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Much of the work done by the BNF during the 1939–45 period was of vital use for the defence industry. This especially included solving many of the corrosion problems of seawater cooled condenser tubes and tube plates that had resulted in many ships being unserviceable and significant improvements in corrosion resistant alloys for seawater pumps and pipe fittings. No work was ever carried out on active materials for nuclear weapons. Some consultancy work was undertaken on paperwork for new designs.
There has been much publicity about Melita Norwood (née Sirnis) who joined the BNF in 1932 as a clerk, was eventually promoted to secretary and retired 1972. As secretary to a Research Superintendent she had access to the papers prepared at the BNF for presentation to the research committees and some contractors. Some of these she chose to copy to Russian intelligence. This information was made use of by them and did occasionally result in one of their research organisations publishing development work on non-ferrous metals similar to and sooner than the BNF in Britain. | 1 | Applied and Interdisciplinary Chemistry |
In HTS, experimenters often compare a large number (hundreds of thousands to tens of millions) of single measurements of unknown samples to positive and negative control samples. The particular choice of experimental conditions and measurements is called an assay. Large screens are expensive in time and resources. Therefore, prior to starting a large screen, smaller test (or pilot) screens are used to assess the quality of an assay, in an attempt to predict if it would be useful in a high-throughput setting. The Z-factor is an attempt to quantify the suitability of a particular assay for use in a full-scale HTS. | 1 | Applied and Interdisciplinary Chemistry |
The rates at which ligands exchange between the first and the second coordination sphere is the first step in ligand substitution reactions. In associative ligand substitution, the entering nucleophile resides in the second coordination sphere. These effects are relevant to practical applications such as contrast agents used in MRI.
The energetics of inner sphere electron transfer reactions are discussed in terms of second coordination sphere. Some proton coupled electron transfer reactions involve atom transfer between the second coordination spheres of the reactants:
:[Fe*(HO)] + [Fe(HO)(OH)] → [Fe(HO)] + [Fe*(HO)(OH)] | 0 | Theoretical and Fundamental Chemistry |
This time step limitation is less restricted than the explicit method. The Crank–Nicolson method is based on the central differencing and hence it is second-order accurate in time. | 1 | Applied and Interdisciplinary Chemistry |
Lauterbur earned his bachelor of science in industrial chemistry from the Case Institute of Technology in 1951, now part of Case Western Reserve University in Cleveland, Ohio where he became a Brother of the Alpha Delta chapter of Phi Kappa Tau fraternity. He then went to work at the Mellon Institute laboratories of the Dow Corning Corporation, with a 2-year break to serve at the Army Chemical Center in Edgewood, Maryland. While working at Mellon Institute he pursued graduate studies in chemistry at the University of Pittsburgh. Earning his PhD in 1962, the following year Lauterbur accepted a position as associate professor at Stony Brook University. As a visiting faculty in chemistry at Stanford University during the 1969–1970 academic year, he undertook NMR-related research with the help of local businesses Syntex and Varian Associates. Lauterbur returned to Stony Brook, continuing there until 1985 when he moved to the University of Illinois. | 0 | Theoretical and Fundamental Chemistry |
Steady-state free precession imaging (SSFP) or balanced SSFP is an MRI technique which uses short repetition times (TR) and low flip angles (about 10 degrees) to achieve steady state of longitudinal magnetizations as the magnetizations does not decay completely nor achieving full T1 relaxation. While spoiled gradient-echo sequences refer to a steady state of the longitudinal magnetization only, SSFP gradient-echo sequences include transverse coherences (magnetizations) from overlapping multi-order spin echoes and stimulated echoes. This is usually accomplished by refocusing the phase-encoding gradient in each repetition interval in order to keep the phase integral (or gradient moment) constant. Fully balanced SSFP MRI sequences achieve a phase of zero by refocusing all imaging gradients.
MP-RAGE (magnetization-prepared rapid acquisition with gradient echo) improves images of multiple sclerosis cortical lesions. | 0 | Theoretical and Fundamental Chemistry |
For economic and other reasons, bitumen is sometimes sold combined with other materials, often without being labeled as anything other than simply "bitumen".
Of particular note is the use of re-refined engine oil bottoms – "REOB" or "REOBs"the residue of recycled automotive engine oil collected from the bottoms of re-refining vacuum distillation towers, in the manufacture of asphalt. REOB contains various elements and compounds found in recycled engine oil: additives to the original oil and materials accumulating from its circulation in the engine (typically iron and copper). Some research has indicated a correlation between this adulteration of bitumen and poorer-performing pavement. | 0 | Theoretical and Fundamental Chemistry |
Body composition can also be expressed in terms of various types of material, such as:
*Muscle
*Fat
*Bone and teeth
*Nervous tissue (brain and nerves)
*Hormones
*Connective tissue
*Body fluids (blood, lymph, urine)
*Contents of digestive tract, including intestinal gas
*Air in lungs
*Epithelium | 1 | Applied and Interdisciplinary Chemistry |
HTK (branded as Custodiol® by Essential Pharmaceuticals LLC), has been presented by industry to surgeons as an alternative solution that exceeds other cardioplegias in myocardial protection during cardiac surgery. This claim relies on the single-dose administration of HTK compared with other multidose cardioplegias (MDC), sparing time in the adjustment of equipment during cardioplegia re-administration, allowing greater time to operate and thus a decreased CPB duration. Other benefits include a lower concentration of sodium, calcium, and potassium compared with other cardioplegias with cardiac arrest arising from the deprivation of sodium. Finally, histidine is thought to aid buffering, mannitol and tryptophan to improve membrane stability, and ketoglutarate to help ATP production during reperfusion.
A 2021 meta-analysis demonstrated no statistical advantage of HTK over blood or other crystalloid cardioplegias during adult cardiac surgery. The only practical advantage of HTK, therefore, is the single-dose administration compared to multi-dose requirements of blood and other crystalloid cardioplegia. | 1 | Applied and Interdisciplinary Chemistry |
The body is able to substantially reduce the amount of iron it absorbs across the mucosa. It does not seem to be able to entirely shut down the iron transport process. Also, in situations where excess iron damages the intestinal lining itself (for instance, when children eat a large quantity of iron tablets produced for adult consumption), even more iron can enter the bloodstream and cause a potentially deadly syndrome of iron overload. Large amounts of free iron in the circulation will cause damage to critical cells in the liver, the heart and other metabolically active organs.
Iron toxicity results when the amount of circulating iron exceeds the amount of transferrin available to bind it, but the body is able to vigorously regulate its iron uptake. Thus, iron toxicity from ingestion is usually the result of extraordinary circumstances like iron tablet over-consumption rather than variations in diet. The type of acute toxicity from iron ingestion causes severe mucosal damage in the gastrointestinal tract, among other problems.
Excess iron has been linked to higher rates of disease and mortality. For example, breast cancer patients with low ferroportin expression (leading to higher concentrations of intracellular iron) survive for a shorter period of time on average, while high ferroportin expression predicts 90% 10-year survival in breast cancer patients. Similarly, genetic variations in iron transporter genes known to increase serum iron levels also reduce lifespan and the average number of years spent in good health. It has been suggested that mutations that increase iron absorption, such as the ones responsible for hemochromatosis (see below), were selected for during Neolithic times as they provided a selective advantage against iron-deficiency anemia. The increase in systemic iron levels becomes pathological in old age, which supports the notion that antagonistic pleiotropy or "hyperfunction" drives human aging.
Chronic iron toxicity is usually the result of more chronic iron overload syndromes associated with genetic diseases, repeated transfusions or other causes. In such cases the iron stores of an adult may reach 50 grams (10 times normal total body iron) or more. The most common diseases of iron overload are hereditary hemochromatosis (HH), caused by mutations in the HFE gene, and the more severe disease juvenile hemochromatosis (JH), caused by mutations in either hemojuvelin (HJV) or hepcidin (HAMP). The exact mechanisms of most of the various forms of adult hemochromatosis, which make up most of the genetic iron overload disorders, remain unsolved. So, while researchers have been able to identify genetic mutations causing several adult variants of hemochromatosis, they now must turn their attention to the normal function of these mutated genes. | 1 | Applied and Interdisciplinary Chemistry |
In contrast to animals, fungi and non-vascular plants, the cells of flowering plants lack dynein motors. However, they contain a larger number of different kinesins. Many of these plant-specific kinesin groups are specialized for functions during plant cell mitosis. Plant cells differ from animal cells in that they have a cell wall. During mitosis, the new cell wall is built by the formation of a cell plate starting in the center of the cell. This process is facilitated by a phragmoplast, a microtubule array unique to plant cell mitosis. The building of cell plate and ultimately the new cell wall requires kinesin-like motor proteins.
Another motor protein essential for plant cell division is kinesin-like calmodulin-binding protein (KCBP), which is unique to plants and part kinesin and part myosin. | 0 | Theoretical and Fundamental Chemistry |
Essential fatty acids (EFAs) are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them. Only two fatty acids are known to be essential for humans: alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid). | 0 | Theoretical and Fundamental Chemistry |
Starting with a linear potential of the form the corresponding Smoluchowski equation becomes,
Where the diffusion constant, , is constant over space and time. The boundary conditions are such that the probability vanishes at with an initial condition of the ensemble of particles starting in the same place, .
Defining and and applying the coordinate transformation,
With the Smoluchowki equation becomes,
Which is the free diffusion equation with solution,
And after transforming back to the original coordinates, | 1 | Applied and Interdisciplinary Chemistry |
The effective neutron multiplication factor can be described using the product of six probability factors that describe a nuclear system. These factors, traditionally arranged chronologically with regards to the life of a neutron in a thermal reactor, include the probability of fast non-leakage , the fast fission factor , the resonance escape probability , the probability of thermal non-leakage , the thermal utilization factor , and the neutron reproduction factor (also called the neutron efficiency factor). The six-factor formula is traditionally written as follows:</blockquote>The factors are described as follows
* describes the probability that a fast neutron will not escape the system without interacting.
** The bounds of this factor are 0 and 1, with a value of 1 describing a system for which fast neutrons will never escape without interacting, i.e. an infinite system.
** Also written as
* is the ratio of total fissions to fissions caused only by thermal neutrons
** Fast neutrons have a small probability to cause fissions in uranium, specifically Uranium-238.
** The fast fission factor describes the contribution of fast fissions to the effective neutron multiplication factor
** The bounds of this factor are 1 and infinity, with a value of 1 describing a system for which only thermal neutrons are causing fissions. A value of 2 would denote a system in which thermal and fast neutrons are causing equal amounts of fissions.
* is the ratio of the number of neutrons that begin thermalization to the number of neutrons that reach thermal energies.
** Many isotopes have "resonances" in their capture cross-section curves that occur in energies between fast and thermal.
** If a neutron begins thermalization (i.e. begins to slow down), there is a possibility it will be absorbed by a non-multiplying material before it reaches thermal energy.
** The bounds of this factor are 0 and 1, with a value of 1 describing a system for which all fast neutrons that do not leak out and do not cause fast fissions eventually reach thermal energies.
* describes the probability that a thermal neutron will not escape the system without interacting.
** The bounds of this factor are 0 and 1, with a value of 1 describing a system for which thermal neutrons will never escape without interacting, i.e. an infinite system.
** Also written as
* is the ratio of number of thermal neutrons absorbed in by fissile nuclei versus the number of neutrons absorbed in all materials in the system.
** This factor describes the efficiency of thermal neutron utilization in the system, hence the name thermal utilization factor.
** The bounds of this factor are 0 and 1, with a value of 1 describing a system for which the entire system is made of fissile nuclei (i.e. thermal neutrons can only react with fissile materials). Similarly, a value of 0.5 describes a system for which reactions with fissile and non-fissile nuclei are equal.
** For a conventional nuclear power reactor, this factor is the only one that can be directly controlled by the operator. With manipulations to the control rods, you can increase the amount of neutrons being absorbed in non-fissile nuclei while simultaneously decreasing the amount of neutrons absorbed in fissile nuclei.
* describes the probability that a neutron absorbed will cause a fission reaction.
** This factor describes the behavior of the fissile material, specifically if a neutron is absorbed, how likely is it to cause a fission, and how many neutrons does the fission produce.
In an infinite medium, the multiplication factor may be described by the four factor formula, which is the same as described above with and both equal to 1. | 0 | Theoretical and Fundamental Chemistry |
In 2004, Germany recycled 2.116 million tons of glass. Reusable glass or plastic (PET) bottles are available for many drinks, especially beer and carbonated water as well as soft drinks (Mehrwegflaschen). The deposit per bottle (Pfand) is €0.08-€0.15, compared to €0.25 for recyclable but not reusable plastic bottles. There is no deposit for glass bottles which do not get refilled.
Non-deposit bottles are collected in three colours: white, green and brown. | 0 | Theoretical and Fundamental Chemistry |
The search for organic molecules at the surface of Mars is a top priority of Mars exploration space missions. Therefore, a key step in interpretation of future data collected by these missions is to understand the preservation of organic matter in the Martian environment. A 1.5-year exposure to Mars-like surface UV radiation conditions in space resulted in complete degradation of the organic compounds (glycine, serine, phthalic acid, phthalic acid in the presence of a mineral phase, and mellitic acid). Their half-lives were between 50 and 150 h for Martian surface conditions.
To understand the chemical behavior of organic molecules in the space environment, amino acids and a dipeptide in pure form and embedded in meteorite powder were exposed to space conditions for 18 months; the samples were returned to Earth and analyzed in the laboratory for reactions caused by solar UV and cosmic radiation. The results show that resistance to irradiation is a function of the chemical nature of the exposed molecules and the wavelengths of the UV light. The most altered compounds were the dipeptide, aspartic acid, and aminobutyric acid. The most resistant were alanine, valine, glycine, and aminoisobutyric acid. The results also demonstrate the protective effect of meteorite powder, which reemphasizes the importance of exogenic contribution to the inventory of prebiotic organics on early Earth. | 1 | Applied and Interdisciplinary Chemistry |
Immunological effects resulting from the cryoablation of tumors was first observed in the 1960s. Since the 1960s, Tanaka treated metastatic breast cancer patients with cryotherapy and reported cryoimmunological reaction resulting from cryotherapy. In the 1970s, systemic immunological response from local cryoablation of prostate cancer was also clinically observed. In the 1980s, Tanaka, of Japan, continued to advance the clinical practice of cryoimmunology with combination treatments including: cryochemotherapy and cryoimmunotherapy. In 1997, Russian scientists confirmed the efficacy of cryoimmunotherapy in inhibiting metastases in advanced cancer. In 2000s, China, following closely with the exciting developments, enthusiastically embraced cryoablation treatment for cancer and has been leading the practice ever since with cryoimmunotherapy treatments available for cancer patients in numerous hospitals and medical clinics throughout China. In the 2010s, American researchers and medical professionals, started to explore cryoimmunotherapy for systemic treatment of cancer. | 1 | Applied and Interdisciplinary Chemistry |
Laser cooling includes several techniques where atoms, molecules, and small mechanical systems are cooled with laser light. The directed energy of lasers is often associated with heating materials, e.g. laser cutting, so it can be counterintuitive that laser cooling often results in sample temperatures approaching absolute zero. Laser cooling relies on the change in momentum when an object, such as an atom, absorbs and re-emits a photon (a particle of light). For example, if laser light illuminates a warm cloud of atoms from all directions and the lasers frequency is tuned below an atomic resonance, the atoms will be cooled. This common type of laser cooling relies on the Doppler effect where individual atoms will preferentially absorb laser light from the direction opposite to the atoms motion. The absorbed light is re-emitted by the atom in a random direction. After repeated emission and absorption of light the net effect on the cloud of atoms is that they will expand more slowly. The slower expansion reflects a decrease in the velocity distribution of the atoms, which corresponds to a lower temperature and therefore the atoms have been cooled. For an ensemble of particles, their thermodynamic temperature is proportional to the variance in their velocity. More homogeneous velocities between particles corresponds to a lower temperature. Laser cooling techniques combine atomic spectroscopy with the aforementioned mechanical effect of light to compress the velocity distribution of an ensemble of particles, thereby cooling the particles.
The 1997 Nobel Prize in Physics was awarded to Claude Cohen-Tannoudji, Steven Chu, and William Daniel Phillips "for development of methods to cool and trap atoms with laser light". | 0 | Theoretical and Fundamental Chemistry |
In general, on the typical laboratory scale, the direct reaction of a haloalkane with sodium hydrosulfide is inefficient owing to the competing formation of sulfides. Instead, alkyl halides are converted to thiols via an S-alkylation of thiourea. This multistep, one-pot process proceeds via the intermediacy of the isothiouronium salt, which is hydrolyzed in a separate step:
: CHCHBr + SC(NH) → [CHCHSC(NH)]Br
: [CHCHSC(NH)]Br + NaOH → CHCHSH + OC(NH) + NaBr
The thiourea route works well with primary halides, especially activated ones. Secondary and tertiary thiols are less easily prepared. Secondary thiols can be prepared from the ketone via the corresponding dithioketals. A related two-step process involves alkylation of thiosulfate to give the thiosulfonate ("Bunte salt"), followed by hydrolysis. The method is illustrated by one synthesis of thioglycolic acid:
:ClCHCOH + NaSO → Na[OSCHCOH] + NaCl
:Na[OSCHCOH] + HO → HSCHCOH + NaHSO
Organolithium compounds and Grignard reagents react with sulfur to give the thiolates, which are readily hydrolyzed:
:RLi + S → RSLi
:RSLi + HCl → RSH + LiCl
Phenols can be converted to the thiophenols via rearrangement of their O-aryl dialkylthiocarbamates.
Thiols are prepared by reductive dealkylation of sulfides, especially benzyl derivatives and thioacetals.
Thiophenols are produced by S-arylation or the replacement of diazonium leaving group with sulfhydryl anion (SH):
: + SH → ArSH + N | 0 | Theoretical and Fundamental Chemistry |
: This type of reactor contains several tubes with small diameters. These tubes contain catalysts and are surrounded by cooling water which removes the heat of the reaction. A fixed-bed reactor is suitable for operation at low temperatures and has an upper-temperature limit of 257 °C (530 K). Excess temperature leads to carbon deposition and hence blockage of the reactor. Since large amounts of the products formed are in liquid state, this type of reactor can also be referred to as a trickle flow reactor system. | 0 | Theoretical and Fundamental Chemistry |
The main advantages are High Sensitivity >93 %, Early detection of active TB. This method does not require a specimen taken from the site of disease, it also may be useful in diagnosis of paucibacillary childhood TB. Secreted antibody may be preserved for long time for further analysis. | 1 | Applied and Interdisciplinary Chemistry |
In many late model automobiles, a Mass Airflow (MAF) sensor is used to accurately determine the mass flow rate of intake air used in the internal combustion engine. Many such mass flow sensors use a heated element and a downstream temperature sensor to indicate the air flowrate. Other sensors use a spring-loaded vane. In either case, the vehicles electronic control unit interprets the sensor signals as a real-time indication of an engines fuel requirement. | 1 | Applied and Interdisciplinary Chemistry |
An iron founder (also iron-founder or ironfounder) in its more general sense is a worker in molten ferrous metal, generally working within an iron foundry. However, the term iron founder is usually reserved for the owner or manager of an iron foundry, a person also known in Victorian England as a master. Workers in a foundry are generically described as foundrymen; however, the various craftsmen working in foundries, such as moulders and pattern makers, are often referred to by their specific trades.
Historically the appellation "founder" was given to the supervisor of a blast furnace, and persons who made castings in iron or other heavy metal. The term is also often applied to the company or works in which an iron foundry operates. | 1 | Applied and Interdisciplinary Chemistry |
A Wahrhaftig diagram (named after Austin L. Wahrhaftig) illustrates the relative contributions in unimolecular ion decomposition of direct fragmentation and fragmentation following rearrangement. The x-axis of the diagram represents the internal energy of the ion. The lower part of the diagram shows the logarithm of the rate constant k for unimolecular dissociation whereas the upper portion of the diagram indicates the probability of forming a particular product ion. The green trace in the lower part of the diagram indicates the rate of the rearrangement reaction given by
and the blue trace indicates the direct cleavage reaction
A rate constant of 10 s is sufficiently fast for ion decomposition within the ion source of a typical mass spectrometer. Ions with rate constants less than 10 s and greater than approximately 10 s (lifetimes between 10 and 10 s) have a high probability of decomposing in the mass spectrometer between the ion source and the detector. These rate constants are indicated in the Wahrhaftig diagram by the log k = 5 and log k = 6 dashed lines.
Indicated on the rate constant plot are the reaction critical energy (also called the activation energy) for the formation of AD, E(AD) and AB, E(AB). These represent the minimum internal energy of ABCD required to form the respective product ions: the difference in the zero point energy of ABCD and that of the activated complex.
When the internal energy of ABCD is greater than E(AD), the ions are metastable (indicated by m); this occurs near log k > 5. A metastable ion has sufficient internal energy to dissociate prior to detection. The energy E(AD) is defined as the internal energy of ABCD that results in an equal probability that ABCDand AD leave the ion source, which occurs at near log k = 6. When the precursor ion has an internal energy equal to E(AB), the rates of formation of AD and AB are equal. | 0 | Theoretical and Fundamental Chemistry |
Three conservation laws are used to solve fluid dynamics problems, and may be written in integral or differential form. The conservation laws may be applied to a region of the flow called a control volume. A control volume is a discrete volume in space through which fluid is assumed to flow. The integral formulations of the conservation laws are used to describe the change of mass, momentum, or energy within the control volume. Differential formulations of the conservation laws apply Stokes' theorem to yield an expression that may be interpreted as the integral form of the law applied to an infinitesimally small volume (at a point) within the flow. | 1 | Applied and Interdisciplinary Chemistry |
The most popular explanation given for the shower-curtain effect is Bernoullis principle. Bernoullis principle states that an increase in velocity results in a decrease in pressure. This theory presumes that the water flowing out of a shower head causes the air through which the water moves to start flowing in the same direction as the water. This movement would be parallel to the plane of the shower curtain. If air is moving across the inside surface of the shower curtain, Bernoulli's principle says the air pressure there will drop. This would result in a pressure differential between the inside and outside, causing the curtain to move inward. It would be strongest when the gap between the bather and the curtain is smallest, resulting in the curtain attaching to the bather. | 1 | Applied and Interdisciplinary Chemistry |
Theoretically, any biomass can be converted into bio-oil using hydrothermal liquefaction regardless of water content, and various different biomasses have been tested, from forestry and agriculture residues, sewage sludges, food process wastes, to emerging non-food biomass such as algae. The composition of cellulose, hemicellulose, protein, and lignin in the feedstock influence the yield and quality of the oil from the process.
Zhang et al., at the University of Illinois, report on a hydrous pyrolysis process in which swine manure is converted to oil by heating the swine manure and water in the presence of carbon monoxide in a closed container. For that process they report that a temperatures of at least is required to convert the swine manure to oil, and temperatures above about reduces the amount of oil produced. The Zhang et al. process produces pressures of about 7 to 18 Mpa (1000 to 2600 psi - 69 to 178 atm), with higher temperatures producing higher pressures. Zhang et al. used a retention time of 120 minutes for the reported study, but report at higher temperatures a time of less than 30 minutes results in significant production of oil.
A commercialized process using hydrous pyrolysis (see the article Thermal depolymerization) used by Changing World Technologies, Inc. (CWT) and its subsidiary Renewable Environmental Solutions, LLC (RES) to convert turkey offal. As a two-stage process, the first stage to convert the turkey offal to hydrocarbons at a temperature of and a second stage to crack the oil into light hydrocarbons at a temperature of near . Adams et al. report only that the first stage heating is "under pressure"; Lemley, in a non-technical article on the CWT process, reports that for the first stage (for conversion) a temperature of about and a pressure of about 600 psi, with a time for the conversion of "usually about 15 minutes". For the second stage (cracking), Lemley reports a temperature of about . | 0 | Theoretical and Fundamental Chemistry |
Enol esters are formed from ketenes with enolisable carbonyl compounds. The following example shows the reaction of ethenone with acetone to form a propen-2-yl acetate: | 0 | Theoretical and Fundamental Chemistry |
In the stratosphere, the atmospheres second layer that is generally between 10 and 50 km above Earths surface, sulfuric acid is formed by the oxidation of volcanic sulfur dioxide by the hydroxyl radical:
Because sulfuric acid reaches supersaturation in the stratosphere, it can nucleate aerosol particles and provide a surface for aerosol growth via condensation and coagulation with other water-sulfuric acid aerosols. This results in the stratospheric aerosol layer. | 0 | Theoretical and Fundamental Chemistry |
The ideal IR source should be monochromatic and tunable within a wide range of wavelength. According to T ∝d/λ, where T is the transmission coefficient, d the aperture diameter and λ is wavelength, the aperture-based NSOM/FTIR transmission is even more limited due to the long infrared wavelength; therefore, an intense IR source is needed to offset the low transmission through the optical fiber. The common bright IR light sources are the free-electron laser (FEL), color-center lasers, CO lasers and laser diodes. FEL is an excellent IR source, with 2–20 μm spectral range, short pulses (picosecond) and high average power (0.1-1 W). Alternately, a tabletop picosecond optical parametric oscillator (OPO) can be used which is less expensive, but has a limited tunability and a lower power-output. | 0 | Theoretical and Fundamental Chemistry |
To design a transition state analogue, the pivotal step is the determination of transition state structure of substrate on the specific enzyme of interest with experimental method, for example, kinetic isotope effect. In addition, the transition state structure can also be predicted with computational approaches as a complementary to KIE. We will explain these two methods in brief. | 1 | Applied and Interdisciplinary Chemistry |
Agosterol A is a bio-active sterol which may have applications in removing multi-drug resistance in various cancers. It was first isolated from marine sponge but has also been produced synthetically. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, Prandtl–Batchelor theorem states that if in a two-dimensional laminar flow at high Reynolds number closed streamlines occur, then the vorticity in the closed streamline region must be a constant. A similar statement holds true for axisymmetric flows. The theorem is named after Ludwig Prandtl and George Batchelor. Prandtl in his celebrated 1904 paper stated this theorem in arguments, George Batchelor unaware of this work proved the theorem in 1956. The problem was also studied in the same year by Richard Feynman and Paco Lagerstrom and by W.W. Wood in 1957. | 1 | Applied and Interdisciplinary Chemistry |
In chemical kinetics, an Arrhenius plot displays the logarithm of a reaction rate constant, ordinate axis) plotted against reciprocal of the temperature abscissa). Arrhenius plots are often used to analyze the effect of temperature on the rates of chemical reactions. For a single rate-limited thermally activated process, an Arrhenius plot gives a straight line, from which the activation energy and the pre-exponential factor can both be determined.
The Arrhenius equation can be given in the form:
where:
* = rate constant
* = pre-exponential factor
* = (molar) activation energy
* = gas constant, (, where is the Avogadro constant).
* = activation energy (for a single reaction event)
* = Boltzmann constant
* = absolute temperature
The only difference between the two forms of the expression is the quantity used for the activation energy: the former would have the unit joule/mole, which is common in chemistry, while the latter would have the unit joule and would be for one molecular reaction event, which is common in physics. The different units are accounted for in using either the gas constant or the Boltzmann constant .
Taking the natural logarithm of the former equation gives:
When plotted in the manner described above, the value of the y-intercept (at ) will correspond to , and the slope of the line will be equal to . The values of y-intercept and slope can be determined from the experimental points using simple linear regression with a spreadsheet.
The pre-exponential factor, , is an empirical constant of proportionality which has been estimated by various theories which take into account factors such as the frequency of collision between reacting particles, their relative orientation, and the entropy of activation.
The expression represents the fraction of the molecules present in a gas which have energies equal to or in excess of activation energy at a particular temperature. In almost all practical cases, , so that this fraction is very small and increases rapidly with In consequence, the reaction rate constant increases rapidly with temperature , as shown in the direct plot of against . (Mathematically, at very high temperatures so that , would level off and approach as a limit, but this case does not occur under practical conditions.) | 0 | Theoretical and Fundamental Chemistry |
In protic solution exchangeable protons such as those in hydroxyl or amine group exchange protons with the solvent. If DO is solvent, deuterons will be incorporated at these positions. The exchange reaction can be followed using a variety of methods (see Detection). Since this exchange is an equilibrium reaction, the molar amount of deuterium should be high compared to the exchangeable protons of the substrate. For instance, deuterium is added to a protein in HO by diluting the HO solution with DO (e.g. tenfold). Usually exchange is performed at physiological pH (7.0–8.0) where proteins are in their most native ensemble of conformational states.
The H/D exchange reaction can also be catalysed, by acid, base or metal catalysts such as platinum. For the backbone amide hydrogen atoms of proteins, the minimum exchange rate occurs at approximately pH 2.6, on average. By performing the exchange at neutral pH and then rapidly changing the pH, the exchange rates of the backbone amide hydrogens can be dramatically slowed, or quenched. The pH at which the reaction is quenched depends on the analysis method. For detection by NMR, the pH may be moved to around 4.0–4.5. For detection by mass spectrometry, the pH is dropped to the minimum of the exchange curve, pH 2.6. In the most basic experiment, the reaction is allowed to take place for a set time before it is quenched.
The deuteration pattern of a molecule that has undergone H/D exchange can be maintained in aprotic environments. However, some methods of deuteration analysis for molecules such as proteins, are performed in aqueous solution, which means that exchange will continue at a slow rate even after the reaction is quenched. Undesired deuterium-hydrogen exchange is referred to as back-exchange and various methods have been devised to correct for this. | 0 | Theoretical and Fundamental Chemistry |
As a simple example, we investigate the properties of the one-dimensional Riemann problem
in gas dynamics
(Toro, Eleuterio F. (1999). Riemann Solvers and Numerical Methods for Fluid Dynamics, Pg 44, Example 2.5)
The initial conditions are given by
where x = 0 separates two different states, together with the linearised gas dynamic equations (see gas dynamics for derivation).
where we can assume without loss of generality .
We can now rewrite the above equations in a conservative form:
where
and the index denotes the partial derivative with respect to the corresponding variable (i.e. x or t).
The eigenvalues of the system are the characteristics of the system
. They give the propagation speed of the medium, including that of any discontinuity, which is the speed of sound here. The corresponding eigenvectors are
By decomposing the left state in terms of the eigenvectors, we get for some
Now we can solve for and :
Analogously
for
Using this, in the domain in between the two characteristics ,
we get the final constant solution:
and the (piecewise constant) solution in the entire domain :
Although this is a simple example, it still shows the basic properties. Most notably, the characteristics decompose the solution into three domains. The propagation speed
of these two equations is equivalent to the propagation speed of sound.
The fastest characteristic defines the Courant–Friedrichs–Lewy (CFL) condition, which sets the restriction for the maximum time step for which an explicit numerical method is stable. Generally as more conservation equations are used, more characteristics are involved. | 1 | Applied and Interdisciplinary Chemistry |
If a gamma spectrometer is used for identifying samples of unknown composition, its energy scale must be calibrated first. Calibration is performed by using the peaks of a known source, such as caesium-137 or cobalt-60. Because the channel number is proportional to energy, the channel scale can then be converted to an energy scale. If the size of the detector crystal is known, one can also perform an intensity calibration, so that not only the energies but also the intensities of an unknown source—or the amount of a certain isotope in the source—can be determined.
Because some radioactivity is present everywhere (i.e., background radiation), the spectrum should be analyzed when no source is present. The background radiation must then be subtracted from the actual measurement. Lead absorbers can be placed around the measurement apparatus to reduce background radiation. | 0 | Theoretical and Fundamental Chemistry |
During the COVID-19 pandemic, some studies attempted to establish a correlation between selenium plasma level and severity of COVID-19 cases. One study done on 33 patients concluded that low plasma selenium levels were correlated with a high mortality rate among COVID-19 patients. However, the median age of deaths in this study was 89 years old; in contrast, survivors' median age was 69 years old, and the study stated that the causality remains unknown.
On the other hand, another study revealed that the mean selenium plasma level was within the normal range among all included COVID-19 patients; however, the mean selenium plasma level was elevated among severe cases of COVID-19. This study concluded that there was a significant elevation of selenium serum level among severe cases compared to non-severe cases of COVID-19, and could be correlated with the disease severity. | 1 | Applied and Interdisciplinary Chemistry |
This gene product is a component of a nucleolar small nuclear ribonucleoprotein (snRNP) particle thought to participate in the first step in processing pre-ribosomal (r)RNA. It is associated with the U3, U8, and U13 small nucleolar RNAs and is located in the dense fibrillar component (DFC) of the nucleolus. The encoded protein contains an N-terminal repetitive domain that is rich in glycine and arginine residues, like fibrillarins in other species. Its central region resembles an RNA-binding domain and contains an RNP consensus sequence. Antisera from approximately 8% of humans with the autoimmune disease scleroderma recognize fibrillarin.
Fibrillarin is a component of several ribonucleoproteins including a nucleolar small nuclear ribonucleoprotein (SnRNP) and one of the two classes of small nucleolar ribonucleoproteins (snoRNPs). SnRNAs function in RNA splicing while snoRNPs function in ribosomal RNA processing.
Fibrillarin is associated with U3, U8 and U13 small nuclear RNAs in mammals and is similar to the yeast NOP1 protein. Fibrillarin has a well conserved sequence of around 320 amino acids, and contains 3 domains, an N-terminal Gly/Arg-rich region; a central domain resembling other RNA-binding proteins and containing an RNP-2-like consensus sequence; and a C-terminal alpha-helical domain. An evolutionarily related pre-rRNA processing protein, which lacks the Gly/Arg-rich domain, has been found in various archaea.
A study by Schultz et al. indicated that the K-turn binding 15.5-kDa protein (called Snu13 in yeast) interacts with spliceosome proteins hPRP31, hPRP3, hPRP4, CYPH and the small nucleolar ribonucleoproteins NOP56, NOP58, and fibrillarin. The 15.5-kDa protein has sequence similarity to other RNA-binding proteins such as ribosomal proteins S12, L7a, and L30 and the snoRNP protein NHP2. The U4/U6 snRNP contains 15.5-kDa protein. The 15.5-kDa protein also exists in a ribonucleoprotein complex that binds the U3 box B/C motif. The 15.5-kDa protein also exists as one of the four core proteins of the C/D small nucleolar ribonucleoprotein that mediates methylation of pre-ribosomal RNAs.
Structural evidence supporting the idea that fibrillarin is the snoRNA methyltransferase has been reviewed. | 1 | Applied and Interdisciplinary Chemistry |
Liquid chromatography as we know it today really got its start in 1969, when the first modern HPLC was designed and marketed as a nucleic acid analyzer. Columns throughout the 1970s were unreliable, pump flow rates were inconsistent, and many biologically active compounds escaped detection by UV and fluorescence detectors. Focus on purification methods in the 70s morphed into faster analyses in the 1980s, when computerized controls were integrated into HPLC equipment. Higher degrees of computerization then led to emphasis on more precise, faster, automated equipment in the 1990s. Atypical of many technologies of the 60s and '70s, the emphasis in improvements was not on “bigger and better,” but on “smaller and better”. At the same time the HPLC user-interface was improving, it was critical to be able to isolate hundreds of peptides or biomarkers from ever decreasing sample sizes.
Laboratory analytical instrumentation has only been recognized as a separate and distinct industry by NAICS and SIC since 1987. This market segmentation includes not only gas and liquid chromatography, but also mass spectrometry and spectrophotometric instruments. Since first recognized as a separate market, sales of analytical laboratory equipment increased from about $3.5 billion in 1987 to more than $26 billion in 2004. Revenues in the world liquid chromatography market, specifically, are expected to grow from $3.4 billion in 2007 to $4.7 billion in 2013, with a slight decrease in spending expected in 2008 and 2009 from the worldwide economic slump and decreased or stagnant spending. The pharmaceutical industry alone accounts for 35% of all the HPLC instruments in use. The main source of growth in LC stems from biosciences and pharmaceutical companies. | 0 | Theoretical and Fundamental Chemistry |
Amasa Stone Bishop (1921 – May 21, 1997) was an American nuclear physicist specializing in fusion physics. He received his B.S. in physics from the California Institute of Technology in 1943. From 1943 to 1946 he was a member of the staff of Radiation Laboratory at the Massachusetts Institute of Technology, where he was involved with radar research and development. Later, he became a staff member of the University of California at Berkeley from 1946 to 1950. Specializing in high energy particle work, he earned his Ph.D. in physics in 1950.
After attaining his Ph.D., Amasa spent three years in Switzerland, acting as research associate at the Federal Institute of Technology in Zürich, and later at the University of Zürich. In 1953 Amasa joined the research division of the Atomic Energy Commission (AEC) in Washington and became the director of the American program to develop controlled fusion, also known as Project Sherwood. He was later presented the AEC Outstanding Service Award for his work. After leaving this position in 1956, Amasa published a book on behalf of the AEC discussing the various attempts at harnessing fusion under Project Sherwood. The book, "Project Sherwood: The U.S. Program in Controlled Fusion", was published in 1958.
After 1956 Amasa also served as the AEC's European scientific representative, based in Paris. He was also an assistant delegate to the European atomic energy agency, Euratom, in Brussels. Later he spent several years in Princeton, New Jersey, and was in charge of the fusion program in Washington.
In 1970 Amasa joined the United Nations in Europe as director of environment of the United Nations Economic Commission for Europe. During this position, he worked with scientists and diplomats to create solutions for various environmental problems. He left this position to retire in 1980. Amasa died on May 21, 1997, of pneumonia related to Alzheimer's disease at the Clinique de Genolier in Genolier, Switzerland.
Bishop was the great-grandson of Industrialist Amasa Stone. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, the enstrophy can be interpreted as another type of potential density; or, more concretely, the quantity directly related to the kinetic energy in the flow model that corresponds to dissipation effects in the fluid. It is particularly useful in the study of turbulent flows, and is often identified in the study of thrusters as well as in combustion theory and meteorology.
Given a domain and a once-weakly differentiable vector field which represents a fluid flow, such as a solution to the Navier-Stokes equations, its enstrophy is given by:where . This quantity is the same as the squared seminorm of the solution in the Sobolev space . | 1 | Applied and Interdisciplinary Chemistry |
The sodium-potassium pump works with the sodium and potassium leak channels to maintain the membrane potential between the cell and the extracellular space. Sodium moves down the concentration gradient from the cytosol into the extracellular matrix. Potassium moves down its concentration gradient from the extracellular matrix into the cytosol. In order to maintain the membrane potential, the sodium-potassium pump acts as a form of direct active transport where the hydrolysis of ATP to ADP and an inorganic phosphate at the P-type ATPase moves 3 potassium ions back out of the cell and 2 sodium ions into the cell.
The sodium-potassium pump plays a large role in neural signaling due to the maintenance of cell membrane potential. This creates an action potential that causes the neurons to polarize and depolarize their membranes by opening and closing the voltage gated channels: this alters voltage potential and leads to neurotransmitter secretion and ultimately signal transmission.
When the pump fails to function, patients are susceptible to illnesses like heart failure and chronic obstructive lung disease (COLD). Those who experienced an event of heart failure had on average, a 40% lower concentration of the sodium-potassium ATPase. This lack of polarization of the membrane leads to an inability of action potentials to propagate at their usual rate, leading to a lowered hear rate and potentially heart failure. In COLD diagnoses, a majority of patients found to have a lowered amount of magnesium and potassium also had a decreased concentration of the sodium-potassium pump in skeletal and smooth muscle during respiratory failure. COLD is treatable in the short term by glucocorticoid which up-regulates the sodium-potassium pump, helping to support muscle endurance and increase muscle activity during these episodes of respiratory failure. | 1 | Applied and Interdisciplinary Chemistry |
There are three molecules that serve as chelator agents that bond to arsenic. These three are British Anti-Lewisite (BAL, Dimercaprol), succimer (DMSA) and Unithiol (DMPS).
When these agents chelate inorganic arsenic, it is converted into an organic form of arsenic because it is bound to the organic chelating agent. The sulfur atoms of the thiol groups are the site of interaction with arsenic. This is because the thiol groups are nucleophilic while the arsenic atoms are electrophilic. Once bound to the chelating agent the molecules can be excreted, and therefore free inorganic arsenic atoms are removed from the body.
Other chelating agents can be used, but may cause more side effects than British Anti-Lewisite (BAL, Dimercaprol), succimer (DMSA) and (DMPS). DMPS and DMSA also have a higher therapeutic index than BAL.
These drugs are efficient for acute poisoning of arsenic, which refers to the instantaneous effects caused by arsenic poisoning. For example, headaches, vomiting or sweating are some of the common examples of an instantaneous effect. In comparison, chronic poisonous effects arise later on, and unexpectedly such as organ damage. Usually it is too late to prevent them once they appear. Therefore, action should be taken as soon as acute poisonous effects arise. | 1 | Applied and Interdisciplinary Chemistry |
The possible tautomerism of favipiravir has been investigated computationally and experimentally. It was found that the enol-like form was substantially more stable in organic solvents than the keto-like form, meaning that Favipiravir likely exists almost exclusively in the enol-like form. In aqueous solution the keto-like tautomer is substantially stabilized due to the specific interaction with the water molecules. Upon protonation the keto form is switched on. | 0 | Theoretical and Fundamental Chemistry |
Marine dinoflagellates at night can emit blue light by bioluminescence, a process also called "the phosphorescence of the seas". Light production in these single celled organisms is produced by small structures in the cytoplasm called scintillons. Among bioluminescent organisms, only dinoflagellates have scintillons. In the dinoflagellates, the biochemical reaction that produces light involves a luciferase-catalysed oxidation of a linear tetrapyrrole called luciferin. The dinoflagellate Lingulodinium polyedra (previously called Gonyaulax polyedra) also contains a second protein called luciferin binding protein (LBP) that has been proposed to protect luciferin from non-luminescent oxidation. Luciferin is released from LBP by a decrease in pH, and the same decreased pH also activates the luciferase. Light production in the dinoflagellates occurs in bioluminescent organelles called scintillons and can be stimulated by agitation of the surrounding seawater. | 1 | Applied and Interdisciplinary Chemistry |
Pyrometers are suited especially to the measurement of moving objects or any surfaces that cannot be reached or cannot be touched. Contemporary multispectral pyrometers are suitable for measuring high temperatures inside combustion chambers of gas turbine engines with high accuracy.
Temperature is a fundamental parameter in metallurgical furnace operations. Reliable and continuous measurement of the metal temperature is essential for effective control of the operation. Smelting rates can be maximized, slag can be produced at the optimal temperature, fuel consumption is minimized and refractory life may also be lengthened. Thermocouples were the traditional devices used for this purpose, but they are unsuitable for continuous measurement because they melt and degrade.
Salt bath furnaces operate at temperatures up to 1300 °C and are used for heat treatment. At very high working temperatures with intense heat transfer between the molten salt and the steel being treated, precision is maintained by measuring the temperature of the molten salt. Most errors are caused by slag on the surface, which is cooler than the salt bath.
The tuyère pyrometer is an optical instrument for temperature measurement through the tuyeres, which are normally used for feeding air or reactants into the bath of the furnace.
A steam boiler may be fitted with a pyrometer to measure the steam temperature in the superheater.
A hot air balloon is equipped with a pyrometer for measuring the temperature at the top of the envelope in order to prevent overheating of the fabric.
Pyrometers may be fitted to experimental gas turbine engines to measure the surface temperature of turbine blades. Such pyrometers can be paired with a tachometer to tie the pyrometer output with the position of an individual turbine blade. Timing combined with a radial position encoder allows engineers to determine the temperature at exact points on blades moving past the probe. | 1 | Applied and Interdisciplinary Chemistry |
There are two equivalent ways to define the meaning of the Miller indices: via a point in the reciprocal lattice, or as the inverse intercepts along the lattice vectors. Both definitions are given below. In either case, one needs to choose the three lattice vectors a, a, and a that define the unit cell (note that the conventional unit cell may be larger than the primitive cell of the Bravais lattice, as the examples below illustrate). Given these, the three primitive reciprocal lattice vectors are also determined (denoted b, b, and b).
Then, given the three Miller indices denotes planes orthogonal to the reciprocal lattice vector:
That is, (hkℓ) simply indicates a normal to the planes in the basis of the primitive reciprocal lattice vectors. Because the coordinates are integers, this normal is itself always a reciprocal lattice vector. The requirement of lowest terms means that it is the shortest reciprocal lattice vector in the given direction.
Equivalently, (hkℓ) denotes a plane that intercepts the three points a/h, a/k, and a/ℓ, or some multiple thereof. That is, the Miller indices are proportional to the inverses of the intercepts of the plane, in the basis of the lattice vectors. If one of the indices is zero, it means that the planes do not intersect that axis (the intercept is "at infinity").
Considering only (hkℓ) planes intersecting one or more lattice points (the lattice planes), the perpendicular distance d between adjacent lattice planes is related to the (shortest) reciprocal lattice vector orthogonal to the planes by the formula: .
The related notation [hkℓ] denotes the direction:
That is, it uses the direct lattice basis instead of the reciprocal lattice. Note that [hkℓ] is not generally normal to the (hkℓ) planes, except in a cubic lattice as described below. | 0 | Theoretical and Fundamental Chemistry |
The energetic deuteron fuses with another deuteron, yielding either a helium nucleus and a neutron or a hydrogen nucleus and a proton. These fusion products may fuse with other deuterons, creating an alpha particle, or with another helium or hydrogen nucleus. Each releases energy, continuing the process. | 0 | Theoretical and Fundamental Chemistry |
Approximately 64% of the maize genome is made up of TEs, as is 44% of the human genome, and almost half of murine genomes.
New discoveries of transposable elements have shown the exact distribution of TEs with respect to their transcription start sites (TSSs) and enhancers. A recent study found that a promoter contains 25% of regions that harbor TEs. It is known that older TEs are not found in TSS locations because TEs frequency starts as a function once there is a distance from the TSS. A possible theory for this is that TEs might interfere with the transcription pausing or the first-intro splicing. Also as mentioned before, the presence of TEs closed by the TSS locations is correlated to their evolutionary age (number of different mutations that TEs can develop during the time). | 1 | Applied and Interdisciplinary Chemistry |
The Florida Everglades system is a prime example of a complex ecological system that underwent an ESEM analysis. | 1 | Applied and Interdisciplinary Chemistry |
The muons are implanted into the sample of interest where they lose energy very quickly. Fortunately, this deceleration process occurs in such a way that it does not jeopardize a μSR measurement. On one side it is very fast (much faster than 100 ps), which is much shorter than a typical μSR time window (up to 20 μs), and on the other side, all the processes involved during the deceleration are Coulombic (ionization of atoms, electron scattering, electron capture) in origin and do not interact with the muon spin, so that the muon is thermalized without any significant loss of polarization.
The positive muons usually adopt interstitial sites of the crystallographic lattice, markedly distinguished by their electronic (charge) state. The spectroscopy of a muon chemically bound to an unpaired electron is remarkably different from that of all other muon states, which motivates the historical distinction in paramagnetic and diamagnetic states. Note that many diamagnetic muon states really behave like paramagnetic centers, according to the standard definition of a paramagnet. For example, in most metallic samples, which are Pauli paramagnets, the muons positive charge is collectively screened by a cloud of conduction electrons. Thus, in metals, the muon is not bound to a single electron, hence it is in the so-called diamagnetic state and behaves like a free muon. In insulators or semiconductors a collective screening cannot take place and the muon will usually pick up one electron and form a so-called muonium (Mu=μ+e), which has similar size (Bohr radius), reduced mass, and ionization energy to the hydrogen atom. This is the prototype of the so-called paramagnetic' state. | 0 | Theoretical and Fundamental Chemistry |
Different related definitions of an ideal solution have been proposed. The simplest definition is that an ideal solution is a solution for which each component obeys Raoult's law for all compositions. Here is the vapor pressure of component above the solution, is its mole fraction and is the vapor pressure of the pure substance at the same temperature.
This definition depends on vapor pressure, which is a directly measurable property, at least for volatile components. The thermodynamic properties may then be obtained from the chemical potential μ (which is the partial molar Gibbs energy g) of each component. If the vapor is an ideal gas,
The reference pressure may be taken as = 1 bar, or as the pressure of the mix, whichever is simpler.
On substituting the value of from Raoult's law,
This equation for the chemical potential can be used as an alternate definition for an ideal solution.
However, the vapor above the solution may not actually behave as a mixture of ideal gases. Some authors therefore define an ideal solution as one for which each component obeys the fugacity analogue of Raoult's law . Here is the fugacity of component in solution and is the fugacity of as a pure substance. Since the fugacity is defined by the equation
this definition leads to ideal values of the chemical potential and other thermodynamic properties even when the component vapors above the solution are not ideal gases. An equivalent statement uses thermodynamic activity instead of fugacity. | 0 | Theoretical and Fundamental Chemistry |
Tidal constituents combine to give an endlessly varying aggregate because of their different and incommensurable frequencies: the effect is visualized in an [http://www.ams.org/featurecolumn/archive/tidesIII3.html animation of the American Mathematical Society] illustrating the way in which the components used to be mechanically combined in the tide-predicting machine. Amplitudes (half of peak-to-peak amplitude) of tidal constituents are given below for six example locations:
Eastport, Maine (ME), Biloxi, Mississippi (MS), San Juan, Puerto Rico (PR), Kodiak, Alaska (AK), San Francisco, California (CA), and Hilo, Hawaii (HI). | 1 | Applied and Interdisciplinary Chemistry |
Lactacystin is an organic compound naturally synthesized by bacteria of the genus Streptomyces first identified as an inducer of neuritogenesis in neuroblastoma cells in 1991. The target of lactacystin was subsequently found to be the proteasome on the basis of its affinity for certain catalytic subunits of the proteasome by Fenteany and co-workers in 1995. The proteasome is a protein complex responsible for the bulk of proteolysis in the cell, as well as proteolytic activation of certain protein substrates. Lactacystin was the first non-peptidic proteasome inhibitor discovered and is widely used as a research tool in biochemistry and cell biology. The transformation product of lactacystin clasto-lactacystin β-lactone (also known as omuralide) covalently modifies the amino-terminal threonine of specific catalytic subunits of the proteasome, a discovery that helped to establish the proteasome as a mechanistically novel class of protease: an amino-terminal threonine protease. The molecule is commonly used in biochemistry and cell biology laboratories as a selective inhibitor of the proteasome. The first total synthesis of lactacystin was developed in 1992 by Corey and Reichard, and a number of other syntheses of this molecule have also been published. There are more than 1,660 entries for lactacystin in PubMed as of January 2019. | 0 | Theoretical and Fundamental Chemistry |
A subgrain is a part of the grain that is only slightly disoriented from other parts of the grain. Current research is being done to see the effect of subgrain strengthening in materials. Depending on the processing of the material, subgrains can form within the grains of the material. For example, when Fe-based material is ball-milled for long periods of time (e.g. 100+ hours), subgrains of 60–90 nm are formed. It has been shown that the higher the density of the subgrains, the higher the yield stress of the material due to the increased subgrain boundary. The strength of the metal was found to vary reciprocally with the size of the subgrain, which is analogous to the Hall–Petch equation. The subgrain boundary strengthening also has a breakdown point of around a subgrain size of 0.1 µm, which is the size where any subgrains smaller than that size would decrease yield strength. | 1 | Applied and Interdisciplinary Chemistry |
MIR elements have been first described in human genome 1989-1991
and were first referred as MB1 family repeats (mirror to sequences of mouse B1 repeat). Then this family repeats were found in other mammalian genomes. Then this family was renamed as "Mammalian interspersed repeats" in 1992 Later this family was shown to be common for vertebrate genomes. | 1 | Applied and Interdisciplinary Chemistry |
Another firm researching hair cloning was ARI (Aderans Research Institute), a Japanese company that operated in the US and was the greatest competitor of Intercytex in developing the therapy. The company worked on what they called the "Ji Gami" process, which involved the removal of a small strip of the scalp, which is broken down into individual follicular stem cells. After the extraction, these cells are cultured, multiplied, and injected back into the bald areas of the scalp. Scientists hoped that after implantation these cloned follicular cells would mature into full-grown hair.
During Phase II trials they found that the process was not suitable for multiplication but instead, it revitalized the follicles and successfully prevented future loss. The trials continued in 2012. Aderans decided to discontinue the funding of its hair multiplication research in July 2013. | 1 | Applied and Interdisciplinary Chemistry |
Friedel's salt could be first tentatively represented as an AFm phase in which two chloride ions would have simply replaced one sulfate ion. This conceptual representation based on the intuition of a simple stoichiometric exchange is very convenient to remind but such a simple mechanism likely does not directly occur and must be considered with caution:
Indeed, the reality appears to be more complex than such a simple stoichiometric exchange between chloride and sulfate ions in the AFm crystal structure. In fact, it seems that chloride ions are electrostatically sorbed onto the positively charged [CaAl(OH) · 2HO] layer of AFm hydrate, or could also exchange with hydroxide ions (OH) also present in the interlayer. So, the simple and "apparent" exchange reaction first presented here above for the sake of ease does not correspond to the reality and is an oversimplified representation.
Similarly, Kuzel’s salt could seem to be formed when only 1 Cl ion exchanges with in AFm (half substitution of sulfate ions):
Glasser et al. (1999) proposed to name this half-substituted salt in honor of his discoverer: Hans-Jürgen Kuzel.
However, Mesbah et al. (2011) have identified two different types of interlayers in the crystallographic structure they have determined and it precludes the common anion exchange reaction presented here above as stated by the authors themselves in their conclusions:
So, if the global chemical composition of Friedels salt and Kuzels salt corresponds well respectively with the stoichiometry of a complete substitution, or a half substitution, of sulfate ions by chloride ions in the crystal structure of AFm, it does not tell directly anything on the exact mechanism of anion substitution in this complicated system. Only detailed and well controlled chloride sorption, or anion exchange, experiments with a complete analysis of all the dissolved species present in aqueous solution (also including OH, Na and Ca ions) can decipher the system. | 0 | Theoretical and Fundamental Chemistry |
*This test is done to ascertain the nature of fluid in the vagina during pregnancy especially when premature rupture of membranes (PROM) is suspect. This test involves putting a drop of fluid obtained from the vagina onto paper strips containing nitrazine dye. The strips change color depending on the pH of the fluid. The strips will turn blue if the pH is greater than 6.0. A blue strip means it's more likely the membranes have ruptured.
This test, however, can produce false positives. If blood gets in the sample or if there is an infection present, the pH of the vaginal fluid may be higher than normal. Semen also has a higher pH, so recent vaginal intercourse can produce a false reading.
* To perform a fecal pH test for diagnosing intestinal infections or other digestive problems
* In civil engineering, to determine the carbonatation spread in concrete structures and therefore assess the state of the rebar's passivation film. | 0 | Theoretical and Fundamental Chemistry |
After the fifth century fall of the Western Roman Empire, medicinal knowledge in Europe suffered due to the loss of Greek medicinal texts and a strict adherence to tradition, although an area of Southern Italy near Salerno remained under Byzantine control and developed a hospital and medical school, which became famous by the 11th century.
In the early 11th century, Salerno scholar Constantinos Africanus translated many Arabic books into Latin, driving a shift from Hippocratic medicine towards a pharmaceutical-driven approach advocated by Galen. In medieval Europe, monks typically did not speak Greek, leaving only Latin texts such as the works of Pliny available until these translations by Constantinos. In addition, Arabic medicine became more widely known due to Muslim Spain.
In the 15th century, the printing press spread medicinal textbooks and formularies; the Antidotarium was the first printed drug formulary.
In Europe pharmacy-like shops began to appear during the 12th century. In 1240 emperor Frederic II issued a decree by which the physicians and the apothecarys professions were separated.
Old pharmacies continue to operate in Dubrovnik, Croatia located inside the Franciscan monastery, opened in 1317. The Town Hall Pharmacy in Tallinn, Estonia, which dates back to at least 1422, is the oldest continuously run pharmacy in the world still operating in the original premises.
The trend towards pharmacy specialization started to take effect in Bruges, Belgium where a new law was passed that forbid physicians to prepare medications for patients.
The oldest pharmacy is claimed to be set up in 1221 in the Church of Santa Maria Novella in Florence, Italy, which now houses a perfume museum. Florence is also the birthplace of the first official pharmacopeia, called the Nuevo Receptario, in which all pharmacies would use that document as guidance for caring for the sickly.
The Royal College of Apothecaries of the City and Kingdom of Valencia was founded in 1441, considered the oldest in the world, with full administrative and legislative powers. The apothecaries of Valencia were the first in the world to elaborate their medicines, with the same criteria that are currently required in the official pharmacopoeias.
The Republic of Venice was the first State with health modern policies which requires that the nature of the drug is public. In actuality, thirteen secrets survive which were offered to sale to the Venetian Republic. | 1 | Applied and Interdisciplinary Chemistry |
Drug repositioning (also called drug repurposing) involves the investigation of existing drugs for new therapeutic purposes. | 1 | Applied and Interdisciplinary Chemistry |
Starting as lecturer at Rivers State University in food chemistry/biochemistry, food process technology, safety and fermentation, toxicology and nutrition in 1975, he has remained there to-date. He is also a researcher in Rivers State University, Port Harcourt (formerly Rivers State University of Science and Technology) and research is mostly centered on the composition and quality evaluation of Nigerian local foodstuff.
As of 2021, Achinewhu serves as professor emeritus at the Rivers State University.
Prior to being appointed vice-chancellor of Rivers State University 2000, Achinewhu held the following positions:
* Dean, Post Graduate School (1998-2000)
* Head of the Department of Food Science & Technology (November 1995 – June 1998)
* Dean, Faculty of Agriculture (1989-1994)
* Director, Rivers Institute of Agricultural Research & Training (RIART), Rivers State University (1986-1989) | 1 | Applied and Interdisciplinary Chemistry |
A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably. Strictly speaking, defoamers eliminate existing foam and anti-foamers prevent the formation of further foam. Commonly used agents are insoluble oils, polydimethylsiloxanes and other silicones, certain alcohols, stearates and glycols. The additive is used to prevent formation of foam or is added to break a foam already formed.
In industrial processes, foams pose serious problems. They cause defects on surface coatings and prevent the efficient filling of containers. A variety of chemical formulae are available to prevent formation of foams. | 0 | Theoretical and Fundamental Chemistry |
Phosphate-buffered saline (PBS) is a buffer solution (pH ~ 7.4) commonly used in biological research. It is a water-based salt solution containing disodium hydrogen phosphate, sodium chloride and, in some formulations, potassium chloride and potassium dihydrogen phosphate. The buffer helps to maintain a constant pH. The osmolarity and ion concentrations of the solutions match those of the human body (isotonic). | 1 | Applied and Interdisciplinary Chemistry |
One goal of structural genomics is to identify novel protein folds. Experimental methods of protein structure determination require proteins that express and/or crystallize well, which may inherently bias the kinds of proteins folds that this experimental data elucidate. A genomic, modeling-based approach such as ab initio modeling may be better able to identify novel protein folds than the experimental approaches because they are not limited by experimental constraints.
Protein function depends on 3-D structure and these 3-D structures are more highly conserved than sequences. Thus, the high-throughput structure determination methods of structural genomics have the potential to inform our understanding of protein functions. This also has potential implications for drug discovery and protein engineering. Furthermore, every protein that is added to the structural database increases the likelihood that the database will include homologous sequences of other unknown proteins. The Protein Structure Initiative (PSI) is a multifaceted effort funded by the National Institutes of Health with various academic and industrial partners that aims to increase knowledge of protein structure using a structural genomics approach and to improve structure-determination methodology. | 1 | Applied and Interdisciplinary Chemistry |
A resin impregnated felt tube made of polyester, fiberglass cloth, spread tow carbon fiber or another resin-impregnable substance, is inserted or pulled through a damaged pipe. It is usually done from the upstream access point (manhole or excavation). It is possible to insert the liner upstream (e.g. from the downstream access point) but this carries greater risk. It is possible to install a liner from the downstream access point, upstream to a blind end; however, this carries the highest risk of all the CIPP installation methods. CIPP is considered a trenchless technology. Little to no digging is involved in this trenchless process, making for a potentially more cost-effective and less disruptive method than traditional "dig and replace" pipe repair methods. The liner can be inserted using water or air pressure. The pressure required for insertion can be generated using pressure vessels, scaffolds or a "chip unit". Hot water or steam can be used to accelerate the curing rate of the resin. If a fiberglass tube is used, the curing of the resin can be triggered though the use of UV light introduced into the tube. As the resin cures, it forms a tight-fitting, joint less and corrosion-resistant replacement pipe. Service laterals are restored internally with robotically controlled cutting devices called cutters in the larger-diameter pipe. Smaller diameters (100 mm) can be opened remotely using smaller cutters designed for small diameter pipe. The service lateral connection can be sealed with specially designed CIPP materials, sometimes referred to as a top-hat. The resin used is typically polyester for mainline lining and epoxy for lateral lines. Since all resins shrink (epoxy resins shrink far less than poly and vinyl ester versions) and it is impossible to bond to a sewer that has fats, oils, and grease an annular space exists between the new CIPP liner and the host pipe. The annular space exists in all installations just some are larger than others and depending on the severity may need additional rehabilitation. There are multiple ways to prevent water from tracking in the annular space and entering back into the waste stream including: water swelling material (hydrophilic), lining of the entire connection and host pipe with a continuous repair (YT repair) gaskets, and point repairs placed at the ends of the host pipe. | 1 | Applied and Interdisciplinary Chemistry |
Application of this discharge are usually seen where production of filter cakes that blind the filter media thoroughly and processes that have low solid concentration slurry. Pre coat discharge is used if slurry with very low solid concentration slurry is used that resulted in difficult cake formation or if the slurry is difficult to filter to produce cake . | 0 | Theoretical and Fundamental Chemistry |
It is common to represent polymers backbones, notably proteins, in internal coordinates; that is, a list of consecutive dihedral angles and bond lengths. However, some types of computational chemistry instead use cartesian coordinates. In computational structure optimization, some programs need to flip back and forth between these representations during their iterations. This task can dominate the calculation time. For processes with many iterations or with long chains, it can also introduce cumulative numerical inaccuracy. While all conversion algorithms produce mathematically identical results, they differ in speed and numerical accuracy. | 0 | Theoretical and Fundamental Chemistry |
The assumption of a Newtonian fluid is essential since Stokes equations will not remain linear and time-independent in an environment that possesses complex mechanical and rheological properties. It is also common knowledge that many living microorganisms live in complex non-Newtonian fluids, which are common in biologically relevant environments. For instance, crawling cells often
migrate in elastic polymeric
fluids.
Non-Newtonian fluids have several properties that can be manipulated to produce small scale locomotion.
First, one such exploitable property is normal
stress differences. These differences will arise from the stretching of the fluid by the flow of
the swimmer. Another exploitable property is stress relaxation. Such time evolution of such stresses contain a memory term, though the extent in which this can be utilized is largely unexplored. Last, non-Newtonian fluids possess viscosities that are dependent on the shear rate. In other words, a swimmer would experience a different Reynolds number environment by altering its rate of motion. Many biologically relevant fluids exhibit shear-thinning, meaning viscosity decreases with shear rate. In such an environment, the rate at which a swimmer exhibits reciprocal motion would be significant as it would no longer be time invariant. This is in stark contrast to what we established where the rate in which a swimmer moves is irrelevant for establishing locomotion. Thus, a reciprocal swimmer can be designed in a non-Newtonian fluid. Qiu et al. (2014) were able to design a micro scallop in a non-Newtonian fluid. | 1 | Applied and Interdisciplinary Chemistry |
In general, the stability of a metal complex correlates with the denticity of the ligands, which can be attributed to the chelate effect. Polydentate ligands such as hexa- or octadentate ligands tend to bind metal ions more strongly than ligands of lower denticity, primarily due to entropic factors. Stability constants are a quantitative measure to assess the thermodynamic stability of coordination complexes. | 0 | Theoretical and Fundamental Chemistry |
*[http://www.simulia.com/products/multiphysics_coupling.html Abaqus Multiphysics Coupling]
*[http://www.altairhyperworks.com/Product,54,AcuSolve.aspx?AspxAutoDetectCookieSupport=1 AcuSolve FSI applications]
*[http://www.adina.com/fluid-structure-interaction.shtml ADINA FSI homepage]
*[https://www.ansys.com/products/platform/multiphysics-simulation/fluid-structure-interaction Ansys' FSI homepage]
*[https://web.archive.org/web/20110128234413/http://epsilon-sa.com/ Altair RADIOSS]
*[https://web.archive.org/web/20131223074755/http://www.autodesk.com/products/autodesk-simulation-family/features/simulation-cfd/all/gallery-view Autodesk Simulation CFD]
*Simcenter STAR-CCM+ from Siemens Digital Industries Software
*[https://web.archive.org/web/20110620191613/http://www.even-ag.ch/index.php/software/colyx CoLyX - FSI and mesh-morphing from EVEN - Evolutionary Engineering AG]
*[http://www.fluidyn.com/fluidyn/multi-physics/coupling-fluids-structures Fluidyn-MP FSI Multiphysics Coupling]
*[http://www.comsol.com/showroom/gallery/361/ COMSOL FSI homepage]
*[http://www.mpcci.de/ MpCCI homepage]
*[http://www.mscsoftware.com/Products/CAE-Tools/MD-Nastran.aspx MSC Software MD Nastran]
*[http://www.mscsoftware.com/Products/CAE-Tools/Dytran.aspx MSC Software Dytran]
*[http://www.open-engineering.com/index.php/eng/Applications/FSI FINE/Oofelie FSI: Fully integrated and strongly coupled for better convergence]
*[http://www.lstc.com/ LS-DYNA Home Page]
*[https://archive.today/20130123235636/http://www.fluidyn.com/fluidyn/coupling-fluid-and-structures Fluidyn-MP FSI: Fluid-Structure Interaction]
*[http://www.compassis.com/compass/en/Productos/Tdyn CompassFEM Tdyn]
*[http://www.compassis.com/compass/en/Productos/SeaFEM CompassFEM SeaFEM]
*[http://www.cradle-cfd.com/products/sctetra/index.html Cradle SC/Tetra CFD Software]
*[http://www.cimne.com/parachutes PARACHUTES FSI HomePage] | 1 | Applied and Interdisciplinary Chemistry |
The bulk electronic band structure of transition metal oxides consists of overlapping 2p orbitals from oxygen atoms, forming the lower energy, highly populated valence band, while the sparsely populated, higher energy conduction band consists of overlapping d orbitals of the transition metal cation. In contrast to metals, having a continuous band of electronic states, semiconductors have a band gap that prevents the recombination of electron/hole pairs that have been separated into the conduction band/ valence band. The nanosecond scale life times of these electron/hole separations allows for charge transfer to occur with an adsorbed species on the semiconductor surface. The Potential of an acceptor must be more positive than the conduction band potential of the semiconductor in order for reduction of the species to commence. Conversely, the potential of the donor species must be more negative than that of the valence band of the semiconductor for oxidation of the species to occur.
Near the surface of a semi-conducting metal oxide the valence and conduction bands are of higher energy, causing the upward bending of the band energy as shown in the band energy diagram, such that promotion of an electron from the valence band to the conduction band by light of energy greater than the band gap results in migration of the electron towards the bulk of the solid or to a counter electrode, while the hole left in the valence band moves towards the surface. The increased concentration of holes near the surface facilitates electron transfer to the solid, such as the example shown in the figure of the oxidation of redox couple D-/D. In the absence of any mechanism to remove electrons from the bulk of the solid irradiation continues to excite electrons to the conduction band producing holes in the valence band. This leads to the reduction of the upward bending of the band energies near the surface, and the subsequent increase in excited electron availability for reduction reactions.
The following equations are useful in describing the populations of valence and conduction bands in terms of holes and electrons for the bulk metal. is the density of electrons in the bulk metal conduction band, and is the density of holes in the bulk metal valence band. E is the lowest energy of the conduction band, E is the Fermi energy (electrochemical energy of the electrons), E is the highest energy of the valence band, N is the effective mass and mobility of an electron in the conduction band (constant), and N is the effective mass and mobility of a valence band hole (constant).
where k is Boltzmanns constant and T is the absolute temperature in kelvins.
The use of quantum mechanics perturbation theory can aid in calculating the probability of an electronic transition taking place. The probability is proportional to the square of the amplitude of the radiation field, E, and the square of the transition dipole moment |μ|.
The quantum yield for an ideal system undergoing photocatalytic events is measured as the number of events occurring per photon absorbed. The typical assumption in determining the quantum yield is that all photons are absorbed on the semiconductor surface, and the quantum yield is referred to as the apparent quantum yield. This assumption is necessary due to the difficulty in measuring the actual photons absorbed by the solid surface. The relation between the quantum yield, the rate of charge transfer, k, and the electron/hole recombination rate, k, is given by the following equation.
Photoinduced molecular transformations at transition metal oxide surfaces can be organized in two general classes. Photoexcitation of the adsorbate which then reacts with the catalyst substrate is classified as a catalyzed photoreaction. Photoexcitation of the catalyst followed by interaction of the catalyst with a ground state reactant is classified as a sensitized photoreaction. | 0 | Theoretical and Fundamental Chemistry |
The issue of using Ff phages for phage display is that they require the protein of interest to be translocated across the bacterial inner membrane before they are assembled into the phage. Some proteins cannot undergo this process and therefore cannot be displayed on the surface of Ff phages. In these cases, T7 phage display is used instead. In T7 phage display, the protein to be displayed is attached to the C-terminus of the gene 10 capsid protein of T7.
The disadvantage of using T7 is that the size of the protein that can be expressed on the surface is limited to shorter peptides because large changes to the T7 genome cannot be accommodated like it is in M13 where the phage just makes its coat longer to fit the larger genome within it. However, it can be useful for the production of a large protein library for scFV selection where the scFV is expressed on an M13 phage and the antigens are expressed on the surface of the T7 phage. | 1 | Applied and Interdisciplinary Chemistry |
Chitin-glucan complex (CGC) is a copolymer (polysaccharide) that makes up fungal cell walls, consisting of covalently-bonded chitin and branched 1,3/1,6-ß-D-glucan. CGCs are alkaline-insoluble. Different species of fungi have different structural compositions of chitin and β-glucan making up the CGCs in their cell walls. Soil composition and other environmental factors can also affect the ratio of chitin to β-glucan found in the CGC. Fungal cell walls may also contain chitosan-glucan complexes, which are similar copolymers but have chitosan instead of chitin. Chitin and chitosan are closely related molecules: greater than 40% of the polymer chain of chitin is made of acetylated glucosamine units, whereas greater than 60% of chitosan is made of deacetylated glucosamine units.
In their natural form, CGCs provide structural support to the fungal cell wall. Biomedical applications of CGCs have been studied, including the immunostimulant properties of A. fumigatus, as well as successful antibacterial activity against S. typhimurium by CGCs from A. niger and M. rouxii. There is some evidence that CGCs can act as an effective prebiotic, as it was tested on growing 100 different bifidobacterial strains as well as on rats in vivo. CGCs have many industrial applications, such as in food, cosmetics, and textiles industries, because they can be prepared easily without toxins. As food additives, they are commonly used due to their ability to adsorb heavy metal ions. Additionally, CGCs are produced in high volume industrially because they can be broken down into their constitutive components by hydrolysis, producing pure chitin (or chitosan) and β-glucans.
Rather than being produced from animal parts, pure chitin can be extracted from the cell walls of the fungus Pichia pastoris, recently classified as Komagataella pastoris. Unlike chitin extracted from crustaceans, for example, this chitin contains no heavy metals. A study revealed that the complex exhibits traces of α-chitin in the molecular structure via x-ray diffraction. The similarities in structure and physical properties suggest that the complex is a suitable alternative to crustacean-based chitin as fungi are a more feasible and reliable source of raw materials. | 1 | Applied and Interdisciplinary Chemistry |
is a Lewis acid as implicated by its tendency to hydrolyze. With the ether THF, reacts to give yellow crystals of . With chloride salts, reacts to form sequentially , (see figure above), and . The reaction of chloride ions with depends on the counterion. and gives the pentacoordinate complex , whereas smaller gives . These reactions highlight the influence of electrostatics on the structures of compounds with highly ionic bonding. | 0 | Theoretical and Fundamental Chemistry |
Eukaryotic photoautotrophs include red algae, haptophytes, stramenopiles, cryptophytes, chlorophytes, and land plants. These organisms perform photosynthesis through organelles called chloroplasts and are believed to have originated about 2 billion years ago. Comparing the genes of chloroplast and cyanobacteria strongly suggests that chloroplasts evolved as a result of endosymbiosis with cyanobacteria that gradually lost the genes required to be free-living. However, it is difficult to determine whether all chloroplasts originated from a single, primary endosymbiotic event, or multiple independent events. Some brachiopods (Gigantoproductus) and bivalves (Tridacna) also evolved photoautotrophy. | 0 | Theoretical and Fundamental Chemistry |
For any 3-dimensional lattice, the conventional unit cells are parallelepipeds, which in special cases may have orthogonal angles, or equal lengths, or both. Seven of the fourteen three-dimensional Bravais lattices are represented using conventional primitive cells, as shown below.
The other seven Bravais lattices (known as the centered lattices) also have primitive cells in the shape of a parallelepiped, but in order to allow easy discrimination on the basis of symmetry, they are represented by conventional cells which contain more than one lattice point. | 0 | Theoretical and Fundamental Chemistry |
The reductive acetyl CoA pathway (CoA) pathway, also known as the Wood-Ljungdahl pathway uses CO as electron acceptor and carbon source, and H as an electron donor to form acetic acid. This metabolism is wide spread within the phylum Bacillota, especially in the Clostridia.
The pathway is also used by methanogens, which are mainly Euryarchaeota, and several anaerobic chemolithoautotrophs, such as sulfate-reducing bacteria and archaea. It is probably performed also by the Brocadiales, an order of Planctomycetota that oxidize ammonia in anaerobic condition. Hydrogenotrophic methanogenesis, which is only found in certain archaea and accounts for 80% of global methanogenesis, is also based on the reductive acetyl CoA pathway.
The Carbon Monoxide Dehydrogenase/Acetyl-CoA Synthase is the oxygen-sensitive enzyme that permits the reduction of CO to CO and the synthesis of acetyl-CoA in several reactions.
One branch of this pathway, the methyl branch, is similar but non-homologous between bacteria and archaea. In this branch happens the reduction of CO to a methyl residue bound to a cofactor. The intermediates are formate for bacteria and formyl-methanofuran for archaea, and also the carriers, tetrahydrofolate and tetrahydropterins respectively in bacteria and archaea, are different, such as the enzymes forming the cofactor-bound methyl group.
Otherwise, the carbonyl branch is homologous between the two domains and consists of the reduction of another molecule of CO to a carbonyl residue bound to an enzyme, catalyzed by the CO dehydrogenase/acetyl-CoA synthase. This key enzyme is also the catalyst for the formation of acetyl-CoA starting from the products of the previous reactions, the methyl and the carbonyl residues.
This carbon fixation pathway requires only one molecule of ATP for the production of one molecule of pyruvate, which makes this process one of the main choice for chemolithoautotrophs limited in energy and living in anaerobic conditions. | 0 | Theoretical and Fundamental Chemistry |
Vector selection requires one to ensure the library made is representative of the entire genome. Any insert of the genome derived from a restriction enzyme should have an equal chance of being in the library compared to any other insert. Furthermore, recombinant molecules should contain large enough inserts ensuring the library size is able to be handled conveniently. This is particularly determined by the number of clones needed to have in a library. The number of clones to get a sampling of all the genes is determined by the size of the organism's genome as well as the average insert size. This is represented by the formula (also known as the Carbon and Clarke formula):
where,
is the necessary number of recombinants
is the desired probability that any fragment in the genome will occur at least once in the library created
is the fractional proportion of the genome in a single recombinant
can be further shown to be:
where,
is the insert size
is the genome size
Thus, increasing the insert size (by choice of vector) would allow for fewer clones needed to represent a genome. The proportion of the insert size versus the genome size represents the proportion of the respective genome in a single clone. Here is the equation with all parts considered: | 1 | Applied and Interdisciplinary Chemistry |
The molar concentration depends on the variation of the volume of the solution due mainly to thermal expansion. On small intervals of temperature, the dependence is
where is the molar concentration at a reference temperature, is the thermal expansion coefficient of the mixture. | 0 | Theoretical and Fundamental Chemistry |
This method of deoxidization involves adding specific metals into the steel. These metals will react with the unwanted oxygen, forming a strong oxide that, compared to pure oxygen, will reduce the steel's strength and qualities by a lesser amount.
The chemical equation for deoxidization is represented by:
where n and m are coefficients, D is the deoxidizing agent, and O is oxygen.
Thus, the chemical equilibrium equation involved is:
where a is the activity, or concentration, of the oxide in the steel,
a is the activity of the deoxidizing agent,
and a is the activity of the oxygen.
An increase in the equilibrium constant K will cause an increase in a, and thus more of the oxide product.
K can be manipulated by the steel temperature via the following equation:
where A and B are parameters specific to different deoxidizers and T is the temperature in K°. Below are the values for certain deoxidizers at a temperature of 1873 K°.
Below is a list of commonly used metallic deoxidizers:
* Ferrosilicon, ferromanganese, calcium silicide - used in steelmaking in production of carbon steels, stainless steels, and other ferrous alloys
* Manganese - used in steelmaking
* Silicon carbide, calcium carbide - used as ladle deoxidizer in steel production
* Aluminum dross - also a ladle deoxidizer, used in secondary steelmaking
* Calcium - used as a deoxidizer, desulfurizer, or decarbonizer for ferrous and non-ferrous alloys
* Titanium - used as a deoxidizer for steels
* Phosphorus, copper(I) phosphide - used in production of oxygen-free copper
* Calcium hexaboride - used in production of oxygen-free copper, yields higher conductivity copper than phosphorus-deoxidized
* Yttrium - used to deoxidize vanadium and other non-ferrous metals
* Zirconium
* Magnesium
* Carbon
* Tungsten | 1 | Applied and Interdisciplinary Chemistry |
Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, such as palladium chloride. | 0 | Theoretical and Fundamental Chemistry |
As of 2018 NIST does not provide certificates for the common stable isotope reference materials. As seen at this [https://www-s.nist.gov/srmors/viewTableV.cfm?tableid=42 link] showing the light stable isotope references currently available from NIST, this category includes all of the isotopic references critical for isotopic measurement of hydrogen, carbon, oxygen, nitrogen, and sulfur. However, for most of these materials NIST does provide a report of investigation, which gives a reference value that is not certified (following the definitions of May et al. (2000)). For the above examples of USGS34 and USGS35, NIST reports reference values but has not certified the results of Böhlke et al. (2003). Conversely, NIST has not provided a reference value for IAEA-SO-5. As seen at this [https://www-s.nist.gov/srmors/viewTable.cfm?tableid=41 link], NIST does certify isotopic reference materials for non-traditional "heavy" isotopic systems including rubidium, nickel, strontium, gallium, and thallium, as well as several isotopic systems that would normally be characterized at "light" but non-traditional such as magnesium and chlorine. While the isotopic composition of several of these materials were certified in the mid-1960s, other materials were certified as recently as 2011 (for example, [https://www-s.nist.gov/srmors/certificates/951a.pdf Boric Acid Isotopic Standard 951a]). | 0 | Theoretical and Fundamental Chemistry |
The tongue is skeletal muscle on the floor of the mouth of most vertebrates, that manipulates food for chewing (mastication) and swallowing (deglutition). It is sensitive and kept moist by saliva. The underside of the tongue is covered with a smooth mucous membrane. The tongue also has a touch sense for locating and positioning food particles that require further chewing. The tongue is used to roll food particles into a bolus before being transported down the esophagus through peristalsis.
The sublingual region underneath the front of the tongue is a location where the oral mucosa is very thin, and underlain by a plexus of veins. This is an ideal location for introducing certain medications to the body. The sublingual route takes advantage of the highly vascular quality of the oral cavity, and allows for the speedy application of medication into the cardiovascular system, bypassing the gastrointestinal tract. | 1 | Applied and Interdisciplinary Chemistry |
Low molecular weight polyols are widely used in polymer chemistry where they function as crosslinking agents and chain extenders. Alkyd resins for example, use polyols in their synthesis and are used in paints and in molds for casting. They are the dominant resin or "binder" in most commercial "oil-based" coatings. Approximately 200,000 tons of alkyd resins are produced each year. They are based on linking reactive monomers through ester formation. Polyols used in the production of commercial alkyd resins are glycerol, trimethylolpropane, and pentaerythritol. In polyurethane prepolymer production, a low molecular weight polyol-diol such as 1,4-butanediol may be used as a chain extender to further increase molecular weight though it does increase viscosity because more hydrogen bonding is introduced. | 0 | Theoretical and Fundamental Chemistry |
Continuous-flow photochemistry offers multiple advantages over batch photochemistry. Photochemical reactions are driven by the number of photons that are able to activate molecules causing the desired reaction. The large surface-area-to-volume ratio of a microreactor maximizes the illumination, and at the same time allows for efficient cooling, which decreases the thermal side products. | 0 | Theoretical and Fundamental Chemistry |
Thermogalvanic cells are a kind of heat engine. Ultimately the driving force behind them is the transport of entropy from the high temperature source to the low temperature sink. Therefore, these cells work thanks to a thermal gradient established between different parts of the cell. Because the rate and enthalpy of chemical reactions depend directly on the temperature, different temperatures at the electrodes imply different chemical equilibrium constants. This translates into unequal chemical equilibrium conditions on the hot side and on the cold side. The thermocell tries to approach an homogeneous equilibrium and, in doing so, produces a flow of chemical species and electrons. The electrons flow through the path of least resistance (the outer circuit) making it possible to extract power from the cell. | 0 | Theoretical and Fundamental Chemistry |
* bicarbonate derived from carbonic anhydrase (CA)-dependent hydration.
* CO metabolism
* Enters through membrane-transporting proteins or cystic fibrosis transmembrane conductance regulators.
* Calcium enters by voltage-dependent Ca channels or by release from the endoplasmic reticulum.
* Hydrogencarbonate and calcium activates sAC in the nucleus.
* sAC inside mitochondria is activated by metabolically generated CO through carbonic anhydrase. | 1 | Applied and Interdisciplinary Chemistry |
Electric power can be sourced from a diversified grid and thus reduce the effects of oil and geopolitics. Petroleum and petroleum-based products were used as a weapon after the Yom Kippur War, quadrupling the price of oil after an OPEC embargo. In 2000, the fuel protests in the United Kingdom virtually crippled UK transport and left transport agencies only a day away from bringing the diesel railway to a standstill. The rate of electrification in Britain is often compared to overseas and many acknowledge it is a geopolitical and resource issue as petroleum is a finite resource. In addition, the 2022 Russian invasion of Ukraine highlighted issues with regards to countries being dependent on hydrocarbons from other countries with embargo risks. | 1 | Applied and Interdisciplinary Chemistry |
Hattori defined the osmium isotope evolution of Earth's mantle, providing evidence for an accretion of chondritic meteorites after the core-mantle separation.
Prior to Hattori's research, the origin of large nuggets of platinum-group metals in streams was a subject of debate, with some proposing river water formation under a tropical climate and others suggesting mechanical erosion from rocks. However, her research presented evidence supporting their formation in rocks at high temperatures, followed by erosion to streams.
Through Hattori's research, it was also revealed that platinum grains found in streams contain oxygen, which led to initial suggestions of platinum oxide; however, using synchrotron techniques, it was demonstrated that the oxygen is combined with iron, not with platinum. | 0 | Theoretical and Fundamental Chemistry |
Phosphorus compounds are usually found as relatively insoluble phosphates in river water and, except in some exceptional circumstances, their origin is agriculture or human sewage. Phosphorus can encourage excessive growths of plants and algae and contribute to eutrophication. If a river discharges into a lake or reservoir phosphate can be mobilised year after year by natural processes. In the summer time, lakes stratify so that warm oxygen rich water floats on top of cold oxygen poor water. In the warm upper layers - the epilimnion- plants consume the available phosphate. As the plants die in the late summer they fall into the cool water layers underneath - the hypolimnion - and decompose. During winter turn-over, when a lake becomes fully mixed through the action of winds on a cooling body of water - the phosphates are spread throughout the lake again to feed a new generation of plants. This process is one of the principal causes of persistent algal blooms at some lakes. | 1 | Applied and Interdisciplinary Chemistry |
Two dimensional correlation analysis is a mathematical technique that is used to study changes in measured signals. As mostly spectroscopic signals are discussed, sometime also two dimensional correlation spectroscopy is used and refers to the same technique.
In 2D correlation analysis, a sample is subjected to an external perturbation while all other parameters of the system are kept at the same value. This perturbation can be a systematic and controlled change in temperature, pressure, pH, chemical composition of the system, or even time after a catalyst was added to a chemical mixture. As a result of the controlled change (the perturbation), the system will undergo variations which are measured by a chemical or physical detection method. The measured signals or spectra will show systematic variations that are processed with 2D correlation analysis for interpretation.
When one considers spectra that consist of few bands, it is quite obvious to determine which bands are subject to a changing intensity. Such a changing intensity can be caused for example by chemical reactions. However, the interpretation of the measured signal becomes more tricky when spectra are complex and bands are heavily overlapping. Two dimensional correlation analysis allows one to determine at which positions in such a measured signal there is a systematic change in a peak, either continuous rising or drop in intensity. 2D correlation analysis results in two complementary signals, which referred to as the 2D synchronous and 2D asynchronous spectrum. These signals allow amongst others
#to determine the events that are occurring at the same time (in phase) and those events that are occurring at different times (out of phase)
#to determine the sequence of spectral changes
#to identify various inter- and intramolecular interactions
#band assignments of reacting groups
#to detect correlations between spectra of different techniques, for example near infrared spectroscopy (NIR) and Raman spectroscopy | 0 | Theoretical and Fundamental Chemistry |
There are several spot tests that are infrequently used due to their limited applicability, but may be useful in situations where particular lichen metabolites need to be detected, or to distinguish between certain species when other tests are negative.
* A 10% solution of barium hydroxide (Ba(OH)) gives a violet colour when tested with diploschistesic acid, a chemical found in some Diploschistes species.
* A saturated solution of barium peroxide (BaO), when tested with olivetoric acid, will turn a yellow colour that becomes green after a few minutes.
* A 1% (weight per volume) solution of ferric chloride (FeCl) in ethanol produces several possible colours when tested with compounds that have phenolic groups.
* The N test uses a 35% solution of nitric acid, which can be used to distinguish species of Melanelia from brown species of Xanthoparmelia.
* The S test uses a sulphuric acid solution (0.5% to 10%) brushed over an acetone-extracted, dried sample from a lichen thallus, followed by heating over a flame for 30 seconds or until colour develops. A persistent violet to bright pink colour indicates the presence of miriquidic acid and can be used to distinguish between the two morphologically similar snow lichens, Stereocaulon alpinum and S. groenlandicum without having to resort to more laborious chemical analysis.
*The Beilstein test involves heating a small sample of the substance to be tested on a copper wire; halogenated compounds cause a temporary deep green flame colour. | 0 | Theoretical and Fundamental Chemistry |
The reactivity ratio of a growing copolymer chain terminating in a given monomer is the ratio of the reaction rate constant for addition of the same monomer and the rate constant for addition of the other monomer. That is, and , where for example is the rate constant for propagation of a polymer chain ending in monomer 1 (or A) by addition of monomer 2 (or B).
The composition and structural type of the copolymer depend on these reactivity ratios r and r according to the Mayo–Lewis equation, also called the copolymerization equation or copolymer equation, for the relative instantaneous rates of incorporation of the two monomers. | 0 | Theoretical and Fundamental Chemistry |
William Gregor (25 December 1761 – 11 June 1817) was an English clergyman and mineralogist who discovered the elemental metal titanium. | 1 | Applied and Interdisciplinary Chemistry |
The bilirubin level found in the body reflects the balance between production and excretion. Blood test results are advised to always be interpreted using the reference range provided by the laboratory that performed the test. The SI units are μmol/L. Typical ranges for adults are:
* 0–0.3 mg/dl – Direct (conjugated) bilirubin level
* 0.1–1.2 mg/dl – Total serum bilirubin level | 1 | Applied and Interdisciplinary Chemistry |
The extremely low coefficient of thermal expansion, about (20–320 °C), accounts for its remarkable ability to undergo large, rapid temperature changes without cracking (see thermal shock).
Fused quartz is prone to phosphorescence and "solarisation" (purplish discoloration) under intense UV illumination, as is often seen in flashtubes. "UV grade" synthetic fused silica (sold under various tradenames including "HPFS", "Spectrosil", and "Suprasil") has a very low metallic impurity content making it transparent deeper into the ultraviolet. An optic with a thickness of 1 cm has a transmittance around 50% at a wavelength of 170 nm, which drops to only a few percent at 160 nm. However, its infrared transmission is limited by strong water absorptions at 2.2 μm and 2.7 μm.
"Infrared grade" fused quartz (tradenames "Infrasil", "Vitreosil IR", and others), which is electrically fused, has a greater presence of metallic impurities, limiting its UV transmittance wavelength to around 250 nm, but a much lower water content, leading to excellent infrared transmission up to 3.6 μm wavelength. All grades of transparent fused quartz/fused silica have nearly identical mechanical properties. | 1 | Applied and Interdisciplinary Chemistry |
Common borate salts include sodium metaborate (NaBO) and borax. Borax is soluble in water, so mineral deposits only occur in places with very low rainfall. Extensive deposits were found in Death Valley and shipped with twenty-mule teams from 1883 to 1889. In 1925, deposits were found at Boron, California on the edge of the Mojave Desert. The Atacama Desert in Chile also contains mineable borate concentrations.
Lithium metaborate, lithium tetraborate, or a mixture of both, can be used in borate fusion sample preparation of various samples for analysis by XRF, AAS, ICP-OES and ICP-MS. Borate fusion and energy dispersive X-ray fluorescence spectrometry with polarized excitation have been used in the analysis of contaminated soils.
Disodium octaborate tetrahydrate (commonly abbreviated DOT) is used as a wood preservative or fungicide. Zinc borate is used as a flame retardant.
Some borates with large anions and multiple cations, like and have been considered for applications in nonlinear optics. | 0 | Theoretical and Fundamental Chemistry |
The best method of controlling hydrogen damage is to control contact between the metal and hydrogen. Many steps can be taken to reduce the entry of hydrogen into metals during critical operations like melting; casting; working (rolling, forging, etc.); welding; and surface preparation, like chemical cleaning, electroplating, and corrosion during their service life. Control of the environment and metallurgical control of the material to decrease its susceptibility to hydrogen are the two major approaches to reduce hydrogen damage. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits