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When heated, orthoboric acid undergoes a three step dehydration. The reported transition temperatures vary substantially from source to source.
When heated above 140 °C, orthoboric acid yields metaboric acid () with loss of one water molecule:
Heating metaboric acid above about 180 °C eliminates another water molecule forming tetraboric acid, also called pyroboric acid ():
Further heating (to about 530 °C) leads to boron trioxide: | 0 | Theoretical and Fundamental Chemistry |
Claudio Luchinat (born February 15, 1952, in Florence) is an Italian chemist. He is author of about 550 publications in Bioinorganic Chemistry, NMR and Structural Biology, and of four books. According to Google scholar, his h-index is 90 and his papers have been quoted more than 33,000 times ().
He earned a PhD in Chemistry from the University of Florence. He has been full professor of Chemistry at the University of Bologna (1986–96).
He is currently a researcher at the University of Florence and full professor of Chemistry at the same university (1996–, CERM and Department of Chemistry). He is member of the Italian Chemical Society, New York Academy of Sciences, American Association for the Advancement of Science. | 0 | Theoretical and Fundamental Chemistry |
Historically, flammable, inflammable and combustible meant capable of burning. The word "inflammable" came through French from the Latin inflammāre = "to set fire to", where the Latin preposition "in-" means "in" as in "indoctrinate", rather than "not" as in "invisible" and "ineligible".
The word "inflammable" may be erroneously thought to mean "non-flammable". The erroneous usage of the word "inflammable" is a significant safety hazard. Therefore, since the 1950s, efforts to put forward the use of "flammable" in place of "inflammable" were accepted by linguists, and it is now the accepted standard in American English and British English. Antonyms of "flammable" or "inflammable" include: non-flammable, non-inflammable, incombustible, non-combustible, not flammable, and fireproof.
Flammable applies to combustible materials that ignite easily and thus are more dangerous and more highly regulated. Less easily ignited less-vigorously burning materials are combustible. For example, in the United States flammable liquids, by definition, have a flash point below —where combustible liquids have a flash point above . Flammable solids are solids that are readily combustible, or may cause or contribute to fire through friction. Readily combustible solids are powdered, granular, or pasty substances that easily ignite by brief contact with an ignition source, such as a burning match, and spread flame rapidly. The technical definitions vary between countries so the United Nations created the Globally Harmonized System of Classification and Labeling of Chemicals, which defines the flash point temperature of flammable liquids as between 0 and and combustible liquids between and . | 0 | Theoretical and Fundamental Chemistry |
With the lone exception of the bis(trifluoromethyl) derivative, the dominant reaction of phosphinous acids is tautomerization:
:PROH → OPRH
Even the pentafluorophenyl compound P(CF)OH is unstable with respect to the phosphine oxide.
Although phosphinous acids are rare, their P-bonded coordination complexes are well established, e.g. Mo(CO)P(OH). | 0 | Theoretical and Fundamental Chemistry |
In fuel cells, electro-osmosis causes protons moving through a proton exchange membrane (PEM) to drag water molecules from one side (anode) to the other (cathode). | 0 | Theoretical and Fundamental Chemistry |
A rotation symmetry in dimension 2 or 3 must move a lattice point to a succession of other lattice points in the same plane, generating a regular polygon of coplanar lattice points. We now confine our attention to the plane in which the symmetry acts , illustrated with lattice vectors in the figure.
Now consider an 8-fold rotation, and the displacement vectors between adjacent points of the polygon. If a displacement exists between any two lattice points, then that same displacement is repeated everywhere in the lattice. So collect all the edge displacements to begin at a single lattice point. The edge vectors become radial vectors, and their 8-fold symmetry implies a regular octagon of lattice points around the collection point. But this is impossible, because the new octagon is about 80% as large as the original. The significance of the shrinking is that it is unlimited. The same construction can be repeated with the new octagon, and again and again until the distance between lattice points is as small as we like; thus no discrete lattice can have 8-fold symmetry. The same argument applies to any k-fold rotation, for k greater than 6.
A shrinking argument also eliminates 5-fold symmetry. Consider a regular pentagon of lattice points. If it exists, then we can take every other edge displacement and (head-to-tail) assemble a 5-point star, with the last edge returning to the starting point. The vertices of such a star are again vertices of a regular pentagon with 5-fold symmetry, but about 60% smaller than the original.
Thus the theorem is proved.
The existence of quasicrystals and Penrose tilings shows that the assumption of a linear translation is necessary. Penrose tilings may have 5-fold rotational symmetry and a discrete lattice, and any local neighborhood of the tiling is repeated infinitely many times, but there is no linear translation for the tiling as a whole. And without the discrete lattice assumption, the above construction not only fails to reach a contradiction, but produces a (non-discrete) counterexample. Thus 5-fold rotational symmetry cannot be eliminated by an argument missing either of those assumptions. A Penrose tiling of the whole (infinite) plane can only have exact 5-fold rotational symmetry (of the whole tiling) about a single point, however, whereas the 4-fold and 6-fold lattices have infinitely many centres of rotational symmetry. | 0 | Theoretical and Fundamental Chemistry |
Synovial Sarcoma X chromosome breakpoint-2 (SSX2) proteins are known to localize in nucleus and work as a transcriptional repressor. In addition, expression of SSX2 is frequently observed in melanoma, but the role of the gene has not been evaluated. Thus, researchers have used the principle of ectopic expression to express SSX2 to different cell lines including cancer model cells. They found important phenotypes of ectopic SSX2 expression that is involved in tumorigenesis: 1) immediate induction of genomic instability, 2) long-term support of tumor cell growth. | 1 | Applied and Interdisciplinary Chemistry |
The signal is measured as the potential difference (voltage) between the working electrode and the reference electrode. The working electrode's potential must depend on the concentration of the analyte in the gas or solution phase. The reference electrode is needed to provide a defined reference potential. | 0 | Theoretical and Fundamental Chemistry |
Hemilabile ligands contain at least two electronically different coordinating groups and form complexes where one of these is easily displaced from the metal center while the other remains firmly bound, a behaviour which has been found to increase the reactivity of catalysts when compared to the use of more traditional ligands. | 0 | Theoretical and Fundamental Chemistry |
The "MAXIM" (MAterials X-ray IMaging) method is another method combining diffraction analysis with spatial resolution. It can be viewed as serial topography with additional angular resolution in the exit beam. In contrast to the Rocking Curve Imaging method, it is more appropriate for more highly disturbed (polycrystalline) materials with lower crystalline perfection. The difference on the instrumental side is that MAXIM uses an array of slits / small channels (a so-called "multi-channel plate" (MCP), the two-dimensional equivalent of a Soller slit system) as an additional X-ray optical element between sample and CCD detector. These channels transmit intensity only in specific, parallel directions, and thus guarantee a one-to-one-relation between detector pixels and points on the sample surface, which would otherwise not be given in the case of materials with high strain and/or a strong mosaicity. The spatial resolution of the method is limited by a combination of detector pixel size and channel plate periodicity, which in the ideal case are identical. The angular resolution is mostly given by the aspect ratio (length over width) of the MCP channels.
Literature: | 0 | Theoretical and Fundamental Chemistry |
:V10AA01 Yttrium (Y) citrate colloid
:V10AA02 Yttrium (Y) ferrihydroxide colloid
:V10AA03 Yttrium (Y) silicate colloid | 1 | Applied and Interdisciplinary Chemistry |
Antoine Jérôme Balard (30 September 1802 – 30 April 1876) was a French chemist and one of the discoverers of bromine. | 1 | Applied and Interdisciplinary Chemistry |
This explanation proposes that a stable product could contribute to the alpha effect, however, this factor could not be the sole factor. | 0 | Theoretical and Fundamental Chemistry |
Terminal inverted repeats have been observed in the DNA of various eukaryotic transposons, even though their source remains unknown. Inverted repeats are principally found at the origins of replication of cell organism and organelles that range from phage plasmids, mitochondria, and eukaryotic viruses to mammalian cells. The replication origins of the phage G4 and other related phages comprise a segment of nearly 139 nucleotide bases that include three inverted repeats that are essential for replication priming. | 1 | Applied and Interdisciplinary Chemistry |
In the United States and India, some coal-producing states have invested in Fischer–Tropsch plants. In Pennsylvania, Waste Management and Processors, Inc. was funded by the state to implement FT technology licensed from Shell and Sasol to convert so-called waste coal (leftovers from the mining process) into low-sulfur diesel fuel. | 0 | Theoretical and Fundamental Chemistry |
The Faraday Society was a British society for the study of physical chemistry, founded in 1903 and named in honour of Michael Faraday. In 1980, it merged with several similar organisations, including the Chemical Society, the Royal Institute of Chemistry, and the Society for Analytical Chemistry to form the Royal Society of Chemistry which is both a learned society and a professional body. At that time, the Faraday Division became one of six units within the Royal Society of Chemistry.
The Faraday Society published Faraday Transactions from 1905 to 1971, when the Royal Society of Chemistry took over the publication.
Of particular note were the conferences called Faraday Discussions, which were published under the same name. The publication includes the discussion of the paper as well as the paper itself. At the meeting, more time is given to the discussion than to the author presenting the paper as the audience are given the papers prior to the meeting. These conferences continue to be run by the Royal Society of Chemistry.
In addition to its presidents, key figures at the Faraday Society included George Stanley Withers Marlow, Secretary and Editor of the society from 1926 to 1948,
and his successor Frederick Clifford Tompkins. Tompkins served as Editor until 1977, and as the President of the Faraday Division of the amalgamated Royal Society of Chemistry from 1978 to 1979.
Prior to the amalgamation, Tompkins received valuable assistance from D. A. Young, who became Editor as of 1977. | 1 | Applied and Interdisciplinary Chemistry |
The equilibrium constant K for a base is usually defined as the association constant for protonation of the base, B, to form the conjugate acid, .
Using similar reasoning to that used before
K is related to K for the conjugate acid. In water, the concentration of the hydroxide ion, , is related to the concentration of the hydrogen ion by , therefore
Substitution of the expression for into the expression for K gives
When K, K and K are determined under the same conditions of temperature and ionic strength, it follows, taking cologarithms, that pK = pK − pK. In aqueous solutions at 25 °C, pK is 13.9965, so
with sufficient accuracy for most practical purposes. In effect there is no need to define pK separately from pK, but it is done here as often only pK values can be found in the older literature.
For an hydrolyzed metal ion, K can also be defined as a stepwise dissociation constant
This is the reciprocal of an association constant for formation of the complex. | 0 | Theoretical and Fundamental Chemistry |
Isomalathion is an impurity found in some batches of malathion. Whereas the structure of malation is, generically, RSP(S)(OCH), the connectivity of isomalathion is RSPO(SCH)(OCH). It arises by heating malathion. Being significantly more toxic to humans than malathion, it has resulted in human poisonings.
In 1976, numerous malaria workers in Pakistan were poisoned by isomalathion. It is an inhibitor of carboxyesterase. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen cyanide was first isolated from a blue pigment (Prussian blue) which had been known since 1706, but whose structure was unknown. It is now known to be a coordination polymer with a complex structure and an empirical formula of hydrated ferric ferrocyanide. In 1752, the French chemist Pierre Macquer made the important step of showing that Prussian blue could be converted to an iron oxide plus a volatile component and that these could be used to reconstitute it. The new component was what is now known as hydrogen cyanide. Following Macquers lead, it was first prepared from Prussian blue by the Swedish chemist Carl Wilhelm Scheele in 1782, and was eventually given the German name Blausäure (lit. "Blue acid") because of its acidic nature in water and its derivation from Prussian blue. In English, it became known popularly as prussic acid.'
In 1787, the French chemist Claude Louis Berthollet showed that prussic acid did not contain oxygen, an important contribution to acid theory, which had hitherto postulated that acids must contain oxygen (hence the name of oxygen itself, which is derived from Greek elements that mean "acid-former" and are likewise calqued into German as Sauerstoff). In 1811, Joseph Louis Gay-Lussac prepared pure, liquified hydrogen cyanide. In 1815, Gay-Lussac deduced Prussic acids chemical formula. The radical cyanide' in hydrogen cyanide was given its name from cyan, not only an English word for a shade of blue but the Greek word for blue (), again owing to its derivation from Prussian blue. | 0 | Theoretical and Fundamental Chemistry |
At atmospheric pressure, three allotropic forms of iron exist, depending on temperature: alpha iron (α-Fe, ferrite), gamma iron (γ-Fe, austenite), and delta iron (δ-Fe). At very high pressure, a fourth form exists, epsilon iron (ε-Fe, hexaferrum). Some controversial experimental evidence suggests the existence of a fifth high-pressure form that is stable at very high pressures and temperatures.
The phases of iron at atmospheric pressure are important because of the differences in solubility of carbon, forming different types of steel. The high-pressure phases of iron are important as models for the solid parts of planetary cores. The inner core of the Earth is generally assumed to consist essentially of a crystalline iron-nickel alloy with ε structure. The outer core surrounding the solid inner core is believed to be composed of liquid iron mixed with nickel and trace amounts of lighter elements. | 1 | Applied and Interdisciplinary Chemistry |
The JAK-STAT signaling pathway is instrumental in the development of limbs, specifically in its ability to regulate bone growth through paracrine signaling of cytokines. However, mutations in this pathway have been implicated in severe forms of dwarfism: thanatophoric dysplasia (lethal) and achondroplasic dwarfism (viable). This is due to a mutation in a Fgf gene, causing a premature and constitutive activation of the Stat1 transcription factor. Chondrocyte cell division is prematurely terminated, resulting in lethal dwarfism. Rib and limb bone growth plate cells are not transcribed. Thus, the inability of the rib cage to expand prevents the newborn's breathing. | 1 | Applied and Interdisciplinary Chemistry |
Once the adsorptive capacity of the activated carbon bed has been exhausted by the adsorption of pollutant molecules, the carbon is transferred to an electrochemical cell (to either the anode or the cathode) in which electrochemical regeneration can occur. | 0 | Theoretical and Fundamental Chemistry |
The earliest steps of a touchdown polymerase chain reaction cycle have high annealing temperatures. The annealing temperature is decreased in increments for every subsequent set of cycles. The primer will anneal at the highest temperature which is least-permissive of nonspecific binding that it is able to tolerate. Thus, the first sequence amplified is the one between the regions of greatest primer specificity; it is most likely that this is the sequence of interest. These fragments will be further amplified during subsequent rounds at lower temperatures, and will outcompete the nonspecific sequences to which the primers may bind at those lower temperatures. If the primer initially (during the higher-temperature phases) binds to the sequence of interest, subsequent rounds of polymerase chain reaction can be performed upon the product to further amplify those fragments. Touchdown increases specificity of the reaction at higher temperatures and increases the efficiency towards the end by lowering the annealing temperature.
From a mathematical point of view products of annealing at smaller temperatures are disadvantaged by for the first annealing in cycle and the second one in cycle for . | 1 | Applied and Interdisciplinary Chemistry |
The Hill coefficient is also intimately connected to the elasticity coefficient where the Hill coefficient can be shown to equal:
where is the fractional saturation, , and the elasticity coefficient.
This is derived by taking the slope of the Hill equation:
and expanding the slope using the quotient rule. The result shows that the elasticity can never exceed since the equation above can be rearranged to: | 1 | Applied and Interdisciplinary Chemistry |
The F portion of ATP synthase is hydrophilic and responsible for hydrolyzing ATP. The F unit protrudes into the mitochondrial matrix space. Subunits α and β make a hexamer with 6 binding sites. Three of them are catalytically inactive and they bind ADP.
Three other subunits catalyze the ATP synthesis. The other F subunits γ, δ, and ε are a part of a rotational motor mechanism (rotor/axle). The γ subunit allows β to go through conformational changes (i.e., closed, half open, and open states) that allow for ATP to be bound and released once synthesized. The F particle is large and can be seen in the transmission electron microscope by negative staining. These are particles of 9 nm diameter that pepper the inner mitochondrial membrane. | 0 | Theoretical and Fundamental Chemistry |
Some inherently chiral molecules contain chirality planes, or planes within a given molecules across which the molecule is dissymmetric. Paracyclophanes often contain chiral planes if the bridge across the phenylene unit is short enough, or if the phenylene contains another substituent, not in the bridge, that hinders rotation of the phenylene unit. | 0 | Theoretical and Fundamental Chemistry |
Ractopamine has been banned in Taiwan since 2006. In the summer of 2007, two US shipments including ractopamine-laced pork were rejected by Taiwans health authorities, while the Taiwan government had been considering lifting the ban on such imports. This resulted in mass protests in the capital city, Taipei, by swine farmers insisting that the ban remain in place. Health Minister Hou Sheng-mou (侯勝茂) declared no lifting of the ban would occur unless related laws were amended. Although the use of ractopamine in livestock is still banned and enforced on the domestic industry, and the government has maintained a "zero tolerance" policy on pork imports that contain it, Taiwans legislature amended the food safety act in August 2012 to allow the import of beef products containing up to a maximum residue level of 10 parts per billion of the additive. The remaining restrictions have been an obstacle to the two nations signing a free-trade agreement, and the Office of the United States Trade Representative (USTR)'s 2018 Trade Policy Agenda and 2017 Annual Report assert that these remaining restrictions "...are not based upon science..." and highlights their removal as among the main priorities for the US in its trade with Taiwan. However, Taiwan plans to ease the import restrictions on US pork commencing January 1, 2021 | 0 | Theoretical and Fundamental Chemistry |
When loaded with the parent isotope germanium-68, these generators function similarly to technetium-99m generators, in both cases using a process similar to ion chromatography. The stationary phase is either metal-free or alumina, TiO or SnO, onto which germanium-68 is adsorbed. The use of metal-free columns allows direct labeling of Ga without prepurification, hence making production of gallium-68-radiolabeled compounds more convenient. The mobile phase is a solvent able to elute (wash out) gallium-68 (III) (Ga) after it has been produced by electron capture decay from the immobilized (absorbed) germanium-68.
Currently, such Ga (III) is easily eluted with a few mL of 0.05 M, 0.1 M or 1.0 M hydrochloric acid from generators using metal-free tin dioxide or titanium dioxide adsorbents, respectively, within 1 to 2 minutes. With generators of tin dioxide and titanium dioxide-based adsorbents, there once remained more than an hour of pharmaceutical preparation to attach the gallium-68 (III) as a tracer to the pharmaceutical molecules DOTATOC or DOTA-TATE, so that the total preparation time for the resulting radiopharmaceutical is typically longer than the Ga isotope half-life. This fact required that these radiopharmaceuticals be made on-site in most cases, and the on-site generator is required to minimize the time losses. However, new kits such as "NETSPOT" for more rapidly preparing Ga-68 edotreotide or DOTATATE from Ga-68 (III) ions have increased the flexibility of sourcing of this radiopharmaceutical for Ga-68 endocrine receptor (octreotide) scans. With NETSPOT the preparation of the Ga-68 DOTATATE is immediate once the Ga-68 has been acquired from the generator and mixed with the reagent. | 0 | Theoretical and Fundamental Chemistry |
Another common add on is the sample box. This is a heavy duty rubber hose that is inserted at the end of the flow line and at the other end emplaced into the sample box itself. The sample box is used to capture samples of drill cuttings for geological logging. The box is typically equipped with a raising door that allows the water and cuttings to escape after a sample is collected. | 1 | Applied and Interdisciplinary Chemistry |
The majority of the computer models available for water and solute transport in the soil (e.g. Swatre, DrainMod ) are based on Richard's differential equation for the movement of water in unsaturated soil in combination with a differential salinity dispersion equation. The models require input of soil characteristics like the relation between unsaturated soil moisture content, water tension, hydraulic conductivity and dispersivity.
These relations vary to a great extent from place to place and are not easy to measure. The models use short time steps and need at least a daily data base of hydrological phenomena. Altogether this makes model application to a fairly large project the job of a team of specialists with ample facilities. | 0 | Theoretical and Fundamental Chemistry |
Protodeboronation is a chemical reaction involving the protonolysis of a boronic acid (or other organoborane compound) in which a carbon-boron bond is broken and replaced with a carbon-hydrogen bond. Protodeboronation is a well-known undesired side reaction, and frequently associated with metal-catalysed coupling reactions that utilise boronic acids (see Suzuki reaction). For a given boronic acid, the propensity to undergo protodeboronation is highly variable and dependent on various factors, such as the reaction conditions employed and the organic substituent of the boronic acid: | 0 | Theoretical and Fundamental Chemistry |
Two-dimensional (thin film) semi-ordered lattices have been studied using an optical microscope, as well as those collected at electrode surfaces. Digital video microscopy has revealed the existence of an equilibrium hexatic phase as well as a strongly first-order liquid-to-hexatic and hexatic-to-solid phase transition. These observations are in agreement with the explanation that melting might proceed via the unbinding of pairs of lattice dislocations. | 0 | Theoretical and Fundamental Chemistry |
In humans, excessive exposure to UV radiation can result in acute and chronic harmful effects on the eye's dioptric system and retina. The risk is elevated at high altitudes and people living in high latitude areas where snow covers the ground right into early summer and sun positions even at zenith are low, are particularly at risk. Skin, the circadian system, and the immune system can also be affected.
The differential effects of various wavelengths of light on the human cornea and skin are sometimes called the "erythemal action spectrum". The action spectrum shows that UVA does not cause immediate reaction, but rather UV begins to cause photokeratitis and skin redness (with lighter skinned individuals being more sensitive) at wavelengths starting near the beginning of the UVB band at 315 nm, and rapidly increasing to 300 nm. The skin and eyes are most sensitive to damage by UV at 265–275 nm, which is in the lower UV‑C band. At still shorter wavelengths of UV, damage continues to happen, but the overt effects are not as great with so little penetrating the atmosphere. The WHO-standard ultraviolet index is a widely publicized measurement of total strength of UV wavelengths that cause sunburn on human skin, by weighting UV exposure for action spectrum effects at a given time and location. This standard shows that most sunburn happens due to UV at wavelengths near the boundary of the UV‑A and UV‑B bands. | 0 | Theoretical and Fundamental Chemistry |
Thiosulfoxides are orthogonally isomeric with disulfides, having the second sulfur branching from the first and not partaking in a continuous chain, i.e. >S=S rather than −S−S−.
Disulfide bonds are analogous but more common than related peroxide, thioselenide, and diselenide bonds. Intermediate compounds of these also exist, for example thioperoxides (also known as oxasulfides) such as hydrogen thioperoxide, have the formula ROSR (equivalently RSOR). These are isomeric to sulfoxides in a similar manner to the above; i.e. >S=O rather than −S−O−.
Thiuram disulfides, with the formula (RNCSS), are disulfides but they behave distinctly because of the thiocarbonyl group.
Compounds with three sulfur atoms, such as CHS−S−SCH, are called trisulfides, or trisulfide bonds. | 0 | Theoretical and Fundamental Chemistry |
Crystal parting occurs when minerals break along planes of structural weakness due to external stress, along twin composition planes, or along planes of weakness due to the exsolution of another mineral. Parting breaks are very similar in appearance to cleavage, but the cause is different. Cleavage occurs because of design weakness while parting results from growth defects (deviations from the basic crystallographic design). Thus, cleavage will occur in all samples of a particular mineral, while parting is only found in samples with structural defects. Examples of parting include the octahedral parting of magnetite, the rhombohedral and basal parting in corundum, and the basal parting in pyroxenes. | 0 | Theoretical and Fundamental Chemistry |
The rank product is a biologically motivated rank test for the detection of differentially expressed genes in replicated microarray experiments.
It is a simple non-parametric statistical method based on ranks of fold changes. In addition to its use in expression profiling, it can be used to combine ranked lists in various application domains, including proteomics, metabolomics, statistical meta-analysis, and general feature selection. | 1 | Applied and Interdisciplinary Chemistry |
Decreased oxygen availability results in decreases in many zooplankton species’ egg production, food intake, respiration, and metabolic rates. Temperature and salinity in areas of decreased oxygen concentrations also affect oxygen availability. Higher temperatures and salinity lower oxygen solubility decrease the partial pressure of oxygen. This decreased partial pressure increases organisms’ respiration rates, causing the oxygen demand of the organism to increase.
In addition to affecting their vital functions, zooplankton alter their distribution in response to hypoxic or anoxic zones. Many species actively avoid low oxygen zones, while others take advantage of their predators’ low tolerance for hypoxia and use these areas as a refuge. Zooplankton that exhibit daily vertical migrations to avoid predation and low oxygen conditions also excrete ammonium near the oxycline and contribute to increased anaerobic ammonium oxidation (anammox, which produces N gas. As hypoxic regions expand vertically and horizontally, the habitable ranges for phytoplankton, zooplankton, and nekton increasingly overlap, increasing their susceptibility to predation and human exploitation. | 0 | Theoretical and Fundamental Chemistry |
The majority of optical tweezers make use of conventional TEM Gaussian beams. However a number of other beam types have been used to trap particles, including high order laser beams i.e. Hermite-Gaussian beams (TEM), Laguerre-Gaussian (LG) beams (TEM) and Bessel beams.
Optical tweezers based on Laguerre-Gaussian beams have the unique capability of trapping particles that are optically reflective and absorptive. Laguerre-Gaussian beams also possess a well-defined orbital angular momentum that can rotate particles. This is accomplished without external mechanical or electrical steering of the beam.
Both zero and higher order Bessel Beams also possess a unique tweezing ability. They can trap and rotate multiple particles that are millimeters apart and even around obstacles.
Micromachines can be driven by these unique optical beams due to their intrinsic rotating mechanism due to the spin and orbital angular momentum of light. | 1 | Applied and Interdisciplinary Chemistry |
In phosphor thermometry, the temperature dependence of the photoluminescence process is exploited to measure temperature. | 0 | Theoretical and Fundamental Chemistry |
Electric field NMR (EFNMR) spectroscopy is the NMR spectroscopy where additional information on a sample being probed is obtained from the effect of a strong, externally applied, electric field on the NMR signal. | 0 | Theoretical and Fundamental Chemistry |
Uranium causes reproductive defects and other health problems in rodents, frogs and other animals. Uranium was also shown to have cytotoxic, genotoxic and carcinogenic effects in animals. It has been shown in rodents and frogs that water-soluble forms of uranium are teratogenic. | 0 | Theoretical and Fundamental Chemistry |
Lactams form from intramolecular attack of linear acyl derivatives from the nucleophilic abstraction reaction. | 0 | Theoretical and Fundamental Chemistry |
Greenwood was a senior research fellow at the Atomic Energy Research Establishment from 1951 until 1953 when he was appointed a lecturer at the University of Nottingham. His first PhD student at Nottingham was Kenneth Wade (1954–1957).
Professor William Wynne-Jones, who was the Chairman of the School of Chemistry at Kings College, Durham (which was to become the University of Newcastle upon Tyne in 1963), recruited Greenwood to the first established chair of inorganic chemistry in the country in 1961.
Greenwood was appointed Professor and Head of the Department of Inorganic and Structural Chemistry at the University of Leeds in 1971, a post which he held until his retirement in 1990 when he was given the title Emeritus Professor.
His wide-ranging researches in inorganic and structural chemistry have made major advances in the chemistry of boron hydrides and other main-group element compounds. He also pioneered the application of Mössbauer spectroscopy to problems in chemistry. He was a prolific writer and inspirational lecturer on chemical and educational themes, and has held numerous visiting professorships throughout the world. He was appointed by NASA as principal investigator in the study of lunar rocks. He served as chairman of the IUPAC Commission on Atomic Weights from 1970 to 1975 and also as president of the IUPAC Inorganic Chemistry Division. | 0 | Theoretical and Fundamental Chemistry |
The metallotranscriptome can be defined as the map of the entire transcriptome in the presence of biologically or environmentally relevant concentrations of an essential or toxic metal, respectively. The metallometabolome constitutes the complete pool of small metabolites in a cell at any given time. This gives rise to the whole metallointeractome and knowledge of this is important in comparative metallomics dealing with toxicity and drug discovery. | 1 | Applied and Interdisciplinary Chemistry |
Depletion forces in colloid-polymer mixtures drive colloids to form aggregates that are densely packed locally. This local dense packing is also observed in colloidal systems without polymer depletants. Without polymer depletants the mechanism is similar, because the particles in dense colloidal suspension act, effectively, as depletants for one another This effect is particularly striking for anisotropically shaped colloidal particles, where the anisotropy of the shape leads to the emergence of directional entropic forces that are responsible for the ordering of hard anisotropic colloids into a wide range of crystal structures. | 0 | Theoretical and Fundamental Chemistry |
Enzyme induction is a process in which a molecule (e.g. a drug) induces (i.e. initiates or enhances) the expression of an enzyme.
Enzyme inhibition can refer to
* the inhibition of the expression of the enzyme by another molecule
* interference at the enzyme-level, basically with how the enzyme works. This can be competitive inhibition, uncompetitive inhibition, non-competitive inhibition or partially competitive inhibition.
If the molecule induces enzymes that are responsible for its own metabolism, this is called auto-induction (or auto-inhibition if there is inhibition). These processes are particular forms of gene expression regulation.
These terms are of particular interest to pharmacology, and more specifically to drug metabolism and drug interactions. They also apply to molecular biology. | 1 | Applied and Interdisciplinary Chemistry |
In the design of a dam the energy of the fast-flowing stream over a spillway must be partially dissipated to prevent erosion of the streambed downstream of the spillway, which could ultimately lead to failure of the dam. This can be done by arranging for the formation of a hydraulic jump to dissipate energy. To limit damage, this hydraulic jump normally occurs on an apron engineered to withstand hydraulic forces and to prevent local cavitation and other phenomena which accelerate erosion.
In the design of a spillway and apron, the engineers select the point at which a hydraulic jump will occur. Obstructions or slope changes are routinely designed into the apron to force a jump at a specific location. Obstructions are unnecessary, as the slope change alone is normally sufficient. To trigger the hydraulic jump without obstacles, an apron is designed such that the flat slope of the apron retards the rapidly flowing water from the spillway. If the apron slope is insufficient to maintain the original high velocity, a jump will occur.
Two methods of designing an induced jump are common:
* If the downstream flow is restricted by the down-stream channel such that water backs up onto the foot of the spillway, that downstream water level can be used to identify the location of the jump.
* If the spillway continues to drop for some distance, but the slope changes such that it will no longer support supercritical flow, the depth in the lower subcritical flow region is sufficient to determine the location of the jump.
In both cases, the final depth of the water is determined by the downstream characteristics. The jump will occur if and only if the level of inflowing (supercritical) water level () satisfies the condition:
: = Upstream Froude Number
: g = acceleration due to gravity (essentially constant for this case)
: h = height of the fluid ( = initial height while = upstream height) | 1 | Applied and Interdisciplinary Chemistry |
The Green-Kubo relations can be used to calculate the thermal transport properties of a mineral. Since the velocities of the ions are stored at each numerical step, one can calculate the time correlation of later velocities with earlier velocities. The integral of these correlations is related to the Fourier thermal coefficient. | 0 | Theoretical and Fundamental Chemistry |
Urea is basic and is protonated readily. It is also a Lewis base, forming metal complexes of the type .
Urea reacts with malonic esters to make barbituric acids. | 0 | Theoretical and Fundamental Chemistry |
: ATP + HO ⟶ ADP + HPO + H
Adenosine triphosphate, or ATP, acts as a free energy "currency" in all living organisms. In a spontaneous dephosphorylation reaction 30.5 kJ/mol is released, which is harnessed to drive cellular reactions. Overall, nonspontaneous reactions coupled to the dephosphorylation of ATP are spontaneous, due to the negative free energy change of the coupled reaction. This is important in driving oxidative phosphorylation. ATP is dephosphorylated to ADP and inorganic phosphate.
On the cellular level, the dephosphorylation of ATPases determines the flow of ions into and out of the cell. Proton pump inhibitors are a class of drug that acts directly on ATPases of the gastrointestinal tract. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, a synthetic jet flow — is a type of jet flow, which is made up of the surrounding fluid. Synthetic jets are produced by periodic ejection and suction of fluid from an opening. This oscillatory motion may be driven by a piston or diaphragm inside a cavity among other ways.
A jet flow is a fluid flow in which a stream of one fluid mixes with a surrounding medium. An example is a water jet that forms when you put your thumb over the end of a hose. The water mixes with air to form a jet. If you increase the flow of water or move your thumb to change the diameter of the exit, the jet will change dramatically.
Jet flows vary depending on velocity and diameter of the flow and the density and viscosity of the fluid (Reynolds number and Mach number). When the velocities in the jet are greater than the speed of sound, important qualitative changes in the flow occur. One such change is that shock waves form.
A synthetic jet flow was so named by Ari Glezer since the flow is "synthesized" from the surrounding or ambient fluid. Producing a convectional jet requires an external source of fluid, such as piped-in compressed air or plumbing for water. | 1 | Applied and Interdisciplinary Chemistry |
In the decades since the laser Doppler velocimetry was first introduced, there has been a wide variety of laser Doppler sensors developed and applied. | 1 | Applied and Interdisciplinary Chemistry |
Fehlings solution was used for many years as a diagnostic test for diabetes, a disease in which blood glucose levels are dangerously elevated by a failure to produce enough insulin (type 1 diabetes) or by an inability to respond to insulin (type 2 diabetes). Measuring the amount of oxidizing agent (in this case, Fehlings solution) reduced by glucose makes it possible to determine the concentration of glucose in the blood or urine. This then enables the right amount of insulin to be injected to bring blood glucose levels back into the normal range. | 0 | Theoretical and Fundamental Chemistry |
High concentrations of aldehydes tend to be very pungent and overwhelming, but low concentrations can evoke a wide range of aromas.
* Acetaldehyde (ethereal)
* Hexanal (green, grassy)
* cis-3-Hexenal (green tomatoes)
* Furfural (burnt oats)
* Hexyl cinnamaldehyde
* Isovaleraldehyde – nutty, fruity, cocoa-like
* Anisic aldehyde – floral, sweet, hawthorn. It is a crucial component of chocolate, vanilla, strawberry, raspberry, apricot, and others.
* Cuminaldehyde (4-propan-2-ylbenzaldehyde) – Spicy, cumin-like, green | 0 | Theoretical and Fundamental Chemistry |
In a hydroelectric power station water flows through turbines using hydropower to generate hydroelectricity. Power is captured from the gravitational force of water falling through penstocks to water turbines connected to generators. The amount of power available is a combination of height and water flow. A wide range of Dams may be built to raise the water level, and create a lake for storing water.
Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. | 1 | Applied and Interdisciplinary Chemistry |
The pore-forming (ion channel) effect is characterized by the formation of cationic channels. It requires surfactin to self-associate inside the membrane since it cannot span across the cellular membrane. Under a hypothesis focused on uncharged membranes with minimal activation energy required to cross between inner and outer leaflets, molecular self-assembly would form a channel structure. | 0 | Theoretical and Fundamental Chemistry |
In the Crank–Nicolson method, the temperature is equally dependent on and . It is a second-order method in time and this method is generally used in diffusion problems. | 1 | Applied and Interdisciplinary Chemistry |
Afterwards, as biofilm becomes established, EPS provides physical stability and resistance to mechanical removal, antimicrobials, and host immunity. Exopolysaccharides and environmental DNA (eDNA) contribute to viscoelasticity of mature biofilms so that detachment of biofilm from the substratum will be challenging even under sustained fluid shear stress or high mechanical pressure. In addition to mechanical resistance, EPS also promotes protection against antimicrobials and enhanced drug tolerance. Antimicrobials cannot diffuse through the EPS barrier, resulting in limited drug access into the deeper layers of the biofilm. Moreover, positively charged agents will bind to negatively charged EPS contributing to the antimicrobial tolerance of biofilms, and enabling inactivation or degradation of antimicrobials by enzymes present in biofilm matrix. EPS also functions as local nutrient reservoir of various biomolecules, such as fermentable polysaccharides. A study on V. cholerae in 2017 suggested that due to osmotic pressure differences in V. cholerae biofilms, the microbial colonies physically swell, therefore maximizing their contact with nutritious surfaces and thus, nutrient uptake. | 1 | Applied and Interdisciplinary Chemistry |
Chemisches Zentralblatt is the first and oldest abstracts journal published in the field of chemistry. It covers the chemical literature from 1830 to 1969 and describes therefore the "birth" of chemistry as science, in contrast to alchemy. The information contained in this German journal is comparable with the content of the leading source of chemical information Chemical Abstracts Service (CAS), which started publishing abstracts in English in 1907.
Chemisches Zentralblatt was founded as Pharmaceutisches Centralblatt by Gustav Theodor Fechner and published by Leopold Voß in Leipzig in 1830. In the first year, 544 pages containing 400 abstracts were published, reporting all relevant research results in pharmaceutical chemistry. In the following 20 years the relevance of chemistry grew so much that in 1850 the title changed in Chemisch-Pharmazeutisch Zentralblatt, and in 1856 it became Chemisches Zentralblatt. In 1969, after 140 years the expenses for the collection of primary literature in many languages and the production of abstracts were too high and the publication of Chemisches Zentralblatt ceased.
In these 140 years, scientific editors reported research progresses in chemistry with approximately 2 million abstracts, publishing over 650,000 pages. Additional 180,000 pages contain indexes such as index of authors, subject indexes, general indexes, register of patents, and formula register.
Chemisches Zentralblatt was completely digitized by [http://www.fiz-chemie.de/home/produkte-services/chemische-daten/chemie-ab-1830.html FIZ Chemie] in Berlin. FIZ Chemie scanned the entire work and developed a full text searchable database for the web. In addition the database can be purchased and integrated in Intranets. The chemical software company [http://www.infochem.de InfoChem], based in Munich, developed an Internet-based database, the [https://web.archive.org/web/20190217013006/http://www.infochem.de/products/databases/czb.shtml Chemisches Zentralblatt Structural Database]. This database provides access to the chemical content within the Chemisches Zentralblatt by performing chemical structure and substructure searches.
Since 2016, Chemisches Zentralblatt is available on the web via subscription as a part of SciFinder. These entries are labeled in SciFinder under codes CZ, CHZE, and CHEMZENT, and they may duplicate entries in other SciFinder sub-databases. | 1 | Applied and Interdisciplinary Chemistry |
The purpose of single cell transcriptomics is to determine what genes are being expressed in each cell. The transcriptome is often used to quantify the gene expression instead of the proteome because of the difficulty currently associated with amplifying protein levels.
There are three major reasons gene expression has been studied using this technique: to study gene dynamics, RNA splicing, and cell typing. Gene dynamics are usually studied to determine what changes in gene expression affect different cell characteristics. For example, this type of transcriptomic analysis has often been used to study embryonic development. RNA splicing studies are focused on understanding the regulation of different transcript isoforms. Single cell transcriptomics has also been used for cell typing, where the genes expressed in a cell are used to identify types of cells. The main goal in cell typing is to find a way to determine the identity of cells that don't have known genetic markers.
RNA expression can serve as a proxy for protein abundance. However, protein abundance is governed by the complex interplay between RNA expression and post-transcriptional processes. While more challenging technically, translation can be monitored by ribosome profiling in single cells. | 1 | Applied and Interdisciplinary Chemistry |
Toxicity assessment/toxicology by metabolic profiling (especially of urine or blood plasma samples) detects the physiological changes caused by toxic insult of a chemical (or mixture of chemicals). In many cases, the observed changes can be related to specific syndromes, e.g. a specific lesion in liver or kidney. This is of particular relevance to pharmaceutical companies wanting to test the toxicity of potential drug candidates: if a compound can be eliminated before it reaches clinical trials on the grounds of adverse toxicity, it saves the enormous expense of the trials.
For functional genomics, metabolomics can be an excellent tool for determining the phenotype caused by a genetic manipulation, such as gene deletion or insertion. Sometimes this can be a sufficient goal in itself—for instance, to detect any phenotypic changes in a genetically modified plant intended for human or animal consumption. More exciting is the prospect of predicting the function of unknown genes by comparison with the metabolic perturbations caused by deletion/insertion of known genes. Such advances are most likely to come from model organisms such as Saccharomyces cerevisiae and Arabidopsis thaliana. The Cravatt laboratory at the Scripps Research Institute has recently applied this technology to mammalian systems, identifying the N-acyltaurines as previously uncharacterized endogenous substrates for the enzyme fatty acid amide hydrolase (FAAH) and the monoalkylglycerol ethers (MAGEs) as endogenous substrates for the uncharacterized hydrolase KIAA1363.
Metabologenomics is a novel approach to integrate metabolomics and genomics data by correlating microbial-exported metabolites with predicted biosynthetic genes. This bioinformatics-based pairing method enables natural product discovery at a larger-scale by refining non-targeted metabolomic analyses to identify small molecules with related biosynthesis and to focus on those that may not have previously well known structures.
Fluxomics is a further development of metabolomics. The disadvantage of metabolomics is that it only provides the user with abundances or concentrations of metabolites, while fluxomics determines the reaction rates of metabolic reactions and can trace metabolites in a biological system over time.
Nutrigenomics is a generalised term which links genomics, transcriptomics, proteomics and metabolomics to human nutrition. In general, in a given body fluid, a metabolome is influenced by endogenous factors such as age, sex, body composition and genetics as well as underlying pathologies. The large bowel microflora are also a very significant potential confounder of metabolic profiles and could be classified as either an endogenous or exogenous factor. The main exogenous factors are diet and drugs. Diet can then be broken down to nutrients and non-nutrients. Metabolomics is one means to determine a biological endpoint, or metabolic fingerprint, which reflects the balance of all these forces on an individual's metabolism. Thanks to recent cost reductions, metabolomics has now become accessible for companion animals, such as pregnant dogs.
Plant metabolomics is designed to study the overall changes in metabolites of plant samples and then conduct deep data mining and chemometric analysis. Specialized metabolites are considered components of plant defense systems biosynthesized in response to biotic and abiotic stresses. Metabolomics approaches have recently been used to assess the natural variance in metabolite content between individual plants, an approach with great potential for the improvement of the compositional quality of crops. | 1 | Applied and Interdisciplinary Chemistry |
Traditional methods of measuring CDOM include UV-visible spectroscopy (absorbance) and fluorometry (fluorescence). Optical proxies have been developed to characterize sources and properties of CDOM, including specific ultraviolet absorbance at 254 nm (SUVA) and spectral slopes for absorbance, and the fluorescence index (FI), biological index (BIX), and humification index (HIX) for fluorescence. Excitation emission matrices (EEMs) can be resolved into components in a technique called parallel factor analysis (PARAFAC), where each component is often labelled as "humic-like", "protein-like", etc. As mentioned above, remote sensing is the newest technique to detect CDOM from space. | 0 | Theoretical and Fundamental Chemistry |
Current methods include liquid chromatography coupled to mass spectrometry (LC-MS), mouse bioassay, protein synthesis inhibition assay, and reverse-phase HPLC-PDA (Photo Diode Array) analysis. A cell free protein synthesis assay has been developed which appears to be comparable to HPLC-MS. | 0 | Theoretical and Fundamental Chemistry |
Free Ocean CO Enrichment (FOCE) is a technology facilitating studies of the consequences of ocean acidification for marine organisms and communities by enabling the precise control of CO enrichment within in situ, partially open, experimental enclosures. Current FOCE systems control experimental CO perturbations by real-time monitoring of differences in seawater pH between treatment (i.e. high-CO) and control (i.e. ambient) seawater within experimental enclosures. | 0 | Theoretical and Fundamental Chemistry |
The pervaporation method uses a membrane that is more permeable to the one constituent than to another to separate the constituents of an azeotrope as it passes from liquid to vapor phase. The membrane is rigged to lie between the liquid and vapor phases. Another membrane method is vapor permeation, where the constituents pass through the membrane entirely in the vapor phase. In all membrane methods, the membrane separates the fluid passing through it into a permeate (that which passes through) and a retentate (that which is left behind). When the membrane is chosen so that is it more permeable to one constituent than another, then the permeate will be richer in that first constituent than the retentate. | 1 | Applied and Interdisciplinary Chemistry |
The enduring contributions of Zervas were made together with Bergmann and involved the first successful synthesis of substantial length oligopeptides. They achieved this using the carboxybenzyl amine protecting group for the masking of the N-terminus of the growing oligopeptide chain to which amino acid residues are added in a serial manner. The carboxybenzyl group discovered by Zervas is introduced by reaction with benzyl chloroformate, originally in aqueous sodium carbonate solution at 0 °C:
The protecting group is abbreviated Cbz or, in honour of Zervas, simply Z. The typical route for deprotection involves hydrogenolysis under mild conditions e.g. with hydrogen gas and a catalyst such as palladium on charcoal.
The discovery of the Bergmann-Zervas synthesis has been characterised as "epoch-making" as it allowed the advent of controlled synthetic peptide chemistry, completing the work started in the early 20th century by Bergmann's mentor Emil Fischer. Previously impossible to synthesise oligopeptides with a highly specific sequence and reactive side chains were consequently produced in the 1930s by Bergmann and Zervas. The ability of Z-protection to prevent racemization of activated derivatives of the protected amino acids and the importance thereof were also noted by the two chemists.
Indeed, their method became the standard in the field for the following two decades until further developments in the early 1950s with the introduction of mixed anhydrides (e.g. the Boc group).
Zervas continued his research on peptide synthesis in New York and later in Greece. The first topic of his research once in Greece was the synthesis of N- or O-phosphorylated amino acids, in which he demonstrated the utility of dibenzyl chlorophosphonate. He continued his efforts on the development of new methods within peptide chemistry, including the introduction of the o-nitrophenylsulfenyl (NPS) amino protecting group and peptide synthesis using N-tritylamino acids.
One of the major issues which occupied his interests was the chemical synthesis of insulin after its characterisation by Frederick Sanger (1951). The insulin peptide hormone features two protein chains cross-linked by disulfide bridges from cysteine thiols. For this reason, Zervas undertook a systematic study on asymmetric cysteine-containing peptides. In his attempts he introduced new mercaptan protecting groups (e.g. trityl, benzhydryl or benzoyl), which finally made it possible to produce disulfide bridges in a controlled manner. This was a triumph for peptide chemistry in the lab, but could not be possibly scaled to industrial procedures. Building on this work, the first complete synthesis of insulin was simultaneously achieved in 1963 in RWTH Aachen University by Helmut Zahn and in the University of Pittsburgh by Panayotis Katsoyannis, a student of Zervas. Further work on asymmetrical cysteine polypeptides was also done in Athens by Iphigenia Photaki, another student of his.
Overall, the research work of Zervas spans across six decades (1925–1979) and amounts to 96 publications in international chemistry journals. | 0 | Theoretical and Fundamental Chemistry |
Substrate unbinding is influenced by various factors. Larger ligands generally stay in the active site longer, as do those with more rotatable bonds (although this may be a side effect of size). When the solvent is excluded from the active site, less flexible proteins result in longer residence times. More hydrogen bonds shielded from the solvent also decrease unbinding. | 1 | Applied and Interdisciplinary Chemistry |
In inorganic chemistry, Fajans' rules, formulated by Kazimierz Fajans in 1923, are used to predict whether a chemical bond will be covalent or ionic, and depend on the charge on the cation and the relative sizes of the cation and anion. They can be summarized in the following table:
Thus sodium chloride (with a low positive charge (+1), a fairly large cation (~1 Å) and relatively small anion (0.2 Å) is ionic; but aluminium iodide (AlI) (with a high positive charge (+3) and a large anion) is covalent.
Polarization will be increased by:
* high charge and small size of the cation
**Ionic potential Å Z+/r+ (= polarizing power)
*High charge and large size of the anion
**The polarizability of an anion is related to the deformability of its electron cloud (i.e. its "softness")
*An incomplete valence shell electron configuration
**Noble gas configuration of the cation produces better shielding and less polarizing power
***e.g. Hg (r+ = 102 pm) is more polarizing than Ca (r+ = 100 pm)
The "size" of the charge in an ionic bond depends on the number of electrons transferred. An aluminum atom, for example, with a +3 charge has a relatively large positive charge. That positive charge then exerts an attractive force on the electron cloud of the other ion, which has accepted the electrons from the aluminum (or other) positive ion.
Two contrasting examples can illustrate the variation in effects. In the case of aluminum iodide an ionic bond with much covalent character is present. In the AlI bonding, the aluminum gains a +3 charge. The large charge pulls on the electron cloud of the iodine. Now, if we consider the iodine atom, we see that it is relatively large and thus the outer shell electrons are relatively well shielded from the nuclear charge. In this case, the aluminum ion's charge will "tug" on the electron cloud of iodine, drawing it closer to itself. As the electron cloud of the iodine nears the aluminum atom, the negative charge of the electron cloud "cancels" out the positive charge of the aluminum cation. This produces an ionic bond with covalent character. A cation having inert gas like configuration has less polarizing power in comparison to cation having pseudo-inert gas like configuration.
The situation is different in the case of aluminum fluoride, AlF. In this case, iodine is replaced by fluorine, a relatively small highly electronegative atom. The fluorine's electron cloud is less shielded from the nuclear charge and will thus be less polarizable. Thus, we get an ionic compound (metal bonded to a nonmetal) with a slight covalent character. | 0 | Theoretical and Fundamental Chemistry |
Butyrate has numerous effects on energy homeostasis and related diseases (diabetes and obesity), inflammation, and immune function (e.g., it has pronounced antimicrobial and anticarcinogenic effects) in humans. These effects occur through its metabolism by mitochondria to generate during fatty acid metabolism or through one or more of its histone-modifying enzyme targets (i.e., the class I histone deacetylases) and G-protein coupled receptor targets (i.e., FFAR2, FFAR3, and Hydroxycarboxylic acid receptor 2|). | 1 | Applied and Interdisciplinary Chemistry |
An ion trap is a combination of electric and/or magnetic fields used to capture charged particles — known as ions — often in a system isolated from an external environment. Atomic and molecular ion traps have a number of applications in physics and chemistry such as precision mass spectrometry, improved atomic frequency standards, and quantum computing. In comparison to neutral atom traps, ion traps have deeper trapping potentials (up to several electronvolts) that do not depend on the internal electronic structure of a trapped ion. This makes ion traps more suitable for the study of light interactions with single atomic systems. The two most popular types of ion traps are the Penning trap, which forms a potential via a combination of static electric and magnetic fields, and the Paul trap which forms a potential via a combination of static and oscillating electric fields.
Penning traps can be used for precise magnetic measurements in spectroscopy. Studies of quantum state manipulation most often use the Paul trap. This may lead to a trapped ion quantum computer and has already been used to create the world's most accurate atomic clocks. Electron guns (a device emitting high-speed electrons, used in CRTs) can use an ion trap to prevent degradation of the cathode by positive ions. | 0 | Theoretical and Fundamental Chemistry |
In 1997, Myles and his co-workers has described the total synthesis of (-)-discodermolide using chelation-controlled alkylation as the key coupling. The titanium-mediated hetero-Diels–Alder reaction of aldehyde with the Danishefsky diene successfully produced the challenging Z-trisubstituted C(13)–C(14) olefin in allylic iodide fragment. The stereogenicity in the C(16)–C(21) subunit was induced by employing Evans
aldol chemistry. The stereogenicity of the final fragment was set by a tin-promoted asymmetric allylation. Notably, the correct oxidation state at C(1) of this fragment would reduce the number of steps after the coupling of fragments. The Myles synthesis of (-)-discodermolide has an overall yield of 1.5% with a longest linear sequence of 25 steps and 44 total steps. | 0 | Theoretical and Fundamental Chemistry |
The modification of A to I is effected by adenosine deaminases that act on RNA (ADARs), of which in mice there are three. The knockdown of these in the cell, therefore, and the subsequent cell–cell comparison of ADAR+ and ADAR- RNA content would be anticipated to provide a basis for A-to-I modification profiling. However, there are further functions of ADAR enzymes within the cell — for example, they have further roles in RNA processing, and in miRNA biogenesis — which would also be likely to change the landscape of cellular mRNA. Recently a map of A-to-I editing in mice was generated using editing-deficient ADAR1 and ADAR2 double-knockout mice as a negative control. Thereby, A-to-I editing was detected with high confidence. | 1 | Applied and Interdisciplinary Chemistry |
Resiniferatoxin (RTX) is a naturally occurring chemical found in resin spurge (Euphorbia resinifera), a cactus-like plant commonly found in Morocco, and in Euphorbia poissonii found in northern Nigeria. It is a potent functional analog of capsaicin, the active ingredient in chili peppers. | 0 | Theoretical and Fundamental Chemistry |
In the 2008 pilot of the crime drama television series Breaking Bad, Walter White poisons two rival gangsters by adding red phosphorus to boiling water to produce phosphine gas. However, this reaction in reality would require white phosphorus instead, and for the water to contain sodium hydroxide. An episode of Homicide: Life on the Street depicted a murder suspect who adulterated beverages, including Sacramental wine, with a poison called "Phosphozine." | 0 | Theoretical and Fundamental Chemistry |
In the standard atmosphere:
* T is (= ), giving a theoretical value of (= = = = ). Values ranging from 331.3 to 331.6 m/s may be found in reference literature, however;
* T is (= = ), giving a value of (= = = = );
* T is (= = ), giving a value of (= = = = ).
In fact, assuming an ideal gas, the speed of sound c depends on temperature and composition only, not on the pressure or density (since these change in lockstep for a given temperature and cancel out). Air is almost an ideal gas. The temperature of the air varies with altitude, giving the following variations in the speed of sound using the standard atmosphere—actual conditions may vary.
Given normal atmospheric conditions, the temperature, and thus speed of sound, varies with altitude: | 1 | Applied and Interdisciplinary Chemistry |
In atomic physics, exoelectron emission (EE) is a weak electron emission, appearing only from pretreated (irradiated, deformed etc.) objects. The pretreatment ("excitation") turns the objects into an unequilibrial state. EE accompanies the relaxation of these unequilibria. The relaxation can be stimulated e.g. by slight heating or longwave illumination, not causing emission from untreated samples. Accordingly, thermo- and photostimulated EE (TSEE, PSEE) are distinguished. Thus, EE is an electron emission analogue of such optical phenomena as phosphorescence, thermo- and photostimulated luminescence. | 0 | Theoretical and Fundamental Chemistry |
Point mutations usually take place during DNA replication. DNA replication occurs when one double-stranded DNA molecule creates two single strands of DNA, each of which is a template for the creation of the complementary strand. A single point mutation can change the whole DNA sequence. Changing one purine or pyrimidine may change the amino acid that the nucleotides code for.
Point mutations may arise from spontaneous mutations that occur during DNA replication. The rate of mutation may be increased by mutagens. Mutagens can be physical, such as radiation from UV rays, X-rays or extreme heat, or chemical (molecules that misplace base pairs or disrupt the helical shape of DNA). Mutagens associated with cancers are often studied to learn about cancer and its prevention.
There are multiple ways for point mutations to occur. First, ultraviolet (UV) light and higher-frequency light have ionizing capability, which in turn can affect DNA. Reactive oxygen molecules with free radicals, which are a byproduct of cellular metabolism, can also be very harmful to DNA. These reactants can lead to both single-stranded and double-stranded DNA breaks. Third, bonds in DNA eventually degrade, which creates another problem to keep the integrity of DNA to a high standard. There can also be replication errors that lead to substitution, insertion, or deletion mutations. | 1 | Applied and Interdisciplinary Chemistry |
The deeper layers of the ocean are greatly unsaturated in CO and its dissolved forms, carbonic and bicarbonic acid, and their salts. At depths greater than 3 km, CO becomes liquefied and sinks to the seafloor due to it being higher density than the surrounding seawater. Mathematical models have shown that CO stored in deep sea sediments beyond 3 km could provide permanent geological storage even with large geomechanical perturbations. Deep ocean storage can present a potential sink for large amounts of anthropogenic CO. Other deep water carbon storage techniques currently being explored include, seaweed farming and algae, ocean fertilization, artificial upwelling, and basalt storage.
The deep blue carbon terminology has been used in passing as early as 2017. The Ocean Frontier Institute has made it a centrepiece of their participation at COP27. It is investing significant resources into deep blue carbon research. In terms of net-new-carbon sequestration deep blue carbon offers an estimated 10-20 times higher potential than coastal blue carbon to achieve net-zero goals. There is still a lack of data in this area along with financial, ecological and environmental concerns. Advancements in research and technical capabilities are raising international interest in this kind of storage. | 0 | Theoretical and Fundamental Chemistry |
Semidiones are radical anions analogous to semiquinones, obtained from the one-electron reduction of non-quinone conjugated dicarbonyls.
The simplest possible semidiones are derived from 1,2-dicarbonyls and have structure , making them the second member of a homologous series starting with ketyl radicals.
They are often transient intermediates, appearing in reactions such as the final reduction step of the acyloin condensation.
Benzil semidione (), synthesized by Auguste Laurent in 1836, is believed to have been the first radical ion ever characterized.
Semidehydroascorbate is a stable semidione produced by the one-electron oxidation of Vitamin C. | 0 | Theoretical and Fundamental Chemistry |
This is a list of known oxidation states of the chemical elements, excluding nonintegral values. The most common states appear in bold. The table is based on that of Greenwood and Earnshaw, with additions noted. Every element exists in oxidation state 0 when it is the pure non-ionized element in any phase, whether monatomic or polyatomic allotrope. The column for oxidation state 0 only shows elements known to exist in oxidation state 0 in compounds. | 0 | Theoretical and Fundamental Chemistry |
Fulgurites have been classified by Pasek et al. (2012) into five types related to the type of sediment in which the fulgurite formed, as follows:
* Type I – sand fulgurites with tubaceous structure; their central axial void may be collapsed
* Type II – soil fulgurites; these are glass-rich, and form in a wide range of sediment compositions, including clay-rich soils, silt-rich soils, gravel-rich soils, and loessoid; these may be tubaceous, branching, vesicular, irregular/slaggy, or may display a combination of these structures, and can produce exogenic fulgurites (droplet fulgurites)
* Type III – caliche or calcic sediment fulgurites, having thick, often surficially glazed granular walls with calcium-rich vitreous groundmass with little or no lechatelierite glass; their shapes are variable, with multiple narrow central channels common, and can span the entire range of morphological and structural variation for fulguritic objects
* Type IV – rock fulgurites, which are either crusts on minimally altered rocks, networks of tunneling within rocks, vesicular outgassed rocks (often glazed by a silicide-rich and/or metal oxide crust), or completely vitrified and dense rock material and masses of these forms with little sedimentary groundmass
* Type V – [droplet] fulgurites (exogenic fulgurites), which show evidence of ejection (e.g. spheroidal, filamentous, or aerodynamic), related by composition to Type II and Type IV fulgurites
* phytofulgurite – a proposed class of objects resulting from partial to total alteration of biomass (e.g. grasses, lichens, moss, wood) by lightning. Pasek et al. (2012) described fulgurites as "natural glasses formed by cloud-to-ground lightning." Pasek et al. excluded phytofulgurites from their classification scheme because they are not glasses, so classifying them as a subset of fulgurites is debatable. | 0 | Theoretical and Fundamental Chemistry |
Various neurotrophic factors such as BDNF and mesencephalic astrocyte-derived neurotrophic factor have been shown to be modulated by various mood stabilizers. | 1 | Applied and Interdisciplinary Chemistry |
* J.W. Steed, D.R. Turner, K. Wallace Core Concepts in Supramolecular Chemistry and Nanochemistry (Wiley, 2007) 315p.
* Brechignac C., Houdy P., Lahmani M. (Eds.) Nanomaterials and Nanochemistry (Springer, 2007) 748p.
* H. Watarai, N. Teramae, T. Sawada Interfacial Nanochemistry: Molecular Science and Engineering at Liquid-Liquid Interfaces (Nanostructure Science and Technology) 2005. 321p.
* Ozin G., Arsenault A.C., Cademartiri L. [http://www.rsc.org/shop/books/2008/9781847558954.asp Nanochemistry: A Chemical Approach to Nanomaterials] 2nd Eds. (Royal Society of Chemistry, 2008) 820p. | 0 | Theoretical and Fundamental Chemistry |
In the wine/water mixing problem, one starts with two barrels, one holding wine and the other an equal volume of water. A cup of wine is taken from the wine barrel and added to the water. A cup of the wine/water mixture is then returned to the wine barrel, so that the volumes in the barrels are again equal. The question is then posed—which of the two mixtures is purer? The answer is that the mixtures will be of equal purity. The solution still applies no matter how many cups of any sizes and compositions are exchanged, or how little or much stirring at any point in time is done to any barrel, as long as at the end each barrel has the same amount of liquid.
The problem can be solved with logic and without resorting to computation. It is not necessary to state the volumes of wine and water, as long as they are equal. The volume of the cup is irrelevant, as is any stirring of the mixtures. | 0 | Theoretical and Fundamental Chemistry |
Hyperspectral imaging is most often applied to either solid or gel samples, and has applications in chemistry, biology, medicine, pharmacy (see also for example: food science, biotechnology, agriculture and industry. NIR, IR and Raman chemical imaging is also referred to as hyperspectral, spectroscopic, spectral or multispectral imaging (also see microspectroscopy). However, other ultra-sensitive and selective imaging techniques are also in use that involve either UV-visible or fluorescence microspectroscopy. Many imaging techniques can be used to analyze samples of all sizes, from the single molecule to the cellular level in biology and medicine, and to images of planetary systems in astronomy, but different instrumentation is employed for making observations on such widely different systems.
Any material that depends on chemical gradients for functionality may be amenable to study by an analytical technique that couples spatial and chemical characterization. To efficiently and effectively design and manufacture such materials, the ‘what’ and the ‘where’ must both be measured. The demand for this type of analysis is increasing as manufactured materials become more complex. Chemical imaging techniques are critical to understanding modern manufactured products and in some cases is a non-destructive technique so that samples are preserved for further testing.
Many materials, both manufactured and naturally occurring, derive their functionality from the spatial distribution of sample components. For example, extended release pharmaceutical formulations can be achieved by using a coating that acts as a barrier layer. The release of active ingredient is controlled by the presence of this barrier, and imperfections in the coating, such as discontinuities, may result in altered performance. In the semi-conductor industry, irregularities or contaminants in silicon wafers or printed micro-circuits can lead to failure of these components. The functionality of biological systems is also dependent upon chemical gradients – a single cell, tissue, and even whole organs function because of the very specific arrangement of components. It has been shown that even small changes in chemical composition and distribution may be an early indicator of disease. | 0 | Theoretical and Fundamental Chemistry |
The creatine phosphate shuttle is an intracellular energy shuttle which facilitates transport of high energy phosphate from muscle cell mitochondria to myofibrils. This is part of phosphocreatine metabolism. In mitochondria, Adenosine triphosphate (ATP) levels are very high as a result of glycolysis, TCA cycle, oxidative phosphorylation processes, whereas creatine phosphate levels are low. This makes conversion of creatine to phosphocreatine a highly favored reaction. Phosphocreatine is a very-high-energy compound. It then diffuses from mitochondria to myofibrils.
In myofibrils, during exercise (contraction) ADP levels are very high, which favors resynthesis of ATP. Thus, phosphocreatine breaks down to creatine, giving its inorganic phosphate for ATP formation. This is done by the enzyme creatine phosphokinase which transduces energy from the transport molecule of phosphocreatine to the useful molecule for contraction demands, ATP, an action performed by ATPase in the myofibril. The resulting creatine product acts as a signal molecule indicating myofibril contraction and diffuses in the opposite direction of phosphocreatine, back towards the mitochondrial intermembrane space where it can be rephosphorylated by creatine phosphokinase.
At the onset of exercise phosphocreatine is broken down to provide ATP for muscle contraction. ATP hydrolysis results in products of ADP and inorganic phosphate. The inorganic phosphate will be transported into the mitochondrial matrix, while the free creatine passes through the outer membrane where it will be resynthesised into PCr. The antiporter transports the ADP into the matrix, while transporting ATP out. Due to the high concentration of ATP around the mitochondrial creatine kinase, it will convert ATP into PCr which will then move back out into the cells cytoplasm to be converted into ATP (by cytoplasmic creatine kinase) to be used as energy for muscle contraction.
In some vertebrates, arginine phosphate plays a similar role. | 1 | Applied and Interdisciplinary Chemistry |
Creatine kinase (CK), also known as creatine phosphokinase (CPK) or phosphocreatine kinase, is an enzyme () expressed by various tissues and cell types. CK catalyses the conversion of creatine and uses adenosine triphosphate (ATP) to create phosphocreatine (PCr) and adenosine diphosphate (ADP). This CK enzyme reaction is reversible and thus ATP can be generated from PCr and ADP.
In tissues and cells that consume ATP rapidly, especially skeletal muscle, but also brain, photoreceptor cells of the retina, hair cells of the inner ear, spermatozoa and smooth muscle, PCr serves as an energy reservoir for the rapid buffering and regeneration of ATP in situ, as well as for intracellular energy transport by the PCr shuttle or circuit. Thus creatine kinase is an important enzyme in such tissues.
Clinically, creatine kinase is assayed in blood tests as a marker of damage of CK-rich tissue such as in myocardial infarction (heart attack), rhabdomyolysis (severe muscle breakdown), muscular dystrophy, autoimmune myositides, and acute kidney injury. | 1 | Applied and Interdisciplinary Chemistry |
Following his father's death, Henry bought another house in town and also a house in Clapham Common (built by Thomas Cubitt), at that time to the south-west of London. The London house contained the bulk of his library, while he kept most of his instruments at Clapham Common, where he carried out most of his experiments. The most famous of those experiments, published in 1798, was to determine the density of the Earth and became known as the Cavendish experiment. The apparatus Cavendish used for weighing the Earth was a modification of the torsion balance built by geologist John Michell, who died before he could begin the experiment. The apparatus was sent in crates to Cavendish, who completed the experiment in 1797–1798 and published the results.
The experimental apparatus consisted of a torsion balance with a pair of 2-inch 1.61-pound lead spheres suspended from the arm of a torsion balance and two much larger stationary lead balls (350 pounds). Cavendish intended to measure the force of gravitational attraction between the two. He noticed that Michell's apparatus would be sensitive to temperature differences and induced air currents, so he made modifications by isolating the apparatus in a separate room with external controls and telescopes for making observations.
Using this equipment, Cavendish calculated the attraction between the balls from the period of oscillation of the torsion balance, and then he used this value to calculate the density of the Earth. Cavendish found that the Earths average density is 5.48 times greater than that of water. John Henry Poynting later noted that the data should have led to a value of 5.448, and indeed that is the average value of the twenty-nine determinations Cavendish included in his paper. The error in the published number was due to a simple arithmetical mistake on his part. What was extraordinary about Cavendishs experiment was its elimination of every source of error and every factor that could disturb the experiment, and its precision in measuring an astonishingly small attraction, a mere 1/50,000,000 of the weight of the lead balls. The result that Cavendish obtained for the density of the Earth is within 1 per cent of the currently accepted figure.
Cavendishs work led others to accurate values for the gravitational constant (G) and Earths mass. Based on his results, one can calculate a value for G of 6.754 × 10N-m/kg, which compares favourably with the modern value of 6.67428 × 10N-m/kg.
Books often describe Cavendishs work as a measurement of either G or the Earths mass. Since these are related to the Earths density by a trivial web of algebraic relations, none of these sources are wrong, but they do not match the exact word choice of Cavendish, and this mistake has been pointed out by several authors. Cavendishs stated goal was to measure the Earth's density.
The first time that the constant got this name was in 1873, almost 100 years after the Cavendish experiment. Cavendishs results also give the Earths mass. | 1 | Applied and Interdisciplinary Chemistry |
Black light is commonly used to authenticate oil paintings, antiques and banknotes. Black lights can be used to differentiate real currency from counterfeit notes because, in many countries, legal banknotes have fluorescent symbols on them that only show under a black light. In addition, the paper used for printing money does not contain any of the brightening agents which cause commercially available papers to fluoresce under black light. Both of these features make illegal notes easier to detect and more difficult to successfully counterfeit. The same security features can be applied to identification cards such as passports or driver's licenses.
Other security applications include the use of pens containing a fluorescent ink, generally with a soft tip, that can be used to "invisibly" mark items. If the objects that are so marked are subsequently stolen, a black light can be used to search for these security markings. At some amusement parks, nightclubs and at other, day-long (or night-long) events, a fluorescent mark is rubber stamped onto the wrist of a guest who can then exercise the option of leaving and being able to return again without paying another admission fee. | 0 | Theoretical and Fundamental Chemistry |
Industrially, tert-butyl hydroperoxide is used to prepare propylene oxide. In the Halcon process, molybdenum-based catalysts are used for this reaction:
:(CH)COOH + CH=CHCH → (CH)COH + CHOCHCH
The byproduct t-butanol can be dehydrated to isobutene and converted to MTBE.
On a much smaller scale, tert-butyl hydroperoxide is used to produce some fine chemicals by the Sharpless epoxidation. | 0 | Theoretical and Fundamental Chemistry |
One approach for generating the high voltage fields needed to accelerate ions in a neutron tube is to use a pyroelectric crystal. In April 2005 researchers at UCLA demonstrated the use of a thermally cycled pyroelectric crystal to generate high electric fields in a neutron generator application. In February 2006 researchers at Rensselaer Polytechnic Institute demonstrated the use of two oppositely poled crystals for this application. Using these low-tech power supplies it is possible to generate a sufficiently high electric field gradient across an accelerating gap to accelerate deuterium ions into a deuterated target to produce the D + D fusion reaction. These devices are similar in their operating principle to conventional sealed-tube neutron generators which typically use Cockcroft–Walton type high voltage power supplies. The novelty of this approach is in the simplicity of the high voltage source. Unfortunately, the relatively low accelerating current that pyroelectric crystals can generate, together with the modest pulsing frequencies that can be achieved (a few cycles per minute) limits their near-term application in comparison with today's commercial products (see below). Also see pyroelectric fusion. | 0 | Theoretical and Fundamental Chemistry |
Corepressors are known to regulate transcription through different activation and inactivation states.
NCoR and SMRT act as a corepressor complex to regulate transcription by becoming activated once the ligand is bound. Knockouts of NCoR resulted in embryo death, indicating its importance in erythrocytic, thymic, and neural system development.
Mutations in certain corepressors can result in deregulation of signals. SMRT contributes to cardiac muscle development, with knockouts of the complex resulting in less developed muscle and improper development.
NCoR has also been found to be an important checkpoint in processes such as inflammation and macrophage activation.
Recent evidence also suggests the role of corepressor RIP140 in metabolic regulation of energy homeostasis. | 1 | Applied and Interdisciplinary Chemistry |
*Quantum yields of reaction (and to a lesser extent, absorption cross sections) are usually temperature and environment-dependent to some extent, and the photostationary state may therefore depend slightly on temperature and solvent as well as on the excitation.
*If thermodynamic interconversion of A and B can take place on a similar timescale to the photochemical reaction, it can complicate experimental measurements. This phenomenon can be important, for example in photochromatic eyeglasses. | 0 | Theoretical and Fundamental Chemistry |
The primary enzyme in the malate–aspartate shuttle is malate dehydrogenase. Malate dehydrogenase is present in two forms in the shuttle system: mitochondrial malate dehydrogenase and cytosolic malate dehydrogenase. The two malate dehydrogenases are differentiated by their location and structure, and catalyze their reactions in opposite directions in this process.
First, in the cytosol, malate dehydrogenase catalyses the reaction of oxaloacetate and NADH to produce malate and NAD. In this process, two electrons generated from NADH, and an accompanying H, are attached to oxaloacetate to form malate.
Once malate is formed, the first antiporter (malate-alpha-ketoglutarate) imports the malate from the cytosol into the mitochondrial matrix and also exports alpha-ketoglutarate from the matrix into the cytosol simultaneously. After malate reaches the mitochondrial matrix, it is converted by mitochondrial malate dehydrogenase into oxaloacetate, during which NAD is reduced with two electrons to form NADH. Oxaloacetate is then transformed into aspartate (since oxaloacetate cannot be transported into the cytosol) by mitochondrial aspartate aminotransferase. Since aspartate is an amino acid, an amino radical needs to be added to the oxaloacetate. This is supplied by glutamate, which in the process is transformed into alpha-ketoglutarate by the same enzyme.
The second antiporter (the glutamate-aspartate antiporter) imports glutamate from the cytosol into the matrix and exports aspartate from the matrix to the cytosol. Once in the cytosol, aspartate is converted by cytosolic aspartate aminotransferase to oxaloacetate.
The net effect of the malate–aspartate shuttle is purely redox: NADH in the cytosol is oxidized to NAD, and NAD in the matrix is reduced to NADH. The NAD in the cytosol can then be reduced again by another round of glycolysis, and the NADH in the matrix can be used to pass electrons to the electron transport chain so ATP can be synthesized.
Since the malate–aspartate shuttle regenerates NADH inside the mitochondrial matrix, it is capable of maximizing the number of ATPs produced in glycolysis (3/NADH), ultimately resulting in a net gain of 38 ATP molecules per molecule of glucose metabolized. Compare this to the glycerol 3-phosphate shuttle, which reduces FAD to produce FADH, donates electrons to the quinone pool in the electron transport chain, and is capable of generating only 2 ATPs per NADH generated in glycolysis (ultimately resulting in a net gain of 36 ATPs per glucose metabolized). (These ATP numbers are prechemiosmotic, and should be reduced in light of the work of Mitchell and many others. Each NADH produces only 2.5 ATPs, and each FADH produces only 1.5 ATPs. Hence, the ATPs per glucose should be reduced to 32 from 38 and 30 from 36. The extra H required to bring in the inorganic phosphate during oxidative-phosphorylation contributes to the 30 and 32 numbers as well). | 1 | Applied and Interdisciplinary Chemistry |
A mode of toxic action is a common set of physiological and behavioral signs that characterize a type of adverse biological response. A mode of action should not be confused with mechanism of action, which refer to the biochemical processes underlying a given mode of action. Modes of toxic action are important, widely used tools in ecotoxicology and aquatic toxicology because they classify toxicants or pollutants according to their type of toxic action. There are two major types of modes of toxic action: non-specific acting toxicants and specific acting toxicants. Non-specific acting toxicants are those that produce narcosis, while specific acting toxicants are those that are non-narcotic and that produce a specific action at a specific target site. | 1 | Applied and Interdisciplinary Chemistry |
Used doctor blades, from gravure and other printing and coating processes, can be inspected with a goniometer, typically with a built-in light source, to examine the blade edge for wear and correct angles. A difference in angle from that set on the machine may indicate excessive pressure, and a range of angles ("rounding") probably indicates a lack of stiffness, or wear, in the blade holder assembly. | 0 | Theoretical and Fundamental Chemistry |
Diimide reductions result in the syn addition of dihydrogen to alkenes and alkynes. This observation has led to the proposal that the mechanism involves concerted hydrogen transfer from cis-diimide to the substrate. The cis isomer is the less stable of the two; however, acid catalysis may speed up equilibration of the trans and cis isomers.
Diimide is typically generated either through the oxidation of hydrazine or the decarboxylation of potassium azodicarboxylate. Kinetic experiments suggest that regardless of its method of generation, the formation of diimide is rate-limiting. The transition state of the hydrogen transfer step is likely early; however, high stereoselectivity has been obtained in many reductions of chiral alkenes.
The order of reactivity of unsaturated substrates is: alkynes, allenes > terminal or strained alkenes > substituted alkenes. Trans alkenes react more rapidly than cis alkenes in general. The reactivity difference between alkynes and alkenes is usually not great enough to isolate intermediate alkenes; however, alkenes can be isolated from allene reductions.
Diimide reduces symmetrical double bonds i.e.,C=C. N=N, O=O etc. unsymmetrical double bonds can not be reduced | 0 | Theoretical and Fundamental Chemistry |
These easily available and sterically constrained compounds are potentially suitable for an application in a wide variety of secondary processes such as small molecule activation or the generation of new catalysts based on main-group and transition-metal elements. | 0 | Theoretical and Fundamental Chemistry |
Notable sources of natural phenols in human nutrition include berries, tea, beer, olive oil, chocolate or cocoa, coffee, pomegranates, popcorn, yerba maté, fruits and fruit based drinks (including cider, wine and vinegar) and vegetables. Herbs and spices, nuts (walnuts, peanut) and algae are also potentially significant for supplying certain natural phenols.
Natural phenols can also be found in fatty matrices like olive oil. Unfiltered olive oil has the higher levels of phenols, or polar phenols that form a complex phenol-protein complex.
Phenolic compounds, when used in beverages, such as prune juice, have been shown to be helpful in the color and sensory components, such as alleviating bitterness.
Some advocates for organic farming claim that organically grown potatoes, oranges, and leaf vegetables have more phenolic compounds and these may provide antioxidant protection against heart disease and cancer. However, evidence on substantial differences between organic food and conventional food is insufficient to support claims that organic food is safer or healthier than conventional food. | 0 | Theoretical and Fundamental Chemistry |
Carbon tetrachloride, also known by many other names (such as carbon tet for short and tetrachloromethane, also recognised by the IUPAC) is a chemical compound with the chemical formula CCl. It is a non-flammable, dense, colourless liquid with a "sweet" chloroform-like odour that can be detected at low levels. It was formerly widely used in fire extinguishers, as a precursor to refrigerants and as a cleaning agent, but has since been phased out because of environmental and safety concerns. Exposure to high concentrations of carbon tetrachloride can affect the central nervous system and degenerate the liver and kidneys. Prolonged exposure can be fatal.
Tradenames include: Carbon-Tet, Katharin (Germany, 1890s), Benzinoform, Carbona and Thawpit in the cleaning industry, Halon-104 in firefighting, Refrigerant-10 in HVACR, and Necatorina and Seretin as a medication. | 1 | Applied and Interdisciplinary Chemistry |
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