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Lipofuscin appears to be the product of the oxidation of unsaturated fatty acids and may be symptomatic of membrane damage, or damage to mitochondria and lysosomes. Aside from a large lipid content, lipofuscin is known to contain sugars and metals, including mercury, aluminium, iron, copper and zinc. Lipofuscin is also accepted as consisting of oxidized proteins (30–70%) as well as lipids (20–50%). It is a type of lipochrome and is specifically arranged around the nucleus.
The accumulation of lipofuscin-like material may be the result of an imbalance between formation and disposal mechanisms. Such accumulation can be induced in rats by administering a protease inhibitor (leupeptin); after a period of three months, the levels of the lipofuscin-like material return to normal, indicating the action of a significant disposal mechanism. However, this result is controversial, as it is questionable if the leupeptin-induced material is true lipofuscin. There exists evidence that "true lipofuscin" is not degradable in vitro; whether this holds in vivo over longer time periods is not clear.
The ABCR -/- knockout mouse has delayed dark adaptation but normal final rod threshold relative to controls. Bleaching the retina with strong light leads to formation of toxic cationic bis-pyridinium salt, N-retinylidene-N-retinyl-ethanolamine (A2E), which causes dry and wet age-related macular degeneration. From this experiment, it was concluded that ABCR has a significant role in preventing formation of A2E in extracellular photoreceptor surfaces during bleach recovery. | 1 | Applied and Interdisciplinary Chemistry |
Paula L. Diaconescu is a Romanian-American chemistry professor at the University of California, Los Angeles. She is known for her research on the synthesis of redox active transition metal complexes, the synthesis of lanthanide complexes, metal-induced small molecule activation, and polymerization reactions. She is a fellow of the American Association for the Advancement of Science. | 0 | Theoretical and Fundamental Chemistry |
There are grating/prism configurations that offer different tradeoffs between simplicity and spectral accuracy.
* Czerny–Turner (discussed below)
* Paschen-Runge
* Eagle
* Wadsworth
* Ebert-Fasti
* Littrow
* Pfund
In the common Czerny–Turner design, the broad-band illumination source (A) is aimed at an entrance slit (B). The amount of light energy available for use depends on the intensity of the source in the space defined by the slit (width × height) and the acceptance angle of the optical system. The slit is placed at the effective focus of a curved mirror (the collimator, C) so that the light from the slit reflected from the mirror is collimated (focused at infinity). The collimated light is diffracted from the grating (D) and then is collected by another mirror (E), which refocuses the light, now dispersed, on the exit slit (F). In a prism monochromator, a reflective Littrow prism takes the place of the diffraction grating, in which case the light is refracted by the prism.
At the exit slit, the colors of the light are spread out (in the visible this shows the colors of the rainbow). Because each color arrives at a separate point in the exit-slit plane, there are a series of images of the entrance slit focused on the plane. Because the entrance slit is finite in width, parts of nearby images overlap. The light leaving the exit slit (F) contains the entire image of the entrance slit of the selected color plus parts of the entrance slit images of nearby colors. A rotation of the dispersing element causes the band of colors to move relative to the exit slit, so that the desired entrance slit image is centered on the exit slit. The range of colors leaving the exit slit is a function of the width of the slits. The entrance and exit slit widths are adjusted together. | 0 | Theoretical and Fundamental Chemistry |
In physical chemistry, supersaturation occurs with a solution when the concentration of a solute exceeds the concentration specified by the value of solubility at equilibrium. Most commonly the term is applied to a solution of a solid in a liquid, but it can also be applied to liquids and gases dissolved in a liquid. A supersaturated solution is in a metastable state; it may return to equilibrium by separation of the excess of solute from the solution, by dilution of the solution by adding solvent, or by increasing the solubility of the solute in the solvent. | 0 | Theoretical and Fundamental Chemistry |
The enthalpy of a chemical system is essentially its energy. The enthalpy change ΔH for a reaction is equal to the heat q transferred out of (or into) a closed system at constant pressure without in- or output of electrical energy. Heat production or absorption in a chemical reaction is measured using calorimetry, e.g. with a bomb calorimeter. One common laboratory instrument is the reaction calorimeter, where the heat flow from or into the reaction vessel is monitored. The heat release and corresponding energy change, Δ, of a combustion reaction can be measured particularly accurately.
The measured heat energy released in an exothermic reaction is converted to ΔH⚬ in Joule per mole (formerly cal/mol). The standard enthalpy change ΔH⚬ is essentially the enthalpy change when the stoichiometric coefficients in the reaction are considered as the amounts of reactants and products (in mole); usually, the initial and final temperature is assumed to be 25 °C. For gas-phase reactions, ΔH⚬ values are related to bond energies to a good approximation by:
:Δ⚬ = total bond energy of reactants − total bond energy of products
In an exothermic reaction, by definition, the enthalpy change has a negative value:
:Δ = H - H < 0
where a larger value (the higher energy of the reactants) is subtracted from a smaller value (the lower energy of the products). For example, when hydrogen burns:
:2H (g) + O (g) → 2HO (g)
:Δ⚬ = −483.6 kJ/mol | 0 | Theoretical and Fundamental Chemistry |
Odors emitted by sewage treatment are typically an indication of an anaerobic or septic condition. Early stages of processing will tend to produce foul-smelling gases, with hydrogen sulfide being most common in generating complaints. Large process plants in urban areas will often treat the odors with carbon reactors, a contact media with bio-slimes, small doses of chlorine, or circulating fluids to biologically capture and metabolize the noxious gases. Other methods of odor control exist, including addition of iron salts, hydrogen peroxide, calcium nitrate, etc. to manage hydrogen sulfide levels. | 1 | Applied and Interdisciplinary Chemistry |
Atomic physics primarily considers atoms in isolation. Atomic models will consist of a single nucleus that may be surrounded by one or more bound electrons. It is not concerned with the formation of molecules (although much of the physics is identical), nor does it examine atoms in a solid state as condensed matter. It is concerned with processes such as ionization and excitation by photons or collisions with atomic particles.
While modelling atoms in isolation may not seem realistic, if one considers atoms in a gas or plasma then the time-scales for atom-atom interactions are huge in comparison to the atomic processes that are generally considered. This means that the individual atoms can be treated as if each were in isolation, as the vast majority of the time they are. By this consideration, atomic physics provides the underlying theory in plasma physics and atmospheric physics, even though both deal with very large numbers of atoms. | 0 | Theoretical and Fundamental Chemistry |
In 1924, Hahn was elected to full membership of the Prussian Academy of Sciences in Berlin, by a vote of thirty white balls to two black. While still remaining the head of his own department, he became Deputy Director of the Kaiser Wilhelm Institute for Chemistry in 1924, and succeeded Alfred Stock as the director in 1928. Meitner became the director of the Physical Radioactivity Division, while Hahn headed the Chemical Radioactivity Division. In the early 1920s, he created a new line of research. Using the "emanation method", which he had recently developed, and the "emanation ability", he founded what became known as "applied radiochemistry" for the researching of general chemical and physical-chemical questions. In 1936 Cornell University Press published a book in English (and later in Russian) titled Applied Radiochemistry, which contained the lectures given by Hahn when he was a visiting professor at Cornell University in Ithaca, New York, in 1933. This important publication had a major influence on almost all nuclear chemists and physicists in the United States, the United Kingdom, France, and the Soviet Union during the 1930s and 1940s.
In 1966, Glenn T. Seaborg, co-discoverer of many transuranium elements, wrote about this book as follows:
Hahn is referred to as the father of nuclear chemistry, which emerged from applied radiochemistry. | 0 | Theoretical and Fundamental Chemistry |
Generally pyridinium photoinitiators are N-substituted pyridine derivatives, with a positive charge placed on the nitrogen. The counter ion is in most cases a non-nucleophilic anion. Upon radiation, homolytic bond cleavage takes place generating a pyridinium cationic radical and a neutral free radical. In most cases, a hydrogen atom is abstracted from the oligomer by the pyridinium radical. The free radical generated from the hydrogen abstraction is then terminated by the free radical in solution. This results in a strong pyridinium acid that can initiate polymerization. | 0 | Theoretical and Fundamental Chemistry |
TALEN has been used to efficiently modify plant genomes, creating economically important food crops with favorable nutritional qualities. They have also been harnessed to develop tools for the production of biofuels. In addition, it has been used to engineer stably modified human embryonic stem cell and induced pluripotent stem cell (IPSCs) clones and human erythroid cell lines, to generate knockout C. elegans, knockout rats, knockout mice, and knockout zebrafish. Moreover, the method can be used to generate knockin organisms. Wu et al.obtained a Sp110 knockin cattle using Talen nickases to induce increased resistance of tuberculosis. This approach has also been used to generate knockin rats by TALEN mRNA microinjection in one-cell embryos.
TALEN has also been utilized experimentally to correct the genetic errors that underlie disease. For example, it has been used in vitro to correct the genetic defects that cause disorders such as sickle cell disease, xeroderma pigmentosum, and epidermolysis bullosa. Recently, it was shown that TALEN can be used as tools to harness the immune system to fight cancers; TALEN-mediated targeting can generate T cells that are resistant to chemotherapeutic drugs and show anti-tumor activity.
In theory, the genome-wide specificity of engineered TALEN fusions allows for correction of errors at individual genetic loci via homology-directed repair from a correct exogenous template. In reality, however, the in situ application of TALEN is currently limited by the lack of an efficient delivery mechanism, unknown immunogenic factors, and uncertainty in the specificity of TALEN binding.
Another emerging application of TALEN is its ability to combine with other genome engineering tools, such as meganucleases. The DNA binding region of a TAL effector can be combined with the cleavage domain of a meganuclease to create a hybrid architecture combining the ease of engineering and highly specific DNA binding activity of a TAL effector with the low site frequency and specificity of a meganuclease.
In comparison to other genome editing techniques, TALEN falls in the middle in terms of difficulty and cost. Unlike ZFNs, TALEN recognizes single nucleotides. It's far more straightforward to engineer interactions between TALEN DNA binding domains and their target nucleotides than it is to create interactions with ZFNs and their target nucleotide triplets. On the other hand, CRISPR relies on ribonucleotide complex formation instead of protein/DNA recognition. gRNAs have occasionally limitations regarding feasibility due to lack of PAM sites in the target sequence and even though they can be cheaply produced, the current development lead to a remarkable decrease of cost for TALENs, so that they are in a similar price and time range like CRISPR based genome editing. | 1 | Applied and Interdisciplinary Chemistry |
Sigurd Hofmann (15 February 1944 – 17 June 2022) was a German physicist known for his work on superheavy elements. | 1 | Applied and Interdisciplinary Chemistry |
Bruce R. Kowalski (March 1942 – December 2012) was an American professor of analytical chemistry who is acknowledged by the world-wide scientific community to be one of the founders of the field of chemometrics. He was the founding editor of Journal of Chemometrics, and the founding director of the Center for Process Analytical Chemistry at University of Washington in Seattle. Kowalski and
Svante Wold formed the Chemometrics Society, which would later become the International Chemometrics Society. | 0 | Theoretical and Fundamental Chemistry |
Glycolysis is a metabolic pathway that takes place in the cytosol of cells in all living organisms. Glycolysis can be literally translated as "sugar splitting", and occurs regardless of oxygen's presence or absence. In aerobic conditions, the process converts one molecule of glucose into two molecules of pyruvate (pyruvic acid), generating energy in the form of two net molecules of ATP. Four molecules of ATP per glucose are actually produced, but two are consumed as part of the preparatory phase. The initial phosphorylation of glucose is required to increase the reactivity (decrease its stability) in order for the molecule to be cleaved into two pyruvate molecules by the enzyme aldolase. During the pay-off phase of glycolysis, four phosphate groups are transferred to four ADP by substrate-level phosphorylation to make four ATP, and two NADH are produced when the pyruvate is oxidized. The overall reaction can be expressed this way:
:Glucose + 2 NAD + 2 P + 2 ADP → 2 pyruvate + 2 H + 2 NADH + 2 ATP + 2 H + 2 HO + energy
Starting with glucose, 1 ATP is used to donate a phosphate to glucose to produce glucose 6-phosphate. Glycogen can be converted into glucose 6-phosphate as well with the help of glycogen phosphorylase. During energy metabolism, glucose 6-phosphate becomes fructose 6-phosphate. An additional ATP is used to phosphorylate fructose 6-phosphate into fructose 1,6-bisphosphate by the help of phosphofructokinase. Fructose 1,6-biphosphate then splits into two phosphorylated molecules with three carbon chains which later degrades into pyruvate. | 1 | Applied and Interdisciplinary Chemistry |
It is carried out in order to:
* Manage the inspection of piping.
* Identifying piping systems/circuits and assign failure modes.
* Capture any changes due to those upgrades or design creep.
* Ensure that circuits are identified to indicate inspection points as well as facilitate the implementation of various inspection techniques.
* Identify potential damage mechanisms and their locations.
Typically, this is performed at the outset of any Mechanical Integrity program i.e. as the facility is built, modified and operated throughout its life.
General Requirements of Circuitization:
* Use an experienced corrosion/materials engineer to define systems in each unit
* Define corrosion circuits within each system based on materials of construction, operating conditions and active damage mechanisms
* Circuit identification and naming convention is used for both API RBI and IDMS programs to provide linking and sharing inspection data
* Circuit corrosion rates are used in API RBI to calculate circuit risk
* Determine the circuit and component next inspection date and inspection effectiveness, including detailed inspection plan
* Review or Placement of CML/TML (Condition Monitoring Locations/Thickness Monitoring Locations) recommended by corrosion/materials engineer
* CML/TML installed and documented on piping isometric drawings | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, the Morton number (Mo) is a dimensionless number used together with the Eötvös number or Bond number to characterize the shape of bubbles or drops moving in a surrounding fluid or continuous phase, c.
It is named after Rose Morton, who described it with W. L. Haberman in 1953. | 1 | Applied and Interdisciplinary Chemistry |
Selenols are organic compounds that contain the functional group with the connectivity . Selenols are sometimes also called selenomercaptans and selenothiols. Selenols are one of the principal classes of organoselenium compounds. A well-known selenol is the amino acid selenocysteine. | 0 | Theoretical and Fundamental Chemistry |
Larive received her Bachelor of Science from South Dakota State University in 1980, and her Master of Science degree from Purdue University in 1982. In 1992, she was awarded a Ph.D. in chemistry from the University of California, Riverside after working under the direction of Dallas L. Rabenstein. | 0 | Theoretical and Fundamental Chemistry |
PAVA is approved for police and prison service use in the United Kingdom. British police forces had traditionally used CS gas spray, but with the more widespread carriage of tasers, PAVA has now entirely replaced its predecessor due to its non-flammable nature.
Both PAVA and CS are prohibited under Section 5 of the Firearms Act 1968 as a "weapon of whatever description designed or adapted for the discharge of any noxious liquid, gas or other thing", meaning that it is unlawful for a member of the public to possess them. Police officers, prison officers and other servants of the Crown have lawful exemption to possess and use PAVA. They are therefore exempt from prosecution under this act and section. | 1 | Applied and Interdisciplinary Chemistry |
Properties of phycobiliproteins, such as their natural antioxidant, anti-inflammatory, food colourant, strong pigment and anti-aging activities, have given them considerable potential for use in food, cosmetics and medicinal applications. They have also proven to be therapeutic in treating diseases such as Alzheimers disease and cancer. Given their large range of applications and potential uses, researchers have been trying to find and develop ways to produce and purify phycobiliproteins to meet the growing demand for them. One such phycobiliprotein is C-phycocyanin (C-PC), which is found in spirulina. A limiting factor of C-PCs usage in these applications is its protein stability, given that in its natural form, C-PC is highly sensitive to light and heat when in aqueous solution, due to its photosensitive phycocyanobilin (PCB) chromophore, which also makes it prone to free-radical oxidation. Like other natural food colourants, C-PC is also sensitive to acidic conditions and oxidant exposure. This has prompted studies to develop methods of stabilising C-PC/PCB and expand their applications to other food systems.
More details on the applications of phycocyanin in food and medicine can be found here. | 1 | Applied and Interdisciplinary Chemistry |
The phosphorus atom in phosphines has a formal oxidation state −3 (σλ) and are the phosphorus analogues of amines. Like amines, phosphines have a trigonal pyramidal molecular geometry although often with smaller C-E-C angles (E = N, P), at least in the absence of steric effects. The C-P-C bond angle is 98.6° for trimethylphosphine increasing to 109.7° when the methyl groups are replaced by tert-butyl groups. When used as ligands, the steric bulk of tertiary phosphines is evaluated by their cone angle. The barrier to pyramidal inversion is also much higher than nitrogen inversion to occur, and therefore phosphines with three different substituents can be resolved into thermally stable optical isomers. Phosphines are often less basic than corresponding amines, for instance the phosphonium ion itself has a pK of −14 compared to 9.21 for the ammonium ion; trimethylphosphonium has a pK of 8.65 compared to 9.76 for trimethylammonium. However, triphenylphosphine (pK 2.73) is more basic than triphenylamine (pK −5), mainly because the lone pair of the nitrogen in NPh is partially delocalized into the three phenyl rings. Whereas the lone pair on nitrogen is delocalized in pyrrole, the lone pair on phosphorus atom in the phosphorus equivalent of pyrrole (phosphole) is not. The reactivity of phosphines matches that of amines with regard to nucleophilicity in the formation of phosphonium salts with the general structure PRX. This property is used in the Appel reaction for converting alcohols to alkyl halides. Phosphines are easily oxidized to the corresponding phosphine oxides, whereas amine oxides are less readily generated. In part for this reason, phosphines are very rarely encountered in nature. | 0 | Theoretical and Fundamental Chemistry |
In general terms, chemotaxis is a biological process where living entities, such as cells or organisms, detect, maneuver, and react in response to a chemical signal in their environment. Such a phenomenon is critical for many biological processes, including but not limited to wound healing, detection of food, and avoidance of many toxins. Chemotaxis also plays an essential role in serval diseases, such as tumor metastasis, the recruitment of T-lymphocytes during inflammation, and HIV-1 entry into T cells. At the core of chemotaxis are specialized sensory cells called chemoreceptors. These cells allow an organism to detect chemical molecules within its environment and respond accordingly. Such chemical molecules are either known as chemoattractants or chemorepellents, which play a crucial role in attracting or repelling the organism towards or away from the source of the chemical signal, respectively. Thus, with this natural process of chemotaxis in mind, researchers have sought to apply the same phenomenon to targeted drug delivery, a medical technique aimed at delivering drugs to a specific cell, tissue, or organ within the body while minimizing its disruptive effects on healthy tissue. By using both chemotaxes to help guide the drug delivery process, researchers aim to reduce toxicity by avoiding healthy tissues, improve drug efficacy by focusing only on the intended site, and decrease drug dosage by delivering the directly rather than throughout the whole body. | 1 | Applied and Interdisciplinary Chemistry |
Natural ventilation is a key factor in reducing the spread of airborne illnesses such as tuberculosis, the common cold, influenza, meningitis or COVID-19. Opening doors and windows are good ways to maximize natural ventilation, which would make the risk of airborne contagion much lower than with costly and maintenance-requiring mechanical systems. Old-fashioned clinical areas with high ceilings and large windows provide the greatest protection. Natural ventilation costs little and is maintenance free, and is particularly suited to limited-resource settings and tropical climates, where the burden of TB and institutional TB transmission is highest. In settings where respiratory isolation is difficult and climate permits, windows and doors should be opened to reduce the risk of airborne contagion. Natural ventilation requires little maintenance and is inexpensive.
Natural ventilation is not practical in much of the infrastructure because of climate. This means that the facilities need to have effective mechanical ventilation systems and or use Ceiling Level UV or FAR UV ventilation systems.
Ventilation is measured in terms of Air Changes Per Hour (ACH). As of 2023, the CDC recommends that all spaces have a minimum of 5 ACH. For hospital rooms with airborne contagions the CDC recommends a minimum of 12 ACH. The challenges in facility ventilation are public unawareness, ineffective government oversight, poor building codes that are based on comfort levels, poor system operations, poor maintenance, and lack of transparency.
Everyone assumes that everything is okay in terms of facility ventilation but that is not the case. The situation is similar to water pollution where unless someone actually assesses the situation, it is likely that there is a problem. The reality is that Heating,_ventilation,_and_air_conditioning rates have been dropping since the energy crisis in the 1970s and the banning of cigarette smoke in the 1980s and 1990s . Today the ventilation rates are dropping even further with the new challenge to reduce carbon footprints. The tradeoffs are reduced carbon footprint versus increased risk of respiratory infection because of insufficient ventilation to reasonably mitigate airborne infections. The research in this area is new as of 2023. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry a halohydrin (also a haloalcohol or β-halo alcohol) is a functional group in which a halogen and a hydroxyl are bonded to adjacent carbon atoms, which otherwise bear only hydrogen or hydrocarbyl groups (e.g. 2-chloroethanol, 3-chloropropane-1,2-diol). The term only applies to saturated motifs, as such compounds like 2-chlorophenol would not normally be considered halohydrins. Megatons of some chlorohydrins, e.g. propylene chlorohydrin, are produced annually as precursors to polymers.
Halohydrins may be categorized as chlorohydrins, bromohydrins, fluorohydrins or iodohydrins depending on the halogen present. | 0 | Theoretical and Fundamental Chemistry |
In the case of photochemical reactions, light provides the activation energy. Simplistically, light is one mechanism for providing the activation energy required for many reactions. If laser light is employed, it is possible to selectively excite a molecule so as to produce a desired electronic and vibrational state. Equally, the emission from a particular state may be selectively monitored, providing a measure of the population of that state. If the chemical system is at low pressure, this enables scientists to observe the energy distribution of the products of a chemical reaction before the differences in energy have been smeared out and averaged by repeated collisions.
The absorption of a photon by a reactant molecule may also permit a reaction to occur not just by bringing the molecule to the necessary activation energy, but also by changing the symmetry of the molecule's electronic configuration, enabling an otherwise-inaccessible reaction path, as described by the Woodward–Hoffmann selection rules. A [2+2] cycloaddition reaction is one example of a pericyclic reaction that can be analyzed using these rules or by the related frontier molecular orbital theory.
Some photochemical reactions are several orders of magnitude faster than thermal reactions; reactions as fast as 10 seconds and associated processes as fast as 10 seconds are often observed.
The photon can be absorbed directly by the reactant or by a photosensitizer, which absorbs the photon and transfers the energy to the reactant. The opposite process, when a photoexcited state is deactivated by a chemical reagent, is called quenching.
Most photochemical transformations occur through a series of simple steps known as primary photochemical processes. One common example of these processes is the excited state proton transfer. | 0 | Theoretical and Fundamental Chemistry |
Screening and disinfection facilities treat CSO without ever storing it. Called "flow-through" facilities, they use fine screens to remove solids and sanitary trash from the combined sewage. Flows are injected with sodium hypochlorite for disinfection and mixed as they travel through a series of fine screens to remove debris. The fine screens have openings that range in size from 4 to 6 mm, or a little less than a quarter inch. The flow is sent through the facility at a rate that provides enough time for the sodium hypochlorite to kill bacteria. All of the materials removed by the screens are then sent to the sewage treatment plant through the interceptor sewer. | 1 | Applied and Interdisciplinary Chemistry |
A Soxhlet extractor is a piece of laboratory apparatus invented in 1879 by Franz von Soxhlet. It was originally designed for the extraction of a lipid from a solid material. Typically, Soxhlet extraction is used when the desired compound has a limited solubility in a solvent, and the impurity is insoluble in that solvent. It allows for unmonitored and unmanaged operation while efficiently recycling a small amount of solvent to dissolve a larger amount of material. | 0 | Theoretical and Fundamental Chemistry |
N-Ethylmaleimide (NEM) is an organic compound that is derived from maleic acid. It contains the amide functional group, but more importantly it is an alkene that is reactive toward thiols and is commonly used to modify cysteine residues in proteins and peptides. | 1 | Applied and Interdisciplinary Chemistry |
Soluforce RTP is tested and acknowledged by the following organisations:
* DNV Certification D-2615 - Soluforce System 4" and 5" with in-line couplings and end fittings
* ASTM - WK11803
* API - RP 15S (oil field service)
* ISO/TS 18226:2006 (gas service)
* DVGW VP 642 (German gas service)
* NYSEARCH project by the Northeast Gas Association (USA) | 1 | Applied and Interdisciplinary Chemistry |
Shaw studied at the University of Manchester where he gained a BSc and a PhD. After three years in the Civil Service at the Torry Research Station in Aberdeen and five years at ICI he was appointed Lecturer in the Department of Inorganic and Structural Chemistry at the University of Leeds in 1962. He was promoted to Reader in 1966 and to a Personal Chair in 1971. He was made head of the university's department of Inorganic Chemistry in 1990 and Emeritus Professor upon his retirement in 1995.
Shaw was at various times a Visiting Professor at the University of Western Ontario, Carnegie Mellon University (1969), the American National University (1983) and the University of Auckland (1986). He was Lecturer at the Royal Society of Chemistry in 1987–88. | 0 | Theoretical and Fundamental Chemistry |
Carboranes and boranes adopt 3-dimensional cage (cluster) geometries in sharp contrast to typical organic compounds. Cages are compatible with sigma—delocalized bonding, whereas hydrocarbons are typically chains or rings.
Like for other electron-delocalized polyhedral clusters, the electronic structure of these cluster compounds can be described by the Wade–Mingos rules. Like the related boron hydrides, these clusters are polyhedra or fragments of polyhedra, and are similarly classified as closo-, nido-, arachno-, hypho-, hypercloso-, iso-, klado-, conjuncto- and megalo-, based on whether they represent a complete (closo-) polyhedron or a polyhedron that is missing one (nido-), two (arachno-), three (hypho-), or more vertices. Carboranes are a notable example of heteroboranes.
The essence, these rules emphasize delocalized, multi-centered bonding for B-B, C-C, and B-C interactions.
Structurally, they can be considered to be related to the icosahedral (I) Dodecaborate| via formal replacement of two of its fragments with CH. | 0 | Theoretical and Fundamental Chemistry |
The ribosome is a complex molecular machine that, in order to synthesize proteins during the translation process, has to decode mRNAs by pairing their codons with matching tRNAs. Decoding is a major determinant of fitness and requires accurate and fast selection of correct tRNAs among many similar competitors. One must have in mind that most binding events are by non-matching (“non-cognate”) tRNAs and the ribosome needs to reject those as fast as possible in order to vacate the binding site. At the same time, the ribosome should keep the matching tRNAs bound long enough to allow the protein synthesis process ensue. Despite the importance of tRNA decoding, it was unclear until recently whether the modern ribosome, and in particular its large conformational changes during decoding, are the outcome of adaptation to its task as a decoder or the result of other constraints. Recent study
derived the energy landscape that provides optimal discrimination between competing tRNA substrates, and thereby optimal tRNA decoding. The optimal landscape is a symmetric one (see image). The study shows that the measured landscape of the prokaryotic ribosome is indeed symmetric. This model suggests that conformational changes of the ribosome and tRNA during decoding are means to obtain such an optimal tRNA decoder. The fact that both homologous recombination and tRNA decoding utilize conformational proofreading suggests that this is a generic mechanism that may be utilized broadly by molecular recognition systems. | 1 | Applied and Interdisciplinary Chemistry |
The two orbital arrays in Figure 3 are just examples and do not correspond to real systems. In inspecting the Möbius one on the left, plus-minus overlaps are seen between orbital pairs 2-3, 3-4, 4-5, 5-6 and 6-1, corresponding to an odd number 5 as required by a Möbius system. Inspection of the Hückel one on the right, plus-minus overlaps are seen between orbital pairs 2-3, 3-4, 4-5, and 6-1, corresponding to an even number 4 as required by a Hückel system.
The plus-minus orientation of each orbital is arbitrary since these are just basis set orbitals and do not correspond to any molecular orbital. If any orbital were to change signs, two plus-minus overlaps are either removed or added and the parity (evenness or oddness) is not changed. One choice of signs leads to zero plus-minus overlaps for the Hückel array on the right. | 0 | Theoretical and Fundamental Chemistry |
The Brønsted–Lowry theory (also called proton theory of acids and bases) is an acid–base reaction theory which was first developed by Johannes Nicolaus Brønsted and Thomas Martin Lowry independently in 1923. The basic concept of this theory is that when an acid and a base react with each other, the acid forms its conjugate base, and the base forms its conjugate acid by exchange of a proton (the hydrogen cation, or H). This theory generalises the Arrhenius theory. | 0 | Theoretical and Fundamental Chemistry |
The outron is an intron-like sequence possessing similar characteristics such as the G+C content and a splice acceptor site that is the signal for trans-splicing. Such a trans-splice site is essentially defined as an acceptor (3) splice site without an upstream donor (5) splice site.
In eukaryotes such as euglenozoans, dinoflagellates, sponges, nematodes, cnidarians, ctenophores, flatworms, crustaceans, chaetognaths, rotifers, and tunicates, the length of spliced leader (SL) outrons range from 30 to 102 nucleotides (nt), with the SL exon length ranging from 16 to 51 nt, and the full SL RNA length ranging from 46 to 141 nt. | 1 | Applied and Interdisciplinary Chemistry |
Informations for this group of inhibitors are quite restricted. Azetidine-based DPP-4 inhibitors can roughly be grouped into three main subcategories: 2-cyanoazetidines, 3-fluoroazetidines, and 2-ketoazetidines. The most potent ketoazetidines and cyanoazetidines have large hydrophobic amino acid groups bound to the azetidine nitrogen and are active below 100nM. | 1 | Applied and Interdisciplinary Chemistry |
A plasmonic antenna-reactor photocatalyst is a photocatalyst that combines a catalyst with attached antenna that increases the catalyst's ability to absorb light, thereby increasing its efficiency.
A Silicon dioxide| catalyst combined with an Au light absorber accelerated hydrogen sulfide-to-hydrogen reactions. The process is an alternative to the conventional Claus process that operates at .
A Fe catalyst combined with a Cu light absorber can produce hydrogen from ammonia () at ambient temperature using visible light. Conventional Cu-Ru production operates at . | 0 | Theoretical and Fundamental Chemistry |
Molecular glue compounds are being explored for their potential in influencing protein interactions associated with neurodegenerative diseases such as Alzheimers and Parkinsons. By modulating these interactions, researchers aim to develop treatments that could slow or prevent the progression of these diseases. Additionally, the versatility of small-molecule molecular glue compounds in targeting various proteins implicated in disease mechanisms provides a valuable avenue for unraveling the complexities of neurodegenerative disorders. | 1 | Applied and Interdisciplinary Chemistry |
The Tattvartha Sutra has the largest number of Jaina bhashyas or commentaries in different Indian languages from the fifth century onward. There are over twenty-five commentaries and translations of Tattvartha Sutra, including those by:
Umasvati himself wrote a commentary on the text. The next oldest and the most famous commentary on the Tattvārthasūtra is Sarvārthasiddhi of Ācārya Pujyapada (sixth century CE). Sarvārthasiddhi along with Akalankas Rajavartika and Vijayanandas Slokavarttika (9th century) form the central texts of Digambara monastic students. | 1 | Applied and Interdisciplinary Chemistry |
FAM227B is a protein that in humans is encoded by FAM227B gene. FAM227B stands for family with sequence similarity 227 member B and encodes protein FAM227B of the same name. Its aliases include C15orf33, MGC57432 and FLJ23800. | 1 | Applied and Interdisciplinary Chemistry |
Isovaleryl-coenzyme A, also known as isovaleryl-CoA, is an intermediate in the metabolism of branched-chain amino acids. | 1 | Applied and Interdisciplinary Chemistry |
Remnants of L2 and L3 elements are found in the human genome. It is estimated that L2 and L3 elements were active ~200-300 million years ago. Due to the age of L2 elements found within therian genomes, they lack flanking target site duplications. The L2 (and L3) elements are in the same group as the CR1 clade, Jockey. | 1 | Applied and Interdisciplinary Chemistry |
Modafinil is contraindicated during pregnancy and 2 months before getting pregnant. Women who take modafinil should not become pregnant, and, additionally, should be aware that modafinil reduces effectiveness of hormonal contraceptives, increasing chances of getting pregnant. Modafinil therapy during pregnancy increases the risk of birth defects, such as with congenital torticollis, hypospadias, and congenital heart defects.
Modafinil is contraindicated for individuals with known hypersensitivity to either modafinil or armodafinil.
Modafinil is also contraindicated in certain cardiac conditions, including uncontrolled moderate to severe hypertension, arrhythmia, cor pulmonale, and in cases with signs of CNS stimulant-induced mitral valve prolapse or left ventricular hypertrophy. The package insert in the United States cautions about using modafinil in people with a documented medical history of left ventricular hypertrophy or those diagnosed with mitral valve prolapse who have previously exhibited symptoms associated with the mitral valve prolapse syndrome while undergoing treatment involving central nervous system stimulants. The reasons why modafinil is contraindicated in certain cardiac conditions are because modafinil affects the autonomic nervous system and, in particular, exerts significant effects on autonomic cardiovascular regulation, leading in some people to notable increases in heart rate and blood pressure. These substantial changes in the autonomic system warrant careful consideration when prescribing modafinil to people with pre-existing cardiovascular conditions. The increase in heart rate and blood pressure can worsen the symptoms of such pre-existing conditions as hypertension, arrhythmia, and cor pulmonale. These changes in the autonomic system induced by modafinil can increase the risk of heart attack, stroke, and heart failure. Modafinil can stimulate the release of norepinephrine and epinephrine, hormones that activate the sympathetic nervous system. This can cause vasoconstriction, which is the narrowing of blood vessels, and increase the heart's workload, which is not desired in people with pre-existing heart conditions. In particular, modafinil can worsen the consequences of mitral valve prolapse or left ventricular hypertrophy, which are structural abnormalities of the heart. These can affect the blood flow and oxygen delivery to the heart and other organs.
Modafinil is also contraindicated in people with congenital problems like galactose intolerance, lactase deficiency, or glucose-galactose malabsorption. | 0 | Theoretical and Fundamental Chemistry |
Hypotonia and Parkinsonism were present in two Turkish siblings, brother and sister. By using exome sequencing, which sequences a selective coding region of the genome, researchers have found a homozygous five-nucleotide deletion in the SPR gene which confirmed both siblings were homozygous. It is predicted that this mutation leads to premature translational termination. Translation is the biological process through which proteins are manufactured. The homozygous mutation of the SPR gene in these two siblings exhibiting early-onset Parkinsonism showcases that SPR gene mutations can vary in combinations of clinical symptoms and movement. These differences result in a wider spectrum for the disease phenotype and increases the genetic heterogeneity causing difficulties in diagnosing the disease. | 1 | Applied and Interdisciplinary Chemistry |
MHD reduces the overall production of hazardous fossil fuel wastes because it increases plant efficiency. In MHD coal plants, the patented commercial "Econoseed" process developed by the U.S. (see below) recycles potassium ionization seed from the fly ash captured by the stack-gas scrubber. However, this equipment is an additional expense. If molten metal is the armature fluid of an MHD generator, care must be taken with the coolant of the electromagnetics and channel. The alkali metals commonly used as MHD fluids react violently with water. Also, the chemical byproducts of heated, electrified alkali metals and channel ceramics may be poisonous and environmentally persistent. | 1 | Applied and Interdisciplinary Chemistry |
Amoxicillin is susceptible to degradation by β-lactamase-producing bacteria, which are resistant to most β-lactam antibiotics, such as penicillin. For this reason, it may be combined with clavulanic acid, a β-lactamase inhibitor. This drug combination is commonly called co-amoxiclav. | 0 | Theoretical and Fundamental Chemistry |
Levonorgestrel has been studied in combination with androgens such as testosterone and dihydrotestosterone as a hormonal contraceptive for men. | 0 | Theoretical and Fundamental Chemistry |
Platinum and palladium are precious metals generally found in ultramafic rocks. The source of platinum and palladium deposits is ultramafic rocks which have enough sulfur to form a sulfide mineral while the magma is still liquid. This sulfide mineral (usually pentlandite, pyrite, chalcopyrite, or pyrrhotite) gains platinum by mixing with the bulk of the magma because platinum is chalcophile and is concentrated in sulfides. Alternatively, platinum occurs in association with chromite either within the chromite mineral itself or within sulfides associated with it.
Sulfide phases only form in ultramafic magmas when the magma reaches sulfur saturation. This is generally thought to be nearly impossible by pure fractional crystallisation, so other processes are usually required in ore genesis models to explain sulfur saturation. These include contamination of the magma with crustal material, especially sulfur-rich wall-rocks or sediments; magma mixing; volatile gain or loss.
Often platinum is associated with nickel, copper, chromium, and cobalt deposits. | 0 | Theoretical and Fundamental Chemistry |
Sulfur from meteorites was determined in the early 1950s to be an adequate reference standard because it exhibited a small variability in isotopic ratios. It was also believed that because of their extraterrestrial provenances, meteors represented primordial terrestrial isotopic conditions. During a meeting of the National Science Foundation in April 1962, troilite from the Canyon Diablo meteorite found in Arizona, US, was established as the standard with which δS values (and other sulfur stable isotopic ratios) could be calculated. Known as Canyon Diablo Troilite (CDT), the standard was established as having a S:S ratio of 22.220 and was used for around three decades. In 1993, the International Atomic Energy Agency (IAEA) established a new standard, Vienna-CDT (VCDT), based on artificially prepared silver sulfide (IAEA-S-1) that was defined to have a δS value of −0.3‰. In 1994, the original CDT material was found not to be isotopically homogeneous, with internal variations as great as 0.4‰, confirming its unsuitability as a reference standard. | 0 | Theoretical and Fundamental Chemistry |
Secondary electrons are electrons generated as ionization products. They are called secondary because they are generated by other radiation (the primary radiation). This radiation can be in the form of ions, electrons, or photons with sufficiently high energy, i.e. exceeding the ionization potential. Photoelectrons can be considered an example of secondary electrons where the primary radiation are photons; in some discussions photoelectrons with higher energy (>50 eV) are still considered "primary" while the electrons freed by the photoelectrons are "secondary". | 0 | Theoretical and Fundamental Chemistry |
Quantum chemistry, a subfield of physical chemistry especially concerned with the application of quantum mechanics to chemical problems, provides tools to determine how strong and what shape bonds are, how nuclei move, and how light can be absorbed or emitted by a chemical compound. Spectroscopy is the related sub-discipline of physical chemistry which is specifically concerned with the interaction of electromagnetic radiation with matter.
Another set of important questions in chemistry concerns what kind of reactions can happen spontaneously and which properties are possible for a given chemical mixture. This is studied in chemical thermodynamics, which sets limits on quantities like how far a reaction can proceed, or how much energy can be converted into work in an internal combustion engine, and which provides links between properties like the thermal expansion coefficient and rate of change of entropy with pressure for a gas or a liquid. It can frequently be used to assess whether a reactor or engine design is feasible, or to check the validity of experimental data. To a limited extent, quasi-equilibrium and non-equilibrium thermodynamics can describe irreversible changes. However, classical thermodynamics is mostly concerned with systems in equilibrium and reversible changes and not what actually does happen, or how fast, away from equilibrium.
Which reactions do occur and how fast is the subject of chemical kinetics, another branch of physical chemistry. A key idea in chemical kinetics is that for reactants to react and form products, most chemical species must go through transition states which are higher in energy than either the reactants or the products and serve as a barrier to reaction. In general, the higher the barrier, the slower the reaction. A second is that most chemical reactions occur as a sequence of elementary reactions, each with its own transition state. Key questions in kinetics include how the rate of reaction depends on temperature and on the concentrations of reactants and catalysts in the reaction mixture, as well as how catalysts and reaction conditions can be engineered to optimize the reaction rate.
The fact that how fast reactions occur can often be specified with just a few concentrations and a temperature, instead of needing to know all the positions and speeds of every molecule in a mixture, is a special case of another key concept in physical chemistry, which is that to the extent an engineer needs to know, everything going on in a mixture of very large numbers (perhaps of the order of the Avogadro constant, 6 x 10) of particles can often be described by just a few variables like pressure, temperature, and concentration. The precise reasons for this are described in statistical mechanics, a specialty within physical chemistry which is also shared with physics. Statistical mechanics also provides ways to predict the properties we see in everyday life from molecular properties without relying on empirical correlations based on chemical similarities. | 0 | Theoretical and Fundamental Chemistry |
As a common noun, English heat or warmth (just as French chaleur, German Wärme, Latin calor, Greek θάλπος, etc.) refers to (the human perception of) either thermal energy or temperature. Speculation on thermal energy or "heat" as a separate form of matter has a long history, identified as caloric theory, phlogiston theory, and fire.
Heat has been discussed in ordinary language by philosophers. An example is this 1720 quote from John Locke:
:::::Heat, is a very brisk agitation of the insensible parts of the object, which produces in us that sensation from whence we denominate the object hot; so what in our sensation is heat, in the object is nothing but motion. This appears by the way, whereby heat is produc’d: for we see that the rubbing of a brass nail upon a board, will make it very hot; and the axle-trees of carts and coaches are often hot, and sometimes to a degree, that it sets them on fire, by the rubbing of the nave of the wheel upon it.
This source was repeatedly quoted by Joule.
John Tyndalls Heat Considered as Mode of Motion' (1863) was instrumental in popularizing the idea of heat as motion to the English-speaking public.
The theory was developed in academic publications in French, English and German. From an early time, the French technical term chaleur used by Carnot was taken as equivalent to the English heat and German Wärme (lit. "warmth", while the equivalent of heat would be German Hitze). | 0 | Theoretical and Fundamental Chemistry |
It is often difficult to distinguish between hydrogen-bond catalysis and general acid catalysis. Hydrogen-bond donors can have varying acidity, from mild to essentially strong Brønsted acids like phosphoric acids. Looking at the extent of proton transfer over the course of the reaction is challenging and has not been investigated thoroughly in most reactions. Nevertheless, strong acid catalysts are often grouped with hydrogen-bond catalysts as they represent an extreme on this continuum and their catalytic behaviors share similarities. The mechanism of activation for these reactions involves initial protonation of the electrophilic partner. This has the effect of rendering the substrate more electrophilic and creating an ion pair, through which it is possible to transfer stereochemical information.
Asymmetric catalysis involving nearly complete protonation of substrate has been effective in Mannich reactions of aromatic aldimines with carbon nucleophiles. In addition, aza-Friedel-Crafts reactions of furans, amidoalkylations of diazocarbonyl compounds, asymmetric hydrophosphonylation of aldimines and transfer hydrogenations have also been reported. Chiral Brønsted acids are often easily prepared from chiral alcohols such as BINOLs, and many are already present in the literature due to their established utility in molecular recognition research. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organyl substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands. Alkoxides, although generally not stable in protic solvents such as water, occur widely as intermediates in various reactions, including the Williamson ether synthesis. Transition metal alkoxides are widely used for coatings and as catalysts.
Enolates are unsaturated alkoxides derived by deprotonation of a bond adjacent to a ketone or aldehyde. The nucleophilic center for simple alkoxides is located on the oxygen, whereas the nucleophilic site on enolates is delocalized onto both carbon and oxygen sites. Ynolates are also unsaturated alkoxides derived from acetylenic alcohols.
Phenoxides are close relatives of the alkoxides, in which the alkyl group is replaced by a phenyl group. Phenol is more acidic than a typical alcohol; thus, phenoxides are correspondingly less basic and less nucleophilic than alkoxides. They are, however, often easier to handle, and yield derivatives that are more crystalline than those of the alkoxides. | 0 | Theoretical and Fundamental Chemistry |
To explain the processes of excitation, optical pumping, and spin exchange easier, the most common alkali metal used for this process, rubidium, will be used as an example. Rubidium has an odd number of electrons, with only one in the outermost shell that can be excited under the right conditions. There are two transitions that can occur, one referred to as the D line where the transition occurs from the 5S state to the 5P state and another referred to the D line where the transition occurs from the 5S to the 5P state. The D and D transitions can occur if the rubidium atoms are illuminated with light at a wavelength of 794.7 nm and 780 nm, respectively (Figure 1). While it is possible to cause either excitation, laser technology is well-developed for causing the D transition to occur. Those lasers are said to be tuned to the D wavelength (794.7 nm) of rubidium.
In order to increase the polarization level above thermal equilibrium, the populations of the spin states must be altered. In the absence of magnetic field, the two spin states of a spin I = ½ nuclei are in the same energy level, but in the presence of a magnetic field, the energy levels split into m = ±1/2 energy levels (Figure 2). Here, m is the spin angular momentum with possible values of +1/2 (spin up) or -1/2 (spin down), often drawn as vectors pointing up or down, respectively. The difference in population between these two energy levels is what produces an NMR signal. For example, the two electrons in the spin down state cancel two of the electrons in the spin up state, leaving only one spin up nucleus to be detected with NMR. However, the populations of these states can be altered via hyperpolarization, allowing the spin up energy level to be more populated and therefore increase the NMR signal. This is done by first optically pumping alkali metal, then transferring the polarization to a noble gas nucleus to increase the population of the spin up state.
The absorption of laser light by the alkali metal is the first process in SEOP. Left-circularly polarized light tuned to the D wavelength of the alkali metal excites the electrons from the spin down S (m=-1/2) state into the spin up P (m=+1/2) state, where collisional mixing then occurs as the noble gas atoms collide with the alkali metal atoms and the m=-1/2 state is partially populated (Figure 3). Circularly polarized light is necessary at low magnetic fields because it allows only one type of angular momentum to be absorbed, allowing the spins to be polarized. Relaxation then occurs from the excited states (m=±1/2) to the ground states (m=±1/2) as the atoms collide with nitrogen, thus quenching any chance of fluorescence and causing the electrons to return to the two ground states in equal populations. Once the spins are depolarized (return to the m=-1/2 state), they are excited again by the continuous wave laser light and the process repeats itself. In this way, a larger population of electron spins in the m=+1/2 state accumulates. The polarization of the rubidium, P, can be calculated by using the formula below:
Where n and n and are the number of atoms in the spin up (m=+1/2) and spin down (m=-1/2) S states.
Next, the optically pumped alkali metal collides with the noble gas, allowing for spin exchange to occur where the alkali metal electron polarization is transferred to the noble gas nuclei (Figure 4). There are two mechanisms in which this can occur. The angular momentum can be transferred via binary collisions (Figure 4A, also called two-body collisions) or while the noble gas, N buffer gas, and vapor phase alkali metal are held in close proximity via van der Waals forces (Figure 4B, also called three body collisions). In cases where van der Waals forces are very small compared to binary collisions (such is the case for He), the noble gas and alkali metal collide and polarization is transferred from the AM to the noble gas. Binary collisions are also possible for Xe. At high pressures, van der Waals forces dominate, but at low pressures binary collisions dominate. | 0 | Theoretical and Fundamental Chemistry |
Low-energy ion scattering spectroscopy (LEIS), sometimes referred to simply as ion scattering spectroscopy (ISS), is a surface-sensitive analytical technique used to characterize the chemical and structural makeup of materials. LEIS involves directing a stream of charged particles known as ions at a surface and making observations of the positions, velocities, and energies of the ions that have interacted with the surface. Data that is thus collected can be used to deduce information about the material such as the relative positions of atoms in a surface lattice and the elemental identity of those atoms. LEIS is closely related to both medium-energy ion scattering (MEIS) and high-energy ion scattering (HEIS, known in practice as Rutherford backscattering spectroscopy, or RBS), differing primarily in the energy range of the ion beam used to probe the surface. While much of the information collected using LEIS can be obtained using other surface science techniques, LEIS is unique in its sensitivity to both structure and composition of surfaces. Additionally, LEIS is one of a very few surface-sensitive techniques capable of directly observing hydrogen atoms, an aspect that may make it an increasingly more important technique as the hydrogen economy is being explored. | 0 | Theoretical and Fundamental Chemistry |
A sulfur-based main group analog of a carbyne complex has been prepared by Seppalt and coworkers. The compound, trifluoro(2,2,2-trifluoroethylidyne)-λ-sulfurane, FC–C≡SF, prepared by dehydrofluorination of FC–CH=SF or FC–CH–SF, is an unstable gas that readily undergoes dimerization to form trans-(CF)(SF)C=C(CF)(SF) at above –50 °C. | 0 | Theoretical and Fundamental Chemistry |
Glycerol 2-phosphate is the conjugate base of phosphoric ester of glycerol. It is commonly known as β-glycerophosphate or BGP. Unlike glycerol 1-phosphate and glycerol 3-phosphate, this isomer is not chiral. It is also less common. | 1 | Applied and Interdisciplinary Chemistry |
In 1698, the physician Sir John Floyer published the first edition of A Treatise of the Asthma, the first English textbook on the malady. In it, he describes how dampness and mold could trigger an asthmatic attack, specifically, "damp houses and fenny [boggy] countries". He also writes of an asthmatic "who fell into a violent fit by going into a Wine-Cellar", presumably due to the "fumes" in the air.
In the 1930s, mold was identified as the cause behind the mysterious deaths of farm animals in Russia and other countries. Stachybotrys chartarum was found growing on the wet grain used for animal feed. Illness and death also occurred in humans when starving peasants ate large quantities of rotten food grains and cereals heavily overgrown with the Stachybotrys mold.
In the 1970s, building construction techniques changed in response to changing economic realities, including the energy crisis. As a result, homes, and buildings became more airtight. Also, cheaper materials such as drywall came into common use. The newer building materials reduced the drying potential of the structures, making moisture problems more prevalent. This combination of increased moisture and suitable substrates contributed to increased mold growth inside buildings.
Today, the US Food and Drug Administration and the agriculture industry closely monitor mold and mycotoxin levels in grains and foodstuffs to keep the contamination of animal feed and human food supplies below specific levels. In 2005, Diamond Pet Foods, a US pet food manufacturer, experienced a significant rise in the number of corn shipments containing elevated levels of aflatoxin. This mold toxin eventually made it into the pet food supply, and dozens of dogs and cats died before the company was forced to recall affected products.
In November 2022, a UK coroner recorded that a two year old child, Awaab Ishak from Rochdale, England, died in 2020 of "acute airway oedema with severe granulomatous tracheobronchitis due to environmental mould exposure" in his home. The finding led to a 2023 change in UK law, known as "Awaab's Law", which will require social housing providers to remedy reported damp and mould within certain time limits. | 1 | Applied and Interdisciplinary Chemistry |
Nine chemical elements – carbon, sulfur, iron, copper, silver, tin, gold, mercury, and lead, have been known since before antiquity, as they are found in their native form and are relatively simple to mine with primitive tools. Around 330 BCE, the Greek philosopher Aristotle proposed that everything is made up of a mixture of one or more roots, an idea originally suggested by the Sicilian philosopher Empedocles. The four roots, which the Athenian philosopher Plato called elements, were earth, water, air and fire. Similar ideas about these four elements existed in other ancient traditions, such as Indian philosophy.
A few extra elements were known in the age of alchemy: zinc, arsenic, antimony, and bismuth. Platinum was also known to pre-Columbian South Americans, but knowledge of it did not reach Europe until the 16th century. | 1 | Applied and Interdisciplinary Chemistry |
Ellingham diagrams are a particular graphical form of the principle that the thermodynamic feasibility of a reaction depends on the sign of ΔG, the Gibbs free energy change, which is equal to ΔH − TΔS, where ΔH is the enthalpy change and ΔS is the entropy change.
The Ellingham diagram plots the Gibbs free energy change (ΔG) for each oxidation reaction as a function of temperature. For comparison of different reactions, all values of ΔG refer to the reaction of the same quantity of oxygen, chosen as one mole O ( mol ) by some authors and one mole by others. The diagram shown refers to 1 mole , so that e.g. the line for the oxidation of chromium shows ΔG for the reaction Cr(s) + (g) → (s), which is of the molar Gibbs energy of formation ΔG°(, s).
In the temperature ranges commonly used, the metal and the oxide are in a condensed state (solid or liquid), and oxygen is a gas with a much larger molar entropy. For the oxidation of each metal, the dominant contribution to the entropy change (ΔS) is the removal of mol , so that ΔS is negative and roughly equal for all metals. The slope of the plots is therefore positive for all metals, with ΔG always becoming more negative with lower temperature, and the lines for all the metal oxides are approximately parallel. Since these reactions are exothermic, they always become feasible at lower temperatures. At a sufficiently high temperature, the sign of ΔG may invert (becoming positive) and the oxide can spontaneously reduce to the metal, as shown for Ag and Cu.
For oxidation of carbon, the red line is for the formation of CO: C(s) + (g) → CO(g) with an increase in the number of moles of gas, leading to a positive ΔS and a negative slope. The blue line for the formation of is approximately horizontal, since the reaction C(s) + (g) → (g) leaves the number of moles of gas unchanged so that ΔS is small.
As with any chemical reaction prediction based on purely thermodynamic grounds, a spontaneous reaction may be very slow if one or more stages in the reaction pathway have very high activation energies E.
If two metals are present, two equilibria have to be considered. The oxide with the more negative ΔG will be formed and the other oxide will be reduced. | 1 | Applied and Interdisciplinary Chemistry |
When photosystem I absorbs light, an electron is excited to a higher energy level in the P700 chlorophyll. The resulting P700 with an excited electron is designated as P700*, which is a strong reducing agent due to its very negative redox potential of -1.2V . | 0 | Theoretical and Fundamental Chemistry |
The oxaloacetate/aspartate family of amino acids is composed of lysine, asparagine, methionine, threonine, and isoleucine. Aspartate can be converted into lysine, asparagine, methionine and threonine. Threonine also gives rise to isoleucine.
The associated enzymes are subject to regulation via feedback inhibition and/or repression at the genetic level. As is typical in highly branched metabolic pathways, additional regulation at each branch point of the pathway. This type of regulatory scheme allows control over the total flux of the aspartate pathway in addition to the total flux of individual amino acids. The aspartate pathway uses L-aspartic acid as the precursor for the biosynthesis of one-fourth of the building block amino acids. | 1 | Applied and Interdisciplinary Chemistry |
*DayGlo fluorescent pigments, developed by Bob Switzer and Joe Switzer of Switzer Brothers, Inc., (now Day-Glo Color Corp.) between the 1930s and 1950s
*Rachel Carson's book Silent Spring, published in 1962 | 1 | Applied and Interdisciplinary Chemistry |
Since its reduction potential is similar to that of oxygen and can be reduced by components of the electron transport chain, large doses of methylene blue are sometimes used as an antidote to potassium cyanide poisoning, a method first successfully tested in 1933 by Dr. Matilda Moldenhauer Brooks in San Francisco, although first demonstrated by Bo Sahlin of Lund University, in 1926. | 0 | Theoretical and Fundamental Chemistry |
During the Cold War, the governments of the U.S., the USSR, Great Britain, and China attempted to educate their citizens about surviving a nuclear attack by providing procedures on minimizing short-term exposure to fallout. This effort commonly became known as Civil Defense.
Fallout protection is almost exclusively concerned with protection from radiation. Radiation from a fallout is encountered in the forms of alpha, beta, and gamma radiation, and as ordinary clothing affords protection from alpha and beta radiation, most fallout protection measures deal with reducing exposure to gamma radiation. For the purposes of radiation shielding, many materials have a characteristic halving thickness: the thickness of a layer of a material sufficient to reduce gamma radiation exposure by 50%. Halving thicknesses of common materials include: 1 cm (0.4 inch) of lead, 6 cm (2.4 inches) of concrete, 9 cm (3.6 inches) of packed earth or 150 m (500 ft) of air. When multiple thicknesses are built, the shielding multiplies. A practical fallout shield is ten halving-thicknesses of a given material, such as 90 cm (36 inches) of packed earth, which reduces gamma ray exposure by approximately 1024 times (2). A shelter built with these materials for the purposes of fallout protection is known as a fallout shelter. | 0 | Theoretical and Fundamental Chemistry |
The costs of subsurface flow constructed wetlands mainly depend on the costs of sand with which the bed has to be filled. Another factor is the cost of land. | 1 | Applied and Interdisciplinary Chemistry |
The advantages of EDXRD are (1) it uses a fixed scattering angle, (2) it works directly in reciprocal space, (3) fast collection time, and (4) parallel data collection. The fixed scattering angle geometry makes EDXRD especially suitable for in situ studies in special environments (e.g. under very low or high temperatures and pressures). When the EDXRD method is used, only one entrance and one exit window are needed. The fixed scattering angle also allows for measurement of the diffraction vector directly. This allows for high-accuracy measurement of lattice parameters. It allows for rapid structure analysis and the ability to study materials that are unstable and only exist for short periods of time. Because the whole spectrum of diffracted radiation is obtained simultaneously, it enables parallel data collection studies where structural changes can be determined over time. | 0 | Theoretical and Fundamental Chemistry |
Each peroxy group is considered to contain one active oxygen atom. The concept of active oxygen content is useful for comparing the relative concentration of peroxy groups in formulations, which is related to the energy content. In general, energy content increases with active oxygen content, and thus the higher the molecular weight of the organic groups, the lower the energy content and, usually, the lower the hazard.
The term active oxygen is used to specify the amount of peroxide present in any organic peroxide formulation. One of the oxygen atoms in each peroxide group is considered "active". The theoretical amount of active oxygen can be described by the following equation:
where is the number of peroxide groups in the molecule, and is the molecular mass of the pure peroxide.
Organic peroxides are often sold as formulations that include one or more phlegmatizing agents. That is, for safety sake or performance benefits the properties of an organic peroxide formulation are commonly modified by the use of additives to phlegmatize (desensitize), stabilize, or otherwise enhance the organic peroxide for commercial use. Commercial formulations occasionally consist of mixtures of organic peroxides, which may or may not be phlegmatized. | 0 | Theoretical and Fundamental Chemistry |
The melting temperature of the amplicon at which the two DNA strands come apart is entirely predictable. It is dependent on the sequence of the DNA bases. If you are comparing two samples from two different people, they should give exactly the same shaped melt curve. However, if one person has a mutation in the DNA region you have amplified, then this will alter the temperature at which the DNA strands melt apart. So now the two melt curves appear different. The difference may only be tiny, perhaps a fraction of a degree, but because the HRM machine has the ability to monitor this process in "high resolution", it is possible to accurately document these changes and therefore identify if a mutation is present or not. | 1 | Applied and Interdisciplinary Chemistry |
A multivariate optical element (MOE), is the key part of a multivariate optical computer; an alternative to conventional spectrometry for the chemical analysis of materials.
It is helpful to understand how light is processed in a multivariate optical computer, as compared to how it is processed in a spectrometer. For example, if we are studying the composition of a powder mixture using diffuse reflectance, a suitable light source is directed at the powder mixture and light is collected, usually with a lens, after it has scattered from the powder surface. Light entering a spectrometer first strikes a device (either a grating or interferometer) that separates light of different wavelengths to be measured. A series of independent measurements is used to estimate the full spectrum of the mixture, and the spectrometer renders a measurement of the spectral intensity at many wavelengths. Multivariate statistics can then be applied to the spectrum produced.
In contrast, when using multivariate optical computing, the light entering the instrument strikes an application specific multivariate optical element, which is uniquely tuned to the pattern that needs to be measured using multivariate analysis.
This system can produce the same result that multivariate analysis of a spectrum would produce. Thus, it can generally produce the same accuracy as laboratory grade spectroscopic systems, but with the fast speed inherent with a pure, passive, optical computer. The multivariate optical computer makes use of optical computing to realize the performance of a full spectroscopic system using traditional multivariate analysis. A side benefit is that the throughput and efficiency of the system is higher than conventional spectrometers, which increases the speed of analysis by orders of magnitude.
While each chemical problem presents its own unique challenges and opportunities, the design of a system for a specific analysis is complex and requires the assembly of several pieces of a spectroscopic puzzle. The data necessary for a successful design are spectral characteristics of light sources, detectors and a variety of optics to be used in the final assemblage, dispersion characteristics of the materials used in the wavelength range of interest, and a set of calibrated sample spectra for pattern-recognition-based analysis. With these pieces assembled, suitable application specific multivariate optical computer designs can be generated and the performance accurately modeled and predicted. | 0 | Theoretical and Fundamental Chemistry |
While most mining companies have shifted from a previously accepted sprinkler method to the percolation of slowly dripping choice chemicals including cyanide or sulfuric acid closer to the actual ore bed, heap leach pads have not changed too much throughout the years. There are still four main categories of pads: conventional, dump leach, valley fills, and on/off pads. Typically, each pad only has a single, geomembrane liner for each pad, with a minimum thickness of 1.5mm, usually thicker.
The conventional pads simplest in design are used for mostly flat or gentle areas and hold thinner layers of crushed ore. Dump leach pads hold more ore and can usually handle a less flat terrain. Valley fills are pads situated at valley bottoms or levels that can hold everything falling into it. On/off pads involve putting significantly larger loads on the pads and removing and reloading it after every cycle.
Many of these mines which previously had digging depths of about 15 meters are digging deeper than ever before to mine materials, approximately 50 meters, sometimes more, which means that, in order to accommodate all of the ground being displaced, pads will have to hold higher weights from more crushed ore being contained in a smaller area (Lupo 2010). With that increase in build up comes in potential for decrease in yield or ore quality, as well as potential either weak spots in the lining or areas of increased pressure buildup. This build up still has the potential to lead to punctures in the liner. As of 2004 cushion fabrics, which could reduce potential punctures and their leaking, were still being debated due to their tendency to increase risks if too much weight on too large a surface was placed on the cushioning (Thiel and Smith 2004). In addition, some liners, depending on their composition, may react with salts in the soil as well as acid from the chemical leaching to affect the successfulness of the liner. This can be amplified over time. | 1 | Applied and Interdisciplinary Chemistry |
The historical term for the relative permittivity is dielectric constant. It is still commonly used, but has been deprecated by standards organizations, because of its ambiguity, as some older reports used it for the absolute permittivity ε. The permittivity may be quoted either as a static property or as a frequency-dependent variant, in which case it is also known as the dielectric function. It has also been used to refer to only the real component ε′ of the complex-valued relative permittivity. | 0 | Theoretical and Fundamental Chemistry |
Lead(II) fluoride is used in low melting glasses, in glass coatings to reflect infrared rays, in phosphors for television-tube screens, and as a catalyst for the manufacture of picoline. The Muon g−2 experiment uses scintillators in conjunction with silicon photomultipliers. | 0 | Theoretical and Fundamental Chemistry |
DTDP-glucose is produced by the enzyme glucose-1-phosphate thymidylyltransferase and is synthesized from dTTP and glucose-1-phosphate. Pyrophosphate is a byproduct of the reaction. | 1 | Applied and Interdisciplinary Chemistry |
SCS is the only enzyme in the citric acid cycle that catalyzes a reaction in which a nucleotide triphosphate (GTP or ATP) is formed by substrate-level phosphorylation. Research studies have shown that E. coli SCSs can catalyze either GTP or ATP formation. However, mammals possess different types of SCSs that are specific for either GTP (G-SCS) or ATP (A-SCS) and are native to different types of tissue within the organism. An interesting study using pigeon cells showed that GTP specific SCSs were located in pigeon liver cells, and ATP specific SCSs were located in the pigeon breast muscle cells. Further research revealed a similar phenomenon of GTP and ATP specific SCSs in rat, mouse, and human tissue. It appears that tissue typically involved in anabolic metabolism (like the liver and kidneys) express G-SCS, whereas tissue involved in catabolic metabolism (like the brain, the heart, and muscular tissue) express A-SCS. | 1 | Applied and Interdisciplinary Chemistry |
Lakes and ponds can be very large and support a complex eco-system in which environmental parameters vary widely in all three physical dimensions and with time. Large lakes in the temperate zone often stratify in the warmer months into a warmer upper layers rich in oxygen and a colder lower layer with low oxygen levels. In the autumn, falling temperatures and occasional high winds result in the mixing of the two layers into a more homogeneous whole. When stratification occurs it not only affects oxygen levels but also many related parameters such as iron, phosphate and manganese which are all changed in their chemical form by change in the redox potential of the environment.
Lakes also receive waters, often from many different sources with varying qualities. Solids from stream inputs will typically settle near the mouth of the stream and depending on a variety of factors the incoming water may float over the surface of the lake, sink beneath the surface or rapidly mix with the lake water. All of these phenomena can skew the results of any environmental monitoring unless the process are well understood. | 1 | Applied and Interdisciplinary Chemistry |
In the tablet pressing process, the appropriate amount of active ingredient must be in each tablet. Hence, all the ingredients should be well mixed. If a sufficiently homogenous mix of the components cannot be obtained with simple blending processes, the ingredients must be granulated prior to compression to assure an even distribution of the active compound in the final tablet. Two basic techniques are used to granulate powders for compression into tablets: wet granulation and dry granulation. Powders that can be mixed well do not require granulation and can be compressed into tablets through direct compression ("DC"). Direct compression is desirable as it is quicker. There is less processing, equipment, labor, and energy consumption. However, DC is difficult when a formulation has a high content of poorly compressible active ingredients. | 1 | Applied and Interdisciplinary Chemistry |
ISO REMCO, the ISO committee responsible for guidance on reference materials within ISO, defines the following classes of reference material:
; Reference Material: Material, sufficiently homogeneous and stable with respect to one or more specified properties, which has been established to be fit for its intended use in a measurement process.
; Certified Reference Material: Reference material characterized by a metrologically valid procedure for one or more specified properties, accompanied by a certificate that provides the value of the specified property, its associated uncertainty, and a statement of metrological traceability. | 0 | Theoretical and Fundamental Chemistry |
A siphon cup is the (hanging) reservoir of paint attached to a spray gun, it is not a siphon as a vacuum pump extracts the paint. This name is to distinguish it from gravity-fed reservoirs. An archaic use of the term is a cup of oil in which the oil is transported out of the cup via a cotton wick or tube to a surface to be lubricated, this is not a siphon but an example of capillary action. | 1 | Applied and Interdisciplinary Chemistry |
This technique is mostly used to produce coatings on structural materials. Such coatings provide protection against high temperatures (for example thermal barrier coatings for exhaust heat management), corrosion, erosion, wear; they can also change the appearance, electrical or tribological properties of the surface, replace worn material, etc. When sprayed on substrates of various shapes and removed, free-standing parts in the form of plates, tubes, shells, etc. can be produced. It can also be used for powder processing (spheroidization, homogenization, modification of chemistry, etc.). In this case, the substrate for deposition is absent and the particles solidify during flight or in a controlled environment (e.g., water). This technique with variation may also be used to create porous structures, suitable for bone ingrowth, as a coating for medical implants.
A polymer dispersion aerosol can be injected into the plasma discharge in order to create a grafting of this polymer on to a substrate surface. This application is mainly used to modify the surface chemistry of polymers. | 1 | Applied and Interdisciplinary Chemistry |
The structural and compositional versatility of clay minerals gives them interesting biological properties. Due to disc-shaped and charged surfaces, clay interacts with a range of drugs, protein, polymers, DNA, or other macromolecules. Some of the applications of clays include drug delivery, tissue engineering, and bioprinting. | 0 | Theoretical and Fundamental Chemistry |
Originally, COMOS was developed as an integrated CAE system for engineering in plant construction: all process engineering trades and the involved disciplines of the Electrical, Instrumentation & Control system engineering should be able to work together seamlessly on one system platform.
The system incorporates the characteristics of object orientation, central data administration, and open system architecture. Interfaces enable the integration into existing IT infrastructures or cooperation with supplementary software systems. The COMOS software system is based on a central data platform and includes applications that can be combined. They help with the engineering and set-up, operation, and shut-down of industrial plants. | 1 | Applied and Interdisciplinary Chemistry |
Nuclear magnetic resonance (NMR) in the geomagnetic field is conventionally referred to as Earth's field NMR (EFNMR). EFNMR is a special case of low field NMR.
When a sample is placed in a constant magnetic field and stimulated (perturbed) by a time-varying (e.g., pulsed or alternating) magnetic field, NMR active nuclei resonate at characteristic frequencies. Examples of such NMR active nuclei are the isotopes carbon-13 and hydrogen-1 (which in NMR is conventionally known as proton NMR). The resonant frequency of each isotope is directly proportional to the strength of the applied magnetic field, and the magnetogyric or gyromagnetic ratio of that isotope. The signal strength is proportional both to the stimulating magnetic field and the number of nuclei of that isotope in the sample. Thus in the 21 tesla magnetic field that may be found in high resolution laboratory NMR spectrometers, protons resonate at 900 MHz. However, in the Earth's magnetic field the same nuclei resonate at audio frequencies of around 2 kHz and generate very weak signals.
The location of a nucleus within a complex molecule affects the chemical environment (i.e. the rotating magnetic fields generated by the other nuclei) experienced by the nucleus. Thus different hydrocarbon molecules containing NMR active nuclei in different positions within the molecules produce slightly different patterns of resonant frequencies.
EFNMR signals can be affected by both magnetically noisy laboratory environments and natural variations in the Earth's field, which originally compromised its usefulness. However this disadvantage has been overcome by the introduction of electronic equipment which compensates changes in ambient magnetic fields.
Whereas chemical shifts are important in NMR, they are insignificant in the Earth's field. The absence of chemical shifts causes features such as spin-spin multiplets (that are separated by high fields) to be superimposed in EFNMR. Instead, EFNMR spectra are dominated by spin-spin coupling (J-coupling) effects. Software optimised for analysing these spectra can provide useful information about the structure of the molecules in the sample. | 0 | Theoretical and Fundamental Chemistry |
The stabilization of a foam is caused by van der Waals forces between the molecules in the foam, electrical double layers created by dipolar surfactants, and the Marangoni effect, which acts as a restoring force to the lamellae.
The Marangoni effect depends on the liquid that is foaming being impure. Generally, surfactants in the solution decrease the surface tension. The surfactants also clump together on the surface and form a layer as shown below.
For the Marangoni effect to occur, the foam must be indented as shown in the first picture. This indentation increases local surface area. Surfactants have a larger diffusion time than the bulk of the solution—so the surfactants are less concentrated in the indentation.
Also, surface stretching makes the surface tension of the indented spot greater than the surrounding area. Consequentially—since diffusion time for the surfactants is large—the Marangoni effect has time to take place. The difference in surface tension creates a gradient, which instigates fluid flow from areas of lower surface tension to areas of higher surface tension. The second picture shows the film at equilibrium after the Marangoni effect has taken place.
Curing a foam solidifies it, making it indefinitely stable at STP. | 0 | Theoretical and Fundamental Chemistry |
AIDS appears to involve a slow and progressive decline in levels of selenium in the body. Whether this decline in selenium levels is a direct result of the replication of HIV or related more generally to the overall malabsorption of nutrients by AIDS patients remains debated. Observational studies have found an association between decreased selenium levels and poorer outcomes in patients with HIV, though these studies were mostly done prior to the currently effective treatments with highly active antiretroviral therapy (HAART). Currently there is inadequate evidence to recommend routine selenium supplementation for HIV patients, and further research is recommended. | 1 | Applied and Interdisciplinary Chemistry |
In 1925, Coward received a Rockefeller Fellowship to continue her studies and research on vitamin A in the Department of Agricultural Chemistry at the University of Wisconsin–Madison under Dr. Harry Steenbock. On her return to Britain, she was appointed head of the Nutrition Department of the Royal Pharmaceutical Society's pharmacological laboratories, the position which she remained until her retirement in 1950. In 1937 she was elected as an honorary member of the Pharmaceuticals Society. | 0 | Theoretical and Fundamental Chemistry |
Raymond's daughter Janet Lemieux was Canadian champion soccer player and was inducted to the Canada Soccer Hall of Fame in 2021. | 0 | Theoretical and Fundamental Chemistry |
Of the 195 countries currently recognised by the United Nations, 141 use RHT and 54 use LHT on roads in general.
A country and its territories and dependencies are counted as one. Whichever directionality is listed first is the type that is used in general in the traffic category. | 0 | Theoretical and Fundamental Chemistry |
A Norrish type II reaction is the photochemical intramolecular abstraction of a γ-hydrogen (a hydrogen atom three carbon positions removed from the carbonyl group) by the excited carbonyl compound to produce a 1,4-biradical as a primary photoproduct. Norrish first reported the reaction in 1937.
Secondary reactions that occur are fragmentation (β-scission) to form an alkene and an enol (which will rapidly tautomerise to a carbonyl), or intramolecular recombination of the two radicals to a substituted cyclobutane (the Norrish–Yang reaction). | 0 | Theoretical and Fundamental Chemistry |
Aeroacoustics is a branch of acoustics that studies noise generation via either turbulent fluid motion or aerodynamic forces interacting with surfaces. Noise generation can also be associated with periodically varying flows. A notable example of this phenomenon is the Aeolian tones produced by wind blowing over fixed objects.
Although no complete scientific theory of the generation of noise by aerodynamic flows has been established, most practical aeroacoustic analysis relies upon the so-called aeroacoustic analogy, proposed by Sir James Lighthill in the 1950s while at the University of Manchester. whereby the governing equations of motion of the fluid are coerced into a form reminiscent of the wave equation of "classical" (i.e. linear) acoustics in the left-hand side with the remaining terms as sources in the right-hand side. | 1 | Applied and Interdisciplinary Chemistry |
* Qualitative Chemical Analysis: Principles and methods, 1931
* General Chemistry for Colleges, 1935
* The Structure and properties of Matter, 1935
* An Introduction to College Chemistry, 1937 | 0 | Theoretical and Fundamental Chemistry |
ChimerDB in computational biology is a database of fusion sequences.
ChimerDB currently consists of three searchable datasets.
*[http://203.255.191.229:8080/chimerdbv31/mchimerkb.cdb ChimerKB] is a curated knowledge base of 1,066 fusion genes sourced from publicly available scientific literature.
*[http://203.255.191.229:8080/chimerdbv31/mchimerpub.cdb ChimerPub] provides continuously updated descriptions on fusion genes text mined from publications.
*[http://203.255.191.229:8080/chimerdbv31/mchimerseq.cdb ChimerSeq] is a database of RNA-seq data of fusion sequences downloaded from the [https://tcga-data.nci.nih.gov/docs/publications/tcga/? TCGA data portal]. | 1 | Applied and Interdisciplinary Chemistry |
The following equations apply to two hard spheres that undergo a perfectly elastic collision. Let and denote the radii of the scattering center and scattered sphere, respectively. The differential cross section is
and the total cross section is
In other words, the total scattering cross section is equal to the area of the circle (with radius ) within which the center of mass of the incoming sphere has to arrive for it to be deflected. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, the Terrace Ledge Kink model (TLK), which is also referred to as the Terrace Step Kink model (TSK), describes the thermodynamics of crystal surface formation and transformation, as well as the energetics of surface defect formation. It is based upon the idea that the energy of an atom’s position on a crystal surface is determined by its bonding to neighboring atoms and that transitions simply involve the counting of broken and formed bonds. The TLK model can be applied to surface science topics such as crystal growth, surface diffusion, roughening, and vaporization. | 0 | Theoretical and Fundamental Chemistry |
Cecil Czerkinsky first described ELISpot in 1983 as a new way to quantify the production of an antigen-specific immunoglobulin by hybridoma cells.
In 1988, Czerkinsky developed an ELISA spot assay that quantified the secretion of a lymphokine by T cells.
In the same year, dual-color ELISpot was combined with computer imaging for the first time, which allowed for the enumeration and analysis of spots.
1988 also marked the first use of membrane-bottomed plates for performing these assays. | 1 | Applied and Interdisciplinary Chemistry |
Grignard reagents or Grignard compounds are chemical compounds with the general formula , where X is a halogen and R is an organic group, normally an alkyl or aryl. Two typical examples are methylmagnesium chloride and phenylmagnesium bromide . They are a subclass of the organomagnesium compounds.
Grignard compounds are popular reagents in organic synthesis for creating new carbon–carbon bonds. For example, when reacted with another halogenated compound in the presence of a suitable catalyst, they typically yield and the magnesium halide as a byproduct; and the latter is insoluble in the solvents normally used. In this aspect, they are similar to organolithium reagents.
Grignard reagents are rarely isolated as solids. Instead, they are normally handled as solutions in solvents such as diethyl ether or tetrahydrofuran using air-free techniques. Grignard reagents are complex with the magnesium atom bonded to two ether ligands as well as the halide and organyl ligands.
The discovery of the Grignard reaction in 1900 was recognized with the Nobel Prize awarded to Victor Grignard in 1912. | 0 | Theoretical and Fundamental Chemistry |
The School has four major research themes as part of EaStCHEM:
The Chemistry/Biology Interface area is broad, with particular strengths in the areas of protein structure and function, mechanistic enzymology, proteomics, biologically targeted synthesis, the application of high throughput and combinatorial approaches and biophysical chemistry, which focuses on the development and application of physicochemical techniques to biological systems.
Chemical Physics/Physical Chemistry is the fundamental study of molecular properties and processes. Areas of expertise include probing molecular structure in the gas phase, clusters and nanoparticles, the development and application of physicochemical techniques such as mass spectrometry to molecular systems and the EaStCHEM surface science group, who study complex molecules on surfaces, probing the structure property-relationships employed in heterogeneous catalysis. A major feature is In Silico Scotland, a world class research computing facility.
Molecular Synthesis encompasses the synthesis and characterisation at ambient and extreme conditions of organic and inorganic compounds, including those with application in homogeneous catalysis, nanotechnology, supramolecular chemistry, drug discovery and ligand design. The development of innovative synthetic and characterisation methodologies (particularly in structural chemistry) is a key feature.
The Materials Chemistry group is one of the largest materials chemistry groups in the UK. Areas of strength include the design, synthesis and characterisation of strongly correlated electronic materials, battery and fuel cell materials and devices, porous solids, materials at extreme pressures and temperatures, polymer microarray technologies and technique development for materials and nanomaterials analysis. | 1 | Applied and Interdisciplinary Chemistry |
In haloalkanes and haloarenes (), Halogen functional groups are prefixed with the bonding position and take the form of fluoro-, chloro-, bromo-, iodo-, etc., depending on the halogen. Multiple groups are dichloro-, trichloro-, etc., and dissimilar groups are ordered alphabetically as before. For example, (chloroform) is trichloromethane. The anesthetic halothane () is 2-bromo-2-chloro-1,1,1-trifluoroethane. | 0 | Theoretical and Fundamental Chemistry |
Sympathetic cooling is a process in which particles of one type cool particles of another type.
Typically, atomic ions that can be directly laser cooled are used to cool nearby ions or atoms, by way of their mutual Coulomb interaction. This technique is used to cool ions and atoms that cannot be cooled directly by laser cooling, which includes most molecular ion species, especially large organic molecules. However, sympathetic cooling is most efficient when the mass/charge ratios of the sympathetic- and laser-cooled ions are similar.
The cooling of neutral atoms in this manner was first demonstrated by Christopher Myatt et al. in 1997. Here, a technique with electric and magnetic fields were used, where atoms with spin in one direction were more weakly confined than those with spin in the opposite direction. The weakly confined atoms with a high kinetic energy were allowed to more easily escape, lowering the total kinetic energy, resulting in a cooling of the strongly confined atoms.
Myatt et al. also showed the utility of their version of sympathetic cooling for the creation of Bose–Einstein condensates. | 0 | Theoretical and Fundamental Chemistry |
The 4th analytical group of cations includes ions that precipitate as sulfides at pH 9. The reagent used is ammonium sulfide or NaS 0.1 M added to the ammonia/ammonium chloride solution used to detect group 3 cations.
It includes: Zn, Ni, Co, and Mn. Zinc will form a white precipitate, nickel and cobalt a black precipitate and manganese a brick/flesh colored precipitate. Dimethylglyoxime can be used to confirm nickel presence, while ammonium thiocyanate in ether will turn blue in the presence of cobalt. This group is sometimes denoted as IIIB since groups III and IV are tested for at the same time, with the addition of sulfide being the only difference. | 0 | Theoretical and Fundamental Chemistry |
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