text stringlengths 105 4.57k | label int64 0 1 | label_text stringclasses 2 values |
|---|---|---|
From pound down to the scruple, the units of the traditional English apothecaries system were a subset of the units of the Roman weight system, although the troy pound and its subdivisions were slightly heavier than the Roman pound and its subdivisions. Similar systems were used all over Europe, but with considerable local variation described below under Variants. The traditional English apothecaries system of weights is shown in the first table in this section: the pound, ounce and grain were identical to the troy pound, ounce and grain (also used to measure weights of precious metals; distinct from the avoirdupois pounds and ounces that were used for measurements of other goods.) The confusing variety of definitions and conversions for pounds and ounces is covered elsewhere in a table of pound definitions.
To unify all weight systems used by apothecaries, the Irish pharmacopœia of 1850 introduced a new variant of the apothecaries system which subdivided a new apothecaries pound of 12 avoirdupois ounces instead of the troy pound. To allow effective use of the new system, new weight pieces were produced. Since an avoirdupois ounce corresponds to 28.35 g, the proposed system was very similar to that in use in Portugal and Spain, and in some locations in Italy. But it would have doubled the value of the avoirdupois drachm (an existing unit, but by then only used for weighing silk). Therefore, it conflicted with other non-standard variations that were based on that nearly obsolete unit.
The Irish proposal was not widely adopted, but British legislation, in the form of the Medicinals Act 1858, was more radical: it prescribed the use of the avoirdupois system for the United Kingdom (then including Ireland), with none of the traditional subdivisions. This innovation was first used in the United British pharmacopœia of 1864, which recommended the adoption in pharmacy of the imperial avoirdupois pound of 7000 grains and ounce of 437.5 grains, and discontinuation of the drachm and scruple. In practice, however, the old apothecaries system based on divisions of the troy pound, or of the troy ounce of 480 grains, was still widely used until it was abolished by the Weights and Measures Act of 1976, since when it may only be used to measure precious metals and stones. (The troy pound had already been declared illegal for most other uses by the Weights and Measures Act 1878, but this act allowed the sale of drugs by apothecaries weight as an exception.)
Apothecaries' units of any kind became obsolete in the UK with the mandatory use of metric drug measurements from January 1, 1971.
In the United States, the apothecaries' system remained official until it was abolished in 1971 in favour of the metric system. | 1 | Applied and Interdisciplinary Chemistry |
A chaotropic agent is a substance which disrupts the structure of, and denatures, macromolecules such as proteins and nucleic acids (e.g. DNA and RNA). Chaotropic solutes increase the entropy of the system by interfering with intermolecular interactions mediated by non-covalent forces such as hydrogen bonds, van der Waals forces, and hydrophobic effects. Macromolecular structure and function is dependent on the net effect of these forces (see protein folding), therefore it follows that an increase in chaotropic solutes in a biological system will denature macromolecules, reduce enzymatic activity and induce stress on a cell (i.e., a cell will have to synthesize stress protectants). Tertiary protein folding is dependent on hydrophobic forces from amino acids throughout the sequence of the protein. Chaotropic solutes decrease the net hydrophobic effect of hydrophobic regions because of a disordering of water molecules adjacent to the protein. This solubilises the hydrophobic region in the solution, thereby denaturing the protein. This is also directly applicable to the hydrophobic region in lipid bilayers; if a critical concentration of a chaotropic solute is reached (in the hydrophobic region of the bilayer) then membrane integrity will be compromised, and the cell will lyse.
Chaotropic salts that dissociate in solution exert chaotropic effects via different mechanisms. Whereas chaotropic compounds such as ethanol interfere with non-covalent intramolecular forces as outlined above, salts can have chaotropic properties by shielding charges and preventing the stabilization of salt bridges. Hydrogen bonding is stronger in non-polar media, so salts, which increase the chemical polarity of the solvent, can also destabilize hydrogen bonding. Mechanistically this is because there are insufficient water molecules to effectively solvate the ions. This can result in ion-dipole interactions between the salts and hydrogen bonding species which are more favorable than normal hydrogen bonds.
Common chaotropic agents include n-butanol, ethanol, guanidinium chloride, lithium perchlorate, lithium acetate, magnesium chloride, phenol, 2-propanol, sodium dodecyl sulfate, thiourea, and urea. | 1 | Applied and Interdisciplinary Chemistry |
Mineralogists, in particular, are interested in morphological appearances of individual crystals, as defined by the actually formed crystal faces (tracht) and their relative sizes (habit). More advanced visualization capabilities allow for displaying surface characteristics, imperfections inside the crystal, lighting (reflection, shadow, and translucency), and 3D effects (interactive rotatability, perspective, and stereo viewing).
Crystal physicists, in particular, are interested in anisotropic physical properties of crystals. The directional dependence of a crystal's physical property is described by a 3D tensor and depends on the orientation of the crystal. Tensor shapes are more palpable by adding lighting effects (reflection and shadow). 2D sections of interest are selected for display by rotating the tensor interactively around one or more axes.
Crystal morphology or physical property data can be stored in specialized databases or added to more comprehensive crystal structure databases. [https://web.archive.org/web/20091219215419/http://nanocrystallography.research.pdx.edu/search.py/search?database=cmd The Crystal Morphology Database (CMD)] is an example for a web-based crystal morphology database with integrated visualization capabilities. | 0 | Theoretical and Fundamental Chemistry |
Two-photon absorption (TPA) is a third-order process in which two photons are nearly simultaneously absorbed by the same molecule. If a second photon is absorbed by the same electron within the same quantum event, the electron enters an excited state.
This is the same phenomenon used in two-photon microscopy (TPM), but there are two key features that distinguish pump–probe microscopy from TPM. First, since the molecule is not necessarily fluorescent, a photodetector measures the probe intensity. Therefore, the signal decreases as two-photon absorption occurs, the reverse of TPM.
Second, pump–probe microscopy uses spectrally separated sources for each photon, whereas conventional TPM uses one source of a single wavelength. This is referred to as degenerate two-photon excitation. | 0 | Theoretical and Fundamental Chemistry |
Natural Resources Engineering, the sixth Abet accredited environmental engineering program in the United States, is a subset of environmental engineering that applies various branches of science in order to create new technology that aims to protect, maintain, and establish sustainable natural resources. Specifically, natural resources engineers are concerned with applying engineering concepts and solutions to prevalent environmental issues. Common natural resources this discipline of engineering works closely with include both living resources such as plants and animals as well as non-living resources such as renewable energy, land, soils, and water. Natural resource engineering also involves researching and evaluating natural and societal forces. The hydrological cycle is the main component of natural forces and the desires of other people attribute to societal forces. Some historical examples of applications of natural resources engineering include the Roman aqueducts and the Hoover Dam.
Natural resource engineering degrees require a basic understanding of core engineering classes including calculus, physics, chemistry, and engineering mechanics, as well as additional courses with a stronger focus on applications of natural resources in environmental systems. These specific courses include soil and water engineering, modeling of biological and physical systems, properties of biological materials, and systems optimization.
The overall purpose of natural resource engineering is mainly categorized as either resource development, environmental management or both. Natural resource engineers often work in a vast variety of environments ranging from urban to rural. Most natural resource engineers can be found working for groups who strive to solve current and future environmental issues such as environmental consulting firms and government agencies. | 1 | Applied and Interdisciplinary Chemistry |
A scintillator ( ) is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the absorbed energy in the form of light). Sometimes, the excited state is metastable, so the relaxation back down from the excited state to lower states is delayed (necessitating anywhere from a few nanoseconds to hours depending on the material). The process then corresponds to one of two phenomena: delayed fluorescence or phosphorescence. The correspondence depends on the type of transition and hence the wavelength of the emitted optical photon. | 0 | Theoretical and Fundamental Chemistry |
When you walk from a point to a point along a line (without changing directions) your net displacement and total distance covered are both equal to the length of said line . If you then return to point (without changing directions) then your net displacement is zero while your total distance covered is . This example captures the essential idea behind the inexact differential in one dimension. Note that if we allowed ourselves to change directions, then we could take a step forward and then backward at any point in time in going from to and in-so-doing increase the overall distance covered to an arbitrarily large number while keeping the net displacement constant.
Reworking the above with differentials and taking to be along the -axis, the net distance differential is , an exact differential with antiderivative . On the other hand, the total distance differential is , which does not have an antiderivative. The path taken is where there exists a time such that is strictly increasing before and strictly decreasing afterward. Then is positive before and negative afterward, yielding the integrals,
exactly the results we expected from the verbal argument before. | 0 | Theoretical and Fundamental Chemistry |
As real measurement signals contain a certain level of noise, the derived 2D spectra are influenced and degraded with substantial higher amounts of noise. Hence, interpretation begins with studying the autocorrelation spectrum on the main diagonal of the 2D synchronous spectrum. In the 2D synchronous main diagonal signal on the right 4 peaks are visible at 10, 20, 30, and 40 (see also the 4 corresponding positive autopeaks in the 2D synchronous spectrum on the right). This indicates that in the original dataset 4 peaks of changing intensity are present. The intensity of peaks on the autocorrelation spectrum are directly proportional to the relative importance of the intensity change in the original spectra. Hence, if an intense band is present at position x, it is very likely that a true intensity change is occurring and the peak is not due to noise.
Additional techniques help to filter the peaks that can be seen in the 2D synchronous and asynchronous spectra. | 0 | Theoretical and Fundamental Chemistry |
Photosynthesis is the natural process that converts CO using light to produce hydrocarbon compounds such as sugar. The depletion of fossil fuels encourages scientists to find alternatives to produce hydrocarbon compounds. Artificial photosynthesis is a promising method mimicking the natural photosynthesis to produce such compounds. The photoelectrochemical reduction of is much studied because of its worldwide impact. Many researchers aim to find new semiconductors to develop stable and efficient photo-anodes and photo-cathodes. | 0 | Theoretical and Fundamental Chemistry |
He received his B.A. in chemistry and physics from Harvard in 1963, and was then a Henry fellow at the MRC Laboratory of Molecular Biology at Cambridge. In 1967, he received his Ph.D. in biophysics from Harvard, was a research fellow there as well as a junior fellow in the Society of Fellows, and joined the Harvard faculty in 1971. | 1 | Applied and Interdisciplinary Chemistry |
Diets in developed countries have lost microbiota-accessible carbohydrates which is the cause of a substantial depletion of gut microbiota taxa. This loss of microbiota diversity is likely involved in the increasing propensity for a broad range of inflammatory diseases, such as allergic disease, asthma, inflammatory bowel disease (IBD), obesity, and associated noncommunicable diseases (NCDs). Rural human communities from South America and Africa have a low prevalence of NCDs and this fact has been related with a higher gut microbiota diversity.
Some of these lost taxa belong to the families of Bacteroidales (Bacteroides fragilis, B. ovatus, B. uniformis, B. distasonis, Parabacteroides gordonii), Clostridiales (Ruminococcus gnavus, Blautia producta, Faecalibacterium prausnitzii) and Verrucomicrobiales (Akkermansia muciniphila).
Introduction of dietary MACs in the diet is insufficient to regain the lost taxa, to restore the gut microbiota to its original state requires the administration of missing taxa, which can be achieved either by administering probiotics (food) or live biotherapeutics (drugs), in combination with dietary MAC consumption. Enriching the food supply with dietary fiber might have an essential role in preventing loss of certain beneficial bacterial species. | 0 | Theoretical and Fundamental Chemistry |
For solution of substances which ionize in solution the activity coefficients of the cation and anion cannot be experimentally determined independently of each other because solution properties depend on both ions. Single ion activity coefficients must be linked to the activity coefficient of the dissolved electrolyte as if undissociated. In this case a mean stoichiometric activity coefficient of the dissolved electrolyte, γ, is used. It is called stoichiometric because it expresses both the deviation from the ideality of the solution and the incomplete ionic dissociation of the ionic compound which occurs especially with the increase of its concentration.
For a 1:1 electrolyte, such as NaCl it is given by the following:
where and are the activity coefficients of the cation and anion respectively.
More generally, the mean activity coefficient of a compound of formula is given by
Single-ion activity coefficients can be calculated theoretically, for example by using the Debye–Hückel equation. The theoretical equation can be tested by combining the calculated single-ion activity coefficients to give mean values which can be compared to experimental values.
The prevailing view that single ion activity coefficients are unmeasurable independently, or perhaps even physically meaningless, has its roots in the work of Guggenheim in the late 1920s. However, chemists have never been able to give up the idea of single ion activities, and by implication single ion activity coefficients. For example, pH is defined as the negative logarithm of the hydrogen ion activity. If the prevailing view on the physical meaning and measurability of single ion activities is correct then defining pH as the negative logarithm of the hydrogen ion activity places the quantity squarely in the unmeasurable category. Recognizing this logical difficulty, International Union of Pure and Applied Chemistry (IUPAC) states that the activity-based definition of pH is a notional definition only. Despite the prevailing negative view on the measurability of single ion coefficients, the concept of single ion activities continues to be discussed in the literature, and at least one author presents a definition of single ion activity in terms of purely thermodynamic quantities and proposes a method of measuring single ion activity coefficients based on purely thermodynamic processes. | 0 | Theoretical and Fundamental Chemistry |
Detonation gun spraying like any other industrial process carries with it a number of safety hazards that need to be managed correctly in order to ensure operator safety whilst in use. These safety precautions primarily fall into the following categories and the hazard minimisation techniques suggested, in some cases have a positive effect on the resultant detonation spray coating. For example, having to automate the spraying process means that a very even and consistent spray coating can be achieved. | 1 | Applied and Interdisciplinary Chemistry |
The Bell–Evans–Polanyi model was developed independently by Ronald Percy Bell and by Meredith Gwynne Evans and Michael Polanyi to explain the apparent linear relationship between activation energy and free energy in acid disassociation, as described in the Brønsted catalysis equation, which was the original linear free-energy relationship published in 1924.
Consider the reaction
The system is assumed to have two degrees of freedom: r, the distance between atoms A and B, and r, the distance between atoms B and C. The distance between A and C is assumed to be fixed such that
As the A—B bond stretches, the energy of the system increases up to the activation energy associated with the transition state, whereupon the bond breaks. The energy then decreases as the B—C bond is formed. Evans and Polanyi approximated the two energy functions between reactants, the transition state, and the products by two straight lines (with slopes m and m respectively) that intersect at the transition state.
For the AB molecule, the energy is given as a function of bond distance r:
At the transition state, r = r and E = E. Therefore, we can write that
which rearranges to give
For the BC molecule, a similar expression of energy as a function of r is given by
The overall enthalpy change ΔH of the system can thus be expressed as
Plugging equation into equation and rearranging gives the following:
The constants in equation can be condensed into the common form of the Evans–Polanyi equation given above. | 0 | Theoretical and Fundamental Chemistry |
The trihexagonal tiling can be geometrically distorted into topologically equivalent tilings of lower symmetry. In these variants of the tiling, the edges do not necessarily line up to form straight lines. | 0 | Theoretical and Fundamental Chemistry |
When the required steel had been formed, it was poured into ladles and then transferred into moulds while the lighter slag was left behind. The conversion process, called the "blow", was completed in approximately 20 minutes. During this period, the progress of the oxidation of the impurities was judged by the appearance of the flame issuing from the mouth of the converter. The modern use of photoelectric methods of recording the characteristics of the flame greatly aided the blower in controlling final product quality. After the blow, the liquid metal was recarburized to the desired point and other alloying materials were added, depending on the desired product.
A Bessemer converter could treat a "heat" (batch of hot metal) of 5 to 30 tons at a time. They were usually operated in pairs, one being blown while another was being filled or tapped. | 1 | Applied and Interdisciplinary Chemistry |
A chiral switch is a chiral drug that has already approved as racemate but has been re-developed as a single enantiomer. The term chiral switching was introduced by Agranat and Caner in 1999 to describe the development of single enantiomers from racemate drugs. For example, levofloxacin is a chiral switch of racemic ofloxacin. The essential principle of a chiral switch is that there is a change in the status of chirality. In general, the term chiral switch is preferred over racemic switch because the switch is usually happening from a racemic drug to the corresponding single enantiomer(s). It is important to understand that chiral switches are treated as a selection invention. A selection invention is an invention that selects a group of new members from a previously known class on the basis of superior properties. To express the pharmacological activities of each of the chiral twins of a racemic drug two technical terms have been coined eutomer and distomer. The member of the chiral twin that has greater physiological activity is referred to as the eutomer and the other one with lesser activity is referred to as distomer. The eutomer/distomer ratio is called the eudisimic ratio and reflects the degree of enantioselectivity of the biological activity.
In case of stereoselectivity in action only one of the components in the racemic mixture is truly active (eutomer). The other isomer, the distomer, should be regarded as impurity or isomeric ballast not contributing to the effects aimed at. It is well documented that the pharmacologically inactive isomer (distomer) may contribute to the toxic or adverse effects of the drugs. There is a wide spectrum of possibilities of distomer actions, many of which are confirmed experimentally. Sometimes the single enantiomer version lacks certain side-effects that the racemate exhibits. And where the two enantiomers are sufficiently different in pharmacological effects, it may be possible to get a patent on one or both isomers (for instance, as in the case of propoxyphene). The chiral twins of propoxyphene are separately sold by Eli Lilly and company. Dextropropoxyphene is an analgesic agent (Darvon) and levopropoxyphene an effective antitussive (Novrad). Interestingly the reversed trade names of the drugs, DARVON and NOVRAD, also reflect the chemical mirror-image relationship. A positive consequence of this redesigning approach is that it has given a new life to an old drug, minimizing or avoiding the undesirable side-effect profile. Whether to go in for a chiral switch is normally made on a case-by-case basis. A pragmatic solution could be in favor of a decision-tree approach, incorporating various factors such as pharmacodynamic, pharmacokinetic, toxicological profile of the enantiomers, enantiomer-enantiomer interaction potential, safety, efficacy, risk-benefit ratio, chiral inversion, distomer liability, physicochemical properties, cost of separation and production, quality control criteria, marketing edge, etc. | 0 | Theoretical and Fundamental Chemistry |
In this type of reaction, a metal atom in a compound or solution is replaced by an atom of another metal. For example, copper is deposited when zinc metal is placed in a copper(II) sulfate solution:
In the above reaction, zinc metal displaces the copper(II) ion from copper sulfate solution and thus liberates free copper metal. The reaction is spontaneous and releases 213 kJ per 65 g of zinc.
The ionic equation for this reaction is:
As two half-reactions, it is seen that the zinc is oxidized:
And the copper is reduced: | 0 | Theoretical and Fundamental Chemistry |
Nuclear quadrupole resonance spectroscopy or NQR is a chemical analysis technique related to nuclear magnetic resonance (NMR). Unlike NMR, NQR transitions of nuclei can be detected in the absence of a magnetic field, and for this reason NQR spectroscopy is referred to as "zero Field NMR". The NQR resonance is mediated by the interaction of the electric field gradient (EFG) with the quadrupole moment of the nuclear charge distribution. Unlike NMR, NQR is applicable only to solids and not liquids, because in liquids the electric field gradient at the nucleus averages to zero (the EFG tensor has trace zero). Because the EFG at the location of a nucleus in a given substance is determined primarily by the valence electrons involved in the particular bond with other nearby nuclei, the NQR frequency at which transitions occur is unique for a given substance. A particular NQR frequency in a compound or crystal is proportional to the product of the nuclear quadrupole moment, a property of the nucleus, and the EFG in the neighborhood of the nucleus. It is this product which is termed the nuclear quadrupole coupling constant for a given isotope in a material and can be found in tables of known NQR transitions. In NMR, an analogous but not identical phenomenon is the coupling constant, which is also the result of an internuclear interaction between nuclei in the analyte. | 0 | Theoretical and Fundamental Chemistry |
Microautoradiography FISH is a technique to combine radio-labeled substrates with conventional FISH to detect phylogenetic groups and metabolic activities simultaneously. | 1 | Applied and Interdisciplinary Chemistry |
Encouraging agricultural use of biosolids is intended to prevent filling landfills with nutrient-rich organic materials from the treatment of domestic sewage that might be recycled and applied as fertilizer to improve and maintain productive soils and stimulate plant growth. Biosolids can be an ideal agricultural conditioner and fertilizer which can help promote crop growth to feed the increasing population. Biosolids may contain macronutrients nitrogen, phosphorus, potassium and sulphur with micronutrients copper, zinc, calcium, magnesium, iron, boron, molybdenum and manganese. | 1 | Applied and Interdisciplinary Chemistry |
In general, children, the elderly, and immunocompromised individuals require a lower dose of a pathogenic organism in order to contract an infection. Presently there are very few studies which are able to quantify the amount of time people are likely to spend in recreational waters and how much water they are likely to ingest. In general, children swim more often, stay in the water longer, submerge their heads more often, and swallow more water. This makes people more fearful of water in the sea as more bacteria will be growing on and around them. | 0 | Theoretical and Fundamental Chemistry |
As in metal–carbonyls, electrons are partially transferred from a d-orbital of the metal to antibonding molecular orbitals of the alkenes and alkynes. This electron transfer strengthens the metal–ligand bond and weakens the C–C bonds within the ligand. In the case of metal-alkenes and alkynes, the strengthening of the M–CR and M–CR bond is reflected in bending of the C–C–R angles which assume greater sp and sp character, respectively. Thus strong π backbonding causes a metal-alkene complex to assume the character of a metallacyclopropane. Alkenes and alkynes with electronegative substituents exhibit greater π backbonding. Some strong π backbonding ligands are tetrafluoroethylene, tetracyanoethylene, and hexafluoro-2-butyne. | 0 | Theoretical and Fundamental Chemistry |
In bioinformatics, a sequence entropy, also known as sequence complexity or information profile, is a numerical sequence providing a quantitative measure of the local complexity of a DNA sequence, independently of the direction of processing. The manipulations of the information profiles enable the analysis of the sequences using alignment-free techniques, such as for example in motif and rearrangements detection. | 1 | Applied and Interdisciplinary Chemistry |
In order to make the equations dimensionless, a characteristic length r, and a characteristic velocity u, need to be defined. These should be chosen such that the dimensionless variables are all of order one. The following dimensionless variables are thus obtained:
Substitution of these inverse relations in the Euler momentum equations, and definition of the Froude number:
and the Euler number:
the equations are finally expressed (with the material derivative and now omitting the indexes):
Cauchy-type equations in the high Froude limit (corresponding to negligible external field) are named free equations. On the other hand, in the low Euler limit (corresponding to negligible stress) general Cauchy momentum equation becomes an inhomogeneous Burgers equation (here we make explicit the material derivative):
This is an inhomogeneous pure advection equation, as much as the Stokes equation is a pure diffusion equation. | 1 | Applied and Interdisciplinary Chemistry |
The School of Chemistry is home to the Laboratory of Advanced Catalysis for Sustainability which is focused broadly on catalysis, sustainable processes and fuels, green chemistry, and organometallic chemistry. Other areas the group is interested in include batteries, nanoparticles, ionic liquids, biofuels, and nanostructured materials.
The research group is led by Prof. Thomas Maschmeyer and consists of ca. 20 researchers. | 1 | Applied and Interdisciplinary Chemistry |
Degrees of german carbonate hardness (°dKH or ; the dKH is from the German deutsche Karbonathärte) is a unit of water hardness, specifically for temporary or carbonate hardness. Carbonate hardness is a measure of the concentration of carbonates such as calcium carbonate (CaCO) and magnesium carbonate (MgCO) per volume of water. As a unit 1 dKH is the same as 1 °dH which is equal to approximately 0.1786 mmol/L or 17.86 milligrams (mg) of calcium carbonate per litre of water, i.e. 17.86 ppm.
The measurements of total hardness (German Gesamthärte (GH)) and carbonate hardness (German Karbonathärte (KH)) are sometimes stated with units dKH and dGH to differentiate them from one another, although in both cases the unit they are measured in is German degrees (°dH). | 0 | Theoretical and Fundamental Chemistry |
One type of chiral auxiliary is based on the trans-2-phenylcyclohexanol motif as introduced by James K. Whitesell and coworkers in 1985. This chiral auxiliary was used in ene reactions of the derived ester of glyoxylic acid.
In the total synthesis of (−)-heptemerone B and (−)-guanacastepene E, attached with trans-2-phenylcyclohexanol, the glyoxylate reacted with 2,4-dimethyl-pent-2-ene, in the presence of tin(IV) chloride, yielding the desired anti adduct as the major product, together with a small amount of its syn isomer with 10:1 diastereomeric ratio.
For even greater conformational control, switching from a phenyl to a trityl group gives trans-2-tritylcyclohexanol (TTC). In 2015, the Brown group published an efficient chiral permanganate-mediated oxidative cyclization with TTC. | 0 | Theoretical and Fundamental Chemistry |
Chloroeremomycin is a member of the glycopeptide family of antibiotics, such as vancomycin. The molecule is a non-ribosomal polypeptide that has been glycosylated. It is composed of seven amino acids and three saccharide units. Although chloroeremomycin has never been in clinical phases, oritavancin, a semi-synthetic derivative of chloroeremomycin, has been investigated.
Chloroeremomycin is a type of glycopeptide antibiotic and works by blocking the construction of a cell wall. Chloroeremomycin is naturally produced by Amycolatopsis orientalis. | 0 | Theoretical and Fundamental Chemistry |
His wife, Akemi, whom Shimomura met at Nagasaki University, is also an organic chemist and was a partner in his research activities. Their son, Tsutomu Shimomura, is a computer security expert who was involved in the arrest of Kevin Mitnick. Their daughter, Sachi Shimomura, is director of Undergraduate Studies for the English Department at Virginia Commonwealth University and the author of Odd Bodies and Visible Ends in Medieval Literature. | 0 | Theoretical and Fundamental Chemistry |
If both the equilibrium constant, and the standard enthalpy change, , for a reaction have been determined experimentally, the standard entropy change for the reaction is easily derived. Since and
To a first approximation the standard enthalpy change is independent of temperature. Using this approximation, definite integration of the van 't Hoff equation
gives
This equation can be used to calculate the value of log K at a temperature, T, knowing the value at temperature T.
The van t Hoff equation also shows that, for an exothermic reaction (), when temperature increases K decreases and when temperature decreases K increases, in accordance with Le Chateliers principle. The reverse applies when the reaction is endothermic.
When K has been determined at more than two temperatures, a straight line fitting procedure may be applied to a plot of against to obtain a value for . Error propagation theory can be used to show that, with this procedure, the error on the calculated value is much greater than the error on individual log K values. Consequently, K needs to be determined to high precision when using this method. For example, with a silver ion-selective electrode each log K value was determined with a precision of ca. 0.001 and the method was applied successfully.
Standard thermodynamic arguments can be used to show that, more generally, enthalpy will change with temperature.
where C is the heat capacity at constant pressure. | 0 | Theoretical and Fundamental Chemistry |
A molecular-weight size marker, also referred to as a protein ladder, DNA ladder, or RNA ladder, is a set of standards that are used to identify the approximate size of a molecule run on a gel during electrophoresis, using the principle that molecular weight is inversely proportional to migration rate through a gel matrix. Therefore, when used in gel electrophoresis, markers effectively provide a logarithmic scale by which to estimate the size of the other fragments (providing the fragment sizes of the marker are known).
Protein, DNA, and RNA markers with pre-determined fragment sizes and concentrations are commercially available. These can be run in either agarose or polyacrylamide gels. The markers are loaded in lanes adjacent to sample lanes before the commencement of the run. | 1 | Applied and Interdisciplinary Chemistry |
Sonoporation uses ultrasonic frequencies to deliver DNA into cells. The process of acoustic cavitation is thought to disrupt the cell membrane and allow DNA to move into cells. | 1 | Applied and Interdisciplinary Chemistry |
Konovalov was born in Ivanovka and went to study at the Mining institute at St. Petersburg in 1878. He became a student of Dmitri Mendeleev in 1890 and later succeeded him as professor of inorganic chemistry at St. Petersburg. He became director of the Mining institute in 1904 and became a deputy minister of trade and industry, while also presiding of the bureau of weights and measures.
Konovalov identified a rule for two liquids in solution and their distillation. He considered two components in a closed system and examined the vapour pressures of the components and stated that at equilibrium, the vapor pressures, and the partial pressures of the components in the vapor, are equal. Konovalov came up with the theory based on a thought experiment and then demonstrated it through experiments. Konovalov's second rule was that the maxima or minima of saturation vapour-pressure curves corresponded to the composition of azeotropic mixtures. Konovalov also examined osmotic pressure across membranes and gave a formula for equilibrium in 1890. He also worked on two component electrolytes and the heat of combustion of organic compounds. | 0 | Theoretical and Fundamental Chemistry |
Most gilding methods are additive: they deposit gold that was not there before onto the surface of an object. By contrast, depletion gilding is a subtractive process whereby material is removed to increase the purity of gold that is already present on an object's surface.
In depletion gilding, other metals are etched away from the surface of an object composed of a gold alloy by the use of acids or salts, often in combination with heat. Since no gold is added, only an object made of an alloy that already contains gold can be depletion gilded.
Depletion gilding relies on the fact that gold is highly resistant to oxidation or corrosion by most common chemicals, whereas many other metals are not. Depletion gilding is most often used to treat alloys of gold with copper or silver. Unlike gold, both copper and silver readily react with a variety of chemicals. For example, nitric acid is effective as an etching agent for both copper and silver. Under the proper circumstances, even ordinary table salt will react with either metal.
The object to be gilded is coated, immersed, or packed in a suitable acid or salt, and usually heated to speed the process. These chemicals then attack the metallic copper and silver in the objects surface, transforming it to various copper and silver compounds. The resulting copper and silver compounds can be removed from the objects surface by a number of processes. Washing, chemical leaching, heating, or even physical absorption by porous materials such as brick dust have all been used historically. Meanwhile, the relatively inert gold is left unaffected. The result is a thin layer of nearly pure gold on the surface of the original object.
There is no well-defined minimum gold content required to successfully depletion gild an object. However, the less gold that is present, the more other material must be etched away to produce the desired surface appearance. In addition, the removal of the other metals usually leaves the surface covered with microscopic voids and pits. This can make the surface soft and "spongy" with a dull or matte appearance. This effect becomes more pronounced as more base metal is removed. For this reason, most depletion gilded objects are burnished to make their surfaces more durable and give them a more attractive polished finish.
Like other gilding processes, depletion gilding provides a way to produce the appearance of pure gold without its disadvantages: its cost and rarity, and its softness and denseness. By producing a layer of gold over a layer of copper or other metal, objects can be made that are lighter, sturdier, and cheaper while still appearing to be nearly pure gold. | 1 | Applied and Interdisciplinary Chemistry |
William H. Peirce (died 1944) was an American civil engineer and metallurgist, who pioneered copper production in the early 20th century. Among his achievements was the , invented with Elias Anton Cappelen Smith. | 1 | Applied and Interdisciplinary Chemistry |
For the hexagonal close-packed structure the derivation is similar. Here the unit cell (equivalent to 3 primitive unit cells) is a hexagonal prism containing six atoms (if the particles in the crystal are atoms). Indeed, three are the atoms in the middle layer (inside the prism); in addition, for the top and bottom layers (on the bases of the prism), the central atom is shared with the adjacent cell, and each of the six atoms at the vertices is shared with other six adjacent cells. So the total number of atoms in the cell is 3 + (1/2)×2 + (1/6)×6×2 = 6. Each atom touches other twelve atoms. Now let be the side length of the base of the prism and be its height. The latter is twice the distance between adjacent layers, i. e., twice the height of the regular tetrahedron whose vertices are occupied by (say) the central atom of the lower layer, two adjacent non-central atoms of the same layer, and one atom of the middle layer "resting" on the previous three. Obviously, the edge of this tetrahedron is . If , then its height can be easily calculated to be , and, therefore, . So the volume of the hcp unit cell turns out to be (3/2) , that is 24 .
It is then possible to calculate the APF as follows: | 0 | Theoretical and Fundamental Chemistry |
α,β-Unsaturated carbonyl compounds are organic compounds with the general structure (O=CR)−C=C-R. Such compounds include enones and enals, but also carboxylic acids and the corresponding esters and amides. In these compounds, the carbonyl group is conjugated with an alkene (hence the adjective unsaturated). Unlike the case for carbonyls without a flanking alkene group, α,β-unsaturated carbonyl compounds are susceptible to attack by nucleophiles at the β-carbon. This pattern of reactivity is called vinylogous. Examples of unsaturated carbonyls are acrolein (propenal), mesityl oxide, acrylic acid, and maleic acid. Unsaturated carbonyls can be prepared in the laboratory in an aldol reaction and in the Perkin reaction. | 0 | Theoretical and Fundamental Chemistry |
Boundary conditions for stress balance describe the capillary surface at the contact line: the line where a solid meets the capillary interface; also, volume constraints can serve as boundary conditions (a suspended drop, for example, has no contact line but clearly must admit a unique solution).
For static surfaces, the most common contact line boundary condition is the implementation of the contact angle, which specifies the angle that one of the fluids meets the solid wall. The contact angle condition on the surface is normally written as:
where is the contact angle. This condition is imposed on the boundary (or boundaries) of the surface. is the unit outward normal to the solid surface, and is a unit normal to . Choice of depends on which fluid the contact angle is specified for.
For dynamic interfaces, the boundary condition showed above works well if the contact line velocity is low. If the velocity is high, the contact angle will change ("dynamic contact angle"), and as of 2007 the mechanics of the moving contact line (or even the validity of the contact angle as a parameter) is not known and an area of active research. | 1 | Applied and Interdisciplinary Chemistry |
One physical explanation for polyamorphism is the existence of a double well inter-atomic pair potential (see lower right diagram). It is well known that the ordinary liquid–gas critical point appears when the inter-atomic pair potential contains a minimum. At lower energies (temperatures) particles trapped in this minimum condense into the liquid state. At higher temperatures however, these particles can escape the well and the sharp definition between liquid and gas is lost. Molecular modelling has shown that addition of a second well produces an additional transition between two different liquids (or fluids) with a second critical point. | 0 | Theoretical and Fundamental Chemistry |
Because malate dehydrogenase is closely tied to the citric acid cycle, studies have proposed and experimentally demonstrated that citrate is an allosteric regulator of malate dehydrogenase depending on the concentrations of L-malate and NAD. This may be due to deviations observed in the kinetic behavior of malate dehydrogenase at high oxaloacetate and L-malate concentrations. Experiments have shown that Citrate can both allosterically activate and inhibit the enzymatic activity of malate dehydrogenase. Citrate has been shown to inhibit the oxidation of L-malate when there are low levels of L-malate and NAD. However, in the presence of high levels of malate and NAD, citrate can stimulate the production of oxaloacetate. Although malate dehydrogenase is typically considered a reversible enzyme, it is believed that there is an allosteric regulatory site on the enzyme where citrate can bind to and drive the reaction equilibrium in either direction.
Glutamate has also been shown to inhibit malate dehydrogenase activity. Furthermore, it has been shown that alpha ketoglutarate dehydrogenase can interact with mitochondrial aspartate aminotransferase to form a complex, which can then bind to malate dehydrogenase, forming a ternary complex that reverses inhibitory action on malate dehydrogenase enzymatic activity by glutamate. Additionally, the formation of this complex enables glutamate to react with aminotransferase without interfering activity of malate dehydrogenase. The formation of this ternary complex also facilitates the release of oxaloacetate from malate dehydrogenase to aminotransferase. Kinetically, the binding of malate dehydrogenase to the binary complex of alpha ketoglutarate dehydrogenase and aminotrannferase has been shown to increase reaction rate of malate dehydrogenase because the Km of malate dehydrogenase is decreased when it is bound as part of this complex. | 1 | Applied and Interdisciplinary Chemistry |
The critical concentration is the concentration of either G-actin (actin) or the alpha,beta- tubulin complex (microtubules) at which the end will remain in an equilibrium state with no net growth or shrinkage. What determines whether the ends grow or shrink is entirely dependent on the cytosolic concentration of available monomer subunits in the surrounding area. Critical concentration differs from the plus (C) and the minus end (C), and under normal physiological conditions, the critical concentration is lower at the plus end than the minus end. Examples of how the cytosolic concentration relates to the critical concentration and polymerization are as follows:
* A cytosolic concentration of subunits above both the C and C ends results in subunit addition at both ends
* A cytosolic concentration of subunits below both the C and C ends results in subunit removal at both ends
Note that the cytosolic concentration of the monomer subunit between the C and C ends is what is defined as treadmilling in which there is growth at the plus end, and shrinking on the minus end.
The cell attempts to maintain a subunit concentration between the dissociation constants at the plus and minus ends of the polymer. | 1 | Applied and Interdisciplinary Chemistry |
The main advantage of diffusion dialysis is the low energy consumption of the unit. This membrane technique operates under normal pressure and does not have a state change. Consequently, the energy required is significantly reduced, which reduces the operating cost. There is also the low installation cost, easy operation and the stability and reliability of the process. Another advantage is that diffusion dialysis does not pollute the environment.
A disadvantage is that a diffusion dialyser has a low processing capability and low processing efficiency. There are other methods such as electrodialysis and reverse osmosis that can achieve better efficiencies than diffusion dialysis. | 1 | Applied and Interdisciplinary Chemistry |
G. Marius Clore MAE, FRSC, FRS is a British-born, American molecular biophysicist and structural biologist. He was born in London, U.K. and is a dual U.S./U.K. Citizen. He is a Member of the National Academy of Sciences, a Fellow of the Royal Society, a NIH Distinguished Investigator, and the Chief of the Molecular and Structural Biophysics Section in the Laboratory of Chemical Physics of the National Institute of Diabetes and Digestive and Kidney Diseases at the U.S. National Institutes of Health. He is known for his foundational work in three-dimensional protein and nucleic acid structure determination by biomolecular NMR spectroscopy, for advancing experimental approaches to the study of large macromolecules and their complexes by NMR, and for developing NMR-based methods to study rare conformational states in protein-nucleic acid and protein-protein recognition. Clores discovery of previously undetectable, functionally significant, rare transient states of macromolecules has yielded fundamental new insights into the mechanisms of important biological processes, and in particular the significance of weak interactions and the mechanisms whereby the opposing constraints of speed and specificity are optimized. Further, Clores work opens up a new era of pharmacology and drug design as it is now possible to target structures and conformations that have been heretofore unseen. | 0 | Theoretical and Fundamental Chemistry |
C-S-H is a nano sized material with some degree of crystallinity as observed by X-ray diffraction techniques. The underlying atomic structure of C-S-H is similar to the naturally occurring mineral tobermorite. It has a layered geometry with calcium silicate sheet structure separated by an interlayer space. The silicates in C-S-H exist as dimers, pentamers and 3n-1 chain units (where n is an integer greater than 0) and calcium ions are found to connect these chains making the three dimensional nano structure as observed by dynamic nuclear polarisation surface-enhanced nuclear magnetic resonance. The exact nature of the interlayer remains unknown. One of the greatest difficulties in characterising C-S-H is due to its variable stoichiometry.
The scanning electron microscope micrographs of C-S-H does not show any specific crystalline form. They usually manifest as foils or needle/oriented foils.
Synthetic C-S-H can be divided in two categories separated at the Ca/Si ratio of about 1.1. There are several indications that the chemical, physical and mechanical characteristics of C-S-H varies noticeably between these two categories. | 0 | Theoretical and Fundamental Chemistry |
Moshers acid, via its acid chloride derivative, reacts readily with alcohols and amines to give esters and amides, respectively. The lack of an alpha-proton on the acid prevents loss of stereochemical fidelity under the reaction conditions. Thus, using an enantiomerically pure Moshers acid allows for determination of the configuration of simple chiral amines and alcohols. For example, the (R)- and (S)-enantiomers of 1-phenylethanol react with (S)-Mosher acid chloride to yield (R,S)- and (S,S)-diastereomers, respectively, that are distinguishable in NMR. | 0 | Theoretical and Fundamental Chemistry |
Larive worked in the field of bioanalytical chemistry, applying analytical tools such as nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry to the products of chemical separations. Much of her research focused on reducing the amount of sample needed for analysis, such as constructing microcoil NMR probes that can measure as little as 25 nL of sample and are usable as part of an capillary isotachophoresis apparatus. This has been applied to structure determination of heparin and heparan sulfate. She developed NMR pulse sequences to study protein ligand interactions in complexes with multiple ligands. She also researches analytical methods for metabolomics and chemogenomics for the reaction of plants to pesticides and hypoxia using NMR and mass spectroscopy.
NMR is often thought of as a low-sensitivity method, but Larive's laboratory has developed ways of increasing the sensitivity of their measurements to obtain precise chemical and structural information. The techniques she has developed are relevant to understanding carbohydrate structure and biosynthesis, designing new drugs and measuring the purity of pharmaceuticals. Her work in developing chemical profiles for substances also has relevance for the authentication of foodstuffs such as wine, olive oil, and pomegranate juice. | 0 | Theoretical and Fundamental Chemistry |
The equation parameter m, called the sensitivity factor of solvolysis, describes the compound’s ability to form the carbocation intermediate in given solvent system. It is the slope of the plot of log(k/k) vs Y values. Since the reference reaction has little solvent nucleophilic assistance, the reactions with m equal to 1 or larger than 1 have almost full ionized intermediates. If the compounds are not so sensitive to the ionizing ability of solvent, then the m values are smaller than 1. That is:
# m ≥ 1, the reactions proceed through S1 mechanism.
# m 1 and S2. | 0 | Theoretical and Fundamental Chemistry |
The classic shape associated with a drop (with a pointy end in its upper side) comes from the observation of a droplet clinging to a surface. The shape of a drop falling through a gas is actually more or less spherical for drops less than 2 mm in diameter. Larger drops tend to be flatter on the bottom part due to the pressure of the gas they move through. As a result, as drops get larger, a concave depression forms which leads to the eventual breakup of the drop. | 1 | Applied and Interdisciplinary Chemistry |
Synaptic degeneration and death of nerve cells are defining features of Alzheimer's disease (AD), the most prevalent age-related neurodegenerative disorders. In AD, neurons in the hippocampus and basal forebrain (brain regions that subserve learning and memory functions) are selectively vulnerable. Studies of postmortem brain tissue from AD people have provided evidence for increased levels of oxidative stress, mitochondrial dysfunction and impaired glucose uptake in vulnerable neuronal populations. Studies of animal and cell culture models of AD suggest that increased levels of oxidative stress (membrane lipid peroxidation, in particular) may disrupt neuronal energy metabolism and ion homeostasis, by impairing the function of membrane ion-motive ATPases, glucose and glutamate transporters. Such oxidative and metabolic compromise may thereby render neurons vulnerable to excitotoxicity and apoptosis. Recent studies suggest that AD can manifest systemic alterations in energy metabolism (e.g., increased insulin resistance and dysregulation of glucose metabolism). Emerging evidence that dietary restriction can forestall the development of AD is consistent with a major "metabolic" component to these disorders, and provides optimism that these devastating brain disorders of aging may be largely preventable. | 0 | Theoretical and Fundamental Chemistry |
* Since set of nodal equations are solved nodal Jacobi matrix is used which is more sparse then the equivalent loop Jacobi matrix which may have negative impact on computational efficiency and usability. | 1 | Applied and Interdisciplinary Chemistry |
Quasi-crystals are supramolecular aggregates exhibiting both crystalline (solid) properties as well as amorphous, liquid-like properties.
Self-organized structures termed "quasi-crystals" were originally described in 1978 by the Israeli scientist Valeri A. Krongauz of the Weizmann Institute of Science, in the Nature paper, Quasi-crystals from irradiated photochromic dyes in an applied electric field.
In his 1978 paper Krongauz coined the term “Quasi-Crystals” for the new self-organized colloidal particles . The Quasi-crystals are supramolecular aggregates manifesting both crystalline properties e.g. Bragg scattering, as well as amorphous, liquid-like properties i.e. drop-like shapes, fluidity, extensibility and elasticity in electric field. The supramolecular Quasi-crystals are produced in photochemical reaction by exposing solutions of photochromic spiropyran molecules to UV radiation. The ultraviolet light induces the conversion of the spiropyrans to merocyanine molecules that manifest electric dipole moments. (see Scheme 1). The quasi-crystals have external shape of submicron globules and their internal structure consists of crystals enveloped by an amorphous matter (see Fig. 1). The crystals are formed by self-assembled stacks of the merocyanine molecular dipoles aligning themselves in a parallel manner, while amorphous envelopes consist of the same merocyanine dipoles aligned in an anti-parallel manner (Fig. 1, Scheme 2). In an applied electrostatic field, quasi-crystals form macroscopic threads that show linear optical dichroism.
Later Krongauz described unusual phase transitions of molecules composed of mesogenic and spiropyran moieties, which he named "quasi-liquid crystals." A micrograph of their mesophase appeared on the cover of Nature in a 1984 paper, “Quasi-Liquid Crystals.” The investigation of spiropyran-merocyanine self-organized systems, including macromolecules (see, for example, Fig. 2), has continued over the years.
These studies have resulted in discoveries of unusual and practically significant phenomena. Thus, in the electrostatic field, quasi-crystals and quasi-liquid crystals have exhibited 2nd order non-linear optical properties.
Potential applications of these fascinating materials have been described and patented.
Work on spiropyran-merocyanine self-assemblies currently continues in several laboratories. | 0 | Theoretical and Fundamental Chemistry |
Sodium ion channels provide an integral service through the body, as they transmit depolarizing impulses at the cellular and intracellular level. This allows sodium ions to coordinate much more intensive processes such as movement and cognition. Sodium ion channels consist of various subunits, however, only the principle subunit is required for function. These sodium ion channels consist of four internally homologous domains, each of which containing six transmembrane segments and resembling a single subunit of a voltage-dependent potassium ion channel. The four domains fold together, forming a central pore. That central pore of the sodium ions dictates the selectivity of the channel: both ionic radius and ionic charge are key in channel selectivity. | 0 | Theoretical and Fundamental Chemistry |
In some places carbon dioxide bubbles out from the sea floor, locally changing the pH and other aspects of the chemistry of the seawater. Studies of these carbon dioxide seeps have documented a variety of responses by different organisms. Coral reef communities located near carbon dioxide seeps are of particular interest because of the sensitivity of some corals species to acidification. In Papua New Guinea, declining pH caused by carbon dioxide seeps is associated with declines in coral species diversity. However, in Palau carbon dioxide seeps are not associated with reduced species diversity of corals, although bioerosion of coral skeletons is much higher at low pH sites. | 0 | Theoretical and Fundamental Chemistry |
Monosaccharides commonly found in eukaryotic glycoproteins include:
The sugar group(s) can assist in protein folding, improve proteins' stability and are involved in cell signalling. | 0 | Theoretical and Fundamental Chemistry |
The cytoskeleton is a highly dynamic part of a cell and cytoskeletal filaments constantly grow and shrink through addition and removal of subunits. Directed crawling motion of cells such as macrophages relies on directed growth of actin filaments at the cell front (leading edge). | 1 | Applied and Interdisciplinary Chemistry |
The surface plasmon polariton is a non-radiative electromagnetic surface wave that propagates in a direction parallel to the negative permittivity/dielectric material interface. Since the wave is on the boundary of the conductor and the external medium (air, water or vacuum for example), these oscillations are very sensitive to any change of this boundary, such as the adsorption of molecules to the conducting surface.
To describe the existence and properties of surface plasmon polaritons, one can choose from various models (quantum theory, Drude model, etc.). The simplest way to approach the problem is to treat each material as a homogeneous continuum, described by a frequency-dependent relative permittivity between the external medium and the surface. This quantity, hereafter referred to as the materials' "dielectric function", is the complex permittivity. In order for the terms that describe the electronic surface plasmon to exist, the real part of the dielectric constant of the conductor must be negative and its magnitude must be greater than that of the dielectric. This condition is met in the infrared-visible wavelength region for air/metal and water/metal interfaces (where the real dielectric constant of a metal is negative and that of air or water is positive).
LSPRs (localized surface plasmon resonances) are collective electron charge oscillations in metallic nanoparticles that are excited by light. They exhibit enhanced near-field amplitude at the resonance wavelength. This field is highly localized at the nanoparticle and decays rapidly away from the nanoparticle/dielectric interface into the dielectric background, though far-field scattering by the particle is also enhanced by the resonance. Light intensity enhancement is a very important aspect of LSPRs and localization means the LSPR has very high spatial resolution (subwavelength), limited only by the size of nanoparticles. Because of the enhanced field amplitude, effects that depend on the amplitude such as magneto-optical effect are also enhanced by LSPRs. | 0 | Theoretical and Fundamental Chemistry |
The monomers, 3-hydroxybutanoic acid and 3-hydroxypentanoic acid, are joined by ester bonds; the back bone of the polymer is made up of carbon and oxygen atoms.
The property of the PHBV depends upon the ratio of these two monomers in it.
3-hydroxybutanoic acid provides stiffness while 3-hydroxypentanoic acid promotes flexibility. Thus PHBV can be made to resemble either polypropylene or polyethylene by changing the ratio of monomers. Increase in the ratio of 3-hydroxybutanoic acid to 3-hydroxypentanoic acid results in an increase in melting point, water permeability, glass transition temperature (T) and tensile strength. However impact resistance is reduced. | 1 | Applied and Interdisciplinary Chemistry |
Consider the case of a thin, solid, parallel-sided rotating disc of axial thickness (L) and radius (L). The disc has a density (M/L), rotates at an angular velocity (T) and this leads to a stress (TLM) in the material. There is a theoretical linear elastic solution, given by Lame, to this problem when the disc is thin relative to its radius, the faces of the disc are free to move axially, and the plane stress constitutive relations can be assumed to be valid. As the disc becomes thicker relative to the radius then the plane stress solution breaks down. If the disc is restrained axially on its free faces then a state of plane strain will occur. However, if this is not the case then the state of stress may only be determined though consideration of three-dimensional elasticity and there is no known theoretical solution for this case. An engineer might, therefore, be interested in establishing a relationship between the five variables. Dimensional analysis for this case leads to the following () non-dimensional groups:
: demand/capacity =
: thickness/radius or aspect ratio =
Through the use of numerical experiments using, for example, the finite element method, the nature of the relationship between the two non-dimensional groups can be obtained as shown in the figure. As this problem only involves two non-dimensional groups, the complete picture is provided in a single plot and this can be used as a design/assessment chart for rotating discs. | 1 | Applied and Interdisciplinary Chemistry |
The basic principles of MRFM imaging and the theoretical possibility of this technology were first described in 1991. The first MRFM image was obtained in 1993 at the IBM Almaden Research Center with 1-μm vertical resolution and 5-μm lateral resolution using a bulk sample of the paramagnetic substance diphenylpicrylhydrazyl. The spatial resolution reached nanometer-scale in 2003. Detection of the magnetic spin of a single electron was achieved in 2004. In 2009 researchers at IBM and Stanford announced that they had achieved resolution of better than 10 nanometers, imaging tobacco mosaic virus particles on a nanometer-thick layer of adsorbed
hydrocarbons. | 0 | Theoretical and Fundamental Chemistry |
Julie Elizabeth Gough is a Professor of Biomaterials and Tissue Engineering at The University of Manchester. She specializes on controlling cellular responses at the cell-biomaterial interface by engineering defined surfaces for mechanically sensitive connective tissues. | 1 | Applied and Interdisciplinary Chemistry |
Vitamin D was discovered in 1922 following on from previous research. American researchers Elmer McCollum and Marguerite Davis in 1914 discovered a substance in cod liver oil which later was called "vitamin A". British doctor Edward Mellanby noticed dogs that were fed cod liver oil did not develop rickets and concluded vitamin A, or a closely associated factor, could prevent the disease. In 1922, Elmer McCollum tested modified cod liver oil in which the vitamin A had been destroyed. The modified oil cured the sick dogs, so McCollum concluded the factor in cod liver oil which cured rickets was distinct from vitamin A. He called it vitamin D because he thought it was the fourth vitamin to be named. It was not initially realized that vitamin D can be synthesized by humans (in the skin) through exposure to UV light, and therefore is technically not a vitamin, but rather can be considered to be a hormone.
In 1925, it was established that when 7-dehydrocholesterol is irradiated with light, a form of a fat-soluble substance is produced (now known as D). Alfred Fabian Hess stated: "Light equals vitamin D." Adolf Windaus, at the University of Göttingen in Germany, received the Nobel Prize in Chemistry in 1928 for his work on the constitution of sterols and their connection with vitamins. In 1929, a group at NIMR in Hampstead, London, were working on the structure of vitamin D, which was still unknown, as well as the structure of steroids. A meeting took place with J.B.S. Haldane, J.D. Bernal, and Dorothy Crowfoot to discuss possible structures, which contributed to bringing a team together. X-ray crystallography demonstrated the sterol molecules were flat, not as proposed by the German team led by Windaus. In 1932, Otto Rosenheim and Harold King published a paper putting forward structures for sterols and bile acids which found immediate acceptance. The informal academic collaboration between the team members Robert Benedict Bourdillon, Otto Rosenheim, Harold King, and Kenneth Callow was very productive and led to the isolation and characterization of vitamin D. At this time, the policy of the Medical Research Council was not to patent discoveries, believing the results of medical research should be open to everybody. In the 1930s, Windaus clarified further the chemical structure of vitamin D.
In 1923, American biochemist Harry Steenbock at the University of Wisconsin demonstrated that irradiation by ultraviolet light increased the vitamin D content of foods and other organic materials. After irradiating rodent food, Steenbock discovered the rodents were cured of rickets. Using of his own money, Steenbock patented his invention. His irradiation technique was used for foodstuffs, most notably for milk. By the expiration of his patent in 1945, rickets had been all but eliminated in the US.
In 1969, a specific binding protein for vitamin D called the vitamin D receptor was identified. Shortly thereafter, the conversion of vitamin D to calcifediol and then to calcitriol, the biologically active form, was confirmed. The photosynthesis of vitamin D in skin via previtamin D and its subsequent metabolism was described in 1980. | 1 | Applied and Interdisciplinary Chemistry |
The use of the chiral pool is illustrated by the synthesis of the anticancer drug paclitaxel (Taxol). The incorporation of the C10 precursor verbenone, a member of the chiral pool, makes the production of paclitaxel more efficient than most alternatives.
Chiral pool synthesis is used to build a part of epothilone (an alternative to paclitaxel) from readily available enantiopure (–)-pantolactone. | 0 | Theoretical and Fundamental Chemistry |
The classic Monod–Wyman–Changeux model (MWC) for cooperativity is generally published in an irreversible form. That is, there are no product terms in the rate equation which can be problematic for those wishing to build metabolic models since there are no product inhibition terms. However, a series of publications by Popova and Sel'kov derived the MWC rate equation for the reversible, multi-substrate, multi-product reaction.
The same problem applies to the classic Hill equation which is almost always shown in an irreversible form. Hofmeyr and Cornish-Bowden first published the reversible form of the Hill equation. The equation has since been discussed elsewhere and the model has also been used in a number of kinetic models such as a model of Phosphofructokinase and Glycolytic Oscillations in the Pancreatic β-cells or a model of a glucose-xylose co-utilizing S. cerevisiae strain. The model has also been discussed in modern enzyme kinetics textbooks. | 0 | Theoretical and Fundamental Chemistry |
Some impellers are similar to small propellers but without the large blades. Among other uses, they are used in water jets to power high speed boats.
Because impellers do not have large blades to turn, they can spin at much higher speeds than propellers. The water forced through the impeller is channeled by the housing, creating a water jet that propels the vessel forward. The housing is normally tapered into a nozzle to increase the speed of the water, which also creates a Venturi effect in which low pressure behind the impeller pulls more water towards the blades, tending to increase the speed.
To work efficiently, there must be a close fit between the impeller and the housing. The housing is normally fitted with a replaceable wear ring which tends to wear as sand or other particles are thrown against the housing side by the impeller.
Vessels using impellers are normally steered by changing the direction of the water jet.
Compare to propeller and jet aircraft engines. | 1 | Applied and Interdisciplinary Chemistry |
The earliest smelted iron object from Europe is a knife blade from the Catacomb culture in present day Ukraine, dated to c. 2500 BC. During most of the Middle and Late Bronze Age in Europe, iron was present, though scarce. It was used for personal ornaments and small knives, for repairs on bronzes, and for bimetallic items. Early smelted iron finds from central Europe include an iron knife or sickle from Ganovce in Slovakia, possibly dating from the 18th century BC, an iron ring from Vorwohlde in Germany dating from circa the 15th century BC, and an iron chisel from Heegermühle in Germany dating from circa 1000 BC.
Iron metallurgy began to be practised in Scandinavia during the later Bronze Age from at least the 9th century BC. In the 11th century BC iron swords replaced bronze swords in Southern Europe, especially in Greece, and in the 10th century BC iron became the prevailing metal in use. In the Carpathian Basin there is a significant increase in iron finds dating from the 10th century BC onwards, with some finds possibly dating as early as the 12th century BC. Iron swords have been found in central Europe dating from the 10th century BC, however the Iron Age began in earnest with the Hallstatt culture from 800 BC.
From 500 BC the La Tène culture saw a significant increase in iron production, with iron metallurgy also becoming common in southern Scandinavia. North of Sweden saw steel manufacturing dating back to around 0 AD through the eastern-western migration of hunter-gatherers in the Cap of the North. The spread of ironworking in Central and Western Europe is associated with Celtic expansion. Celtic smiths produced steel from circa 800 BC as part of the production of swords, and the production of high-carbon steel is attested in Britain after circa 490 BC. By the 1st century BC, Noric steel was famous for its quality and sought-after by the Roman military.
The annual iron output of the Roman Empire is estimated at 84,750 t. | 1 | Applied and Interdisciplinary Chemistry |
In general, , , and may vary with space and time. In cases in which they depend on concentration as well, the equation becomes nonlinear, giving rise to many distinctive mixing phenomena such as Rayleigh–Bénard convection when depends on temperature in the heat transfer formulation and reaction–diffusion pattern formation when depends on concentration in the mass transfer formulation. | 1 | Applied and Interdisciplinary Chemistry |
In cattle and swine tissue, it was found in 2007 that a procedure for the analysis of ractopamine residues in liver or muscle can be performed by high performance liquid chromatography (HPLC) with fluorescence detection. The confirmatory method include reversed-phase HPLC/electrospray ionization triple tandem quadrupole mass spectrometry. The limit of quantification of the drug using this LC/MS instrument was shown to be 1 ng/g (1 ppb). In cattle, a 2018 Chinese study promoted the use of hair as an indelible test of feed containing ractopamine. | 0 | Theoretical and Fundamental Chemistry |
Salla disease is an extremely rare illness which is considered the mildest form of the free sialic acid accumulation disorders though its childhood form is considered an aggressive variant and people who suffer from it have mental retardation. It is an autosomic recessive disorder caused by a mutation of the chromosome 6. It mainly affects the nervous system and it is caused by a lysosomal storage irregularity which comes from a deficit of a specific sialic acid carrier located on the lysosomal membrane Currently, there is no cure for this disease and the treatment is supportive, focusing on the control of symptoms. | 0 | Theoretical and Fundamental Chemistry |
The super-Tonks–Girardeau gas was experimentally observed in Ref. using an ultracold gas of cesium atoms. Reducing the magnitude of the attractive interactions caused the gas to became unstable to collapse into cluster-like bound states. Repulsive dipolar interactions stabilize the gas when instead using highly magnetic dysprosium atoms. This enabled the creation of prethermal quantum many-body scar states via the topological pumping of these super-Tonks-Girardeau gases. | 0 | Theoretical and Fundamental Chemistry |
Ferulic acid decarboxylases (Fdc) are decarboxylase enzymes capable of the reversible decarboxylation of aromatic carboxylic acids such as ferulic acid and cinnamic acid. Fdcs are fungal homologues of the E.coli' UbiD enzyme which is involved in ubiquinone biosynthesis. This places Fdc within the wider UbiD enzyme family, representing a distinct clade within the family
Presence of fdc1 and the associated pad1 genes (Pad1 homologous to UbiX in E.coli) were shown to be required for the decarboxylation of phenylacrylic acids in Saccharomyces cerevisiae.
In 2015 the cofactor prFMN was discovered in the active site of Fdc1 from Aspergillus niger (AnFdc) by crystallography, prior to this genetic studies had led to the assumption that both UbiD and UbiX encoded isofunctional decarboxylases. In actuality UbiX/Pad were found to be flavin preyltransferases supplying the prFMN cofactor to UbiD/Fdc where it is utilised for the reversible decarboxylation of alpha-beta unsaturated carboxylic acid substrates. Since the discovery of prFMN AnFDC has become the most well understood representative of the UbiD enzyme family | 1 | Applied and Interdisciplinary Chemistry |
Zeta potential titration is a titration of heterogeneous systems, for example colloids and emulsions. Solids in such systems have very high surface area. This type of titration is used to study the zeta potential of these surfaces under different conditions. Details of zeta potential definition and measuring techniques can be found in the International Standard. | 0 | Theoretical and Fundamental Chemistry |
The A15 phases (also known as β-W or CrSi structure types) are series of intermetallic compounds with the chemical formula AB (where A is a transition metal and B can be any element) and a specific structure. The A15 phase is also one of the members in the Frank–Kasper phases family. Many of these compounds have superconductivity at around , which is comparatively high, and remain superconductive in magnetic fields of tens of teslas (hundreds of kilogauss). This kind of superconductivity (Type-II superconductivity) is an important area of study as it has several practical applications. | 1 | Applied and Interdisciplinary Chemistry |
The following genes are part of the chemical pathway for making heme:
*ALAD: aminolevulinic acid, δ-, dehydratase (deficiency causes ala-dehydratase deficiency porphyria)
*ALAS1: aminolevulinate, δ-, synthase 1
*ALAS2: aminolevulinate, δ-, synthase 2 (deficiency causes sideroblastic/hypochromic anemia)
*CPOX: coproporphyrinogen oxidase (deficiency causes hereditary coproporphyria)
*FECH: ferrochelatase (deficiency causes erythropoietic protoporphyria)
*HMBS: hydroxymethylbilane synthase (deficiency causes acute intermittent porphyria)
*PPOX: protoporphyrinogen oxidase (deficiency causes variegate porphyria)
*UROD: uroporphyrinogen decarboxylase (deficiency causes porphyria cutanea tarda)
*UROS: uroporphyrinogen III synthase (deficiency causes congenital erythropoietic porphyria) | 1 | Applied and Interdisciplinary Chemistry |
Attempts to model the formation of the "first" star from the pure hydrogen and helium gas clouds below about 10,000 K show that the heat generated in the gravitational contraction phase must be somehow radiatively released for further cooling to be possible. This is no problem as long as temperatures are still high enough so that free electrons exist: electrons are efficient emitters when interacting with neutrals (bremsstrahlung). However, at the lower temperatures in neutral gases, the recombination of hydrogen atoms to
H molecules is a process that generates enormous amounts of heat that must somehow be radiated away in CIE processes; if CIE were non-existing, molecule formation could not take place and temperatures could not fall further. Only CIE processes permit further cooling, so that molecular hydrogen will accumulate. A dense, cool environment will thus develop so that a gravitational collapse and star formation can actually proceed. | 0 | Theoretical and Fundamental Chemistry |
When Rutherford began his studies at Cambridge, he was among the first aliens (those without a Cambridge degree) allowed to do research at the university, and was additionally honoured to study under J. J. Thomson.
With Thomson's encouragement, Rutherford detected radio waves at , and briefly held the world record for the distance over which electromagnetic waves could be detected, although when he presented his results at the British Association meeting in 1896, he discovered he had been outdone by Guglielmo Marconi, whose radio waves had sent a message across nearly . | 1 | Applied and Interdisciplinary Chemistry |
HMB is sold as an over-the-counter dietary supplement in the free acid form, β-hydroxy β-methylbutyric acid (HMB-FA), and as a monohydrated calcium salt of the conjugate base, calcium monohydrate (HMB-Ca, CaHMB). Since only a small fraction of HMB's metabolic precursor, , is metabolized into HMB, pharmacologically active concentrations of the compound in blood plasma and muscle can only be achieved by supplementing HMB directly. A healthy adult produces approximately 0.3 grams per day, while supplemental HMB is usually taken in doses of grams per day. HMB is sold at a cost of about per month when taken in doses of 3 grams per day. HMB is also contained in several nutritional products and medical foods marketed by Abbott Laboratories (e.g., certain formulations of Ensure and Juven), and is present in insignificant quantities in certain foods, such as alfalfa, asparagus, avocados, cauliflower, grapefruit, and catfish. | 1 | Applied and Interdisciplinary Chemistry |
Ingested methylmercury is readily and completely absorbed by the gastrointestinal tract. It is mostly found complexed with free cysteine and with proteins and peptides containing that amino acid. The methylmercuric-cysteinyl complex is recognized by amino acids transporting proteins in the body as methionine, another essential amino acid. Because of this mimicry, it is transported freely throughout the body including across the blood–brain barrier and across the placenta, where it is absorbed by the developing fetus. Also for this reason as well as its strong binding to proteins, methylmercury is not readily eliminated. Methylmercury has a half-life in human blood of about 50 days.
Several studies indicate that methylmercury is linked to subtle developmental deficits in children exposed in utero such as loss of IQ points, and decreased performance in tests of language skills, memory function and attention deficits. Methylmercury exposure in adults has also been linked to increased risk of cardiovascular disease including heart attack. Some evidence also suggests that methylmercury can cause autoimmune effects in sensitive individuals. Despite some concerns about the relationship between methylmercury exposure and autism, there are few data that support such a link. Although there is no doubt that methylmercury is toxic in several respects, including through exposure of the developing fetus, there is still some controversy as to the levels of methylmercury in the diet that can result in adverse effects. Recent evidence suggests that the developmental and cardiovascular toxicity of methylmercury may be mitigated by co-exposures to omega-3 fatty acids and perhaps selenium, both found in fish and elsewhere.
There have been several episodes in which large numbers of people were severely poisoned by food contaminated with high levels of methylmercury, notably the dumping of industrial waste that resulted in the pollution and subsequent mass poisoning in Minamata and Niigata, Japan and the situation in Iraq in the 1960s and 1970s in which wheat treated with methylmercury as a preservative and intended as seed grain was fed to animals and directly consumed by people (see Basra poison grain disaster). These episodes resulted in neurological symptoms including paresthesias, loss of physical coordination, difficulty in speech, narrowing of the visual field, hearing impairment, blindness, and death. Children who had been exposed in utero through their mothers' ingestion were also affected with a range of symptoms including motor difficulties, sensory problems and intellectual disability.
At present, exposures of this magnitude are rarely seen and are confined to isolated incidents. Accordingly, concern over methylmercury pollution is currently focused on more subtle effects that may be linked to levels of exposure presently seen in populations with high to moderate levels of dietary fish consumption. These effects are not necessarily identifiable on an individual level or may not be uniquely recognizable as due to methylmercury. However, such effects may be detected by comparing populations with different levels of exposure. There are isolated reports of various clinical health effects in individuals who consume large amounts of fish; however, the specific health effects and exposure patterns have not been verified with larger, controlled studies.
Many governmental agencies, the most notable ones being the United States Environmental Protection Agency (EPA), the United States Food and Drug Administration (FDA), Health Canada, and the European Union Health and Consumer Protection Directorate-General, as well as the World Health Organization (WHO) and the United Nations Food and Agriculture Organization (FAO), have issued guidance for fish consumers that is designed to limit methylmercury exposure from fish consumption. At present, most of this guidance is based on protection of the developing fetus; future guidance, however, may also address cardiovascular risk. In general, fish consumption advice attempts to convey the message that fish is a good source of nutrition and has significant health benefits, but that consumers, in particular pregnant women, women of child-bearing age, nursing mothers, and young children, should avoid fish with high levels of methylmercury, limit their intake of fish with moderate levels of methylmercury, and consume fish with low levels of methylmercury no more than twice a week. | 0 | Theoretical and Fundamental Chemistry |
As in simpler alkanes, carbon in the CFCs bond with tetrahedral symmetry. Because the fluorine and chlorine atoms differ greatly in size and effective charge from hydrogen and from each other, the methane-derived CFCs deviate from perfect tetrahedral symmetry.
The physical properties of CFCs and HCFCs are tunable by changes in the number and identity of the halogen atoms. In general, they are volatile but less so than their parent alkanes. The decreased volatility is attributed to the molecular polarity induced by the halides, which induces intermolecular interactions. Thus, methane boils at −161 °C whereas the fluoromethanes boil between −51.7 (CFH) and −128 °C (CF). The CFCs have still higher boiling points because the chloride is even more polarizable than fluoride. Because of their polarity, the CFCs are useful solvents, and their boiling points make them suitable as refrigerants. The CFCs are far less flammable than methane, in part because they contain fewer C-H bonds and in part because, in the case of the chlorides and bromides, the released halides quench the free radicals that sustain flames.
The densities of CFCs are higher than their corresponding alkanes. In general, the density of these compounds correlates with the number of chlorides.
CFCs and HCFCs are usually produced by halogen exchange starting from chlorinated methanes and ethanes. Illustrative is the synthesis of chlorodifluoromethane from chloroform:
:HCCl + 2 HF → HCFCl + 2 HCl
Brominated derivatives are generated by free-radical reactions of hydrochlorofluorocarbons, replacing C-H bonds with C-Br bonds. The production of the anesthetic 2-bromo-2-chloro-1,1,1-trifluoroethane ("halothane") is illustrative:
:CFCHCl + Br → CFCHBrCl + HBr | 1 | Applied and Interdisciplinary Chemistry |
The building blocks of materials are the chemical elements. These can be identified by their atomic number Z, which is the number of protons in the nucleus. An element can have more than one value for N, the number of neutrons in the nucleus. The sum of these is the mass number, which is roughly equal to the atomic mass. Atoms with the same atomic number but different neutron numbers are called isotopes. A given isotope is identified by a letter for the element preceded by a superscript for the mass number. For example, two common isotopes of chlorine are Cl and Cl. There are about 1700 known combinations of Z and N, of which only about 260 are stable. However, most of the unstable isotopes do not occur in nature. In geochemistry, stable isotopes are used to trace chemical pathways and reactions, while radioactive isotopes are primarily used to date samples.
The chemical behavior of an atom – its affinity for other elements and the type of bonds it forms – is determined by the arrangement of electrons in orbitals, particularly the outermost (valence) electrons. These arrangements are reflected in the position of elements in the periodic table. Based on position, the elements fall into the broad groups of alkali metals, alkaline earth metals, transition metals, semi-metals (also known as metalloids), halogens, noble gases, lanthanides and actinides.
Another useful classification scheme for geochemistry is the Goldschmidt classification, which places the elements into four main groups. Lithophiles combine easily with oxygen. These elements, which include Na, K, Si, Al, Ti, Mg and Ca, dominate in the Earths crust, forming silicates and other oxides. Siderophile elements (Fe, Co, Ni, Pt, Re, Os) have an affinity for iron and tend to concentrate in the core. Chalcophile elements (Cu, Ag, Zn, Pb, S) form sulfides; and atmophile' elements (O, N, H and noble gases) dominate the atmosphere. Within each group, some elements are refractory, remaining stable at high temperatures, while others are volatile, evaporating more easily, so heating can separate them. | 0 | Theoretical and Fundamental Chemistry |
Tm is an abbreviation for anionic tridentate ligand based on three imidazole-2-thioketone groups bonded to a borohydride center. They are examples of scorpionate ligands. Various ligands in this family are known, differing in what substituents are on the imidazoles. The most common is Tm, which has a methyl group on the nitrogen. It is easily prepared by the reaction of molten methimazole (1-methylimidazole-2-thione) with sodium borohydride, giving the sodium salt of the ligand. Salts of the Tm anion are known also for lithium and potassium. Other alkyl- and aryl-group variations are likewise named Tm according to those groups. | 0 | Theoretical and Fundamental Chemistry |
In Southeast Asia during the Vietnam War, the Rainbow Herbicides were a group of tactical-use chemicals used by the United States military. The environmental destruction caused by this defoliation has been described by Swedish Prime Minister Olof Palme, lawyers, historians and other academics as an ecocide. | 1 | Applied and Interdisciplinary Chemistry |
BEDT-TTF is the short form of bisethylenedithio-tetrathiafulvalene commonly abbreviated with ET. These molecules form planes which are separated by anions. The pattern of the molecules in the planes is not unique but there are several different phases growing, depending on the anion and the growth conditions. Important phases concerning superconductivity are the α- and θ- phase with the molecules ordering in a fishbone structure and the β- and especially κ-phase which order in a checkerboard structure with molecules being dimerized in the κ-phase. This dimerization makes the κ-phases special as they are not quarter- but half-filled systems, driving them into superconductivity at higher temperatures compared to the other phases.
The amount of possible anions separating two sheets of ET-molecules is nearly infinite. There are simple anions such as triiodide (), polymeric ones such as the very famous Cu[N(CN)]Br and anions containing solvents for example Ag(CF)·112DCBE. The electronic properties of the ET-based crystals are determined by its growing phase, its anion and by the external pressure applied. The external pressure needed to drive an ET-salt with insulating ground state to a superconducting one is much less than those needed for Bechgaard salts. For example, κ-(ET)Cu[N(CN)]Cl needs only a pressure of about 300 bar to become superconducting, which can be achieved by placing a crystal in grease frozen below and then providing sufficient stress to induce the superconducting transition. The crystals are very sensitive, which can be observed impressively in α-(ET)I lying several hours in the sun (or more controlled in an oven at ). After this treatment one gets α-(ET)I which is superconducting.
In contrast to the Fabre or Bechgaard salts universal phase diagrams for all the ET-based salts have only been proposed yet. Such a phase diagram would depend not only on temperature and pressure (i.e. bandwidth), but also on electronic correlations. In addition to the superconducting ground state these materials show charge-order, antiferromagnetism or remain metallic down to lowest temperatures. One compound is even predicted to be a spin liquid.
The highest transition temperatures at ambient pressure and with external pressure are both found in κ-phases with very similar anions. κ-(ET)Cu[N(CN)]Br becomes superconducting at T = 11.8 K at ambient pressure, and a pressure of 300 bar drives deuterated κ-(ET)Cu[N(CN)]Cl from an antiferromagnetic to a superconducting ground state with a transition temperature of T = 13.1 K. The following table shows only a few exemplary superconductors of this class. For more superconductors, see Lebed (2008) in the references.
Even more superconductors can be found by changing the ET-molecules slightly either by replacing the sulfur atoms by selenium (BEDT-TSF, BETS) or by oxygen (BEDO-TTF, BEDO).
Some two-dimensional organic superconductors of the κ-(ET)X and λ(BETS)X families are candidates for the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase when superconductivity is suppressed by an external magnetic field. | 0 | Theoretical and Fundamental Chemistry |
Physiological ketosis is the non-pathological (normal functioning) elevation of ketone bodies that can result from any state of increased fatty acid oxidation including fasting, prolonged exercise, or very low-carbohydrate diets such as the ketogenic diet. In physiological ketosis, serum ketone levels generally remain below 3 mM. | 1 | Applied and Interdisciplinary Chemistry |
Surface magnetic resonance (or magnetic resonance sounding) is based on the principle of nuclear magnetic resonance (NMR) and measurements can be used to indirectly estimate the water content of saturated and unsaturated zones in the earth's subsurface. SNMR is used to estimate aquifer properties, including quantity of water contained in the aquifer, porosity, and hydraulic conductivity. | 0 | Theoretical and Fundamental Chemistry |
* Cross-coupling reactions
** Castro-Stephens coupling
** Heck reaction
** Stille reaction
** Suzuki reaction
** Negishi coupling
** Kumada coupling
* Transmetalation | 0 | Theoretical and Fundamental Chemistry |
*[https://i-aps.org Inter-American Photochemical Society]
*[https://www.photochemistry.eu European Photochemistry Association]
*Asian and Oceanian Photochemistry Association | 0 | Theoretical and Fundamental Chemistry |
Primary aromatic amines yield diazonium ions in a solution of sodium nitrite. Upon heating this solution with copper(I) chloride, the diazonium group is replaced by -Cl. This is a comparatively easy method to make aryl halides as the gaseous product can be separated easily from aryl halide.
When an iodide is to be made, copper chloride is not needed. Addition of potassium iodide with gentle shaking produces the haloalkane. | 0 | Theoretical and Fundamental Chemistry |
Accurate detection and quantification are the most vital components of the TOC analysis process. Conductivity and non-dispersive infrared (NDIR) are the two common detection methods used in modern TOC analyzers. | 0 | Theoretical and Fundamental Chemistry |
In dairy cattle, ketosis commonly occurs during the first weeks after giving birth to a calf and is sometimes referred to as acetonemia. This is the result of an energy deficit when intake is inadequate to compensate for the increased metabolic demand of lactating. The elevated β-hydroxybutyrate concentrations can depress gluconeogenesis, feed intake and the immune system, as well as have an impact on milk composition. Point of care diagnostic tests can be useful to screen for ketosis in cattle.
In sheep, ketosis, evidenced by hyperketonemia with beta-hydroxybutyrate in blood over 0.7 mmol/L, is referred to as pregnancy toxemia. This may develop in late pregnancy in ewes bearing multiple fetuses and is associated with the considerable metabolic demands of the pregnancy. In ruminants, because most glucose in the digestive tract is metabolized by rumen organisms, glucose must be supplied by gluconeogenesis. Pregnancy toxemia is most likely to occur in late pregnancy due to metabolic demand from rapid fetal growth and may be triggered by insufficient feed energy intake due to weather conditions, stress or other causes. Prompt recovery may occur with natural parturition, Caesarean section or induced abortion. Prevention through appropriate feeding and other management is more effective than treatment of advanced stages of pregnancy toxemia. | 1 | Applied and Interdisciplinary Chemistry |
The daughter nuclide of a decay event may also be unstable (radioactive). In this case, it too will decay, producing radiation. The resulting second daughter nuclide may also be radioactive. This can lead to a sequence of several decay events called a decay chain (see this article for specific details of important natural decay chains). Eventually, a stable nuclide is produced. Any decay daughters that are the result of an alpha decay will also result in helium atoms being created.
Some radionuclides may have several different paths of decay. For example, % of bismuth-212 decays, through alpha-emission, to thallium-208 while % of bismuth-212 decays, through beta-emission, to polonium-212. Both thallium-208 and polonium-212 are radioactive daughter products of bismuth-212, and both decay directly to stable lead-208. | 0 | Theoretical and Fundamental Chemistry |
In HR-EBSD analysis, the lattice distortion field is calculated relative to a reference pattern or point (EBSP) per grain in the map, and is dependent on the lattice distortion at the point. The lattice distortion field in each grain is measured with respect to this point; therefore, the absolute lattice distortion at the reference point (relative to the unstrained crystal) is excluded from the HR-EBSD elastic strain and rotation maps. This ‘reference pattern problem’ is similar to the ‘d problem’ in X-ray diffraction, and affects the nominal magnitude of HR-EBSD stress fields. However, selecting the reference pattern (EBSP) plays a key role, as severely deformed EBSP adds phantom lattice distortions to the map values, thus, decreasing the measurement precision.
The local lattice distortion at the EBSP influences the resultant HR-EBSD map, e.g., a reference pattern deformed in tension will directly reduce the HR-EBSD map tensile strain magnitude while indirectly influencing the other component magnitude and the strains spatial distribution. Furthermore, the choice of EBSP slightly affects the GND density distribution and magnitude, and choosing a reference pattern with a higher GND density reduces the cross-correlation quality, changes the spatial distribution and induces more errors than choosing a reference pattern with high lattice distortion. Additionally, there is no apparent connection between EBSP’s IQ and EBSPs local lattice distortion.
The use of simulated reference patterns for absolute strain measurement is still an active area of research and scrutiny as difficulties arise from the variation of inelastic electron scattering with depth which limits the accuracy of dynamical diffraction simulation models, and imprecise determination of the pattern centre which leads to phantom strain components which cancel out when using experimentally acquired reference patterns. Other methods assumed that absolute strain at EBSP can be determined using crystal plasticity finite-element (CPFE) simulations, which then can be then combined with the HR-EBSD data (e.g., using linear ‘top-up’ method or displacement integration) to calculate the absolute lattice distortions.
In addition, GND density estimation is nominally insensitive to (or negligibly dependent upon) EBSP choice, as only neighbour point-to-point differences in the lattice rotation maps are used for GND density calculation. However, this assumes that the absolute lattice distortion of EBSP only changes the relative lattice rotation map components by a constant value which vanishes during derivative operations, i.e., lattice distortion distribution is insensitive to EBSP choice. | 0 | Theoretical and Fundamental Chemistry |
FAHFAs (fatty acid esters of hydroxy fatty acids) are formed in adipose tissue, improve glucose tolerance and also reduce adipose tissue inflammation. Palmitic acid esters of hydroxy-stearic acids (PAHSAs) are among the most bioactive members able to activate G-protein coupled receptors 120. Docosahexaenoic acid ester of hydroxy-linoleic acid (DHAHLA) exert anti-inflammatory and pro-resolving properties. | 1 | Applied and Interdisciplinary Chemistry |
This is the most common use for galvanized metal, and hundreds of thousands of tons of steel products are galvanized annually worldwide. In developed countries most larger cities have several galvanizing factories, and many items of steel manufacture are galvanized for protection. Typically these include: street furniture, building frameworks, balconies, verandahs, staircases, ladders, walkways, and more. Hot dip galvanized steel is also used for making steel frames as a basic construction material for steel frame buildings. | 1 | Applied and Interdisciplinary Chemistry |
On April 13, 2024, Kang married Busan MBC weathercaster Jung Min-kyung, whom he started dating prior to Phantom Singer 2. | 1 | Applied and Interdisciplinary Chemistry |
Because her interests leaned to the humanities, Weeks was drawn to the history of chemistry. Initially, she wrote about the elements as a hobby. From 1932-1933, while at the University of Kansas, Weeks wrote a series of 21 articles on the discovery of the elements for the Journal of Chemical Education.
Due to demand for reprints, the articles were collected and published in book form in 1933. Discovery of the Elements went through multiple editions. Both book and the earlier articles were liberally illustrated with pictures of chemists from the collection of Frank B. Dains, an older Kansas colleague of Weeks.
By 1968, Discovery of the Elements had appeared in seven editions, and had been updated to include the 94 elements that were discovered between 1524 and 1964. Editions included a wartime release in limited numbers due to restrictions on use of paper. The book had been translated into multiple languages. Weeks, who spoke French, German, Italian, Japanese, Spanish, Swedish, and Russian, focused on translation for much of her time at Wayne State University.
The seventh edition was identified as a "classic of chemistry". It was hailed as "a new edition of an old favorite", a "definitive and unique work" whose "value is well established and recognized by all". Revised by Weeks and Henry M. Leicester, it contained 2,688 references and 373 illustrations. Her work was one of the inspirations for The Lost Elements: The Periodic Tables Shadow Side' (2015). | 1 | Applied and Interdisciplinary Chemistry |
An effective sample preparation protocol, usually involving either liquid-liquid extraction (LLE) or solid phase extraction (SPE) and frequently derivatisation can remove ion suppressing species from the sample matrix prior to analysis. These common approaches may also remove other interferences, such as isobaric species.
Protein precipitation is another method that can be employed for small molecule analysis. Removal of all protein species from the sample matrix may be effective in some cases, although for many analytes, ion suppressing species are not of protein origin and so this technique is often used in conjunction with extraction and derivatisation. | 0 | Theoretical and Fundamental Chemistry |
During periods of high blood sugar, glucose 6-phosphate from glycolysis is diverted to the glycogen-storing pathway. It is changed to glucose-1-phosphate by phosphoglucomutase and then to UDP-glucose by UTP--glucose-1-phosphate uridylyltransferase. Glycogen synthase adds this UDP-glucose to a glycogen chain. | 1 | Applied and Interdisciplinary Chemistry |
Airbeams, inflatable spars, inflatable wings, and tensairity-enhanced inflatable bladders provide a means to structure practical objects.
Inflatable ballute structures have been proposed for use during aerocapture, aerobraking and atmospheric entry of cubesat and nanosat satellites. The inflatable structures for these applications may take a variety of engineered shapes including stacked toroidal, tension cone and isotensoid ballute form factors.
Inflatable space habitats have been proposed since the 1960s and one expandable space station is currently planned for launch in 2015. | 1 | Applied and Interdisciplinary Chemistry |
The epiglottis is a flap of elastic cartilage attached to the entrance of the larynx. It is covered with a mucous membrane and there are taste buds on its lingual surface which faces into the mouth. Its laryngeal surface faces into the larynx. The epiglottis functions to guard the entrance of the glottis, the opening between the vocal folds. It is normally pointed upward during breathing with its underside functioning as part of the pharynx, but during swallowing, the epiglottis folds down to a more horizontal position, with its upper side functioning as part of the pharynx. In this manner it prevents food from going into the trachea and instead directs it to the esophagus, which is behind. During swallowing, the backward motion of the tongue forces the epiglottis over the glottis' opening to prevent any food that is being swallowed from entering the larynx which leads to the lungs; the larynx is also pulled upwards to assist this process. Stimulation of the larynx by ingested matter produces a strong cough reflex in order to protect the lungs. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.