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The pressure inside an ideal spherical bubble can be derived from thermodynamic free energy considerations. The above free energy can be written as:
where is the pressure difference between the inside (A) and outside (B) of the bubble, and is the bubble volume. In equilibrium, , and so,
For a spherical bubble, the volume and surface area are given simply by
and
Substituting these relations into the previous expression, we find
which is equivalent to the Young–Laplace equation when . | 0 | Theoretical and Fundamental Chemistry |
Solvent effects on colors and stability are often attributable to changes in the second coordination sphere. Such effects can be pronounced in complexes where the ligands in the first coordination sphere are strong hydrogen-bond donors and acceptors, e.g. respectively [Co(NH)] and [[Ferricyanide|[Fe(CN)]]]. Crown-ethers bind to polyamine complexes through their second coordination sphere. Polyammonium cations bind to the nitrogen centres of cyanometallates. | 0 | Theoretical and Fundamental Chemistry |
Photoelectrochemical processes are processes in photoelectrochemistry; they usually involve transforming light into other forms of energy. These processes apply to photochemistry, optically pumped lasers, sensitized solar cells, luminescence, and photochromism. | 0 | Theoretical and Fundamental Chemistry |
Boric acid is used in some nuclear power plants as a neutron poison. The boron in boric acid reduces the probability of thermal fission by absorbing some thermal neutrons. Fission chain reactions are generally driven by the probability that free neutrons will result in fission and is determined by the material and geometric properties of the reactor. Natural boron consists of approximately 20% boron-10 and 80% boron-11 isotopes. Boron-10 has a high cross-section for absorption of low energy (thermal) neutrons. By increasing boric acid concentration in the reactor coolant, the probability that a neutron will cause fission is reduced. Changes in boric acid concentration can effectively regulate the rate of fission taking place in the reactor. During normal at power operation, boric acid is used only in pressurized water reactors (PWRs), whereas boiling water reactors (BWRs) employ control rod pattern and coolant flow for power control, although BWRs can use an aqueous solution of boric acid and borax or sodium pentaborate for an emergency shutdown system if the control rods fail to insert. Boric acid may be dissolved in spent fuel pools used to store spent fuel elements. The concentration is high enough to keep neutron multiplication at a minimum. Boric acid was dumped over Reactor 4 of the Chernobyl nuclear power plant after its meltdown to prevent another reaction from occurring. | 0 | Theoretical and Fundamental Chemistry |
Gases are compressible and change volume when placed under pressure, are heated or are cooled. A volume of gas under one set of pressure and temperature conditions is not equivalent to the same gas under different conditions. References will be made to "actual" flow rate through a meter and "standard" or "base" flow rate through a meter with units such as acm/h (actual cubic meters per hour), sm/sec (standard cubic meters per second), kscm/h (thousand standard cubic meters per hour), LFM (linear feet per minute), or MMSCFD (million standard cubic feet per day).
Gas mass flow rate can be directly measured, independent of pressure and temperature effects, with ultrasonic flow meters, thermal mass flowmeters, Coriolis mass flowmeters, or mass flow controllers. | 1 | Applied and Interdisciplinary Chemistry |
The metal-dependent Fdh's feature Mo or W at their active sites. These active sites resemble the motif seen in DMSO reductase, with two molybdopterin cofactors bound to Mo/W in a bidentate fashion. The fifth and sixth ligands are sulfide and either cysteinate or selenocysteinate.
The mechanism of action appears to involve 2e redox of the metal centers, induced by hydride transfer from formate and release of carbon dioxide:
In this scheme, represents the four thiolate-like ligands provided by the two dithiolene cofactors, the molybdopterins. The dithiolene and cysteinyl/selenocysteinyl ligands are redox-innocent. In terms of the molecular details, the mechanism remains uncertain, despite numerous investigations. Most mechanisms assume that formate does not coordinate to Mo/W, in contrast to typical Mo/W oxo-transferases (e.g., DMSO reductase). A popular mechanistic proposal entails transfer of H from formate to the Mo/W=S group. | 1 | Applied and Interdisciplinary Chemistry |
Once Boltwood was offered a full professorship and chair of radiochemistry position at Yale in 1910, his career became more academic and he no longer actively pursued research. He was elected to both the United States National Academy of Sciences and the American Philosophical Society in 1911. He was elected to the American Academy of Arts and Sciences in 1913. In 1918, Boltwood became the director of Yale College chemical laboratory. As he took on more responsibilities at the college, he began overseeing the setup of two laboratories – Sloane Physics and Sterling Chemistry. During this time of added stress, he experienced bouts of depression and was forced to take time off to recover from a mental breakdown in 1924. He returned with renewed zeal and continued his work, but fell into periods of depression over the following years. On August 15, 1927, he took his own life in Hancock Point, Maine at the age of 57. | 0 | Theoretical and Fundamental Chemistry |
Chinese descriptions of alchemical laboratory equipment vary among texts and traditions, but share some common terminology. The following outline concerns alchemical hardware rather than liturgical or magical artifacts such as the sword, sun and moon mirrors, and peach-wood talismans.
The alchemy laboratory was called the Chamber of Elixirs ( , , or ). Sources differ about how to construct one. One text says the Chamber is ideally built near a mountain stream on in a secluded place (compare a clandestine drug lab), and has two doors, facing east and south; another says it should never be built over an old well or tomb, and has doors facing in all directions except north.
A layered "laboratory bench" called "altar; platform" was placed either in the center or along a wall of the Chamber. It was commonly depicted as a three-tiered clay stove platform, with eight ventilating openings on each tier—8 numerologically signifying (lit. eight directions) "eight points of the compass; all directions". The alchemists heating apparatus, interchangeably called stove; furnace or (kitchen) stove, was placed on the highest tier of the platform. Owing to inconsistent textual terminology, it translates as stove or furnace in some sources and as oven or combustion chamber' in others. Depending upon the alchemical formula, rice hulls, charcoal, or horse manure served as fuel.
A alchemical crucible; cauldron was placed over the stove or sometimes inside it. The double crucible was commonly made of red clay and had two halves joined to each other by their mouths. Another type of crucible had an iron lower half and clay upper one. After placing the ingredients in a crucible, the alchemist would hermetically seal it by applying several layers of a lute clay preparation inside and outside. The classic alchemical luting mixture was Six-and-One Mud with seven ingredients, typically alum, Turkestan rock salt ( ), lake salt, arsenolite, oyster shells, red clay, and talc.
Two common types of open alchemical reaction vessels were called tripod; container; cauldron and box; casing; container; aludel. Ding originally named a "tripod cauldron" Chinese ritual bronze, but alchemists used the term (and ) in reference to numerous metal or clay instruments with different shapes and functions. generally named both pots and various other reaction vessels to which fire was applied externally—as distinguished from that contained fire within. (an old character for cupboard; cabinet) was an alchemical name for a reaction vessel casing that was placed within a reaction chamber. Broadly speaking, had lids while were open at the top.
Besides the more open bowl-like or crucible forms of reaction vessels, whether lidded or not, many kinds of sealed containers were employed. Two common ones were the (lit. divine chamber) corresponding to the aludel subliming pot used in Arabic alchemy, and the pyx; bomb vessel composed of two roughly hemispherical crucible-like bowls with flanges placed mouth to mouth.
In addition to these basic tools, the alchemical apparatus also includes both common utensils (like mortars and pestles) and various specialized laboratory instruments for steaming, condensation, sublimation, distillation, and extraction. | 1 | Applied and Interdisciplinary Chemistry |
In April 1989, MIM Holdings Limited acquired the world rights to the Jameson Cell from TUNRA, with TUNRA retaining the rights to use the Cell for waste water treatment.
After the initial applications within the MIM Holdings group of companies, the years to 1994 saw Jameson Cells installed by various base and precious metals companies in Asia, South Africa, Canada and the United States, mainly in concentrate cleaning duties, but also in SX–EW electrolyte cleaning duties. The installation by Phelps Dodge (now Freeport-McMoRan) for electrolyte cleaning at its Morenci operation in Arizona was notable for having a large cell 6.5 m in diameter with 30 downcomers. The Morenci Jameson Cell consistently recovered over 82% of the organic extractant.
Toward the end of the period, Cells were installed in coal preparation plants operated by the BHP Mitsubishi Alliance and by Peabody for fines recovery. | 1 | Applied and Interdisciplinary Chemistry |
An electrode electrolyte interface behaves like a capacitance called electrochemical double-layer capacitance . The equivalent circuit for the redox reaction in Fig. 2 includes the double-layer capacitance as well as the charge transfer resistance . Another analog circuit commonly used to model the electrochemical double-layer is called a constant phase element.
The electrical impedance of this circuit is easily obtained remembering the impedance of a capacitance which is given by:
where is the angular frequency of a sinusoidal signal (rad/s), and .
It is obtained:
Nyquist diagram of the impedance of the circuit shown in Fig. 3 is a semicircle with a diameter and an angular frequency at the apex equal to (Fig. 3). Other representations, Bode plots, or Black plans can be used. | 0 | Theoretical and Fundamental Chemistry |
The EPS process (see Figure 2) begins with hot rolled strip steel in coil form. This steel pays off of an uncoiler, then passes through a machine which serves the purpose of "scale breaker", "leveler" or both. This machine (see Figure 2) works the material between sets of hardened rollers. This has the effect of removing the curvature of the strip ("coil set") and breaking loose the outer layers of mill scale which encase the steel strip.
After passing through the "scale breaker/leveler" machine, the steel strip enters the first "EPS slurry blasting cell". Slurry blasting is a wet abrasive blasting process that combines a fine-particle metallic abrasive with a "carrier liquid" (the most common one being water). This abrasive + water slurry mixture is fed into a rotating impeller which propels it at high velocity across the object to be cleaned (see Figure 3). Slurry blasting is a method for removing rust/scale, for blast cleaning and shot peening. Cleaning agents can be introduced into the carrier liquid to reduce smut and aid in rust prevention.
An EPS slurry blasting cell is composed of eight of the slurry discharge heads shown in Figure 3 – four for the top surface and four for the bottom surface of the strip. Inside the slurry blasting cell, jets of water cleanse the steel strip of both the abrasive particles and the dislodged mill scale. An EPS production system may use multiple EPS slurry blasting cells arranged in tandem, so the steel strip passes from one cell into the next, then into the next, and so on. Multiple cells increase the exposure of the steel strip to the slurry blast streams, thereby allowing the strip to move faster, yet still achieve the necessary level of scale removal. The strip speed and, therefore, system output increases in rough proportion to the number of EPS slurry blasting cells used.
The strip emerges from the final blasting cell and is dried using high-velocity air blowers. At this point the strip passes beneath a real-time oxide detector camera, which provides feedback to the line control to assure full oxide removal is accomplished.
To conclude the process, the strip may, optionally, have an oil film or lubricant applied, then it is recoiled. Of note is that tension created by the force of the recoiler pulling the strip through the scale breaker/leveler serves to flatten the strip, removing bow, edge wave and minor coil breaks. Also, not shown in Figure 2 is the slurry delivery/recirculation/filtering system. This closed-loop system collects the carrier liquid, abrasive and removed scale, filters out the removed scale, other contaminants and "undersized" abrasive particles, and returns a cleansed slurry mixture back to the blasting cells. | 1 | Applied and Interdisciplinary Chemistry |
Rotational–vibrational spectroscopy is a branch of molecular spectroscopy that is concerned with infrared and Raman spectra of molecules in the gas phase. Transitions involving changes in both vibrational and rotational states can be abbreviated as rovibrational (or ro-vibrational) transitions. When such transitions emit or absorb photons (electromagnetic radiation), the frequency is proportional to the difference in energy levels and can be detected by certain kinds of spectroscopy. Since changes in rotational energy levels are typically much smaller than changes in vibrational energy levels, changes in rotational state are said to give fine structure to the vibrational spectrum. For a given vibrational transition, the same theoretical treatment as for pure rotational spectroscopy gives the rotational quantum numbers, energy levels, and selection rules. In linear and spherical top molecules, rotational lines are found as simple progressions at both higher and lower frequencies relative to the pure vibration frequency. In symmetric top molecules the transitions are classified as parallel when the dipole moment change is parallel to the principal axis of rotation, and perpendicular when the change is perpendicular to that axis. The ro-vibrational spectrum of the asymmetric rotor water is important because of the presence of water vapor in the atmosphere. | 0 | Theoretical and Fundamental Chemistry |
Cram once admitted that his career wasnt without sacrifice. His first wife was Rollins classmate, Jean Turner, who also graduated in 1941, and went on to receive a masters degree in social work from Columbia University. His second wife, Jane, is a former chemistry professor at Mount Holyoke College. Cram chose not to have any children, "because I would either be a bad father or a bad scientist."
Cram died of cancer in 2001, at the age of 82. | 0 | Theoretical and Fundamental Chemistry |
Bond length is related to bond order: when more electrons participate in bond formation the bond is shorter. Bond length is also inversely related to bond strength and the bond dissociation energy: all other factors being equal, a stronger bond will be shorter. In a bond between two identical atoms, half the bond distance is equal to the covalent radius.
Bond lengths are measured in the solid phase by means of X-ray diffraction, or approximated in the gas phase by microwave spectroscopy. A bond between a given pair of atoms may vary between different molecules. For example, the carbon to hydrogen bonds in methane are different from those in methyl chloride. It is however possible to make generalizations when the general structure is the same. | 0 | Theoretical and Fundamental Chemistry |
A combination of radiochemistry and radiation chemistry is used to study nuclear reactions such as fission and fusion. Some early evidence for nuclear fission was the formation of a short-lived radioisotope of barium which was isolated from neutron irradiated uranium (Ba, with a half-life of 83 minutes and Ba, with a half-life of 12.8 days, are major fission products of uranium). At the time, it was thought that this was a new radium isotope, as it was then standard radiochemical practice to use a barium sulfate carrier precipitate to assist in the isolation of radium. More recently, a combination of radiochemical methods and nuclear physics has been used to try to make new superheavy elements; it is thought that islands of relative stability exist where the nuclides have half-lives of years, thus enabling weighable amounts of the new elements to be isolated. For more details of the original discovery of nuclear fission see the work of Otto Hahn. | 0 | Theoretical and Fundamental Chemistry |
Surprisal (a term coined in this context by Myron Tribus) was first introduced to better understand the specificity of energy release and selectivity of energy requirements of elementary chemical reactions. This gave rise to a series of new experiments which demonstrated that in elementary reactions, the nascent products could be probed and that the energy is preferentially released and not statistically distributed. Surprisal analysis was initially applied to characterize a small three molecule system that did not seemingly conform to principles of thermodynamics and a single dominant constraint was identified that was sufficient to describe the dynamic behavior of the three molecule system. Similar results were then observed in nuclear reactions, where differential states with varying energy partitioning are possible. Often chemical reactions require energy to overcome an activation barrier. Surprisal analysis is applicable to such applications as well. Later, surprisal analysis was extended to mesoscopic systems, bulk systems and to dynamical processes. | 0 | Theoretical and Fundamental Chemistry |
* Faculty of Humanities
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* Faculty of Chemistry and Technology of Rare Elements and electronic materials
* Faculty of Biotechnology and Organic synthesis
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* Institute of Polymer Technologies and Materials
* The State Institute of Professional Development and Retraining chemical, microbiological and medical industry
* Institute of Distance Education | 1 | Applied and Interdisciplinary Chemistry |
When comparing a polar and nonpolar molecule with similar molar masses, the polar molecule in general has a higher boiling point, because the dipole–dipole interaction between polar molecules results in stronger intermolecular attractions. One common form of polar interaction is the hydrogen bond, which is also known as the H-bond. For example, water forms H-bonds and has a molar mass M = 18 and a boiling point of +100 °C, compared to nonpolar methane with M = 16 and a boiling point of –161 °C. | 0 | Theoretical and Fundamental Chemistry |
One application of molecular imprinting technology is in affinity-based separations for biomedical, environmental, and food analysis. Sample preconcentration and treatment can be carried out by removing targeted trace amounts of analytes in samples using MIPs. The feasibility of MIPs in solid-phase extraction, solid-phase microextraction, and stir bar sorption extraction has been studied in several publications. Moreover, chromatography techniques such as HPLC and TLC can make use of MIPs as packing materials and stationary phases for the separation of template analytes. The kinetics of noncovalently imprinted materials were observed to be faster than materials prepared by the covalent approach, so noncovalent MIPs are more commonly used in chromatography.
Another application is the use of molecularly imprinted materials as chemical and biological sensors. They have been developed to target herbicides, sugars, drugs, toxins, and vapors. MIP-based sensors not only have high selectivity and high sensitivity, but they can also generate output signals (electrochemical, optical, or piezoelectric) for detection. This allows them to be utilized in fluorescence sensing, electrochemical sensing, chemiluminescence sensing, and UV-Vis sensing. Forensic applications that delve into detections of illicit drugs, banned sport drugs, toxins, and chemical warfare agents are also an area of growing interest.
Molecular imprinting has steadily been emerging in fields like drug delivery and biotechnology. The selective interaction between template and polymer matrix can be utilized in preparation of artificial antibodies. In the biopharmaceutical market, separation of amino acids, chiral compounds, hemoglobin, and hormones can be achieved with MIP adsorbents. Methods to utilize molecular imprinting techniques for mimicking linear and polyanionic molecules, such as DNA, proteins, and carbohydrates have been researched. An area of challenges is protein imprinting. Large, water-soluble biological macromolecules have posed a difficulty for molecular imprinting because their conformational integrity cannot be ensured in synthetic environments. Current methods to navigate this include immobilizing template molecules at the surface of solid substrates, thereby minimizing aggregation and controlling the template molecules to locate at the surface of imprinted materials. However, a critical review of molecular imprinting of proteins by scientists from Utrecht University found that further testing is required.
Pharmaceutical applications include selective drug delivery and control drug release systems, which make use of MIPs’ stable conformations, fast equilibrium release, and resistance to enzymatic and chemical stress. Intelligent drug release, the release of a therapeutic agent as a result of a specific stimuli, has also been explored. Molecularly imprinted materials of insulin and other drugs at the nanoscale were shown to exhibit high adsorption capacity for their respective targets, showing huge potential for newfound drug delivery systems. In comparison with natural receptors, MIPs also have higher chemical and physical stability, easier availability, and lower cost. MIPs could especially be used for stabilization of proteins, particularly selective protection of proteins against denaturation from heat. | 0 | Theoretical and Fundamental Chemistry |
The entropy due to a set of states that can be either occupied with probability or empty with probability can be written as:
where is Boltzmann constant.
For a continuously distributed set of states as a function of energy, such as the eigenstates in an electronic band structure, the above sum can be written as an integral over the possible energy values, rather than a sum. Switching from summing over individual states to integrating over energy levels, the entropy can be written as:
where is the density of states of the solid. The probability of occupation of each eigenstate is given by the Fermi function, :
where is the Fermi energy and is the absolute temperature. One can then re-write the entropy as:
This is the general formulation of the density-of-states based electronic entropy. | 0 | Theoretical and Fundamental Chemistry |
Norsteroids (nor-, L. norma, from "normal" in chemistry, indicating carbon removal) are a structural class of steroids that have had an atom or atoms (typically carbon) removed, biosynthetically or synthetically, from positions of branching off of rings or side chains (e.g., removal of methyl groups), or from within rings of the steroid ring system. For instance, 19-norsteroids (e.g., 19-norprogesterone) constitute an important class of natural and synthetic steroids derived by removal of the methyl group of the natural product progesterone; the equivalent change between testosterone and 19-nortestosterone (nandrolone) is illustrated below. | 1 | Applied and Interdisciplinary Chemistry |
The concept of shear flow is particularly useful when analyzing semi-monocoque structures, which can be idealized using the skin-stringer model. In this model, the longitudinal members, or stringers, carry only axial stress, while the skin or web resists the externally applied torsion and shear force. In this case, since the skin is a thin-walled structure, the internal shear stresses in the skin can be represented as shear flow. In design, the shear flow is sometimes known before the skin thickness is determined, in which case the skin thickness can simply be sized according to allowable shear stress. | 1 | Applied and Interdisciplinary Chemistry |
Deoxyguanosine monophosphate (dGMP), also known as deoxyguanylic acid or deoxyguanylate in its conjugate acid and conjugate base forms, respectively, is a derivative of the common nucleic acid guanosine triphosphate (GTP), in which the –OH (hydroxyl) group on the 2 carbon on the nucleotides pentose has been reduced to just a hydrogen atom (hence the "deoxy-" part of the name). It is used as a monomer in DNA. | 1 | Applied and Interdisciplinary Chemistry |
Electro-electrodialysis is an electromembrane process utilizing three compartments, which combines electrodialysis and electrolysis. It is commonly used to recover acid from a solution using AEM, CEM and electrolysis. The three compartments are separated by two barriers, which are the ion exchange membranes. The compartment in the middle has the water to be treated. The compartments located on the sides contain clean water. The anions pass through the AEM, while the cations pass through the CEM. The electricity creates H in the anions side and OH in the cations side, which react with the respective ions. | 1 | Applied and Interdisciplinary Chemistry |
Pulsed sources allow for the utilization of Fourier-transform spectroscopy principles in scanning near-field optical microscopy techniques. Particularly in nano-FTIR, where the scattering from a sharp probe-tip is used to perform spectroscopy of samples with nanoscale spatial resolution, a high-power illumination from pulsed infrared lasers makes up for a relatively small scattering efficiency (often < 1%) of the probe. | 0 | Theoretical and Fundamental Chemistry |
The Eschenmoser sulfide contraction is an organic reaction first described by Albert Eschenmoser for the synthesis of 1,3-dicarbonyl compounds from a thioester. The method requires a base and a tertiary phosphine. The method is of some relevance to organic chemistry and has been notably applied in the vitamin B total synthesis.
A base abstracts the labile hydrogen atom in the thioester, a sulfide anion is formed through an episulfide intermediate which is removed by the phosphine. | 0 | Theoretical and Fundamental Chemistry |
* [https://sosradon.org/devices National radon program services]. Kansas State University. Accessed 17 October 2017. | 1 | Applied and Interdisciplinary Chemistry |
Because of the ambiguity of the term valence, other notations are currently preferred. Beside the lambda notation, as used in the IUPAC nomenclature of inorganic chemistry, oxidation state is a more clear indication of the electronic state of atoms in a molecule.
The oxidation state of an atom in a molecule gives the number of valence electrons it has gained or lost. In contrast to the valency number, the oxidation state can be positive (for an electropositive atom) or negative (for an electronegative atom).
Elements in a high oxidation state have an oxidation state higher than +4, and also, elements in a high valence state (hypervalent elements) have a valence higher than 4. For example, in perchlorates , chlorine has 7 valence bonds (thus, it is heptavalent, in other words, it has valence 7), and it has oxidation state +7; in ruthenium tetroxide , ruthenium has 8 valence bonds (thus, it is octavalent, in other words, it has valence 8), and it has oxidation state +8.
In some molecules, there is a difference between valence and oxidation state for a given atom. For example, in disulfur decafluoride molecule , each sulfur atom has 6 valence bonds (5 single bonds with fluorine atoms and 1 single bond with the other sulfur atom). Thus, each sulfur atom is hexavalent or has valence 6, but has oxidation state +5. In the dioxygen molecule , each oxygen atom has 2 valence bonds and so is divalent (valence 2), but has oxidation state 0. In acetylene , each carbon atom has 4 valence bonds (1 single bond with hydrogen atom and a triple bond with the other carbon atom). Each carbon atom is tetravalent (valence 4), but has oxidation state −1. | 0 | Theoretical and Fundamental Chemistry |
GaN is another option, because metal nitrides usually have a narrow band gap that could encompass almost the entire solar spectrum. GaN has a narrower band gap than but is still large enough to allow water splitting to occur at the surface. GaN nanowires exhibited better performance than GaN thin films, because they have a larger surface area and have a high single crystallinity which allows longer electron-hole pair lifetimes. Meanwhile, other non-oxide semiconductors such as GaAs, Molybdenum disulfide|, and are used as n-type electrode, due to their stability in chemical and electrochemical steps in the photocorrosion reactions. | 0 | Theoretical and Fundamental Chemistry |
Absolute size-exclusion chromatography (ASEC) is a technique that couples a light scattering instrument, most commonly multi-angle light scattering (MALS) or another form of static light scattering (SLS), but possibly a dynamic light scattering (DLS) instrument, to a size-exclusion chromatography system for absolute molar mass and/or size measurements of proteins and macromolecules as they elute from the chromatography system.
The definition of “absolute” in this case is that calibration of retention time on the column with a set of reference standards is not required to obtain molar mass or the hydrodynamic size, often referred to as hydrodynamic diameter (D in units of nm). Non-ideal column interactions, such as electrostatic or hydrophobic surface interactions that modulate retention time relative to standards, do not impact the final result. Likewise, differences between conformation of the analyte and the standard have no effect on an absolute measurement; for example, with MALS analysis, the molar mass of inherently disordered proteins are characterized accurately even though they elute at much earlier times than globular proteins with the same molar mass, and the same is true of branched polymers which elute late compared to linear reference standards with the same molar mass. Another benefit of ASEC is that the molar mass and/or size is determined at each point in an eluting peak, and therefore indicates homogeneity or polydispersity within the peak. For example, SEC-MALS analysis of a monodisperse protein will show that the entire peak consists of molecules with the same molar mass, something that is not possible with standard SEC analysis.
Determination of molar mass with SLS requires combining the light scattering measurements with concentration measurements. Therefore SEC-MALS typically includes the light scattering detector and either a differential refractometer or UV/Vis absorbance detector. In addition, MALS determines the rms radius R of molecules above a certain size limit, typically 10 nm. SEC-MALS can therefore analyze the conformation of polymers via the relationship of molar mass to R. For smaller molecules, either DLS or, more commonly, a differential viscometer is added to determine hydrodynamic radius and evaluate molecular conformation in the same manner.
In SEC-DLS, the sizes of the macromolecules are measured as they elute into the flow cell of the DLS instrument from the size exclusion column set. The hydrodynamic size of the molecules or particles are measured and not their molecular weights. For proteins a Mark-Houwink type of calculation can be used to estimate the molecular weight from the hydrodynamic size.
A major advantage of DLS coupled with SEC is the ability to obtain enhanced DLS resolution. Batch DLS is quick and simple and provides a direct measure of the average size, but the baseline resolution of DLS is a ratio of 3:1 in diameter. Using SEC, the proteins and protein oligomers are separated, allowing oligomeric resolution. Aggregation studies can also be done using ASEC. Though the aggregate concentration may not be calculated with light scattering (an online concentration detector such as that used in SEC-MALS for molar mass measurement also determines aggregate concentration), the size of the aggregate can be measured, only limited by the maximum size eluting from the SEC columns.
Limitations of ASEC with DLS detection include flow-rate, concentration, and precision. Because a correlation function requires anywhere from 3–7 seconds to properly build, a limited number of data points can be collected across the peak. ASEC with SLS detection is not limited by flow rate and measurement time is essentially instantaneous, and the range of concentration is several orders of magnitude larger than for DLS. However, molar mass analysis with SEC-MALS does require accurate concentration measurements. MALS and DLS detectors are often combined in a single instrument for more comprehensive absolute analysis following separation by SEC. | 1 | Applied and Interdisciplinary Chemistry |
In a manuscript from 1704, Newton describes his attempts to extract scientific information from the Bible and estimates that the world would end no earlier than 2060. In predicting this, he said, "This I mention not to assert when the time of the end shall be, but to put a stop to the rash conjectures of fanciful men who are frequently predicting the time of the end, and by doing so bring the sacred prophesies into discredit as often as their predictions fail." | 1 | Applied and Interdisciplinary Chemistry |
This equipment is a spectroscopic (light gathering) apparatus and corresponding method for rapidly detecting and analyzing analytes in a sample. The sample is irradiated by an excitation source in optical communication with the sample. The excitation source may include, but is not limited to, a laser, a flash lamp, an arc lamp, a light-emitting diode, or the like.
Figure 1 depicts the current version of the SOFIA system. Four linear arrays (101) extend from a sample holder (102), which houses an elongated, transparent sample container which is open at both ends, to an end port (103). The distal end of the endport (104) is inserted into an end port assembly (200). The linear arrays (101) comprise a plurality of optical fibers having a first end and a second end, the plurality of optical fibers optionally surrounded by a protective and/or insulating sheath. The optical fibers are linearly arranged, meaning that they are substantially coplanar with respect to one another so as to form an elongated row of fibers. | 1 | Applied and Interdisciplinary Chemistry |
When the receptor is inactive, the GEF domain may be bound to an also inactive α-subunit of a heterotrimeric G-protein. These "G-proteins" are a trimer of α, β, and γ subunits (known as Gα, Gβ, and Gγ, respectively) that is rendered inactive when reversibly bound to Guanosine diphosphate (GDP) (or, alternatively, no guanine nucleotide) but active when bound to guanosine triphosphate (GTP). Upon receptor activation, the GEF domain, in turn, allosterically activates the G-protein by facilitating the exchange of a molecule of GDP for GTP at the G-protein's α-subunit. The cell maintains a 10:1 ratio of cytosolic GTP:GDP so exchange for GTP is ensured. At this point, the subunits of the G-protein dissociate from the receptor, as well as each other, to yield a Gα-GTP monomer and a tightly interacting Gβγ dimer, which are now free to modulate the activity of other intracellular proteins. The extent to which they may diffuse, however, is limited due to the palmitoylation of Gα and the presence of an isoprenoid moiety that has been covalently added to the C-termini of Gγ.
Because Gα also has slow GTP→GDP hydrolysis capability, the inactive form of the α-subunit (Gα-GDP) is eventually regenerated, thus allowing reassociation with a Gβγ dimer to form the "resting" G-protein, which can again bind to a GPCR and await activation. The rate of GTP hydrolysis is often accelerated due to the actions of another family of allosteric modulating proteins called regulators of G-protein signaling, or RGS proteins, which are a type of GTPase-activating protein, or GAP. In fact, many of the primary effector proteins (e.g., adenylate cyclases) that become activated/inactivated upon interaction with Gα-GTP also have GAP activity. Thus, even at this early stage in the process, GPCR-initiated signaling has the capacity for self-termination. | 1 | Applied and Interdisciplinary Chemistry |
The glucose transporter (GLUTs) is a type of uniporter responsible for the facilitated diffusion of glucose molecules across cell membranes.Glucose is a vital energy source for most living cells, however, due to its large size, it cannot freely move through the cell membrane. The glucose transporter is specialized in transporting glucose specifically across the membrane. The GLUT proteins have several types of isoforms, each distributed in different tissues and exhibiting different kinetic properties.
GLUTs are integral membrane proteins composed of 12 α-helix membrane spanning regions. The GLUT proteins are encoded by the SLC2 genes and categorized into three classes based on amino acid sequence similarity. Humans have been found to express fourteen GLUT proteins. Class I GLUTs include GLUT1, one of the most studied isoforms, and GLUT2. GLUT1 is found in various tissues like the red blood cells, brain, and blood-brain barrier and is responsible for basal glucose uptake. GLUT2 is predominantly found in the liver, pancreas, and small intestines. It plays an important role in insulin secretion from pancreatic beta cells. Class II includes the GLUT3 and GLUT4. GLUT3, primarily found in the brain, neurons and placenta, has a high affinity for glucose in facilitating glucose uptake into neurons. GLUT4 plays a role in insulin-regulated glucose uptake and is mainly found in insulin-sensitive tissues such as muscle and adipose tissue. Class III includes GLUT5, found in the small intestine, kidney, testes, and skeletal muscle. Unlike the other GLUTs, GLUT5 specifically transports fructose rather than glucose.
Glucose transporters allow glucose molecules to move down their concentration gradient from areas of high glucose concentration to areas of low concentration. This process often involves bringing glucose from the extracellular space or blood into the cell. The concentration gradient set up by glucose concentrations fuels the process without the need for ATP.
When glucose binds to the glucose transporter, the protein channels change shape and undergo a conformational change to transport the glucose across the membrane. Once the glucose unbinds, the protein returns to its original shape. The glucose transporter is essential for carrying out physiological processes that require high energy demands in the brain, muscles, and kidneys by providing an adequate amount of energy substrate for metabolism. Diabetes, an example of a condition that involves glucose metabolism, highlights the importance of the regulation of glucose uptake in disease management. | 1 | Applied and Interdisciplinary Chemistry |
Biotechnology,
Bioluminescence,
Molecular chemistry,
Enzymatic chemistry,
Genetic engineering,
Pharmaceuticals,
Endocrinology,
Neurochemistry,
Hematology,
Nutrition,
Photosynthesis,
Environmental,
Toxicology | 1 | Applied and Interdisciplinary Chemistry |
The 17-bp transcriptional complex has an 8-bp DNA-RNA hybrid, that is, 8 base-pairs involve the RNA transcript bound to the DNA template strand. As transcription progresses, ribonucleotides are added to the 3′ end of the RNA transcript and the RNAP complex moves along the DNA. The characteristic elongation rates in prokaryotes and eukaryotes are about 10–100 nts/sec.
Aspartyl (asp) residues in the RNAP will hold on to Mg ions, which will, in turn, coordinate the phosphates of the ribonucleotides. The first Mg will hold on to the α-phosphate of the NTP to be added. This allows the nucleophilic attack of the 3′-OH from the RNA transcript, adding another NTP to the chain. The second Mg will hold on to the pyrophosphate of the NTP. The overall reaction equation is:
:(NMP) + NTP → (NMP) + PP | 1 | Applied and Interdisciplinary Chemistry |
Subsequent research on DNA computing has produced [https://ieeexplore.ieee.org/document/8642913 reversible DNA computing], bringing the technology one step closer to the silicon-based computing used in (for example) PCs. In particular, [https://web.archive.org/web/20190201104419/https://users.cs.duke.edu/~reif/index.htm John Reif] and his group at Duke University have proposed two different techniques to reuse the computing DNA complexes. The first design uses dsDNA gates, while the second design uses DNA hairpin complexes.
While both the designs face some issues (such as reaction leaks), this appears to represent a significant breakthrough in the field of DNA computing. Some other groups have also attempted to address the gate reusability problem.
Using strand displacement reactions (SRDs), reversible proposals are presented in the [https://www.mdpi.com/2073-8994/13/7/1242 "Synthesis Strategy of Reversible Circuits on DNA Computers" paper] for implementing reversible gates and circuits on DNA computers by combining DNA computing and reversible computing techniques. This paper also proposes a universal reversible gate library (URGL) for synthesizing n-bit reversible circuits on DNA computers with an average length and cost of the constructed circuits better than the previous methods. | 1 | Applied and Interdisciplinary Chemistry |
The cross-over temperature from the normal hadronic to the QGP phase is about . This "crossover" may actually not be only a qualitative feature, but instead one may have to do with a true (second order) phase transition, e.g. of the universality class of the three-dimensional Ising model. The phenomena involved correspond to an energy density of a little less than . For relativistic matter, pressure and temperature are not independent variables, so the equation of state is a relation between the energy density and the pressure. This has been found through lattice computations, and compared to both perturbation theory and string theory. This is still a matter of active research. Response functions such as the specific heat and various quark number susceptibilities are currently being computed. | 0 | Theoretical and Fundamental Chemistry |
Photophoresis denotes the phenomenon that small particles suspended in gas (aerosols) or liquids (hydrocolloids) start to migrate when illuminated by a sufficiently intense beam of light. The existence of this phenomenon is owed to a non-uniform distribution of temperature of an illuminated particle in a fluid medium. Separately from photophoresis, in a fluid mixture of different kinds of particles, the migration of some kinds of particles may be due to differences in their absorptions of thermal radiation and other thermal effects collectively known as thermophoresis. In laser photophoresis, particles migrate once they have a refractive index different from their surrounding medium. The migration of particles is usually possible when the laser is slightly or not focused. A particle with a higher refractive index compared to its surrounding molecule moves away from the light source due to momentum transfer from absorbed and scattered light photons. This is referred to as a radiation pressure force. This force depends on light intensity and particle size but has nothing to do with the surrounding medium. Just like in Crookes radiometer, light can heat up one side and gas molecules bounce from that surface with greater velocity, hence push the particle to the other side. Under certain conditions, with particles of diameter comparable to the wavelength of light, the phenomenon of a negative indirect photophoresis occurs, due to the unequal heat generation on the laser irradiation between the back and front sides of particles, this produces a temperature gradient in the medium around the particle such that molecules at the far side of the particle from the light source may get to heat up more, causing the particle to move towards the light source.
If the suspended particle is rotating, it will also experience the Yarkovsky effect.
Discovery of photophoresis is usually attributed to Felix Ehrenhaft in the 1920s, though earlier observations were made by others including Augustin-Jean Fresnel. | 0 | Theoretical and Fundamental Chemistry |
Barbas has a Ph.D. from Complutense University of Madrid. From 2005 until 2006 she was a Marie Curie fellow at King's College London. As of 2022 she is a professor of analytical chemistry at the Universidad CEU San Pablo and is the president of the Madrid section of the Spanish Royal Society of Chemistry. | 0 | Theoretical and Fundamental Chemistry |
The corrosive effects of nitric acid are exploited for some specialty applications, such as etching in printmaking, pickling stainless steel or cleaning silicon wafers in electronics.
A solution of nitric acid, water and alcohol, nital, is used for etching metals to reveal the microstructure. ISO 14104 is one of the standards detailing this well known procedure.
Nitric acid is used either in combination with hydrochloric acid or alone to clean glass cover slips and glass slides for high-end microscopy applications. It is also used to clean glass before silvering when making silver mirrors.
Commercially available aqueous blends of 5–30% nitric acid and 15–40% phosphoric acid are commonly used for cleaning food and dairy equipment primarily to remove precipitated calcium and magnesium compounds (either deposited from the process stream or resulting from the use of hard water during production and cleaning). The phosphoric acid content helps to passivate ferrous alloys against corrosion by the dilute nitric acid.
Nitric acid can be used as a spot test for alkaloids like LSD, giving a variety of colours depending on the alkaloid. | 0 | Theoretical and Fundamental Chemistry |
Excessive doses of escitalopram usually cause relatively minor untoward effects, such as agitation and tachycardia. However, dyskinesia, hypertonia, and clonus may occur in some cases. Therapeutic blood levels of escitalopram are usually in the range of 20–80 μg/L but may reach 80–200 μg/L in the elderly, patients with hepatic dysfunction, those who are poor CYP2C19 metabolizers or following acute overdose. Monitoring of the drug in plasma or serum is generally accomplished using chromatographic methods. Chiral techniques are available to distinguish escitalopram from its racemate, citalopram. | 0 | Theoretical and Fundamental Chemistry |
A large group of organocatalysts incorporate the urea or the thiourea moiety. These catalytically effective (thio)urea derivatives termed (thio)urea organocatalysts provide explicit double hydrogen-bonding interactions to coordinate and activate H-bond accepting substrates.
Their current uses are restricted to asymmetric multicomponent reactions, including those involving Michael addition, asymmetric multicomponent reactions for the synthesis of spirocycles, asymmetric multicomponent reactions involving acyl Strecker reactions, asymmetric Petasis reactions, asymmetric Biginelli reactions, asymmetric Mannich reactions, asymmetric aza-Henry reactions, and asymmetric reductive coupling reactions. | 0 | Theoretical and Fundamental Chemistry |
Before gunpowder was applied to civil engineering, there were two ways to break up large rocks, by hard labor or by heating with large fires followed by rapid quenching. The earliest record for the use of gunpowder in mines comes from Hungary in 1627. It was introduced to Britain in 1638 by German miners, after which records are numerous. Until the invention of the safety fuse by William Bickford in 1831, the practice was extremely dangerous. Another reason for danger were the dense fumes given off and the risk of igniting flammable gas when used in coal mines. | 1 | Applied and Interdisciplinary Chemistry |
The monocyte activation test (MAT) is another proposed method to test for endotoxins based on monocytes in human blood. It measures the release of cytokines from these due to the presence of pyrogens, basically mirroring the process by which these toxins cause fever in humans (and rabbits, as in the original pyrogen test). A protocol for the MAT test, using cultured cells, is described in the European Pharmacopoeia.
A recent study employing genetically engineered monocytes was able to significantly enhance the sensitivity of monocyte-based detection assays by bringing down the assay-completion time from more than 20 hours to 2–3 hours. | 0 | Theoretical and Fundamental Chemistry |
Oseltamivir total synthesis concerns the total synthesis of the antiinfluenza drug oseltamivir marketed by Hoffmann-La Roche under the trade name Tamiflu. Its commercial production starts from the biomolecule shikimic acid harvested from Chinese star anise and from recombinant E. coli. Control of stereochemistry is important: the molecule has three stereocenters and the sought-after isomer is only 1 of 8 stereoisomers. | 0 | Theoretical and Fundamental Chemistry |
The following table lists some of the most important radiogenic isotope systems used in geology, in order of decreasing half-life of the radioactive parent isotope. The values given for half-life and decay constant are the current consensus values in the Isotope Geology community.
</big> indicates ultimate decay product of a series.
Units used in this table years years years | 0 | Theoretical and Fundamental Chemistry |
* Lauro Magnani, Chiesa di Sant’Anna Guide di Genova, 90, Genova, SAGEP Edizioni, 1979,
* Antonio Corvi ed Ernesto Riva, La farmacia monastica e conventuale, Pacini Editore, 1996.
* Antonio Corvi, "La Medicina curativa di Le Roy", in Atti e Memorie dell'Associazione Italiana Storia Della Farmacia, XIV n. 2 1997 p. 137
* Osservatorio Civis, Genova, guida alle botteghe storiche, De Ferrari & Devega Editori, Genova, 2002.
* Paolo Oliveri, La Farmacia di SantAnna dei Padri Carmelitani Scalzi in Genova, in Rivista di Storia della Farmacia', XXV, n. 1., Aprile 2008.
* Corinna Praga, Andar per creuse oltre il centro storico 2, Itinerari dal Portello, dal Vico della Croce Bianca e da via Balbi verso la Porta delle Chiappe, Italia Nostra, Genova, ERGA, 2016.
* Ezio Battaglia e Silvia Piacentini, Il Convento di SantAnna e la sua Antica Farmacia a Genova', SAGEP Editori, Genova 2020.
* Catalogo Generale dei Beni Culturali, Bottega storica, Farmacia, Antica Farmacia SantAnna.' | 1 | Applied and Interdisciplinary Chemistry |
The chloroplast gene rbcL, which codes for the large subunit of RuBisCO has been widely used as an appropriate locus for analysis of phylogenetics in plant taxonomy. | 0 | Theoretical and Fundamental Chemistry |
* 1801 - René Just Haüy published his multi-volume Traité de Minéralogie in Paris. A second edition under the title Traité de Cristallographie was published in 1822.
* 1801 - Déodat de Dolomieu published his Sur la philosophie minéralogique et sur lespèce minéralogique' in Paris.
* 1815 - René Just Haüy published his Law of Symmetry.
* 1815 - Christian Samuel Weiss, founder of the dynamist school of crystallography, developed a geometric treatment of crystals in which crystallographic axes are the basis for classification of crystals rather than Haüy’s polyhedral molecules.
* 1819 - Eilhard Mitscherlich discovered crystallographic isomorphism.
* 1822 - Friedrich Mohs attempted to bring the molecular approach of Haüy and the geometric approach of Weiss into agreement.
* 1823 - Franz Ernst Neumann invented a system of crystal face notation, by using the reciprocals of the intercepts with crystal axes, which becomes the standard for the next 60 years.
* 1824 - Ludwig August Seeber conceived of the concept of using an array of discrete (molecular) points to represent a crystal.
* 1826 - Moritz Ludwig Frankenheim deriveed the 32 crystal classes by using the crystallographic restriction, consistent with Haüy’s laws, that only 2, 3, 4 and 6-fold rotational axes are permitted.
* 1830 - Johann F. C. Hessel publishes an independent geometrical derivation of the 32 point groups (crystal classes).
* 1832 - Friedrich Wöhler and Justus von Liebig discovered polymorphism in molecular crystals, using the example of benzamide.
* 1839 - William Hallowes Miller invented zonal relations by projecting the faces of a crystal upon the surface of a circumscribed sphere. Miller indices are defined which form a notation system in crystallography for planes in crystal (Bravais) lattices.
* 1840 - Gabriel Delafosse, independently of Seeber, represented crystal structure as an array of discrete points generated by defined translations.
* 1842 - Moritz Frankenheim derived 15 different theoretical networks of points in space not dependent on molecular shape.
* 1848 - Louis Pasteur discovered that sodium ammonium tartrate can crystallize in left- and right-handed forms and showed that the two forms can rotate polarized light in opposite directions. This was the first demonstration of molecular chirality, and also the first explanation of isomerism.
* 1850 - Auguste Bravais derived the 14 space lattices.
* 1869 - Axel Gadolin, independently of Hessel, derived the 32 crystal classes using stereographic projection.
* 1877 - Paul Heinrich von Groth founded the journal Zeitschrift für Krystallographie und Mineralogie, and served as its editor for 44 years.
* 1877 - Ernest-François Mallard, building on the work of Auguste Bravais, published a memoir on optically “anomalous” crystals (that is, those crystals the morphology of which seems to be of greater symmetry than their optics), in which the importance of crystal twinning and "pseudosymmetry" were used as explanatory concepts.
* 1879 - Leonhard Sohncke listed the 65 crystallographic point systems using rotations and reflections in addition to translations.
* 1880 - Pierre Curie and Paul-Jacques Curie discovered piezoelectricity in crystals. In 1881 they demonstrated the reverse effect: that crystals could be made to deform when subject to an electric field.
* 1888 - Friedrich Reinitzer discovered the existence of liquid crystals during investigations of cholesteryl benzoate.
* 1889 - Otto Lehmann, after receiving a letter from Friedrich Reinitzer, used polarizing light to explain the phenomenon of liquid crystals.
* 1891 - Derivation of the 230 space groups (by adding mirror-image symmetry to Sohncke’s work) by a collaborative effort of Evgraf Fedorov and Arthur Schoenflies.
* 1894 - William Barlow, using a sphere packing approach, independently derived the 230 space groups.
* 1894 - Pierre Curie described the now called Curie's principle for the symmetry properties of crystals.
* 1895 - Wilhelm Conrad Röntgen on 8 November 1895 produced and detected electromagnetic radiation in a wavelength range now known as X-rays or Röntgen rays, an achievement that earned him the first Nobel Prize in Physics in 1901. X-rays became the major mode of crystallographic research in the 20th century. | 1 | Applied and Interdisciplinary Chemistry |
Reef Ball Development Group was founded in 1993 by Todd Barber, with the goal of helping to preserve and protect coral reefs for the benefit of future generations. Barber witnessed his favorite coral reef on Grand Cayman destroyed by Hurricane Gilbert, and wanted to do something to help increase the resiliency of eroding coral reefs. Barber and his father patented the idea of building reef substrate modules with a central inflatable bladder, so that the modules would be buoyant, making them easy to deploy by hand or with a small boat, rather than requiring heavy machinery.
Over the next few years, with the help of research colleagues at University of Georgia, Nationwide Artificial Reef Coordinators and the Florida Institute of Technology (FIT), Barber, his colleagues, and business partners worked to perfect the design. In 1997, Kathy Kirbo established The Reef Ball Foundation, Inc as a non-profit organization with original founders being Todd Barber as chairman and charter member, Kathy Kirbo founding executive director, board secretary, and charter member, Larry Beggs as vice president and a charter member and Eric Krasle as treasurer and a charter member, Jay Jorgensen as a charter member. Reef balls can be found in almost every coastal state in the United States, and on every continent including Antarctica. The foundation has expanded the scope of its projects to include coral rescue, propagation and transplant operations, beach restorations, mangrove restorations and nursery development. Reef Ball also participates in education and outreach regarding environmental stewardship and coral reefs.
In 2001, Reef Ball Foundation took control of the Reef Ball Development Group, and operates all aspects of the business as a non-profit organization. By 2007, the foundation has deployed 550,000 reef balls worldwide.
In 2019, Reef Ball Foundation deployed 1,400 reef balls in the shores of Progreso, Yucatán in Mexico. Artificial reefs were also built in Quintana Roo, Baja California, Colima, Veracruz, and Campache. Almost 25,000 reef balls have been established in the surrounding seas of Mexico. | 1 | Applied and Interdisciplinary Chemistry |
Gas chromatography (GC) coupled to mass spectrometry (MS) is one of the most widespread routine technologies applied to the large scale screening and discovery of novel biomarkers in metabolomics. However, the majority of MSTs currently measured in plant metabolomic profiling experiments remains unidentified due to the lack of authenticated pure reference substances and the expensive and time-consuming effort to maintain mass spectral RI libraries required for compound identification by GC-MS.
As the communication of analytical results and other approach-related details such as mass spectral and RI reference information within the scientific community is becoming increasingly popular, open access platforms for information exchange, such as the GMD, are obligatory.
Due to the lack of mandatory standards it remains difficult to compare individual mass spectrums.
While the different mass detector technologies, namely
quadrupole, ion trap and time of flight, can be deemed irrelevant, the chromatography settings such as temperature programming, type of capillary column and choice of column manufacturer heavily affect the empirically determined RI properties. Procedures for the transfer of RI properties between chromatography variants are, therefore, highly relevant for a shared library use. The GMD assesses the accuracy of RI transfer between chromatography variants and implements means to transfer empirically determined RI properties.
Aiming at the classification and identification of un-identified MSTs, the GMD accesses the information on available reference compounds. These compounds serve as training set of data to apply decision trees (DT) as a supervised machine learning approach. Structural feature extraction was applied to classify the metabolite space of the GMD prior to DT training. DT-based predictions of the most frequent substructures classify low resolution GC-MS mass spectra of the linked (potentially unknown) metabolite with respect to the presence or absence of the chemical moieties.
The web-based frontend supports conventional mass spectral and RI comparison by ranked hit lists as well as advanced DT supported substructure prediction. Batch processing is enabled via Simple Object Access Protocol (SOAP)-based web services while web-based data access services expose particular data base entities adapting Representational State Transfer (ReST) principles and mass spectral standards such as NIST-MSP and JCAMP-DX.
The GMD visualise quantitative metabolite pool size changes data. | 0 | Theoretical and Fundamental Chemistry |
The relative motion between a droplet and the gas results in an increase of the heat and mass transfer rates in the gas film surrounding the droplet. A convective boundary layer and a wake can surround the droplet. Furthermore, the shear force on the liquid surface causes an internal circulation that enhances the heating of the liquid. As a consequence, the vaporization rate increases with the droplet Reynolds number. Many different models exist for the single convective droplet vaporization case. Vaporizing droplet models can be seen to belong to six different classes:
# Constant droplet temperature model (d-law)
# Infinite liquid conductivity model
# Spherically symmetric transient droplet heating model
# Effective conductivity model
# Vortex model of droplet heating
# Navier-Stokes solution
The main difference between all these models is the treatment of the heating of the liquid phase which is usually the rate controlling phenomenon in droplet vaporization. The first three models do not consider internal liquid circulation. The effective conductivity model (4) and the vortex model of droplet heating (5) account for internal circulation and internal convective heating. The direct resolution of the Navier-Stokes equations provide, in principle, exact solutions both for the gas phase and the liquid phase.
Model (1) is a simplification of model (2) which is in turn a simplification of model (3). The spherically symmetric transient droplet heating model (3) solves the equation for heat diffusion through the liquid phase. A droplet heating time τ can be defined as the time required for a thermal diffusion wave to penetrate from the droplet surface to its center. The droplet heating time is compared to the droplet lifetime, τ. If the droplet heating time is short compared to the droplet lifetime we can assume that the temperature field inside the droplet is uniform and model (2) is obtained. In the infinite liquid conductivity model (2) the temperature of the droplet is uniform but varies with time. It is possible to go one step further and find the conditions for which we can neglect the temporal variation of the droplet temperature. The liquid temperature varies in time until the wet-bulb temperature is reached. If the wet-bulb temperature is reached in a time of the same order of magnitude as the droplet heating time, then the liquid temperature can be considered to be constant with regard to time; model (1), the d-law, is obtained.
The infinite liquid conductivity model is widely used in industrial spray calculations: for its balance between computational costs and accuracy. To account for the convective effects which enhanced the heat and mass transfer rates around the droplet, a correction is applied to the spherically symmetric expressions of the Sherwood and Nusselt numbers
Abramzon and Sirignano suggest the following formulation for the modified Sherwood and Nusselt numbers:
where and account for surface blowing which results in a thickening of the boundary layer surrounding the droplet.
and can be found from the well-known Frössling, or Ranz-Marshall, correlation:
where
* is the Schmidt number,
* is the Prandtl number,
* is the Reynolds number.
The expressions above show that the heat and mass transfer rates increase with increasing Reynolds number. | 1 | Applied and Interdisciplinary Chemistry |
The woodsprite (Atokirina in Navi) is an animal, also called seed, of the "holy tree", appearing similar to airborne jellyfish. Neytiri describes them as very pure spirits, and slaps Jake for shooing two of them away. The Omaticaya Clan plants one of these seeds on the body of a deceased Navi, so the Navis consciousness will become part of Eywa. | 1 | Applied and Interdisciplinary Chemistry |
The Colebrook equation is usually solved numerically due to its implicit nature. Recently, the Lambert W function has been employed to obtain explicit reformulation of the Colebrook equation.
or
will get:
then: | 1 | Applied and Interdisciplinary Chemistry |
Arsenic exposure in small children distorts the ratio of T helper cells (CD4) to cytotoxic T cells (CD8), which are responsible for immunodepression. In addition, arsenic also increases the number of inflammatory molecules being secreted through macrophages. The excess amount of granulocytes and monocytes lead to a chronic state of inflammation, which might result in cancer development. | 1 | Applied and Interdisciplinary Chemistry |
The Westinghouse Lamp Plant was constructed on Arlington Avenue in 1920 near the Watsessing Station of the rail line in the Watsessing neighborhood that connected Montclair, Glen Ridge and Bloomfield. The population in the area had grown since the time that the Township of Bloomfield was incorporated as a township from portions of Newark Township by an act of the New Jersey Legislature on March 23, 1812 until World War II. The population boom was contributed by the manufacturing jobs at the Westinghouse Lamp Plant along with other manufacturing plants such as General Electric, Lehn and Fink and Schering during the war time.
The Westinghouse Lamp Plant was devoted to lamp manufacturing in its early years. The plant had a research department to find a new suitable material for a light bulb filament. After World War I, the department led by Harvey C. Rentschler, and his deputy, John W. Marden, started looking into uranium to discover whether there was any similarity with tungsten to be used as a filament. The problem at the time was to make uranium into a metal form so that researchers could work with it. Westinghouse failed to establish uranium as a viable filament material, however, the research department continued to experiment with it until they found an electrolysis method to use a fused uranium salt to produce a metal. The metal was pure enough for nuclear research in many university laboratories during the 1930s. By 1941, Westinghouse Lamp Plant had the only practical process for producing pure uranium metal. | 1 | Applied and Interdisciplinary Chemistry |
* The mass-market application of microchannel plates is in image intensifier tubes of night vision goggles, which amplify visible and invisible light to make dark surroundings visible to the human eye.
* A 1 GHz real-time display CRT for an analog oscilloscope (the Tektronix 7104) used a microchannel plate placed behind the phosphor screen to intensify the image. Without the plate, the image would be excessively dim, because of the electron-optical design.
* MCP detectors are often employed in instrumentation for physical research, and they can be found in devices such as electron and mass spectrometers. | 0 | Theoretical and Fundamental Chemistry |
According to momentum theory, a velocity is imparted to the air passing through the propeller, and half of this velocity is given the air by the time it reaches the propeller plane. This increase of velocity of the air as it passes into the propeller disc is called the inflow velocity. It is always found where there is pressure discontinuity in a fluid. In the case of a wing moving horizontally, the air is given a downward velocity, as shown in Fig. 4., and theoretically half of this velocity is imparted in front of and above the wing, and the other half below and behind.
This induced downflow is present in the model wing tests from which the airfoil coefficients used in the blade-element theory are obtained; the inflow indicated by the momentum theory is therefore automatically taken into account in the simple blade-element theory. However, the induced downflow is widely different for different aspect ratios, being zero for infinite aspect ratio. Most model airfoil tests are made with rectangular wings having an arbitrarily chosen aspect ratio of 6, and there is no reason to suppose that the downflow in such a test corresponds to the inflow for each element of a propeller blade. In fact, the general conclusion drawn from an exhaustive series of tests, in which the pressure distribution was measured over 12 sections of a model propeller running in a wind tunnel, is that the lift coefficient of the propeller blade element differs considerably from that measured at the same angle of attack on an airfoil of aspect ratio 6. This is one of the greatest weaknesses of the simple blade-element theory.
Another weakness is that the interference between the propeller blades is not considered. The elements of the blades at any particular radius form a cascade similar to a multiplane with negative stagger, as shown in Fig. 4. Near the tips where the gap is large the interference is very small, but in toward the blade roots it is quite large.
In actual propellers there is a tip loss which the blade-element theory does not take into consideration. The thrust and torque forces as computed by means of the theory are therefore greater for the elements near the tip than those found by experiment.
In order to eliminate scale effect, the wind tunnel tests on model wings should be run at the same value of Reynolds number (scale) as the corresponding elements in the propeller blades. Airfoil characteristics measured at such a low scale as, for example, an air velocity of 30 m.p.h. with a 3-in. chord airfoil, show peculiarities not found when the tests are run at a scale comparable with that of propeller elements. The standard propeller section characteristics given in Figs. 11, 12, 13, and 14 were obtained from high Reynolds-number tests in the Variable Density Tunnel of the N.A.C.A., and, fortunately, for all excepting the thickest of these sections there is very little difference in characteristics at high and low Reynolds numbers. These values may be used with reasonable accuracy as to scale for propellers operating at tip speeds well below the speed of sound in air, and therefore relatively free from any effects of compressibility.
The poor accuracy of the simple blade-element theory is very well shown in a report by Durand and Lesley, in which they have computed the performance of a large number of model propellers (80) and compared the computed values with the actual performances obtained from tests on the model propellers themselves. In the words of the authors: The airfoils were tested in two different wind tunnels and in one of the tunnels at two different air velocities, and the propeller characteristics computed from the three sets of airfoil data differ by as much as 28%, illustrating quite forcibly the necessity for having the airfoil tests made at the correct scale.
In spite of all its inaccuracies the simple blade-element theory has been a useful tool in the hands of experienced propeller designers. With it a skilful designer having a knowledge of suitable empirical factors can design propellers which usually fit the main conditions imposed upon them fairly well in that they absorb the engine power at very nearly the proper revolution speed. They are not, however, necessarily the most efficient propellers for their purpose, for the simple theory is not sufficiently accurate to show slight differences in efficiency due to changes in pitch distribution, plan forms, etc. | 1 | Applied and Interdisciplinary Chemistry |
Though many people conceptualize images and diffraction patterns separately, they contain principally the same information. In the simplest approximation, the two are simply Fourier transforms of one another. Thus, the effects of beam precession on diffraction patterns also have significant effects on the corresponding images in the TEM. Specifically, the reduced dynamical intensity transfer between beams that is associated with PED results in reduced dynamical contrast in images collected during precession of the beam. This includes a reduction in thickness fringes, bend contours, and strain fields. While these features can often provide useful information, their suppression enables a more straightforward interpretation of diffraction contrast and mass contrast in images. | 0 | Theoretical and Fundamental Chemistry |
:For a synthetic analogue see also 3,5-Difluoro-4-hydroxybenzylidene imidazolinone.
Mechanistically, the process involves base-mediated cyclization followed by dehydration and oxidation. In the reaction of 7a to 8 involves the formation of an enamine from the imine, while in the reaction of 7b to 9 a proton is abstracted. The formed HBI fluorophore is highlighted in green.
The reactions are catalyzed by residues Glu222 and Arg96. An analogous mechanism is also possible with threonine in place of Ser65. | 1 | Applied and Interdisciplinary Chemistry |
The Lydersen method is a group contribution method for the estimation of critical properties temperature (T), pressure (P) and volume (V). The Lydersen method is the prototype for and ancestor of many new models like Joback, Klincewicz,
Ambrose,
Gani-Constantinou and others.
The Lydersen method is based in case of the critical temperature on the Guldberg rule which establishes a relation between the normal boiling point and the critical temperature. | 0 | Theoretical and Fundamental Chemistry |
Clean up efforts have led to a reconstructed Hazeltine Creek, although the contaminated slurry that made its way into Polley Lake and Quesnel Lake remains in the waterways. A drinking water ban was lifted within weeks of the spill and regular water testing is being conducted by the B.C. government, the Mount Polley mine, the University of Northern British Columbia and local residents.
Other remediation and reconstruction efforts have included investigation on impacts to human health and safety and affected ecosystems while removing the tailings spill, reconstructing creek shorelines, installing fish habitats, and replanting trees and other local vegetation. Investigation by the remediation team showed elevated levels of selenium, arsenic and other metals. | 1 | Applied and Interdisciplinary Chemistry |
Medications that contain more than 10% pseudoephedrine are prohibited under the Stimulants Control Law in Japan. | 0 | Theoretical and Fundamental Chemistry |
While the carbamate acetylcholinesterase inhibitors are commonly referred to as "carbamate insecticides" due to their generally high selectivity for insect acetylcholinesterase enzymes over the mammalian versions, the most potent compounds such as aldicarb and carbofuran are still capable of inhibiting mammalian acetylcholinesterase enzymes at low enough concentrations that they pose a significant risk of poisoning to humans, especially when used in large amounts for agricultural applications. Other carbamate based acetylcholinesterase inhibitors are known with even higher toxicity to humans, and some such as T-1123 and EA-3990 were investigated for potential military use as nerve agents. However, since all compounds of this type have a quaternary ammonium group with a permanent positive charge, they have poor blood–brain barrier penetration, and also are only stable as crystalline salts or aqueous solutions, and so were not considered to have suitable properties for weaponisation. | 0 | Theoretical and Fundamental Chemistry |
The inductive effect also plays a vital role in deciding the acidity and basicity of a molecule. Groups having +I effect (Inductive effect) attached to a molecule increases the overall electron density on the molecule and the molecule is able to donate electrons, making it basic. Similarly, groups having -I effect attached to a molecule decreases the overall electron density on the molecule making it electron deficient which results in its acidity. As the number of -I groups attached to a molecule increases, its acidity increases; as the number of +I groups on a molecule increases, its basicity increases. | 0 | Theoretical and Fundamental Chemistry |
A settling chamber where the two phases separate by static decantation. Coalescence plates facilitate the separation of the emulsion into two phases (heavy and light). The two phases then pass to continuous stages by overflowing the light phase and heavy phase weirs. The height of the heavy phase weir can be adjusted in order to position the heavy/light interphase in the settling chamber based on the density of each one of the phases.
The settler is a calm pool downstream of the mixer where the liquids are allowed to separate by gravity. The liquids are then removed separately from the end of the mixer. | 0 | Theoretical and Fundamental Chemistry |
Recently, there has been an interest in magnetic surface plasmons. These require materials with large negative magnetic permeability, a property that has only recently been made available with the construction of metamaterials. | 0 | Theoretical and Fundamental Chemistry |
The nonribosomal code refers to key amino acid residues and their positions within the primary sequence of an adenylation domain of a nonribosomal peptide synthetase used to predict substrate specificity and thus (partially) the final product. Analogous to the nonribosomal code is prediction of peptide composition by DNA/RNA codon reading, which is well supported by the central dogma of molecular biology and accomplished using the genetic code simply by following the DNA codon table or RNA codon table. However, prediction of natural product/secondary metabolites by the nonribosomal code is not as concrete as DNA/RNA codon-to-amino acid and much research is still needed to have a broad-use code. The increasing number of sequenced genomes and high-throughput prediction software has allowed for better elucidation of predicted substrate specificity and thus natural products/secondary metabolites. Enzyme characterization by, for example, ATP-pyrophosphate exchange assays for substrate specificity, in silico substrate-binding pocket modelling and structure-function mutagenesis (in vitro tests or in silico modelling) helps support predictive algorithms. Much research has been done on bacteria and fungi, with prokaryotic bacteria having easier-to-predict products.
The nonribosomal peptide synthetase (NRPS), a multi-modular enzyme complex, minimally contains repeating, tri-domains (adenylation (A), peptidyl carrier protein (PCP) and lastly condensation(C)). The adenylation domain (A) is the focus for substrate specificity since it is the initiating and substrate recognition domain. In one example, adenylation substrate-binding pocket (defined by 10 residue within) alignments led to clusters giving rise to defined specificity (i.e. the residues of the enzyme pocket can predict nonribosomal peptide sequence). In silico mutations of substrate-determining residues also led to varying or relaxed specificity. Additionally, the NRPS collinearity principle/rule dictates that given the order of adenylation domains (and substrate-specificity code) throughout the NRPS one can predict the amino acid sequence of the produced small peptide. NRPS, NRPS-like or NRPS-PKS complexes also exist and have domain variations, additions and/or exclusions. | 1 | Applied and Interdisciplinary Chemistry |
According to the main source, Ibn Hayyan, Ziryab had eight sons and two daughters. Five of the sons and both daughters became musicians of some prominence. These children kept their father's music school alive, but the female slave singers he trained also were regarded as reliable sources for his repertoire in the following generation. | 1 | Applied and Interdisciplinary Chemistry |
Since 1978, the institute has operated a nationwide air quality monitoring network. Sponsored by the Central Pollution Control Board (CPCB) since 1990. Receptor modelling techniques are used. CSIR-NEERI is involved in the design and development of air pollution control systems.
The institute has also developed a water purification system called NEERI ZAR. In the 1960s and 1970s, the Institute developed guidelines for deflouridation techniques. They have sometimes formed a departure point for the development of other techniques. The Institute tests samples for research on deflouridation and the measurement of particulate matter in air.
The institute has been entrusted by the courts to provide an inspection of the current environmental and legal framework. | 1 | Applied and Interdisciplinary Chemistry |
Deoxycytidine monophosphate (dCMP), also known as deoxycytidylic acid or deoxycytidylate in its conjugate acid and conjugate base forms, respectively, is a deoxynucleotide, and one of the four monomers that make up DNA. In a DNA double helix, it will base pair with deoxyguanosine monophosphate. | 1 | Applied and Interdisciplinary Chemistry |
Fibrous proteins, such as proteins involved in Alzheimer's disease and prion proteins fulfil the requirements for UV LD in that they are a class of long, thin molecules. In addition, cytoskeletal proteins can also be measured using LD. | 0 | Theoretical and Fundamental Chemistry |
A primordial element is a chemical element with at least one primordial nuclide. There are 251 stable primordial nuclides and 35 radioactive primordial nuclides, but only 80 primordial stable elements—hydrogen through lead, atomic numbers 1 to 82, with the exceptions of technetium (43) and promethium (61)—and three radioactive primordial elements—bismuth (83), thorium (90), and uranium (92). If plutonium (94) turns out to be primordial (specifically, the long-lived isotope Pu), then it would be a fourth radioactive primordial, though practically speaking it would still be more convenient to produce synthetically. Bismuth's half-life is so long that it is often classed with the 80 primordial stable elements instead, since its radioactivity is not a cause for serious concern. The number of elements is smaller than the number of nuclides, because many of the primordial elements are represented by multiple isotopes. See chemical element for more information. | 0 | Theoretical and Fundamental Chemistry |
Ketones containing alkene and alkyne units are often called unsaturated ketones. The most widely used member of this class of compounds is methyl vinyl ketone, , which is useful in the Robinson annulation reaction. Lest there be confusion, a ketone itself is a site of unsaturation; that is, it can be hydrogenated. | 0 | Theoretical and Fundamental Chemistry |
Dexmethylphenidate, sold under the brand name Focalin among others, is a potent central nervous system (CNS) stimulant used to treat attention deficit hyperactivity disorder (ADHD) in those over the age of five years. It is taken by mouth. The immediate release formulation lasts up to five hours while the extended release formulation lasts up to twelve hours. It is the more active enantiomer of methylphenidate.
Common side effects include abdominal pain, loss of appetite, and fever. Serious side effects may include abuse, psychosis, sudden cardiac death, mania, anaphylaxis, seizures, and dangerously prolonged erection. Safety during pregnancy and breastfeeding is unclear. Dexmethylphenidate is a central nervous system (CNS) stimulant. How it works in ADHD is unclear.
Dexmethylphenidate was approved for medical use in the United States in 2001. It is available as a generic medication. In 2021, it was the 121st most commonly prescribed medication in the United States, with more than 4million prescriptions. | 0 | Theoretical and Fundamental Chemistry |
In the seventh chapter discusses qualities such as color and taste as a function of heat, time, object and subject. Kanada dedicates a significant number of Sutras to his theory and importance of measurement. | 1 | Applied and Interdisciplinary Chemistry |
Approximately 95% of hydroxylamine is used in the synthesis of cyclohexanone oxime, a precursor to Nylon 6. The treatment of this oxime with acid induces the Beckmann rearrangement to give caprolactam (3). The latter can then undergo a ring-opening polymerization to yield Nylon 6. | 0 | Theoretical and Fundamental Chemistry |
* Budget analyses
*Parameter estimation
* Scaling in time and space
* Data assimilation
* Quality control of data – see for example Double mass analysis | 1 | Applied and Interdisciplinary Chemistry |
Higher temperatures can also affect the chemical stability of the polymer and thus its use properties. If a polymer's ceiling temperature is exceeded, it will partially revert to its monomers, destroying its usability. More generally, polymer degradation also occurs during devolatilization, limiting the temperature and residence time available for the process. | 1 | Applied and Interdisciplinary Chemistry |
The boiling point is an important property because it determines the speed of evaporation. Small amounts of low-boiling-point solvents like diethyl ether, dichloromethane, or acetone will evaporate in seconds at room temperature, while high-boiling-point solvents like water or dimethyl sulfoxide need higher temperatures, an air flow, or the application of vacuum for fast evaporation.
*Low boilers: boiling point below 100 °C (boiling point of water)
*Medium boilers: between 100 °C and 150 °C
*High boilers: above 150 °C | 1 | Applied and Interdisciplinary Chemistry |
After serious opposition about plans and negotiations between Mongolia with Japan and the United States of America to build nuclear-waste facilities in Mongolia, Mongolia stopped all negotiations in September 2011. These negotiations had started after U.S. Deputy Secretary of Energy Daniel Poneman visited Mongolia in September 2010. Talks took place in Washington, D.C. between officials of Japan, the United States, and Mongolia in February 2011. After this the United Arab Emirates (UAE), which wanted to buy nuclear fuel from Mongolia, joined in the negotiations. The talks were kept secret and, although the Mainichi Daily News reported on them in May, Mongolia officially denied the existence of these negotiations. However, alarmed by this news, Mongolian citizens protested against the plans and demanded the government withdraw the plans and disclose information. The Mongolian President Tsakhiagiin Elbegdorj issued a presidential order on September 13 banning all negotiations with foreign governments or international organizations on nuclear-waste storage plans in Mongolia. The Mongolian government has accused the newspaper of distributing false claims around the world. After the presidential order, the Mongolian president fired the individual who was supposedly involved in these conversations. | 0 | Theoretical and Fundamental Chemistry |
As mentioned, negative resists are photopolymers that become insoluble upon exposure to radiation. They have found a variety of commercial applications, especially in the area of designing and printing small chips for electronics. A characteristic found in most negative tone resists is the presence of multifunctional branches on the polymers used. Radiation of the polymers in the presence of an initiator results in the formation of a chemically resistant network polymer. A common functional group used in negative resists is epoxy functional groups. An example of a widely used polymer of this class is SU-8. SU-8 was one of the first polymers used in this field, and found applications in wire board printing. In the presence of a cationic photoinitiator photopolymer, SU-8 forms networks with other polymers in solution. Basic scheme shown below.
SU-8 is an example of an intramolecular photopolymerization forming a matrix of cross-linked material. Negative resists can also be made using co-polymerization. In the event that two different monomers, or oligomers, are in solution with multiple functionalities, it is possible for the two to polymerize and form a less soluble polymer.
Manufacturers also use light curing systems in OEM assembly applications such as specialty electronics or medical device applications. | 0 | Theoretical and Fundamental Chemistry |
Many definitions that describe a specific conformer (IUPAC Gold Book) exist, developed by William Klyne and Vladimir Prelog, constituting their Klyne–Prelog system of nomenclature:
* a torsion angle of ±60° is called gauche
* a torsion angle between 0° and ±90° is called syn (s)
* a torsion angle between ±90° and 180° is called anti (a)
* a torsion angle between 30° and 150° or between –30° and –150° is called clinal
* a torsion angle between 0° and 30° or 150° and 180° is called periplanar (p)
* a torsion angle between 0° to 30° is called synperiplanar or syn- or cis-conformation (sp)
* a torsion angle between 30° to 90° and –30° to –90° is called synclinal or gauche or skew (sc)
* a torsion angle between 90° to 150°, and –90° to –150° is called anticlinal (ac)
* a torsion angle between ±150° to 180° is called antiperiplanar or anti or trans (ap).
Torsional strain results from resistance to twisting about a bond. | 0 | Theoretical and Fundamental Chemistry |
An enzyme inducer is a type of drug that increases the metabolic activity of an enzyme either by binding to the enzyme and activating it, or by increasing the expression of the gene coding for the enzyme. It is the opposite of an enzyme repressor. There are specific types of enzyme inducers that create cytoprotective pathways that play a role in prevention and treatment of cancer and other diseases including cardiovascular disease and neurodegenerative diseases. Enzyme inducers can be either naturally occurring or synthetically made. | 1 | Applied and Interdisciplinary Chemistry |
RapiGest SF, the brand-name for sodium 3-[(2-methyl-2-undecyl-1,3-dioxolan-4-yl)methoxy]-1-propanesulfonate, is an acid-cleavable anionic detergent marketed by Waters Corporation and AOBIOUS INC. | 0 | Theoretical and Fundamental Chemistry |
There are two types of overlayers: commensurate and incommensurate. In the former the substrate-adsorbate interaction tends to dominate over any lateral adsorbate-adsorbate interaction, while in the latter the adsorbate-adsorbate interactions are of similar magnitude to those between adsorbate and substrate. | 0 | Theoretical and Fundamental Chemistry |
:V09FX01 Technetium (Tc) pertechnetate
:V09FX02 Sodium iodide (I)
:V09FX03 Sodium iodide (I)
:V09FX04 Sodium iodide (I) | 1 | Applied and Interdisciplinary Chemistry |
Ammonium perrhenate may be prepared from virtually all common sources of rhenium. The metal, oxides, and sulfides can be oxidized with nitric acid and the resulting solution treated with aqueous ammonia. Alternatively an aqueous solution of ReO can be treated with ammonia followed by crystallisation. | 0 | Theoretical and Fundamental Chemistry |
Pourbaix diagrams have many applications in different fields dealing with e.g., corrosion problems, geochemistry, and environmental sciences. Using the Pourbaix diagram correctly will help shedding light not only on the nature of the species present in aqueous solution, or in the solid phases, but may also help to understand the reaction mechanism. | 0 | Theoretical and Fundamental Chemistry |
In addition to the method of proton extrusion discussed above, it is believed that the general method of cellular respiration is different in obligate alkaliphiles as compared to neutrophiles. Generally, ATP production operates by establishing a proton gradient (greater H+ concentration outside the membrane) and a transmembrane electrical potential (with a positive charge outside the membrane). However, since alkaliphiles have a reversed pH gradient, it would seem that ATP production—which is based on a strong proton-motive force – would be severely reduced. However, the opposite is true. It has been proposed that while the pH gradient has been reversed, the transmembrane electrical potential is greatly increased. This increase in charge causes the production of greater amounts of ATP by each translocated proton when driven through an ATPase. Research in this area is ongoing. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, an acyl group is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. It contains a double-bonded oxygen atom and an organyl group () or hydrogen in the case of formyl group (). In organic chemistry, the acyl group (IUPAC name alkanoyl if the organyl group is alkyl) is usually derived from a carboxylic acid, in which case it has the formula , where R represents an organyl group or hydrogen. Although the term is almost always applied to organic compounds, acyl groups can in principle be derived from other types of acids such as sulfonic acids and phosphonic acids. In the most common arrangement, acyl groups are attached to a larger molecular fragment, in which case the carbon and oxygen atoms are linked by a double bond. | 0 | Theoretical and Fundamental Chemistry |
Hydrostatic tests are conducted under the constraints of either the industrys or the customers specifications, or may be required by law. The vessel is filled with a nearly incompressible liquid – usually water or oil – pressurised to test pressure, and examined for leaks or permanent changes in shape. Red or fluorescent dyes may be added to the water to make leaks easier to see. The test pressure is always considerably higher than the operating pressure to give a factor of safety. This factor of safety is typically 166.66%, 143% or 150% of the designed working pressure, depending on the regulations that apply. For example, if a cylinder was rated to DOT-2015 PSI (approximately 139 bar), it would be tested at around 3360 PSI (approximately 232 bar).
Water is commonly used because it is cheap and easily available, and is usually harmless to the system to be tested. Hydraulic fluids and oils may be specified where contamination with water could cause problems. These fluids are nearly incompressible, therefore requiring relatively little work to develop a high pressure, and is therefore also only able to release a small amount of energy in case of a failure - only a small volume will escape under high pressure if the container fails. If high pressure gas were used, then the gas would expand to V=(nRT)/p with its compressed volume resulting in an explosion, with the attendant risk of damage or injury.
Small pressure vessels are normally tested using a water jacket test. The vessel is visually examined for defects and then placed in a container filled with water, and in which the change in volume of the vessel can be measured, usually by monitoring the water level in a calibrated tube. The vessel is then pressurised for a specified period, usually 30 or more seconds, and if specified, the expansion will be measured by reading off the amount of liquid that has been forced into the measuring tube by the volume increase of the pressurised vessel. The vessel is then depressurised, and the permanent volume increase due to plastic deformation while under pressure () is measured by comparing the final volume in the measuring tube with the volume before pressurisation.
A leak will give a similar result to permanent set, but will be detectable by holding the volume in the pressurised vessel by closing the inlet valve for a period before depressurising, as the pressure will drop steadily during this period if there is a leak. In most cases a permanent set that exceeds the specified maximum will indicate failure. A leak may also be a failure criterion, but it may be that the leak is due to poor sealing of the test equipment. If the vessel fails, it will normally go through a condemning process marking the cylinder as unsafe.
The information needed to specify the test is stamped onto the cylinder. This includes the design standard, serial number, manufacturer, and manufacture date. After testing, the vessel or its nameplate will usually be stamp marked with the date of the successful test, and the test facility's identification mark.
A simpler test, that is also considered a hydrostatic test but can be performed by anyone who has a garden hose, is to pressurise the vessel by filling it with water and to physically examine the outside for leaks. This type of test is suitable for containers such as boat fuel tanks, which are not pressure vessels but must work under the hydrostatic pressure of the contents. A hydrostatic test head is usually specified as a height above the tank top. The tank is pressurised by filling water to the specified height through a temporary standpipe if necessary. It may be necessary to seal vents and other outlets during the test. | 1 | Applied and Interdisciplinary Chemistry |
The Rayleigh–Taylor instability is another application of hydrodynamic stability and also occurs between two fluids but this time the densities of the fluids are different. Due to the difference in densities, the two fluids will try to reduce their combined potential energy. The less dense fluid will do this by trying to force its way upwards, and the more dense fluid will try to force its way downwards. Therefore, there are two possibilities: if the lighter fluid is on top the interface is said to be stable, but if the heavier fluid is on top, then the equilibrium of the system is unstable to any disturbances of the interface. If this is the case then both fluids will begin to mix. Once a small amount of heavier fluid is displaced downwards with an equal volume of lighter fluid upwards, the potential energy is now lower than the initial state, therefore the disturbance will grow and lead to the turbulent flow associated with Rayleigh–Taylor instabilities.
This phenomenon can be seen in interstellar gas, such as the Crab Nebula. It is pushed out of the Galactic plane by magnetic fields and cosmic rays and then becomes Rayleigh–Taylor unstable if it is pushed past its normal scale height. This instability also explains the mushroom cloud which forms in processes such as volcanic eruptions and atomic bombs.
Rayleigh–Taylor instability has a big effect on the Earth's climate. Winds that come from the coast of Greenland and Iceland cause evaporation of the ocean surface over which they pass, increasing the salinity of the ocean water near the surface, and making the water near the surface denser. This then generates plumes which drive the ocean currents. This process acts as a heat pump, transporting warm equatorial water North. Without the ocean overturning, Northern Europe would likely face drastic drops in temperature. | 1 | Applied and Interdisciplinary Chemistry |
Persephin has been found to be less potent than other members of the GDNF family. It has been found to support the survival and morphological differentiation of tyrosine hydroxylase immunoreactive neurons, although less so than both GDNF and neurturin. The mRNA levels of persephin in developing neurons has been low compared to other neurotrophic factors, but relatively higher levels of persephin mRNA have been found in embryonic neurons.
Similarly to the other members of the GDNF family of ligands, persephin uses a receptor that consists of the tyrosine kinase signaling component Ret and a unit of glycosylphosphatidylinsitol (GPI)-anchored receptor (GFRα). Persephin specifically binds to GFRα4.
Persephin acts on both neurons in the CNS and PNS, but also has the ability to act as a renal ramogen. | 1 | Applied and Interdisciplinary Chemistry |
Westinghouse continued its manufacturing and research at the plant after the war. In 1964, Westinghouse was issued a permit from United States Atomic Energy Commission to conduct research using thorium and uranium to produce thorium-tungsten wire. In 1983, Westinghouse sold its lamp manufacturing operation to North American Phillips Lighting Corporation. The manufacturing of thorium-tungsten wire was continued at the plant until 1984. In 1986, North American Phillips Lighting Corporation returned the control of the plant back to Westinghouse. | 1 | Applied and Interdisciplinary Chemistry |
The nano guitar is a microscopically small carved guitar. It was developed by Dustin W. Carr in 1997, under the direction of Professor Harold G. Craighead, in the Cornell Nanofabrication Facility. The idea came about as a fun way to illustrate nanotechnology, and captured popular attention. It is disputed as to whether the nano guitar should be classified as a guitar, but it is the common opinion that it is in fact a guitar. | 0 | Theoretical and Fundamental Chemistry |
An increased plasma transferrin level is often seen in patients with iron deficiency anemia, during pregnancy, and with the use of oral contraceptives, reflecting an increase in transferrin protein expression. When plasma transferrin levels rise, there is a reciprocal decrease in percent transferrin iron saturation, and a corresponding increase in total iron binding capacity in iron deficient states
A decreased plasma transferrin level can occur in iron overload diseases and protein malnutrition. An absence of transferrin results from a rare genetic disorder known as atransferrinemia, a condition characterized by anemia and hemosiderosis in the heart and liver that leads to heart failure and many other complications as well as to H63D syndrome.
Studies reveal that a transferrin saturation (serum iron concentration ÷ total iron binding capacity) over 60 percent in men and over 50 percent in women identified the presence of an abnormality in iron metabolism (Hereditary hemochromatosis, heterozygotes and homozygotes) with approximately 95 percent accuracy. This finding helps in the early diagnosis of Hereditary hemochromatosis, especially while serum ferritin still remains low. The retained iron in Hereditary hemochromatosis is primarily deposited in parenchymal cells, with reticuloendothelial cell accumulation occurring very late in the disease. This is in contrast to transfusional iron overload in which iron deposition occurs first in the reticuloendothelial cells and then in parenchymal cells. This explains why ferritin levels remain relative low in Hereditary hemochromatosis, while transferrin saturation is high.
Transferrin and its receptor have been shown to diminish tumour cells when the receptor is used to attract antibodies. | 1 | Applied and Interdisciplinary Chemistry |
Differences in the abundance of stable isotopes among natural materials are usually very small (natural differences in the ratio of rare to common isotope are almost always below 0.1%, and sometimes much smaller). Nevertheless, these very small differences can record meaningful biological and geological processes. To facilitate comparison of these small but meaningful differences, isotope abundances in natural materials are often reported relative to isotope abundances in designated standards. The convention for reporting the measured difference between a sample and a standard is called "delta notation." For example, imagine an element X for which we wish to compare the rare, heavy stable isotope with atomic mass A (X) to the light, common isotope with atomic mass B (X). The abundance of X and X in any given material is reported with the notation δX. δX for the sample material is calculated as follows:
:R = (total amount of X)/(total amount of X)
:δX = (R − R)/R
δ values are most commonly reported in parts per thousand, commonly referred to in isotope chemistry as per mille and represented by the symbol ‰. To report δ values in per mille, the δ value as calculated above should be multiplied by 1000:
:δX (‰) = ((R − R)/R) * 1000 | 0 | Theoretical and Fundamental Chemistry |
If the β phase is replaced by a flat rigid surface, as shown in Figure 5, then β = π, and the second net force equation simplifies to the Young equation,
which relates the surface tensions between the three phases: solid, liquid and gas. Subsequently, this predicts the contact angle of a liquid droplet on a solid surface from knowledge of the three surface energies involved. This equation also applies if the "gas" phase is another liquid, immiscible with the droplet of the first "liquid" phase. | 0 | Theoretical and Fundamental Chemistry |
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