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Carbon dioxide affects the curve in two ways. First, CO accumulation causes carbamino compounds to be generated through chemical interactions, which bind to hemoglobin forming carbaminohemoglobin. CO is considered an Allosteric regulation as the inhibition happens not at the binding site of hemoglobin. Second, it influences intracellular pH due to formation of bicarbonate ion. Formation of carbaminohemoglobin stabilizes T state hemoglobin by formation of ion pairs. Only about 5–10% of the total CO content of blood is transported as carbamino compounds, whereas (80–90%) is transported as bicarbonate ions and a small amount is dissolved in the plasma. The formation of a bicarbonate ion will release a proton into the plasma, decreasing pH (increased acidity), which also shifts the curve to the right as discussed above; low CO levels in the blood stream results in a high pH, and thus provides more optimal binding conditions for hemoglobin and O. This is a physiologically favored mechanism, since hemoglobin will drop off more oxygen as the concentration of carbon dioxide increases dramatically where tissue respiration is happening rapidly and oxygen is in need. | 1 | Applied and Interdisciplinary Chemistry |
The conjugation of 1,3-butadiene was first evaluated by Kistiakowsky, a conjugative contribution of 3.5 kcal/mol was found based on the energetic comparison of hydrogenation between conjugated species and unconjugated analogues. Rogers who used the method first applied by Kistiakowsky, reported that the conjugation stabilization of 1,3-butadiyne was zero, as the difference of ΔH between first and second hydrogenation was zero. The heats of hydrogenation (ΔH) were obtained by computational G3(MP2) quantum chemistry method.
Another group led by Houk suggested the methods employed by Rogers and Kistiakowsky was inappropriate, because that comparisons of heats of hydrogenation evaluate not only conjugation effects but also other structural and electronic differences. They obtained -70.6 kcal/mol and -70.4 kcal/mol for the first and second hydrogenation respectively by ab initio calculation, which confirmed Rogers’ data. However, they interpreted the data differently by taking into account the hyperconjugation stabilization. To quantify hyperconjugation effect, they designed the following isodesmic reactions in 1-butyne and 1-butene.
Deleting the hyperconjugative interactions gives virtual states that have energies that are 4.9 and 2.4 kcal/mol higher than those of 1-butyne and 1-butene, respectively. Employment of these virtual states results in a 9.6 kcal/mol conjugative stabilization for 1,3-butadiyne and 8.5 kcal/mol for 1,3-butadiene. | 0 | Theoretical and Fundamental Chemistry |
The Phage-ligand technology is a technology to detect, bind and remove bacteria and bacterial toxins by using highly specific bacteriophage derived proteins. | 1 | Applied and Interdisciplinary Chemistry |
Metabolic networks can be used to detect comorbidity patterns in diseased patients. Certain diseases, such as obesity and diabetes, can be present in the same individual concurrently, sometimes one disease being a significant risk factor for the other disease. The disease phenotypes themselves are normally the consequence of the cell's inability to breakdown or produce an essential substrate. However, an enzyme defect at one reaction may affect the fluxes of other subsequent reactions. These cascading effects couple the metabolic diseases associated with subsequent reactions resulting in comorbidity effects. Thus, metabolic disease networks can be used to determine if two disorders are connected due to their correlated reactions. | 1 | Applied and Interdisciplinary Chemistry |
Nanoparticles can also be formed using radiation chemistry. Radiolysis from gamma rays can create strongly active free radicals in solution. This relatively simple technique uses a minimum number of chemicals. These including water, a soluble metallic salt, a radical scavenger (often a secondary alcohol), and a surfactant (organic capping agent). High gamma doses on the order of 10 gray are required. In this process, reducing radicals will drop metallic ions down to the zero-valence state. A scavenger chemical will preferentially interact with oxidizing radicals to prevent the re-oxidation of the metal. Once in the zero-valence state, metal atoms begin to coalesce into particles. A chemical surfactant surrounds the particle during formation and regulates its growth. In sufficient concentrations, the surfactant molecules stay attached to the particle. This prevents it from dissociating or forming clusters with other particles. Formation of nanoparticles using the radiolysis method allows for tailoring of particle size and shape by adjusting precursor concentrations and gamma dose. | 0 | Theoretical and Fundamental Chemistry |
Chiral purity is a measure of the purity of a chiral drug. Other synonyms employed include enantiomeric excess, enantiomer purity, enantiomeric purity, and optical purity. Optical purity is an obsolete term since today most of the chiral purity measurements are done using chromatographic techniques (not based on optical principles). Enantiomeric excess tells the extent (in %) to which the chiral substance contains one enantiomer over the other. For a racemic drug the enantiomeric excess will be 0%. There are number of chiral analysis tools such as polarimetry, NMR spectroscopy with the use of chiral shift reagents, chiral GC (gas chromatography), chiral HPLC (high performance liquid chromatography), chiral TLC (thin-layer chromatography) and other chiral chromatographic techniques, that are employed to evaluate chiral purity. Assessing the purity of a unichiral drug or enantiopure drug is of great importance from a drug safety and efficacy perspective. | 0 | Theoretical and Fundamental Chemistry |
Polytetrafluoroethylene (PTFE) is a polymer used in many applications including non-stick coatings, beauty products, and lubricants. PTFE is a hydrophobic molecule composed of carbon and fluorine. Carbon-fluorine bonds cause PTFE to be a low-friction material, conducive in high temperature environments and resistant to stress cracking. These properties cause PTFE to be non-reactive and used in a wide array of applications. | 0 | Theoretical and Fundamental Chemistry |
The Lauritzen–Hoffman plot (right) models the three different regimes when (logG) + U*/k(T-T) is plotted against (TΔT). It can be used to describe the rate at which secondary nucleation competes with lateral addition at the growth front among the different temperatures. This theory can be used to help understand the preferences of nucleation and growth based on the polymer's properties including its standard melting temperature. | 0 | Theoretical and Fundamental Chemistry |
Trabectedin, sold under the brand name Yondelis, is an antitumor chemotherapy medication for the treatment of advanced soft-tissue sarcoma and ovarian cancer.
The most common adverse reactions include nausea, fatigue, vomiting, constipation, decreased appetite, diarrhea, peripheral edema, dyspnea, and headache.
It is sold by Pharma Mar S.A. and Johnson and Johnson. It is approved for use in the European Union, Russia, South Korea and the United States. The European Commission and the U.S. Food and Drug Administration (FDA) granted orphan drug status to trabectedin for soft-tissue sarcomas and ovarian cancer. | 0 | Theoretical and Fundamental Chemistry |
The simplest form of a blast wave has been described and termed the Friedlander waveform. It occurs when a high explosive detonates in a free field, that is, with no surfaces nearby with which it can interact.
Blast waves have properties predicted by the physics of waves. For example, they can diffract through a narrow opening, and refract as they pass through materials. Like light or sound waves, when a blast wave reaches a boundary between two materials, part of it is transmitted, part of it is absorbed, and part of it is reflected. The impedances of the two materials determine how much of each occurs.
The equation for a Friedlander waveform describes the pressure of the blast wave as a function of time:
where P is the peak pressure and t* is the time at which the pressure first crosses the horizontal axis (before the negative phase).
Blast waves will wrap around objects and buildings. Therefore, persons or objects behind a large building are not necessarily protected from a blast that starts on the opposite side of the building. Scientists use sophisticated mathematical models to predict how objects will respond to a blast in order to design effective barriers and safer buildings. | 1 | Applied and Interdisciplinary Chemistry |
Acidogenesis is the second stage in the four stages of anaerobic digestion:
* Hydrolysis: A chemical reaction where particulates are solubilized and large polymers converted into simpler monomers;
* Acidogenesis: A biological reaction where simple monomers are converted into volatile fatty acids;
* Acetogenesis: A biological reaction where volatile fatty acids are converted into acetic acid, carbon dioxide, and hydrogen
* Methanogenesis: A biological reaction where acetates are converted into methane and carbon dioxide, while hydrogen is consumed.
Anaerobic digestion is a complex biochemical process of biologically mediated reactions by a consortium of microorganisms to convert organic compounds into methane and carbon dioxide. It is a stabilization process, reducing odor, pathogens, and mass reduction.
Hydrolytic bacteria form a variety of reduced end-products from the fermentation of a given substrate. One fundamental question that arises concerns the metabolic features that control carbon and electron flow to a given reduced end-product during pure culture and mixed methanogenic cultures of hydrolytic bacteria. Thermoanaerobium brockii is a representative thermophilic, hydrolytic bacterium, which ferments glucose, via the Embden–Meyerhof Parnas Pathway. T. brockii is an atypical hetero-lactic acid bacterium because it forms molecular hydrogen (H), in addition to lactic acid and ethanol. The reduced end-products of glucose fermentation are enzymatically formed from pyruvate, via the following mechanisms: lactate by fructose 1-6 all-phosphate (F6P) activated lactate dehydrogenase; H2 by pyruvate ferredoxin oxidoreductase and hydrogenase; and ethanol via NADH- and NADPH-linked alcohol dehydrogenase.
By its side, the acidogenic activity was found in the early 20th century, but it was not until the mid-1960s that the engineering of phases separation was assumed in order to improve the stability and waste digesters treatment. In this phase, complex molecules (carbohydrates, lipids, and proteins) are depolymerized into soluble compounds by hydrolytic enzymes (cellulases, hemicellulases, amylases, lipases and proteases). The hydrolyzed compounds are fermented into volatile fatty acids (acetate, propionate, butyrate, and lactate), neutral compounds (ethanol, methanol), ammonia, hydrogen and carbon dioxide.
Acetogenesis is one of the main reactions of this stage, in this, the intermediary metabolites produced are metabolized to acetate, hydrogen and carbonic gas by the three main groups of bacteria:
* homoacetogens;
* syntrophes; and
* sulphoreductors.
For the acetic acid production are considered three kind of bacteria:
* Clostridium aceticum;
* Acetobacter woodii; and
* Clostridium termoautotrophicum.
Winter y Wolfe, in 1979, demonstrated that A. woodii in syntrophic association with Methanosarcina produce methane and carbon dioxide from fructose, instead of three molecules of acetate. Moorella thermoacetica and Clostridium formiaceticum are able to reduce the carbonic gas to acetate, but they do not have hydrogenases which inhabilite the hydrogen use, so they can produce three molecules of acetate from fructose. Acetic acid is equally a co-metabolite of the organic substrates fermentation (sugars, glycerol, lactic acid, etc.) by diverse groups of microorganisms which produce different acids:
*Propionic bacteria (propionate + acetate);
* Clostridium (butyrate + acetate);
* Enterobacteria (acetate + lactate); and
* Hetero-fermentative bacteria (acetate, propionate, butyrate, valerate, etc.). | 1 | Applied and Interdisciplinary Chemistry |
There are several ways to retrieve the lost phases. The phase problem must be solved in x-ray crystallography, neutron crystallography, and electron crystallography.
Not all of the methods of phase retrieval work with every wavelength (x-ray, neutron, and electron) used in crystallography. | 0 | Theoretical and Fundamental Chemistry |
Active sensors are sensing devices which contain active components; usually this solution allows for a more precise measurement with respect to passive components.
In fact, a passive receiving antenna collects energy from the electromagnetic field being measured and makes it available at a RF cable connector. This signal then goes to the spectrum analyzer but the field characteristics can be someway modified by the presence of the cable, especially in near-field conditions.
On the other hand, an effective solution is to transfer on an optical carrier, the electric (or magnetic) field component sensed with an active probe.
The basic components of the system are a receiving electro-optical antenna which is able to transfer, on an optical carrier, the individual electric (or magnetic) field component picked up and to return it in the form of an electrical signal at the output port of an opto-electric converter.
The modulated optical carrier is transferred by means of a fiber-optic link to a converter which extracts the modulating signal and converts it back to an electrical signal.
The electrical signal thus obtained can be then sent to a spectrum analyzer with a 50 Ω common RF cable. | 1 | Applied and Interdisciplinary Chemistry |
Flutamide has been used in case reports to decrease the frequency of spontaneous orgasms, for instance in men with post-orgasmic illness syndrome. | 0 | Theoretical and Fundamental Chemistry |
Because of the cumbersome nature of expressing certain dimensionless quantities per SI guidelines, the International Union of Pure and Applied Physics (IUPAP) in 1999 proposed the adoption of the special name "uno" (symbol: U) to represent the number 1 in dimensionless quantities. In 2004, a report to the International Committee for Weights and Measures (CIPM) stated that the response to the proposal of the uno "had been almost entirely negative", and the principal proponent "recommended dropping the idea". To date, the uno has not been adopted by any standards organization. | 1 | Applied and Interdisciplinary Chemistry |
The gas analyzers directly measure concentrations of multiple gas species using mid-infrared laser absorption spectroscopy with QCLs as light sources. This allows for highly specific and accurate gas detection along with maximum measurement sensitivity. | 0 | Theoretical and Fundamental Chemistry |
The structure of β-rhombohedral boron is complicated by the presence of partial occupancies and vacancies. The idealized unit cell, has been shown to be electron-deficient and hence metallic according to theoretical studies, but β-boron is a semiconductor. Application of the Jemmis rule shows that the partial occupancies and vacancies are necessary for electron sufficiency.
can be conceptually divided into a fragment and a () fragment. According to Wades rule, the fragment requires 8 electrons (the icosahedron at the centre (green) requires 2 electrons; each of the six pentagonal pyramids (black and red) completes an icosahedron in the extended structure; as such the electronic requirement for each of them is 1). The or is formed by the condensation of 6 icosahedra and two trigonal bipyramids. Here, m + n + o + p − q' = 8 + 57 + 1 + 0 − 0 = 66 pairs required for stability, but are available. Therefore the fragment has 3 excess electrons and the idealized is missing 5 electrons. The 3 excess electrons in the fragment can be removed by removing one B atom, which leads to (). The requirement of 8 electrons by the fragment can be satisfied by boron atoms and the unit cell contains 48 + 56 + = , which is very close to the experimental result. | 0 | Theoretical and Fundamental Chemistry |
A key feature of this interface is to produce top quality EI spectra from compounds dissolved in a liquid phase. In this case, quality is intended as a measure of the degree of success in a virtual comparison with thousands of spectra stored in the electronic libraries. Identification capability in real-world applications, when peaks are small and noise is high, can be greatly influenced by the quality of ionization. A NIST library version 2.0d was used for comparison. In this case, identification capability is not compromised by the presence of solvent vapor residues and matching quality tops that of a typical GC-MS system. | 0 | Theoretical and Fundamental Chemistry |
In thermodynamics, a departure function is defined for any thermodynamic property as the difference between the property as computed for an ideal gas and the property of the species as it exists in the real world, for a specified temperature T and pressure P. Common departure functions include those for enthalpy, entropy, and internal energy.
Departure functions are used to calculate real fluid extensive properties (i.e. properties which are computed as a difference between two states). A departure function gives the difference between the real state, at a finite volume or non-zero pressure and temperature, and the ideal state, usually at zero pressure or infinite volume and temperature.
For example, to evaluate enthalpy change between two points h(v,T) and h(v,T) we first compute the enthalpy departure function between volume v and infinite volume at T = T, then add to that the ideal gas enthalpy change due to the temperature change from T to T, then subtract the departure function value between v and infinite volume.
Departure functions are computed by integrating a function which depends on an equation of state and its derivative. | 0 | Theoretical and Fundamental Chemistry |
The Federation of the European Biochemical Societies (FEBS) is an international scientific society promoting activities in biochemistry, molecular biology and related research areas in Europe and neighbouring regions. It was founded in 1964 and includes over 35,000 members across 39 Constituent Societies. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, a hemiaminal (also carbinolamine) is a functional group or type of chemical compound that has a hydroxyl group and an amine attached to the same carbon atom: . R can be hydrogen or an alkyl group. Hemiaminals are intermediates in imine formation from an amine and a carbonyl by alkylimino-de-oxo-bisubstitution. Hemiaminals can be viewed as a blend of aminals and geminal diol. They are a special case of amino alcohols. | 0 | Theoretical and Fundamental Chemistry |
There are just 230 different ways of arranging objects in regular three-dimensional arrays. In molecular crystallography, these arrangements are called space groups. However, only 65 of these arrangements are accessible to chiral objects or chiral molecules. The remaining 165 space groups contain either a center of symmetry or a mirror plane and are thus not accessible to natural globular proteins, which are chiral molecules. Wukowitz and Yeates developed a mathematical theory to explain the preference of globular proteins to crystallize in certain space groups. They suggested the preferred space group was determined by the number of degrees of freedom (D) or dimensionality as a measure of the ease with which a given symmetry can be formed. They analyzed the number of degrees of freedom for both chiral and achiral space groups where it was found that the space group P1(bar) with D=8 is theoretically the most dominant space group. Since the achiral space group had a higher degree of freedom compared to the chiral space groups, they predicted that racemic mixtures of protein enantiomers would crystallize more readily compared to the natural L-proteins alone by forming achiral {L-protein plus D-protein} pairs. While space group P1(bar) is most preferred, P21/c and C2/c are also highly preferred, whereas the other achiral space groups are expected to appear less frequently. Hence, P1(bar), P21/c, and C2/c are considered common centrosymmetric space groups in racemic mixtures. | 0 | Theoretical and Fundamental Chemistry |
Compliance constants are the elements of an inverted Hessian matrix. The calculation of compliance constants provides an alternative description of chemical bonds in comparison with the widely used force constants explicitly ruling out the dependency on the coordinate system. They provide the unique description of the mechanical strength for covalent and non-covalent bonding. While force constants (as energy second derivatives) are usually given in aJ/Å or N/cm, compliance constants are given in Å/aJ or Å/mdyn. | 0 | Theoretical and Fundamental Chemistry |
Materials such as starch, cellulose, wood, sugar and biomass are used as a substitute for fossil fuel resources to produce bioplastics; this makes the production of bioplastics a more sustainable activity compared to conventional plastic production. The environmental impact of bioplastics is often debated, as there are many different metrics for "greenness" (e.g., water use, energy use, deforestation, biodegradation, etc.). Hence bioplastic environmental impacts are categorized into nonrenewable energy use, climate change, eutrophication and acidification. Bioplastic production significantly reduces greenhouse gas emissions and decreases non-renewable energy consumption. Firms worldwide would also be able to increase the environmental sustainability of their products by using bioplastics
Although bioplastics save more nonrenewable energy than conventional plastics and emit less greenhouse gasses compared to conventional plastics, bioplastics also have negative environmental impacts such as eutrophication and acidification. Bioplastics induce higher eutrophication potentials than conventional plastics. Biomass production during industrial farming practices causes nitrate and phosphate to filtrate into water bodies; this causes eutrophication, the process in which a body of water gains excessive richness of nutrients. Eutrophication is a threat to water resources around the world since it causes harmful algal blooms that create oxygen dead zones, killing aquatic animals. Bioplastics also increase acidification. The high increase in eutrophication and acidification caused by bioplastics is also caused by using chemical fertilizer in the cultivation of renewable raw materials to produce bioplastics.
Other environmental impacts of bioplastics include exerting lower human and terrestrial ecotoxicity and carcinogenic potentials compared to conventional plastics. However, bioplastics exert higher aquatic ecotoxicity than conventional materials. Bioplastics and other bio-based materials increase stratospheric ozone depletion compared to conventional plastics; this is a result of nitrous oxide emissions during fertilizer application during industrial farming for biomass production. Artificial fertilizers increase nitrous oxide emissions especially when the crop does not need all the nitrogen. Minor environmental impacts of bioplastics include toxicity through using pesticides on the crops used to make bioplastics. Bioplastics also cause carbon dioxide emissions from harvesting vehicles. Other minor environmental impacts include high water consumption for biomass cultivation, soil erosion, soil carbon losses and loss of biodiversity, and they are mainly are a result of land use associated with bioplastics. Land use for bioplastics production leads to lost carbon sequestration and increases the carbon costs while diverting land from its existing uses
Although bioplastics are extremely advantageous because they reduce non-renewable consumption and GHG emissions, they also negatively affect the environment through land and water consumption, using pesticide and fertilizer, eutrophication and acidification; hence one's preference for either bioplastics or conventional plastics depends on what one considers the most important environmental impact.
Another issue with bioplastics, is that some bioplastics are made from the edible parts of crops. This makes the bioplastics compete with food production because the crops that produce bioplastics can also be used to feed people. These bioplastics are called "1st generation feedstock bioplastics".
2nd generation feedstock bioplastics use non-food crops (cellulosic feedstock) or waste materials from 1st generation feedstock (e.g. waste vegetable oil). Third generation feedstock bioplastics use algae as the feedstock. | 0 | Theoretical and Fundamental Chemistry |
Early models to explain the origin of the index of refraction treated an electron in an atomic system classically according to the model of Paul Drude and Hendrik Lorentz. The theory was developed to attempt to provide an origin for the wavelength-dependent refractive index n of a material. In this model, incident electromagnetic waves forced an electron bound to an atom to oscillate. The amplitude of the oscillation would then have a relationship to the frequency of the incident electromagnetic wave and the resonant frequencies of the oscillator. The superposition of these emitted waves from many oscillators would then lead to a wave which moved more slowly. | 0 | Theoretical and Fundamental Chemistry |
It is assumed that the Beer–Lambert law applies.
where is the optical path length, is a molar absorbance at unit path length and is a concentration. More than one of the species may contribute to the absorbance. In principle absorbance may be measured at one wavelength only, but in present-day practice it is common to record complete spectra. | 0 | Theoretical and Fundamental Chemistry |
Conformational isomers exist in a dynamic equilibrium, where the relative free energies of isomers determines the population of each isomer and the energy barrier of rotation determines the rate of interconversion between isomers:
where K is the equilibrium constant, ΔG° is the difference in standard free energy between the two conformers in kcal/mol, R is the universal gas constant (1.987×10 kcal/mol K), and T is the system's temperature in kelvins. In units of kcal/mol at 298 K,
Thus, every 1.36 kcal/mol corresponds to a factor of about 10 in term of equilibrium constant at temperatures around room temperature. (The "1.36 rule" is useful in general for estimation of equilibrium constants at room temperature from free energy differences. At lower temperatures, a smaller energy difference is needed to obtain a given equilibrium constant.)
Three isotherms are given in the diagram depicting the equilibrium distribution of two conformers at different temperatures. At a free energy difference of 0 kcal/mol, this gives an equilibrium constant of 1, meaning that two conformers exist in a 1:1 ratio. The two have equal free energy; neither is more stable, so neither predominates compared to the other. A negative difference in free energy means that a conformer interconverts to a thermodynamically more stable conformation, thus the equilibrium constant will always be greater than 1. For example, the ΔG° for the transformation of butane from the gauche conformer to the anti conformer is −0.47 kcal/mol at 298 K. This gives an equilibrium constant is about 2.2 in favor of the anti conformer, or a 31:69 mixture of gauche:anti conformers at equilibrium. Conversely, a positive difference in free energy means the conformer already is the more stable one, so the interconversion is an unfavorable equilibrium (K < 1). Even for highly unfavorable changes (large positive ΔG°), the equilibrium constant between two conformers can be increased by increasing the temperature, so that the amount of the less stable conformer present at equilibrium increases (although it always remains the minor conformer). | 0 | Theoretical and Fundamental Chemistry |
In chemistry, electron counting is a formalism for assigning a number of valence electrons to individual atoms in a molecule. It is used for classifying compounds and for explaining or predicting their electronic structure and bonding. Many rules in chemistry rely on electron-counting:
*Octet rule is used with Lewis structures for main group elements, especially the lighter ones such as carbon, nitrogen, and oxygen,
*18-electron rule in inorganic chemistry and organometallic chemistry of transition metals,
*Hückel's rule for the π-electrons of aromatic compounds,
*Polyhedral skeletal electron pair theory for polyhedral cluster compounds, including transition metals and main group elements and mixtures thereof, such as boranes.
Atoms are called "electron-deficient" when they have too few electrons as compared to their respective rules, or "hypervalent" when they have too many electrons. Since these compounds tend to be more reactive than compounds that obey their rule, electron counting is an important tool for identifying the reactivity of molecules. While the counting formalism considers each atom separately, these individual atoms (with their hypothetical assigned charge) do not generally exist as free species. | 0 | Theoretical and Fundamental Chemistry |
Geneticist Dean Hamer has suggested that a particular allele of the SLC18A2 gene correlates with spirituality using data from a smoking survey, which included questions intended to measure "self-transcendence". Hamer performed the spirituality study on the side, independently of the National Cancer Institute smoking study. His findings were published in the mass-market book The God Gene: How Faith Is Hard-Wired into Our Genes. Hamer himself notes that SLC18A2 plays at most a minor role in influencing spirituality. Furthermore, Hamers claim that the SLC18A2 gene contributes to spirituality is controversial. Hamers study has not been published in a peer-reviewed journal and a reanalysis of the correlation demonstrates that it is not statistically significant. | 1 | Applied and Interdisciplinary Chemistry |
The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for zinc in 2001. The current EARs for zinc for women and men ages 14 and up is 6.8 and 9.4 mg/day, respectively. The RDAs are 8 and 11 mg/day. RDAs are higher than EARs so as to identify amounts that will cover people with higher than average requirements. RDA for pregnancy is 11 mg/day. RDA for lactation is 12 mg/day. For infants up to 12 months the RDA is 3 mg/day. For children ages 1–13 years the RDA increases with age from 3 to 8 mg/day. As for safety, the IOM sets Tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of zinc the adult UL is 40 mg/day (lower for children). Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).
The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL are defined the same as in the United States. For people ages 18 and older the PRI calculations are complex, as the EFSA has set higher and higher values as the phytate content of the diet increases. For women, PRIs increase from 7.5 to 12.7 mg/day as phytate intake increases from 300 to 1200 mg/day; for men the range is 9.4 to 16.3 mg/day. These PRIs are higher than the U.S. RDAs. The EFSA reviewed the same safety question and set its UL at 25 mg/day, which is much lower than the U.S. value.
For U.S. food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of Daily Value (%DV). For zinc labeling purposes 100% of the Daily Value was 15 mg, but on May 27, 2016, it was revised to 11 mg. A table of the old and new adult daily values is provided at Reference Daily Intake. | 1 | Applied and Interdisciplinary Chemistry |
The same approach that produces an ionization event can be used to access the dense manifold of near-threshold Rydberg states with laser experiments. These experiments often involve a laser operating at one wavelength to access the intermediate Rydberg state and a second wavelength laser to access the near-threshold Rydberg state region. Because of the photoabsorption selection rules, these Rydberg electrons are expected to be in highly elliptical angular momentum states. It is the Rydberg electrons excited to nearly circular angular momentum states that are expected to have the longest lifetimes. The conversion between a highly elliptical and a nearly circular near-threshold Rydberg state might happen in several ways, including encountering small stray electric fields. | 0 | Theoretical and Fundamental Chemistry |
The dissociation mechanism of chlorophenol red is similar to that of phenolphthalein meaning it can be used as a color indicator. The dissociation of hydroxyl and hydrogen atoms creates the dissociate scheme of chlorophenol red to change color from yellow to red. The pH properties of chlorophenol red are used to selectively determine the amount of chlorine dioxide in drinking water. Chlorophenol red selectively reacts with 0.1–1.9 mg/L chlorine dioxide at pH 7. The electrochemical properties of Chlorophenol red allows it to be a chromogenic label and can undergo oxidation creating several phenolic intermediates. The bacterial hydrolysis of a chlorophenol red labelled substrate produces chlorine retaining intermediates on electrodes. | 0 | Theoretical and Fundamental Chemistry |
Hydrogels also possess a degree of flexibility very similar to natural tissue due to their significant water content. As responsive "smart materials", hydrogels can encapsulate chemical systems which upon stimulation by external factors such as a change of pH may cause specific compounds such as glucose to be liberated to the environment, in most cases by a gel–sol transition to the liquid state. Chemomechanical polymers are mostly also hydrogels, which upon stimulation change their volume and can serve as actuators or sensors. | 0 | Theoretical and Fundamental Chemistry |
Signal transduction is a mechanism in which the cell responds to a signal from the environment by activating several proteins and enzymes that will give a response to the signal.
Feedback mechanism might involve negative and positive feedbacks. In the negative feedback, the pathway is inhibited and the result of the transduction pathway is reduced or limited. In positive feedback, the transduction pathway is promoted and stimulated to produce more products. | 1 | Applied and Interdisciplinary Chemistry |
Thermodynamic potentials are functions that characterize the equilibrium state of a substance. An example is the Gibbs free energy , which is a function of pressure and temperature. Knowing any one thermodynamic potential is sufficient to compute all equilibrium properties of a substance, often simply by taking derivatives of . Thus, a single correlation for can replace separate correlations for individual properties. Conversely, a variety of experimental measurements (e.g., density, heat capacity, vapor pressure) can be incorporated into the same fit; in principle, this would allow one to predict hard-to-measure properties like heat capacity in terms of other, more readily available measurements (e.g., vapor pressure). | 0 | Theoretical and Fundamental Chemistry |
The history of metallurgy in the Urals stands out to historians and economists as a separate stage in the history of Russian industry and covers the period from the 4th millennium BC to the present day. The emergence of the mining district is connected with the history of Ural metallurgy. The geography of the Ural metallurgy covers the territories of modern Perm Krai, Sverdlovsk Oblast, Udmurtia, Bashkortostan, Chelyabinsk Oblast and Orenburg Oblast.
In the 18th century, periods of formation and development of industrial metallurgical centers stand out in Urals metallurgy, for example, the rapid construction and economic growth of more than two hundred metallurgy factories during the 18th to the first half of the 19th centuries until the abolition of serfdom on February 19, 1861 in the Russian Empire, which led to reductions in the labor force. There was also a sharp drop in production rates in the early 1900s but that was followed by recovery and growth by 1913. In the 20th century, after recovering from the decline caused by the Russian Revolution(s): 1905, February 1917, and October 1917 and the Russian Civil War (November 1917 - June 1923), Ural metallurgy had a strategic impact on ensuring the defense of the USSR on the Eastern Front of World War II which is known in Russia as the Great Patriotic War. In the 21st century, the development of metallurgical enterprises in the Urals is associated with the formation of vertically integrated full cycle companies.
The main milestones in the development of metal production technologies in the Urals include the transition from bloomery or the old iron production method to the Kontuazsky forge (for remelting heavy scrap) and the puddling method in the second half of the 19th century. Later, there was the development of hot blast at the end of the 19th century. Further, there was a transition to coke fuel and the introduction of steam engines. Finally, there was the development of open-hearth and Bessemer methods of steel production at the beginning of the 20th century. | 1 | Applied and Interdisciplinary Chemistry |
Nutrients dissolved in seawater are essential for the survival of marine life. Nitrogen and phosphorus are particularly important. They are regarded as limiting nutrients in many marine environments, because primary producers, like algae and marine plants, cannot grow without them. They are critical for stimulating primary production by phytoplankton. Other important nutrients are silicon, iron, and zinc.
The process of cycling nutrients in the sea starts with biological pumping, when nutrients are extracted from surface waters by phytoplankton to become part of their organic makeup. Phytoplankton are either eaten by other organisms, or eventually die and drift down as marine snow. There they decay and return to the dissolved state, but at greater ocean depths. The fertility of the oceans depends on the abundance of the nutrients, and is measured by the primary production, which is the rate of fixation of carbon per unit of water per unit time. "Primary production is often mapped by satellites using the distribution of chlorophyll, which is a pigment produced by plants that absorbs energy during photosynthesis. The distribution of chlorophyll is shown in the figure above. You can see the highest abundance close to the coastlines where nutrients from the land are fed in by rivers. The other location where chlorophyll levels are high is in upwelling zones where nutrients are brought to the surface ocean from depth by the upwelling process..."
"Another critical element for the health of the oceans is the dissolved oxygen content. Oxygen in the surface ocean is continuously added across the air-sea interface as well as by photosynthesis; it is used up in respiration by marine organisms and during the decay or oxidation of organic material that rains down in the ocean and is deposited on the ocean bottom. Most organisms require oxygen, thus its depletion has adverse effects for marine populations. Temperature also affects oxygen levels as warm waters can hold less dissolved oxygen than cold waters. This relationship will have major implications for future oceans, as we will see... The final seawater property we will consider is the content of dissolved . is nearly opposite to oxygen in many chemical and biological processes; it is used up by plankton during photosynthesis and replenished during respiration as well as during the oxidation of organic matter. As we will see later, content has importance for the study of deep-water aging." | 0 | Theoretical and Fundamental Chemistry |
Chlorosulfuric acid is a tetrahedral molecule. The formula is more descriptively written SO(OH)Cl, but HSOCl is traditional. It is an intermediate, chemically and conceptually, between sulfuryl chloride (SOCl) and sulfuric acid (HSO). The compound is rarely obtained pure. Upon standing with excess sulfur trioxide, it decomposes to pyrosulfuryl chlorides:
:2 ClSOH + SO → HSO + SOCl | 0 | Theoretical and Fundamental Chemistry |
One of the main applications of static light scattering for molecular mass determination is in the field of macromolecules, such as proteins and polymers, as it is possible to measure the molecular mass of proteins without any assumption about their shape. Static light scattering is usually combined with other particle characterization techniques, such as size-exclusion chromatography (SEC), dynamic light scattering (DLS), and electrophoretic light scattering (ELS). | 0 | Theoretical and Fundamental Chemistry |
Calculating rates of VO and/or VCO requires knowledge of the flow rates into and out of the chamber, plus fractional concentrations of the gas mixtures into and out of the animal chamber. In general, metabolic rates are calculated from steady-state conditions (i.e., animal's metabolic rate is assumed to be constant). To know the rates of oxygen consumed, one needs to know the location of the flow meter relative to the animal chamber (if positioned before the chamber, the flow meter is "upstream," if positioned after the chamber, the flow meter is "downstream"), and whether or not reactive gases are present (e.g., CO, water, methane, see inert gas).
For an open system with upstream flow meter, water (e.g., anhydrous calcium sulfate) and CO removed prior to the oxygen analyzer, a suitable equation is
For an open system with downstream flow meter, water and CO removed prior to the oxygen analyzer, a suitable equation is
where
*FR is the volumetric flow rate adjusted to STP (see Standard conditions for temperature and pressure)
*FO is the fractional amount of oxygen present in the incurrent air stream (the baseline or reference), and
*FO is the fractional amount of oxygen present in the excurrent air stream (what the animal has consumed relative to baseline per unit time).
For example, values for BMR of a 20 g mouse (Mus musculus) might be FR = 200 mL/min, and readings of fractional concentration of O from an oxygen analyzer are FO = 0.2095, FO = 0.2072. The calculated rate of oxygen consumption is 0.58 mL/min or 35 mL/hour. Assuming an enthalpy of combustion for O of 20.1 joules per milliliter, we would then calculate the heat production (and therefore metabolism) for the mouse as 703.5 J/h. | 1 | Applied and Interdisciplinary Chemistry |
Planktonic copepods are important to global ecology and the carbon cycle. They are usually the dominant members of the zooplankton, and are major food organisms for small fish such as the dragonet, banded killifish, Alaska pollock, and other crustaceans such as krill in the ocean and in fresh water. Some scientists say they form the largest animal biomass on earth. Copepods compete for this title with Antarctic krill (Euphausia superba). C. glacialis inhabits the edge of the Arctic icepack, especially in polynyas where light (and photosynthesis) is present, in which they alone comprise up to 80% of zooplankton biomass. They bloom as the ice recedes each spring. The ongoing large reduction in the annual ice pack minimum may force them to compete in the open ocean with the much less nourishing C. finmarchicus, which is spreading from the North Sea and the Norwegian Sea into the Barents Sea.
Because of their smaller size and relatively faster growth rates, and because they are more evenly distributed throughout more of the worlds oceans, copepods almost certainly contribute far more to the secondary productivity of the worlds oceans, and to the global ocean carbon sink than krill, and perhaps more than all other groups of organisms together. The surface layers of the oceans are believed to be the world's largest carbon sink, absorbing about 2 billion tons of carbon a year, the equivalent to perhaps a third of human carbon emissions, thus reducing their impact. Many planktonic copepods feed near the surface at night, then sink (by changing oils into more dense fats) into deeper water during the day to avoid visual predators. Their moulted exoskeletons, faecal pellets, and respiration at depth all bring carbon to the deep sea.
About half of the estimated 14,000 described species of copepods are parasitic
and many have adapted extremely modified bodies for their parasitic lifestyles.
They attach themselves to bony fish, sharks, marine mammals, and many kinds of invertebrates such as corals, other crustaceans, molluscs, sponges, and tunicates. They also live as ectoparasites on some freshwater fish. | 1 | Applied and Interdisciplinary Chemistry |
Glucose is mainly metabolized by a very important ten-step pathway called glycolysis, the net result of which is to break down one molecule of glucose into two molecules of pyruvate. This also produces a net two molecules of ATP, the energy currency of cells, along with two reducing equivalents of converting NAD (nicotinamide adenine dinucleotide: oxidized form) to NADH (nicotinamide adenine dinucleotide: reduced form). This does not require oxygen; if no oxygen is available (or the cell cannot use oxygen), the NAD is restored by converting the pyruvate to lactate (lactic acid) (e.g. in humans) or to ethanol plus carbon dioxide (e.g. in yeast). Other monosaccharides like galactose and fructose can be converted into intermediates of the glycolytic pathway. | 1 | Applied and Interdisciplinary Chemistry |
Lake Okeechobee is an ideal habitat for cyanobacteria because its shallow, sunny, and laden with nutrients from Floridas agriculture. The Okeechobee Waterway connects the lake to the Atlantic Ocean and the Gulf of Mexico through the St. Lucie River and the Caloosahatchee respectively. This means that harmful algal blooms are carried down the estuaries as water is released during the wet summer months. In July 2018 up to 90% of Lake Okeechobee was covered in algae. Water draining from the lake filled the region with a noxious odor and caused respiratory problems in some humans during the following month. To make matters worse, harmful red tide blooms are historically common on Floridas coasts during these same summer months. Cyanobacteria in the rivers die as they reach saltwater but their nitrogen fixation feeds the red tide on the coast. Areas at the mouth of the estuaries such as Cape Coral and Port St. Lucie therefore experience the compounded effects of both types of harmful algal bloom. Cleanup crews hired by authorities in Lee County - where the Caloosahatchee meets the Gulf of Mexico - removed more than 1700 tons of dead marine life in August 2018. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, molecularity is the number of molecules that come together to react in an elementary (single-step) reaction and is equal to the sum of stoichiometric coefficients of reactants in the elementary reaction with effective collision (sufficient energy) and correct orientation.
Depending on how many molecules come together, a reaction can be unimolecular, bimolecular or even trimolecular.
The kinetic order of any elementary reaction or reaction step is equal to its molecularity, and the rate equation of an elementary reaction can therefore be determined by inspection, from the molecularity.
The kinetic order of a complex (multistep) reaction, however, is not necessarily equal to the number of molecules involved. The concept of molecularity is only useful to describe elementary reactions or steps. | 0 | Theoretical and Fundamental Chemistry |
SCORE is especially used as detection method in bio- and chemosensors. It is a label-free technique like Reflectometric interference spectroscopy (RIfS), Bio-layer Interferometry (BLI) and Surface plasmon resonance (SPR), which allows time-resolved observation of binding events on the sensor surface without the use of fluorescence or radioactive labels.
The SCORE technology was commercialised by Biametrics GmbH, a service provider and instrument manufacturer with headquarters in Tübingen, Germany. In January 2020, Biametrics GmbH and its technology was acquired by BioCopy Holding AG, headquartered in Aadorf, Switzerland. | 0 | Theoretical and Fundamental Chemistry |
The majority of benzylic functionalization reactions of tricarbonyl(arene)chromium complexes proceed by mechanisms analogous to those followed by the free arenes. The aromatic ring and benzylic position are activated towards solvolysis, deprotonation, and nucleophilic attack (at the ortho and para positions of the arene) upon complexation to chromium, which is able to stabilize developing charges in the arene ligand. As a result, these reactions of chromium arene complexes are often faster than analogous reactions of free arenes.
Second, in benzylic cations and anions of chromium arene complexes, rotation about the bond connecting the benzylic carbon and aromatic ring is severely restricted. This bond possesses a significant amount of double bond character due to the delocalization of charge into the aromatic ring (and the stabilization of that charge by chromium).
Finally, the chromium tri(carbonyl) moiety serves as a sterically bulky group in reactions of arene chromium complexes, preventing the approach of a reagent endo to chromium. In addition, ortho-substituted aromatic aldehydes and styrenes prefer to adopt a conformation in which the doubly bound oxygen or carbon is pointed away from the ortho substituent. As a result, only one face of the double bond is exposed on the exo face of the aromatic ring. If this were not the case, addition to styrenes and aromatic aldehydes would not be diastereoselective, despite the presence of the chromium tri(carbonyl) group. The ortho substituent is necessary for high stereoselectivity; meta-substituted arenes exhibit very low diastereoselectivity. | 0 | Theoretical and Fundamental Chemistry |
ATR systems offer flue gas cleanup and emissions performance that meet or exceed the strictest clean air laws in the United States and the European Union. Emissions from an ATR plant contain fewer metals, dioxins and conventional pollutants than other EfW approaches.
ATR systems increase a facility’s "diversion rate" – the percentage of materials coming into plants that are destroyed or converted to energy and useful byproducts. Most EfW plants in the US, after incineration and recovery of some metals, combine both bottom ash and fly ash (20-25% of MSW input by weight) and send it to a landfill. ATR systems, by contrast, landfill less than 2 percent of a plant’s MSW input; all remaining MSW is converted into either energy or usable products. | 1 | Applied and Interdisciplinary Chemistry |
The first total synthesis of carpanone was the biomimetic approach published by Chapman et al. in 1971. The required desmethylcarpacin (2-allylsesamol), shown below as the starting molecule in the scheme, is acquired in two high-yield steps involving three transformations:
* allylation of the phenolic anion generated after treatment of sesamol with potassium carbonate and allyl bromide,
* followed by a thermal Claisen rearrangement to move the O-allyl group onto the adjacent site on the aromatic ring, and then
* thermal isomerization of the Claisen product, to move the terminal olefin (alkene) into conjugation with the ring (with e.g., potassium tert-butoxide as base).
This procedure is one of several that gives the required desmethylcarpacin (carpacin with the methyl of its methoxy group removed). Though oxidative dimerizations of phenols normally used a 1-electron oxidant, Chapman then followed a precedent involving a 2-electron oxidant and treated desmethylcarpacin with PdCl in the presence of sodium acetate (e.g., dissolved in a mixture of methanol and water); the reaction was perceived to proceed via a complexation of a pair of carpacins to the Pd(II) metal via their phenolic anions (as shown in scheme, below right), followed by a classic 8-8 (β-β) oxidative phenolic coupling of the two olefin tails—shown crossing in the image—to give a dimeric trans-ortho-quinone methide-type of lignan intermediate. A particular conformation of this dimer then places a 4-electron enone of one ring over the 2-electron enol of the other (shown adjacent in image for clarity), setting the state for a variant of the Diels-Alder reaction termed an inverse demand Diels-Alder reaction (see curved arrows in image), which closes the 2 new rings and generates the 5 contiguous stereocenters. The carpanone is produced in yields of ≈50% by the original method, and in yields >90% in modern variants (see below). The synthesis of a single diastereomer was confirmed in the original Chapman work, using X-ray crystallography.
For the elegance of its "one-pot construction of a tetracyclic scaffold with complete stereocontrol of five contiguous stereo centers", the original Chapman design and synthesis is "[n]ow considered a classic in total synthesis" that "highlights the power of biomimetic synthesis". | 0 | Theoretical and Fundamental Chemistry |
The leukotriene (LT) receptors are G protein-coupled receptors that bind and are activated by the leukotrienes. They include the following proteins:
* Leukotriene B4 receptors (BLTRs) – bind to and are activated by LTB4:
** BLT (Leukotriene B receptor 1) –
** BLT (Leukotriene B receptor 2) –
* Cysteinyl leukotriene receptors (CysLTRs) – bind to and are activated by LTC4, LTD4, and LTE4:
** CysLT (Cysteinyl leukotriene receptor 1) –
** CysLT (Cysteinyl leukotriene receptor 2) –
The recently elucidated CysLT, represented by GPR99/OXGR1, may constitute a third CysLTR. | 1 | Applied and Interdisciplinary Chemistry |
In certain enzymatic processes, redox non-innocent cofactors provide redox equivalents to complement the redox properties of metalloenzymes. Of course, most redox reactions in nature involve innocent systems, e.g. [[ferrodoxin|[4Fe-4S] clusters]]. The additional redox equivalents provided by redox non-innocent ligands are also used as controlling factors to steer homogeneous catalysis. | 0 | Theoretical and Fundamental Chemistry |
An artificial metalloenzyme (ArM) is a metalloprotein made in the laboratory which cannot be found in the nature and can catalyze certain desired chemical reactions. Despite fitting into classical enzyme categories, ArMs also have potential in chemical reactivity like catalyzing Suzuki coupling, metathesis and so on, which are never reported in natural enzymatic reaction. With the progress in organometallic synthesis and protein engineering, more and more new kind of design of ArMs came out, showing promising future in both academia and industrial aspects.
In 2018, one half of the Nobel Prize in Chemistry was awarded to Frances H. Arnold “for the directed evolution of enzymes”, which elegantly evolved the artificial metalloenzymes to realize efficient and highly selective abiotic chemical reaction in vitro and in vivo. | 0 | Theoretical and Fundamental Chemistry |
ATP consists of an adenine attached by the 9-nitrogen atom to the 1′ carbon atom of a sugar (ribose), which in turn is attached at the 5' carbon atom of the sugar to a triphosphate group. In its many reactions related to metabolism, the adenine and sugar groups remain unchanged, but the triphosphate is converted to di- and monophosphate, giving respectively the derivatives ADP and AMP. The three phosphoryl groups are labeled as alpha (α), beta (β), and, for the terminal phosphate, gamma (γ).
In neutral solution, ionized ATP exists mostly as ATP, with a small proportion of ATP. | 1 | Applied and Interdisciplinary Chemistry |
Peptidoglycan or murein is a unique large macromolecule, a polysaccharide, consisting of sugars and amino acids that forms a mesh-like peptidoglycan layer (sacculus) that surrounds the bacterial cytoplasmic membrane. The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). Attached to the N-acetylmuramic acid is an oligopeptide chain made of three to five amino acids. The peptide chain can be cross-linked to the peptide chain of another strand forming the 3D mesh-like layer. Peptidoglycan serves a structural role in the bacterial cell wall, giving structural strength, as well as counteracting the osmotic pressure of the cytoplasm. This repetitive linking results in a dense peptidoglycan layer which is critical for maintaining cell form and withstanding high osmotic pressures, and it is regularly replaced by peptidoglycan production. Peptidoglycan hydrolysis and synthesis are two processes that must occur in order for cells to grow and multiply, a technique carried out in three stages: clipping of current material, insertion of new material, and re-crosslinking of existing material to new material.
The peptidoglycan layer is substantially thicker in Gram-positive bacteria (20 to 80 nanometers) than in Gram-negative bacteria (7 to 8 nanometers). Depending on pH growth conditions, the peptidoglycan forms around 40 to 90% of the cell wall's dry weight of Gram-positive bacteria but only around 10% of Gram-negative strains. Thus, presence of high levels of peptidoglycan is the primary determinant of the characterisation of bacteria as Gram-positive. In Gram-positive strains, it is important in attachment roles and serotyping purposes. For both Gram-positive and Gram-negative bacteria, particles of approximately 2 nm can pass through the peptidoglycan.
It is difficult to tell whether an organism is gram-positive or gram-negative using a microscope; Gram staining, created by Hans Christian Gram in 1884, is required. The bacteria are stained with several dyes such as crystal violet, iodine alcohol, and safranin. Gram positive cells are purple after staining, while Gram negative cells stain pink. | 1 | Applied and Interdisciplinary Chemistry |
The maximum wave steepness, for periodic and propagating deep-water waves, is , so the wave height is about one-seventh () of the wavelength λ. And surface gravity waves of this maximum height have a sharp wave crest – with an angle of 120° (in the fluid domain) – also for finite depth, as shown by Stokes in 1880.
An accurate estimate of the highest wave steepness in deep water () was already made in 1893, by John Henry Michell, using a numerical method. A more detailed study of the behaviour of the highest wave near the sharp-cornered crest has been published by Malcolm A. Grant, in 1973. The existence of the highest wave on deep water with a sharp-angled crest of 120° was proved by John Toland in 1978. The convexity of η(x) between the successive maxima with a sharp-angled crest of 120° was independently proven by C.J. Amick et al. and Pavel I. Plotnikov in 1982
The highest Stokes wave – under the action of gravity – can be approximated with the following simple and accurate representation of the free surface elevation η(x,t):
with
for
and shifted horizontally over an integer number of wavelengths to represent the other waves in the regular wave train. This approximation is accurate to within 0.7% everywhere, as compared with the "exact" solution for the highest wave.
Another accurate approximation – however less accurate than the previous one – of the fluid motion on the surface of the steepest wave is by analogy with the swing of a pendulum in a grandfather clock.
Large library of Stokes waves computed with high precision for the case of infinite depth, represented with high accuracy (at least 27 digits after decimal point) as a Padé approximant can be found at StokesWave.org | 1 | Applied and Interdisciplinary Chemistry |
With radioligand therapy, there is always the risk of damage to non-cancerous surrounding tissues along with radioisotope toxicity which is always a challenge in determining how to administer and create the radioligand. Furthermore, the radioligand vial is only viable for a limited time and under specific conditions which challenges transport and storage along with feasible application to the patient.
Another limitation is the lack of centers that have trained personnel and equipment for radioligand therapy. Furthermore, individual characteristics affect the exact radiosensitivity to the therapy (thus affecting dosimetry) and are hard to predict without radiobiological models. | 1 | Applied and Interdisciplinary Chemistry |
TIChE was established to force the chemical engineering professional certificate isolated from the industrial engineering. The conference in 1990 was the first effort to establish the organization by the cooperation of Department of Chemical Engineering and Department of Chemical Technology, Chulalongkorn University, and Department of Chemical Engineering, King Mongkut's University of Technology Thonburi. In the 4th conference at Khon Kaen University, 1994, TIChE was formally established and permitted by law on November 15, 1996. Now, TIChE composes 18 university members. | 1 | Applied and Interdisciplinary Chemistry |
Metabolic regulation achieves a balance between the rate of input of a substrate and the rate that it is degraded or converted, and thus maintains steady state. The rate of metabolic flow, or flux, is variable and subject to metabolic demands. However, in a metabolic pathway, steady state is maintained by balancing the rate of substrate provided by a previous step and the rate that the substrate is converted into product, keeping substrate concentration relatively constant.
Thermodynamically speaking, living organisms are open systems, meaning that they constantly exchange matter and energy with their surroundings. A constant supply of energy is required for maintaining steady state, as maintaining a constant concentration of a molecule preserves internal order and thus is entropically unfavorable. When a cell dies and no longer utilizes energy, its internal composition will proceed toward equilibrium with its surroundings.
In some occurrences, it is necessary for cells to adjust their internal composition in order to reach a new steady state. Cell differentiation, for example, requires specific protein regulation that allows the differentiating cell to meet new metabolic requirements. | 0 | Theoretical and Fundamental Chemistry |
After protein amino acid sequences have been translated from nucleic acid chains, they can be edited by appropriate enzymes. Although this is a form of protein affecting protein sequence, not explicitly covered by the central dogma, there are not many clear examples where the associated concepts of the two fields have much to do with each other. | 1 | Applied and Interdisciplinary Chemistry |
Specific speed N, is used to characterize turbomachinery speed. Common commercial and industrial practices use dimensioned versions which are of equal utility. Specific speed is most commonly used in pump applications to define the suction specific speed [http://nptel.ac.in/courses/112104117/chapter_1/1_7.html]—a quasi non-dimensional number that categorizes pump impellers as to their type and proportions. In Imperial units it is defined as the speed in revolutions per minute at which a geometrically similar impeller would operate if it were of such a size as to deliver one gallon per minute against one foot of hydraulic head. In metric units flow may be in l/s or m/s and head in m, and care must be taken to state the units used.
Performance is defined as the ratio of the pump or turbine against a reference pump or turbine, which divides the actual performance figure to provide a unitless figure of merit. The resulting figure would more descriptively be called the "ideal-reference-device-specific performance." This resulting unitless ratio may loosely be expressed as a "speed," only because the performance of the reference ideal pump is linearly dependent on its speed, so that the ratio of [device-performance to reference-device-performance] is also the increased speed at which the reference device would need to operate, in order to produce the performance, instead of its reference speed of "1 unit."
Specific speed is an index used to predict desired pump or turbine performance. i.e. it predicts the general shape of a pumps impeller. It is this impellers "shape" that predicts its flow and head characteristics so that the designer can then select a pump or turbine most appropriate for a particular application. Once the desired specific speed is known, basic dimensions of the unit's components can be easily calculated.
Several mathematical definitions of specific speed (all of them actually ideal-device-specific) have been created for different devices and applications. | 1 | Applied and Interdisciplinary Chemistry |
Many of the islands along the Azerbaijani coast retain great geopolitical and economic importance for demarcation-line oil fields relying on their national status. Bulla Island, Pirallahı Island, and Nargin, which is still used as a former Soviet base and is the largest island in the Baku bay, hold oil reserves.
The collapse of the Soviet Union allowed the market opening of the region. This led to intense investment and development by international oil companies. In 1998, Dick Cheney commented that "I cant think of a time when weve had a region emerge as suddenly to become as strategically significant as the Caspian."
A key problem to further local development is arriving at precise, agreed demarcation lines among the five littoral states. The current disputes along Azerbaijan's maritime borders with Turkmenistan and Iran could impinge future development.
Much controversy currently exists over the proposed Trans-Caspian oil and gas pipelines. These projects would allow Western markets easier access to Kazakh oil and, potentially, Uzbek and Turkmen gas as well. Russia officially opposes the project on environmental grounds. However, analysts note that the pipelines would bypass Russia completely, thereby denying the country valuable transit fees, as well as destroying its current monopoly on westward-bound hydrocarbon exports from the region. Recently, both Kazakhstan and Turkmenistan have expressed their support for the Trans-Caspian Pipeline.
Leaked U.S. diplomatic cables revealed that BP covered up a gas leak and blowout incident in September 2008 at an operating gas field in the Azeri-Chirag-Guneshi area of the Azerbaijan Caspian Sea. | 1 | Applied and Interdisciplinary Chemistry |
Through negative feedback inhibition, the end-products UTP and UDP prevent the enzyme CAD from catalyzing the reaction in animals. Conversely, PRPP and ATP act as positive effectors that enhance the enzyme's activity. | 1 | Applied and Interdisciplinary Chemistry |
In the case that the fluid is irrotational, that is , we can then write and thus write our equations of motion as
The second equation tells us that
And the use of this equation in the continuity equation tells us that
This simplifies to
Thus the velocity potential obeys the wave equation in the limit of small disturbances. The boundary conditions required to solve for the potential come from the fact that the velocity of the fluid must be 0 normal to the fixed surfaces of the system.
Taking the time derivative of this wave equation and multiplying all sides by the unperturbed density, and then using the fact that tells us that
Similarly, we saw that . Thus we can multiply the above equation appropriately and see that
Thus, the velocity potential, pressure, and density all obey the wave equation. Moreover, we only need to solve one such equation to determine all other three. In particular, we have | 1 | Applied and Interdisciplinary Chemistry |
Huang Weiyuan (; December 15, 1921 – November 17, 2015) was a Chinese organic chemist and an academician of the Chinese Academy of Sciences. He served as President of the Shanghai Institute of Organic Chemistry and President of the Chinese Chemical Society. | 0 | Theoretical and Fundamental Chemistry |
Still another type of photochemical reaction is the di--methane rearrangement. Two further early examples were the rearrangement of 1,1,5,5-tetraphenyl-3,3-dimethyl-1,4-pentadiene (the "Mariano" molecule) and the rearrangement of barrelene to semibullvalene. We note that, in contrast to the cyclohexadienone reactions which used n-* excited states, the di--methane rearrangements utilize -* excited states. | 0 | Theoretical and Fundamental Chemistry |
Pitting corrosion, or pitting, is a form of extremely localized corrosion that leads to the random creation of small holes in metal. The driving power for pitting corrosion is the depassivation of a small area, which becomes anodic (oxidation reaction) while an unknown but potentially vast area becomes cathodic (reduction reaction), leading to very localized galvanic corrosion. The corrosion penetrates the mass of the metal, with a limited diffusion of ions.
Another term arises, pitting factor, which is defined as the ratio of the depth of the deepest pit (resulting due to corrosion) to the average penetration, which can be calculated based on the weight loss. | 1 | Applied and Interdisciplinary Chemistry |
To give a simple illustration of physisorption, we can first consider an adsorbed hydrogen atom in front of a perfect conductor, as shown in Fig. 1. A nucleus with positive charge is located at R = (0, 0, Z), and the position coordinate of its electron, r = (x, y, z) is given with respect to the nucleus. The adsorption process can be viewed as the interaction between this hydrogen atom and its image charges of both the nucleus and electron in the conductor. As a result, the total electrostatic energy is the sum of attraction and repulsion terms:
The first term is the attractive interaction of nucleus and its image charge, and the second term is due to the interaction of the electron and its image charge. The repulsive interaction is shown in the third and fourth terms arising from the interaction between the nucleus and the image electron, and, the interaction between the electron and the image nucleus, respectively.
By Taylor expansion in powers of |r| / |R|, this interaction energy can be further expressed as:
One can find from the first non-vanishing term that the physisorption potential depends on the distance Z between adsorbed atom and surface as Z, in contrast with the r dependence of the molecular van der Waals potential, where r is the distance between two dipoles. | 0 | Theoretical and Fundamental Chemistry |
In the solvent extraction a mixture of an extractant in a diluent is used to extract a metal from one phase to another. In solvent extraction this mixture is often referred to as the "organic" because the main constituent (diluent) is some type of oil.
The PLS (pregnant leach solution) is mixed to emulsification with the stripped organic and allowed to separate. The metal will be exchanged from the PLS to the organic they are modified. The resulting streams will be a loaded organic and a raffinate. When dealing with electrowinning, the loaded organic is then mixed to emulsification with a lean electrolyte and allowed to separate. The metal will be exchanged from the organic to the electrolyte. The resulting streams will be a stripped organic and a rich electrolyte. The organic stream is recycled through the solvent extraction process while the aqueous streams cycle through leaching and electrowinning processes respectively. | 1 | Applied and Interdisciplinary Chemistry |
Creating a genetically modified organism (GMO) is a multi-step process. Genetic engineers must isolate the gene they wish to insert into the host organism. This gene can be taken from a cell or artificially synthesized. If the chosen gene or the donor organism's genome has been well studied it may already be accessible from a genetic library. The gene is then combined with other genetic elements, including a promoter and terminator region and a selectable marker.
A number of techniques are available for inserting the isolated gene into the host genome. Bacteria can be induced to take up foreign DNA, usually by exposed heat shock or electroporation. DNA is generally inserted into animal cells using microinjection, where it can be injected through the cells nuclear envelope directly into the nucleus, or through the use of viral vectors. In plants the DNA is often inserted using Agrobacterium'-mediated recombination, biolistics or electroporation.
As only a single cell is transformed with genetic material, the organism must be regenerated from that single cell. In plants this is accomplished through tissue culture. In animals it is necessary to ensure that the inserted DNA is present in the embryonic stem cells. Further testing using PCR, Southern hybridization, and DNA sequencing is conducted to confirm that an organism contains the new gene.
Traditionally the new genetic material was inserted randomly within the host genome. Gene targeting techniques, which creates double-stranded breaks and takes advantage on the cells natural homologous recombination repair systems, have been developed to target insertion to exact locations. Genome editing uses artificially engineered nucleases that create breaks at specific points. There are four families of engineered nucleases: meganucleases, zinc finger nucleases, transcription activator-like effector nucleases (TALENs), and the Cas9-guideRNA system (adapted from CRISPR). TALEN and CRISPR are the two most commonly used and each has its own advantages. TALENs have greater target specificity, while CRISPR is easier to design and more efficient. | 1 | Applied and Interdisciplinary Chemistry |
The internal elements of a valve are collectively referred to as a valve's trim. According to API Standards 600, "Steel Gate Valve-Flanged and Butt-welding Ends, Bolted Bonnets", the trim consists of stem, seating surface in the body, gate seating surface, bushing or a deposited weld for the backseat and stem hole guide, and small internal parts that normally contact the service fluid, excluding the pin that is used to make a stem-to-gate connection (this pin shall be made of an austenitic stainless steel material). | 1 | Applied and Interdisciplinary Chemistry |
In biology, energy homeostasis, or the homeostatic control of energy balance, is a biological process that involves the coordinated homeostatic regulation of food intake (energy inflow) and energy expenditure (energy outflow). The human brain, particularly the hypothalamus, plays a central role in regulating energy homeostasis and generating the sense of hunger by integrating a number of biochemical signals that transmit information about energy balance. Fifty percent of the energy from glucose metabolism is immediately converted to heat.
Energy homeostasis is an important aspect of bioenergetics. | 1 | Applied and Interdisciplinary Chemistry |
Early mining operations often did not take adequate steps to make tailings areas environmentally safe after closure. Modern mines, particularly those in jurisdictions with well-developed mining regulations and those operated by responsible mining companies, often include the rehabilitation and proper closure of tailings areas in their costs and activities. For example, the Province of Quebec, Canada, requires not only the submission of a closure plan before the start of mining activity, but also the deposit of a financial guarantee equal to 100% of the estimated rehabilitation costs. Tailings dams are often the most significant environmental liability for a mining project.
Mine tailings may have economic value in carbon sequestration due to the large exposed surface area of the minerals. | 1 | Applied and Interdisciplinary Chemistry |
When combining a passive daytime radiative cooling system with thermal insulation and evaporative cooling, one study found a 300% increase in ambient cooling power when compared to a stand-alone radiative cooling surface, which could extend the shelf life of food by 40% in humid climates and 200% in desert climates without refrigeration. The system's evaporative cooling layer would require water "re-charges" every 10 days to a month in humid areas and every 4 days in hot and dry areas. | 0 | Theoretical and Fundamental Chemistry |
Pauling's rules are five rules published by Linus Pauling in 1929 for predicting and rationalizing the crystal structures of ionic compounds. | 0 | Theoretical and Fundamental Chemistry |
New technology has been developed to wind rubber and reinforcement layers on the (cylindrical or bellows-shaped) mandrel automatically using industrial robots instead of manual wrapping. This is fast and accurate and provides repeatable high quality. Another aspect of using industrial robots for the production of rubber expansion joints is the possibility to apply an individual reinforcement layer instead of using pre-woven fabric. The fabric reinforcement is pre-woven and cut at the preferred bias angle. With individual reinforcement it is possible to add more or less fiber material at different sections of the product by changing the fiber angles over the length of the product. | 1 | Applied and Interdisciplinary Chemistry |
Quantum photoelectrochemistry is the investigation of the quantum mechanical nature of photoelectrochemistry, the subfield of study within physical chemistry concerned with the interaction of light with electrochemical systems, typically through the application of quantum chemical calculations. Quantum photoelectrochemistry provides an expansion of quantum electrochemistry to processes involving also the interaction with light (photons). It therefore also includes essential elements of photochemistry. Key aspects of quantum photoelectrochemistry are calculations of optical excitations, photoinduced electron and energy transfer processes, excited state evolution, as well as interfacial charge separation and charge transport in nanoscale energy conversion systems.
Quantum photoelectrochemistry in particular provides fundamental insight into basic light-harvesting and photoinduced electro-optical processes in several emerging solar energy conversion technologies for generation of both electricity (photovoltaics) and solar fuels. Examples of such applications where quantum photoelectrochemistry provides insight into fundamental processes include photoelectrochemical cells, semiconductor photochemistry, as well as light-driven electrocatalysis in general, and artificial photosynthesis in particular.
Quantum photoelectrochemistry constitutes an active line of current research, with several publications appearing in recent years that relate to several different types of materials and processes, including light-harvesting complexes, light-harvesting polymers, as well as nanocrystalline semiconductor materials. | 0 | Theoretical and Fundamental Chemistry |
* In Chesapeake Shores, the O'Brien family lives in a small town in the Bay, not far from Baltimore.
* In MeatEater by Steven Rinella, Season 8, Episode 3-4 "Ghosts of the Chesapeake" features the Chesapeake Bay eastern shore. | 1 | Applied and Interdisciplinary Chemistry |
C/EBPβ and δ are transiently induced during the early stages of adipocyte differentiation (adipogenesis), while C/EBPα is upregulated during the terminal stages of adipogenesis. In vitro and in vivo studies have demonstrated that each plays an important role in this process. For example, Murine Embryonic Fibroblasts (MEFs) from mice lacking both C/EBPβ and C/EBPδ show impaired adipocyte differentiation in response to adipogenic stimuli. In contrast, ectopic expression of C/EBPβ and δ in 3T3-L1 preadipocytes promotes adipogenesis, even in the absence of adipogenic stimuli. C/EBPβ and δ promote adipogenesis, at least in part by inducing the expression of the "master" adipogenic transcription factors C/EBPα and PPARγ.
C/EBPα is required both for adipogenesis and for normal adipocyte function. For example, mice lacking C/EBPα in all tissues except the liver (where it is needed to avoid postnatal lethality) show abnormal adipose tissue formation. Moreover, ectopic expression of C/EBPα in various fibroblast cell lines promotes adipogenesis. C/EBPα probably promotes adipogenesis by inducing the expression of PPARγ. | 1 | Applied and Interdisciplinary Chemistry |
Polychlorinated biphenyls have been discovered in organisms living in the Mariana trench in the Pacific Ocean. Levels were as high as 1,900 nanograms per gram of amphipod tissue in the organisms analyzed. | 1 | Applied and Interdisciplinary Chemistry |
The refrigeration capacity of a refrigeration system is the product of the evaporators enthalpy rise and the evaporators mass flow rate. The measured capacity of refrigeration is often dimensioned in the unit of kW or BTU/h. Domestic and commercial refrigerators may be rated in kJ/s, or Btu/h of cooling. For commercial and industrial refrigeration systems, the kilowatt (kW) is the basic unit of refrigeration, except in North America, where both ton of refrigeration and BTU/h are used.
A refrigeration systems coefficient of performance (CoP) is very important in determining a systems overall efficiency. It is defined as refrigeration capacity in kW divided by the energy input in kW. While CoP is a very simple measure of performance, it is typically not used for industrial refrigeration in North America. Owners and manufacturers of these systems typically use performance factor (PF). A systems PF is defined as a systems energy input in horsepower divided by its refrigeration capacity in TR. Both CoP and PF can be applied to either the entire system or to system components. For example, an individual compressor can be rated by comparing the energy needed to run the compressor versus the expected refrigeration capacity based on inlet volume flow rate. It is important to note that both CoP and PF for a refrigeration system are only defined at specific operating conditions, including temperatures and thermal loads. Moving away from the specified operating conditions can dramatically change a system's performance.
Air conditioning systems used in residential application typically use SEER (Seasonal Energy Efficiency Ratio)for the energy performance rating. Air conditioning systems for commercial application often use EER (Energy Efficiency Ratio) and IEER (Integrated Energy Efficiency Ratio) for the energy efficiency performance rating. | 0 | Theoretical and Fundamental Chemistry |
The first reported steps towards the discovery of the shape-memory effect were taken in the 1930s. According to Otsuka and Wayman, Arne Ölander discovered the pseudoelastic behavior of the Au-Cd alloy in 1932. Greninger and Mooradian (1938) observed the formation and disappearance of a martensitic phase by decreasing and increasing the temperature of a Cu-Zn alloy. The basic phenomenon of the memory effect governed by the thermoelastic behavior of the martensite phase was widely reported a decade later by Kurdjumov and Khandros (1949) and also by Chang and Read (1951).
The nickel-titanium alloys were first developed in 1962–1963 by the United States Naval Ordnance Laboratory and commercialized under the trade name Nitinol (an acronym for Nickel Titanium Naval Ordnance Laboratories). Their remarkable properties were discovered by accident. A sample that was bent out of shape many times was presented at a laboratory management meeting. One of the associate technical directors, Dr. David S. Muzzey, decided to see what would happen if the sample was subjected to heat and held his pipe lighter underneath it. To everyone's amazement the sample stretched back to its original shape.
There is another type of SMA, called a ferromagnetic shape-memory alloy (FSMA), that changes shape under strong magnetic fields. These materials are of particular interest as the magnetic response tends to be faster and more efficient than temperature-induced responses.
Metal alloys are not the only thermally-responsive materials; shape-memory polymers have also been developed, and became commercially available in the late 1990s. | 1 | Applied and Interdisciplinary Chemistry |
Some provitamins are:
* "Provitamin A" is a name for β-carotene, which has only about 1/6 the biological activity of retinol (vitamin A); the body uses an enzyme to convert β-carotene to retinol. In other contexts, both β-carotene and retinol are simply considered to be different forms (vitamers) of vitamin A.
* "Provitamin B5" is a name for panthenol, which may be converted in the body to vitamin B (pantothenic acid).
* Menadione is a synthetic provitamin of vitamin K.
* Provitamin D is ergosterol, and provitamin D is 7-dehydrocholesterol. They are converted by UV light into vitamin D. The human body produces provitamin D naturally; deficiency is usually caused by a lack of sun exposure, not a lack of the provitamin. | 1 | Applied and Interdisciplinary Chemistry |
Following the catastrophic failure of the Fukushima I Nuclear Power Plant in Japan that resulted from the 2011 Tōhoku earthquake and tsunami, and the subsequent widespread public opposition against nuclear power, high energy, lower emission (HELE) coal power plants were increasingly favored by the Shinzō Abe-led government to recoup lost energy capacity from the partial shutdown of nuclear power plants in Japan and to replace aging coal and oil-fired power plants, while meeting 2030 emission targets of the Paris Agreement. 45 HELE power plants have been planned, purportedly to employ integrated gasification fuel cell cycle, a further development of integrated gasification combined cycle.
Japan had adopted prior pilot projects on IGCC coal power plants in the early-1990s and late-2000s. | 1 | Applied and Interdisciplinary Chemistry |
Willard was born on June 3, 1881, in Erie, Pennsylvania. His family relocated to Union City, Michigan, in 1883 and he spent the rest of his early life there. His father and later his high school teachers encouraged his interest in chemistry, which he pursued as an undergraduate at the University of Michigan. He received his A.B. in 1903 and his M.A. in 1905. Meanwhile, he was briefly hired as an instructor of chemistry, but at the encouragement of coworkers he decided to pursue his Ph.D. at Harvard University. He received his Ph.D. in 1909 under the supervision of Theodore William Richards. | 0 | Theoretical and Fundamental Chemistry |
Sputtering (in particular radio-frequency magnetron sputtering) has been applied to the fabrication of LAGP thin-films starting from a LAGP target. Depending on the temperature of the substrate during the deposition, LAGP can be deposited in the cold sputtering or hot sputtering configuration.
The film stoichiometry and microstructure can be tuned by controlling the deposition parameters, especially the power density, the chamber pressure, and the substrate temperature. Both amorphous and crystalline films are obtained, with a typical thickness around 1 μm. The room-temperature ionic conductivity and the activation energy of sputtered and annealed LAGP films are comparable with those of bulk pellets, i.e. 10 S/cm and 0.31 eV. | 0 | Theoretical and Fundamental Chemistry |
Small quantities of hydrogen present inside certain metallic materials make the latter brittle and susceptible to sub-critical crack growth under stress. Hydrogen embrittlement may occur as a side effect of electroplating processes.
Delayed failure is the fracture of a component under stress after an elapsed time, is a characteristic feature of hydrogen embrittlement (2). Hydrogen entry into the material may be effected during plating, pickling, phosphating, melting, casting or welding. Corrosion during service in moist environments generates hydrogen, part of which may enter the metal as atomic hydrogen (H) and cause embrittlement. Presence of a tensile stress, either inherent or externally applied, is necessary for metals to be damaged. As in the case of stress corrosion cracking, hydrogen embrittlement may also lead to a decrease in the threshold stress intensity factor for crack propagation or an increase in the sub-critical crack growth velocity of the material. The most visible effect of hydrogen in materials is a drastic reduction in ductility during tensile tests. It may increase, decrease or leave unaffected the yield strength of the material.
Hydrogen may also cause serrated yielding in certain metals such as niobium, nickel and some steels (3). | 1 | Applied and Interdisciplinary Chemistry |
When people think of DNA analysis, they often think about television shows like NCIS or CSI, which portray DNA samples coming into a lab and being instantly analyzed, followed by the pulling up of a picture of the suspect within minutes. However, the reality is quite different, and perfect DNA samples are often not collected from the scene of a crime. Homicide victims are frequently left exposed to harsh conditions before they are found, and objects that are used to commit crimes have often been handled by more than one person. The two most prevalent issues that forensic scientists encounter when analyzing DNA samples are degraded samples and DNA mixtures. | 1 | Applied and Interdisciplinary Chemistry |
Copper-clad steel (CCS), also known as copper-covered steel or the trademarked name Copperweld is a bi-metallic product, mainly used in the wire industry that combines the high mechanical strength of steel with the conductivity and corrosion resistance of copper.
It is mainly used for grounding purposes, line tracing to locate underground utilities, drop wire of telephone cables, and inner conductor of coaxial cables, including thin hookup cables like RG-174 and CATV cable. It is also used in some antennas for RF conducting wires. | 1 | Applied and Interdisciplinary Chemistry |
Chlorodifluoromethane or difluoromonochloromethane is a hydrochlorofluorocarbon (HCFC). This colorless gas is better known as HCFC-22, or R-22, or . It was commonly used as a propellant and refrigerant. These applications were phased out under the Montreal Protocol in developed countries in 2020 due to the compound's ozone depletion potential (ODP) and high global warming potential (GWP), and in developing countries this process will be completed by 2030. R-22 is a versatile intermediate in industrial organofluorine chemistry, e.g. as a precursor to tetrafluoroethylene. | 1 | Applied and Interdisciplinary Chemistry |
Glass disease is caused by an inherent fault in the chemical composition of the original glass formula.
Glass contains three types of components: network formers establish basic structure, network stabilizers make glass strong and water resistant, and flux lowers the melting point at which the glass can be formed.
Common formulations of glass may include silica (SiO) as a former, alkali oxides such as soda (NaO) or potash (KO) for flux, and alkaline earth oxides such as lime (CaO) for stabilizing.
Structurally, glass is composed of a network of SiO-tetrahedrons. In addition to the network former silicon which establishes its principal structure, glass contains network modifying agents such as the alkali ions Na+ and K+ and the alkali earth ions Ca+ and Mg+. Glass does not have a defined stoichiometry, rather the network is flexible. It can incorporate other ions, depending upon factors such as the main composition and firing conditions of the glass. This causes almost all glass to be chemically unstable to some extent.
Electron charge differences of ions within the structure form the basis of its bonding. Both viscosity and transition temperature are related to the availability of oxygen bonds in the glass's composition. Modifying agents tend to lower the melting point of the silica. Higher contents of SiO increase acidity of the glass. Higher contents of CaO, NaO, and KO increase basicity.
The chemical stability of glass decreases when only NaO and KO are added as flux, because bonding becomes weaker. The chemical stability of glass can be increased by adding CaO, MgO, ZnO, and AlO. To be stable, glass composition must balance temperature lowering agents with stabilizing agents.
Exposure of a glass surface to moisture, either in solution or from humidity in the atmosphere, causes chemical reactions to occur on and below the surface of the glass. The exchange of alkali metal ions (from within the glass) and hydrogen ions (from outside) can cause chemical and structural changes to the glass. When alkali metal cations in the near-surface layer are replaced by smaller hydrogen ions, structural differences between the affected surface layer and the unaffected lower layers of glass cause increasing tensile stress, which in turn can cause cracking.
The likelihood of degradation due to glass disease depends on the amount and proportion of alkaline compounds mixed with silica, and on surrounding conditions.
Inadequate calcium oxide causes the alkalis in the glass to remain water-soluble at a low level of humidity. Exposure to higher levels of relative humidity during storage or display causes alkali to hydrate and leach out of the glass. Repeated changes in humidity can be particularly damaging. It is important to realize that any glass object can deteriorate if it is exposed to unsuitable environmental conditions. Crystal, historic glass, or treasured family items should never be exposed to the high temperatures and water pressure of a dishwasher.
Energy dispersive x-ray analysis (EDXA), scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS) can be used to study exchange reactions in different types of glass. By quantifying and studying chemical structure and reactions at the near-surface layer, the mechanisms of glass disease can be better understood.
Measurement of the pH of glass surfaces is particularly important if glass objects have a matte surface, or have been exposed to kaolin or other substances. In the case of extremely small objects such as glass beads, pH measurement may be necessary to determine whether alkaline salts are present and changes in the glass are occurring. | 0 | Theoretical and Fundamental Chemistry |
In the fall of 1785, Scheele began to suffer from symptoms described as kidney disease. In early 1786, he also contracted a disease of the skin, which, combined with his kidney problems, so enfeebled him that he could foresee an early death. With that in mind, he married the widow of his predecessor, Pohl, two days before he died, so that he could pass undisputed title to his pharmacy and his possessions to her.
While Scheele's experiments generated substances which have long since been found to be hazardous, the compounds and elements he used to start his experiments were dangerous to begin with, especially heavy metals. Like most of his contemporaries, in an age where there were few methods of chemical characterisation, Scheele would smell and taste any new substances he discovered. Cumulative exposure to arsenic, mercury, lead, and their compounds and, perhaps, hydrofluoric acid, which he had discovered, as well as other substances, took their toll on Scheele. He died at the early age of 43, on 21 May 1786, at his home in Köping. Doctors said that he died of mercury poisoning. | 1 | Applied and Interdisciplinary Chemistry |
The R/S system is an important nomenclature system for denoting enantiomers. This approach labels each chiral center R or S according to a system by which its substituents are each assigned a priority, according to the Cahn–Ingold–Prelog priority rules (CIP), based on atomic number. When the center is oriented so that the lowest-priority substituent of the four is pointed away from the viewer, the viewer will then see two possibilities: if the priority of the remaining three substituents decreases in clockwise direction, it is labeled R (for right); if it decreases in counterclockwise direction, it is S (for left).
(R) or (S) is written in italics and parentheses. If there are multiple chiral carbons, e.g. (1R,4S), a number specifies the location of the carbon preceding each configuration.
The R/S system also has no fixed relation to the system. For example, the side-chain one of serine contains a hydroxyl group, −OH. If a thiol group, −SH, were swapped in for it, the labeling would, by its definition, not be affected by the substitution. But this substitution would invert the molecules R/S labeling, because the CIP priority of CHOH is lower than that for COH but the CIP priority of CHSH is higher than that for COH. For this reason, the system remains in common use in certain areas of biochemistry, such as amino acid and carbohydrate chemistry, because it is convenient to have the same chiral label for the commonly occurring structures of a given type of structure in higher organisms. In the system, nearly all naturally occurring amino acids are all , while naturally occurring carbohydrates are nearly all . All proteinogenic amino acids are S, except for cysteine, which is R'. | 0 | Theoretical and Fundamental Chemistry |
There is no simple relationship between the scattering cross section and the physical size of the particles, as the scattering cross section depends on the wavelength of radiation used. This can be seen when looking at a halo surrounding the Moon on a decently foggy evening: Red light photons experience a larger cross sectional area of water droplets than photons of higher energy. The halo around the Moon thus has a perimeter of red light due to lower energy photons being scattering further from the center of the Moon. Photons from the rest of the visible spectrum are left within the center of the halo and perceived as white light. | 0 | Theoretical and Fundamental Chemistry |
Dynamic kinetic resolution (DKR) occurs when the starting material racemate is able to epimerize easily, resulting in an essentially racemic starting material mix at all points during the reaction. Then, the enantiomer with the lower barrier to activation can form in, theoretically, up to 100% yield. This is in contrast to standard kinetic resolution, which necessarily has a maximum yield of 50%. For this reason, dynamic kinetic resolution has extremely practical applications to organic synthesis. The observed dynamics are based on the Curtin-Hammett principle. The barrier to reaction of either enantiomer is necessarily higher than the barrier to epimerization, resulting in a kinetic well containing the racemate. This is equivalent to writing, for k>k,
A number of excellent reviews have been published, most recently in 2008, detailing the theory and practical applications of DKR. | 0 | Theoretical and Fundamental Chemistry |
Mutations that prevent the expression of Rab27 (knock out mutations) cause the hypopigmentation and immunodeficiency disorder known as type II Griscelli syndrome, while a decrease in Rab27 prenylation is thought to be involved in choroideremia.
The symptoms of type II Griscelli syndrome have shown that Rab27 is involved in melanosome transport in melanocytes and in cytotoxic killing activity in cytotoxic T lymphoblasts. In melanocytes Rab27 binds the melanosome. The melanosome is transported along the microtubule. Rab27 then recruits Slac2A and myosin Va, these enzymes are essential for the transfer of the melanosomes from the microtubules to actin filaments. The melanosomes can now continue on their path towards the cell periphery. If either Rab27, Slac2A or myosin Va are absent then the melanosomes remain in the perinuclear region of the cell. This disruption in pigmentation results in the hypopigmentation seen in the silvery hair colour of patients with Griscelli syndrome. | 1 | Applied and Interdisciplinary Chemistry |
The Büchner–Curtius–Schlotterbeck reaction can be used to facilitate one carbon ring expansions when the substrate ketone is cyclic. For instance, the reaction of cyclopentanone with diazomethane forms cyclohexanone (shown below). The Büchner ring expansion reactions utilizing diazoalkanes have proven to be synthetically useful as they can not only be used to form 5- and 6-membered rings, but also more unstable 7- and 8-membered rings.
An acyl-diazomethane can react with an aldehyde to form a β-diketone in the presence of a transition metal catalyst (SnCl in the example shown below). β-Diketones are common biological products, and as such, their synthesis is relevant to biochemical research. Furthermore, the acidic β-hydrogens of β-diketones are useful for broader synthetic purposes, as they can be removed by common bases.
Acyl-diazomethane can also add to esters to form β-keto esters, which are important for fatty acid synthesis. As mentioned above, the acidic β-hydrogens also have productive functionality.
The Büchner–Curtius–Schlotterbeck reaction can also be used to insert a methylene bridge between a carbonyl carbon and a halogen of an acyl halide. This reaction allows conservation of the carbonyl and halide functionalities.
It is possible to isolate nitrogen-containing compounds using the Büchner–Curtius–Schlotterbeck reaction. For example, an acyl-diazomethane can react with an aldehyde in the presence of a DBU catalyst to form isolable α-diazo-β-hydroxy esters (shown below). | 0 | Theoretical and Fundamental Chemistry |
After oral administration, peak serum concentration is reached after 12 hours, and up to 99% of the drug is bound to plasma proteins. The majority of ibuprofen is metabolized and eliminated within 24 hours in the urine; however, 1% of the unchanged drug is removed through biliary excretion. | 0 | Theoretical and Fundamental Chemistry |
Unlike other bioaerosols, bacteria are able to complete full reproductive cycles within the days or weeks that they survive in the atmosphere, making them a major component of the air biota ecosystem. These reproductive cycles support a currently unproven theory that bacteria bioaerosols form communities in an atmospheric ecosystem. The survival of bacteria depends on water droplets from fog and clouds that provide bacteria with nutrients and protection from UV light. The four known bacterial groupings that are abundant in aeromicrobial environments around the world include Bacillota, Actinomycetota, Pseudomonadota, and Bacteroidota. | 0 | Theoretical and Fundamental Chemistry |
Tritium was released to the atmosphere during atmospheric testing of nuclear bombs. Radioactive decay of tritium produces the noble gas helium-3. Comparing the ratio of tritium to helium-3 (H/He) allows estimation of the age of recent ground waters. A small amount of tritium is also produced naturally by cosmic ray spallation and spontaneous ternary fission in natural uranium and thorium, but due to the relatively short half-life of tritium and the relatively small quantities (compared to those from anthropogenic sources) those sources of tritium usually play only a secondary role in the analysis of groundwater.
* [http://water.usgs.gov/lab/3h3he/background/ USGS Tritium/Helium-3 Dating]
* [http://wwwrcamnl.wr.usgs.gov/isoig/period/he_iig.html Hydrologic Isotope Tracers - Helium] | 0 | Theoretical and Fundamental Chemistry |
Simeon Chituru Achinewhu (born 15 August, 1946) is a Nigerian food and nutrition biochemist, scholar and university administrator who served as the past president-general of Ogbakor Ikwerre Socio-cultural Organisation Worldwide. He was vice–chancellor of River State University (formerly Rivers State University of Science and Technology), from October 2000 until May 2007. In 2005 he was named the most research active vice-chancellor in the Nigerian university system. | 1 | Applied and Interdisciplinary Chemistry |
Although details have not surfaced, it appears that the University of Utah forced the 23 March 1989 Fleischmann and Pons announcement to establish priority over the discovery and its patents before the joint publication with Jones. The Massachusetts Institute of Technology (MIT) announced on 12 April 1989 that it had applied for its own patents based on theoretical work of one of its researchers, Peter L. Hagelstein, who had been sending papers to journals from 5 to 12 April. An MIT graduate student applied for a patent but was reportedly rejected by the USPTO in part by the citation of the "negative" MIT Plasma Fusion Center's cold fusion experiment of 1989. On 2 December 1993 the University of Utah licensed all its cold fusion patents to ENECO, a new company created to profit from cold fusion discoveries, and in March 1998 it said that it would no longer defend its patents.
The U.S. Patent and Trademark Office (USPTO) now rejects patents claiming cold fusion. Esther Kepplinger, the deputy commissioner of patents in 2004, said that this was done using the same argument as with perpetual motion machines: that they do not work. Patent applications are required to show that the invention is "useful", and this utility is dependent on the inventions ability to function. In general USPTO rejections on the sole grounds of the inventions being "inoperative" are rare, since such rejections need to demonstrate "proof of total incapacity", and cases where those rejections are upheld in a Federal Court are even rarer: nevertheless, in 2000, a rejection of a cold fusion patent was appealed in a Federal Court and it was upheld, in part on the grounds that the inventor was unable to establish the utility of the invention.
A U.S. patent might still be granted when given a different name to disassociate it from cold fusion, though this strategy has had little success in the US: the same claims that need to be patented can identify it with cold fusion, and most of these patents cannot avoid mentioning Fleischmann and Pons' research due to legal constraints, thus alerting the patent reviewer that it is a cold-fusion-related patent. David Voss said in 1999 that some patents that closely resemble cold fusion processes, and that use materials used in cold fusion, have been granted by the USPTO. The inventor of three such patents had his applications initially rejected when they were reviewed by experts in nuclear science; but then he rewrote the patents to focus more on the electrochemical parts so they would be reviewed instead by experts in electrochemistry, who approved them. When asked about the resemblance to cold fusion, the patent holder said that it used nuclear processes involving "new nuclear physics" unrelated to cold fusion. Melvin Miles was granted in 2004 a patent for a cold fusion device, and in 2007 he described his efforts to remove all instances of "cold fusion" from the patent description to avoid having it rejected outright.
At least one patent related to cold fusion has been granted by the European Patent Office.
A patent only legally prevents others from using or benefiting from one's invention. However, the general public perceives a patent as a stamp of approval, and a holder of three cold fusion patents said the patents were very valuable and had helped in getting investments. | 0 | Theoretical and Fundamental Chemistry |
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