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The AFM is interfaced with an infrared spectrometer. For work using Fourier transform infrared spectroscopy (FTIR), the spectrometer is equipped with a conventional black body infrared source. A particular region of the sample may first be chosen on the basis of the image obtained using the AFM imaging mode of operation. Then, when material at this location absorbs the electromagnetic radiation, heat is generated, which diffuses, giving rise to a decaying temperature profile. The thermal probe then detects the photothermal response of this region of the sample. The resultant measured temperature fluctuations provide an interferogram that replaces the interferogram obtained by a conventional FTIR setup, e.g., by direct detection of the radiation transmitted by a sample. The temperature profile can be made sharp by modulating the excitation beam. This results in the generation of thermal waves whose diffusion length is inversely proportional to the root of the modulation frequency. An important advantage of the thermal approach is that it permits to obtain depth-sensitive subsurface information from surface measurement, thanks to the dependence of thermal diffusion length on modulation frequency. | 0 | Theoretical and Fundamental Chemistry |
The bacteria and their energy source are held in a bioreactor chamber that is impermeable to air and oxygen free. The proper temperature for the bacterial species is maintained in the bioreactor. The bacteria are sustained with a carbohydrate diet consisting of simple saccharide molecules. The carbohydrates are typically sourced from agricultural or forestry waste. | 1 | Applied and Interdisciplinary Chemistry |
The widely accepted method to categorize two-phase flows is to consider the velocity of each phase as if there is not other phases available. The parameter is a hypothetical concept called Superficial velocity. | 1 | Applied and Interdisciplinary Chemistry |
Cerevisterol is widely distributed in the fungal kingdom. In the division Basidiomycota, it occurs in several members of the fungal family Boletaceae, the edible mushrooms Cantharellus cibarius, Volvariella volvacea, Pleurotus sajor-caju, Laetiporus sulphureus, and Suillus luteus, in the milk mushroom Lactarius hatsudake, and the coral fungus Ramaria botrytis. In the division Ascomycota, it has been reported in Auricularia polytricha, Bulgaria inquinans, Engleromyces goetzei, Acremonium luzulae, and Pencillium herquei, as well as the lichens Ramalina hierrensis and Stereocaulon azoreum. It has also been found in the endophytes Alternaria brassicicola, Fusarium oxysporum, and a strain of Gliocladium, and the deep-sea fungus Aspergillus sydowi. In 2013, the sterol was reported in the South China Sea gorgonian coral Muriceoopsis flavida. A 9-hydroxylated analogue of cerevisterol was found in R. botrytis. A modified version of the compound, (22E, 24R)-cerevisterol, has been reported from the coral Subergorgia mollis. It was shown to be moderately cytotoxic to embryos of the zebrafish Danio rerio. | 1 | Applied and Interdisciplinary Chemistry |
Because solids have thermal energy, their atoms vibrate about fixed mean positions within the ordered (or disordered) lattice. The spectrum of lattice vibrations in a crystalline or glassy network provides the foundation for the kinetic theory of solids. This motion occurs at the atomic level, and thus cannot be observed or detected without highly specialized equipment, such as that used in spectroscopy.
Thermal properties of solids include thermal conductivity, which is the property of a material that indicates its ability to conduct heat. Solids also have a specific heat capacity, which is the capacity of a material to store energy in the form of heat (or thermal lattice vibrations). | 0 | Theoretical and Fundamental Chemistry |
Because peanut agglutinin specifically binds a particular carbohydrate sequence it finds use in a range of methods for cell biology and biochemistry. For example in PNA-affinity chromatography the binding specificity of peanut agglutinin is used to isolate glycosylated molecules which have the sugar sequence Gal-β(1-3)-GalNAc. Peanut agglutinin activity is inhibited by lactose and galactose which compete for the binding site.
Other uses include:
* Potent anti-T cell activity.
* Distinguishing between human lymphocyte subsets.
* Identification of cone cell inner and outer segments and to a lesser extent rod cell inner segments in the mammalian retina.
* Tumour tissue determination for transitional mucosa malignancies.
* Identification of mammalian-infective metacyclic promastigote Leishmania major parasites from other life cycle forms also found in the sandfly host.
* Identification of the outer acrosome membrane in sperm, indicating acrosome integrity. | 1 | Applied and Interdisciplinary Chemistry |
The Castner process for production of sodium metal was introduced in 1888 by Hamilton Castner. At that time (prior to the introduction in the same year of the Hall-Héroult process) the primary use for sodium metal was as a reducing agent to produce aluminium from its purified ores. The Castner process reduced the cost of producing sodium in comparison to the old method of reducing sodium carbonate at high temperature using carbon. This in turn reduced the cost of producing aluminium, although the reduction-by-sodium method still could not compete with Hall-Héroult. The Castner process continued nevertheless due to Castner's finding new markets for sodium. In 1926, the Downs cell replaced the Castner process. | 1 | Applied and Interdisciplinary Chemistry |
A monochromator can use either the phenomenon of optical dispersion in a prism, or that of diffraction using a diffraction grating, to spatially separate the colors of light. It usually has a mechanism for directing the selected color to an exit slit. Usually the grating or the prism is used in a reflective mode. A reflective prism is made by making a right triangle prism (typically, half of an equilateral prism) with one side mirrored. The light enters through the hypotenuse face and is reflected back through it, being refracted twice at the same surface. The total refraction, and the total dispersion, is the same as would occur if an equilateral prism were used in transmission mode. | 0 | Theoretical and Fundamental Chemistry |
The Creighton process involves the hydrogenation of a 6 carbon chain aldehyde. The reactant is 2,3,4,5,6-pentahydroxyhexanal (an aldehyde) and the product is 1,2,3,4,5,6-hexanehexol (an alcohol). The product thus has two more hydrogen atoms than the reactant: -CHO is replaced by -CHOH.
The Creighton process was patented in the 1920s. | 0 | Theoretical and Fundamental Chemistry |
Pedro de Castro Lazera founded the company Imifarma on 2 December 1960. It was initially focused on the drug distribution market.
In the 1990s, Imifarma started to operate in the retail market through its own network of pharmacies under the name Extrafarma. The store chain began in the city of Belém and expanded to other areas in the state of Pará and in the neighbor state of Amapá. Later, it expanded to the states of Maranhão, Ceará, Piauí and Rio Grande do Norte.
In 2013, Extrafarma was acquired by Ultra. With the acquisition, Ultra entered the pharmaceutical retail industry and made Extrafarma its third distribution business and specialty retail chain, along with Ipiranga and Ultragaz. With the acquisition, Extrafarma will expand and open new pharmacy stores inside Ipiranga gas stations and Ultragaz resellers. | 1 | Applied and Interdisciplinary Chemistry |
Disulfides have a C-S-S-C dihedral angle approaching 90°. The S-S bond length is 2.03 Å in diphenyl disulfide, similar to that in elemental sulfur.
Two kinds of disulfides are recognized, symmetric and unsymmetric. Symmetrical disulfides are compounds of the formula . Most disulfides encountered in organo sulfur chemistry are symmetrical disulfides. Unsymmetrical disulfides (also called heterodisulfides or mixed disulfides) are compounds of the formula . Unsymmetrical disulfide are less common in organic chemistry, but many disulfides in nature are unsymmetrical. Illustrative of a symmetric disulfide is cystine. | 0 | Theoretical and Fundamental Chemistry |
The GeneXpert Infinity is an automated cartridge-based nucleic acid amplification test (NAAT) which is able to tell whether the subject fluid contains shreds of the SARS-CoV-2 virus, amongst others. It is manufactured by Cepheid Inc. | 1 | Applied and Interdisciplinary Chemistry |
Media for 3D optical data storage have been suggested in several form factors: disk, card and crystal.
A disc media offers a progression from CD/DVD, and allows reading and writing to be carried out by the familiar spinning disc method.
A credit card form factor media is attractive from the point of view of portability and convenience, but would be of a lower capacity than a disc.
Several science fiction writers have suggested small solids that store massive amounts of information, and at least in principle this could be achieved with 5D optical data storage. | 0 | Theoretical and Fundamental Chemistry |
Operando spectroscopy requires measurement of the catalyst under (ideally) real working conditions, involving comparable temperature and pressure environments to those of industrially catalyzed reactions, but with a spectroscopic device inserted into the reaction vessel. The parameters of the reaction are then measured continuously during the reaction using the appropriate instrumentation, i.e., online mass spectrometry, gas chromatography or IR/NMR spectroscopy.
Operando instruments (in situ cells) must ideally allow for spectroscopic measurement under optimal reaction conditions. Most industrial catalysis reactions require excessive pressure and temperature conditions which subsequently degrades the quality of the spectra by lowering the resolution of signals. Currently many complications of this technique arise due to the reaction parameters and the cell design. The catalyst may interact with the components of the operando apparatus; open space in the cell can have an effect on the absorption spectra, and the presence of spectator species in the reaction may complicate analysis of the spectra. Continuing development of operando reaction-cell design is in line with working towards minimizing the need for compromise between optimal catalysis conditions and spectroscopy. These reactors must handle specific temperature and pressure requirements while still providing access for spectrometry.
Other requirements considered when designing operando experiments include reagent and product flow rates, catalyst position, beam paths, and window positions and sizes. All of these factors must also be accounted for while designing operando experiments, as the spectroscopic techniques used may alter the reaction conditions. An example of this was reported by Tinnemans et al., which noted that local heating by a Raman laser can give spot temperatures exceeding 100 °C. Also, Meunier reports that when using DRIFTS, there is a noticeable temperature difference (on the order of hundreds of degrees) between the crucible core and the exposed surface of the catalyst due to losses caused by the IR-transparent windows necessary for analysis. | 0 | Theoretical and Fundamental Chemistry |
JSS is a peer-reviewed journal covering fundamental and applied areas of solid-state science and technology, including experimental and theoretical aspects of the chemistry and physics of materials and devices. | 0 | Theoretical and Fundamental Chemistry |
Although immunogold labeling is typically used for transmission electron microscopy, when the gold is silver-enhanced it can be seen using brightfield microscopy. The silver enhancement increases the particle size, also making scanning electron microscopy possible. In order to produce the silver-enhanced gold particles, colloidal gold particles are placed in an acidic enhancing solution containing silver ions. Gold particles then act as a nucleation site and silver is deposited onto the particle. An example of the application of silver-enhanced immunogold labeling (IGSS) was in the identification of the pathogen Erwinia amylovora. | 1 | Applied and Interdisciplinary Chemistry |
* [https://web.archive.org/web/20110103135037/http://www.organicgardeninfo.com/feather-meal.html Organic gardening information] | 0 | Theoretical and Fundamental Chemistry |
The energy of Rydberg states can be refined by including a correction called the quantum defect in the Rydberg formula. The "quantum defect" correction is associated with the presence of a distributed ionic core. Even for many electronically excited molecular systems, the ionic core interaction with an excited electron can take on the general aspects of the interaction between the proton and the electron in the hydrogen atom. The spectroscopic assignment of these states follows the Rydberg formula and they are called Rydberg states of molecules. | 0 | Theoretical and Fundamental Chemistry |
Parkeol is a relatively uncommon sterol secondary metabolite found mostly in plants, particularly noted in Butyrospermum parkii (now called Vitellaria paradoxa, or the shea tree). It can be synthesized as a minor product by several oxidosqualene cyclase enzymes, and is the sole product of the enzyme parkeol synthase.
Parkeol is the dominant sterol found in the planctomycete Gemmata obscuriglobus, a rare example of a sterol-synthesizing prokaryote. The only other sterol identified in this organism is lanosterol, a key component of the sterol biosynthetic pathway in animals and fungi; this relatively limited sterol repertoire may resemble the early evolution of sterol synthesis, which is ubiquitous in eukaryotes. | 0 | Theoretical and Fundamental Chemistry |
An example of a photoacid which undergoes excited-state proton transfer without prior photolysis is the fluorescent dye pyranine (8-hydroxy-1,3,6-pyrenetrisulfonate or HPTS).
The Förster cycle was proposed by Theodor Förster and combines knowledge of the ground state acid dissociation constant (pK), absorption, and fluorescence spectra to predict the pK in the excited state of a photoacid.
The name photoacid can be abbreviated PAH, where the H does not stand for a word starting with H, but rather for a hydrogen atom which is lost when the molecule reacts as a Brønsted acid. This use of PAH should not be confused with other meanings of PAH in chemistry and in medicine. | 0 | Theoretical and Fundamental Chemistry |
The use of heat to empower galvanic cells was first studied around 1880. However it was not until the decade of 1950 that more serious research was undertaken in this field. | 0 | Theoretical and Fundamental Chemistry |
During the 1950s, theoretical condensed matter physicists arrived at an understanding of "conventional" superconductivity, through a pair of remarkable and important theories: the phenomenological Ginzburg–Landau theory (1950) and the microscopic BCS theory (1957).
In 1950, the phenomenological Ginzburg–Landau theory of superconductivity was devised by Landau and Ginzburg. This theory, which combined Landau's theory of second-order phase transitions with a Schrödinger-like wave equation, had great success in explaining the macroscopic properties of superconductors. In particular, Abrikosov showed that Ginzburg–Landau theory predicts the division of superconductors into the two categories now referred to as Type I and Type II. Abrikosov and Ginzburg were awarded the 2003 Nobel Prize for their work (Landau had received the 1962 Nobel Prize for other work, and died in 1968). The four-dimensional extension of the Ginzburg–Landau theory, the Coleman-Weinberg model, is important in quantum field theory and cosmology.
Also in 1950, Maxwell and Reynolds et al. found that the critical temperature of a superconductor depends on the isotopic mass of the constituent element. This important discovery pointed to the electron-phonon interaction as the microscopic mechanism responsible for superconductivity.
The complete microscopic theory of superconductivity was finally proposed in 1957 by Bardeen, Cooper and Schrieffer. This BCS theory explained the superconducting current as a superfluid of Cooper pairs, pairs of electrons interacting through the exchange of phonons. For this work, the authors were awarded the Nobel Prize in 1972.
The BCS theory was set on a firmer footing in 1958, when N. N. Bogolyubov showed that the BCS wavefunction, which had originally been derived from a variational argument, could be obtained using a canonical transformation of the electronic Hamiltonian. In 1959, Lev Gor'kov showed that the BCS theory reduced to the Ginzburg–Landau theory close to the critical temperature.
Generalizations of BCS theory for conventional superconductors form the basis for the understanding of the phenomenon of superfluidity, because they fall into the lambda transition universality class. The extent to which such generalizations can be applied to unconventional superconductors is still controversial. | 0 | Theoretical and Fundamental Chemistry |
Coronaviruses are enveloped viruses with a positive-sense RNA genome and with a nucleocapsid of helical symmetry. They infect the upper respiratory and gastrointestinal tract of mammals and birds. They are the cause of a wide range of diseases in cats, dog, pigs, rodents, cattle and humans. Transmission is by the faecal-oral route. | 1 | Applied and Interdisciplinary Chemistry |
Fibrin monomers are monomers of fibrin which are formed by the cleavage of fibrinogen by thrombin. Levels of fibrin monomers can be measured using blood tests and can serve as a marker of in vivo fibrinogenesis and coagulation activation. They may be useful in the evaluation hypercoagulability.
Levels of fibrin monomers may be increased with pregnancy and by estrogen-containing combined birth control pills. | 1 | Applied and Interdisciplinary Chemistry |
Sevoflurane was discovered by Ross Terrell and independently by Bernard M Regan. A detailed report of its development and properties appeared in 1975 in a paper authored by Richard Wallin, Bernard Regan, Martha Napoli and Ivan Stern. It was introduced into clinical practice initially in Japan in 1990 by Maruishi Pharmaceutical Co., Ltd. Osaka, Japan. The rights for sevoflurane worldwide were held by AbbVie. It is now available as a generic drug. | 1 | Applied and Interdisciplinary Chemistry |
The Global Meteoric Water Line (GMWL) describes the global annual average relationship between hydrogen and oxygen isotope (oxygen-18 and deuterium) ratios in natural meteoric waters. The GMWL was first developed in 1961 by Harmon Craig, and has subsequently been widely used to track water masses in environmental geochemistry and hydrogeology. | 0 | Theoretical and Fundamental Chemistry |
Extensive clinical research has not demonstrated drug tolerance, defined as a reduction in response, to wakefulness-promoting and anti-fatigue properties of modafinil, even with therapeutic use extending up to 40 weeks.
While modafinil is generally found to be safe and significant adverse effects are rare, including in pediatric narcolepsy cases (sleep disorders in children), there is evidence that long-term usage can lead to tolerance in some individuals. This necessitates higher doses to maintain the same level of cognitive enhancement or relief from sleepiness.
People with current or past substance addictions and those with a family history of addiction are particularly at risk for developing tolerance.
The mechanisms driving tolerance to modafinil, which may involve its impact on dopamine and norepinephrine levels in the brain, are not fully understood.
Repeated administration of modafinil for off-label use, such as increased alertness and cognitive-enhancing effects in sleep deprivation, can lead to drug tolerance, which means that the effectiveness of the drug may decrease over time. Still, modafinil therapy as a eugeroic agent to treat narcolepsy does not typically lead to drug tolerance, i.e., the effectiveness does not usually decrease on prolonged use, although individual responses may vary. | 0 | Theoretical and Fundamental Chemistry |
Abé (1996) explores the record of iron and steel firms in Victorian England by analyzing Bolckow Vaughan & Company. It was wedded for too long to obsolescent technology and was a very late adopter of the open hearth furnace method. Abé concludes that the firm—and the British steel industry—suffered from a failure of entrepreneurship and planning.
Blair (1997) explores the history of the British Steel industry since the Second World War to evaluate the impact of government intervention in a market economy. Entrepreneurship was lacking in the 1940s; the government could not persuade the industry to upgrade its plants. For generations the industry had followed a patchwork growth pattern which proved inefficient in the face of world competition. In 1946 the first steel development plan was put into practice with the aim of increasing capacity; the Iron and Steel Act 1949 meant nationalization of the industry in the form of the Iron and Steel Corporation of Great Britain. However, the reforms were dismantled by the Conservative Party governments in the 1950s. In 1967, under Labour Party control again, the industry was again nationalized. But by then twenty years of political manipulation had left companies such as the British Steel Corporation with serious problems: a complacency with existing equipment, plants operating under capacity (low efficiency), poor quality assets, outdated technology, government price controls, higher coal and oil costs, lack of funds for capital improvement, and increasing world market competition. By the 1970s the Labour government had its main goal to keep employment high in the declining industry. Since British Steel was a main employer in depressed regions, it had kept many mills and facilities that were operating at a loss. In the 1980s, Conservative Prime Minister Margaret Thatcher re-privatized BSC as British Steel plc. | 1 | Applied and Interdisciplinary Chemistry |
Particle physicists have only observed or inferred left-chiral fermions and right-chiral antifermions engaging in the charged weak interaction. In the case of the weak interaction, which can in principle engage with both left- and right-chiral fermions, only two left-handed fermions interact. Interactions involving right-handed or opposite-handed fermions have not been shown to occur, implying that the universe has a preference for left-handed chirality. This preferential treatment of one chiral realization over another violates parity, as first noted by Chien Shiung Wu in her famous experiment known as the Wu experiment. This is a striking observation, since parity is a symmetry that holds for all other fundamental interactions.
Chirality for a Dirac fermion is defined through the operator , which has eigenvalues ±1; the eigenvalues sign is equal to the particles chirality: +1 for right-handed, −1 for left-handed. Any Dirac field can thus be projected into its left- or right-handed component by acting with the projection operators or on .
The coupling of the charged weak interaction to fermions is proportional to the first projection operator, which is responsible for this interaction's parity symmetry violation.
A common source of confusion is due to conflating the , chirality operator with the helicity operator. Since the helicity of massive particles is frame-dependent, it might seem that the same particle would interact with the weak force according to one frame of reference, but not another. The resolution to this paradox is that , for which helicity is not frame-dependent. By contrast, for massive particles, chirality is not the same as helicity, or, alternatively, helicity is not Lorentz invariant, so there is no frame dependence of the weak interaction: a particle that couples to the weak force in one frame does so in every frame.
A theory that is asymmetric with respect to chiralities is called a chiral theory, while a non-chiral (i.e., parity-symmetric) theory is sometimes called a vector theory. Many pieces of the Standard Model of physics are non-chiral, which is traceable to anomaly cancellation in chiral theories. Quantum chromodynamics is an example of a vector theory, since both chiralities of all quarks appear in the theory, and couple to gluons in the same way.
The electroweak theory, developed in the mid 20th century, is an example of a chiral theory. Originally, it assumed that neutrinos were massless, and assumed the existence of only left-handed neutrinos and right-handed antineutrinos. After the observation of neutrino oscillations, which imply that neutrinos are massive (like all other fermions) the revised theories of the electroweak interaction now include both right- and left-handed neutrinos. However, it is still a chiral theory, as it does not respect parity symmetry.
The exact nature of the neutrino is still unsettled and so the electroweak theories that have been proposed are somewhat different, but most accommodate the chirality of neutrinos in the same way as was already done for all other fermions. | 0 | Theoretical and Fundamental Chemistry |
Photocatalyst activity indicator inks are a recent advance in the visual demonstration of photocatalysis and the assessment of the activity of photocatalyst materials. They are inexpensive, easy to use and provide a very quick route to demonstrating the presence of a photocatalytic film, even under low levels of UV light. Unlike the photo-oxidative bleaching of methylene blue, they use the underlying semiconductor photocatalyst film to photoreduce the dye (D in figure 2), in the ink coating, to another (usually colourless) form, (D in figure 2) whilst simultaneously oxidising an easily oxidised organic species, a sacrificial electron donor (SED), such as glycerol, which is also present in the ink. The kinetics of reduction of the dye in a paii have been studied in great detail. Figure 2 illustrates the basic principles of operation of a paii when applied to a product that has a thin photocatalyst film coating. | 0 | Theoretical and Fundamental Chemistry |
Electrocatalysis can occur at the surface of some bulk materials, such as platinum metal. Bulk metal surfaces of gold have been employed for the decomposition methanol for hydrogen production. Water electrolysis is conventionally conducted at inert bulk metal electrodes such as platinum or iridium. The activity of an electrocatalyst can be tuned with a chemical modification, commonly obtained by alloying two or more metals. This is due to a change in the electronic structure, especially in the d band which is considered to be responsible for the catalytic properties of noble metals. | 0 | Theoretical and Fundamental Chemistry |
Once a substitution is made on a parent molecule, its structural symmetry is usually reduced, meaning that atoms that were formerly equivalent may no longer be so. Thus substitution of two or more equivalent atoms by the same element may generate more than one positional isomer.
The classical example is the derivatives of benzene. Its six hydrogens are all structurally equivalent, and so are the six carbons; because the structure is not changed if the atoms are permuted in ways that correspond to flipping the molecule over or rotating it by multiples of 60 degrees. Therefore, replacing any hydrogen by chlorine yields only one chlorobenzene. However, with that replacement, the atom permutations that moved that hydrogen are no longer valid. Only one permutation remains, that corresponds to flipping the molecule over while keeping the chlorine fixed. The five remaining hydrogens then fall into three different equivalence classes: the one opposite to the chlorine is a class by itself (called the para position), the two closest to the chlorine form another class (ortho), and the remaining two are the third class (meta). Thus a second substitution of hydrogen by chlorine can yield three positional isomers: 1,2- or ortho-, 1,3- or meta-, and 1,4- or para-dichlorobenzene.
For the same reason, there is only one phenol (hydroxybenzene), but three benzenediols; and one toluene (methylbenzene), but three toluols, and three xylenes.
On the other hand, the second replacement (by the same substituent) may preserve or even increase the symmetry of the molecule, and thus may preserve or reduce the number of equivalence classes for the next replacement. Thus, the four remaining hydrogens in meta-dichlorobenzene still fall into three classes, while those of ortho- fall into two, and those of para- are all equivalent again. Still, some of these 3 + 2 + 1 = 6 substitutions end up yielding the same structure, so there are only three structurally distinct trichlorobenzenes: 1,2,3-, 1,2,4-, and 1,3,5-.
If the substituents at each step are different, there will usually be more structural isomers. Xylenol, which is benzene with one hydroxyl substituent and two methyl substituents, has a total of 6 isomers: | 0 | Theoretical and Fundamental Chemistry |
Quantifying gene expression by traditional DNA detection methods is unreliable. Detection of mRNA on a northern blot or PCR products on a gel or Southern blot does not allow precise quantification. For example, over the 20–40 cycles of a typical PCR, the amount of DNA product reaches a plateau that is not directly correlated with the amount of target DNA in the initial PCR.
Real-time PCR can be used to quantify nucleic acids by two common methods: relative quantification and absolute quantification. Absolute quantification gives the exact number of target DNA molecules by comparison with DNA standards using a calibration curve. It is therefore essential that the PCR of the sample and the standard have the same amplification efficiency.
Relative quantification is based on internal reference genes to determine fold-differences in expression of the target gene. The quantification is expressed as the change in expression levels of mRNA interpreted as complementary DNA (cDNA, generated by reverse transcription of mRNA). Relative quantification is easier to carry out as it does not require a calibration curve as the amount of the studied gene is compared to the amount of a control reference gene.
As the units used to express the results of relative quantification are unimportant the results can be compared across a number of different RTqPCR. The reason for using one or more housekeeping genes is to correct non-specific variation, such as the differences in the quantity and quality of RNA used, which can affect the efficiency of reverse transcription and therefore that of the whole PCR process. However, the most crucial aspect of the process is that the reference gene must be stable.
The selection of these reference genes was traditionally carried out in molecular biology using qualitative or semi-quantitative studies such as the visual examination of RNA gels, northern blot densitometry or semi-quantitative PCR (PCR mimics). Now, in the genome era, it is possible to carry out a more detailed estimate for many organisms using transcriptomic technologies. However, research has shown that amplification of the majority of reference genes used in quantifying the expression of mRNA varies according to experimental conditions. It is therefore necessary to carry out an initial statistically sound methodological study in order to select the most suitable reference gene.
A number of statistical algorithms have been developed that can detect which gene or genes are most suitable for use under given conditions. Those like geNORM or BestKeeper can compare pairs or geometric means for a matrix of different reference genes and tissues. | 1 | Applied and Interdisciplinary Chemistry |
In the classical mechanics framework, a rough surface, such as a machined metal surface, randomizes the probability distribution function governing the incoming particles, leading to net momentum loss of the particle flux. | 0 | Theoretical and Fundamental Chemistry |
Gadolin was knighted and is registered under number 245 in the Finnish House of Nobility. He was also awarded the Order of Saint Vladimir and the Order of Saint Anna. His heraldic device was: | 1 | Applied and Interdisciplinary Chemistry |
The effect was theoretically predicted in 1979, in a mathematical description of hyper Raman scattering optical activity. Within this theoretical model, upon setting the initial and final frequencies of light to the same value, the mathematics describe the hyper Rayleigh scattering optical activity. The theory was well in advance of its time, and the effect remained elusive for 40 years. Its author David L. Andrews referred to it as the "impossible theory". However, in January 2019, an experimental demonstration was reported by Ventsislav K. Valev and his team. The team investigated the hyper Rayleigh scattering (at the second harmonic generation frequency) from chiral nanohelices made of silver. Valev and his team observed that the intensity of the hyper Rayleigh scattering light depended on the direction of circularly polarized light and that this dependence reversed with the chirality of the nanohelices. Valev's work unambiguously established that the effect is physically possible, opening the way for nonlinear chiroptical investigations of a variety of chiral light-scattering materials; including molecules, plasmonic metal nanoparticles and semiconductor nanoparticles. | 0 | Theoretical and Fundamental Chemistry |
Plane-wave topography is in some sense the opposite of white-beam topography, making use of monochromatic (single-wavelength) and parallel incident beam. In order to achieve diffraction conditions, the sample under study must be precisely aligned. The contrast observed strongly depends on the exact position of the angular working point on the rocking curve of the sample, i.e. on the angular distance between the actual sample rotation position and the theoretical position of the Bragg peak. A sample rotation stage is therefore an essential instrumental precondition for controlling and varying the contrast conditions. | 0 | Theoretical and Fundamental Chemistry |
Osmolarity and tonicity are related but distinct concepts. Thus, the terms ending in -osmotic (isosmotic, hyperosmotic, hyposmotic) are not synonymous with the terms ending in -tonic (isotonic, hypertonic, hypotonic). The terms are related in that they both compare the solute concentrations of two solutions separated by a membrane. The terms are different because osmolarity takes into account the total concentration of penetrating solutes and non-penetrating solutes, whereas tonicity takes into account the total concentration of non-freely penetrating solutes only.
Penetrating solutes can diffuse through the cell membrane, causing momentary changes in cell volume as the solutes "pull" water molecules with them. Non-penetrating solutes cannot cross the cell membrane; therefore, the movement of water across the cell membrane (i.e., osmosis) must occur for the solutions to reach equilibrium.
A solution can be both hyperosmotic and isotonic. For example, the intracellular fluid and extracellular can be hyperosmotic, but isotonic – if the total concentration of solutes in one compartment is different from that of the other, but one of the ions can cross the membrane (in other words, a penetrating solute), drawing water with it, thus causing no net change in solution volume. | 0 | Theoretical and Fundamental Chemistry |
Lactonase hydrolyzes the ester bond of the homoserine lactone ring of acylated homoserine lactones. In hydrolysing the lactone bond, lactonase prevents these signaling molecules from binding to their target transcriptional regulators, thus inhibiting quorum sensing. | 1 | Applied and Interdisciplinary Chemistry |
An allomone (from Ancient Greek "other" and pheromone) is a type of semiochemical produced and released by an individual of one species that affects the behaviour of a member of another species to the benefit of the originator but not the receiver. Production of allomones is a common form of defense against predators, particularly by plant species against insect herbivores. In addition to defense, allomones are also used by organisms to obtain their prey or to hinder any surrounding competitors.
Many insects have developed ways to defend against these plant defenses (in an evolutionary arms race). One method of adapting to allomones is to develop a positive reaction to them; the allomone then becomes a kairomone. Others alter the allomones to form pheromones or other hormones, and yet others adopt them into their own defensive strategies, for example by regurgitating them when attacked by an insectivorous insect.
A third class of allelochemical (chemical used in interspecific communication), synomones, benefit both the sender and receiver. | 1 | Applied and Interdisciplinary Chemistry |
Pipe fitters are often exposed to hazardous or dangerous materials, such as asbestos, lead, ammonia, steam, flammable gases, various resins and solvents including benzene and various refrigerants. Much progress was made in the 20th century toward eliminating or reducing hazardous materials exposures. Many aspects of hazardous materials are now regulated by law in most countries, including asbestos usage and removal and refrigerant selection and handling.
Other occupational hazards include exposure to the weather, heavy lifting, crushing hazards, lacerations, and other risks normal to the construction industry. | 1 | Applied and Interdisciplinary Chemistry |
Rhodizonic acid is a member of a chain of oxidation products: benzenehexol , tetrahydroxybenzoquinone (THBQ) , rhodizonic acid , and cyclohexanehexone . Lithium rhodizonate, together with salts of THBQ and benzenehexol, has been considered for possible use in rechargeable electrical batteries. The monovalent anion has been detected in mass spectrometry experiments.
Rhodizonic acid and the rhodizonate anion can lose one of the CO units to yield croconic acid and the croconate anion , respectively, by mechanisms that are still imperfectly known. In basic solutions (pH > 10), rhodizonic acid quickly converts to the THBQ anion in the absence of oxygen, and to croconic acid in its presence. At pH 8.3 and exposure to light, solutions are stable for days in the absence of oxygen, and decompose to croconic acid and other products (possibly including cyclohexanehexone or dodecahydroxycyclohexane) in its presence. | 0 | Theoretical and Fundamental Chemistry |
Gene silencing techniques have been widely used by researchers to study genes associated with disorders. These disorders include cancer, infectious diseases, respiratory diseases, and neurodegenerative disorders. Gene silencing is also currently being used in drug discovery efforts, such as synthetic lethality, high-throughput screening, and miniaturized RNAi screens. | 1 | Applied and Interdisciplinary Chemistry |
Typically a traditional liquid rheostat consists of a steel cylinder (the negative), about in size, standing on insulators, in which was suspended a hollow steel cylinder. This acted as the positive electrode and was supported by a steel rope and insulator from an adjustable pulley. The water pipe connection included an insulated section. The tank contained salt water, but not at the concentration that could be described as “brine”. The whole device was fenced off for safety.
Operation was very simple, as adding more salt, more water or varying the height of the centre electrode would vary the load. The load proved to be quite stable, varying only slightly as the water heated up, which never came to boil. Power dissipation was about 1 megawatt, at a potential of about 700 volts and current of about 1,500 amperes.
Modern designs use stainless steel electrodes, and sodium carbonate, or other salts, and do not use the container as one electrode.
Systems with frequent starting may include water circulation to external heat exchangers. In such cases anti-freeze and anti-corrosion additives must be carefully chosen to not change the resistance or support the growth of algae or bacteria. | 0 | Theoretical and Fundamental Chemistry |
First, the soil and sediment structures will determine how tightly PCBs are adhered to them and affect the absorption of PCBs into cells. The PCBs’ availability suffers from increasing organic carbon and clay content, for they promote the absorption of PCBs into soil or sediment matrices. Second, the soil contains necessary nutrition for the growth of microbes and anaerobic and aerobic environments. Finally, the local microbial population has significant impacts on the rate of degradation of PCBs, which varies based on the microbial strains and their activities. Then, if there is no history of exposure to PCBs, it may take months for microbes to activates their ability to dechlorinate PCBs and break them down. | 1 | Applied and Interdisciplinary Chemistry |
The typical current density at which electromigration occurs in Cu or Al interconnects is 10 to 10 A/cm. For solder joints (SnPb or SnAgCu lead-free) used in IC chips, however, electromigration occurs at much lower current densities, e.g. 10 A/cm.
It causes a net atom transport along the direction of electron flow. The atoms accumulate at the anode, while voids are generated at the cathode and back stress is induced during electromigration. The typical failure of a solder joint due to electromigration will occur at the cathode side. Due to the current crowding effect, voids form first at the corners of the solder joint. Then the voids extend and join to cause a failure. Electromigration also influences formation of intermetallic compounds, as the migration rates are a function of atomic mass. | 0 | Theoretical and Fundamental Chemistry |
Mefloquine is used as a treatment for chloroquine-sensitive or resistant Plasmodium falciparum malaria, and is deemed a reasonable alternative for uncomplicated chloroquine-resistant Plasmodium vivax malaria. It is one of several drugs recommended by the United States' Centers for Disease Control and Prevention.
It is not recommended for severe malaria infections, particularly infections from P. falciparum, which should be treated with intravenous antimalarials. Mefloquine does not eliminate parasites in the liver phase of the disease, and people with P. vivax malaria should be treated with a second drug that is effective for the liver phase, such as primaquine. | 0 | Theoretical and Fundamental Chemistry |
The elements can be divided into several categories:
The condensation temperatures are the temperatures at which 50% of the element will be in the form of a solid (rock) under a pressure of 10 bar. However, slightly different groups and temperature ranges are used sometimes. Refractory material are also often divided into refractory lithophile elements and refractory siderophile elements. | 0 | Theoretical and Fundamental Chemistry |
Deficiency of this enzyme will increase the possibility of cholesterol gallstones.
Disruption of CYP7A1 from classic bile acid synthesis in mice leads to either increased postnatal death or a milder phenotype with elevated serum cholesterol. The latter is similar to the case in humans, where CYP7A1 mutations associate with high plasma low-density lipoprotein and hepatic cholesterol content, as well as deficient bile acid excretion. There is also a synergy between plasma low-density lipoprotein cholesterol (LDL-C) and risks of coronary artery disease (CAD). Glucose signaling also induces CYP7A1 gene transcription by epigenetic regulation of the histone acetylation status. Glucose induction of bile acid synthesis have an important implication in metabolic control of glucose, lipid, and energy homeostasis under normal and diabetic conditions. CYP7A1-rs3808607 and apolipoprotein E (APOE) isoform are associated with the extent of reduction in circulating LDL cholesterol in response to plant sterol consumption and could serve as potential predictive genetic markers to identify individuals who would derive maximum LDL cholesterol lowering with plant sterol consumption. Genetic variations in CYP7A1 influence its expression and thus may affect the risk of gallstone disease and gallbladder cancer.
One of the many lipid lowering effects of the fibrate drug class is mediated through the inhibition of transcription of this enzyme. This inhibition leads to more cholesterol in the bile, which is the body's only route of cholesterol excretion. This also increases the risk of cholesterol gallstone formation.
Inhibition of CYP7A1 is thought to be involved in or responsible for the hepatotoxicity associated with ketoconazole. The levorotatory enantiomer of ketoconazole, levoketoconazole, shows 12-fold reduced potency in inhibition of this enzyme, and is under development for certain indications (e.g., Cushing's syndrome) as a replacement for ketoconazole with reduced toxicity and improved tolerability and safety. | 1 | Applied and Interdisciplinary Chemistry |
Photolysis occurs in the atmosphere as part of a series of reactions by which primary pollutants such as hydrocarbons and nitrogen oxides react to form secondary pollutants such as peroxyacyl nitrates. See Photochemical smog.
The two most important photodissociation reactions in the troposphere are firstly:
which generates an excited oxygen atom which can react with water to give the hydroxyl radical:
The hydroxyl radical is central to atmospheric chemistry as it initiates the oxidation of hydrocarbons in the atmosphere and so acts as a detergent.
Secondly the reaction:
is a key reaction in the formation of tropospheric ozone.
The formation of the ozone layer is also caused by photodissociation. Ozone in the Earth's stratosphere is created by ultraviolet light striking oxygen molecules containing two oxygen atoms (), splitting them into individual oxygen atoms (atomic oxygen). The atomic oxygen then combines with unbroken to create ozone, . In addition, photolysis is the process by which CFCs are broken down in the upper atmosphere to form ozone-destroying chlorine free radicals. | 0 | Theoretical and Fundamental Chemistry |
In inorganic chemistry, an orthoborate is a polyatomic anion with formula or a salt containing the anion; such as trisodium orthoborate . It is one of several boron oxyanions, or borates.
The name is also used in organic chemistry for the trivalent functional group , or any compound (ester) that contains it, such as triethyl orthoborate . | 0 | Theoretical and Fundamental Chemistry |
Drospirenone is available in the following formulations, brand names, and indications:
* Drospirenone 4 mg (Slynd) – progestogen-only birth control pill
* Drospirenone 3 mg and estetrol 14.2 mg (Nextstellis (US)) – combined birth control pill
* Ethinylestradiol 30 μg and drospirenone 3 mg (Ocella, Syeda, Yasmin, Zarah, Zumandimine) – combined birth control pill
* Ethinylestradiol 20 μg and drospirenone 3 mg (Gianvi, Jasmiel, Loryna, Lo-Zumandimine, Nikki, Vestura, Yaz) – combined birth control pill, acne, PMS, PMDD, dysmenorrhea
* Ethinylestradiol 30 μg, drospirenone 3 mg, and levomefolate calcium 0.451 mg (Beyaz, Tydemy) – combined birth control pill with vitamin B supplementation, acne, PMS
* Estetrol 15 mg and drospirenone 3 mg (Nextstellis (CA)) – combined birth control pill
* Estradiol 0.5 or 1 mg and drospirenone 0.25 or 0.5 mg (Angeliq) – menopausal hormone therapy (menopausal syndrome, postmenopausal osteoporosis) | 0 | Theoretical and Fundamental Chemistry |
Nitrate is a polyatomic ion with the chemical formula . Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insoluble nitrate is bismuth oxynitrate. | 0 | Theoretical and Fundamental Chemistry |
* Belyi, Alexander Andreyevich (b. in 1940) – the Russian literary critic, known Pushkin Pushkin scholar and member of the commission.
* Dashkevich, Vladimir Sergeevich (20 January 1934, Moscow) – Soviet and Russian composer and music theorist. Laureate of the State Prize of the USSR (1991).
* Kirov, Biser, (b. 4 September 1942, Silistra, Bulgaria Kingdom) – Bulgarian pop singer (tenor), who is called in the press most popular Bulgarian in the USSR.
* Korotaeva, Lubov Georgievna (27 October 1918, d Vereya, Ramenskii district of the Moscow region – 18 January 2000, Moscow) – the only female participant (in a group of 20 people) climbing Elbrus for removal and installation of the banners of Nazi flags of the USSR 13–17 February 1943. Co-author (with A.A. Gryaznov and N.A. Persiyaninov) of the song "Baksanskaya" dedicated to the soldiers of climbers. After the war – Associate Professor, Department of General Chemistry PFUR them. Patrice Lumumba.
* Guseva, Natalia Evgenievna (15 February 1972, Zvenigorod, Moscow region, USSR) – Soviet film actress of the 1980s, became widely known after her role as Alice Selezneva in the cult children's television movie "The Guest from the Future ", directed by Paul Arsenov.
* Tkachev, Alexander Vasilievich (18 January 1955, Moscow – 9 November 2010, Moscow) – Russian poet, writer and performer of songs. | 1 | Applied and Interdisciplinary Chemistry |
In axial compensation, the thermal expansion of a straight line section between two fixed points is absorbed by an axial expansion joint. The distance between two fixed points defines the pipeline length requiring compensation, and thus determines the axial movement that must be achieved by the expansion joint.
The following basic principles apply to axial compensation:
* The single-plane or multi-plane piping system is subdivided into straight sections by fixed point in such a way that each section can be compensated by a single axial expansion joint.
* The fixed points must be designed to withstand the pressure and spring forces of the axial expansion joint, the frictional forces of the pipe guides and the flow forces.
* Long pipes must be protected against kinking between the fixed points using pipe guides.
* The axial expansion joint should be installed in the immediate vicinity of a fixed point and a pipe guide.
* Impermissibly large fixed point loads can be prevented by using axial expansion joints that are relieved of pressure forces. | 1 | Applied and Interdisciplinary Chemistry |
Transposons and retrotransposons are mobile genetic elements. Retrotransposon repeated sequences, which include long interspersed nuclear elements (LINEs) and short interspersed nuclear elements (SINEs), account for a large proportion of the genomic sequences in many species. Alu sequences, classified as a short interspersed nuclear element, are the most abundant mobile elements in the human genome. Some examples have been found of SINEs exerting transcriptional control of some protein-encoding genes.
Endogenous retrovirus sequences are the product of reverse transcription of retrovirus genomes into the genomes of germ cells. Mutation within these retro-transcribed sequences can inactivate the viral genome.
Over 8% of the human genome is made up of (mostly decayed) endogenous retrovirus sequences, as part of the over 42% fraction that is recognizably derived of retrotransposons, while another 3% can be identified to be the remains of DNA transposons. Much of the remaining half of the genome that is currently without an explained origin is expected to have found its origin in transposable elements that were active so long ago (> 200 million years) that random mutations have rendered them unrecognizable. Genome size variation in at least two kinds of plants is mostly the result of retrotransposon sequences. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, phosphorochloridites are a class of organophosphorus compound with the formula (RO)PCl (R = organic substituent). They are pyramidal in shape, akin to regular phosphites (P(OR)). They are usually colorless and sensitive toward hydrolysis and, to some extent, oxidation to the corresponding phosphorochloridates ((RO)P(O)Cl). | 0 | Theoretical and Fundamental Chemistry |
The organisation was set up jointly by the Chemical Industries Association and the University of York in 1988 as the Chemical Industry Education Centre; it changed its name in 2014.
In June 2016 it won the Royal Society of Chemistry's Inspiration and Industry Award. | 1 | Applied and Interdisciplinary Chemistry |
Prior to World War II, the center of organic chemistry research and industrial production was Germany. Students interested in pursuing a career in organic chemistry needed to learn German to read articles and textbooks, and often went to graduate school in Germany. When the war broke out, an effort to jumpstart a native US organic chemical industry and academic network was initiated. As part of this effort, the journal was launched. The first volume was published in 1942, with Roger Adams as editor-in-chief. In the early years a volume would come out every two years or so, but the pace of publishing has accelerated, with volume 100 issued in 2019. | 0 | Theoretical and Fundamental Chemistry |
The aromatic component of the quinine molecule is a quinoline with a methoxy substituent. The amine component has a quinuclidine skeleton and the methylene bridge in between the two components has a hydroxyl group. The substituent at the 3 position is a vinyl group. The molecule is optically active with five stereogenic centers (the N1 and C4 constituting a single asymmetric unit), making synthesis potentially difficult because it is one of 16 stereoisomers. | 0 | Theoretical and Fundamental Chemistry |
Modulation of purine metabolism has pharmacotherapeutic value.
Purine synthesis inhibitors inhibit the proliferation of cells, especially leukocytes. These inhibitors include azathioprine, an immunosuppressant used in organ transplantation, autoimmune disease such as rheumatoid arthritis or inflammatory bowel disease such as Crohn's disease and ulcerative colitis.
Mycophenolate mofetil is an immunosuppressant drug used to prevent rejection in organ transplantation; it inhibits purine synthesis by blocking inosine monophosphate dehydrogenase (IMPDH).
Methotrexate also indirectly inhibits purine synthesis by blocking the metabolism of folic acid (it is an inhibitor of the dihydrofolate reductase).
Allopurinol is a drug that inhibits the enzyme xanthine oxidoreductase and, thus, lowers the level of uric acid in the body. This may be useful in the treatment of gout, which is a disease caused by excess uric acid, forming crystals in joints. | 1 | Applied and Interdisciplinary Chemistry |
Most countries in Europe mainly install flanges according to standard DIN EN 1092-1 (forged stainless or steel flanges). Similar to the ASME flange standard, the EN 1092-1 standard has the basic flange forms, such as weld neck flange, blind flange, lapped flange, threaded flange (thread ISO7-1 instead of NPT), weld on collar, pressed collars, and adapter flange such as flange coupling GD press fittings. The different forms of flanges within the EN 1092-1 (European Norm/Euronorm) is indicated within the flange name through the type.
Similar to ASME flanges, EN1092-1 steel and stainless flanges, have several different versions of raised or none raised faces. According to the European form the seals are indicated by different form:
Furthermore, for sanitary applications such as in the food and beverage and pharmaceutical industries, sanitary flanges according to DIN 11853-2 STC are utilized. The primary distinction between sanitary flanges according to DIN 11853-2 and DIN/EN flanges lies in the restricted dead-room and the interior polishing according to hygienic levels of H1 to H4. Usually the flange traders that hold the Standard DIN EN 1092-1 such as Hage Fittings, do not hold Sanitary flanges as the storage requirements are different. Sanitary flanges a more delicate and need to stay clean. Usually the O-Ring according to DIn 11853 are our of FPM or EPDM. | 1 | Applied and Interdisciplinary Chemistry |
Though many genes have simple structures, as with much of biology, others can be quite complex or represent unusual edge-cases. Eukaryotic genes often have introns are often much larger than their exons, and those introns can even have other genes nested inside them. Associated enhancers may be many kilobase away, or even on entirely different chromosomes operating via physical contact between two chromosomes. A single gene can encode multiple different functional products by alternative splicing, and conversely gene may be split across chromosomes but those transcripts are concatenated back together into a functional sequence by trans-splicing. It is also possible for overlapping genes to share some of their DNA sequence, either on opposite strands or the same strand (in a different reading frame, or even the same reading frame). | 1 | Applied and Interdisciplinary Chemistry |
*Subhash Kak (2016), Matter and Mind: The Vaiśeṣika Sūtra of Kaṇāda
*O'Flaherty, Wendy Doniger. Textual Sources for the Study of Hinduism (Textual Sources for the Study of Religion). . | 1 | Applied and Interdisciplinary Chemistry |
Micronutrients are essential dietary elements required in varying quantities throughout life to serve metabolic and physiological functions.
* Dietary minerals, such as copper and iron, are elements native to Earth, and cannot be synthesized. They are required in the diet in microgram or milligram amounts. As plants obtain minerals from the soil, dietary minerals derive directly from plants consumed or indirectly from edible animal sources.
* Vitamins are organic compounds required in microgram or milligram amounts. The importance of each dietary vitamin was first established when it was determined that a disease would develop if that vitamin was absent from the diet. | 0 | Theoretical and Fundamental Chemistry |
Potentially acid sulfate soils (also called cat-clays) are often not cultivated or, if they are, planted with rice, so that the soil can be kept wet preventing oxidation. Subsurface drainage of these soils is normally not advisable.
When cultivated, acid sulfate soils cannot be kept wet continuously because of climatic dry spells and shortages of irrigation water, surface drainage may help to remove the acidic and toxic chemicals (formed in the dry spells) during rainy periods. In the long run surface drainage can help to reclaim acid sulfate soils. The indigenous population of Guinea Bissau has thus managed to develop the soils, but it has taken them many years of careful management and toil.
In an article on cautious land drainage, the author describes the successful application of subsurface drainage in acid sulfate soils in coastal polders of Kerala state, India.
Also in the Sunderbans, West Bengal, India, acid sulfate soils have been taken in agricultural use.
A study in South Kalimantan, Indonesia, in a perhumid climate, has shown that the acid sulfate soils with a widely spaced subsurface drainage system have yielded promising results for the cultivation of upland rice, peanut and soybean. The local population, of old, had already settled in this area and were able to produce a variety of crops (including tree fruits), using hand-dug drains running from the river into the land until reaching the back swamps. The crop yields were modest, but provided enough income to make a decent living.
Reclaimed acid sulfate soils have a well-developed soil structure thanks to the abundance of trivalent cations (mainly Al) which have a very strong flocculating effect; they are well permeable, but infertile due to the leaching that has occurred.
In the second half of the 20th century, in many parts of the world, waterlogged and potentially acid sulfate soils have been drained aggressively to make them productive for agriculture. The results were disastrous. The soils are unproductive, the lands look barren and the water is very clear (again, due to the flocculating effect of Al), devoid of silt and life. The soils can be colorful, though. | 0 | Theoretical and Fundamental Chemistry |
*EIF1 aka SUI1
*EIF1AD
*EIF1B
*EIF2A
*EIF2AK1
*EIF2AK3
*EIF2AK4
*EIF2AK1
*EIF2B2
*EIF2B3
*EIF2B4
*EIF2S2
*EIF3A
*EIF3B
*EIF3D formerly EIF3S4
*EIF3G
*EIF3I
*EIF3H
*EIF3J
*EIF3K
*EIF3L
*EIF3M
*EIF3S5
*EIF3S8
*EIF4A1
*EIF4A2
*EIF4A3
*EIF4E2
*EIF4G1
*EIF4G2
*EIF4G3
*EIF4H
*EIF5
*EIF5
*EIF5A
*EIF5AL1
*EIF5B
*EIF6
*TUFM Tu translational elongation factor mitochondrial | 1 | Applied and Interdisciplinary Chemistry |
Arthur Waldorf Thomas (February 18, 1891 - March 22, 1982) was a professor and chemist who specialized in colloid chemistry. He studied and taught at Columbia University for 50 years. | 0 | Theoretical and Fundamental Chemistry |
These have been no reports of serious adverse effects with overdose of drospirenone. Symptoms that may occur in the event of an overdose may include nausea, vomiting, and vaginal bleeding. There is no antidote for overdose of drospirenone and treatment of overdose should be based on symptoms. Since drospirenone has antimineralocorticoid activity, levels of potassium and sodium should be measured and signs of metabolic acidosis should be monitored. | 0 | Theoretical and Fundamental Chemistry |
Each year, approximately 0.3 gigatons of elemental sulfur is converted into organic matter by photosynthetic organisms. This organic sulfur is allocated into a diversity of compounds such as amino acids – namely cysteine (Cys) and methionine (Met) – proteins, cofactors, antioxidants, sulfate groups, Fe-S centers and secondary metabolites. The three main sources of sulfur are atmospheric, soil, and aquatic.
Most vegetation can acquire sulfur from gaseous atmospheric compounds or various ions either in soil solutions or water bodies. Uptake of gaseous and dissolved sulfur compounds apparently occurs with little accompanying isotopic selectivity. Dissolved sulfate (SO) is considered to be the central pool which is metabolized by microorganisms and plants as most forms of atmospheric sulfur is oxidized into sulfate. Atmospheric sulfur is eventually returned to the soil when it is scrubbed from the atmosphere during precipitation or through dryfall. | 0 | Theoretical and Fundamental Chemistry |
Typical anionic detergents are alkylbenzene sulfonates. The alkylbenzene portion of these anions is lipophilic and the sulfonate is hydrophilic. Two varieties have been popularized, those with branched alkyl groups and those with linear alkyl groups. The former were largely phased out in economically advanced societies because they are poorly biodegradable.
Anionic detergents is the most common form of detergents, and an estimated 6 billion kilograms of anionic detergents are produced annually for the domestic markets.
Bile acids, such as deoxycholic acid (DOC), are anionic detergents produced by the liver to aid in digestion and absorption of fats and oils. | 0 | Theoretical and Fundamental Chemistry |
*1947 George Sayers
*1948 J. Garrott Allen
*1949 Mark Nickerson
*1950 George B. Koelle
*1951 Walter F. Riker, Jr.
*1952 David F. Marsh
*1953 Herbert L. Borison
*1954 Eva King Killam
*1955 Theodore M. Brody
*1956 Fred W. Schueler
*1957 Dixon M. Woodbury
*1958 H. George Mandel
*1959 Parkhurst A. Shore
*1960 Jack L. Strominger
*1961 Don W. Esplin
*1962 John P. Long
*1963 Steven E. Mayer
*1964 James R. Fouts
*1965 Eugene Braunwald
*1966 Lewis S. Schanker
*1967 Frank S. LaBella
*1968 Richard J. Wurtman
*1969 Ronald Kuntzman
*1970 Solomon H. Snyder
*1971 Thomas R. Tephly
*1972 Pedro Cuatrecasas
*1973 Colin F. Chignell
*1974 Philip Needleman
*1975 Alfred G. Gilman
*1976 Alan P. Poland
*1977 Jerry R. Mitchell
*1978 Robert J. Lefkowitz
*1979 Joseph T. Coyle
*1980 Salvatore J. Enna
*1981 Sydney D. Nelson
*1982 Theodore A. Slotkin
*1983 Richard J. Miller
*1984 F. Peter Guengerich
*1985 P. Michael Conn
*1986 Gordon M. Ringold
*1987 Lee E. Limbird
*1988 Robert R. Ruffolo, Jr.
*1989 Kenneth P. Minneman
*1990 Alan R. Saltiel
*1991 Terry D. Reisine
*1992 Frank J. Gonzalez
*1993 Susan G. Amara
*1994 Brian Kobilka
*1995 Thomas M. Michel
*1996 John D. Scott
*1997 David J. Mangelsdorf
*1998 Masashi Yanigasawa
*1999 Donald P. McDonell
*2000 William C. Sessa
*2002 Steven A. Kliewer
*2003 David S. Bredt
*2004 David Siderovski
*2005 Randy A. Hall
*2006 Christopher M. Counter
*2007 Michael D. Ehlers
*2008 Katerina Akassoglou
*2009 John J. Tesmer
*2010 Russell Debose-Boyd
*2011 Laura M. Bohn
*2012 Jin Zhang
*2013 Arthur Christopoulos
*2014 Craig W. Lindsley
*2015 Pieter C. Dorrestein
*2016 Jing Yang
*2017 Samie R. Jaffrey
*2018 Kirill A. Martemyanov
*2019 Namandjé Bumpus
*2020 Andrew Goodman
*2021 Michael R. Bruchas
*2022 Mikel Garcia-Marcos | 1 | Applied and Interdisciplinary Chemistry |
*Elmer V. McCollum (1917–1944)
*Roger M. Herriott (1948–1975)
*Lawrence Grossman (1975–1990)
*Roger McMacken (1990–2008)
*Barry Zirkin (2008) Interim
*Pierre A. Coulombe (2008–2017)
*Michael Matunis (2017–2019) Interim
*Ashani Weeraratna (2019–present) | 1 | Applied and Interdisciplinary Chemistry |
Boronate affinity electrophoresis utilizes boronic acid infused acrylamide gels to purify NAD-RNA. This purification allows for researchers to easily measure the kinetic activity of NAD-RNA decapping enzymes. | 1 | Applied and Interdisciplinary Chemistry |
* During energy transformations in living systems, order and organization must be compensated by releasing energy which will increase entropy of the surrounding.
* Organisms are open systems that exchange materials and energy with the environment. They are never at equilibrium with the surrounding.
* Energy is spent to create and maintain order in the cells, and surplus energy and other simpler by-products are released to create disorder such that there is an increase in entropy of the surrounding.
* In a reversible process, entropy remains constant where as in an irreversible process (more common to real-world scenarios), entropy tends to increase.
* During phase changes (from solid to liquid, or to gas), entropy increases because the number of possible arrangements of particles increases.
* If ∆G<0, the chemical reaction is spontaneous and favourable in that direction.
* If ∆G=0, the reactants and products of chemical reaction are at equilibrium.
* If ∆G>0, the chemical reaction is non-spontaneous and unfavorable in that direction.
* ∆G is not an indicator for velocity or rate of chemical reaction at which equilibrium is reached. It depends on amount of enzyme and energy activation. | 1 | Applied and Interdisciplinary Chemistry |
The resonance structures below show the 1,3-dipole contribution, in which the two carbon atoms adjacent to the nitrogen have a negative or positive charge. The most common representation of azomethine ylides is that in which the nitrogen is positively charged, and the negative charge is shared between the two carbon atoms. The relative contributions of the different resonance structures depend on the substituents on each atom. The carbon containing electron-withdrawing substituents will have a more partial negative charge, due to the ability of the nearby electron-withdrawing group to stabilize the negative charge.
Three different ylide shapes are possible, each leading to different stereochemistry in the products of 1,3-dipolar cycloaddition reactions. W-shaped, U-shaped, and S-shaped ylides are possible. The W- and U-shaped ylides, in which the R substituents are on the same side, result in syn cycloaddition products, whereas S-shaped ylides result in anti products. In the examples below, where the R substituent ends up in the product depends on the substituent's steric and electronic nature (see regioselectivity of 1,3 dipolar cycloadditions). The stereochemistry of R and R in the cycloaddition product is derived from the dipole. The stereochemistry of R is derived from the dipolarophile—if the dipolarophile is more than mono-substituted (and prochiral), up to four new stereocenters can result in the product. | 0 | Theoretical and Fundamental Chemistry |
Eogan (1994) noted that around 250 surviving gold objects are known to date to the Early Bronze Age, 165 of those from Ireland, and the other 83 from Britain. From analysing the designs of the earliest gold artefacts in Britain, Eogan noted that they "form a homogeneous group" which, when "taken in conjunction with other metal types demonstrate that a new technology was introduced." Early Bronze Age pieces are generally much smaller, with very thin decorated discs or plaques common. Two small gold cups have been found in England, the Rillaton Cup and the similar but now crushed Ringlemere Cup.
Due to its natural resources, Ireland had a "rich Early Bronze Age [metal-working] industry", producing large quantities of metal axes, halberds and daggers, and as a part of this also had a "major gold industry", seeing the production of lunulae and gold disks on a far larger scale than Britain. | 1 | Applied and Interdisciplinary Chemistry |
Because duplex sequencing provides a significantly higher sequencing accuracy and uses information in both strands of DNA, this method needs a much higher sequencing depth and therefore is a costly approach. The expense limits its application to targeted and amplicon sequencing at present time and will not be applicable for whole genome sequencing approaches. However, the application of duplex sequencing for larger DNA targets will be more feasible when the cost of NGS decreases. | 1 | Applied and Interdisciplinary Chemistry |
PIP binds directly to ion channels and modulates their activity. PIP was shown to directly agonizes Inward rectifying potassium channels(K). In this regard intact PIP signals as a bona fide neurotransmitter-like ligand. PIP's interaction with many ion channels suggest that the intact form of PIP has an important signaling role independent of second messenger signaling. | 1 | Applied and Interdisciplinary Chemistry |
Coordinated ligands display reactivity distinct from the free ligands. For example, the acidity of the ammonia ligands in [[Cobalt(III) hexammine chloride|[Co(NH)]]] is elevated relative to NH itself. Alkenes bound to metal cations are reactive toward nucleophiles whereas alkenes normally are not. The large and industrially important area of catalysis hinges on the ability of metals to modify the reactivity of organic ligands. Homogeneous catalysis occurs in solution and heterogeneous catalysis occurs when gaseous or dissolved substrates interact with surfaces of solids. Traditionally homogeneous catalysis is considered part of organometallic chemistry and heterogeneous catalysis is discussed in the context of surface science, a subfield of solid state chemistry. But the basic inorganic chemical principles are the same. Transition metals, almost uniquely, react with small molecules such as CO, H, O, and CH. The industrial significance of these feedstocks drives the active area of catalysis. Ligands can also undergo ligand transfer reactions such as transmetalation. | 0 | Theoretical and Fundamental Chemistry |
Segregation of a solute to surfaces and grain boundaries in a solid produces a section of material with a discrete composition and its own set of properties that can have important (and often deleterious) effects on the overall properties of the material. These zones with an increased concentration of solute can be thought of as the cement between the bricks of a building. The structural integrity of the building depends not only on the material properties of the brick, but also greatly on the properties of the long lines of mortar in between.
Segregation to grain boundaries, for example, can lead to grain boundary fracture as a result of temper brittleness, creep embrittlement, stress relief cracking of weldments, hydrogen embrittlement, environmentally assisted fatigue, grain boundary corrosion, and some kinds of intergranular stress corrosion cracking. A very interesting and important field of study of impurity segregation processes involves AES of grain boundaries of materials. This technique includes tensile fracturing of special specimens directly inside the UHV chamber of the Auger Electron Spectrometer that was developed by Ilyin.
Segregation to grain boundaries can also affect their respective migration rates, and so affects sinterability, as well as the grain boundary diffusivity (although sometimes these effects can be used advantageously).
Segregation to free surfaces also has important consequences involving the purity of metallurgical samples. Because of the favorable segregation of some impurities to the surface of the material, a very small concentration of impurity in the bulk of the sample can lead to a very significant coverage of the impurity on a cleaved surface of the sample. In applications where an ultra-pure surface is needed (for example, in some nanotechnology applications), the segregation of impurities to surfaces requires a much higher purity of bulk material than would be needed if segregation effects did not exist. The following figure illustrates this concept with two cases in which the total fraction of impurity atoms is 0.25 (25 impurity atoms in 100 total). In the representation on the left, these impurities are equally distributed throughout the sample, and so the fractional surface coverage of impurity atoms is also approximately 0.25. In the representation to the right, however, the same number of impurity atoms are shown segregated on the surface, so that an observation of the surface composition would yield a much higher impurity fraction (in this case, about 0.69). In fact, in this example, were impurities to completely segregate to the surface, an impurity fraction of just 0.36 could completely cover the surface of the material. In an application where surface interactions are important, this result could be disastrous.
While the intergranular failure problems noted above are sometimes severe, they are rarely the cause of major service failures (in structural steels, for example), as suitable safety margins are included in the designs. Perhaps the greater concern is that with the development of new technologies and materials with new and more extensive mechanical property requirements, and with the increasing impurity contents as a result of the increased recycling of materials, we may see intergranular failure in materials and situations not seen currently. Thus, a greater understanding of all of the mechanisms surrounding segregation might lead to being able to control these effects in the future. Modeling potentials, experimental work, and related theories are still being developed to explain these segregation mechanisms for increasingly complex systems. | 0 | Theoretical and Fundamental Chemistry |
Coherent microwave scattering is a diagnostic technique used in the characterization of classical microplasmas. In this technique, the plasma to be studied is irradiated with a long-wavelength microwave field relative to the characteristic spatial dimensions of the plasma. For plasmas with sufficiently low skin-depths, the target is periodically polarized in a uniform fashion, and the scattered field can be measured and analyzed. In this case, the emitted radiation resembles that of a short-dipole predominantly determined by electron contributions rather than ions. The scattering is correspondingly referred to as constructive elastic. Various properties can be derived from the measured radiation such as total electron numbers, electron number densities (if the plasma volume is known), local magnetic fields through magnetically-induced depolarization, and electron collision frequencies for momentum transfer through the scattered phase. Notable advantages of the technique include a high sensitivity, ease of calibration using a dielectric scattering sample, good temporal resolution, low shot noise, non-intrusive probing, species-selectivity when coupled with resonance-enhanced multiphoton ionization (REMPI), single-shot acquisition, and the capability of time-gating due to continuous scanning. | 0 | Theoretical and Fundamental Chemistry |
In nanobiotechnology, a peptoid nanosheet is a synthetic protein structure made from peptoids. Peptoid nanosheets have a thickness of about three nanometers and a length of up to 100 micrometers, meaning that they have a two-dimensional, flat shape that resembles paper on the nanoscale.
This makes them one of the thinnest known two-dimensional organic crystalline materials with an area to thickness ratio of greater than 10 nm. Peptoid nanosheets were discovered in the laboratory of Dr. Ron Zuckermann at the Lawrence Berkeley National Laboratory in 2010. Due to the ability to customize peptoids and therefore the properties of the peptoid nanosheet, it has possible applications in the areas of drug and small molecule delivery and biosensing. | 0 | Theoretical and Fundamental Chemistry |
There are three basic steps in the methylcitrate cycle, as outlined below. Additionally, the mechanism is shown with its reactants, products, intermediates, and enzymes.
The major enzymes involved in this process are methylcitrate synthase (MCS) in step one, methylcitrate dehydratase (MCD) in step two, and 2-methylisocitrate lyase (MCL) in step three.
The PrpC gene, which encodes for enzyme methylcitrate synthase in the first step of the methylcitrate cycle, is the gene responsible for propionate metabolism in the process. Without this gene, the methylcitrate cycle and ultimate metabolism would not occur, but rather catabolism. The reaction of the methylcitrate cycle both overlaps and intertwines with the citric acid cycle and the glyoxylate cycle. Odd-chain fatty acids acetate and propionate are broken down by the β-oxidation cycle to form acetyl-CoA, which is further oxidized by the citric acid cycle, and propionyl-CoA, which is oxidized by the methylcitrate cycle. The substrate oxaloacetate is generated by the citric acid and glyoxylate cycles, and the product succinate is taken from the methylcitrate cycle to be used in the citric acid cycle. | 1 | Applied and Interdisciplinary Chemistry |
A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend the definition to include substances like aerosols and gels. The term colloidal suspension refers unambiguously to the overall mixture (although a narrower sense of the word suspension is distinguished from colloids by larger particle size). A colloid has a dispersed phase (the suspended particles) and a continuous phase (the medium of suspension). The dispersed phase particles have a diameter of approximately 1 nanometre to 1 micrometre.
Some colloids are translucent because of the Tyndall effect, which is the scattering of light by particles in the colloid. Other colloids may be opaque or have a slight color.
Colloidal suspensions are the subject of interface and colloid science. This field of study began in 1845 by Francesco Selmi, who called them pseudosolutions, and expanded by Michael Faraday and Thomas Graham, who coined the term colloid in 1861. | 0 | Theoretical and Fundamental Chemistry |
In gamma spectrometry, the Compton edge is a feature of a detector output spectrum that results from Compton scattering in such as a scintillation detector or Photodiode detector. It occurs when a gamma-ray scatters within the detector and some of the interaction energy escapes so that only a fraction is detected. The amount of energy deposited in the detector depends on the scattering angle of the photon, leading to a spectrum of energies each corresponding to a different scattering angle. The highest energy that can be deposited, corresponding to full backscatter, is called the Compton edge. In mathematical terms, the Compton edge is the inflection point of the high-energy side of the Compton region. | 0 | Theoretical and Fundamental Chemistry |
Enzymes are generally in a state that is not only a compromise between stability and catalytic efficiency, but also for specificity and evolvability, the latter two dictating whether an enzyme is a generalist (highly evolvable due to large promiscuity, but low main activity) or a specialist (high main activity, poorly evolvable due to low promiscuity). Examples of these are enzymes for primary and secondary metabolism in plants (§ Plant secondary metabolism below). Other factors can come into play, for example the glycerophosphodiesterase (gpdQ) from Enterobacter aerogenes shows different values for its promiscuous activities depending on the two metal ions it binds, which is dictated by ion availability.
In some cases promiscuity can be increased by relaxing the specificity of the active site by enlarging it with a single mutation as was the case of a D297G mutant of the E. coli L-Ala-D/L-Glu epimerase (ycjG) and E323G mutant of a pseudomonad muconate lactonizing enzyme II, allowing them to promiscuously catalyse the activity of O-succinylbenzoate synthase (menC). Conversely, promiscuity can be decreased as was the case of γ-humulene synthase (a sesquiterpene synthase) from Abies grandis that is known to produce 52 different sesquiterpenes from farnesyl diphosphate upon several mutations.
Studies on enzymes with broad-specificity—not promiscuous, but conceptually close—such as mammalian trypsin and chymotrypsin, and the bifunctional isopropylmalate isomerase/homoaconitase from Pyrococcus horikoshii have revealed that active site loop mobility contributes substantially to the catalytic elasticity of the enzyme. | 1 | Applied and Interdisciplinary Chemistry |
Difference density maps are usually calculated using Fourier coefficients which are the differences between the observed structure factor amplitudes from the X-ray diffraction experiment and the calculated structure factor amplitudes from the current model, using the phase from the model for both terms (since no phases are available for the observed data). The two sets of structure factors must be on the same scale.
It is now normal to also include maximum-likelihood weighting terms which take into account the estimated errors in the current model:
where m is a figure of merit which is an estimate of the cosine of the error in the phase, and D is a "σ" scale factor. These coefficients are derived from the gradient of the likelihood function of the observed structure factors on the basis of the current model. A difference map built with m and D is known as a mFo – DFc map.
The use of ML weighting reduces model bias (due to using the model's phase) in the 2 Fo–Fc map, which is the main estimate of the true density. However, it does not fully eliminate such bias. | 0 | Theoretical and Fundamental Chemistry |
For example, in a two electrons couple like : the reduction potential becomes ~ 30 mV (or more exactly, 59.16 mV/2 = 29.6 mV) more positive for every power of ten increase in the ratio of the oxidised to the reduced form. | 1 | Applied and Interdisciplinary Chemistry |
Wolfgang Kautek is an Austrian Physical chemist and the head of the Physical chemistry department at the University of Vienna.
He is the President of the Erwin Schrödinger Society for Nanosciences (ESG) and the Chairman of the Research Group "Physical Chemistry" at the Austrian Chemical Society (GÖCh). | 0 | Theoretical and Fundamental Chemistry |
Pharmaceutical medications are commonly described as "ubiquitous" in nearly every type of environmental medium (i.e. lakes, rivers, streams, estuaries, seawater, and soil) worldwide. Their chemical components are typically present at relatively low concentrations in the ng/L to μg/L ranges. The primary avenue for medications reaching the environment are through the effluent of wastewater treatment plants, both from industrial plants during production, and from municipal plants after consumption. Agricultural pollution is another significant source derived from the prevalence of antibiotic use in livestock.
Scientists generally divide environmental impacts of a chemical into three primary categories: persistence, bioaccumulation, and toxicity. Since medications are inherently bio-active, most are naturally degradable in the environment, however they are classified as "pseudopersistent" because they are constantly being replenished from their sources. These Environmentally Persistent Pharmaceutical Pollutants (EPPPs) rarely reach toxic concentrations in the environment, however they have been known to bioaccumulate in some species. Their effects have been observed to compound gradually across food webs, rather than becoming acute, leading to their classification by the US Geological Survey as "Ecological Disrupting Compounds." | 1 | Applied and Interdisciplinary Chemistry |
Before TFH identified it, it had several names. It was isolated in 1989 isolated from rat liver, known by factor transcription delta. When identified from cancer cells it was known that time as Basic transcription factor 2. Also, when isolated from yeast it was termed transcription factor B. Finally, in 1992 known as TFH. | 1 | Applied and Interdisciplinary Chemistry |
Aspirins effects on blood clotting (as an antiplatelet agent) were first noticed in 1950 by Lawrence Craven. Craven, a family doctor in California, had been directing tonsillectomy patients to chew Aspergum, an aspirin-laced chewing gum. He found that an unusual number of patients had to be hospitalized for severe bleeding, and that those patients had been using very high amounts of Aspergum. Craven began recommending daily aspirin to all his patients, and claimed that the patients who followed the aspirin regimen (about 8,000 people) had no signs of thrombosis. However, Cravens studies were not taken seriously by the medical community, because he had not done a placebo-controlled study and had published only in obscure journals.
The idea of using aspirin to prevent clotting diseases (such as heart attacks and strokes) was revived in the 1960s, when medical researcher Harvey Weiss found that aspirin had an anti-adhesive effect on blood platelets (and unlike other potential antiplatelet drugs, aspirin had low toxicity). Medical Research Council haematologist John OBrien picked up on Weisss finding and, in 1963, began working with epidemiologist Peter Elwood on aspirins anti-thrombosis drug potential. Elwood began a large-scale trial of aspirin as a preventive drug for heart attacks. Nicholas Laboratories agreed to provide aspirin tablets, and Elwood enlisted heart attack survivors in a double-blind controlled study—heart attack survivors were statistically more likely to suffer a second attack, greatly reducing the number of patients necessary to reliably detect whether aspirin had an effect on heart attacks. The study began in February 1971, though the researchers soon had to break the double-blinding when a study by American epidemiologist Hershel Jick suggested that aspirin prevented heart attacks but suggested that the heart attacks were more deadly. Jick had found that fewer aspirin-takers were admitted to his hospital for heart attacks than non-aspirin-takers, and one possible explanation was that aspirin caused heart attack sufferers to die before reaching the hospital; Elwoods initial results ruled out that explanation. When the Elwood trial ended in 1973, it showed a modest but not statistically significant reduction in heart attacks among the group taking aspirin.
Several subsequent studies put aspirins effectiveness as a heart drug on firmer ground, but the evidence was not incontrovertible. However, in the mid-1980s, with the relatively new technique of meta-analysis, statistician Richard Peto convinced the U.S. FDA and much of the medical community that the aspirin studies, in aggregate, showed aspirins effectiveness with relative certainty. By the end of the 1980s, aspirin was widely used as a preventive drug for heart attacks and had regained its former position as the top-selling analgesic in the U.S.
In 2018, three major clinical trials cast doubt on that conventional wisdom, finding few benefits and consistent bleeding risks associated with daily aspirin use. Taken together, the findings led the American Heart Association and American College of Cardiology to change clinical practice guidelines in early 2019, recommending against the routine use of aspirin in people older than 70 years or people with increased bleeding risk who do not have existing cardiovascular disease. | 1 | Applied and Interdisciplinary Chemistry |
Site-specific recombination makes use of phage integrases instead of restriction enzymes, eliminating the need for having restriction sites in the DNA fragments. Instead, integrases make use of unique attachment (att) sites, and catalyse DNA rearrangement between the target fragment and the destination vector. The Invitrogen Gateway cloning system was invented in the late 1990s and uses two proprietary enzyme mixtures, BP clonase and LR clonase. The BP clonase mix catalyses the recombination between attB and attP sites, generating hybrid attL and attR sites, while the LR clonase mix catalyse the recombination of attL and attR sites to give attB and attP sites. As each enzyme mix recognises only specific att sites, recombination is highly specific and the fragments can be assembled in the desired sequence.
Vector design and assembly
Because Gateway cloning is a proprietary technology, all Gateway reactions must be carried out with the Gateway kit that is provided by the manufacturer. The reaction can be summarised into two steps. The first step involves assembling the entry clones containing the DNA fragment of interest, while the second step involves inserting this fragment of interest into the destination clone.
# Entry clones must be made using the supplied "Donor" vectors containing a Gateway cassette flanked by attP sites. The Gateway cassette contains a bacterial suicide gene (e.g. ccdB) that will allow for survival and selection of successfully recombined entry clones. A pair of attB sites are added to flank the DNA fragment of interest, and this will allow recombination with the attP sites when the BP clonase mix is added. Entry clones are produced, and the fragment of interest is flanked by attL sites.
# The destination vector also comes with a Gateway cassette, but is instead flanked by a pair of attR sites. Mixing this destination plasmid with the entry clones and the LR clonase mix will allow for recombination to occur between the attR and attL sites. A destination clone is produced, with the fragment of interest successfully inserted. The lethal gene is inserted into the original vector, and bacteria transformed with this plasmid will die. The desired vector can thus be easily selected.
The earliest iterations of the Gateway cloning method only allowed for only one entry clone to be used for each destination clone produced. However, further research revealed that four more orthogonal att sequences could be generated, allowing for the assembly of up to four different DNA fragments, and this process is now known as the Multisite Gateway technology.
Besides Gateway cloning, non-commercial methods using other integrases have also been developed. For example, the Serine Integrase Recombinational Assembly (SIRA) method uses the ϕC31 integrase, while the Site-Specific Recombination-based Tandem Assembly (SSRTA) method uses the Streptomyces phage φBT1 integrase. Other methods, like the HomeRun Vector Assembly System (HVAS), build on the Gateway cloning system and further incorporate homing endonucleases to design a protocol that could potentially support the industrial synthesis of synthetic DNA constructs. | 1 | Applied and Interdisciplinary Chemistry |
As an acid–base indicator, its useful range lies between pH 3.0 and 4.6. It changes from yellow at pH 3.0 to blue at pH 4.6; this reaction is reversible. Bromophenol blue is structurally related to phenolphthalein (a popular indicator). | 0 | Theoretical and Fundamental Chemistry |
The first reported decarboxylative cross coupling reaction was an Ullmann reaction, in 1966 by Nilsson et al. Thermal decarboxylation of copper benzoates, in the presence of an aryl halide, was found to produce (both symmetric and unsymmetric) biaryls through aryl-Cu intermediates.
This monometallic copper system required drastic conditions for complete cross-coupling, and had various intrinsic limitations, both of which prevented development of a catalytic, preparatory version of this reaction.
It was not until 2009 that Liu and Shang et al. found that decarboxylative cross-coupling of aryl bromides and iodides with potassium polyfluorobenzoates could be achieved using monometallic copper iodide as a catalyst. The oxidative addition step was determined to be the rate-limiting step in the copper-only catalyst cycle (a contrast with Pd-catalyzed decarboxylative cross-coupling).
Cu(I)-only systems have also been found to promote coupling of alkynyl carboxylic acids with aryl halides (see aryl alkynes below), as well as decarboxylative dehydrogenative cross-coupling of amino acids with alkynes (or similar nucleophiles).
Catalysts for decarboxylative cross-coupling are of the general form ML2, with a wide variety of ligand types optimized for different substrates. Copper (and silver) centers are often complexed with phenanthrolines, and activity is reported to increase with electron-rich substituents on the ligands. | 0 | Theoretical and Fundamental Chemistry |
In the quantum mechanical framework, this scattering is most noticeable in confined systems, in which the energies for charge carriers are determined by the locations of interfaces. An example of such a system is a quantum well, which may be constructed from a sandwich of different layers of semiconductor. Variations in the thickness of these layers therefore causes the energy of particles to be dependent on their in-plane location in the layer. Classification of the roughness at a given position, , is complex, but as in the classical models, it has been modeled as a Gaussian distribution by some researchers
This assumption may be formulated in terms of the ensemble average for some given characteristic height, , and correlation length, , such that | 0 | Theoretical and Fundamental Chemistry |
Common bioactive materials available commercially for clinical use include 45S5 bioactive glass, A/W bioactive glass ceramic, dense synthetic HA, and bioactive composites such as a polyethylene–HA mixture. All these materials form an interfacial bond with adjacent tissue.
High-purity alumina bioceramics are currently commercially available from various producers. U.K. manufacturer Morgan Advanced Ceramics (MAC) began manufacturing orthopaedic devices in 1985 and quickly became a recognised supplier of ceramic femoral heads for hip replacements. MAC Bioceramics has the longest clinical history for alumina ceramic materials, manufacturing HIP Vitox® alumina since 1985. Some calcium-deficient phosphates with an apatite structure were thus commercialised as "tricalcium phosphate" even though they did not exhibit the expected crystalline structure of tricalcium phosphate.
Currently, numerous commercial products described as HA are available in various physical forms (e.g. granules, specially designed blocks for specific applications). HA/polymer composite (HA/polyethyelene, HAPEXTM) is also commercially available for ear implants, abrasives, and plasma-sprayed coating for orthopedic and dental implants.
Bioceramics are also been used in cannabis or delta 8 devices as wicks for the vaporization of such extracts. | 0 | Theoretical and Fundamental Chemistry |
As explained above, Gene Targeting is technically capable of creating a range of sizes of genetic changes; from single base-pair mutations through to insertion of longer sequences, including potentially transgenes. This means that products of gene targeting can be indistinguishable from natural mutation, or can be equivalent to GMOs due to their insertion of a transgene (see Venn diagram above). Hence regulating products of Gene Targeting can be challenging and different countries have taken different approaches or are reviewing how to do so as part of broader regulatory reviews into the products of gene-editing. Broadly adopted classifications split gene-edited organisms into 3 classes of "SDN1-3", referring to Site Directed Nucleases (such as CRISPR-Cas) that are used to generate gene-edited organisms. These SDN classifications can guide national regulations as to which class of SDN they will consider to be ‘GMOs’ and therefore which are subject to potentially strict regulations.
* SDN1 = organisms created through Non-homologous End Joining of an SDN-catalysed break in the DNA. Hence random mutations have occurred through the error prone NHEJ, and no repair template has been used (hence is not Gene-Targeting). Often subject to less stringent regulatory oversight due to the lack of use of a DNA repair template and equivalence to conventional breeding techniques (in the case of plant breeding).
* SDN2 = one or several specific mutations have been introduced into the target gene at the SDN cut-site through use of a homology-repair template (hence this is Gene Targeting).
* SDN3 = longer sequences have been inserted at the cut-site, via homologous recombination (i.e. Gene Targeting) or through NHEJ. "Longer sequences" typically refer to entire genetic elements such as promoters or protein-coding regions. These are often considered transgenic and therefore often classed as GMO.
Historically the European Union (EU) has broadly been opposed to Genetic Modification technology, on grounds of its precautionary principle. In 2018 the European Court of Justice (ECJ) ruled that gene-edited crops (including gene-targeted crops) should be considered as genetically modified and therefore were subject to the GMO Directive, which places significant regulatory burdens on GMO use. However this decision was received negatively by the European scientific community. In 2021 the European Commission deemed that current EU legislation governing Genetic Modification and Gene-Editing techniques (or NGTs – New Genomic Techniques) was ‘not fit for purpose’ and needed adapting to reflect scientific and technological progress. In July 2023 the European Commission published a proposal to change rules for certain products of gene-editing to reduce the regulatory requirements for organisms developed with gene-editing that contained genetic changes that could have occurred naturally. | 1 | Applied and Interdisciplinary Chemistry |
Beside his scientific publications Speter was an active science popularizer and communicator. As a member of the Deutsches Museum's founding team, he arranged the chemical, physical, and mineralogical exhibits. After leaving this position, he remained an advisor to the museum, consulting about new exhibits. Later on, he used to publish popular humorous and illustrated versions of his works in newspapers and popular science magazines. Between 1924 and 1926 he gave a series of radio lectures. | 1 | Applied and Interdisciplinary Chemistry |
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