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Mars Guy Fontana graduated with a Bachelor of Science followed by a Master of Science and then awarded a Doctor of Philosophy in the field of metallurgical engineering from the University of Michigan. He was known as a researcher/engineer who added to the field of knowledge in the fairly specialized area of corrosion and its various applications in engineering – corrosion engineering. As well as writing numerous papers he wrote the textbook Corrosion Engineering which was first published in 1967 ; there have been a number of updated editions since then. This book has been used as the primary textbook and recommended reading for at least one highly ranked University masters degree course. In his lifetime he wrote many papers in various scientific and engineering journals/periodicals. He also authored Corrosion: A Compilation.
In the late 1940s, he was given the chair in the Corrosion Center at Ohio State University. At the time it was the largest university corrosion research department in the United States. He combined the disciplines of engineering design, Material Science and Corrosion so they could be viewed together.
His contribution at the university was of such significance that he has a building named after him - the Fontana Laboratories. He also has a professorship named after him. | 1 | Applied and Interdisciplinary Chemistry |
Diel vertically migrating krill, salps, smaller zooplankton and fish can actively transport carbon to depth by consuming POC in the surface layer at night, and metabolising it at their daytime, mesopelagic residence depths. Depending on species life history, active transport may occur on a seasonal basis as well.
Without vertical migration the biological pump wouldn't be nearly as efficient. Organisms migrate up to feed at night so when they migrate back to depth during the day they defecate large sinking fecal pellets. Whilst some larger fecal pellets can sink quite fast, the speed that organisms move back to depth is still faster. At night organisms are in the top 100 metres of the water column, but during the day they move down to between 800 and 1000 metres. If organisms were to defecate at the surface it would take the fecal pellets days to reach the depth that they reach in a matter of hours. Therefore, by releasing fecal pellets at depth they have almost 1000 metres less to travel to get to the deep ocean. This is something known as active transport. The organisms are playing a more active role in moving organic matter down to depths. Because a large majority of the deep sea, especially marine microbes, depends on nutrients falling down, the quicker they can reach the ocean floor the better.
Zooplankton and salps play a large role in the active transport of fecal pellets. 15–50% of zooplankton biomass is estimated to migrate, accounting for the transport of 5–45% of particulate organic nitrogen to depth. Salps are large gelatinous plankton that can vertically migrate 800 metres and eat large amounts of food at the surface. They have a very long gut retention time, so fecal pellets usually are released at maximum depth. Salps are also known for having some of the largest fecal pellets. Because of this they have a very fast sinking rate, small detritus particles are known to aggregate on them. This makes them sink that much faster. So while currently there is still much research being done on why organisms vertically migrate, it is clear that vertical migration plays a large role in the active transport of dissolved organic matter to depth. | 0 | Theoretical and Fundamental Chemistry |
The dimer, digold hexabromide, has structural properties similar to those of the other gold trihalide dimeric compounds, such as gold(III) chloride. The gold centers exhibit square planar coordination with bond angles of roughly 90 degrees.
Calculations indicate that in the hypothetical monomeric forms of the gold trihalides, the Jahn-Teller effect causes differences to arise in the structures of the gold halide complexes. For instance, gold(III) bromide contains one long and two short gold-bromine bonds whereas gold(III) chloride and gold(III) fluoride consist of two long and one short gold-halogen bonds. Moreover, gold tribromide does not exhibit the same coordination around the central gold atom as gold trichloride or gold trifluoride. In the latter complexes, the coordination exhibits a T-conformation, but in gold tribromide the coordination exists as more of a dynamic balance between a Y-conformation and a T-conformation. This coordination difference can be attributed to the Jahn-Teller effect but more so to the decrease in π-back bonding of the gold atoms with the bromine ligands compared to the π-back bonding found with fluorine and chlorine ligands. It is also this decrease in π-back bonding which explains why gold tribromide is less stable than its trifluoride and trichloride counterparts. | 0 | Theoretical and Fundamental Chemistry |
The Indian Institute of Chemical Engineers (IIChE) is the professional body for chemical engineers in India. The headquarter of IIChE is in the campus of Jadavpur University, Kolkata. The organization has 42 regional centers along with 172 student chapters spread throughout India. The institution's membership comprises academics, professionals from the chemical industry, researchers, and students.
IIChE also publishes scientific journal "Indian Chemical Engineer", which is published in two sections – A and B. Section A provides an international platform for presenting original research work, interpretative reviews and discussions on new developments in the expansive areas of Chemical Engineering and its allied fields. The journal invites papers describing novel theories and practical applications, including reports of experimental work – carefully executed and soundly interpreted. Section B features technical articles or overview of technology with a view to guiding practicing chemical engineers, news snippets on research developments, industry updates, issues of environment and health hazards, etc. This section also offers in-house news for those associated with the institute. | 1 | Applied and Interdisciplinary Chemistry |
* Several inconsistencies exist between gene, enzyme, reaction databases, and published literature sources regarding the metabolic information of an organism. A reconstruction is a systematic verification and compilation of data from various sources that takes into account all of the discrepancies.
* The combination of relevant metabolic and genomic information of an organism.
* Metabolic comparisons can be performed between various organisms of the same species as well as between different organisms.
* Analysis of synthetic lethality
* Predict adaptive evolution outcomes
* Use in metabolic engineering for high value outputs
Reconstructions and their corresponding models allow the formulation of hypotheses about the presence of certain enzymatic activities and the production of metabolites that can be experimentally tested, complementing the primarily discovery-based approach of traditional microbial biochemistry with hypothesis-driven research. The results these experiments can uncover novel pathways and metabolic activities and decipher between discrepancies in previous experimental data. Information about the chemical reactions of metabolism and the genetic background of various metabolic properties (sequence to structure to function) can be utilized by genetic engineers to modify organisms to produce high value outputs whether those products be medically relevant like pharmaceuticals; high value chemical intermediates such as terpenoids and isoprenoids; or biotechnological outputs like biofuels, or polyhydroxybutyrates also known as bioplastics.
Metabolic network reconstructions and models are used to understand how an organism or parasite functions inside of the host cell. For example, if the parasite serves to compromise the immune system by lysing macrophages, then the goal of metabolic reconstruction/simulation would be to determine the metabolites that are essential to the organisms proliferation inside of macrophages. If the proliferation cycle is inhibited, then the parasite would not continue to evade the hosts immune system. A reconstruction model serves as a first step to deciphering the complicated mechanisms surrounding disease. These models can also look at the minimal genes necessary for a cell to maintain virulence. The next step would be to use the predictions and postulates generated from a reconstruction model and apply it to discover novel biological functions such as drug-engineering and drug delivery techniques. | 1 | Applied and Interdisciplinary Chemistry |
T-complex protein Ring Complex (TRiC), otherwise known as Chaperonin Containing TCP-1 (CCT), is a multiprotein complex and the chaperonin of eukaryotic cells. Like the bacterial GroEL, the TRiC complex aids in the folding of ~10% of the proteome, and actin and tubulin are some of its best known substrates. TRiC is an example of a biological machine that folds substrates within the central cavity of its barrel-like assembly using the energy from ATP hydrolysis. | 1 | Applied and Interdisciplinary Chemistry |
According to the International Standards Organization (ISO) technical specification 80004, a nanoparticle is an object with all three external dimensions in the nanoscale, whose longest and shortest axes do not differ significantly, with a significant difference typically being a factor of at least 3. | 0 | Theoretical and Fundamental Chemistry |
Heart rate is determined by the medulla oblongata and part of the pons, two organs located inferior to the hypothalamus on the brain stem. Heart rate is important for basal metabolic rate and resting metabolic rate because it drives the blood supply, stimulating the Krebs cycle. During exercise that achieves the anaerobic threshold, it is possible to deliver substrates that are desired for optimal energy utilization. The anaerobic threshold is defined as the energy utilization level of heart rate exertion that occurs without oxygen during a standardized test with a specific protocol for accuracy of measurement, such as the Bruce Treadmill protocol (see metabolic equivalent of task). With four to six weeks of targeted training the body systems can adapt to a higher perfusion of mitochondrial density for increased oxygen availability for the Krebs cycle, or tricarboxylic cycle, or the glycolytic cycle. This in turn leads to a lower resting heart rate, lower blood pressure, and increased resting or basal metabolic rate.
By measuring heart rate we can then derive estimations of what level of substrate utilization is actually causing biochemical metabolism in our bodies at rest or in activity. This in turn can help a person to maintain an appropriate level of consumption and utilization by studying a graphical representation of the anaerobic threshold. This can be confirmed by blood tests and gas analysis using either direct or indirect calorimetry to show the effect of substrate utilization. The measures of basal metabolic rate and resting metabolic rate are becoming essential tools for maintaining a healthy body weight. | 1 | Applied and Interdisciplinary Chemistry |
The pure rotation spectrum of water vapor extends into the microwave region.
Liquid water has a broad absorption spectrum in the microwave region, which has been explained in terms of changes in the hydrogen bond network giving rise to a broad, featureless, microwave spectrum. The absorption (equivalent to dielectric loss) is used in microwave ovens to heat food that contains water molecules. A frequency of 2.45 GHz, wavelength 122 mm, is commonly used.
Radiocommunication at GHz frequencies is very difficult in fresh waters and even more so in salt waters. | 0 | Theoretical and Fundamental Chemistry |
In 1976, concern over the toxicity and persistence (chemical stability) of PCBs in the environment led the United States Congress to ban their domestic production, effective January 1, 1978, pursuant to the Toxic Substances Control Act. To implement the law, EPA banned new manufacturing of PCBs, but issued regulations that allowed for their continued use in electrical equipment for economic reasons. EPA began issuing regulations for PCB usage and disposal in 1979. The agency has issued guidance publications for safe removal and disposal of PCBs from existing equipment.
EPA defined the "maximum contaminant level goal" for public water systems as zero, but because of the limitations of water treatment technologies, a level of 0.5 parts per billion is the actual regulated level (maximum contaminant level). | 1 | Applied and Interdisciplinary Chemistry |
Photoacoustic spectroscopy has become a powerful technique to study concentrations of gases at the part per billion or even part per trillion levels. Modern photoacoustic detectors still rely on the same principles as Bell's apparatus; however, to increase the sensitivity, several modifications have been made.
Instead of sunlight, intense lasers are used to illuminate the sample since the intensity of the generated sound is proportional to the light intensity; this technique is referred to as laser photoacoustic spectroscopy (LPAS). The ear has been replaced by sensitive microphones. The microphone signals are further amplified and detected using lock-in amplifiers. By enclosing the gaseous sample in a cylindrical chamber, the sound signal is amplified by tuning the modulation frequency to an acoustic resonance of the sample cell.
By using cantilever enhanced photoacoustic spectroscopy sensitivity can still be further improved enabling reliable monitoring of gases on ppb-level. | 0 | Theoretical and Fundamental Chemistry |
An extreme case of intercalation is the complete separation of the layers of the material. This process is called exfoliation. Typically aggressive conditions are required involving highly polar solvents and aggressive reagents. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, a triol is an organic compound containing three hydroxyl groups ( functional groups), such as glycerol. | 0 | Theoretical and Fundamental Chemistry |
Methylene blue has been used as a placebo; physicians would tell their patients to expect their urine to change color and view this as a sign that their condition had improved. This same side effect makes methylene blue difficult to use in traditional placebo-controlled clinical studies, including those testing for its efficacy as a treatment. | 0 | Theoretical and Fundamental Chemistry |
This library construction process is also similar to that of short-jump library except that transfection using the E. coli vector is required for amplification of large (40 kb) DNA fragments. In addition, the fosmids can be modified to facilitate the conversion into jumping library compatible with certain next generation sequencers. | 1 | Applied and Interdisciplinary Chemistry |
In the late 1930s, the first four actinides (actinium, thorium, protactinium, and uranium) were known. They were believed to form a fourth series of transition metals, characterized by the filling of 6d orbitals, in which thorium, protactinium, and uranium were respective homologs of hafnium, tantalum, and tungsten. This view was widely accepted as chemical investigations of these elements revealed various high oxidation states and characteristics that closely resembled the 5d transition metals. Nevertheless, research into quantum theory by Niels Bohr and subsequent publications proposed that these elements should constitute a 5f series analogous to the lanthanides, with calculations that the first 5f electron should appear in the range from atomic number 90 (thorium) to 99 (einsteinium). Inconsistencies between theoretical models and known chemical properties thus made it difficult to place these elements in the periodic table.
The first appearance of the actinide concept may have been in a 32-column periodic table constructed by Alfred Werner in 1905. Upon determining the arrangement of the lanthanides in the periodic table, he placed thorium as a heavier homolog of cerium, and left spaces for hypothetical radioelements in the seventh period, though he did not establish the correct order of the known actinides.
Following the discoveries of transuranic elements neptunium and plutonium in 1940 and preliminary investigations of their chemistry, their placement as a fourth transition metal series was challenged. These new elements exhibited various properties that suggested a close chemical similarity to uranium rather than their supposed transition metal homologs. Subsequent experiments targeting the then-unknown elements americium and curium raised further questions. Seaborg et al. failed to identify these elements under the premise that they were transition metals, but they were successfully separated and discovered in 1944, following the assumption that they would be chemically similar to the lanthanides. Further experiments corroborated the hypothesis of an actinide (then referred to as "thorides" or "uranides") series. A spectroscopic study at the Los Alamos National Laboratory by McMillan, Wahl, and Zachariasen indicated that 5f orbitals, rather than 6d orbitals, were being filled. However, these studies could not unambiguously determine the first element with 5f electrons and therefore the first element in the actinide series. | 0 | Theoretical and Fundamental Chemistry |
When energetic ions collide with atoms of a target material, an exchange of momentum takes place between them.
These ions, known as "incident ions", set off collision cascades in the target. Such cascades can take many paths; some recoil back toward the surface of the target. If a collision cascade reaches the surface of the target, and its remaining energy is greater than the target's surface binding energy, an atom will be ejected. This process is known as "sputtering". If the target is thin (on an atomic scale), the collision cascade can reach through to its back side; the atoms ejected in this fashion are said to escape the surface binding energy "in transmission".
The average number of atoms ejected from the target per incident ion is called the "sputter yield". The sputter yield depends on several things: the angle at which ions collide with the surface of the material, how much energy they strike it with, their masses, the masses of the target atoms, and the target's surface binding energy. If the target possesses a crystal structure, the orientation of its axes with respect to the surface is an important factor.
The ions that cause sputtering come from a variety of sources—they can come from plasma, specially constructed ion sources, particle accelerators, outer space (e.g. solar wind), or radioactive materials (e.g. alpha radiation).
A model for describing sputtering in the cascade regime for amorphous flat targets is Thompson's analytical model. An algorithm that simulates sputtering based on a quantum mechanical treatment including electrons stripping at high energy is implemented in the program TRIM.
Another mechanism of physical sputtering is called "heat spike sputtering". This can occur when the solid is dense enough, and the incoming ion heavy enough, that collisions occur very close to each other. In this case, the binary collision approximation is no longer valid, and the collisional process should be understood as a many-body process. The dense collisions induce a heat spike (also called thermal spike), which essentially melts a small portion of the crystal. If that portion is close enough to its surface, large numbers of atoms may be ejected, due to liquid flowing to the surface and/or microexplosions. Heat spike sputtering is most important for heavy ions (e.g. Xe or Au or cluster ions) with energies in the keV–MeV range bombarding dense but soft metals with a low melting point (Ag, Au, Pb, etc.). The heat spike sputtering often increases nonlinearly with energy, and can for small cluster ions lead to dramatic sputtering yields per cluster of the order of 10,000. For animations of such a process see "Re: Displacement Cascade 1" in the external links section.
Physical sputtering has a well-defined minimum energy threshold, equal to or larger than the ion energy at which the maximum energy transfer from the ion to a target atom equals the binding energy of a surface atom. That is to say, it can only happen when an ion is capable of transferring more energy into the target than is required for an atom to break free from its surface.
This threshold is typically somewhere in the range of ten to a hundred eV.
Preferential sputtering can occur at the start when a multicomponent solid target is bombarded and there is no solid state diffusion. If the energy transfer is more efficient to one of the target components, or it is less strongly bound to the solid, it will sputter more efficiently than the other. If in an AB alloy the component A is sputtered preferentially, the surface of the solid will, during prolonged bombardment, become enriched in the B component, thereby increasing the probability that B is sputtered such that the composition of the sputtered material will ultimately return to AB. | 0 | Theoretical and Fundamental Chemistry |
One of the largest volume uses for ICP-MS is in the medical and forensic field, specifically, toxicology. A physician may order a metal assay for a number of reasons, such as suspicion of heavy metal poisoning, metabolic concerns, and even hepatological issues. Depending on the specific parameters unique to each patient's diagnostic plan, samples collected for analysis can range from whole blood, urine, plasma, serum, to even packed red blood cells. Another primary use for this instrument lies in the environmental field. Such applications include water testing for municipalities or private individuals all the way to soil, water and other material analysis for industrial purposes.
In recent years, industrial and biological monitoring has presented another major need for metal analysis via ICP-MS. Individuals working in factories where exposure to metals is likely and unavoidable, such as a battery factory, are required by their employer to have their blood or urine analyzed for metal toxicity on a regular basis. This monitoring has become a mandatory practice implemented by the U.S. Occupational Safety and Health Administration, in an effort to protect workers from their work environment and ensure proper rotation of work duties (i.e. rotating employees from a high exposure position to a low exposure position).
ICP-MS is also used widely in the geochemistry field for radiometric dating, in which it is used to analyze relative abundance of different isotopes, in particular uranium and lead. ICP-MS is more suitable for this application than the previously used thermal ionization mass spectrometry, as species with high ionization energy such as osmium and tungsten can be easily ionized. For high precision ratio work, multiple collector instruments are normally used to reduce the effect noise on the calculated ratios.
In the field of flow cytometry, a new technique uses ICP-MS to replace the traditional fluorochromes. Briefly, instead of labelling antibodies (or other biological probes) with fluorochromes, each antibody is labelled with a distinct combinations of lanthanides. When the sample of interest is analysed by ICP-MS in a specialised flow cytometer, each antibody can be identified and quantitated by virtue of a distinct ICP "footprint". In theory, hundreds of different biological probes can thus be analysed in an individual cell, at a rate of ca. 1,000 cells per second. Because elements are easily distinguished in ICP-MS, the problem of compensation in multiplex flow cytometry is effectively eliminated.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a powerful technique for the elemental analysis of a wide variety of materials encountered in forensic casework. (LA-ICP-MS) has already successfully been applied to applications in forensics, metals, glasses, soils, car paints, bones and teeth, printing inks, trace elemental, fingerprint, and paper. Among these, forensic glass analysis stands out as an application for which this technique has great utility to provide highly.
Car hit and runs, burglaries, assaults, drive-by shootings and bombings such as these situations may cause glass fragments that could be used as evidence of association in glass transfer conditions. LA-ICP-MS is considered one of the best techniques for analysis of glass due to the short time for sample preparation and sample, small sample size of less than 250 nanograms. In addition there is no need for complex procedure and handling of dangerous materials that is used for digestion of the samples. This allows detecting major, minor and tracing elements with high level of precision and accuracy. There are set of properties that are used to measure glass sample such as physical and optical properties including color, thickness, density, refractive index (RI) and also, if necessary, elemental analysis can be conducted in order to enhance the value of an association. | 0 | Theoretical and Fundamental Chemistry |
TNP refers to the chemical compound 2,4,6-trinitrophenol, also known as Picric acid. It is a primary constituent of many unexploded landmines, and is a cousin to TNT, but less stable. It is recognized as an environmental contaminant and is toxic to many organisms. It is still commonly used in the manufacturing of fireworks, explosives, and rocket fuels, as well as in leather, pharmaceutical, and dye industries.
ATP is an essential mediator of life. It is used to overcome unfavorable energy barriers to initiate and fuel chemical reactions. It is also used to drive biological machinery and regulate a number of processes via protein-phosphorylation. However, the proteins that bind ATP for both regulation and enzymatic reactions are very diverse—many yet undiscovered—and for many proteins their relationship to ATP in terms of number of binding sites, binding constants, and dissociation constants remain unclear. | 0 | Theoretical and Fundamental Chemistry |
The Fluid Dynamics Prize is a prize that has been awarded annually by the American Physical Society (APS) since 1979. The recipient is chosen for "outstanding achievement in fluid dynamics research". The prize is currently valued at . In 2004, the Otto Laporte Award—another APS award on fluid dynamics—was merged into the Fluid Dynamics Prize. | 1 | Applied and Interdisciplinary Chemistry |
Biogenic silica (bSi), also referred to as opal, biogenic opal, or amorphous opaline silica, forms one of the most widespread biogenic minerals. For example, microscopic particles of silica called phytoliths can be found in grasses and other plants.
Silica is an amorphous metalloid oxide formed by complex inorganic polymerization processes. This is opposed to the other major biogenic minerals, comprising carbonate and phosphate, which occur in nature as crystalline iono-covalent solids (e.g. salts) whose precipitation is dictated by solubility equilibria. Chemically, bSi is hydrated silica (SiO·nHO), which is essential to many plants and animals.
Diatoms in both fresh and salt water extract dissolved silica from the water to use as a component of their cell walls. Likewise, some holoplanktonic protozoa (Radiolaria), some sponges, and some plants (leaf phytoliths) use silicon as a structural material. Silicon is known to be required by chicks and rats for growth and skeletal development. Silicon is in human connective tissues, bones, teeth, skin, eyes, glands and organs. | 1 | Applied and Interdisciplinary Chemistry |
When one atom substitutes for one of the principal atomic components within the crystal structure, alteration in the electrical and thermal properties of the material may ensue. Impurities may also manifest as electron spin impurities in certain materials. Research on magnetic impurities demonstrates that substantial alteration of certain properties such as specific heat may be affected by small concentrations of an impurity, as for example impurities in semiconducting ferromagnetic alloys may lead to different properties as first predicted in the late 1960s. | 0 | Theoretical and Fundamental Chemistry |
The third paper of 1864 was concerned with the kinetics of the same equilibrium system. Writing the dissociated active mass at some point in time as x, the rate of reaction was given as
Likewise the reverse reaction of A with B proceeded at a rate given by
The overall rate of conversion is the difference between these rates, so at equilibrium (when the composition stops changing) the two rates of reaction must be equal. Hence | 0 | Theoretical and Fundamental Chemistry |
In 1920, Ingold was awarded the British Empire Medal (BEM) for his wartime research involving "great courage in carrying out work in a poisonous atmosphere, and risking his life on several occasions in preventing serious accidents," though he subsequently never discussed the award or this period in his life.
Ingold was elected a Fellow of the Royal Society (FRS) in 1924. He received the Longstaff Medal of the Royal Society of Chemistry in 1951, the Royal Medal of the Royal Society in 1952, and was knighted in 1958.
The chemistry department of University College London is now housed in the Sir Christopher Ingold building, opened in 1969. | 0 | Theoretical and Fundamental Chemistry |
In October 2022, researchers from the Japan-based Yokohama National University successfully cloned fully-grown mouse hair follicles for the first time in history. It may take 5-10 years for this technology to be tested successfully in humans. | 1 | Applied and Interdisciplinary Chemistry |
Phototropins are photoreceptor proteins (more specifically, flavoproteins) that mediate phototropism responses in various species of algae, fungi and higher plants. Phototropins can be found throughout the leaves of a plant. Along with cryptochromes and phytochromes they allow plants to respond and alter their growth in response to the light environment. Phototropins may also be important for the opening of stomata and the movement of chloroplasts. These blue light receptors are seen across the entire green plant lineage. When Phototropins are hit with blue light, they induce a signal transduction pathway that alters the plant cells' functions in different ways.
Phototropins are part of the phototropic sensory system in plants that causes various environmental responses in plants. Phototropins specifically will cause stems to bend towards light and stomata to open. Phototropins have been shown to impact the movement of chloroplast inside the cell. In addition phototropins mediate the first changes in stem elongation in blue light prior to cryptochrome activation. Phototropin is also required for blue light mediated transcript destabilization of specific mRNAs in the cell. They are present in the guard cell. | 1 | Applied and Interdisciplinary Chemistry |
DNP can be performed to enhance the NMR signals but also to introduce an inherent spatial dependence: the magnetization enhancement takes place in the vicinity of the irradiated electrons and propagates throughout the sample. Spatial selectivity can finally be obtained using magnetic resonance imaging (MRI) techniques, so that signals from similar parts can be separated based on their location in the sample.
DNP has triggered enthusiasm in the NMR community because it can enhance sensitivity in solid-state NMR. In DNP, a large electronic spin polarization is transferred onto the nuclear spins of interest using a microwave source. There are two main DNP approaches for solids. If the material does not contain suitable unpaired electrons, exogenous DNP is applied: the material is impregnated by a solution containing a specific radical. When possible, endogenous DNP is performed using the electrons in transition metal ions (metal-ion dynamic nuclear polarization, MIDNP) or conduction electrons. The experiments usually need to be performed at low temperatures with magic angle spinning. It is important to note that DNP was only performed ex situ as it usually requires low temperature to lower electronic relaxation. | 0 | Theoretical and Fundamental Chemistry |
The Norrish reaction has been studied in relation to environmental chemistry with respect to the photolysis of the aldehyde heptanal, a prominent compound in Earth's atmosphere. Photolysis of heptanal in conditions resembling atmospheric conditions results in the formation of 1-pentene and acetaldehyde in 62% chemical yield together with cyclic alcohols (cyclobutanols and cyclopentanols) both from a Norrish type II channel and around 10% yield of hexanal from a Norrish type I channel (the initially formed n-hexyl radical attacked by oxygen).
In one study the photolysis of an acyloin derivative in water in presence of hydrogen tetrachloroaurate (HAuCl) generated nanogold particles with 10 nanometer diameter. The species believed to responsible for reducing Au to Au is the Norrish generated ketyl radical.
Leo Paquette's 1982 synthesis of dodecahedrane involves three separate Norrish-type reactions in its approximately 29-step sequence.
An example of a synthetically useful Norrish type II reaction can be found early in the total synthesis of the biologically active cardenolide ouabagenin by Phil Baran and coworkers. The optimized conditions minimize side reactions, such as the competing Norrish type I pathway, and furnish the desired intermediate in good yield on a multi-gram scale. | 0 | Theoretical and Fundamental Chemistry |
In 2013, the International Agency for Research on Cancer (IARC) classified dioxin-like PCBs as human carcinogens.
According to the U.S. EPA, PCBs have been shown to cause cancer in animals and evidence supports a cancer-causing effect in humans. Per the EPA, studies have found increases in malignant melanoma and rare liver cancers in PCB workers.
In 2013, the IARC determined that the evidence for PCBs causing non-Hodgkin lymphoma is "limited" and "not consistent". In contrast an association between elevated blood levels of PCBs and non-Hodgkin lymphoma had been previously accepted. PCBs may play a role in the development of cancers of the immune system because some tests of laboratory animals subjected to very high doses of PCBs have shown effects on the animals' immune system, and some studies of human populations have reported an association between environmental levels of PCBs and immune response. | 1 | Applied and Interdisciplinary Chemistry |
Triptan structures were designed from the structure of 5-HT to attain affinity to 5-HT receptors, hence the identical indole structure. The hydroxyl group (-OH) on the hexane of the indole core and the alkyl-amine side chain on position C on 5-HT have been replaced with other compounds, such as sulfonamides or azol-ring structured derivatives and different amine-alkyl side chains. An electro-negative group can form a hydrogen bond with Thr in the pocket of the receptor. Sulfonamide derivatives attached to the hexane ring of the indole structure have electro-negative properties, as well as the triazole and 2-oxazolidone on rizatriptan and zolmitriptan respectively. This can increase binding ability of the compound and the efficacy, especially with the 5-HT receptor.
A schematic drawing of the binding of sumatriptan to 5-HT receptor can be seen in figure 4. One study showed that sumatriptan fits better in the binding site of the receptor when the side chain with the protonated nitrogen atom is folded back over the indole structure. This alignment contributes to the hydrogen bonding between the nitrogen in the sulfonamine and the Ser138 in the binding site. It is also favorable to the formation of the hydrogen bond between the oxygen of the sulfonamine and Thr202. Other binding in the pocket of the binding site occurs with the nitrogen atom in the pentene ring of the indole structure of the triptan and the amino acid Ser352. This energetically favorable position of the agonist makes it possible for additional binding of the ligand to other Ser in the binding site, along with additional anchoring between Phe in the pocket of the binding site and the indole of the agonist. The binding of Phe and the triptan is caused by π stacking interactions of the indole and amino acid and an additional effect on this interaction is because of dispersive effect of amino acid leucine (Leu; not shown in figure 4). The amino acids Trp343 and Tyr346 both have electron rich π-systems in their aromatic structures. With their position in the binding site they create a sort of aromatic cage around the protonated nitrogen atom of the side chain on position C on the triptans (this nitrogen atom is protonated at physiological condition), and thereby stabilizes the ion bond the nitrogen atom has formed with a carboxylate on aspartic acid. Side chains of the surrounding amino acids can have an effect on the binding of the nitrogen atom, mainly three Phe can affect the methyl groups bound to the nitrogen atom (not shown in figure 4).
Eletriptan has higher affinity for the receptor, which is probably a result of the bulky substituents of the structure. The amine is protonated at physiological pH condition, triggering better uptake. The uptake rate of the agonist is different depending on whether the amine in R is primary, secondary or tertiary but the latter seem to give the best results. For the R substituent an electron rich sulfonamide groups and amide group has shown the best results in receptor binding and activity. It has been observed that a relationship is between absorption and molecular size hence larger hydrophilic molecules tended to have poor absorption. A small R substituent is necessary to maintain the rapid oral bioavailability of triptans.
By placing an electron-withdrawing group or large group on position C on the indole structure the 5-HT agonist is conversed into an antagonist. This is thought to be because the indole ring is unable to occupy the aromatic part of the binding site. | 1 | Applied and Interdisciplinary Chemistry |
The Winkler test is used to determine the concentration of dissolved oxygen in water samples. Dissolved oxygen (D.O.) is widely used in water quality studies and routine operation of water reclamation facilities to analyze its level of oxygen saturation.
In the test, an excess of manganese(II) salt, iodide (I) and hydroxide (OH) ions are added to a water sample causing a white precipitate of Mn(OH) to form. This precipitate is then oxidized by the oxygen that is present in the water sample into a brown manganese-containing precipitate with manganese in a more highly oxidized state (either Mn(III) or Mn(IV)).
In the next step, a strong acid (either hydrochloric acid or sulfuric acid) is added to acidify the solution. The brown precipitate then converts the iodide ion (I) to iodine. The amount of dissolved oxygen is directly proportional to the titration of iodine with a thiosulfate solution. Today, the method is effectively used as its colorimetric modification, where the trivalent manganese produced on acidifying the brown suspension is directly reacted with ethylenediaminetetraacetic acid to give a pink color. As manganese is the only common metal giving a color reaction with ethylenediaminetetraacetic acid, it has the added effect of masking other metals as colorless complexes. | 0 | Theoretical and Fundamental Chemistry |
The study of TOR originated in the 1960s with an expedition to Easter Island (known by the island inhabitants as Rapa Nui), with the goal of identifying natural products from plants and soil with possible therapeutic potential. In 1972, Suren Sehgal identified a small molecule, from a soil bacterium Streptomyces hygroscopicus, that he purified and initially reported to possess potent antifungal activity. He appropriately named it rapamycin, noting its original source and activity. However, early testing revealed that rapamycin also had potent immunosuppressive and cytostatic anti-cancer activity. Rapamycin did not initially receive significant interest from the pharmaceutical industry until the 1980s, when Wyeth-Ayerst supported Sehgals efforts to further investigate rapamycins effect on the immune system. This eventually led to its FDA approval as an immunosuppressant following kidney transplantation. However, prior to its FDA approval, how rapamycin worked remained completely unknown. | 1 | Applied and Interdisciplinary Chemistry |
Hemozoin formation is an excellent drug target, since it is essential to malaria parasite survival and absent from the human host. The drug target hematin is host-derived and largely outside the genetic control of the parasite, which makes the development of drug resistance more difficult. Many clinically used drugs are thought to act by inhibiting the formation of hemozoin in the food vacuole. This prevents the detoxification of the heme released in this compartment, and kills the parasite.
The best-understood examples of such hematin biocrystallization inhibitors are quinoline drugs such as chloroquine and mefloquine. These drugs bind to both free heme and hemozoin crystals, and therefore block the addition of new heme units onto the growing crystals. The small, most rapidly growing face is the face to which inhibitors are believed to bind. | 1 | Applied and Interdisciplinary Chemistry |
The Weismann barrier, proposed by August Weismann in 1892, distinguishes between the "immortal" germ cell lineages (the germ plasm) which produce gametes and the "disposable" somatic cells. Hereditary information moves only from germline cells to somatic cells (that is, somatic mutations are not inherited). This, before the discovery of the role or structure of DNA, does not predict the central dogma, but does anticipate its gene-centric view of life, albeit in non-molecular terms. | 1 | Applied and Interdisciplinary Chemistry |
Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, AlSiO(OH)), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces.
Clay minerals form in the presence of water and have been important to life, and many theories of abiogenesis involve them. They are important constituents of soils, and have been useful to humans since ancient times in agriculture and manufacturing. | 0 | Theoretical and Fundamental Chemistry |
Sodium methoxide, also called sodium methylate and sodium methanolate, is a white powder when pure. It is used as an initiator of an anionic addition polymerization with ethylene oxide, forming a polyether with high molecular weight. Both sodium methoxide and its counterpart prepared with potassium are frequently used as catalysts for commercial-scale production of biodiesel. In this process, vegetable oils or animal fats, which chemically are fatty acid triglycerides, are transesterified with methanol to give fatty acid methyl esters (FAMEs).
Sodium methoxide is produced on an industrial scale and available from a number of chemical companies. | 0 | Theoretical and Fundamental Chemistry |
In analytical chemistry, sample preparation (working-up) refers to the ways in which a sample is treated prior to its analyses. Preparation is a very important step in most analytical techniques, because the techniques are often not responsive to the analyte in its in-situ form, or the results are distorted by interfering species. Sample preparation may involve dissolution, extraction, reaction with some chemical species, pulverizing, treatment with a chelating agent (e.g. EDTA), masking, filtering, dilution, sub-sampling or many other techniques.
Treatment is done to prepare the sample into a form ready for analysis by specified analytical equipment.
Sample preparation could involve: crushing and dissolution, chemical digestion with acid or alkali, sample extraction, sample clean up and sample pre-concentration. | 0 | Theoretical and Fundamental Chemistry |
Fretting in Aluminium causes black debris to be present in the contact area due to the fine oxide particles. | 1 | Applied and Interdisciplinary Chemistry |
Since its founding in 1959, EAS has become a premier venue for analysts to learn about new technologies, new applications for older technologies, and developments in such diverse fields as bioanalysis, pharmaceutical analysis, forensic science, laboratory management, and environmental analysis. Throughout the years, the EAS has been the place where innovations in analytical science have been introduced to the community of analytical scientists.
The first EAS was held in 1959 at the Hotel New Yorker in New York City, with 1200 attendees at 12 technical sessions. The exposition had 38 exhibitors who displayed the latest in analytical supplies and instrumentation. During the early years in New York, the EAS was held at various hotels in the city, as the attendance grew. At the 10th EAS, a workshop on electrochemical techniques was the origin of the exhibitor workshops, which later would become a standard feature of the EAS program. By the 15th symposium, major awards were given out as part of the program of the Symposium, including the Meggers Memorial Award, the Hassler Award in Applied Spectroscopy, and the Anachem Award.
In 1973, the EAS was suspended to support the emerging FACSS (Federation of Analytical Chemistry and Spectroscopy Societies), whose meetings were held at a similar time of the year. After two years, an EAS mini-symposium was held, and in 1977, the EAS returned to its original format in New York City. During the late 1970s and the 1980s, the EAS was moved from location to location New York City, as attendance continued to expand. During this period, the Governing Board of the Eastern Analytical Symposium began to present its own awards for excellence in analysis. In 1986, the first EAS Award for Outstanding Contributions in the Fields of Analytical Chemistry was presented to Professor George Morrison, who - aside from his many scientific contributions - had been instrumental in the early development of EAS. At the same meeting, the EAS Award for Outstanding Contributions to Separations Science was presented to Professor Csaba Horvath. In subsequent years, EAS awards of contributions to other areas would be added to recognize contributions to various areas of analysis. Currently, the EAS presents the six major awards listed above to distinguished scientists from around the world at the annual Symposium.
As the 1990s dawned, it became necessary for the Eastern Analytical Symposium to find a venue for the meeting to meet the needs of a growing meeting. In 1990, the EAS moved to the then-new Garden State Convention and Exhibit Center in Somerset, New Jersey. As the symposium continued to grow, even the GSCEC seemed limited. In 2000, the EAS was moved to the Atlantic City Convention Center, where it remained for two years. However, beginning in the early 2000s, it was decided to move the EAS back to the Garden State Convention and Exhibit Center.
Although the Eastern Analytical Symposium started as a regional meeting, where persons interested in practical analytical chemistry from laboratories in the Northeast could meet to discuss problems of common interest, it has grown to international stature, with attendance from analysts from laboratories in companies and universities across the world. The Symposium has further grown to emphasize a wide variety of technologies and areas of application that could only be dreamed of in 1959. Applications to traditional areas of analysis are still represented among the talks, but unique to the Eastern Analytical Symposium are areas such as cultural heritage and forensic science. As the 21st century has dawned, EAS continues to provide an inclusive home for practical analytical studies, to educate about the latest technologies, and to inform its audience about the current state of analysis.
After several decades of holding the meeting in Somerset, NJ, the annual symposium was moved to nearby Princeton, NJ in 2017. | 0 | Theoretical and Fundamental Chemistry |
Alkyltellurols are colorless liquids with strong odors. Samples usually appear yellowish owing to the presence of dialkylditelluride impurities. Near room temperature, methanetellurol degrades with loss of elemental tellurium. It is reported to ignite in air.
Aryltellurols are more robust and have been obtained as colorless crystals. Some of the most stable tellurols are the bulky silylated derivatives of tris(trimethylsilyl)methane and analogues. One series of readily isolable tellurols is , , and . | 0 | Theoretical and Fundamental Chemistry |
ASL maps can mainly be analyzed using the same tools to analyze fMRI and VBM. Many ASL-specific toolboxes have been developed to assist in ASL analysis, such as BASIL (Bayesian inference for arterial spin labelling MRI), part of the FSL neuroimaging package and also Ze Wang's ASL toolbox (using MATLAB) to assist in the subtraction and averaging of the tagged/control pairs. A visual quality check is often needed to make sure that the perfusion map is valid (such as correct registration, or correct segmentation of non-cerebral materials such as the dura mater). A whole brain/voxel-wise approach can be analyzed by registering the ASL map into MNI space for group comparisons. A region of interest approach can be analyzed by registering the ASL map into a selected cluster, or an atlas, like a standard (such as the Harvard-Oxford Cortical atlas) or an individual atlas developed by software like FreeSurfer. The recommended procedure of ASL registration for voxel-wise analysis is to register the perfusion map to a gray matter segmentation of each individual in a non-rigid procedure.
Gray matter often requires more oxygenation and is the source of more brain activity compared to white matter. Therefore, gray matter CBF is often higher than white matter CBF. The single value of gray matter CBF is often isolated in order to give a broad overview of CBF differences. Gray matter and white matter CBF can be localized using atlases or Freesurfer.
ASL functional connectivity can be designed with parameters conducive to a long scan time. Studies have suggested that ASL complement resting state fMRI findings well but can differentiate between resting brain networks (such as the default mode network) less. | 0 | Theoretical and Fundamental Chemistry |
*1990 Günter Snatzke, Germany
*1991 Hannes Aiginger, Austria; Peter Wobrauschek]], Austria; Joachim Knoth]], Germany; Heinrich Schwenke]], Germany
*1992 Kurt Laqua, Germany; Arnulf Röseler]], Germany
*1993 Boris L'vov, Russia
*1994 D. Bruce Chase, United States; W. J. Orville-Thomas, Great Britain
*1995 Paul W.J.M. Boumans, Netherlands
*1998 Annemie Bogaerts, Belgium
*2000 Dieter Fischer, Germany
*2001 John A. McLean, United States
*2002 Jürgen Popp, Germany
*2003 Sergei Boulyga, Germany
*2004 Ewa Bulska, Poland
*2005 Nicolas Bings, Germany
*2006 Volker Deckert, Germany
*2007 Jörg Bettmer, Germany
*2008 Sebastian Schlücke, Germany
*2009 Joachim Koch, Switzerland
*2010 Janina Kneipp, Germany
*2011 Daniel Pröfrock, Germany
*2012 Christoph Haisch, Germany
*2013 Maria Montes-Bayón, Spain
*2014 Oliver Reich, Germany
*2015 Martín Resano, Spain
*2016 Torsten Frosch, Germany
*2017 Jacob T. Shelley, United States
*2018 , Hungary
*2020 Natalia P. Ivleva
*2022 Carlos Abad Andrade | 0 | Theoretical and Fundamental Chemistry |
According to the adsorption behavior, the adsorption of gases on solids can be classified into three temperature ranges relative to :
1.Subcritical region (T)
2.Near-critical region (+10)
3. The region T>+10
Isotherms in the first region will show the feature of subcritical adsorption. Isotherms in the second region will show the feature of mechanism transition. Isotherms in the third region will show the feature of supercritical adsorption. The transition will take a continuous way if the isotherms in both sides of the critical temperature belong to the same type, such as adsorption on microporous activated carbon. However, discontinuous transition could be observed on isotherms in the second region if there is a transformation of isotherm types, such as adsorption on mesoporous silica gel. The decisive factor in such a classification of adsorption is merely temperature, irrespective of pressure. This is because a fluid cannot undergo a transition to a liquid phase at above-critical temperature, regardless of the pressure applied. This fundamental law determines the different adsorption mechanism for the subcritical and supercritical regions. For the subcritical region, the highest equilibrium pressure of adsorption is the saturation pressure of adsorbate. Beyond condensation happens. Adsorbate in the adsorbed phase is largely in liquid state, based on which different adsorption and thermodynamic theories as well as their applications were developed. For supercritical region, condensation cannot happen, no matter how great the pressure is. | 0 | Theoretical and Fundamental Chemistry |
When grown in glucose-rich media, trypanosomatid parasites degrade glucose via aerobic fermentation. In this group, this phenomenon is not a pre-adaptation to/or remnant of anaerobic life, shown through their inability to survive in anaerobic conditions. It is believed that this phenomenon developed due to the capacity for a high glycolytic flux and the high glucose concentrations of their natural environment. The mechanism for repression of respiration in these conditions is not yet known. | 1 | Applied and Interdisciplinary Chemistry |
Oncometabolism is the field of study that focuses on the metabolic changes that occur in cells that make up the tumor microenvironment (TME) and accompany oncogenesis and tumor progression toward a neoplastic state.
Cells with increased growth and survivability differ from non-tumorigenic cells in terms of metabolism. The Warburg Effect, which describes how cancer cells change their metabolism to become more oncogenic in order to proliferate and eventually invade other tissues in a process known as metastasis.
The chemical reactions associated with oncometabolism are triggered by the alteration of oncogenes, which are genes that have the potential to cause cancer. These genes can be functional and active during physiological conditions, producing normal amounts of metabolites. Their upregulation as a result of DNA damage can result in an overabundance of these metabolites, and lead to tumorigenesis. These metabolites are known as oncometabolites, and can act as biomarkers. | 1 | Applied and Interdisciplinary Chemistry |
The global annual mean wind stress forces the global ocean circulation. Typical values for the wind stress are about 0.1Pa and, in general, the zonal wind stress is stronger than the meridional wind stress as can be seen in figures 2.1 and 2.2. It can also be seen that the largest values of the wind stress occur in the Southern Ocean for the zonal direction with values of about 0.3Pa. Figures 2.3 and 2.4 show that monthly variations in the wind stress patterns are only minor and the general patterns stay the same during the whole year. It can be seen that there are strong easterly winds (i.e. blowing toward the West), called easterlies or trade winds near the equator, very strong westerly winds at midlatitudes (between ±30° and ±60°), called westerlies, and weaker easterly winds at polar latitudes. Also, on a large annual scale, the wind-stress field is fairly zonally homogeneous. Important meridional wind stress patterns are northward (southward) currents on the eastern (western) coasts of continents in the Northern Hemisphere and on the western (eastern) coast in the Southern Hemisphere since these generate coastal upwelling which causes biological activity. Examples of such patterns can be observed in figure 2.2 on the East coast of North America and on the West coast of South America. | 1 | Applied and Interdisciplinary Chemistry |
The RACI is a member of the Federation of Australian Scientific and Technological Societies (FASTS), and the Federation of Asian Chemical Societies (FACS).
It has branches in all states and territories in Australia and divisions for the following areas of chemistry:
*Analytical and Environmental chemistry
*Carbon science
*Chemical education
*Interfaces, Colloids and Surface science
*Electrochemistry
*Industrial chemistry
*Inorganic chemistry
*Materials chemistry
*Medicinal chemistry and Chemical biology
*Organic chemistry
*Physical chemistry
*Polymer chemistry
*Radiochemistry
In 2022, the Green and Sustainable Chemistry (GASC) National Group was established.
In addition to the divisions having organised conferences, they have co-operated in running occasional national conventions since 1953. | 1 | Applied and Interdisciplinary Chemistry |
*Panel methods are inviscid solutions. You will not capture viscous effects except via user "modeling" by changing the geometry.
*Solutions are invalid as soon as the flow changes locally from subsonic to supersonic (i.e. the critical Mach number has been exceeded) or vice versa. | 1 | Applied and Interdisciplinary Chemistry |
Hilaire Marin Rouelle (15 February 1718 – 7 April 1779) was an 18th-century French chemist. Commonly cited as the 1773 discoverer of urea, he was not the first to do so. Dutch scientist Herman Boerhaave had discovered this chemical as early as 1727. Rouelle is known as "le cadet" (the younger) to distinguish him from his older brother, Guillaume-François Rouelle, who was also a chemist. | 1 | Applied and Interdisciplinary Chemistry |
While less rhodium than ruthenium and palladium is formed (around 3.6% yield), the mixture of fission products still contains a significant amount of this metal. Due to the high prices of ruthenium, rhodium, and palladium, some work has been done on the separation of these metals to enable them to be used at a later date. Because of the possibility of the metals being contaminated by radioactive isotopes, they are not suitable for making consumer products such as jewellery. However, this source of the metals could be used for catalysts in industrial plants such as petrochemical plants.
A dire example of people being exposed to radiation from contaminated jewellery occurred in the United States. It is thought that gold seeds used to contain radon were recycled into jewellery. The gold indeed did contain radioactive decay products of Rn.
Some other rhodium isotopes exist as "transitory states" of ruthenium decaying before further decaying towards stable isotopes of Palladium. If the low level radioactivity of Palladium (see below) is deemed excessive - for example for use as an investment or jewelry - either of its predecessors can be extracted from relatively "young" spent fuel and allowed to decay before extracting the stable end-product of the decay series. | 0 | Theoretical and Fundamental Chemistry |
Wild-type p53 has been shown to repress survivin expression at the mRNA level. Using an adenovirus vector for wild-type p53, human ovarian cancer cell line 2774qw1 (which expresses mutant p53) was transfected. mRNA levels of survivin were analyzed by real-time quantitative PCR (RT-PCR) and showed time-dependent down regulation of survivin mRNA levels when the cells were infected with wild-type p53. A 3.6 fold decrease of survivin mRNA level was observed 16 hours after infection initiation and decreased 6.7 fold 24 hours after infection. Western blot results do show that there is indeed the p53 from the adenoviral vector was being expressed in the cells using antibody specific for p53. The expression of p53 levels indicative of its role in survivin repression shows that p53 started to be expressed 6 hours into infection and had its highest level at 16–24 hours. To further confirm that endogenous wild-type p53 is really causing the repression of survivin gene expression, the authors induced A549 (human lung cancer cell line with wild-type p53) and T47D (human breast cancer cell line with mutant p53) cells with DNA-damaging agent adriamycin to trigger the physiological p53 apoptotic response in these cancer cells and compare the survivin levels measured to the same cells without DNA damage induction. The A549 line, which intrinsically has functioning wild-type p53, showed significant reduction in survivin levels compared to non-induced cells. This same effect was not seen in T47D cells that carry mutant inactive p53.
P53's normal function is to regulate genes that control apoptosis. As survivin is a known inhibitor of apoptosis, it can be implied that p53 repression of survivin is one mechanism by which cells can undergo apoptosis upon induction by apoptotic stimuli or signals. When survivin is over-expressed in the cell lines mentioned in the previous paragraph, apoptotic response from DNA-damaging agent adriamycin decreased in a dose-dependent manner. This suggests that down-regulation of survivin by p53 is important for p53-mediated apoptotic pathway to successfully result in apoptosis. It is known that a defining characteristic of most tumors is the over-expression of survivin and the complete loss of wild-type p53. The evidence put forth by Mirza et al. shows that there exists a link between survivin and p53 that can possibly explain a critical event that contributes to cancer progression. | 1 | Applied and Interdisciplinary Chemistry |
Uranium mining produces toxic tailings that are radioactive and may contain other toxic elements such as radon. Dust and water leaving tailing sites may carry long-lived radioactive elements that enter water sources and the soil, increase background radiation, and eventually be ingested by humans and animals. A 2013 analysis in a medical journal found that, "The effects of all these sources of contamination on human health will be subtle and widespread, and therefore difficult to detect both clinically and epidemiologically." A 2019 analysis of the global uranium industry said that the industry was shifting mining activities toward the Global South where environmental regulations are typically less stringent; and that people in impacted communities would "surely experience adverse environmental consequences" and public health issues arising from mining activities carried out by powerful multi-national corporations or mining companies based in foreign countries. | 0 | Theoretical and Fundamental Chemistry |
Gases will dissolve in liquids to an extent that is determined by the equilibrium between the undissolved gas and the gas that has dissolved in the liquid (called the solvent). The equilibrium constant for that equilibrium is:
where:
* = the equilibrium constant for the solvation process
* = partial pressure of gas in equilibrium with a solution containing some of the gas
* = the concentration of gas in the liquid solution
The form of the equilibrium constant shows that the concentration of a solute gas in a solution is directly proportional to the partial pressure of that gas above the solution. This statement is known as Henrys law and the equilibrium constant is quite often referred to as the Henrys law constant.
Henry's law is sometimes written as:
where is also referred to as the Henrys law constant. As can be seen by comparing equations () and () above, is the reciprocal of . Since both may be referred to as the Henrys law constant, readers of the technical literature must be quite careful to note which version of the Henry's law equation is being used.
Henry's law is an approximation that only applies for dilute, ideal solutions and for solutions where the liquid solvent does not react chemically with the gas being dissolved. | 0 | Theoretical and Fundamental Chemistry |
Amorphous materials will have some degree of short-range order at the atomic-length scale due to the nature of intermolecular chemical bonding. Furthermore, in very small crystals, short-range order encompasses a large fraction of the atoms; nevertheless, relaxation at the surface, along with interfacial effects, distorts the atomic positions and decreases structural order. Even the most advanced structural characterization techniques, such as X-ray diffraction and transmission electron microscopy, have difficulty distinguishing amorphous and crystalline structures at short-length scales. | 0 | Theoretical and Fundamental Chemistry |
A graph of fission product yield against the mass number of the fission fragments has two pronounced but fairly flat peaks, at around 90 to 100, and 130 to 140. With thermal neutrons, yields of fission products with mass between the peaks, such as Cd, Sn, Sn, Sn, Sb, Sn, and Sb are very low.
The higher the energy of the state that undergoes nuclear fission, the more likely a symmetric fission is, hence as the neutron energy increases and/or the energy of the fissioning atom increases, the valley between the two peaks becomes more shallow; for instance, the curve of yield against mass for Pu has a more shallow valley than that observed for U, when the neutrons are thermal neutrons. The curves for the fission of the later actinides tend to make even more shallow valleys. In extreme cases such as Fm, only one peak is seen. | 0 | Theoretical and Fundamental Chemistry |
The lagoon covers an area of . Created by the rise in water levels at the end of the Last Glacial Period (colloquially known as the last ice age), this small inland sea is composed of three parts: the principal body of water, the Étang de Vaïne to the east and the Étang de Bolmon to the south-east.
The Étang de Berre is fed with fresh water by the rivers Arc, Touloubre and Cadière and – since 1966 – by Électricité de Frances . Two canals link it to the Mediterranean, the open air leading towards Port-de-Bouc and the Canal de Marseille au Rhône which leads towards LEstaque through the Rove Tunnel; the Rove Tunnel has been closed since 1963, after a section of the tunnel collapsed.
The Marseille Provence Airport is located in the southeast portion of the Étang de Berre, with its main runway extending into the water on reclaimed land. | 1 | Applied and Interdisciplinary Chemistry |
*The cytochrome P450 isozymes play important roles in metabolism and steroidogenesis.
*The multiple forms of phosphodiesterase also play major roles in various biological processes. Although more than one form of these enzymes have been found in individual cells, these isoforms of the enzyme are unequally distributed in the various cells of an organism. From the clinical standpoint they have been found to be selectively activated and inhibited, an observation which has led to their use in therapy. | 1 | Applied and Interdisciplinary Chemistry |
In materials science and soil mechanics, a slip line field or slip line field theory is a technique often used to analyze the stresses and forces involved in the major deformation of metals or soils. In essence, in some problems including plane strain and plane stress elastic-plastic problems, elastic part of the material prevent unrestrained plastic flow but in many metal-forming processes, such as rolling, drawing, gorging, etc., large unrestricted plastic flows occur except for many small elastic zones. In effect we are concerned with a rigid-plastic material under condition of plane strain. it turns out that the simplest way of solving stress equations is to express them in terms of a coordinate system that is along potential slip (or failure) surfaces. It is for this reason that this type of analysis is termed slip line analysis or the theory of slip line fields in the literature. | 1 | Applied and Interdisciplinary Chemistry |
When a system undergoes a change from one state to another, it is said to traverse a path. The path can be described by how the properties change, like isothermal (constant temperature) or isobaric (constant pressure) paths.
Thermodynamics sets up an idealized conceptual structure that can be summarized by a formal scheme of definitions and postulates. Thermodynamic states are amongst the fundamental or primitive objects or notions of the scheme, for which their existence is primary and definitive, rather than being derived or constructed from other concepts.
A thermodynamic system is not simply a physical system. Rather, in general, infinitely many different alternative physical systems comprise a given thermodynamic system, because in general a physical system has vastly many more microscopic characteristics than are mentioned in a thermodynamic description. A thermodynamic system is a macroscopic object, the microscopic details of which are not explicitly considered in its thermodynamic description. The number of state variables required to specify the thermodynamic state depends on the system, and is not always known in advance of experiment; it is usually found from experimental evidence. The number is always two or more; usually it is not more than some dozen. Though the number of state variables is fixed by experiment, there remains choice of which of them to use for a particular convenient description; a given thermodynamic system may be alternatively identified by several different choices of the set of state variables. The choice is usually made on the basis of the walls and surroundings that are relevant for the thermodynamic processes that are to be considered for the system. For example, if it is intended to consider heat transfer for the system, then a wall of the system should be permeable to heat, and that wall should connect the system to a body, in the surroundings, that has a definite time-invariant temperature.
For equilibrium thermodynamics, in a thermodynamic state of a system, its contents are in internal thermodynamic equilibrium, with zero flows of all quantities, both internal and between system and surroundings. For Planck, the primary characteristic of a thermodynamic state of a system that consists of a single phase, in the absence of an externally imposed force field, is spatial homogeneity. For non-equilibrium thermodynamics, a suitable set of identifying state variables includes some macroscopic variables, for example a non-zero spatial gradient of temperature, that indicate departure from thermodynamic equilibrium. Such non-equilibrium identifying state variables indicate that some non-zero flow may be occurring within the system or between system and surroundings. | 0 | Theoretical and Fundamental Chemistry |
Biochemists are typically employed in the life sciences, where they work in the pharmaceutical or biotechnology industry in a research role. They are also employed in academic institutes, where in addition to pursuing their research they may also be involved with teaching undergraduates, training graduate students, and collaborating with post-doctoral fellows.
The U.S. Bureau of Labor Statistics (BLS) estimates that jobs in the biochemist, combined with the statistics of biophysicists, field would increase by 31% between 2004 and 2014 because of the demand in medical research and development of new drugs and products, and the preservation of the environment.
Because of a biochemists' background in both biology and chemistry, they may also be employed in the medical, industrial, governmental, and environmental fields. Slightly more than half of the biological scientists are employed by the Federal State and local governments. The field of medicine includes nutrition, genetics, biophysics, and pharmacology; industry includes beverage and food technology, toxicology, and vaccine production; while the governmental and environmental fields includes forensic science, wildlife management, marine biology, and viticulture.
The average income of a biochemist was $82,150 in 2017. The range of the salaries begin around 44,640 to 153,810, reported in 2017. The Federal Government in 2005 reported the average salaries in different fields associated with biochemistry and being a biochemist. General biological scientists in nonsupervisory, supervisory, and managerial positions earned an average salary of $69,908; microbiologists, $80,798; ecologists, $72,021; physiologists, $93,208; geneticists, $85,170; zoologists, $101,601; and botanists, $62,207. | 1 | Applied and Interdisciplinary Chemistry |
Atomic-force microscopy is used to study the local roughness and mechanical properties of a surface. AFM is also used to characterize adhesion and friction properties for micro- and nano-patterned superhydrophobic surfaces. Results can be used to fit a curve to the surface topography and determine the radius of curvature of nanostructures. | 0 | Theoretical and Fundamental Chemistry |
A diazaquinone is a chemical compound that has an heterocyclic aromatic core including two consecutive doubly-bonded nitrogen atoms , with the two carbon units adjacent to the nitrogens replaced by carbonyl (ketone) groups . These carbon and nitrogen atoms then comprise a diacyl diimide unit, .
Two canonical examples are 3,6-pyridazinedione (a quinone of pyridine), emerald-green; and 1,4-phthalazinedione (a quinone of phthalazine) a green crystalline solid (both soluble in acetone and stable at -77 °C).
The name was proposed by Thomas J. Kealy in 1962. | 0 | Theoretical and Fundamental Chemistry |
The word "nitinol" is derived from its composition and its place of discovery: (Nickel Titanium-Naval Ordnance Laboratory). William J. Buehler along with Frederick E. Wang, discovered its properties during research at the Naval Ordnance Laboratory in 1959. Buehler was attempting to make a better missile nose cone, which could resist fatigue, heat and the force of impact. Having found that a 1:1 alloy of nickel and titanium could do the job, in 1961 he presented a sample at a laboratory management meeting. The sample, folded up like an accordion, was passed around and flexed by the participants. One of them applied heat from his pipe lighter to the sample and, to everyone's surprise, the accordion-shaped strip contracted and took its previous shape.
While the potential applications for nitinol were realized immediately, practical efforts to commercialize the alloy did not take place until a decade later. This delay was largely because of the extraordinary difficulty of melting, processing and machining the alloy. Even these efforts encountered financial challenges that were not readily overcome until the 1980s, when these practical difficulties finally began to be resolved.
The discovery of the shape-memory effect in general dates back to 1932, when Swedish chemist Arne Ölander first observed the property in gold–cadmium alloys. The same effect was observed in Cu-Zn (brass) in the early 1950s. | 1 | Applied and Interdisciplinary Chemistry |
SVA elements are present at lower levels than SINES and LINEs in humans. The starts of SVA and Alu elements are similar, followed by repeats and an end similar to endogenous retrovirus. LINEs bind to sites flanking SVA elements to transpose them. SVA are one of the youngest transposons in great apes genome and among the most active and polymorphic in the human population. SVA was created by a fusion between an Alu element, a VNTR (variable number tandem repeat), and an LTR fragment. | 1 | Applied and Interdisciplinary Chemistry |
Convergent beam electron diffraction (CBED) is an electron diffraction technique where a convergent or divergent beam (conical electron beam) of electrons is used to study materials. | 0 | Theoretical and Fundamental Chemistry |
* Moscow University in the Great Patriotic War, 4th edition, revised and supplemented. M.: Moscow State University, 2020. 65, 116, 117, 118, 551s. ISBN 978-5-19-011499-7.
* Great Soviet Encyclopedia. Article: Nesmeyanov Alexander Nikolayevich.
* Levchenkov S.I.. Great Russian Encyclopedia. Article: Nesmeyanov Alexander Nikolayevich
* Nesmeyanov M.A. The Light of Love: Memories of Alexander Nikolevich Nesmeyanov. M.: Nauka Publishing House, 1999. ISBN 5-02-008355-0.
* Goryacheva R.I., Orlova V.Ya. Fokin A.V. etc. Alexander Nikolayevich Nesmeyanov: 1899-1980. Moscow: Nauka Publishing House, 1992. ISBN 5-02-001607-1.
* Ilchenko E.V., Ilchenko V.I. Academician Alexander Nikolayevich Nesmeyanov - Rector of Moscow University and President of the Academy of Sciences of the Soviet Union. Moscow: Moscow State University, 2014. 440 p. ISBN 978-5-19-010865-1.
* Ilchenko E.V., Ilchenko V.I. Academician Alexander Nikolayevich Nesmeyanov - Rector of Moscow University and President of the Academy of Sciences of the Soviet Union. Moscow: Moscow State University, 2014. 440 p. ISBN 978-5-19-010865-1. | 0 | Theoretical and Fundamental Chemistry |
In fluid statics, capillary pressure () is the pressure between two immiscible fluids in a thin tube (see capillary action), resulting from the interactions of forces between the fluids and solid walls of the tube. Capillary pressure can serve as both an opposing or driving force for fluid transport and is a significant property for research and industrial purposes (namely microfluidic design and oil extraction from porous rock). It is also observed in natural phenomena. | 1 | Applied and Interdisciplinary Chemistry |
NANOHISPA and NIMS-MANA were both ranked first, both making about 54 turns and covering 678 nm and 1054 nm, respectively. The first demonstrated a change of lane for overpassing while the latter crossed a trench and go back. StrasNanocar ranked third covering 476 nm and performing 28 turns. | 0 | Theoretical and Fundamental Chemistry |
;From PCl
Phosphite esters are typically prepared by treating phosphorus trichloride with an alcohol. For alkyl alcohols the displaced chloride ion can attack the phosphite, causing dealkylation to give a dialkylphosphite and an organochlorine compound. The overall reaction is as follows:
:PCl + 3 CHOH → (CHO)P(O)H + 2 HCl + CHCl
Alternatively, when the alcoholysis is conducted in the presence of proton acceptors (typically an amine base), one obtains the C-symmetric trialkyl derivatives:
:PCl + 3 CHOH + 3 RN → (CHO)P + 3 RNHCl
A base is not essential when using aromatic alcohols such as phenols, as they are not susceptible to attack by chloride, however it does catalyse the esterification reaction and is therefore often included.
;By transesterification
Phosphite esters can also be prepared by transesterification, as they undergo alcohol exchange upon heating with other alcohols. This process is reversible and can be used to produce mixed alkyl phosphites. Alternatively, if the phosphite of a volatile alcohol is used, such as trimethyl phosphite, then the by product (methanol) can be removed by distillation, allowing the reaction to be driven to completion. | 0 | Theoretical and Fundamental Chemistry |
Since cells do not produce double-stranded RNA during normal nucleic acid metabolism, natural selection has favored the evolution of enzymes that destroy dsRNA on contact. The best known class of this type of enzymes is Dicer. It is hoped that broad-spectrum anti-virals could be synthesized that take advantage of this vulnerability of double-stranded RNA viruses. | 1 | Applied and Interdisciplinary Chemistry |
Deep-level transient spectroscopy (DLTS) is an experimental tool for studying electrically active defects (known as charge carrier traps) in semiconductors. DLTS establishes fundamental defect parameters and measures their concentration in the material. Some of the parameters are considered as defect "finger prints" used for their identifications and analysis.
DLTS investigates defects present in a space charge (depletion) region of a simple electronic device. The most commonly used are Schottky diodes or p-n junctions. In the measurement process the steady-state diode reverse polarization voltage is disturbed by a voltage pulse. This voltage pulse reduces the electric field in the space charge region and allows free carriers from the semiconductor bulk to penetrate this region and recharge the defects causing their non-equilibrium charge state. After the pulse, when the voltage returns to its steady-state value, the defects start to emit trapped carriers due to the thermal emission process. The technique observes the device space charge region capacitance where the defect charge state recovery causes the capacitance transient. The voltage pulse followed by the defect charge state recovery are cycled allowing an application of different signal processing methods for defect recharging process analysis.
The DLTS technique has a higher sensitivity than almost any other semiconductor diagnostic technique. For example, in silicon it can detect impurities and defects at a concentration of one part in 10 of the material host atoms. This feature together with a technical simplicity of its design made it very popular in research labs and semiconductor material production factories.
The DLTS technique was pioneered by David Vern Lang at Bell Laboratories in 1974. A US Patent was awarded to Lang in 1975. | 0 | Theoretical and Fundamental Chemistry |
Ethyl cyanohydroxyiminoacetate (oxyma) is the oxime of ethyl cyanoacetate and finds use as an additive for carbodiimides, such as dicyclohexylcarbodiimide (DCC) in peptide synthesis. It acts as a neutralizing reagent for the basicity or nucleophilicity of the DCC due to its pronounced acidity (pKa 4.60) and suppresses base catalyzed side reactions, in particular racemization. | 0 | Theoretical and Fundamental Chemistry |
Photoelectron photoion coincidence spectroscopy (PEPICO) is a combination of photoionization mass spectrometry and photoelectron spectroscopy. It is largely based on the photoelectric effect. Free molecules from a gas-phase sample are ionized by incident vacuum ultraviolet (VUV) radiation. In the ensuing photoionization, a cation and a photoelectron are formed for each sample molecule. The mass of the photoion is determined by time-of-flight mass spectrometry, whereas, in current setups, photoelectrons are typically detected by velocity map imaging. Electron times-of-flight are three orders of magnitude smaller than those of ions, which allows electron detection to be used as a time stamp for the ionization event, starting the clock for the ion time-of-flight analysis. In contrast with pulsed experiments, such as REMPI, in which the light pulse must act as the time stamp, this allows to use continuous light sources, e.g. a discharge lamp or a synchrotron light source. No more than several ion–electron pairs are present simultaneously in the instrument, and the electron–ion pairs belonging to a single photoionization event can be identified and detected in delayed coincidence. | 0 | Theoretical and Fundamental Chemistry |
Acid rain has a much less harmful effect on oceans on a global scale, but it creates an amplified impact in the shallower waters of coastal waters. Acid rain can cause the oceans pH to fall, known as ocean acidification, making it more difficult for different coastal species to create their exoskeletons that they need to survive. These coastal species link together as part of the oceans food chain, and without them being a source for other marine life to feed off of, more marine life will die. Coral's limestone skeleton is particularly sensitive to pH decreases, because the calcium carbonate, a core component of the limestone skeleton, dissolves in acidic (low pH) solutions.
In addition to acidification, excess nitrogen inputs from the atmosphere promote increased growth of phytoplankton and other marine plants, which, in turn, may cause more frequent harmful algal blooms and eutrophication (the creation of oxygen-depleted "dead zones") in some parts of the ocean. | 1 | Applied and Interdisciplinary Chemistry |
In August 2018, scientists announced the transformation of gaseous deuterium into a liquid metallic form. This may help researchers better understand giant gas planets, such as Jupiter, Saturn and related exoplanets, since such planets are thought to contain a large quantity of liquid metallic hydrogen, which may be responsible for their observed powerful magnetic fields. | 0 | Theoretical and Fundamental Chemistry |
This is the standard drum filter discharge. A scraper blade, which serves to redirect the filter cake into the discharge chute, removes the cake from the filter cloth just before re-entering the vat. Scraper discharge is used if the desired separation requires high filtration rate or if heavy solid slurry is used or if the slurry is easy to filter to produce cake formation or if a longer wear resistance is desired for the separation of the mentioned slurry. | 0 | Theoretical and Fundamental Chemistry |
Dark pigments in the substantia nigra were first described in 1838 by Purkyně, and the term neuromelanin was proposed in 1957 by Lillie, though it has been thought to serve no function until recently. It is now believed to play a vital role in preventing cell death in certain parts of the brain. It has been linked to Parkinson's disease and because of this possible connection, neuromelanin has been heavily researched in the last decade. | 1 | Applied and Interdisciplinary Chemistry |
In contrast to the flux summation theorem, the concentration summation theorem sums to zero. The implications of this are that some enzymes will cause a given metabolite to increase while others, in order to satisfy the summation to zero, must cause the same metabolite to decrease. This is particularly noticeable in a linear chain of enzyme reactions where, given a metabolite located in the center of the pathway, an increase in expression of any enzyme upstream of the metabolite will cause the metabolite to increase in concentration. In contrast, an increase in expression of any enzyme downstream of the metabolite will cause the given metabolite to decrease in concentration. | 1 | Applied and Interdisciplinary Chemistry |
RT-PCR is commonly used in research methods to measure gene expression. For example, Lin et al. used qRT-PCR to measure expression of Gal genes in yeast cells. First, Lin et al. engineered a mutation of a protein suspected to participate in the regulation of Gal genes. This mutation was hypothesized to selectively abolish Gal expression. To confirm this, gene expression levels of yeast cells containing this mutation were analyzed using qRT-PCR. The researchers were able to conclusively determine that the mutation of this regulatory protein reduced Gal expression. Northern blot analysis is used to study the RNA's gene expression further. | 1 | Applied and Interdisciplinary Chemistry |
Railway electrification in Great Britain started in the late 19th century. After World War II and the nationalisation of the railways in 1948 and the 1955 Modernisation Plan, electrification commenced in earnest. After a pause, the West Coast Main Line north of Weaver Junction to just south of Glasgow was electrified between 1970 and 1974. Small amounts of the rail system then followed, with more electrification occurring in the 1980s, including the East Coast Main Line.
From the mid-1990s to late 2000s, electrification of the network stalled. In 2009, Lord Adonis was appointed Secretary of State for Transport. After a gap of more than a decade, electrification was back on the agenda and Adonis announced plans to electrify the Great Western Main Line from London as far as Swansea, as well as infill electrification schemes in the North West of England. In July 2012 the UK coalition government announced new electrification schemes, all at 25 kV AC, and reconfirmed schemes previously announced by Adonis. Devolved rail transport in Scotland has allowed the Scottish government to pursue electrification with multiple schemes in the Central Belt. This has been followed up by a further commitment to a low carbon economy and a modal shift to enable it. The 2009 government document was refreshed in January 2015.
However, electrification has not been without controversy, with cost overruns and late-running schemes, particularly on the Great Western Main Line. This led to cancellations of projects and various appearances of the Secretary of State for Transport called before the Transport Select Committee. Shortly after this, Campaign to Electrify Britain's Railway was launched to try and mitigate the boom and bust cycle. | 1 | Applied and Interdisciplinary Chemistry |
Persistent triplet state carbenes have been prepared by photochemical decomposition of a diazomethane product via the expulsion of nitrogen gas, at a wavelength of 300 nm in benzene. | 0 | Theoretical and Fundamental Chemistry |
Regulatory networks allow bacteria to adapt to almost every environmental niche on earth. A network of interactions among diverse types of molecules including DNA, RNA, proteins and metabolites, is utilised by the bacteria to achieve regulation of gene expression. In bacteria, the principal function of regulatory networks is to control the response to environmental changes, for example nutritional status and environmental stress. A complex organization of networks permits the microorganism to coordinate and integrate multiple environmental signals.
One example stress is when the environment suddenly becomes poor of nutrients. This triggers a complex adaptation process in bacteria, such as E. coli. After this environmental change, thousands of genes change expression level. However, these changes are predictable from the topology and logic of the gene network that is reported in RegulonDB. Specifically, on average, the response strength of a gene was predictable from the difference between the numbers of activating and repressing input transcription factors of that gene. | 1 | Applied and Interdisciplinary Chemistry |
R-454B is not the only blend of R-32 and R-1234yf to be proposed as a refrigerant. Other blends include R-454A (35 percent R-32, 65 percent R-1234yf) and R-454C (21.5 percent R-32, 78.5 percent R1234yf). There are also several blends that include a third component. | 1 | Applied and Interdisciplinary Chemistry |
#Curves in the Ellingham diagrams for the formation of metallic oxides are basically straight lines with a positive slope. The slope is proportional to ΔS, which is approximately constant with temperature.
#The lower the position of a metal's line in the Ellingham diagram, the greater is the stability of its oxide. For example, the line for Al (oxidation of aluminium) is found to be below that for Fe (formation of ) meaning that aluminium oxide is more stable than iron(III) oxide.
#Stability of metallic oxides decreases with increase in temperature. Highly unstable oxides like and HgO easily undergo thermal decomposition.
#The formation free energy of carbon dioxide () is almost independent of temperature, while that of carbon monoxide (CO) has negative slope and crosses the line near 700 °C. According to the Boudouard reaction, carbon monoxide is the dominant oxide of carbon at higher temperatures (above about 700 °C), and the higher the temperature (above 700 °C) the more effective a reductant (reducing agent) carbon is.
#If the curves for two metals at a given temperature are compared, the metal with the lower Gibbs free energy of oxidation on the diagram will reduce the oxide with the higher Gibbs free energy of formation. For example, metallic aluminium can reduce iron oxide to metallic iron, the aluminium itself being oxidized to aluminium oxide. (This reaction is employed in thermite.)
#The greater the gap between any two lines, the greater the effectiveness of the reducing agent corresponding to the lower line.
#The intersection of two lines implies an oxidation-reduction equilibrium. Reduction using a given reductant is possible at temperatures above the intersection point where the ΔG line of that reductant is lower on the diagram than that of the metallic oxide to be reduced. At the point of intersection the free energy change for the reaction is zero, below this temperature it is positive and the metallic oxide is stable in the presence of the reductant, while above the point of intersection the Gibbs energy is negative and the oxide can be reduced. | 1 | Applied and Interdisciplinary Chemistry |
Austenitization means to heat the iron, iron-based metal, or steel to a temperature at which it changes crystal structure from ferrite to austenite. The more-open structure of the austenite is then able to absorb carbon from the iron-carbides in carbon steel. An incomplete initial austenitization can leave undissolved carbides in the matrix.
For some iron metals, iron-based metals, and steels, the presence of carbides may occur during the austenitization step. The term commonly used for this is two-phase austenitization. | 1 | Applied and Interdisciplinary Chemistry |
The non-enzymatic glycosylation is also known as glycation or non-enzymatic glycation. It is a spontaneous reaction and a type of post-translational modification of proteins meaning it alters their structure and biological activity. It is the covalent attachment between the carbonil group of a reducing sugar (mainly glucose and fructose) and the amino acid side chain of the protein. In this process the intervention of an enzyme is not needed. It takes place across and close to the water channels and the protruding tubules.
At first, the reaction forms temporary molecules which later undergo different reactions (Amadori rearrangements, Schiff base reactions, Maillard reactions, crosslinkings...) and form permanent residues known as Advanced Glycation end-products (AGEs).
AGEs accumulate in long-lived extracellular proteins such as collagen which is the most glycated and structurally abundant protein, especially in humans. Also, some studies have shown lysine may trigger spontaneous non-enzymatic glycosylation. | 0 | Theoretical and Fundamental Chemistry |
Before a 2007 report by Alber and coworkers, crotonyl-coA carboxylases and reductases (CCRs) were known for reducing crotonyl-coA to butyryl-coA. A report by Alber and coworkers concluded that a specific CCR homolog was able to reduce crotonyl-coA to (2S)-ethyl malonyl-coA which was a favorable reaction. The specific CCR homolog came from the bacterium Rhodobacter sphaeroides. | 1 | Applied and Interdisciplinary Chemistry |
The Freundlich adsorption isotherm is mathematically expressed as
In Freundlichs notation (used for his experiments dealing with the adsorption of organic acids on coal in aqueous solutions), signifies the ratio between the adsorbed mass or adsorbate and the mass of the adsorbent , which in Freundlichs studies was coal. In the figure above, the x-axis represents , which denotes the equilibrium concentration of the adsorbate within the solvent.
Freundlich's numerical analysis of the three organic acids for the parameters and according to equation
were:
Freundlich's experimental data can also be used in a contemporary computer based fit. These values are added to appreciate the numerical work done in 1907.
△ K and △ n values are the error bars of the computer based fit. The K and n values itself are used to calculate the dotted lines in the figure.
Equation can also be written as
Sometimes also this notation for experiments in the gas phase can be found:
: = mass of adsorbate
: = mass of adsorbent
: = equilibrium pressure of the gaseous adsorbate in case of experiments made in the gas phase (gas/solid interaction with gaseous species/adsorbed species)
and are constants for a given adsorbate and adsorbent at a given temperature (from there, the term isotherm needed to avoid significant gas pressure fluctuations due to uncontrolled temperature variations in the case of adsorption experiments of a gas onto a solid phase).
: = distribution coefficient
: = correction factor
At high pressure , hence extent of adsorption becomes independent of pressure.
The Freundlich equation is unique; consequently, if the data fit the equation, it is only likely, but not proved, that the surface is heterogeneous. The heterogeneity of the surface can be confirmed with calorimetry. Homogeneous surfaces (or heterogeneous surfaces that exhibit homogeneous adsorption (single site)) have a constant of adsorption. On the other hand, heterogeneous adsorption (multi-site) have a variable of adsorption depending on the percent of sites occupied. When the adsorbate pressure in the gas phase (or the concentration in solution) is low, high-energy sites will be occupied first. As the pressure in the gas phase (or the concentration in solution) increases, the low-energy sites will then be occupied resulting in a weaker of adsorption. | 0 | Theoretical and Fundamental Chemistry |
There are two types of free-radical photoinitators: A two component system where the radical is generated through abstraction of a hydrogen atom from a donor compound (also called co-initiator), and a one-component system where two radicals are generated by cleavage. Examples of each type of free-radical photoinitiator is shown below.
Benzophenone, xanthones, and quinones are examples of abstraction type photoinitiators, with common donor compounds being aliphatic amines. The resulting R• species from the donor compound becomes the initiator for the free radical polymerization process, while the radical resulting from the starting photoinitiator (benzophenone in the example shown above) is typically unreactive.
Benzoin ethers, Acetophenones, Benzoyl Oximes, and Acylphosphines are some examples of cleavage-type photoinitiators. Cleavage readily occurs for the species, giving two radicals upon absorption of light, and both radicals generated can typically initiate polymerization. Cleavage type photoinitiators do not require a co-initiator, such as aliphatic amines. This can be beneficial since amines are also effective chain transfer species. Chain-transfer processes reduce the chain length and ultimately the crosslink density of the resulting film. | 0 | Theoretical and Fundamental Chemistry |
In the regulation of heating and cooling, thermostats that operate over a wide range of temperatures are used. In these, one end of the bimetallic strip is mechanically fixed and attached to an electrical power source, while the other (moving) end carries an electrical contact. In adjustable thermostats another contact is positioned with a regulating knob or lever. The position so set controls the regulated temperature, called the set point.
Some thermostats use a mercury switch connected to both electrical leads. The angle of the entire mechanism is adjustable to control the set point of the thermostat.
Depending upon the application, a higher temperature may open a contact (as in a heater control) or it may close a contact (as in a refrigerator or air conditioner).
The electrical contacts may control the power directly (as in a household iron) or indirectly, switching electrical power through a relay or the supply of natural gas or fuel oil through an electrically operated valve. In some natural gas heaters the power may be provided with a thermocouple that is heated by a pilot light (a small, continuously burning, flame). In devices without pilot lights for ignition (as in most modern gas clothes dryers and some natural gas heaters and decorative fireplaces) the power for the contacts is provided by reduced household electrical power that operates a relay controlling an electronic ignitor, either a resistance heater or an electrically powered spark generating device. | 1 | Applied and Interdisciplinary Chemistry |
These processes involve high-temperature blending of iron ore and coal powder, with a little limestone to reduce the acidity of the ore. Processes such as Carl Wilhelm Siemens', based on the use of a short drum, first appeared at the end of the 19th century. The tool used then evolved into a long tubular rotary kiln, inspired by those used in cement works, as in the Basset process, developed in the 1930s.
A process of historic importance is the Krupp-Renn. Developed in the 1930s, there were as many as 38 furnaces in 1945 which, although they only had a capacity of 1 Mt/year at the time, were installed all over the world. This process was improved and inspired the German Krupp-CODIR furnaces and the Japanese Kawasaki and Koho processes. Both Japanese processes integrate a pelletizing unit for steel by-products upstream of the rotary furnaces. Two units of each process were built between 1968 (Kawasaki) and 1975 (Koho).
The ACCAR process, developed in the late 1960s and used confidentially until 1987, uses a mixture of 80% coal and 20% oil or gas: the hydrocarbons, although more expensive, enrich the reducing gas with hydrogen. The German Krupp-CODIR process, operational since 1974, has had little more success: only three units have been commissioned. Finally, Indian steelmakers are behind the SIIL, Popurri, Jindal, TDR and OSIL processes, which are simply variants developed to meet specific technical and economic constraints.
Other processes, built on the same principle, failed to develop, such as the Strategic-Udy, consisting of a single plant commissioned in 1963 and shut down in 1964.
The SL/RN process, developed in 1964, dominated coal-fired processes in 2013. In 1997, it accounted for 45% of pre-reduced coal production. In 2012, however, production capacity for this process had fallen to just 1.8 Mt/year, out of a total of 17.06 Mt attributed to coal-fired processes. | 1 | Applied and Interdisciplinary Chemistry |
Lamy was born in the commune of Ney in the department of Jura, France in 1820. He studied at the École Normale Supérieure, Paris. After he graduated from University in 1842 he became a teacher at Lille then at Limoges and again in Lille. In 1851 he received his Ph.D. In 1854 he became a professor at the faculty of sciences of Lille (Université Lille Nord de France). He taught at École des arts industriels et des mines (École centrale de Lille). In 1866 he changed to the École Centrale des Arts et Manufactures (École centrale de Paris). Lamy died in 1878. | 1 | Applied and Interdisciplinary Chemistry |
Researchers at the Center for Exploitation of Solar Energy at the University of Copenhagen Department of Chemistry are studying the photochromic dihydroazulene–vinylheptafulvene system as a method to harvest and store solar energy. | 0 | Theoretical and Fundamental Chemistry |
Finally, favorable economics can be achieved by using the purged material from the calcium looping cycle in cement production. The raw feed for cement production includes ~ 85 wt% limestone with the remaining material consisting of clay and additives (e.g. SiO, AlO etc.). The first step in the process involves calcinating limestone to produce CaO, which is then mixed with other materials in a kiln to produce clinker.
Using purged material from a Ca-looping system would reduce the raw material costs for cement production. Waste CaO and ash can be used in place of CaCO (the main constituent cement feed). The ash could also fulfill the aluminosilicate requirements otherwise supplied by additives. Since over 60% of the energy used in cement production goes into heat input for the precalciner, this integration with Ca-looping and the consequent reduced need for a calcination step, could lead to substantial energy savings (EU, 2001). However, there are problems with using the waste CaO in cement manufacture. If the technology is applied on a large scale, the purge rate of CaO should be optimized to minimize waste. | 1 | Applied and Interdisciplinary Chemistry |
The method is, to a large degree, nonintrusive. The added tracers (if they are properly chosen) generally cause negligible distortion of the fluid flow.
Optical measurement avoids the need for Pitot tubes, hotwire anemometers or other intrusive Flow measurement probes. The method is capable of measuring an entire two-dimensional cross section (geometry) of the flow field simultaneously.
High speed data processing allows the generation of large numbers of image pairs which, on a personal computer may be analysed in real time or at a later time, and a high quantity of near-continuous information may be gained.
Sub pixel displacement values allow a high degree of accuracy, since each vector is the statistical average for many particles within a particular tile. Displacement can typically be accurate down to 10% of one pixel on the image plane. | 1 | Applied and Interdisciplinary Chemistry |
In quantum mechanics, an absorption band is a range of wavelengths, frequencies or energies in the electromagnetic spectrum that are characteristic of a particular transition from initial to final state in a substance.
According to quantum mechanics, atoms and molecules can only hold certain defined quantities of energy, or exist in specific states. When such quanta of electromagnetic radiation are emitted or absorbed by an atom or molecule, energy of the radiation changes the state of the atom or molecule from an initial state to a final state. | 0 | Theoretical and Fundamental Chemistry |
The GLD-2 protein together with 136 proteins more, is involved in the molecular process of hematopoietic progenitor cell differentiation, in the human proteome. This is the process in which precursor cell type acquires the specialized features of a hematopoietic progenitor cell, a kind of cell types including myeloid progenitor cells and lymphoid progenitor cells. | 1 | Applied and Interdisciplinary Chemistry |
The Proterozoic is the transition era between anoxic and oxygenated oceans. The classic model is that the end of the Banded iron formations (BIFs) was due to the injection of oxygen into the deep ocean, an approximately 0.6 billion year lag behind the Great Oxygenation Event. Canfield, however, argued that anoxia lasted much longer, and the end of the banded iron formations was due to the introduction of sulfide. Supporting Canfield's original hypothesis, 1.84 billion year old sedimentary records have been found in the Animike group in Canada that exhibit close to full pyritization on top of the last of the banded iron formations, showing evidence of a transition to euxinic conditions in that basin. In order for full pyritization to happen, nearly all of the sulfate in the water was reduced to sulfide, which stripped the iron from the water, forming pyrite. Because this basin was open to the ocean, deep euxinia was interpreted as being a widespread phenomena. This euxinia is hypothesized to have lasted until about 0.8 billion years ago, making basin bottom euxinia a potentially widespread feature throughout the Boring Billion.
Further evidence for euxinia was discovered in the McArthur Basin in Australia, where similar iron chemistry was found. The degree of pyritization and the δS were both high, supporting the presence of anoxia and sulfide, as well as the depletion of sulfate. A different study found biomarkers for green sulfur bacteria and purple sulfur bacteria in the same area, providing further evidence for the reduction of sulfate to hydrogen sulfide.
Molybdenum isotopes have been used to examine the distribution of euxinia in the Proterozoic eon, and suggest that perhaps euxinia was not as widespread as Canfield initially postulated. Bottom waters may have been more widely suboxic than anoxic, and there could have been negative feedback between euxinia and the high levels of surface primary production needed to sustain euxinic conditions. Further work has suggested that from 700 million years ago (late Proterozoic) and onward, the deep oceans may have actually been anoxic and iron rich with conditions similar to those during the formation of BIFs. | 0 | Theoretical and Fundamental Chemistry |
Golden rain demonstration is made by combining two colorless solutions, potassium iodide solution and Lead(II) nitrate solution at room temperature to form yellow precipitate. During the chemical reaction, golden particles gently drop from the top of Erlenmeyer flask to the bottom, similar to watching the rain through a window. The golden rain chemical reaction demonstrates the formation of a solid precipitate. The golden rain experiment involves two soluble ionic compounds, potassium iodide (KI) and lead(II) nitrate (Pb(NO)). They are initially dissolved in separate water solutions, which are each colorless. When mixed, as the lead from one solution and the iodide from the other combine to form lead(II) iodide (PbI), which is insoluble at low temperature and has a bright golden-yellow color. Although this is a reaction solely of the dissociated ions in solution, it is sometimes referred to as a double displacement reaction:
:Pb(NO) + 2 KI → 2 KNO + PbI
At higher temperature, this substance easily re-dissolves by dissociation to its colorless ions. The actual change (net ionic equation) is thus: | 1 | Applied and Interdisciplinary Chemistry |
Patina ( or ) is a thin layer that variously forms on the surface of copper, brass, bronze, and similar metals and metal alloys (tarnish produced by oxidation or other chemical processes), or certain stones and wooden furniture (sheen produced by age, wear, and polishing), or any similar acquired change of a surface through age and exposure.
Additionally, the term is used to describe the aging of high-quality leather. The patinas on leather goods are unique to the type of leather, frequency of use, and exposure.
Patinas can provide a protective covering to materials that would otherwise be damaged by corrosion or weathering. They may also be aesthetically appealing. | 1 | Applied and Interdisciplinary Chemistry |
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