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Supercritical water gasification is a process of exploiting the beneficial effect of supercritical water to convert aqueous biomass streams into clean water and gases like H, CH, CO, CO etc. | 7 | Physical Chemistry |
In 1945, Corbett was appointed as a lecturer in chemistry at Otago. After returning from Cambridge in 1950, Corbett rose to become a professor in 1966, and the Mellor Professor of Chemistry in 1972. When he retired in 1983, he was accorded the title of professor emeritus.
Corbetts research at Otago was primarily concerned with the study and structural elucidation of essential oils isolated from New Zealand native plants by steam distillation. Under his supervision in 1970, doctoral student Denis Lauren first isolated the diterpene compound from the rimu tree (Dacrydium cupressinum') that came to be known as laurenene. Corbett also investigated extractives from barks, leaves, heartwoods and lichens, and determined the structures of many new, and derivatives of known, di-, tri- and sesquiterpenoids. He also studied the synthesis and rearrangement of some of the compounds that his team isolated. | 0 | Organic Chemistry |
Harmful algal blooms in freshwater lakes and rivers, or at estuaries, where rivers flow into the ocean, are caused by cyanobacteria, which are commonly referred to as "blue-green algae", but are in fact prokaryotic bacteria, as opposed to algae which are eukaryotes. Some cyanobacteria, including the widespread genus Microsystis, can produce hazardous cyanotoxins such as microcystins, which are hepatotoxins that harm the liver of mammals. Other types of cyanobacteria can also produce hepatotoxins, as well as neurotoxins, cytotoxins, and endotoxins. Water purification plants may be unable to remove these toxins, leading to increasingly common localised advisories against drinking tap water, as happened in Toledo, Ohio in August 2014.
In August 2021, there were 47 lakes confirmed to have algal blooms in New York State alone. In September 2021, Spokane Countys Environmental Programs issued a HAB alert for Newman Lake following tests showing potentially harmful toxicity levels for cyanobacteria, while in the same month record-high levels of microcystins were reported leading to an extended Do Not Drink advisory for 280 households at Clear Lake, Californias second-largest freshwater lake. Water conditions in Florida, meanwhile, continue to deteriorate under increasing nutrient inflows, causing severe HAB events in both freshwater and marine areas.
HABs also cause harm by blocking the sunlight used by plants and algae to photosynthesise, or by depleting the dissolved oxygen needed by fish and other aquatic animals, which can lead to fish die-offs. When such oxygen-depleted water covers a large area for an extended period of time, it can become hypoxic or even anoxic; these areas are commonly called dead zones. These dead zones can be the result of numerous different factors ranging from natural phenomenon to deliberate human intervention, and are not just limited to large bodies of fresh water as found in the great lakes, but are also prone to bodies of salt water as well. | 3 | Analytical Chemistry |
A nickel-catalyzed 1,n arylboration was developed in 2019 by Yin and coworkers and remains the only example of a chain-walking arylboration. This was accomplished via a nitrogen-based ligand and a three-component coupling. The general scheme plus proposed mechanism is shown. | 0 | Organic Chemistry |
Sialidases, also called neuraminidases, catalyze the hydrolysis of terminal sialic acid residues from the newly formed virions and from the host cell receptors. Sialidase activities include assistance in the mobility of virus particles through the respiratory tract mucus and in the elution of virion progeny from the infected cell. | 0 | Organic Chemistry |
For example, consider the following two rounds of shotgun reads:
In this extremely simplified example, none of the reads cover the full length of the original sequence, but the four reads can be assembled into the original sequence using the overlap of their ends to align and order them. In reality, this process uses enormous amounts of information that are rife with ambiguities and sequencing errors. Assembly of complex genomes is additionally complicated by the great abundance of repetitive sequences, meaning similar short reads could come from completely different parts of the sequence.
Many overlapping reads for each segment of the original DNA are necessary to overcome these difficulties and accurately assemble the sequence. For example, to complete the Human Genome Project, most of the human genome was sequenced at 12X or greater coverage; that is, each base in the final sequence was present on average in 12 different reads. Even so, current methods have failed to isolate or assemble reliable sequence for approximately 1% of the (euchromatic) human genome, as of 2004. | 1 | Biochemistry |
Cobalt oleate is an organometallic compound with the formula Co(CHO). When cobalt oleate is added to non-polar solvents, the viscosity rapidly increases, and then continues increasing over time. This unusual viscosity effect is caused by the formation of a weak coordination complex with the solvent molecules. | 0 | Organic Chemistry |
After Planck identified that Wien's law can be extended to all frequencies, even very low ones, by interpolating with the classical equipartition law for radiation, physicists wanted to understand the quantum behavior of other systems.
The Planck radiation law quantized the motion of the field oscillators in units of energy proportional to the frequency:
The quantum can only depend on the energy/frequency by adiabatic invariance, and since the energy must be additive when putting boxes end-to-end, the levels must be equally spaced.
Einstein, followed by Debye, extended the domain of quantum mechanics by considering the sound modes in a solid as quantized oscillators. This model explained why the specific heat of solids approached zero at low temperatures, instead of staying fixed at as predicted by classical equipartition.
At the Solvay conference, the question of quantizing other motions was raised, and Lorentz pointed out a problem, known as Rayleigh–Lorentz pendulum. If you consider a quantum pendulum whose string is shortened very slowly, the quantum number of the pendulum cannot change because at no point is there a high enough frequency to cause a transition between the states. But the frequency of the pendulum changes when the string is shorter, so the quantum states change energy.
Einstein responded that for slow pulling, the frequency and energy of the pendulum both change, but the ratio stays fixed. This is analogous to Wien's observation that under slow motion of the wall the energy to frequency ratio of reflected waves is constant. The conclusion was that the quantities to quantize must be adiabatic invariants.
This line of argument was extended by Sommerfeld into a general theory: the quantum number of an arbitrary mechanical system is given by the adiabatic action variable. Since the action variable in the harmonic oscillator is an integer, the general condition is
This condition was the foundation of the old quantum theory, which was able to predict the qualitative behavior of atomic systems. The theory is inexact for small quantum numbers, since it mixes classical and quantum concepts. But it was a useful half-way step to the new quantum theory. | 7 | Physical Chemistry |
The non-pathogenic and gram-negative bacteria, Pseudomonas fluorescens, is used for high level production of recombinant proteins; commonly for the development bio-therapeutics and vaccines. P. fluorescens is a metabolically versatile organism, allowing for high throughput screening and rapid development of complex proteins. P. fluorescens is most well known for its ability to rapid and successfully produce high titers of active, soluble protein. | 1 | Biochemistry |
The Curiosity rover from the Mars Science Laboratory mission, with its Curiosity rover is currently assessing the potential past and present habitability of the Martian environment and is attempting to detect biosignatures on the surface of Mars. Considering the MSL instrument payload package, the following classes of biosignatures are within the MSL detection window: organism morphologies (cells, body fossils, casts), biofabrics (including microbial mats), diagnostic organic molecules, isotopic signatures, evidence of biomineralization and bioalteration, spatial patterns in chemistry, and biogenic gases. The Curiosity rover targets outcrops to maximize the probability of detecting fossilized organic matter preserved in sedimentary deposits. | 2 | Environmental Chemistry |
Pradeep Mathur, born on 17 August 1955 in Teheran to Damyanti and Amrit Dayal. Mathur and his older brother, renowned physicist at TIFR, Deepak Mathur (married to Helen Mathur) were both brought up and educated in London whilst their father Amrit Dayal worked as a senior diplomatic official at the Indian High Commission in London and Accra. Mathur continued to live in England till he moved to Yale. He gained an honours degree at the University of North London in 1976 and secured a PhD from Keele University in 1981 before moving onto Yale University as a post-doctoral researcher. Mathur chose to move to India and joined Indian Institute of Technology, Mumbai in 1984 as a member of the faculty of chemistry where he held several positions before reaching the position of a professor and the head of the National Single Crystal X-ray Diffraction Facility. When the Indian Institute of Technology, Indore was established in 2009, Mathur was appointed as its founder director. At the end of his first five-year term, his contract was extended for a second term and he continues to hold the position, simultaneously serving as a professor of the department of chemistry. He has been a visiting professor at University of Cambridge, University of Freiburg and University of Karlsruhe and has been associated with a number of scientific journals, viz. Organometallics, Journal of Organometallic Chemistry and Journal of Cluster Science as a member of their editorial boards.
Mathur is married to Vinita and the couple have two daughters, Nehika and Saloni. | 0 | Organic Chemistry |
Nitrile ylides can be obtained by the addition of electrophilic carbenes to nitriles, by the photochemical ring opening of azirines and by dehydrochlorination of imidoyl chlorides. The latter is the most reliable method. | 0 | Organic Chemistry |
In 1960 Almin was bought by Imperial Aluminium Company (Impalco), a company formed between the Aluminium Company of America (Alcoa) and Imperial Chemical Industries (ICI) which incorporated the whole of ICIs aluminium facilities. Impalcos primary interest in buying Almin was to acquire the facilities of International Alloys, a member of the Almin group. Thus Fulmer was acquired incidentally and it did not fit easily into the Impalco group. Since Impalco had huge research facilities in-house, it had no need of Fulmers services. Impalcos rival companies were also reluctant to place large contracts with Fulmer under this ownership. | 8 | Metallurgy |
Diagnostic qualitative PCR is applied to rapidly detect nucleic acids that are diagnostic of, for example, infectious diseases, cancer and genetic abnormalities. The introduction of qualitative PCR assays to the clinical microbiology laboratory has significantly improved the diagnosis of infectious diseases, and is deployed as a tool to detect newly emerging diseases, such as new strains of flu and coronavirus, in diagnostic tests. | 1 | Biochemistry |
Xenin is a 25-amino acid polypeptide. The amino acid sequence of xenin is identical to the N-terminal end of cytoplasmic coatomer subunit alpha, from which xenin can be cleaved by aspartic proteases. Xenin is structurally related to the amphibian peptide xenopsin and to the neuropeptide neurotensin.
Surpassed by insulin, xenin reflects the second highest degree of homology traced along the evolutionary tree among the regulatory peptides, indicating its prominent structural conservatism. | 1 | Biochemistry |
In the final stages of the synthesis (Scheme 5), the hydroxyl group in 46 was deprotected to give alcohol 47. Reaction of the lithium alkoxide of 47 with the Ojima lactam 48 adds the tail in 49. Deprotection of the triethylsilyl ether with hydrofluoric acid and removal of the BOM group under reductive conditions gave (−)-Taxol 51 in 46 steps. | 0 | Organic Chemistry |
* 1983: Humboldt Prize.
* 1997: The Advisory Committee on Antarctic Names (US-ACAN) named Stuiver Valley in Antarctica after Minze Stuiver for his work on radiocarbon dating Antarctic samples.
* 1993: The 13th Pomerance Award of the Archaeological Institute of America for Scientific Contributions to Archaeology went to Minze Stuiver along with Michael G. L. Baillie, Bernd Becker, Gordon W. Pearson, Jonathan R. Pilcher, and Hans Suess.
* 2000: Received The American Quaternary Association Distinguished Career Award.
* 2001: Thomson Reuters most cited paper in geosciences for the 1990s.
* 2005: Awarded the Geological Society of America's Penrose Gold Medal for outstanding original contributions or achievements that mark a major advance in the science of geology.
* 2009: Awarded an honorary doctorate at Queen's University Belfast. | 9 | Geochemistry |
The period immediately after the 10th century marked the widespread application of several innovations in the field of mining and ore treatment: a shift to large-scale and better quality production. Medieval miners and metallurgists had to find solutions for the practical problems that limited former metal production, in order to meet the market demands for metals. This increased demand for metal was due to the population growth from the 11th to the 13th centuries. This growth had an impact on agriculture, trade, and building construction, including Gothic churches.
The main problem was the inefficient means for draining water out of shafts and tunnels in underground mining. This resulted in the flooding of mines which limited the extraction of ore to shallow depths close to the surface. The secondary problem was the separation of the metal-bearing minerals from the worthless material that surrounds it, or is closely mixed with it. There was, additionally, the difficulty of transporting the ore, which resulted in subsequently high costs.
The economic value of mining led to investment in the development of solutions to these problems, which had a distinctly positive impact on medieval metal output. This included innovations such as water power using waterwheels for powering draining engines, bellows, hammers, and the introduction of advanced types of furnaces.
These innovations were not adopted all at once or applied to all mines and smelting sites. Throughout the medieval period, these technical innovations, and traditional techniques coexisted. Their application depended on the time period and geographical region. Water power in medieval mining and metallurgy was introduced well before the 11th century, but it was only in the 11th century that it was widely applied. The introduction of the blast furnace, mostly for iron smelting, in all the established centers of metallurgy contributed to the quantitative and qualitative improvement of the metal output, making metallic iron available at a lower price.
In addition, cupellation, developed in the 8th century, was more often used for the refinement of lead-silver ores, to separate the silver from the lead (Bayley 2008). Parallel production with more than one technical method, and different treatment of ores would occur wherever multiple ores were present at one site. (Rehren et al. 1999).
Underground work in shafts, although limited in depth, was accomplished either by fire-setting for massive ore bodies or with iron tools for smaller scale extraction of limited veins. The sorting of base and precious metal ores was completed underground and they were transferred separately (Martinon-Torres & Rehren in press, b).
Permanent mining in Sweden proper begun in the High Middle Ages and did not spread to Finland until 1530 when the first iron mine began operations there. | 8 | Metallurgy |
Through studies using mammalian model organisms, there are two main hypotheses for the location of oxygen sensing in chemoreceptor cells: the membrane hypothesis and the mitochondrial hypothesis. The membrane hypothesis was proposed for the carotid body in mice, and it predicts that oxygen sensing is an ion balance initiated process. The mitochondrial hypothesis was also proposed for the carotid body of mice, but it relies on the levels of oxidative phosphorylation and/or reactive oxygen species (ROS) production as a cue for hypoxia. Specifically, the oxygen sensitive K currents are inhibited by HO and NADPH oxidase activation. There is evidence for both of these hypotheses depending on the species used for the study. For the neuroepithelial cells in the zebrafish gills, there is strong evidence supporting the "membrane hypothesis" due to their capacity to respond to hypoxia after removal of the contents of the cell. However, there is no evidence against multiple sites for oxygen sensing in organisms. | 9 | Geochemistry |
Histamine N-methyltransferase (HNMT) is a protein encoded by the HNMT gene in humans. It belongs to the methyltransferases superfamily of enzymes and plays a crucial role in the inactivation of histamine, a biomolecule that is involved in various physiological processes. Methyltransferases are present in every life form including archaeans, with 230 families of methyltransferases found across species.
Specifically, HNMT transfers a methyl (-CH) group from S-adenosyl--methionine (SAM-e) to histamine, forming an inactive metabolite called N-methylhistamine, in a chemical reaction called N-methylation. In mammals, HNMT operates alongside diamine oxidase (DAO) as the only two enzymes responsible for histamine metabolism; however, what sets HNMT apart is its unique presence within the central nervous system (CNS), where it governs histaminergic neurotransmission, that is a process where histamine acts as a messenger molecule between the neurons—nerve cells—in the brain. By degrading and regulating levels of histamine specifically within the CNS, HNMT ensures the proper functioning of neural pathways related to arousal, appetite regulation, sleep-wake cycles, and other essential brain functions.
Research on knockout mice—that are genetically modified mice lacking the Hnmt gene—has revealed that the absence of this enzyme leads to increased brain histamine concentrations and behavioral changes such as heightened aggression and disrupted sleep patterns. These findings highlight the critical role played by HNMT in maintaining normal brain function through precise regulation of neuronal signaling involving histamine. Genetic variants affecting HNMT activity have also been implicated in various neurological disorders like Parkinson's disease and attention deficit disorder. | 1 | Biochemistry |
Very analogous to ketones and aldehydes, primary imines are susceptible to attack by carbanion equivalents. The method allow for the synthesis of secondary amines:
:RC=NR + R"Li → RR"CN(Li)R
:RR"CN(Li)R + HO → RR"CNHR + LiOH | 0 | Organic Chemistry |
Thermometric titrimetry offers a rapid, highly precise method for the determination of aluminium in solution. A solution of aluminium is conditioned with acetate buffer and an excess of sodium and potassium ions. Titration with sodium or potassium fluoride yields the exothermic precipitation of an insoluble alumino-fluoride salt.
: Al + Na + 2K + 6F ↔ KNaAlF↓
Because 6 mole of fluoride react with one mole of aluminium, the titration is particularly precise, and a coefficient of variance (CV) of 0.03 has been achieved in the analysis of alum.
When aluminium ion (say as aluminium nitrate) is employed as the titrant, fluoride can be determined using the same chemistry. This titration is useful in the determination of fluoride in complex acid mixtures used as etchants in the semi-conductor industry. | 3 | Analytical Chemistry |
In the Calvin cycle, DHAP is one of the products of the sixfold reduction of 1,3-bisphosphoglycerate by NADPH. It is also used in the synthesis of sedoheptulose 1,7-bisphosphate and fructose 1,6-bisphosphate, both of which are used to reform ribulose 5-phosphate, the key carbohydrate of the Calvin cycle.
DHAP is also the product of the dehydrogenation of -glycerol-3-phosphate, which is part of the entry of glycerol (sourced from triglycerides) into the glycolytic pathway. Conversely, reduction of glycolysis-derived DHAP to -glycerol-3-phosphate provides adipose cells with the activated glycerol backbone they require to synthesize new triglycerides. Both reactions are catalyzed by the enzyme glycerol 3-phosphate dehydrogenase with NAD/NADH as cofactor.
DHAP also has a role in the ether-lipid biosynthesis process in the protozoan parasite Leishmania mexicana.
DHAP is a precursor to 2-oxopropanal. This conversion is the basis of a potential biotechnological route to the commodity chemical 1,2-propanediol. | 5 | Photochemistry |
An interwoven grid complex has been used to template the synthesis of a doubly-twisted [2]catenane (otherwise known as a Solomon Link). The unique arrangement of interwoven ligands around the planar array of iron, zinc, or cobalt ions generated the crossing points required to covalently trap the interlocked structure using ring-closing metathesis. Building on this discovery, 2 × 2 interwoven grids were used to template the synthesis of more topologically complex molecules: a six-crossing doubly-interlocked [2]catenane and a granny knot. In 2021, the first report of a 3 × 3 interwoven grid was published. It was used to template the synthesis of a molecular Endless Knot. | 6 | Supramolecular Chemistry |
Acetic anhydride is a major industrial chemical widely used for preparing acetate esters, e.g. cellulose acetate. Maleic anhydride is the precursor to various resins by copolymerization with styrene. Maleic anhydride is a dienophile in the Diels-Alder reaction.
Dianhydrides, molecules containing two acid anhydride functions, are used to synthesize polyimides and sometimes polyesters and polyamides. Examples of dianhydrides: pyromellitic dianhydride (PMDA), 3,3’, 4,4’ - oxydiphtalic dianhydride (ODPA), 3,3’, 4,4’-benzophenone tetracarboxylic dianhydride (BTDA), 4,4’-diphtalic (hexafluoroisopropylidene) anhydride (6FDA), benzoquinonetetracarboxylic dianhydride, ethylenetetracarboxylic dianhydride. Polyanhydrides are a class of polymers characterized by anhydride bonds that connect repeat units of the polymer backbone chain. | 0 | Organic Chemistry |
The ocean biological pump is the oceans biologically driven sequestration of carbon from the atmosphere and land runoff to the deep ocean interior and seafloor sediments. The biological pump is not so much the result of a single process, but rather the sum of a number of processes each of which can influence biological pumping. The pump transfers about 11 billion tonnes of carbon every year into the oceans interior. An ocean without the biological pump would result in atmospheric CO levels about 400 ppm higher than the present day.
Most carbon incorporated in organic and inorganic biological matter is formed at the sea surface where it can then start sinking to the ocean floor. The deep ocean gets most of its nutrients from the higher water column when they sink down in the form of marine snow. This is made up of dead or dying animals and microbes, fecal matter, sand and other inorganic material.
The biological pump is responsible for transforming dissolved inorganic carbon (DIC) into organic biomass and pumping it in particulate or dissolved form into the deep ocean. Inorganic nutrients and carbon dioxide are fixed during photosynthesis by phytoplankton, which both release dissolved organic matter (DOM) and are consumed by herbivorous zooplankton. Larger zooplankton - such as copepods, egest fecal pellets - which can be reingested, and sink or collect with other organic detritus into larger, more-rapidly-sinking aggregates. DOM is partially consumed by bacteria and respired; the remaining refractory DOM is advected and mixed into the deep sea. DOM and aggregates exported into the deep water are consumed and respired, thus returning organic carbon into the enormous deep ocean reservoir of DIC.
A single phytoplankton cell has a sinking rate around one metre per day. Given that the average depth of the ocean is about four kilometres, it can take over ten years for these cells to reach the ocean floor. However, through processes such as coagulation and expulsion in predator fecal pellets, these cells form aggregates. These aggregates have sinking rates orders of magnitude greater than individual cells and complete their journey to the deep in a matter of days.
About 1% of the particles leaving the surface ocean reach the seabed and are consumed, respired, or buried in the sediments. The net effect of these processes is to remove carbon in organic form from the surface and return it to DIC at greater depths, maintaining a surface-to-deep ocean gradient of DIC. Thermohaline circulation returns deep-ocean DIC to the atmosphere on millennial timescales. The carbon buried in the sediments can be subducted into the earth's mantle and stored for millions of years as part of the slow carbon cycle (see next section). | 5 | Photochemistry |
Black pepper contains the alkaloid guineesine, which is an anandamide reuptake inhibitor. It may therefore increase anandamide's physiological effects.
Low-dose anandamide has an anxiolytic effect, while in one study, high doses injected directly into the cerebral fluid of the brain of mice shows evident cell apoptosis (programmed cell death) in vitro as opposed to necrosis. That being said, another study conducted under similar conditions demonstrated neuronal growth both in vitro and in vivo.
Endocannabinoids may disturb homeostasis in several ways: by enhancing hunger sensations, encouraging increased food intake, and shifting energy balance towards energy storage. A resultant decrease in energy expenditure is observed.
Another study with rats found that reductions in AEA signaling through FAAH overexpression within the basolateral complex of amygdala (BLA) appeared to reliably reduce measurements of anxiety and overall levels of corticosterone, a primary glucocorticoid in animals like birds, rodents, reptiles and amphibians responsible for energy regulation, immune and stress responses. This is similar to the main glucocorticoid cortisol in humans. Reduction of AEA in the BLA has been shown to suppress fear behavior and promote fear extinction. This suggests possible involvement of AEA intervention in the future for the treatment of psychological disorders. However, further work in this area of study is needed, as reduced anandamide signaling is believed at this moment to involve CB1 receptors as well as GABAergic and glutamatergic interactions.
Cortical glutamatergic transmission may be modulated by endocannabinoids during stress and fear habituation. Glutamatergic interaction in the BLA believed to be responsible for changes in anxiety, appears to normalize stress-induced anxiety-like behavior. A study indicated that infusion of the GluK1 receptor agonist ATPA into the BLA enhanced GABAergic neurotransmission, which is currently believed to have a large role in the reduction of anxiety symptoms.
Additionally, the ECs, along with AEA, have been highlighted for their potential involvement in obesity development and harmful effects on lipid and glucose metabolism, which may contribute to insulin resistance and deficiency, both of which are major risk factors for developing type 2 diabetes mellitus. Blockade of CB1 receptors was found significantly to improve lipid resistance and lipid profile in obese subjects, but also has potential to increase fat accumulation through increased food intake, favored lipogenesis and reduced energy expenditure. This may affect downstream systems like the pancreas, liver, adipose tissue, and skeletal muscle, with inflammation and apoptosis in the case of the pancreas. CB1R inhibition with peripherally restricted antagonists and inverse agonists may aid in the treatment of diabetic neuropathy and neuropathy. CB2R agonists may show promise for the treatment of inflammation, which contributes to renal injury.
AEA was associated with nonalcoholic fatty liver disease, nonalcoholic steatohepatitis (NASH), and liver fibrosis. Data suggests AEA as a marker for cardiometabolic disease and NAFLD severity. NAFLD can progress to more severe diseases, like NASH, cirrhosis, and hepatocellular carcinoma.
A Scottish woman with a rare mutation in her FAAH gene that resulted in elevated anandamide levels was reported to be immune to anxiety, unable to experience fear, and insensitive to pain. The frequent burns and cuts she suffered due to her hypoalgesia healed more rapidly than was expected.
Topical Anandamide was found to reduce peripheral neuropathic pain by interaction with peripheral cannabinoid receptors.
The American Academy of Dermatology has named topical Anandamide a promising therapy for cutaneous lupus erythematosus. | 1 | Biochemistry |
If a clone library is constructed in parallel to the T-RFLP analysis then the clones can be used to assess and interpret the T-RFLP profile. In this method the TRF of each clone is determined either directly (i.e. performing T-RFLP analysis on each single clone) or by in silico analysis of that clone’s sequence. By comparing the T-RFLP profile to a clone library it is possible to validate each of the peaks as genuine as well as to assess the relative abundance of each variant in the library. | 1 | Biochemistry |
In organometallic chemistry, a dicarbollide is an anion of the formula [CBH]. Various isomers exist, but most common is 1,2-dicarbollide derived from ortho-carborane. These dianions function as ligands, related to the cyclopentadienyl anion. Substituted dicarbollides are also known such as [CBH(pyridine)] (pyridine bonded to B) and [CRBH] (R groups bonded to carbon). | 7 | Physical Chemistry |
Hexagonal crystals of green rust (carbonate and/or sulfate) have also been obtained as a byproducts of bioreduction of ferric oxyhydroxides by dissimilatory iron-reducing bacteria, such as Shewanella putrefaciens, that couple the reduction of with the oxidation of organic matter. This process has been conjectured to occur in soil solutions and aquifers.
In one experiment, a 160 mM suspension of orange lepidocrocite γ- in a solution containing formate (), incubated for 3 days with a culture of S. putrefaciens, turned dark green due to the conversion of the hydroxide to GR(), in the form of hexagonal platelets with diameter ~7 µm. In this process, the formate was oxidized to bicarbonate which provided the carbonate anions for the formation of the green rust. The live bacteria were shown to be necessary for the formation of the green rust. | 8 | Metallurgy |
ERVs have been found to be associated to disease not only through disease-causing relations, but also through immunity. The frequency of ERVs in long terminal repeats (LTRs) likely correlates to viral adaptations to take advantage of immunity signaling pathways that promote viral transcription and replication. A study done in 2016 investigated the benefit of ancient viral DNA integrated into a host through gene regulation networks induced by interferons, a branch of innate immunity. These cytokines are first to respond to viral infection and are also important in immunosurveillance for malignant cells. ERVs are predicted to act as cis-regulatory elements, but much of the adaptive consequences of this for certain physiological functions is still unknown. There is data that supports the general role of ERVs in the regulation of human interferon response, specifically to interferon-gamma (IFNG). For example, interferon-stimulated genes were found to be greatly enriched with ERVs bound by signal transducer and activator of transcription 1 (STAT1) and/or Interferon regulatory factor (IRF1) in CD14+ macrophages.
HERVs also play various roles shaping the human innate immunity response, with some sequences activating the system and others suppressing it. They may also protect from exogenous retroviral infections: the virus-like transcripts can activate pattern recognition receptors, and the proteins can interfere with active retroviruses. A gag protein from HERV-K(HML2) is shown to mix with HIV Gag, impairing HIV capsid formation as a result. | 1 | Biochemistry |
The invention of antibody phage display revolutionised antibody drug discovery. Initial work was done by laboratories at the MRC Laboratory of Molecular Biology (Greg Winter and John McCafferty), the Scripps Research Institute (Richard Lerner and Carlos F. Barbas) and the German Cancer Research Centre (Frank Breitling and Stefan Dübel). In 1991, The Scripps group reported the first display and selection of human antibodies on phage. This initial study described the rapid isolation of human antibody Fab that bound tetanus toxin and the method was then extended to rapidly clone human anti-HIV-1 antibodies for vaccine design and therapy.
Phage display of antibody libraries has become a powerful method for both studying the immune response as well as a method to rapidly select and evolve human antibodies for therapy. Antibody phage display was later used by Carlos F. Barbas at The Scripps Research Institute to create synthetic human antibody libraries, a principle first patented in 1990 by Breitling and coworkers (Patent CA 2035384), thereby allowing human antibodies to be created in vitro from synthetic diversity elements.
Antibody libraries displaying millions of different antibodies on phage are often used in the pharmaceutical industry to isolate highly specific therapeutic antibody leads, for development into antibody drugs primarily as anti-cancer or anti-inflammatory therapeutics. One of the most successful was adalimumab, discovered by Cambridge Antibody Technology as D2E7 and developed and marketed by Abbott Laboratories. Adalimumab, an antibody to TNF alpha, was the world's first fully human antibody to achieve annual sales exceeding $1bn. | 1 | Biochemistry |
Modern weather satellites produce imagery in a variety of spectra.
In the case of Landsat satellites, several different band designations have been used, with as many as 11 bands (Landsat 8) comprising a multispectral image. Spectral imaging with a higher radiometric resolution
(involving hundreds or thousands of bands), finer spectral resolution (involving smaller bands), or wider spectral coverage may be called hyperspectral or ultraspectral. | 7 | Physical Chemistry |
When using RFLP, the theoretical risk of a coincidental match is 1 in 100 billion (100,000,000,000) although the practical risk is actually 1 in 1,000 because monozygotic twins are 0.2% of the human population. Moreover, the rate of laboratory error is almost certainly higher than that and actual laboratory procedures often do not reflect the theory under which the coincidence probabilities were computed. For example, coincidence probabilities may be calculated based on the probabilities that markers in two samples have bands in precisely the same location, but a laboratory worker may conclude that similar but not precisely-identical band patterns result from identical genetic samples with some imperfection in the agarose gel. However, in that case, the laboratory worker increases the coincidence risk by expanding the criteria for declaring a match. Studies conducted in the 2000s quoted relatively-high error rates, which may be cause for concern. In the early days of genetic fingerprinting, the necessary population data to compute a match probability accurately was sometimes unavailable. Between 1992 and 1996, arbitrary-low ceilings were controversially put on match probabilities used in RFLP analysis, rather than the higher theoretically computed ones. | 1 | Biochemistry |
For dilute systems (e.g. gases), the correlations in the positions of the particles that accounts for are only due to the potential engendered by the reference particle, neglecting indirect effects. In the first approximation, it is thus simply given by the Boltzmann distribution law:
If were zero for all – i.e., if the particles did not exert any influence on each other, then for all and the mean local density would be equal to the mean density : the presence of a particle at O would not influence the particle distribution around it and the gas would be ideal. For distances such that is significant, the mean local density will differ from the mean density , depending on the sign of (higher for negative interaction energy and lower for positive ).
As the density of the gas increases, the low-density limit becomes less and less accurate since a particle situated in experiences not only the interaction with the particle in O but also with the other neighbours, themselves influenced by the reference particle. This mediated interaction increases with the density, since there are more neighbours to interact with: it makes physical sense to write a density expansion of , which resembles the virial equation:
This similarity is not accidental; indeed, substituting () in the relations above for the thermodynamic parameters (Equations , and ) yields the corresponding virial expansions. The auxiliary function is known as the cavity distribution function. It has been shown that for classical fluids at a fixed density and a fixed positive temperature, the effective pair potential that generates a given under equilibrium is unique up to an additive constant, if it exists.
In recent years, some attention has been given to develop pair correlation functions for spatially-discrete data such as lattices or networks. | 7 | Physical Chemistry |
Atomic-scale imaging of graphene, semiconductor surfaces and adsorbed organic molecules were obtained in ultra high-vacuum. Angstrom-resolution images of hydration layers formed on proteins and Young's modulus map of a metal-organic frame work, purple membrane and a lipid bilayer were reported in aqueous solutions. | 6 | Supramolecular Chemistry |
Besides the amount of radiation reaching a plant in the PAR region of the spectrum, it is also important to consider the quality of such radiation. Radiation reaching a plant contains entropy as well as energy, and combining those two concepts the exergy can be determined. This sort of analysis is known as exergy analysis or second law analysis, and the exergy represents a measure of the useful work, i.e., the useful part of radiation which can be transformed into other forms of energy.
The spectral distribution of the exergy of radiation is defined as:
One of the advantages of working with the exergy is that it depends not only on the temperature of the emitter (the Sun), , but also on the temperature of the receiving body (the plant), , i.e., it includes the fact that the plant is emitting radiation. Naming and , the exergy emissive power of radiation in a region is determined as:
Where is a special function called the polylogarithm.
By definition, the exergy obtained by the receiving body is always lower than the energy radiated by the emitting blackbody, as a consequence of the entropy content in radiation.
Thus, as a consequence of the entropy content, not all the radiation reaching the Earth's surface is "useful" to produce work. Therefore, the efficiency of a process involving radiation should be measured against its exergy, not its energy.
Using the expression above, the optimal efficiency or second law efficiency for the conversion of radiation to work in the PAR region (from 400 nm to 700 nm), for a blackbody at = 5800 K and an organism at = 300 K is determined as:
about 8.3% lower than the value considered until now, as a direct consequence of the fact that the organisms which are using solar radiation are also emitting radiation as a consequence of their own temperature. Therefore, the conversion factor of the organism will be different depending on its temperature, and the exergy concept is more suitable than the energy one. | 5 | Photochemistry |
The proton-motive force is derived from the Gibbs free energy. Let N denote the inside of a cell, and P denote the outside. Then
where
* is the Gibbs free energy change per unit amount of cations transferred from P to N;
* is the charge number of the cation ;
* is the electric potential of N relative to P;
* and are the cation concentrations at P and N, respectively;
* is the Faraday constant;
* is the gas constant; and
* is the temperature.
The molar Gibbs free energy change is frequently interpreted as a molar electrochemical ion potential .
For an electrochemical proton gradient and as a consequence:
where
Mitchell defined the proton-motive force (PMF) as
For example, implies . At this equation takes the form:
Note that for spontaneous proton import from the P side (relatively more positive and acidic) to the N side (relatively more negative and alkaline), is negative (similar to ) whereas PMF is positive (similar to redox cell potential ).
It is worth noting that, as with any transmembrane transport process, the PMF is directional. The sign of the transmembrane electric potential difference is chosen to represent the change in potential energy per unit charge flowing into the cell as above. Furthermore, due to redox-driven proton pumping by coupling sites, the proton gradient is always inside-alkaline. For both of these reasons, protons flow in spontaneously, from the P side to the N side; the available free energy is used to synthesize ATP (see below). For this reason, PMF is defined for proton import, which is spontaneous. PMF for proton export, i.e., proton pumping as catalyzed by the coupling sites, is simply the negative of PMF(import).
The spontaneity of proton import (from the P to the N side) is universal in all bioenergetic membranes. This fact was not recognized before the 1990s, because the chloroplast thylakoid lumen was interpreted as an interior phase, but in fact it is topologically equivalent to the exterior of the chloroplast. Azzone et al. stressed that the inside phase (N side of the membrane) is the bacterial cytoplasm, mitochondrial matrix, or chloroplast stroma; the outside (P) side is the bacterial periplasmic space, mitochondrial intermembrane space, or chloroplast lumen. Furthermore, 3D tomography of the mitochondrial inner membrane shows its extensive invaginations to be stacked, similar to thylakoid disks; hence the mitochondrial intermembrane space is topologically quite similar to the chloroplast lumen.:
The energy expressed here as Gibbs free energy, electrochemical proton gradient, or proton-motive force (PMF), is a combination of two gradients across the membrane:
* the concentration gradient (via ) and
* electric potential gradient .
When a system reaches equilibrium, ; nevertheless, the concentrations on either side of the membrane need not be equal. Spontaneous movement across the potential membrane is determined by both concentration and electric potential gradients.
The molar Gibbs free energy of ATP synthesis
is also called phosphorylation potential. The equilibrium concentration ratio can be calculated by comparing and , for example in case of the mammalian mitochondrion:
H / ATP = ΔG / (Δp / 10.4 kJ·mol/mV) = 40.2 kJ·mol / (173.5 mV / 10.4 kJ·mol/mV) = 40.2 / 16.7 = 2.4. The actual ratio of the proton-binding c-subunit to the ATP-synthesizing beta-subunit copy numbers is 8/3 = 2.67, showing that under these conditions, the mitochondrion functions at 90% (2.4/2.67) efficiency.
In fact, the thermodynamic efficiency is mostly lower in eukaryotic cells because ATP must be exported from the matrix to the cytoplasm, and ADP and phosphate must be imported from the cytoplasm. This "costs" one "extra" proton import per ATP, hence the actual efficiency is only 65% (= 2.4/3.67). | 1 | Biochemistry |
In physics, an atomic mirror is a device which reflects neutral atoms in a way similar to the way a conventional mirror reflects visible light. Atomic mirrors can be made of electric fields or magnetic fields, electromagnetic waves or just silicon wafer; in the last case, atoms are reflected by the attracting tails of the van der Waals attraction (see quantum reflection). Such reflection is efficient when the normal component of the wavenumber of the atoms is small or comparable to the effective depth of the attraction potential (roughly, the distance at which the potential becomes comparable to the kinetic energy of the atom). To reduce the normal component, most atomic mirrors are blazed at the grazing incidence.
At grazing incidence, the efficiency of the quantum reflection can be enhanced by a surface covered with ridges (ridged mirror).
The set of narrow ridges reduces the van der Waals attraction of atoms to the surfaces and enhances the reflection. Each ridge blocks part of the wavefront, causing Fresnel diffraction.
Such a mirror can be interpreted in terms of the Zeno effect.
We may assume that the atom is "absorbed" or "measured" at the ridges. Frequent measuring (narrowly spaced ridges) suppresses the transition of the particle to the half-space with absorbers, causing specular reflection. At large separation between thin ridges, the reflectivity of the ridged mirror is determined by dimensionless momentum , and does not depend on the origin of the wave; therefore, it is suitable for reflection of atoms. | 7 | Physical Chemistry |
Aurin (C.I. 43800), sometimes named rosolic acid or corallin is an organic compound, forming yellowish or deep-red crystals with greenish metallic luster. It is practically insoluble in water, freely soluble in alcohol. It is soluble in strong acids to form yellow solution, or in aqueous alkalis to form carmine red solutions. Due to this behaviour it can be used as pH indicator with pH transition range 5.0 - 6.8. It is used as an intermediate in manufacturing of dyes. | 3 | Analytical Chemistry |
Certain NMTs are therapeutic targets for development of drugs against bacterial infections. Myristoylation has been shown to be necessary for the survival of a number of disease-causing fungi, among them C. albicans and C. neoformans. In addition to prokaryotic bacteria, the NMTs of numerous disease-causing eukaryotic organisms have been identified as drug targets as well. Proper NMT functioning in the protozoa Leishmania major and Leishmania donovani (leishmaniasis), Trypanosoma brucei (African sleeping sickness), and P. falciparum (malaria) is necessary for survival of the parasites. Inhibitors of these organisms are under current investigation. A pyrazole sulfonamide inhibitor has been identified that selectively binds T. brucei, competing for the peptide binding site, thus inhibiting enzymatic activity and eliminating the parasite from the bloodstream of mice with African sleeping sickness. | 1 | Biochemistry |
In response to the environmental disasters at Love Canal and Times Beach, Missouri, Congress passed the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), commonly known as the Superfund legislation. CERCLA gave EPA primary responsibility for identifying, investigating, and cleaning up hazardous waste sites. CERCLA also authorized the establishment of ATSDR to assess the presence and nature of health hazards to communities living near Superfund sites, to help prevent or reduce harmful exposures, and to expand the knowledge base about the health effects that result from exposure to hazardous substances. ATSDR was created as an agency under the Department of Health and Human Services on April 19, 1983, and James O. Mason served as the agencys first administrator. The Hazardous and Solid Waste Amendments of 1984 to the Resource Conservation and Recovery Act (RCRA) gave ATSDR additional authority related to hazardous waste storage facilities. ATSDR was charged with conducting public health assessments at these sites when requested by EPA, states, or individuals, as well as assisting EPA to determine which substances should be regulated and the levels at which chemicals may pose a threat to human health. ATSDR was formally organized as an agency on June 11, 1985. The Superfund Amendments and Reauthorization Act of 1986 (SARA) broadened ATSDRs responsibilities in the areas of public health assessments, establishment and maintenance of toxicological databases, information dissemination, and medical education. In 2003, the position of assistant administrator was replaced with a director who is shared with NCEH. | 1 | Biochemistry |
In humans, DNA methylation occurs at the 5′ position of the pyrimidine ring of the cytosine residues within CpG sites to form 5-methylcytosines. The presence of multiple methylated CpG sites in CpG islands of promoters causes stable inhibition (silencing) of genes. Silencing of transcription of a gene may be initiated by other mechanisms, but this is often followed by methylation of CpG sites in the promoter CpG island to cause the stable silencing of the gene. | 1 | Biochemistry |
The reverse transcriptase employs a "right hand" structure similar to that found in other viral nucleic acid polymerases. In addition to the transcription function, retroviral reverse transcriptases have a domain belonging to the RNase H family, which is vital to their replication. By degrading the RNA template, it allows the other strand of DNA to be synthesized. Some fragments from the digestion also serve as the primer for the DNA polymerase (either the same enzyme or a host protein), responsible for making the other (plus) strand. | 1 | Biochemistry |
Darken’s equations can be applied to almost any scenario involving the diffusion of two different components that have different diffusion coefficients. This holds true except in situations where there is an accompanying volume change in the material because this violates one of Darken’s critical assumptions that atomic volume is constant. More complicated equations than presented must be used in cases where there is convection. One application in which Darken’s equations play an instrumental role is in analyzing the process of diffusion bonding. Diffusion bonding is used widely in manufacturing to connect two materials without using adhesives or welding techniques. Diffusion bonding works because atoms from both materials diffuse into the other material, resulting in a bond that is formed between the two materials. The diffusion of atoms between the two materials is achieved by placing the materials in contact with each other at high pressure and temperature, while not exceeding the melting temperature of either material. Darken’s equations, particularly Darken’s second equation, come into play when determining the diffusion coefficients for the two materials in the diffusion couple. Knowing the diffusion coefficients is necessary for predicting the flux of atoms between the two materials, which can then be used in numerical models of the diffusion bonding process, as, for example, was looked at in the paper by Orhan, Aksoy, and Eroglu when creating a model to determine the amount of time required to create a diffusion bond. In a similar manner, Darken’s equations were used in a paper by Watanabe et al., on the nickel-aluminum system, to verify the interdiffusion coefficients that were calculated for nickel aluminum alloys.
Application of Darken’s first equation has important implications for analyzing the structural integrity of materials. Darken’s first equation, , can be rewritten in terms of vacancy flux, . Use of Darken’s equation in this form has important implications for determining the flux of vacancies into a material undergoing diffusion bonding, which, due to the Kirkendall effect, could lead to porosity in the material and have an adverse effect on its strength. This is particularly important in materials such as aluminum nickel superalloys that are used in jet engines, where the structural integrity of the materials is extremely important. Porosity formation, known as Kirkendall porosity, in these nickel-aluminum superalloys have been observed when diffusion bonding has been used. It is important then to use Darken’s findings to predict this porosity formation. | 7 | Physical Chemistry |
Alternatives to acid–base extraction include:
* Filtering the mixture through a plug of silica gel or alumina — if the product is a charged salt, it will remain strongly adsorbed to the silica gel or alumina.
* Ion exchange chromatography can separate acids, bases, or mixtures of strong and weak acids and bases by their varying affinities to the column medium at different pH.
* Using column chromatography to separate the neutral compounds according to their ratio-of-fronts values.
* Gel electrophoresis, which separates large biomolecules based on their charge and size. | 7 | Physical Chemistry |
In theoretical chemistry, molecular electronic transitions take place when electrons in a molecule are excited from one energy level to a higher energy level. The energy change associated with this transition provides information on the structure of the molecule and determines many of its properties, such as colour. The relationship between the energy involved in the electronic transition and the frequency of radiation is given by Planck's relation. | 7 | Physical Chemistry |
In density functional theory, surface energy can be calculated from the following expression:
where
: is the total energy of surface slab obtained using density functional theory.
: is the number of atoms in the surface slab.
: is the bulk energy per atom.
: is the surface area.
For a slab, we have two surfaces and they are of the same type, which is reflected by the number 2 in the denominator. To guarantee this, we need to create the slab carefully to make sure that the upper and lower surfaces are of the same type.
Strength of adhesive contacts is determined by the work of adhesion which is also called relative surface energy of two contacting bodies. The relative surface energy can be determined by detaching of bodies of well defined shape made of one material from the substrate made from the second material. For example, the relative surface energy of the interface "acrylic glass – gelatin" is equal to 0.03 N/m. Experimental setup for measuring relative surface energy and its function can be seen in the video. | 7 | Physical Chemistry |
Soil structure refers to the manner in which these individual soil particles are grouped together to form clusters of particles called aggregates. This is determined by the types of soil formation, parent material, and texture. Soil structure can be influenced by a wide variety of biota as well as management methods by humans. | 9 | Geochemistry |
The mechanism of epoxidation with dioxiranes most likely involves concerted oxygen transfer through a spiro transition state. As oxygen transfer occurs, the plane of the oxirane is perpendicular to and bisects the plane of the alkene pi system. The configuration of the alkene is maintained in the product, ruling out long-lived radical intermediates. In addition, the spiro transition state has been used to explain the sense of selectivity in enantioselective epoxidations with chiral ketones.
Diastereoselective epoxidation may be achieved through the use of alkene starting materials with diastereotopic faces. When racemic 3-isopropylcyclohexene was subjected to DMD oxidation, the trans epoxide, which resulted from attack on the less hindered face of the double bond, was the major product. | 0 | Organic Chemistry |
When blood glucose levels are too low, the pancreas is signaled to release glucagon, which has essentially the opposite effect of insulin and therefore opposes the reduction of glucose in the blood. Glucagon is delivered directly to the liver, where it connects to the glucagon receptors on the membranes of the liver cells, signals the conversion of the glycogen already stored in the liver cells into glucose. This process is called glycogenolysis.
Conversely, when the blood glucose levels are too high, the pancreas is signaled to release insulin. Insulin is delivered to the liver and other tissues throughout the body (e.g., muscle, adipose). When the insulin is introduced to the liver, it connects to the insulin receptors already present, that is tyrosine kinase receptor. These receptors have two alpha subunits (extracellular) and two beta subunits (intercellular) which are connected through the cell membrane via disulfide bonds. When the insulin binds to these alpha subunits, glucose transport 4 (GLUT4) is released and transferred to the cell membrane to regulate glucose transport in and out of the cell. With the release of GLUT4, the allowance of glucose into cells is increased, and therefore the concentration of blood glucose might decrease. This, in other words, increases the utilization of the glucose already present in the liver. This is shown in the adjacent image. As glucose increases, the production of insulin increases, which thereby increases the utilization of the glucose, which maintains the glucose levels in an efficient manner and creates an oscillatory behavior. | 1 | Biochemistry |
Recombinant human insulin has almost completely replaced insulin obtained from animal sources (e.g. pigs and cattle) for the treatment of type 1 diabetes. A variety of different recombinant insulin preparations are in widespread use. Recombinant insulin is synthesized by inserting the human insulin gene into E. coli, or yeast (Saccharomyces cerevisiae) which then produces insulin for human use. Insulin produced by E. coli requires further post translational modifications (e.g. glycosylation) whereas yeasts are able to perform these modifications themselves by virtue of being more complex host organisms. The advantage of recombinant human insulin is after chronic use patients don't develop an immune defence against it the way animal sourced insulin stimulates the human immune system. | 1 | Biochemistry |
In 2011, the Magnetic Space Groups data compiled from H.T. Stokes & B.J. Campbells and D. Litvins's works general positions/symmetry operations and Wyckoff positions for different settings, along with systematic absence rules have also been incorporated into the server and a new shell has been dedicated to the related tools ([http://www.cryst.ehu.es/cgi-bin/cryst/programs/magget_gen.pl MGENPOS], [http://www.cryst.ehu.es/cgi-bin/cryst/programs/magget_wp.pl MWYCKPOS], [http://www.cryst.ehu.es/cryst/magnext.html MAGNEXT]). | 3 | Analytical Chemistry |
The basic unit of the polycatenane can differ from the relatively simple organic macrocycle. When organic and inorganic building blocks come together can form a coordination cages (or macromolecular cages) that can interlock one another to form a polycatenane structure. The mechanism is still unexplored but generally the subunits self-assemble into a 0D cage and, in a concerted process, they interlock together into a linear or more intricate catenane structure. Sometimes the catenated cages structure is more stable with respect to the monomeric cage state, and it can be formed passing through a favored reaction intermediate. The synthesis can follow a statistical or a directed routes, forming more or less product, but there are some cases when post-synthetic modifications can increase the product yields. Catenated cages can be applied in a wide range of application due to the high presence of voids. | 6 | Supramolecular Chemistry |
The concentration of purified protein solutions in the laboratory is useful in determining yield and measuring the success of a prep. MDS reports concentration as well as size for each test.
Since the detection is not based on inherent fluorescence of tryptophan or tyrosine residues, MDS has been used as an alternative to A280 UV-Vis quantification. | 1 | Biochemistry |
Orbiting Carbon Observatory-2 (OCO-2) is an American environmental science satellite which launched on 2 July 2014. A NASA mission, it is a replacement for the Orbiting Carbon Observatory which was lost in a launch failure in 2009. It is the second successful high-precision (better than 0.3%) observing satellite, after GOSAT. | 2 | Environmental Chemistry |
Measurement of the field metabolic rate is made using the doubly labeled water method, although alternative techniques, such as monitoring heart rates, can also be used. The advantages and disadvantages of the alternative approaches have been reviewed by Butler et al. Several summary reviews have been published. | 1 | Biochemistry |
Phosphates move quickly through plants and animals; however, the processes that move them through the soil or ocean are very slow, making the phosphorus cycle overall one of the slowest biogeochemical cycles.
The global phosphorus cycle includes four major processes:
:(i) tectonic uplift and exposure of phosphorus-bearing rocks such as apatite to surface weathering;
:(ii) physical erosion, and chemical and biological weathering of phosphorus-bearing rocks to provide dissolved and particulate phosphorus to soils, lakes and rivers;
:(iii) riverine and subsurface transportation of phosphorus to various lakes and run-off to the ocean;
:(iv) sedimentation of particulate phosphorus (e.g., phosphorus associated with organic matter and oxide/carbonate minerals) and eventually burial in marine sediments (this process can also occur in lakes and rivers).
In terrestrial systems, bioavailable P (‘reactive P’) mainly comes from weathering of phosphorus-containing rocks. The most abundant primary phosphorus-mineral in the crust is apatite, which can be dissolved by natural acids generated by soil microbes and fungi, or by other chemical weathering reactions and physical erosion. The dissolved phosphorus is bioavailable to terrestrial organisms and plants and is returned to the soil after their decay. Phosphorus retention by soil minerals (e.g., adsorption onto iron and aluminum oxyhydroxides in acidic soils and precipitation onto calcite in neutral-to-calcareous soils) is usually viewed as the most important process in controlling terrestrial P-bioavailability in the mineral soil. This process can lead to the low level of dissolved phosphorus concentrations in soil solution. Various physiological strategies are used by plants and microorganisms for obtaining phosphorus from this low level of phosphorus concentration.
Soil phosphorus is usually transported to rivers and lakes and can then either be buried in lake sediments or transported to the ocean via river runoff. Atmospheric phosphorus deposition is another important marine phosphorus source to the ocean. In surface seawater, dissolved inorganic phosphorus, mainly orthophosphate (PO), is assimilated by phytoplankton and transformed into organic phosphorus compounds. Phytoplankton cell lysis releases cellular dissolved inorganic and organic phosphorus to the surrounding environment. Some of the organic phosphorus compounds can be hydrolyzed by enzymes synthesized by bacteria and phytoplankton and subsequently assimilated. The vast majority of phosphorus is remineralized within the water column, and approximately 1% of associated phosphorus carried to the deep sea by the falling particles is removed from the ocean reservoir by burial in sediments. A series of diagenetic processes act to enrich sediment pore water phosphorus concentrations, resulting in an appreciable benthic return flux of phosphorus to overlying bottom waters. These processes include
: (i) microbial respiration of organic matter in sediments,
: (ii) microbial reduction and dissolution of iron and manganese (oxyhydr)oxides with subsequent release of associated phosphorus, which connects the phosphorus cycle to the iron cycle, and
: (iii) abiotic reduction of iron (oxyhydr)oxides by hydrogen sulfide and liberation of iron-associated phosphorus.
Additionally,
: (iv) phosphate associated with calcium carbonate and
: (v) transformation of iron oxide-bound phosphorus to vivianite play critical roles in phosphorus burial in marine sediments.
These processes are similar to phosphorus cycling in lakes and rivers.
Although orthophosphate (PO), the dominant inorganic P species in nature, is oxidation state (P5+), certain microorganisms can use phosphonate and phosphite (P3+ oxidation state) as a P source by oxidizing it to orthophosphate. Recently, rapid production and release of reduced phosphorus compounds has provided new clues about the role of reduced P as a missing link in oceanic phosphorus. | 9 | Geochemistry |
Scientists associated with the initial development of recombinant DNA methods recognized that the potential existed for organisms containing recombinant DNA to have undesirable or dangerous properties. At the 1975 Asilomar Conference on Recombinant DNA, these concerns were discussed and a voluntary moratorium on recombinant DNA research was initiated for experiments that were considered particularly risky. This moratorium was widely observed until the National Institutes of Health (USA) developed and issued formal guidelines for rDNA work. Today, recombinant DNA molecules and recombinant proteins are usually not regarded as dangerous. However, concerns remain about some organisms that express recombinant DNA, particularly when they leave the laboratory and are introduced into the environment or food chain. These concerns are discussed in the articles on genetically modified organisms and genetically modified food controversies. Furthermore, there are concerns about the by-products in biopharmaceutical production, where recombinant DNA result in specific protein products. The major by-product, termed host cell protein, comes from the host expression system and poses a threat to the patient's health and the overall environment. | 1 | Biochemistry |
Darken's second equation relates the chemical diffusion coefficient, , of a binary system to the atomic fractions of the two components. Similar to the first equation, this equation is applicable when the system does not undergo a volume change. This equation also only applies to multicomponent systems, including binary systems, that obey the equations of state and the Gibbs–Duhem equations. | 7 | Physical Chemistry |
The blast furnace remains an important part of modern iron production. Modern furnaces are highly efficient, including Cowper stoves to pre-heat the blast air and employ recovery systems to extract the heat from the hot gases exiting the furnace. Competition in industry drives higher production rates. The largest blast furnace in the world is in South Korea, with a volume around . It can produce around of iron per year.
This is a great increase from the typical 18th-century furnaces, which averaged about per year. Variations of the blast furnace, such as the Swedish electric blast furnace, have been developed in countries which have no native coal resources.
According to Global Energy Monitor, the blast furnace is likely to become obsolete to meet climate change objectives of reducing carbon dioxide emission, but BHP disagrees. An alternative process involving direct reduced iron is likely to succeed it, but this also needs to use a blast furnace to melt the iron and remove the gangue (impurities) unless the ore is very high quality. | 8 | Metallurgy |
Illicit diversion of pseudoephedrine in Australia has caused significant changes to the way the products are regulated. , all products containing pseudoephedrine have been rescheduled as either "Pharmacist Only Medicines" (Schedule 3) or "Prescription Only Medicines" (Schedule 4), depending on the amount of pseudoephedrine in the product. A Pharmacist Only Medicine may only be sold to the public if a pharmacist is directly involved in the transaction. These medicines must be kept behind the counter, away from public access.
Pharmacists are also encouraged (and in some states required) to log purchases with the online database Project STOP.
As a result, some pharmacies no longer stock Sudafed, the common brand of pseudoephedrine cold/sinus tablets, opting instead to sell Sudafed PE, a phenylephrine product that has not been proven effective in clinical trials. | 4 | Stereochemistry |
Amoxicillin is used in the treatment of a number of infections, including acute otitis media, streptococcal pharyngitis, pneumonia, skin infections, urinary tract infections, Salmonella infections, Lyme disease, and chlamydia infections. | 4 | Stereochemistry |
Isocyanides also form extensive families of complexes that are related to the metal carbonyls. Typical isocyanide ligands are methyl isocyanide and t-butyl isocyanide (MeCNC). A special case is CFNC, an unstable molecule that forms stable complexes whose behavior closely parallels that of the metal carbonyls. | 0 | Organic Chemistry |
Carbenes and carbenoid precursors can dimerize to alkenes. This is often, but not always, an unwanted side reaction; metal carbene dimerization has been used in the synthesis of polyalkynylethenes and is the major industrial route to Teflon (see ). Persistent carbenes equilibrate with their respective dimers, the Wanzlick equilibrium. | 0 | Organic Chemistry |
*"The Stereochemistry of the Ketonization Reaction of Enols," Zimmerman, H. E. J. Org. Chem., 1955, 20, 549-557.
*"The Stereochemistry of the Ivanov and Reformatsky Reactions. I," Zimmerman, H. E.; Traxler, M. D. J. Am. Chem. Soc., 1957, 79, 1920-1923.
*"The Photochemical Rearrangement of 4,4-Diphenylcyclohexadienone. Paper I on a General Theory of Photochemical Reactions," Zimmerman, H. E.; Schuster, D. I. J. Am. Chem. Soc., 1961, 83, 4486-4487.
*"On Molecular Orbital Correlation Diagrams, the Occurrence of Möbius Systems in Cyclization Reactions, and Factors Controlling Ground and Excited State Reactions. I," Zimmerman, H. E. J. Am. Chem. Soc., 1966, 88, 1564-1565.
*"Photochemical Migratory Aptitudes in Cyclohexenones. Mechanistic and Exploratory Organic Photochemistry. XXIII," Zimmerman, H. E.; Rieke, R. D.; Scheffer, J. R. J. Am. Chem. Soc., 1967, 89, 2033-2047.
*"The Di-π-Methane Rearrangement. Interaction of Electronically Excited Vinyl Chromophores. Zimmerman, H. E.; Mariano, P. S. J. Am. Chem. Soc., 1969, 91, 1718-1727.
*"The Barrelene to Semibullvalene Transformation. Correlation of Excited State Potential Energy Surfaces With Reactivity. Mechanistic and Exploratory Organic Photochemistry. XLIV," Zimmerman, H. E.; Binkley, R. W.; Givens, R. S.; Sherwin, M. A.; Grunewald, G. L.; J. Am. Chem. Soc., 1969, 91, 3316-3323. .
*"The Möbius-Hückel Concept in Organic Chemistry. Application to Organic Molecules and Reactions," Zimmerman, H. E. Acc. Chem. Res., 1971, 4, 272-280.
*"Quantum Mechanics for Organic Chemists," Zimmerman, H. E. Academic Press, New York, 1975.
*"Some Theoretical Aspects of Organic Photochemistry," Zimmerman, H. E. Accts. of Chem. Research, 1982, 10, 312-317.
*"Kinetic Protonation of Enols, Enolates and Analogs; The Stereochemistry of Ketonization," Zimmerman, H. E.. Accounts of Chem. Res.', 1987, 20, 263-268.
*"Regioselectivity of the Birch Reduction", Zimmerman, H. E.; Wang, P. A., J. Am. Chem. Soc., 1993, 115, 2205-2216.
*"The Meta Effect in Organic Photochemistry; Mechanistic and Exploratory Organic Photochemistry", Zimmerman, H. E., J. Am. Chem. Soc. 1995, 117, 8988-8991.
*"Synthetic Aspects of the Di-π-methane Rearrangement", Zimmerman, H. E.; Armesto, D. Chem. Revs, 1996, 96, 3065-3112.
*"Energy Distribution and Redistribution and Chemical Reactivity. The Generalized Delta Overlap-Density Method for Ground State and Electron Transfer Reactions; A new Quantitative Counterpart of Electron Pushing”, Zimmerman, H. E.; Alabugin, I. V. J. Am. Chem. Soc. 2001, 121, 2265-2270
*“Inter and Intramolecular Stereoselective Protonation of Enols”, Zimmerman, H. E.; Wang, P., J. Org. Chem. 2002, 69, 9216-9226.
*"Triplet Photochemistry of Vinyl Cyclopropenes; Mechanistic and Exploratory Organic Photochemistry", Zimmerman, H. E., J Org. Chem. 2009, 73, 1247-1251. . | 5 | Photochemistry |
R.T. Sanderson has also noted the relationship between Mulliken electronegativity and atomic size, and has proposed a method of calculation based on the reciprocal of the atomic volume. With a knowledge of bond lengths, Sandersons model allows the estimation of bond energies in a wide range of compounds. Sandersons model has also been used to calculate molecular geometry, s-electron energy, NMR spin-spin coupling constants and other parameters for organic compounds. This work underlies the concept of electronegativity equalization, which suggests that electrons distribute themselves around a molecule to minimize or to equalize the Mulliken electronegativity. This behavior is analogous to the equalization of chemical potential in macroscopic thermodynamics. | 3 | Analytical Chemistry |
An ATP test is the process of rapidly measuring active microorganisms in water through detection adenosine triphosphate (ATP). ATP is a molecule found only in and around living cells, and as such it gives a direct measure of biological concentration and health. ATP is quantified by measuring the light produced through its reaction with the naturally occurring enzyme firefly luciferase using a luminometer. The amount of light produced is directly proportional to the amount of biological energy present in the sample.
Second generation ATP tests are specifically designed for water, wastewater and industrial applications where, for the most part, samples contain a variety of components that can interfere with the ATP assay. | 3 | Analytical Chemistry |
Binary carbonyl clusters consist only of metal and CO. They are the most widely studied and used metal carbonyl clusters. They arise in general by the condensation of unsaturated metal carbonyls. Dissociation of CO from Ru(CO) would give Ru(CO), which could trimerize to Ru(CO). The reaction mechanisms are more complicated than this simple scenario. Condensation of low-molecular-weight metal carbonyls requires decarbonylation, which can be induced thermally, photochemically, or using various reagents. The nuclearity (number of metal centers) of binary metal carbonyl clusters is usually no greater than six. | 7 | Physical Chemistry |
Levosalbutamol is the INN while levalbuterol is the USAN.
Levalbuterol was approved in the United States as a solution to be used with a nebulizer device in March 1999 and in March 2015 became available in a formulation with a metered-dose inhaler under the trade name Xopenex HFA (levalbuterol tartrate inhalation aerosol). | 4 | Stereochemistry |
The Krupp–Renn process is a direct reduction process that uses a long tubular furnace similar to those found in cement production. The most recent units constructed have a diameter of approximately 4.5 meters and a length of 110 meters. The residence time of the product is influenced by the slope and speed of rotation of the rotary kiln, which is inclined at an angle of roughly 2.5 percent.
Prior to usage, the iron ore is crushed to less than 6 mm in particle size. The iron ore is introduced into the furnace upstream and mixed with a small amount of fuel, typically hard coal. After 6 to 8 hours, it exits the furnace as pre-reduced iron ore at 1,000 °C. The amount of iron recovered ranges from 94% to 97.5% of the initial iron in the ore.
A burner located at the lower end of the furnace provides heat, transforming it into a counter-current reactor. The fuel comprises finely pulverized coal, which, upon high-temperature combustion, generates reducing gas primarily consisting of CO. Once the furnace reaches an optimal temperature, the ore-coal mixture can serve as the primary fuel source.
The fumes exiting the furnace's upper end attain temperatures ranging from 850 to 900 °C and are subsequently cooled and purged of dust by water injection before discharge through the chimney.
The process is efficient in producing ferronickel due to the proximity of its constituent elements. At 800 °C, carbon easily reduces iron and nickel oxides, while the gangue's other oxides are not significantly reduced. Specifically, iron(II) oxide (or wustite), which is the stable iron oxide at 800 °C, has a reducibility similar to that of nickel(II) oxide, making it impossible to reduce one without reducing the other. | 8 | Metallurgy |
The relationship between pressure and volume was first noted by Richard Towneley and Henry Power in the 17th century. Robert Boyle confirmed their discovery through experiments and published the results. According to Robert Gunther and other authorities, it was Boyles assistant, Robert Hooke, who built the experimental apparatus. Boyles law is based on experiments with air, which he considered to be a fluid of particles at rest in between small invisible springs. Boyle may have begun experimenting with gases due to an interest in air as an essential element of life; for example, he published works on the growth of plants without air. Boyle used a closed J-shaped tube and after pouring mercury from one side he forced the air on the other side to contract under the pressure of mercury. After repeating the experiment several times and using different amounts of mercury he found that under controlled conditions, the pressure of a gas is inversely proportional to the volume occupied by it.
The French physicist Edme Mariotte (1620–1684) discovered the same law independently of Boyle in 1679, after Boyle had published it in 1662. Mariotte did, however, discover that air volume changes with temperature. Thus this law is sometimes referred to as Mariotte's law or the Boyle–Mariotte law. Later, in 1687 in the , Newton showed mathematically that in an elastic fluid consisting of particles at rest, between which are repulsive forces inversely proportional to their distance, the density would be directly proportional to the pressure, but this mathematical treatise does not involve any Mariott temperature dependance and is not the proper physical explanation for the observed relationship. Instead of a static theory, a kinetic theory is needed, which was developed over the next two centuries by Daniel Bernoulli (1738) and more fully by Rudolf Clausius (1857), Maxwell and Boltzmann.
This law was the first physical law to be expressed in the form of an equation describing the dependence of two variable quantities. | 7 | Physical Chemistry |
The main geologic history locally had two stages. The first is the Miocene, determined by tectonic events that correlate with the closing of the Tethys Sea. The second is the Pleistocene noted for its glaciation cycles and the full run of the present Volga. During the first stage, the Tethys Sea had evolved into the Sarmatian Lake, that was created from the modern Black Sea and south Caspian, when the collision of the Arabian peninsula with West Asia pushed up the Kopet Dag and Caucasus Mountains, lasting south and west limits to the basin. This orogenic movement was continuous, while the Caspian was regularly disconnected from the Black Sea. In the late Pontian stage, a mountain arch rose across the south basin and divided it into the Khachmaz and Lankaran Lakes (or early Balaxani). The period of restriction to the south basin was reversed during the Akchagylian – the lake became more than three times its size today and took again the first of a series of contacts with the Black Sea and with Lake Aral. A recession of Lake Akchagyl completed stage one. | 2 | Environmental Chemistry |
Reactive transport modeling requires input from numerous fields, including hydrology, geochemistry and biogeochemistry, microbiology, soil physics, and fluid dynamics. The numerical formulation and solution of reactive transport problems can be especially difficult due to errors arising in the coupling process, beyond those inherent to the individual processes. Valocchi and Malmstead (1992), for example, reported on the potential errors arising from the operator splitting technique.
Even in the absence of numerical difficulties, the general lack of knowledge available to practitioners creates uncertainty. Field sites are typically heterogeneous, both physically and chemically, and sampling is often sparse. The prevailing assumption of Fickian dispersion is often inadequate. Equilibrium constants and kinetic rate laws for relevant reactions are often poorly known. The complexity of many processes requires expertise in one or more of the aforementioned fields. Many processes, such as long-term nuclear waste storage, cannot be experimentally verified; reactive transport problems can only attempt to predict such long-term behavior. The current descriptions of multi-phase flow and mechanical deformation processes are still being developed. | 9 | Geochemistry |
Whether a process can occur spontaneously depends not only on the enthalpy change but also on the entropy change () and absolute temperature . If a process is a spontaneous process at a certain temperature, the products have a lower Gibbs free energy than the reactants (an exergonic process), even if the enthalpy of the products is higher. Thus, an endothermic process usually requires a favorable entropy increase () in the system that overcomes the unfavorable increase in enthalpy so that still . While endothermic phase transitions into more disordered states of higher entropy, e.g. melting and vaporization, are common, spontaneous chemical processes at moderate temperatures are rarely endothermic. The enthalpy increase in a hypothetical strongly endothermic process usually results in , which means that the process will not occur (unless driven by electrical or photon energy). An example of an endothermic and exergonic process is | 7 | Physical Chemistry |
In one of the syntheses, 7-aminocephalosporanic acid (7-ACA) is reacted with bromoacetyl chloride to give the amide. The halo group is then displaced by 4-thiopyridine. | 4 | Stereochemistry |
Early photosynthetic systems, such as those in green and purple sulfur and green and purple nonsulfur bacteria, are thought to have been anoxygenic, and used various other molecules than water as electron donors. Green and purple sulfur bacteria are thought to have used hydrogen and sulfur as electron donors. Green nonsulfur bacteria used various amino and other organic acids as electron donors. Purple nonsulfur bacteria used a variety of nonspecific organic molecules. The use of these molecules is consistent with the geological evidence that Earth's early atmosphere was highly reducing at that time.
With a possible exception of Heimdallarchaeota, photosynthesis is not found in archaea. Haloarchaea are phototrophic and can absorb energy from the sun, but do not harvest carbon from the atmosphere and are therefore not photosynthetic. Instead of chlorophyll they use rhodopsins, which convert light-energy to ion gradients but cannot mediate electron transfer reactions.
In bacteria eight photosynthetic lineages are currently known:
*Cyanobacteria, the only prokaryotes performing oxygenic photosynthesis and the only prokaryotes that contain two types of photosystems (type I (RCI), also known as Fe-S type, and type II (RCII), also known as quinone type). The seven remaining prokaryotes have anoxygenic photosynthesis and use versions of either type I or type II.
*Chlorobi (green sulfur bacteria) Type I
*Heliobacteria Type I
*Chloracidobacterium Type I
*Proteobacteria (purple sulfur bacteria and purple non-sulfur bacteria) Type II
*Chloroflexota (green non-sulfur bacteria) Type II
*Gemmatimonadota Type II
*Eremiobacterota Type II | 5 | Photochemistry |
An RA plot, like its cousin, the MA plot, is a re-scaled and (45-degree) rotated version of a simple two-dimensional scatter plot of a versus b where a and b are equal-length vectors of positive measurements. This rescaling and rotation allows for better visibility and emphasis of important outliers points that vary between the two measurement conditions. Essentially it is a plot of the log ratio [R] vs the average log [A] of each pairing of the elements of a and b. Unlike an MA plot, however, because the RA plot takes non-negative integer counts as input, it must employ work-arounds to include mathematically invisible points (such as points where one or both element(s) of the pair is zero).
If we modify our original a (or b) vector via:
where
then R and A can be defined as:
R, like M, is plotted on the y-axis and represents a log (fold change) ratio between a and b. A is plotted on the x-axis and represents the average abundance for a coordinate pair. The RA plot provides a quick overview of the distribution and size of a dataset consisting of non-zero counts. | 1 | Biochemistry |
Amoxicillin may interact with these drugs:
* Anticoagulants (dabigatran, warfarin).
* Methotrexate (chemotherapy and immunosuppressant).
* Typhoid, Cholera and BCG vaccines.
* Probenecid reduces renal excretion and increases blood levels of amoxicillin.
* Oral contraceptives potentially become less effective.
* Allopurinol (gout treatment).
* Mycophenolate (immunosuppressant) | 4 | Stereochemistry |
Matte is a term used in the field of pyrometallurgy given to the molten metal sulfide phases typically formed during smelting of copper, nickel, and other base metals. Typically, a matte is the phase in which the principal metal being extracted is recovered prior to a final reduction process (usually converting) to produce blister copper. The matte may also collect some valuable minor constituents such as noble metals, minor base metals, selenium or tellurium. Mattes may also be used to collect impurities from a metal phase, such as in the case of antimony smelting. Molten mattes are insoluble in both slag and metal phases. This insolubility, combined with differences in specific gravities between mattes, slags, and metals, allows for separation of the molten phases. | 8 | Metallurgy |
In organic chemistry, the anomeric effect or Edward-Lemieux effect (after J. T. Edward and Raymond Lemieux) is a stereoelectronic effect that describes the tendency of heteroatomic substituents adjacent to a heteroatom within a cyclohexane ring to prefer the axial orientation instead of the less-hindered equatorial orientation that would be expected from steric considerations. This effect was originally observed in pyranose rings by J. T. Edward in 1955 when studying carbohydrate chemistry.
The term anomeric effect was introduced in 1958. The name comes from the term used to designate the lowest-numbered ring carbon of a pyranose, the anomeric carbon. Isomers that differ only in the configuration at the anomeric carbon are called anomers. The anomers of -glucopyranose are diastereomers, with the beta anomer having a hydroxyl () group pointing up equatorially, and the alpha anomer having that () group pointing down axially.
The anomeric effect can also be generalized to any cyclohexyl or linear system with the general formula , where Y is a heteroatom with one or more lone pairs, and X is an electronegative atom or group. The magnitude of the anomeric effect is estimated at about 4-8 kJ/mol in the case of sugars, but is different for every molecule.
In the above case, the methoxy group ) on the cyclohexane ring (top) prefers the equatorial position. However, in the tetrahydropyran ring (bottom), the methoxy group prefers the axial position. This is because in the cyclohexane ring, Y = carbon, which is not a heteroatom, so the anomeric effect is not observed and sterics dominates the observed substituent position. In the tetrahydropyran ring, Y = oxygen, which is a heteroatom, so the anomeric effect contributes and stabilizes the observed substituent position. In both cases, X = methoxy group.
The anomeric effect is most often observed when Y = oxygen, but can also be seen with other lone pair bearing heteroatoms in the ring, such as nitrogen, sulfur, and phosphorus.
The exact method by which the anomeric effect causes stabilization is a point of controversy, and several hypotheses have been proposed to explain it. | 7 | Physical Chemistry |
A cell-counting assay may determine the number of living cells, the number of dead cells, or the ratio of one cell type to another, such as enumerating and typing red versus different types of white blood cells. This is measured by different physical methods (light transmission, electric current change). But other methods use biochemical probing cell structure or physiology (stains). Another application is to monitor cell culture (assays of cell proliferation or cytotoxicity).
A cytotoxicity assay measures how toxic a chemical compound is to cells.
*MTT assay
*Cell Counting Kit-8 (WST-8 based cell viability assay)
*SRB (Sulforhodamine B) assay
*CellTiter-Glo® Luminescent Cell Viability Assay
*Cell counting instruments and methods: CASY cell counting technology, Coulter counter, Electric cell-substrate impedance sensing
*Cell viability assays: resazurin method, ATP test, Ethidium homodimer assay (detect dead or dying cells), Bacteriological water analysis, Clonogenic assays, ... | 1 | Biochemistry |
Substitution, nucleophilic bimolecular reactions are concerted reactions where both the nucleophile and substrate are involved in the rate limiting step. Since this reaction is concerted, the reaction occurs in one step, where the bonds are broken, while new bonds are formed. Therefore, to interpret this reaction, it is important to look at the transition state, which resembles the concerted rate limiting step. In the "Depiction of S2 Reaction" figure, the nucleophile forms a new bond to the carbon, while the halide (L) bond is broken. | 7 | Physical Chemistry |
The reaction of an acid in water solvent is often described as a dissociation
where HA is a proton acid such as acetic acid, CHCOOH. The double arrow means that this is an equilibrium process, with dissociation and recombination occurring at the same time. This implies that the acid dissociation constant
However a more explicit description is provided by the Brønsted–Lowry acid–base theory, which specifies that the proton H+ does not exist as such in solution but is instead accepted by (bonded to) a water molecule to form the hydronium ion HO.
The reaction can therefore be written as
and better described as an ionization or formation of ions (for the case when HA has no net charge). The equilibrium constant is then
where is not included because in dilute solution the solvent is essentially a pure liquid with a thermodynamic activity of one.
K is variously named a dissociation constant, an acid ionization constant, an acidity constant or an ionization constant. It serves as an indicator of the acid strength: stronger acids have a higher K value (and a lower pK value). | 7 | Physical Chemistry |
Suspension array technology (or SAT) is a high throughput, large-scale, and multiplexed screening platform used in molecular biology. SAT has been widely applied to genomic and proteomic research, such as single nucleotide polymorphism (SNP) genotyping, genetic disease screening, gene expression profiling, screening drug discovery and clinical diagnosis. SAT uses microsphere beads (5.6 um in diameter) to prepare arrays. SAT allows for the simultaneous testing of multiple gene variants through the use of these microsphere beads as each type of microsphere bead has a unique identification based on variations in optical properties, most common is fluorescent colour. As each colour and intensity of colour has a unique wavelength, beads can easily be differentiated based on their wavelength intensity. Microspheres are readily suspendable in solution and exhibit favorable kinetics during an assay. Similar to flat microarrays (e.g. DNA microarray), an appropriate receptor molecule, such as DNA oligonucleotide probes, antibodies, or other proteins, attach themselves to the differently labeled microspheres. This produces thousands of microsphere array elements. Probe-target hybridization is usually detected by optically labeled targets, which determines the relative abundance of each target in the sample. | 1 | Biochemistry |
Organisms that rely on light energy to fix carbon, and thus participate in primary production, are referred to as photoautotrophs.
Photoautotrophs exists across the tree of life. Many bacterial taxa are known to be photoautotrophic such as cyanobacteria and some Pseudomonadota (formerly proteobacteria). Eukaryotic organisms gained the ability to participate in photosynthesis through the development of plastids derived from endosymbiotic relationships. Archaeplastida, which includes red algae, green algae, and plants, have evolved chloroplasts originating from an ancient endosymbiotic relationship with an Alphaproteobacteria. The productivity of plants, while being photoautotrophs, is also dependent on factors such as salinity and abiotic stressors from the surrounding environment. The rest of the eukaryotic photoautotrophic organisms are within the SAR clade (Comprising Stramenopila, Alveolata, and Rhizaria). Organisms in the SAR clade that developed plastids did so through a secondary or a tertiary endosymbiotic relationships with green algae and/or red algae. The SAR clade includes many aquatic and marine primary producers such as Kelp, Diatoms, and Dinoflagellates. | 9 | Geochemistry |
The Unruh effect would also cause the decay rate of accelerating particles to differ from inertial particles. Stable particles like the electron could have nonzero transition rates to higher mass states when accelerating at a high enough rate. | 7 | Physical Chemistry |
In addition to simple oxidation of aromatic rings to form carbonyl compounds (see ), trifluoroperacetic acid can fully cleave the carbon–carbon bonds within the ring. Unlike other oxidations of alkylaromatic structures, which yield benzoic acids and related compounds by cleavage of the alkyl chain at the reactive benzylic position, trifluoroperacetic acid causes an "inverse oxidation", cleaving the aromatic ring itself while leaving the alkyl group intact.
This selectivity for certain types of bonds allows it to be used to decompose complex mixtures of hydrocarbons, such as coal, in order to determine structural details.
Aromatic systems containing heteroatoms are resistant to this ring-opening as heteroatom oxidation occurs preferentially and deactivates the ring towards electrophilic attack by the peroxy acid. For example, purines, pyridines, and quinolines instead form N-oxides, while sulfur systems like octafluorodibenzothiophene are converted to sulfones.
Aromatic systems with ring-activating substituents can be oxidised to form phenols instead of undergoing a ring-opening reaction. Mesitylene, for example, reacts with trifluoroperacetic acid to form mesitol (2,4,6-trimethylphenol). Researchers attempting to form a lactone by Baeyer–Villiger oxidation of 7-oxodeacetamidocolchicine were unable to prepare the desired product, but did achieve oxidation of the aromatic ring to produce a phenol-derivative in high yield: | 0 | Organic Chemistry |
A chemical synthesis of captopril by treatment of -proline with (2S)-3-acetylthio-2-methylpropanoyl chloride under basic conditions (NaOH), followed by aminolysis of the protective acetyl group to unmask the drug's free thiol, is depicted in the figure at right.
Procedure 2 taken out of patent US4105776. See examples 28, 29a and 36. | 4 | Stereochemistry |
The Washoe process, a variation of pan amalgamation, was developed in the 1860s by Almarin B. Paul and others, to work the ore from the Comstock Lode in Nevada, United States (Washoe was an early name for the area and the local tribe who still exists today; see Washoe Valley). In the Washoe process, the copper pans were replaced by iron tanks with mechanical agitators. Each tank ("pan") was circular, and commonly held 1,200 to 1,500 pounds of ore that had been crushed to sand size. Water was added to make a pulp, and 60 to 70 pounds of mercury, along with one-half to three pounds each of salt (sodium chloride) and bluestone (copper(II) sulfate) were also added. A circular iron plate called a muller was mounted on a vertical shaft and lowered into the pan, and was rotated to provide both agitation and additional grinding. Heat was delivered to the pans by steam pipes. The iron filings worn from the muller and pan proved to be an essential ingredient in the process. | 8 | Metallurgy |
The use of racemic amlodipine is commonly associated with adverse events like peripheral edema and other side effects like headache, dizziness, flushing and abdominal pain. Controlled clinical trials showed that levamlodipine is rarely associated with these side effects. No controlled clinical study of levamlodipine has been performed in patients with hepatic impairment and renal impairment. Clinical studies in patients with normal liver function have shown that there is no elevation in the hepatic enzymes with the use of levamlodipine. However, caution should be taken while administering levamlodipine to such patients.
In a postmarketing surveillance study, levamlodipine (2.5/5 mg) was found to be well tolerated (n = 1859) in patients with hypertension. Out of 314 patients, who reported peripheral edema with conventional amlodipine were switched over to levamlodipine and edema was resolved in 310 patients (98.72%) at the end of 4 weeks. Only in 4 patients was edema sustained. Only 30 patients (out of 1859) reported side effects. These side effects included vertigo, tachycardia, cough, headache, fever, mild difficulty in breathing and edema. Adverse events were mild in nature and no serious adverse events were reported. | 4 | Stereochemistry |
Animal studies have shown the benefit of targeted temperature management in traumatic central nervous system (CNS) injuries. Clinical trials have shown mixed results with regards to the optimal temperature and delay of cooling. Achieving therapeutic temperatures of is thought to prevent secondary neurological injuries after severe CNS trauma. A systematic review of randomised controlled trials in traumatic brain injury (TBI) suggests there is no evidence that hypothermia is beneficial. | 1 | Biochemistry |
The above-ground nuclear tests that occurred in several countries between 1955 and 1980 (see nuclear test list) dramatically increased the amount of carbon-14 in the atmosphere and subsequently in the biosphere; after the tests ended, the atmospheric concentration of the isotope began to decrease, as radioactive was fixed into plant and animal tissue, and dissolved in the oceans.
One side-effect of the change in atmospheric carbon-14 is that this has enabled some options (e.g., bomb-pulse dating) for determining the birth year of an individual, in particular, the amount of carbon-14 in tooth enamel, or the carbon-14 concentration in the lens of the eye.
In 2019, Scientific American reported that carbon-14 from nuclear bomb testing has been found in the bodies of aquatic animals found in one of the most inaccessible regions of the earth, the Mariana Trench in the Pacific Ocean.
The concentration of carbon-14 in atmospheric CO, reported as the ratio of carbon-14 to carbon-12 with respect to a standard, has now (approximately since the year 2022) declined to levels similar to those prior to the above-ground nuclear tests of the 1950s and 1960s. Although the extra carbon-14 atoms generated during those nuclear tests have not disappeared from the atmosphere, oceans and biosphere, they are diluted because of the Suess effect. | 9 | Geochemistry |
A Walloon forge (or Walloon process) is a type of finery forge that decarbonizes pig iron into wrought iron.
The process was conceived in the Liège region, and from there extended to France, then England around the end of the 15th century. Louis de Geer brought it to Roslagen in Sweden at the beginning of the 17th century, with Walloon blacksmiths.
The Walloon process spread to Sweden in the Uppland province north of Stockholm, where it was used to produce a specific kind of wrought iron called oregrounds iron. | 8 | Metallurgy |
K-Mold is a fracture test method. Liquid metal is cast into a mold containing notches. Once solidified, the resulting bar is bent to expose a fracture surface. The visual observation of inclusions on the fracture is used to determine a K-value for the melt and compared to a preset standard. This method is rather imprecise and therefore only suitable when metal contains large inclusions and inclusion clusters. | 8 | Metallurgy |
This method mainly identifies variant function based on the information whether the variant loci are in the known functional region that harbor genomic or epigenomic signals. The function of non-coding variants are extensive in terms of the affected genomic region and they involve in almost all processes of gene regulation from transcriptional to post translational level | 1 | Biochemistry |
Acids with a pH of less than 2 or alkalis with a pH above 12 are capable of causing the most extensive injuries in ingestions. Alkalis damage tissue by saponifying fats, leading to liquefaction necrosis which allows the alkalis to reach deeper tissues. Acids denature proteins via coagulation necrosis, this type of necrosis is thought to prevent the acid from reaching deeper tissues. Clinically, the pH, concentration, volume of ingested substance in addition to the duration of time in contact with tissue as well as percentage of body surface area involved determine the severity of the injury. | 8 | Metallurgy |
As access to an ionized calcium is not always available a corrected calcium may be used instead. To calculate a corrected calcium in mmol/L one takes the total calcium in mmol/L and adds it to ((40 minus the serum albumin in g/L) multiplied by 0.02). There is, however, controversy around the usefulness of corrected calcium as it may be no better than total calcium. It may be more useful to correct total calcium for both albumin and the anion gap. | 1 | Biochemistry |
Coenzyme A is available from various chemical suppliers as the free acid and lithium or sodium salts. The free acid of coenzyme A is detectably unstable, with around 5% degradation observed after 6 months when stored at −20 °C, and near complete degradation after 1 month at 37 °C. The lithium and sodium salts of CoA are more stable, with negligible degradation noted over several months at various temperatures. Aqueous solutions of coenzyme A are unstable above pH 8, with 31% of activity lost after 24 hours at 25 °C and pH 8. CoA stock solutions are relatively stable when frozen at pH 2–6. The major route of CoA activity loss is likely the air oxidation of CoA to CoA disulfides. CoA mixed disulfides, such as CoA-S–S-glutathione, are commonly noted contaminants in commercial preparations of CoA. Free CoA can be regenerated from CoA disulfide and mixed CoA disulfides with reducing agents such as dithiothreitol or 2-mercaptoethanol. | 1 | Biochemistry |
The Society for Applied Spectroscopy (SAS) is an organization promoting research and education in the fields of spectroscopy, optics, and analytical chemistry. Founded in 1958, it is currently headquartered in Frederick, MD. In 2006 it had about 2,000 members worldwide.
SAS is perhaps best known for its technical conference with the Federation of Analytical Chemistry and Spectroscopy Societies and short courses on various aspects of spectroscopy and data analysis. The society publishes the scientific journal Applied Spectroscopy.
SAS is affiliated with American Institute of Physics (AIP), Coblentz, Council for Near Infrared Spectroscopy (CNIRS), Federation of Analytical Chemistry and Spectroscopy Societies (FACSS), The Instrumentation, Systems, and Automation Society (ISA), and Optical Society of America (OSA).
SAS provides a number of awards with honorariums to encourage and recognize outstanding achievements. | 7 | Physical Chemistry |
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