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In these processes, the ore is fed into a tank, where it remains until it is completely reduced. The vessel is then emptied of its pre-reduced ore, and filled with another charge of untreated ore. These processes can therefore be easily extrapolated from laboratory experiments. What's more, their principle, based on batch production, facilitates process control. | 1 | Applied and Interdisciplinary Chemistry |
Early studies showed that, when inflammation is induced, the affected organ unexpectedly develops an enormous capacity to generate prostaglandins. It was demonstrated that the increase is due to de novo synthesis of fresh enzyme. In 1991, during the investigation of the expression of early-response genes in fibroblasts transformed with Rous sarcoma virus, a novel mRNA transcript that was similar, but not identical, to the seminal COX enzyme was identified. It was suggested that an isoenzyme of COX had been discovered. Another group discovered a novel cDNA species encoding a protein with similar structure to COX-1 while studying phorbol-ester-induced genes in Swiss 3T3 cells. The same laboratory showed that this gene truly expressed a novel COX enzyme. The two enzymes were renamed COX-1, referring to the original enzyme and COX-2.
Building on those results, scientists started focusing on selective COX-2 inhibitors. Enormous effort was spent on the development of NSAIDs between the 1960s and 1980 so there were numerous pharmacophores to test when COX-2 was discovered. Early efforts focused on modification on two lead compounds, DuP-697 and NS-398. These compounds differ greatly from NSAIDs that are arylalkonic acid analogs. Encouraged by the "concept testing" experiments with selective inhibitors, and armed with several solid leads and clear idea of the nature of the binding site, development of this field was rapid. In vitro recombinant enzyme assays provided powerful means for assessing COX selectivity and potency and led to the discovery and clinical development of the first rationally designed COX-2 selective inhibitor, celecoxib. Efforts have been made to convert NSAIDs into selective COX-2 inhibitors such as indometacin by lengthening of the alkylcarboxylic acid side-chain, but none have been marketed. | 1 | Applied and Interdisciplinary Chemistry |
The International Union of Pure and Applied Chemistry (IUPAC) recommends using CHNO as the experimental standard; however in practice many spectroscopists utilize pressurized NH(l) instead. For N, chemical shifts referenced with NH(l) are 380.5 ppm upfield from CHNO (δNON are somewhat erratic but typically they span a range of -400 ppm to 1100 ppm with respect to CHNO. Below is a summary of N chemical shifts for common organic groups referenced with respect to NH, whose chemical shift is assigned 0 ppm. | 0 | Theoretical and Fundamental Chemistry |
Studies in female pregnant rats have shown minor fetal skeletal abnormalities when given maximum recommended human doses of levetiracetam orally throughout pregnancy and lactation.
Studies were conducted to look for increased adverse effects in the elderly population as compared to younger patients. One such study published in Epilepsy Research showed no significant increase in incidence of adverse symptoms experienced by young or elderly patients with central nervous system (CNS) disorders. | 0 | Theoretical and Fundamental Chemistry |
The Orientation-Cum-Selection-Camp (OCSC), Chemistry, consists of rigorous training and testing in theory and experiment. The top four performers here are selected to represent India in the International Chemistry Olympiad. Before the INChO, the selected team undergoes rigorous training in theory and experiments in a Pre-Departure Training Camp held in HBCSE. | 1 | Applied and Interdisciplinary Chemistry |
Sarfati was a founder of the Wellington Christian Apologetics Society in New Zealand, and has long retained an interest in Christian apologetics and the creation–evolution controversy. His first two books, Refuting Evolution in 1999, and Refuting Evolution 2 in 2002, are intended as rebuttals to the National Academy of Sciences publication Teaching about Evolution and the Nature of Science and the PBS/Nova series Evolution, respectively. Refuting Compromise, published in 2004, is Sarfatis rebuttal of the day-age creationist teachings of Hugh Ross, who attempts to harmonise the Genesis account of creation with mainstream science regarding the age of the Earth and the possible size of the Biblical Flood, against which Sarfati defends a literal biblical timeline and a global flood. Eugenie Scott and Glenn Branch of the National Center for Science Education called Sarfatis Refuting Evolution 2' a "crude piece of propaganda".
Sarfati is a critic of geocentrism, the Myth of the flat Earth and flat Earth teaching, homosexual behaviour, and abortion except to save the life of the mother. While opposing embryonic stem cell research, he supports adult stem cell research. Sarfati also supports vaccination and rebuts anti-vaccination arguments. | 0 | Theoretical and Fundamental Chemistry |
Although migration of cells was detected from the early days of the development of microscopy by Leeuwenhoek, a Caltech lecture regarding chemotaxis propounds that erudite description of chemotaxis was only first made by T. W. Engelmann (1881) and W. F. Pfeffer (1884) in bacteria, and H. S. Jennings (1906) in ciliates. The Nobel Prize laureate I. Metchnikoff also contributed to the study of the field during 1882 to 1886, with investigations of the process as an initial step of phagocytosis. The significance of chemotaxis in biology and clinical pathology was widely accepted in the 1930s, and the most fundamental definitions underlying the phenomenon were drafted by this time. The most important aspects in quality control of chemotaxis assays were described by H. Harris in the 1950s. In the 1960s and 1970s, the revolution of modern cell biology and biochemistry provided a series of novel techniques that became available to investigate the migratory responder cells and subcellular fractions responsible for chemotactic activity. The availability of this technology led to the discovery of C5a, a major chemotactic factor involved in acute inflammation. The pioneering works of J. Adler modernized Pfeffer's capillary assay and represented a significant turning point in understanding the whole process of intracellular signal transduction of bacteria. | 1 | Applied and Interdisciplinary Chemistry |
Dr. Gofman earned his medical degree from the University of California, San Francisco, in 1946. After that, he and his collaborators investigated the body's lipoproteins, which contain both proteins and fats, and their circulation within the bloodstream. The researchers described low-density and high-density lipoproteins and their roles in metabolic disorders and coronary disease. This work continued throughout the late 1940s and early 1950s. | 0 | Theoretical and Fundamental Chemistry |
Vector gauge theories with massless Dirac fermion fields exhibit chiral symmetry, i.e., rotating the left-handed and the right-handed components independently makes no difference to the theory. We can write this as the action of rotation on the fields:
: and
or
: and
With flavors, we have unitary rotations instead: .
More generally, we write the right-handed and left-handed states as a projection operator acting on a spinor. The right-handed and left-handed projection operators are
and
Massive fermions do not exhibit chiral symmetry, as the mass term in the Lagrangian, , breaks chiral symmetry explicitly.
Spontaneous chiral symmetry breaking may also occur in some theories, as it most notably does in quantum chromodynamics.
The chiral symmetry transformation can be divided into a component that treats the left-handed and the right-handed parts equally, known as vector symmetry, and a component that actually treats them differently, known as axial symmetry. (cf. Current algebra.) A scalar field model encoding chiral symmetry and its breaking is the chiral model.
The most common application is expressed as equal treatment of clockwise and counter-clockwise rotations from a fixed frame of reference.
The general principle is often referred to by the name chiral symmetry. The rule is absolutely valid in the classical mechanics of Newton and Einstein, but results from quantum mechanical experiments show a difference in the behavior of left-chiral versus right-chiral subatomic particles. | 0 | Theoretical and Fundamental Chemistry |
DNAzymes have found practical use in metal biosensors. A DNAzyme based biosensor for lead ion was used to detect lead ion in water in St. Paul Public Schools in Minnesota. Furthermore, DNAzymes have been used in combination of aptamers and nucleic acid bioreceptors for the development of a multiplex bioassay. | 0 | Theoretical and Fundamental Chemistry |
Electroreflectance (also: electromodulated reflectance) is the change of reflectivity of a solid due to the influence of an electric field close to, or at the interface of the solid with a liquid. The change in reflectivity is most noticeable at very specific ranges of photon energy, corresponding to the band gaps at critical points of the Brillouin zone.
The electroreflectance effect can be used to get a clearer picture of the band structure at critical points where there is a lot of near degeneracy. Normally, the band structure at critical points (points of special interest) has to be measured within a background of adsorption from non-critical points at the Brillouin zone boundary. Using a strong electric field, the adsorption spectrum can be changed to a spectrum that shows peaks at these critical points, essentially lifting the critical points from the background.
The effect was first discovered and understood in semiconductor materials, but later research proved that metals also exhibit electroreflectance. An early observation of the changing optical reflectivity of gold due to a present electric field was attributed to a change in refractive index of the neighboring liquid. However, it was shown that this could not be the case. The new conclusion was that the effect had to come from a modulation of the near-surface layer of the gold. | 0 | Theoretical and Fundamental Chemistry |
Warren Richard Roper FRS FRSNZ FNZIC (born 1938) is a New Zealand chemist and Emeritus Professor at the University of Auckland.
Roper was educated at Nelson College from 1952 to 1956, and was dux in his final year. He then studied chemistry at the University of Canterbury, and undertook his PhD under the supervision of CJ Wilkins. He completed his PhD in 1963, and spent three years undertaking postdoctoral research at the University of North Carolina in the United States before returning to New Zealand. At that point Roper was appointed as lecturer at the University of Auckland, where he remained until his retirement (apart from visiting lectureships at other institutions).
Roper's research has focused on synthetic and structural organometallic chemistry, and particularly compounds with metal-carbon, -silicon, -tin or -boron bonds. He was made a fellow of the Royal Society of New Zealand (RSNZ) in 1984, and a fellow of the Royal Society in 1989. The RSNZ awarded Roper the Hector Memorial Medal in 1991. He gave a valedictory address at the 2006 New Zealand Institute of Chemistry Conference in honour of his retirement. | 0 | Theoretical and Fundamental Chemistry |
Tartaric acid and its derivatives have a plethora of uses in the field of pharmaceuticals. For example, it has been used in the production of effervescent salts, in combination with citric acid, to improve the taste of oral medications. The potassium antimonyl derivative of the acid known as tartar emetic is included, in small doses, in cough syrup as an expectorant.
Tartaric acid also has several applications for industrial use. The acid has been observed to chelate metal ions such as calcium and magnesium. Therefore, the acid has served in the farming and metal industries as a chelating agent for complexing micronutrients in soil fertilizer and for cleaning metal surfaces consisting of aluminium, copper, iron, and alloys of these metals, respectively. | 0 | Theoretical and Fundamental Chemistry |
Owing to the simple preparative accessibility, the uncritical behavior at temperatures below 80 °C and in particular because of the high yields and the low racemization of the peptides obtained, ethyl cyanohydroxyiminoacetate has now become widely used as an additive in peptide syntheses.
Ethyl cyanohydroxyiminoacetate can be used as a coupling additive in the conventional peptide linking in solution, as in automated Merrifield synthesis on a solid-phase peptide synthesis, together with coupling reagents such as carbodiimides (for example dicyclohexylcarbodiimide (DCC)), diisopropylcarbodiimide (DIC) or the water-soluble 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDCI)).
For example, the stepwise liquid-phase synthesis of the dipeptide Z-L-Phg-L-Val-OMe yields the LL-product with 81-84% which is free from racemic DL dipeptide, using From N-protected Z-L-α-phenylglycine (with the benzyloxycarbonyl group, Z group) and L-valine methyl ester with the coupling reagent DIC and the additive ethyl cyanohydroxyiminoacetate.
More recently, a variety of derivatives of ethyl cyanohydroxyiminoacetate (Oxyma) have been developed as acylation reagents, such as Fmoc-oxyma for the transfer of the fluorenylmethoxycarbonyl protective group
or the coupling reagent COMU which is readily soluble as a dimethylmorpholine-uronium salt and which, like Oxyma, is superior to the standard additive HOBt for the suppression of racemization and acylation efficiency and is comparable to HOAt without presenting an explosion risk such as the benzotriazoles.
With water-soluble derivatives of ethyl cyanohydroxyiminoacetate (glyceroacetonide-oxyma) as additive and DIC as coupling reagent even in weakly basic aqueous solutions the linking of protected amino acids to oligopeptides is possible with a yield of 95% and a diastereomeric excess of> 99% using the model substances Z-L-Phg-OH and L-H-Pro-NH.
In the coupling of amino acids, frequently occurring secondary reactions largely suppressed, which would be the formation of symmetrical acid anhydrides, racemization and epimerization and the cyclization to oxazolinones or - especially for dipeptides - to 2,5-diketopiperazines. | 0 | Theoretical and Fundamental Chemistry |
Rhabdoviruses are a diverse family of single stranded, negative sense RNA viruses that infect a wide range of hosts, from plants and insects, to fish and mammals. The Rhaboviridae family consists of six genera, two of which, cytorhabdoviruses and nucleorhabdoviruses, only infect plants. Novirhabdoviruses infect fish, and vesiculovirus, lyssavirus and ephemerovirus infect mammals, fish and invertebrates. The family includes pathogens such as rabies virus, vesicular stomatitis virus and potato yellow dwarf virus that are of public health, veterinary, and agricultural significance. | 1 | Applied and Interdisciplinary Chemistry |
Both acetoacetate and beta-hydroxybutyrate are acidic, and, if levels of these ketone bodies are too high, the pH of the blood drops, resulting in ketoacidosis. Ketoacidosis is known to occur in untreated type I diabetes (see diabetic ketoacidosis) and in alcoholics after prolonged binge-drinking without intake of sufficient carbohydrates (see alcoholic ketoacidosis).
The production and use of ketones can be ineffective in people with defects in the pathway for beta-oxidation, in the genes for ketogenesis (HMGCS2 and HMGCL), for ketolysis (OXCT1, ACAT1). Defects in this pathway can cause varying degrees of inability to cope with fasting. HMGCS2 deficiency, for example, can cause hypoglycemic crises that lead to brain damage, and death.
Individuals with diabetes mellitus can experience overproduction of ketone bodies due to a lack of insulin. Without insulin to help extract glucose from the blood, tissues the levels of malonyl-CoA are reduced, and it becomes easier for fatty acids to be transported into mitochondria, causing the accumulation of excess acetyl-CoA. The accumulation of acetyl-CoA in turn produces excess ketone bodies through ketogenesis. The result is a rate of ketone production higher than the rate of ketone disposal, and a decrease in blood pH. In extreme cases the resulting acetone can be detected in the patient's breath as a faint, sweet odor.
There are some health benefits to ketone bodies and ketogenesis as well. It has been suggested that a low-carb, high fat ketogenic diet can be used to help treat epilepsy in children. Additionally, ketone bodies can be anti-inflammatory. Some kinds of cancer cells are unable to use ketone bodies, as they do not have the necessary enzymes to engage in ketolysis. It has been proposed that actively engaging in behaviors that promote ketogenesis could help manage the effects of some cancers. | 1 | Applied and Interdisciplinary Chemistry |
The usage of passive daytime radiative cooling in fabrics to regulate body temperatures during extreme heat is in research and development. While other fabrics are useful for heat accumulation, they "may lead to heat stroke in hot weather." Zeng et al. states that "incorporating passive radiative cooling structures into personal thermal management technologies could effectively defend humans against intensifying global climate change."
Wearable PDRCs can come in different forms and be particularly useful for outdoor workers. Readily available wearable PDRCs are not yet available, although prototypes have been developed. This field of research is referred to as personal thermal management (PTM). Although most textiles developed are in white, colored wearable materials have also been developed, although only in select colors that are relatively successful for solar reflectance to minimize heat gain. | 0 | Theoretical and Fundamental Chemistry |
Aluminium foam sandwich (AFS) is a sandwich panel product which is made of two metallic dense face sheets and a metal foam core made of an aluminium alloy. AFS is an engineering structural material owing to its stiffness-to-mass ratio and energy absorption capacity ideal for application such as the shell of a high-speed train. | 0 | Theoretical and Fundamental Chemistry |
Imperfect inverted repeats can lead to mutations through intrastrand and interstrand switching. The antithrombin III gene's coding region is an example of an imperfect inverted repeat as shown in the figure on the right.
The stem-loop structure forms with a bump at the bottom because the G and T do not pair up. A strand switch event could result in the G (in the bump) being replaced by an A which removes the "imperfection" in the inverted repeat and provides a stronger stem-loop structure. However, the replacement also creates a point mutation converting the GCA codon to ACA. If the strand switch event is followed by a second round of DNA replication, the mutation may become fixed in the genome and lead to disease. Specifically, the missense mutation would lead to a defective gene and a deficiency in antithrombin which could result in the development of venous thromboembolism (blood clots within a vein). | 1 | Applied and Interdisciplinary Chemistry |
Isotope biogeochemistry has been used to investigate the timeline surrounding life and its earliest iterations on Earth. Isotopic fingerprints typical of life, preserved in sediments, have been used to suggest, but do not necessarily prove, that life was already in existence on Earth by 3.85 billion years ago.
Sulfur isotope evidence has also been used to corroborate the timing of the Great Oxidation Event, during which the Earth's atmosphere experienced a measurable rise in oxygen (to about 9% of modern values) for the first time about 2.3-2.4 billion years ago. Mass-independent sulfur isotope fractionations are found to be widespread in the geologic record before about 2.45 billion years ago, and these isotopic signatures have since ceded to mass-dependent fractionation, providing strong evidence that the atmosphere shifted from anoxic to oxygenated at that threshold.
Modern sulfate-reducing bacteria are known to favorably reduce lighter S instead of S, and the presence of these microorganisms can measurably alter the sulfur isotope composition of the ocean. Because the δS values of sulfide minerals is primarily influenced by the presence of sulfate-reducing bacteria, the absence of sulfur isotope fractionations in sulfide minerals suggests the absence of these bacterial processes or the absence of freely available sulfate. Some have used this knowledge of microbial sulfur fractionation to suggest that minerals (namely pyrite) with large sulfur isotope fractionations relative to the inferred seawater composition may be evidence of life. This claim is not clear-cut, however, and is sometimes contested using geologic evidence from the ~3.49 Ga sulfide minerals found in the Dresser Formation of Western Australia, which are found to have δS values as negative as -22‰. Because it has not been proven that the sulfide and barite minerals formed in the absence of major hydrothermal input, it is not conclusive evidence of life or of the microbial sulfate reduction pathway in the Archean. | 0 | Theoretical and Fundamental Chemistry |
The veterinary doctor Maurice Crowther Hall (1881-1938) discovered in 1921 that carbon tetrachloride was incredibly effective as an anthelminthic in eradicating hookworm via ingestion. In one of the clinical trials of carbon tetrachloride, it was tested on criminals to determine its safety for use in human beings. Beginning in 1922, capsules of pure carbon tetrachloride were marketed by Merck under the name Necatorina (variants include Neo-necatorina and Necatorine). Necatorina was used as a medication against parasitic diseases in humans. This medication was most prevalently used in Latin American countries. Its toxicity was not well understood at the time and toxic effects were attributed to impurities in the capsules rather than carbon tetrachloride itself. Due to carbon tetrachloride's toxicity, tetrachloroethylene (which was also investigated by Hall in 1925) replaced its use as an anthelmintic by the 1940s. | 1 | Applied and Interdisciplinary Chemistry |
An example of this is the Coulter counter, which measures the momentary changes in the conductivity of a liquid passing through an orifice that take place when individual non-conducting particles pass through. The particle count is obtained by counting pulses. This pulse is proportional to the volume of the sensed particle.
Advantages: very small sample aliquots can be examined.
Disadvantages: sample must be dispersed in a liquid medium... some particles may (partially or fully) dissolve in the medium altering the size distribution. The results are only related to the projected cross-sectional area that a particle displaces as it passes through an orifice. This is a physical diameter, not really related to mathematical descriptions of particles (e.g. terminal settling velocity). | 0 | Theoretical and Fundamental Chemistry |
In addition to a reduction in the rate of protein synthesis, it appears that some species of hypoxia-tolerant fish conserve energy by employing Hochachka's ion channel arrest hypothesis. This hypothesis makes two predictions:
# Hypoxia-tolerant animals naturally have low membrane permeabilities
# Membrane permeability decreases even more during hypoxic conditions (ion channel arrest)
The first prediction holds true. When membrane permeability to Na+ and K+ ions was compared between reptiles and mammals, reptile membranes were discovered to be five times less leaky. The second prediction has been more difficult to prove experimentally, however, indirect measures have showed a decrease in Na+/K+-ATPase activity in eel and trout hepatocytes during hypoxic conditions. Results seem to be tissue-specific, as crucian carp exposed to hypoxia do not undergo a reduction in Na+/K+ ATPase activity in their brain. Although evidence is limited, ion channel arrest enables organisms to maintain ion channel concentration gradients and membrane potentials without consuming large amounts of ATP. | 0 | Theoretical and Fundamental Chemistry |
*ENCODE Project: [http://dnase.genome.duke.edu/ Regulatory Elements DB]
*Plant DHSs : [http://plantdhs.org/ PlantDHS] | 1 | Applied and Interdisciplinary Chemistry |
Cyclohexylthiophthalimide (abbreviated CTP) is an organosulfur compound that is used in production of rubber. It is a white solid, although commercial samples often appear yellow. It features the sulfenamide functional group, being a derivative of phthalimide and cyclohexanethiol. In the production of synthetic rubber, CTP impedes the onset of sulfur vulcanization. | 0 | Theoretical and Fundamental Chemistry |
In solid-state NMR spectroscopy, magic-angle spinning (MAS) is a technique routinely used to produce better resolution NMR spectra. MAS NMR consists in spinning the sample (usually at a frequency of 1 to 130 kHz) at the magic angle θ (ca. 54.74°, where cosθ=1/3) with respect to the direction of the magnetic field.
Three main interactions responsible in solid state NMR (dipolar, chemical shift anisotropy, quadrupolar) often lead to very broad and featureless NMR lines. However, these three interactions in solids are orientation-dependent and can be averaged to some extent by MAS:
* The nuclear dipolar interaction has a dependence, where is the angle between the internuclear axis and the main magnetic field. As a result, the dipolar interaction vanish at the magic angle θ and the interaction contributing to the line broadening is removed. Even though all internuclear vectors cannot be all set to the magic angle, rotating the sample around this axis produces the same effect, provided the frequency is comparable to that of the interaction. In addition, a set of spinning sidebands appear on the spectra, which are sharp lines separated from the isotropic resonance frequency by a multiple of the spinning rate.
* The chemical shift anisotropy (CSA) represents the orientation-dependence of the chemical shift. Powder patterns generated by the CSA interaction can be averaged by MAS, resulting to one single resonance centred at the isotropic chemical shift (centre of mass of the powder pattern).
* The quadrupolar interaction is only partially averaged by MAS leaving a residual secondary quadrupolar interaction.
In solution-state NMR, most of these interactions are averaged out because of the rapid time-averaged molecular motion that occurs due to the thermal energy (molecular tumbling).
The spinning of the sample is achieved via an impulse air turbine mechanism, where the sample tube is lifted with a frictionless compressed gas bearing and spun with a gas drive. Sample tubes are hollow cylinders coming in a variety of outer diameters ranging from 0.70 to 7 mm, mounted with a turbine cap. The rotors are typically made from zirconium oxide, although other ceramic materials (silicon nitride) or polymers (poly(methyl methacrylate) (PMMA), polyoxymethylene (POM)) can be found. Removable caps close the ends of the sample tube. They are made from a range of materials typically Kel-F, Vespel, or zirconia and boron nitride for an extended temperature range.
Magic-angle spinning was first described in 1958 by Edward Raymond Andrew, A. Bradbury, and R. G. Eades and independently in 1959 by I. J. Lowe. The name "magic-angle spinning" was coined in 1960 by Cornelis J. Gorter at the AMPERE congress in Pisa. | 0 | Theoretical and Fundamental Chemistry |
Physical biochemistry is a branch of biochemistry that deals with the theory, techniques, and methodology used to study the physical chemistry of biomolecules.
It also deals with the mathematical approaches for the analysis of biochemical reaction and the modelling of biological systems. It provides insight into the structure of macromolecules, and how chemical structure influences the physical properties of a biological substance.
It involves the use of physics, physical chemistry principles, and methodology to study biological systems. It employs various physical chemistry techniques such as chromatography, spectroscopy, Electrophoresis, X-ray crystallography, electron microscopy, and hydrodynamics. | 0 | Theoretical and Fundamental Chemistry |
Levosalbutamol, also known as levalbuterol, is a short-acting β adrenergic receptor agonist used in the treatment of asthma and chronic obstructive pulmonary disease (COPD). Evidence is inconclusive regarding the efficacy of levosalbutamol versus salbutamol or salbutamol-levosalbutamol combinations, though levosalbutamol is believed to have a better safety profile due to its more selective binding to β receptors (primarily in the lungs) versus β (primarily in heart muscle).
The drug is the (R)-(−)-enantiomer of its prototype drug salbutamol. It is available in some countries in generic formulations from pharmaceutical companies including Cipla, Teva, and Dey, among others. | 0 | Theoretical and Fundamental Chemistry |
Biogasoline is gasoline produced from biomass. Like traditionally produced gasoline, it contains between 6 (hexane) and 12 (dodecane) carbon atoms per molecule and can be used in internal-combustion engines. | 1 | Applied and Interdisciplinary Chemistry |
The roots of the term absorbance are in the Beer–Lambert law. As light moves through a medium, it will become dimmer as it is being "extinguished". Bouguer recognized that this extinction (now often called attenuation) was not linear with distance traveled through the medium, but related by what we now refer to as an exponential function.
If is the intensity of the light at the beginning of the travel and is the intensity of the light detected after travel of a distance the fraction transmitted, is given by
where is called an attenuation constant (a term used in various fields where a signal is transmitted though a medium) or coefficient. The amount of light transmitted is falling off exponentially with distance. Taking the natural logarithm in the above equation, we get
For scattering media, the constant is often divided into two parts, separating it into a scattering coefficient and an absorption coefficient obtaining
If a size of a detector is very small compared to the distance traveled by the light, any light that is scattered by a particle, either in the forward or backward direction, will not strike the detector. (Bouguer was studying astronomical phenomena, so this condition was met.) In such case, a plot of as a function of wavelength will yield a superposition of the effects of absorption and scatter. Because the absorption portion is more distinct and tends to ride on a background of the scatter portion, it is often used to identify and quantify the absorbing species. Consequently, this is often referred to as absorption spectroscopy, and the plotted quantity is called "absorbance", symbolized as Some disciplines by convention use decadic (base 10) absorbance rather than Napierian (natural) absorbance, resulting in: (with the subscript 10 usually not shown). | 0 | Theoretical and Fundamental Chemistry |
Fossil footprints made by tetrapod vertebrates are difficult to identify to a particular species of animal, but they can provide valuable information such as the speed, weight, and behavior of the organism that made them. Such trace fossils are formed when amphibians, reptiles, mammals, or birds walked across soft (probably wet) mud or sand which later hardened sufficiently to retain the impressions before the next layer of sediment was deposited. Some fossils can even provide details of how wet the sand was when they were being produced, and hence allow estimation of paleo-wind directions.
Assemblages of trace fossils occur at certain water depths, and can also reflect the salinity and turbidity of the water column. | 1 | Applied and Interdisciplinary Chemistry |
* Luminol: 5-amino-2,3-dihydro-1,4 ; 3-amino-phthalhydrazide ; 1,4-phthalazinedione, 5-amino-2,3-dihydro ; CAS: [521-31-3]HNO – MW: 177.16 (in 0.1 N NaOH) λ 1 : 347 nm & λ 2 : 300 nm; EC (at λ 1): 7650 L/mol × cm / λ (MeOH): 355/413 nm
* Luminol, sodium salt: sodium 3-amino-phthalhydrazide; CAS: [20666-12-0]HNONa – MW: 199.12
* Luminol hemihydrate: a hydrate of sodium 3-amino-phthalhydrazide; CAS: [206658-90-4]HNONa – MW: 217.16
* Luminol hydrochloride: 3-amino-phthalhydrazide hydrochloride; CAS: [74165-64-3]HNO · HCl MW: 213.62
* Isoluminol: 4-aminophthalhydrazide; CAS: [3682-14-1]HNO – MW: 117.16 (Xi)
* Isoluminol monohydrate: 4-aminophthalhydrazide monohydrateHNO – MW: 195.15
* Isoluminol ABEI: 4-aminophthalhydrazide monohydrate; CAS: [66612-29-1] | 0 | Theoretical and Fundamental Chemistry |
Hansgirg was born in Graz, Austria in 1891 and received a PhD degree in chemistry from the University of Graz. He was married to Josephine Marie (née Heller). Heller's son from her first marriage, Peter Robert Hofstätter, graduated from the University of Vienna, and served as a military psychologist in the German army during World War II. | 0 | Theoretical and Fundamental Chemistry |
Exemestane, sold under the brand name Aromasin among others, is a medication used to treat breast cancer. It is a member of the class of antiestrogens known as aromatase inhibitors. Some breast cancers require estrogen to grow. Those cancers have estrogen receptors (ERs), and are called ER-positive. They may also be called estrogen-responsive, hormonally-responsive, or hormone-receptor-positive. Aromatase is an enzyme that synthesizes estrogen. Aromatase inhibitors block the synthesis of estrogen. This lowers the estrogen level, and slows the growth of cancers. | 0 | Theoretical and Fundamental Chemistry |
Many decarboxylative cross coupling reactions involve the breaking of C–COOH bonds, therefore subsequent studies have attempted to enable cross coupling with </sub>C carboxylic acids. One such reaction by Shang et al. described a palladium catalyzed cross coupling that enables the formation of functionalized pyridines, pyrazines, quinolines, benzothiazoles, and benzoxazoles. The position of the nitrogen atom in the 2 position relative to the linkage is found to be required, therefore implying its binding to Pd in a transition state. | 0 | Theoretical and Fundamental Chemistry |
Numerous niche applications exploit the intense color of MG. It is used as a biological stain for microscopic analysis of cell biology and tissue samples. In the Gimenez staining method, basic fuchsin stains bacteria red or magenta, and malachite green is used as a blue-green counterstain. Malachite green is also used in endospore staining, since it can directly stain endospores within bacterial cells; here a safranin counterstain is often used. Malachite green is a part of Alexander's pollen stain. Malachite green can also be used as a saturable absorber in dye lasers, or as a pH indicator between pH 0.2–1.8. However, this use is relatively rare. Leuco-malachite green (LMG) is used as a detection method for latent blood in forensic science. Hemoglobin catalyzes the reaction between LMG and hydrogen peroxide, converting the colorless LMG into malachite green. Therefore, the appearance of a green color indicates the presence of blood.
A set of malachite green derivatives is also a key component in a fluorescence microscopy tool called the fluorogen activating protein/fluorogen system. Malachite green is in a class of molecules called fluorophores. When malachite greens rotational freedom is restricted, it transforms from a non fluorescent molecule to a highly fluorescent molecule. In the fluorogen activating protein tool, established by a group at Carnegie Mellon University, Malachite green binds a specific fluorogen activating protein to become highly fluorescent. Expression of the fluorogen activating protein as fusions of targeting domains can impart subcellular localization. Its use is similar to that of GFP but has the added benefit of having a dark state' before the malachite green fluorophore is added. This is especially useful for FRET studies. | 0 | Theoretical and Fundamental Chemistry |
The following table lists historical approximations to the Colebrook–White relation for pressure-driven flow. Churchill equation (1977) is the only equation that can be evaluated for very slow flow (Reynolds number < 1), but the Cheng (2008), and Bellos et al. (2018) equations also return an approximately correct value for friction factor in the laminar flow region (Reynolds number < 2300). All of the others are for transitional and turbulent flow only. | 1 | Applied and Interdisciplinary Chemistry |
The carbon center of a nitrile is electrophilic, hence it is susceptible to nucleophilic addition reactions:
* with an organozinc compound in the Blaise reaction
* with alcohols in the Pinner reaction.
* with amines, e.g. the reaction of the amine sarcosine with cyanamide yields creatine
* Nitriles react in Friedel–Crafts acylation in the Houben–Hoesch reaction to ketones | 0 | Theoretical and Fundamental Chemistry |
Psychrophiles include bacteria, lichens, snow algae, phytoplankton, fungi, and insects.
Among the bacteria that can tolerate extreme cold are Arthrobacter sp., Psychrobacter sp. and members of the genera Halomonas, Pseudomonas, Hyphomonas, and Sphingomonas. Another example is Chryseobacterium greenlandensis, a psychrophile that was found in 120,000-year-old ice.
Umbilicaria antarctica and Xanthoria elegans are lichens that have been recorded photosynthesizing at temperatures ranging down to −24 °C, and they can grow down to around −10 °C. Some multicellular eukaryotes can also be metabolically active at sub-zero temperatures, such as some conifers; those in the Chironomidae family are still active at −16 °C.
Microalgae that live in snow and ice include green, brown, and red algae. Snow algae species such as Chloromonas sp., Chlamydomonas sp., and Chlorella sp. are found in polar environments.
Some phytoplankton can tolerate extremely cold temperatures and high salinities that occur in brine channels when sea ice forms in polar oceans. Some examples are diatoms like Fragilariopsis cylindrus, Nitzchia lecointeii, Entomoneis kjellmanii, Nitzchia stellata, Thalassiosira australis, Berkelaya adeliense, and Navicula glaciei.
Penicillium is a genus of fungi found in a wide range of environments including extreme cold.
Among the psychrophile insects, the Grylloblattidae or ice crawlers, found on mountaintops, have optimal temperatures between 1–4 °C. The wingless midge (Chironomidae) Belgica antarctica can tolerate salt, being frozen and strong ultraviolet, and has the smallest known genome of any insect. The small genome, of 99 million base pairs, is thought to be adaptive to extreme environments. | 1 | Applied and Interdisciplinary Chemistry |
In the original work of Taylor and Green, a particular flow is analyzed in three spatial dimensions, with the three velocity components at time specified by
The continuity equation determines that . The small time behavior of the flow is then found through simplification of the incompressible Navier–Stokes equations using the initial flow to give a step-by-step solution as time progresses.
An exact solution in two spatial dimensions is known, and is presented below. | 1 | Applied and Interdisciplinary Chemistry |
Improvements can be divided into those that are aimed at improving the flow of the river, particularly in flood conditions, and those that aim to hold back the flow, primarily for navigation purposes, although power generation is often an important factor. The former is known in the US as channelization and the latter is generally referred to as canalization. | 1 | Applied and Interdisciplinary Chemistry |
An orifice plate is a plate with a hole through it, placed perpendicular to the flow; it constricts the flow, and measuring the pressure differential across the constriction gives the flow rate. It is basically a crude form of Venturi meter, but with higher energy losses. There are three type of orifice: concentric, eccentric, and segmental. | 1 | Applied and Interdisciplinary Chemistry |
Some gourmets believe sea salt tastes better and has a better texture than ordinary table salt. In applications that retain sea salt's coarser texture, it can provide a different mouthfeel, and may change flavor due to its different rate of dissolution. The mineral content also affects the taste. The colors and variety of flavors are due to local clays and algae found in the waters the salt is harvested from. For example, some boutique salts from Korea and France are pinkish gray and some from India are black. Black and red salts from Hawaii may even have powdered black lava and baked red clay added in. Some sea salt contains sulfates. It may be difficult to distinguish sea salt from other salts, such as pink Himalayan salt, Maras salt from the ancient Inca hot springs, or rock salt (halite) .
Black lava salt is a marketing term for sea salt harvested from various places around the world that has been blended and colored with activated charcoal. The salt is used as a decorative condiment to be shown at the table. | 0 | Theoretical and Fundamental Chemistry |
By using exome sequencing, fixed-cost studies can sequence samples to much higher depth than could be achieved with whole genome sequencing. This additional depth makes exome sequencing well suited to several applications that need reliable variant calls. | 1 | Applied and Interdisciplinary Chemistry |
The term cryostasis was introduced to name the reversible preservation technology for live biological objects which is based on using clathrate-forming gaseous substances under increased hydrostatic pressure and hypothermic temperatures.
Living tissues cooled below the freezing point of water are damaged by the dehydration of the cells as ice is formed between the cells. The mechanism of freezing damage in living biological tissues has been elucidated by Renfret.
The vapor pressure of the ice is lower than the vapor pressure of the solute water in the surrounding cells and as heat is removed at the freezing point of the solutions, the ice crystals grow between the cells, extracting water from them. As the ice crystals grow, the volume of the cells shrinks, and the cells are crushed between the ice crystals. Additionally, as the cells shrink, the solutes inside the cells are concentrated in the remaining water, increasing the intracellular ionic strength and interfering with the organization of the proteins and other organized intercellular structures. Eventually, the solute concentration inside the cells reaches the eutectic and freezes. The final state of frozen tissues is pure ice in the former extracellular spaces, and inside the cell membranes a mixture of concentrated cellular components in ice and bound water. In general, this process is not reversible to the point of restoring the tissues to life.
Cryostasis utilizes clathrate-forming gases that penetrate and saturate the biological tissues causing clathrate hydrates formation (under specific pressure-temperature conditions) inside the cells and in the extracellular matrix. Clathrate hydrates are a class of solids in which gas molecules occupy "cages" made up of hydrogen-bonded water molecules. These "cages" are unstable when empty, collapsing into conventional ice crystal structure, but they are stabilised by the inclusion of the gas molecule within them. Most low molecular weight gases (including CH, HS, Ar, Kr, and Xe) will form a hydrate under some pressure-temperature conditions.
Clathrates formation will prevent the biological tissues from dehydration which will cause irreversible inactivation of intracellular enzymes. | 1 | Applied and Interdisciplinary Chemistry |
The General Conference of the IIR defines the general policy of the IIR and convenes once every four years during its international congress. It includes representatives appointed by member countries.
The General Conference elects the president and vice-presidents of the executive committee. | 0 | Theoretical and Fundamental Chemistry |
Phase-boundary catalytic (PBC) systems can be contrasted with conventional catalytic systems. PBC is primarily applicable to reactions at the interface of an aqueous phase and organic phase. In these cases, an approach such as PBC is needed due to the immiscibility of aqueous phases with most organic substrate. In PBC, the catalyst acts at the interface between the aqueous and organic phases. The reaction medium of phase boundary catalysis systems for the catalytic reaction of immiscible aqueous and organic phases consists of three phases; an organic liquid phase, containing most of the substrate, an aqueous liquid phase containing most of the substrate in aqueous phase and the solid catalyst.
In case of conventional catalytic system;
*When the reaction mixture is vigorously stirred, an apparently homogeneous emulsion is obtained, which segregates very rapidly into two liquid phases when the agitation ceases. Segregation occurs by formation of organic bubbles in the emulsion which move downwards to form the aqueous phase, indicating that emulsion consists of dispersed particles of the aqueous phase in the organic phase.
*Due to the triphasic reactions conditions, the overall reaction between aqueous phase and organic phase substrates on solid catalyst requires different transfer processes. The following steps are involved:
*# transfer of aqueous phase from organic phase to the external surface of solid catalyst;
*# transfer of aqueous phase inside the pore volume of solid catalyst;
*# transfer of the substrate from aqueous phase to the interphase between aqueous and organic phases
*# transfer of the substrate from the interphase to the aqueous phase;
*# mixing and diffusion of the substrate in the aqueous phase;
*# transfer of the substrate from the aqueous phase to the external surface of solid catalyst;
*# transfer of the substrate inside the pore volume of the solid catalyst;
*# catalytic reaction (adsorption, chemical reaction and desorption).
In some systems, without vigorous stirring, no reactivity of the catalyst is observed in conventional catalytic system. Stirring and mass transfer from the organic to the aqueous phase and vice versa are required for conventional catalytic system. Conversely, in PBC, stirring is not required because the mass transfer is not the rate determining step in this catalytic system. It is already demonstrated that this system works for alkene epoxidation without stirring or the addition of a co-solvent to drive liquid–liquid phase transfer. The active site located on the external surface of the zeolite particle were dominantly effective for the observed phase boundary catalytic system. | 0 | Theoretical and Fundamental Chemistry |
NacNac is a class of anionic bidentate ligands. 1,3-Diketimines are often referred to as "HNacNac", a modification of the abbreviation Hacac used for 1,3-diketones. These species can exist as a mixture of tautomers. | 0 | Theoretical and Fundamental Chemistry |
Despite the fact that the radioactive isotopes mentioned above are now effectively extinct, the record of their existence is found in their decay products and are very useful to geologists who wish to use them as geochronometers. Their usefulness derives from a few factors such as the fact that their short half-lives provide high chronological resolution and the chemical mobility of various elements can date unique geological processes such as igneous fractionation and surface weathering. There are, however, hurdles to overcome when using extinct nuclides. The need for high-precision isotope ratio measurements is paramount as the extinct radionuclides contribute such a small fraction of the daughter isotopes. Compounding this problem is the increasing contribution that high-energy cosmic rays have on already minute amounts of daughter isotopes formed from the extinct nuclides. Distinguishing the source and abundance of these effects is critical to obtaining accurate ages from extinct nuclides. Additionally, more work needs to be done in determining a more precise half-life for some of these isotopes, such as Fe and Sm. | 0 | Theoretical and Fundamental Chemistry |
While relative entropy is a statistical distance, it is not a metric on the space of probability distributions, but instead it is a divergence. While metrics are symmetric and generalize linear distance, satisfying the triangle inequality, divergences are asymmetric in general and generalize squared distance, in some cases satisfying a generalized Pythagorean theorem. In general does not equal , and while this can be symmetrized (see ), the asymmetry is an important part of the geometry.
It generates a topology on the space of probability distributions. More concretely, if is a sequence of distributions such that
then it is said that
Pinsker's inequality entails that
where the latter stands for the usual convergence in total variation. | 0 | Theoretical and Fundamental Chemistry |
Sapropels have been recorded in the Mediterranean sediments since the closure of the Eastern Tethys Ocean 13.5 million years ago. The formation of sapropel events in the Mediterranean Sea occurs approximately every 21,000 years and last between 3,000 and 5,000 years. The first identification of these events occurred in the mid-20th century. Since then, their formulative conditions of have been investigated.
The occurrence of sapropels has been related to the Earth's orbital parameters (Milankovitch cycles). The precession cycles influence the African monsoon, which influences the Mediterranean circulation through increases in freshwater inputs.
Sapropels develop during episodes of reduced oxygen availability in bottom waters, such as an oceanic anoxic event (OAE). Most studies of formational mechanisms infer some degree of reduced deep-water circulation. Oxygen can only reach the deep sea by new deep-water formation and consequent "ventilation" of deep basins. There are two main causes of OAE: reduction in deep-water circulation or raised oxygen demand from upper level.
A reduction in deep-water circulation will eventually lead to a serious decrease in deep-water oxygen concentrations due to biochemical oxygen demand associated with the decay of organic matter. This sinks into the deep sea as a result of export production from surface waters. Oxygen depletion in bottom waters then favors the enhanced preservation of the organic matter during burial by the sediments. Organic-rich sediments may also form in well-ventilated settings that have highly productive surface waters; here the high surface demand simply extracts the oxygen before it can enter the deep circulation current thus depriving the bottom waters of oxygen. | 0 | Theoretical and Fundamental Chemistry |
The Wohlwill process is an industrial-scale chemical procedure used to refine gold to the highest degree of purity (99.999%). The process was invented in 1874 by Emil Wohlwill. This electrochemical process involves using a cast gold ingot, often called a doré bar, of 95%+ gold to serve as an anode. Lower percentages of gold in the anode will interfere with the reaction, especially when the contaminating metal is silver or one of the platinum group elements. The cathodes for this reaction are small sheets of pure (24k) gold sheeting or stainless steel. Current is applied to the system, and electricity travels through the electrolyte of chloroauric acid. Gold and other metals are dissolved at the anode, and pure gold (coming through the chloroauric acid by ion transfer) is plated onto the gold cathode. When the anode is dissolved, the cathode is removed and melted or otherwise processed in the manner required for sale or use. The resulting gold is 99.999% pure, and of higher purity than gold produced by the other common refining method, the Miller process, which produces gold of 99.5% purity.
For industrial gold production the Wohlwill process is necessary for highest purity gold applications. When lower purity gold is required, refiners often utilize the Miller process for its relative ease and quicker turnaround times and because it does not require a large inventory of gold, in the form of chloroauric acid. | 1 | Applied and Interdisciplinary Chemistry |
Dichloromethane is the most important halomethane-based solvent. Its volatility, low flammability, and ability to dissolve a wide range of organic compounds makes this colorless liquid a useful solvent. It is widely used as a paint stripper and a degreaser. In the food industry, it was previously used to decaffeinate coffee and tea as well as to prepare extracts of hops and other flavorings. Its volatility has led to its use as an aerosol spray propellant and as a blowing agent for polyurethane foams. | 1 | Applied and Interdisciplinary Chemistry |
The first assessment based on cost and value composite curves of hydrogen resources of a hydrogen network was proposed by Tower et al. (1996). Alves developed the hydrogen pinch analysis approach based on the concept of heat pinch analysis in 1999. Nick Hallale and Fang Liu extended this original work, adding pressure constraints and mathematical programming for optimisation. This was followed by developments at AspenTech, producing commercial software for industrial application. | 1 | Applied and Interdisciplinary Chemistry |
London dispersion forces (LDF, also known as dispersion forces, London forces, instantaneous dipole–induced dipole forces, fluctuating induced dipole bonds or loosely as van der Waals forces) are a type of intermolecular force acting between atoms and molecules that are normally electrically symmetric; that is, the electrons are symmetrically distributed with respect to the nucleus. They are part of the van der Waals forces. The LDF is named after the German physicist Fritz London. They are the weakest intermolecular force. | 0 | Theoretical and Fundamental Chemistry |
Craftsmen and designers utilize copper's inherent benefits to build aesthetically pleasing and long-lasting building systems. From cathedrals to castles and from homes to offices, copper is used in many products: low-sloped and pitched roofs, soffits, fascias, flashings, gutters, downspouts, building expansion joints, domes, spires, and vaults. Copper is also used to clad walls and other surfaces in the exterior and interior environment. | 1 | Applied and Interdisciplinary Chemistry |
The principles involved can be understood by considering the most efficient way of packing together equal-sized spheres and stacking close-packed atomic planes in three dimensions. For example, if plane A lies beneath plane B, there are two possible ways of placing an additional atom on top of layer B. If an additional layer were placed directly over plane A, this would give rise to the following series:
:...ABABABAB...
This arrangement of atoms in a crystal structure is known as hexagonal close packing (hcp).
If, however, all three planes are staggered relative to each other and it is not until the fourth layer is positioned directly over plane A that the sequence is repeated, then the following sequence arises:
:...ABCABCABC...
This type of structural arrangement is known as cubic close packing (ccp).
The unit cell of a ccp arrangement of atoms is the face-centered cubic (fcc) unit cell. This is not immediately obvious as the closely packed layers are parallel to the {111} planes of the fcc unit cell. There are four different orientations of the close-packed layers. | 0 | Theoretical and Fundamental Chemistry |
An independent water and power plant (IWPP) or an integrated water and power project is a combined facility which serves as both a desalination plant and a power plant. IWPPs are more common in the Middle East, where demand for both electricity and salt water desalinisation are high.
Independent water and power producers negotiate both a feed-in power tariff and a water tariff in the same deal with the utility company, who also purchases both products. IWPPs tend to have an installed capacity of over 1 gigawatt (1,000 megawatts) and generates power in a typical thermal power station setup. Seawater is purified by integrating MSF, MED, TVC, or RO water desalination technologies with the power plant, thus increasing overall efficiency. | 1 | Applied and Interdisciplinary Chemistry |
miR-324-5p is a reverse strand miRNA, meaning it is produced from the 5' end of the associated RNA, and spans from position 7,223,342 to 7,223,364 on chromosome 17. Its sequence is CGCAUCCCCUAGGGCAUUGGUG.
miRNA forms following cleavage of pre-miRNA at the hairpin loop by the enzyme dicer within the cytosol. Interestingly, both strands of miR-324's pre-miRNA hairpin loop structure, miR-324-5p and miR-324-3p, become active miRNAs with distinct targets and functions. miR-324-5p has between 166 and 469 predicted targets, including regulators of cell growth, proliferation, survival, cytoskeletal structure, ATP transport, and ion channels. Though miR-324-5p is found on chromosome 17, its targets span across all chromosomes. | 1 | Applied and Interdisciplinary Chemistry |
In fluid mechanics a Riabouchinsky solid is a technique used for approximating boundary layer separation from a bluff body using potential flow. It is named after Dimitri Pavlovitch Riabouchinsky.
Riabouchinsky solids are typically used for analysing the behaviour of bodies moving through otherwise quiescent fluid (examples would include moving cars, or buildings in a windfield).
Typically the streamline that touches the edge of the body is modelled as having no transverse pressure gradient and thus may be styled as a free surface after separation.
The use of Riabouchinsky solids renders dAlemberts paradox void; the technique typically gives reasonable estimates for the drag offered by bluff bodies moving through inviscid fluids. | 1 | Applied and Interdisciplinary Chemistry |
Not all biomarkers should be used as surrogate endpoints to assess clinical outcomes. Biomarkers can be difficult to validate and require different levels of validation depending on their intended use. If a biomarker is to be used to measure the success of a therapeutic intervention, the biomarker should reflect a direct effect of that medicine. | 1 | Applied and Interdisciplinary Chemistry |
Ketone bodies are produced mainly in the mitochondria of liver cells, and synthesis can occur in response to an unavailability of blood glucose, such as during fasting. Other cells, e.g. human astrocytes, are capable of carrying out ketogenesis, but they are not as effective at doing so. Ketogenesis occurs constantly in a healthy individual. Ketogenesis in healthy individuals is ultimately under the control of the master regulatory protein AMPK, which is activated during times of metabolic stress, such as carbohydrate insufficiency. Its activation in the liver inhibits lipogenesis, promotes fatty acid oxidation, switches off acetyl-CoA carboxylase, turns on malonyl-CoA decarboxylase, and consequently induces ketogenesis. Ethanol is a potent AMPK inhibitor and therefore can cause significant disruptions in the metabolic state of the liver, including halting of ketogenesis, even in the context of hypoglycemia.
Ketogenesis takes place in the setting of low glucose levels in the blood, after exhaustion of other cellular carbohydrate stores, such as glycogen. It can also take place when there is insufficient insulin (e.g. in type 1 (and less commonly type 2) diabetes), particularly during periods of "ketogenic stress" such as intercurrent illness.
The production of ketone bodies is then initiated to make available energy that is stored as fatty acids. Fatty acids are enzymatically broken down in β-oxidation to form acetyl-CoA. Under normal conditions, acetyl-CoA is further oxidized by the citric acid cycle (TCA/Krebs cycle) and then by the mitochondrial electron transport chain to release energy. However, if the amounts of acetyl-CoA generated in fatty-acid β-oxidation challenge the processing capacity of the TCA cycle; i.e. if activity in TCA cycle is low due to low amounts of intermediates such as oxaloacetate, acetyl-CoA is then used instead in biosynthesis of ketone bodies via acetoacetyl-CoA and β-hydroxy-β-methylglutaryl-CoA (HMG-CoA). Furthermore, since there is only a limited amount of coenzyme A in the liver, the production of ketogenesis allows some of the coenzyme to be freed to continue fatty-acid β-oxidation. Depletion of glucose and oxaloacetate can be triggered by fasting, vigorous exercise, high-fat diets or other medical conditions, all of which enhance ketone production. Deaminated amino acids that are ketogenic, such as leucine, also feed TCA cycle, forming acetoacetate & ACoA and thereby produce ketones. Besides its role in the synthesis of ketone bodies, HMG-CoA is also an intermediate in the synthesis of cholesterol, but the steps are compartmentalised. Ketogenesis occurs in the mitochondria, whereas cholesterol synthesis occurs in the cytosol, hence both processes are independently regulated. | 1 | Applied and Interdisciplinary Chemistry |
There appear to be two main kinds of methodology used for the calculation of energy quality. These can be classed as either receiver or donor methods. One of the main differences that distinguishes these classes is the assumption of whether energy quality can be upgraded in an energy transformation process.
Receiver methods: view energy quality as a measure and indicator of the relative ease with which energy converts from one form to another. That is, how much energy is received from a transformation or transfer process. For example, A. Grubler [http://www.iiasa.ac.at/Research/TNT/WEB/Publications/Transition_in_Energy_Use/transitions-euse-ene_encyclop_2004.pdf] used two types of indicators of energetic quality pars pro toto: the hydrogen/carbon (H/C) ratio, and its inverse, the carbon intensity of energy. Grubler used the latter as an indicator of relative environmental quality. However Ohta says that in multistage industrial conversion systems, such as a hydrogen production system using solar energy, the energy quality is not upgraded (1994, p. 125).
Donor methods: view energy quality as a measure of the amount of energy used in an energy transformation, and that goes into sustaining a product or service (H.T.Odum 1975, p. 3). That is how much energy is donated to an energy transformation process. These methods are used in ecological physical chemistry, and ecosystem evaluation. From this view, in contrast with that outlined by Ohta, energy quality is upgraded in the multistage trophic conversions of ecological systems. Here, upgraded energy quality has a greater capacity to feedback and control lower grades of energy quality. Donor methods attempt to understand the usefulness of an energetic process by quantifying the extent to which higher quality energy controls lower quality energy. | 0 | Theoretical and Fundamental Chemistry |
Fins are extensions on exterior surfaces of objects that increase the rate of heat transfer to or from the object by increasing convection. This is achieved by increasing the surface area of the body, which in turn increases the heat transfer rate by a sufficient degree. This is an efficient way of increasing the rate, since the alternative way of doing so is by increasing either the heat transfer coefficient (which depends on the nature of materials being used and the conditions of use) or the temperature gradient (which depends on the conditions of use). Clearly, changing the shape of the bodies is more convenient. Fins are therefore a very popular solution to increase the heat transfer from surfaces and are widely used in a number of objects. The fin material should preferably have high thermal conductivity.
In most applications the fin is surrounded by a fluid in motion, which heats or cools it quickly due to the large surface area, and subsequently the heat gets transferred to or from the body quickly due to the high thermal conductivity of the fin.
For optimal Heat transfer performance with minimal cost, the dimensions and shape of the fin have to be calculated for specific applications, and this is called design of a fin. A common way of doing so is by creating a model of the fin and then simulating it under required service conditions. | 1 | Applied and Interdisciplinary Chemistry |
Lavoisiers researches on combustion were carried out in the midst of a very busy schedule of public and private duties, especially in connection with the Ferme Générale. There were also innumerable reports for and committees of the Academy of Sciences to investigate specific problems on order of the royal government. Lavoisier, whose organizing skills were outstanding, frequently landed the task of writing up such official reports. In 1775 he was made one of four commissioners of gunpowder appointed to replace a private company, similar to the Ferme Générale, which had proved unsatisfactory in supplying France with its munitions requirements. As a result of his efforts, both the quantity and quality of French gunpowder greatly improved, and it became a source of revenue for the government. His appointment to the Gunpowder Commission brought one great benefit to Lavoisiers scientific career as well. As a commissioner, he enjoyed both a house and a laboratory in the Royal Arsenal. Here he lived and worked between 1775 and 1792.
Lavoisier was a formative influence in the formation of the Du Pont gunpowder business because he trained Éleuthère Irénée du Pont, its founder, on gunpowder-making in France; the latter said that the Du Pont gunpowder mills "would never have been started but for his kindness to me." | 1 | Applied and Interdisciplinary Chemistry |
In 1801, John Dalton published the law of partial pressures from his work with ideal gas law relationship: The pressure of a mixture of non reactive gases is equal to the sum of the pressures of all of the constituent gases alone. Mathematically, this can be represented for n species as:
: Pressure = Pressure + Pressure + ... + Pressure
The image of Dalton's journal depicts symbology he used as shorthand to record the path he followed. Among his key journal observations upon mixing unreactive "elastic fluids" (gases) were the following:
*Unlike liquids, heavier gases did not drift to the bottom upon mixing.
*Gas particle identity played no role in determining final pressure (they behaved as if their size was negligible). | 0 | Theoretical and Fundamental Chemistry |
Bitumen ( , ) is an immensely viscous constituent of petroleum. Depending on its exact composition it can be a sticky, black liquid or an apparently solid mass that behaves as a liquid over very large time scales. In the U.S., the material is commonly referred to as asphalt. Whether found in natural deposits or refined from petroleum, the substance is classed as a pitch. Prior to the 20th century the term asphaltum was in general use. The word derives from the ancient Greek ἄσφαλτος ásphaltos, which referred to natural bitumen or pitch. The largest natural deposit of bitumen in the world is the Pitch Lake of southwest Trinidad, which is estimated to contain 10 million tons.
70% of annual bitumen production is destined for road construction, its primary use. In this application bitumen is used to bind aggregate particles like gravel and forms a substance referred to as asphalt concrete, which is colloquially termed asphalt. Its other main uses lie in bituminous waterproofing products, such as roofing felt and roof sealant.
In material sciences and engineering the terms "asphalt" and "bitumen" are often used interchangeably and refer both to natural and manufactured forms of the substance, although there is regional variation as to which term is most common. Worldwide, geologists tend to favor the term "bitumen" for the naturally occurring material. For the manufactured material, which is a refined residue from the distillation process of selected crude oils, "bitumen" is the prevalent term in much of the world; however, in American English, "asphalt" is more commonly used. To help avoid confusion, the phrases "liquid asphalt", "asphalt binder", or "asphalt cement" are used in the U.S. to distinguish it from asphalt concrete. Colloquially, various forms of asphalt are sometimes referred to as "tar", as in the name of the La Brea Tar Pits.
Naturally occurring bitumen is sometimes specified by the term "crude bitumen". Its viscosity is similar to that of cold molasses while the material obtained from the fractional distillation of crude oil boiling at is sometimes referred to as "refined bitumen". The Canadian province of Alberta has most of the world's reserves of natural bitumen in the Athabasca oil sands, which cover , an area larger than England. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, phase-boundary catalysis (PBC) is a type of heterogeneous catalytic system which facilitates the chemical reaction of a particular chemical component in an immiscible phase to react on a catalytic active site located at a phase boundary. The chemical component is soluble in one phase but insoluble in the other. The catalyst for PBC has been designed in which the external part of the zeolite is hydrophobic, internally it is usually hydrophilic, notwithstanding to polar nature of some reactants. In this sense, the medium environment in this system is close to that of an enzyme. The major difference between this system and enzyme is lattice flexibility. The lattice of zeolite is rigid, whereas the enzyme is flexible. | 0 | Theoretical and Fundamental Chemistry |
Benzene, as well as most other annulenes (cyclodecapentaene excepted) with the formula CH where n is an even number, such as cyclotetradecaheptaene. | 0 | Theoretical and Fundamental Chemistry |
Isofalcarintriol (IUPAC name (3S,8R,9R,E)-heptadeca-10-en-4,6-diyne-3,8,9-triol) is a polyacetylene contained in the root of carrots (Daucus carota). | 1 | Applied and Interdisciplinary Chemistry |
The best-known version of the experiment was started in 1927 by Professor Thomas Parnell of the University of Queensland in Brisbane, Australia, to demonstrate to students that some substances which appear solid are highly viscous fluids. Parnell poured a heated sample of the pitch into a sealed funnel and allowed it to settle for three years. In 1930, the seal at the neck of the funnel was cut, allowing the pitch to start flowing. A glass dome covers the funnel and it is placed on display outside a lecture theatre. Each droplet forms and falls over a period of about a decade.
The seventh drop fell at approximately 4:45 p.m. on 3 July 1988, while the experiment was on display at Brisbane's World Expo 88. However, apparently no one witnessed the drop fall itself; Professor Mainstone had stepped out to get a drink at the moment it occurred.
The eighth drop fell on 28 November 2000, allowing experimenters to calculate the pitch as having a viscosity of approximately 230 billion times that of water.
This experiment is recorded in Guinness World Records as the "world's longest continuously running laboratory experiment", and it is expected there is enough pitch in the funnel to allow it to continue for at least another hundred years. This experiment is predated by two other (still-active) scientific devices, the Oxford Electric Bell (1840) and the Beverly Clock (1864), but each of these has experienced brief interruptions since 1937.
The experiment was not originally carried out under any special controlled atmospheric conditions, meaning the viscosity could vary throughout the year with fluctuations in temperature. Sometime after the seventh drop fell (1988), air conditioning was added to the location where the experiment takes place. The lower average temperature has lengthened each drop's stretch before it separates from the rest of the pitch in the funnel, and correspondingly the typical interval between drops has increased from eight years to 12–13 years.
In October 2005, John Mainstone and the late Thomas Parnell were awarded the Ig Nobel Prize in physics, a parody of the Nobel Prize, for the pitch drop experiment. Mainstone subsequently commented:
The experiment is monitored by a webcam but technical problems prevented the November 2000 drop from being recorded. The pitch drop experiment is on public display on Level 2 of Parnell building in the School of Mathematics and Physics at the St Lucia campus of the University of Queensland. Hundreds of thousands of Internet users check the live stream each year.
Professor John Mainstone died on 23 August 2013, aged 78, following a stroke. Custodianship then passed to Professor Andrew White.
The ninth drop touched the eighth drop on 12 April 2014; however, it was still attached to the funnel. On 24 April, Professor White decided to replace the beaker holding the previous eight drops before the ninth drop fused to them (which would have permanently affected the ability of further drops to form). While the bell jar was being lifted, the wooden base wobbled and the ninth drop snapped away from the funnel. | 1 | Applied and Interdisciplinary Chemistry |
Magnetic refrigeration, or adiabatic demagnetization, is a cooling technology based on the magnetocaloric effect, an intrinsic property of magnetic solids. The refrigerant is often a paramagnetic salt, such as cerium magnesium nitrate. The active magnetic dipoles in this case are those of the electron shells of the paramagnetic atoms.
A strong magnetic field is applied to the refrigerant, forcing its various magnetic dipoles to align and putting these degrees of freedom of the refrigerant into a state of lowered entropy. A heat sink then absorbs the heat released by the refrigerant due to its loss of entropy. Thermal contact with the heat sink is then broken so that the system is insulated, and the magnetic field is switched off. This increases the heat capacity of the refrigerant, thus decreasing its temperature below the temperature of the heat sink.
Because few materials exhibit the needed properties at room temperature, applications have so far been limited to cryogenics and research. | 0 | Theoretical and Fundamental Chemistry |
Emission coefficient is a coefficient in the power output per unit time of an electromagnetic source, a calculated value in physics. The emission coefficient of a gas varies with the wavelength of the light. It has units of mssr. It is also used as a measure of environmental emissions (by mass) per MWh of electricity generated, see: Emission factor. | 0 | Theoretical and Fundamental Chemistry |
Gerard ONeill, noting the problem of high launch costs in the early 1970s, proposed building the SPSs in orbit with materials from the Moon. Launch costs from the Moon are potentially much lower than from Earth because of the lower gravity and lack of atmospheric drag. This 1970s proposal assumed the then-advertised future launch costing of NASAs space shuttle. This approach would require substantial upfront capital investment to establish mass drivers on the Moon. Nevertheless, on 30 April 1979, the Final Report ("Lunar Resources Utilization for Space Construction") by General Dynamics Convair Division, under NASA contract NAS9-15560, concluded that use of lunar resources would be cheaper than Earth-based materials for a system of as few as thirty solar power satellites of 10 GW capacity each.
In 1980, when it became obvious NASAs launch cost estimates for the space shuttle were grossly optimistic, ONeill et al. published another route to manufacturing using lunar materials with much lower startup costs. This 1980s SPS concept relied less on human presence in space and more on partially self-replicating systems on the lunar surface under remote control of workers stationed on Earth. The high net energy gain of this proposal derives from the Moon's much shallower gravitational well.
Having a relatively cheap per pound source of raw materials from space would lessen the concern for low mass designs and result in a different sort of SPS being built. The low cost per pound of lunar materials in ONeills vision would be supported by using lunar material to manufacture more facilities in orbit than just solar power satellites. Advanced techniques for launching from the Moon may reduce the cost of building a solar power satellite from lunar materials. Some proposed techniques include the lunar mass driver and the lunar space elevator, first described by Jerome Pearson. It would require establishing silicon mining and solar cell manufacturing facilities on the Moon. | 0 | Theoretical and Fundamental Chemistry |
The generally accepted model of the formation of the Universe states that it happened as the result of the Big Bang. In this model, in the time interval of 10–10 s after the Big Bang, matter existed in the form of a quark–gluon plasma. It is possible to reproduce the density and temperature of matter existing of that time in laboratory conditions to study the characteristics of the very early Universe. So far, the only possibility is the collision of two heavy atomic nuclei accelerated to energies of more than a hundred GeV. Using the result of a head-on collision in the volume approximately equal to the volume of the atomic nucleus, it is possible to model the density and temperature that existed in the first instants of the life of the Universe. | 0 | Theoretical and Fundamental Chemistry |
Helicase activities are initiated by the N-terminal arm and the Ski2 insertion domain. In yeast, the complex guides RNA molecules to the exosome complex for degradation via a fourth protein, called Ski7, which contains a GTPase-like protein. Ski7 involves the 3’ to 5’ degradation of RNA through two different pathways, 3’ poly(A) tail shortening and the binding of the Ski2, Ski3, and Ski8 tetramer and the exosome.
Degradation of the 3 mRNA overhang occurs by association with the 80s ribosome. The 3 end of the mRNA is threaded through the ribosome to Ski2, preparing it for the degradation process.
Biochemical studies also show that the Ski complex can thread RNA through the exosome complex, thereby coupling the Ski2 protein helicase function with the exoribonuclease activity, leading to degradation of the RNA strand. | 1 | Applied and Interdisciplinary Chemistry |
Absorbance of a material is also related to its decadic attenuation coefficient by
where
* is the thickness of that material through which the light travels, and
* is the decadic attenuation coefficient of that material at .
If a(z) is uniform along the path, the attenuation is said to be a linear attenuation, and the relation becomes
Sometimes the relation is given using the molar attenuation coefficient of the material, that is its attenuation coefficient divided by its molar concentration:
where
* is the molar attenuation coefficient of that material, and
* is the molar concentration of that material at .
If is uniform along the path, the relation becomes
The use of the term "molar absorptivity" for molar attenuation coefficient is discouraged. | 0 | Theoretical and Fundamental Chemistry |
The approach relies on a combination of companion crops to be planted around and among maize or sorghum. Both domestic and wild grasses can help to protect the crops by attracting and trapping the stemborers. The grasses are planted in the border around the maize and sorghum fields where invading adult moths become attracted to chemicals emitted by the grasses themselves. Instead of landing on the maize or sorghum plants, the insects head for what appears to be a tastier meal. These grasses provide the "pull" in the "push–pull" strategy. They also serve as a haven for the borers natural enemies. Good trap crops include well-known grasses such as Napier grass (Pennisetum purpureum), Signal grass (Brachiaria brizantha), and Sudan grass (Sorghum vulgare sudanense'). Napier grass produces significantly higher levels of attractive volatile compounds (green leaf volatiles), cues used by gravid stemborer females to locate host plants, than maize or sorghum. There is also an increase of approximately 100-fold in the total amounts of these compounds produced in the first hour of nightfall by Napier grass (scotophase), the period at which stemborer moths seek host plants for laying eggs, causing the differential oviposition preference. However, many of the stemborer larvae, about 80%, do not survive, as Napier grass tissues produce sticky sap in response to feeding by the larvae, which traps them, causing the death of about 80% of larvae. | 1 | Applied and Interdisciplinary Chemistry |
Paucimannosidic glycans span the base composition ManGlcNAc. Additional modifications with Fuc, Xyl and/or Galactose (Gal) are common in mammals ref, plants and invertebrates, respectively. Paucimannosidic glycans expressed by insects and nematodes are particularly rich in structural diversity. | 1 | Applied and Interdisciplinary Chemistry |
Medium-pressure mercury-vapor lamps have historically been the industry standard for curing products with ultraviolet light. The bulbs work by sending an electric discharge to excite a mixture of mercury and noble gases, generating a plasma. Once the mercury reaches a plasma state, it irradiates a high spectral output in the UV region of the electromagnetic spectrum. Major peaks in light intensity occur in the 240-270 nm and 350-380 nm regions. These intense peaks, when matched with the absorption profile of a photoinitiator, cause the rapid curing of materials. By modifying the bulb mixture with different gases and metal halides, the distribution of wavelength peaks can be altered, and material interactions are changed.
Medium-pressure lamps can either be standard gas-discharge lamps or electrodeless lamps, and typically use an elongated bulb to emit energy. By incorporating optical designs such an elliptical or even aconic reflector, light can either be focused or projected over a far distance. These lamps can often operate at over 900 degrees Celsius and produce UV energy levels over 10 W/cm. | 0 | Theoretical and Fundamental Chemistry |
The Volta potential measured by SKP is directly proportional to the corrosion potential of a material, as such SKP has found widespread use in the study of the fields of corrosion and coatings. In the field of coatings for example, a scratched region of a self-healing shape memory polymer coating containing a heat generating agent on aluminium alloys was measured by SKP. Initially after the scratch was made the Volta potential was noticeably higher and wider over the scratch than over the rest of the sample, implying this region is more likely to corrode. The Volta potential decreased over subsequent measurements, and eventually the peak over the scratch completely disappeared implying the coating has healed. Because SKP can be used to investigate coatings in a non-destructive way it has also been used to determine coating failure. In a study of polyurethane coatings, it was seen that the work function increases with increasing exposure to high temperature and humidity. This increase in work function is related to decomposition of the coating likely from hydrolysis of bonds within the coating.
Using SKP the corrosion of industrially important alloys has been measured. In particular with SKP it is possible to investigate the effects of environmental stimulus on corrosion. For example, the microbially induced corrosion of stainless steel and titanium has been examined. SKP is useful to study this sort of corrosion because it usually occurs locally, therefore global techniques are poorly suited. Surface potential changes related to increased localized corrosion were shown by SKP measurements. Furthermore, it was possible to compare the resulting corrosion from different microbial species. In another example SKP was used to investigate biomedical alloy materials, which can be corroded within the human body. In studies on Ti-15Mo under inflammatory conditions, SKP measurements showed a lower corrosion resistance at the bottom of a corrosion pit than at the oxide protected surface of the alloy. SKP has also been used to investigate the effects of atmospheric corrosion, for example to investigate copper alloys in marine environment. In this study Kelvin potentials became more positive, indicating a more positive corrosion potential, with increased exposure time, due to an increase in thickness of corrosion products. As a final example SKP was used to investigate stainless steel under simulated conditions of gas pipeline. These measurements showed an increase in difference in corrosion potential of cathodic and anodic regions with increased corrosion time, indicating a higher likelihood of corrosion. Furthermore, these SKP measurements provided information about local corrosion, not possible with other techniques.
SKP has been used to investigate the surface potential of materials used in solar cells, with the advantage that it is a non-contact, and therefore a non-destructive technique. It can be used to determine the electron affinity of different materials in turn allowing the energy level overlap of conduction bands of differing materials to be determined. The energy level overlap of these bands is related to the surface photovoltage response of a system.
As a non-contact, non-destructive technique SKP has been used to investigate latent fingerprints on materials of interest for forensic studies. When fingerprints are left on a metallic surface they leave behind salts which can cause the localized corrosion of the material of interest. This leads to a change in Volta potential of the sample, which is detectable by SKP. SKP is particularly useful for these analyses because it can detect this change in Volta potential even after heating, or coating by, for example, oils.
SKP has been used to analyze the corrosion mechanisms of schreibersite-containing meteorites. The aim of these studies has been to investigate the role in such meteorites in releasing species utilized in prebiotic chemistry.
In the field of biology SKP has been used to investigate the electric fields associated with wounding, and acupuncture points.
In the field of electronics, KPFM is used to investigate the charge trapping in High-k gate oxides/interfaces of electronic devices. | 0 | Theoretical and Fundamental Chemistry |
The Great Oxygenation Event (GOE) that occurred 2.4 billion years ago altered the course of life on Earth forever by increasing the abundance of oxygen in the atmosphere. Bacteria that existed before the GEO did not rely on the presence of oxygen as a source for metabolism, such as the billion-year-old Cyanobacteria. Melainabacteria is a close relative to Cyanobacteria, though Melainabacteria diverged and do not photosynthesize. Cyanobacteria produced atmospheric oxygen and supported the development of early plant cells. | 1 | Applied and Interdisciplinary Chemistry |
POSCO, one of the world's biggest steel production companies, in 1986, initiated a founding of a science and technology university in the city of Pohang, about 200 miles southeast of Seoul, the capital city of Korea. Pohang University of Science and Technology (POSTECH) has now become one of the top research universities in Asia. GIFT was founded to provide an academic environment for education and research on ferrous materials. | 1 | Applied and Interdisciplinary Chemistry |
The mitochondria is believed to be important in controlling the supply of oxygen available for making light in fireflies. An increased rate of respiration decreases the intracellular oxygen concentration which reduces the amount available for light production. The mitochondria of the photocyte exists near the perimeter of the cell while the peroxisome is typically found closer to the middle of the cell. It is worth noting that not all bioluminescence in the firefly light organ occurs in the granules of the photocyte. Some fluorescent protein has been found to exist in the posterior region of the organ. | 1 | Applied and Interdisciplinary Chemistry |
Membrane emulsification (ME) is a relatively novel technique for producing all types of single and multiple emulsions for DDS (drug delivery systems), solid micro carriers for encapsulation of drug or nutrient, solder particles for surface-mount technology, mono dispersed polymer microspheres (for analytical column packing, enzyme carriers, liquid crystal display spacers, toner core particles). Membrane emulsification was introduced by Nakashima and Shimizu in the late 1980s in Japan. | 0 | Theoretical and Fundamental Chemistry |
If a railway track runs over a bridge which has expansion joints that move more than a few millimeters, the track must be able to compensate this longer expansion or contraction. On the other hand, the track must always provide a continuous surface for the wheels traveling over it. These conflicting requirements are served by special expansion joints, where two rails glide along with each other at a very acute angle during expansion or contraction. They are typically seen near one or both ends of large steel bridges. Such an expansion joint looks somewhat like the tongue of a railroad switch, but with a different purpose and operation. | 1 | Applied and Interdisciplinary Chemistry |
Glycosyltransferases have been widely used in both the targeted synthesis of specific glycoconjugates as well as the synthesis of differentially glycosylated libraries of drugs, biological probes or natural products in the context of drug discovery and drug development (a process known as glycorandomization). Suitable enzymes can be isolated from natural sources or produced recombinantly. As an alternative, whole cell-based systems using either endogenous glycosyl donors or cell-based systems containing cloned and expressed systems for synthesis of glycosyl donors have been developed. In cell-free approaches, the large-scale application of glycosyltransferases for glycoconjugate synthesis has required access to large quantities of the glycosyl donors. On the flip-side, nucleotide recycling systems that allow the resynthesis of glycosyl donors from the released nucleotide have been developed. The nucleotide recycling approach has a further benefit of reducing the amount of nucleotide formed as a by-product, thereby reducing the amount of inhibition caused to the glycosyltransferase of interest – a commonly observed feature of the nucleotide byproduct. | 0 | Theoretical and Fundamental Chemistry |
A beam path is a river section of low ecological condition that borders on sections of higher ecological potential. An enhancing beam path is a type of beam path into which organisms of a nearby beam source can migrate or are at least temporarily settle. Furthermore, typical organisms can only drift or migrate through the beam path, which is then called a transit beam path. In a beam path a biocenosis can be established which is only possible due to the presence of adjacent beam origins. | 1 | Applied and Interdisciplinary Chemistry |
* 2015 elected board member, European Academy of Microbiology (EAM)
* 2013 elected member, European Academy of Microbiology (EAM)
* 2012 iGEM Team Groningen: European and World Champion 2012 (Kuipers was supervisor/coach/coordinator of the iGEM team Groningen from 2008-2015)
* 2011 elected member, Royal Netherlands Academy of Arts and Sciences (KNAW)
* 2011 Simon Stevin Meester Award (Science and Technology Award of STW, NWO, the Netherlands) €500,000 | 0 | Theoretical and Fundamental Chemistry |
The design of a galvanic anode CP system should consider many factors, including the type of structure, the resistivity of the electrolyte (soil or water) it will operate in, the type of coating and the service life.
The primary calculation is how much anode material will be required to protect the structure for the required time. Too little material may provide protection for a while, but need to be replaced regularly. Too much material would provide protection at an unnecessary cost. The mass in kg is given by equation ().
* The design life is in years (1 year = 8760 hours).
* The utilisation factor (UF) of the anode is a constant value, depending on the shape of the anode and how it is attached, which signifies how much of the anode can be consumed before it ceases to be effective. A value of 0.8 indicates that 80% of the anode can be consumed, before it should be replaced. A long slender stand off anode (installed on legs to keep the anode away from the structure) has a UF value of 0.9, whereas the UF of a short, flush mounted anode is 0.8.
* Anode capacity is an indication of how much material is consumed as current flows over time. The value for zinc in seawater is 780 Ah/kg but aluminium is 2000 Ah/kg, which reflects the lower atomic mass of aluminium and means that, in theory, aluminium can produce much more current per weight than zinc before being depleted and this is one of the factors to consider when choosing a particular material.
The amount of current required corresponds directly to the surface area of the metal exposed to the soil or water, so the application of a coating drastically reduces the mass of anode material required. The better the coating, the less anode material is needed.
Once the required mass of material is known, the particular type of anode is chosen. Differently shaped anodes will have a different resistance to earth, which governs how much current can be produced, so the resistance of the anode is calculated to ensure that sufficient current will be available. If the resistance of the anode is too high, either a differently shaped or sized anode is chosen, or a greater quantity of anodes must be used.
The arrangement of the anodes is then planned so as to provide an even distribution of current over the whole structure. For example, if a particular design shows that a pipeline long needs 10 anodes, then approximately one anode per kilometre would be more effective than putting all 10 anodes at one end or in the centre. | 0 | Theoretical and Fundamental Chemistry |
A Winkler bottle is a piece of laboratory glassware specifically made for carrying out the Winkler test. These bottles have conical tops and a close fitting stopper to aid in the exclusion of air bubbles when the top is sealed. This is important because oxygen in trapped air would be included in the measurement and would affect the accuracy of the test. | 0 | Theoretical and Fundamental Chemistry |
FSL have been used to create human red cell kodecytes that have been used to detect and identify blood group allo-antibodies as ABO sub-group mimics, ABO quality control systems, serologic teaching kits and a syphilis diagnostic. Kodecytes have also demonstrated that FSL-FLRO4 is a suitable reagent for labelling packed red blood cells (PRBC) at any point during routine storage and look to facilitate the development of immunoassays and transfusion models focused on addressing the mechanisms involved in tansfusion-related immunomodulation (TRIM). Murine kodecytes have been experimentally used to determine in vivo cell survival, and create model transfusion reactions. Zebrafish kodecytes have been used to determine real time in vivo cell migration. Kodecytes have been used to create influenza diagnostics. Kodecytes which have been modified with FSL-GB3 were unable to be infected with the HIV virus. | 1 | Applied and Interdisciplinary Chemistry |
Reid became interested in chemistry whilst at high school. She eventually studied chemistry at the University of Edinburgh, where she earned her bachelor's degree in 1986. She remained there for her doctoral research, where she studied macrocyclic complexes. After earning her degree in 1989, and a 2 year postdoctoral research position in Edinburgh, Reid moved to a lectureship in the University of Southampton. | 0 | Theoretical and Fundamental Chemistry |
The Gill Mantle ("Txampaysye" in Navi) is a large jellyfish like creature native to Pandoras reefs. The Navi can bond with them in the water, which can supply them with oxygen through the water allowing Navi to remain underwater much longer. They are primarily used by Kiri throughout Avatar: The Way of Water. | 1 | Applied and Interdisciplinary Chemistry |
First article which touches antigen transfer was published in 2004. Experiments from this study reveal that clonal deletion of autoreactive CD4 T cells, apart from CD8 T cells, requires indirect presentation of TRAs by bone marrow (BM) derived APCs. Direct presentation of TRAs by mTECs was shown to be insufficient in this case. Requirement of indirect presentation of some mTEC-derived TRAs in the case of recessive tolerance was perceived also by additional studies which both firstly demonstrated antigen transfer as an instrument that enables this process. Need of TRA indirect presentation is probably closely related with above mentioned "processing of TRAs by different microenvironments".
N.B.: BM derived APCs don´t express TRAs, this process is uniquely dedicated to mTECs. Exception is represented by thymic B cells which were shown to express TRAs and Aire. | 1 | Applied and Interdisciplinary Chemistry |
The essential parts of a colorimeter are:
* a light source (often an ordinary low-voltage filament lamp);
* an adjustable aperture;
* a set of colored filters;
* a cuvette to hold the working solution;
* a detector (usually a photoresistor) to measure the transmitted light;
* a meter to display the output from the detector.
In addition, there may be:
* a voltage regulator, to protect the instrument from fluctuations in mains voltage;
* a second light path, cuvette and detector. This enables comparison between the working solution and a "blank", consisting of pure solvent, to improve accuracy.
There are many commercialized colorimeters as well as open source versions with construction documentation for education and for research. | 0 | Theoretical and Fundamental Chemistry |
Several physical properties of superconductors vary from material to material, such as the critical temperature, the value of the superconducting gap, the critical magnetic field, and the critical current density at which superconductivity is destroyed. On the other hand, there is a class of properties that are independent of the underlying material. The Meissner effect, the quantization of the magnetic flux or permanent currents, i.e. the state of zero resistance are the most important examples. The existence of these "universal" properties is rooted in the nature of the broken symmetry of the superconductor and the emergence of off-diagonal long range order. Superconductivity is a thermodynamic phase, and thus possesses certain distinguishing properties which are largely independent of microscopic details. Off diagonal long range order is closely connected to the formation of Cooper pairs. | 0 | Theoretical and Fundamental Chemistry |
FACIT collagen (Fibril Associated Collagens with Interrupted Triple helices) is a type of collagen and also a proteoglycan that have two or more triple-helical domains that connect to collagen fibrils and share protein domains with non-collagen matrix molecules. FACIT collagens derive their name from their association and interaction with fibrillar collagens. Unlike fibrillar collagens, which form long fibers.
FACIT collagens have interruptions in their triple helical structure. They are involved in assembling fibrillar collagens and other ECM components. Interruptions in the triple helical structure of FACIT collagens occur due to the presence of non-triple helical domains within the collagen molecule. These collagens are typically found alongside fibrillar collagens in various tissues and organs. Fibril-associated collagens with interrupted triple helices (FACIT collagens) are a subset of collagens that contribute to the organization and stabilization of the extracellular matrix (ECM). These collagens are typically found alongside fibrillar collagens in various tissues and organs. These domains vary in length and composition and provide flexibility and additional binding sites for other components of the extracellular matrix. There are eight known types of FACIT collagens: collagens IX, XII, XIV, XVI, XIX, XXI, and XXII.
The general FACIT collagen structure contains short triple helical COL domains (COL1, COL2, COL3) interrupted by NC domains with an N-terminal NC domain facing toward the interfibrillar space. FACIT collagen is found in various tissue areas to modulate the surface properties of collagen fibrils and generate tissue-specific three-dimensional patterns in the extracellular matrix. For example, collagen XIV connects the fibrillar networks of the cartilage and skin, and XII is found in connective tissues, particularly at the tendons, ligaments, and periodontium. These collagen types can be directly or indirectly associated with fibrils at different affinities to modulate the frictional properties of fibril surfaces. In addition, collagen XIV association with a propeptide suggests FACIT function can extend to providing binding sites for fibril-modifying extracellular enzymes.
Other collagen types such as Collagen XX, which are smaller in size are mostly expressed in the connective tissue such as cartilage, tendon, and cornea while Collagen XIX is found in the skin, muscle cells, and the hippocampus. There are also collagens that are expressed in the basement membrane zones, which are extracellular matrices composed of macromolecule networks, and collagen XXII is one example located in the myotendinous junctions in the skeletal and heart muscles.
COL22A1 is also included in this class. | 1 | Applied and Interdisciplinary Chemistry |
Here we give the flow field of a squirmer in the case of a non-deformable axisymmetric spherical squirmer (radius ). These expressions are given in a spherical coordinate system.
<br />
Here are constant coefficients, are Legendre polynomials, and . <br />
One finds .<br />
The expressions above are in the frame of the moving particle. At the interface one finds and . | 1 | Applied and Interdisciplinary Chemistry |
AGEs are the subject of ongoing research. There are three therapeutic approaches: preventing the formation of AGEs, breaking crosslinks after they are formed and preventing their negative effects.
Compounds that have been found to inhibit AGE formation in the laboratory include Vitamin C, Agmatine, benfotiamine, pyridoxamine, alpha-lipoic acid, taurine, pimagedine, aspirin, carnosine, metformin, pioglitazone, and pentoxifylline. Activation of the TRPA-1 receptor by lipoic acid or podocarpic acid has been shown to reduce the levels of AGES by enhancing the detoxification of methylglyoxal, a major precursor of several AGEs.
Studies in rats and mice have found that natural phenols such as resveratrol and curcumin can prevent the negative effects of the AGEs.
Compounds that are thought to break some existing AGE crosslinks include Alagebrium (and related ALT-462, ALT-486, and ALT-946) and N-phenacyl thiazolium bromide. One in vitro study shows that rosmarinic acid out performs the AGE breaking potential of ALT-711.
There is, however, no agent known that can break down the most common AGE, glucosepane, which appears 10 to 1,000 times more common in human tissue than any other cross-linking AGE.
Some chemicals, on the other hand, like aminoguanidine, might limit the formation of AGEs by reacting with 3-deoxyglucosone. | 1 | Applied and Interdisciplinary Chemistry |
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