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The growth and development of normal cells follow a cycle in a controlled and ordered manner. When they are damaged, they will die through a process called apoptosis. However, apoptosis is disrupted in cancer cells, allowing them to divide and grow uncontrollably, potentially invading other tissues or organs. They will not undergo the normal death process of body cells.
Hepatocellular carcinoma (HCC) is a prevalent type of liver cancer that accounts for over 80% of cases. It is lethal cancer due to the remarkable drug tolerance, spread potential and high chance of relapse. Scientists have carried out many kinds of research in finding out the risk factors of HCC progression. | 1 | Applied and Interdisciplinary Chemistry |
There are several parameters to consider for optimization of binding-induced electrochemical signal gain. The aptamer probe packing density, the nature of the self-assembling monolayer, and the ACV frequency are factors that affect detecting and measuring of signal. Two main factors are considered when fabricating the packing density on the probe surface. The concentration of aptamer and the surface chemistry of the self-assembling monolayer (SAM) enable variations of desired probe packing density. | 0 | Theoretical and Fundamental Chemistry |
A major challenge in bisulfite sequencing is the degradation of DNA that takes place concurrently with the conversion. The conditions necessary for complete conversion, such as long incubation times, elevated temperature, and high bisulfite concentration, can lead to the degradation of about 90% of the incubated DNA. Given that the starting amount of DNA is often limited, such extensive degradation can be problematic. The degradation occurs as depurinations resulting in random strand breaks. Therefore, the longer the desired PCR amplicon, the more limited the number of intact template molecules will likely be. This could lead to the failure of the PCR amplification, or the loss of quantitatively accurate information on methylation levels resulting from the limited sampling of template molecules. Thus, it is important to assess the amount of DNA degradation resulting from the reaction conditions employed, and consider how this will affect the desired amplicon. Techniques can also be used to minimize DNA degradation, such as cycling the incubation temperature.
In 2020, New England Biolabs developed NEBNext Enzymatic Methyl-seq an alternative enzymatic approach to minimize DNA damage. | 1 | Applied and Interdisciplinary Chemistry |
A study that utilized climate modeling to simulate the effects of predicted increases in water temperature and salinity as a result of climate change on C. finmarchicus of the eastern shelf of North America forecasts lower abundance of copepods. The decrease in favorable environmental conditions is expected to decrease the size and density of C. finmarchius, and will likely have negative effects on whales and other components of the food web that are inextricably tied to copepods. The impact of diapause and variation in seasonal productivity was not explicitly included as increasing model complexity and more accurate accounting for Calanus spp. metabolic processes during diapause is required. The importance of diapause timing with spring plankton blooms is well-established, suggesting that there is potential for additional population impacts as a result of climate change, which would further reverberate throughout the ecosystem. | 0 | Theoretical and Fundamental Chemistry |
It has been noted that radial distribution functions alone are insufficient to characterize structural information. Distinct point processes may possess identical or practically indistinguishable radial distribution functions, known as the degeneracy problem. In such cases, higher order correlation functions are needed to further describe the structure.
Higher-order distribution functions with were less studied, since they are generally less important for the thermodynamics of the system; at the same time, they are not accessible by conventional scattering techniques. They can however be measured by coherent X-ray scattering and are interesting insofar as they can reveal local symmetries in disordered systems. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, a color reaction or colour reaction is a chemical reaction that is used to transform colorless chemical compounds into colored derivatives which can be detected visually or with the aid of a colorimeter.
The concentration of a colorless solution cannot normally be determined with a colorimeter. The addition of a color reagent leads to a color reaction and the absorbance of the colored product can then be measured with a colorimeter.
A change in absorbance in the ultraviolet range cannot be detected by eye but can be measured by a suitably equipped colorimeter. A special colorimeter is required because standard colorimeters cannot operate below a wavelength of 400 nanometers. It is also necessary to use fused quartz cuvettes because glass is opaque to ultraviolet. | 0 | Theoretical and Fundamental Chemistry |
This type of boundary condition is used where boundary values of pressure are known and the exact details of the flow distribution are unknown. This includes pressure inlet and outlet conditions mainly. Typical examples that utilize this boundary condition include buoyancy driven flows, internal flows with multiple outlets, free surface flows and external flows around objects. An example is flow outlet into atmosphere where pressure is atmospheric. | 1 | Applied and Interdisciplinary Chemistry |
There are three types of magnetic effects in electrochemistry:
* on electrolytes
* on mass transfer
* on metal deposition | 0 | Theoretical and Fundamental Chemistry |
Catenation occurs most readily with carbon, which forms covalent bonds with other carbon atoms to form longer chains and structures. This is the reason for the presence of the vast number of organic compounds in nature. Carbon is most well known for its properties of catenation, with organic chemistry essentially being the study of catenated carbon structures (and known as catenae). Carbon chains in biochemistry combine any of various other elements, such as hydrogen, oxygen, and biometals, onto the backbone of carbon.
However, carbon is by no means the only element capable of forming such catenae, and several other main-group elements are capable of forming an expansive range of catenae, including hydrogen, boron, silicon, phosphorus, sulfur and halogens.
The ability of an element to catenate is primarily based on the bond energy of the element to itself, which decreases with more diffuse orbitals (those with higher azimuthal quantum number) overlapping to form the bond. Hence, carbon, with the least diffuse valence shell p orbital is capable of forming longer p-p sigma bonded chains of atoms than heavier elements which bond via higher valence shell orbitals. Catenation ability is also influenced by a range of steric and electronic factors, including the electronegativity of the element in question, the molecular orbital n and the ability to form different kinds of covalent bonds. For carbon, the sigma overlap between adjacent atoms is sufficiently strong that perfectly stable chains can be formed. With other elements this was once thought to be extremely difficult in spite of plenty of evidence to the contrary. | 0 | Theoretical and Fundamental Chemistry |
Electrochemical quartz crystal microbalance (EQCM) is the combination of electrochemistry and quartz crystal microbalance, which was generated in the eighties. Typically, an EQCM device contains an electrochemical cells part and a QCM part. Two electrodes on both sides of the quartz crystal serve two purposes. Firstly, an alternating electric field is generated between the two electrodes for making up the oscillator. Secondly, the electrode contacting electrolyte is used as a working electrode (WE), together with a counter electrode (CE) and a reference electrode (RE), in the potentiostatic circuit constituting the electrochemistry cell. Thus, the working electrode of electrochemistry cell is the sensor of QCM.
As a high mass sensitive in-situ measurement, EQCM is suitable to monitor the dynamic response of reactions at the electrode–solution interface at the applied potential. When the potential of a QCM metal electrode changes, a negative or positive mass change is monitored depending on the ratio of anions adoption on the electrode surface and the dissolution of metal ions into solution. | 0 | Theoretical and Fundamental Chemistry |
A hexagonal phase of lyotropic liquid crystal is formed by some amphiphilic molecules when they are mixed with water or another polar solvent. In this phase, the amphiphile molecules are aggregated into cylindrical structures of indefinite length and these cylindrical aggregates are disposed on a hexagonal lattice, giving the phase long-range orientational order.
In normal topology hexagonal phases, which are formed by type I amphiphiles, the hydrocarbon chains are contained within the cylindrical aggregates such that the polar-apolar interface has a positive mean curvature. Inverse topology hexagonal phases have water within the cylindrical aggregates and the hydrocarbon chains fill the voids between the hexagonally packed cylinders. Normal topology hexagonal phases are denoted by H while inverse topology hexagonal phases are denoted by H. When viewed by polarization microscopy, thin films of both normal and inverse topology hexagonal phases exhibit birefringence, giving rise to characteristic optical textures. Typically, these textures are smoke-like, fan-like or mosaic in appearance. The phases are highly viscous and small air bubbles trapped within the preparation have highly distorted shapes. Size and shapes of lamellar, micellar and hexagonal phases of lipid bilayer phase behavior and mixed lipid polymorphism in aqueous dispersions can be easily identified and characterized by negative staining transmission electron microscopy too. | 0 | Theoretical and Fundamental Chemistry |
The study of materials at extreme conditions, high pressure and high temperature uses a wide array of techniques to achieve these conditions and probe the behavior of material while in the extreme environment. Percy Williams Bridgman, the great pioneer of high-pressure research during the first half of the 20th century, revolutionized the field of high pressures with his development of an opposed anvil device with small flat areas that were pressed one against the other with a lever-arm. The anvils were made of tungsten carbide (WC). This device could achieve pressure of a few gigapascals, and was used in electrical resistance and compressibility measurements.
The first diamond anvil cell was created in 1957-1958. The principles of the DAC are similar to the Bridgman anvils, but in order to achieve the highest possible pressures without breaking the anvils, they were made of the hardest known material: a single crystal diamond. The first prototypes were limited in their pressure range and there was not a reliable way to calibrate the pressure.
The diamond anvil cell became the most versatile pressure generating device that has a single characteristic that sets it apart from the other pressure devices – its optical transparency. This provided the early high pressure pioneers with the ability to directly observe the properties of a material while under pressure. With just the use of an optical microscope, phase boundaries, color changes and recrystallization could be seen immediately, while x-ray diffraction or spectroscopy required time to expose and develop photographic film. The potential for the diamond anvil cell was realized by Alvin Van Valkenburg while he was preparing a sample for IR spectroscopy and was checking the alignment of the diamond faces.
The diamond cell was created at the National Bureau of Standards (NBS) by Charles E. Weir, Ellis R. Lippincott, and Elmer N. Bunting. Within the group, each member focused on different applications of the diamond cell. Van Valkenburg focused on making visual observations, Weir on XRD, Lippincott on IR Spectroscopy. The group members were well experienced in each of their techniques before they began outside collaboration with university researchers such as William A. Bassett and Taro Takahashi at the University of Rochester.
During the first experiments using diamond anvils, the sample was placed on the flat tip of the diamond (the culet) and pressed between the diamond faces. As the diamond faces were pushed closer together, the sample would be pressed and extrude out from the center. Using a microscope to view the sample, it could be seen that a smooth pressure gradient existed across the sample with the outermost portions of the sample acting as a kind of gasket. The sample was not evenly distributed across the diamond culet but localized in the center due to the "cupping" of the diamond at higher pressures. This cupping phenomenon is the elastic stretching of the edges of the diamond culet, commonly referred to as the "shoulder height". Many diamonds were broken during the first stages of producing a new cell or any time an experiment is pushed to higher pressure. The NBS group was in a unique position where almost endless supplies of diamonds were available to them. Customs officials occasionally confiscated diamonds from people attempting to smuggle them into the country. Disposing of such valuable confiscated materials could be problematic given rules and regulations. One solution was simply to make such materials available to people at other government agencies if they could make a convincing case for their use. This became an unrivaled resource as other teams at the University of Chicago, Harvard University, and General Electric entered the high pressure field.
During the following decades DACs have been successively refined, the most important innovations being the use of gaskets and the ruby pressure calibration. The DAC evolved to be the most powerful lab device for generating static high pressure. The range of static pressure attainable today extends to 640 GPa, much higher than the estimated pressures at the Earth's center (~360 GPa). | 0 | Theoretical and Fundamental Chemistry |
In 1964 zidovudine (AZT) was synthesized by Horwitz at the Michigan Cancer Foundation. The 3´hydroxyl group in the deoxyribose ring of thymidine is replaced by an azido group which gives us zidovudine. The lack of the 3´hydroxyl group which provides the attachment point for the next nucleotide in the growing DNA chain during the reverse transcription makes it an obligate chain terminator. Ziduvodine is incorporated in place of thymidine and is an extremely potent inhibitor of HIV replication. This compound had been prepared in 1964 as a potential anti-cancer agent but was shown to be ineffective. In 1974 zidovudine was reported to have activity against retroviruses and was subsequently re-screened as an antiviral when the AIDS epidemic hit Western societies during the mid-1980s. However, zidovudine is relatively toxic since it is converted into the triphosphate by the cellular enzymes and therefore it is activated in uninfected cells. | 1 | Applied and Interdisciplinary Chemistry |
The northern blot is for the detection of specific RNA sequences in complex samples. Northern blotting first separates samples by size via gel electrophoresis before they are transferred to a blotting matrix and detected with labeled RNA probes. | 1 | Applied and Interdisciplinary Chemistry |
* Theodore von Karman Medal, 1976
* Otto Laporte Award, 1977
* Worcester Reed Warner Medal, 1984
* Jean-Leonard-Marie Poiseuille Award, 1986
* Timoshenko Medal, 1991
* Lissner Award for Bioengineering, from ASME
* Borelli Medal, from ASB
* Landis Award, from Microcirculation Society
* Alza Award, from BMES
* Melville Medal, 1994
* United States National Academy of Engineering Founders Award (NAE Founders Award), 1998
* National Medal of Science, 2000
* Fritz J. and Dolores H. Russ Prize, 2007 ("for the characterization and modeling of human tissue mechanics and function leading to prevention and mitigation of trauma.")
* Revelle Medal, from UC San Diego, 2016
Fung was elected to the United States National Academy of Sciences (1993), the National Academy of Engineering (1979), the Institute of Medicine (1991), the Academia Sinica (1968), and was a Foreign Member of the Chinese Academy of Sciences (1994 election). | 1 | Applied and Interdisciplinary Chemistry |
Fluorine is a relatively new element in human applications. In ancient times, only minor uses of fluorine-containing minerals existed. The industrial use of fluorite, fluorines source mineral, was first described by early scientist Georgius Agricola in the 16th century, in the context of smelting. The name "fluorite" (and later "fluorine") derives from Agricolas invented Latin terminology. In the late 18th century, hydrofluoric acid was discovered. By the early 19th century, it was recognized that fluorine was a bound element within compounds, similar to chlorine. Fluorite was determined to be calcium fluoride.
Because of fluorine's tight bonding as well as the toxicity of hydrogen fluoride, the element resisted many attempts to isolate it. In 1886, French chemist Henri Moissan, later a Nobel Prize winner, succeeded in making elemental fluorine by electrolyzing a mixture of potassium fluoride and hydrogen fluoride. Large-scale production and use of fluorine began during World War 2 as part of the Manhattan Project. Earlier in the century, the main fluorochemicals were commercialized by the DuPont company: refrigerant gases (Freon) and polytetrafluoroethylene plastic (Teflon). | 1 | Applied and Interdisciplinary Chemistry |
At the initial stage of his research activity (1911-1917), V. G. Khlopin was mainly concerned with problems related to inorganic and analytical chemistry. In 1913, together with L. A. Chugaev, he worked on the synthesis of complex compounds of platonitrite with dithioethers. Of his further works, especially important are those aimed at the development of a new method for the preparation of various derivatives of univalent nickel, and the creation of a device for determining the solubility of compounds at different temperatures.
To the most interesting works of this period belongs the discovery of hydroxopentamine series of complex compounds of platinum made in 1915 by L. A. Chugaev and V. G. Khlopin; curiously, but methodologically, from the point of view of the theory of cognition, it is quite natural that historically it was made somewhat earlier than the discovery by L. A. Chugaev and N. A. Vladimirov of the pentamine series, later called Chugaev's salts.
Two works hold a special place in this period of V. G. Khlopin's scientific work:
1. The action of hydrosulfur sodium salt on metallic selenium and tellurium, leading to the development of a convenient method of obtaining sodium telluride and selenide and a convenient synthesis of organic compounds of tellurium and selenium (1914),
2. On the action of hydrosulfurosodium salt on nickel salts in the presence of nitrous sodium salt. The work led to the synthesis of univalent nickel derivatives (1915), which were much later (in 1925) obtained in Germany by S. Mansho and co-workers by the action of carbon monoxide and nitric oxide on nickel salts.
Here, at the same department, already in the First World War, on the assignment of the Chemical Committee of the Main Artillery Department, V.G. Khlopin performed his first technological work - he developed a method of obtaining pure platinum from Russian raw materials. The importance of this work was due to the sharp reduction of imports. His participation in several expeditions aimed at identifying Russia's natural resources was subordinated to the solution of the same problems. He wrote reviews on rare elements: boron, lithium, rubidium, cesium and zirconium. | 0 | Theoretical and Fundamental Chemistry |
If a molecule contains two asymmetric centers, there are up to four possible configurations, and they cannot all be non-superposable mirror images of each other. The possibilities for different isomers continue to multiply as more stereocenters are added to a molecule. In general, the number of stereoisomers of a molecule can be determined by calculating 2, where n = the number of chiral centers in the molecule. This holds true except in cases where the molecule has meso forms. These meso compounds are molecules that contain stereocenters, but possess an internal plane of symmetry allowing it to be superposed on its mirror image. These equivalent configurations cannot be considered diastereomers.
For n = 3, there are eight stereoisomers. Among them, there are four pairs of enantiomers: R,R,R and S,S,S; R,R,S and S,S,R; R,S,S and S,R,R; and R,S,R and S,R,S. There are many more pairs of diastereomers, because each of these configurations is a diastereomer with respect to every other configuration excluding its own enantiomer (for example, R,R,R is a diastereomer of R,R,S; R,S,R; and R,S,S). For n = 4, there are sixteen stereoisomers, or eight pairs of enantiomers. The four enantiomeric pairs of aldopentoses and the eight enantiomeric pairs of aldohexoses (subsets of the five- and six-carbon sugars) are examples of sets of compounds that differ in this way. | 0 | Theoretical and Fundamental Chemistry |
The development of the Ferrier carbocyclization has been useful for the synthesis of numerous natural products that contain the carbocycle group. In 1991, Bender and co-workers reported a synthetic route to pure enantiomers of myo-inositol derivatives using this reaction. It has also been applied to the synthesis of aminocyclitols in work done by Barton and co-workers. Finally, Amano et al. used the Ferrier conditions to synthesise complex conjugated cyclohexanones in 1998. | 0 | Theoretical and Fundamental Chemistry |
Electrons are often removed from the electron transport chains to charge NADP with electrons, reducing it to NADPH. Like ATP synthase, ferredoxin-NADP reductase, the enzyme that reduces NADP, releases the NADPH it makes into the stroma, right where it is needed for the dark reactions.
Because NADP reduction removes electrons from the electron transport chains, they must be replaced—the job of photosystem II, which splits water molecules (HO) to obtain the electrons from its hydrogen atoms. | 0 | Theoretical and Fundamental Chemistry |
On the surface of cells, there are many proteins. Some proteins are involved in recognition, attachment, or transportation. The citrate-malate shuttle system consists of citrate shuttle and malate shuttle, which are carrier proteins. Carrier proteins are present on the cell surface. They transport different molecules across the mitochondria. In this system, the substances being transported are malate and citrate.
The starting material is acetyl-CoA. It is a molecule that is involved in ATP synthesis, protein metabolism, and lipid metabolism. As the inner membrane is not permeable to this molecule, acetyl-CoA needs to be converted into other products for effective transport. It is also the first step of the reaction. | 1 | Applied and Interdisciplinary Chemistry |
Faraday concluded after several experiments on electric current in a non-spontaneous process that the mass of the products yielded on the electrodes was proportional to the value of current supplied to the cell, the length of time the current existed, and the molar mass of the substance analyzed. In other words, the amount of a substance deposited on each electrode of an electrolytic cell is directly proportional to the quantity of electricity passed through the cell.
Below is a simplified equation of Faraday's first law:
where
:m is the mass of the substance produced at the electrode (in grams),
:Q is the total electric charge that passed through the solution (in coulombs),
:n is the valence number of the substance as an ion in solution (electrons per ion),
:M is the molar mass of the substance (in grams per mole). | 0 | Theoretical and Fundamental Chemistry |
According to the Poisson summation formula:
is a reciprocal lattice vector of the periodic potential and is the volume of its unit cell. By comparison of (3) and (4), we find that the Laue equation must be satisfied for scattering to occur:
(5) is a statement of the conservation of crystal momentum. Particles scattered in a crystal experience a change in wave vector equal to a reciprocal lattice vector of the crystal. When they do, the contribution to the matrix element is simply a finite constant. Thus, we find an important link between scattered particles and the scattering crystal. The Laue condition, which states that crystal momentum must be conserved, is equivalent to the Bragg condition , which demands constructive interference for scattered particles. Now that we see how the first factor of (3) determines whether or not incident particles are scattered, we consider how the second factor influences scattering. | 0 | Theoretical and Fundamental Chemistry |
Cobalt(II) thiocyanate is an inorganic compound with the formula Co(SCN). The anhydrous compound is a coordination polymer with a layered structure. The trihydrate, Co(SCN)(HO), is a isothiocyanate complex used in the cobalt thiocyanate test (or Scott test) for detecting cocaine. The test has been responsible for widespread false positives and false convictions. | 0 | Theoretical and Fundamental Chemistry |
MHD generators have difficult problems in regard to materials, both for the walls and the electrodes. Materials must not melt or corrode at very high temperatures. Exotic ceramics were developed for this purpose and must be selected to be compatible with the fuel and ionization seed. The exotic materials and the difficult fabrication methods contribute to the high cost of MHD generators.
Also, MHDs work better with stronger magnetic fields. The most successful magnets have been superconducting, and very close to the channel. A major difficulty was refrigerating these magnets while insulating them from the channel. The problem is worse because the magnets work better when they are closer to the channel. There are also severe risks of damage to the hot, brittle ceramics from differential thermal cracking. The magnets are usually near absolute zero, while the channel is several thousand degrees.
For MHDs, both alumina (AlO) and magnesium peroxide (MgO) were reported to work for the insulating walls. Magnesium peroxide degrades near moisture. Alumina is water-resistant and can be fabricated to be quite strong, so in practice, most MHDs have used alumina for the insulating walls.
For the electrodes of clean MHDs (i.e. burning natural gas), one good material was a mix of 80% CeO, 18% ZrO, and 2% TaO.
Coal-burning MHDs have intensely corrosive environments with slag. The slag both protects and corrodes MHD materials. In particular, migration of oxygen through the slag accelerates corrosion of metallic anodes. Nonetheless, very good results have been reported with stainless steel electrodes at 900K. Another, perhaps superior option is a spinel ceramic, FeAlO - FeO. The spinel was reported to have electronic conductivity, absence of a resistive reaction layer but with some diffusion of iron into the alumina. The diffusion of iron could be controlled with a thin layer of very dense alumina, and water cooling in both the electrodes and alumina insulators.
Attaching the high-temperature electrodes to conventional copper bus bars is also challenging. The usual methods establish a chemical passivation layer, and cool the busbar with water. | 1 | Applied and Interdisciplinary Chemistry |
Those phenomena which involve the change in color of a chemical compound under an external stimulus fall under the generic term of chromisms. They take their individual names from the type of the external influence, which can be either chemical or physical, that is involved. Many of these phenomena are reversible. The following list includes all the classic chromisms plus many others of increasing interest in newer outlets.
There are also chromisms which involve two or more stimuli. Examples include:
*Photoelectrochromism – Photovoltachromism – Bioelectrochromism – Solvatophotochromism – Thermosolvatochromism – Halosolvatochromism – Electromechanochromism.
Color changes are also observed on the interaction of metallic nanoparticles and their attached ligands with another stimulus. Examples include plasmonic solvatochromism, plasmonic ionochromism, plasmonic chronochromism and plasmonic vapochromism. | 0 | Theoretical and Fundamental Chemistry |
As an undergraduate, Kowalski attended Millikin University, double majoring in chemistry and mathematics. He completed his PhD in chemistry at University of Washington in 1969 under researcher Tom Isenhour. | 0 | Theoretical and Fundamental Chemistry |
A fundamental assumption in this interpretation of the f-ratio is the spatial separation of primary production and nitrification. Indeed, in their original paper, Eppley & Peterson noted that: "To relate new production to export requires that nitrification in the euphotic zone be negligible." However, subsequent observational work on the distribution of nitrification has found that nitrification can occur at shallower depths, and even within the photic zone.
As the adjacent diagram shows, if ammonium is indeed nitrified to nitrate in the ocean's surface waters it essentially "short circuits" the deep pathway of nitrate. In practice, this would lead to an overestimation of new production and a higher f-ratio, since some of the ostensibly new production would actually be fuelled by recently nitrified nitrate that had never left the surface ocean. After including nitrification measurements in its parameterisation, an ecosystem model of the oligotrophic subtropical gyre region (specifically the BATS site) found that, on an annual basis, around 40% of surface nitrate was recently nitrified (rising to almost 90% during summer). A further study synthesising geographically diverse nitrification measurements found high variability but no relationship with depth, and applied this in a global-scale model to estimate that up to a half of surface nitrate is supplied by surface nitrification rather than upwelling.
Although measurements of the rate of nitrification are still relatively rare, they do suggest that the f-ratio is not as straightforward a proxy for the biological pump as was once thought. For this reason, some workers have proposed distinguishing between the f-ratio and the ratio of particulate export to primary production, which they term the pe-ratio. While quantitatively different from the f-ratio, the pe-ratio shows similar qualitative variation between high productivity/high biomass/high export regimes and low productivity/low biomass/low export regimes.
In addition, a further process that potentially complicates the use of the f-ratio to estimate "new" and "regenerated" production is dissimilatory nitrate reduction to ammonium (DNRA). In low oxygen environments, such as oxygen minimum zones and seafloor sediments, chemoorganoheterotrophic microbes use nitrate as an electron acceptor for respiration, reducing it to nitrite, then to ammonium. Since, like nitrification, DNRA alters the balance in the availability of nitrate and ammonium, it has the potential to introduce inaccuracy to the calculated f-ratio. However, as DNRA's occurrence is limited to anaerobic situations, its importance is less widespread than nitrification, although it can occur in association with primary producers. | 0 | Theoretical and Fundamental Chemistry |
Phosphorus-31 NMR spectroscopy is an analytical chemistry technique that uses nuclear magnetic resonance (NMR) to study chemical compounds that contain phosphorus. Phosphorus is commonly found in organic compounds and coordination complexes (as phosphines), making it useful to measure - NMR spectra routinely. Solution P-NMR is one of the more routine NMR techniques because P has an isotopic abundance of 100% and a relatively high gyromagnetic ratio. The P nucleus also has a spin of , making spectra relatively easy to interpret. The only other highly sensitive NMR-active nuclei spin that are monoisotopic (or nearly so) are H and F. | 0 | Theoretical and Fundamental Chemistry |
In syndiotactic or syntactic macromolecules the substituents have alternate positions along the chain. The macromolecule consists 100% of racemo diads. Syndiotactic polystyrene, made by metallocene catalysis polymerization, is crystalline with a melting point of 161 °C. Gutta percha is also an example for Syndiotactic polymer. | 0 | Theoretical and Fundamental Chemistry |
A Levenspiel plot is a plot used in chemical reaction engineering to determine the required volume of a chemical reactor given experimental data on the chemical reaction taking place in it. It is named after the late chemical engineering professor Octave Levenspiel. | 1 | Applied and Interdisciplinary Chemistry |
Restriction enzyme DNA assembly has cloning standards to minimize the change in cloning efficiency and the function of the plasmid, which can be caused by compatibility of the restriction sites on the insert and those on the vector.
Golden Gate assembly's cloning standards have two tiers. First-tier Golden Gate assembly constructs the single-gene construct by adding in genetic elements such as promoter, open reading frames, and terminators. Then, second-tier Golden Gate assembly combine several constructs made in first-tier assembly to make a multigene construct. To achieve second-tier assembly, modular cloning (MoClo) system and GoldenBraid2.0 standard are used. | 1 | Applied and Interdisciplinary Chemistry |
One researcher has documented that "Laudanum, as listed in the London Pharmacopoeia (1618), was a pill made from opium, saffron, castor, ambergris, musk and nutmeg". | 1 | Applied and Interdisciplinary Chemistry |
The symmetry factor (or barrier symmetry factor) is a coefficient similar to the transfer coefficient, but applicable only to single-step reactions.
The sum of anodic symmetry factor and cathodic symmetry factor is equal to one: | 0 | Theoretical and Fundamental Chemistry |
In the case of a scale-invariant type of system (where a system of volume has exactly the same set of microstates as systems of volume ), then when the system expands new particles and energy will flow in from the reservoir to fill the new volume with a homogeneous extension of the original system.
The pressure, then, must be constant with respect to changes in volume:
and all extensive quantities (particle number, energy, entropy, potentials, ...) must grow linearly with volume, e.g.
In this case we simply have , as well as the familiar relationship for the Gibbs free energy.
The value of can be understood as the work that can be extracted from the system by shrinking it down to nothing (putting all the particles and energy back into the reservoir). The fact that is negative implies that the extraction of particles from the system to the reservoir requires energy input.
Such homogeneous scaling does not exist in many systems. For example, when analyzing the ensemble of electrons in a single molecule or even a piece of metal floating in space, doubling the volume of the space does double the number of electrons in the material.
The problem here is that, although electrons and energy are exchanged with a reservoir, the material host is not allowed to change.
Generally in small systems, or systems with long range interactions (those outside the thermodynamic limit), . | 0 | Theoretical and Fundamental Chemistry |
See below. Most stars, including the Sun, generate energy over most of their lives by fusing hydrogen into heavier elements; yet such fusion of light hydrogen (protium) has never been successful in the conditions attainable on Earth. Thus, all artificial fusion, including the hydrogen fusion in hydrogen bombs, requires heavy hydrogen (deuterium, tritium, or both). | 0 | Theoretical and Fundamental Chemistry |
It is prepared by disulfonation of naphthalene with oleum:
:CH + 2 SO → CH(SOH)
Further sulfonation gives The 1,3,5-trisulfonic acid derivative. | 0 | Theoretical and Fundamental Chemistry |
has an extended (chain or network) structure in which xenon and oxygen have coordination numbers of four and two respectively. The geometry at xenon is square planar, consistent with VSEPR theory for four ligands and two lone pairs (or AXE in the notation of VSEPR theory).
In addition, the existence of an XeO molecule was predicted by an ab initio quantum chemistry method several years earlier by Pyykkö and Tamm, but these authors did not consider an extended structure. | 0 | Theoretical and Fundamental Chemistry |
Metalworking generally is divided into three categories: forming, cutting, and joining. Most metal cutting is done by high speed steel tools or carbide tools. Each of these categories contains various processes.
Prior to most operations, the metal must be marked out and/or measured, depending on the desired finished product.
Marking out (also known as layout) is the process of transferring a design or pattern to a workpiece and is the first step in the handcraft of metalworking. It is performed in many industries or hobbies, although in industry, the repetition eliminates the need to mark out every individual piece. In the metal trades area, marking out consists of transferring the engineer's plan to the workpiece in preparation for the next step, machining or manufacture.
Calipers are hand tools designed to precisely measure the distance between two points. Most calipers have two sets of flat, parallel edges used for inner or outer diameter measurements. These calipers can be accurate to within one-thousandth of an inch (25.4 μm). Different types of calipers have different mechanisms for displaying the distance measured. Where larger objects need to be measured with less precision, a tape measure is often used. | 1 | Applied and Interdisciplinary Chemistry |
Retention uniformity, or R, is a concept in thin layer chromatography. It is designed for the quantitative measurement of equal-spreading of the spots on the chromatographic plate and is one of the Chromatographic response functions. | 0 | Theoretical and Fundamental Chemistry |
It is worth reiterating that magma chambers are not usually static single entities. The typical magma chamber is formed from a series of injections of melt and magma, and most are also subject to some form of partial melt extraction.
Granite magmas are generally much more viscous than mafic magmas and are usually more homogeneous in composition. This is generally considered to be caused by the viscosity of the magma, which is orders of magnitude higher than mafic magmas. The higher viscosity means that, when melted, a granitic magma will tend to move in a larger concerted mass and be emplaced as a larger mass because it is less fluid and able to move. This is why granites tend to occur as large plutons, and mafic rocks as dikes and sills.
Granites are cooler and are therefore less able to melt and assimilate country rocks. Wholesale contamination is therefore minor and unusual, although mixing of granitic and basaltic melts is not unknown where basalt is injected into granitic magma chambers.
Mafic magmas are more liable to flow, and are therefore more likely to undergo periodic replenishment of a magma chamber. Because they are more fluid, crystal precipitation occurs much more rapidly, resulting in greater changes by fractional crystallisation. Higher temperatures also allow mafic magmas to assimilate wall rocks more readily and therefore contamination is more common and better developed. | 0 | Theoretical and Fundamental Chemistry |
A detailed and comprehensive literature review on the various aspects of sophorolipids production (e.g. producing micro-organisms, bio-synthetic pathway, effect of medium components and other fermentation conditions and downstream process of sophorolipids is available in the published work of Van Bogaert et al. This work also discusses potential application of sophorolipids (and their derivatives) as well as the potential for genetic engineering strains to enhance sophorolipid yields. Researchers have focused on optimization of sophorolipid production in submerged fermentation, but some efforts have also investigated the possibility of sophorololipid production using solid state fermentation (SSF). The production process can be significantly impacted by the specific properties of the carbon and oil substrates used; and several inexpensive alternatives to more traditional substrates have been investigated. These potential substrates include: biodiesel by-product streams, waste frying oil, restaurant waste oil, industrial fatty acid residues, mango seed fat, and soybean dark oil. The use of most of these substrates have resulted in lower yields compared to traditional fermentation substrates. | 0 | Theoretical and Fundamental Chemistry |
Intuitively, the slightly deformed eigenfunctions of the full Hamiltonian H are the in and out states. The are noninteracting states that resemble the in and out states in the infinite past and infinite future. | 0 | Theoretical and Fundamental Chemistry |
In an isotropic and linear medium, this polarization field P is proportional and parallel to the electric field E:
where χ is the electric susceptibility of the medium. The relation between D and E is thus:
where
is the dielectric constant of the medium. The value 1+χ is called the relative permittivity of the medium, and is related to the refractive index n, for non-magnetic media, by | 0 | Theoretical and Fundamental Chemistry |
Retinitis pigmentosa is an inherited disease which leads to progressive night blindness and loss of peripheral vision as a result of photoreceptor cell death. Most people who suffer from RP are born with rod cells that are either dead or dysfunctional, so they are effectively blind at nighttime, since these are the cells responsible for vision in low levels of light. What follows often is the death of cone cells, responsible for color vision and acuity, at light levels present during the day. Loss of cones leads to full blindness as early as five years old, but may not onset until many years later. There have been multiple hypotheses about how the lack of rod cells can lead to the death of cone cells. Pinpointing a mechanism for RP is difficult because there are more than 39 genetic loci and genes correlated with this disease. In an effort to find the cause of RP, there have been different gene therapy techniques applied to address each of the hypotheses.
Different types of inheritance can attribute to this disease; autosomal recessive, autosomal dominant, X-linked type, etc. The main function of rhodopsin is initiating the phototransduction cascade. The opsin proteins are made in the photoreceptor inner segments, then transported to the outer segment, and eventually phagocytized by the RPE cells. When mutations occur in the rhodopsin the directional protein movement is affected because the mutations can affect protein folding, stability, and intracellular trafficking. One approach is introducing AAV-delivered ribozymes designed to target and destroy a mutant mRNA.
The way this system operates was shown in animal model that have a mutant rhodopsin gene. The injected AAV-ribozymes were optimized in vitro and used to cleave the mutant mRNA transcript of P23H (where most mutation occur) in vivo.
Another mutation in the rhodopsin structural protein, specifically peripherin 2 which is a membrane glycoprotein involved in the formation of photoreceptor outersegment disk, can lead to recessive RP and macular degeneration in human (19). In a mouse experiment, AAV2 carrying a wild-type peripherin 2 gene driven by a rhodopsin promoter was delivered to the mice by subretinal injection. The result showed improvement in photoreceptor structure and function which was detected by ERG (electroretinogram). The result showed improvement of photoreceptor structure and function which was detected by ERG. Also peripherin 2 was detected at the outer segment layer of the retina 2 weeks after injection and therapeutic effects were noted as soon as 3 weeks after injection. A well-defined outer segment containing both peripherin2 and rhodopsin was present 9-month after injection.
Since apoptosis can be the cause of photoreceptor death in most of the retinal dystrophies. It has been known that survival factors and antiapoptoic reagents can be an alternative treatment if the mutation is unknown for gene replacement therapy. Some scientists have experimented with treating this issue by injecting substitute trophic factors into the eye. One group of researchers injected the rod derived cone viability factor (RdCVF) protein (encoded for by the Nxnl1 (Txnl6) gene) into the eye of the most commonly occurring dominant RP mutation rat models. This treatment demonstrated success in promoting the survival of cone activity, but the treatment served even more significantly to prevent progression of the disease by increasing the actual function of the cones. Experiments were also carried out to study whether supplying AAV2 vectors with cDNA for glial cell line-derived neurotrophic factor (GDNF) can have an anti-apoptosis effect on the rod cells.
In looking at an animal model, the opsin transgene contains a truncated protein lacking the last 15 amino acids of the C terminus, which causes alteration in rhodopsin transport to the outer segment and leads to retinal degeneration. When the AAV2-CBA-GDNF vector is administered to the subretinal space, photoreceptor stabilized and rod photoreceptors increased and this was seen in the improved function of the ERG analysis. Successful experiments in animals have also been carried out using ciliary neurotrophic factor (CNTF), and CNTF is currently being used as a treatment in human clinical trials. | 1 | Applied and Interdisciplinary Chemistry |
In 1954, charge-transfer salts derived from perylene with iodine or bromine were reported with resistivities as low as 8 ohm·cm. In 1973, it was discovered that a combination of tetracyanoquinodimethane (TCNQ) and tetrathiafulvalene (TTF) forms a strong charge-transfer complex referred to as TTF-TCNQ. The solid shows almost metallic electrical conductance and was the first-discovered purely organic conductor. In a TTF-TCNQ crystal, TTF and TCNQ molecules are arranged independently in separate parallel-aligned stacks, and an electron transfer occurs from donor (TTF) to acceptor (TCNQ) stacks. Hence, electrons and electron holes are separated and concentrated in the stacks and can traverse in a one-dimensional direction along the TCNQ and TTF columns, respectively, when an electric potential is applied to the ends of a crystal in the stack direction.
Superconductivity is exhibited by tetramethyl-tetraselenafulvalene-hexafluorophosphate (TMTSFPF), which is a semi-conductor at ambient conditions, shows superconductivity at low temperature (critical temperature) and high pressure: 0.9 K and 12 kbar. Critical current densities in these complexes are very small. | 0 | Theoretical and Fundamental Chemistry |
With the current methods, the instrumental error in the measured hairpin length is 1-1.5 nm. The length of a basepair, or 2 extended single-stranded nucleotides, is approximately 0.85 nm. Therefore, the resolution of the system is at a few nucleotides. The sources of noise arise from length-dependent Brownian motion of the bead anchored by the extended hairpin, statistical error in bead position determination, and slow mechanical drifts. However, as mentioned earlier, such resolution is sufficient for the current sequencing method because changes in >4 nm are being measured. | 1 | Applied and Interdisciplinary Chemistry |
Plutonium silicide forms gray crystals of orthorhombic crystal system, space group Pnma, cell parameters: a = 0.7933 nm, b = 0.3847 nm, c = 0.5727 nm, Z = 4, TiSi type structure.
At a temperature of 72 K, plutonium silicide undergoes a ferromagnetic transition. | 0 | Theoretical and Fundamental Chemistry |
C/EBP proteins interact with the CCAAT (cytosine-cytosine-adenosine-adenosine-thymidine) box motif, which is present in several gene promoters. They are characterized by a highly conserved basic-leucine zipper (bZIP) domain at the C-terminus. This domain is involved in dimerization and DNA binding, as are other transcription factors of the leucine zipper domain-containing family (c-Fos and c-jun). The bZIP domain structure of C/EBPs is composed of an α-helix that forms a "coiled coil" structure when it dimerizes. Members of the C/EBP family can form homodimers or heterodimers with other C/EBPs and with other transcription factors, which may or may not contain the leucine zipper domain. The dimerization is necessary to enable C/EBPs to bind specifically to DNA through a palindromic sequence in the major groove of the DNA. C/EBP proteins also contain activation domains at the N-terminus and regulatory domains.
These proteins are found in hepatocytes, adipocytes, hematopoietic cells, spleen, kidney, brain, and many other organs. C/EBP proteins are involved in different cellular responses, such as in the control of cellular proliferation, growth and differentiation, in metabolism, and in immunity. Nearly all the members of the C/EBP family can induce transcription through their activation domains by interacting with components of the basal transcription apparatus. (C/EBPγ is an exception that lacks a functional transcriptional activation domain.) Their expression is regulated at multiple levels, including through hormones, mitogens, cytokines, nutrients, and other factors.
This protein is expressed in the mammalian nervous system and plays a significant role in the development and function of nerve cells. C/EBPβ plays a role in neuronal differentiation, in learning, in memory processes, in glial and neuronal cell functions, and in neurotrophic factor expression. | 1 | Applied and Interdisciplinary Chemistry |
The side effects of flutamide are sex-dependent. In men, a variety of side effects related to androgen deprivation may occur, the most common being gynecomastia and breast tenderness. Others include hot flashes, decreased muscle mass, decreased bone mass and an associated increased risk of fractures, depression, and sexual dysfunction including reduced libido and erectile dysfunction. In women, flutamide is, generally, relatively well tolerated, and does not interfere with ovulation. The only common side effect of flutamide in women is dry skin (75%), which can be attributed to a reduction of androgen-mediated sebum production. General side effects that may occur in either sex include dizziness, lack of appetite, gastrointestinal side effects such as nausea, vomiting, and diarrhea, a greenish-bluish discoloration of the urine, and hepatic changes. Because flutamide is a pure antiandrogen, unlike steroidal antiandrogens like cyproterone acetate and megestrol acetate (which additionally possess progestogenic activity), it does not appear to have a risk of cardiovascular side effects (e.g., thromboembolism) or fluid retention. | 0 | Theoretical and Fundamental Chemistry |
In sensory neurons, action potentials result from an external stimulus. However, some excitable cells require no such stimulus to fire: They spontaneously depolarize their axon hillock and fire action potentials at a regular rate, like an internal clock. The voltage traces of such cells are known as pacemaker potentials. The cardiac pacemaker cells of the sinoatrial node in the heart provide a good example. Although such pacemaker potentials have a natural rhythm, it can be adjusted by external stimuli; for instance, heart rate can be altered by pharmaceuticals as well as signals from the sympathetic and parasympathetic nerves. The external stimuli do not cause the cell's repetitive firing, but merely alter its timing. In some cases, the regulation of frequency can be more complex, leading to patterns of action potentials, such as bursting. | 0 | Theoretical and Fundamental Chemistry |
Sevoflurane is a greenhouse gas. The twenty-year global-warming potential, GWP(20), for sevoflurane is 349. | 1 | Applied and Interdisciplinary Chemistry |
Hexacoordinate phosphorus molecules involving nitrogen, oxygen, or sulfur ligands provide examples of Lewis acid-Lewis base hexacoordination. For the two similar complexes shown below, the length of the C–P bond increases with decreasing length of the N–P bond; the strength of the C–P bond decreases with increasing strength of the N–P Lewis acid–Lewis base interaction. | 0 | Theoretical and Fundamental Chemistry |
"Biological activity is a dominant force shaping the chemical structure and evolution of the earth surface environment. The presence of an oxygenated atmosphere-hydrosphere surrounding an otherwise highly reducing solid earth is the most striking consequence of the rise of life on earth. Biological evolution and the functioning of ecosystems, in turn, are to a large degree conditioned by geophysical and geological processes. Understanding the interactions between organisms and their abiotic environment, and the resulting coupled evolution of the biosphere and geosphere is a central theme of research in biogeology. Biogeochemists contribute to this understanding by studying the transformations and transport of chemical substrates and products of biological activity in the environment."
"Since the Cambrian explosion, mineralized body parts have been secreted in large quantities by biota. Because calcium carbonate, silica and calcium phosphate are the main mineral phases constituting these hard parts, biomineralization plays an important role in the global biogeochemical cycles of carbon, calcium, silicon and phosphorus" | 0 | Theoretical and Fundamental Chemistry |
Moroidin is one of several biologically active compounds isolated from the venom of Dendrocnide moroides, a member of the stinging nettle family. The plant stores its venom in silica hairs that break off when touched, delivering the toxins through the skin and inducing extreme pain. Moroidin also produces a similar pain response when injected subdermally, so it is thought to be partially responsible for the plant’s toxicity. However, moroidin injections are not as potent as injections of crude matter isolated from Dendrocnide moroides, suggesting that there are additional stinging toxins in the venom. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, an acyl halide (also known as an acid halide) is a chemical compound derived from an oxoacid by replacing a hydroxyl group () with a halide group (, where X is a halogen).
If the acid is a carboxylic acid (), the compound contains a functional group, which consists of a carbonyl group () singly bonded to a halogen atom. The general formula for such an acyl halide can be written RCOX, where R may be, for example, an alkyl group, CO is the carbonyl group, and X represents the halide, such as chloride. Acyl chlorides are the most commonly encountered acyl halides, but acetyl iodide is the one produced (transiently) on the largest scale. Billions of kilograms are generated annually in the production of acetic acid. | 0 | Theoretical and Fundamental Chemistry |
Polyoxotechnetates form only in strongly acidic conditions, such as in pertechnetic acid| or trifluoromethanesulfonic acid solutions. The first empirically isolated polyoxotechnetate was the red . It contains both Tc(V) and Tc(VII) in ratio 4: 16 and is obtained as the hydronium salt by concentrating an solution. Corresponding ammonium polyoxotechnetate salt was recently isolated from trifluoromethanesulfonic acid and it has very similar structure.
The only polyoxorhenate formed in acidic conditions in presence of pyrazolium cation. The first empirically isolated polyoxorhenate was the white . It contains Re(VII) in both octahedral and tetrahedral coordination. | 0 | Theoretical and Fundamental Chemistry |
At the moment of death, carbon uptake is ended. Considering that tissue that contained the bomb pulse C was rapidly diminishing with a rate of 4% per year, it has been possible to establish the time of death of two women in a court case by examining tissues with a rapid turnover. Another important application has been the identification of victims of the Southeast Asian tsunami 2004 by examining their teeth. | 0 | Theoretical and Fundamental Chemistry |
American chemist Sherry Yennello has called him the "grandfather of superheavy elements". Oganessian is the author of three discoveries, a monograph, 11 inventions, and more than 300 scientific papers.
Oganessian has been considered worthy of a Nobel laureate in Chemistry, including by Alexander Sergeev, former head of the Russian Academy of Sciences. | 1 | Applied and Interdisciplinary Chemistry |
Electron magnetic circular dichroism (EMCD) (also known as electron energy-loss magnetic chiral dichroism) is the EELS equivalent of XMCD.
The effect was first proposed in 2003 and experimentally confirmed in 2006 by the group of Prof. Peter Schattschneider at the Vienna University of Technology.
Similarly to XMCD, EMCD is a difference spectrum of two EELS spectra taken in a magnetic field with opposite helicities. Under appropriate scattering conditions virtual photons with specific circular polarizations can be absorbed, giving rise to spectral differences. The largest difference is expected between the case where one virtual photon with left circular polarization and one with right circular polarization are absorbed. By closely analyzing the difference in the EMCD spectrum, information can be obtained on the magnetic properties of the atom, such as its spin and orbital magnetic moment.
In the case of transition metals such as iron, cobalt, and nickel, the absorption spectra for EMCD are usually measured at the L-edge. This corresponds to the excitation of a 2p electron to a 3d state by the absorption of a virtual photon providing the ionisation energy. The absorption is visible as a spectral feature in the electron energy loss spectrum (EELS). Because the 3d electron states are the origin of the magnetic properties of the elements, the spectra contain information on the magnetic properties. Moreover, since the energy of each transition depends on the atomic number, the information obtained is element specific, that is, it is possible to distinguish the magnetic properties of a given element by examining the EMCD spectrum at its characteristic energy (708 eV for iron).
Since in both EMCD and XMCD the same electronic transitions are probed, the information obtained is the same. However EMCD has a higher spatial resolution and depth sensitivity than its X-ray counterpart. Moreover, EMCD can be measured on any TEM equipped with an EELS detector, whereas XMCD is normally measured only on dedicated synchrotron beamlines.
A disadvantage of EMCD in its original incarnation is its requirement of crystalline materials with a thickness and orientation that just precisely gives the correct 90 degree phase shift needed for EMCD. However, a new method has recently demonstrated that electron vortex beams can also be used to measure EMCD without the geometrical constraints of the original procedure. | 0 | Theoretical and Fundamental Chemistry |
Anomers are different in structure, and thus have different stabilizing and destabilizing effects from each other. The major contributors to the stability of a certain anomer are:
*The anomeric effect, which stabilizes the anomer that has an electron withdrawing group (typically an oxygen or nitrogen atom) in axial orientation on the ring. This effect is abolished in polar solvents such as water.
*1,3-diaxial interactions, which usually destabilize the anomer that has the anomeric group in an axial orientation on the ring. This effect is especially noticeable in pyranoses and other six-membered ring compounds. This is a major factor in water.
*Hydrogen bonds between the anomeric group and other groups on the ring, leading to stabilization of the anomer.
*Dipolar repulsion between the anomeric group and other groups on the ring, leading to destabilization of the anomer.
For -glucopyranoside, the β-anomer is the more stable anomer in water. For -mannopyranose, the α-anomer is the more stable anomer.
Because anomers are diastereomers of each other, they often differ in physical and chemical properties. One of the most important physical properties that is used to study anomers is the specific rotation, which can be monitored by polarimetry. | 0 | Theoretical and Fundamental Chemistry |
Guliye trained many other scientists. From 1951 to 1960 he was the Chair of Organic Chemistry in Baku State University. From 1960 to 1974, he chaired the department. In 1958, Guliyev was elected a correspondent member of Azerbaijan, and in 1959, academician of AS of Azerbaijan. | 0 | Theoretical and Fundamental Chemistry |
The boiling point elevation is a colligative property, which means that it is dependent on the presence of dissolved particles and their number, but not their identity. It is an effect of the dilution of the solvent in the presence of a solute. It is a phenomenon that happens for all solutes in all solutions, even in ideal solutions, and does not depend on any specific solute–solvent interactions. The boiling point elevation happens both when the solute is an electrolyte, such as various salts, and a nonelectrolyte. In thermodynamic terms, the origin of the boiling point elevation is entropic and can be explained in terms of the vapor pressure or chemical potential of the solvent. In both cases, the explanation depends on the fact that many solutes are only present in the liquid phase and do not enter into the gas phase (except at extremely high temperatures).
Put in vapor pressure terms, a liquid boils at the temperature when its vapor pressure equals the surrounding pressure. For the solvent, the presence of the solute decreases its vapor pressure by dilution. A nonvolatile solute has a vapor pressure of zero, so the vapor pressure of the solution is less than the vapor pressure of the solvent. Thus, a higher temperature is needed for the vapor pressure to reach the surrounding pressure, and the boiling point is elevated.
Put in chemical potential terms, at the boiling point, the liquid phase and the gas (or vapor) phase have the same chemical potential (or vapor pressure) meaning that they are energetically equivalent. The chemical potential is dependent on the temperature, and at other temperatures either the liquid or the gas phase has a lower chemical potential and is more energetically favorable than the other phase. This means that when a nonvolatile solute is added, the chemical potential of the solvent in the liquid phase is decreased by dilution, but the chemical potential of the solvent in the gas phase is not affected. This means in turn that the equilibrium between the liquid and gas phase is established at another temperature for a solution than a pure liquid, i.e., the boiling point is elevated.
The phenomenon of freezing-point depression is analogous to boiling point elevation. However, the magnitude of the freezing point depression is larger than the boiling point elevation for the same solvent and the same concentration of a solute. Because of these two phenomena, the liquid range of a solvent is increased in the presence of a solute. | 0 | Theoretical and Fundamental Chemistry |
Hattori and De Hoog, after considering the debate surrounding the cause of varying oxidation conditions in igneous rocks at shallow crustal levels, documented that highly oxidized conditions of rocks are an intrinsic character of the source magma in the mantle. They emphasized the capability of oxidized magmas to transport large quantities of sulfur and metals as well.
In her 1995 work, Hattori provided the initial documentation of oxidized arsenic in the overall reduced mantle, as arsenic is present by replacing Si. One of her PhD students, Jian Wangm, evaluated the redox state of mantle rocks and discovered that carbon is the primary control for the oxidation conditions of the mantle in subduction zones. | 0 | Theoretical and Fundamental Chemistry |
When the electrons in the atom are excited, for example by being heated, the additional energy pushes the electrons to higher energy orbitals. When the electrons fall back down and leave the excited state, energy is re-emitted in the form of a photon. The wavelength (or equivalently, frequency) of the photon is determined by the difference in energy between the two states. These emitted photons form the element's spectrum.
The fact that only certain colors appear in an element's atomic emission spectrum means that only certain frequencies of light are emitted. Each of these frequencies are related to energy by the formula:
where is the energy of the photon, is its frequency, and is Planck's constant.
This concludes that only photons with specific energies are emitted by the atom. The principle of the atomic emission spectrum explains the varied colors in neon signs, as well as chemical flame test results (described below).
The frequencies of light that an atom can emit are dependent on states the electrons can be in. When excited, an electron moves to a higher energy level or orbital. When the electron falls back to its ground level the light is emitted.
The above picture shows the visible light emission spectrum for hydrogen. If only a single atom of hydrogen were present, then only a single wavelength would be observed at a given instant. Several of the possible emissions are observed because the sample contains many hydrogen atoms that are in different initial energy states and reach different final energy states. These different combinations lead to simultaneous emissions at different wavelengths. | 0 | Theoretical and Fundamental Chemistry |
The ore to be treated is ground into particles (comminution). In the idealized case, the individual minerals are physically separated, a process known as full liberation. The particle sizes are typically in the range 2–500 micrometers in diameter. For froth flotation, an aqueous slurry of the ground ore is treated with the frothing agent. An example is sodium ethyl xanthate as a collector in the flotation of galena (lead sulfide) to separate it from sphalerite (zinc sulfide). The polar part of xanthate anion attaches to the ore particles and the non-polar hydrocarbon part forms a hydrophobic layer. The particles are brought to the water surface by air bubbles. About 300 g/t of ore is required for efficient separation. With increasing length of the hydrocarbon chain in xanthates, the efficiency of the hydrophobic action increases, but the selectivity to ore type decreases. The chain is shortest in sodium ethyl xanthate that makes it highly selective to copper, nickel, lead, gold, and zinc ores. Aqueous solutions (10%) with pH = 7–11 are normally used in the process. This slurry (more properly called the pulp) of hydrophobic particles and hydrophilic particles is then introduced to tanks known as flotation cells that are aerated to produce bubbles. The hydrophobic particles attach to the air bubbles, which rise to the surface, forming a froth. The froth is skimmed from the cell, producing a concentrate ("conc") of the target mineral.
The minerals that do not float into the froth are referred to as the flotation tailings or flotation tails. These tailings may also be subjected to further stages of flotation to recover the valuable particles that did not float the first time. This is known as scavenging. The final tailings after scavenging are normally pumped for disposal as mine fill or to tailings disposal facilities for long-term storage.
Flotation is normally undertaken in several stages to maximize the recovery of the target mineral or minerals and the concentration of those minerals in the concentrate, while minimizing the energy input. | 1 | Applied and Interdisciplinary Chemistry |
The clinical significance of bilirubin glucuronide is involved in many conditions. Drugs that inhibit the activities of the components involved in bilirubin metabolism can give rise to accumulation of bilirubin in the blood. In comparison, conjugation of some drugs is also usually impaired if the liver cannot normally metabolize indirect bilirubin. | 1 | Applied and Interdisciplinary Chemistry |
* NATO Research Award (postdoctoral fellowship, 01.1996–01.1997, The University of Cambridge, United Kingdom);
* [http://www.uic.unn.ru/new_grant/intas1.htm INTAS] grants (research visits, 08.1993 and 10.1994,The University of Cambridge, United Kingdom);
* [http://www.ifs.se/ ISF grants] (1998, research project, Taras Shevchenko National University of Kyiv);
* Grants of the Royal Society of Chemistry for authors (1999, 2000);
* Alexander von Humboldt Research [https://www.humboldt-foundation.de/web/3997980.html Fellowship] (postdoctoral stay in Rostock, Germany, 2000–2001);
* Georg Forster Research Award (2015);
* Title "Merited Figure of Science and Technology of Ukraine" (2016). | 0 | Theoretical and Fundamental Chemistry |
Rapamycin and rapalogs crosslink the immunophilin FK506 binding protein, tacrolimus or FKBP-12, through its methoxy group. The rapamycin-FKBP12 complex interferes with FRB domain of mTOR. Molecular interaction between FKBP12, mTOR, and rapamycin can last for about three days (72 hours). The inhibition of mTOR blocks the binding of the accessory protein raptor (regulatory-associated protein of mTOR) to mTOR, but that is necessary for downstream phosphorylation of S6K1 and 4EBP1.
As a consequence, S6K1 dephosphorylates, which reduces protein synthesis and decreases cell mortality and size. Rapamycin induces dephosphorylation of 4EBP1 as well, resulting in an increase in p27 and a decrease in cyclin D1 expression. That leads to late blockage of G1/S cell cycle. Rapamycin has shown to induce cancer cell death by stimulating autophagy or apoptosis, but the molecular mechanism of apoptosis in cancer cells has not yet been fully resolved. One suggestion of the relation between mTOR inhibition and apoptosis might be through the downstream target S6K1, which can phosphorylate BAD, a pro-apoptotic molecule, on Ser136. That reaction breaks the binding of BAD to BCL-XL and BCL2, a mitochondrial death inhibitors, resulting in inactivation of BAD and decreased cell survival. Rapamycin has also shown to induce p53-independent apoptosis in certain types of cancer. | 1 | Applied and Interdisciplinary Chemistry |
In 1905, in an article entitled "Radiation through a foggy atmosphere", Arthur Schuster published a solution to the equation of radiative transfer, which describes the propagation of radiation through a medium, affected by absorption, emission, and scattering processes. His mathematics used a two flux approximation; i.e., all light is assumed to travel with a component either in the same direction as the incident beam, or in the opposite direction. He used the word scattering rather than reflection, and considered scatter to be in all directions. He used the symbols k and s for absorption and isotropic scattering coefficients, and repeatedly refers to radiation entering a "layer", which ranges in size from infinitesimal to infinitely thick. In his treatment, the radiation enters the layers at all possible angles, referred to as "diffuse illumination". | 0 | Theoretical and Fundamental Chemistry |
MiRNA expression profiles are altered in psychiatric conditions, including depression, anxiety, and PTSD. It has been demonstrated that miR-324-5p expression is altered in the brains of suicide victims with depression and in the amygdala, the fear center of the brain, in PTSD. MiRNAs are an underexplored potential biomarker and target for treatment for psychiatric disease. | 1 | Applied and Interdisciplinary Chemistry |
Hypothiocyanite occurs naturally in the antimicrobial immune system of the human respiratory tract in a redox reaction catalyzed by the enzyme lactoperoxidase. It has been researched extensively for its capabilities as an alternative antibiotic as it is harmless to human body cells while being cytotoxic to bacteria. The exact processes for making hypothiocyanite have been patented as such an effective antimicrobial has many commercial applications. | 1 | Applied and Interdisciplinary Chemistry |
REMS scans on femur and spine last 40 and 80 seconds, respectively, allowing the acquisition of several thousands of ultrasound signals related to the skeletal site under examination. The patented algorithm (see for more details) automatically processes these signals on the basis of their spectral features; each signal can be classified as reliable and included in the pipeline for the computation of the diagnostic parameters or, alternatively, classified as unreliable and discarded. During the analysis phase, the acquired spectra are compared to the spectral models stored in the database; afterwards, the values obtained by each comparison are averaged, leading to a precise and repeatable estimation of the diagnostic parameters of interest. | 0 | Theoretical and Fundamental Chemistry |
After a cell has been depolarized, it undergoes one final change in internal charge. Following depolarization, the voltage-gated sodium ion channels that had been open while the cell was undergoing depolarization close again. The increased positive charge within the cell now causes the potassium channels to open. Potassium ions (K) begin to move down the electrochemical gradient (in favor of the concentration gradient and the newly established electrical gradient). As potassium moves out of the cell the potential within the cell decreases and approaches its resting potential once more. The sodium potassium pump works continuously throughout this process. | 0 | Theoretical and Fundamental Chemistry |
The avalanche occurs in a gaseous medium that can be ionised (such as air). The electric field and the mean free path of the electron must allow free electrons to acquire an energy level (velocity) that can cause impact ionisation. If the electric field is too small, then the electrons do not acquire enough energy. If the mean free path is too short, the electron gives up its acquired energy in a series of non-ionising collisions. If the mean free path is too long, then the electron reaches the anode before colliding with another molecule.
The avalanche mechanism is shown in the accompanying diagram. The electric field is applied across a gaseous medium; initial ions are created with ionising radiation (for example, cosmic rays). An original ionisation event produces an ion pair; the positive ion accelerates towards the cathode while the free electron accelerates towards the anode. If the electric field is strong enough, the free electron can gain sufficient velocity (energy) to liberate another electron when it next collides with a molecule. The two free electrons then travel towards the anode and gain sufficient energy from the electric field to cause further impact ionisations, and so on. This process is effectively a chain reaction that generates free electrons. Initially, the number of collisions grows exponentially. The total number of electrons reaching the anode is equal to 2 with n the number of collisions, plus the single initiating free electron. Eventually, this relationship will break down - the limit to the multiplication in an electron avalanche is known as the Raether limit.
The Townsend avalanche can have a large range of current densities. In common gas-filled tubes, such as those used as gaseous ionisation detectors, magnitudes of currents flowing during this process can range from about 10 amperes to about 10 amperes. | 0 | Theoretical and Fundamental Chemistry |
One distinct section of cell engineering involves the alteration and tuning of stem cells. Much of the recent research on stem cell therapies and treatments falls under the aforementioned cell engineering methods. Stem cells are unique in that they may differentiate into various other types of cells which may then be altered to produce novel therapeutics or provide a foundation for further cell engineering efforts. One example of directed stem cell engineering includes partially differentiating stem cells into myocytes to enable production of pro-myogenic factors for the treatment of sarcopenia or muscle disuse atrophy. | 1 | Applied and Interdisciplinary Chemistry |
A native antigen is an antigen that is not yet processed by an APC to smaller parts. T cells cannot bind native antigens, but require that they be processed by APCs, whereas B cells can be activated by native ones. | 1 | Applied and Interdisciplinary Chemistry |
The chemical redox reaction between potassium permanganate and glycerol is often used to demonstrate the powerful oxidizing property of potassium permanganate, especially in the presence of organic compounds such as glycerol. The exothermic (heat producing) reaction between potassium permanganate (KMnO), a strong oxidizing agent, and glycerol (CH(OH)), a readily oxidised organic substance, is an example of an experiment sometimes referred to as a "chemical volcano". | 1 | Applied and Interdisciplinary Chemistry |
Many calculational studies have been used to compare the feasibility of different proposed geometries. Using the quantum semi-empirical method of MINDO/3, researchers were not able to conclude which geometry of the 2-norbornyl cation was most energetically favorable. However, the classical structure was found to be the only potential minimum for the alkyl-substituted 2-methyl-2-norbornyl cation. Additional calculations using Extended Hückel Theory for Molecular Orbitals were found to favor the non-classical geometry of the cation with reflectional symmetry. | 0 | Theoretical and Fundamental Chemistry |
In the Goiânia accident of 1987, an improperly disposed of radiation therapy system from an abandoned clinic in Goiânia, Brazil, was removed, then cracked to be sold in junkyards. The glowing caesium salt was then to be sold to curious, unadvised buyers. This led to four confirmed deaths and several serious injuries from radiation contamination. | 0 | Theoretical and Fundamental Chemistry |
*Two-hybrid screens are low-tech; they can be carried out in any lab without sophisticated equipment.
*Two-hybrid screens can provide an important first hint for the identification of interaction partners.
*The assay is scalable, which makes it possible to screen for interactions among many proteins. Furthermore, it can be automated, and by using robots many proteins can be screened against thousands of potentially interacting proteins in a relatively short time. Two types of large screens are used: the library approach and the matrix approach.
*Yeast two-hybrid data can be of similar quality to data generated by the alternative approach of coaffinity purification followed by mass spectrometry (AP/MS). | 1 | Applied and Interdisciplinary Chemistry |
Arrhenius argued that for reactants to transform into products, they must first acquire a minimum amount of energy, called the activation energy E. At an absolute temperature T, the fraction of molecules that have a kinetic energy greater than E can be calculated from statistical mechanics. The concept of activation energy explains the exponential nature of the relationship, and in one way or another, it is present in all kinetic theories.
The calculations for reaction rate constants involve an energy averaging over a Maxwell–Boltzmann distribution with as lower bound and so are often of the type of incomplete gamma functions, which turn out to be proportional to . | 0 | Theoretical and Fundamental Chemistry |
Mold health issues refer to the harmful health effects of molds ("moulds" in British English) and their mycotoxins. However, recent research has shown these adverse health effects are caused not exclusively by molds, but also other microbial agents and biotoxins associated with dampness, mold, and water-damaged buildings, such as gram-negative bacteria that produce endotoxins, as well as actinomycetes and their associated exotoxins. Approximately 47% of houses in the United States have substantial levels of mold, with over 85% of commercial and office buildings found to have water damage predictive of mold. As many as 21% of asthma cases may result from exposure to mold. Substantial and statistically significant increases in the risks of both respiratory infections and bronchitis have been associated with dampness in homes and the resulting mold.
Molds and many related microbial agents are ubiquitous in the biosphere, and mold spores are a common component of household and workplace dust. While the most molds in the outdoor environment are not hazardous to humans, many found inside buildings are known to be. Reaction to molds can vary between individuals, from relatively minor allergic reactions through to severe multi-system inflammatory effects, neurological problems, and death. The United States Centers for Disease Control and Prevention (CDC) reported in its June 2006 report, Mold Prevention Strategies and Possible Health Effects in the Aftermath of Hurricanes and Major Floods, that "excessive exposure to mold-contaminated materials can cause adverse health effects in susceptible persons regardless of the type of mold or the extent of contamination." Mold spores and associated toxins can cause harm primarily via inhalation, ingestion, and contact. In higher quantities such as those found in water-damaged buildings, they can present especially hazardous health risks to humans after sufficient exposure, with three generally accepted mechanisms of harm and a fourth probable mechanism:
# Allergic reactions, including allergic bronchopulmonary aspergillosis
# Invasive mold infections (mycosis)
# Toxicity (poisoning by mycotoxins)
# Innate immune dysfunction. | 1 | Applied and Interdisciplinary Chemistry |
In case of the fungus Neurospora crassa, the circadian clock is controlled by two light-sensitive domains, known as the white-collar-complex (WCC) and the LOV domain vivid (VVD-LOV). WCC is primarily responsible for the light-induced transcription on the control-gene frequency (FRQ) under day-light conditions, which drives the expression of VVD-LOV and governs the negative feedback loop onto the circadian clock. By contrast, the role of VVD-LOV is mainly modulatory and does not directly affect FRQ. | 1 | Applied and Interdisciplinary Chemistry |
A pulsed field magnet is a strong electromagnet which is powered by a brief pulse of electric current through its windings rather than a continuous current, producing a brief but strong pulse of magnetic field. Pulsed field magnets are used in research in fields such as materials science to study the effect of strong magnetic fields, since they can produce stronger fields than continuous magnets. The maximum field strength that continuously-powered high-field electromagnets can produce is limited by the enormous waste heat generated in the windings by the large currents required. Therefore by applying brief pulses of current, with time between the pulses to allow the heat to dissipate, stronger currents can be used and thus stronger magnetic fields can be generated. The magnetic field produced by pulsed field magnets can reach between 50 and 100 T, and lasts several tens of milliseconds. | 0 | Theoretical and Fundamental Chemistry |
The Sm proteins are synthesized in the cytoplasm by ribosomes translating Sm messenger RNA, just like any other protein. These are stored in the cytoplasm in the form of three partially assembled rings complexes all associated with the pICln protein. They are a 6S pentamer complex of SmD1, SmD2, SmF, SmE and SmG with pICln, a 2-4S complex of SmB, possibly with SmD3 and pICln and the 20S methylosome, which is a large complex of SmD3, SmB, SmD1, pICln and the arginine methyltransferase-5 (PRMT5) protein. SmD3, SmB and SmD1 undergo post-translational modification in the methylosome. These three Sm proteins have repeated arginine-glycine motifs in the C-terminal ends of SmD1, SmD3 and SmB, and the arginine side chains are symmetrically dimethylated to ω-N, N-dimethyl-arginine. It has been suggested that pICln, which occurs in all three precursor complexes but is absent in the mature snRNPs, acts as a specialized chaperone, preventing premature assembly of Sm proteins. | 1 | Applied and Interdisciplinary Chemistry |
The nuclear cross section of a nucleus is used to describe the probability that a nuclear reaction will occur. The concept of a nuclear cross section can be quantified physically in terms of "characteristic area" where a larger area means a larger probability of interaction. The standard unit for measuring a nuclear cross section (denoted as σ) is the barn, which is equal to , or . Cross sections can be measured for all possible interaction processes together, in which case they are called total cross sections, or for specific processes, distinguishing elastic scattering and inelastic scattering; of the latter, amongst neutron cross sections the absorption cross sections are of particular interest.
In nuclear physics it is conventional to consider the impinging particles as point particles having negligible diameter. Cross sections can be computed for any nuclear process, such as capture scattering, production of neutrons, or nuclear fusion. In many cases, the number of particles emitted or scattered in nuclear processes is not measured directly; one merely measures the attenuation produced in a parallel beam of incident particles by the interposition of a known thickness of a particular material. The cross section obtained in this way is called the total cross section and is usually denoted by a σ or σ.
Typical nuclear radii are of the order 10 m. Assuming spherical shape, we therefore expect the cross sections for nuclear reactions to be of the order of or (i.e., 1 barn). Observed cross sections vary enormously: for example, slow neutrons absorbed by the (n, ) reaction show a cross section much higher than 1,000 barns in some cases (boron-10, cadmium-113, and xenon-135), while the cross sections for transmutations by gamma-ray absorption are in the region of 0.001 barn. | 0 | Theoretical and Fundamental Chemistry |
Plasmids may also be used for gene transfer as a potential treatment in gene therapy so that it may express the protein that is lacking in the cells. Some forms of gene therapy require the insertion of therapeutic genes at pre-selected chromosomal target sites within the human genome. Plasmid vectors are one of many approaches that could be used for this purpose. Zinc finger nucleases (ZFNs) offer a way to cause a site-specific double-strand break to the DNA genome and cause homologous recombination. Plasmids encoding ZFN could help deliver a therapeutic gene to a specific site so that cell damage, cancer-causing mutations, or an immune response is avoided. | 1 | Applied and Interdisciplinary Chemistry |
The Shilov system is a classic example of catalytic C-H bond activation and oxidation which preferentially activates stronger C-H bonds over weaker C-H bonds for an overall partial oxidation. | 0 | Theoretical and Fundamental Chemistry |
In the A/B approach to cobyric acid, the Harvard A-D-component was coupled to the ETH B-C-component between rings D and C, and then closed to a corrin between rings A and B. Both these critical steps were accomplished by C,C-coupling via sulfide contraction, a new reaction type developed in the synthesis of the B-C-component at ETH. The A-D-component was synthesized at Harvard from a ring-A precursor (prepared from achiral starting materials), and a ring-D precursor prepared from (−)-camphor. A model A-D-component was used to explore the coupling conditions; this component differed from the A-D-component used in the final synthesis by having as the functional group at the ring-D f-side chain a methyl ester group (like all other side chains) instead of a nitrile group. | 0 | Theoretical and Fundamental Chemistry |
Pyridine is diamagnetic. Its critical parameters are: pressure 5.63 MPa, temperature 619 K and volume 248 cm·mol. In the temperature range 340–426 °C its vapor pressure p can be described with the Antoine equation
where T is temperature, A = 4.16272, B = 1371.358 K and C = −58.496 K. | 0 | Theoretical and Fundamental Chemistry |
Tripotassium phosphate, also called tribasic potassium phosphate is a water-soluble salt with the chemical formula KPO(HO) (x = 0, 3, 7, 9). Tripotassium phosphate is basic. | 0 | Theoretical and Fundamental Chemistry |
Triptans are specific and selective agonists for the 5-HT receptors. Sumatriptan binds to 5-HT receptors, zolmitriptan, rizatriptan, naratriptan, almotriptan, and frovatriptan binds to 5-HT and eletriptan binds to 5-HT receptors. Triptans are believed to exert their effects through vasoconstriction, leading to reduced carotid arterial circulation without affecting cerebral blood flow, peripheral neuronal inhibition, or inhibition of transmission through second order neurons of the trigeminocervical complex. | 1 | Applied and Interdisciplinary Chemistry |
Energy expenditure is mainly a sum of internal heat produced and external work. The internal heat produced is, in turn, mainly a sum of basal metabolic rate (BMR) and the thermic effect of food. External work may be estimated by measuring the physical activity level (PAL). | 1 | Applied and Interdisciplinary Chemistry |
One example of imbibition in nature is the absorption of water by hydrophilic colloids. Matrix potential contributes significantly to water in such substances. Dry seeds germinate in part by imbibition. Imbibition can also control circadian rhythms in Arabidopsis thaliana and (probably) other plants. The Amott test employs imbibition.
Proteins have high imbibition capacities, so proteinaceous pea seeds swell more than starchy wheat seeds.
Imbibition of water increases imbibant volume, which results in imbibitional pressure (IP). The magnitude of such pressure can be demonstrated by the splitting of rocks by inserting dry wooden stalks in their crevices and soaking them in water, a technique used by early Egyptians to cleave stone blocks.
Skin grafts (split thickness and full thickness) receive oxygenation and nutrition via imbibition, maintaining cellular viability until the processes of inosculation and revascularisation have re-established a new blood supply within these tissues. | 0 | Theoretical and Fundamental Chemistry |
Rainwater can be highly radioactive due to high levels of radon and its decay progenies Bi and Pb; the concentrations of these radioisotopes can be high enough to seriously disrupt radiation monitoring at nuclear power plants. The highest levels of radon in rainwater occurs during thunderstorms, and it is hypothesized that radon is concentrated in thunderstorms on account of the atoms positive electrical charge. Estimates of the age of rain drops have been obtained from measuring the isotopic abundance of radons short-lived decay progeny in rainwater. | 0 | Theoretical and Fundamental Chemistry |
SQUIDs are a type of magnetometer used both as survey and as laboratory magnetometers. SQUID magnetometry is an extremely sensitive absolute magnetometry technique. However SQUIDs are noise sensitive, making them impractical as laboratory magnetometers in high DC magnetic fields, and in pulsed magnets. Commercial SQUID magnetometers are available for temperatures between 300 mK and 400 K, and magnetic fields up to 7 tesla. | 0 | Theoretical and Fundamental Chemistry |
The chiral stationary phase, CSP, can interact differently with two enantiomers, by a process known as chiral recognition. Chiral recognition depends on various interactions such as hydrogen bonding, π-π interaction, dipole stacking, inclusion complexation, steric, hydrophobic and electrostatic interaction, charge-transfer interactions, ionic interactions etc, between the analyte and the CSP, to form in-situ transient-diastereomeric complexes.
Most of the types of stationary phases can be classified as Pirkle type (Brush type), Protein-based, Cyclodextrins based, Polymer-based carbohydrates (polysaccharide-based CSPs), Macrocyclic antibiotic, Chiral crown ethers, imprinted polymers, etc. | 0 | Theoretical and Fundamental Chemistry |
Industrial applications of alkene insertions include metal-catalyzed routes to polyethylene and polypropylene. Typically these conversions are catalyzed heterogeneously by titanium trichloride which are activated by aluminium alkyls. This technology is known as Ziegler–Natta catalysts. In these reactions, ethylene coordinates to titanium metal followed by its insertion. These steps can be repeated multiple times, potentially leading to high molecular weight polymers. | 0 | Theoretical and Fundamental Chemistry |
In the case catalytic or adsorbent systems where a metal species is dispersed upon a support (or carrier) material (often quasi-inert oxides, such as alumina or silica), it is possible for an adsorptive species to indirectly adsorb to the support surface under conditions where such adsorption is thermodynamically unfavorable. The presence of the metal serves as a lower-energy pathway for gaseous species to first adsorb to the metal and then diffuse on the support surface. This is possible because the adsorbed species attains a lower energy state once it has adsorbed to the metal, thus lowering the activation barrier between the gas phase species and the support-adsorbed species.
Hydrogen spillover is the most common example of an adsorptive spillover. In the case of hydrogen, adsorption is most often accompanied with dissociation of molecular hydrogen (H) to atomic hydrogen (H), followed by spillover of the hydrogen atoms present.
The spillover effect has been used to explain many observations in heterogeneous catalysis and adsorption. | 0 | Theoretical and Fundamental Chemistry |
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