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Methyl green (CI 42585) is a cationic or positive charged stain related to Ethyl Green that has been used for staining DNA since the 19th century. It has been used for staining cell nuclei either as a part of the classical Unna-Pappenheim stain or as a nuclear counterstain ever since.<br>
In recent years, its fluorescent properties, when bound to DNA, have positioned it as useful for far-red imaging of live cell nuclei.
Fluorescent DNA staining is routinely used in cancer prognosis.
Methyl green also emerges as an alternative stain for DNA in agarose gels, fluorometric assays, and flow cytometry. It has also been shown that it can be used as an exclusion viability stain for cells.
Its interaction with DNA has been shown to be non-intercalating, in other words, not inserting itself into the DNA, but instead electrostatic with the DNA major groove. It is used in combination with pyronin in the methyl green–pyronin stain, which stains and differentiates DNA and RNA.
When excited at 244 or 388 nm in a neutral aqueous solution, methyl green produces a fluorescent emission at 488 or 633 nm, respectively. The presence or absence of DNA does not affect these fluorescence behaviors. When binding DNA under neutral aqueous conditions, methyl green also becomes fluorescent in the far red with an excitation maximum of 633 nm and an emission maximum of 677 nm.
Commercial Methyl green preparations are often contaminated with Crystal violet. Crystal violet can be removed by chloroform extraction. | 1 | Applied and Interdisciplinary Chemistry |
The agriculture industry uses 1 million pounds per year as a fertilizer. In particular, its use has been suggested for treatment of whiptail in broccoli and cauliflower in molybdenum-deficient soils. However, care must be taken because at a level of 0.3 ppm sodium molybdate can cause copper deficiencies in animals, particularly cattle.
It is used in industry for corrosion inhibition, as it is a non-oxidizing anodic inhibitor. The addition of sodium molybdate significantly reduces the nitrite requirement of fluids inhibited with nitrite-amine, and improves the corrosion protection of carboxylate salt fluids. In industrial water treatment applications where galvanic corrosion is a potential due to bimetallic construction, the application of sodium molybdate is preferred over sodium nitrite. Sodium molybdate has the advantage in that the dosing of lower ppm's of molybdate allow for lower conductivity of the circulating water. Sodium molybdate at levels of 50-100 ppm offer the same levels of corrosion inhibition as sodium nitrite at levels of 800+ ppm. By utilizing lower concentrations of sodium molybdate, conductivity is kept at a minimum and thus galvanic corrosion potentials are decreased. | 0 | Theoretical and Fundamental Chemistry |
In atmospheric chemistry, mixing ratio usually refers to the mole ratio r, which is defined as the amount of a constituent n divided by the total amount of all other constituents in a mixture:
The mole ratio is also called amount ratio.
If n is much smaller than n (which is the case for atmospheric trace constituents), the mole ratio is almost identical to the mole fraction. | 0 | Theoretical and Fundamental Chemistry |
Osama Kamal helped establish Egyptian Petrochemicals Holding Company (Echem) in 2002, which belongs to Egypts petroleum ministry, and is mandated with managing and developing Egypts petrochemicals industry. Kamal was appointed chairman of Echem in 2009. While Kamal was in charge of Echem, a crisis erupted pertaining the Agrium fertiliser plant in the Nile Delta city of Damietta. In 2008, Agrium, which is 30% owned by Echem, was faced with a popular campaign that alleged that the factory was bad for the environment, causing Egypt's government to abruptly cancel the project. Agrium was offered a 26% stake in the state-owned Egyptian fertilizer producer MOPCO instead. However, the project resumed in 2011, which dragged Agrium and Echem into more controversy. The project was completed and started operation in 2016. | 1 | Applied and Interdisciplinary Chemistry |
Microbial production of Succinic acid can be performed with wild bacteria like Actinobacillus succinogenes, Mannheimia succiniciproducens and Anaerobiospirillum succiniciproducens or genetically modified Escherichia coli, Corynebacterium glutamicum and Saccharomyces cerevisiae. Understanding of the central carbon metabolism of these organisms is crucial in determining the maximum obtainable yield of succinic acid on the carbon source employed as substrate. | 1 | Applied and Interdisciplinary Chemistry |
Grasselli Brown was born in 1928 to Hungarian immigrant parents Nicholas and Vera Gecsy. She grew up in a Hungarian neighborhood in the Buckeye Road area in Cleveland, Ohio during the Great Depression.
Her parents valued education and encouraged her to receive a college education in spite of economic and family difficulties.
Around 1946, her father opened a business in Elyria, Ohio, making sand cast aluminum parts. The foundry eventually failed and the family went bankrupt. Her brother Robert died from Hodgkin's lymphoma. While she was in college, her parents divorced. | 0 | Theoretical and Fundamental Chemistry |
Flammability is the ease with which a combustible substance can be ignited, causing fire or combustion or even an explosion. The degree of difficulty required to cause the combustion of a substance is quantified through fire testing. Internationally, a variety of test protocols exist to quantify flammability. The ratings achieved are used in building codes, insurance requirements, fire codes and other regulations governing the use of building materials as well as the storage and handling of highly flammable substances inside and outside of structures and in surface and air transportation. For instance, changing an occupancy by altering the flammability of the contents requires the owner of a building to apply for a building permit to make sure that the overall fire protection design basis of the facility can take the change into account. | 0 | Theoretical and Fundamental Chemistry |
Alkalis are all Arrhenius bases, ones which form hydroxide ions (OH) when dissolved in water. Common properties of alkaline aqueous solutions include:
* Moderately concentrated solutions (over 10 M) have a pH of 10 or greater. This means that they will turn phenolphthalein from colorless to pink.
* Concentrated solutions are caustic (causing chemical burns).
* Alkaline solutions are slippery or soapy to the touch, due to the saponification of the fatty substances on the surface of the skin.
* Alkalis are normally water-soluble, although some like barium carbonate are only soluble when reacting with an acidic aqueous solution. | 0 | Theoretical and Fundamental Chemistry |
* dicyanoacetylene - or , also called carbon subnitride or but-2-ynedinitrile
* tetracyanoethylene - or
* tetracyanomethane - or
* 2,2-diisocyanopropanedinitrile - or
* hexacyanoethane - or
* hexacyanocyclopropane - or
* hexacyanobutadiene - or | 0 | Theoretical and Fundamental Chemistry |
* 1925 – Laboratory of crystallography at the Mineralogical Museum (Leningrad).
* 1932 – Crystallographic section of the Lomonosov Institute of Geochemistry, Mineralogy and Petrography of the USSR Academy of Sciences.
* 1937 – Crystallographic Laboratory becomes part of the Geological Group of the USSR Academy of Sciences.
* 1941 – During World War II the majority of academic institutes were evacuated from Moscow to the East. The Crystallographic Laboratory continued its work in 1941-43 in the Sverdlovsk Oblast (in the Urals) where a series of important scientific and applied crystallographic problems were solved.
* 1943 – The Laboratory returns to Moscow and is transferred to the Department of Physical and Mathematical Sciences and renamed the Institute of Crystallography.
* 1944 – Organization of the Institute of Crystallography. Alexei Shubnikov was appointed Director of the Institute.
* 1956 – Founding of the journal Kristallografiya in which most of the institutes research is subsequently published. This journal is available in English translation as Soviet Physics Crystallography (ISSN 0038-5638) 1956-1992 (vols. 1-37) continued as Crystallography Reports' (ISSN 1063-7745) 1993- (vol. 38-)
* 1957 – Recognition outside the USSR of the establishment of the new field of antisymmetry and colour symmetry by A.V. Shubnikov and N.V. Belov
* 1962 – Boris Konstantinovich Weinstein is appointed Director of the Institute.
* 1969 – Award of the Order of the Red Banner of Labour.
* 1998 – Professor Mikhail Kovalchuk elected Director of the Institute.
* 2016 – The Institute was subsumed within the new «Crystallography and Photonics» Federal Research Center of the Russian Academy of Sciences (KiF RAS) which is now known as the «Crystallography and Photonics» FLNIK. | 0 | Theoretical and Fundamental Chemistry |
A spoil tip (also called a boney pile, culm bank, gob pile, waste tip or bing) is a pile built of accumulated spoil – waste material removed during mining. Spoil tips are not formed of slag, but in some areas, such as England and Wales, they are referred to as slag heaps. In Scotland the word bing is used. In North American English the term is mine dump or mine waste dump.
The term "spoil" is also used to refer to material removed when digging a foundation, tunnel, or other large excavation. Such material may be ordinary soil and rocks (after separation of coal from waste), or may be heavily contaminated with chemical waste, determining how it may be disposed of. Clean spoil may be used for land reclamation.
Spoil is distinct from tailings, which is the processed material that remains after the valuable components have been extracted from ore. | 1 | Applied and Interdisciplinary Chemistry |
Damage to buildings, equipment and people can result from a large-scale, short-duration deflagration. The potential damage is primarily a function of the total amount of fuel burned in the event (total energy available), the maximum reaction velocity that is achieved, and the manner in which the expansion of the combustion gases is contained. Vented deflagrations tend to be less violent or damaging than contained deflagrations.
In free-air deflagrations, there is a continuous variation in deflagration effects relative to the maximum flame velocity. When flame velocities are low, the effect of a deflagration is to release heat, such as in a flash fire. At flame velocities near the speed of sound, the energy released is in the form of pressure, and the resulting high pressure can damage equipment and buildings. | 0 | Theoretical and Fundamental Chemistry |
At least 41 thread sizes have been defined, ranging from ⁄ to 18, although of these only 15 are included in ISO 7 and 24 in ISO 228. The size number was originally based on the inner diameter (measured in inches) of a steel tube for which the thread was intended, but contemporary pipes tend to use thinner walls to save material, and thus have an inner diameter larger than this nominal size. In the modern standard metric version, it is simply a size number, where listed diameter size is the major outer diameter of the external thread. For a taper thread, it is the diameter at the "gauge length" (plus/minus one thread pitch) from the small end of the thread. The taper is 1:16, meaning that for each 16 units of measurement increase in the distance from the end, the diameter increases by 1 unit of measurement.
These standard pipe threads are formally referred to by the following sequence of blocks:
* the words, Pipe thread,
* the document number of the standard (e.g., ISO 7 or EN 10226)
* the symbol for the pipe thread type:
** G, external and internal parallel (ISO 228)
** R, external taper (ISO 7)
** Rp, internal parallel (ISO 7/1)
** Rc, internal taper (ISO 7)
** Rs, external parallel
* the thread size
Threads are normally right-hand. For left-hand threads, the letters, LH, are appended.
Example: Pipe thread EN 10226 Rp
The terminology for the use of G and R originated from Germany (G for gas, as it was originally designed for use on gas pipes; R for rohr, meaning pipe.) | 1 | Applied and Interdisciplinary Chemistry |
In E2 elimination reactions, a base abstracts a proton that is beta to a leaving group, such as a halide. The removal of the proton and the loss of the leaving group occur in a single, concerted step to form a new double bond. When a small, unhindered base – such as sodium hydroxide, sodium methoxide, or sodium ethoxide – is used for an E2 elimination, the Zaytsev product is typically favored over the least substituted alkene, known as the Hofmann product. For example, treating 2-Bromo-2-methyl butane with sodium ethoxide in ethanol produces the Zaytsev product with moderate selectivity.
Due to steric interactions, a bulky base – such as potassium tert-butoxide, triethylamine, or 2,6-lutidine – cannot readily abstract the proton that would lead to the Zaytsev product. In these situations, a less sterically hindered proton is preferentially abstracted instead. As a result, the Hofmann product is typically favored when using bulky bases. When 2-Bromo-2-methyl butane is treated with potassium tert-butoxide instead of sodium ethoxide, the Hofmann product is favored.
Steric interactions within the substrate also prevent the formation of the Zaytsev product. These intramolecular interactions are relevant to the distribution of products in the Hofmann elimination reaction, which converts amines to alkenes. In the Hofmann elimination, treatment of a quaternary ammonium iodide salt with silver oxide produces hydroxide ions, which act as a base and eliminate the tertiary amine to give an alkene.
In the Hofmann elimination, the least substituted alkene is typically favored due to intramolecular steric interactions. The quaternary ammonium group is large, and interactions with alkyl groups on the rest of the molecule are undesirable. As a result, the conformation necessary for the formation of the Zaytsev product is less energetically favorable than the conformation required for the formation of the Hofmann product. As a result, the Hofmann product is formed preferentially. The Cope elimination is very similar to the Hofmann elimination in principle but occurs under milder conditions. It also favors the formation of the Hofmann product, and for the same reasons. | 0 | Theoretical and Fundamental Chemistry |
In nuclear physics and nuclear chemistry, the fission barrier is the activation energy required for a nucleus of an atom to undergo fission. This barrier may also be defined as the minimum amount of energy required to deform the nucleus to the point where it is irretrievably committed to the fission process. The energy to overcome this barrier can come from either neutron bombardment of the nucleus, where the additional energy from the neutron brings the nucleus to an excited state and undergoes deformation, or through spontaneous fission, where the nucleus is already in an excited and deformed state.
It is important to note that efforts to understand fission processes are still an ongoing and have been a very difficult problem to solve since fission was first discovered by Lise Meitner, Otto Hahn, and Fritz Strassmann in 1938. While nuclear physicists understand many aspects of the fission process, there is currently no encompassing theoretical framework that gives a satisfactory account of the basic observations. | 0 | Theoretical and Fundamental Chemistry |
Marcus published his theory in 1956. For many years there was an intensive search for the inverted region which would be a proof of the theory. But all experiments with series of reactions of more and more negative ΔG revealed only an increase of the reaction rate up to the diffusion limit, i.e. to a value indicating that every encounter lead to electron transfer, and that limit held also for very negative ΔG values (Rehm-Weller behaviour). It took about 30 years until the inverted region was unequivocally substantiated by Miller, Calcaterra and Closs for an intramolecular electron transfer in a molecule where donor and acceptor are kept at a constant distance by means of a stiff spacer (Fig.4).
A posteriori one may presume that in the systems where the reaction partners may diffuse freely the optimum distance for the electron jump may be sought, i.e. the distance for which ΔG = 0 and ΔG = - λ. For λ is dependent on R, λ increases for larger R and the opening of the parabola smaller. It is formally always possible to close the parabola in Fig. 2 to such an extent, that the f-parabola intersects the i-parabola in the apex. Then always ΔG = 0 and the rate k reaches the maximum diffusional value for all very negative ΔG. There are, however, other concepts for the phenomenon, e.g. the participation of excited states or that the decrease of the rate constants would be so far in the inverted region that it escapes measurement.
R. A. Marcus and his coworkers have further developed the theory outlined here in several aspects. They have included inter alia statistical aspects and quantum effects, they have applied the theory to chemiluminescence and electrode reactions. R. A. Marcus received the Nobel Prize in Chemistry in 1992, and his Nobel Lecture gives an extensive view of his work. | 0 | Theoretical and Fundamental Chemistry |
The nitronium ion is isoelectronic with carbon dioxide and nitrous oxide, and has the same linear structure and bond angle of 180°. For this reason it has a similar vibrational spectrum to carbon dioxide. Historically, the nitronium ion was detected by Raman spectroscopy, because its symmetric stretch is Raman-active but infrared-inactive. The Raman-active symmetrical stretch was first used to identify the ion in nitrating mixtures. | 0 | Theoretical and Fundamental Chemistry |
LAs may enhance the effects of depolarisation and nondepolarising NMBAs through pre and post-synaptic interactions at the NMJ. It may result in blood levels high enough to potentiate NMBA-induced neuromuscular block. Epidurally administered levobupivacaine and mepivacaine potentiate amino-steroidal NMBAs and delay recovery from neuromuscular blockade. | 1 | Applied and Interdisciplinary Chemistry |
RNA is multifunctional, its primary function is to encode proteins, according to the instructions within a cell's DNA. They control and regulate many aspects of protein synthesis in eukaryotes.
RNA encodes genetic information that can be translated into the amino acid sequence of proteins, as evidenced by the messenger RNA molecules present within every cell, and the RNA genomes of a large number of viruses. The single-stranded nature of RNA, together with tendency for rapid breakdown and a lack of repair systems means that RNA is not so well suited for the long-term storage of genetic information as is DNA.
In addition, RNA is a single-stranded polymer that can, like proteins, fold into a very large number of three-dimensional structures. Some of these structures provide binding sites for other molecules and chemically active centers that can catalyze specific chemical reactions on those bound molecules. The limited number of different building blocks of RNA (4 nucleotides vs >20 amino acids in proteins), together with their lack of chemical diversity, results in catalytic RNA (ribozymes) being generally less-effective catalysts than proteins for most biological reactions.
The Major Macromolecules: | 0 | Theoretical and Fundamental Chemistry |
Magmatic water, also known as juvenile water, is an aqueous phase in equilibrium with minerals that have been dissolved by magma deep within the Earth's crust and is released to the atmosphere during a volcanic eruption. It plays a key role in assessing the crystallization of igneous rocks, particularly silicates, as well as the rheology and evolution of magma chambers. Magma is composed of minerals, crystals and volatiles in varying relative natural abundance. Magmatic differentiation varies significantly based on various factors, most notably the presence of water. An abundance of volatiles within magma chambers decreases viscosity and leads to the formation of minerals bearing halogens, including chloride and hydroxide groups. In addition, the relative abundance of volatiles varies within basaltic, andesitic, and rhyolitic magma chambers, leading to some volcanoes being exceedingly more explosive than others. Magmatic water is practically insoluble in silicate melts but has demonstrated the highest solubility within rhyolitic melts. An abundance of magmatic water has been shown to lead to high-grade deformation, altering the amount of δO and δH within host rocks. | 0 | Theoretical and Fundamental Chemistry |
Plants contain CaM-related proteins (CMLs) apart from the typical CaM proteins. The CMLs have about 15% amino acid similarity with the typical CaMs. Arabidopsis thaliana contains about 50 different CML genes which leads to the question of what purpose these diverse ranges of proteins serve in the cellular function. All plant species exhibit this diversity in the CML genes. The different CaMs and CMLs differ in their affinity to bind and activate the CaM-regulated enzymes in vivo. The CaM or CMLs are also found to be located in different organelle compartments. | 1 | Applied and Interdisciplinary Chemistry |
CAM is an adaptation for increased efficiency in the use of water, and so is typically found in plants growing in arid conditions. (CAM is found in over 99% of the known 1700 species of Cactaceae and in nearly all of the cacti producing edible fruits.) | 0 | Theoretical and Fundamental Chemistry |
As sedimentation field flow fractionation (SFFF) is one of field flow fractionation separation techniques, it is appropriate for fractionation and characterization of particulate materials and soluble samples in the colloid size range. Differences in interaction between a centrifugal force field and particles with different masses or sizes lead to the separation. An exponential distribution of particles of a certain size or weight is results due to the Brownian motion. Some of the assumptions to develop the theoretical equations include that there is no interaction between individual particles and equilibrium can occur anywhere in separation channels. | 0 | Theoretical and Fundamental Chemistry |
Arusi and his family members experienced several critical events during the era of Muammar Gaddafi. In June 1998, he was detained and sentenced on the grounds that he was allegedly a member of the underground Muslim Brotherhood movement. He spent eight years of a life-sentence in Abu Salim prison. He was released in April 2006. His father also spent some time in Abu Salim in the early 1970s. One of his brothers was killed in Zawiya during the Libyan Civil War. In addition, another brother was fatally beaten and lost an eye during the uprising. Arusi's son Abdulrahman was also jailed for a month in July 2011. | 1 | Applied and Interdisciplinary Chemistry |
It has been concluded that acetylcholine and related compounds must be in the gauche (bent) configuration when bound to the nicotinic receptor. Beers and Reich's studies on cholinergic receptors in 1970 showed a relationship affecting whether a compound was muscarinic or nicotinic. They showed that the distance from the centre of the quaternary N atom to the van der Waals extension of the respective O atom (or an equivalent H-bond acceptor) is a determining factor. If the distance is 0.44 nm, the compound shows muscarinic properties—and if the distance is 0.59 nm, nicotinic properties dominate.) | 1 | Applied and Interdisciplinary Chemistry |
A synonymous substitution (often called a silent substitution though they are not always silent) is the evolutionary substitution of one base for another in an exon of a gene coding for a protein, such that the produced amino acid sequence is not modified. This is possible because the genetic code is "degenerate", meaning that some amino acids are coded for by more than one three-base-pair codon; since some of the codons for a given amino acid differ by just one base pair from others coding for the same amino acid, a mutation that replaces the "normal" base by one of the alternatives will result in incorporation of the same amino acid into the growing polypeptide chain when the gene is translated. Synonymous substitutions and mutations affecting noncoding DNA are often considered silent mutations; however, it is not always the case that the mutation is silent.
Since there are 22 codes for 64 codons, roughly we should expect a random substitution to be synonymous with probability about 22/64 = 34%. The actual value is around 20%.
A synonymous mutation can affect transcription, splicing, mRNA transport, and translation, any of which could alter the resulting phenotype, rendering the synonymous mutation non-silent. The substrate specificity of the tRNA to the rare codon can affect the timing of translation, and in turn the co-translational folding of the protein. This is reflected in the codon usage bias that is observed in many species. A nonsynonymous substitution results in a change in amino acid that may be arbitrarily further classified as conservative (a change to an amino acid with similar physiochemical properties), semi-conservative (e.g. negatively to positively charged amino acid), or radical (vastly different amino acid). | 1 | Applied and Interdisciplinary Chemistry |
* Reduction of acyloins give diols.
* Oxidation of acyloins give diones.
* α-hydroxy ketones give positive Tollens and Fehlings test.
* Some acyloins rearrange with positions swapped under the influence of base in the Lobry–de Bruyn–van Ekenstein transformation
* A similar reaction is the so-called Voigt amination where an acyloin reacts with a primary amine and phosphorus pentoxide to an α-keto amine:
* Indole synthesis, compare Bischler–Möhlau | 0 | Theoretical and Fundamental Chemistry |
*as compiler with Joseph LeRoy Harrison:
*as compiler with Joseph LeRoy Harrison:
*as compiler with Joseph LeRoy Harrison:
* as editor with Edward L. Gordy:
* (revision of 1942 book The stone that burns) | 1 | Applied and Interdisciplinary Chemistry |
The primary function of a hydraulic fluid is to convey power. In use, however, there are other important functions of hydraulic fluid such as protection of the hydraulic machine components. The table below lists the major functions of a hydraulic fluid and the properties of a fluid that affect its ability to perform that function: | 1 | Applied and Interdisciplinary Chemistry |
The notation common with mass density underlines the connection between the two quantities (the mass concentration being the mass density of a component in the solution), but it can be a source of confusion especially when they appear in the same formula undifferentiated by an additional symbol (like a star superscript, a bolded symbol or varrho). | 0 | Theoretical and Fundamental Chemistry |
Adsorbed species on single crystal surfaces are frequently found to exhibit long-range ordering; that is to say that the adsorbed species form a well-defined overlayer structure. Each particular structure may only exist over a limited coverage range of the adsorbate, and in some adsorbate/substrate systems a whole progression of adsorbate structure are formed as the surface coverage is gradually increased.
The periodicity of the overlayer (which often is larger than that of the substrate unit cell) can be determined by low-energy electron diffraction (LEED), because there will be additional diffraction beams associated with the overlayer. | 0 | Theoretical and Fundamental Chemistry |
* Roger Bacon grows "graphite wiskers" in an arc-discharge apparatus and use electron microscopy to show that the structure consist of rolled up graphene sheets in concentric cylinders.
* Bollmann and Spreadborough discuss friction properties of carbon due to rolling sheets of graphene in Nature. Electron microscope picture clearly shows a Multi-walled carbon nanotube, MWCNT. | 1 | Applied and Interdisciplinary Chemistry |
Circuit topology categorises intra-chain contacts based on their arrangements. Circuit topology is a determinant of protein folding kinetics and stability. | 0 | Theoretical and Fundamental Chemistry |
An equivalent statement of the Dulong–Petit law in modern terms is that, regardless of the nature of the substance, the specific heat capacity c of a solid element (measured in joule per kelvin per kilogram) is equal to 3R/M, where R is the gas constant (measured in joule per kelvin per mole) and M is the molar mass (measured in kilogram per mole). Thus, the heat capacity per mole of many elements is 3R.
The initial form of the Dulong–Petit law was:
where K is a constant which we know today is about 3R.
In modern terms the mass m of the sample divided by molar mass M gives the number of moles n.
Therefore, using uppercase C for the full heat capacity (in joule per kelvin), we have:
or
Therefore, the heat capacity of most solid crystalline substances is 3R per mole of substance.
Dulong and Petit did not state their law in terms of the gas constant R (which was not then known). Instead, they measured the values of heat capacities (per weight) of substances and found them smaller for substances of greater atomic weight as inferred by Dalton and other early atomists. Dulong and Petit then found that when multiplied by these atomic weights, the value for the heat capacity per mole was nearly constant, and equal to a value which was later recognized to be 3R.
In other modern terminology, the dimensionless heat capacity C/(nR) is equal to 3.
The law can also be written as a function of the total number of atoms N in the sample:
where k is Boltzmann constant. | 0 | Theoretical and Fundamental Chemistry |
A phagosome is a vacuole formed around a particle absorbed by phagocytosis. The vacuole is formed by the fusion of the cell membrane around the particle. A phagosome is a cellular compartment in which pathogenic microorganisms can be killed and digested. Phagosomes fuse with lysosomes in their maturation process, forming phagolysosomes. In humans, Entamoeba histolytica can phagocytose red blood cells. | 1 | Applied and Interdisciplinary Chemistry |
Pioneer factors can exhibit their greatest range of effects on transcription through the modulation of epigenetic factors by recruiting activating or repressing histone modification enzymes and controlling CpG methylation by protecting specific cysteine residues. This has effects on controlling the timing of transcription during cell differentiation processes. | 1 | Applied and Interdisciplinary Chemistry |
* D. Markovitsi, Processes triggered in guanine quadruplexes by direct absorption of UV radiation: From fundamental studies toward optoelectronic biosensors, Photochem. Photobiol. 2023, doi.org/10.1111/php.13826.
* Balanikas, E.; Banyasz, A.; Baldacchino, G.; Markovitsi, D. Deprotonation Dynamics of Guanine Radical Cations. Photochem. Photobiol. 2022, 98, 523-531.
* Gustavsson, T.; Markovitsi, D. Fundamentals of the Intrinsic DNA Fluorescence. Acc. Chem. Res. 2021, 54, 1226-1235.
* Balanikas, E.; Banyasz, A.; Douki, T.; Baldacchino, G.; Markovitsi, D. Guanine Radicals Induced in DNA by Low-Energy Photoionization. Acc. Chem. Res. 2020, 53, 1511–1519.
* Banyasz, A.; Vay, I.; Changenet-Barret, P.; Gustavsson, T.; Douki, T.; Markovitsi, D. Base-pairing enhances fluorescence and favors cyclobutane dimer formation induced upon absorption of UVA radiation by DNA. J. Am. Chem. Soc. 2011, 133, 5163-5165.
* Ecoffet, C.; Markovitsi, D.; Millie, P.; Lemaistre, J. Electronic excitations in organized molecular systems. A model for columnar aggregates of ionic compounds. Chem. Phys. 1993, 177, 629-643. | 0 | Theoretical and Fundamental Chemistry |
Tritium was first detected in 1934 by Ernest Rutherford, Mark Oliphant and Paul Harteck after bombarding deuterium with deuterons (deuterium nuclei). Deuterium is another isotope of hydrogen, which occurs naturally with an abundance of 0.015%. Their experiment could not isolate tritium, which was first accomplished in 1939 by Luis Alvarez and Robert Cornog, who also realized tritium's radioactivity. Willard Libby recognized in 1954 that tritium could be used for radiometric dating of water and wine. | 0 | Theoretical and Fundamental Chemistry |
HIVE is a massively parallel distributed computing environment where the distributed storage library and the distributed computational powerhouse are linked seamlessly. The system is both robust and flexible due to maintaining both storage and the metadata database on the same network. The distributed storage layer of software is the key component for file and archive management and is the backbone for the deposition pipeline. The data deposition back-end allows automatic uploads and downloads of external datasets into HIVE data repositories. The metadata database can be used to maintain specific information about extremely large files ingested into the system (big data) as well as metadata related to computations run on the system. This metadata then allows details of a computational pipeline to be brought up easily in the future in order to validate or replicate experiments. Since the metadata is associated with the computation, it stores the parameters of any computation in the system eliminating manual record keeping.
Differentiating HIVE from other object oriented databases is that HIVE implements a set of unified APIs to search, view, and manipulate data of all types. The system also facilitates a highly secure hierarchical access control and permission system, allowing determination of data access privileges in a finely granular manner without creating a multiplicity of rules in the security subsystem. The security model, designed for sensitive data, provides comprehensive control and auditing functionality in compliance with HIVE's designation as a FISMA Moderate system. | 1 | Applied and Interdisciplinary Chemistry |
The concept of chemical similarity can be expanded to consider chemical similarity network theory, where descriptive network properties and graph theory can be applied to analyze large chemical space, estimate chemical diversity and predict drug target. Recently, 3D chemical similarity networks based on 3D ligand conformation have also been developed, which can be used to identify scaffold hopping ligands. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, Bent's rule describes and explains the relationship between the orbital hybridization and the electronegativities of substituents. The rule was stated by Henry A. Bent as follows:
Valence bond theory gives a good approximation of molecular structure. Bents rule addresses disparities between the observed and idealized geometries. According to Bents rule, a central atom bonded to multiple groups will rehybridize so that orbitals with more s character are directed towards electropositive groups, and orbitals with more p character will be directed towards groups that are more electronegative. By removing the assumption that all hybrid orbitals are equivalent, Bents rule leads to improved predictions of molecular geometry and bond strengths. Bents rule can be justified through the relative energy levels of s and p orbitals. Bent's rule represents a modification of VSEPR theory for molecules of lower than ideal symmetry. For bonds with the larger atoms from the lower periods, trends in orbital hybridization depend strongly on both electronegativity and orbital size. | 0 | Theoretical and Fundamental Chemistry |
Ketones give positive results in Bradys test, the reaction with 2,4-dinitrophenylhydrazine to give the corresponding hydrazone. Ketones may be distinguished from aldehydes by giving a negative result with Tollens reagent or with Fehlings solution. Methyl ketones give positive results for the iodoform test. Ketones also give positive results when treated with m'-dinitrobenzene in presence of dilute sodium hydroxide to give violet coloration. | 0 | Theoretical and Fundamental Chemistry |
Scarlett was a Fellow of the Royal Academy of Engineering, a Fellow of the Institute of Physics, and a Fellow of the Institution of Chemical Engineers. He was awarded honorary doctorates (DSc) by the University of Coimbra (1997) and Loughborough University (1999).
In 2000, the American Institute of Chemical Engineers gave him their Award for Lifetime Achievement in Particle Technology.
In 2006 the Fifth World Congress on Particle Technology had a Brian Scarlett Memorial Session of invited papers, with another at the Seventh in 2014.
In 2010 a Brian Scarlett Scholarship Fund was set up by the Royal Society of Chemistry to support student travel to particle technology events. | 1 | Applied and Interdisciplinary Chemistry |
* CCA1 – The CCA1 gene, also known as Circadian and Clock Associated Gene 1, is a gene that is especially important in maintaining the rhythmicity of plant cellular oscillations. Overexpression, results in the loss of rhythmic expression of clock controlled genes (CCGs), loss of photoperiod control, and loss of rhythmicity in LHY expression. See LHY gene below for more information.
* LHY – The LHY gene, also known as the Late Elongated Hypocotyl gene, is a gene found in plants that encodes components of mutually regulatory negative feedback loops with CCA1 in which overexpression of either results in dampening of both of their expression. This negative feedback loop affects the rhythmicity of multiple outputs creating a daytime protein complex.
* Toc1 gene – Toc1, also known as Timing of CAB Expression 1 gene, is an oscillating gene found in the plants that is known to control the expression of CAB. It has been shown to affect the period of circadian rhythms through its repression of transcription factors. This was found through mutations of toc1 in plants that had shortened period of CAB expression. | 1 | Applied and Interdisciplinary Chemistry |
Waste enters a MRF when it is dumped onto the tipping floor by the collection trucks. The materials are then scooped up and placed onto conveyor belts, which transports it to the pre-sorting area. Here, human workers remove some items that are not recyclable, which will either be sent to a landfill or an incinerator. Between 5 and 45% of "dirty" MRF material is recovered. Potential hazards are also removed, such as lithium batteries, propane tanks, and aerosol cans, which can create fires. Materials like plastic bags and hoses, which can entangle the recycling equipment, are also removed. From there, materials are transported via another conveyer belt to the disk screen, which separates wide and flat materials like flattened cardboard boxes from items like cans, jars, paper, and bottles. Flattened boxes ride across the disk screen to the other side, while all other materials fall below, where paper is separated from the waste stream with a blower. The stream of cardboard and paper is overseen by more human workers, who ensure no plastic, metal, or glass is present. Newer MRFs or retrofitted ones may use industrial robots instead of humans for pre-sorting and for quality control. However, complete removal of human labor from the sortation process is unlikely for the foreseeable future, as one needs to replicate the dexterity of the human hand and nervous system for removing every type of contaminant within a material stream. The technical limitations of this involve advanced concepts in mechatronics and computer science, where a robot hand would need to be designed, and a highly flexible algorithm that creates another precise movement algorithm within the time constraints of the system (say, the highly approximate estimate of 30,000 lines of code to do this on a modern processor would trigger too long of a delay to be effective on a sortation line). In other words, one would need to search an encyclopedia of said robotic hand motions for every configuration of waste for every pick, and this may be computationally insurmountable, even with quantum computing, as every conditional would need to be checked every iteration.
Metal is separated from plastics and glass first with electromagnets, which removes ferrous metals. Non-ferrous metals like aluminum are then removed with eddy current separators.
The glass and plastic streams are separated by further disk screens. The glass is crushed into cullet for ease of transportation. The plastics are then separated by polymer type, often using infrared technology (optical sorting). Infrared light reflects differently off different polymer types; once identified, a jet of air shoots the plastic into the appropriate bin. MRFs might only collect and recycle a few polymers of plastic, sending the rest to landfills or incinerators. The separated materials are baled and sent to the shipping dock of the facility. | 1 | Applied and Interdisciplinary Chemistry |
Consider a cylindrical coordinate system ( ρ , φ , z ), with the z–axis the line around which the incompressible flow is axisymmetrical, φ the azimuthal angle and ρ the distance to the z–axis. Then the flow velocity components u and u can be expressed in terms of the Stokes stream function by:
The azimuthal velocity component u does not depend on the stream function. Due to the axisymmetry, all three velocity components ( u , u , u ) only depend on ρ and z and not on the azimuth φ.
The volume flux, through the surface bounded by a constant value ψ of the Stokes stream function, is equal to 2π ψ. | 1 | Applied and Interdisciplinary Chemistry |
Activated carbon has strong affinity for many gases and has an adsorption cross section of 0.162 nm for nitrogen adsorption at liquid-nitrogen temperature (77 K). BET theory can be applied to estimate the specific surface area of activated carbon from experimental data, demonstrating a large specific surface area, even around 3000 m/g. However, this surface area is largely overestimated due to enhanced adsorption in micropores, and more realistic methods should be used for its estimation, such as the subtracting pore effect (SPE) method. | 0 | Theoretical and Fundamental Chemistry |
Sedoheptulose 7-phosphate is an intermediate in the pentose phosphate pathway.
It is formed by transketolase and acted upon by transaldolase.
Sedoheptulokinase is an enzyme that uses sedoheptulose and ATP to produce ADP and sedoheptulose 7-phosphate.
Sedoheptulose-bisphosphatase is an enzyme that uses sedoheptulose 1,7-bisphosphate and HO to produce sedoheptulose 7-phosphate and phosphate. | 1 | Applied and Interdisciplinary Chemistry |
Because natural moissanite is extremely scarce, most silicon carbide is synthetic. Silicon carbide is used as an abrasive, as well as a semiconductor and diamond simulant of gem quality. The simplest process to manufacture silicon carbide is to combine silica sand and carbon in an Acheson graphite electric resistance furnace at a high temperature, between and . Fine SiO particles in plant material (e.g. rice husks) can be converted to SiC by heating in the excess carbon from the organic material. The silica fume, which is a byproduct of producing silicon metal and ferrosilicon alloys, can also be converted to SiC by heating with graphite at .
The material formed in the Acheson furnace varies in purity, according to its distance from the graphite resistor heat source. Colorless, pale yellow and green crystals have the highest purity and are found closest to the resistor. The color changes to blue and black at greater distance from the resistor, and these darker crystals are less pure. Nitrogen and aluminium are common impurities, and they affect the electrical conductivity of SiC.
Pure silicon carbide can be made by the Lely process, in which SiC powder is sublimed into high-temperature species of silicon, carbon, silicon dicarbide (SiC), and disilicon carbide (SiC) in an argon gas ambient at 2500 °C and redeposited into flake-like single crystals, sized up to 2 × 2 cm, at a slightly colder substrate. This process yields high-quality single crystals, mostly of 6H-SiC phase (because of high growth temperature).
A modified Lely process involving induction heating in graphite crucibles yields even larger single crystals of 4 inches (10 cm) in diameter, having a section 81 times larger compared to the conventional Lely process.
Cubic SiC is usually grown by the more expensive process of chemical vapor deposition (CVD) of silane, hydrogen and nitrogen. Homoepitaxial and heteroepitaxial SiC layers can be grown employing both gas and liquid phase approaches.
To form complexly shaped SiC, preceramic polymers can be used as precursors which form the ceramic product through pyrolysis at temperatures in the range 1000–1100 °C. Precursor materials to obtain silicon carbide in such a manner include polycarbosilanes, poly(methylsilyne) and polysilazanes. Silicon carbide materials obtained through the pyrolysis of preceramic polymers are known as polymer derived ceramics or PDCs. Pyrolysis of preceramic polymers is most often conducted under an inert atmosphere at relatively low temperatures. Relative to the CVD process, the pyrolysis method is advantageous because the polymer can be formed into various shapes prior to thermalization into the ceramic.
SiC can also be made into wafers by cutting a single crystal either using a diamond wire saw or by using a laser. SiC is a useful semiconductor used in power electronics. | 1 | Applied and Interdisciplinary Chemistry |
He worked as part of the DNA synthesis group at Genentech from 1986 to 1990, before joining Gilead in 1990 as Director of Organic Chemistry. In 1993, he began work, as head of a team, to create Tamiflu. In 1996, clinical studies were carried out on the drug, which was the first orally active commercially developed anti-influenza medication. Explaining the motivation behind this, he said, "We decided to create a pill and not a medication to inhale because especially people who suffer from influenza struggle with breathing difficulties. And the agent would only reach the lung," Three years later, the right to market and develop Tamiflu were sold to Roche, with Bischofberger and Gilead retaining the intellectual rights to it.
Bischofberger has publicly displayed pessimism over the risk viruses pose, saying, "I think the threat by new bacterial or viral agents is higher than the potential of a nuclear war." | 0 | Theoretical and Fundamental Chemistry |
HITRAN2020 also has an aerosols refractive indices section, with data in the visible, infrared, and millimeter spectral ranges of many types of cloud and aerosol particles. Knowledge of the refractive indices of the aerosols and cloud particles and their size distributions is necessary in order to specify their optical properties. | 0 | Theoretical and Fundamental Chemistry |
In 2007, Applied Biosystems started selling a new type of sequencer called SOLiD System. The technology allowed users to sequence 60 gigabases per run.
In June 2009, Illumina announced that they were launching their own Personal Full Genome Sequencing Service at a depth of 30× for $48,000 per genome. In August, the founder of Helicos Biosciences, Stephen Quake, stated that using the companys Single Molecule Sequencer he sequenced his own full genome for less than $50,000. In November, Complete Genomics published a peer-reviewed paper in Science' demonstrating its ability to sequence a complete human genome for $1,700.
In May 2011, Illumina lowered its Full Genome Sequencing service to $5,000 per human genome, or $4,000 if ordering 50 or more.
Helicos Biosciences, Pacific Biosciences, Complete Genomics, Illumina, Sequenom, ION Torrent Systems, Halcyon Molecular, NABsys, IBM, and GE Global appear to all be going head to head in the race to commercialize full genome sequencing.
With sequencing costs declining, a number of companies began claiming that their equipment would soon achieve the $1,000 genome: these companies included Life Technologies in January 2012, Oxford Nanopore Technologies in February 2012, and Illumina in February 2014. In 2015, the NHGRI estimated the cost of obtaining a whole-genome sequence at around $1,500. In 2016, Veritas Genetics began selling whole genome sequencing, including a report as to some of the information in the sequencing for $999. In summer 2019 Veritas Genetics cut the cost for WGS to $599. In 2017, BGI began offering WGS for $600.
However, in 2015 some noted that effective use of whole gene sequencing can cost considerably more than $1000. Also, reportedly there remain parts of the human genome that have not been fully sequenced by 2017. | 1 | Applied and Interdisciplinary Chemistry |
The eastern meadow vole (Microtus pennsylvanicus), sometimes called the field mouse or meadow mouse, is a North American vole found in eastern Canada and the United States. Its range extends farther south along the Atlantic coast.
The western meadow vole, Florida salt marsh vole, and beach vole were formerly considered regional variants or subspecies of M. pennsylvanicus, but have all since been designated as distinct species.
The eastern meadow vole is active year-round, usually at night. It also digs burrows, where it stores food for the winter and females give birth to their young. Although these animals tend to live close together, they are aggressive towards one another. This is particularly evident in males during the breeding season. They can cause damage to fruit trees, garden plants, and commercial grain crops. | 1 | Applied and Interdisciplinary Chemistry |
Neutrinos are conventionally produced in weak decays. Weak beta decays normally produce one electron (or positron), emit an antineutrino (or neutrino) and increase the nucleus proton number by one. The nucleus mass (i.e. binding energy) is then lower and thus more favorable. There exist a number of elements that can decay into a nucleus of lower mass, but they cannot emit one electron only because the resulting nucleus is kinematically (that is, in terms of energy) not favorable (its energy would be higher). These nuclei can only decay by emitting two electrons (that is, via double beta decay). There are about a dozen confirmed cases of nuclei that can only decay via double beta decay. The corresponding decay equation is:
It is a weak process of second order. A simultaneous decay of two nucleons in the same nucleus is extremely unlikely. Thus, the experimentally observed lifetimes of such decay processes are in the range of years. A number of isotopes have been observed already to show this two-neutrino double beta decay.
This conventional double beta decay is allowed in the Standard Model of particle physics. It has thus both a theoretical and an experimental foundation. | 0 | Theoretical and Fundamental Chemistry |
:Pericline also refers to a doubly plunging anticline or syncline.
Pericline is a form of albite exhibiting elongate prismatic crystals.
Pericline twinning is a type of crystal twinning which show fine parallel twin laminae typically found in the alkali feldspars microcline. The twinning results from a structural transformation between high temperature and low temperature forms. | 0 | Theoretical and Fundamental Chemistry |
In the area of solid state chemistry. graphite intercalation compounds are materials prepared by intercalation of diverse guests into graphite. The materials have the formula (guest)C where n can range from 8 to 40's. The distance between the carbon layers increases significantly upon insertion of the guests. Common guests are reducing agents such as alkali metals. Strong oxidants, such as arsenic pentafluoride also intercalate into graphite. Intercalation involves electron transfer into or out of the host. The properties of these materials differ from those of the parent graphite. | 0 | Theoretical and Fundamental Chemistry |
The only known exceptions to the Mattauch isobar rule are the cases of antimony-123 and tellurium-123 and of hafnium-180 and tantalum-180m, where both nuclei are observationally stable. It is predicted that Te would undergo electron capture to form Sb, but this decay has not yet been observed; Ta should be able to undergo isomeric transition to Ta, beta decay to W, electron capture to Hf, or alpha decay to Lu, but none of these decay modes have been observed.
In addition, beta decay has been seen for neither curium-247 nor berkelium-247, though it is expected that the former should decay into the latter. Both nuclides are alpha-unstable.
As mentioned above, the Mattauch isobar rule cannot make predictions as to the half-lives of the beta-unstable isotopes. Hence there are a few cases where isobars of adjacent elements both occur primordially, as the half-life of the unstable isobar is over a billion years. This occurs for the following mass numbers:
* 40 (Ar and Ca stable; K unstable)
* 50 (Ti and Cr stable; V unstable)
* 87 (Sr stable; Rb unstable)
* 113 (In stable; Cd unstable)
* 115 (Sn stable; In unstable)
* 138 (Ba and Ce stable; La unstable)
* 176 (Yb and Hf stable; Lu unstable)
* 187 (Os stable; Re unstable) | 0 | Theoretical and Fundamental Chemistry |
Stickland fermentation or The Stickland Reaction is the name for a chemical reaction that involves the coupled oxidation and reduction of amino acids to organic acids. The electron donor amino acid is oxidised to a volatile carboxylic acid one carbon atom shorter than the original amino acid. For example, alanine with a three carbon chain is converted to acetate with two carbons. The electron acceptor amino acid is reduced to a volatile carboxylic acid the same length as the original amino acid. For example, glycine with two carbons is converted to acetate.
In this way, amino acid fermenting microbes can avoid using hydrogen ions as electron acceptors to produce hydrogen gas. Amino acids can be Stickland acceptors, Stickland donors, or act as both donor and acceptor. Only histidine cannot be fermented by Stickland reactions, and is oxidised. With a typical amino acid mix, there is a 10% shortfall in Stickland acceptors, which results in hydrogen production. Under very low hydrogen partial pressures, increased uncoupled anaerobic oxidation has also been observed.
It occurs in proteolytic clostridiums such as:
C. perfringens,
C. difficile,
C. sporogenes,
and C. botulinum.
Additionally, sarcosine and betaine can act as electron acceptors. | 1 | Applied and Interdisciplinary Chemistry |
Butler worked as a postdoctoral fellow at University of California, Los Angeles with Joan S. Valentine and at California Institute of Technology with Harry B. Gray. She was appointed to the faculty at University of California, Santa Barbara in 1986. Here she was awarded an American Cancer Society Junior Faculty Research Award. She was awarded the 34th University of California, Santa Barbara Harold J Plous Award.
She looks to discover new siderophores, small molecules that bind iron in microorganisms. She uses genomics and bioinformatics to predict new siderophore structures. She explores how siderophores adhere to mica and look at how they can promote surface colonisation. She identified that siderophores become sticky when wet, which may help to develop underwater adhesives. Her current research considers the uptake of microbial iron, vanadium haloperoxidases in microbial quorum sensing and cryptic halogenation, bio-inspired wet adhesion using catechol compounds, and the oxidative disassembly of lignin. Her research into the bioinorganic chemistry of iron is funded by the National Institutes of Health and National Science Foundation. She studies how transition metal ions are used by marine organisms.
In 2012, she became the President of the Society for Biological Inorganic Chemistry, and served until 2014. She was made a Fellow of the American Chemical Society in July 2012. She delivered the 2016 Douglas Eveleigh Endowed Lecture at the Waksman Institute of Microbiology. In 2018, she was awarded the American Chemical Society Alfred Bader Award for her work on siderophores.
In 2019, she was elected to the American Academy of Arts and Sciences, received the American Chemical Societys Arthur C. Cope Scholar award for excellence in organic chemistry, and received the Royal Society of Chemistrys Inorganic Mechanisms Award. Butler also received the 2019-2020 Faculty Research Lecturer Award, the highest honor that University of California, Santa Barbara faculty can bestow on their members. | 0 | Theoretical and Fundamental Chemistry |
Eigencolloid formation occurs readily in groundwater upon storage of radioactive waste. Colloid-facilitated transport is a mechanism responsible for the mobilisation of radionuclides into the wider environment, causing radioactive contamination. This is a public health concern, since elevated radioactivity in the environment is mutagenic and can lead to cancer.
Eigencolloids have been implicated in the long-range transport of plutonium on the Nevada Test Site. | 0 | Theoretical and Fundamental Chemistry |
The usual equipment includes a seal-able metabolic chamber, an oxygen sensor, and devices for data recording, stirring, thermostatisation and a way to introduce chemicals into the chamber. As described above for whole-animal respirometry the choice of materials is very important. Plastic materials are not suitable for the chamber because of their oxygen storage capacity. When plastic materials are unavoidable (e.g. for o-rings, coatings of stirrers, or stoppers) polymers with a very low oxygen permeability (like PVDF as opposed to e.g. PTFE) may be used. Remaining oxygen diffusion into or out of the chamber materials can be handled by correcting the measured oxygen fluxes for the instrumental oxygen background flux. The entire instrument comprising the mentioned components is often called an oxygraph. The companies providing equipment for whole-animal rspirometry mentioned above are usually not involved in mitochondrial respiromety. The community is serviced at widely varying levels of price and sophistication by companies like Oroboros Instruments, Hansatech, Respirometer Systems & Applications, YSI Life Sciences or Strathkelvin Instruments . | 1 | Applied and Interdisciplinary Chemistry |
Carbon acids which can be deprotonated by sodium amide in liquid ammonia include terminal alkynes,
methyl ketones,
cyclohexanone, phenylacetic acid and its derivatives
and diphenylmethane. Acetylacetone loses two protons to form a dianion. Sodium amide will also deprotonate indole and piperidine. | 0 | Theoretical and Fundamental Chemistry |
Phosphinites are prepared by alcoholysis of organophosphinous chlorides. For example, treatment of chlorodiphenylphosphine with methanol and base gives methyl diphenylphosphinite:
:ClPPh + CHOH → CHOPPh + HCl
Although they are esters of phosphinous acids (RPOH), phosphinites are not made via such intermediates. | 0 | Theoretical and Fundamental Chemistry |
The Gaia hypothesis continues to be broadly skeptically received by the scientific community. For instance, arguments both for and against it were laid out in the journal Climatic Change in 2002 and 2003. A significant argument raised against it are the many examples where life has had a detrimental or destabilising effect on the environment rather than acting to regulate it. Several recent books have criticised the Gaia hypothesis, expressing views ranging from "... the Gaia hypothesis lacks unambiguous observational support and has significant theoretical difficulties" to "Suspended uncomfortably between tainted metaphor, fact, and false science, I prefer to leave Gaia firmly in the background" to "The Gaia hypothesis is supported neither by evolutionary theory nor by the empirical evidence of the geological record". The CLAW hypothesis, initially suggested as a potential example of direct Gaian feedback, has subsequently been found to be less credible as understanding of cloud condensation nuclei has improved. In 2009 the Medea hypothesis was proposed: that life has highly detrimental (biocidal) impacts on planetary conditions, in direct opposition to the Gaia hypothesis.
In a 2013 book-length evaluation of the Gaia hypothesis considering modern evidence from across the various relevant disciplines, Toby Tyrrell concluded that: "I believe Gaia is a dead end. Its study has, however, generated many new and thought provoking questions. While rejecting Gaia, we can at the same time appreciate Lovelock's originality and breadth of vision, and recognize that his audacious concept has helped to stimulate many new ideas about the Earth, and to champion a holistic approach to studying it". Elsewhere he presents his conclusion "The Gaia hypothesis is not an accurate picture of how our world works". This statement needs to be understood as referring to the "strong" and "moderate" forms of Gaia—that the biota obeys a principle that works to make Earth optimal (strength 5) or favourable for life (strength 4) or that it works as a homeostatic mechanism (strength 3). The latter is the "weakest" form of Gaia that Lovelock has advocated. Tyrrell rejects it. However, he finds that the two weaker forms of Gaia—Coeveolutionary Gaia and Influential Gaia, which assert that there are close links between the evolution of life and the environment and that biology affects the physical and chemical environment—are both credible, but that it is not useful to use the term "Gaia" in this sense and that those two forms were already accepted and explained by the processes of natural selection and adaptation. | 0 | Theoretical and Fundamental Chemistry |
Ligands are classified according to the number of electrons that they "donate" to the metal. L ligands are Lewis bases. L ligands are represented by amines, phosphines, CO, N, and alkenes. Examples of L ligands extend to include dihydrogen and hydrocarbons that interact by agostic interactions. X ligands are halides and pseudohalides. X ligands typically are derived from anionic precursors such as chloride but includes ligands where salts of anion do not really exist such as hydride and alkyl.
Especially in the area of organometallic chemistry, ligands are classified according to the "CBC Method" for Covalent Bond Classification, as popularized by M. L. H. Green and "is based on the notion that there are three basic types [of ligands]... represented by the symbols L, X, and Z, which correspond respectively to 2-electron, 1-electron and 0-electron neutral ligands." | 0 | Theoretical and Fundamental Chemistry |
Ligands where the coordinating atom bear nonbonding lone pairs often stabilize unsaturated complexes. Metal amides and alkoxides often violate the 18e rule | 0 | Theoretical and Fundamental Chemistry |
An analysis of two infants suffering from cholelithiasis observed that a substantial amount of stercobilin was present in brown pigment gallstones. This study suggested that brown pigment gallstones could form spontaneously in infants suffering from bacterial infections of the biliary tract. | 1 | Applied and Interdisciplinary Chemistry |
In the absence of the original amino acid (-leucine) in an environment, -photo-leucine is used just as its naturally occurring analog in the protein processing mechanisms of the cell. Therefore, it can be used as a substitute for leucine in the primary structure of the protein. This property of photo-leucine is very useful for studying protein-protein interactions (PPIs), due to the fact that the photo-leucine molecule, because of its molecular structure, participates in the covalent cross-linking of proteins in the protein-protein interaction (PPI) domains when it is activated by ultraviolet (UV) light. This fact allows to determine and describe stable and transient protein interactions within cells without using any additional chemical cross-linkers, which could damage the cell structure being studied.
The study of these protein-protein interactions is important because they are crucial in organizing cellular processes in space and time. In fact, interest in protein-protein interactions is not confined only to basic research: many of these interactions involved in viral fusion or in growth-factor signaling are promising targets for antiviral and anticancer drugs. Photo-affinity labeling is a powerful tool to identify protein targets of biologically active small molecules and to probe the structure of ligand binding sites, reason due to which photo amino acids, including photo-leucine, are so useful. | 0 | Theoretical and Fundamental Chemistry |
Based on the first high frequency, high precision, in situ atmospheric and archived air measurements, sulfuryl fluoride has an atmospheric lifetime of 30–40 years, much longer than the 5 years earlier estimated.
Sulfuryl fluoride has been reported to be a greenhouse gas which is about 4000–5000 times more efficient in trapping infrared radiation (per kg) than carbon dioxide (per kg). The amount of sulfuryl fluoride released into the atmosphere is about 2000 metric tons per year. The most important loss process of sulfuryl fluoride is dissolution of atmospheric sulfuryl fluoride in the ocean followed by hydrolysis. | 1 | Applied and Interdisciplinary Chemistry |
In the field of drug discovery, retrometabolic drug design is a strategy for the design of safer drugs either using predictable metabolism to an inactive moiety or using targeted drug delivery approaches. The phrase retrometabolic drug design was coined by Nicholas Bodor. The method is analogous to retrosynthetic analysis where the synthesis of a target molecule is planned backwards. In retrometabolic drug design, metabolic reaction information of drugs is used to design parent drugs whose metabolism and distribution can be controlled to target and eliminate the drug to increase efficacy and minimize undesirable side effects. The new drugs thus designed achieve selective organ and/or therapeutic site drug targeting and produce safe therapeutic agents and safe environmental chemicals. These approaches represent systematic methodologies that thoroughly integrate structure-activity (SAR) and structure-metabolism (SMR) relationships and are aimed at designing safe, locally active compounds with improved therapeutic index (ratio of benefit vs. side effect). | 1 | Applied and Interdisciplinary Chemistry |
para-Dimethylaminobenzaldehyde is the main ingredient in Ehrlich's reagent. It acts as a strong electrophile which reacts with the electron-rich α-carbon (2-position) of indole rings to form a blue-colored adduct. It can be used to detect the presence of indole alkaloids. Not all indole alkaloids give a colored adduct as result of steric hindrance which does not allow the reaction to proceed.
Ehrlich's reagent is also used as a stain in thin layer chromatography and as a reagent to detect urobilinogen in fresh, cool urine. If a urine sample is left to oxidize in air to form urobilin the reagent will not detect the urobilinogen. By adding few drops of reagent to 3 mL of urine in a test tube one can see a change of color, to dark pink or red. The degree of color change is proportional to the amount of urobilinogen in the urine sample. | 0 | Theoretical and Fundamental Chemistry |
It is common in E1 and S1 reactions for a poor leaving group to be transformed into a good one by protonation or complexation with a Lewis acid. Thus, it is by protonation before departure that a molecule can formally lose such poor leaving groups as hydroxide.
The same principle is at work in the Friedel-Crafts reaction. Here, a strong Lewis acid is required to generate either a carbocation from an alkyl halide in the Friedel-Crafts alkylation reaction or an acylium ion from an acyl halide.
In the vast majority of cases, reactions that involve leaving group activation generate a cation in a separate step, before either nucleophilic attack or elimination. For example, S1 and E1 reactions may involve an activation step, whereas S2 and E2 reactions generally do not. | 0 | Theoretical and Fundamental Chemistry |
Early work examined the dechlorinations with copper. Substrates included DDT, endrin, chloroform, and hexachlorocyclopentadiene. Aluminum and magnesium behave similarly in the laboratory. Ground water treatment most generally focuses on the use of iron. | 1 | Applied and Interdisciplinary Chemistry |
Polychlorinated biphenyls (PCBs) are various biphenyl based artificial products that are widely used as a dielectric fluid, industrial coolant, and lubricants in the 1960s and 1970s. There is no evidence its synthesis occurs naturally. They are classified as persistent organic pollutants. PCBs share the basic chemical structure of biphenyl and one or more of the hydrogen atoms on the aromatic rings are replaced by chlorine atoms.
PCBs is in viscous liquid form at normal temperature and has a poor solubility in water. The aromatic hydrocarbon structure gives PCBs relatively high molecular stability. The chlorine substitution further reinforces its insolubility and chemical stability. Hence, the degradation of PCBs in the natural environment is very slow, which can range from 3 to 37 years depending on the number of chloride substitutions and their positions. | 1 | Applied and Interdisciplinary Chemistry |
Eszopiclone, sold under the brand name Lunesta among others, is a medication used in the treatment of insomnia. Evidence supports slight to moderate benefit up to six months. It is taken by mouth.
Common side effects include headache, dry mouth, nausea, and dizziness. Severe side effects may include suicidal thoughts, hallucinations, and angioedema. Rapid decreasing of the dose may result in withdrawal. Eszopiclone is classified as a nonbenzodiazepine or Z-drug and a sedative and hypnotic of the cyclopyrrolone group. It is the S-stereoisomer of zopiclone. It works by interacting with the GABA receptors.
Approved for medical use in the United States in 2004, eszopiclone is available as a generic medication. In 2020, it was the 232nd most commonly prescribed medication in the United States, with more than 1million prescriptions. Eszopiclone is not sold in the European Union, as of 2009, the European Medicines Agency (EMA) ruled that it was too similar to zopiclone to be considered a new active substance. | 0 | Theoretical and Fundamental Chemistry |
CK2 is a protein kinase responsible for phosphorylation of substrates in various pathways within a cell; ATP or GTP can be used as phosphate source. CK2 has a dual functionality with involvement in cell growth/proliferation and suppression of apoptosis. CK2s anti-apoptotic function is in the continuation of the cell cycle; from G1 to S phase and G2 to M phase checkpoints. This function is achieved by protecting proteins from caspase-mediated apoptosis via phosphorylation of sites adjacent to the caspase cleavage site, blocking the activity of caspase proteins. CK2 also protects from drug-induced apoptosis via similar methods but it is not as well understood. Knockdown studies of both α and α’ sub-units have been used to verify this anti-apoptotic function.
Important phosphorylation events also regulated by CK2 are found in DNA damage repair pathways, and multiple stress-signaling pathways. Examples are phosphorylation of p53 or MAPK, which both regulate many interactions within their respective cellular pathways.
Another indication of separate function of α subunits is that mice that lack CK2α’ have a defect in the morphology of developing sperm. | 1 | Applied and Interdisciplinary Chemistry |
Like most metal fluorides, UF is a dense highly crosslinked inorganic polymer. As established by X-ray crystallography, the U centres are eight-coordinate with square antiprismatic coordination spheres. The fluoride centres are doubly bridging. | 0 | Theoretical and Fundamental Chemistry |
The analogous calculation for electron capture must take into account the binding energy of the electrons. This is because the atom will be left in an excited state after capturing the electron, and the binding energy of the captured innermost electron is significant. Using the generic equation for electron capture
we have
which simplifies to
where is the binding energy of the captured electron.
Because the binding energy of the electron is much less than the mass of the electron, nuclei that can undergo β decay can always also undergo electron capture, but the reverse is not true. | 0 | Theoretical and Fundamental Chemistry |
A method employing very gentle cell lysis in yeast followed by co-immunoprecipitation with an antibody to a mediator subunit (Med 17) has confirmed almost all previously reported or predicted interactions and revealed many previously unsuspected specific interactions of various proteins with mediator. | 1 | Applied and Interdisciplinary Chemistry |
Many eukaryotic organisms have electron transport chains that differ from the much-studied mammalian enzymes described above. For example, plants have alternative NADH oxidases, which oxidize NADH in the cytosol rather than in the mitochondrial matrix, and pass these electrons to the ubiquinone pool. These enzymes do not transport protons, and, therefore, reduce ubiquinone without altering the electrochemical gradient across the inner membrane.
Another example of a divergent electron transport chain is the alternative oxidase, which is found in plants, as well as some fungi, protists, and possibly some animals. This enzyme transfers electrons directly from ubiquinol to oxygen.
The electron transport pathways produced by these alternative NADH and ubiquinone oxidases have lower ATP yields than the full pathway. The advantages produced by a shortened pathway are not entirely clear. However, the alternative oxidase is produced in response to stresses such as cold, reactive oxygen species, and infection by pathogens, as well as other factors that inhibit the full electron transport chain. Alternative pathways might, therefore, enhance an organism's resistance to injury, by reducing oxidative stress. | 1 | Applied and Interdisciplinary Chemistry |
EcoProIT is a project initiated at Chalmers University of Technology at the department of Product and Production Development. The project aims to provide production engineers a tool for detailed ecological footprint analyses, which are becoming more important in terms of marketing and legislation. A published report by MIT in 2011 showed companies thought that environmental sustainable strategy is, or will be, vital to be competitive. The report included many sectors, e.g. covering medicals, automobiles and consumer products. EcoProIT will design a tool for industrial applications used for detailed environmental footprint analyses of their production systems and the products produced using simulation. The tool will simulate the production and analyze the product's environmental footprint in a standardized way. It will also be possible to use the tool for bench marking between different sites. The aim for the tool puts high requirements on standardized methods and data management. | 1 | Applied and Interdisciplinary Chemistry |
The urea molecule is planar when in a solid crystal because of sp hybridization of the N orbitals. It is non-planar with C symmetry when in the gas phase or in aqueous solution, with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°. In solid urea, the oxygen center is engaged in two N–H–O hydrogen bonds. The resulting dense and energetically favourable hydrogen-bond network is probably established at the cost of efficient molecular packing: The structure is quite open, the ribbons forming tunnels with square cross-section. The carbon in urea is described as sp hybridized, the C-N bonds have significant double bond character, and the carbonyl oxygen is relatively basic. Urea's high aqueous solubility reflects its ability to engage in extensive hydrogen bonding with water.
By virtue of its tendency to form porous frameworks, urea has the ability to trap many organic compounds. In these so-called clathrates, the organic "guest" molecules are held in channels formed by interpenetrating helices composed of hydrogen-bonded urea molecules.
As the helices are interconnected, all helices in a crystal must have the same molecular handedness. This is determined when the crystal is nucleated and can thus be forced by seeding. The resulting crystals have been used to separate racemic mixtures. | 0 | Theoretical and Fundamental Chemistry |
Thermocouples are often used at high temperatures and in reactive furnace atmospheres. In this case, the practical lifetime is limited by thermocouple aging. The thermoelectric coefficients of the wires in a thermocouple that is used to measure very high temperatures may change with time, and the measurement voltage accordingly drops. The simple relationship between the temperature difference of the junctions and the measurement voltage is only correct if each wire is homogeneous (uniform in composition). As thermocouples age in a process, their conductors can lose homogeneity due to chemical and metallurgical changes caused by extreme or prolonged exposure to high temperatures. If the aged section of the thermocouple circuit is exposed to a temperature gradient, the measured voltage will differ, resulting in error.
Aged thermocouples are only partly modified; for example, being unaffected in the parts outside the furnace. For this reason, aged thermocouples cannot be taken out of their installed location and recalibrated in a bath or test furnace to determine error. This also explains why error can sometimes be observed when an aged thermocouple is pulled partly out of a furnace—as the sensor is pulled back, aged sections may see exposure to increased temperature gradients from hot to cold as the aged section now passes through the cooler refractory area, contributing significant error to the measurement. Likewise, an aged thermocouple that is pushed deeper into the furnace might sometimes provide a more accurate reading if being pushed further into the furnace causes the temperature gradient to occur only in a fresh section. | 1 | Applied and Interdisciplinary Chemistry |
The historical development of PIV has been driven by the need for accurate and non-intrusive flow measurements in various fields of science and engineering. The early years of PIV were marked by the development of basic PIV techniques, such as two-frame PIV, and the application of PIV in fundamental fluid dynamics research, primarily in academic settings. As PIV gained popularity, researchers started using it in more practical applications, such as aerodynamics, combustion, and oceanography.
As PIV continues to advance and evolve, it is expected to find further applications in a wide range of fields, from fundamental research in fluid dynamics to practical applications in engineering, environmental science, and medicine. The continued development of PIV techniques, including advancements in lasers, cameras, image analysis algorithms, and integration with other measurement techniques, will further enhance its capabilities and broaden its applications.
In aerodynamics, PIV has been used to study the flow over aircraft wings, rotor blades, and other aerodynamic surfaces, providing insights into the flow behavior and aerodynamic performance of these systems.
As PIV gained popularity, it found applications in a wide range of fields beyond aerodynamics, including combustion, oceanography, biofluids, and microscale flows. In combustion research, PIV has been used to study the details of combustion processes, such as flame propagation, ignition, and fuel spray dynamics, providing valuable insights into the complex interactions between fuel and air in combustion systems. In oceanography, PIV has been used to study the motion of water currents, waves, and turbulence, aiding in the understanding of ocean circulation patterns and coastal erosion. In biofluids research, PIV has been applied to study blood flow in arteries and veins, respiratory flow, and the motion of cilia and flagella in microorganisms, providing important information for understanding physiological processes and disease mechanisms.
PIV has also been used in new and emerging fields, such as microscale and nanoscale flows, granular flows, and multiphase flows. Micro-PIV and nano-PIV have been used to study flows in microchannels, nanopores, and biological systems at the microscale and nanoscale, providing insights into the unique behaviors of fluids at these length scales. PIV has been applied to study the motion of particles in granular flows, such as avalanches and landslides, and to investigate multiphase flows, such as bubbly flows and oil-water flows, which are important in environmental and industrial processes. In microscale flows, conventional measurement techniques are challenging to apply due to the small length scales involved. Micro-PIV has been used to study flows in microfluidic devices, such as lab-on-a-chip systems, and to investigate phenomena such as droplet formation, mixing, and cell motion, with applications in drug delivery, biomedical diagnostics, and microscale engineering.
PIV has also found applications in advanced manufacturing processes, such as additive manufacturing, where understanding and optimizing fluid flow behavior is critical for achieving high-quality and high-precision products. PIV has been used to study the flow dynamics of gases, liquids, and powders in additive manufacturing processes, providing insights into the process parameters that affect the quality and properties of the manufactured products.
PIV has also been used in environmental science to study the dispersion of pollutants in air and water, sediment transport in rivers and coastal areas, and the behavior of pollutants in natural and engineered systems. In energy research, PIV has been used to study the flow behavior in wind turbines, hydroelectric power plants, and combustion processes in engines and turbines, aiding in the development of more efficient and environmentally friendly energy systems. | 1 | Applied and Interdisciplinary Chemistry |
In nerve terminals, synaptic vesicles are produced quickly to compensate for their rapid depletion during neurotransmitter release. Their biogenesis involves segregating synaptic vesicle membrane proteins from other cellular proteins and packaging those distinct proteins into vesicles of appropriate size. Besides, it entails the endocytosis of synaptic vesicle membrane proteins from the plasma membrane.
Synaptoblastic and synaptoclastic refer to synapse-producing and synapse-removing activities within the biochemical signalling chain. This terminology is associated with the Bredesen Protocol for treating Alzheimers disease, which conceptualizes Alzheimers as an imbalance between these processes. As of October 2023, studies concerning this protocol remain small and few results have been obtained within a standardized control framework. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, a Mach wave, also known as a weak discontinuity, is a pressure wave traveling with the speed of sound caused by a slight change of pressure added to a compressible flow. These weak waves can combine in supersonic flow to become a shock wave if sufficient Mach waves are present at any location. Such a shock wave is called a Mach stem or Mach front. Thus, it is possible to have shockless compression or expansion in a supersonic flow by having the production of Mach waves sufficiently spaced (cf. isentropic compression in supersonic flows). A Mach wave is the weak limit of an oblique shock wave where time averages of flow quantities don't change (a normal shock is the other limit). If the size of the object moving at the speed of sound is near 0, then this domain of influence of the wave is called a Mach cone. | 1 | Applied and Interdisciplinary Chemistry |
Agmatine was found to exert modulatory actions directly and indirectly at multiple key molecular targets underlying cellular control mechanisms of cardinal importance in health and disease. It is considered capable of exerting its modulatory actions simultaneously at multiple targets. The following outline indicates the categories of control mechanisms and identifies their molecular targets:
* Neurotransmitter receptors and receptor ionophores. Nicotinic, imidazoline I1 and I2, α2-adrenergic, glutamate NMDAr, and serotonin 5-HT2A and 5HT-3 receptors.
* Ion channels. Including: ATP-sensitive K+ channels, voltage-gated Ca channels, and acid-sensing ion channels (ASICs).
* Membrane transporters. Agmatine specific-selective uptake sites, organic cation transporters (mostly OCT2 subtype), extraneuronal monoamine transporters (ENT), polyamine transporters, and mitochondrial agmatine specific-selective transport system.
* Nitric oxide (NO) synthesis modulation. Both differential inhibition and activation of NO synthase (NOS) isoforms is reported.
* Polyamine metabolism. Agmatine is a precursor for polyamine synthesis, competitive inhibitor of polyamine transport, inducer of spermidine/spermine acetyltransferase (SSAT), and inducer of antizyme.
* Protein ADP-ribosylation. Inhibition of protein arginine ADP-ribosylation.
* Matrix metalloproteases (MMPs). Indirect down-regulation of the enzymes MMP 2 and 9.
* Advanced glycation end product (AGE) formation. Direct blockade of AGEs formation.
* NADPH oxidase. Activation of the enzyme leading to HO production. | 1 | Applied and Interdisciplinary Chemistry |
Two drops of gastric juice are mixed with two drops of Gunzberg's reagent in an evaporating dish. The mixture is evaporated and if red is seen, free hydrochloric acid is present. | 0 | Theoretical and Fundamental Chemistry |
Tautomers () are structural isomers (constitutional isomers) of chemical compounds that readily interconvert. The chemical reaction interconverting the two is called tautomerization. This conversion commonly results from the relocation of a hydrogen atom within the compound. The phenomenon of tautomerization is called tautomerism, also called desmotropism. Tautomerism is for example relevant to the behavior of amino acids and nucleic acids, two of the fundamental building blocks of life.
Care should be taken not to confuse tautomers with depictions of "contributing structures" in chemical resonance. Tautomers are distinct chemical species that can be distinguished by their differing atomic connectivities, molecular geometries, and physicochemical and spectroscopic properties, whereas resonance forms are merely alternative Lewis structure (valence bond theory) depictions of a single chemical species, whose true structure is a quantum superposition, essentially the "average" of the idealized, hypothetical geometries implied by these resonance forms. | 0 | Theoretical and Fundamental Chemistry |
Carbohydrate synthesis is a sub-field of organic chemistry concerned with generating complex carbohydrate structures from simple units (monosaccharides) through natural or unnatural processes. The generation of carbohydrate structures involves linking glycosyl groups like monosaccharides or oligosaccharides through glycosidic bonds is called glycosylation. Carbohydrate synthesis aims to generate the polysaccharides with controlled structures through atomically economic methods. Therefore, it is important to construct glycosidic linkages that have optimum molecular geometry (stereoselectivity) and the stable bond (regioselectivity) at the reaction site (anomeric centre). | 0 | Theoretical and Fundamental Chemistry |
A nanofactory is a proposed system in which nanomachines (resembling molecular assemblers, or industrial robot arms) would combine reactive molecules via mechanosynthesis to build larger atomically precise parts. These, in turn, would be assembled by positioning mechanisms of assorted sizes to build macroscopic (visible) but still atomically-precise products.
A typical nanofactory would fit in a desktop box, in the vision of K. Eric Drexler published in Nanosystems: Molecular Machinery, Manufacturing and Computation (1992), a notable work of "exploratory engineering". During the 1990s, others have extended the nanofactory concept, including an analysis of nanofactory convergent assembly by Ralph Merkle, a systems design of a replicating nanofactory architecture by J. Storrs Hall, Forrest Bishops "Universal Assembler", the patented exponential assembly process by Zyvex, and a top-level systems design for a primitive nanofactory by Chris Phoenix (director of research at the Center for Responsible Nanotechnology). All of these nanofactory designs (and more) are summarized in Chapter 4 of Kinematic Self-Replicating Machines' (2004) by Robert Freitas and Ralph Merkle. The Nanofactory Collaboration, founded by Freitas and Merkle in 2000, is a focused, ongoing effort involving 23 researchers from 10 organizations and 4 countries that is developing a practical research agenda specifically aimed at positionally-controlled diamond mechanosynthesis and diamondoid nanofactory development.
In 2005, an animated short film of the nanofactory concept was produced by John Burch, in collaboration with Drexler. Such visions have been the subject of much debate, on several intellectual levels. No one has discovered an insurmountable problem with the underlying theories and no one has proved that the theories can be translated into practice. However, the debate continues, with some of it being summarized in the molecular nanotechnology article.
If nanofactories could be built, severe disruption to the world economy would be one of many possible negative impacts, though it could be argued that this disruption would have little negative effect, if everyone had such nanofactories. Great benefits also would be anticipated. Various works of science fiction have explored these and similar concepts. The potential for such devices was part of the mandate of a major UK study led by mechanical engineering professor Dame Ann Dowling. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, Darwin drift refers to the phenomenon that a fluid parcel is permanently displaced after the passage of a body through a fluid – the fluid being at rest far away from the body.
Consider a plane of fluid parcels perpendicular to the direction of the bodys constant velocity vector, far before the passage of the body. During the passage of the body the fluid parcels move, according to their Lagrangian motion. Far after the passage of the body, the fluid parcels are permanently displaced. The volume between the initial plane of the fluid parcels and the surface consisting of the parcel positions long after the bodys passage is called the Darwin drift volume.
The phenomenon is named after Sir Charles Galton Darwin, who proved in 1953 that the drift volume multiplied with the fluid density equals the added mass of the body, – known as Darwin's theorem.
As shown by Eames and McIntyre in 1999, Darwin drift (by the passage of a body through a fluid otherwise at rest) and Stokes drift (in the fluid motion associated with surface waves) are closely related. | 1 | Applied and Interdisciplinary Chemistry |
Freezing is a common method of food preservation that slows both food decay and the growth of micro-organisms. Besides the effect of lower temperatures on reaction rates, freezing makes water less available for bacteria growth. Freezing is one of the oldest and most widely used methods of food preservation; since as long ago as 1842, freezing has been used in an ice and salt brine. In freezing, flavours, smell and nutritional content generally remain unchanged. Freezing became commercially applicable after the advent (introduction) of mechanical refrigeration. Freezing has been successfully employed for long term preservation of many foods providing a significantly extended shelf-life. Freezing preservation is generally regarded as superior to canning and dehydration with respect to retention in sensory attributes and nutritive attributes. | 1 | Applied and Interdisciplinary Chemistry |
In organometallic chemistry, the activation of cyclopropanes by transition metals is a research theme with implications for organic synthesis and homogeneous catalysis. Being highly strained, cyclopropanes are prone to oxidative addition to transition metal complexes. The resulting metallacycles are susceptible to a variety of reactions. These reactions are rare examples of C-C bond activation. The rarity of C-C activation processes has been attributed to Steric effects that protect C-C bonds. Furthermore, the directionality of C-C bonds as compared to C-H bonds makes orbital interaction with transition metals less favorable. Thermodynamically, C-C bond activation is more favored than C-H bond activation as the strength of a typical C-C bond is around 90 kcal per mole while the strength of a typical unactivated C-H bond is around 104 kcal per mole.
Two main approaches achieve C-C bond activation using a transition metal. One strategy is to increase the ring strain and the other is to stabilize the resulting cleaved C-C bond complex (e.g. through aromatization or chelation). Because of the large ring strain energy of cyclopropanes (29.0 kcal per mole), they are often used as substrates for C-C activation through oxidative addition of a transition metal into one of the three C-C bonds leading to a metallacyclobutane intermediate.
Substituents on the cyclopropane affect the course of its activation. | 0 | Theoretical and Fundamental Chemistry |
The vast majority of important organic molecules contain heteroatoms, which polarize carbon skeletons by virtue of their electronegativity. Therefore, in standard organic reactions, the majority of new bonds are formed between atoms of opposite polarity. This can be considered to be the "normal" mode of reactivity.
One consequence of this natural polarization of molecules is that 1,3- and 1,5- heteroatom substituted carbon skeletons are extremely easy to synthesize (Aldol reaction, Claisen condensation, Michael reaction, Claisen rearrangement, Diels-Alder reaction), whereas 1,2-, 1,4-, and 1,6- heteroatom substitution patterns are more difficult to access via "normal" reactivity. It is therefore important to understand and develop methods to induce umpolung in organic reactions. | 0 | Theoretical and Fundamental Chemistry |
The pharmacological action represents a mechanism by means of a specific effect can be obtained. Depending on the class and type of the drug, the pharmacological action may be different.
In the case of electrophysiology, the drug directly acts at the level of the cells, affecting the mechanism of opening/closing of the ionic channels, as it happens with the anti-arrhythmic drugs. Due to the ionic permeability properties of the cardiac cells membrane, during the action potential, the opening of the ion channels generates ion currents that flow in/out of the lipophilic cell membrane.
The anti-arrhythmic drugs action is that of modifying such ion currents, acting on the structure of the ion channel, and trying to restore the physiological opening/closing mechanism of the ion channels. It may be that, instead of providing a benefit to the heart, such as the aforementioned desired effect, a new drug can negatively affect the ion currents, ending up to excessively modifying the amount of ion currents flowing throughout the cell membrane, thus increasing the risk of inducing a potentially fatal arrhythmias. | 1 | Applied and Interdisciplinary Chemistry |
The extensive use of gold during early Philippine history is well-documented, both in the archeological record and in the various written accounts from precolonial and early Spanish colonial times. Gold was used throughout the Philippine archipelago in various decorative and ceremonial items, as clothing, and also as currency.
Gold was readily available throughout the Philippine archipelago, and gold items were valued as symbols of power and markers of elite status, although studies of grave artifacts suggest that these items were not as valued in precolonial Philippines as traded ornaments were. Gold was plentiful enough that local elites did not feel the need to acquire large amounts of it, and only sought it as the need arose, by trading with settlements which produced it through low intensity mining.
Among the most prominent sites for gold mining in early Philippine history were Aringay-Tonglo-Balatok trade route covering the Cordillera Mountain Range and the Lingayen gulf towns of Agoo and Aringay; the mines of Paracale on the Bicol Peninsula which were a major source of gold for the trading centers of the Visayan islands, particularly Panay and Cebu; and the Butuan-Surigao area, particularly along the Agusan river on the island of Mindanao, which made Butuan (historical polity) an important trading center. | 1 | Applied and Interdisciplinary Chemistry |
ppGpp inhibits IF2-mediated fMet-Phe initiation dipeptide formation, probably by interfering with 30S and 50S subunit interactions. E. coli accumulates more ppGpp than pppGpp during amino acid starvation, and ppGpp has about 8-fold greater efficiency than that of pppGpp. While B. subtilis accumulates more pppGpp than ppGpp. | 1 | Applied and Interdisciplinary Chemistry |
The term zero-point energy (ZPE) is a translation from the German .
Sometimes used interchangeably with it are the terms zero-point radiation and ground state energy. The term zero-point field (ZPF) can be used when referring to a specific vacuum field, for instance the QED vacuum which specifically deals with quantum electrodynamics (e.g., electromagnetic interactions between photons, electrons and the vacuum) or the QCD vacuum which deals with quantum chromodynamics (e.g., color charge interactions between quarks, gluons and the vacuum). A vacuum can be viewed not as empty space but as the combination of all zero-point fields. In quantum field theory this combination of fields is called the vacuum state, its associated zero-point energy is called the vacuum energy and the average energy value is called the vacuum expectation value (VEV) also called its condensate. | 0 | Theoretical and Fundamental Chemistry |
Secular equilibrium can occur in a radioactive decay chain only if the half-life of the daughter radionuclide B is much shorter than the half-life of the parent radionuclide A. In such a case, the decay rate of A and hence the production rate of B is approximately constant, because the half-life of A is very long compared to the time scales considered. The quantity of radionuclide B builds up until the number of B atoms decaying per unit time becomes equal to the number being produced per unit time. The quantity of radionuclide B then reaches a constant, equilibrium value. Assuming the initial concentration of radionuclide B is zero, full equilibrium usually takes several half-lives of radionuclide B to establish.
The quantity of radionuclide B when secular equilibrium is reached is determined by the quantity of its parent A and the half-lives of the two radionuclide. That can be seen from the time rate of change of the number of atoms of radionuclide B:
where λ and λ are the decay constants of radionuclide A and B, related to their half-lives t by , and N and N are the number of atoms of A and B at a given time.
Secular equilibrium occurs when , or
Over long enough times, comparable to the half-life of radionuclide A, the secular equilibrium is only approximate; N decays away according to
and the "equilibrium" quantity of radionuclide B declines in turn. For times short compared to the half-life of A, and the exponential can be approximated as 1. | 0 | Theoretical and Fundamental Chemistry |
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