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ScBCSi (x = 0.030, y = 0.36 and z = 0.026) has a cubic crystal structure with space group F3m (No. 216) and lattice constant a = 2.03085(5) nm. This compound was initially identified as ScBC (phase I in the Sc-B-C phase diagram of figure 17). A small amount of Si was added into the floating zone crystal growth and thus this phase is a quaternary compound. Its rare cubic structure has 26 sites in the unit cell: three Sc sites, two Si sites, one C site and 20 B sites; 4 out of 20 B sites are boron-carbon mixed-occupancy sites. Atomic coordinates, site occupancies and isotropic displacement factors are listed in table VIII.
In the unit cell, there are three independent icosahedra, I1, I2 and I3, and a B polyhedron which are formed by the B1–B4, B5–B8, B9–B13 and B14–B17 sites, respectively. The B polyhedron has not been observed previously and it is shown in figure 23. The icosahedron I2 has a boron-carbon mixed-occupancy site B,C6 whose occupancy is B/C=0.58/0.42. Remaining 3 boron-carbon mixed-occupancy sites are bridge sites; C and Si sites are also bridge sites.
More than 1000 atoms are available in the unit cell, which is built up by large structure units such as two supertetrahedra T(1) and T(2) and one superoctahedron O(1). As shown in figure 24a, T(1) consists of 4 icosahedra I(1) which have no direct bonding but are bridged by four B and C20 atoms. These atoms also form tetrahedron centered by the Si2 sites. The supertetrahedron T(2) that consists of 4 icosahedra I(2) is the same as shown in figure 18b; its mixed-occupancy sites B and C6 directly bond with each other. The superoctahedron O(1) consists of 6 icosahedra I(3) and bridge sites B, C18, C1 and Si1; here Si1 and C1 exhibit a tetrahedral arrangement at the center of O(1). The B polyhedra also arrange octahedrally, without the central atom, as shown in figure 24c where the B and C19 atoms bridge the B polyhedra to form the octahedral supercluster of the B polyhedra.
Using these large polyhedra, the crystal structure of ScBCSi can be described as shown in figure 25. Owing to the crystal symmetry, the tetrahedral coordination between these superstructure units is again a key factor. The supertetrahedron T(1) lies at the body center and at the edge center of the unit cell. The superoctahedra O(1) locate at the body center (0.25, 0.25, 0.25) of the quarter of the unit cell. They coordinate tetrahedrally around T(1) forming a giant tetrahedron. The supertetrahedra T(2) are located at the symmetry-related positions (0.25, 0.25, 0.75); they also form a giant tetrahedron surrounding T(1). Edges of both giant tetrahedra orthogonally cross each other at their centers; at those edge centers, each B polyhedron bridges all the super-structure clusters T(1), T(2) and O(1). The superoctahedron built of B polyhedra is located at each cubic face center.
Scandium atoms reside in the voids of the boron framework. Four Sc1 atoms form a tetrahedral arrangement inside the B polyhedron-based superoctahedron. Sc2 atoms sit between the B polyhedron-based superoctahedron and the O(1) superoctahedron. Three Sc3 atoms form a triangle and are surrounded by three B polyhedra, a supertetrahedron T(1) and a superoctahedron O(1). | 0 | Theoretical and Fundamental Chemistry |
Artifact replication plays an important role in comparing artifact use. Often objects are made not just to prove a manufacturing process or to sit in a display case, but to show that a given object will show signs of wear that are similar to those present in the archaeological record. Roberts and Ottaway conducted such experimental reconstructions by casting bronze axes using them in a preconceived manner and then comparing the results against known archaeological remains. Results gathered from such experimentation have found that objects have comparable wear patterns and there are European socketed axes that were deposited used as well as unused. Tool mark identification can also go the opposite ways using experimental reconstruction to show the difference between various material media and the wear patterns they leave. Greenfield gives one such experiment where steel, bronze, and stone tool marks on bone are all researched and examples are given for how they might be seen in the archaeological record.
Energy consumption and efficiency is another topic of interest in archaeometallurgy. Tree felling and land clearing experiments involving comparison of stone, bronze, and steel axes are popular with a number of archaeologists In these types of experiments, factors such as time spent and oxygen intake of the researchers are taken into account to try to find similarities in past life ways use of energy. | 1 | Applied and Interdisciplinary Chemistry |
Most modern laboratories use a refinement of total plate count in which serial dilutions of the sample are vacuum filtered through purpose made membrane filters and these filters are themselves laid on nutrient medium within sealed plates. The methodology is otherwise similar to conventional total plate counts. Membranes have a printed millimetre grid printed on and can be reliably used to count the number of colonies under a binocular microscope. | 0 | Theoretical and Fundamental Chemistry |
The equations and assumptions above are not representative for the actual observations of the Ekman spiral. The differences between the theory and the observations are that the angle is between 5–20 degrees instead of the 45 degrees as expected and that the Ekman layer depth and thus the Ekman spiral is less deep than expected. There are three main factors which contribute to the reason why this is, stratification, turbulence and horizontal gradients. Other less important factors which play a role in this are the Stokes drift, waves and the Stokes-Coriolis force. | 1 | Applied and Interdisciplinary Chemistry |
Hicks earned her bachelor's degree at Marshall University in 2001, and went on to earn her doctorate at the University of Illinois Urbana-Champaign in 2005. She was an Assistant Member and Principal Investigator at the Donald Danforth Plant Science Center from 2006 to 2013, and an adjunct professor in the Department of Biology at Washington University in St. Louis before beginning her current position as a professor at UNC. She was named Sherman Fairchild Foundation Chancellor’s Science Scholars Term Associate Professor in 2022. | 0 | Theoretical and Fundamental Chemistry |
Cis and trans isomers have distinct physical properties. Their differing shapes influences the dipole moments, boiling, and especially melting points.
These differences can be very small, as in the case of the boiling point of straight-chain alkenes, such as pent-2-ene, which is 37 °C in the cis isomer and 36 °C in the trans isomer. The differences between cis and trans isomers can be larger if polar bonds are present, as in the 1,2-dichloroethenes. The cis isomer in this case has a boiling point of 60.3 °C, while the trans isomer has a boiling point of 47.5 °C. In the cis isomer the two polar C–Cl bond dipole moments combine to give an overall molecular dipole, so that there are intermolecular dipole–dipole forces (or Keesom forces), which add to the London dispersion forces and raise the boiling point. In the trans isomer on the other hand, this does not occur because the two C−Cl bond moments cancel and the molecule has a net zero dipole moment (it does however have a non-zero quadrupole moment).
The differing properties of the two isomers of butenedioic acid are often very different.
Polarity is key in determining relative boiling point as strong intermolecular forces raise the boiling point. In the same manner, symmetry is key in determining relative melting point as it allows for better packing in the solid state, even if it does not alter the polarity of the molecule. Another example of this is the relationship between oleic acid and elaidic acid; oleic acid, the cis isomer, has a melting point of 13.4 °C, making it a liquid at room temperature, while the trans isomer, elaidic acid, has the much higher melting point of 43 °C, due to the straighter trans isomer being able to pack more tightly, and is solid at room temperature.
Thus, trans alkenes, which are less polar and more symmetrical, have lower boiling points and higher melting points, and cis alkenes, which are generally more polar and less symmetrical, have higher boiling points and lower melting points.
In the case of geometric isomers that are a consequence of double bonds, and, in particular, when both substituents are the same, some general trends usually hold. These trends can be attributed to the fact that the dipoles of the substituents in a cis isomer will add up to give an overall molecular dipole. In a trans isomer, the dipoles of the substituents will cancel out due to being on opposite sides of the molecule. Trans isomers also tend to have lower densities than their cis counterparts.
As a general trend, trans alkenes tend to have higher melting points and lower solubility in inert solvents, as trans alkenes, in general, are more symmetrical than cis alkenes.
Vicinal coupling constants (J), measured by NMR spectroscopy, are larger for trans (range: 12–18 Hz; typical: 15 Hz) than for cis (range: 0–12 Hz; typical: 8 Hz) isomers. | 0 | Theoretical and Fundamental Chemistry |
The active zone is present in all chemical synapses examined so far and is present in all animal species. The active zones examined so far have at least two features in common, they all have protein dense material that project from the membrane and tethers synaptic vesicles close to the membrane and they have long filamentous projections originating at the membrane and terminating at vesicles slightly farther from the presynaptic membrane. The protein dense projections vary in size and shape depending on the type of synapse examined. One striking example of the dense projection is the ribbon synapse (see below) which contains a "ribbon" of protein dense material that is surrounded by a halo of synaptic vesicles and extends perpendicular to the presynaptic membrane and can be as long as 500 nm. The glutamate synapse contains smaller pyramid like structures that extend about 50 nm from the membrane. The neuromuscular synapse contains two rows of vesicles with a long proteinaceous band between them that is connected to regularly spaced horizontal ribs extending perpendicular to the band and parallel with the membrane. These ribs are then connected to the vesicles which are each positioned above a peg in the membrane (presumably a calcium channel). Previous research indicated that the active zone of glutamatergic neurons contained a highly regular array of pyramid shaped protein dense material and indicated that these pyramids were connected by filaments. This structure resembled a geometric lattice where vesicles were guided into holes of the lattice. This attractive model has come into question by recent experiments. Recent data shows that the glutamatergic active zone does contain the dense protein material projections but these projections were not in a regular array and contained long filaments projecting about 80 nm into the cytoplasm.
There are at least five major scaffold proteins that are enriched in the active zone; UNC13B/Munc13, RIMS1 (Rab3-interacting molecule), Bassoon, Piccolo/aczonin, ELKS, and liprins-α. These scaffold proteins are thought to be the constituents of the dense pyramid like structures of the active zone and are thought to bring the synaptic vesicles into close proximity to the presynaptic membrane and the calcium channels. The protein ELKS binds to the cell adhesion protein, β-neurexin, and other proteins within the complex such as Piccolo and Bassoon. β-neurexin then binds to cell adhesion molecule, neuroligin located on the postsynaptic membrane. Neuroligin then interacts with proteins that bind to postsynaptic receptors. Protein interactions like that seen between Piccolo/ELKS/β-neurexin/neuroligin ensures that machinery that mediates vesicle fusion is in close proximity to calcium channels and that vesicle fusion is adjacent to postsynaptic receptors. This close proximity vesicle fusion and postsynaptic receptors ensures that there is little delay between the activation of the postsynaptic receptors and the release of neurotransmitters. | 1 | Applied and Interdisciplinary Chemistry |
In 1973, the Freeport-McMoRan Copper and Gold ("Freeport") smelter at Miami, Arizona, installed a 51 MW electric furnace at its Miami smelter. The decision was based on a long-term electrical power contract with the Salt River Project that provided the company with a very low rate for electricity. This contract expired in 1990 and the resulting increase in electricity prices prompted the owners of the smelter, Cyprus Miami Mining Corporation ("Cyprus"), to seek alternative smelting technologies for lower operating costs.
The technologies evaluated included:
* Contop flame cyclone reactor
* Inco flash furnace
* ISASMELT
* Mitsubishi furnace
* Noranda reactor
* Outokumpu flash furnace
* Teniente furnace.
The Contop, Inco, Mitsubishi and Outokumpu processes "were all eliminated primarily because of their high dust levels, high capital costs and poor adaptability to the existing facility". The Teniente converter was ruled out because it required the use of the electric furnace for partial smelting. The Noranda reactor was not selected "because of its high refractory wear and its poor adaptability to the existing plant due to the handling of the reactor slag". ISASMELT was chosen as the preferred technology and a licence agreement was signed with MIM in October 1990. The major factor in the decision to select the ISASMELT technology was the ability to fit it into the existing plant and to maximise the use of existing equipment and infrastructure, while the major disadvantage was seen to be the risks associated with scaling up the technology from the Mount Isa demonstration plant.
The Miami copper ISASMELT furnace was designed to treat 590,000 t/y (650,000 short tons per year) of copper concentrate, a treatment rate that was constrained by the capacity of the sulfuric acid plant used to capture the sulfur dioxide from the smelter's waste gases. The existing electric furnace was converted from smelting duties to a slag cleaning furnace and providing matte surge capacity for the converters. The ISASMELT furnace was commissioned on 11 June 1992 and in 2002 treated over 700,000 t/y of concentrate. The modernisation of the Miami smelter cost an estimated US$95 million.
In 1993, the Cyprus Minerals Company merged with AMAX to form the Cyprus Amax Minerals company, which was in turn taken over by the Phelps Dodge Corporation in late 1999. After the take-over, Phelps Dodge closed its Hidalgo and Chino smelters. Phelps Dodge was acquired by Freeport in 2006.
The Miami smelter is one of only two remaining operating copper smelters in the United States, down from 16 in 1979. | 1 | Applied and Interdisciplinary Chemistry |
Citrate is a chelator which binds to certain transition metals and radioactive actinides. Stable complexes such as bidentate, tridentate (ligands with more than one atom bound) and polynuclear complexes (with several radioactive atoms) can be formed with citrate and radionuclides, which receive a microbial action. Anaerobically, Desulfovibrio desulfuricans and species of the genera Shewanella and Clostridium are able to reduce bidentate complexes of uranyl-citrate (VI) to uranyl-citrate (IV) and make them precipitate, despite not being able to degrade metabolically complexed citrate at the end of the process. In denitrifying and aerobic conditions, however, it has been determined that it is not possible to reduce or degrade these uranium complexes. Bioreduction do not get a head when they are citrate complex mixed metal complexes or when they are tridentate, monomeric or polynuclear complexes, since they become recalcitrant and persistent in the environment. From this knowledge exists a system that combines the degradation of radionuclide-citrate complex with subsequent photodegradation of remaining reduced uranyl-citrate (previously not biodegradated but sensitive to light), which allows for stable precipitates of uranium and also of thorium, strontium or cobalt from contaminated lands. | 1 | Applied and Interdisciplinary Chemistry |
Jani Ingram is a professor of chemistry and biochemistry at Northern Arizona University. Ingram researches the chemistry and health impacts of environmental pollutants, especially uranium and arsenic. Ingram is a member of the Navajo tribe, and the Naneesht’ezhi clan. She leads the Bridging Arizona Native American Students to Bachelor's Degrees (NIH Bridges to Baccalaureate) program and the Native American Cancer Prevention Program. She promotes educational and professional opportunities for Native American students in chemistry through a number of initiatives and for this work was awarded the 2018 American Chemical Society Award for Encouraging Disadvantaged Students into Careers in the Chemical Sciences. | 0 | Theoretical and Fundamental Chemistry |
* Seals for adjustable pipes and fittings, shrinkable or adjustable pipes.
* Braille reprintable boards and reprintable advertisements.
* Adjustable anti-corrosion films.
* Hair for dolls, toys, hair styling items.
* New items packaged in smaller volume and that change their shape upon first use.
* Protections for automobiles, fenders, etc.
* Artificial nails.
* Smart textiles. | 0 | Theoretical and Fundamental Chemistry |
*Koss K, Maxton D, Jankowski JAZ. The potential use of fecal dimeric M2 pyruvate kinase (Tumor M2-PK) in screening for colorectal cancer (CRC). Abstract from Digestive Disease Week, May 2005; Chicago, USA.
*Mc Loughlin R, Shiel E, Sebastian S, Ryan B, O´Connor HJ, O´Morain C. Tumor M2-PK, a novel screening tool for colorectal cancer. Abstract from Digestive Disease Week, May 2005, Chicago/USA | 1 | Applied and Interdisciplinary Chemistry |
A zeotropic mixture, or non-azeotropic mixture, is a mixture with liquid components that have different boiling points. For example, nitrogen, methane, ethane, propane, and isobutane constitute a zeotropic mixture. Individual substances within the mixture do not evaporate or condense at the same temperature as one substance. In other words, the mixture has a temperature glide, as the phase change occurs in a temperature range of about four to seven degrees Celsius, rather than at a constant temperature. On temperature-composition graphs, this temperature glide can be seen as the temperature difference between the bubble point and dew point. For zeotropic mixtures, the temperatures on the bubble (boiling) curve are between the individual components boiling temperatures. When a zeotropic mixture is boiled or condensed, the composition of the liquid and the vapor changes according to the mixturess temperature-composition diagram.
Zeotropic mixtures have different characteristics in nucleate and convective boiling, as well as in the organic Rankine cycle. Because zeotropic mixtures have different properties than pure fluids or azeotropic mixtures, zeotropic mixtures have many unique applications in industry, namely in distillation, refrigeration, and cleaning processes. | 1 | Applied and Interdisciplinary Chemistry |
Divalent sulfur exhibits bond angles approaching 90°. Such acute angles are also seen in the M-S-C angles of metal thiolates. Having filled p-orbitals of suitable symmetry, thiolates are pi-donor ligands. This property plays a role in the stabilization of Fe(IV) states in the enzyme cytochrome P450. | 0 | Theoretical and Fundamental Chemistry |
The C and N contents of feedstocks is generally known from lookup tables listing common types of feedstock. It is important to deduct the moisture content if the listed value is for dry material.
For foodstuffs with a nutrition analysis, the N content may be estimated from the protein content as , reversing the crude protein calculation. The C content may be estimated from crude ash content (often reported in animal feed) or from reported macronutrient levels as .
Given the C:N ratio and one of C and N contents, the other content may be calculated using the very definition of the ratio. When only the ratio is known, one must estimate the total C+N% or one of the contents to get both values. | 0 | Theoretical and Fundamental Chemistry |
He was awarded a DSc by the University of Liverpool in 1950 and an honorary DSc by Victoria University of Wellington in 1970; a Fellowship of the Royal Society of New Zealand in 1951 and the Hector Medal in 1955. In the 1959 New Year Honours he was appointed an Officer of the Order of the British Empire, in recognition of his role as director of the Fats Research Institute, and in 1990 he received the New Zealand 1990 Commemoration Medal. In 1969 he was awarded an honorary fellowship of the New Zealand Institute of Food Science and Technology. | 0 | Theoretical and Fundamental Chemistry |
Although the system for maintaining optimal salt and water balance in the body is a complex one, one of the primary ways in which the human body keeps track of loss of body water is that osmoreceptors in the hypothalamus sense a balance of sodium and water concentration in extracellular fluids. Relative loss of body water will cause sodium concentration to rise higher than normal, a condition known as hypernatremia. This ordinarily results in thirst. Conversely, an excess of body water caused by drinking will result in too little sodium in the blood (hyponatremia), a condition which is again sensed by the hypothalamus, causing a decrease in vasopressin hormone secretion from the posterior pituitary, and a consequent loss of water in the urine, which acts to restore blood sodium concentrations to normal.
Severely dehydrated persons, such as people rescued from ocean or desert survival situations, usually have very high blood sodium concentrations. These must be very carefully and slowly returned to normal, since too-rapid correction of hypernatremia may result in brain damage from cellular swelling, as water moves suddenly into cells with high osmolar content.
In humans, a high-salt intake was demonstrated to attenuate nitric oxide production. Nitric oxide (NO) contributes to vessel homeostasis by inhibiting vascular smooth muscle contraction and growth, platelet aggregation, and leukocyte adhesion to the endothelium. | 1 | Applied and Interdisciplinary Chemistry |
George Hammond published a hypothesis in physical organic chemistry which describes the geometric structure of the transition state in an organic chemical reaction in his publication, Hammond's principle.
His 1955 publication asserted:
Therefore, the geometric structure of a state can be predicted by comparing its energy to the species neighboring it along the reaction coordinate. For example, in an exothermic reaction the transition state is closer in energy to the reactants than to the products. Therefore, the transition state will be more geometrically similar to the reactants than to the products. In contrast, however, in an endothermic reaction the transition state is closer in energy to the products than to the reactants. So, according to Hammond's postulate the structure of the transition state would resemble the products more than the reactants. This type of comparison is especially useful because most transition states cannot be characterized experimentally.
Hammonds postulate also helps to explain and rationalize the Bell–Evans–Polanyi principle. Namely, this principle describes the experimental observation that the rate of a reaction, and therefore its activation energy, is affected by the enthalpy change of that reaction. Hammonds postulate explains this observation by describing how varying the enthalpy of a reaction would also change the structure of the transition state. In turn, this change in geometric structure would alter the energy of the transition state, and therefore the activation energy and reaction rate as well.
The postulate has also been used to predict the shape of reaction coordinate diagrams. For example, electrophilic aromatic substitutions involves a distinct intermediate and two less well defined states. By measuring the effects of aromatic substituents and applying Hammond's postulate it was concluded that the rate-determining step involves formation of a transition state that should resemble the intermediate complex.
During the 1940s and 1950s, chemists had trouble explaining why even slight changes in the reactants caused significant differences in the rate and product distributions of a reaction. In 1955 George S. Hammond, a young professor at Iowa State University, postulated that transition-state theory could be used to qualitatively explain the observed structure-reactivity relationships. Notably, John E. Leffler of Florida State University proposed a similar idea in 1953. However, Hammonds version has received more attention since its qualitative nature was easier to understand and employ than Lefflers complex mathematical equations. Hammond's postulate is sometimes called the Hammond-Leffler postulate to give credit to both scientists. | 0 | Theoretical and Fundamental Chemistry |
Virtually all the aluminium hydroxide used commercially is manufactured by the Bayer process which involves dissolving bauxite in sodium hydroxide at temperatures up to . The waste solid, bauxite tailings, is removed and aluminium hydroxide is precipitated from the remaining solution of sodium aluminate. This aluminium hydroxide can be converted to aluminium oxide or alumina by calcination.
The residue or bauxite tailings, which is mostly iron oxide, is highly caustic due to residual sodium hydroxide. It was historically stored in lagoons; this led to the Ajka alumina plant accident in 2010 in Hungary, where a dam bursting led to the drowning of nine people. An additional 122 sought treatment for chemical burns. The mud contaminated of land and reached the Danube. While the mud was considered non-toxic due to low levels of heavy metals, the associated slurry had a pH of 13. | 0 | Theoretical and Fundamental Chemistry |
He started his research in the chemistry of natural products. At Washington State University he established early steps in metabolism of d-neomethyl-α-D-glucoside in pipermint (Mentha piperita) rhizomes via in vivo studies. Bhushan developed a de novo method for direct resolution of certain racemates by liquid chromatography. Later, the approach was applied for direct enantioseparation of several active pharmaceutical ingredients (APIs). It is now an established approach in literature. 1994 onwards, the method was extended to such resolutions by ligand exchange principle. The method is of significant importance to pharmaceutical industry and analytical laboratories associated with regulatory agencies for determination and control of enantiomeric purity (and isolation of native enantiomers) of a variety of APIs since many of them are marketed and administered as racemic mixture while only one enantiomer is therapeutically useful.
Bhushan supervised the Ph.D. theses of > 30 scholars and has published more than 270 research papers. | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, in the biological context of organisms' regulation of gene expression and production of gene products, downregulation is the process by which a cell decreases the production and quantities of its cellular components, such as RNA and proteins, in response to an external stimulus. The complementary process that involves increase in quantities of cellular components is called upregulation.
An example of downregulation is the cellular decrease in the expression of a specific receptor in response to its increased activation by a molecule, such as a hormone or neurotransmitter, which reduces the cell's sensitivity to the molecule. This is an example of a locally acting (negative feedback) mechanism.
An example of upregulation is the response of liver cells exposed to such xenobiotic molecules as dioxin. In this situation, the cells increase their production of cytochrome P450 enzymes, which in turn increases degradation of these dioxin molecules.
Downregulation or upregulation of an RNA or protein may also arise by an epigenetic alteration. Such an epigenetic alteration can cause expression of the RNA or protein to no longer respond to an external stimulus. This occurs, for instance, during drug addiction or progression to cancer. | 1 | Applied and Interdisciplinary Chemistry |
Iron is required for life. The iron–sulfur clusters are pervasive and include nitrogenase, the enzymes responsible for biological nitrogen fixation. Iron-containing proteins participate in transport, storage and use of oxygen. Iron proteins are involved in electron transfer. The ubiquity of Iron in life has led to the Iron–sulfur world hypothesis that iron was a central component of the environment of early life.
Examples of iron-containing proteins in higher organisms include hemoglobin, cytochrome (see high-valent iron), and catalase. The average adult human contains about 0.005% body weight of iron, or about four grams, of which three quarters is in hemoglobin – a level that remains constant despite only about one milligram of iron being absorbed each day, because the human body recycles its hemoglobin for the iron content.
Microbial growth may be assisted by oxidation of iron(II) or by reduction of iron (III). | 1 | Applied and Interdisciplinary Chemistry |
Bitumen was used in early photographic technology. In 1826, or 1827, it was used by French scientist Joseph Nicéphore Niépce to make the oldest surviving photograph from nature. The bitumen was thinly coated onto a pewter plate which was then exposed in a camera. Exposure to light hardened the bitumen and made it insoluble, so that when it was subsequently rinsed with a solvent only the sufficiently light-struck areas remained. Many hours of exposure in the camera were required, making bitumen impractical for ordinary photography, but from the 1850s to the 1920s it was in common use as a photoresist in the production of printing plates for various photomechanical printing processes.
Bitumen was the nemesis of many artists during the 19th century. Although widely used for a time, it ultimately proved unstable for use in oil painting, especially when mixed with the most common diluents, such as linseed oil, varnish and turpentine. Unless thoroughly diluted, bitumen never fully solidifies and will in time corrupt the other pigments with which it comes into contact. The use of bitumen as a glaze to set in shadow or mixed with other colors to render a darker tone resulted in the eventual deterioration of many paintings, for instance those of Delacroix. Perhaps the most famous example of the destructiveness of bitumen is Théodore Géricault's Raft of the Medusa (1818–1819), where his use of bitumen caused the brilliant colors to degenerate into dark greens and blacks and the paint and canvas to buckle. | 0 | Theoretical and Fundamental Chemistry |
With credit to the previously listed techniques, biomarkers were found in petroleum and source rock extract. These are fossils from organisms, but are closer in size to molecules than to visible hand samples. They display the same structure as their parent biomolecules and are used in the identification of the organic matter from which the petroleum is derived. Biomarkers are also used in correlating oils and source rocks, finding the oil's maturity, regional differences found between multiple samples, and the history of the basin in which the source rock was located. | 0 | Theoretical and Fundamental Chemistry |
The US states of Montana and Wisconsin, the Czech Republic, Hungary, have banned cyanide mining. The European Commission rejected a proposal for such a ban, noting that existing regulations (see below) provide adequate environmental and health protection. Several attempts to ban gold cyanidation in Romania were rejected by the Romanian Parliament. There are currently protests in Romania calling for a ban on the use of cyanide in mining (see 2013 Romanian protests against the Roșia Montană Project).
In the EU, industrial use of hazardous chemicals is controlled by the so-called Seveso II Directive (Directive 96/82/EC, which replaced the original Seveso Directive (82/501/EEC brought in after the 1976 dioxin disaster. "Free cyanide and any compound capable of releasing free cyanide in solution" are further controlled by being on List I of the Groundwater Directive (Directive 80/68/EEC) which bans any discharge of a size which might cause deterioration in the quality of the groundwater at the time or in the future. The Groundwater Directive was largely replaced in 2000 by the Water Framework Directive (2000/60/EC).
In response to the 2000 Baia Mare cyanide spill, the European Parliament and the Council adopted Directive 2006/21/EC on the management of waste from extractive industries. Article 13(6) requires "the concentration of weak acid dissociable cyanide in the pond is reduced to the lowest possible level using best available techniques", and at most all mines started after 1 May 2008 may not discharge waste containing over 10ppm WAD cyanide, mines built or permitted before that date are allowed no more than 50ppm initially, dropping to 25ppm in 2013 and 10ppm by 2018.
Under Article 14, companies must also put in place financial guarantees to ensure clean-up after the mine has finished. This in particular may affect smaller companies wanting to build gold mines in the EU, as they are less likely to have the financial strength to give these kinds of guarantees.
The industry has come up with a voluntary "Cyanide Code" that aims to reduce environmental impacts with third party audits of a company's cyanide management. | 1 | Applied and Interdisciplinary Chemistry |
* Norris Award (1968)
* Priestley Medal (1976)
* Golden Plate Award of the American Academy of Achievement (1976)
* National Medal of Science (1994)
* Glenn T. Seaborg Medal (1994)
* Othmer Gold Medal (2003) | 0 | Theoretical and Fundamental Chemistry |
In plasma spraying process, the material to be deposited (feedstock)—typically as a powder, sometimes as a liquid, suspension or wire—is introduced into the plasma jet, emanating from a plasma torch. In the jet, where the temperature is on the order of 10,000 K, the material is melted and propelled towards a substrate. There, the molten droplets flatten, rapidly solidify and form a deposit. Commonly, the deposits remain adherent to the substrate as coatings; free-standing parts can also be produced by removing the substrate. There are a large number of technological parameters that influence the interaction of the particles with the plasma jet and the substrate and therefore the deposit properties. These parameters include feedstock type, plasma gas composition and flow rate, energy input, torch offset distance, substrate cooling, etc. | 1 | Applied and Interdisciplinary Chemistry |
Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. Organisms capable of producing methane for energy conservation have been identified only from the domain Archaea, a group phylogenetically distinct from both eukaryotes and bacteria, although many live in close association with anaerobic bacteria. The production of methane is an important and widespread form of microbial metabolism. In anoxic environments, it is the final step in the decomposition of biomass. Methanogenesis is responsible for significant amounts of natural gas accumulations, the remainder being thermogenic. | 1 | Applied and Interdisciplinary Chemistry |
The scientific goals of RSN are significant. A vast array of natural phenomena that occur throughout the world's oceans and seafloor are found in the Northeast Pacific Ocean. As a whole, the mission of RSN is to provide a human telepresence in the ocean that will serve researchers, students, educators, policymakers, and the public. Scientists will be able to conduct local investigations of such global processes as major ocean currents, active earthquake zones, creation of new seafloor, and rich environments of marine plants and animals.
RSN is also designed to help anticipate both short and long-term ocean-generated threats and opportunities. Notably, RSN will be able to monitor the tectonic activity along the plate boundary. There is hope that seismic sensors could be installed at key areas along the spreading center which would serve as an early warning system for earthquakes and tsunamis.
The existence of a long-term cabled observatory will allow for long-term measurements of biological communities. In particular, the Juan de Fuca plate's divergent plate boundary has resulted in the existence of seafloor hydrothermal vents ecosystems, and other similar groups. These deep sea communities, thriving in extremely harsh environments, pose a number of unsolved scientific questions which RSN will be capable of investigating. | 0 | Theoretical and Fundamental Chemistry |
*McMillan P.W., "The glass phase in glass-ceramics", Glass Technology, 1974, Vol. 15 (1), P. 5-15
*Bach H. (Editor), "Low thermal expansion glass ceramics", Springer-Verlag (1995).
*Holand, Wolfram and Beall, George H. Glass-Ceramic Technology. Wiley, 2002. | 0 | Theoretical and Fundamental Chemistry |
The activated sludge process is a biological process used to oxidise carbonaceous biological matter, oxidising nitrogenous matter (mainly ammonium and nitrogen) in biological matter, and removing nutrients (nitrogen and phosphorus). | 1 | Applied and Interdisciplinary Chemistry |
As the nanotechnology industry has grown, nanoparticles have brought UFPs more public and regulatory attention. UFP risk assessment research is still in the very early stages. There are continuing debates about whether to regulate UFPs and how to research and manage the health risks they may pose. As of March 19, 2008, the EPA does not yet regulate or research ultrafine particles, but has drafted a Nanomaterial Research Strategy, open for independent, external peer review beginning February 7, 2008 (Panel review on April 11, 2008). There is also debate about how the European Union (EU) should regulate UFPs. | 0 | Theoretical and Fundamental Chemistry |
[http://digicoll.library.wisc.edu/cgi-bin/HistSciTech/HistSciTech-idx?type=turn&entity=HistSciTech000900240238&isize=L] | 1 | Applied and Interdisciplinary Chemistry |
A Guinier–Preston zone, or GP-zone, is a fine-scale metallurgical phenomenon, involving early stage precipitation.
GP-zones are associated with the phenomenon of age hardening, whereby room-temperature reactions continue to occur within a material through time, resulting in changing physical properties. In particular, this occurs in several aluminium series, such as the 6000 and 7000 series alloys.
Physically, GP zones are extremely fine-scaled (on the order of 3–10 nm in size) solute enriched regions of the material, which offer physical obstructions to the motion of dislocations, above that of the solid solution strengthening of the solute components. In 7075 aluminium for example, Zn–Mg clusters precede the formation of equilibrium MgZn precipitates.
The zone is named after André Guinier and George Dawson Preston who independently identified the zones in 1938. | 0 | Theoretical and Fundamental Chemistry |
An ideal polarizable electrode (also ideally polarizable electrode or ideally polarized electrode or IPE) is a hypothetical electrode characterized by an absence of net DC current between the two sides of the electrical double layer, i.e., no faradic current exists between the electrode surface and the electrolyte. Any transient current that may be flowing is considered non-faradaic. The reason for this behavior is that the electrode reaction is infinitely slow, with zero exchange current density, and behaves electrically as a capacitor.
The concept of the ideal polarizability has been first introduced by F.O. Koenig in 1934. | 0 | Theoretical and Fundamental Chemistry |
Target-mediated drug disposition (TMDD), is the process in which a drug binds with high affinity to its pharmacological target (for example, a receptor) to such an extent that this affects its pharmacokinetic characteristics. Various drug classes can exhibit TMDD, most often these are large compounds (biologics such as antibodies, cytokines or growth factors) but also smaller compounds can exhibit TMDD (such as warfarin).
A typical TMDD pattern of antibodies displays non-linear clearance and can be seen at concentration ranges that are usually defined as mid-to-low. In this concentration range, the target is partly saturated. | 1 | Applied and Interdisciplinary Chemistry |
In the field of drug discovery, classical pharmacology, also known as forward pharmacology, or phenotypic drug discovery (PDD), relies on phenotypic screening (screening in intact cells or whole organisms) of chemical libraries of synthetic small molecules, natural products or extracts to identify substances that have a desirable therapeutic effect. Using the techniques of medicinal chemistry, the potency, selectivity, and other properties of these screening hits are optimized to produce candidate drugs. | 1 | Applied and Interdisciplinary Chemistry |
Radiocarbon ages from hyraceum are not subject to reservoir effects or the inclusion of new carbon. This is primarily a function of middens being isolated systems, and that through respiration the hyraceum is brought into equilibrium with atmospheric C at the time of deposition. Published data show that hyrax middens can be of considerable antiquity, and middens from the Groenfontein site in the Cederberg Mountains of South Africa are considered to have begun accumulating ~70,000 years ago
It has been commonly observed that many middens are no longer actively accumulating. Often this is controlled by the shelters in which they are found, with accumulation ceasing when the middens grow to such an extent that the hyraxes can no longer physically enter the shelters. Until recently, field sampling was limited to the collection of middens that were most accessible and easiest to sample. In many cases this meant that the individual sampled middens were relatively thin (<5 cm) with aggregate records subsequently constructed from fragments of as many as 25 separate middens. (Scott and Woodborne, 2007a, b). With recent developments in sampling tools and techniques, larger, more stratigraphically coherent middens are more regularly sampled, which better represent the full period of accumulation at a given site | 0 | Theoretical and Fundamental Chemistry |
Attosecond pump-probe experiments with simple atoms is a fundamental tool to measure the time duration of an attosecond pulse and to explore several quantum proprieties of matter.
This kind of experiments can be easily described within strong field approximation by exploiting the results of Eq. , as discussed below.
As a simple model, consider the interaction between a single active electron in a single-level atom and two fields: an intense femtosecond infrared (IR) pulse (,
and a weak attosecond pulse (centered in the extreme ultraviolet (XUV) region) .
Then, by substituting these fields to it results
with
At this point, we can divide Eq. in two contributions: direct ionization and strong field ionization (multiphoton regime), respectively.
Typically, these two terms are relevant in different energetic regions of the continuum.
Consequently, for typical experimental condition, the latter process is disregarded, and only direct ionization from the attosecond pulse is considered.
Then, since the attosecond pulse is weaker than the infrared one, it holds . Thus, is typically neglected in Eq. .
In addition to that, we can re-write the attosecond pulse as a delayed function with respect to the IR field, .
Therefore, the probability distribution, , of finding an electron ionized in the continuum with momentum , after the interaction has occurred (at ), in a pump-probe experiments,
with an intense IR pulse and a delayed-attosecond XUV pulse, is given by:
with
Equation describes the photoionization phenomenon of two-color interaction (XUV-IR) with a single-level atom and single active electron.
This peculiar result can be regarded as a quantum interference process between all the possible ionization paths, started by a delayed XUV attosecond pulse, with a following motion in the continuum states driven by a strong IR field.
The resulting 2D photo-electron (momentum, or equivalently energy, vs delay) distribution is called streaking trace. | 0 | Theoretical and Fundamental Chemistry |
Several routes exist for the production of cyclohexenone. For the laboratory scale, it can be produced from resorcinol via 1,3-cyclohexanedione.
Cyclohexenone is obtained by Birch reduction of anisole followed by acid hydrolysis.
It can be obtained from cyclohexanone by α-bromination followed by treatment with base. Hydrolysis of 3-chloro cyclohexene followed by oxidation of the cyclohexenol is yet another route.
Cyclohexenone is produced industrially by catalytic oxidation of cyclohexene, for example with hydrogen peroxide and vanadium catalysts. Several patents describe diverse oxidizing agents and catalysts. | 0 | Theoretical and Fundamental Chemistry |
In 1968, Dr. Josef Pacák, Zdeněk Točík and Miloslav Černý at the Department of Organic Chemistry, Charles University, Czechoslovakia were the first to describe the synthesis of FDG. Later, in the 1970s, Tatsuo Ido and Al Wolf at the Brookhaven National Laboratory were the first to describe the synthesis of FDG labeled with fluorine-18. The compound was first administered to two normal human volunteers by Abass Alavi in August, 1976 at the University of Pennsylvania. Brain images obtained with an ordinary (non-PET) nuclear scanner demonstrated the concentration of [F]FDG in that organ (see history reference below).
Beginning in August 1990, and continuing throughout 1991, a shortage of oxygen-18, a raw material for FDG, made it necessary to ration isotope supplies. Israel's oxygen-18 facility had shut down due to the Gulf War, and the U.S. government had shut down its isotopes of carbon, oxygen and nitrogen facility at Los Alamos National Laboratory, leaving Isotec as the main supplier. Please see the comparative figure below for further history of the FDG molecule. | 1 | Applied and Interdisciplinary Chemistry |
The PV diagram, then called an indicator diagram, was developed in 1796 by James Watt and his employee John Southern. Volume was traced by a plate moving with the piston, while pressure was traced by a pressure gauge whose indicator moved at right angles to the piston. A pencil was used to draw the diagram. Watt used the diagram to make radical improvements to steam engine performance. | 0 | Theoretical and Fundamental Chemistry |
In petroleum engineering, Lak wettability index is a quantitative indicator to measure wettability of rocks from relative permeability data. This index is based on a combination of Craigs first rule. and modified Craigs second rule
where
: : Lak wettability index (index values near -1 and 1 represent strongly oil-wet and strongly water-wet rocks, respectively)
: : Water relative permeability measured at residual oil saturation
: : Water saturation at the intersection point of water and oil relative permeability curves (fraction)
: : Residual oil saturation (in fraction)
: : Irreducible water saturation (in fraction)
: : Reference crossover saturation (in fraction) defined as:
and and are two constant coefficients defined as:
: and if
: and if
: and if
To use the above formula, relative permeability is defined as the effective permeability divided by the oil permeability measured at irreducible water saturation. | 0 | Theoretical and Fundamental Chemistry |
While Be(II) is one of the more common oxidation states, there is also further research on a Be(I) and Be(0) complex. Low-valent main group compounds have recently become desirable synthetic targets due to their interesting reactivity comparable to transition metal complexes. In one work, stabilized cyclic (alkyl)(amino)carbene ligands were used to isolate and characterize the first neutral compounds containing beryllium, with the Be(0) compound stabilized by a strongly σ-donating and π-accepting cyclic CAAC ligand.
Be(I) is another example of a rare phenomenon and few publications were reported, but one example of a Be(I) was a CAAC ligand already coordinated with Be. Gilliard and his group created a more stable beryllium radical cation. Because of well-established challenges concerning the reduction of Be(II) to Be(I), they pursued the radical via an oxidation strategy using TEMPO ((2,2,6,6-Tetramethylpiperidin-1-yl) oxyl). This reaction resulted in a Be(I) compound just by stabilizing the Be radical. | 0 | Theoretical and Fundamental Chemistry |
Nanoparticles occur in a great variety of shapes, which have been given many informal names such as nanospheres, nanorods, nanochains, decagedral nanoparticles, nanostars, nanoflowers, nanoreefs, nanowhiskers, nanofibers, and nanoboxes.
The shapes of nanoparticles may be determined by the intrinsic crystal habit of the material, or by the influence of the environment around their creation, such as the inhibition of crystal growth on certain faces by coating additives, the shape of emulsion droplets and micelles in the precursor preparation, or the shape of pores in a surrounding solid matrix. Some applications of nanoparticles may require specific shapes, as well as specific sizes or size ranges.
Amorphous particles typically adopt a spherical shape (due to their microstructural isotropy).
The study of fine particles is called micromeritics. | 0 | Theoretical and Fundamental Chemistry |
The effect of impurities can be significant when making high-precision measurements. Chemical desiccants can be used to dry the air, but will, in turn, contaminate the sample. The air can be dried cryogenically, but this has the effect of removing the carbon dioxide as well; therefore many high-precision measurements are performed with air free of carbon dioxide rather than with natural air. A 2002 review found that a 1963 measurement by Smith and Harlow using a cylindrical resonator gave "the most probable value of the standard speed of sound to date." The experiment was done with air from which the carbon dioxide had been removed, but the result was then corrected for this effect so as to be applicable to real air. The experiments were done at but corrected for temperature in order to report them at . The result was for dry air at STP, for frequencies from to . | 1 | Applied and Interdisciplinary Chemistry |
After graduation, Ekimov moved to the Vavilov State Optical Institute to conduct research. He began studying semiconductor-activated glasses, known as Schott glasses, and developing theories to explain their color. When the glasses were heated and then cooled, copper chloride crystals formed, as revealed by X-rays, creating blue colors. Smaller crystals produced bluer glass.
In 1981, Ekimov, along with Alexei A. Onushchenko, reported the discovery of quantum size effects in copper chloride nanocrystals in glass, a phenomenon known now known as quantum dots. During his time at the institute he further investigated these system and developed the theory of quantum confinement with Alexander Efros.
Since 1999, Ekimov has been living and working in the United States as a scientist for Nanocrystals Technology, a company based in New York State. | 0 | Theoretical and Fundamental Chemistry |
The first successful solid-hybrid dye-sensitized solar cells were reported.
To improve electron transport in these solar cells, while maintaining the high surface area needed for dye adsorption, two researchers have designed alternate semiconductor morphologies, such as arrays of nanowires and a combination of nanowires and nanoparticles, to provide a direct path to the electrode via the semiconductor conduction band. Such structures may provide a means to improve the quantum efficiency of DSSCs in the red region of the spectrum, where their performance is currently limited.
In August 2006, to prove the chemical and thermal robustness of the 1-ethyl-3 methylimidazolium tetracyanoborate solar cell, the researchers subjected the devices to heating at 80 °C in the dark for 1000 hours, followed by light soaking at 60 °C for 1000 hours. After dark heating and light soaking, 90% of the initial photovoltaic efficiency was maintained – the first time such excellent thermal stability has been observed for a liquid electrolyte that exhibits such a high conversion efficiency. Contrary to silicon solar cells, whose performance declines with increasing temperature, the dye-sensitized solar-cell devices were only negligibly influenced when increasing the operating temperature from ambient to 60 °C. | 0 | Theoretical and Fundamental Chemistry |
The steam-electric power station is a power station in which the electric generator is steam driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser. The greatest variation in the design of steam-electric power plants is due to the different fuel sources.
Almost all coal, nuclear, geothermal, solar thermal electric power plants, waste incineration plants as well as many natural gas power plants are steam-electric. Natural gas is frequently combusted in gas turbines as well as boilers. The waste heat from a gas turbine can be used to raise steam, in a combined cycle plant that improves overall efficiency.
Worldwide, most electric power is produced by steam-electric power plants. The only widely used alternatives are photovoltaics, direct mechanical power conversion as found in hydroelectric and wind turbine power as well as some more exotic applications like tidal power or wave power and finally some forms of geothermal power plants. Niche applications for methods like betavoltaics or chemical power conversion (including electrochemistry) are only of relevance in batteries and atomic batteries. Fuel cells are a proposed alternative for a future hydrogen economy. | 1 | Applied and Interdisciplinary Chemistry |
In 2000, Wong-Ng became a fellow of the International Centre for Diffraction Data (ICDD). She was awarded fellow of the American Ceramic Society in 2002. In 2002 and 2008, she won the Department of Commerce Bronze Medal. In 2014, Wong-Ng was made fellow of the American Crystallographic Association. In 2012, she became a distinguished fellow of the ICDD and a Fellow of the American Association for the Advancement of Science. She became an academician of the World Academy of Ceramics in 2018. | 0 | Theoretical and Fundamental Chemistry |
In coupling reactions between aromatic compounds and metal-trifluoromethyl complexes the metal is usually copper, Pd and Ni are less prominent. The reactions are stoichiometric or catalytic. In the McLoughlin-Thrower reaction (1962) iodobenzene reacts with trifluoroiodomethane (CFI) and copper powder in dimethylformamide at 150 °C to trifluoromethylbenzene. The intermediate in this reaction type is a perfluoromethyl-metal complex.
A palladium acetate catalysed reaction described in 1982 used zinc powder with the main intermediate believed to be CFZnI with Pd(0) is the active catalyst. The first copper catalysed coupling was reported in 2009 and based on an iodoarene, a trifluoromethylsilane, copper iodide and 1,10-phenanthroline. Variations include another CF donor potassium (trifluoromethyl)trimethoxyborate, the use of aryl boronic acids or the use of a trifluoromethyl sulfonium salt or the use of a trifluoromethylcopper(I) phenanthroline complex. A catalytic palladium catalysed reaction was reported in 2010 using aryl halides, (trifluoromethyl)triethylsilane and allylpalladium chloride dimer | 0 | Theoretical and Fundamental Chemistry |
In the case of ATI the photoelectron peaks should appear at
where the integer n represents the minimal number of photons absorbed, and the integer s represents the number of additional photons absorbed. W is the ionization energy, and is the electron kinetic energy of the peak corresponding to s additional photons being absorbed. | 0 | Theoretical and Fundamental Chemistry |
The degree of coordinative unsaturation of a surface cation measures the number of bonds involving the cation that have to be broken to form a surface. As the degree of coordinative unsaturation increases, more bonds are broken and the metal cation becomes destabilized. The destabilization of the cation increases the surface Gibbs energy, which decreases the overall stability. For example, the rutile (110) surface is more stable than the rutile (100) and (001) surfaces because it has a lower degree of coordinative unsaturation. | 0 | Theoretical and Fundamental Chemistry |
GRE Subject Biochemistry, Cell and Molecular Biology was a standardized exam provided by ETS (Educational Testing Service) that was discontinued in December 2016. It is a paper-based exam and there are no computer-based versions of it. ETS places this exam three times per year: once in April, once in October and once in November. Some graduate programs in the United States recommend taking this exam, while others require this exam score as a part of the application to their graduate programs. ETS sends a bulletin with a sample practice test to each candidate after registration for the exam. There are 180 questions within the biochemistry subject test.
Scores are scaled and then reported as a number between 200 and 990; however, in recent versions of the test, the maximum and minimum reported scores have been 760 (corresponding to the 99 percentile) and 320 (1 percentile) respectively. The mean score for all test takers from July, 2009, to July, 2012, was 526 with a standard deviation of 95.
After learning that test content from editions of the GRE® Biochemistry, Cell and Molecular Biology (BCM) Test has been compromised in Israel, ETS made the decision not to administer this test worldwide in 2016–17. | 1 | Applied and Interdisciplinary Chemistry |
writing the potential energy as depending on a continuous parameter,
one has the exact result
This can either be directly verified from definitions or seen from the limit of the above Gibbs-Bogoliubov inequalities when
we can therefore write
which is the thermodynamic integration (or TI) result. It can be approximated by dividing the range between states A and B into many values of λ at which the expectation value is estimated, and performing numerical integration. | 0 | Theoretical and Fundamental Chemistry |
* Heywood, John B., "Internal Combustion Engine Fundamentals," McGraw Hill, 1988.
* van Basshuysen, Richard, and Schäfer, Fred, "Internal Combustion Engine Handbook," SAE International, 2004.
* "Bosch Automotive Handbook," 3rd Edition, Robert Bosch GmbH, 1993. | 1 | Applied and Interdisciplinary Chemistry |
Cooperativity is a phenomenon displayed by systems involving identical or near-identical elements, which act dependently of each other, relative to a hypothetical standard non-interacting system in which the individual elements are acting independently. One manifestation of this is enzymes or receptors that have multiple binding sites where the affinity of the binding sites for a ligand is apparently increased, positive cooperativity, or decreased, negative cooperativity, upon the binding of a ligand to a binding site. For example, when an oxygen atom binds to one of hemoglobin's four binding sites, the affinity to oxygen of the three remaining available binding sites increases; i.e. oxygen is more likely to bind to a hemoglobin bound to one oxygen than to an unbound hemoglobin. This is referred to as cooperative binding.
We also see cooperativity in large chain molecules made of many identical (or nearly identical) subunits (such as DNA, proteins, and phospholipids), when such molecules undergo phase transitions such as melting, unfolding or unwinding. This is referred to as subunit cooperativity. However, the definition of cooperativity based on apparent increase or decrease in affinity to successive ligand binding steps is problematic, as the concept of "energy" must always be defined relative to a standard state. When we say that the affinity is increased upon binding of one ligand, it is empirically unclear what we mean since a non-cooperative binding curve is required to rigorously define binding energy and hence also affinity. A much more general and useful definition of positive cooperativity is: A process involving multiple identical incremental steps, in which intermediate states are statistically underrepresented relative to a hypothetical standard system (null hypothesis) where the steps occur independently of each other.
Likewise, a definition of negative cooperativity would be a process involving multiple identical incremental steps, in which the intermediate states are overrepresented relative to a hypothetical standard state in which individual steps occur independently. These latter definitions for positive and negative cooperativity easily encompass all processes which we call "cooperative", including conformational transitions in large molecules (such as proteins) and even psychological phenomena of large numbers of people (which can act independently of each other, or in a co-operative fashion). | 1 | Applied and Interdisciplinary Chemistry |
The Puerto Mosquito Bioluminescent Bay (), or Mosquito Bio Bay, is a bay in the island of Vieques famous for its bioluminescence produced by the dinoflagellate Pyrodinium bahamense, which glows blue when agitated. This species of phytoplankton is found in bays in the Virgin Islands, Puerto Rico and The Bahamas. | 1 | Applied and Interdisciplinary Chemistry |
Gary M. Hieftje is an analytical chemist, Distinguished Professor, and the Robert & Marjorie Mann Chair of Chemistry at Indiana University in Bloomington, Indiana. Gary M. Hieftje received his A.B. degree at Hope College in Holland, Michigan in 1964, and his PhD from University of Illinois at Urbana–Champaign in 1969. In 1969, he started his career in teaching and research at Indiana University. Hieftje was named a Distinguished Professor in 1985, and entered emeritus status in 2018. As of 2018, Dr. Hieftje has been involved in over 600 publications.
Research in the Hieftje Group mainly focuses on studying and improving the mechanisms and methods of atomic emission and absorption, fluorescence, and mass spectrometry. He also works to develop new methods of analysis for atoms, molecules, and biomolecules. His group even developed an online computer program to control their experiments. Some areas of interest to his research are: finding new applications of lasers, linear response theory, near-infrared correlation methods of analysis, time-resolved luminescence, and fiber-optic sensors.
Professor Hieftje has authored many books. Perhaps, the most well-known is “Chemical Separations and Measurements - The Theory and Practice of Analytical Chemistry” with colleagues Dennis G. Peters and John M. Hayes published by Saunders in Philadelphia in 1974. | 0 | Theoretical and Fundamental Chemistry |
To determine the mass of liquid in a sample given the mass of solids and the mass fraction:
By definition
therefore
and
then
and therefore
where
: is the solids fraction of the slurry
: is the mass or mass flow of solids in the sample or stream
: is the mass or mass flow of slurry in the sample or stream
: is the mass or mass flow of liquid in the sample or stream | 1 | Applied and Interdisciplinary Chemistry |
There are a number of biophysical techniques for determining sequence information. Protein sequence can be determined by Edman degradation, in which the N-terminal residues are hydrolyzed from the chain one at a time, derivatized, and then identified. Mass spectrometer techniques can also be used. Nucleic acid sequence can be determined using gel electrophoresis and capillary electrophoresis. Lastly, mechanical properties of these biopolymers can often be measured using optical tweezers or atomic force microscopy. Dual-polarization interferometry can be used to measure the conformational changes or self-assembly of these materials when stimulated by pH, temperature, ionic strength or other binding partners. | 1 | Applied and Interdisciplinary Chemistry |
A major focus in the field of protein engineering is on creating DNA libraries that sample regions of sequence space, often with the goal of finding mutants of proteins with enhanced functions compared to the wild type. These libraries are created either by using a wild type sequence as a template and applying one or more mutagenesis techniques to make different variants of it, or by creating proteins from scratch using artificial gene synthesis. These libraries are then screened or selected, and ones with improved phenotypes are used for the next round of mutagenesis. | 1 | Applied and Interdisciplinary Chemistry |
Cudbear is a dye extracted from orchil lichens that produces colours in the purple range. It can be used to dye wool and silk, without the use of mordant. The lichen is first boiled in a solution of ammonium carbonate. The mixture is then cooled and ammonia is added and the mixture is kept damp for 3–4 weeks. Then the lichen is dried and ground to powder.
Cudbear was the first dye to be invented in modern times, and one of the few dyes to be credited to a named individual: Dr Cuthbert Gordon of Scotland: production began in 1758, and it was patented in 1758, British patent 727. John Glassford invested in the new process with funds from his slave-labor tobacco business by establishing a dyeworks in Dennistoun in 1777. The manufacture details were carefully protected, with a ten-feet high wall being built around the manufacturing facility, and staff consisting of Highlanders sworn to secrecy. The lichen consumption soon reached 250 tons per year and import from Norway and Sweden had to be arranged.
A similar process was developed in France. The lichen is extracted by urine or ammonia, then the extract is acidified, the dissolved dye precipitates out and is washed. Then it is dissolved in ammonia again, the solution is heated in air until it becomes purple, then it is precipitated out with calcium chloride. The resulting insoluble purple solid is known as French purple, a fast lichen dye that was much more stable than other lichen dyes. | 0 | Theoretical and Fundamental Chemistry |
Hydrogen sulfide chemosynthesis is a form of chemosynthesis which uses hydrogen sulfide. It is common in hydrothermal vent microbial communities Due to the lack of light in these environments this is predominant over photosynthesis
Giant tube worms use bacteria in their trophosome to fix carbon dioxide (using hydrogen sulfide as their energy source) and produce sugars and amino acids. Some reactions produce sulfur:
: hydrogen sulfide chemosynthesis:
:: 18H + 6CO + 3 → CHO (carbohydrate) + 12H + 18
In the above process, hydrogen sulfide serves as a source of electrons for the reaction. Instead of releasing oxygen gas while fixing carbon dioxide as in photosynthesis, hydrogen sulfide chemosynthesis produces solid globules of sulfur in the process.
Mechanism of Action
In deep sea environments, different organisms have been observed to have the ability to oxidize reduced compounds such as hydrogen sulfide. Oxidation is the loss of electrons in a chemical reaction. Most chemosynthetic bacteria form symbiotic associations with other small eukaryotes The electrons that are released from hydrogen sulfide will provide the energy to sustain a proton gradient across the bacterial cytoplasmic membrane. This movement of protons will eventually result in the production of adenosine triphosphate. The amount of energy derived from the process is also dependent on the type of final electron acceptor.
Other Examples Of Chemosynthetic Organisms (using HS as electron donor)
Across the world, researchers have observed different organisms in various locations capable of carrying out the process. Yang and colleagues in 2011 surveyed five Yellowstone thermal springs of varying depths and observed that the distribution of chemosynthetic microbes coincided with temperature as Sulfurihydrogenibiom was found at higher temperatures while Thiovirga inhabited cooler waters Miyazaki et al., in 2020 also found an endosymbiont capable of hydrogen sulfide chemosynthesis which contained campylobacter species and a gastropod from the genus Alviniconcha oxidise hydrogen sulfide in the Indian Ocean Furthermore, chemosynthetic bacteria such as purple sulfur bacteria have yellow globules of sulfur visible in their cytoplasm. | 1 | Applied and Interdisciplinary Chemistry |
* Gene therapy for color blindness
* Gene therapy for epilepsy
* Gene therapy for osteoarthritis
* Gene therapy in Parkinson's disease
* Gene therapy of the human retina
Gene therapies are under development for:
* Usher syndrome deafness
* Otoferlin mutation deafness | 1 | Applied and Interdisciplinary Chemistry |
Beryllium oxalate is an inorganic compound, a salt of beryllium metal and oxalic acid with the chemical formula . It forms colorless crystals, dissolves in water, and also forms crystalline hydrates. The compound is used to prepare ultra-pure beryllium oxide by thermal decomposition. | 0 | Theoretical and Fundamental Chemistry |
Metabolic flux and more specifically how metabolism is affected due to changes in the various pathways has grown in importance since it was observed that tumour cells exhibit enhanced glucose metabolism compared to normal cells. Through studying these changes, it is possible to better understand the mechanisms of cell growth and where possible develop treatments to counter the effects of enhanced metabolism. | 1 | Applied and Interdisciplinary Chemistry |
Bilirubin (BR) (from the Latin for "red bile") is a red-orange compound that occurs in the normal catabolic pathway that breaks down heme in vertebrates. This catabolism is a necessary process in the body's clearance of waste products that arise from the destruction of aged or abnormal red blood cells. In the first step of bilirubin synthesis, the heme molecule is stripped from the hemoglobin molecule. Heme then passes through various processes of porphyrin catabolism, which varies according to the region of the body in which the breakdown occurs. For example, the molecules excreted in the urine differ from those in the feces. The production of biliverdin from heme is the first major step in the catabolic pathway, after which the enzyme biliverdin reductase performs the second step, producing bilirubin from biliverdin.
Ultimately, bilirubin is broken down within the body, and its metabolites excreted through bile and urine; elevated levels may indicate certain diseases. It is responsible for the yellow color of healing bruises and the yellow discoloration in jaundice. The bacterial enzyme bilirubin reductase is responsible for the breakdown of bilirubin in the gut. One breakdown product, urobilin, is the main component of the straw-yellow color in urine. Another breakdown product, stercobilin, causes the brown color of feces.
Although bilirubin is usually found in animals rather than plants, at least one plant species, Strelitzia nicolai, is known to contain the pigment. | 1 | Applied and Interdisciplinary Chemistry |
Lichen identification uses growth form, microscopy and reactions to chemical tests.
The outcome of the "Pd test" is called "Pd", which is also used as an abbreviation for the chemical used in the test, para-phenylenediamine. If putting a drop on a lichen turns an area bright yellow to orange, this helps identify it as belonging to either the genus Cladonia or Lecanora. | 1 | Applied and Interdisciplinary Chemistry |
The Edinburgh Pharmacopoeia was a medical guide consisting of recipes and methods for making medicine. It was first published by the Royal College of Physicians of Edinburgh in 1699 as the Pharmacopoea Collegii Regii Medicorum Edimburgensium. The Edinburgh Pharmacopeia merged with the London and Dublin Pharmacopoeia's in 1864 creating the British Pharmacopoeia. | 1 | Applied and Interdisciplinary Chemistry |
Linear dichroism (LD) or diattenuation is the difference between absorption of light polarized parallel and polarized perpendicular to an orientation axis. It is the property of a material whose transmittance depends on the orientation of linearly polarized light incident upon it. As a technique, it is primarily used to study the functionality and structure of molecules. LD measurements are based on the interaction between matter and light and thus are a form of electromagnetic spectroscopy.
This effect has been applied across the EM spectrum, where different wavelengths of light can probe a host of chemical systems. The predominant use of LD currently is in the study of bio-macromolecules (e.g. DNA) as well as synthetic polymers. | 0 | Theoretical and Fundamental Chemistry |
PHBV is synthesized by bacteria as storage compounds under growth limiting conditions. It can be produced from glucose and propionate by the recombinant Escherichia coli strains. Many other bacteria like Paracoccus denitrificans and Ralstonia eutropha are also capable of producing it.
It can also be synthesized from genetically engineered plants.
PHBV is a copolymer of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid. PHBV may also be synthesized from butyrolactone and valerolactone in the presence of oligomeric aluminoxane as catalyst. | 1 | Applied and Interdisciplinary Chemistry |
These are devices incorporated in nuclear weapons which produce a pulse of neutrons when the bomb is detonated to initiate the fission reaction in the fissionable core (pit) of the bomb, after it is compressed to a critical mass by explosives. Actuated by an ultrafast switch like a krytron, a small particle accelerator drives ions of tritium and deuterium to energies above the 15 keV or so needed for deuterium-tritium fusion and directs them into a metal target where the tritium and deuterium are adsorbed as hydrides. High-energy fusion neutrons from the resulting fusion radiate in all directions. Some of these strike plutonium or uranium nuclei in the primary's pit, initiating a nuclear chain reaction. The quantity of neutrons produced is large in absolute numbers, allowing the pit to quickly achieve neutron levels that would otherwise need many more generations of chain reaction, though still small compared to the total number of nuclei in the pit. | 0 | Theoretical and Fundamental Chemistry |
The smaller scale of microflow reactors or microreactors can make them ideal for process development experiments. Although it is possible to operate flow processes at a ton scale, synthetic efficiency benefits from improved thermal and mass transfer as well as mass transport. | 1 | Applied and Interdisciplinary Chemistry |
The glycocalyx (: glycocalyces or glycocalyxes), also known as the pericellular matrix and sometime cell coat, is a glycoprotein and glycolipid covering that surrounds the cell membranes of bacteria, epithelial cells, and other cells. It was described in a review article in 1970.
Animal epithelial cells have a fuzz-like coating on the external surface of their plasma membranes. This viscous coating is the glycocalyx that consists of several carbohydrate moieties of membrane glycolipids and glycoproteins, which serve as backbone molecules for support. Generally, the carbohydrate portion of the glycolipids found on the surface of plasma membranes helps these molecules contribute to cell–cell recognition, communication, and intercellular adhesion.
The glycocalyx is a type of identifier that the body uses to distinguish between its own healthy cells and transplanted tissues, diseased cells, or invading organisms. Included in the glycocalyx are cell-adhesion molecules that enable cells to adhere to each other and guide the movement of cells during embryonic development. The glycocalyx plays a major role in regulation of endothelial vascular tissue, including the modulation of red blood cell volume in capillaries.
The term was initially applied to the polysaccharide matrix coating epithelial cells, but its functions have been discovered to go well beyond that. | 1 | Applied and Interdisciplinary Chemistry |
Attempts to find anesthetics with less metabolism led to halogenated ethers such as enflurane and isoflurane. The incidence of hepatic reactions with these agents is lower. The exact degree of hepatotoxic potential of enflurane is debated, although it is minimally metabolized. Isoflurane is essentially not metabolized and reports of associated liver injury are quite rare. Small amounts of trifluoroacetic acid can be formed from both halothane and isoflurane metabolism and possibly accounts for cross sensitization of patients between these agents.
The main advantage of the more modern agents is lower blood solubility, resulting in faster induction of and recovery from anaesthesia. | 0 | Theoretical and Fundamental Chemistry |
Static light scattering measures the product of weight-averaged molar mass and concentration of macromolecules in solution. Given a fixed total concentration of one or more species over the measurement time, the scattering signal is a direct measure of the weight-averaged molar mass of the solution, which will vary as complexes form or dissociate.
Hence the measurement quantifies the stoichiometry of the complexes as well as kinetics. Light scattering assays of protein kinetics is a very general technique that does not require an enzyme. | 1 | Applied and Interdisciplinary Chemistry |
For the analysis of water electrolysis, we shall use HO ions (also known as oxonium ions) at the cathode, as an example to explain the traditional reactions.
Water molecules self-ionize to HO and OH ions. Near the cathode surface (within the double layer region), newly generated HO ions become hydrogen gas after obtaining electrons from the cathode; however because there is nearly no electric field inside the bulk solution (see section "Electric field distribution"), OH ions can only transport through the bulk solution very slowly by diffusion. Moreover, in pure water the intrinsic HO concentration is only 10 mol/L, not enough to neutralize the newly generated OH ions. In this way OH ions accumulate locally at the cathode surface (turning the solution near cathode into alkaline). Due to Le Chatelier's principle for water self-ionization,
the OH ions accumulation impede further self-ionization of the water, which reduces the hydrogen evolution rate and eventually prevents water electrolysis. In this case water electrolysis becomes very slow or even halts; this manifests as a large equivalent resistance between the two electrodes.
This is why in the macrosystem pure water cannot be electrolyzed efficiently - the fundamental reason is the lack of rapid ion transport inside the bulk solution. | 0 | Theoretical and Fundamental Chemistry |
Ibuprofen is used primarily to treat fever (including postvaccination fever), mild to moderate pain (including pain relief after surgery), painful menstruation, osteoarthritis, dental pain, headaches, and pain from kidney stones. About 60% of people respond to any NSAID; those who do not respond well to a particular one may respond to another. A Cochrane medical review of 51 trials of NSAIDS for the treatment of lower back pain found that "NSAIDs are effective for short-term symptomatic relief in patients with acute low back pain".
It is used for inflammatory diseases such as juvenile idiopathic arthritis and rheumatoid arthritis. It is also used for pericarditis and patent ductus arteriosus. | 0 | Theoretical and Fundamental Chemistry |
There are generally accepted rules and conventions used for naming genes in bacteria. Standards were proposed in 1966 by Demerec et al. | 1 | Applied and Interdisciplinary Chemistry |
The Geochemical Society publishes, co-publishes, or sponsors the following:
* Geochimica et Cosmochimica Acta (GCA) – peer-reviewed journal with 24 issues per year, co-sponsored with the Meteoritical Society.
* Elements: An International Magazine of Mineralogy, Geochemistry, and Petrology – 6 issues per year
* Geochemical News – electronic newsletter published weekly
* Special Publications Series – published at various times
* Reviews in Mineralogy and Geochemistry (RiMG) – peer-reviewed multi-author volumes on topics approved by the governing councils of the Geochemical Society and the Mineralogical Society of America.
* Geochemistry, Geophysics, Geosystems (G-cubed) – online journal with peer-reviewed original research papers. 12 issues per year published in collaboration with the American Geophysical Union. | 0 | Theoretical and Fundamental Chemistry |
Phenethylamine, being similar to amphetamine in its action at their common biomolecular targets, releases norepinephrine and dopamine. Phenethylamine also appears to induce acetylcholine release via a glutamate-mediated mechanism.
Phenethylamine has been shown to bind to human trace amine-associated receptor 1 (hTAAR1) as an agonist. β-PEA is also an odorant binding TAAR4 in mice thought to mediate predator avoidance. | 1 | Applied and Interdisciplinary Chemistry |
ChemPhysChem is a biweekly peer-reviewed scientific journal published by Wiley-VCH on behalf of Chemistry Europe. It was established in 2000 and covers all aspects of chemical physics and physical chemistry. Initially published monthly, the journal moved to 18 issues per year in 2007, and further to biweekly in 2016. | 0 | Theoretical and Fundamental Chemistry |
Absorption also varies depending on bioactivity, resonance, the inductive effect, isosterism, bio-isosterism, and consideration, amongst others. | 1 | Applied and Interdisciplinary Chemistry |
__NOTOC__
A magnetohydrodynamic converter (MHD converter) is an electromagnetic machine with no moving parts involving magnetohydrodynamics, the study of the kinetics of electrically conductive fluids (liquid or ionized gas) in the presence of electromagnetic fields. Such converters act on the fluid using the Lorentz force to operate in two possible ways: either as an electric generator called an MHD generator, extracting energy from a fluid in motion; or as an electric motor called an MHD accelerator or magnetohydrodynamic drive, putting a fluid in motion by injecting energy. MHD converters are indeed reversible, like many electromagnetic devices.
Michael Faraday first attempted to test a MHD converter in 1832. MHD converters involving plasmas were highly studied in the 1960s and 1970s, with many government funding and dedicated international conferences. One major conceptual application was the use of MHD converters on the hot exhaust gas in a coal fired power plant, where it could extract some of the energy with very high efficiency, and then pass it into a conventional steam turbine. The research almost stopped after it was considered the electrothermal instability would severely limit the efficiency of such converters when intense magnetic fields are used, although solutions may exist.
<br> | 1 | Applied and Interdisciplinary Chemistry |
*Maxwell's demon: entropy, information, computing, edited by H.S.Leff and A.F. Rex (IOP publishing, 1990)
*Maxwell's demon, 2: entropy, classical and quantum information, edited by H.S.Leff and A.F. Rex (IOP publishing, 2003)
*The emperor's new mind: concerning computers, minds, and the laws of physics, by Roger Penrose (Oxford university press, 2002)
*[http://magnetooptics.phy.bme.hu/research/topics/optical-properties-of-multiferroic-materials/ Multiferroic] materials with time-reversal breaking optical properties
*CP violation, by I.I. Bigi and A.I. Sanda (Cambridge University Press, 2000)
*[http://pdg.lbl.gov/2004/reviews/cpviolrpp.pdf Particle Data Group on CP violation]
**the [http://www-public.slac.stanford.edu/babar/ Babar] experiment in SLAC
**the [http://belle.kek.jp BELLE] experiment in KEK
**the [https://web.archive.org/web/20050404165826/http://kpasa.fnal.gov:8080/public/ktev.html KTeV] experiment in Fermilab
**the [http://cplear.web.cern.ch/cplear/Welcome.html CPLEAR] experiment in CERN | 0 | Theoretical and Fundamental Chemistry |
Biophotons (from the Greek βίος meaning "life" and φῶς meaning "light") are photons of light in the ultraviolet and low visible light range that are produced by a biological system. They are non-thermal in origin, and the emission of biophotons is technically a type of bioluminescence, though bioluminescence is generally reserved for higher luminance luciferin/luciferase systems. The term biophoton used in this narrow sense should not be confused with the broader field of biophotonics, which studies the general interaction of light with biological systems.
Biological tissues typically produce an observed radiant emittance in the visible and ultraviolet frequencies ranging from 10 to 10 W/cm (approx 1-1000 photons/cm/second). This low level of light has a much weaker intensity than the visible light produced by bioluminescence, but biophotons are detectable above the background of thermal radiation that is emitted by tissues at their normal temperature.
While detection of biophotons has been reported by several groups, hypotheses that such biophotons indicate the state of biological tissues and facilitate a form of cellular communication are still under investigation, Alexander Gurwitsch, who discovered the existence of biophotons, was awarded the Stalin Prize in 1941 for his work. | 1 | Applied and Interdisciplinary Chemistry |
One primary application of the Bland–Altman plot is to compare two clinical measurements each of which produced some error in their measures. It can also be used to compare a new measurement technique or method with a gold standard, as even a gold standard does not—and should not—imply it to be without error. See Analyse-it, MedCalc, NCSS, GraphPad Prism, R, StatsDirect, or JASP for software providing Bland–Altman plots.
Bland–Altman plots are extensively used to evaluate the agreement among two different instruments or two measurements techniques. Bland–Altman plots allow identification of any systematic difference between the measurements (i.e., fixed bias) or possible outliers. The mean difference is the estimated bias, and the SD of the differences measures the random fluctuations around this mean. If the mean value of the difference differs significantly from 0 on the basis of a 1-sample t-test, this indicates the presence of fixed bias. If there is a consistent bias, it can be adjusted for by subtracting the mean difference from the new method. It is common to compute 95% limits of agreement for each comparison (average difference ± 1.96 standard deviation of the difference), which tells us how far apart measurements by two methods were more likely to be for most individuals. If the differences within mean ± 1.96 SD are not clinically important, the two methods may be used interchangeably. The 95% limits of agreement can be unreliable estimates of the population parameters especially for small sample sizes so, when comparing methods or assessing repeatability, it is important to calculate confidence intervals for 95% limits of agreement. This can be done by Bland and Altman's approximate method or by more precise methods.
Bland–Altman plots were also used to investigate any possible relationship of the discrepancies between the measurements and the true value (i.e., proportional bias). The existence of proportional bias indicates that the methods do not agree equally through the range of measurements (i.e., the limits of agreement will depend on the actual measurement). To evaluate this relationship formally, the difference between the methods should be regressed on the average of the 2 methods. When a relationship between the differences and the true value was identified (i.e., a significant slope of the regression line), regression-based 95% limits of agreement should be provided. | 0 | Theoretical and Fundamental Chemistry |
An ion trap mass spectrometer may incorporate a Penning trap (Fourier-transform ion cyclotron resonance), Paul trap or the Kingdon trap. The Orbitrap, introduced in 2005, is based on the Kingdon trap. Other types of mass spectrometers may also use a linear quadrupole ion trap as a selective mass filter. | 0 | Theoretical and Fundamental Chemistry |
At first glance, using the fact that it would appear that two measurements of would suffice to be able to obtain an accurate value of :
where and are the equilibrium constant values obtained at temperatures and respectively. However, the precision of values obtained in this way is highly dependent on the precision of the measured equilibrium constant values.
The use of error propagation shows that the error in will be about 76 kJ/mol times the experimental uncertainty in , or about 110 kJ/mol times the uncertainty in the values. Similar considerations apply to the entropy of reaction obtained from .
Notably, when equilibrium constants are measured at three or more temperatures, values of and are often obtained by straight-line fitting. The expectation is that the error will be reduced by this procedure, although the assumption that the enthalpy and entropy of reaction are constant may or may not prove to be correct. If there is significant temperature dependence in either or both quantities, it should manifest itself in nonlinear behavior in the Van t'Hoff plot; however, more than three data points would presumably be needed in order to observe this. | 0 | Theoretical and Fundamental Chemistry |
To place multiferroic materials in their appropriate historical context, one also needs to consider magnetoelectric materials, in which an electric field modifies the magnetic properties and vice versa. While magnetoelectric materials are not necessarily multiferroic, all ferromagnetic ferroelectric multiferroics are linear magnetoelectrics, with an applied electric field inducing a change in magnetization linearly proportional to its magnitude. Magnetoelectric materials and the corresponding magnetoelectric effect have a longer history than multiferroics, shown in blue in the graph to the right. The first known mention of magnetoelectricity is in the 1959 Edition of Landau & Lifshitz Electrodynamics of Continuous Media which has the following comment at the end of the section on piezoelectricity: "Let us point out two more phenomena, which, in principle, could exist. One is piezomagnetism, which consists of linear coupling between a magnetic field in a solid and a deformation (analogous to piezoelectricity). The other is a linear coupling between magnetic and electric fields in a media, which would cause, for example, a magnetization proportional to an electric field. Both these phenomena could exist for certain classes of magnetocrystalline symmetry. We will not however discuss these phenomena in more detail because it seems that till present, presumably, they have not been observed in any substance."' One year later, [http://www.itp.ac.ru/en/persons/dzyaloshinskii-igor-ekhielevich/ I. E. Dzyaloshinskii] showed using symmetry arguments that the material CrO should have linear magnetoelectric behavior, and his prediction was rapidly verified by D. Astrov. Over the next decades, research on magnetoelectric materials continued steadily in a number of groups in Europe, in particular in the former Soviet Union and in the group of [http://physicstoday.scitation.org/do/10.1063/PT.5.6173/full/ H. Schmid] at U. Geneva. A series of East-West conferences entitled Magnetoelectric Interaction Phenomena in Crystals (MEIPIC) was held between 1973 (in Seattle) and [http://www.icmr.ucsb.edu/programs/MEIPIC6.html 2009 (in Santa Barbara)], and indeed the term "multi-ferroic magnetoelectric" was first used by H. Schmid in the proceedings of the 1993 MEIPIC conference (in Ascona). | 0 | Theoretical and Fundamental Chemistry |
Mantle oxidation state can be quantified as the oxygen fugacity () of the system within the framework of thermodynamics. A higher oxygen fugacity implies a more oxygen-rich and more oxidized environment. At each given pressure-temperature conditions, for any compound or element M that bears the potential to be oxidized by oxygen, we can write
For example, if M is Fe, the redox equilibrium reaction can be Fe+1/2O=FeO; if M is FeO, the redox equilibrium reaction can be 2FeO+1/2O=FeO.
Gibbs energy change associated with this reaction is therefore
Along each isotherm, the partial derivation of ΔG with respect to P is ΔV,
Combining the 2 equations above,
Therefore,
(note that ln(e as the base) changed to log(10 as the base) in this formula.
For a closed system, there might exist more than one of these equilibrium oxidation reactions, but since all these reactions share a same , examining one of them would allow extraction of oxidation state of the system. | 0 | Theoretical and Fundamental Chemistry |
Cyclodextrin (CD) is composed of several glucose units and connects by ether bonds. There are three kinds of CDs, α-CD (6 units), β-CD (7 units), and γ-CD (8 units). The heights of the structure are all around 8 Å, while the cavity sizes of them are different, around 5, 6, and 8 Å, respectively. By comparing the size of the guest molecule and the CD, the binding behavior can be predicted. For instance, if the guest molecule is larger than the CD, it can be assumed that the binding will not occur. Typically, the α-CD can thread onto one PEG chain, while γ-CD can thread onto 2 PEG chains. β-CD can bind with thiophene-based molecule. | 0 | Theoretical and Fundamental Chemistry |
Caking is a powder's tendency to form lumps or masses. The formation of lumps interferes with packaging, transport, flowability, and consumption. Usually caking is undesirable, but it is useful when pressing powdered substances into pills or briquettes. Granular materials can also be subject to caking, particularly those that are hygroscopic such as salt, sugar, and many chemical fertilizers. Anticaking agents are commonly added to control caking.
Caking properties must be considered when designing and constructing bulk material handling equipment. Powdered substances that need to be stored, and flow smoothly at some time in the future, are often pelletized or made into pills. | 1 | Applied and Interdisciplinary Chemistry |
Biomanipulation is the deliberate alteration of an ecosystem by adding or removing species, especially predators. | 1 | Applied and Interdisciplinary Chemistry |
Ibuprofen is practically insoluble in water, but very soluble in most organic solvents like ethanol (66.18g/100mL at 40°C for 90% EtOH), methanol, acetone and dichloromethane.
The original synthesis of ibuprofen by the Boots Group started with the compound isobutylbenzene. The synthesis took six steps. A modern, greener technique with fewer waste byproducts for the synthesis involves only three steps was developed in the 1980s by the Celanese Chemical Company. The synthesis is initiated with the acylation of isobutylbenzene using the recyclable Lewis acid catalyst hydrogen fluoride. The following catalytic hydrogenation of isobutylacetophenone is performed with either Raney nickel or palladium on carbon to lead into the key-step, the carbonylation of 1-(4-isobutylphenyl)ethanol. This is achieved by a PdCl(PPh) catalyst, at around 50 bar of CO pressure, in the presence of HCl (10%). The reaction presumably proceeds through the intermediacy of the styrene derivative (acidic elimination of the alcohol) and (1-chloroethyl)benzene derivative (Markovnikow addition of HCl to the double bond). | 0 | Theoretical and Fundamental Chemistry |
Typically, photochromic lenses darken substantially in response to UV light in less than one minute, and continue to darken a little more over the next fifteen minutes. The lenses begin to clear in the absence of UV light, and will be noticeably lighter within two minutes, mostly clear within five minutes, and fully back to their non-exposed state in about fifteen minutes. A report by the Institute of Ophthalmology at the University College London suggested that at their clearest photochromic lenses can absorb up to 20% of ambient light.
Because photochromic compounds fade back to their clear state by a thermal process, the higher the temperature, the less dark photochromic lenses will be. This thermal effect is called "temperature dependency" and prevents these devices from achieving true sunglass darkness in very hot weather. Conversely, photochromic lenses will get very dark in cold weather conditions. Once inside, away from the triggering UV light, the cold lenses take longer to regain their transparency than warm lenses.
Photochromic lenses filter 100% UVA as well as UVB. UVB light is more energetic and causes sunburn as well as skin damage including cancers, UVA light causes skincancers but not usually sunburn. UVB is blocked by all glass, UVA light is not blocked by ordinary windows or lenses glass.
A number of sunglass manufacturers and suppliers including INVU, BIkershades, Tifosi, Intercast, Oakley, Serengeti Eyewear, and Persol provide tinted lenses that use photochromism to go from a dark to a darker state. They are typically used for outdoor sunglasses rather than as general-purpose lenses. | 0 | Theoretical and Fundamental Chemistry |
Yttrium oxalate is highly insoluble in water and converts to the oxide when heated. Yttrium oxalate forms crystalline hydrates (colorless crystals) with the formula Y(CO)•n HO, where n = 4, 9, and 10.
Decomposes when heated:
The solubility product of yttrium oxalate at 25 °C is 5.1 × 10.
The trihydrate Y(CO)•3HO is formed by heating more hydrated varieties at 110 °C.
Y(CO)•2HO, which is formed by heating the decahydrate at 210 °C) forms monoclinic crystals with unit cell dimensions a=9.3811 Å, b=11.638 Å, c=5.9726 Å, β=96.079°. | 0 | Theoretical and Fundamental Chemistry |
In their classical text on fluid mechanics, Landau and Lifshitz derive an aeroacoustic equation analogous to Lighthills (i.e., an equation for sound generated by "turbulent" fluid motion), but for the incompressible flow of an inviscid fluid. The inhomogeneous wave equation that they obtain is for the pressure rather than for the density of the fluid. Furthermore, unlike Lighthills equation, Landau and Lifshitz's equation is not exact; it is an approximation.
If one is to allow for approximations to be made, a simpler way (without necessarily assuming the fluid is incompressible) to obtain an approximation to Lighthill's equation is to assume that , where and are the (characteristic) density and pressure of the fluid in its equilibrium state. Then, upon substitution the assumed relation between pressure and density into we obtain the equation (for an inviscid fluid, σ = 0)
And for the case when the fluid is indeed incompressible, i.e. (for some positive constant ) everywhere, then we obtain exactly the equation given in Landau and Lifshitz, namely
A similar approximation [in the context of equation ], namely , is suggested by Lighthill [see Eq. (7) in the latter paper].
Of course, one might wonder whether we are justified in assuming that . The answer is affirmative, if the flow satisfies certain basic assumptions. In particular, if and , then the assumed relation follows directly from the linear theory of sound waves (see, e.g., the linearized Euler equations and the acoustic wave equation). In fact, the approximate relation between and that we assumed is just a linear approximation to the generic barotropic equation of state of the fluid.
However, even after the above deliberations, it is still not clear whether one is justified in using an inherently linear relation to simplify a nonlinear wave equation. Nevertheless, it is a very common practice in nonlinear acoustics as the textbooks on the subject show: e.g., Naugolnykh and Ostrovsky and Hamilton and Morfey. | 1 | Applied and Interdisciplinary Chemistry |
Metal spraying equipment uses compressed gases which create noise. Sound levels vary with the type of spraying equipment, the material being sprayed, and the operating parameters. Typical sound pressure levels are measured at 1 meter behind the arc. | 1 | Applied and Interdisciplinary Chemistry |
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