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The Thraustochytrium mitochondrial code (translation table 23) is a genetic code found in the mitochondria of the labyrinthulid protist Thraustochytrium aureum. The mitochondrial genome was sequenced by the Organelle Genome Megasequencing Program. | 1 | Applied and Interdisciplinary Chemistry |
Shikimic acid is a precursor for:
* indole, indole derivatives and aromatic amino acid tryptophan and tryptophan derivatives such as the psychedelic compound dimethyltryptamine
* many alkaloids and other aromatic metabolites | 1 | Applied and Interdisciplinary Chemistry |
An important application of Z-HIT is the examination of experimental impedance spectra for artifacts. The examination of EIS series measurements is often difficult due to the tendency of examined objects to undergo changes during the measurement. This may occur in many standard EIS applications such as the evaluation of fuel cells or batteries during discharge. Further examples include the investigation of light-sensitive systems under illumination (e.g. Photoelectrochemistry) or the analysis of water uptake of lacquers on metal surfaces (e.g. corrosion-protection).
A descriptive example for an unsteady system is a Lithium-ion battery. Under cyclization or discharging, the amount of charge in the battery changes over time. The change in charge is coupled with a chemical redox reaction, transferring to a change in concentrations of the involved substances. This violates the principles of stationarity and causality which are prerequisites for proper EIS measurements. In theory, this would exclude drift-affected samples from valid evaluation. Using the ZHIT-algorithm, these and similar artifacts can be recognized and spectra following causality can even be reconstructed, which are consistent with the Kramers–Kronig relations and thereby valid for analysis. | 0 | Theoretical and Fundamental Chemistry |
Diorganophosphites are derivatives of phosphorus(V) and can be viewed as the di-esters of phosphorous acid ((HO)P(O)H). They exhibit tautomerism, however, the equilibrium overwhelmingly favours the right-hand (phosphonate-like) form:
:(RO)POH ⇌ (RO)P(O)H
The P-H bond is the site of high reactivity in these compounds (for example in the Atherton–Todd reaction and Hirao coupling), whereas in tri-organophosphites the lone pair on phosphorus is the site of high reactivity. Diorganophosphites do however undergo transesterification. | 0 | Theoretical and Fundamental Chemistry |
Changes to the surface of the planet, such as an absence of volcanoes or higher sea levels, which would reduce the amount of land surface exposed to weathering can change the rates at which different processes in this cycle take place. Over tens to hundreds of millions of years, carbon dioxide levels in the atmosphere may vary due to natural perturbations in the cycle but even more generally, it serves as a critical negative feedback loop between carbon dioxide levels and climate changes. For example, if CO builds up in the atmosphere, the greenhouse effect will serve to increase the surface temperature, which will in turn increase the rate of rainfall and silicate weathering, which will remove carbon from the atmosphere. In this way, over long timescales, the carbonate-silicate cycle has a stabilizing effect on the Earths climate, which is why it has been called the Earths thermostat. | 0 | Theoretical and Fundamental Chemistry |
Liquids can form solutions with gases, solids, and other liquids.
Two liquids are said to be miscible if they can form a solution in any proportion; otherwise they are immiscible. As an example, water and ethanol (drinking alcohol) are miscible whereas water and gasoline are immiscible. In some cases a mixture of otherwise immiscible liquids can be stabilized to form an emulsion, where one liquid is dispersed throughout the other as microscopic droplets. Usually this requires the presence of a surfactant in order to stabilize the droplets. A familiar example of an emulsion is mayonnaise, which consists of a mixture of water and oil that is stabilized by lecithin, a substance found in egg yolks. | 0 | Theoretical and Fundamental Chemistry |
To date, iron is one of the most widely studied trace metals, and iron isotope compositions are relatively well-documented. Based on measurements, iron isotopes exhibit minimal variation (±3‰) in the terrestrial environment. A list of iron isotopic values of different materials from different environments is presented below. | 0 | Theoretical and Fundamental Chemistry |
Tim9 and Tim10 make up the group of essential small Tim proteins that assist in transport of hydrophobic precursors across the intermembrane space in mammalian cells. Both Tim9 and Tim10 form a hexamer, the Tim9-Tim10 complex, that when associated, functions as a chaperone to assist translocation of preproteins from the outer mitochondrial membrane to the translocase of the inner membrane. The functional Tim9-Tim10 complex not only directs preproteins to the inner mitochondrial membrane in order to interact with the TIM22 complex, but also guides β-barrel precursor proteins to the sorting and assembly machinery (SAM) of the outer membrane. | 1 | Applied and Interdisciplinary Chemistry |
Peptides based hydrogels possess exceptional biocompatibility and biodegradability qualities, giving rise to their wide use of applications, particularly in biomedicine; as such, their physical properties can be fine-tuned in order to maximise their use. Methods to do this are: modulation of the amino acid sequence, pH, chirality, and increasing the number of aromatic residues. The order of amino acids within the sequence is crucial for gelation, as has been shown many times. In one example, a short peptide sequence Fmoc-Phe-Gly readily formed a hydrogel, whereas Fmoc-Gly-Phe failed to do so as a result of the two adjacent aromatic moieties being moved, hindering the aromatic interactions. Altering the pH can also have similar effects, an example involved the use of the naphthalene (Nap) modified dipeptides Nap-Gly-Ala, and Nap- Ala-Gly, where a drop in pH induced gelation of the former, but led to crystallisation of the latter. A controlled pH decrease method using glucono-δ-lactone (GdL), where the GdL is hydrolysed to gluconic acid in water is a recent strategy that has been developed as a way to form homogeneous and reproducible hydrogels. The hydrolysis is slow, which allows for a uniform pH change, and thus resulting in reproducible homogenous gels. In addition to this, the desired pH can be achieved by altering the amount of GdL added. The use of GdL has been used various times for the hydrogelation of Fmoc and Nap-dipeptides. In another direction, Morris et al reported the use of GdL as a molecular trigger to predict and control the order of gelation. Chirality also plays an essential role in gel formation, and even changing the chirality of a single amino acid from its natural L-amino acid to its unnatural D-amino acid can significantly impact the gelation properties, with the natural forms not forming gels. Furthermore, aromatic interactions play a key role in hydrogel formation as a result of π- π stacking driving gelation, shown by many studies. | 0 | Theoretical and Fundamental Chemistry |
After completing his PhD, he became an assistant and lecturer at Technical University of Munich (1965–1968). From 1968 to 1973, he was Professor and Director at Technical University of Hannover; then, he became a professor at Institute for Physical Chemistry, Ludwig Maximilian University of Munich (1973–1986). During the 1970s and 80s, he was also a visiting professor at the California Institute of Technology (1976–1977), the University of Wisconsin–Milwaukee (1979) and the University of California, Berkeley (1981–82).
He became the director at the Fritz Haber Institute of the MPG from 1986 till his retirement in 2004. In 1986, as honors, he was named "Honorary Professor" at the Free University of Berlin and at the Technical University of Berlin, and in 1996 at the Humboldt University of Berlin.
From 2008 to 2016, Ertl served as a member of the university council of Technische Universität Darmstadt. | 0 | Theoretical and Fundamental Chemistry |
Bonds can fall between one of two extremescompletely nonpolar or completely polar. A completely nonpolar bond occurs when the electronegativities are identical and therefore possess a difference of zero. A completely polar bond is more correctly called an ionic bond, and occurs when the difference between electronegativities is large enough that one atom actually takes an electron from the other. The terms "polar" and "nonpolar" are usually applied to covalent bonds, that is, bonds where the polarity is not complete. To determine the polarity of a covalent bond using numerical means, the difference between the electronegativity of the atoms is used.
Bond polarity is typically divided into three groups that are loosely based on the difference in electronegativity between the two bonded atoms. According to the Pauling scale:
* Nonpolar bonds generally occur when the difference in electronegativity between the two atoms is less than 0.5
* Polar bonds generally occur when the difference in electronegativity between the two atoms is roughly between 0.5 and 2.0
* Ionic bonds generally occur when the difference in electronegativity between the two atoms is greater than 2.0
Pauling based this classification scheme on the partial ionic character of a bond, which is an approximate function of the difference in electronegativity between the two bonded atoms. He estimated that a difference of 1.7 corresponds to 50% ionic character, so that a greater difference corresponds to a bond which is predominantly ionic.
As a quantum-mechanical description, Pauling proposed that the wave function for a polar molecule AB is a linear combination of wave functions for covalent and ionic molecules: ψ = aψ(A:B) + bψ(AB). The amount of covalent and ionic character depends on the values of the squared coefficients a and b. | 0 | Theoretical and Fundamental Chemistry |
Biological photovoltaics, also called biophotovoltaics or BPV, is an energy-generating technology which uses oxygenic photoautotrophic organisms, or fractions thereof, to harvest light energy and produce electrical power. Biological photovoltaic devices are a type of biological electrochemical system, or microbial fuel cell, and are sometimes also called photo-microbial fuel cells or “living solar cells”. In a biological photovoltaic system, electrons generated by photolysis of water are transferred to an anode. A relatively high-potential reaction takes place at the cathode, and the resulting potential difference drives current through an external circuit to do useful work. It is hoped that using a living organism (which is capable of self-assembly and self-repair) as the light harvesting material, will make biological photovoltaics a cost-effective alternative to synthetic light-energy-transduction technologies such as silicon-based photovoltaics. | 0 | Theoretical and Fundamental Chemistry |
:V09DA01 Technetium (Tc) disofenin
:V09DA02 Technetium (Tc) etifenin
:V09DA03 Technetium (Tc) lidofenin
:V09DA04 Technetium (Tc) mebrofenin
:V09DA05 Technetium (Tc) galtifenin | 1 | Applied and Interdisciplinary Chemistry |
HRMAS is usually applied to solutions and gels where dipole-dipole interactions are insufficiently averaged by the intermediate molecular motion. HRMAS can dramatically average out residual dipolar interactions and result in spectra with linewidths similar to solution-state NMR. HRMAS links the gap between solution-state and solid-state NMR, and enable the use of solution-state experiments
HRMAS and its medical research application was first described in a 1997 study of human brain tissues from a neurodegenerative disorder. | 0 | Theoretical and Fundamental Chemistry |
Catecholaminergic cell groups refers to collections of neurons in the central nervous system that have been demonstrated by histochemical fluorescence to contain one of the neurotransmitters dopamine or norepinephrine. Thus, it represents the combination of dopaminergic cell groups and noradrenergic cell groups. Some authors include in this category putative adrenergic cell groups, collections of neurons that stain for PNMT, the enzyme that converts norepinephrine to epinephrine (adrenaline).
Catecholaminergic cell groups and Parkinsons disease have an interactive relationship. Catecholaminergic neurons containing neuromelanin are more susceptible to Parkinsons related cell death than nonmelanized catecholaminergic neurons. Neuromelanin is an autoxidation byproduct of catecholamines, and it has been suggested that catecholaminergic neurons surrounded by a low density of glutathione peroxidase cells are more susceptible to degeneration in Parkinsons disease than those protected against oxidative stress. Hyperoxidation may be responsible for the selective degeneration of catecholaminergic neurons, specifically in the substantia nigra'. | 1 | Applied and Interdisciplinary Chemistry |
Amine oxides are used as protecting group for amines and as chemical intermediates. Long-chain alkyl amine oxides are used as amphoteric surfactants and foam stabilizers.
Amine oxides are highly polar molecules and have a polarity close to that of quaternary ammonium salts. Small amine oxides are very hydrophilic and have an excellent water solubility and a very poor solubility in most organic solvents.
Amine oxides are weak bases with a pK of around 4.5 that form , cationic hydroxylamines, upon protonation at a pH below their pK. | 0 | Theoretical and Fundamental Chemistry |
Zero-point energy is fundamentally related to the Heisenberg uncertainty principle. Roughly speaking, the uncertainty principle states that complementary variables (such as a particles position and momentum, or a fields value and derivative at a point in space) cannot simultaneously be specified precisely by any given quantum state. In particular, there cannot exist a state in which the system simply sits motionless at the bottom of its potential well, for then its position and momentum would both be completely determined to arbitrarily great precision. Therefore, the lowest-energy state (the ground state) of the system must have a distribution in position and momentum that satisfies the uncertainty principle, which implies its energy must be greater than the minimum of the potential well.
Near the bottom of a potential well, the Hamiltonian of a general system (the quantum-mechanical operator giving its energy) can be approximated as a quantum harmonic oscillator,
where is the minimum of the classical potential well.
The uncertainty principle tells us that
making the expectation values of the kinetic and potential terms above satisfy
The expectation value of the energy must therefore be at least
where is the angular frequency at which the system oscillates.
A more thorough treatment, showing that the energy of the ground state actually saturates this bound and is exactly , requires solving for the ground state of the system. | 0 | Theoretical and Fundamental Chemistry |
Amplified fragment length polymorphism (AFLP-PCR or AFLP) is a PCR-based tool used in genetics research, DNA fingerprinting, and in the practice of genetic engineering. Developed in the early 1990s by KeyGene, AFLP uses restriction enzymes to digest genomic DNA, followed by ligation of adaptors to the sticky ends of the restriction fragments. A subset of the restriction fragments is then selected to be amplified. This selection is achieved by using primers complementary to the adaptor sequence, the restriction site sequence and a few nucleotides inside the restriction site fragments (as described in detail below). The amplified fragments are separated and visualized on denaturing on agarose gel electrophoresis, either through autoradiography or fluorescence methodologies, or via automated capillary sequencing instruments.
Although AFLP should not be used as an acronym, it is commonly referred to as "Amplified fragment length polymorphism". However, the resulting data are not scored as length polymorphisms, but instead as presence-absence polymorphisms.
AFLP-PCR is a highly sensitive method for detecting polymorphisms in DNA. The technique was originally described by Vos and Zabeau in 1993. In detail, the procedure of this technique is divided into three steps:
#Digestion of total cellular DNA with one or more restriction enzymes and ligation of restriction half-site specific adaptors to all restriction fragments.
#Selective amplification of some of these fragments with two PCR primers that have corresponding adaptor and restriction site specific sequences.
#Electrophoretic separation of amplicons on a gel matrix, followed by visualisation of the band pattern. | 1 | Applied and Interdisciplinary Chemistry |
Lead(II) fluoride can be prepared by treating lead(II) hydroxide or lead(II) carbonate with hydrofluoric acid:
: Pb(OH) + 2 HF → PbF + 2 HO
Alternatively, it is precipitated by adding hydrofluoric acid to a lead(II) salt solution, or by adding a fluoride salt to a lead salt, such as potassium fluoride to a lead(II) nitrate solution,
: 2 KF + Pb(NO) → PbF + 2 KNO
or sodium fluoride to a lead(II) acetate solution.
: 2 NaF + Pb(CHCOO) → PbF + 2 NaCHCOO
It appears as the very rare mineral fluorocronite. | 0 | Theoretical and Fundamental Chemistry |
Subsurface flow wetlands can treat a variety of different wastewaters, such as household wastewater, agricultural, paper mill wastewater, mining runoff, tannery or meat processing wastes, storm water.
The quality of the effluent is determined by the design and should be customized for the intended reuse application (like irrigation or toilet flushing) or the disposal method. | 1 | Applied and Interdisciplinary Chemistry |
Although the most common perovskite compounds contain oxygen, there are a few perovskite compounds that form without oxygen. Fluoride perovskites such as NaMgF are well known. A large family of metallic perovskite compounds can be represented by RTM (R: rare-earth or other relatively large ion, T: transition metal ion and M: light metalloids). The metalloids occupy the octahedrally coordinated "B" sites in these compounds. RPdB, RRhB and CeRuC are examples. MgCNi is a metallic perovskite compound and has received lot of attention because of its superconducting properties. An even more exotic type of perovskite is represented by the mixed oxide-aurides of Cs and Rb, such as CsAuO, which contain large alkali cations in the traditional "anion" sites, bonded to O and Au anions. | 0 | Theoretical and Fundamental Chemistry |
The protein encoded by this gene was initially named CA-related protein because of sequence similarity to other known carbonic anhydrase genes. However, the gene product lacks carbonic anhydrase activity (i.e., the reversible hydration of carbon dioxide). The gene product continues to carry a carbonic anhydrase designation based on clear sequence identity to other members of the carbonic anhydrase gene family. The absence of CA8 gene transcription in the cerebellum of the lurcher mutant in mice with a neurologic defect suggests an important role for this acatalytic form. | 1 | Applied and Interdisciplinary Chemistry |
It is the similar to the bacterial code (translation table 11) but it contains an additional stop codon (TTA) and also has a different set of start codons. | 1 | Applied and Interdisciplinary Chemistry |
Shape-based molecular similarity approaches have been established as important and popular virtual screening techniques. At present, the highly optimized screening platform ROCS (Rapid Overlay of Chemical Structures) is considered the de facto industry standard for shape-based, ligand-centric virtual screening. It uses a Gaussian function to define molecular volumes of small organic molecules. The selection of the query conformation is less important, rendering shape-based screening ideal for ligand-based modeling: As the availability of a bioactive conformation for the query is not the limiting factor for screening — it is more the selection of query compound(s) that is decisive for screening performance. | 1 | Applied and Interdisciplinary Chemistry |
At lower temperatures, about 400–450 °C, an interdiffusion process takes place at the junction, leading to formation of layers of different gold-aluminum intermetallic compounds with different growth rates. Gaps are formed as the denser and faster-growing layers consume the slower-growing layers. This process is known as the Kirkendall voiding, which leads to both increased electrical resistance and mechanical weakening of the wire bond. When the voids forms along the diffusion front, this process is aided by contaminants present in the lattice, and is known as the Horsting voiding, which is a similar process to the Kirkendall voiding. | 1 | Applied and Interdisciplinary Chemistry |
Reverse osmosis (RO) is a water purification process that uses a semi-permeable membrane to separate water molecules from other substances. RO applies pressure to overcome osmotic pressure that favors even distributions. RO can remove dissolved or suspended chemical species as well as biological substances (principally bacteria), and is used in industrial processes and the production of potable water. RO retains the solute on the pressurized side of the membrane and the purified solvent passes to the other side. It relies on the relative sizes of the various molecules to decide what passes through. "Selective" membranes reject large molecules, while accepting smaller molecules (such as solvent molecules, e.g., water).
RO is most commonly known for its use in drinking water purification from seawater, removing the salt and other effluent materials from the water molecules.
As of 2013 the world's largest RO desalination plant was in Sorek, Israel, outputting . | 0 | Theoretical and Fundamental Chemistry |
Kermes mineral or Alkermes mineral was a compound of antimony oxides and sulfides, more specifically, antimony trioxide and trisulfide. It can be made or obtained in the laboratory by the actions of potassium carbonate (KCO) on antimony sulfide. The compound is reddish brown in color and described as a velvety powder which is insoluble in water. It was used extensively in the medical field until the general use of antimony compounds declined due to toxic effects. | 1 | Applied and Interdisciplinary Chemistry |
Reactions on surfaces are reactions in which at least one of the steps of the reaction mechanism is the adsorption of one or more reactants. The mechanisms for these reactions, and the rate equations are of extreme importance for heterogeneous catalysis. Via scanning tunneling microscopy, it is possible to observe reactions at the solid gas interface in real space, if the time scale of the reaction is in the correct range. Reactions at the solid–gas interface are in some cases related to catalysis. | 0 | Theoretical and Fundamental Chemistry |
Tertiary carbons form the most stable carbocations due to a combination of factors. The three alkyl groups on the tertiary carbon contribute to a strong inductive effect. This is because each alkyl group will share its electron density with the central carbocation to stabilize it. Additionally, the surrounding sp3 hybridized carbons can stabilize the carbocation through hyperconjugation. This occurs when adjacent sp3 orbitals have a weak overlap with the vacant p orbital; since there are 3 surrounding carbons with sp3 hybridization, there are more opportunities for overlap, which contributes to increasing carbocation stability. | 0 | Theoretical and Fundamental Chemistry |
Gene therapy is a medical technology that aims to produce a therapeutic effect through the manipulation of gene expression or through altering the biological properties of living cells.
The first attempt at modifying human DNA was performed in 1980, by Martin Cline, but the first successful nuclear gene transfer in humans, approved by the National Institutes of Health, was performed in May 1989. The first therapeutic use of gene transfer as well as the first direct insertion of human DNA into the nuclear genome was performed by French Anderson in a trial starting in September 1990. Between 1989 and December 2018, over 2,900 clinical trials were conducted, with more than half of them in phase I. In 2003, Gendicine became the first gene therapy to receive regulatory approval. Since that time, further gene therapy drugs were approved, such as Glybera (2012), Strimvelis (2016), Kymriah (2017), Luxturna (2017), Onpattro (2018), Zolgensma (2019), Abecma (2021), Adstiladrin, Roctavian and Hemgenix (all 2022). Most of these approaches utilize adeno-associated viruses (AAVs) and lentiviruses for performing gene insertions, in vivo and ex vivo, respectively. AAVs are characterized by stabilizing the viral capsid, lower immunogenicity, ability to transduce both dividing and nondividing cells, the potential to integrate site specifically and to achieve long-term expression in the in-vivo treatment. ASO / siRNA approaches such as those conducted by Alnylam and Ionis Pharmaceuticals require non-viral delivery systems, and utilize alternative mechanisms for trafficking to liver cells by way of GalNAc transporters.
Not all medical procedures that introduce alterations to a patient's genetic makeup can be considered gene therapy. Bone marrow transplantation and organ transplants in general have been found to introduce foreign DNA into patients. | 1 | Applied and Interdisciplinary Chemistry |
Martin Fleischmann of the University of Southampton and Stanley Pons of the University of Utah hypothesized that the high compression ratio and mobility of deuterium that could be achieved within palladium metal using electrolysis might result in nuclear fusion. To investigate, they conducted electrolysis experiments using a palladium cathode and heavy water within a calorimeter, an insulated vessel designed to measure process heat. Current was applied continuously for many weeks, with the heavy water being renewed at intervals. Some deuterium was thought to be accumulating within the cathode, but most was allowed to bubble out of the cell, joining oxygen produced at the anode. For most of the time, the power input to the cell was equal to the calculated power leaving the cell within measurement accuracy, and the cell temperature was stable at around 30 °C. But then, at some point (in some of the experiments), the temperature rose suddenly to about 50 °C without changes in the input power. These high temperature phases would last for two days or more and would repeat several times in any given experiment once they had occurred. The calculated power leaving the cell was significantly higher than the input power during these high temperature phases. Eventually the high temperature phases would no longer occur within a particular cell.
In 1988, Fleischmann and Pons applied to the United States Department of Energy for funding towards a larger series of experiments. Up to this point they had been funding their experiments using a small device built with $100,000 out-of-pocket. The grant proposal was turned over for peer review, and one of the reviewers was Steven Jones of Brigham Young University. Jones had worked for some time on muon-catalyzed fusion, a known method of inducing nuclear fusion without high temperatures, and had written an article on the topic entitled "Cold nuclear fusion" that had been published in Scientific American in July 1987. Fleischmann and Pons and co-workers met with Jones and co-workers on occasion in Utah to share research and techniques. During this time, Fleischmann and Pons described their experiments as generating considerable "excess energy", in the sense that it could not be explained by chemical reactions alone. They felt that such a discovery could bear significant commercial value and would be entitled to patent protection. Jones, however, was measuring neutron flux, which was not of commercial interest. To avoid future problems, the teams appeared to agree to publish their results simultaneously, though their accounts of their 6 March meeting differ. | 0 | Theoretical and Fundamental Chemistry |
The first demonstration of the ProTide approach was made in 1992, when the efficiency of aryloxy phosphates and phosphoramidates was noted. In particular, diaryl phosphates were prepared from zidovudine (AZT) using simple phosphorochloridate chemistry. For the first time, the anti-HIV activity of these phosphate derivatives of AZT exceeded that of the parent nucleoside in some cases. Moreover, while AZT was almost inactive (EC 100μM) in the JM cell line, the substituted diaryl phosphate was 10 times more active (EC 10μM). At the time, JM was considered AZT-insensitive due to poor phosphorylation. It later emerged that an AZT-efflux pump was the source of this poor AZT sensitivity. However, the conclusion remains valid that the diaryl phosphate was more able to retain activity in the JM cell line and that this may imply a (small) degree of intracellular phosphate delivery. The electron-withdrawing power of the p-nitro groups and putative enhancements in aryl leaving group ability were suggested as the major driving force of this SAR.
Subsequently, a series of aryloxy phosphoramidates of AZT were prepared with various p-aryl substituents and several amino acids. These compounds were studied exclusively in the AZT-resistant JM cell line to explore potential (implied) AZT-monophosphate release, with the alanine phosphoramidate proving to be exceptionally effective. In all HIV-1 infected JM cultures, AZT was inhibited at a concentration of 100μM, while the phenyl methoxy alaninyl phosphoramidate was active at 0.8μM. This was taken as the first evidence of a successful nucleotide delivery. It was also noted that in other series, there was a marked preference for alanine over leucine (10-fold) and glycine (>100-fold). Furthermore, although electron-withdrawing aryl substitution had proven highly effective in diaryl systems, it was detrimental in this context. Para fluoro substitution had a slight adventitious effect, but not significantly so, while para-nitro substitution led to a 100-fold loss of activity. In a subsequent study, the range of aryl substituents was expanded, and compounds were tested in both TK+ (thymidine kinase competent) and TK- (thymidine kinase deficient) cell lines. None of the phosphoramidates retained the high (2–4 nM) potency of AZT in TK-competent cell lines (CEM and MT-4) against either HIV-1 or HIV-2. However, while AZT lost all of its activity in the TK- deficient cell line CEM/TK-, most of the phosphoramidates retained antiviral activity, thus being ca >10–35-fold more active than AZT in this assay. Again, alanine emerged as an important component, with the glycine analogue being inactive in HIV-infected CEM/TK- all cultures. In this assay, leucine and phenylalanine were as effective as alanine, although they were less so in CEM/TK+ assays. Thus, the parent phenyl methoxy alanyl phosphoramidate emerged as an important lead compound.
Stavudine (d4T) was an early application of the ProTide approach. This was a rational choice based on the known kinetics of phosphorylation of d4T. Thus, while the second phosphorylation (AZT-monophosphate to AZT-diphosphate) but not the first phosphorylation (AZT to AZT-monophosphate) is regarded as rate limiting for AZT activation to the triphosphate, the first step (d4T to d4T monophosphate) is thought in general to be the slow step for d4T. Thus, an intracellular (mono)nucleotide delivery should have a maximal impact for d4T and similar nucleosides. In the first instance (halo)alkyloxy phosphoramidates of d4T were prepared and found to retain activity in d4T-resistant JM cells. The activity was dependent on the haloalkyl group; the parent propyl system was poorly active. Subsequent studies in HIV-infected CEM/TK- cell cultures revealed the aryloxy phosphoramidates of d4T to be highly effective and, notably, to retain their full activity in CEM/TK- cells. In this study the benzyl ester emerged as slightly more potent than the parent methyl compound, being almost 10-times more active than d4T in CEM/TK+ assays and thus ca 300-500 fold more active than d4T, in CEM/TK- assays. | 1 | Applied and Interdisciplinary Chemistry |
Materia medica (lit.: medical material/substance) is a Latin term from the history of pharmacy for the body of collected knowledge about the therapeutic properties of any substance used for healing (i.e., medications). The term derives from the title of a work by the Ancient Greek physician Pedanius Dioscorides in the 1st century AD, , On medical material (Περὶ ὕλης ἰατρικῆς, Peri hylēs iatrikēs, in Greek).
The term materia medica was used from the period of the Roman Empire until the 20th century, but has now been generally replaced in medical education contexts by the term pharmacology. The term survives in the title of the British Medical Journals "Materia Non Medica" column. | 1 | Applied and Interdisciplinary Chemistry |
Methylazoxymethanol acetate, MAM, is a neurotoxin which reduces DNA synthesis used in making animal models of neurological diseases including schizophrenia and epilepsy. MAM is found in cycad seeds, and causes zamia staggers. It selectively targets neuroblasts in the central nervous system. In rats, administration of MAM affects structures in the brain which are developing most quickly. It is an acetate of methylazoxymethanol. | 1 | Applied and Interdisciplinary Chemistry |
The primary mutualistic interaction between transposon and host organism is in the formation of epialleles. True to the name, an epiallele is a kind of epigenetic mutant of a certain allelic type that produces distinct morphological differences from the wild type. The predominant research into this subject has been conducted on Arabidopsis thaliana, which has the dual disadvantages of being both TE-poor and an overly genetically stable organism. The manner of formation of epialleles is somewhat unclear, but it is thought to be due to the fact that some transposable elements, in stealing pieces of genetic code from their host organism, blend in so well as to confuse the host cellular machinery into thinking that its own genes are the transposons, which leads to epigenetic silencing of certain alleles, forming an epiallele. Some examples of this are:
* FWA, a dominant allele in arabidopsis, turned off by transposon regulation elements. The overall effect of this heritable silencing is to delay flowering.
* BNS, a recessive allele in arabiopsis, hypermethylated via siRNA co-opting of RISC complex, which results in silencing. The overall effect of this is the loss of a putative anaphase promoting complex gene.
* FLC, the flowering locus C gene, which represses flowering time in arabidopsis, can be partially inactivated by the insertion of a Mu-like element (MULE) into the first intron of the gene, resulting in earlier flowering time.
There is also evidence to suggest that trasposons play a more general role than was previously thought in the formation of miRNAs as well as in the silencing of centromeres. | 1 | Applied and Interdisciplinary Chemistry |
The rate for a bimolecular gas-phase reaction, A + B → product, predicted by collision theory is
where:
*k is the rate constant in units of (number of molecules)⋅s⋅m.
* n is the number density of A in the gas in units of m.
* n is the number density of B in the gas in units of m. E.g. for a gas mixture with gas A concentration 0.1 mol⋅L and B concentration 0.2 mol⋅L, the number of density of A is 0.1×6.02×10÷10 = 6.02×10 m, the number of density of B is 0.2×6.02×10÷10 = 1.2×10 m
* Z is the collision frequency in units of m⋅s.
* is the steric factor.
* E is the activation energy of the reaction, in units of J⋅mol.
* T is the temperature in units of K.
* R is the gas constant in units of J molK.
The unit of r(T) can be converted to mol⋅L⋅s, after divided by (1000×N), where N is the Avogadro constant.
For a reaction between A and B, the collision frequency calculated with the hard-sphere model with the unit number of collisions per m per second is:
where:
* n is the number density of A in the gas in units of m.
* n is the number density of B in the gas in units of m. E.g. for a gas mixture with gas A concentration 0.1 mol⋅L and B concentration 0.2 mol⋅L, the number of density of A is 0.1×6.02×10÷10 = 6.02×10 m, the number of density of B is 0.2×6.02×10÷10 = 1.2×10 m.
*σ is the reaction cross section (unit m), the area when two molecules collide with each other, simplified to , where r the radius of A and r the radius of B in unit m.
* k is the Boltzmann constant unit J⋅K.
* T is the absolute temperature (unit K).
* μ is the reduced mass of the reactants A and B, (unit kg).
* N is the Avogadro constant.
* [A] is molar concentration of A in unit mol⋅L.
* [B] is molar concentration of B in unit mol⋅L.
* Z can be converted to mole collision per liter per second dividing by 1000N.
If all the units that are related to dimension are converted to dm, i.e. mol⋅dm for [A] and [B], dm for σ, dm⋅kg⋅s⋅K for the Boltzmann constant, then
unit mol⋅dm⋅s. | 0 | Theoretical and Fundamental Chemistry |
Cucurbiturils have also been explored as supramolecular catalysts. Larger cucurbiturils, such as cucurbit[8]uril can bind multiple guest molecules. CB[8] forms a complex 2:1 (guest:host) with (E)-diaminostilbene dihydrochloride which is accommodated by CB[8]'s larger internal diameter of 8.8 angstrom and height 9.1 angstrom. The close proximity and optimal orientation of the guest molecules within the cavity enhances the rate of the photochemical cyclization to give cyclobutane dimer with a 19:1 stereoselectivity for the syn configuration when bound to CB[8]. In the absence of CB[8] the cyclization reaction does not occur, but only the isomerization of the trans isomer to the cis isomer is observed. | 0 | Theoretical and Fundamental Chemistry |
The method was first described by Williams et al. in the clinical context. The method was used by numerous other studies. This is perhaps the simplest of all the mathematical methods for the calculation of K but the one most sensitive to noise present in the data. A tissue TAC is modelled as a convolution of measured arterial input function with IRF, the estimates for IRF are obtained iteratively to minimise the differences between the left- and right-hand side of the following Equation:
where, is a convolution operator, C(t) is the bone tissue activity concentration of tracer (in units: MBq/ml) over a period of time t, C(t) is the plasma concentration of tracer (in units: MBq/ml) over a period of time t, and IRF(t) is the impulse response of the system (i.e., a tissue in this case). The K is obtained from the IRF in a similar fashion to that obtained for the spectral analysis, as shown in the figure. | 1 | Applied and Interdisciplinary Chemistry |
To measure the partial molar property of a binary solution, one begins with the pure component denoted as and, keeping the temperature and pressure constant during the entire process, add small quantities of component ; measuring after each addition. After sampling the compositions of interest one can fit a curve to the experimental data. This function will be .
Differentiating with respect to will give .
is then obtained from the relation: | 0 | Theoretical and Fundamental Chemistry |
Porphobilinogen (PBG) is an organic compound that occurs in living organisms as an intermediate in the biosynthesis of porphyrins, which include critical substances like hemoglobin and chlorophyll.
The structure of the molecule can be described as molecule of pyrrole with sidechains substituted for hydrogen atoms at positions 2, 3 and 4 in the ring (1 being the nitrogen atom); respectively, an aminomethyl group , an acetic acid (carboxymethyl) group , and a propionic acid (carboxyethyl) group . | 1 | Applied and Interdisciplinary Chemistry |
The transcriptome encompasses all the ribonucleic acid (RNA) transcripts present in a given organism or experimental sample. RNA is the main carrier of genetic information that is responsible for the process of converting DNA into an organisms phenotype. A gene can give rise to a single-stranded messenger RNA (mRNA) through a molecular process known as transcription; this mRNA is complementary to the strand of DNA it originated from. The enzyme RNA polymerase II attaches to the template DNA strand and catalyzes the addition of ribonucleotides to the 3 end of the growing sequence of the mRNA transcript.
In order to initiate its function, RNA polymerase II needs to recognize a promoter sequence, located upstream (5') of the gene. In eukaryotes, this process is mediated by transcription factors, most notably Transcription factor II D (TFIID) which recognizes the TATA box and aids in the positioning of RNA polymerase at the appropriate start site. To finish the production of the RNA transcript, termination takes place usually several hundred nuclecotides away from the termination sequence and cleavage takes place. This process occurs in the nucleus of a cell along with RNA processing by which mRNA molecules are capped, spliced and polyadenylated to increase their stability before being subsequently taken to the cytoplasm. The mRNA gives rise to proteins through the process of translation that takes place in ribosomes. | 1 | Applied and Interdisciplinary Chemistry |
* N-Iodosuccinimide (NIS), the iodine analog of N-chlorosuccinimide.
* N-bromosuccinimide (NBS), the bromine analog of N-chlorosuccinimide.
* Other N-chloro compounds that are commercially available include chloramine-T, trichloroisocyanuric acid ((OCNCl)), 1,3-dichloro-5,5-dimethylhydantoin. | 0 | Theoretical and Fundamental Chemistry |
For thermal transport between two contacting bodies, such as particles in a granular medium, the contact pressure is the factor of most influence on overall contact conductance. As contact pressure grows, true contact area increases and contact conductance grows (contact resistance becomes smaller).
Since the contact pressure is the most important factor, most studies, correlations and mathematical models for measurement of contact conductance are done as a function of this factor.
The thermal contact resistance of certain sandwich kinds of materials that are manufactured by rolling under high temperatures may sometimes be ignored because the decrease in thermal conductivity between them is negligible. | 0 | Theoretical and Fundamental Chemistry |
The lost-wax method is well documented in ancient Indian literary sources. The Shilpa Shastras, a text from the Gupta Period (–550 AD), contains detailed information about casting images in metal. The 5th-century AD Vishnusamhita, an appendix to the Vishnu Purana, refers directly to the modeling of wax for making metal objects in chapter XIV: "if an image is to be made of metal, it must first be made of wax." Chapter 68 of the ancient Sanskrit text Mānasāra Silpa details casting idols in wax and is entitled Maduchchhista Vidhānam, or the "lost wax method". The 12th century text Mānasollāsa, allegedly written by King Someshvara III of the Western Chalukya Empire, also provides detail about lost-wax and other casting processes.
In a 16th-century treatise, the Uttarabhaga of the Śilparatna written by Srïkumāra, verses 32 to 52 of Chapter 2 ("Linga Lakshanam"), give detailed instructions on making a hollow casting. | 1 | Applied and Interdisciplinary Chemistry |
LID has multiple benefits, such as protecting animal habitats, improving management of runoff and flooding, and reducing impervious surfaces. For example, Dr. Allen Davis from the University of Maryland, College Park conducted research on the runoff management from LID rain gardens. His data indicated that LID rain gardens can hold up to 90% of water after a major rain event and release this water over a time scale of up to two weeks. LID also improves groundwater quality and increases its quantity, which increases aesthetics, therefore raising community value.
LID can also be used to eliminate the need for stormwater ponds, which occupy expensive land. Incorporating LID into designs enables developers to build more homes on the same plot of land and maximize their profits.
In some municipalities, LID can be a cost-effective way to reduce the incidence of combined sewer overflows (CSO).
According to the co-benefits approach, LID is an opportunity to technically mitigate urban heat island (UHI) phenomenon with higher compatibilities in cool pavement and green infrastructures. Although there are some intrinsic discrepancies among understandings of LID and UHI mitigation towards blue infrastructure, the osmotic pool, wet pond, and regulating pond are essential supplements to urban water bodies, performing their roles in nourishing vegetation and evaporating for cooling in UHI mitigation. LID pilot projects have already provided the financial foundation for taking the UHI mitigation further. It is an attempt for people in different disciplines to synergistically think about how to mitigate UHI effects, which is conducive to the generation of holistic policies, guidelines and regulations. Furthermore, the inclusion of UHI mitigation can be a driver to public participation in SPC construction, which can consolidate the PPP model for more funds. | 1 | Applied and Interdisciplinary Chemistry |
MetPetDB is a relational database and repository for global geochemical data on and images collected from metamorphic rocks from the Earth's crust. MetPetDB is designed and built by a global community of metamorphic petrologists in collaboration with computer scientists at Rensselaer Polytechnic Institute as part of the National Cyberinfrastructure Initiative and supported by the National Science Foundation. MetPetDB is unique in that it incorporates image data collected by a variety of techniques, e.g. photomicrographs, backscattered electron images (SEM), and X-ray maps collected by wavelength dispersive spectroscopy or energy dispersive spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
This period was one of rapid growth for the Jameson Cells in the existing applications. Seventy-seven Cells were installed in concentrators around the world, mainly in coal and base metal operations. However, during this time, the Cell also moved into the Canadian oil sands industry for the flotation of bitumen. | 1 | Applied and Interdisciplinary Chemistry |
Soil biota affect soil pH directly through excretion, and indirectly by acting on the physical environment. Many soil fungi, although not all of them, acidify the soil by excreting oxalic acid, a product of their respiratory metabolism. Oxalic acid precipitates calcium, forming insoluble crystals of calcium oxalate and thus depriving the soil solution from this necessary element. On the opposite side, earthworms exert a buffering effect on soil pH through their excretion of mucus, endowed with amphoteric properties.
By mixing organic matter with mineral matter, in particular clay particles, and by adding mucus as a glue for some of them, burrowing soil animals, e.g. fossorial rodents, moles, earthworms, termites, some millipedes and fly larvae, contribute to decrease the natural acidity of raw organic matter, as observed in mull humus forms. | 0 | Theoretical and Fundamental Chemistry |
The word Thylakoid comes from the Greek word thylakos or θύλακος, meaning "sac" or "pouch". Thus, thylakoid means "sac-like" or "pouch-like". | 0 | Theoretical and Fundamental Chemistry |
Supercritical carbon dioxide (SCD) can be used instead of PERC (perchloroethylene) or other undesirable solvents for dry-cleaning. Supercritical carbon dioxide sometimes intercalates into buttons, and, when the SCD is depressurized, the buttons pop, or break apart. Detergents that are soluble in carbon dioxide improve the solvating power of the solvent. CO-based dry cleaning equipment uses liquid CO, not supercritical CO, to avoid damage to the buttons. | 0 | Theoretical and Fundamental Chemistry |
One last area that has been actively studied is the synergy of different materials in promoting superior electroactive performance. Whether through various charge transport material, electrochemical species, or morphologies, exploiting the synergetic relationship between different materials has paved the way for even newer counter electrode materials.
In 2016, Lu et al. mixed nickel cobalt sulfide microparticles with reduced graphene oxide (rGO) nanoflakes to create the counter electrode. Lu et al. discovered not only that the rGO acted as a co-catalyst in accelerating the triiodide reduction, but also that the microparticles and rGO had a synergistic interaction that decreased the charge transfer resistance of the overall system. Although the efficiency of this system was slightly lower than its platinum analog (efficiency of NCS/rGO system: 8.96%; efficiency of Pt system: 9.11%), it provided a platform on which further research can be conducted. | 0 | Theoretical and Fundamental Chemistry |
Drospirenone is an antagonist of the AR, the biological target of androgens like testosterone and dihydrotestosterone (DHT). It has about 1 to 65% of the affinity of the synthetic anabolic steroid metribolone for the AR. The medication is more potent as an antiandrogen than spironolactone, but is less potent than cyproterone acetate, with about 30% of its antiandrogenic activity in animals. Progesterone displays antiandrogenic activity in some assays similarly to drospirenone, although this issue is controversial and many researchers regard progesterone as having no significant antiandrogenic activity.
Drospirenone shows antiandrogenic effects on the serum lipid profile, including higher HDL cholesterol and triglyceride levels and lower LDL cholesterol levels, at a dose of 3 mg/day in women. The medication does not inhibit the effects of ethinylestradiol on sex hormone-binding globulin (SHBG) and serum lipids, in contrast to androgenic progestins like levonorgestrel but similarly to other antiandrogenic progestins like cyproterone acetate. SHBG levels are significantly higher with ethinylestradiol and cyproterone acetate than with ethinylestradiol and drospirenone, owing to the more potent antiandrogenic activity of cyproterone acetate relative to drospirenone. Androgenic progestins like levonorgestrel have been found to inhibit the procoagulatory effects of estrogens like ethinylestradiol on hepatic synthesis of coagulation factors, whereas this may occur less or not at all with weakly androgenic progestins like desogestrel and antiandrogenic progestins like drospirenone. | 0 | Theoretical and Fundamental Chemistry |
Ethyl bromoacetate is the chemical compound with the formula . It is the ethyl ester of bromoacetic acid and is prepared in two steps from acetic acid. It is a lachrymator and has a fruity, pungent odor. It is also a highly toxic alkylating agent and may be fatal if inhaled. | 0 | Theoretical and Fundamental Chemistry |
A fixed bed of porous materials (e.g. activated carbons and zeolites) is pressurized and purged with a carrier gas. After becoming stationary one or more adsorptives are added to the carrier gas, resulting in a step-wise change of the inlet concentration. This is in contrast to chromatographic separation processes, where pulse-wise changes of the inlet concentrations are used. The course of the adsorptive concentrations at the outlet of the fixed bed are monitored. | 0 | Theoretical and Fundamental Chemistry |
Hexaamminenickel chloride is the chemical compound with the formula [Ni(NH)]Cl. It is the chloride salt of the metal ammine complex [Ni(NH)]. The cation features six ammonia (called ammines in coordination chemistry) ligands attached to the nickel(II) ion. | 0 | Theoretical and Fundamental Chemistry |
In the late 1990s, evidence began accumulating to suggest that some GPCRs are able to signal without G proteins. The ERK2 mitogen-activated protein kinase, a key signal transduction mediator downstream of receptor activation in many pathways, has been shown to be activated in response to cAMP-mediated receptor activation in the slime mold D. discoideum despite the absence of the associated G protein α- and β-subunits.
In mammalian cells, the much-studied β-adrenoceptor has been demonstrated to activate the ERK2 pathway after arrestin-mediated uncoupling of G-protein-mediated signaling. Therefore, it seems likely that some mechanisms previously believed related purely to receptor desensitisation are actually examples of receptors switching their signaling pathway, rather than simply being switched off.
In kidney cells, the bradykinin receptor B2 has been shown to interact directly with a protein tyrosine phosphatase. The presence of a tyrosine-phosphorylated ITIM (immunoreceptor tyrosine-based inhibitory motif) sequence in the B2 receptor is necessary to mediate this interaction and subsequently the antiproliferative effect of bradykinin. | 1 | Applied and Interdisciplinary Chemistry |
Chemical testing might have a variety of purposes, such as to:
* Determine if, or verify that, the requirements of a specification, regulation, or contract are met
* Decide if a new product development program is on track: Demonstrate proof of concept
* Demonstrate the utility of a proposed patent
* Determine the interactions of a sample with other known substances
* Determine the composition of a sample
* Provide standard data for other scientific, medical, and Quality assurance functions
* Validate suitability for end-use
* Provide a basis for Technical communication
* Provide a technical means of comparison of several options
* Provide evidence in legal proceedings | 0 | Theoretical and Fundamental Chemistry |
An essential amino acid is an amino acid that is required by an organism but cannot be synthesized de novo by it, and therefore must be supplied in its diet. Out of the twenty standard protein-producing amino acids, nine cannot be endogenously synthesized by humans: phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine. | 0 | Theoretical and Fundamental Chemistry |
As an architectural metal, copper provides excellent corrosion resistance. Copper surfaces form tough oxide-sulfate patina coatings that protect underlying copper surfaces and resist corrosion for a very long time.
Copper corrodes at negligible rates in unpolluted air, water, de-aerated non-oxidizing acids, and when exposed to saline solutions, alkaline solutions, and organic chemicals. Copper roofing in rural atmospheres corrodes at rates of less than in 200 years.
Unlike most other metals, copper does not suffer from underside corrosion that can cause premature failures in roofing. With a copper roof, supporting substrates and structures usually fail long before the copper on the roof.
Architectural copper is, however, susceptible to corrosive attack under certain conditions. Oxidizing acids, oxidizing heavy-metal salts, alkalis, sulfur and nitrogen oxides, ammonia, and some sulfur and ammonium compounds can expedite copper corrosion. Precipitation in areas with a pH less than 5.5 may corrode copper, possibly before a patina or protective oxide film has the time to form. Acidic precipitation, known as acid rain, is due to emissions from fossil fuel combustion, chemical manufacturing, or other processes that release sulfur and nitrogen oxides into the atmosphere. Erosion corrosion may occur when acidic water from a non-copper roof that does not neutralise the acidity, such as tile, slate, wood, or asphalt, falls on a small area of copper. Line corrosion can occur if the drip edge of an inert roofing material rests directly on copper. A solution to this may be to raise the lower edge of the shingles with a cant strip, or to provide a replaceable reinforcing strip between the shingles and the copper. Proper water-shedding design and detailing, which reduces the dwell time of acidic water on metal surfaces, can prevent the majority of atmospheric corrosion problems.
Brass, an alloy of copper and zinc, has good resistance to atmospheric corrosion, alkalis, and organic acids. In some potable waters and in seawater, however, brass alloys with 20% or more zinc may suffer corrosive attack. | 1 | Applied and Interdisciplinary Chemistry |
ANCAP reports that some RHD cars imported to Australia did not perform as well on crash tests as the LHD versions, although the cause is unknown, and may be due to differences in testing methodology. | 0 | Theoretical and Fundamental Chemistry |
The Rare Earths Facility was a production plant for various chemicals and metals including thorium, uranium, and radium. It was located in West Chicago, Illinois, USA. | 1 | Applied and Interdisciplinary Chemistry |
There are other LISICON type solid electrolytes which make use of other elements to achieve higher ionic conductivities. One such material has the chemical formula of LiGeVO, where the value of x is between 0 and 1. There are two compositions, LiGeVO and LiGeVO, which had ionic conductivities of 4*10 S/cm and 10 S/cm, an order of magnitude of improvement upon the base LISICON structure. These materials show good thermal stability and are stable in contact with CO and ambient atmosphere, dealing with some problems extant with the original structure.
There are materials with the chemical structure of LiSiPO. This is a solid solution between LiSiO and LiPO. This solid solution can be formed over the whole composition range at room temperature. The highest ionic conductivity are achieved at compositions of LiSiPO and LiSiP, with conductivity on the order of 10 S/cm. This results from the substitution of some Si for P in the lattice, resulting in the addition of interstitial Li-ions which diffuse much more easily. The ionic conductivity is further improved with the doping of Cl to replace O in the lattice. The compositions LiSiPCl and LiGePCl achieved ionic conductivities of 1.03 * 10 S/cm and 3.7*10 S/cm respectively. This is theorized to be the due to the widening of the “bottlenecks” between interstitial points due to the Cl ions smaller size, and the weakening of the ionic bonding Li ions experienced due to chlorine's lower electronegativity.
The conductivities are almost 100 times higher in thio-LISICONs, where oxygen is replaced by sulfur, i.e. the corresponding thiosilicates. The bonding between S and Li is weaker than that between O and Li, allowing for the Li in the sulfide structure to be far more normal than its oxide counterparts. Ceramic thio-LISCON materials based on the chemical formula LiGePS are promising electrolyte materials, with ionic conductivities on the order of 10 S/m or 10 S/m. | 0 | Theoretical and Fundamental Chemistry |
A bond graph in solid-state chemistry is a chemical formula of an extended structure, in which direct bonding connectivities are shown. An example is the perovskite, the unit cell of which is drawn on the left and the bond graph (with added numerical values) on the right:
We see that the oxygen atom bonds to the six nearest rubidium cations, each of which has 4 bonds to the auride anion. The bond graph summarizes these connectivities. The bond orders (also called bond valences) sum up to oxidation states according to the attached sign of the bond's ionic approximation (there are no formal charges in bond graphs).
Determination of oxidation states from a bond graph can be illustrated on ilmenite, . We may ask whether the mineral contains and , or and . Its crystal structure has each metal atom bonded to six oxygens and each of the equivalent oxygens to two irons and two titaniums, as in the bond graph below. Experimental data show that three metal-oxygen bonds in the octahedron are short and three are long (the metals are off-center). The bond orders (valences), obtained from the bond lengths by the bond valence method, sum up to 2.01 at Fe and 3.99 at Ti; which can be rounded off to oxidation states +2 and +4, respectively: | 0 | Theoretical and Fundamental Chemistry |
Karat is a variant of carat. First attested in English in the mid-15th century, the word carat came from Middle French , in turn derived either from Italian or Medieval Latin . These were borrowed into Medieval Europe from the Arabic meaning "fruit of the carob tree", also "weight of 5 grains", () and was a unit of mass though it was probably not used to measure gold in classical times. The Arabic term ultimately originates from the Greek () meaning carob seed (literally "small horn") (diminutive of – , "horn").
In 309 CE, Roman Emperor Constantine I began to mint a new gold coin solidus that was of a libra (Roman pound) of gold equal to a mass of 24 siliquae, where each siliqua (or carat) was of a libra. This is believed to be the origin of the value of the karat. | 1 | Applied and Interdisciplinary Chemistry |
The previously described study by Timby et al. (2015) also assessed the effects of MFGM supplementation in term infants on the risk of infectious diseases and other disease symptoms. In particular, the cumulative incidence of acute otitis media was analyzed between the two randomized feeding groups (control formula or MFGM- supplemented formula to 6 months of age), and compared to a breastfed reference group. The MFGM-supplemented group experienced a significant reduction in episodes of acute otitis media up to 6 months of age compared with infants fed control formula (1% vs 9%; P=0.034); with no significant difference in otitis media incidence compared to the breastfed group (0%). In addition, a significantly lower incidence and longitudinal prevalence of antipyretic drug use was seen in the MFGM-supplemented group (25%) compared with the control formula group (43%). Timby et al. (2017) further showed that the MFGM supplementation influenced the infants’ oral microbiota; the authors noted that, Moraxella catarrhalis, a common bacterial cause of acute otitis media, was less prevalent in infants fed the MFGM-supplemented formula than in those fed control formula.
Zavaleta et al. (2011) evaluated the effects of an MFGM-enriched complementary food on health outcomes in term infants 6 to 11 months of age in Peru. In this double-blind RCT, 499 primarily breast-fed infants were fed for 6 months with a daily milk-based complementary food that included either whey protein concentrate enriched in MFGM, or an equal amount of additional protein from skim milk (control). Results showed that the group with the MFGM-supplemented diet had a significantly lower prevalence of diarrhea during the study compared to the control group (3.84% vs 4.37%; P<0.05), as well as a significant reduction (46%) in episodes of bloody diarrhea compared to the control group (P=0.025).
Later through analyzing the metabolome and immune markers of those infants, Lee et al. (2018) reported that supplementation with MFGM may improve micronutrient status, amino acid, and energy metabolism along with a reduced proinflammatory response (e.g. interleukin-2).
The previously described study by Veereman-Wauters et al. (2012) in preschool-age children (2.5 to 6 years old) also reported the effect of MFGM-supplemented formula consumption on health outcomes. Children receiving the MFGM-supplemented formula reported a significant reduction in the number of days with fever, and particularly the number of short febrile episodes (<3 days), compared to the control group. | 1 | Applied and Interdisciplinary Chemistry |
DNA is a relatively rigid polymer, typically modelled as a worm-like chain. It has three significant degrees of freedom; bending, twisting, and compression, each of which cause certain limits on what is possible with DNA within a cell. Twisting-torsional stiffness is important for the circularisation of DNA and the orientation of DNA bound proteins relative to each other and bending-axial stiffness is important for DNA wrapping and circularisation and protein interactions. Compression-extension is relatively unimportant in the absence of high tension. | 0 | Theoretical and Fundamental Chemistry |
To use physical habitat models to analyze and predict ecosystem potential, compositions must also be determined of the native fish community and a subset of species must be selected for model development. The development of a Reference Fish Community (RFC) is based on the Target Fish Community approach, described by Bain and Meixler (2000). A comprehensive list of species is generated from literature sources and available regional data collected on relatively intact river reaches. The species are ranked on the basis of abundance in long-term fish collection data from multiple rivers of similar character. Securing habitat for naturally occurring dominant species (ecology) should preserve the most profound characteristics of the ecosystem, providing survival conditions for the majority of the aquatic community and therefore a reference for restoration efforts. The simplest way to create a river habitat model is therefore to select the five to ten highest ranking species for model development. It can then be assumed that community structure reflects habitat structure; therefore, the most common species should indicate the most common habitat. Since habitat availability forms the structure of aquatic fauna, the affinity between the structure of the river habitat and the structure of the fish community can be used as a measure of habitat quality.
The results of MesoHABSIM creates the framework for integrative analysis of many aspects of the ecosystem. It also allows managers to recreate reference conditions and evaluate possible instream and watershed restoration measures or alterations (such as dam removals or changes in water withdrawals). From the perspective of resource managers, it not only allows for quantitative measures of ecological integrity, but also creates a basis for making decisions where trade-offs between resource use and river restoration need to be considered. | 1 | Applied and Interdisciplinary Chemistry |
Carbonyl metallurgy is used to manufacture products of iron, nickel, steel, and other metals. Coatings are produced by vapor plating using metal carbonyl vapors. These are metal-ligand complexes where carbon monoxide is bonded to individual atoms of metals .
Iron carbonyl is stable as iron pentacarbonyl, where five carbon monoxide molecules are pendently bonded to the iron atom, while nickel carbonyl is stable as nickel tetracarbonyl, which has four carbon monoxide molecules pendantly bonded to the nickel atom. Both can be formed by the exposure of the powdered metal to carbon monoxide gas at temperatures of around 75 degrees Celsius. Both the metal carbonyls decompose near 175 °C, resulting in a vapor plated metallic coating. The thickness of the vapor plated deposit can be increased to desired thicknesses by controlling the amount of metal carbonyl used and the duration of the plating process.
Vale Inco produces over 100 million pounds (ca. 45000 tonnes) of nickel metal annually by the carbonyl process. The carbonyl process has been used to produce molds in custom shapes for industry. Such molds have been used in plastic molding and other manufacturing techniques.
William Jenkin developed many of the techniques and procedures used in carbonyl metallurgy.
Carbonyl metallurgy is useful as a low-temperature metal coating technique that may find many applications in the future. | 1 | Applied and Interdisciplinary Chemistry |
Ocean-atmospheric exchanges rates of CO depend on the concentration of carbon dioxide already present in both the atmosphere and the ocean, temperature, salinity, and wind speed. This exchange rate can be approximated by Henry's law and can be calculated as S = kP, where the solubility (S) of the carbon dioxide gas is proportional to the amount of gas in the atmosphere, or its partial pressure. | 0 | Theoretical and Fundamental Chemistry |
If antibubbles can be stabilized they can be used to form a long lasting froth — antifoam. Possible uses for antifoam are as a lubricant or using the thin passageways permeating antifoam as a filter for air or other gasses.
Antibubbles themselves could be used for chemical processes such as removing pollutants from a smokestack. Replacing the air in antibubble shells with another liquid could be used for a drug delivery system by creating a shell of liquid-polymer around a drug. Hardening the polymer with ultraviolet light would create a drug filled capsule.
Microscopic antibubbles have demonstrated their feasibility in harmonic imaging.
It has been proposed to incorporate therapeutics into antibubble cores. Such drug-loaded antibubbles might be used in ultrasound-guided drug delivery, where acoustic waves create sufficient pulsations of the antibubble surface to release its drug-containing core. | 1 | Applied and Interdisciplinary Chemistry |
The full ecological consequences of the changes in calcification due to ocean acidification are complex but it appears likely that many calcifying species will be adversely affected by ocean acidification. Increasing ocean acidification makes it more difficult for shell-accreting organisms to access carbonate ions, essential for the production of their hard exoskeletal shell. Oceanic calcifying organism span the food chain from autotrophs to heterotrophs and include organisms such as coccolithophores, corals, foraminifera, echinoderms, crustaceans and molluscs.
Overall, all marine ecosystems on Earth will be exposed to changes in acidification and several other ocean biogeochemical changes. Ocean acidification may force some organisms to reallocate resources away from productive endpoints in order to maintain calcification. For example, the oyster Magallana gigas is recognized to experience metabolic changes alongside altered calcification rates due to energetic tradeoffs resulting from pH imbalances.
Under normal conditions, calcite and aragonite are stable in surface waters since the carbonate ions are supersaturated with respect to seawater. However, as ocean pH falls, the concentration of carbonate ions also decreases. Calcium carbonate thus becomes undersaturated, and structures made of calcium carbonate are vulnerable to calcification stress and dissolution. In particular, studies show that corals, coccolithophores, coralline algae, foraminifera, shellfish and pteropods experience reduced calcification or enhanced dissolution when exposed to elevated . Even with active marine conservation practices it may be impossible to bring back many previous shellfish populations.
Some studies have found different responses to ocean acidification, with coccolithophore calcification and photosynthesis both increasing under elevated atmospheric p, and an equal decline in primary production and calcification in response to elevated , or the direction of the response varying between species.
Similarly, the sea star, Pisaster ochraceus, shows enhanced growth in waters with increased acidity.
Reduced calcification from ocean acidification may affect the ocean's biologically driven sequestration of carbon from the atmosphere to the ocean interior and seafloor sediment, weakening the so-called biological pump. Seawater acidification could also reduce the size of Antarctic phytoplankton, making them less effective at storing carbon. Such changes are being increasingly studied and synthesized through the use of physiological frameworks, including the Adverse Outcome Pathway (AOP) framework. | 0 | Theoretical and Fundamental Chemistry |
Ethanol can be made from mineral oil or from sugars or starches. Starches are cheapest. The starchy crop with highest energy content per acre is cassava, which grows in tropical countries.
Thailand already had a large cassava industry in the 1990s, for use as cattle feed and as a cheap admixture to wheat flour. Nigeria and Ghana are already establishing cassava-to-ethanol plants. Production of ethanol from cassava is currently economically feasible when crude oil prices are above US$120 per barrel.
New varieties of cassava are being developed, so the future situation remains uncertain.
Currently, cassava can yield between 25 and 40 tonnes per hectare (with irrigation and fertilizer), and from a tonne of cassava roots, circa 200 liters of ethanol can be produced (assuming cassava with 22% starch content). A liter of ethanol contains circa 21.46 MJ of energy. The overall energy efficiency of cassava-root to ethanol conversion is circa 32%.
The yeast used for processing cassava is Endomycopsis fibuligera, sometimes used together with bacterium Zymomonas mobilis. | 1 | Applied and Interdisciplinary Chemistry |
Accelerator-based light-ion fusion is a technique using particle accelerators to achieve particle kinetic energies sufficient to induce light-ion fusion reactions.
Accelerating light ions is relatively easy, and can be done in an efficient manner—requiring only a vacuum tube, a pair of electrodes, and a high-voltage transformer; fusion can be observed with as little as 10 kV between the electrodes. The system can be arranged to accelerate ions into a static fuel-infused target, known as beam–target fusion, or by accelerating two streams of ions towards each other, beam–beam fusion. The key problem with accelerator-based fusion (and with cold targets in general) is that fusion cross sections are many orders of magnitude lower than Coulomb interaction cross-sections. Therefore, the vast majority of ions expend their energy emitting bremsstrahlung radiation and the ionization of atoms of the target. Devices referred to as sealed-tube neutron generators are particularly relevant to this discussion. These small devices are miniature particle accelerators filled with deuterium and tritium gas in an arrangement that allows ions of those nuclei to be accelerated against hydride targets, also containing deuterium and tritium, where fusion takes place, releasing a flux of neutrons. Hundreds of neutron generators are produced annually for use in the petroleum industry where they are used in measurement equipment for locating and mapping oil reserves.
A number of attempts to recirculate the ions that "miss" collisions have been made over the years. One of the better-known attempts in the 1970s was Migma, which used a unique particle storage ring to capture ions into circular orbits and return them to the reaction area. Theoretical calculations made during funding reviews pointed out that the system would have significant difficulty scaling up to contain enough fusion fuel to be relevant as a power source. In the 1990s, a new arrangement using a field-reverse configuration (FRC) as the storage system was proposed by Norman Rostoker and continues to be studied by TAE Technologies . A closely related approach is to merge two FRC's rotating in opposite directions, which is being actively studied by Helion Energy. Because these approaches all have ion energies well beyond the Coulomb barrier, they often suggest the use of alternative fuel cycles like p-B that are too difficult to attempt using conventional approaches. | 0 | Theoretical and Fundamental Chemistry |
Solar neutrinos are produced in the core of the Sun through various nuclear fusion reactions, each of which occurs at a particular rate and leads to its own spectrum of neutrino energies. Details of the more prominent of these reactions are described below.
The main contribution comes from the proton–proton chain. The reaction is:
or in words:
: two protons deuteron + positron + electron neutrino.
Of all Solar neutrinos, approximately 91% are produced from this reaction. As shown in the figure titled "Solar neutrinos (proton–proton chain) in the standard solar model", the deuteron will fuse with another proton to create a He nucleus and a gamma ray. This reaction can be seen as:
The isotope He can be produced by using the He in the previous reaction which is seen below.
With both helium-3 and helium-4 now in the environment, one of each weight of helium nucleus can fuse to produce beryllium:
Beryllium-7 can follow two different paths from this stage: It could capture an electron and produce the more stable lithium-7 nucleus and an electron neutrino, or alternatively, it could capture one of the abundant protons, which would create boron-8. The first reaction via lithium-7 is:
This lithium-yielding reaction produces approximately 7% of the solar neutrinos. The resulting lithium-7 later combines with a proton to produce two nuclei of helium-4. The alternative reaction is proton capture, that produces boron-8, which then beta decays into beryllium-8 as shown below:
This alternative boron-yielding reaction produces about 0.02% of the solar neutrinos; although so few that they would conventionally be neglected, these rare solar neutrinos stand out because of their higher average energies. The asterisk (*) on the beryllium-8 nucleus indicates that it is in an excited, unstable state. The excited beryllium-8 nucleus then splits into two helium-4 nuclei: | 0 | Theoretical and Fundamental Chemistry |
Mantle oxidation state (redox state) applies the concept of oxidation state in chemistry to the study of the Earth's mantle. The chemical concept of oxidation state mainly refers to the valence state of one element, while mantle oxidation state provides the degree of decreasing of increasing valence states of all polyvalent elements in mantle materials confined in a closed system. The mantle oxidation state is controlled by oxygen fugacity and can be benchmarked by specific groups of redox buffers.
Mantle oxidation state changes because of the existence of polyvalent elements (elements with more than one valence state, e.g. Fe, Cr, V, Ti, Ce, Eu, C and others). Among them, Fe is the most abundant (~8 wt% of the mantle) and its oxidation state largely reflects the oxidation state of mantle. Examining the valence state of other polyvalent elements could also provide the information of mantle oxidation state.
It is well known that the oxidation state can influence the partitioning behavior of elements and liquid water between melts and minerals, the speciation of C-O-H-bearing fluids and melts, as well as transport properties like electrical conductivity and creep.
The formation of diamond requires both reaching high pressures and high temperatures and a carbon source. The most common carbon source in deep Earth is not elemental carbon and redox reactions need to be involved in diamond formation. Examining the oxidation state can help us predict the P-T conditions of diamond formation and elucidate the origin of deep diamonds. | 0 | Theoretical and Fundamental Chemistry |
David Israel Schuster is a chemist who is currently a professor emeritus at New York University. His research program focused on organic photochemistry and later on fullerenes. | 0 | Theoretical and Fundamental Chemistry |
Zirconium alloys can undergo stress corrosion cracking when exposed to iodine; the iodine is formed as a fission product which depending on the nature of the fuel can escape from the pellet. It has been shown that iodine causes the rate of cracking in pressurised zircaloy-4 tubing to increase. | 0 | Theoretical and Fundamental Chemistry |
*1930s – first reports of the use of sucrose for gel electrophoresis; moving-boundary electrophoresis (Tiselius)
*1950 – introduction of "zone electrophoresis" (Tiselius); paper electrophoresis
*1955 – introduction of starch gels, mediocre separation (Smithies)
*1959 – introduction of acrylamide gels; discontinuous electrophoresis (Ornstein and Davis); accurate control of parameters such as pore size and stability; and (Raymond and Weintraub)
*1965 – introduction of free-flow electrophoresis (Hannig)
*1966 – first use of agar gels
*1969 – introduction of denaturing agents especially SDS separation of protein subunit (Weber and Osborn)
*1970 – Lämmli separated 28 components of T4 phage using a stacking gel and SDS
*1972 – agarose gels with ethidium bromide stain
*1975 – 2-dimensional gels (O’Farrell); isoelectric focusing, then SDS gel electrophoresis
*1977 – sequencing gels (Sanger)
*1981 – introduction of capillary electrophoresis (Jorgenson and Lukacs)
*1983 – pulsed-field gel electrophoresis enables separation of large DNA molecules (Sweeley)
*2004 – introduction of a standardized polymerization time for acrylamide gel solutions to optimize gel properties, in particular thermodynamic stability, during electrophoresis (Kastenholz)
A 1959 book on electrophoresis by Milan Bier cites references from the 1800s. However, Oliver Smithies made significant contributions. Bier states: "The method of Smithies ... is finding wide application because of its unique separatory power." Taken in context, Bier clearly implies that Smithies' method is an improvement. | 1 | Applied and Interdisciplinary Chemistry |
V̇O may also be calculated by the Fick equation:
, when these values are obtained during exertion at a maximal effort. Here Q is the cardiac output of the heart, CO is the arterial oxygen content, and CO is the venous oxygen content. (CO – CO) is also known as the arteriovenous oxygen difference.
The Fick equation may be used to measure V̇O in critically ill patients, but its usefulness is low even in non-exerted cases. Using a breath-based VO to estimate cardiac output, on the other hand, seems to be reliable enough. | 1 | Applied and Interdisciplinary Chemistry |
Allylic strain, or A strain is closely associated to syn-pentane strain. An example of allylic strain can be seen in the compound 2-pentene. It's possible for the ethyl substituent of the olefin to rotate such that the terminal methyl group is brought near to the vicinal methyl group of the olefin. These types of compounds usually take a more linear conformation to avoid the steric strain between the substituents. | 0 | Theoretical and Fundamental Chemistry |
Once an attosecond light source is available, one has to drive the pulse towards the sample of interest and, then, measure its dynamics.
The most suitable experimental observables to analyze the electron dynamics in matter are:
* Angular asymmetry in the velocity distribution of molecular photo-fragment.
* Quantum yield of molecular photo-fragments.
* XUV-SXR spectrum transient absorption.
* XUV-SXR spectrum transient reflectivity.
* Photo-electron kinetic energy distribution.
The general strategy is to use a pump-probe scheme to "image" through one of the aforementioned observables the ultra-fast dynamics occurring in the material under investigation. | 0 | Theoretical and Fundamental Chemistry |
The [4+2] cycloaddition of singlet oxygen to cyclopentadiene to create cis-2-cyclopentene-1,4-diol is a common step involved in the synthesis of prostaglandins. The initial addition singlet oxygen, through the concerted [4+2] cycloaddition, forms an unstable endoperoxide. Subsequent reduction of the peroxide bound produces the two alcohol groups. | 0 | Theoretical and Fundamental Chemistry |
The viral vectors described above have natural host cell populations that they infect most efficiently. Retroviruses have limited natural host cell ranges, and although adenovirus and adeno-associated virus are able to infect a relatively broader range of cells efficiently, some cell types are resistant to infection by these viruses as well. Attachment to and entry into a susceptible cell is mediated by the protein envelope on the surface of a virus. Retroviruses and adeno-associated viruses have a single protein coating their membrane, while adenoviruses are coated with both an envelope protein and fibers that extend away from the surface of the virus. The envelope proteins on each of these viruses bind to cell-surface molecules such as heparin sulfate, which localizes them upon the surface of the potential host, as well as with the specific protein receptor that either induces entry-promoting structural changes in the viral protein, or localizes the virus in endosomes wherein acidification of the lumen induces this refolding of the viral coat. In either case, entry into potential host cells requires a favorable interaction between a protein on the surface of the virus and a protein on the surface of the cell.
For the purposes of gene therapy, one might either want to limit or expand the range of cells susceptible to transduction by a gene therapy vector. To this end, many vectors have been developed in which the endogenous viral envelope proteins have been replaced by either envelope proteins from other viruses, or by chimeric proteins. Such chimera would consist of those parts of the viral protein necessary for incorporation into the virion as well as sequences meant to interact with specific host cell proteins. Viruses in which the envelope proteins have been replaced as described are referred to as pseudotyped viruses. For example, the most popular retroviral vector for use in gene therapy trials has been the lentivirus Simian immunodeficiency virus coated with the envelope proteins, G-protein, from Vesicular stomatitis virus. This vector is referred to as VSV G-pseudotyped lentivirus, and infects an almost universal set of cells. This tropism is characteristic of the VSV G-protein with which this vector is coated. Many attempts have been made to limit the tropism of viral vectors to one or a few host cell populations. This advance would allow for the systemic administration of a relatively small amount of vector. The potential for off-target cell modification would be limited, and many concerns from the medical community would be alleviated. Most attempts to limit tropism have used chimeric envelope proteins bearing antibody fragments. These vectors show great promise for the development of "magic bullet" gene therapies. | 1 | Applied and Interdisciplinary Chemistry |
In reaction kinetics, a rate effect is sometimes observed between different isotopomers of the same chemical. This kinetic isotope effect can be used to study reaction mechanisms by analyzing how the differently massed atom is involved in the process. | 0 | Theoretical and Fundamental Chemistry |
Identity by descent (IBD) mapping generally uses single nucleotide polymorphism (SNP) arrays to survey known polymorphic sites throughout the genome of affected individuals and their parents and/or siblings, both affected and unaffected. While these SNPs probably do not cause the disease, they provide valuable insight into the makeup of the genomes in question. A region of the genome is considered identical by descent if contiguous SNPs share the same genotype. When comparing an affected individual to his/her affected sibling, all identical regions are recorded (ex. Shaded in red in above figure). Given that an affected sibling and an unaffected sibling do not have the same disease phenotype, their DNA must by definition be different (barring the presence of a genetic or environmental modifier). Thus, the IBD mapping results can be further supplemented by removing any regions that are identical in both affected individuals and unaffected siblings. This is then repeated for multiple families, thus generating a small, overlapping fragment, which theoretically contains the disease gene. | 1 | Applied and Interdisciplinary Chemistry |
The wave method is based on the physically accurate concept that transient pipe flow occurs as a result of pressure waves generated and propagated from a disturbance in the pipe system (valve closure, pump trip, etc.) This method was developed and first described by Don J. Wood in 1966. A pressure wave, which represents a rapid pressure and associated flow change, travels at sonic velocity for the liquid pipe medium, and the wave is partially transmitted and reflected at all discontinuities in the pipe system (pipe junctions, pumps, open or closed ends, surge tanks, etc.) A pressure wave can also be modified by pipe wall resistance. This description is one that closely represents the actual mechanism of transient pipe flow. | 1 | Applied and Interdisciplinary Chemistry |
Charles Moureu died on June 13, 1929.
Subscribers funded the creation of a monument in his honor in the Parc Beaumont in Pau in 1933. The bust was sculpted by Ernest Gabard. Further celebrations were held in Pau and Mourenx on the centenary of his birthday in 1963. | 0 | Theoretical and Fundamental Chemistry |
* AsP
* [GeSn]
* [SnBi]
* [SnBi]
* [PbSb]
* SnSb
* [InBi]
* BiGe
* [GaBi]
* [InBi]
* [TlSn]
* [TlSn]
* [Sb@InSb]
* [Sb@InSb] | 0 | Theoretical and Fundamental Chemistry |
The proper identification of splice sites has to be highly precise as the consensus splice sequences are very short and there are many other sequences similar to the authentic splice sites within gene sequences, which are known as cryptic, non-canonical, or pseudo splice sites. When an authentic or real splice site is mutated, any cryptic splice sites present close to the original real splice site could be erroneously used as authentic site, resulting in an aberrant mRNA. The erroneous mRNA may include a partial sequence from the neighboring intron or lose a partial exon, which may result in a premature stop codon. The result may be a truncated protein that would have lost its function completely.
Shapiro–Senapathy algorithm can identify the cryptic splice sites, in addition to the authentic splice sites. Cryptic sites can often be stronger than the authentic sites, with a higher S&S score. However, due to the lack of an accompanying complementary donor or acceptor site, this cryptic site will not be active or used in a splicing reaction. When a neighboring real site is mutated to become weaker than the cryptic site, then the cryptic site may be used instead of the real site, resulting in a cryptic exon and an aberrant transcript.
Numerous diseases have been caused by cryptic splice site mutations or usage of cryptic splice sites due to the mutations in authentic splice sites. | 1 | Applied and Interdisciplinary Chemistry |
Dr. Robert K. Crane, a Harvard graduate, had been working in the field of carbohydrate biochemistry for quite some time. His experience in the areas of glucose-6-phosphate biochemistry, carbon dioxide fixation, hexokinase and phosphate studies led him to hypothesize cotransport of glucose along with sodium through the intestine. Pictured right is of Dr. Crane and his drawing of the cotransporter system he proposed in 1960, at the international meet on membrane transport and metabolism. His studies were confirmed by other groups and are now used as the classical model to understand cotransporters. | 1 | Applied and Interdisciplinary Chemistry |
As widely reported in the scientific literature, bone density is just one of the components of bone strength thus it only partially predicts bone fragility. In order to overcome this limitation, a novel parameter, Fragility Score, has been developed. Fragility Score evaluates bone microstructural features independently from BMD and it is based on the assumption that a fragile bone structure has microstructural features which, in turn, influence the spectral characteristics of the acquired ultrasound signal, being different from those reflecting a robust bone structure. Fragility Score is an adimensional parameter, ranging from 0 to 100, obtained by comparing the spectra of the acquired ultrasound signals with the spectral reference models obtained from patients who did, or did not, developed an osteoporotic fracture. This parameter has been validated through clinical studies and its accuracy has demonstrated a performance similar to DXA BMD. | 0 | Theoretical and Fundamental Chemistry |
A cDNA library represents a sample of the mRNA purified from a particular source (either a collection of cells, a particular tissue, or an entire organism), which has been converted back to a DNA template by the use of the enzyme reverse transcriptase. It thus represents the genes that were being actively transcribed in that particular source under the physiological, developmental, or environmental conditions that existed when the mRNA was purified. cDNA libraries can be generated using techniques that promote "full-length" clones or under conditions that generate shorter fragments used for the identification of "expressed sequence tags".
cDNA libraries are useful in reverse genetics, but they only represent a very small (less than 1%) portion of the overall genome in a given organism.
Applications of cDNA libraries include:
* Discovery of novel genes
* Cloning of full-length cDNA molecules for in vitro study of gene function
* Study of the repertoire of mRNAs expressed in different cells or tissues
* Study of alternative splicing in different cells or tissues | 1 | Applied and Interdisciplinary Chemistry |
The classical acetoacetatic ester synthesis utilizes the 1:1 conjugate base. Ethyl acetoacetate is however diprotic:
:CHC(O)CHCOEt + NaH → CHC(O)CH(Na)COEt + H
:CHC(O)CH(Na)COEt + BuLi → LiCHC(O)CH(Na)COEt + BuH
The dianion (i.e., LiCHC(O)CH(Na)COEt) adds electrophile to the terminal carbon as depicted in the following simplified form:
:LiCHC(O)CH(Na)COEt + RX → RCHC(O)CH(Na)COEt + LiX | 0 | Theoretical and Fundamental Chemistry |
A list of required tools and packages for SSCS and DCS analysis can be found [https://github.com/loeblab/Duplex-Sequencing|DS online.] | 1 | Applied and Interdisciplinary Chemistry |
One mechanism, considered important for small atomic numbers is the scattering of a free electron at the shell electrons of an atom or molecule. Since electron–electron bremsstrahlung is a function of and the usual electron-nucleus bremsstrahlung is a function of electron–electron bremsstrahlung is negligible for metals. For air, however, it plays an important role in the production of terrestrial gamma-ray flashes. | 0 | Theoretical and Fundamental Chemistry |
Raymond Urgel Lemieux, CC, AOE, FRS (June 16, 1920 – July 22, 2000) was a Canadian organic chemist, who pioneered many discoveries in the field of chemistry, his first and most famous being the synthesis of sucrose. His contributions include the discovery of the anomeric effect and the development of general methodologies for the synthesis of saccharides still employed in the area of carbohydrate chemistry. He was a fellow of the Royal Society of Canada and the Royal Society (England), and a recipient of the prestigious Albert Einstein World Award of Science and Wolf Prize in Chemistry. | 0 | Theoretical and Fundamental Chemistry |
Biochemical Predestination is a 1969 book by Dean H. Kenyon and Gary Steinman which argued in support of biochemical evolution.
In the book, Kenyon and Steinman conclude that "Life might have been biochemically predestined by the properties of attraction that exist between its chemical parts, especially between amino acids in proteins." They argued that life originated with the chemical properties of amino acids causing them to be attracted to each other, forming long protein chains, most important in every living cell. Kenyon believed that proteins were directly formed by attraction between amino acids without DNA coding, and that these were derivatives from non-living raw chemicals in a conducive environment.
In 1976 Kenyon was persuaded by the young Earth creationist arguments of A. E. Wilder-Smith. In the 1982 foreword he wrote to What Is Creation Science? by Henry M. Morris and Gary Parker, Kenyon said that he no longer accepted the pro-evolution arguments in Biochemical Predestination. At the Edwards v. Aguillard trial he provided an affidavit in support of creation science and noted the book as one of his publications. In 1989 Kenyon became a co-author of Of Pandas and People which rebranded creation science as intelligent design. | 1 | Applied and Interdisciplinary Chemistry |
SIT theory was first proposed by Brønsted and was further developed by Guggenheim. Scatchard extended the theory to allow the interaction coefficients to vary with ionic strength. The theory was mainly of theoretical interest until 1945 because of the difficulty of determining equilibrium constants before the glass electrode was invented. Subsequently, Ciavatta developed the theory further.
The activity coefficient of the jth ion in solution is written as γ when concentrations are on the molal concentration scale and as y when concentrations are on the molar concentration scale. (The molality scale is preferred in thermodynamics because molal concentrations are independent of temperature). The basic idea of SIT theory is that the activity coefficient can be expressed as
: (molalities)
or
: (molar concentrations)
where z is the electrical charge on the ion, I is the ionic strength, ε and b are interaction coefficients and m and c are concentrations. The summation extends over the other ions present in solution, which includes the ions produced by the background electrolyte. The first term in these expressions comes from Debye–Hückel theory. The second term shows how the contributions from "interaction" are dependent on concentration. Thus, the interaction coefficients are used as corrections to Debye–Hückel theory when concentrations are higher than the region of validity of that theory.
The activity coefficient of a neutral species can be assumed to depend linearly on ionic strength, as in
where k is a Sechenov coefficient.
In the example of a monobasic acid HA, assuming that the background electrolyte is the salt NaNO, the interaction coefficients will be for interaction between H and NO, and between A and Na. | 0 | Theoretical and Fundamental Chemistry |
Reflections, or mirror isometries, denoted by F, where c is a point in the plane and v is a unit vector in R. (F is for "flip".) have the effect of reflecting the point p in the line L that is perpendicular to v and that passes through c. The line L is called the reflection axis or the associated mirror. To find a formula for F, we first use the dot product to find the component t of p − c in the v direction,
and then we obtain the reflection of p by subtraction,
The combination of rotations about the origin and reflections about a line through the origin is obtained with all orthogonal matrices (i.e. with determinant 1 and −1) forming orthogonal group O(2). In the case of a determinant of −1 we have:
which is a reflection in the x-axis followed by a rotation by an angle θ, or equivalently, a reflection in a line making an angle of θ/2 with the x-axis. Reflection in a parallel line corresponds to adding a vector perpendicular to it. | 0 | Theoretical and Fundamental Chemistry |
Autoinducers are signaling molecules that are produced in response to changes in cell-population density. As the density of quorum sensing bacterial cells increases so does the concentration of the autoinducer. Detection of signal molecules by bacteria acts as stimulation which leads to altered gene expression once the minimal threshold is reached. Quorum sensing is a phenomenon that allows both Gram-negative and Gram-positive bacteria to sense one another and to regulate a wide variety of physiological activities. Such activities include symbiosis, virulence, motility, antibiotic production, and biofilm formation. Autoinducers come in a number of different forms depending on the species, but the effect that they have is similar in many cases. Autoinducers allow bacteria to communicate both within and between different species. This communication alters gene expression and allows bacteria to mount coordinated responses to their environments, in a manner that is comparable to behavior and signaling in higher organisms. Not surprisingly, it has been suggested that quorum sensing may have been an important evolutionary milestone that ultimately gave rise to multicellular life forms. | 1 | Applied and Interdisciplinary Chemistry |
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