cases. Precise characterization is complicated in some cases by disproportionation, which converts alkyoxyaluminium hydrides into alkoxyaluminates and metal aluminium hydride:<br> | 0 | Theoretical and Fundamental Chemistry |
Friedrich Wöhler () FRS(For) HonFRSE (31 July 180023 September 1882) was a German chemist known for his work in both organic and inorganic chemistry, being the first to isolate the chemical elements beryllium and yttrium in pure metallic form. He was the first to prepare several inorganic compounds, including silane and silicon nitride.
Wöhler is also known for seminal contributions in organic chemistry, in particular, the Wöhler synthesis of urea. His synthesis of the organic compound urea in the laboratory from inorganic substances contradicted the belief that organic compounds could only be produced by living organisms due to a "life force". However, the exact extent of Wöhler's role in diminishing the belief in vitalism is considered by some to be questionable. | 1 | Applied and Interdisciplinary Chemistry |
T independent antigen elicits antibody production by B lymphocytes without T lymphocyte involvement. There are 2 distinct subgroups of TI antigens, different in mechanism of activating B lymphocytes. TI-1 antigen, which has an activity that can directly activate B cells and TI-2 antigen, which has highly repetitive structure and causes simultaneous cross-linking of specific B cell receptors (BCR) on B lymphocyte. The most commonly released isotype of antibodies in this type of immune reaction is low affinity IgM. | 1 | Applied and Interdisciplinary Chemistry |
Chemistry education is important because the field of chemistry is fundamental to our world. The universe is subject to the laws of chemistry, while human beings depend on the orderly progress of chemical reactions within their bodies. Described as the central science, chemistry connects physical sciences with the life sciences and applied sciences. Chemistry has applications in food, medicine, industry, the environment, and other areas. Learning chemistry allows students to learn about the scientific method and gain skills in critical thinking, deductive reasoning, problem-solving, and communication. Teaching chemistry to students at a young age can increase student interest in STEM careers. Chemistry also provides students with many transferable skills that can be applied to any career. | 1 | Applied and Interdisciplinary Chemistry |
In hydroesterification, alkenes and alkynes insert into the bond of carboxylic acids. Vinyl acetate is produced industrially by the addition of acetic acid to acetylene in the presence of zinc acetate catalysts: Presently, zinc acetate is used as the catalyst:
Vinyl acetate can also be produced by palladium-catalyzed reaction of ethylene, acetic acid, and oxygen:
Silicotungstic acid is used to manufacture ethyl acetate by the alkylation of acetic acid by ethylene: | 0 | Theoretical and Fundamental Chemistry |
The Beilstein Journal of Organic Chemistry is a peer-reviewed open-access scientific journal established in 2005. It is published by the Beilstein Institute for the Advancement of Chemical Sciences, a German non-profit foundation. The editor-in-chief is Peter Seeberger (Max Planck Institute of Colloids and Interfaces).
According to the Journal Citation Reports, the journal has a 2020 impact factor of 2.88.
Scientific videos are available for selected articles of the journal. | 0 | Theoretical and Fundamental Chemistry |
In principle, cis–trans notation should not be used for alkenes with two or more different substituents. Instead the E–Z notation is used based on the priority of the substituents using the Cahn–Ingold–Prelog (CIP) priority rules for absolute configuration. The IUPAC standard designations E and Z are unambiguous in all cases, and therefore are especially useful for tri- and tetrasubstituted alkenes to avoid any confusion about which groups are being identified as cis or trans to each other.
Z (from the German ) means "together". E (from the German ) means "opposed" in the sense of "opposite". That is, Z has the higher-priority groups cis to each other and E has the higher-priority groups trans to each other. Whether a molecular configuration is designated E or Z is determined by the CIP rules; higher atomic numbers are given higher priority. For each of the two atoms in the double bond, it is necessary to determine the priority of each substituent. If both the higher-priority substituents are on the same side, the arrangement is Z; if on opposite sides, the arrangement is E.
Because the cis–trans and E–Z systems compare different groups on the alkene, it is not strictly true that Z corresponds to cis and E corresponds to trans. For example, trans-2-chlorobut-2-ene (the two methyl groups, C1 and C4, on the but-2-ene backbone are trans to each other) is (Z)-2-chlorobut-2-ene (the chlorine and C4 are together because C1 and C4 are opposite). | 0 | Theoretical and Fundamental Chemistry |
Sulfuric acid is used in large quantities by the iron and steelmaking industry to remove oxidation, rust, and scaling from rolled sheet and billets prior to sale to the automobile and major appliances industry. Used acid is often recycled using a spent acid regeneration (SAR) plant. These plants combust spent acid with natural gas, refinery gas, fuel oil or other fuel sources. This combustion process produces gaseous sulfur dioxide () and sulfur trioxide () which are then used to manufacture "new" sulfuric acid. SAR plants are common additions to metal smelting plants, oil refineries, and other industries where sulfuric acid is consumed in bulk, as operating a SAR plant is much cheaper than the recurring costs of spent acid disposal and new acid purchases.
Hydrogen peroxide () can be added to sulfuric acid to produce piranha solution, a powerful but very toxic cleaning solution with which substrate surfaces can be cleaned. Piranha solution is typically used in the microelectronics industry, and also in laboratory settings to clean glassware. | 0 | Theoretical and Fundamental Chemistry |
By changing specific amino acids by mutating the corresponding DNA base-pairs in the plasmids used, the importance of those amino acid residues in maintaining the interaction can be determined.
After using bacterial cell-based method to select DNA-binding proteins, it is necessary to check the specificity of these domains as there is a limit to the extent to which the bacterial cell genome can act as a sink for domains with an affinity for other sequences (or indeed, a general affinity for DNA). | 1 | Applied and Interdisciplinary Chemistry |
Inverse beta decay, commonly abbreviated to IBD, is a nuclear reaction involving an electron antineutrino scattering off a proton, creating a positron and a neutron. This process is commonly used in the detection of electron antineutrinos in neutrino detectors, such as the first detection of antineutrinos in the Cowan–Reines neutrino experiment, or in neutrino experiments such as KamLAND and Borexino. It is an essential process to experiments involving low-energy neutrinos (< 60 MeV) such as those studying neutrino oscillation, reactor neutrinos, sterile neutrinos, and geoneutrinos. | 0 | Theoretical and Fundamental Chemistry |
In female elephants, the two compounds 3-ethyl phenol and 2-ethyl 4,5 dimethylphenol have been detected in urine samples. Temporal glands secretion examination showed the presence of phenol, m-cresol and p-cresol (4-methyl phenol) during musth in male elephants.
p-Cresol and o-cresol are also components of the human sweat. P-cresol is also a major component in pig odor.
4-Ethylphenol, 1,2-dihydroxybenzene, 3-hydroxyacetophenone, 4-methyl-1,2-dihydroxybenzene, 4-methoxyacetophenone, 5-methoxysalicylic acid, salicylaldehyde, and 3-hydroxybenzoic acid are components of castoreum, the exudate from the castor sacs of the mature North American beaver (Castor canadensis) and the European beaver (Castor fiber), used in perfumery. | 0 | Theoretical and Fundamental Chemistry |
In continuum mechanics and thermodynamics, a control volume (CV) is a mathematical abstraction employed in the process of creating mathematical models of physical processes. In an inertial frame of reference, it is a fictitious region of a given volume fixed in space or moving with constant flow velocity through which the continuuum (a continuous medium such as gas, liquid or solid) flows. The closed surface enclosing the region is referred to as the control surface.
At steady state, a control volume can be thought of as an arbitrary volume in which the mass of the continuum remains constant. As a continuum moves through the control volume, the mass entering the control volume is equal to the mass leaving the control volume. At steady state, and in the absence of work and heat transfer, the energy within the control volume remains constant. It is analogous to the classical mechanics concept of the free body diagram. | 0 | Theoretical and Fundamental Chemistry |
After receiving his PhD, Corson spent the next two years as a post-doctoral fellow in the Radiation Laboratory at the University of California, Berkeley to help construct a 60-inch cyclotron. In 1939, Emilio Segrè suggested that the cyclotron could be used to bombard bismuth (element 83) with alpha particles to produce the then-unknown element 85. Corson, Kenneth Ross MacKenzie, and Segrè discovered and isolated the element in 1940. They named it "astatine" in 1947.
In 1946 Corson came to Cornell University as an assistant professor of physics and helped design the Cornell synchrotron. He was appointed associate professor of physics in 1947, became a full professor in 1956, was named chairman of the physics department in 1956, and became dean of the College of Engineering in 1959. Following the 1969 resignation of James A. Perkins, Corson became president of Cornell and served until 1977 after which he served for three years as chancellor. In 1979, he was elected by the Board of Trustees as president emeritus. | 1 | Applied and Interdisciplinary Chemistry |
Alkynylation finds use in synthesis of pharmaceuticals, particularly in the preparation of steroid hormones. For example, ethynylation of 17-ketosteroids produces important contraceptive medications known as progestins. Examples include drugs such as Norethisterone, Ethisterone, and Lynestrenol. Hydrogenation of these compounds produces anabolic steroids with oral bioavailability, such as Norethandrolone.
Alkynylation is used to prepare commodity chemicals such as propargyl alcohol, butynediol, 2-methylbut-3-yn-2-ol (a precursor to isoprenes such as vitamin A), 3-hexyne-2,5-diol (a precursor to Furaneol), and sulcatone (a precursor to Linalool). | 0 | Theoretical and Fundamental Chemistry |
The International Chemistry Olympiad (IChO) is an annual competition for the world’s most talented chemistry students at the secondary school level. Nations around the world send a team of four students who are tested on their chemistry knowledge and skills in a five-hour laboratory practical exam and a five-hour written theoretical examination that are held on separate days with the practical examination usually being before the theoretical examination. Countries who wish to participate in the IChO must send observers to two consecutive Olympiads before their students can participate in the event. Presently, around 80 countries participate in the International Chemistry Olympiad.
All participants are ranked based on their individual scores and no official team scores are given. Gold medals are awarded to the top 12% of students, silver medals are awarded to the next 22% of students, and bronze medals are awarded to the next 32% of students. Honorable mentions are awarded to the top 10% of non medalist participants. One special award is given to the student that achieves the highest score overall. Two separate special awards are given to the students who get the best score in the theoretical and practical examinations. Preparation for the International Chemistry Olympiad demands a high level of understanding and interest in chemistry and an outstanding ability to relate chemical subjects with one another as well as with the practical world. | 1 | Applied and Interdisciplinary Chemistry |
Ocean tracers are used to deduce small scale flow patterns, large-scale ocean circulation, water mass formation and changes, "dating" of water masses, and carbon dioxide storage and uptake.
Temperature, salinity, density, and other conservative tracers are often used to track currents, circulation and water mass mixing. An interesting example was when 28,000 plastic ducks fell over board from a container ship in the middle of the Pacific Ocean. The following twelve years oceanographers recorded where the ducks washed ashore, some thousands of miles from the spill site, and this data was used to calibrate and verify the circulation patterns of the North Pacific Gyre.
Transient tracers change over time, such as radioactive material (Tritium and Cesium-137) and chemical concentrations (CFCs and SF6), which are used to date water masses and can also track mixing. In the mid-1900s, Nuclear weapons testing and chemical production released tons of compounds that are not naturally found in the environment. While extremely unfortunate, scientists were able to use the concentrations of anthropogenic compounds and half-lives of radioactive material to determine how old a water body is. The Fukushima nuclear disaster was really well studied by oceanographers, who tracked the radioactive material spread throughout the Pacific Ocean, and used that to better understand ocean currents and mixing patterns.
Biological tracers can also be used to track water masses in the ocean. Phytoplankton blooms can be seen by satellites and move with the changing currents. They can be used as a "check point" to see how well water masses are mixing. Subtropical water is often warm, which is ideal for phytoplankton, but nutrient poor, which inhibits their growth, while subpolar water is cold and nutrient rich. When these two types of water masses mix, such as the Kuroshio Current in the north Pacific, it often causes huge phytoplankton blooms, because they now how conditions they need to grow—warm temperatures and high nutrients. Vertical mixing and eddy formation can also cause phytoplankton blooms, and these blooms are tracked by satellites to observe current patterns and mixing. | 1 | Applied and Interdisciplinary Chemistry |
A pair-instability supernova is believed to result from runaway oxygen fusion in the core of a massive, 130–250 solar mass, low to moderate metallicity star. According to theory, in such a star, a large but relatively low density core of nonfusing oxygen builds up, with its weight supported by the pressure of gamma rays produced by the extreme temperature. As the core heats further, the gamma rays eventually begin to pass the energy threshold needed for collision-induced decay into electron-positron pairs, a process called pair production. This causes a drop in the pressure within the core, leading it to contract and heat further, causing more pair production, a further pressure drop, and so on. The core starts to undergo gravitational collapse. At some point this ignites runaway oxygen fusion, releasing enough energy to obliterate the star. These explosions are rare, perhaps about one per 100,000 supernovae. | 1 | Applied and Interdisciplinary Chemistry |
Aquatic and marine dead zones can be caused by an increase in nutrients (particularly nitrogen and phosphorus) in the water, known as eutrophication. These nutrients are the fundamental building blocks of single-celled, plant-like organisms that live in the water column, and whose growth is limited in part by the availability of these materials. With more available nutrients, single-celled aquatic organisms (such as algae and cyanobacteria) have the resources necessary to exceed their previous growth limit and begin to multiply at an exponential rate. Exponential growth leads to rapid increases in the density of certain types of these phytoplankton, a phenomenon known as an algal bloom.
Limnologist David Schindler, whose research at the Experimental Lakes Area led to the banning of harmful phosphates in detergents, warned about algal blooms and dead zones,
The major groups of algae are cyanobacteria, green algae, dinoflagellates, coccolithophores and diatom algae. An increase in the input of nitrogen and phosphorus generally causes cyanobacteria to bloom. Other algae are consumed and thus do not accumulate to the same extent as cyanobacteria. Cyanobacteria are not good food for zooplankton and fish and hence accumulate in water, die, and then decompose. The bacterial degradation of their biomass consumes the oxygen in the water, thereby creating the state of hypoxia.
Dead zones can be caused by natural and by anthropogenic factors. Natural causes include coastal upwelling, changes in wind, and water circulation patterns. Other environmental factors that determine the occurrence or intensity of a dead zone include long water residence times, high temperatures, and high levels of sunlight penetration through the water column.
Additionally, natural oceanographic phenomena can cause deoxygenation of parts of the water column. For example, enclosed bodies of water, such as fjords or the Black Sea, have shallow sills at their entrances, causing water to be trapped there for a long time. The eastern tropical Pacific Ocean and northern Indian Ocean have lowered oxygen concentrations which are thought to be in regions where there is minimal circulation to replace the oxygen that is consumed. These areas are also known as oxygen minimum zones (OMZ). In many cases, OMZs are permanent or semi-permanent areas.
Remains of organisms found within sediment layers near the mouth of the Mississippi River indicate four hypoxic events before the advent of synthetic fertilizer. In these sediment layers, anoxia-tolerant species are the most prevalent remains found. The periods indicated by the sediment record correspond to historic records of high river flow recorded by instruments at Vicksburg, Mississippi.
Changes in ocean circulation triggered by ongoing climate change could also add or magnify other causes of oxygen reductions in the ocean.
Anthropogenic causes include use of chemical fertilizers and their subsequent presence in water runoff and groundwater, direct sewage discharge into rivers and lakes, and nutrient discharge into groundwater from large, accumulated quantities of animal waste. Use of chemical fertilizers is considered the major human-related cause of dead zones around the world. However, runoff from sewage, urban land use, and fertilizers can also contribute to eutrophication.
In August 2017, a report suggested that the US meat industry and agroeconomic system are predominantly responsible for the largest-ever dead zone in the Gulf of Mexico. Soil runoff and leached nitrate, exacerbated by agricultural land management and tillage practices as well as manure and synthetic fertilizer usage, contaminated water from the Heartland to the Gulf of Mexico. A large portion of the plant matter by-products from crops grown in this region are used as major feed components in the production of meat animals for agribusiness companies, like Tyson and Smithfield Foods. Over 86% of the livestock feed is inedible for humans.
Notable dead zones in the United States include the northern Gulf of Mexico region, surrounding the outfall of the Mississippi River, the coastal regions of the Pacific Northwest, and the Elizabeth River in Virginia Beach, all of which have been shown to be recurring events over the last several years. Around the world, dead zones have developed in continental seas, such as the Baltic Sea, Kattegat, Black Sea, Gulf of Mexico, and East China Sea, all of which are major fishery areas. | 0 | Theoretical and Fundamental Chemistry |
Thermonuclear weapons, also known as hydrogen bombs, are nuclear weapons that use energy released by a burning plasma's fusion reactions to produce part of their explosive yield. This is in contrast to pure-fission weapons, which produce all of their yield from a neutronic nuclear fission reaction. The first thermonuclear explosion, and thus the first man-made burning plasma, was the Ivy Mike test carried out by the United States in 1952. All high-yield nuclear weapons today are thermonuclear weapons. | 0 | Theoretical and Fundamental Chemistry |
Naturally occurring asphalt/bitumen, a type of pitch, is a viscoelastic polymer. This means that even though it seems to be solid at room temperature and can be shattered with a hard impact, it is actually fluid and will flow over time, but extremely slowly. The pitch drop experiment taking place at University of Queensland is a long-term experiment which demonstrates the flow of a piece of pitch over many years. For the experiment, pitch was put in a glass funnel and allowed to slowly drip out. Since the pitch was allowed to start dripping in 1930, only nine drops have fallen. It was calculated in the 1980s that the pitch in the experiment has a viscosity approximately 230 billion (2.3×10) times that of water. The eighth drop fell on 28 November 2000, and the ninth drop fell on 17 April 2014. Another experiment was started by a colleague of Nobel Prize winner Ernest Walton in the physics department of Trinity College in Ireland in 1944. Over the years, the pitch had produced several drops, but none had been recorded. On July 11, 2013, scientists at Trinity College caught pitch dripping from a funnel on camera for the first time.
Winchester College has a pitch glacier demonstration which has been running since 21 July 1906, but does not have records of regular measurements. | 0 | Theoretical and Fundamental Chemistry |
Caesium-137 (), cesium-137 (US), or radiocaesium, is a radioactive isotope of caesium that is formed as one of the more common fission products by the nuclear fission of uranium-235 and other fissionable isotopes in nuclear reactors and nuclear weapons. Trace quantities also originate from spontaneous fission of uranium-238. It is among the most problematic of the short-to-medium-lifetime fission products. Caesium-137 has a relatively low boiling point of and easily becomes volatile when released suddenly at high temperature, as in the case of the Chernobyl nuclear accident and with atomic explosions, and can travel very long distances in the air. After being deposited onto the soil as radioactive fallout, it moves and spreads easily in the environment because of the high water solubility of caesium's most common chemical compounds, which are salts. Caesium-137 was discovered by Glenn T. Seaborg and Margaret Melhase. | 0 | Theoretical and Fundamental Chemistry |
The Sullivan reaction is a chemical test used for detecting the presence of cysteine or cystine in proteins. A red colour appears when a protein with cysteine or cystine is heated with sodium 1,2-naphthoquinone-4-sulfonate (Folin's reagent) and sodium dithionite under alkaline conditions. This was pioneered by the American organic and industrial chemist Eugene Cornelius Sullivan (1872–1962). | 0 | Theoretical and Fundamental Chemistry |
Currently, there are two main types of silencers in DNA, which are the classical silencer element and the non-classical negative regulatory element (NRE). In classical silencers, the gene is actively repressed by the silencer element, mostly by interfering with general transcription factor (GTF) assembly. NREs passively repress the gene, usually by inhibiting other elements that are upstream of the gene. Of the NREs, there are certain silencers that are orientation-dependent meaning that the binding factor binds in a particular direction relative to other sequences. Promoter-dependent silencers are understood to be silencer elements because they are position and orientation-dependent but must also use a promoter-specific factor. There has been a recent discovery of Polycomb-group Response Elements (PREs), which can allow and inhibit repression depending on the protein bound to it, and the presence of non-coding transcription. | 1 | Applied and Interdisciplinary Chemistry |
Orbiting bodies can also be heated by tidal heating, geothermal energy which is driven by radioactive decay in the core of the planet, or accretional heating. These internal processes will cause the effective temperature (a blackbody temperature that produces the observed radiation from a planet) to be warmer than the equilibrium temperature (the blackbody temperature that one would expect from solar heating alone).
For example, on Saturn, the effective temperature is approximately 95 K, compared to an equilibrium temperature of about 63 K. This corresponds to a ratio between power emitted and solar power received of ~2.4, indicating a significant internal energy source. Jupiter and Neptune have ratios of power emitted to solar power received of 2.5 and 2.7, respectively.
Close correlation between the effective temperature and equilibrium temperature of Uranus can be taken as evidence that processes producing an internal flux are negligible on Uranus compared to the other giant planets.
Earth has insufficient geothermal heating to significantly affect its global temperature, with geothermal heating supplying only 0.03% of Earth's total energy budget. | 0 | Theoretical and Fundamental Chemistry |
In crystallography and the theory of infinite vertex-transitive graphs, the coordination sequence of a vertex is an integer sequence that counts how many vertices are at each possible distance from . That is, it is a sequence
where each is the number of vertices that are steps away from . If the graph is vertex-transitive, then the sequence is an invariant of the graph that does not depend on the specific choice of . Coordination sequences can also be defined for sphere packings, by using either the contact graph of the spheres or the Delaunay triangulation of their centers, but these two choices may give rise to different sequences.
As an example, in a square grid, for each positive integer , there are grid points that are steps away from the origin. Therefore, the coordination sequence of the square grid is the sequence
in which, except for the initial value of one, each number is a multiple of four.
The concept was proposed by Georg O. Brunner and Fritz Laves and later developed by Michael O'Keefe. The coordination sequences of many low-dimensional lattices and uniform tilings are known.
The coordination sequences of periodic structures are known to be quasi-polynomial. | 0 | Theoretical and Fundamental Chemistry |
A simple form of accumulator is an enclosed volume, filled with air. A vertical section of pipe, often enlarged diameter, may be enough and fills itself with air, trapped as the pipework fills.
Such accumulators typically do not have enough capacity to be useful for storing significant power since they cannot be pre-charged with high pressure gas, but they can act as a buffer to absorb fluctuations in pressure. They are used to smooth out the delivery from piston pumps. Another use is as a shock absorber to damp out water hammer; this application is an integral part of most ram pumps. Loss of air will result in loss of effectiveness. If air will be lost over time, the design must include some way to renew it. | 1 | Applied and Interdisciplinary Chemistry |
Conditions have been developed for the transformation of pseudoephedrine amides into enantiomerically enriched carboxylic acids, alcohols, aldehydes, and ketones - after cleavage, the auxiliary can be recovered and reused.
<br /> | 0 | Theoretical and Fundamental Chemistry |
Keith Christopher Rowley , (born 24 October 1949) is a Trinidadian politician serving as the seventh prime minister of Trinidad and Tobago, first elected into office on 9 September 2015 and again following the 2020 general election. He has led the People's National Movement (PNM) since May 2010 and was Leader of the Opposition from 2010 to 2015. He has also served as the Member of the House of Representatives for Diego Martin West since 1991. He is a volcanologist by profession, holding a doctorate in geology, specializing in geochemistry. | 0 | Theoretical and Fundamental Chemistry |
As discussed previously, the 4n rule mainly deals with clusters with electron counts of , in which approximately 4 electrons are on each vertex. As more electrons are added per vertex, the number of the electrons per vertex approaches 5. Rather than adopting structures based on deltahedra, the 5n-type clusters have structures based on a different series of polyhedra known as the 3-connected polyhedra, in which each vertex is connected to 3 other vertices. The 3-connected polyhedra are the duals of the deltahedra. The common types of 3-connected polyhedra are listed below.
The 5n rules are as follows.
Example: P
:Electron count: 4 × P = 4 × 5 = 20
:It is a 5n structure with n = 4, so it is tetrahedral
Example: PS
:Electron count 4 × P + 3 × S = 4 × 5 + 3 × 6 = 38
:It is a 5n + 3 structure with n = 7. Three vertices are inserted into edges
Example: PO
:Electron count 4 × P + 6 × O = 4 × 5 + 6 × 6 = 56
:It is a 5n + 6 structure with n = 10. Six vertices are inserted into edges | 0 | Theoretical and Fundamental Chemistry |
The quantum yield of a photochemical reaction describes the number of molecules undergoing a photochemical event per absorbed photon:
In a chemical photodegradation process, when a molecule dissociates after absorbing a light quantum, the quantum yield is the number of destroyed molecules divided by the number of photons absorbed by the system. Since not all photons are absorbed productively, the typical quantum yield will be less than 1.
Quantum yields greater than 1 are possible for photo-induced or radiation-induced chain reactions, in which a single photon may trigger a long chain of transformations. One example is the reaction of hydrogen with chlorine, in which as many as 10 molecules of hydrogen chloride can be formed per quantum of blue light absorbed.
Quantum yields of photochemical reactions can be highly dependent on the structure, proximity and concentration of the reactive chromophores, the type of solvent environment as well as the wavelength of the incident light. Such effects can be studied with wavelength-tunable lasers and the resulting quantum yield data can help predict conversion and selectivity of photochemical reactions.
In optical spectroscopy, the quantum yield is the probability that a given quantum state is formed from the system initially prepared in some other quantum state. For example, a singlet to triplet transition quantum yield is the fraction of molecules that, after being photoexcited into a singlet state, cross over to the triplet state. | 0 | Theoretical and Fundamental Chemistry |
In the United Kingdom, following animal experiments and the recommendations of a government commissioned expert committee, the Human Fertilisation and Embryology (Research Purposes) Regulations were passed in 2001 regulating and allowing research into human embryos. In 2004, Newcastle University applied for a license to develop pronuclear transfer to avoid the transmission of mitochondrial diseases, and was granted the license in 2005. Following further research by Newcastle and the Wellcome Trust, scientific review, public consultations, and debate, the UK government recommended that mitochondrial donation be legalized in 2013. In 2015 parliament passed the Human Fertilisation and Embryology (Mitochondrial Donation) Regulations, which came into force on 29 October 2015, making human mitochondrial donation legal in the UK. The Human Fertilisation and Embryology Authority (HFEA) was authorized to license and regulate medical centers which wanted to use human mitochondrial donation. In February 2016, the US National Academy of Sciences issued a report describing technologies then current and the surrounding ethical issues.
The HFEA Safety Committee issued its fourth report in November 2016 recommending procedures under which HFEA should authorize MRT, the HFEA issued their regulations in December 2016 and granted their first license (to Newcastle Fertility Centre; Newcastle upon Tyne Hospital NHS Foundation Trust led by Dr Jane Stewart as Person Responsible to the HFEA) in March 2017. Between August 2017 and January 2019, the HFEA received 15 requests from women to undergo MRT, of which 14 were granted. As of 2020, if children have been born from these procedures, the details have not been published because of the wishes of the parents.
Douglass Turnbull, the driving force behind mitochondrial research at Newcastle University, was awarded a knighthood in 2016. | 1 | Applied and Interdisciplinary Chemistry |
The global meridional Turner angle distributions at the surface and 300-m depth in different seasons are investigated by Tippins, Duncan & Tomczak, Matthias (2003), which indicates the overall stability of the ocean over a long-time scale. It's worth noting that 300-m depth is deep enough to be beneath the mixed layer during all seasons over most of the subtropics, yet shallow enough to be located entirely in the permanent thermocline, even in the tropics.
At the surface, as the temperature and salinity increase from the Subpolar Front towards subtropics, the Turner angle is positive, while it becomes negative due to the meridional salinity gradient being reversed on the equatorial side of the subtropical surface salinity maximum. Tu becomes positive again in the Pacific and Atlantic Oceans near the equator. A band of negative Tu in the South Pacific extends westward along 45°S, produced by the low salinities because of plenty of rainfall, off the southern coast of Chile.
In 300-m depth, it is dominated by positive Tu nearly everywhere except for only narrow bands of negative Turner angles. This reflects the shape of the permanent thermocline, which sinks to its greatest depth in the center of the oceanic gyres and then rises again towards the equator, and which also indicates a vertical structure in temperature and salinity where both decrease with depth. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen termination removes dangling bonds. All surface Si atoms are tetrahedral. Hydrogen termination confers stability in ambient environments. So again, the surface is both clean (of oxides) and relatively inert. These materials can be handled in air without special care for several minutes.
The Si-H bond in fact is stronger than the Si-Si bonds. Two kinds of Si-H centers are proposed, both featuring terminal Si-H bonds. One kind of site has one Si-H bond. The other kind of site features SiH centers.
Like organic hydrosilanes, the H-Si groups on the surface react with terminal alkenes and diazo groups. The reaction is called hydrosilylation. Many kinds of organic compounds with various functions can be introduced onto the silicon surface by the hydrosilylation of a hydrogen-terminated surface. The infrared spectrum of hydrogen-terminated silicon shows a band near 2090 cm, not very different from νSi-H for organic hydrosilanes. | 0 | Theoretical and Fundamental Chemistry |
The first proposed mechanism for a thermal rearrangement of an aromatic compound was for the automerization of naphthalene. It was suggested that the rearrangement of naphthalene occurred due to reversibility of the isomerization of azulene to naphthalene. This mechanism would therefore involve an azulene intermediate and is depicted below:
Subsequent work showed that the isomerization of azulene to naphthalene is not readily reversible ( the free energy of a naphthalene to azulene isomerization was too high - approximately 90 kcal/mol). A new reaction mechanism was suggested that involved a carbene intermediate and consecutive 1,2-hydrogen and 1,2-carbon shifts across the same C-C bond but in opposite directions. This is currently the preferred mechanism and is as follows: | 0 | Theoretical and Fundamental Chemistry |
Reynolds operators are used in fluid dynamics, functional analysis, and invariant theory, and the notation and definitions in these areas differ slightly. A Reynolds operator acting on φ is sometimes denoted by or .
Reynolds operators are usually linear operators acting on some algebra of functions, satisfying the identity
and sometimes some other conditions, such as commuting with various group actions. | 1 | Applied and Interdisciplinary Chemistry |
Starting as a biomass technology licensor In Summer of 2012 SGC Energia (SGCE) successfully commissioned a pilot multi tubular Fischer–Tropsch process unit and associated product upgrading units at the Pasadena, Tx Technology Center. The technology center focused on the development and operations of their XTLH solution which optimized processing of low value carbon waste streams into advanced fuels and wax products. This unit also serves as an operations training environment for the 1100 BPD Juniper GTL facility constructed in Westlake, LA. | 0 | Theoretical and Fundamental Chemistry |
To become functional, the 4-phospho-pantetheine sidechain of acyl-CoA molecules has to be attached to the PCP-domain by 4PP transferases (Priming) and the S-attached acyl group has to be removed by specialized associated thioesterases (TE-II) (Deblocking). | 1 | Applied and Interdisciplinary Chemistry |
The dynamic stall is one of the hazardous phenomena on helicopter rotors, which can cause the onset of large torsional airloads and vibrations on the rotor blades. Unlike fixed-wing aircraft, of which the stall occurs at relatively low flight speed, the dynamic stall on a helicopter rotor emerges at high airspeeds or/and during manoeuvres with high load factors of helicopters, when the angle of attack(AOA) of blade elements varies intensively due to time-dependent blade flapping, cyclic pitch and wake inflow. For example, during forward flight at the velocity close to V, velocity, never exceed, the advancing and retreating blades almost reach their operation limits whereas flows are still attached to the blade surfaces. That is, the advancing blades operate at high Mach numbers so low values of AOA is needed but shock-induced flow separation may happen, while the retreating blade operates at much lower Mach numbers but the high values of AoA result in the stall (also see advancing blade compressibility and retreating blade stall). | 1 | Applied and Interdisciplinary Chemistry |
Hyperconjugation was suggested as the reason for the increased stability of carbon-carbon double bonds as the degree of substitution increases. Early studies in hyperconjugation were performed by in the research group of George Kistiakowsky. Their work, first published in 1937, was intended as a preliminary progress report of thermochemical studies of energy changes during addition reactions of various unsaturated and cyclic compounds. The importance of hyperconjugation in accounting for this effect has received support from quantum chemical calculations. The key interaction is believed to be the donation of electron density from the neighboring C–H σ bond into the π* antibonding orbital of the alkene (σ→π*). The effect is almost an order of magnitude weaker than the case of alkyl substitution on carbocations (σ→p), since an unfilled p orbital is lower in energy, and, therefore, better energetically matched to a σ bond. When this effect manifests in the formation of the more substituted product in thermodynamically controlled E1 reactions, it is known as Zaitsevs rule, although in many cases the kinetic product also follows this rule. (See Hofmanns rule for cases where the kinetic product is the less substituted one.)
One set of experiments by Kistiakowsky involved collected heats of hydrogenation data during gas-phase reactions of a range of compounds that contained one alkene unit. When comparing a range of monoalkyl-substituted alkenes, they found any alkyl group noticeably increased the stability, but that the choice of different specific alkyl groups had little to no effect.
A portion of Kistiakowsky's work involved a comparison of other unsaturated compounds in the form of CH=CH(CH)n-CH=CH (n=0,1,2). These experiments revealed an important result; when n=0, there is an effect of conjugation to the molecule where the ΔH value is lowered by 3.5 kcal. This is likened to the addition of two alkyl groups into ethylene. Kistiakowsky also investigated open chain systems, where the largest value of heat liberated was found to be during the addition to a molecule in the 1,4-position. Cyclic molecules proved to be the most problematic, as it was found that the strain of the molecule would have to be considered. The strain of five-membered rings increased with a decrease degree of unsaturation. This was a surprising result that was further investigated in later work with cyclic acid anhydrides and lactones. Cyclic molecules like benzene and its derivatives were also studied, as their behaviors were different from other unsaturated compounds.
Despite the thoroughness of Kistiakowsky's work, it was not complete and needed further evidence to back up his findings. His work was a crucial first step to the beginnings of the ideas of hyperconjugation and conjugation effects. | 0 | Theoretical and Fundamental Chemistry |
A spectroscopic peak may be fitted to multiples of the above functions or to sums or products of functions with variable parameters. The above functions are all symmetrical about the position of their maximum. Asymmetric functions have also been used. | 0 | Theoretical and Fundamental Chemistry |
Water scarcity has prompted efforts to reuse waste water once it has been properly treated, known as "water reclamation" (also called wastewater reuse, water reuse, or water recycling). Among the treatment technologies available to reclaim wastewater, membrane processes stand out for their capacity to retain solids and salts and even to disinfect water, producing water suitable for reuse in irrigation and other applications.
A semipermeable membrane is a material that allows the selective flow of certain substances.
In the case of water purification or regeneration, the aim is to allow the water to flow through the membrane whilst retaining undesirable particles on the originating side. By varying the type of membrane, it is possible to get better pollutant retention of different kinds. Some of the required characteristics in a membrane for wastewater treatment are chemical and mechanical resistance for five years of operation and capacity to operate stably over a wide pH range.
There are two main types of membrane materials available on the market: organic-based polymeric membranes and ceramic membranes. Polymeric membranes are the most commonly used materials in water and wastewater treatment. In particular, polyvinylidene difluoride (PVDF) is the most prevalent material due to its long lifetime and chemical and mechanical resistance.
When used with domestic wastewater, membrane bioreactor processes can produce effluent of high enough quality for discharge into the oceans, surfaces, brackish bodies, or urban irrigation waterways. Other advantages of membrane bioreactors over conventional processes include reduced footprints and simpler retrofitting.
It is possible to operate membrane bioreactor processes at higher mixed liquor suspended solids concentrations compared to conventional settlement separation systems, thus reducing the reactor volume to achieve the same loading rate.
Recent technical innovation and significant membrane cost reduction have enabled membrane bioreactors to become an established process option to treat wastewater. Membrane bioreactors have become an attractive option for the treatment and reuse of industrial and municipal wastewater, as evidenced by their consistently rising numbers and capacity. The current membrane bioreactor market was estimated to be worth around US $216 million in 2006 and US$838.2 million in 2011, grounding projections that the market for membrane bioreactors was growing at an average rate of 22.4% and would reach a market size of US $3.44 billion in 2018.
The global membrane bioreactor market is expected to grow in the near future due to various driving forces, for instance increasing scarcity of water worldwide which makes wastewater reclamation more profitable; this will likely be further aggravated by continuing climate change. Growing environmental concerns over industrial wastewater disposal along with declining freshwater resources across developing economies also account for increasing demand for membrane bioreactor technology. Population growth, urbanization, and industrialization will further complicate the business outlook.
However, high initial investments and operational expenditure may hamper the global membrane bioreactor market. In addition, technological limitations, particularly the recurrent costs of membrane fouling, are likely to hinder production adoption. Ongoing research and development progress toward increasing output and minimizing sludge formation are anticipated to fuel industry growth.
Membrane bioreactors can be used to reduce the footprint of an activated sludge sewage treatment system by removing some of the liquid components of the mixed liquor. This leaves a concentrated waste product that is then treated using the activated sludge process.
Recent studies show the opportunity to use nanomaterials for the realization of more efficient and sustainable membrane bioreactors for wastewater treatment. | 1 | Applied and Interdisciplinary Chemistry |
Potassium azodicarboxylate is a chemical compound with the formula CKNO. This chemical is used as a precursor to diimide. It can be synthesized by the reaction of potassium hydroxide with azodicarbonamide and it reacts with carboxylic acids to form diimide. | 0 | Theoretical and Fundamental Chemistry |
Pump–probe microscopy is a non-linear optical imaging modality used in femtochemistry to study chemical reactions. It generates high-contrast images from endogenous non-fluorescent targets. It has numerous applications, including materials science, medicine, and art restoration. | 0 | Theoretical and Fundamental Chemistry |
F-ATPase gene linkage and gene order are widely conserved across ancient prokaryote lineages, implying that this system already existed at a date before the last universal common ancestor, the LUCA. | 0 | Theoretical and Fundamental Chemistry |
Two simple examples are . The MB cores (M = Fe or Co) of these two compounds adopt structures expected for nido 5-vertex clusters. The iron compound is produced by reaction of diiron nonacarbonyl with pentaborane. and cyclobutadieneiron tricarbonyl have similar structures. | 0 | Theoretical and Fundamental Chemistry |
NCAs are typically prepared by phosgenation of amino acids:
They were first synthesized by Hermann Leuchs by heating an N-ethoxycarbonyl or N-methoxycarbonyl amino acid chloride in a vacuum at 50-70 °C:
A moisture-tolerant route to unprotected NCAs employs epoxides as scavengers of hydrogen chloride.
This synthesis of NCAs is sometimes called the . The relatively high temperatures necessary for this cyclization results in the decomposition of several NCAs. Of several improvements, one notable procedure involves treating an unprotected amino acid with phosgene or its trimer. | 0 | Theoretical and Fundamental Chemistry |
In the 1970s–80s, it was realized that nanosized systems may affect ionic conductivity, opening a new field of nanoionics. In 1973, it was reported that ionic conductivity of lithium iodide (LiI) crystals could be increased 50 times by adding to it a fine powder of ‘’insulating’’ material (alumina). This effect was reproduced in the 1980s in Ag- and Tl-halides doped with alumina nanoparticles. Similarly, addition of insulating nanoparticles helped increase the conductivity of ionic polymers. These unexpected results were explained by charge separation at the matrix-nanoparticle interface that provided additional conductive channels to the matrix, and the small size of the filler particles was required to increase the area of this interface. Similar charge-separation effects were observed for grain boundaries in crystalline ionic conductors. | 0 | Theoretical and Fundamental Chemistry |
Between 1992 and 1997, Japans Ministry of International Trade and Industry sponsored a "New Hydrogen Energy (NHE)" program of US$20 million to research cold fusion. Announcing the end of the program in 1997, the director and one-time proponent of cold fusion research Hideo Ikegami stated "We couldnt achieve what was first claimed in terms of cold fusion. (...) We can't find any reason to propose more money for the coming year or for the future." In 1999 the Japan C-F Research Society was established to promote the independent research into cold fusion that continued in Japan. The society holds annual meetings. Perhaps the most famous Japanese cold fusion researcher was Yoshiaki Arata, from Osaka University, who claimed in a demonstration to produce excess heat when deuterium gas was introduced into a cell containing a mixture of palladium and zirconium oxide, a claim supported by fellow Japanese researcher Akira Kitamura of Kobe University and Michael McKubre at SRI. | 0 | Theoretical and Fundamental Chemistry |
The effects of calcium on human cells are specific, meaning that different types of cells respond in different ways. However, in certain circumstances, its action may be more general. Ca ions are one of the most widespread second messengers used in signal transduction. They make their entrance into the cytoplasm either from outside the cell through the cell membrane via calcium channels (such as calcium-binding proteins or voltage-gated calcium channels), or from some internal calcium storages such as the endoplasmic reticulum and mitochondria. Levels of intracellular calcium are regulated by transport proteins that remove it from the cell. For example, the sodium-calcium exchanger uses energy from the electrochemical gradient of sodium by coupling the influx of sodium into cell (and down its concentration gradient) with the transport of calcium out of the cell. In addition, the plasma membrane Ca ATPase (PMCA) obtains energy to pump calcium out of the cell by hydrolysing adenosine triphosphate (ATP). In neurons, voltage-dependent, calcium-selective ion channels are important for synaptic transmission through the release of neurotransmitters into the synaptic cleft by vesicle fusion of synaptic vesicles.
Calcium's function in muscle contraction was found as early as 1882 by Ringer. Subsequent investigations were to reveal its role as a messenger about a century later. Because its action is interconnected with cAMP, they are called synarchic messengers. Calcium can bind to several different calcium-modulated proteins such as troponin-C (the first one to be identified) and calmodulin, proteins that are necessary for promoting contraction in muscle.
In the endothelial cells which line the inside of blood vessels, Ca ions can regulate several signaling pathways which cause the smooth muscle surrounding blood vessels to relax. Some of these Ca-activated pathways include the stimulation of eNOS to produce nitric oxide, as well as the stimulation of K channels to efflux K and cause hyperpolarization of the cell membrane. Both nitric oxide and hyperpolarization cause the smooth muscle to relax in order to regulate the amount of tone in blood vessels. However, dysfunction within these Ca-activated pathways can lead to an increase in tone caused by unregulated smooth muscle contraction. This type of dysfunction can be seen in cardiovascular diseases, hypertension, and diabetes.
Calcium coordination plays an important role in defining the structure and function of proteins. An example a protein with calcium coordination is von Willebrand factor (vWF) which has an essential role in blood clot formation process. It was discovered using single molecule optical tweezers measurement that calcium-bound vWF acts as a shear force sensor in the blood. Shear force leads to unfolding of the A2 domain of vWF whose refolding rate is dramatically enhanced in the presence of calcium. | 1 | Applied and Interdisciplinary Chemistry |
TFD is itself composed of TBP and several subunits called TATA-binding protein Associated Factors (TBP-associated factors, or TAFs). In a test tube, only TBP is necessary for transcription at promoters that contain a TATA box. TAFs, however, add promoter selectivity, especially if there is no TATA box sequence for TBP to bind to. TAFs are included in two distinct complexes, TFD and B-TFD. The TFD complex is composed of TBP and more than eight TAFs. But, the majority of TBP is present in the B-TFD complex, which is composed of TBP and TAFII170 (BTAF1) in a 1:1 ratio. TFD and B-TFD are not equivalent, since transcription reactions utilizing TFD are responsive to gene specific transcription factors such as SP1, while reactions reconstituted with B-TFD are not.
Subunits in the TFD complex include:
* TBP (TATA binding protein), or:
** TBP-related factors in animals (TBPL1; TBPL2)
* TAF1 (TAFII250)
* TAF2 (CIF150)
* TAF3 (TAFII140)
* TAF4 (TAFII130/135)
* TAF4B (TAFII105)
* TAF5 (TAFII100)
* TAF6 (TAFII70/80)
* TAF7 (TAFII55)
* TAF8 (TAFII43)
* TAF9 (TAFII31/32)
* TAF9B (TAFII31L)
* TAF10 (TAFII30)
* TAF11 (TAFII28)
* TAF12 (TAFII20/15)
* TAF13 (TAFII18)
* TAF15 (TAFII68) | 1 | Applied and Interdisciplinary Chemistry |
Low field NMR spans a range of different nuclear magnetic resonance (NMR) modalities, going from NMR conducted in permanent magnets, supporting magnetic fields of a few tesla (T), all the way down to zero field NMR, where the Earths field is carefully shielded such that magnetic fields of nanotesla (nT) are achieved where nuclear spin precession is close to zero. In a broad sense, Low-field NMR is the branch of NMR that is not conducted in superconducting high-field magnets. Low field NMR also includes Earths field NMR where simply the Earth's magnetic field is exploited to cause nuclear spin-precession which is detected. With magnetic fields on the order of μT and below magnetometers such as SQUIDs or atomic magnetometers (among others) are used as detectors. "Normal" high field NMR relies on the detection of spin-precession with inductive detection with a simple coil.
However, this detection modality becomes less sensitive as the magnetic field and the associated frequencies decrease. Hence the push toward alternative detection methods at very low fields. | 0 | Theoretical and Fundamental Chemistry |
The die casting process forces molten metal under high pressure into mold cavities (which are machined into dies). Most die castings are made from nonferrous metals, specifically zinc, copper, and aluminium-based alloys, but ferrous metal die castings are possible. The die casting method is especially suited for applications where many small to medium-sized parts are needed with good detail, a fine surface quality and dimensional consistency. | 1 | Applied and Interdisciplinary Chemistry |
The structure of DNA shows a variety of forms, both double-stranded and single-stranded. The mechanical properties of DNA, which are directly related to its structure, are a significant problem for cells. Every process which binds or reads DNA is able to use or modify the mechanical properties of DNA for purposes of recognition, packaging and modification. The extreme length (a chromosome may contain a 10 cm long DNA strand), relative rigidity and helical structure of DNA has led to the evolution of histones and of enzymes such as topoisomerases and helicases to manage a cell's DNA. The properties of DNA are closely related to its molecular structure and sequence, particularly the weakness of the hydrogen bonds and electronic interactions that hold strands of DNA together compared to the strength of the bonds within each strand.
Experimental methods which can directly measure the mechanical properties of DNA are relatively new, and high-resolution visualization in solution is often difficult. Nevertheless, scientists have uncovered large amount of data on the mechanical properties of this polymer, and the implications of DNA's mechanical properties on cellular processes is a topic of active current research.
The DNA found in many cells can be macroscopic in length: a few centimetres long for each human chromosome. Consequently, cells must compact or package DNA to carry it within them. In eukaryotes this is carried by spool-like proteins named histones, around which DNA winds. It is the further compaction of this DNA-protein complex which produces the well known mitotic eukaryotic chromosomes.
In the late 1970s, alternate non-helical models of DNA structure were briefly considered as a potential solution to problems in DNA replication in plasmids and chromatin. However, the models were set aside in favor of the double-helical model due to subsequent experimental advances such as X-ray crystallography of DNA duplexes, and later the nucleosome core particle, and the discovery of topoisomerases. Such non-double-helical models are not currently accepted by the mainstream scientific community. | 0 | Theoretical and Fundamental Chemistry |
Disulfides can undergo dynamic exchange reactions with free thiols. The reaction is well documented within the realm of DCvC, and is one of the first reactions demonstrated to have dynamic properties. The application of disulfide chemistry has the added advantage of being a biological motif. Cysteine residues can form disulfide bonds in natural systems. | 0 | Theoretical and Fundamental Chemistry |
Bharat graduated with a BA in Biological Sciences from the University of Oxford, UK. His studies were supported by a Rhodes Scholarship. He then undertook research at the European Molecular Biology Laboratory in Heidelberg, Germany for his PhD working with John A. G. Briggs. He studied the structure and assembly of pathogenic viruses using cryogenic electron microscopy and tomography. His work on several viral capsid proteins improved understanding of how viruses are assembled within infected cells. | 1 | Applied and Interdisciplinary Chemistry |
Quantum mechanics developed in two distinct phases. The first phase, known as the old quantum theory, began around 1900 with radically new approaches to explanations physical phenomena not understood by classical mechanics of the 1800s. | 1 | Applied and Interdisciplinary Chemistry |
Natural products chemistry is a distinct area of chemical research which was important in the development and history of chemistry. Isolating and identifying natural products has been important to source substances for early preclinical drug discovery research, to understand traditional medicine and ethnopharmacology, and to find pharmacologically useful areas of chemical space. To achieve this, many technological advances have been made, such as the evolution of technology associated with chemical separations, and the development of modern methods in chemical structure determination such as NMR. Early attempts to understand the biosynthesis of natural products, saw chemists employ first radiolabelling and more recently stable isotope labeling combined with NMR experiments. In addition, natural products are prepared by organic synthesis, to provide confirmation of their structure, or to give access to larger quantities of natural products of interest. In this process, the structure of some natural products have been revised, and the challenge of synthesising natural products has led to the development of new synthetic methodology, synthetic strategy, and tactics. In this regard, natural products play a central role in the training of new synthetic organic chemists, and are a principal motivation in the development of new variants of old chemical reactions (e.g., the Evans aldol reaction), as well as the discovery of completely new chemical reactions (e.g., the Woodward cis-hydroxylation, Sharpless epoxidation, and Suzuki–Miyaura cross-coupling reactions). | 1 | Applied and Interdisciplinary Chemistry |
The properties of HFMs can be characterized using the same techniques commonly used for other types of membranes. The primary properties of interest for HFMs are average pore diameter and pore distribution, measurable via a technique known as porosimetry, a feature of several laboratory instruments used for measuring pore size. Pore diameter can also be measured via a technique known as evapoporometry, in which evaporation of 2-propanol through the pores of a membrane is related to pore-size via the Kelvin equation. Depending on the diameters of pores in an HFM, scanning electron microscopy or transmission electron microscopy can be used to yield a qualitative perspective of pore size. | 0 | Theoretical and Fundamental Chemistry |
A dihedral angle is the angle between two intersecting planes or half-planes. In chemistry, it is the clockwise angle between half-planes through two sets of three atoms, having two atoms in common. In solid geometry, it is defined as the union of a line and two half-planes that have this line as a common edge. In higher dimensions, a dihedral angle represents the angle between two hyperplanes.
The planes of a flying machine are said to be at positive dihedral angle when both starboard and port main planes (commonly called "wings") are upwardly inclined to the lateral axis; when downwardly inclined they are said to be at a negative dihedral angle. | 0 | Theoretical and Fundamental Chemistry |
Ultrapotassic igneous rocks are a class of rare, volumetrically minor, generally ultramafic or mafic silica-depleted igneous rocks.
While there are debates on the exact classifications of ultrapotassic rocks, they are defined by using the chemical screens KO/NaO > 3 in much of the scientific literature. However caution is indicated in interpreting the use of the term "ultrapotassic", and the nomenclature of these rocks continues to be debated, with some classifications using KO/NaO > 2 to indicate a rock is ultrapotassic. | 0 | Theoretical and Fundamental Chemistry |
Halogen bonding is a type of non-covalent interaction which does not involve the formation nor breaking of actual bonds, but rather is similar to the dipole–dipole interaction known as hydrogen bonding. In halogen bonding, a halogen atom acts as an electrophile, or electron-seeking species, and forms a weak electrostatic interaction with a nucleophile, or electron-rich species. The nucleophilic agent in these interactions tends to be highly electronegative (such as oxygen, nitrogen, or sulfur), or may be anionic, bearing a negative formal charge. As compared to hydrogen bonding, the halogen atom takes the place of the partially positively charged hydrogen as the electrophile.
Halogen bonding should not be confused with halogen–aromatic interactions, as the two are related but differ by definition. Halogen–aromatic interactions involve an electron-rich aromatic π-cloud as a nucleophile; halogen bonding is restricted to monatomic nucleophiles. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, the dispersity is a measure of the heterogeneity of sizes of molecules or particles in a mixture. A collection of objects is called uniform if the objects have the same size, shape, or mass. A sample of objects that have an inconsistent size, shape and mass distribution is called non-uniform. The objects can be in any form of chemical dispersion, such as particles in a colloid, droplets in a cloud, crystals in a rock,
or polymer macromolecules in a solution or a solid polymer mass. Polymers can be described by molecular mass distribution; a population of particles can be described by size, surface area, and/or mass distribution; and thin films can be described by film thickness distribution.
IUPAC has deprecated the use of the term polydispersity index, having replaced it with the term dispersity, represented by the symbol Đ (pronounced D-stroke) which can refer to either molecular mass or degree of polymerization. It can be calculated using the equation Đ = M/M, where M is the weight-average molar mass and M is the number-average molar mass. It can also be calculated according to degree of polymerization, where Đ = X/X, where X is the weight-average degree of polymerization and X is the number-average degree of polymerization. In certain limiting cases where Đ = Đ, it is simply referred to as Đ. IUPAC has also deprecated the terms monodisperse, which is considered to be self-contradictory, and polydisperse, which is considered redundant, preferring the terms uniform and non-uniform instead. The terms monodisperse and polydisperse are however still preferentially used to describe particles in an aerosol. | 0 | Theoretical and Fundamental Chemistry |
Throughout the 1800s many studies investigated details in the spectrum of intensity versus frequency for light emitted by flames, by the Sun, or red-hot objects. Rydberg's formula effectively summarized the dark lines seen in the spectrum, but he provided no physical model to explain them. The spectrum emitted by red-hot objects could be explained at high or low wavelengths but the two theories differed. | 1 | Applied and Interdisciplinary Chemistry |
In India, guns made of bronze were recovered from Calicut (1504) and Diu (1533). By the 17th century, Indians were manufacturing a diverse variety of firearms; large guns in particular, became visible in Tanjore, Dacca, Bijapur and Murshidabad. Gujarāt supplied Europe saltpeter for use in gunpowder warfare during the 17th century. Bengal and Mālwa participated in saltpeter production. The Dutch, French, Portuguese, and English used Chāpra as a center of saltpeter refining.
Fathullah Shirazi (c. 1582), who worked for Akbar the Great as a mechanical engineer, developed an early multi gun shot. Shirazi's rapid-firing gun had multiple gun barrels that fired hand cannons loaded with gunpowder.
Mysorean rockets were an Indian military weapon, the first iron-cased rockets successfully deployed for military use. The Mysorean army, under Hyder Ali and his son Tipu Sultan, used the rockets effectively against the British East India Company during the 1780s and 1790s. | 1 | Applied and Interdisciplinary Chemistry |
The classic synthesis is the Fischer esterification, which involves treating a carboxylic acid with an alcohol in the presence of a dehydrating agent:
The equilibrium constant for such reactions is about 5 for typical esters, e.g., ethyl acetate. The reaction is slow in the absence of a catalyst. Sulfuric acid is a typical catalyst for this reaction. Many other acids are also used such as polymeric sulfonic acids. Since esterification is highly reversible, the yield of the ester can be improved using Le Chatelier's principle:
* Using the alcohol in large excess (i.e., as a solvent).
* Using a dehydrating agent: sulfuric acid not only catalyzes the reaction but sequesters water (a reaction product). Other drying agents such as molecular sieves are also effective.
* Removal of water by physical means such as distillation as a low-boiling azeotropes with toluene, in conjunction with a Dean-Stark apparatus.
Reagents are known that drive the dehydration of mixtures of alcohols and carboxylic acids. One example is the Steglich esterification, which is a method of forming esters under mild conditions. The method is popular in peptide synthesis, where the substrates are sensitive to harsh conditions like high heat. DCC (dicyclohexylcarbodiimide) is used to activate the carboxylic acid to further reaction. 4-Dimethylaminopyridine (DMAP) is used as an acyl-transfer catalyst.
Another method for the dehydration of mixtures of alcohols and carboxylic acids is the Mitsunobu reaction:
Carboxylic acids can be esterified using diazomethane:
Using this diazomethane, mixtures of carboxylic acids can be converted to their methyl esters in near quantitative yields, e.g., for analysis by gas chromatography. The method is useful in specialized organic synthetic operations but is considered too hazardous and expensive for large-scale applications. | 0 | Theoretical and Fundamental Chemistry |
Multiple new inhibitors based on non-carbohydrate templates have been synthesized. With focus on positioning the double bond in the inhibitor to more closely resemble the transition state of the substrate and replacing the glycerol side chain with a lipophilic group on the basis of the hydrophobic backbone of the glycerol interacting with the protein lead to the discovery of GS 4071. GS 4071 is cyclohexene based and has 3-pentyl ether, found to be optimal, instead of the glycerol as the side chain. The GS 4071 inhibitor is more lipophilic than the predecessor Zanamivir but does not have more bioavailability. Oseltamivir, the ethyl ester of GS 4071 was produced as a prodrug and is actively converted to the active drug in vivo. | 1 | Applied and Interdisciplinary Chemistry |
Levonorgestrel acetate (LNG-A), or levonorgestrel 17β-acetate, also known as 3-ketonorgestimate, is a progestin which was never marketed. It is a progestogen ester and is the C17β acetate ester and a prodrug of levonorgestrel. Norgestimate is the C3 oxime of LNG-A. The drug is a minor active metabolite of norgestimate, which is a prodrug of norelgestromin and to a lesser extent of levonorgestrel and LNG-A. LNG-A has high affinity for the progesterone receptor, about 135% of that of promegestone (relative to 150% for levonorgestrel). Along with levonorgestrel butanoate, LNG-A was investigated as a hormonal contraceptive by the Population Council. | 0 | Theoretical and Fundamental Chemistry |
Corona treatment is a surface modification method using a low temperature corona discharge to increase the surface energy of a material, often polymers and natural fibers. Most commonly, a thin polymer sheet is rolled through an array of high-voltage electrodes, using the plasma created to functionalize the surface. The limited penetration depth of such treatment provides vastly improved adhesion while preserving bulk mechanical properties.
Commercially, corona treatment has been used widely for improved dye adhesion before printing text and images on plastic packaging materials. The hazardous nature of remnant ozone after corona treatment stipulates careful filtration and ventilation during processing, restricting its implementation to applications with strict catalytic filtered systems. This limitation prevents widespread use within open-line manufacturing processes
Several factors influence the efficiency of the flame treatment such as air-to-gas ratio, thermal output, surface distance, and oxidation zone dwell time. Upon conception of the process, a corona treatment immediately followed film extrusions, but the development of careful transportation techniques allows treatment at an optimized location. Conversely, in-line corona treatments have been implemented into full-scale production lines such as those in the newspaper industry. These in-line solutions are developed to counteract the decrease in wetting characteristics caused by excessive solvent use. | 0 | Theoretical and Fundamental Chemistry |
Invoking the theory of rubber elasticity, one considers a polymer chain in a cross-linked network as an entropic spring. When the chain is stretched, the entropy is reduced by a large margin because there are fewer conformations available. Therefore, there is a restoring force, which causes the polymer chain to return to its equilibrium or unstretched state, such as a high entropy random coil configuration, once the external force is removed. This is the reason why rubber bands return to their original state. Two common models for rubber elasticity are the freely-jointed chain model and the worm-like chain model. | 0 | Theoretical and Fundamental Chemistry |
Molecules, by definition, are most often held together with covalent bonds involving single, double, and/or triple bonds, where a "bond" is a shared pair of electrons (the other method of bonding between atoms is called ionic bonding and involves a positive cation and a negative anion).
Molecular geometries can be specified in terms of bond lengths, bond angles and torsional angles. The bond length is defined to be the average distance between the nuclei of two atoms bonded together in any given molecule. A bond angle is the angle formed between three atoms across at least two bonds. For four atoms bonded together in a chain, the torsional angle is the angle between the plane formed by the first three atoms and the plane formed by the last three atoms.
There exists a mathematical relationship among the bond angles for one central atom and four peripheral atoms (labeled 1 through 4) expressed by the following determinant. This constraint removes one degree of freedom from the choices of (originally) six free bond angles to leave only five choices of bond angles. (The angles θ, θ, θ, and θ are always zero and that this relationship can be modified for a different number of peripheral atoms by expanding/contracting the square matrix.)
Molecular geometry is determined by the quantum mechanical behavior of the electrons. Using the valence bond approximation this can be understood by the type of bonds between the atoms that make up the molecule. When atoms interact to form a chemical bond, the atomic orbitals of each atom are said to combine in a process called orbital hybridisation. The two most common types of bonds are sigma bonds (usually formed by hybrid orbitals) and pi bonds (formed by unhybridized p orbitals for atoms of main group elements). The geometry can also be understood by molecular orbital theory where the electrons are delocalised.
An understanding of the wavelike behavior of electrons in atoms and molecules is the subject of quantum chemistry. | 0 | Theoretical and Fundamental Chemistry |
Video camera tubes in the early days of television used the photoelectric effect, for example, Philo Farnsworth's "Image dissector" used a screen charged by the photoelectric effect to transform an optical image into a scanned electronic signal. | 0 | Theoretical and Fundamental Chemistry |
As a class, esters serve as protecting groups for carboxylic acids. Protecting a carboxylic acid is useful in peptide synthesis, to prevent self-reactions of the bifunctional amino acids. Methyl and ethyl esters are commonly available for many amino acids; the t-butyl ester tends to be more expensive. However, t-butyl esters are particularly useful because, under strongly acidic conditions, the t-butyl esters undergo elimination to give the carboxylic acid and isobutylene, simplifying work-up. | 0 | Theoretical and Fundamental Chemistry |
* Weber et al. 2005 determined that the inactive X-chromosome in females is hypermethylated on a chromosome wide level using MeDIP coupled with microarray.
* Keshet et al. 2006 performed a study on colon and prostate cancer cells using MeDIP-chip. The result is a genome-wide analysis of genes lying in hypermethylated regions as well as conclude that there is an instructive mechanism of de novo methylation in cancer cells.
* Zhang et al. 2006 obtained a high resolution methylome mapping in Arabidopsis using MeDIP-chip.
* Novak et al. 2006 used the MeDIP-chip approach to investigate human breast cancer for methylation associated silencing and observed the inactivation of the HOXA gene cluster | 1 | Applied and Interdisciplinary Chemistry |
Thermopiles are used for measuring the intensity of incident radiation, typically visible or infrared light, which heats the hot junctions, while the cold junctions are on a heat sink. It is possible to measure radiative intensities of only a few μW/cm with commercially available thermopile sensors. For example, some laser power meters are based on such sensors; these are specifically known as thermopile laser sensor.
The principle of operation of a thermopile sensor is distinct from that of a bolometer, as the latter relies on a change in resistance. | 1 | Applied and Interdisciplinary Chemistry |
The chloride-hydrogen antiporter facilitates the exchange of chloride ions for hydrogen ions across plasma membranes, thus playing a critical role in maintaining acid-base balance and chloride homeostasis. It is found in various tissues, including the gastrointestinal tract, kidneys, and pancreas. The well-known chloride-hydrogen antiporters belong in the CLC family, which have isoforms from CLC-1 to CLC-7, each with a distinct tissue distribution. Their structure involves two CLC proteins coming together to form a homodimer or a heterodimer where both monomers contain an ion translocation pathway. CLC proteins can either be ion channels or anion-proton exchangers, so CLC-1 and CLC-2 are membrane chloride channels, while CLC-3 through CLC-7 are chloride-hydrogen exchangers.
CLC-4 is a member of the CLC family that is prominent in the brain, but is also located in the liver, kidneys, heart, skeletal muscle, and intestine. It likely resides in endosomes and participates in their acidification, but can also be expressed in the endoplasmic reticulum and plasma membrane. Its roles are not entirely clear, but CLC-4 has been found to possibly participate in endosomal acidification, transferrin trafficking, renal endocytosis, and the hepatic secretory pathway.
CLC-5 is one of the best-studied members of this protein family. It shares 80% of its amino acid sequence with CLC-3 and CLC-4, but it is mainly found in the kidney, especially in the proximal tubule, collecting duct, and ascending limb of the loop of Henle. It functions to transport substances through the endosomal membrane, so it is crucial for pinocytosis, receptor-mediated endocytosis, and endocytosis of plasma membrane proteins from the apical surface.
CLC-7 is another example of a CLC family protein. It is ubiquitously expressed as the chloride-hydrogen antiporter in lysosomes and in the ruffled border of osteoclasts. CLC-7 may be important for regulating to concentration of chloride in lysosomes. It is associated with a protein called Ostm1, forming a complex that allows CLC-7 to carry out its functions. For example, these proteins are crucial to the process of acidifying the resorption lacuna, which enables bone remodeling to occur.
CLC-4 has been connected with mental retardation involving seizure disorders, facial abnormalities, and behavior disorders. Studies found frameshift and missense mutations in patients exhibiting these symptoms. Because these symptoms were mostly exhibited in males, with less severe pathology in females, it is likely X-linked. Studies done on animal models have also shown the possibility of a connection between nonfunctional CLC-4 and impaired neural branching of hippocampus neurons.
Defects in the CLC-5 gene were shown to be the cause of 60% of cases of Dents disease, which is characterized by tubular proteinuria, formation of kidney stones, excess calcium in the urine, nephrocalcinosis, and chronic kidney failure. This is caused by abnormalities that occur in the endocytosis process when CLC-5 is mutated. Dents disease itself is one of the causes of Fanconi syndrome, which occurs when the proximal convoluted tubules of the kidney do not perform an adequate level of reabsorption. It causes molecules produced by metabolic pathways, such as amino acids, glucose, and uric acid to be excreted in the urine instead of being reabsorbed. The result is polyuria, dehydration, rickets in children, osteomalacia in adults, acidosis, and hypokalemia.
CLC-7's role in osteoclast function was revealed by studies on knockout mice that developed severe osteopetrosis. These mice were smaller, had shortened long bones, disorganized trabecular structure, a missing medullary cavity, and their teeth did not erupt. This was found to be caused by deletion mutations, missense mutations, and gain-of-function mutations that sped up the gating of CLC-7. CLC-7 is expressed in almost every neuronal cell type, and its loss led to widespread neurodegeneration in mice, especially in the hippocampus. In longer-lived models, the cortex and hippocampus had almost entirely disappeared after 1.5 years. Finally, because of its importance in lysosomes, altered expression of CLC-7 can lead to lysosomal storage disorders. Mice with a mutation introduced to the CLC-7 gene developed lysosomal storage disease and retinal degeneration. | 1 | Applied and Interdisciplinary Chemistry |
Plants such as Zea mays, Arabidopsis thaliana and Tradescantia have been used in various test assays for mutagenecity of chemicals. | 0 | Theoretical and Fundamental Chemistry |
GLD-2 (which stands for Germ Line Development 2) is a cytoplasmic poly(A) polymerase (cytoPAPs) which adds successive AMP monomers to the 3’ end of specific RNAs, forming a poly(A) tail, which is a process known as polyadenylation.
For RNA specificity, GLD-2 associates with an RNA-binding protein, typically a GLD-3, to form a heterodimer that acts as a cytoplasmic PAP. This protein has an enzymatic function and belongs to a family (DNA polymerase type-B-like family) which includes several similar enzymes such as GLD-1, GLD-3 and GLD-4.
This family of cytoplasmic PAPs has been described in several different species including Homo sapiens, Caenorhabditis elegans, Xenopus, Mus musculus and Drosophila.
Moreover, as it is a cytoplasmtaic PAP it differs from nuclear PAPs in some aspects. While nuclear PAPs contain a catalytic domain and an RNA-binding domain, GLD-2 family members have only a catalytic domain. | 1 | Applied and Interdisciplinary Chemistry |
The process of creating these luxuriously inlaid objects is somewhat complicated and has multiple stages. First, designs are formed on the surface of the metal (usually copper or brass) by relief, piercing, engraving, or chasing. Color is then added to the crevices of the surface by encrustation, overlay or, most commonly, inlay of precious metals. These metal inlays could be sheets or wires hammered into place. The area around the inlaid design was often roughened or covered with some sort of black material. Each craftsman in the industry had their own personal specialization. This specialization could be in a particular metal, technique, object, or step in the process. There are two reasons the casting step of the process usually took place in an urban workshop. The first is simply because most patrons were located in these urban areas. The second is because it would be too difficult to move all of the heavy equipment necessary for casting from one rural location to the next. Inlayers and precious metalworkers were able to travel with ease and were not confined to the workshops as casters were. There were three main inlay innovations that are believed to have originated in Mosul in the thirteenth century- gold inlays, black inlay, and background scrolls inlaid with silver.
The designs themselves are quite varied in subject matter. Some of the popular motifs include: astrology, hunting, enthronements, battles, court life, and genre scenes. Genre scenes, images of everyday life are particularly prominent. Among the original design traditions there is evidence that can trace them to East Asia through the designs within textiles. Mosul was a great textile industry during the same period that they were producing these inlaid objects and they happened to specialize in reproductions of Chinese silks. It is speculated that many of the traditional metalwork designs were heavily influenced or even direct copies of these silk reproductions.
Historically, many scholars have argued that the Mongol sack of Mosul led to the demise of the luxury metalworking industry, however modern scholarship and an abundance of evidence disproves this. For example, it is known that Mosul metalworkers received an imperial commission by Il-Khan Abu Sa'id in the last years of the Ilkanate. Not only did Mosul continue to produce elaborate inlaid objects after the Mongol sack, they also altered their traditional stylistic choices to coalesce with Mongol taste. There was a new emphasis on minuscule style, the figures represented reflect the Ilkanhid fashion of the period, and they started to put more emphasis on pattern over figuration.
One of the finest examples of the Mosul school of metalworking is the Blacas Ewer.
Another item tentatively attributed to Mosul is the Courtauld bag, which is thought to be the world's oldest surviving handbag. | 1 | Applied and Interdisciplinary Chemistry |
The ORNL conducted FACE experiments where levels were increased above ambient levels in forest stands. These experiments showed:
* Increased root production stimulated by increased , resulting in more soil carbon.
* An initial increase of net primary productivity, which was not sustained.
* Faster decline in nitrogen availability in increased forest plots.
* Change in plant community structure, with minimal change in microbial community structure.
* Enhanced cannot significantly increase the leaf carrying capacity or leaf area index of an area.
FACE experiments have been criticized as not being representative of the entire globe. These experiments were not meant to be extrapolated globally. Similar experiments are being conducted in other regions such as in the Amazon rainforest in Brazil. | 1 | Applied and Interdisciplinary Chemistry |
The journal is abstracted and indexed by BIOSIS Previews, Chemical Abstracts, Chemistry Citation Index, Embase/Excerpta Medica, Index Medicus/MEDLINE/PubMed, Science Citation Index Expanded, and Scopus. According to the Journal Citation Reports, the journal has a 2020 impact factor of 3.808. | 1 | Applied and Interdisciplinary Chemistry |
A dye-sensitized solar cell (DSSC, DSC, DYSC or Grätzel cell) is a low-cost solar cell belonging to the group of thin film solar cells. It is based on a semiconductor formed between a photo-sensitized anode and an electrolyte, a photoelectrochemical system. The modern version of a dye solar cell, also known as the Grätzel cell, was originally co-invented in 1988 by Brian O'Regan and Michael Grätzel at UC Berkeley and this work was later developed by the aforementioned scientists at the École Polytechnique Fédérale de Lausanne (EPFL) until the publication of the first high efficiency DSSC in 1991. Michael Grätzel has been awarded the 2010 Millennium Technology Prize for this invention.
The DSSC has a number of attractive features; it is simple to make using conventional roll-printing techniques, is semi-flexible and semi-transparent which offers a variety of uses not applicable to glass-based systems, and most of the materials used are low-cost. In practice it has proven difficult to eliminate a number of expensive materials, notably platinum and ruthenium, and the liquid electrolyte presents a serious challenge to making a cell suitable for use in all weather. Although its conversion efficiency is less than the best thin-film cells, in theory its price/performance ratio should be good enough to allow them to compete with fossil fuel electrical generation by achieving grid parity. Commercial applications, which were held up due to chemical stability problems, had been forecast in the European Union Photovoltaic Roadmap to significantly contribute to renewable electricity generation by 2020. | 0 | Theoretical and Fundamental Chemistry |
According to the Final Project 4.1 report, the Bravo test exposed 239 Marshallese on the Utirik, Rongelap, and Ailinginae Atolls to significant level of radiation, and 28 Americans stationed on the Rongerik Atoll were also exposed. Those on the Rongelap Atoll were the most seriously affected, receiving approximately 175 rads of radiation before they were evacuated. Those on Ailinginae received 69 rads, those on Utirik received 14 rads, and the Americans on Rongerik received an average dose of 78 rads.
The results of the original Project 4.1 were published by the study's authors in professional medical journals in 1955, such as the Journal of the American Medical Association.
In 2010 it was calculated that by sub-population, the projected proportion of cancers attributable to radiation from fallout from all nuclear tests conducted in the Marshall Islands is 55% (with a 28% to 69% uncertainty range) among 82 persons exposed in 1954 on Rongelap Atoll and Ailinginae Atoll.
Most of the individuals exposed did not immediately show signs of radiation sickness, though within a few days other effects of significant radiation exposure manifested: loss of hair and significant skin damage, including "raw, weeping lesions", among the Rongelap and Ailinginae groups. The lesions healed quickly, however, consistent with radiation exposure. The report abstract concluded that "estimates of total body burden indicate that there is no long term hazard."
Additional follow-up checks on the Marshallese studied in Project 4.1 were conducted at regular intervals afterwards every year since 1954. Though the Marshallese experienced far milder immediate effects than the Japanese fishermen exposed to Bravo fallout on the fishing boat Daigo Fukuryū Maru, the long-term effects were more pronounced as they depended largely on subsistence living and were relocated to the site of the testing in Bikini, Ene Wetak, and Rongelap while the Japanese fisherman were returned to Japan. For the first decade after the test, the effects were ambiguous and statistically difficult to correlate to radiation exposure: miscarriages and stillbirths among exposed Rongelap women doubled in the first five years after the accident, but then returned to normal; some developmental difficulties and impaired growth appeared in children, but in no clear-cut pattern. In the decades that followed, though, the effects were undeniable. Children began to disproportionately develop thyroid cancer (due to exposure to radioiodines), and almost a third of those exposed developed neoplasms by 1974. | 0 | Theoretical and Fundamental Chemistry |
Evolution of metal ions in biological systems refers to the incorporation of metallic ions into living organisms and how it has changed over time. Metal ions have been associated with biological systems for billions of years, but only in the last century have scientists began to truly appreciate the scale of their influence. Major (iron, manganese, magnesium and zinc) and minor (copper, cobalt, nickel, molybdenum, tungsten) metal ions have become aligned with living organisms through the interplay of biogeochemical weathering and metabolic pathways involving the products of that weathering. The associated complexes have evolved over time.
Natural development of chemicals and elements challenged organisms to adapt or die. Current organisms require redox reactions to induce metabolism and other life processes. Metals have a tendency to lose electrons and are important for redox reactions. Metals are also toxic so a balance must be acquired to regulate where the metals are in an organism as well as in what quantities. Many organisms have flexible systems in which they can exchange one metal for another if one is scarce. Metals in this discussion are naturally occurring elements that have a tendency to undergo oxidation. Vanadium, molybdenum, cobalt, copper, chromium, iron, manganese, nickel, and zinc are deemed essential because without them biological function is impaired. | 0 | Theoretical and Fundamental Chemistry |
Sephadex is used to separate molecules by molecular weight. Sephadex is a faster alternative to dialysis (de-salting), requiring a low dilution factor (as little as 1.4:1), with high activity recoveries. Sephadex is also used for buffer exchange and the removal of small molecules during the preparation of large biomolecules, such as ampholytes, detergents, radioactive or fluorescent labels, and phenol (during DNA purification).
A special hydroxypropylated form of Sephadex resin, named Sephadex LH-20, is used for the separation and purification of small organic molecules such as steroids, terpenoids, lipids. An example of use is the purification of cholesterol. | 1 | Applied and Interdisciplinary Chemistry |
Surfactant immune function is primarily attributed to two proteins: SP-A and SP-D. These proteins can bind to sugars on the surface of pathogens and thereby opsonize them for uptake by phagocytes. It also regulates inflammatory responses and interacts with the adaptive immune response. Surfactant degradation or inactivation may contribute to enhanced susceptibility to lung inflammation and infection. | 0 | Theoretical and Fundamental Chemistry |
A monochromator is an optical device that transmits a mechanically selectable narrow band of wavelengths of light or other radiation chosen from a wider range of wavelengths available at the input. The name is from the Greek roots mono-, "single", and chroma, "colour", and the Latin suffix -ator, denoting an agent. | 0 | Theoretical and Fundamental Chemistry |
In chemical thermodynamics, the fugacity of a real gas is an effective partial pressure which replaces the mechanical partial pressure in an accurate computation of chemical equilibrium. It is equal to the pressure of an ideal gas which has the same temperature and molar Gibbs free energy as the real gas.
Fugacities are determined experimentally or estimated from various models such as a Van der Waals gas that are closer to reality than an ideal gas. The real gas pressure and fugacity are related through the dimensionless fugacity coefficient
For an ideal gas, fugacity and pressure are equal, and so . Taken at the same temperature and pressure, the difference between the molar Gibbs free energies of a real gas and the corresponding ideal gas is equal to .
The fugacity is closely related to the thermodynamic activity. For a gas, the activity is simply the fugacity divided by a reference pressure to give a dimensionless quantity. This reference pressure is called the standard state and normally chosen as 1 atmosphere or 1 bar.
Accurate calculations of chemical equilibrium for real gases should use the fugacity rather than the pressure. The thermodynamic condition for chemical equilibrium is that the total chemical potential of reactants is equal to that of products. If the chemical potential of each gas is expressed as a function of fugacity, the equilibrium condition may be transformed into the familiar reaction quotient form (or law of mass action) except that the pressures are replaced by fugacities.
For a condensed phase (liquid or solid) in equilibrium with its vapor phase, the chemical potential is equal to that of the vapor, and therefore the fugacity is equal to the fugacity of the vapor. This fugacity is approximately equal to the vapor pressure when the vapor pressure is not too high. | 0 | Theoretical and Fundamental Chemistry |
Fans may be installed in various ways, according to the application. They are often used in a free installation, without any housing of any kind. There are also some specialised installations. | 0 | Theoretical and Fundamental Chemistry |
Electromerism is a type of isomerism between a pair of molecules (electromers, electro-isomers) differing in the way electrons are distributed among the atoms and the connecting chemical bonds. In some literature electromerism is equated to valence tautomerism, a term usually reserved for tautomerism involving reconnecting chemical bonds.
One group of electromers are excited electronic states but isomerism is usually limited to ground state molecules. Another group of electromers are also called redox isomers: metal ions that can exchange their oxidation state with their ligands (see non-innocent ligand). One of the first instances was a cobalt bis(quinone) complex described by Buchanan and Pierpont in 1980 with a cobalt(II) complex in chemical equilibrium with the cobalt(III) complex. Ligands commonly found are based on dioxolenes, phenoxyl radicals and polychlorotriphenylmethyl radicals. Metalloporphyrins have also been studied. A set of electromers not requiring redox-active ligands have been described as well as a set without a metal. A new group of electromers has also been described recently. | 0 | Theoretical and Fundamental Chemistry |
Photopolymers can be used to generate printing plates, which are then pressed onto paper-like metal type. This is often used in modern fine printing to achieve the effect of embossing (or the more subtly three-dimensional effect of letterpress printing) from designs created on a computer without needing to engrave designs into metal or cast metal type. It is often used for business cards. | 0 | Theoretical and Fundamental Chemistry |
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