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The Voigt profile is normalized:
since it is a convolution of normalized profiles. The Lorentzian profile has no moments (other than the zeroth), and so the moment-generating function for the Cauchy distribution is not defined. It follows that the Voigt profile will not have a moment-generating function either, but the characteristic function for the Cauchy distribution is well defined, as is the characteristic function for the normal distribution. The characteristic function for the (centered) Voigt profile will then be the product of the two:
Since normal distributions and Cauchy distributions are stable distributions, they are each closed under convolution (up to change of scale), and it follows that the Voigt distributions are also closed under convolution. | 0 | Theoretical and Fundamental Chemistry |
MITF recognizes E-box (CAYRTG) and M-box (TCAYRTG or CAYRTGA) sequences in the promoter regions of target genes. Known target genes (confirmed by at least two independent sources) of this transcription factor include,
Additional genes identified by a microarray study (which confirmed the above targets) include the following, | 1 | Applied and Interdisciplinary Chemistry |
The biochemical transformation of radionuclides into stable isotopes by bacterial species significantly differs from the metabolism of organic compounds coming from carbon sources. They are highly energetic radioactive forms which can be converted indirectly by the process of microbial energy transfer.
Radioisotopes can be transformed directly through changes in valence state by acting as acceptors or by acting as cofactors to enzymes. They can also be transformed indirectly by reducing and oxidizing agents produced by microorganisms that cause changes in pH or redox potential. Other processes include precipitation and complexation of surfactants, or chelating agents that bind to radioactive elements. Human intervention, on the other hand, can improve these processes through genetic engineering and omics, or by injection of microorganisms or nutrients into the treatment area. | 1 | Applied and Interdisciplinary Chemistry |
The Penning source is a low gas pressure, cold cathode ion source which utilizes crossed electric and magnetic fields. The ion source anode is at a positive potential, either dc or pulsed, with respect to the source cathode. The ion source voltage is normally between 2 and 7 kilovolts. A magnetic field, oriented parallel to the source axis, is produced by a permanent magnet. A plasma is formed along the axis of the anode which traps electrons which, in turn, ionize gas in the source. The ions are extracted through the exit cathode. Under normal operation, the ion species produced by the Penning source are over 90% molecular ions. This disadvantage is however compensated for by the other advantages of the system.
One of the cathodes is a cup made of soft iron, enclosing most of the discharge space. The bottom of the cup has a hole through which most of the generated ions are ejected by the magnetic field into the acceleration space. The soft iron shields the acceleration space from the magnetic field, to prevent a breakdown.
Ions emerging from the exit cathode are accelerated through the potential difference between the exit cathode and the accelerator electrode. The schematic indicates that the exit cathode is at ground potential and the target is at high (negative) potential. This is the case in many sealed tube neutron generators. However, in cases when it is desired to deliver the maximum flux to a sample, it is desirable to operate the neutron tube with the target grounded and the source floating at high (positive) potential. The accelerator voltage is normally between 80 and 180 kilovolts.
The accelerating electrode has the shape of a long hollow cylinder. The ion beam has a slightly diverging angle (about 0.1 radian). The electrode shape and distance from target can be chosen so the entire target surface is bombarded with ions. Acceleration voltages of up to 200 kV are achievable.
The ions pass through the accelerating electrode and strike the target. When ions strike the target, 2–3 electrons per ion are produced by secondary emission. In order to prevent these secondary electrons from being accelerated back into the ion source, the accelerator electrode is biased negative with respect to the target. This voltage, called the suppressor voltage, must be at least 500 volts and may be as high as a few kilovolts. Loss of suppressor voltage will result in damage, possibly catastrophic, to the neutron tube.
Some neutron tubes incorporate an intermediate electrode, called the focus or extractor electrode, to control the size of the beam spot on the target. The gas pressure in the source is regulated by heating or cooling the gas reservoir element. | 0 | Theoretical and Fundamental Chemistry |
Urban stream syndrome (USS) is a consistent observed ecological degradation of streams caused by urbanization. This kind of stream degradation is commonly found in areas near or in urban areas. USS also considers hydrogeomorphology changes which are characterized by a deeper, wider catchment, reduced living space for biota, and altered sediment transport rates. Keep in mind the status of water quality is difficult to assess in urban areas because of the complexity of the pollutions sources. This could be from mining and deforestation, but the main cause can be attributed to urban and suburban development. This is because such land use has a domino effect that can be felt tens of kilometers away. Consistent decrease to ecological health of streams can be from many things, but most can be directly or indirectly attributed to human infrastructure and action. Urban streams tend to be “flashier” meaning they have more frequent and larger high flow events.
Urban streams also suffer from chemical alterations due to pollutants and waste being uncleanly dumped back into rivers and lakes. An example of this is Onondaga Lake. Historically one of the most polluted freshwater lakes in the world, its salinity and toxic constituents like mercury rose to unsafe levels as large corporations begun to set up shop around the lake. High levels of salinity would be disastrous for any native freshwater marine life and pollutants like mercury are dangerous to most organisms.
Higher levels of urbanization typically mean a greater presence of urban stream syndrome.
Hydrology plays a key role in urban stream syndrome. As urbanization of these streams continue, there is in turn a decrease in the perviousness of the catchment to precipitation, which leads to a decrease in the infiltration and an increase in the surface runoff. This can cause problems during flood discharges. For example, flood discharges in urban catchments were at least 250% higher in urban catchments than in forested catchments in New York and Texas during similar storms. | 1 | Applied and Interdisciplinary Chemistry |
An inexpensive, non-toxic example of a non-Newtonian fluid is a suspension of starch (e.g., cornstarch/cornflour) in water, sometimes called "oobleck", "ooze", or "magic mud" (1 part of water to 1.5–2 parts of corn starch). The name "oobleck" is derived from the Dr. Seuss book Bartholomew and the Oobleck.
Because of its dilatant properties, oobleck is often used in demonstrations that exhibit its unusual behavior. A person may walk on a large tub of oobleck without sinking due to its shear thickening properties, as long as the individual moves quickly enough to provide enough force with each step to cause the thickening. Also, if oobleck is placed on a large subwoofer driven at a sufficiently high volume, it will thicken and form standing waves in response to low frequency sound waves from the speaker. If a person were to punch or hit oobleck, it would thicken and act like a solid. After the blow, the oobleck will go back to its thin liquid-like state. | 1 | Applied and Interdisciplinary Chemistry |
Diarylethene is the general name of a class of chemical compounds that have aromatic functional groups bonded to each end of a carbon–carbon double bond. The simplest example is stilbene, which has two geometric isomers, E and Z.
Under the influence of light, these compounds can generally perform two kinds of reversible isomerizations:
*E to Z isomerizations, most common for stilbenes (and azobenzenes). This process goes through an excited state energy minimum where the aromatic rings lie at 90° to each other. This conformation drops to the ground state and generally relaxes to trans and cis forms in a 1:1 ratio, thus the quantum yield for E-Z isomerization is very rarely greater than 0.5.
*6π electrocyclizations of the Z form, leading to an additional bond between the two aryl functionalities and a disruption of the aromatic character of these groups. The quantum yield of this reaction is generally less than 0.1, and in most diarylethenes the close-ring form is thermally unstable, reverting to the cis-form in a matter of seconds or minutes under ambient conditions.
Thermal isomerization is also possible. In E-Z isomerization, the thermal equilibrium lies well towards the trans-form because of its lower energy (~15 kJ mol in stilbene). The activation energy for thermal E-Z isomerization is 150–190 kJ mol for stilbene, meaning that temperatures above 200°C are required to isomerize stilbene at a reasonable rate, but most derivatives have lower energy barriers (e.g. 65 kJ mol for 4-aminostilbene). The activation energy of the electrocyclization is 73 kJ mol for stilbene.
Both processes are often applied in molecular switches and for photochromism (reversible state changes from exposure to light).
After the 6π electrocyclization of the Z form to the "close-ring" form, most unsubstituted diarylethenes are prone to oxidation, leading to a re-aromatization of the π-system. The most common example is (E)-stilbene, which upon irradiation undergoes an E to Z isomerization, which can be followed by a 6π electrocyclization. Reaction of the product of this reaction with molecular oxygen affords phenanthrene, and it has been suggested by some studies that dehydrogenation may even occur spontaneously. The dihydrophenanthrene intermediate has never been isolated, but it has been detected spectroscopically in pump-probe experiments by virtue of its long wavelength optical absorption band. Although both the E-Z isomerization and the 6π electrocyclization are reversible processes, this oxidation renders the entire sequence irreversible. | 0 | Theoretical and Fundamental Chemistry |
The Indian Space Research Organization (ISRO) commissioned three major facilities, namely a Hypersonic Wind Tunnel, a Shock Tunnel and a Plasma Tunnel at Vikram Sarabhai Space Center as part of its continuous and concerted efforts to minimize cost of access into space. This integrated facility was named as Satish Dhawan Wind Tunnel Complex as a tribute to Prof. Satish Dhawan, who has made very significant contributions in the field of wind tunnels and aerodynamics. ISRO Chairman A. S. Kiran Kumar said commissioning of such facilities would provide adequate data for design and development of current and future space transportation systems in India.
Defence Research and Development Organisation (DRDO) commissioned an advanced Hypersonic Wind Tunnel (HWT) test facility at Dr APJ Abdul Kalam Missile Complex on 20 December 2020 as part of facility development programme for Hypersonic Technology Demonstrator Vehicle project. | 1 | Applied and Interdisciplinary Chemistry |
Bents rule can be used to explain trends in both molecular structure and reactivity. After determining how the hybridisation of the central atom should affect a particular property, the electronegativity of substituents can be examined to see if Bents rule holds. | 0 | Theoretical and Fundamental Chemistry |
There are two common mechanisms by which the size of a particular restriction fragment can vary. In the first schematic, a small segment of the genome is being detected by a DNA probe (thicker line). In allele A, the genome is cleaved by a restriction enzyme at three nearby sites (triangles), but only the rightmost fragment will be detected by the probe. In allele a, restriction site 2 has been lost by a mutation, so the probe now detects the larger fused fragment running from sites 1 to 3. The second diagram shows how this fragment size variation would look on a Southern blot, and how each allele (two per individual) might be inherited in members of a family.
In the third schematic, the probe and restriction enzyme are chosen to detect a region of the genome that includes a variable number tandem repeat (VNTR) segment (boxes in schematic diagram). In allele c, there are five repeats in the VNTR, and the probe detects a longer fragment between the two restriction sites. In allele d, there are only two repeats in the VNTR, so the probe detects a shorter fragment between the same two restriction sites. Other genetic processes, such as insertions, deletions, translocations, and inversions, can also lead to polymorphisms. RFLP tests require much larger samples of DNA than do short tandem repeat (STR) tests. | 1 | Applied and Interdisciplinary Chemistry |
The negative charge of its phosphate backbone moves the DNA towards the positively charged anode during electrophoresis. However, the migration of DNA molecules in solution, in the absence of a gel matrix, is independent of molecular weight during electrophoresis. The gel matrix is therefore responsible for the separation of DNA by size during electrophoresis, and a number of models exist to explain the mechanism of separation of biomolecules in gel matrix. A widely accepted one is the Ogston model which treats the polymer matrix as a sieve. A globular protein or a random coil DNA moves through the interconnected pores, and the movement of larger molecules is more likely to be impeded and slowed down by collisions with the gel matrix, and the molecules of different sizes can therefore be separated in this sieving process.
The Ogston model however breaks down for large molecules whereby the pores are significantly smaller than size of the molecule. For DNA molecules of size greater than 1 kb, a reptation model (or its variants) is most commonly used. This model assumes that the DNA can crawl in a "snake-like" fashion (hence "reptation") through the pores as an elongated molecule. A biased reptation model applies at higher electric field strength, whereby the leading end of the molecule become strongly biased in the forward direction and pulls the rest of the molecule along. Real-time fluorescence microscopy of stained molecules, however, showed more subtle dynamics during electrophoresis, with the DNA showing considerable elasticity as it alternately stretching in the direction of the applied field and then contracting into a ball, or becoming hooked into a U-shape when it gets caught on the polymer fibres. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, hydroboration refers to the addition of a hydrogen-boron bond to certain double and triple bonds involving carbon (, , , and ). This chemical reaction is useful in the organic synthesis of organic compounds.
Hydroboration produces organoborane compounds that react with a variety of reagents to produce useful compounds, such as alcohols, amines, or alkyl halides. The most widely known reaction of the organoboranes is oxidation to produce alcohols typically by hydrogen peroxide. This type of reaction has promoted research on hydroboration because of its mild condition and a wide scope of tolerated alkenes. Another research subtheme is metal-catalysed hydroboration.
The development of this technology and the underlying concepts were recognized by the Nobel Prize in Chemistry to Herbert C. Brown. He shared the prize with Georg Wittig in 1979 for his pioneering research on organoboranes as important synthetic intermediates. A complement to hydroboration is carboboration, where a carbon moiety is incorporated rather than hydrogen. | 0 | Theoretical and Fundamental Chemistry |
Choi began her independent career at Purdue University as an assistant professor in 2002, and was later promoted to associate professor. She was a visiting scholar at the National Renewable Energy Laboratory in 2008. In 2012, she moved to University of Wisconsin-Madison as a full professor of chemistry.
Choi has served as an associate editor of the journal Chemistry of Materials since 2014. | 0 | Theoretical and Fundamental Chemistry |
Arctic Apples are a suite of trademarked apples that contain a nonbrowning trait created by using gene silencing to reduce the expression of polyphenol oxidase (PPO). It is the first approved food product to use this technique. | 1 | Applied and Interdisciplinary Chemistry |
THF is deprotonated by butyllithium, especially in the presence of TMEDA, by loss of one of four protons adjacent to oxygen. This process, which consumes butyllithium to generate butane, induces a ring opening to give enolate of acetaldehyde and ethylene. Therefore, reactions of BuLi in THF are typically conducted at low temperatures, such as –78 °C, as is conveniently produced by a freezing bath of dry ice and acetone. Higher temperatures (−25 °C or even −15 °C) are also used. | 0 | Theoretical and Fundamental Chemistry |
In women, progesterone levels are relatively low during the preovulatory phase of the menstrual cycle, rise after ovulation, and are elevated during the luteal phase, as shown in the diagram above. Progesterone levels tend to be less than 2 ng/mL prior to ovulation and greater than 5 ng/mL after ovulation. If pregnancy occurs, human chorionic gonadotropin is released, maintaining the corpus luteum and allowing it to maintain levels of progesterone. Between 7 and 9 weeks, the placenta begins to produce progesterone in place of the corpus luteum in a process called the luteal-placental shift.
After the luteal-placental shift, progesterone levels start to rise further and may reach 100 to 200 ng/mL at term. Whether a decrease in progesterone levels is critical for the initiation of labor has been argued and may be species-specific. After delivery of the placenta and during lactation, progesterone levels are very low.
Progesterone levels are low in children and postmenopausal women. Adult males have levels similar to those in women during the follicular phase of the menstrual cycle. | 0 | Theoretical and Fundamental Chemistry |
*If is a solution to Emden–Chandrasekhar equation, then is also a solution of the equation, where is an arbitrary constant.
*The solutions of the Emden–Chandrasekhar equation which are finite at the origin have necessarily at | 1 | Applied and Interdisciplinary Chemistry |
The Faculty of Chemistry (since 2014 The Institute of Chemistry) at Saint Petersburg State University is one of the leading chemistry faculties in Russia. | 1 | Applied and Interdisciplinary Chemistry |
AREsite is a database of AU-rich elements (ARE) in vertebrate mRNA 3'-untranslated regions (UTRs). AU-rich elements are involved in the control of gene expression. They are the most common determinant of RNA stability in mammalian cells. The most recent version of AREsite is called AREsite 2. It represents an update that allows for more detailed analysis of ARE, GRE, and URE (AU, GU, and U-rich elements). | 1 | Applied and Interdisciplinary Chemistry |
* Adkins, C.J. (1968/1983). Equilibrium Thermodynamics, (1st edition 1968), third edition 1983, Cambridge University Press, Cambridge UK, .
* Atkins, P., de Paula, J. (1978/2010). Physical Chemistry, (first edition 1978), ninth edition 2010, Oxford University Press, Oxford UK, .
* Bacon, F. (1620). Novum Organum Scientiarum, translated by Devey, J., P.F. Collier & Son, New York, 1902.
* Bailyn, M. (1994). A Survey of Thermodynamics, American Institute of Physics Press, New York, .
* Born, M. (1949). [https://archive.org/details/naturalphilosoph032159mbp Natural Philosophy of Cause and Chance], Oxford University Press, London.
* Bryan, G.H. (1907). [https://archive.org/details/ost-physics-thermodynamicsin00bryauoft Thermodynamics. An Introductory Treatise dealing mainly with First Principles and their Direct Applications], B.G. Teubner, Leipzig.
*Buchdahl, H.A. (1966). The Concepts of Classical Thermodynamics, Cambridge University Press, Cambridge UK.
* Callen, H.B. (1960/1985). Thermodynamics and an Introduction to Thermostatistics, (1st edition 1960) 2nd edition 1985, Wiley, New York, .
* A translation may be found [http://neo-classical-physics.info/uploads/3/0/6/5/3065888/caratheodory_-_thermodynamics.pdf here]. A mostly reliable translation is to be found at Kestin, J. (1976). The Second Law of Thermodynamics, Dowden, Hutchinson & Ross, Stroudsburg PA.
* Chandrasekhar, S. (1961). Hydrodynamic and Hydromagnetic Stability, Oxford University Press, Oxford UK.
* Clausius, R. (1854). Annalen der Physik (Poggendoffs Annalen), Dec. 1854, vol. xciii. p. 481; translated in the Journal de Mathematiques, vol. xx. Paris, 1855, and in the Philosophical Magazine', August 1856, s. 4. vol. xii, p. 81.
* Clausius, R. (1865/1867). [https://books.google.com/books?id=8LIEAAAAYAAJ&q=necessitating+any+other The Mechanical Theory of Heat – with its Applications to the Steam Engine and to Physical Properties of Bodies], London: John van Voorst. 1867. Also the second edition translated into English by W.R. Browne (1879) [https://archive.org/details/cu31924101120883 here] and [http://www3.nd.edu/~powers/ame.20231/clausius1879.pdf here].
* De Groot, S.R., Mazur, P. (1962). Non-equilibrium Thermodynamics, North-Holland, Amsterdam. Reprinted (1984), Dover Publications Inc., New York, .
* Denbigh, K. (1955/1981). The Principles of Chemical Equilibrium, Cambridge University Press, Cambridge .
* Greven, A., Keller, G., Warnecke (editors) (2003). Entropy, Princeton University Press, Princeton NJ, .
* , Lecture on Matter, Living Force, and Heat. 5 and 12 May 1847.
* Kittel, C. Kroemer, H. (1980). Thermal Physics, second edition, W.H. Freeman, San Francisco, .
* Kondepudi, D., Prigogine, I. (1998). Modern Thermodynamics: From Heat Engines to Dissipative Structures, John Wiley & Sons, Chichester, .
* Landau, L., Lifshitz, E.M. (1958/1969). [https://archive.org/details/StatisticalPhysics Statistical Physics], volume 5 of Course of Theoretical Physics, translated from the Russian by J.B. Sykes, M.J. Kearsley, Pergamon, Oxford.
* Lebon, G., Jou, D., Casas-Vázquez, J. (2008). Understanding Non-equilibrium Thermodynamics: Foundations, Applications, Frontiers, Springer-Verlag, Berlin, e-.
* Lieb, E.H., Yngvason, J. (2003). The Entropy of Classical Thermodynamics, Chapter 8 of Entropy, Greven, A., Keller, G., Warnecke (editors) (2003).
* Pippard, A.B. (1957/1966). Elements of Classical Thermodynamics for Advanced Students of Physics, original publication 1957, reprint 1966, Cambridge University Press, Cambridge.
* Planck, M., (1897/1903). [https://archive.org/details/treatiseonthermo00planrich Treatise on Thermodynamics], translated by A. Ogg, first English edition, Longmans, Green and Co., London.
* Planck. M. (1914). [https://archive.org/details/theoryofheatradi00planrich The Theory of Heat Radiation], a translation by Masius, M. of the second German edition, P. Blakiston's Son & Co., Philadelphia.
* Planck, M., (1923/1927). Treatise on Thermodynamics, translated by A. Ogg, third English edition, Longmans, Green and Co., London.
* Shavit, A., Gutfinger, C. (1995). Thermodynamics. From Concepts to Applications, Prentice Hall, London, .
* Truesdell, C. (1969). Rational Thermodynamics: a Course of Lectures on Selected Topics, McGraw-Hill Book Company, New York.
* Truesdell, C. (1980). The Tragicomical History of Thermodynamics 1822–1854, Springer, New York, . | 0 | Theoretical and Fundamental Chemistry |
Anadara trapezia, the Sydney cockle (NSW), or ark cockle (Queensland), is an estuarine filter-feeding bivalve. Its calcareous, heavily ribbed shell can grow to approximately across. Its range is along the east coast of Australia, from Queensland to Victoria. It has previously existed in Western Australia, South Australia, and the coast of New Zealand during the Middle Holocene. It has been used as a bioindicator/indicator species to study levels of the metals selenium, copper and cadmium. | 1 | Applied and Interdisciplinary Chemistry |
Production of a radiopharmaceutical involves two processes:
* The production of the radionuclide on which the pharmaceutical is based.
* The preparation and packaging of the complete radiopharmaceutical.
Radionuclides used in radiopharmaceuticals are mostly radioactive isotopes of elements with atomic numbers less than that of bismuth, that is, they are radioactive isotopes of elements that also have one or more stable isotopes. These may be roughly divided into two classes:
* Those with more neutrons in the nucleus than those required for stability are known as proton-deficient, and tend to be most easily produced in a nuclear reactor. The majority of radiopharmaceuticals are based on proton deficient isotopes, with technetium-99m being the most commonly used medical isotope, and therefore nuclear reactors are the prime source of medical radioisotopes.
* Those with fewer neutrons in the nucleus than those required for stability are known as neutron-deficient, and tend to be most easily produced using a proton accelerator such as a medical cyclotron. | 1 | Applied and Interdisciplinary Chemistry |
A wetting transition (Cassie–Wenzel transition) may occur during the process of wetting of a solid (or liquid) surface with a liquid. The transition corresponds to a certain change in contact angle, the macroscopic parameter characterizing wetting. Various contact angles can co-exist on the same solid substrate. Wetting transitions may occur in a different way depending on whether the surface is flat or rough. | 0 | Theoretical and Fundamental Chemistry |
The reaction mechanism is not known in detail. Supposedly, the reaction begins with a nucleophilic attack of the amino group on the carbonyl carbon of the anhydride group of the N-carboxylic acid anhydride (1). After an intramolecular proton migration, a 1,4-proton shift and the cleavage of carbon dioxide follows, resulting in the peptide bond in the final product (2): | 1 | Applied and Interdisciplinary Chemistry |
Cell signaling involves many different processes and proteins. One of the most studied cell signaling phenomena involving proline is the interactions with p53 and prolyl isomerases, specifically Pin1. The protein p53, along with p63 and p73, are responsible for ensuring that alterations to the genome are corrected and for preventing the formation and growth of tumors. proline residues are found throughout the p53 proteins and without the phosphorylation and isomerization of specific Serine/Threonine-Proline motifs within p53, they cannot exhibit control over their target genes. The main signalling processes that are affected by p53 are apoptosis and cell cycle arrest, both of which are controlled by specific isomerization of the prolines in p53. | 0 | Theoretical and Fundamental Chemistry |
Within the inner coma of comets, many reactions are theorized to be relevant to the formation and reactivity of the NS radical. | 0 | Theoretical and Fundamental Chemistry |
Capsaicin (fig. 2) has three functional regions: an aromatic A region where a parent homovanillyl (3-methoxy 4-hydroxybenzyl) group is optimal, a B region known as the ester or amide linker and the aliphatic C region where a lipophilic octanyl moiety is associated with the highest potency. The homovanillyl motif and amide bond regions contain dipolar groups which are implicated in hydrogen bonding interactions.
Phenolic hydroxide and amide moieties appear to be vital for inducing capsaicin responses. Removal of the phenolic hydroxide or amide bond in capsaicin analogues leads to reduction of potency. The phenolic hydroxide and amide moieties in capsaicin share potential multiple hydrogen bond interactions with the TRPV1 receptor. Capsaicinoids and capsinoids are characterized by an oxygenated aromatic moiety bound via an amide (capsaicinoids) or ester (capsinoids) linker to a lipophilic acyl group. The vanillyl and carbonyl linker contain polar groups capable of forming hydrogen bonds essential for activity, whereas the lipophilic moiety interacts with a corresponding cleft of the vanilloid binding site on TRPV1. Replacement of the medium-sized branched fatty acid of capsaicin with longer fatty acids is damaging for activity, but the presence of unsaturations restores and potentiates activity e.g. oleoylvanillamine (olvanil)(fig. 3a), is 10-fold more potent than capsaicin in TRPV1 activation assays. | 1 | Applied and Interdisciplinary Chemistry |
Octasulfur is an inorganic substance with the chemical formula . It is an odourless and tasteless yellow solid, and is a major industrial chemical. It is the most common allotrope of sulfur and occurs widely in nature. | 1 | Applied and Interdisciplinary Chemistry |
The Hellmann–Feynman theorem is actually a direct, and to some extent trivial, consequence of the variational principle (the Rayleigh-Ritz variational principle) from which the Schrödinger equation may be derived. This is why the Hellmann–Feynman theorem holds for wave-functions (such as the Hartree–Fock wave-function) that, though not eigenfunctions of the Hamiltonian, do derive from a variational principle. This is also why it holds, e.g., in density functional theory, which is not wave-function based and for which the standard derivation does not apply.
According to the Rayleigh–Ritz variational principle, the eigenfunctions of the Schrödinger equation are stationary points of the functional (which is nicknamed Schrödinger functional for brevity):
The eigenvalues are the values that the Schrödinger functional takes at the stationary points:
where satisfies the variational condition:
By differentiating Eq. (3) using the chain rule, the following equation is obtained:
Due to the variational condition, Eq. (4), the second term in Eq. (5) vanishes. In one sentence, the Hellmann–Feynman theorem states that the derivative of the stationary values of a function(al) with respect to a parameter on which it may depend, can be computed from the explicit dependence only, disregarding the implicit one. On account of the fact that the Schrödinger functional can only depend explicitly on an external parameter through the Hamiltonian, Eq. (1) trivially follows. | 0 | Theoretical and Fundamental Chemistry |
The POCIS device was developed and patented by Jimmie D. Petty, James N. Huckins, and David A. Alvarez, of the Columbia Environmental Research Center. Integrative passive samplers are an effective way to monitor the concentration of organic contaminants in aquatic systems over time. Most aquatic monitoring programs rely on collecting individual samples, often called grab samples, at a specific time. The grab sampling method is associated with many disadvantages that can be resolved by passive sampling techniques. When contaminants are present in trace amounts, grab sampling may require the collection of large volumes of water. Also, lab analysis of the sample can only provide a snapshot of contaminant levels at the time of collection. This approach therefore has drawbacks when monitoring in environments where water contamination varies over time and episodic contamination events occur. Passive sampling techniques have been able to provide a time-integrated sample of water contamination with low detection limits and in situ extraction of analytes. | 0 | Theoretical and Fundamental Chemistry |
Fluoroform, or trifluoromethane, is the chemical compound with the formula . It is a hydrofluorocarbon as well as being apart of the haloforms, a class of compounds with the formula (X = halogen) with C symmetry. Fluoroform is used in diverse applications in organic synthesis. It is not an ozone depleter but is a greenhouse gas. | 1 | Applied and Interdisciplinary Chemistry |
Lichens often have a regular but very slow growth rate of less than a millimeter per year.
In crustose lichens, the area along the margin is where the most active growth is taking place. Most crustose lichens grow only 1–2 mm in diameter per year. | 1 | Applied and Interdisciplinary Chemistry |
Cyclooctatetraene is another example of a molecule which is not antiaromatic, even though it might initially appear to be so. Cyclooctatetraene assumes a tub (i.e., boat-like) conformation. As it is not planar, even though it has 4n π-electrons, these electrons are not delocalized and conjugated. The molecule is therefore non-aromatic. | 0 | Theoretical and Fundamental Chemistry |
The rocket engine uses the same basic physical principles of thrust as a form of reaction engine, but is distinct from the jet engine in that it does not require atmospheric air to provide oxygen; the rocket carries all components of the reaction mass. However some definitions treat it as a form of jet propulsion.
Because rockets do not breathe air, this allows them to operate at arbitrary altitudes and in space.
This type of engine is used for launching satellites, space exploration and crewed access, and permitted landing on the Moon in 1969.
Rocket engines are used for high altitude flights, or anywhere where very high accelerations are needed since rocket engines themselves have a very high thrust-to-weight ratio.
However, the high exhaust speed and the heavier, oxidizer-rich propellant results in far more propellant use than turbofans. Even so, at extremely high speeds they become energy-efficient.
An approximate equation for the net thrust of a rocket engine is:
Where is the net thrust, is the specific impulse, is a standard gravity, is the propellant flow in kg/s, is the cross-sectional area at the exit of the exhaust nozzle, and is the atmospheric pressure. | 1 | Applied and Interdisciplinary Chemistry |
The second approach of bioprinting is autonomous self-assembly. This approach relies on the physical process of embryonic organ development as a model to replicate the tissues of interest. When cells are in their early development, they create their own extracellular matrix building block, the proper cell signaling, and independent arrangement and patterning to provide the required biological functions and micro-architecture. Autonomous self-assembly demands specific information about the developmental techniques of the tissues and organs of the embryo. There is a "scaffold-free" model that uses self-assembling spheroids that subjects to fusion and cell arrangement to resemble evolving tissues. Autonomous self-assembly depends on the cell as the fundamental driver of histogenesis, guiding the building blocks, structural and functional properties of these tissues. It demands a deeper understanding of how embryonic tissues mechanisms develop as well as the microenvironment surrounded to create the bioprinted tissues. | 1 | Applied and Interdisciplinary Chemistry |
Khlobystov started his post-doctoral career at the Department of Materials at the University of Oxford from 2002 until 2004 under Andrew Briggs, where he began exploring carbon nanotube as nanoscale containers for molecules. He applied transmission electron microscopy (TEM) for imaging structures of individual molecules and studying their dynamic behaviour in direct space and real time, which shed light on intermolecular interactions, and the translation and rotational motion of molecules at nanoscale. In his time at Oxford he was part of the team awarded a Guinness World Record for performing a chemical reaction inside carbon nanotubes.
In 2004, Khlobystov moved to the University of Nottingham as a Leverhulme Trust research fellow. At Nottingham, he built the Nottingham Nanocarbon Group, which has demonstrated that nanoscale confinement can lead to new products inaccessible by other synthetic methods. In 2005, his research group was awarded a European Young Investigator award and a Royal Society University Research Fellowship. Around this time, he was featured in Times Higher Educations series of emerging researchers in the physical sciences. In 2008, the Nanocarbon Group presented at the Royal Societys Summer Science Exhibition, with a display entitled "Wonder in carbon land: how do you hold a molecule?", showcasing the potential of utilising nanocages and nanotubes to control chemical reactions. Khlobystov's team has discovered mechanisms of interactions between carbon nanostructures and molecules or nanoparticles which enabled the design of nanoreactor systems with tuneable size and functionality. This research was supported by numerous grants including a European Research Council Starting Grant in 2011.
In 2016, to commemorate the opening of the nano- and micro-Research Centre (nmRC) at the University of Nottingham, Khlobystov led a team that utilised a Focused Ion Beam Scanning Electron Microscope (FIB-SEM) to etch a birthday message onto a corgi hair to commemorate Queen Elizabeth II's 90th birthday. In 2020, Khlobystov led a team that captured a video of the chemical bond between two metal atoms breaking and forming for the first time. This followed previous work which embraced the observer effect, utilising the electron beam present in an electron microscopy to provide the source of energy to drive chemical reactions and enable them to be directly observed, and was given the moniker ChemTEM.
Since 2021, Khlobystov has been PI for the MASI programme grant, which is investigating solvent-free routes to preparing and understanding single metal atoms and metal nanoclusters on surfaces for use as catalysts for electrochemical hydrogen production, ammonia synthesis and carbon dioxide reduction. | 0 | Theoretical and Fundamental Chemistry |
The most popular model to describe the electrical double layer is the Poisson-Boltzmann (PB) model. This model can be equally used to evaluate double layer forces. Let us discuss this model in the case of planar geometry as shown in the figure on the right. In this case, the electrical potential profile ψ(z) near a charged interface will only depend on the position z. The corresponding Poisson's equation reads in SI units
where ρ is the charge density per unit volume, ε the dielectric permittivity of the vacuum, and ε the dielectric constant of the liquid. For a symmetric electrolyte consisting of cations and anions having a charge ±q, the charge density can be expressed as
where c = N/V are the concentrations of the cations and anions, where N are their numbers and V the sample volume. These profiles can be related to the electrical potential by considering the fact that the chemical potential of the ions is constant. For both ions, this relation can be written as
where is the reference chemical potential, T the absolute temperature, and k the Boltzmann constant. The reference chemical potential can be eliminated by applying the same equation far away from the surface where the potential is assumed to vanish and concentrations attain the bulk concentration c. The concentration profiles thus become
where β = 1/(kT). This relation reflects the Boltzmann distribution of the ions with the energy ±qψ. Inserting these relations into the Poisson equation one obtains the PB equation
The potential profile between two plates is normally obtained by solving this equation numerically.
Once the potential profile is known, the force per unit area between the plates expressed as the disjoining pressure Π can be obtained as follows. The starting point is the Gibbs–Duhem relation for a two component system at constant temperature
Introducing the concentrations c and using the expressions of the chemical potentials μ given above one finds
The concentration difference can be eliminated with the Poisson equation and the resulting equation can be integrated from infinite separation of the plates to the actual separation h by realizing that
Expressing the concentration profiles in terms of the potential profiles one obtains
From a known electrical potential profile ψ(z) one can calculate the disjoining pressure from this equation at any suitable position z. Alternative derivation of the same relation for disjoining pressure involves the stress tensor. | 0 | Theoretical and Fundamental Chemistry |
A hypothetical schematic diagram for the transition to an H state by photo excitation is shown in the Figure (After ). An absorbed photon causes an electron from the ground state G to an excited state E (red arrow). State E rapidly relaxes via Franck-Condon relaxation to an intermediate locally reordered state I. Through interactions with others of its kind, this state collectively orders to form a macroscopically ordered metastable state H, further lowering its energy as a result. The new state has a broken symmetry with respect to the G or E state, and may also involve further relaxation compared to the I state. The barrier E prevents state H from reverting to the ground state G. If the barrier is sufficiently large compared to thermal energy kT, where k is the Boltzmann constant, the H state can be stable indefinitely. | 0 | Theoretical and Fundamental Chemistry |
Reaction kinetics in uniform supersonic flow (, CRESU) is an experiment investigating chemical reactions taking place at very low temperatures.
The technique involves the expansion of a gas or mixture of gases through a de Laval nozzle from a high-pressure reservoir into a vacuum chamber. As it expands, the nozzle collimates the gas into a uniform supersonic beam, which is essentially collision-free and has a temperature that, in the centre-of-mass frame, can be significantly below that of the reservoir gas. Each nozzle produces a characteristic temperature. This way, any temperature between room temperature and about 10 K can be achieved. | 0 | Theoretical and Fundamental Chemistry |
A micelle is an aggregation of surfactants or block copolymer in aqueous solution or organic solution, often spherical. | 0 | Theoretical and Fundamental Chemistry |
Organic chemistry has a strong tradition of naming a specific reaction to its inventor or inventors and a long list of so-called named reactions exists, conservatively estimated at 1000. A very old named reaction is the Claisen rearrangement (1912) and a recent named reaction is the Bingel reaction (1993). When the named reaction is difficult to pronounce or very long as in the Corey–House–Posner–Whitesides reaction it helps to use the abbreviation as in the CBS reduction. The number of reactions hinting at the actual process taking place is much smaller, for example the ene reaction or aldol reaction.
Another approach to organic reactions is by type of organic reagent, many of them inorganic, required in a specific transformation. The major types are oxidizing agents such as osmium tetroxide, reducing agents such as lithium aluminium hydride, bases such as lithium diisopropylamide and acids such as sulfuric acid.
Finally, reactions are also classified by mechanistic class. Commonly these classes are (1) polar, (2) radical, and (3) pericyclic. Polar reactions are characterized by the movement of electron pairs from a well-defined source (a nucleophilic bond or lone pair) to a well-defined sink (an electrophilic center with a low-lying antibonding orbital). Participating atoms undergo changes in charge, both in the formal sense as well as in terms of the actual electron density. The vast majority of organic reactions fall under this category. Radical reactions are characterized by species with unpaired electrons (radicals) and the movement of single electrons. Radical reactions are further divided into chain and nonchain processes. Finally, pericyclic reactions involve the redistribution of chemical bonds along a cyclic transition state. Although electron pairs are formally involved, they move around in a cycle without a true source or sink. These reactions require the continuous overlap of participating orbitals and are governed by orbital symmetry considerations. Of course, some chemical processes may involve steps from two (or even all three) of these categories, so this classification scheme is not necessarily straightforward or clear in all cases. Beyond these classes, transition-metal mediated reactions are often considered to form a fourth category of reactions, although this category encompasses a broad range of elementary organometallic processes, many of which have little in common and very specific. | 0 | Theoretical and Fundamental Chemistry |
The gamma ray sky (see illustration at right) is dominated by the more common and longer-term production of gamma rays that emanate from pulsars within the Milky Way. Sources from the rest of the sky are mostly quasars. Pulsars are thought to be neutron stars with magnetic fields that produce focused beams of radiation, and are far less energetic, more common, and much nearer sources (typically seen only in our own galaxy) than are quasars or the rarer gamma-ray burst sources of gamma rays. Pulsars have relatively long-lived magnetic fields that produce focused beams of relativistic speed charged particles, which emit gamma rays (bremsstrahlung) when those strike gas or dust in their nearby medium, and are decelerated. This is a similar mechanism to the production of high-energy photons in megavoltage radiation therapy machines (see bremsstrahlung). Inverse Compton scattering, in which charged particles (usually electrons) impart energy to low-energy photons boosting them to higher energy photons. Such impacts of photons on relativistic charged particle beams is another possible mechanism of gamma ray production. Neutron stars with a very high magnetic field (magnetars), thought to produce astronomical soft gamma repeaters, are another relatively long-lived star-powered source of gamma radiation. | 0 | Theoretical and Fundamental Chemistry |
Green Infrastructure can be traced as far back as the 17th century in European society beginning in France. France used the presence of nature to provide social and spatial organization to their towns. Originally, nature in cities was used to provide social areas to interact, and plants were grown in these spaces to provide food in close proximity to the inhabitants. In this period, Large open spaces were used to provide a calm setting that could give "sites of power with sites of sanctity" across France. These sites were used by the French elites to bring rural country town house beauty to their new urban houses in a showcase of power and elaborate display of wealth. The French implemented many different types of infrastructure throughout the 17th century that involved incorporating nature in some shape or form. Another example would be the use of promenades that were used by the French elites to flee the unhealthy living conditions of the cities and to avoid the filthy public areas available to the common folks. These areas were lush gardens that had a wide variety of vegetation and foliage that kept the air clean for the wealthy while allowing them to relax away from the poorer members of French society. Again, Mathis goes on to state, "The first cours [or promenades] were established in the capital at the instigation of Marie de Medici: the Mail de l'Arsenal (1604) and above all the Allée du Cours-la-Reine (1616), 1300 mètres long and lined with elms, running along the Seine, from the Tuileries Garden to the high ground of Chaillot," establishing the use of nature as a symbol of power and achievement amongst French royalty and the common people at the time.
Keeping and making cities green were at the forefront for city planners in France. They often incorporated design elements blending urbanism and nature, forming a relationship that showcased how the French grew alongside nature and often made it a key aspect of their expansion.
In 18th Century France, Citizens were able to request to have old and battered city walls destroyed to make room for new gardens, vegetation sites, and green walkways. This opened up new areas to the city landscape and incorporated greenery into the new areas where the walls were torn down. Along with this, the town hall as well as the city center were elaborately decorated with different types of vegetation and trees, especially rare and unique species that had been brought from other countries. Mathis goes on to state, "A French-style garden is linked to the town hall to make the view of it more sublime", showing the use of foliage as a way to impress and beautify French cities. | 1 | Applied and Interdisciplinary Chemistry |
Lactones readily form polyesters according to the formula, and have been shown to oligomerize without catalyst as well:
The double lactone called lactide polymerizes to polylactic acid (polylactide). The resulting materials, polylactic acid, have many attractive properties. | 0 | Theoretical and Fundamental Chemistry |
Crystal twinning occurs when two or more adjacent crystals of the same mineral are oriented so that they share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals that are tightly bonded to each other. The surface along which the lattice points are shared in twinned crystals is called a composition surface or twin plane.
Crystallographers classify twinned crystals by a number of twin laws, which are specific to the crystal structure. The type of twinning can be a diagnostic tool in mineral identification. There are three main types of twinning. The first is growth twinning which can occur both in very large and very small particles. The second is transformation twinning, where there is a change in the crystal structure. The third is deformation twinning, in which twinning develops in a crystal in response to a shear stress, and is an important mechanism for permanent shape changes in a crystal. | 0 | Theoretical and Fundamental Chemistry |
The scientific branch that studies and diagnoses diseases on the cellular level is called cytopathology. Cytopathology is generally used on samples of free cells or tissue fragments, in contrast to the pathology branch of histopathology, which studies whole tissues. Cytopathology is commonly used to investigate diseases involving a wide range of body sites, often to aid in the diagnosis of cancer but also in the diagnosis of some infectious diseases and other inflammatory conditions. For example, a common application of cytopathology is the Pap smear, a screening test used to detect cervical cancer, and precancerous cervical lesions that may lead to cervical cancer. | 1 | Applied and Interdisciplinary Chemistry |
Methylidyne-like species are implied intermediates in the Fischer–Tropsch process, the hydrogenation of CO to produce hydrocarbons. Methylidyne entities are assumed to bond to the catalyst's surface. A hypothetical sequence is:
:MCO + H → MCOH
:MCOH + H → MCH + HO
:MCH + H → MCH
The MCH intermediate has a tridentate methylidine ligand. The methylene ligand (HC) is then poised couple to CO or to another methylene, thereby growing the C–C chain. | 0 | Theoretical and Fundamental Chemistry |
Countries including India and China are electrifying and building new lines at a fast pace. Europe is following this trend but the UK ranks 21st as a percentage electrified. Germany ranks eighth. Worldwide the electrification volume market remains high. Geopolitics and the desire to reduce reliance on oil has once again put rail electrification high on the agenda.
There are a number of reasons why progress in the United Kingdom is much slower. One of the reasons were the delays and cost overruns on the 21st-century modernisation of the Great Western Main Line project. In addition, there were problems with the GOBLIN electrification project. Another reason cited is apportioning blame between the various parties. The boom and bust cycle over the years has also increased costs as expertise is lost. | 1 | Applied and Interdisciplinary Chemistry |
Coacervates are a type of lyophilic colloid; that is, the dense phase retains some of the original solvent – generally water – and does not collapse into solid aggregates, rather keeping a liquid property. Coacervates can be characterized as complex or simple based on the driving force for the LLPS: associative or segregative. Associative LLPS is dominated by attractive interactions between macromolecules (such as electrostatic force between oppositely charged polymers), and segregative LLPS is driven by the minimization of repulsive interactions (such as hydrophobic effect on proteins containing a disordered region).
The thermodynamics of segregative LLPS can be described by a Flory-Huggins polymer mixing model (see equation). In ideal polymer solutions, the free-energy of mixing (ΔG) is negative because the mixing entropy (ΔS, combinatorial in the Flory-Huggins approach) is positive and the interaction enthalpies are all taken as equivalent (ΔH or χ = 0). In non-ideal solutions, ΔH can be different from zero, and the process endothermic enough to overcome the entropic term and favor the de-mixed state (the blue curve shifts up). Low molecular-weight solutes will hardly reach such non-ideality, whereas for polymeric solutes, with increasing interactions sites N and therefore decreasing entropic contribution, simple coacervation is much more likely.
The phase diagram of the mixture can be predicted by experimentally determining the two-phase boundary, or binodal curve. In a simplistic theoretical approach, the binodes are the compositions at which the free energy of de-mixing is minimal (
), across different temperatures (or other interaction parameter). Alternatively, by minimizing the change in free energy of de-mixing in regards to composition (), the spinodal curve is defined. The conditions of the mixture in comparison to the two curves defines the phase separation mechanism: nucleation-growth of coacervate droplets (when the binodal region is crossed slowly) and spinodal decomposition.
Associative LLPS is more complex to describe, as both solute polymers are present in the dilute and dense phase. Electrostatic-based complex coacervates are the most common, and in that case the solutes are two polyelectrolytes of opposite charge. The Voorn-Overbeek approach applies the Debye-Hückel approximation to the enthalpic term in the Flory-Huggins model, and considers two polyelectrolytes of the same length and at the same concentration. Complex coacervates are a subset of aqueous two-phase systems (ATPS), which also include segregatively separated systems in which both phases are enriched in one type of polymer. | 0 | Theoretical and Fundamental Chemistry |
Cheluviation is the process in which the metal ions in the upper layer of the soil are combined with organic ligands to form coordination complexes or chelates, moving downwards through eluviation and then depositing.
Metal ions that can participate in chelation include Fe, Al, Mn, Ca, Mg and trace elements in soil, while the organic ligands combined with these metal ions come mainly from the soil organic matter. Soil organic matter includes relatively stable complex organic compounds (such as lignin, protein, humus, etc.), as well as some simple organic acids and intermediate products of microbial decomposition of organic matter. These organic coordination compounds all contain active groups to varying degrees. Chain organic coordination compounds are complexed with metal ions to generate complexes, and these generated complexes containing multiple coordination atoms in a cyclic structure with metal ions are called chelates. The stability of the chelate is related to the number of atoms in the chelate ring, the stability constant of the chelation reaction, and the concentration of organic chelating agents and metal ions. The chelates produced by fulvic acid and metal ions in soil humus have strong leaching and deposition effects, and therefore are an important manifestation of soil cheluviation, which is generally resulting in the formation of gray-white leaching layers and dark brown/red deposited layer. | 0 | Theoretical and Fundamental Chemistry |
A mass spectrum of an organic compound will usually contain a small peak of one mass unit greater than the apparent molecular ion peak (M) of the whole molecule. This is known as the M+1 peak and comes from the few molecules that contain a C atom in place of a C. A molecule containing one carbon atom will be expected to have an M+1 peak of approximately 1.1% of the size of the M peak, as 1.1% of the molecules will have a C rather than a C. Similarly, a molecule containing two carbon atoms will be expected to have an M+1 peak of approximately 2.2% of the size of the M peak, as there is double the previous likelihood that any molecule will contain a C atom.
In the above, the mathematics and chemistry have been simplified, however it can be used effectively to give the number of carbon atoms for small- to medium-sized organic molecules. In the following formula the result should be rounded to the nearest integer:
where C = number of C atoms, X = amplitude of the M ion peak, and Y = amplitude of the M +1 ion peak.
C-enriched compounds are used in the research of metabolic processes by means of mass spectrometry. Such compounds are safe because they are non-radioactive. In addition, C is used to quantify proteins (quantitative proteomics). One important application is in stable isotope labeling by amino acids in cell culture (SILAC). C-enriched compounds are used in medical diagnostic tests such as the urea breath test. Analysis in these tests is usually of the ratio of C to C by isotope ratio mass spectrometry.
The ratio of C to C is slightly higher in plants employing C4 carbon fixation than in plants employing C3 carbon fixation. Because the different isotope ratios for the two kinds of plants propagate through the food chain, it is possible to determine if the principal diet of a human or other animal consists primarily of C3 plants or C4 plants by measuring the isotopic signature of their collagen and other tissues. | 0 | Theoretical and Fundamental Chemistry |
Graft copolymers are a special type of branched copolymer wherein the side chains are structurally distinct from the main chain. Typically, the main chain is formed from one type of monomer (A) and branches are formed from another monomer (B), or the side-chains have constitutional or configurational features that differ from those in the main chain.
The individual chains of a graft copolymer may be homopolymers or copolymers. Note that different copolymer sequencing is sufficient to define a structural difference, thus an A-B diblock copolymer with A-B alternating copolymer side chains is properly called a graft copolymer.
For example, polystyrene chains may be grafted onto polybutadiene, a synthetic rubber which retains one reactive C=C double bond per repeat unit. The polybutadiene is dissolved in styrene, which is then subjected to free-radical polymerization. The growing chains can add across the double bonds of rubber molecules forming polystyrene branches. The graft copolymer is formed in a mixture with ungrafted polystyrene chains and rubber molecules.
As with block copolymers, the quasi-composite product has properties of both "components." In the example cited, the rubbery chains absorb energy when the substance is hit, so it is much less brittle than ordinary polystyrene. The product is called high-impact polystyrene, or HIPS. | 0 | Theoretical and Fundamental Chemistry |
Metrnl participates in the control of inflammatory responses and is a critical regulator of muscle regeneration. | 1 | Applied and Interdisciplinary Chemistry |
;Magnesium–halogen exchange
Grignard reagents can be prepared by treating a preformed Grignard reagent with an organic halide. This method offers the advantage that the Mg transfer tolerates many functional groups. A typical reaction involves isopropylmagnesium chloride and aryl bromide or iodides:
: i-PrMgCl + ArCl → i-PrCl + ArMgCl
Magnesium ate complexes metalate aryl halides:
: ArBr + Li[MgBu] → ArMgBu + BuBr
;Zinc–halogen exchange
Zinc–halogen exchange:
: LiBuZn + R−I → Li[R−ZnBu] + BuI | 0 | Theoretical and Fundamental Chemistry |
The idea that superfluidity exists inside neutron stars was first proposed by Arkady Migdal. By analogy with electrons inside superconductors forming Cooper pairs because of electron-lattice interaction, it is expected that nucleons in a neutron star at sufficiently high density and low temperature can also form Cooper pairs because of the long-range attractive nuclear force and lead to superfluidity and superconductivity. | 0 | Theoretical and Fundamental Chemistry |
DMAP can be prepared in a two-step procedure from pyridine, which is first oxidized to 4-pyridylpyridinium cation. This cation then reacts with dimethylamine: | 0 | Theoretical and Fundamental Chemistry |
In 1976 Energy completed construction of a new plant on in the Monticello Industrial park. In 1985 Energy Manufacturing Company was sold to CGF Industries of Topeka, Kansas. CGF also purchased an Omaha Nebraska company called "Williams Machine and Tool". In 1997 Energy was purchased by Lincolnshire Partners and in 1999 Energy was purchased by Textron, Inc. Textron ran the company for 5 years until Energy was acquired by an investment group. On November 15, 2005 Energy added to the facility office space for administrative and manufacturing support. | 1 | Applied and Interdisciplinary Chemistry |
The epidermis is the outer layer of cells covering the leaf. It is covered with a waxy cuticle which is impermeable to liquid water and water vapor and forms the boundary separating the plant's inner cells from the external world. The cuticle is in some cases thinner on the lower epidermis than on the upper epidermis, and is generally thicker on leaves from dry climates as compared with those from wet climates. The epidermis serves several functions: protection against water loss by way of transpiration, regulation of gas exchange and secretion of metabolic compounds. Most leaves show dorsoventral anatomy: The upper (adaxial) and lower (abaxial) surfaces have somewhat different construction and may serve different functions.
The epidermis tissue includes several differentiated cell types; epidermal cells, epidermal hair cells (trichomes), cells in the stomatal complex; guard cells and subsidiary cells. The epidermal cells are the most numerous, largest, and least specialized and form the majority of the epidermis. They are typically more elongated in the leaves of monocots than in those of dicots.
Chloroplasts are generally absent in epidermal cells, the exception being the guard cells of the stomata. The stomatal pores perforate the epidermis and are surrounded on each side by chloroplast-containing guard cells, and two to four subsidiary cells that lack chloroplasts, forming a specialized cell group known as the stomatal complex. The opening and closing of the stomatal aperture is controlled by the stomatal complex and regulates the exchange of gases and water vapor between the outside air and the interior of the leaf. Stomata therefore play the important role in allowing photosynthesis without letting the leaf dry out. In a typical leaf, the stomata are more numerous over the abaxial (lower) epidermis than the adaxial (upper) epidermis and are more numerous in plants from cooler climates. | 0 | Theoretical and Fundamental Chemistry |
Immunomodulation and immunoregulation were a particular focus of early myokine research, as, according to Dr. Bente Klarlund Pedersen and her colleagues, "the interactions between exercise and the immune system provided a unique opportunity to evaluate the role of underlying endocrine and cytokine mechanisms."
Muscle has an impact on the trafficking and inflammation of lymphocytes and neutrophils. During exercise, both neutrophils and NK cells and other lymphocytes enter the blood. Long-duration, high-intensity exercise leads to a decrease in the number of lymphocytes, while the concentration of neutrophils increases through mechanisms including adrenaline and cortisol.Interleukin-6 has been shown to mediate the increase in Cortisol: IL-6 stimulates the production of cortisol and therefore induces leukocytosis and lymphocytopenia. | 1 | Applied and Interdisciplinary Chemistry |
Related to the Carothers equation are the following equations (for the simplest case of linear polymers formed from two monomers in equimolar quantities):
where:
:*X is the weight average degree of polymerization,
:*M is the number average molecular weight,
:*M is the weight average molecular weight,
:*M is the molecular weight of the repeating monomer unit,
:*Đ is the dispersity index. (formerly known as polydispersity index, symbol PDI)
The last equation shows that the maximum value of the Đ is 2, which occurs at a monomer conversion of 100% (or p = 1). This is true for step-growth polymerization of linear polymers. For chain-growth polymerization or for branched polymers, the Đ can be much higher.
In practice the average length of the polymer chain is limited by such things as the purity of the reactants, the absence of any side reactions (i.e. high yield), and the viscosity of the medium. | 0 | Theoretical and Fundamental Chemistry |
Understanding the entrance length is important for the design and analysis of flow systems. The entrance region will have different velocity, temperature, and other profiles than exist in the fully developed region of the pipe. | 1 | Applied and Interdisciplinary Chemistry |
* CHCHDCH and CHCHCHD are a pair of structural isotopomers of propane.
* (R)- and (S)-CHCHDOH are isotopic stereoisomers of ethanol.
* (Z)- and (E)-CHCH=CHD are examples of isotopic stereoisomers of propene. | 0 | Theoretical and Fundamental Chemistry |
Boiling-point elevation is the phenomenon whereby the boiling point of a liquid (a solvent) will be higher when another compound is added, meaning that a solution has a higher boiling point than a pure solvent. This happens whenever a non-volatile solute, such as a salt, is added to a pure solvent, such as water. The boiling point can be measured accurately using an ebullioscope. | 0 | Theoretical and Fundamental Chemistry |
Fluoride-containing compounds, such as sodium fluoride or sodium monofluorophosphate are used in topical and systemic fluoride therapy for preventing tooth decay, but the exact biochemical reason is unknown. They are used for water fluoridation and in many products associated with oral hygiene. Originally, sodium fluoride was used to fluoridate water; hexafluorosilicic acid (HSiF) and its salt sodium hexafluorosilicate (NaSiF) are more commonly used additives, especially in the United States. The fluoridation of water is known to prevent tooth decay and is considered by the U.S. Centers for Disease Control and Prevention to be "one of 10 great public health achievements of the 20th century". In some countries where large, centralized water systems are uncommon, fluoride is delivered to the populace by fluoridating table salt. For the method of action for cavity prevention, see Fluoride therapy. Fluoridation of water has its critics (see water fluoridation controversy). Fluoridated toothpaste is in common use. Meta-analysis show the efficacy of 500 ppm fluoride in toothpastes. However, no beneficial effect can be detected when more than one fluoride source is used for daily oral care. | 1 | Applied and Interdisciplinary Chemistry |
The corrosion resistance of a stainless steel is dependent on the presence of an ultra-thin protective oxide film (passive film) on its surface, but it is possible under certain conditions for this oxide film to break down, for example in halide solutions or reducing acids. Areas where the oxide film can break down can also sometimes be the result of the way components are designed, for example under gaskets, in sharp re-entrant corners or associated with incomplete weld penetration or overlapping surfaces. These can all form crevices which can promote corrosion. To function as a corrosion site, a crevice has to be of sufficient width to permit entry of the corrodent, but narrow enough to ensure that the corrodent remains stagnant. Accordingly crevice corrosion usually occurs in gaps a few micrometres wide, and is not found in grooves or slots in which circulation of the corrodent is possible. This problem can often be overcome by paying attention to the design of the component, in particular to avoiding formation of crevices or at least keeping them as open as possible. Crevice corrosion is a very similar mechanism to pitting corrosion; alloys resistant to one are generally resistant to both. Crevice corrosion can be viewed as a less severe form of localized corrosion when compared with pitting. The depth of penetration and the rate of propagation in pitting corrosion are significantly greater than in crevice corrosion.
Crevices can develop a local chemistry which is very different from that of the bulk fluid. For example, in boilers, concentration of non-volatile impurities may occur in crevices near heat-transfer surfaces because of the continuous water vaporization. "Concentration factors" of many millions are not uncommon for common water impurities like sodium, sulfate or chloride ions. The concentration process is often referred to as "hideout" (HO), whereas the opposite process, whereby the concentrations tend to even out (e.g., during shutdown) is called "hideout return" (HOR). In a neutral pH solution, the pH inside the crevice can drop to 2, a highly acidic condition that accelerates the corrosion of most metals and alloys.
For a given crevice type, two factors are important in the initiation of crevice corrosion: the chemical composition of the electrolyte in the crevice and the electrical potential drop into the crevice. Researchers had previously claimed that either one or the other of the two factors was responsible for initiating crevice corrosion, but recently it has been shown that it is a combination of the two that causes active crevice corrosion. Both the drop of potential and the change in composition of the crevice electrolyte are produced by the oxygen depletion of the solution inside the crevice (oxygen consumption caused by the metal oxidation at the inner surface of the occluded cavity) and the separation of electroactive areas, with net anodic reactions (oxidation) occurring within the crevice and net cathodic reactions (reduction) occurring at the exterior of the crevice (on the bold surface). The ratio of the surface areas between the cathodic and anodic region is significant.
Some of the phenomena occurring within the crevice may be somewhat reminiscent of galvanic corrosion:
;galvanic corrosion: two connected metals + single environment
;crevice corrosion: one metal part + two connected environments
The mechanism of crevice corrosion can be (but is not always) similar to that of pitting corrosion. However, there are sufficient differences to warrant a separate treatment. For example, in crevice corrosion, one has to consider the geometry of the crevice and the nature of the concentration process leading to the development of the differential local chemistry. The extreme and often unexpected local chemistry conditions inside the crevice need to be considered. Galvanic effects can play a role in crevice degradation. | 1 | Applied and Interdisciplinary Chemistry |
The oxidative release of natural glycans technique was developed at the center. This process involves household bleach treatment of tissues to release glycans for glycomics. The eventual aim of this approach is to make glycomics accessible by a larger community of scientists by the development of tools which are easily available. | 0 | Theoretical and Fundamental Chemistry |
A pore in a microstructure, unless desired, is a disadvantage for the properties. In fact, in nearly all of the materials, a pore will be the starting point for the rupture of the material. It is the initiation point for the cracks. Furthermore, a pore is usually quite hard to get rid of. Those techniques described later involve a high temperature process. However, even those processes can sometimes make the pore even bigger. Pores with large coordination number (surrounded by many particles) tend to grow during the thermal process. This is caused by the thermal energy being converted to a driving force for the growth of the particles which will induce the growth of the pore as the high coordination number prohibits the growth towards the pore.
For many materials, it can be seen from their phase diagram that multiple phases can exist at the same time. Those different phases might exhibit different crystal structure, thus exhibiting different mechanical properties. Furthermore, these different phases also exhibit a different microstructure (grain size, orientation). This can also improve some mechanical properties as crack deflection can occur, thus pushing the ultimate breakdown further as it creates a more tortuous crack path in the coarser microstructure. | 1 | Applied and Interdisciplinary Chemistry |
Spinning cone columns are used in a form of low temperature vacuum steam distillation to gently extract volatile chemicals from liquid foodstuffs while minimising the effect on the taste of the product. For instance, the columns can be used to remove some of the alcohol from wine, off smells from cream, and to capture aroma compounds that would otherwise be lost in coffee processing. | 0 | Theoretical and Fundamental Chemistry |
The electronic structure of diazo compounds is characterized by π electron density delocalized over the α-carbon and two nitrogen atoms, along with an orthogonal π system with electron density delocalized over only the terminal nitrogen atoms. Because all octet rule-satisfying resonance forms of diazo compounds have formal charges, they are members of a class of compounds known as 1,3-dipoles. Some of the most stable diazo compounds are α-diazo-β-diketones and α-diazo-β-diesters, in which the electron density is further delocalized into an electron-withdrawing carbonyl group. In contrast, most diazoalkanes without electron-withdrawing substituents, including diazomethane itself, are explosive. A commercially relevant diazo compound is ethyl diazoacetate (NCHCOOEt). A group of isomeric compounds with only few similar properties are the diazirines, where the carbon and two nitrogens are linked as a ring.
Four resonance structures can be drawn:
Compounds with the diazo moiety should be distinguished from diazonium compounds, which have the same terminal azo group but bear an overall positive charge, and azo compounds in which the azo group bridges two organic substituents. | 0 | Theoretical and Fundamental Chemistry |
The vertebrate neural retina composed of several layers and distinct cell types (see anatomy of the human retina). A number of these cell types are implicated in retinal diseases, including retinal ganglion cells, which degenerate in glaucoma, the rod and cone photoreceptors, which are responsive to light and degenerate in retinitis pigmentosa, macular degeneration, and other retinal diseases, and the retinal pigment epithelium (RPE), which supports the photoreceptors and is also implicated in retinitis pigmentosa and macular degeneration.
In retinal gene therapy, AAV is capable of "transducing" these various cell types by entering the cells and expressing the therapeutic DNA sequence. Since the cells of the retina are non-dividing, AAV continues to persist and provide expression of the therapeutic DNA sequence over a long time period that can last several years. | 1 | Applied and Interdisciplinary Chemistry |
CARS spectroscopy can be used for temperature measurements; because the CARS signal is temperature dependent. The strength of the signal scales (non-linearly) with the difference in the ground state population and the vibrationally excited state population. Since the population of states follows the temperature dependent Boltzmann distribution, the CARS signal carries an intrinsic temperature dependence as well. This temperature dependence makes CARS a popular technique for monitoring the temperature of hot gases and flames. | 0 | Theoretical and Fundamental Chemistry |
In thermodynamics, a diathermal wall between two thermodynamic systems allows heat transfer but does not allow transfer of matter across it.
The diathermal wall is important because, in thermodynamics, it is customary to assume a priori, for a closed system, the physical existence of transfer of energy across a wall that is impermeable to matter but is not adiabatic, transfer which is called transfer of energy as heat, though it is not customary to label this assumption separately as an axiom or numbered law. | 0 | Theoretical and Fundamental Chemistry |
In the field of molecular biology, the cAMP-dependent pathway, also known as the adenylyl cyclase pathway, is a G protein-coupled receptor-triggered signaling cascade used in cell communication. | 1 | Applied and Interdisciplinary Chemistry |
For isotropic materials the volumetric thermal expansion coefficient is three times the linear coefficient:
This ratio arises because volume is composed of three mutually orthogonal directions. Thus, in an isotropic material, for small differential changes, one-third of the volumetric expansion is in a single axis. As an example, take a cube of steel that has sides of length . The original volume will be and the new volume, after a temperature increase, will be
We can easily ignore the terms as ΔL is a small quantity which on squaring gets much smaller and on cubing gets smaller still.
So
The above approximation holds for small temperature and dimensional changes (that is, when and are small), but it does not hold if trying to go back and forth between volumetric and linear coefficients using larger values of . In this case, the third term (and sometimes even the fourth term) in the expression above must be taken into account.
Similarly, the area thermal expansion coefficient is two times the linear coefficient:
This ratio can be found in a way similar to that in the linear example above, noting that the area of a face on the cube is just . Also, the same considerations must be made when dealing with large values of .
Put more simply, if the length of a cubic solid expands from 1.00 m to 1.01 m, then the area of one of its sides expands from 1.00 m to 1.02 m and its volume expands from 1.00 m to 1.03 m. | 0 | Theoretical and Fundamental Chemistry |
The isolobal analogy has applications beyond simple octahedral complexes. It can be used with a variety of ligands, charged species and non-octahedral complexes. | 0 | Theoretical and Fundamental Chemistry |
In biology, an effector is a general term that can refer to several types of molecules or cells depending on the context:
Small molecule effectors
* A small molecule that selectively binds to a protein to regulate its biological activity can be called an effector. In this manner, effector molecules act as ligands that can increase or decrease enzyme activity, gene expression, influence cell signaling, or other protein functions. An example of such an effector is oxygen, which is an allosteric effector of hemoglobin - oxygen binding to one of the four hemoglobin subunits greatly increases the affinity of the rest of the subunits to oxygen. Certain drug molecules also fall into this category - for example the antibiotic rifampicin used in the treatment of tuberculosis binds the initiation σ factor subunit of the bacterial RNA polymerase, preventing the transcription of bacterial genes.
* The term can also be used to describe small molecules that can directly bind to and regulate the expression of mRNAs. One example for such an effector is guanine, which can be recognised by specific sequences (known as riboswitches) found on mRNAs, and its binding to those sequences prevents the translation of the mRNA into a protein. See also: purine riboswitch.
Protein effectors
* An effector can also be used to refer to a protein that is involved in cellular signal transduction cascades. Such an example are RAS effector proteins, which are all able to bind RAS.GTP, but trigger different cell pathways upon doing so - such as the Ras-Raf-MEK-ERK pathway, the PI3K pathway or several others.
* An effector hormone is a hormone that acts on a particular tissue - an example of such a hormone is thyroxine (T4), which regulates metabolism in many tissues throughout the body.
* Antibody Effectors are effectors involved with the production and secretion of molecules involved in pathogen defense, such as Immunoglobulin. Many antibodies then act as effector molecules for the immune system of the organism.
* Bacterial effector proteins are proteins injected by (usually pathogenic) bacterial cells into the cells of their host. The injected proteins serve different functions dependent on the bacteria of origin, but typically serve the purpose of inhibiting the host cells immune response. An example of these are the Transcription activator-like effector (TALE) proteins secreted by bacteria from the genus Xanthomonas.
* Fungal effectors are secreted by pathogenic or beneficial fungi into and around host cells by invasive hyphae to disable defense components or facilitate colonization. Protein secretion systems in fungi involve the Spitzenkörper.
RNA effectors
* Certain plant pathogens, such as Botrytis cinerea, secrete small RNAs (sRNAs) into the host cells and downregulate plant proteins involved in the immune response by RNA interference.
Effector cells
* In immunology, effector cells are cells of either the innate or the adaptive immune system that mediate the immune response.
* Effector neurons can be used to refer to population of neurons in the nervous system, which are responsible for a certain brain function. An example are the neurons in the mesopontine tegmental anesthesia area (MPTA) of the brainstem, which have been mapped as the region of the brain that is responsive to anaesthetics in a rodent model. | 1 | Applied and Interdisciplinary Chemistry |
Computational findings suggest valence p-orbitals on the metal participate in metal-ligand bonding, albeit weakly. However, Weinhold and Landis within the context of natural bond orbitals do not count the metal p-orbitals in metal-ligand bonding, although these orbitals are still included as polarization functions. This results in a duodectet (12-electron) rule for five d-orbitals and one s-orbital only.
The current consensus in the general chemistry community is that unlike the singular octet rule for main group elements, transition metals do not strictly obey either the 12-electron or 18-electron rule, but that the rules describe the lower bound and upper bound of valence electron count respectively. Thus, while transition metal d-orbital and s-orbital bonding readily occur, the involvement of the higher energy and more spatially diffuse p-orbitals in bonding depends on the central atom and coordination environment. | 0 | Theoretical and Fundamental Chemistry |
Sulfuric acid can be used to produce hydrogen from water:
The compounds of sulfur and iodine are recovered and reused, hence the process is called the sulfur–iodine cycle. This process is endothermic and must occur at high temperatures, so energy in the form of heat has to be supplied. The sulfur–iodine cycle has been proposed as a way to supply hydrogen for a hydrogen-based economy. It is an alternative to electrolysis, and does not require hydrocarbons like current methods of steam reforming. But note that all of the available energy in the hydrogen so produced is supplied by the heat used to make it. | 0 | Theoretical and Fundamental Chemistry |
The function was first introduced by Wu (1952) and has acquired the widely used name rothalpy.
This quantity is commonly called rothalpy, a compound word combining the terms rotation and enthalpy. However, its construction does not conform to the established rules for formation of new words in the English language, namely, that the roots of the new word originate from the same language. The word trothalpy satisfies this requirement as trohos is the Greek root for wheel and enthalpy is to put heat in, whereas rotation is derived from Latin rotare. | 1 | Applied and Interdisciplinary Chemistry |
Gastruloids are three dimensional aggregates of embryonic stem cells (ESCs) that, when cultured in specific conditions, exhibit an organization resembling that of an embryo. They develop with three orthogonal axes and contain the primordial cells for various tissues derived from the three germ layers, without the presence of extraembryonic tissues. Notably, they do not possess forebrain, midbrain, and hindbrain structures. Gastruloids serve as a valuable model system for studying mammalian development, including human development, as well as diseases associated with it. They are a model system an embryonic organoid for the study of mammalian development (including humans) and disease. | 1 | Applied and Interdisciplinary Chemistry |
Fish emulsion is a fertilizer emulsion that is produced from the fluid remains of fish processed for fish oil and fish meal industrially. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, stream thrust averaging is a process used to convert three-dimensional flow through a duct into one-dimensional uniform flow. It makes the assumptions that the flow is mixed adiabatically and without friction. However, due to the mixing process, there is a net increase in the entropy of the system. Although there is an increase in entropy, the stream thrust averaged values are more representative of the flow than a simple average as a simple average would violate the second Law of Thermodynamics. | 1 | Applied and Interdisciplinary Chemistry |
Ionic polymerization is a chain polymerization in which the kinetic-chain carriers are ions or ion pairs. It can be further divided into anionic polymerization and cationic polymerization.
Ionic polymerization generates many polymers used in daily life, such as butyl rubber, polyisobutylene, polyphenylene, polyoxymethylene, polysiloxane, polyethylene oxide, high density polyethylene, isotactic polypropylene, butadiene rubber, etc. Living anionic polymerization was developed in the 1950s. The chain will remain active indefinitely unless the reaction is transferred or terminated deliberately, which allows the control of molar weight and dispersity (or polydispersity index, PDI). | 0 | Theoretical and Fundamental Chemistry |
A preprohormone is the precursor protein to one or more prohormones, which are in turn precursors to peptide hormones. In general, the protein consists of the amino acid chain that is created by the hormone-secreting cell, before any changes have been made to it. It contains a signal peptide, the hormone(s) itself (themselves), and intervening amino acids. Before the hormone is released from the cell, the signal peptide and other amino acids are removed. | 1 | Applied and Interdisciplinary Chemistry |
Pulvermacher patented the chain battery in the US in 1853. This was soon followed by the wearable chain battery belt, or electric belt. Electric belts became enormously popular in the US, far more so than in Europe. This led to the company headquarters being moved to Cincinnati by the 1880s as the Pulvermacher Galvanic Company, but still calling themselves Pulvermacher's of London for the prestige of a European connection. Early models had to be soaked in vinegar before use as in England, but later on models that worked purely by galvanic action with body sweat were introduced. Since the device was being sold essentially as a quack cure it was only necessary to generate enough electricity that the wearer could feel it, no matter how slightly, and know that it was working.
Electric belts were made for every conceivable part of the human anatomy: limbs, abdomen, chest, neck – sometimes all worn at the same time. Pulvermacher even had a model designed to attach to the male genitals in a special sac which was claimed to cure impotence and erectile dysfunction. Pulvermacher promoted a theory that loss of "male vigour" in later life was a consequence of masturbation in early life and that a limited supply of semen, which provided the vigour, would run out before time if wasted. Pulvermacher's device was meant to address this shortcoming.
Competition was very intense for this lucrative market and the claimed benefits became ever more extravagant. Amongst Pulvermachers many competitors in the US were the German Electric Belt Company (actually New York based), Dr Crystals, Dr. Horns, Addisons, Edsons, Edisons, Owens and Heidelbergs. Edisons was founded by Thomas Edison Junior, whose father was the famous Thomas Edison. Owens was originally New York based but expanded across the country until they were put out of business due to fraud. In Europe too, there were competitors. The Medical Battery Company of England made a popular belt. They attempted (unsuccessfully) to sue the Electrical Review when that paper accused them of quackery in 1892. The Iona Company, an Oregon-based company founded by Henry Gaylord Wilshire was still selling belts in 1926 and making large profits: $36,000 ($ inflation adjusted) net from 2,445 belts in five months. By the end of the 1920s the electric belts popularity had severely declined (but not the publics appetite for other quack electric cures) and the scientific market had long since moved on to better electrical generation technology than chain batteries. | 0 | Theoretical and Fundamental Chemistry |
Prior to HPLC, scientists used benchtop column liquid chromatographic techniques. Liquid chromatographic systems were largely inefficient due to the flow rate of solvents being dependent on gravity. Separations took many hours, and sometimes days to complete. Gas chromatography (GC) at the time was more powerful than liquid chromatography (LC), however, it was obvious that gas phase separation and analysis of very polar high molecular weight biopolymers was impossible. GC was ineffective for many life science and health applications for biomolecules, because they are mostly non-volatile and thermally unstable at the high temperatures of GC. As a result, alternative methods were hypothesized which would soon result in the development of HPLC.
Following on the seminal work of Martin and Synge in 1941, it was predicted by Calvin Giddings, Josef Huber, and others in the 1960s that LC could be operated in the high-efficiency mode by reducing the packing-particle diameter substantially below the typical LC (and GC) level of 150 μm and using pressure to increase the mobile phase velocity. These predictions underwent extensive experimentation and refinement throughout the 60s into the 70s until these very days. Early developmental research began to improve LC particles, for example the historic Zipax, a superficially porous particle.
The 1970s brought about many developments in hardware and instrumentation. Researchers began using pumps and injectors to make a rudimentary design of an HPLC system. Gas amplifier pumps were ideal because they operated at constant pressure and did not require leak-free seals or check valves for steady flow and good quantitation. Hardware milestones were made at Dupont IPD (Industrial Polymers Division) such as a low-dwell-volume gradient device being utilized as well as replacing the septum injector with a loop injection valve.
While instrumentation developments were important, the history of HPLC is primarily about the history and evolution of particle technology. After the introduction of porous layer particles, there has been a steady trend to reduced particle size to improve efficiency. However, by decreasing particle size, new problems arose. The practical disadvantages stem from the excessive pressure drop needed to force mobile fluid through the column and the difficulty of preparing a uniform packing of extremely fine materials. Every time particle size is reduced significantly, another round of instrument development usually must occur to handle the pressure. | 0 | Theoretical and Fundamental Chemistry |
Assuming that the concentration of fermions does not change with temperature, then the total chemical potential µ (Fermi level) of the three-dimensional ideal Fermi gas is related to the zero temperature Fermi energy E by a Sommerfeld expansion (assuming ):
where T is the temperature.
Hence, the internal chemical potential, µ-E, is approximately equal to the Fermi energy at temperatures that are much lower than the characteristic Fermi temperature T. This characteristic temperature is on the order of 10 K for a metal, hence at room temperature (300 K), the Fermi energy and internal chemical potential are essentially equivalent. | 0 | Theoretical and Fundamental Chemistry |
Solid-state dewetting of the metal thin films describe the transformation of a thin film into an energetically favoured set of droplets or particles at temperatures well below the melting point. The driving force for dewetting is the minimization of the total energy of the free surfaces of the film and substrate as well as of the film-substrate interface. The dedicated heating stage in SEM has been widely used to accurately control sample temperature through a thermocouple to observe the in-situ behaviour of the material, and can be recorded as a video format. Meanwhile, the two-dimensional morphology can be directly observed and characterised. ie. the partially dewetted Ni film is itself a workable fuel electrode for SOCs as it provides long TPB lines if the structure is fine enough, the connectivity of the nickel and pore phases as well as the TPB lines can be used for SOFC characterisation. | 0 | Theoretical and Fundamental Chemistry |
Thalidomide causes birth defects. The U.S. Food and Drug Administration (FDA) and other regulatory agencies have approved marketing of the drug only with an auditable risk evaluation and mitigation strategy that ensures that people using the drug are aware of the risks and avoid pregnancy; this applies to both men and women, as the drug can be transmitted in semen.
There is a high risk that thalidomide can cause excessive blood clots. There is also a high risk that thalidomide can interfere with production of several types of new blood cells, creating a risk of infection via neutropenia, leukopenia, and lymphopenia, and risks that blood will not clot via thrombocytopenia. There is also a risk of anemia via lack of red blood cells. The drug can also damage nerves, causing potentially irreversible peripheral neuropathy.
Thalidomide has several adverse cardiovascular effects, including risk of heart attacks, pulmonary hypertension, and changes in heart rhythm, such as syncope, bradycardia, and atrioventricular block.
Thalidomide can cause liver damage and severe skin reactions like Stevens–Johnson syndrome. It tends to make people sleepy, which creates risk when driving and operating other machinery. As it kills cancer cells, it can cause tumor lysis syndrome. Thalidomide can prevent menstruation.
In addition, very common (reported in more than 10% of people) adverse effects include tremor, dizziness, tingling, numbness, constipation, and peripheral edema.
Common adverse effects (reported by 1–10% of people) include confusion, depressed mood, reduced coordination, heart failure, difficulty breathing, interstitial lung disease, lung inflammation, vomiting, dry mouth, rashes, dry skin, fever, weakness, and a sense of unwellness. | 0 | Theoretical and Fundamental Chemistry |
Current research on bioremediation techniques is fairly advanced and molecular mechanisms that govern them are well known. However, there are many doubts about the effectiveness and possible adversities of these processes in combination with the addition of agrochemicals. In soils, the role of mycorrhizae on radioactive waste is poorly described and sequestration patterns of radionuclides are not known with certainty.
Longevity effects of some bacterial processes, such as maintenance of uranium in insoluble form because of bioreductions or biomineralizations, are unknown. There are not clear details about the electronic transfer from some radionuclides with these bacterial species either.
Another important aspect is the change of ex situ or laboratory scale processes to their real application in situ, in which soil heterogeneity and environmental conditions generate reproduction deficiencies of optimal biochemical status of the used species, a fact that decreases the efficiency. This implies finding what are the best conditions in which to carry out an efficient bioremediation with anions, metals, organic compounds or other chelating radionuclides that can compete with the uptake of interest radioactive waste. Nevertheless, in many cases research is focused on the extraction of soil and water and its ex situ biological treatment to avoid these problems.
Finally, the potential of GMOs is limited by regulatory agencies in terms of responsibility and bioethical issues. Their release require support on the action zone and comparability with indigenous species. Multidisciplinary research is focused on defining more precisely necessary genes and proteins to establish new cell-free systems which may avoid possible side effects on the environment by the intrusion of transgenic or invasive species. | 1 | Applied and Interdisciplinary Chemistry |
Open channel flow describes cases where flowing liquid has a top surface open to the air; the cross-section of the flow is only determined by the shape of the channel on the lower side, and is variable depending on the depth of liquid in the channel. Techniques appropriate for a fixed cross-section of flow in a pipe are not useful in open channels. Measuring flow in waterways is an important open-channel flow application; such installations are known as stream gauges. | 1 | Applied and Interdisciplinary Chemistry |
The problem of pairwise additivity is completely avoided in the Lifshitz theory, where the molecular structure is ignored and the bodies are treated as continuous media. The forces between the bodies are now derived in terms of their bulk properties, such as dielectric constant and refractive index, which already contain all the necessary information from the original molecular structure.
The original Lifshitz 1955 paper proposed this method relying on quantum field theory principles, and is, in essence, a generalization of the Casimir effect, from two parallel, flat, ideally conducting surfaces, to two surfaces of any material. Later papers by Langbein, Ninham, Parsegian and Van Kampen showed that the essential equations could be derived using much simpler theoretical techniques, an example of which is presented here. | 0 | Theoretical and Fundamental Chemistry |
Localized spins are frustrated if there exist competing exchange interactions that can not all be satisfied at the same time, leading to a large degeneracy of the system's ground state. A triangle of Ising spins (meaning that the only possible orientation of the spins are either "up" or "down"), which interact antiferromagnetically, is a simple example for frustration. In the ground state, two of the spins can be antiparallel but the third one cannot. This leads to an increase of possible orientations (six in this case) of the spins in the ground state, enhancing fluctuations and thus suppressing magnetic ordering.
A recent research work used this concept in analyzing brain networks and surprisingly indicated frustrated interactions in the brain corresponding to flexible neural interactions. This observation highlights the generalization of the frustration phenomenon and proposes its investigation in biological systems. | 0 | Theoretical and Fundamental Chemistry |
Tonics, electrolytes and mineral preparations (including iron preparations and magnesium preparations), parenteral nutrition, vitamins, anti-obesity drugs, anabolic drugs, haematopoietic drugs, food product drugs. | 1 | Applied and Interdisciplinary Chemistry |
F NMR chemical shifts in the literature vary strongly, commonly by over 1 ppm, even within the same solvent. Although the reference compound for F NMR spectroscopy, neat CFCl (0 ppm), has been used since the 1950s, clear instructions on how to measure and deploy it in routine measurements were not present until recently. An investigation of the factors influencing the chemical shift in fluorine NMR spectroscopy revealed the solvent to have the largest effect (Δδ = ±2 ppm or more). A solvent-specific reference table with 5 internal reference compounds has been prepared (CFCl, CHF, PhCF, CF and CFCOH) to allow reproducible referencing with an accuracy of Δδ = ±30 ppb. As the chemical shift of CFCl is also affected by the solvent, care must be taken when using dissolved CFCl as reference compound with regards to the chemical shift of neat CFCl (0 ppm). Example of chemical shifts determined against neat CFCl:
For a complete list the reference compounds chemical shifts in 11 deuterated solvents the reader is referred to the cited literature.
A concise list of appropriately referenced chemical shifts of over 240 fluorinated chemicals has also been recently provided. | 0 | Theoretical and Fundamental Chemistry |
In chemistry a phosphine imide (sometimes abbreviated to phosphinimide) also known as a iminophosphorane is a functional group with the formula RP=NR. While structurally related to phosphine oxide its chemistry has more in common with phosphonium ylides.
Anions of this group, with the structure RP=N, are called phosphinoimidates and are used as ligands to form phosphinimide complexes which are highly active catalysts in some olefin polymerization reactions. | 0 | Theoretical and Fundamental Chemistry |
From the chart, it is evident that the friction factor is never zero, even for smooth pipes because of some roughness at the microscopic level.
The friction factor for laminar flow of Newtonian fluids in round tubes is often taken to be:
where Re is the Reynolds number of the flow.
For a square channel the value used is: | 1 | Applied and Interdisciplinary Chemistry |
Ziryab revolutionized the court at Córdoba and made it the style capital of its time. Whether introducing new clothes, styles, foods, hygiene products, or music, Ziryab changed Andalusian culture forever. Ziryab's musical contributions laid the early groundwork for classic Spanish music. Thanks to his broad contributions, Ziryab became a revolutionary cultural figure in 8th and 9th century Iberia.
Ziryab's students took the trends and inventions he started to North Africa and Europe. | 1 | Applied and Interdisciplinary Chemistry |
Prior to World War II, he worked as a physicist in Berlin and as a colloid chemist in Cambridge. During World War II he joined the Chemical Defence Experimental Station at Porton Down, Wiltshire, but in 1940 was transferred to the Air Ministry's Assistant Directorate of Intelligence (Science) and spent the rest of the war with the Air Ministry. Due to his work he was made Officer of the Most Excellent Order of the British Empire in 1946.
After the war he moved to the University of Bristol Physics Department to do research in solid state physics, but switched to research on crystal dislocation. His work with William Keith Burton and Nicolás Cabrera was to demonstrate the role dislocations played in the growth of crystals.
Apart from crystal defects, his wide-ranging research interests at Bristol included the mechanical properties of polymers, the theory of liquid crystals, the mechanics of the interior of the Earth, and the origin of biological homochirality.
He was appointed Reader in 1951, Melville Wills Professor in 1954 and Henry Overton Wills Professor and Director of the H.H. Wills Physics Laboratory in 1969. He retired in 1976 but remained active in attending conferences, writing papers and corresponding with colleagues well into the 1990s. He edited the Farm Hall Transcripts from Operation Epsilon well into his eighties. | 0 | Theoretical and Fundamental Chemistry |
Hyperactive mTOR pathways have been identified in certain lymphoproliferative diseases such as autoimmune lymphoproliferative syndrome (ALPS), multicentric Castleman disease, and post-transplant lymphoproliferative disorder (PTLD). | 1 | Applied and Interdisciplinary Chemistry |
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