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Many of the same people who created Rosetta@home worked on Foldit. The public beta version was released in May 2008 and has 240,000 registered players.
Since 2008, Foldit has participated in Critical Assessment of Techniques for Protein Structure Prediction (CASP) experiments, submitting its best solutions to targets based on unknown protein structures. CASP is an international program to assess methods of protein structure prediction and identify those that are most productive. | 1 | Applied and Interdisciplinary Chemistry |
Glycopolymer is synthetic polymer with pendant carbohydrates. Glycopolymers play an important role in many biological recognition events such as cell–cell adhesion, development of new tissues and infectious behavior of virus and bacteria. They have high potential in targeted drug delivery, tissue engineering and synthesis of bio-compatible materials.
The first glycopolymer was synthesized in 1978 by free-radical polymerization. Subsequent efforts have been devoted to synthesizing glycopolymers with various structures and sizes, and the synthesis techniques have widened to controlled/living radical polymerisation, ring-opening polymerization, ring-opening metathesis polymerization and post-functionalization. | 0 | Theoretical and Fundamental Chemistry |
Many bumblebee species have been observed to use pheromones in the process of brood recognition. In the species Bombus vosnesenskii, brood recognition, and subsequently, brood clump incubation, has been shown to be pheromone induced. Queens will deposit chemical signals on a brood clump to help herself and her workers identify the eggs. However, these pheromones appear to be species' specific, as opposed to specific to individual queens, as queens will also incubate the eggs of conspecific bees. | 1 | Applied and Interdisciplinary Chemistry |
As heating a thick fluid decreases its viscosity, it reduces losses occurring in a pipe. Therefore, the net positive suction head (pressure difference) available can be raised, decreasing the likelihood of cavitation when pumping. However, care must be taken not to increase the vapour pressure of the fluid too much, as this would have a strong side effect on the available head, possibly outweighing any benefit. | 1 | Applied and Interdisciplinary Chemistry |
After his PhD, he was a postdoctoral researcher with Hugh Felkin at the Institut de Chimie des Substances Naturelles at Gif-sur-Yvette, near Paris. He was a postdoctoral fellow (1973–1975) and then attaché de recherche (1975–1977). At the end of that time he was chargé de recherche. In 1977 Crabtree took an assistant professorship in Inorganic Chemistry at Yale University. He served as associate professor from 1982 to 1985, and as full professor from 1985 to 2021. In retirement, he now serves as an emeritus professor of chemistry. | 0 | Theoretical and Fundamental Chemistry |
Endoreversible thermodynamics is a subset of irreversible thermodynamics aimed at making more realistic assumptions about heat transfer than are typically made in reversible thermodynamics. It gives an upper bound on the power that can be derived from a real process that is lower than that predicted by Carnot for a Carnot cycle, and accommodates the exergy destruction occurring as heat is transferred irreversibly.
It is also called finite-time thermodynamics, entropy generation minimization, or thermodynamic optimization. | 0 | Theoretical and Fundamental Chemistry |
*Pacey, A.J. & Fisher, S.J. (1967) "Daniel Bernoulli and the vis viva of compressed air", The British Journal for the History of Science 3 (4), pp. 388–392,
*British Transport Commission (1957) Handbook for Railway Steam Locomotive Enginemen, London : B.T.C., p. 81, (facsimile copy publ. Ian Allan (1977), ) | 0 | Theoretical and Fundamental Chemistry |
Not all irreversible inhibitors form covalent adducts with their enzyme targets. Some reversible inhibitors bind so tightly to their target enzyme that they are essentially irreversible. These tight-binding inhibitors may show kinetics similar to covalent irreversible inhibitors. In these cases some of these inhibitors rapidly bind to the enzyme in a low-affinity EI complex and this then undergoes a slower rearrangement to a very tightly bound EI* complex (see the "irreversible inhibition mechanism" diagram). This kinetic behaviour is called slow-binding. This slow rearrangement after binding often involves a conformational change as the enzyme "clamps down" around the inhibitor molecule. Examples of slow-binding inhibitors include some important drugs, such methotrexate, allopurinol, and the activated form of acyclovir. | 1 | Applied and Interdisciplinary Chemistry |
The alpha process generally occurs in large quantities only if the star is sufficiently massive, ( being the mass of the sun); these stars contract as they age, increasing core temperature and density to high enough levels to enable the alpha process. Requirements increase with atomic mass, especially in later stages -- sometimes referred to as silicon burning -- and thus most commonly occur in supernovae. Type II supernovae mainly synthesize oxygen and the alpha-elements (Ne, Mg, Si, S, Ar, Ca, and Ti) while Type Ia supernovae mainly produce elements of the iron peak (Ti, V, Cr, Mn, Fe, Co, and Ni). Sufficiently massive stars can synthesize elements up to and including the iron peak solely from the hydrogen and helium that initially comprises the star.
Typically, the first stage of the alpha process (or alpha-capture) follows from the helium-burning stage of the star once helium becomes depleted; at this point, free capture helium to produce . This process continues after the core finishes the helium burning phase as a shell around the core will continue burning helium and convecting into the core. The second stage (neon burning) starts as helium is freed by the photodisintegration of one atom, allowing another to continue up the alpha ladder. Silicon burning is then later initiated through the photodisintegration of in a similar fashion; after this point, the peak discussed previously is reached. The supernova shock wave produced by stellar collapse provides ideal conditions for these processes to briefly occur.
During this terminal heating involving photodisintegration and rearrangement, nuclear particles are converted to their most stable forms during the supernova and subsequent ejection through, in part, alpha processes. Starting at and above, all the product elements are radioactive and will therefore decay into a more stable isotope -- e.g. is formed and decays into . | 0 | Theoretical and Fundamental Chemistry |
Geoffrey Norman Malcolm (23 April 1931 – 11 August 2019) was a New Zealand physical chemist. Appointed in 1969, he was the first chemistry professor at Massey University. | 0 | Theoretical and Fundamental Chemistry |
A thorough review of trace amine-associated receptors that discusses the historical evolution of this research particularly well is that of Grandy. | 1 | Applied and Interdisciplinary Chemistry |
The restoration of pharmacological activity after covalent irreversible inhibition requires re-synthesis of the protein target. This has important and potentially advantageous consequences for drug pharmacodynamics in which the level and frequency of dosing relates to the extent and duration of the resulting pharmacological effect. | 1 | Applied and Interdisciplinary Chemistry |
Moulay Rachid Idrissi (; 1939 – October 18, 1971) was a Moroccan nuclear chemist and engineer. Idrissi gained notoriety after his work on the recovery of uranium from phosphates, where he discovered a significant amount of uranium in Moroccan phosphates. Shortly after this discovery, he died in a traffic accident near Rabat, the circumstances of which remain contested. | 0 | Theoretical and Fundamental Chemistry |
Specifically, the diagram records the pressure of steam versus the volume of steam in a cylinder, throughout a piston's cycle of motion in a steam engine. The diagram enables calculation of the work performed and thus can provide a measure of the power produced by the engine.
To exactly calculate the work done by the system it is necessary to calculate the integral of the pressure with respect to volume. One can often quickly calculate this using the PV diagram as it is simply the area enclosed by the cycle.
Note that in some cases specific volume will be plotted on the x-axis instead of volume, in which case the area under the curve represents work per unit mass of the working fluid (i.e. J/kg). | 0 | Theoretical and Fundamental Chemistry |
The first equation tells that is just function of , the function is defined as
Different authors defines the function differently, for example, Landau defines the function with a factor . But following Whitham, Rosenhead the momentum equation becomes
Now letting
the and momentum equations reduce to
and substituting this into the previous equation(to eliminate pressure) results in
Multiplying by and integrating once,
where are constants to be determined from the boundary conditions. The above equation can be re-written conveniently with three other constants as roots of a cubic polynomial, with only two constants being arbitrary, the third constant is always obtained from other two because sum of the roots is .
The boundary conditions reduce to
where is the corresponding Reynolds number. The solution can be expressed in terms of elliptic functions. For convergent flow , the solution exists for all , but for the divergent flow , the solution exists only for a particular range of . | 1 | Applied and Interdisciplinary Chemistry |
Weighting of the contributing structures in terms of their contribution to the overall structure can be calculated in multiple ways, using "Ab initio" methods derived from Valence Bond theory, or else from the Natural Bond Orbitals (NBO) approaches of Weinhold [http://www.chem.wisc.edu/~nbo5 NBO5] , or finally from empirical calculations based on the Hückel method. A Hückel method-based software for teaching resonance is available on the [http://www.hulis.free.fr HuLiS] Web site. | 0 | Theoretical and Fundamental Chemistry |
There are several patterns that can be used for learning the nomenclature of polyatomic anions. First, when the prefix bi is added to a name, a hydrogen is added to the ions formula and its charge is increased by 1, the latter being a consequence of the hydrogen ions +1 charge. An alternative to the bi- prefix is to use the word hydrogen in its place: the anion derived from . For example, let us consider carbonate() ion.
It is either called as bicarbonate or hydrogen carbonate.
This process is called protonation.
Most of the common polyatomic anions are oxyanions, conjugate bases of oxyacids (acids derived from the oxides of non-metallic elements). For example, the sulfate anion, , is derived from , which can be regarded as + .
The second rule is based on the oxidation state of the central atom in the ion, which in practice is often (but not always) directly related to the number of oxygen atoms in the ion, following the pattern shown below. The following table shows the chlorine oxyanion family:
As the number of oxygen atoms bound to chlorine increases, the chlorines oxidation number becomes more positive. This gives rise to the following common pattern: first, the -ate ion is considered to be the base name; adding a per- prefix adds an oxygen, while changing the -ate suffix to -ite will reduce the oxygens by one, and keeping the suffix -ite and adding the prefix hypo- reduces the number of oxygens by one more, all without changing the charge. The naming pattern follows within many different oxyanion series based on a standard root for that particular series. The -ite has one less oxygen than the -ate, but different -ate' anions might have different numbers of oxygen atoms.
These rules do not work with all polyatomic anions, but they do apply to several of the more common ones. The following table shows how these prefixes are used for some of these common anion groups.
Some oxo-anions can dimerize with loss of an oxygen atom. The prefix pyro is used, as the reaction that forms these types of chemicals often involves heating to form these types of structures. The prefix pyro is also denoted by the prefix di- . For example, dichromate ion is a dimer. | 0 | Theoretical and Fundamental Chemistry |
* bis(allyl)nickel
* bis(allyl)palladium
* bis(allyl)platinum
*tris(allyl)chromium
* tris(allyl)rhodium
* tris(allyl)iridium | 0 | Theoretical and Fundamental Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2022 impact factor of 6.8. | 1 | Applied and Interdisciplinary Chemistry |
Chromic phenomena are those phenomena in which color is produced when light interacts with materials, often called chromic materials in a variety of ways. These can be categorized under the following five headings:
*Stimulated (reversible) color change
*The absorption and reflection of light
*The absorption of energy followed by the emission of light
*The absorption of light and energy transfer (or conversion)
*The manipulation of light. | 0 | Theoretical and Fundamental Chemistry |
Three main processes (or pumps) that make up the marine carbon cycle bring atmospheric carbon dioxide (CO) into the ocean interior and distribute it through the oceans. These three pumps are: (1) the solubility pump, (2) the carbonate pump, and (3) the biological pump. The total active pool of carbon at the Earth's surface for durations of less than 10,000 years is roughly 40,000 gigatons C (Gt C, a gigaton is one billion tons, or the weight of approximately 6 million blue whales), and about 95% (~38,000 Gt C) is stored in the ocean, mostly as dissolved inorganic carbon. The speciation of dissolved inorganic carbon in the marine carbon cycle is a primary controller of acid-base chemistry in the oceans. | 0 | Theoretical and Fundamental Chemistry |
Dr. Karl Lark-Horovitz, professor of physics at Purdue, had a keen interest in the development of the cyclotron and the application of physical techniques to solve biological problems, and sought to develop methods that utilized radioactive tracers produced from the cyclotron. With the assistance of Leng and Donald Tendam, radioactive tracers were employed following an intense regimen to develop these methods. Key studies concerned sodium and potassium in the human body and their uptake, distribution and excretion; sodium and potassium distribution in human blood cells; and the analysis of enteric coatings for medications. Leng was awarded an American Association of University Women fellowship for work at Purdue. The fellowship permitted her the freedom to pursue the pioneer research on radioactive tracer materials.
In 1943, Leng moved to New York City to accept a faculty appointment in physics at Rensselaer Polytechnic Institute (RPI) and in 1966 was promoted to become RPI's first female full professor. | 0 | Theoretical and Fundamental Chemistry |
The GADV-protein world hypothesis was first proposed by Kenji Ikehara at Nara Women's University. It is supported by GNC-SNS primitive gene code hypothesis (GNC hypothesis) also formulated by him. In the GNC hypothesis, the origin of the present standard genetic code is considered to be the GNC genetic code that includes the codons GGC, GCC, GAC, GUC, respectively coding glycine, alanine, aspartic acid, and valine; it also follows the SNS primitive genetic code that codes ten amino acids, where N denotes arbitrary four RNA bases and S denotes guanine (G) and cytosine (C).
The GADV hypothesis proposes these mechanisms:
* Analysis on present proteins and simulation using chemical factors of amino acid shows GADV-proteins that contains almost the same amount of the four amino acids can form four basic structures of protein, namely, hydrophobic and hydrophilic structures, α-helices and β-sheets.
* Therefore, GADV-proteins polymerized from randomly chosen amino acids from the four choices, probably becoming globular and water-soluble like some present proteins.
* Proteins generated like this have different primary structures. However, their simple composition leads to the formation of similar spherical and water-soluble proteins that have bulky and hydrophobic valines inside and hydrophilic aspartic acids outside.
* GADV-peptides can polymerize by simple cycles of evaporation and hydration. This gives a rationale for the production of GADV-peptides in tide pools on the early Earth. Moreover, GADV-peptides randomly polymerized as above have the catalytic activity to hydrolyze peptide bonds in bovine serum albumin. Therefore, they can catalyze the formation of peptide bonds as the reverse reaction.
* GADV-proteins can multiply by pseudo-replication in the absence of genes, considering the features above. | 0 | Theoretical and Fundamental Chemistry |
Cyp33 in mammals causes isomerization in MLL1. MLL1 is a multiprotein complex that regulates gene expression and chromosomal translocations involving this gene often lead to leukemia. MLL's target genes include HOXC8, HOXA9, CDKN1B, and C-MYC. MLL also has two binding domains: a Cyp33 RNA-recognition motif domain (RRM), and a PHD3 domain that binds to H3K4me3 or Cyp33 RRM. Cyp33 has the ability to downregulate the expression of these genes through proline isomerization at the peptide bond between His1628 and Pro1629 within MLL. This bond lies in a sequence between the PHD3 finger of MLL1 and the bromeodomain of MLL1, and its isomerization mediates the bonding of the PHD3 domain and the Cyp33 RRM domain. When these two domains are bonded transcription is repressed through recruitment of histone deacetylases to MLL1 and inhibition of H3K4me3. | 0 | Theoretical and Fundamental Chemistry |
The diagnosis is generally based on symptoms and supported by a lithium level blood level. Blood levels are most useful six to twelve hours after the last dose. The normal blood serum lithium level in those on treatment is between 0.6-1.2 mEq/L. Some blood tubes contain lithium heparin which may result in falsely positive results.
When lithium toxicity is suspected tests may include:
*fingerstick glucose
* serum lithium concentration
*basic metabolic panel to assess renal function
* serum acetaminophen and salicylate concentrations to rule out other sources of acute ingestion
*urine pregnancy tests to ensure management does not cause abortion
Imaging tests are not helpful. | 1 | Applied and Interdisciplinary Chemistry |
GPCRs are integral membrane proteins that possess seven membrane-spanning domains or transmembrane helices. The extracellular parts of the receptor can be glycosylated. These extracellular loops also contain two highly conserved cysteine residues that form disulfide bonds to stabilize the receptor structure. Some seven-transmembrane helix proteins (channelrhodopsin) that resemble GPCRs may contain ion channels, within their protein.
In 2000, the first crystal structure of a mammalian GPCR, that of bovine rhodopsin (), was solved. In 2007, the first structure of a human GPCR was solved This human β-adrenergic receptor GPCR structure proved highly similar to the bovine rhodopsin. The structures of activated or agonist-bound GPCRs have also been determined. These structures indicate how ligand binding at the extracellular side of a receptor leads to conformational changes in the cytoplasmic side of the receptor. The biggest change is an outward movement of the cytoplasmic part of the 5th and 6th transmembrane helix (TM5 and TM6). The structure of activated beta-2 adrenergic receptor in complex with G confirmed that the Gα binds to a cavity created by this movement.
GPCRs exhibit a similar structure to some other proteins with seven transmembrane domains, such as microbial rhodopsins and adiponectin receptors 1 and 2 (ADIPOR1 and ADIPOR2). However, these 7TMH (7-transmembrane helices) receptors and channels do not associate with G proteins. In addition, ADIPOR1 and ADIPOR2 are oriented oppositely to GPCRs in the membrane (i.e. GPCRs usually have an extracellular N-terminus, cytoplasmic C-terminus, whereas ADIPORs are inverted). | 1 | Applied and Interdisciplinary Chemistry |
In 1994 he was elected Fellow of the Royal Society of Edinburgh (FRSE) and Fellow of the Royal Society of Chemistry (FRSC), and in 2016 he was elected Member of Academia Europaea (MAE). He is currently a Member of Council of the Engineering and Physical Sciences Research Council (EPSRC). He has held a Leverhulme Trust Senior Research Fellowship, and has Honorary Degrees from Tallinn Technical University and from Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences. In 2020, he was awarded the Nyholm Prize for Inorganic Chemistry by the Royal Society of Chemistry. | 0 | Theoretical and Fundamental Chemistry |
Flash photolysis is an alternative to pulse radiolysis that uses high-power light pulses (e.g. from an excimer laser) rather than beams of electrons to initiate chemical reactions. Typically ultraviolet light is used which requires less radiation shielding than required for the X-rays emitted in pulse radiolysis. | 0 | Theoretical and Fundamental Chemistry |
In the early 1950s two groundbreaking series of papers were written independently on the relationship between grain boundaries and strength.
In 1951, while at the University of Sheffield, E. O. Hall wrote three papers which appeared in volume 64 of the Proceedings of the Physical Society. In his third paper, Hall showed that the length of slip bands or crack lengths correspond to grain sizes and thus a relationship could be established between the two. Hall concentrated on the yielding properties of mild steels.
Based on his experimental work carried out in 1946–1949, N. J. Petch of the University of Leeds, England published a paper in 1953 independent from Halls. Petchs paper concentrated more on brittle fracture. By measuring the variation in cleavage strength with respect to ferritic grain size at very low temperatures, Petch found a relationship exact to that of Hall's. Thus this important relationship is named after both Hall and Petch. | 1 | Applied and Interdisciplinary Chemistry |
In atmospheric science, geostrophic flow () is the theoretical wind that would result from an exact balance between the Coriolis force and the pressure gradient force. This condition is called geostrophic equilibrium or geostrophic balance (also known as geostrophy). The geostrophic wind is directed parallel to isobars (lines of constant pressure at a given height). This balance seldom holds exactly in nature. The true wind almost always differs from the geostrophic wind due to other forces such as friction from the ground. Thus, the actual wind would equal the geostrophic wind only if there were no friction (e.g. above the atmospheric boundary layer) and the isobars were perfectly straight. Despite this, much of the atmosphere outside the tropics is close to geostrophic flow much of the time and it is a valuable first approximation. Geostrophic flow in air or water is a zero-frequency inertial wave. | 1 | Applied and Interdisciplinary Chemistry |
Hess's Law states that the sum of the energy changes of all thermochemical equations included in an overall reaction is equal to the overall energy change. Since ΔH is a state function and is not dependent on how reactants become products as a result, steps (in the form of several thermochemical equations) can be used to find the ΔH of the overall reaction. For instance:
:Reaction 1: C + O → CO
This reaction is the result of two steps (a reaction sequence):
:C + ½O → CO
:ΔH = −110.5 kJ
:CO + ½O → CO
:ΔH = −283.0 kJ
Adding these two reactions together results in Reaction 1, which allows ΔH to be found, so whether or not agents in the reaction sequence are equal to each other is verified. The reaction sequences are then added together. In the following example, CO is not in Reaction 1 and equals another reaction.
:C + ½O + ½O → CO
and
:C + O → CO, Reaction (1)
To solve for ΔH, the ΔHs of the two equations in the reaction sequence are added together:
:(−110.5 kJ) + (−283.0 kJ) = (−393.5 kJ) = ΔH of Reaction (1)
Another example involving thermochemical equations is that when methane gas is combusted, heat is released, making the reaction exothermic. In the process, 890.4 kJ of heat is released, so the heat is written as a product of the reaction. | 0 | Theoretical and Fundamental Chemistry |
The structure of triethyloxonium tetrafluoroborate has not been characterized by X-ray crystallography, but the structure of triethyloxonium hexafluorophosphate has been examined. The measurements confirm that the cation is pyramidal with C-O-C angles in the range 109.4°–115.5°. The average C–O distance is 1.49 Å. | 0 | Theoretical and Fundamental Chemistry |
The deposits consist of a multitude of pancake-like splats called lamellae, formed by flattening of the liquid droplets. As the feedstock powders typically have sizes from micrometers to above 100 micrometers, the lamellae have thickness in the micrometer range and lateral dimension from several to hundreds of micrometers. Between these lamellae, there are small voids, such as pores, cracks and regions of incomplete bonding. As a result of this unique structure, the deposits can have properties significantly different from bulk materials. These are generally mechanical properties, such as lower strength and modulus, higher strain tolerance, and lower thermal and electrical conductivity. Also, due to the rapid solidification, metastable phases can be present in the deposits. | 1 | Applied and Interdisciplinary Chemistry |
ASC works with its customer's to solve problems involving the flow of fluids (gases or liquids) in or around a wide variety of equipment or goods. Some problems include simply the flow itself. These include such things as reducing pressure drop, eliminating flow induced vibrations, or ensuring uniform flow through an equipment that processes elements of the flow. Since fluid flow carries energy, heat transfer problems such as improving thermal mixing or heating/cooling characteristics are often solved. Similarly, ASC undertakes many problems involving the pneumatic transport of particulate and droplets. The chemical reactions in a flowing gas or liquid are also the subject of ASC studies. Methods used to solve these problems include: Numerical simulation (including Computational fluid dynamics), Wind tunnel testing, Laboratory modeling (including Scale models), and Flow measurement/Field testing. | 1 | Applied and Interdisciplinary Chemistry |
Many smartphones contain miniaturized microelectromechanical systems (MEMS) magnetometers which are used to detect magnetic field strength and are used as compasses. The iPhone 3GS has a magnetometer, a magnetoresistive permalloy sensor, the AN-203 produced by Honeywell. In 2009, the price of three-axis magnetometers dipped below US$1 per device and dropped rapidly. The use of a three-axis device means that it is not sensitive to the way it is held in orientation or elevation. Hall effect devices are also popular.
Researchers at Deutsche Telekom have used magnetometers embedded in mobile devices to permit touchless 3D interaction. Their interaction framework, called MagiTact, tracks changes to the magnetic field around a cellphone to identify different gestures made by a hand holding or wearing a magnet. | 0 | Theoretical and Fundamental Chemistry |
The Caspian Summit is a head of state-level meeting of the five littoral states. The fifth Caspian Summit took place on August 12, 2018, in the Kazakh port city of Aktau. The five leaders signed the Convention on the Legal Status of the Caspian Sea.
Representatives of the Caspian littoral states held a meeting in the capital of Kazakhstan on September 28, 2018, as a follow-up to the Aktau Summit. The conference was hosted by the Kazakh Ministry of Investment and Development. The participants in the meeting agreed to host an investment forum for the Caspian region every two years. | 1 | Applied and Interdisciplinary Chemistry |
*Bibliotheca Philosophica Hermetica
*European Society for the Study of Western Esotericism
*Freemasonry
*Rosicrucianism | 1 | Applied and Interdisciplinary Chemistry |
To annotate the vast amounts of available NGS data, currently a large number of SNPs annotation tools are available. Some of them are specific to specific SNPs while others are more general. Some of the available SNPs annotation tools are as follows SNPeff, Ensembl Variant Effect Predictor (VEP), ANNOVAR, FATHMM, PhD-SNP, PolyPhen-2, SuSPect, F-SNP, AnnTools, SeattleSeq, SNPit, SCAN, Snap, SNPs&GO, LS-SNP, Snat, TREAT, TRAMS, Maviant, MutationTaster, SNPdat, Snpranker, NGS – SNP, SVA, VARIANT, SIFT, LIST-S2, PhD-SNP and FAST-SNP. The functions and approaches used in SNPs annotation tools are listed below. | 1 | Applied and Interdisciplinary Chemistry |
Redox mediators are often added to experimental systems to improve the rate of electron export from the biological material and/or electron transfer to the anode, especially when whole cells are employed as the light harvesting material. Quinones, phenazines, and viologens have all been successfully employed to increase current output from photosynthetic organisms in biological photovoltaic devices. Adding artificial mediators is considered an unsustainable practice in scaled-up applications, so most modern research is on mediator-free systems. | 0 | Theoretical and Fundamental Chemistry |
During the initial phases of glycolysis and the TCA cycle, cofactors such as NAD+ donate and accept electrons that aid in the electron transport chain's ability to produce a proton gradient across the inner mitochondrial membrane. The ATP synthase complex exists within the mitochondrial membrane (F portion) and protrudes into the matrix (F portion). The energy derived as a result of the chemical gradient is then used to synthesize ATP by coupling the reaction of inorganic phosphate to ADP in the active site of the ATP synthase enzyme; the equation for this can be written as ADP + P → ATP. | 1 | Applied and Interdisciplinary Chemistry |
At and below, pure tin transforms from the silvery, ductile metallic allotrope of β-form white tin to the brittle, nonmetallic, α-form grey tin with a diamond cubic structure. The transformation is slow to initiate due to a high activation energy but the presence of germanium (or crystal structures of similar form and size) or very low temperatures of roughly −30 °C aids the initiation. There is also a large volume increase of about 27% associated with the phase change to the nonmetallic low temperature allotrope. This frequently makes tin objects (like buttons) decompose into powder during the transformation, hence the name tin pest. The decomposition will catalyze itself, which is why the reaction accelerates once it starts. The mere presence of tin pest leads to tin pest. Tin objects at low temperatures will simply disintegrate. | 1 | Applied and Interdisciplinary Chemistry |
They are also utilized in military electronics such as active electronically scanned array radars.
Thales Group introduced the Ground Master 400 radar in 2010 utilizing GaN technology. In 2021 Thales put in operation more than 50,000 GaN Transmitters on radar systems.
The U.S. Army funded Lockheed Martin to incorporate GaN active-device technology into the AN/TPQ-53 radar system to replace two medium-range radar systems, the AN/TPQ-36 and the AN/TPQ-37. The AN/TPQ-53 radar system was designed to detect, classify, track, and locate enemy indirect fire systems, as well as unmanned aerial systems. The AN/TPQ-53 radar system provided enhanced performance, greater mobility, increased reliability and supportability, lower life-cycle cost, and reduced crew size compared to the AN/TPQ-36 and the AN/TPQ-37 systems.
Lockheed Martin fielded other tactical operational radars with GaN technology in 2018, including TPS-77 Multi Role Radar System deployed to Latvia and Romania. In 2019, Lockheed Martin's partner ELTA Systems Limited, developed a GaN-based ELM-2084 Multi Mission Radar that was able to detect and track air craft and ballistic targets, while providing fire control guidance for missile interception or air defense artillery.
On April 8, 2020, Saab flight tested its new GaN designed AESA X-band radar in a JAS-39 Gripen fighter. Saab already offers products with GaN based radars, like the Giraffe radar, Erieye, GlobalEye, and Arexis EW. Saab also delivers major subsystems, assemblies and software for the AN/TPS-80 (G/ATOR) | 0 | Theoretical and Fundamental Chemistry |
Algae can be used to produce green diesel (also known as renewable diesel, hydrotreating vegetable oil or hydrogen-derived renewable diesel) through a hydrotreating refinery process that breaks molecules down into shorter hydrocarbon chains used in diesel engines. It has the same chemical properties as petroleum-based diesel meaning that it does not require new engines, pipelines or infrastructure to distribute and use. It has yet to be produced at a cost that is competitive with petroleum. While hydrotreating is currently the most common pathway to produce fuel-like hydrocarbons via decarboxylation/decarbonylation, there is an alternative process offering a number of important advantages over hydrotreating. In this regard, the work of Crocker et al. and Lercher et al. is particularly noteworthy. For oil refining, research is underway for catalytic conversion of renewable fuels by decarboxylation. As the oxygen is present in crude oil at rather low levels, of the order of 0.5%, deoxygenation in petroleum refining is not of much concern, and no catalysts are specifically formulated for oxygenates hydrotreating. Hence, one of the critical technical challenges to make the hydrodeoxygenation of algae oil process economically feasible is related to the research and development of effective catalysts. | 1 | Applied and Interdisciplinary Chemistry |
Fumarylacetoacetic acid (fumarylacetoacetate) is an intermediate in the metabolism of tyrosine. It is formed through the conversion of maleylacetoacetate into fumarylacetoacetate by the enzyme maleylacetoacetate isomerase. | 1 | Applied and Interdisciplinary Chemistry |
In a nanorecording application, a certain rotaxane is deposited as a Langmuir–Blodgett film on ITO-coated glass. When a positive voltage is applied with the tip of a scanning tunneling microscope probe, the rotaxane rings in the tip area switch to a different part of the dumbbell and the resulting new conformation makes the molecules stick out 0.3 nanometer from the surface. This height difference is sufficient for a memory dot. It is not yet known how to erase such a nanorecording film. | 0 | Theoretical and Fundamental Chemistry |
Krypton-85, with a half-life 10.76 years, is formed by the fission process with
a fission yield of about 0.3%. Only 20% of the fission products of mass 85 become Kr itself; the rest passes through a short-lived nuclear isomer and then to stable Rb. If irradiated reactor fuel is reprocessed, this radioactive krypton may be released into the air. This krypton release can be detected and used as a means of detecting clandestine nuclear reprocessing. Strictly speaking, the stage which is detected is the dissolution of used nuclear fuel in nitric acid, as it is at this stage that the krypton and other fission gases like the more abundant xenon are released. Despite the industrial applications of Krypton-85 and the relatively high prices of both Krypton and Xenon, they are not currently extracted from spent fuel to any appreciable extent even though Krypton and Xenon both become solid at the temperature of liquid nitrogen and could thus be captured in a cold trap if the flue gas of a voloxidation process were cooled by liquid nitrogen.
Increase of fission gases above a certain limit can lead to fuel pin swelling and even puncture, so that fission gas measurement after discharging the fuel from the reactor is most important to make burn-up calculations, to study the nature of fuel inside the reactor, behaviour with pin materials, for effective utilization of fuel and also reactor safety. In addition to that, they are a nuisance in a nuclear reactor due to being neutron poisons, albeit not to the same extent as isotopes of xenon, another noble gas produced by fission. | 0 | Theoretical and Fundamental Chemistry |
The cyanohydrins are a special class of nitriles. Classically they result from the addition of alkali metal cyanides to aldehydes in the cyanohydrin reaction. Because of the polarity of the organic carbonyl, this reaction requires no catalyst, unlike the hydrocyanation of alkenes. O-Silyl cyanohydrins are generated by the addition trimethylsilyl cyanide in the presence of a catalyst (silylcyanation). Cyanohydrins are also prepared by transcyanohydrin reactions starting, for example, with acetone cyanohydrin as a source of HCN. | 0 | Theoretical and Fundamental Chemistry |
Cavitation can occur in the xylem of vascular plants. The sap vaporizes locally so that either the vessel elements or tracheids are filled with water vapor. Plants are able to repair cavitated xylem in a number of ways. For plants less than 50 cm tall, root pressure can be sufficient to redissolve the vapor. Larger plants direct solutes into the xylem via ray cells, or in tracheids, via osmosis through bordered pits. Solutes attract water, the pressure rises and vapor can redissolve. In some trees, the sound of the cavitation is audible, particularly in summer, when the rate of evapotranspiration is highest. Some deciduous trees have to shed leaves in the autumn partly because cavitation increases as temperatures decrease. | 1 | Applied and Interdisciplinary Chemistry |
In melt spinning, the alloy or metal is first melted in a crucible. Then, an inert gas, usually argon, is used to jet the molten material out of a nozzle located on the underside of the crucible. The resulting stream of liquid is directed onto the outer circumferential surface of a rotating wheel or drum which is cooled internally. The drums outer surface is located extremely close to the nozzle but does not touch it. Generally, the velocity of the drums surface must be between 10 m/s and 60 m/s in order to avoid the formation of globules (droplets) or breaking the ribbon respectively. Once the stream contacts the drums surface, a small puddle of melt (molten material) is formed. Due to the low viscosity of the melt, the shear forces generated by the relative movement of the drums surface underneath the melt only extend a few microns into the puddle. In other words, only a small amount of the puddle is affected by the friction from the rotation of the drum. Consequently, as the drum spins, most of the melt puddle remains held between the nozzle and the drum by surface tension. However, the melt on the very bottom of the puddle, which is in direct contact with the drum, rapidly solidifies into a thin ribbon. The solidified ribbon is carried away from under the nozzle on the drums surface for up to 10° of rotation before centrifugal force from the drums rotation ejects it.
This process occurs continuously, so as solidified material is removed from underneath the puddle of melt, more liquid material is added to the puddle from the nozzle. | 1 | Applied and Interdisciplinary Chemistry |
Although Golden Gate Cloning speeds up multisegment cloning, careful design of donor and recipient plasmids is required. Scientists at New England Biolabs have successfully demonstrated the assembly of 35 fragments via a single-tube Golden Gate Assembly reaction. Critical to this method of assembly, the vector backbone of the destination plasmid and all the assembly fragments are flanked by Type IIS restriction enzyme recognition sites, as this subtype of restriction enzymes cut downstream from their recognition sites. After cutting, each assembly active piece of DNA has unique overhangs that anneal to the next fragment of DNA in the planned assembly and become ligated, building the assembly. While it is also possible for an overhang to anneal back to its original complementary overhang associated with the upstream recognition site and become ligated, re-forming the original sequence, this will be susceptible to further cutting throughout the assembly reaction. | 1 | Applied and Interdisciplinary Chemistry |
A conservative replacement (also called a conservative mutation or a conservative substitution) is an amino acid replacement in a protein that changes a given amino acid to a different amino acid with similar biochemical properties (e.g. charge, hydrophobicity and size).
Conversely, a radical replacement, or radical substitution, is an amino acid replacement that exchanges an initial amino acid by a final amino acid with different physicochemical properties. | 1 | Applied and Interdisciplinary Chemistry |
Compound 48/80 is a polymer produced by the condensation of N-methyl-p-methoxyphenethylamine with formaldehyde. It promotes histamine release, and in biochemical research, compound 48/80 is used to promote mast cell degranulation. | 1 | Applied and Interdisciplinary Chemistry |
First, Vlasov argues that the standard kinetic approach based on the Boltzmann equation has difficulties when applied to a description of the plasma with long-range Coulomb interaction. He mentions the following problems arising when applying the kinetic theory based on pair collisions to plasma dynamics:
# Theory of pair collisions disagrees with the discovery by Rayleigh, Irving Langmuir and Lewi Tonks of natural vibrations in electron plasma.
# Theory of pair collisions is formally not applicable to Coulomb interaction due to the divergence of the kinetic terms.
# Theory of pair collisions cannot explain experiments by Harrison Merrill and Harold Webb on anomalous electron scattering in gaseous plasma.
Vlasov suggests that these difficulties originate from the long-range character of Coulomb interaction. He starts with the collisionless Boltzmann equation (sometimes called the Vlasov equation, anachronistically in this context), in generalized coordinates:
explicitly a PDE:
and adapted it to the case of a plasma, leading to the systems of equations shown below. Here is a general distribution function of particles with momentum at coordinates and given time . Note that the term is the force acting on the particle. | 1 | Applied and Interdisciplinary Chemistry |
The law was named after scientist Jacques Charles, who formulated the original law in his unpublished work from the 1780s.
In two of a series of four essays presented between 2 and 30 October 1801, John Dalton demonstrated by experiment that all the gases and vapours that he studied expanded by the same amount between two fixed points of temperature. The French natural philosopher Joseph Louis Gay-Lussac confirmed the discovery in a presentation to the French National Institute on 31 Jan 1802, although he credited the discovery to unpublished work from the 1780s by Jacques Charles. The basic principles had already been described by Guillaume Amontons and Francis Hauksbee a century earlier.
Dalton was the first to demonstrate that the law applied generally to all gases, and to the vapours of volatile liquids if the temperature was well above the boiling point. Gay-Lussac concurred. With measurements only at the two thermometric fixed points of water (0°C and 100°C), Gay-Lussac was unable to show that the equation relating volume to temperature was a linear function. On mathematical grounds alone, Gay-Lussacs paper does not permit the assignment of any law stating the linear relation. Both Daltons and Gay-Lussac's main conclusions can be expressed mathematically as:
where is the volume occupied by a given sample of gas at 100 °C; is the volume occupied by the same sample of gas at 0 °C; and is a constant which is the same for all gases at constant pressure. This equation does not contain the temperature and so is not what became known as Charles Law. Gay-Lussacs value for (), was identical to Dalton's earlier value for vapours and remarkably close to the present-day value of . Gay-Lussac gave credit for this equation to unpublished statements by his fellow Republican citizen J. Charles in 1787. In the absence of a firm record, the gas law relating volume to temperature cannot be attributed to Charles.
Dalton's measurements had much more scope regarding temperature than Gay-Lussac, not only measuring the volume at the fixed points of water but also at two intermediate points. Unaware of the inaccuracies of mercury thermometers at the time, which were divided into equal portions between the fixed points, Dalton, after concluding in Essay II that in the case of vapours, “any elastic fluid expands nearly in a uniform manner into 1370 or 1380 parts by 180 degrees (Fahrenheit) of heat”, was unable to confirm it for gases. | 0 | Theoretical and Fundamental Chemistry |
Positive-sense (5′-to-3′) viral RNA signifies that a particular viral RNA sequence may be directly translated into viral proteins (e.g., those needed for viral replication). Therefore, in positive-sense RNA viruses, the viral RNA genome can be considered viral mRNA, and can be immediately translated by the host cell. Unlike negative-sense RNA, positive-sense RNA is of the same sense as mRNA. Some viruses (e.g. Coronaviridae) have positive-sense genomes that can act as mRNA and be used directly to synthesize proteins without the help of a complementary RNA intermediate. Because of this, these viruses do not need to have an RNA polymerase packaged into the virion—the RNA polymerase will be one of the first proteins produced by the host cell, since it is needed in order for the virus's genome to be replicated. | 1 | Applied and Interdisciplinary Chemistry |
While many in vitro and in vivo studies have been tested in animal models, the translation from animal models to humans has not begun. Factors such as the size of surgical cut sites, duration of the procedure, and available resources and cost must all be considered. Synthetic nanomaterials have the potential to advance scaffoldings used in tissue engineering of heart valves. The use of nanotechnology could help expand beneficial properties of fabricated scaffolds such as higher tensile strength. | 1 | Applied and Interdisciplinary Chemistry |
Unlike viruses, bacteria are not as susceptible to silencing by siRNA. This is largely due to how bacteria replicate. Bacteria replicate outside of the host cell and do not contain the necessary machinery for RNAi to function. However, bacterial infections can still be suppressed by siRNA by targeting the host genes that are involved in the immune response caused by the infection or by targeting the host genes involved in mediating the entry of bacteria into cells. For instance, siRNA was used to reduce the amount of pro-inflammatory cytokines expressed in the cells of mice treated with lipopolysaccharide (LPS). The reduced expression of the inflammatory cytokine, tumor necrosis factor α (TNFα), in turn, caused a reduction in the septic shock felt by the LPS-treated mice. In addition, siRNA was used to prevent the bacteria, Psueomonas aeruginosa, from invading murine lung epithelial cells by knocking down the caveolin-2 (CAV2) gene. Thus, though bacteria cannot be directly targeted by siRNA mechanisms, they can still be affected by siRNA when the components involved in the bacterial infection are targeted. | 1 | Applied and Interdisciplinary Chemistry |
The enzymes are encoded and used by viruses that use reverse transcription as a step in the process of replication. Reverse-transcribing RNA viruses, such as retroviruses, use the enzyme to reverse-transcribe their RNA genomes into DNA, which is then integrated into the host genome and replicated along with it. Reverse-transcribing DNA viruses, such as the hepadnaviruses, can allow RNA to serve as a template in assembling and making DNA strands. HIV infects humans with the use of this enzyme. Without reverse transcriptase, the viral genome would not be able to incorporate into the host cell, resulting in failure to replicate. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a chemical test is a qualitative or quantitative procedure designed to identify, quantify, or characterise a chemical compound or chemical group. | 0 | Theoretical and Fundamental Chemistry |
Proposed disposal routes of waste sorbent include:
* Landfill;
* Disposal at sea;
* Use in cement manufacture;
* Use in flue gas desulfurisation (FGD).
The lifecycle CO emissions for power generation with CaL and the first three disposal techniques have been calculated. Before disposal of the CaO coal power with CaL has a similar level of lifecycle emissions as amine scrubbing but with the CO-absorbing properties of CaO CaL becomes significantly less polluting. Ocean disposal was found to be the best, but current laws relating to dumping waste at sea prevent this. Next best was use in cement manufacture, reducing emissions over an unabated coal plant by 93%. | 1 | Applied and Interdisciplinary Chemistry |
A large number of researchers have dedicated and are dedicating their efforts to the study of the Warburg effect that is intimately associated with the Warburg hypothesis. In oncology, the Warburg effect is the observation that most cancer cells predominantly produce energy by a high rate of glycolysis followed by lactic acid fermentation in the cytosol, rather than by a comparatively low rate of glycolysis followed by oxidation of pyruvate in mitochondria as in most normal cells. Interestingly, researchers found that under obesity, tumor cells invert the metabolic flow by producing glucose by gluconeogenesis using lactic acid and other metabolic sources as substrates. This process in known as Warburg effect inversion.
In particular, almost 18,000 publications have been published on the matter of ATP and the Warburg effect in the period 2000 to 2015. Most of the functions of the Warburg Effect have been the object of study. Thousands of publications claim to have determined its functions or causes.
Thomas N. Seyfried and Peter L. Pedersen are leading supporters of the Warburg hypothesis of the cause of cancer and consider experimental and other evidence to overwhelming favor it over the widely accepted somatic mutation theory. | 1 | Applied and Interdisciplinary Chemistry |
Exposure assessment is the process of estimating or measuring the magnitude, frequency and duration of exposure to an agent, along
with the number and characteristics of the population exposed. Ideally, it describes the sources, pathways, routes, and the uncertainties in the assessment. It is a necessary part of risk analysis and hence risk assessment.
Exposure analysis is the science that describes how an individual or population comes in contact with a contaminant, including quantification of the amount of contact across space and time. Exposure assessment and exposure analysis are often used as synonyms in many practical contexts. Risk is a function of exposure and hazard. For example, even for an extremely toxic (high hazard) substance, the risk of an adverse outcome is unlikely if exposures are near zero. Conversely, a moderately toxic substance may present substantial risk if an individual or a population is highly exposed. | 1 | Applied and Interdisciplinary Chemistry |
Converting is a type of metallurgical smelting that includes several processes; the most commercially important form is the treatment of molten metal sulfides to produce crude metal and slag, as in the case of copper and nickel converting. A now-uncommon form is batch treatment of pig iron to produce steel by the Bessemer process. The vessel used was called the Bessemer converter. Modern steel mills use basic oxygen process converters. | 1 | Applied and Interdisciplinary Chemistry |
Photodegradation involves the transformation of CDOM into smaller and less colored molecules (e.g., organic acids), or into inorganic carbon (CO, CO), and nutrient salts (NH, HPO). Therefore, it generally means that photodegradation transforms recalcitrant into labile DOC molecules that can be rapidly used by prokaryotes for biomass production and respiration. However, it can also increase CDOM through the transformation of compounds such as triglycerides, into more complex aromatic compounds, which are less degradable by microbes. Moreover, UV radiation can produce e.g., reactive oxygen species, which are harmful to microbes. The impact of photochemical processes on the DOC pool depends also on the chemical composition, with some studies suggesting that recently produced autochthonous DOC becomes less bioavailable while allochthonous DOC becomes more bioavailable to prokaryotes after sunlight exposure, albeit others have found the contrary. Photochemical reactions are particularly important in coastal waters which receive high loads of terrestrial derived CDOM, with an estimated ~20–30% of terrestrial DOC being rapidly photodegraded and consumed. Global estimates also suggests that in marine systems photodegradation of DOC produces ~180 Tg C yr of inorganic carbon, with an additional 100 Tg C yr of DOC made more available to microbial degradation. Another attempt at global ocean estimates also suggest that photodegradation (210 Tg C yr) is approximately the same as the annual global input of riverine DOC (250 Tg C yr;), while others suggest that direct photodegradation exceeds the riverine DOC inputs. | 1 | Applied and Interdisciplinary Chemistry |
The first attempts at general anesthesia were probably herbal remedies administered in prehistory. Alcohol is the oldest known sedative; it was used in ancient Mesopotamia thousands of years ago. | 1 | Applied and Interdisciplinary Chemistry |
When superheating a substance, nucleate pool boiling and convective flow boiling occur when the temperature of the surface used to heat a liquid is higher than the liquid's boiling point by the wall superheat. | 1 | Applied and Interdisciplinary Chemistry |
Asymmetric hydrogenations are used in the production of several drugs, such as the antibacterial levofloxin, the antibiotic carbapenem, and the antipsychotic agent BMS181100.
Knowles' research into asymmetric hydrogenation and its application to the production scale synthesis of L-Dopa gave asymmetric hydrogenation a strong start in the industrial world. A 2001 review indicated that asymmetric hydrogenation accounted for 50% of production scale, 90% of pilot scale, and 74% of bench scale catalytic, enantioselective processes in industry, with the caveat that asymmetric catalytic methods in general were not yet widely used.
Asymmetric hydrogenation has replaced kinetic resolution based methods has resulted in substantial improvements in the processs efficiency. can be seen in a number of specific cases where the For example, Roches Catalysis Group was able to achieve the synthesis of (S,S)-Ro 67-8867 in 53% overall yield, a dramatic increase above the 3.5% that was achieved in the resolution based synthesis. Roche's synthesis of mibefradil was likewise improved by replacing resolution with asymmetric hydrogenation, reducing the step count by three and increasing the yield of a key intermediate to 80% from the original 70%.
<br />
Noyori-inspired hydrogenation catalysts have been applied to the commercial synthesis of number of fine chemicals. (R)-1,2-Propandiol, precursor to the antibacterial levofloxacin, can be efficiently synthesized from hydroxyacetone using Noyori asymmetric hydrogenation:
Newer routes focus on the hydrogenation of (R)-methyl lactate.
An antibiotic carbapenem is also prepared using Noyori asymmetric hydrogenation via (2S,3R)-methyl 2-(benzamidomethyl)-3-hydroxybutanoate, which is synthesized from racemic methyl 2-(benzamidomethyl)-3-oxobutanoate by dynamic kinetic resolution.
An antipsychotic agent BMS 181100 is synthesized using BINAP/diamine-Ru catalyst. | 0 | Theoretical and Fundamental Chemistry |
Oxoalkoxometalates are clusters that contain both oxide and alkoxide ligands. Typically they lack terminal oxo ligands. Examples include the dodecatitanate TiO(OPri) (where OPri stands for an alkoxy group), the iron oxoalkoxometalates and iron and copper Keggin ions. | 0 | Theoretical and Fundamental Chemistry |
Volatilization is the primary removal mechanism on most ERH sites. However, ERH can also be used to enhance other processes, some naturally occurring, to reduce the cost for treatment of a plume. ERH can be used to provide controlled low temperature heating for projects with remediation processes that do not involve steam stripping. "Low temperature heating" refers to the targeting of a subsurface temperature that is less than the boiling point of water. Examples of low temperature ERH include heat-enhanced bioremediation, heating the subsurface to temperatures above the solubility of dissolved gasses to induce VOC stripping (most notably carbon dioxide ebullition), heat enhanced in situ chemical oxidation (especially for persulfate activation), and heat-enhanced reduction (such as with iron-catalyzed reactions). ERH low-temperature heating can also be used to hydrolyze chlorinated alkanes in-situ at sub-boiling temperatures where hydrochloric acid released during hydrolysis further reacts with subsurface carbonates and bicarbonates to produce carbon dioxide for subsurface stripping of VOCs.
Using low temperature heating coupled with bioremediation, chemical oxidation, or dechlorination will result in increased reaction rates. This can significantly reduce the time required for these remediation processes as compared to a remediation at ambient temperature. In addition, a low temperature option does not require the use of the above grade treatment system for recovered vapors, as boiling temperatures will not be reached. This means less above grade infrastructure and lower overall cost.
When heat is combined with multi-phase extraction, the elevated temperatures will reduce the viscosity and surface tension of the recovered fluids which makes removal faster and easier. This is the original purpose for the development of ERH - to enhance oil recovery (see above). | 1 | Applied and Interdisciplinary Chemistry |
Tho-Radia was a French pharmaceutical company making cosmetics between 1932 and 1968. Tho-Radia-branded creams, toothpastes and soaps were notable for containing radium and thorium until 1937, as a scheme to exploit popular interest for radium after it was discovered by Pierre and Marie Curie, in a fad of radioactive quackery. | 0 | Theoretical and Fundamental Chemistry |
The Uptake of Hexose Phosphates (Uhp) is a protein system found in bacteria. It is a type of two-component sensory transduction pathway which helps bacteria react to their environment. | 1 | Applied and Interdisciplinary Chemistry |
The joint-stock company was founded on 20 November 1913 with a share capital of 4 million francs for a period of 50 years. The initial capital was increased to 2.5 mio francs in 1919, to 4.25 mio francs in April 1923 and to 5 mio francs in May 1929.
Messrs M. Siegfried, A. Cailler, J. Lindenmeyer, G. Bonnet, P. Bourcart, H. Gunthert, G. Roussy and M. Obellianne were appointed to the Board of Directors. | 1 | Applied and Interdisciplinary Chemistry |
A buildings HVAC (heating, ventilating, and air conditioning) system can make use of an air-side economizer to save energy in buildings by using cool outside air as a means of cooling the indoor space. When the temperature of the outside air is less than the temperature of the recirculated air, conditioning with the outside air is more energy efficient than conditioning with recirculated air. When the outside air is both sufficiently cool and sufficiently dry (depending on the climate) the amount of enthalpy in the air is acceptable and no additional conditioning of it is needed; this portion of the air-side economizer control scheme is called free cooling'.
Air-side economizers can reduce HVAC energy costs in cold and temperate climates while also potentially improving indoor air quality, but are most often not appropriate in hot and humid climates. With the appropriate controls, economizers can be used in climates which experience various weather systems.
When the outside airs dry- and wet-bulb temperatures are low enough, a water-side economizer can use water cooled by a wet cooling tower or a dry cooler (also called a fluid cooler) to cool buildings without operating a chiller. They are historically known as the strainer cycle', but the water-side economizer is not a true thermodynamic cycle. Also, instead of passing the cooling tower water through a strainer and then to the cooling coils, which causes fouling, more often a plate-and-frame heat exchanger is inserted between the cooling tower and chilled water loops.
Good controls, and valves or dampers, as well as maintenance, are needed to ensure proper operation of the air- and water-side economizers. | 0 | Theoretical and Fundamental Chemistry |
* A miniature binary weapon is used in an assassination in the Frederick Forsyth novel The Devils Alternative'. It consists of two half-capsules, a non-resistant one containing potassium cyanide and an acid-resistant one containing hydrochloric acid. The substances mix after the halves are assembled and the seal between them is broken, and form hydrogen cyanide. The surplus acid eats through the capsule walls of the non-resistant half, and after a delay of several hours, the lethal content is released into the intestinal tract of whoever ingested it. While technically possible, the assassination tool as discussed in the novel is presumably fictional. However, there are claims that in September 2003, the SVR (Russian Foreign Intelligence Service) prepared to assassinate Boris Berezovsky with a similar device.
* In the 10th and 11th episodes of the 6th season of TV-series Dexter are shown preparation and application of binary weapon consisting of two containers filled with DF and isopropyl alcohol. When mixed, the two substances form sarin.
* The 2002 movie xXx features a Soviet-made binary chemical weapon codenamed "Silent Night", after its supposed ability to render an area silent by killing its inhabitants. In the movie, the chemical was acquired by the terrorist group Anarchy-99, and their leader, Yorgi, plans to launch missiles containing Silent Night from an autonomous solar-powered submarine called Ahab, with the intent to sow chaos among civilized nations as they all blame each other for the attacks.
* Michael Crichtons 1972 novel Binary' uses a binary nerve agent "VZ" as the main plot device intended to kill the President of the United States, and indirectly most of the inhabitants of San Diego. | 1 | Applied and Interdisciplinary Chemistry |
Copepods jump out of the water - porpoising. The biophysics of this motion has been described by Waggett and Buskey 2007 and Kim et al 2015. | 1 | Applied and Interdisciplinary Chemistry |
The Mystery of Matter: Search for the Elements is a 2014 American documentary miniseries, which premiered nationwide on August 19, 2015. The PBS documentary, in three-episodes of one hour each, was directed by Stephen Lyons and Muffie Meyer.
The series, which took ten years to make, describes the search for the basic chemical elements that form matter by focusing on the lives and times of seven scientific visionaries. Hosted by actor Michael Emerson, the series depicts the creative process of the scientists, with actors describing the process of discovery in the scientists' own words and reenacting their major discoveries using replicas of their original laboratory equipment. | 1 | Applied and Interdisciplinary Chemistry |
Light sources emitting in the UV spectral region are widely used in techniques involving photo-chemical processes, e.g., curing of inks, adhesives, varnishes and coatings, photolithography, UV induced growth of dielectrics, UV induced surface modification, and cleaning or material deposition. Incoherent sources of UV radiation have some advantages over laser sources because of their lower cost, a huge area of irradiation, and ease of use, especially when large-scale industrial processes are envisaged.
Mercury lamps (λ = 253.7 nm) are widely spread UV sources, but their production, use, and disposal of old lamps pose a threat to human health and environmental pollution. Comparing with commonly used mercury lamps, excimer lamps have a number of advantages. A specific feature of an excimer molecule is the absence of a strong bond in the ground electronic state. Thanks to this, high-intensity UV radiation can be extracted from a plasma without significant self-absorption. This makes possible to convert efficiently energy deposited to the active medium into UV radiation.
Excimer lamps are referred to cold sources of UV radiation since the radiating surface of excimer lamps remains at relatively low temperatures in contrast with traditional UV lamps like a mercury one. Because the medium does not need to be heated, excimer lamps reach their peak output almost immediately after they are turned on.
Rare gas and rare gas-halide excimer lamps generally radiate in the ultraviolet (UV) and vacuum-ultraviolet (VUV) spectral regions (see table). Their unique narrow-band emission characteristics, high quantum efficiency, and high-energy photons make them suitable for applications such as absorption spectroscopy, UV curing, UV coating, disinfection, ozone generation, destruction of gaseous organic waste, photo-etching and photo-deposition and more other applications.
Light sources emitting photons in the energy range of 3.5–10 eV find applications in many fields due to the ability of high-energy photons to cleave most chemical bonds and kill microbes destroying nucleic acids and disrupting their DNA. Examples of excimer lamp applications include purification and disinfection of drinking water, pool water, air, sewage purification, decontamination of industrial waste, photochemical synthesis and degradation of organic compounds in flue gases and water, photopolymerization of organic coatings and paints, and photo-enhanced chemical vapor deposition. In all cases UV photons excite species or cleave chemical bonds, resulting in the formation of radicals or other chemical reagents, which initiate a required reaction.
An excimer lamp has selective action. UV radiation of a given wavelength can selectively excite species or generate required radicals. Such lamps can be useful for photophysical and photochemical processing such as UV curing of paints, varnishes, and adhesives, cleansing and modifying surface properties, polymerization of lacquers and paints, and photo-degradation of a variety of pollutants. Photo-etching of polymers is possible using different wavelengths: 172 nm by xenon excimer, 222 nm by krypton chloride, and 308 nm by xenon chloride. Excimer UV sources can be used for microstructuring large-area polymer surfaces. XeCl-excimer lamps (308 nm) are especially suitable to get tan.
Fluorescence spectroscopy is one of the most common methods for detecting biomolecules. Biomolecules can be labeled with fluoroprobe, which then is excited by a short pulse of UV light, leading to re-emission in the visible spectral region. Detecting this re-emitted light, one can judge the density of labeled molecules. Lanthanide complexes are commonly used as fluoroprobes. Due to their long lifetime, they play an important role in Förster resonance energy transfer (FRET) analysis.
At present, excimer lamps are coming into use in ecology, photochemistry, photobiology, medicine, criminalistics, petrochemistry, physics, microelectronics, different engineering tasks, wide-ranging technologies, science, various branches of industry including the food industry, and many others. | 0 | Theoretical and Fundamental Chemistry |
The diagram was created in 1904, when Richard Mollier plotted the total heat against entropy .
At the 1923 Thermodynamics Conference held in Los Angeles it was decided to name, in his honor, as a "Mollier diagram" any thermodynamic diagram using the enthalpy as one of its axes. | 0 | Theoretical and Fundamental Chemistry |
There are six steps in the mechanism of TFIIB action in the formation of the PIC and transcription initiation:
#RNA polymerase II is recruited to DNA through the TFIIB B core and B ribbon.
#RNA polymerase II unwinds DNA, aided by the TFIIB B linker and B reader (open complex formation).
#RNA polymerase II selects a transcription start site, aided by the TFIIB B reader.
#RNA polymerase II forms the first phosphodiester bond.
#RNA polymerase II produces short abortive transcripts due to clashes between nascent RNA and the TFIIB B reader loop.
#Extension of nascent RNA to 12-13 nucleotides leads to ejection of TFIIB due to further clashes with TFIIB. | 1 | Applied and Interdisciplinary Chemistry |
The thiol-yne reaction (also known as alkyne hydrothiolation) is an organic reaction between a thiol and an alkyne. The reaction product is an alkenyl sulfide. The reaction was first reported in 1949 with thioacetic acid as reagent and rediscovered in 2009. It is used in click chemistry and in polymerization, especially with dendrimers.
This addition reaction is typically facilitated by a radical initiator or UV irradiation and proceeds through a sulfanyl radical species. With monoaddition a mixture of (E/Z)-alkenes form. The mode of addition is anti-Markovnikov. The radical intermediate can engage in secondary reactions such as cyclisation. With diaddition the 1,2-disulfide or the 1,1- dithioacetal forms. Reported catalysts for radical additions are triethylborane, indium(III) bromide and AIBN. The reaction is also reported to be catalysed by cationic rhodium and iridium complexes, by thorium and uranium complexes, by rhodium complexes, by caesium carbonate and by gold.
Diphenyl disulfide reacts with alkynes to a 1,2-bis(phenylthio)ethylene. Reported alkynes are ynamides. A photoredox thiol-yne reaction has been reported. | 0 | Theoretical and Fundamental Chemistry |
Open-chain monosaccharides with same molecular graph may exist as two or more stereoisomers. The Fischer projection is a systematic way of drawing the skeletal formula of an open-chain monosaccharide so that each stereoisomer is uniquely identified.
Two isomers whose molecules are mirror-images of each other are identified by prefixes - or -, according to the handedness of the chiral carbon atom that is farthest from the carbonyl. In the Fischer projection, that is the second carbon from the bottom; the prefix is - or - according to whether the hydroxyl on that carbon lies to the right or left of the backbone, respectively.
If the molecular graph is symmetrical (H(CHOH)(CO)(CHOH)H) and the two halves are mirror images of each other, then the molecule is identical to its mirror image, and there is no - form.
A distinct common name, such as "glucose" or "ribose", is traditionally assigned to each pair of mirror-image stereoisomers, and to each achiral stereoisomer. These names have standard three-letter abbreviations, such as Glc for glucose and Rib for ribose.
Another nomenclature uses the systematic name of the molecular graph, a - or - prefix to indicate the position of the last chiral hydroxyl on the Fischer diagram (as above), and another italic prefix to indicate the positions of the remaining hydroxyls relative to the first one, read from bottom to top in the diagram, skipping the keto group if any. These prefixes are attached to the systematic name of the molecular graph. So for example, -glucose is -gluco-hexose, -ribose is -ribo-pentose, and -psicose is -ribo-hexulose. Note that, in this nomenclature, mirror-image isomers differ only in the / prefix, even though all their hydroxyls are reversed.
The following tables shows the Fischer projections of selected monosaccharides (in open-chain form), with their conventional names. The table shows all aldoses with 3 to 6 carbon atoms, and a few ketoses. For chiral molecules, only the - form (with the next-to-last hydroxyl on the right side) is shown; the corresponding forms have mirror-image structures. Some of these monosaccharides are only synthetically prepared in the laboratory and not found in nature. | 0 | Theoretical and Fundamental Chemistry |
* by pets, assistance animals, or working animals: animal-assisted therapy
** by horses: equine therapy, hippotherapy
** by dogs: pet therapy with therapy dogs, including grief therapy dogs
** by cats: pet therapy with therapy cats
* by fish: ichthyotherapy (wading with fish), aquarium therapy (watching fish)
* by maggots: maggot therapy
* by worms:
** by internal worms: helminthic therapy
** by leeches: leech therapy
* by immersion: animal bath | 1 | Applied and Interdisciplinary Chemistry |
NMR quantum computing uses the spin states of nuclei within molecules as qubits. NMR differs from other implementations of quantum computers in that it uses an ensemble of systems; in this case, molecules. | 0 | Theoretical and Fundamental Chemistry |
The wide-ranged biological purposes of bio-luminescence include but are not limited to attraction of mates, defense against predators, and warning signals. In the case of bioluminescent bacteria, bio-luminescence mainly serves as a form of dispersal. It has been hypothesized that enteric bacteria (bacteria that survive in the guts of other organisms) - especially those prevalent in the depths of the ocean - employ bio-luminescence as an effective form of distribution. After making their way into the digestive tracts of fish and other marine organisms and being excreted in fecal pellets, bioluminescent bacteria are able to utilize their bio-luminescent capabilities to lure in other organisms and prompt ingestion of these bacterial-containing fecal pellets. The bio-luminescence of bacteria thereby ensures their survival, persistence, and dispersal as they are able to enter and inhabit other organisms. | 1 | Applied and Interdisciplinary Chemistry |
The only type of Mach reflection possible in steady flow is direct-Mach reflection, in which the Mach stem is convex away from the oncoming flow, and the slip plane slopes towards the reflecting surface.
By new results there is a new configuration of shock waves - configuration with a negative angle of reflection in steady flow. Numerical simulations demonstrate two forms of this configuration - one with a kinked reflected shock wave, and an unstable double Mach configuration, depending on the transition path.
In pseudo-steady flows, the triple point moves away from the reflecting surface and the reflection is a direct-Mach reflection. In unsteady flows, it is also possible that the triple point remains stationary relative to the reflecting surface (stationary-Mach reflection), or moves toward the reflecting surface (inverse-Mach reflection). In inverse Mach reflection, the Mach stem is convex toward the oncoming flow, and the slip plane curves away from the reflecting surface. Each one of these configurations can assume one of the following three possibilities: single-Mach reflection, transitional-Mach reflection and double-Mach reflection. | 1 | Applied and Interdisciplinary Chemistry |
* Member then Chairman of the Inorganic Chemistry Nomenclature Commission of the International Union of Pure and Applied Chemistry (IUPAC)
* Member of the IUPAC Bureau, then President (1989-1991)
* Correspondent of the French Academy of sciences (1980) (member of the Sealed Folds Commission, the Philosophy and History of Science Commission, the Metrology Commission, President of the French Committee of International Scientific Unions - COFUSI)
* Doctor Honoris Causa of the University of Leeds (1990)
* Winner of the Alexander von Humboldt Prize (1990)
* Visiting Professor at the Universities of Hamburg, Heidelberg and Munich (Technische Universität)
* Chevalier in the Ordre National du Mérite, Officier of the Ordre des Palmes Académiques | 0 | Theoretical and Fundamental Chemistry |
MCT2 transporters within the peroxisome function to transport pyruvate into the peroxisome where it is reduced by peroxisomal LDH (pLDH) to lactate. In turn, NADH is converted to NAD+, regenerating this necessary component for subsequent β-oxidation. Lactate is then shuttled out of the peroxisome via MCT2, where it is oxidized by cytoplasmic LDH (cLDH) to pyruvate, generating NADH for energy use and completing the cycle (see figure). | 1 | Applied and Interdisciplinary Chemistry |
In its earliest form, liquid chromatography was used to separate the pigments of chlorophyll by a Russian botanist. Decades later, other chemists used the procedure for the study of carotins. Liquid chromatography was then used for the isolation of small molecules and organic compounds like amino acids, and most recently has been used in peptide and DNA research. Monolith columns have been instrumental in advancing the field of biomolecular research.
In recent trade shows and international meetings for HPLC, interest in column monoliths and biomolecular applications has grown steadily, and this correlation is no coincidence. Monoliths have been shown to possess great potential in the “omics” fields- genomics, proteomics, metabolomics, and pharmacogenomics, among others. The reductionist approach to understanding the chemical pathways of the body and reactions to different stimuli, like drugs, are essential to new waves of healthcare like personalized medicine.
Pharmacogenomics studies how responses to pharmaceutical products differ in efficacy and toxicity based on variations in the patients genome; it is a correlation of drug response to gene expression in a patient. Jeremy K. Nicholson of the Imperial College, London, used a postgenomic viewpoint to understand adverse drug reactions and the molecular basis of human disesase. His group studied gut microbial metabolic profiles and were able to see distinct differences in reactions to drug toxicity and metabolism even among various geographical distributions of the same race. Affinity monolith chromatography provides another approach to drug response measurements. David Hage at the University of Nebraska binds ligands to monolithic supports and measures the equilibrium phenomena of binding interactions between drugs and serum proteins. A monolith-based approach at the University of Bologna, Italy, is currently in use for high-speed screening of drug candidates in the treatment of Alzheimers. In 2003, Regnier and Liu of Purdue University described a multi-dimensional LC procedure for identifying single nucleotide polymorphisms (SNPs) in proteins. SNPs are alterations in the genetic code that can sometimes cause changes in protein conformation, as is the case with sickle cell anemia. Monoliths are particularly useful in these kinds of separations because of their superior mass transport capabilities, low backpressures coupled with faster flow rates, and relative ease of modification of the support surface.
Bioseparations on a production scale are enhanced by monolith column technologies as well. The fast separations and high resolving power of monoliths for large molecules means that real-time analysis on production fermentors is possible. Fermentation is well known for its use in making alcoholic beverages, but is also an essential step in the production of vaccines for rabies and other viruses. Real-time, on-line analysis is critical for monitoring of production conditions, and adjustments can be made if necessary. Boehringer Ingelheim Austria has validated a method with cGMP (commercial good manufacturing practices) for production of pharmaceutical-grade DNA plasmids. They are able to process 200L of fermentation broth on an 800mL monolith. At BIA Separations, processing time of the tomato mosaic virus decreased considerably from the standard five days of manually intensive work to equivalent purity and better recovery in only two hours with a monolith column. Other viruses have been purified on monoliths as well.
Another area of interest for HPLC is forensics. GC-MS (Gas Chromatography-Mass Spectroscopy) is generally considered the gold standard for forensic analysis. It is used in conjunction with online databases for rapid analysis of compounds in tests for blood alcohol, cause of death, street drugs, and food analysis, especially in poisoning cases. Analysis of buprenorphine, a heroin substitute, demonstrated the potential utility of multidimensional LC as a low-level detection method. HPLC methods can measure this compound at 40 ng/mL, compared to GC-MS at 0.5 ng/mL, but LC-MS-MS can detect buprenorphine at levels as low as 0.02 ng/mL. The sensitivity of multidimensional LC is therefore 2000 times greater than that of conventional HPLC. | 0 | Theoretical and Fundamental Chemistry |
Baffle rings are rigid rings placed within the inside of a tank to retard the flow of liquid between sections. The location and orifice size of the rings yield varying performance for a given application. | 1 | Applied and Interdisciplinary Chemistry |
This machine uses a motor-driven plate to hold a precisely flat disk (known as a "lap") for the purpose of cutting or polishing. Diamond abrasives bonded to metal or resin are typically used for cutting laps, and a wide variety of materials are used for polishing laps in conjunction with either very fine diamond powder or oxide-based polishes. Water is typically used for cutting, while either oil or water is used for the polishing process.
The machine uses a system generally called a "mast" which consists of an angle readout, height adjustment and typically a gear (called an "index gear") with a particular number of teeth is used as a means of setting the rotational angle. The angles of rotation are evenly divided by the number of teeth present on the gear, though many machines include additional means of adjusting the rotational angle in finer increments, often called a "cheater". The stone is bonded to a (typically metal) rod known as a "dop" or "dop stick" and is held in place by part of the mast referred to as the "quill". | 0 | Theoretical and Fundamental Chemistry |
Metal ions are essential to virtually all biological systems and hence studying their concentrations with effective probes is highly advantageous. Since metal ions are key to the causes of cancer, diabetes, and other diseases, monitoring them with probes that can provide insight into their concentrations with spatial and temporal resolution is of great interest to the scientific community. There are many applications that one can envision for small molecule sensors. It has been shown that one can use them to differentiate effectively between acceptable and harmful concentrations of mercury in fish. Further, since some types of neurons uptake zinc during their operation, these probes can be used as a way to track activity in the brain and could serve as an effective alternative to functional MRI. One can also track and quantify the growth of a cell, such as a fibroblast, that uptakes metal ions as it constructs itself. Numerous other biological processes can be tracked using small molecule sensors as many change metal concentrations as they occur, which can then be monitored. Still, the sensor must be tailored for its specific environment and sensing requirements. Depending on the application, the metal sensor should be selective for a certain type of metal, and especially needs to be able to bind its target metal with greater affinity than metals that naturally exist at high concentrations within the cell . Further, they should provide a response with a strong modulation in fluorescent spectrum and hence provide a high signal-to-noise ratio. Finally, it is essential that a sensor is not toxic to the biological system in which it is used. | 0 | Theoretical and Fundamental Chemistry |
A pyroelectric can be repeatedly heated and cooled (analogously to a heat engine) to generate usable electrical power. An example of a heat engine is the movement of the pistons in an internal combustion engine like that found in a gasoline powered automobile.
One group calculated that a pyroelectric in an Ericsson cycle could reach 50% of Carnot efficiency, while a different study found a material that could, in theory, reach 84-92% of Carnot efficiency (these efficiency values are for the pyroelectric itself, ignoring losses from heating and cooling the substrate, other heat-transfer losses, and all other losses elsewhere in the system).
Possible advantages of pyroelectric generators for generating electricity (as compared to the conventional heat engine plus electrical generator) include:
* Harvesting energy from waste-heat
* Potentially lower operating temperatures
* Less bulky equipment
* Fewer moving parts.
Although a few patents have been filed for such a device, such generators do not appear to be anywhere close to commercialization. | 0 | Theoretical and Fundamental Chemistry |
YouTube science entertainer Mark Rober has created a variation of the experiment, named "Devils Toothpaste", which has a far more pronounced reaction than the version usually performed in classroom settings. The ingredients to create the devils toothpaste reaction are the same as the regular elephant's toothpaste reaction, the only difference being the use of 50% HO instead of the usual 35%. | 1 | Applied and Interdisciplinary Chemistry |
Flowers play an important decorative role in China. Legend has it that once on the 7th day of the 1st lunar month, while Princess Shouyang, daughter of Emperor Wu of Liu Song, was resting under the eaves of Hanzhang Palace near the plum trees after wandering in the gardens, a plum blossom drifted down onto her fair face, leaving a floral imprint on her forehead that enhanced her beauty further. The court ladies were said to be so impressed, that they started decorating their own foreheads with a small delicate plum blossom design. This is also the mythical origin of the floral fashion, meihua zhuang (梅花妝; literally "plum blossom makeup"), that originated in the Southern dynasties (420–589) and became popular amongst ladies in the Tang (618–907) and Song (960–1279) dynasties. | 1 | Applied and Interdisciplinary Chemistry |
Zero Liquid Discharge (ZLD) is a classification of water treatment processes intended to reduce wastewater efficiently and produce clean water that is suitable for reuse (e.g., irrigation). ZLD systems employ wastewater treatment technologies and desalination to purify and recycle virtually all wastewater received.
ZLD technologies help industrial facilities meet discharge and water reuse requirements, enabling them to meet government discharge regulations, reach higher water recovery (%), and treat and recover valuable materials from the wastewater streams such as potassium sulfate, caustic soda, sodium sulfate, lithium, and gypsum.
Thermal technologies are the conventional means to achieve ZLD, such as evaporators (for instance multi stage flash distillation), multi effect distillation, mechanical vapor compression, crystallization, and condensate recovery. ZLD plants produce solid waste. | 1 | Applied and Interdisciplinary Chemistry |
Magnetic flowmeters, often called "mag meter"s or "electromag"s, use a magnetic field applied to the metering tube, which results in a potential difference proportional to the flow velocity perpendicular to the flux lines. The potential difference is sensed by electrodes aligned perpendicular to the flow and the applied magnetic field. The physical principle at work is Faraday's law of electromagnetic induction. The magnetic flowmeter requires a conducting fluid and a nonconducting pipe liner. The electrodes must not corrode in contact with the process fluid; some magnetic flowmeters have auxiliary transducers installed to clean the electrodes in place. The applied magnetic field is pulsed, which allows the flowmeter to cancel out the effect of stray voltage in the piping system. | 1 | Applied and Interdisciplinary Chemistry |
A gerontoplast is a plastid that develops from a chloroplast during the senescing of plant foliage. Gerontoplast development is generally seen to be the process of grana being unstacked, loss of thylakoid membranes, and large accumulation of plastoglobuli. | 0 | Theoretical and Fundamental Chemistry |
Over the past few decades, AMMs have diversified rapidly and their design principles, properties, and characterization methods have been outlined more clearly. A major starting point for the design of AMMs is to exploit the existing modes of motion in molecules. For instance, single bonds can be visualized as axes of rotation, as can be metallocene complexes. Bending or V-like shapes can be achieved by incorporating double bonds, that can undergo cis-trans isomerization in response to certain stimuli (typically irradiation with a suitable wavelength), as seen in numerous designs consisting of stilbene and azobenzene units. Similarly, ring-opening and -closing reactions such as those seen for spiropyran and diarylethene can also produce curved shapes. Another common mode of movement is the circumrotation of rings relative to one another as observed in mechanically interlocked molecules (primarily catenanes). While this type of rotation can not be accessed beyond the molecule itself (because the rings are confined within one another), rotaxanes can overcome this as the rings can undergo translational movements along a dumbbell-like axis. Another line of AMMs consists of biomolecules such as DNA and proteins as part of their design, making use of phenomena like protein folding and unfolding.
AMM designs have diversified significantly since the early days of the field. A major route is the introduction of bistability to produce molecular switches, featuring two distinct configurations for the molecule to convert between. This has been perceived as a step forward from the original molecular shuttle which consisted of two identical sites for the ring to move between without any preference, in a manner analogous to the ring flip in an unsubstituted cyclohexane. If these two sites are different from each other in terms of features like electron density, this can give rise to weak or strong recognition sites as in biological systems — such AMMs have found applications in catalysis and drug delivery. This switching behavior has been further optimized to acquire useful work that gets lost when a typical switch returns to its original state.
Inspired by the use of kinetic control to produce work in natural processes, molecular motors are designed to have a continuous energy influx to keep them away from equilibrium to deliver work.
Various energy sources are employed to drive molecular machines today, but this was not the case during the early years of AMM development. Though the movements in AMMs were regulated relative to the random thermal motion generally seen in molecules, they could not be controlled or manipulated as desired. This led to the addition of stimuli-responsive moieties in AMM design, so that externally applied non-thermal sources of energy could drive molecular motion and hence allow control over the properties. Chemical energy (or "chemical fuels") was an attractive option at the beginning, given the broad array of reversible chemical reactions (heavily based on acid-base chemistry) to switch molecules between different states. However, this comes with the issue of practically regulating the delivery of the chemical fuel and the removal of waste generated to maintain the efficiency of the machine as in biological systems. Though some AMMs have found ways to circumvent this, more recently waste-free reactions such based on electron transfers or isomerization have gained attention (such as redox-responsive viologens). Eventually, several different forms of energy (electric, magnetic, optical and so on) have become the primary energy sources used to power AMMs, even producing autonomous systems such as light-driven motors. | 0 | Theoretical and Fundamental Chemistry |
The valence electrons of this compound match those of nitric oxide. Sulfur mononitride can be described as some average of a set of resonance structures. The singly bonded structure (first resonance structure shown) has little contribution. The formal bond order is considered to be 2.5. | 0 | Theoretical and Fundamental Chemistry |
In order to qualify for SQT assessment chemistry, toxicity, and in situ measurements must be collected synoptically using standardized methods of sediment quality. A control sample is necessary to evaluate impact of contaminated sites. An appropriate reference is a whole sediment sample (particles and associated pore water) collected near area of concern and is representative of background conditions in the absence of contaminants. Evidence of contaminant exposure and biological effect is required in order to assign a site as chemically impacted. | 1 | Applied and Interdisciplinary Chemistry |
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