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After the discovery of x-rays by Wilhelm Röntgen in 1895, and of the principles of X-ray diffraction by Laue and the Bragg family, it took several decades for the benefits of diffraction imaging to be fully recognized, and the first useful experimental techniques to be developed. The first systematic reports of laboratory topography techniques date from the early 1940s. In the 1950s and 1960s, topographic investigations played a role in detecting the nature of defects and improving crystal growth methods for germanium and (later) silicon as materials for semiconductor microelectronics.
For a more detailed account of the historical development of topography, see J.F. Kelly – "A brief history of X-ray diffraction topography".
From about the 1970s on, topography profited from the advent of synchrotron x-ray sources which provided considerably more intense x-ray beams, allowing to achieve shorter exposure times, better contrast, higher spatial resolution, and to investigate smaller samples or rapidly changing phenomena.
Initial applications of topography were mainly in the field of metallurgy, controlling the growth of better crystals of various metals. Topography was later extended to semiconductors, and generally to materials for microelectronics. A related field are investigations of materials and devices for X-ray optics, such as monochromator crystals made of Silicon, Germanium or Diamond, which need to be checked for defects prior to being used. Extensions of topography to organic crystals are somewhat more recent.
Topography is applied today not only to volume crystals of any kind, including semiconductor wafers, but also to thin layers, entire electronic devices, as well as to organic materials such as protein crystals and others. | 0 | Theoretical and Fundamental Chemistry |
On August 5, 2010, the DOE announced a retooling of the FutureGen project, dubbed FutureGen 2.0. The revised plan includes retrofitting a shuttered coal-fired power plant in Meredosia, Illinois to demonstrate advanced oxy-combustion technology, and piping the carbon dioxide 175 miles to Mattoon for underground storage. Due to these changes, leaders in Mattoon decided to drop out of the FutureGen project.
The Illinois sites vying for the underground storage portion of the project were in Christian, Douglas, Fayette, and Morgan counties, after sites in Adams and Pike counties were cut in December 2010. In February 2011, Morgan County was chosen for the sequestration site.
In Sept, 2014 FutureGen received the first-ever EPA permits for four class VI carbon dioxide sequestration wells in Morgan County, with plans to store 1.1 million metric tons per year for 20 years.
Also in 2014 FutureGen survived a lawsuit from Illinois Electric utility ComEd, which challenged the state's ability to impose a surcharge on all customers to pay for FutureGen electricity.
According to critics, including the Illinois Policy Institute, the plan presents major environmental and fiscal pitfalls. | 1 | Applied and Interdisciplinary Chemistry |
In modern gas turbines, the turbine entry temperature (~1750K) exceeds superalloy incipient melting temperature (~1600K), with the help of surface engineering. | 1 | Applied and Interdisciplinary Chemistry |
Recombinant antibodies (rAbs) are produced in vitro by the means of expression systems based on mammalian cells. Their monospecific binding to a specific epitope makes rAbs eligible not only for research purposes, but also as therapy options against certain cancer types, infections and autoimmune diseases. | 1 | Applied and Interdisciplinary Chemistry |
In 1949 expatriate German Ronald Richter proposed the Huemul Project in Argentina, announcing positive results in 1951. These turned out to be fake, but prompted others' interest. Lyman Spitzer began considering ways to solve problems involved in confining a hot plasma, and, unaware of the Z-pinch efforts, he created the stellarator. Spitzer applied to the US Atomic Energy Commission for funding to build a test device.
During this period, James L. Tuck, who had worked with the UK teams on Z-pinch, had been introducing the stellarator concept to his coworkers at LANL. When he heard of Spitzer's pitch, he applied to build a pinch machine of his own, the Perhapsatron.
Spitzer's idea won funding and he began work under Project Matterhorn. His work led to the creation of Princeton Plasma Physics Laboratory (PPPL). Tuck returned to LANL and arranged local funding to build his machine. By this time it was clear that the pinch machines were afflicted by instability, stalling progress. In 1953, Tuck and others suggested solutions that led to a second series of pinch machines, such as the ZETA and Sceptre devices.
Spitzers first machine, A worked, but his next one, B', suffered from instabilities and plasma leakage.
In 1954 AEC chair Lewis Strauss foresaw electricity as "too cheap to meter". Strauss was likely referring to fusion power, part of the secret Project Sherwood—but his statement was interpreted as referring to fission. The AEC had issued more realistic testimony regarding fission to Congress months before, projecting that "costs can be brought down... [to]... about the same as the cost of electricity from conventional sources..." | 0 | Theoretical and Fundamental Chemistry |
The production of trichloroacetonitrile by dehydration of trichloroacetamide was first described in 1873 by L. Bisschopinck at the Katholieke Universiteit Leuven.
Trichloroacetonitrile can be obtained by chlorination of acetonitrile on a zinc, copper and alkaline earth metal halide-impregnated activated carbon catalyst at 200–400 °C with a 54% yield.
The high temperatures required by this process favours the formation of byproducts, such as tetrachloromethane. In contrast, the chlorination of acetonitrile saturated with hydrogen chloride leads to pure trichloroacetonitrile even at 50–80 °C in good yields.
Like other halogenated acetonitriles, trichloroacetonitrile is produced from organic substances such as algae, humic acids and proteinaceous material in the disinfecting chlorination of water from natural sources. | 0 | Theoretical and Fundamental Chemistry |
The static mixer traces its origins to an invention for a mixing device filed on Nov. 29, 1965 by the Arthur D. Little Company. This device was the housed-elements type and was licensed to the Kenics Corporation and marketed as the Kenics Motionless Mixer. Today, the Kenics brand is owned by National Oilwell Varco. The plate type static mixer patent was issued on November 24, 1998, to Robert W. Glanville of Westfall Manufacturing. | 1 | Applied and Interdisciplinary Chemistry |
RNA silencing describes several mechanistically related pathways which are involved in controlling and regulating gene expression. RNA silencing pathways are associated with the regulatory activity of small non-coding RNAs (approximately 20–30 nucleotides in length) that function as factors involved in inactivating homologous sequences, promoting endonuclease activity, translational arrest, and/or chromatic or DNA modification. In the context in which the phenomenon was first studied, small RNA was found to play an important role in defending plants against viruses. For example, these studies demonstrated that enzymes detect double-stranded RNA (dsRNA) not normally found in cells and digest it into small pieces that are not able to cause disease.
While some functions of RNA silencing and its machinery are understood, many are not. For example, RNA silencing has been shown to be important in the regulation of development and in the control of transposition events. RNA silencing has been shown to play a role in antiviral protection in plants as well as insects. Also in yeast, RNA silencing has been shown to maintain heterochromatin structure. However, the varied and nuanced role of RNA silencing in the regulation of gene expression remains an ongoing scientific inquiry. A range of diverse functions have been proposed for a growing number of characterized small RNA sequences—e.g., regulation of developmental, neuronal cell fate, cell death, proliferation, fat storage, haematopoietic cell fate, insulin secretion.
RNA silencing functions by repressing translation or by cleaving messenger RNA (mRNA), depending on the amount of complementarity of base-pairing. RNA has been largely investigated within its role as an intermediary in the translation of genes into proteins. More active regulatory functions, however, only began to be addressed by researchers beginning in the late-1990s. The landmark study providing an understanding of the first identified mechanism was published in 1998 by Fire et al., demonstrating that double-stranded RNA could act as a trigger for gene silencing. Since then, various other classes of RNA silencing have been identified and characterized. Presently, the therapeutic potential of these discoveries is being explored, for example, in the context of targeted gene therapy.
While RNA silencing is an evolving class of mechanisms, a common theme is the fundamental relationship between small RNAs and gene expression. It has also been observed that the major RNA silencing pathways currently identified have mechanisms of action which may involve both post-transcriptional gene silencing (PTGS) as well as chromatin-dependent gene silencing (CDGS) pathways. CDGS involves the assembly of small RNA complexes on nascent transcripts and is regarded as encompassing mechanisms of action which implicate transcriptional gene silencing (TGS) and co-transcriptional gene silencing (CTGS) events. This is significant at least because the evidence suggests that small RNAs play a role in the modulation of chromatin structure and TGS.
Despite early focus in the literature on RNA interference (RNAi) as a core mechanism which occurs at the level of messenger RNA translation, others have since been identified in the broader family of conserved RNA silencing pathways acting at the DNA and chromatin level. RNA silencing refers to the silencing activity of a range of small RNAs and is generally regarded as a broader category than RNAi. While the terms have sometimes been used interchangeably in the literature, RNAi is generally regarded as a branch of RNA silencing. To the extent it is useful to craft a distinction between these related concepts, RNA silencing may be thought of as referring to the broader scheme of small RNA related controls involved in gene expression and the protection of the genome against mobile repetitive DNA sequences, retroelements, and transposons to the extent that these can induce mutations. The molecular mechanisms for RNA silencing were initially studied in plants but have since broadened to cover a variety of subjects, from fungi to mammals, providing strong evidence that these pathways are highly conserved.
At least three primary classes of small RNA have currently been identified, namely: small interfering RNA (siRNA), microRNA (miRNA), and piwi-interacting RNA (piRNA). | 1 | Applied and Interdisciplinary Chemistry |
In ionic curing processes, an ionic photoinitiator is used to activate the functional group of the oligomers that are going to participate in cross-linking. Typically photopolymerization is a very selective process and it is crucial that the polymerization takes place only where it is desired to do so. In order to satisfy this, liquid neat oligomer can be doped with either anionic or cationic photoinitiators that will initiate polymerization only when radiated with light. Monomers, or functional groups, employed in cationic photopolymerization include: styrenic compounds, vinyl ethers, N-vinyl carbazoles, lactones, lactams, cyclic ethers, cyclic acetals, and cyclic siloxanes. The majority of ionic photoinitiators fall under the cationic class; anionic photoinitiators are considerably less investigated. There are several classes of cationic initiators, including onium salts, organometallic compounds and pyridinium salts. As mentioned earlier, one of the drawbacks of the photoinitiators used for photopolymerization is that they tend to absorb in the short UV region. Photosensitizers, or chromophores, that absorb in a much longer wavelength region can be employed to excite the photoinitiators through an energy transfer. Other modifications to these types of systems are free radical assisted cationic polymerization. In this case, a free radical is formed from another species in solution that reacts with the photoinitiator in order to start polymerization. Although there are a diverse group of compounds activated by cationic photoinitiators, the compounds that find most industrial uses contain epoxides, oxetanes, and vinyl ethers. One of the advantages to using cationic photopolymerization is that once the polymerization has begun it is no longer sensitive to oxygen and does not require an inert atmosphere to perform well.
:::M = Monomer | 0 | Theoretical and Fundamental Chemistry |
In nuclear physics, spectral bands refer to the electromagnetic emission of polyatomic systems, including condensed materials, large molecules, etc. Each spectral line corresponds to the difference in two energy levels of an atom. In molecules these levels can split. When the number of atoms is large, one gets a continuum of energy levels, the so-called "spectral bands". They are often labeled in the same way as the monatomic lines.
The bands may overlap. In general, the energy spectrum can be given by a density function, describing the number of energy levels of the quantum system for a given interval. Spectral bands have constant density, and when the bands overlap, the corresponding densities are added.
Band spectra is the name given to a group of lines that are closely spaced and arranged in a regular sequence that appears to be a band. It is a colored band, separated by dark spaces on the two sides and arranged in a regular sequence. In one band, there are various sharp and wider color lines, that are closer on one side and wider on other. The intensity in each band falls off from definite limits and indistinct on the other side. In complete band spectra, there is a number lines in a band.
This spectra is produced when the emitting substance is in the molecular state. Therefore, they are also called molecular spectra.
It is emitted by a molecule in vacuum tube, C-arc core with metallic salt. The band spectrum is the combination of many different spectral lines, resulting from molecular vibrational, rotational, and electronic transition.
Spectroscopy studies spectral bands for astronomy and other purposes.
Many systems are characterized by the spectral band to which they respond. For example:
* Musical instruments produce different ranges of notes within the hearing range.
* The electromagnetic spectrum can be divided into many different ranges such as visible light, infrared or ultraviolet radiation, radio waves, X-rays and so on, and each of these ranges can in turn be divided into smaller ranges.
* A radio communications signal must occupy a range of frequencies carrying most of its energy, called its bandwidth. A frequency band may represent one communication channel or be subdivided into many. Allocation of radio frequency ranges to different uses is a major function of radio spectrum allocation. | 0 | Theoretical and Fundamental Chemistry |
A structure field map is typically two-dimensional, although higher dimensional versions are feasible. The axes in an SFM are the ionic sequences. For example, in oxide perovskites ABO, where A and B represent two metallic cations, the two axes are ionic radii of the A-site and B-site cations. SFMs are constructed according to the oxidation states of the constituent cations. For perovskites of the type ABO, three ways of cation pairings exist: ABO, ABO, and ABO, therefore, three different SFMs exist for each pairs of cation oxidation states. | 0 | Theoretical and Fundamental Chemistry |
Viruses that infect plant and animal cells have also been manipulated to introduce foreign genes into plant and animal cells. The natural ability of viruses to adsorb to cells, introduce their DNA and replicate have made them ideal vehicles to transfer foreign DNA into eukaryotic cells in culture. A vector based on Simian virus 40 (SV40) was used in first cloning experiment involving mammalian cells. A number of vectors based on other type of viruses like Adenoviruses and Papilloma virus have been used to clone genes in mammals. At present, retroviral vectors are popular for cloning genes in mammalian cells. In case of plants like Cauliflower mosaic virus, Tobacco mosaic virus and Gemini viruses have been used with limited success. | 1 | Applied and Interdisciplinary Chemistry |
For dilute thermodynamic conditions, the ideal-gas equation of state (EoS) provides sufficiently accurate results in modelling the fluid thermodynamics. This occurs in general for low values of reduced pressure and high values of reduced temperature, where the term reduced refers to the ratio of a certain thermodynamic quantity and its critical value. For some fluids such as air, the assumption of considering ideal conditions is perfectly reasonable and it is widely used.
On the other hand, when thermodynamic conditions approach condensation and the critical point or when high pressures are involved, real-gas models are needed in order to capture the real fluid behavior. In these conditions, in fact, intermolecular forces and compressibility effects come into play.
A measure of the fluid non-ideality is given by the compressibility factor , defined as
where
* is the pressure [Pa];
* is the specific volume [m/kg];
* is the specific gas constant [J/(kg K)], namely the universal gas constant divided by the fluid's molecular mass;
* is the absolute temperature [K].
The compressibility factor is a dimensionless quantity which is equal to 1 for ideal gases and deviates from unity for increasing levels of non-ideality.
Several non-ideal models exist, from the simplest cubic equations of state (such as the Van der Waals and the Peng-Robinson models) up to complex multi-parameter ones, including the Span-Wagner equation of state.
State-of-the-art equations of state are easily accessible through thermodynamic libraries, such as FluidProp or the open-source software CoolProp. | 0 | Theoretical and Fundamental Chemistry |
Bacterial cells are widely used for cloning processes, genetic modification and small-scale productions. Escherichia coli (E. Coli) is widely utilised due to its highly explored genetics, widely available genetic tools for gene expression, accurate profiling and its ability to grow in inexpensive media at high cell densities.
E. Coli is mostly appropriate for structurally simple proteins owing to its inability to carry out post-translational modifications, lack of protein secretary system and the potential for producing inclusion bodies that require additional solubilisation. Regarding application, E.Coli is being utilised as the expression system of the dengue vaccine. | 1 | Applied and Interdisciplinary Chemistry |
*Atmospheric circulation
*Ocean current
*Ocean dynamics
*Thermohaline circulation
*Boundary current
*Sverdrup balance
*Subsurface currents | 1 | Applied and Interdisciplinary Chemistry |
Cetilistat is a synthetic lipase inhibitor. Instead of having a β-lactone structure like most of the lipase inhibitors, it has a bicyclic benzoxazinone ring. It is also a lipophilic compound but differs in the hydro- and lipophilic side chain.
The structure and more information about Cetilistat is shown in the table on the right. | 1 | Applied and Interdisciplinary Chemistry |
Underwater air retaining surfaces are of great interest for technical applications. If a transfer of the effect to a technical surface is successful, ship hulls could be coated with this surface to reduce friction between ship and water resulting in less fuel consumption, fuel costs and reduction of its negative environmental impact (antifouling effect by the air layer). In 2007 first test boats already achieved a ten percent friction reduction and the principle was subsequently patented. By now scientists assume a friction reduction of over 30%.
The underlying principle is schematically shown in a figure. Two flow profiles of laminar flow in water over a solid surface and water flowing over an air retaining surface are compared here.
If water flows over a smooth solid surface, the velocity at the surface is zero due to the friction between water and surface molecules. If an air layer is situated between the solid surface and the water the velocity is higher than zero. The lower viscosity of air (55 times lower than the viscosity of water) reduces the transmission of friction forces by the same factor.
Researchers are currently working on the development of a biomimetic, permanently air retaining surface modeled on S. molesta to reduce friction on ships. Salvinia-Effect surfaces have been proven to quickly and efficiently adsorb oil and can be used for oil-water separation applications | 0 | Theoretical and Fundamental Chemistry |
Assay offices are institutions set up to assay (test the purity of) precious metals. This is often done to protect consumers from buying fake items. Upon successful completion of an assay (i.e. if the metallurgical content is found be equal or better than that claimed by the maker and it otherwise conforms to the prevailing law) the assay offices typically stamp a hallmark on the item to certify its metallurgical content. Hallmarking first appeared in France, with the Goldsmiths' Statute of 1260 promulgated under Étienne Boileau, Provost of Paris, for King Louis IX. | 0 | Theoretical and Fundamental Chemistry |
In eukaryotic cells, in general, stable disulfide bonds are formed in the lumen of the RER (rough endoplasmic reticulum) and the mitochondrial intermembrane space but not in the cytosol. This is due to the more oxidizing environment of the aforementioned compartments and more reducing environment of the cytosol (see glutathione). Thus disulfide bonds are mostly found in secretory proteins, lysosomal proteins, and the exoplasmic domains of membrane proteins.
There are notable exceptions to this rule. For example, many nuclear and cytosolic proteins can become disulfide-crosslinked during necrotic cell death. Similarly, a number of cytosolic proteins which have cysteine residues in proximity to each other that function as oxidation sensors or redox catalysts; when the reductive potential of the cell fails, they oxidize and trigger cellular response mechanisms. The virus Vaccinia also produces cytosolic proteins and peptides that have many disulfide bonds; although the reason for this is unknown presumably they have protective effects against intracellular proteolysis machinery.
Disulfide bonds are also formed within and between protamines in the sperm chromatin of many mammalian species. | 0 | Theoretical and Fundamental Chemistry |
India approved and commissioned NWDA in June 2005 to identify and complete feasibility studies of intra-State projects that would inter-link rivers within that state. The Governments of Nagaland, Meghalaya, Kerala, Punjab, Delhi, Sikkim, Haryana, Union Territories of Puducherry, Andaman & Nicobar islands, Daman & Diu and Lakshadweep responded that they have no intrastate river connecting proposals. Govt. of Puducherry proposed Pennaiyar – Sankarabarani link (even though it is not an intrastate project). The States Government of Bihar proposed 6 inter-linking projects, Maharashtra 20 projects, Gujarat 1 project, Orissa 3 projects, Rajasthan 2 projects, Jharkhand 3 projects and Tamil Nadu proposed 1 inter-linking proposal between rivers inside their respective territories. Since 2005, NWDA completed feasibility studies on the projects, found 1 project infeasible, 20 projects as feasible, 1 project was withdrawn by Government of Maharashtra, and others are still under study. | 1 | Applied and Interdisciplinary Chemistry |
Cryptoregiochemistry refers to the site of initial oxidative attack in double bond formation by enzymes such as fatty acid desaturases. This is a mechanistic parameter that is usually determined through the use of kinetic isotope effect experiments, based on the premise that the initial C-H bond cleavage step should be energetically more difficult and therefore more sensitive to isotopic substitution than the second C-H bond breaking step. | 0 | Theoretical and Fundamental Chemistry |
Absinthin's (1) complex structure is classified as a sesquiterpene lactone, meaning it belongs to a large category of natural products chemically derived from 5-carbon "building blocks" (3) derived from isoprene (4). The complete structure consists of two identical monomers (2) that are attached via a suspected naturally occurring Diels Alder reaction occurring at the alkenes on the 5-membered ring of the guaianolide. | 0 | Theoretical and Fundamental Chemistry |
Aside from his oft-cited Plasma chemistry in electrical discharges published 1967 in 16 editions in 4 languages, McTaggart was author or co-author on a number of papers in journals including Australian Journal of Chemistry, Nature, and the Journal of Applied Chemistry on experimental research into its physics and chemistry and its applications. | 0 | Theoretical and Fundamental Chemistry |
The definition of a good ecological status is a matter of interpretation. For member states of the European Union, the Water Framework Directive defines two different ecological target states, which are the good ecological status and the good ecological potential. The good ecological status refers to a natural body of surface water, whereas the good ecological potential specifically relates to a heavily modified or even artificial body of water that was created by human activity. | 1 | Applied and Interdisciplinary Chemistry |
Planned
* EnMAP
Current and Past
*AVIRIS — airborne
*MODIS — on board EOS Terra and Aqua platforms
*MERIS — on board Envisat
*Hyperion — on board Earth Observing-1
*Several commercial manufacturers for laboratory, ground-based, aerial, or industrial imaging spectrographs | 0 | Theoretical and Fundamental Chemistry |
Near-field scanning optical microscopy (NSOM) was described in 1984, and used in many applications since then. The combination of Raman scattering and NSOM techniques was first realized in 1995, when it was used for imaging a Rb-doped KTP crystal at a spatial resolution of 250 nm.
NSOM employs two different methods for data collection and analysis: the fiber tip aperture approach and the apertureless metal tip approach. NSOM with aperture probes has a smaller aperture that can increase the spatial resolution of NSOM; however, the transmission of light to the sample and the collection efficiency of the scattered/emitted light is also diminished. The apertureless near-field scanning microscopy (ANSOM) was developed in the 1990s. ANSOM employs a metalized tip instead of an optical fiber probe. The performance of the ANSOM strongly depends on the electric field enhancement factor of the metalized tip. This technique is based on surface plasmon resonance (SPR) which is the precursor of tip-enhanced Raman scattering (TERS) and surface-enhanced Raman scattering (SERS).
In 1997, Martin and Girard demonstrated theoretically that electric field under a metallic or dielectric tip (belonging to NSOM apertureless technique) can be strongly enhanced if the incident field is along the tip axis. Since then a few groups have reported Raman or fluorescence enhancement in near field optical spectroscopy by apertureless microscopy. In 2000, T. Kalkbrenner et al. used a single gold particle as a probe for apertureless scanning and presented images of an aluminium film with 3 μm holes on a glass substrate. The resolution of this apertureless method was 100 nm, that is comparable to that of fiber-based systems Recently, a carbon nanotube (CNT) having a conical end, tagged with gold nanoparticles, was applied as a nanometer-resolution optical probe tip for NSOM. NSOM images were obtained with a spatial resolution of ~5 nm, demonstrating the potential of a composite CNT probe tip for nanoscale-resolution optical imaging. | 0 | Theoretical and Fundamental Chemistry |
An approach that is amenable to algebraic calculation by computer algebra methods is to differentiate in log space. Since the elasticity can be defined logarithmically, that is:
differentiating in log space is an obvious approach. Logarithmic differentiation is particularly convenient in algebra software such as Mathematica or Maple, where logarithmic differentiation rules can be defined.
A more detailed examination and the rules differentiating in log space can be found at Elasticity of a function. | 0 | Theoretical and Fundamental Chemistry |
Numerous commentaries have been written on Nyāya-Sutra since its composition. Some of these commentaries are available on [https://archive.org/ www.archive.org] for reference. A few of the commentaries are mentioned below:
# Nyaya-Sutra by Gotama or Aksapada
# Nyaya-Bhasya by Vatsyayana
# Nyaya-Varttika by Udyotakar
# Nyaya-Varttika tatparya-tika by Vacaspati Misra
# Nyaya-Varttika-tatparayatika-parisuddhi by Udayans
# Parisuddhiprakasa by Vardhamana
# Vardhamanedu by Padmanabha Misra
# Nyayalankara by Srikantha
# Nyayalankara Vrtti by Jayanta
# Nyaya-manjari by Jayanta
# Nyaya-Vrtti by Abhayatilakopadhyaya
# Nyaya-Vrtti by Visvanatha
# Mitabhasini Vrtti by Mahadeva Vedanti
# Nyayaprakasa by Kesava Misra
# Nyayabodhini by Govardhana
# Nyaya Sutra Vyakhya by Mathuranatha | 1 | Applied and Interdisciplinary Chemistry |
Cell toxicity tests are performed for applications such as cell growth scaffolds. By growing the cell with the ability to produce fluorescent protein, the growth of the cell can be monitored with fluorescent imaging techniques. | 0 | Theoretical and Fundamental Chemistry |
The results showed that global warming potential and acidification potential were the most significant environmental impacts. On average producing a tonne of steel emits 1.8 tonnes of . However, a steel mill using a top gas recycling blast furnace (TGRBF) producing a tonne of steel will emit 0.8 to 1.3 tonnes of depending upon the recycle rate of the TGRBF. | 1 | Applied and Interdisciplinary Chemistry |
In October 2019, a French-Spanish team of scientists published an article in Nature Ecology and Evolution that concludes that while the salt plains are teeming with halophilic microorganisms, there is no life in Dallol's multi-extreme ponds due to the combination of hyperacidic and hypersaline environments, and the abundance of magnesium (which catalyzes the denaturation of biomolecules). However another team reported for the first time evidence of life existing with these hot springs using a combination of morphological and molecular analyses. Ultra-small structures are shown to be entombed within mineral deposits, which are identified as members of the Order Nanohaloarchaea. | 0 | Theoretical and Fundamental Chemistry |
Kinetic fractionation of dissolved iron occurs as a result of diffusion. When isotopes diffuse, the lower mass isotopes diffuse more quickly than the heavier isotopes, resulting in fractionation. This difference in diffusion rates has been approximated as:
In this equation, D and D are the diffusivities of the isotopes, m and m are the masses of the isotopes, and β, which can vary between 0 and 0.5, depending on the system. More work is required to fully understand fractionation as a result of diffusion, studies of diffusion of iron on metal have consistently given β values of approximately 0.25. Iron diffusion between silicate melts and basaltic/rhyolitic melts have given lower β values (~0.030). In aqueous environments, a β value of 0.0025 has been obtained. | 0 | Theoretical and Fundamental Chemistry |
In 1968, Lusk described the limitation of bacterial (Escherichia coli) growth on Mg-poor media, suggesting that bacteria required Mg and were likely to actively take this ion from the environment. The following year, the same group and another group, Silver, independently described the uptake and efflux of Mg in metabolically active E. coli cells using Mg. By the end of 1971, two papers had been published describing the interference of Co, Ni and Mn on the transport of Mg in E. coli and in Aerobacter aerogenes and Bacillus megaterium. In the last major development before the cloning of the genes encoding the transporters, it was discovered that there was a second Mg uptake system that showed similar affinity and transport kinetics to the first system, but had a different range of sensitivities to interfering cations. This system was also repressible by high extracellular concentrations of Mg | 1 | Applied and Interdisciplinary Chemistry |
Electrophilic alkylation uses Lewis acids and Brønsted acids, sometimes both. Classically, Lewis acids, e.g., aluminium trichloride, are employed when the alkyl halide are used. Brønsted acids are used when alkylating with olefins. Typical catalysts are zeolites, i.e. solid acid catalysts, and sulfuric acid. Silicotungstic acid is used to manufacture ethyl acetate by the alkylation of acetic acid by ethylene: | 0 | Theoretical and Fundamental Chemistry |
Bicarbonate, originally known as bi-carbonate of potash, was coined by William Hyde Wollaston in 1814 based on hydrocarbonate's potential to release two molar equivalents of carbon dioxide (referred to as carbonic acid at the time) as released by both potassium hydrocarbonate (initially known as carbonate of potash, suggested to become bicarbonate) and potassium carbonate (vaguely known as subcarbonate, suggested to become carbonate) upon formation of potash (potassium oxide).
Bicarbonates have historically been defined as, "combinations of the bases with the carbonic acid, in which two atoms of the latter are united to one of the former" In other words, potash (potassium oxide) was well-understood to be a caustic base and essentially the core molecule that subsequent chemical nomenclature was built upon. Carbonate of potash (potassium carbonate) must contain a carbonic acid species fixated within potashs alternative composition (see fixed air above). Since "bi-carbonate of potash" liberates a double dose of carbonic acid, to distinguish between the similar substances, the prefix bi- indicates the bi-carbonate of potash (potassium hydrocarbonate) contains twice as much fixated in this form potashs composition relative to the carbonate of potash. The same ancient logic (prior to the understanding of molecular formulas and reaction stoichiometry) applied to soda, carbonate of soda, and bicarbonate of soda.
The word saleratus, from Latin sal æratus (meaning "aerated salt"), was widely used beginning in the 1840s. | 1 | Applied and Interdisciplinary Chemistry |
In thermodynamics, adiabatic changes are those that do not increase the entropy. They occur slowly in comparison to the other characteristic timescales of the system of interest and allow heat flow only between objects at the same temperature. For isolated systems, an adiabatic change allows no heat to flow in or out. | 0 | Theoretical and Fundamental Chemistry |
* IMP dehydrogenase (IMPDH) converts IMP into XMP
* GMP synthase converts XMP into GMP
* GMP reductase converts GMP back into IMP | 1 | Applied and Interdisciplinary Chemistry |
In 1788 he was once more promoted and as Gubernialrath he held a powerful position in the administration of Transylvania. Müller was knighted by Leopold II to the lowest title of nobility, Edler, in the same year. From that point on he carried the name Franz-Joseph Müller Edler von Reichenstein. He was elected as a member of the Berlin Society of Friends of Natural Science.
In 1798 Müller became court counsellor and was appointed to the court in Vienna, where he was part of the imperial council. In 1818 Müller retired from his duties but held his position in the council until his death. He became Knight of the Order of Saint Stephen of Hungary in 1818 and became a noble by receiving the title of a Freiherr in 1820. Both honours were granted by the Emperor Franz I (II). Müller died in his 80s in 1825 or 1826 in Vienna. | 1 | Applied and Interdisciplinary Chemistry |
Thioketenes are electrophilic. They add amines to give thioamides:
With peroxyacids, they produce thioketene-S-oxides:
Thioketenes bind to metal carbonyls giving adducts. | 0 | Theoretical and Fundamental Chemistry |
Salts comprising these cations are typically prepared by alkylation of thiourea:
:SC(NH) + RX → [RSC(NH)]X | 0 | Theoretical and Fundamental Chemistry |
William Hyde Wollaston (; 6 August 1766 – 22 December 1828) was an English chemist and physicist who is famous for discovering the chemical elements palladium and rhodium. He also developed a way to process platinum ore into malleable ingots. | 1 | Applied and Interdisciplinary Chemistry |
A common nitrate test, known as the brown ring test can be performed by adding iron(II) sulfate to a solution of a nitrate, then slowly adding concentrated sulfuric acid such that the acid forms a layer below the aqueous solution. A brown ring will form at the junction of the two layers, indicating the presence of the nitrate ion. Note that the presence of nitrite ions will interfere with this test.
The overall reaction is the reduction of the nitrate ion to nitric oxide by iron(II), which is oxidised to iron(III), followed by the formation of nitrosyl ferrous sulfate between the nitric oxide and the remaining iron(II), where nitric oxide is reduced to NO.
:2HNO + 3HSO + 6FeSO → 3Fe(SO) + 2NO + 4HO
:[Fe(HO)]SO + NO → [Fe(HO)(NO)]SO + HO
This test is sensitive up to 2.5 micrograms and a concentration of 1 in 25,000 parts. | 0 | Theoretical and Fundamental Chemistry |
Tellus Series B: Chemical and Physical Meteorology is a scientific journal that was published by Blackwell Publishing for the International Meteorological Institute in Stockholm, Sweden until December 2011. From January 2012 the issues are published online by Co-action Publishing as an open access journal. The journal publishes original articles, short contributions, and correspondence on atmospheric chemistry, surface exchange processes, long-range and global transport, aerosol science, and cloud physics including related radiation transfer. Biogeochemical cycles including related aspects of marine chemistry and geochemistry also represent a central theme.
Tellus B is the companion to Tellus Series A: Dynamic Meteorology and Oceanography. | 0 | Theoretical and Fundamental Chemistry |
Prouts hypothesis remained influential in chemistry throughout the 1820s. However, more careful measurements of the atomic weights, such as those compiled by Jacob Berzelius in 1828 or Edward Turner in 1832, disproved the hypothesis. In particular, the atomic weight of chlorine, which is 35.45 times that of hydrogen, could not at the time be explained in terms of Prouts hypothesis. Some came up with the ad hoc claim that the basic unit was one-half of a hydrogen atom, but further discrepancies surfaced. This resulted in the hypothesis that one-quarter of a hydrogen atom was the common unit. Although they turned out to be wrong, these conjectures catalyzed further measurement of atomic weights.
The discrepancy in the atomic weights was by 1919 suspected to be the result of the natural occurrence of multiple isotopes of the same element. F. W. Aston discovered multiple stable isotopes for numerous elements using a mass spectrograph. In 1919, Aston studied neon with sufficient resolution to show that the two isotopic masses are very close to the integers 20 and 22, and that neither is equal to the known molar mass (20.2) of neon gas.
By 1925, the problematic chlorine was found to be composed of the isotopes Cl and Cl, in proportions such that the average weight of natural chlorine was about 35.45 times that of hydrogen. For all elements, each individual isotope of mass number A was eventually found to have a mass very close to A times the mass of a hydrogen atom, with an error always less than 1%. This is a near miss to Prout's law being correct. Nevertheless, the rule was not found to predict isotope masses better than this for all isotopes, due mostly to mass defects resulting from release of binding energy in atomic nuclei when they are formed.
Although all elements are the product of nuclear fusion of hydrogen into higher elements, it is now understood that atoms consist of both protons (hydrogen nuclei) and neutrons. The modern version of Prouts rule is that the atomic mass of an isotope of proton number (atomic number) Z and neutron number N is equal to sum of the masses of its constituent protons and neutrons, minus the mass of the nuclear binding energy, the mass defect. According to the whole number rule proposed by Francis Aston, the mass of an isotope is roughly, but not exactly, its mass number A (Z + N') times an atomic mass unit (u), plus or minus binding energy discrepancy – atomic mass unit being the modern approximation for "mass of a proton, neutron, or hydrogen atom". For example iron-56 atoms (which have among the highest binding-energies) weigh only about 99.1% as much as 56 hydrogen atoms. The missing 0.9% of mass represents the energy lost when the nucleus of iron was made from hydrogen inside a star (see stellar nucleosynthesis). | 1 | Applied and Interdisciplinary Chemistry |
Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms that form the structure of molecules and their manipulation. The study of stereochemistry focuses on the relationships between stereoisomers, which by definition have the same molecular formula and sequence of bonded atoms (constitution), but differ in the geometric positioning of the atoms in space. For this reason, it is also known as 3D chemistry—the prefix "stereo-" means "three-dimensionality".
Stereochemistry spans the entire spectrum of organic, inorganic, biological, physical and especially supramolecular chemistry. Stereochemistry includes methods for determining and describing these relationships; the effect on the physical or biological properties these relationships impart upon the molecules in question, and the manner in which these relationships influence the reactivity of the molecules in question (dynamic stereochemistry). | 0 | Theoretical and Fundamental Chemistry |
Major control and isolation valves in traditional fire sprinkler systems are typically large gate valves of the "Outside Screw and Yoke" (OS&Y) type, sometimes called "rising stem" valves; or butterfly valves. The position (open or closed) of these valves can be determined visually. Alarm sensors may be attached to monitor the settings of these valves, which are critical to overall building safety. | 1 | Applied and Interdisciplinary Chemistry |
2-Phenylpyridine is an organic compound with the formula CHCHN (or CHN). It is a colourless viscous liquid. The compound and related derivatives have attracted interest as precursors to highly fluorescent metal complexes of possible value as organic light emitting diodes (OLEDs).
The compound is prepared by the reaction of phenyl lithium with pyridine:
:CHLi + CHN → CH-CHN + LiH
The reaction of iridium trichloride with 2-phenylpyridine proceeds via cyclometallation to give the chloride-bridged complex:
:4 CH-CHN + 2 IrCl(HO) → IrCl(CH-CHN) + 4 HCl
This complex can be converted to the pictured tris(cyclometallated) derivative tris(2-phenylpyridine)iridium. | 0 | Theoretical and Fundamental Chemistry |
The EBF organizes annual symposia to involve the bioanalytical community: pharmaceutical industry, academia, CRO, instrument providers and regulatory agencies. It is the intention of the organisation to inform their business partners and peers about the discussion held and agreements achieved and to open the forum for challenging procedures or techniques as well as for new regulatory requirements.
The EBF has also reached out to participate in international scientific meetings representing the bioanalytical voice of the European pharmaceutical industry. Selective examples are: American Association of Pharmaceutical Scientists meetings, The Boston Society Applied Pharmaceutical Analysis meetings, and Canadian Validation Group meeting. | 0 | Theoretical and Fundamental Chemistry |
Some kinds of cheese also, kefir, kumis (mare milk), shubat (camel milk), ayran, cultured milk products such as quark, filmjölk, crème fraîche, smetana, skyr, and yogurt | 1 | Applied and Interdisciplinary Chemistry |
Liebig formulated his own theory claiming that the production of alcohol was not a biological process but a chemical process, discrediting the idea that fermentation could occur due to microscopic organisms. He believed that vibrations emanating from the decomposition of organic matter would spread to the sugar resulting in the production of solely carbon dioxide and alcohol.
The change was facilitated by ferment or yeast, which has the characters of a compound of nitrogen in the state of putrefaction. Given that the ferment's susceptibility to change, it is submitted to decomposition, by the action of air (from which oxygen is provided), water (from which moisture is obtained), and a favorable temperature. Prior to contact with oxygen, the constituents are arranged together without action on each other. Through the oxygen, the state of rest (or equilibrium) of the attractions that keep the elements together has been disturbed. As a consequence of this disturbance, a separation or new arrangement of the elements has been formed. Fermentation occurs due to the transference of molecular instability from the ferment (atoms in motion) to the sugar molecules, and continues as long as the decomposition of the ferment continues.
Liebig's view of fermentation can be said to fall under a mechanism point of view. From his work, he saw that fermentation, as well as other catalysts happened by a chemical and mechanical process. | 1 | Applied and Interdisciplinary Chemistry |
A typical method of top-down fabrication includes photolithography to define the geometry of channels on a substrate wafer. The geometry is created by several thin-film deposition and etching steps to form trenches. The substrate wafer is then bonded to another wafer to seal the trenches and form channels. Other technologies to fabricate nano-channels include surface micromachining with sacrificial layers, nano-imprinting lithography, and soft-lithography. | 0 | Theoretical and Fundamental Chemistry |
Transcriptomics is most commonly applied to the mRNA content of the cell. However, the same techniques are equally applicable to non-coding RNAs (ncRNAs) that are not translated into a protein, but instead have direct functions (e.g. roles in protein translation, DNA replication, RNA splicing, and transcriptional regulation). Many of these ncRNAs affect disease states, including cancer, cardiovascular, and neurological diseases. | 1 | Applied and Interdisciplinary Chemistry |
The earliest evidence for iron-making is a small number of iron fragments with the appropriate amounts of carbon admixture found in the Proto-Hittite layers at Kaman-Kalehöyük and dated to 2200–2000 BCE. Souckova-Siegolová (2001) shows that iron implements were made in Central Anatolia in very limited quantities around 1800 BCE and were in general use by elites, though not by commoners, during the New Hittite Empire (~1400–1200 BCE).
Archaeologists have found indications of iron working in Ancient Egypt, somewhere between the Third Intermediate Period and 23rd Dynasty (ca. 1100–750 BCE). Significantly though, they have found no evidence of iron ore smelting in any (pre-modern) period. In addition, very early instances of carbon steel were in production around 2000 years ago (around the first-century CE.) in northwest Tanzania, based on complex preheating principles. These discoveries are significant for the history of metallurgy.
Most early processes in Europe and Africa involved smelting iron ore in a bloomery, where the temperature is kept low enough so that the iron does not melt. This produces a spongy mass of iron called a bloom, which then must be consolidated with a hammer to produce wrought iron. The earliest evidence to date for the bloomery smelting of iron is found at Tell Hammeh, Jordan ([http://www.ironsmelting.net/www/smelting/]), and dates to 930 BCE (C14 dating). | 1 | Applied and Interdisciplinary Chemistry |
Cell–cell fusogens have several different applications. These chemical agents can play a significant part in sexual and asexual reproduction by promoting the fusion of the membrane bilayers. With sexual reproduction, evidence found to prove that in mice, some mandatory sperm-egg fusogens are responsible for fusion; two particular proteins were IZUMO1 and CD9. After comparing the data of experiments done with plants, fungi, and invertebrates, it was seen that several crucial genes could have been responsible for fertilization. However, like yeasts, there were no genes found to be adequate for the fertilization process. As of late, another protein has been classified as a gamete fusogen (HAP2 or GCS1). Like the previous example, this protein is present in plants, protists, and invertebrates. This fusogen resembles the eukaryotic somatic fusogen mentioned earlier, EFF-1. The presence of HAP2 induces hemifusion and the mixing of cell content. Yet when considering asexual reproduction, somatic cells can also undergo cell-cell fusion or self-fusion. Two particular fusogens observed were SO and MAK-2. Evidence supports that these proteins control and regulate efficient protein concentration and localization. | 1 | Applied and Interdisciplinary Chemistry |
Jupiter, like all the gas giants, has an atmospheric methane cycle. Recent studies indicate a hydrological cycle of water-ammonia vastly different to the type operating on terrestrial planets like Earth and also a cycle of hydrogen sulfide.
Significant chemical cycles exist on Jupiter's moons. Recent evidence points to Europa possessing several active cycles, most notably a water cycle. Other studies suggest an oxygen and radiation induced carbon dioxide cycle. Io and Europa, appear to have radiolytic sulphur cycles involving their lithospheres. In addition, Europa is thought to have a sulfur dioxide cycle. In addition, the Io plasma torus contributes to a sulphur cycle on Jupiter and Ganymede. Studies also imply active oxygen cycles on Ganymede and oxygen and radiolytic carbon dioxide cycles on Callisto. | 0 | Theoretical and Fundamental Chemistry |
A chemical composition specifies the identity, arrangement, and ratio of the chemical elements making up a compound by way of chemical and atomic bonds.
Chemical formulas can be used to describe the relative amounts of elements present in a compound. For example, the chemical formula for water is HO: this means that each molecule of water is constituted by 2 atoms of hydrogen (H) and 1 atom of oxygen (O). The chemical composition of water may be interpreted as a 2:1 ratio of hydrogen atoms to oxygen atoms. Different types of chemical formulas are used to convey composition information, such as an empirical or molecular formula.
Nomenclature can be used to express not only the elements present in a compound but their arrangement within the molecules of the compound. In this way, compounds will have unique names which can describe their elemental composition. | 0 | Theoretical and Fundamental Chemistry |
Boom method (aka Boom nucleic acid extraction method) is a solid phase extraction method for isolating nucleic acid from a biological sample. This method is characterized by "absorbing the nucleic acids (NA) to the silica beads". | 1 | Applied and Interdisciplinary Chemistry |
Casting achieves a specific form by pouring molten metal into a mold and allowing it to cool, with no mechanical force. Forms of casting include:
* Investment casting (called lost wax casting in art)
* Centrifugal casting
* Die casting
* Sand casting
* Shell casting
* Spin casting | 1 | Applied and Interdisciplinary Chemistry |
The following forces play an important role in the interaction of colloid particles:
*Excluded volume repulsion: This refers to the impossibility of any overlap between hard particles.
*Electrostatic interaction: Colloidal particles often carry an electrical charge and therefore attract or repel each other. The charge of both the continuous and the dispersed phase, as well as the mobility of the phases are factors affecting this interaction.
*van der Waals forces: This is due to interaction between two dipoles that are either permanent or induced. Even if the particles do not have a permanent dipole, fluctuations of the electron density gives rise to a temporary dipole in a particle. This temporary dipole induces a dipole in particles nearby. The temporary dipole and the induced dipoles are then attracted to each other. This is known as van der Waals force, and is always present (unless the refractive indexes of the dispersed and continuous phases are matched), is short-range, and is attractive.
*Steric forces between polymer-covered surfaces or in solutions containing non-adsorbing polymer can modulate interparticle forces, producing an additional steric repulsive force (which is predominantly entropic in origin) or an attractive depletion force between them. | 0 | Theoretical and Fundamental Chemistry |
The traditional method for attaching sugars to natural products, drugs or drug leads is by chemical glycosylation. This classical approach typically requires multiple protection/deprotection steps in addition to the key anomeric activation/coupling reaction which, depending upon the glycosyl donor/acceptor pair, can lead to a mixture of anomers. Unlike classical chemical glycosylation, glycorandomization methods are divergent (i.e., diverge from a common starting material, see divergent synthesis) and are not dependent upon sugar/aglycon protection/deprotection or sugar anomeric activation. Two complementary strategies to achieve glycorandomization/diversification have been developed: an enzyme-based strategy referred to as chemoenzymatic glycorandomization and a chemoselective method known as neoglycorandomization. Both methods start with free reducing sugars and a target aglycon to afford a library of compounds which differ solely by the sugars appended to the target natural product, drug or drug lead. | 0 | Theoretical and Fundamental Chemistry |
Before the use of gas chromatography-mass spectrometry and biomarkers, correlation of locations' geology was used to find how different formations relate to each other and to their environment. Oil-oil correlations (comparing petroleum to other oil found locally or in other areas) and oil-source correlations (comparing petroleum and its source) were performed; infrared spectrometry, refractive indices, solvent extractable organic matter, compound class distribution, and elemental analysis are all methods of doing oil-source correlations. | 0 | Theoretical and Fundamental Chemistry |
The resting potential must be established within a cell before the cell can be depolarized. There are many mechanisms by which a cell can establish a resting potential, however there is a typical pattern of generating this resting potential that many cells follow. The generation of a negative resting potential within the cell involves the utilization of ion channels, ion pumps, and voltage-gated ion channels by the cell. However, the process of generating the resting potential within the cell also creates an environment outside the cell that favors depolarization. The sodium potassium pump is largely responsible for the optimization of conditions on both the interior and the exterior of the cell for depolarization. By pumping three positively charged sodium ions (Na) out of the cell for every two positively charged potassium ions (K) pumped into the cell, not only is the resting potential of the cell established, but an unfavorable concentration gradient is created by increasing the concentration of sodium outside the cell and increasing the concentration of potassium within the cell. While there is an excessive amount of potassium in the cell and sodium outside the cell, the generated resting potential maintains the closure of voltage-gated ion channels in the plasma membrane. This not only prevents the diffusion of ions pumped across the membrane but also involves the activity of potassium leak channels, allowing a controlled passive efflux of potassium ions, which contributes to the establishment of the negative resting potential. Additionally, despite the high concentration of positively-charged potassium ions, most cells contain internal components (of negative charge), which accumulate to establish a negative inner charge. | 0 | Theoretical and Fundamental Chemistry |
As an example of isotopic symmetry (in compositional, and not in geometrical sense) affecting the kinetics of physic-chemical processes, see mass independent isotope fractionation in ozone O. | 0 | Theoretical and Fundamental Chemistry |
* Austria Viktor Obendrauf
* China Zhou Ning-Huai
* Egypt Mahmoud K. El-Marsafy
* Germany Angela Koehler-Kruetzfeld, Peter Schwarz, Waltraud Habelitz-Tkotz, Michael Tausch, John McCaskill, Theodor Grofe, Bernd-Heinrich Brand, Gregor von Borstel, Stephan Mattusek
* Hong Kong Winghong Chan
* Israel Mordechai Livneh
* Japan Kazuko Ogino
* Macedonia Metodija Najdoski
* Mexico Jorge Ibanez, Arturo Fregoso, Carmen Doria, Rosa Maria Mainero, Margarita Hernandez, et al.
* [http://www.centrumchemii.torun.pl Poland] Aleksander Kazubski, Dominika Strutyńska, Łukasz Sporny, Piotr Wróblewski
*Portugal M. Elisa Maia
* South Africa John Bradley Marie DuToit
* Sweden Christer Gruvberg
* USA
**[http://www.nationalmicroscalecc.org] National Microscale Chemistry Center
**[http://www.smallscalechemistry.colostate.edu USA] National Small Scale Chemistry Center
**[http://mattson.creighton.edu USA] Microscale Gas Chemistry; Bruce Mattson
**Kenneth M. Doxsee
* Thailand Supawan Tantyanon
* Kuwait Abdulaziz Alnajjar
* India Govt. Victoria College, Palakkad,Kerala
* United Kingdom Bob Worley, CLEAPSS, Chis LLoyd SSERC | 1 | Applied and Interdisciplinary Chemistry |
Conventional voltammetry offers a limited picture of the enzyme-electrode interface and on the structure of the species involved in the reaction. Complementing standard electrochemistry with other methods can provide a more complete picture of catalysis. | 0 | Theoretical and Fundamental Chemistry |
Fluorination by sulfur tetrafluoride produces organofluorine compounds from oxygen-containing organic functional groups using sulfur tetrafluoride. The reaction has broad scope, and SF is an inexpensive reagent. It is however hazardous gas whose handling requires specialized apparatus. Thus, for many laboratory scale fluorinations diethylaminosulfur trifluoride ("DAST") is used instead. | 0 | Theoretical and Fundamental Chemistry |
Prelog was born in Sarajevo, Condominium of Bosnia and Herzegovina, at that time within Austria-Hungary, to Croat parents who were working there. His father, Milan, a native of Zagreb, was a history professor at a gymnasium in Sarajevo and later at the University of Zagreb. As an 8-year-old boy, he stood near the place where the assassination of Franz Ferdinand occurred. | 0 | Theoretical and Fundamental Chemistry |
Bacteria and archaea also can use chemiosmosis to generate ATP. Cyanobacteria, green sulfur bacteria, and purple bacteria synthesize ATP by a process called photophosphorylation. These bacteria use the energy of light to create a proton gradient using a photosynthetic electron transport chain. Non-photosynthetic bacteria such as E. coli also contain ATP synthase. In fact, mitochondria and chloroplasts are the product of endosymbiosis and trace back to incorporated prokaryotes. This process is described in the endosymbiotic theory. The origin of the mitochondrion triggered the origin of eukaryotes, and the origin of the plastid the origin of the Archaeplastida, one of the major eukaryotic supergroups.
Chemiosmotic phosphorylation is the third pathway that produces ATP from inorganic phosphate and an ADP molecule. This process is part of oxidative phosphorylation. | 1 | Applied and Interdisciplinary Chemistry |
MHD propulsion has been considered as the main propulsion system for both marine and space ships since there is no need to produce lift to counter the gravity of Earth in water (due to buoyancy) nor in space (due to weightlessness), which is ruled out in the case of flight in the atmosphere.
Nonetheless, considering the current problem of the electric power source solved (for example with the availability of a still missing multi-megawatt compact fusion reactor), one could imagine future aircraft of a new kind silently powered by MHD accelerators, able to ionize and direct enough air downward to lift several tonnes. As external flow systems can control the flow over the whole wetted area, limiting thermal issues at high speeds, ambient air would be ionized and radially accelerated by Lorentz forces around an axisymmetric body (shaped as a cylinder, a cone, a sphere…), the entire airframe being the engine. Lift and thrust would arise as a consequence of a pressure difference between the upper and lower surfaces, induced by the Coandă effect. In order to maximize such pressure difference between the two opposite sides, and since the most efficient MHD converters (with a high Hall effect) are disk-shaped, such MHD aircraft would be preferably flattened to take the shape of a biconvex lens. Having no wings nor airbreathing jet engines, it would share no similarities with conventional aircraft, but it would behave like a helicopter whose rotor blades would have been replaced by a "purely electromagnetic rotor" with no moving part, sucking the air downward. Such concepts of flying MHD disks have been developed in the peer review literature from the mid 1970s mainly by physicists Leik Myrabo with the Lightcraft, and Subrata Roy with the Wingless Electromagnetic Air Vehicle (WEAV).
These futuristic visions have been advertised in the media although they still remain beyond the reach of modern technology. | 1 | Applied and Interdisciplinary Chemistry |
Alkalinity roughly refers to the molar amount of bases in a solution that can be converted to uncharged species by a strong acid. For example, 1 mole of in solution represents 1 molar equivalent, while 1 mole of is 2 molar equivalents because twice as many H ions would be necessary to balance the charge. The total charge of a solution always equals zero. This leads to a parallel definition of alkalinity that is based upon the charge balance of ions in a solution.
Certain ions, including Na, K, Ca, Mg, Cl, , and are "conservative" such that they are unaffected by changes in temperature, pressure or pH. Others such as are affected by changes in pH, temperature, and pressure. By isolating the conservative ions on one side of this charge balance equation, the nonconservative ions which accept or donate protons and thus define alkalinity are clustered on the other side of the equation.
This combined charge balance and proton balance is called total alkalinity. Total alkalinity is not (much) affected by temperature, pressure, or pH, and is thus itself a conservative measurement, which increases its usefulness in aquatic systems. All anions except and have low concentrations in Earth's surface water (streams, rivers, and lakes). Thus carbonate alkalinity, which is equal to is also approximately equal to the total alkalinity in surface water. | 0 | Theoretical and Fundamental Chemistry |
"No wake zones" may prohibit wakes in marinas, near moorings and within some distance of shore in order to facilitate recreation by other boats and reduce the damage wakes cause. Powered narrowboats on British canals are not permitted to create a breaking wash (a wake large enough to create a breaking wave) along the banks, as this erodes them. This rule normally restricts these vessels to or less.
Wakes are occasionally used recreationally. Swimmers, people riding personal watercraft, and aquatic mammals such as dolphins can ride the leading edge of a wake. In the sport of wakeboarding the wake is used as a jump. The wake is also used to propel a surfer in the sport of wakesurfing. In the sport of water polo, the ball carrier can swim while advancing the ball, propelled ahead with the wake created by alternating armstrokes in crawl stroke, a technique known as dribbling. Furthermore, in the sport of canoe marathon, competitors use the wake of fellow kayaks in order to save energy and gain an advantage, through the practice of sitting their boats on the wake of another, so their kayak is propelled by the wash. | 1 | Applied and Interdisciplinary Chemistry |
Oladipo attended St. Johns Catholic Grammar School, Ile-Ife, from 1972 to 1976. During this period, he achieved a Grade 1 in the West African Senior Certificate Examination. He then pursued his bachelors degree in Chemistry (Education) at Obafemi Awolowo University (formerly University of Ife), Ile-Ife, graduating with Second Class (Upper Division) honors in 1981. Following his undergraduate studies, he continued his education abroad at the Université Claude Bernard, Lyon I, Villeurbanne, France, where he obtained an MPhil and a PhD in Analytical Chemistry (Nuclear Techniques) With more than five publications in 1984-1988, under the active supervision of Professor JP Thomas. | 0 | Theoretical and Fundamental Chemistry |
Iron–sulfur clusters occur in many biological systems, often as components of electron transfer proteins. The ferredoxin proteins are the most common Fe–S clusters in nature. They feature either 2Fe–2S or 4Fe–4S centers. They occur in all branches of life.
Fe–S clusters can be classified according to their Fe:S stoichiometry [2Fe–2S], [4Fe–3S], [3Fe–4S], and [4Fe–4S]. The [4Fe–4S] clusters occur in two forms: normal ferredoxins and high potential iron proteins (HiPIP). Both adopt cuboidal structures, but they utilize different oxidation states. They are found in all forms of life.
The relevant redox couple in all Fe–S proteins is Fe(II)/Fe(III).
Many clusters have been synthesized in the laboratory with the formula [FeS(SR)], which are known for many R substituents, and with many cations. Variations have been prepared including the incomplete cubanes [FeS(SR)]. | 0 | Theoretical and Fundamental Chemistry |
Fallout Protection: What To Know And Do About Nuclear Attack was an official United States federal government booklet released in December 1961 by the United States Department of Defense and the Office of Civil Defense.
The first page of the book is a note from then-U.S. Secretary of Defense Robert McNamara explaining that the booklet is a 48 page book made for the result of the first task he was given when he assumed responsibility for the Federal Civil Defense Program in August 1961. The task, assigned by President John F. Kennedy, was to "give the American people the facts they need to know about the dangers of a thermonuclear attack and what they can do to protect themselves." | 0 | Theoretical and Fundamental Chemistry |
Process network synthesis (PNS) is a method to represent a process structure in a directed bipartite graph. Process network synthesis uses the P-graph method to create a process structure. The scientific aim of this method is to find optimum structures.
Process network synthesis uses a bipartite graph method P-graph and employs combinatorial rules to find all feasible network solutions (maximum structure) and links raw materials to desired products related to the given problem. With a branch and bound optimisation routine and by defining the target value an optimum structure can be generated that optimises a chosen target function.
Process Network Synthesis was originally developed to solve chemical process engineering processes. Target value as well as the structure can be changed depending on the field of application. Thus many more fields of application followed. | 1 | Applied and Interdisciplinary Chemistry |
Pierre Curie died in a street collision in Paris on 19 April 1906. Crossing the busy Rue Dauphine in the rain at the Quai de Conti, he slipped and fell under a heavy horse-drawn cart. One of the wheels ran over his head, fracturing his skull and killing him instantly.
Both the Curies experienced radium burns, both accidentally and voluntarily, and were exposed to extensive doses of radiation while conducting their research. They experienced radiation sickness and Marie Curie died from radiation-induced aplastic anemia in 1934. Even now, all their papers from the 1890s, even her cookbooks, are too dangerous to touch. Their laboratory books are kept in special lead boxes and people who want to see them have to wear protective clothing. Most of these items can be found at . Had Pierre Curie not been killed in an accident as he was, he would most likely have eventually died of the effects of radiation, as did his wife, their daughter Irène, and her husband Frédéric Joliot.
In April 1995, Pierre and Marie Curie were moved from their original resting place, a family cemetery, and enshrined in the crypt of the Panthéon in Paris. | 1 | Applied and Interdisciplinary Chemistry |
This term could be used to describe the action of acetylcholine on nicotinic receptors, glutamate on NMDA receptors or GABA on GABAa receptors. | 1 | Applied and Interdisciplinary Chemistry |
The major advantage this polymerization technique presents over LCP lies in the fact that the polymer can be end capped on both sides of the chain with stimuli-responsive groups. The tuning process of PPA by these functional groups have not only expanded the set of applications this polymer can be used in, but has also improved its properties and attributes. For instance, by controlling the o-phthalaldehyde monomer/alcohol initiator concentration ratio, ultra-high molecular weights (50-150 KDa) PPA can be obtained. Furthermore, PPA synthesized through LAP is more thermally and mechanically stable. Generally, the presence of endcaps on both ends stabilizes the polymer and results in a more flexible chain with a high thermal stability. And because linear polymers synthesized by LAP method can be end capped whereas cyclic polymers prepared via LCP method cannot be end capped with functional groups, LAP results in more thermally stable polymers. It has a much lower PDI ranging between 1.3 and 1.9 as opposed to PPA synthesized through LCP which has a PDI ranging between 2 and 4.5. This is because of the ability to control the character, molecular weight, and end group of the polymer. Furthermore, the initiator used in LAP synthesis method, which is a strong nucleophile, acts as the first endcap, and hence by controlling the amount of initiator used, a control over the molar mass and PDI can be obtained. This is in contrary to cyclic PPA which is synthesized through LCP where the initiator (Lewis acid) will not be part of the final PPA product, and hence, controlling the amount of Lewis acid used will have no to little effect on the final molar mass and PDI of cyclic PPA polymer. | 0 | Theoretical and Fundamental Chemistry |
Attainable region (AR) theory is a branch of chemical engineering, specifically chemical reaction engineering, that uses geometric and mathematical optimization concepts to assist in the design of networks of chemical reactors. AR theory is a method to help define the best reactor flowsheet using graphical techniques for a desired duty or objective function. | 1 | Applied and Interdisciplinary Chemistry |
Werner was born in 1866 in Mulhouse, Alsace (which was then part of France, but which was annexed by Germany in 1871). He was raised as Roman Catholic. He was the fourth and last child of Jean-Adam Werner, a foundry worker, and his second wife, Salomé Jeanette Werner, who originated from a wealthy family. He went to Switzerland to study chemistry at the Swiss Federal Institute (polytechnikum) in Zurich. Still, since this institute was not empowered to grant doctorates until 1909, Werner received a doctorate formally from the University of Zürich in 1890. After postdoctoral study in Paris, he returned to the Swiss Federal Institute to teach (1892). In 1893 he moved to the University of Zurich, where he became a professor in 1895. In 1894 he became a Swiss citizen.
In his last year, he suffered from a general, progressive, degenerative arteriosclerosis, especially of the brain, aggravated by years of excessive drinking and overwork. He died in a psychiatric hospital in Zürich.
Werner died on 15 November 1919 of arteriosclerosis in Zürich at the age of 52. | 0 | Theoretical and Fundamental Chemistry |
The American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME) is a professional association for mining and metallurgy, with over 145,000 members. The association was founded in 1871 by 22 mining engineers in Wilkes-Barre, Pennsylvania, and was one of the first national engineering societies in the country.
The association's charter is to "advance and disseminate, through the programs of the Member Societies, knowledge of engineering and the arts and sciences involved in the production and use of minerals, metals, energy sources and materials for the benefit of humankind."
It is the parent organization of four Member Societies, the Society for Mining, Metallurgy, and Exploration (SME), The Minerals, Metals & Materials Society (TMS), the Association for Iron and Steel Technology (AIST), and the Society of Petroleum Engineers (SPE). The organization is currently based in San Ramon, California. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, the electrochemical equivalent (Eq or Z) of a chemical element is the mass of that element (in grams) transported by a specific quantity of electricity, usually expressed in grams per coulomb of electric charge. The electrochemical equivalent of an element is measured with a voltameter. | 0 | Theoretical and Fundamental Chemistry |
ORs, which are located on the membranes of the cilia have been classified as a complex type of ligand-gated metabotropic channels. There are approximately 1000 different genes that code for the ORs, making them the largest gene family. An odorant will dissolve into the mucus of the olfactory epithelium and then bind to an OR. ORs can bind to a variety of odor molecules, with varying affinities. The difference in affinities causes differences in activation patterns resulting in unique odorant profiles. The activated OR in turn activates the intracellular G-protein, GOLF (GNAL), adenylate cyclase and production of cyclic AMP (cAMP) opens ion channels in the cell membrane, resulting in an influx of sodium and calcium ions into the cell, and an efflux of chloride ions. This influx of positive ions and efflux of negative ions causes the neuron to depolarize, generating an action potential. | 1 | Applied and Interdisciplinary Chemistry |
1. Bandla, M, D., Chambers, M, R., Sutula, C. L., Immunoassay and method of use, U.S. Patent Number: 7,585,641
2. Roe, R. M., Bailey, W. D., Gould, F., Kennedy, G. G., Sutula, C. L., Insecticide Resistance Assay. U.S. Patent Number: 6,517,856. (2003)
3. Geister, R. L., Bandla, M. D., Sutula, C. L., Multiplex enzyme-linked immunosorbent assay for detecting multiple analytes, U.S. Patent Appl. Number: 20040231776
4. Stiso, S. N., Sutula, C. L., Method, composition and device for determining the specific gravity or osmolality of a liquid, U.S. Patent Number: 4,108,727
5. Sena, E. A., Tolbert, B. M., Sutula, C. L., Liquid scintillation, counting and compositions, U.S. Patent Number: 3,928,227
6. Sutula, C. L., Wilson, J. E., Cleaning porous solids, U.S. Patent Number: 3,325,309 | 0 | Theoretical and Fundamental Chemistry |
*Taube, H., Jackson, J. A. & J. F. Lemons. [https://www.osti.gov/biblio/4728857-oxygen-nmr-shifts-caused-cr-sup-++-aqueous-solutions "Oxygen-17 NMR Shifts Caused by Cr{Sup ++} in Aqueous Solutions"], Los Alamos Scientific Laboratory, United States Department of Energy (through predecessor agency the Atomic Energy Commission), (1962).
*Taube, H. [https://www.osti.gov/biblio/4766921-reactions-solvated-ions-final-report "Reactions of Solvated Ions Final Report"], University of Chicago, United States Department of Energy (through predecessor agency the Atomic Energy Commission), (September 24, 1962).
*Taube, H. & A. Viste. [https://www.osti.gov/biblio/4465612-isotopic-discrimination-some-solutes-liquid-ammonia "Isotopic Discrimination of Some Solutes in Liquid Ammonia"], University of Chicago, Stanford University, United States Department of Energy (through predecessor agency the Atomic Energy Commission), (1966).
*Taube, H. [https://www.osti.gov/biblio/4556030-final-technical-report-research "Final Technical Report of Research"], Stanford University, United States Department of Energy (through predecessor agency the Atomic Energy Commission), (April 3, 1972). | 0 | Theoretical and Fundamental Chemistry |
The terrestrial biosphere includes the organic carbon in all land-living organisms, both alive and dead, as well as carbon stored in soils. About 500 gigatons of carbon are stored above ground in plants and other living organisms, while soil holds approximately 1,500 gigatons of carbon. Most carbon in the terrestrial biosphere is organic carbon, while about a third of soil carbon is stored in inorganic forms, such as calcium carbonate. Organic carbon is a major component of all organisms living on earth. Autotrophs extract it from the air in the form of carbon dioxide, converting it into organic carbon, while heterotrophs receive carbon by consuming other organisms.
Because carbon uptake in the terrestrial biosphere is dependent on biotic factors, it follows a diurnal and seasonal cycle. In CO measurements, this feature is apparent in the Keeling curve. It is strongest in the northern hemisphere because this hemisphere has more land mass than the southern hemisphere and thus more room for ecosystems to absorb and emit carbon.
Carbon leaves the terrestrial biosphere in several ways and on different time scales. The combustion or respiration of organic carbon releases it rapidly into the atmosphere. It can also be exported into the ocean through rivers or remain sequestered in soils in the form of inert carbon. Carbon stored in soil can remain there for up to thousands of years before being washed into rivers by erosion or released into the atmosphere through soil respiration. Between 1989 and 2008 soil respiration increased by about 0.1% per year. In 2008, the global total of CO released by soil respiration was roughly 98 billion tonnes, about 3 times more carbon than humans are now putting into the atmosphere each year by burning fossil fuel (this does not represent a net transfer of carbon from soil to atmosphere, as the respiration is largely offset by inputs to soil carbon). There are a few plausible explanations for this trend, but the most likely explanation is that increasing temperatures have increased rates of decomposition of soil organic matter, which has increased the flow of CO. The length of carbon sequestering in soil is dependent on local climatic conditions and thus changes in the course of climate change. prior to 1940, switching subsequently to a net sink. --> | 0 | Theoretical and Fundamental Chemistry |
Addition-elimination reactions are addition reactions immediately followed by elimination reactions. In general, these reactions take place when esters (or related functional groups) react with nucleophiles. In fact, the only requirement for an addition-elimination reaction to proceed is that the group being eliminated is a better leaving group than the incoming nucleophile. | 0 | Theoretical and Fundamental Chemistry |
Prior to the onset of World War II, Max von Laue and James Franck had sent their gold Nobel Prize medals to Denmark to keep them from being confiscated by the Nazis. After the Nazi invasion of Denmark this placed them in danger; it was illegal at the time to send gold out of Germany, and were it discovered that Laue and Franck had done so, they could have faced prosecution. To prevent this, de Hevesy concealed the medals by dissolving them in aqua regia and placing the resulting solution on a shelf in his laboratory at the Niels Bohr Institute in Copenhagen. After the war, he returned to find the solution undisturbed and precipitated the gold out of the acid. The Nobel Society then recast the medals using the recovered gold and returned them to the two laureates.
By 1943, Copenhagen was no longer safe for a Jewish scientist and de Hevesy fled to Sweden, where he worked at the University of Stockholm until 1961. In Stockholm, de Hevesy was received at the department of chemistry by the Swedish professor and Nobel Prize winner Hans von Euler-Chelpin, who remained strongly pro-German throughout the war. Despite this, de Hevesy and von Euler-Chelpin collaborated on many scientific papers during and after the war.
While in Stockholm, de Hevesy received the Nobel Prize in chemistry. He was later inducted into the Royal Swedish Academy of Sciences and received the Copley Medal, of which he was particularly proud. De Hevesy stated: "The public thinks the Nobel Prize in chemistry for the highest honor that a scientist can receive, but it is not so. Forty or fifty have received Nobel chemistry prizes, but there are only ten foreign members of the Royal Swedish Academy, and only two have received a Copley." (Bohr was the other one.) He received the Atoms for Peace Award in 1958 for his peaceful use of radioactive isotopes. | 1 | Applied and Interdisciplinary Chemistry |
The Arc transcript is dependent upon activation of the mitogen-activated protein kinase or MAP kinase (MAPK) cascade, a pathway important for regulation of cell growth and survival. Extracellular signaling to neuronal dendrites activates postsynaptic sites to increase Arc levels through a wide variety of signaling molecules, including mitogens such as epidermal growth factor (EGF), nerve growth factor (NGF), and brain-derived neurotrophic factor (BDNF), glutamate acting at NMDA receptors, dopamine through activation of the D1 receptor subtype, and dihydroxyphenylglycine (DHPG). The common factor for these signaling molecules involves activation of cyclic-AMP and its downstream target protein kinase A (PKA). As such, direct pharmacological activation of cAMP by forskolin or 8-Br-cAMP robustly increases Arc levels while H89, a PKA antagonist, blocks these effects as does further downstream blockade of mitogen-activated protein kinase kinase [sic] (MEK). Note that the MAPK cascade is a signaling pathway involving multiple kinases acting sequentially [MAPKKK→ MAPKK→ MAPK].
MAPK is able to enter the nucleus and perform its phosphotransferase activity on a number of gene regulatory components that have implications for the regulation of immediate-early genes. Several transcription factors are known to be involved in regulating the Arc gene (see above), including serum response factor (SRF), CREB, MEF2, and zif268. | 1 | Applied and Interdisciplinary Chemistry |
In stoichiometry of a chemical reaction to produce a chemical product, it may be observed or predicted that with amounts supplied in specified proportions, one of the reactants will be consumed by the reaction before the others. The amount of product is thus limited by the supply of this reagent. This limiting reagent determines the theoretical yield of the reaction. The other reactants are said to be non-limiting or in excess. This distinction makes sense only when the chemical equilibrium so favors the products to cause the complete consumption of one of the reactants.
In studies of reaction kinetics, the rate of progress of the reaction may be limited by the concentration of one of the reactants or catalyst. In multi-step reactions, a step may be rate-limiting in terms of production of the final product. In vivo, in an organism or in an ecologic system, such factors as those may be rate-limiting, or in the overall analysis of a multi-step process including biologic, geologic, hydrologic, or atmospheric transport and chemical reactions, transport of a reactant may be limiting. | 0 | Theoretical and Fundamental Chemistry |
In Southeast Asia, cannons were used by the Ayutthaya Kingdom in 1352 during its invasion of the Khmer Empire. Within a decade large quantities of gunpowder could be found in the Khmer Empire. By the end of the century firearms were also used by the Trần dynasty in Đại Việt.
The Mongol invasion of Java in 1293 brought gunpowder technology to the Nusantara archipelago in the form of cannon (Chinese: 炮—Pào). The knowledge of making gunpowder-based weapon has been known after the failed Mongol invasion of Java. The predecessor of firearms, the pole gun (bedil tombak), was recorded as being used in Java by 1413, while the knowledge of making "true" firearms came much later, after the middle of 15th century. It was brought by the Muslim traders from West Asia, most probably the Arabs. The precise year of introduction is unknown, but it may be safely concluded to be no earlier than 1460.
Portuguese influence to local weaponry after the capture of Malacca (1511) resulted in a new type of hybrid tradition matchlock firearm, the istinggar. Saltpeter harvesting was recorded by Dutch and German travelers as being common in even the smallest villages and was collected from the decomposition process of large dung hills specifically piled for this purpose. The Dutch punishment for possession of non-permitted gunpowder appears to have been amputation. Ownership and manufacture of gunpowder was later prohibited by the colonial Dutch occupiers. According to colonel McKenzie quoted in the book The History of Java (1817) by Thomas Stamford Raffles, the purest sulfur was supplied from a crater from a mountain near the straits of Bali. | 1 | Applied and Interdisciplinary Chemistry |
Rotational spectroscopy is concerned with the measurement of the energies of transitions between quantized rotational states of molecules in the gas phase. The rotational spectrum (power spectral density vs. rotational frequency) of polar molecules can be measured in absorption or emission by microwave spectroscopy or by far infrared spectroscopy. The rotational spectra of non-polar molecules cannot be observed by those methods, but can be observed and measured by Raman spectroscopy. Rotational spectroscopy is sometimes referred to as pure rotational spectroscopy to distinguish it from rotational-vibrational spectroscopy where changes in rotational energy occur together with changes in vibrational energy, and also from ro-vibronic spectroscopy (or just vibronic spectroscopy) where rotational, vibrational and electronic energy changes occur simultaneously.
For rotational spectroscopy, molecules are classified according to symmetry into a spherical top, linear and symmetric top; analytical expressions can be derived for the rotational energy terms of these molecules. Analytical expressions can be derived for the fourth category, asymmetric top, for rotational levels up to J=3, but higher energy levels need to be determined using numerical methods. The rotational energies are derived theoretically by considering the molecules to be rigid rotors and then applying extra terms to account for centrifugal distortion, fine structure, hyperfine structure and Coriolis coupling. Fitting the spectra to the theoretical expressions gives numerical values of the angular moments of inertia from which very precise values of molecular bond lengths and angles can be derived in favorable cases. In the presence of an electrostatic field there is Stark splitting which allows molecular electric dipole moments to be determined.
An important application of rotational spectroscopy is in exploration of the chemical composition of the interstellar medium using radio telescopes. | 0 | Theoretical and Fundamental Chemistry |
Ionic conductivity (denoted by ) is a measure of a substance's tendency towards ionic conduction. Ionic conduction is the movement of ions. The phenomenon is observed in solids and solutions. Ionic conduction is one mechanism of current. | 0 | Theoretical and Fundamental Chemistry |
As promoters are typically immediately adjacent to the gene in question, positions in the promoter are designated relative to the transcriptional start site, where transcription of DNA begins for a particular gene (i.e., positions upstream are negative numbers counting back from -1, for example -100 is a position 100 base pairs upstream). | 1 | Applied and Interdisciplinary Chemistry |
The PDE5 inhibitors sildenafil, vardenafil and tadalafil are competitive and reversible inhibitors of cGMP hydrolysis by the catalytic side of PDE5. The structures of vardenafil and sildenafil are similar, they both contain similar structured purine ring of cGMP that contributes their features to act as a competitive inhibitor of PDE5. The difference of the molecular structures is the reason for interaction with the catalytic site of PDE5 and improves the affinity of these compounds compared with cGMP selectivity. | 1 | Applied and Interdisciplinary Chemistry |
UPt forms crystals of hexagonal symmetry (some studies hypothesize a trigonal structure instead), space group P6/mmc, cell parameters a = 0.5766 nm and c = 0.4898 nm (c should be understood as distance from planes), with a structure similar to nisnite (NiSn) and MgCd.
The compound congruently melts at 1700 °C. The enthalpy of formation of the compound is -111 kJ/mol.
At temperatures below 1 K it becomes superconducting, thought to be due to the presence of heavy fermions (the uranium atoms). | 1 | Applied and Interdisciplinary Chemistry |
Chloromethane and bromomethane are used to introduce methyl groups in organic synthesis. Chlorodifluoromethane is the main precursor of tetrafluoroethylene, which is the monomeric precursor to Teflon. | 1 | Applied and Interdisciplinary Chemistry |
The shikimate pathway is a seven-step metabolic route used by bacteria, fungi, algae, parasites, and plants for the biosynthesis of aromatic amino acids (phenylalanine, tyrosine, and tryptophan). This pathway is not found in animals; therefore, phenylalanine and tryptophan represent essential amino acids that must be obtained from the animal's diet (animals can synthesise tyrosine from phenylalanine, and therefore is not an essential amino acid except for individuals unable to hydroxylate phenylalanine to tyrosine).
The seven enzymes involved in the shikimate pathway are DAHP synthase, 3-dehydroquinate synthase, 3-dehydroquinate dehydratase, shikimate dehydrogenase, shikimate kinase, EPSP synthase, and chorismate synthase. The pathway starts with two substrates, phosphoenol pyruvate and erythrose-4-phosphate and ends with chorismate, a substrate for the three aromatic amino acids. The fifth enzyme involved is the shikimate kinase, an enzyme that catalyzes the ATP-dependent phosphorylation of shikimate to form shikimate 3-phosphate (shown in the figure below). Shikimate 3-phosphate is then coupled with phosphoenol pyruvate to give 5-enolpyruvylshikimate-3-phosphate via the enzyme 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase.
Then 5-enolpyruvylshikimate-3-phosphate is transformed into chorismate by a chorismate synthase.
Prephenic acid is then synthesized by a Claisen rearrangement of chorismate by chorismate mutase.
Prephenate is oxidatively decarboxylated with retention of the hydroxyl group to give p-hydroxyphenylpyruvate, which is transaminated using glutamate as the nitrogen source to give tyrosine and α-ketoglutarate. | 1 | Applied and Interdisciplinary Chemistry |
The simplest phase diagrams are pressure–temperature diagrams of a single simple substance, such as water. The axes correspond to the pressure and temperature. The phase diagram shows, in pressure–temperature space, the lines of equilibrium or phase boundaries between the three phases of solid, liquid, and gas.
The curves on the phase diagram show the points where the free energy (and other derived properties) becomes non-analytic: their derivatives with respect to the coordinates (temperature and pressure in this example) change discontinuously (abruptly). For example, the heat capacity of a container filled with ice will change abruptly as the container is heated past the melting point. The open spaces, where the free energy is analytic, correspond to single phase regions. Single phase regions are separated by lines of non-analytical behavior, where phase transitions occur, which are called phase boundaries.
In the diagram on the right, the phase boundary between liquid and gas does not continue indefinitely. Instead, it terminates at a point on the phase diagram called the critical point. This reflects the fact that, at extremely high temperatures and pressures, the liquid and gaseous phases become indistinguishable, in what is known as a supercritical fluid. In water, the critical point occurs at around T = , p = and ρ = 356 kg/m.
The existence of the liquid–gas critical point reveals a slight ambiguity in labelling the single phase regions. When going from the liquid to the gaseous phase, one usually crosses the phase boundary, but it is possible to choose a path that never crosses the boundary by going to the right of the critical point. Thus, the liquid and gaseous phases can blend continuously into each other. The solid–liquid phase boundary can only end in a critical point if the solid and liquid phases have the same symmetry group.
For most substances, the solid–liquid phase boundary (or fusion curve) in the phase diagram has a positive slope so that the melting point increases with pressure. This is true whenever the solid phase is denser than the liquid phase. The greater the pressure on a given substance, the closer together the molecules of the substance are brought to each other, which increases the effect of the substance's intermolecular forces. Thus, the substance requires a higher temperature for its molecules to have enough energy to break out of the fixed pattern of the solid phase and enter the liquid phase. A similar concept applies to liquid–gas phase changes.
Water is an exception which has a solid-liquid boundary with negative slope so that the melting point decreases with pressure. This occurs because ice (solid water) is less dense than liquid water, as shown by the fact that ice floats on water. At a molecular level, ice is less dense because it has a more extensive network of hydrogen bonding which requires a greater separation of water molecules. Other exceptions include antimony and bismuth.
At very high pressures above 50 GPa (500 000 atm), liquid nitrogen undergoes a liquid-liquid phase transition to a polymeric form and becomes denser than solid nitrogen at the same pressure. Under these conditions therefore, solid nitrogen also floats in its liquid.
The value of the slope dP/dT is given by the Clausius–Clapeyron equation for fusion (melting)
where ΔH is the heat of fusion which is always positive, and ΔV is the volume change for fusion. For most substances ΔV is positive so that the slope is positive. However for water and other exceptions, ΔV is negative so that the slope is negative. | 0 | Theoretical and Fundamental Chemistry |
The image shows a periodic table extract with the electronegativity values of metals.
Wulfsberg distinguishes:<br> very electropositive metals with electronegativity values below 1.4<br>
electropositive metals with values between 1.4 and 1.9; and<br>
electronegative metals with values between 1.9 and 2.54.
From the image, the group 1–2 metals and the lanthanides and actinides are very electropositive to electropositive; the transition metals in groups 3 to 12 are very electropositive to electronegative; and the post-transition metals are electropositive to electronegative. The noble metals, inside the dashed border (as a subset of the transition metals) are very electronegative. | 0 | Theoretical and Fundamental Chemistry |
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