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Employment of scavenger resins has become increasingly popular in solution-phase combinatorial chemistry. Used primarily in the synthesis of medicinal drugs, solution-phase combinatorial chemistry allows for the creation of large libraries of structurally related compounds. When purifying a solution, many approaches can be taken. In general chemical synthesis laboratories, a number of traditional techniques for purification are used as opposed to the employment of scavenger resins. Whether or not scavenger resins are used often depends on the quantity of product desired, how much time you have to produce the wanted product, and the use of the product. Some of the advantages and disadvantages to using scavenger resins as a means for purification are described later. Traditional methods of purification of these compounds becomes time consuming and does not always produce entirely pure products. The ability to specialize a scavenger resin allows for significantly reduce purification times and more pure products. Furthermore, the use of scavenger resins creates a situation where the product can remain in solution and the reaction can be monitored. Conversely, many scavenger resins must be used in large amounts to purify a given product, presenting physical purification issues. Furthermore, when discussing the use of scavenger resins it is important to think about the different types of solid support "beads" that will hold the selected functional group. These polymer beads can be describe most often in two ways, lightly crosslinked and highly crosslinked. The different solid supports are chosen at the preference of the chemist. | 0 | Organic Chemistry |
In thermodynamics, an activity coefficient is a factor used to account for deviation of a mixture of chemical substances from ideal behaviour. In an ideal mixture, the microscopic interactions between each pair of chemical species are the same (or macroscopically equivalent, the enthalpy change of solution and volume variation in mixing is zero) and, as a result, properties of the mixtures can be expressed directly in terms of simple concentrations or partial pressures of the substances present e.g. Raoults law. Deviations from ideality are accommodated by modifying the concentration by an activity coefficient'. Analogously, expressions involving gases can be adjusted for non-ideality by scaling partial pressures by a fugacity coefficient.
The concept of activity coefficient is closely linked to that of activity in chemistry. | 7 | Physical Chemistry |
Lipotoxicity affects the pancreas when excess free fatty acids are found in beta cells, causing their dysfunction and death. The effects of the lipotoxicity is treated with leptin therapy and insulin sensitizers. | 1 | Biochemistry |
Chain-growth polymerization (AE) or chain-growth polymerisation (BE) is a polymerization technique where unsaturated monomer molecules add onto the active site on a growing polymer chain one at a time. There are a limited number of these active sites at any moment during the polymerization which gives this method its key characteristics.
Chain-growth polymerization involves 3 types of reactions :
# Initiation: An active species I* is formed by some decomposition of an initiator molecule I
# Propagation: The initiator fragment reacts with a monomer M to begin the conversion to the polymer; the center of activity is retained in the adduct. Monomers continue to add in the same way until polymers P* are formed with the degree of polymerization i
# Termination: By some reaction generally involving two polymers containing active centers, the growth center is deactivated, resulting in dead polymer | 7 | Physical Chemistry |
Very recently scalable all-perovskite based PEC photoelectrochemical system as solar hydrogen panel has been developed with >123 cm2 area. | 5 | Photochemistry |
A protein skimmer or foam fractionator is a device used to remove organic compounds such as food and waste particles from water. It is most commonly used in commercial applications like municipal water treatment facilities, public aquariums, and aquaculture facilities. Smaller protein skimmers are also used for filtration of home saltwater aquariums and even freshwater aquariums and ponds. | 3 | Analytical Chemistry |
GC content is found to be variable with different organisms, the process of which is envisaged to be contributed to by variation in selection, mutational bias, and biased recombination-associated DNA repair.
The average GC-content in human genomes ranges from 35% to 60% across 100-Kb fragments, with a mean of 41%. The GC-content of Yeast (Saccharomyces cerevisiae) is 38%, and that of another common model organism, thale cress (Arabidopsis thaliana), is 36%. Because of the nature of the genetic code, it is virtually impossible for an organism to have a genome with a GC-content approaching either 0% or 100%. However, a species with an extremely low GC-content is Plasmodium falciparum (GC% = ~20%), and it is usually common to refer to such examples as being AT-rich instead of GC-poor.
Several mammalian species (e.g., shrew, microbat, tenrec, rabbit) have independently undergone a marked increase in the GC-content of their genes. These GC-content changes are correlated with species life-history traits (e.g., body mass or longevity) and genome size, and might be linked to a molecular phenomenon called the GC-biased gene conversion. | 1 | Biochemistry |
Excimer lamps are quasimonochromatic light sources operating over a wide range of wavelengths in the ultraviolet (UV) and vacuum ultraviolet (VUV) spectral regions. Operation of an excimer lamp is based on the formation of excited dimers (excimers), which spontaneously transiting from the excited state to the ground state result in the emission of UV photons. The spectral maximum of excimer lamp radiation is specified by a working excimer molecule:
Excimers are diatomic molecules (dimers) or polyatomic molecules that have stable excited electronic states and an unbound or weakly bound (thermally unstable) ground state. Initially, only homonuclear diatomic molecules with a stable excited state but a repulsive ground state were called excimers (excited dimers). The term "excimer" was later extended to refer any polyatomic molecule with a repulsive or weakly bound ground state. One can also come across the term "exciplex" (from "excited complex"). It is also an excimer molecule but not a homonuclear dimer. For instance, Xe*, Kr*, Ar* are excimer molecules, while XeCl*, KrCl*, XeBr*, ArCl*, XeCl* are referred to exciplex molecules. Dimers of rare gases and rare-gas–halogen dimers are the most spread and studied excimers. Rare-gas–halide trimers, metal excimers, metal–rare-gas excimers, metal–halide excimers, and rare-gas–oxide excimers are also known, but they are rarely used.
An excimer molecule can exist in an excited electronic state for a limited time, as a rule from a few to a few tens of nanoseconds. After that, an excimer molecule transits to the ground electronic state, while releasing the energy of internal electronic excitation in the form of a photon. Owing to a specific electronic structure of an excimer molecule, the energy gap between the lowest bound excited electronic state and the ground state amounts from 3.5 to 10 eV, depending on a kind of an excimer molecule and provides light emission in the UV and VUV spectral region. A typical spectral characteristic of excimer lamp radiation consists mainly of one intense narrow emission band. About 70–80% of the whole radiation power of an excimer lamp is concentrated in this emission band. The full width at half maximum of the emission band depends on a kind of an excimer molecule and excitation conditions and ranges within 2 to 15 nm. In fact, excimer lamps are sources of quasimonochromatic light. Therefore, such sources are suitable for spectral-selective irradiation and can even replace lasers in some cases. | 5 | Photochemistry |
The JAK-STAT signaling pathway is instrumental in the development of limbs, specifically in its ability to regulate bone growth through paracrine signaling of cytokines. However, mutations in this pathway have been implicated in severe forms of dwarfism: thanatophoric dysplasia (lethal) and achondroplasic dwarfism (viable). This is due to a mutation in a Fgf gene, causing a premature and constitutive activation of the Stat1 transcription factor. Chondrocyte cell division is prematurely terminated, resulting in lethal dwarfism. Rib and limb bone growth plate cells are not transcribed. Thus, the inability of the rib cage to expand prevents the newborn's breathing. | 1 | Biochemistry |
This salt is used as a flotation agent in the purification of molybdenite (MoS) from other components of the ores, where it is usually known as "Nokes reagent" (after Charles M. Nokes, who patented it in 1948). The salt is generated by the reaction of phosphorus pentasulfide with sodium hydroxide, often using impure reagents to obtain a mixture of the desired salt and related thiophosphates and oxidized species. Molybdenite particles, which are normally hydrophobic, become hydrophilic in the presence of this salt. In this context, the Nokes reagent is called a "depressant," because it suppresses the flotation tendency of the solids other than molybdenite. | 8 | Metallurgy |
Tetrakis(hydroxymethyl)phosphonium chloride has industrial importance in the production of crease-resistant and flame-retardant finishes on cotton textiles and other cellulosic fabrics. A flame-retardant finish can be prepared from THPC by the Proban Process, in which THPC is treated with urea. The urea condenses with the hydroxymethyl groups on THPC. The phosphonium structure is converted to phosphine oxide as the result of this reaction. | 0 | Organic Chemistry |
The carbonate-silicate cycle is the primary control on carbon dioxide levels over long timescales. It can be seen as a branch of the carbon cycle, which also includes the organic carbon cycle, in which biological processes convert carbon dioxide and water into organic matter and oxygen via photosynthesis. | 9 | Geochemistry |
The prolemuris (Syaksyuk in Navi) are blue, hexapodal creatures based on Earths lemurs. They have two eyes, small nostrils, and their two upper arms on each side are partially fused. Like most Pandoran creatures, they have a queue on the back of their heads. They have lateral skin membranes on each side of the body. They have large eyes and grow 1.5 meters tall. | 1 | Biochemistry |
Extractive metallurgy is a branch of metallurgical engineering wherein process and methods of extraction of metals from their natural mineral deposits are studied. The field is a materials science, covering all aspects of the types of ore, washing, concentration, separation, chemical processes and extraction of pure metal and their alloying to suit various applications, sometimes for direct use as a finished product, but more often in a form that requires further working to achieve the given properties to suit the applications.
The field of ferrous and non-ferrous extractive metallurgy have specialties that are generically grouped into the categories of mineral processing, hydrometallurgy, pyrometallurgy, and electrometallurgy based on the process adopted to extract the metal. Several processes are used for extraction of the same metal depending on occurrence and chemical requirements. | 8 | Metallurgy |
Prescriptions of thalidomide are accompanied by strict measures to avoid any risk of pregnancy. In the United States, the prescribing doctor is required to ensure that contraception is being used, and that regular pregnancy tests are taken. | 4 | Stereochemistry |
*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 | 8 | Metallurgy |
Hydrofluorocarbons are included in the Kyoto Protocol and are regulated under the Kigali Amendment to the Montreal Protocol due to their very high Global Warming Potential and the recognition of halocarbon contributions to climate change.
On September 21, 2007, approximately 200 countries agreed to accelerate the elimination of hydrochlorofluorocarbons entirely by 2020 in a United Nations-sponsored Montreal summit. Developing nations were given until 2030. Many nations, such as the United States and China, who had previously resisted such efforts, agreed with the accelerated phase out schedule. India successfully phased out HCFCs by 2020. | 2 | Environmental Chemistry |
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. | 9 | Geochemistry |
A quinone methide is a type of conjugated organic compound that contain a cyclohexadiene with a carbonyl and an exocyclic methylidene or extended alkene unit. It is analogous to a quinone, but having one of the double bonded oxygens replaced with a carbon. The carbonyl and methylidene are usually oriented either ortho or para to each other. There are some examples of transient synthetic meta quinone methides. | 0 | Organic Chemistry |
Various bioinformatics tools can be used to analyze end-sequence profiling. Common ones include BreakDancer, PEMer, Variation Hunter, common LAW, GASV, and Spanner. ESP can be used to map structural variation at high-resolution in disease tissue. This technique is mainly used on tumor samples from different cancer types. Accurate identification of copy neutral chromosomal abnormalities is particularly important as translocation can lead to fusion proteins, chimeric proteins, or misregulated proteins that can be seen in tumors. This technique can also be used in evolution studies by identifying large structural variation between different populations. Similar methods are being developed for various applications. For example, a barcoded Illumina paired-end sequencing (BIPES) approach was used to assess microbial diversity by sequencing the 16S V6 tag. | 1 | Biochemistry |
The degradation of organic matter through respiration in the modern ocean is facilitated by different electron acceptors, their favorability based on Gibbs free energy law, and the laws of thermodynamics. This redox chemistry is the basis for life in deep sea sediments and determines the obtainability of energy to organisms that live there. From the water interface moving toward deeper sediments, the order of these acceptors is oxygen, nitrate, manganese, iron, and sulfate. The zonation of these favored acceptors can be seen in Figure 1. Moving downwards from the surface through the zonation of these deep ocean sediments, acceptors are used and depleted. Once depleted the next acceptor of lower favorability takes its place. Thermodynamically, oxygen represents the most favorable electron accepted but is quickly used up in the water sediment interface and concentrations extends only millimeters to centimeters down into the sediment in most locations of the deep sea. This favorability indicates an organism's ability to obtain higher energy from the reaction which helps them compete with other organisms. In the absence of these acceptors, organic matter can also be degraded through methanogenesis, but the net oxidation of this organic matter is not fully represented by this process. Each pathway and the stoichiometry of its reaction are listed in table 1.
Due to this quick depletion of in the surface sediments, a majority of microbes use anaerobic pathways to metabolize other oxides such as manganese, iron, and sulfate. It is also important to figure in bioturbation and the constant mixing of this material which can change the relative importance of each respiration pathway. For the microbial perspective please reference the electron transport chain. | 9 | Geochemistry |
Induction heating is a non contact heating process which uses the principle of electromagnetism induction to produce heat in a work-piece. In this case thermal expansion is used in a mechanical application to fit parts over one another, e.g. a bushing can be fitted over a shaft by making its inner diameter slightly smaller than the diameter of the shaft, then heating it until it fits over the shaft, and allowing it to cool after it has been pushed over the shaft, thus achieving a shrink fit. By placing a conductive material into a strong alternating magnetic field, electric current can be made to flow in the metal thereby creating heat due to the IR losses in the material. The current generated flows predominantly in the surface layer. The depth of this layer being dictated by the frequency of the alternating field and the permeability of the material. Induction heaters for shrink fitting fall into two broad categories:
* Mains frequency (MF) units using magnetic cores (iron)
* Solid state MF and radio frequency (RF) heaters | 8 | Metallurgy |
Human immunodeficiency virus is a viral infection that targets the lymph nodes. HIV binds to the immune CD4 cell and reverse transcriptase alters the host cell genome to allow integration of the viral DNA via integrase. The virus replicates using the host cell's machinery and then leaves the cell to infect additional cells via budding. | 1 | Biochemistry |
Oscar Paul Kuipers (Rotterdam, May 12, 1956) is a Dutch professor of molecular genetics at the University of Groningen. His areas of expertise include microbiology, biochemistry, molecular and cell biology, and biotechnology. | 0 | Organic Chemistry |
Fluorescence spectroscopy (also known as fluorimetry or spectrofluorometry) is a type of electromagnetic spectroscopy that analyzes fluorescence from a sample. It involves using a beam of light, usually ultraviolet light, that excites the electrons in molecules of certain compounds and causes them to emit light; typically, but not necessarily, visible light. A complementary technique is absorption spectroscopy. In the special case of single molecule fluorescence spectroscopy, intensity fluctuations from the emitted light are measured from either single fluorophores, or pairs of fluorophores.
Devices that measure fluorescence are called fluorometers. | 7 | Physical Chemistry |
Most experimentally determined values of the thermal contact resistance fall between
0.000005 and 0.0005 m K/W (the corresponding range of thermal contact
conductance is 200,000 to 2000 W/m K). To know whether the thermal contact resistance is significant or not, magnitudes of the thermal resistances of the layers are compared with typical values of thermal contact resistance. Thermal contact resistance is significant and may dominate for good heat conductors such as metals but can be neglected for poor heat conductors such as insulators.
Thermal contact conductance is an important factor in a variety of applications, largely because many physical systems contain a mechanical combination of two materials. Some of the fields where contact conductance is of importance are:
* Electronics
** Electronic packaging
** Heat sinks
** Brackets
* Industry
** Nuclear reactor cooling
** Gas turbine cooling
** Internal combustion engines
** Heat exchangers
** Thermal insulation
** Press hardening of automotive steels
* Flight
** Hypersonic flight vehicles
** Thermal supervision for space vehicles
* Residential/building science
** Performance of building envelopes | 7 | Physical Chemistry |
Nitrifying bacteria are chemolithotrophic organisms that include species of genera such as Nitrosomonas, Nitrosococcus, Nitrobacter, Nitrospina, Nitrospira and Nitrococcus. These bacteria get their energy from the oxidation of inorganic nitrogen compounds. Types include ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). Many species of nitrifying bacteria have complex internal membrane systems that are the location for key enzymes in nitrification: ammonia monooxygenase (which oxidizes ammonia to hydroxylamine), hydroxylamine oxidoreductase (which oxidizes hydroxylamine to nitric oxide - which is further oxidized to nitrite by a currently unidentified enzyme), and nitrite oxidoreductase (which oxidizes nitrite to nitrate). | 1 | Biochemistry |
Zinc was extracted in India as early as in the 4th to 3rd century BCE. Zinc production may have begun in India, and ancient northwestern India is the earliest known civilization that produced zinc on an industrial scale. The distillation technique was developed around 1200 CE at Zawar in Rajasthan.
In the 17th century, China exported Zinc to Europe under the name of totamu or tutenag. The term tutenag may derive from the South Indian term Tutthanagaa (zinc). In 1597, Libavius, a metallurgist in England received some quantity of Zinc metal and named it as Indian/Malabar lead. In 1738, William Champion is credited with patenting in Britain a process to extract zinc from calamine in a smelter, a technology that bore a strong resemblance to and was probably inspired by the process used in the Zawar zinc mines in Rajasthan. His first patent was rejected by the patent court on grounds of plagiarising the technology common in India. However, he was granted the patent on his second submission of patent approval. Postlewayts Universal Dictionary of 1751 still wasnt aware of how Zinc was produced.
The Arthashastra describes the production of zinc. The Rasaratnakara by Nagarjuna describes the production of brass and zinc. There are references of medicinal uses of zinc in the Charaka Samhita (300 BCE). The Rasaratna Samuchaya (800 CE) explains the existence of two types of ores for zinc metal, one of which is ideal for metal extraction while the other is used for medicinal purpose. It also describes two methods of zinc distillation. | 8 | Metallurgy |
A yeast two-hybrid screening (Y2H) tests a "bait" protein against many potential interacting proteins ("prey") to identify physical protein–protein interactions. This system is based on a transcription factor, originally GAL4, whose separate DNA-binding and transcription activation domains are both required in order for the protein to cause transcription of a reporter gene. In a Y2H screen, the "bait" protein is fused to the binding domain of GAL4, and a library of potential "prey" (interacting) proteins is recombinantly expressed in a vector with the activation domain. In vivo interaction of bait and prey proteins in a yeast cell brings the activation and binding domains of GAL4 close enough together to result in expression of a reporter gene. It is also possible to systematically test a library of bait proteins against a library of prey proteins to identify all possible interactions in a cell. | 1 | Biochemistry |
Two widely employed applications of migratory insertion of carbonyl groups are hydroformylation and the production of acetic acid by carbonylation of methanol. The former converts alkenes, hydrogen, and carbon monoxide into aldehydes. The production of acetic acid by carbonylation proceeds via two similar industrial processes. More traditional is the Monsanto acetic acid process, which relies on a rhodium-iodine catalyst to transform methanol into acetic acid. This process has been superseded by the Cativa process which uses a related iridium catalyst, [Ir(CO)I] (1). By 2002, worldwide annual production of acetic acid stood at 6 million tons, of which approximately 60% is produced by the Cativa process.
The Cativa process catalytic cycle, shown above, includes both insertion and de-insertion steps. The oxidative addition reaction of methyl iodide with (1) involves the formal insertion of the iridium(I) centre into the carbon-iodine bond, whilst step (3) to (4) is an example of migratory insertion of carbon monoxide into the iridium-carbon bond. The active catalyst species is regenerated by the reductive elimination of acetyl iodide from (4), a de-insertion reaction. | 0 | Organic Chemistry |
In interfacial shear rheology, the interfacial area remains the same throughout the measurement. Instead, the interfacial area is sheared in order to be able to measure the surface stress present. The equations are similar to dilatational interfacial rheology but shear modulus is often marked with G instead of E like in dilational methods. In a general case, G and E are not equal.
Since interfacial rheological properties are relatively weak, it causes challenges for the measurement equipment. For high sensitivity, it is essential to maximize the contribution of the interface while minimizing the contribution of the bulk phase. The Boussinesq number, Bo, depicts how sensitive a measurement method is for detecting the interfacial viscoelasticity.
The commercialized measurement techniques for interfacial shear rheology include magnetic needle method, rotating ring method and rotating bicone method. The magnetic needle method, developed by Brooks et al., has the highest Boussinesq number of the commercialized methods. In this method, a thin magnetic needle is oscillated at the interface using a magnetic field. By following the movement of the needle with a camera, the viscoelastic properties of the interface can be detected. This method is often used in combination with a Langmuir trough in order to be able to conduct the experiment as a function of the packing density of the molecules or particles. | 7 | Physical Chemistry |
The concept of gene therapy is to fix a genetic problem at its source. If, for instance, a mutation in a certain gene causes the production of a dysfunctional protein resulting (usually recessively) in an inherited disease, gene therapy could be used to deliver a copy of this gene that does not contain the deleterious mutation and thereby produces a functional protein. This strategy is referred to as gene replacement therapy and could be employed to treat inherited retinal diseases.
While the concept of gene replacement therapy is mostly suitable for recessive diseases, novel strategies have been suggested that are capable of also treating conditions with a dominant pattern of inheritance.
* The introduction of CRISPR gene editing has opened new doors for its application and utilization in gene therapy, as instead of pure replacement of a gene, it enables correction of the particular genetic defect. Solutions to medical hurdles, such as the eradication of latent human immunodeficiency virus (HIV) reservoirs and correction of the mutation that causes sickle cell disease, may be available as a therapeutic option in the future.
* Prosthetic gene therapy aims to enable cells of the body to take over functions they physiologically do not carry out. One example is the so-called vision restoration gene therapy, that aims to restore vision in patients with end-stage retinal diseases. In end-stage retinal diseases, the photoreceptors, as the primary light sensitive cells of the retina are irreversibly lost. By the means of prosthetic gene therapy light sensitive proteins are delivered into the remaining cells of the retina, to render them light sensitive and thereby enable them to signal visual information towards the brain.
In vivo, gene editing systems using CRISPR have been used in studies with mice to treat cancer and have been effective at reducing tumors. In vitro, the CRISPR system has been used to treat HPV cancer tumors. Adeno-associated virus, Lentivirus based vectors have been to introduce the genome for the CRISPR system. | 1 | Biochemistry |
ERH has been used for over 15 years for treatment of unconsolidated soils in both the vadose and saturated zones. Recent advancements and results show that ERH can be an effective treatment method for bedrock. At an ERH site, the primary electrical current path is on the thin layer of water immediately adjacent to the soil or rock grains. Little current is carried by the water in the pore volume. It is not the pore fluid that dominates the electrical conductivity; it is the grain wetting fluid that dominates the electrical conductivity. Sedimentary rock will typically possess the thin layer of water required for current flow. This means ERH can effectively be used for treatment of sedimentary bedrock, which typically has significant primary porosity. | 2 | Environmental Chemistry |
Strong evidence of metallurgical activities has been revealed in levels 9 to 6, dating to the Ubaid period, and especially in level 7 (4166 +/- 170 cal BC). Hearths or natural draft furnaces, slag, ore, and pigment had been recovered throughout the site. This was in the context of architectural complexes typical of southern Mesopotamian architecture.
Unusually, the metallurgical activities at the site appear to have been limited to the melting and casting of copper objects. Arsenical copper objects were clearly manufactured on site, yet the technological aspects of this productions remain unclear. This is because the primary smelting of ore seems to have been undertaken elsewhere, perhaps already at the mining sites. So questions remain as to whether or not arsenic was already present in the ores, or added later.
In contrast, the related Norşuntepe site provides a better context of production, and demonstrates that some form of arsenic alloying was indeed taking place by the 4th millennium BC. Since the slag identified at Norşuntepe contains no arsenic, this means that arsenic was added separately. | 8 | Metallurgy |
Non-linear inverse Compton scattering (NICS), also known as non-linear Compton scattering and multiphoton Compton scattering, is the scattering of multiple low-energy photons, given by an intense electromagnetic field, in a high-energy photon (X-ray or gamma ray) during the interaction with a charged particle, in many cases an electron. This process is an inverted variant of Compton scattering since, contrary to it, the charged particle transfers its energy to the outgoing high-energy photon instead of receiving energy from an incoming high-energy photon. Furthermore, differently from Compton scattering, this process is explicitly non-linear because the conditions for multiphoton absorption by the charged particle are reached in the presence of a very intense electromagnetic field, for example, the one produced by high-intensity lasers.
Non-linear inverse Compton scattering is a scattering process belonging to the category of light-matter interaction phenomena. The absorption of multiple photons of the electromagnetic field by the charged particle causes the consequent emission of an X-ray or a gamma ray with energy comparable or higher with respect to the charged particle rest energy.
The normalized vector potential helps to isolate the regime in which non-linear inverse Compton scattering occurs ( is the electron charge, is the electron mass, <math>c
the vector potential). If , the emission phenomenon can be reduced to the scattering of a single photon by an electron, which is the case of inverse Compton scattering. While, if , NICS occurs and the probability amplitudes of emission have non-linear dependencies on the field. For this reason, in the description of non-linear inverse Compton scattering, is called classical non-linearity parameter. | 7 | Physical Chemistry |
An "ion-channel forming" molecule can often show multiple types of conductance activities in planar bilayer membranes. Each of these modes of action can be characterized by their
* open duration (sub-ms---hours), related to whether the active structure is kinetically labile,
* unit conductance (pS---nS), related to the geometry of the active structure, and
* open probability, a fraction related to the thermodynamic stability of that active structure relative to inactive forms.
These events are not necessarily uniform throughout their durations, and as a result a variety of shapes of conducting traces are possible. | 6 | Supramolecular Chemistry |
Transposons and retrotransposons are mobile genetic elements. Retrotransposon repeated sequences, which include long interspersed nuclear elements (LINEs) and short interspersed nuclear elements (SINEs), account for a large proportion of the genomic sequences in many species. Alu sequences, classified as a short interspersed nuclear element, are the most abundant mobile elements in the human genome. Some examples have been found of SINEs exerting transcriptional control of some protein-encoding genes.
Endogenous retrovirus sequences are the product of reverse transcription of retrovirus genomes into the genomes of germ cells. Mutation within these retro-transcribed sequences can inactivate the viral genome.
Over 8% of the human genome is made up of (mostly decayed) endogenous retrovirus sequences, as part of the over 42% fraction that is recognizably derived of retrotransposons, while another 3% can be identified to be the remains of DNA transposons. Much of the remaining half of the genome that is currently without an explained origin is expected to have found its origin in transposable elements that were active so long ago (> 200 million years) that random mutations have rendered them unrecognizable. Genome size variation in at least two kinds of plants is mostly the result of retrotransposon sequences. | 1 | Biochemistry |
Quantitative chemical analysis is a key part of environmental chemistry, since it provides the data that frame most environmental studies.
Common analytical techniques used for quantitative determinations in environmental chemistry include classical wet chemistry, such as gravimetric, titrimetric and electrochemical methods. More sophisticated approaches are used in the determination of trace metals and organic compounds. Metals are commonly measured by atomic spectroscopy and mass spectrometry: Atomic Absorption Spectrophotometry (AAS) and Inductively Coupled Plasma Atomic Emission (ICP-AES) or Inductively Coupled Plasma Mass Spectrometric (ICP-MS) techniques. Organic compounds, including PAHs, are commonly measured also using mass spectrometric methods, such as Gas chromatography-mass spectrometry (GC/MS) and Liquid chromatography-mass spectrometry (LC/MS). Tandem Mass spectrometry MS/MS and High Resolution/Accurate Mass spectrometry HR/AM offer sub part per trillion detection. Non-MS methods using GCs and LCs having universal or specific detectors are still staples in the arsenal of available analytical tools.
Other parameters often measured in environmental chemistry are radiochemicals. These are pollutants which emit radioactive materials, such as alpha and beta particles, posing danger to human health and the environment. Particle counters and Scintillation counters are most commonly used for these measurements. Bioassays and immunoassays are utilized for toxicity evaluations of chemical effects on various organisms. Polymerase Chain Reaction PCR is able to identify species of bacteria and other organisms through specific DNA and RNA gene isolation and amplification and is showing promise as a valuable technique for identifying environmental microbial contamination. | 2 | Environmental Chemistry |
*Porphyrins, and phthalocyanines have highly tunable photochemical and electrochemical activity as well as the potential to form complexes.
*Photochromic and photoisomerizable groups can change their shapes and properties, including binding properties, upon exposure to light.
*Tetrathiafulvalene (TTF) and quinones have multiple stable oxidation states, and therefore can be used in redox reactions and electrochemistry.
*Other units, such as benzidine derivatives, viologens, and fullerenes, are useful in supramolecular electrochemical devices. | 6 | Supramolecular Chemistry |
Ca ions are usually kept at nanomolar levels in the cytosol of plant cells, and act in a number of signal transduction pathways as second messengers. | 1 | Biochemistry |
* 24 August 2007: A large buildup of sea foam occurred on the coast of Yamba, northern New South Wales.
* January–February 2008: Sea foam occurrences at Caloundra and Point Cartwright on Queensland's Sunshine Coast attracted world-wide media attention.
* December 2011: The coast road at Cleveleys, Lancashire was swamped by meter-high drifts of sea foam.
* 2012: During live coverage of Hurricane Irene in Ocean City, Maryland, Tucker Barnes was covered in sea foam.
* 24–25 September 2012: Following storms and high winds, the beach front of the Footdee area of Aberdeen was engulfed with sea foam.
* 27–28 January 2013: The Sunshine Coast in Queensland, Australia had masses of foam wash up on land from ex-tropical cyclone Oswald.
* June 2016: Sea foam occurred across the East coast of Australia, whipped up by storms.
* 28 March 2017: Sea foam was generated by Cyclone Debbie at Sarina Beach in Queensland, Australia.
* 16 October 2017: Hurricane Ophelia covered Cleveleys, Lancashire with spume.
* January 2018: Storm Eleanor causes widespread foam to appear across coastal Europe.
* 11 October 2019: Subtropical storm Melissa brought sea foam to Nantasket Beach in Hull, Massachusetts.
* 21 January 2020: Storm Gloria floods Tossa de Mar, Spain, with thick sea foam on top of major flooding.
* 11 May 2020: Five surfers die in The Netherlands, presumably upon drowning after becoming disoriented in over 2 meters thick sea foam.
* 13 July 2020: The Cape Town storm, South Africa | 9 | Geochemistry |
There are four commonly used types of applications for nitinol:
; Free recovery
: Nitinol is deformed at a low temperature, remains deformed, and then is heated to recover its original shape through the shape memory effect.
; Constrained recovery
: Similar to free recovery, except that recovery is rigidly prevented and thus a stress is generated.
; Work production
: The alloy is allowed to recover, but to do so it must act against a force (thus doing work).
; Superelasticity
: Nitinol acts as a super spring through the superelastic effect.
Superelastic materials undergo stress-induced transformation and are commonly recognized for their "shape-memory" property. Due to its superelasticity, NiTi wires exhibit "elastocaloric" effect, which is stress-triggered heating/cooling. NiTi wires are currently under research as the most promising material for the technology. The process begins with tensile loading on the wire, which causes fluid (within the wire) to flow to HHEX (hot heat exchanger). Simultaneously, heat will be expelled, which can be used to heat the surrounding. In the reverse process, tensile unloading of the wire leads to fluid flowing to CHEX (cold heat exchanger), causing the NiTi wire to absorb heat from the surrounding. Therefore, the temperature of the surrounding can be decreased (cooled).
Elastocaloric devices are often compared with magnetocaloric devices as new methods of efficient heating/cooling. Elastocaloric device made with NiTi wires has an advantage over magnetocaloric device made with gadolinium due to its specific cooling power (at 2 Hz), which is 70X better (7 kWh/kg vs. 0.1 kWh/kg). However, elastocaloric device made with NiTi wires also have limitations, such as its short fatigue life and dependency on large tensile forces (energy consuming).
In 1989 a survey was conducted in the United States and Canada that involved seven organizations. The survey focused on predicting the future technology, market, and applications of SMAs. The companies predicted the following uses of nitinol in a decreasing order of importance: (1) Couplings, (2) Biomedical and medical, (3) Toys, demonstration, novelty items, (4) Actuators, (5) Heat Engines, (6) Sensors, (7) Cryogenically activated die and bubble memory sockets, and finally (8) lifting devices. | 8 | Metallurgy |
In the early 2000s, Zhao's group reported that visible light can accelerate the degradation of organic pollutants with aqueous
solutions of iron tetrasulfophthalocyanine ([Fe(PcS)]) and Hydrogen peroxide|. They also found out FeBR (Fe complex of 2,2′-bipyridine) is efficient in eliminating organic pollutants such as rhodamine B (RhB), malachite green (MG) and N, N-dimethylaniline (DMA). They did several control experiments, in the dark or under irradiation, with or without irradiation. They proposed that when light is introduced, excitation of [Fe(PcS)] can result in electron transfer from ligand(L) to Fe, then Fe can be reduced to Fe. The Fe-L complex can react with to produce HO, leading to the degradation of pollutants. | 2 | Environmental Chemistry |
Kendomycin is an anticancer macrolide first isolated from Streptomyces violaceoruber. It has potent activity as an endothelin receptor antagonist and anti-osteoporosis agent.
It also has strong cytotoxicity against various tumor cell lines. | 0 | Organic Chemistry |
Combining operando Raman, UV–Vis and ATR-IR is particularly useful for studying homogeneous catalysis in solution. Transition-metal complexes can perform catalytic oxidation reactions on organic molecules; however, much of the corresponding reaction pathways are still unclear. For example, an operando study of the oxidation of veratryl alcohol by salcomine catalyst at high pH determined that the initial oxidation of the two substrate molecules to aldehydes is followed by the reduction of molecular oxygen to water, and that the rate determining step is the detachment of the product. Understanding organometallic catalytic activity on organic molecules is incredibly valuable for the further development of material science and pharmaceuticals. | 7 | Physical Chemistry |
Many forms of oxyhydrogen lamps have been described, such as the limelight, which used an oxyhydrogen flame to heat a piece of lime to white hot incandescence. Because of the explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting. | 7 | Physical Chemistry |
This method tries to identify 4-bp long end motifs from each stands 5 end on bisulfite sequencing reads of plasma cfDNAs. Hierarchical clustering of the motifs is done to detect any under/overrepresentation of these motifs due to cancer existence. The method incorporates Support Vector Machines and Logistic Regression to predict cancer patients from healthy ones. The method is also applied to transplant patients with clustering and multidimensional scaling (MDS) analysis and shows applicability. The same analysis types also proved that this method applies to prenetal testing. This method is also informative for cell type origins. | 1 | Biochemistry |
Glycobiology is a monthly peer-reviewed scientific journal covering all aspects of the field of glycobiology and the official journal of the Society for Glycobiology. It is published by Oxford University Press. The journal was established in September 1990. It publishes primary research on the "biological functions of glycans, including glycoproteins, glycolipids, proteoglycans and free oligosaccharides, and on proteins that specifically interact with glycans." | 1 | Biochemistry |
The δSi value of sediment porewater may be affected by post-depositional (diagenetic) precipitation or dissolution of Si. It is important to understand the extent and isotopic fractionations of these processes, as they alter the δSi values of the originally deposited sediments, and determine the δSi preserved in the rock record. Generally, precipitation of Si prefers the light isotope (Si) and leads to Si-enriched dissolved Si in the hosting solution. The isotopic effect of Si dissolution in porewater is yet to be clear, as some studies report a preference for Si during dissolution, while other studies document that isotopic fractionation was not expressed during dissolution of sediments. | 9 | Geochemistry |
Pletz grouped the explosophores into eight distinct categories.
;I.
:These represent:
:* the nitro group, a nitrogen atom bound to two oxygen atoms as well as an organic molecule (e.g. TNT, RDX)
:* the nitrate ion, a nitrogen atom bound to three oxygen atoms, (e.g. nitroglycerin, ANFO)
:* the nitrite ion, a nitrogen atom bound to two oxygen atoms
:Most commercially used explosives include the nitrate ion or the nitro group.
;II.
:The azo and azide groups respectively, connected to organic/inorganic compounds (e.g. silver azide , lead azide , ammonium azide )
;III.
:The halogenated nitrogen group X:halogen (e.g. nitrogen triiodide and nitrogen trichloride )
;IV.
:The fulminate group (e.g. fulminic acid HONC and mercury fulminate )
;V.
:The chlorate and perchlorate groups respectively, connected to organics/inorganics (e.g. potassium chlorate , fluorine perchlorate )
;VI.
:The peroxide and ozonide groups respectively, connected to organics/inorganics (e.g. acetone peroxide, butanone peroxide)
;VII.
:The acetylide group with its metal derivatives (e.g. silver acetylide , copper acetylide )
;VIII. A metal atom connected by an unstable bond to the carbon of certain organic radicals
:This class contains for instance organic compounds of mercury, thallium, and lead.
;Other
:Other substances have been characterised as explosophores outside of the eight classes as defined by Pletz. | 0 | Organic Chemistry |
Annonins are a group of chemical compounds classified as acetogenins. They are found in the extracts of Annona seeds (A. squamosa and A. muricata). Annonin-based bioinsecticides are used to control Coleoptera (beetle) pests commonly found in stored organic cereal and beans in the country of Brazil. Other different types of annonin-based insecticides, derived from A. mucosa, fight off lepidopteran (moth) pests that infest cabbage leaves, also found in the tropical climates of Brazil. The benefit of using these bioinsecticides is their relatively low cost and no phytotoxicity. These annonin molecules act as overpowering inhibitors of complex I (NADH: ubiquinone oxidoreductase) in the electron-transport chain in the mitochondria of quarry pests. In cell membranes of these same pests, annonins also inhibit coenzyme NADH, causing these arthropods to die. | 1 | Biochemistry |
The Schikorr reaction formally describes the conversion of the iron(II) hydroxide (Fe(OH)) into iron(II,III) oxide (FeO). This transformation reaction was first studied by Gerhard Schikorr. The global reaction follows:
It is of special interest in the context of the serpentinization, the formation of hydrogen by the action of water on a common mineral. | 8 | Metallurgy |
Volatile phenolic compounds are found in plant resin where they may attract benefactors such as parasitoids or predators of the herbivores that attack the plant.
In the kelp species Alaria marginata, phenolics act as chemical defence against herbivores. In tropical Sargassum and Turbinaria species that are often preferentially consumed by herbivorous fishes and echinoids, there is a relatively low level of phenolics and tannins. Marine allelochemicals generally are present in greater quantity and diversity in tropical than in temperate regions. Marine algal phenolics have been reported as an apparent exception to this biogeographic trend. High phenolic concentrations occur in brown algae species (orders Dictyotales and Fucales) from both temperate and tropical regions, indicating that latitude alone is not a reasonable predictor of plant phenolic concentrations. | 0 | Organic Chemistry |
The scientific work of Leonidas Zervas had a global resonance and his contribution was recognised by multiple awards throughout his life. In 1960 he received an honorary doctorate from the University of Basel on the occasion of the university's 500th anniversary, upon recommendation of Hans Erlenmeyer and Nobel laureate Tadeusz Reichstein. In 1969 he was bestowed honorary membership of the American Society of Biological Chemists. In 1976 he was conferred the (1st class) by the Socialist Republic of Romania. In the same year Zervas was made Foreign Member of the USSR Academy of Sciences, an indication of the great respect for his work in the Eastern Block, too. The Max-Bergmann-Kreis company of German peptide chemists planned to present Zervas with the first Max Bergmann golden medal for peptide chemistry in 1980, but his sudden death necessitated a posthumous award ceremony.
In honour of Zervas, a commemorative bust has been unveiled in his birthtown Megalopolis in 1991 and the main conference hall of the National Hellenic Research Foundation is called the "Leonidas Zervas amphitheatre".
The European Peptide Society has established the Leonidas Zervas Award "in commemoration of his outstanding contributions to peptide science", awarded biennially since 1988. The award is given to the "scientist who has made the most outstanding contributions to the chemistry, biochemistry and/or biology of peptides in the five years preceding the date of selection". | 0 | Organic Chemistry |
Tools and weapons, chisels and axe-heads, spearheads or dagger-blades, are the only surviving artifacts of the Copper Age, and do not show artistic treatment. But some Early Minoan pottery forms are plainly copied from metal prototypes, cups and jugs of simple construction and rather elaborate design. The cups are conical and sometimes a stem-foot; there are oval jars with long tubular spouts, and beaked jugs with round shoulders set on conical bodies. Heads of rivets which tie the metal parts together are often reproduced as a decorative element in clay. The spouted jars and pierced type of axe-head indicate that metallurgical connections of Early Minoan Crete were partly Mesopotamian. | 8 | Metallurgy |
Museomics is the study of genomic data obtained from ancient DNA (aDNA) and historic DNA (hDNA) specimens in museum collections.
Early research in this area focused on short sequences of DNA from mitochondrial genes, but sequencing of whole genomes has become possible.
Next-generation sequencing (NGS) and high-throughput sequencing (HTS) methods can be applied to the analysis of genetic datasets extracted from collections materials. Such techniques have been described as a "third revolution in sequencing technology". Like radiocarbon dating, the techniques of museomics are a transformative technology. Results are revising and sometimes overturning previously accepted theories about a wide variety of topics such as the domestication of the horse.
Museum collections contain unique resources such as natural history specimens, which can be used for genome-scale examinations of species, their evolution, and their responses to environmental change. Ancient DNA provides a unique window into genetic change over time. It enables scientists to directly study evolutionary and ecological processes, comparing ancient and modern populations, identifying distinct populations, and revealing patterns of change such as extinctions and migrations. Research may be used to identify isolated populations and inform conservation priorities.
However, museum specimens can be poorly preserved and are subject to degradation and contamination. Genomic analyses face considerable challenges as a result of the highly degraded DNA typical of museum specimens. DNA from such samples is often subject to post-mortem nucleotide damage such as the hydrolytic deamination of cytosine (C) to uracil (U) residues. PCR amplification of damaged templates can further substitute uracils with thymine (T), completing a C to T substitution path. Such errors tend to occur towards the ends of molecules, accumulate with time, and can be significant in specimens a century-old or later. Robust genomic and statistical techniques are needed to rigorously detect and avoid errors and genotyping uncertainties when carrying out analyses based on museum collections. Optimal methods for working with hDNA and aDNA can differ as a result of differences in their DNA degradation history.
Museomics also involves destructive sampling, irreversibly removing parts of sometimes rare specimens to obtain DNA. This can be contentious for curators and collection staff, involving a variety of ethical issues around the handling and destruction of objects, colonial acquisition and repatriation practices, and present-day social and political implications of research. Museums, universities and journals are increasingly developing ethics statements, best practices and guidelines for such work. | 3 | Analytical Chemistry |
In stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocenters and are not mirror images of each other.
When two diastereoisomers differ from each other at only one stereocenter, they are epimers. Each stereocenter gives rise to two different configurations and thus typically increases the number of stereoisomers by a factor of two.
Diastereomers differ from enantiomers in that the latter are pairs of stereoisomers that differ in all stereocenters and are therefore mirror images of one another.
Enantiomers of a compound with more than one stereocenter are also diastereomers of the other stereoisomers of that compound that are not their mirror image (that is, excluding the opposing enantiomer).
Diastereomers have different physical properties (unlike most aspects of enantiomers) and often different chemical reactivity.
Diastereomers differ not only in physical properties but also in chemical reactivity — how a compound reacts with others. Glucose and galactose, for instance, are diastereomers. Even though they share the same molar weight, glucose is more stable than galactose. This difference in stability causes galactose to be absorbed slightly faster than glucose in human body.
Diastereoselectivity is the preference for the formation of one or more than one diastereomer over the other in an organic reaction. In general, stereoselectivity is attributed to torsional and steric interactions in the stereocenter resulting from electrophiles approaching the stereocenter in reaction. | 4 | Stereochemistry |
Ashing is a test to deduce the amount of ash forming material present in a petroleum product so as to decide its use in certain applications. Ash-forming materials are considered to be undesirable impurities or contaminants.
In the ash analysis of petroleum products, ash content represents the incombustible component remaining after a sample of the furnace oil is completely burned. The ash content of petroleum products is generally low. It is defined as the inorganic residue that remains after combustion of the oil in air at specific high temperature. Ash typically ranges from 0.1 to 0.2% in oil. Some of the ash forming constituents occur naturally in crude oil; others are present as a result of refining or contamination during storage or distribution. Knowledge of the amount of ash-forming material present in a product can provide information as to whether or not the product is suitable application.
In the ash analysis of coal and other solid fuels, the amount of sulfur retained in the ash during the ashing process is not constant, but rather is dependent upon the conditions of ashing as well as the other inorganic constituents in the ash that may form sulfates during the ashing procedure. As such, different ashing procedures may yield different ash contents. | 3 | Analytical Chemistry |
Lipidology is the scientific study of lipids. Lipids are a group of biological macromolecules that have a multitude of functions in the body. Clinical studies on lipid metabolism in the body have led to developments in therapeutic lipidology for disorders such as cardiovascular disease. | 1 | Biochemistry |
Response regulator proteins typically consist of a receiver domain and one or more effector domains, although in some cases they possess only a receiver domain and exert their effects through protein-protein interactions. In two-component signaling, a histidine kinase responds to environmental changes by autophosphorylation on a histidine residue, following which the response regulator receiver domain catalyzes transfer of the phosphate group to its own recipient aspartate residue. This induces a conformational change that alters the function of the effector domains, usually resulting in increased transcription of target genes. The mechanisms by which this occurs are diverse and include allosteric activation of the effector domain or oligomerization of phosphorylated response regulators. In a common variation on this theme, called a phosphorelay, a hybrid histidine kinase possesses its own receiver domain, and a histidine phosphotransfer protein performs the final transfer to a response regulator.
In many cases, histidine kinases are bifunctional and also serve as phosphatases, catalyzing the removal of phosphate from response regulator aspartate residues, such that the signal transduced by the response regulator reflects the balance between kinase and phosphatase activity. Many response regulators are also capable of autodephosphorylation, which occurs on a wide range of time scales. In addition, phosphoaspartate is relatively chemically unstable and may be hydrolyzed non-enzymatically.
Histidine kinases are highly specific for their cognate response regulators; there is very little cross-talk between different two-component signaling systems in the same cell. | 1 | Biochemistry |
Schwabs research interests seem to have switched to kinetics under the guidance of Max Bodenstein while at Nernsts Institute of Physical Chemistry in Berlin. Some of the problems on which Schwab worked on his own in this period included the thermal decomposition of methane, chemical reactions taking place during a cold cathode discharge, and the speed of dissolution of gases.
In Würzburg, he continued along a similar line of work studying gas dissolution, the thermal decomposition of ammonia, and the kinetics of photochlorination reactions. | 7 | Physical Chemistry |
PECO has also shown promise as a means of air purification. For people with severe allergies, air purifiers are important to protect them from allergens within their own homes. However, some allergens are too small to be removed by normal purification methods. Air purifiers using PECO filters are able to remove particles as small as 0.1 nm.
These filters work as photons excite a photocatalyst, creating hydroxyl free radicals, which are extremely reactive and oxidize organic material and microorganisms that cause allergy symptoms, forming harmless products like carbon dioxide and water. Researchers testing this technology with patients suffering from allergies drew promising conclusions from their studies, observing significant reductions in total symptom scores (TSS) for both nasal (TNSS) and ocular (TOSS) allergies after just 4 weeks of using the PECO filter. This research demonstrates strong potential for impactful health improvements who suffer from severe allergies and asthma. | 5 | Photochemistry |
* Contrast in Ramsey fringes
** The coherence time is the time at which the contrast in Ramsey fringes drops to 1/e.
* Damping of Rabi oscillations
** The coherence time is the time at which the amplitude of the Rabi oscillation has dropped to 1/e. | 7 | Physical Chemistry |
Researchers at Sandia Labs, Ames National Laboratory and Iowa State University reported a 3D-printed superalloy composed of 42% aluminum, 25% titanium, 13% niobium, 8% zirconium, 8% molybdenum and 4% tantalum. Most alloys are made chiefly of one primary element, combined with low amounts of other elements. In contrast MPES have substantial amounts of three or more elements.
Such alloys promise improvements on high-temperature applications, strength-to-weight, fracture toughness, corrosion and radiation resistance, wear resistance, and others. They reported hardness and density of 1.8–2.6 GPa-cm/g, which surpasses all known alloys, including intermetallic compounds, titanium aluminides, refractory MPEAs, and conventional Ni-based superalloys. This represents a 300% improvement over Inconel 718 based on measured peak hardness of 4.5 GPa and density of 8.2 g/cm, (0.55 GPa-cm/g).
The material is stable at 800 °C, hotter than the 570+ °C found in typical coal-based power plants.
The researchers acknowledged that the 3D printing process produces microscopic cracks when forming large parts, and that the feedstock includes metals that limit applicability in cost-sensitive applications. | 8 | Metallurgy |
In vivo ultrasound mediated drug delivery was first reported in 1991 and many other preclinical studies involving sonoporation have followed. This method is being used to deliver therapeutic drugs or genes to treat a variety of diseases including: Stroke, Cancer, Parkinsons, Alzheimers... The preclinical utility of sonoporation is well illustrated through past tumor radiation treatments which have reported a more than 10-fold cellular destruction when ionizing radiation is coupled with ultrasound-mediated microbubble vascular disruption. This increase in delivery efficiency could allow for the appropriate reduction in therapeutic dosing. | 1 | Biochemistry |
The modern X-ray fluorescence (XRF) is also a non-destructive technique that is suitable for normal assaying requirements. It typically has an accuracy of 2 to 5 parts per thousand and is well-suited to relatively flat and large surfaces. It is a quick technique taking about three minutes, and the results can be automatically printed out by computer.
One process for X-ray fluorescence assay involves melting the material in a furnace and stirring to make a homogeneous mix. Following this, a sample is taken from the centre of the molten sample. Samples are typically taken using a vacuum pin tube. The sample is then tested by X-ray fluorescence spectroscopy. Metallurgical assay is typically completed in this way to ensure that an accurate assay is performed. | 8 | Metallurgy |
In analytical and organic chemistry, elution is the process of extracting one material from another by washing with a solvent: washing of loaded ion-exchange resins to remove captured ions, or eluting proteins or other biopolymers from a gel electrophoresis or chromatography column.
In a liquid chromatography experiment, for example, an analyte is generally adsorbed by ("bound to") an adsorbent in a liquid chromatography column. The adsorbent, a solid phase, called a "stationary phase", is a powder which is coated onto a solid support. Based on an adsorbent's composition, it can have varying affinities to "hold onto" other molecules—forming a thin film on the surface of its particles. Elution then is the process of removing analytes from the adsorbent by running a solvent, called an "eluent", past the adsorbent-analyte complex. As the solvent molecules "elute", or travel down through the chromatography column, they can either pass by the adsorbent-analyte complex or displace the analyte by binding to the adsorbent in its place. After the solvent molecules displace the analyte, the analyte can be carried out of the column for analysis. This is why as the mobile phase, called an "eluate", passes out of the column, it typically flows into a detector or is collected by a fraction collector for compositional analysis.
Predicting and controlling the order of elution is a key aspect of column chromatographic and column electrophoretic methods. | 3 | Analytical Chemistry |
In organic chemistry, alkynylation is an addition reaction in which a terminal alkyne () is added to a carbonyl group () to form an α-alkynyl alcohol ().
When the acetylide is formed from acetylene (), the reaction gives an α-ethynyl alcohol. This process is often referred to as ethynylation. Such processes often involve metal acetylide intermediates. | 0 | Organic Chemistry |
Basically there are five types of discharge that are used for the rotary vacuum drum filter such as belt, scraper, roll, string and pre coat discharge. | 3 | Analytical Chemistry |
The shape of the zero-phonon line is Lorentzian with a width determined by the excited state lifetime T according to the Heisenberg uncertainty principle. Without the influence of the lattice, the natural line width (full width at half maximum) of the chromophore is γ = 1/T . The lattice reduces the lifetime of the excited state by introducing radiationless decay mechanisms. At absolute zero the lifetime of the excited state influenced by the lattice is T. Above absolute zero, thermal motions will introduce random perturbations to the chromophores local environment. These perturbations shift the energy of the electronic transition, introducing a temperature dependent broadening of the line width. The measured width of a single chromophores zero phonon line, the homogeneous line width, is then γ(T) ≥ 1/T' .
The line shape of the phonon side band is that of a Poisson distribution as it expresses a discrete number of events, electronic transitions with phonons, during a period of time. At higher temperatures, or when the chromophore interacts strongly with the matrix, the probability of multiphonon is high and the phonon side band approximates a Gaussian distribution.
The distribution of intensity between the zero-phonon line and the phonon sideband is characterized by the Debye-Waller factor α. | 7 | Physical Chemistry |
Glycorandomization, is a drug discovery and drug development technology platform to enable the rapid diversification of bioactive small molecules, drug leads and/or approved drugs through the attachment of sugars. Initially developed as a facile method to manipulate carbohydrate substitutions of naturally occurring glycosides to afford the corresponding differentially glycosylated natural product libraries, glycorandomization applications have expanded to include both small molecules (drug leads and approved drugs) and even macromolecules (proteins). Also referred to as glycodiversification, glycorandomization has led to the discovery of new glycoside analogs which display improvements in potency, selectivity and/or ADMET as compared to the parent molecule. | 0 | Organic Chemistry |
The same process of photoemission can be used to produce electricity from any spectrum, although the number of semiconductor materials that will have just the right bandgap for an arbitrary hot object is limited. Instead, semiconductors that have tuneable bandgaps are needed. It is also difficult to produce solar-like thermal output; an oxyacetylene torch is about 3400 K (~3126 °C), and more common commercial heat sources like coal and natural gas burn at much lower temperatures around 900 °C to about 1300 °C. This further limits the suitable materials. In the case of TPV most research has focused on gallium antimonide (GaSb), although germanium (Ge) is also suitable.
Another problem with lower-temperature sources is that their energy is more spread out, according to Wien's displacement law. While one can make a practical solar cell with a single bandgap tuned to the peak of the spectrum and just ignore the losses in the IR region, doing the same with a lower temperature source will lose much more of the potential energy and result in very low overall efficiency. This means TPV systems almost always use multi-junction cells in order to reach reasonable double-digit efficiencies. Current research in the area aims at increasing system efficiencies while keeping the system cost low, but even then their roles tend to be niches similar to those of multi-junction solar cells. | 7 | Physical Chemistry |
The suffix -one is used in organic chemistry to form names of organic compounds containing the -C(=O)- group: see ketone. Sometimes a number between hyphens is inserted before it to state which atom the =O atom is attached to. This suffix was extracted from the word acetone. The final "-e" disappears if it is followed by another suffix that starts with a vowel. | 0 | Organic Chemistry |
The Danheiser benzannulation is a regiocontrolled phenol annulation. This annulation provides an efficient route to form an aromatic ring in one step. It is a thermal combination of a substituted cyclobutenones with heterosubstituted acetylenes to produce highly substituted aromatic compounds, specifically phenols or resorcinols (Scheme 1). This benzannulation reaction creates previously unaccessed aromatic substitution patterns. A variety of substituted aromatic rings can be prepared using this method including: phenols, naphthalenes, benzofurans, benzothiophenes, indoles, and carbazoles.
The modified Danheiser benzannulation allows the synthesis of polycyclic aromatic and heteroaromatic systems. This also includes napthalenes, benzofurans and indoles. This second generation aromatic annulation is achieved by irradiation of a solution of acetylene and a vinyl or aryl α-diazo ketone in dichloroethane. This reaction utilizes the photochemical Wolff rearrangement of a diazoketone to generate an aryl or vinylketene. These ketene intermediates cannot be isolated due to their high reactivity to form diketenes. These rearrangements are performed in the presence of unsaturated compounds which undergo [2+2] cycloadditions with the in situ generated ketenes. When ketenes are formed in the presence of alkynes they proceed through pericyclic reactions to generate a substituted aromatic ring (Scheme 2). Avoiding the use of the high energy cyclobutenone starting materials provides access to a wider variety of substituted aromatic compounds.
This reaction is quite complementary to the Wulff–Dötz reaction. This is a [2+1] cycloaddition of a carbene to an alkyne or alkene (more specifically in the Dӧtz reaction a carbene coordinated to a metal carbonyl group) to produce substituted aromatic phenols. | 0 | Organic Chemistry |
When a cluster of microparticles are trapped within a monochromatic laser beam, the organization of the microparticles within the optical trapping is heavily dependent on the redistributing of the optical trapping forces amongst the microparticles. This redistribution of light forces amongst the cluster of microparticles provides a new force equilibrium on the cluster as a whole. As such we can say that the cluster of microparticles are somewhat bound together by light. One of the first experimental evidence of optical binding was reported by Michael M. Burns, Jean-Marc Fournier, and Jene A. Golovchenko, though it was originally predicted by T. Thirunamachandran. One of the many recent studies on optical binding has shown that for a system of chiral nanoparticles, the magnitude of the binding forces are dependent on the polarisation of the laser beam and the handedness of interacting particles themselves, with potential applications in areas such as enantiomeric separation and optical nanomanipulation. | 1 | Biochemistry |
Cyclic AMP-dependent protein kinases (protein kinase A) are activated by the signal chain coming from the G protein (that was activated by the receptor) via adenylate cyclase and cyclic AMP (cAMP). In a feedback mechanism, these activated kinases phosphorylate the receptor. The longer the receptor remains active the more kinases are activated and the more receptors are phosphorylated. In β-adrenoceptors, this phosphorylation results in the switching of the coupling from the G class of G-protein to the G class. cAMP-dependent PKA mediated phosphorylation can cause heterologous desensitisation in receptors other than those activated. | 1 | Biochemistry |
The Qubit fluorometer is a laboratory instrument developed and distributed by Invitrogen, which is now a part of Thermo Fisher. It is used for the quantification of DNA, RNA, and protein. | 7 | Physical Chemistry |
Merrilactone A was found to exhibit a significant neurotrophic activity, such as greatly promoting neurite outgrowth in the primary cultures of fetal rat cortical neurons at concentrations from 10 to 0.1 μmol/L. It was also found that this compound had a property of neuroprotection at same concentration. | 0 | Organic Chemistry |
Online non-intrusive ultrasonic thickness sensors are a popular choice for corrosion monitoring in various industries, including oil and gas, chemical processing, and power generation. These sensors can provide accurate and reliable thickness measurements of metal structures without requiring physical access or disruption to the equipment. The sensors can be installed permanently and remotely connected to a monitoring system, allowing for continuous data collection and analysis. With the ability to detect corrosion early on, online ultrasonic thickness sensors can help prevent equipment failure, reduce downtime, and improve overall safety and efficiency. | 8 | Metallurgy |
* F. Geiss (1987): Fundamentals of thin layer chromatography planar chromatography, Heidelberg, Hüthig,
* Justus G. Kirchner (1978): Thin-layer chromatography, 2nd edition, Wiley
* Joseph Sherma, Bernard Fried (1991): Handbook of Thin-Layer Chromatography (= Chromatographic Science. Bd. 55). Marcel Dekker, New York NY, .
* Elke Hahn-Deinstorp: Applied Thin-Layer Chromatography. Best Practice and Avoidance of Mistakes. Wiley-VCH, Weinheim u. a. 2000, | 3 | Analytical Chemistry |
* Books (chronological order):
** Tanner, Brian: X-ray diffraction topography. Pergamon Press (1976)..
** Authier, André and Lagomarsino, Stefano and Tanner, Brian K. (editors): X-Ray and Neutron Dynamical Diffraction – Theory and Applications. Plenum Press / Kluwer Academic Publishers (1996). .
** Bowen, Keith and Tanner, Brian: High Resolution X-Ray Diffractometry and Topography. Taylor and Francis (1998). .
** Authier, André: Dynamical theory of X-ray diffraction. IUCr monographs on crystallography, no. 11. Oxford University Press (1st edition 2001/ 2nd edition 2003). .
* Reviews
** Lang, A. R.: Techniques and interpretation in X-ray topography. In: Diffraction and Imaging Techniques in Materials Science (edited by Amelinckx S., Gevers R. and Van Landuyt J.) 2nd ed. rev. (1978), pp 623–714. Amsterdam: North Holland.
** Klapper, Helmut: X-ray topography of organic crystals. In: Crystals: Growth, Properties and Applications, vol. 13 (1991), pp 109–162. Berlin-Heidelberg: Springer.
** Lang, A. R.: Topography. In: International Tables for Crystallography, Vol. C (1992), Section 2.7, p. 113. Kluwer, Dordrecht.
** Tuomi, T: Synchrotron X-ray topography of electronic materials. Journal of Synchrotron Radiation (2002) 9, 174-178.
** Baruchel, J. and Härtwig, J. and Pernot-Rejmánková, P.: Present state and perspectives of synchrotron radiation diffraction imaging. Journal of Synchrotron Radiation (2002) 9, 107-114.
* Selected original articles (chronological order):
** X-ray topography
*** T. Tuomi, K. Naukkarinen, E. Laurila, P. Rabe: Rapid high resolution X-ray topography with synchrotron radiation. Acta Polytechnica Scandinavica, Ph. Incl. Nucleonics Series No. 100, (1973), 1-8.
** Special applications:
** Instrumentation and beamlines for topography: | 3 | Analytical Chemistry |
Landes was an undergraduate student in chemistry at George Mason University. She moved to Georgia Tech for her doctoral research, where she majored in physical chemistry under the supervision of Mostafa El-Sayed. After earning her doctorate, Landes joined the University of Oregon as a postdoctoral researcher with Geraldine L. Richmond, where she spent one year before joining the University of Texas at Austin with Paul Barbara. | 7 | Physical Chemistry |
For double bonded molecules, Cahn–Ingold–Prelog priority rules (CIP rules) are followed to determine the priority of substituents of the double bond. If both of the high priority groups are on the same side of the double bond (cis configuration), then the stereoisomer is assigned the configuration Z (zusammen, German word meaning "together"). If the high priority groups are on opposite sides of the double bond ( trans configuration ), then the stereoisomer is assigned the configuration E (entgegen, German word meaning "opposed") | 4 | Stereochemistry |
In chemistry, a C–H···O interaction is occasionally described as a special type of weak hydrogen bond. These interactions frequently occur in the structures of important biomolecules like amino acids, proteins, sugars, DNA and RNA. | 0 | Organic Chemistry |
The zooplanktonic Calanus spp. are not only important for moving carbon out of the photic zone and into the deep ocean, but these lipid-rich organisms play a critical role in the success of many marine species that depend on them as food. They comprise the majority of diets for fishes, seabirds and even large mammals such as whales. Copepods can account for about 70–90% of total zooplankton biomass, depending on region. Additionally, their eggs are a main source of food for commercially important fish stocks. The copepod eggs are buoyant and will rise to the sea surface, but are susceptible to predation by fish and other organisms. Copepods also provide the benthic community with food via sinking fecal pellets, meaning that as fish and smaller invertebrates excrete waste, that waste falls to the sea floor and organisms on the sea floor compete for the pellets as food. The role of copepods in the food web is crucially intertwined amongst other organisms.
Copepod abundance, specifically the C. finmarchicus, has a direct impact on the endangered right whales of the North Atlantic. North Atlantic right whales rely on copepods as their primary prey in order to meet their nutritional needs. To meet the right whales energetic requirements they need about 500 kg of C. finmarchicus a day. Each copepod measures about 2–4 millimetres long which is about the size of a grain of rice and they weigh, on average, between 1.0274 and 1.0452 g cm. A loss in C. finmarchicus has the potential to affect the right whales migration, reproduction, and/or ability to successfully nurse their young (only for lactating females). | 9 | Geochemistry |
In chemistry, the Terrace Ledge Kink model (TLK), which is also referred to as the Terrace Step Kink model (TSK), describes the thermodynamics of crystal surface formation and transformation, as well as the energetics of surface defect formation. It is based upon the idea that the energy of an atom’s position on a crystal surface is determined by its bonding to neighboring atoms and that transitions simply involve the counting of broken and formed bonds. The TLK model can be applied to surface science topics such as crystal growth, surface diffusion, roughening, and vaporization. | 7 | Physical Chemistry |
Two of the drugs three components were originally developed at the Public Health Agency of Canadas National Microbiology Laboratory (NML), and a third at the U.S. Army Medical Research Institute of Infectious Diseases; the cocktail was optimized by Gary Kobinger, then branch chief of the NML, and is undergoing further development by Leaf Biopharmaceutical (LeafBio, Inc.), a San Diego-based arm of Mapp Biopharmaceutical. LeafBio created ZMapp in collaboration with its parent and Defyrus Inc., each of which had licensed its own cocktail of antibodies, called MB-003 and ZMab. | 1 | Biochemistry |
In inorganic chemistry, metal–metal bonds describe attractive interactions between metal centers. The simplest examples are found in bimetallic complexes. Metal–metal bonds can be "supported", i.e. be accompanied by one or more bridging ligands, or "unsupported". They can also vary according to bond order. The topic of metal–metal bonding is usually discussed within the framework of coordination chemistry, but the topic is related to extended metallic bonding, which describes interactions between metals in extended solids such as bulk metals and metal subhalides. | 7 | Physical Chemistry |
Nanorods, similar in size to quantum dots, have tunable optical and electronic properties. Based on their size and material composition, it is possible to tune the maximum absorption peak for nanorods during their synthesis. This control has led to the creation of photosensitizing nanorods. | 5 | Photochemistry |
The BBE-like enzyme's optimum pH is 8.9, this means it works in an alkaline medium, but the isoelectric point of the homogeneous enzyme is located at pH 4.9, which is a rather an acid medium. This value was obtained with isoelectric focusing and chromatofocusing techniques.
The enzyme broad temperature range is between 40-50 degrees Celsius. The molecular weight of the protein was determined by two processes that show two different results: by SDS gel electrophoresis comes to be 54 kD, and by gel filtration on AcA 54 the enzyme corresponds to a molecular weight of 49 kD, adopting globular shape. A purification study shows that the true molecular weight is in the range of 52 ±4 kD.
On the other hand, total activity decreases drastically during the stationary phase. | 1 | Biochemistry |
* Lactase (breaks down lactose into glucose and galactose)
* Maltase (breaks down maltose into 2 glucoses)
* Sucrase (breaks down sucrose into glucose and fructose)
* Trehalase (breaks down trehalose into 2 glucoses)
<br />For a thorough scientific overview of small-intestinal disaccharidases, one can consult chapter 75 of OMMBID. For more online resources and references, see inborn error of metabolism. | 1 | Biochemistry |
A major pathway of induced health effects arises from spills or leaks of solvents, especially chlorinated solvents, that reach the underlying soil. Since solvents readily migrate substantial distances, the creation of widespread soil contamination is not uncommon; this is particularly a health risk if aquifers are affected. Vapor intrusion can occur from sites with extensive subsurface solvent contamination. | 2 | Environmental Chemistry |
Diamonds cubic structure is in the Fdm space group (space group 227), which follows the face-centered cubic Bravais lattice. The lattice describes the repeat pattern; for diamond cubic crystals this lattice is "decorated" with a motif of two tetrahedrally bonded atoms in each primitive cell, separated by of the width of the unit cell in each dimension. The diamond lattice can be viewed as a pair of intersecting face-centered cubic lattices, with each separated by of the width of the unit cell in each dimension. Many compound semiconductors such as gallium arsenide, β-silicon carbide, and indium antimonide adopt the analogous zincblende structure, where each atom has nearest neighbors of an unlike element. Zincblendes space group is F3m, but many of its structural properties are quite similar to the diamond structure.
The atomic packing factor of the diamond cubic structure (the proportion of space that would be filled by spheres that are centered on the vertices of the structure and are as large as possible without overlapping) is significantly smaller (indicating a less dense structure) than the packing factors for the face-centered and body-centered cubic lattices. Zincblende structures have higher packing factors than 0.34 depending on the relative sizes of their two component atoms.
The first-, second-, third-, fourth-, and fifth-nearest-neighbor distances in units of the cubic lattice constant are respectively. | 3 | Analytical Chemistry |
Soldiers can be exposed to a wide variety of chemical hazards. These threats are mostly invisible but detectable by hyperspectral imaging technology. The Telops Hyper-Cam, introduced in 2005, has demonstrated this at distances up to 5 km. | 7 | Physical Chemistry |
The Henrys law constants mentioned so far do not consider any chemical equilibria in the aqueous phase. This type is called the intrinsic, or physical, Henrys law constant. For example, the intrinsic Henry's law solubility constant of formaldehyde can be defined as
In aqueous solution, formaldehyde is almost completely hydrated:
The total concentration of dissolved formaldehyde is
Taking this equilibrium into account, an effective Henry's law constant can be defined as
For acids and bases, the effective Henrys law constant is not a useful quantity because it depends on the pH of the solution. In order to obtain a pH-independent constant, the product of the intrinsic Henrys law constant and the acidity constant is often used for strong acids like hydrochloric acid (HCl):
Although is usually also called a Henrys law constant, it is a different quantity and it has different units than . | 7 | Physical Chemistry |
A chemical composition specifies the identity, arrangement, and ratio of the chemical elements making up a compound by way of chemical and atomic bonds.
Chemical formulas can be used to describe the relative amounts of elements present in a compound. For example, the chemical formula for water is HO: this means that each molecule of water is constituted by 2 atoms of hydrogen (H) and 1 atom of oxygen (O). The chemical composition of water may be interpreted as a 2:1 ratio of hydrogen atoms to oxygen atoms. Different types of chemical formulas are used to convey composition information, such as an empirical or molecular formula.
Nomenclature can be used to express not only the elements present in a compound but their arrangement within the molecules of the compound. In this way, compounds will have unique names which can describe their elemental composition. | 3 | Analytical Chemistry |
Interchange pathways apply to substitution reactions where intermediates are not observed, which is more common than pure dissociative pathways. If the reaction rate is insensitive to the nature of the attacking nucleophile, the process is called dissociative interchange, abbreviated I. An illustrative process comes from the "anation" (reaction with an anion) of cobalt(III) complexes: | 0 | Organic Chemistry |
The thermodynamics of the host and guest interaction can be assessed by NMR spectroscopy, UV/visible spectroscopy, and isothermal titration calorimetry. Quantitative analysis of binding constant values provides useful thermodynamic information.
An association constant, can be defined by the expression
where {HG} is the thermodynamic activity of the complex at equilibrium. {H} represents the activity of the host and {G} the activity of the guest. The quantities , and are the corresponding concentrations and is a quotient of activity coefficients.
In practice the equilibrium constant is usually defined in terms of concentrations.
When this definition is used, it is implied that the quotient of activity coefficients has a numerical value of one. It then appears that the equilibrium constant, has the dimension 1/concentration, but that cannot be true since the standard Gibbs free energy change, is proportional to the logarithm of K.
This apparent paradox is resolved when the dimension of is defined to be the reciprocal of the dimension of the quotient of concentrations. The implication is that is regarded as having a constant value under all relevant experimental conditions. Nevertheless it is common practice to attach a dimension, such as millimole per litre or micromole per litre, to a value of K that has been determined experimentally.
A Large value indicates that host and guest molecules interact strongly to form the host–guest complex. | 6 | Supramolecular Chemistry |
Coherent anti-Stokes Raman spectroscopy (CARS) is a non-
linear process in which the energy difference of a pair of incoming photons
matches the energy of the vibrational mode of a molecular bond of interest.
This phonon population is coherently probed by a third photon and anti-
Stokes radiation is emitted. | 3 | Analytical Chemistry |
In 1957, Ronald Breslow proposed that a relatively stable nucleophilic carbene, a thiazol-2-ylidene derivative of vitamin B (thiamine), was the catalyst involved in the benzoin condensation that yields furoin from furfural.
In this cycle, the vitamin's thiazolium ring exchanges a hydrogen atom (attached to carbon 2 of the ring) for a furfural residue. In deuterated water, the C2-proton was found to rapidly exchange for a deuteron in a statistical equilibrium.
This exchange was proposed to proceed via intermediacy of a thiazol-2-ylidene. In 2012 the isolation of the so-called Breslow intermediate was reported.
In 1960, Hans-Werner Wanzlick and coworkers conjectured that carbenes derived from dihydroimidazol-2-ylidene were produced by vacuum pyrolysis of the corresponding 2-trichloromethyl dihydroimidazole compounds with the loss of chloroform.
They conjectured that the carbene existed in equilibrium with its dimer, a tetraaminoethylene derivative, the so-called Wanzlick equilibrium. This conjecture was challenged by Lemal and coworkers in 1964, who presented evidence that the dimer did not dissociate; and by Winberg in 1965. However, subsequent experiments by Denk, Herrmann and others have confirmed this equilibrium, albeit in specific circumstances. | 0 | Organic Chemistry |
Subsets and Splits