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Photoacoustic spectroscopy is the measurement of the effect of absorbed electromagnetic energy (particularly of light) on matter by means of acoustic detection. The discovery of the photoacoustic effect dates to 1880 when Alexander Graham Bell showed that thin discs emitted sound when exposed to a beam of sunlight that was rapidly interrupted with a rotating slotted disk. The absorbed energy from the light causes local heating, generating a thermal expansion which creates a pressure wave or sound. Later Bell showed that materials exposed to the non-visible portions of the solar spectrum (i.e., the infrared and the ultraviolet) can also produce sounds.
A photoacoustic spectrum of a sample can be recorded by measuring the sound at different wavelengths of the light. This spectrum can be used to identify the absorbing components of the sample. The photoacoustic effect can be used to study solids, liquids and gases. | 0 | Theoretical and Fundamental Chemistry |
Q-vectors can be determined wholly with: geopotential height () and temperature on a constant pressure surface. Q-vectors always point in the direction of ascending air. For an idealized cyclone and anticyclone in the Northern Hemisphere (where ), cyclones have Q-vectors which point parallel to the thermal wind and anticyclones have Q-vectors that point antiparallel to the thermal wind. This means upward motion in the area of warm air advection and downward motion in the area of cold air advection.
In frontogenesis, temperature gradients need to tighten for initiation. For those situations Q-vectors point toward ascending air and the tightening thermal gradients. In areas of convergent Q-vectors, cyclonic vorticity is created, and in divergent areas, anticyclonic vorticity is created. | 1 | Applied and Interdisciplinary Chemistry |
In 2006, American Elements discovered new technology allowing for the casting of seamless iridium rings for use in spacecraft and satellites. In 2016, the company utilized the same technology to introduce a line of iridium wedding bands marketed under the trademark Smithson Tennant. | 1 | Applied and Interdisciplinary Chemistry |
Thermophysical properties - [http://twt.mpei.ac.ru/TTHB/2/R410a-eng.html Properties of refrigerant R410a] | 1 | Applied and Interdisciplinary Chemistry |
Organic scintillators are aromatic hydrocarbon compounds which contain benzene ring structures interlinked in various ways. Their luminescence typically decays within a few nanoseconds.
Some organic scintillators are pure crystals. The most common types are anthracene (, decay time ≈30 ns), stilbene (, 4.5 ns decay time), and naphthalene (, few ns decay time). They are very durable, but their response is anisotropic (which spoils energy resolution when the source is not collimated), and they cannot be easily machined, nor can they be grown in large sizes; hence they are not very often used. Anthracene has the highest light output of all organic scintillators and is therefore chosen as a reference: the light outputs of other scintillators are sometimes expressed as a percentage of anthracene light output. | 0 | Theoretical and Fundamental Chemistry |
Ferenc Szabadváry (1 September 1923 – 21 May 2006) was a Hungarian chemist and historian. From 1971 he was director at the Hungarian National Museum for Science and Technology.
In 1960 he published a history of analytical chemistry in Hungarian. A translation was made by Gyula Svehla in 1966, first published with Pergamon Press and later Gordon and Breach.
Szabadváry received the Dexter Award in 1970. | 1 | Applied and Interdisciplinary Chemistry |
LDH is involved in tumor initiation and metabolism. Cancer cells rely on increased glycolysis resulting in increased lactate production in addition to aerobic respiration in the mitochondria, even under oxygen-sufficient conditions (a process known as the Warburg effect). This state of fermentative glycolysis is catalyzed by the A form of LDH. This mechanism allows tumorous cells to convert the majority of their glucose stores into lactate regardless of oxygen availability, shifting use of glucose metabolites from simple energy production to the promotion of accelerated cell growth and replication.
LDH A and the possibility of inhibiting its activity has been identified as a promising target in cancer treatments focused on preventing carcinogenic cells from proliferating. Chemical inhibition of LDH A has demonstrated marked changes in metabolic processes and overall survival of carcinoma cells. Oxamate is a cytosolic inhibitor of LDH A that significantly decreases ATP production in tumorous cells as well as increasing production of reactive oxygen species (ROS). These ROS drive cancer cell proliferation by activating kinases that drive cell cycle progression growth factors at low concentrations, but can damage DNA through oxidative stress at higher concentrations. Secondary lipid oxidation products can also inactivate LDH and impact its ability to regenerate NADH, directly disrupting the enzymes ability to convert lactate to pyruvate.
While recent studies have shown that LDH activity is not necessarily an indicator of metastatic risk, LDH expression can act as a general marker in the prognosis of cancers. Expression of LDH5 and VEGF in tumors and the stroma has been found to be a strong prognostic factor for diffuse or mixed-type gastric cancers. | 1 | Applied and Interdisciplinary Chemistry |
Secondary electrons are also the main means of viewing images in the scanning electron microscope (SEM). The range of secondary electrons depends on the energy. Plotting the inelastic mean free path as a function of energy often shows characteristics of the "universal curve" familiar to electron spectroscopists and surface analysts. This distance is on the order of a few nanometers in metals and tens of nanometers in insulators. This small distance allows such fine resolution to be achieved in the SEM.
For SiO, for a primary electron energy of 100 eV, the secondary electron range is up to 20 nm from the point of incidence. | 0 | Theoretical and Fundamental Chemistry |
In 1989–2013, 1,236 publications of the National Environmental Engineering Research Institute were assessed. The institute technique for enrichment of ilmenite with titanium dioxide has been evaluated externally. | 1 | Applied and Interdisciplinary Chemistry |
Van den Bergh reaction is a chemical reaction used to measure bilirubin levels in blood. More specifically, it determines the amount of conjugated bilirubin in the blood. The reaction produces azobilirubin.
Principle: bilirubin reacts with diazotised sulphanilic acid to produce purple coloured azobilirubin. This reaction is highly useful in understanding the nature of jaundice. This was pioneered by the Dutch physician, Abraham Albert Hijmans van den Bergh (1869–1943) of Utrecht. This test helps to identify the type of jaundice. The serum of the patient is mixed with diazo reagent. If a red colour develops immediately it is called a direct positive. It happens if conjugated bilirubin is present.
In an indirect positive test, the patient's serum is first treated with alcohol and later mixed with diazo reagent. This causes development of a red colour. It is seen if unconjugated bilirubin is present.
If both conjugated and unconjugated bilirubin are present the reaction is termed a biphasic reaction. | 0 | Theoretical and Fundamental Chemistry |
Malate dehydrogenase () (MDH) is an enzyme that reversibly catalyzes the oxidation of malate to oxaloacetate using the reduction of NAD to NADH. This reaction is part of many metabolic pathways, including the citric acid cycle. Other malate dehydrogenases, which have other EC numbers and catalyze other reactions oxidizing malate, have qualified names like malate dehydrogenase (NADP). | 1 | Applied and Interdisciplinary Chemistry |
Alkanediazonium ions, otherwise rarely encountered in organic chemistry, are implicated as the causative agents in the carcinogens. Specifically, nitrosamines are thought to undergo metabolic activation to produce alkanediazonium species. | 0 | Theoretical and Fundamental Chemistry |
Denmarks first full-scale wind-Hydrogen energy plant and testing facility, the Lolland Hydrogen Community, began operation in May 2007. It is also the European Unions first full-scale Hydrogen Community Demonstration facility for residential Fuel Cell Combined Heat and Power (CHP).
Phase 3 of the project that ran until 2012 and was the installing of fuel cell micro combined heat and power plants.
Located in the city of Nakskov on the island of Lolland, where wind power is abundant, the hydrogen energy plant was received with funding from the Danish Energy Authority, which is a joint partnership between the Municipality of Lolland, IRD Fuel Cells, and Baltic Sea Solutions.
The island of Lolland is producing 50% more energy from renewable energy sources than it consumes, and the hydrogen project was seeking to locally store excess wind power in the form of hydrogen, for use in residential and industrial facilities.
Hydrogen is produced by using excess wind power to electrolyze water to produce hydrogen and oxygen. The oxygen is used in the municipal water treatment plant nearby to speed up the biological process. The hydrogen is stored in low-pressure storage tanks at six bars and fuels two PEM Fuel Cell Micro Combined Heat and Power (CHP) stations of 2 kilowatts (kW) and 6.5 kW, respectively. | 0 | Theoretical and Fundamental Chemistry |
However, according to the authors of the paper entitled, “Method for optimizing design and rehabilitation of water distribution systems”, “the least capacity is not a desirable solution to a sustainable water supply network in a long term, due to the uncertainty of the future demand”. It is preferable to provide extra pipe capacity to cope with unexpected demand growth and with water outages. The problem changes from a single objective optimization problem (minimizing cost), to a multi-objective optimization problem (minimizing cost and maximizing flow capacity). | 1 | Applied and Interdisciplinary Chemistry |
For water waves on an incompressible fluid and irrotational flow in the plane, the boundary conditions at the free surface elevation are:
where:
* is the horizontal flow velocity component: ,
* is the vertical flow velocity component: ,
* is the acceleration by gravity.
Now the Boussinesq approximation for the velocity potential , as given above, is applied in these boundary conditions. Further, in the resulting equations only the linear and quadratic terms with respect to and are retained (with the horizontal velocity at the bed ). The cubic and higher order terms are assumed to be negligible. Then, the following partial differential equations are obtained:
;set A – Boussinesq (1872), equation (25)
This set of equations has been derived for a flat horizontal bed, i.e. the mean depth is a constant independent of position . When the right-hand sides of the above equations are set to zero, they reduce to the shallow water equations.
Under some additional approximations, but at the same order of accuracy, the above set A can be reduced to a single partial differential equation for the free surface elevation :
;set B – Boussinesq (1872), equation (26)
From the terms between brackets, the importance of nonlinearity of the equation can be expressed in terms of the Ursell number.
In dimensionless quantities, using the water depth and gravitational acceleration for non-dimensionalization, this equation reads, after normalization:
with: | 1 | Applied and Interdisciplinary Chemistry |
A mixture of copper and iron sulfides referred to as matte is treated in converters to oxidize iron in the first stage, and oxidize copper in the second stage. In the first stage oxygen enriched air is blown through the tuyeres to partially convert metal sulfides to oxides:
:FeS + O → FeO + SO
:CuS + O → CuO + SO
Since iron has greater affinity to oxygen, the produced copper oxide reacts with the remaining iron sulfide:
:CuO + FeS → CuS + FeO
The bulk of the copper oxide is turned back into the form of sulfide. In order to separate the obtained iron oxide, flux (mainly silica) is added into the converter. Silica reacts with iron oxide to produce a light slag phase, which is poured off through the hood when the converter is tilted around the rotation axis:
:2 FeO + SiO → FeSiO (sometimes denoted as 2FeO•SiO, fayalite)
After the first portion of slag is poured off the converter, a new portion of matte is added, and the converting operation is repeated many times until the converter is filled with the purified copper sulfide. The converter slag is usually recycled to the smelting stage due to the high content of copper in this by-product. Converter gas contains more than 10% of sulfur dioxide, which is usually captured for the production of sulfuric acid.
The second stage of converting is aimed at oxidizing the copper sulfide phase (purified in the first stage), and produces blister copper. The following reaction takes place in the converter:
:CuS + O → Cu + SO
Copper content in the obtained blister copper is typically more than 95%. Blister copper is the final product of converting. | 1 | Applied and Interdisciplinary Chemistry |
Lyophilized drugs are stored in vials, cartridges, dual chamber syringes, and prefilled mixing systems.
Lyophilization, or freeze drying, is a process that removes water from a liquid drug creating a solid powder, or cake. The lyophilized product is stable for extended periods of time and could allow storage at higher temperatures. In protein formulations, stabilizers are added to replace the water and preserve the structure of the molecule.
Before administration, a lyophilized drug is reconstituted as a liquid before being administered. This is done by combining a liquid diluent with the freeze-dried powder, mixing, then injecting. Reconstitution usually requires a reconstitution and delivery system to ensure that the drug is correctly mixed and administered. | 1 | Applied and Interdisciplinary Chemistry |
Tensile testings were performed on nanocomposite hydrogels to measure the stress and strain it experiences when elongated under room temperature. The results show that this material can be stretched up to 1000% of its original length. | 0 | Theoretical and Fundamental Chemistry |
* [https://archive.org/details/theorysound00raylgoog The Theory of Sound vol. I] (London : Macmillan, 1877, 1894) (alternative link: [http://gallica.bnf.fr/ark:/12148/bpt6k951307 Bibliothèque Nationale de France] OR (Cambridge: University Press, reissued 2011, )
* [https://archive.org/details/theorysound05raylgoog The Theory of Sound vol.II] (London : Macmillan, 1878, 1896) (alternative link: [http://gallica.bnf.fr/ark:/12148/bpt6k95131k Bibliothèque Nationale de France]) OR (Cambridge: University Press, reissued 2011, )
* [https://archive.org/details/scientificpaper01raylgoog Scientific papers (Vol. 1: 1869–1881)] (Cambridge : University Press, 1899–1920, reissued by the publisher 2011, )
* [https://archive.org/details/scientificpapers02rayliala Scientific papers (Vol. 2: 1881–1887)] (Cambridge : University Press, 1899–1920, reissued by the publisher 2011, )
* [https://archive.org/details/scientificpapers03rayliala Scientific papers (Vol. 3: 1887–1892)] (Cambridge : University Press, 1899–1920, reissued by the publisher 2011, )
* [https://archive.org/details/scientificpapers04rayliala Scientific papers (Vol. 4: 1892–1901)] (Cambridge : University Press, 1899–1920, reissued by the publisher 2011, )
* [https://archive.org/details/scientificpapers05rayliala Scientific papers (Vol. 5: 1902–1910)] (Cambridge : University Press, 1899–1920, reissued by the publisher 2011, )
* [https://archive.org/details/scientificpapers06rayliala Scientific papers (Vol. 6: 1911–1919)] (Cambridge : University Press, 1899–1920, reissued by the publisher 2011, ) | 1 | Applied and Interdisciplinary Chemistry |
PUREX (plutonium uranium reduction extraction) is a chemical method used to purify fuel for nuclear reactors or nuclear weapons. PUREX is the de facto standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used nuclear fuel (spent nuclear fuel, or irradiated nuclear fuel). It is based on liquid–liquid extraction ion-exchange.
PUREX is applied to spent nuclear fuel, which consists primarily of very high atomic-weight (actinoid or "actinide") elements (e.g. uranium, plutonium, americium) along with smaller amounts of material composed of lighter atoms, notably the fission products produced by reactor operation.
The actinoid elements in this case consist primarily of the unconsumed remains of the original fuel (typically U-235, U-238, and/or Pu-239). | 0 | Theoretical and Fundamental Chemistry |
Electron transfer reactions are central to myriad processes and properties in soils, and redox potential, quantified as Eh (platinum electrode potential (voltage) relative to the standard hydrogen electrode) or pe (analogous to pH as -log electron activity), is a master variable, along with pH, that controls and is governed by chemical reactions and biological processes. Early theoretical research with applications to flooded soils and paddy rice production was seminal for subsequent work on thermodynamic aspects of redox and plant root growth in soils. Later work built on this foundation, and expanded it for understanding redox reactions related to heavy metal oxidation state changes, pedogenesis and morphology, organic compound degradation and formation, free radical chemistry, wetland delineation, soil remediation, and various methodological approaches for characterizing the redox status of soils. | 0 | Theoretical and Fundamental Chemistry |
*Biochemical Society, London
*American Chemical Society
*Grandmaster, United Grand Masonic Lodge of Queensland | 0 | Theoretical and Fundamental Chemistry |
Cisplatin is administered intravenously as short-term infusion in normal saline for treatment of solid and haematological malignancies. It is used to treat various types of cancers, including sarcomas, some carcinomas (e.g., small cell lung cancer, squamous cell carcinoma of the head and neck and ovarian cancer), lymphomas, bladder cancer, cervical cancer, and germ cell tumors.
The introduction of cisplatin as a standard treatment for testicular cancer improved remission rates from 5-10% before 1974 to 75-85% by 1984. | 1 | Applied and Interdisciplinary Chemistry |
Small RNA sequencing (Small RNA-Seq) is a type of RNA sequencing based on the use of NGS technologies that allows to isolate and get information about noncoding RNA molecules in order to evaluate and discover new forms of small RNA and to predict their possible functions. By using this technique, it is possible to discriminate small RNAs from the larger RNA family to better understand their functions in the cell and in gene expression. Small RNA-Seq can analyze thousands of small RNA molecules with a high throughput and specificity. The greatest advantage of using RNA-seq is represented by the possibility of generating libraries of RNA fragments starting from the whole RNA content of a cell. | 1 | Applied and Interdisciplinary Chemistry |
Eukaryotic ribosomes are known to bind to transcripts in a mechanism unlike the one involving the 5' cap, at a sequence called the internal ribosome entry site. This process is not dependent on the full set of translation initiation factors (although this depends on the specific IRES) and is commonly found in the translation of viral mRNA. | 1 | Applied and Interdisciplinary Chemistry |
The following Radiological protection instruments can be used to detect and measure ionizing radiation:
*Ionization chambers
*Gaseous ionization detectors
*Geiger counters
*Photodetectors
*Scintillation counters
*Semiconductor detectors
category:Radiation protection | 0 | Theoretical and Fundamental Chemistry |
The metallothermic reduction of anhydrous rare-earth fluorides to rare-earth metals is also referred to as the Ames process.
The study of rare earths was also advanced during World War II: Synthetic plutonium was believed to be rare-earth-like, it was assumed that knowledge of rare earths would assist in planning for and the study of transuranic elements; ion-exchange methods developed for actinide processing were forerunners to processing methods for rare-earth oxides; methods used for uranium were modified for plutonium, which were subsequently the basis for rare-earth metal preparation. | 1 | Applied and Interdisciplinary Chemistry |
With Lewis acid catalysts like ferric chloride or aluminium chloride, acyl chlorides participate in Friedel-Crafts acylations, to give aryl ketones:
Because of the harsh conditions and the reactivity of the intermediates, this otherwise quite useful reaction tends to be messy, as well as environmentally unfriendly. | 0 | Theoretical and Fundamental Chemistry |
Quantity of heat transferred can be measured by calorimetry, or determined through calculations based on other quantities.
Calorimetry is the empirical basis of the idea of quantity of heat transferred in a process. The transferred heat is measured by changes in a body of known properties, for example, temperature rise, change in volume or length, or phase change, such as melting of ice.
A calculation of quantity of heat transferred can rely on a hypothetical quantity of energy transferred as adiabatic work and on the first law of thermodynamics. Such calculation is the primary approach of many theoretical studies of quantity of heat transferred. | 0 | Theoretical and Fundamental Chemistry |
The specific gas constant of a gas or a mixture of gases (R) is given by the molar gas constant divided by the molar mass (M) of the gas or mixture:
Just as the molar gas constant can be related to the Boltzmann constant, so can the specific gas constant by dividing the Boltzmann constant by the molecular mass of the gas:
Another important relationship comes from thermodynamics. Mayer's relation relates the specific gas constant to the specific heat capacities for a calorically perfect gas and a thermally perfect gas:
where c is the specific heat capacity for a constant pressure and c is the specific heat capacity for a constant volume.
It is common, especially in engineering applications, to represent the specific gas constant by the symbol R. In such cases, the universal gas constant is usually given a different symbol such as to distinguish it. In any case, the context and/or unit of the gas constant should make it clear as to whether the universal or specific gas constant is being referred to.
In case of air, using the perfect gas law and the standard sea-level conditions (SSL) (air density ρ = 1.225 kg/m, temperature T = 288.15 K and pressure p = ), we have that R = P/(ρT) = . Then the molar mass of air is computed by M = R/R = . | 0 | Theoretical and Fundamental Chemistry |
*Bibliography of atmospheric dispersion modeling
*AP 42 Compilation of Air Pollutant Emission Factors
*Atmospheric dispersion modeling
*Roadway air dispersion modeling
*Useful conversions and formulas for air dispersion modeling
*List of atmospheric dispersion models
*Yamartino method
* Air pollution forecasting | 1 | Applied and Interdisciplinary Chemistry |
His greatest contribution to the development of Islamic philosophy was his efforts to make Greek thought both accessible and acceptable to a Muslim audience. Al-Kindi carried out this mission from the House of Wisdom (Bayt al-Hikma), an institute of translation and learning patronized by the Abbasid Caliphs, in Baghdad. As well as translating many important texts, much of what was to become standard Arabic philosophical vocabulary originated with al-Kindi; indeed, if it had not been for him, the work of philosophers like al-Farabi, Avicenna, and al-Ghazali might not have been possible.
In his writings, one of al-Kindi's central concerns was to demonstrate the compatibility between philosophy and natural theology on the one hand, and revealed or speculative theology on the other (though in fact he rejected speculative theology). Despite this, he did make clear that he believed revelation was a superior source of knowledge to reason because it guaranteed matters of faith that reason could not uncover. And while his philosophical approach was not always original, and was even considered clumsy by later thinkers (mainly because he was the first philosopher writing in the Arabic language), he successfully incorporated Aristotelian and (especially) neo-Platonist thought into an Islamic philosophical framework. This was an important factor in the introduction and popularization of Greek philosophy in the Muslim intellectual world. | 1 | Applied and Interdisciplinary Chemistry |
In the visible and near-ultraviolet regions, the hexacyanoferrate(III) ion (Fe(CN)) exhibits three strong absorptions at 24500, 32700, and 40500 cm, which have been ascribed to ligand to metal charge transfer (LMCT) transitions. They all have lower energy than the lowest-energy intense band for the Fe(II) complex Fe(CN) found at 46000 cm. The red shift with increasing oxidation state of the metal is characteristic of LMCT bands. Additionally, only A terms, which are temperature independent, should be involved in MCD structure for closed-shell species.
These features can be explained as follows. The ground state of the anion is T, which derives from the electronic configuration (t). So, there would be an unpaired electron in the d orbital of Fe
From that, the three bands can be assigned to the transitions t→t, t →t, t →t. Two of the excited states are of the same symmetry, and, based on the group theory, they could mix with each other so that there are no pure σ and π characters in the two t states, but for t, there would be no intermixing. The A terms are also possible from the degenerate excited states, but the studies of temperature dependence showed that the A terms are not as dependent as the C term.
An MCD study of Fe(CN) embedded in a thin polyvinyl alcohol (PVA) film revealed a temperature dependence of the C term. The room-temperature C/D values for the three bands in the Fe(CN) spectrum are 1.2, −0.6, and 0.6, respectively, and their signs (positive, negative, and positive) establish the energy ordering as t→tt→tt→t | 0 | Theoretical and Fundamental Chemistry |
If irradiated with select projectile nuclei at kinetic energies E, target solid thin-film chemical elements can undergo a nuclear reaction under resonance conditions for a sharply defined resonance energy. The reaction product is usually a nucleus in an excited state which immediately decays, emitting ionizing radiation.
To obtain depth information the initial kinetic energy of the projectile nucleus (which has to exceed the resonance energy) and its stopping power (energy loss per distance traveled) in the sample has to be known. To contribute to the nuclear reaction the projectile nuclei have to slow down in the sample to reach the resonance energy. Thus each initial kinetic energy corresponds to a depth in the sample where the reaction occurs (the higher the energy, the deeper the reaction). | 0 | Theoretical and Fundamental Chemistry |
POMs are employed as commercial catalysts for oxidation of organic compounds.
Efforts continue to extend this theme. POM-based aerobic oxidations have been promoted as alternatives to chlorine-based wood pulp bleaching processes, a method of decontaminating water, and a method to catalytically produce formic acid from biomass (OxFA process). Polyoxometalates have been shown to catalyse water splitting. | 0 | Theoretical and Fundamental Chemistry |
A foam is considered open-celled if at least two of its facets are holes rather than walls. In this case the entirety of the load on the foam is on the cross-beams that make up the edges of the cell. If no more than one of the walls of the cell are holes, the foam is considered closed-celled in nature. For most synthetic foams, a mixture of closed cell and open cell character is observed due to cells rupturing during the foaming process and then the matrix solidifying.
The mechanical properties of the foam then depend on the closed cell character of the foam as derived by Gibson and Ashby:
Where E is the elastic modulus, ρ is the density of the material, φ is the ratio of the volume of the face to the volume of the edge of the material, and the subscript s denotes the bulk property of the material rather than that of the foam sample. | 0 | Theoretical and Fundamental Chemistry |
Many sulfonic acids are prepared by hydrolysis of sulfonyl halides and related precursors. Thus, perfluorooctanesulfonic acid is prepared by hydrolysis of the sulfonyl fluoride, which in turn is generated by the electrofluorination of octanesulfonic acid. Similarly the sulfonyl chloride derived from polyethylene is hydrolyzed to the sulfonic acid. These sulfonyl chlorides are produced by free-radical reactions of chlorine, sulfur dioxide, and the hydrocarbons using the Reed reaction.
Vinylsulfonic acid is derived by hydrolysis of carbyl sulfate, (), which in turn is obtained by the addition of sulfur trioxide to ethylene. | 0 | Theoretical and Fundamental Chemistry |
Doubly labeled water may be administered by injection, or orally (the usual route in humans). Since the isotopes will be diluted in body water, there is no need to administer them in a state of high isotopic purity, no need to employ water in which all or even most atoms are heavy atoms, or even to begin with water which is doubly labeled. It is also unnecessary to administer exactly one atom of O for every two atoms of deuterium. This matter in practice is governed by the economics of buying O enriched water, and the sensitivity of the mass-spectrographic equipment available.
In practice, doses of doubly labeled water for metabolic work are prepared by simply mixing a dose of deuterium oxide (heavy water) (90 to 99%) with a second dose of HO, which is water which has been separately enriched with O (though usually not to a high level, since doing this would be expensive, and unnecessary for this use), but otherwise contains normal hydrogen. The mixed water sample then contains both types of heavy atoms, in a far higher degree than normal water, and is now "doubly labeled." The free interchange of hydrogens between water molecules (via normal ionization) in liquid water ensures that the pools of oxygen and hydrogen in any sample of water (including the body's pool of water) will be separately equilibrated in a short time with any dose of added heavy isotope(s). | 0 | Theoretical and Fundamental Chemistry |
Questions could arise as to why the technique of encapsulation of cells is even required when therapeutic products could just be injected at the site. An important reason for this is that the encapsulated cells would provide a source of sustained continuous release of therapeutic products for longer durations at the site of implantation. Another advantage of cell microencapsulation technology is that it allows the loading of non-human and genetically modified cells into the polymer matrix when the availability of donor cells is limited. Microencapsulation is a valuable technique for local, regional and oral delivery of therapeutic products as it can be implanted into numerous tissue types and organs. For prolonged drug delivery to the treatment site, implantation of these drug loaded artificial cells would be more cost effective in comparison to direct drug delivery. Moreover, the prospect of implanting artificial cells with similar chemical composition in several patients irrespective of their leukocyte antigen could again allow reduction in costs. | 1 | Applied and Interdisciplinary Chemistry |
The Phosphate (Pho) regulon is a regulatory mechanism used for the conservation and management of inorganic phosphate within the cell. It was first discovered in Escherichia coli as an operating system for the bacterial strain, and was later identified in other species. The Pho system is composed of various components including extracellular enzymes and transporters that are capable of phosphate assimilation in addition to extracting inorganic phosphate from organic sources. This is an essential process since phosphate plays an important role in cellular membranes, genetic expression, and metabolism within the cell. Under low nutrient availability, the Pho regulon helps the cell survive and thrive despite a depletion of phosphate within the environment. When this occurs, phosphate starvation-inducible (psi) genes activate other proteins that aid in the transport of inorganic phosphate. | 1 | Applied and Interdisciplinary Chemistry |
The evolution of the RTI follows four main stages. In the first stage, the perturbation amplitudes are small when compared to their wavelengths, the equations of motion can be linearized, resulting in exponential instability growth. In the early portion of this stage, a sinusoidal initial perturbation retains its sinusoidal shape. However, after the end of this first stage, when non-linear effects begin to appear, one observes the beginnings of the formation of the ubiquitous mushroom-shaped spikes (fluid structures of heavy fluid growing into light fluid) and bubbles (fluid structures of light fluid growing into heavy fluid). The growth of the mushroom structures continues in the second stage and can be modeled using buoyancy drag models, resulting in a growth rate that is approximately constant in time. At this point, nonlinear terms in the equations of motion can no longer be ignored. The spikes and bubbles then begin to interact with one another in the third stage. Bubble merging takes place, where the nonlinear interaction of mode coupling acts to combine smaller spikes and bubbles to produce larger ones. Also, bubble competition takes places, where spikes and bubbles of smaller wavelength that have become saturated are enveloped by larger ones that have not yet saturated. This eventually develops into a region of turbulent mixing, which is the fourth and final stage in the evolution. It is generally assumed that the mixing region that finally develops is self-similar and turbulent, provided that the Reynolds number is sufficiently large. | 1 | Applied and Interdisciplinary Chemistry |
Friedrich Deusch used the impressed mark "Deusch 1000 / 1000" on the early items. This mark was punched directly into the silver. Very often one may also find a red three-digit number on the bottom of the porcelain or glass which indicates this early production. Later, it was replaced by a red stamp which shows a coffeepot and the name Deusch. In addition, to these marks, the following marks may also be found: "1000 / 1000 Silber" or "1000 / 1000 Feinsilber". Later items may have the additional mark "Made in Western Germany".
Alfred and Manfred Veyhl used many different marks, stamps and labels (always placed on the bottom of the item). Vehyl's work often shows the "1000/1000 silver" mark included in the body of the design. Some rare items are signed by handwritten monogram (MV for Manfred Veyhl) and the word "Handgemalt" (handpainted).
Friedrich Wilhelm Spahr mostly used marks impressed directly into the silver. The very earliest and rarest of Spahr's marks began with "MSG 1000 10" ("MSG" standing for "Manufaktur Schwäbisch Gmünd"). This mark was followed by "Spahr 1000 10" (sometimes stamped in black letters on a porcelain base), later with "Spahr 1000", and finally with transparent plastic labels on the bottom printed "Spahr Feinsilberauflage 1000 / 1000".
Alvin Corporation, which was later owned by the Gorham Mfg. Co. after 1928, also used special marks. They manufactures pieces of sterling silver flatware, as well as hollowware and special toilet ware.
The La Pierre Manufacturing Company also sued special marks. It was established by Frank H. La Pierre in 1885, and headquartered at 18 East 14th Street, NY. It relocated its offices to Newark, NJ before its incorporation in 1895. Their special marks appear on their silver overlay item such as hollowware and novelty items.
The Rockwell Silver Company established in Meriden, CT around 1905 created a number designs which featured silver overlay, however they were merged with Silver City Glass Company in 1978, so even though they have done extensive work, there are no unique marks associated with the company.
The Gorham Manufacturing Co. which was active from 1848 till 1865 used a lion as their mark. They also used a rams head and the phrase "coin" to mark their items. | 1 | Applied and Interdisciplinary Chemistry |
Chain polymerization products are widely used in many aspects of life, including electronic devices, food packaging, catalyst carriers, medical materials, etc. At present, the world's highest yielding polymers such as polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), etc. can be obtained by chain polymerization.
In addition, some carbon nanotube polymer is used for electronical devices. Controlled living chain-growth conjugated polymerization will also enable the synthesis of well-defined advanced structures, including block copolymers. Their industrial applications extend to water purification, biomedical devices and sensors. | 0 | Theoretical and Fundamental Chemistry |
Three roll bending of tubes and open profiles can also be performed with simpler machines, often semi-automatic and non CNC controlled, able to feed the tube into the bending zone by friction. These machines have often a vertical layout, i.e. the three rolls lie on a vertical plane. | 1 | Applied and Interdisciplinary Chemistry |
A critical parameter affecting the performance of proton exchange membranes is the water content. Water is typically supplied to the fuel cell by humidifying the gas feed stream. The level of hydration within the proton exchange membrane is vital to its performance: if the hydration level is too low, the polymers exhibit greatly reduced ionic conductivity; if hydration level is too high, excess water can flood the pores in the gas diffusion layer and impede mass transport within the electrode structure. For these reasons, DVS has been used to study the water sorption and transport properties of proton exchange membranes. | 0 | Theoretical and Fundamental Chemistry |
DOC is a basic nutrient, supporting growth of microorganisms and plays an important role in the global carbon cycle through the microbial loop. In some organisms (stages) that do not feed in the traditional sense, dissolved matter may be the only external food source. Moreover, DOC is an indicator of organic loadings in streams, as well as supporting terrestrial processing (e.g., within soil, forests, and wetlands) of organic matter. Dissolved organic carbon has a high proportion of biodegradable dissolved organic carbon (BDOC) in first order streams compared to higher order streams. In the absence of extensive wetlands, bogs, or swamps, baseflow concentrations of DOC in undisturbed watersheds generally range from approximately 1 to 20 mg/L carbon. Carbon concentrations considerably vary across ecosystems. For example, the Everglades may be near the top of the range and the middle of oceans may be near the bottom. Occasionally, high concentrations of organic carbon indicate anthropogenic influences, but most DOC originates naturally.
The BDOC fraction consists of organic molecules that heterotrophic bacteria can use as a source of energy and carbon. Some subset of DOC constitutes the precursors of disinfection byproducts for drinking water. BDOC can contribute to undesirable biological regrowth within water distribution systems.
The dissolved fraction of total organic carbon (TOC) is an operational classification. Many researchers use the term "dissolved" for compounds that pass through a 0.45 μm filter, but 0.22 μm filters have also been used to remove higher colloidal concentrations.
A practical definition of dissolved typically used in marine chemistry is all substances that pass through a GF/F filter, which has a nominal pore size of approximately 0.7 μm (Whatman glass microfiber filter, 0.6–0.8 μm particle retention). The recommended procedure is the HTCO technique, which calls for filtration through pre-combusted glass fiber filters, typically the GF/F classification. | 1 | Applied and Interdisciplinary Chemistry |
Hemoglycin is a completely abiotic molecule that forms in molecular clouds going on to protoplanetary disks, way before biochemistry on exoplanets like Earth begins. Hemoglycin via its glycine could seed an exoplanet (one able to support early biochemistry) but its main function appears to be the accretion of matter via formation of an extensive low-density lattice in space in a protoplanetary disk. Besides being present in carbonaceous meteorites, hemoglycin has also been extracted and crystallized from a fossil stromatolite that formed on Earth 2.1 billion years ago. Potentially this fossil hemoglycin was delivered during the Late Heavy Bombardment (LHB) to Earth. Data to support this being the hemoglycin in the fossil has extraterrestrial isotopes similar to that in meteorites.
The polymer on the precambrian Earth could have functioned to drive the Great Oxygenation Event (GOE) beginning 2.4 Gya by splitting water in response to ultraviolet irradiation. Also, it could provide an energy source to early biochemistry and/or it simply delivered a source of polymer glycine. | 0 | Theoretical and Fundamental Chemistry |
Natural antisense short interfering RNA (natsiRNA) is a type of siRNA. They are endogenous RNA regulators which are between 21 and 24 nucleotides in length, and are generated from complementary mRNA transcripts which are further processed into siRNA.
natsiRNA has been implicated in several developmental and response mechanisms in plants, such as pathogen resistance, salt tolerance and cell wall biosynthesis. natsiRNA has also been shown to alter gene expression in plants responding to environmental stressors. | 1 | Applied and Interdisciplinary Chemistry |
Carbon can be produced in stars at least as massive as the Sun by fusion of three helium-4 nuclei: He + He + He --> C. This is the triple alpha process.
In stars as massive as the Sun, carbon 12 is also converted to carbon 13 and then onto nitrogen 14 by fusion with protons. C + H --> C + e. C + H --> N. In more massive stars, two carbon nuclei can fuse to magnesium, or a carbon and an oxygen to sulfur. | 0 | Theoretical and Fundamental Chemistry |
CCL7 was first characterized from osteosarcoma supernatant. CCL7 consists of 99 amino acids, which contains 23-amino acid signal peptide. The mature protein about 76 amino acids is secreted after cleavage of the signal peptide. In contrast to most chemokines, CCL7 exists in a general monomeric form, differing from the dimer formed in a highly concentrated solution.
CCL7 can exist in four different glycotypes with a molecular weight 11, 13, 17 and 18 kDa in COS cells.
CCL7 mediates effects on the immune cell types through binding to numerous receptors, including CCR1, CCR2, CCR3, CCR5, and CCR10. These receptors belongs to the G protein-coupled seven-transmembrane receptors. CCL7 can also interact with cell surface glycosaminoglycans (GAGs) present on all animal cell surfaces. | 1 | Applied and Interdisciplinary Chemistry |
Since RuBisCO is often rate-limiting for photosynthesis in plants, it may be possible to improve photosynthetic efficiency by modifying RuBisCO genes in plants to increase catalytic activity and/or decrease oxygenation rates. This could improve sequestration of and be a strategy to increase crop yields. Approaches under investigation include transferring RuBisCO genes from one organism into another organism, engineering Rubisco activase from thermophilic cyanobacteria into temperature sensitive plants, increasing the level of expression of RuBisCO subunits, expressing RuBisCO small chains from the chloroplast DNA, and altering RuBisCO genes to increase specificity for carbon dioxide or otherwise increase the rate of carbon fixation. | 0 | Theoretical and Fundamental Chemistry |
Not all of the generated power of a plant is necessarily delivered into a distribution system. Power plants typically also use some of the power themselves, in which case the generation output is classified into gross generation, and net generation.
Gross generation or gross electric output is the total amount of electricity generated by a power plant over a specific period of time. It is measured at the generating terminal and is measured in kilowatt-hours (kW·h), megawatt-hours (MW·h), gigawatt-hours (GW·h) or for the largest power plants terawatt-hours (TW·h). It includes the electricity used in the plant auxiliaries and in the transformers.
:Gross generation = net generation + usage within the plant (also known as in-house loads)
Net generation is the amount of electricity generated by a power plant that is transmitted and distributed for consumer use. Net generation is less than the total gross power generation as some power produced is consumed within the plant itself to power auxiliary equipment such as pumps, motors and pollution control devices. Thus
:Net generation = gross generation − usage within the plant ( in-house loads) | 1 | Applied and Interdisciplinary Chemistry |
The iodolactonization reaction includes a number of nuances that affect product formation including regioselectivity, ring size preference, and thermodynamic and kinetic control. In terms of regioselectivity, iodolactonization preferentially occurs at the most hindered carbon atom adjacent to the iodonium cation. This is due to the fact that the more substituted carbon is better able to maintain a partial positive charge and is thus more electrophilic and susceptible to nucleophilic attack. When multiple double bonds in a molecule are equally reactive, conformational preferences dominate. However, when one double bond is more reactive, that reactivity always dominates regardless of conformational preference.
Both five- and six-membered rings could be formed in the iodolactonization shown below, but the five-membered ring is formed preferentially as predicted by Baldwin's rules for ring closure.
According to the rules, 5-exo-tet ring closures are favored while 6-endo-tet ring closures are disfavored. The regioselectivity of each iodolactonization can be predicted and explained using Baldwin's rules.
Stereoselective iodolactonizations have been seen in literature and can be very useful in synthesizing large molecules such as the aforementioned vernopelin and vernomenin because the lactone can be formed while maintaining other stereocenters. The ring closure can even be driven by stereocenters adjacent to the carbon-carbon multiple bond as shown below.
Even in systems without existing stereocenters, Bartlett and coworkers found that stereoselectivity was achievable. They were able to synthesize the cis and trans five membered lactones by adjusting reactions conditions such as temperature and reaction time. The trans product was formed under thermodynamic conditions (e.g. a long reaction time) while the cis product was formed under kinetic conditions (e.g. a relatively shorter reaction time). | 0 | Theoretical and Fundamental Chemistry |
For Möbius systems there is an odd number of plus-minus sign inversions in the basis set in proceeding around the cycle. A circle mnemonic was advanced which provides the MO energies of the system; this was the counterpart of the Frost–Musulin mnemonic for ordinary Hückel systems. It was concluded that 4n electrons is the preferred number for Möbius moieties in contrast to the common 4n + 2 electrons for Hückel systems. | 0 | Theoretical and Fundamental Chemistry |
The environmental bacterium and opportunistic pathogen Pseudomonas aeruginosa uses quorum sensing to coordinate the formation of biofilm, swarming motility, exopolysaccharide production, virulence, and cell aggregation. These bacteria can grow within a host without harming it until they reach a threshold concentration. Then they become aggressive, developing to the point at which their numbers are sufficient to overcome the hosts immune system, and form a biofilm, leading to disease within the host as the biofilm is a protective layer encasing the bacterial population. The relative ease of growth, handling, and genetic manipulation of Pseudomonas aeruginosa has lent much research effort to the quorum sensing circuits of this relatively common bacterium. Quorum sensing in Pseudomonas aeruginosa typically encompasses two complete AHL synthase-receptor circuits, LasI-LasR and RhlI-RhlR, as well as the orphan receptor-regulator QscR, which is also activated by the LasI-generated signal. Together, the multiple AHL quorum sensing circuits of Pseudomonas aeruginosa' influence regulation of hundreds of genes.
Another form of gene regulation that allows the bacteria to rapidly adapt to surrounding changes is through environmental signaling. Recent studies have discovered that anaerobiosis can significantly impact the major regulatory circuit of quorum sensing. This important link between quorum sensing and anaerobiosis has a significant impact on the production of virulence factors of this organism. There is hope among some humans that the therapeutic enzymatic degradation of the signaling molecules will be possible when treating illness caused by biofilms, and prevent the formation of such biofilms and possibly weaken established biofilms. Disrupting the signaling process in this way is called quorum sensing inhibition. | 1 | Applied and Interdisciplinary Chemistry |
A city with miles of dark hot pavement absorbs and radiates heat into the surrounding atmosphere at a greater rate than a natural landscapes do. This is urban heat island effect causing an increase in air temperatures. The EPA estimates that the average air temperature of a city with one million people or more can be warmer than surrounding areas. Higher temperatures reduce air quality by increasing smog. In Los Angeles, a 1 degree temperature increase makes the air roughly 3 percent more smog. Green roofs and other forms of green infrastructure help improve air quality and reduce smog through their use of vegetation. Plants not only provide shade for cooling, but also absorb pollutants like carbon dioxide and help reduce air temperatures through evaporation and evapotranspiration. | 1 | Applied and Interdisciplinary Chemistry |
The first commercial production of MSA, developed in the 1940s by Standard Oil of Indiana, was based on oxidation of dimethylsulfide by from air. Although inexpensive, this process suffered from a poor product quality and explosion hazards.
In 1967, the Pennwalt Corporation (USA) developed a different process for dimethylsulfide (as a water-based emulsion) oxidation using chlorine, followed by extraction-purification. In 2022 this chlorine-oxidation process was used only by Arkema (France) for making high-purity MSA. This process is not popular on a large scale, because it co-produces large quantities of hydrochloric acid.
Between years 1970 and 2000 MSA was used only on a relatively small-scale in niche markets (for example, in the microelectronic and electroplating industries since the 1980s), which was mainly due to its rather high price and limited availability. However, this situation changed around 2003, when BASF launched commercial production of MSA in Ludwigshafen based on a modified version of the aforementioned air oxidation process, oxidising dimethyldisulfide with nitric acid which is then restored using atmospheric oxygen. The former is produced in one step from methanol from syngas, hydrogen and sulfur.
An even better (lower-cost and environmentally friendlier) process of making methanesulfonic acid was developed in 2016 by Grillo-Werke AG (Germany). It is based on a direct reaction between methane and oleum at around 50 °C and 100 bar in the presence of a potassium persulfate initiator. This technology was acquired and commercialized by BASF in 2019. | 0 | Theoretical and Fundamental Chemistry |
Trapped bubbles of air and water within fossil amber can be analyzed to provide direct evidence of the climate conditions existing when the resin or tree sap formed. The analysis of these trapped air bubbles provides a record of atmosphere composition going back 140 million years. The data indicate that the oxygen content of the atmosphere reached a high of nearly 35% during the Cretaceous Period and then plummeted to near present levels during the early Tertiary. The abrupt decline corresponds to or closely follows the Cretaceous–Paleogene extinction event and may be the result of a major meteorite impact that created the Chicxulub Crater.
In paleoceanography studies, fluid inclusions can inform about the chemical composition of seawater. The trapped seawater in sediments evaporates and leaves behind the salt content. The depth at which these evaporites are found relative to the composition of the trapped salt allows oceanographers to reconstruct seawater evolution. Air bubbles trapped within the deep ice caps can also be analyzed for clues to ancient climate conditions. | 0 | Theoretical and Fundamental Chemistry |
In a fluid, the only non-zero stiffness is to volumetric deformation (a fluid does not sustain shear forces).
Hence the speed of sound in a fluid is given by
where is the bulk modulus of the fluid. | 1 | Applied and Interdisciplinary Chemistry |
Stagnation pressure is the static pressure a gas retains when brought to rest isentropically from Mach number M.
or, assuming an isentropic process, the stagnation pressure can be calculated from the ratio of stagnation temperature to static temperature:
where:
: is the stagnation pressure
: is the static pressure
: is the stagnation temperature
: is the static temperature
: is the ratio of specific heats
The above derivation holds only for the case when the gas is assumed to be calorically perfect (specific heats and the ratio of the specific heats are assumed to be constant with temperature). | 1 | Applied and Interdisciplinary Chemistry |
This technique measures a concentration change of proteins in bulk solution before and after adsorption, Δc. Any protein concentration change is attributed to the adsorbed layer, Γ.
Γ = Δc V/A
where:
*V = total volume of protein solution
*A = Total area available for adsorption
This method also requires a high surface area material such as particulate and beaded adsorbents. | 1 | Applied and Interdisciplinary Chemistry |
The POCIS sampler consists of an array of sampling disks mounted on a support rod. Each disk consists of a solid sorbent sandwiched between two polyethersoulfone (PES) microporous membranes which are then compressed between two stainless steel rings which expose a sampling area. A standard POCIS disk consists of a sampling surface area to sorbent mass ratio of approximately 180 cmg. Because the amount of chemical sampled is directly related to the sample surface area, it is sometimes necessary to combine extracts from multiple POCIS disks into one sample. Stainless steel rings, or other rigid inert material, are essential to prevent sorbent loss as the PES membranes are not able to be heat sealed. The POCIS array is then inserted and deployed within a protective canister. This canister is usually made of stainless steel or PVC and works to deflect debris that may displace the POCIS array during its deployment.
The PES membrane acts as a semipermeable barrier between the sorbent and surrounding aquatic environment. It allows dissolved contaminants to pass through the sorbent while selectively excluding any particles larger than 100 nm. The membrane resists biofouling because the polyethersulphone used in the design is less prone than other materials. The POCIS is versatile in that the sorbents can be changed to target different classes of contaminants. However, only two sorbent classes are considered as standards of all POCIS deployments to date. | 0 | Theoretical and Fundamental Chemistry |
A series heating cable is made of a run of high-resistance wire, insulated and often enclosed in a protective jacket. It is powered at a specific voltage and the resistance heat of the wire creates heat. The downside of these types of heaters is that if they are crossed over themselves they can overheat and burn out, they are provided in specific lengths and cannot be shortened in the field, also, a break anywhere along the line will result in a failure of the entire cable. The upside is that they are typically inexpensive (if plastic style heaters) or, as is true with mineral insulated heating cables, they can be exposed to very high temperatures. Mineral insulated heating cables are good for maintaining high temperatures on process lines or maintaining lower temperatures on lines which can get extremely hot such as high temperature steam lines.
Typically series elements are used on long pipe line process heating, for example long oil pipe lines and quay side of load pipes on oil refineries. | 1 | Applied and Interdisciplinary Chemistry |
Cyanopyrrolidines have two key interactions to the DPP-4 complex:
1. Nitrile in the position of the scissile bond of the peptidic substrate that is important for high potency. The nitrile group forms reversible covalent bonds with the catalytically active serine hydroxyl (Ser630), i.e. cyanopyrrolidines are competitive inhibitors with slow dissociation kinetics.
2. Hydrogen bonding network between the protonated amino group and a negatively charged region of the protein surface, Glu205, Glu206 and Tyr662. All cyanopyrrolidines have basic, primary or secondary amine, which makes this network possible but these compounds usually drop in potency if these amines are changed. Nonetheless, two patent applications unveil that the amino group can be changed, i.e. replaced by a hydrazine, but it is claimed that these compounds do not only act via DPP-4 inhibition but also prevent diabetic vascular complications by acting as a radical scavenger. | 1 | Applied and Interdisciplinary Chemistry |
Desmodium also enhances soil quality by increasing soil organic matter, nitrogen content, and soil biodiversity, as well as conserving moisture, moderating soil temperature and preventing erosion. | 1 | Applied and Interdisciplinary Chemistry |
External fields are the most common directors of self-assembly. Electric and magnetic fields allow induced interactions to align the particles. The fields take advantage of the polarizability of the nanoparticle and its functional groups. When these field-induced interactions overcome random Brownian motion, particles join to form chains and then assemble. At more modest field strengths, ordered crystal structures are established due to the induced dipole interactions. Electric and magnetic field direction requires a constant balance between thermal energy and interaction energies. | 0 | Theoretical and Fundamental Chemistry |
The enzymes that make and use NAD and NADH are important in both pharmacology and the research into future treatments for disease. Drug design and drug development exploits NAD in three ways: as a direct target of drugs, by designing enzyme inhibitors or activators based on its structure that change the activity of NAD-dependent enzymes, and by trying to inhibit NAD biosynthesis.
Because cancer cells utilize increased glycolysis, and because NAD enhances glycolysis, nicotinamide phosphoribosyltransferase (NAD salvage pathway) is often amplified in cancer cells.
It has been studied for its potential use in the therapy of neurodegenerative diseases such as Alzheimers and Parkinsons disease as well as multiple sclerosis. A placebo-controlled clinical trial of NADH (which excluded NADH precursors) in people with Parkinson's failed to show any effect.
NAD is also a direct target of the drug isoniazid, which is used in the treatment of tuberculosis, an infection caused by Mycobacterium tuberculosis. Isoniazid is a prodrug and once it has entered the bacteria, it is activated by a peroxidase enzyme, which oxidizes the compound into a free radical form. This radical then reacts with NADH, to produce adducts that are very potent inhibitors of the enzymes enoyl-acyl carrier protein reductase, and dihydrofolate reductase.
Since many oxidoreductases use NAD and NADH as substrates, and bind them using a highly conserved structural motif, the idea that inhibitors based on NAD could be specific to one enzyme is surprising. However, this can be possible: for example, inhibitors based on the compounds mycophenolic acid and tiazofurin inhibit IMP dehydrogenase at the NAD binding site. Because of the importance of this enzyme in purine metabolism, these compounds may be useful as anti-cancer, anti-viral, or immunosuppressive drugs. Other drugs are not enzyme inhibitors, but instead activate enzymes involved in NAD metabolism. Sirtuins are a particularly interesting target for such drugs, since activation of these NAD-dependent deacetylases extends lifespan in some animal models. Compounds such as resveratrol increase the activity of these enzymes, which may be important in their ability to delay aging in both vertebrate, and invertebrate model organisms. In one experiment, mice given NAD for one week had improved nuclear-mitochrondrial communication.
Because of the differences in the metabolic pathways of NAD biosynthesis between organisms, such as between bacteria and humans, this area of metabolism is a promising area for the development of new antibiotics. For example, the enzyme nicotinamidase, which converts nicotinamide to nicotinic acid, is a target for drug design, as this enzyme is absent in humans but present in yeast and bacteria.
In bacteriology, NAD, sometimes referred to factor V, is used as a supplement to culture media for some fastidious bacteria. | 0 | Theoretical and Fundamental Chemistry |
In mammals, progesterone, like all other steroid hormones, is synthesized from pregnenolone, which itself is derived from cholesterol.
Cholesterol undergoes double oxidation to produce 22R-hydroxycholesterol and then 20α,22R-dihydroxycholesterol. This vicinal diol is then further oxidized with loss of the side chain starting at position C22 to produce pregnenolone. This reaction is catalyzed by cytochrome P450scc.
The conversion of pregnenolone to progesterone takes place in two steps. First, the 3β-hydroxyl group is oxidized to a keto group and second, the double bond is moved to C4, from C5 through a keto/enol tautomerization reaction. This reaction is catalyzed by 3β-hydroxysteroid dehydrogenase/δ-isomerase.
Progesterone in turn is the precursor of the mineralocorticoid aldosterone, and after conversion to 17α-hydroxyprogesterone, of cortisol and androstenedione. Androstenedione can be converted to testosterone, estrone, and estradiol, highlighting the critical role of progesterone in testosterone synthesis.
Pregnenolone and progesterone can also be synthesized by yeast.
Approximately 25 mg of progesterone is secreted from the ovaries per day in women, while the adrenal glands produce about 2 mg of progesterone per day. | 0 | Theoretical and Fundamental Chemistry |
Fluid films, such as soap films, are commonly encountered in everyday experience. A soap film can be formed by dipping a closed contour wire into a soapy solution as in the figure on the right. Alternatively, a catenoid can be formed by dipping two rings in the soapy solution and subsequently separating them while maintaining the coaxial configuration.
Stationary fluid films form surfaces of minimal surface area, leading to the Plateau problem.
On the other hand, fluid films display rich dynamic properties. They can undergo enormous deformations away from the equilibrium configuration. Furthermore, they display several orders of magnitude variations in thickness from nanometers to millimeters. Thus, a fluid film can simultaneously display nanoscale and macroscale phenomena.
In the study of the dynamics of free fluid films, such as soap films, it is common to model the film as two dimensional manifolds. Then the variable thickness of the film is captured by the two dimensional density .
The dynamics of fluid films can be described by the following system of exact nonlinear Hamiltonian equations which, in that respect, are a complete analogue of Eulers inviscid equations of fluid dynamics. In fact, these equations reduce to Eulers dynamic equations for flows in stationary Euclidean spaces.
The foregoing relies on the formalism of tensors, including the summation convention and the raising and lowering of tensor indices. | 1 | Applied and Interdisciplinary Chemistry |
Integrating traditional and modern methods is a useful way to process albumin.
There are three main steps that combine Cohn fractionation with chromatography: 1) factors I, II, and III are removed via cold ethanol fractionation, 2) Sepharose fast flow ion exchange and sepharose fast flow chromatography procedures are run, and 3) gel filtration is run. The result is albumin with 9% lower aluminum levels with a processing time that is almost twice as fast.
Although it was hard to make chromatographic processing methods widely adopted, global expansion is a work in progress. Various blood components must be readily available at various medical treatment centers around the world. The Institute of Transfusion Medicine in Skopje, North Macedonia is a plasma fractionation center in the Balkans. Their modernized albumin purification process consists of five steps:
# Starting material is plasma that has been pretreated by centrifugation,
# A round of gel filtration is run,
# ion exchange on DEAE Sepharose is run to bind the albumin to the column,
# Albumin is eluted with a sodium acetate buffer, and
# Final polishing with gel filtration.
The end result is a highly pure and safe batch of albumin that is 100% non-pyrogenic, sterile, and free of active HIV virus. The product purity is greater than 98% and the protein content is about 50 g/L. | 0 | Theoretical and Fundamental Chemistry |
In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal gas mixture is the sum of the partial pressures of the gases in the mixture (Dalton's Law).
The partial pressure of a gas is a measure of thermodynamic activity of the gas's molecules. Gases dissolve, diffuse, and react according to their partial pressures but not according to their concentrations in gas mixtures or liquids. This general property of gases is also true in chemical reactions of gases in biology. For example, the necessary amount of oxygen for human respiration, and the amount that is toxic, is set by the partial pressure of oxygen alone. This is true across a very wide range of different concentrations of oxygen present in various inhaled breathing gases or dissolved in blood; consequently, mixture ratios, like that of breathable 20% oxygen and 80% Nitrogen, are determined by volume instead of by weight or mass. Furthermore, the partial pressures of oxygen and carbon dioxide are important parameters in tests of arterial blood gases. That said, these pressures can also be measured in, for example, cerebrospinal fluid. | 0 | Theoretical and Fundamental Chemistry |
Slippery sequences can potentially make the reading ribosome "slip" and skip a number of nucleotides (usually only 1) and read a completely different frame thereafter. In programmed −1 ribosomal frameshifting, the slippery sequence fits a X_XXY_YYH motif, where XXX is any three identical nucleotides (though some exceptions occur), YYY typically represents UUU or AAA, and H is A, C or U. In the case of +1 frameshifting, the slippery sequence contains codons for which the corresponding tRNA is more rare, and the frameshift is favored because the codon in the new frame has a more common associated tRNA. One example of a slippery sequence is the polyA on mRNA, which is known to induce ribosome slippage even in the absence of any other elements. | 1 | Applied and Interdisciplinary Chemistry |
For allowed decays, the net orbital angular momentum is zero, hence only spin quantum numbers are considered.
The electron and antineutrino are fermions, spin-1/2 objects, therefore they may couple to total (parallel) or (anti-parallel).
For forbidden decays, orbital angular momentum must also be taken into consideration. | 0 | Theoretical and Fundamental Chemistry |
Bioluminescence has only been observed in three classes of mollusks: Cephalopoda, Gastropoda, and Bivalvia. Bioluminescence is widely spread among cephalopods, but much rarer among the other classes of mollusk. Most species of biolumenescent mollusk that have been discovered are found in the ocean with the exception of the genera Latia and Quantula found in freshwater and terrestrial habitats respectively; however, more recent research has discovered luminescence in the Phuphania genus. It is hypothesized that terrestrial mollusks that use bioluminescence developed it as a strategy to deter predation. The green color emanated by the mollusk's photocytes is thought to be the most visible color to nocturnal predators. | 1 | Applied and Interdisciplinary Chemistry |
Fluorescence recovery after photobleaching (FRAP) is a method for determining the kinetics of diffusion through tissue or cells. It is capable of quantifying the two-dimensional lateral diffusion of a molecularly thin film containing fluorescently labeled probes, or to examine single cells. This technique is very useful in biological studies of cell membrane diffusion and protein binding. In addition, surface deposition of a fluorescing phospholipid bilayer (or monolayer) allows the characterization of hydrophilic (or hydrophobic) surfaces in terms of surface structure and free energy.
Similar, though less well known, techniques have been developed to investigate the 3-dimensional diffusion and binding of molecules inside the cell; they are also referred to as FRAP. | 1 | Applied and Interdisciplinary Chemistry |
A quantum jump is the abrupt transition of a quantum system (atom, molecule, atomic nucleus) from one quantum state to another, from one energy level to another. When the system absorbs energy, there is a transition to a higher energy level (excitation); when the system loses energy, there is a transition to a lower energy level.
The concept was introduced by Niels Bohr, in his 1913 Bohr model.
A quantum jump is a phenomenon that is peculiar to quantum systems and distinguishes them from classical systems, where any transitions are performed gradually. In quantum mechanics, such jumps are associated with the non-unitary evolution of a quantum-mechanical system during measurement.
A quantum jump can be accompanied by the emission or absorption of photons; energy transfer during a quantum jump can also occur by non-radiative resonant energy transfer or in collisions with other particles.
In modern physics, the concept of a quantum jump is rarely used; as a rule scientists speak of transitions between quantum states or energy levels. | 0 | Theoretical and Fundamental Chemistry |
Scleroderma, also known as systemic sclerosis, is a chronic systemic autoimmune disease characterised by hardening (sclero) of the skin (derma) that affects internal organs in its more severe forms. mTOR plays a role in fibrotic diseases and autoimmunity, and blockade of the mTORC pathway is under investigation as a treatment for scleroderma. | 1 | Applied and Interdisciplinary Chemistry |
Before the 2019 redefinition of the SI base units, the mole was defined as the amount of substance of a system that contains as many elementary entities as there are atoms in 12 grams of carbon-12 (the most common isotope of carbon).
The term gram-molecule was formerly used to mean one mole of molecules, and gram-atom for one mole of atoms. For example, 1 mole of MgBr is 1 gram-molecule of MgBr but 3 gram-atoms of MgBr.
In 2011, the 24th meeting of the General Conference on Weights and Measures (CGPM) agreed to a plan for a possible revision of the SI base unit definitions at an undetermined date.
On 16 November 2018, after a meeting of scientists from more than 60 countries at the CGPM in Versailles, France, all SI base units were defined in terms of physical constants. This meant that each SI unit, including the mole, would not be defined in terms of any physical objects but rather they would be defined by physical constants that are, in their nature, exact.
Such changes officially came into effect on 20 May 2019. Following such changes, "one mole" of a substance was redefined as containing "exactly elementary entities" of that substance. | 0 | Theoretical and Fundamental Chemistry |
The filtrate cakes that are thin and fragile are usually the end products of this discharge lie. The materials are capable of changing phases, from solid to liquid, due to instability and disturbance. Two rollers guide the strings back to drum surface and at the same time separation of the filtrate cake occurs as they pass the rollers. Application of the string discharge can be seen at the pharmaceutical and starch industries. String discharge is used if the high solid concentration slurry is used or if the slurry is easy to filter to produce cake formation or if the discharged solid is fibrous, stringy or pulpy or if a longer wear resistance is desired for the separation of the mentioned slurry. | 0 | Theoretical and Fundamental Chemistry |
Jordi Folch Pi (March 25, 1911October 3, 1979) was a Spanish biochemist at Harvard University (McLean Hospital) who was recognized universally as one of the founders of the field of structural chemistry of complex lipids and as a leader in the development of Neurochemistry , as a distinct discipline within the Neurosciences. | 1 | Applied and Interdisciplinary Chemistry |
More than 371 drugs approved by the FDA between the years of 1951 and 2020 contain either a phenol or a phenolic ether (a phenol with an alkyl), with nearly every class of small molecule drugs being represented, and natural products making up a large portion of this list. | 0 | Theoretical and Fundamental Chemistry |
# The saturation pressure at the maximum temperature of the cycle should not be excessive. Very high pressures lead to mechanical stress problems, and therefore, unnecessarily expensive components may be required.
# The saturation pressure at the minimum temperature of the cycle (i.e. the condensing pressure) should not be so low as to lead to problems of sealing against infiltration of the atmospheric air into the system.
# The triple point should lie below the expected minimum ambient temperature. This ensures that the fluid does not solidify at any point during the cycle nor whilst being handled outside the system.
# The working fluid should possess a low value of the liquid viscosity, a high latent heat of vaporisation, a high liquid thermal conductivity and a good wetting capability. These ensure that the working fluid pressure drops in passing through the heat exchangers and the auxiliary piping are low and that the heat transfer rates in the exchangers are high.
# The working fluid should have low vapour and liquid specific volumes. These properties affect the rates of heat transfer in the heat exchangers. The vapour specific volume relates directly to the size and cost of the cycle components. Moreover, a high vapour specific volume leads to larger volumetric flows requiring a multiplicity of exhaust ends of the expander at heat engines or compressor in refrigeration cycles and resulting in significant pressure losses. The specific volume of the liquid at the condenser pressure should be as small as possible in order to minimise the required feedwater pump work.
# Non-corrosivity and compatibility with common system materials are important selection criteria.
# The fluid should be chemically stable over the whole temperature and pressure range employed. The thermal decomposition resistance of the working fluid in the presence of lubricants and container materials is a highly important criterion. In addition to making the replacement of the working fluid necessary, chemical decomposition of the fluid can produce non-condensable gases which lower the heat transfer rate in the heat exchangers, as well as compounds, which have corrosive effects on the materials of the system.
# Non-toxicity, non-flammability, non-explosiveness, non-radioactiveness and current industrial acceptability are also desirable attributes.
# The fluid should meet the criteria of environmental protection requirements such as a low grade ozone depletion potential (ODP) and global warming potential (GWP).
# The fluid should possess good lubrication properties to reduce friction between surfaces in mutual contact, which reduces the heat generated when the surfaces move and ultimately increases cycle performance.
# The substance should be of low cost and readily available in large quantities.
# Long-term (operational) experience with the working fluid and possible fluid recycling is also beneficial. | 0 | Theoretical and Fundamental Chemistry |
In writing down the reaction equation, in a way analogous to a chemical equation, one may, in addition, give the reaction energy on the right side:
For the particular case discussed above, the reaction energy has already been calculated as Q = 22.2 MeV. Hence:
The reaction energy (the "Q-value") is positive for exothermal reactions and negative for endothermal reactions, opposite to the similar expression in chemistry. On the one hand, it is the difference between the sums of kinetic energies on the final side and on the initial side. But on the other hand, it is also the difference between the nuclear rest masses on the initial side and on the final side (in this way, we have calculated the Q-value above). | 0 | Theoretical and Fundamental Chemistry |
An insertion reaction is a chemical reaction where one chemical entity (a molecule or molecular fragment) interposes itself into an existing bond of typically a second chemical entity e.g.:
The term only refers to the result of the reaction and does not suggest a mechanism. Insertion reactions are observed in organic, inorganic, and organometallic chemistry. In cases where a metal-ligand bond in a coordination complex is involved, these reactions are typically organometallic in nature and involve a bond between a transition metal and a carbon or hydrogen. It is usually reserved for the case where the coordination number and oxidation state of the metal remain unchanged. When these reactions are reversible, the removal of the small molecule from the metal-ligand bond is called extrusion or elimination.
There are two common insertion geometries— 1,1 and 1,2 (pictured above). Additionally, the inserting molecule can act either as a nucleophile or as an electrophile to the metal complex. These behaviors will be discussed in more detail for CO, nucleophilic behavior, and SO, electrophilic behavior. | 0 | Theoretical and Fundamental Chemistry |
Amphibians, particularly anurans (frogs and toads), are increasingly used as bioindicators of contaminant accumulation in pollution studies. Anurans absorb toxic chemicals through their skin and their larval gill membranes and are sensitive to alterations in their environment. They have a poor ability to detoxify pesticides that are absorbed, inhaled, or ingested by eating contaminated food. This allows residues, especially of organochlorine pesticides, to accumulate in their systems. They also have permeable skin that can easily absorb toxic chemicals, making them a model organism for assessing the effects of environmental factors that may cause the declines of the amphibian population. These factors allow them to be used as bioindicator organisms to follow changes in their habitats and in ecotoxicological studies due to humans increasing demands on the environment.
Knowledge and control of environmental agents is essential for sustaining the health of ecosystems. Anurans are increasingly utilized as bioindicator organisms in pollution studies, such as studying the effects of agricultural pesticides on the environment. Environmental assessment to study the environment in which they live is performed by analyzing their abundance in the area as well as assessing their locomotive ability and any abnormal morphological changes, which are deformities and abnormalities in development. Decline of anurans and malformations could also suggest increased exposure to ultra-violet light and parasites. Expansive application of agrochemicals such as glyphosate have been shown to have harmful effects on frog populations throughout their lifecycle due to run off of these agrochemicals into the water systems these species live and their proximity to human development.
Pond-breeding anurans are especially sensitive to pollution because of their complex life cycles, which could consist of terrestrial and aquatic living. During their embryonic development, morphological and behavioral alterations are the effects most frequently cited in connection with chemical exposures. Effects of exposure may result in shorter body length, lower body mass and malformations of limbs or other organs. The slow development, late morphological change, and small metamorph size result in increased risk of mortality and exposure to predation. | 1 | Applied and Interdisciplinary Chemistry |
Arsenic is an element with a vaporization point of 615 °C, such that arsenical oxide will be lost from the melt before or during casting, and fumes from fire setting for mining and ore processing have long been known to attack the nervous system, eyes, lungs, and skin.
Chronic arsenic poisoning leads to peripheral neuropathy, which can cause weakness in the legs and feet. It has been speculated that this lay behind the legend of lame smiths in many cultures and myths, such as the Greek god Hephaestus. As Hephaestus was an iron-age smith, not a bronze-age smith, the connection would be one from ancient folk memory.
A well-preserved mummy of a man who lived around 3,200 BC found in the Ötztal Alps, popularly known as Ötzi, showed high levels of both copper particles and arsenic in his hair. This, along with Ötzi's copper axe blade, which is 99.7% pure copper, has led scientists to speculate that he was involved in copper smelting. | 1 | Applied and Interdisciplinary Chemistry |
Influenza virus neuraminidase (vNEU) consists of 4 co-planar roughly spherical subunits predominantly made of β-sheets, characterized as a 6-fold β-propeller and a hydrophobic region embedded in the virus’ membrane. The active site is located near the middle of the pseudo-symmetric sphere. Influenza virus neuraminidase only cleaves terminal Neu5Ac residues. X-ray crystallography has shown a distorted half-chair arrangement of the Neu5Ac substrate in the active site. This distorted structure forms a sialosyl cation after the release of the aglycon and is then trapped in the active site by a nucleophilic attack of the tyrosine residue. The orientation of the substrate in the active site is facilitated mainly by three strain-preserved Arginine residues binding the C1 acid group with salt bridges. Furthermore, the active site consists of eight other highly conserved amino acid-residues that make direct contact to the substrate or its derivatives. Including a glutamic acid residue binding the C7 and C9 alcohol groups on the glycerol side-chain (at C6) with hydrogen bonds and several hydrophobic residues correlating with the methyl group on the C5 N-acetyl and the hydrophobic backbone of the glycerol. | 1 | Applied and Interdisciplinary Chemistry |
DNA replication is for the most part extremely accurate, however errors (mutations) do occur. The error rate in eukaryotic cells can be as low as 10 per nucleotide per replication, whereas for some RNA viruses it can be as high as 10. This means that each generation, each human genome accumulates around 30 new mutations. Small mutations can be caused by DNA replication and the aftermath of DNA damage and include point mutations in which a single base is altered and frameshift mutations in which a single base is inserted or deleted. Either of these mutations can change the gene by missense (change a codon to encode a different amino acid) or nonsense (a premature stop codon). Larger mutations can be caused by errors in recombination to cause chromosomal abnormalities including the duplication, deletion, rearrangement or inversion of large sections of a chromosome. Additionally, DNA repair mechanisms can introduce mutational errors when repairing physical damage to the molecule. The repair, even with mutation, is more important to survival than restoring an exact copy, for example when repairing double-strand breaks.
When multiple different alleles for a gene are present in a speciess population it is called polymorphic. Most different alleles are functionally equivalent, however some alleles can give rise to different phenotypic traits. A genes most common allele is called the wild type, and rare alleles are called mutants. The genetic variation in relative frequencies of different alleles in a population is due to both natural selection and genetic drift. The wild-type allele is not necessarily the ancestor of less common alleles, nor is it necessarily fitter.
Most mutations within genes are neutral, having no effect on the organisms phenotype (silent mutations). Some mutations do not change the amino acid sequence because multiple codons encode the same amino acid (synonymous mutations). Other mutations can be neutral if they lead to amino acid sequence changes, but the protein still functions similarly with the new amino acid (e.g. conservative mutations). Many mutations, however, are deleterious or even lethal, and are removed from populations by natural selection. Genetic disorders are the result of deleterious mutations and can be due to spontaneous mutation in the affected individual, or can be inherited. Finally, a small fraction of mutations are beneficial, improving the organisms fitness and are extremely important for evolution, since their directional selection leads to adaptive evolution. | 1 | Applied and Interdisciplinary Chemistry |
Fowler has published approximately 530 papers. The following are a few of the most cited:
* Inhibition of monoamine oxidase B in the brains of smokers. Fowler, J.S., Volkow, N.D., Wang, G.-J., et al. Nature. Volume 379, Issue 6567, 22 February 1996, Pages 733-736
* Distribution volume ratios without blood sampling from graphical analysis of PET data. Logan, J., Fowler, J.S., Volkow, N.D., et al. Journal of Cerebral Blood Flow and Metabolism. Volume 16, Issue 5, 1996, Pages 834-840
* Decreased dopamine D2 receptor availability is associated with reduced frontal metabolism in cocaine abusers. Volkow, N.D., Fowler, J.S., Wang, G.-J., et al. Synapse. Volume 14, Issue 2, 1993, Pages 169-177
* Brain dopamine and obesity. Wang, G.-J., Volkow, N., Fowler, J., et al. The Lancet. Volume 327, Issue 9253, 2001, Pages 354–357.
* Cocaine cues and dopamine in dorsal striatum: mechanism of craving in cocaine addiction. Volkow, N., Wang, G.-J., Fowler, J., et al. Journal of Neuroscience. Volume 26, Issue 24, 2006, Pages 6583-6588 | 0 | Theoretical and Fundamental Chemistry |
In nuclear magnetic resonance (NMR) spectroscopy, the chemical shift is the resonant frequency of an atomic nucleus relative to a standard in a magnetic field. Often the position and number of chemical shifts are diagnostic of the structure of a molecule. Chemical shifts are also used to describe signals in other forms of spectroscopy such as photoemission spectroscopy.
Some atomic nuclei possess a magnetic moment (nuclear spin), which gives rise to different energy levels and resonance frequencies in a magnetic field. The total magnetic field experienced by a nucleus includes local magnetic fields induced by currents of electrons in the molecular orbitals (electrons have a magnetic moment themselves). The electron distribution of the same type of nucleus (e.g. ) usually varies according to the local geometry (binding partners, bond lengths, angles between bonds, and so on), and with it the local magnetic field at each nucleus. This is reflected in the spin energy levels (and resonance frequencies). The variations of nuclear magnetic resonance frequencies of the same kind of nucleus, due to variations in the electron distribution, is called the chemical shift. The size of the chemical shift is given with respect to a reference frequency or reference sample (see also chemical shift referencing), usually a molecule with a barely distorted electron distribution. | 0 | Theoretical and Fundamental Chemistry |
The corundum structure has the space group hexagonal crystal family#Crystal classes|. It typically exists in binary compounds of the type AB, where A is metallic and B is nonmetallic, including sesquioxides (AO), sesquisulfides (AS), etc. When A is nonmetallic and B is metallic, the structure becomes the antiphase of corundum, called the anticorundum structure type, with examples including β-CaN and borates. Ternary and multinary compounds can also exists in the corundum structure. The corundum-like structure with the composition ABB'O is called double corundum. A list of examples are tabulated below. | 0 | Theoretical and Fundamental Chemistry |
The execution of the Chen-Kao reaction is simple, needs little practice and limited skills.
Also, the violet color obtained in the reaction is easy to define.
For a correct execution, it is important to note that the typical colors develop relatively slowly, and that a good color intensity requires a sample of a few milligrams of the substances tested (i.e., more than what would typically be required for most other tests included in the UN test kits).
Of all ephedrine-related compounds, only ephedrine and pseudoephedrine produce the typical, stable violet color. Other ephedrine-related compounds produce a blue to greenish-blue precipitate. This precipitate could be seen as characteristic for the members of the ephedrine group other than pseudoephedrine and ephedrine itself, hence, the Chen-Kao test appears to show a significant specificity within the ephedrine group. However, it is known from previously published cross-testing work that various pharmaceuticals not related to the ephedrine group may produce similar blue copper complexes.
The two keto-amines, cathinone and methcathinone, initially also produce blue-colored complexes with the Chen-Kao reagent. However, a slow transition of the initial color into yellow, followed by an orange-brown color can be observed with both compounds, thus indicating the instability of the complexes initially formed, and an obvious decomposition of the two compounds under the alkaline conditions of this color reaction.
The results of the solvent extractions, summarized in Table II appear to add little novelty to the results of the original Chen-Kao reactions. However, in cases of doubts, they may serve as confirmatory steps. | 0 | Theoretical and Fundamental Chemistry |
Recently, chemists and those involved in nanotechnology have begun to explore the possibility of creating molecular motors de novo. These synthetic molecular motors currently suffer many limitations that confine their use to the research laboratory. However, many of these limitations may be overcome as our understanding of chemistry and physics at the nanoscale increases. One step toward understanding nanoscale dynamics was made with the study of catalyst diffusion in the Grubb's catalyst system. Other systems like the nanocars, while not technically motors, are also illustrative of recent efforts towards synthetic nanoscale motors.
Other non-reacting molecules can also behave as motors. This has been demonstrated by using dye molecules that move directionally in gradients of polymer solution through favorable hydrophobic interactions. Another recent study has shown that dye molecules, hard and soft colloidal particles are able to move through gradient of polymer solution through excluded volume effects. | 0 | Theoretical and Fundamental Chemistry |
A cDNA library is a combination of cloned cDNA (complementary DNA) fragments inserted into a collection of host cells, which constitute some portion of the transcriptome of the organism and are stored as a "library". cDNA is produced from fully transcribed mRNA found in the nucleus and therefore contains only the expressed genes of an organism. Similarly, tissue-specific cDNA libraries can be produced. In eukaryotic cells the mature mRNA is already spliced, hence the cDNA produced lacks introns and can be readily expressed in a bacterial cell. While information in cDNA libraries is a powerful and useful tool since gene products are easily identified, the libraries lack information about enhancers, introns, and other regulatory elements found in a genomic DNA library. | 1 | Applied and Interdisciplinary Chemistry |
By analyzing the chemical composition of a cows rumen, researchers can determine the effects of different feeds and processes on bovine digestion. Many of the earliest documented reports of cannulated cows were made by researchers working to understand how feed is processed through cows. For instance, a 1939 study discovered via cannulated cows that the pH of rumen varies throughout the day, becoming most alkaline just prior to feeding. A 1956 study used cannulated cows to determine that a hay-only diet does not change the proportion of fatty acids in a cows rumen, but every other type of feed measured does. | 1 | Applied and Interdisciplinary Chemistry |
For chronic diseases, whose treatment may require patients to take medications for years, accurate diagnosis is particularly important, especially when strong side effects are expected from the treatment. In these cases, biomarkers are becoming more and more important, because they can confirm a difficult diagnosis or even make it possible in the first place.
A number of diseases, such as Alzheimer's disease or rheumatoid arthritis, often begin with an early, symptom-free phase. In such symptom-free patients there may be more or less probability of actually developing symptoms. In these cases, biomarkers help to identify high-risk individuals reliably and in a timely manner so that they can either be treated before onset of the disease or as soon as possible thereafter.
In order to use a biomarker for diagnostics, the sample material must be as easy to obtain as possible. This may be a blood sample taken by a doctor, a urine or saliva sample, or a drop of blood like those diabetes patients extract from their own fingertips for regular blood-sugar monitoring.
For rapid initiation of treatment, the speed with which a result is obtained from the biomarker test is critical. A rapid test, which delivers a result after only a few minutes, is optimal. This makes it possible for the physician to discuss with the patient how to proceed and if necessary to start treatment immediately after the test.
Naturally, the detection method for a biomarker must be accurate and as easy to carry out as possible. The results from different laboratories may not differ significantly from each other, and the biomarker must naturally have proven its effectiveness for the diagnosis, prognosis, and risk assessment of the affected diseases in independent studies.
A biomarker for clinical use needs good sensitivity and specificity e.g. ≥0.9, and good specificity e.g. ≥0.9 although they should be chosen with the population in mind so positive predictive value and negative predictive value are more relevant. | 1 | Applied and Interdisciplinary Chemistry |
Initiation of translation is regulated by the accessibility of ribosomes to the Shine-Dalgarno sequence. This stretch of four to nine purine residues are located upstream the initiation codon and hybridize to a pyrimidine-rich sequence near the 3 end of the 16S RNA within the 30S bacterial ribosomal subunit. Polymorphism in this particular sequence has both positive and negative effects on the efficiency of base-pairing and subsequent protein expression. Initiation is also regulated by proteins known as initiation factors which provide kinetic assistance to the binding between the initiation codon and tRNA, which supplies the 3-UAC-5' anticodon. IF1 binds the 30S subunit first, instigating a conformational change that allows for the additional binding of IF2 and IF3. IF2 ensures that tRNA remains in the correct position while IF3 proofreads initiation codon base-pairing to prevent non-canonical initiation at codons such as AUU and AUC. Generally, these initiation factors are expressed in equal proportion to ribosomes, however experiments using cold-shock conditions have shown to create stoichiometric imbalances between these translational machinery. In this case, two to three fold changes in expression of initiation factors coincide with increased favorability towards translation of specific cold-shock mRNAs. | 1 | Applied and Interdisciplinary Chemistry |
Short-chain CPs are classified as persistent and their physical properties (octanol-water partition coefficient (logK) 4.4–8, depending on the chlorination degree) imply a high potential for bioaccumulation. SCCPs are classified as toxic to aquatic organisms, and carcinogenic to rats and mice. Therefore, it was concluded that SCCPs have PBT and vPvB properties and they were added to the Candidate List of substances of very high concern for Authorisation under REACH Regulation. SCCPs (average chain length of C, chlorination degree 60 wt%) were categorised in group 2B as possibly carcinogenic to humans from the International Agency for Research on Cancer (IARC). In 2017, it was agreed to globally ban SCCPs under the Stockholm Convention on Persistent Organic Pollutants, effective December 2018. However, also MCCPs are toxic to the aquatic environment and persistent; MCCPs in soil, biota, and most of the sediment cores show increasing time trends over the last years to decades; MCCP concentrations in sediment close to local sources exceed toxicity thresholds such as the PNEC. In July 2021 also MCCPs were added to the Candidate List of Substances of Very High Concern (SVHC) under the REACH Regulation.
Chlorinated paraffins have been detected in marine life such as cetaceans (whales) and bivalves (molluscs). Of particular concern is fetal accumulation in whales, with the chemicals beginning to build-up in the offspring before they are even born. | 1 | Applied and Interdisciplinary Chemistry |
A member of the Royal Australian Chemical Institute is designated with the honorific postnominal "MRACI". As the professional body for chemistry in Australia, the institute is empowered to award the status of Chartered Chemist ("CChem") to suitably qualified candidates. Election to Fellow of the institute ("FRACI") is dependent on a position of eminence, services rendered, academic honours, experience and status, creative achievement, responsibility and contribution to chemical science, and recommendation by the RACI Assessment Committee. The institute also accepts undergraduate and postgraduate student members, associate members, school affiliate members, and industry affiliate members. | 1 | Applied and Interdisciplinary Chemistry |
If a container with an ideal gas is expanded instantaneously, the temperature of the gas doesn't change at all, because none of the molecules slow down. The molecules keep their kinetic energy, but now the gas occupies a bigger volume. If the container expands slowly, however, so that the ideal gas pressure law holds at any time, gas molecules lose energy at the rate that they do work on the expanding wall. The amount of work they do is the pressure times the area of the wall times the outward displacement, which is the pressure times the change in the volume of the gas:
If no heat enters the gas, the energy in the gas molecules is decreasing by the same amount. By definition, a gas is ideal when its temperature is only a function of the internal energy per particle, not the volume. So
where is the specific heat at constant volume. When the change in energy is entirely due to work done on the wall, the change in temperature is given by
This gives a differential relationship between the changes in temperature and volume, which can be integrated to find the invariant. The constant is just a unit conversion factor, which can be set equal to one:
So
is an adiabatic invariant, which is related to the entropy
Thus entropy is an adiabatic invariant. The N log(N) term makes the entropy additive, so the entropy of two volumes of gas is the sum of the entropies of each one.
In a molecular interpretation, S is the logarithm of the phase-space volume of all gas states with energy E(T) and volume V.
For a monatomic ideal gas, this can easily be seen by writing down the energy:
The different internal motions of the gas with total energy E define a sphere, the surface of a 3N-dimensional ball with radius . The volume of the sphere is
where is the gamma function.
Since each gas molecule can be anywhere within the volume V, the volume in phase space occupied by the gas states with energy E is
Since the N gas molecules are indistinguishable, the phase-space volume is divided by , the number of permutations of N molecules.
Using Stirlings approximation for the gamma function, and ignoring factors that disappear in the logarithm after taking N' large,
Since the specific heat of a monatomic gas is 3/2, this is the same as the thermodynamic formula for the entropy. | 0 | Theoretical and Fundamental Chemistry |
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