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In some cases the particles will, due to their higher density, not perfectly follow the motion of the fluid (gas/liquid). If experiments are done in water, for instance, it is easily possible to find very cheap particles (e.g. plastic powder with a diameter of ~60 µm) with the same density as water. If the density still does not fit, the density of the fluid can be tuned by increasing/ decreasing its temperature. This leads to slight changes in the Reynolds number, so the fluid velocity or the size of the experimental object has to be changed to account for this.
Particle image velocimetry methods will in general not be able to measure components along the z-axis (towards to/away from the camera). These components might not only be missed, they might also introduce an interference in the data for the x/y-components caused by parallax. These problems do not exist in Stereoscopic PIV, which uses two cameras to measure all three velocity components.
Since the resulting velocity vectors are based on cross-correlating the intensity distributions over small areas of the flow, the resulting velocity field is a spatially averaged representation of the actual velocity field. This obviously has consequences for the accuracy of spatial derivatives of the velocity field, vorticity, and spatial correlation functions that are often derived from PIV velocity fields.
PIV systems used in research often use class IV lasers and high-resolution, high-speed cameras, which bring cost and safety constraints. | 1 | Applied and Interdisciplinary Chemistry |
Macroscopically, the ideal gas law states that, for an ideal gas, the product of pressure and volume is proportional to the product of amount of substance and absolute temperature :
where is the molar gas constant (). Introducing the Boltzmann constant as the gas constant per molecule (being N the Avogadro constant) transforms the ideal gas law into an alternative form:
where is the number of molecules of gas. | 0 | Theoretical and Fundamental Chemistry |
Many atropisomers occur in nature, and some have applications to drug design. The natural product mastigophorene A has been found to aid in nerve growth.
Other examples of naturally occurring atropisomers include vancomycin isolated from an Actinobacterium, and knipholone, which is found in the roots of Kniphofia foliosa of the family Asphodelaceae. The structure complexity in vancomycin is significant because it can bind with peptides due to the complexity of its stereochemistry, which includes multiple stereocenters, two chiral planes in its stereogenic biaryl axis. Knipholone, with its axial chirality, occurs in nature and has been shown to offer good antimalarial and antitumor activities particularly in the M form.
The use of atropisomeric drugs provides an additional way for drugs to have stereochemical variations and specificity in design. One example is , a drug that was discovered to aid in chemotherapy cancer treatment.
Telenzepine is atropisomeric in the conformation of its central thienobenzodiazepine ring. The two enantiomers have been resolved, and it was found that the (+)-isomer which is about 500-fold more active than the (–)-isomer at muscarinic receptors in rat cerebral cortex. However, drug design is not always aided by atropisomerism. In some cases, making drugs from atropisomers is challenging because isomers may interconvert faster than expected. Atropisomers also might interact differently in the body, and as with other types of stereoisomers, it is important to examine these properties before administering drugs to patients. | 0 | Theoretical and Fundamental Chemistry |
The solid sample is taken in a Petri dish and melted by heating it on a standard hot plate. The bubble free liquefied sample is poured from the Petri dish and cast into the ring. The brass shouldered rings in this apparatus have 6.4 mm depth. The cast sample in the ring is kept undisturbed for one hour to solidify. Excess material is removed with a hot knife. The ring is set with the ball on top with ball guides on the grooved plate within the heating bath. As the temperature rises, the balls begin to sink through the rings carrying a portion of the softened sample with it. The temperature at which the steel balls touch the bottom plate determines the softening point in degrees Celsius. | 0 | Theoretical and Fundamental Chemistry |
In 1938, Pyotr Kapitsa, John Allen and Don Misener discovered that helium-4 became a new kind of fluid, now known as a superfluid, at temperatures less than 2.17 K (the lambda point). Superfluid helium has many unusual properties, including zero viscosity (the ability to flow without dissipating energy) and the existence of quantized vortices. It was quickly believed that the superfluidity was due to partial Bose–Einstein condensation of the liquid. In fact, many properties of superfluid helium also appear in gaseous condensates created by Cornell, Wieman and Ketterle (see below). Superfluid helium-4 is a liquid rather than a gas, which means that the interactions between the atoms are relatively strong; the original theory of Bose–Einstein condensation must be heavily modified in order to describe it. Bose–Einstein condensation remains, however, fundamental to the superfluid properties of helium-4. Note that helium-3, a fermion, also enters a superfluid phase (at a much lower temperature) which can be explained by the formation of bosonic Cooper pairs of two atoms (see also fermionic condensate). | 0 | Theoretical and Fundamental Chemistry |
The term "fine chemicals" was in use as early as 1908. The emergence of the fine chemical industry as a distinct entity dates to the late 1970s, when the overwhelming success of the histamine H receptor antagonists Tagamet (cimetidine) and Zantac (ranitidine hydrochloride) created a strong demand for advanced organic chemicals used in their manufacture. As the in-house production capacities of the originators, the pharmaceutical companies Smith, Kline, & French and Glaxo, could not keep pace with the rapidly increasing requirements, both companies (now merged as GlaxoSmithKline) outsourced part of the manufacturing to chemical companies experienced in producing relatively sophisticated organic molecules. Lonza, Switzerland, which already had supplied an early intermediate, methyl acetoacetate, during drug development, soon became the main supplier of more and more advanced precursors. The signature of a first, simple supply contract is generally acknowledged as the historical document marking the beginning of the fine chemical industry.
In subsequent years, the business developed and Lonza was the first fine chemical company entering in a strategic partnership with SKF. In a similar way, Fine Organics, UK became the supplier of the thioethyl-N'-methyl-2-nitro-1,1-ethenediamine moiety of ranitidine, the second H2 receptor antagonist, marketed as Zantac by Glaxo. Other pharmaceutical and agrochemical companies gradually followed suit and started outsourcing the procurement of fine chemicals. An example in case is F.I.S., Italy, which partnered with Roche, Switzerland for custom manufacturing precursors of the benzodiazepine class of tranquilizers, such as Librium (chlordiazepoxide HCl) and Valium (diazepam).
The growing complexity and potency of new pharmaceuticals and agrochemicals requiring production in multipurpose, instead of dedicated plants and, more recently, the advent of biopharmaceuticals had a major impact on the demand for fine chemicals and the evolution of the fine chemical industry as a distinct entity. For many years, the life science industry continued considering captive production of the active ingredients of their drugs and agrochemicals as a core competency. Outsourcing was used only in exceptional cases, such as capacity shortfalls, processes requiring hazardous chemistry or new products, where uncertainties existed about the chance of a successful launch. | 0 | Theoretical and Fundamental Chemistry |
In genetics, a master regulator gene is a regulator gene at the top of a gene regulation hierarchy, particularly in regulatory pathways related to cell fate and differentiation. | 1 | Applied and Interdisciplinary Chemistry |
Because of the widespread use and importance of iron and steel products, the prevention or slowing of rust is the basis of major economic activities in a number of specialized technologies. A brief overview of methods is presented here; for detailed coverage, see the cross-referenced articles.
Rust is permeable to air and water, therefore the interior metallic iron beneath a rust layer continues to corrode. Rust prevention thus requires coatings that preclude rust formation. | 1 | Applied and Interdisciplinary Chemistry |
Prior to 1971, Monsanto marketed a series of polychlorinated biphenyl-(PCB)-containing heat transfer fluids designated as Therminol FR series in the United States and Santotherm FR series in Europe. FR series Therminol heat transfer fluids contained PCBs, which imparted fire resistance. Monsanto voluntarily ceased sales of these fluids in 1971. No form of Therminol heat transfer fluids have contained PCBs since that time. Polychlorinated biphenyl was banned by the United States Congress in 1979 and the Stockholm Convention on Persistent Organic Pollutants in 2001. | 1 | Applied and Interdisciplinary Chemistry |
In molecular biology and genetics, transcription coregulators are proteins that interact with transcription factors to either activate or repress the transcription of specific genes. Transcription coregulators that activate gene transcription are referred to as coactivators while those that repress are known as corepressors. The mechanism of action of transcription coregulators is to modify chromatin structure and thereby make the associated DNA more or less accessible to transcription. In humans several dozen to several hundred coregulators are known, depending on the level of confidence with which the characterisation of a protein as a coregulator can be made. One class of transcription coregulators modifies chromatin structure through covalent modification of histones. A second ATP dependent class modifies the conformation of chromatin. | 1 | Applied and Interdisciplinary Chemistry |
Physics is central to Kaṇāda's assertion that all that is knowable is based on motion. His ascribing centrality to physics in the understanding of the universe also follows from his invariance principles. For example, he says that the atom must be spherical since it should be the same in all dimensions. He asserts that all substances are composed of atoms, two of which have mass and two are massless.
The philosophy in Vaiseshika sutra is atomistic pluralism, states Jayatilleke. Its ideas are known for its contributions to "inductive inference", and often coupled with the "deductive logic" of the sister school of Hinduism called the Nyaya. James Thrower and others call Vaiśeṣika philosophy to be naturalism.
The text states:
* There are nine constituents of realities: four classes of atoms (earth, water, fire and air), space (akasha), time (kāla), direction (disha), infinity of souls (Atman), mind (manas).
* Every object of creation is made of atoms (parmanu) which in turn connect with each other to form molecules (anu). Atoms are eternal, and their combinations constitute the empirical material world.
* Individual souls are eternal and pervade material body for a time.
* There are six categories (padārtha) of experience — substance, quality, activity, generality, particularity, and inherence.
Several traits of substances (dravya) are given as color, taste, smell, touch, number, size, the separate, coupling and uncoupling, priority and posterity, comprehension, pleasure and pain, attraction and revulsion, and wishes. Like many foundational texts of classical schools of Hindu philosophy, God is not mentioned in the sutra, and the text is non-theistic. | 1 | Applied and Interdisciplinary Chemistry |
When atoms land on a surface, there are two possibilities. First, they would diffuse on the surface and find other atoms to make a cluster, which will be discussed below. Second, they could come off of the surface or so-called desorption process. The desorption is described exactly as in the absorption process, with the exception of a different activation energy barrier.
For example, if all positions on the surface of the crystal are energy equivalent, the rate of growth can be calculated from Turnbull formula:
where is the rate of growth, ∆G = E – E, A, A are frequencies to go in or out of crystal for any given molecule on the surface, h is the height of the molecule in the growth direction and C the concentration of the molecules in direct distance from the surface. | 0 | Theoretical and Fundamental Chemistry |
Lovastatin is usually well tolerated, with the most common side effects being, in approximately descending order of frequency: creatine phosphokinase elevation, flatulence, abdominal pain, constipation, diarrhoea, muscle aches or pains, nausea, indigestion, weakness, blurred vision, rash, dizziness and muscle cramps. As with all statin drugs, it can rarely cause myopathy, hepatotoxicity (liver damage), dermatomyositis or rhabdomyolysis. This can be life-threatening if not recognised and treated in time, so any unexplained muscle pain or weakness whilst on lovastatin should be promptly mentioned to the prescribing doctor. Other uncommon side effects that should be promptly mentioned to either the prescribing doctor or an emergency medical service include:
These less serious side effects should still be reported if they persist or increase in severity: | 0 | Theoretical and Fundamental Chemistry |
Hydrogen embrittlement is a complex process involving a number of distinct contributing micro-mechanisms, not all of which need to be present. The mechanisms include the formation of brittle hydrides, the creation of voids that can lead to high-pressure bubbles, enhanced decohesion at internal surfaces and localised plasticity at crack tips that assist in the propagation of cracks. There is a great variety of mechanisms that have been proposed and investigated as to the cause of brittleness once diffusible hydrogen has been dissolved into the metal. In recent years, it has become widely accepted that HE is a complex, material and environmental dependent process, so that no single mechanism applies exclusively.
* Internal pressure: At high hydrogen concentrations, absorbed hydrogen species recombine in voids to form hydrogen molecules (H), creating pressure from within the metal. This pressure can increase to levels where cracks form, commonly designated hydrogen-induced cracking (HIC), as well as blisters forming on the specimen surface, designated hydrogen-induced blistering. These effects can reduce ductility and tensile strength.
* Hydrogen enhanced localised plasticity (HELP): Hydrogen increases the nucleation and movement of dislocations at a crack tip. HELP results in crack propagation by localised ductile failure at the crack tip with less deformation occurring in the surrounding material, which gives a brittle appearance to the fracture.
* Hydrogen decreased dislocation emission: Molecular dynamics simulations reveal a ductile-to-brittle transition caused by the suppression of dislocation emission at the crack tip by dissolved hydrogen. This prevents the crack tip rounding-off, so the sharp crack then leads to brittle-cleavage failure.
* Hydrogen enhanced decohesion (HEDE): Interstitial hydrogen lowers the stress required for metal atoms to fracture apart. HEDE can only occur when the local concentration of hydrogen is high, such as due to the increased hydrogen solubility in the tensile stress field at a crack tip, at stress concentrators, or in the tension field of edge dislocations.
* Metal hydride formation: The formation of brittle hydrides with the parent material allows cracks to propagate in a brittle fashion. This is particularly a problem with vanadium alloys, but most structural alloys do not easily form hydrides.
* Phase transformations: Hydrogen can induce phase transformations in some materials, and the new phase may be less ductile. | 0 | Theoretical and Fundamental Chemistry |
Zinc pest (from German Zinkpest "zinc plague"), also known as zinc rot and zamak rot, is a destructive, intercrystalline corrosion process of zinc alloys containing lead impurities. While impurities of the alloy are the primary cause of the problem, environmental conditions such as high humidity (greater than 65%) may accelerate the process.
It was first discovered to be a problem in 1923, and primarily affects die-cast zinc articles that were manufactured during the 1920s through 1950s. The New Jersey Zinc Company developed zamak alloys in 1929 using 99.99% pure zinc metal to avoid the problem, and articles made after 1960 are usually considered free of the risk of zinc pest since the use of purer materials and more controlled manufacturing conditions make zinc pest degradation unlikely.
Affected objects may show surface irregularities such as small cracks and fractures, blisters or pitting. Over time, the material slowly expands, cracking, buckling and warping in an irreversible process that makes the object exceedingly brittle and prone to fracture, and can eventually shatter the object, destroying it altogether. Due to the expansion process, attached normal material may also be damaged. The occurrence and severity of zinc pest in articles made of susceptible zinc alloys depends both on the concentration of lead impurities in the metal and on the storage conditions of the article in the ensuing decades. Zinc pest is dreaded by collectors of vintage die-cast model trains, toys, or radios, because rare or otherwise valuable items can inescapably be rendered worthless as the process of zinc pest destroys them. Because castings of the same object were usually made from various batches of metal over the production process, some examples of a given toy or model may survive today completely unaffected, while other identical examples may have completely disintegrated. It has also affected carburetors, hubcaps, door handles and automobile trim on cars of the 1920s and 1930s.
Since the 1940s, some model railroad hobbyists have claimed, with varying degrees of success, that a method of "pickling" zinc alloy parts by soaking them in vinegar or oxalic acid solution for several minutes before painting and assembling them could prevent or delay the effects of zinc pest.
Engine parts of older vehicles or airplanes, and military medals made of zinc alloys, may also be affected. In addition, the post-1982 copper-plated zinc Lincoln cents have been known to be affected.
Zinc pest is not related to tin pest, and is also different from a superficial white corrosion oxidation process ("Weissrost") that affects some zinc articles. | 1 | Applied and Interdisciplinary Chemistry |
An early example of this bonding mode was provided by prepared from diazomethane:
Another example of this family of compounds is Tebbe's reagent. It features a methylene bridge joining titanium and aluminum. | 0 | Theoretical and Fundamental Chemistry |
With the advancement of tissue engineering an alternative approach was developed: the full-thickness engineered oral mucosa. Full-thickness engineered oral mucosa is a better simulation of the in vivo situation because they take the anatomical structure of native oral mucosa into account. Problems, such as tissue shortage and donor site morbidity, do not occur when using full-thickness engineered oral mucosa.
The main goal when producing full-thickness engineered oral mucosa is to make it resemble normal oral mucosa as much as possible. This is achieved by using a combination of different cell types and scaffolds.
* Lamina propria: is mimicked by seeding oral fibroblasts, producing extracellular matrix, into a biocompatible (porous) scaffold and culturing them in a fibroblast differentiation medium.
* Basement membrane: containing type IV collagen, laminin, fibronectin and integrins. Ideally, the basement membrane must contain a lamina lucida and a lamina densa.
* Stratified squamous epithelium: is simulated by oral keratinocytes cultured in a medium containing keratinocyte growth factors such as the epidermal growth factor (EGF).
To obtain the best results, the type and origin of the fibroblasts and keratinocytes used in oral mucosa tissue engineering are important factors to hold into account. Fibroblasts are usually taken from the dermis of the skin or oral mucosa. Kertinocytes can be isolated from different areas of the oral cavity (such as the palate or gingiva). It is important that the fibroblasts and keratinocytes are used in the earliest stage possible as the function of these cells decreases with time. The transplanted keratinocytes and fibroblasts should adapt to their new environment and adopt their function. There is a risk of losing the transplanted tissue if the cells do not adapt properly. This adaptation goes more smoothly when the donor tissue cells resemble the cells of the native tissue. | 1 | Applied and Interdisciplinary Chemistry |
The core histone proteins contains a characteristic structural motif termed the "histone fold", which consists of three alpha-helices (α1-3) separated by two loops (L1-2). In solution, the histones form H2A-H2B heterodimers and H3-H4 heterotetramers. Histones dimerise about their long α2 helices in an anti-parallel orientation, and, in the case of H3 and H4, two such dimers form a 4-helix bundle stabilised by extensive H3-H3' interaction. The H2A/H2B dimer binds onto the H3/H4 tetramer due to interactions between H4 and H2B, which include the formation of a hydrophobic cluster.
The histone octamer is formed by a central H3/H4 tetramer sandwiched between two H2A/H2B dimers. Due to the highly basic charge of all four core histones, the histone octamer is stable only in the presence of DNA or very high salt concentrations. | 1 | Applied and Interdisciplinary Chemistry |
Tethered intramolecular [2+2] reactions entail the formation of cyclobutane and cyclobutanone via intramolecular 2+2 photocycloadditions. Tethering ensures formation of a multi-cyclic system.
The length of the tether affects the stereochemical outcome of the [2+2] reaction. Longer tethers tend to generate the "straight" product where the terminal carbon of the alkene is linked to the -carbon of the enone. When the tether consists only two carbons, the “bent” product is generated where the -carbon of the enone is connected to the terminal carbon of the alkene.
Tethered [2+2] reactions have been used to synthesize organic compounds with interesting ring systems and topologies. For example, [2+2] photocyclization was used to construct the tricyclic core structure in ginkgolide B. | 0 | Theoretical and Fundamental Chemistry |
The Indian National Science Academy awarded Kulkarni the Young Scientist Medal in 1981, making him the first chemical engineer to receive the honor. He received another award in 1981, the Amar Dye Chem Award of the Indian Institute of Chemical Engineers; IIChE would honor him again in 1988 with the Herdillia Award for Excellence in Basic Research in Chemical Engineering. The Council of Scientific and Industrial Research awarded him the Shanti Swarup Bhatnagar Prize, one of the highest Indian science awards the same year. The National Chemical Laboratory selected him s the Best Scientist of the Year in 1992 and the year 2000 brought him two awards, ChemTech-CEW Award of the ChemTech Foundation and the FICCI Award of the Federation of Indian Chambers of Commerce & Industry.
Kulkarni, a CSIR Distinguished Scientist at NCL, was elected as a fellow by Maharashtra Academy of Sciences in 1988, the same year as he became a fellow of the Indian Academy of Sciences. He received the elected fellowship of the Indian National Academy of Engineering and the Golden Jubilee Fellowship of the Institute of Chemical Technology (then known as the University Department of Chemical Technology-UDCT) in 1989. The Indian National Science Academy elected him as a fellow in 1990 and The World Academy of Sciences chose him as an elected fellow in 2002. When the Science and Engineering Research Board of the Department of Science and Technology selected scientists for the J. C. Bose National Fellowship in 2009, he was also included in the list of recipients. Industrial & Engineering Chemistry Research, the official journal of the American Chemical Society, issued a festschrift on him in 2009 titled Kulkarni Issue with the guest editorial written by his mentor, L. K. Doraiswmy and the issue featured his biosketch jointly written by Ganapati D. Yadav, V. K. Jayaraman and V. Ravikumar, all known chemical engineers. | 1 | Applied and Interdisciplinary Chemistry |
When carbon dioxide diffuses as a dissolved gas from the tissue capillaries, it binds to the α-amino terminus of the globulin chain, forming Carbaminohemoglobin. Carbaminohemoglobin is able to directly stabilise the T conformation as part of the carbon dioxide Bohr effect. Deoxyhemoglobin in turn subsequently increases the uptake of carbon dioxide in the form of favouring the formation of Bicarbonate as well as Carbaminohemoglobin through the Haldane effect. | 1 | Applied and Interdisciplinary Chemistry |
The facultative lagoon in the pond sequence functions like the primary clarifier of a conventional sewage treatment system. Heavy solids will settle to the bottom of the lagoon, and lighter solids will float. This facultative lagoon lacks the sludge removal capability of a primary clarifier, so a population of anaerobic organisms will colonize accumulated sludge on the bottom of the lagoon. The surface area of the lagoon should be large enough to provide an atmospheric oxygen transfer rate adequate to prevent anaerobic conditions on the lagoon surface. Intermediate depths of the lagoon support facultative micro-organisms capable of oxidizing both the dissolved and suspended organics from the original wastewater and the products of anaerobic catabolism on the bottom of the lagoon.
Areas with a consistently cool, but frost-free, climate may sustain facultative conditions in the first stabilization pond when treating lightly polluted water at low temperatures favorable to high concentrations of dissolved oxygen with low metabolic rates. Facultative pond stratification becomes unstable during cold weather increasing release of malodorous gas when water temperatures drop below 4 degrees Celsius (39 degrees Fahrenheit); and formation of ice on the pond surface will effectively prevent transfer of atmospheric oxygen to the pond biome. Stabilization ponds in climates with significant seasonal temperature variation may release malodorous gas during the season of rising temperatures as the pond biome consumes wastes accumulated during cold weather with increasing metabolic rates exceeding the atmospheric oxygen transfer rate at the pond surface. | 1 | Applied and Interdisciplinary Chemistry |
In the male the LHCGR has been identified on the Leydig cells that are critical for testosterone production, and support spermatogenesis.
Normal LHCGR functioning is critical for male fetal development, as the fetal Leydig cells produce androstenedione which is converted to testosterone in fetal Sertoli cells to induce masculinization. | 1 | Applied and Interdisciplinary Chemistry |
There are many different effective medium approximations, each of them being more or less accurate in distinct conditions. Nevertheless, they all assume that the macroscopic system is homogeneous and, typical of all mean field theories, they fail to predict the properties of a multiphase medium close to the percolation threshold due to the absence of long-range correlations or critical fluctuations in the theory.
The properties under consideration are usually the conductivity or the dielectric constant of the medium. These parameters are interchangeable in the formulas in a whole range of models due to the wide applicability of the Laplace equation. The problems that fall outside of this class are mainly in the field of elasticity and hydrodynamics, due to the higher order tensorial character of the effective medium constants.
EMAs can be discrete models, such as applied to resistor networks, or continuum theories as applied to elasticity or viscosity. However, most of the current theories have difficulty in describing percolating systems. Indeed, among the numerous effective medium approximations, only Bruggeman's symmetrical theory is able to predict a threshold. This characteristic feature of the latter theory puts it in the same category as other mean field theories of critical phenomena. | 0 | Theoretical and Fundamental Chemistry |
Cell-penetrating peptides (CPPs), also known as peptide transduction domains (PTDs), are short peptides (< 40 amino acids) that efficiently pass through cell membranes while being covalently or non-covalently bound to various molecules, thus facilitating these molecules' entry into cells. Cell entry occurs primarily by endocytosis but other entry mechanisms also exist. Examples of cargo molecules of CPPs include nucleic acids, liposomes, and drugs of low molecular weight.
CPP cargo can be directed into specific cell organelles by incorporating localization sequences into CPP sequences. For example, nuclear localization sequences are commonly used to guide CPP cargo into the nucleus. For guidance into mitochondria, a mitochondrial targeting sequence can be used; this method is used in protofection (a technique that allows for foreign mitochondrial DNA to be inserted into cells' mitochondria). | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen cyanide is a poisonous gas that interferes with cellular respiration. Cyanide prevents the cell from producing adenosine triphosphate (ATP) by binding to one of the proteins involved in the electron transport chain. This protein, cytochrome c oxidase, contains several subunits and has ligands containing iron groups. The cyanide component of Zyklon B can bind at one of these iron groups, heme a3, forming a more stabilized compound through metal-to-ligand pi bonding. As a result of the formation of this new iron–cyanide complex, the electrons that would situate themselves on the heme a3 group can no longer do so. Instead, these electrons destabilize the compound; thus, the heme group no longer accepts them. Consequently, electron transport is halted, and cells can no longer produce the energy needed to synthesize ATP. Death occurs in a human being weighing within two minutes of inhaling 70 mg of hydrogen cyanide. | 1 | Applied and Interdisciplinary Chemistry |
An example due to photodissociation is triphenylsulfonium triflate. This colourless salt consists of a sulfonium cation and the triflate anion. Many related salts are known including those with other noncoordinating anions and those with diverse substituents on the phenyl rings.
The triphenylsulfonium salts absorb at a wavelength of 233 nm, which induces a dissociation of one of the three phenyl rings. This dissociated phenyl radical then re-combines with remaining diphenylsulfonium to liberate an H ion. The second reaction is irreversible, and therefore the entire process is irreversible, so triphenylsulfonium triflate is a photoacid generator. The ultimate products are thus a neutral organic sulfide and the strong acid triflic acid.
:[(CH)S][CFSO] + hν → [(CH)S][CFSO] + CH
:[(CH)S][CFSO] + CH → (CHCH)(CH)S + [[Triflic acid|[CFSO][H]]]
Applications of these photoacids include photolithography and catalysis of the polymerization of epoxides. | 0 | Theoretical and Fundamental Chemistry |
Batesian mimicry is a form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species directed at a predator of them both. It is named after the English naturalist Henry Walter Bates, who worked on butterflies in the rainforests of Brazil.
Batesian mimicry is the most commonly known and widely studied of mimicry complexes, such that the word mimicry is often treated as synonymous with Batesian mimicry. There are many other forms however, some very similar in principle, others far separated. It is often contrasted with Müllerian mimicry, a form of mutually beneficial convergence between two or more harmful species. However, because the mimic may have a degree of protection itself, the distinction is not absolute. It can also be contrasted with functionally different forms of mimicry. Perhaps the sharpest contrast here is with aggressive mimicry where a predator or parasite mimics a harmless species, avoiding detection and improving its foraging success.
The imitating species is called the mimic, while the imitated species (protected by its toxicity, foul taste or other defenses) is known as the model. The predatory species mediating indirect interactions between the mimic and the model is variously known as the [signal] receiver, dupe or operator. By parasitising the honest warning signal of the model, the Batesian mimic gains an advantage, without having to go to the expense of arming itself. The model, on the other hand, is disadvantaged, along with the dupe. If impostors appear in high numbers, positive experiences with the mimic may result in the model being treated as harmless. At higher frequency there is also a stronger selective advantage for the predator to distinguish mimic from model. For this reason, mimics are usually less numerous than models, an instance of frequency-dependent selection. Some mimetic populations have evolved multiple forms (polymorphism), enabling them to mimic several different models and thereby to gain greater protection. Batesian mimicry is not always perfect. A variety of explanations have been proposed for this, including limitations in predators' cognition.
While visual signals have attracted most study, Batesian mimicry can employ deception of any of the senses; some moths mimic the ultrasound warning signals sent by unpalatable moths to bat predators, constituting auditory Batesian mimicry, while some weakly electric fish appear to mimic the electrolocation signals of strongly electric fish, probably constituting electrical mimicry. | 1 | Applied and Interdisciplinary Chemistry |
He appears as a character in the Russian film Prediction by Eldar Ryazanov and has a tiny cameo mention in The Eighth Life, the prize-winning epic novel by Nino Haratischwili. | 1 | Applied and Interdisciplinary Chemistry |
Sulfating roasting oxidizes certain sulfide ores to sulfates in a supply of air to enable leaching of the sulfate for further processing. | 1 | Applied and Interdisciplinary Chemistry |
Nucleic acid extraction apparatus based on the Tajima pipette (see Fig. 2) are one of the most widespread instruments to perform the Boom method.
The Tajima pipette was invented by Hideji Tajima, founder and president of
Precision System Sciences (PSS) Inc., a Japanese manufacturer of precision and measuring instruments.
Tajima pipette is a Core Technology of PSS Inc.
PSS Inc. provides OEM product based on this technology (for example MagNA Pure(R) )
for several leading reagent manufacturers such as Hoffmann-La Roche, Life Technologies, ... and so on.
After the Tajima et al. patent was filed, similar patent applications have also been filed by other parties.
The Tajima pipette performs magnetic particle control method and procedure, which can separate magnetic particles combined with a target substance from the liquid by magnetic force and suspend them in a liquid. | 1 | Applied and Interdisciplinary Chemistry |
* F. Asinger: Methanol, Chemie- und Energierohstoff. Akademie-Verlag, Berlin, 1987, , .
* Martin Bertau, Heribert Offermanns, Ludolf Plass, Friedrich Schmidt, Hans-Jürgen Wernicke: Methanol: The Basic Chemical and Energy Feedstock of the Future: Asingers Vision Today', 750 Seiten, Verlag Springer; 2014,
* †George A. Olah, Alain Goeppert, G. K. Surya Prakash, Beyond Oil and Gas: The Methanol Economy – Third, Updated and Enlarged Edition, Wiley-VCH, 2018, . | 1 | Applied and Interdisciplinary Chemistry |
Due to the electronegativity difference between carbon and nitrogen, the nitroso group has a relatively strong -I effect, but not as strong as the nitro group. (Positively charged nitrogen atoms on alkylammonium cations and on nitro groups have a much stronger -I effect) | 0 | Theoretical and Fundamental Chemistry |
A limiting factor is a variable of a system that causes a noticeable change in output or another measure of a type of system. The limiting factor is in a pyramid shape of organisms going up from the producers to consumers and so on. A factor not limiting over a certain domain of starting conditions may yet be limiting over another domain of starting conditions, including that of the factor. | 0 | Theoretical and Fundamental Chemistry |
Unlike the other assimilatory pathways, the serine cycle uses carboxylic acids and amino acids as intermediates instead of carbohydrates. First, 2 molecules of formaldehyde are added to 2 molecules of the amino acid glycine. This produces two molecules of the amino acid serine, the key intermediate of this pathway. These serine molecules eventually produce 2 molecules of 2-phosphoglycerate, with one molecule going towards biomass and the other being used to regenerate glycine. Notably, the regeneration of glycine requires a molecule of as well, therefore the Serine pathway also differs from the other 3 pathways by its requirement of both formaldehyde and . | 0 | Theoretical and Fundamental Chemistry |
This reagent is not commercially available due to its short shelf life, so it must be freshly prepared in the laboratory. One common preparation involves two steps. First a few drops of dilute sodium hydroxide are added to some aqueous 0.1 M silver nitrate. The ions convert the silver aquo complex form into silver(I) oxide, , which precipitates from the solution as a brown solid:
In the next step, sufficient aqueous ammonia is added to dissolve the brown silver(I) oxide. The resulting solution contains the [Ag(NH)] complexes in the mixture, which is the main component of Tollens' reagent. Sodium hydroxide is reformed:
Alternatively, aqueous ammonia can be added directly to silver nitrate solution. At first, ammonia will induce formation of solid silver oxide, but with additional ammonia, this solid precipitate dissolves to give a clear solution of diamminesilver(I) coordination complex, . Filtering the reagent before use helps to prevent false-positive results. | 0 | Theoretical and Fundamental Chemistry |
Each tablet contains 2, 4, or 8 mg of the tert-butylamine salt of perindopril. Perindopril is also available under the trade name Coversyl Plus, containing 4 mg of perindopril combined with 1.25 mg indapamide, a thiazide-like diuretic.
In Australia, each tablet contains 2.5, 5, or 10 mg of perindopril arginine. Perindopril is also available under the trade name Coversyl Plus, containing 5 mg of perindopril arginine combined with 1.25 mg indapamide and Coversyl Plus LD, containing 2.5 mg of perindopril arginine combined with 0.625 mg indapamide.
The efficacy and tolerability of a fixed-dose combination of 4 mg perindopril and 5 mg amlodipine, a calcium channel antagonist, has been confirmed in a prospective, observational multicenter trial of 1,250 hypertensive patients. A preparation of the two drugs is available commercially as Coveram. | 0 | Theoretical and Fundamental Chemistry |
In eukaryote cells, RNA polymerase III (also called Pol III) is a protein that transcribes DNA to synthesize 5S ribosomal RNA, tRNA, and other small RNAs.
The genes transcribed by RNA Pol III fall in the category of "housekeeping" genes whose expression is required in all cell types and most environmental conditions. Therefore, the regulation of Pol III transcription is primarily tied to the regulation of cell growth and the cell cycle and thus requires fewer regulatory proteins than RNA polymerase II. Under stress conditions, however, the protein Maf1 represses Pol III activity. Rapamycin is another Pol III inhibitor via its direct target TOR. | 1 | Applied and Interdisciplinary Chemistry |
In order for pathogenic bacteria to invade a cell, communication with the host cell is required. The first step for invading bacteria is usually adhesion to host cells. Strong anchoring, a characteristic that determines virulence, prevents the bacteria from being washed away before infection occurs. Bacterial cells can bind to many host cell surface structures such as glycolipids and glycoproteins which serve as attachment receptors. Once attached, the bacteria begin to interact with the host to disrupt its normal functioning and disrupt or rearrange its cytoskeleton. Proteins on the bacteria surface can interact with protein receptors on the host thereby affecting signal transduction within the cell. Alterations to signaling are favorable to bacteria because these alterations provide conditions under which the pathogen can invade. Many pathogens have Type III secretion systems which can directly inject protein toxins into the host cells. These toxins ultimately lead to rearrangement of the cytoskeleton and entry of the bacteria. | 1 | Applied and Interdisciplinary Chemistry |
Generally related to metallurgy or materials science, corrosion engineering also relates to non-metallics including ceramics, cement, composite material, and conductive materials such as carbon and graphite. Corrosion engineers often manage other not-strictly-corrosion processes including (but not restricted to) cracking, brittle fracture, crazing, fretting, erosion, and more typically categorized as Infrastructure asset management. In the 1990s, Imperial College London even offered a Master of Science degree entitled "The Corrosion of Engineering Materials". UMIST – University of Manchester Institute of Science and Technology and now part of the University of Manchester also offered a similar course. Corrosion Engineering master's degree courses are available worldwide and the curricula contain study material about the control and understanding of corrosion. Ohio State University has a corrosion center named after one of the more well known corrosion engineers Mars G Fontana. | 1 | Applied and Interdisciplinary Chemistry |
In some cases, additional functional groups will need to be added to molecules to facilitate the other separation and analysis methods. Derivatization can change the properties of an analyte; for instance, it would make a polar and non-volatile compound non-polar and more volatile, which would be necessary for analysis in certain types of chromatography. It is important to note, however, that derivatization is not ideal for site-specific analyses as it adds additional elements that must be accounted for in analyses. | 0 | Theoretical and Fundamental Chemistry |
A potential socioeconomic drawback associated with solar energy conversion is a disruption to the electric utility business model. In America, the economic viability of regional “monopoly” utilities is based on the large aggregation of local customers who balance out each other's variable load. Therefore, the widespread installation of rooftop solar systems that are not connected to the grid poses a threat to the stability of the utility market. This phenomenon is known as Grid Defection. The pressure on electric utilities is exacerbated by an aging grid infrastructure that has yet to adapt to the new challenges posed by renewable energy (mainly regarding inertia, reverse power flow and relay protection schemes). However, some analysts make the case that with the steady increase in natural disasters (which destroy vital grid infrastructure), solar microgrid installation may be necessary to ensure emergency energy access. This emphasis on contingency preparation has expanded the off-grid energy market dramatically in recent years, especially in areas prone to natural disasters. | 0 | Theoretical and Fundamental Chemistry |
It is often required to optimize several glass properties simultaneously, including production costs.
This can be performed, e.g., by simplex search, or in a spreadsheet as follows:
# Listing of the desired properties;
# Entering of models for the reliable calculation of properties based on the glass composition, including a formula for estimating the production costs;
# Calculation of the squares of the differences (errors) between desired and calculated properties;
# Reduction of the sum of square errors using the Solver option in Microsoft Excel with the glass components as variables. Other software (e.g. Microcal Origin) can also be used to perform these optimizations.
It is possible to weight the desired properties differently. Basic information about the principle can be found in an article by Huff et al. The combination of several glass models together with further relevant technological and financial functions can be used in six sigma optimization. | 0 | Theoretical and Fundamental Chemistry |
Similar to mineralization processes that take place within rocks, mineralization can also occur under the sea. The rate of dissolution of carbon dioxide from atmosphere to oceanic regions is determined by the circulation period of the ocean and buffering ability of subducting surface water. Researchers have demonstrated that the carbon dioxide marine storage at several kilometers depth could be viable for up to 500 years, but is dependent on injection site and conditions. Several studies have shown that although it may fix carbon dioxide effectively, carbon dioxide may be released back to the atmosphere over time. However, this is unlikely for at least a few more centuries. The neutralization of CaCO, or balancing the concentration of CaCO on the seafloor, land and in the ocean, can be measured on a timescale of thousands of years. More specifically, the predicted time is 1700 years for ocean and approximately 5000 to 6000 years for land. Further, the dissolution time for CaCO can be improved by injecting near or downstream of the storage site.
In addition to carbon mineralization, another proposal is deep sea sediment injection. It injects liquid carbon dioxide at least 3000 m below the surface directly into ocean sediments to generate carbon dioxide hydrate. Two regions are defined for exploration: 1) the negative buoyancy zone (NBZ), which is the region between liquid carbon dioxide denser than surrounding water and where liquid carbon dioxide has neutral buoyancy, and 2) the hydrate formation zone (HFZ), which typically has low temperatures and high pressures. Several research models have shown that the optimal depth of injection requires consideration of intrinsic permeability and any changes in liquid carbon dioxide permeability for optimal storage. The formation of hydrates decreases liquid carbon dioxide permeability, and injection below HFZ is more energetically favored than within the HFZ. If the NBZ is a greater column of water than the HFZ, the injection should happen below the HFZ and directly to the NBZ. In this case, liquid carbon dioxide will sink to the NBZ and be stored below the buoyancy and hydrate cap. Carbon dioxide leakage can occur if there is dissolution into pore fluid or via molecular diffusion. However, this occurs over thousands of years. | 0 | Theoretical and Fundamental Chemistry |
The history of ferrous metallurgy in the Indian subcontinent began in the 2nd millennium BC. Archaeological sites in Gangetic plains have yielded iron implements dated between 1800 and 1200 BC. By the early 13th century BC, iron smelting was practiced on a large scale in India. In Southern India (present day Mysore) iron was in use 12th to 11th centuries BC. The technology of iron metallurgy advanced in the politically stable Maurya period and during a period of peaceful settlements in the 1st millennium BC.
Iron artifacts such as spikes, knives, daggers, arrow-heads, bowls, spoons, saucepans, axes, chisels, tongs, door fittings, etc., dated from 600 to 200 BC, have been discovered at several archaeological sites of India. The Greek historian Herodotus wrote the first western account of the use of iron in India. The Indian mythological texts, the Upanishads, have mentions of weaving, pottery and metallurgy, as well. The Romans had high regard for the excellence of steel from India in the time of the Gupta Empire.
Perhaps as early as 500 BC, although certainly by 200 AD, high-quality steel was produced in southern India by the crucible technique. In this system, high-purity wrought iron, charcoal, and glass were mixed in a crucible and heated until the iron melted and absorbed the carbon. Iron chain was used in Indian suspension bridges as early as the 4th century.
Wootz steel was produced in India and Sri Lanka from around 300 BC. Wootz steel is famous from Classical Antiquity for its durability and ability to hold an edge. When asked by King Porus to select a gift, Alexander is said to have chosen, over gold or silver, thirty pounds of steel. Wootz steel was originally a complex alloy with iron as its main component together with various trace elements. Recent studies have suggested that its qualities may have been due to the formation of carbon nanotubes in the metal. According to Will Durant, the technology passed to the Persians and from them to Arabs who spread it through the Middle East. In the 16th century, the Dutch carried the technology from South India to Europe, where it was mass-produced.
Steel was produced in Sri Lanka from 300 BC by furnaces blown by the monsoon winds. The furnaces were dug into the crests of hills, and the wind was diverted into the air vents by long trenches. This arrangement created a zone of high pressure at the entrance, and a zone of low pressure at the top of the furnace. The flow is believed to have allowed higher temperatures than bellows-driven furnaces could produce, resulting in better-quality iron. Steel made in Sri Lanka was traded extensively within the region and in the Islamic world.
One of the world's foremost metallurgical curiosities is an iron pillar located in the Qutb complex in Delhi. The pillar is made of wrought iron (98% Fe), is almost seven meters high and weighs more than six tonnes. The pillar was erected by Chandragupta II Vikramaditya and has withstood 1,600 years of exposure to heavy rains with relatively little corrosion. | 1 | Applied and Interdisciplinary Chemistry |
In 2001, a cow named Bessie gave birth to a cloned Asian gaur, an endangered species, but the calf died after two days. In 2003, a banteng was successfully cloned, followed by three African wildcats from a thawed frozen embryo. These successes provided hope that similar techniques (using surrogate mothers of another species) might be used to clone extinct species. Anticipating this possibility, tissue samples from the last bucardo (Pyrenean ibex) were frozen in liquid nitrogen immediately after it died in 2000. Researchers are also considering cloning endangered species such as the Giant panda and Cheetah.
In 2002, geneticists at the Australian Museum announced that they had replicated DNA of the thylacine (Tasmanian tiger), at the time extinct for about 65 years, using polymerase chain reaction. However, on 15 February 2005 the museum announced that it was stopping the project after tests showed the specimens' DNA had been too badly degraded by the (ethanol) preservative. On 15 May 2005 it was announced that the thylacine project would be revived, with new participation from researchers in New South Wales and Victoria.
In 2003, for the first time, an extinct animal, the Pyrenean ibex mentioned above was cloned, at the Centre of Food Technology and Research of Aragon, using the preserved frozen cell nucleus of the skin samples from 2001 and domestic goat egg-cells. The ibex died shortly after birth due to physical defects in its lungs. | 1 | Applied and Interdisciplinary Chemistry |
In a 1964 New York Times piece science fiction author Isaac Asimov speculated what the 2014 World's Fair would look like. He deemed the Underground World Home a "sign of the future" with controlled temperatures which allowed occupants to live free from the weather. The home was not a draw, however, and was scarcely to appear in popular memory. Priced at $80,000 (approximately four times the cost of an average home that year), none were commissioned. | 0 | Theoretical and Fundamental Chemistry |
Levosulpiride is a substituted benzamide derivative and a selective dopamine D antagonist with antipsychotic and antidepressant activity. Other benzamide derivatives include metoclopramide, tiapride, and sultopride. | 0 | Theoretical and Fundamental Chemistry |
TCF4 proteins act as transcription factors which will bind to the immunoglobulin enhancer mu-E5/kappa-E2 motif. TCF4 activates transcription by binding to the E-box (5’-CANNTG-3’) found usually on SSTR2-INR, or somatostatin receptor 2 initiator element. TCF4 is primarily involved in neurological development of the fetus during pregnancy by initiating neural differentiation by binding to DNA. It is found in the central nervous system, somites, and gonadal ridge during early development. Later in development it will be found in the thyroid, thymus, and kidneys while in adulthood TCF4 it is found in lymphocytes, muscles, mature neurons, and gastrointestinal system. | 1 | Applied and Interdisciplinary Chemistry |
The binding of oxygen is affected by molecules such as carbon monoxide (for example, from tobacco smoking, exhaust gas, and incomplete combustion in furnaces). CO competes with oxygen at the heme binding site. Hemoglobins binding affinity for CO is 250 times greater than its affinity for oxygen, meaning that small amounts of CO dramatically reduce hemoglobins ability to deliver oxygen to the target tissue. Since carbon monoxide is a colorless, odorless and tasteless gas, and poses a potentially fatal threat, carbon monoxide detectors have become commercially available to warn of dangerous levels in residences. When hemoglobin combines with CO, it forms a very bright red compound called carboxyhemoglobin, which may cause the skin of CO poisoning victims to appear pink in death, instead of white or blue. When inspired air contains CO levels as low as 0.02%, headache and nausea occur; if the CO concentration is increased to 0.1%, unconsciousness will follow. In heavy smokers, up to 20% of the oxygen-active sites can be blocked by CO.
In similar fashion, hemoglobin also has competitive binding affinity for cyanide (CN), sulfur monoxide (SO), and sulfide (S), including hydrogen sulfide (HS). All of these bind to iron in heme without changing its oxidation state, but they nevertheless inhibit oxygen-binding, causing grave toxicity.
The iron atom in the heme group must initially be in the ferrous (Fe) oxidation state to support oxygen and other gases' binding and transport (it temporarily switches to ferric during the time oxygen is bound, as explained above). Initial oxidation to the ferric (Fe) state without oxygen converts hemoglobin into "hemiglobin" or methemoglobin, which cannot bind oxygen. Hemoglobin in normal red blood cells is protected by a reduction system to keep this from happening. Nitric oxide is capable of converting a small fraction of hemoglobin to methemoglobin in red blood cells. The latter reaction is a remnant activity of the more ancient nitric oxide dioxygenase function of globins. | 0 | Theoretical and Fundamental Chemistry |
A venturi scrubber is a converging/diverging section of duct. The converging section accelerates the gas stream to high velocity. When the liquid stream is injected at the throat, which is the point of maximum velocity, the turbulence caused by the high gas velocity atomizes the liquid into small droplets, which creates the surface area necessary for mass transfer to take place. The higher the pressure drop in the venturi, the smaller the droplets and the higher the surface area. The penalty is in power consumption.
For simultaneous removal of and fly ash, venturi scrubbers can be used. In fact, many of the industrial sodium-based throwaway systems are venturi scrubbers originally designed to remove particulate matter. These units were slightly modified to inject a sodium-based scrubbing liquor. Although removal of both particles and in one vessel can be economic, the problems of high pressure drops and finding a scrubbing medium to remove heavy loadings of fly ash must be considered. However, in cases where the particle concentration is low, such as from oil-fired units, it can be more effective to remove particulate and simultaneously. | 1 | Applied and Interdisciplinary Chemistry |
The Nysted reagent is a reagent used in organic synthesis for the methylenation of a carbonyl group. It was discovered in 1975 by Leonard N. Nysted in Chicago, Illinois. It was originally prepared by reacting dibromomethane and activated zinc in THF. A proposed mechanism for the methenylation reaction runs as follows:
A similar reagent is Tebbe's reagent. In the Nysted olefination, the Nysted reagent reacts with TiCl to methylenate a carbonyl group. The biggest problem with these reagents are that the reactivity has not been well documented. It is believed that the TiCl acts as a mediator in the reaction. Nysted reagent can methylenate different carbonyl groups in the presence of different mediators. For example, in the presence of BF•OEt, the reagent will methylenate aldehydes. On the other hand, in the presence of TiCl, TiCl or TiCl and BF•OEt, the reagent can methylenate ketones. Most commonly, it is used to methylenate ketones because of their general difficulty to methylenate due to crowding around the carbonyl group. The Nysted reagent is able to overcome the additional steric hindrance found in ketones, and more easily methylenate the carbonyl group. In contrast to the Wittig reaction the neutral reaction conditions of the Nysted reagent make it a useful alternative for the methylenation of easily enolizable ketones.
There is little research on Nysted reagent because of the hazards and high reactivity and the difficulty of keeping the reagent stable while it is in use. More specifically, it can form explosive peroxides when exposed to air and is extremely flammable. Also, it reacts violently with water. These make this reagent very dangerous to work with. | 0 | Theoretical and Fundamental Chemistry |
Reductive elimination of square planar complexes can progress through a variety of mechanisms: dissociative, nondissociative, and associative. Similar to octahedral complexes, a dissociative mechanism for square planar complexes initiates with loss of a ligand, generating a three-coordinate intermediate that undergoes reductive elimination to produce a one-coordinate metal complex. For a nondissociative pathway, reductive elimination occurs from the four-coordinate system to afford a two-coordinate complex. If the eliminating ligands are trans to each other, the complex must first undergo a trans to cis isomerization before eliminating. In an associative mechanism, a ligand must initially associate with the four-coordinate metal complex to generate a five-coordinate complex that undergoes reductive elimination synonymous to the dissociation mechanism for octahedral complexes. | 0 | Theoretical and Fundamental Chemistry |
The experimental setup to perform Raman spectroelectrochemistry consists of a light source, a spectrometer, a potentiostat, a spectroelectrochemical cell, a three-electrode system, radiation beam conducting devices, data collection and analysis devices. Nowadays, there are commercial instruments that integrate all these elements in a single instrument, significantly simplifying the performance of spectroelectrochemical experiments.
* Light source. It provides the monochromatic electromagnetic radiation that interacts with the sample during the electrochemical process. In Raman-SEC, the light source is usually a laser corresponding to the VIS or NIR regions, which commonly emits at 532, 633, 785 or 1064 nm, although there is the possibility of using many other lasers, including UV-lasers.
* Spectrometer. It records the scattered radiation and provides the Raman spectra of the molecules. In Raman-SEC, spectrometers are usually combined with confocal microscopes (micro-Raman) to remove the information out of the focus, obtaining an excellent spectral resolution. However, it is possible to work with low resolution Raman spectrometers obtaining very good results.
* Potentiostat/Galvanostat. It is the electronic device that allows controlling the potential of the working electrode respect to the reference electrode, or controlling the current that passes respect to the auxiliary electrode.
* Three-electrode system. It contains a working electrode, a reference electrode and an auxiliary electrode. This system can be simplified by using screen-printed electrodes that include all three electrodes in a single holder.
* Spectroelectrochemical cell (SEC cell). It is the device that includes the three-electrode system and allows the simultaneous recording of the Raman spectra of the species and the electrochemical signal. It is the link between optical and electrochemical techniques.
* Devices for conducting the radiation beam: lenses, mirrors and/or optical fibres. The last ones conduct the electromagnetic radiation over long distances with hardly any losses. In addition, they simplify the optical configurations since they allow working with a small amount of solution; in this way, it is easier to conduct and collect the light in the nearness of the electrode.
* Data collection and analysis devices. It consists of a computer to collect simultaneously the signals provided by the spectrometer and the electrochemical instrument. Using an appropriate software, the generated signals can be acquired, transformed, analyzed and interpreted. | 0 | Theoretical and Fundamental Chemistry |
The Old Copper Complex in North America has been radiometrically dated to 9500 BP—i.e., about 7480 BCE—making it one of the oldest known examples of copper extraction in the world. The earliest evidence of the cold-hammering of native copper comes from the excavation at Çayönü Tepesi in eastern Anatolia, which dates between 7200 to 6600 BCE. Among the various items considered to be votive or amulets, there was one that looked like a fishhook and one like an awl. Another find, at Shanidar Cave in Mergasur, Iraq, contained copper beads, and dates back to 8,700 BCE.
One of the world's oldest known copper mines, as opposed to usage of surface deposits, is at Timna Valley, Israel, and has been used since the fourth millennium BC, with surface deposit usage occurring in the fifth and sixth millennium.
The Pločnik archaeological site in southeastern Europe (Serbia) contains the oldest securely dated evidence of copper making at high temperature, from 5,000 BCE. The find in June 2010 extends for an additional 500 years, dated to 5th millennium BCE, representing the earlier record of copper smelting from Rudna Glava (Serbia). | 1 | Applied and Interdisciplinary Chemistry |
Defect sites can interfere with the stability of metal oxide surfaces, so it is important to locate and determine methods to control these sites. Oxides exhibit an abundance of point defect sites. In rocksalt surfaces, oxygen and metal cation vacancies are the most common point defects. The vacancies are produced by electron bombardment and annealing to extremely high temperatures. However, oxygen vacancies are more common and have a greater impact than metal cation vacancies. Oxygen vacancies cause reduction in between surface cations, which significantly affect the electronic energy levels. Steps and kinks are two other defects that impact rocksalt surfaces. These structural defects reduce the coordination environment of the four adjacent surface cations from 5 to 4.
In rutile surfaces, the most common type of defect is oxygen vacancies. There are two types of oxygen vacancies, which result from either the removal of a bridging O ions or the removal of an inplane O ion. Both of these will reduce the coordination of the surface cations. | 0 | Theoretical and Fundamental Chemistry |
Oxazolidinone auxiliaries, popularized by David A. Evans, have been applied to many stereoselective transformations, including aldol reactions, alkylation reactions, and Diels-Alder reactions. The oxazolidinones are substituted at the 4 and 5 positions. Through steric hindrance, the substituents direct the direction of substitution of various groups. The auxiliary is subsequently removed e.g. through hydrolysis. | 0 | Theoretical and Fundamental Chemistry |
Due to increased blood glucose levels, methylglyoxal has higher concentrations in diabetics and has been linked to arterial atherogenesis. Damage by methylglyoxal to low-density lipoprotein through glycation causes a fourfold increase of atherogenesis in diabetics. Methylglyoxal binds directly to the nerve endings and by that increases the chronic extremity soreness in diabetic neuropathy. | 1 | Applied and Interdisciplinary Chemistry |
Inhibiting only three proteins, interferon-β, STAT2, and EIF2AK2 is sufficient to rescue human fibroblasts from the cell death caused by frequent transfection with long, protein-encoding RNA. Inhibiting interferon signaling disrupts the positive-feedback loop that normally hypersensitizes cells exposed to exogenous long RNA. Researchers have recently used this technique to express reprogramming proteins in primary human fibroblasts. | 1 | Applied and Interdisciplinary Chemistry |
Born in 1879 in Livorno, Italy to a wealthy Jewish family, Mieli was raised in Chianciano, a small spa town in Tuscany, to which his family moved in 1880.
In 1904 he obtained a degree in chemistry, followed by six months of study at the University of Leipzig, attending the lectures of the chemist Wilhelm Ostwald. His chemistry career continued, and in 1908 he moved to the Sapienza University of Rome to work with Emanuele Paterno. He subsequently became a university lecturer in chemistry at the University. | 1 | Applied and Interdisciplinary Chemistry |
Units of activity (the curie and the becquerel) also refer to a quantity of radioactive atoms. Because the probability of decay is a fixed physical quantity, for a known number of atoms of a particular radionuclide, a predictable number will decay in a given time. The number of decays that will occur in one second in one gram of atoms of a particular radionuclide is known as the specific activity of that radionuclide.
The activity of a sample decreases with time because of decay.
The rules of radioactive decay may be used to convert activity to an actual number of atoms. They state that 1 Ci of radioactive atoms would follow the expression
: N (atoms) × λ (s) = 1 Ci = 3.7 × 10 Bq,
and so
: N = 3.7 × 10 Bq / λ,
where λ is the decay constant in s.
Here are some examples, ordered by half-life: | 0 | Theoretical and Fundamental Chemistry |
The principle can be stated in two ways, formally different, but substantially equivalent, and, in a sense, mutually reciprocal. The two ways illustrate the Maxwell relations, and the stability of thermodynamic equilibrium according to the second law of thermodynamics, evident as the spread of energy amongst the state variables of the system in response to an imposed change.
The two ways of statement share an index experimental protocol (denoted that may be described as changed driver, moderation permitted. Along with the driver change it imposes a constant with and allows the uncontrolled moderating variable response along with the index response of interest
The two ways of statement differ in their respective compared protocols. One way posits a changed driver, no moderation protocol (denoted The other way posits a fixed driver, imposed moderation protocol (denoted ) | 0 | Theoretical and Fundamental Chemistry |
Asemota was born in Nigeria. She earned a Bachelor of Science from the University of Benin, a Master of Science from Ahmadu Bello University, and a Doctor of Philosophy from the University of Benin/Frankfurt University. | 1 | Applied and Interdisciplinary Chemistry |
Ellipsometry is an optical technique for investigating the dielectric properties (complex refractive index or dielectric function) of thin films. Ellipsometry measures the change of polarization upon reflection or transmission and compares it to a model.
It can be used to characterize composition, roughness, thickness (depth), crystalline nature, doping concentration, electrical conductivity and other material properties. It is very sensitive to the change in the optical response of incident radiation that interacts with the material being investigated.
A spectroscopic ellipsometer can be found in most thin film analytical labs. Ellipsometry is also becoming more interesting to researchers in other disciplines such as biology and medicine. These areas pose new challenges to the technique, such as measurements on unstable liquid surfaces and microscopic imaging. | 0 | Theoretical and Fundamental Chemistry |
Because most gases are difficult to observe directly, they are described through the use of four physical properties or macroscopic characteristics: pressure, volume, number of particles (chemists group them by moles) and temperature. These four characteristics were repeatedly observed by scientists such as Robert Boyle, Jacques Charles, John Dalton, Joseph Gay-Lussac and Amedeo Avogadro for a variety of gases in various settings. Their detailed studies ultimately led to a mathematical relationship among these properties expressed by the ideal gas law (see section below).
Gas particles are widely separated from one another, and consequently, have weaker intermolecular bonds than liquids or solids. These intermolecular forces result from electrostatic interactions between gas particles. Like-charged areas of different gas particles repel, while oppositely charged regions of different gas particles attract one another; gases that contain permanently charged ions are known as plasmas. Gaseous compounds with polar covalent bonds contain permanent charge imbalances and so experience relatively strong intermolecular forces, although the compounds net charge remains neutral. Transient, randomly induced charges exist across non-polar covalent bonds of molecules and electrostatic interactions caused by them are referred to as Van der Waals forces. The interaction of these intermolecular forces varies within a substance which determines many of the physical properties unique to each gas. A comparison of boiling points' for compounds formed by ionic and covalent bonds leads us to this conclusion.
Compared to the other states of matter, gases have low density and viscosity. Pressure and temperature influence the particles within a certain volume. This variation in particle separation and speed is referred to as compressibility. This particle separation and size influences optical properties of gases as can be found in the following list of refractive indices. Finally, gas particles spread apart or diffuse in order to homogeneously distribute themselves throughout any container. | 0 | Theoretical and Fundamental Chemistry |
Birch won a scholarship to attend the University of Sydney graduating with a BSc in 1937 and a MSc in 1938. He travelled to the University of Oxford to undertake his D.Phil., graduating in 1940. | 0 | Theoretical and Fundamental Chemistry |
One of its early professors, Victor Grignard, obtained the Nobel Prize in Chemistry in 1912 for his invention of the organo-metallic compounds known as "Grignard's reagents". After the Second World War, ENSIC introduced to France chemical engineering principles developed in the English-speaking world.
The school created a foundation in December 2008 to support its activities, called Fondation ENSIC, with the participation of Arkema. | 1 | Applied and Interdisciplinary Chemistry |
Polyurethane foam has been widely used to insulate fuel tanks on Space Shuttles. However, it requires a perfect application, as any air pocket, dirt or an uncovered tiny spot can knock it off due to extreme conditions of liftoff. Those conditions include violent vibrations, air friction and abrupt changes in temperature and pressure. For a perfect application of the foam there have been two obstacles: limitations related to wearing protective suits and masks by workers and inability to test for cracks before launch, such testing is done only by naked eye. The loss of foam caused the Space Shuttle Columbia disaster. According to the Columbia accident report, NASA officials found foam loss in over 80% of the 79 missions for which they have pictures.
By 2009 researchers created a superior polyimide foam to insulate the reusable cryogenic propellant tanks of Space Shuttles. | 0 | Theoretical and Fundamental Chemistry |
Materials used in the construction of an in vivo bioreactor space vary widely depending on the type of substrate, type of tissue, and mechanical demands of said tissue being grown. At its simplest, a bioreactor space will be created between tissue layers through the use of hydrogel injections to create a bioreactor space. Early models used an impermeable silicone shroud to encase a scaffold, though more recent studies have begun 3D printing custom bioreactor molds to further enhance the mechanical growth properties of the bioreactors. The choice of bioreactor chamber material generally requires that it is nontoxic and medical grade, examples include: "silicon, polycarbonate, and acrylic polymer". Recently both Teflon and titanium have been used in the growth of bone. One study utilized Polymethyl methacrylate as a chamber material and 3D printed hollow rectangular blocks. Yet another study pushed the limits of the in vivo bioreactor by proving that the omentum is suitable as a bioreactor space and chamber. Specifically, highly vascularized and functional bladder tissue was grown within the omentum space. | 1 | Applied and Interdisciplinary Chemistry |
Recently, real-time applications of NMR in liquid media have been developed using specifically designed flow probes (flow cell assemblies) which can replace standard tube probes. This has enabled techniques that can incorporate the use of high performance liquid chromatography (HPLC) or other continuous flow sample introduction devices. These flow probes have used in various online process monitoring such as chemical reactions and environmental pollutant degradation. | 0 | Theoretical and Fundamental Chemistry |
The applications of fluorescence resonance energy transfer (FRET) have expanded tremendously in the last 25 years, and the technique has become a staple in many biological and biophysical fields. FRET can be used as a spectroscopic ruler to measure distance and detect molecular interactions in a number of systems and has applications in biology and biochemistry. | 1 | Applied and Interdisciplinary Chemistry |
Antonella Buccianti (born 1960) is an Italian statistician and earth scientist, known for her work on the statistics of compositional data and its applications in geochemistry and geostatistics. She is an associate professor in the department of earth sciences at the University of Florence. | 0 | Theoretical and Fundamental Chemistry |
Attempts to establish rates of vancomycin-induced ototoxicity are even more difficult due to the scarcity of quality evidence. The current consensus is that clearly related cases of vancomycin ototoxicity are rare. The association between vancomycin serum levels and ototoxicity is also uncertain. While cases of ototoxicity have been reported in patients whose vancomycin serum level exceeded 80 µg/mL, cases have been reported in patients with therapeutic levels, as well. Thus, whether therapeutic drug monitoring of vancomycin for the purpose of maintaining "therapeutic" levels will prevent ototoxicity also remains unproven. Still, therapeutic drug monitoring can be used during vancomycin therapy to minimize the risk of ototoxicity associated with excessive drug exposure. | 0 | Theoretical and Fundamental Chemistry |
Compression fittings use a soft metal or thermoplastic ring (the compression ring or "ferrule") which is squeezed onto the pipe and into the fitting by a compression nut. The soft metal conforms to the surface of the tubing and the fitting, and creates a seal. Compression connections do not typically have the long life that sweat connections offer, but are advantageous in many cases because they are easy to make using basic tools. A disadvantage in compression connections is that they take longer to make than sweat, and sometimes require retightening over time to stop leaks. | 1 | Applied and Interdisciplinary Chemistry |
meta-Chloroperoxybenzoic acid (mCPBA or mCPBA) is a peroxycarboxylic acid. It is a white solid often used widely as an oxidant in organic synthesis. mCPBA is often preferred to other peroxy acids because of its relative ease of handling. mCPBA is a strong oxidizing agent that may cause fire upon contact with flammable material. | 0 | Theoretical and Fundamental Chemistry |
The BioCyc website contains a variety of software tools for searching, visualizing, comparing, and analyzing genome and pathway information. It includes a genome browser, and browsers for metabolic and regulatory networks. The website also includes tools for painting large-scale ("omics") datasets onto metabolic and regulatory networks, and onto the genome. | 1 | Applied and Interdisciplinary Chemistry |
Opposite to false positives, false negative biosignatures arise in a scenario where life may be present on another planet, but some processes on that planet make potential biosignatures undetectable. This is an ongoing problem and area of research in preparation for future telescopes that will be capable of observing exoplanetary atmospheres. | 1 | Applied and Interdisciplinary Chemistry |
Pirkle and co-workers pioneered the development of a variety of CSPs based on charge-transfer complexation and simultaneous hydrogen bonding. These phases are also referred to as Brush-type CSPs. The Pirkle phases are based on aromatic π-acid (3,5-dinitrobenzoyI ring) and π- basic (naphthalene) derivative. In addition to π-π interaction sites, they have hydrogen-bonding and dipole-dipole interaction sites provided by an amide, urea or ester functionality. Strong three-point interaction, according to Dalgleish's model, enables enantioseparation. These phases are classified into π-electron-acceptor, π-electron-donor or π-electron acceptor-donor phase.
A number of Pirkle-type CSPs are commercially available. They are used most often in the normal phase mode. The ionic form of the DNPBG (3,5-dinitrobenzoyl-phenylglycine) CSP has been successfully employed to achieve separation of racemic propranolol in biological fluid. Many compounds of pharmaceutical interest including enantiomers of naproxen and metoprolol has been separated using Pirkle CSP. | 0 | Theoretical and Fundamental Chemistry |
In electronics, one of the earliest devices using the principle are ultrasonic distance-measuring devices, which emit an ultrasonic pulse and are able to measure the distance to a solid object based on the time taken for the wave to bounce back to the emitter. The ToF method is also used to estimate the electron mobility. Originally, it was designed for measurement of low-conductive thin films, later adjusted for common semiconductors. This experimental technique is used for metal-dielectric-metal structures as well as organic field-effect transistors. The excess charges are generated by application of the laser or voltage pulse.
For Magnetic Resonance Angiography (MRA), ToF is a major underlying method. In this method, blood entering the imaged area is not yet saturated, giving it a much higher signal when using short echo time and flow compensation. It can be used in the detection of aneurysm, stenosis or dissection.
In time-of-flight mass spectrometry, ions are accelerated by an electrical field to the same kinetic energy with the velocity of the ion depending on the mass-to-charge ratio. Thus the time-of-flight is used to measure velocity, from which the mass-to-charge ratio can be determined. The time-of-flight of electrons is used to measure their kinetic energy.
In near-infrared spectroscopy, the ToF method is used to measure the media-dependent optical pathlength over a range of optical wavelengths, from which composition and properties of the media can be analyzed.
In ultrasonic flow meter measurement, ToF is used to measure speed of signal propagation upstream and downstream of flow of a media, in order to estimate total flow velocity. This measurement is made in a collinear direction with the flow.
In planar Doppler velocimetry (optical flow meter measurement), ToF measurements are made perpendicular to the flow by timing when individual particles cross two or more locations along the flow (collinear measurements would require generally high flow velocities and extremely narrow-band optical filters).
In optical interferometry, the pathlength difference between sample and reference arms can be measured by ToF methods, such as frequency modulation followed by phase shift measurement or cross correlation of signals. Such methods are used in laser radar and laser tracker systems for medium-long range distance measurement.
In neutron time-of-flight scattering, a pulsed monochromatic neutron beam is scattered by a sample. The energy spectrum of the scattered neutrons is measured via time of flight.
In kinematics, ToF is the duration in which a projectile is traveling through the air. Given the initial velocity of a particle launched from the ground, the downward (i.e. gravitational) acceleration , and the projectiles angle of projection θ' (measured relative to the horizontal), then a simple rearrangement of the SUVAT equation
results in this equation
for the time of flight of a projectile. | 0 | Theoretical and Fundamental Chemistry |
Attempts at treatment for cancer cells with constitutively phosphorylated STAT5 have included both indirect and direct inhibition of STAT5 activity. While more medicinal work has been done in indirect inhibition, this approach can lead to increased toxicity in cells and can also result in non-specific effects, both of which are better handled by direct inhibition.
Indirect inhibition targets kinases associated with STAT5, or targets proteases that carry out terminal truncation of proteins. Different inhibitors have been designed to target different kinases:
* Inhibition of BCR/ABl constitutes the basis of the functioning of drugs like imatinib
* Inhibition of FLT3 is carried out by drugs like lestaurtinib
* Inhibition of JAK2 is carried out by the drug CYT387, which was successful in preclinical trials and is currently undergoing clinical trials.
Direct inhibition of STAT5 activity makes use of small molecule inhibitors that prevent STAT5 from properly binding to DNA or prevent proper dimerization. The inhibiting of DNA binding utilizes RNA interference, antisense oligodeoxynucleotide, and short hairpin RNA. The inhibition of proper dimerization, on the other hand, is brought about by the use of small molecules that target the SH2 domain. Recent work on drug development in the latter field have proved particularly effective. | 1 | Applied and Interdisciplinary Chemistry |
Alvaro Alonso Barba was a secular Catholic priest and metallurgist born in Lepe in 1569.
Antonio (1786) says, "Baeticus ex oppido Lepe, apud Potosi"; hence Barba is assumed to be of Andalusian origin, from the ancient Roman province of Baetica.
He lived at Potosí during the period when its silver mines were most productive and luxury among the Spanish residents and mine owners had nearly reached its height. Barba divided his time between his priestly duties and a close study of the ores of this region and their treatment. There had been, since 1570, a complete revolution in the treatment of silver ores, through the application of mercury, and a number of improvements followed, of which Barba had knowledge.
In 1609, he invented the pan amalgamation process (in Spanish the cazo or fondo process) for extracting silver from ore by mixing it with salt and mercury and heating it in shallow copper vessels. In 1640 he published in Madrid a book entitled Arte de los Metales, the earliest work on South American ores and minerals. It includes information on mineral localities in Bolivia. The book has been republished in Spanish, French, English and German. | 1 | Applied and Interdisciplinary Chemistry |
The earliest known writing about medicine was a 110-page Egyptian papyrus. It was supposedly written by the god Thoth in about 16 BC. The Ebers papyrus is an ancient recipe book dated to approximately 1552 BC. It contains a mixture of magic and medicine with invocations to banish disease and a catalogue of useful plants, minerals, magic amulets and spells. The most famous Egyptian physician was Imhotep, who lived in Memphis around 2500 B.C. Imhotep's materia medica consisted of procedures for treating head and torso injuries, tending of wounds, and prevention and curing of infections, as well as advanced principles of hygiene. | 1 | Applied and Interdisciplinary Chemistry |
Water quality deteriorate due to corrosion of metal pipe surfaces and connections in distribution systems. Pipe corrosion shows in water as color, taste and odor, any of which may cause health concerns.
Health issues relate to releases of trace metals such as lead, copper or cadmium into the water. Lead exposure can cause delays in physical and mental development in children. Long term exposure to copper may cause liver and kidney damage. High or long term exposure of cadmium may cause damage to various organs. Corrosion of iron pipes causes rusty or red water. Corrosion of zinc and iron pipes can cause metallic taste.
Various techniques can be used to control internal corrosion, for example, pH level adjustment, adjustment of carbonate and calcium to create calcium carbonate as pipe surface coating, and applying a corrosion inhibitor. For example, phosphate products that form films over pipe surfaces is a type of corrosion inhibitor. This reduces the chance of leaching of trace metals from the pipe materials into the water. | 1 | Applied and Interdisciplinary Chemistry |
Prairie restoration is a conservation effort to restore prairie lands that were destroyed due to industrial, agricultural, commercial, or residential development. The primary aim is to return areas and ecosystems to their previous state before their depletion. The mass of SOC able to be stored in these restored plots is typically greater than the previous crop, acting as a more effective carbon sink. | 0 | Theoretical and Fundamental Chemistry |
The word neo-organ comes from the Greek word "neos," which means new. Organ transplants have been successfully used for medical purposes since 1954. The difficulty with the traditional process of organ transplants is that it requires waiting for a viable donor to donate an organ. The process of matching the organ to make sure it is compatible with the patient has also proven to be challenging. There are two main challenges: finding the right candidate for the patient and avoiding the patient rejecting the organ even if it is a match. Neo-organs can be used to avoid the process of organ matching and donating. | 1 | Applied and Interdisciplinary Chemistry |
The dynamics of the particles in complex fluids are an area of current research. Energy lost due to friction may be a nonlinear function of the velocity and normal forces. The topological inhibition to flow by the crowding of constituent particles is a key element in these systems. Under certain conditions, including high densities and low temperatures, when externally driven to induce flow, complex fluids are characterized by irregular intervals of solid-like behavior followed by stress relaxations due to particle rearrangements. The dynamics of these systems are highly nonlinear in nature. The increase in stress by an infinitesimal amount or a small displacement of a single particle can result in the difference between an arrested state and fluid-like behavior.
Although many materials found in nature can fit into the class of complex fluids, very little is well understood about them. Inconsistent and controversial conclusions concerning their material properties still persist. The careful study of these systems may lead to "new physics" and new states of matter. For example, it has been suggested that these systems can jam and a "jamming phase diagram" can be used to consider how these systems can jam and unjam. It is not known whether further research will demonstrate these findings, or whether such a theoretical framework will prove useful. As yet this large body of theoretical work has been poorly supported with experiments. | 1 | Applied and Interdisciplinary Chemistry |
For simplicity consider a two-level atomic system with ground and excited states and , respectively (using the Dirac bracket notation). Let the energy difference between the states be so that is the transition frequency of the system. Then the unperturbed Hamiltonian of the atom can be written as
Suppose the atom experiences an external classical electric field of frequency , given by
; e.g., a plane wave propagating in space. Then under the dipole approximation the interaction Hamiltonian between the atom and the electric field can be expressed as
where is the dipole moment operator of the atom. The total Hamiltonian for the atom-light system is therefore The atom does not have a dipole moment when it is in an energy eigenstate, so This means that defining allows the dipole operator to be written as
(with denoting the complex conjugate). The interaction Hamiltonian can then be shown to be
where is the Rabi frequency and is the counter-rotating frequency. To see why the terms are called counter-rotating consider a unitary transformation to the interaction or Dirac picture where the transformed Hamiltonian is given by
where is the detuning between the light field and the atom. | 0 | Theoretical and Fundamental Chemistry |
Biological carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. The compounds are then used to store energy and as structure for other biomolecules. Carbon is primarily fixed through photosynthesis, but some organisms use a process called chemosynthesis in the absence of sunlight.
Organisms that grow by fixing carbon are called autotrophs, which include photoautotrophs (which use sunlight), and lithoautotrophs (which use inorganic oxidation). Heterotrophs are not themselves capable of carbon fixation but are able to grow by consuming the carbon fixed by autotrophs or other heterotrophs. "Fixed carbon", "reduced carbon", and "organic carbon" may all be used interchangeably to refer to various organic compounds. Chemosynthesis is carbon fixation driven by chemical energy, rather than from sunlight. Sulfur- and hydrogen-oxidizing bacteria often use the Calvin cycle or the reductive citric acid cycle. | 0 | Theoretical and Fundamental Chemistry |
The limit of quantification (LoQ, or LOQ) is the lowest value of a signal (or concentration, activity, response...) that can be quantified with acceptable precision and accuracy.
The LoQ is the limit at which the difference between two distinct signals / values can be discerned with a reasonable certainty, i.e., when the signal is statistically different from the background. The LoQ may be drastically different between laboratories, so another detection limit is commonly used that is referred to as the Practical Quantification Limit (PQL). | 0 | Theoretical and Fundamental Chemistry |
* Sinyan Shen, Surface Second Sound in Superfluid Helium. PhD Dissertation (1973). http://adsabs.harvard.edu/abs/1973PhDT.......142S
* V. Peshkov, "Second Sound in Helium II," J. Phys. (Moscow) 8, 381 (1944)
* U. Piram, [http://www.inf.ethz.ch/personal/fcellier/MS/piram_ms.pdf "Numerical investigation of second sound in liquid helium,"] Dipl.-Ing. Dissertation (1991). Retrieved on April 15, 2007. | 0 | Theoretical and Fundamental Chemistry |
X-ray fluorescence holography (XFH) is a holography method with atomic resolution based on atomic fluorescence. It is a relatively new technique that benefits greatly from the coherent high-power X-rays available from synchrotron sources, such as the Japanese SPring-8 facility. | 0 | Theoretical and Fundamental Chemistry |
In 1992, Ülgen joined the faculty at Boğaziçi University as in instructor in the department of chemical engineering. She was promoted to assistant professor in 1994, associate professor in 1996, and professor in 2002. She served as head of the chemical engineering department from 2009 to 2011. Ülgen served as associate dean of the faculty of engineering from 2012 to December 2015.
Ülgen researches pharmacophore modelling to identify pharmacological chaperones to treat infectious diseases, genetic diseases, and cancer. She uses a systems biology approach to investigate the reconstruction of signaling networks in yeast, worms, and humans. She also researches protein purification, computational physiology, and metabolic pathway engineering. | 1 | Applied and Interdisciplinary Chemistry |
Maximum catalytic current density for CO reduction that can be achieved in aqueous media is only 10 mA cm based solubility of CO and diffusion limitations. The integrated maximum photocurrent under Air Mass 1.5 illumination, in the conventional Shockley-Quiesser limit for solar energy conversion for p-Si (1.12 eV), p-InP (1.3 eV), p-GaAs (1.4 eV), and p-GaP (2.3 eV) are 44.0 mA cm, 37.0 mA cm, 32.5 mA cm and 9.0 mA cm, respectively. Therefore, non-aqueous media such as DMF, acetonitrile, methanol are explored as solvent for CO electrochemical reduction. In addition, Methanol has been industrially used as a physical absorber of CO in the Rectisol method. Similarly to aqueous media system, p-Si, p-InP, p-GaAs, p-GaP and p-CdTe are explored for CO photoelectrochemical reduction. Among these, p-GaP has lowest overpotential, whereas, p-CdTe has moderate overpotential but high catalytic current density in DMF with 5% water mixture system. Main product of CO reduction in non-aqueous media is carbon monoxide. Competitive hydrogen generation is minimized in non-aqueous media. Proposed mechanism for CO reduction to CO in non-aqueous media involves single electron reduction of CO to CO radical anion and adsorption of radical anion to surface followed by disproportionate reaction between unreduced CO and CO radical anion to form CO and CO. | 0 | Theoretical and Fundamental Chemistry |
Interleukin-15 stimulates fat oxidation, glucose uptake, mitochondrial biogenesis and myogenesis in skeletal muscle and adipose tissue. In humans, basal concentrations of IL-15 and its alpha receptor (IL-15Rα) in blood have been inversely associated with physical inactivity and fat mass, particularly trunk fat mass. Moreover, in response to a single session of resistance exercise the IL-15/IL-15Rα complex has been related to myofibrillar protein synthesis (hypertrophy). | 1 | Applied and Interdisciplinary Chemistry |
Under specific assumptions, the GEBIK and GEBIF equations become equivalent to the equation for steady-state kinetic isotope fractionation in both chemical and biochemical reactions. Here two mathematical treatments are proposed: (i) under biomass-free and enzyme-invariant (BFEI) hypothesis and (ii) under quasi-steady-state (QSS) hypothesis. | 0 | Theoretical and Fundamental Chemistry |
Landau–Placzek ratio is a ratio of the integrated intensity of Rayleigh scattering to the combined integrated intensity of Brillouin scattering of a triplet frequency spectrum of light scattered by homogenous liquids or gases. The triplet consists of two frequency shifted Brillouin scattering and a central unshifted Rayleigh scattering line split. The triplet structure was explained by Lev Landau and George Placzek in 1934 in a short publication, summarizing major results of their analysis. Landau and Placzek noted in their short paper that a more detailed discussion will be published later although that paper does not seem to have been published. However, a detailed discussion is provided in Lev Landau and Evgeny Lifshitz's book.
The Landau–Placzek ratio is defined as
where
* is the integral intensity of central Rayleigh peak
* is the integral intensity of Brillouin peak.
The Landau–Placzek formula provides an approximate theoretical prediction for the Landau–Placzek ratio,
where
* is the specific heat at constant pressure
* is the specific heat at constant volume. | 0 | Theoretical and Fundamental Chemistry |
Oil sampling is a procedure for collecting a volume of fluid from lubricated or hydraulic machinery for the purpose of oil analysis. Much like collecting forensic evidence at a crime scene, when collecting an oil sample, it is important to ensure that procedures are used to minimize disturbance of the sample during and after the sampling process. Oil samples are typically drawn into a small, clean bottle which is sealed and sent to a laboratory for analysis. | 0 | Theoretical and Fundamental Chemistry |
There are at least three stages involve in the operation of a vacuum disc filter:
Stage 1: Cake formation
The discs rotate in a slurry trough, compartmentalized to reduce the volume held in it at any one time, and therefore to reduce the residence time of slurry in the trough. The time available for this stage depends on two factors, the rotation speed of the disc and the height of the slurry level in the basin. A vacuum is applied inside the discs to promote cake filtration.
Stage 2: Cake dewatering
Washing is largely restricted to the upper portions where the cake surface is nearly horizontal in orientation, which occurs at the temperature of the feed. The ceramic filter uses a sintered alumina disc to dewater slurry under low vacuum. The dewatering occurs by drawing water from the slurry by capillary action. This ensures that no air or particles are drawn into the filter medium to cause blockage. However, if too much wash water is applied then it can cascade down the cake and into the feed trough, where it merely dilutes the slurry.
Stage 3: Cake drying
The final water (moisture) content in the cake is regulated by passing dry (cold or hot) air or gas through the cake. Drying time is dependent on the distribution valve timing, slurry level on the basin, rotation speed, and scraper position.
Stage 4: Cake discharge
These are the typical conditions for the overall operation of the vacuum ceramic filter:
* Slurry level: must be higher than the top of the sectors as they pass through the trough (otherwise air would simply pass through the cloth during cake formation).
* Solids throughput: up to 4,000 kg/mh
* Typical filtration capacity: 200-5,000 L/mh
* Typical air consumption/ flow rate: 50–80 m/h·m at 500 Torr vacuum
* Pressure difference: Typically, the pressure difference with ceramic disc is between 0.90 and 0.95 bar. However, pressure differences across the filter are usually limited to less than 85 kPa making it possible to process a wide range of feed materials in a continuous manner.
* Rotating speed: Higher rotating speeds enable greater solid production rates by formation of thinner cakes. However, this may not be wholly desirable as washing efficiency is likely to be compromised. Moreover, an increased rotating speed requires more electrical power.
* Minimum cake thickness: 3/8-1/2 in or 10–13 mm (for effective discharge)
* Submergence required for cake discharge: 25% of cycle
* Effective maximum submergence of the disk: 28% of cycle. | 0 | Theoretical and Fundamental Chemistry |
Major families of biopolymers are polysaccharides (carbohydrates), peptides, and polynucleotides. Many variants of each are known. | 0 | Theoretical and Fundamental Chemistry |
Few rocks were visible on the surface where Opportunity landed, but bedrock that was exposed in craters was examined by the suite of instruments on the Rover. Bedrock rocks were found to be sedimentary rocks with a high concentration of sulfur in the form of calcium and magnesium sulfates. Some of the sulfates that may be present in bedrocks are kieserite, sulfate anhydrate, bassanite, hexahydrite, epsomite, and gypsum. Salts, such as halite, bischofite, antarcticite, bloedite, vanthoffite, or glauberite may also be present.
The rocks contained the sulfates had a light tone compared to isolated rocks and rocks examined by landers/rovers at other locations on Mars. The spectra of these light toned rocks, containing hydrated sulfates, were similar to spectra taken by the Thermal Emission Spectrometer on board the Mars Global Surveyor. The same spectrum is found over a large area, so it is believed that water once appeared over a wide region, not just in the area explored by Opportunity Rover.
The Alpha Particle X-ray Spectrometer (APXS) found rather high levels of phosphorus in the rocks. Similar high levels were found by other rovers at Ares Vallis and Gusev Crater, so it has been hypothesized that the mantle of Mars may be phosphorus-rich. The minerals in the rocks could have originated by acid weathering of basalt. Because the solubility of phosphorus is related to the solubility of uranium, thorium, and rare earth elements, they are all also expected to be enriched in rocks.
When Opportunity rover traveled to the rim of Endeavour crater, it soon found a white vein that was later identified as being pure gypsum. It was formed when water carrying gypsum in solution deposited the mineral in a crack in the rock. A picture of this vein, called "Homestake" formation, is shown below. | 0 | Theoretical and Fundamental Chemistry |
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