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There are various classification schemes. A commonly used scheme is based on the number of carbons and was devised by Jeffrey Harborne and Simmonds in 1964 and published in 1980: | 0 | Theoretical and Fundamental Chemistry |
An arrastra (or arastra) is a primitive mill for grinding and pulverizing (typically) gold or silver ore. Its simplest form is two or more flat-bottomed drag stones placed in a circular pit paved with flat stones, and connected to a center post by a long arm. With a horse, mule or human providing power at the other end of the arm, the stones were dragged slowly around in a circle, crushing the ore. Some arrastras were powered by a water wheel; a few were powered by steam or gasoline engines, and even electricity.
Arrastras were widely used throughout the Mediterranean region since Phoenician times. The Spanish introduced the arrastra to the New World in the 16th century. The word "arrastra" comes from the Spanish language arrastrar, meaning to drag along the ground. Arrastras were suitable for use in small or remote mines, since they could be built from local materials and required little investment capital.
For gold ore, the gold was typically recovered by amalgamation with quicksilver. The miner would add clean mercury to the ground ore, continue grinding, rinse out the fines, then add more ore and repeat the process. At cleanup, the gold amalgam was carefully recovered from the low places and crevices in the arrastra floor. The amalgam was then heated in a distillation retort to recover the gold, and the mercury was saved for reuse.
For silver ore, the patio process, invented in Mexico in 1554, was generally used to recover the silver from ore ground in the arrastra. | 1 | Applied and Interdisciplinary Chemistry |
The fine chemical industry has undergone several boom and bust phases during its almost 30 years of existence. The biggest boom took place in the late 1990s, when high-dosage, high volume anti-AIDS drugs and COX-2 inhibitors gave a big boost to custom manufacturing. After the end of the "irrational exuberance" in 2000, the industry suffered a first bust in 2003, as a result of capacity expansions, the advent of Asian competitors and a ruinous M&A activity, several billion dollars of shareholder value were destroyed. The most recent –minor- boom is associated with stockpiling of GlaxoSmithKlines Relenza (zanamivir) and Roches Tamiflu (oseltamivir phosphate) by many countries in order to prepare for a possible avian flu epidemic. Surprisingly, the main cause for the 2009 slump had not been the general recession, but slow-downs of the growth and, even more so, inventory adjustments by the pharma industry. They resulted in postponements or cancellations of orders. The unfavorable development was in sharp contrast to the very optimistic growth forecasts, which many fine chemical companies, had announced. They had been based on equally promising sector reports from investment banks, which in turn had evolved from forward projections of the preceding boom period. In most cases, these projections have been missed by a large margin.
At the end of the "irrational exuberance" at the turn of the millennium and again in 2009 almost half of the industry achieved a return on sales (ROS) of more than 10%, and less than 10% an ROS below 5%. In the worst years, 2003 and 2009, almost half of the companies suffered from an ROS of less than 5%. Whereas during the period under review, 2000–2009. the average EBITDA / sales and EBIT / sales ratios of representative companies, resp. divisions were 15% and 7%, respectively, in the period 2000–2009, the numbers were 20% and 10–13% in the boom, and 10% and 5% in the bust phases. The factor 2 between the high and low numbers reflects the volatility of the industry's profitability. All in all, the average Western fine-chemical firms have been making a return below the cost of capital, i.e. they are not reinvestment grade. | 0 | Theoretical and Fundamental Chemistry |
Johannes Wislicenus (; 24 June 18355 December 1902) was a German chemist, most famous for his work in early stereochemistry. | 0 | Theoretical and Fundamental Chemistry |
The following table outlines several channels that have been closed using sand, illustrating the technique's application and effectiveness.
Note: Several compartments did not encompass fully enclosed basins, making a surface area metric inapplicable.
During the closure of the Geul at the mouth of the Oosterschelde—characterised by a tidal capacity of roughly 30 million cubic metres and a maximum depth of 10 metres below mean sea level (MSL)—the Oosterschelde dam between the working islands of Noordland and Neeltje Jans in 1972 witnessed minimised sand losses thanks to the employment of high-capacity suction dredging. This strategy achieved a sand extraction rate exceeding 500,000 cubic metres per week, distributed across three suction dredgers. It was also demonstrated that initiating the closure from one side and progressing towards the shallowest part of the gap effectively reduces sand losses. This approach ensured the shortest possible distance for the sand to be deposited towards the closure's culmination, particularly during periods of maximum flow velocity.
This technique partly accounts for the significant sand losses, approximately 45%, observed during the closure of the Brielse Gat, which has a maximum depth of 2 metres below MSL and where sand was deposited from both sides towards the centre. Opting for a single sand deposit site, while reducing sand losses, necessitates substantial suction capacity and results in a notably wider closure dam to accommodate all discharge pipelines. | 1 | Applied and Interdisciplinary Chemistry |
Relative inductive effects have been experimentally measured through the resulting s of a nearby carboxylic acid group (see ). In increasing order of -I effect or decreasing order of +I effect, common functional groups are:
Hydrogen subsituents also exhibit an isotope effect: relative to the same order,
where H is hydrogen, D deuterium, and T tritium.
The strength of inductive effect is also dependent on the distance between the substituent group and the main group that react; the longer the distance, the weaker the effect.
Inductive effects can be expressed quantitatively through the Hammett equation, which describes the relationship between reaction rates and equilibrium constants with respect to substituent. | 0 | Theoretical and Fundamental Chemistry |
Blood types are an example of how glycolipids on cell membranes mediate cell interactions with the surrounding environment. The four main human blood types (A, B, AB, O) are determined by the oligosaccharide attached to a specific glycolipid on the surface of red blood cells, which acts as an antigen. The unmodified antigen, called the H antigen, is the characteristic of type O, and is present on red blood cells of all blood types. Blood type A has an N-acetylgalactosamine added as the main determining structure, type B has a galactose, and type AB has all three of these antigens. Antigens which are not present in an individual's blood will cause antibodies to be produced, which will bind to the foreign glycolipids. For this reason, people with blood type AB can receive transfusions from all blood types (the universal acceptor), and people with blood type O can act as donors to all blood types (the universal donor). | 0 | Theoretical and Fundamental Chemistry |
It has recently been found that Acinetobacter sp. also show quorum sensing activity. This bacterium, an emerging pathogen, produces AHLs. Acinetobacter sp. shows both quorum sensing and quorum quenching activity. It produces AHLs and can also degrade the AHL molecules. | 1 | Applied and Interdisciplinary Chemistry |
Moungi Bawendi was born in Paris, France, the son of Tunisian mathematician Mohammed Salah Baouendi. After periods living in France and Tunisia, Bawendi and his family migrated to the United States when he was a child. They lived in West Lafayette, Indiana, as Salah worked in the math department at Purdue University. Bawendi graduated from West Lafayette Junior-Senior High School in 1978. | 0 | Theoretical and Fundamental Chemistry |
Some humans produce flatus that contains methane. In one study of the feces of nine adults, five of the samples contained archaea capable of producing methane. Similar results are found in samples of gas obtained from within the rectum.
Even among humans whose flatus does contain methane, the amount is in the range of 10% or less of the total amount of gas. | 1 | Applied and Interdisciplinary Chemistry |
While chemically pure materials have a single melting point, chemical mixtures often partially melt at the solidus temperature (T or T), and fully melt at the higher liquidus temperature (T or T). The solidus is always less than or equal to the liquidus, but they need not coincide. If a gap exists between the solidus and liquidus it is called the freezing range, and within that gap, the substance consists of a mixture of solid and liquid phases (like a slurry). Such is the case, for example, with the olivine (forsterite-fayalite) system, which is common in Earth's mantle. | 0 | Theoretical and Fundamental Chemistry |
Pyruvate dehydrogenase is inhibited when one or more of the three following ratios are increased: ATP/ADP, NADH/NAD and acetyl-CoA/CoA.
In eukaryotes PDC is tightly regulated by its own specific pyruvate dehydrogenase kinase (PDK) and pyruvate dehydrogenase phosphatase (PDP), deactivating and activating it respectively.
* PDK phosphorylates three specific serine residues on E1 with different affinities. Phosphorylation of any one of them (using ATP) renders E1 (and in consequence the entire complex) inactive.
* Dephosphorylation of E1 by PDP reinstates complex activity.
Products of the reaction act as allosteric inhibitors of the PDC, because they activate PDK. Substrates in turn inhibit PDK, reactivating PDC.
During starvation, PDK increases in amount in most tissues, including skeletal muscle, via increased gene transcription. Under the same conditions, the amount of PDP decreases. The resulting inhibition of PDC prevents muscle and other tissues from catabolizing glucose and gluconeogenesis precursors. Metabolism shifts toward fat utilization, while muscle protein breakdown to supply gluconeogenesis precursors is minimized, and available glucose is spared for use by the brain.
Calcium ions have a role in regulation of PDC in muscle tissue, because it activates PDP, stimulating glycolysis on its release into the cytosol - during muscle contraction. Some products of these transcriptions release H2 into the muscles. This can cause calcium ions to decay over time. | 1 | Applied and Interdisciplinary Chemistry |
Human artificial chromosome may be potentially useful as a gene transfer vectors for gene delivery into human cells, and a tool for expression studies and determining human chromosome function. It can carry very large DNA fragment (there is no upper limit on size for practical purposes), therefore it does not have the problem of limited cloning capacity of other vectors, and it also avoids possible insertional mutagenesis caused by integration into host chromosomes by viral vector. | 1 | Applied and Interdisciplinary Chemistry |
As a trenchless technology, CIPP does not require excavation to rehabilitate a pipeline that is either leaking or structurally unsound. Depending upon design considerations an excavation may be made, but the liner is often installed through a manhole or other existing access point. Liner is installed as it is wet out on site in these instances. In the case of sewerlines, lateral connections are also restored without excavation via a remote controlled device that drills a hole in the liner at the point of the lateral connection. If larger than 24" and it is safe to do so someone will reinstate laterals by hand. CIPP has a smooth interior and no joints. While CIPP can repair a pipe with bends, special design considerations must be taken into account to prevent wrinkling and stretching. CIPP can effectively reduce infiltration and leaks in pipeline systems without digging. | 1 | Applied and Interdisciplinary Chemistry |
The formation of 5-phosphoribosylamine from glutamine and PRPP catalysed by PRPP amino transferase is the regulation point for purine synthesis. The enzyme is an allosteric enzyme, so it can be converted from IMP, GMP and AMP in high concentration binds the enzyme to exerts inhibition while PRPP is in large amount binds to the enzyme which causes activation. So IMP, GMP and AMP are inhibitors while PRPP is an activator. Between the formation of 5-phosphoribosyl, aminoimidazole and IMP, there is no known regulation step. | 1 | Applied and Interdisciplinary Chemistry |
MTBE removal from groundwater and soil contamination in the U.S. was estimated to cost from $1 billion to US$30 billion, including removing the compound from aquifers and municipal water supplies and replacing leaky underground oil tanks. In one case, the cost to oil companies to clean up the MTBE in wells belonging to the city of Santa Monica, California was estimated to exceed $200 million. In another case, New York City estimated a $250 million cost for cleanup of a single wellfield in the borough of Queens in 2009. In 2013 a jury awarded the State of New Hampshire $236 million in damages in order to treat groundwater contaminated by MTBE.
Many lawsuits are still pending regarding MTBE contamination of public and private drinking water supplies. | 1 | Applied and Interdisciplinary Chemistry |
The B Horizon has dark layer where minerals, organic matter and bases are being illuviated (washed in/accumulated). Below this is a red/orange layer of iron and aluminium sesquioxides deposit. Some bases remain in the soil, though others may be lost by throughflow. In many podsols, Iron Pans are created. This can cause water logging which may then saturate the A horizon leading to mottling or a gleyed podsol.
Also useful: soil chemistry | 0 | Theoretical and Fundamental Chemistry |
Similarly to drugs, medical or surgical procedures may be subjected to clinical trials, such as comparing different surgical approaches in treatment of fibroids for subfertility. However, when clinical trials are unethical or logistically impossible in the surgical setting, case-controlled studies will be replaced. | 1 | Applied and Interdisciplinary Chemistry |
As mentioned above, the noise due to the Brownian fluctuations of the bead increases with length. Robust sequencing tests have yet to be performed to determine the maximum read length of this system. However, the ligation of a 7-mer in the middle of a 1241 nucleotide-long hairpin was successfully detected, suggesting that the current system is sufficient to sequence up to ~500 bp. | 1 | Applied and Interdisciplinary Chemistry |
PPA is known to have a rigid and brittle backbone which limits its flexibility and usage in some applications. However, it can be easily tuned by adding additives rendering it a soft material. The mechanical properties of cyclic PPA films drop cast using different solvents have recently been investigated. The study showed the polymer to possess a large elastic modulus of 2.5-3 GPa which was also previously reported in another study, in addition to tensile strength values ranging between 25 and 35 MPa and a failure strain of 1-1.5% that is highly dependent of the solvent used. | 0 | Theoretical and Fundamental Chemistry |
The applications of chemotactic drug delivery systems include but are not limited to cancer therapy, wound healing, and inflammation. The ability to target specific cells and locations within the body through chemical cues has opened up new avenues for the field of drug delivery, allowing for increased drug efficacy and reducing harmful side effects. | 1 | Applied and Interdisciplinary Chemistry |
The nucleus of an atom consists of neutrons and protons, which in turn are the manifestation of more elementary particles, called quarks, that are held in association by the nuclear strong force in certain stable combinations of hadrons, called baryons. The nuclear strong force extends far enough from each baryon so as to bind the neutrons and protons together against the repulsive electrical force between the positively charged protons. The nuclear strong force has a very short range, and essentially drops to zero just beyond the edge of the nucleus. The collective action of the positively charged nucleus is to hold the electrically negative charged electrons in their orbits about the nucleus. The collection of negatively charged electrons orbiting the nucleus display an affinity for certain configurations and numbers of electrons that make their orbits stable. Which chemical element an atom represents is determined by the number of protons in the nucleus; the neutral atom will have an equal number of electrons orbiting that nucleus. Individual chemical elements can create more stable electron configurations by combining to share their electrons. It is that sharing of electrons to create stable electronic orbits about the nuclei that appears to us as the chemistry of our macro world.
Protons define the entire charge of a nucleus, and hence its chemical identity. Neutrons are electrically neutral, but contribute to the mass of a nucleus to nearly the same extent as the protons. Neutrons can explain the phenomenon of isotopes (same atomic number with different atomic mass). The main role of neutrons is to reduce electrostatic repulsion inside the nucleus. | 0 | Theoretical and Fundamental Chemistry |
The full stack for DNA computing looks very similar to a traditional computer architecture. At the highest level, a C-like general purpose programming language is expressed using a set of chemical reaction networks (CRNs). This intermediate representation gets translated to domain-level DNA design and then implemented using a set of DNA strands. In 2010, [http://www.dna.caltech.edu/~winfree/ Erik Winfrees group] showed that DNA can be used as a substrate to implement arbitrary chemical reactions. This opened the way to design and synthesis of biochemical controllers since the expressive power of CRNs is equivalent to a Turing machine. Such controllers can potentially be used in vivo' for applications such as preventing hormonal imbalance. | 1 | Applied and Interdisciplinary Chemistry |
Many synthetic supramolecular systems are designed to copy functions of biological systems. These biomimetic architectures can be used to learn about both the biological model and the synthetic implementation. Examples include photoelectrochemical systems, catalytic systems, protein design and self-replication. | 0 | Theoretical and Fundamental Chemistry |
NeSSI is used for process analytical measurements in the petrochemical, chemical and oil refining industries. These measurements may be for quality control of raw material or final product, environmental compliance, safety, energy reduction or process control purposes. Vapour applications may include hydrocarbon feed stocks and intermediates (ethylene, ethane, propylene, etc.), natural gas streams, liquefied petroleum gas (LPG) streams, hydrogen and air gas streams.
Liquid systems suitable for use with the Generation I mechanical portion of NeSSI are hydrocarbons such as diesel fuel as well as aqueous streams. Highly viscous fluids and solids are not suitable for use with NeSSI. Very dirty, high particulate streams need to be filtered. Some liquid service applications may be limited by pressure drops associated with components hooked up in a serial configuration. NeSSI systems have found applications in areas other than the process analytical environments including micro reactor, mini plant and laboratory environments where small size, unskilled assembly and flexible configuration is important. | 1 | Applied and Interdisciplinary Chemistry |
Carborane acids (X, Y, Z = H, Alk, F, Cl, Br, CF) are a class of superacids, some of which are estimated to be at least one million times stronger than 100% pure sulfuric acid in terms of their Hammett acidity function values (H ≤ –18) and possess computed pK values well below –20, establishing them as some of the strongest known Brønsted acids. The best-studied example is the highly chlorinated derivative . The acidity of was found to vastly exceed that of triflic acid, , and bistriflimide, , compounds previously regarded as the strongest isolable acids.
Their high acidities stem from the extensive delocalization of their conjugate bases, carboranate anions (CXBYZ), which are usually further stabilized by electronegative groups like Cl, F, and CF. Due to the lack of oxidizing properties and the exceptionally low nucleophilicity and high stability of their conjugate bases, they are the only superacids known to protonate C fullerene without decomposing it. Additionally, they form stable, isolable salts with protonated benzene, CH, the parent compound of the Wheland intermediates encountered in electrophilic aromatic substitution reactions.
The fluorinated carborane acid, , is even stronger than chlorinated carborane acid. It is able to protonate butane to form tert-butyl cation at room temperature and is the only known acid to protonate carbon dioxide to give the bridged cation, , making it possibly the strongest known acid. In particular, CO does not undergo observable protonation when treated with the mixed superacids HF-SbF or HSOF-SbF.
As a class, the carborane acids form the most acidic group of well-defined, isolable substances known, far more acidic than previously known single-component strong acids like triflic acid or perchloric acid. In certain cases, like the nearly perhalogenated derivatives mentioned above, their acidities rival (and possibly exceed) those of the traditional mixed Lewis-Brønsted superacids like magic acid and fluoroantimonic acid. (However, a head-to-head comparison has not been possible thus far, due to the lack of a measure of acidity that is suitable for both classes of acids: pK values are ill-defined for the chemically complex mixed acids while H values cannot be measured for the very high melting carborane acids). | 0 | Theoretical and Fundamental Chemistry |
An inflatable is an object that can be inflated with a gas, usually with air, but hydrogen, helium, and nitrogen are also used. One of several advantages of an inflatable is that it can be stored in a small space when not inflated, since inflatables depend on the presence of a gas to maintain their size and shape. Function fulfillment per mass used compared with non-inflatable strategies is a key advantage. Stadium cushions, impact guards, vehicle wheel inner tubes, emergency air bags, and inflatable space habitats employ the inflatable principle. Inflation occurs through several strategies: pumps, ram-air, blowing, and suction.
Although the term inflatable can refer to any type of inflatable object, the term is often used in boating to specifically refer to inflatable boats. | 1 | Applied and Interdisciplinary Chemistry |
There are about 44,000 gigatonnes of carbon in the atmosphere and oceans. A gigatonne is one billion metric tonnes, equivalent to the mass of water in over 400,000 Olympic-size swimming pools. Large as this quantity is, it only amounts to a small fraction of one percent of Earth's carbon. Over 90% may reside in the core, most of the rest being in the crust and mantle.
In the photosphere of the Sun, carbon is the fourth most abundant element. The Earth likely started with a similar ratio but lost a lot of it to evaporation as it accreted. Even accounting for evaporation, however, the silicates making up the crust and mantle of the Earth have a carbon concentration that is five to ten times less than in CI chondrites, a form of meteor that is believed to represent the composition of the solar nebula before the planets formed. Some of this carbon may have ended up in the core. Depending on the model, carbon is predicted to contribute between 0.2 and 1 percent by weight in the core. Even at the lower concentration, this would account for half Earth's carbon.
Estimates of the carbon content in the upper mantle come from measurements of the chemistry of mid-ocean ridge basalts (MORBs). These must be corrected for degassing of carbon and other elements. Since the Earth formed, the upper mantle has lost 40–90% of its carbon by evaporation and transport to the core in iron compounds. The most rigorous estimate gives a carbon content of 30 parts per million (ppm). The lower mantle is expected to be much less depleted – about 350 ppm. | 0 | Theoretical and Fundamental Chemistry |
The crystal structure describes the three-dimensional periodic arrangement of atoms, ions, or molecules in a crystal. The unit cell represents the simplest repeating unit of the crystal structure. It is a parallelepiped containing a certain spatial arrangement of atoms, ions, molecules, or molecular fragments. From the unit cell the crystal structure can be fully reconstructed via translations.
The visualization of a crystal structure can be reduced to the arrangement of atoms, ions, or molecules in the unit cell, with or without cell outlines. Structure elements extending beyond single unit cells, such as isolated molecular or polyhedral units as well as chain, net, or framework structures, can often be better understood by extending the structure representation into adjacent cells.
The space group of a crystal is a mathematical description of the symmetry inherent in the structure. The motif of the crystal structure is given by the asymmetric unit, a minimal subset of the unit cell contents. The unit cell contents can be fully reconstructed via the symmetry operations of the space group on the asymmetric unit. Visualization interfaces usually allow for switching between asymmetric unit and full structure representations.
Bonds between atoms or ions can be identified by characteristic short distances between them. They can be classified as covalent, ionic, hydrogen, or other bonds including hybrid forms. Bond angles can be deduced from the bond vectors in groups of atoms or ions. Bond distances and angles can be made available to the user in tabular form or interactively, by selecting pairs or groups of atoms or ions. In ball-and-stick models of crystal structures, balls represent atoms and sticks represent bonds.
Since organic chemists are particularly interested in molecular structures, it might be useful to be able to single out individual molecular units interactively from the drawing. Organic molecular units need to be given both as 2D structural formulae and full 3D molecular structures. Molecules on special-symmetry positions need to be reconstructed from the asymmetric unit. Protein crystallographers are interested in molecular structures of biological macromolecules, so that provisions need to be made to be able to represent molecular subunits as helices, sheets, or coils, respectively.
Crystal structure visualization can be integrated into a crystallographic database. Alternatively, the crystal structure data are exchanged between the database and the visualization software, preferably using the CIF format. Web-based crystallographic databases can integrate crystal structure visualization capability. Depending on the complexity of the structure, lighting, and 3D effects, crystal structure visualization can require a significant amount of processing power, which is why the actual visualization is typically run on the client.
Currently, web-integrated crystal structure visualization is based on Java applets from open-source projects such as Jmol. Web-integrated crystal structure visualization is tailored for examining crystal structures in web browsers, often supporting wide color spectra (up to 32 bit) and window size adaptation. However, web-generated crystal structure images are not always suitable for publishing due to issues such as resolution depth, color choice, grayscale contrast, or labeling (positioning, font type, font size). | 0 | Theoretical and Fundamental Chemistry |
Substituted tryptamines, or serotonin analogues, are organic compounds which may be thought of as being derived from tryptamine itself. The molecular structures of all tryptamines contain an indole ring, joined to an amino (NH) group via an ethyl (−CH2–CH2−) sidechain. In substituted tryptamines, the indole ring, sidechain, and/or amino group are modified by substituting another group for one of the hydrogen (H) atoms.
Well-known tryptamines include serotonin, an important neurotransmitter, and melatonin, a hormone involved in regulating the sleep-wake cycle. Tryptamine alkaloids are found in fungi, plants and animals; and sometimes used by humans for the neurological or psychotropic effects of the substance. Prominent examples of tryptamine alkaloids include psilocybin (from "psilocybin mushrooms") and DMT. In South America, dimethyltryptamine is obtained from numerous plant sources, like chacruna, and it is often used in ayahuasca brews. Many synthetic tryptamines have also been made, including the migraine drug sumatriptan, and psychedelic drugs. A 2022 study has found the variety of tryptamines present in wild mushrooms may affect the therapeutic impact.
The tryptamine structure, in particular its indole ring, may be part of the structure of some more complex compounds, for example: LSD, ibogaine, mitragynine and yohimbine. A thorough investigation of dozens of tryptamine compounds was published by Ann and Alexander Shulgin under the title TiHKAL. | 0 | Theoretical and Fundamental Chemistry |
A piped water supply and distribution system is intermittent when water continuity is for less than 24 hours a day or not on all days of the week. During this continuity defining factors are water pressure and equity. At least 45 countries have intermittent water supply (IWS) systems. It is contrasted with a continuous or "24/7" water supply, the service standard. No system is intentionally designed to be intermittent, but they may become that way because of system overexpansion, leakage and other factors. As of 2022, there was no feasible method for modelling IWS, including no computer-aided tools. Contamination issues can be associated with an intermittent water distribution system. Global public health impact includes millions of cases of infections and diarrhea, and 1560 deaths annually.
A continuous supply is not practical in all situations. In the short term, an IWS may have some benefits. These may include addressing demand with a limited supply in a more economical manner. An intermittent supply may be temporary (e.g., when water reserves are low) or permanent (e.g., where the piped system cannot sustain a continuous supply). Associated factors resulting from an intermittent supply include water extraction by users at the same time, resulting in low pressure and a possible higher peak demand. | 1 | Applied and Interdisciplinary Chemistry |
The attention of Newton was also directed to the discharge of water from orifices in the bottom of vessels. He supposed a cylindrical vessel full of water to be perforated in its bottom with a small hole by which the water escaped, and the vessel to be supplied with water in such a manner that it always remained full at the same height. He then supposed this cylindrical column of water to be divided into two parts – the first, which he called the "cataract," being an hyperboloid generated by the revolution of an hyperbola of the fifth degree around the axis of the cylinder which should pass through the orifice, and the second the remainder of the water in the cylindrical vessel. He considered the horizontal strata of this hyperboloid as always in motion, while the remainder of the water was in a state of rest, and imagined that there was a kind of cataract in the middle of the fluid.
When the results of this theory were compared with the quantity of water actually discharged, Newton concluded that the velocity with which the water issued from the orifice was equal to that which a falling body would receive by descending through half the height of water in the reservoir. This conclusion, however, is absolutely irreconcilable with the known fact that jets of water rise nearly to the same height as their reservoirs, and Newton seems to have been aware of this objection. Accordingly, in the second edition of his Principia, which appeared in 1713, he reconsidered his theory. He had discovered a contraction in the vein of fluid (vena contracta) which issued from the orifice, and found that, at the distance of about a diameter of the aperture, the section of the vein was contracted in the subduplicate ratio of two to one. He regarded, therefore, the section of the contracted vein as the true orifice from which the discharge of water ought to be deduced, and the velocity of the effluent water as due to the whole height of water in the reservoir; and by this means his theory became more conformable to the results of experience, though still open to serious objections. | 1 | Applied and Interdisciplinary Chemistry |
Tablet presses, also called tableting machines, range from small, inexpensive bench-top models that make one tablet at a time (single-station presses), with only around a half-ton pressure, to large, computerized, industrial models (multi-station rotary presses) that can make hundreds of thousands to millions of tablets an hour with much greater pressure. The tablet press is an essential piece of machinery for any pharmaceutical and nutraceutical manufacturer. Tablet presses must allow the operator to adjust the position of the lower and upper punches accurately, so that the tablet weight, thickness and density/hardness can each be controlled. This is achieved using a series of cams, rollers, or tracks that act on the tablet tooling (punches). Mechanical systems are also incorporated for die filling, and for ejecting and removing the tablets from the press after compression. Pharmaceutical tablet presses are required to be easy to clean and quick to reconfigure with different tooling, because they are usually used to manufacture many different products.
There are two main standards of tablet tooling used in pharmaceutical industry: American standard TSM and European standard EU. TSM and EU configurations are similar to each other but cannot be interchanged.
Modern tablet presses reach output volumes of up to 1,700,000 tablets per hour. These huge volumes require frequent in-process quality control for the tablet weight, thickness and hardness. Due to reduce rejects rates and machine down-time, automated tablet testing devices are used on-line with the tablet press or off-line in the IPC-labs. | 1 | Applied and Interdisciplinary Chemistry |
Albert mentions friendship in his work, De bono, as well as presenting his ideals and morals of friendship in the very beginning of Tractatus II. Later in his life he published Super Ethica. With his development of friendship throughout his work it is evident that friendship ideals and morals took relevance as his life went on. Albert comments on Aristotles view of friendship with a quote from Cicero, who writes, "friendship is nothing other than the harmony between things divine and human, with goodwill and love". Albert agrees with this commentary but he also adds in harmony or agreement. Albert calls this harmony, consensio, itself a certain kind of movement within the human spirit. Albert fully agrees with Aristotle in the sense that friendship is a virtue. Albert relates the inherent metaphysical contentedness between friendship and moral goodness. Albert describes several levels of goodness; the useful (utile), the pleasurable (delectabile) and the authentic or unqualified good (honestum). Then in turn there are three levels of friendship based on each of those levels, namely friendship based on usefulness (amicitia utilis), friendship based on pleasure (amicitia delectabilis), and friendship rooted in unqualified goodness (amicitia honesti; amicitia quae fundatur super honestum'). | 1 | Applied and Interdisciplinary Chemistry |
Examples of restriction enzymes include:
Key:<br/>
= blunt ends<br/>
N = C or G or T or A<br/>
W = A or T | 1 | Applied and Interdisciplinary Chemistry |
The Arthashastra lays down the role of the Director of Metals, the Director of Forest Produce and the Director of Mining. It is the duty of the Director of Metals to establish factories for different metals. The Director of Mines is responsible for the inspection of mines. The Arthashastra also refers to counterfeit coins. | 1 | Applied and Interdisciplinary Chemistry |
* [https://www.youtube.com/watch?v=iIXI_pl-Akk&feature=emb_logo Solar power from space] 5-minute video about space-based solar power plants by the European Space Agency
* [https://web.archive.org/web/20091020135852/http://www.thefutureschannel.com/dockets/realworld/space_based_solar_power/ Powering the Planet] 20-minute streaming video from The Futures Channel that provides a "101" on space-based solar power
* [https://www.youtube.com/watch?v=eTdJw30Pg4Q Space Solar Power] NewSpace 2010 Panel, 72 minutes
* [https://www.youtube.com/watch?v=kMW64hqipGI Space Solar Power and Space Energy Systems] SSI – Space Manufacturing 14 Panel – 2010 – 27 min
* [https://www.youtube.com/watch?v=og9UvxrHA9E NASA DVD in 16 Parts] Exploring New Frontiers for Tomorrow's Energy Needs
* [https://www.youtube.com/watch?v=2E_z6L9Hn0Q Space Solar Power] Press Conference September 12, 2008 (71 minutes) National Space Society
* [https://www.bbc.co.uk/programmes/p00yjt99 BBC One - Bang Goes the Theory, Series 6, Episode 5, Transmitting power without wires] BBC/Lighthouse DEV Eye-safe Laser Based Power Beaming Demo | 0 | Theoretical and Fundamental Chemistry |
Determining the parameters of the Michaelis–Menten equation typically involves running a series of enzyme assays at varying substrate concentrations , and measuring the initial reaction rates , i.e. the reaction rates are measured after a time period short enough for it to be assumed that the enzyme-substrate complex has formed, but that the substrate concentration remains almost constant, and so the equilibrium or quasi-steady-state approximation remain valid. By plotting reaction rate against concentration, and using nonlinear regression of the Michaelis–Menten equation with correct weighting based on known error distribution properties of the rates, the parameters may be obtained.
Before computing facilities to perform nonlinear regression became available, graphical methods involving linearisation of the equation were used. A number of these were proposed, including the Eadie–Hofstee plot of against , the Hanes plot of against , and the Lineweaver–Burk plot (also known as the double-reciprocal plot) of against . Of these, the Hanes plot is the most accurate when is subject to errors with uniform standard deviation. From the point of view of visualizaing the data the Eadie–Hofstee plot has an important property: the entire possible range of values from to occupies a finite range of ordinate scale, making it impossible to choose axes that conceal a poor experimental design.
However, while useful for visualization, all three linear plots distort the error structure of the data and provide less precise estimates of and than correctly weighted non-linear regression. Assuming an error on , an inverse representation leads to an error of on (Propagation of uncertainty), implying that linear regression of the double-reciprocal plot should include weights of . This was well understood by Lineweaver and Burk, who had consulted the eminent statistician W. Edwards Deming before analysing their data. Unlike nearly all workers since, Burk made an experimental study of the error distribution, finding it consistent with a uniform standard error in , before deciding on the appropriate weights. This aspect of the work of Lineweaver and Burk received virtually no attention at the time, and was subsequently forgotten.
The direct linear plot is a graphical method in which the observations are represented by straight lines in parameter space, with axes and : each line is drawn with an intercept of on the axis and on the axis. The point of intersection of the lines for different observations yields the values of and . | 0 | Theoretical and Fundamental Chemistry |
The pressure-fed engine is a class of rocket engine designs. A separate gas supply, usually helium, pressurizes the propellant tanks to force fuel and oxidizer to the combustion chamber. To maintain adequate flow, the tank pressures must exceed the combustion chamber pressure.
Pressure fed engines have simple plumbing and have no need for complex and occasionally unreliable turbopumps. A typical startup procedure begins with opening a valve, often a one-shot pyrotechnic device, to allow the pressurizing gas to flow through check valves into the propellant tanks. Then the propellant valves in the engine itself are opened. If the fuel and oxidizer are hypergolic, they burn on contact; non-hypergolic fuels require an igniter. Multiple burns can be conducted by merely opening and closing the propellant valves as needed. If the pressurization system also has activating valves, they can be operated electrically, or by gas pressure controlled by smaller electrically operated valves.
Care must be taken, especially during long burns, to avoid excessive cooling of the pressurizing gas due to adiabatic expansion. Cold helium won't liquify, but it could freeze a propellant, decrease tank pressures, or damage components not designed for low temperatures. The Apollo Lunar Module Descent Propulsion System was unusual in storing its helium in a supercritical but very cold state. It was warmed as it was withdrawn through a heat exchanger from the ambient temperature fuel.
Spacecraft attitude control and orbital maneuvering thrusters are almost universally pressure-fed designs.
Examples include the Reaction Control (RCS) and the Orbital Maneuvering (OMS) engines of the Space Shuttle orbiter; the RCS and Service Propulsion System (SPS) engines on the Apollo Command/Service Module; the SuperDraco (in-flight abort) and Draco (RCS) engines on the SpaceX Dragon 2; and the RCS, ascent and descent engines on the Apollo Lunar Module.
Some launcher upper stages also use pressure-fed engines. These include the Aerojet AJ10 and TRW TR-201 used in the second stage of Delta II launch vehicle,
and the Kestrel engine of the Falcon 1 by SpaceX.
The 1960s Sea Dragon concept by Robert Truax for a big dumb booster would have used pressure-fed engines.
Pressure-fed engines have practical limits on propellant pressure, which in turn limits combustion chamber pressure. High pressure propellant tanks require thicker walls and stronger materials which make the vehicle tanks heavier, thereby reducing performance and payload capacity. The lower stages of launch vehicles often use either solid fuel or pump-fed liquid fuel engines instead, where high pressure ratio nozzles are considered desirable.
Other vehicles or companies using pressure-fed engine:
*OTRAG (rocket)
*Quad (rocket) of Armadillo Aerospace
*XCOR EZ-Rocket of XCOR Aerospace
*Masten Space Systems
*Aquarius Launch Vehicle
*NASA's Project Morpheus prototype lander
*NASA Mighty Eagle mini lunar lander
*CONAE's Tronador II upper stage
*Copenhagen Suborbitals' Spica | 0 | Theoretical and Fundamental Chemistry |
The enzyme is present in organisms capable of oxygenic photosynthesis, which includes plants, algae, and cyanobacteria. Plastid terminal oxidase and alternative oxidase are thought to have originated from a common ancestral di-iron carboxylate protein. Oxygen reductase activity was likely an ancient mechanism to scavenge oxygen in the early transition from an anaerobic to aerobic world. The plastid oxidase first evolved in ancient cyanobacteria and the alternative oxidase in Pseudomonadota before eukaryotic evolution and endosymbiosis events. Through endosymbiosis, the plastid oxidase was vertically inherited by eukaryotes that evolved into plants and algae. Sequenced genomes of various plant and algae species shows that the amino acid sequence is more than 25% conserved, which is a significant amount of conservation for an oxidase. This sequence conservation further supports the theory that both the alternative and plastid oxidases evolved before endosymbiosis and did not significantly change through eukaryote evolution.
There also exist PTOX cyanophages that contain copies of the gene for the plastid oxidase. They are known to act as viral vectors for movement of the gene between cyanobacterial species. Some evidence suggests that the phages may use the oxidase to influence photosynthetic electron flow to produce more ATP and less NADPH because viral synthesis utilizes more ATP. | 0 | Theoretical and Fundamental Chemistry |
The addition of the myristoyl group proceeds via a nucleophilic addition-elimination reaction. First, myristoyl coenzyme A (CoA) is positioned in its binding pocket of NMT so that the carbonyl faces two amino acid residues, phenylalanine 170 and leucine 171. This polarizes the carbonyl so that there is a net positive charge on the carbon, making it susceptible to nucleophilic attack by the glycine residue of the protein to be modified. When myristoyl CoA binds, NMT reorients to allow binding of the peptide. The C-terminus of NMT then acts as a general base to deprotonate the NH, activating the amino group to attack at the carbonyl group of myristoyl-CoA. The resulting tetrahedral intermediate is stabilized by the interaction between a positively charged oxyanion hole and the negatively charged alkoxide anion. Free CoA is then released, causing a conformational change in the enzyme that allows the release of the myristoylated peptide. | 1 | Applied and Interdisciplinary Chemistry |
Metabolic fluxes are a function of gene expression, translation, post translational protein modifications and protein-metabolite interactions. | 1 | Applied and Interdisciplinary Chemistry |
* by electric energy as electric current: electrotherapy, electroconvulsive therapy
** Transcranial magnetic stimulation
** Vagus nerve stimulation
* by magnetic energy:
** magnet therapy
** pulsed electromagnetic field therapy
** magnetic resonance therapy
* by electromagnetic radiation (EMR):
** by light: light therapy (phototherapy)
*** ultraviolet light therapy
**** PUVA therapy
*** photodynamic therapy
**** photothermal therapy
**** cytoluminescent therapy
*** blood irradiation therapy
*** by darkness: dark therapy
*** by lasers: laser therapy
**** low level laser therapy
** by gamma rays: radiosurgery
*** Gamma Knife radiosurgery
*** stereotactic radiation therapy
*** cobalt therapy
** by radiation generally: radiation therapy (radiotherapy)
*** intraoperative radiation therapy
*** by EMR particles:
**** particle therapy
***** proton therapy
***** electron therapy
****** intraoperative electron radiation therapy
****** Auger therapy
***** neutron therapy
****** fast neutron therapy
****** neutron capture therapy of cancer
*** by radioisotopes emitting EMR:
**** by nuclear medicine
**** by brachytherapy
** quackery type: electromagnetic therapy (alternative medicine)
* by mechanical: manual therapy as massotherapy and therapy by exercise as in physical therapy
** inversion therapy
* by sound:
** by ultrasound:
*** ultrasonic lithotripsy
**** extracorporeal shockwave therapy
*** sonodynamic therapy
** by music: music therapy
* by temperature
** by heat: heat therapy (thermotherapy)
*** by moderately elevated ambient temperatures: hyperthermia therapy
**** by dry warm surroundings: Waon therapy
**** by dry or humid warm surroundings: sauna, including infrared sauna, for sweat therapy
** by cold:
*** by extreme cold to specific tissue volumes: cryotherapy
*** by ice and compression: cold compression therapy
*** by ambient cold:
**** hypothermia therapy for neonatal encephalopathy (in newborns)
**** targeted temperature management (therapeutic hypothermia, protective hypothermia)
** by hot and cold alternation: contrast bath therapy | 1 | Applied and Interdisciplinary Chemistry |
In biochemistry, paucimannosylation is an enzymatic post-translational modification involving the attachment of relatively simple mannose (Man) and N-Acetylglucosamine (GlcNAc) containing carbohydrates (glycans) to proteins. The paucimannosidic glycans may also be modified with other types of monosaccharides including fucose (Fuc) and xylose (Xyl) depending on the species, tissue and cell origin.
Paucimannosylation forms a separate sub-type in the asparagine N-linked glycosylation system. The short paucimannosidic glycans neither structurally nor functionally fit into the three well-established N-glycan classes i.e. oligomannosidic-, hybrid- and complex-type N-glycans.
Paucimannosylation has traditionally been referred to as a N-glycosylation type of "lower organisms", mostly documented in insects, worms and plants. Recent findings have, however, added nuances to this view, by showing their presence and roles in mammals in the areas of immunity, cellular development, pathogen infection and cancer. To this end, paucimannosylation is therefore now considered to be a distinct type of N-glycosylation that adds diversity to the highly heterogeneous glycoproteome across the eukaryotic domain. | 1 | Applied and Interdisciplinary Chemistry |
Coelenterazine is found in radiolarians, ctenophores, cnidarians, squid, brittle stars, copepods, chaetognaths, fish, and shrimp. It is the prosthetic group in the protein aequorin responsible for the blue light emission. | 1 | Applied and Interdisciplinary Chemistry |
Pasquill atmospheric stability classes – oldest and, for a great many years, the most commonly used method of categorizing the amount of atmospheric turbulence present was the method developed by Pasquill in 1961.
He categorized the atmospheric turbulence into six stability classes named A, B, C, D, E and F with class A being the most unstable or most turbulent class, and class F the most stable or least turbulent class.
* Table 1 lists the six classes
* Table 2 provides the meteorological conditions that define each class. The stability classes demonstrate a few key ideas. Solar radiation increases atmospheric instability through warming of the Earth's surface so that warm air is below cooler (and therefore denser) air promoting vertical mixing. Clear nights push conditions toward stable as the ground cools faster establishing more stable conditions and inversions. Wind increases vertical mixing, breaking down any type of stratification and pushing the stability class towards neutral (D).
Table 1: The Pasquill stability classes
Table 2: Meteorological conditions that define the Pasquill stability classes
Incoming solar radiation is based on the following: strong (> 700 W m), moderate (350–700 W m), slight () | 1 | Applied and Interdisciplinary Chemistry |
The fixation of atmospheric nitrogen is an energy-intensive process, as it involves breaking the very stable triple bond between the nitrogen atoms. The nitrogenases catalyze the process. One such enzyme occurs in Rhizobium bacteria. There are three components to its action: a molybdenum atom at the active site, iron–sulfur clusters that are involved in transporting the electrons needed to reduce the nitrogen, and an abundant energy source in the form of magnesium ATP. This last is provided by a mutualistic symbiosis between the bacteria and a host plant, often a legume. The reaction may be written symbolically as
:N + 16 MgATP + 8 e → 2 NH + 16 MgADP +16 P + H
where P stands for inorganic phosphate. The precise structure of the active site has been difficult to determine. It appears to contain a MoFeS cluster that is able to bind the dinitrogen molecule and, presumably, enable the reduction process to begin. The electrons are transported by the associated "P" cluster, which contains two cubical FeS clusters joined by sulfur bridges. | 1 | Applied and Interdisciplinary Chemistry |
Aequorin is presumably encoded in the genome of Aequorea. At least four copies of the gene were recovered as cDNA from the animal. Because the genome has not been sequenced, it is unclear if the cDNA variants can account for all of the isoforms of the protein. | 1 | Applied and Interdisciplinary Chemistry |
A check dam placed in the ditch, swale, or channel interrupts the flow of water and flattens the gradient of the channel, thereby reducing the velocity. In turn, this obstruction induces infiltration and reduces eroding. They can be used not only to slow flow velocity but also to distribute flows across a swale to avoid preferential paths and guide flows toward vegetation. Although some sedimentation may result behind the dam, check dams do not primarily function as sediment-trapping devices.
For instance, on the Graliwdo River in Ethiopia, an increase of hydraulic roughness by check dams and water transmission losses in deposited sediments is responsible for the delay of runoff to reach the lower part of the river channels. The reduction of peak runoff discharge was larger in the river segment with check dams and vegetation (minus 12%) than in segment without treatment (minus 5.5%). Reduction of total runoff volume was also larger in the river with check dams than in the untreated river. The implementation of check dams combined with vegetation reduced peak flow discharge and total runoff volume as large parts of runoff infiltrated in the sediments deposited behind the check dams. As gully check dams are implemented in a large areas of northern Ethiopia, this contributes to groundwater recharge and increased river base flow. | 1 | Applied and Interdisciplinary Chemistry |
Countercurrent exchange is a mechanism occurring in nature and mimicked in industry and engineering, in which there is a crossover of some property, usually heat or some chemical, between two flowing bodies flowing in opposite directions to each other. The flowing bodies can be liquids, gases, or even solid powders, or any combination of those. For example, in a distillation column, the vapors bubble up through the downward flowing liquid while exchanging both heat and mass.
The maximum amount of heat or mass transfer that can be obtained is higher with countercurrent than co-current (parallel) exchange because countercurrent maintains a slowly declining difference or gradient (usually temperature or concentration difference). In cocurrent exchange the initial gradient is higher but falls off quickly, leading to wasted potential. For example, in the adjacent diagram, the fluid being heated (exiting top) has a higher exiting temperature than the cooled fluid (exiting bottom) that was used for heating. With cocurrent or parallel exchange the heated and cooled fluids can only approach one another. The result is that countercurrent exchange can achieve a greater amount of heat or mass transfer than parallel under otherwise similar conditions.
See: flow arrangement.
Countercurrent exchange when set up in a circuit or loop can be used for building up concentrations, heat, or other properties of flowing liquids. Specifically when set up in a loop with a buffering liquid between the incoming and outgoing fluid running in a circuit, and with active transport pumps on the outgoing fluid's tubes, the system is called a countercurrent multiplier, enabling a multiplied effect of many small pumps to gradually build up a large concentration in the buffer liquid.
Other countercurrent exchange circuits where the incoming and outgoing fluids touch each other are used for retaining a high concentration of a dissolved substance or for retaining heat, or for allowing the external buildup of the heat or concentration at one point in the system.
Countercurrent exchange circuits or loops are found extensively in nature, specifically in biologic systems. In vertebrates, they are called a rete mirabile, originally the name of an organ in fish gills for absorbing oxygen from the water. It is mimicked in industrial systems. Countercurrent exchange is a key concept in chemical engineering thermodynamics and manufacturing processes, for example in extracting sucrose from sugar beet roots.
Countercurrent multiplication is a similar but different concept where liquid moves in a loop followed by a long length of movement in opposite directions with an intermediate zone. The tube leading to the loop passively building up a gradient of heat (or cooling) or solvent concentration while the returning tube has a constant small pumping action all along it, so that a gradual intensification of the heat or concentration is created towards the loop. Countercurrent multiplication has been found in the kidneys as well as in many other biological organs. | 1 | Applied and Interdisciplinary Chemistry |
The heat transfer at an interface is considered a transient heat flow. To analyze this problem, the Biot number is important to understand how the system behaves. The Biot number is determined by:
The heat transfer coefficient , is introduced in this formula, and is measured in . If the system has a Biot number of less than 0.1, the material behaves according to Newtonian cooling, i.e. with negligible temperature gradient within the body. If the Biot number is greater than 0.1, the system behaves as a series solution. The temperature profile in terms of time can be derived from the equation
which becomes
The heat transfer coefficient, , is measured in , and represents the transfer of heat at an interface between two materials. This value is different at every interface and is an important concept in understanding heat flow at an interface.
The series solution can be analyzed with a nomogram. A nomogram has a relative temperature as the coordinate and the Fourier number, which is calculated by
The Biot number increases as the Fourier number decreases. There are five steps to determine a temperature profile in terms of time.
# Calculate the Biot number
# Determine which relative depth matters, either x or L.
# Convert time to the Fourier number.
# Convert to relative temperature with the boundary conditions.
# Compared required to point to trace specified Biot number on the nomogram. | 1 | Applied and Interdisciplinary Chemistry |
In the last ten years, many experiments have been conducted numerically and analytically to validate the importance of nanofluids.
From the table 1 it is clear that nanofluid-based collector have a higher efficiency than a conventional collector. So, it is clear that we can improve conventional collector simply by adding trace amounts of nano-particles.
It has also been observed through numerical simulation that mean outlet temperature increase by increasing volume fraction of nanoparticles, length of tube and decreases by decreasing velocity. | 0 | Theoretical and Fundamental Chemistry |
In 1939, ten years after work ceased at St. Marys, a team of scientists at the Sir William Dunn School of Pathology at the University of Oxford, led by Howard Florey that included Edward Abraham, Ernst Chain, Norman Heatley and Margaret Jennings, began researching penicillin. Their starting point was Flemings largely forgotten paper and a sample of penicillin mould Fleming had given to their laboratory in 1930. They developed a method for cultivating the mould and extracting, purifying and storing penicillin from it, together with an assay for measuring its purity. Chain hit upon the idea of freeze drying it, which enabled the water to be removed, resulting in a dry, brown powder. They carried out experiments with animals to determine penicillin's safety and effectiveness before conducting clinical trials and field tests. They derived its chemical structure and determined how it works. The private sector and the United States Department of Agriculture located and produced new strains and developed mass production techniques. During the Second World War penicillin became an important part of the Allied war effort, and is credited with saving the lives of thousands of soldiers.
When the news of the curative properties of penicillin broke, Fleming revelled in the publicity. Journalists told a familiar story of a lone British scientist and a serendipitous discovery. The British medical historian Bill Bynum wrote:
In 1943, the Nobel committee received a single nomination for the Nobel Prize in Physiology or Medicine for Fleming and Florey from the British biochemist Rudolph Peters. The secretary of the Nobel committee, Göran Liljestrand, made an assessment of Fleming and Florey in the same year, but little was known about penicillin in Sweden at the time, and he concluded that more information was required. The following year, there was one nomination for Fleming alone and one for Fleming, Florey and Chain. Liljestrand and Nanna Svartz considered their work, and while both judged Fleming and Florey equally worthy of a Nobel Prize, the Nobel committee was divided, and decided to award the prize that year to Joseph Erlanger and Herbert S. Gasser instead.
In 1945 there were a large number of nominations for Florey and Fleming or both, and one for Chain, from Liljestrand, who nominated all three. Liljestrand noted that thirteen of the first sixteen nominations that came in mentioned Fleming, but only three mentioned him alone. This time evaluations were made by Liljestrand, and , who endorsed all three. The Nobel Assembly at the Karolinska Institute considered awarding half to Fleming and one-quarter each to Florey and Chain, but in the end decided to divide it equally three ways. On 25 October 1945, it announced that Fleming, Florey and Chain equally shared the 1945 Nobel Prize in Physiology or Medicine "for the discovery of penicillin and its curative effect in various infectious diseases." | 1 | Applied and Interdisciplinary Chemistry |
A wide variety of algorithms have been developed to facilitate detection of promoters in genomic sequence, and promoter prediction is a common element of many gene prediction methods. A promoter region is located before the -35 and -10 Consensus sequences. The closer the promoter region is to the consensus sequences the more often transcription of that gene will take place. There is not a set pattern for promoter regions as there are for consensus sequences. | 1 | Applied and Interdisciplinary Chemistry |
Trisoxazolines have been used for the copper catalysed Friedel–Crafts alkylation of indoles, largely with alkylidene malonates, with good yields and ee's reported. A number of interesting solvent effects have also been observed, including a relationship between enantioselectivity and the steric bulk of the solvent when using of alcohols and a reversal of enantioselectivity when changing the reaction solvent from coordinating solvents to weakly coordinating solvents. | 0 | Theoretical and Fundamental Chemistry |
Using the Weed Science Society of America (WSSA) and herbicide Resistance and World Grains (HRAC) systems, herbicides are classified by mode of action. Eventually the Herbicide Resistance Action Committee (HRAC) and the Weed Science Society of America (WSSA) developed a classification system. Groups in the WSSA and the HRAC systems are designated by numbers and letters, inform users awareness of herbicide mode of action and provide more accurate recommendations for resistance management. | 1 | Applied and Interdisciplinary Chemistry |
The central carbon in 1,3-dicarbonyl compound is known as an activated methylene group. This is because, owing to the structure, the carbon is especially acidic and can easily be deprotonated to form a methylene group. | 0 | Theoretical and Fundamental Chemistry |
Some DNA viruses encode a recombinase that facilitates homologous recombination. A well-studied example is the UvsX recombinase encoded by bacteriophage T4. UvsX is homologous to bacterial RecA. UvsX, like RecA, can facilitate the assimilation of linear single-stranded DNA into an homologous DNA duplex to produce a D-loop. | 1 | Applied and Interdisciplinary Chemistry |
Turbidimetry (the name being derived from turbidity) is the process of measuring the loss of intensity of transmitted light due to the scattering effect of particles suspended in it. Light is passed through a filter creating a light of known wavelength which is then passed through a cuvette containing a solution. A photoelectric cell collects the light which passes through the cuvette. A measurement is then given for the amount of absorbed light.
Turbidimetry can be used in biology to find the number of cells in a suspension.
Turbidity-is an expression of optical look of a suspension caused by radiation to the scattered and absorbed wavelength. Scattering of light is elastic so both incident and scattered radiation have same wavelength.
A turbidometer measures the amount of radiation that passes through a fluid in forward direction, analogous to absorption spectrophotometry.
Standard for turbidimetry is prepared by dissolving 5g of hydrazinium (2+) sulfate(N2H4H2SO4) and 50g of hexamethylenetertramine in 1liter of distilled water is defined as 4000 nephelometric Turbidity Unit(NTU)
Application
Determination of water
Clarity of pharma products and drinks
Immunoassay in lab
Turbidimetry offers little advantage than nephelometry in measurement of sensitivity in low level antigen a antibody immunoassay.
Antigen excess and matrix effects are limitations encountered | 0 | Theoretical and Fundamental Chemistry |
Using a single body-centered cubic colloidal crystal, the occurrence of Kossel lines in diffraction patterns were used to monitor the initial nucleation and subsequent motion caused distortion of the crystal. Continuous or homogeneous deformations occurring beyond the elastic limit produce a flowing crystal, where the nucleation site density increases significantly with increasing particle concentration. Lattice dynamics have been investigated for longitudinal as well as transverse modes. The same technique was used to evaluate the crystallization process near the edge of a glass tube. The former might be considered analogous to a homogeneous nucleation event—whereas the latter would clearly be considered a heterogeneous nucleation event, being catalyzed by the surface of the glass tube. | 0 | Theoretical and Fundamental Chemistry |
Radicals are either (1) formed from spin-paired molecules or (2) from other radicals. Radicals are formed from spin-paired molecules through homolysis of weak bonds or electron transfer, also known as reduction. Radicals are formed from other radicals through substitution, addition, and elimination reactions. | 1 | Applied and Interdisciplinary Chemistry |
Darodipine is an experimental calcium channel blocker that based on animal models may reduce neuronal cytoskeletal alterations during aging and in neurodegenerative disorders. Studies performed on rats have shown darodipine to have an effect on brain serotonergic systems. Darodipine increased the 5-HIAA/5-HT ratio within various parts of the brain. Darodipine has also been shown to impair memory and learning processes on mice.
The longterm effect of darodipine was tested in the rats and it shows that there is no significant change in their body and brain weight values but, there is a significant change in their alkaline phosphate reactive capillary profile values. Alkaline phosphate enzymes plays an important role in the functioning of the cerebral capillary activities. The effect of darodipine on plasma concentration was also tested on a group of healthy male human volunteers. The result showed that darodipine resulted in the change in heart rate and diastolic blood pressure which is related to the plasma concentration.
Darodipine (50–500 nM), the sensitivity of DMPO‐COO.− adduct decreased by more than that of the DMPO‐OH adduct and the concentration-dependent drop in signal intensity. It has additional preventive effects, because of its calcium antagonistics, against free-radical mediated electrophysiological alterations; it is likely because of the trapping of such radical molecules. | 1 | Applied and Interdisciplinary Chemistry |
In 2010 bay health improved slightly in terms of the overall health of its ecosystem, earning a rating of 31 out of 100, up from a 28 rating in 2008. An estimate in 2006 from a "blue ribbon panel" said cleanup costs would be $15 billion. Compounding the problem is that 100,000 new residents move to the area each year. A 2008 Washington Post report suggested that government administrators had overstated progress on cleanup efforts as a way to "preserve the flow of federal and state money to the project." In January 2011, there were reports that millions of fish had died, but officials suggested it was probably the result of extremely cold weather.
The health of the Chesapeake Bay improved in 2015, marking three years of gains over a four-year period, according to a 2016 report by the University of Maryland Center for Environmental Science (UMCES). In 2021 scientists at the UMCES reported slight improvements in bay water quality compared to levels measured in 2020. The greatest improvements were seen in the lower bay areas, while the Patapsco River and Back River (Maryland) regions showed minimal improvement. Positive indicators included decreased nitrogen levels and increases in dissolved oxygen.
The CBF reported that as of 2022 pollution control efforts in the bay have continued to show mixed results, with no improvement in levels of toxic contaminants, nitrogen and dissolved oxygen, and a small decrease in water clarity compared to 2020 levels (measured as Secchi depth). Oyster and rockfish populations in the bay have improved, but blue crab populations have continued to decline. | 1 | Applied and Interdisciplinary Chemistry |
Current Medicinal Chemistry is a peer-reviewed medical journal published by Bentham Science Publishers. The editor-in-chief is Atta-ur-Rahman, FRS (Kings College University of Cambridge Cambridge, UK). The journal covers developments in medicinal chemistry and rational drug design and publishes original research reports and review papers.
A related journal titled Current Medicinal Chemistry – Anti-Cancer Agents was launched in 2001, and retitled as Anti-Cancer Agents in Medicinal Chemistry from the start of 2006 with (print), (online). | 1 | Applied and Interdisciplinary Chemistry |
In thermodynamics, an adiabatic wall between two thermodynamic systems does not allow heat or chemical substances to pass across it, in other words there is no heat transfer or mass transfer.
In theoretical investigations, it is sometimes assumed that one of the two systems is the surroundings of the other. Then it is assumed that the work transferred is reversible within the surroundings, but in thermodynamics it is not assumed that the work transferred is reversible within the system. The assumption of reversibility in the surroundings has the consequence that the quantity of work transferred is well defined by macroscopic variables in the surroundings. Accordingly, the surroundings are sometimes said to have a reversible work reservoir.
Along with the idea of an adiabatic wall is that of an adiabatic enclosure. It is easily possible that a system has some boundary walls that are adiabatic and others that are not. When some are not adiabatic, then the system is not adiabatically enclosed, though adiabatic transfer of energy as work can occur across the adiabatic walls.
The adiabatic enclosure is important because, according to one widely cited author, Herbert Callen, "An essential prerequisite for the measurability of energy is the existence of walls that do not permit the transfer of energy in the form of heat." In thermodynamics, it is customary to assume a priori the physical existence of adiabatic enclosures, though it is not customary to label this assumption separately as an axiom or numbered law. | 0 | Theoretical and Fundamental Chemistry |
A biaxial nematic is a spatially homogeneous liquid crystal with three distinct optical axes. This is to be contrasted to a simple nematic, which has a single preferred axis, around which the system is rotationally symmetric. The symmetry group of a biaxial nematic is i.e. that of a rectangular right parallelepiped, having 3 orthogonal axes and three orthogonal mirror planes. In a frame co-aligned with optical axes the second rank order parameter tensor of a biaxial nematic has the form
where is the standard nematic scalar order parameter and is a measure of the biaxiality.
The first report of a thermotropic biaxial nematic appeared in 2004 based on a boomerang shaped oxadiazole bent-core mesogen. The biaxial nematic phase for this particular compound only occurs at temperatures around 200 °C and is preceded by as yet unidentified smectic phases.
It is also found that this material can segregate into chiral domains of opposite handedness. For this to happen the boomerang shaped molecules adopt a helical superstructure.
In one azo bent-core mesogen a thermal transition is found from a uniaxial N to a biaxial nematic N mesophase, as predicted by theory and simulation. This transition is observed on heating from the N phase with Polarizing optical microscopy as a change in Schlieren texture and increased light transmittance and from x-ray diffraction as the splitting of the nematic reflection. The transition is a second order transition with low energy content and therefore not observed in differential scanning calorimetry. The positional order parameter for the uniaxial nematic phase is 0.75 to 1.5 times the mesogen length and for the biaxial nematic phase 2 to 3.3 times the mesogen length.
Another strategy towards biaxial nematics is the use of mixtures of classical rodlike mesogens and disklike discotic mesogens. The biaxial nematic phase is expected to be located below the minimum in the rod-disk phase diagram. In one study a miscible system of rods and disks is actually found although the biaxial nematic phase remains elusive. | 0 | Theoretical and Fundamental Chemistry |
Sampling is largely outside the control of the Public Analyst.
Local authorities have a duty to check the safety of food and to provide adequate protection of the consumer. To achieve that, they devise sampling plans, seeking to balance their need to monitor food against limited resources and other demands on their budgets. A typical sampling plan for a local authority might include samples of the following:
* samples from a particular source - a supermarket, manufacturer or caterer or country
* meat products - to check %meat or %fat or non-meat or additives or species
* product marketing claims
* undeclared ingredients in prepared foods
* contaminated products
* nutritional content of prepared meals | 1 | Applied and Interdisciplinary Chemistry |
Drug repurposing and chiral switches are part of the secondary pharmaceuticals strategy. The COVID-19 pandemic has increased drug repurposing and this approach suggests combining the two strategies for better results. This combination strategy is not new, but has not been intentional until now. The combination strategy may improve pharmacology, patents, reduce costs, speed up approval times, and increase regulatory exclusivities. The benefits of the combination strategy include superior pharmacology, stronger patents, shorter approval times, and more exclusivity. Patenting this combination strategy is not considered evergreening, product hopping, or me-too. This perspective calls for a comprehensive search for worldwide-approved racemic drugs to be repurposed and combined with chiral switches. | 0 | Theoretical and Fundamental Chemistry |
In 2023, researchers in the United States developed a method to determine BET surface areas using a thermogravimetric analyzer (TGA). This method uses a TGA to heat a porous sample loaded with an adsorbate, the produced plot of sample mass vs. temperature is then mapped into a standard isotherm to which BET theory is applied as normal. Common fluids, e.g. water or toluene, can be used as adsorbates for the TGA method allowing the specific interactions of different adsorbates to be determined, as these frequently differ from the commonly used nitrogen. | 0 | Theoretical and Fundamental Chemistry |
In genetic engineering, the 2A peptides are used to cleave a longer peptide into two shorter peptides. The 2A peptides can be applied when the fused protein doesn’t work. Inserting the CDS of a 2A peptide into the fusing point or replacing the linker sequence with the CDS of a 2A peptide protein can cleave the fused protein into two separated peptides, rescuing the function of the two peptides.
2A peptides, when combined (or not) with the IRES elements, can make it possible to generate multiple separated peptides within a single transcript. | 1 | Applied and Interdisciplinary Chemistry |
For several centuries, farmers knew that certain nutrients were essential for plant growth. In different parts of the world, farmers developed different methods of fertilizing the farmland. In China, human waste was scattered in rice fields. Justus von Liebig (1803 – 1873), German chemist and founder of industrial agriculture, claimed that England had "stolen" 3.5 million skeletons from Europe to obtain phosphorus for fertilizer. In Paris, as many as one million tons of horse dung was collected annually to fertilize city gardens. Throughout the nineteenth century, bison bones from the American West were brought back to East Coast factories for the production of phosphorus and phosphate fertilizer.
From the 1820s to the 1860s, the Chincha Islands of Peru were exploited for their high quality guano deposits, which they exported to the United States, France and the United Kingdom. The guano-boom increased economic activity in Peru considerably for a few decades until all 12.5 million tons of guano deposits were exhausted.
Research was initiated to find alternative sources of fertilizer. The Atacama Desert, at that time part of Peru, was home to significant amounts of saltpeter (sodium nitrate). At the time of the discovery of these deposits, the saltpeter had limited agricultural use. Then chemists successfully developed a process to purify the saltpeter in order to produce gunpowder. The saltpeter was also converted into nitric acid, the precursor of powerful explosives, such as nitroglycerine and dynamite. As exports from this region increased, tensions between Peru and its neighbors increased as well.
In 1879, Bolivia, Chile, and Peru went to war over possession of Atacama Desert, the so-called "Saltpeter War". Bolivian forces were quickly defeated by the Chileans. In 1881, Chile defeated Peru and seized control of nitrate exploitation in the Atacama Desert. Consumption of Chilean saltpeter for agriculture quickly grew and Chileans standard of living rose significantly.
Technological developments in Europe brought an end to these days. In the twentieth century, the minerals from this region "contribute[d] minimally to global nitrogen supply." | 1 | Applied and Interdisciplinary Chemistry |
The axes of the Frost diagram show (horizontally) the oxidation state of the species in question and (vertically) the electron exchange number multiplied by the voltage (nE) or the Gibbs free energy per unit of the Faraday constant, ΔG/F. | 0 | Theoretical and Fundamental Chemistry |
The total stress on the bed of an open channel of infinite width is given by the hydrostatic pressure acting on the bed. For a fluid of density , an acceleration due to gravity , and a flow depth , the pressure exerted on the bed is simply the weight of an element of fluid, , times the depth of the flow, . From this, we get the expression for the total pressure, , acting on the bed. | 1 | Applied and Interdisciplinary Chemistry |
Because ELPs are protein-based biopolymers, synthesis involves manipulation of genes to continually express the monomeric repeat unit. Various techniques have been employed in the production of ELPs of various sizes, including unidirectional ligation or concatemerization, overlap extension polymerase chain reaction (OEPCR), and recursive directional ligation (RDL). Also, ELPs can be experimentally modified through conjugation with other polymers or through SpyTag/SpyCatcher reaction, allowing for the synthesis of copolymers with unique morphology. | 0 | Theoretical and Fundamental Chemistry |
Because of the magnitude and severity of the problems with chemical shift referencing in biomolecular NMR, a number of computer programs have been developed to help mitigate the problem (see Table 1 for a summary). The first program to comprehensively tackle chemical shift mis-referencing in biomolecular NMR was SHIFTCOR.
Table 1. Summary and comparison of different chemical shift re-referencing and mis-assignment detection programs. | 0 | Theoretical and Fundamental Chemistry |
Source: [https://crcq.ca/prix-michel-sarrazin/ CRCQ]
*1977 – Michel Chrétien
*1978 – Jean-Marie Delage
*1979 – Guy Lemieux
*1980 – Charles Philippe Leblond
*1981 – René Simard
*1982 – Louis Poirier
*1983 – André Barbeau
*1984 – Jacques R. Ducharme
*1985 – André Lanthier
*1986 – Claude Fortier
*1987 – Domenico Regoli
*1988 – Charles Scriver
*1989 – Serge Carrière
*1990 – Fernand Labrie
*1991 – Étienne LeBel
*1992 – Réginald Nadeau
*1993 – Claude C. Roy
*1994 – Jacques Leblanc
*1995 – Clarke Fraser
*1996 – Jacques Genest
*1997 – Samuel Solomon
*1998 – Jacques de Champlain
*1999 – Claude Laberge
*2000 – Martial G. Bourassa
*2001 – Jean Davignon
*2002 – Brenda Milner
*2003 – Peter T. Macklem
*2004 – Francis Glorieux
*2005 – Pavel Hamet
*2006 – Marek Rola-Pleszczynski
*2007 – Rémi Quirion
*2008 – Serge Rossignol
*2009 – Jacques P. Tremblay
*2010 – Michel Bouvier
*2011 – Stanley Nattel
*2012 – Michel L. Tremblay
*2013 – Vassilios Papadopoulos
*2014 – Roger Lecomte
*2015 – Claude Perreault
*2016 – Michel G. Bergeron
*2017 – Anne-Marie Mes-Masson
*2018 – William D. Fraser | 1 | Applied and Interdisciplinary Chemistry |
Nitrate was also used as a film stock through nitrocellulose. Due to its high combustibility, the studios swapped to acetate safety film in 1950. | 0 | Theoretical and Fundamental Chemistry |
Cyclamin can be extracted from cyclamen plants such as the species mirabile and trocopteranthum. Cyclamen are known houseplants; this raises concerns about the awareness of the toxicity of this flower. The compound cyclamin belongs to the family of triterpene saponins, which are derived from the saponin structure. Triterpenoid compounds contain one or more sugar moieties attached to triterpenoid aglycones. The large diversity of structures causes saponins to exhibit a wide range of biological and pharmacological properties. In China, cyclamin has been used as a traditional medicine for years. Cyclamen has been used against menstrual disorders, digestive disorders, and anxiety in women. However, this is only the case for the leaves, the roots of the plants are known to be harmful if ingested. In these roots, cyclamin is found, as well as in the bulbs. Therefore, cyclamin is suspected to be the compound which causes the toxicity of these roots and bulbs in cyclamen plants. | 0 | Theoretical and Fundamental Chemistry |
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 | Theoretical and Fundamental Chemistry |
Hypoxia can modify normal behavior. Parental behaviour meant to provide oxygen to the eggs is often affected by hypoxia. For example, fanning behavior (swimming on the spot near the eggs to create a flow of water over them, and thus a constant supply of oxygen) is often increased when oxygen is less available. This has been documented in sticklebacks, gobies, and clownfishes, among others. Gobies may also increase the size of the openings in the nest they build, even though this may increase the risk of predation on the eggs. Rainbow cichlids often move their young fry closer to the water surface, where oxygen is more available, during hypoxic episodes.
Behavioural adaptations meant to survive when oxygen is scarce include reduced activity levels, aquatic surface respiration, and air breathing. | 0 | Theoretical and Fundamental Chemistry |
Sulfinamides do not undergo inversion. They can therefore be synthesised and/or isolated in enantiopure forms. This has led to their use as chiral ammonia equivalents and more broadly as chiral auxiliaries. | 0 | Theoretical and Fundamental Chemistry |
In 2010, when Craig Venter unveiled the first fully functioning, reproducing cell controlled by synthetic DNA he described how his team used frequent stop codons to create watermarks in RNA and DNA to help confirm the results were indeed synthetic (and not contaminated or otherwise), using it to encode authors' names and website addresses. | 1 | Applied and Interdisciplinary Chemistry |
Each fission of a parent atom produces a different set of fission product atoms. However, while an individual fission is not predictable, the fission products are statistically predictable. The amount of any particular isotope produced per fission is called its yield, typically expressed as percent per parent fission; therefore, yields total to 200%, not 100%. (The true total is in fact slightly greater than 200%, owing to rare cases of ternary fission.)
While fission products include every element from zinc through the lanthanides, the majority of the fission products occur in two peaks. One peak occurs at about (expressed by atomic masses 85 through 105) strontium to ruthenium while the other peak is at about tellurium to neodymium (expressed by atomic masses 130 through 145). The yield is somewhat dependent on the parent atom and also on the energy of the initiating neutron.
In general the higher the energy of the state that undergoes nuclear fission, the more likely that the two fission products have similar mass. Hence, as the neutron energy increases and/or the energy of the fissile atom increases, the valley between the two peaks becomes more shallow.
For instance, the curve of yield against mass for Pu has a more shallow valley than that observed for U when the neutrons are thermal neutrons. The curves for the fission of the later actinides tend to make even more shallow valleys. In extreme cases such as Fm, only one peak is seen; this is a consequence of symmetric fission becoming dominant due to shell effects.
The adjacent figure shows a typical fission product distribution from the fission of uranium. Note that in the calculations used to make this graph, the activation of fission products was ignored and the fission was assumed to occur in a single moment rather than a length of time. In this bar chart results are shown for different cooling times (time after fission).
Because of the stability of nuclei with even numbers of protons and/or neutrons, the curve of yield against element is not a smooth curve but tends to alternate. Note that the curve against mass number is smooth. | 0 | Theoretical and Fundamental Chemistry |
To date, the use of rAAV mediated genome engineering has been published in over 2100 peer reviewed scientific journals.
Another emerging application of rAAV based genome editing is for gene therapy in patients, due to the accuracy and lack of off-target recombination events afforded by the approach. | 1 | Applied and Interdisciplinary Chemistry |
C-reactive protein (CRP), a marker of systemic inflammation, is also increased in obstructive sleep apnea (OSA). CRP and interleukin-6 (IL-6) levels were significantly higher in patients with OSA compared to obese control subjects. Patients with OSA have higher plasma CRP concentrations that increased corresponding to the severity of their apnea-hypopnea index score. Treatment of OSA with CPAP (continuous positive airway pressure) significantly alleviated the effect of OSA on CRP and IL-6 levels. | 1 | Applied and Interdisciplinary Chemistry |
The STAT3-Ser/Hes3 signaling axis is a specific type of intracellular signaling pathway that regulates several fundamental properties of cells. | 1 | Applied and Interdisciplinary Chemistry |
Dynamic energy budget theory presents a quantitative framework of metabolic organization common to all life forms, which could help to understand evolution of metabolic organization since the origin of life. As such, it has a common aim with the other widely used metabolic theory: the West-Brown-Enquist (WBE) metabolic theory of ecology, which prompted side-by-side analysis of the two approaches. Though the two theories can be regarded as complementary to an extent, they were built on different assumptions and have different scope of applicability. In addition to a more general applicability, the DEB theory does not suffer from consistency issues pointed out for the WBE theory. | 1 | Applied and Interdisciplinary Chemistry |
The compilation contains information about the electromagnetic scattering by hexagonal ice crystals, large raindrops, and relevant links and applications. | 0 | Theoretical and Fundamental Chemistry |
Material may be separated by means of air elutriation, which employs an apparatus with a vertical tube through which fluid is passed at a controlled velocity. When the particles are introduced, often through a side tube, the smaller particles are carried over in the fluid stream while the large particles settle against the upward current. If we start with low flow rates small less dense particle attain terminal velocities, and flow with the stream, the particle from the stream is collected in overflow and hence will be separated from the feed. Flow rates can be increased to separate higher size ranges. Further size fractions may be collected if the overflow from the first tube is passed vertically upwards through a second tube of greater cross-section, and any number of such tubes can be arranged in series.
Advantages: a bulk sample is analyzed using centrifugal classification and the technique is non-destructive. Each cut-point can be recovered for future size-respective chemical analyses. This technique has been used for decades in the air pollution control industry (data used for design of control devices). This technique determines particle size as a function of settling velocity in an air stream (as opposed to water, or some other liquid).
Disadvantages: a bulk sample (about ten grams) must be obtained. It is a fairly time-consuming analytical technique. The actual test method has been withdrawn by ASME due to obsolescence. Instrument calibration materials are therefore no longer available. | 0 | Theoretical and Fundamental Chemistry |
The business of automated mineralogy is concerned with the commercialisation of the technology and software in terms of development and marketing of integrated solutions. This includes all aspects of: service; maintenance; customer support; R&D; marketing and sales. Customers of automated mineralogy solutions include: laboratory facilities; mine sites, well sites, and research institutions. | 0 | Theoretical and Fundamental Chemistry |
The end groups that are found on polymers formed through free radical polymerization are a result from the initiators and termination method used. There are many types of initiators used in modern free radical polymerizations, and below are examples of some well-known ones. For example, azobisisobutyronitrile or AIBN forms radicals that can be used as the end groups for new starting polymer chains with styrene to form polystyrene. Once the polymer chain has formed and the reaction is terminated, the end group opposite from the initiator is a result of the terminating agent or the chain transfer agent used. | 0 | Theoretical and Fundamental Chemistry |
It was first shown by Faraday that optical activity (the Faraday effect) could be induced in matter by a longitudinal magnetic field (a field in the direction of light propagation). The development of MCD really began in the 1930s when a quantum mechanical theory of MOR (magnetic optical rotatory dispersion) in regions outside absorption bands was formulated. The expansion of the theory to include MCD and MOR effects in the region of absorptions, which were referred to as "anomalous dispersions" was developed soon thereafter. There was, however, little effort made to refine MCD as a modern spectroscopic technique until the early 1960s. Since that time there have been numerous studies of MCD spectra for a very large variety of samples, including stable molecules in solutions, in isotropic solids, and in the gas phase, as well as unstable molecules entrapped in noble gas matrices. More recently, MCD has found useful application in the study of biologically important systems including metalloenzymes and proteins containing metal centers. | 0 | Theoretical and Fundamental Chemistry |
Many metal sulfides are so insoluble in water that they are probably not very toxic. Some metal sulfides, when exposed to a strong mineral acid, including gastric acids, will release toxic hydrogen sulfide.
Organic sulfides are highly flammable. When a sulfide burns it produces sulfur dioxide (SO) gas.
Hydrogen sulfide, some of its salts, and almost all organic sulfides have a strong and putrid stench; rotting biomass releases these. | 0 | Theoretical and Fundamental Chemistry |
A hydrotrope is a compound that solubilizes hydrophobic compounds in aqueous solutions by means other than micellar solubilization. Typically, hydrotropes consist of a hydrophilic part and a hydrophobic part (similar to surfactants), but the hydrophobic part is generally too small to cause spontaneous self-aggregation. Hydrotropes do not have a critical concentration above which self-aggregation spontaneously starts to occur (as found for micelle- and vesicle-forming surfactants, which have a critical micelle concentration (cmc) and a critical vesicle concentration (cvc)). Instead, some hydrotropes aggregate in a step-wise self-aggregation process, gradually increasing aggregation size. However, many hydrotropes do not seem to self-aggregate at all, unless a solubilizate has been added. Examples of hydrotropes include urea, tosylate, cumenesulfonate and xylenesulfonate.
The term hydrotropy was originally put forward by Carl Neuberg to describe the increase in the solubility of a solute by the addition of fairly high concentrations of alkali metal salts of various organic acids. However, the term has been used in the literature to designate non-micelle-forming substances, either liquids or solids, capable of solubilizing insoluble compounds.
The chemical structure of the conventional Neuberg's hydrotropic salts (proto-type, sodium benzoate) consists generally of two essential parts, an anionic group and a hydrophobic aromatic ring or ring system. The anionic group is involved in bringing about high aqueous solubility, which is a prerequisite for a hydrotropic substance. The type of anion or metal ion appeared to have a minor effect on the phenomenon. On the other hand, planarity of the hydrophobic part has been emphasized as an important factor in the mechanism of hydrotropic solubilization
To form a hydrotrope, an aromatic hydrocarbon solvent is sulfonated, creating an aromatic sulfonic acid. It is then neutralized with a base.
Additives may either increase or decrease the solubility of a solute in a given solvent. These salts that increase solubility are said to "salt in" the solute and those salts that decrease the solubility "salt out" the solute. The effect of an additive depends very much on the influence it has on the structure of water or its ability to compete with the solvent water molecules.
A convenient quantitation of the effect of a solute additive on the solubility of another solute may be obtained by the Setschetow equation:
where
: S is the solubility in the absence of the additive
: S is the solubility in the presence of the additive
: C is the concentration of the additive
: K is the salting coefficient, which is a measure of the sensitivity of the activity coefficient of the solute towards the salt. | 0 | Theoretical and Fundamental Chemistry |
During the last couple of years there has been developments of CSPs based on novel chiral selectors viz. chitosan derivatives, cylofructan derivatives and chiral porous materials for HPLC chiral separation. | 0 | Theoretical and Fundamental Chemistry |
The ideal picture of liquid state NMR (LSNMR) quantum information processing (QIP) is based on a molecule in which some of its atom's nuclei behave as spin-½ systems. Depending on which nuclei we are considering they will have different energy levels and different interaction with its neighbours and so we can treat them as distinguishable qubits. In this system we tend to consider the inter-atomic bonds as the source of interactions between qubits and exploit these spin-spin interactions to perform 2-qubit gates such as CNOTs that are necessary for universal quantum computation. In addition to the spin-spin interactions native to the molecule an external magnetic field can be applied (in NMR laboratories) and these impose single qubit gates. By exploiting the fact that different spins will experience different local fields we have control over the individual spins.
The picture described above is far from realistic since we are treating a single molecule. NMR is performed on an ensemble of molecules, usually with as many as 10^15 molecules. This introduces complications to the model, one of which is introduction of decoherence. In particular we have the problem of an open quantum system interacting with a macroscopic number of particles near thermal equilibrium (~mK to ~300 K). This has led the development of decoherence suppression techniques that have spread to other disciplines such as trapped ions. The other significant issue with regards to working close to thermal equilibrium is the mixedness of the state. This required the introduction of ensemble quantum processing, whose principal limitation is that as we introduce more logical qubits into our system we require larger samples in order to attain discernable signals during measurement. | 0 | Theoretical and Fundamental Chemistry |
In cardiac ventriculography, a radionuclide, usually Tc, is injected, and the heart is imaged to evaluate the flow through it, to evaluate coronary artery disease, valvular heart disease, congenital heart diseases, cardiomyopathy, and other cardiac disorders. As a nuclear stress test, the average radiation exposure is 9.4 mSv, which when compared with a typical 2 view chest X-ray (.1 mSv) is equivalent to 94 Chest X-Rays. It exposes patients to less radiation than comparable chest X-ray studies. | 0 | Theoretical and Fundamental Chemistry |
This technology can be used to diminish the effect of droughts by effectively treating the wastewater in such a way that it can be reused, specifically for agricultural purposes.
In addition, the AnMBR properly treats the organic load in wastewater such that it is not being released into the environment. The technology also produces less sludge due to the conversion into biogas, which provides more of an opportunity for recycling.
When compared to its counterparts, the traditional Membrane Bioreactor and the Aerobic Membrane Bioreactor, the AnMBR comes up ahead due to the higher quality of effluent that it discharges as well as the lesser amount of sludge, due to biogas production. | 1 | Applied and Interdisciplinary Chemistry |
The principle of minimum energy is essentially a restatement of the second law of thermodynamics. It states that for a closed system, with constant external parameters and entropy, the internal energy will decrease and approach a minimum value at equilibrium. External parameters generally means the volume, but may include other parameters which are specified externally, such as a constant magnetic field.
In contrast, for isolated systems (and fixed external parameters), the second law states that the entropy will increase to a maximum value at equilibrium. An isolated system has a fixed total energy and mass. A closed system, on the other hand, is a system which is connected to another, and cannot exchange matter (i.e. particles), but can transfer other forms of energy (e.g. heat), to or from the other system. If, rather than an isolated system, we have a closed system, in which the entropy rather than the energy remains constant, then it follows from the first and second laws of thermodynamics that the energy of that system will drop to a minimum value at equilibrium, transferring its energy to the other system. To restate:
* The maximum entropy principle: For a closed system with fixed internal energy (i.e. an isolated system), the entropy is maximized at equilibrium.
* The minimum energy principle: For a closed system with fixed entropy, the total energy is minimized at equilibrium. | 0 | Theoretical and Fundamental Chemistry |
Cavitation plays a role in the spore dispersal mechanisms of certain plants. In ferns, for example, the fern sporangium acts as a catapult that launches spores into the air. The charging phase of the catapult is driven by water evaporation from the annulus cells, which triggers a pressure decrease. When the compressive pressure reaches approximately 9MPa, cavitation occurs. This rapid event triggers spore dispersal due to the elastic energy released by the annulus structure. The initial spore acceleration is extremely large – up to 10 times the gravitational acceleration. | 1 | Applied and Interdisciplinary Chemistry |
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