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Because polymers and polymer solution often have a very high viscosity, the flow in devolatilizers is laminar, leading to low heat transfer coefficients, which can also be a limiting factor. | 1 | Applied and Interdisciplinary Chemistry |
Invented by Arnold O. Beckman in 1940 , the spectrophotometer was created with the aid of his colleagues at his company National Technical Laboratories founded in 1935 which would become Beckman Instrument Company and ultimately Beckman Coulter. This would come as a solution to the previously created spectrophotometers which were unable to absorb the ultraviolet correctly. He would start with the invention of Model A where a glass prism was used to absorb the UV light. It would be found that this did not give satisfactory results, therefore in Model B, there was a shift from a glass to a quartz prism which allowed for better absorbance results. From there, Model C was born with an adjustment to the wavelength resolution which ended up having three units of it produced. The last and most popular model became Model D which is better recognized now as the DU spectrophotometer which contained the instrument case, hydrogen lamp with ultraviolet continuum, and a better monochromator. It was produced from 1941 to 1976 where the price for it in 1941 was US$723 (far-UV accessories were an option at additional cost). In the words of Nobel chemistry laureate Bruce Merrifield, it was "probably the most important instrument ever developed towards the advancement of bioscience."
Once it became discontinued in 1976, Hewlett-Packard created the first commercially available diode-array spectrophotometer in 1979 known as the HP 8450A. Diode-array spectrophotometers differed from the original spectrophotometer created by Beckman because it was the first single-beam microprocessor-controlled spectrophotometer that scanned multiple wavelengths at a time in seconds. It irradiates the sample with polychromatic light which the sample absorbs depending on its properties. Then it is transmitted back by grating the photodiode array which detects the wavelength region of the spectrum. Since then, the creation and implementation of spectrophotometry devices has increased immensely and has become one of the most innovative instruments of our time. | 0 | Theoretical and Fundamental Chemistry |
The case for an oscillating far-field flow, with the plate held at rest, can easily be constructed from the previous solution for an oscillating plate by using linear superposition of solutions. Consider a uniform velocity oscillation far away from the plate and a vanishing velocity at the plate . Unlike the stationary fluid in the original problem, the pressure gradient here at infinity must be a harmonic function of time. The solution is then given by
which is zero at the wall y = 0, corresponding with the no-slip condition for a wall at rest. This situation is often encountered in sound waves near a solid wall, or for the fluid motion near the sea bed in water waves. The vorticity, for the oscillating flow near a wall at rest, is equal to the vorticity in case of an oscillating plate but of opposite sign. | 1 | Applied and Interdisciplinary Chemistry |
Ibuprofen, polyunsaturated fatty acids, and beta-blockers have been reported in some preliminary studies to decrease REE, which may allow patients to meet their caloric needs and gain weight. | 1 | Applied and Interdisciplinary Chemistry |
The USPS warned that a number of products could be adversely affected, such as seeds, photographic film, biological samples, food, medicines, and electronic equipment. In the process of irradiation, mail is exposed to extreme heat. Paper is weakened and may appear to have been aged, with discoloration (e.g., yellowing), and brittleness. Pages may break, crumble, or fuse to other pages. Documents bound with glue may have loose pages. The printing on pages may be distorted or offset onto adjacent pages. If tape is affixed to address labels, the address may be illegible.
Irradiations effects on paper caused some alarm in the philatelic world, which sends large numbers of rare postage stamps and covers through the mail. A number of auction houses stopped sending material through the mail, and Linns Stamp News regularly featured reports on stamps and covers that had been ruined by irradiation.
Although at one time the USPS expected to irradiate all mail, it later scaled back to just treating mail sent to government offices, including all mail directed to the White House, Congress, and the Library of Congress. | 0 | Theoretical and Fundamental Chemistry |
In biology, iron plays a number of roles. Iron is widespread in most living organisms and is essential for their function. In microbes, iron redox chemistry is utilized as an electron donor or receptor in microbial metabolism, allowing microbes to generate energy. In the oceans, iron is essential for the growth and survival of phytoplankton, which use iron to fix nitrogen. Iron is also important in plants, given that they need iron to transfer electrons during photosynthesis. Finally, in animals, iron plays many roles, however, its most essential function is to transport oxygen in the bloodstream throughout the body. Thus, iron undergoes many biological processes, each of which have variations in which isotopes of iron they preferentially use. While iron isotopic fractionations are observed in many organisms, they are still not well understood. Improvements in the understanding the iron isotope fractionations observed in biology will enable the development of a more complete knowledge of the enzymatic, metabolic, and other biologic pathways in different organisms. Below, the known iron isotopic variations for different classes of organisms are described. | 0 | Theoretical and Fundamental Chemistry |
Questioning the current dogma is a design feature of Guy Bertrand's research program. He has made many important contributions to the chemistry of main group elements and new binding systems in inorganic, organometallic and organic chemistry. Throughout his career, he has isolated a variety of species that were supposed to be only transitional intermediates, and are now powerful tools for chemists.
Its best-known contribution was the discovery in 1988 of the first stable carbene, a (phosphino)(silyl)carbene, three years before Arduengo's report on a stable N-heterocyclic carbene. Guy Bertrand is at the origin of the chemistry of stable carbenes. Since then, he has made several revolutionary discoveries that have allowed us to better understand the stability of carbenes. He was the first to isolate cyclopropenylidenes, mesoionic carbenes that cannot dimerize, resulting in a relaxation of steric requirements for their isolation More importantly, he discovered cyclic (alkyl) (amino) (amino) carbenes (CAACs), including the recently published six-membered version. CAACs are even richer in electrons than NHCs and phosphines, but at the same time, due to the presence of a single pair of free electrons on nitrogen, CAACs are more accepting than NHCs. The electronic properties of CAACs stabilize highly reactive species, including organic and major group radicals, as well as paramagnetic metal species, such as gold complexes (0), which were completely unknown. CAACs have also allowed the isolation of bis(copper)acetylide complexes, which are key catalytic intermediates in the famous "Click Reaction", and which were supposed to be only transient species. He also used CAACs to prepare and isolate the first isoelectronic nucleophilic tricoordinated organoborane from amines. These recent developments appear paradoxical since they consist in using carbenes long considered as prototypic reactive intermediates to isolate otherwise unstable molecules. Among the large-scale applications already known of CAACs are their use as a ligand for transition metal catalysts. For example, in collaboration with Grubbs, Guy Bertrand has shown that ruthenium catalysts bearing a CAAC are extremely active in the ethenolysis of methyl oleate. This is the first time that a series of metathesis catalysts have performed so well in cross-metathesis reactions using ethylene gas, with sufficient activity to make ethenolysis applicable to the industrial production of linear alpha-olefins (LAOs) and other olefinic end products from biomass.
Today, hundreds of academic and industrial groups use Guy Bertrand's CAACs and other carbenes in transition metal catalysis, but also for other purposes. The most recent developments cover a wide range from nanoparticle stabilization to the antibacterial and anti-cancer properties of silver (I) and gold (I) complexes. A CAAC-copper complex even allows OLEDs to be used with a quantum efficiency close to 100% at high brightness. The discovery of stable carbenes was a breakthrough for fundamental chemistry, a real paradigm shift, but its importance also comes, and perhaps more importantly, from applications. In his review article on "N-heterocyclic carbenes", a terminology that includes carbenes, Glorius et al. wrote: "The discovery and development of N-heterocyclic carbenes is undoubtedly one of the greatest successes of recent chemical research", "N-heterocyclic carbenes are today among the most powerful tools in organic chemistry, with many applications in commercially important processes", "the meteoric rise of NHC is far from over".
Guy Bertrand's contribution is not limited to carbenes. Recent highlights include the isolation of the first stable nitrenes and phosphinidenes. He showed that the first can be used to transfer a nitrogen atom to organic fragments, a difficult task for nitrido complexes of transition metals. For the second, it has recently demonstrated that it mimics the behaviour of transition metals, just like carbenes. | 0 | Theoretical and Fundamental Chemistry |
From the digging of ancient Roman ruins, one knows that approximately 95% of the concretes and mortars constituting the Roman buildings consist of a very simple lime cement, which hardened slowly through the precipitating action of carbon dioxide , from the atmosphere and formation of calcium silicate hydrate (C-S-H). This is a very weak to medium good material that was used essentially in the making of foundations and in buildings for the populace.
But for the building of their "ouvrages d’art", especially works related to water storage (cisterns, aqueducts), the Roman architects did not hesitate to use more sophisticated and expensive ingredients. These outstanding Roman cements are based on the calcic activation of ceramic aggregates (in Latin testa, analogue to our modern metakaolin MK-750) and alkali-rich volcanic tuffs (cretoni, zeolitic pozzolan), respectively with lime. MAS-NMR Spectroscopy investigations were carried out on these high-tech Roman cements dating to the 2nd century AD. They show their geopolymeric make-up. | 0 | Theoretical and Fundamental Chemistry |
thumb|right|450px|Fig. 2. Ser-Recombinases: The (essentially irreversible) subunit-rotation pathway.<br /><br />Contrary to Tyr-recombinases, the four participating DNA strands are cut in synchrony at points staggered by only 2 bp (leaving little room for proofreading). Subunit-rotation (180°) permits the exchange of strands while covalently linked to the protein partner. The intermediate exposure of double-strand breaks bears risks of triggering illegitimate recombination and thereby secondary reactions.<br /><br />Here, the synaptic complex arises from the association of pre-formed recombinase dimers with the respective target sites (CTD/NTD, C-/N-terminal domain). Like for Tyr-recombinases, each site contains two arms, each accommodating one protomer. As both arms are structured slightly differently, the subunits become conformationally tuned and thereby prepared for their respective role in the recombination cycle. Contrary to members of the Tyr-class the recombination pathway converts two different substrate sites (attP and attB) to site-hybrids [[site-specific recombinase technology|(attL and attR). This explains the irreversible nature of this particular recombination pathway, which can only be overcome by auxiliary "recombination directionality factors" (RDFs).]]
Based on amino acid sequence homologies and mechanistic relatedness, most site-specific recombinases are grouped into one of two families: the tyrosine (Tyr) recombinase family or serine (Ser) recombinase family. The names stem from the conserved nucleophilic amino acid residue present in each class of recombinase which is used to attack the DNA and which becomes covalently linked to it during strand exchange. The earliest identified members of the serine recombinase family were known as resolvases or DNA invertases, while the founding member of the tyrosine recombinases, lambda phage integrase (using attP/B recognition sites), differs from the now well-known enzymes such as Cre (from the P1 phage) and FLP (from the yeast Saccharomyces cerevisiae). Famous serine recombinases include enzymes such as gamma-delta resolvase (from the Tn1000 transposon), Tn3 resolvase (from the Tn3 transposon), and φC31 integrase (from the φC31 phage).
Although the individual members of the two recombinase families can perform reactions with the same practical outcomes, the families are unrelated to each other, having different protein structures and reaction mechanisms. Unlike tyrosine recombinases, serine recombinases are highly modular, as was first hinted by biochemical studies and later shown by crystallographic structures. Knowledge of these protein structures could prove useful when attempting to re-engineer recombinase proteins as tools for genetic manipulation. | 1 | Applied and Interdisciplinary Chemistry |
Note that
where m is the mass of particle i.
To prove this, we need to use two facts:
:*The square of a particle's four momentum is the square of its mass,
:*And conservation of four-momentum,
So, to begin,
Then adding the three while inserting squared masses leads to,
Then note that the last four terms add up to zero using conservation of four-momentum,
So finally, | 0 | Theoretical and Fundamental Chemistry |
Electrophilic substitution of unsaturated silanes involves attack of an electrophile on an allyl- or vinylsilane. An allyl or vinyl group is incorporated at the electrophilic center after loss of the silyl group. | 0 | Theoretical and Fundamental Chemistry |
The Kalpa Sūtra () is a Jain text containing the biographies of the Jain Tirthankaras, notably Parshvanatha and Mahavira. Traditionally ascribed to Bhadrabahu, which would place it in the 4th century BCE, it was probably put in writing 980 or 993 years after the Nirvana (Moksha) of Mahavira. | 1 | Applied and Interdisciplinary Chemistry |
An EOSFET or electrolyte–oxide–semiconductor field-effect transistor is a FET, like a MOSFET, but with an electrolyte solution replacing the metal for the detection of neuronal activity. Many EOSFETs are integrated in a neurochip. | 0 | Theoretical and Fundamental Chemistry |
A number of different types of chemical cycles geochemical cycles occur on Earth. Biogeochemical cycles play an important role in sustaining the biosphere.
Notable active chemical cycles on Earth include:
* Carbon cycle – consisting of an atmospheric carbon cycle (and carbon dioxide cycle), terrestrial biological carbon cycle, oceanic carbon cycle and geological carbon cycle
* Nitrogen cycle – which converts nitrogen between its forms through fixation, ammonification, nitrification, and denitrification
* Oxygen cycle and Ozone–oxygen cycle – a biogeochemical cycle of circulating oxygen between the atmosphere, biosphere (the global sum of all ecosystems), and the lithosphere
* Ozone-oxygen cycle – continually regenerates ozone in the atmosphere and converts ultraviolet radiation (UV) into heat
* Water cycle – moves water continuously on, above and below the surface shifting between states of liquid, solution, ice and vapour
* Methane cycle – moves methane between geological and biogeochemical sources and reactions in the atmosphere
* Hydrogen cycle – a biogeochemical cycle brought about by a combination of biological and abiological processes
* Phosphorus cycle – the movement of phosphorus through the lithosphere, hydrosphere, and biosphere
* Sulfur cycle – a biogeochemical process resulting form the mineralization of organic sulfur, oxidation, reduction and incorporation into organic compounds
* Carbonate–silicate cycle transforms silicate rocks to carbonate rocks by weathering and sedimentation and transforms carbonate rocks back into silicates by metamorphism and magmatism.
* Rock cycle – switches rock between its three forms: sedimentary, metamorphic, and igneous
* Mercury cycle – a biogeochemical process in which naturally occurring mercury is bioaccumulated before recombining with sulfur and returning to geological sources as sediments
Other chemical cycles include hydrogen peroxide. | 0 | Theoretical and Fundamental Chemistry |
Carbohydrate chemistry is a subdiscipline of chemistry primarily concerned with the detection, synthesis, structure, and function of carbohydrates. Due to the general structure of carbohydrates, their synthesis is often preoccupied with the selective formation of glycosidic linkages and the selective reaction of hydroxyl groups; as a result, it relies heavily on the use of protecting groups. | 0 | Theoretical and Fundamental Chemistry |
O adducts derived from cobalt(II) and iron(II) complexes of porphyrin (and related anionic macrocyclic ligands) exhibit this bonding mode. Myoglobin and hemoglobin are famous examples, and many synthetic analogues have been described that behave similarly. Binding of O is usually described as proceeding by electron transfer from the metal(II) center to give superoxide () complexes of metal(III) centers. As shown by the mechanisms of cytochrome P450 and alpha-ketoglutarate-dependent hydroxylase, Fe-η-O bonding is conducive to formation of Fe(IV) oxo centers. O can bind to one metal of a bimetallic unit via the same modes discussed above for mononuclear complexes. A well-known example is the active site of the protein hemerythrin, which features a diiron carboxylate that binds O at one Fe center. Dinuclear complexes can also cooperate in the binding, although the initial attack of O probably occurs at a single metal. | 0 | Theoretical and Fundamental Chemistry |
Drosophila melanogaster has three transferrin genes and is highly divergent from all other model clades, Ciona intestinalis one, Danio rerio has three highly divergent from each other, as do Takifugu rubripes and Xenopus tropicalis and Gallus gallus, while Monodelphis domestica has two divergent orthologs, and Mus musculus has two relatively close and one more distant ortholog. Relatedness and orthology/paralogy data are also available for Dictyostelium discoideum, Arabidopsis thaliana, and Pseudomonas aeruginosa. | 1 | Applied and Interdisciplinary Chemistry |
* 2024 Medal of the Order of Australia (OAM)
* 2023 Society for Biological Inorganic Chemistry Early Career Award
* 2022 Australian Financial Review Emerging Leader in Higher Education
* 2020 Chemosensors Young Investigator Award
* 2019 Malcolm McIntosh Prize for Physical Scientist of the Year
*2018 Royal Society of New South Wales Edgeworth David Medal
* 2018 3M Eureka Prize for Emerging Leader in Science
* 2018 Fellow of the Royal Society of New South Wales
* 2017 Royal Australian Chemical Institute Rennie Memorial Medal
* 2017 Royal Australian Chemical Institute Educator of the Year Award
* 2016 New South Wales Early Career Researcher of the Year
* 2015 Office of Learning and Teaching Teaching Excellence Award
* 2015 Young Tall Poppy Science Award
* 2015 Selby Research Award
* 2015 Vice-Chancellor award for Outstanding Teaching
* 2014 Royal Australian Chemical Institute Nyholm Lectureship, 2014-2015
* 2014 Asian Biological Inorganic Chemistry Early Career Research Award
* 2011 Royal Society of Chemistry Dalton Young Researchers Award
* 2005 University of Sydney The University Medal | 0 | Theoretical and Fundamental Chemistry |
Pan evaporation is a measurement that combines or integrates the effects of several climate elements: temperature, humidity, rain fall, drought dispersion, solar radiation, and wind. Evaporation is greatest on hot, windy, dry, sunny days; and is greatly reduced when clouds block the sun and when air is cool, calm, and humid. Pan evaporation measurements enable farmers and ranchers to understand how much water their crops will need. | 1 | Applied and Interdisciplinary Chemistry |
In statistical mechanics, the microcanonical ensemble is a particular statistical ensemble which is used to make predictions about the outcomes of experiments performed on isolated systems that are believed to be in equilibrium with an exactly known energy. The microcanonical ensemble is based upon the assumption that, when such an equilibrated system is probed, the probability for it to be found in any of the microscopic states with the same total energy have equal probability. With this assumption, the ensemble average of an observable quantity is found by averaging the value of that observable over all microstates with the correct total energy:
Importantly, this quantity is independent of everything about the initial state except for its energy.
The assumptions of ergodicity are well-motivated in classical mechanics as a result of dynamical chaos, since a chaotic system will in general spend equal time in equal areas of its phase space. If we prepare an isolated, chaotic, classical system in some region of its phase space, then as the system is allowed to evolve in time, it will sample its entire phase space, subject only to a small number of conservation laws (such as conservation of total energy). If one can justify the claim that a given physical system is ergodic, then this mechanism will provide an explanation for why statistical mechanics is successful in making accurate predictions. For example, the hard sphere gas has been rigorously proven to be ergodic.
This argument cannot be straightforwardly extended to quantum systems, even ones that are analogous to chaotic classical systems, because time evolution of a quantum system does not uniformly sample all vectors in Hilbert space with a given energy. Given the state at time zero in a basis of energy eigenstates
the expectation value of any observable is
Even if the are incommensurate, so that this expectation value is given for long times by
the expectation value permanently retains knowledge of the initial state in the form of the coefficients .
In principle it is thus an open question as to whether an isolated quantum mechanical system, prepared in an arbitrary initial state, will approach a state which resembles thermal equilibrium, in which a handful of observables are adequate to make successful predictions about the system. However, a variety of experiments in cold atomic gases have indeed observed thermal relaxation in systems which are, to a very good approximation, completely isolated from their environment, and for a wide class of initial states. The task of explaining this experimentally observed applicability of equilibrium statistical mechanics to isolated quantum systems is the primary goal of the eigenstate thermalization hypothesis. | 0 | Theoretical and Fundamental Chemistry |
The hijack of an enhancer from another gene allows the analysis of the function of that enhancer. This, especially if the reporter gene is for a fluorescent protein, can be used to help map expression of the mutated gene through the organism, and is a very powerful tool. It is a useful tool for looking at gene expression patterns (temporally and spatially). | 1 | Applied and Interdisciplinary Chemistry |
The Society of Environmental Toxicology and Chemistry (SETAC) is an international environmental toxicology and environmental chemistry organization. | 1 | Applied and Interdisciplinary Chemistry |
The analogy between heat transfer and mass transfer is strictly limited to binary diffusion in dilute (ideal) solutions for which the mass transfer rates are low enough that mass transfer has no effect on the velocity field. The concentration of the diffusing species must be low enough that the chemical potential gradient is accurately represented by the concentration gradient (thus, the analogy has limited application to concentrated liquid solutions). When the rate of mass transfer is high or the concentration of the diffusing species is not low, corrections to the low-rate heat transfer coefficient can sometimes help. Further, in multicomponent mixtures, the transport of one species is affected by the chemical potential gradients of other species.
The heat and mass analogy may also break down in cases where the governing equations differ substantially. For instance, situations with substantial contributions from generation terms in the flow, such as bulk heat generation or bulk chemical reactions, may cause solutions to diverge. | 1 | Applied and Interdisciplinary Chemistry |
*[http://www.crystalimpact.com/match/Default.htm Match!] (method: powder diffraction fingerprinting)
*[https://web.archive.org/web/20080616153210/http://www.nist.gov/srd/nist3.htm NIST Crystal Data] (method: lattice matching)
*[http://www.icdd.com/ Powder Diffraction File (PDF)] (method: powder diffraction fingerprinting) | 0 | Theoretical and Fundamental Chemistry |
Fung was born in Jiangsu Province, China in 1919. He earned a bachelors degree in 1941 and a masters degree in 1943 from the National Central University (later renamed Nanjing University in mainland China and reinstated in Taiwan), and earned a Ph.D. from the California Institute of Technology in 1948. Fung was Professor Emeritus and Research Engineer at the University of California San Diego. He published prominent texts along with Pin Tong who was then at Hong Kong University of Science & Technology. Fung died at the Jacobs Medical Center in San Diego, California, aged 100, on December 15, 2019.
Fung was married to Luna Yu Hsien-Shih, a former mathematician and cofounder of the UC San Diego International Center, until her death in 2017. The couple raised two children. | 1 | Applied and Interdisciplinary Chemistry |
Chiral analysis refers to the quantification of component enantiomers of racemic drug substances or pharmaceutical compounds. Other synonyms commonly used include enantiomer analysis, enantiomeric analysis, and enantioselective analysis. Chiral analysis includes all analytical procedures focused on the characterization of the properties of chiral drugs. Chiral analysis is usually performed with chiral separation methods where the enantiomers are separated on an analytical scale and simultaneously assayed for each enantiomer.
Many compounds of biological and pharmacological interest are chiral. Pharmacodynamic, pharmacokinetic, and toxicological properties of the enantiomers of racemic chiral drugs has expanded significantly and become a key issue for both the pharmaceutical industry and regulatory agencies. Typically one of the enantiomers is more active pharmacologically (eutomer). In several cases, unwanted side effects or even toxic effects may occur with the inactive enantiomer (distomer). Even if the side effects are not that serious, the inactive enantiomer has to be metabolized, this puts an unnecessary burden on the already stressed out system of the patient. Large differences in activity between enantiomers reveal the need to accurate assessment of enantiomeric purity of pharmaceutical, agrochemicals, and other chemical entities like fragrances and flavors become very important. Moreover, the moment a racemic therapeutic is placed in a biological system, a chiral environment, it is no more 50:50 due enantioselective absorption, distribution, metabolism, and elimination (ADME) process. Hence to track the individual enantiomeric profile there is a need for chiral analysis tool.
Chiral technology is an active subject matter related to asymmetric synthesis and enantioselective analysis, particularly in the area of chiral chromatography. As a consequence of the advances in chiral technology, a number of pharmaceuticals currently marketed as racemic drugs are undergoing re-assessment as chiral specific products or chiral switches. Despite the choice to foster either a single enantiomer or racemic drug, in the current regulatory environment, there will be a need for enantioselective investigations. This poses a big challenge to pharmaceutical analysts and chromatographers involved in drug development process. In pharmaceutical research and development stereochemical analytical methodology may be required to comprehend enantioselective drug action and disposition, chiral purity assessment, study stereochemical stability during formulation and production, assess dosage forms, enantiospecific bioavailability and bioequivalence investigations of chiral drugs. Besides pharmaceutical applications chiral analysis plays a major role in the study of biological and environmental samples and also in the forensic field. Chiral analysis methods and applications between the period 2010 and 2020 are exhaustively reviewed recently. There are number of articles, columns, and interviews in [https://www.chromatographyonline.com/ LCGC] relating to emerging trends in chiral analysis and its application in drug discovery and development process.
For chiral examination there is a need to have the right chiral environment. This could be provided as a plane polarized light, an additional chiral compound or by exploiting the inborn chirality of nature. The chiral analytical strategies incorporate physical, biological, and separation science techniques. Recently an optical-based absolute chiral analysis has been reported. The most frequently employed technique in enantioselective analysis involve the separation science techniques, in particular chiral chromatographic methods or chiral chromatography. Today wide range of CSPs are available commercially based on various chiral selectors including polysaccharides, cyclodextrins, glycopeptide antibiotics, proteins, Pirkle, crown ethers, etc. to achieve analysis of chiral molecules. | 0 | Theoretical and Fundamental Chemistry |
For angiogenesis inhibition activity, an intact glutarimide ring seems to be required. Different groups were tested in the R position. The substances that had nitrogen salts as the R group showed good activity. The improved angiogenesis inhibitory activity could be due to increased solubility or that the positively charged nitrogen has added interaction with the active site. Tetrafluorination of the phthaloyl ring seems to increase the angiogenesis inhibition. | 1 | Applied and Interdisciplinary Chemistry |
In 2018, deulinoleate ethyl was given to a patient with amyotrophic lateral sclerosis (ALS) under a "compassionate use scheme". | 1 | Applied and Interdisciplinary Chemistry |
In glycol cleavage, the C−C bond in a vicinal diol is cleaved with formation of ketone or aldehyde functional groups. See Diol oxidation. | 0 | Theoretical and Fundamental Chemistry |
Because of anisomycins wide use as a protein synthesis inhibitor, there have been many studies centered on the biosynthesis of anisomycin. One study by Butler in 1974 proposed possible precursors to this natural product. Fermentation of Streptomyces' with labeled amino acids was followed by a degradation of the radioactive anisomycin and deacetylanisomycin products to determine the locations of the labeled carbons. Although its pyrrolidine-based structure suggests that it is derived from proline, the results from the experiments indicated that tyrosine, glycine, methionine, and acetate are the primary precursors for the biosynthesis of anisomycin. Tyrosine and, to a limited degree, phenylalanine, contribute to C-2 of the pyrrolidine ring. Methionine is likely responsible for the methylation of the hydroxyl group on the aromatic ring as S-adenosylmethionine (SAM). Glycine or acetate account for C-4 and C-5 on the pyrrolidine ring. It was noted that deacetylanisomycin was a prominent product in the first few days of fermentation, suggesting that acetylation of the C-3 hydroxyl group by acetyl Co-A is the final step in the biosynthesis of anisomycin. The source of the nitrogen within the ring and C-3 were undetermined. However, C-3 is not likely to be provided by the carboxylic acid group of tyrosine because tracking of radioactivity indicated that tyrosine undergoes decarboxylation during fermentation. | 1 | Applied and Interdisciplinary Chemistry |
Antimony oxychloride, known since the 15th century, has been known by a plethora of alchemical names. Since the compound functions as both an emetic and a laxative, it was originally used as a purgative. | 1 | Applied and Interdisciplinary Chemistry |
Photo-oxidation is the combined action of UV-light and oxygen and is the most significant factor in the weathering of plastics. Although many polymers do not absorb UV-light, they often contain impurities like hydroperoxide and carbonyl groups introduced during thermal processing, which do. These act as photoinitiators to give complex free radical chain reactions where the mechanisms of autoxidation and photodegradation combine. Photo-oxidation can be held back by light stabilizers such as hindered amine light stabilizers (HALS). | 0 | Theoretical and Fundamental Chemistry |
Glycorandomization, is a drug discovery and drug development technology platform to enable the rapid diversification of bioactive small molecules, drug leads and/or approved drugs through the attachment of sugars. Initially developed as a facile method to manipulate carbohydrate substitutions of naturally occurring glycosides to afford the corresponding differentially glycosylated natural product libraries, glycorandomization applications have expanded to include both small molecules (drug leads and approved drugs) and even macromolecules (proteins). Also referred to as glycodiversification, glycorandomization has led to the discovery of new glycoside analogs which display improvements in potency, selectivity and/or ADMET as compared to the parent molecule. | 0 | Theoretical and Fundamental Chemistry |
In August, MPMC submitted an interim erosion plan and a sediment control plan to mitigate ongoing erosion and sediment transport downstream, to control further flow from the tailings area, and to improve the quality of water flowing into Quesnel Lake. In the beginning of September 2014, a berm to prevent further spread of tailings was nearing completion and laid off workers, about 40 of the mine's approximately 300 workers demanded to reopen the mine. a spokesman at the Ministry of Mine said operations would require permits and approvals and could only go ahead after a rigorous review. The primary phase of the restoration and remediation strategy implemented work to reduce the environmental effect on Quesnel Lake. | 1 | Applied and Interdisciplinary Chemistry |
In the mid- to late 1980s, researchers have increasingly focused on genetic studies with the advancing sequencing technologies. The GenBank database was established in 1982 for the collection, management, storage, and distribution of DNA sequence data due to the increasing availability of DNA sequences. With the increasing number of genetic data, biotechnological companies have been able to use human DNA sequence to develop protein and antibody drugs through genome mining since 1992. In the late 1990s, many companies, such as Amgen, Immunec, Genentech were able to develop drugs that progressed to the clinical stage by adopting genome mining. Since the Human Genome Project was completed in the early 2000, researchers have been sequencing the genomes of many microorganisms. Subsequently, many of these genomes have been carefully studied to identify new genes and biosynthetic pathways. | 1 | Applied and Interdisciplinary Chemistry |
Metal ions are essential to the function of many proteins present in living organisms, such as metalloproteins and enzymes that require metal ions as cofactors. Processes including oxygen transport and DNA replication are carried out using enzymes such as DNA polymerase, which in humans requires magnesium and zinc to function properly. Other biomolecules also contain metal ions in their structure, such as iodine in human thyroid hormones.
The uses of some of them are listed below. The list is not exhaustive, because it covers only the principal class members; others that are trace metals of especially low bioconcentration are not explored herein. Some elements that are nonmetals or metalloids (such as selenium) are beyond the scope of this article. | 1 | Applied and Interdisciplinary Chemistry |
The citric acid cycle is regulated mainly by the availability of key substrates, particularly the ratio of NAD to NADH and the concentrations of calcium, inorganic phosphate, ATP, ADP, and AMP. Citrate – the ion that gives its name to the cycle – is a feedback inhibitor of citrate synthase and also inhibits PFK, providing a direct link between the regulation of the citric acid cycle and glycolysis. | 1 | Applied and Interdisciplinary Chemistry |
Elevated levels of the hormone insulin in the blood trigger downregulation of the associated receptors. When insulin binds to its receptors on the surface of a cell, the hormone receptor complex undergoes endocytosis and is subsequently attacked by intracellular lysosomal enzymes. The internalization of the insulin molecules provides a pathway for degradation of the hormone, as well as for regulation of the number of sites that are available for binding on the cell surface. At high plasma concentrations, the number of surface receptors for insulin is gradually reduced by the accelerated rate of receptor internalization and degradation brought about by increased hormonal binding. The rate of synthesis of new receptors within the endoplasmic reticulum and their insertion in the plasma membrane do not keep pace with their rate of destruction. Over time, this self-induced loss of target cell receptors for insulin reduces the target cell's sensitivity to the elevated hormone concentration.
This process is illustrated by the insulin receptor sites on target cells, e.g. liver cells, in a person with type 2 diabetes. Due to the elevated levels of blood glucose in an individual, the β-cells (islets of Langerhans) in the pancreas must release more insulin than normal to meet the demand and return the blood to homeostatic levels. The near-constant increase in blood insulin levels results from an effort to match the increase in blood glucose, which will cause receptor sites on the liver cells to downregulate and decrease the number of receptors for insulin, increasing the subject's resistance by decreasing sensitivity to this hormone. There is also a hepatic decrease in sensitivity to insulin. This can be seen in the continuing gluconeogenesis in the liver even when blood glucose levels are elevated. This is the more common process of insulin resistance, which leads to adult-onset diabetes.
Another example can be seen in diabetes insipidus, in which the kidneys become insensitive to arginine vasopressin. | 1 | Applied and Interdisciplinary Chemistry |
The Société Chimique de France (SCF) is a learned society and professional association founded in 1857 to represent the interests of French chemists in a variety of ways in local, national and international contexts. Until 2009 the organization was known as the Société Française de Chimie. | 1 | Applied and Interdisciplinary Chemistry |
Boardsport riders are "footed" in one of two stances, generally called "regular" and "goofy". Riders will generally quickly choose a preferred stance that becomes permanently preferred. A "regular" stance indicates the left foot leading on the board with the right foot pushing, while a "goofy" stance leads with the right foot on the board, pushing with the left. Professionals seem to be evenly distributed between the stances. Practice can yield a high level of ambidexterity between the two stances, such that even seasoned participants of a boardsport have difficulty discerning the natural footedness of an unfamiliar rider in action.
To increase the difficulty, variety, and aesthetic value of tricks, riders can ride "switch stance" (abbreviated to "switch"). For example, a goofy-footed skateboarder normally performs an ollie with the right foot forward, but a "switch ollie" would have the rider standing with the left foot at the front of the board. In sports where switch riding is common and expected, like street skateboarding, riders have the goal of appearing natural at, and performing the same tricks in, both regular and goofy stances. Some sports like kitesurfing and windsurfing generally require the rider to be able to switch stance depending on the wind or travel direction rather than rider preference. Each time direction is changed, the stance changes. Snowboarders who ride switch may adopt a "duck stance", where the feet are mounted turned out, or pointed away from the mid-line of the body, typically at a roughly 15-degree angle. In this position, the rider will have the leading foot facing forward in either regular or switch stance. | 0 | Theoretical and Fundamental Chemistry |
The second ORF of L1 encodes a protein that has endonuclease and reverse transcriptase activity. The encoded protein has a molecular weight of 150 kDa. The structure of the ORF2 protein was solved in 2023. Its protein core contains three domains of unknown functions, termed "tower/EN-linker" and "wrist/RNA-binding domain" that bind Alu RNA's polyA tail and C-terminal domain that binds Alu RNA stem loop.
The nicking and reverse transcriptase activities of L1 ORF2p are boosted by single-stranded DNA structures likely present on the active replication forks. Unlike viral RTs, L1 ORF2p can be primed by RNA, including RNA hairpin primers produced by the Alu element. | 1 | Applied and Interdisciplinary Chemistry |
By the above assumptions the flowfield is Conservative vector field, which means that there
exists a perturbation velocity potential such that the total velocity vector is given by
and that satisfies Laplace's equation.
Laplace's equation is a second order linear equation, and being so it is subject
to the principle of superposition. Which means that if and are two solutions of
the linear differential equation, then the linear combination is also a solution for any values of the constants and . As Anderson put it "A complicated flow pattern
for an irrotational, incompressible flow can be synthesized by adding together a number of elementary flows, which are also irrotational and incompressible.”. Such elementary flows are the point source or sink, the doublet and the vortex line, each being a solution of Laplace's equation. These may be superposed in many ways to create the formation of line sources, vortex sheets and so on. In the Vortex Lattice method, each such elementary flow is the velocity field of a horseshoe vortex with some strength . | 1 | Applied and Interdisciplinary Chemistry |
Oxaloacetate is an intermediate of the citric acid cycle, where it reacts with acetyl-CoA to form citrate, catalyzed by citrate synthase. It is also involved in gluconeogenesis, the urea cycle, the glyoxylate cycle, amino acid synthesis, and fatty acid synthesis. Oxaloacetate is also a potent inhibitor of complex II. | 1 | Applied and Interdisciplinary Chemistry |
Historically, the reduction of iron ore without smelting is the oldest process for obtaining steel. Low-temperature furnaces, unable to reach the melting temperatures of iron alloys, produce a burr, a heterogeneous agglomerate of metallic iron more or less impregnated with carbon, gangue, and charcoal. This process was gradually succeeded, from the 1st century in China and the 13th century in Europe, by the blast furnace, which simultaneously reduces and melts iron.
Elaborate low furnaces, such as the tatara or the Catalan forge, survived until the early 19th century. Compared with the indirect process (reduction-melting in the blast furnace, followed by cast-iron refining), these processes only survived when they enjoyed at least one of the following two advantages:
* ability to process ores that are incompatible with blast furnaces (such as iron sands that clog blast furnaces, or ores that generate slag that is too pasty to be drained);
* a more "reasonable" size than that of giant plants and their constraints (ore and capital requirements, production to sell off, etc.). | 1 | Applied and Interdisciplinary Chemistry |
Historically, many places kept left, while many others kept right, often within the same country. There are many myths that attempt to explain why one or the other is preferred. About 90 percent of people are right-handed, and many explanations reference this. Horses are traditionally mounted from the left, and led from the left, with the reins in the right hand. So people walking horses might use RHT, to keep the animals separated. Also referenced is the need for pedestrians to keep their swords in the right hand and pass on the left as in LHT, for self-defence. It has been suggested that wagon-drivers whipped their horses with their right hand, and thus sat on the left-hand side of the wagon, as in RHT. Academic Chris McManus notes that writers have stated that in the year 1300, Pope Boniface VIII directed pilgrims to keep left; however, others suggest that he directed them to keep to the right, and there is no documented evidence to back either claim. | 0 | Theoretical and Fundamental Chemistry |
The knowledge of transition state structure has been used to design oseltamivir analogues. For example, the triazole-containing carbocycles by Von Itzstein and Pinto group and the phosphonate analogue of oseltamivir has been reported to show stronger activity resulted from a pertinent binding mode of phosphonate with three Arginine residues in the active site. | 1 | Applied and Interdisciplinary Chemistry |
There was another small group of scientists at Tufts College in Medford, Massachusetts that had become involved in research of the pinch effect. Although their work was not officially part of the Atomic Energy Commission, some of their personnel attended the Sherwood conferences. | 0 | Theoretical and Fundamental Chemistry |
* [https://github.com/RaymondMcGuire/GPU-Based-Image-Processing-Tools GPU Based Image Processing Tools by Raymond McGuire]
* [https://www.paraview.org/Wiki/ParaView/Line%20Integral%20Convolution ParaView : Line Integral Convolution]
* [https://github.com/andresbejarano/2DFlowVisualization A 2D flow visualization tool based on LIC and RK4. Developed using C++ and VTK. by Andres Bejarano]
* [https://reference.wolfram.com/language/ref/LineIntegralConvolutionPlot.html Wolfram Research (2008), LineIntegralConvolutionPlot, Wolfram Language function, https://reference.wolfram.com/language/ref/LineIntegralConvolutionPlot.html (updated 2014).] | 1 | Applied and Interdisciplinary Chemistry |
There are several techniques for the assembly of glycoproteins. One technique utilizes recombination. The first consideration for this method is the choice of host, as there are many different factors that can influence the success of glycoprotein recombination such as cost, the host environment, the efficacy of the process, and other considerations. Some examples of host cells include E. coli, yeast, plant cells, insect cells, and mammalian cells. Of these options, mammalian cells are the most common because their use does not face the same challenges that other host cells do such as different glycan structures, shorter half life, and potential unwanted immune responses in humans. Of mammalian cells, the most common cell line used for recombinant glycoprotein production is the Chinese hamster ovary line. However, as technologies develop, the most promising cell lines for recombinant glycoprotein production are human cell lines. | 0 | Theoretical and Fundamental Chemistry |
Along with the emerging diagnostic capabilities of pharmacometabolomics, there are limitations introduced when individual variability is looked at. The ability to determine an individual's physiological state by measurement of metabolites is not contested, but the extreme variability that can be introduced by age, nutrition, and commensal organisms suggest problems in creating generalized pharmacometabolomes for patient groups. However, as long as meaningful metabolic signatures can be elucidated to create baseline values, there still exists a possible means of comparison.
Issues surrounding the measurement of metabolites in an individual can also arise from the methodology of metabolite detection, and there are arguments both for and against NMR and mass spectrometry (MS). Other limitations surrounding metabolite analysis include the need for proper handling and processing of samples, as well as proper maintenance and calibration of the analytical and computational equipment. These tasks require skilled and experienced technicians, and potential instrument repair costs due to continuous sample processing can be costly. The cost of the processing and analytical platforms alone is very high, making it difficult for many facilities to afford pharmacometabolomics-based treatment analyses. | 1 | Applied and Interdisciplinary Chemistry |
* At high glucose levels, acetyl-CoA is produced through glycolysis. Pyruvate undergoes oxidative decarboxylation in which it loses its carboxyl group (as carbon dioxide) to form acetyl-CoA, giving off 33.5 kJ/mol of energy. The oxidative conversion of pyruvate into acetyl-CoA is referred to as the pyruvate dehydrogenase reaction. It is catalyzed by the pyruvate dehydrogenase complex. Other conversions between pyruvate and acetyl-CoA are possible. For example, pyruvate formate lyase disproportionates pyruvate into acetyl-CoA and formic acid.
* At low glucose levels, the production of acetyl-CoA is linked to β-oxidation of fatty acids. Fatty acids are first converted to acyl-CoA. Acyl-CoA is then degraded in a four-step cycle of oxidation, hydration, oxidation and thiolysis catalyzed by four respective enzymes, namely acyl-CoA dehydrogenase, enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, and thiolase. The cycle produces a new fatty acid chain with two fewer carbons and acetyl-CoA as a byproduct. | 1 | Applied and Interdisciplinary Chemistry |
*Tenofovir alafenamide: A pro-drug of the nucleotide analogue tenofovir, critical for HIV treatment.
*AMPA: Aminomethylphosphonic acid, degradation product of glyphosate
*Vinylphosphonic acid: monomer
*Dimethyl methylphosphonate (DMMP), one of the simplest phosphonate diesters
*Etidronic acid (HEDP): 1-hydroxyethylidene-1,1-diphosphonic acid, used in detergents, water treatment, cosmetics and pharmaceuticals
*ATMP: Aminotris(methylenephosphonic acid), chelating agent
*EDTMP: Ethylenediaminetetra(methylenephosphonic acid), chelating agent
*TDTMP: Tetramethylenediaminetetra(methylenephosphonic acid), chelating agent
*HDTMP: Hexamethylenediaminetetra(methylenephosphonic acid), chelating agent
*DTPMP: Diethylenetriaminepenta(methylenephosphonic acid), chelating agent
*PBTC: Phosphonobutanetricarboxylic acid
*PMIDA: N-(phosphonomethyl)iminodiacetic acid
*CEPA: 2-carboxyethyl phosphonic acid
*HPAA: 2-Hydroxyphosphonocarboxylic acid
*AMP: Aminotris(methylenephosphonic acid)
*BPMG: N,N-Bis(phosphonomethyl)glycine
*Glyphosate: a common agricultural herbicide
*Foscarnet: for treatment of herpes
*Perzinfotel: for treatment of stroke
*SF2312: a natural product phosphonate antibiotic inhibitor of enolase
*Selfotel: an abandoned experimental drug for stroke | 0 | Theoretical and Fundamental Chemistry |
The Inco Superstack in Sudbury, Ontario, with a height of , is the tallest chimney in Canada and the Western Hemisphere, and the second-tallest freestanding chimney in the world after the Ekibastuz GRES-2 Power Station in Kazakhstan. It is also the second-tallest freestanding structure of any type in Canada, behind the CN Tower but ahead of First Canadian Place. As of 2023, it is the 51st-tallest freestanding structure in the world. The Superstack is located on top of the largest nickel smelting operation in the world at Vale's Copper Cliff processing facility in the city of Greater Sudbury.
In 2018, Vale announced that the stack would be decommissioned and dismantled, beginning in 2020. Two new, smaller stacks were constructed under the company's Clean Atmospheric Emissions Reduction Project. In July 2020, Vale announced that the Superstack had been officially taken out of service, but would remain operational in standby mode for two more months as a backup in the event of a malfunction in the new system, following which the dismantling of the Superstack would begin. As of 2024, however, Vale has not yet announced the awarding of a demolition contract on the Superstack, and it remains unknown when demolition will actually begin; some have called for the stack to be left in place as a tourist attraction.
In addition to further reducing sulphur dioxide emissions by 85 per cent, the decommissioning of the stack is expected to cut the complex's natural gas consumption in half. | 1 | Applied and Interdisciplinary Chemistry |
Figure 1 to the right explains the basic principle, in which the organic extractant E is contained inside the pores of a porous particle. The solute S, which is initially dissolved in the aqueous phase surrounding the SIR particle, physically dissolves in the organic extractant phase during the extraction process. Furthermore, the solute S can react with the extractant to form a complex ES. This complexation of the solute with the extractant shifts the overall extraction equilibrium further towards the organic phase. This way, the extraction of the solute is enhanced.
While during conventional liquid-liquid extraction the solvent and the extractant have to be dispersed, in a SIR setup the dispersion is already achieved by the impregnated particles. This also prevents an additional phase separation step, which would be necessary after the emulsification occurring in liquid-liquid extraction. In order to elucidate the effect of emulsification, Figure 2 (to the left) compares the two systems of an extractant in liquid-liquid equilibrium with water, left, and SIR particles in equilibrium with water, right. The figure shows that no emulsification occurs in the SIR system, whereas the liquid-liquid system shows turbidity implying emulsification. Also, the impregnation step decreases the solvent loss into the aqueous phase compared to liquid-liquid extraction. This decrease of extractant loss is contributed to physical sorption of the extractant on the particle surface, which means that the extractant inside the pores does not entirely behave as a bulk liquid. Depending on the pore size of the used particles, capillary forces may also play a role in retaining the extractant. Otherwise, van-der-Waals forces, pi-pi-interactions or hydrophobic interactions might stabilize the extractant inside the particle pores. However, the possible decrease of extractant loss depends largely on the pore size and the water solubility of the extractant. Nonetheless, SIRs have a significant advantage over e.g. custom made ion-exchange resins with chemically bonded ligands. SIRs can be reused for different separation tasks by just rinsing one complexing agent out and re-impregnating them with another more suitable extractant. This way, potentially expensive design and production steps of e.g. affinity resins can be avoided. Finally, by filling the whole volume of the particle pores with an extractant (complexing agent), a higher capacity for solutes can be achieved than with ordinary adsorption or ion exchange resins, where only the surface area is available.
However, there are possible drawbacks of SIR technology, such as leaching of the extractant or clogging of a fixed bed by attrition of the particles. These might be remedied by choosing the proper particle-extractant-system. This implies selecting a suitable extractant with low water solubility, which is sufficiently retained inside the pores, and selecting mechanically stable particles as a solid support for the extractant. Additionally, SIRs can be stabilized by coating them, as shown by D. Muraviev et al. As coating material, A. W. Trochimczuk et al. used polyvinyl alcohol.
In order to remove or recover the extracted solute, SIR particles can be regenerated using low pressure steam stripping, which is particularly effective for the recovery of volatile hydrocarbons. However, if the vapor pressure of the extracted solute is too low, or if the complexation between solute and extractant is too strong, other techniques need to be applied, e.g. pH swing. | 0 | Theoretical and Fundamental Chemistry |
Ratsimamanga was awarded the Grand Cross of the Malagasy National Order, First Class Grand Cross of the Order of Merit of the Federal Republic of Germany, Grand Officer of the Legion of Honor of France, Grand Officer of the National Order of Scientific Merit of France, National Order of the Lion of Senegal, Commander of the Ordre des Palmes académiques, Commander of the Order of Merit of Congo - Brazzaville, Commander of the Ordre national du Mérite of France, and Grand Prize from the Royal Academy for Overseas Sciences. He was selected Madagascars Man of the Century' in 1999.
Ratsimamanga was a Founder Fellow of the World Academy of Sciences (FTWAS) in 1983, and the African Academy of Sciences in 1985 (FAAS). He was awarded an Honorary Doctorate from the Cheikh Anta Diop University in 1973. | 1 | Applied and Interdisciplinary Chemistry |
Waters was appointed as a lecturer in chemistry at Auckland in 1961, rising to the rank of full professor in 1970. In 1969, he was awarded the degree of Doctor of Science by the University of Auckland on the basis of published papers submitted.
Waters served as assistant vice chancellor of the University of Auckland between 1979 and 1981, including a period in 1980 as acting vice chancellor. He left Auckland at the end of 1982, and was accorded the title of professor emeritus by the university in 1984.
In 1983, Waters was appointed as principal and vice chancellor of Massey University, serving in that role until 1995. In 1995, Massey also bestowed the title of professor emeritus on Waters.
During his career, Waters served on a range of university, science sector, and government bodies, including: the council of the Australian and New Zealand Association for the Advancement of Science from 1977 to 1979; the board of the New Zealand University Grants Committee in 1982; the New Zealand Vice Chancellors' Committee from 1983 to 1995, including periods as chair in 1984–85 and 1994; the council of Palmerston North College of Education from 1983 to 1988, the council of Manawatu Polytechnic from 1983 to 1990, as chair of the Foundation for Research, Science and Technology between 1995 and 1998; and chair of the New Zealand Qualifications Authority from 1995 to 1999. | 0 | Theoretical and Fundamental Chemistry |
The name "zincate" may also refer to a polymeric anion with formula approaching [], which forms salts such as ·, or to mixed oxides of zinc and less electronegative elements, such as . | 0 | Theoretical and Fundamental Chemistry |
Since many algal blooms are caused by a major influx of nutrient-rich runoff into a water body, programs to treat wastewater, reduce the overuse of fertilizers in agriculture and reducing the bulk flow of runoff can be effective for reducing severe algal blooms at river mouths, estuaries, and the ocean directly in front of the river's mouth.
The nitrates and phosphorus in fertilizers cause algal blooms when they run off into lakes and rivers after heavy rains. Modifications in farming methods have been suggested, such as only using fertilizer in a targeted way at the appropriate time exactly where it can do the most good for crops to reduce potential runoff. A method used successfully is drip irrigation, which instead of widely dispersing fertilizers on fields, drip-irrigates plant roots through a network of tubes and emitters, leaving no traces of fertilizer to be washed away. Drip irrigation also prevents the formation of algal blooms in reservoirs for drinking water while saving up to 50% of water typically used by agriculture.
There have also been proposals to create buffer zones of foliage and wetlands to help filter out the phosphorus before it reaches water. Other experts have suggested using conservation tillage, changing crop rotations, and restoring wetlands. It is possible for some dead zones to shrink within a year under proper management.
There have been a few success stories in controlling chemicals. After Norway's lobster fishery collapsed in 1986 due to low oxygen levels, for instance, the government in neighboring Denmark took action and reduced phosphorus output by 80 percent which brought oxygen levels closer to normal. Similarly, dead zones in the Black Sea and along the Danube River recovered after phosphorus applications by farmers were reduced by 60%.
Nutrients can be permanently removed from wetlands harvesting wetland plants, reducing nutrient influx into surrounding bodies of water. Research is ongoing to determine the efficacy of floating mats of cattails in removing nutrients from surface waters too deep to sustain the growth of wetland plants.
In the U.S., surface runoff is the largest source of nutrients added to rivers and lakes, but is mostly unregulated under the federal Clean Water Act. Locally developed initiatives to reduce nutrient pollution are underway in various areas of the country, such as the Great Lakes region and the Chesapeake Bay. To help reduce algal blooms in Lake Erie, the State of Ohio presented a plan in 2016 to reduce phosphorus runoff. | 0 | Theoretical and Fundamental Chemistry |
Gottfried Münzenberg was born on 17 March 1940, into a family of Protestant ministers (father Pastor Heinz and mother Helene Münzenberg). All his life he was deeply concerned about the philosophical and theological implications of physics. He studied physics at Justus-Liebig-Universität in Giessen and Leopold-Franzens-Universität Innsbruck and completed his studies with a Ph.D. at the University of Giessen, Germany, in 1971. In 1976, he moved to the department of nuclear chemistry at GSI in Darmstadt, Germany, which was headed by Peter Armbruster. He played a leading role in the construction of SHIP, the Separator of Heavy Ion Reaction Products. He was the driving force in the discovery of the cold heavy ion fusion and the discovery of the elements bohrium (Z = 107), hassium (Z = 108), meitnerium (Z = 109), darmstadtium (Z = 110), roentgenium (Z = 111), and copernicium (Z = 112). In 1984, he became head of the new GSI project, the fragment separator, a project which opened new research topics, such as interactions of relativistic heavy ions with matter, production and separation of exotic nuclear beams and structure of exotic nuclei. He directed the Nuclear Structure and Nuclear Chemistry department of the GSI and was professor of physics at the University of Mainz until he retired in March 2005.
Among the rewards he received should be mentioned the Röntgen-Prize of the University of Giessen in 1983 and (together with Sigurd Hofmann) the Otto Hahn Prize of the City of Frankfurt am Main in 1996.
Münzenberg died in Greifswald on 2 January 2024, at the age of 83. | 1 | Applied and Interdisciplinary Chemistry |
Sulfonyl chlorides react with water to give the corresponding sulfonic acid:
These compounds react readily with many other nucleophiles as well, most notably alcohols and amines (see Hinsberg reaction). If the nucleophile is an alcohol, the product is a sulfonate ester; if it is an amine, the product is a sulfonamide. Using sodium sulfite as the nucleophilic reagent, p-toluenesulfonyl chloride is converted to its sulfinate salt, . Chlorosulfonated alkanes are susceptible to crosslinking via reactions with various nucleophiles.
Sulfonyl chlorides readily undergo Friedel–Crafts reactions with arenes giving sulfones, for example:
The desulfonation of arylsulfonyl chlorides provides a route to aryl chlorides:
1,2,4-Trichlorobenzene is made industrially in this way.
Treatment of alkanesulfonyl chlorides having α-hydrogens with amine bases can give sulfenes, highly unstable species that can be trapped:
Sulfonamides can be prepared by reaction of sulfonyl chlorides with amines:
A readily available sulfonyl chloride source is tosyl chloride.
Reduction with tetrathiotungstate ions () induces dimerization to the disulfide. | 0 | Theoretical and Fundamental Chemistry |
To determine saponification value, the sample is treated with an excess of alkali (usually an ethanolic solution of potassium hydroxide) for half an hour under reflux. The KOH is consumed by reaction with triglycerides, which consume three equivalents of base. Diglycerides consume two equivalents of KOH. Monoglycerides and free fatty acids, as well as by other esters such as lactones consume one equivalent of base At the end of the reaction the quantity of KOH is determined by titration using standard solution of hydrochloric acid (HCl). Key to the method is the use of phenolphthalein indicator, which indicates the consumption of strong base (KOH) by the acid, not the weak base (potassium carboxylates). The SV (mg KOH/ g of sample) is calculated as following:
:where:
: is the volume of HCl solution used for the blank run, in mL;
: is the volume of HCl solution used for the tested sample, in mL;
: is the molarity of HCl solution, in mol / L;
: is the molecular weight of KOH, in g / mol;
: is the weight of sample, in g.
For example, standard methods for determination of SV of vegetable and animal fats are as follows:
The SV can also be calculated from the fatty acid composition as determined by gas chromatography (AOCS Cd 3a-94).
Handmade soap makers who aim for bar soap use sodium hydroxide (NaOH), commonly known as lye, rather than KOH (caustic potash) which produces soft paste, gel or liquid soaps. In order to calculate the lye amount needed to make bar soap, KOH values of SV can be converted to NaOH values by dividing KOH values by the ratio of the molecular weights of KOH and NaOH (1.403). | 0 | Theoretical and Fundamental Chemistry |
SDS may reduce the amount of bad breath-causing volatile sulfur compounds (VSCs) in the mouth. A series of small crossover studies (25–34 patients) have supported the efficacy of SLS in the reduction of VSCs, and its related positive impact on breath malodor, although these studies have been generally noted to reflect technical challenges in the control of study design variables. | 1 | Applied and Interdisciplinary Chemistry |
The table below lists common flocculants along with their chemical formulas, net electrical charge, molecular weight and current applications. | 0 | Theoretical and Fundamental Chemistry |
A frozen zoo is a storage facility in which genetic materials taken from animals (e.g. DNA, sperm, eggs, embryos and live tissue) are stored at very low temperatures (−196 °C) in tanks of liquid nitrogen. Material preserved in this way can be stored indefinitely and used for artificial insemination, in vitro fertilization, embryo transfer, and cloning. There are a few frozen zoos across the world that implement this technology for conservation efforts. Several different species have been introduced to this technology, including the Pyrenean ibex, Black-footed ferret, and potentially the white rhinoceros. | 1 | Applied and Interdisciplinary Chemistry |
HIV-1 RT is an asymmetric heterodimer which is 1000 amino acid long and is composed of two subunits. The larger subunit, p66, is 560 amino acid long and it exhibits all the enzymatic activities of the RT. The smaller subunit, called p51, is 440 amino acid long and it is considered to stabilize the heterodimer but also it may take part in the binding of the tRNA primer. The p66 subunit has the two active sites: polymerase and ribonuclease H. The polymerase has four subdomains that have been named “fingers“, “thumb“, “connection“ and “palm“ for it has been compared to the right hand. | 1 | Applied and Interdisciplinary Chemistry |
Among historians of philosophy and science, the verse is often understood as a reference to the supposed effects of celestial mechanics upon terrestrial events. This would include the effects of the Sun upon the change of seasons, or those of the Moon upon the tides, but also more elaborate astrological effects.
According to another common interpretation, the verse refers to the structural similarities (or correspondences) between the macrocosm (from Greek makros kosmos, "the great world"; the universe as a whole, understood as a great living being) and the microcosm (from Greek mikros kosmos, "the small world"; the human being, understood as a miniature universe). This type of view is found in many philosophical systems world-wide, the most relevant here being ancient Greek and Hellenistic philosophy, where notable proponents included Anaximander (c. 610 – c. 546 BCE), Plato (c. 428 or 424 – c. 348 BCE), the Hippocratic authors (late fifth or early fourth century BCE and onwards), and the Stoics (third century BCE and onwards). | 1 | Applied and Interdisciplinary Chemistry |
This is accomplished by comparing the different HERV from different evolutionary periods. For example, this study was done for different hominoids, which ranged from humans to apes and to monkeys. This is difficult to do with PERV because of the large diversity present. | 1 | Applied and Interdisciplinary Chemistry |
The MAM is enriched in enzymes involved in lipid biosynthesis, such as phosphatidylserine synthase on the ER face and phosphatidylserine decarboxylase on the mitochondrial face. Because mitochondria are dynamic organelles constantly undergoing fission and fusion events, they require a constant and well-regulated supply of phospholipids for membrane integrity. But mitochondria are not only a destination for the phospholipids they finish synthesis of; rather, this organelle also plays a role in inter-organelle trafficking of the intermediates and products of phospholipid biosynthetic pathways, ceramide and cholesterol metabolism, and glycosphingolipid anabolism.
Such trafficking capacity depends on the MAM, which has been shown to facilitate transfer of lipid intermediates between organelles. In contrast to the standard vesicular mechanism of lipid transfer, evidence indicates that the physical proximity of the ER and mitochondrial membranes at the MAM allows for lipid flipping between opposed bilayers. Despite this unusual and seemingly energetically unfavorable mechanism, such transport does not require ATP. Instead, in yeast, it has been shown to be dependent on a multiprotein tethering structure termed the ER-mitochondria encounter structure, or ERMES, although it remains unclear whether this structure directly mediates lipid transfer or is required to keep the membranes in sufficiently close proximity to lower the energy barrier for lipid flipping.
The MAM may also be part of the secretory pathway, in addition to its role in intracellular lipid trafficking. In particular, the MAM appears to be an intermediate destination between the rough ER and the Golgi in the pathway that leads to very-low-density lipoprotein, or VLDL, assembly and secretion. The MAM thus serves as a critical metabolic and trafficking hub in lipid metabolism. | 1 | Applied and Interdisciplinary Chemistry |
Substantial findings indicate photosynthetic picoplankton, picocyanobacteria, and phytoplankton activity creates favorable conditions for carbonate precipitation. This link arises as a result of [http://www.genomenewsnetwork.org/articles/02_02/bloom_art.shtml planktonic blooms] being observed coinciding with the events. Subsequently, via photosynthesis, these organisms uptake inorganic carbon, raise water pH, and alter water alkalinity, which promotes calcium carbonate precipitation. The thermodynamic influence of inorganic carbon on whiting calcium carbonate production is shown in the equation below. Furthermore, cases exist in which the type of calcium carbonate found in the whiting cloud matches the type found on local cyanobacteria membranes. Its hypothesized that the extracellular polymeric substances (EPS) these microorganisms produce can act as seed crystals that provide a start for the precipitation process. Current research on the specifics of these EPS and the exact physiological mechanisms of the microorganisms carbon uptake, however, are limited.
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Aside from sharing the same absolute stereochemistry as leptomycin B, callystatin A was discovered to have similar biological activity with leptomycin B as well. The anti-tumor activity of leptomycin B and callystatin A arises because many NES-cargo molecules blocked by these antibiotics are those involved in the cellular processes of proliferation, differentiation, and development, learning and memory, and hormone action. These molecules include regulatory proteins such as Rev, MAPK/MEK1, c-Abl, Cyclin B1, MDM2/p53, IkB, MPF, and PKA.
The most important role of leptomycin B is its inhibitory effect on the NES-dependent nuclear export mechanism, leading to the cell cycle arrest during G1 and G2 phases in eukaryotic cells. In wild-type cells, macromolecules in the nucleus with the leucine-rich nuclear export signal (NES) can be transported to the cytoplasm by binding to a karyopherin protein called chromosome region maintenance 1 (CRM1)/exportin 1. This CRM1/exportin1/NES-cargo interaction is stabilized by Ran-GTP binding which forms a complex that can transport the cargo to the cytoplasm. There, the cargo will be released when the Ran-GTP protein is hydrolyzed by a cytoplasmic Ran-GTPase enzyme to form Ran-GDP. This step completes the transport process and CRM1/exportin1 reenters the nucleus for more cargo binding. Leptomycin B and callystatin A inhibit the action of CRM1/exportin1 by a likely Michael-type addition of the thiol group from a cysteine residue of CRM1/exportin1 to form a covalent bond. This interaction prevents CRM1/exportin1 from recognizing and binding the NES of the cargo molecules because it occurs within the same binding site. Thus, macromolecules intended to be transported out of the nucleus will accumulate there instead. | 0 | Theoretical and Fundamental Chemistry |
William Procter, Jr., who graduated from, then taught at the Philadelphia College of Pharmacy for 20 years, went on to exert so much influence over the formative years of professional pharmacy that hes now widely considered the "Father of American Pharmacy." Procter successfully argued for the establishment of a chair of Pharmacy for pharmacist-professors at the PCP in 1844, then wrote "the first American pharmacy textbook," which came to be known as Mohr, Redwood, and Procters Practical Pharmacy (1849). The book was not commercially successful, but became a model for subsequent "works of long-lived popularity: Edward Parrishs An Introduction to Practical Pharmacy (1855-1884), and Joseph P. Remingtons Practice of Pharmacy (1888-1995 [19th ed.])". Procter also led the American Journal of Pharmacy for 22 years, served 30 years on the U.S.P. Revision Committee, where he did much to improve the U.S. Pharmacopeia, and following five years as the American Pharmaceutical Associations corresponding secretary, he became the APhAs president, leading delegations of American pharmacists in conferences with their counterparts offshore. At the Second International Congress of Pharmacy in Paris, France, August 21 to 24, 1867, Procter argued forcefully against the "compulsory limitation of pharmacies" (capping their number in a given city or province) under consideration, telling the assembled delegates that, in the U.S., "there is not the slightest obstacle toward a multiplication of drug stores save that a lack of success" and that the American public is "a forceful agent of reform" to keep unscrupulous operators in check. Procter's declaration was later seen as a defining statement of "the American Way of Pharmacy." | 1 | Applied and Interdisciplinary Chemistry |
The first phase, from 2020 to 2025, would be structured to build the foundation for a concerted global effort, and would aim to collect, characterize and make available existing pharmacological modulators for key representatives from all proteins families in the current druggable genome (~4,000 proteins), as well as to develop critical and centralized infrastructure to facilitate data collection, curation, dissemination, and mining that will power the scientific community worldwide. This phase might also create centralized facilities to provide quantitative genome-scale biochemical and cell-based profiling assays to the federated community, as well as to coordinate the development of new technologies to extend the definition of druggability. This first phase will complement and extend ongoing efforts to create chemical tools and chemogenomic libraries to blanket priority gene families, such as kinases and epigenetics families.
One year into Target 2035 has so far yielded infrastructure to house [https://gateway.eubopen.org/ data] on chemogenomic compounds reported in the literature. A progress update was published recently. Towards the development of new technologies, Target 2035 started a new initiative [https://www.cache-challenge.org/ Critical Assessment of Computational Hit-Finding Experiments] (CACHE) aimed at benchmarking computational methods for hit-finding. The first [https://www.cache-challenge.org/competitions/competition-1 competition] - finding ligands for the WD40 domain of LRRK2 - started in March 2022. The first round of predictions have been submitted. In the meantime, applications for the second CACHE benchmarking - [https://www.cache-challenge.org/challenges/finding-ligands-targeting-the-conserved-rna-binding-site-of-sars-cov-2-nsp13 predicting ligands for the RNA-binding domain for Nsp13] - has been posted. | 1 | Applied and Interdisciplinary Chemistry |
Crimped or pressed connections use special copper fittings which are permanently attached to rigid copper tubing with a powered crimper. The special fittings, manufactured with sealant already inside, slide over the tubing to be connected. Thousands of pounds-force per square inch of pressure are used to deform the fitting and compress the sealant against the inner copper tubing, creating a watertight seal. Advantages of this method are:
*A correctly crimped connection should last as long as the tubing.
*It takes less time to complete than other methods.
*It is cleaner in both appearance and the materials used to make the connection.
*No open flame is used during the connection process.
Disadvantages are:
*The fittings used are harder to find and cost significantly more than sweat type fittings.
*The fittings are not re-usable. If a design change is required or if a joint is found to be defective or improperly crimped, the already installed fittings must be cut out and discarded. In addition, the cutting required to remove the fitting often will leave insufficient tubing to install the new fitting, So couplers and additional tubing will need to be installed on either side of the replacement fitting. Whereas with a soldered fitting, a defective joint can just be re-soldered, or heated and turned if a minor change is required, or heated and removed without requiring any of the tubing to be cut away. This also allows more expensive fittings like valves to be re-used if they are otherwise in good to new condition, something not possible if the fitting is crimped on.
*The cost of the tooling is very expensive. , a basic toolkit required to sweat solder all the copper pipes of a typical single family residence, including fuel and solder, can be purchased for approximately $200. By contrast, the minimum cost of a basic powered crimping tool starts at around $1800, and can be as high as $4000 for the better brands with a complete set of crimping dies. | 1 | Applied and Interdisciplinary Chemistry |
The classical examples of the two nearly ideal types of electrodes, polarizable and non-polarizable, are the mercury droplet electrode in contact with an oxygen-free KCl solution and the silver/silver chloride electrode, respectively. | 0 | Theoretical and Fundamental Chemistry |
The Young's modulus of a mineral can be predicted by varying one cell parameter at a time and observing the evolution of the stress tensor. Because the raw output of a simulation includes energy and volume, the integrated version of the Birch-Murnaghan equation of state is often used to determine bulk modulus. | 0 | Theoretical and Fundamental Chemistry |
Ernst was born in Winterthur, Switzerland on 14 August 1933 to Robert Ernst and Irma Ernst-Brunner. He was the oldest of three children of Irma Brunner and Robert Ernst. He grew up in a house built in 1898 by his grandfather, who was a merchant. During his childhood, he was interested in music, playing the violoncello and even considering a career as a musical composer. At 13-years old, Ernst stumbled upon a box of chemicals belonging to his late uncle, a metallurgical engineer. Young Ernst was excited by what he found, and set about trying all conceivable reactions, some of which resulted in explosions that terrified his parents. | 0 | Theoretical and Fundamental Chemistry |
Wet storage stain can be prevented for a limited amount of time by coating in a light oil, chromate conversion coatings, or phosphate conversion coatings. A more permanent solution is to paint the surface. | 1 | Applied and Interdisciplinary Chemistry |
is used in the semiconductor industry in plasma etching of silicon oxide and silicon nitride. Known as R-23 or HFC-23, it was also a useful refrigerant, sometimes as a replacement for chlorotrifluoromethane (CFC-13) and is a byproduct of its manufacture.
When used as a fire suppressant, the fluoroform carries the DuPont trade name, FE-13. is recommended for this application because of its low toxicity, its low reactivity, and its high density. HFC-23 has been used in the past as a replacement for Halon 1301(CFC-13B1) in fire suppression systems as a total flooding gaseous fire suppression agent. | 1 | Applied and Interdisciplinary Chemistry |
In November 1940 McTaggart worked at Carbide Works at Electrona in Tasmania until mid-1941, then returned to Melbourne to live at 4 Kenilworth Gve. Glen Iris. | 0 | Theoretical and Fundamental Chemistry |
Chemogenetics is the process by which macromolecules can be engineered to interact with previously unrecognized small molecules. Chemogenetics as a term was originally coined to describe the observed effects of mutations on chalcone isomerase activity on substrate specificities in the flowers of Dianthus caryophyllus. This method is very similar to optogenetics; however, it uses chemically engineered molecules and ligands instead of light and light-sensitive channels known as opsins.
In recent research projects, chemogenetics has been widely used to understand the relationship between brain activity and behavior. Prior to chemogenetics, researchers used methods such as transcranial magnetic stimulation and deep brain stimulation to study the relationship between neuronal activity and behavior. | 1 | Applied and Interdisciplinary Chemistry |
Results will vary depending on sample adulteration, quantity, temperature, lighting, exposure to air, storage, as well as reagent quality and degradation. Colorimetric techniques have been developed.
If more than one bottle are open at the same time and the cap are put on the wrong reagent bottle, this may cross-contaminate the reagents and ruin them.
According to a 2003 research published in Pharmacotherapy, neither the Marquis, Mecke, nor Simon's reagents should be used by the public for harm reduction purposes. These agents do not help identify pure MDMA tablets. The research team suggests using gas chromatography-mass spectrometry as the most sensitive and specific testing method for identifying MDMA and its contaminants but this is out of reach for users in most countries and reagent tests remain popular, often distributed by harm-reduction organisations due to their low cost and high utility when multiple test reagents are used. | 0 | Theoretical and Fundamental Chemistry |
Since different radiation types have different biological effects for the same deposited energy, a corrective radiation weighting factor W, which is dependent on the radiation type and on the target tissue, is applied to convert the absorbed dose measured in the unit gray to determine the equivalent dose. The result is given the unit sievert.
The equivalent dose is calculated by multiplying the absorbed energy, averaged by mass over an organ or tissue of interest, by a radiation weighting factor appropriate to the type and energy of radiation. To obtain the equivalent dose for a mix of radiation types and energies, a sum is taken over all types of radiation energy dose.
where
: is the equivalent dose absorbed by tissue T,
: is the absorbed dose in tissue T by radiation type R and
: is the radiation weighting factor defined by regulation.
Thus for example, an absorbed dose of 1 Gy by alpha particles will lead to an equivalent dose of 20 Sv.
This may seem to be a paradox. It implies that the energy of the incident radiation field in joules has increased by a factor of 20, thereby violating the laws of conservation of energy. However, this is not the case. The sievert is used only to convey the fact that a gray of absorbed alpha particles would cause twenty times the biological effect of a gray of absorbed x-rays. It is this biological component that is being expressed when using sieverts rather than the actual energy delivered by the incident absorbed radiation. | 0 | Theoretical and Fundamental Chemistry |
Late transition metals from groups 10, 11, and 12 when placed at the anomeric carbon show strong axial preferences. This phenomenon termed as the metallo-anomeric effect originates from stabilizing hyperconjugative interactions between oxygen or other heteroatoms with lone pairs and C-M anti-bonding orbitals that act as good acceptors. The generalized metallo-anomeric effect refers to thermodynamic stabilization of synclinal conformers of compounds with the general formula M-CH-OR. Axial/equatorial preferences can be influenced by ligands attached to the metal and electronic configuration. In general terms, moving from a lighter to a heavier element in the group, the magnitude of the metallo-anomeric effect increases. Furthermore, higher oxidation states favor axial/synclinal conformers. | 0 | Theoretical and Fundamental Chemistry |
Any form of TST, such as microcanonical variational TST, canonical variational TST, and improved canonical variational TST, in which the transition state is not necessarily located at the saddle point, is referred to as generalized transition state theory. | 0 | Theoretical and Fundamental Chemistry |
The diphosphorus allotrope () can normally be obtained only under extreme conditions (for example, from at 1100 kelvin). In 2006, the diatomic molecule was generated in homogeneous solution under normal conditions with the use of transition metal complexes (for example, tungsten and niobium).
Diphosphorus is the gaseous form of phosphorus, and the thermodynamically stable form between 1200 °C and 2000 °C. The dissociation of tetraphosphorus () begins at lower temperature: the percentage of at 800 °C is ≈ 1%. At temperatures above about 2000 °C, the diphosphorus molecule begins to dissociate into atomic phosphorus. | 0 | Theoretical and Fundamental Chemistry |
In nuclear chemistry, the actinide concept (also known as actinide hypothesis) proposed that the actinides form a second inner transition series homologous to the lanthanides. Its origins stem from observation of lanthanide-like properties in transuranic elements in contrast to the distinct complex chemistry of previously known actinides. Glenn Theodore Seaborg, one of the researchers who synthesized transuranic elements, proposed the actinide concept in 1944 as an explanation for observed deviations and a hypothesis to guide future experiments. It was accepted shortly thereafter, resulting in the placement of a new actinide series comprising elements 89 (actinium) to 103 (lawrencium) below the lanthanides in Dmitri Mendeleev's periodic table of the elements. | 0 | Theoretical and Fundamental Chemistry |
Hydrolysis of the terminal phosphoanhydridic bond is a highly exergonic process. The amount of released energy depends on the conditions in a particular cell. Specifically, the energy released is dependent on concentrations of ATP, ADP and P. As the concentrations of these molecules deviate from values at equilibrium, the value of Gibbs free energy change (ΔG) will be increasingly different. In standard conditions (ATP, ADP and P concentrations are equal to 1M, water concentration is equal to 55 M) the value of ΔG is between -28 and -34 kJ/mol.
The range of the ΔG value exists because this reaction is dependent on the concentration of Mg cations, which stabilize the ATP molecule. The cellular environment also contributes to differences in the ΔG value since ATP hydrolysis is dependent not only on the studied cell, but also on the surrounding tissue and even the compartment within the cell. Variability in the ΔG values is therefore to be expected.
The relationship between the standard Gibbs free energy change ΔG and chemical equilibrium is revealing. This relationship is defined by the equation ΔG = -RT ln(K), where K is the equilibrium constant, which is equal to the reaction quotient Q in equilibrium. The standard value of ΔG for this reaction is, as mentioned, between -28 and -34 kJ/mol; however, experimentally determined concentrations of the involved molecules reveal that the reaction is not at equilibrium. Given this fact, a comparison between the equilibrium constant, K, and the reaction quotient, Q, provides insight. K takes into consideration reactions taking place in standard conditions, but in the cellular environment the concentrations of the involved molecules (namely, ATP, ADP, and P) are far from the standard 1 M. In fact, the concentrations are more appropriately measured in mM, which is smaller than M by three orders of magnitude. Using these nonstandard concentrations, the calculated value of Q is much less than one. By relating Q to ΔG using the equation ΔG = ΔG + RT ln(Q), where ΔG is the standard change in Gibbs free energy for the hydrolysis of ATP, it is found that the magnitude of ΔG is much greater than the standard value. The nonstandard conditions of the cell actually result in a more favorable reaction.
In one particular study, to determine ΔG in vivo in humans, the concentration of ATP, ADP, and P was measured using nuclear magnetic resonance. In human muscle cells at rest, the concentration of ATP was found to be around 4 mM and the concentration of ADP was around 9 μM. Inputing these values into the above equations yields ΔG = -64 kJ/mol. After ischemia, when the muscle is recovering from exercise, the concentration of ATP is as low as 1 mM and the concentration of ADP is around 7 μM. Therefore, the absolute ΔG would be as high as -69 kJ/mol.
By comparing the standard value of ΔG and the experimental value of ΔG, one can see that the energy released from the hydrolysis of ATP, as measured in humans, is almost twice as much as the energy produced under standard conditions. | 1 | Applied and Interdisciplinary Chemistry |
Methanesulfonyl chloride is mainly used to give methanesulfonates by its reaction with alcohols in the presence of a non-nucleophilic base. In contrast to the formation of toluenesulfonates from alcohols and p-toluenesulfonyl chloride in the presence of pyridine, the formation of methanesulfonates is believed to proceed via a mechanism wherein methanesulfonyl chloride first undergoes an E1cb elimination to generate the highly reactive parent sulfene (), followed by attack by the alcohol and rapid proton transfer to generate the observed product. This mechanistic proposal is supported by isotope labeling experiments and the trapping of the transient sulfene as cycloadducts.
Methanesulfonates are used as intermediates in substitution reactions, elimination reactions, reductions, and rearrangement reactions. When treated with a Lewis acid, oxime methanesulfonates undergo facile Beckmann rearrangement.
Methanesulfonates are occasionally used as a protecting group for alcohols. They are stable to acidic conditions and is cleaved back to the alcohol using sodium amalgam. | 0 | Theoretical and Fundamental Chemistry |
Leon Francis Phillips (14 July 1935 – 24 September 2023) was a New Zealand physical chemist who specialised in the gas-liquid interface and atmospheric chemistry. | 0 | Theoretical and Fundamental Chemistry |
RdRp differs from DNA dependent RNA polymerase as it works to catalyze the synthesis of an RNA strand complementary to a given RNA template, rather than using a DNA template. The RNA replication process is a four-step mechanism, as described.
# Nucleoside triphosphate (NTP) binding – initially, the RdRp presents with a vacant active site in which an NTP binds, complementary to the corresponding nucleotide on the template strand. Correct NTP binding causes the RdRp to undergo a conformational change.
# Active site closure – the conformational change, initiated by the correct NTP binding, results in the restriction of active site access and produces a catalytically competent state.
# Phosphodiester bond formation – two Mg ions are present in the catalytically active state and arrange themselves in such a way around the newly synthesized RNA chain that the substrate NTP is able to undergo a phosphatidyl transfer and form a phosphodiester bond with the newly synthesized chain. Without the use of these Mg ions, the active site is no longer catalytically stable and the RdRp complex changes to an open conformation.
# Translocation – once the active site is open, the RNA template strand is able to move by one position through the RdRp protein complex and continue chain elongation by binding a new NTP, unless otherwise specified by the template.
RNA synthesis can be performed by means of a primer-independent (de novo) or a primer-dependent mechanism that utilizes a viral protein genome-linked (VPg) primer. The de novo initiation consists in the addition of a nucleoside triphosphate (NTP) to the 3'-OH of the first initiating NTP. During the following so-called elongation phase, this nucleotidyl transfer reaction is repeated with subsequent NTPs to generate the complementary RNA product. Termination of the nascent RNA chain produced by RdRp is not completely known, however, it has been shown that RdRp termination is sequence-independent.
One major drawback of RNA-dependent RNA polymerase replication is the immense error rate during transcription. RdRps are known to have a lack of fidelity on the order of 10 nucleotides, which is thought to be a direct result of its insufficient proofreading abilities. This high rate of variation is favored in viral genomes as it allows for the pathogen to overcome defenses developed by hosts trying to avoid infection allowing for evolutionary growth. | 1 | Applied and Interdisciplinary Chemistry |
The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for iodine in 2000. For people age 14 and up, the iodine RDA is 150 μg/day; the RDA for pregnant women is 220 μg/day and the RDA during lactation is 290 μg/day. For children aged 1–8 years, the RDA is 90 μg/day; for children aged 8–13 years, it is 130 μg/day. As a safety consideration, the IOM sets tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. The UL for iodine for adults is 1,100 μg/day. This UL was assessed by analyzing the effect of supplementation on thyroid-stimulating hormone. Collectively, the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).
The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR; AI and UL are defined the same as in the United States. For women and men ages 18 and older, the PRI for iodine is set at 150 μg/day; the PRI during pregnancy or lactation is 200 μg/day. For children aged 1–17 years, the PRI increases with age from 90 to 130 μg/day. These PRIs are comparable to the U.S. RDAs with the exception of that for lactation. The EFSA reviewed the same safety question and set its adult UL at 600 μg/day, which is a bit more than half the U.S. value. Notably, Japan reduced its adult iodine UL from 3,000 to 2,200 µg/day in 2010, but then increased it back to 3,000 µg/day in 2015.
As of 2000, the median observed intake of iodine from food in the United States was 240 to 300 μg/day for men and 190 to 210 μg/day for women. In Japan, consumption is much higher due to the frequent consumption of seaweed or kombu kelp. The average daily intake in Japan ranges from 1,000 to 3,000 μg/day; previous estimates suggested an average intake as high as 13,000 μg/day. | 1 | Applied and Interdisciplinary Chemistry |
Methyl chloroformate forms highly flammable vapour-air mixtures. The compound has a flash point of 10 °C.
Methyl chloroformate, if heated, releases phosgene. It produces hydrogen chloride upon contact with water. It will cause skin damage if in contact with skin. | 0 | Theoretical and Fundamental Chemistry |
The origins of vinegars obtained by bacterial or chemical oxidation of ethanol resulting from the fermentation of various sugars can be identified by the H-SNIF-NMR. It allows to control the quality of vinegar and to determine if it comes from sugar cane, wine, malt, cider, and alcohol or from a chemical synthesis. | 0 | Theoretical and Fundamental Chemistry |
For a cell reaction characterized by the chemical equation:
at constant temperature and pressure, the thermodynamic voltage (minimum voltage required to drive the reaction) is given by the Nernst equation:
where is the Gibbs energy and F is the Faraday constant. The standard thermodynamic voltage (i.e. at standard temperature and pressure) is given by:
and the Nernst equation can be used to calculate the standard potential at other conditions.
The cell reaction is generally endothermic: i.e. it will extract heat from its environment. The Gibbs energy calculation generally assumes an infinite thermal reservoir to maintain a constant temperature, but in a practical case, the reaction will cool the electrode interface and slow the reaction occurring there.
If the cell voltage is increased above the thermodynamic voltage, the product of that voltage and the current will generate heat, and if the voltage is such that the heat generated matches the heat required by the reaction to maintain a constant temperature, that voltage is called the "thermoneutral voltage". The rate of delivery of heat is equal to where T is the temperature (the standard temperature, in this case) and dS/dt is the rate of entropy production in the cell. At the thermoneutral voltage, this rate will be zero, which indicates that the thermoneutral voltage may be calculated from the enthalpy. | 0 | Theoretical and Fundamental Chemistry |
The IIR produces an electronic monthly newsletter that features news and updates on the refrigeration sector: regulation, events, economic data, monitoring, technological progress, etc.
It provides a detailed overview of the general developments within the sector worldwide and as acts a regular information tool for readers. | 0 | Theoretical and Fundamental Chemistry |
Within the European Union, microbial food cultures are regarded as food ingredients and are regulated by Regulation 178/2002, commonly referred to as the General Food Law.
Since 2007, the European Food Safety Authority (EFSA) has been maintaining a list of microorganisms having qualified presumption of safety (QPS). The QPS list covers only a limited number of microorganisms, which have been referred to EFSA for safety assessment. It has been conceived as an internal evaluation tool for microorganisms used in the food production chain (e.g. feed cultures, cell factories producing enzymes or additives, plant protection) that need an evaluation by EFSA scientific panels before being marketed in the EU. Microbial food cultures with a long history of safe use are, however, considered to be traditional food ingredients and are legally permitted for use in human food without EFSA evaluation. | 1 | Applied and Interdisciplinary Chemistry |
In one variation the mechanism is thought to be as follows:
The dichromate oxidizes the mercury, forming a layer of mercury oxide. In the process the dichromate is reduced to the chromium(III) ion. The oxidized layer on the mercury reduces the surface tension of the blob and the blob flattens out coming in contact with the iron nail. Then the mercury sulfate oxidizes the iron to the iron(II) ion, and in the process is reduced back to metallic mercury. Once there is no oxide coating left on the mercury blob, the surface tension increases and the blob rounds up and loses contact with the nail, ready to start the process over again.
The net reaction is that the dichromate oxidizes the iron. This favorable reaction drives the mercury oxidations/reductions and the oscillations in shape. When the dichromate is fully reduced, the reaction stops.
There may be other mechanisms involved, however. Lin et al. appear to report that the oscillations occur without the presence of the oxidizing agent, though the mercury does not appear to get an oxidizing layer on it and the oscillations are much weaker.
An electrical double layer forms between the surface of the mercury droplet and the electrolyte solution. At rest this layer is uniform. When the iron tip is introduced, a redox reaction starts in which iron is oxidized to the ferric ion and the oxidizing reagent is spent (e.g. when hydrogen peroxide together with hydronium ions is reduced to water). Because the oxidation only takes place in the vicinity of the tip, and the reduction process covers the whole droplet surface, the surface tension is no longer homogeneous; this results in the observed oscillations.
Although this reaction is mediated by changes in surface tension, it is very similar in mechanism to other chemical oscillators such as the Belousov–Zhabotinsky reaction, which has several intermediate redox reactions driven by the oxidation of malate by bromine. | 0 | Theoretical and Fundamental Chemistry |
Random chimeragenesis on transient templates (RACHITT) is a method to perform molecular mutagenesis at a high recombination rate. For example, RACHITT can be used to generate increased rate and extent of biodesulfurization of diesel by modification of dibenzothiophene mono-oxygenase. DNA shuffling is a similar but less powerful method used in directed evolution experiments. | 1 | Applied and Interdisciplinary Chemistry |
Peroxisomes (microbodies) were first described by a Swedish doctoral student, J. Rhodin in 1954. They were identified as organelles by the Belgian cytologist Christian de Duve in 1967. De Duve and co-workers discovered that peroxisomes contain several oxidases involved in the production of hydrogen peroxide (HO) as well as catalase involved in the decomposition of HO to oxygen and water. Due to their role in peroxide metabolism, De Duve named them “peroxisomes”, replacing the formerly used morphological term “microbodies”. Later, it was described that firefly luciferase is targeted to peroxisomes in mammalian cells, allowing the discovery of the import targeting signal for peroxisomes, and triggering many advances in the peroxisome biogenesis field. | 1 | Applied and Interdisciplinary Chemistry |
As a reagent in organic chemistry, DBU is used as a ligand and base. As a base, protonation occurs at the imine nitrogen. Lewis acids also attach to the same nitrogen.
These properties recommend DBU for use as a catalyst, for example as a curing agent for epoxy resins and polyurethane.
It is used in the separation of fullerenes in conjunction with trimethylbenzene. It reacts with C and higher fullerenes, but not with C.
It is useful for dehydrohalogenations. | 0 | Theoretical and Fundamental Chemistry |
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