text stringlengths 105 4.57k | label int64 0 1 | label_text stringclasses 2
values |
|---|---|---|
In chemistry, biochemistry and environmental sciences, deuterium is used as a non-radioactive, stable isotopic tracer, for example, in the doubly labeled water test. In chemical reactions and metabolic pathways, deuterium behaves somewhat similarly to ordinary hydrogen (with a few chemical differences, as noted). It can be distinguished from ordinary hydrogen most easily by its mass, using mass spectrometry or infrared spectrometry. Deuterium can be detected by femtosecond infrared spectroscopy, since the mass difference drastically affects the frequency of molecular vibrations; deuterium-carbon bond vibrations are found in spectral regions free of other signals.
Measurements of small variations in the natural abundances of deuterium, along with those of the stable heavy oxygen isotopes O and O, are of importance in hydrology, to trace the geographic origin of Earth's waters. The heavy isotopes of hydrogen and oxygen in rainwater (so-called meteoric water) are enriched as a function of the environmental temperature of the region in which the precipitation falls (and thus enrichment is related to mean latitude). The relative enrichment of the heavy isotopes in rainwater (as referenced to mean ocean water), when plotted against temperature falls predictably along a line called the global meteoric water line (GMWL). This plot allows samples of precipitation-originated water to be identified along with general information about the climate in which it originated. Evaporative and other processes in bodies of water, and also ground water processes, also differentially alter the ratios of heavy hydrogen and oxygen isotopes in fresh and salt waters, in characteristic and often regionally distinctive ways. The ratio of concentration of H to H is usually indicated with a delta as δH and the geographic patterns of these values are plotted in maps termed as isoscapes. Stable isotopes are incorporated into plants and animals and an analysis of the ratios in a migrant bird or insect can help suggest a rough guide to their origins. | 0 | Theoretical and Fundamental Chemistry |
Metal complexes containing only nitrosyl ligands are called isoleptic nitrosyls. They are rare, the premier member being Cr(NO). Even trinitrosyl complexes are uncommon, whereas polycarbonyl complexes are routine. | 0 | Theoretical and Fundamental Chemistry |
The recommendations describe three ways of assigning "parent" names to homonuclear monocyclic hydrides (i.e single rings consisting of one element):
* the Hantzsch–Widman nomenclature (the method preferred for rings of size 3–10)
* "skeletal replacement nomenclature"—specifying the replacement of carbon atoms in the corresponding carbon compound with atoms of another element (e.g. silicon becomes sila, germanium, germa) and a multiplicative prefix tri, tetra, penta etc)( the method preferred for rings greater than 10)
* by adding the prefix cyclo to the name of the corresponding unbranched, unsubstituted chain | 0 | Theoretical and Fundamental Chemistry |
By modifying the amino acid sequence of sunflower trypsin inhibitor, more specifically, sunflower trypsin inhibitor-1 (SFTI-1), researchers have been able to develop synthetic serine protease inhibitors that have specificity and improved inhibitory activity towards certain serine proteases that are found in the human body, such as tissue kallikreins and human matriptase-1. For instance, researchers from the Institute of Child Health and the Department of Chemistry of the University College London, have created two SFTI-1 analogs (I10G and I10H) by substituting residue 10 of SFTI-1 (isoleucine, I) with glycine (G) and histidine (H), respectively. Out of the two analogs, SFTI-I10H was found to be the more potent KLK5 inhibitor. Another group of researchers from the previously mentioned institute and department of the University College London, conducted further research on the development of synthetic kallikrein inhibitors by modifying the amino acid sequence of SFTI-I10H. Out of the six SFTI-I10H variants that were constructed by modifying SFTI-I10H, the first and second variant (K5R_I10H and I10H_F12W) demonstrated improved KLK5 inhibition and the sixth variant (K5R_I10H_F12W) showed dual-inhibition of KLK5 and KLK7, improved KLK5 inhibition potency, and specificity for KLK5 and KLK14. The first variant (K5R_I10H) was made by replacing residue 5 of SFTI-I10H (lysine, K) with arginine (R), and in order to get the second variant (I10H_F12W) residue 12 (phenylalanine, F) was replaced with tryptophan (W). Lastly, the sixth variant (K5R_I10H_F12W) was developed by combining the amino acid substitutions of the first and second variants.
Moreover, researchers from the Clemens-Schöpf Institute of Organic Chemistry and Biochemistry and Helmholtz-Institute for Pharmaceutical Research Saarland, developed potent synthetic human matriptase-1 inhibitors based on a different SFTI-1 variant, SDMI-1. SFTI-1 derived matriptase inhibitor-1 (SDMI-1) was previously developed by replacing residue 10 of SFTI-1 (isoleucine, I) with arginine (R) and residue 12 (phenylalanine, F) with histidine (H). Further modifications of SDMI-1 resulted in synthetic matriptase-1 inhibitors with improved inhibitory activity, matriptase binding, and inhibition potency. The SDMI-1 variant that resulted in enhanced inhibitory activity was developed by replacing residue 1 of SDMI-1 (glycine, G) with lysine (K) and by keeping it as a monocyclic structure. The SDMI-1 variant that resulted in improved matriptase binding was created by using the same amino acid substitutions of the previously mentioned SDMI-1 variant and by attaching a bulky fluorescein moiety to the side chain of lysine. Lastly, the SDMI-1 variant that had enhanced inhibition potency was developed by applying the same amino acid substitutions of the previous variants, cleaving the proline-aspartic acid sequence found at the C-terminus (PD-OH), and by making it a bicyclic compound via tail-to-side-chain cyclization. | 1 | Applied and Interdisciplinary Chemistry |
A major breakthrough that allowed the large scale manufacture of fluorocarbons was the Fowler process. In this process, cobalt trifluoride is used as the source of fluorine. Illustrative is the synthesis of perfluorohexane:
The resulting cobalt difluoride is then regenerated, sometimes in a separate reactor:
Industrially, both steps are combined, for example in the manufacture of the Flutec range of fluorocarbons by F2 chemicals Ltd, using a vertical stirred bed reactor, with hydrocarbon introduced at the bottom, and fluorine introduced halfway up the reactor. The fluorocarbon vapor is recovered from the top. | 1 | Applied and Interdisciplinary Chemistry |
Conventional measurement of the EQE will give the efficiency of the overall device. However it is often useful to have a map of the EQE over large area of the device. This mapping provides an efficient way to visualize the homogeneity and/or the defects in the sample. It was realized by researchers from the Institute of Researcher and Development on Photovoltaic Energy (IRDEP) who calculated the EQE mapping from electroluminescence measurements taken with a hyperspectral imager. | 0 | Theoretical and Fundamental Chemistry |
The potential HCV resistance against DAA drugs is a concern. Among the HCV quasispecies there are pre-existing variants with the potential to confer resistance to NS5A inhibitors without having any previous exposure to those drugs. Generally, the replication of these variants happens only in minute quantities, making them undetectable by current techniques. On the other hand, it is possible to selectively grow immune variants in the presence of NS5A inhibitors. HCV resistance is characterized by a certain escape pattern. This pattern is often associated with amino acid substitutions that confer upon the virus a robust drug resistance without impairing the viral fitness. It has been established that NS5A inhibitors possess a relatively low threshold for resistance, and variants that are associated with NS5A resistance have been shown to endure for up to six months in patients following treatment cessation. Therefore, combination therapies produce higher efficacy and shorter treatment periods. | 1 | Applied and Interdisciplinary Chemistry |
QR is synthesized by a condensation reaction between the methyl group of 1-ethyl-2-methylquinolinium iodide and the carbonyl of para-dimethylaminobenzaldehyde. | 0 | Theoretical and Fundamental Chemistry |
Since its introduction in 1977, Northern blot has been used extensively for RNA quantification despite its shortcomings: (a) time-consuming technique, (b) requires a large quantity of RNA for detection, and (c) quantitatively inaccurate in the low abundance of RNA content. However, since PCR was invented by Kary Mullis in 1983, RT PCR has since displaced Northern blot as the method of choice for RNA detection and quantification.
RT-PCR has risen to become the benchmark technology for the detection and/or comparison of RNA levels for several reasons: (a) it does not require post PCR processing, (b) a wide range (>10-fold) of RNA abundance can be measured, and (c) it provides insight into both qualitative and quantitative data. Due to its simplicity, specificity and sensitivity, RT-PCR is used in a wide range of applications from experiments as simple as quantification of yeast cells in wine to more complex uses as diagnostic tools for detecting infectious agents such as the avian flu virus and SARS-CoV-2. | 1 | Applied and Interdisciplinary Chemistry |
The amplitude of oscillation is also an important parameter for the stall behaviour of an airfoil. With a larger oscillating angle, deep dynamic stall tends to occur. | 1 | Applied and Interdisciplinary Chemistry |
When insulin binds to the cell's receptor, it results in negative feedback by limiting or stopping some other actions in the cell. It inhibits the release and production of glucose from the cells which is an important part in reducing the glucose blood level. Insulin will also inhibit the breakdown of glycogen into glucose by inhibiting the expression of the enzymes that catalyzes the degradation of Glycogen.
An example of negative feedback is slowing or stopping the intake of glucose after the pathway was activated. Negative feedback is shown in the insulin signal transduction pathway by constricting the phosphorylation of the insulin-stimulated tyrosine. The enzyme that deactivates or phosphorylates the insulin-stimulated tyrosine is called tyrosine phosphatases (PTPases). When activated, this enzyme provides a negative feedback by catalyzing the dephosphorylation of the insulin receptors. The dephosphorylation of the insulin receptor slows down glucose intake by inhibiting the activation (phosphorylation) of proteins responsible for further steps of the insulin transduction pathway. | 1 | Applied and Interdisciplinary Chemistry |
One of the first companies to begin experimenting with hair cloning was Intercytex. Researchers at the company were convinced that their approach was the cure for baldness, and if the technology is fully developed, they can basically eliminate hair loss due to hereditary factors. This therapy would also eliminate the need for donor hair, as it can be simply grown from the patient's own cells.
Intercytex tried to clone new hair follicles from the stem cells harvested from the back of the neck. They hoped that if they multiplied (cloned) the follicles and then implanted them back in the scalp in the bald areas they would be successful in regrowing the hair itself. They tested the method in their Phase II trials, which showed very promising results as two-thirds of the bald male patients were able to grow new hair after the treatment.
The company was hoping to complete the research so they can make it available to the public, so they began Phase III trials. They estimated they would be able to finish the process in a few years. However, these tests did not show the expected progress. In 2008 Intercytex admitted that they failed in fully developing the hair cloning therapy and decided to discontinue all research.
This was not solely the result of the failed tests, as the company's financial background also became unstable in 2008 and they had to implement several cost-cutting measures. They laid off a great number of staff members and cut funding to the research projects such as hair cloning. In 2010 they went out of business. | 1 | Applied and Interdisciplinary Chemistry |
Two-metal dual activation represents the combination of the enolate activation mode and the alkyne activation mode into a single reaction system. Generally, a hard, oxophilic metal (K, Na, Ag) activates the enolate oxygen, while a soft, carbophilic metal (Pd, Cu, Mo) coordinates with the alkyne. In some instances, however, the precise role of each metal is unclear. For example, in a 2005 study Toste et al. found that treatment of an alkynyl-tethered β-ketoester with a Pd(II) phosphine complex and Yb(OTf) effected asymmetric cyclization to the corresponding cyclopentane. It is proposed that a Pd-enolate adds into a Yb-activated alkyne, though there is also precedent for Pd activation of alkynes. | 0 | Theoretical and Fundamental Chemistry |
Armodafinil is currently FDA-approved to treat excessive daytime sleepiness associated with obstructive sleep apnea, narcolepsy, and shift work disorder. It is commonly used off-label to treat attention deficit hyperactivity disorder, chronic fatigue syndrome, and major depressive disorder, and has been repurposed as an adjunctive treatment for bipolar disorder. It has been shown to improve vigilance in air traffic controllers, however in the United States, sleep prevention medications such as modafinil (Provigil) and armodafinil (Nuvigil) are not approved by the FAA for civilian controllers or pilots. | 0 | Theoretical and Fundamental Chemistry |
The Curtin–Hammett principle has been invoked to explain selectivity in a variety of synthetic pathways. One example is observed en route to the antitumor antibiotic AT2433-A1, in which a Mannich-type cyclization proceeds with excellent regioselectivity. Studies demonstrate that the cyclization step is irreversible in the solvent used to run the reaction, suggesting that Curtin–Hammett kinetics can explain the product selectivity. | 0 | Theoretical and Fundamental Chemistry |
The cellular level of β-catenin is mostly controlled by its ubiquitination and proteosomal degradation. The E3 ubiquitin ligase TrCP1 (also known as β-TrCP) can recognize β-catenin as its substrate through a short linear motif on the disordered N-terminus. However, this motif (Asp-Ser-Gly-Ile-His-Ser) of β-catenin needs to be phosphorylated on the two serines in order to be capable to bind β-TrCP. Phosphorylation of the motif is performed by Glycogen Synthase Kinase 3 alpha and beta (GSK3α and GSK3β). GSK3s are constitutively active enzymes implicated in several important regulatory processes. There is one requirement, though: substrates of GSK3 need to be pre-phosphorylated four amino acids downstream (C-terminally) of the actual target site. Thus it also requires a "priming kinase" for its activities. In the case of β-catenin, the most important priming kinase is Casein Kinase I (CKI). Once a serine-threonine rich substrate has been "primed", GSK3 can "walk" across it from C-terminal to N-terminal direction, phosphorylating every 4th serine or threonine residues in a row. This process will result in dual phosphorylation of the aforementioned β-TrCP recognition motif as well. | 1 | Applied and Interdisciplinary Chemistry |
Multiple displacement amplification (MDA) is a DNA amplification technique. This method can rapidly amplify minute amounts of DNA samples to a reasonable quantity for genomic analysis. The reaction starts by annealing random hexamer primers to the template: DNA synthesis is carried out by a high fidelity enzyme, preferentially Φ29 DNA polymerase. Compared with conventional PCR amplification techniques, MDA does not employ sequence-specific primers but amplifies all DNA, generates larger-sized products with a lower error frequency, and works at a constant temperature. MDA has been actively used in whole genome amplification (WGA) and is a promising method for application to single cell genome sequencing and sequencing-based genetic studies. | 1 | Applied and Interdisciplinary Chemistry |
Though there are many methods to detect protein–protein interactions, the majority of these methods—such as co-immunoprecipitation, fluorescence resonance energy transfer (FRET) and dual polarisation interferometry—are not screening approaches. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, chlorins are tetrapyrrole pigments that are partially hydrogenated porphyrins. The parent chlorin is an unstable compound which undergoes air oxidation to porphine. The name chlorin derives from chlorophyll. Chlorophylls are magnesium-containing chlorins and occur as photosynthetic pigments in chloroplasts. The term "chlorin" strictly speaking refers to only compounds with the same ring oxidation state as chlorophyll.
Chlorins are excellent photosensitizing agents. Various synthetic chlorins analogues such as m-tetrahydroxyphenylchlorin (mTHPC) and mono-L-aspartyl chlorin e6 are effectively employed in experimental photodynamic therapy as photosensitizer. | 1 | Applied and Interdisciplinary Chemistry |
The ARC design incorporates major departures from traditional tokamaks, while retaining conventional D–T (deuterium - tritium) fuel. | 0 | Theoretical and Fundamental Chemistry |
The mercury beating heart was first observed in the year 1800 by Alessandro Volta and William Henry. The chemical phenomenon in the form best known today was first described by German chemist Friedlieb Ferdinand Runge, the discoverer of caffeine. | 0 | Theoretical and Fundamental Chemistry |
Anion and π–aromatic systems (typically electron-deficient) create an interaction that is associated with the repulsive forces of the structures. These repulsive forces involve electrostatic and anion-induced polarized interactions. This force allows for the systems to be used as receptors and channels in supramolecular chemistry for applications in the medical (synthetic membranes, ion channels) and environmental fields (e.g. sensing, removal of ions from water).
The first X-ray crystal structure that depicted anion–π interactions was reported in 2004. In addition to this being depicted in the solid state, there is also evidence that the interaction is present in solution. | 0 | Theoretical and Fundamental Chemistry |
The isotope Zr has been applied to the tracking and quantification of molecular antibodies with PET cameras (a method called "immuno-PET").
The biological half-life of antibodies is typically on the order of days, see daclizumab and erenumab by way of example. To visualize and quantify the distribution of such antibodies in the body, the PET isotope Zr is well suited because its physical half-life matches the typical biological half-life of antibodies, see table above. | 1 | Applied and Interdisciplinary Chemistry |
For 18th-century discoveries, around the time that Antoine Lavoisier first questioned the phlogiston theory, the recognition of a new "earth" has been regarded as being equivalent to the discovery of a new element (as was the general practice then). For some elements (e.g. Be, B, Na, Mg, Al, Si, K, Ca, Mn, Co, Ni, Zr, Mo), this presents further difficulties as their compounds were widely known since medieval or even ancient times, even though the elements themselves were not. Since the true nature of those compounds was sometimes only gradually discovered, it is sometimes very difficult to name one specific discoverer. In such cases the first publication on their chemistry is noted, and a longer explanation given in the notes. | 1 | Applied and Interdisciplinary Chemistry |
*Isaaks, Edward H., and Srivastava, R. Mohan. An Introduction to Applied Geostatistics. Oxford University Press, Oxford, NY, USA, 1989.
*David, M., Handbook of Applied Advanced Geostatistical Ore Reserve Estimation. Elsevier, Amsterdam, 1988.
*Mineral Processing Plant Design, Practice, and Control - Proceedings. Ed. Mular, A., Halbe, D., and Barratt, D. Society for Mining, Metallurgy, and Exploration, Inc. 2002.
*Mineral Comminution Circuits - Their Operation and Optimisation. Ed. Napier-Munn, T.J., Morrell, S., Morrison, R.D., and Kojovic, T. JKMRC, The University of Queensland, 1996 | 1 | Applied and Interdisciplinary Chemistry |
There are a variety of ethical positions regarding the possibilities of cloning, especially human cloning. While many of these views are religious in origin, the questions raised by cloning are faced by secular perspectives as well. Perspectives on human cloning are theoretical, as human therapeutic and reproductive cloning are not commercially used; animals are currently cloned in laboratories and in livestock production.
Advocates support development of therapeutic cloning to generate tissues and whole organs to treat patients who otherwise cannot obtain transplants, to avoid the need for immunosuppressive drugs, and to stave off the effects of aging. Advocates for reproductive cloning believe that parents who cannot otherwise procreate should have access to the technology.
Opponents of cloning have concerns that technology is not yet developed enough to be safe and that it could be prone to abuse (leading to the generation of humans from whom organs and tissues would be harvested), as well as concerns about how cloned individuals could integrate with families and with society at large. Cloning humans could lead to serious violations of human rights.
Religious groups are divided, with some opposing the technology as usurping "Gods place" and, to the extent embryos are used, destroying a human life; others support therapeutic clonings potential life-saving benefits. There is at least one religion, Raëlism, in which cloning plays a major role.
Contemporary work on this topic is concerned with the ethics, adequate regulation and issues of any cloning carried out by humans, not potentially by extraterrestrials (including in the future), and largely also not replication – also described as mind cloning – of potential whole brain emulations.
Cloning of animals is opposed by animal-groups due to the number of cloned animals that suffer from malformations before they die, and while food from cloned animals has been approved as safe by the US FDA, its use is opposed by groups concerned about food safety.
In practical terms, the inclusion of "licensing requirements for embryo research projects and fertility clinics, restrictions on the commodification of eggs and sperm, and measures to prevent proprietary interests from monopolizing access to stem cell lines" in international cloning regulations has been proposed, albeit e.g. effective oversight mechanisms or cloning requirements have not been described. | 1 | Applied and Interdisciplinary Chemistry |
The Joint Global Ocean Flux Study (JGOFS) was an international research programme on the fluxes of carbon between the atmosphere and ocean, and within the ocean interior. Initiated by the Scientific Committee on Oceanic Research (SCOR), the programme ran from 1987 through to 2003, and became one of the early core projects of the International Geosphere-Biosphere Programme (IGBP).
The overarching goal of JGOFS was to advance the understanding of, as well as improve the measurement of, the biogeochemical processes underlying the exchange of carbon across the air—sea interface and within the ocean. The programme aimed to study these processes from regional to global spatial scales, and from seasonal to interannual temporal scales, and to establish their sensitivity to external drivers such as climate change.
Early in the programme in 1988, two long-term time-series projects were established in the Atlantic and Pacific basins. These — Bermuda Atlantic Time-series Study (BATS) and Hawaii Ocean Time-series (HOT) — continue to make observations of ocean hydrography, chemistry and biology to the present-day. In 1989, JGOFS undertook the multinational North Atlantic Bloom Experiment (NABE) to investigate and characterise the annual spring bloom of phytoplankton, a key feature in the carbon cycle of the open ocean.
An important aspect of JGOFS lay in its objective to develop an increased network of observations, made using routine procedures, and curated such that they were easily available to researchers. JGOFS also oversaw the development of models of the marine system based on understanding gained from its observational programme. | 0 | Theoretical and Fundamental Chemistry |
Nanoscale allows for the preparation of quantum systems in physical states without classical analogs. There, complex out-of-equilibrium scenarios may be produced by the initial preparation of either the working substance or the reservoirs of quantum particles, the latter dubbed as "engineered reservoirs". There are different forms of engineered reservoirs. Some of them involve subtle quantum coherence or correlation effects, while others rely solely on nonthermal classical probability distribution functions.
Interesting phenomena may emerge from the use of engineered reservoirs such as efficiencies greater than the Otto limit,
violations of Clausius inequalities, or simultaneous extraction of heat and work from the reservoirs. | 0 | Theoretical and Fundamental Chemistry |
The open and closed conformations refer to the state of the DNA and whether the template strand has been separated from the non-template strand within the PIC. The place at which the DNA opens to form the bubble lies above a tunnel that is lined by the B-core, B-linker and B-reader as well as parts of RNA polymerase II. The B linker is found directly aligned with the point at which the DNA opens and in the open complex it is found between the two DNA strands, suggesting that it has a role in promoter melting, but it does not have a role in the catalytic RNA synthesis. Although TFIIB keeps a similar structure in both conformations some of the intramolecular interactions between the core and the B reader are disrupted upon DNA opening.
After DNA melting the transcription initiator (Inr) must be located on the DNA so the TSS can be identified by the RNA polymerase II and transcription can begin. This is done by passing the DNA through the template tunnel and the DNA is scanned, looking for the Inr and placing it in a position that ensures the transcription start site is located in the correct place by the RNA polymerase active site. The B reader of TFIIB is found in the template tunnel and is important in locating the Inr, mutations in the B reader cause the TSS to change and therefore incorrect transcription to occur (although PIC formation and DNA melting still take place). Yeast are a particularly good example of this alignment as the yeast Inr motif has a strictly conserved A residue at position 28 and in the open complex model a complementary T residue can be found in the B reader helix. When this T residue is mutated, transcription was significantly less effective emphasizing the role of the B reader.
The B reader loop is further thought to stabilise NTPs in the active site and, due to its flexibility, allow the nucleic acids to remain in contact during the early synthesis of the RNA molecule (i.e. stabilises the growing RNA-DNA hybrid) | 1 | Applied and Interdisciplinary Chemistry |
The Regional Scale Nodes (RSN) is a component of the National Science Foundations (NSFs) Ocean Observatories Initiative (OOI). The NSF's OOI is managed and coordinated by the OOI Project Office at the [http://www.oceanleadership.org Consortium for Ocean Leadership] (COL) in Washington, D.C. The UW, located in Seattle, Washington, is the RSN Implementing Organization for the COL.
The [http://www.interactiveoceans.washington.edu/story/Mission_and_Vision vision] behind RSN is to launch a new era of scientific discovery and understanding of the oceans.
The RSN consists of two infrastructures: primary and secondary. The primary infrastructure network, which was designed, qualified, manufactured, and installed in 2012 by [http://www.l-3mps.com/maripro/index.aspx L-3 Maripro], consists of a shore facility located in Pacific City, Oregon; two fiber-optic cable lines covering a distance of 800 kilometers, and seven primary science nodes.
The RSN system delivers 200 kilowatts of power and 240Gbit/s of TCP/IP Internet data communications to the seven primary science nodes. RSN is designed to last for 25 years and is capable of significant expansion to serve future science needs. | 0 | Theoretical and Fundamental Chemistry |
Wilkinson was born at Springside, Todmorden, in the West Riding of Yorkshire. His father, Henry Wilkinson, was a master house painter and decorator; his mother, Ruth, worked in a local cotton mill. One of his uncles, an organist and choirmaster, had married into a family that owned a small chemical company making Epsom and Glauber's salts for the pharmaceutical industry; this is where he first developed an interest in chemistry.
He was educated at the local council primary school and, after winning a County Scholarship in 1932, went to Todmorden Grammar School. His physics teacher there, Luke Sutcliffe, had also taught Sir John Cockcroft, who received a Nobel Prize for "splitting the atom". In 1939 he obtained a Royal Scholarship for study at Imperial College London, from where he graduated in 1941, with his PhD awarded in 1946 entitled "Some physico-chemical observations of hydrolysis in the homogeneous vapour phase". | 0 | Theoretical and Fundamental Chemistry |
Because many Archaea have adapted to life in extreme environments such as polar regions, hot springs, acidic springs, alkaline springs, salt lakes, and the high pressure of deep ocean water, they possess enzymes that are functional under quite unusual conditions. These enzymes are of potential use in the food, chemical, and pharmaceutical industries, where biotechnological processes frequently involve high temperatures, extremes of pH, high salt concentrations, and / or high pressure. Examples of enzymes identified to date include amylases, pullulanases, cyclodextrin glycosyltransferases, cellulases, xylanases, chitinases, proteases, alcohol dehydrogenase, and esterases. Archaea represent a source of novel chemical compounds also, for example isoprenyl glycerol ethers 1 and 2 from Thermococcus S557 and Methanocaldococcus jannaschii, respectively. | 1 | Applied and Interdisciplinary Chemistry |
The Coulomb barrier, named after Coulomb's law, which is in turn named after physicist Charles-Augustin de Coulomb, is the energy barrier due to electrostatic interaction that two nuclei need to overcome so they can get close enough to undergo a nuclear reaction. | 0 | Theoretical and Fundamental Chemistry |
* Capital expenditure is comparable with the annual operational cost of conventional bioremediation systems.
* Can be developed and operated in combination with conventional systems to improve the performance of the latter.
* Reduce the ecotoxicity of the man-made substances released into the water bodies and facilitate the eco-assimilation of those pollutants into the ecological cycles thus reducing the quantum of hazardous residues to zero which otherwise require costly secured landfill and incineration techniques. | 1 | Applied and Interdisciplinary Chemistry |
Dyakonov surface waves (DSWs) are surface electromagnetic waves that travel along the interface in between an isotropic and an uniaxial-birefringent medium. They were theoretically predicted in 1988 by the Russian physicist Mikhail Dyakonov. Unlike other types of acoustic and electromagnetic surface waves, the DSW's existence is due to the difference in symmetry of materials forming the interface. He considered the interface between an isotropic transmitting medium and an anisotropic uniaxial crystal, and showed that under certain conditions waves localized at the interface should exist. Later, similar waves were predicted to exist at the interface between two identical uniaxial crystals with different orientations.
The previously known electromagnetic surface waves, surface plasmons and surface plasmon polaritons, exist under the condition that the permittivity of one of the materials forming the interface is negative, while the other one is positive (for example, this is the case for the air/metal interface below the plasma frequency). In contrast, the DSW can propagate when both materials are transparent; hence they are virtually lossless, which is their most fascinating property.
In recent years, the significance and potential of the DSW have attracted the attention of many researchers: a change of the constitutive properties of one or both of the two partnering materials – due to, say, infiltration by any chemical or biological agent – could measurably change the characteristics of the wave. Consequently, numerous potential applications are envisaged, including devices for integrated optics, chemical and biological surface sensing, etc.
However, it is not easy to satisfy the necessary conditions for the DSW, and because of this the first proof-of-principle experimental observation of DSW
was reported only 20 years after the original prediction.
A large number of theoretical work appeared dealing with various aspects of this phenomenon, see the detailed review. In particular, DSW propagation at magnetic interfaces, in left-handed materials, in electro-optical, and chiral materials was studied. Resonant transmission due to DSW in structures using prisms was predicted, and combination and interaction between DSW and surface plasmons (Dyakonov plasmons) was studied and observed. | 0 | Theoretical and Fundamental Chemistry |
Meta-analyses found that increased perceived psychological stress was associated with a small decrease in telomere length—but that these associations attenuate to no significant association when accounting for publication bias. The literature concerning telomeres as integrative biomarkers of exposure to stress and adversity is dominated by cross-sectional and correlational studies, which makes causal interpretation problematic. A 2020 review argued that the relationship between psychosocial stress and telomere length appears strongest for stress experienced in utero or early life. | 1 | Applied and Interdisciplinary Chemistry |
In the jump method, the top cylinder is mounted to a pair of cantilever springs, while the bottom cylinder is brought up towards the top cylinder. While the bottom cylinder approaches the top, there comes a point when they will "jump" into contact with each other. The measurements, in this case, are based on the distance from which they jump and the spring constant. These measurements are usually between surfaces 1.25 nm and 20 nm apart. | 0 | Theoretical and Fundamental Chemistry |
Vorticity for Stokes flow satisfies to the vorticity equation
or in terms of the Fourier coefficients in the expansion by polar angle
where
From no-slip condition follows
Finally, integrating by parts, we obtain the Robin boundary condition for the vorticity:
Then the solution of the boundary-value problem can be expressed via Weber's integral above. | 1 | Applied and Interdisciplinary Chemistry |
The polymer-supported synthesis of β-mannosides based on the Crich’s protocol has also been studied in the same laboratories. As shown in Scheme 4, diol 17 was first reacted with polystyrylboronic acid (18) to offer the bound donor 19, in which 4,6-O-phenylboronates served as the torsionally disarming protecting group. With that, activation of the thioglycoside 19 was readily achieved, and the coupling reaction with the acceptor alcohol underwent smoothly to provide the bound β-mannoside 20. After removal of the excess reagents and byproducts from the resin, 20 was then treated with aqueous acetone to release 4,6-diol 21. Overall, this is a powerful method for solid-phase synthesis of β-mannosides, which has great potential to be further extended, was established. | 0 | Theoretical and Fundamental Chemistry |
A river mouth is where a river flows into a larger body of water, such as another river, a lake/reservoir, a bay/gulf, a sea, or an ocean. At the river mouth, sediments are often deposited due to the slowing of the current, reducing the carrying capacity of the water.
The water from a river can enter the receiving body in a variety of different ways. The motion of a river is influenced by the relative density of the river compared to the receiving water, the rotation of the Earth, and any ambient motion in the receiving water, such as tides or seiches.
If the river water has a higher density than the surface of the receiving water, the river water will plunge below the surface. The river water will then either form an underflow or an interflow within the lake. However, if the river water is lighter than the receiving water, as is typically the case when fresh river water flows into the sea, the river water will float along the surface of the receiving water as an overflow.
Alongside these advective transports, inflowing water will also diffuse. | 1 | Applied and Interdisciplinary Chemistry |
Arginase is a binuclear manganese metalloprotein that catalyses the hydrolysis of L-arginine to L-ornithine and urea. It is also regarded as a drug target for the treatment of asthma. The mechanism of hydrolysis of L-arginine is carried out via nucleophilic attack on the guanidino group by water, forming a tetrahedral intermediate. Studies shown that a boronic acid moiety adopts a tetrahedral configuration and serves as an inhibitor. In addition, the sulfonamide functional group can also mimic the transition state structure. Evidence of boronic acid mimics as transition state analogue inhibitors of human arginase I was elucidated by x-ray crystal structures. | 1 | Applied and Interdisciplinary Chemistry |
The advantages of this method include good separation of large molecules from the small molecules with a minimal volume of eluate, and that various solutions can be applied without interfering with the filtration process, all while preserving the biological activity of the particles to separate. The technique is generally combined with others that further separate molecules by other characteristics, such as acidity, basicity, charge, and affinity for certain compounds. With size exclusion chromatography, there are short and well-defined separation times and narrow bands, which lead to good sensitivity. There is also no sample loss because solutes do not interact with the stationary phase.
The other advantage to this experimental method is that in certain cases, it is feasible to determine the approximate molecular weight of a compound. The shape and size of the compound (eluent) determine how the compound interacts with the gel (stationary phase). To determine approximate molecular weight, the elution volumes of compounds with their corresponding molecular weights are obtained and then a plot of “K” vs “log(Mw)” is made, where and Mw is the molecular mass. This plot acts as a calibration curve, which is used to approximate the desired compound's molecular weight. The V component represents the volume at which the intermediate molecules elute such as molecules that have partial access to the beads of the column. In addition, V is the sum of the total volume between the beads and the volume within the beads. The V component represents the volume at which the larger molecules elute, which elute in the beginning. Disadvantages are, for example, that only a limited number of bands can be accommodated because the time scale of the chromatogram is short, and, in general, there must be a 10% difference in molecular mass to have a good resolution. | 1 | Applied and Interdisciplinary Chemistry |
Κ-casein labeled with the fluorochrome fluorescein isothiocyanate (FITC) to yield the fluorescein thiocarbamoyl (FTC) derivative. This substrate is used to determinate the milk clotting activity of proteases.
FTC-κ-casein method affords accurate and precise determinations of κ-caseinolytic degradation, the first step in the milk-clotting process. This method is the result of a modification to the one described by S.S. Twining (1984). The main modification was substituting the substrate previously used (casein) by κ-casein labeled with the fluorochrome fluorescein isothiocyanate (FITC) to yield the fluorescein thiocarbamoyl (FTC) derivative. This variation allows quantification of the κ-casein molecules degraded in a more precise and specific way, detecting only those enzymes able to degrade such molecules. The method described by Twining (1984), however, was designed to detect the proteolytic activity of a considerably larger variety of enzymes.
FTC-κ-casein allows the detection of different types of proteases at levels when no milk clotting is yet apparent, demonstrating its higher sensitivity over currently used assay procedures.
Therefore, the method may find application as an indicator during the purification or characterization of new
milk-clotting enzymes. | 1 | Applied and Interdisciplinary Chemistry |
Phosphites are oxidized to phosphate esters:
:P(OR) + [O] → OP(OR)
This reaction underpins the commercial use of some phosphite esters as stabilizers in polymers.
Alkyl phosphite esters are used in the Perkow reaction for the formation of vinyl phosphonates, and in the Michaelis–Arbuzov reaction to form phosphonates. Aryl phosphite esters may not undergo these reactions and hence are commonly used as stabilizers in halogen-bearing polymers such as PVC.
Phosphite esters may be used as reducing agents in more specialised cases. For example, triethylphosphite is known to reduce certain hydroperoxides to alcohols formed by autoxidation (scheme). In this process the phosphite is converted to a phosphate ester. This reaction type is also utilized in the Wender Taxol total synthesis. | 0 | Theoretical and Fundamental Chemistry |
Helium-4 is a liquid at normal pressure near absolute zero, a consequence of its high zero-point energy (ZPE). The ZPE of protons in a dense state is also high, and a decline in the ordering energy (relative to the ZPE) is expected at high pressures. Arguments have been advanced by Neil Ashcroft and others that there is a melting point maximum in compressed hydrogen, but also that there might be a range of densities, at pressures around 400 GPa, where hydrogen would be a liquid metal, even at low temperatures.
Geng predicted that the ZPE of protons indeed lowers the melting temperature of hydrogen to a minimum of at pressures of .
Within this flat region there might be an elemental mesophase intermediate between the liquid and solid state, which could be metastably stabilized down to low temperature and enter a supersolid state. | 0 | Theoretical and Fundamental Chemistry |
Supermicelle is a hierarchical micelle structure (supramolecular assembly) where individual components are also micelles. Supermicelles are formed via bottom-up chemical approaches, such as self-assembly of long cylindrical micelles into radial cross-, star- or dandelion-like patterns in a specially selected solvent; solid nanoparticles may be added to the solution to act as nucleation centers and form the central core of the supermicelle. The stems of the primary cylindrical micelles are composed of various block copolymers connected by strong covalent bonds; within the supermicelle structure they are loosely held together by hydrogen bonds, electrostatic or solvophobic interactions. | 0 | Theoretical and Fundamental Chemistry |
The form of the Kelvin equation here is not the form in which it appeared in Lord Kelvins article of 1871. The derivation of the form that appears in this article from Kelvins original equation was presented by Robert von Helmholtz (son of German physicist Hermann von Helmholtz) in his dissertation of 1885. In 2020, researchers found that the equation was accurate down to the 1nm scale. | 0 | Theoretical and Fundamental Chemistry |
Free fatty acids cannot penetrate any biological membrane due to their negative charge. Free fatty acids must cross the cell membrane through specific transport proteins, such as the SLC27 family fatty acid transport protein. Once in the cytosol, the following processes bring fatty acids into the mitochondrial matrix so that beta-oxidation can take place.
# Long-chain-fatty-acid—CoA ligase catalyzes the reaction between a fatty acid with ATP to give a fatty acyl adenylate, plus inorganic pyrophosphate, which then reacts with free coenzyme A to give a fatty acyl-CoA ester and AMP.
# If the fatty acyl-CoA has a long chain, then the carnitine shuttle must be utilized (shown in the table below):
#* Acyl-CoA is transferred to the hydroxyl group of carnitine by carnitine palmitoyltransferase I, located on the cytosolic faces of the outer and inner mitochondrial membranes.
#* Acyl-carnitine is shuttled inside by a carnitine-acylcarnitine translocase, as a carnitine is shuttled outside.
#* Acyl-carnitine is converted back to acyl-CoA by carnitine palmitoyltransferase II, located on the interior face of the inner mitochondrial membrane. The liberated carnitine is shuttled back to the cytosol, as an acyl-carnitine is shuttled into the matrix.
# If the fatty acyl-CoA contains a short chain, these short-chain fatty acids can simply diffuse through the inner mitochondrial membrane. | 1 | Applied and Interdisciplinary Chemistry |
Levetiracetam has been studied in the past for treating symptoms of neurobiological conditions such as Tourette syndrome, and anxiety disorder. However, its most serious adverse effects are behavioral, and its benefit-risk ratio in these conditions is not well understood.
Levetiracetam is being tested as a drug to reduce hyperactivity in the hippocampus in Alzheimer's disease.
Additionally, Levetiracetam has been experimentally shown to reduce Levodopa-induced dyskinesia, a type of movement disorder, or dyskinesia associated with the use of Levodopa, a medication used to treat Parkinson's disease.
Of the ten medications evaluated in a 2023 systematic review of the literature, levetiracetam was found to be the only medication with sufficient evidence showing that it may cause seizure freedom in some infants. Further, adverse effects from levetiracetam were rarely severe enough for the medication to be discontinued in this age group. Because available research included only 2 published studies reporting seizure freedom rates, however, the strength of the evidence was judged to be low. | 0 | Theoretical and Fundamental Chemistry |
While the aggregates can explain much of the protein fouling found in milk processing, this does not account for it all. A third type of fouling has been discovered that is explained by the chemical interactions of the denatured β-lg proteins.
β-lg contains 5 cysteine residues, four of which are covalently bonded to each other, forming an S-S bond. When β-lg is denatured, the fifth cysteine residue is exposed to the water. This residue then bonds to other β-lg proteins, including those already adsorbed to the surface. This produces a strong interaction between the denatured proteins and the surface of the container. | 1 | Applied and Interdisciplinary Chemistry |
The first isolation of deoxyribonucleic acid (DNA) was done in 1869 by Friedrich Miescher. DNA extraction is the process of isolating DNA from the cells of an organism isolated from a sample, typically a biological sample such as blood, saliva, or tissue. It involves breaking open the cells, removing proteins and other contaminants, and purifying the DNA so that it is free of other cellular components. The purified DNA can then be used for downstream applications such as PCR, sequencing, or cloning. Currently, it is a routine procedure in molecular biology or forensic analyses.
This process can be done in several ways, depending on the type of the sample and the downstream application, the most common methods are: mechanical, chemical and enzymatic lysis, precipitation, purification, and concentration. The specific method used to extract the DNA, such as phenol-chloroform extraction, alcohol precipitation, or silica-based purification.
For the chemical method, many different kits are used for extraction, and selecting the correct one will save time on kit optimization and extraction procedures. PCR sensitivity detection is considered to show the variation between the commercial kits.
There are many different methods for extracting DNA, but some common steps include:
# Lysis: This step involves breaking open the cells to release the DNA. For example, in the case of bacterial cells, a solution of detergent and salt (such as SDS) can be used to disrupt the cell membrane and release the DNA. For plant and animal cells, mechanical or enzymatic methods are often used.
# Precipitation: Once the DNA is released, proteins and other contaminants must be removed. This is typically done by adding a precipitating agent, such as alcohol (such as ethanol or isopropanol), or a salt (such as ammonium acetate). The DNA will form a pellet at the bottom of the solution, while the contaminants will remain in the liquid.
# Purification: After the DNA is precipitated, it is usually further purified by using column-based methods. For example, silica-based spin columns can be used to bind the DNA, while contaminants are washed away. Alternatively, a centrifugation step can be used to purify the DNA by spinning it down to the bottom of a tube.
# Concentration: Finally, the amount of DNA present is usually increased by removing any remaining liquid. This is typically done by using a vacuum centrifugation or a lyophilization (freeze-drying) step.
It's worth noting that some variations on these steps may be used depending on the specific DNA extraction protocol. Additionally, some kits are commercially available that include reagents and protocols specifically tailored to a specific type of sample. | 1 | Applied and Interdisciplinary Chemistry |
Affinity electrophoresis is a general name for many analytical methods used in biochemistry and biotechnology. Both qualitative and quantitative information may be obtained through affinity electrophoresis. Cross electrophoresis, the first affinity electrophoresis method, was created by Nakamura et al. Enzyme-substrate complexes have been detected using cross electrophoresis. The methods include the so-called electrophoretic mobility shift assay, charge shift electrophoresis and affinity capillary electrophoresis. The methods are based on changes in the electrophoretic pattern of molecules (mainly macromolecules) through biospecific interaction or complex formation. The interaction or binding of a molecule, charged or uncharged, will normally change the electrophoretic properties of a molecule. Membrane proteins may be identified by a shift in mobility induced by a charged detergent. Nucleic acids or nucleic acid fragments may be characterized by their affinity to other molecules. The methods have been used for estimation of binding constants, as for instance in lectin affinity electrophoresis or characterization of molecules with specific features like glycan content or ligand binding. For enzymes and other ligand-binding proteins, one-dimensional electrophoresis similar to counter electrophoresis or to "rocket immunoelectrophoresis", affinity electrophoresis may be used as an alternative quantification of the protein. Some of the methods are similar to affinity chromatography by use of immobilized ligands. | 1 | Applied and Interdisciplinary Chemistry |
An ultraviolet detector (also known as UV detector or UV-Vis detector) is a type of non-destructive chromatography detector which measures the amount of ultraviolet or visible light absorbed by components of the mixture being eluted off the chromatography column. They are often used as detectors for high-performance liquid chromatography.
The vast majority of Liquid Chromatographic systems are equipped with ultraviolet (UV) absorption detectors, and the vast majority of them are variable wavelength detectors, which are in fact UV spectrophotometers on the flow. In this detector, it is decided in advance at which wavelength is needed for the detection, and its absorbance as function of time is collected in a graphic format called chromatogram.
As can be seen in Figure 1, These detectors have a light source, a dispersion element that is a diffraction grating or prism, a flow cell, to where the sample arrives directly from the chromatographic column, an optical bench of lenses and mirrors, and a diode that receives the light coming from the optical system and translates it into a signal proportional to light intensity. When the user selects a wavelength for the detector, the optical system rotates the grating or prism in the space, so that the desired wavelength passes through optical system, then the flow cell and reaches the diode. The UV/VIS detector then produces a chromatogram as a two-dimensional (2D) output. This output plots time on the x-axis and response in absorbance units (AU) on the y-axis. The chromatogram is then analyzed by integrating the peaks curves to get their area, then getting their retention time (RT) from the peak maximum to identify them, and then perform quantitative analysis, by comparing their area to those of samples whose concentrations are known, i.e, standards. | 0 | Theoretical and Fundamental Chemistry |
* Gyftopoulos, E.P., & Beretta, G.P. (1991). Thermodynamics: foundations and applications. (Dover Publications)
* Hatsopoulos, G.N., & Keenan, J.H. (1981). Principles of general thermodynamics. RE Krieger Publishing Company. | 0 | Theoretical and Fundamental Chemistry |
When a crystalline material that contains atoms with uncompensated electron spins is cooled down, ordering of these spins generally occurs once the thermal energy is small enough not to overrule the interactions between neighboring spins. If the ordering does not exhibit the same symmetry as the original unit cell of the crystallographic lattice, a superstructure will result. In this case, the superspots are typically only visible in neutron diffraction patterns, because the neutron is scattered both by the nucleus and by the magnetic moments of the electron spins. | 0 | Theoretical and Fundamental Chemistry |
Its crystal structure has the tetragonal space group P4/nmm, which is a distorted version of the NHCl crystal structure; the unit cell has approximate dimensions 634×634×462 pm. The hydrogen bonding in the system causes the cations to orient such that the hydrogen atoms point toward the anions. | 0 | Theoretical and Fundamental Chemistry |
In November 1945, Smolková-Keulemansová's dream to return to Prague and continue her studies became a reality. She completed grammar school and realized that her biggest struggle in her supplementary exams was chemistry, so she began to study chemistry at Charles University in Prague, leading to her lifelong devotion and love for the subject. She graduated from the Faculty of Natural Sciences at Charles University in 1952. | 0 | Theoretical and Fundamental Chemistry |
Animals that commonly cause injury to plants include pests such as insects, mites, and nematodes. These variously bite or abrade plant parts such as leaves, stems, and roots, or as is common among the true bugs, pierce the plants surface and suck plant juices. The resulting injuries may admit plant pathogens such as bacteria and fungi, which may extend the injury. Caterpillar larvae of agricultural pests such as cabbage white butterflies (Pieridae) can completely defoliate Brassica' crops.
Molluscs such as snails graze on plants including grasses and forbs, abrading them with their rasp-like radula; they can inflict substantial damage to crops.
Grazing mammals including livestock such as cattle, too, bite off or break parts of plants including grasses, forbs, and forest trees, causing injury, and again, potentially admitting pathogens. | 1 | Applied and Interdisciplinary Chemistry |
Most standard HIV drug therapies revolve around inhibiting the reverse transcriptase enzyme (RT), an enzyme that is necessary to the HIV-1 virus and other retroviruses to complete their life cycle. The RT enzyme serves two key functions. First, it controls the replication of the viruses genetic material via its polymerase activity. It converts the viral single-stranded RNA into an integration competent double stranded DNA. Subsequently, the generated DNA is translocated into the nucleus of the host cell where it is integrated in its genome by the retroviral integrase. The other role of the RT is its ribonuclease H activity that degrades RNA only when it is in a heteroduplex with DNA. | 1 | Applied and Interdisciplinary Chemistry |
HPTLC finds extensive application in various fields, including pharmaceutical industries, clinical chemistry, forensic chemistry, biochemistry, cosmetology, food and drug analysis, environmental analysis, and more, owing to its numerous advantages. It distinguishes itself by being the only chromatographic method capable of presenting results as images and offers simplicity, cost-effectiveness, parallel analysis of samples, high sample capacity, rapid results, and the option for multiple detection methods.
Le Roux's research team assessed HPTLC for determining salbutamol serum levels in clinical trials and concluded that it is a suitable method for analyzing serum samples.
HPTLC has also been used successfully in the separation of various lipid subclasses, with reproducible and promising results obtained for 20 different lipid subclasses. Numerous reports related to clinical medicine studies have been published in various journals. As a result, HPTLC is now strongly recommended for drug analysis in serum and other tissues. | 0 | Theoretical and Fundamental Chemistry |
Acid–base imbalance is an abnormality of the human body's normal balance of acids and bases that causes the plasma pH to deviate out of the normal range (7.35 to 7.45). In the fetus, the normal range differs based on which umbilical vessel is sampled (umbilical vein pH is normally 7.25 to 7.45; umbilical artery pH is normally 7.18 to 7.38). It can exist in varying levels of severity, some life-threatening. | 0 | Theoretical and Fundamental Chemistry |
Alvero-Al Mahdi began her career at first in Manila as a trainee of the Department of Environment and Natural Resources. She helped in reviving a biologically dead river called Pasig. After six months of finishing up her work on Pasig, she took on the job at Galadari Hoshiery Mills, a textile factory in the United Arabic Emirates as a quality control engineer in 1992. Her employers soon saw that she was overly qualified for the job and soon she promoted from Galadari Hoshiery Mills to Al Futtaim Wimpey Laboratories. She worked her way up to higher positions such as, chemist to civil engineer to Chief Chemist. After working for Al Futtaim Wimpey Laboratories for six years, she was scouted by the Geoscience Testing Laboratories to become a Quality Assurance Officer. Similar to her career in Al Futtaim Wimpey Laboratories, she rose to several promotions to finally the position of CEO of Geoscience Testing Laboratory in 2003. | 1 | Applied and Interdisciplinary Chemistry |
The typical EDI installation has the following components: electrodes, anion exchange membranes, cation exchange membranes, and resin. The simplest configurations comprise three compartments. To increase production intensity or efficiency, the number of compartments or cells can be increased as desired.
Once the system is installed and feedwater begins to flow through it, cations flow toward the cathode and anions flow toward the anode. Only anions can go through the anion exchange membrane, and only cations can go through the cation exchange membrane. This configuration allows anions and cations to flow in only one direction because of the selectivity of the membranes and the electrical forces, rendering the feedwater relatively free of ions. It also allows for the separate collection of cation and anion concentration flows, creating the opportunity for more selective waste disposal, recycling, or reuse; this is especially useful in the removal of heavy metal cations. | 0 | Theoretical and Fundamental Chemistry |
Emerging methods of drug delivery involving nanotechnological methods can be useful by improving bodily response, specific targeting, and non-toxic metabolism. Many nanotechnological methods and materials can be functionalized for drug delivery. Ideal materials employ a controlled-activation nanomaterial to carry a drug cargo into the body. Mesoporous silica nanoparticles (MSN) have increased in research popularity due to their large surface area and flexibility for various individual modifications while maintaining high-resolution performance under imaging techniques. Activation methods greatly vary across nanoscale drug delivery molecules, but the most commonly used activation method uses specific wavelengths of light to release the cargo. Nanovalve-controlled cargo release uses low-intensity light and plasmonic heating to release the cargo in a variation of MSN containing gold molecules. The two-photon activated photo-transducer (2-NPT) uses near infrared wavelengths of light to induce the breaking of a disulfide bond to release the cargo. Recently, nanodiamonds have demonstrated potential in drug delivery due to non-toxicity, spontaneous absorption through the skin, and the ability to enter the blood–brain barrier.
The unique structure of carbon nanotubes also gives rise to many innovative inventions of new medical methods. As more medicine is made at the nano level to revolutionize the ways for human to detect and treat diseases, carbon nanotubes become a stronger candidate in new detection methods and therapeutic strategies. Specially, carbon nanotubes can be transformed into sophisticated biomolecule and allow its detection through changes in the carbon nanotube fluorescence spectra. Also, carbon nanotubes can be designed to match the size of small drug and endocitozed by a target cell, hence becoming a delivery agent. | 0 | Theoretical and Fundamental Chemistry |
ICOS consists of a network of standardized, long-term, high-precision integrated monitoring of atmospheric greenhouse gas concentrations and fluxes. The infrastructure integrates terrestrial and atmospheric observations at various sites into a single, coherent, highly precise dataset. This data allows a unique regional top-down assessment of fluxes from atmospheric data, and a bottom-up assessment from ecosystem measurements and fossil fuel inventories. Target is a daily mapping of sources and sinks at scales down to about 10 km, as a basis for understanding the exchange processes between the atmosphere, the terrestrial surface and the ocean. ICOS contributes to the implementation of the Integrated Global Carbon Observation System IGCO. | 1 | Applied and Interdisciplinary Chemistry |
Nanofoams are a class of nanostructured, porous materials (foams) containing a significant population of pores with diameters less than 100 nm. Aerogels are one example of nanofoam. | 0 | Theoretical and Fundamental Chemistry |
In non-contact atomic force microscopy mode, the tip of the cantilever does not contact the sample surface. The cantilever is instead oscillated at either its resonant frequency (frequency modulation) or just above (amplitude modulation) where the amplitude of oscillation is typically a few nanometers (<10 nm) down to a few picometers. The van der Waals forces, which are strongest from 1 nm to 10 nm above the surface, or any other long-range force that extends above the surface acts to decrease the resonance frequency of the cantilever. This decrease in resonant frequency combined with the feedback loop system maintains a constant oscillation amplitude or frequency by adjusting the average tip-to-sample distance. Measuring the tip-to-sample distance at each (x,y) data point allows the scanning software to construct a topographic image of the sample surface.
Non-contact mode AFM does not suffer from tip or sample degradation effects that are sometimes observed after taking numerous scans with contact AFM. This makes non-contact AFM preferable to contact AFM for measuring soft samples, e.g. biological samples and organic thin film. In the case of rigid samples, contact and non-contact images may look the same. However, if a few monolayers of adsorbed fluid are lying on the surface of a rigid sample, the images may look quite different. An AFM operating in contact mode will penetrate the liquid layer to image the underlying surface, whereas in non-contact mode an AFM will oscillate above the adsorbed fluid layer to image both the liquid and surface.
Schemes for dynamic mode operation include frequency modulation where a phase-locked loop is used to track the cantilever's resonance frequency and the more common amplitude modulation with a servo loop in place to keep the cantilever excitation to a defined amplitude. In frequency modulation, changes in the oscillation frequency provide information about tip-sample interactions. Frequency can be measured with very high sensitivity and thus the frequency modulation mode allows for the use of very stiff cantilevers. Stiff cantilevers provide stability very close to the surface and, as a result, this technique was the first AFM technique to provide true atomic resolution in ultra-high vacuum conditions.
In amplitude modulation, changes in the oscillation amplitude or phase provide the feedback signal for imaging. In amplitude modulation, changes in the phase of oscillation can be used to discriminate between different types of materials on the surface. Amplitude modulation can be operated either in the non-contact or in the intermittent contact regime. In dynamic contact mode, the cantilever is oscillated such that the separation distance between the cantilever tip and the sample surface is modulated.
Amplitude modulation has also been used in the non-contact regime to image with atomic resolution by using very stiff cantilevers and small amplitudes in an ultra-high vacuum environment. | 0 | Theoretical and Fundamental Chemistry |
In water treatment, coagulation and flocculation involve the addition of compounds that promote the clumping of fine floc into larger floc so that they can be more easily separated from the water. Coagulation is a chemical process that involves neutralization of charge whereas flocculation is a physical process and does not involve neutralization of charge. The coagulation-flocculation process can be used as a preliminary or intermediary step between other water or wastewater treatment processes like filtration and sedimentation. Iron and aluminium salts are the most widely used coagulants but salts of other metals such as titanium and zirconium have been found to be highly effective as well. | 1 | Applied and Interdisciplinary Chemistry |
Quantum mechanics uses the word degenerate in two ways: degenerate energy levels and as the low temperature ground state limit for states of matter. The electron degeneracy pressure occurs in the ground state systems which are non-degenerate in energy levels. The term "degeneracy" derives from work on the specific heat of gases that pre-dates the use of the term in quantum mechanics.
In 1914 Walther Nernst described the reduction of the specific heat of gases at very low temperature as "degeneration"; he attributed this to quantum effects. In subsequent work in various papers on quantum thermodynamics by Albert Einstein, by Max Planck, and by Erwin Schrödinger, the effect at low temperatures came to be called "gas degeneracy". A fully degenerate gas has no volume dependence on pressure when temperature approaches absolute zero.
Early in 1927 Enrico Fermi and separately Llewellyn Thomas developed a semi-classical model for electrons in a metal. The model treated the electrons as a gas. Later in 1927, Arnold Sommerfeld applied the Pauli principle via Fermi-Dirac statistics to this electron gas model, computing the specific heat of metals; the result became Fermi gas model for metals. Sommerfeld called the low temperature region with quantum effects a "wholly degenerate gas".
Also in 1927 Ralph H. Fowler applied Fermi's model to the puzzle of the stability of white dwarf stars. This approach was extended to relativistic models by later studies and with the work of Subrahmanyan Chandrasekhar became the accepted model for star stability. | 0 | Theoretical and Fundamental Chemistry |
12-Crown-4 can be synthesized using a modified Williamson ether synthesis, using LiClO as a templating cation:
: (CHOCHCHCl) + (CHOH) + 2 NaOH → (CHCHO) + 2 NaCl + 2 HO
It also forms from the cyclic oligomerization of ethylene oxide in the presence of gaseous boron trifluoride. | 0 | Theoretical and Fundamental Chemistry |
In many documented cases, dextromethorphan has produced psychological dependence in people who used it recreationally. It is considered less addictive than other common cough suppressants, such as the weak opiate codeine. Since dextromethorphan also acts as a serotonin reuptake inhibitor, users report that regular recreational use over a long period of time can cause withdrawal symptoms similar to those of antidepressant discontinuation syndrome. Additionally, disturbances have been reported in sleep, senses, movement, mood, and thinking. | 0 | Theoretical and Fundamental Chemistry |
Silicon-infiltrated carbon-carbon composite is used for high performance "ceramic" brake disks, as they are able to withstand extreme temperatures. The silicon reacts with the graphite in the carbon-carbon composite to become carbon-fiber-reinforced silicon carbide (C/SiC). These brake disks are used on some road-going sports cars, supercars, as well as other performance cars including the Porsche Carrera GT, the Bugatti Veyron, the Chevrolet Corvette ZR1, the McLaren P1, Bentley, Ferrari, Lamborghini and some specific high-performance Audi cars. Silicon carbide is also used in a sintered form for diesel particulate filters. It is also used as an oil additive to reduce friction, emissions, and harmonics. | 1 | Applied and Interdisciplinary Chemistry |
Lightfastness is a property of a colourant such as dye or pigment that describes its resistance to fading when exposed to light. Dyes and pigments are used for example for dyeing of fabrics, plastics or other materials and manufacturing paints or printing inks.
The bleaching of the color is caused by the impact of ultraviolet radiation in the chemical structure of the molecules giving the color of the subject. The part of a molecule responsible for its color is called the chromophore.
Light encountering a painted surface can either alter or break the chemical bonds of the pigment, causing the colors to bleach or change in a process known as photodegradation. Materials that resist this effect are said to be lightfast. The electromagnetic spectrum of the sun contains wavelengths from gamma waves to radio waves. The high energy of ultraviolet radiation in particular accelerates the fading of the dye.
The photon energy of UVA-radiation which is not absorbed by atmospheric ozone exceeds the dissociation energy of the carbon-carbon single bond, resulting in the cleavage of the bond and fading of the color. Inorganic colourants are considered to be more lightfast than organic colourants. Black colourants are usually considered the most lightfast.
Lightfastness is measured by exposing a sample to a lightsource for a predefined period of time and then comparing it to an unexposed sample. | 0 | Theoretical and Fundamental Chemistry |
Sit was born in 1941 and attended Tanjong Katong Girls' School. She studied science at the National University of Singapore and obtained first-class honours when she graduated top of her class. She obtained her PhD in biochemistry from McGill University. | 1 | Applied and Interdisciplinary Chemistry |
You can find different kinds of food services in and around the campus.
- Restaurant universitaire (RU): this is the place where the majority of the students come every day. The choice is between three different main courses: todays special, worlds dish, and the grill. Patrons can also take a starter and a dessert, the whole for 3€15. Dining is in a large room with all the campus' students: CPI, engineers, and students of the IUT Louis Pasteur.
- Mini R : Its a new concept ! Its located above the RU. The principle is the same as a cafeteria. You choose what you want: sandwiches, fagottini, fruits, desserts, drinks, and some hot food like pizzas, paninis, pasta and wok boxes, kebab, hot dog, etc. One can eat there or take away.
- Vending machine: in the school, next to the coffee machine. There are several kinds of sandwiches, but all of them are industrial.
- In the common room: it is mainly the place where the engineers eat because they are contributors (prices are less expansive for them). For those bringing food from their flat, you can warm up there; there are ovens and stovetops.
- Fast food and supermarkets: Finally, there is an area next to the IUT Louis Pasteur with fast food like Mac Donald, Mezzo di Pasta or supermarkets (Liddl, Intermarché). | 1 | Applied and Interdisciplinary Chemistry |
Often, reactivity and reaction mechanisms are pictured as the behavior of isolated molecules in which the solvent is treated as a passive support. However, the nature of the solvent can actually influence reaction rates and order of a chemical reaction.
Performing a reaction without solvent can affect reaction-rate for reactions with bimolecular mechanisms, for example, by maximizing the concentration of the reagents. Ball milling is one of several mechanochemical techniques where physical methods are used to control reactions rather than solvents are methods are methods for affecting reactions in the absence of solvent. | 0 | Theoretical and Fundamental Chemistry |
His main research have been on tumor suppressor hDlg which includes an in-depth characterization of the combinations of hDlg isoforms present in multiple tissues and cell lines to correlate the presence of specific alternatively spliced insertions with a specific function of this tumor suppressor. He also studies the perturbation of hDlg distribution in two skin disease: psoriasis, characterized by a hyper-proliferation of basal cells, and Darier's disease, characterized by blisters resulting from the loss of cell adhesion in the supra-basal layers.
He is a founding member of BioVisions. | 1 | Applied and Interdisciplinary Chemistry |
Laurie Ellen Locascio (born November 21, 1961) is an American biomedical engineer, analytical chemist, and former academic administrator serving as the under secretary of commerce for standards and technology and the director of National Institute of Standards and Technology. From 2017 to 2021, Locascio was vice president for research of University of Maryland, College Park and University of Maryland, Baltimore. | 0 | Theoretical and Fundamental Chemistry |
Chimpanzees emit alarm calls in response to predators, such as leopards and snakes. They produce three types of alarm calls: acoustically-variable hoos, barks, and SOS screams. Alarm signalling is impacted by receiver knowledge and caller age, can be coupled with receiver monitoring, and is important to the understanding of the evolution of hominoid communication. | 1 | Applied and Interdisciplinary Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2022 impact factor of 4.2. | 1 | Applied and Interdisciplinary Chemistry |
The statistical analysis of the large quantity of data generated from sequencing approaches is a challenge. Even by only sequencing the exomes of individuals, a large quantity of data and sequence information is generated which requires a significant amount of data analysis. Challenges associated with the analysis of this data include changes in programs used to align and assemble sequence reads. Various sequencing technologies also have different error rates and generate various read-lengths which can pose challenges in comparing results from different sequencing platforms.
False positive and false negative findings are associated with genomic resequencing approaches and are critical issues. A few strategies have been developed to improve the quality of exome data such as:
* Comparing the genetic variants identified between sequencing and array-based genotyping
* Comparing the coding SNPs to a whole genome sequenced individual with the disorder
* Comparing the coding SNPs with Sanger sequencing of HapMap individuals
Rare recessive disorders may not have single nucleotide polymorphisms (SNPs) in public databases such as dbSNP. More common recessive phenotypes would be more likely to have disease-causing variants reported in dbSNP. For example, the most common cystic fibrosis variant has an allele frequency of about 3% in most populations. Screening out such variants might erroneously exclude such genes from consideration. Genes for recessive disorders are usually easier to identify than dominant disorders because the genes are less likely to have more than one rare nonsynonymous variant. The system that screens common genetic variants relies on dbSNP which may not have accurate information about the variation of alleles. Using lists of common variation from a study exome or genome-wide sequenced individual would be more reliable. A challenge in this approach is that as the number of exomes sequenced increases, dbSNP will also increase in the number of uncommon variants. It will be necessary to develop thresholds to define the common variants that are unlikely to be associated with a disease phenotype.
Genetic heterogeneity and population ethnicity are also major limitations as they may increase the number of false positive and false negative findings which will make the identification of candidate genes more difficult. Of course, it is possible to reduce the stringency of the thresholds in the presence of heterogeneity and ethnicity, however this will reduce the power to detect variants as well. Using a genotype-first approach to identify candidate genes might also offer a solution to overcome these limitations.
Unlike common variant analysis, the analysis of rare variants in whole-exome sequencing studies evaluates variant sets rather than single variants. Functional annotations predict the effect or function of rare variants and help prioritize rare functional variants. Incorporating these annotations can effectively boost the power of genetic association of rare variants analysis of whole genome sequencing studies. Some methods and tools have been developed to perform functionally-informed rare variant association analysis by incorporating functional annotations to empower analysis in whole exome sequencing studies. | 1 | Applied and Interdisciplinary Chemistry |
Of the 80 elements with a stable isotope, the largest number of stable isotopes observed for any element is ten (for the element tin). No element has nine or eight stable isotopes. Five elements have seven stable isotopes, eight have six stable isotopes, ten have five stable isotopes, nine have four stable isotopes, five have three stable isotopes, 16 have two stable isotopes (counting as stable), and 26 elements have only a single stable isotope (of these, 19 are so-called mononuclidic elements, having a single primordial stable isotope that dominates and fixes the atomic weight of the natural element to high precision; 3 radioactive mononuclidic elements occur as well). In total, there are 251 nuclides that have not been observed to decay. For the 80 elements that have one or more stable isotopes, the average number of stable isotopes is 251/80 ≈ 3.14 isotopes per element. | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, denaturation is a process in which proteins or nucleic acids lose the quaternary structure, tertiary structure, and secondary structure which is present in their native state, by application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent (e.g., alcohol or chloroform), agitation and radiation, or heat. If proteins in a living cell are denatured, this results in disruption of cell activity and possibly cell death. Protein denaturation is also a consequence of cell death. Denatured proteins can exhibit a wide range of characteristics, from conformational change and loss of solubility or dissociation of cofactors to aggregation due to the exposure of hydrophobic groups. The loss of solubility as a result of denaturation is called coagulation. Denatured proteins lose their 3D structure, and therefore, cannot function.
Proper protein folding is key to whether a globular or membrane protein can do its job correctly; it must be folded into the native shape to function. However, hydrogen bonds and cofactor-protein binding, which play a crucial role in folding, are rather weak, and thus, easily affected by heat, acidity, varying salt concentrations, chelating agents, and other stressors which can denature the protein. This is one reason why cellular homeostasis is physiologically necessary in most life forms.
This concept is unrelated to denatured alcohol, which is alcohol that has been mixed with additives to make it unsuitable for human consumption. | 1 | Applied and Interdisciplinary Chemistry |
As stated, the quadratic Stark effect is described by second-order perturbation theory. The zeroth-order eigenproblem
is assumed to be solved. The perturbation theory gives
with the components of the polarizability tensor α defined by
The energy E gives the quadratic Stark effect.
Neglecting the hyperfine structure (which is often justified — unless extremely weak electric fields are considered), the polarizability tensor of atoms is isotropic,
For some molecules this expression is a reasonable approximation, too.
For the ground state is always positive, i.e., the quadratic Stark shift is always negative. | 0 | Theoretical and Fundamental Chemistry |
Ketamine is a widely used anaesthetic agent. It is a chiral molecule that is administered as a racemate. Studies show that (S)-(+)-ketamine is the active anaesthetic and the undesired side-effects (hallucination and agitation) reside in the distomer, (R)-(-)-ketamine. | 0 | Theoretical and Fundamental Chemistry |
Liquid forms drops because it exhibits surface tension.
A simple way to form a drop is to allow liquid to flow slowly from the lower end of a vertical tube of small diameter. The surface tension of the liquid causes the liquid to hang from the tube, forming a pendant. When the drop exceeds a certain size it is no longer stable and detaches itself. The falling liquid is also a drop held together by surface tension. | 1 | Applied and Interdisciplinary Chemistry |
An ideal chain (or freely-jointed chain) is the simplest model in polymer chemistry to describe polymers, such as nucleic acids and proteins. It assumes that the monomers in a polymer are located at the steps of a hypothetical random walker that does not remember its previous steps. By neglecting interactions among monomers, this model assumes that two (or more) monomers can occupy the same location. Although it is simple, its generality gives insight about the physics of polymers.
In this model, monomers are rigid rods of a fixed length , and their orientation is completely independent of the orientations and positions of neighbouring monomers. In some cases, the monomer has a physical interpretation, such as an amino acid in a polypeptide. In other cases, a monomer is simply a segment of the polymer that can be modeled as behaving as a discrete, freely jointed unit. If so, is the Kuhn length. For example, chromatin is modeled as a polymer in which each monomer is a segment approximately 14-46 kbp in length. | 0 | Theoretical and Fundamental Chemistry |
Mao completed her BSc in chemistry from Nanjing University in 1988 and obtained her PhD in chemical engineering from the University of Minnesota in 1994. She then completed her postdoctoral fellowship at the same institution in 1995. | 1 | Applied and Interdisciplinary Chemistry |
Paucimannosidic glycans form the main component of the N-glycome of insects such as Drosophila melanogaster. Glycoprofiling of the venom component of the western honeybee, Apis mellifera, identified that paucimannosylation is a common modification of key proteins including hyaluronidase and phospholipase.
Insect cells lines are frequently utilised for recombinant expression of mammalian glycoproteins, which therefore are decorated with paucimannosidic glycans e.g. mouse interferon-β, human IgG and calf alkaline phosphatase. | 1 | Applied and Interdisciplinary Chemistry |
A nucleotidase is a hydrolytic enzyme that catalyzes the hydrolysis of a nucleotide into a nucleoside and a phosphate.
: A nucleotide + HO = a nucleoside + phosphate
For example, it converts adenosine monophosphate to adenosine, and guanosine monophosphate to guanosine.
Nucleotidases have an important function in digestion in that they break down consumed nucleic acids.
They can be divided into two categories, based upon the end that is hydrolyzed:
* : 5'-nucleotidase - NT5C, NT5C1A, NT5C1B, NT5C2, NT5C3
* : 3'-nucleotidase - NT3
5-Nucleotidases cleave off the phosphate from the 5 end of the sugar moiety. They can be classified into various kinds depending on their substrate preferences and subcellular localization. Membrane-bound 5-nucleotidases display specificity toward adenosine monophosphates and are involved predominantly in the salvage of preformed nucleotides and in signal transduction cascades involving purinergic receptors. Soluble 5-nucleotidases are all known to belong to the haloacid dehalogenase superfamily of enzymes, which are two domain proteins characterised by a modified Rossman fold as the core and variable cap or hood. The soluble forms are further subclassified based on the criterion mentioned above. mdN and cdN are mitochondrial and cytosolic 5-3-pyrimidine nucleotidases. cN-I is a cytosolic nucleotidase(cN) characterized by its affinity toward AMP as its substrate. cN-II is identified by its affinity toward either IMP or GMP or both. cN-III is a pyrimidine 5-nucleotidase. A new class of nucleotidases called IMP-specific 5-nucleotidase has been recently defined. 5'-Nucleotidases are involved in varied functions like cell–cell communication, nucleic acid repair, purine salvage pathway for the synthesis of nucleotides, signal transduction, membrane transport, etc. | 1 | Applied and Interdisciplinary Chemistry |
Splicing occurs in all the kingdoms or domains of life, however, the extent and types of splicing can be very different between the major divisions. Eukaryotes splice many protein-coding messenger RNAs and some non-coding RNAs. Prokaryotes, on the other hand, splice rarely and mostly non-coding RNAs. Another important difference between these two groups of organisms is that prokaryotes completely lack the spliceosomal pathway.
Because spliceosomal introns are not conserved in all species, there is debate concerning when spliceosomal splicing evolved. Two models have been proposed: the intron late and intron early models (see intron evolution). | 1 | Applied and Interdisciplinary Chemistry |
Clumped isotopes are heavy isotopes that are bonded to other heavy isotopes. The relative abundance of clumped isotopes (and multiply-substituted isotopologues) in molecules such as methane, nitrous oxide, and carbonate is an area of active investigation. The carbonate clumped-isotope thermometer, or "C–O order/disorder carbonate thermometer", is a new approach for paleoclimate reconstruction, based on the temperature dependence of the clumping of C and O into bonds within the carbonate mineral lattice. This approach has the advantage that the O ratio in water is not necessary (different from the δO approach), but for precise paleotemperature estimation, it also needs very large and uncontaminated samples, long analytical runs, and extensive replication. Commonly used sample sources for paleoclimatological work include corals, otoliths, gastropods, tufa, bivalves, and foraminifera. Results are usually expressed as Δ47 (said as "cap 47"), which is the deviation of the ratio of isotopologues of CO with a molecular weight of 47 to those with a weight of 44 from the ratio expected if they were randomly distributed. | 0 | Theoretical and Fundamental Chemistry |
Grape and wine proteins tend to aggregate and form hazes and sediment in finished wines, especially white wines. Haze-causing proteins can persist in wine due to low settling velocities or charge repulsion on individual particles. Fining agents, such as bentonite clays, are used to clarify wine by removing these proteins. Also, proteinaceous agents such as albumin, casein, or gelatin are used in wine clarification to remove tannins or other phenols. | 1 | Applied and Interdisciplinary Chemistry |
Before being taken to the ingenio (amalgamation refinery), excess material would be broken off of the silver ore. At the refiner, it was ground to a fine sand (harina) by an arrastra or stamp mill, which consisted of a rotating shaft fitted with heavy iron stamps that crushed the ore against a mortar block. The harina was then placed in heaps of 2,000 lbs or more, to which was added salt, water, magistral (essentially an impure form of copper sulfate, CuSO), and mercury. This was then mixed by bare-legged Indian laborers or by horses or mules and spread in a 1-to-2-foot-thick (0.30 to 0.61 m) layer in a patio (a shallow-walled, open enclosure). After six to eight weeks of mixing and soaking in the sun, a complex reaction converted the silver to native metal, which formed an amalgam with the mercury. The mixture was then washed and strained through a canvas bag before being placed into a hooded oven. Heating this amalgam vaporized the mercury, leaving the silver. The mercury vapor would then condense on the cooled hood, where it could be collected and reused. The amount of salt and copper sulfate varied from one-quarter to ten pounds of one or the other, or both, per ton of ore treated. The decision of how much of each ingredient to add, how much mixing was needed, and when to halt the process depended on the skill of an (English: quicksilver man). The loss of mercury in amalgamation processes is generally one to two times the weight of silver recovered.
The patio process was the first form of amalgamation. However, it is unclear whether this process or a similar process—in which amalgamation occurred in heated vats rather than open patios—was the predominant form of amalgamation in New Spain, as the earliest known illustration of the patio process dates from 1761. There is substantial evidence that both processes were used from an early date in New Spain, while open patios were never adopted in Peru. Instead, Andean refiners placed milled ore in stone tanks vaulted over a fire, which helped accelerate amalgamation by mitigating the bitterly cold temperatures at the high elevation of the Andean mines. Both processes required that ore be crushed and refiners quickly established mills to process ore once amalgamation was introduced. Water mills were common in the Andes, powered by man-made dams, while in New Spain, where water was relatively scarce, mills were often powered by horses or other draft animals.
Due to amalgamation's reliance upon mercury, an expansion of mercury production was central to the expansion of silver production. A key source of mercury was at Huancavelica, Peru, where vast deposits were discovered in 1563. Additional mercury was sourced from Almadén, Spain, and Idrija in present-day Slovenia. From shortly after the invention of mercury amalgamation to the end of the colonial period, the Spanish crown maintained a monopoly on mercury production and distribution, ensuring a steady supply of royal income. Fluctuations in mercury prices generally resulted in corresponding increases and decreases in silver production. Crown control over these prices could be used to intentionally depress or stimulate silver production in Spanish colonies. | 1 | Applied and Interdisciplinary Chemistry |
Social insects commonly use trail pheromones. For example, ants mark their paths with pheromones consisting of volatile hydrocarbons. Certain ants lay down an initial trail of pheromones as they return to the nest with food. This trail attracts other ants and serves as a guide. As long as the food source remains available, visiting ants will continuously renew the pheromone trail. The pheromone requires continuous renewal because it evaporates quickly. When the food supply begins to dwindle, the trail-making ceases. Pharaoh ants (Monomorium pharaonis) mark trails that no longer lead to food with a repellent pheromone, which causes avoidance behaviour in ants.
Repellent trail markers may help ants to undertake more efficient collective exploration.
The army ant Eciton burchellii provides an example of using pheromones to mark and maintain foraging paths. When species of wasps such as Polybia sericea found new nests, they use pheromones to lead the rest of the colony to the new nesting site.
Gregarious caterpillars, such as the forest tent caterpillar, lay down pheromone trails that are used to achieve group movement. | 1 | Applied and Interdisciplinary Chemistry |
TPVs promise efficient and economically viable power systems for both military and commercial applications. Compared to traditional nonrenewable energy sources, burner TPVs have little NO emissions and are virtually silent. Solar TPVs are a source of emission-free renewable energy. TPVs can be more efficient than PV systems owing to recycling of unabsorbed photons. However, losses at each energy conversion step lower efficiency. When TPVs are used with a burner source, they provide on-demand energy. As a result, energy storage may not be needed. In addition, owing to the PV's proximity to the radiative source, TPVs can generate current densities 300 times that of conventional PVs. | 0 | Theoretical and Fundamental Chemistry |
The liquid is placed within the annulus of one cylinder inside another. One of the cylinders is rotated at a set speed. This determines the shear rate inside the annulus. The liquid tends to drag the other cylinder round, and the force it exerts on that cylinder (torque) is measured, which can be converted to a shear stress.
One version of this is the Fann V-G Viscometer, which runs at two speeds, (300 and 600 rpm) and therefore only gives two points on the flow curve. This is sufficient to define a Bingham plastic model which was once widely used in the oil industry for determining the flow character of drilling fluids. In recent years rheometers that spin at 600, 300, 200, 100, 6 & 3 RPM have become more commonplace. This allows for more complex fluids models such as Herschel–Bulkley to be used. Some models allow the speed to be continuously increased and decreased in a programmed fashion, which allows the measurement of time-dependent properties. | 1 | Applied and Interdisciplinary Chemistry |
Synapses function as ensembles within particular brain networks to control the amount of neuronal activity, which is essential for memory, learning, and behavior. Consequently, synaptic disruptions might have negative effects. In fact, alterations in cell-intrinsic molecular systems or modifications to environmental biochemical processes can lead to synaptic dysfunction. The synapse is the primary unit of information transfer in the nervous system, and correct synaptic contact creation during development is essential for normal brain function. In addition, several mutations have been connected to neurodevelopmental disorders, and that compromised function at different synapse locations is a hallmark of neurodegenerative diseases.
Synaptic defects are causally associated with early appearing neurological diseases, including autism spectrum disorders (ASD), schizophrenia (SCZ), and bipolar disorder (BP). On the other hand, in late-onset degenerative pathologies, such as Alzheimers (AD), Parkinsons (PD), and Huntington's (HD) diseases, synaptopathy is thought to be the inevitable end-result of an ongoing pathophysiological cascade. These diseases are identified by a gradual loss in cognitive and behavioral function and a steady loss of brain tissue. Moreover, these deteriorations have been mostly linked to the gradual build-up of protein aggregates in neurons, the composition of which may vary based on the pathology; all have the same deleterious effects on neuronal integrity. Furthermore, the high number of mutations linked to synaptic structure and function, as well as dendritic spine alterations in post-mortem tissue, has led to the association between synaptic defects and neurodevelopmental disorders, such as ASD and SCZ, characterized by abnormal behavioral or cognitive phenotypes.
Nevertheless, due to limited access to human tissue at late stages and a lack of thorough assessment of the essential components of human diseases in the available experimental animal models, it has been difficult to fully grasp the origin and role of synaptic dysfunction in neurological disorders. | 1 | Applied and Interdisciplinary Chemistry |
Dda is a molecular motor, specifically a helicase that moves in the 5 end to 3 direction along a nucleic acid phosphodiester backbone, separating two annealed nucleic acid strands, using the free energy released by the hydrolysis of adenosine triphosphate. The National Center for Biotechnology Information (NCBI) Reference Sequence accession number is NP_049632. | 1 | Applied and Interdisciplinary Chemistry |
Tactoids are liquid crystal microdomains nucleated in isotropic phases, which can be distinguished as spherical or spindle-shaped birefringent microdroplets under polarized light microscopy. Tactoids are a transition state between isotropic and macroscopic liquid crystalline phases. The first observation of tactoids was made by Zocher in 1925, when he studied the nematic phase formed in vanadium pentoxide sols. After that, tactoids have been found in the phase transition processes in many lyotropic liquid crystalline substances, such as tobacco mosaic virus, polypeptides, and cellulose nanocrystals. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.