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In some chain-growth polymerizations there is also a chain transfer step, in which the growing polymer chain RM° takes an atom X from an inactive molecule XY, terminating the growth of the polymer chain: RM° + XY → RMX + Y°. The Y fragment ls a new active center which adds more monomer M to form a new growing chain YM°. This can happen in free radical polymerization for chains RM°, in ionic polymerization for chains RM or RM, or in coordination polymerization. In most cases chain transfer will generate a by-product and decrease the molar mass of the final polymer. | 0 | Theoretical and Fundamental Chemistry |
There is great variation in the carbon isotope composition of amino acids within a single organism. In cyanobacteria, Macko et al. observed a ~30‰ range in δC values amongst the amino acids. Amino acids produced from the same precursors also had widely varying compositions. It is difficult to explain these trends because of limited data on the kinetic isotope effects associated with reactions that synthesize amino acid carbon skeletons. Nevertheless, some insights can be gained by applying the logic above to the reaction networks responsible for amino acid biosynthesis.
Consider the amino acids synthesized from pyruvate. Pyruvate is produced during glycolysis and can be decarboxylated by pyruvate dehydrogenase to generate acetyl groups. These acetyl groups enter the citric acid cycle as acetyl-CoA or can be used to synthesize lipids. There is a large kinetic isotope effect associated with this reaction, so the remaining pyruvate pool becomes enriched in C relative to the acetyl groups. This enriched pyruvate can be transaminated to produce alanine. In the experiments by Macko et al., alanine indeed had a δC value slightly higher than that of cyanobacterial photosynthate.
Valine is synthesized by the addition of a C depleted acetyl group to pyruvate. Consistent with this mechanism, Takano et al. found valine to be depleted in C relative to alanine in anaerobic methanotrophic archaea. However, in cyanobacteria, Macko et al. observed a higher δC value for valine than alanine. This could be due to the branch point at the intermediate α-ketoisovalerate, which can be transaminated to produce valine or further acetylated to generate leucine. There may be different isotope effects associated with the addition of an amino or acetyl group at position C-2 in α-ketoisovalerate. As discussed above, the isotopic consequences of this branch point would depend on the relative rates of leucine vs valine production.
One would also expect relative depletion of C in leucine because its synthesis requires the addition of another isotopically light acetyl group. In Escherichia coli, the carboxyl carbon in leucine (derived from acetyl-CoA) has a δC value roughly 13‰ lower than that of the entire molecule. Curiously, the same depletion is not observed in photoautotrophs. Further, there is little consistency in the δC of most amino acids between cyanobacteria and eukaryotic photoautotrophs. These discrepancies demonstrate the limits of our understanding of the mechanisms that set amino acid isotopic compositions. Regardless, isotopic variations between different taxa have been used to great effect in ecology. | 0 | Theoretical and Fundamental Chemistry |
During the last two decades, eco-evolutionary studies have investigated the relevance of life-history traits and environmental conditions on telomeres of wildlife. Most of these studies have been conducted in endotherms, i.e. birds and mammals. They have provided evidence for the inheritance of telomere length; however, heritability estimates vary greatly within and among species. Age and telomere length often negatively correlate in vertebrates, but this decline is variable among taxa and linked to the method used for estimating telomere length. In contrast, the available information shows no sex differences in telomere length across vertebrates. Phylogeny and life history traits such as body size or the pace of life can also affect telomere dynamics. For example, it has been described across species of birds and mammals. In 2019, a meta-analysis confirmed that the exposure to stressors (e.g. pathogen infection, competition, reproductive effort and high activity level) was associated with shorter telomeres across different animal taxa.
Studies on ectotherms, and other non-mammalian organisms, show that there is no single universal model of telomere erosion; rather, there is wide variation in relevant dynamics across Metazoa, and even within smaller taxonomic groups these patterns appear diverse. | 1 | Applied and Interdisciplinary Chemistry |
Water quality guidelines for South Africa are grouped according to potential user types (e.g. domestic, industrial) in the 1996 Water Quality Guidelines. Drinking water quality is subject to the South African National Standard (SANS) 241 Drinking Water Specification. | 0 | Theoretical and Fundamental Chemistry |
Novec 649 is a low-temperature heat-transfer fluid. It has been used as a full-immersion fluid in a proof of concept data center cooling system by Intel and SGI. As it boils off easily due to its boiling point, it is used in two-phase immersion cooling system with a condensing loop running cold water. Effects of evaporative cooling was utilized to remove additional heat. Novec 649 is also being considered to be used for cooling silicon photomultiplier (SiPM) sensors to in single-phase configuration as part of Large Hadron Collider’s high luminosity upgrade.
Traditional perfluorocarbon (PFC) based compounds used for cooling, such as Fluorinert, display high global warming potentials (GWPs), typically 5,000 to 10,000 times that of CO. Novec 649 was chosen as a good drop-in replacement due to it having similar thermo-physical properties to Fluorinert FC-72 (perfluorohexane, C6F14) while exhibiting a very low global warming potential of 1. | 1 | Applied and Interdisciplinary Chemistry |
In the presence of an anionic initiator (M X), the reagent reacts with aldehydes and ketones to give a trimethylsilyl ether, the net product of insertion of the carbonyl into the Si-CF bond. Hydrolysis gives trifluoromethyl methanols. The reagent also converts esters to trifluoromethyl ketones. A typical initiator is a soluble fluoride-containing species such as tetrabutylammonium fluoride; however, simple alkoxides such as KOtBu are also effective. The mechanism begins by generation of Si(CH)X and a highly reactive [CF] (trifluoromethide) intermediate. The [CF] attacks the carbonyl to generate an alkoxide anion. The alkoxide is silylated by the reagent to give the overall addition product, plus [CF], thus propagating an anionic chain reaction. The reagent competes with the carbonyl for the reactive intermediate, rapidly sequestering [CF] in a reversibly-generated -ate complex [(CF)Si(CH)]. This -ate complex is unable to react directly with the carbonyl, resulting in powerful inhibition of the chain reaction by the reagent. This inhibitory process is common to all anion-initiated reactions of the reagent, with the identity of the counter-cation (M) playing a major role in controlling the overall rate.
The reagent has largely supplanted trifluoromethyllithium, which is not isolable and rapidly decomposes to yield lithium fluoride and difluorocarbene. | 0 | Theoretical and Fundamental Chemistry |
The Briggs–Rauscher oscillating reaction is one of a small number of known oscillating chemical reactions. It is especially well suited for demonstration purposes because of its visually striking color changes: the freshly prepared colorless solution slowly turns an amber color, suddenly changing to a very dark blue. This slowly fades to colorless and the process repeats, about ten times in the most popular formulation. | 1 | Applied and Interdisciplinary Chemistry |
In Scanning fluorescence correlation spectroscopy (sFCS) the measurement volume is moved across the sample in a defined way. The introduction of scanning is motivated by its ability to alleviate or remove several distinct problems often encountered in standard FCS, and thus, to extend the range of applicability of fluorescence correlation methods in biological systems.
Some variations of FCS are only applicable to serial scanning laser microscopes. Image Correlation Spectroscopy and its variations all were implemented on a scanning confocal or scanning two photon microscope, but transfer to other microscopes, like a spinning disk confocal microscope. Raster ICS (RICS), and position sensitive FCS (PSFCS) incorporate the time delay between parts of the image scan into the analysis. Also, low-dimensional scans (e.g. a circular ring)—only possible on a scanning system—can access time scales between single point and full image measurements. Scanning path has also been made to adaptively follow particles. | 0 | Theoretical and Fundamental Chemistry |
Brønsted and Lowry characterized an acid–base equilibrium as involving a proton exchange reaction:
:acid + base conjugate base + conjugate acid.
An acid is a proton donor; the proton is transferred to the base, a proton acceptor, creating a conjugate acid. For aqueous solutions of an acid HA, the base is water; the conjugate base is A and the conjugate acid is the solvated hydrogen ion. In solution chemistry, it is usual to use H as an abbreviation for the solvated hydrogen ion, regardless of the solvent. In aqueous solution H denotes a solvated hydronium ion.
The Brønsted–Lowry definition applies to other solvents, such as dimethyl sulfoxide: the solvent S acts as a base, accepting a proton and forming the conjugate acid SH. A broader definition of acid dissociation includes hydrolysis, in which protons are produced by the splitting of water molecules. For example, boric acid, , acts as a weak acid, even though it is not a proton donor, because of the hydrolysis equilibrium
: + + H.
Similarly, metal ion hydrolysis causes ions such as to behave as weak acids:
Acid–base equilibria are important in a very wide range of applications, such as acid–base homeostasis, ocean acidification, pharmacology and analytical chemistry. | 0 | Theoretical and Fundamental Chemistry |
Kagome () is a traditional Japanese woven bamboo pattern; its name is composed from the words kago, meaning "basket", and me, meaning "eye(s)", referring to the pattern of holes in a woven basket.
The kagome pattern is common in bamboo weaving in East Asia. In 2022, archaeologists found bamboo weaving remains at the Dongsunba ruins in Chongqing, China, 200 BC. After 2200 years, the kagome pattern is still clear.
It is a woven arrangement of laths composed of interlaced triangles such that each point where two laths cross has four neighboring points, forming the pattern of a trihexagonal tiling. The woven process gives the Kagome a chiral wallpaper group symmetry, p6 (632). | 0 | Theoretical and Fundamental Chemistry |
Ruthenium(II) complexes of amine ligands are known for engaging in the outer-sphere mechanism, during which the imine/iminium substrate does not bind to the metal center directly. Instead, substrate receives the elements of H by interaction with Ru-H and N-H sites. This process is utilized by the Shvo catalyst and many ruthenium amine complexes. One such complex is Baratta's catalyst RuCl(PPh)(ampy) (ampy = 2-picolylamine) for transfer hydrogenation. | 0 | Theoretical and Fundamental Chemistry |
The Set-Point Theory, first introduced in 1953, postulated that each body has a preprogrammed fixed weight, with regulatory mechanisms to compensate. This theory was quickly adopted and used to explain failures in developing effective and sustained weight loss procedures. A 2019 systematic review of multiple weight change interventions on humans, including dieting, exercise and overeating, found systematic "energetic errors", the non-compensated loss or gain of calories, for all these procedures. This shows that the body cannot precisely compensate for errors in energy/calorie intake, contrary to what the Set-Point Theory hypothesizes, and potentially explaining both weight loss and weight gain such as obesity. This review was conducted on short-term studies, therefore such a mechanism cannot be excluded in the long term, as evidence is currently lacking on this timeframe. | 1 | Applied and Interdisciplinary Chemistry |
Radionuclides are produced as an unavoidable result of nuclear fission and thermonuclear explosions. The process of nuclear fission creates a wide range of fission products, most of which are radionuclides. Further radionuclides can be created from irradiation of the nuclear fuel (creating a range of actinides) and of the surrounding structures, yielding activation products. This complex mixture of radionuclides with different chemistries and radioactivity makes handling nuclear waste and dealing with nuclear fallout particularly problematic. | 0 | Theoretical and Fundamental Chemistry |
* Chemistry of vegetable tannins, 1 edition – first published in 1966
* The shikimate pathway, 2 editions – first published in 1974
* Metabolites and metabolism, 1 edition – first published in 1985
* Plant polyphenols: vegetable tannins revisited, 1 edition – first published in 1989
* Shikimic acid, 1 edition – first published in 1993
* Practical Polyphenolics, 2 editions – first published in 1998, | 0 | Theoretical and Fundamental Chemistry |
Several smartphone companies have released handsets with optical image stabilisation (OIS) modules incorporating SMA actuators, manufactured under licence from Cambridge Mechatronics. | 1 | Applied and Interdisciplinary Chemistry |
A predominance diagram purports to show the conditions of concentration and pH where a chemical species has the highest concentration in solutions in which there are multiple acid-base equilibria. The lines on a predominance diagram indicate where adjacent species have the same concentration. Either side of such a line one species or the other predominates, that is, has higher concentration relative to the other species.
To illustrate a predominance diagram, part of the one for chromate is shown at the right. pCr stands for minus the logarithm of the chromium concentration and pH stands for minus the logarithm of the hydrogen ion concentration. There are two independent equilibria, with equilibrium constants defined as follows.
A third equilibrium constant can be derived from K and K.
The species and are only formed at very low pH so they do not appear on this diagram. Published values for log K and log K are 5.89 and 2.05, respectively. Using these values and the equality conditions, the concentrations of the three species, chromate , hydrogen chromate and dichromate can be calculated, for various values of pH, by means of the equilibrium expressions. The chromium concentration is calculated as the sum of the species' concentrations in terms of chromium content.
The three species all have concentrations equal to at pH = pK, for which [Cr] = . The three lines on this diagram meet at that point.
; Green line: Chromate and hydrogen chromate have equal concentrations. Setting [] equal to [] in eq. , [] = , or pH = log K. This relationship is independent of pCr, so it requires a vertical line to be drawn on the predominance diagram.
; Red line: Hydrogen chromate and dichromate have equal concentrations. Setting [] equal to [] in Eq. , [] = ; from Eq. , then, [] = .
; Blue line: Chromate and dichromate have equal concentrations. Setting [] equal to [] in Eq. gives [] = .
The predominance diagram is interpreted as follows. The chromate ion is the predominant species in the region to the right of the green and blue lines. Above pH ~6.75 it is always the predominant species. At pH ) the hydrogen chromate ion is predominant in dilute solution but the dichromate ion is predominant in more concentrated solutions.
Predominance diagrams can become very complicated when many polymeric species can be formed as, for example, with vanadate, molybdate and tungstate. Another complication is that many of the higher polymers are formed extremely slowly, such that equilibrium may not be attained even in months, leading to possible errors in the equilibrium constants and the predominance diagram. | 0 | Theoretical and Fundamental Chemistry |
The hexapede (Yerik in Navi) are hexapodal deer-like creatures. They are dark blue herbivores with white and yellow stripes. Twin horn structures sheathe a thin, patterned membrane structure. Their small, sloped skull is topped by this light-colored fan structure. This fan has an eye pattern on it similar to those found in actual insects. A skin membrane hangs under the jaw and runs the length of the neck. Twin lines of dark hairlike bristles run down the hexapedes back. The antennae are at the back at the head. As a threat display, the hexapede flares up its twin membrane structure like a satellite dish and retracts both lips. It is scientifically known as Sexcruscervus caeruleus. | 1 | Applied and Interdisciplinary Chemistry |
In nearly all species of eukaryotic algae (Chloromonas being one notable exception), upon induction of the CCM, ~95% of RuBisCO is densely packed into a single subcellular compartment: the pyrenoid. Carbon dioxide is concentrated in this compartment using a combination of CO pumps, bicarbonate pumps, and carbonic anhydrases. The pyrenoid is not a membrane bound compartment, but is found within the chloroplast, often surrounded by a starch sheath (which is not thought to serve a function in the CCM). | 0 | Theoretical and Fundamental Chemistry |
Normal modes are generated in the Earth from long wavelength seismic waves from large earthquakes interfering to form standing waves.
For an elastic, isotropic, homogeneous sphere, spheroidal, toroidal and radial (or breathing) modes arise. Spheroidal modes only involve P and SV waves (like Rayleigh waves) and depend on overtone number n and angular order l but have degeneracy of azimuthal order m. Increasing l concentrates fundamental branch closer to surface and at large l this tends to Rayleigh waves. Toroidal modes only involve SH waves (like Love waves) and do not exist in fluid outer core. Radial modes are just a subset of spheroidal modes with l=0. The degeneracy does not exist on Earth as it is broken by rotation, ellipticity and 3D heterogeneous velocity and density structure.
It may be assumed that each mode can be isolated, the self-coupling approximation, or that many modes close in frequency resonate, the cross-coupling approximation. Self-coupling will solely change the phase velocity and not the number of waves around a great circle, resulting in a stretching or shrinking of standing wave pattern. Modal cross-coupling occurs due to the rotation of the Earth, from aspherical elastic structure, or due to Earth's ellipticity and leads to a mixing of fundamental spheroidal and toroidal modes. | 0 | Theoretical and Fundamental Chemistry |
Physical organic chemistry is the study of the interrelationships between structure and reactivity in organic molecules. It can be seen as the study of organic chemistry using tools of physical chemistry such as chemical equilibrium, chemical kinetics, thermochemistry, and quantum chemistry. | 0 | Theoretical and Fundamental Chemistry |
The high purity, moisture barrier, clarity, and sterilization compatibility of COC resins make them an excellent alternative to glass in a wide range of medical products. Breakage prevention and weight reduction are common reasons for choosing COC in these applications. COC has a very low-energy and nonreactive surface, which can extend shelf life and purity of medications such as insulin and other protein drugs in applications such as vials, syringes and cartridges. The high UV transmission of COC also drives diagnostic applications such as cuvettes and microplates. COC plays an increasingly important role in microfluidics due to its chemical resistance, clarity and unusually high mold detail replication which makes it possible to reliably mold submicron features. Most COC grades can undergo sterilization by gamma radiation, steam, or ethylene oxide. | 0 | Theoretical and Fundamental Chemistry |
Only energy and momentum are transferred.
*(p,p') tests differences between nuclear states.
*(α,α') measures nuclear surface shapes and sizes. Since α particles that hit the nucleus react more violently, elastic and shallow inelastic α scattering are sensitive to the shapes and sizes of the targets, like light scattered from a small black object.
*(e,e') is useful for probing the interior structure. Since electrons interact less strongly than do protons and neutrons, they reach to the centers of the targets and their wave functions are less distorted by passing through the nucleus. | 0 | Theoretical and Fundamental Chemistry |
Spot analysis, spot test analysis, or spot test is a chemical test, a simple and efficient technique where analytic assays are executed in only one, or a few drops, of a chemical solution, preferably in a great piece of filter paper, without using any sophisticated instrumentation. The development and popularization of the test is credited to Fritz Feigl.
A spot test or spot assay can also refer to a test often used in microbiology. | 0 | Theoretical and Fundamental Chemistry |
HEPPS (EPPS) is a buffering agent used in biology and biochemistry. The pKa of HEPPS is 8.00. It is ones of Good's buffers.
Research on mice with Alzheimers disease-like amyloid beta plaques has shown that HEPPS can cause the plaques to break up, reversing some of the symptoms in the mice. HEPPS was reported to dissociate amyloid beta oligomers in patients plasma samples enabling blood diagnosis of Alzheimer's disease. | 1 | Applied and Interdisciplinary Chemistry |
This article provides an error analysis of time discretization applied to spatially discrete approximation of the stationary and nonstationary Navier-Stokes equations. The nonlinearity of the convection term is the main problem in solving a stationary or nonstationary Navier-Stokes equation or Euler equation problems. Stoke incorporated ‘the method of artificial compressibility’ to solve these problems. | 1 | Applied and Interdisciplinary Chemistry |
Between 1840 and 1843, Joule carefully studied the heat produced by an electric current. From this study, he developed Joules laws of heating, the first of which is commonly referred to as the Joule effect. Joules first law expresses the relationship between heat generated in a conductor and current flow, resistance, and time. | 0 | Theoretical and Fundamental Chemistry |
Pyridine is not abundant in nature, except for the leaves and roots of belladonna (Atropa belladonna) and in marshmallow (Althaea officinalis). Pyridine derivatives, however, are often part of biomolecules such as alkaloids.
In daily life, trace amounts of pyridine are components of the volatile organic compounds that are produced in roasting and canning processes, e.g. in fried chicken, sukiyaki, roasted coffee, potato chips, and fried bacon. Traces of pyridine can be found in Beaufort cheese, vaginal secretions, black tea, saliva of those suffering from gingivitis, and sunflower honey. | 0 | Theoretical and Fundamental Chemistry |
* Lactase (breaks down lactose into glucose and galactose)
* Maltase (breaks down maltose into 2 glucoses)
* Sucrase (breaks down sucrose into glucose and fructose)
* Trehalase (breaks down trehalose into 2 glucoses)
<br />For a thorough scientific overview of small-intestinal disaccharidases, one can consult chapter 75 of OMMBID. For more online resources and references, see inborn error of metabolism. | 1 | Applied and Interdisciplinary Chemistry |
Multicomponent solvents appeared after World War II in the USSR, and continue to be used and produced in the post-Soviet states. These solvents may have one or more applications, but they are not universal preparations. | 1 | Applied and Interdisciplinary Chemistry |
The related ion is the most prevalent molecular ion in interstellar space. It is believed to have played a crucial role in the cooling of early stars in the history of the Universe through its ability readily to absorb and emit photons. One of the most important chemical reactions in interstellar space is + e H and then H + H. | 0 | Theoretical and Fundamental Chemistry |
In the process of photosynthesis, the phosphorylation of ADP to form ATP using the energy of sunlight is called photophosphorylation. Cyclic photophosphorylation occurs in both aerobic and anaerobic conditions, driven by the main primary source of energy available to living organisms, which is sunlight. All organisms produce a phosphate compound, ATP, which is the universal energy currency of life. In photophosphorylation, light energy is used to pump protons across a biological membrane, mediated by flow of electrons through an electron transport chain. This stores energy in a proton gradient. As the protons flow back through an enzyme called ATP synthase, ATP is generated from ADP and inorganic phosphate. ATP is essential in the Calvin cycle to assist in the synthesis of carbohydrates from carbon dioxide and NADPH. | 0 | Theoretical and Fundamental Chemistry |
Rothalpy has applications in turbomachinery and study of relative flows in rotating systems.
One such application is that for steady, adiabatic and irreversible flow in a turbomachine, the value of rothalpy across a blade remains constant along a flow streamline:
so Euler equation of turbomachinery can be written in terms of rothalpy.
This form of the Euler work equation shows that, for rotating blade rows, the relative stagnation enthalpy is constant through the blades provided the blade speed is constant. In other words, , if the radius of a streamline passing through the blades stays the same. This result is important for analyzing turbomachinery flows in the relative frame of reference. | 1 | Applied and Interdisciplinary Chemistry |
A thermodynamic system is a body of matter and/or radiation separate from its surroundings that can be studied using the laws of thermodynamics.
Thermodynamic systems can be passive and active according to internal processes. According to internal processes, passive systems and active systems are distinguished: passive, in which there is a redistribution of available energy, active, in which one type of energy is converted into another.
Depending on its interaction with the environment, a thermodynamic system may be an isolated system, a closed system, or an open system. An isolated system does not exchange matter or energy with its surroundings. A closed system may exchange heat, experience forces, and exert forces, but does not exchange matter. An open system can interact with its surroundings by exchanging both matter and energy.
The physical condition of a thermodynamic system at a given time is described by its state, which can be specified by the values of a set of thermodynamic state variables. A thermodynamic system is in thermodynamic equilibrium when there are no macroscopically apparent flows of matter or energy within it or between it and other systems. | 0 | Theoretical and Fundamental Chemistry |
Until the last quarter of the 20th century, the real existence of the bismuthyl ion was not in doubt; it was fully present in all reference books and manuals on inorganic chemistry, including German and English ones. The most famous compound of this class was considered bismuthyl chloride, the chemical properties of which were studied in detail and were considered titular for all other bismuth compounds. In addition, the compound with the calculation formula BiOCl exists in nature in the form of bismoclitea, one of the secondary metamorphosed minerals from the class of halides.
In the fundamental three-volume book “Modern Inorganic Chemistry” by Nobel laureate Frank Cotton and Geoffrey Wilkinson, summarizing the latest achievements of science in the first half of the 20th century, the real existence of the bismuthyl cation is not only not questioned, but is not even discussed in any detail. This inorganic radical is mentioned without further explanation and is by default considered a legacy of the fundamental corpus of inorganic chemistry of the 19th century. First of all, the authors note that of the entire group of pnictogens, only bismuth has a truly extensive and detailed cation chemistry. According to the authors, aqueous solutions of bismuth salts contain well-defined hydrated cations. Moreover, bismuthyl in the newest version at that time also acquires quasi-polymeric properties, connecting into chains or hexagons. For example, in neutral perchlorate solutions the main ions are [BiO] or its hydrated form [Bi(OH)], and at higher pH values [BiO(OH)] are formed. | 1 | Applied and Interdisciplinary Chemistry |
Soluforce is used for the following applications:
* Oil and/or gas flowlines
* Oil field waste water disposal lines
* Oil field injection lines
* Offshore water injection risers
* Offshore oil flowlines
* High pressure Water injection lines
* High pressure gas transport lines
* Relining existing pipes
Although these kind of pipes have been developed for the oil and gas industry, they are also used for domestic gas, mining, Carbon dioxide| and hydrogen applications. | 1 | Applied and Interdisciplinary Chemistry |
The theory is a powerful theoretical framework used to predict and analyze the intensities of electronic transitions within the 4f electron shell of rare-earth ions in solid-state materials. The transitions, which are parity forbidden in free ions, are made partially allowed in a solid matrix due to the effects of the crystal field. This field induces a mixing of electronic states, allowing transitions that would not occur in an isolated ion. The theory quantitatively describes this mixing using three phenomenological parameters, denoted as (where ). These parameters account for the asymmetric nature of the crystal field and enable the calculation of transition probabilities, oscillator strengths, and radiative lifetimes of excited states, which are crucial for the development of various photonic devices such as lasers and optical amplifiers.
The theory is named after Brian G. Judd and George S. Ofelt, who independently developed it in 1962. It has become a standard tool in the field of lanthanide spectroscopy, providing insights into the optical properties of rare earth-doped materials and aiding in the design of materials for color display systems, fluorescent lamps, and lasers. | 0 | Theoretical and Fundamental Chemistry |
Fecal sludge management (FSM) (or faecal sludge management in British English) is the storage, collection, transport, treatment and safe end use or disposal of fecal sludge. Together, the collection, transport, treatment and end use of fecal sludge constitute the "value chain" or "service chain" of fecal sludge management. Fecal sludge is defined very broadly as what accumulates in onsite sanitation systems (e.g. pit latrines, septic tanks and container-based solutions) and specifically is not transported through a sewer. It is composed of human excreta, but also anything else that may go into an onsite containment technology, such as flushwater, cleansing materials (e.g. toilet paper and anal cleansing materials), menstrual hygiene products, grey water (i.e. bathing or kitchen water, including fats, oils and grease), and solid waste. Fecal sludge that is removed from septic tanks is called septage.
It is estimated that one-third of the world's population is served by onsite sanitation, and that in low-income countries less than 10% of urban areas are served by sewers. In low-income countries, the majority of fecal sludge is discharged untreated into the urban environment, placing a huge burden on public and environmental health. Hence, FSM plays a critical role in safely managed sanitation and the protection of public health. FSM services are provided by a range of formal and informal private sector services providers, local governments, water authorities, and public utilities. This can also result in unreliable services with relatively high costs at the household level.
Although new technology now allows for fecal sludge to be treated onsite (see Mobile Treatment Units below) the majority of fecal sludge is collected and either disposed of into the environment or treated offsite. Fecal sludge collection can be arranged on a scheduled basis or on a call-for-service basis (also known as on-demand, on-request, or non-scheduled services). The collected fecal sludge may be manually or mechanically emptied, and then transported to treatment plants with a vacuum truck, a tank and pump mounted on a flatbed truck, a small tank pulled by a motorcycle, or in containers on a handcart. The wider use of multiple decentralized sludge treatment facilities within cities (to avoid long haulage distances) is currently being researched and piloted.
Fecal sludge is different to wastewater and cannot simply be co-treated at sewage treatment plants. Small additions of fecal sludge are possible if plants are underutilized and able to take the additional load, and facilities to separate liquids and solids are available. A variety of mechanized and non-mechanized processing technologies may be used, including settling tanks, planted and unplanted drying beds, and waste stabilization ponds. The treatment process can produce resource recovery end-products such as treated effluent that can be used for irrigation, co-composting as a soil conditioner, anaerobic digestion for the production of biogas, forms of dry-combustion fuel such as pellets or biochar, charcoal, biodiesel, sludge and plants or protein production as animal fodder. | 1 | Applied and Interdisciplinary Chemistry |
The silver-stained spots on the microarray are clearly visible. By using a transmission microarray scanner, the signals are transformed into digital values which are finally available as an image file. | 1 | Applied and Interdisciplinary Chemistry |
Grignard is most noted for devising a new method for generating carbon-carbon bonds using magnesium to couple ketones and alkyl halides. This reaction is valuable in organic synthesis. It occurs in two steps:
#Formation of the "Grignard reagent", which is an organomagnesium compound made by the reaction of an organohalide, R-X (R = alkyl or aryl; and X is a halide, usually bromide or iodide) with magnesium metal. The Grignard reagent is usually described with the general chemical formula R-Mg-X, although its structure is more complex.
#Addition of the carbonyl, in which a ketone or an aldehyde is added to the solution containing the Grignard reagent. The carbon atom that is bonded to Mg transfers to the carbonyl carbon atom, and the oxygen of the carbonyl carbon becomes attached to the magnesium to give an alkoxide. The process is an example of a nucleophilic addition to a carbonyl. After the addition, the reaction mixture is treated with aqueous acid to give an alcohol, and the magnesium salts are subsequently discarded. | 0 | Theoretical and Fundamental Chemistry |
Theoretical quantum-mechanical calculations become rather accurate to describe the energy structure of some simple electronic configurations. The results of theoretical developments were summarized by Condon and Shortley in 1935.
Edlén thoroughly analyzed spectra of MIA for many chemical elements and derived regularities in energy structures of MIA for many isoelectronic sequences (ions with the same number of electrons, but different nuclear charges). Spectra of rather high ionization stages (e.g. Cu XIX) were observed.
The most exciting event was in 1942, when Edlén proved the identification of some solar coronal lines on the basis of his precise analyses of spectra of MIA. This implied that the solar corona has a temperature of a million degrees, and strongly advanced understanding of solar and stellar physics.
After the WW II experiments on balloons and rockets were started to observe the VUV radiation of the Sun. (See X-ray astronomy). More intense research continued since 1960 including spectrometers on satellites.
In the same period the laboratory spectroscopy of MIA becomes relevant as a diagnostic tool for hot plasmas of thermonuclear devices (see Nuclear fusion) which begun with building Stellarator in 1951 by Spitzer, and continued with tokamaks, z-pinches and the laser produced plasmas. Progress in ion accelerators stimulated beam-foil spectroscopy as a means to measure lifetimes of exited states of MIA. Many various data on highly exited energy levels, autoionization and inner-core ionization states were obtained. | 0 | Theoretical and Fundamental Chemistry |
It was proposed that increased synthesis of (p)ppGpp would cause polyphosphate (PolyP) accumulation in E. coli. The alarmone could interact with exopolyphosphatase PPX, which would inhibit the hydrolysis of PolyP, thus causing its accumulation in bacteria. Although it has recently been shown that it is actually DksA and not (p)ppGpp that causes this buildup. It has been shown in Pseudomonas aeruginosa that the phoU mutant (phoU belongs to the Pho Regulon) synthesizes more (p)ppGpp and this would be one of the reasons that it accumulates more polyphosphate. | 1 | Applied and Interdisciplinary Chemistry |
If the particles interact via identical pairwise potentials: , the average internal energy per particle is: | 0 | Theoretical and Fundamental Chemistry |
Sintering in practice is the control of both densification and grain growth. Densification is the act of reducing porosity in a sample, thereby making it denser. Grain growth is the process of grain boundary motion and Ostwald ripening to increase the average grain size. Many properties (mechanical strength, electrical breakdown strength, etc.) benefit from both a high relative density and a small grain size. Therefore, being able to control these properties during processing is of high technical importance. Since densification of powders requires high temperatures, grain growth naturally occurs during sintering. Reduction of this process is key for many engineering ceramics. Under certain conditions of chemistry and orientation, some grains may grow rapidly at the expense of their neighbours during sintering. This phenomenon, known as abnormal grain growth (AGG), results in a bimodal grain size distribution that has consequences for the mechanical, dielectric and thermal performance of the sintered material.
For densification to occur at a quick pace it is essential to have (1) an amount of liquid phase that is large in size, (2) a near complete solubility of the solid in the liquid, and (3) wetting of the solid by the liquid. The power behind the densification is derived from the capillary pressure of the liquid phase located between the fine solid particles. When the liquid phase wets the solid particles, each space between the particles becomes a capillary in which a substantial capillary pressure is developed. For submicrometre particle sizes, capillaries with diameters in the range of 0.1 to 1 micrometres develop pressures in the range of to for silicate liquids and in the range of to for a metal such as liquid cobalt.
Densification requires constant capillary pressure where just solution-precipitation material transfer would not produce densification. For further densification, additional particle movement while the particle undergoes grain-growth and grain-shape changes occurs. Shrinkage would result when the liquid slips between particles and increases pressure at points of contact causing the material to move away from the contact areas, forcing particle centers to draw near each other.
The sintering of liquid-phase materials involves a fine-grained solid phase to create the needed capillary pressures proportional to its diameter, and the liquid concentration must also create the required capillary pressure within range, else the process ceases. The vitrification rate is dependent upon the pore size, the viscosity and amount of liquid phase present leading to the viscosity of the overall composition, and the surface tension. Temperature dependence for densification controls the process because at higher temperatures viscosity decreases and increases liquid content. Therefore, when changes to the composition and processing are made, it will affect the vitrification process. | 1 | Applied and Interdisciplinary Chemistry |
The mound system includes a septic tank, a dosing chamber, and a mound. Wastes from homes are sent to the septic tank where the solid portion sinks to the bottom of the tank. Effluents are sent to a second tank called a dosing chamber, from which they are distributed to the mound at a metered rate (in doses). Wastewater is partially treated as it moves through the mound sand. Final treatment and disposal occur in the soil beneath the mound. The mound system does not allow all the effluent to enter the mound at once, accordingly allowing it to clean the effluent more effectively and helping keep the system from failing.
The absorption mound is built in layers. The layer depths are determined by the depth of the limiting layer of the soil, which may be a seasonal water table, bedrock, fragrant, or glacial till. Standards created by Ohio State University state that 24 inches of soil should be above the limiting layer in the soil. A 24-inch layer of specifically sized sand is placed on top of the soil. The distribution pipes that are fed by the dosing chamber are placed on top of the sand in gravel. Then construction fabric and additional soil are placed on top of the gravel to help keep the pipes from freezing. The top layer of soil also allows the mound to be planted with grass or non-woody plants to control erosion
The primary waste liquids cleaning and purification actions in a drain field are performed by a biofilm in the loose fill surrounding the perforated drain tile. If the soil permeability is too low, the liquid is not absorbed fast enough. If the soil permeability is too high or is exposed to fractured bedrock, the wastewater reaches the water table before the biofilm has time to purify the water, contaminating the aquifer. In either situation, the mound system provides an ideal habitat for the biofilm and has the correct permeability to assure slow absorption of effluent into the mound before exiting as purified water into the surrounding environment.
When installing a mound system, the soil in the area where the mound is to be placed will be compacted or disturbed. Any trees that in the mound area are cut away, and the roots and stumps retained. The surface of the area for the mound is then roughened with a chisel plow. This prepares the area for the sand. Work is done from upslope of the mound area so that the ground downslope of the mound does not get compacted. Tyler tables are used to help determine the mound size.
Time dosing is another important aspect of the functioning of the mound system. Short frequent doses of effluent onto sand filters with orifices that are closely spaced helps to improve effluent quality. By contrast, demand dosing releases large amounts of effluent at once, which rapidly passes through the sand. This does not give the biota the proper amount of time to clean the effluent. | 1 | Applied and Interdisciplinary Chemistry |
Construction of MOSE was authorised by the "Comitatone" on 3April 2003 and the associated construction sites opened the same year. Work began simultaneously and continues in parallel at the three inlets of Lido, Malamocco and Chioggia. Work on the structural parts (foundations, mobile barrier abutments, gate housing structures), associated structures (breakwaters, small craft harbours, locks) and parts for operating the system (technical buildings, plant) is now at an advanced stage.
Currently about 4000 people are employed in the construction of MOSE.
As well as the construction sites at the inlets, fabrication of the main components of MOSE (the hinges, the technological heart of the system which constrain the gates to their housing and allow them to move, and the gates) is also proceeding. Restructuring of the buildings and spaces in the area of the Venice Arsenal where maintenance of MOSE and management of the system will be located is also underway. | 1 | Applied and Interdisciplinary Chemistry |
Trimethylenemethane is a neutral, four-carbon molecule composed of four pi bonds; thus, it must be expressed either as a non-Kekulé molecule or a zwitterion. The orbital energy levels of TMM reveal that it possesses singlet and triplet states; generally, these states exhibit different reactivity and selectivity profiles. A singlet (3+2) cycloaddition, when it is concerted, is believed to proceed under frontier orbital control. When electron-rich TMMs are involved, the A orbital serves as the HOMO (leading to fused products if the TMM is cyclic). When electron-poor (or unsubstituted) TMMs are involved, the S orbital serves as the HOMO (leading to bridged products if the TMM is cyclic). Cycloadditions involving the triplet state are stepwise, and usually result in configurational scrambling in the two-atom component.
The rapid closure of TMMs to methylidenecyclopropanes is a general problem that affects the rate and yield of (3+2) cycloaddition reactions involving this class of reaction intermediates. The problem is generally less severe for five-membered, cyclic TMMs due to ring strain in the corresponding MCPs. When ring closure and TMM dimerization can be controlled, (3+2) cycloaddition affords isomeric mixtures of methylenecyclopentanes. Three classes of compounds have been used to generate synthetically useful TMM intermediates: diazenes, silyl-substituted allylic acetates and methylenecyclopropenes. Transition metal catalysis can be used with the latter two classes, although polar MCPs may open under light or heat (see below). | 0 | Theoretical and Fundamental Chemistry |
Wastewater enters the basin and very fine particles in the water are separated by means of gravity. The water must be in the basin long enough for the desired particle size to be removed. Smaller particles require longer periods for removal and thus larger basins. In some basins a flocculant may be added to help smaller particles stick together and form larger particles. Stokes law can be used to calculate the size of a settling basin needed in order to remove a desired particle size. Stokes law gives a settling velocity determining an effective settling basin depth; so solids removal depends upon effective settling basin surface area, while the depth component of settling basin volume remains important for storage of settled solids.
Translation of required settling time surface area to settling basin geometry requires consideration of short circuiting and turbulence induced by wind, bottom scour, or inlet and overflow design. Settling basin geometry is important because effective time of settling within the basin will be the time a volume of water spends in non-turbulent conditions before reaching the settling basin overflow. Median time is always less than the mean time calculated by dividing available volume by anticipated flow. The median time of passage through a short, wide settling basin may be significantly less than the median time of passage through a long, narrow settling basin. Settling basins with overflow structures near the entrance points may hold a large volume of stagnant water while newly admitted water rapidly reaches the overflow point before settling can occur. Effective surface area for settling seldom extends perpendicularly more than a tenth the distance of a flow line from basin entrance to overflow unless baffles are installed. Effective surface area and geometry may change as accumulating sediment fills part of the originally constructed volume. Short cut channels may rapidly form through heavier sediment accumulations near the entrance to the settling basin. Flow through shallow portions of the settling basin may cause turbulence resuspending sediment from the bottom of the basin. Two feet has been recommended as a minimum settling basin depth to avoid bottom scour. | 1 | Applied and Interdisciplinary Chemistry |
Many forms of oxyhydrogen lamps have been described, such as the limelight, which used an oxyhydrogen flame to heat a piece of lime to white hot incandescence. Because of the explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting. | 0 | Theoretical and Fundamental Chemistry |
The National Research Council's 2006 report emphasized that accurate communication of results is essential for the proper use of biomonitoring surveys, but at the same time noted "there is no accepted standard for good biomonitoring communications." In 2007, the Boston University School of Public Health organized a panel on this topic.
An expert panel on Biomonitoring Equivalents has published guidelines for communicating information to the general public and health care providers.
Charles McKay of the Connecticut Poison Control Center is interviewed in a video titled "A Medical Doctor's Perspective on Biomonitoring", which is focused on helping the general public better understand biomonitoring. | 1 | Applied and Interdisciplinary Chemistry |
When discussing the properties of acids it is usual to specify equilibrium constants as acid dissociation constants, denoted by K, with numerical values given the symbol pK.
On the other hand, association constants are used for bases.
However, general purpose computer programs that are used to derive equilibrium constant values from experimental data use association constants for both acids and bases. Because stability constants for a metal-ligand complex are always specified as association constants, ligand protonation must also be specified as an association reaction. The definitions show that the value of an acid dissociation constant is the reciprocal of the value of the corresponding association constant:
Notes
# For a given acid or base in water, , the self-ionization constant of water.
# The association constant for the formation of a supramolecular complex may be denoted as K; in such cases "a" stands for "association", not "acid".
# For polyprotic acids, the numbering of stepwise association constants is the reverse of the numbering of the dissociation constants. For example, for phosphoric acid (details in the polyprotic acids section below): | 0 | Theoretical and Fundamental Chemistry |
The Conservation of Vector Current hypothesis was created out of the Gamow–Teller theory. The Fermi decay is the result of a vector current and is dominant in the decay of the neutron to a proton while the Gamow–Teller decay is an axial-current transition. Conservation of Vector Current is the assumption that the weak vector current responsible for the decay is conserved. Another observation is that the Fermi transitions illustrate how the nucleons inside the nucleus interact as free particles despite being surrounded by mesons mediating the nuclear force. This is useful in considering the barrier tunnelling mechanism involved with alpha decay and in deriving the Geiger–Nuttall law. | 0 | Theoretical and Fundamental Chemistry |
Adair Crawford FRS FRSE (174829 July 1795), a chemist and physician, was a pioneer in the development of calorimetric methods for measuring the specific heat capacity of substances and the heat of chemical reactions. In his influential 1779 book "Experiments and Observations on Animal Heat", Crawford presented new experiments proving that respiratory gas exchange in animals is a combustion (two years after Antoine Lavoisiers influential "On combustion in general'"). Crawford also was involved in the discovery of the element strontium. | 1 | Applied and Interdisciplinary Chemistry |
In the early 20th century, galvanized piping replaced previously-used cast iron and lead in cold-water plumbing. Typically, galvanized piping rusts from the inside out, building up layers of plaque on the inside of the piping, causing both water pressure problems and eventual pipe failure. These plaques can flake off, leading to visible impurities in water and a slight metallic taste. The life expectancy of galvanized piping is about 40–50 years, but it may vary on how well the pipes were built and installed. Pipe longevity also depends on the thickness of zinc in the original galvanizing, which ranges on a scale from G01 to G360. | 1 | Applied and Interdisciplinary Chemistry |
Innovative remediation techniques used at distressed brownfields in recent years include in situ thermal remediation, bioremediation and in situ oxidation. Often, these strategies are used in conjunction with each other or with other remedial strategies such as soil vapor extraction. In this process, vapor from the soil phase is extracted from soils and treated, which has the effect of removing contaminants from the soils and groundwater beneath a site. Binders can be added to contaminated soil to prevent chemical leaching. Some brownfields with heavy metal contamination have even been cleaned up through an innovative approach called phytoremediation, which uses deep-rooted plants to soak up metals in soils into the plant structure as the plant grows. After they reach maturity, the plants – which now contain the heavy metal contaminants in their tissues – are removed and disposed of as hazardous waste.
Research is under way to see if some brownfields can be used to grow crops, specifically for the production of biofuels. Michigan State University, in collaboration with DaimlerChrysler and NextEnergy, has small plots of soybean, corn, canola, and switchgrass growing in a former industrial dump site in Oakland County, Michigan. The intent is to see if the plants can serve two purposes simultaneously: assist with phytoremediation, and contribute to the economical production of biodiesel and/or ethanol fuel.
The regeneration of brownfields in the United Kingdom and in other European countries has gained prominence due to greenfield land restrictions as well as their potential to promote the urban renaissance. Development of brownfield sites also presents an opportunity to reduce the environmental impact on communities, and considerable assessments need to take place in order to evaluate the size of this opportunity. | 1 | Applied and Interdisciplinary Chemistry |
*Density: 2.203 g/cm
*Hardness: 5.3–6.5 (Mohs scale), 8.8 GPa
*Tensile strength: 48.3 MPa
*Compressive strength: > 1.1 GPa
*Bulk modulus: ~37 GPa
*Rigidity modulus: 31 GPa
*Young's modulus: 71.7 GPa
*Poisson's ratio: 0.17
*Lamé elastic constants: λ = 15.87 GPa, μ = 31.26 GPa
*Coefficient of thermal expansion: 5.5 × 10/K (average 20–320 °C)
*Thermal conductivity: 1.3 W/(m·K)
*Specific heat capacity: 45.3 J/(mol·K)
*Softening point: ≈ 1665 °C
*Annealing point: ≈ 1140 °C
*Strain point: 1070 °C
*Electrical resistivity: > 10 Ω·m
*Dielectric constant: 3.75 at 20 °C 1 MHz
*Dielectric loss factor: less than 0.0004 at 20 °C 1 MHz typically 6 × 10 at 10 GHz
*Dielectric strength: 250–400 kV/cm at 20 °C
*Magnetic susceptibility: −11.28 × 10 (SI, 22 °C)
*Hamaker constant: A = 6.5 × 10 J.
*Surface tension: 0.300 N/m at 1800–2400 °C
*Index of refraction: n = 1.4585 (at 587.6 nm)
*Change of refractive index with temperature: 1.28 × 10/K (20–30 °C)
*Stress-optic coefficients: p = 0.113, p = 0.252.
*Abbe number: Vd = 67.82 | 1 | Applied and Interdisciplinary Chemistry |
There is an increased risk of central nervous system depression when eszopiclone is taken together with other CNS depressant agents, including antipsychotics, sedative hypnotics (like barbiturates or benzodiazepines), antihistamines, opioids, phenothiazines, and some antidepressants. There is also increased risk of central nervous system depression with other medications that inhibit the metabolic activities of the CYP3A4 enzyme system of the liver. Medications that inhibit this enzyme system include nelfinavir, ritonavir, ketoconazole, itraconazole and clarithromycin. Alcohol also has an additive effect when used concurrently with eszopiclone. Eszopiclone is most effective if it is not taken after a heavy meal with high fat content. | 0 | Theoretical and Fundamental Chemistry |
One of the hallmarks of cancer is altered metabolism or deregulating cellular energetics. Cancers cells often have reprogrammed their glucose metabolism to perform lactic acid fermentation, in the presence of oxygen, rather than send the pyruvate made through glycolysis to the mitochondria. This is referred to as the Warburg effect and is associated with high consumption of glucose and a high rate of glycolysis. ATP production in these cancer cells is often only through the process of glycolysis and pyruvate is broken down by the fermentation process in the cell's cytoplasm.
This phenomenon is often seen as counterintuitive, since cancer cells have higher energy demands due to the continued proliferation and respiration produces significantly more ATP than glycolysis alone (fermentation produces no additional ATP). Typically, there is an up-regulation in glucose transporters and enzymes in the glycolysis pathway (also seen in yeast). There are many parallel aspects of aerobic fermentation in tumor cells that are also seen in Crabtree-positive yeasts. Further research into the evolution of aerobic fermentation in yeast such as S. cerevisiae can be a useful model for understanding aerobic fermentation in tumor cells. This has a potential for better understanding cancer and cancer treatments. | 1 | Applied and Interdisciplinary Chemistry |
Entropy is a function of state, and therefore the entropy change can be computed directly from the knowledge of the final and initial equilibrium states. For an ideal gas, the change in entropy is the same as for isothermal expansion where all heat is converted to work:
For an ideal monatomic gas, the entropy as a function of the internal energy , volume , and number of moles is given by the Sackur–Tetrode equation:
In this expression is the particle mass and Planck's constant. For a monatomic ideal gas , with the molar heat capacity at constant volume.
A second way to evaluate the entropy change is to choose a route from the initial state to the final state where all the intermediate states are in equilibrium. Such a route can only be realized in the limit where the changes happen infinitely slowly. Such routes are also referred to as quasistatic routes. In some books one demands that a quasistatic route has to be reversible, here we don't add this extra condition. The net entropy change from the initial state to the final state is independent of the particular choice of the quasistatic route, as the entropy is a function of state.
Here is how we can effect the quasistatic route. Instead of letting the gas undergo a free expansion in which the volume is doubled, a free expansion is allowed in which the volume expands by a very small amount . After thermal equilibrium is reached, we then let the gas undergo another free expansion by and wait until thermal equilibrium is reached. We repeat this until the volume has been doubled. In the limit to zero, this becomes an ideal quasistatic process, albeit an irreversible one. Now, according to the fundamental thermodynamic relation, we have:
As this equation relates changes in thermodynamic state variables, it is valid for any quasistatic change, regardless of whether it is irreversible or reversible. For the above defined path we have that and thus , and hence the increase in entropy for the Joule expansion is
A third way to compute the entropy change involves a route consisting of reversible adiabatic expansion followed by heating. We first let the system undergo a reversible adiabatic expansion in which the volume is doubled. During the expansion, the system performs work and the gas temperature goes down, so we have to supply heat to the system equal to the work performed to bring it to the same final state as in case of Joule expansion.
During the reversible adiabatic expansion, we have . From the classical expression for the entropy it can be derived that the temperature after the doubling of the volume at constant entropy is given as:
for the monoatomic ideal gas. Heating the gas up to the initial temperature increases the entropy by the amount
We might ask what the work would be if, once the Joule expansion has occurred, the gas is put back into the left-hand side by compressing it. The best method (i.e. the method involving the least work) is that of a reversible isothermal compression, which would take work given by
During the Joule expansion the surroundings do not change, i.e. the entropy of the surroundings is constant. Therefore the entropy change of the so-called "universe" is equal to the entropy change of the gas which is . | 0 | Theoretical and Fundamental Chemistry |
The relation of equilibrium vapor pressure to the saturation vapor pressure can be thought of as a relative humidity measurement for the atmosphere. As P/P increases, vapor will continue to condense inside a given capillary. If P/P decreases, liquid will begin to evaporate into the atmosphere as vapor molecules. The figure below demonstrates four different systems in which P/P is increasing from left to right.
System A → P=0, no vapor is present in the system
System B → P=P, capillary condensation occurs and liquid/vapor equilibrium is reached
System C → P=P, P, as vapor pressure is increased condensation continues in order to satisfy the Kelvin equation
System D → P=P, vapor pressure is increased to its maximum allowed value and the pore is filled completely
This figure is used to demonstrate the concept that by increasing the vapor pressure in a given system, more condensation will occur. In a porous medium, capillary condensation will always occur if P≠0. | 1 | Applied and Interdisciplinary Chemistry |
The development of the Lemieux–Johnson oxidation was preceded by an analogous process, developed by Lemieux and Ernst Von Rudloff (sometimes called the Lemieux-Von Rudloff reaction), which used an aqueous solution of sodium periodate with a low (catalytic) concentration of potassium permanganate. This mixture became known as Lemieux reagent and has been used to determine the position of double bonds and for preparing carbonyl compounds. Unlike the Lemieux–Johnson oxidation, which normally stops at the aldehyde, this older method could continue to give a mixture of aldehydes and carboxylic acids. | 0 | Theoretical and Fundamental Chemistry |
By the time of the 2nd Chapman Conference on the Gaia Hypothesis, held at Valencia, Spain, on 23 June 2000, the situation had changed significantly. Rather than a discussion of the Gaian teleological views, or "types" of Gaia hypotheses, the focus was upon the specific mechanisms by which basic short term homeostasis was maintained within a framework of significant evolutionary long term structural change.
The major questions were:
# "How has the global biogeochemical/climate system called Gaia changed in time? What is its history? Can Gaia maintain stability of the system at one time scale but still undergo vectorial change at longer time scales? How can the geologic record be used to examine these questions?"
# "What is the structure of Gaia? Are the feedbacks sufficiently strong to influence the evolution of climate? Are there parts of the system determined pragmatically by whatever disciplinary study is being undertaken at any given time or are there a set of parts that should be taken as most true for understanding Gaia as containing evolving organisms over time? What are the feedbacks among these different parts of the Gaian system, and what does the near closure of matter mean for the structure of Gaia as a global ecosystem and for the productivity of life?"
# "How do models of Gaian processes and phenomena relate to reality and how do they help address and understand Gaia? How do results from Daisyworld transfer to the real world? What are the main candidates for "daisies"? Does it matter for Gaia theory whether we find daisies or not? How should we be searching for daisies, and should we intensify the search? How can Gaian mechanisms be collaborated with using process models or global models of the climate system that include the biota and allow for chemical cycling?"
In 1997, Tyler Volk argued that a Gaian system is almost inevitably produced as a result of an evolution towards far-from-equilibrium homeostatic states that maximise entropy production, and Axel Kleidon (2004) agreed stating: "...homeostatic behavior can emerge from a state of MEP associated with the planetary albedo"; "...the resulting behavior of a symbiotic Earth at a state of MEP may well lead to near-homeostatic behavior of the Earth system on long time scales, as stated by the Gaia hypothesis". M. Staley (2002) has similarly proposed "...an alternative form of Gaia theory based on more traditional Darwinian principles... In [this] new approach, environmental regulation is a consequence of population dynamics. The role of selection is to favor organisms that are best adapted to prevailing environmental conditions. However, the environment is not a static backdrop for evolution, but is heavily influenced by the presence of living organisms. The resulting co-evolving dynamical process eventually leads to the convergence of equilibrium and optimal conditions". | 0 | Theoretical and Fundamental Chemistry |
Cellular composites extend stretch-dominated lattices to the ultralight regime (below ten milligrams per cubic centimeter). Performance depends positively on the framework rigidity of the lattice, node connectivity, slenderness of strut members and the scaling of the density cost of mechanical connections.
Conventional fiber composites make truss cores and structural frames, with bonded assembly of substructures or continuous fiber winding. Examples of such truss cores have been reported with continuous two-dimensional (2D) geometric symmetry and nearly ideal but highly anisotropic specific modulus scaling.
Three-dimensional open-cell lattice materials occur in natural and engineered systems, spanning many length scales. Their mechanical properties scale with relative density according to the geometry. They display either stretch-dominated or transverse beam bending-dominated microstructural behavior, based on periodic mechanical models. For Young’s modulus E, ideal stretch-dominated scaling with density ρ follows a proportional law E∝ρ, while common stochastic foams follow a quadratic law E∝ρ2 otherwise associated with transverse beam bending-dominated behavior. At ultralight densities a further reduced cubic scaling law E∝ρ3 is common, such as with aerogels and aerogel composites.
The dependence of scaling on geometry is seen in periodic lattice-based materials that have nearly ideal E∝ρ scaling, with high node connectedness relative to stochastic foams. These structures have previously been implemented only in relatively dense engineered materials. For the ultralight regime the E∝ρ2 scaling seen in denser stochastic cellular materials applies to electroplated tubular nickel micro-lattices, as well as carbon-based open-cell stochastic foams, including carbon microtube aerographite and graphene cork. | 0 | Theoretical and Fundamental Chemistry |
The shape of the molecule is predicted to be an equilateral triangle. Vibrations can occur in the molecule in two ways, firstly the molecule can expand and contract retaining the equilateral triangle shape (breathing), or one atom can move relative to the others distorting the triangle (bending). The bending vibration has a dipole moment and thus couples to infrared radiation. | 0 | Theoretical and Fundamental Chemistry |
The Earth-atmosphere system is radiatively cooled, emitting long-wave (infrared) radiation which balances the absorption of short-wave (visible light) energy from the sun.
Convective transport of heat, and evaporative transport of latent heat are both important in removing heat from the surface and distributing it in the atmosphere. Pure radiative transport is more important higher up in the atmosphere. Diurnal and geographical variation further complicate the picture.
The large-scale circulation of the Earth's atmosphere is driven by the difference in absorbed solar radiation per square meter, as the sun heats the Earth more in the Tropics, mostly because of geometrical factors. The atmospheric and oceanic circulation redistributes some of this energy as sensible heat and latent heat partly via the mean flow and partly via eddies, known as cyclones in the atmosphere. Thus the tropics radiate less to space than they would if there were no circulation, and the poles radiate more; however in absolute terms the tropics radiate more energy to space. | 0 | Theoretical and Fundamental Chemistry |
Although the concept of using a single optical element for analyte regression and detection was suggested in 1986, the first full MOC concept device was published in 1997 from the Myrick group at the University of South Carolina, with a subsequent demonstration in 2001. The technique has received much recognition in the optics industry as a new method to perform optical analysis with advantages for harsh environment sensing. The technique has been applied to Raman spectroscopy, fluorescence spectroscopy, absorbance spectroscopy in the UV-Vis, NIR and MIR, microscopy, reflectance spectroscopy and hyperspectral imaging. In the years since first demonstration, applications have been demonstrated for defence, forensics, monitoring of chemical reactions, environmental monitoring, recycling, food and drug, medical and life sciences, and the petroleum industry. The first published demonstration for use of MOC in the harsh environments, was 2012 with a laboratory study with temperatures from 150F to 350F and pressures from 3000psi to 20,000psi, followed in 2013 with field trials in oil wells. | 0 | Theoretical and Fundamental Chemistry |
Theoretically, IVF could be performed by collecting the contents from the fallopian tubes or uterus after natural ovulation, mixing it with sperm, and reinserting the fertilised ova into the uterus. However, without additional techniques, the chances of pregnancy would be extremely small. The additional techniques that are routinely used in IVF include ovarian hyperstimulation to generate multiple eggs, ultrasound-guided transvaginal oocyte retrieval directly from the ovaries, co-incubation of eggs and sperm, as well as culture and selection of resultant embryos before embryo transfer into a uterus. | 1 | Applied and Interdisciplinary Chemistry |
The stereochemical term enantiotopic refers to the relationship between two groups in a molecule which, if one or the other were replaced, would generate a chiral compound. The two possible compounds resulting from that replacement would be enantiomers.
For example, the two hydrogen atoms attached to the second carbon in butane are enantiotopic. Replacement of one hydrogen atom (colored blue) with a bromine atom will produce (R)-2-bromobutane. Replacement of the other hydrogen atom (colored red) with a bromine atom will produce the enantiomer (S)-2-bromobutane.
Enantiotopic groups are identical and indistinguishable except in chiral environments. For instance, the CH hydrogens in ethanol (CHCHOH) are normally enantiotopic, but can be made different (diastereotopic) if combined with a chiral center, for instance by conversion to an ester of a chiral carboxylic acid such as lactic acid, or if coordinated to a chiral metal center, or if associated with an enzyme active site, since enzymes are constituted of chiral amino acids. Indeed, in the presence of the enzyme LADH, one specific hydrogen is removed from the CH group during the oxidation of ethanol to acetaldehyde, and it gets replaced in the same place during the reverse reaction. The chiral environment needs not be optically pure for this effect.
Enantiotopic groups are mirror images of each other about an internal plane of symmetry. A chiral environment removes that symmetry. Enantiotopic pairs of NMR-active nuclei are also indistinguishable by NMR and produce a single signal.
Enantiotopic groups need not be attached to the same atom. For example, two hydrogen atoms adjacent to the carbonyl group in cis-2,6-dimethylcyclohexanone are enantiotopic; they are related by an internal plane of symmetry passing through the carbonyl group, but deprotonation on one side of the carbonyl group or on the other will generate compounds that are enantiomers. Similarly, the replacement of one or the other with deuterium will generate enantiomers. | 0 | Theoretical and Fundamental Chemistry |
Generally distinct types of unsaturated organic compounds are recognized.
For hydrocarbons:
*alkene (unsaturated) vs alkane (saturated)
*alkyne (unsaturated) vs alkane (saturated)
*arene (unsaturated) vs cycloalkane (saturated)
For organic compounds containing heteroatoms (other than C and H), the list of unsaturated groups is long but some common types are:
*carbonyl, e.g. ketones, aldehydes, esters, carboxylic acids (unsaturated) vs alcohol or ether (saturated)
*nitrile (unsaturated) vs amine (saturated)
*nitro (unsaturated) vs amine (saturated)
Unsaturated compounds generally carry out typical addition reactions that are not possible with saturated compounds such as alkanes. A saturated organic compound has only single bonds between carbon atoms. An important class of saturated compounds are the alkanes. Many saturated compounds have functional groups, e.g., alcohols. | 0 | Theoretical and Fundamental Chemistry |
The Reef Ball Foundation manufactures reef balls for open ocean deployment in sizes from in diameter and in weight. Reef balls are hollow, and typically have several convex-concave holes of varying sizes to most closely approximate natural coral reef conditions by creating whirlpools. Reef balls are made from pH-balanced microsilica concrete, and are treated to create a rough surface texture, in order to promote settling by marine organisms such as corals, algae, coralline algae and sponges.
Over the last decade, research has been conducted with respect to the ability of artificial reefs to produce or attract biomass, the effectiveness of reef balls in replicating natural habitat, and mitigating disasters. The use of reef balls as breakwaters and for beach stabilization has been extensively studied. | 1 | Applied and Interdisciplinary Chemistry |
Carbopalladations can be a description of the elementary step of a reaction catalyzed by a palladium catalyst (Mizoroki-Heck reaction) and can also refer to a carbometalation reaction with a palladium catalyst (alkene difunctionalization, hydrofunctionalization, or reductive Heck) | 0 | Theoretical and Fundamental Chemistry |
Recent studies have shown that SK channels do not only regulate afterhyperpolarization, they also have an effect on synaptic plasticity. This is the activity-dependent adaptation of the strength of synaptic transmission. Synaptic plasticity is an important mechanism underlying learning and memory processes. Apamin is expected to influence these processes by inhibiting SK channels. It has been shown that apamin enhances learning and memory in rats and mice. This may provide a basis for the use of apamin as a treatment for memory disorders and cognitive dysfunction. However, due to the risk of toxic effects, the therapeutic window is very narrow.
SK channel blockers may have a therapeutic effect on Parkinson's disease. Dopamine, which is depleted in this disease, will be released from midbrain dopaminergic neurons when these SK channels are inhibited. SK channels have also been proposed as targets for the treatment of epilepsy, emotional disorders and schizophrenia. | 1 | Applied and Interdisciplinary Chemistry |
Many methods exist for the preparation of ketones in industrial scale and academic laboratories. Ketones are also produced in various ways by organisms; see the section on biochemistry below.
In industry, the most important method probably involves oxidation of hydrocarbons, often with air. For example, a billion kilograms of cyclohexanone are produced annually by aerobic oxidation of cyclohexane. Acetone is prepared by air-oxidation of cumene.
For specialized or small scale organic synthetic applications, ketones are often prepared by oxidation of secondary alcohols:
Typical strong oxidants (source of "O" in the above reaction) include potassium permanganate or a Cr(VI) compound. Milder conditions make use of the Dess–Martin periodinane or the Moffatt–Swern methods.
Many other methods have been developed, examples include:
* By geminal halide hydrolysis.
* By hydration of alkynes. Such processes occur via enols and require the presence of an acid and mercury(II) sulfate (). Subsequent enol–keto tautomerization gives a ketone. This reaction always produces a ketone, even with a terminal alkyne, the only exception being the hydration of acetylene, which produces acetaldehyde.
*From Weinreb Amides using stoichiometric organometallic reagents.
* Aromatic ketones can be prepared in the Friedel–Crafts acylation, the related Houben–Hoesch reaction, and the Fries rearrangement.
* Ozonolysis, and related dihydroxylation/oxidative sequences, cleave alkenes to give aldehydes or ketones, depending on alkene substitution pattern.
* In the Kornblum–DeLaMare rearrangement ketones are prepared from peroxides and base.
* In the Ruzicka cyclization, cyclic ketones are prepared from dicarboxylic acids.
* In the Nef reaction, ketones form by hydrolysis of salts of secondary nitro compounds.
* In the Fukuyama coupling, ketones form from a thioester and an organozinc compound.
* By the reaction of an acid chloride with organocadmium compounds or organocopper compounds.
* The Dakin–West reaction provides an efficient method for preparation of certain methyl ketones from carboxylic acids.
* Ketones can be prepared by the reaction of Grignard reagents with nitriles, followed by hydrolysis.
* By decarboxylation of carboxylic anhydride.
* Ketones can be prepared from haloketones in reductive dehalogenation of halo ketones.
* In ketonic decarboxylation symmetrical ketones are prepared from carboxylic acids.
* Hydrolysis of unsaturated secondary amides, β-Keto acid esters, or β-diketones (the acetoacetic ester synthesis).
* Acid-catalysed rearrangement of 1,2-diols, or Criegee oxidation of the same. | 0 | Theoretical and Fundamental Chemistry |
Reverse transcriptases were discovered by Howard Temin at the University of Wisconsin–Madison in Rous sarcoma virions and independently isolated by David Baltimore in 1970 at MIT from two RNA tumour viruses: murine leukemia virus and again Rous sarcoma virus. For their achievements, they shared the 1975 Nobel Prize in Physiology or Medicine (with Renato Dulbecco).
Well-studied reverse transcriptases include:
* HIV-1 reverse transcriptase from human immunodeficiency virus type 1 () has two subunits, which have respective molecular weights of 66 and 51 kDas.
* M-MLV reverse transcriptase from the Moloney murine leukemia virus is a single 75 kDa monomer.
* AMV reverse transcriptase from the avian myeloblastosis virus also has two subunits, a 63 kDa subunit and a 95 kDa subunit.
* Telomerase reverse transcriptase that maintains the telomeres of eukaryotic chromosomes. | 1 | Applied and Interdisciplinary Chemistry |
The Debye–Hückel theory was proposed by Peter Debye and Erich Hückel as a theoretical explanation for departures from ideality in solutions of electrolytes and plasmas.
It is a linearized Poisson–Boltzmann model, which assumes an extremely simplified model of electrolyte solution but nevertheless gave accurate predictions of mean activity coefficients for ions in dilute solution. The Debye–Hückel equation provides a starting point for modern treatments of non-ideality of electrolyte solutions. | 0 | Theoretical and Fundamental Chemistry |
Development of the chromatogram is done by allowing the solvent to travel down the paper. Here, the mobile phase is placed in a solvent holder at the top. The spot is kept at the top and solvent flows down the paper from above. | 0 | Theoretical and Fundamental Chemistry |
Gravimetric biosensors use the basic principle of a response to a change in mass. Most gravimetric biosensors use thin piezoelectric quartz crystals, either as resonating crystals (QCM), or as bulk/surface acoustic wave (SAW) devices. In the majority of these the mass response is inversely proportional to the crystal thickness. Thin polymer films are also used in which biomolecules can be added to the surface with known surface mass. Acoustic waves can be projected to the thin film to produce an oscillatory device, which then follows an equation that is nearly identical to the Sauerbrey equation used in the QCM method. Biomolecules, such as proteins or antibodies can bind and its change in mass gives a measureable signal proportional to the presence of the target analyte in the sample. | 1 | Applied and Interdisciplinary Chemistry |
An Oligopeptidase is an enzyme that cleaves peptides but not proteins. This property is due to its structure: the active site of this enzyme is located at the end of a narrow cavity which can only be reached by peptides. | 1 | Applied and Interdisciplinary Chemistry |
Hybridization is the process of complementary base pairs binding to form a double helix. Melting is the process by which the interactions between the strands of the double helix are broken, separating the two nucleic acid strands. These bonds are weak, easily separated by gentle heating, enzymes, or physical force. Melting occurs preferentially at certain points in the nucleic acid. T and A rich sequences are more easily melted than C and G rich regions. Particular base steps are also susceptible to DNA melting, particularly T A and T G base steps. These mechanical features are reflected by the use of sequences such as TATAA at the start of many genes to assist RNA polymerase in melting the DNA for transcription.
Strand separation by gentle heating, as used in PCR, is simple providing the molecules have fewer than about 10,000 base pairs (10 kilobase pairs, or 10 kbp). The intertwining of the DNA strands makes long segments difficult to separate. The cell avoids this problem by allowing its DNA-melting enzymes (helicases) to work concurrently with topoisomerases, which can chemically cleave the phosphate backbone of one of the strands so that it can swivel around the other. Helicases unwind the strands to facilitate the advance of sequence-reading enzymes such as DNA polymerase. | 0 | Theoretical and Fundamental Chemistry |
Herzberg pointed out direct evidence of H molecules in the atmospheres of the outer planets. The atmospheres of the inner planets and of Saturns big moon Titan also show significant CIA in the infrared due to concentrations of nitrogen, oxygen, carbon dioxide and other molecular gases. However, the total CIA contribution of Earths major gases, N and O, to the atmospheres natural greenhouse effect is relatively minor except near the poles. Extrasolar planets have been discovered with hot atmospheres (a thousand kelvin or more) which otherwise resemble Jupiters atmosphere (mixtures of mostly H and He) where relatively strong CIA exists. | 0 | Theoretical and Fundamental Chemistry |
There are numerous types of restriction enzymes, each of which will cut DNA differently. Most commonly used restriction enzymes are Type II restriction endonuclease (See article on Restriction enzymes for examples). There are some that cut a three base pair sequence while others can cut four, six, and even eight. Each enzyme has distinct properties that determine how efficiently it can cut and under what conditions. Most manufacturers that produce such enzymes will often provide a specific buffer solution that contains the unique mix of cations and other components that aid the enzyme in cutting as efficiently as possible. Different restriction enzymes may also have different optimal temperatures under which they function.
Note that for efficient digest of DNA, the restriction site should not be located at the very end of a DNA fragment. The restriction enzymes may require a minimum number of base pairs between the restriction site and the end of the DNA for the enzyme to work efficiently. This number may vary between enzymes, but for most commonly used restriction enzymes around 6–10 base pair is sufficient. | 1 | Applied and Interdisciplinary Chemistry |
Triphosgene's low vapor pressure makes it possible for it to reach concentrations that are considered toxicologically unsafe. While several properties of triphosgene are not yet readily available, it is known that it is very toxic if inhaled. A toxic gas is emitted if it comes in contact with water. There is a lack of information and variability regarding the proper handling of triphosgene. It is assumed to have the same risks as phosgene. | 0 | Theoretical and Fundamental Chemistry |
The chemical consists of rings of 8 sulfur atoms. It adopts a crown conformation with D point group symmetry. The S–S bond lengths are equal, at about 2.05 Å. Octasulfur crystallizes in three distinct polymorphs: rhombohedral, and two monoclinic forms, of which only two are stable at standard conditions. The rhombohedral crystal form is the accepted standard state. The remaining polymorph is only stable between 96 and 115 °C at 100 kPa. Octasulfur forms several allotropes: α-sulfur, β-sulfur, γ-sulfur, and λ-sulfur.
λ-Sulfur is the liquid form of octasulfur, from which γ-sulfur can be crystallised by quenching. If λ-sulfur is crystallised slowly, it will revert to β-sulfur. Since it must have been heated over 115 °C, neither crystallised β-sulfur or γ-sulfur will be pure. The only known method of obtaining pure γ-sulfur is by crystallising from solution.
Octasulfur easily forms large crystals, which are typically yellow and are somewhat translucent. | 1 | Applied and Interdisciplinary Chemistry |
Plasma treatment of surfaces is essentially a dry etching of the surface. This is achieved by filling a chamber with gas, such as oxygen, fluorine, or chlorine, and accelerating ions species from an ion source through plasma. The ion acceleration towards the surface forms deep grooves within the surface. In addition to the topography, plasma treatment can also provide surface functionalization by using different gases to deposit different elements on surfaces. Surface roughness is dependent on the duration of plasma etching. | 0 | Theoretical and Fundamental Chemistry |
Microemulsions have many commercially important uses:
* Water-in-oil microemulsions for some dry cleaning processes
* Floor polishers and cleaners
* Personal care products
* Pesticide formulations
* Cutting oils
* Drugs
Much of the work done on these systems have been motivated by their possible use to mobilize petroleum trapped in porous sandstone for enhanced oil recovery. A fundamental reason for the uses of these systems is that a microemulsion phase sometimes has an ultralow interfacial tension with a separate oil or aqueous phase, which may release or mobilize them from solid phases even in conditions of slow flow or low pressure gradients.
Microemulsions also have industrial applications, one of them being the synthesis of polymers. Microemulsion polymerization is a complex heterogeneous process where transport of monomers, free radicals and other species (such as chain transfer agent, co-surfactant and inhibitors) between the aqueous and organic phases, takes place. Compared with other heterogeneous polymerization processes (suspension or emulsion) microemulsion polymerization is a more complicated system. Polymerization rate is controlled by monomer partitioning between the phases, particle nucleation, and adsorption and desorption of radicals. Particle stability is affected by the amount and type of surfactant and pH of dispersing medium.
It is also used in the process of creating nanoparticles.
The kinetics of microemulsion polymerization has much in common with emulsion polymerization kinetics, the most characteristic feature of which is the compartmentalization, where the radicals growing inside the particles are separated from each other, thus suppressing termination to a high extent and, as a consequence, providing high rates of polymerization. | 0 | Theoretical and Fundamental Chemistry |
The invariance of a Hamiltonian of an isolated system under time translation implies its energy does not change with the passage of time. Conservation of energy implies, according to the Heisenberg equations of motion, that .
or:
Where is the time-translation operator which implies invariance of the Hamiltonian under the time-translation operation and leads to the conservation of energy. | 0 | Theoretical and Fundamental Chemistry |
Source:
*1997 Ahmed Zewail
*1998 Robin M. Hochstrasser
*1999 Richard N. Zare
*2000 Ad Bax
*2001 William A. Klemperer
*2002 Takeshi Oka
*2003 Marilyn E. Jacox
*2004 James K.G. Watson
*2005 Eizi Hirota
*2006 Donald H. Levy
*2007 Michael D. Fayer
*2008 Jack H. Freed
*2009 Paul F. Barbara
*2010 George W. Flynn
*2011 Veronica Vaida
*2012 Robert W. Field
*2013 Steven G. Boxer
*2014 Richard P. Van Duyne
*2015 R. J. Dwayne Miller
*2016 Robert G. Griffin
*2017 David J. Nesbitt
*2018 Richard J. Saykally
*2019 Martin Moskovits
*2020 Angela M. Gronenborn | 0 | Theoretical and Fundamental Chemistry |
Potassium is the main intracellular ion for all types of cells, while having a major role in maintenance of fluid and electrolyte balance. Potassium is necessary for the function of all living cells, and is thus present in all plant and animal tissues. It is found in especially high concentrations within plant cells, and in a mixed diet, it is most highly concentrated in fruits. The high concentration of potassium in plants, associated with comparatively very low amounts of sodium there, historically resulted in potassium first being isolated from the ashes of plants (potash), which in turn gave the element its modern name. The high concentration of potassium in plants means that heavy crop production rapidly depletes soils of potassium, and agricultural fertilizers consume 93% of the potassium chemical production of the modern world economy.
The functions of potassium and sodium in living organisms are quite different. Animals, in particular, employ sodium and potassium differentially to generate electrical potentials in animal cells, especially in nervous tissue. Potassium depletion in animals, including humans, results in various neurological dysfunctions. Characteristic concentrations of potassium in model organisms are: 30–300mM in E. coli, 300mM in budding yeast, 100mM in mammalian cell and 4mM in blood plasma. | 1 | Applied and Interdisciplinary Chemistry |
A thermodynamic limit does not exist in all cases. Usually, a model is taken to the thermodynamic limit by increasing the volume together with the particle number while keeping the particle number density constant. Two common regularizations are the box regularization, where matter is confined to a geometrical box, and the periodic regularization, where matter is placed on the surface of a flat torus (i.e. box with periodic boundary conditions). However, the following three examples demonstrate cases where these approaches do not lead to a thermodynamic limit:
* Particles with an attractive potential that (unlike the Van der Waals force between molecules) doesn't turn around and become repulsive even at very short distances: In such a case, matter tends to clump together instead of spreading out evenly over all the available space. This is the case for gravitational systems, where matter tends to clump into filaments, galactic superclusters, galaxies, stellar clusters and stars.
* A system with a nonzero average charge density: In this case, periodic boundary conditions cannot be used because there is no consistent value for the electric flux. With a box regularization, on the other hand, matter tends to accumulate along the boundary of the box instead of being spread more or less evenly with only minor fringe effects.
* Certain quantum mechanical phenomena near absolute zero temperature present anomalies; e.g., Bose–Einstein condensation, superconductivity and superfluidity.
* Any system that is not H-stable; this case is also called catastrophic. | 0 | Theoretical and Fundamental Chemistry |
Cryo- is from the Ancient Greek κρύος (krúos, “ice, icy cold, chill, frost”). Uses of the prefix Cryo- include: | 1 | Applied and Interdisciplinary Chemistry |
Firstly, mRNA template needs to be isolated for the creation of cDNA libraries. Since mRNA only contains exons, the integrity of the isolated mRNA should be considered so that the protein encoded can still be produced. Isolated mRNA should range from 500 bp to 8 kb. Several methods exist for purifying RNA such as trizol extraction and column purification. Column purification can be done using oligomeric dT nucleotide coated resins, and features of mRNA such as having a poly-A tail can be exploited where only mRNA sequences containing said feature will bind. The desired mRNA bound to the column is then eluted. | 1 | Applied and Interdisciplinary Chemistry |
The concentration of Cu in bulk silicate Earth is ~30 ppm, slightly less than its average concentration (~72 ppm) in fresh mid-oceanic ridge basalt (MORB) glass. and form a variety of sulfides (often in association with Fe), as well as carbonates and hydroxides (e.g., chalcopyrite, chalcocite, cuprite and malachite). In mafic and ultramafic rocks, Cu tends to be concentrated in sulfidic materials. In freshwater, the predominant form of Cu is free Cu; in seawater, Cu complexes with carbonate ligands to form and . | 0 | Theoretical and Fundamental Chemistry |
Proteins that are to be targeted to a particular organelle or for secretion have an N-terminal signal peptide that directs the protein to its final destination. This signal peptide is removed by proteolysis after their transport through a membrane. | 1 | Applied and Interdisciplinary Chemistry |
The metabolism of bacteria is adversely affected by silver ions at concentrations of 0.01–0.1 mg/L. Therefore, even less soluble silver compounds, such as silver chloride, also act as bactericides or germicides, but not the much less soluble silver sulfide. In the presence of atmospheric oxygen, metallic silver also has a bactericidal effect due to the formation of silver oxide, which is soluble enough to cause it. Even objects with a solid silver surface (e.g., table silver, silver coins, or silver foil) have a bactericidal effect. Silver drinking vessels were carried by military commanders on expeditions for protection against disease. It was once common to place silver foil or even silver coins on wounds for the same reason.
Silver sulfadiazine is used as an antiseptic ointment for extensive burns. An equilibrium dispersion of colloidal silver with dissolved silver ions can be used to purify drinking water at sea. Silver is incorporated into medical implants and devices such as catheters. Surfacine (silver iodide) is a relatively new antimicrobial for application to surfaces. Silver-impregnated wound dressings have proven especially useful against antibiotic-resistant bacteria. Silver nitrate is used as a hemostatic, antiseptic and astringent. At one time, many states required that the eyes of newborns be treated with a few drops of silver nitrate to guard against an infection of the eyes called gonorrheal neonatal ophthalmia, which the infants might have contracted as they passed through the birth canal. Silver ions are increasingly incorporated into many hard surfaces, such as plastics and steel, as a way to control microbial growth on items such as toilet seats, stethoscopes, and even refrigerator doors. Among the newer products being sold are plastic food containers infused with silver nanoparticles, which are intended to keep food fresher, and silver-infused athletic shirts and socks, which claim to minimize odors. | 1 | Applied and Interdisciplinary Chemistry |
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), and Valine (Val, V). | 1 | Applied and Interdisciplinary Chemistry |
Nils Gabriel Sefström (2 June 1787 – 30 November 1845) was a Swedish chemist. Sefström was a student of Berzelius and, when studying the brittleness of steel in 1830, he rediscovered a new chemical element, to which he gave the name vanadium.
Vanadium was first discovered by the Spanish-Mexican mineralogist Andrés Manuel del Río in 1801. He named it erythronium. Friedrich Wöhler later confirmed that vanadium and erythronium were the same substance.
Sefström was member of the Royal Swedish Academy of Sciences from 1815.
The Spitzbergen glacier Sefströmbreen, and the mountain ridge of Sefströmkammen, are named after him. | 1 | Applied and Interdisciplinary Chemistry |
The strangeness production and its diagnostic potential as a signature of quark–gluon plasma has been discussed for nearly 30 years. The theoretical work in this field today focuses on the interpretation of the overall particle production data and the derivation of the resulting properties of the bulk of quark–gluon plasma at the time of breakup. The global description of all produced particles can be attempted based on the picture of hadronizing hot drop of quark–gluon plasma or, alternatively, on the picture of confined and equilibrated hadron matter. In both cases one describes the data within the statistical thermal production model, but considerable differences in detail differentiate the nature of the source of these particles. The experimental groups working in the field also like to develop their own data analysis models and the outside observer sees many different analysis results. There are as many as 10–15 different particles species that follow the pattern predicted for the QGP as function of reaction energy, reaction centrality, and strangeness content. At yet higher LHC energies saturation of strangeness yield and binding to heavy flavor open new experimental opportunities. | 0 | Theoretical and Fundamental Chemistry |
The products and services offered by the fine chemical industry fall into two broad categories: (1) "Exclusives", a.k.a. custom manufacturing (CM) and (2) "standard" or "catalogue" products. "Exclusives", provided mostly under contract research or custom manufacturing arrangements, prevail in business with life science companies; "standards" prevail in other target markets. Service-intense custom manufacturing (CM) constitutes the most prominent activity of the fine chemical industry. CM is the antonym of outsourcing. In custom manufacturing, a specialty-chemicals company outsources the process development, pilot plant, and, finally, industrial-scale production of an active ingredient, or a predecessor thereof, to one, or a few, fine chemical companies. The intellectual property of the product, and generally also the manufacturing process, stay with the customer. The customer-supplier relationship is governed by an exclusive supply agreement. At the beginning of cooperation, the customer provides a "tech package", which in its simplest version, includes a laboratory synthesis description and SHE recommendations. In this case, the whole scale up, which comprises a factor of about one million (10 gram → 10 ton quantities), is done by the fine chemical company. | 0 | Theoretical and Fundamental Chemistry |
The Federal Radon Action Plan, also known as FRAP, was created in 2010 and launched in 2011. It was piloted by the U.S. Environmental Protection Agency in conjunction with the U.S. Departments of Health and Human Services, Agriculture, Defense, Energy, Housing and Urban Development, the Interior, Veterans Affairs, and the General Services Administration. The goal set forth by FRAP was to eliminate radon induced cancer that can be prevented by expanding radon testing, mitigating high levels of radon exposure, and developing radon resistant construction, and to meet Healthy People 2020 radon objectives. They identified the barriers to change as limited public knowledge of the dangers of radon exposure, the perceived high costs of mitigation, and the availability of radon testing. As a result, they also identified major ways to create change: demonstrate the importance of testing and the ease of mitigation, provide incentives for testing and mitigation, and build the radon services industry. To complete these goals, representatives from each organization and department established specific commitments and timelines to complete tasks and continued to meet periodically. However, FRAP was concluded in 2016 as The National Radon Action Plan took over. In the final report on commitments, it was found that FRAP completed 88% of their commitments. They reported achieving the highest rates of radon mitigation and new construction mitigation in the United States as of 2014. FRAP concluded that because of their efforts, at least 1.6 million homes, schools, and childcare facilities received direct and immediate positive effects. | 1 | Applied and Interdisciplinary Chemistry |
Iron reducing bacteria reduce ferric iron to ferrous iron under anaerobic conditions. One of the first studies that studied iron fractionation in iron-reducing bacteria studied the bacterium Shewanella algae. S. algae was grown on a ferrihydrite substrate, and was then allowed to reduce iron. The study found that S. algae preferentially reduced Fe over Fe, with a δFe value of -1.3‰.
More recent experiments have studied the bacterium Shewanella putrefaciens and its reduction of Fe(III) in goethite. These studies have found δFe values of -1.2‰ relative to the goethite. The kinetics of this fractionation were also studied in this experiment, and it was suggested that the iron isotope fractionation is likely related to the kinetics of the electron transfer step.
Most studies of other iron reducing bacteria have found δFe values of approximately -1.3‰. At high Fe(III) reduction rates, δFe values of -2 – -3‰ relative to the substrate have been observed. The study of iron isotopes in iron reducing bacteria enable the development of an improved understanding regarding the metabolic processes operating in these organisms. | 0 | Theoretical and Fundamental Chemistry |
The main geologic history locally had two stages. The first is the Miocene, determined by tectonic events that correlate with the closing of the Tethys Sea. The second is the Pleistocene noted for its glaciation cycles and the full run of the present Volga. During the first stage, the Tethys Sea had evolved into the Sarmatian Lake, that was created from the modern Black Sea and south Caspian, when the collision of the Arabian peninsula with West Asia pushed up the Kopet Dag and Caucasus Mountains, lasting south and west limits to the basin. This orogenic movement was continuous, while the Caspian was regularly disconnected from the Black Sea. In the late Pontian stage, a mountain arch rose across the south basin and divided it into the Khachmaz and Lankaran Lakes (or early Balaxani). The period of restriction to the south basin was reversed during the Akchagylian – the lake became more than three times its size today and took again the first of a series of contacts with the Black Sea and with Lake Aral. A recession of Lake Akchagyl completed stage one. | 1 | Applied and Interdisciplinary Chemistry |
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