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Based on low-quality evidence, levetiracetam is about as effective as phenytoin for prevention of early seizures after traumatic brain injury. It may be effective for prevention of seizures associated with subarachnoid hemorrhages. | 0 | Theoretical and Fundamental Chemistry |
Transcriptome analysis have been used to study the evolution and diversification process of plant species. In 2014, the 1000 Plant Genomes Project was completed in which the transcriptomes of 1,124 plant species from the families viridiplantae, glaucophyta and rhodophyta were sequenced. The protein coding sequences were subsequently compared to infer phylogenetic relationships between plants and to characterize the time of their diversification in the process of evolution. Transcriptome studies have been used to characterize and quantify gene expression in mature pollen. Genes involved in cell wall metabolism and cytoskeleton were found to be overexpressed. Transcriptome approaches also allowed to track changes in gene expression through different developmental stages of pollen, ranging from microspore to mature pollen grains; additionally such stages could be compared across species of different plants including Arabidopsis, rice and tobacco. | 1 | Applied and Interdisciplinary Chemistry |
Flotation can be performed in rectangular or cylindrical mechanically agitated cells or tanks, flotation columns, Jameson Cells or deinking flotation machines. Classified by the method of air absorption manner, it is fair to state that two distinct groups of flotation equipment have arisen:pneumatic and mechanical machines. Generally pneumatic machines give a low-grade concentrate and little operating troubles.
Mechanical cells use a large mixer and diffuser mechanism at the bottom of the mixing tank to introduce air and provide mixing action. Flotation columns use air spargers to introduce air at the bottom of a tall column while introducing slurry above. The countercurrent motion of the slurry flowing down and the air flowing up provides mixing action. Mechanical cells generally have a higher throughput rate, but produce material that is of lower quality, while flotation columns generally have a low throughput rate but produce higher quality material.
The Jameson cell uses neither impellers nor spargers, instead combining the slurry with air in a downcomer where high shear creates the turbulent conditions required for bubble particle contacting. | 1 | Applied and Interdisciplinary Chemistry |
Oxygen depletion can result from a number of natural factors, but is most often a concern as a consequence of pollution and eutrophication in which plant nutrients enter a river, lake, or ocean, and phytoplankton blooms are encouraged. While phytoplankton, through photosynthesis, will raise DO saturation during daylight hours, the dense population of a bloom reduces DO saturation during the night by respiration. When phytoplankton cells die, they sink towards the bottom and are decomposed by bacteria, a process that further reduces DO in the water column. If oxygen depletion progresses to hypoxia, fish kills can occur and invertebrates like worms and clams on the bottom may be killed as well.
Hypoxia may also occur in the absence of pollutants. In estuaries, for example, because freshwater flowing from a river into the sea is less dense than salt water, stratification in the water column can result. Vertical mixing between the water bodies is therefore reduced, restricting the supply of oxygen from the surface waters to the more saline bottom waters. The oxygen concentration in the bottom layer may then become low enough for hypoxia to occur. Areas particularly prone to this include shallow waters of semi-enclosed water bodies such as the Waddenzee or the Gulf of Mexico, where land run-off is substantial. In these areas a so-called "dead zone" can be created. Low dissolved oxygen conditions are often seasonal, as is the case in Hood Canal and areas of Puget Sound, in Washington State. The World Resources Institute has identified 375 hypoxic coastal zones around the world, concentrated in coastal areas in Western Europe, the Eastern and Southern coasts of the US, and East Asia, particularly in Japan.
Hypoxia may also be the explanation for periodic phenomena such as the Mobile Bay jubilee, where aquatic life suddenly rushes to the shallows, perhaps trying to escape oxygen-depleted water. Recent widespread shellfish kills near the coasts of Oregon and Washington are also blamed on cyclic dead zone ecology. | 0 | Theoretical and Fundamental Chemistry |
Gene silencing is the regulation of gene expression in a cell to prevent the expression of a certain gene. Gene silencing can occur during either transcription or translation and is often used in research. In particular, methods used to silence genes are being increasingly used to produce therapeutics to combat cancer and other diseases, such as infectious diseases and neurodegenerative disorders.
Gene silencing is often considered the same as gene knockdown. When genes are silenced, their expression is reduced. In contrast, when genes are knocked out, they are completely erased from the organism's genome and, thus, have no expression. Gene silencing is considered a gene knockdown mechanism since the methods used to silence genes, such as RNAi, CRISPR, or siRNA, generally reduce the expression of a gene by at least 70% but do not eliminate it. Methods using gene silencing are often considered better than gene knockouts since they allow researchers to study essential genes that are required for the animal models to survive and cannot be removed. In addition, they provide a more complete view on the development of diseases since diseases are generally associated with genes that have a reduced expression. | 1 | Applied and Interdisciplinary Chemistry |
A lead star is a low-metallicity star with an overabundance of lead and bismuth as compared to other products of the S-process. | 0 | Theoretical and Fundamental Chemistry |
The island of stability is a region outside the valley of stability where it is predicted that a set of heavy isotopes with near magic numbers of protons and neutrons will locally reverse the trend of decreasing stability in elements heavier than uranium.
The hypothesis for the island of stability is based upon the nuclear shell model, which implies that the atomic nucleus is built up in "shells" in a manner similar to the structure of the much larger electron shells in atoms. In both cases, shells are just groups of quantum energy levels that are relatively close to each other. Energy levels from quantum states in two different shells will be separated by a relatively large energy gap. So when the number of neutrons and protons completely fills the energy levels of a given shell in the nucleus, the binding energy per nucleon will reach a local maximum and thus that particular configuration will have a longer lifetime than nearby isotopes that do not possess filled shells.
A filled shell would have "magic numbers" of neutrons and protons. One possible magic number of neutrons for spherical nuclei is 184, and some possible matching proton numbers are 114, 120 and 126. These configurations imply that the most stable spherical isotopes would be flerovium-298, unbinilium-304 and unbihexium-310. Of particular note is Fl, which would be "doubly magic" (both its proton number of 114 and neutron number of 184 are thought to be magic). This doubly magic configuration is the most likely to have a very long half-life. The next lighter doubly magic spherical nucleus is lead-208, the heaviest known stable nucleus and most stable heavy metal. | 0 | Theoretical and Fundamental Chemistry |
Diaminophosphorus chlorides and tris(dimethylamino)phosphine are precursors to phosphenium ions of the type [(RN)P]:
:RPCl + AlCl → [RP]AlCl
:P(NMe) + 2 HOTf → [P(NMe)]OTf + [HNMe]OTf | 0 | Theoretical and Fundamental Chemistry |
The dominant effect of a nuclear weapon (the blast and thermal radiation) are the same physical damage mechanisms as conventional explosives, but the energy produced by a nuclear explosive is millions of times more per gram and the temperatures reached are in the tens of megakelvin. Nuclear weapons are quite different from conventional weapons because of the huge amount of explosive energy that they can put out and the different kinds of effects they make, like high temperatures and ionizing radiation.
The devastating impact of the explosion does not stop after the initial blast, as with conventional explosives. A cloud of nuclear radiation travels from the hypocenter of the explosion, causing an impact to life forms even after the heat waves have ceased. The health effects on humans from nuclear explosions comes from the initial shockwave, the radiation exposure, and the fallout. The initial shockwave and radiation exposure come from the immediate blast which has different effects on the health of humans depending on the distance from the center of the blast. The shockwave can rupture eardrums and lungs, can also throw people back, and cause buildings to collapse. Radiation exposure is delivered at the initial blast and can continue for an extended amount of time in the form of nuclear fallout. The main health effect of nuclear fallout is cancer and birth defects because radiation causes changes in cells that can either kill or make them abnormal. Any nuclear explosion (or nuclear war) would have wide-ranging, long-term, catastrophic effects. Radioactive contamination would cause genetic mutations and cancer across many generations. | 0 | Theoretical and Fundamental Chemistry |
Fatty acid synthesis is an anabolic process that starts from the conversion of acetyl-CoA to malonyl-CoA by acetyl-CoA carboxylase. Malonyl CoA leads to fatty acid synthesis (FAS) and is involved in the elongation of fatty acids through Fatty acid synthase (FASN). Although aerobic glycolysis is the best documented metabolic phenotype of tumor cells, it is not a universal feature of all human cancers. Amino acids and fatty acids have been shown to function as fuels for tumor cells to proliferate. The carnitine palmitoyltransferase enzymes that regulate the β-oxidation of fatty acids may have a key role in determining some of these phenotypes. Enhanced fatty acid synthesis provides lipids for membrane biogenesis to tumor cells and hence, it gives advantage in both growth and survival of the cell. | 1 | Applied and Interdisciplinary Chemistry |
The pancreas is a major organ functioning as an accessory digestive gland in the digestive system. It is both an endocrine gland and an exocrine gland. The endocrine part secretes insulin when the blood sugar becomes high; insulin moves glucose from the blood into the muscles and other tissues for use as energy. The endocrine part releases glucagon when the blood sugar is low; glucagon allows stored sugar to be broken down into glucose by the liver in order to re-balance the sugar levels. The pancreas produces and releases important digestive enzymes in the pancreatic juice that it delivers to the duodenum. The pancreas lies below and at the back of the stomach. It connects to the duodenum via the pancreatic duct which it joins near to the bile duct's connection where both the bile and pancreatic juice can act on the chyme that is released from the stomach into the duodenum. Aqueous pancreatic secretions from pancreatic duct cells contain bicarbonate ions which are alkaline and help with the bile to neutralise the acidic chyme that is churned out by the stomach.
The pancreas is also the main source of enzymes for the digestion of fats and proteins. Some of these are released in response to the production of cholecystokinin in the duodenum. (The enzymes that digest polysaccharides, by contrast, are primarily produced by the walls of the intestines.) The cells are filled with secretory granules containing the precursor digestive enzymes. The major proteases, the pancreatic enzymes which work on proteins, are trypsinogen and chymotrypsinogen. Elastase is also produced. Smaller amounts of lipase and amylase are secreted. The pancreas also secretes phospholipase A2, lysophospholipase, and cholesterol esterase. The precursor zymogens, are inactive variants of the enzymes; which avoids the onset of pancreatitis caused by autodegradation. Once released in the intestine, the enzyme enteropeptidase present in the intestinal mucosa activates trypsinogen by cleaving it to form trypsin; further cleavage results in chymotripsin. | 1 | Applied and Interdisciplinary Chemistry |
In bacteria and eukaryotes, proteins TFIIB and sigma factor are involved in the initiation of transcription, where they facilitate preinitiation complex formation and specific RNA Polymerase-DNA binding. The archaeal counterpart to these two proteins is TFB, which was first identified in the species Pyrococcus woesei in 1992. Since then, research has found that archaeal species must contain at least one copy of TFB to function, although some species may have multiple isoforms in their genome. | 1 | Applied and Interdisciplinary Chemistry |
Occupational exposure limits are based on available toxicology and epidemiology data to protect nearly all workers over a working lifetime. Exposure assessments in occupational settings are most often performed by occupational/industrial hygiene (OH/IH) professionals who gather "basic characterization" consisting of all relevant information and data related to workers, agents of concern, materials, equipment and available exposure controls. The exposure assessment is initiated by selecting the appropriate exposure limit averaging time and "decision statistic" for the agent. Typically the statistic for deciding acceptable exposure is chosen to be the majority (90%, 95% or 99%) of all exposures to be below the selected occupational exposure limit. For retrospective exposure assessments performed in occupational environments, the "decision statistic" is typically a central tendency such as the arithmetic mean or geometric mean or median for each worker or group of workers. Methods for performing occupational exposure assessments can be found in "A Strategy for Assessing and Managing Occupational Exposures".
Exposure assessment is a continuous process that is updated as new information and data becomes available. | 1 | Applied and Interdisciplinary Chemistry |
In Pakistan's academia and nuclear society, Qureshi was well known for his interests in classical music theory and love of playing the guitar and sitar, which he played on several occasions. He also had an interest in American poetry, which he often quoted among his peers while working on the bomb program, and played tennis avidly during his later life. He was married twice; his first wife died in the 1980s and he later remarried. He had two sons, one a neurosurgeon while the other is a computer scientist. | 0 | Theoretical and Fundamental Chemistry |
For a pure substance in solution, if the color and path length are fixed and the specific rotation is known, the observed rotation can be used to calculate the concentration. This usage makes a polarimeter a tool of great importance to those trading in or using sugar syrups in bulk. | 0 | Theoretical and Fundamental Chemistry |
Safranin (Safranin O or basic red 2) is a biological stain used in histology and cytology. Safranin is used as a counterstain in some staining protocols, colouring cell nuclei red. This is the classic counterstain in both Gram stains and endospore staining. It can also be used for the detection of cartilage, mucin and mast cell granules.
Safranin typically has the chemical structure shown at right (sometimes described as dimethyl safranin). There is also trimethyl safranin, which has an added methyl group in the ortho- position (see Arene substitution pattern) of the lower ring. Both compounds behave essentially identically in biological staining applications, and most manufacturers of safranin do not distinguish between the two. Commercial safranin preparations often contain a blend of both types.
Safranin is also used as redox indicator in analytical chemistry. | 0 | Theoretical and Fundamental Chemistry |
Phototherapy may cause lipid peroxidation leading to rupture of red blood cell cell membranes in this way.
In addition, end-products of lipid peroxidation may be mutagenic and carcinogenic. For instance, the end-product MDA reacts with deoxyadenosine and deoxyguanosine in DNA, forming DNA adducts to them, primarily MG.
Reactive aldehydes can also form Michael adducts or Schiff bases with thiol or amine groups in amino acid side chains. Thus, they are able to inactivate sensitive proteins through electrophilic stress.
The toxicity of lipid hydroperoxides to animals is best illustrated by the lethal phenotype of glutathione peroxidase 4 (GPX4) knockout mice. These animals do not survive past embryonic day 8, indicating that the removal of lipid hydroperoxides is essential for mammalian life.
On the other hand, it's unclear whether dietary lipid peroxides are bioavailable and play a role in disease, as a healthy human body has protective mechanisms in place against such hazards. | 1 | Applied and Interdisciplinary Chemistry |
Large molecules may have isomers that differ by the topology of their overall arrangement in space, even if there is no specific geometric constraint that separate them. For example, long chains may be twisted to form topologically distinct knots, with interconversion prevented by bulky substituents or cycle closing (as in circular DNA and RNA plasmids). Some knots may come in mirror-image enantiomer pairs. Such forms are called topological isomers or topoisomers.
Also, two or more such molecules may be bound together in a catenane by such topological linkages, even if there is no chemical bond between them. If the molecules are large enough, the linking may occur in multiple topologically distinct ways, constituting different isomers. Cage compounds, such as helium enclosed in dodecahedrane (He@) and carbon peapods, are a similar type of topological isomerism involving molecules with large internal voids with restricted or no openings. | 0 | Theoretical and Fundamental Chemistry |
Wehrlite is an ultramafic and ultrabasic rock that is a mixture of olivine and clinopyroxene. It is a subdivision of the peridotites.
The nomenclature allows up to a few percent of orthopyroxene. Accessory minerals include ilmenite, chromite, magnetite and an aluminium-bearing mineral (plagioclase, spinel or garnet).
Wehrlites occur as mantle xenoliths and in ophiolites. Another occurrence is as cumulate in gabbro and norite layered intrusions. Some meteorites can also be classified as wehrlites (e.g. NWA 4797).
Wehrlite is named after Alois Wehrle. He was born 1791 in Kroměříž, Czech Republic (then Kremsier in Mähren) and was a professor at the "Ungarische Bergakademie" (Hungarian Mining School) in Banská Štiavnica, Slovakia (then Schemnitz, Kingdom of Hungary). | 0 | Theoretical and Fundamental Chemistry |
The far-eastern blot, or far-eastern blotting, is a technique for the analysis of lipids separated by high-performance thin layer chromatography (HPTLC). When executing the technique, lipids are transferred from HPTLC plates to a PVDF membrane for further analysis, for example by enzymatic or ligand binding assays and mass spectrometry. It was developed in 1994 by Taki and colleagues at the Tokyo Medical and Dental University, Japan. | 1 | Applied and Interdisciplinary Chemistry |
The branching index measures the effect of long-chain branches on the size of a macromolecule in solution. It is defined as g = >/>, where s is the mean square radius of gyration of the branched macromolecule in a given solvent, and s is the mean square radius of gyration of an otherwise identical linear macromolecule in the same solvent at the same temperature. A value greater than 1 indicates an increased radius of gyration due to branching. | 0 | Theoretical and Fundamental Chemistry |
The G protein-coupled receptor kinases (GRKs) are protein kinases that phosphorylate only active GPCRs. G-protein-coupled receptor kinases (GRKs) are key modulators of G-protein-coupled receptor (GPCR) signaling. They constitute a family of seven mammalian serine-threonine protein kinases that phosphorylate agonist-bound receptor. GRKs-mediated receptor phosphorylation rapidly initiates profound impairment of receptor signaling and desensitization. Activity of GRKs and subcellular targeting is tightly regulated by interaction with receptor domains, G protein subunits, lipids, anchoring proteins and calcium-sensitive proteins.
Phosphorylation of the receptor can have two consequences:
# Translocation: The receptor is, along with the part of the membrane it is embedded in, brought to the inside of the cell, where it is dephosphorylated within the acidic vesicular environment and then brought back. This mechanism is used to regulate long-term exposure, for example, to a hormone, by allowing resensitisation to follow desensitisation. Alternatively, the receptor may undergo lysozomal degradation, or remain internalised, where it is thought to participate in the initiation of signalling events, the nature of which depending on the internalised vesicle's subcellular localisation.
# Arrestin linking: The phosphorylated receptor can be linked to arrestin molecules that prevent it from binding (and activating) G proteins, in effect switching it off for a short period of time. This mechanism is used, for example, with rhodopsin in retina cells to compensate for exposure to bright light. In many cases, arrestin's binding to the receptor is a prerequisite for translocation. For example, beta-arrestin bound to β-adrenoreceptors acts as an adaptor for binding with clathrin, and with the beta-subunit of AP2 (clathrin adaptor molecules); thus, the arrestin here acts as a scaffold assembling the components needed for clathrin-mediated endocytosis of β-adrenoreceptors. | 1 | Applied and Interdisciplinary Chemistry |
The studies of crystalline ionic conductors where excess ions were provided by point defect continued through 1950s, and the specific mechanism of conduction was established for each compound depending on its ionic structure. The emergence of glassy and polymeric electrolytes in the late 1970s provided new ionic conduction mechanisms. A relatively wide range of conductivities was attained in glasses, wherein mobile ions were dynamically decoupled from the matrix. It was found that the conductivity could be increased by doping a glass with certain salts, or by using a glass mixture. The conductivity values could be as high as 0.03 S/cm at room temperature, with activation energies as low as 20 kJ/mol. Compared to crystals, glasses have isotropic properties, continuously tunable composition and good workability; they lack the detrimental grain boundaries and can be molded into any shape, but understanding their ionic transport was complicated by the lack of long-range order.
Historically, an evidence for ionic conductivity was provided back in the 1880s, when German scientists noticed that a well-calibrated thermometer made of Thuringian glass would show −0.5 °C instead of 0 °C when placed in ice shortly after immersion in boiling water, and recover only after several months. In 1883, they reduced this effect 10 times by replacing a mixture of sodium and potassium in the glass by either sodium or potassium. This finding helped Otto Schott develop the first accurate lithium-based thermometer. More systematic studies on ionic conductivity in glass appeared in 1884, but received broad attention only a century later. Several universal laws have been empirically formulated for ionic glasses and extended to other ionic conductors, such as the frequency dependence of electrical conductivity σ(ν) – σ(0) ~ ν, where the exponent p depends on the material, but not on temperature, at least below ~100 K. This behavior is a fingerprint of activated hopping conduction among nearby sites. | 0 | Theoretical and Fundamental Chemistry |
Nanoparticles are naturally produced by many cosmological, geological, meteorological, and biological processes. A significant fraction (by number, if not by mass) of interplanetary dust, that is still falling on the Earth at the rate of thousands of tons per year, is in the nanoparticle range; and the same is true of atmospheric dust particles. Many viruses have diameters in the nanoparticle range. | 0 | Theoretical and Fundamental Chemistry |
Abnormal proteolytic activity is associated with many diseases. In pancreatitis, leakage of proteases and their premature activation in the pancreas results in the self-digestion of the pancreas. People with diabetes mellitus may have increased lysosomal activity and the degradation of some proteins can increase significantly. Chronic inflammatory diseases such as rheumatoid arthritis may involve the release of lysosomal enzymes into extracellular space that break down surrounding tissues. Abnormal proteolysis may result in many age-related neurological diseases such as Alzheimer's due to generation and ineffective removal of peptides that aggregate in cells.
Proteases may be regulated by antiproteases or protease inhibitors, and imbalance between proteases and antiproteases can result in diseases, for example, in the destruction of lung tissues in emphysema brought on by smoking tobacco. Smoking is thought to increase the neutrophils and macrophages in the lung which release excessive amount of proteolytic enzymes such as elastase, such that they can no longer be inhibited by serpins such as α-antitrypsin, thereby resulting in the breaking down of connective tissues in the lung. Other proteases and their inhibitors may also be involved in this disease, for example matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs).
Other diseases linked to aberrant proteolysis include muscular dystrophy, degenerative skin disorders, respiratory and gastrointestinal diseases, and malignancy. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a diradical is a molecular species with two electrons occupying molecular orbitals (MOs) which are degenerate. The term "diradical" is mainly used to describe organic compounds, where most diradicals are extremely reactive and in fact rarely isolated. Diradicals are even-electron molecules but have one fewer bond than the number permitted by the octet rule.
Examples of diradical species can also be found in coordination chemistry, for example among bis(1,2-dithiolene) metal complexes. | 0 | Theoretical and Fundamental Chemistry |
Photosensitizers can be placed into 3 generalized domains based on their molecular structure. These three domains are organometallic photosensitizers, organic photosensitizers, and nanomaterial photosensitizers. | 0 | Theoretical and Fundamental Chemistry |
Kode Technology has been used for the in vitro modification of murine embryos, spermatozoa, zebra fish, epithelial/endometrial cells and red blood cells to create cellular quality controls systems, serologic kits (teaching), rare antigen expression, add infectious markers onto cells, modified cell adhesion/interaction/separation/immobilisation, and labelling. It has also been intravascularly infused for in vivo modification of blood cells and neutralisation of circulating antibodies and in in vivo imaging of circulating bone marrow kodecytes in zebrafish. Kode FSL constructs have also been applied to non-biological surfaces such as modified cellulose, paper, silica, polymers, natural fibers, glass and metals and has been shown to be ultra-fast in labelling these surfaces. | 1 | Applied and Interdisciplinary Chemistry |
Jābir analyzed each Aristotelian element in terms of Aristotles four basic qualities of hotness, coldness, dryness, and moistness. For example, fire is a substance that is hot and dry, as shown in the table. According to Jābir, in each metal two of these qualities were interior and two were exterior. For example, lead was externally cold and dry but internally hot and moist; gold, on the other hand, was externally hot and moist but internally cold and dry. He believed that metals were formed in the Earth by fusion of sulfur (giving the hot and dry qualities) with mercury (giving the cold and moist.) These elements, mercury and sulfur, should be thought of as not the ordinary elements but ideal, hypothetical substances. Which metal is formed depends on the purity of the mercury and sulfur and the proportion in which they come together. The later alchemist al-Rāzī (c. 865–925) followed Jābirs mercury-sulfur theory, but added a third, salty, component.
Thus, Jābir theorized, by rearranging the qualities of one metal, a different metal would result. By this reasoning, the search for the philosophers stone was introduced to Western alchemy. Jābir developed an elaborate numerology whereby the root letters of a substances name in Arabic, when treated with various transformations, held correspondences to the element's physical properties. | 1 | Applied and Interdisciplinary Chemistry |
Condensation polymers baring cleavable groups such as esters and amides can also be completely depolymerised by hydrolysis or solvolysis. This can be a purely chemical process but may also be promoted by enzymes. Such technologies are less well developed than those of thermal depolymerisation, but have the potential for lower energy costs. Thus far, polyethylene terephthalate has been the most heavily studied polymer. Alternatively, waste plastic may be converted into other valuable chemicals (not necessarily monomers) by microbial action. | 0 | Theoretical and Fundamental Chemistry |
# Clone the P element into a plasmid and transform and grow this in bacteria.
# Eliminate the P transposase and replace it with your gene of interest.
#Microinject the posterior end of an early-stage (pre-cellularization) embryo with DNA coding for transposase and a plasmid with the reporter gene, gene of interest and transposase recognition sequences.
#Random transposition occurs, inserting the gene of interest and reporter gene.
# Once the gene of interest has been inserted it is no longer mobile because it cannot produce its own P transposase.
#Grow flies and cross to remove genetic variation between the cells of the organism. (Only some of the cells of the organism will have been transformed. Hopefully, some of these transformed cells end up in the germ line. A transformed gamete will give rise to an organism with no variation between its cells).
#Look for flies expressing the reporter gene. These carry the inserted gene of interest, so can be investigated to determine the phenotype due to the gene of interest.
The inserted gene may have damaged the function of one of the host's genes. Several lines of flies are required so comparison can take place and ensure that no additional genes have been knocked out. | 1 | Applied and Interdisciplinary Chemistry |
In vitro studies using purified 20S proteasomes showed that salinosporamide A has lower EC50 for trypsin-like (T-L) activity than does bortezomib. In vivo animal model studies show marked inhibition of T-L activity in response to salinosporamide A, whereas bortezomib enhances T-L proteasome activity.
Initial results from early-stage clinical trials of salinosporamide A in relapsed/refractory multiple myeloma patients were presented at the 2011 American Society of Hematology annual meeting. Further early-stage trials of the drug in a number of different cancers are ongoing. | 0 | Theoretical and Fundamental Chemistry |
The name NANOG derives from Tír na nÓg (Irish for "Land of the Young"), a name given to the Celtic Otherworld in Irish and Scottish mythology. | 1 | Applied and Interdisciplinary Chemistry |
In the conversion of carbon dioxide to useful materials, the water–gas shift reaction is used to produce carbon monoxide from hydrogen and carbon dioxide. This is sometimes called the reverse water–gas shift reaction.
Water gas is defined as a fuel gas consisting mainly of carbon monoxide (CO) and hydrogen (H). The term ‘shift’ in water–gas shift means changing the water gas composition (CO:H) ratio. The ratio can be increased by adding CO or reduced by adding steam to the reactor. | 0 | Theoretical and Fundamental Chemistry |
A carbon atom that is attached to four different substituent groups is called an asymmetric carbon atom or chiral carbon. Chiral carbons are the most common type of chirality center. | 0 | Theoretical and Fundamental Chemistry |
These fission yields were calculated for U assuming thermal neutrons (0.0253 eV) using data from the chart of the nuclides. | 0 | Theoretical and Fundamental Chemistry |
Snf3 is a plasma membrane protein in yeasts that consists of 12 (2x6) transmembrane domains, like the homologous glucose transporters. Its structure is distinct from the homologous transporters in particular by a long C-terminal tail which is predicted to reside in the cytoplasm.
The long C-terminal tail plays an important role in glucose signaling and is probably the signaling domain itself. A soluble version of the C-terminal tail alone is sufficient to induce glucose transport.
All glucose transporters including Snf3 contain an arginine residue situated in a cytoplasmic loop preceding the fifth transmembrane domain. If this position is mutated, Snf3 adopts a state of constant glucose induction irrespective of whether there are nutrients present or not; this suggests an involvement in the glucose sensing process. | 1 | Applied and Interdisciplinary Chemistry |
On 23 November 2007, the use and trade of pseudoephedrine in Mexico was made illegal as it was argued that it was extremely popular as a precursor in the synthesis of methamphetamine. | 0 | Theoretical and Fundamental Chemistry |
The regulation of modafinil as a doping agent has been controversial in the sporting world, with high-profile cases attracting press coverage since several prominent American athletes tested positive for the substance. Some athletes who used modafinil protested that the drug was not on the prohibited list at the time of their offenses. However, the World Anti-Doping Agency (WADA) maintains that modafinil was related to already-banned substances. The Agency added modafinil to its list of prohibited substances on August 3, 2004, ten days before the start of the 2004 Summer Olympics.
Several athletes (such as sprinter Kelli White in 2003, cyclist David Clinger and basketball player Diana Taurasi in 2010, and rower Timothy Grant in 2015) were accused of using modafinil as a performance-enhancing doping agent. Taurasi and another player—Monique Coker, tested at the same lab—were later cleared. Kelli White, who tested positive after her 100m victory at the 2003 World Championships in Paris, was stripped of her gold medals. She claimed that she used modafinil to treat narcolepsy, but the International Association of Athletics Federations (IAAF) ruled that modafinil was a performance-enhancing drug.
The BALCO scandal brought to light an unsubstantiated (but widely published) account of Major League Baseballs all-time leading home-run hitter Barry Bonds supplemental chemical regimen that included modafinil in addition to anabolic steroids and human growth hormone. | 0 | Theoretical and Fundamental Chemistry |
The slow processing speed of a DNA computer (the response time is measured in minutes, hours or days, rather than milliseconds) is compensated by its potential to make a high amount of multiple parallel computations. This allows the system to take a similar amount of time for a complex calculation as for a simple one. This is achieved by the fact that millions or billions of molecules interact with each other simultaneously. However, it is much harder to analyze the answers given by a DNA computer than by a digital one. | 1 | Applied and Interdisciplinary Chemistry |
Enantioselective intermolecular cyclopropanation has been applied to the synthesis of the chiral cyclopropane antibiotics cilastatin.
Tandem cyclopropanation/fragmentation is a key step in the synthesis of 12-hydroxyeicosatetraenoic acid. | 0 | Theoretical and Fundamental Chemistry |
A standpipe or riser is a type of rigid water piping which is built into multi-story buildings in a vertical position, or into bridges in a horizontal position, to which fire hoses can be connected, allowing manual application of water to the fire. Within the context of a building or bridge, a standpipe serves the same purpose as a fire hydrant. | 1 | Applied and Interdisciplinary Chemistry |
Although the heat from the carbonator is not at a high enough temperature to be used in the calciner, the high temperatures involved (>600 °C) mean that a relatively efficient Rankine cycle for generating electricity can be operated.
Note that the waste heat from the market-leading amine scrubbing CO capture process is emitted at a maximum of 150 °C. The low temperature of this heat means that it contains much less exergy and can generate much less electricity through a Rankine or organic Rankine cycle.
This electricity generation is one of the main benefits of CaL over lower-temperature post-combustion capture processes as the electricity is an extra revenue stream (or reduces costs). | 1 | Applied and Interdisciplinary Chemistry |
Many authors, for example Greco and Hakala, have claimed that non-linear regression is always superior to regression of the linear forms of the Michaelis–Menten equation. However, that is correct only if the appropriate weighting scheme is used, preferably on the basis of experimental investigation, something that is almost never done. As noted above, Burk carried out the appropriate investigation, and found that the error structure of his data was consistent with a uniform standard deviation in . More recent studies found that a uniform coefficient of variation (standard deviation expressed as a percentage) was closer to the truth with the techniques in use in the 1970s. However, this truth may be more complicated than any dependence on alone can represent.
Uniform standard deviation of . If the rates are considered to have a uniform standard deviation the appropriate weight for every value for non-linear regression is 1. If the double-reciprocal plot is used each value of should have a weight of , whereas if the Hanes plot is used each value of should have a weight of .
Uniform coefficient variation of . If the rates are considered to have a uniform coefficient variation the appropriate weight for every value for non-linear regression is . If the double-reciprocal plot is used each value of should have a weight of , whereas if the Hanes plot is used each value of should have a weight of .
Ideally the in each of these cases should be the true value, but that is always unknown. However, after a preliminary estimation one can use the calculated values for refining the estimation. In practice the error structure of enzyme kinetic data is very rarely investigated experimentally, therefore almost never known, but simply assumed. It is, however, possible to form an impression of the error structure from internal evidence in the data. This is tedious to do by hand, but can readily be done in the computer. | 0 | Theoretical and Fundamental Chemistry |
Interaction of E. coli exometabolites with C. elegans affects life span.
Bacteria and yeast in dairy systems. | 1 | Applied and Interdisciplinary Chemistry |
Herbicides (, ), also commonly known as weed killers, are substances used to control undesired plants, also known as weeds. Selective herbicides control specific weed species while leaving the desired crop relatively unharmed, while non-selective herbicides (sometimes called "total weed killers") kill plants indiscriminately. The combined effects of herbicides, nitrogen fertilizer, and improved cultivars has increased yields (per acre) of major crops by 3x to 6x from 1900 to 2000.
In the United States in 2012, about 91% of all herbicide usage, determined by weight applied, was in agriculture. In 2012, world pesticide expenditures totaled nearly $24.7 billion; herbicides were about 44% of those sales and constituted the biggest portion, followed by insecticides, fungicides, and fumigants. Herbicide is also used in forestry, where certain formulations have been found to suppress hardwood varieties in favor of conifers after clearcutting, as well as pasture systems. | 1 | Applied and Interdisciplinary Chemistry |
In 1992, a Japan–U.S. joint-team proposed a novel direct energy conversion system for 14.7 MeV protons produced by D-He fusion reactions, whose energy is too high for electrostatic converters.
The conversion is based on a Traveling-Wave Direct Energy Converter (TWDEC). A gyrotron converter first guides fusion product ions as a beam into a 10-meter long microwave cavity filled with a 10-tesla magnetic field, where 155 MHz microwaves are generated and converted to a high voltage DC output through rectennas.
The Field-Reversed Configuration reactor ARTEMIS in this study was designed with an efficiency of 75%. The traveling-wave direct converter has a maximum projected efficiency of 90%. | 0 | Theoretical and Fundamental Chemistry |
The Ružička large-ring synthesis or Ružička reaction or Ružička cyclization is an organic reaction in which a dicarboxylic acid is converted to a cyclic ketone via heating with a thorium oxide catalyst. The reaction is named after Lavoslav Ružička, who invented it in 1926.
The reaction has been applied in the synthesis of Exaltone, a low-toxicity synthetic musk. | 0 | Theoretical and Fundamental Chemistry |
A ketyl group in organic chemistry is an anion radical that contains a group RCO. It is the product of the 1-electron reduction of a ketone.
Another mesomeric structure has the radical position on carbon and the negative charge on oxygen.
Ketyls can be formed as radical anions by one-electron reduction of carbonyls with alkali metals. Sodium and potassium metal reduce benzophenone in THF solution to the soluble ketyl radical. Ketyls are also invoked as intermediates in the pinacol coupling reaction. | 0 | Theoretical and Fundamental Chemistry |
* Bacteriophytochrome
* sensory bacteriorhodopsin
* Halorhodopsin
* Proteorhodopsin
* Cyanobacteriochrome | 1 | Applied and Interdisciplinary Chemistry |
A final substrate-level phosphorylation now forms a molecule of pyruvate and a molecule of ATP by means of the enzyme pyruvate kinase. This serves as an additional regulatory step, similar to the phosphoglycerate kinase step.
Cofactors: Mg | 1 | Applied and Interdisciplinary Chemistry |
Endergonic reactions can be achieved if they are either pulled or pushed by an exergonic (stability increasing, negative change in free energy) process. Of course, in all cases the net reaction of the total system (the reaction under study plus the puller or pusher reaction) is exergonic. | 0 | Theoretical and Fundamental Chemistry |
* M.J.R Cantow Polymer Fractionation Academic Press, New York (1967)
* L.H. Tung Fractionation of Synthetic Polymers Marcel Dekker, New York (1977)
* F. Francuskiewicz Polymer Fractionation Springer, Berlin (1994)
* R. Koningsveld, L.D. Kleintjens, H. Geerissen, P. Schützeichel, B.A. Wolf „Fractionation“ in: Comprehensive Polymer Science Volume 1 Pergamon Press, Oxford (1989) 293-312 | 0 | Theoretical and Fundamental Chemistry |
Hydrology considers quantifying surface water flow and solute transport, although the treatment of flows in large rivers is sometimes considered as a distinct topic of hydraulics or hydrodynamics. Surface water flow can include flow both in recognizable river channels and otherwise. Methods for measuring flow once the water has reached a river include the stream gauge (see: discharge), and tracer techniques. Other topics include chemical transport as part of surface water, sediment transport and erosion.
One of the important areas of hydrology is the interchange between rivers and aquifers. Groundwater/surface water interactions in streams and aquifers can be complex and the direction of net water flux (into surface water or into the aquifer) may vary spatially along a stream channel and over time at any particular location, depending on the relationship between stream stage and groundwater levels. | 1 | Applied and Interdisciplinary Chemistry |
The orientation of a glide plane is given by the position of the symbol in the Hermann–Mauguin designation, just as with mirror planes.
They are noted by a, b, or c depending on which axis (direction) the glide is along. There is also the n glide, which is a glide along the half of a diagonal of a face, and the d glide, which is along a quarter of either a face or space diagonal of the unit cell. The d glide is often called the diamond glide plane as it features in the diamond structure. In cases where there are two possibilities among a, b, and c (such as a or b), the letter e is used. (In these cases, centering entails that both glides occur.) To summarize:
* a, b, or c glide translation along half the lattice vector of this face.
* n glide translation along half a face diagonal.
* d glide planes with translation along a quarter of a face diagonal or of a space diagonal.
* e two glides with the same glide plane and translation along two (different) half-lattice vectors. | 0 | Theoretical and Fundamental Chemistry |
Metabolic network modelling aims at reproducing cellular metabolism in silico. Metabolite damage and repair create cellular energy costs, and consequently need to be incorporated into genome-scale metabolic models so that these models can more effectively guide metabolic engineering design.
In addition, genes encoding so-far unrecognized metabolite damage-control systems may constitute a significant fraction of the many conserved genes of unknown function found in the genomes of all organisms. | 1 | Applied and Interdisciplinary Chemistry |
In physical chemistry and materials science, texture is the distribution of crystallographic orientations of a polycrystalline sample (it is also part of the geological fabric). A sample in which these orientations are fully random is said to have no distinct texture. If the crystallographic orientations are not random, but have some preferred orientation, then the sample has a weak, moderate or strong texture. The degree is dependent on the percentage of crystals having the preferred orientation.
Texture is seen in almost all engineered materials, and can have a great influence on materials properties. The texture forms in materials during thermo-mechanical processes, for example during production processes e.g. rolling. Consequently, the rolling process is often followed by a heat treatment to reduce the amount of unwanted texture. Controlling the production process in combination with the characterization of texture and the materials microstructure help to determine the materials properties, i.e. the processing-microstructure-texture-property relationship'. Also, geologic rocks show texture due to their thermo-mechanic history of formation processes.
One extreme case is a complete lack of texture: a solid with perfectly random crystallite orientation will have isotropic properties at length scales sufficiently larger than the size of the crystallites. The opposite extreme is a perfect single crystal, which likely has anisotropic properties by geometric necessity. | 1 | Applied and Interdisciplinary Chemistry |
The included cutting angles of all kinds of sharp edge blades are measured using a laser reflecting goniometer. Developed by the Cutlery and Allied Trades Research Association (CATRA) in the UK, a range of devices can accurately determine the cutting edge profile, including a rounding of the tip to ½°. The included angle of a blade is important in controlling its cutting ability and edge strength—i.e., a low angle makes a thin sharp edge optimized for cutting softer materials, while a large angle makes a thick edge that is less sharp but stronger, which may be better for cutting harder materials. | 0 | Theoretical and Fundamental Chemistry |
Roughly 5 grams of iron are present in the human body and is the most abundant trace metal. It is absorbed in the intestine as heme or non-heme iron depending on the food source. Heme iron is derived from the digestion of hemoproteins in meat. Non-heme iron is mainly derived from plants and exist as iron(II) or iron(III) ions.
Iron is essential for more than 500 hemeproteins, the likes of which include hemoglobin and myoglobin, and account for 80% of iron usage. The other 20% is present in ferritin, hemosiderin, iron-sulfur (Fe/S) proteins, such as ferrochelatase, and more. | 0 | Theoretical and Fundamental Chemistry |
Stream metabolism, often referred to as aquatic ecosystem metabolism in both freshwater (lakes, rivers, wetlands, streams, reservoirs) and marine ecosystems, includes gross primary productivity (GPP) and ecosystem respiration (ER) and can be expressed as net ecosystem production (NEP = GPP - ER). Analogous to metabolism within an individual organism, stream metabolism represents how energy is created (primary production) and used (respiration) within an aquatic ecosystem. In heterotrophic ecosystems, GPP:ER is <1 (ecosystem using more energy than it is creating); in autotrophic ecosystems it is >1 (ecosystem creating more energy than it is using).[https://doi.org/10.4319/lo.1956.1.2.0102] Most streams are heterotrophic.[https://doi.org/10.1016/B978-0-12-813047-6.00012-7] A heterotrophic ecosystem often means that allochthonous (coming from outside the ecosystem) inputs of organic matter, such as leaves or debris fuel ecosystem respiration rates, resulting in respiration greater than production within the ecosystem. However, autochthonous (coming from within the ecosystem) pathways also remain important to metabolism in heterotrophic ecosystems. In an autotrophic ecosystem, conversely, primary production (by algae, macrophytes) exceeds respiration, meaning that ecosystem is producing more organic carbon than it is respiring.
Stream metabolism can be influenced by a variety of factors, including physical characteristics of the stream (slope, width, depth, and speed/volume of flow), biotic characteristics of the stream (abundance and diversity of organisms ranging from bacteria to fish), light and nutrient availability to fuel primary production, organic matter to fuel respiration, water chemistry and temperature, and natural or human-caused disturbance, such as dams, removal of riparian vegetation, nutrient pollution, wildfire or flooding.
Measuring stream metabolic state is important to understand how disturbance may change the available primary productivity, and whether and how that increase or decrease in NEP influences foodweb dynamics, allochthonous/autochthonous pathways, and trophic interactions. Metabolism (encompassing both ER and GPP) must be measured rather than primary productivity alone, because simply measuring primary productivity does not indicate excess production available for higher trophic levels. One commonly used method for determining metabolic state in an aquatic system is daily changes in oxygen concentration, from which GPP, ER, and net daily metabolism can be estimated.
Disturbances can affect trophic relationships in a variety of ways, such as simplifying foodwebs, causing trophic cascades, and shifting carbon sources and major pathways of energy flow (Power et al. 1985, Power et al. 2008). Part of understanding how disturbance will impact trophic dynamics lies in understanding disturbance impacts to stream metabolism (Holtgrieve et al. 2010). For example, in Alaska streams, disturbance of the benthos by spawning salmon caused distinct changes in stream metabolism; autotrophic streams became net heterotrophic during the spawning run, then reverted to autotrophy after the spawning season (Holtgrieve and Schindler 2011). There is evidence that this seasonal disturbance impacts trophic dynamics of benthic invertebrates and in turn their vertebrate predators (Holtgrieve and Schindler 2011, Moore and Schindler 2008). Wildfire disturbance may have similar metabolic and trophic impacts in streams. | 1 | Applied and Interdisciplinary Chemistry |
As with the case of superfluid liquid helium, atomic nuclei are an example of a state in which both (1) "ordinary" particle physical rules for volume and (2) non-intuitive quantum mechanical rules for a wave-like nature apply. In superfluid helium, the helium atoms have volume, and essentially "touch" each other, yet at the same time exhibit strange bulk properties, consistent with a Bose–Einstein condensation. The nucleons in atomic nuclei also exhibit a wave-like nature and lack standard fluid properties, such as friction. For nuclei made of hadrons which are fermions, Bose-Einstein condensation does not occur, yet nevertheless, many nuclear properties can only be explained similarly by a combination of properties of particles with volume, in addition to the frictionless motion characteristic of the wave-like behavior of objects trapped in Erwin Schrödinger's quantum orbitals. | 0 | Theoretical and Fundamental Chemistry |
The third stage of DNA demethylation is removal of the intermediate products of demethylation generated by a TET enzyme by base excision repair. As indicated above in Stage 2, after 5mC is first oxidized by a TET to form 5hmC, further oxidation of 5hmC by TET yields 5fC and oxidation of 5fC by TET yields 5caC. Both 5fC and 5caC are recognized by a DNA glycosylase, TDG, a base excision repair enzyme, as an abnormal base. As shown in the Figure in this section, TDG removes the abnormal base (e.g. 5fC) while leaving the sugar-phosphate backbone intact, creating an apurinic/apyrimidinic site, commonly referred to as an AP site. In this Figure, the 8-OHdG is left in the DNA, since it may have been present when OGG1 attracted TET1 to the CpG site with a methylated cytosine. After an AP site is formed, AP endonuclease creates a nick in the phosphodiester backbone of the AP site that was formed when the TDG DNA glycosylase removed the 5fC or 5caC. The human AP endonuclease incises DNA 5′ to the AP site by a hydrolytic mechanism, leaving a 3′-hydroxyl and a 5′-deoxyribose phosphate (5' dRP) residue. This is followed by either short patch or long patch repair. In short patch repair, 5′ dRP lyase trims the 5′ dRP end to form a phosphorylated 5′ end. This is followed by DNA polymerase β (pol β) adding a single cytosine to pair with the pre-existing guanine in the complementary strand and then DNA ligase to seal the cut strand. In long patch repair, DNA synthesis is thought to be mediated by polymerase δ and polymerase ε performing displacement synthesis to form a flap. Pol β can also perform long-patch displacement synthesis. Long-patch synthesis typically inserts 2–10 new nucleotides. Then flap endonuclease removes the flap, and this is followed by DNA ligase to seal the strand. At this point there has been a complete replacement of the 5-methylcytosine by cytosine (demethylation) in the DNA sequence. | 1 | Applied and Interdisciplinary Chemistry |
The insertion of alkenes into both metal-carbon is important. The insertion of ethylene and propylene into titanium alkyls is the cornerstone of Ziegler–Natta catalysis, the main source of polyethylene and polypropylene. The majority of this technology involves heterogeneous catalysts, but it is widely assumed that the principles and observations on homogeneous systems are applicable to the solid-state versions. Related technologies include the Shell Higher Olefin Process which produces detergent precursors. | 0 | Theoretical and Fundamental Chemistry |
Part of the extraordinary potential of hyrax middens as palaeoenvironmental archives is the large range of proxies that are contained within them. Initially, when their diachronic nature was less evident, they were viewed as the poor relation to the better studied pack rat middens. While pack rat middens are rich in identifiable macrofossils, which can be directly dated and provide high taxonomic resolution, hyrax middens are poor in macroremains. Those that are found are almost exclusively masticated material that has been incorporated into the deposits as faecal pellets. While some studies have analysed these midden components, more recent work suggests that this approach does not maximise the full potential of hyrax middens as palaeoenvironmental archives
Hyrax middens contain a suite of proxies that have the potential to provide clear insights into past climate and vegetation change. Working within the context of the middens’ stratigraphy, and building on robust chronologies indicating predictable and consistent accumulation rates, sampling methodologies are now more akin to those applied to speleothems rather than to packrat middens. Whereas the early focus was on small (N), as the relative roles of climatic forcing versus vegetation dynamics related to competitive processes within an ecosystem can be better resolved, resulting in a fuller and more reliable understanding of palaeoenvironmental dynamics | 0 | Theoretical and Fundamental Chemistry |
The liquid junction potential cannot be measured directly but calculated. The electromotive force (EMF) of a concentration cell with transference includes the liquid junction potential.
The EMF of a concentration cell without transport is:
where and are activities of HCl in the two solutions, is the universal gas constant, is the temperature and is the Faraday constant.
The EMF of a concentration cell with transport (including the ion transport number) is:
where and are activities of HCl solutions of right and left hand electrodes, respectively, and is the transport number of Cl.
Liquid junction potential is the difference between the two EMFs of the two concentration cells, with and without ionic transport: | 0 | Theoretical and Fundamental Chemistry |
The RNA integrity number (RIN) is an algorithm for assigning integrity values to RNA measurements.
The integrity of RNA is a major concern for gene expression studies and traditionally has been evaluated using the 28S to 18S rRNA ratio, a method that has been shown to be inconsistent. This inconsistency arises because subjective, human interpretation is necessary to compare the 28S and 18S gel images. The RIN algorithm was devised to overcome this issue. The RIN algorithm is applied to electrophoretic RNA measurements, typically obtained using capillary gel electrophoresis, and based on a combination of different features that contribute information about the RNA integrity to provide a more universal measure. RIN has been demonstrated to be robust and reproducible in studies comparing it to other RNA integrity calculation algorithms, cementing its position as a preferred method of determining the quality of RNA to be analyzed.
A major criticism to RIN is when using with plants or in studies of eukaryotic-prokaryotic cells interactions. The RIN algorithm is unable to differentiate eukaryotic/prokaryotic/chloroplastic ribosomal RNA, creating serious quality index underestimation in such situations. | 1 | Applied and Interdisciplinary Chemistry |
Ground water is water beneath Earth's surface, often pumped for drinking water. Groundwater hydrology (hydrogeology) considers quantifying groundwater flow and solute transport. Problems in describing the saturated zone include the characterization of aquifers in terms of flow direction, groundwater pressure and, by inference, groundwater depth (see: aquifer test). Measurements here can be made using a piezometer. Aquifers are also described in terms of hydraulic conductivity, storativity and transmissivity. There are a number of geophysical methods for characterizing aquifers. There are also problems in characterizing the vadose zone (unsaturated zone). | 1 | Applied and Interdisciplinary Chemistry |
Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluorescence, a phosphorescent material does not immediately reemit the radiation it absorbs. Instead, a phosphorescent material absorbs some of the radiation energy and reemits it for a much longer time after the radiation source is removed.
In a general sense, there is no distinct boundary between the emission times of fluorescence and phosphorescence (i.e.: if a substance glows under a black light it is generally considered fluorescent, and if it glows in the dark it is often simply called phosphorescent). In a modern, scientific sense, the phenomena can usually be classified by the three different mechanisms that produce the light, and the typical timescales during which those mechanisms emit light. Whereas fluorescent materials stop emitting light within nanoseconds (billionths of a second) after the excitation radiation is removed, phosphorescent materials may continue to emit an afterglow ranging from a few microseconds to many hours after the excitation is removed.
There are two separate mechanisms that may produce phosphorescence, called triplet phosphorescence (or simply phosphorescence) and persistent phosphorescence (or persistent luminescence). Triplet phosphorescence occurs when an atom absorbs a high-energy photon, and the energy becomes locked in the spin multiplicity of the electrons, generally changing from a fluorescent "singlet state" to a slower emitting "triplet state". The slower timescales of the reemission are associated with "forbidden" energy state transitions in quantum mechanics. As these transitions occur relatively slowly in certain materials, absorbed radiation is reemitted at a lower intensity, ranging from a few microseconds to as much as one second after the excitation is removed.
On the other hand, persistent phosphorescence occurs when a high-energy photon is absorbed by an atom and its electron becomes trapped in a defect in the lattice of the crystalline or amorphous material. A defect such as a missing atom (vacancy defect) can trap an electron like a pitfall, storing that electron's energy until released by a random spike of thermal (vibrational) energy. Such a substance will then emit light of gradually decreasing intensity, ranging from a few seconds to up to several hours after the original excitation.
Everyday examples of phosphorescent materials are the glow-in-the-dark toys, stickers, paint, and clock dials that glow after being charged with a bright light such as in any normal reading or room light. Typically, the glow slowly fades out, sometimes within a few minutes or up to a few hours in a dark room.
The study of phosphorescent materials led to the discovery of radioactive decay. | 0 | Theoretical and Fundamental Chemistry |
The third case described by Asakura and Oosawa is two plates in a solution of polymers. Due to the size of the polymers, the concentration of polymers in the neighborhood of the plates is reduced, which result the conformational entropy of the polymers being decreased. The case can be approximated by modeling it as diffusion in a vessel with walls which absorb diffusing particles. The force, , can then be calculated according to:
In this equation is the attraction from the osmotic effect. is the repulsion due to chain molecules confined between plates. is on order of , the mean end-to-end distance of chain molecules in free space. | 0 | Theoretical and Fundamental Chemistry |
Planning practices include several related approaches that were developed independently by various practitioners. These differently named approaches include similar concepts and share similar goals in protecting water quality.
*Conservation design, also called Conservation Development
*Better Site Design
*Green Infrastructure.
Planners select structural LID practices for an individual site in consideration of the site's land use, hydrology, soil type, climate and rainfall patterns. There are many variations on these LID practices, and some practices may not be suitable for a given site. Many are practical for retrofit or site renovation projects, as well as for new construction. Optimal places for retrofitting LID are single houses, school/university areas, and parks. Frequently used practices include:
*Bioretention cells, also known as rain gardens
*Cisterns and rain barrels
*Green roofs
*Pervious concrete, also called "porous pavement", similar to Permeable paving
*Grassed swales, also known as bioswales.
*Commercially manufactured stormwater management devices that capture pollutants (e.g., media filters) and/or aid in on-site infiltration.
*Tree pits | 1 | Applied and Interdisciplinary Chemistry |
Chemical bleaching is achieved by oxidation or reduction. Oxidation can destroy the dye completely, e.g. through the use of sodium hypochlorite (NaClO, common bleach) or hydrogen peroxide. Reduction of methyl violet occurs in microorganisms but can be attained chemically using sodium dithionite. | 0 | Theoretical and Fundamental Chemistry |
In 1978, Hoffmann reported the first asymmetric carbonyl allylation using a chiral allylmetal reagent, an allylborane derived from camphor. Such methods utilize preformed allyl metal reagents. The approach is well developed using allyl boranes
As illustrated by the Keck allylation, catalytic enantioselective additions of achiral allylmetal reagents to carbonyl compounds also are possible by organostannane additions.
Allylic boronate and -borane reagents have also been developed for enantioselective addition to carbonyls—in this class of reactions, the allylic boron reagent confers stereochemical control | 0 | Theoretical and Fundamental Chemistry |
Much of the analysis of what was viewed in the pipeline is conducted at the time of the inspection by the camera operator, but the entire inspection is always recorded and saved for review. Commercial software and hardware for video pipe inspection are available from a variety of vendors, including Cues, ITpipes, and WinCan. | 1 | Applied and Interdisciplinary Chemistry |
China banned expanded polystyrene takeout/takeaway containers and tableware in 1999, but later revoked the policy in 2013 amidst industry lobbying. Haiti banned foam food containers in 2012 to reduce waste in canals and roadside drains. In 2019, the European Parliament voted 560 to 35 to ban all food and beverage containers made from expanded polystyrene throughout the European Union member states. Canada amended its Canadian Environmental Protection Act, 1999 in 2022 to prohibit foodservice ware made of expanded or extruded polystyrene, and also polyvinyl chloride, black colored plastics, or oxo-degraded plastics. | 0 | Theoretical and Fundamental Chemistry |
The negative charge of its phosphate backbone moves the DNA towards the positively charged anode during electrophoresis. However, the migration of DNA molecules in solution, in the absence of a gel matrix, is independent of molecular weight during electrophoresis, i.e. there is no separation by size without a gel matrix. Hydrodynamic interaction between different parts of the DNA are cut off by streaming counterions moving in the opposite direction, so no mechanism exists to generate a dependence of velocity on length on a scale larger than screening length of about 10 nm. This makes it different from other processes such as sedimentation or diffusion where long-ranged hydrodynamic interaction are important.
The gel matrix is therefore responsible for the separation of DNA by size during electrophoresis, however the precise mechanism responsible the separation is not entirely clear. A number of models exists for the mechanism of separation of biomolecules in gel matrix, a widely accepted one is the Ogston model which treats the polymer matrix as a sieve consisting of randomly distributed network of inter-connected pores. A globular protein or a random coil DNA moves through the connected pores large enough to accommodate its passage, and the movement of larger molecules is more likely to be impeded and slowed down by collisions with the gel matrix, and the molecules of different sizes can therefore be separated in this process of sieving.
The Ogston model however breaks down for large molecules whereby the pores are significantly smaller than size of the molecule. For DNA molecules of size greater than 1 kb, a reptation model (or its variants) is most commonly used. This model assumes that the DNA can crawl in a "snake-like" fashion (hence "reptation") through the pores as an elongated molecule. At higher electric field strength, this turned into a biased reptation model, whereby the leading end of the molecule become strongly biased in the forward direction, and this leading edge pulls the rest of the molecule along. In the fully biased mode, the mobility reached a saturation point and DNA beyond a certain size cannot be separated. Perfect parallel alignment of the chain with the field however is not observed in practice as that would mean the same mobility for long and short molecules. Further refinement of the biased reptation model takes into account of the internal fluctuations of the chain.
The biased reptation model has also been used to explain the mobility of DNA in PFGE. The orientation of the DNA is progressively built up by reptation after the onset of a field, and the time it reached the steady state velocity is dependent on the size of the molecule. When the field is changed, larger molecules take longer to reorientate, it is therefore possible to discriminate between the long chains that cannot reach its steady state velocity from the short ones that travel most of the time in steady velocity. Other models, however, also exist.
Real-time fluorescence microscopy of stained molecules showed more subtle dynamics during electrophoresis, with the DNA showing considerable elasticity as it alternately stretching in the direction of the applied field and then contracting into a ball, or becoming hooked into a U-shape when it gets caught on the polymer fibres. This observation may be termed the "caterpillar" model. Other model proposes that the DNA gets entangled with the polymer matrix, and the larger the molecule, the more likely it is to become entangled and its movement impeded. | 1 | Applied and Interdisciplinary Chemistry |
Unlike wet coating processes, metal evaporated (ME) media are fabricated by physical deposition of vaporized cobalt or cobalt-nickel mix in a vacuum chamber. There is no synthetic binder to hold particles together; instead, they adhere directly to polyester tape substrate. An electron beam melts source metal, creating a continuous directional flow of cobalt atoms towards the tape. The zone of contact between the beam and the tape is blown with a controlled flow of oxygen, which helps formation of polycrystalline metal-oxide coating. A massive liquid-cooled rotating drum, which pulls the tape into the contact zone, protects it from overheating.
Metal evaporated coatings, along with barium ferrite, have the highest information density of all rerecordable media. The technology was introduced in 1978 by Panasonic, initially in the form of audio microcassettes, and matured through the 1980s. Metal evaporated media established itself in analogue (Hi8) and digital (Digital8, DV and MicroMV) videotape market, and data storage (Advanced Intelligent Tape, Linear Tape Open). The technology seemed promising for analogue audio recording; however, very thin metal evaporated layers were too fragile for consumer cassette decks, the coatings too thin for good MOL, and manufacturing costs were prohibitively high. Panasonic Type I, Type II and Type IV metal evaporated cassettes, introduced in 1984, were sold for only a few years in Japan alone, and remained unknown in the rest of the world. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry and biochemistry it is customary to use pK values for acid dissociation equilibria.
where log denotes a logarithm to base 10 or common logarithm, and K is a stepwise acid dissociation constant. For bases, the base association constant, pK is used. For any given acid or base the two constants are related by , so pK can always be used in calculations.
On the other hand, stability constants for metal complexes, and binding constants for host–guest complexes are generally expressed as association constants. When considering equilibria such as
:M + HL ML + H
it is customary to use association constants for both ML and HL. Also, in generalized computer programs dealing with equilibrium constants it is general practice to use cumulative constants rather than stepwise constants and to omit ionic charges from equilibrium expressions. For example, if NTA, nitrilotriacetic acid, N(CHCOH) is designated as HL and forms complexes ML and MHL with a metal ion M, the following expressions would apply for the dissociation constants.
The cumulative association constants can be expressed as
Note how the subscripts define the stoichiometry of the equilibrium product. | 0 | Theoretical and Fundamental Chemistry |
A noise barrier (also called a soundwall, noise wall, sound berm, sound barrier, or acoustical barrier) is an exterior structure designed to protect inhabitants of sensitive land use areas from noise pollution. Noise barriers are the most effective method of mitigating roadway, railway, and industrial noise sources –
other than cessation of the source activity or use of source controls.
In the case of surface transportation noise, other methods of reducing the source noise intensity include encouraging the use of hybrid and electric vehicles, improving automobile aerodynamics and tire design, and choosing low-noise paving material. Extensive use of noise barriers began in the United States after noise regulations were introduced in the early 1970s. | 1 | Applied and Interdisciplinary Chemistry |
The second generation EGFR inhibitors Afatinib and Mobocertinib have been approved for the treatment of EGFR driven lung cancer and Dacomitinib is in late stage clinical testing. The third generation EGFR inhibitors which target mutant EGFR which is specific to the tumor but are selective against wild-type EGFR that are expected to lead to a wider therapeutic index. | 1 | Applied and Interdisciplinary Chemistry |
Potassium tert-butoxide catalyzes the reaction of hydrosilanes and heterocyclic compounds to give the silyl derivatives, with release of H. | 0 | Theoretical and Fundamental Chemistry |
ASC customers include manufacturing and processing firms from a wide variety of industries, including:
* Electricity / power generation
* Renewable energy
* Food processing
* Manufacturing
* Metals processing / heat treating
* Heating, Ventilation, and Air Conditioning (HVAC) of buildings
* Cement and mineral production and mining
* Pulp and paper
* Sporting equipment Aerodynamics
* Steel producers
* Automotive industry and auto racing companies
* Class I railroads and railcar manufacturers
* Biotechnology firms
ASC has performed over 4000 engineering studies worldwide since 1975. | 1 | Applied and Interdisciplinary Chemistry |
Isotope electrochemistry is a field within electrochemistry concerned with various topics like electrochemical separation of isotopes, electrochemical estimation of isotopic exchange equilibrium constants, electrochemical kinetic isotope effect, electrochemical isotope sensors, etc.
It is an active domain of investigation. It overlaps with many other domains of both theoretical and practical importance like nuclear engineering, radiochemistry, electrochemical technology, geochemistry, sensors and instrumentation. | 0 | Theoretical and Fundamental Chemistry |
Given the short sequences of most promoter elements, promoters can rapidly evolve from random sequences. For instance, in E. coli, ~60% of random sequences can evolve expression levels comparable to the wild-type lac promoter with only one mutation, and that ~10% of random sequences can serve as active promoters even without evolution. | 1 | Applied and Interdisciplinary Chemistry |
Studies in 2007 have catalogued nucleosome positions in yeast and shown that nucleosomes are depleted in promoter regions and origins of replication.
About 80% of the yeast genome appears to be covered by nucleosomes and the pattern of nucleosome positioning clearly relates to DNA regions that regulate transcription, regions that are transcribed and regions that initiate DNA replication. Most recently, a new study examined dynamic changes in nucleosome repositioning during a global transcriptional reprogramming event to elucidate the effects on nucleosome displacement during genome-wide transcriptional changes in yeast (Saccharomyces cerevisiae). The results suggested that nucleosomes that were localized to promoter regions are displaced in response to stress (like heat shock). In addition, the removal of nucleosomes usually corresponded to transcriptional activation and the replacement of nucleosomes usually corresponded to transcriptional repression, presumably because transcription factor binding sites became more or less accessible, respectively. In general, only one or two nucleosomes were repositioned at the promoter to effect these transcriptional changes. However, even in chromosomal regions that were not associated with transcriptional changes, nucleosome repositioning was observed, suggesting that the covering and uncovering of transcriptional DNA does not necessarily produce a transcriptional event. After transcription, the rDNA region has to protected from any damage, it suggested HMGB proteins play a major role in protecting the nucleosome free region. | 1 | Applied and Interdisciplinary Chemistry |
Volume Bragg gratings (VBG) or volume holographic gratings (VHG) consist of a volume where there is a periodic change in the refractive index. Depending on the orientation of the refractive index modulation, VBG can be used either to transmit or reflect a small bandwidth of wavelengths. Bragg's law (adapted for volume hologram) dictates which wavelength will be diffracted:
where is the Bragg order (a positive integer), the diffracted wavelength, Λ the fringe spacing of the grating, the angle between the incident beam and the normal () of the entrance surface and the angle between the normal and the grating vector (). Radiation that does not match Bragg's law will pass through the VBG undiffracted. The output wavelength can be tuned over a few hundred nanometers by changing the incident angle (). VBG are being used to produce widely tunable laser source or perform global hyperspectral imagery (see Photon etc.). | 0 | Theoretical and Fundamental Chemistry |
Nitrogen is present in the environment in a wide variety of chemical forms including organic nitrogen, ammonium (), nitrite (), nitrate (), nitrous oxide (), nitric oxide (NO) or inorganic nitrogen gas (). Organic nitrogen may be in the form of a living organism, humus or in the intermediate products of organic matter decomposition. The processes in the nitrogen cycle is to transform nitrogen from one form to another. Many of those processes are carried out by microbes, either in their effort to harvest energy or to accumulate nitrogen in a form needed for their growth. For example, the nitrogenous wastes in animal urine are broken down by nitrifying bacteria in the soil to be used by plants. The diagram alongside shows how these processes fit together to form the nitrogen cycle. | 1 | Applied and Interdisciplinary Chemistry |
Dharmastikaay means the principles of Motion that pervade the entire universe. Dharmastikaay and Adharmastikaay are by themselves not motion or rest but mediate motion and rest in other bodies. Without Dharmastikaay motion is not possible. The medium of motion helps matter and the sentient that are prone to motion to move, like water (helps) fish. However, it does not set in motion those that do not move. | 1 | Applied and Interdisciplinary Chemistry |
TCL is a small (~21 kDa) signaling G protein (more specifically a GTPase), and is a member of the Rho family of GTPases.,.
TCL (TC10-like) shares 85% and 78% amino acid similarity to TC10 and Cdc42, respectively. TCL mRNA is 2.5 kb long and is mainly expressed in heart. In vitro, TCL shows rapid GDP/GTP exchange and displays higher GTP dissociation and hydrolysis rates than TC10. Like other Rac/Cdc42/RhoUV members, GTP-bound TCL interacts with CRIB domains, such as those found in PAK and WASP. TCL produces large and dynamic F-actin-rich ruffles on the dorsal cell membrane in REF-52 fibroblasts. TCL activity is blocked by dominant negative Rac1 and Cdc42 mutants, suggesting a cross-talk between these three Rho GTPases.
TCL is unrelated to TCL1A, a proto-oncogene implicated in the development of T-Cell Leukemias. | 1 | Applied and Interdisciplinary Chemistry |
FSM is considered an entry point for sanitation improvement programs that are led by local governments. Such programs may include tariffs or user fees, promotions campaigns to raise the willingness to pay for the service, and local ordinances that define the rules and regulations governing FSM. In the Philippines, tariffs around US$1 per family per month are generally enough to achieve full cost recovery within a period of 3 to 7 years. Promotional campaigns are used to raise the willingness to pay for services, and local procedures and ordinances provide additional incentives for compliance. | 1 | Applied and Interdisciplinary Chemistry |
AMCA membership is open to any company that manufactures or holds the design of a product that falls under the AMCA scope.
AMCA publications and standards are developed when sufficient interest has been expressed by AMCA members. Publication and standard writing committees are composed of volunteers, which include both AMCA members and interested individuals with a technical background. All AMCA standards are proposed as American National Standards.
AMCA lobbies code bodies on the behalf of member companies to ensure that member company products are represented in local and national codes.
AMCA hosts two educational seminars in alternating years. The Technical Seminar, next occurring in 2009, provides engineers with basic information regarding devices and engineering principles relevant to the air movement and air control industry. The Engineering Conference is a discussion forum for presentation of engineering papers written by engineers and experts in the air movement and control industry. U.S. licensed engineers attending either seminar are eligible for approximately 12 Professional Development Hours.
The AMCA headquarters is located at 30 West University Drive, Arlington Heights, IL 60004 USA. | 1 | Applied and Interdisciplinary Chemistry |
Robert Guillaumont began his research in 1959 on the chemistry of protactinium in solution. He showed that the electronic filling of the 5f underlay begins for this element. The UV absorption spectrum of Pa is typical of a 5f6d transition (Pa atom: 5f6d7s). Together with his collaborators, he extended his methodology for studying the behaviour of radioelements in imponderable quantities to other actinides. The rest of his work can be linked to the common thread of the consequences of filling the atomic underlayer 5f on the physicochemical properties of actinides. This filling plays an essential role in the behaviour of the 15 actinides, especially when these electrons are delocalized, from protactinium (Pa) to americium (Am). This results in a high richness of oxidation degrees of the first actinides (usually from 3 to 6) and in the manifestation of particular effects in the series (electronic states characterized by the quantum number J). Thus, he studied the thermodynamic consequences of the population of sublayer 5f on a series of solution complexes (citric complexes of trivalent actinides from Am to fermium (Fm). He showed the existence of the "tetrad effect" for trivalent actinide complexes, an effect that reflects an extra-stabilization of the fundamental state of actinides for 1/4, 1/2 and 3/4 of the filling of the 5f underlay. After the curium (Cm), it is necessary, to carry out experiments, to synthesize isotopes of berkelium (Bk), einstenium (Es) and Fm by nuclear reactions with particle accelerators, and separate them from irradiated targets, which he did at Orsay. To conduct most of his research he developed the methodology for studying species and equilibria between species in extremely diluted solutions (which radioactivity allows until about 10 M), and he pushed, at the theoretical level, the description of the thermodynamic behaviour of a few atoms in terms of deviation from the law of mass action, which gave a foundation to chemical experiments on elements 6d (Z>103), produced atom by atom by radiochemists at accelerators.
At the same time, he participated in the study of thermodynamic and spectroscopic properties of elements 5f (and 4f) in connection with electronic transfers between these elements and their environment: covalence in two-phase solvent extraction systems and crystal field effect on solids, in particular single crystals examined at 4 K.
Finally, he continued his research on the fundamental problems of radionuclide migration in the environment (speciation, concentration effect, retention on colloids) and selective separation of actinides/lanthanides from the elements constituting spent nuclear fuel. R. Guillaumont's research themes are upstream of the many chemistry/radiochemistry problems encountered in "nuclear": chemistry of actinides from uranium to curium in the various stages of nuclear fuel cycles and radioactive waste management.
He has published more than 200 scientific articles, popular articles and has written several books. | 0 | Theoretical and Fundamental Chemistry |
Over the time, methods for supramolecular polymerization has expanded, and the range of its useable monomers has diversified. In addition to plethora of molecular motifs, biomolecules such as DNA, DNA nanostructures and proteins as well as inorganic objects as unconventional monomers has recently been investigated for supramolecular polymerization. In all of these cases, monomers are in much higher size, usually several nanometers, and the non-covalent interactions varies from hydrogen bonding, host-guest and metal coordination. A notable example is Mgassisted multivalent supramolecular polymerization of ATP-responsive biomolecular machines, chaperonine GroEL, resulting in a highly stable protein nanotube. Importantly, this nanotube shows an ATPase activity and dissociates into short-chain oligomers when treated with ATP because of the opening/closing motions of the constituent GroEL units. | 0 | Theoretical and Fundamental Chemistry |
Let the unperturbed atom or molecule be in a g-fold degenerate state with orthonormal zeroth-order state functions . (Non-degeneracy is the special case g = 1). According to perturbation theory the first-order energies are the eigenvalues of the g × g matrix with general element
If g = 1 (as is often the case for electronic states of molecules) the first-order energy becomes proportional to the expectation (average) value of the dipole operator ,
Because the electric dipole moment is a vector (tensor of the first rank), the diagonal elements of the perturbation matrix V vanish between states with a certain parity. Atoms and molecules possessing inversion symmetry do not have a (permanent) dipole moment and hence do not show a linear Stark effect.
In order to obtain a non-zero matrix V for systems with an inversion center it is necessary that some of the unperturbed functions have opposite parity (obtain plus and minus under inversion), because only functions of opposite parity give non-vanishing matrix elements. Degenerate zeroth-order states of opposite parity occur for excited hydrogen-like (one-electron) atoms or Rydberg states. Neglecting fine-structure effects, such a state with the principal quantum number n is n-fold degenerate and
where is the azimuthal (angular momentum) quantum number. For instance, the excited n = 4 state contains the following states,
The one-electron states with even are even under parity, while those with odd are odd under parity. Hence hydrogen-like atoms with n>1 show first-order Stark effect.
The first-order Stark effect occurs in rotational transitions of symmetric top molecules (but not for linear and asymmetric molecules). In first approximation a molecule may be seen as a rigid rotor. A symmetric top rigid rotor has the unperturbed eigenstates
with 2(2J+1)-fold degenerate energy for |K| > 0 and (2J+1)-fold degenerate energy for K=0.
Here D is an element of the Wigner D-matrix. The first-order perturbation matrix on basis of the unperturbed rigid rotor function is non-zero and can be diagonalized. This gives shifts and splittings
in the rotational spectrum. Quantitative analysis of these Stark shift yields the permanent electric dipole moment of the symmetric top molecule. | 0 | Theoretical and Fundamental Chemistry |
The cement industry uses the LOI method by heating a cement sample to 900-1000 °C until the mass of the sample stabilizes. Once the mass stabilizes, the mass loss due to LOI is determined. This is usually done to assess the high water content in the cement or carbonation, as these factors diminish the quality of cement. High losses are generally attributed to poor cement storage conditions or manipulation of cement quality by suppliers. This practice ensures that the cement used on a site adheres to the correct composition, meeting safety protocols and customer requirements.
In the mining industry, the utilization of LOI is essential for determining the moisture and volatile material present in the rock. Thus, when performing whole-rock analysis to ascertain total volatiles, the LOI method is employed. To eliminate all volatiles and convert all iron into iron oxides, the LOI temperature is set at 900-1000 °C. | 0 | Theoretical and Fundamental Chemistry |
Ultracold atoms have a variety of applications owing to their unique quantum properties and the great experimental control available in such systems. For instance, ultracold atoms have been proposed as a platform for quantum computation and quantum simulation, accompanied by very active experimental research to achieve these goals.
Quantum simulation is of great interest in the context of condensed matter physics, where it may provide valuable insights into the properties of interacting quantum systems. The ultracold atoms are used to implement an analogue of the condensed matter system of interest, which can then be explored using the tools available in the particular implementation. Since these tools may differ greatly from those available in the actual condensed matter system, one can thus experimentally probe otherwise inaccessible quantities. Furthermore, ultracold atoms may even allow to create exotic states of matter, which cannot otherwise be observed in nature.
All atoms are identical, making ensembles of atoms ideal for universal timekeeping. In 1967, the SI definition of the second was changed to reference a hyperfine transition frequency in Cesium atoms. Atomic clocks based on alkaline earth atoms or alkaline earth like ions (such as Al) have now been developed making use of narrow-line optical transitions. To achieve high numbers of non-interacting atoms, which assists in the precision of these clocks, neutral atoms can be trapped in optical lattices. On the other hand, ion traps permit long interrogation times.
Ultracold atoms are also used in experiments for precision measurements enabled by the low thermal noise and, in some cases, by exploiting quantum mechanics to exceed the standard quantum limit. In addition to potential technical applications, such precision measurements may serve as tests of our current understanding of physics. | 0 | Theoretical and Fundamental Chemistry |
Upon hearing her husbands friend talking about a secret project at the University of Chicago that hired scientists, she applied and was hired in the Biology Division of the Metallurgical Laboratory. Lathrop, who previously avoided work that involved animal experimentation, was now studying the uptake, retention, distribution, and excretion of radioactive materials in animals. Lathrops assignment in the project was to test the biological effects radiation had on animals. She worked on the Manhattan Project from 1945 to 1946. | 0 | Theoretical and Fundamental Chemistry |
The major difference between RNA and DNA is the presence of a hydroxyl group at the 2-position of the ribose sugar in RNA (illustration, right). This group makes the molecule less stable because, when not constrained in a double helix, the 2 hydroxyl can chemically attack the adjacent phosphodiester bond to cleave the phosphodiester backbone. The hydroxyl group also forces the ribose into the C3-endo sugar conformation unlike the C2-endo conformation of the deoxyribose sugar in DNA. This forces an RNA double helix to change from a B-DNA structure to one more closely resembling A-DNA.
RNA also uses a different set of bases than DNA—adenine, guanine, cytosine and uracil, instead of adenine, guanine, cytosine and thymine. Chemically, uracil is similar to thymine, differing only by a methyl group, and its production requires less energy. In terms of base pairing, this has no effect. Adenine readily binds uracil or thymine. Uracil is, however, one product of damage to cytosine that makes RNA particularly susceptible to mutations that can replace a GC base pair with a GU (wobble) or AU base pair.
RNA is thought to have preceded DNA, because of their ordering in the biosynthetic pathways. The deoxyribonucleotides used to make DNA are made from ribonucleotides, the building blocks of RNA, by removing the 2'-hydroxyl group. As a consequence, a cell must have the ability to make RNA before it can make DNA. | 0 | Theoretical and Fundamental Chemistry |
In the British Isles there are only a few Hoffmann kilns remaining, some of which have been preserved.
The only ones with a chimney are at Prestongrange Industrial Heritage Museum and Llanymynech Heritage Area. The site at Llanymynech, close to Oswestry was used for lime-burning and has recently been partially restored as part of an industrial archaeology conservation project supported by English Heritage and the Heritage Lottery Fund.
Two examples in North Yorkshire, the Hoffmann lime-burning kiln at Meal Bank Quarry, Ingleton, and that at the former Craven and Murgatroyd lime works, Langcliffe, are scheduled ancient monuments.
There is an intact but abandoned Hoffmann kiln without a chimney present at Minera Limeworks; the site is abandoned but all entrances to the kiln have been grated-off, preventing access. The kiln is in a very poor state of repair, with trees growing out of the walls and the roof. Minera Quarry Trust hopes one day to develop the area into something of a tourist attraction. The Grade II listed Hoffmann brick kiln in Ilkeston, Derbyshire, is also badly neglected, although the recently installed fencing offers some protection for the building and for visitors.
At Prestongrange Museum, outside Prestonpans in East Lothian, the Hoffman kiln is still standing and visitors can listen to more about it via a mobile phone tour.
There is a nearly complete kiln in Horeb, Carmarthenshire.
There is still a working kiln at Kings Dyke in Peterborough, which is the last site of the London Brick Company, owned by Forterra PLC. | 1 | Applied and Interdisciplinary Chemistry |
One proprietary material for ISCR is the EHC technology created by Adventus. This particular product is actually a mixture of carbon, nutrients, and zero-valent iron. The theory behind this product is that the carbon in the mixture will promote bacterial growth in the subsurface. The growing bacteria consume oxygen, which easily accepts electrons, present in the subsurface which increases reducing potential. The growing bacteria also ferment and produce fatty acids that act as electron donors to other bacteria and substances. Adventus uses this combination of biotic and abiotic processes to implement ISCR. EHC is injected as a "slurry" (a mixture that is 15 to 40% solids and weight with the rest being liquid) into the substratum.
Another material worth mentioning is EZVI (emulsified ZVI) which is a NASA technology. EZVI is used mainly to treat halogenated hydrocarbons and DNAPLs. EZVI is nanoscale iron that is placed into a biodegradable oil emulsion. The emulsion is then injected into the substratum. | 1 | Applied and Interdisciplinary Chemistry |
Dicyanopolyynes are composed of a chain of carbon atoms with alternating single and triple bonds, terminated by nitrogen atoms. Although not a polyyne dicyanoacetylene () otherwise fits within this series.
* or , (dicyanodiacetylene)
* or , dicyanohexatriyne
* or
* or
* or
* or
* or
* or
* or | 0 | Theoretical and Fundamental Chemistry |
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