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The gray is conventionally used to express the severity of what are known as "tissue effects" from doses received in acute exposure to high levels of ionizing radiation. These are effects that are certain to happen, as opposed to the uncertain effects of low levels of radiation that have a probability of causing damage. A whole-body acute exposure to 5 grays or more of high-energy radiation usually leads to death within 14 days. LD is 2.5 Gy, LD is 5 Gy and LD is 8 Gy. The LD dose represents 375 joules for a 75 kg adult. | 0 | Theoretical and Fundamental Chemistry |
The chirality of a molecule is based on the molecular symmetry of its conformations. A conformation of a molecule is chiral if and only if it belongs to the C, D, T, O, I point groups (the chiral point groups). However, whether the molecule itself is considered to be chiral depends on whether its chiral conformations are persistent isomers that could be isolated as separated enantiomers, at least in principle, or the enantiomeric conformers rapidly interconvert at a given temperature and timescale through low-energy conformational changes (rendering the molecule achiral). For example, despite having chiral gauche conformers that belong to the C point group, butane is considered achiral at room temperature because rotation about the central C–C bond rapidly interconverts the enantiomers (3.4 kcal/mol barrier). Similarly, cis-1,2-dichlorocyclohexane consists of chair conformers that are nonidentical mirror images, but the two can interconvert via the cyclohexane chair flip (~10 kcal/mol barrier). As another example, amines with three distinct substituents (RRRN:) are also regarded as achiral molecules because their enantiomeric pyramidal conformers rapidly invert and interconvert through a planar transition state (~6 kcal/mol barrier).
However, if the temperature in question is low enough, the process that interconverts the enantiomeric chiral conformations becomes slow compared to a given timescale. The molecule would then be considered to be chiral at that temperature. The relevant timescale is, to some degree, arbitrarily defined: 1000 seconds is sometimes employed, as this is regarded as the lower limit for the amount of time required for chemical or chromatographic separation of enantiomers in a practical sense. Molecules that are chiral at room temperature due to restricted rotation about a single bond (barrier to rotation ≥ ca. 23 kcal/mol) are said to exhibit atropisomerism.
A chiral compound can contain no improper axis of rotation (S), which includes planes of symmetry and inversion center. Chiral molecules are always dissymmetric (lacking S) but not always asymmetric (lacking all symmetry elements except the trivial identity). Asymmetric molecules are always chiral.
The following table shows some examples of chiral and achiral molecules, with the Schoenflies notation of the point group of the molecule. In the achiral molecules, X and Y (with no subscript) represent achiral groups, whereas X and X or Y and Y represent enantiomers. Note that there is no meaning to the orientation of an S axis, which is just an inversion. Any orientation will do, so long as it passes through the center of inversion. Also note that higher symmetries of chiral and achiral molecules also exist, and symmetries that do not include those in the table, such as the chiral C or the achiral S.
An example of a molecule that does not have a mirror plane or an inversion and yet would be considered achiral is 1,1-difluoro-2,2-dichlorocyclohexane (or 1,1-difluoro-3,3-dichlorocyclohexane). This may exist in many conformers (conformational isomers), but none of them has a mirror plane. In order to have a mirror plane, the cyclohexane ring would have to be flat, widening the bond angles and giving the conformation a very high energy. This compound would not be considered chiral because the chiral conformers interconvert easily.
An achiral molecule having chiral conformations could theoretically form a mixture of right-handed and left-handed crystals, as often happens with racemic mixtures of chiral molecules (see Chiral resolution#Spontaneous resolution and related specialized techniques), or as when achiral liquid silicon dioxide is cooled to the point of becoming chiral quartz. | 0 | Theoretical and Fundamental Chemistry |
The colour change from morphine is proposed to be a result of two molecules of morphine and two molecules of formaldehyde condensing to the dimeric product which is protonated to the oxocarbenium salt. | 0 | Theoretical and Fundamental Chemistry |
RuBisCO is one of many enzymes in the Calvin cycle. When Rubisco facilitates the attack of at the C2 carbon of RuBP and subsequent bond cleavage between the C3 and C2 carbon, 2 molecules of glycerate-3-phosphate are formed. The conversion involves these steps: enolisation, carboxylation, hydration, C-C bond cleavage, and protonation. | 0 | Theoretical and Fundamental Chemistry |
Wood particles used to make various types of products rely on particle-size analysis to maintain high quality standards. By doing so, companies reduce waste and become more productive. | 0 | Theoretical and Fundamental Chemistry |
The first symptoms of apitoxin (bee venom), that are now thought to be caused by apamin, were described back in 1936 by Hahn and Leditschke. Apamin was first isolated by Habermann in 1965 from Apis mellifera, the Western honey bee. Apamin was named after this bee. Bee venom contains many other compounds, like histamine, phospholipase A2, hyaluronidase, MCD peptide, and the main active component melittin. Apamin was separated from the other compounds by gel filtration and ion exchange chromatography. | 1 | Applied and Interdisciplinary Chemistry |
Water clarity is measured using multiple techniques. These measurements include: Secchi depth, light attenuation, turbidity, beam attenuation, absorption by colored dissolved organic matter, the concentration of chlorophyll-a pigment, and the concentration of total suspended solids. Clear water generally has a deep Secchi depth, low light attenuation (deeper light penetration), low turbidity, low beam attenuation, and low concentrations of dissolved substances, chlorophyll-a, and/or total suspended solids. More turbid water generally has a shallow Secchi depth, high light attenuation (less light penetration to depth), high turbidity, high beam attenuation, and high concentrations of dissolved substances, chlorophyll-a, and/or total suspended solids. | 0 | Theoretical and Fundamental Chemistry |
Pauling first proposed the concept of electronegativity in 1932 to explain why the covalent bond between two different atoms (A–B) is stronger than the average of the A–A and the B–B bonds. According to valence bond theory, of which Pauling was a notable proponent, this "additional stabilization" of the heteronuclear bond is due to the contribution of ionic canonical forms to the bonding.
The difference in electronegativity between atoms A and B is given by:
where the dissociation energies, E, of the A–B, A–A and B–B bonds are expressed in electronvolts, the factor (eV) being included to ensure a dimensionless result. Hence, the difference in Pauling electronegativity between hydrogen and bromine is 0.73 (dissociation energies: H–Br, 3.79 eV; H–H, 4.52 eV; Br–Br 2.00 eV)
As only differences in electronegativity are defined, it is necessary to choose an arbitrary reference point in order to construct a scale. Hydrogen was chosen as the reference, as it forms covalent bonds with a large variety of elements: its electronegativity was fixed first at 2.1, later revised to 2.20. It is also necessary to decide which of the two elements is the more electronegative (equivalent to choosing one of the two possible signs for the square root). This is usually done using "chemical intuition": in the above example, hydrogen bromide dissolves in water to form H and Br ions, so it may be assumed that bromine is more electronegative than hydrogen. However, in principle, since the same electronegativities should be obtained for any two bonding compounds, the data are in fact overdetermined, and the signs are unique once a reference point has been fixed (usually, for H or F).
To calculate Pauling electronegativity for an element, it is necessary to have data on the dissociation energies of at least two types of covalent bonds formed by that element. A. L. Allred updated Pauling's original values in 1961 to take account of the greater availability of thermodynamic data, and it is these "revised Pauling" values of the electronegativity that are most often used.
The essential point of Pauling electronegativity is that there is an underlying, quite accurate, semi-empirical formula for dissociation energies, namely:
or sometimes, a more accurate fit
These are approximate equations but they hold with good accuracy. Pauling obtained the first equation by noting that a bond can be approximately represented as a quantum mechanical superposition of a covalent bond and two ionic bond-states. The covalent energy of a bond is approximate, by quantum mechanical calculations, the geometric mean of the two energies of covalent bonds of the same molecules, and there is additional energy that comes from ionic factors, i.e. polar character of the bond.
The geometric mean is approximately equal to the arithmetic mean—which is applied in the first formula above—when the energies are of a similar value, e.g., except for the highly electropositive elements, where there is a larger difference of two dissociation energies; the geometric mean is more accurate and almost always gives positive excess energy, due to ionic bonding. The square root of this excess energy, Pauling notes, is approximately additive, and hence one can introduce the electronegativity. Thus, it is these semi-empirical formulas for bond energy that underlie the concept of Pauling electronegativity.
The formulas are approximate, but this rough approximation is in fact relatively good and gives the right intuition, with the notion of the polarity of the bond and some theoretical grounding in quantum mechanics. The electronegativities are then determined to best fit the data.
In more complex compounds, there is an additional error since electronegativity depends on the molecular environment of an atom. Also, the energy estimate can be only used for single, not for multiple bonds. The enthalpy of formation of a molecule containing only single bonds can subsequently be estimated based on an electronegativity table, and it depends on the constituents and the sum of squares of differences of electronegativities of all pairs of bonded atoms. Such a formula for estimating energy typically has a relative error on the order of 10% but can be used to get a rough qualitative idea and understanding of a molecule. | 0 | Theoretical and Fundamental Chemistry |
Van de Flierdt grew up in rural western Germany. In 2000 van de Flierdt completed a diploma in Geology at the University of Bonn. She earned a PhD at ETH Zurich in 2003, working with Alexander Halliday. | 0 | Theoretical and Fundamental Chemistry |
The Lippmann–Schwinger equation (named after Bernard Lippmann and Julian Schwinger) is one of the most used equations to describe particle collisions – or, more precisely, scattering – in quantum mechanics. It may be used in scattering of molecules, atoms, neutrons, photons or any other particles and is important mainly in atomic, molecular, and optical physics, nuclear physics and particle physics, but also for seismic scattering problems in geophysics. It relates the scattered wave function with the interaction that produces the scattering (the scattering potential) and therefore allows calculation of the relevant experimental parameters (scattering amplitude and cross sections).
The most fundamental equation to describe any quantum phenomenon, including scattering, is the Schrödinger equation. In physical problems, this differential equation must be solved with the input of an additional set of initial and/or boundary conditions for the specific physical system studied. The Lippmann–Schwinger equation is equivalent to the Schrödinger equation plus the typical boundary conditions for scattering problems. In order to embed the boundary conditions, the Lippmann–Schwinger equation must be written as an integral equation. For scattering problems, the Lippmann–Schwinger equation is often more convenient than the original Schrödinger equation.
The Lippmann–Schwinger equation's general form is (in reality, two equations are shown below, one for the sign and other for the sign):
The potential energy describes the interaction between the two colliding systems. The Hamiltonian describes the situation in which the two systems are infinitely far apart and do not interact. Its eigenfunctions are and its eigenvalues are the energies . Finally, is a mathematical technicality necessary for the calculation of the integrals needed to solve the equation. It is a consequence of causality, ensuring that scattered waves consist only of outgoing waves. This is made rigorous by the limiting absorption principle. | 0 | Theoretical and Fundamental Chemistry |
* K. S. Krane, [https://doi.org/10.1007%2FBF02398283 Nuclear orientation and nuclear structure]. Hyperfine Interactions, Volume 43, Numbers 1–4, pages 3–14, December, 1988.
* B. Bleaney, [https://www.jstor.org/stable/53459 Cross-relaxation and nuclear orientation in ytterbium vanadate]. Proceedings: Mathematical, Physical and Engineering Sciences, Volume 455, Number 1988, pages 2835–2839, 8 August 1999. Published by The Royal Society.
* B. Bleaney, [https://doi.org/10.1007%2FBF03162437 Dynamic nuclear polarization and nuclear orientation in terbium vanadate]. Applied Magnetic Resonance, Volume 21, Number 1, pages 35–38, December, 1988. | 0 | Theoretical and Fundamental Chemistry |
Glass Circularity is a concept that aims towards achieving Circular economy by closing the life-cycle loop of glass. Circularity of glass can be achieved via reuse of post-consumer glasses or by recycling to get a unique product that can be used for several other purposes. Circularity of glass can help minimize the use of raw materials (sand), generation of landfilled waste and pollution emissions. For every 10% increase in the amount of recycled glass, or cullet, that is used to make containers, emissions are reduced by 5% and the amount of energy needed goes down 3%.
Finely ground recycled glass can be substituted for a portion of cement in concrete as fly ash and slag which if substituted, will help reduce the emission of given off as a by-product during concrete production. This can reduce the carbon footprint of concrete by 20-40%.
Also, recycled crushed glass (on its own or in blends with natural or recycled aggregates) can be used in a range of road work applications including subbase, embankments material and drainage media in roads. | 0 | Theoretical and Fundamental Chemistry |
Plasma processing, corona treatment, and flame treatment can all be classified as surface oxidation mechanisms. These methods all involve cleavage of polymer chains in the material and the incorporation of carbonyl, and hydroxyl functional groups. The incorporation of oxygen into the surface creates a higher surface energy allowing the substrate to be coated. | 0 | Theoretical and Fundamental Chemistry |
Several antibiotics exert their action by targeting the translation process in bacteria. They exploit the differences between prokaryotic and eukaryotic translation mechanisms to selectively inhibit protein synthesis in bacteria without affecting the host. | 1 | Applied and Interdisciplinary Chemistry |
Carbene dimerization is a type of organic reaction in which two carbene or carbenoid precursors react in a formal dimerization to an alkene. This reaction is often considered an unwanted side-reaction but it is also investigated as a synthetic tool. In this reaction type either the two carbenic intermediates react or a carbenic intermediate reacts with a carbene precursor. An early pioneer was Christoph Grundmann reporting on a carbene dimerisation in 1938. In the domain of persistent carbenes the Wanzlick equilibrium describes an equilibrium between a carbene and its alkene.
A reoccurring substrate is a diazo compound and more specifically an alpha-carbonyl diazo compound. For example, ethyl diazoacetate is converted to diethyl maleate using the ruthenium catalyst chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium:
Grubbs catalyst is also effective In this reaction type the active intermediate is a transition metal carbene complex. A diazo cross-coupling reaction has also been reported between ethyl diazoacetate and methyl phenyldiazoacetate' using the rhodium catalyst [Rh(OPiv)].
A direct metal carbene dimerization has been used in the synthesis of novel Polyalkynylethenes | 0 | Theoretical and Fundamental Chemistry |
In the absorption column (V) the hydrogen chloride compound of the saturated roast gas leaving the preconcentrator is adiabatically absorbed in water (which in many cases is acid rinse water from a carbon steel pickling line). Regenerated acid (typical strength: 18% wt/wt) is collected at absorption column bottom. | 0 | Theoretical and Fundamental Chemistry |
The attractive forces between polymer chains play a large part in determining the polymer's properties. Because polymer chains are so long, they have many such interchain interactions per molecule, amplifying the effect of these interactions on the polymer properties in comparison to attractions between conventional molecules. Different side groups on the polymer can lend the polymer to ionic bonding or hydrogen bonding between its own chains. These stronger forces typically result in higher tensile strength and higher crystalline melting points.
The intermolecular forces in polymers can be affected by dipoles in the monomer units. Polymers containing amide or carbonyl groups can form hydrogen bonds between adjacent chains; the partially positively charged hydrogen atoms in N-H groups of one chain are strongly attracted to the partially negatively charged oxygen atoms in C=O groups on another. These strong hydrogen bonds, for example, result in the high tensile strength and melting point of polymers containing urethane or urea linkages. Polyesters have dipole-dipole bonding between the oxygen atoms in C=O groups and the hydrogen atoms in H-C groups. Dipole bonding is not as strong as hydrogen bonding, so a polyesters melting point and strength are lower than Kevlars (Twaron), but polyesters have greater flexibility. Polymers with non-polar units such as polyethylene interact only through weak Van der Waals forces. As a result, they typically have lower melting temperatures than other polymers.
When a polymer is dispersed or dissolved in a liquid, such as in commercial products like paints and glues, the chemical properties and molecular interactions influence how the solution flows and can even lead to self-assembly of the polymer into complex structures. When a polymer is applied as a coating, the chemical properties will influence the adhesion of the coating and how it interacts with external materials, such as superhydrophobic polymer coatings leading to water resistance. Overall the chemical properties of a polymer are important elements for designing new polymeric material products. | 0 | Theoretical and Fundamental Chemistry |
Even with the same composition, morphology of the nanoparticles that make up the counter electrode play such an integral role in determining the efficiency of the overall photovoltaic. Because a material's electrocatalytic potential is highly dependent on the amount of surface area available to facilitate the diffusion and reduction of the redox species, numerous research efforts have been focused towards understanding and optimizing the morphology of nanostructures for DSSC counter electrodes.
In 2017, Huang et al. utilized various surfactants in a microemulsion-assisted hydrothermal synthesis of CoSe/CoSeO composite crystals to produce nanocubes, nanorods, and nanoparticles. Comparison of these three morphologies revealed that the hybrid composite nanoparticles, due to having the largest electroactive surface area, had the highest power conversion efficiency of 9.27%, even higher than its platinum counterpart. Not only that, the nanoparticle morphology displayed the highest peak current density and smallest potential gap between the anodic and cathodic peak potentials, thus implying the best electrocatalytic ability.
With a similar study but a different system, Du et al. in 2017 determined that the ternary oxide of NiCoO had the greatest power conversion efficiency and electrocatalytic ability as nanoflowers when compared to nanorods or nanosheets. Du et al. realized that exploring various growth mechanisms that help to exploit the larger active surface areas of nanoflowers may provide an opening for extending DSSC applications to other fields. | 0 | Theoretical and Fundamental Chemistry |
To describe the geometry of graphical surfaces that illustrate equilibrium relations between thermodynamic functions of state, no one can fictively think of so-called "reversible processes". They are convenient theoretical objects that trace paths across graphical surfaces. They are called "processes" but do not describe naturally occurring processes, which are always irreversible. Because the points on the paths are points of thermodynamic equilibrium, it is customary to think of the "processes" described by the paths as fictively "reversible". Reversible processes are always quasistatic processes, but the converse is not always true. | 0 | Theoretical and Fundamental Chemistry |
Ideality of solutions is analogous to ideality for gases, with the important difference that intermolecular interactions in liquids are strong and cannot simply be neglected as they can for ideal gases. Instead we assume that the mean strength of the interactions are the same between all the molecules of the solution.
More formally, for a mix of molecules of A and B, then the interactions between unlike neighbors (U) and like neighbors U and U must be of the same average strength, i.e., 2 U = U + U and the longer-range interactions must be nil (or at least indistinguishable). If the molecular forces are the same between AA, AB and BB, i.e., U = U = U, then the solution is automatically ideal.
If the molecules are almost identical chemically, e.g., 1-butanol and 2-butanol, then the solution will be almost ideal. Since the interaction energies between A and B are almost equal, it follows that there is only a very small overall energy (enthalpy) change when the substances are mixed. The more dissimilar the nature of A and B, the more strongly the solution is expected to deviate from ideality. | 0 | Theoretical and Fundamental Chemistry |
Molecular recognition takes place in a noisy, crowded biological environment and the recognizer often has to cope with the task of selecting its target among a variety of similar competitors. For example, the ribosome has to select the correct tRNA that matches the mRNA codon among many structurally similar tRNAs. If the recognizer and its correct target match perfectly like a lock and a key, then the binding probability will be high since no deformation is required upon binding. At the same time, the recognizer might also bind to a competitor with a similar structure with high probability. Introducing an energy barrier, in particular, structural mismatch between the recognizer (lock) and the key, reduces the binding probability to the correct target but reduces even more the binding probability to a similar wrong target and thus improves the specificity. Yet, introducing too much deformation drastically reduces binding probability to the correct target. Therefore, the optimal balance between maximizing the correct binding probability and minimizing the incorrect binding probability is achieved when the recognizer is slightly off target. This suggests that conformational changes during molecular recognition processes, such as the induced fit mechanism, are advantageous for enhancing the specificity of recognition. Such conformational changes may be fine-tuned by mutations that affect the mechanical response of the recognizer, also at positions far from the binding site. | 1 | Applied and Interdisciplinary Chemistry |
Plants that have been called glassworts include:
*Arthroceras subterminale (Parish's glasswort)
*Eriogonum salicornioides (glasswort buckwheat)
*Species in the genus Salicornia (glasswort or jointed glasswort):
**Salicornia bigelovii (dwarf glasswort)
**Salicornia blackiana (thick-head glasswort)
**Salicornia europaea (common glasswort or marsh samphire)
**Salicornia maritima (slender glasswort)
**Salicornia pacifica (Pacific glasswort)
**Salicornia perennis (perennial glasswort)
**Salicornia quinqueflora (beaded glasswort)
**Salicornia ramosissima (purple glasswort)
**Salicornia virginica (American, Virginia or woody glasswort)
*Salsola kali (prickly glasswort)
*Tecticornia:
**Tecticornia arbuscula (shrubby glasswort)
**Tecticornia flabelliformis (bead glasswort)
**Tecticornia pergranulata (blackseed glasswort) | 0 | Theoretical and Fundamental Chemistry |
A kinetic and regional chemical study of the Evelyn effect has been described. The results, in the Journal of Chemical Education, made claims involving the mechanism by which the dehydrations occurred.
The article looks into the claim of having E1 and E2 mechanisms occur in the reaction.
The researchers measured the kinetics of the formation of a 3 degree carbocation’s and compared them to theoretical calculations that would occur if the experiment ran as an E2 reaction. Instead, the reaction showed a mechanism that initially formed a 2 degree carbocation, utilizing an E1 pathway. Their conclusion was that the mechanism is neither E1 or E2 but rather “E-2 like”, exhibiting first order kinetics. | 0 | Theoretical and Fundamental Chemistry |
The organosilane is activated with fluoride (as some sort of salt such as TBAF or TASF) or a base to form a pentavalent silicon center which is labile enough to allow for the breaking of a C-Si bond during the transmetalation step. The general scheme to form this key intermediate is shown below. This step occurs in situ or at the same time as the catalytic cycle in the reaction.
The mechanism for the Hiyama coupling follows a catalytic cycle, including an A) oxidative addition step, in which the organic halide adds to the palladium oxidizing the metal from palladium(0) to palladium(II); a B) transmetalation step, in which the C-Si bond is broken and the second carbon fragment is bound to the palladium center; and finally C) a reductive elimination step, in which the C-C bond is formed and the palladium returns to its zero-valent state to start the cycle over again. The catalytic cycle is shown below. | 0 | Theoretical and Fundamental Chemistry |
A third mission, called EXPOSE-R2, was launched on 24 July 2014 aboard the Russian Progress M-24M, carrying 46 species of bacteria, fungi and arthropods, in 758 different samples that were exposed to different conditions, under different filters, and for various time periods. It was attached on 18 August 2014 to the exterior of the ISS on the Russian module Zvezda, and exposure was finished on 3 February 2016, and were stored inside the ISS until their return to Earth on 18 June 2016. Two main experiments (BIOMEX and BOSS) tested a desert strain of cyanobacterium called Chroococcidiopsis and Deinococcus geothermalis, as well as bacteria, yeast (including Kombucha culture,) archaea, algae, fungi, lichens and mosses, while the Biochip experiment will test affinity receptors to biomolecules. The organisms and organic compounds were exposed to partial and full space conditions for 12 to 18 months, and were returned to Earth in early 2016 for analyses.
* The Biology and Mars Experiment (BIOMEX). Its objective is to measure to what extent biomolecules, such as biological pigments, cellular components, and biofilms are resistant to and able to maintain their stability under space and Mars-like conditions. The results of BIOMEX will be relevant for space-proven biosignature definition and for building a biosignature data base.
:The secondary scientific objective of BIOMEX is to analyze to what extent selected terrestrial extremophiles are able to survive in space and to determine which interactions between biological samples and selected minerals (including terrestrial, Moon and Mars analogs) can be observed under space and Mars-like conditions. BIOMEX contains numerous chambers that are filled with biomolecules and organisms that include bacteria, archaea, algae, fungi, lichens and mosses. The samples will spend up to one and a half years outside the space station, and the organisms will be monitored with temperature sensors and dosimeters, which monitor radiation exposure. Scientists will continuously monitor the survival of the organisms and the stability of important cellular components like membrane lipids, pigments, proteins, and DNA. These investigations could thus enhance the chances of detecting organic traces of life on Mars. At the completion of the experiment, BIOMEX samples will be returned to Earth for study. BIOMEX is led by Jean-Pierre de Vera, from the German Aerospace Center (DLR), together with a team from 27 institutes in 12 countries.
* The second major experiment is called Biofilm Organisms Surfing Space (BOSS). The hypothesis to be tested is that "microorganisms grown as biofilms, hence embedded in self-produced extracellular polymeric substances, are more tolerant to space and Martian conditions compared to their planktonic counterparts." Two of the organisms being exposed are Deinococcus geothermalis and Chroococcidiopsis.
* The Biochip experiment will study the resistance of various biochip models to space constraints, especially cosmic radiation and extreme changes of temperature. Their detection principle is based on the recognition of a target molecule by affinity receptors (antibodies and aptamers) fixed on a solid surface. It is hoped it will eventually be deployed in planetary missions to help the search for biomolecules of past or present extraterrestrial life.
* The BIODIVERSITY experiment was provided by Russia. | 1 | Applied and Interdisciplinary Chemistry |
Cryoneurolysis, also referred to as cryoanalgesia, is a medical procedure that temporarily blocks nerve conduction along peripheral nerve pathways. The procedure, which inserts a small probe to freeze the target nerve, can facilitate complete regeneration of the structure and function of the affected nerve. Cryoneurolysis has been used to treat a variety of painful conditions. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, a cnoidal wave is a nonlinear and exact periodic wave solution of the Korteweg–de Vries equation. These solutions are in terms of the Jacobi elliptic function cn, which is why they are coined cnoidal waves. They are used to describe surface gravity waves of fairly long wavelength, as compared to the water depth.
The cnoidal wave solutions were derived by Korteweg and de Vries, in their 1895 paper in which they also propose their dispersive long-wave equation, now known as the Korteweg–de Vries equation. In the limit of infinite wavelength, the cnoidal wave becomes a solitary wave.
The Benjamin–Bona–Mahony equation has improved short-wavelength behaviour, as compared to the Korteweg–de Vries equation, and is another uni-directional wave equation with cnoidal wave solutions. Further, since the Korteweg–de Vries equation is an approximation to the Boussinesq equations for the case of one-way wave propagation, cnoidal waves are approximate solutions to the Boussinesq equations.
Cnoidal wave solutions can appear in other applications than surface gravity waves as well, for instance to describe ion acoustic waves in plasma physics. | 1 | Applied and Interdisciplinary Chemistry |
About 70% of the ingested imidapril is absorbed quickly from the gut; this percentage is reduced significantly when taken with a fatty meal. It reaches highest blood plasma concentrations after two hours and has a biological half-life of two hours. The substance is a prodrug and is activated to imidaprilat, which reaches highest plasma concentrations after 7 hours, has an initial half-life of 7 to 9 hours and a terminal half-life of more than 24 hours. The absolute bioavailability of imidaprilat is 42%.
About 40% of the drug is excreted via the urine and 50% via the bile and faeces. | 0 | Theoretical and Fundamental Chemistry |
According to the Vaisheshika school, all things that exist, that can be cognized and named are s (literal meaning: the meaning of a word), the objects of experience. All objects of experience can be classified into six categories, dravya (substance), (quality), karma (activity), (generality), (particularity) and (inherence). Later s ( and Udayana and ) added one more category abhava (non-existence). The first three categories are defined as artha (which can perceived) and they have real objective existence. The last three categories are defined as (product of intellectual discrimination) and they are logical categories.
# Dravya (substance): There are nine substances. They are, (earth), ap (water), tejas (fire), (air), (ether), (time), dik (space), (self or soul) and manas (mind). The first five are called s, the substances having some specific qualities so that they could be perceived by one or the other external senses.
# Guṇa (quality): The mentions 17 s (qualities), to which added another 7. While a substance is capable of existing independently by itself, a (quality) cannot exist so. The original 17 s (qualities) are, (colour), rasa (taste), gandha (smell), (touch), (number), (size/dimension/quantity), (individuality), (conjunction/accompaniments), (disjunction), (priority), aparatva (posteriority), buddhi (knowledge), sukha (pleasure), (pain), (desire), (aversion) and prayatna (effort). To these added gurutva (heaviness), dravatva (fluidity), sneha (viscosity), dharma (merit), adharma (demerit), (sound) and (faculty).
# Karma (activity): The karmas (activities) like s (qualities) have no separate existence, they belong to the substances. But while a quality is a permanent feature of a substance, an activity is a transient one. (ether), (time), dik (space) and (self), though substances, are devoid of karma (activity).
# Sāmānya (generality): Since there are plurality of substances, there will be relations among them. When a property is found common to many substances, it is called .
# (particularity): By means of , we are able to perceive substances as different from one another. As the ultimate atoms are innumerable so are the s.
# (inherence): defined as the relation between the cause and the effect. defined it as the relationship existing between the substances that are inseparable, standing to one another in the relation of the container and the contained. The relation of is not perceivable but only inferable from the inseparable connection of the substances.
# Abhava (non-existence) | 1 | Applied and Interdisciplinary Chemistry |
SBO has benefited from the funds of the European Molecular Biology Laboratory and the National Institute of General Medical Sciences. | 1 | Applied and Interdisciplinary Chemistry |
The SNIF-NMR is applied on pure (or purified) molecules. Therefore, some preparation steps may be required in the lab before analysis.
For example, for the SNIF-NMR of ethanol, according to official methods:
* Fermentation (for fruit juice)
* Quantitative extraction of ethanol by distillation
* Standardized preparation of NMR samples
* NMR acquisition
* Interpretation of results and report on the authenticity
At each step of the SNIF-NMR analysis, efforts should be made to avoid parasite isotopic fractionation. Control measures such as determining the alcoholic strength of the intermediate products of the analysis (fermented juice or distillate) are performed on each sample. | 0 | Theoretical and Fundamental Chemistry |
Coil coating is the continuous and highly automated industrial process for efficiently coating metal coils. Because the metal is treated before it is cut and formed, the entire surface is cleaned and treated, providing tightly-bonded finishes. (Formed parts can have many holes, recessed areas, valleys, and hidden areas that make it difficult to clean and uniformly paint.) Coil-coated metal (often called prepainted metal) is often considered more durable and more corrosion-resistant than most post painted metal.
Annually, 4.5 million tons of coil-coated steel and aluminum are produced and shipped in North America, and 5 million tons in Europe. In almost every five-year period since the early 1980s, the growth rate of coil-coated metal has exceeded the growth rates of either steel and/or aluminum production. | 1 | Applied and Interdisciplinary Chemistry |
In materials science, grain growth is the increase in size of grains (crystallites) in a material at high temperature. This occurs when recovery and recrystallisation are complete and further reduction in the internal energy can only be achieved by reducing the total area of grain boundary. The term is commonly used in metallurgy but is also used in reference to ceramics and minerals. The behaviors of grain growth is analogous to the coarsening behaviors of grains, which implied that both of grain growth and coarsening may be dominated by the same physical mechanism. | 1 | Applied and Interdisciplinary Chemistry |
The oxide crystal structure is based on a close-pack array of oxygen anions, with metal cations occupying interstitial sites. The close-packed arrays, such as face-centered-cubic (fcc) and hexagonal-close packed (hcp), have both octahedral and tetrahedral interstices. | 0 | Theoretical and Fundamental Chemistry |
In materials science, misorientation is the difference in crystallographic orientation between two crystallites in a polycrystalline material.
In crystalline materials, the orientation of a crystallite is defined by a transformation from a sample reference frame (i.e. defined by the direction of a rolling or extrusion process and two orthogonal directions) to the local reference frame of the crystalline lattice, as defined by the basis of the unit cell. In the same way, misorientation is the transformation necessary to move from one local crystal frame to some other crystal frame. That is, it is the distance in orientation space between two distinct orientations. If the orientations are specified in terms of matrices of direction cosines and , then the misorientation operator going from to can be defined as follows:
where the term is the reverse operation of , that is, transformation from crystal frame back to the sample frame. This provides an alternate description of misorientation as the successive operation of transforming from the first crystal frame () back to the sample frame and subsequently to the new crystal frame ().
Various methods can be used to represent this transformation operation, such as: Euler angles, Rodrigues vectors, axis/angle (where the axis is specified as a crystallographic direction), or unit quaternions. | 0 | Theoretical and Fundamental Chemistry |
A fluorogen is a ligand (fluorogenic ligand) which is not itself fluorescent, but when it is bound by a specific protein or RNA structure becomes fluorescent.
For instance, FAST is a variant of photoactive yellow protein which was engineered to bind chemical mimics of the GFP tripeptide chromophore.
Likewise, the spinach aptamer is an engineered RNA sequence which can bind GFP chromophore chemical mimics, thereby conferring conditional and reversible fluorescence on RNA molecules containing the sequence. | 1 | Applied and Interdisciplinary Chemistry |
Stepwise elongation, in which the amino acids are connected step-by-step in turn, is ideal for small peptides containing between 2 and 100 amino acid residues. Another method is fragment condensation, in which peptide fragments are coupled. Although the former can elongate the peptide chain without racemization, the yield drops if only it is used in the creation of long or highly polar peptides. Fragment condensation is better than stepwise elongation for synthesizing sophisticated long peptides, but its use must be restricted in order to protect against racemization. Fragment condensation is also undesirable since the coupled fragment must be in gross excess, which may be a limitation depending on the length of the fragment.
A new development for producing longer peptide chains is chemical ligation: unprotected peptide chains react chemoselectively in aqueous solution. A first kinetically controlled product rearranges to form the amide bond. The most common form of native chemical ligation uses a peptide thioester that reacts with a terminal cysteine residue.
Other methods applicable for covalently linking polypeptides in aqueous solution include the use of split inteins, spontaneous isopeptide bond formation and sortase ligation.
In order to optimize synthesis of long peptides, a method was developed in Medicon Valley for converting peptide sequences. The simple pre-sequence (e.g. Lysine (Lysn); Glutamic Acid (Glun); (LysGlu)n) that is incorporated at the C-terminus of the peptide to induce an alpha-helix-like structure. This can potentially increase biological half-life, improve peptide stability and inhibit enzymatic degradation without altering pharmacological activity or profile of action. | 1 | Applied and Interdisciplinary Chemistry |
Lynette Cegelski is an American physical chemist and chemical biologist who studies extracellular structures such as biofilms and membrane proteins. She is an associate professor of chemistry and, by courtesy, of chemical engineering at Stanford University. She is a Stanford Bio-X and Stanford ChEM-H affiliated faculty member. | 0 | Theoretical and Fundamental Chemistry |
Kowalski served as the inaugural director of the Center for Process Analytical Chemistry (CPAC), established in 1984, at the University of Washington. Initially CPAC was a National Science Foundation (NSF) Industry-University Cooperative Research Center (IUCRC). It has since been renamed Center for Process Analysis and Control and has become self-sustaining. Writing for Analytical Chemistry, Alan Newman called CPAC the "brainchild" of Kowalski, who proposed the idea in 1982, and said in the field of analytical chemistry, "CPAC offers a unique model of how chemists can successfully forge bonds with industry, government, and allied academic disciplines to foster new ideas. At the same time, the center establishes a two-way flow of ideas between basic researchers in academia and scientists in industry and government." | 0 | Theoretical and Fundamental Chemistry |
* Thioacetone (2-propanethione) A lightly studied organosulfur. Its smell is so potent it can be detected several hundred meters downwind mere seconds after a container is opened.
* Allyl thiol (2-propenethiol; allyl mercaptan; CH=CHCHSH) (garlic volatiles and garlic breath)
* (Methylthio)methanethiol (CHSCHSH), the "mouse thiol", found in mouse urine and functions as a semiochemical for female mice
* Ethanethiol, commonly called ethyl mercaptan (added to propane or other liquefied-petroleum gases used as fuel gases)
* 2-Methyl-2-propanethiol, commonly called tert-butyl mercaptan, is added as a blend of other components to natural gas used as fuel gas.
* Butane-1-thiol, commonly called butyl mercaptan, is a chemical intermediate.
* Grapefruit mercaptan (grapefruit)
* Methanethiol, commonly called methyl mercaptan (after eating Asparagus)
* Furan-2-ylmethanethiol, also called furfuryl mercaptan (roasted coffee)
* Benzyl mercaptan (leek or garlic-like) | 0 | Theoretical and Fundamental Chemistry |
Neutral methylene complexes undergo different chemical reactions depending on the pi character of the coordinate bond to the carbon centre. A weak contribution, such as in diazomethane, yields mainly substitution reactions, whereas a strong contribution, such as in ethenone, yields mainly addition reactions. Upon treatment with a standard base, complexes with a weak contribution convert to a metal methoxide. With strong acids (e.g., fluorosulfuric acid), they can be protonated to give . Oxidation of these complexes yields formaldehyde, and reduction yields methane.
Free methylene undergoes the typical chemical reactions of a carbene. Addition reactions are very fast and exothermic.
When the methylene molecule is in its state of lowest energy, the unpaired valence electrons are in separate atomic orbitals with independent spins, a configuration known as triplet state.
Methylene may gain an electron yielding a monovalent anion methanidyl (), which can be obtained as the trimethylammonium (()) salt by the reaction of phenyl sodium () with trimethylammonium bromide (()). The ion has bent geometry, with a H-C-H angle of about 103°. | 0 | Theoretical and Fundamental Chemistry |
MHD has no moving parts, which means that a good design might be silent, reliable, and efficient. Additionally, the MHD design eliminates many of the wear and friction pieces of the drivetrain with a directly driven propeller by an engine. Problems with current technologies include expense and slow speed compared to a propeller driven by an engine. The extra expense is from the large generator that must be driven by an engine. Such a large generator is not required when an engine directly drives a propeller.
The first prototype, a 3-meter (10-feet) long submarine called EMS-1, was designed and tested in 1966 by Stewart Way, a professor of mechanical engineering at the University of California, Santa Barbara. Way, on leave from his job at Westinghouse Electric, assigned his senior year undergraduate students to build the operational unit. This MHD submarine operated on batteries delivering power to electrodes and electromagnets, which produced a magnetic field of 0.015 tesla. The cruise speed was about 0.4 meter per second (15 inches per second) during the test in the bay of Santa Barbara, California, in accordance with theoretical predictions.
Later, a Japanese prototype, the 3.6-meter long "ST-500", achieved speeds of up to 0.6 m/s in 1979.
In 1991, the worlds first full-size prototype Yamato 1' was completed in Japan after 6 years of research and development (R&D) by the Ship & Ocean Foundation (later known as the Ocean Policy Research Foundation). The ship successfully carried a crew of ten plus passengers at speeds of up to in Kobe Harbour in June 1992.
Small-scale ship models were later built and studied extensively in the laboratory, leading to successful comparisons between the measurements and the theoretical prediction of ship terminal speeds.
Military research about underwater MHD propulsion included high-speed torpedoes, remotely operated underwater vehicles (ROV), autonomous underwater vehicles (AUV), up to larger ones such as submarines. | 1 | Applied and Interdisciplinary Chemistry |
Demethylation is the chemical process resulting in the removal of a methyl group (CH) from a molecule. A common way of demethylation is the replacement of a methyl group by a hydrogen atom, resulting in a net loss of one carbon and two hydrogen atoms.
The counterpart of demethylation is methylation. | 0 | Theoretical and Fundamental Chemistry |
In electromagnetism, the Townsend discharge or Townsend avalanche is an ionisation process for gases where free electrons are accelerated by an electric field, collide with gas molecules, and consequently free additional electrons. Those electrons are in turn accelerated and free additional electrons. The result is an avalanche multiplication that permits significantly increased electrical conduction through the gas. The discharge requires a source of free electrons and a significant electric field; without both, the phenomenon does not occur.
The Townsend discharge is named after John Sealy Townsend, who discovered the fundamental ionisation mechanism by his work circa 1897 at the Cavendish Laboratory, Cambridge. | 0 | Theoretical and Fundamental Chemistry |
A pneumatic motor (air motor), or compressed-air engine, is a type of motor which does mechanical work by expanding compressed air. Pneumatic motors generally convert the compressed-air energy to mechanical work through either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor, piston air motor, air turbine or gear type motor.
Pneumatic motors have existed in many forms over the past two centuries, ranging in size from hand-held motors to engines of up to several hundred horsepower. Some types rely on pistons and cylinders; others on slotted rotors with vanes (vane motors) and others use turbines. Many compressed-air engines improve their performance by heating the incoming air or the engine itself. Pneumatic motors have found widespread success in the hand-held tool industry, but are also used stationary in a wide range of industrial applications. Continual attempts are being made to expand their use to the transportation industry. However, pneumatic motors must overcome inefficiencies before being seen as a viable option in the transportation industry. | 1 | Applied and Interdisciplinary Chemistry |
The detected hemolithin protein was reported to have been found inside two CV3 meteorites Allende and Acfer 086. Acfer-086, where the complete molecule was detected rather than fragments (Allende), was discovered in Agemour, Algeria in 1990. | 0 | Theoretical and Fundamental Chemistry |
Neutrinoless double beta decay (0νββ) is a commonly proposed and experimentally pursued theoretical radioactive decay process that would prove a Majorana nature of the neutrino particle. To this day, it has not been found.
The discovery of neutrinoless double beta decay could shed light on the absolute neutrino masses and on their mass hierarchy (Neutrino mass). It would mean the first ever signal of the violation of total lepton number conservation. A Majorana nature of neutrinos would confirm that the neutrino is its own antiparticle.
To search for neutrinoless double beta decay, there are currently a number of experiments underway, with several future experiments for increased sensitivity proposed as well. | 0 | Theoretical and Fundamental Chemistry |
In order to visualize functional relations and provide better understanding of experimental data, the graphical interface emphasize user interactivity and functional interconnection. There are two visualization tools in the suite: one depicting single material while another being focused on intergrowths of two different materials. | 0 | Theoretical and Fundamental Chemistry |
Cobalts trichloride was detected in 1952 by Schäfer and Krehl in the gas phase when cobalt(II) chloride is heated in an atmosphere of chlorine . The trichloride is formed through the equilibrium
At 918 K (below the melting point of , 999 K), the trichloride was the predominant cobalt species in the vapor, with partial pressure of 0.72 mm Hg versus 0.62 for the dichloride. However, equilibrium shifts to the left at higher temperatures. At 1073 K, the partial pressures were 7.3 and 31.3 mm Hg, respectively.
Cobalt trichloride, in amounts sufficient to study spectroscopically, was obtained by Green and others in 1983, by sputtering cobalt electrodes with chlorine atoms and trapping the resulting molecules in frozen argon at 14 K.
A report from 1969 claims that treatment of solid cobalt(III) hydroxide · with anhydrous ether saturated with at −20 °C produces a green solution (stable at −78 °C) with the characteristic spectrum of .
In a 1932 report, the compound was claimed to arise in the electrolysis of cobalt(II) chloride in anhydrous ethanol. | 0 | Theoretical and Fundamental Chemistry |
The Wnt protein family includes a large number of cysteine-rich glycoproteins. The Wnt proteins activate signal transduction cascades via three different pathways, the canonical Wnt pathway, the noncanonical planar cell polarity (PCP) pathway, and the noncanonical Wnt/Ca pathway. Wnt proteins appear to control a wide range of developmental processes and have been seen as necessary for control of spindle orientation, cell polarity, cadherin mediated adhesion, and early development of embryos in many different organisms. Current research has indicated that deregulation of Wnt signaling plays a role in tumor formation, because at a cellular level, Wnt proteins often regulated cell proliferation, cell morphology, cell motility, and cell fate. | 1 | Applied and Interdisciplinary Chemistry |
As the temperature decreases, further physiological systems falter and heart rate, respiratory rate, and blood pressure all decrease. This results in an expected heart rate in the 30s at a temperature of .
There is often cold, inflamed skin, hallucinations, lack of reflexes, fixed dilated pupils, low blood pressure, pulmonary edema, and shivering is often absent. Pulse and respiration rates decrease significantly, but fast heart rates (ventricular tachycardia, atrial fibrillation) can also occur. Atrial fibrillation is not typically a concern in and of itself. | 1 | Applied and Interdisciplinary Chemistry |
crystallizes in two forms (polymorphs). At room temperature, the compound is stable in the orthorhombic cotunnite (Lead(II) chloride|) structure, whereas the cubic fluorite structure (calcium fluoride|) is stable between 925 and 963 °C. Both polymorphs accommodate the preference of the large ion for coordination numbers greater than six. The coordination of is 8 in the fluorite structure and 9 in the cotunnite structure. When cotunnite-structure is subjected to pressures of 7–10 GPa, it transforms to a third structure, a monoclinic post-cotunnite phase. The coordination number of increases from 9 to 10.
In aqueous solution behaves as a simple salt; in water it is a 1:2 electrolyte and the solution exhibits a neutral pH. Its solutions react with sulfate ion to produce a thick white solid precipitate of barium sulfate.
This precipitation reaction is used in chlor-alkali plants to control the sulfate concentration in the feed brine for electrolysis.
Oxalate effects a similar reaction:
When it is mixed with sodium hydroxide, it gives barium hydroxide, which is moderately soluble in water.
is stable in the air at room temperature, but loses one water of crystallization above , becoming , and becomes anhydrous above . may be formed by shaking the dihydrate with methanol.
readily forms eutectics with alkali metal chlorides. | 0 | Theoretical and Fundamental Chemistry |
When the ribosome movement on the mRNA is not linear, the ribosome gets paused at different regions without a precise reason. The ribosome pause position will help to identify the mRNA sequence features, structure, and the transacting factor that modulates this process. The advantage of ribosomal pause sites that are located at protein domain boundaries are aiding the folding of a protein. There are times when the ribosomal pause does not cause an advantage and it needs to be restricted. In translation, elF5A inhibits ribosomal pausing for translation to function better. Ribosomal pausing can cause more non-canonical start codons without elF5A in eukaryotic cells. When there is a lack of elF5A in the eukaryotic cell, it can cause an increase in ribosomal pausing. The ribosomal pausing process can also be used by amino acids to control translation. | 1 | Applied and Interdisciplinary Chemistry |
* R. Tao, Editor (2011). Electro-Rheological Fluids And Magneto-Rheological Suspensions: Proceedings of the 12th International Conference. World Scientific. .
*[http://spie.org/x648.html?product_id=731251 Chunlin Miao, et al., "Magnetorheological fluid template for basic studies of mechanical-chemical effects during polishing," Proceedings of SPIE, Vol. 6671 pp. 667110 (2007), abstract and full text (pdf)]
*Stanway, R – Smart Fluids: Current and Future Developments. Materials Science and Technology, 20, pp931–939, 2004
*Jolly, M R; Bender, J W and Carlson D J – Properties and Applications of Commercial Magnetorheological Fluids. SPIE 5th Annual Int Symposium on Smart Structures and Materials, 1998. | 1 | Applied and Interdisciplinary Chemistry |
Herman was born on 24 March 1934 in Libušín. He studied physical chemistry and radiochemistry at the School of Mathematics and Physics of Charles University, Prague (1952–1957). He then joined the Institute of Physical Chemistry of the Czech Academy of Sciences, to which he remained affiliated.
Herman's early work, with Vladimír Čermák concerned mass spectrometric studies of the kinetics of collision and ionization processes of ions (chemical reaction of ions, Penning and associative ionization). During his post-doctoral years (1964–1965), with Richard Wolfgang at Yale University, Herman built one of the first crossed beam machines to study ion-molecule processes.
Herman also built an improved crossed beam machine that was used in Prague with colleagues to investigate the dynamics of ion-molecule and charge transfer reactions of cations and dications, and ion-surface collisions by the scattering method (1970–2010).
Herman has published over 240 scientific articles in this field. | 0 | Theoretical and Fundamental Chemistry |
Most permutations of hydrogen, fluorine, chlorine, bromine, and iodine on one carbon atom have been evaluated experimentally. | 1 | Applied and Interdisciplinary Chemistry |
MicroRNAs, or miRNAs for short, are small (~22nt) segments of RNA which have been found to play a crucial role in gene regulation. One of the most commonly used methods for cloning and identifying miRNAs within a cell or tissue was developed in the Bartel Lab and published in a paper by Lau et al. (2001). Since then, several variant protocols have arisen, but most have the same basic format. The procedure is quite similar to SAGE: The small RNA are isolated, then linkers are added to each, and the RNA is converted to cDNA by RT-PCR. Following this, the linkers, containing internal restriction sites, are digested with the appropriate restriction enzyme and the sticky ends are ligated together into concatamers. Following concatenation, the fragments are ligated into plasmids and are used to transform bacteria to generate many copies of the plasmid containing the inserts. Those may then be sequenced to identify the miRNA present, as well as analysing expression levels of a given miRNA by counting the number of times it is present, similar to SAGE. | 1 | Applied and Interdisciplinary Chemistry |
In LS AAS the high resolution that is required for the measurement of atomic absorption is provided by the narrow line emission of the radiation source, and the monochromator simply has to resolve the analytical line from other radiation emitted by the lamp. This can usually be accomplished with a band pass between 0.2 and 2 nm, i.e., a medium-resolution monochromator. Another feature to make LS AAS element-specific is modulation of the primary radiation and the use of a selective amplifier that is tuned to the same modulation frequency, as already postulated by Alan Walsh. This way any (unmodulated) radiation emitted for example by the atomizer can be excluded, which is imperative for LS AAS. Simple monochromators of the Littrow or (better) the Czerny-Turner design are typically used for LS AAS. Photomultiplier tubes are the most frequently used detectors in LS AAS, although solid state detectors might be preferred because of their better signal-to-noise ratio. | 0 | Theoretical and Fundamental Chemistry |
The human gut-on-a-chip contains two microchannels that are separated by the flexible porous Extracellular Matrix (ECM)-coated membrane lined by the gut epithelial cells: Caco-2, which has been used extensively as the intestinal barrier. Caco-2 cells are cultured under spontaneous differentiation of its parental cell, a human colon adenocarcinoma, that represent the model of protective and absorptive properties of the gut. The microchannels are fabricated from polydimethylsiloxane (PDMS) polymer. In order to mimic the gut microenvironment, peristalsis-like fluid flow is designed. By inducing suction in the vacuum chambers along both sides of the main cell channel bilayer, cyclic mechanical strain of stretching and relaxing are developed to mimic the gut behaviors. Furthermore, cells undergo spontaneous villus morphogenesis and differentiation, which generalizes characteristics of intestinal cells. Under the three-dimensional villi scaffold, cells not only proliferate, but metabolic activities are also enhanced. Another important player in the gut is the microbes, namely gut microbiota. Many microbial species in the gut microbiota are strict anaerobes. In order to co-culture these oxygen intolerant anaerobes with the oxygen favorable intestinal cells, a polysulfone fabricated gut-on-a-chip is designed. The system maintained the co-culture of colon epithelial cells, goblet-like cells, and bacteria Faecalibacterium prausnitzii, [https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=39491 Eubacterium rectale], and Bacteroides thetaiotaomicron.
Oral administration is one of the most common methods for drug administration. It allows patients, especially out-patients, to self-serve the drugs with minimal possibility of experiencing acute drug reactions and in most cases: pain-free. However, the drug's action in the body can be largely influenced by the first pass effect. The gut, which plays an important role in the human digestive system, determines the effectiveness of a drug by absorbing its chemical and biological properties selectively. While it is costly and time consuming to develop new drugs, the fact that the gut-on-a-chip technology attains a high level of throughput has significantly decreased research and development costs and time for new drugs.
Even though the cause for inflammatory bowel disease (IBD) is elusive, its pathophysiology involves the gut microbiota. Current methods of inducing IBD are using inflammatory cues to activate Caco-2. It was found that the intestinal epithelium experienced a reduction in barrier function and increased cytokine concentrations. The gut-on-a-chip allowed for the assessment on drug transport, absorption and toxicity as well as potential developments in studying pathogenesis and interactions in the microenvironment overall. Immune cells are essential in mediating inflammatory processes in many gastrointestinal disorders, a recent gut-on-a-chip system also includes multiple immune cells, e.g., macrophages, dendritic cells, and CD4+ T cells in the system. Additionally, the gut-on-a-chip allows the testing of anti-inflammatory effects of bacterial species.
The chip was used to model human radiation-induced injury to the intestine in vitro as it recapitulated the injuries at both cellular and tissue levels. Injuries include but not limited to: inhabitation of mucus production, promotion of villus blunting, and distortion of microvilli. | 1 | Applied and Interdisciplinary Chemistry |
Felix Bloch (23 October 1905 – 10 September 1983) was a Swiss-American physicist and Nobel physics laureate who worked mainly in the U.S. He and Edward Mills Purcell were awarded the 1952 Nobel Prize for Physics for "their development of new ways and methods for nuclear magnetic precision measurements." In 1954–1955, he served for one year as the first director-general of CERN. Felix Bloch made fundamental theoretical contributions to the understanding of ferromagnetism and electron behavior in crystal lattices. He is also considered one of the developers of nuclear magnetic resonance. | 0 | Theoretical and Fundamental Chemistry |
A. Louis Allred and Eugene G. Rochow considered that electronegativity should be related to the charge experienced by an electron on the "surface" of an atom: The higher the charge per unit area of atomic surface the greater the tendency of that atom to attract electrons. The effective nuclear charge, Z, experienced by valence electrons can be estimated using Slaters rules, while the surface area of an atom in a molecule can be taken to be proportional to the square of the covalent radius, r. When r' is expressed in picometres, | 0 | Theoretical and Fundamental Chemistry |
In organic synthesis, vinyl oxocarbenium ions (structure on right) can be utilized in a wide range of cycloaddition reactions. They are commonly employed as dienophiles in the Diels–Alder reaction. An electron withdrawing ketone is often added to the dienophile to increase the rate of the reaction, and these ketones are often converted to vinyl oxocarbenium ions during the reaction It is not clear that an oxocarbenium ion necessarily will form, but Roush and co-workers demonstrated the oxocarbenium intermediate in the cyclization shown below. Two products were observed in this reaction, which could only form if the oxocarbenium ring is present as an intermediate. [4+3], [2+2], [3+2] and [5+2] cycloadditions with oxocarbenium intermediates have also been reported. | 0 | Theoretical and Fundamental Chemistry |
In 1988, The NIST group in Washington led by William Phillips first measured temperatures below the Doppler limit in sodium atoms in an optical molasses, prompting the search for the theoretical underpinnings of sub-Doppler cooling.
The next year, Jean Dalibard and Claude Cohen-Tannoudji identified the cause as the multi-photon process of Sisyphus cooling,
and Steven Chu's group likewise modeled sub-Doppler cooling as fundamentally an optical pumping scheme.
As a result of their efforts, Phillips, Cohen-Tannoudji, and Chu jointly won the 1997 Nobel Prize in Physics. T.W. Hänsch, et al., first outlined the theoretical formulation of gray molasses in 1994,
and a four-beam experimental realization in cesium was achieved by G. Grynberg the next year.
It has since been regularly used to cool all the other alkali (hydrogenic) metals. | 0 | Theoretical and Fundamental Chemistry |
Membrane-introduction mass spectrometry (MIMS) is a method of introducing analytes into the mass spectrometer's vacuum chamber via a semi-permeable membrane. Usually a thin, gas-permeable, hydrophobic membrane is used, for example polydimethylsiloxane. Samples can be almost any fluid including water, air or sometimes even solvents. The great advantage of the method of sample introduction is its simplicity. MIMS can be used to measure a variety of analytes in real-time, with little or no sample preparation. MIMS is most useful for the measurement of small, non-polar molecules, since molecules of this type have a greater affinity for the membrane material than the sample. The advantage of this method is that complex samples that cannot diffuse through the membrane are not incorporated into the mass spectroscopic measurements, highlighting the simplicity of only analyzing (small) molecules of interest. | 0 | Theoretical and Fundamental Chemistry |
In the 1960s and 70s various studies showed that the D–L test was not specific to cannabis, although some flawed studies claimed to show the opposite. A 1969 UK government scientist reported twenty-five plant substances giving a D–L test result very similar to that of cannabis and warned that the D–L test "should never be relied upon as the only positive evidence." Another 1969 study found false positives from "a variety of vegetable extracts".
The study most cited in favour of the specificity of the D–L test is Thornton and Nakamura (1972). The authors themselves reported that the D–L test gave false positives, but declared the D–L test confirmatory when combined with the presence of cystolithic hairs, which marijuana plants possess. However, many plant species have such hairs, and the study only confirmed that 82 of them did not give D–L test false positives.
A 2000 study by the US NIST examined 12 chemical spot tests, and concluded that all the tests examined "may indicate a specific drug or class of drugs is in the sample, but the tests are not always specific for a single drug or [class]", and noted that "mace, nutmeg and tea reacted with the modified Duquenois–Levine [test]".
A 2012 Brazilian study tested 40 vegetal drugs with Duquenóis-Levine test and obtained false-positive results to Chilean boldo (Peumus boldus Molina), pot marigold (Calendula officinalis L.), leather hat (Echinodorus grandiflorus (Cham. & Schltdl.) Micheli.), cecropia (Cecropia hololeuca Miq.), lemon balm (Melissa officinalis), anise (Pimpinella anisum L.), guaraná (Paulinia cupana Kunth.), jaborandi (Pilocarpus jaborandi Holmes.) and laurel (Laurus nobilis L.). | 0 | Theoretical and Fundamental Chemistry |
Carbon-neutral fuels can lead to greenhouse gas remediation because carbon dioxide gas would be reused to produce fuel instead of being released into the atmosphere. Capturing the carbon dioxide in flue gas emissions from power plants would eliminate their greenhouse gas emissions, although burning the fuel in vehicles would release that carbon because there is no economical way to capture those emissions. This approach would reduce net carbon dioxide emission by about 50% if it were used on all fossil fuel power plants. Most coal and natural gas power plants have been predicted to be economically retrofittable with carbon dioxide scrubbers for carbon capture to recycle flue exhaust or for carbon sequestration. Such recycling is expected to not only cost less than the excess economic impacts of climate change if it were not done, but also to pay for itself as global fuel demand growth and peak oil shortages increase the price of petroleum and fungible natural gas.
Capturing CO directly from the air, known as direct air capture, or extracting carbonic acid from seawater would also reduce the amount of carbon dioxide in the environment, and create a closed cycle of carbon to eliminate new carbon dioxide emissions. Use of these methods would eliminate the need for fossil fuels entirely, assuming that enough renewable energy could be generated to produce the fuel. Using synthetic hydrocarbons to produce synthetic materials such as plastics could result in permanent sequestration of carbon from the atmosphere. | 0 | Theoretical and Fundamental Chemistry |
On December 11, 2008, the DOE-SC announced the selection of Michigan State University to design and establish FRIB.
The project earned Critical Decision 1 (CD-1) approval in September 2010 which established a preferred alternative and the associated established cost and schedule ranges.
On August 1, 2013, DOE-SC approved the project baseline (CD-2) and the start of civil construction (CD-3a), pending a notice to proceed. Civil construction could not start under the continuing appropriations resolution, which disallowed new construction starts.
On February 25, 2014, the board of the Michigan Strategic Fund met at Michigan State University and approved nearly $91 million to support the construction of FRIB.
The FRIB marked the official start of civil construction with a groundbreaking ceremony March 17, 2014. In attendance were representatives from the Michigan delegation, State of Michigan, Michigan State University, and the U.S. Department of Energy Office of Science. Technical construction started in October 2014, following a CD-3b approval by DOE-SC.
In March 2017, FRIB achieved beneficial occupancy of civil construction, and technical installation activities escalated as a result.
In February 2019, FRIB accelerated beams through the first 15 (of 46 total) cryomodules to 10 percent of FRIB's final beam energy. In August 2019, the radio-frequency quadrupole (RFQ) was conditioned above 100 kW, the CW power needed to achieve the FRIB mission goal of accelerating uranium beams. The RFQ prepares the beam for further acceleration in the linac.
Construction on two MSU-funded building additions was substantially completed in January 2020. The Cryogenic Assembly Building will be used for cryomodule maintenance and to perform cryogenic-engineering research. The High Rigidity Spectrometer and Isotope Harvesting Vault will house isotope-harvesting research equipment and provide space for experiments.
In March 2020, FRIB accelerated an argon-36 beam through 37 of 46 superconducting cryomodules to 204 MeV/nucleon or 57 percent of the speed of light.
In September 2020, DOE designated FRIB as a DOE-SC User Facility. U.S. Secretary of Energy Dan Brouillette announced the designation at a special ceremony held outdoors at MSU, under a tent adjacent to FRIB.
On February 24, 2021, the FRIB announced that 82 proposals requesting 9,784 hours of beam time and six letters of intent were submitted, covering 16 of the 17 National Academies benchmarks for FRIB, in response to their first call for proposals. These proposals represent FRIB's international user community of more than 1,500 scientists. Respondents include 597 individual scientists, 354 of whom are from the United States. They represent 130 institutions in 30 countries and 26 U.S. states.
On January 25, 2022, the FRIB project team delivered the first heavy-ion beam to the focal plane of the FRIB fragment separator, marking technical completion of the FRIB project.
On February 1–2, 2022, a review by the DOE-SC Office of Project Assessment reviewed FRIB's readiness for project completion and recommended that FRIB is ready for Critical Decision 4 (Approve Project Completion).
Michigan State University announced a ribbon-cutting ceremony for May 2, 2022.
On June 22, 2022, the first experiment at FRIB, which studied the beta decay of calcium-48 fragments that are so unstable that they only exist for mere fractions of a second, concluded successfully. FRIB's first scientific user experiment had participation from Argonne National Laboratory, Brookhaven National Laboratory, Florida State University, FRIB, Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, Louisiana State University, Los Alamos National Laboratory, Mississippi State University, Oak Ridge National Laboratory, and the University of Tennessee. On November 14, 2022, the results of the first experiment were published in Physical Review Letters. | 0 | Theoretical and Fundamental Chemistry |
Chloridizing roasting transforms certain metal compounds to chlorides through oxidation or reduction. Some metals such as uranium, titanium, beryllium and some rare earths are processed in their chloride form. Certain forms of chloridizing roasting may be represented by the overall reactions:
:2NaCl + MS + 2O -> NaSO + MCl,
:4NaCl + 2MO + S + 3O -> 2NaSO + 2MCl
The first reaction represents the chlorination of a sulfide ore involving an exothermic reaction. The second reaction involving an oxide ore is facilitated by addition of elemental sulfur. Carbonate ores react in a similar manner as the oxide ore, after decomposing to their oxide form at high temperatures. | 1 | Applied and Interdisciplinary Chemistry |
* TEs are also a widely used tool for mutagenesis of most experimentally tractable organisms. The Sleeping Beauty transposon system has been used extensively as an insertional tag for identifying cancer genes.
* The Tc1/mariner-class of TEs Sleeping Beauty transposon system, awarded Molecule of the Year in 2009, is active in mammalian cells and is being investigated for use in human gene therapy.
* TEs are used for the reconstruction of phylogenies by the means of presence/absence analyses. Transposons can act as biological mutagen in bacteria.
* Common organisms which the use of Transposons has been well developed are:
**Drosophila
** Arabidopsis thaliana
** Escherichia coli | 1 | Applied and Interdisciplinary Chemistry |
Although ischemic cell death is the accepted name of the process, the alternative name of oncosis was introduced as the process involves the affected cell(s) swelling to an abnormally large size in known models. This is thought to be caused by failure of the plasma membranes ionic pumps. The name oncosis (derived from ónkos, meaning largeness, and ónkosis', meaning swelling) was first introduced in 1910 by pathologist Friedrich Daniel von Recklinghausen. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen cyanide (also known as prussic acid) is a chemical compound with the formula HCN and structural formula . It is a colorless, extremely poisonous, and flammable liquid that boils slightly above room temperature, at . HCN is produced on an industrial scale and is a highly valued precursor to many chemical compounds ranging from polymers to pharmaceuticals. Large-scale applications are for the production of potassium cyanide and adiponitrile, used in mining and plastics, respectively. It is more toxic than solid cyanide compounds due to its volatile nature.
Whether hydrogen cyanide is an organic compound or not is a topic of debate among chemists, and opinions vary from author to author. Traditionally, it is considered inorganic by significant part of authors. Contrary to them, it is considered organic by other authors, because hydrogen cyanide belongs to the class of organic compounds known as nitriles which have the formula , where R is typically organyl group (e.g., alkyl or aryl) or hydrogen. In the case of hydrogen cyanide, the R group is hydrogen H, so the other names of hydrogen cyanide are methanenitrile and formonitrile. | 0 | Theoretical and Fundamental Chemistry |
A plate less than one inch thick has enough resistance to turn a .30-06 Springfield standard-issue M2 armour-piercing bullet to dust. The test plate outperformed a solid metal plate of similar thickness, while weighing far less. Other potential applications include nuclear waste (shielding X-rays, gamma rays and neutron radiation) transfer and thermal insulation for space vehicle atmospheric re-entry, with many times the resistance to fire and heat as the plain metals. Another study testing CMF's resistance to .50 caliber rounds found that CMF could stop such rounds at less than half the weight of rolled homogeneous armour. | 0 | Theoretical and Fundamental Chemistry |
Photosensitizers that are readily incorporated into the external tissues can increase the rate at which reactive oxygen species are generated upon exposure to UV light (such as UV-containing sunlight). Some photosensitizing agents, such as St. John's Wort, appear to increase the incidence of inflammatory skin conditions in animals and have been observed to slightly reduce the minimum tanning dose in humans.
Some examples of photosensitizing medications (both investigatory and approved for human use) are:
* St. John's Wort
* 9-me-bc
* Doxepin
* Amoxapine
* Ethinyl estradiol | 0 | Theoretical and Fundamental Chemistry |
As previously mentioned, Hox genes encode transcription factors that regulate embryonic and post-embryonic developmental processes. The expression of Hox genes is regulated in part by the tight, spatial arrangement of conserved coding and non-coding DNA regions. The potential for evolutionary alterations in Hox cluster composition is viewed to be small among vertebrates. On the other hand, recent studies of a small number of non-mammalian taxa propose greater dissimilarity than initially considered. Next, generation sequencing of considerable genomic fragments greater than 100 kilobases from the eastern newt (Notophthalmus viridescens) was analyzed. Subsequently, it was found that the composition of Hox cluster genes were conserved relative to orthologous regions from other vertebrates. Furthermore, it was found that the length of introns and intergenic regions varied. In particular, the distance between HoxD13 and HoxD11 is longer in newt than orthologous regions from vertebrate species with expanded Hox clusters and is predicted to exceed the length of the entire HoxD clusters (HoxD13–HoxD4) of humans, mice, and frogs. Many recurring DNA sequences were recognized for newt Hox clusters, counting an enrichment of DNA transposon-like sequences similar to non-coding genomic fragments. Researchers found the results to suggest that Hox cluster expansion and transposon accumulation are common features of non-mammalian tetrapod vertebrates.
After the loss of a limb, cells draw together to form a clump known as a blastema. This superficially appears undifferentiated, but cells that originated in the skin later develop into new skin, muscle cells into new muscle and cartilage cells into new cartilage. It is only the cells from just beneath the surface of the skin that are pluripotent and able to develop into any type of cell. Salamander Hox genomic regions show elements of conservation and variety in comparison to other vertebrate species. Whereas the structure and organization of Hox coding genes is conserved, newt Hox clusters show variation in the lengths of introns and intergenic regions, and the HoxD13–11 region exceeds the lengths of orthologous segments even among vertebrate species with expanded Hox clusters. Researchers have suggested that the HoxD13–11 expansion predated a basal salamander genome size amplification that occurred approximately 191 million years ago, because it preserved in all three extant amphibian groups. Supplementary verification supports the proposal that Hox clusters are acquiescent to structural evolution and variation is present in the lengths of introns and intergenic regions, relatively high numbers of repetitive sequences, and non-random accumulations of DNA transposons in newts and lizards. Researchers found that the non-random accretion of DNA-like transposons could possibly change developmental encoding by generating sequence motifs for transcriptional control.
In conclusion, the available data from several non-mammalian tetrapods suggest that Hox structural flexibility is the rule, not the exception. It is thought that this elasticity may allow for developmental variation across non-mammalian taxa. This is of course true for both embryogenesis and during the redeployment of Hox genes during post-embryonic developmental processes, such as metamorphosis and regeneration. | 1 | Applied and Interdisciplinary Chemistry |
Cobalt chloride can be prepared in aqueous solution from cobalt(II) hydroxide or cobalt(II) carbonate and hydrochloric acid:
: + 2 HCl → + +
: + 2 HCl → + 2
The solid dihydrate and hexahydrate can be obtained by evaporation. Cooling saturated aqueous solutions yields the dihydrate between 120.2 °C and 51.25 °C, and the hexahydrate below 51.25 °C. Water ice, rather than cobalt chloride, will crystallize from solutions with concentration below 29%. The monohydrate and the anhydrous forms can be obtained by cooling solutions only under high pressure, above 206 °C and 335 °C, respectively.
The anhydrous compound can be prepared by heating the hydrates.
On rapid heating or in a closed container, each of the 6-, 2-, and 1- hydrates partially melts into a mixture of the next lower hydrate and a saturated solution—at 51.25 °C, 206 °C, and 335 °C, respectively. On slow heating in an open container, so that the water vapor pressure over the solid is practically zero, water evaporates out of each of the solid 6-, 2-, and 1- hydrates, leaving the next lower hydrate, at about 40°C, 89°C, and 125°C, respectively. If the partial pressure of the water vapor is in equilibrium with the solid, as in a confined but not pressurized contained, the decomposition occurs at about 115°C, 145°C, and 195°C, respectively.
Dehydration can also be effected with trimethylsilyl chloride:
:•6 + 12 → + 6 + 12 HCl
The anhydrous compound can be purified by sublimation in vacuum. | 0 | Theoretical and Fundamental Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2021 impact factor of 3.570.<ref https://benthamscience.com/press-releases/220070401/</ref> | 1 | Applied and Interdisciplinary Chemistry |
In 1709, at Coalbrookdale in Shropshire, England, Abraham Darby began to fuel a blast furnace with coke instead of charcoal. Cokes initial advantage was its lower cost, mainly because making coke required much less labor than cutting trees and making charcoal, but using coke also overcame localized shortages of wood, especially in Britain and on the Continent. Metallurgical grade coke will bear heavier weight than charcoal, allowing larger furnaces. A disadvantage is that coke contains more impurities than charcoal, with sulfur being especially detrimental to the irons quality. Coke's impurities were more of a problem before hot blast reduced the amount of coke required and before furnace temperatures were hot enough to make slag from limestone free flowing. (Limestone ties up sulfur. Manganese may also be added to tie up sulfur.)
Coke iron was initially only used for foundry work, making pots and other cast iron goods. Foundry work was a minor branch of the industry, but Darbys son built a new furnace at nearby Horsehay, and began to supply the owners of finery forges with coke pig iron for the production of bar iron. Coke pig iron was by this time cheaper to produce than charcoal pig iron. The use of a coal-derived fuel in the iron industry was a key factor in the British Industrial Revolution. Darbys original blast furnace has been archaeologically excavated and can be seen in situ at Coalbrookdale, part of the Ironbridge Gorge Museums. Cast iron from the furnace was used to make girders for the world's first cast iron bridge in 1779. The Iron Bridge crosses the River Severn at Coalbrookdale and remains in use for pedestrians. | 1 | Applied and Interdisciplinary Chemistry |
Zara's wedding to Raja Nazrin Shah was held at Istana Iskandariah on 17 May 2007.
A day after the solemnisation of their vows, there was a special proclamation ceremony to bestowed upon her with the honorific prefix of Tuanku and the official title as Raja Puan Besar (Crown Princess) of Perak, a title reserved for the royal wife of the Raja Muda (Crown Prince) of Perak that had been vacant since April 1987.
The royal wedding reception took place on 19 May 2007.
The couples first child, a son named Raja Azlan Muzzaffar Shah, the Raja Kecil Besar of Perak' was born 14 March 2008. Their second child, a daughter named Raja Nazira Safya, was born 2 August 2011. | 1 | Applied and Interdisciplinary Chemistry |
In the more general case, channels with non-uniform non-circular cross-sectional area, such as the Tesla valve, the hydraulic diameter is defined as:
where
: is the total wetted volume of the channel,
: is the total wetted surface area.
This definition is reduced to for uniform non-circular cross-section channels, and for circular pipes. | 1 | Applied and Interdisciplinary Chemistry |
Under the ODA and EU legislation, many orphan drugs have been developed, including drugs to treat glioma, multiple myeloma, cystic fibrosis, phenylketonuria, snake venom poisoning, and idiopathic thrombocytopenic purpura.
The Pharmaceutical Executive opines, that the "ODA is nearly universally acknowledged to be a success".
Before the US Congress enacted the ODA in 1983, only 38 drugs were approved in the US specifically to treat orphan diseases. In the US, from January 1983 to June 2004, 249 orphan drugs received marketing authorization and 1,129 received different orphan drug designations, compared to fewer than ten such products in the decade prior to 1983. From 1983 until May 2010, the FDA approved 353 orphan drugs and granted orphan designations to 2,116 compounds. As of 2010, 200 of the roughly 7,000 officially designated orphan diseases have become treatable.
Critics have questioned whether orphan drug legislation was the real cause of this increase, claiming that many of the new drugs were for disorders which were already being researched anyway, and would have had drugs developed regardless of the legislation, and whether the ODA has truly stimulated the production of non-profitable drugs; the act also has been criticised for allowing some pharmaceutical companies to make a large profit off drugs which have a small market but sell for a high price.
While the European Medicines Agency grants orphan drugs market access in all member states, in practice, they only reach the market when a member state decides that its national health system will reimburse for the drug. For example, in 2008, 44 orphan drugs reached the market in the Netherlands, 35 in Belgium, and 28 in Sweden, while in 2007, 35 such drugs reached the market in France and 23 in Italy.
Though not technically an orphan disease, research and development into the treatment for AIDS has been heavily linked to the Orphan Drug Act. In the beginning of the AIDS epidemic the lack of treatment for the disease was often accredited to a believed lack of commercial base for a medication linked to HIV infection. This encouraged the FDA to use the Orphan Drug Act to help bolster research in this field, and by 1995 13 of the 19 drugs approved by the FDA to treat AIDS had received orphan drug designation, with 10 receiving marketing rights. These are in addition to the 70 designated orphan drugs designed to treat other HIV related illnesses. | 1 | Applied and Interdisciplinary Chemistry |
SDS is used in cleaning procedures, and is commonly used as a component for lysing cells during RNA extraction or DNA extraction, inhibiting the activity of nucleases, enzymes that can degrade DNA, protecting the integrity of the isolated genetic material, and for denaturing proteins in preparation for electrophoresis in the SDS-PAGE technique.
In the case of SDS-PAGE, the compound works by disrupting non-covalent bonds in the proteins, and so denaturing them, i.e. causing the protein molecules to lose their native conformations and shapes. By binding to proteins at a ratio of one SDS molecule per 2 amino acid residues, the negatively charged detergent provides all proteins with a similar net negative charge and therefore a similar charge-to-mass ratio. In this way, the difference in mobility of the polypeptide chains in the gel can be attributed solely to their length as opposed to both their native charge and shape. This separation based on the size of the polypeptide chain simplifies the analysis of protein molecules. | 1 | Applied and Interdisciplinary Chemistry |
In the late 20th and early 21st century, there has been a global movement towards the phase-out of polystyrene foam as a single use plastic (SUP). Early bans of polystyrene foam intended to eliminate ozone-depleting chlorofluorocarbons (CFCs), formerly a major component.
Expanded polystyrene, often termed Styrofoam, is a contributor of microplastics from both land and maritime activities. Polystyrene is not biodegradeable but is susceptible to photo-oxidation, and degrades slowly in the ocean as microplastic marine debris. Animals do not recognize polystyrene foam as an artificial material, may mistake it for food, and show toxic effects after substantial exposure.
Full or partial bans of expanded and polystyrene foam commonly target disposable food packaging. Such bans have been enacted through national legislation globally, and also at sub-national or local levels in many countries. | 0 | Theoretical and Fundamental Chemistry |
Human EH3 is a recently characterized protein with epoxy hydrolase activity for metabolizing epoxyeicosatrienoic acids (EETs) and vernolic acids (leukotoxins) to their corresponding diols; in these capacities they may thereby limit the cell signaling activity of the EETs and contribute to the toxicity of the leukotoxins. mRNA for EH3 is most strongly expressed in the lung, skin, and upper gastrointestinal tract tissues of mice. The function of EH3 in humans, mice, or other mammals has not yet been determined although the gene for EH3 has been validated as being hypermethylated on CpG sites in its promoter region in human prostate cancer tissue, particularly in the tissues of more advanced or morphologically-based (i.e. Gleason score) more aggressive cancers; this suggests that the gene silencing of EH3 due to this hypermethylation may contribute to the onset and/or progression of prostate cancer. Similar CpG site hypermethylations in the promoter of for the EH3 gene have been validated for other cancers. This promoter methylation pattern, although not yet validated, was also found in human malignant melanoma. | 1 | Applied and Interdisciplinary Chemistry |
This type of BCA assay seems to only be available from Thermo Fisher Scientific. Reportedly it uses "the same copper reduction method as the traditional BCA Protein Assay with a unique [proprietary] copper chelator.", that absorbs at 480 nm instead of 562 nm. This proprietor chelator and presumed optimized Biuret reaction formulation allows the assay to provide rapid (<5 min) results without the 37˚C+ incubation of the original BCA assay. However the assay has a different interference profile from other non-protein components. The Pierce Quantitative Colorimetric Peptide Assay (now owned by and available from Thermo Fisher Scientific) appears to use a similar or identical 480 nm absorbing proprietary copper chelator. | 1 | Applied and Interdisciplinary Chemistry |
pCO, pCO, or is the partial pressure of carbon dioxide (CO), often used in reference to blood but also used in meteorology, climate science, oceanography, and limnology to describe the fractional pressure of CO as a function of its concentration in gas or dissolved phases. The units of pCO are mmHg, atm, torr, Pa, or any other standard unit of atmospheric pressure. The pCO of Earth's atmosphere has risen from approximately 280 ppm (parts-per-million) to a mean 2019 value of 409.8 ppm as a result of anthropogenic release of carbon dioxide from fossil fuel burning. This is the highest atmospheric concentration to have existed on Earth for at least the last 800,000 years. | 0 | Theoretical and Fundamental Chemistry |
Reinecke's salt is an inorganic compound with the formula NH[Cr(NCS)(NH)]·HO. The dark-red crystalline compound is soluble in boiling water, acetone, and ethanol. It can be classified as a metal isothiocyanate complex. | 0 | Theoretical and Fundamental Chemistry |
Some promoters are called constitutive as they are active in all circumstances in the cell, while others are regulated, becoming active in the cell only in response to specific stimuli. | 1 | Applied and Interdisciplinary Chemistry |
The bifidus factor might be lacto-N-biose I [LNB], which is a derivative of mucin sugars. However, the exact structure and mechanism behind the bifidus factor remains unknown.
The bacteria would break down lactic acid and acetic acid. The environment of the intestine would become acidic, preventing the growth of any harmful pathogens. The function of LBN is unknown and it is possible that oligosaccharides with terminals of Galβ1-3GlcNAc are the bifidus factors.
Bifidobacteria might suppress infections in infants and children. | 1 | Applied and Interdisciplinary Chemistry |
From the above stoichiometric equations, we can find that:
:1 mole of O → 2 moles of MnO(OH) → 2 mole of I → 4 mole of
Therefore, after determining the number of moles of iodine produced, we can work out the number of moles of oxygen molecules present in the original water sample. The oxygen content is usually presented in milligrams per liter (mg/L). | 0 | Theoretical and Fundamental Chemistry |
* Poolman is ISI highly cited researcher in microbiology. He has published over 275 peer-reviewed papers in international scientific journals, which have been cited more than 25,000 times. His H-index (Google Scholar) is 83, and he holds four patents. Poolman shares his findings with wide audiences through newspaper, radio and TV appearances. In 2012 Schrauwers and Poolman wrote the book Synthetische Biologie: de Mens als Schepper (Synthetic Biology: Man as a Creator) to convey the developments in synthetic biology to a lay audience. | 0 | Theoretical and Fundamental Chemistry |
The Boekelheide reaction is a rearrangement of α-picoline-N-oxides to hydroxymethylpyridines. It is named after Virgil Boekelheide who first reported it in 1954. Originally the reaction was carried out using acetic anhydride, which typically required a period at reflux (~140 °C). The reaction can be performed using trifluoroacetic anhydride (TFAA), which often allows for a room temperature reaction. | 0 | Theoretical and Fundamental Chemistry |
The main objectives of ecological sanitation are to reduce the health risks related to sanitation, contaminated water and waste; to prevent groundwater pollution and surface water pollution; and to reuse nutrients or energy contained within wastes. | 1 | Applied and Interdisciplinary Chemistry |
One would expect that enrichment of heavy isotopes leads to progressively slower reactions, but the IsoRes hypothesis suggests that there exist certain resonance compositions for which kinetics increases even for higher abundances of heavy stable isotopes. For example, at 9.5% C, 10.9% N and 6.6% O (when all three elements are 10-35 times enriched compared to their natural abundances) and normal deuterium composition (150 ppm or 0.015%), a very strong resonance (Fig. 1C) is predicted (“super-resonance”).
Yet another nontrivial prediction of the IsoRes hypothesis is that at ≈250-350 ppm deuterium content, the terrestrial resonance becomes “perfect”, and the rates of biochemical reactions and growth of terrestrial organisms further increase. This prediction seems to be matched by at least some experimental observations. | 0 | Theoretical and Fundamental Chemistry |
Thermometric titrimetry offers a rapid, highly precise method for the determination of aluminium in solution. A solution of aluminium is conditioned with acetate buffer and an excess of sodium and potassium ions. Titration with sodium or potassium fluoride yields the exothermic precipitation of an insoluble alumino-fluoride salt.
: Al + Na + 2K + 6F ↔ KNaAlF↓
Because 6 mole of fluoride react with one mole of aluminium, the titration is particularly precise, and a coefficient of variance (CV) of 0.03 has been achieved in the analysis of alum.
When aluminium ion (say as aluminium nitrate) is employed as the titrant, fluoride can be determined using the same chemistry. This titration is useful in the determination of fluoride in complex acid mixtures used as etchants in the semi-conductor industry. | 0 | Theoretical and Fundamental Chemistry |
GC-content is usually expressed as a percentage value, but sometimes as a ratio (called G+C ratio or GC-ratio). GC-content percentage is calculated as
whereas the AT/GC ratio is calculated as
The GC-content percentages as well as GC-ratio can be measured by several means, but one of the simplest methods is to measure the melting temperature of the DNA double helix using spectrophotometry. The absorbance of DNA at a wavelength of 260 nm increases fairly sharply when the double-stranded DNA molecule separates into two single strands when sufficiently heated. The most commonly used protocol for determining GC-ratios uses flow cytometry for large numbers of samples.
In an alternative manner, if the DNA or RNA molecule under investigation has been reliably sequenced, then GC-content can be accurately calculated by simple arithmetic or by using a variety of publicly available software tools, such as the [http://www.basic.northwestern.edu/biotools/oligocalc.html free online GC calculator]. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, coalescence is a process in which two phase domains of the same composition come together and form a larger phase domain. In other words, the process by which two or more separate masses of miscible substances
seem to "pull" each other together should they make the slightest
contact. | 0 | Theoretical and Fundamental Chemistry |
Despite the reduced efficiency verses reversed phase HPLC, hundreds of applications have been reported using MLC. One of the most advantageous is the ability to directly inject physiological fluids. Micelles have an ability to solubilize proteins which enables MLC to be useful in analyzing untreated biological fluids such as plasma, serum, and urine. Martinez et al. found MLC to be highly useful in analyzing a class of drugs called b-antagonists, so called beta-blockers, in urine samples. The main advantage of the use of MLC with this type of sample, is the great time savings in sample preparation. Alternative methods of analysis including reversed phase HPLC require lengthy extraction and sample work up procedures before analysis can begin. With MLC, direct injection is often possible, with retention times of less than 15 minutes for the separation of up to nine b-antagonists.
Another application compared reversed phase HPLC with MLC for the analysis of desferrioxamine in serum. Desferrioxamine (DFO) is a commonly used drug for removal of excess iron in patients with chronic and acute levels. The analysis of DFO along with its chelated complexes, Fe(III) DFO and Al(III) DFO has proven to be difficult at best in previous attempts. This study found that direct injection of the serum was possible for MLC, verses an ultrafiltration step necessary in HPLC. This analysis proved to have difficulties with the separation of the chelated DFO compounds and with the sensitivity levels for DFO itself when MLC was applied. The researcher found that, in this case, reverse phase HPLC, was a better, more sensitive technique despite the time savings in direct injection.
Analysis of pharmaceuticals by MLC is also gaining popularity. The selectivity and peak shape of MLC over commonly used ion-pair chromatography is much enhanced. MLC mimics, yet enhances, the selectivity offered by ion-pairing reagents for the separation of active ingredients in pharmaceutical drugs. For basic drugs, MLC improves the excessive peak tailing frequently observed in ion-pairing. Hydrophilic drugs are often unretained using conventional HPLC, are retained by MLC due to solubilization into the micelles. Commonly found drugs in cold medications such as acetaminophen, L-ascorbic acid, phenylpropanolamine HCL, tipepidine hibenzate, and chlorpheniramine maleate have been successfully separated with good peak shape using MLC. Additional basic drugs like many narcotics, such as codeine and morphine, have also been successfully separated using MLC.
Another novel application of MLC involves the separation and analysis of inorganic compounds, mostly simple ions. This is a relatively new area for MLC, but has seen some promising results. MLC has been observed to provide better selectivity of inorganic ions that ion-exchange or ion-pairing chromatography. While this application is still in the beginning stages of development, the possibilities exist for novel, much enhanced separations of inorganic species.
Since the technique was first reported on in 1980, micellar liquid chromatography has been used in hundreds of applications. This micelle controlled technique provides for unique opportunities for solving complicated separation problems. Despite the poor efficiency of MLC, it has been successfully used in many applications. The use of MLC in the future appears to be extremely advantages in the areas of physiological fluids, pharmaceuticals, and even inorganic ions. The technique has proven to be superior over ion-pairing and ion-exchange for many applications. As new approaches are developed to combat the poor efficiency of MLC, its application is sure to spread and gain more acceptance. | 0 | Theoretical and Fundamental Chemistry |
Some complications that can arise with the use of an Olszewski tube include disruption of the thermocline and excessive water loss. The thermocline separates the upper layer of water that is mixed temperatures with the deeper, cooler water. If the thermocline is disrupted, it could alter the ecology of the lake, potentially making it uninhabitable. Another complication is that the installation must be a long-term process. Short-term uses of Olszewski tubes have largely failed because it takes some time for the anoxic condition of the hypolimnetic layer to increase in dissolved oxygen. Also, it must be a slow process in order to avoid disrupting the thermocline in a lake. If the Olszewski tube is operated slowly enough, the rate of water going in and going out will be fairly constant causing the thermocline to stay intact. | 1 | Applied and Interdisciplinary Chemistry |
Schuster was born in Brooklyn, New York in 1935 and raised in Far Rockaway. He attended Columbia University as an undergraduate and received his bachelors degree in chemistry in 1956. He then moved to the California Institute of Technology, from which he received his Ph.D. in 1961 under the mentorship of John D. Roberts. During Schusters time in the Roberts laboratory, the group began experimenting with some of the first applications of NMR spectroscopy to organic chemistry. Schuster next joined Howard Zimmerman's group at the University of Wisconsin as a postdoctoral fellow, where he spent a year studying mechanistic organic photochemistry. | 0 | Theoretical and Fundamental Chemistry |
Many contaminated brownfield sites sit unused for decades because the cost of cleaning them to safe standards is more than the land would be worth after redevelopment, in the process becoming involuntary parks as they grow over. However, redevelopment has become more common in the first decade of the 21st century, as developable land has become less available in highly populated areas, and brownfields contribute to environmental stigma which can delay redevelopment. Also, the methods of studying contaminated land have become more sophisticated and costly.
Some states and localities have spent considerable money assessing the contamination on local brownfield sites, to quantify the cleanup costs in an effort to move the redevelopment process forward. Therefore, federal and state programs have been developed to help developers interested in cleaning up brownfield sites and restoring them to practical uses.
In the process of cleaning contaminated brownfield sites, previously unknown underground storage tanks, buried drums or buried railroad tank cars containing wastes are sometimes encountered. Unexpected circumstances increase the cost for study and clean-up. As a result, the cleanup work may be delayed or stopped entirely. To avoid unexpected contamination and increased costs, many developers insist that a site be thoroughly investigated (via a Phase II Site Investigation or Remedial Investigation) prior to commencing remedial cleanup activities. | 1 | Applied and Interdisciplinary Chemistry |
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