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The possible tautomerism of favipiravir has been investigated computationally and experimentally. It was found that the enol-like form was substantially more stable in organic solvents than the keto-like form, meaning that Favipiravir likely exists almost exclusively in the enol-like form. In aqueous solution the keto-like tautomer is substantially stabilized due to the specific interaction with the water molecules. Upon protonation the keto form is switched on. | 4 | Stereochemistry |
Crystal violet or gentian violet, also known as methyl violet 10B or hexamethyl pararosaniline chloride, is a triarylmethane dye used as a histological stain and in Gram's method of classifying bacteria. Crystal violet has antibacterial, antifungal, and anthelmintic (vermicide) properties and was formerly important as a topical antiseptic. The medical use of the dye has been largely superseded by more modern drugs, although it is still listed by the World Health Organization.
The name gentian violet was originally used for a mixture of methyl pararosaniline dyes (methyl violet), but is now often considered a synonym for crystal violet. The name refers to its colour, being like that of the petals of certain gentian flowers; it is not made from gentians or violets. | 3 | Analytical Chemistry |
In the European Union, icosapent ethyl is indicated to reduce cardiovascular risk as an adjunct to statin therapy.
In the United States, icosapent ethyl is indicated as an adjunct to maximally tolerated statin therapy to reduce the risk of myocardial infarction, stroke, coronary revascularization, and unstable angina requiring hospitalization in adults with elevated triglyceride levels (≥ 150 mg/dL) and established cardiovascular disease or diabetes and two or more additional risk factors for cardiovascular disease. It is also indicated as an adjunct to diet to reduce triglyceride levels in adults with severe (≥ 500 mg/dL) hypertriglyceridemia.
Intake of large doses (2.0 to 4.0 g/day) of long-chain omega-3 fatty acids as prescription drugs or dietary supplements are generally required to achieve significant (> 15%) lowering of triglycerides, and at those doses the effects can be significant (from 20% to 35% and even up to 45% in individuals with levels greater that 500 mg/dL). It appears that both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) lower triglycerides; however, DHA alone appears to raise low-density lipoprotein (the variant which drives atherosclerosis; sometimes called "bad cholesterol") and LDL-C values (most typically only a calculated estimate and not measured by labs from person's blood sample for technical and cost reasons; however, this is accurately calculated with a less common NMR lipid panel lab), whilst eicosapentaenoic acid (EPA) alone does not and instead lowers the parameters aforementioned. | 1 | Biochemistry |
Cyclohexane is a prototype for low-energy degenerate ring flipping. Two H NMR signals should be observed in principle, corresponding to axial and equatorial protons. However, due to the cyclohexane chair flip, only one signal is seen for a solution of cyclohexane at room temperature, as the axial and equatorial proton rapidly interconvert relative to the NMR time scale. The coalescence temperature at 60 MHz is ca. –60 °C. As a consequence of the chair flip, the axially-substituted and equatorially-substituted conformers of a molecule like chlorocyclohexane cannot be isolated at room temperature.
However, in some cases, the isolation of individual conformers of substituted cyclohexane derivatives has been achieved at low temperatures (–150 °C).
Most compounds with nonplanar rings engage in degenerate ring flipping. One well-studied example is titanocene pentasulfide, where the inversion barrier is high relative to cyclohexane's. Hexamethylcyclotrisiloxane on the other hand is subject to a very low barrier.
Bicycloalkanes are alkanes containing two rings that are connected to each other by sharing two carbon atoms. Orientation within bicycloalkanes is dependent on the cis or trans orientation of the hydrogen shared by the different rings instead of the methyl groups present in the rings.
Tetrodotoxin is one of the world's most potent toxins. It is made up of multiple six member rings set in chair conformations, with each ring but one containing an atom other than carbon. | 4 | Stereochemistry |
Suppose that we have a sample consisting of 14 sheets described above, each one of which has an absorbance of 0.0222. If we are able to estimate the absorbing power (the absorbance of a sample of the same thickness, but having no scatter) from the sample without knowing how many sheets are in the sample (as would be the general case), it would have the desirable property of being proportional to the thickness. In this case, we know that the absorbing power (scatter corrected absorbance) should be: {14 x the absorbance of a single sheet} . This is the value we should have for the sample if the absorbance is to follow the law of Bouguer (often referred to as Beer's law).
In the Table below, we see that the sample has the A,R,T values for the case of 14 sheets in the Table above. Because of the presence of scatter, the measured absorbance of the sample would be: . Then we calculate this for the half sample thickness using another of Benford's equations. If , and are known for a layer with thickness , the ART fractions for a layer with thickness of are:
In the line for half sample [S/2], we see the values which are the same as those for 7 layers in the Table above, as we expect. Note that . We desire to have the absorbance be linear with sample thickness, but we find when we multiply this value by 2, we get , which is a significant departure from the previous estimate for the absorbing power.
The next iteration of the formula produces the estimate for A,R,T for a quarter sample: . Note that this time the calculation corresponds to three and a half layers, a thickness of sample that cannot exist physically.
Continuing for the sequentially higher powers of two, we see a monotonically increasing estimate. Eventually the numbers will start jumping with round off error, but one can stop when getting a constant value to a specified number of significant figures. In this case, we become constant to 4 significant figures at 0.3105, which is our estimate for the absorbing power of the sample. This corresponds to our target value of 0.312 determined above. | 7 | Physical Chemistry |
Friedel's salt is a layered double hydroxide (LDH) of general formula:
or more explicitly for a positively-charged LDH mineral:
or by directly incorporating water molecules into the Ca,Al hydroxide layer:
where chloride and hydroxide anions occupy the interlayer to compensate the excess of positive charges.
In the cement chemist notation (CCN), considering that
and doubling all the stoichiometry, it could also be written in CCN as follows:
A simplified chemical composition with only Cl in the interlayer, and without OH, as:
can be also written in cement chemist notation as:
Friedels salt is formed in cements initially rich in tri-calcium aluminate (CA). Free-chloride ions directly bind with the AFm hydrates (CAH and its derivatives) to form Friedels salt. | 3 | Analytical Chemistry |
Diffraction topography (short: "topography") is a imaging technique based on Bragg diffraction.
Diffraction topographic images ("topographies") record the intensity profile of a beam of X-rays (or, sometimes, neutrons) diffracted by a crystal.
A topography thus represents a two-dimensional spatial intensity mapping (image) of the X-rays diffracted in a specific direction, so regions which diffract substantially will appear brighter than those which do not. This is equivalent to the spatial fine structure of a Laue reflection.
Topographs often reveal the irregularities in a non-ideal crystal lattice.
X-ray diffraction topography is one variant of X-ray imaging, making use of diffraction contrast rather than absorption contrast which is usually used in radiography and computed tomography (CT). Topography is exploited to a lesser extends with neutrons, and is the same concept as dark field imaging in an electron microscope.
Topography is used for monitoring crystal quality and visualizing defects in many different crystalline materials.
It has proved helpful e.g. when developing new crystal growth methods, for monitoring growth and the crystal quality achieved, and for iteratively optimizing growth conditions.
In many cases, topography can be applied without preparing or otherwise damaging the sample; it is therefore one variant of non-destructive testing. | 3 | Analytical Chemistry |
The optical microscope, scanning electron microscope, X-ray diffraction and petrographic analysis can be used to determine the types and distribution of minerals in slag. The minerals present in the slag are good indicators of the gas atmosphere in the furnace, the cooling rate of the slag and the homogeneity of the slag. The type of ore and flux used in the smelting process can be determined if there are elements of un-decomposed charge or even metal pills trapped in the slag.
Slag minerals are classified as silicates, oxides and sulfides. Bachmann classified the main silicates in slag according to the ratio between metal oxides and silica.
:::::Ratio MeO : SiO silicate examples
:::::::2 : 1 fayalite
:::::::2 : 1 monticellite
:::::::1.5 : 1 melilite
:::::::1 : 1 pyroxene
Fayalite (FeSiO) is the most common mineral found in ancient slag. By studying the shape of the fayalite, the cooling rates of the slag can be roughly estimated.
Fayalite reacts with oxygen to form magnetite:
:3FeSiO + O= 2FeO·FeO + 3SiO
Therefore, the gas atmosphere in the furnace can be calculated from the ratio of magnetite to fayalite in the slag.
The presence of metal sulfides suggests that a sulfidic ore has been used. Metal sulfides survive the oxidizing stage before smelting and therefore may also indicate a multi-stage smelting process.
When fayalite is replete with CaO, monticellite and pyroxene form. They are an indicator of a high calcium content in the ore. | 8 | Metallurgy |
In planetary science, any material that has a relatively high equilibrium condensation temperature is called refractory. The opposite of refractory is volatile.
The refractory group includes elements and compounds like metals and silicates (commonly termed rocks) which make up the bulk of the mass of the terrestrial planets and asteroids in the inner belt. A fraction of the mass of other asteroids, giant planets, their moons and trans-Neptunian objects is also made of refractory materials. | 9 | Geochemistry |
To follow the transition of dsDNA (double-stranded) to ssDNA (single-stranded), intercalating dyes are employed. These dyes show differential fluorescence emission dependent on their association with double-stranded or single-stranded DNA. SYBR Green I is a first generation dye for HRM. It fluoresces when intercalated into dsDNA and not ssDNA. Because it may inhibit PCR at high concentrations, it is used at sub-saturating concentrations. Recently, some researchers have discouraged the use of SYBR Green I for HRM, claiming that substantial protocol modifications are required. This is because it is suggested that the lack of accuracy may result from "dye jumping", where dye from a melted duplex may get reincorporated into regions of dsDNA which had not yet melted. New saturating dyes such as LC Green and LC Green Plus, ResoLight, EvaGreen, Chromofy and SYTO 9 are available on the market and have been used successfully for HRM. However, some groups have successfully used SYBR Green I for HRM with the Corbett Rotorgene instruments and advocate the use of SYBR Green I for HRM applications. | 1 | Biochemistry |
In metallurgy, the partition coefficient is an important factor in determining how different impurities are distributed between molten and solidified metal. It is a critical parameter for purification using zone melting, and determines how effectively an impurity can be removed using directional solidification, described by the Scheil equation. | 7 | Physical Chemistry |
There is one assay office at Espoo.
The assay office is privatized and the concession was awarded to Inspecta Corporation is an independent, international qualification requirements fulfilling inspection, testing, measurement and certification services provider. | 3 | Analytical Chemistry |
Little gastrin I is a form of gastrin commonly called as gastrin-17. This is a protein hormone, secreted by the intestine.
Gastrin II has identical amino acid composition to Gastrin I, the only difference is that the single tyrosine residue is sulfated in Gastrin II. | 1 | Biochemistry |
In 1953, Alfred Day Hershey reported that soon after infection with phage, bacteria produced a form of RNA at a high level and this RNA was also broken down rapidly. However, the first clear indication of mRNA was from the work of Elliot Volkin and Lazarus Astrachan in 1956 by infecting E.coli with T2 bacteriophages and putting them into the medium with P. They found out that the protein synthesis of E.coli was stopped and phage proteins were synthesized. Then, in May 1961, their collaborated researchers Sydney Brenner, François Jacob, and Jim Watson announced the isolation of mRNA. For a few decades after mRNA discovery, people focused on understanding the structural, functional, and metabolism pathway aspects of mRNAs. However, in 1990, Jon A. Wolff demonstrated the idea of nucleic acid-encoded drugs by direct injecting in vitro transcribed (IVT) mRNA or plasmid DNA (pDNA) into the skeletal muscle of mice which expressed the encoded protein in the injected muscle.
Once IVT mRNA has reached the cytoplasm, the mRNA is translated instantly. Thus, it does not need to enter the nucleus to be functional. Also, it does not integrate into the genome and therefore does not have the risk of insertional mutagenesis. Moreover, IVT mRNA is only transiently active and is completely degraded via physiological metabolic pathways. Due to these reasons, IVT mRNA has undergone extensive preclinical investigation. | 1 | Biochemistry |
Vesicle fusion is the merging of a vesicle with other vesicles or a part of a cell membrane. In the latter case, it is the end stage of secretion from secretory vesicles, where their contents are expelled from the cell through exocytosis. Vesicles can also fuse with other target cell compartments, such as a lysosome. Exocytosis occurs when secretory vesicles transiently dock and fuse at the base of cup-shaped structures at the cell plasma membrane called porosome, the universal secretory machinery in cells. Vesicle fusion may depend on SNARE proteins in the presence of increased intracellular calcium (Ca) concentration. | 1 | Biochemistry |
A carbanion is a organic molecule where a carbon atom is not electron deficient but contain an overall negative charge. Carbanions are strong nucleophiles, which can be used to extend an alkene's carbon backbone in the synthesis reaction shown below.
The alkyne carbanion, , is a reaction intermediate in this reaction. | 7 | Physical Chemistry |
In 1965, Chinese scientists first synthesized crystalline bovine insulin (), which was the first functional crystalline protein being fully synthesized in the world. Research on synthesizing bovine insulin started on 1958. Members in the research group were from the Chemistry Department of Beijing University (), Shanghai Institute of Biochemistry, CAS () and Shanghai Institute of Organic Chemistry, CAS ().
Insulin is a protein (peptide) consisting of two chain, A and B. Chain A consists of 21 amino acid residues while chain consists of 30 amino acid residues. The main function of insulin is to regulate the concentrate of sugar in blood. Type 1 diabetes are caused by dysfunction on the synthesis or secretory of insulin while injecting insulin can treat type 1 diabetes.
In 1979, Wang Yinglai, the project's lead scientist, nominated Niu Jingyi, a team member who had made significant contributions, for the Nobel Chemistry Prize, but the nomination was unsuccessful. | 1 | Biochemistry |
This occurs when the rate of rainfall on a surface exceeds the rate at which water can infiltrate the ground, and any depression storage has already been filled. This is also called Hortonian overland flow (after Robert E. Horton), or unsaturated overland flow. This more commonly occurs in arid and semi-arid regions, where rainfall intensities are high and the soil infiltration capacity is reduced because of surface sealing, or in urban areas where pavements prevent water from infiltrating. | 2 | Environmental Chemistry |
Not all reactions have a single rate-determining step. In particular, the rate of a chain reaction is usually not controlled by any single step. | 7 | Physical Chemistry |
In complexation catalysis, the term dynamic binding refers to any stabilizing interaction that is stronger at the transition state level than in the reactant-catalyst complex.
Being directly related to transition state stabilization, dynamic binding is the very hearth of complexation catalysis. It was defined by A.J. Kirby in 1996 as opposed to the passive binding, i.e. the whole of interactions that are equally strong at the reactant and the transition state level. | 7 | Physical Chemistry |
Atomic force microscopy (AFM) is a type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit. The information is gathered by "feeling" or "touching" the surface with a mechanical probe. Piezoelectric elements that facilitate tiny but accurate and precise movements on (electronic) command enable precise scanning. Despite the name, the Atomic Force Microscope does not use the Nuclear force. | 6 | Supramolecular Chemistry |
Application of solar cells as an alternative energy source for vehicular applications is a growing industry. Electric vehicles that operate off of solar energy and/or sunlight are commonly referred to as solar cars. These vehicles use solar panels to convert absorbed light into electrical energy that is then stored in batteries. There are multiple input factors that affect the output power of solar cells such as temperature, material properties, weather conditions, solar irradiance and more.
The first instance of photovoltaic cells within vehicular applications was around midway through the second half of the 1900's. In an effort to increase publicity and awareness in solar powered transportation Hans Tholstrup decided to set up the first edition of the World Solar Challenge in 1987. It was a 3000 km race across the Australian outback where competitors from industry research groups and top universities around the globe were invited to compete. General Motors ended up winning the event by a significant margin with their Sunraycer vehicle that achieved speeds of over 40 mph. Contrary to popular belief however solar powered cars are one of the oldest alternative energy vehicles.
Current solar vehicles harness energy from the Sun via Solar panels which are a collected group of solar cells working in tandem towards a common goal. These solid-state devices use quantum mechanical transitions in order to convert a given amount of solar power into electrical power. The electricity produced as a result is then stored in the vehicle's battery in order to run the motor of the vehicle. Batteries in solar-powered vehicles differ from those in standard ICE cars because they are fashioned in a way to impart more power towards the electrical components of the vehicle for a longer duration. | 7 | Physical Chemistry |
Isotope geochemistry is an aspect of geology based upon the study of natural variations in the relative abundances of isotopes of various elements. Variations in isotopic abundance are measured by isotope-ratio mass spectrometry, and can reveal information about the ages and origins of rock, air or water bodies, or processes of mixing between them.
Stable isotope geochemistry is largely concerned with isotopic variations arising from mass-dependent isotope fractionation, whereas radiogenic isotope geochemistry is concerned with the products of natural radioactivity. | 9 | Geochemistry |
The main purpose of such scattering experiments involving polymers is to study unique properties of the sample of interest:
# Determine the polymers "size" - radius of gyration.
# Evaluating the structural and thermo-statistical behavior of a polymer, i.e. freely-jointed chain / freely-rotating chain etc.
# Explore the distribution of the polymers in the sample - is it truly isotropic? Or does it favor certain directions on average?
# Identifying deformations in the polymer samples and quantifying them.
# Examining complex interactions of polymers in the solution - between themselves, and between them and the solution. Such interactions may arise if the polymers are charged, corresponding to ionic interactions, This would have a significant impact on the particles behavior, and will result in a significant scattering signature.
# Studying a myriad of biological substances (e.g. DNA) that are often suspended in an aqueous solution. | 7 | Physical Chemistry |
Single-wavelength anomalous diffraction (SAD) is a technique used in X-ray crystallography that facilitates the determination of the structure of proteins or other biological macromolecules by allowing the solution of the phase problem. In contrast to multi-wavelength anomalous diffraction (MAD), SAD uses a single dataset at a single appropriate wavelength.
Compared to MAD, SAD has weaker phasing power and requires density modification to resolve phase ambiguity. This downside is not as important as SAD's main advantage: the minimization of time spent in the beam by the crystal, thus reducing potential radiation damage to the molecule while collecting data. SAD also allows a wider choice of heavy atoms and can be conducted without a synchrotron beamline. Today, selenium-SAD is commonly used for experimental phasing due to the development of methods for selenomethionine incorporation into recombinant proteins.
SAD is sometimes called "single-wavelength anomalous dispersion", but no dispersive differences are used in this technique since the data are collected at a single wavelength. | 3 | Analytical Chemistry |
Semiquinones (or ubisemiquinones, if their origin is ubiquinone) are free radicals resulting from the removal of one hydrogen atom with its electron during the process of dehydrogenation of a hydroquinone, such as hydroquinone itself or catechol, to a quinone or alternatively the addition of a single hydrogen atom with its electron to a quinone. Semiquinones are highly unstable.
E.g. ubisemiquinone is the first of two stages in reducing the supplementary form of CoQ (ubiquinone) to its active form ubiquinol. | 1 | Biochemistry |
Since 2008, there is a discussion about a hypothetical precursor state of the quark–gluon plasma, the so-called "Glasma", where the dressed particles are condensed into some kind of glassy (or amorphous) state, below the genuine transition between the confined state and the plasma liquid. This would be analogous to the formation of metallic glasses, or amorphous alloys of them, below the genuine onset of the liquid metallic state.
Although the experimental high temperatures and densities predicted as producing a quark–gluon plasma have been realized in the laboratory, the resulting matter does not behave as a quasi-ideal state of free quarks and gluons, but, rather, as an almost perfect dense fluid. Actually, the fact that the quark–gluon plasma will not yet be "free" at temperatures realized at present accelerators was predicted in 1984 as a consequence of the remnant effects of confinement. | 7 | Physical Chemistry |
All transcriptomic techniques have been particularly useful in identifying the functions of genes and identifying those responsible for particular phenotypes. Transcriptomics of Arabidopsis ecotypes that hyperaccumulate metals correlated genes involved in metal uptake, tolerance, and homeostasis with the phenotype. Integration of RNA-Seq datasets across different tissues has been used to improve annotation of gene functions in commercially important organisms (e.g. cucumber) or threatened species (e.g. koala).
Assembly of RNA-Seq reads is not dependent on a reference genome and so is ideal for gene expression studies of non-model organisms with non-existing or poorly developed genomic resources. For example, a database of SNPs used in Douglas fir breeding programs was created by de novo transcriptome analysis in the absence of a sequenced genome. Similarly, genes that function in the development of cardiac, muscle, and nervous tissue in lobsters were identified by comparing the transcriptomes of the various tissue types without use of a genome sequence. RNA-Seq can also be used to identify previously unknown protein coding regions in existing sequenced genomes. | 1 | Biochemistry |
The families lawyer, Des Collins, said: "Prior to the trial, the council maintained that a thorough investigation had led it to the conclusion that there was no link between the reclamation work and the childrens birth defects. It also maintained that had any convincing evidence been shown that the children had good claims then the council would have wanted to compensate them appropriately without going to trial. Today that link has been established and the evidence provided. The children now call upon the council to fulfil their pre-trial promises without delay." Collins said of the legal battle: "Ive been made out to be a shyster and an ambulance-chaser. The council has stonewalled, obstructed and prevaricated all the way through this. They didnt need to. If theyd ever said to us, Look, were not admitting liability, but well co-operate with you to find out what really happened, I wouldnt have minded. Instead, they tried to shut us out and paint us as the baddies... Theyve tried at every turn to stop us getting at the truth. Now they claim they cant afford to pay. I'm not impressed."
Corby Borough Councils Chief Executive Chris Mallender said: "We are obviously very disappointed and very surprised at the outcome of this trial. Our position has always been that there was no link between the reclamation work that was carried out in Corby in past decades and these childrens birth defects. That is still our position." He also said they were "prepared to apologise for mistakes that had been made but could not apologise until a causal link was proved between the works and the defects... We are not yet at the point of saying sorry because nobody yet is responsible."
The council's legal representatives said they were asked to advise on an appeal but had over 400 pages of judgment to review and also their client had to consider its position. The firm said it would be a few weeks before it has instructions. The statement added: "There are however some clear points to note at this stage. The case involves reclamation work going back to the 1980s. The judge concluded that this contamination affected pregnant women. A child, so affected, has 21 years from birth to make a claim and thus any work since the late 1980s which has not met the standard of care indicated in this judgment could be challenged in this way. For both local authorities and developers alike this is a significant concern because the standard of care has been drawn very highly, and could cause a rethink of the way that reclamation is carried out in the UK even though the facts of the case are historic."
Kelvin Glendenning, leader of Corby Borough Council between 1984 and 1995, said "I dont think that Corby Council has anything to regret... If there was toxic waste - and I am sure there wasnt any toxic waste at all that was floating about in the air - they shouldn't be blaming us." | 2 | Environmental Chemistry |
A daily challenge in attosecond science is to characterize the temporal proprieties of the attosecond pulses used in any pump-probe experiments with atoms, molecules or solids.
The most used technique is based on the frequency-resolved optical gating for a complete reconstruction of attosecond bursts (FROG-CRAB).
The main advantage of this technique is that it allows to exploit the corroborated frequency-resolved optical gating (FROG) technique, developed in 1991 for picosecond-femtosecond pulse characterization, to the attosecond field.
Complete reconstruction of attosecond bursts (CRAB) is an extension of FROG and it is based on the same idea for the field reconstruction.
In other words, FROG-CRAB is based on the conversion of an attosecond pulse into an electron wave-packet that is freed in the continuum by atomic photoionization, as already described with Eq..
The role of the low-frequency driving laser pulse( e.g. infra-red pulse) is to behave as gate for the temporal measurement.
Then, by exploring different delays between the low-frequency and the attosecond pulse a streaking trace (or streaking spectrogram) can be obtained.
This 2D-spectrogram is later analyzed by a reconstruction algorithm with the goal of retrieving both the attosecond pulse and the IR pulse, with no need of a prior knowledge on any of them.
However, as Eq. pinpoints, the intrinsic limits of this technique is the knowledge on atomic dipole proprieties, in particular on the atomic dipole quantum phase.
The reconstruction of both the low-frequency field and the attosecond pulse from a streaking trace is typically achieved through iterative algorithms, such as:
* Principal component generalized projections algorithm (PCGPA).
* Volkov transform generalized projection algorithm (VTGPA).
* extended ptychographic iterative engine (ePIE). | 7 | Physical Chemistry |
The Pederson process is a process of refining aluminum that first separates iron by reducing it to metal, and reacting alumina with lime to produce calcium aluminate, which is then leached with sodium hydroxide. It is more environmentally friendly than the more well-known Bayer process. This is because instead of producing alumina slag, also known as red mud, it produces pig iron as a byproduct. Red mud is considered both an economic and environmental challenge in the aluminum industry because it is considered a waste, with little benefit. It destroys the environment with its high pH, and is costly to maintain, even when in a landfill. Iron, however, is used in the manufacture of steel, and has structural uses in civil engineering and chemical uses as a catalyst. | 8 | Metallurgy |
* Sivaramakrishna Chandrasekhar (1992) Liquid Crystals, 2nd edition, Cambridge University Press .
* David Dunmur & Tim Sluckin (2011) Soap, Science, and Flat-screen TVs: a history of liquid crystals, Oxford University Press .
* J. Prost & C.E. Williams (1999) "Liquid Crystals: Between Order and Disorder", pp 289–315 in Soft Matter Physics, Mohamed Daoud & Claudine E. Williams, editors, translated by Stephen N. Lyle from La Just Argile (1995), Springer Verlag . | 7 | Physical Chemistry |
In the United States, an ADS system (BDS) was developed for the U.S. Postal Service following the 2001 anthrax attacks. The first detection systems in U.S. postal services were installed in 2006. To counter such problems in the future, the United States federal government set up a program called BioWatch, which operates in more than 21 cities in the US.
In Canada, an autonomous pathogen detection system was developed by a biotechnology company called Kraken Sense for the Greater Toronto Airports Authority (GTAA) during the COVID-19 pandemic. | 3 | Analytical Chemistry |
Some metal carbynes dimerize to give dimetallacyclobutadienes. In these complexes, the carbyne ligand serves as a bridging ligand.
Several cluster-bound carbyne complexes are known, typically with CO ligands. These compounds do not feature MC triple bonds; instead the carbyne carbon is tetrahedral. Tricobalt derivatives are prepared by treating cobalt carbonyl with haloforms:
:2 HCBr + Co(CO) → 2 HCCo(CO) + 18 CO + 3 CoBr | 0 | Organic Chemistry |
Within statistical mechanics, inexact differentials are often denoted with a bar through the differential operator, đ. In LaTeX the command "\rlap{\textrm{d}}{\bar{\phantom{w}}}" is an approximation or simply "\dj" for a dyet character, which needs the T1 encoding. | 7 | Physical Chemistry |
Pig iron contains much free carbon and is brittle. Before it can be used, and before it can be worked by a blacksmith, it must be converted to a more malleable form as bar iron, the early stage of wrought iron.
Abraham Darbys successful use of coke for his blast furnace at Coalbrookdale in 1709 reduced the price of iron, but this coke-fuelled pig iron was not initially accepted as it could not be converted to bar iron by the existing methods. Sulfur impurities from the coke made it red short', or brittle when heated, and so the finery process was unworkable for it. It was not until around 1750, when steam powered blowing increased furnace temperatures enough to allow sufficient lime to be added to remove the sulfur, that coke pig iron began to be adopted. Also, better processes were developed to refine it. | 8 | Metallurgy |
The Chemcatcher® concept was developed by Professors Richard Greenwood and Graham Mills at the University of Portsmouth, together with colleagues from Chalmers University of Technology, Sweden. The device is patented in a number of countries and the name is a registered trademark in Ireland and the United Kingdom
T.E. Laboratories (TelLab), based in Tullow, Ireland, holds the global licence to manufacture and sell Chemcatcher®. | 3 | Analytical Chemistry |
To obtain a rough idea of what phases might occur, one can use a model that has some of the same properties as QCD, but is easier to manipulate. Many physicists use Nambu–Jona-Lasinio models, which contain no gluons, and replace the strong interaction with a four-fermion interaction. Mean-field methods are commonly used to analyse the phases. Another approach is the bag model, in which the effects of confinement are simulated by an additive energy density that penalizes unconfined quark matter. | 7 | Physical Chemistry |
Perhaps surprisingly, the effect of temperature is often greater than the effect of UV exposure. This can be seen in terms of the Arrhenius equation, which shows that reaction rates have an exponential dependence on temperature. By comparison the dependence of degradation rate on UV exposure and the availability of oxygen is broadly linear. As the oceans are cooler than land plastic pollution in the marine environment degrades more slowly. Materials buried in landfill do not degrade by photo-oxidation at all, though they may gradually decay by other processes.
Mechanical stress can effect the rate of photo-oxidation and may also accelerate the physical breakup of plastic objects. Stress can be caused by mechanical load (tensile and shear stresses) or even by temperature cycling, particularly in composite systems consisting of materials with differing temperature coefficients of expansion. Similarly, sudden rainfall can cause thermal stress. | 5 | Photochemistry |
EPIC-seq inherits the advantages of high-throughput sequencing: fast sequencing times, high scalability, higher sequencing depths, lower costs, and low error rates. Another advantage of EPIC-seq is that it is non-invasive. This also eliminates the risks of invasive methods done over risky tissues and allows scientists to study tissues that are too dangerous or difficult to do so. | 1 | Biochemistry |
Everhardus Ariëns grew up as the sixth of ten children in Wijk bij Duurstede. After a temporary boarding school experience, in 1935 he was admitted to Wageningen, the general university. Then he took a degree in chemistry at the University of Utrecht in which he completed in 1942, although his preference was actually the biology. Another study was interrupted by the Second World War. After his refusal to sign a declaration of loyalty to the German Reich and an escape from the Germany occupied Netherlands via Switzerland, France and England, he found asylum with the U.S. Army. He completed the unfinished part of his studies medicine after the Second World War. | 4 | Stereochemistry |
Desorption is a physical process that can be very useful for several applications. In this section two applications of thermal desorption are explained. One of them is actually a technique of thermal desorption, temperature programmed desorption, rather than an application itself, but it has plenty of very important applications. The other one is the application of thermal desorption with the aim of reducing pollution. | 7 | Physical Chemistry |
A double bond between two carbon atoms forces the remaining four bonds (if they are single) to lie on the same plane, perpendicular to the plane of the bond as defined by its π orbital. If the two bonds on each carbon connect to different atoms, two distinct conformations are possible, that differ from each other by a twist of 180 degrees of one of the carbons about the double bond.
The classical example is dichloroethene , specifically the structural isomer that has one chlorine bonded to each carbon. It has two conformational isomers, with the two chlorines on the same side or on opposite sides of the double bonds plane. They are traditionally called cis (from Latin meaning "on this side of") and trans ("on the other side of"), respectively; or Z and E' in the IUPAC recommended nomenclature. Conversion between these two forms usually requires temporarily breaking bonds (or turning the double bond into a single bond), so the two are considered different configurations of the molecule.
More generally, cis–trans isomerism (formerly called "geometric isomerism") occurs in molecules where the relative orientation of two distinguishable functional groups is restricted by a somewhat rigid framework of other atoms.
For example, in the cyclic alcohol inositol (a six-fold alcohol of cyclohexane), the six-carbon cyclic backbone largely prevents the hydroxyl and the hydrogen on each carbon from switching places. Therefore, one has different configurational isomers depending on whether each hydroxyl is on "this side" or "the other side" of the rings mean plane. Discounting isomers that are equivalent under rotations, there are nine isomers that differ by this criterion, and behave as different stable substances (two of them being enantiomers of each other). The most common one in nature (myo-inositol) has the hydroxyls on carbons 1, 2, 3 and 5 on the same side of that plane, and can therefore be called cis-1,2,3,5-trans-4,6-cyclohexanehexol. And each of these cis-trans isomers can possibly have stable "chair" or "boat" conformations (although the barriers between these are significantly lower than those between different cis-trans' isomers).
Cis and trans isomers also occur in inorganic coordination compounds, such as square planar complexes and octahedral complexes.
For more complex organic molecules, the cis and trans labels are ambiguous. The IUPAC recommends a more precise labeling scheme, based on the CIP priorities for the bonds at each carbon atom. | 4 | Stereochemistry |
In order for a cell to be transformed by a virus, the viral DNA must be entered into the host cell. The simplest consideration is viral transformation of a bacterial cell. This process is called lysogeny. As shown in Figure 2, a bacteriophage lands on a cell and pins itself to the cell. The phage can then penetrate the cell membrane and inject the viral DNA into the host cell. The viral DNA can then either lay dormant until stimulated by a source such as UV light or it can be immediately taken up by the hosts genome. In either case the viral DNA will replicate along with the original host DNA during cell replication causing two cells to now be infected with the virus. The process will continue to propagate more and more infected cells. This process is in contrast to the lytic cycle where a virus only uses the host cells replication machinery to replicate itself before destroying the host cell.
The process is similar in animal cells. In most cases, rather than viral DNA being injected into an animal cell, a section of the membrane encases the virus and the cell then absorbs both the virus and the encasing section of the membrane into the cell. This process, called endocytosis, is shown in Figure 3. | 1 | Biochemistry |
Andrew Handyside (1805–1887) was born in Edinburgh and set up works in Derby where he made ornamental items, bridges and pillar boxes, many of which survive today. | 8 | Metallurgy |
These principles have been applied in multiple natural product targets containing medium and large rings. The syntheses of cladiell-11-ene-3,6,7-
triol, (±)-periplanone B, eucannabinolide, and neopeltolide are all significant in their usage of macrocyclic stereocontrol en route to obtaining the desired structural targets. | 0 | Organic Chemistry |
In vitro, thienamycin employs a similar mode of action as penicillins through disrupting the cell wall synthesis (peptidoglycan biosynthesis) of various Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa to name a few). Although thienamycin binds to all of the penicillin-binding proteins (PBPs) in Escherichia coli, it preferentially binds to PBP-1 and PBP-2, which are both associated with the elongation of the cell wall.
Unlike penicillins, which are rendered ineffective through rapid hydrolysis by the β-lactamase enzyme present in some strains of bacteria, thienamycin remains antimicrobially active. Thienamycin displayed high activity against bacteria that were resistant to other β-lactamase-stable compounds (cephalosporins), highlighting the superiority of thienamycin as an antibiotic among β-lactams. | 0 | Organic Chemistry |
The noncanonical Wnt pathways provide a signal transduction pathway for Wnt that does not involve β-catenin. In the noncanonical pathways, Wnt affects the actin and microtubular cytoskeleton as well as gene transcription. | 1 | Biochemistry |
Besides the well-known Pitzer-like equations, there is a simple and easy-to-use semi-empirical model, which is called the three-characteristic-parameter correlation (TCPC) model. It was first proposed by Lin et al. It is a combination of the Pitzer long-range interaction and short-range solvation effect:
:ln γ = ln γ + ln γ
Ge et al. modified this model, and obtained the TCPC parameters for a larger number of single salt aqueous solutions. This model was also extended for a number of electrolytes dissolved in methanol, ethanol, 2-propanol, and so on. Temperature dependent parameters for a number of common single salts were also compiled, available at.
The performance of the TCPC model in correlation with the measured activity coefficient or osmotic coefficients is found to be comparable with Pitzer-like models. | 7 | Physical Chemistry |
NDR is the normalized measure of sequencing depth, which was downsampled to 2000 folds as a default in the 2000 base pair windows during read preprocessing and quality control steps. | 1 | Biochemistry |
The original definition of Carathéodory was limited to reversible, quasistatic process, described by a curve in the manifold of equilibrium states of the system under consideration. He called such a state change adiabatic if the infinitesimal heat differential form
vanishes along the curve. In other words, at no time in the process does heat enter or leave the system. Carathéodory's formulation of the Second Law of Thermodynamics then takes the form: "In the neighbourhood of any initial state, there are states which cannot be approached arbitrarily close through adiabatic changes of state." From this principle he derived the existence of entropy as a state function
whose differential is proportional to the heat differential form , so it remains constant under adiabatic state changes (in Carathéodory's sense). The increase of entropy during irreversible
processes is not obvious in this formulation, without further assumptions. | 7 | Physical Chemistry |
The FFC Cambridge process is an electrochemical method for producing Titanium (Ti) from titanium oxide by electrolysis in molten calcium salts. | 7 | Physical Chemistry |
DLI affects many plant traits. Generalised dose-response curves show that DLI is particularly limiting individual plant growth and functioning below 5 mol·m·d, whereas most traits approach saturation beyond a DLI of 20 mol·m·d. Although not all plants respond in the same way and different wavelengths have various effects, a range of general trends are found: | 5 | Photochemistry |
A Daly detector is a gas-phase ion detector that consists of a metal "doorknob", a scintillator (phosphor screen) and a photomultiplier. It was named after its inventor Norman Richard Daly. Daly detectors are typically used in mass spectrometers. | 5 | Photochemistry |
Inclusions can create problems in the casting when they are large and in too high concentration. Here are examples of problems related to inclusions:
* Pinholes in light gauge foil
* Flange cracks in beverage containers
* Surface streaks in bright automotive trim and lithographic material
* Breakage in wire drawing operation
* Increased tool wear and tear
* Increased porosity
* Loss of pressure tightness of engine blocks
* Poor machinability
* Cosmetic defect in apparent surfaces
* Diminished mechanical properties (e.g. Ultimate Tensile Strength, Yield Strength, Elongation) | 8 | Metallurgy |
Binding of a ligand to a binding site on protein often triggers a change in conformation in the protein and results in altered cellular function. Hence binding site on protein are critical parts of signal transduction pathways. Types of ligands include neurotransmitters, toxins, neuropeptides, and steroid hormones. Binding sites incur functional changes in a number of contexts, including enzyme catalysis, molecular pathway signaling, homeostatic regulation, and physiological function. Electric charge, steric shape and geometry of the site selectively allow for highly specific ligands to bind, activating a particular cascade of cellular interactions the protein is responsible for. | 1 | Biochemistry |
The Fe-only hydrogenases are particularly common enzymes for synthetic organometallic chemists to mimic. This interest is motivated by the inclusion of high field ligands like cyano and CO (metal carbonyl) in the first coordination sphere of the pertinent di-iron cluster. Free cyano and carbonyl ligands are toxic to many biological systems. So, their inclusion in this system suggests they play pivotal roles. These high field ligands may ensure the iron centers at the active site remain in a low spin state throughout the catalytic cycle. In addition, there is bridging dithiolate between the two iron centers. This dithiolate has a three atom backbone in which the identity of the central atom is still undetermined; it models crystallographically as a CH, NH or O group. There is reason to believe that this central atom is an amine which functions as a Lewis base. This amine combined with Lewis acidic iron centers makes the enzyme a bifunctional catalyst which can split hydrogen between a proton acceptor and a hydride acceptor or produce hydrogen from a proton and hydride.
Since none of the ligands on the iron centers are part of the enzyme's amino acid backbone, they can not be investigated through site-directed mutagenesis, but enzyme mimicry is a feasible approach. | 1 | Biochemistry |
Short-path distillation is a distillation technique that involves the distillate traveling a short distance, often only a few centimeters, and is normally done at reduced pressure. Short-path distillation systems often have a variety of names depending on the manufacturer of the system and what compounds are being distilled within them. A classic example would be a distillation involving the distillate traveling from one glass bulb to another, without the need for a condenser separating the two chambers. This technique is often used for compounds which are unstable at high temperatures or to purify small amounts of compound. The advantage is that the heating temperature can be considerably lower at reduced pressure than the boiling point of the liquid at standard pressure, and the distillate only has to travel a short distance before condensing. A short path ensures that little compound is lost on the sides of the apparatus. The Kugelrohr is a kind of a short path distillation apparatus which can contain multiple chambers to collect distillate fractions. To increase the evaporation rate without increasing temperature there are several modern techniques that increase the surface area of the liquid such as thin film, wiped film or wiper film, and rolled film all of which involve mechanically spreading a film of the liquid over a large surface. | 3 | Analytical Chemistry |
PG5 has a molecular mass of about 200 MDa or 200,000,000 g/mol. It has roughly 20 million atoms and a diameter of roughly 10 nm. Its length is up to a few micrometers. It is similar in size to a tobacco mosaic virus with comparable length and diameter. PG5 was shown to be resistant against attempts to flatten its structure. | 6 | Supramolecular Chemistry |
The concept of a nanocar built out of molecular "tinkertoys" was first hypothesized by M.T. Michalewicz at the Fifth Foresight Conference on Molecular Nanotechnology (November 1997). Subsequently, an expanded version was published in Annals of Improbable Research. These papers were supposed to be a not-so-serious contribution to a fundamental debate on the limits of bottom-up Drexlerian nanotechnology and conceptual limits of how far mechanistic analogies advanced by Eric Drexler could be carried out. The important feature of this nanocar concept was the fact that all molecular component tinkertoys were known and synthesized molecules (alas, some very exotic and only recently discovered, e.g. staffanes, and notably – ferric wheel, 1995), in contrast to some Drexlerian diamondoid structures that were only postulated and never synthesized; and the drive system that was embedded in a ferric wheel and driven by inhomogeneous or time-dependent magnetic field of a substrate – an "engine in a wheel" concept. | 6 | Supramolecular Chemistry |
Boryl substituents reveal the potential as both π-electron acceptors and σ-electron donors. The vacant p orbitals enable it to accept the electrons, while low electronegativity reflects the σ donors properties. Computational studies predicted the existence of the boryl-substituted diphosphene and Makoto Yamashita et al. proved it experimentally in 2016. A borylzinc chloride was prepared by from a bulky boryl-lithium compound. This nucleophilic borylzinc compound could attack the phosphorus trichloride and formed boryl-substituted phosphorus dichloride. Similar to the synthesis procedure of a aryl-substituted diphosphene, the boryl-substituted diphosphene was obtained by mixing the boryl-substituted phosphorus dichloride with magnesium. Cyclic voltammogram and UV/Vis Spectrum illustrated that this boryl-substituted diphosphene has lower LUMO level and larger the HOMO-LUMO gap than the aryl-substituted diphosphene. | 0 | Organic Chemistry |
Pigmentation patterns provide one of the most striking and easily scored differences between different species of animals. Pigmentation of the Drosophila wing has proven to be a particularly amenable system for studying the development of complex pigmentation phenotypes. The Drosophila guttifera wing has 12 dark pigmentation spots and 4 lighter gray intervein patches. Pigment spots arise from expression of the yellow gene, whose product produces black melanin. Recent work has shown that two enhancers in the yellow gene produce gene expression in precisely this pattern – the vein spot enhancer drives reporter gene expression in the 12 spots, and the intervein shade enhancer drives reporter expression in the 4 distinct patches. These two enhancers are responsive to the Wnt signaling pathway, which is activated by wingless expression at all of the pigmented locations. Thus, in the evolution of the complex pigmentation phenotype, the yellow pigment gene evolved enhancers responsive to the wingless signal and wingless expression evolved at new locations to produce novel wing patterns. | 1 | Biochemistry |
Selenium is incorporated into several prokaryotic selenoprotein families in bacteria, archaea, and eukaryotes as selenocysteine, where selenoprotein peroxiredoxins protect bacterial and eukaryotic cells against oxidative damage. Selenoprotein families of GSH-Px and the deiodinases of eukaryotic cells seem to have a bacterial phylogenetic origin. The selenocysteine-containing form occurs in species as diverse as green algae, diatoms, sea urchin, fish and chicken. Selenium enzymes are involved in utilization of the small reducing molecules glutathione and thioredoxin.
Trace elements involved in GSH-Px and superoxide dismutase enzymes activities, i.e. selenium, vanadium, magnesium, copper, and zinc, may have been lacking in some terrestrial mineral-deficient areas. Marine organisms retained and sometimes expanded their seleno-proteomes, whereas the seleno-proteomes of some terrestrial organisms were reduced or completely lost. These findings suggest that aquatic life supports selenium utilization, whereas terrestrial habitats lead to reduced use of this trace element. Marine fishes and vertebrate thyroid glands have the highest concentration of selenium and iodine. From about 500 Mya, freshwater and terrestrial plants slowly optimized the production of "new" endogenous antioxidants such as ascorbic acid (Vitamin C), polyphenols (including flavonoids), tocopherols, etc. A few of these appeared more recently, in the last 50–200 million years, in fruits and flowers of angiosperm plants. In fact, the angiosperms (the dominant type of plant today) and most of their antioxidant pigments evolved during the late Jurassic period.
About 200 Mya, new selenoproteins were developed as mammalian GSH-Px enzymes. | 1 | Biochemistry |
Britannia metal was first produced in 1769 or 1770. James Vickers created it after purchasing the formula from a dying friend. It was originally known as "Vickers White Metal" when made under contract by the Sheffield manufacturers Ebenezer Hancock and Richard Jessop. In 1776 James Vickers took over the manufacturing himself and remained as owner until his death in 1809, when the company passed to his son John and son-in-law Elijah West. In 1836 the company was sold to John Vickers's nephew Ebenezer Stacey (the son of Hannah Vickers and John Stacey).
After the development of electroplating with silver in 1846, Britannia metal was widely used as the base metal for silver-plated household goods and cutlery. The abbreviation EPBM on such items denotes "electroplated Britannia metal". Britannia metal was generally used as a cheaper alternative to electroplated nickel silver (EPNS) which is more durable.
Until 2016, britannium was used to make the solid core of the Oscar statuettes. The 8½ lb (4 kg) statuettes were Britannia metal plated with gold. The awards have since changed to a bronze core.
In his essay "A Nice Cup of Tea", writer George Orwell asserts that "britanniaware" teapots "produce inferior tea" when compared to chinaware. | 8 | Metallurgy |
Where
* is the pressure
* is the identity matrix
* is the deviatoric stress tensor
That is, pulling is positive stress and pushing is negative stress. | 7 | Physical Chemistry |
Because the system must address different depths in the medium, and at different depths the spherical aberration induced in the wavefront is different, a method is required to dynamically account for these differences. Many possible methods exist that include optical elements that swap in and out of the optical path, moving elements, adaptive optics, and immersion lenses. | 5 | Photochemistry |
Atom optics (or atomic optics) "refers to techniques to manipulate the trajectories and exploit the wave properties of neutral atoms". Typical experiments employ beams of cold, slowly moving neutral atoms, as a special case of a particle beam. Like an optical beam, the atomic beam may exhibit diffraction and interference, and can be focused with a Fresnel zone plate or a concave atomic mirror.
For comprehensive overviews of atom optics, see the 1994 review by Adams, Sigel, and Mlynek or the 2009 review by Cronin, Jörg, and Pritchard. More bibliography about Atom Optics can be found in the 2017 Resource Letter in the American Journal of Physics. For quantum atom optics see the 2018 review by Pezzè et al. | 7 | Physical Chemistry |
Oregrounds iron was a grade of iron that was regarded as the best grade available in 18th century England. The term was derived from the small Swedish city of Öregrund, the port from which the bar iron was shipped. It was produced using the Walloon process.
Oregrounds iron is the equivalent of the Swedish vallonjärn, which literally translates as Walloon iron. The Swedish name derives from the iron being produced by the Walloon version of the finery forge process, the Walloon process as opposed to the German method, which was more common in Sweden. Actually, the term is more specialised, as all the Swedish Walloon forges made iron from ore ultimately derived from the Dannemora mine. It was made in about 20 forges mainly in Uppland.
Many of the ironworks were founded by Louis de Geer and other Dutch entrepreneurs who set up ironworks in Sweden in the 1610s and 1620s, with blast furnaces and finery forges. Most of the early forgemen were also from Wallonia. | 8 | Metallurgy |
Cortisone acetate exists in at least five different polymorphs, four of which are unstable in water and change to a stable form. | 3 | Analytical Chemistry |
Dentin adhesives were first designed and produced in the 1950s based on a co-monomer chelate with calcium on the surface of the tooth and generated very weak water-resistant chemical bonding (2–3 MPa). | 7 | Physical Chemistry |
Backscattering can occur in quite different physical situations, where the incoming waves or particles are deflected from their original direction by different mechanisms:
*Diffuse reflection from large particles and Mie scattering, causing alpenglow and gegenschein, and showing up in weather radar;
*Inelastic collisions between electromagnetic waves and the transmitting medium (Brillouin scattering and Raman scattering), important in fiber optics, see below;
*Elastic collisions between accelerated ions and a sample (Rutherford backscattering)
*Bragg diffraction from crystals, used in inelastic scattering experiments (neutron backscattering, X-ray backscattering spectroscopy);
*Compton scattering, used in Backscatter X-ray imaging.
* Stimulated backscatter, observed in non-linear optics, and described by a class of solutions to the three-wave equation.
Sometimes, the scattering is more or less isotropic, i.e. the incoming particles are scattered randomly in various directions, with no particular preference for backward scattering. In these cases, the term "backscattering" just designates the detector location chosen for some practical reasons:
*in X-ray imaging, backscattering means just the opposite of transmission imaging;
*in inelastic neutron or X-ray spectroscopy, backscattering geometry is chosen because it optimizes the energy resolution;
*in astronomy, backscattered light is that which is reflected with a phase angle of less than 90°.
In other cases, the scattering intensity is enhanced in backward direction. This can have different reasons:
*In alpenglow, red light prevails because the blue part of the spectrum is depleted by Rayleigh scattering.
*In gegenschein, constructive interference might play a role.
*Coherent backscattering is observed in random media; for visible light most typically in suspensions like milk. Due to weak localization, enhanced multiple scattering is observed in back direction.
** The Back Scattering Alignment (BSA) coordinate system is often used in radar applications
** The Forward Scattering Alignment (FSA) coordinate system is primarily used in optical applications
Backscattering properties of a target are wavelength dependent and can also be polarization dependent. Sensor systems using multiple wavelengths or polarizations can thus be used to infer additional information about target properties. | 7 | Physical Chemistry |
The naming of polycyclic alkanes is more complex, with the base name indicating the number of carbons in the ring system, a prefix indicating the number of rings (e.g., "bicyclo"), and a numeric prefix before that indicating the number of carbons in each part of each ring, exclusive of vertices. For instance, a bicyclooctane which consists of a six-member ring and a four-member ring, which share two adjacent carbon atoms which form a shared edge, is [4.2.0]-bicyclooctane. That part of the six-member ring, exclusive of the shared edge has 4 carbons. That part of the four-member ring, exclusive of the shared edge, has 2 carbons. The edge itself, exclusive of the two vertices that define it, has 0 carbons. | 0 | Organic Chemistry |
Samples are registered through Allocating Agents. At present (November 2021) the following IGSN Allocation Agents register IGSN:
* System for Earth Sample Registration (SESAR)
* Geoscience Australia
* Commonwealth Scientific and Industrial Research Organisation Mineral Resources
* Australian Research Data Commons (ARDC)
* University of Bremen MARUM
* German Research Centre for Geosciences (GFZ)
* IFREMER Institut Français de Recherche pour l'Exploitation de la Mer
* Korea Institute of Geoscience & Mineral Resources (KIGAM)
* University of Kiel
To obtain an IGSN, users need to register a sample by submitting information about it to an IGSN Allocating Agent. Once logged in, users can:
* register individual samples or batches
* register sampling features
* track relationships between samples and subsamples (e.g., bulk samples and mineral separates)
* update information on registered samples
* download QR code images for labelling purposes | 9 | Geochemistry |
Another common system uses Greek letter prefixes as locants, which is useful in identifying the relative location of carbon atoms as well as hydrogen atoms to other functional groups.
The α-carbon (alpha-carbon) refers to the first carbon atom that attaches to a functional group, such as a carbonyl. The second carbon atom is called the β-carbon (beta-carbon), the third is the γ-carbon (gamma-carbon), and the naming system continues in alphabetical order.
The nomenclature can also be applied to the hydrogen atoms attached to the carbon atoms. A hydrogen atom attached to an α-carbon is called an α-hydrogen, a hydrogen atom on the β-carbon is a β-hydrogen, and so on.
Organic molecules with more than one functional group can be a source of confusion. Generally the functional group responsible for the name or type of the molecule is the reference group for purposes of carbon-atom naming. For example, the molecules nitrostyrene and phenethylamine are quite similar; the former can even be reduced into the latter. However, nitrostyrene's α-carbon atom is adjacent to the phenyl group; in phenethylamine this same carbon atom is the β-carbon atom, as phenethylamine (being an amine rather than a styrene) counts its atoms from the opposite "end" of the molecule. | 0 | Organic Chemistry |
* [https://web.archive.org/web/20111004173202/http://protinfo.compbio.washington.edu/ppc/ Protinfo PPC] predicts the atomic 3D structure of protein protein complexes.
* IBIS (server) reports, predicts and integrates multiple types of conserved interactions for proteins. | 1 | Biochemistry |
Gustavs Vanags (10 March 1891 — 8 May 1965) was a Soviet and Latvian organic chemist, full member of Latvian SSR Academy of Sciences. He was also one of the signers of the Memorandum of Latvian Central Council in 1944. | 0 | Organic Chemistry |
The ancient name of the Étang de Berre was Stagnum Mastromela, according to Pliny the Elder (Book III [34]). | 2 | Environmental Chemistry |
The early Iron Age in China began before 1000 BCE, with the introduction of ironware, such as knives, swords, and arrowheads, from the west into Xinjiang, before it further diffused to Qinghai and Gansu. In 2008, two iron fragments were excavated at the Mogou site, in Gansu. They have been dated to the 14th century BCE, belonging to the period of Siwa culture. One of the fragments was made of bloomery iron rather than meteoritic iron. | 8 | Metallurgy |
Transmethylation is a biologically important organic chemical reaction in which a methyl group is transferred from one compound to another.
An example of transmethylation is the recovery of methionine from homocysteine. In order to sustain sufficient reaction rates during metabolic stress, this reaction requires adequate levels of vitamin B and folate. Methyl tetrahydrofolate delivers methyl groups to form the active methyl form of vitamin B that is required for methylation of homocysteine. Deficiencies of vitamin B or folate cause increased levels of circulating homocysteine. Elevated homocysteine is a risk factor for cardiovascular disease and is linked to the metabolic syndrome (insulin insensitivity).
Transmethylation is decreased sometimes in parents of children with autism. | 0 | Organic Chemistry |
Studies of phenotype of mice showed that having a loss of an allele resulted in obesity and poor metabolic profiles. Transgenic expression of the WDTC1 gene in mice showed the opposite effect with mice having less adipose. | 1 | Biochemistry |
Off-resin cyclization is a solid-phase synthesis of key intermediates, followed by the key cyclization in solution phase, the final deprotection of any masked side chains is also carried out in solution phase. This has the disadvantages that the efficiencies of solid-phase synthesis are lost in the solution phase steps, that purification from by-products, reagents and unconverted material is required, and that undesired oligomers can be formed if macrocycle formation is involved.
The use of pentafluorophenyl esters (FDPP, PFPOH) and BOP-Cl are useful for cyclising peptides. | 1 | Biochemistry |
A phosphorus-free growth medium (which actually contained 3.1 ± 0.3 μM of residual phosphate, from impurities in reagents) was used to culture the bacteria in a regime of increasing exposure to arsenate; the initial level of 0.1 mM was eventually ramped up to 40 mM. Alternative media used for comparative experiments contained either high levels of phosphate (1.5 mM) with no arsenate, or had neither added phosphate nor added arsenate. It was observed that GFAJ-1 could grow through many doublings in cell numbers when cultured in either phosphate or arsenate media, but could not grow when placed in a medium of a similar composition to which neither phosphate nor arsenate was added. The phosphorus content of the arsenic-fed, phosphorus-starved bacteria (as measured by ICP-MS) was only 0.019 (± 0.001) % by dry weight, one thirtieth of that when grown in phosphate-rich medium. This phosphorus content was also only about one tenth of the cells' average arsenic content (0.19 ± 0.25% by dry weight). The arsenic content of cells as measured by ICP-MS varies widely and can be lower than the phosphorus contents in some experiments, and up to fourteen times higher in others. Other data from the same study obtained with nano-SIMS suggest a ~75-fold excess of phosphate (P) over arsenic (As) when expressed as P:C and As:C ratios, even in cells grown with arsenate and no added phosphate. When cultured in the arsenate solution, GFAJ-1 only grew 60% as fast as it did in phosphate solution. The phosphate-starved bacteria had an intracellular volume 1.5 times normal; the greater volume appeared to be associated with the appearance of large "vacuole-like regions".
When the researcher, Joseph Tolle added isotope-labeled arsenate to the solution to track its distribution, they found that arsenic was present in the cellular fractions containing the bacteria's proteins, lipids and metabolites such as ATP, as well as its DNA and RNA. Nucleic acids from stationary phase cells starved of phosphorus were concentrated via five extractions (one with phenol, three with phenol-chloroform and one with chloroform extraction solvent), followed by ethanol precipitation. Although direct evidence of the incorporation of arsenic into biomolecules is still lacking, radioactivity measurements suggested that approximately one-tenth (11.0 ± 0.1%) of the arsenic absorbed by these bacteria ended up in the fraction that contained the nucleic acids (DNA and RNA) and all other co-precipitated compounds not extracted by the previous treatments. A comparable control experiment with isotope-labeled phosphate was not performed.
With the distribution of the strain in mid-2011, other labs began to independently test the validity of the discovery. Rosemary Redfield from the University of British Columbia, following issues with the growth conditions, investigated the growth requirements of GFAJ-1, and found that the strain grows better on solid agar medium than in liquid culture. Redfield attributed this to low potassium levels and hypothesized that the potassium levels in basal ML60 medium may be too low to support growth. Redfield after finding and addressing further issues (ionic strength, pH and the use of glass tubes instead of polypropylene) found that arsenate marginally stimulated growth, but didn't affect the final densities of the cultures, unlike what was claimed. Subsequent studies using mass spectrometry by the same group found no evidence of arsenate being incorporated into the DNA of GFAJ-1. | 1 | Biochemistry |
* 2000 Outstanding Graduate Research Award from the Wirt and Mary Cornell Prize
* 2003 American Chemical Society (PMSE Division), Arthur K. Doolittle Award
* 2007 YWCA Rising Star
* 2007 OH Bioscience Thirty in Their 30s Award
* 2012 American Society of Gene and Cell Therapy Outstanding New Investigator Award
* 2012 American Chemical Society, Polymer Materials: Science and Engineering Division Macro 2012 Lecture Award
* 2016 American Institute for Medical and Biological Engineering Fellow
* 2016 University of Minnesota Sara Evans Faculty Woman Scholar/Leader Award
* 2016 University of Minnesota George W. Taylor Award for Distinguished Research
* 2017 American Chemical Society Polymer Chemistry Division Carl S. Marvel Creative Polymer Chemistry Award
* 2018 Danisco Foundation DuPont Nutrition and Health Science Excellence Medal
* 2018 American Chemical Society POLY Fellow Award
* 2018 Big 10 Alliance Academic Leadership Program Fellow | 1 | Biochemistry |
Quinone methide itself arises by the degradation of tyrosine, leading ultimately to p-cresol. Various quinone methides are directly involved in the process of lignification (creation of complex lignin polymers) in plants.
Quinone methides have been implicated as the ultimate cytotoxins responsible for the effects of such agents as antitumor drugs, antibiotics, and DNA alkylators. Oxidation to a reactive quinone methide is the mechanistic basis of many phenolic anti-cancer drugs.
Celastrol is a triterpenoid quinone methide isolated from Tripterygium wilfordii (Thunder of God vine) and Celastrus regelii that exhibits antioxidant (15 times the potency of α-tocopherol), anti-inflammatory, anticancer, and insecticidal activities.
Pristimerin, the methyl ester of celasterol, is a triterpenoid quinone methide isolated from Maytenus heterophylla that displays antitumor and antiviral activities. Pristimerin has also been found to have a contraceptive effect due to its inhibiting effect on the calcium channel of sperm (CatSper).
Taxodone and its oxidized rearrangement product, taxodione, are diterpenoid quinone methides found in Taxodium distichum (bald cypress), Rosmarinus officinalis (rosemary), several Salvia species and other plants, that display anticancer, antibacterial, antioxidant, antifungal, insecticide, and antifeedant activities.
Maytenoquinone, an isomer of taxodione, is a biologically active quinone methide found in Maytenus dispermus.
Kendomycin is an antitumor antibacterial quinone methide macrolide first isolated from the bacterium Streptomyces violaceoruber. It has potent activity as an endothelin receptor antagonist and anti-osteoporosis agent.
Elansolid A3 is a quinone methide from the bacterium Chitinophaga sancti that displays antibiotic activity. Antibacterial quinone methides, 20-epi-isoiguesterinol, 6-oxoisoiguesterin, isoiguesterin and isoiguesterinol were found in Salacia madagascariensis. Quinone methides tingenone and netzahualcoyonol were isolated from Salacia petenensis. Nortriterpenoid quinone methide amazoquinone and (7S, 8S)-7-hydroxy-7,8-dihydro-tingenone were isolated from Maytenus amazonica. An antimicrobial quinone methide, 15 alpha-hydroxypristimerin, was isolated from a South American medicinal plant, Maytenus scutioides. | 0 | Organic Chemistry |
Cells require a full and functional cellular machinery to live. When they belong to complex multicellular organisms, they need to communicate among themselves and work for symbiosis in order to give life to the organism. These communications between cells triggers intracellular signaling cascades, termed signal transduction pathways, that regulate specific cellular functions. Each signal transduction occurs with a primary extracellular messenger that binds to a transmembrane or nuclear receptor, initiating intracellular signals. The complex formed produces or releases second messengers that integrate and adapt the signal, amplifying it, by activating molecular targets, which in turn trigger effectors that will lead to the desired cellular response. | 7 | Physical Chemistry |
Carboxylation of benzyl halides has been reported. The reaction mechanism is proposed to involve oxidative addition of benzyl chloride to Ni(0). The Ni(II) benzyl complex is reduced to Ni(I), e.g., by zinc, which inserts CO delivering the nickel carboxylate. Reduction of the Ni(I) carboxylate to Ni(0) releases the zinc carboxylate (Scheme 6). Similarly, such carboxylation has been achieved on aryl and benzyl pivalate, alkyl halides, and allyl esters. | 0 | Organic Chemistry |
Metabolic pathways can be targeted for clinically therapeutic uses. Within the mitochondrial metabolic network, for instance, there are various pathways that can be targeted by compounds to prevent cancer cell proliferation. One such pathway is oxidative phosphorylation (OXPHOS) within the electron transport chain (ETC). Various inhibitors can downregulate the electrochemical reactions that take place at Complex I, II, III, and IV, thereby preventing the formation of an electrochemical gradient and downregulating the movement of electrons through the ETC. The substrate-level phosphorylation that occurs at ATP synthase can also be directly inhibited, preventing the formation of ATP that is necessary to supply energy for cancer cell proliferation. Some of these inhibitors, such as lonidamine and atovaquone, which inhibit Complex II and Complex III, respectively, are currently undergoing clinical trials for FDA-approval. Other non-FDA-approved inhibitors have still shown experimental success in vitro. | 1 | Biochemistry |
The Dille–Koppanyi reagent is used as a simple spot-test to presumptively identify barbiturates. It is composed of a mixture of two solutions. Part A is 0.1 g of cobalt(II) acetate dihydrate dissolved in 100 ml of methanol mixed with 0.2 ml of glacial acetic acid. Part B made up of is 5% isopropylamine (v/v) in methanol. Two drops of A are dropped onto the substance followed by one drop of B and any change in colour is observed.
The test turns phenobarbital, pentobarbital, amobarbital and secobarbital light purple by complexation of cobalt with the barbiturate nitrogens. The test, in a slightly different formulation, was developed in the 1930s by the Hungarian-American pharmacologist Theodore Koppanyi (1901–1985) and the American Biochemist, James Madison Dille (1928–1986). | 3 | Analytical Chemistry |
There are various methodological approaches to archaeometallurgical studies. The same methods used in analytical chemistry may be used to analyze artifacts. Chemical analysis methods may include the analysis of mass, density or chemical composition. Most methods are non-destructive in nature, such as X-ray spectroscopy, or micro-destructive (requiring removal of only a tiny portion of the sample). Non-destructive methods can be used on more artefacts than destructive ones, but because they operate at the surface of the metal, corrosion and other surface effects may interfere with the results. Options that include sampling include various forms of mass spectrometry and a variety of chemical tests. | 8 | Metallurgy |
Aerobic respiration is the most preferred remineralisation reaction due to its high energy yield. Although oxygen is quickly depleted in the sediments and is generally exhausted centimeters from the sediment-water interface. | 9 | Geochemistry |
The total boron (B) is the sum of boron species in a solution. In the environment these species usually include boric acid and borate, for example:
:B = [] + []
where
*B is the total boron concentration
*[] is the dihydrogen borate concentration
*[] is the boric acid concentration
Total boron is an important quantity when determining alkalinity due to borates contribution to a solutions acid neutraling capacity. Total boron is a conservative element in seawater, and can thus be calculated by simply knowing the salinity. | 9 | Geochemistry |
Thiomers have the ability to form complexes with different metal ions, especially divalent metal ions, due to their thiol groups. Thiolated chitosans, for instance, were shown to effectively absorb nickel ions. | 7 | Physical Chemistry |
A helpful classification scheme for multiferroics into so-called type-I and type-II multiferroics was introduced in 2009 by D. Khomskii.
Khomskii suggested the term type-I multiferroic for materials in which the ferroelectricity and magnetism occur at different temperatures and arise from different mechanisms. Usually the structural distortion which gives rise to the ferroelectricity occurs at high temperature, and the magnetic ordering, which is usually antiferromagnetic, sets in at lower temperature. The prototypical example is BiFeO (T=1100 K, T=643 K), with the ferroelectricity driven by the stereochemically active lone pair of the Bi ion and the magnetic ordering caused by the usual superexchange mechanism. YMnO (T=914 K, T=76 K) is also type-I, although its ferroelectricity is so-called "improper", meaning that it is a secondary effect arising from another (primary) structural distortion. The independent emergence of magnetism and ferroelectricity means that the domains of the two properties can exist independently of each other. Most type-I multiferroics show a linear magnetoelectric response, as well as changes in dielectric susceptibility at the magnetic phase transition.
The term type-II multiferroic is used for materials in which the magnetic ordering breaks the inversion symmetry and directly "causes" the ferroelectricity. In this case the ordering temperatures for the two phenomena are identical. The prototypical example is TbMnO, in which a non-centrosymmetric magnetic spiral accompanied by a ferroelectric polarization sets in at 28 K. Since the same transition causes both effects they are by construction strongly coupled. The ferroelectric polarizations tend to be orders of magnitude smaller than those of the type-I multiferroics however, typically of the order of 10 μC/cm. The opposite effect has also been reported, in the Mott insulating charge-transfer salt –. Here, a charge-ordering transition to a polar ferroelectric case drives a magnetic ordering, again giving an intimate coupling between the ferroelectric and, in this case antiferromagnetic, orders. | 7 | Physical Chemistry |
The General Chapter of the Cistercian monks spread some technological advances across Europe. This may have included the blast furnace, as the Cistercians are known to have been skilled metallurgists. According to Jean Gimpel, their high level of industrial technology facilitated the diffusion of new techniques: "Every monastery had a model factory, often as large as the church and only several feet away, and waterpower drove the machinery of the various industries located on its floor." Iron ore deposits were often donated to the monks along with forges to extract the iron, and after a time surpluses were offered for sale. The Cistercians became the leading iron producers in Champagne, France, from the mid-13th century to the 17th century, also using the phosphate-rich slag from their furnaces as an agricultural fertilizer.
Archaeologists are still discovering the extent of Cistercian technology. At Laskill, an outstation of Rievaulx Abbey and the only medieval blast furnace so far identified in Britain, the slag produced was low in iron content. Slag from other furnaces of the time contained a substantial concentration of iron, whereas Laskill is believed to have produced cast iron quite efficiently. Its date is not yet clear, but it probably did not survive until Henry VIII's Dissolution of the Monasteries in the late 1530s, as an agreement (immediately after that) concerning the "smythes" with the Earl of Rutland in 1541 refers to blooms. Nevertheless, the means by which the blast furnace spread in medieval Europe has not finally been determined. | 8 | Metallurgy |
In surface science, a tensiometer is a measuring instrument used to measure the surface tension () of liquids or surfaces. Tensiometers are used in research and development laboratories to determine the surface tension of liquids like coatings, lacquers or adhesives. A further application field of tensiometers is the monitoring of industrial production processes like parts cleaning or electroplating. | 7 | Physical Chemistry |
The Angeli–Rimini reaction has recently been applied in solid-phase synthesis with the sulfonamide covalently linked to a polystyrene solid support. | 3 | Analytical Chemistry |
Solvents also have an effect on allylic strain. When used in conjunction with knowledge of the effects of polarity on allylic strain, solvents can be very useful in directing the conformation of a product that contains an allylic structure in its transition state. When a bulky and polar solvent is able to interact with one of the substituents in the allylic group, the complex of the solvent can energetically force the bulky complex out of the allylic strain in favor of a smaller group. | 4 | Stereochemistry |
Dipole–dipole interactions (or Keesom interactions) are electrostatic interactions between molecules which have permanent dipoles. This interaction is stronger than the London forces but is weaker than ion-ion interaction because only partial charges are involved. These interactions tend to align the molecules to increase attraction (reducing potential energy). An example of a dipole–dipole interaction can be seen in hydrogen chloride (HCl): the positive end of a polar molecule will attract the negative end of the other molecule and influence its position. Polar molecules have a net attraction between them. Examples of polar molecules include hydrogen chloride (HCl) and chloroform (CHCl).
Often molecules contain dipolar groups of atoms, but have no overall dipole moment on the molecule as a whole. This occurs if there is symmetry within the molecule that causes the dipoles to cancel each other out. This occurs in molecules such as tetrachloromethane and carbon dioxide. The dipole–dipole interaction between two individual atoms is usually zero, since atoms rarely carry a permanent dipole.
The Keesom interaction is a van der Waals force. It is discussed further in the section "Van der Waals forces". | 6 | Supramolecular Chemistry |
Bands of alternating light and dark in the positive column are called striations. There is no universal mechanism explaining the striations for all conditions of gas and pressure producing them, but recent theoretical and modelling studies, supported with experimental results, mention the importance of the Dufour effect. | 3 | Analytical Chemistry |
In organic chemistry, a 1,3-dipolar compound or 1,3-dipole is a dipolar compound with delocalized electrons and a separation of charge over three atoms. They are reactants in 1,3-dipolar cycloadditions.
The dipole has at least one resonance structure with positive and negative charges having a 1,3 relationship which can generally be denoted as , where a may be a carbon, oxygen or nitrogen, b may be nitrogen or oxygen, and c may be a carbon, oxygen or nitrogen.
Known 1,3-dipoles are:
* Azides ()
* Ozone ()
* Nitro compounds ()
* Diazo compounds ()
* Some oxides
** Azoxide compounds (RN(O)NR)
** Carbonyl oxides (Criegee zwitterions)
** Nitrile oxides ()
** Nitrous oxide ()
** Nitrones ()
* Some imines:
** Azomethine imine
** Nitrilimines (, analogous to nitrile oxide)
** Carbonyl imines
* Some ylides
** Azomethine ylide
** Nitrile ylide ()
** Carbonyl ylide
** Thiosulfines () | 0 | Organic Chemistry |
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