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Lev T. Perelman, principal scientist at MIT, and Vadim Backman, graduate student in Harvard- MIT Health Sciences and Technology program introduced LSS in 1998. | 0 | Theoretical and Fundamental Chemistry |
The production of BCF and similar chlorofluorocarbons has been banned in most countries since January 1, 1994 as part of the Montreal Protocol on ozone depleting substances. Halon 1211 is also a potent greenhouse gas with a 100-year global warming potential 2,070 times that of carbon dioxide and an atmospheric lifetime of 16.0 years.
Recycling of Halon 1211 allows it to remain in use, although parts availability is limited to a few manufacturers and can be an issue. Halon 1211 is still widely used in the United States, despite its high cost, with the US military being the biggest user. Europe and Australia have banned its use for all but "critical applications" such as aviation, military, and police use. The manufacture of UL Listed halon 1211 extinguishers was supposed to cease on October, 2009. The future listing is still in discussion. Halotron I, the replacement extinguishing agent, requires a larger volume to get the same ratings as 1211. | 1 | Applied and Interdisciplinary Chemistry |
The conversion of malate to pyruvate and lactate is catalyzed by
*NAD(P) dependent malate decarboxylase (malic enzyme; EC 1.1.1.39 and 1.1.1.40) and
*lactate dehydrogenase (LDH; EC 1.1.1.27)
according to the following equations:
*malate + NAD(P)→ pyruvate + NAD(P)H + H + CO
*pyruvate + NADH + H → lactate + NAD | 1 | Applied and Interdisciplinary Chemistry |
The first large scale British civil defence issue was the Geiger–Müller counter Meter, Contamination, No. 1 set — stock number "5CG0012", of 1953. It had 0–10 mR/hour range with external probe and headphones. This was designed to use two 150 volt batteries, although later they were fitted with a vibrator power pack which used four 1.35 volt mercury cells or, alternatively, a mains electricity power pack. Many of these units remained in service until the 1980s. There was also a Mk. 2 model which used rubber connectors and cable for the probe unit, compared to the Plessey connectors of the Mk.1.
This used cold-cathode valves and very high impedance circuitry throughout to extend useful battery life as long as possible with the existing technology. | 0 | Theoretical and Fundamental Chemistry |
Fuel costs: about 0.8 to 2.0 USD/L plus deposit for IBC container. For middle scale amounts of hydrogen (bundle of gas cylinders) price for 0.13 kg of fossile hydrogen is usually about 5 to 12 USD plus rental fee for the cylinders. The significantly higher price for hydrogen compared to methanol is amongst others caused by the complex logistics and storage of hydrogen. Whereas biomethanol and renewable e-Methanol are available at distributors, green hydrogen is typically not yet available at distributors. Prices for renewable hydrogen as well as for renewable methanol are expected to decrease in future. Energy conversion: | 1 | Applied and Interdisciplinary Chemistry |
Micrometeorites have been collected from deep-sea sediments, sedimentary rocks and polar sediments. They were previously collected primarily from polar snow and ice because of their low concentrations on the Earth's surface, but in 2016 a method to extract micrometeorites in urban environments was discovered. | 0 | Theoretical and Fundamental Chemistry |
The synthesis of nanocomposite hydrogels is a process that requires specific material and method. These polymers need to be made up of equally spaced out, 30 nm in diameter, clay platelets that can swell and exfoliate in the presence of water. The platelets act as cross-links to modify molecular functions to enable the hydrogels to have superior elasticity and toughness that resembles closely that of biological tissue. Using clay platelets that do not swell or exfoliate in water, using an organic cross-linker such as N,N-methylenebisacrylamide(BIS), mixing of clay and BIS, or preparing nanocomposite hydrogels in a method other than cross-link, will be unsuccessful.
Despite all the specifications, the process of synthesizing nanocomposite hydrogels is simple and because of the flexible nature of the material, these hydrogels can be easily made to come in different shapes such as huge blocks, sheets, thin films, rods, hollow tubes, spheres, bellows and uneven sheets. | 0 | Theoretical and Fundamental Chemistry |
Recent work has demonstrated that the scope of "soft" nucleophiles can be expanded to include some pronucleophiles that have much higher than ~ 25. Some of these "soft" nucleophiles have ranging all the way to 32, and even more basic pronucleophiles (~44) have been shown to act as soft nucleophiles with the addition of Lewis acids that help to facilitate deprotonation. The improved pKa range of "soft" nucleophiles is critical because these nucleophiles are the only ones that have been explored for enantioselective reactions until very recently (although non-enantioselective reactions of "hard" nucleophiles have been known for some time). By increasing the scope of pronucleophiles that act as "soft" nucleophiles, these substrates can also be incorporated into enantioselective reactions using previously reported and well characterized methods. | 0 | Theoretical and Fundamental Chemistry |
Oxophilic reagents are often used to extract or exchange oxygen centers in organic substrates, especially carbonyls (esters, ketones, amides) and epoxides. The highly oxophilic reagent generated from tungsten hexachloride and butyl lithium is useful for the deoxygenation of epoxides. Such conversions are sometimes valuable in organic synthesis. In the McMurry reaction, ketones are converted into alkenes using oxophilic reagents:
:2 RCO + Ti → RC=CR + TiO
Similarly, Tebbe's reagent is used in olefination reactions:
: CpTiCHAlCl(CH) + RC=O → CpTiO + 0.5 (AlCl(CH)) + RC=CH
Oxophilic main group compounds are also well known and useful. The highly oxophilic reagent SiCl stereospecifically deoxygenates phosphine oxides. Phosphorus pentasulfide and the related Lawesson's reagent convert certain organic carbonyls to the corresponding sulfur derivatives:
:PS + n RC=O → PSO + n RC=S
Owing to the high stability of carbon dioxide, many carbon compounds such as phosgene are oxophilic. This reactivity is used for recycling of triphenylphosphine oxide:
:OPPh + COCl → ClPPh + CO | 0 | Theoretical and Fundamental Chemistry |
Some enzymes can carry out thousands of chemical reactions each second. However, RuBisCO is slow, fixing only 3-10 carbon dioxide molecules each second per molecule of enzyme. The reaction catalyzed by RuBisCO is, thus, the primary rate-limiting factor of the Calvin cycle during the day. Nevertheless, under most conditions, and when light is not otherwise limiting photosynthesis, the speed of RuBisCO responds positively to increasing carbon dioxide concentration.
RuBisCO is usually only active during the day, as ribulose 1,5-bisphosphate is not regenerated in the dark. This is due to the regulation of several other enzymes in the Calvin cycle. In addition, the activity of RuBisCO is coordinated with that of the other enzymes of the Calvin cycle in several other ways: | 0 | Theoretical and Fundamental Chemistry |
Microscopic algae that can tolerate extremely cold temperatures can survive in snow, ice, and very cold seawater. On snow, cold-tolerant algae can bloom on the snow surface covering land, glaciers, or sea ice when there is sufficient light. These snow algae darken the surface of the snow and can contribute to snow melt. In seawater, phytoplankton that can tolerate both very high salinities and very cold temperatures are able to live in sea ice. One example of a psychrophilic phytoplankton species is the ice-associated diatom Fragilariopsis cylindrus. Phytoplankton living in the cold ocean waters near Antarctica often have very high protein content, containing some of the highest concentrations ever measured of enzymes like Rubisco. | 1 | Applied and Interdisciplinary Chemistry |
It is extremely difficult to generalize at what pressures or temperatures the deviation from the ideal gas becomes important. As a rule of thumb, the ideal gas law is reasonably accurate up to a pressure of about 2 atm, and even higher for small non-associating molecules. For example, methyl chloride, a highly polar molecule and therefore with significant intermolecular forces, the experimental value for the compressibility factor is at a pressure of 10 atm and temperature of 100 °C. For air (small non-polar molecules) at approximately the same conditions, the compressibility factor is only (see table below for 10 bars, 400 K). | 0 | Theoretical and Fundamental Chemistry |
In the 1990s, the Niihama copper refinery, owned by Sumitomo Metal Mining Company Limited (“Sumitomo”), treated copper anode slimes generated in-house, together with anode slimes from Sumitomo’s Toyo refinery and lead refinery slime from the Harima Imperial Smelting Process smelter. A total of 1200 tonnes per year (“t/y”) of anode slimes and 400 t/y of lead refinery slimes were treated using a process flow sheet that included a chloridizing step to remove separate the lead as lead chloride (PbCl) and a reverberatory-type doré furnace. It produced about 200 t of silver, 22 t of gold, 1.5 t of palladium, 300 kilograms (“kg”) of platinum and 40 kg of rhodium, as well as 60 t of selenium, 50 t of bismuth, 900 kg of tellurium and 150 t of antimony alloy annually.
The gold production doubled during the decade to 1996, as its concentration in anode slimes and the quantity of anode slimes increased. To enable this, Sumitomo decided in 1990 to upgrade the refinery, and as part of that upgrade, installed a 3.5 t-capacity BBOC to replace its reverberatory doré furnace in October 1992.
Sumitomo reported that, while the old oil-fired reverberatory furnace had served it well for many years, it had the following drawbacks:
* its operation was labor-intensive
* it had a low fuel efficiency
* there was a high waste gas volume
* the reaction rate was low.
Sumitomo investigated both the TBRC and BBOC furnaces before making a selection. It chose the BBOC over the TBRC technology because of the ease of control of the bath temperature, its high oxygen efficiency and its simple maintenance.
Sumitomo found that the impurity contents of BBOC doré anodes was high when the furnace was first commissioned. This was because it was important to determine the endpoint of the oxidation reactions to maximize the quality of the anodes. Sumitomo found that this could be determined by measuring the oxygen content of the off-gas using oxygen sensors based on stabilized zirconia with an Fe/FeO reference electrode.
Sumitomo subsequently adapted the BBOC to allow the chloridizing step to be undertaken in the furnace, thus eliminating the need for a separate chloridizing furnace for lead chloride production. This was done in February 1994 and was reported to be “giving very good results.” | 1 | Applied and Interdisciplinary Chemistry |
Wu Yundong () is a Chinese chemist. He is a theoretical organic chemist based in the Hong Kong University of Science and Technology and holds a concurrent position in Peking University. He was born 10 May 1957 in Liyang, Jiangsu, China. He graduated with a BS from Lanzhou University in 1982 and received his PhD in 1986 from the University of Pittsburgh, working with Kendall N. Houk in computational organic chemistry. He went on to become a research associate in University of California Los Angeles from 1989 to 1992, before beginning his independent research career in Hong Kong.
Professor Wu has received numerous awards in his career; in December 2005, he was elected as an Academician of the prestigious Chinese Academy of Sciences. His research interest focuses mainly on the elucidation of reaction mechanisms, protein-protein interactions/aggregations (Alzheimer's disease etc.) and conformational features of natural and unnatural peptides. | 0 | Theoretical and Fundamental Chemistry |
The use of copper had become very apparent to civilizations, such as its properties of elasticity and plasticity that allow it to be hammered into useful shapes, along with its ability to be melted and poured into intricate shapes. Although, the advantages of copper were many, the material was too soft to find large scale usefulness. Through experimentation or by chance, additions to copper lead to increased hardness of a new metal alloy, called bronze. Bronze was originally composed of copper and arsenic, forming arsenic bronze. | 1 | Applied and Interdisciplinary Chemistry |
The Nanodragster, dubbed the worlds smallest hot rod, is a molecular nanocar. The design improves on previous nanocar designs and is a step towards creating molecular machines. The name comes from the nanocars resemblance to a dragster, as its staggered wheel fitment has a shorter axle with smaller wheels in the front and a larger axle with larger wheels in the back.
The nanocar was developed at Rice University’s Richard E. Smalley Institute Nanoscale Science and Technology by the team of James Tour, Kevin Kelly and other colleagues involved in its research. The previous nanocar developed was 3 to 4 nanometers which was a little a strand of DNA and was around 20,000 times thinner than a human hair. These nanocars were built with carbon buckyballs as their four wheels, and the surface on which they were placed required a temperature of to get it moving. On the other hand, a nanocar which utilized p-carborane wheels moves as if sliding on ice, rather than rolling. Such observations led to the production of nanocars which had both wheel designs.
The nanodragster is 50,000 times thinner than a human hair and has a top speed of 0.014 millimeters per hour (0.0006 in/h or 3.89×10 m/s). The rear wheels are spherical fullerene molecules, or buckyballs, composed of sixty carbon atoms each, which are attracted to a dragstrip that is made up of a very fine layer of gold. This design also enabled Tour’s team to operate the device at lower temperatures.
The nanodragster and other nano-machines are designed for use in transporting items. The technology can be used in manufacturing computer circuits and electronic components, or in conjunction with pharmaceuticals inside the human body. Tour also speculated that the knowledge gained from the nanocar research would help build efficient catalytic systems in the future. | 0 | Theoretical and Fundamental Chemistry |
First results to these problems were obtained by Leonard Adleman.
* In 1994: Solving a Hamiltonian path in a graph with 7 summits.
* In 2002: Solving a NP-complete problem as well as a 3-SAT problem with 20 variables. | 1 | Applied and Interdisciplinary Chemistry |
Pan Britannica Industries Ltd (PBI) was a household and agrochemical formulation company incorporated in 1932 and based at Britannica House, Stewardstone Road, Waltham Abbey and with a distribution presence in Wisbech in Cambridgeshire. PBI was, in common with many other UK household names, both a manufacturer and marketing organisation for both agricultural and horticultural products.
PBI produced many agro-chemical formulations for farmers, however it was perhaps best known for its product Baby Bio, a liquid plant food that came in a small perfume-shaped bottle. PBI was also the original publisher of the Expert range of gardening books, starting with Be Your Own Gardening Expert written in 1958 by Dr D.G. Hessayon, who later became the company's chairman.
The company was sold to Sumitomo Corporation on 28 September 1990, and rebranded as PBI Home & Garden in 1998. In March 1999 the company was acquired by global conglomerate Bayer. The company has ceased production at Waltham Abbey, the works have been demolished and the site redeveloped for a Tesco supermarket. The rebranded company, PBI Home and Garden, was dissolved in 2015. | 1 | Applied and Interdisciplinary Chemistry |
In physical chemistry, the Evans–Polanyi principle (also referred to as the Bell–Evans–Polanyi principle, Brønsted–Evans–Polanyi principle, or Evans–Polanyi–Semenov principle) observes that the difference in activation energy between two reactions of the same family is proportional to the difference of their enthalpy of reaction.
This relationship can be expressed as
where
: is the activation energy of a reference reaction of the same class,
: is the enthalpy of reaction,
: characterizes the position of the transition state along the reaction coordinate (such that ).
The Evans–Polanyi model is a linear energy relationship that serves as an efficient way to calculate activation energy of many reactions within a distinct family. The activation energy may be used to characterize the kinetic rate parameter of a given reaction through application of the Arrhenius equation.
The Evans–Polanyi model assumes that the pre-exponential factor of the Arrhenius equation and the position of the transition state along the reaction coordinate are the same for all reactions belonging to a particular reaction family. | 0 | Theoretical and Fundamental Chemistry |
During DNA damage or cellular stress PARPs are activated, leading to an increase in the amount of poly(ADP-ribose) and a decrease in the amount of NAD. For over a decade it was thought that PARP1 was the only poly(ADP-ribose)polymerase in mammalian cells, therefore this enzyme has been the most studied. Caspases are a family of cysteine proteases that are known to play an essential role in programmed cell death. This protease cleaves PARP-1 into two fragments, leaving it completely inactive, to limit poly(ADP-ribose) production. One of its fragments migrates from the nucleus to the cytoplasm and is thought to become a target of autoimmunity.
During caspase-independent apoptosis, also called parthanatos, poly(ADP-ribose) accumulation can occur due to activation of PARPs or inactivation of poly(ADP-ribose)glycohydrolase, an enzyme that hydrolyses poly(ADP-ribose) to produce free ADP-ribose. Studies have shown poly(ADP-ribose) drives the translocation of the apoptosis inducing factor protein to the nucleus where it will mediate DNA fragmentation. It has been suggested that if a failure of caspase activation under stress conditions were to occur, necroptosis would take place. Overactivation of PARPs has led to a necrotic cell death regulated by the tumor necrosis factor protein. Though the mechanism is not yet understood, PARP inhibitors have been shown to affect necroptosis. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen darkening is a physical degradation of the optical properties of glass. Free hydrogen atoms are able to bind to the SiO silica glass compound forming hydroxyl (OH)—a chemical compound that interferes with the passage of light through the glass.
The problem is particularly relevant to fiber-optic cables—particularly in oil and gas wells where fiber optic cables are used for distributed temperature sensing (DTS). Hydrogen can be present due to the cracking of hydrocarbons in the well. The darkening of the fiber can distort the DTS reading and possibly render the DTS system inoperable due to the optical loss budget being exceeded.
To prevent this, coatings such as carbon are applied to the fiber, and hydrogen capturing gels are used to buffer the fiber and other proprietary techniques may be used to prevent hydrogen atoms from reaching the glass fiber via the cable sheath. | 0 | Theoretical and Fundamental Chemistry |
In this region, the dominant deformation mechanism is power law creep, such that the strain rate goes as the stress raised to a stress exponent n. This region is dominated by dislocation creep. The value of this stress exponent is dependent upon the material and the microstructure. If deformation is occurring by slip, n=1-8, and for grain boundary sliding n=2 or 4.
The general equation for power law creep is as follows, where <math>A_2
is the applied shear stress, and is the effective diffusion constant.
Within the power law creep region, there are two subsections corresponding to low temperature power law creep that is dominated by core controlled dislocation motion and high temperature power law creep that is controlled by diffusion in the lattice. Low temperature core diffusion, sometimes called pipe diffusion, occurs because dislocations are more quickly able to diffuse through the pipe-like core of a dislocation. The effective diffusion coefficient in the strain rate equation depends on whether or not the system is dominated by core diffusion or lattice diffusion and can be generalized as follows where is the volumetric lattice diffusion constant, is the area corresponding to the dislocation core, is the diffusion coefficient for the core, and b is the Burger's vector.
In the high temperature region, the effective diffusion constant is simply the volumetric lattice diffusion constant, whereas at low temperatures the diffusion constant is given by the expression . Thus in the high temperature power law creep region, the strain rate goes as , and in the low temperature power law creep region the strain rate goes as . | 1 | Applied and Interdisciplinary Chemistry |
The amount of useful work which may be extracted from a thermodynamic system is determined by the second law of thermodynamics. Under many practical situations this can be represented by the thermodynamic availability, or Exergy, function. Two important cases are: in thermodynamic systems where the temperature and volume are held constant, the measure of useful work attainable is the Helmholtz free energy function; and in systems where the temperature and pressure are held constant, the measure of useful work attainable is the Gibbs free energy. | 0 | Theoretical and Fundamental Chemistry |
The following list of glass database contents is not complete, and it may not be up to date. For full features see the references section below. All databases contain citations to the original data sources and the chemical composition of the glasses or ceramics.
*SciGlass: Viscosity, density, mechanical properties, optical properties (including optical spectra), thermal expansion and other thermal properties, electrical properties, chemical durability, liquidus temperatures, crystallization characteristics, ternary diagrams of glass formation, glass property calculation methods, patent and trademark index, subject index etc.
*Interglad: Viscosity, density, mechanical properties, optical properties, electrical properties, statistical analysis, liquidus temperatures, ternary property diagrams
*Phase Equilibria Diagrams: Phase diagrams, including liquidus and solidus temperatures, eutectic points, crystalline phases, primary crystalline phases | 0 | Theoretical and Fundamental Chemistry |
CDP recognizes companies with high-quality disclosure in its annual scoring process, with top companies making it onto CDP's so-called A-list.
Scores are calculated according to a standardized method which measures whether and how well a company responds to each question. A company goes through four main steps, starting with disclosure of their current position, moving to awareness which looks at whether a company is conscious of its environmental impact, to management, and finally leadership.
A high CDP score is supposed to be indicative of a company's environmental awareness, advanced sustainability governance and leadership to address climate change. | 1 | Applied and Interdisciplinary Chemistry |
The Boord olefin synthesis is an organic reaction forming alkenes from ethers carrying a halogen atom 2 carbons removed from the oxygen atom (β-halo-ethers) using a metal such as magnesium or zinc. The reaction, discovered by Cecil E. Boord in 1930 is a classic named reaction with high yields and broad scope.
The reaction type is an elimination reaction with magnesium forming an intermediate Grignard reagent. The alkoxy group is a poor leaving group and therefore an E1cB elimination reaction mechanism is proposed. The original publication describes the organic synthesis of the compound isoheptene in several steps.
In a 1931 publication the scope is extended to 1,4-dienes with magnesium replaced by zinc (see also: Barbier reaction). In the first part of the reaction the allyl Grignard acts as a nucleophile in nucleophilic aliphatic substitution. | 0 | Theoretical and Fundamental Chemistry |
The dilution in welding terms is defined as the weight of the base metal melted divided by the total weight of the weld metal. For example, if we have a dilution of 0.40, the fraction of the weld metal that came from the consumable electrode is 0.60. | 0 | Theoretical and Fundamental Chemistry |
Flash smelting () is a smelting process for sulfur-containing ores including chalcopyrite. The process was developed by Outokumpu in Finland and first applied at the Harjavalta plant in 1949 for smelting copper ore. It has also been adapted for nickel and lead production.
A second flash smelting system was developed by the International Nickel Company (INCO) and has a different concentrate feed design compared to the Outokumpu flash furnace. The Inco flash furnace has end-wall concentrate injection burners and a central waste gas off-take, while the Outokumpu flash furnace has a water-cooled reaction shaft at one end of the vessel and a waste gas off-take at the other end. While the INCO flash furnace at Sudbury was the first commercial use of oxygen flash smelting, fewer smelters use the INCO flash furnace than the Outokumpu flash furnace.
Flash smelting with oxygen-enriched air (the reaction gas) makes use of the energy contained in the concentrate to supply most of the energy required by the furnaces. The concentrate must be dried before it is injected into the furnaces and, in the case of the Outokumpu process, some of the furnaces use an optional heater to warm the reaction gas typically to 100–450 °C.
The reactions in the flash smelting furnaces produce copper matte, iron oxides and sulfur dioxide. The reacted particles fall into a bath at the bottom of the furnace, where the iron oxides react with fluxes, such as silica and limestone, to form a slag.
In most cases, the slag can be discarded, perhaps after some cleaning, and the matte is further treated in converters to produce blister copper. In some cases where the flash furnaces are fed with concentrate containing a sufficiently high copper content, the concentrate is converted directly to blister in a single Outokumpu furnace and further converting is unnecessary.
The sulfur dioxide produced by flash smelting is typically captured in a sulfuric acid plant, removing the major environmental effect of smelting.
Outotec, formerly the technology division of Outokumpu, now holds Outokumpu's patents to the technology and licenses it worldwide.
INCO was acquired by Brazil's Vale in 2006. | 1 | Applied and Interdisciplinary Chemistry |
Ocean surface habitats sit at the interface between the ocean and the atmosphere. The biofilm-like habitat at the surface of the ocean harbours surface-dwelling microorganisms, commonly referred to as neuston. This vast air–water interface sits at the intersection of major air–water exchange processes spanning more than 70% of the global surface area . Bacteria in the surface microlayer of the ocean, called bacterioneuston, are of interest due to practical applications such as air-sea gas exchange of greenhouse gases, production of climate-active marine aerosols, and remote sensing of the ocean. Of specific interest is the production and degradation of surfactants (surface active materials) via microbial biochemical processes. Major sources of surfactants in the open ocean include phytoplankton, terrestrial runoff, and deposition from the atmosphere.
Unlike coloured algal blooms, surfactant-associated bacteria may not be visible in ocean colour imagery. Having the ability to detect these "invisible" surfactant-associated bacteria using synthetic aperture radar has immense benefits in all-weather conditions, regardless of cloud, fog, or daylight. This is particularly important in very high winds, because these are the conditions when the most intense air-sea gas exchanges and marine aerosol production take place. Therefore, in addition to colour satellite imagery, SAR satellite imagery may provide additional insights into a global picture of biophysical processes at the boundary between the ocean and atmosphere, air-sea greenhouse gas exchanges and production of climate-active marine aerosols. | 0 | Theoretical and Fundamental Chemistry |
Newly built coal-fired power plants can be made to immediately use gasification of the coal prior to combustion. This makes it much easier to separate off the from the exhaust fumes, making the process cheaper. This gasification process is done in new coal-burning power plants such as the coal-burning power plant at Tianjin, called "GreenGen". | 1 | Applied and Interdisciplinary Chemistry |
Radionuclides are used in two major ways: either for their radiation alone (irradiation, nuclear batteries) or for the combination of chemical properties and their radiation (tracers, biopharmaceuticals).
* In biology, radionuclides of carbon can serve as radioactive tracers because they are chemically very similar to the nonradioactive nuclides, so most chemical, biological, and ecological processes treat them in a nearly identical way. One can then examine the result with a radiation detector, such as a Geiger counter, to determine where the provided atoms were incorporated. For example, one might culture plants in an environment in which the carbon dioxide contained radioactive carbon; then the parts of the plant that incorporate atmospheric carbon would be radioactive. Radionuclides can be used to monitor processes such as DNA replication or amino acid transport.
* in physics and biology radionuclide X-ray fluorescence spectrometry is used to determine chemical composition of the compound. Radiation from a radionuclide source hits the sample and excites characteristic X-rays in the sample. This radiation is registered and the chemical composition of the sample can be determined from the analysis of the measured spectrum. By measuring the energy of the characteristic radiation lines, it is possible to determine the proton number of the chemical element that emits the radiation, and by measuring the number of emitted photons, it is possible to determine the concentration of individual chemical elements.
* In nuclear medicine, radioisotopes are used for diagnosis, treatment, and research. Radioactive chemical tracers emitting gamma rays or positrons can provide diagnostic information about internal anatomy and the functioning of specific organs, including the human brain. This is used in some forms of tomography: single-photon emission computed tomography and positron emission tomography (PET) scanning and Cherenkov luminescence imaging. Radioisotopes are also a method of treatment in hemopoietic forms of tumors; the success for treatment of solid tumors has been limited. More powerful gamma sources sterilise syringes and other medical equipment.
* In food preservation, radiation is used to stop the sprouting of root crops after harvesting, to kill parasites and pests, and to control the ripening of stored fruit and vegetables. Food irradiation usually uses beta-decaying nuclides with strong gamma emissions like cobalt-60 or caesium-137.
* In industry, and in mining, radionuclides are used to examine welds, to detect leaks, to study the rate of wear, erosion and corrosion of metals, and for on-stream analysis of a wide range of minerals and fuels.
* In spacecraft, radionuclides are used to provide power and heat, notably through radioisotope thermoelectric generators (RTGs) and radioisotope heater units (RHUs).
* In astronomy and cosmology, radionuclides play a role in understanding stellar and planetary process.
* In particle physics, radionuclides help discover new physics (physics beyond the Standard Model) by measuring the energy and momentum of their beta decay products (for example, neutrinoless double beta decay and the search for weakly interacting massive particles).
* In ecology, radionuclides are used to trace and analyze pollutants, to study the movement of surface water, and to measure water runoffs from rain and snow, as well as the flow rates of streams and rivers.
* In geology, archaeology, and paleontology, natural radionuclides are used to measure ages of rocks, minerals, and fossil materials. | 0 | Theoretical and Fundamental Chemistry |
The definitions of the thermodynamic potentials may be differentiated and, along with the first and second laws of thermodynamics, a set of differential equations known as the fundamental equations follow. (Actually they are all expressions of the same fundamental thermodynamic relation, but are expressed in different variables.) By the first law of thermodynamics, any differential change in the internal energy of a system can be written as the sum of heat flowing into the system subtracted by the work done by the system on the environment, along with any change due to the addition of new particles to the system:
where is the infinitesimal heat flow into the system, and is the infinitesimal work done by the system, is the chemical potential of particle type and is the number of the type particles. (Neither nor are exact differentials, i.e., they are thermodynamic process path-dependent. Small changes in these variables are, therefore, represented with rather than .)
By the second law of thermodynamics, we can express the internal energy change in terms of state functions and their differentials. In case of reversible changes we have:
where
: is temperature,
: is entropy,
: is pressure,
and is volume, and the equality holds for reversible processes.
This leads to the standard differential form of the internal energy in case of a quasistatic reversible change:
Since , and are thermodynamic functions of state (also called state functions), the above relation also holds for arbitrary non-reversible changes. If the system has more external variables than just the volume that can change, the fundamental thermodynamic relation generalizes to:
Here the are the generalized forces corresponding to the external variables .
Applying Legendre transforms repeatedly, the following differential relations hold for the four potentials (fundamental thermodynamic equations or fundamental thermodynamic relation):
The infinitesimals on the right-hand side of each of the above equations are of the natural variables of the potential on the left-hand side. Similar equations can be developed for all of the other thermodynamic potentials of the system. There will be one fundamental equation for each thermodynamic potential, resulting in a total of fundamental equations.
The differences between the four thermodynamic potentials can be summarized as follows: | 0 | Theoretical and Fundamental Chemistry |
Favipiravir has been approved to treat influenza in Japan. It is, however, only indicated for novel influenza (strains that cause more severe disease) rather than seasonal influenza. As of 2020, the probability of resistance developing appears low. | 0 | Theoretical and Fundamental Chemistry |
A thermal loop is a movement of air driven by warm air rising at one end of the loop, and cool air descending at the other end, creating a constantly moving loop of air. They can be used to precisely control the temperature of a specific area. Thermal loops also occur in liquids.
Thermal loops are size-independent; that is to say, they may occur in a space as small as a room or as large as a global hemisphere. The Hadley cell is an example of a global-scale thermal loop. | 1 | Applied and Interdisciplinary Chemistry |
The first industrial applications - mainly for water, soil extracts and fertilizer - used the same hardware and techniques as clinical methods, but from the mid-1970s special techniques and modules were developed so that by 1990 it was possible to perform solvent extraction, distillation, on-line filtration and UV digestion in the continuously flowing stream. In 2005 about two thirds of systems sold worldwide were for water analysis of all kinds, ranging from sub-ppb levels of nutrients in seawater to much higher levels in waste water; other common applications are for soil, plant, tobacco, food, fertilizer and wine analysis. | 0 | Theoretical and Fundamental Chemistry |
In general, eukaryotic cells sense the presence of chemotactic stimuli through the use of 7-transmembrane (or serpentine) heterotrimeric G-protein-coupled receptors, a class representing a significant portion of the genome. Some members of this gene superfamily are used in eyesight (rhodopsins) as well as in olfaction (smelling). The main classes of chemotaxis receptors are triggered by:
* Formyl peptides - formyl peptide receptors (FPR),
* Chemokines - chemokine receptors (CCR or CXCR), and
* Leukotrienes - leukotriene receptors (BLT).
However, induction of a wide set of membrane receptors (e.g., cyclic nucleotides, amino acids, insulin, vasoactive peptides) also elicit migration of the cell. | 1 | Applied and Interdisciplinary Chemistry |
It is disputed that Wöhlers synthesis sparked the downfall of the theory of vitalism, which states that organic matter possessed a certain vital force' common to all living things. Prior to the Wöhler synthesis, the work of John Dalton and Jöns Jacob Berzelius had already convinced chemists that organic and inorganic matter obey the same chemical laws. It took until 1845 when Kolbe reported another inorganic – organic conversion (of carbon disulfide to acetic acid) before vitalism started to lose support. Wöhler also did not, as some textbooks have claimed, act as a "crusader" against vitalism. A 2000 survey by historian Peter Ramberg found that 90% of chemical textbooks repeat some version of the Wöhler myth. | 0 | Theoretical and Fundamental Chemistry |
An epitaxial layer can be doped during deposition by adding impurities to the source gas, such as arsine, phosphine, or diborane. Dopants in the source gas, liberated by evaporation or wet etching of the surface, may also diffuse into the epitaxial layer and cause autodoping. The concentration of impurity in the gas phase determines its concentration in the deposited film. Doping can also be achieved by a site-competition technique, where the growth precursor ratios are tuned to enhance the incorporation of vacancies, specific dopant species or vacant-dopant clusters into the lattice. Additionally, the high temperatures at which epitaxy is performed may allow dopants to diffuse into the growing layer from other layers in the wafer (out-diffusion). | 0 | Theoretical and Fundamental Chemistry |
Whereas the initial experimental demonstration of hyper-Rayleigh scattering optical activity was observed at the second harmonic of the illumination frequency of light, the effect is general and can be observed at higher harmonics. The first demonstration of hyper-Rayleigh scattering optical activity at the third harmonic was reported by Valev's team in 2021, from sliver nanohelices. | 0 | Theoretical and Fundamental Chemistry |
Ziryab is said to have improved the Oud (or Laúd) by adding a fifth pair of strings, and using an eagle's beak or quill instead of a wooden pick. Ziryab also dyed the four strings a color to symbolize the Aristotelian humors, and the fifth string to represent the soul. He is said to have created a unique and influential style of musical performance, and written songs that were performed in Iberia for generations. He was a great influence on Spanish music, and is considered the founder of the Andalusian music traditions of North Africa.
Ziryab's Baghdadi musical style became very popular in the court of Abd al-Rahman II. Ziryab also became the example of how a courtier, a person who attended aristocratic courts, should act. According to Ibn Hayyan, in common with erudite men of his time he was well versed in many areas of classical study such as astronomy, history, and geography.
According to al-Tifashi, Ziryab appears to have popularized an early song-sequence, which may have been a precursor to the nawba (originally simply a performer's "turn" to perform for the prince), or Nuba, which is known today as the classical Arabic music of North Africa, though the connections are tenuous at best.
Abd al-Rahman II was a great patron of the arts and Ziryab was given a great deal of freedom. He established one of the first schools of music in Córdoba. This school incorporated both male and female students, who were very popular amongst the aristocracy of the time. According to Ibn Hayyan, Ziryab developed various tests for them. If a student didn't have a large vocal capacity, for instance, he would put pieces of wood in their jaw to force them to hold their mouth open. Or he would tie a sash tightly around the waist to make them breathe in a particular way, and he would test incoming students by having them sing as loudly and as long a note as they possibly could to see whether they had lung capacity. | 1 | Applied and Interdisciplinary Chemistry |
Since ethanol boils at a much lower temperature than water, simple distillation can separate ethanol from water by applying heat to the mixture. Historically, a copper vessel was used for this purpose, since copper removes undesirable sulfur-based compounds from the alcohol. However, many modern stills are made of stainless steel pipes with copper linings to prevent erosion of the entire vessel and lower copper levels in the waste product (which in large distilleries is processed to become animal feed). Copper is the preferred material for stills because it yields an overall better-tasting spirit. The taste is improved by the chemical reaction between the copper in the still and the sulfur compounds created by the yeast during fermentation. These unwanted and flavor-changing sulfur compounds are chemically removed from the final product resulting in a smoother, better-tasting drink. All copper stills will require repairs about every eight years due to the precipitation of copper-sulfur compounds. The beverage industry was the first to implement a modern distillation apparatus and led the way in developing equipment standards which are now widely accepted in the chemical industry.
There is also an increasing usage of the distillation of gin under glass and PTFE, and even at reduced pressures, to facilitate a fresher product. This is irrelevant to alcohol quality because the process starts with triple distilled grain alcohol, and the distillation is used solely to harvest botanical flavors such as limonene and other terpene like compounds. The ethyl alcohol is relatively unchanged.
The simplest standard distillation apparatus is commonly known as a pot still, consisting of a single heated chamber and a vessel to collect purified alcohol. A pot still incorporates only one condensation, whereas other types of distillation equipment have multiple stages which result in higher purification of the more volatile component (alcohol). Pot still distillation gives an incomplete separation, but this can be desirable for the flavor of some distilled beverages.
If a purer distillate is desired, a reflux still is the most common solution. Reflux stills incorporate a fractionating column, commonly created by filling copper vessels with glass beads to maximize available surface area. As alcohol boils, condenses, and reboils through the column, the effective number of distillations greatly increases. Vodka and gin and other neutral grain spirits are distilled by this method, then diluted to concentrations appropriate for human consumption.
Alcoholic products from home distilleries are common throughout the world but are sometimes in violation of local statutes. The product of illegal stills in the United States is commonly referred to as moonshine and in Ireland, poitín. However, poitín, although made illegal in 1661, has been legal for export in Ireland since 1997. Note that the term moonshine itself is often misused as many believe it to be a specific kind of high-proof alcohol that was distilled from corn, but the term can refer to any illicitly distilled alcohol. | 0 | Theoretical and Fundamental Chemistry |
The Wilfley Table was conceived by Arthur Wilfley, a mining engineer based in Kokomo, Colorado in the United States. As a silver mine operator, Wilfley spent many years refining his separation table design in order to make the extraction of silver more economic. Rather than using heating processes (smelting) to concentrate the ore, Wilfley had been experimenting on mineral separation by use mineral density contrasts.
Wilfley was able to perfect a mechanical solution for the recovery of gold and silver from low-grade ores by means of the Wilfley table. The first Wilfley table was built on a preliminary scale in May 1895. The first full-sized table was used in Wilfley's own mill in Kokomo, in May 1896, while the first table sold for installation was placed in the Puzzle Mill, Breckinridge, Colorado, in August 1896. Patented in 1897, the Wilfley table made mining lower-grade ores profitable. Pulverised ore, suspended in a water solution, was washed across a sloping riffled vibrating table so that metals separated as they drained off.
The Wilfley Table was said to have revolutionised ore dressing worldwide and more than 25,000 were in service by the 1930s. | 1 | Applied and Interdisciplinary Chemistry |
Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:
() 0.5 M HClO | 0 | Theoretical and Fundamental Chemistry |
Sulfur isotopes of sediments are often measured for studying environments in the Earth's past (Paleoenvironment). Disproportionation of sulfur intermediates, being one of the processes affecting sulfur isotopes of sediments, has drawn attention from geoscientists for studying the redox conditions in the oceans in the past.
Sulfate-reducing bacteria fractionate sulfur isotopes as they take in sulfate and produce sulfide. Prior to 2010s, it was thought that sulfate reduction could fractionate sulfur isotopes up to 46 permil and fractionation larger than 46 permil recorded in sediments must be due to disproportionation of sulfur intermediates in the sediment. This view has changed since the 2010s. As substrates for disproportionation are limited by the product of sulfate reduction, the isotopic effect of disproportionation should be less than 16 permil in most sedimentary settings.
Disproportionation can be carried out by microorganisms obligated to disproportionation or microorganisms that can carry out sulfate reduction as well. Common substrates for disproportionation include elemental sulfur, thiosulfate and sulfite. | 0 | Theoretical and Fundamental Chemistry |
Sulfuric acid produced by microorganisms will interact with the surface of the structure material. For ordinary Portland cement, it reacts with the calcium hydroxide in concrete to form calcium sulfate. This change simultaneously destroys the polymeric nature of calcium hydroxide and substitutes a larger molecule into the matrix causing pressure and spalling of the adjacent concrete and aggregate particles. The weakened crown may then collapse under heavy overburden loads. Even within a well-designed sewer network, a rule of thumb in the industry suggests that 5% of the total length may/will suffer from biogenic corrosion. In these specific areas, biogenic sulfide corrosion can deteriorate metal or several millimeters per year of concrete (see Table).
For calcium aluminate cements, processes are completely different because they are based on another chemical composition. At least three different mechanisms contribute to the better resistance to biogenic corrosion:
* The first barrier is the larger acid neutralizing capacity of calcium aluminate cements vs. ordinary Portland Cement; one gram of calcium aluminate cement can neutralize around 40% more acid than a gram of ordinary Portland Cement. For a given production of acid by the biofilm, a calcium aluminate cement concrete will last longer.
* The second barrier is due to the precipitation, when the surficial pH gets below 10, of a layer of alumina gel (AH3 in cement chemistry notation). AH3 is a stable compound down to a pH of 4 and it will form an acid-resistant barrier as long as the surface pH is not lowered below 3-4 by the bacterial activity.
* The third barrier is the bacteriostatic effect locally activated when the surface reaches pH values less than 3–4. At this level, the alumina gel is no longer stable and will dissolve, liberating aluminum ions. These ions will accumulate in the thin biofilm. Once the concentration reaches 300-500 ppm, it will produce a bacteriostatic effect on bacteria metabolism. In other word, bacteria will stop oxidizing the sulfur from HS to produce acid, and the pH will stop decreasing.
A mortar made of calcium aluminate cement combined with
calcium aluminate aggregates, i.e. a 100% calcium aluminate material, will last much longer as aggregates can also limit microorganisms’ growth and inhibits the acid generation at the source itself. | 1 | Applied and Interdisciplinary Chemistry |
The Caspian Sea is at its South Caspian Basin, like the Black Sea, a remnant of the ancient Paratethys Sea. Its seafloor is, therefore, a standard oceanic basalt and not a continental granite body. It is estimated to be about 30 million years old, and became landlocked in the Late Miocene, about 5.5 million years ago, due to tectonic uplift and a fall in sea level. The Caspian Sea was a comparatively small endorheic lake during the Pliocene, but its surface area increased fivefold around the time of the Pliocene-Pleistocene transition. During warm and dry climatic periods, the landlocked sea almost dried up, depositing evaporitic sediments like halite that were covered by wind-blown deposits and were sealed off as an evaporite sink when cool, wet climates refilled the basin. (Comparable evaporite beds underlie the Mediterranean.) Due to the current inflow of fresh water in the north, the Caspian Sea water is almost fresh in its northern portions, getting more brackish toward the south. It is most saline on the Iranian shore, where the catchment basin contributes little flow. Currently, the mean salinity of the Caspian is one third that of Earth's oceans. The Garabogazköl lagoon, which dried up when water flow from the main body of the Caspian was blocked in the 1980s but has since been restored, routinely exceeds oceanic salinity by a factor of 10. | 1 | Applied and Interdisciplinary Chemistry |
Starting in the mid-late 2010s, many pieces of US climate and environment policy have sought to make use of the climate change mitigation potential of carbon sequestration. Many of these policies involve either conservation of carbon sink ecosystems, such as forests and wetlands, or encouraging agricultural and land use practices designed to increase carbon sequestration such as carbon farming or agroforestry, often through financial incentivization for farmers and landowners.
The Executive Order on Tackling the Climate Crisis at Home and Abroad, signed by president Joe Biden on January 27, 2021, includes several mentions of carbon sequestration via conservation and restoration of carbon sink ecosystems, such as wetlands and forests. These include emphasizing the importance of farmers, landowners, and coastal communities in carbon sequestration, directing the Treasury Department to promote conservation of carbon sinks through market based mechanisms, and directing the Department of the Interior to collaborate with other agencies to create a Civilian Climate Corps to increase carbon sequestration in agriculture, among other things. | 0 | Theoretical and Fundamental Chemistry |
The nucleus accumbens (NAc) has a significant role in addiction. In the nucleus accumbens of mice, repeated cocaine exposure resulted in reduced TET1 messenger RNA (mRNA) and reduced TET1 protein expression. Similarly, there was a ~40% decrease in TET1 mRNA in the NAc of human cocaine addicts examined postmortem.
As indicated above in learning and memory, a short hairpin RNA (shRNA) is an artificial RNA molecule with a tight hairpin turn that can be used to silence target gene expression via RNA interference. Feng et al. injected shRNA targeted to TET1 in the NAc of mice. This could reduce TET1 expression in the same manner as reduction of TET1 expression with cocaine exposure. They then used an indirect measure of addiction, conditioned place preference. Conditioned place preference can measure the amount of time an animal spends in an area that has been associated with cocaine exposure, and this can indicate an addiction to cocaine. Reduced Tet1 expression caused by shRNA injected into the NAc robustly enhanced cocaine place conditioning. | 1 | Applied and Interdisciplinary Chemistry |
The Ark Two Shelter is a nuclear fallout shelter built by Bruce Beach (14 April 1934 – 10 May 2021) in the village of Horning's Mills (north of Toronto, Ontario). The shelter first became habitable in 1980 and has been continuously expanded and improved since then. The shelter is composed of 42 school buses, which were buried underground as patterns for concrete that was then poured over to provide the main structure, onto which up to 5 meters (14 feet) of earth were piled to provide fallout protection.
With construction beginning in the early 1980s (during the cold war), the shelter was designed to accommodate as many as five hundred people for the length of time required to allow the widespread nuclear fallout to decay to a level allowing a safe return to the surface after a cataclysmic nuclear event.
Powered by redundant diesel generators, the heavily fortified ("virtually impenetrable to anything short of a direct nuclear strike") shelter includes two commercial kitchens, full plumbing (including a private well for potable water and a motel-sized septic tank), three months' worth of diesel, a radio-based communications centre, a chapel, and a decontamination room.
Ark Two is equipped with a communications room capable of broadcasting locally on the FM broadcast band and throughout Canada and the United States on the AM and Shortwave bands. A particularly novel feature is a collapsible, weather-balloon-deployed antenna, capable of being launched from within the shelter. All Ark Two communication equipment is EMP-hardened and generator-powered so as to be able to transmit survival information to the general public in the event of nuclear war.
Beach did not charge money for admission to the shelter, instead guaranteeing individuals admission in return for sweat equity and active involvement in the Ark Two communities various activities. In addition, "Everyone is welcome here, regardless of religion, race, nationality, political views..." In return for the promise of safe haven in times of nuclear attack, a person residing in nearby areas might be expected to, for example, work at the shelter several weekends each year, assisting in the routine maintenance or continuing renovations of the facility. A large percentage of the shelter population is expected to be children, as the primary purpose of the shelter is to serve as an "underground orphanage, a place where a new generation could be saved from nuclear apocalypse," which, according to Beach, would otherwise wipe out over 80% of the worlds population. "Were going to say to people: Well, we have room for your children, but we dont have room for you. That's the nature of life... this is the lifeboat."
Beach believed that the majority of preppers are too concerned with personal survival, when they should be focused on reconstructing the world after a cataclysmic disaster. He ran an online "reconstruction network" (the "SAFE" community) through which he shared information about Ark Two and his evacuation plans.
Ark Two was featured in Beachs interview for National Geographics Doomsday Preppers, episode 8: "Its Gonna Get Worse". It was also featured on the Global Television Network series 16:9, and on the Showtime series Penn & Teller: Bullshit!' episode "End of the World" and How the World Ends - "Nostradamus".
Beach died on May 10, 2021, of a heart attack.
Beach has authored two related books: Society After Doomsday and TRIAD Individual Networking: Preparedness For Disastrous Times. | 0 | Theoretical and Fundamental Chemistry |
It is the primary reactant in Yamaguchi esterification. 2,4,6-Trichlorobenzoyl chloride readily reacts with alcohols. This newly formed reagent, when mixed with a stoichiometric amount of 4-dimethylaminopyridine, cyclizes and forms esters. This reaction creates 2,4,6-trichlorobenzoic acid as a byproduct. | 0 | Theoretical and Fundamental Chemistry |
The variation in the Lagrangian with respect to variations in the velocity potential Φ(x,z,t), as well as with respect to the surface elevation , have to be zero. We consider both variations subsequently. | 1 | Applied and Interdisciplinary Chemistry |
There are three pairs of main salivary glands and between 800 and 1,000 minor salivary glands, all of which mainly serve the digestive process, and also play an important role in the maintenance of dental health and general mouth lubrication, without which speech would be impossible. The main glands are all exocrine glands, secreting via ducts. All of these glands terminate in the mouth. The largest of these are the parotid glands—their secretion is mainly serous. The next pair are underneath the jaw, the submandibular glands, these produce both serous fluid and mucus. The serous fluid is produced by serous glands in these salivary glands which also produce lingual lipase. They produce about 70% of the oral cavity saliva. The third pair are the sublingual glands located underneath the tongue and their secretion is mainly mucous with a small percentage of saliva.
Within the oral mucosa, and also on the tongue, palates, and floor of the mouth, are the minor salivary glands; their secretions are mainly mucous and they are innervated by the facial nerve (CN7). The glands also secrete amylase a first stage in the breakdown of food acting on the carbohydrate in the food to transform the starch content into maltose. There are other serous glands on the surface of the tongue that encircle taste buds on the back part of the tongue and these also produce lingual lipase. Lipase is a digestive enzyme that catalyses the hydrolysis of lipids (fats). These glands are termed Von Ebner's glands which have also been shown to have another function in the secretion of histatins which offer an early defense (outside of the immune system) against microbes in food, when it makes contact with these glands on the tongue tissue. Sensory information can stimulate the secretion of saliva providing the necessary fluid for the tongue to work with and also to ease swallowing of the food. | 1 | Applied and Interdisciplinary Chemistry |
The Electrochemical Society was founded in 1902 in Philadelphia, PA. At the beginning, ECS was called the American Electrochemical Society.
The 19th century saw many applications of electricity to chemical processes and chemical understanding. Bridging the gap between electrical engineering and chemistry led people in industrial and academic circles to search for a new forum to discuss developments in the burgeoning field of electrochemistry.
The original constitution of the Society called for holding meetings and publishing papers presented there and the ensuing discussions. In 1902 the Society ushered in a new publication, Transactions of the American Electrochemical Society. In 1907 the first “local” section was formed at the University of Wisconsin. That same year, the American Electrochemical Society Bulletin was launched; it became the Journal of The Electrochemical Society in 1948.
In the 1920s, topical interest area divisions began to be founded, including the High Temperature Materials Division and the Electrodeposition Division. In 1930, the international nature of the Society was officially recognized by dropping “American” from the name. A new category of membership was started in 1941 to permit industrial companies to support the Society’s mission. ECS began fulfilling the need for critical textbooks with the publication of its second monograph, the Corrosion Handbook, by H. H. Uhlig in 1948.
Throughout the latter half of the 20th century, the Society continued to grow in size and importance, expanding the number of its publications, and the significance of the technical research unveiled at its meetings.
Over time, the Society’s members and publications’ authors have included many distinguished scientists and engineers. The Society’s original charter members included:
* E. G. Acheson, who commercialized carborundum, an artificial graphite;
* H. H. Dow, the founder of Dow Chemical Company;
* C. M. Hall, the inventor of the Hall process for the manufacture of aluminum;
* Edward Weston, the founder of Weston Instruments.
Thomas A. Edison joined the Society in 1903 and enjoyed membership for 28 years. In 1965, Gordon Moores seminal prediction, Moores Law, developed its roots within the Society. ECS has included numerous Nobel laureates among its members, most recently the three co-winners of the 2019 Nobel Prize in Chemistry. John B. Goodenough, M. Stanley Whittingham, and Akira Yoshino shared the prize “for the development of lithium-ion batteries.” | 0 | Theoretical and Fundamental Chemistry |
* German Physical Society
* Academia Europaea
* Member of the Russian Academy of Natural Sciences
* Foreign member of the Polish Academy of Arts and Sciences | 1 | Applied and Interdisciplinary Chemistry |
In host–guest chemistry, a carcerand () is a host molecule that completely entraps its guest (which can be an ion, atom or other chemical species) so that it will not escape even at high temperatures. This type of molecule was first described in 1985 by Donald J. Cram and coworkers. The complexes formed by a carcerand with permanently imprisoned guests are called carceplexes.
In contrast, hemicarcerands allow guests to enter and exit the cavity at high temperatures but will form stable complexes at ambient temperatures. The complexes formed by a hemicarcerand and a guest are called hemicarceplexes. | 0 | Theoretical and Fundamental Chemistry |
The School of Chemistry, University of Sydney is a school of the Faculty of Science at the University of Sydney.
Two Nobel Laureates are associated with the School: John Cornforth completed his undergraduate degree in the School, graduating in 1938 with First Class Honours and the University Medal; and Robert Robinson was appointed as the first Professor of Pure and Applied Organic Chemistry at the university in 1912. | 1 | Applied and Interdisciplinary Chemistry |
This term was introduced by Kelvin in 1904, the year that he published his Baltimore Lecture of 1884. Kelvin used the term homochirality as a relationship between two molecules, i.e. two molecules are homochiral if they have the same chirality. Recently, however, homochiral has been used in the same sense as enantiomerically pure. This is permitted in some journals (but not encouraged), its meaning changing into the preference of a process or system for a single optical isomer in a pair of isomers in these journals. | 0 | Theoretical and Fundamental Chemistry |
StochSim is a particle-based stochastic simulator used mainly to model chemical reactions and other molecular transitions. The algorithm used in StochSim is different from the more widely known Gillespie stochastic algorithm in that it operates on individual entities, not entity pools, making it particle-based rather than population-based.
In StochSim, each molecular species can be equipped with a number of binary state flags representing a particular modification. Reactions can be made dependent on a set of state flags set to particular values. In addition, the outcome of a reaction can include a state flag being changed. Moreover, entities can be arranged in geometric arrays (for instance, for holoenzymes consisting of several subunits), and reactions can be "neighbor-sensitive", i.e. the probability of a reaction for a given entity is affected by the value of a state flag on a neighboring entity. These properties make StochSim ideally suited to modeling multi-state molecules arranged in holoenzymes or complexes of specified size. Indeed, StochSim has been used to model clusters of bacterial chemotactic receptors, and CaMKII holoenzymes.
An extension to StochSim includes a particle-based simulator DYNSTOC, which uses a StochSim-like algorithm to simulate models specified in the BioNetGen language (BNGL), and improves the handling of molecules within macromolecular complexes.
Another particle-based stochastic simulator that can read BNGL input files is RuleMonkey. Its simulation algorithm differs from the algorithms underlying both StochSim and DYNSTOC in that the simulation time step is variable.
The Network-Free Stochastic Simulator (NFSim) differs from those described above by allowing for the definition of reaction rates as arbitrary mathematical or conditional expressions and thereby facilitates selective coarse-graining of models. RuleMonkey and NFsim implement distinct but related simulation algorithms. A detailed review and comparison of both tools is given by Yang and Hlavacek.
It is easy to imagine a biological system where some components are complex multi-state molecules, whereas others have few possible states (or even just one) and exist in large numbers. A hybrid approach has been proposed to model such systems: Within the Hybrid Particle/Population (HPP) framework, the user can specify a rule-based model, but can designate some species to be treated as populations (rather than particles) in the subsequent simulation. This method combines the computational advantages of particle-based modeling for multi-state systems with relatively low molecule numbers and of population-based modeling for systems with high molecule numbers and a small number of possible states. Specification of HPP models is supported by BioNetGen, and simulations can be performed with NFSim. | 1 | Applied and Interdisciplinary Chemistry |
In most countries, a separate definition of VOCs is used with regard to indoor air quality that comprises each organic chemical compound that can be measured as follows: adsorption from air on Tenax TA, thermal desorption, gas chromatographic separation over a 100% nonpolar column (dimethylpolysiloxane). VOC (volatile organic compounds) are all compounds that appear in the gas chromatogram between and including n-hexane and n-hexadecane. Compounds appearing earlier are called VVOC (very volatile organic compounds); compounds appearing later are called SVOC (semi-volatile organic compounds).
France, Germany (AgBB/DIBt), Belgium, Norway (TEK regulation), and Italy (CAM Edilizia) have enacted regulations to limit VOC emissions from commercial products. European industry has developed numerous voluntary ecolabels and rating systems, such as EMICODE, M1, Blue Angel, GuT (textile floor coverings), Nordic Swan Ecolabel, EU Ecolabel, and Indoor Air Comfort. In the United States, several standards exist; California Standard CDPH Section 01350 is the most common one. These regulations and standards changed the marketplace, leading to an increasing number of low-emitting products. | 0 | Theoretical and Fundamental Chemistry |
Biological cells which form bonds with a substrate and are at the same time subject to a flow can form long thin membrane cylinders called tethers. These tethers connect the adherent area of the substrate to the main body of the cell. Under physiological conditions, neutrophil tethers can extend to several micrometers.
In biochemistry, a tether is a molecule that carries one or two carbon intermediates from one active site to another. They are commonly used in lipid synthesis, gluconeogenesis, and the conversion of pyruvate into Acetyl CoA via PDH complex. Common tethers are lipoate -lysine residue complex associated with dihydrolipoyl transacetylase, which is used for carrying hydroxyethyl from hydroxyethyl TPP. This compound forms Acetyl- CoA, a convergent molecule in metabolic pathways.
Another tether is biotin-lysine residue complex associated with pyruvate carboxylase, an enzyme which plays an important role in gluconeogenesis. It is involved in the production of oxaloacetate from pyruvate.
One of the biological tethers used in the synthesis of fats is a β- mercaptoethylamine-pantothenate complex associated with an acyl carrier protein. | 1 | Applied and Interdisciplinary Chemistry |
There is a simplified special case for the spectroscopic parameters of a sheet. This sheet consists of three plane parallel layers (1:front surface, 2:interior, 3:rear surface) in which the surfaces both have the same remission fraction when illuminated from either direction, regardless of the relative refractive indices of the two media on either side of the surface. For the case of zero absorption in the interior, the total remission and transmission from the layer can be determined from the infinite series, where is the remission from the surface:
These formulas can be modified to account for absorption. Alternatively, the spectroscopic parameters of a sheet (or slab) can be built up from the spectroscopic parameters of the individual pieces that compose the layer: surface, interior, surface. This can be done using an approach developed by Kubelka for treatment of inhomogeneous layers. Using the example from the previous section: { , , } {, , }.
We will assume the interior of the sheet is composed of a material that has Napierian absorption coefficient of 0.5 cm, and the sheet is 1 mm thick (). For this case, on a single trip through the interior, according to the Bouguer-Lambert law, , which according to our assumptions yields and . Thus { , , }.
Then one of Benford's equations can be applied. If , and are known for layer and and are known for layer , the ART fractions for a sample composed of layer and layer are:
:(The symbol means the reflectance of layer when the direction of illumination is antiparallel to that of the incident beam. The difference in direction is important when dealing with inhomogeneous layers. This consideration was added by Paul Kubelka in 1954. He also pointed out that transmission was independent of the direction of illumination, but absorption and remission were not.) | 0 | Theoretical and Fundamental Chemistry |
* Roof impact sprinkler
* Gutter sprays
* Window spray / deluge
Commercial sprays designed for EWSS are available, but most systems use commonly available irrigation sprinklers/sprays. | 1 | Applied and Interdisciplinary Chemistry |
Clinical trials are only a small part of the research that goes into developing a new treatment. Potential drugs, for example, first have to be discovered, purified, characterized, and tested in labs (in cell and animal studies) before ever undergoing clinical trials. In all, about 1,000 potential drugs are tested before just one reaches the point of being tested in a clinical trial. For example, a new cancer drug has, on average, six years of research behind it before it even makes it to clinical trials. But the major holdup in making new cancer drugs available is the time it takes to complete clinical trials themselves. On average, about eight years pass from the time a cancer drug enters clinical trials until it receives approval from regulatory agencies for sale to the public. Drugs for other diseases have similar timelines.
Some reasons a clinical trial might last several years:
* For chronic conditions such as cancer, it takes months, if not years, to see if a cancer treatment has an effect on a patient.
* For drugs that are not expected to have a strong effect (meaning a large number of patients must be recruited to observe any effect), recruiting enough patients to test the drug's effectiveness (i.e., getting statistical power) can take several years.
* Only certain people who have the target disease condition are eligible to take part in each clinical trial. Researchers who treat these particular patients must participate in the trial. Then they must identify the desirable patients and obtain consent from them or their families to take part in the trial.
A clinical trial might also include an extended post-study follow-up period from months to years for people who have participated in the trial, a so-called "extension phase", which aims to identify long-term impact of the treatment.
The biggest barrier to completing studies is the shortage of people who take part. All drug and many device trials target a subset of the population, meaning not everyone can participate. Some drug trials require patients to have unusual combinations of disease characteristics. It is a challenge to find the appropriate patients and obtain their consent, especially when they may receive no direct benefit (because they are not paid, the study drug is not yet proven to work, or the patient may receive a placebo). In the case of cancer patients, fewer than 5% of adults with cancer will participate in drug trials. According to the Pharmaceutical Research and Manufacturers of America (PhRMA), about 400 cancer medicines were being tested in clinical trials in 2005. Not all of these will prove to be useful, but those that are may be delayed in getting approved because the number of participants is so low.
For clinical trials involving potential for seasonal influences (such as airborne allergies, seasonal affective disorder, influenza, and skin diseases), the study may be done during a limited part of the year (such as spring for pollen allergies), when the drug can be tested.
Clinical trials that do not involve a new drug usually have a much shorter duration. (Exceptions are epidemiological studies, such as the Nurses' Health Study). | 1 | Applied and Interdisciplinary Chemistry |
In polymer chemistry, the molar mass distribution (or molecular weight distribution) describes the relationship between the number of moles of each polymer species () and the molar mass () of that species. In linear polymers, the individual polymer chains rarely have exactly the same degree of polymerization and molar mass, and there is always a distribution around an average value. The molar mass distribution of a polymer may be modified by polymer fractionation. | 0 | Theoretical and Fundamental Chemistry |
Since scraping applications are important for non-Newtonian fluid (for example, scraping paint, nail polish, cream, butter, honey, etc.,), it is essential to consider this case. The analysis was carried out by J. Riedler and Wilhelm Schneider in 1983 and they were able to obtain self-similar solutions for power-law fluids satisfying the relation for the apparent viscosity
where and are constants. The solution for the streamfunction of the flow created by the plate moving towards right is given by
where
and
where is the root of . It can be verified that this solution reduces to that of Taylor's for Newtonian fluids, i.e., when . | 1 | Applied and Interdisciplinary Chemistry |
The [https://www.scotlime.org Scottish Lime Centre Trust] (SLCT) was established in 1994 by a pioneer in the re-introduction of lime in building repairs in Scotland, Pat Gibbons (Mrs Patricia). She was the founder and first Director, an architect with many years experience of building conservation in Scotland. Previously she had been a Senior Architect with Historic Scotland. The Director since 2005 is Roz Artis. Housed in an historic Charlestown building, the former Estate workshop, the Centre enjoys an international reputation for its work in promoting and training in the use of lime in building.
The aims and objectives of the Trust are to:
* Promote for the public benefit the appropriate repair of Scotland's traditional and historic buildings
* Advance education through the provision of advice, training and practical experience in the use of lime for the repair and conservation of such buildings
* Promote and further the preservation and development of Scottish building traditional, crafts and skills. | 1 | Applied and Interdisciplinary Chemistry |
Germicidal lamps are used to sterilize workspaces and tools used in biology laboratories and medical facilities. If the quartz envelope transmits shorter wavelengths, such as the 185 nm mercury emission line, they can also be used wherever ozone is desired, for example, in the sanitizing systems of hot tubs and aquariums. They are also used by geologists to provoke fluorescence in mineral samples, aiding in their identification. In this application, the light produced by the lamp is usually filtered to remove as much visible light as possible, leaving just the UV light. Germicidal lamps are also used in waste water treatment in order to kill microorganisms.
The light produced by germicidal lamps is also used to erase EPROMs; the ultraviolet photons are sufficiently energetic to allow the electrons trapped on the transistors' floating gates to tunnel through the gate insulation, eventually removing the stored charge that represents binary ones and zeroes. | 0 | Theoretical and Fundamental Chemistry |
NBS can α-brominate carbonyl derivatives via either a radical pathway (as above) or via acid-catalysis. For example, hexanoyl chloride 1 can be brominated in the alpha-position by NBS using acid catalysis.
The reaction of enolates, enol ethers, or enol acetates with NBS is the preferred method of α-bromination as it is high-yielding with few side-products. | 0 | Theoretical and Fundamental Chemistry |
The ultrasensitivity (sigmoidality) of a Goldbeter–Koshland module can be measured by its Hill Coefficient:
where EC90 and EC10 are the input values needed to produce the 10% and 90% of the maximal response, respectively.
In a living cell, Goldbeter–Koshland modules are embedded in a bigger network with upstream and downstream components. This components may constrain the range of inputs that the module will receive as well as the range of the module’s outputs that network will be able to detect. Altszyler et al. (2014) studied how the effective ultrasensitivity of a modular system is affected by these restrictions. They found that Goldbeter–Koshland modules are highly sensitive to dynamic range limitations imposed by downstream components. However, in the case of asymmetric Goldbeter–Koshland modules, a moderate downstream constrain can produce effective sensitivities much larger than that of the original module when considered in isolation. | 0 | Theoretical and Fundamental Chemistry |
As a post-doctoral researcher she worked with Robert G Griffin at The Massachusetts Institute of Technology. She joined Columbia University in 1991.
McDermott is a member of the board of trustees for Harvey Mudd College. She is also a member of the Board of the New York Structural Biology Center. | 0 | Theoretical and Fundamental Chemistry |
Sanitary sewer overflow can occur due to blocked or broken sewer lines, infiltration of excessive stormwater or malfunction of pumps. In these cases untreated sewage is discharged from a sanitary sewer into the environment prior to reaching sewage treatment facilities. To avoid such overflows, maintenance is required. Blockage prevention campaigns or regulations (e.g. requiring the use of grease interceptors by some customers) may also be necessary.
The maintenance requirements vary with the type of sanitary sewer. In general, all sewers deteriorate with age, but infiltration and inflow are problems unique to sanitary sewers, since both combined sewers and storm drains are sized to carry these contributions. Holding infiltration to acceptable levels requires a higher standard of maintenance than necessary for structural integrity considerations of combined sewers. A comprehensive construction inspection program is required to prevent inappropriate connection of cellar, yard, and roof drains to sanitary sewers. The probability of inappropriate connections is higher where combined sewers and sanitary sewers are found in close proximity, because construction personnel may not recognize the difference. Many older cities still use combined sewers while adjacent suburbs were built with separate sanitary sewers.
For decades, when sanitary sewer pipes cracked or experienced other damage, the only option was an expensive excavation, removal and replacement of the damaged pipe, typically requiring street repavement afterwards. In the mid-1950s a unit was invented where two units at each end with a special cement mixture in between was pulled from one manhole cover to the next, coating the pipe with the cement under high pressure, which then cured rapidly, sealing all cracks and breaks in the pipe. Today, a similar method using epoxy resin is used by some municipalities to re-line aging or damaged pipes, effectively creating a "pipe in a pipe". These methods may be unsuitable for locations where the full diameter of the original pipe is required to carry expected flows, and may be an unwise investment if greater wastewater flows may be anticipated from population growth, increased water use, or new service connections within the expected service life of the repair.
Another popular method for replacing aged or damaged lines is called pipe bursting, where a new pipe, typically PVC or ABS plastic, is drawn through the old pipe behind an "expander head" that breaks apart the old pipe as the new one is drawn through behind it.
These methods are most suitable for trunk sewers, since repair of lines with lateral connections is complicated by making provisions to receive lateral flows without accepting undesirable infiltration from inadequately sealed junctions. | 1 | Applied and Interdisciplinary Chemistry |
Arginine fingers are also present in Ras GTPases, where they help cleave GTP to turn Ras off. Ras is a GTPase which functions in signal transduction to regulate cell growth and division. In addition to being positively charged, which helps arginine fingers function as a catalyst, the arginine finger in Ras displaces solvent molecules and creates an optional charge distribution. Like those of dUPTases, the arginine fingers of Ras GTPases are assisted by a magnesium ion. Furthermore, multiple arginine finger residues can all point towards the same point, thus focusing their effect. Mutations affecting the arginine fingers of Ras lead to trouble catalyzing GTP by factors of around two to five orders of magnitude. Thus, as Ras is an oncogene and is activated and deactivated by the hydrolysis of GTP, mutations in Rass arginine finger residues can lead to cancer. Glutamate also plays a role near arginine fingers and is stabilized by the arginines backbone chain carboxyl groups, which are known as knuckles. | 1 | Applied and Interdisciplinary Chemistry |
Any polar chromatographic surface can be used for HILIC separations. Even non-polar bonded silicas have been used with extremely high organic solvent composition, thanks to the exposed patches of silica in between the bonded ligands on the support, which can affect the interactions. With that exception, HILIC phases can be grouped into five categories of neutral polar or ionic surfaces:
*simple unbonded silica silanol or diol bonded phases
*amino or anionic bonded phases
*amide bonded phases
*cationic bonded phases
*zwitterionic bonded phases | 1 | Applied and Interdisciplinary Chemistry |
Transparent hydrogel fibers can be used as optical fiber, and stimuli-responsive functional groups can be grafted on to create optical sensors. For example, in the research done by Yun et al. the glucose-sensitive phenylboronic acid was grafted onto the polymer network. When the glucose concentration changes, the adsorption of the phenylboronic acid will change accordingly and can be recorded with the light intensity at a certain wavelength. | 0 | Theoretical and Fundamental Chemistry |
There are two types. One uses semiconductor, or less efficient metal, i.e. thermocouples, working on the principles of the Peltier-Seebeck effect. The other relies on vacuum tubes and the principles of thermionic emission. | 0 | Theoretical and Fundamental Chemistry |
Asakura and Oosawa assumed low concentrations of macromolecules. However, at high concentrations of macromolecules, structural correlation effects in the macromolecular liquid become important. Additionally, the repulsive interaction strength strongly increases for large values of (large radius/small radius). In order to account for these issues, the Derjaguin approximation, which is valid for any type of force law, has been applied to depletion forces. The Derjaguin approximation relates the force between two spheres to the force between two plates. The force is then integrated between small regions on one surface and the opposite surface, which is assumed to be locally flat. | 0 | Theoretical and Fundamental Chemistry |
In semiconductor physics the Photo-Dember effect (named after its discoverer H. Dember) consists in the formation of a charge dipole in the vicinity of a semiconductor surface after ultra-fast photo-generation of charge carriers. The dipole forms owing to the difference of mobilities (or diffusion constants) for holes and electrons which combined with the break of symmetry provided by the surface lead to an effective charge separation in the direction perpendicular to the surface. | 0 | Theoretical and Fundamental Chemistry |
AMPylation is involved in bacterial homeostasis. The most famous example is AMPylator GS-ATase (GlnE), which contributes in complex regulation of nitrogen metabolism through AMPylation of glutamine synthetase that was introduced in the AMPylation and DeAMPylation parts.
Another example of AMPylators that play a role in bacterial homeostasis is the class I Fic AMPylators (FicT), which modifies the GyrB subunit of DNA gyrase, the conserved tyrosine residue for ATP binding of ParE subunit at Topoisomerase IV. This DNA gyrase inactivation by AMPylation leads to the activation of SOS response, which is the cellular response to DNA damage. The activity of FicT AMPylation is reversible and only leads to growth arrest, but not cell death. Therefore, FicT AMPylation plays a role in regulating cell stress, which is shown in the Wolbachia bacteria that the level of FicT increases in response to doxycycline.
A Class III Fic AMPylator NmFic of N. meningtidis is also found to modify AMPylate GyrB at the conserved tyrosine for ATP binding. This shows that Fic domains are highly conserved that indicates the important role of AMPylation in regulating cellular stress in bacteria. The regulation of NmFic involves the concentration-dependent monomerization and autoAMPylation for activation of NmFic activity. | 1 | Applied and Interdisciplinary Chemistry |
The heating programme to be used depends very much on the form and reactivity of the reactants. In the control of either temperature or atmosphere, nature of the reactant chemicals are considered in detail. A good furnace is used for heat treatment. Pelleting of samples is preferred prior to heating, since it increases the area of contact between the grains. | 1 | Applied and Interdisciplinary Chemistry |
In most cases Type 1 pitting can be avoided by good working practices. Always use tubes that have been manufactured to BS EN 1057. Tubes greater than 10 mm in diameter made to this standard will always be marked the number of the standard, the nominal size, wall thickness and temper of the tube, the manufacturer’s identification mark and the date of production at least every 600 mm. Tubes less than 10 mm in diameter will be similarly marked at each end.
Once a system has been commissioned it should be either put immediately into service or drained down and dried. If either of these options is not possible then the system should be flushed though regularly until it is put into use. It should not be left to stand for more than a week. At present stagnation is the most common cause of Type 1 pitting.
Flux should be used sparingly. A small quantity should be painted over the areas to be joined and any excess removed after the joint has been made. Some fluxes are marked as water-soluble but under some circumstances they are not removed before pitting has initiated. | 1 | Applied and Interdisciplinary Chemistry |
Plutonium occurs in a variety of allotropes, even at ambient pressure. These allotropes differ widely in crystal structure and density; the α and δ allotropes differ in density by more than 25% at constant pressure. | 0 | Theoretical and Fundamental Chemistry |
Early studies on donor-acceptor complexes focused on the solvatochromism exhibited by iodine, which often results from I forming adducts with electron donors such as amines and ethers. Dihalogens X (X = Cl, Br, I) and interhalogens XY(X = I; Y = Cl, Br) are Lewis acid species capable of forming a variety of products when reacted with donor species. Among these species (including oxidation or protonated products), CT adducts D·XY have been largely investigated. The CT interaction has been quantified and is the basis of many schemes for parameterizing donor and acceptor properties, such as those devised by Gutmann, Childs, Beckett, and the ECW model.
Many organic species featuring chalcogen or pnictogen donor atoms form CT salts. The nature of the resulting adducts can be investigated both in solution and in the solid state.
In solution, the intensity of charge-transfer bands in the UV-Vis absorbance spectrum is strongly dependent upon the degree (equilibrium constant) of this association reaction. Methods have been developed to determine the equilibrium constant for these complexes in solution by measuring the intensity of absorption bands as a function of the concentration of donor and acceptor components in solution. The Benesi-Hildebrand method, named for its developers, was first described for the association of iodine dissolved in aromatic hydrocarbons.
In the solid state a valuable parameter is the elongation of the X–X or X–Y bond length, resulting from the antibonding nature of the σ* LUMO. The elongation can be evaluated by means of structural determinations (XRD) and FT-Raman spectroscopy.
A well-known example is the complex formed by iodine when combined with starch, which exhibits an intense purple charge-transfer band. This has widespread use as a rough screen for counterfeit currency. Unlike most paper, the paper used in US currency is not sized with starch. Thus, formation of this purple color on application of an iodine solution indicates a counterfeit. | 0 | Theoretical and Fundamental Chemistry |
In its earliest manifestations, molecular biology—the name was coined by Warren Weaver of the Rockefeller Foundation in 1938—was an idea of physical and chemical explanations of life, rather than a coherent discipline. Following the advent of the Mendelian-chromosome theory of heredity in the 1910s and the maturation of atomic theory and quantum mechanics in the 1920s, such explanations seemed within reach. Weaver and others encouraged (and funded) research at the intersection of biology, chemistry and physics, while prominent physicists such as Niels Bohr and Erwin Schrödinger turned their attention to biological speculation. However, in the 1930s and 1940s it was by no means clear which—if any—cross-disciplinary research would bear fruit; work in colloid chemistry, biophysics and radiation biology, crystallography, and other emerging fields all seemed promising.
In 1940, George Beadle and Edward Tatum demonstrated the existence of a precise relationship between genes and proteins. In the course of their experiments connecting genetics with biochemistry, they switched from the genetics mainstay Drosophila to a more appropriate model organism, the fungus Neurospora; the construction and exploitation of new model organisms would become a recurring theme in the development of molecular biology. In 1944, Oswald Avery, working at the Rockefeller Institute of New York, demonstrated that genes are made up of DNA (see Avery–MacLeod–McCarty experiment). In 1952, Alfred Hershey and Martha Chase confirmed that the genetic material of the bacteriophage, the virus which infects bacteria, is made up of DNA (see Hershey–Chase experiment). In 1953, James Watson and Francis Crick discovered the double helical structure of the DNA molecule based on the discoveries made by Rosalind Franklin. In 1961, François Jacob and Jacques Monod demonstrated that the products of certain genes regulated the expression of other genes by acting upon specific sites at the edge of those genes. They also hypothesized the existence of an intermediary between DNA and its protein products, which they called messenger RNA. Between 1961 and 1965, the relationship between the information contained in DNA and the structure of proteins was determined: there is a code, the genetic code, which creates a correspondence between the succession of nucleotides in the DNA sequence and a series of amino acids in proteins.
In April 2023, scientists, based on new evidence, concluded that Rosalind Franklin was a contributor and "equal player" in the discovery process of DNA, rather than otherwise, as may have been presented subsequently after the time of the discovery.
The chief discoveries of molecular biology took place in a period of only about twenty-five years. Another fifteen years were required before new and more sophisticated technologies, united today under the name of genetic engineering, would permit the isolation and characterization of genes, in particular those of highly complex organisms. | 1 | Applied and Interdisciplinary Chemistry |
Deficiency of ETF-QO results in a disorder known as glutaric acidemia type II (also known as MADD for multiple acyl-CoA dehydrogenase deficiency), in which there is an improper buildup of fats and proteins in the body. Complications can involve acidosis or hypoglycemia, with other symptoms such as general weakness, liver enlargement, increased heart failure, and carnitine deficiency. More severe cases involve congenital defects and full metabolic crisis. Genetically, it is an autosomal recessive disorder, making its occurrence fairly rare. Most affected patients are the result of single point mutations around the FAD ubiquinone interface. Milder forms of the disorder have been responsive to riboflavin therapy and are coined riboflavin-responsive MADD (RR-MADD), although due to the varying mutations causing the disease treatment and symptoms can vary considerably. | 1 | Applied and Interdisciplinary Chemistry |
A recently developed technique, acoustic force spectroscopy (AFS), allows the force manipulation of hundreds of single-molecules and single-cells in parallel, providing high experimental throughput. In this technique, a piezo element resonantly excites planar acoustic waves over a microfluidic chip. The generated acoustic waves are capable of exerting forces on microspheres with different density than the surrounding medium. Biomolecules, such as DNA, RNA or proteins, can be individually tethered between the microspheres and a surface and then probed by the acoustic forces exerted by the piezo sensor. With AFS devices it is possible to apply forces ranging from 0 to several hundreds of picoNewtons on hundreds of microspheres and obtain force-extension curves or histograms of rupture forces of many individual events in parallel.
This technique is mostly utilized to study DNA-bindings protein. For example, AFS was used to examine bacterial transcription with presence of antibacterial agents. Viral proteins also can be studied by AFS, for instance this technique was used to explore DNA compaction along with other single-molecule approaches.
Cells also can be manipulated by the acoustic forces directly, or by using microspheres as handles. | 0 | Theoretical and Fundamental Chemistry |
The Pfeiffer effect is an optical phenomenon whereby the presence of an optically active compound influences the optical rotation of a racemic mixture of a second compound.
Racemic mixtures do not rotate plane polarized light, but the equilibrium concentration of the two enantiomers can shift from unity in the presence of a strongly interacting chiral species. Paul Pfeiffer, a student of Alfred Werner and inventor of the salen ligand, reported this phenomenon. The first example of the effect is credited to Eligio Perucca, who observed optical rotations in the visible part of the spectrum when crystals of sodium chlorate, which are chiral and colourless, were stained with a racemic dye. The effect is attributed to the interaction of the optically pure substance with the second coordination sphere of the racemate. | 0 | Theoretical and Fundamental Chemistry |
Some drugs that contain a catechol group react with phosphomolybdic acid (HPMoO) to give the heteropoly-molybdenum blue colour. Micro quantities of the drugs can be determined. | 0 | Theoretical and Fundamental Chemistry |
Bufothionine is a sulfur-containing compound which is present in the bufotoxins secreted by the parotoid gland of certain toads of the genera Bufo and Chaunus. This specific compound can be found in the skin of certain species of toad such as the Asiatic Toad, Chaunus arunco, Chaunus crucifer, Chaunus spinulosus, and Chaunus arenarum. | 1 | Applied and Interdisciplinary Chemistry |
The primary debate concerning the mechanism of the rearrangement centers on whether it is a concerted (sigmatropic) or stepwise (diradical) process. Mechanistic experiments have shown that trans-divinylcyclopropanes epimerize to the corresponding cis isomers and undergo the rearrangement via what is most likely a concerted pathway. A boat-like transition state has been proposed and helps explain the observed stereospecificity of the process. Whether the initial epimerization of trans substrates occurs via a one- or two-center process is unclear in most cases.
Transition-metal-catalyzed versions of the rearrangement are known, and mechanisms vary. In one example employing rhodium bis(ethylene) hexafluoroacetylacetonate, coordination and formation of a bis-π-allyl complex precede electrocyclic ring closure and catalyst release. | 0 | Theoretical and Fundamental Chemistry |
There are actually two versions in mathematics of the abstract dual lattice concept, for a given lattice L in a real vector space V, of finite dimension.
The first, which generalises directly the reciprocal lattice construction, uses Fourier analysis. It may be stated simply in terms of Pontryagin duality. The dual group V^ to V is again a real vector space, and its closed subgroup L^ dual to L turns out to be a lattice in V^. Therefore, L^ is the natural candidate for dual lattice, in a different vector space (of the same dimension).
The other aspect is seen in the presence of a quadratic form Q on V; if it is non-degenerate it allows an identification of the dual space V of V with V. The relation of V to V is not intrinsic; it depends on a choice of Haar measure (volume element) on V. But given an identification of the two, which is in any case well-defined up to a scalar, the presence of Q allows one to speak to the dual lattice to L while staying within V.
In mathematics, the dual lattice of a given lattice L in an abelian locally compact topological group G is the subgroup L of the dual group of G consisting of all continuous characters that are equal to one at each point of L.
In discrete mathematics, a lattice is a locally discrete set of points described by all integral linear combinations of linearly independent vectors in R. The dual lattice is then defined by all points in the linear span of the original lattice (typically all of R) with the property that an integer results from the inner product with all elements of the original lattice. It follows that the dual of the dual lattice is the original lattice.
Furthermore, if we allow the matrix B to have columns as the linearly independent vectors that describe the lattice, then the matrix has columns of vectors that describe the dual lattice. | 0 | Theoretical and Fundamental Chemistry |
Carly Stevens is a professor of plant ecology and soil biogeochemistry at University of Lancaster, UK. Her work focuses on how changes in the atmospheric nitrogen cycle affect plant communities, particularly grasslands. | 0 | Theoretical and Fundamental Chemistry |
Only natural processes occur in nature. For thermodynamics, a natural process is a transfer between systems that increases the sum of their entropies, and is irreversible. Natural processes may occur spontaneously upon the removal of a constraint, or upon some other thermodynamic operation, or may be triggered in a metastable or unstable system, as for example in the condensation of a supersaturated vapour. Planck emphasised the occurrence of friction as an important characteristic of natural thermodynamic processes that involve transfer of matter or energy between system and surroundings. | 0 | Theoretical and Fundamental Chemistry |
A cordial is any invigorating and stimulating preparation that is intended for a medicinal purpose. The term derives from an obsolete usage. Various concoctions were formerly created that were believed to be beneficial to ones health, especially for the heart (cor' in Latin).
Some cordials, with their flecks of gold leaf and bright yellow hue, took their name from the "cordial virtues" of the rays of the sun, which some alchemists thought they contained. | 1 | Applied and Interdisciplinary Chemistry |
In atomic, molecular, and optical physics, above-threshold ionization (ATI) is a multi-photon effect where an atom is ionized with more than the energetically required number of photons. It was first observed in 1979 by Pierre Agostini and colleagues in xenon gas. | 0 | Theoretical and Fundamental Chemistry |
Rhee and Pugh introduce ChIP-exo by performing analyses on a small collection of transcription factors: Reb1, Gal4, Phd1, Rap1 in yeast and CTCF in human. Reb1 sites were often found in clusters and these clusters had ~10-fold higher occupancy than expected. Secondary sites in clusters were found ~40 bp from a primary binding site. Binding motifs of Gal4 showed a strong preference for three of the four nucleotides, suggesting a negative interaction between Gal4 and the excluded nucleotide. Phd1 recognizes three different motifs which explains previous reports of the ambiguity of Phd1's binding motif. Rap1 was found to recognize four motifs.
Ribosomal protein genes bound by this protein had a tendency to use a particular motif with a stronger consensus sequence. Other genes often used clusters of weaker consensus motifs, possibly to achieve a similar occupancy. Binding motifs of CTCF employed four "modules". Half of the bound CTCF sites used modules 1 and 2, while the rest used some combination of the four. It is believed that CTCF uses its zinc fingers to recognize different combinations of these modules.
Rhee and Pugh analyzed pre-initiation complex (PIC) structure and organization in Saccharomyces genomes. Using ChIP-exo, they were able to, among other discoveries, precisely identify TATA-like features in promoters reported to be TATA-less. | 1 | Applied and Interdisciplinary Chemistry |
Walter McCrone was born in Wilmington, Delaware, but he grew up mostly in New York State. His father was a civil engineer in charge of one of the first DuPont plants to manufacture cellophane. McCrone received a bachelors degree in chemistry from Cornell University in 1938 and a Ph.D. in organic chemistry from the same institution in 1942. From 1942 to 1944 he was a post-doctoral researcher at Cornell. In 1944, McCrone published a detailed study on The Microscopic Examination of High Explosives and Boosters'.
In 1944 McCrone began to work as a microscopist and materials scientist at the Armour Research Foundation, now the Illinois Institute of Technology (IIT) Research Institute. He was also a professor at IIT and served as assistant chairman of its Chemistry and Chemical Engineering Department. In 1948, McCrone and IIT electron microscopist Charles F. Tufts organized the first of the meetings that are now the International Microscopy Conference (Inter/Micro). Among the speakers at the first conference was Nobel laureate Frits Zernike.
In 1956 McCrone left IIT and founded an analytical consulting firm, McCrone Associates, which is now located in Westmont, Illinois. In 1960, he established the McCrone Research Institute, a nonprofit organization for teaching and research in microscopy and crystallography, based in Chicago. In 1979 he retired from McCrone Associates in order to dedicate himself to teaching full time. The proceeds from his work as a consulting chemist allowed McCrone to endow the Émile M. Chamot Professorship of Chemistry at Cornell, named in honor of McCrone's university mentor. According to chemist and forensic scientist John A. Reffner, "during McCrone’s life, he taught microscopy to more students than anyone else in history."
For more than thirty years McCrone edited and published The Microscope, an international quarterly journal of microscopy that had been established in 1937 by the British microscopist Arthur L. E. Barron. McCrone also wrote more than 400 technical articles along with sixteen books or chapters. He is credited with expanding the usefulness of the optical microscopy to chemists, who had previously regarded it as primarily a tool for biologists. One of his publications was the Particle Atlas, first published in 1967, which provided an exhaustive description of small particles and how to identify them with the aid of a microscope. That work became widely used in forensic laboratories. The Particle Atlas, which was written in collaboration with other staff members of McCrone Associates, appeared in a six-volume second edition in 1973. In 1992 it became available in CD-ROM.
Walter McCrone served on the board of directors and as president of the Ada S. McKinley Community Services, a nonprofit social services agency in Chicago. He died of congestive heart failure at his home in Chicago, at the age of 86. From 1957 until his death in 2002, he was married to Lucy B. McCrone, née Beman. The two had met while she was working as an analytical chemist for the management consulting firm Arthur D. Little, in Cambridge, Massachusetts. After their marriage, Lucy McCrone worked as a chemical microanalyst for McCrone Associates in Chicago and was co-founder and director of the McCrone Research Institute until 1984. | 0 | Theoretical and Fundamental Chemistry |
In the context of nuclear magnetic resonance (NMR), the term magnetic inequivalence refers to the distinction between magnetically active nuclear spins by their NMR signals, owing to a difference in either chemical shift (magnetic inequivalence by the chemical shift criterion) or spin-spin coupling (J-coupling) (magnetic inequivalence by the coupling criterion). Since chemically inequivalent spins (i.e. nuclei not related by symmetry) are expected to also be magnetically distinct (barring accidental overlap of signals), and since an observed difference in chemical shift makes their inequivalence clear, the term magnetic inequivalence most commonly refers solely to the latter type, i.e. to situations of chemically equivalent spins differing in their coupling relationships.
This situation can arise in a number of ways and can give rise to complexities in the corresponding NMR signals (beyond what a first-order analysis would handle) that range from the unnoticeable to the dramatic. | 0 | Theoretical and Fundamental Chemistry |
Cegelski has authored or co-authored multiple publications that have been cited 100 or more times. As of January 2021, these include:
* "The biology and future prospects of antivirulence therapies," Nature Reviews Microbiology.
* "Morphological plasticity as a bacterial survival strategy," Nature Reviews Microbiology.
* "Small-molecule inhibitors target Escherichia coli amyloid biogenesis and biofilm formation," Nature Chemical Biology.
* "Conformation of microtubule-bound paclitaxel determined by fluorescence spectroscopy and REDOR NMR," Biochemistry.
* "Oritavancin exhibits dual mode of action to inhibit cell-wall biosynthesis in Staphylococcus aureus," Journal of Molecular Biology.
* "Mechanochemical unzipping of insulating polyladderene to semiconducting polyacetylene," Science.
* "Phosphoethanolamine cellulose: a naturally produced chemically modified cellulose," Science. | 0 | Theoretical and Fundamental Chemistry |
Encoded Self-Assembling Chemical (ESAC) libraries rely on the principle that two sublibraries of a size of x members (e.g. 10) containing a constant complementary hybridization domain can yield a combinatorial DNA-duplex library after hybridization with a complexity of x uniformly represented library members (e.g. 10). Each sub-library member would consist of an oligonucleotide containing a variable, coding region flanked by a constant DNA sequence, carrying a suitable chemical modification at the oligonucleotide extremity. The ESAC sublibraries can be used in at least four different embodiments.
* A sub-library can be paired with a complementary oligonucleotide and used as a DNA encoded library displaying a single covalently linked compound for affinity-based selection experiments.
* A sub-library can be paired with an oligonucleotide displaying a known binder to the target, thus enabling affinity maturation strategies.
* Two individual sublibraries can be assembled combinatorially and used for the de novo identification of bindentate binding molecules.
* Three different sublibraries can be assembled to form a combinatorial triplex library.
Preferential binders isolated from an affinity-based selection can be PCR-amplified and decoded on complementary oligonucleotide microarrays or by concatenation of the codes, subcloning and sequencing. The individual building blocks can eventually be conjugated using suitable linkers to yield a drug-like high-affinity compound. The characteristics of the linker (e.g. length, flexibility, geometry, chemical nature and solubility) influence the binding affinity and the chemical properties of the resulting binder.(Fig.3)
Bio-panning experiments on HSA of a 600-member ESAC library allowed the isolation of the 4-(p-iodophenyl)butanoic moiety. The compound represents the core structure of a series of portable albumin binding molecules and of Albufluor a recently developed fluorescein angiographic contrast agent currently under clinical evaluation.
ESAC technology has been used for the isolation of potent inhibitors of bovine trypsin and for the identification of novel inhibitors of stromelysin-1 (MMP-3), a matrix metalloproteinase involved in both physiological and pathological tissue remodeling processes, as well as in disease processes, such as arthritis and metastasis. | 1 | Applied and Interdisciplinary Chemistry |
It is part of PHEs Radiation Protection Adviser Services. PHE was the UKs first Radiation Protection Adviser Body, under the Ionising Radiations Regulations (IRR) 17 (which came from the International Commission on Radiological Protection). | 1 | Applied and Interdisciplinary Chemistry |
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