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Nitrite can enter two kinds of reaction, depending on the physico-chemical environment.
* Nitrosylation is adding a nitrosyl ion to a metal (e.g. iron) or a thiol, leading to nitrosyl iron (e.g., in nitrosylated heme = nitrosylheme) or S-nitrosothiols (RSNOs).
* Nitrosation is adding a nitrosonium ion to an amine – leading to a nitrosamine. This conversion occurs at acidic pH, particularly in the stomach, as shown in the equation for the formation of N-phenylnitrosamine:
Many primary alkyl N-nitroso compounds, such as , tend to be unstable with respect to hydrolysis to the alcohol. Those derived from secondary amines (e.g., derived from dimethylamine) are more robust. It is these N-nitrosamines that are carcinogens in rodents. | 0 | Theoretical and Fundamental Chemistry |
Increases in carbon capture and sequestration have been observed in both mangrove and seagrass ecosystems which have been subjected to high nutrient loads, either intentionally or due to waste from human activities.
Research done on mangrove soils from the Red Sea have shown that increases in nutrient loads to these soils do not increase carbon mineralization and subsequent CO release. This neutral effect of fertilization was not found to be true in all mangrove forest types. Carbon capture rates also increased in these forests due to increased growth rates of the mangroves. In forests with increases in respiration there were also increases in mangrove growth of up to six times the normal rate. | 0 | Theoretical and Fundamental Chemistry |
Hydrofluoric acid, the water solution of hydrogen fluoride (HF), is a contact poison. Even though it is from a chemical perspective a relatively weak acid, it is far more dangerous than conventional strong mineral acids, such as nitric acid, sulfuric acid, or hydrochloric acid. Owing to its lesser chemical dissociation in water (remaining a neutral molecule), hydrogen fluoride penetrates tissue more quickly than typical acids. Poisoning can occur readily through the skin or eyes or when inhaled or swallowed. From 1984 to 1994, at least nine workers died in the United States from accidents with HF.
Once in the blood, hydrogen fluoride reacts with calcium and magnesium, resulting in electrolyte imbalances, potentially including hypocalcemia. The consequent effect on the heart (cardiac arrhythmia) may be fatal. Formation of insoluble calcium fluoride also causes severe pain. Burns with areas larger than 160 cm, about the size of a man's hand, can cause serious systemic toxicity.
Symptoms of exposure to hydrofluoric acid may not be immediately evident, with an eight-hour delay for 50% HF and up to 24 hours for lower concentrations. Hydrogen fluoride interferes with nerve function, meaning that burns may not initially be painful. If the burn has been initially noticed, then HF should be washed off with a forceful stream of water for ten to fifteen minutes to prevent its further penetration into the body. Clothing used by the person burned may also present a danger. Hydrofluoric acid exposure is often treated with calcium gluconate, a source of Ca that binds with the fluoride ions. Skin burns can be treated with a water wash and 2.5 percent calcium gluconate gel or special rinsing solutions. Because HF is absorbed, further medical treatment is necessary. Calcium gluconate may be injected or administered intravenously. Use of calcium chloride is contraindicated and may lead to severe complications. Sometimes surgical excision of tissue or amputation is required. | 1 | Applied and Interdisciplinary Chemistry |
Penicillamine was developed to treat Wilsons disease, a rare hereditary disease that can lead to a fatal accumulation of copper in the body. This drug was later found to be effective in treating arthritis. Bis-choline tetrathiomolybdate is currently under investigation as a therapy against Wilsons disease. | 1 | Applied and Interdisciplinary Chemistry |
The Lely method, also known as the Lely process or Lely technique, is a crystal growth technology used for producing silicon carbide crystals for the semiconductor industry. The patent for this method was filed in the Netherlands in 1954 and in the United States in 1955 by Jan Anthony Lely of Philips Electronics. The patent was subsequently granted on 30 September 1958, then was refined by D. R. Hamilton et al. in 1960, and by V. P. Novikov and V. I. Ionov in 1968. | 0 | Theoretical and Fundamental Chemistry |
Rural areas with low population density may not need formal FSM services if the local practice is to cover and rebuild latrines when they fill up. However, if this is not possible, rural areas often lack treatment facilities within a reasonable (say 30 minutes drive) distance; are difficult for tankers to access and often have limited demand for emptying making transport and treatment uneconomic, and unaffordable for most people. Therefore, options such as relocating latrines on-site, double (alternating) pit or Arborloo toilets could be considered. Also sharing decentralized FSM services and sludge treatment between nearby villages, or direct safe removal burial of waste could be considered and organized. | 1 | Applied and Interdisciplinary Chemistry |
*Glutamine is the most abundant amino acid in the plasma and an additional energy source in tumor cells especially when glycolytic energy production is low due to a high amount of the dimeric form of M2-PK.
*Glutamine and its degradation products glutamate and aspartate are precursors for nucleic acid and serine synthesis.
*Glutaminolysis is insensitive to high concentrations of reactive oxygen species (ROS).
*Due to the truncation of the citric acid cycle the amount of acetyl-CoA infiltrated in the citric acid cycle is low and acetyl-CoA is available for de novo synthesis of fatty acids and cholesterol. The fatty acids can be used for phospholipid synthesis or can be released.
*Fatty acids represent an effective storage vehicle for hydrogen. Therefore, the release of fatty acids is an effective way to get rid of cytosolic hydrogen produced within the glycolytic glyceraldehyde 3-phosphate dehydrogenase (GAPDH; EC 1.2.1.9) reaction.
*Glutamate and fatty acids are immunosuppressive. The release of both metabolites may protect tumor cells from immune attacks.
*It has been discussed that the glutamate pool may drive the endergonic uptake of other amino acids by system ASC.
*Glutamine can be converted to citrate without NADH production, uncoupling NADH production from biosynthesis. | 1 | Applied and Interdisciplinary Chemistry |
CDP-glucose is produced from CTP and glucose-1-phosphate by the enzyme glucose-1-phosphate cytidylyltransferase. | 1 | Applied and Interdisciplinary Chemistry |
All of the known 251 stable nuclides, plus another 35 nuclides that have half-lives long enough to have survived from the formation of the Earth, occur as primordial nuclides. These 35 primordial radionuclides represent isotopes of 28 separate elements.
Cadmium, tellurium, xenon, neodymium, samarium, osmium, and uranium each have two primordial radioisotopes (, ; , ; , ; , ; , ; , ; and , ).
Because the age of the Earth is (4.6 billion years), the half-life of the given nuclides must be greater than about (100 million years) for practical considerations. For example, for a nuclide with half-life (60 million years), this means 77 half-lives have elapsed, meaning that for each mole () of that nuclide being present at the formation of Earth, only 4 atoms remain today.
The seven shortest-lived primordial nuclides (i.e., the nuclides with the shortest half-lives) to have been experimentally verified are (), (), (), (), (), (), and ().
These are the seven nuclides with half-lives comparable to, or somewhat less than, the estimated age of the universe. (Rb, Re, Lu, and Th have half-lives somewhat longer than the age of the universe.) For a complete list of the 35 known primordial radionuclides, including the next 28 with half-lives much longer than the age of the universe, see the complete list below. For practical purposes, nuclides with half-lives much longer than the age of the universe may be treated as if they were stable. Rb, Re, Lu, Th, and U have half-lives long enough that their decay is limited over geological time scales; K and U have shorter half-lives and are hence severely depleted, but are still long-lived enough to persist significantly in nature.
The longest-lived isotope not proven to be primordial is , which has a half-life of , followed by () and (). Pu has been reported to exist in nature as a primordial nuclide, although a later study did not detect it. Taking into account that all these nuclides must exist for at least , Sm must survive 45 half-lives (and hence be reduced by 2 ≈ ), Pu must survive 57 (and be reduced by a factor of 2 ≈ ), and Nb must survive 130 (and be reduced by 2 ≈ ). Mathematically, considering the likely initial abundances of these nuclides, primordial Sm and Pu should persist somewhere within the Earth today, even if they are not identifiable in the relatively minor portion of the Earth's crust available to human assays, while Nb and all shorter-lived nuclides should not. Nuclides such as Nb that were present in the primordial solar nebula but have long since decayed away completely are termed extinct radionuclides if they have no other means of being regenerated.
Because primordial chemical elements often consist of more than one primordial isotope, there are only 83 distinct primordial chemical elements. Of these, 80 have at least one observationally stable isotope and three additional primordial elements have only radioactive isotopes (bismuth, thorium, and uranium). | 0 | Theoretical and Fundamental Chemistry |
Nitric acid is normally considered to be a strong acid at ambient temperatures. There is some disagreement over the value of the acid dissociation constant, though the pK value is usually reported as less than −1. This means that the nitric acid in diluted solution is fully dissociated except in extremely acidic solutions. The pK value rises to 1 at a temperature of 250 °C.
Nitric acid can act as a base with respect to an acid such as sulfuric acid:
:;Equilibrium constant: K ≈ 22
The nitronium ion, , is the active reagent in aromatic nitration reactions. Since nitric acid has both acidic and basic properties, it can undergo an autoprotolysis reaction, similar to the self-ionization of water: | 0 | Theoretical and Fundamental Chemistry |
XeO should be handled with great caution. Samples have detonated when undisturbed at room temperature. Dry crystals react explosively with cellulose. | 0 | Theoretical and Fundamental Chemistry |
In coordination chemistry, the first coordination sphere refers to the array of molecules and ions (the ligands) directly attached to the central metal atom. The second coordination sphere consists of molecules and ions that attached in various ways to the first coordination sphere. | 0 | Theoretical and Fundamental Chemistry |
A proteolysis targeting chimera (PROTAC) is a heterobifunctional molecule composed of two active domains and a linker, capable of removing specific unwanted proteins. Rather than acting as a conventional enzyme inhibitor, a PROTAC works by inducing selective intracellular proteolysis. PROTACs consist of two covalently linked protein-binding molecules: one capable of engaging an E3 ubiquitin ligase, and another that binds to a target protein meant for degradation. Recruitment of the E3 ligase to the target protein results in ubiquitination and subsequent degradation of the target protein via the proteasome. Because PROTACs need only to bind their targets with high selectivity (rather than inhibit the target protein's enzymatic activity), there are currently many efforts to retool previously ineffective inhibitor molecules as PROTACs for next-generation drugs.
Initially described by Kathleen Sakamoto, Craig Crews and Ray Deshaies in 2001, the PROTAC technology has been applied by a number of drug discovery labs using various E3 ligases, including pVHL, CRBN, Mdm2, beta-TrCP1, DCAF15, DCAF16, RNF114, and c-IAP1. Yale University licensed the PROTAC technology to Arvinas in 2013–14.
In 2019, Arvinas put two PROTACs into clinical trials: ARV-110, an androgen receptor degrader, and ARV-471, an estrogen receptor degrader. | 1 | Applied and Interdisciplinary Chemistry |
Paul Walden (; ; ; 26 July 1863 – 22 January 1957) was a Russian, Latvian and German chemist known for his work in stereochemistry and history of chemistry. In particular, he discovered the Walden rule, he invented the stereochemical reaction known as Walden inversion and synthesized the first room-temperature ionic liquid, ethylammonium nitrate. | 0 | Theoretical and Fundamental Chemistry |
Lead(II) azide is prepared by the reaction of sodium azide and lead(II) nitrate in aqueous solution. Lead(II) acetate can also be used.
Thickeners such as dextrin or polyvinyl alcohol are often added to the solution to stabilize the precipitated product. In fact, it is normally shipped in a dextrinated solution that lowers its sensitivity. | 0 | Theoretical and Fundamental Chemistry |
Although the Pidgeon process has many perks, there are some environmental disadvantages of the process as well. Since increased demand for magnesium has risen in recent years, production through ore reduction has been emitting large amounts of carbon dioxide and particulate matter. Due to the lightweight nature of magnesium as well as its high energy density, suggestions have been made about the global consumption of this versatile metal drastically increasing even more than it already has. There are environmental impacts because to create light weight materials in the first place, more energy is needed compared to the material being replaced, typically iron or steel. As an approximate, around 10.4 kg of coal is burned and 37 kg of carbon dioxide is released, per 1 kg of magnesium obtained. In China, production of magnesium using the Pidgeon process has a 60% higher global warming impact than aluminum, a competing metal mass produced in the country as well. Ultimately, more information and research is needed to make new energy saving changes to reduce the environmental impact of magnesium production on a global scale. | 1 | Applied and Interdisciplinary Chemistry |
Hyperfine interactions, the internal magnetic fields of local magnetic isotopes, play a significant role as well in the spin dynamics of radical-pairs. | 0 | Theoretical and Fundamental Chemistry |
Verbal suggestion can cause hyperalgesia (increased sensitivity to pain) and allodynia (perception of a tactile stimulus as painful) as a result of the nocebo effect. Nocebo hyperalgesia is believed to involve the activation of cholecystokinin receptors. | 1 | Applied and Interdisciplinary Chemistry |
Coal, being mostly carbon, emits a lot of when burnt: it has a high emission intensity. Natural gas, being methane (), has 4 hydrogen atoms to burn for each one of carbon and thus has medium emission intensity. | 1 | Applied and Interdisciplinary Chemistry |
FRET (Förster resonance energy transfer) is a property in which the energy of the excited electron of one fluorphore, called the donor, is passed on to a nearby acceptor dye, either a dark quencher or another fluorophore, which has an excitation spectrum which overlaps with the emission spectrum of the donor dye resulting in a reduced fluorescence.
This can be used to:
* detect if two labelled protein or nucleic acids come into contact or a doubly labelled single molecules is hydrolysed;
* detect changes in conformation;
* measure concentration by a competitive binding assay. | 1 | Applied and Interdisciplinary Chemistry |
There are three main classes of biopolymers: polysaccharides, polypeptides, and polynucleotides.
In living cells, they may be synthesized by enzyme-mediated processes, such as the formation of DNA catalyzed by DNA polymerase. The synthesis of proteins involves multiple enzyme-mediated processes to transcribe genetic information from the DNA to RNA and subsequently translate that information to synthesize the specified protein from amino acids. The protein may be modified further following translation in order to provide appropriate structure and functioning. There are other biopolymers such as rubber, suberin, melanin, and lignin. | 0 | Theoretical and Fundamental Chemistry |
The signatories to the 1904 Petition are:
# Lucy Boole
# Katherine Alice Burke
# Clare de Brereton Evans
# Elizabeth Eleanor Field
# Emily Fortey
# Ida Freund
# Mildred Gostling (Mrs Mills)
# Hilda Hartle
# Edith Humphrey
# Dorothy Marshall
# Margaret Seward (Mrs McKillop)
# Ida Smedley (Mrs Maclean)
# Alice Emily Smith
# Millicent Taylor
# M. Beatrice Thomas
# Grace Toynbee (Mrs Frankland)
# Martha Whiteley
# Sibyl Widdows
# Katherine Isabella Williams
The network that allowed these women to co-sponsor the petition has been examined. Smedley, Freund, and Whiteley led the petition. Smedley attended the King Edward VI High School as did Thomas and Hartle. Freund was a demonstrator and a lecturer at Newnham College, Cambridge between 1887 and 1912, as were Elizabeth Eleanor Field, Dorothy Marshall, and Mildred Gostling. Thomas, Field, Whiteley, and Gostling spent time at Royal Holloway College, from where there were two additional petitioners: Margaret Seward and Sibyl Widdows. Clare de Brereton Evans and Millicent Taylor attended the Cheltenham Ladies' College, Cheltenham and Taylor had connections with the University of Bristol, where Emily Fortey and Katherine Williams studied. Lucy Boole studied at the London School of Medicine for Women and Katherine Burke studied at University College London under the supervision of William Ramsay - both of these women knew de Brereton Evans. Grace Toynbee studied at the University of Birmingham, and was possibly connected with Hartle. Two petitioners Edith Humphrey and Alice Smith have unknown connections to the remainder, but it is proposed that they were connected by male chemists keen to promote their cause, such William Ramsay. | 1 | Applied and Interdisciplinary Chemistry |
The third group of chemokines is known as the C chemokines (or γ chemokines), and is unlike all other chemokines in that it has only two cysteines; one N-terminal cysteine and one cysteine downstream. Two chemokines have been described for this subgroup and are called XCL1 (lymphotactin-α) and XCL2 (lymphotactin-β). | 1 | Applied and Interdisciplinary Chemistry |
Irène Joliot-Curie (; ; 12 September 1897 – 17 March 1956) was a French chemist, physicist and politician, the elder daughter of Pierre Curie and Marie Skłodowska–Curie, and the wife of Frédéric Joliot-Curie. Jointly with her husband, Joliot-Curie was awarded the Nobel Prize in Chemistry in 1935 for their discovery of induced radioactivity, making them the second-ever married couple (after her parents) to win the Nobel Prize, while adding to the Curie family legacy of five Nobel Prizes. This made the Curies the family with the most Nobel laureates to date.
Her mother Marie Skłodowska–Curie and herself also form the only mother–daughter pair to have won Nobel Prizes whilst Pierre and Irène Curie form the only father-daughter pair to have won Nobel Prizes by the same occasion, whilst there are 6 father-son pairs who have won Nobel Prizes by comparison.
She was also one of the first three women to be a member of a French government, becoming undersecretary for Scientific Research under the Popular Front in 1936. Both children of the Joliot-Curies, Hélène and Pierre, are also prominent scientists.
In 1945, she was one of the six commissioners of the new French Alternative Energies and Atomic Energy Commission (CEA) created by de Gaulle and the Provisional Government of the French Republic. She died in Paris on 17 March 1956 from an acute leukemia linked to her exposure to polonium and X-rays. | 0 | Theoretical and Fundamental Chemistry |
The marine carbon cycle is composed of processes that exchange carbon between various pools within the ocean as well as between the atmosphere, Earth interior, and the seafloor. The carbon cycle is a result of many interacting forces across multiple time and space scales that circulates carbon around the planet, ensuring that carbon is available globally. The Oceanic carbon cycle is a central process to the global carbon cycle and contains both inorganic carbon (carbon not associated with a living thing, such as carbon dioxide) and organic carbon (carbon that is, or has been, incorporated into a living thing). Part of the marine carbon cycle transforms carbon between non-living and living matter.
Three main processes (or pumps) that make up the marine carbon cycle bring atmospheric carbon dioxide (CO) into the ocean interior and distribute it through the oceans. These three pumps are: (1) the solubility pump, (2) the carbonate pump, and (3) the biological pump. The total active pool of carbon at the Earth's surface for durations of less than 10,000 years is roughly 40,000 gigatons C (Gt C, a gigaton is one billion tons, or the weight of approximately 6 million blue whales), and about 95% (~38,000 Gt C) is stored in the ocean, mostly as dissolved inorganic carbon. The speciation of dissolved inorganic carbon in the marine carbon cycle is a primary controller of acid-base chemistry in the oceans. | 0 | Theoretical and Fundamental Chemistry |
When multiple assays measure the same target their results and utility may or may not be comparable depending on the natures of the assay and their methodology, reliability etc. Such comparisons are possible through study of general quality attributes of the assays e.g. principles of measurement (including identification, amplification and detection), dynamic range of detection (usually the range of linearity of the standard curve), analytic sensitivity, functional sensitivity, analytic specificity, positive, negative predictive values, turn around time i.e. time taken to finish a whole cycle from the preanalytic steps till the end of the last post analytic step (report dispatch/transmission), throughput i.e. number of assays done per unit time (usually expressed as per hour) etc. Organizations or laboratories that perform Assays for professional purposes e.g. medical diagnosis and prognostics, environmental analysis, forensic proceeding, pharmaceutical research and development must undergo well regulated quality assurance procedures including method validation, regular calibration, analytical quality control, proficiency testing, test accreditation, test licensing and must document appropriate certifications from the relevant regulating bodies in order to establish the reliability of their assays, especially to remain legally acceptable and accountable for the quality of the assay results and also to convince customers to use their assay commercially/professionally. | 1 | Applied and Interdisciplinary Chemistry |
NAPCO was the first company which was able to progress to registration of final 14001 certification. This was primarily due to the increased costs of surveillance audits and an absence of market incentives to promote this certificate as the gold standard within the Australian beef industry. A ‘cluster approach’ was utilised by the company when working towards certification; this meant that the entire company qualified for certification, rather than each individual worker. The effect of the ‘cluster approach’ was to reduce the substantive cost involved in certification and the subsequent surveillance audits that would have to be implemented; this meant that cost was able to be reduced by approximately 50%. This approach also provided a means by which workload and ideas between producers could be collectively distributed. | 1 | Applied and Interdisciplinary Chemistry |
The Barton evaporation engine is a heat engine based on a cycle producing power and cooled moist air from the evaporation of water into hot dry air. | 0 | Theoretical and Fundamental Chemistry |
In living cells, signals are processed by networks of proteins that can act as complex computational devices. These networks rely on the ability of single proteins to exist in a variety of functionally different states achieved through multiple mechanisms, including post-translational modifications, ligand binding, conformational change, or formation of new complexes. Similarly, nucleic acids can undergo a variety of transformations, including protein binding, binding of other nucleic acids, conformational change and DNA methylation.
In addition, several types of modifications can co-exist, exerting a combined influence on a biological macromolecule at any given time. Thus, a biomolecule or complex of biomolecules can often adopt a very large number of functionally distinct states. The number of states scales exponentially with the number of possible modifications, a phenomenon known as "combinatorial explosion". This is of concern for computational biologists who model or simulate such biomolecules, because it raises questions about how such large numbers of states can be represented and simulated. | 1 | Applied and Interdisciplinary Chemistry |
In addition to diagnosis and classification, EPIC-seq holds promise in predicting patient response to various cancer therapies, including immune-checkpoint inhibition (ICI). By analyzing changes in gene expression patterns captured through EPIC-seq, researchers can forecast patient response to PD-(L)1 blockade therapy, which can provide great help in personalized cancer treatment. EPIC-seq-derived indices have shown significant correlation with treatment response, offering potential prognostic markers for therapy outcome prediction. | 1 | Applied and Interdisciplinary Chemistry |
DCP incurs several key disadvantages in comparison to ICP. In addition to the lower sensitivity, spectra generated by DCP generally present fewer spectral lines. DCP samples are often incompletely volatilized due to the relatively short amount of time spent in the hottest region of the plasma. Furthermore, DCP requires more regular upkeep than ICP, because the graphite electrodes wear out after a few hours and must be exchanged
However, DCP is not without a few advantages over ICP. The amount of argon needed for DCP is much less than that needed for ICP. Also, DCP can analyze samples that have a higher percentage of solid in solution than can be handled by ICP. | 0 | Theoretical and Fundamental Chemistry |
Oxyhemoglobin is formed during physiological respiration when oxygen binds to the heme component of the protein hemoglobin in red blood cells. This process occurs in the pulmonary capillaries adjacent to the alveoli of the lungs. The oxygen then travels through the blood stream to be dropped off at cells where it is utilized as a terminal electron acceptor in the production of ATP by the process of oxidative phosphorylation. It does not, however, help to counteract a decrease in blood pH. Ventilation, or breathing, may reverse this condition by removal of carbon dioxide, thus causing a shift up in pH.
Hemoglobin exists in two forms, a taut (tense) form (T) and a relaxed form (R). Various factors such as low pH, high CO and high 2,3 BPG at the level of the tissues favor the taut form, which has low oxygen affinity and releases oxygen in the tissues. Conversely, a high pH, low CO, or low 2,3 BPG favors the relaxed form, which can better bind oxygen. The partial pressure of the system also affects O affinity where, at high partial pressures of oxygen (such as those present in the alveoli), the relaxed (high affinity, R) state is favoured. Inversely, at low partial pressures (such as those present in respiring tissues), the (low affinity, T) tense state is favoured. Additionally, the binding of oxygen to the iron(II) heme pulls the iron into the plane of the porphyrin ring, causing a slight conformational shift. The shift encourages oxygen to bind to the three remaining heme units within hemoglobin (thus, oxygen binding is cooperative).
Classically, the iron in oxyhemoglobin is seen as existing in the iron(II) oxidation state. However, the complex of oxygen with heme iron is diamagnetic, whereas both oxygen and high-spin iron(II) are paramagnetic. Experimental evidence strongly suggests heme iron is in the iron(III) oxidation state in oxyhemoglobin, with the oxygen existing as superoxide anion (O) or in a covalent charge-transfer complex. | 0 | Theoretical and Fundamental Chemistry |
A caged protein is a protein that is activated in the presence of a stimulating light source. In most cases, photo-uncaging is the technique revealing the active region of a compound by the process of photolysis of the shielding molecule (‘cage’). However, uncaging the protein requires an appropriate wavelength, intensity, and timing of the light. Achieving this is possible due to the fact that the optical fiber may be modified to deliver specific amounts of light. In addition, short bursts of stimulation allow results similar to the physiological norm. The steps of photostimulation are time independent in that protein delivery and light activation can be done at different times. This is because the two steps are dependent on each other for activation of the protein.
Some proteins are innately photosensitive and function in the presence of light. Proteins known as opsins form the crux of the photosensitive proteins. These proteins are often found in the eye. In addition, many of these proteins function as ion channels and receptors. One example is when a certain wavelength of light is put onto certain channels, the blockage in the pore is relieved and allows ion transduction.
To uncage molecules, a photolysis system is required to cleave the covalent bond. An example system can consist of a light source (generally a laser or a lamp), a controller for the amount of light that enters, a guide for the light, and a delivery system. Often, the design function in such a way that a medium is met between the diffusing light that may cause additional, unwanted photolysis and light attenuation; both being significant problems with a photolysis system. | 1 | Applied and Interdisciplinary Chemistry |
Jean-Claude Duplessy, a former student of the Ecole Normale Supérieure (Ulm), a physics graduate, is a geochemist. His work has contributed to a better understanding of how the ocean has functioned over the recent history of the Earth. He is a recognized pioneer in rebuilding ocean dynamics through the use of carbon isotopes and foraminiferous shell oxygen in marine sediments. He was one of the first to see the importance of a high quality chronology for a reliable interpretation of measurements related to climate variations in the Earth's past. | 0 | Theoretical and Fundamental Chemistry |
One way to identify the expression pattern of a particular gene is to place a reporter gene downstream of its promoter. In this configuration, the promoter gene will cause the reporter gene to be expressed only where and when the gene of interest is expressed. The expression distribution of the reporter gene can be determined by visualizing it. For example, the reporter gene green fluorescent protein can be visualized by stimulating it with blue light and then using a digital camera to record green fluorescent emission.
If the promoter of the gene of interest is unknown, there are several ways to identify its spatiotemporal distribution. Immunohistochemistry involves preparing an antibody with specific affinity for the protein associated with the gene of interest. This distribution of this antibody can then be visualized by a technique such as fluorescent labeling. Immunohistochemistry has the advantages of being methodologically feasible and relatively inexpensive. Its disadvantages include non-specificity of the antibody leading to false positive identification of expression. Poor penetrance of the antibody into the target tissue can lead to false negative results. Furthermore, since immunohistochemistry visualizes the protein generated by the gene, if the protein product diffuses between cells, or has a particularly short or long half-life relative to the mRNA that is used to translate the protein, this can lead to distorted interpretation of which cells are expressing the mRNA.
In situ hybridization is an alternate method in which a "probe," a synthetic nucleic acid with a sequence complementary to the mRNA of the gene, is added to the tissue. This probe is then chemically tagged so that it can be visualized later. This technique enables visualization specifically of mRNA-producing cells without any of the artifacts associated with immunohistochemistry. However, it is notoriously difficult, and requires knowledge of the sequence of DNA corresponding to the gene of interest.
A method called enhancer-trap screening reveals the diversity of spatiotemporal gene expression patterns possible in an organism. In this technique, DNA that encodes a reporter gene is randomly inserted into the genome. Depending on the gene promoters proximal to the insertion point, the reporter gene will be expressed in particular tissues at particular points in development. While enhancer-trap derived expression patterns do not necessarily reflect the actual patterns of expression of specific genes, they reveal the variety of spatiotemporal patterns that are accessible to evolution.
Reporter genes can be visualized in living organisms, but both immunohistochemistry and in situ hybridization must be performed in fixed tissues. Techniques that require fixation of tissue can only generate a single temporal time point per individual organism. However, using live animals instead of fixed tissue can be crucial in dynamically understanding expression patterns over an individual's lifespan. Either way, variation between individuals can confound the interpretation of temporal expression patterns. | 1 | Applied and Interdisciplinary Chemistry |
British Approved Names (BANs) are devised or selected by the British Pharmacopoeia Commission (BPC), and published by the Health Ministers, on the recommendation of the Commission on Human Medicines, to provide a list of names of substances or articles referred to in Section 100 of the Medicines Act 1968. BANs are short, distinctive names for substances, where the systematic chemical or other scientific names are too complex for convenient general use.
As a consequence of Directive 2001/83/EC, as amended, the British Approved Names, since 2002, may be assumed to be the recommended International Non-proprietary Name (rINN), except where otherwise stated. A World Health Organization (WHO) [https://www.who.int/medicines/services/inn/en/ INN] identifies a pharmaceutical substance or active pharmaceutical ingredient by a unique name that is globally recognised, and in which no party can claim any proprietary rights. A non-proprietary name is also known as a generic name. | 1 | Applied and Interdisciplinary Chemistry |
The dispersion of a monochromator is characterized as the width of the band of colors per unit of slit width, 1 nm of spectrum per mm of slit width for instance. This factor is constant for a grating, but varies with wavelength for a prism. If a scanning prism monochromator is used in a constant bandwidth mode, the slit width must change as the wavelength changes. Dispersion depends on the focal length, the grating order and grating resolving power. | 0 | Theoretical and Fundamental Chemistry |
The 5-HT receptors are a subfamily of the 5-HT serotonin receptors that bind to the endogenous neurotransmitter serotonin (also known as 5-hydroxytryptamine, or 5-HT). The 5-HT subfamily consists of five G protein-coupled receptors (GPCRs) that share 40% to 63% overall sequence homology, including 5-HT, 5-HT, 5-HT, 5-HT, and 5-HT. Receptors of the 5-HT type, specifically, the 5-HT and 5-HT receptor subtypes, are present on the cell bodies. Receptors of the 5-HT1 type, specifically, the 5-HT and 5-HT receptor subtypes, are also present on the nerve terminals. These receptors are broadly distributed throughout the brain and are recognized to play a significant part in regulating synaptic levels of 5-HT.
The receptor subfamily is coupled to G/G and mediate inhibitory neurotransmission by inhibiting the function of adenylate cyclase and modulating downstream ionic effects. This R-coupling to G/G proteins leads to a reduction in local concentrations of cAMP, proving that 5-HT are primarily inhibitory. There is no 5-HT receptor, as it was reclassified as the 5-HT receptor. For more information, please see the respective main articles of the individual subtypes: | 1 | Applied and Interdisciplinary Chemistry |
A concentration cell is an electrochemical cell where the two electrodes are the same material, the electrolytes on the two half-cells involve the same ions, but the electrolyte concentration differs between the two half-cells.
An example is an electrochemical cell, where two copper electrodes are submerged in two copper(II) sulfate solutions, whose concentrations are 0.05 M and 2.0 M, connected through a salt bridge. This type of cell will generate a potential that can be predicted by the Nernst equation. Both can undergo the same chemistry (although the reaction proceeds in reverse at the anode)
:Cu + 2 e → Cu
Le Chateliers principle indicates that the reaction is more favorable to reduction as the concentration of Cu ions increases. Reduction will take place in the cells compartment where the concentration is higher and oxidation will occur on the more dilute side.
The following cell diagram describes the concentration cell mentioned above:
:Cu | Cu (0.05 M) || Cu (2.0 M) | Cu
where the half cell reactions for oxidation and reduction are:
:Oxidation: Cu → Cu (0.05 M) + 2 e
:Reduction: Cu (2.0 M) + 2 e → Cu
:Overall reaction: Cu (2.0 M) → Cu (0.05 M)
The cell's emf is calculated through the Nernst equation as follows:
The value of E° in this kind of cell is zero, as electrodes and ions are the same in both half-cells.
After replacing values from the case mentioned, it is possible to calculate cell's potential:
or by:
However, this value is only approximate, as reaction quotient is defined in terms of ion activities which can be approximated with the concentrations as calculated here.
The Nernst equation plays an important role in understanding electrical effects in cells and organelles. Such effects include nerve synapses and cardiac beat as well as the resting potential of a somatic cell. | 0 | Theoretical and Fundamental Chemistry |
Adenosine-to-Inosine (A-to-I) modifications were described well before the conception of epitranscriptomics. These modifications are very common in tissues and cells of the nervous system, and malfunctions in this deamination can result in a variety of different human diseases. A-to-I deamination has been shown to cause changes in the overall RNA structure or cause changes to the protein-coding mRNAs, although changes in codons and the amino acid they code for are not commonly seen. A-to-I RNA editing is described in more detail on the RNA editing page. | 1 | Applied and Interdisciplinary Chemistry |
In general, carboxylic acids () are named with the suffix -oic acid (etymologically a back-formation from benzoic acid). As with aldehydes, the carboxyl functional group must take the "1" position on the main chain and so the locant need not be stated. For example, (lactic acid) is named 2-hydroxypropanoic acid with no "1" stated. Some traditional names for common carboxylic acids (such as acetic acid) are in such widespread use that they are retained in IUPAC nomenclature, though systematic names like ethanoic acid are also used. Carboxylic acids attached to a benzene ring are structural analogs of benzoic acid () and are named as one of its derivatives.
If there are multiple carboxyl groups on the same parent chain, multiplying prefixes are used: Malonic acid, , is systematically named propanedioic acid. Alternatively, the suffix can be used in place of "oic acid", combined with a multiplying prefix if necessary – mellitic acid is benzenehexacarboxylic acid, for example. In the latter case, the carbon atoms in the carboxyl groups do not count as being part of the main chain, a rule that also applies to the prefix form "carboxy-". Citric acid serves as an example: it is formally named rather than . | 0 | Theoretical and Fundamental Chemistry |
A fiber (or other hydrophilic material) that has been exposed to the atmosphere will usually contain some water even if it feels dry. The water can be driven off by heating in an oven, leading to a measurable decrease in weight, which will gradually be regained if the fiber is returned to a normal atmosphere. This effect is crucial in the textile industry – where the proportion of a materials weight made up by water is called the moisture regain'. | 0 | Theoretical and Fundamental Chemistry |
Methanesulfonic anhydride (MsO) is the acid anhydride of methanesulfonic acid. Like methanesulfonyl chloride (MsCl), it may be used to generate mesylates (methanesulfonyl esters). | 0 | Theoretical and Fundamental Chemistry |
A "lasagna cell" is accidentally produced when salty moist food such as lasagna is stored in a steel baking pan and is covered with aluminium foil. After a few hours the foil develops small holes where it touches the lasagna, and the food surface becomes covered with small spots composed of corroded aluminium. In this example, the salty food (lasagna) is the electrolyte, the aluminium foil is the anode, and the steel pan is the cathode. If the aluminium foil touches the electrolyte only in small areas, the galvanic corrosion is concentrated, and corrosion can occur fairly rapidly. If the aluminium foil was not used with a dissimilar metal container, the reaction was probably a chemical one. It is possible for heavy concentrations of salt, vinegar or some other acidic compounds to cause the foil to disintegrate. The product of either of these reactions is an aluminium salt. It does not harm the food, but any deposit may impart an undesired flavor and color. | 1 | Applied and Interdisciplinary Chemistry |
Not all the clusters are stable. The stability of nanoclusters depends on the number of atoms in the nanocluster, valence electron counts and encapsulating scaffolds. In the 1990s, Heer and his coworkers used supersonic expansion of an atomic cluster source into a vacuum in the presence of an inert gas and produced atomic cluster beams. Heers team and Brack et al. discovered that certain masses of formed metal nanoclusters were stable and were like magic clusters. The number of atoms or size of the core of these magic clusters corresponds to the closing of atomic shells. Certain thiolated clusters such as Au25(SR)18, Au38(SR)24, Au102(SR)44 and Au144(SR)60 also showed magic number stability. Häkkinen et al' explained this stability with a theory that a nanocluster is stable if the number of valence electrons corresponds to the shell closure of atomic orbitals as (1S, 1P, 1D, 2S 1F, 2P 1G, 2D 3S 1H.......). | 0 | Theoretical and Fundamental Chemistry |
The chemically stable anion of Fluorine-18-Fluoride is a bone-seeking radiotracer in skeletal imaging. [F]NaF has an affinity to deposit at areas where the bone is newly mineralizing. Many studies have [F]NaF PET to measure bone metabolism at the hip, lumbar spine, and humerus. [F]NaF is taken-up in an exponential manner representing the equilibration of tracer with the extracellular and cellular fluid spaces with a half-life of 0.4 hours, and with kidneys with a half-life of 2.4 hours. The single passage extraction of [F]NaF in bone is 100%. After an hour, only 10% of the injected activity remains in the blood.
F- ions are considered to occupy extracellular fluid spaces because, firstly, they equilibrate with transcellular fluid spaces and secondly, they are not entirely extracellular ions. Fluoride undergoes equilibrium with hydrogen fluoride, which has a high permeability allowing fluoride to cross the plasma blood membrane. The fluoride circulation in red blood cells accounts for 30%. However, it is freely available to the bone surface for uptake because the equilibrium between erythrocytes and plasma is much faster than the capillary transit time. This is supported by studies reporting 100% single-passage extraction of whole-blood F- ion by bone and the rapid release of F- ions from erythrocytes with a rate constant of 0.3 per second.
[F]NaF is also taken-up by immature erythrocytes in the bone marrow, which plays a role in fluoride kinetics. The plasma protein binding of [F]NaF is negligible. [F]NaF renal clearance is affected by diet and pH level, due to its re-absorption in the nephron, which is mediated by hydrogen fluoride. However, large differences in urine flow rate are avoided for controlled experiments by keeping patents well hydrated.
The exchangeable pool and the size of the metabolically active surfaces in bones determines the amount of tracer accumulated or exchanged with bone extracellular fluid, chemisorption onto hydroxyapatite crystals to form fluorapatite, as shown in Equation-1:
Equation-1
Fluoride ions from the crystalline matrix of bone are released when the bone is remodelled, thus providing a measure of the rate of bone metabolism. | 1 | Applied and Interdisciplinary Chemistry |
MPSS allows mRNA transcripts to be identified through the generation of a 17–20 bp (base pair) signature sequence adjacent to the 3-end of the 3-most site of the designated restriction enzyme (commonly Sau3A or DpnII). Each signature sequence is cloned onto one of a million microbeads. The technique ensures that only one type of DNA sequence is on a microbead. So if there are 50 copies of a specific transcript in the biological sample, these transcripts will be captured onto 50 different microbeads, each bead holding roughly 100,000 amplified copies of the specific signature sequence. The microbeads are then arrayed in a flow cell for sequencing and quantification. The sequence signatures are deciphered by the parallel identification of four bases by hybridization to fluorescently labeled encoders (Figure 5). Each of the encoders has a unique label which is detected after hybridization by taking an image of the microbead array. The next step is to cleave and remove that set of four bases and reveal the next four bases for a new round of hybridization to encoders and image acquisition. The raw output is a list of 17–20 bp signature sequences, that can be annotated to the human genome for gene identification. | 1 | Applied and Interdisciplinary Chemistry |
Scintillators are used by the American government as Homeland Security radiation detectors. Scintillators can also be used in particle detectors, new energy resource exploration, X-ray security, nuclear cameras, computed tomography and gas exploration. Other applications of scintillators include CT scanners and gamma cameras in medical diagnostics, and screens in older style CRT computer monitors and television sets. Scintillators have also been proposed as part of theoretical models for the harnessing of gamma-ray energy through the photovoltaic effect, for example in a nuclear battery.
The use of a scintillator in conjunction with a photomultiplier tube finds wide use in hand-held survey meters used for detecting and measuring radioactive contamination and monitoring nuclear material. Scintillators generate light in fluorescent tubes, to convert the ultra-violet of the discharge into visible light. Scintillation detectors are also used in the petroleum industry as detectors for Gamma Ray logs. | 0 | Theoretical and Fundamental Chemistry |
Clark has an undergraduate degree in geological sciences completed at The State University of New York at Geneseo in 2013, a master's degree in geological sciences from The University of Alabama completed in 2015, and a PhD in geological and earth sciences completed at The University of Houston in 2021. | 0 | Theoretical and Fundamental Chemistry |
The first N-sulfinyl imines in racemic form were formed by oxidation of p-toluene-sulfenyl imines with m-CPBA. Enantiopure p-toluene-sulfinyl imines arise by the reaction of the commercially available Andersen reagent (menthyl p-toluenesulfinate) with metallo-ketimines but is limited to ketone derived N-sulfinyl imines. A more general method for the preparation of N-sulfinyl imines is the asymmetric oxidation of achiral sulfenyl imines with a chiral oxaziridine. The utility of this method is limited by the availability of the N-sulfonyloxaziridine, which is difficult to prepare. More practical is the one-pot procedure from the Andersen reagent making a variety of p-toluene-sulfinyl imines available from both aromatic and aliphatic aldehydes.
A widely used method for the asymmetric synthesis of N-sulfinyl imines is the condensation of enantiopure primary sulfinamides with aldehyde or ketones. A mild Lewis acid dehydrating reagents such as titanium ethoxide facilitate the condensation. Many sulfinamides are commercially available in both (R)- and (S)-forms. The two most commonly used are the Davis p-toluene-sulfinamide and the Ellman tert-butanesulfinamide | 0 | Theoretical and Fundamental Chemistry |
Closed fullerenes encapsulating small molecules have been synthesized. Representative are the synthesis of the dihydrogen endofullerene H@C, the water endofullerene HO@C, the hydrogen fluoride endofullerene HF@C, and the methane endofullerene CH@C. The encapsulated molecules display unusual physical properties which have been studied by a variety of physical methods. As shown theoretically, compression of molecular endofullerenes (e.g., H@C) may lead to dissociation of the encapsulated molecules and reaction of their fragments with interiors of the fullerene cage. Such reactions should result in endohedral fullerene adducts, which are currently unknown. | 0 | Theoretical and Fundamental Chemistry |
Crystal structure is described in terms of the geometry of arrangement of particles in the unit cells. The unit cell is defined as the smallest repeating unit having the full symmetry of the crystal structure. The geometry of the unit cell is defined as a parallelepiped, providing six lattice parameters taken as the lengths of the cell edges (a, b, c) and the angles between them (α, β, γ). The positions of particles inside the unit cell are described by the fractional coordinates (x, y, z) along the cell edges, measured from a reference point. It is thus only necessary to report the coordinates of a smallest asymmetric subset of particles, called the crystallographic asymmetric unit. The asymmetric unit may be chosen so that it occupies the smallest physical space, which means that not all particles need to be physically located inside the boundaries given by the lattice parameters. All other particles of the unit cell are generated by the symmetry operations that characterize the symmetry of the unit cell. The collection of symmetry operations of the unit cell is expressed formally as the space group of the crystal structure. | 0 | Theoretical and Fundamental Chemistry |
The UC Berkeley College of Chemistry is one of the fifteen schools and colleges at the University of California, Berkeley. It houses the department of chemistry and the department of chemical and biomolecular engineering, both of which are ranked among the best in the world. Its faculty and alumni have won 18 Nobel Prizes, 9 Wolf Prizes, and 11 National Medals of Science.
The College offers bachelor of science degrees in chemistry, chemical engineering, and chemical biology. Chemistry undergraduates have the option to earn a bachelor of arts degree in chemistry from the College of Letters and Science or to specialize in a materials chemistry concentration. With the College of Engineering, the College of Chemistry offers two joint majors: chemical engineering/materials science & engineering and chemical engineering/nuclear engineering. Its graduate programs confer M.S. and Ph.D. degrees in chemical engineering, a Ph.D. in chemistry, and three professional master's degrees. | 1 | Applied and Interdisciplinary Chemistry |
In the Brazilian rain forest, sudden rainfall can trigger flooding at a moment's notice. Given that flooding can potentially destroy a colony and drown the insects, fire ants have developed a unique adaptation to this situation. While individual fire ants are hydrophobic and flounder at the waters surface, large groups of ants can link together to form a living raft. As the queen and larvae are evacuated from the flooding colony, they sit upon this living raft, floating along the waterline until reaching some solid land.
The importance of flexibility in this self-assembled ant raft is several fold. The extra weight-bearing that flexibility imparts is vital as hungry fish will swim along the underside of the raft and eat at many of the members. Furthermore, as waves travel along the water surface, the ant raft's flexibility allows it to effectively "roll" with the wave and minimize disturbances it would otherwise cause for a similar but rigid structure. | 1 | Applied and Interdisciplinary Chemistry |
Depending on their chemical structures, polymers may be either semi-crystalline or amorphous. Semi-crystalline polymers can undergo crystallization and melting transitions, whereas amorphous polymers do not. In polymers, crystallization and melting do not suggest solid-liquid phase transitions, as in the case of water or other molecular fluids. Instead, crystallization and melting refer to the phase transitions between two solid states (i.e., semi-crystalline and amorphous). Crystallization occurs above the glass-transition temperature (T) and below the melting temperature (T). | 0 | Theoretical and Fundamental Chemistry |
A thermal reservoir, also thermal energy reservoir or thermal bath, is a thermodynamic system with a heat capacity so large that the temperature of the reservoir changes relatively little when a significant amount of heat is added or extracted. As a conceptual simplification, it effectively functions as an infinite pool of thermal energy at a given, constant temperature. Since it can act as an inertial source and sink of heat, it is often also referred to as a heat reservoir or heat bath.
Lakes, oceans and rivers often serve as thermal reservoirs in geophysical processes, such as the weather. In atmospheric science, large air masses in the atmosphere often function as thermal reservoirs.
Since the temperature of a thermal reservoir does not change during the heat transfer, the change of entropy in the reservoir is
The microcanonical partition sum of a heat bath of temperature has the property
where is the Boltzmann constant. It thus changes by the same factor when a given amount of energy is added. The exponential factor in this expression can be identified with the reciprocal of the Boltzmann factor.
For an engineering application, see geothermal heat pump. | 0 | Theoretical and Fundamental Chemistry |
Transition metal nitroso complexes are coordination complexes containing one or more organonitroso ligands (RNO). | 0 | Theoretical and Fundamental Chemistry |
An old standing dynamic problem is how DNA "self-replication" takes place in living cells that should involve transient uncoiling of supercoiled DNA fibers. Although DNA consists of relatively rigid, very large elongated biopolymer molecules called fibers or chains (that are made of repeating nucleotide units of four basic types, attached to deoxyribose and phosphate groups), its molecular structure in vivo undergoes dynamic configuration changes that involve dynamically attached water molecules and ions. Supercoiling, packing with histones in chromosome structures, and other such supramolecular aspects also involve in vivo DNA topology which is even more complex than DNA molecular geometry, thus turning molecular modeling of DNA into an especially challenging problem for both molecular biologists and biotechnologists. Like other large molecules and biopolymers, DNA often exists in multiple stable geometries (that is, it exhibits conformational isomerism) and configurational, quantum states which are close to each other in energy on the potential energy surface of the DNA molecule.
Such varying molecular geometries can also be computed, at least in principle, by employing ab initio quantum chemistry methods that can attain high accuracy for small molecules, although claims that acceptable accuracy can be also achieved for polynuclelotides, and DNA conformations, were recently made on the basis of vibrational circular dichroism (VCD) spectral data. Such quantum geometries define an important class of ab initio molecular models of DNA which exploration has barely started, especially related to results obtained by VCD in solutions. More detailed comparisons with such ab initio quantum computations are in principle obtainable through 2D-FT NMR spectroscopy and relaxation studies of polynucleotide solutions or specifically labeled DNA, as for example with deuterium labels.
In an interesting twist of roles, the DNA molecule was proposed to be used for quantum computing via DNA. Both DNA nanostructures and DNA computing biochips have been built. | 0 | Theoretical and Fundamental Chemistry |
The termination of translation requires coordination between release factor proteins, the mRNA sequence, and ribosomes. Once a termination codon is read, release factors RF-1, RF-2, and RF-3 contribute to the hydrolysis of the growing polypeptide, which terminates the chain. Bases downstream the stop codon affect the activity of these release factors. In fact, some bases proximal to the stop codon suppress the efficiency of translation termination by reducing the enzymatic activity of the release factors. For instance, the termination efficiency of a UAAU stop codon is near 80% while the efficiency of UGAC as a termination signal is only 7%. | 1 | Applied and Interdisciplinary Chemistry |
There are at least four families of chromatin remodelers in eukaryotes: SWI/SNF, ISWI, NuRD/Mi-2/CHD, and INO80 with first two remodelers being very well studied so far, especially in the yeast model. Although all of remodelers share common ATPase domain, their functions are specific based on several biological processes (DNA repair, apoptosis, etc.). This is due to the fact that each remodeler complex has unique protein domains (Helicase, bromodomain, etc.) in their catalytic ATPase region and also has different recruited subunits. | 1 | Applied and Interdisciplinary Chemistry |
In the laboratory, triflic acid is useful in protonations because the conjugate base of triflic acid is nonnucleophilic. It is also used as an acidic titrant in nonaqueous acid-base titration because it behaves as a strong acid in many solvents (acetonitrile, acetic acid, etc.) where common mineral acids (such as HCl or HSO) are only moderately strong.
With a K = , pK = , triflic acid qualifies as a superacid. It owes many of its useful properties to its great thermal and chemical stability. Both the acid and its conjugate base CFSO, known as triflate, resist oxidation/reduction reactions, whereas many strong acids are oxidizing, such as perchloric or nitric acid. Further recommending its use, triflic acid does not sulfonate substrates, which can be a problem with sulfuric acid, fluorosulfuric acid, and chlorosulfonic acid. Below is a prototypical sulfonation, which triflic acid does not undergo:
Triflic acid fumes in moist air and forms a stable solid monohydrate, CFSOH·HO, melting point 34 °C. | 0 | Theoretical and Fundamental Chemistry |
In the study of metallomes the transcriptome, proteome and the metabolome constitutes the whole metallome. A study of the metallome is done to arrive at the metallointeractome. | 1 | Applied and Interdisciplinary Chemistry |
Bioremediation is a waste removal method that uses microorganisms to degrade or remove wastes like organic waste and heavy metal from contaminated sites including both soil and water. The advantages of bioremediation are that it is environment-friendly, inexpensive and can remove multiple wastes simultaneously comparing with traditional chemical and physical processes. | 1 | Applied and Interdisciplinary Chemistry |
Only a few lists of information will be output from a calculation, in general. For the ions, the position, velocity and net force on each ion are recorded at each step. For electrons, the guess as to the electronic state function may be recorded as well. Finally, the total energy of the system is recorded. From these three types of information, we may deduce a number of properties. | 0 | Theoretical and Fundamental Chemistry |
Being a major hotspots of biodiversity, coral reefs are very important to the ecosystem and livelihood of marine and human life. Countries around the world depend on reefs as a source of food and income, especially for civilizations that inhabit small islands. With over a 60% decrease in available fishing around coral reefs, many countries, will be forced to adapt. Coral Reefs are also important for a countries economy, as reefs provide various forms of tourist activities, that can generate a lot of revenue for the economy. These can also contribute to individual levels of wellness, as the owners of these business, profit off of increased visitation and usage. Coral Reefs also provide, a form of coastal infrastructure, that acts as a barrier between us a major ocean catastrophes, such as tsunamis and coastal storms. | 0 | Theoretical and Fundamental Chemistry |
The natural bite angle (β) of diphosphines, obtained using molecular mechanics calculations, is defined as the preferred chelation angle determined only by ligand backbone and not by metal valence angles (Figure 3).
Both steric bite angle effect and the electronic bite angle effects are recognized. The steric bite angle effect involves the steric interactions between ligands or between a ligand and a substrate. The electronic bite angle effect, on the other hand, relates to the electronic changes that occur when the bite angle is modified. This effect is sensitive to the hybridization of metal orbitals. This flexibility range accounts for the diverse conformations of the ligand with energies slightly above the strain energy of the natural bite angle.
The bite angle of a diphosphine ligand also indicates the distortion from the ideal geometry of a complex based on VSEPR models. Octahedral and square planar complexes prefer angles near 90° while tetrahedral complexes prefer angles near 110°. Since catalysts often interconvert between various geometries, the rigidity of the chelate ring can be decisive. A bidentate phosphine with a natural bite angle of 120° may preferentially occupy two equatorial sites in a trigonal bipyramidal complex whereas a bidentate phosphine with a natural bite angle of 90° may preferentially occupy apical-equatorial positions. Diphosphine ligands with bite angles of over 120° are obtained using a bulky, stiff diphosphine backbones. Diphosphines of wide bite angles are used in some industrial processes. | 0 | Theoretical and Fundamental Chemistry |
The Society of Chemical Industry (America Section) is a registered nonprofit organization, with administrative offices in Philadelphia, PA. SCI America is directed by a set of officers including a chair and vice-chair, and an executive committee. Frank Bozich, President and Chief Executive Officer of [https://www.trinseo.com/ Trinseo], serves as the current chair. Previous chairpersons include John Paro of Hallstar, Max Tishler, Ralph Landau, Harold Sorgenti, Charles O. Holliday, and Christopher D. Pappas. Resa Thomason serves as the Executive Director. | 1 | Applied and Interdisciplinary Chemistry |
Proteins have many different functions in a cell and the function may vary based on the polypeptides they interact with and their cellular environment. Chaperone proteins work to stabilize newly synthesized proteins. They ensure the new protein folds into its correct functional conformation in addition to making sure products do not aggregate in areas where they should not. Proteins can also function as enzymes, increasing the rate of various biochemical reactions and turning substrates into products. Products can be modified by attaching groups such as phosphate via an enzyme to specific amino acids in the primary sequence. Proteins can also be used to move molecules in the cell to where they are needed, these are called motor proteins. The shape of the cell is supported by proteins. Proteins such as actin, microtubules and intermediate filaments provide structure to the cell. Another class of proteins are found in plasma membranes. Membrane proteins can be associated with the plasma membrane in different ways, depending on their structure. These proteins allow the cell to import or export cell products, nutrients or signals to and from the extracellular space. Other proteins help the cell to perform regulatory functions. For example, transcription factors bind to DNA to help transcription of RNA. | 1 | Applied and Interdisciplinary Chemistry |
Xylenes are produced by the methylation of toluene and benzene. Commercial or laboratory-grade xylene produced usually contains about 40–65% of m-xylene and up to 20% each of o-xylene, p-xylene and ethylbenzene. The ratio of isomers can be shifted to favor the highly valued p-xylene via the patented UOP-Isomar process or by transalkylation of xylene with itself or trimethylbenzene. These conversions are catalyzed by zeolites.
ZSM-5 is used to facilitate some isomerization reactions leading to mass production of modern plastics. | 1 | Applied and Interdisciplinary Chemistry |
*[http://pubs.acs.org/doi/pdf/10.1021/ac00053a012 Separation of amino acid homopolymers by capillary gel electrophoresis].
*[https://pubs.acs.org/doi/abs/10.1021/ac50042a043 Retention indices for programmed-temperature capillary-column gas chromatography of polycyclic aromatic hydrocarbons].
*[https://www.nature.com/articles/35015572 Ultrasensitive Pheromone Detection by mammalian vomeronasal neurons].
*[https://pubs.acs.org/doi/abs/10.1021/ac00221a013 Electrophoretic separations of proteins in capillaries with hydrolytically-stable surface structures].
*[https://academic.oup.com/glycob/article/17/4/411/602457 Comparison of the methods for profiling glycoprotein glycans—HUPO Human Disease Glycomics/Proteome Initiative multi-institutional study].
*[https://pubs.acs.org/doi/abs/10.1021/cr0103017 Structural Investigations of Glycoconjugates at High Sensitivity]. | 0 | Theoretical and Fundamental Chemistry |
Another Henry's law solubility constant is:
Here is the molar mixing ratio in the aqueous phase. For a dilute aqueous solution the conversion between and is:
where is the density of water and is the molar mass of water. Thus
The SI unit for is Pa, although atm is still frequently used. | 0 | Theoretical and Fundamental Chemistry |
Swedish law required bars of iron to have the forges mark stamped into it for quality control reasons. In Britain, the iron was known by these marks', and the quality of each brand was well-known to the buyers in London, Sheffield, Birmingham and elsewhere. It was divided into two grades:
* First oregrounds came from Österby (double bullet), Leufsta (now Lövsta - hoop L), and Åkerby (PL crown). Later Gimo joined them.
* Second oregrounds came from the other forges, including Forsmark, Harg, Vattholma, and Ullfors.
Its special property was its purity. The manganese content of the Dannemora ore caused impurities, which would otherwise have remained in the iron, to react preferentially with the manganese and to be carried off into the slag. This level of purity meant that the iron was particularly suitable for conversion to steel by being re-carburized, using the cementation process. This made it particularly suitable for making steel, oregrounds iron was an indispensable raw material for metal manufactures, particularly the Sheffield cutlery industry. Substantial quantities were also (until about 1808) bought for use by the British Navy.
This and other uses absorbed substantially the whole output of the industry. The trade in oregrounds iron was controlled from the 1730s to the 1850s by a cartel of merchants, of whom the longest enduring members were the Sykes family of Hull. Other participants were resident in (or controlling imports through) London and Bristol. These merchants advanced money to Swedish exporting houses, which in turn advanced it to the ironmasters, thus buying up the output of the forges several years in advance. | 1 | Applied and Interdisciplinary Chemistry |
Hitchins helped to determine the atomic weight of lead based on measurements of radioactive ores, work that was important in developing an understanding of isotopes. The samples of distilled lead which Hitchins prepared from Ceylon thorite were used by Frederick Soddy and supplied by him to Otto Hönigschmid, who did important work confirming that the atomic weight of thorium lead is higher than that of common lead.
Soddy indicated that Hitchins also worked on the actual analyses, in his published report of 1917: "According to analyses by Miss A. F. R. Hitchins and myself, the 20 kilos of selected thorite worked upon contained 0-4 per cent, of lead, 57 per cent, of thorium, 1-03 per cent, of uranium, and 0-5 c.c. of helium per gram." This work proved that atomic weight was not a constant. Chemically pure elements could be mixtures of isotopes with differing atomic weights. | 0 | Theoretical and Fundamental Chemistry |
There are about 2 dozen computational NMR services available that can be divided into:
* Processing: MDD NMR
* Assignment: Auto Assign • MARS • UNIO
* Analysis: TALOS+ • AnisoFIT • MaxOcc • iCing
* Structure Calculation: CS-ROSETTA • CYANA • UNIO • Xplor-NIH
* Molecular Dynamics: AMBER • GROMACS
* Modelling: 3D-DART • HADDOCK
* Tools: Format Converter • SHIFTX2 • Antechamber • PREDITOR • RCI • UPLABEL | 1 | Applied and Interdisciplinary Chemistry |
He enrolled in the Eidgenössische Technische Hochschule (ETH) in Zurich to study chemistry and received his diploma in 1957 as a “Diplomierter Ingenieur Chemiker. He was disappointed in the course content, so conducted further research and taught himself quantum mechanics and thermodynamics in his spare time. After a break to complete his military service, Ernst earned his Ph.D. in physical chemistry in 1962 from ETH Zurich. His dissertation was on nuclear magnetic resonance in the field of physical chemistry. | 0 | Theoretical and Fundamental Chemistry |
In isentropic flow the ratio of total pressure to static pressure is given by:
where:
is total pressure
is static pressure
is the ratio of specific heats<br />
is the freestream Mach number
Taking to be 1.4, and since
Expressing the incompressible dynamic pressure as and expanding by the binomial series gives:
where:
is dynamic pressure | 1 | Applied and Interdisciplinary Chemistry |
Solid ceramic electrolytes – ions migrate through the ceramic phase by means of vacancies or interstitials within the lattice. There are also glassy-ceramic electrolytes. | 0 | Theoretical and Fundamental Chemistry |
He was a Fellow of The American Physical Society and American Academy of Arts and Sciences, a John Simon Guggenheim Fellow and had been a visiting professor at the University of Paris in Sorbonne. | 0 | Theoretical and Fundamental Chemistry |
The Emerson Cavitation Tunnel is a propeller testing facility that is part of the School of Engineering at Newcastle University. | 1 | Applied and Interdisciplinary Chemistry |
The DNA of one organism is labelled, then mixed with the unlabelled DNA to be compared against. The mixture is incubated to allow DNA strands to dissociate and then cooled to form renewed hybrid double-stranded DNA. Hybridized sequences with a high degree of similarity will bind more firmly, and require more energy to separate them: i.e. they separate when heated at a higher temperature than dissimilar sequences, a process known as "DNA melting".
To assess the melting profile of the hybridized DNA, the double-stranded DNA is bound to a column or filter and the mixture is heated in small steps. At each step, the column or filter is washed; sequences that melt become single-stranded and wash off. The temperatures at which labelled DNA comes off reflects the amount of similarity between sequences (and the self-hybridization sample serves as a control). These results are combined to determine the degree of genetic similarity between organisms.
One method was introduced for hybridizing large numbers of DNA samples against large numbers of DNA probes on a single membrane. These samples would have to be separated in their own lanes inside the membranes and then the membrane would have to be rotated to a different angle where it would result in simultaneous hybridization with many different DNA probes. | 1 | Applied and Interdisciplinary Chemistry |
Carbon-neutral fuel is fuel which produces no net-greenhouse gas emissions or carbon footprint. In practice, this usually means fuels that are made using carbon dioxide (CO) as a feedstock. Proposed carbon-neutral fuels can broadly be grouped into synthetic fuels, which are made by chemically hydrogenating carbon dioxide, and biofuels, which are produced using natural CO-consuming processes like photosynthesis.
The carbon dioxide used to make synthetic fuels may be directly captured from the air, recycled from power plant flue exhaust gas or derived from carbonic acid in seawater. Common examples of synthetic fuels include ammonia and methane, although more complex hydrocarbons such as gasoline and jet fuel have also been successfully synthesized artificially. In addition to being carbon neutral, such renewable fuels can alleviate the costs and dependency issues of imported fossil fuels without requiring either electrification of the vehicle fleet or conversion to hydrogen or other fuels, enabling continued compatible and affordable vehicles. In order to be truly carbon-neutral, any energy required for the process must be itself be carbon-neutral or emissions-free, like renewable energy or nuclear energy.
If the combustion of carbon-neutral fuels is subject to carbon capture at the flue, they result in net-negative carbon dioxide emission and may thus constitute a form of greenhouse gas remediation. Negative emissions are widely considered an indispensable component of efforts to limit global warming, although negative emissions technologies are currently not economically viable for private sector companies. Carbon credits are likely to play an important role for carbon-negative fuels. | 0 | Theoretical and Fundamental Chemistry |
The activity of malate–aspartate shuttle is modulated by arginine methylation of malate dehydrogenase 1 (MDH1). Protein arginine N-methyltransferase CARM1 methylates and inhibits MDH1 by disrupting its dimerization, which represses malate–aspartate shuttle and inhibits mitochondria respiration of pancreatic cancer cells. | 1 | Applied and Interdisciplinary Chemistry |
The essence of NSOM/FTIR is that it allows the detection of non-propagating evanescent waves in the near-field (less than one wavelength from the sample), thus yielding high spatial resolution. Depending on the detection modes of these non-propagating evanescent waves, two NSOM/FTIR instrumentations are available: apertureless NSOM/FTIR and aperture-based NSOM/FTIR.
;Aperture-based NSOM/FTIR
In aperture-based NSOM/FTIR, the probe is a waveguide with a tapered tip with a very small, sub-wavelength size aperture. When the aperture is brought into the near-field, it collects the non-propagating light and guides it to the detector. In general, there are two modes when the aperture is scanned over the sample: illumination mode and collection mode (Figure 7).
The high-quality infrared fiber tip is very important in realizing NSOM/FTIR technique. There are several types of fibers, such as sapphire, chalcogenide glass, fluoride glass and hollow silica guides. Chalcogenide glasses are widely used because of their high transmittance in the broad IR range of 2–12 μm. The fluoride fibers also exhibit low transmitting losses beyond 3.0 μm.
;Apertureless NSOM/FTIR
The probe is a sharp metal tip ending with a single or a few atoms. The sample is illuminated from far-field and the radiation is focused at the contact area between probe and sample. When this tip approaches the sample, usually within 10 nm, the incident electromagnetic field is enhanced due to the resonant surface plasma excitation as well as due to hot-spots in the sharp tip. The dipole interaction between the tip and sample change the non-propagating waves into propagating waves by scattering, and a detector collects the signal in the far-field. An apertureless NSOM/FTIR usually has better resolution (~5–30 nm) compared with aperture-based NSOM/FTIR (~50–150 nm). One main challenge in apertureless NSOM/FTIR is a strong background signal because the scattering is obtained from both near-field and remote area of the probe. Thus, the small near-field contribution to the signal has to be extracted from the background. One solution is to use a very flat sample with only optical spatial fluctuation. Another solution is to apply constant-height mode scanning or pseudo-constant-height mode scanning.
;Experimental scheme of aperture-based NSOM/FTIR
Figure 8 shows the experimental setup used in NSOM/FTIR in the external reflection mode. FEL source is focused on the sample from the far-field using a mirror. The distance between the probe and a sample is kept at a few nanometers during scanning.
Figure 9 is the cross-section of a NSOM/FTIR instrument. As shown below, sample is placed on a piezo-electric tube scanner, in which the x-y tube has four parts, namely x+, x-, y+ and y-. Lateral (x-y plane) oscillation of the fiber tip is induced by applying an AC voltage to a dither piezo-scanner. Also, the fiber tip is fixed to a bimorph piezo-scanner so that the amplitude of the oscillation of the tip can be monitored through the scanner. | 0 | Theoretical and Fundamental Chemistry |
Geophysical fluid dynamics, in its broadest meaning, refers to the fluid dynamics of naturally occurring flows, such as lava flows, oceans, and planetary atmospheres, on Earth and other planets.
Two physical features that are common to many of the phenomena studied in geophysical fluid dynamics are rotation of the fluid due to the planetary rotation and stratification (layering). The applications of geophysical fluid dynamics do not generally include the circulation of the mantle, which is the subject of geodynamics, or fluid phenomena in the magnetosphere. | 1 | Applied and Interdisciplinary Chemistry |
In general, igneous, metamorphic and sedimentary processes do not appear to strongly fractionate Cu isotopes, while δCu values of Cu minerals vary widely. The average Cu isotopic composition of bulk silicate Earth has been measured as 0.06 ± 0.20‰ based on 132 different terrestrial samples. MORBs and oceanic island basalts (OIBs) generally have homogenous Cu isotopic compositions that fall around 0‰, while arc and continental basalts have more heterogeneous Cu isotope compositions that range from -0.19 to +0.47‰. These Cu isotope ratios of basalts suggest that mantle partial melting imparts negligible Cu isotopic fractionation, while recycling of crustal materials leads to widely variable δCu values. The Cu isotope compositions of copper-containing minerals vary over a wide range, likely due to alteration of the primary high-temperature deposits. In one study that investigated Cu isotopic compositions of various minerals from hydrothermal fields along the mid-Atlantic ridge, chalcopyrite from mafic igneous rocks had δCu values of -0.1 to -0.2‰, while Cu minerals in black smokers (chalcopyrite, bornite, covellite and atacamite) exhibited a wider range of δCu values from -1.0 to +4.0‰. Additionally, atacamite lining the outer rims of black smokers can be up to 2.5‰ heavier than chalcopyrite contained within the black smoker. δCu values of Cu minerals (including chrysocolle, azurite, malachite, cuprite and native copper) in low-temperature deposits have been observed to vary widely over a range of -3.0 to +5.6‰. | 0 | Theoretical and Fundamental Chemistry |
Carbon-14 is produced in the upper troposphere and the stratosphere by thermal neutrons absorbed by nitrogen atoms. When cosmic rays enter the atmosphere, they undergo various transformations, including the production of neutrons. The resulting neutrons (n) participate in the following n-p reaction (p is proton):
: + n → + p
The highest rate of carbon-14 production takes place at altitudes of and at high geomagnetic latitudes.
The rate of production can be modelled, yielding values of 16,400 or 18,800 atoms of per second per square meter of the Earths surface, which agrees with the global carbon budget that can be used to backtrack, but attempts to measure the production time directly in situ were not very successful. Production rates vary because of changes to the cosmic ray flux caused by the heliospheric modulation (solar wind and solar magnetic field), and, of great significance, due to variations in the Earths magnetic field. Changes in the carbon cycle however can make such effects difficult to isolate and quantify.
Occasional spikes may occur; for example, there is evidence for an unusually high production rate in AD 774–775, caused by an extreme
solar energetic particle event, the strongest such event to have occurred within the last ten millennia. Another "extraordinarily large" increase (2%) has been associated with a 5480 BC event, which is unlikely to be a solar energetic particle event.
Carbon-14 may also be produced by lightning but in amounts negligible, globally, compared to cosmic ray production. Local effects of cloud-ground discharge through sample residues are unclear, but possibly significant. | 0 | Theoretical and Fundamental Chemistry |
The Beilby Medal and Prize is awarded annually to a scientist or engineer for work that has exceptional practical significance in chemical engineering, applied materials science, energy efficiency or a related field. The prize is jointly administered by the Institute of Materials, Minerals and Mining, the Royal Society of Chemistry and the Society of Chemical Industry, who make the award in rotation.
The award is open to members of the Institute of Materials, Minerals and Mining, the Royal Society of Chemistry and the Society of Chemical Industry as well as other scientists and engineers worldwide. The aim of the award is to recognise the achievements of early-career scientists, and nominees should be no older than 39 years of age.
The Beilby Medal and Prize is awarded in memory of Scottish scientist Sir George Thomas Beilby FRS. Born in 1850, he joined the Oakbank Oil Company in 1869 following his studies at the University of Edinburgh. He later became President of all three organisations or their precursor societies, acting as President of the Society of Chemical Industry from 1898–99, The Institute of Chemistry from 1902–12 and the Institute of Metals from 1916-18.
Recipients of the award receive a medal, a certificate and a prize of £1,000. The first award was made in 1930. | 1 | Applied and Interdisciplinary Chemistry |
A meter is a thermodynamic system which displays some aspect of its thermodynamic state to the observer. The nature of its contact with the system it is measuring can be controlled, and it is sufficiently small that it does not appreciably affect the state of the system being measured. The theoretical thermometer described below is just such a meter.
In some cases, the thermodynamic parameter is actually defined in terms of an idealized measuring instrument. For example, the zeroth law of thermodynamics states that if two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. This principle, as noted by James Maxwell in 1872, asserts that it is possible to measure temperature. An idealized thermometer is a sample of an ideal gas at constant pressure.
From the ideal gas law, the volume of such a sample can be used as an indicator of temperature; in this manner it defines temperature. Although pressure is defined mechanically, a pressure-measuring device called a barometer may also be constructed from a sample of an ideal gas held at a constant temperature. A calorimeter is a device which is used to measure and define the internal energy of a system.
Some common thermodynamic meters are:
* Thermometer - a device which measures temperature as described above
* Barometer - a device which measures pressure, most notably atmospheric pressure. An ideal gas barometer may be constructed by mechanically connecting an ideal gas to the system being measured, while thermally insulating it. The volume will then measure pressure, by the ideal gas equation P=NkT/V .
* Calorimeter - a device which measures the heat energy added to a system. A simple calorimeter is simply a thermometer connected to a thermally isolated system. | 0 | Theoretical and Fundamental Chemistry |
It is common to model such a network with a set of coupled ordinary differential equations (ODEs) or SDEs, describing the reaction kinetics of the constituent parts. Suppose that our regulatory network has nodes, and let represent the concentrations of the corresponding substances at time . Then the temporal evolution of the system can be described approximately by
where the functions express the dependence of on the concentrations of other substances present in the cell. The functions are ultimately derived from basic principles of chemical kinetics or simple expressions derived from these e.g. Michaelis–Menten enzymatic kinetics. Hence, the functional forms of the are usually chosen as low-order polynomials or Hill functions that serve as an ansatz for the real molecular dynamics. Such models are then studied using the mathematics of nonlinear dynamics. System-specific information, like reaction rate constants and sensitivities, are encoded as constant parameters.
By solving for the fixed point of the system:
for all , one obtains (possibly several) concentration profiles of proteins and mRNAs that are theoretically sustainable (though not necessarily stable). Steady states of kinetic equations thus correspond to potential cell types, and oscillatory solutions to the above equation to naturally cyclic cell types. Mathematical stability of these attractors can usually be characterized by the sign of higher derivatives at critical points, and then correspond to biochemical stability of the concentration profile. Critical points and bifurcations in the equations correspond to critical cell states in which small state or parameter perturbations could switch the system between one of several stable differentiation fates. Trajectories correspond to the unfolding of biological pathways and transients of the equations to short-term biological events. For a more mathematical discussion, see the articles on nonlinearity, dynamical systems, bifurcation theory, and chaos theory. | 1 | Applied and Interdisciplinary Chemistry |
An ideal Fermi gas or free Fermi gas is a physical model assuming a collection of non-interacting fermions in a constant potential well. Fermions are elementary or composite particles with half-integer spin, thus follow Fermi–Dirac statistics. The equivalent model for integer spin particles is called the Bose gas (an ensemble of non-interacting bosons). At low enough particle number density and high temperature, both the Fermi gas and the Bose gas behave like a classical ideal gas.
By the Pauli exclusion principle, no quantum state can be occupied by more than one fermion with an identical set of quantum numbers. Thus a non-interacting Fermi gas, unlike a Bose gas, concentrates a small number of particles per energy. Thus a Fermi gas is prohibited from condensing into a Bose–Einstein condensate, although weakly-interacting Fermi gases might form a Cooper pair and condensate (also known as BCS-BEC crossover regime). The total energy of the Fermi gas at absolute zero is larger than the sum of the single-particle ground states because the Pauli principle implies a sort of interaction or pressure that keeps fermions separated and moving. For this reason, the pressure of a Fermi gas is non-zero even at zero temperature, in contrast to that of a classical ideal gas. For example, this so-called degeneracy pressure stabilizes a neutron star (a Fermi gas of neutrons) or a white dwarf star (a Fermi gas of electrons) against the inward pull of gravity, which would ostensibly collapse the star into a black hole. Only when a star is sufficiently massive to overcome the degeneracy pressure can it collapse into a singularity.
It is possible to define a Fermi temperature below which the gas can be considered degenerate (its pressure derives almost exclusively from the Pauli principle). This temperature depends on the mass of the fermions and the density of energy states.
The main assumption of the free electron model to describe the delocalized electrons in a metal can be derived from the Fermi gas. Since interactions are neglected due to screening effect, the problem of treating the equilibrium properties and dynamics of an ideal Fermi gas reduces to the study of the behaviour of single independent particles. In these systems the Fermi temperature is generally many thousands of kelvins, so in human applications the electron gas can be considered degenerate. The maximum energy of the fermions at zero temperature is called the Fermi energy. The Fermi energy surface in reciprocal space is known as the Fermi surface.
The nearly free electron model adapts the Fermi gas model to consider the crystal structure of metals and semiconductors, where electrons in a crystal lattice are substituted by Bloch electrons with a corresponding crystal momentum. As such, periodic systems are still relatively tractable and the model forms the starting point for more advanced theories that deal with interactions, e.g. using the perturbation theory. | 0 | Theoretical and Fundamental Chemistry |
Creating a CCP involves three steps: initiation, multiplication and mixture. The population then goes into the maintenance phase. | 1 | Applied and Interdisciplinary Chemistry |
Gamma spectroscopy systems are selected to take advantage of several performance characteristics. Two of the most important include detector resolution and detector efficiency. | 0 | Theoretical and Fundamental Chemistry |
Achiral components may form a chiral arrangement. In this case, chirality is not an intrinsic property of the components, but rather imposed extrinsically by their relative positions and orientations. This concept is typically applied to experimental arrangements, for example, an achiral (meta)material illuminated by a beam of light, where the illumination direction makes the whole experiment different from its mirror image. Extrinsic planar chirality results from illumination of any periodically structured interface for suitable illumination directions. Starting from normal incidence onto a periodically structured interface, extrinsic planar chirality arises from tilting the interface around any axis that does not coincide with a line of mirror symmetry of the interface. In the presence of losses, extrinsic planar chirality can result in circular conversion dichroism, as described above. | 0 | Theoretical and Fundamental Chemistry |
Following their development of Au-catalyzed Conia-ene reactions, Toste and coworkers employed such a transformation toward the alkaloid natural product lycopladine A. Starting from chiral cyclohexenone 1, a series of enone functionalizations gave silyl enol ether 2 as the Conia-ene precursor. To effect cyclization, 2 was treated with catalytic AuCl(PPh) and AgBF to furnish vinyl iodide 3 in high yield as a single diastereomer. The remainder of the molecule was completed in three steps to give (+)-lycopladine A in eight steps and 17% overall yield.
In 2012, Carreira et al. synthesized , a halogenated terpene isolated from the red algae Laurencia majuscula, and employed Au-catalyzed Conia-ene cyclization as the penultimate step. Having obtained silyl enol ether 7 in 11 steps from bicycle 6, itself the product of a Diels–Alder cycloaddition between 4 and enone 5, the authors subject 7 to 50 mol% Echavarren’s catalyst to deliver tricycle 8 in 65% yield. This compound is then elaborated to by chlorination of the exo-methylene.
In 2020, Yang and coworkers employed a diastereoselective Conia-ene reaction during their asymmetric synthesis of (+)-waihoensene, a structurally dense terpenoid from Podocarpus totara var. waihoensis, first synthesized by the Lee group in 2017. Vinylogous ester 9 was first functionalized in six steps to chiral Conia-ene precursor 10. Subsequent treatment of 10 with tBuOK in DMSO gave bicycle 11 in 83% yield as a single diastereomer. This compound then required eight additional transformations to reach (+)-waihoensene in 15 steps and 4% overall yield. | 0 | Theoretical and Fundamental Chemistry |
Ferritin is a universal intracellular protein that stores iron and releases it in a controlled fashion. The protein is produced by almost all living organisms, including archaea, bacteria, algae, higher plants, and animals. It is the primary intracellular iron-storage protein in both prokaryotes and eukaryotes, keeping iron in a soluble and non-toxic form. In humans, it acts as a buffer against iron deficiency and iron overload.
Ferritin is found in most tissues as a cytosolic protein, but small amounts are secreted into the serum where it functions as an iron carrier. Plasma ferritin is also an indirect marker of the total amount of iron stored in the body; hence, serum ferritin is used as a diagnostic test for iron-deficiency anemia. Aggregated ferritin transforms into a toxic form of iron called hemosiderin.
Ferritin is a globular protein complex consisting of 24 protein subunits forming a hollow nanocage with multiple metal–protein interactions. Ferritin that is not combined with iron is called apoferritin. | 1 | Applied and Interdisciplinary Chemistry |
Aluminium-based nanogalvanic alloys were discovered by researchers of the Metals Branch of ARL's Weapons and Materials Research Directorate (WMRD) of the U.S. Army Research Laboratory (ARL) in the early 2010s during testing of a new nanostructured aluminium alloy intended for structural materials applications. During metallographic polishing for microhardness experiments, they noticed that the aluminium was disappearing upon contact with water and soon realized that it was creating hydrogen gas in the process. The alloy powder was later repurposed for energy applications. A patent was filed for the invention in June 2018 in order to license the aluminium powder to industry. In 2019, the hydrogen fuel company H2 Power, LLC was the first to receive an exclusive license to use the aluminium-based nanogalvanic alloys to investigate automotive and transportation power generation applications for cars, trucks, motorcycles, and other vehicles. As of 2019, ARL researchers are looking for ways to improve the production and manufacturing process of the aluminium-based nanogalvanic alloys. | 1 | Applied and Interdisciplinary Chemistry |
The magnetic moment of a gyrating particle is
which respects special relativity. is the relativistic Lorentz factor, is the rest mass, is the velocity perpendicular to the magnetic field, and is the magnitude of the magnetic field.
is a constant of the motion to all orders in an expansion in , where is the rate of any changes experienced by the particle, e.g., due to collisions or due to temporal or spatial variations in the magnetic field. Consequently, the magnetic moment remains nearly constant even for changes at rates approaching the gyrofrequency. When is constant, the perpendicular particle energy is proportional to , so the particles can be heated by increasing , but this is a "one-shot" deal because the field cannot be increased indefinitely. It finds applications in magnetic mirrors and magnetic bottles.
There are some important situations in which the magnetic moment is not invariant:
; Magnetic pumping: If the collision frequency is larger than the pump frequency, μ is no longer conserved. In particular, collisions allow net heating by transferring some of the perpendicular energy to parallel energy.
; Cyclotron heating: If B is oscillated at the cyclotron frequency, the condition for adiabatic invariance is violated, and heating is possible. In particular, the induced electric field rotates in phase with some of the particles and continuously accelerates them.
; Magnetic cusps: The magnetic field at the center of a cusp vanishes, so the cyclotron frequency is automatically smaller than the rate of any changes. Thus the magnetic moment is not conserved, and particles are scattered relatively easily into the loss cone. | 0 | Theoretical and Fundamental Chemistry |
Starting with a biological question, a ChIP-on-chip experiment can be divided into three major steps: The first is to set up and design the experiment by selecting the appropriate array and probe type. Second, the actual experiment is performed in the wet-lab. Last, during the dry-lab portion of the cycle, gathered data are analyzed to either answer the initial question or lead to new questions so that the cycle can start again. | 1 | Applied and Interdisciplinary Chemistry |
The equation for an incompressible Newtonian Stokes flow can be solved by the stream function method in planar or in 3-D axisymmetric cases | 1 | Applied and Interdisciplinary Chemistry |
Wender Taxol total synthesis in organic chemistry describes a Taxol total synthesis (one of six to date) by the group of Paul Wender at Stanford University published in 1997. This synthesis has much in common with the Holton Taxol total synthesis in that it is a linear synthesis starting from a naturally occurring compound with ring construction in the order A,B,C,D. The Wender effort is shorter by approximately 10 steps.
Raw materials for the preparation of Taxol by this route include verbenone, prenyl bromine, allyl bromide, propiolic acid, Gilman reagent, and Eschenmoser's salt. | 0 | Theoretical and Fundamental Chemistry |
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