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Commercially available siliconates include potassium methyl siliconate (CAS 31795-24-1, CHKOSi) and sodium methyl siliconate (CAS 16589-43-8, CHNaOSi). These are supplied as a concentrate in water with an active content of between 30 and 40% by weight. This solution is further diluted in water prior to their application by spraying, dipping or rolling to a mineral building material, such as brickwork, to make the surface water repellent. The dilution is clear, stable with a high pH of 13 to 14. When applied to a surface the siliconate reacts with carbon dioxide in the air to form an insoluble water resistant treatment within 24 hours.
:CHKOSi + silanol functional substrate OHSi → CHOSi + KOH
The methyl group has now attached itself to the substrata.
:2KOH + CO → KCO + HO
The salts formed by this reaction are often the cause of white efflorescence when too much of the solution is applied to the surface. | 0 | Theoretical and Fundamental Chemistry |
Depletion of inorganic phosphate within the cell is required for activation of the Pho regulon in most prokaryotes. In the most commonly studied bacterium, E. coli, seven total proteins are used to detect intracellular levels of inorganic phosphate along with transfusing that signal appropriately. Of the seven proteins, one is a metal binding protein (PhoU) and four are phosphate-specific transporters (Pst S, Pst C, Pst A, and Pst B). The transcriptional response regulator PhoR activates PhoB when it senses low intracellular inorganic phosphate levels. | 1 | Applied and Interdisciplinary Chemistry |
A number of metal halides intercalate into graphite. The chloride derivatives have been most extensively studied. Examples include (M = Zn, Ni, Cu, Mn), (M = Al, Fe, Ga), (M = Zr, Pt), etc. The materials consists of layers of close-packed metal halide layers between sheets of carbon. The derivative exhibits spin glass behavior. It proved to be a particularly fertile system on which to study phase transitions. A stage n magnetic graphite intercalation compounds has n graphite layers separating successive magnetic layers. As the stage number increases the interaction between spins in successive magnetic layers becomes weaker and 2D magnetic behaviour may arise. | 0 | Theoretical and Fundamental Chemistry |
Rodents are usually used in animal test. The chemicals under
test are usually administered in the food and in the drinking water, but sometimes by dermal application, by gavage, or by inhalation, and carried out over the major part of the life span for rodents. In tests that check for carcinogens, maximum tolerated dosage is first determined, then a range of doses are given to around 50 animals throughout the notional lifespan of the animal of two years. After death the animals are examined for sign of tumours. Differences in metabolism between rat and human however means that human may not respond in exactly the same way to mutagen, and dosages that produce tumours on the animal test may also be unreasonably high for a human, i.e. the equivalent amount required to produce tumours in human may far exceed what a person might encounter in real life.
Mice with recessive mutations for a visible phenotype may also be used to check for mutagens. Females with recessive mutation crossed with wild-type males would yield the same phenotype as the wild-type, and any observable change to the phenotype would indicate that a mutation induced by the mutagen has occurred.
Mice may also be used for dominant lethal assays where early embryonic deaths are monitored. Male mice are treated with chemicals under test, mated with females, and the females are then sacrificed before parturition and early fetal deaths are counted in the uterine horns.
Transgenic mouse assay using a mouse strain infected with a viral shuttle vector is another method for testing mutagens. Animals are first treated with suspected mutagen, the mouse DNA is then isolated and the phage segment recovered and used to infect E. coli. Using similar method as the blue-white screen, the plaque formed with DNA containing mutation are white, while those without are blue. | 0 | Theoretical and Fundamental Chemistry |
An enzyme repressor is a substance that negatively regulates the amount of an enzyme by decreasing the rate of its biosynthesis. It is the opposite of an enzyme inducer. | 1 | Applied and Interdisciplinary Chemistry |
Nanorods, similar in size to quantum dots, have tunable optical and electronic properties. Based on their size and material composition, it is possible to tune the maximum absorption peak for nanorods during their synthesis. This control has led to the creation of photosensitizing nanorods. | 0 | Theoretical and Fundamental Chemistry |
Golden Elixir Press is an independent publisher of books and occasional papers on Taoism and Taoist Internal Alchemy (Neidan). The press was founded in 2009. As of March 2019, it had published about two dozen works, some of which are concerned with other traditions, such as Hinduism, Buddhism, and Sufism.
According to an interview with the press founder, originally published in the Silent Tao website, the intended audience of Golden Elixir Press is "everyone who is interested for any reason in the doctrines of the Way of the Golden Elixir". Although the books published by the press are mainly addressed to the general public, they have also been well-received by the academic community.
Publications of Golden Elixir Press include translations of some of the main texts of Taoist Internal Alchemy: the Cantong qi (Seal of the Unity of the Three), the Wuzhen pian (Awakening to Reality), and the Yinfu jing (Book of the Hidden Agreement).
The press is closely related to Fabrizio Pregadio, a scholar who, in addition to his academic research, publishes translations of original Chinese texts addressed to a wider audience. | 1 | Applied and Interdisciplinary Chemistry |
Trommel screens have a rotating drum on a shallow angle with screen panels around the diameter of the drum. The feed material always sits at the bottom of the drum and, as the drum rotates, always comes into contact with clean screen. The oversize travels to the end of the drum as it does not pass through the screen, while the undersize passes through the screen into a launder below. | 1 | Applied and Interdisciplinary Chemistry |
DPN evolved directly from AFM so it is not a surprise that people often assume that any commercial AFM can perform DPN experiments. In fact, DPN does not require an AFM, and an AFM does not necessarily have real DPN capabilities. There is an excellent analogy with scanning electron microscopy (SEM) and electron beam (E-beam) lithography. E-beam evolved directly from SEM technology and both use a focused electron beam, but it is not possible to perform modern E-beam lithography experiments on a SEM that lacks the proper lithography hardware and software components.
It is also important to consider one of the unique characteristics of DPN, namely its force independence. With virtually all ink/substrate combinations, the same feature size will be patterned no matter how hard the tip is pressing down against the surface. As long as robust SiN tips are used, there is no need for complicated feedback electronics, no need for lasers, no need for quad photo-diodes, and no need for an AFM. | 1 | Applied and Interdisciplinary Chemistry |
* Cross-linkage: another irreversible method that does not require a support material for the attachment of enzyme molecules. In this technique, the molecules of enzymes are covalently bonded to each other to create a matrix consisting of almost only enzyme. The reaction ensures that the binding site does not cover the enzyme's active site, the activity of the enzyme is only affected by immobility. However, the inflexibility of the covalent bonds precludes the self-healing properties exhibited by chemo-adsorbed self-assembled monolayers. Use of a spacer molecule like poly(ethylene glycol) helps in the reduction of steric hindrance by the substrate in this case. | 0 | Theoretical and Fundamental Chemistry |
The action of water on rock over long periods of time typically leads to weathering and water erosion, physical processes that convert solid rocks and minerals into soil and sediment, but under some conditions chemical reactions with water occur as well, resulting in metasomatism or mineral hydration, a type of chemical alteration of a rock which produces clay minerals. It also occurs when Portland cement hardens.
Water ice can form clathrate compounds, known as clathrate hydrates, with a variety of small molecules that can be embedded in its spacious crystal lattice. The most notable of these is methane clathrate, 4 , naturally found in large quantities on the ocean floor. | 1 | Applied and Interdisciplinary Chemistry |
The Kurnakov test is sometimes used to detect transplatin in samples of the drug cisplatin. In hot aqueous solution, the cis-compound reacts with aqueous thiourea (tu) to give a deeper yellow solution, from which yellow needles of [Pt(tu)]Cl chloride deposit on cooling. The trans-compound gives a colourless solution, from which snow-white needles of trans-[Pt(tu)(NH)]Cl deposit on cooling. | 0 | Theoretical and Fundamental Chemistry |
Plant breeders emphasize selection and development of disease-resistant plant lines. Plant diseases can also be partially controlled by use of pesticides and by cultivation practices such as crop rotation, tillage, planting density, disease-free seeds and cleaning of equipment, but plant varieties with inherent (genetically determined) disease resistance are generally preferred. Breeding for disease resistance began when plants were first domesticated. Breeding efforts continue because pathogen populations are under selection pressure and evolve increased virulence, pathogens move (or are moved) to new areas, changing cultivation practices or climate favor some pathogens and can reduce resistance efficacy, and plant breeding for other traits can disrupt prior resistance. A plant line with acceptable resistance against one pathogen may lack resistance against others.
Breeding for resistance typically includes:
* Identification of plants that may be less desirable in other ways, but which carry a useful disease resistance trait, including wild plant lines that often express enhanced resistance.
* Crossing of a desirable but disease-susceptible variety to a plant that is a source of resistance.
* Growth of breeding candidates in a disease-conducive setting, possibly including pathogen inoculation. Attention must be paid to the specific pathogen isolates, to address variability within a single pathogen species.
* Selection of disease-resistant individuals that retain other desirable traits such as yield, quality and including other disease resistance traits.
Resistance is termed durable if it continues to be effective over multiple years of widespread use as pathogen populations evolve. "Vertical resistance" is specific to certain races or strains of a pathogen species, is often controlled by single R genes and can be less durable. Horizontal or broad-spectrum resistance against an entire pathogen species is often only incompletely effective, but more durable, and is often controlled by many genes that segregate in breeding populations. Durability of resistance is important even when future improved varieties are expected to be on the way: The average time from human recognition of a new fungal disease threat to the release of a resistant crop for that pathogen is at least twelve years.
Crops such as potato, apple, banana and sugarcane are often propagated by vegetative reproduction to preserve highly desirable plant varieties, because for these species, outcrossing seriously disrupts the preferred traits. See also asexual propagation. Vegetatively propagated crops may be among the best targets for resistance improvement by the biotechnology method of plant transformation to manage genes that affect disease resistance.
Scientific breeding for disease resistance originated with Sir Rowland Biffen, who identified a single recessive gene for resistance to wheat yellow rust. Nearly every crop was then bred to include disease resistance (R) genes, many by introgression from compatible wild relatives. | 1 | Applied and Interdisciplinary Chemistry |
Sanger–Black apparatus is a piece of chemical laboratory ware used for quantitative and semi-quantitative determination of arsenic element in the solution. It is constituted by glass bottle of volume ca. 30 mL, sealed with rubber stopper with one or two holes. Through one hole a thistle tube is inserted, almost reaching the bottom, for filling the bottle (what can be done also when the stopper is taken out – for semi-quantitative determination). The second, S-shaped tube is for outflow of the gases and joined by another rubber stopper to a bulg tube, with bulb containing pre-dried cotton as adsorbent, presumably intended for homogenizing the gas flow. A thin reagent paper, impregnated with mercury(II) chloride (nowadays replaced by mercury(II) bromide) or silver(I) nitrate, is placed in the open end of the bulb tube. If the semi-quantitative variant is to be performed, the paper is put in the (only) thistle tube – i. e., vertically, not horizontally. During the test ca. 3 g of Zn granules are placed into the bottle, just below the end of thistle tube, and then acid solution is added (ca. 15 mL; authors recommend that HCl is preferable to HSO). About 10 minutes are required to let H flow along the reagent paper, while this flow and moisture content inside it is stabilizing. Then the sample is introduced, and in case of sample solution containing arsenic the paper becomes more or less stained.
The Sanger–Black determination is based on the so-called Gutzeit reaction (1879):
AsH is forming from arsenic in any oxidation state when it reduces with the hydrogen in statu nascendi, produced from the acid. Gutzeit originally used AgNO for determination. The innovation to the Gutzeit method by Sanger and Black is the use of long and narrow paper, so that gas flow is directed along it and the product of reaction used as analytic signal deposits almost uniquely in the surface layers of the paper, so that stain area is quantitative analytic signal (if all the prerequisites for determination are fulfilled). Unfortunately, yellow colour is not that human eye is especially sensitive for, so photometric tools were introduced for quantitative analysis quite a long time ago (in 1944).
Zinc naturally contains some trace amounts of arsenic, so a modest yellow stain appears almost in any case on the reagent paper. This limits the sensitivity of this test, as arsenic amounts in zinc vary from one supplier to another. That is why later Zn was replaced by sodium borohydride NaBH; then, strong and corrosive hydrochloric acid was also replaced with sulfamic acid NHSOH. | 0 | Theoretical and Fundamental Chemistry |
Where
* is the pressure
* is the identity matrix
* is the deviatoric stress tensor
That is, pulling is positive stress and pushing is negative stress. | 0 | Theoretical and Fundamental Chemistry |
Soil gases have been used for multiple scientific studies to explore topics such as microseepage, earthquakes, and gaseous exchange between the soil and the atmosphere. Microseepage refers to the limited release of hydrocarbons on the soil surface and can be used to look for petroleum deposits based on the assumption that hydrocarbons vertically migrate to the soil surface in small quantities. Migration of soil gases, specifically radon, can also be examined as earthquake precursors. Furthermore, for processes such as soil thawing and rewetting, for example, large sudden changes in soil respiration can cause increased flux of soil gases such as carbon dioxide and methane, which are greenhouse gases. These fluxes and interactions between soil gases and atmospheric air can further be analyzed by distance from the soil surface. | 0 | Theoretical and Fundamental Chemistry |
:q = Heat per unit mass added into the system
Strictly speaking, enthalpy is a function of both temperature and density. However, invoking the common assumption of a calorically perfect gas, enthalpy can
be converted directly into temperature as given above, which enables one to define a stagnation temperature in terms of the more fundamental property,
stagnation enthalpy.
Stagnation properties (e.g. stagnation temperature, stagnation pressure) are useful in jet engine performance calculations. In engine operations, stagnation temperature is often called total air temperature. A bimetallic thermocouple is often used to measure stagnation temperature, but allowances for thermal radiation must be made. | 1 | Applied and Interdisciplinary Chemistry |
The origin of surface stress is the difference between bonding in the bulk and at a surface. The bulk spacings set the values of the in-plane surface spacings, and consequently the in-plane distance between atoms. However, the atoms at the surface have a different bonding, so would prefer to be at a different spacing, often (but not always) closer together. If they want to be closer, then will be positive—a tensile or expansive strain will increase the surface energy.
For many metals the derivative is positive, but in other cases it is negative, for instance solid argon and some semiconductors. The sign can also strongly depend upon molecules adsorbed on the surface. If these want to be further apart that will introduce a negative component. | 0 | Theoretical and Fundamental Chemistry |
Usually only of transient existence, complexes of isonitrosyl ligands are known where the NO is coordinated by its oxygen atom. They can be generated by UV-irradiation of nitrosyl complexes. | 0 | Theoretical and Fundamental Chemistry |
is also formed in this process, via (n,2n) reactions between fast neutrons and , , and :
Unlike most even numbered heavy isotopes, is also a fissile fuel fissioning just over half the time when it absorbs a thermal neutron. has a relatively short half-life (), and some decay products emit high energy gamma radiation, such as , and particularly . The full decay chain, along with half-lives and relevant gamma energies, is:
decays to where it joins the decay chain of
Thorium-cycle fuels produce hard gamma emissions, which damage electronics, limiting their use in bombs. cannot be chemically separated from from used nuclear fuel; however, chemical separation of thorium from uranium removes the decay product and the radiation from the rest of the decay chain, which gradually build up as reaccumulates. The contamination could also be avoided by using a molten-salt breeder reactor and separating the before it decays into . The hard gamma emissions also create a radiological hazard which requires remote handling during reprocessing. | 0 | Theoretical and Fundamental Chemistry |
The concentration of Zn in bulk silicate Earth is ~55 ppm, while its average concentration in fresh mid-oceanic ridge basalt (MORB) glass is ~87 ppm. Like Cu, Zn commonly associates with Fe to form a variety of zinc sulfide minerals such as sphalerite. Additionally, Zn associates with carbonates and hydroxides to form numerous diverse minerals (e.g., smithsonite, sweetite, etc.). In mafic and ultramafic rocks, Zn tends to concentrate in oxides such as spinel and magnetite. In freshwater, Zn predominantly complexes with water to form an octahedrally coordinated aqua ion . In seawater, Cl ions replace up to four water molecules in the Zn aqua ion, forming , and . | 0 | Theoretical and Fundamental Chemistry |
The name Golden Gate Assembly comes from a proposal of Yuri Gleba. It shall refer on the one hand to the Gateway Technology, on the other hand picture the higher precision with a bridge connecting the streets of two shores seamlessly. One of the most well known bridges is the Golden Gate Bridge in San Francisco. | 1 | Applied and Interdisciplinary Chemistry |
Sulfonyl bromides have the general formula RSOBr. In contrast to sulfonyl chlorides, sulfonyl bromides readily undergo light-induced homolysis affording sulfonyl radicals, which can add to alkenes, as illustrated by the use of bromomethanesulfonyl bromide, BrCHSOBr in Ramberg–Bäcklund reaction syntheses. | 0 | Theoretical and Fundamental Chemistry |
EDLs have an additional parameter defining their characterization: differential capacitance. Differential capacitance, denoted as C, is described by the equation below:
where σ is the surface charge and ψ is the electric surface potential. | 0 | Theoretical and Fundamental Chemistry |
Junes Ipaktschi (born October 25, 1940, in Tabriz, Iran) is an Iranian organic chemist and professor of the Department of Organic Chemistry at the University of Giessen. | 0 | Theoretical and Fundamental Chemistry |
Unlike typical diffusion, anomalous diffusion is described by a power law, where is the so-called generalized diffusion coefficient and is the elapsed time. The classes of anomalous diffusions are classified as follows:
* α < 1: subdiffusion. This can happen due to crowding or walls. For example, a random walker in a crowded room, or in a maze, is able to move as usual for small random steps, but cannot take large random steps, creating subdiffusion. This appears for example in protein diffusion within cells, or diffusion through porous media. Subdiffusion has been proposed as a measure of macromolecular crowding in the cytoplasm.
* α = 1: Brownian motion.
* : superdiffusion. Superdiffusion can be the result of active cellular transport processes or due to jumps with a heavy-tail distribution.
* α = 2: ballistic motion. The prototypical example is a particle moving at constant velocity: .
* : hyperballistic. It has been observed in optical systems.
In 1926, using weather balloons, Lewis Fry Richardson demonstrated that the atmosphere exhibits super-diffusion. In a bounded system, the mixing length (which determines the scale of dominant mixing motions) is given by the Von Kármán constant according to the equation , where is the mixing length, is the Von Kármán constant, and is the distance to the nearest boundary. Because the scale of motions in the atmosphere is not limited, as in rivers or the subsurface, a plume continues to experience larger mixing motions as it increases in size, which also increases its diffusivity, resulting in super-diffusion. | 0 | Theoretical and Fundamental Chemistry |
For the special case of simple cubic crystals, the lattice vectors are orthogonal and of equal length (usually denoted a); similarly for the reciprocal lattice. So, in this common case, the Miller indices (ℓmn) and [ℓmn] both simply denote normals/directions in Cartesian coordinates. For cubic crystals with lattice constant a, the spacing d between adjacent (ℓmn) lattice planes is (from above):
Because of the symmetry of cubic crystals, it is possible to change the place and sign of the integers and have equivalent directions and planes:
*Coordinates in angle brackets such as denote a family of directions that are equivalent due to symmetry operations, such as [100], [010], [001] or the negative of any of those directions.
*Coordinates in curly brackets or braces such as {100} denote a family of plane normals that are equivalent due to symmetry operations, much the way angle brackets denote a family of directions.
For face-centered cubic (fcc) and body-centered cubic (bcc) lattices, the primitive lattice vectors are not orthogonal. However, in these cases the Miller indices are conventionally defined relative to the lattice vectors of the cubic supercell and hence are again simply the Cartesian directions. | 0 | Theoretical and Fundamental Chemistry |
In winter conditions, or in cold climates, when the temperature falls below , the crystallization of ice in the pores of concrete is also a physical mechanism (change of state) responsible for the volumetric expansion of a substance exerting a high tensile strength inside the concrete matrix. When the tensile strength of concrete is exceeded, cracks appear. Adding an air entrainment agent during the mixing of fresh concrete induces the formation of tiny air bubbles in the fresh concrete slurry. This creates numerous small air-filled micro-cavities in the hardened concrete serving as empty volume reserve to accommodate the volumetric expansion of ice and delays the moment tensile stress will develop. Air entrainment makes concrete more workable during placement, and increases its durability when hardened, particularly in climates subject to freeze-thaw cycles. | 1 | Applied and Interdisciplinary Chemistry |
Using this notation, Woodward and Hoffmann state in their 1969 review the general formulation for all pericyclic reactions as follows:
and (4r) components is odd.</blockquote>
Here, (4q + 2) and (4r) refer to suprafacial (4q + 2)-electron and antarafacial (4r)-electron components, respectively. Moreover, this criterion should be interpreted as both sufficient (stated above) as well as necessary (not explicitly stated above, see: if and only if) | 0 | Theoretical and Fundamental Chemistry |
Within computational biology, an MA plot is an application of a Bland–Altman plot for visual representation of genomic data. The plot visualizes the differences between measurements taken in two samples, by transforming the data onto M (log ratio) and A (mean average) scales, then plotting these values. Though originally applied in the context of two channel DNA microarray gene expression data, MA plots are also used to visualise high-throughput sequencing analysis. | 1 | Applied and Interdisciplinary Chemistry |
An apoenzyme (or, generally, an apoprotein) is the protein without any small-molecule cofactors, substrates, or inhibitors bound. It is often important as an inactive storage, transport, or secretory form of a protein. This is required, for instance, to protect the secretory cell from the activity of that protein.
Apoenzymes become active enzymes on addition of a cofactor. Cofactors can be either inorganic (e.g., metal ions and iron-sulfur clusters) or organic compounds, (e.g., [Flavin group|flavin] and heme). Organic cofactors can be either prosthetic groups, which are tightly bound to an enzyme, or coenzymes, which are released from the enzyme's active site during the reaction. | 0 | Theoretical and Fundamental Chemistry |
P700, or photosystem I primary donor, is the reaction-center chlorophyll a molecular dimer associated with photosystem I in plants, algae, and cyanobacteria. | 0 | Theoretical and Fundamental Chemistry |
The NRTL parameters are fitted to activity coefficients that have been derived from experimentally determined phase equilibrium data (vapor–liquid, liquid–liquid, solid–liquid) as well as from heats of mixing. The source of the experimental data are often factual data banks like the Dortmund Data Bank. Other options are direct experimental work and predicted activity coefficients with UNIFAC and similar models.
Noteworthy is that for the same liquid mixture several NRTL parameter sets might exist. The NRTL parameter set to use depends on the kind of phase equilibrium (i.e. solid–liquid (SL), liquid–liquid (LL), vapor–liquid (VL)). In the case of the description of a vapor–liquid equilibria it is necessary to know which saturated vapor pressure of the pure components was used and whether the gas phase was treated as an ideal or a real gas. Accurate saturated vapor pressure values are important in the determination or the description of an azeotrope. The gas fugacity coefficients are mostly set to unity (ideal gas assumption), but for vapor-liquid equilibria at high pressures (i.e. > 10 bar) an equation of state is needed to calculate the gas fugacity coefficient for a real gas description.
Determination of NRTL parameters from LLE data is more complicated than parameter regression from VLE data as it involves solving isoactivity equations which are highly non-linear. In addition, parameters obtained from LLE may not always represent the real activity of components due to lack of knowledge on the activity values of components in the data regression. For this reason it is necessary to confirm the consistency of the obtained parameters in the whole range of compositions (including binary subsystems, experimental and calculated lie-lines, Hessian matrix, etc.). | 0 | Theoretical and Fundamental Chemistry |
In physical chemistry, a hot atom is an atom that has a high kinetic or internal energy.
When molecule AB adsorbs on a surface dissociatively,
# both A and B adsorb on the surface, or
# only A adsorbs on the surface, and B desorbs from the surface.
In case 2, B gains a high translational energy from the adsorption energy of A, and hot atom B is generated. For example, the hydrogen molecule, because of its light mass, gets a high translational energy. Such a hot atom does not fly into vacuum but is trapped on the surface, where it diffuses with high energy.
Hot atoms are expected to play important roles in catalytic reactions. For example, a reaction of a hydrogen atom with hydrogen atoms on a silicon surface and a reaction of an oxygen atom with oxygen molecules on Pt(111) have been reported. Hot atoms can also be generated by degenerating molecules on a metal surface with UV light. It has been reported that the reactivity of an oxygen atom generated in such a way on a platinum surface is different from that of chemisorbed oxygen atoms. Elucidating the role of hot atoms on surfaces will lead to a deeper understanding of the mechanism of reactions. | 0 | Theoretical and Fundamental Chemistry |
The electron transport protein plastocyanin is present in the lumen and shuttles electrons from the cytochrome b6f protein complex to photosystem I. While plastoquinones are lipid-soluble and therefore move within the thylakoid membrane, plastocyanin moves through the thylakoid lumen.
The lumen of the thylakoids is also the site of water oxidation by the oxygen evolving complex associated with the lumenal side of photosystem II.
Lumenal proteins can be predicted computationally based on their targeting signals. In Arabidopsis, out of the predicted lumenal proteins possessing the Tat signal, the largest groups with known functions are 19% involved in protein processing (proteolysis and folding), 18% in photosynthesis, 11% in metabolism, and 7% redox carriers and defense. | 0 | Theoretical and Fundamental Chemistry |
Most herbicides are applied as water-based sprays using ground equipment. Ground equipment varies in design, but large areas can be sprayed using self-propelled sprayers equipped with long booms, of with spray nozzles spaced every apart. Towed, handheld, and even horse-drawn sprayers are also used. On large areas, herbicides may also at times be applied aerially using helicopters or airplanes, or through irrigation systems (known as chemigation).
Weed-wiping may also be used, where a wick wetted with herbicide is suspended from a boom and dragged or rolled across the tops of the taller weed plants. This allows treatment of taller grassland weeds by direct contact without affecting related but desirable shorter plants in the grassland sward beneath. The method has the benefit of avoiding spray drift. In Wales, a scheme offering free weed-wiper hire was launched in 2015 in an effort to reduce the levels of MCPA in water courses.
There is little difference in forestry in the early growth stages, when the height similarities between growing trees and growing annual crops yields a similar problem with weed competition. Unlike with annuals however, application is mostly unnecessary thereafter and is thus mostly used to decrease the delay between productive economic cycles of lumber crops. | 1 | Applied and Interdisciplinary Chemistry |
Apart from life sciences, specialty chemicals -and therefore also their active ingredients, commodities or fine chemicals, as the case may be- are used ubiquitously, in both industrial applications, such as biocides and corrosion inhibitors in cooling water towers, and consumer applications, such as personal care and household products. The active ingredients extend from high-price / low-volume fine chemicals, used for liquid crystal displays to large-volume / low-price amino acids used as feed additives.
fine chemicals merchant market size, growth potential
Examples of applications in eight areas, ranging from adhesives to specialty polymers, are listed in Table 8. Overall, the attractiveness for the fine chemical industry is smaller than the life science industry. The total market, expressed in finished product sales, amounts to $150–200 billion, or about one fourth of the pharma market. The embedded fine chemicals account for an estimated $15 billion (see Table 5). Further disadvantages are the backward integration of the big players, e.g. Akzo-Nobel, Netherlands; Ajinomoto, Japan; Danone, France; Everlight Chemical Industrial Corp., Taiwan; Evonik-Degussa, Germany; Givaudan and Nestlé, Switzerland, Novozymes, Denmark, Procter & Gamble, and Unilever USA. Last but not least, innovation is rather based on new formulations of existing products, rather than the development of new fine chemicals. It is most likely to happen in application areas unrelated to human health (where NCEs are subject to very extensive testing). | 0 | Theoretical and Fundamental Chemistry |
* Antibiotics
** Actinomycin
** Bacitracin
** Calcium dependent antibiotic
** Daptomycin
** Vancomycin
** Teixobactin
** Tyrocidine
** Gramicidin
** Zwittermicin A
* Antibiotic precursors
** ACV-Tripeptide
* Cytostatics
** Epothilone
**Fabclavine
** Bleomycin
* Immunosuppressants
** Ciclosporin (Cyclosporine A)
* Siderophores
** Pyoverdine
** Enterobactin
** Myxochelin A
* Pigments
** Indigoidine
* Toxins
** Microcystins and
** Nodularins, cyanotoxins from cyanobacteria.
* Nitrogen storage polymers
** Cyanophycin – produced by some cyanobacteria
* Phytotoxins
** HC-toxin – a virulence factor made by the plant pathogenic fungus Cochliobolus (Helminthosporium) carbonum
** AM-toxin – made by the plant pathogenic fungus Alternaria alternata pv. Mali
** victorin – a chlorinated cyclic pentapeptide made by the pathogenic fungus Cochliobolus victoriae. Its nonribosomal synthesis has not been established. | 1 | Applied and Interdisciplinary Chemistry |
Although little is known about the mechanism of the adaptive response, it is believed that changes in gene transcription and the activation of cellular defenses are involved. It has recently been suggested that specific mechanistic pathways of the adaptive response can active the important tumor suppressor protein p53. A key experiment that reveals the underlying mechanisms is that which involves the treatment with protein synthesis inhibitors to Oedogonium Chlamydomonas and Closterium cells. This experiment resulted in DNA-binding proteins being synthesized in the cells conditioned with the stressor. Furthermore, reverse adaptive response suggests that a high conditioning dose followed by a second low dose produces roughly the same magnitude of response. This could suggest that the mechanisms work by cellular response modulation, not prevention, to the impending damage. The adaptive response is not instantaneous and takes several hours to develop, however after development it can last for months given that the stressor exposure is limited and will not overwhelm the cell. This is known as being dose and time-dependent with a maximum response occurring at 4 hours after an initial conditioning dose of 100 cGy (centigray) radiation stressor. | 1 | Applied and Interdisciplinary Chemistry |
LAGP crystals belong to the space group D - Rc. The factor group analysis of NASICON-type materials with general formula MMPO (where M stands for a monovalent metal ion like Na, Li or K, and M represents a tetravalent cation such as Ti, Ge, Sn, Zr or Hf) is usually performed assuming the separation between internal vibrational modes (i.e. modes originating in PO units) and external modes (i.e. modes arising from the translations of the M and M cations, from PO translations, and from PO librations).
Focusing on internal modes only, the factor group analysis for Rc space group identifies 14 Raman-active modes for the PO units: 6 of these modes correspond to stretching vibrations and 8 to bending vibrations.
On the contrary, the analysis of external modes leads to many available vibrations: since the number of irreducible representations within the rhombohedral Rc space group is restricted, interactions among different modes could be expected and a clear assignment or discrimination becomes unfeasible. | 0 | Theoretical and Fundamental Chemistry |
From 1946 through 1993, thirteen countries used ocean disposal or ocean dumping as a method to dispose of nuclear/radioactive waste with an approximation of 200,000 tons sourcing mainly from the medical, research and nuclear industry.
Ocean floor disposal of radioactive waste has been suggested by the finding that deep waters in the North Atlantic Ocean do not present an exchange with shallow waters for about 140 years based on oxygen content data recorded over a period of 25 years. They include burial beneath a stable abyssal plain, burial in a subduction zone that would slowly carry the waste downward into the Earth's mantle, and burial beneath a remote natural or human-made island. While these approaches all have merit and would facilitate an international solution to the problem of disposal of radioactive waste, they would require an amendment of the Law of the Sea.
Nuclear submarines have been lost and these vessels reactors must also be counted in the amount of radioactive waste deposited at sea.
Article 1 (Definitions), 7., of the 1996 Protocol to the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, (the London Dumping Convention) states:
:""Sea" means all marine waters other than the internal waters of States, as well as the seabed and the subsoil thereof; it does not include sub-seabed repositories accessed only from land." | 0 | Theoretical and Fundamental Chemistry |
Ekman pumping is the component of Ekman transport that results in areas of downwelling due to the convergence of water. As discussed above, the concept of mass conservation requires that a pile up of surface water must be pushed downward. This pile up of warm, nutrient-poor surface water gets pumped vertically down the water column, resulting in areas of downwelling.
Ekman pumping has dramatic impacts on the surrounding environments. Downwelling, due to Ekman pumping, leads to nutrient poor waters, therefore reducing the biological productivity of the area. Additionally, it transports heat and dissolved oxygen vertically down the water column as warm oxygen rich surface water is being pumped towards the deep ocean water.
Ekman pumping can be found along the coasts as well as in the open ocean. Along the Pacific Coast in the Southern Hemisphere northerly winds move parallel to the coastline. Due to the Coriolis effect the surface water gets pulled 90° to the left of the wind current, therefore causing the water to converge along the coast boundary, leading to Ekman pumping. In the open ocean Ekman pumping occurs with gyres. Specifically, in the subtropics, between 20°N and 50°N, there is Ekman pumping as the tradewinds shift to westerlies causing a pile up of surface water. | 1 | Applied and Interdisciplinary Chemistry |
The daily light integral (DLI) is the number of photosynthetically active photons (photons in the PAR range) accumulated in a square meter over the course of a day. It is a function of photosynthetic light intensity and duration (day length) and is usually expressed as moles of light (mol photons) per square meter (m) per day (d), or: mol·m·d.
DLI is usually calculated by measuring the photosynthetic photon flux density (PPFD) in μmol·m·s (number of photons in the PAR range received in a square meter per second) as it changes throughout the day, and then using that to calculate total estimated number of photons in the PAR range received over a 24-hour period for a specific area. In other words, DLI describes the sum of the per second PPFD measurements during a 24-hour period.
If the photosynthetic light intensity stays the same for the entire 24-hour period, DLI in mol m d can be estimated from the instantaneous PPFD from the following equation: μmol m s multiplied by 86,400 (number of seconds in a day) and divided by 10 (number of μmol in a mol). Thus, 1 μmol m s = 0.0864 mol m d if light intensity stays the same for the entire 24 hour period. | 0 | Theoretical and Fundamental Chemistry |
The radius ratio rule defines a critical radius ratio for different crystal structures, based on their coordination geometry. The idea is that the anions and cations can be treated as incompressible spheres, meaning the crystal structure can be seen as a kind of unequal sphere packing. The allowed size of the cation for a given structure is determined by the critical radius ratio. If the cation is too small, then it will attract the anions into each other and they will collide hence the compound will be unstable due to anion-anion repulsion; this occurs when the radius ratio drops below the critical radius ratio for that particular structure. At the stability limit the cation is touching all the anions and the anions are just touching at their edges. For radius ratios greater than the critical ratius ratio, the structure is expected to be stable.
The rule is not obeyed for all compounds. By one estimate, the crystal structure can only be guessed about 2/3 of the time. Errors in prediction are partly due to the fact that real chemical compounds are not purely ionic, they display some covalent character.
The table below gives the relation between critical radius ratio, , and coordination number, , which may be obtained from a simple geometrical proof. | 0 | Theoretical and Fundamental Chemistry |
A crystal family is determined by lattices and point groups. It is formed by combining crystal systems that have space groups assigned to a common lattice system. In three dimensions, the hexagonal and trigonal crystal systems are combined into one hexagonal crystal family. | 0 | Theoretical and Fundamental Chemistry |
The build-up of calc-sinter material in the Eifel Aqueduct was commercially exploited in the 11th and 12th centuries. With deposits up to thick, the material was cut into vertical columns of polished brown rock with impressive layered patterns, which made it much in demand by cathedral builders across large parts of central Europe and beyond. In England it was used to provide polychromy, contrasting with the pale limestone favoured by Norman English Cathedrals. The stone was for many years known as Onyx Marble despite being very obviously neither onyx nor marble. Those studying the stonework at Canterbury Cathedral were unaware of its origins in the aqueduct until 2011. Such large-scale use as the cloisters around a cathedral quadrangle needed many hundreds of columns, which must have been supplied by a well-organised extraction and transport operation. The Eifel deposits, have also been identified at Rochester and in the now lost Romanesque cloister at Norwich as well as the Infirmary Cloister, Chapter House windows, Anselm Chapel door and the Treasury gateway at Canterbury. | 0 | Theoretical and Fundamental Chemistry |
The International Union of Pure and Applied Chemistry (IUPAC) recommends definitions for several classes of chain-growth polymerization. | 0 | Theoretical and Fundamental Chemistry |
*Theodor Körner Prize for Science and Art in Austria, 1970
*Ernst Späth Prize of the Austrian Academy of Sciences, 1976
*Sandoz Prize, 1977
*Election to corresponding member of the New York Academy of Sciences, 1989
*Election to corresponding member of the Mathematical and Natural Sciences Class of the Austrian Academy of Sciences, 1992
*Upper Austrian Prize for Science, 1993
*Election to full member of the Mathematical and Natural Sciences Class of the Austrian Academy of Sciences, 1997
*Josef Loschmidt Medal of the Austrian Chemical Society, 1998
*Scientific award of the Rudolf Trauner Stiftung, 2003
*Silver medal of the government of Upper Austria, 2009 | 0 | Theoretical and Fundamental Chemistry |
The periodic presence of euxinic conditions in the Lower Cambrian has been supported by evidence found on the Yangtze platform in South China. Sulfur isotopes during the transition from Proterozoic to Phanerozoic give evidence for widespread euxinia, perhaps lasting throughout the Cambrian period. Towards the end of the Lower Cambrian, the euxinic chemocline grew deeper until euxinia was present only in the sediments, and once sulfate became limiting, conditions became anoxic instead of euxinic. Some areas eventually became oxic, while others eventually returned to euxinic for some time.
Geological records from the paleozoic in the Selwyn Basin in Northern Canada have also shown evidence for episodic stratification and mixing, where, using δS, it was determined that hydrogen sulfide was more prevalent than sulfate. Although this was not originally attributed to euxinia, further studies found that seawater in that time likely had low concentrations of sulfate, meaning that the sulfur in the water was primarily in the form of sulfide. This combined with organic-rich black shale provide strong evidence for euxinia.
There is similar evidence in the black shales in the mid-continent North America from the Devonian and early Mississippian periods. Isorenieratene, a pigment known as a proxy for an anoxic photic zone, has been found in the geological record in Illinois and Michigan. Although present, these events were probably ephemeral and did not last for longer periods of time. Similar periodic evidence of euxinia can also be found in the Sunbury shales of Kentucky.
Evidence for euxinia has also been tied to the Kellwasser events of the Late Devonian Extinction event. Euxinia in basinal waters in what is now central Europe (Germany, Poland, and France) persisted for part of the late Devonian, and may have spread up into shallow waters, contributing to the extinction event.
There was perhaps a period of oxygenation of bottom waters during the Carboniferous, most likely between the Late Devonian Extinction and the Permian-Triassic Extinction, at which point euxinia would be very rare in the paleo oceans.
The Permian–Triassic extinction event may also have some ties to euxinia, with hypercapnia and hydrogen sulfide toxicity killing off many species. Presence of a biomarker for anaerobic photosynthesis by green sulfur bacteria has been found spanning from the Permian to early Triassic in sedimentary rock in both Australia and China, meaning that euxinic conditions extended up quite shallow in the water column, contributing to the extinctions and perhaps even slowed the recovery. It is uncertain, however, just how widespread photic zone euxinia was during this period. Modelers have hypothesized that due to environmental conditions anoxia and sulfide may have been brought up from a deep, vast euxinic reservoir in upwelling areas, but stable, gyre-like areas remained oxic. | 0 | Theoretical and Fundamental Chemistry |
* [https://archive.org/stream/philtrans00033709/00033709#page/n0/mode/2up On the force of percussion], 1805 | 1 | Applied and Interdisciplinary Chemistry |
An absorption or release of nuclear energy occurs in nuclear reactions or radioactive decay; those that absorb energy are called endothermic reactions and those that release energy are exothermic reactions. Energy is consumed or released because of differences in the nuclear binding energy between the incoming and outgoing products of the nuclear transmutation.
The best-known classes of exothermic nuclear transmutations are nuclear fission and nuclear fusion. Nuclear energy may be released by fission, when heavy atomic nuclei (like uranium and plutonium) are broken apart into lighter nuclei. The energy from fission is used to generate electric power in hundreds of locations worldwide. Nuclear energy is also released during fusion, when light nuclei like hydrogen are combined to form heavier nuclei such as helium. The Sun and other stars use nuclear fusion to generate thermal energy which is later radiated from the surface, a type of stellar nucleosynthesis. In any exothermic nuclear process, nuclear mass might ultimately be converted to thermal energy, emitted as heat.
In order to quantify the energy released or absorbed in any nuclear transmutation, one must know the nuclear binding energies of the nuclear components involved in the transmutation. | 0 | Theoretical and Fundamental Chemistry |
Pseudocopulation is achieved when a flower successfully mimics the appearance and the pheromones emitted by the female of an insect species. The chemicals emitted by the mimicking species work to draw these pollinators to the plant and increase the number of visits to and time spent on the flower. This increases the chances that pollen will efficiently stick to the organism or that pollen already stuck to it is transferred to the plant.
In one study on mining bees (Andrena nigroaenea) and spider orchids (Ophrys sphegodes Mill.) it was found that unpollinated spider orchids emitted odours that consisted of hydrocarbons that were an exact match for the odours released by virgin female bees. As a result, male mining bees are extremely attracted to the flowers of the spider orchid, triggering more quick visits to the flower and in some cases the male bees attempt copulation, either getting themselves sufficiently covered in pollen or successfully transferring it to another plant. | 1 | Applied and Interdisciplinary Chemistry |
Mechanical revolving blade fans are made in a wide range of designs. They are used on the floor, table, desk, or hung from the ceiling (ceiling fan), and can be built into a window, wall, roof, etc. Electronic systems generating significant heat such as computers incorporate fans. Appliances such as hair dryers and space heaters also use fans. They move air in air-conditioning systems and in automotive engines. Fans used for comfort inside a room create a wind chill by increasing the heat transfer coefficient but do not lower temperatures directly. Fans used to cool electrical equipment or in engines or other machines do cool the equipment directly by exhausting hot air into the cooler environment outside of the machine so that cooler air flows in.
There are three main types of fans used for moving air, axial, centrifugal (also called radial) and cross flow (also called tangential). The American Society of Mechanical Engineers Performance Testing Code 11 (PTC) provides standard procedures for conducting and reporting tests on fans, including those of the centrifugal, axial, and mixed flows. | 0 | Theoretical and Fundamental Chemistry |
Proteins are normally hydrolysed slowly even without enzymes or bacteria, with a half life of 460 years, but can be preserved if they are desiccated, pickled or frozen. Being enclosed in bone also helps preservation. Over time the amino acids tend to racemize, and those with more functional groups are lost earlier. Protein still will degrade on the timescale of a million years. DNA degrades rapidly, lasting only about four years in water. Cellulose and chitin have a half life in water at 25° of about 4.7 million years. Enzymes can accelerate this by a factor of 10. About 10 tons of chiting are produced each year, but it is almost all degraded.
Lignin is only efficiently degraded by fungi, white rot, or brown rot. These require oxygen.
Lipids are hydrolysed to fatty acids over long time periods. Plant cuticle waxes are very difficult to degrade, and may survive over geological time periods. | 0 | Theoretical and Fundamental Chemistry |
Dragendorffs reagent is a color reagent to detect alkaloids in a test sample or as a stain for chromatography plates. Alkaloids, if present in the solution of sample, will react with Dragendorffs reagent and produce an orange or orange-red precipitate. This reagent was invented by the German pharmacologist, Johann Georg Dragendorff (1836–1898) at the University of Dorpat. | 0 | Theoretical and Fundamental Chemistry |
A Light-oxygen-voltage-sensing domain (LOV domain) is a protein sensor used by a large variety of higher plants, microalgae, fungi and bacteria to sense environmental conditions. In higher plants, they are used to control phototropism, chloroplast relocation, and stomatal opening, whereas in fungal organisms, they are used for adjusting the circadian temporal organization of the cells to the daily and seasonal periods. They are a subset of PAS domains. | 1 | Applied and Interdisciplinary Chemistry |
Nano spray dryers refer to using spray drying to create particles in the nanometer range. Spray drying is a gentle method for producing powders with a defined particle size out of solutions, dispersions, and emulsions which is widely used for pharmaceuticals, food, biotechnology, and other industrial materials synthesis.
In the past, the limitations of spray drying were the particle size (minimum 2 micrometres), the yield (maximum around 70%), and the sample volume (minimum 50 ml for devices in lab scale). Recently, minimum particle sizes have been reduced to 300 nm, yields up to 90% are possible, and the sample amount can be as small as 1 ml. These expanded limits are possible due to new technological developments to the spray head, the heating system, and the electrostatic particle collector.
To emphasize the small particle sizes possible with this new technology, it has been described as "nano" spray drying. However, the smallest particles produced are in the sub-micrometre range common to fine particles rather than the nanometer scale of ultrafine particles. | 0 | Theoretical and Fundamental Chemistry |
In 2011, the U.S. Army product manager for the Decontamination Family of Systems (DFoS) began a market research project to identify potential prototype CIDAS technologies that could help soldiers locate chemical and biological warfare agents (CBWA), non-traditional agents (NTAs) and toxic industrial chemicals (TICs) on military equipment and vehicles.
After public input, the U.S. Army Contracting Command Aberdeen Proving Ground (ACC-APG) Contracting Center issued a request for proposal (RFP) in early 2013.
In 2014, the Joint Project Manager of Protection of the Joint Program Executive Office of Chemical and Biological Defense (JPEO-CBD) announced that it would seek two specific CIDAS devices to be used in level four "Mission Oriented Protective Posture gear." One device would be under 12 pounds and other device would be under 24 pounds, and both devices would be required to detect agents in under 5 minutes. | 1 | Applied and Interdisciplinary Chemistry |
The cytoplasmic domains of the EpoR contain a number of phosphotyrosines that are phosphorylated by Jak2 and serve as docking sites for a variety of intracellular pathway activators and Stats (such as Stat5). In addition to activating Ras/AKT and ERK/MAP kinase, phosphatidylinositol 3-kinase/AKT pathway and STAT transcription factors, phosphotyrosines also serve as docking sites for phosphatases that negatively affect EpoR signaling in order to prevent overactivation that may lead to such disorders as erythrocytosis. In general, the defects in the erythropoietin receptor may produce erythroleukemia and familial erythrocytosis. Mutations in Jak2 kinases associated with EpoR can also lead to polycythemia vera. | 1 | Applied and Interdisciplinary Chemistry |
The polymerase chain reaction (PCR) is a commonly used molecular biology tool for amplifying DNA, and various techniques for PCR optimization which have been developed by molecular biologists to improve PCR performance and minimize failure. | 1 | Applied and Interdisciplinary Chemistry |
Nathan Gallup Williams Haynes (29 July 1886, Detroit – 16 November 1970, Stonington, Connecticut) was an American journalist, editor, publisher, and historian of chemistry. He is best known for his 6-volume American Chemical Industry: A History. | 1 | Applied and Interdisciplinary Chemistry |
Diazomethane is both isomeric and isoelectronic with the more stable cyanamide, but they cannot interconvert.
Many substituted derivatives of diazomethane have been prepared:
*The very stable (CF)CN (2-diazo-1,1,1,3,3,3-hexafluoropropane; b.p. 12–13 °C),
*PhCN (diazodiphenylmethane; m.p. 29–30 °C).
*(CH)SiCHN (trimethylsilyldiazomethane), which is commercially available as a solution and is as effective as CHN for methylation.
*PhC(H)N, a red liquid b.p.< 25 °C at 0.1 mm Hg. | 0 | Theoretical and Fundamental Chemistry |
B. subtilis is a soil-dwelling microbe that uses quorum sensing to regulate two different biological processes: competence and sporulation. During stationary growth phase when B. subtilis are at high cell density, approximately 10% of the cells in a population are induced to become competent. It is believed that this subpopulation becomes competent to take up DNA that could potentially be used for the repair of damaged (mutated) chromosomes. ComX (also known as competence factor) is a 10-amino acid peptide that is processed from a 55-amino acid peptide precursor. Like most autoinducers, ComX is secreted and accumulates as a function of cell density. Once a threshold extracellular level is achieved, ComX is detected by a two-component ComP/ComA sensor kinase/response regulator pair. Phosphorylation of ComA activates the expression of comS gene, ComS inhibits the degradation of ComK, and finally ComK activates the expression of a number of genes required for competence.
Sporulation, on the other hand, is a physiological response of B. subtilis to depletion of nutrients within a particular environment. It is also regulated by extracellular signaling. When B. subtilis populations sense waning conditions, they respond by undergoing asymmetric cell division. This ultimately produces spores that are adapted for dispersal and survival in unfavorable conditions. Sporulation in B. subtilis is mediated by CSF (sporulation factor), a pentapeptide cleaved from the precursor peptide PhrC. CSF is secreted into the extracellular environment and is taken back up into cells via the ABC transporter Opp where it acts intracellularly. While low internal concentrations of CSF contribute to competence, high concentrations induce sporulation. CSF inhibits a phosphatase, RabB, which increases the activity of Spo0A, favoring a switch in commitment from competence to the sporulation pathway | 1 | Applied and Interdisciplinary Chemistry |
Only few naturally occurring compounds exhibit the isocyanide functionality. The first was discovered in 1957 in an extract of the mold Penicillium notatum. The compound xanthocillin later was used as an antibiotic. Since then numerous other isocyanides have been isolated. Most of the marine isocyanides are terpenoid, while some of the terrestrial isocyanides originate from α-aminoacids. | 0 | Theoretical and Fundamental Chemistry |
The study of these airs interfaced with phlogiston theory.
The therapeutic potential of factitious airs were widely investigated with significant contributions by Thomas Beddoes, James Watt, James Lind, Humphry Davy, and others at the Pneumatic Institution. Georgiana Cavendish, Duchess of Devonshire (related to Henry through marriage) had a profound interest in chemistry with interest in Henry's research in pneumatic chemistry. She played a pivotal role in advancing the study of factitious airs through partnering with Thomas Beddoes to establish the Pneumatic Institution.
Tuberculosis was a primary disease physicians had attempted to treat with factitious airs, particularly since James Watts daughter died of the disease. John Carmichael had reported successfully treating a patient suffering from tuberculosis using hydrocarbonate. This application of factitious air was pioneering research relevant to the modern era as carbon monoxide currently has preclinical evidence of treating Mycobacterium tuberculosis' infection progression by inducing dormancy, stimulating host immune response, and ameliorating host inflammation. | 1 | Applied and Interdisciplinary Chemistry |
While it is useful to study bulk cell entities, there is an underlying need to study an individual or single cell as it will provide a better understanding of how it contributes to the entity as a whole. It was found that the utilization of electrochemical techniques could analyze cells without interrupting cellular activity as well as provide a highly resolute spectrum. This analysis method was first completed by Wightman in 1982. In this method of analysis, a carbon microfiber electrode is placed near the studied cell; this electrode can monitor the call via methods of voltammetry or amperometry. Before the measure can be taken, the cell must be stimulated by an ejection pipette to cause a cellular release. This can be cellular release can be measured via the aforementioned methods. From this method, it was seen that instrumental advances were needed in order to perform quality SEE measurements. | 0 | Theoretical and Fundamental Chemistry |
The completed core snRNP-snurportin 1 complex is transported into the nucleus via the protein importin β. Inside the nucleus, the core snRNPs appear in the Cajal bodies, where final assembly of the snRNPs take place. This consists of additional proteins and other modifications specific to the particular snRNP (U1, U2, U4, U5). The biogenesis of the U6 snRNP occurs in the nucleus, although large amounts of free U6 are found in the cytoplasm. The LSm ring may assemble first, and then associate with the U6 snRNA. | 1 | Applied and Interdisciplinary Chemistry |
Dicerandrol C is a natural product. It is a less toxic isomer of phomoxanthone A (PXA) and phomoxanthone B (PXB), all three of which are members of the class of phomoxanthone compounds. The phomoxanthones are named after the fungus Phomopsis, from which they were first isolated, and after their xanthonoid structure. Chemically, they are dimers of two tetrahydroxanthones that are covalently linked to each other. Dicerandrol C itself is a homodimer of two identical diacetylated tetrahydroxanthones. The position of the link between the two tetrahydroxanthones is the only structural difference between dicerandrol C and its isomers PXA and PXB: In PXA, the two xanthonoid monomers are symmetrically linked at C-4,4’, while in PXB, they are asymmetrically linked at C-2,4’, and in dicerandrol C, they are symmetrically linked at C-2,2’. | 1 | Applied and Interdisciplinary Chemistry |
Amongst the other newly steel-producing countries, in 2017 South Korea produces 71 million tonnes, nearly double Germany; and Brazil 34 million tonnes; all three countries have not changed much since 2011.
Indian steel production in 2017 is just over 100 million tonnes; up substantially from 70 million tonnes in 2011 – compared to only 1 million tonnes at the time of its independence in 1947. By 1991, when the economy was opened up steel production grew to around 14 million tonnes. Thereafter, it doubled in the next 10 years, and then it is doubling again, maybe over a slightly longer span.
The world steel industry flattened from 2007 to 2009 at 1,300 million tonnes, before rising again, due to worldwide recession starting in 2008, with its heavy cutbacks in construction, sharply lowered demand and prices falling 40%.
Showing the impact of that plateau, in 2007 ThyssenKrupp spent $12 billion to build the two most modern mills in the world, situated in Alabama and Brazil. They lost $11 billion on the new plants, which sold steel below the cost of production. Finally in 2013, the plants were sold at under $4 billion.
Nowadays, the steel industry is on the edge of a major technological evolution to deal with the huge amounts of CO produced in the conventional steelmaking process. The use of blast furnaces and basic oxygen furnace produces around 1.8 ton of CO per ton of steel produced. In order to reach the climate objectives as stated in the Paris Climate Agreement, the European Green Deal, etc., the steel industry will have to implement carbon capture and sequestration or carbon capture and utilization technology or change to less conventional steelmaking technologies such as the electric arc furnace route. Other alternatives are the use of biomass, plastic waste or hydrogen as reducing agent in the blast furnace instead of coal. | 1 | Applied and Interdisciplinary Chemistry |
Infiltration basins must be carefully designed to infiltrate the soil on a given site at a rate that will not cause flooding. They may be less effective in areas with:
* High groundwater levels, close to the infiltrating surface
* Compacted soils
* High levels of sediment in stormwater
* High clay soil content.
At some sites infiltration basins have worked effectively where the installation also includes an extended detention basin as a pretreatment stage, to remove sediment. The basins may fail where they cannot be frequently maintained, and their use is discouraged in some areas of the United States. For example, they are not recommended for use in the U.S. state of Georgia, which has many areas with high clay soil content, unless soil on the particular site is modified ("engineered soil") during construction, to improve the infiltration characteristics. | 1 | Applied and Interdisciplinary Chemistry |
Spiling is a traditional technique used in temperate regions of the world for the prevention of erosion to river and stream banks.
Willow spiling is currently used in the United Kingdom; live willow rods are woven between live willow uprights and the area behind is filled with soil for the willow to root into.
Kiplings poem The Land mentions it: "They spiled along the water-course with trunks of willow-trees, And planks of elms behind em and immortal oaken knees."
The species of willow used are riparian (associated with rivers); the posts, in diameter, are usually Salix alba or S. fragilis, and S. viminalis varieties are used for the interwoven rods. The living willow posts are driven into the bank, to a depth of or more, at intervals and the thinner rods are woven in between, the rods are best woven at an angle slightly above horizontal to ensure good survival rates. A row of stones, gabions or wooden planks held by posts can be added to the bottom of each "spile" to prevent undercutting when the willow is establishing itself. All works should be done during the dormant period, winter in temperate zones. A layer of seeded coir matting can be pegged onto the soil on top of the spiles to prevent the soil being washed out during flood events. This method is an example of soft engineering, techniques which tend to be less expensive and more sustainable than others. | 1 | Applied and Interdisciplinary Chemistry |
Besides the above-mentioned two most commonly used family of techniques, a wide range of protocols were developed to measure chemotactic activity. Some of them are only qualitative, like aggregation tests, where small pieces of agar or filters are placed onto a slide and accumulation of cells around is measured.
In another semiquantitative technique, cells are overlaid the test substance and changes in opalescence of the originally cell-free compartment is recorded during the incubation time.
The third frequently used qualitative technique is the T-maze and its adaptations for microplates. In the original version, a container drilled in a peg is filled with cells. Then the peg is twisted and the cells get contact with two other containers filled with different substances. The incubation is stopped by resetting the peg and the cell number is counted from the containers.
Also, lately, microfluidic devices have been used more and more frequently to test quantitatively, and precisely, for chemotaxis. | 1 | Applied and Interdisciplinary Chemistry |
The first synthetic porphyrin isomer was reported by Emanual Vogel and coworkers in 1986. This isomer [18]porphyrin-(2.0.2.0) is named as porphycene, and the central N Cavity forms a rectangle shape as shown in figure. Porphycenes showed interesting photophysical behavior and found versatile compound towards the photodynamic therapy. This inspired Vogel and Sessler to took up the challenge of preparing [18]porphyrin-(2.1.0.1) and named it as corrphycene or porphycerin. The third porphyrin that is [18]porphyrin-(2.1.1.0), was reported by Callot and Vogel-Sessler. Vogel and coworkers reported successful isolation of [18]porphyrin-(3.0.1.0) or isoporphycene. The Japanese scientist Furuta and Polish scientist Latos-Grażyński almost simultaneously reported the N-confused porphyrins. The inversion of one of the pyrrolic subunits in the macrocyclic ring resulted in one of the nitrogen atoms facing outwards from the core of the macrocycle. | 1 | Applied and Interdisciplinary Chemistry |
Leaching is done in long pressure vessels which are cylindrical (horizontal or vertical) or of horizontal tube form known as autoclaves. A good example of the autoclave leach process can also be found in the metallurgy of zinc. It is best described by the following chemical reaction:
This reaction proceeds at temperatures above the boiling point of water, thus creating a vapour pressure inside the vessel. Oxygen is injected under pressure, making the total pressure in the autoclave more than 0.6 MPa and temperature at 473-523 K .
The leaching of precious metals such as gold can be carried out with cyanide or ozone under mild conditions. | 1 | Applied and Interdisciplinary Chemistry |
1,1,2,2-Tetrafluoroethane (also called R-134 or HFC-134) is a hydrofluorocarbon, a fluorinated alkane. It is an isomer of the more-used 1,1,1,2-tetrafluoroethane (R-134a). It is used as a foam expansion agent and heat transfer fluid. | 1 | Applied and Interdisciplinary Chemistry |
Contrastingly, reversible electroporation occurs when the electricity applied with the electrodes is below the electric field threshold of the target tissue. Because the electricity applied is below the cells' threshold, it allows the cells to repair their phospholipid bilayer and continue on with their normal cell functions. Reversible electroporation is typically done with treatments that involve getting a drug or gene (or other molecule that is not normally permeable to the cell membrane) into the cell. Not all tissue has the same electric field threshold; therefore careful calculations need to be made prior to a treatment to ensure safety and efficacy.
One major advantage of using N-TIRE is that, when done correctly according to careful calculations, it only affects the target tissue. Proteins, the extracellular matrix, and critical structures such as blood vessels and nerves are all unaffected and left healthy by this treatment. This allows for a quicker recovery, and facilitates a more rapid replacement of dead tumor cells with healthy cells.
Before doing the procedure, scientists must carefully calculate exactly what needs to be done and treat each patient on an individual case-by-case basis. To do this, imaging technology such as CT scans and MRI's are commonly used to create a 3D image of the tumor. From this information, they can approximate the volume of the tumor and decide on the best course of action including the insertion site of electrodes, the angle they are inserted in, the voltage needed, and more, using software technology. Often, a CT machine will be used to help with the placement of electrodes during the procedure, particularly when the electrodes are being used to treat tumors in the brain.
The entire procedure is very quick, typically taking about five minutes. The success rate of these procedures is high and is very promising for future treatment in humans. One disadvantage to using N-TIRE is that the electricity delivered from the electrodes can stimulate muscle cells to contract, which could have lethal consequences depending on the situation. Therefore, a paralytic agent must be used when performing the procedure. The paralytic agents that have been used in such research are successful; however, there is always some risk, albeit slight, when using anesthetics. | 1 | Applied and Interdisciplinary Chemistry |
The "a" of the penta- prefix is not dropped before a vowel. As the IUPAC Red Book 2005 page 69 states, "The final vowels of multiplicative prefixes should not be elided (although monoxide, rather than monooxide, is an allowed exception because of general usage)."
There are a number of exceptions and special cases that violate the above rules. Sometimes the prefix is left off the initial atom: IO is known as iodine pentaoxide, but it should be called diiodine pentaoxide. NO is called nitrogen sesquioxide (sesqui- means ).
The main oxide of phosphorus is called phosphorus pentaoxide. It should actually be diphosphorus pentaoxide, but it is assumed that there are two phosphorus atoms (PO), as they are needed in order to balance the oxidation numbers of the five oxygen atoms. However, people have known for years that the real form of the molecule is PO, not PO, yet it is not normally called tetraphosphorus decaoxide.
In writing formulas, ammonia is NH even though nitrogen is more electronegative (in line with the convention used by IUPAC as detailed in Table VI of the red book). Likewise, methane is written as CH even though carbon is more electronegative (Hill system). | 0 | Theoretical and Fundamental Chemistry |
In June 1791, Lavoisier made a loan of 71,000 livres to Pierre Samuel du Pont de Nemours to buy a printing works so that du Pont could publish a newspaper, La Correspondance Patriotique. The plan was for this to include both reports of debates in the National Constituent Assembly as well as papers from the Academy of Sciences. The revolution quickly disrupted the elder du Ponts first newspaper, but his son E.I. du Pont soon launched Le Republicain and published Lavoisiers latest chemistry texts.
Lavoisier also chaired the commission set up to establish a uniform system of weights and measures which in March 1791 recommended the adoption of the metric system. The new system of weights and measures was adopted by the Convention on 1 August 1793. Lavoisier was one of the 27 Farmers General who, by order of the Convention, were all to be detained. Although temporarily going into hiding, on 30 November 1793 he handed himself into the Port Royal convent for questioning. He claimed he had not operated on this commission for many years, having instead devoted himself to science.
Lavoisier himself was removed from the commission on weights and measures on 23 December 1793, together with mathematician Pierre-Simon Laplace and several other members, for political reasons.
One of his last major works was a proposal to the National Convention for the reform of French education. He also intervened on behalf of a number of foreign-born scientists including mathematician Joseph Louis Lagrange, helping to exempt them from a mandate stripping all foreigners of possessions and freedom. | 1 | Applied and Interdisciplinary Chemistry |
The material was first described in 1908. The catalyst was developed in North America by Homer Burton Adkins and Wilbur Arthur Lazier, partly based on interrogation of German chemists after World War II in relation to the Fischer–Tropsch process. For this reason it is sometimes referred to as the Adkins catalyst or the Lazier catalyst. | 0 | Theoretical and Fundamental Chemistry |
Oxacillin, a derivative of methicillin, was first synthesized in the early 1960s as part of a research initiative led by Peter Doyle and John Naylor of Beecham, in consort with Bristol-Myers. Members of the isoxazolyl penicillin family, which includes cloxacillin, dicloxacillin, and oxacillin, were synthesized to counter the increasing prevalence of infections caused by penicillin-resistant Staphylococcus aureus. While methicillin could only be administered via injection, the isoxazolyl penicillins, including oxacillin, could be given orally or by injection. Following the synthesis of cloxacillin and oxacillin, Beecham retained the right to commercially develop cloxacillin in the United Kingdom while Bristol-Myers was given the marketing rights for oxacillin in the United States. | 0 | Theoretical and Fundamental Chemistry |
The principle of the test is simple:
• A defined amount of distilled or deionized water is poured into the floor pan of the test chamber.
• The samples are placed in the chamber above the water level. The door or hood of the chamber is tightly closed and hermetically sealed for safety.
• A fixed volume of sulfur dioxide is introduced into the chamber, usually either 1 L (0.33%) or 2 L (0.66%) Volume of SO.
The test is performed in two sections,
o Test section 1: 8 hours warm-up to 40±3 °C (relative humidity 100%)
o Test section 2: 16 hours cooling to 18 to 28 °C (relative humidity max. 75 %)
The test is usually carried out in cycles of 24 hours each.
Caution: The atmosphere containing sulfur dioxide must not be released into the room air. | 1 | Applied and Interdisciplinary Chemistry |
Siloxanes are a premier example of an inorganic polymer, even though they have extensive organic substituents. Their backbond is composed of alternating silicon and oxygen atoms, i.e. Si-O-Si-O... The silicon atoms bear two substituents, usually methyl as in the case of polydimethylsiloxane. Some uncommon but illustrative inorganic polymers include polythiazyl ((SN)x) with alternating S and N atoms, and polyphosphates ((PO)). | 0 | Theoretical and Fundamental Chemistry |
Loam molding has been used to produce large symmetrical objects such as cannon and church bells. Loam is a mixture of clay and sand with straw or dung. A model of the produced is formed in a friable material (the chemise). The mold is formed around this chemise by covering it with loam. This is then baked (fired) and the chemise removed. The mold is then stood upright in a pit in front of the furnace for the molten metal to be poured. Afterwards the mold is broken off. Molds can thus only be used once, so that other methods are preferred for most purposes. | 1 | Applied and Interdisciplinary Chemistry |
Linear electron transport through a photosystem will leave the reaction center of that photosystem oxidized. Elevating another electron will first require re-reduction of the reaction center. The excited electrons lost from the reaction center (P700) of photosystem I are replaced by transfer from plastocyanin, whose electrons come from electron transport through photosystem II. Photosystem II, as the first step of the Z-scheme, requires an external source of electrons to reduce its oxidized chlorophyll a reaction center. The source of electrons for photosynthesis in green plants and cyanobacteria is water. Two water molecules are oxidized by the energy of four successive charge-separation reactions of photosystem II to yield a molecule of diatomic oxygen and four hydrogen ions. The electrons yielded are transferred to a redox-active tyrosine residue that is oxidized by the energy of P680. This resets the ability of P680 to absorb another photon and release another photo-dissociated electron. The oxidation of water is catalyzed in photosystem II by a redox-active structure that contains four manganese ions and a calcium ion; this oxygen-evolving complex binds two water molecules and contains the four oxidizing equivalents that are used to drive the water-oxidizing reaction (Kok's S-state diagrams). The hydrogen ions are released in the thylakoid lumen and therefore contribute to the transmembrane chemiosmotic potential that leads to ATP synthesis. Oxygen is a waste product of light-dependent reactions, but the majority of organisms on Earth use oxygen and its energy for cellular respiration, including photosynthetic organisms. | 0 | Theoretical and Fundamental Chemistry |
Dimensional analysis is most often used in physics and chemistry – and in the mathematics thereof – but finds some applications outside of those fields as well. | 1 | Applied and Interdisciplinary Chemistry |
Photaki was selected in 1962 by the US Department of Health, Education and Welfare among an international pool of candidates to conduct research by the side of Nobel laureate Vincent du Vigneaud at Cornell University. While in New York, she also delivered a short series of lectures both in Cornell and at the National Institutes of Health (NIH).
Back in the University of Athens after Cornell, Photaki continued her research and was soon habilitated in 1965 following a thesis on oxytocin, building on the work she started under du Vigneaud. Despite her internationally distinguished research and sizeable recent grants from the NHRF and the United States NIH, she was not allowed to teach by the Greek military junta until 1969 and was intensively interrogated by the Cities Police Security Directorate on account of her anti-dictatorial political beliefs.
Photaki's teaching career was purposefully hindered by the Ministry of Education until the restoration of democracy in 1974; indeed, in 1975 she was promoted to extraordinary professor, a decade after receiving her habilitation. Shortly afterwards, in 1977, she was promoted to full professor (as Professor of Organic Chemistry) and Head of the Organic Chemistry Laboratory, both positions once held by her mentor Zervas. Photaki died in 1983 at the age of 62.
She was reported to spend very long hours at the laboratory, occasionally from "8 in the morning till 10 in the evening". In her 20-year career as a member of the University of Athens faculty, she supervised (alone or jointly with other colleagues) more than 15 doctoral dissertations. | 0 | Theoretical and Fundamental Chemistry |
The room at University College that Bowen used was subsequently named the Bowen room. It was used by Emeritus Fellows of the college and later occupied by Prof. Ruth Chang. Bowen's papers (1931–1980) are held by the Museum of the History of Science in Oxford. | 0 | Theoretical and Fundamental Chemistry |
Powder diffraction patterns of very small single crystals, or crystallites, are subject to size-dependent peak broadening, which, below a certain size, renders powder diffraction fingerprinting useless. In this case, peak resolution is only possible in 3D reciprocal space,
i.e. by applying single-crystal electron diffraction techniques.
High-Resolution Transmission Electron Microscopy (HRTEM) provides images and diffraction patterns of nanometer sized crystallites. Fourier transforms of HRTEM images and electron diffraction patterns both supply information about the projected reciprocal lattice geometry
for a certain crystal orientation, where the projection axis coincides with the optical axis of the microscope.
Projected lattice geometries can be represented by so-called ‘lattice-fringe fingerprint plots’ (LFFPs), also called angular covariance plots. The horizontal axis of such a plot is given in reciprocal lattice length and is limited by the point resolution of the microscope. The vertical axis is defined as acute angle between Fourier transformed lattice fringes or electron diffraction spots. A 2D data point is defined by the length of a reciprocal lattice vector and its (acute) angle with another reciprocal lattice vector. Sets of 2D data points that obey Weiss's zone law are subsets of the entirety of data points in an LFFP. A suitable search-match algorithm using LFFPs, therefore, tries to find matching zone axis subsets in the database. It is, essentially, a variant of a lattice matching algorithm.
In the case of electron diffraction patterns, structure factor amplitudes can be used, in a later step, to further discern among a selection of candidate structures (so-called structure factor fingerprinting). Structure factor amplitudes from electron diffraction data are far less reliable than their counterparts from X-ray single-crystal and powder diffraction data. Existing precession electron diffraction techniques greatly improve the quality of structure factor amplitudes, increase their number and, thus, make structure factor amplitude information much more useful for the fingerprinting process.
Fourier transforms of HRTEM images, on the other hand, supply information not only about the projected reciprocal lattice geometry and structure factor amplitudes, but also structure factor phase angles. After crystallographic image processing, structure factor phase angles are far more reliable than structure factor amplitudes. Further discernment of candidate structures is then mainly based on structure factor phase angles and, to a lesser extent, structure factor amplitudes (so-called structure factor fingerprinting). | 0 | Theoretical and Fundamental Chemistry |
Potassium tert-butoxide is a very strong base that rapidly attacks living tissue.
Potassium tert-butoxide forms explosive mixtures when treated with dichloromethane. | 0 | Theoretical and Fundamental Chemistry |
In meteorology, convective available potential energy (commonly abbreviated as CAPE), is the integrated amount of work that the upward (positive) buoyancy force would perform on a given mass of air (called an air parcel) if it rose vertically through the entire atmosphere. Positive CAPE will cause the air parcel to rise, while negative CAPE will cause the air parcel to sink.
Nonzero CAPE is an indicator of atmospheric instability in any given atmospheric sounding, a necessary condition for the development of cumulus and cumulonimbus clouds with attendant severe weather hazards. | 1 | Applied and Interdisciplinary Chemistry |
We begin with the incompressible form of the momentum equation. The equation has been divided through by the density (P = p/ρ) and density has been absorbed into the body force term.
The equation is integrated over the control volume of a computational cell.
The time-dependent term and the body force term are assumed constant over the volume of the cell. The divergence theorem is applied to the advection, pressure gradient, and diffusion terms.
where n is the normal of the surface of the control volume and V is the volume. If the control volume is a polyhedron and values are assumed constant over each face, the area integrals can be written as summations over each face.
where the subscript nbr denotes the value at any given face. | 1 | Applied and Interdisciplinary Chemistry |
A key insight applied by Boltzmann was to determine the collision term resulting solely from two-body collisions between particles that are assumed to be uncorrelated prior to the collision. This assumption was referred to by Boltzmann as the "" and is also known as the "molecular chaos assumption". Under this assumption the collision term can be written as a momentum-space integral over the product of one-particle distribution functions:
where and are the momenta of any two particles (labeled as A and B for convenience) before a collision, and are the momenta after the collision,
is the magnitude of the relative momenta (see relative velocity for more on this concept), and is the differential cross section of the collision, in which the relative momenta of the colliding particles turns through an angle into the element of the solid angle , due to the collision. | 1 | Applied and Interdisciplinary Chemistry |
Alternative splicing results in two transcript variants encoding the same protein. This gene and the gene that encodes ribonuclease, RNase A family, 4 share promoters and 5' exons. Each gene splices to a unique downstream exon that contains its complete coding region. | 1 | Applied and Interdisciplinary Chemistry |
Zintl phases that contain molecule-like polyanions will often separate into its constituent anions and cations in liquid ammonia, ethylenediamene, crown ethers, or cryptand solutions. Therefore, they are referred to as Zintl ions. The term clusters is also used to emphasize them as groups with homonuclear bonding. The structures can be described by Wade's rules and occupy an area of transition between localized covalent bonds and delocalized skeletal bonding. Beyond the "aesthetic simplicity and beauty of their structures" and distinctive electronic properties, Zintl ions are also of interest in synthesis because of their unique and unpredictable behavior in solution.
The largest subcategory of Zintl ions is homoatomic clusters of group 14 or 15 elements. Some examples are listed below.
Many examples similarly exist for heteroatomic clusters where the polyanion is composed of greater than one main group element. Some examples are listed below. Zintl ions are also capable of reacting with ligands and transition metals, and further 'heteroatomic examples are discussed below (intermetalloid clusters). In some solvents, atoms exchange can occur between heteroatomic clusters. Additionally, it is notable that fewer large cluster examples exist. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, a cross-coupling reaction is a reaction where two different fragments are joined. Cross-couplings are a subset of the more general coupling reactions. Often cross-coupling reactions require metal catalysts. One important reaction type is this:
: (R, R' = organic fragments, usually aryl; M = main group center such as Li or MgX; X = halide)
These reactions are used to form carbon–carbon bonds but also carbon-heteroatom bonds. Cross-coupling reaction are a subset of coupling reactions.
Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki were awarded the 2010 Nobel Prize in Chemistry for developing palladium-catalyzed coupling reactions. | 0 | Theoretical and Fundamental Chemistry |
As mentioned previously, Pseudomonas aeruginosa has the ability to metabolise a variety of substrates including n-alkanes, hexadecane and oils. Uptake of these hydrophobic substrates is speculated to rely on the production of rhamnolipids. It is thought that rhamnolipids either cause the Pseudomonas aeruginosa cell surface to become hydrophobic, promoting an interaction between the substrate and the cell, or secreted rhamnolipids emulsify the substrate and allow it to be taken up by the Pseudomonas aeruginosa cell. There is evidence that rhamnolipids are highly adsorbent to the Pseudomonas aeruginosa cell surface, causing it to become hydrophobic. It has also been shown that production of rhamnolipids promotes uptake of hexadecane by overcoming the inhibitory effect of the hydrophilic interactions caused by LPS. Production of rhamnolipids is observed on hydrophobic substrates but equally high yields are achievable on other carbon sources such as sugars. Furthermore, although mono-rhamnolipids have been shown to interact with the Pseudomonas aeruginosa cell membrane and cause it to become hydrophobic, di-rhamnolipids do not interact well with the cell membrane because the polar head group is too large to penetrate the LPS layer. Therefore, although Rhamnolipids may play a part in interaction of Pseudomonas aeruginosa with hydrophobic carbon sources, they are likely to have additional functions. | 0 | Theoretical and Fundamental Chemistry |
These systems check for large scale changes to the chromosomes and may be used with cell culture or in animal test. The chromosomes are stained and observed for any changes. Sister chromatid exchange is a symmetrical exchange of chromosome material between sister chromatids and may be correlated to the mutagenic or carcinogenic potential of a chemical. In micronucleus Test, cells are examined for micronuclei, which are fragments or chromosomes left behind at anaphase, and is therefore a test for clastogenic agents that cause chromosome breakages. Other tests may check for various chromosomal aberrations such as chromatid and chromosomal gaps and deletions, translocations, and ploidy. | 0 | Theoretical and Fundamental Chemistry |
Microalgae have gained attention in recent years due to several reasons including their greater sensitivity to pollutants than many other organisms. In addition, they occur abundantly in nature, they are an essential component in very many food webs, they are easy to culture and to use in assays and there are few if any ethical issues involved in their use.
Euglena gracilis is a motile, freshwater, photosynthetic flagellate. Although Euglena is rather tolerant to acidity, it responds rapidly and sensitively to environmental stresses such as heavy metals or inorganic and organic compounds. Typical responses are the inhibition of movement and a change of orientation parameters. Moreover, this organism is very easy to handle and grow, making it a very useful tool for eco-toxicological assessments. One very useful particularity of this organism is gravitactic orientation, which is very sensitive to pollutants. The gravireceptors are impaired by pollutants such as heavy metals and organic or inorganic compounds. Therefore, the presence of such substances is associated with random movement of the cells in the water column. For short-term tests, gravitactic orientation of E. gracilis is very sensitive.
Other species such as Paramecium biaurelia (see Paramecium aurelia) also use gravitactic orientation.
Automatic bioassay is possible, using the flagellate Euglena gracilis in a device which measures their motility at different dilutions of the possibly polluted water sample, to determine the EC (the concentration of sample which affects 50 percent of organisms) and the G-value (lowest dilution factor at which no-significant toxic effect can be measured). | 1 | Applied and Interdisciplinary Chemistry |
The thermometric titrimetric analysis of sodium aluminate liquor ("Bayer liquor") in the production of alumina from bauxite is accomplished in an automated two titration sequence. This is an adaptation of a classic thermometric titration application (VanDalen and Ward, 1973). In the first titration, tartrate solution is added to an aliquot of liquor to complex aluminate, releasing one mole of hydroxyl for each mole of aluminate present. This is titrated acidimetrically along with "free" hydroxyl present and the carbonate content (as a second endpoint). The second titration is preceded by the automatic addition of fluoride solution. The alumina-tartrate complex is broken in favour of the formation of an aluminium fluoride complex and the concomitant release of three moles of hydroxyl for each mole of aluminium present, which are then titrated acidimetrically. The whole determination can be completed in less than 5 minutes. | 0 | Theoretical and Fundamental Chemistry |
The concept of additive effect is analogous to the concept of simple addition in mathematics. However, the additive effect is not simply the arithmetic summation of two (or more) drugs in most cases. For an additive inhibition effect, drug A and drug B could each inhibit 20% individually, but the additive effect is not 40%. The effect cannot be simply arithmetic because if drug A and drug B each inhibits 60% cannot theoretically exert an inhibitory effect of 120%. With 60% inhibitory effect each, the remaining function would be at (1-60%)×(1-60%)=16%, meaning the additive inhibitory effect would be 84%. Since the application of additive effect is commonly seen in clinical practice, avoiding the common misconceptions of additive effect is crucial to understanding the clinical significance of additive effect. | 1 | Applied and Interdisciplinary Chemistry |
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