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The chemical composition of tall oil varies with the species of trees used in pulping, and in turn with geographical location. For example, the coastal areas of the southeastern United States have a high proportion of Slash Pine (Pinus elliottii); inland areas of the same region have a preponderance of Loblolly Pine (Pinus taeda). Slash Pine generally contains a higher concentration of resin acids than Loblolly Pine.
In general, the tall oil produced in coastal areas of the southeastern United States contains over 40% resin acids and sometimes as much as 50% or more. The fatty acids fraction is usually lower than the resin acids, and unsaponifiables amount to 6-8%. Farther north in Virginia, where Pitch Pine (Pinus rigida)and Shortleaf Pine (Pinus echinata) are more dominant, the resin acid content decreases to as low as 30-35% with a corresponding increase in the fatty acids present.
In Canada, where mills process Lodgepole Pine (Pinus contorta) in interior British Columbia and Alberta, Jack Pine (Pinus banksiana), Alberta to Quebec and Eastern White Pine (Pinus strobus) and Red Pine (Pinus resinosa), Ontario to New Brunswick, resin acid levels of 25% are common with unsaponifiable contents of 12-25%. Similar variations may be found in other parts of the United States and in other countries. For example, in Finland, Sweden and Russia, resin acid values from Scots Pine (Pinus sylvestris) may vary from 20 to 50%, fatty acids from 35 to 70%, and unsaponifiables from 6 to 30%. | 1 | Applied and Interdisciplinary Chemistry |
One product of fatty acid metabolism are the prostaglandins, compounds having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are enzymatically derived from arachidonic acid, a 20-carbon polyunsaturated fatty acid. Every prostaglandin therefore contains 20 carbon atoms, including a 5-carbon ring. They are a subclass of eicosanoids and form the prostanoid class of fatty acid derivatives.
The prostaglandins are synthesized in the cell membrane by the cleavage of arachidonate from the phospholipids that make up the membrane. This is catalyzed either by phospholipase A acting directly on a membrane phospholipid, or by a lipase acting on DAG (diacyl-glycerol). The arachidonate is then acted upon by the cyclooxygenase component of prostaglandin synthase. This forms a cyclopentane ring roughly in the middle of the fatty acid chain. The reaction also adds 4 oxygen atoms derived from two molecules of O. The resulting molecule is prostaglandin G, which is converted by the hydroperoxidase component of the enzyme complex into prostaglandin H. This highly unstable compound is rapidly transformed into other prostaglandins, prostacyclin and thromboxanes. These are then released into the interstitial fluids surrounding the cells that have manufactured the eicosanoid hormone.
If arachidonate is acted upon by a lipoxygenase instead of cyclooxygenase, Hydroxyeicosatetraenoic acids and leukotrienes are formed. They also act as local hormones.
Prostaglandins have two derivatives: prostacyclins and thromboxanes. Prostacyclins are powerful locally acting vasodilators and inhibit the aggregation of blood platelets. Through their role in vasodilation, prostacyclins are also involved in inflammation. They are synthesized in the walls of blood vessels and serve the physiological function of preventing needless clot formation, as well as regulating the contraction of smooth muscle tissue. Conversely, thromboxanes (produced by platelet cells) are vasoconstrictors and facilitate platelet aggregation. Their name comes from their role in clot formation (thrombosis). | 1 | Applied and Interdisciplinary Chemistry |
V̇O max (also maximal oxygen consumption, maximal oxygen uptake or maximal aerobic capacity) is the maximum rate of oxygen consumption attainable during physical exertion. The name is derived from three abbreviations: "V̇" for volume (the dot over the V indicates "per unit of time" in Newton's notation), "O" for oxygen, and "max" for maximum and usually normalized per kilogram of body mass. A similar measure is V̇O peak (peak oxygen consumption), which is the measurable value from a session of physical exercise, be it incremental or otherwise. It could match or underestimate the actual V̇O max. Confusion between the values in older and popular fitness literature is common. The capacity of the lung to exchange oxygen and carbon dioxide is constrained by the rate of blood oxygen transport to active tissue.
The measurement of V̇O max in the laboratory provides a quantitative value of endurance fitness for comparison of individual training effects and between people in endurance training. Maximal oxygen consumption reflects cardiorespiratory fitness and endurance capacity in exercise performance. Elite athletes, such as competitive distance runners, racing cyclists or Olympic cross-country skiers, can achieve V̇O max values exceeding 90 mL/(kg·min), while some endurance animals, such as Alaskan huskies, have V̇O max values exceeding 200 mL/(kg·min).
In physical training, especially in its academic literature, V̇O max is often used as a reference level to quantify exertion levels, such as 65% V̇O max as a threshold for sustainable exercise, which is generally regarded as more rigorous than heart rate, but is more elaborate to measure. | 1 | Applied and Interdisciplinary Chemistry |
As noted above, J.R. Partington points out that a state of thermodynamic equilibrium is stable against small transient perturbations. Without this condition, in general, experiments intended to study systems in thermodynamic equilibrium are in severe difficulties. | 0 | Theoretical and Fundamental Chemistry |
In 1969, Pinewood film studios hired a chemistry laboratory at Fulmer for use as a film set for the film "The Chairman" (also known as "The Most Dangerous Man in the World"), starring Gregory Peck. | 1 | Applied and Interdisciplinary Chemistry |
Dibutylboron trifluoromethanesulfonate (also called dibutylboron triflate or DBBT) is a reagent in organic chemistry. Its chemical formula is CHBFOS. It is used in asymmetric synthesis for example in the formation of boron enolates in the aldol reaction. | 0 | Theoretical and Fundamental Chemistry |
Organotantalum chemistry is the chemistry of chemical compounds containing a carbon-to-tantalum chemical bond. A wide variety of compound have been reported, initially with cyclopentadienyl and CO ligands. Oxidation states vary from Ta(V) to Ta(-I). | 0 | Theoretical and Fundamental Chemistry |
In genetics, an isochore is a large region of genomic DNA (greater than 300 kilobases) with a high degree of uniformity in GC content; that is, guanine (G) and cytosine (C) bases. The distribution of bases within a genome is non-random: different regions of the genome have different amounts of G-C base pairs, such that regions can be classified and identified by the proportion of G-C base pairs they contain.
Bernardi and colleagues first noticed the compositional non-uniformity of vertebrate genomes using thermal melting and density gradient centrifugation.
The DNA fragments extracted by the gradient centrifugation were later termed "isochores", which was subsequently defined as "very long (much greater than 200 KB) DNA segments" that "are fairly homogeneous in base composition and belong to a small number of major classes distinguished by differences in guanine-cytosine (GC) content". Subsequently, the isochores "grew" and were claimed to be ">300 kb in size."
The theory proposed that the isochore composition of genomes varies markedly between "warm-blooded" (homeotherm) vertebrates and "cold-blooded" (poikilotherm) vertebrates and later became known as the isochore theory. | 1 | Applied and Interdisciplinary Chemistry |
* 1946–1962 Ernest Basil Verney
* 1962–1971 Arnold Burgen
* 1973–1978 Gustav Victor Rudolf Born
* 1979–1999 Alan Cuthbert
* 1999–2013 Peter Anthony McNaughton
* 2017–2022 John Michael Edwardson
* 2022–present Mark Howarth | 1 | Applied and Interdisciplinary Chemistry |
Delivery systems are primarily divided into polymer-based delivery systems (microspheres and liposomes) and live delivery systems (gram-positive bacteria, gram-negative bacteria and viruses) | 1 | Applied and Interdisciplinary Chemistry |
Grahams law of effusion (also called Grahams law of diffusion) was formulated by Scottish physical chemist Thomas Graham in 1848. Graham found experimentally that the rate of effusion of a gas is inversely proportional to the square root of the molar mass of its particles. This formula is stated as:
where:
:Rate is the rate of effusion for the first gas. (volume or number of moles per unit time).
:Rate is the rate of effusion for the second gas.
:M is the molar mass of gas 1
:M is the molar mass of gas 2.
Grahams law states that the rate of diffusion or of effusion of a gas is inversely proportional to the square root of its molecular weight. Thus, if the molecular weight of one gas is four times that of another, it would diffuse through a porous plug or escape through a small pinhole in a vessel at half the rate of the other (heavier gases diffuse more slowly). A complete theoretical explanation of Grahams law was provided years later by the kinetic theory of gases. Graham's law provides a basis for separating isotopes by diffusion—a method that came to play a crucial role in the development of the atomic bomb.
Graham's law is most accurate for molecular effusion which involves the movement of one gas at a time through a hole. It is only approximate for diffusion of one gas in another or in air, as these processes involve the movement of more than one gas.
In the same conditions of temperature and pressure, the molar mass is proportional to the mass density. Therefore, the rates of diffusion of different gases are inversely proportional to the square roots of their mass densities:
where:
:ρ is the mass density. | 0 | Theoretical and Fundamental Chemistry |
Maternal overnutrition can have detrimental effects on the health of the offspring later in life. This area is less well studied and understood but some progress has been made in identifying specific genes that are affected. Studies have investigated hypermethylation of DNA and found it to be higher in obese mothers to those of a healthy BMI. More specific studies have investigated Leptin (LEP) as a possible gene which is altered via metabolic imprinting in response to overnutrition in utero, and found hypermethylation of LEP in the placenta of those born to overly nourished mothers. This hypermethylation has been found to cause changes in the levels of circulating Leptin, as well as to leptin sensitivity and the development of neural circuits involved in the control of homeostasis which causes the higher risk of metabolic disease.
Upon investigation it was found that a mother who was obese before conception was likely to have a higher level of placental LEP than the placenta of a mother of a healthy weight. One strategy for overcoming obesity is the use of gastric bypass and other such surgeries, while this does not entirely alleviate the risk of altered metabolic imprinting it has been found that siblings born post maternal surgery are less likely to have as high body fat percentages than over nutrition as siblings born before the surgery.
Paternal overnutrition can also have a detrimental effect and new-borns have shown changes in methylation of DNA generally, with substantial hypomethylation at the gene Insulin-like Growth factor 2 (IGF2). However, this topic is much less studied than maternal nutrition. | 1 | Applied and Interdisciplinary Chemistry |
Governments may alter the flow or course of an urban stream to prevent localized flooding by river engineering: lining stream beds with concrete or other hardscape materials, diverting the stream into culverts and storm sewers, or other means. Some urban streams, such as the subterranean rivers of London, run completely underground. These modifications have often reduced habitat for fish and other species, caused downstream flooding due to alterations of flood plains, and worsened water quality. | 1 | Applied and Interdisciplinary Chemistry |
Identifying the pH associated with any stage in the titration process is relatively simple for monoprotic acids and bases. A monoprotic acid is an acid that donates one proton. A monoprotic base is a base that accepts one proton. A monoprotic acid or base only has one equivalence point on a titration curve.
A diprotic acid donates two protons and a diprotic base accepts two protons. The titration curve for a diprotic solution has two equivalence points.
A polyprotic substance has multiple equivalence points.
All titration reactions contain small buffer regions that appear horizontal on the graph. These regions contain comparable concentrations of acid and base, preventing sudden changes in pH when additional acid or base is added. | 0 | Theoretical and Fundamental Chemistry |
Ylides can be formed from münchnones, which are mesoionic heterocycles, and act as cyclic azomethine ylides. | 0 | Theoretical and Fundamental Chemistry |
While the synthesis of nanocrystalline feedstocks in the form of foils, powders, and wires is relatively straightforward, the tendency of nanocrystalline feedstocks to coarsen upon extended exposure to elevated temperatures means that low-temperature and rapid densification techniques are necessary to consolidate these feedstocks into bulk components. A variety of techniques show potential in this respect, such as spark plasma sintering or ultrasonic additive manufacturing, although the synthesis of bulk nanocrystalline components on a commercial scale remains untenable. | 1 | Applied and Interdisciplinary Chemistry |
The two principal methods of measuring total dissolved solids are gravimetric analysis and conductivity. Gravimetric methods are the most accurate and involve evaporating the liquid solvent and measuring the mass of residues left. This method is generally the best, although it is time-consuming. If inorganic salts comprise the great majority of TDS, conductivity-based methods are appropriate.
Conductivity of water is directly related to the concentration of dissolved ionized solids. These ions allow the water to conduct electric current. This electric current can be measured using a conventional conductivity meter or TDS meter. When correlated with laboratory TDS measurements, conductivity provides an approximate value for the TDS concentration, with around 10% accuracy.
The relationship of TDS and specific conductance of groundwater can be approximated by the following equation:
:TDS = kEC
where TDS is expressed in mg/L and EC is the electrical conductivity in microsiemens per centimeter at 25 °C. The conversion factor k varies between 0.55 and 0.8.
Some TDS meters use an electrical conductivity measurement to the ppm using the above formula. Regarding units, 1 ppm indicates 1 mg of dissolved solids per 1000 g of water. | 1 | Applied and Interdisciplinary Chemistry |
It is uncertain whether the oxhide ingots served as a form of currency. Ingots found in excavations at Mycenae are now part of the exhibits of the Numismatic Museum of Athens. Cemal Pulak argues that the weights of the Uluburun ingots are similar enough to have allowed "a rough but quick reckoning of a given quantity of raw metal prior to weighing". But George Bass proposes, via the Gelidonya ingots, whose weights are approximately the same if somewhat lower than the Uluburun ingot weights, that the weights were not standard and thus the ingots were not a currency. Another theory is that the oxhide shape, as well as the bun shape that some ingots took, was a visual statement that the ingot at hand is part of a legitimate trade. In Sardinia, oxhide ingot fragments have been found in hoards with bun ingots and scrap metal and, in some cases, in a metallurgical workshop. Citing this evidence, Vasiliki Kassianidou argues that the oxhide ingots "were meant to be used rather than to be kept as prestige goods". | 1 | Applied and Interdisciplinary Chemistry |
Born in Oklahoma in 1942, Richard Allan Andersen was raised and educated in the small town of Yankton, South Dakota. He obtained his bachelors degree in 1965 from the University of South Dakota. Andersen pursued graduate studies at the University of Wyoming, working under the supervision of Professor Geoffrey Coates. Andersen was Coates last student. In 1973, Andersen earned his Ph.D. with several fundamental organometallic and alkoxide compounds of beryllium.
Andersen then spent a year as postdoctoral researcher at the Oslo Centre for Industrial Research. On the day it was announced that Geoffrey Wilkinson and Ernst O. Fisher would share the 1973 Nobel Prize in Chemistry, Andersen received an offer to conduct his postdoctoral research in Wilkinsons laboratory at Imperial College London. Andersen took up this post a few months later, in 1974. In June 1976 he joined the faculty at the University of California, Berkeleys department of chemistry. He remained a professor in the department until his death in 2019.
Andersen was also active in teaching throughout his career, and was well-known for teaching from the primary inorganic chemistry literature, as well as his hands-on approach to teaching undergraduate laboratory courses. | 0 | Theoretical and Fundamental Chemistry |
Photoprotection is the biochemical process that helps organisms cope with molecular damage caused by sunlight. Plants and other oxygenic phototrophs have developed a suite of photoprotective mechanisms to prevent photoinhibition and oxidative stress caused by excess or fluctuating light conditions. Humans and other animals have also developed photoprotective mechanisms to avoid UV photodamage to the skin, prevent DNA damage, and minimize the downstream effects of oxidative stress. | 0 | Theoretical and Fundamental Chemistry |
Upon cell entry, a tether about 24 nucleotides in length that attaches the viral protein NS1, essential in replication, to the virion is cleaved off the virion to be reattached later. After cell entry, virions accumulate in the cell nucleus while the genome is still contained within the capsid. These capsids may be reconfigured to an open or transitioned state during entry. The exact mechanism by which the genome leaves the capsid is unclear. For AAV, it has been suggested that nuclear factors disassemble the capsid, whereas for MVM, it appears as if the genome is ejected in a 3′-to-5′ direction from an opening in the capsid called a portal.
Parvoviruses lack genes capable of inducing resting cells to enter their DNA synthesis phase (S-phase). Additionally, naked ssDNA is likely to be unstable, perceived as foreign by the host cell, or improperly replicated by host DNA repair. For these reasons, the genome must either be converted rapidly to its less obstructive, more stable duplex form or retained within the capsid until it is uncoated during S-phase. Typically, the latter occurs and virion remains silent in the nucleus until the host cell enters S-phase by itself. During this waiting period, virions may make use of certain strategies to evade host defense mechanisms to protect their hairpins and DNA to reach S-phase, though it is unclear how this occurs. Since the genome is packaged as ssDNA, creation of a complementary strand is necessary before gene expression.
DNA polymerases are only able to synthesize DNA in a 5′ to 3′ direction, and they require a basepair primer to begin synthesis. Parvoviruses address these limitations by using their termini as primers for complementary strand synthesis. A 3′ hydroxyl end of the left-hand (3′) terminus pairs with an internal base to prime initial DNA synthesis, resulting in the conversion of the ssDNA genome to its first duplex form. This is a monomeric double-stranded DNA molecule in which the two strands are covalently cross-linked to each other at the left-end by a single copy of the viral telomere. Synthesis of the duplex form precedes NS1 expression so that when the replication fork during initial complementary strand synthesis reaches the right (5′) end, it does not displace and copy the right-end hairpin. This allows the 3′-end of the new DNA strand to be covalently ligated to the 5′-end of the right hairpin by a host ligase, thereby creating the duplex molecule. During this step, the tether sequence that was present before viral entry into the cell is resynthesized. | 1 | Applied and Interdisciplinary Chemistry |
The carboxyl radical, •COOH, only exists briefly. The acid dissociation constant of •COOH has been measured using electron paramagnetic resonance spectroscopy. The carboxyl group tends to dimerise to form oxalic acid. | 0 | Theoretical and Fundamental Chemistry |
Progress in isolating the element was slowed by the exceptional dangers of generating fluorine: several 19th century experimenters, the "fluorine martyrs", were killed or blinded. Humphry Davy, as well as the notable French chemists Joseph Louis Gay-Lussac and Louis Jacques Thénard, experienced severe pains from inhaling hydrogen fluoride gas; Davy's eyes were damaged. Irish chemists Thomas and George Knox developed fluorite apparatus for working with hydrogen fluoride, but nonetheless were severely poisoned. Thomas nearly died and George was disabled for three years. French chemist Henri Moissan was poisoned several times, which shortened his life. Belgian chemist Paulin Louyet and French chemist tried to follow the Knox work, but they died from HF poisoning even though they were aware of the dangers.
Initial attempts to isolate the element were also hindered by material difficulties: the extreme corrosiveness and reactivity of hydrogen fluoride (and of fluorine gas) as well as problems getting a suitable conducting liquid for electrolysis. Davy tried to electrolyze HF but had to stop because the electrodes were damaged. He then shifted to (unsuccessful) chemical reactions.
Edmond Frémy thought that passing electric current through pure hydrofluoric acid (dry HF) might work. Previously, hydrogen fluoride was only available in a water solution. Frémy therefore devised a method for producing dry hydrogen fluoride by acidifying potassium bifluoride (KHF). Unfortunately, pure hydrogen fluoride did not pass an electric current. Frémy also tried electrolyzing molten calcium fluoride and probably produced some fluorine (since he made calcium metal at the other electrode), but he was unable to collect the gas.
English chemist George Gore also tried electrolyzing dry HF and may have made small quantities of fluorine gas in 1860. He reported an explosion after running his cell (hydrogen and fluorine recombine dramatically), but he recognized that an oxygen leak could have also caused the reaction. | 1 | Applied and Interdisciplinary Chemistry |
In 1969, he left HP and joined Fairchild Semiconductor. He was the vice president and general manager of the Microwave & Optoelectronics division, from its inception in May 1969 up until November 1971. He continued his work on light-emitting diodes (LEDs), proposing they could be used for indicator lights and optical readers in 1971. He later left Fairchild in 1972. | 0 | Theoretical and Fundamental Chemistry |
Sputter deposition is a method of depositing thin films by sputtering that involves eroding material from a "target" source onto a "substrate", e.g. a silicon wafer, solar cell, optical component, or many other possibilities. Resputtering, in contrast, involves re-emission of the deposited material, e.g. SiO during the deposition also by ion bombardment.
Sputtered atoms are ejected into the gas phase but are not in their thermodynamic equilibrium state, and tend to deposit on all surfaces in the vacuum chamber. A substrate (such as a wafer) placed in the chamber will be coated with a thin film. Sputtering deposition usually uses an argon plasma because argon, a noble gas, will not react with the target material. | 0 | Theoretical and Fundamental Chemistry |
In 1954, the International Committee for Weights and Measures (CIPM) established the definition of the Kelvin as 1/273.16 of the absolute temperature of the triple point of water. Waters with different isotopic compositions had slightly different triple points. Thus, the International Committee for Weights and Measures specified in 2005 that the definition of the kelvin temperature scale would refer to water with a composition of the nominal specification of VSMOW. The decision was welcomed in 2007 by Resolution 10 of the 23rd CGPM. The triple point is measured in triple-point cells, where the water is held at its triple point and allowed to reach equilibrium with its surroundings. Using ordinary waters, the range of inter-laboratory measurements of the triple point can be about . With VSMOW, the inter-laboratory range of measurements of the triple point is about .
After the 2019 redefinition of the SI base units, the kelvin is defined in terms of the Boltzmann constant, which makes its definition completely independent of the properties of water. The defined value for the Boltzmann constant was selected so that the measured value of the VSMOW triple point is identical to the prior defined value, within measurable accuracy. Triple-point cells remain a practical method of calibrating thermometers. | 0 | Theoretical and Fundamental Chemistry |
N,-Diisopropylcarbodiimide is a carbodiimide used in peptide synthesis. As a liquid, it is easier to handle than the commonly used N,-dicyclohexylcarbodiimide, a waxy solid. In addition, N,-diisopropylurea, its byproduct in many chemical reactions, is soluble in most organic solvents, a property that facilitates work-up. | 1 | Applied and Interdisciplinary Chemistry |
The basic form of the apothecaries system is essentially a subset of the Roman weight system. An apothecaries pound normally consisted of 12 ounces. (In France this was changed to 16 ounces, and in Spain, the customary unit was the , a mark of 8 ounces.) In the south of Europe and in France, the scruple was generally divided into 24 grains, so that one ounce consisted of 576 grains. Nevertheless, the subdivision of an ounce was somewhat more uniform than that of a pound, and a common feature of all variants is that 12 ounces are roughly 100 drachms (96–128 drachms) and a grain is roughly the weight of a physical grain.
It is most convenient to compare the various local weight standards by the metric weights of their ounces. The actual mass of an ounce varied by ±17% (5 g) around the typical value of 30 g. The table only shows approximate values for the most important standards; even the same nominal standard could vary slightly between one city and its neighbour. The range from 25 g to 31 g is filled with numerous variants, especially the Italian range up to 28 g. But there is a relatively large gap between the troy ounces of 31 g and the Habsburg ounce of 35 g. The latter is the product of an 18th-century weight reform.
Even in Turkey a system of weights similar to the European apothecaries system was used for the same purpose. For medical purposes the tcheky (approx. 320 g) was divided in 100 drachms, and the drachm in (16 kilos or) 64 grains. This is close to the classical Greek weight system, where a mina (corresponding roughly to a Roman libra') was also divided into 100 drachms.
With the beginning of metrication, some countries standardized their apothecaries' pound to an easily remembered multiple of the French gramme. E.g. in the Netherlands the Dutch troy pound of 369.1 g was standardized in 1820 to 375.000 g, to match a similar reform in France. The British troy pound retained its value of 373.202 g until in 2000 it was legally defined in metric terms, as 373.2417216 g. (At this time its use was mainly confined to trading precious metals.) | 1 | Applied and Interdisciplinary Chemistry |
In the physical realm, many irreversible processes are present to which the inability to achieve 100% efficiency in energy transfer can be attributed. The following is a list of spontaneous events which contribute to the irreversibility of processes.
* Ageing (this claim is disputed, as aging has been demonstrated to be reversed in mice. NAD+ and telomerase have also been demonstrated to reverse ageing.)
* Death
* Time
* Heat transfer through a finite temperature difference
* Friction
* Plastic deformation
* Flow of electric current through a resistance
* Magnetization or polarization with a hysteresis
* Unrestrained expansion of fluids
* Spontaneous chemical reactions
* Spontaneous mixing of matter of varying composition/states
A Joule expansion is an example of classical thermodynamics, as it is easy to work out the resulting increase in entropy. It occurs where a volume of gas is kept in one side of a thermally isolated container (via a small partition), with the other side of the container being evacuated; the partition between the two parts of the container is then opened, and the gas fills the whole container. The internal energy of the gas remains the same, while the volume increases. The original state cannot be recovered by simply compressing the gas to its original volume, since the internal energy will be increased by this compression. The original state can only be recovered by then cooling the re-compressed system, and thereby irreversibly heating the environment. The diagram to the right applies only if the first expansion is "free" (Joule expansion), i.e. there can be no atmospheric pressure outside the cylinder and no weight lifted. | 0 | Theoretical and Fundamental Chemistry |
The concept of using D-PUFAs to inhibit LPO has been tested in numerous cell and animal
models, including:
* Parkinson's disease (MPTP and a-Syn models in mice and rats)
* Huntington's disease (in mice)
* Alzheimer's disease (APP/PS1 and ALDH2 mouse models)
* Diabetic retinopathy (Akita mice)
* Age-related macular degeneration (light irradiation in rats, eye iron overload in mice)
* Atherosclerosis (Leiden mice) | 0 | Theoretical and Fundamental Chemistry |
HCN is obtainable from fruits that have a pit, such as cherries, apricots, apples, and bitter almonds, from which almond oil and flavoring are made. Many of these pits contain small amounts of cyanohydrins such as mandelonitrile and amygdalin, which slowly release hydrogen cyanide. One hundred grams of crushed apple seeds can yield about 70 mg of HCN. So-called "bitter" roots of the cassava plant may contain up to 1 gram of HCN per kilogram. Some millipedes, such as Harpaphe haydeniana, Desmoxytes purpurosea, and Apheloria release hydrogen cyanide as a defense mechanism, as do certain insects, such as burnet moths and the larvae of Paropsisterna eucalyptus. Hydrogen cyanide is contained in the exhaust of vehicles, and in smoke from burning nitrogen-containing plastics. | 0 | Theoretical and Fundamental Chemistry |
The practical performances of polycrystalline materials are strongly affected by the formed microstructure inside, which is mostly dominated by grain growth behaviors. For example, most materials exhibit the Hall–Petch effect at room-temperature and so display a higher yield stress when the grain size is reduced (assuming abnormal grain growth has not taken place). At high temperatures the opposite is true since the open, disordered nature of grain boundaries means that vacancies can diffuse more rapidly down boundaries leading to more rapid Coble creep. Since boundaries are regions of high energy they make excellent sites for the nucleation of precipitates and other second-phases e.g. Mg–Si–Cu phases in some aluminium alloys or martensite platlets in steel. Depending on the second phase in question this may have positive or negative effects. | 1 | Applied and Interdisciplinary Chemistry |
The zinc coating, when intact, prevents corrosive substances from reaching the underlying iron. Additional electroplating such as a chromate conversion coating may be applied to provide further surface passivation to the substrate material. | 1 | Applied and Interdisciplinary Chemistry |
Discovered in 1953 by Jacques Monod and colleagues, the trp operon in E. coli was the first repressible operon to be discovered. While the lac operon can be activated by a chemical (allolactose), the tryptophan (Trp) operon is inhibited by a chemical (tryptophan). This operon contains five structural genes: trp E, trp D, trp C, trp B, and trp A, which encodes tryptophan synthetase. It also contains a promoter which binds to RNA polymerase and an operator which blocks transcription when bound to the protein synthesized by the repressor gene (trp R) that binds to the operator. In the lac operon, lactose binds to the repressor protein and prevents it from repressing gene transcription, while in the trp operon, tryptophan binds to the repressor protein and enables it to repress gene transcription. Also unlike the lac operon, the trp operon contains a leader peptide and an attenuator sequence which allows for graded regulation. This is an example of the corepressible model. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, conditioning is a process in which chemical reaction factors are stabilized or enhanced. Examples include increasing the quality of a material by using another material (a conditioner) or improving the ability of solids to capture and physically or chemically treat water. There are three main conditioning systems: heat, inorganic compounds and organic polymers. | 0 | Theoretical and Fundamental Chemistry |
Electrophilic aminating reagents rely on the presence of an electron-withdrawing functional group attached to nitrogen. A variety of hydroxylamine derivatives have been used for this purpose. Sulfonylhydroxylamines are able to aminate a wide array of carbanions.
Azo compounds afford hydrazines after addition to the N=N bond. These additions have been rendered enantioselective through the use of chiral auxiliaries (see above) and chiral catalysts. Although the enantioselectivity of the proline-catalyzed process is good, yields are low and reaction times are long.
Upon treatment with sulfonyl azides, a variety of Grignard reagents or enolates may be converted into azides or amines. A significant side reaction that occurs under these conditions is the diazo transfer reaction: instead of fragmenting into an azide and sulfinic acid, the intermediate triazene salt may break down to a diazo compound and sulfonamide. Changing workup conditions may favor one product over another. In general, for reactions of enolates substituted with Evans oxazolidinones, trifluoroacetic acid promotes diazo transfer while acetic acid encourages azidation (the reasons for this are unclear). Solvent and the enolate counterion also influence the observed ratio of diazo to azide products.
Other electrophilic aminating reagents include oxaziridines, diazo compounds, and in rare cases, imines. | 0 | Theoretical and Fundamental Chemistry |
Samples are dissolved or suspended in a "cocktail" containing a solvent (historically aromatic organics such as xylene or toluene, but more recently less hazardous solvents are used), typically some form of a surfactant, and "fluors" or scintillators which produce the light measured by the detector. Scintillators can be divided into primary and secondary phosphors, differing in their luminescence properties.
Beta particles emitted from the isotopic sample transfer energy to the solvent molecules: the π cloud of the aromatic ring absorbs the energy of the emitted particle. The energized solvent molecules typically transfer the captured energy back and forth with other solvent molecules until the energy is finally transferred to a primary scintillator. The primary phosphor will emit photons following absorption of the transferred energy. Because that light emission may be at a wavelength that does not allow efficient detection, many cocktails contain secondary phosphors that absorb the fluorescence energy of the primary phosphor and re-emit at a longer wavelength. Two widely used primary and secondary
fluors are 2,5-diphenyloxazole (PPO) with an emission maximum of 380 nm and 1,4-bis-2-(5-phenyloxazolyl)benzene (POPOP) with an emission maximum of 420 nm.
The radioactive samples and cocktail are placed in small transparent or translucent (often glass or plastic) vials that are loaded into an instrument known as a liquid scintillation counter. Newer machines may use 96-well plates with individual filters in each well. Many counters have two photo multiplier tubes connected in a coincidence circuit. The coincidence circuit assures that genuine light pulses, which reach both photomultiplier tubes, are counted, while spurious pulses (due to line noise, for example), which would only affect one of the tubes, are ignored.
Counting efficiencies under ideal conditions range from about 30% for tritium (a low-energy beta emitter) to nearly 100% for phosphorus-32, a high-energy beta emitter. Some chemical compounds (notably chlorine compounds) and highly colored samples can interfere with the counting process. This interference, known as "quenching", can be overcome through data correction or through careful sample preparation. | 0 | Theoretical and Fundamental Chemistry |
Selected area (electron) diffraction (abbreviated as SAD or SAED) is a crystallographic experimental technique typically performed using a transmission electron microscope (TEM). It is a specific case of electron diffraction used primarily in material science and solid state physics as one of the most common experimental techniques. Especially with appropriate analytical software, SAD patterns (SADP) can be used to determine crystal orientation, measure lattice constants or examine its defects. | 0 | Theoretical and Fundamental Chemistry |
Triflic acid is one of the strongest acids. Contact with skin causes severe burns with delayed tissue destruction. On inhalation it causes fatal spasms, inflammation and edema.
Like sulfuric acid, triflic acid must be slowly added to polar solvents to prevent thermal runaway. | 0 | Theoretical and Fundamental Chemistry |
Magnetic nanoparticles conjugated to an antibody against an antigen of interest are not always available, but there is a way to circumvent it. Since fluorophore-conjugated antibodies are much more prevalent, it is possible to use magnetic nanoparticles coated with anti-fluorochrome antibodies. They are incubated with the fluorescent-labelled antibodies against the antigen of interest and may thus serve for cell separation with respect to the antigen. | 1 | Applied and Interdisciplinary Chemistry |
Hypermetabolism is defined as an elevated resting energy expenditure (REE) > 110% of predicted REE. Hypermetabolism is accompanied by a variety of internal and external symptoms, most notably extreme weight loss, and can also be a symptom in itself. This state of increased metabolic activity can signal underlying issues, especially hyperthyroidism. Patients with Fatal familial insomnia can also present with hypermetabolism; however, this universally fatal disorder is exceedingly rare, with only a few known cases worldwide. The drastic impact of the hypermetabolic state on patient nutritional requirements is often understated or overlooked as well. | 1 | Applied and Interdisciplinary Chemistry |
Mitochondrial diseases are usually caused by mutation in mitochondrial DNA. These genes regulate different proteins synthesis, including carrier proteins and certain enzymes.
The replication of mitochondrial DNA follows binary fission. In this process, 1 set of genes would divide into 2 sets. The mitochondrial gene of children is inherited from their mother only. If there are any genetic defects or mutations in the mother’s mitochondrial DNA, it would be inherited by the children. If those changes in genes can cause mitochondrial diseases, the children have a 100% possibility of acquiring the diseases.
For the malate-oxaloacetate shuttle, 4 major genes are involved. They are PMDH1, MDH, PMDH2, mMDH1. PMDH-1 and PMDH-2 encode two different enzymes that provide NAD for the oxidation of malate. In addition, MDH and mMDH1 encode for an enzyme that directly oxidizes malate. | 1 | Applied and Interdisciplinary Chemistry |
Unbound AR is mainly located in the cytoplasm, like a typical steroid receptor, and is associated with a complex of heat shock proteins (HSP) through interactions with LBD. Androgens, either agonists or antagonists, position themselves in the ligand-binding pocket (LBP) of the cytosolic AR and bind to the LBD, see figure 2. The AR goes through a series of conformational changes and HSP dissociate from AR. The transformed AR undergoes dimerisation, phosphorylation and translocates to the nucleus. The translocated receptor then binds to the androgen-response elements (ARE) on the promoter of the androgen responsive gene, a consensus sequence located either upstream or downstream of the transcription start site (TSS) of AR target genes. Recruitment of other transcription co-factors (including co-activators and co-repressors) and general transcriptional machinery further ensures the transactivation of AR-regulated gene expression. All these complicated processes are initiated by the ligand-induced conformational changes in the LBD. Ligand specific recruitment of coregulators might be crucial for the agonist or antagonist activity of AR ligands. Binding of DNA is also required for AR-regulated gene expression, also known as classic genomic gene function of AR. | 1 | Applied and Interdisciplinary Chemistry |
Iron working came into prominence from about 1,200 BCE. In the 10th century BCE, glass production began in ancient Near East. In the 3rd century BCE, people in ancient India developed wootz steel, the first crucible steel. In the 1st century BCE, glassblowing techniques flourished in Phoenicia. In the 2nd century, CE steel-making became widespread in Han Dynasty China. The 4th century CE saw the production of the Iron pillar of Delhi, the oldest surviving example of corrosion-resistant steel. | 1 | Applied and Interdisciplinary Chemistry |
*How to model it: Problem Solving for the Computer Age (1990) ISBN 978-0808779704
*Active Learning: Cooperation in the College Classroom (1991) ISBN 978-0939603145
*Cooperative learning: Increasing college faculty instructional productivity (1991) ISBN 978-1878380095
*New paradigms for College Teaching (1997) ISBN 978-0939603268
*Teamwork and Project Management, 4th edition, (2014) ISBN 978-0073534909 | 1 | Applied and Interdisciplinary Chemistry |
With increasing number of fluorine atoms on the same (geminal) carbon the other bonds become stronger and shorter. This can be seen by the changes in bond length and strength (BDE) for the fluoromethane series, as shown on the table below; also, the partial charges (q and q) on the atoms change within the series. The partial charge on carbon becomes more positive as fluorines are added, increasing the electrostatic interactions, and ionic character, between the fluorines and carbon. | 0 | Theoretical and Fundamental Chemistry |
Drug discovery and development are very expensive; of all compounds investigated for use in humans only a small fraction are eventually approved in most nations by government-appointed medical institutions or boards, who have to approve new drugs before they can be marketed in those countries. In 2010 18 NMEs (New Molecular Entities) were approved and three biologics by the FDA, or 21 in total, which is down from 26 in 2009 and 24 in 2008. On the other hand, there were only 18 approvals in total in 2007 and 22 back in 2006. Since 2001, the Center for Drug Evaluation and Research has averaged 22.9 approvals a year.
This approval comes only after heavy investment in pre-clinical development and clinical trials, as well as a commitment to ongoing safety monitoring. Drugs which fail part-way through this process often incur large costs, while generating no revenue in return. If the cost of these failed drugs is taken into account, the cost of developing a successful new drug (new chemical entity, or NCE), has been estimated at US$1.3 billion (not including marketing expenses). Professors Light and Lexchin reported in 2012, however, that the rate of approval for new drugs has been a relatively stable average rate of 15 to 25 for decades.
Industry-wide research and investment reached a record $65.3 billion in 2009. While the cost of research in the U.S. was about 34.2 billion between 1995 and 2010, revenues rose faster (revenues rose by 200.4 billion in that time).
A study by the consulting firm Bain & Company reported that the cost for discovering, developing and launching (which factored in marketing and other business expenses) a new drug (along with the prospective drugs that fail) rose over a five-year period to nearly $1.7 billion in 2003. According to Forbes, by 2010 development costs were between $4 billion to $11 billion per drug.
Some of these estimates also take into account the opportunity cost of investing capital many years before revenues are realized (see Time-value of money). Because of the very long time needed for discovery, development, and approval of pharmaceuticals, these costs can accumulate to nearly half the total expense. A direct consequence within the pharmaceutical industry value chain is that major pharmaceutical multinationals tend to increasingly outsource risks related to fundamental research, which somewhat reshapes the industry ecosystem with biotechnology companies playing an increasingly important role, and overall strategies being redefined accordingly. Some approved drugs, such as those based on re-formulation of an existing active ingredient (also referred to as Line-extensions) are much less expensive to develop. | 1 | Applied and Interdisciplinary Chemistry |
As access to an ionized calcium is not always available a corrected calcium may be used instead. To calculate a corrected calcium in mmol/L one takes the total calcium in mmol/L and adds it to ((40 minus the serum albumin in g/L) multiplied by 0.02). There is, however, controversy around the usefulness of corrected calcium as it may be no better than total calcium. It may be more useful to correct total calcium for both albumin and the anion gap. | 1 | Applied and Interdisciplinary Chemistry |
To introduce a reporter gene into an organism, scientists place the reporter gene and the gene of interest in the same DNA construct to be inserted into the cell or organism. For bacteria or prokaryotic cells in culture, this is usually in the form of a circular DNA molecule called a plasmid. For viruses, this is known as a viral vector. It is important to use a reporter gene that is not natively expressed in the cell or organism under study, since the expression of the reporter is being used as a marker for successful uptake of the gene of interest.
Commonly used reporter genes that induce visually identifiable characteristics usually involve fluorescent and luminescent proteins. Examples include the gene that encodes jellyfish green fluorescent protein (GFP), which causes cells that express it to glow green under blue or ultraviolet light, the enzyme luciferase, which catalyzes a reaction with luciferin to produce light, and the red fluorescent protein from the gene . The GUS gene has been commonly used in plants but luciferase and GFP are becoming more common.
A common reporter in bacteria is the E. coli lacZ gene, which encodes the protein beta-galactosidase. This enzyme causes bacteria expressing the gene to appear blue when grown on a medium that contains the substrate analog X-gal. An example of a selectable marker which is also a reporter in bacteria is the chloramphenicol acetyltransferase (CAT) gene, which confers resistance to the antibiotic chloramphenicol. | 1 | Applied and Interdisciplinary Chemistry |
Considerable effort and research continues to be made into discovering and refining better methods of tailings disposal. Research at the Porgera Gold Mine is focusing on developing a method of combining tailings products with coarse waste rock and waste muds to create a product that can be stored on the surface in generic-looking waste dumps or stockpiles. This would allow the current use of riverine disposal to cease. Considerable work remains to be done. However, co-disposal has been successfully implemented by several designers including AMEC at, for example, the Elkview Mine in British Columbia. | 1 | Applied and Interdisciplinary Chemistry |
Chelation is a type of bonding of ions and the molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central metal atom. These ligands are called chelants, chelators, chelating agents, or sequestering agents. They are usually organic compounds, but this is not a necessity.
The word chelation is derived from Greek χηλή, chēlē, meaning "claw"; the ligands lie around the central atom like the claws of a crab. The term chelate was first applied in 1920 by Sir Gilbert T. Morgan and H. D. K. Drew, who stated: "The adjective chelate, derived from the great claw or chele (Greek) of the crab or other crustaceans, is suggested for the caliperlike groups which function as two associating units and fasten to the central atom so as to produce heterocyclic rings."
Chelation is useful in applications such as providing nutritional supplements, in chelation therapy to remove toxic metals from the body, as contrast agents in MRI scanning, in manufacturing using homogeneous catalysts, in chemical water treatment to assist in the removal of metals, and in fertilizers. | 0 | Theoretical and Fundamental Chemistry |
One of the most important features introduced by Eyring, Polanyi and Evans was the notion that activated complexes are in quasi-equilibrium with the reactants. The rate is then directly proportional to the concentration of these complexes multiplied by the frequency (kT/h) with which they are converted into products. Below, a non-rigorous plausibility argument is given for the functional form of the Eyring equation. However, the key statistical mechanical factor kT/h will not be justified, and the argument presented below does not constitute a true "derivation" of the Eyring equation. | 0 | Theoretical and Fundamental Chemistry |
One of the most interesting questions is if there is a threshold in reaction energy and/or volume size which needs to be exceeded in order to form a domain in which quarks can move freely. It is natural to expect that if such a threshold exists the particle yields/ratios we have shown above should indicate that. One of the most accessible signatures would be the relative Kaon yield ratio. A possible structure has been predicted, and indeed, an unexpected structure is seen in the ratio of particles comprising the positive kaon K (comprising anti s-quarks and up-quark) and positive pion particles, seen in the figure (solid symbols). The rise and fall (square symbols) of the ratio has been reported by the CERN NA49. The reason the negative kaon particles do not show this "horn" feature is that the s-quarks prefer to hadronize bound in the Lambda particle, where the counterpart structure is observed. Data point from BNL–RHIC–STAR (red stars) in figure agree with the CERN data.
In view of these results the objective of ongoing NA61/SHINE experiment at CERN SPS and the proposed low energy run at BNL RHIC where in particular the STAR detector can search for the onset of production of quark–gluon plasma as a function of energy in the domain where the horn maximum is seen, in order to improve the understanding of these results, and to record the behavior of other related quark–gluon plasma observables. | 0 | Theoretical and Fundamental Chemistry |
Carbon inhalation aerosol labeled with technetium-99m (Technegas) is indicated for the visualization of pulmonary ventilation and the evaluation of pulmonary embolism. | 0 | Theoretical and Fundamental Chemistry |
An alternative mechanism to the one described above was proposed by Russian scientists in the mid-1850s, the hypothesis of abiogenic petroleum origin (petroleum formed by inorganic means), but this is contradicted by geological and geochemical evidence. Abiogenic sources of oil have been found, but never in commercially profitable amounts. "The controversy isnt over whether abiogenic oil reserves exist," said Larry Nation of the American Association of Petroleum Geologists. "The controversy is over how much they contribute to Earths overall reserves and how much time and effort geologists should devote to seeking them out." | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, the Cunningham correction factor, or Cunningham slip correction factor (denoted ), is used to account for non-continuum effects when calculating the drag on small particles. The derivation of Stokes' law, which is used to calculate the drag force on small particles, assumes a no-slip condition which is no longer correct at high Knudsen numbers. The Cunningham slip correction factor allows predicting the drag force on a particle moving a fluid with Knudsen number between the continuum regime and free molecular flow.
The drag coefficient calculated with standard correlations is divided by the Cunningham correction factor, , given below.
Ebenezer Cunningham derived the correction factor in 1910 and with Robert Andrews Millikan, verified the correction in the same year.
where
* is the correction factor
* is the mean free path
* is the particle diameter
* are experimentally determined coefficients.
:For air (Davies, 1945):
::A = 1.257
::A = 0.400
::A = 0.55
The Cunningham correction factor becomes significant when particles become smaller than 15 micrometers, for air at ambient conditions.
For sub-micrometer particles, Brownian motion must be taken into account. | 1 | Applied and Interdisciplinary Chemistry |
The nuclear fuel can swell during use, this is because of effects such as fission gas formation in the fuel and the damage which occurs to the lattice of the solid. The fission gases accumulate in the void that forms in the center of a fuel pellet as burnup increases. As the void forms, the once-cylindrical pellet degrades into pieces. The swelling of the fuel pellet can cause pellet-cladding interaction when it thermally expands to the inside of the cladding tubing. The swollen fuel pellet imposes mechanical stresses upon the cladding. A document on the subject of the swelling of the fuel can be downloaded from the NASA web site. | 0 | Theoretical and Fundamental Chemistry |
A crystal system is a set of point groups in which the point groups themselves and their corresponding space groups are assigned to a lattice system. Of the 32 point groups that exist in three dimensions, most are assigned to only one lattice system, in which case the crystal system and lattice system both have the same name. However, five point groups are assigned to two lattice systems, rhombohedral and hexagonal, because both lattice systems exhibit threefold rotational symmetry. These point groups are assigned to the trigonal crystal system.
In total there are seven crystal systems: triclinic, monoclinic, orthorhombic, tetragonal, trigonal, hexagonal, and cubic. | 0 | Theoretical and Fundamental Chemistry |
Paludiculture is wet agriculture and forestry on peatlands. Paludiculture combines the reduction of greenhouse gas emissions from drained peatlands through rewetting with continued land use and biomass production under wet conditions. “Paludi” comes from the Latin “palus” meaning “swamp, morass” and "paludiculture" as a concept was developed at Greifswald University. Paludiculture is a sustainable alternative to drainage-based agriculture, intended to maintain carbon storage in peatlands. This differentiates paludiculture from agriculture like rice paddies, which involve draining, and therefore degrading wetlands. | 1 | Applied and Interdisciplinary Chemistry |
The YoctoReactor (yR) is a 3D proximity-driven approach which exploits the self-assembling nature of DNA oligonucleotides into 3, 4 or 5-way junctions to direct small molecule synthesis at the center of the junction. Figure 5 illustrates the basic concept with a 4-way DNA junction.
The center of the DNA junction constitutes a volume on the order of a yoctoliter, hence the name YoctoReactor. This volume contains a single molecule reaction yielding reaction concentrations in the high mM range. The effective concentration facilitated by the DNA greatly accelerates chemical reactions that otherwise would not take place at the actual concentration several orders of magnitude lower. | 1 | Applied and Interdisciplinary Chemistry |
Boric acid may be prepared by reacting borax (sodium tetraborate decahydrate) with a mineral acid, such as hydrochloric acid:
: ·10 + 2 HCl → 4 + 2 NaCl + 5
It is also formed as a by product of hydrolysis of boron trihalides and diborane:
: + 3 → + 3 HX (X = Cl, Br, I) | 0 | Theoretical and Fundamental Chemistry |
Dispersive adhesion, also called adsorptive adhesion, is a mechanism for adhesion which attributes attractive forces between two materials to intermolecular interactions between molecules of each material. This mechanism is widely viewed as the most important of the five mechanisms of adhesion due to its presence in every type of adhesive system and its relative strength. | 0 | Theoretical and Fundamental Chemistry |
Pervaporation is effective for dilute solutions containing trace or minor amounts of the component to be removed. Based on this, hydrophilic membranes are used for dehydration of alcohols containing small amounts of water and hydrophobic membranes are used for removal/recovery of trace amounts of organics from aqueous solutions.
Pervaporation is an efficient energy conserving alternative to processes such as distillation and evaporation. It allows the exchange of two phases without direct contact.
Examples include solvent dehydration: dehydrating the ethanol/water and isopropanol/water azeotropes, continuous ethanol removal from yeast fermentors, continuous water removal from condensation reactions such as esterifications to enhance conversion and rate of the reaction, membrane introduction mass spectrometry, removing organic solvents from industrial waste waters, combination of distillation and pervaporation/vapour permeation, and concentration of hydrophobic flavour compounds in aqueous solutions (using hydrophobic membranes).
Recently, a number of organophilic pervaporation membranes have been introduced to the market. Organophilic pervaporation membranes can be used for the separation of organic-organic mixtures, e.g.: reduction of the aromatics content in refinery streams, breaking of azeotropes, purification of extraction media, purification of product stream after extraction, and purification of organic solvents. | 0 | Theoretical and Fundamental Chemistry |
In simple manual columns, the eluent is collected in constant volumes, known as fractions. The more similar the particles are in size the more likely they are in the same fraction and not detected separately. More advanced columns overcome this problem by constantly monitoring the eluent.
The collected fractions are often examined by spectroscopic techniques to determine the concentration of the particles eluted. Common spectroscopy detection techniques are refractive index (RI) and ultraviolet (UV). When eluting spectroscopically similar species (such as during biological purification), other techniques may be necessary to identify the contents of each fraction. It is also possible to analyze the eluent flow continuously with RI, LALLS, Multi-Angle Laser Light Scattering MALS, UV, and/or viscosity measurements.
The elution volume (Ve) decreases roughly linear with the logarithm of the molecular hydrodynamic volume. Columns are often calibrated using 4-5 standard samples (e.g., folded proteins of known molecular weight), and a sample containing a very large molecule such as thyroglobulin to determine the void volume. (Blue dextran is not recommended for Vo determination because it is heterogeneous and may give variable results) The elution volumes of the standards are divided by the elution volume of the thyroglobulin (Ve/Vo) and plotted against the log of the standards' molecular weights. | 1 | Applied and Interdisciplinary Chemistry |
Resazurin is reduced to resorufin by aerobic respiration of metabolically active cells, and it can be used as an indicator of cell viability. It was first used to quantify bacterial content in milk by Pesch and Simmert in 1929. It can be used to detect the presence of viable cells in mammalian cell cultures. It was introduced commercially initially under Alamar Blue trademark (Trek Diagnostic Systems, Inc), and now also available under other names such as AB assay, Vybrant (Molecular Probes) and UptiBlue (Interchim).
Resazurin based assays show excellent correlation to reference viability assays such as formazan-based assays (MTT/XTT) and tritiated thymidine based techniques. The low toxicity makes it suitable for longer studies, and it has been applied for animal cells, bacteria, and fungi for cell culture assays such as cell counting, cell survival, and cell proliferation. In antimicrobial assays, resazurin is commonly utilized to assess the minimum inhibitory concentration (MIC) or minimum bactericidal concentration (MBC) of antimicrobial agents.
To take the place of a standard live/dead assay, resazurin also be multiplexed with chemiluminescent assays, such as cytokine assays, caspase assays to measure apoptosis, or reporter assays to measure a gene or a protein expression.
The irreversible reaction of resazurin to resorufin is proportional to aerobic respiration. | 0 | Theoretical and Fundamental Chemistry |
Bees can use trail pheromones to mark food sources and the entrance of their hives. Oftentimes, when finding a source, bees will mark that exact location as well as secreting pheromones along the flight back to their hives. Employment of trail pheromones is extensively studied in honey bees and stingless bees, for both are highly social.
The trail pheromone of the stingless bee Trigona recursa is produced by its labial glands. One of its key compounds is hexyl decanoate, and when secreted, the pheromone will recruit other bees towards the source. The stingless bee Scaptotrigona pectoralis, like ants, can utilize another colonys food trail. Specifically, they can learn foreign pheromone trails at a source, broadening their options for foraging. However, in some cases of aggressive bees, like Trigona corvina', encounters between individuals from different colonies at a food source will result in fights and ultimately death amongst both parties. | 1 | Applied and Interdisciplinary Chemistry |
The general form of the Eyring–Polanyi equation somewhat resembles the Arrhenius equation:
where is the rate constant, is the Gibbs energy of activation, is the transmission coefficient, is the Boltzmann constant, is the temperature, and is the Planck constant.
The transmission coefficient is often assumed to be equal to one as it reflects what fraction of the flux through the transition state proceeds to the product without recrossing the transition state. So, a transmission coefficient equal to one means that the fundamental no-recrossing assumption of transition state theory holds perfectly. However, is typically not one because (i) the reaction coordinate chosen for the process at hand is usually not perfect and (ii) many barrier-crossing processes are somewhat or even strongly diffusive in nature. For example, the transmission coefficient of methane hopping in a gas hydrate from one site to an adjacent empty site is between 0.25 and 0.5. Typically, reactive flux correlation function (RFCF) simulations are performed in order to explicitly calculate from the resulting plateau in the RFCF. This approach is also referred to as the Bennett-Chandler approach, which yields a dynamical correction to the standard transition state theory-based rate constant.
It can be rewritten as:
One can put this equation in the following form:
where:
* = reaction rate constant
* = absolute temperature
* = enthalpy of activation
* = gas constant
* = transmission coefficient
* = Boltzmann constant = R/N, N = Avogadro constant
* = Planck constant
* = entropy of activation
If one assumes constant enthalpy of activation, constant entropy of activation, and constant transmission coefficient, this equation can be used as follows: A certain chemical reaction is performed at different temperatures and the reaction rate is determined. The plot of versus gives a straight line with slope from which the enthalpy of activation can be derived and with intercept from which the entropy of activation is derived. | 0 | Theoretical and Fundamental Chemistry |
Glass bottles and jars are infinitely recyclable. The use of recycled glass in manufacturing conserves raw materials and reduces energy consumption. Because the chemical energy required to melt the raw materials has already been expended, the use of cullet can significantly reduce energy consumption compared with manufacturing new glass from silica (SiO), soda ash (NaCO), and calcium carbonate (CaCO). Soda lime glass from virgin raw materials theoretically requires approximately 2.671 GJ/tonne compared to 1.886 GJ/tonne to melt 100% glass cullet. As a general rule, every 10% increase in cullet usage results in an energy savings of 2–3% in the melting process, with a theoretical maximum potential of 30% energy saving. Every metric ton (1,000 kg) of waste glass recycled into new items saves of carbon dioxide from being released into the atmosphere during the manufacture of new glass. But recycling glass does not avoid the remelting process, which accounts for 75% of the energy consumption during production. | 0 | Theoretical and Fundamental Chemistry |
The Karlsruhe meeting started with no firm agreement on the vexing problem of atomic and molecular weights. However, on the meetings last day reprints of Stanislao Cannizzaros 1858 paper on atomic weights, in which he utilized earlier work by Amedeo Avogadro and André-Marie Ampère, were distributed. Cannizzaros efforts exerted a heavy and, in some cases, an almost immediate influence on the delegates. Lothar Meyer later wrote that on reading Cannizzaros paper,
An important long-term result of the Karlsruhe Congress was the adoption of the now-familiar atomic weights. Prior to the Karlsruhe meeting, and going back to John Dalton's work in 1803, several systems of atomic weights were in use. In one case, a value of 1 was adopted as the weight of hydrogen (the base unit), with 6 for carbon and 8 for oxygen. As long as there were uncertainties over atomic weights then the compositions of many compounds remained in doubt. Following the Karlsruhe meeting, values of about 1 for hydrogen, 12 for carbon, 16 for oxygen, and so forth were adopted. This was based on a recognition that certain elements, such as hydrogen, nitrogen, and oxygen, were composed of diatomic molecules and not individual atoms. | 1 | Applied and Interdisciplinary Chemistry |
* G. Reginald Bashforth, The manufacture of iron and steel, vol. 2: Steel production, London, Chapman & Hall Ltd, 1951, 461 p.
* Thomas Turner (dir.), The metallurgy of iron: By Thomas Turner...: Being one of a series of treatises on metallurgy written by associates of the Royal school of mines, C. Griffin & company, limited, coll. "Griffin's metallurgical series", 1908, 3rd ed., 463 p.
* Walter MacFarlane, The principles and practice of iron and steel manufacture, Longmans, Green, and Co, 1917, 5th ed.
* R.W. Burnie, Memoir and letters of Sidney Gilchrist Thomas, Inventor, John Murray, 1891
* William Tulloch Jeans, The Creators of the Age of Steel, 1884, 356 p.
* Hermann Wedding (translated from German by: William B. Phillips, Ph.D. & Ernst Prochaska), Weddings basic Bessemer process' ["Basische Bessemer - oder Thomas-Process"], New York Scientific Publishing Company, 1891, 224 p.
* Jean Duflot, Encyclopædia Universalis, "Sidérurgie" | 1 | Applied and Interdisciplinary Chemistry |
The gene for EH4, EPHX4, is projected to encode an epoxide hydrolase closely related in amino acid sequence and structure to mEH, sEH, and EH3. The activity and function of EH4 has not yet been defined. | 1 | Applied and Interdisciplinary Chemistry |
5-Bromouracil (5-BrU, 5BrUra, or br5Ura) is a brominated derivative of uracil that acts as an antimetabolite or base analog, substituting for thymine in DNA, and can induce DNA mutation in the same way as 2-aminopurine. It is used mainly as an experimental mutagen, but its deoxyriboside derivative (5-bromo-2-deoxy-uridine) is used to treat neoplasms.
5-BrU exists in three tautomeric forms that have different base pairing properties. The keto form (shown in the infobox) is complementary to adenine, so it can be incorporated into DNA by aligning opposite adenine residues during DNA replication (see below left). Alternatively, the enol (below right) and ion forms are complementary to guanine. This means that 5-BrU can be present in DNA either opposite adenine or guanine.
The three forms frequently interchange so base-pairing properties can become altered at any time. The result of this is that during a subsequent round of replication a different base is aligned opposite the 5-BrU residue. Further rounds of replication fix the change by incorporating a normal nitrogen base into the complementary strand.
Thus 5-BrU induces a point mutation via base substitution. This base pair will change from an A-T to a G-C or from a G-C to an A-T after a number of replication cycles, depending on whether 5-BrU is within the DNA molecule or is an incoming base when it is enolized or ionized. | 1 | Applied and Interdisciplinary Chemistry |
Though separated from one another within the cell, nuclear genes and those of mitochondria and chloroplasts can affect each other in a number of ways. Nuclear genes play major roles in the expression of chloroplast genes and mitochondrial genes. Additionally, gene products of mitochondria can themselves affect the expression of genes within the cell nucleus. This can be done through metabolites as well as through certain peptides trans-locating from the mitochondria to the nucleus, where they can then affect gene expression. | 1 | Applied and Interdisciplinary Chemistry |
Fresh blastocyst (day 5 to 6) stage transfer seems to be more effective than cleavage (day 2 or 3) stage transfer in assisted reproductive technologies. The Cochrane study showed a small improvement in live birth rate per couple for blastocyst transfers. This would mean that for a typical rate of 31% in clinics that use early cleavage stage cycles, the rate would increase to 32% to 41% live births if clinics used blastocyst transfer. Recent systematic review showed that along with selection of embryo, the techniques followed during transfer procedure may result in successful pregnancy outcome. The following interventions are supported by the literature for improving pregnancy rates:
Abdominal ultrasound guidance for embryo transfer
Removal of cervical mucus
Use of soft embryo transfer catheters
Placement of embryo transfer tip in the upper or middle (central) area of the uterine cavity, greater than 1 cm from the fundus, for embryo expulsion
Immediate ambulation once the embryo transfer procedure is completed | 1 | Applied and Interdisciplinary Chemistry |
Neutron spectroscopy is a spectroscopic method of measuring atomic and magnetic motions by measuring the kinetic energy of emitted neutrons. The measured neutrons may be emitted directly (for example, by nuclear reactions), or they may scatter off cold matter before reaching the detector. Inelastic neutron scattering observes the change in the energy of the neutron as it scatters from a sample and can be used to probe a wide variety of different physical phenomena such as the motions of atoms (diffusional or hopping), the rotational modes of molecules, sound modes and molecular vibrations, recoil in quantum fluids, magnetic and quantum excitations or even electronic transitions.
Since its discovery, neutron spectroscopy has become useful in medicine as it has been applied to radiation protection and radiation therapy.
It is also used in nuclear fusion experiments, where the neutron spectrum can be used to infer the plasma temperature, density, and composition, in addition to the total fusion power.
Although neutron spectroscopy is currently capable of operating on many orders of neutron energy, much research focuses on expanding these capabilities to higher energies. In 2001, US researchers were able to measure neutrons with energies up to 100 gigaelectronvolts | 0 | Theoretical and Fundamental Chemistry |
The dispersion relation describes the relationship between wavelength and frequency in waves. Distinction can be made between pure capillary waves – fully dominated by the effects of surface tension – and gravity–capillary waves which are also affected by gravity. | 1 | Applied and Interdisciplinary Chemistry |
Zhong Zhong (, born 27 November 2017) and Hua Hua (, born 5 December 2017) are a pair of identical crab-eating macaques (also referred to as cynomolgus monkeys) that were created through somatic cell nuclear transfer (SCNT), the same cloning technique that produced Dolly the sheep in 1996. They are the first cloned primates produced by this technique. Unlike previous attempts to clone monkeys, the donated nuclei came from fetal cells, not embryonic cells. The primates were born from two independent surrogate pregnancies at the Institute of Neuroscience of the Chinese Academy of Sciences in Shanghai. | 1 | Applied and Interdisciplinary Chemistry |
The sum activity of peripheral deiodinases (G, also referred to as deiodination capacity, total deiodinase activity or, if calculated from levels of thyroid hormones, as SPINA-GD) is the maximum amount of triiodothyronine produced per time-unit under conditions of substrate saturation. It is assumed to reflect the activity of deiodinases outside the central nervous system and other isolated compartments. GD is therefore expected to reflect predominantly the activity of type I deiodinase. | 1 | Applied and Interdisciplinary Chemistry |
For introduction of radionuclides into organism, ingestion is the most important route. Insoluble compounds are not absorbed from the gut and cause only local irradiation before they are excreted. Soluble forms however show wide range of absorption percentages. | 0 | Theoretical and Fundamental Chemistry |
A typical amphiphilic flexible surfactant can form aggregates through a self-assembly process that results of specific interactions between the molecules of the amphiphilic mesogen and those of the non-mesogenic solvent.
In aqueous media, the driving force of the aggregation is the "hydrophobic effect". The aggregates formed by amphiphilic molecules are characterised by structures in which the hydrophilic head-groups expose their surface to aqueous solution, shielding the hydrophobic chains from contact with water.
For most lyotropic systems aggregation occurs only when the concentration of the amphiphile exceeds a critical concentration (known variously as the critical micelle concentration (CMC) or the critical aggregation concentration (CAC)).
At very low amphiphile concentration, the molecules will be dispersed randomly without any ordering. At slightly higher (but still low) concentration, above the CMC, self-assembled amphiphile aggregates exist as independent entities in equilibrium with monomeric amphiphiles in solution, but with no long ranged orientational or positional (translational) order. As a result, phases are isotropic (i.e. not liquid crystalline). These dispersions are generally referred to as micellar solutions, often denoted by the symbol L, while the constituent spherical aggregates are known as micelles.
At higher concentration, the assemblies will become ordered. True lyotropic liquid crystalline phases are formed as the concentration of amphiphile in water is increased beyond the point where the micellar aggregates are forced to be disposed regularly in space. For amphiphiles that consist of a single hydrocarbon chain the concentration at which the first liquid crystalline phases are formed is typically in the range 25–30 wt%. | 0 | Theoretical and Fundamental Chemistry |
Hexafluorophosphazene is an inorganic compound with the formula . It takes the form of a white powder or lumps. It is sensitive to moisture and heat. | 0 | Theoretical and Fundamental Chemistry |
In the pendant drop test, a drop of liquid is suspended from the end of a tube or by any surface by surface tension. The force due to surface tension is proportional to the length of the boundary between the liquid and the tube, with the proportionality constant usually denoted . Since the length of this boundary is the circumference of the tube, the force due to surface tension is given by
where d is the tube diameter.
The mass m of the drop hanging from the end of the tube can be found by equating the force due to gravity () with the component of the surface tension in the vertical direction () giving the formula
where α is the angle of contact with the tubes front surface, and g' is the acceleration due to gravity.
The limit of this formula, as α goes to 90°, gives the maximum weight of a pendant drop for a liquid with a given surface tension, .
This relationship is the basis of a convenient method of measuring surface tension, commonly used in the petroleum industry. More sophisticated methods are available to take account of the developing shape of the pendant as the drop grows. These methods are used if the surface tension is unknown. | 1 | Applied and Interdisciplinary Chemistry |
All transcriptomic techniques have been particularly useful in identifying the functions of genes and identifying those responsible for particular phenotypes. Transcriptomics of Arabidopsis ecotypes that hyperaccumulate metals correlated genes involved in metal uptake, tolerance, and homeostasis with the phenotype. Integration of RNA-Seq datasets across different tissues has been used to improve annotation of gene functions in commercially important organisms (e.g. cucumber) or threatened species (e.g. koala).
Assembly of RNA-Seq reads is not dependent on a reference genome and so is ideal for gene expression studies of non-model organisms with non-existing or poorly developed genomic resources. For example, a database of SNPs used in Douglas fir breeding programs was created by de novo transcriptome analysis in the absence of a sequenced genome. Similarly, genes that function in the development of cardiac, muscle, and nervous tissue in lobsters were identified by comparing the transcriptomes of the various tissue types without use of a genome sequence. RNA-Seq can also be used to identify previously unknown protein coding regions in existing sequenced genomes. | 1 | Applied and Interdisciplinary Chemistry |
P-NMR spectroscopy is useful to assay purity and to assign structures of phosphorus-containing compounds because these signals are well resolved and often occur at characteristic frequencies. Chemical shifts and coupling constants span a large range but sometimes are not readily predictable. The Gutmann-Beckett method uses EtPO in conjunction with P-NMR spectroscopy to assess the Lewis acidity of molecular species. | 0 | Theoretical and Fundamental Chemistry |
Iodosobenzene is prepared from iodobenzene. It is prepared by first oxidizing iodobenzene by peracetic acid. Hydrolysis of resulting diacetate affords "PhIO":
The structure of iodosobenzene has been verified by crystallographically. Related derivatives are also oligomeric. Its low solubility in most solvents and vibrational spectroscopy indicate that it is not molecular, but is polymeric, consisting of –I–O–I–O– chains. The related diacetate, , illustrates the ability of iodine(III) to adopt a T-shaped geometry without multiple bonds.
Theoretical studies show that the bonding between the iodine and oxygen atoms in iodosobenzene represents a single dative I-O sigma bond, confirming the absence of the double I=O bond.
A monomeric derivative iodosylbenzene is known in the form of 2-(tert-butylsulfonyl)iodosylbenzene, a yellow solid. C-I-O angle is 94.78°, C-I and I-O distances are 2.128 and 1.848 Å. | 0 | Theoretical and Fundamental Chemistry |
The reaction requires metal catalysts. Most commercially important processes employ heterogeneous catalysts. The heterogeneous catalysts are often prepared by in-situ activation of a metal halide (MCl) using organoaluminium or organotin compounds, e.g. combining MCl–EtAlCl. A typical catalyst support is alumina. Commercial catalysts are often based on molybdenum and ruthenium. Well-defined organometallic compounds have mainly been investigated for small-scale reactions or in academic research. The homogeneous catalysts are often classified as Schrock catalysts and Grubbs catalysts. Schrock catalysts feature molybdenum(VI)- and tungsten(VI)-based centers supported by alkoxide and imido ligands.
Grubbs catalysts, on the other hand, are ruthenium(II) carbenoid complexes. Many variations of Grubbs catalysts are known. Some have been modified with a chelating isopropoxybenzylidene ligand to form the related Hoveyda–Grubbs catalyst. | 0 | Theoretical and Fundamental Chemistry |
Researchers at the Université de Montréal are working with Photon etc. and Optina Diagnostics to test the use of hyperspectral photography in the diagnosis of retinopathy and macular edema before damage to the eye occurs. The metabolic hyperspectral camera will detect a drop in oxygen consumption in the retina, which indicates potential disease. An ophthalmologist will then be able to treat the retina with injections to prevent any potential damage. | 0 | Theoretical and Fundamental Chemistry |
The phosphaethynolate anion is the heavier isoelectronic congener of the cyanate anion. It has been shown that it behaves in a similar way to its lighter analogue, as an ambidentate nucleophile. This ambidentate character of the anion means that it is able to bind via both the phosphorus and oxygen atoms depending on the nature of the centre being coordinated.
Computational studies carried out on the anion such as Natural Bond Orbital (NBO) and Natural Resonance Theory (NRT) analyses can go part way to explain why PCO can react in such a manner . The two dominant resonance forms of the phosphaethynolate anion localise negative charge on either the phosphorus or oxygen atoms meaning both are sites of nucleophilicity. The same applies for the cyanate anion hence why PCO is observed to have similar pseudo-halogenic behaviour. | 0 | Theoretical and Fundamental Chemistry |
The reaction between tricarbonylchromium complexes Cr(CO)L and electron-rich or electron-neutral aromatic rings produces tricarbonyl(arene)chromium complexes (arene)Cr(CO). Complexation to chromium(0) activates the side chain of the arene, facilitating dissociation of a benzylic proton, leaving group, or nucleophilic addition to the homobenzylic position of styrenes. Further transformations of the resulting conformationally restricted, benzylic anion or cation involve the approach of reagents exo to the chromium fragment. Thus, benzylic functionalization reactions of planar chiral chromium arene complexes are highly diastereoselective. Additionally, the chromium tri(carbonyl) fragment can be used as a blocking element in addition reactions to ortho-substituted aromatic aldehydes and alkenes. An ortho substituent is necessary in these reactions to restrict conformations available to the aldehyde or alkene. Removal of the chromium fragment to afford the metal-free functionalized aromatic compound is possible photolytically or with an oxidant. | 0 | Theoretical and Fundamental Chemistry |
Isotopes which undergo this decay and thereby emit positrons include, but are not limited to: carbon-11, nitrogen-13, oxygen-15, fluorine-18, copper-64, gallium-68, bromine-78, rubidium-82, yttrium-86, zirconium-89, sodium-22, aluminium-26, potassium-40, strontium-83, and iodine-124. As an example, the following equation describes the beta plus decay of carbon-11 to boron-11, emitting a positron and a neutrino: | 0 | Theoretical and Fundamental Chemistry |
Other examples of non-Kekulé molecules are the biradicaloid quinodimethanes, that have a six-membered ring with methylene substituents.
Non-Kekulé polynuclear aromatic hydrocarbons are composed of several fused six-membered rings. The simplest member of this class is triangulene. After unsuccessful attempts by Erich Clar in 1953, trioxytriangulene was synthesized by Richard J. Bushby in 1995, and kinetically stabilized triangulene by Kazuhiro Nakasuji in 2001. However, in 2017 a project led by David Fox and Anish Mistry from the University of Warwick in collaboration with IBM synthesized and imaged triangulene. In 2019, larger homologues of triangulene, consisting of ten ([4]triangulene) and fifteen fused six-membered rings ([5]triangulene) were synthesized in 2019. In 2021, synthesis of the hitherto largest triangulene homologue, consisting of twenty-eight fused six-membered rings ([7]triangulene) was achieved. Scanning tunneling microscopy experiments on triangulene spin chains have revealed the clearest proof yet of the existence of Haldane gap and fractional edge states predicted for spin-1 Heisenberg chain. A related class of biradicals are para-benzynes.
Other studied biradicals are those based on pleiadene, extended viologens, corannulenes, nitronyl-nitroxide, bis(phenalenyl)s and teranthenes.
Pleiadene has been synthesised from acenaphthylene and anthranilic acid / amyl nitrite: | 0 | Theoretical and Fundamental Chemistry |
Kang is a native of Busan. He aspired to be a musician since childhood but his parents had been against it. Instead, he focused on his studies and was admitted to Pusan National University on a scholarship, eventually graduating with a degree in chemical engineering.
After completing his mandatory military service and graduating from college, he worked for Lotte BP (now Lotte INEOS) in research and development. During his tenure at Lotte, he co-authored at least one chemical patent. He co-authored several research papers, as well. | 1 | Applied and Interdisciplinary Chemistry |
Settling is the process by which particulates move towards the bottom of a liquid and form a sediment. Particles that experience a force, either due to gravity or due to centrifugal motion will tend to move in a uniform manner in the direction exerted by that force. For gravity settling, this means that the particles will tend to fall to the bottom of the vessel, forming sludge or slurry at the vessel base.
Settling is an important operation in many applications, such as mining, wastewater and drinking water treatment, biological science, space propellant reignition,
and scooping. | 0 | Theoretical and Fundamental Chemistry |
Muscarinic acetylcholine receptors are also present and distributed throughout the local nervous system, in post-synaptic and pre-synaptic positions. There is also some evidence for postsynaptic receptors on sympathetic neurons allowing the parasympathetic nervous system to inhibit sympathetic effects. | 1 | Applied and Interdisciplinary Chemistry |
To act as glycosyl donors, those monosaccharides should exist in a highly energetic form. This occurs as a result of a reaction between nucleoside triphosphate (NTP) and glycosyl monophosphate (phosphate at anomeric carbon). The recent discovery of the reversibility of many glycosyltransferase-catalyzed reactions calls into question the designation of sugar nucleotides as activated donors. | 0 | Theoretical and Fundamental Chemistry |
The offset phase can be defined as the amount of time in between the conclusion of the peak and shifting into a sober state. This is colloquially referred to as "coming down." | 1 | Applied and Interdisciplinary Chemistry |
This vast scope of functionality for a single protein makes it the ideal model for research regarding other zinc proteases of unknown structure. Recent biomedical research on collagenase, enkephalinase, and angiotensin-converting enzyme used carboxypeptidase A for inhibitor synthesis and kinetic testing. For example, a drug that treats high blood pressure, Captopril, was designed based on a carboxypeptidase A inhibitor. Carboxypeptidase A and the target enzyme of Captopril, angiotensin-converting enzyme, have very similar structures, as they both contain a zinc ion within the active site. This allowed for a potent carboxypeptidase A inhibitor to be used to inhibit the enzyme and, thus, lower blood pressure through the renin-angiotensin-aldosterone system. | 1 | Applied and Interdisciplinary Chemistry |
Optical physics is the study of the generation of electromagnetic radiation, the properties of that radiation, and the interaction of that radiation with matter, especially its manipulation and control. It differs from general optics and optical engineering in that it is focused on the discovery and application of new phenomena. There is no strong distinction, however, between optical physics, applied optics, and optical engineering, since the devices of optical engineering and the applications of applied optics are necessary for basic research in optical physics, and that research leads to the development of new devices and applications. Often the same people are involved in both the basic research and the applied technology development, for example the experimental demonstration of electromagnetically induced transparency by S. E. Harris and of slow light by Harris and Lene Vestergaard Hau.
Researchers in optical physics use and develop light sources that span the electromagnetic spectrum from microwaves to X-rays. The field includes the generation and detection of light, linear and nonlinear optical processes, and spectroscopy. Lasers and laser spectroscopy have transformed optical science. Major study in optical physics is also devoted to quantum optics and coherence, and to femtosecond optics. In optical physics, support is also provided in areas such as the nonlinear response of isolated atoms to intense, ultra-short electromagnetic fields, the atom-cavity interaction at high fields, and quantum properties of the electromagnetic field.
Other important areas of research include the development of novel optical techniques for nano-optical measurements, diffractive optics, low-coherence interferometry, optical coherence tomography, and near-field microscopy. Research in optical physics places an emphasis on ultrafast optical science and technology. The applications of optical physics create advancements in communications, medicine, manufacturing, and even entertainment. | 0 | Theoretical and Fundamental Chemistry |
The C5 fragment 24 required for the synthesis of the C ring (scheme 3) was prepared from 2,3-dibromopropene (20) by reaction with ethyl acetate (21), n-butyllithium and a copper salt, followed by organic reduction of acetate 22 to alcohol 23 (lithium aluminium hydride) and its TES silylation. Michael addition of 24 with the cyclooctane 19 to 25 with t-BuLi was catalyzed by copper cyanide. After removal of the TES group (HCl, THF), the alcohol 26 was oxidized to aldehyde 27 (TPAP, NMO)which enabled the intramolecular Aldol reaction to bicycle 28. | 0 | Theoretical and Fundamental Chemistry |
In biochemical engineering, sparging can remove low-boiling liquids from a solution. The low-boiling components evaporate more rapidly, so the gas bubbles remove more of them from the bulk solution containing higher-boiling components. It is an alternative to distillation, and it does not require heat. | 1 | Applied and Interdisciplinary Chemistry |
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