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* Theophilus Redwood: 1875–1876
* August Dupré: 1877–1878
* John Muter: 1879–1880
* Charles Heisch: 1881–1882
* George William Wigner: 1883–1884
* Dr Alfred Hill: 1885–1886
* Alfred Henry Allen: 1887–1888
* Matthew Adams: 1889–1890
* Otto Hehner: 1891–1892
* Sir Charles Alexander Cameron: 1893–1894
* Sir Thomas Stevenson: 1895–1896
* Bernard Dyer: 1897–1898
* Walter Fisher: 1899–1900
* Edward Voelcker: 1901–1902
* Thomas Fairley: 1903–1904
* Edward Bevan: 1905–1906
* John Clark: 1907
* Robert Rattray Tatlock: 1908–1909
* Edward Voelcker: 1910–1911
* Leonard Archbutt: 1912–1913
* Alfred Chaston Chapman: 1914–1915
* George Embrey: 1916–1917
* Samuel Rideal: 1918–1919
* Alfred Smetham: 1920–1921
* Percy Andrew Ellis Richards: 1922–1923
* George Rudd Thompson: 1924–1925
* Edward Richards Bolton: 1926–1927
* Edward Hinks: 1928–1929
* John Thomas Dunn: 1930–1931
* Francis William Frederick Annaud: 1932–1933
* John Evans: 1934–1935
* Gerald Roche Lynch: 1936–1937
* William Henry Roberts: 1938–1939
* Edwin Burnthorpe Hughes: 1940–1942
* Samuel Ernest Melling: 1943–1944
* Gordon Wickham Monier-Williams: 1945–1946
* Lewis Eynon: 1947–1948
* George Taylor: 1949–1950
* John Ralph Nicholls: 1951–1952
* Douglas William Kent-Jones: 1953–1954
* Kenneth Alan Williams: 1955–1956
* Jack Hubert Hamence: 1957–1958
* Ralph Clark Chirnside: 1959–1960
* Arthur James Amos: 1961–1962
* Donald Clarence Garrett: 1962–1963
* Albert Arthur Smales: 1964–1966
* Arthur George Jones: 1967–1968
* Thomas Summers West: 1969–1970
* Clifford Whalley: 1971–1972 | 1 | Applied and Interdisciplinary Chemistry |
Temperature plays a major role in the conversion of biomass to bio-oil. The temperature of the reaction determines the depolymerization of the biomass to bio-oil, as well as the repolymerization into char. While the ideal reaction temperature is dependent on the feedstock used, temperatures above ideal lead to an increase in char formation and eventually increased gas formation, while lower than ideal temperatures reduce depolymerization and overall product yields.
Similarly to temperature, the rate of heating plays a critical role in the production of the different phase streams, due to the prevalence of secondary reactions at non-optimum heating rates. Secondary reactions become dominant in heating rates that are too low, leading to the formation of char. While high heating rates are required to form liquid bio-oil, there is a threshold heating rate and temperature where liquid production is inhibited and gas production is favored in secondary reactions. | 0 | Theoretical and Fundamental Chemistry |
In 1975, J. P. Gollub and H. L. Swinney published a paper on the onset of turbulence in rotating fluid. In a Taylor–Couette flow system, they observed that, as the rotation rate increases, the fluid stratifies into a pile of "fluid donuts". With further increases in the rotation rate, the donuts oscillate and twist and finally become turbulent. Their study helped establish the Ruelle–Takens scenario in turbulence, which is an important contribution by Floris Takens and David Ruelle towards understanding how hydrodynamic systems transition from stable flow patterns into turbulent. While the principal, governing factor for this transition is the Reynolds number, there are other important influencing factors: whether the flow is open (meaning there is a lateral up- and downstream) or closed (flow is laterally bound; e.g. rotating), and bounded (influenced by wall effects) or unbounded (not influenced by wall effects). According to this classification the Taylor–Couette flow is an example of a flow pattern forming in a closed, bounded flow system. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen cyanide is a linear molecule, with a triple bond between carbon and nitrogen. The tautomer of HCN is HNC, hydrogen isocyanide.
Hydrogen cyanide is weakly acidic with a pK of 9.2. It partially ionizes in water to give the cyanide anion, CN. A solution of hydrogen cyanide in water, represented as HCN, is called hydrocyanic acid. The salts of the cyanide anion are known as cyanides.
HCN has a faint bitter almond-like odor that some people are unable to detect owing to a recessive genetic trait. The volatile compound has been used as inhalation rodenticide and human poison, as well as for killing whales. Cyanide ions interfere with iron-containing respiratory enzymes. | 0 | Theoretical and Fundamental Chemistry |
Continuous quantum engines are the quantum analogues of turbines. The work output mechanism is coupling to an external periodic field, typically the electromagnetic field. Thus the heat engine is a model for a laser.
The models differ by the choice of their working substance
and heat source and sink. Externally driven two-level, three level four-level and coupled harmonic oscillators have been studied.
The periodic driving splits the energy level structure of the working medium. This splitting allows the two level engine to couple
selectively to the hot and cold baths and produce power. On the other hand, ignoring this splitting in the derivation of the equation of motion will violate the second law of thermodynamics.
Non thermal fuels have been considered for quantum heat engines. The idea is to increase the energy content of the hot bath without
increasing its entropy. This can be achieved by employing coherence or a squeezed thermal bath. These devices do not violate the second law of thermodynamics. | 0 | Theoretical and Fundamental Chemistry |
Process integration is a term in chemical engineering which has two possible meanings.
# A holistic approach to process design which emphasizes the unity of the process and considers the interactions between different unit operations from the outset, rather than optimising them separately. This can also be called integrated process design or process synthesis. El-Halwagi (1997 and 2006) and Smith (2005) describe the approach well. An important first step is often product design (Cussler and Moggridge 2003) which develops the specification for the product to fulfil its required purpose.
# Pinch analysis, a technique for designing a process to minimise energy consumption and maximise heat recovery, also known as heat integration, energy integration or pinch technology. The technique calculates thermodynamically attainable energy targets for a given process and identifies how to achieve them. A key insight is the pinch temperature, which is the most constrained point in the process. The most detailed explanation of the techniques is by Linnhoff et al. (1982), Shenoy (1995), Kemp (2006) and Kemp and Lim (2020), and it also features strongly in Smith (2005). This definition reflects the fact that the first major success for process integration was the thermal pinch analysis addressing energy problems and pioneered by Linnhoff and co-workers. Later, other pinch analyses were developed for several applications such as mass-exchange networks (El-Halwagi and Manousiouthakis, 1989), water minimization (Wang and Smith, 1994), and material recycle (El-Halwagi et al., 2003). A very successful extension was "Hydrogen Pinch", which was applied to refinery hydrogen management (Nick Hallale et al., 2002 and 2003). This allowed refiners to minimise the capital and operating costs of hydrogen supply to meet ever stricter environmental regulations and also increase hydrotreater yields. | 1 | Applied and Interdisciplinary Chemistry |
Vacuum induction melting (VIM) utilizes electric currents to melt metal within a vacuum. The first prototype was developed in 1920. Induction heating induces eddy currents within conductors. Eddy currents create heating effects to melt the metal. Vacuum induction melting has been used in both the aerospace and nuclear industries. | 1 | Applied and Interdisciplinary Chemistry |
One accepted scientific hypothesis is that the Earth was formed by accretion of material with a chondritic composition through impacts with differentiated planetesimals. During this accretionary phase, planetary differentiation separated the Earth's core, where heavy metallic siderophile elements accumulated, from the surrounding undifferentiated primitive mantle. Further differentiation would take place later, creating the different chemical reservoirs of crust and mantle material, with incompatible elements accumulating in the crust.
Today, differentiation still continues in the upper mantle, resulting in two types of mantle reservoirs: those depleted in lithophile elements (depleted reservoirs), and those composed of "fresh" undifferentiated mantle material (enriched or primitive reservoirs). Volcanic rocks from hotspot areas often have a primitive composition, and because the magma at hotspots is supposed to have been taken to the surface from the deepest regions of the mantle by mantle plumes, geochemists assume there must be a relatively closed and very undifferentiated primitive reservoir somewhere in the lower mantle. One hypothesis to describe this assumption is the existence of the D"-layer at the core-mantle boundary. | 0 | Theoretical and Fundamental Chemistry |
RNA primers are used by living organisms in the initiation of synthesizing a strand of DNA. A class of enzymes called primases add a complementary RNA primer to the reading template de novo on both the leading and lagging strands. Starting from the free 3’-OH of the primer, known as the primer terminus, a DNA polymerase can extend a newly synthesized strand. The leading strand in DNA replication is synthesized in one continuous piece moving with the replication fork, requiring only an initial RNA primer to begin synthesis. In the lagging strand, the template DNA runs in the 5′→3′ direction. Since DNA polymerase cannot add bases in the 3′→5′ direction complementary to the template strand, DNA is synthesized ‘backward’ in short fragments moving away from the replication fork, known as Okazaki fragments. Unlike in the leading strand, this method results in the repeated starting and stopping of DNA synthesis, requiring multiple RNA primers. Along the DNA template, primase intersperses RNA primers that DNA polymerase uses to synthesize DNA from in the 5′→3′ direction.
Another example of primers being used to enable DNA synthesis is reverse transcription. Reverse transcriptase is an enzyme that uses a template strand of RNA to synthesize a complementary strand of DNA. The DNA polymerase component of reverse transcriptase requires an existing 3' end to begin synthesis. | 1 | Applied and Interdisciplinary Chemistry |
Nuclear magnetic resonance (NMR) is a technique used to obtain physical, chemical, electronic and structural information about molecules due to the chemical shift of the resonance frequencies of nuclear spins in the sample. Its combination with electrochemical techniques can provide detailed and quantitative information about the functional groups, topology, dynamics and the three-dimensional structure of molecules in solution during a charge transfer process. The area under an NMR peak is related to the ratio of the number of turns involved and the peak integrals to determine the composition quantitatively. | 0 | Theoretical and Fundamental Chemistry |
The process of soil formation is dominated by chemical weathering of silicate minerals, aided by acidic products of pioneering plants and organisms as well as carbonic acid inputs from the atmosphere. Carbonic acid is produced in the atmosphere and soil layers through the carbonation reaction.
This is the dominant form of chemical weathering and aides in the breakdown of carbonate minerals (such as calcite and dolomite) and silicate minerals (such as feldspar). The breakdown of the Na-feldspar, albite, by carbonic acid to form kaolinite clay is as follows:
Evidence of this reaction in the field would be elevated levels of bicarbonate (), sodium and silica ions in the water runoff.
The breakdown of carbonate minerals:
The further dissolution of carbonic acid (HCO) and bicarbonate () produces CO gas. Oxidization is also a major contributor to the breakdown of many silicate minerals and formation of secondary minerals (diagenesis) in the early soil profile. Oxidation of olivine (FeMgSiO) releases Fe, Mg and Si ions. The Mg is soluble in water and is carried in the runoff, but the Fe often reacts with oxygen to precipitate FeO (hematite), the oxidized state of iron oxide. Sulfur, a byproduct of decaying organic material, will also react with iron to form pyrite (FeS) in reducing environments. Pyrite dissolution leads to low pH levels due to elevated H ions and further precipitation of FeO ultimately changing the redox conditions of the environment. | 0 | Theoretical and Fundamental Chemistry |
Source:
A large range of functional groups have already been made into FSL Kode constructs. These include:
* Carbohydrates – ranging from monosaccharides to polysaccharides and including blood group antigens, hyaluronic acid oligomers and sialic acid residues
* Peptide/protein – ranging from single amino acids to proteins as large as antibodies
* Labels – including fluorophores, radioisotopes, biotin, etc.
* Other – chemical moieties such as maleimide, click residues, PEG, charged compounds
Note 1: Multimeric – the presentation of the F residue can be as multimers with controlled spacing and be variable.
Note 2: Mass – the mass that can be anchored by an FSL Kode constructs can range from 200 to >1x10 Da | 1 | Applied and Interdisciplinary Chemistry |
British endocrinologist Albert T. W. Simeons proposed HCG as an adjunct to an ultra-low-calorie weight-loss diet (fewer than 500 calories). Simeons, while studying pregnant women in India on a calorie-deficient diet, and fat boys with pituitary problems (Frölichs syndrome) treated with low-dose HCG, observed that both lost fat rather than lean (muscle) tissue. He reasoned that HCG must be programming the hypothalamus to do this in the former cases in order to protect the developing fetus by promoting mobilization and consumption of abnormal, excessive adipose deposits. Simeons in 1954 published a book entitled Pounds and Inches', designed to combat obesity. Simeons, practicing at Salvator Mundi International Hospital in Rome, Italy, recommended low-dose daily HCG injections (125 IU) in combination with a customized ultra-low-calorie (500 cal/day, high-protein, low-carbohydrate/fat) diet, which was supposed to result in a loss of adipose tissue without loss of lean tissue.
Other researchers did not find the same results when attempting experiments to confirm Simeons' conclusions, and in 1976 in response to complaints the FDA required Simeons and others to include the following disclaimer on all advertisements:
There was a resurgence of interest in the "HCG diet" following promotion by Kevin Trudeau, who was banned from making HCG diet weight-loss claims by the U.S. Federal Trade Commission in 2008, and eventually jailed over such claims.
A 1976 study in the American Journal of Clinical Nutrition concluded that HCG is not more effective as a weight-loss aid than dietary restriction alone.
A 1995 meta analysis found that studies supporting HCG for weight loss were of poor methodological quality and concluded that "there is no scientific evidence that HCG is effective in the treatment of obesity; it does not bring about weight-loss or fat-redistribution, nor does it reduce hunger or induce a feeling of well-being".
On November 15, 2016, the American Medical Association (AMA) passed policy that "The use of human chorionic gonadotropin (HCG) for weight loss is inappropriate."
According to the American Society of Bariatric Physicians, no new clinical trials have been published since the definitive 1995 meta-analysis.
The scientific consensus is that any weight loss reported by individuals on an "HCG diet" may be attributed entirely to the fact that such diets prescribe calorie intake of between 500 and 1,000 calories per day, substantially below recommended levels for an adult, to the point that this may risk health effects associated with malnutrition. | 1 | Applied and Interdisciplinary Chemistry |
The global estimates of the biological pump have yet to include the elements of the lipid pump which could represent 50–100% of C export that is not accounted for. This is likely due to many observational challenges pertaining to the analysis of these seasonal migrations. As described above, more accurate ways to measure both mortality and respiration rates of overwintering zooplankton are being conducted in recent work, which are the two factors that primarily control the amount of lipid carbon that is sequestered at depth. For the zooplankton that survive overwintering, their upward migration during the spring returns a fraction of the lipid reserves to the surface as nonrespired carbon, with losses attributed to predation by deep-dwelling predators, disease, starvation, and other sources of mortality generally not accounted for. Similar to the lysis shunt, the dynamics of the lipid shunt causes uncertainty in observational methods of the lipid pump when comparing its efficiency to that of the biological pump. Additionally, large zooplankton usually avoid mooring instruments such as sediment traps during seasonal migrations which further explains why the lipid pump has yet to become incorporated into estimates of the global carbon export flux. These observations can be challenging to make given the remote locations they are conducted in and the harsh, deep sampling conditions, but these adaptations in the data collection are needed to better integrate global estimates of the carbon export flux provided by the lipid pump. | 0 | Theoretical and Fundamental Chemistry |
Photolithography and X-ray lithography have been used to etch substrates, often silicon. A resist, or photosensitive material, is coated onto a substrate. A mask is applied above the resist that often consists of gold or other compounds that absorb X-rays. The region exposed to light either becomes soluble in a photoresist developer (e.g. radical species) or insoluble in a photoresist developer (e.g. crosslinked species), ultimately resulting in a patterned surface. X-ray sources are beneficial over UV-visible light sources as the shorter wavelengths enable production of smaller features. | 0 | Theoretical and Fundamental Chemistry |
The Goldbeter–Koshland kinetics describe a steady-state solution for a 2-state biological system. In this system, the interconversion between these two states is performed by two enzymes with opposing effect. One example would be a protein Z that exists in a phosphorylated form Z and in an unphosphorylated form Z; the corresponding kinase Y and phosphatase X interconvert the two forms. In this case we would be interested in the equilibrium concentration of the protein Z (Goldbeter–Koshland kinetics only describe equilibrium properties, thus no dynamics can be modeled). It has many applications in the description of biological systems.
The Goldbeter–Koshland kinetics is described by the Goldbeter–Koshland function:
with the constants
Graphically the function takes values between 0 and 1 and has a sigmoid behavior. The smaller the parameters J and J the steeper the function gets and the more of a switch-like behavior is observed. Goldbeter–Koshland kinetics is an example of ultrasensitivity. | 0 | Theoretical and Fundamental Chemistry |
Pre-action sprinkler systems are specialized for use in locations where accidental activation is especially undesirable, such as in museums with rare art works, manuscripts, or books; and data centers, for protection of computer equipment from accidental water discharge.
There are two main sub-types of pre-action systems: single interlock, and double interlock.
The operation of single interlock systems are similar to wet systems except that these systems require that a "preceding" fire detection event, typically the activation of a heat or smoke detector takes place prior to the "action" of water introduction into the system's piping by opening the pre-action valve which is a mechanically latched valve (i.e. similar to a deluge valve). In this way, the system is essentially converted from a dry system into a wet system. The intent is to reduce the undesirable time delay of water delivery to sprinklers that is inherent in dry systems. Prior to fire detection, if the sprinkler operates, or the piping system develops a leak, loss of air pressure in the piping will activate a trouble alarm. In this case, the pre-action valve will not open due to loss of supervisory pressure, and water will not enter the piping.
Double interlock systems require that both activation of a heat or smoke detector, and an automatic sprinkler operation take place prior to the "action" of water introduction into the system's piping. Activation of either the fire detectors alone, or sprinklers alone, without the concurrent operation of the other will not allow water to enter the piping. Because water does not enter the piping until a sprinkler operates, double interlock systems are considered as dry systems in terms of water delivery times, and similarly require a larger design area. | 1 | Applied and Interdisciplinary Chemistry |
Five basic modes of alternative splicing are generally recognized.
* Exon skipping or cassette exon: in this case, an exon may be spliced out of the primary transcript or retained. This is the most common mode in mammalian pre-mRNAs.
* Mutually exclusive exons: One of two exons is retained in mRNAs after splicing, but not both.
* Alternative donor site: An alternative 5 splice junction (donor site) is used, changing the 3 boundary of the upstream exon.
* Alternative acceptor site: An alternative 3 splice junction (acceptor site) is used, changing the 5 boundary of the downstream exon.
* Intron retention: A sequence may be spliced out as an intron or simply retained. This is distinguished from exon skipping because the retained sequence is not flanked by introns. If the retained intron is in the coding region, the intron must encode amino acids in frame with the neighboring exons, or a stop codon or a shift in the reading frame will cause the protein to be non-functional. This is the rarest mode in mammals but the most common in plants.
In addition to these primary modes of alternative splicing, there are two other main mechanisms by which different mRNAs may be generated from the same gene; multiple promoters and multiple polyadenylation sites. Use of multiple promoters is properly described as a transcriptional regulation mechanism rather than alternative splicing; by starting transcription at different points, transcripts with different 5-most exons can be generated. At the other end, multiple polyadenylation sites provide different 3 end points for the transcript. Both of these mechanisms are found in combination with alternative splicing and provide additional variety in mRNAs derived from a gene.
<br>These modes describe basic splicing mechanisms, but may be inadequate to describe complex splicing events. For instance, the figure to the right shows 3 spliceforms from the mouse hyaluronidase 3 gene. Comparing the exonic structure shown in the first line (green) with the one in the second line (yellow) shows intron retention, whereas the comparison between the second and the third spliceform (yellow vs. blue) exhibits exon skipping. A model nomenclature to uniquely designate all possible splicing patterns has recently been proposed. | 1 | Applied and Interdisciplinary Chemistry |
Learning and memory have levels of permanence, differing from other mental processes such as thought, language, and consciousness, which are temporary in nature. Learning and memory can be either accumulated slowly (multiplication tables) or rapidly (touching a hot stove), but once attained, can be recalled into conscious use for a long time. Rats subjected to one instance of contextual fear conditioning create an especially strong long-term memory. At 24 hours after training, 9.17% of the genes in the genomes of rat hippocampus neurons were found to be differentially methylated. This included more than 2,000 differentially methylated genes at 24 hours after training, with over 500 genes being demethylated. Similar results to that in the rat hippocampus were also obtained in mice with contextual fear conditioning.
The hippocampus region of the brain is where contextual fear memories are first stored (see figure of the brain, this section), but this storage is transient and does not remain in the hippocampus. In rats contextual fear conditioning is abolished when the hippocampus is subjected to hippocampectomy just one day after conditioning, but rats retain a considerable amount of contextual fear when hippocampectomy is delayed by four weeks. In mice, examined at 4 weeks after conditioning, the hippocampus methylations and demethylations were reversed (the hippocampus is needed to form memories but memories are not stored there) while substantial differential CpG methylation and demethylation occurred in cortical neurons during memory maintenance. There were 1,223 differentially methylated genes in the anterior cingulate cortex of mice four weeks after contextual fear conditioning. Thus, while there were many methylations in the hippocampus shortly after memory was formed, all these hippocampus methylations were demethylated as soon as four weeks later. | 1 | Applied and Interdisciplinary Chemistry |
Between May 13–14, 2004 the site was enclosed with temporary mesh fencing and plain-clothed security guards commenced patrols of the public areas. At 02:00 on May 15 bulldozers arrived at the site and tree-felling began at 07:00. The work caused immediate concern to nearby residents who feared the work might unsettle asbestos deposits in the ground. Residents formed the Save Spodden Valley action group the following week. Residents also protested to Rochdale Council, which subsequently issued an emergency tree preservation order on six parts of the site, preventing the removal of trees without permission of planning officers, and carrying a fine of up to £20,000 per tree. The Health and Safety Executive (HSE) also secured a voluntary arrangement to halt any work that could disturb soil on the site pending soil sampling. Former Turner's employees and local residents claimed that, as recently as the 1960s, asbestos dust and fibres were clearly visible hanging from the trees, and that a disused coalmine shaft exposed by the tree felling had been used over a period of decades to dump hundreds of tonnes of asbestos waste. | 1 | Applied and Interdisciplinary Chemistry |
Levetiracetam does not undergo extensive metabolism, and the metabolites formed are not active and do not exert pharmacological activity. Metabolism of levetiracetam is not by liver cytochrome P450 enzymes, but through other metabolic pathways such as hydrolysis and hydroxylation. | 0 | Theoretical and Fundamental Chemistry |
The flow equations of the Rankine half body are solved using the principle of superposition, combining the solutions of the linear flow of the stream and the circular flow of the source.
Given the linear flow field and the source , we have
The stagnation point for this flow can be determined by equating the velocity to zero in either directions. Because of symmetry of flow in y-direction, stagnation point must lie on x-axis.
Equating both and to zero, we obtain .
At and we have stagnation points.
Now, we note that , so following this constant streamline gives the outline of the body:
Then, describes the half body outline. | 1 | Applied and Interdisciplinary Chemistry |
* "Surface Tension", (1891) Nature, 46, 437.
* "[https://archive.org/details/paper-doi-10_1038_046418e0/mode/2up On the relative contamination of the water-surface by equal quantities of different substances]", (1892) Nature 47, 418.
* "Relations between the surface tension and relative contamination of water surfaces", (1893) Nature, 48, 152.
* "On the spreading of oil upon water", (1894) Nature 50, 223.
* "Beobachtungen über die Adhäsion verschiedener Flüssigkeiten an Glas", (Observations about the Adhesion of Different Liquids on Glass), (1898) Naturwissenschaftliche Rundschau, 14, 190.
* "Randwinkel gesättigter Lösungen an Kristallen" (Contact Angles of Saturated Solutions on Crystals), (1899), Naturwissenschaftliche Rundschau, 14, 383.
* "Untersuchungen von Grenzflächenspannungen mit der Cohäsionswaage", (Investigations of the Surface Tension with the Cohesion Balance), (1899) Annalen der Physik, 67, 668.
* "Über das spontane Sinken der Oberflächenspannung von Wasser, wässerigen Lösungen und Emulsionen", (On the Spontaneous Decrease of the Surface Tension of Water, Aqueous Solutions and Emulsions), (1902) Annalen der Physik', 8, 854.
* "Über Randwinkel und Ausbreitung von Flüssigkeiten auf festen Körpern" (On Contact Angles and the Flow of Fluids on Solid Bodies), (1914) Physikalische Zeitschrift, 15, 39.
* "Zur Frage der zeitlichen Veränderung der Oberflächenspannun" (On the Changes of the Surface Tension with Time), (1916) Physikalische Zeitschrift', 17, 141
* "Über die Ausbreitung reiner und gemischter Flüssigkeiten auf Wasser" (On the Spreading of Pure and Mixed Liquids on Water) (1916) Physikalische Zeitschrift, 17, 142.
* "Die Anomalie der Wasseroberfläche" (The Anomalous State of the Water Surface) (1917) Die Naturwissenschaften, 5, 137 u. 149.
* "Zur Frage der Ölflecke auf Seen" (On Oil Stains on Lakes) (1918) Die Naturwissenschaften, 6, 118.
* "The measurement of surface tension with the balance" (1926) Science 64, 304. | 0 | Theoretical and Fundamental Chemistry |
Mound systems are used to help purify and transport water efficiently.
Some soils are too high in permeability, allowing water to quickly pass through it, hindering purification effectiveness and allowing contamination to spread to nearby water sources or ecosystems. .
Areas of low soil permeability, such as areas with high water tables and limited soil cover over porous bedrock, can result in contaminated surface pooling. | 1 | Applied and Interdisciplinary Chemistry |
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Water () is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, which is nearly colorless apart from an inherent hint of blue. It is by far the most studied chemical compound and is described as the "universal solvent" and the "solvent of life". It is the most abundant substance on the surface of Earth and the only common substance to exist as a solid, liquid, and gas on Earth's surface. It is also the third most abundant molecule in the universe (behind molecular hydrogen and carbon monoxide).
Water molecules form hydrogen bonds with each other and are strongly polar. This polarity allows it to dissociate ions in salts and bond to other polar substances such as alcohols and acids, thus dissolving them. Its hydrogen bonding causes its many unique properties, such as having a solid form less dense than its liquid form, a relatively high boiling point of 100 °C for its molar mass, and a high heat capacity.
Water is amphoteric, meaning that it can exhibit properties of an acid or a base, depending on the pH of the solution that it is in; it readily produces both hydron (chemistry)| and hydroxide| ions. Related to its amphoteric character, it undergoes self-ionization. The product of the activities, or approximately, the concentrations of and is a constant, so their respective concentrations are inversely proportional to each other. | 1 | Applied and Interdisciplinary Chemistry |
is a double-decker sandwich compound consisting of a ion coordinated to two the conjugate base of two phthalocyanines. The rings are arranged in a staggered conformation. The extremities of the two ligands are slightly distorted outwards. The complex features a non-innocent ligand, in the sense that the macrocycles carry an extra electron. It is a free radical with the unpaired electron sitting in a half-filled molecular orbital between the highest occupied and lowest unoccupied orbitals, allowing its electronic properties to be finely tuned. | 0 | Theoretical and Fundamental Chemistry |
Analytical light scattering (ALS), also loosely referred to as SEC-MALS, is the implementation of static light scattering (SLS) and dynamic light scattering (DLS) techniques in an online or flow mode. A typical ALS instrument consists of an HPLC/FPLC chromatography system coupled in-line with appropriate light scattering and refractive index detectors. The advantage of ALS over conventional steady-state light scattering methods is that it allows separation of molecules/macromolecules on a chromatography column prior to analysis with light scattering detectors. Accordingly, ALS enables one to determine hydrodynamic properties of a single monodisperse species as opposed to bulk or average measurements on a sample afforded by conventional light scattering. | 0 | Theoretical and Fundamental Chemistry |
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha, beta, and gamma decay. The weak force is the mechanism that is responsible for beta decay, while the other two are governed by the electromagnetism and nuclear force.
Radioactive decay is a stochastic (i.e., random) process at the level of single atoms. According to quantum theory, it is impossible to predict when a particular atom will decay, regardless of how long the atom has existed. However, for a significant number of identical atoms, the overall decay rate can be expressed as a decay constant or as half-life. The half-lives of radioactive atoms have a huge range; from nearly instantaneous to far longer than the age of the universe.
The decaying nucleus is called the parent radionuclide (or parent radioisotope), and the process produces at least one daughter nuclide. Except for gamma decay or internal conversion from a nuclear excited state, the decay is a nuclear transmutation resulting in a daughter containing a different number of protons or neutrons (or both). When the number of protons changes, an atom of a different chemical element is created.
There are 28 naturally occurring chemical elements on Earth that are radioactive, consisting of 34 radionuclides (six elements have two different radionuclides) that date before the time of formation of the Solar System. These 34 are known as primordial nuclides. Well-known examples are uranium and thorium, but also included are naturally occurring long-lived radioisotopes, such as potassium-40. | 0 | Theoretical and Fundamental Chemistry |
The most important members of this group are the phosphoric acids, where each phosphorus atom bonded to four oxygen atoms, one of them through a double bond, arranged as the corners of a tetrahedron. Two or more of these tetrahedra may be connected by shared single-bonded oxygens, forming linear or branched chains, cycles, or more complex structures. The single-bonded oxygen atoms that are not shared are completed with acidic hydrogen atoms. Their generic formula is HPO, where n is the number of phosphorus atoms and x is the number of fundamental cycles in the molecule's structure.
These acids, and their esters and salts ("phosphates") include some of the best-known and most important compounds of phosphorus.
The simplest member of this class is:
* Phosphoric acid proper (also called orthophosphoric acid or monophosphoric acid), (or ), a triprotic acid. It forms orthophosphate salt and esters, commonly called phosphates.
The smallest compounds of this class with two or more phosphorus atoms are called "oligophosphoric acids", and the larger ones, with linear –P–O– backbones, are "polyphosphoric acids"; with no definite separation between the two. Some of the most important members are:
* Pyrophosphoric acid, (or –O–), with four acid hydrogens. Forms pyrophosphates.
* Triphosphoric acid (or tripolyphosphoric acid), (or –O––O–), with five acidic hydrogens. Forms triphosphates or tripolyphosphates.
* Tetraphosphoric acid, (or (–O–)–O–), with six acidic hydrogens. Forms tetraphosphates.
The backbone may be branched, as in:
* Triphosphono phosphoric acid, or P(O)(–), a branched isomer of tetrapolyphosphoric acid.
The tetrahedra may be connected to form closed –P–O– chains, as in:
* Trimetaphosphoric acid (or cyclotriphosphoric acid), (or , (–P(O)(OH)–O–)), a cyclic molecule with three acidic hydrogens. Forms the trimetaphosphate salts and esters.
Metaphosphoric acid is a general term for phosphoric acids with a single cycle, (–P(O)(OH)–O–), whose elemental formula is .
Another compound that may be included in this class is
* Peroxomonophosphoric acid, HPO (or OP(OH)(OOH)), which can be seen as monophosphoric acid with a peroxide group replacing the oxygen atom in one of the hydroxyl groups | 0 | Theoretical and Fundamental Chemistry |
Here a parabolic shear in the outer velocity is introduced.
Then the solution to the first-order approximation is
where is the homogeneous solution to the Laplace equation which restores the boundary conditions. | 1 | Applied and Interdisciplinary Chemistry |
Inhabitants should plan to remain sheltered for at least two weeks (with an hour out at the end of the first week – see Swiss Civil Defense guidelines), then work outside for gradually increasing amounts of time, to four hours a day at three weeks. The normal work is to sweep or wash fallout into shallow trenches to decontaminate the area. They should sleep in a shelter for several months. Evacuation at three weeks is recommended by official authorities.
If available, inhabitants may take potassium iodide at the rate of 130 mg/day per adult (65 mg/day per child) as an additional measure to protect the thyroid gland from the uptake of dangerous radioactive iodine, a component of most fallout and reactor waste. | 0 | Theoretical and Fundamental Chemistry |
In petrology and geochemistry, an incompatible element is one that is unsuitable in size and/or charge to the cation sites of the minerals in which it is included. It is defined by a partition coefficient between rock-forming minerals and melt being much smaller than 1.
During the fractional crystallization of magma and magma generation by the partial melting of the Earth's mantle and crust, elements that have difficulty in entering cation sites of the minerals are concentrated in the melt phase of the magma (liquid phase).
Two groups of incompatible elements that have difficulty entering the solid phase are known by acronyms. One group includes elements having large ionic radius, such as potassium, rubidium, caesium, strontium, and barium (called LILE, or large-ion lithophile elements), and the other group includes elements of large ionic valences (or high electrical charges), such as zirconium, niobium, hafnium, rare-earth elements (REE), thorium, uranium and tantalum (called HFSE, or high-field-strength elements).
Another way to classify incompatible elements is by mass (lanthanide series): light rare-earth elements (LREE) are La, Ce, Pr, Nd, and Sm, and heavy rare-earth elements (HREE) are Eu–Lu. Rocks or magmas that are rich, or only slightly depleted, in light rare-earth elements are referred to as "fertile", and those with strong depletions in LREE are referred to as "depleted". | 0 | Theoretical and Fundamental Chemistry |
Primary clarifier effluent was discharged directly to natural wetlands for decades before environmental regulations discouraged the practice. Subsurface flow constructed wetlands with sand filter beds have their origin in China and are now used in Asia in small cities. | 1 | Applied and Interdisciplinary Chemistry |
Shorter (large ) waves (e.g. 2 mm for the water–air interface), which are proper capillary waves, do the opposite: an individual wave appears at the front of the group, grows when moving towards the group center and finally disappears at the back of the group. Phase velocity is two thirds of group velocity in this limit. | 1 | Applied and Interdisciplinary Chemistry |
Plants have many protection mechanisms to cope with stresses from the environment, which include ultraviolet light, cold or hot weather, windy days, and mechanical wounding. There are multiple pathways, but one pathway that plants have been able to develop is a self-defense mechanism by recognize pathogens through pathogen-associated molecular patterns (PAMPs) via cell surface-located pathogen-recognition receptors. These receptors induce intracellular signal pathways within the plant cells, while also resulting in PAMP-triggered immunity. Responses to PAMPs target broadly instead of specifically. This immunity requires downstream components via the MAPK cascade to activate the MAP kinases. The flagellin, a peptide of flg22, triggers a rapid and strong activation of MPK3, MPK4, and MPK6. MPK4 and MPK6 can be activated by harpin proteins. MPK3 and MPK6 are very similar proteins and have a function as regulators in abscission, stomatal development, signaling various abiotic stresses, and defense responses to certain pathogens. Experimentation has proposed that the MAPK module MEKK1-MKK4/MKK5-MPK3/MPK6 may be responsible for flg22 signal transmission. All of the proposed modules appear to be correct expect for MEKK1 because plants with mekk1 mutated have a compromised flg22-triggered activation of MPK4, yet they have normal activation of MPK3 and MPK6. Data has shown that MAPK cascade is composed of MKK4/MKK5 and MPK3/MPK6 in response to fungal pathogens. The observation shows that the activation of MPK3/MPK6 in conditional gain-of-function plants for MKK4/MKK5 or MEKK1/MKKKa is sufficient to induce camalexin, which is a major phytoalexin in Arabidopsis. The stomata are considered to be the entry point for pathogenic invaders because microbial invaders enter the plant at the stomata. A recent study has shown that MAPK cascades play a role in abiotic and biotic stress responses. The main pathways in stomatal development and dynamics are MPK3 and MPK6. During a drought, the stomata closes and is believed to be mediated by the phytohormone, abscisic acid, and involves MKK1, MPK3, and MPK6. Another way of closing the stomata is through a closing process that is called pathogen-induced, which is an innate response from the plant. Campestris (Xcc) excretes a chemical that reverts stomatal closure that was caused by bacteria and abscisic acid (ABA). Most stomata close in the presence of ABA, but some are unresponsive to bacteria. In Arabidopsis Xcc does not revert bacteria-induced or ABA-induced stomatal closure. Scientists are not certain if MAPK cascades are responsible for the signaling, so further investigation is needed for this. | 1 | Applied and Interdisciplinary Chemistry |
* Healthy Waterways Raingardens Program promotes a simple and effective form of stormwater treatment, and aims to raise peoples' awareness about how good stormwater management contributes to healthy waterways. The program encourages people to build rain gardens at home, and has achieved its target is to see 10,000 rain gardens built across Melbourne by 2013.
* Melbourne Waters database of Water Sensitive Urban Design projects, including 57 case studies relating to rain gardens/bioretention systems. Melbourne Water is the Victorian State Government agency responsible for managing Melbournes water supply catchments.
* Water By Design is a capacity building program that supports the uptake of Water Sensitive Urban Design, including rain gardens, in South East Queensland. It was established by the South East Queensland Healthy Waterways Partnership in 2005, as an integral component of the SEQ Healthy Waterways Strategy. | 1 | Applied and Interdisciplinary Chemistry |
Many metal complexes catalyze the dehydrogenation of amine-borane (AB). Catalysis in the absence of metals has also been observed. | 0 | Theoretical and Fundamental Chemistry |
Performance testing of solar thermal collectors utilizes the term stagnation temperature to indicate the maximum achievable collector temperature with a stagnant fluid (no motion), an ambient temperature of 30C, and incident solar radiation of 1000W/m. The aforementioned figures are worst case scenario values that allow collector designers to plan for potential overheat scenarios in the event of collector system malfunctions. | 1 | Applied and Interdisciplinary Chemistry |
Although polyadenylation is seen in almost all organisms, it is not universal. However, the wide distribution of this modification and the fact that it is present in organisms from all three domains of life implies that the last universal common ancestor of all living organisms, it is presumed, had some form of polyadenylation system. A few organisms do not polyadenylate mRNA, which implies that they have lost their polyadenylation machineries during evolution. Although no examples of eukaryotes that lack polyadenylation are known, mRNAs from the bacterium Mycoplasma gallisepticum and the salt-tolerant archaean Haloferax volcanii lack this modification.
The most ancient polyadenylating enzyme is polynucleotide phosphorylase. This enzyme is part of both the bacterial degradosome and the archaeal exosome, two closely related complexes that recycle RNA into nucleotides. This enzyme degrades RNA by attacking the bond between the 3′-most nucleotides with a phosphate, breaking off a diphosphate nucleotide. This reaction is reversible, and so the enzyme can also extend RNA with more nucleotides. The heteropolymeric tail added by polynucleotide phosphorylase is very rich in adenine. The choice of adenine is most likely the result of higher ADP concentrations than other nucleotides as a result of using ATP as an energy currency, making it more likely to be incorporated in this tail in early lifeforms. It has been suggested that the involvement of adenine-rich tails in RNA degradation prompted the later evolution of polyadenylate polymerases (the enzymes that produce poly(A) tails with no other nucleotides in them).
Polyadenylate polymerases are not as ancient. They have separately evolved in both bacteria and eukaryotes from CCA-adding enzyme, which is the enzyme that completes the 3′ ends of tRNAs. Its catalytic domain is homologous to that of other polymerases. It is presumed that the horizontal transfer of bacterial CCA-adding enzyme to eukaryotes allowed the archaeal-like CCA-adding enzyme to switch function to a poly(A) polymerase. Some lineages, like archaea and cyanobacteria, never evolved a polyadenylate polymerase.
Polyadenylate tails are observed in several RNA viruses, including Influenza A, Coronavirus, Alfalfa mosaic virus, and Duck Hepatitis A. Some viruses, such as HIV-1 and Poliovirus, inhibit the cells poly-A binding protein (PABPC1) in order to emphasize their own genes expression over the host cell's. | 1 | Applied and Interdisciplinary Chemistry |
The trace amount of samples collected from crime scenes can be amplified by MDA to the quantity that is enough for forensic DNA analysis, which is commonly used in identifying victims and suspects. | 1 | Applied and Interdisciplinary Chemistry |
In a typical TAP pulse-response experiment, very small (~10 mol) and narrow (~100 μs) gas pulses are introduced into the evacuated (~10 torr) microreactor
containing a catalytic sample. While the injected gas molecules traverse the microreactor packing through the interstitial voids,
they encounter the catalyst on which they may undergo chemical transformations. Unconverted and newly formed gas molecules eventually
reach the reactor's outlet and escape into an adjacent vacuum chamber, where they are detected with millisecond time resolution
by the QMS. The exit-flow rates of reactants, products and inert molecules recorded by the QMS are then
used to quantify catalytic properties and deduce reaction mechanisms. The same TAP instrument can
typically accommodate other types of kinetic measurements, including atmospheric pressure flow experiments (10 Pa),
Temperature-Programmed Desorption (TPD), and Steady-State Isotopic Transient Kinetic Analysis (SSITKA). | 0 | Theoretical and Fundamental Chemistry |
Capillary electrophoresis may be used for the simultaneous determination of the ions NH, Na, K, Mg and Ca in saliva.
One of the main applications of CE in forensic science is the development of methods for amplification and detection of DNA fragments using polymerase chain reaction (PCR), which has led to rapid and dramatic advances in forensic DNA analysis. DNA separations are carried out using thin CE 50-mm fused silica capillaries filled with a sieving buffer. These capillaries have excellent capabilities to dissipate heat, permitting much higher electric field strengths to be used than slab gel electrophoresis. Therefore separations in capillaries are rapid and efficient. Additionally, the capillaries can be easily refilled and changed for efficient and automated injections. Detection occurs via fluorescence through a window etched in the capillary. Both single-capillary and capillary-array instruments are available with array systems capable of running 16 or more samples simultaneously for increased throughput.
A major use of CE by forensic biologists is typing of STR from biological samples to generate a profile from highly polymorphic genetic markers which differ between individuals. Other emerging uses for CE include the detection of specific mRNA fragments to help identify the biological fluid or tissue origin of a forensic sample.
Another application of CE in forensics is ink analysis, where the analysis of inkjet printing inks is becoming more necessary due to increasingly frequent counterfeiting of documents printed by inkjet printers. The chemical composition of inks provides very important information in cases of fraudulent documents and counterfeit banknotes. Micellar electrophoretic capillary chromatography (MECC) has been developed and applied to the analysis of inks extracted from paper. Due to its high resolving power relative to inks containing several chemically similar substances, differences between inks from the same manufacturer can also be distinguished. This makes it suitable for evaluating the origin of documents based on the chemical composition of inks. It is worth noting that because of the possible compatibility of the same cartridge with different printer models, the differentiation of inks on the basis of their MECC electrophoretic profiles is a more reliable method for the determination of the ink cartridge of origin (its producer and cartridge number) rather than the printer model of origin.
A specialized type of CE, affinity capillary electrophoresis (ACE), utilizes intermolecular binding interactions to understand protein-ligand interactions. Pharmaceutical companies use ACE for a multitude of reasons, with one of the main ones being the association/binding constants for drugs and ligands or drugs and certain vehicle systems like micelles. It is a widely used technique because of its simplicity, rapid results, and low analyte usage. The use of ACE can provide specific details in binding, separation, and detection of analytes and is proven to be highly practical for studies in life sciences. Aptamer-based affinity capillary electrophoresis is utilized for the analysis and modifications of specific affinity reagents. Modified aptamers ideally exhibit and high binding affinity, specificity, and nuclease resistance. Ren et al. incorporated modified nucleotides in aptamers to introduce new confrontational features and high affinity interactions from the hydrophobic and polar interactions between IL-1α and the aptamer. Huang et al. uses ACE to investigate protein-protein interactions using aptamers. A α-thrombin binding aptamer was labeled with 6-carboxyfluorescein for use as a selective fluorescent probe and was studied to elucidate information on binding sites for protein-protein and protein-DNA interactions.
Capillary electrophoresis (CE) has become an important, cost-effective approach to do DNA sequencing that provides high throughput and high accuracy sequencing information. Woolley and Mathies used a CE chip to sequence DNA fragments with 97% accuracy and a speed of 150 bases in 540 seconds. They used a 4-color labeling and detection format to collect fluorescent data. Fluorescence is used to view the concentrations of each part of the nucleic acid sequence, A, T, C and G, and these concentration peaks that are graphed from the detection are used to determine the sequence of the DNA. | 0 | Theoretical and Fundamental Chemistry |
The symbol used to represent density in equations is ρ (rho) with SI units of kilograms per cubic meter. This term is the reciprocal of specific volume.
Since gas molecules can move freely within a container, their mass is normally characterized by density. Density is the amount of mass per unit volume of a substance, or the inverse of specific volume. For gases, the density can vary over a wide range because the particles are free to move closer together when constrained by pressure or volume. This variation of density is referred to as compressibility. Like pressure and temperature, density is a state variable of a gas and the change in density during any process is governed by the laws of thermodynamics. For a static gas, the density is the same throughout the entire container. Density is therefore a scalar quantity. It can be shown by kinetic theory that the density is inversely proportional to the size of the container in which a fixed mass of gas is confined. In this case of a fixed mass, the density decreases as the volume increases. | 0 | Theoretical and Fundamental Chemistry |
A better alternative to the use of potentially hazardous oxidizers is an NMR tube cleaner (right). It is an apparatus which uses a vacuum to flush solvent and/or a detergent solution through the entire length of the NMR tube.
In this apparatus, the NMR tube 1 (with the cap 3 fixed to the base of the NMR tube), is placed upside down on the apparatus. The NMR tube fits over an inner tube 5 linked to the solvent reservoir 6. The NMR cap rests on the outer tube of the apparatus 4. A vacuum is applied (usually via a water aspirator via the vacuum inlet). The NMR tube cap forms a vacuum seal. Solvent 7 is drawn from the solvent reservoir 6 and is forced to the base of the NMR tube and flushes the NMR tube out 9 with solvent cleaning it. Note to complete the vacuum a flask is attached to the NMR tube cleaning apparatus.
This sort of apparatus is commercially available, though it is costly and easy to destroy by shattering or breaking off the cleaning tube. Equivalent designs may be assembled from ordinary labware as well. | 0 | Theoretical and Fundamental Chemistry |
During the formation of a crystalline structure, different impurities, irregularities, and other defects can form. These imperfections can form through deformation of the solid, rapid cooling, or high energy radiation. Types of defects include point defects, line defects, as well as edge dislocation. | 1 | Applied and Interdisciplinary Chemistry |
Industrial fermentation is the intentional use of fermentation in manufacturing processes. In addition to the mass production of fermented foods and drinks, industrial fermentation has widespread applications in chemical industry. Commodity chemicals, such as acetic acid, citric acid, and ethanol are made by fermentation. Moreover, nearly all commercially produced industrial enzymes, such as lipase, invertase and rennet, are made by fermentation with genetically modified microbes. In some cases, production of biomass itself is the objective, as is the case for single-cell proteins, baker's yeast, and starter cultures for lactic acid bacteria used in cheesemaking.
In general, fermentations can be divided into four types:
* Production of biomass (viable cellular material)
* Production of extracellular metabolites (chemical compounds)
* Production of intracellular components (enzymes and other proteins)
* Transformation of substrate (in which the transformed substrate is itself the product)
These types are not necessarily disjoined from each other, but provide a framework for understanding the differences in approach. The organisms used are typically microorganisms, particularly bacteria, algae, and fungi, such as yeasts and molds, but industrial fermentation may also involve cell cultures from plants and animals, such as CHO cells and insect cells. Special considerations are required for the specific organisms used in the fermentation, such as the dissolved oxygen level, nutrient levels, and temperature. The rate of fermentation depends on the concentration of microorganisms, cells, cellular components, and enzymes as well as temperature, pH and level of oxygen for aerobic fermentation. Product recovery frequently involves the concentration of the dilute solution. | 1 | Applied and Interdisciplinary Chemistry |
The natural reactor of Oklo has been used to check if the atomic fine-structure constant α might have changed over the past 2 billion years. That is because α influences the rate of various nuclear reactions. For example, captures a neutron to become , and since the rate of neutron capture depends on the value of α, the ratio of the two samarium isotopes in samples from Oklo can be used to calculate the value of α from 2 billion years ago.
Several studies have analysed the relative concentrations of radioactive isotopes left behind at Oklo, and most have concluded that nuclear reactions then were much the same as they are today, which implies α was the same too. | 0 | Theoretical and Fundamental Chemistry |
MR fluids often contain surfactants including, but not limited to:
* oleic acid
* tetramethylammonium hydroxide
* citric acid
* soy lecithin
These surfactants serve to decrease the rate of ferroparticle settling, of which a high rate is an unfavorable characteristic of MR fluids. The ideal MR fluid would never settle, but developing this ideal fluid is as highly improbable as developing a perpetual motion machine according to our current understanding of the laws of physics. Surfactant-aided prolonged settling is typically achieved in one of two ways: by addition of surfactants, and by addition of spherical ferromagnetic nanoparticles. Addition of the nanoparticles results in the larger particles staying suspended longer since the non-settling nanoparticles interfere with the settling of the larger micrometre-scale particles due to Brownian motion. Addition of a surfactant allows micelles to form around the ferroparticles. A surfactant has a polar head and non-polar tail (or vice versa), one of which adsorbs to a ferroparticle, while the non-polar tail (or polar head) sticks out into the carrier medium, forming an inverse or regular micelle, respectively, around the particle. This increases the effective particle diameter. Steric repulsion then prevents heavy agglomeration of the particles in their settled state, which makes fluid remixing (particle redispersion) occur far faster and with less effort. For example, magnetorheological dampers will remix within one cycle with a surfactant additive, but are nearly impossible to remix without them.
While surfactants are useful in prolonging the settling rate in MR fluids, they also prove detrimental to the fluid's magnetic properties (specifically, the magnetic saturation), which is commonly a parameter which users wish to maximize in order to increase the maximum apparent yield stress. Whether the anti-settling additive is nanosphere-based or surfactant-based, their addition decreases the packing density of the ferroparticles while in its activated state, thus decreasing the fluids on-state/activated viscosity, resulting in a "softer" activated fluid with a lower maximum apparent yield stress. While the on-state viscosity (the "hardness" of the activated fluid) is also a primary concern for many MR fluid applications, it is a primary fluid property for the majority of their commercial and industrial applications and therefore a compromise must be met when considering on-state viscosity, maximum apparent yields stress, and settling rate of an MR fluid. | 1 | Applied and Interdisciplinary Chemistry |
Early studies in Caenorhabditis elegans and Drosophila melanogaster saw large-scale, systematic loss of function (LOF) screens performed through saturation mutagenesis, demonstrating the potential of this approach to characterise genetic pathways and identify genes with unique and essential functions. The saturation mutagenesis technique was later applied in other organisms, for example zebrafish and mice.
Targeted approaches for gene knockdown emerged in the 1980s with techniques such as homologous recombination, trans-cleaving ribozymes, and antisense technologies.
By the year 2000, RNA interference (RNAi) technology had emerged as a fast, simple, and inexpensive technique for targeted gene knockdown, and was routinely being used to study in vivo gene function in C. elegans. Indeed, in the span of only a few years following its discovery by Fire et al. (1998), almost all of the ~19,000 genes in C. elegans had been analysed using RNAi-based knockdown.
The production of RNAi libraries facilitated the application of this technology on a genome-wide scale, and RNAi-based methods became the predominant approach for genome-wide knockdown screens.
Nevertheless, RNAi-based approaches to genome-wide knockdown screens have their limitations. For one, the high off-target effects cause issues with false-positive observations. Additionally, because RNAi reduces gene expression at the post-transcriptional level by targeting RNA, RNAi-based screens only result in partial and short-term suppression of genes. Whilst partial knockdown may be desirable in certain situations, a technology with improved targeting efficiency and fewer off-target effects was needed.
Since initial identification as a prokaryotic adaptive immune system, the bacterial type II clustered regularly interspaced short palindrome repeats (CRISPR)/Cas9 system has become a simple and efficient tool for generating targeted LOF mutations. It has been successfully applied to edit human genomes, and has started to displace RNAi as the dominant tool in mammalian studies. In the context of genome-wide knockout screens, recent studies have demonstrated that CRISPR/Cas9 screens are able to achieve highly efficient and complete protein depletion, and overcome the off-target issues seen with RNAi screens. In summary, the recent emergence of CRISPR-Cas9 has dramatically increased our ability to perform large-scale LOF screens. The versatility and programmability of Cas9, coupled with the low noise, high knockout efficiency and minimal off-target effects, have made CRISPR the platform of choice for many researchers engaging in gene targeting and editing. | 1 | Applied and Interdisciplinary Chemistry |
Hydraulic Engineering Circular Manual No. 18 (HEC-18) was published by the FHWA, and includes several techniques of estimating scour depth. The empirical scour equations for live-bed scour, clear-water scour, and local scour at piers and abutments are shown in the Chapter 5General Scour section. The total scour depth is determined by adding three scour components which includes the long-term aggradation and degradation of the river bed, general scour at the bridge and local scour at the piers or abutment. However, research has shown that the standard equations in HEC-18 over-predict scour depth for a number of hydraulic and geologic conditions. Most of the HEC-18 relationships are based on laboratory flume studies conducted with sand-sized sediments increased with factors of safety that are not easily recognizable or adjustable. Sand and fine gravel are the most easily eroded bed materials, but streams frequently contain much more scour resistant materials such as compact till, stiff clay, and shale. The consequences of using design methods based on a single soil type are especially significant for many major physiographic provinces with distinctly different geologic conditions and foundation materials. This can lead to overly conservative design values for scour in low risk or non-critical hydrologic conditions. Thus, equation improvements are continued to be made in an effort to minimize the underestimation and overestimation of scour. | 1 | Applied and Interdisciplinary Chemistry |
Polycrystalline silicon, or multicrystalline silicon (multi-Si) cells are made from cast square ingots—large blocks of molten silicon carefully cooled and solidified. They consist of small crystals giving the material its typical metal flake effect. Polysilicon cells are the most common type used in photovoltaics and are less expensive, but also less efficient, than those made from monocrystalline silicon. | 0 | Theoretical and Fundamental Chemistry |
Because the urea conversion is incomplete, the urea must be separated from the unconverted reactants, including the ammonium carbamate. Various commercial urea processes are characterized by the conditions under which urea forms and the way that unconverted reactants are further processed. | 0 | Theoretical and Fundamental Chemistry |
Ratsimamanga married Suzanne Urverg-Ratsimamanga on 23 March 1963. She was a French Ashkenazi Jewish biochemist, a Fellow of the World Academy of Sciences (1989), and the African Academy of Sciences (1987), and IMRAs Chair and Alberts closest collaborator. With Albert, she co-founded "Albert and Suzanne Rakoto Ratsimamanga Foundation" within IMRA.
Ratsimamanga died on 16 September 2001, aged 93, in Antananarivo, Madagascar. A state funeral was held for him. | 1 | Applied and Interdisciplinary Chemistry |
The main driver of the concept is the beam effect, which indicates the influence of sections in very good ecological condition on sections in less good or rather poor condition with respect to their ecological status. There are two categories of beam effects which are biotic and abiotic. The biotic beam effect relies on the migration or drift of typical aquatic organisms; the abiotic beam effect refers to the transport of positive environmental conditions from one directed downstream. In general, the beam effect is not tied to the flow direction of the running water and can occur both upstream and downstream.
In contrast, negative long-distance and vicinity effects cause the opposite effect to the positive beam effect, thus deteriorate the ecological condition of running waters. For instance, negative biotic effects are migration or drift of atypical aquatic organisms, that might have a negative effect on domestic species in their habitats; carry-over of fine sediments, material load or temperature influences are examples of negative abiotic effects on the ecological condition. Another negative effect is given by the so-called colmation, which is the accumulation of fine particles on gravel deposits. Since the pores are used by organisms for spawning, over time the sediments cut off the oxygen supply, cover the gravels with a solid layer and destroy the habitat of local species. | 1 | Applied and Interdisciplinary Chemistry |
In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence of chemical reactions catalyzed by enzymes. In most cases of a metabolic pathway, the product of one enzyme acts as the substrate for the next. However, side products are considered waste and removed from the cell.
Different metabolic pathways function in the position within a eukaryotic cell and the significance of the pathway in the given compartment of the cell. For instance, the electron transport chain and oxidative phosphorylation all take place in the mitochondrial membrane. In contrast, glycolysis, pentose phosphate pathway, and fatty acid biosynthesis all occur in the cytosol of a cell.
There are two types of metabolic pathways that are characterized by their ability to either synthesize molecules with the utilization of energy (anabolic pathway), or break down complex molecules and release energy in the process (catabolic pathway).
The two pathways complement each other in that the energy released from one is used up by the other. The degradative process of a catabolic pathway provides the energy required to conduct the biosynthesis of an anabolic pathway. In addition to the two distinct metabolic pathways is the amphibolic pathway, which can be either catabolic or anabolic based on the need for or the availability of energy.
Pathways are required for the maintenance of homeostasis within an organism and the flux of metabolites through a pathway is regulated depending on the needs of the cell and the availability of the substrate. The end product of a pathway may be used immediately, initiate another metabolic pathway or be stored for later use. The metabolism of a cell consists of an elaborate network of interconnected pathways that enable the synthesis and breakdown of molecules (anabolism and catabolism). | 1 | Applied and Interdisciplinary Chemistry |
It is now known from study of the Sun and primitive meteorites that the solar system was initially almost homogeneous in isotopic composition. Deviations from the (evolving) galactic average, locally sampled around the time that the Sun's nuclear burning began, can generally be accounted for by mass fractionation (see the article on mass-independent fractionation) plus a limited number of nuclear decay and transmutation processes. There is also evidence for injection of short-lived (now-extinct) isotopes from a nearby supernova explosion that may have triggered solar nebula collapse. Hence deviations from natural abundance on Earth are often measured in parts per thousand (per mille or ‰) because they are less than one percent (%).
An exception to this lies with the presolar grains found in primitive meteorites. These small grains condensed in the outflows of evolved ("dying") stars and escaped the mixing and homogenization processes in the interstellar medium and the solar accretion disk (also known as the solar nebula or protoplanetary disk). As stellar condensates ("stardust"), these grains carry the isotopic signatures of specific nucleosynthesis processes in which their elements were made. In these materials, deviations from "natural abundance" are sometimes measured in factors of 100. | 0 | Theoretical and Fundamental Chemistry |
In 1960, physicist John H. Reynolds discovered that certain meteorites contained an isotopic anomaly in the form of an overabundance of Xe. He inferred that this must be a decay product of long-decayed radioactive I. This isotope is produced in quantity in nature only in supernova explosions. As the half-life of I is comparatively short in astronomical terms, this demonstrated that only a short time had passed between the supernova and the time the meteorites had solidified and trapped the I. These two events (supernova and solidification of gas cloud) were inferred to have happened during the early history of the Solar System, as the I isotope was likely generated before the Solar System was formed, but not long before, and seeded the solar gas cloud isotopes with isotopes from a second source. This supernova source may also have caused collapse of the solar gas cloud. | 0 | Theoretical and Fundamental Chemistry |
UNSCEAR recommends a reference value of 9 nSv (Bq·h/m).
For example, a person living (7000 h/year) in a concentration of 40 Bq/m receives an effective dose of 1 mSv/year.
Studies of miners exposed to radon and its decay products provide a direct basis for assessing their lung cancer risk. The BEIR VI report, entitled Health Effects of Exposure to Radon, reported an excess relative risk from exposure to radon that was equivalent to 1.8% per megabecquerel hours per cubic meter (MBq·h/m) (95% confidence interval: 0.3, 35) for miners with cumulative exposures below 30 MBq·h/m. Estimates of risk per unit exposure are 5.38×10 per WLM; 9.68×10/WLM for ever smokers; and 1.67×10 per WLM for never smokers.
According to the UNSCEAR modeling, based on these miner's studies, the excess relative risk from long-term residential exposure to radon at 100 Bq/m is considered to be about 0.16 (after correction for uncertainties in exposure assessment), with about a threefold factor of uncertainty higher or lower than that value.
In other words, the absence of ill effects (or even positive hormesis effects) at 100 Bq/m are compatible with the known data.
The ICPR 65 model follows the same approach, and estimates the relative lifelong risk probability of radon-induced cancer death to 1.23 × 10 per Bq/(m·year). This relative risk is a global indicator; the risk estimation is independent of sex, age, or smoking habit. Thus, if a smokers chances of dying of lung cancer are 10 times that of a nonsmokers, the relative risks for a given radon exposure will be the same according to that model, meaning that the absolute risk of a radon-generated cancer for a smoker is (implicitly) tenfold that of a nonsmoker.
The risk estimates correspond to a unit risk of approximately 3–6 × 10 per Bq/m, assuming a lifetime risk of lung cancer of 3%. This means that a person living in an average European dwelling with 50 Bq/m has a lifetime excess lung cancer risk of 1.5–3 × 10. Similarly, a person living in a dwelling with a high radon concentration of 1000 Bq/m has a lifetime excess lung cancer risk of 3–6%, implying a doubling of background lung cancer risk.
The BEIR VI model proposed by the National Academy of Sciences of the USA is more complex. It is a multiplicative model that estimates an excess risk per exposure unit. It takes into account age, elapsed time since exposure, and duration and length of exposure, and its parameters allow for taking smoking habits into account.
In the absence of other causes of death, the absolute risks of lung cancer by age 75 at usual radon concentrations of 0, 100, and 400 Bq/m would be about 0.4%, 0.5%, and 0.7%, respectively, for lifelong nonsmokers, and about 25 times greater (10%, 12%, and 16%) for cigarette smokers.
There is great uncertainty in applying risk estimates derived from studies in miners to the effects of residential radon, and direct estimates of the risks of residential radon are needed.
As with the miner data, the same confounding factor of other carcinogens such as dust applies. | 1 | Applied and Interdisciplinary Chemistry |
A further method to differentiate converted from unconverted bisulfite-treated DNA is using high-resolution melting analysis (HRM), a quantitative PCR-based technique initially designed to distinguish SNPs. The PCR amplicons are analyzed directly by temperature ramping and resulting liberation of an intercalating fluorescent dye during melting. The degree of methylation, as represented by the C-to-T content in the amplicon, determines the rapidity of melting and consequent release of the dye. This method allows direct quantitation in a single-tube assay, but assesses methylation in the amplified region as a whole rather than at specific CpG sites. | 1 | Applied and Interdisciplinary Chemistry |
In Suzuki-Miyaura cross-couplings, the traditional coupling partners are organobromides and organoboron compounds. While Suzuki-Miyaura cross-couplings typically employ organobromides as coupling partners, organochlorides are more desirable electrophiles for cross-coupling due to their lower cost. The sluggish reactivity of the C-Cl bond is often a problem. With the advent of Pd-NHC complexes, organochlorides have emerged as viable partners in Suzuki-Miyaura cross coupling. | 0 | Theoretical and Fundamental Chemistry |
A domestic refrigerator is an example of a heat pump: a heat engine in reverse. Work is used to create a heat differential. Many cycles can run in reverse to move heat from the cold side to the hot side, making the cold side cooler and the hot side hotter. Internal combustion engine versions of these cycles are, by their nature, not reversible.
Refrigeration cycles include:
*Air cycle machine
*Gas-absorption refrigerator
*Magnetic refrigeration
*Stirling cryocooler
*Vapor-compression refrigeration
*Vuilleumier cycle | 0 | Theoretical and Fundamental Chemistry |
Vaginal aplasia is a rare medical condition in which the vagina does not form properly before birth. Those with the condition may have a partially formed vagina, or none at all. The condition is typically treated by reconstructive surgery. First a space is surgically created where the vagina would typically exist. Then tissue from another part of the body is harvested, molded into the shape of a vagina, and grafted into the vagina cavity. This technique has significant drawbacks. Typically, the implanted tissue does not function normally as a muscle, which can lead to low enjoyment of sexual intercourse. Additionally, stenosis (narrowing of the cavity) can occur over time. Most women require multiple surgeries before a satisfactory result is achieved. An alternative to traditional reconstructive surgery is transplantation. | 1 | Applied and Interdisciplinary Chemistry |
Ethanol contained in alcoholic beverages is produced by means of fermentation induced by yeast.
* Wine is produced by fermentation of the natural sugars present in grapes; cider and perry are produced by similar fermentation of natural sugar in apples and pears, respectively; and other fruit wines are produced from the fermentation of the sugars in any other kinds of fruit. Brandy and eaux de vie (e.g. slivovitz) are produced by distillation of these fruit-fermented beverages.
* Mead is produced by fermentation of the natural sugars present in honey.
* Beer, whiskey, and sometimes vodka are produced by fermentation of grain starches that have been converted to sugar by the enzyme amylase, which is present in grain kernels that have been malted (i.e. germinated). Other sources of starch (e.g. potatoes and unmalted grain) may be added to the mixture, as the amylase will act on those starches as well. It may also be amylase-induce fermented with saliva in a few countries. Whiskey and vodka are also distilled; gin and related beverages are produced by the addition of flavoring agents to a vodka-like feedstock during distillation.
* Rice wines (including sake) are produced by the fermentation of grain starches converted to sugar by the mold Aspergillus oryzae. Baijiu, soju, and shōchū are distilled from the product of such fermentation.
* Rum and some other beverages are produced by fermentation and distillation of sugarcane. Rum is usually produced from the sugarcane product molasses.
In all cases, fermentation must take place in a vessel that allows carbon dioxide to escape but prevents outside air from coming in. This is to reduce risk of contamination of the brew by unwanted bacteria or mold and because a buildup of carbon dioxide creates a risk the vessel will rupture or fail, possibly causing injury or property damage. | 1 | Applied and Interdisciplinary Chemistry |
A chemical structure can be represented by a bond network of the kind familiar in molecular diagrams. The infinitely connected bond networks found in crystals can be simplified into finite networks by extracting one formula unit and reconnecting any broken bonds to each other. If the bond network is not known, a plausible network can be created by connecting well matched cations and anions that satisfy Eq. 4. If the finite network contains only cation-anion bonds, every bond can be treated as an electric capacitor (two equal and opposite charges linked by electrostatic flux). The bond network is thus equivalent to a capacitive electrical circuit with the charge on each capacitor being equivalent to the bond valence. The individual bond capacitors are not initially known, but in the absence of any information to the contrary we assume that they are all equal. In this case the circuit can be solved using the Kirchhoff equations, yielding the valences of each bond. Eq. 2 can then be used to calculate bond lengths which are found to lie within a few picometres of the observed bond lengths if no additional constraints are present. Additional constraints include electronic anisotropies (lone pairs and Jahn-Teller distortions) or steric constraints, (bonds stretched or compressed in order to fit them into three-dimensional space). Hydrogen bonds are an example of a steric constraint. The repulsion resulting from the close approach of the donor and acceptor atoms causes the bonds to be stretched, and under this constraint the distortion theorem predicts that the hydrogen atom will move off-center.
The bond valence is a vector directed along the bond since it represents the electrostatic field linking the ions. If the atom is unconstrained, the sum of the bond valence vectors around an atom is expected to be zero, a condition that limits the range of possible bond angles. | 0 | Theoretical and Fundamental Chemistry |
The word polyurea is derived from the Greek words πολυ- - poly- meaning "many"; and ουρίας - oûron meaning "to urinate" (referring to the substance urea, found in urine). Urea or carbamide is an organic compound with the chemical formula (NH)CO. The molecule has two amine groups (–NH) joined by a carbonyl functional group (C=O). In a polyurea, alternating monomer units of isocyanates and amines react with each other to form urea linkages. Ureas can also be formed from the reaction of isocyanates and water which forms a carbamic acid intermediate. This acid quickly decomposes by splitting off carbon dioxide and leaving behind an amine. This amine then reacts with another isocyanate group to form the polyurea linkage. This two step reaction is used to make what is commonly but improperly called polyurethane foam. The carbon dioxide that is liberated in this reaction is the primary blowing (foaming) agent especially in many polyurethane foams which more precisely should be called polyurethane/urea foams. | 0 | Theoretical and Fundamental Chemistry |
Boger fluids are named after David V. Boger, who in the late 1970s was the primary researcher pushing for the study of constant viscosity elastic liquids. He released his first paper on Boger fluids in 1977, titled "A Highly Elastic Constant-Viscosity Fluid", where he described the ideal fluid for experimentation as a fluid that is "highly viscous and highly elastic at room temperature and at the same time is optically clear". The main purpose of the paper was to experiment on the highly viscous and highly elastic fluid and record the fundamental rheometric properties of the fluid. Such a fluid would allow for experimentation under conditions not affected by inertia and shear thinning effects, and influence of inertia would easily be distinguishable.
He began his research using maltose syrups (corn syrups) mixed with a small amount of water. He then tested shear stress versus shear rate of the solution to prove that the solution was a Newtonian fluid. This was done by using a R16 Weissenberg rheogoniometer (a rheogoniometer calibrated to measure specifically the behavior of a viscoelastic polymer solution) for the low range shear stress rates, and the high rates were measured using a capillary rheometer, a device used to measure shear stress rates under high stress. The data proved that there was a linear relationship between shear stress and shear rate with the slope being very close to one, meaning the maltose syrup was indeed a Newtonian fluid. Once 0.08% of the polymer polyacrylamide was added, the flow properties drastically changed. Elastic properties were introduced to the fluid while only a slight amount of shear thinning was observed, small enough to be ignored. The syrup solution had properties very similar to a polymer melt, but there was no shear thinning and the materials could be produced at room temperature. | 1 | Applied and Interdisciplinary Chemistry |
Fundamentally, two types of diffusion are distinguished:
* Tracer diffusion and Self-diffusion, which is a spontaneous mixing of molecules taking place in the absence of concentration (or chemical potential) gradient. This type of diffusion can be followed using isotopic tracers, hence the name. The tracer diffusion is usually assumed to be identical to self-diffusion (assuming no significant isotopic effect). This diffusion can take place under equilibrium. An excellent method for the measurement of self-diffusion coefficients is pulsed field gradient (PFG) NMR, where no isotopic tracers are needed. In a so-called NMR spin echo experiment this technique uses the nuclear spin precession phase, allowing to distinguish chemically and physically completely identical species e.g. in the liquid phase, as for example water molecules within liquid water. The self-diffusion coefficient of water has been experimentally determined with high accuracy and thus serves often as a reference value for measurements on other liquids. The self-diffusion coefficient of neat water is: 2.299·10 m·s at 25 °C and 1.261·10 m·s at 4 °C.
* Chemical diffusion occurs in a presence of concentration (or chemical potential) gradient and it results in net transport of mass. This is the process described by the diffusion equation. This diffusion is always a non-equilibrium process, increases the system entropy, and brings the system closer to equilibrium.
The diffusion coefficients for these two types of diffusion are generally different because the diffusion coefficient for chemical diffusion is binary and it includes the effects due to the correlation of the movement of the different diffusing species. | 1 | Applied and Interdisciplinary Chemistry |
Whether or not a GMO is present in a sample can be tested by Q-PCR, but also by multiplex PCR. Multiplex PCR uses multiple, unique primer sets within a single PCR reaction to produce amplicons of varying sizes specific to different DNA sequences, i.e. different transgenes. By targeting multiple genes at once, additional information may be gained from a single test run that otherwise would require several times the reagents and more time to perform. Annealing temperatures for each of the primer sets must be optimized to work correctly within a single reaction, and amplicon sizes, i.e., their base pair length, should be different enough to form distinct bands when visualized by gel electrophoresis. | 1 | Applied and Interdisciplinary Chemistry |
Because free cysteine rarely occurs on protein surface, it is an excellent choice for chemoselective modification. Under basic condition, the cysteine residues will be deprotonated to generate a thiolate nucleophile, which will react with soft electrophiles, such as maleimides and iodoacetamides (shown in the first two reactions in Figure 2 below). As a result, a carbon-sulfur bond is formed. Another modification of cysteine residues involves the formation of disulfide bond (shown in the third reaction in Figure 2). The reduced cysteine residues react with exogenous disulfides, generating new a disulfide bond on the protein. An excess of disulfides is often used to drive the reaction, such as 2-thiopyridone and 3-carboxy-4-nitrothiophenol. Electron-deficient alkynes were demonstrated to selectively react with cysteine residues of proteins in the presence of other nucleophilic amino acid residues. Depending on the alkyne substitution, these reactions can produce either cleavable (when alkynone derivatives are used), or hydrolytically stable bioconjugates (when 3-arylpropiolonitriles are used; the last reaction below in Figure 2). | 1 | Applied and Interdisciplinary Chemistry |
The malate shuttle allows the mitochondria to move electrons from NADH without the consumption of metabolites and it uses two antiporters to transport metabolites and keep balance within the mitochondrial matrix and cytoplasm.
On the cytoplasmic side a transaminase enzyme is used to remove an amino group from aspartate which is converted into oxaloacetate, then malate dehydrogenase enzyme uses an NADH cofactor to reduce oxaloacetate to malate which can be transported across the membrane because of the presence of a transporter.
Once the malate is inside the matrix its converted back to oxaloacetate, which is converted to aspartate and can be transported back outside the mitochondria to allow the cycle to continue. The movement of oxaloacetate across the membrane transports electrons and is known as the outer ring. The inner ring primary function is not to move electrons but regenerate the metabolites. | 1 | Applied and Interdisciplinary Chemistry |
Carbodiimides such as dicyclohexylcarbodiimide (DCC) and diisopropylcarbodiimide (DIC) are frequently used for amide bond formation. The reaction proceeds via the formation of a highly reactive O-acylisourea. This reactive intermediate is attacked by the peptide N-terminal amine, forming a peptide bond. Formation of the O-acylisourea proceeds fastest in non-polar solvents such as dichloromethane.
DIC is particularly useful for SPPS since as a liquid it is easily dispensed, and the urea byproduct is easily washed away. Conversely, the related carbodiimide 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) is often used for solution-phase peptide couplings as its urea byproduct can be removed by washing during aqueous work-up.
Carbodiimide activation opens the possibility for racemization of the activated amino acid. Racemization can be circumvented with racemization suppressing additives such as the triazoles 1-hydroxy-benzotriazole (HOBt), and 1-hydroxy-7-aza-benzotriazole (HOAt). These reagents attack the O-acylisourea intermediate to form an active ester, which subsequently reacts with the peptide to form the desired peptide bond. Ethyl cyanohydroxyiminoacetate (Oxyma), an additive for carbodiimide coupling, acts as an alternative to HOAt. | 1 | Applied and Interdisciplinary Chemistry |
In the US, nominal pipe sizes vary from 3 inches up to 64 inches, in increments of at least 1 inch, and are standardised according to the American AWWA C-151 | 1 | Applied and Interdisciplinary Chemistry |
Cooling curves are important in controlling the quality of a casting. The most important part of the cooling curve is the cooling rate which affects the microstructure and properties. Generally speaking, an area of the casting which is cooled quickly will have a fine grain structure and an area which cools slowly will have a coarse grain structure. Below is an example cooling curve of a pure metal or eutectic alloy, with defining terminology.
Note that before the thermal arrest the material is a liquid and after it the material is a solid; during the thermal arrest the material is converting from a liquid to a solid. Also, note that the greater the superheat the more time there is for the liquid material to flow into intricate details.
The above cooling curve depicts a basic situation with a pure metal, however, most castings are of alloys, which have a cooling curve shaped as shown below.
Note that there is no longer a thermal arrest, instead there is a freezing range. The freezing range corresponds directly to the liquidus and solidus found on the phase diagram for the specific alloy. | 1 | Applied and Interdisciplinary Chemistry |
The stochastic empirical loading and dilution model (SELDM) is a stormwater quality model. SELDM is designed to transform complex scientific data into meaningful information about the risk of adverse effects of runoff on receiving waters, the potential need for mitigation measures, and the potential effectiveness of such management measures for reducing these risks. The U.S. Geological Survey developed SELDM in cooperation with the Federal Highway Administration to help develop planning-level estimates of event mean concentrations, flows, and loads in stormwater from a site of interest and from an upstream basin. SELDM uses information about a highway site, the associated receiving-water basin, precipitation events, stormflow, water quality, and the performance of mitigation measures to produce a stochastic population of runoff-quality variables. Although SELDM is, nominally, a highway runoff model is can be used to estimate flows concentrations and loads of runoff-quality constituents from other land use areas as well. SELDM was developed by the U.S. Geological Survey so the model, source code, and all related documentation are provided free of any copyright restrictions according to U.S. copyright laws and the USGS Software User Rights Notice. SELDM is widely used to assess the potential effect of runoff from highways, bridges, and developed areas on receiving-water quality with and without the use of mitigation measures. Stormwater practitioners evaluating highway runoff commonly use data from the Highway Runoff Database (HRDB) with SELDM to assess the risks for adverse effects of runoff on receiving waters.
SELDM is a stochastic mass-balance model. A mass-balance approach (figure 1) is commonly applied to estimate the concentrations and loads of water-quality constituents in receiving waters downstream of an urban or highway-runoff outfall. In a mass-balance model, the loads from the upstream basin and runoff source area are added to calculate the discharge, concentration, and load in the receiving water downstream of the discharge point.
SELDM can do a stream-basin analysis and a lake-basin analysis. The stream-basin analysis uses a stochastic mass-balance analysis based on multi-year simulations including hundreds to thousands of runoff events. SELDM generates storm-event values for the site of interest (the highway site) and the upstream receiving stream to calculate flows, concentrations, and loads in the receiving stream downstream of the stormwater outfall. The lake-basin analysis also is a stochastic multi-year mass-balance analysis. The lake-basin analysis uses the highway loads that occur during runoff periods, the total annual loads from the lake basin to calculate annual loads to and from the lake. The lake basin analysis uses the volume of the lake and pollutant-specific attenuation factors to calculate a population of average-annual lake concentrations.
The annual flows and loads SELDM calculates for the stream and lake analyses also can be used to estimate total maximum daily loads (TMDLs) for the site of interest and the upstream lake basin. The TMDL can be based on the average of annual loads because product of the average load times the number of years of record will be the sum-total load for that (simulated) period of record. The variability in annual values can be used to estimate the risk of exceedance and the margin of safety for the TMDL analysis | 1 | Applied and Interdisciplinary Chemistry |
Phenols are produced by heating aqueous solutions of arenediazonium salts:
This reaction goes by the German name Phenolverkochung ("cooking down to yield phenols"). The phenol formed may react with the diazonium salt and hence the reaction is carried in the presence of an acid which suppresses this further reaction. A Sandmeyer-type hydroxylation is also possible using and in water. | 0 | Theoretical and Fundamental Chemistry |
Multiferroics are defined as materials that exhibit more than one of the primary ferroic properties in the same phase:
* ferromagnetism – a magnetisation that is switchable by an applied magnetic field
* ferroelectricity – an electric polarisation that is switchable by an applied electric field
* ferroelasticity – a deformation that is switchable by an applied stress
While ferroelectric ferroelastics and ferromagnetic ferroelastics are formally multiferroics, these days the term is usually used to describe the magnetoelectric multiferroics that are simultaneously ferromagnetic and ferroelectric. Sometimes the definition is expanded to include nonprimary order parameters, such as antiferromagnetism or ferrimagnetism. In addition, other types of primary order, such as ferroic arrangements of magnetoelectric multipoles of which ferrotoroidicity is an example, were proposed.
Besides scientific interest in their physical properties, multiferroics have potential for applications as actuators, switches, magnetic field sensors and new types of electronic memory devices. | 0 | Theoretical and Fundamental Chemistry |
Le Bail analysis is a whole diffraction pattern profile fitting technique used to characterize the properties of crystalline materials, such as structure. It was invented by Armel Le Bail around 1988. | 0 | Theoretical and Fundamental Chemistry |
A J-aggregate is a type of dye with an absorption band that shifts to a longer wavelength (bathochromic shift) of increasing sharpness (higher absorption coefficient) when it aggregates under the influence of a solvent or additive or concentration as a result of supramolecular self-organisation. The dye can be characterized further by a small Stokes shift with a narrow band. The J in J-aggregate refers to E.E. Jelley who discovered the phenomenon in 1936. The dye is also called a Scheibe aggregate after G. Scheibe who also independently published on this topic in 1937.
Scheibe and Jelley independently observed that in ethanol the dye PIC chloride has two broad absorption maxima at around 19,000 cm and 20,500 cm (526 and 488 nm respectively) and that in water a third sharp absorption maximum appears at 17,500 cm (571 nm). The intensity of this band further increases on increasing concentration and on adding sodium chloride. In the oldest aggregation model for PIC chloride the individual molecules are stacked like a roll of coins forming a supramolecular polymer but the true nature of this aggregation phenomenon is still under investigation. Analysis is complicated because PIC chloride is not a planar molecule. The molecular axis can tilt in the stack creating a helix pattern. In other models the dye molecules orient themselves in a brickwork, ladder, or staircase fashion. In various experiments the J-band was found to split as a function of temperature, liquid crystal phases were found with concentrated solutions and CryoTEM revealed aggregate rods 350 nm long and 2.3 nm in diameter.
J-aggregate dyes are found with polymethine dyes in general, with cyanines, merocyanines, squaraine and perylene bisimides. Certain π-conjugated macrocycles, reported by Swager and co-workers at MIT, were also found to form J-aggregates and exhibited exceptionally high photoluminescence quantum yields. In 2020, a famous cyanine dye (TDBC) was reported with enhanced photoluminescence quantum yield (> 50%) in the solution at room-temperature.
Molecular PIC aggregates exhibiting J-like properties have been shown to spontaneously template into sequence specific DNA duplex strands. These DNA based J-aggregates, known as J-bits, have been sought after as a bottom-up method of self-assembling PIC J-aggregates into large scale multi-functional DNA scaffolds. Critically, J-bits have been observed to engage in energy transfer when in proximity to quantum dots as well as organic dyes such as Alexa Fluor dyes. Prototypical DNA energy transfer arrays, which are based on the molecular photonic wire design, use FRET to transfer excitons step-wise down an energy gradient. Since the FRET efficiency between two Fluorophores decays by their separation distance to the 6th power, the spatial limitations of these systems are highly constrained. It is hypothesized that integrating J-bit relays between FRET nodes would allow some of this energy loss to be recouped. In theory, dense packing and rigid alignment of the PIC monomers enables superposition of the transition dipoles allowing excitons to propagate through the length of the aggregate with low loss. | 0 | Theoretical and Fundamental Chemistry |
When the central density becomes large, i.e., or equivalently , the governing equation reduces to
subjected to the conditions and . This is exactly the Lane–Emden equation with polytropic index . Note that in this limit of large densities, the radius
tends to zero. The mass of the white dwarf however tends to a finite limit
The Chandrasekhar limit follows from this limit. | 1 | Applied and Interdisciplinary Chemistry |
*Federal Interagency Stream Restoration Working Group (United States)(2001). [https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/water/manage/?&cid=stelprdb1043448 Stream Corridor Restoration: Principles, Processes, and Practices.] GPO Item No. 0120-A; SuDocs No. A 57.6/2:EN 3/PT.653. . | 1 | Applied and Interdisciplinary Chemistry |
Averaging pitot tubes (also called impact probes) extend the theory of pitot tube to more than one dimension. A typical averaging pitot tube consists of three or more holes (depending on the type of probe) on the measuring tip arranged in a specific pattern. More holes allow the instrument to measure the direction of the flow velocity in addition to its magnitude (after appropriate calibration). Three holes arranged in a line allow the pressure probes to measure the velocity vector in two dimensions. Introduction of more holes, e.g. five holes arranged in a "plus" formation, allow measurement of the three-dimensional velocity vector. | 1 | Applied and Interdisciplinary Chemistry |
Phospholipid liposomes are used as targeted drug delivery systems. Hydrophilic drugs can be carried as solution inside the SUVs or MLVs and hydrophobic drugs can be incorporated into lipid bilayer of these liposomes. If injected into circulation of human/animal body, MLVs are preferentially taken up phagocytic cells, and thus drugs can be targeted to these cells. For general or overall delivery, SUVs may be used. For topical applications on skin, specialized lipids like phospholipids and sphingolipids may be used to make drug-free liposomes as moisturizers, and with drugs such as for anti-ultraviolet radiation applications.
In biomedical research, unilamellar liposomes are extremely useful to study biological systems and mimicking cell functions. As a living cell is very complicated to study, unilamellar liposomes provide a simple tool to study membrane interaction events such as membrane fusion, protein localization in the plasma membrane, study ion channels, etc. | 0 | Theoretical and Fundamental Chemistry |
The A-stage, or adsorption stage is the most innovative component of the process. It is not preceded by primary treatment. Influent organic matter is removed in the A-stage mainly by flocculation and sorption to sludge due to the high loading rates (2–10 g BOD • g VSS • d) and low sludge age (typically 4–10 h). Hydrolysis of complex organic molecules occurs improving biodegradability of the influent of the B-stage. High loading rates and low sludge age favours development of dynamic biocoenosis with a large fraction of microorganisms present in the exponential growth phase. Diverse sludge biocoenosis increase variety of organic compounds that can be degraded in the A-stage and makes the process more stable towards the shock loads. Altogether, up to 80% of the influent organic matter can be removed in the A-stage. The required reactor volume and oxygen supply are lower if compared to the removal in the conventional activated sludge process.
The B-stage, or bio-oxidation stage, is a typical low-loaded activated sludge process, where biodegradation of the remaining organic material occurs. The B-stage can be designed for nitrogen and/or phosphorus removal by alternating aerobic, anoxic and anaerobic zones in the reactor. | 1 | Applied and Interdisciplinary Chemistry |
Systems similar to Ames test have been developed in yeast. Saccharomyces cerevisiae is generally used. These systems can check for forward and reverse mutations, as well as recombinant events. | 0 | Theoretical and Fundamental Chemistry |
HYSYS is a portmanteau formed from Hyprotech, the name of the company which created the software, and Systems. | 1 | Applied and Interdisciplinary Chemistry |
In 1972, C.W. Horsting of the RCA Corporation published a paper which reported test results on the reliability of semiconductor devices in which the connections were made using aluminium wires bonded ultrasonically to gold plated posts. His paper demonstrated the importance of the Kirkendall effect in wire bonding technology, but also showed the significant contribution of any impurities present to the rate at which precipitation occurred at the wire bonds. Two of the important contaminants that have this effect, known as Horsting effect (Horsting voids) are fluorine and chlorine. Both Kirkendall voids and Horsting voids are known causes of wire bond fractures, though historically this cause is often confused with the purple colored appearance of one of the five different gold-aluminium intermetallics, commonly referred to as "purple plague" and less often "white plague". | 1 | Applied and Interdisciplinary Chemistry |
The synthesis of the ligands often involves the reaction between 1,3-dibromoethylbenzene with a secondary phosphine followed by deprotonation of the quaternary phosphorus intermediates to generate the ligand.
To generate the metal complex, two common routes are employed. One is a simple oxidative addition of the ipso-C-X bond where X = Br, I to a metal centre, often a M(0) (M = Pd, Mo, Fe, Ru, Ni, Pt) though other metal complexes with higher oxidation states available can also be used (e.g. Rh(COD)Cl).
The other significant method of metal introduction is through C-H bond activation., The major difference is that the metal used in this method is already in a higher oxidation state (e.g. PdCl – Pd(II) species). However, these reactions have been found to proceed much more efficiently by employing metal complexes with weakly-bound ligands (e.g. Pd(BF)(CHCN) or Pd(OTf)(CHCN) where OTf = FCOSO). | 0 | Theoretical and Fundamental Chemistry |
An example of the operations of the nucleic acid extraction apparatus which incorporates
Tajima pipette are typically as shown in Fig. 1. | 1 | Applied and Interdisciplinary Chemistry |
EDC is commercially available. It may be prepared by coupling ethyl isocyanate to N,N-dimethylpropane-1,3-diamine to give a urea, followed by dehydration: | 1 | Applied and Interdisciplinary Chemistry |
The bypass transition scenario was first observed experimentally by P. S. Klebanoff, during his experiments in elevated free-stream turbulence flow. Klebanoff identified an important aspect of the bypass transition. In an experiment using hot wires, he studied flow over a flat plate that was subjected to a 0.3% free-stream turbulence level. At this moderate free-stream turbulence level, he observed a velocity perturbation signal with a frequency under 12Hz, much smaller than the usual Tollmien-Schlichting wave frequency. He also observed fluctuations in boundary layer thickness, which does not occur in low-turbulence free-stream flow. | 1 | Applied and Interdisciplinary Chemistry |
The butyrate or butanoate ion, , is the conjugate base of butyric acid. It is the form found in biological systems at physiological pH. A butyric (or butanoic) compound is a carboxylate salt or ester of butyric acid. | 1 | Applied and Interdisciplinary Chemistry |
Phosphaalkynes with small substituents (H, F, Me, Ph, etc.) undergo decomposition at or below room temperature by way of polymerization/oligimerization to yield mixtures of products which are challenging to characterize. The same is largely true of kinetically stable phosphaalkynes, which undergo oligomerization reactions at elevated temperature. In spite of the challenges associated with isolating and identifying the products of these oligimerizations, however, cuboidal tetramers of tert-butylphosphaalkyne and tert-pentylphosphaalkyne have been isolated (albeit in low yield) and identified following heating of the respective phosphaalkyne.
Computational chemistry has proved a valuable tool for studying these synthetically complex reactions, and it has been shown that while the formation of phosphaalkyne dimers is thermodynamically favorable, the formation of trimers, tetramers, and higher order oligomeric species tends to be more favorable, accounting for the generation of intractable mixtures upon inducing oligomerization of phosphaalkynes experimentally. | 0 | Theoretical and Fundamental Chemistry |
A number of datable minerals occur as common detrital grains in sandstones, and if the strata have not been buried too deeply, these minerals grains retain information about the source rock. Fission track analysis of these minerals provides information about the thermal evolution of the source rocks and therefore can be used to understand provenance and the evolution of mountain belts that shed the sediment. This technique of detrital analysis is most commonly applied to zircon because it is very common and robust in the sedimentary system, and in addition it has a relatively high annealing temperature so that in many sedimentary basins the crystals are not reset by later heating.
Fission-track dating of detrital zircon is a widely applied analytical tool used to understand the tectonic evolution of source terrains that have left a long and continuous erosional record in adjacent basin strata. Early studies focused on using the cooling ages in detrital zircon from stratigraphic sequences to document the timing and rate of erosion of rocks in adjacent orogenic belts (mountain ranges). A number of recent studies have combined U/Pb and/or Helium dating (U+Th/He) on single crystals to document the specific history of individual crystals. This double-dating approach is an extremely powerful provenance tool because a nearly complete crystal history can be obtained, and therefore researchers can pinpoint specific source areas with distinct geologic histories with relative certainty. Fission-track ages on detrital zircon can be as young as 1 Ma to as old as 2000 Ma. | 0 | Theoretical and Fundamental Chemistry |
Surface plasmon resonance can be implemented in analytical instrumentation. SPR instruments consist of a light source, an input scheme, a prism with analyte interface, a detector, and computer. | 0 | Theoretical and Fundamental Chemistry |
At equilibrium, the sum of the chemical potentials of the reactants is equal to the sum of the chemical potentials of the products. The Gibbs free energy change for the reactions, ΔG, is equal to the difference between these sums and therefore, at equilibrium, is equal to zero. Thus, for an equilibrium such as
Substitute in the expressions for the chemical potential of each reactant:
Upon rearrangement this expression becomes
The sum
is the standard free energy change for the reaction, .
Therefore,
where is the equilibrium constant. Note that activities and equilibrium constants are dimensionless numbers.
This derivation serves two purposes. It shows the relationship between standard free energy change and equilibrium constant. It also shows that an equilibrium constant is defined as a quotient of activities. In practical terms this is inconvenient. When each activity is replaced by the product of a concentration and an activity coefficient, the equilibrium constant is defined as
where [S] denotes the concentration of S, etc. In practice equilibrium constants are determined in a medium such that the quotient of activity coefficient is constant and can be ignored, leading to the usual expression
which applies under the conditions that the activity quotient has a particular (constant) value. | 0 | Theoretical and Fundamental Chemistry |
An early C-symmetric ligand, diphosphine catalytic ligand DIPAMP, was developed in 1968 by William S. Knowles and coworkers of Monsanto Company, who shared the 2001 Nobel Prize in Chemistry. This ligand was used in the industrial production of -DOPA.
Some classes of C-symmetric ligands are called privileged ligands, which are ligands that are broadly applicable to multiple catalytic processes, not only a single reaction type. | 0 | Theoretical and Fundamental Chemistry |
Conductivity measurement is a versatile tool in process control. The measurement is simple and fast, and most advanced sensors require only a little maintenance. The measured conductivity reading can be used to make various assumptions on what is happening in the process. In some cases it is possible to develop a model to calculate the concentration of the liquid.
Concentration of pure liquids can be calculated when the conductivity and temperature is measured. The preset curves for various acids and bases are commercially available. For example, one can measure the concentration of high purity hydrofluoric acid using conductivity-based concentration measurement [Zhejiang Quhua Fluorchemical, China Valmet Concentration 3300]. A benefit of conductivity- and temperature-based concentration measurement is the superior speed of inline measurement compared to an on-line analyzer.
Conductivity-based concentration measurement has limitations. The concentration-conductivity dependence of most acids and bases is not linear. Conductivity-based measurement cannot determine on which side of the peak the measurement is, and therefore the measurement is only possible on a linear section of the curve.
Kraft pulp mills use conductivity-based concentration measurement to control alkali additions to various stages of the cook. Conductivity measurement will not determine the specific amount of alkali components, but it is a good indication on the amount of effective alkali (NaOH + NaS as NaOH or NaO) or active alkali (NaOH + NaS as NaOH or NaO) in the cooking liquor. The composition of the liquor varies between different stages of the cook. Therefore, it is necessary to develop a specific curve for each measurement point or to use commercially available products.
The high pressure and temperature of cooking process, combined with high concentration of alkali components, put a heavy strain on conductivity sensors that are installed in process. The scaling on the electrodes needs to be taken into account, otherwise the conductivity measurement drifts, requiring increased calibration and maintenance. | 0 | Theoretical and Fundamental Chemistry |
The United States Environmental Protection Agency has set a maximum contaminant level for benzene in drinking water at 0.0005 mg/L (5 ppb), as promulgated via the U.S. National Primary Drinking Water Regulations. This regulation is based on preventing benzene leukemogenesis. The maximum contaminant level goal (MCLG), a nonenforceable health goal that would allow an adequate margin of safety for the prevention of adverse effects, is zero benzene concentration in drinking water. The EPA requires that spills or accidental releases into the environment of 10 pounds (4.5 kg) or more of benzene be reported.
The U.S. Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit of 1 part of benzene per million parts of air (1 ppm) in the workplace during an 8-hour workday, 40-hour workweek. The short term exposure limit for airborne benzene is 5 ppm for 15 minutes. These legal limits were based on studies demonstrating compelling evidence of health risk to workers exposed to benzene. The risk from exposure to 1 ppm for a working lifetime has been estimated as 5 excess leukemia deaths per 1,000 employees exposed. (This estimate assumes no threshold for benzene's carcinogenic effects.) OSHA has also established an action level of 0.5 ppm to encourage even lower exposures in the workplace.
The U.S. National Institute for Occupational Safety and Health (NIOSH) revised the Immediately Dangerous to Life and Health (IDLH) concentration for benzene to 500 ppm. The current NIOSH definition for an IDLH condition, as given in the NIOSH Respirator Selection Logic, is one that poses a threat of exposure to airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment. The purpose of establishing an IDLH value is (1) to ensure that the worker can escape from a given contaminated environment in the event of failure of the respiratory protection equipment and (2) is considered a maximum level above which only a highly reliable breathing apparatus providing maximum worker protection is permitted. In September 1995, NIOSH issued a new policy for developing recommended exposure limits (RELs) for substances, including carcinogens. As benzene can cause cancer, NIOSH recommends that all workers wear special breathing equipment when they are likely to be exposed to benzene at levels exceeding the REL (10-hour) of 0.1 ppm. The NIOSH short-term exposure limit (STEL – 15 min) is 1 ppm.
American Conference of Governmental Industrial Hygienists (ACGIH) adopted Threshold Limit Values (TLVs) for benzene at 0.5 ppm TWA and 2.5 ppm STEL. | 1 | Applied and Interdisciplinary Chemistry |
Rain gardens are a form of stormwater management using water capture. Rain gardens are shallow depressed areas in the landscape, planted with shrubs and plants that are used to collect rainwater from roofs or pavement and allows for the stormwater to slowly infiltrate into the ground.
Ubiquitous lawn grass is not a solution for controlling runoff, so an alternative is required to reduce urban and suburban first flush (highly toxic) runoff and to slow the water down for infiltration. In residential applications, water runoff can be reduced by 30% with the use of rain gardens in the homeowner’s yard. A minimum size of 150 sq. ft. up to a range of 300 sq. ft. is the usual size considered for a private property residence. The cost per square foot is about $5–$25, depending on the type of plants you use and the slope of the property. Native trees, shrubs, and herbaceous perennials of the wetland and riparian zones being the most useful for runoff detoxification. | 1 | Applied and Interdisciplinary Chemistry |
SOFIA comprises a multiwell plate sample container, an automated means for successively transporting samples from the multiwell plate sample container to a transparent capillary contained within a sample holder, an excitation source in optical communication with the sample, wherein radiation from the excitation source is directed along the length of the capillary, and wherein the radiation induces a signal which is emitted from the sample, and, at least one linear array. | 1 | Applied and Interdisciplinary Chemistry |
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