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The safety profile of HMB in adult humans is based upon evidence from clinical trials in humans and animal studies. In humans, no adverse effects in young adults or older adults have been reported when HMB is taken in doses of 3 grams per day for up to a year. Studies on young adults taking 6 grams of HMB per day for up to 2 months have also reported no adverse effects. Studies with supplemental HMB on young, growing rats and livestock have reported no adverse effects based upon clinical chemistry or observable characteristics; for humans younger than 18, there is limited data on the safety of supplemental HMB. The human equivalent dose of HMB for the no-observed-adverse-effect level (NOAEL) that was identified in a rat model is approximately 0.4 g/kg of body weight per day.
Two animal studies have examined the effects of HMB supplementation in pregnant pigs on the offspring and reported no adverse effects on the fetus. No clinical testing with supplemental HMB has been conducted on pregnant women, and pregnant and lactating women are advised not to take HMB by Metabolic Technologies, Inc., the company that grants licenses to include HMB in dietary supplements, due to a lack of safety studies. | 1 | Applied and Interdisciplinary Chemistry |
EPANET uses a binary file format, but also includes the capability for importing and exporting data in dxf, metafile, and ASCII file formats. EPANET's ASCII file format is called an input file within EPANET, and uses a file extension ".inp". The input file can include data describing network topology, water consumption, and control rules, and is supported by many free and commercial modeling packages.
While EPANET is used as the computational engine for most water distribution system models, most models are developed and maintained in hydraulic modeling packages based on EPANET's computational engine. Some of the major hydraulic modeling packages are:
*[https://www.innovyze.com/en-us/products/water-distribution InfoWorks WS Pro, InfoWater Pro, and InfoWater], developed by Innovyze [An Autodesk Company]
*[https://qatium.com Qatium], developed by Qatium
*[https://www.fluidit.com Fluidit Water], developed by Fluidit
*[http://kypipe.com Pipe2000], developed by KYPipe, LLC
*MIKE URBAN, developed by DHI
* WaterCAD, WaterGEMS, HAMMER, and SewerCAD developed by Bentley's Haestad Methods (Hydraulics & Hydrology) group.
*WatDis, developed by Transparent Blue
* WaterNAM, Water Network Analysis Model, Developed by Streamstech Inc.
* Giswater, open source software developed by the Giswater Association
* [https://gispipe.com GISpipe], software which is easily used for the analysis, design, and operation of water distribution networks Integrated with GIS system developed by Jinbosoft
* [http://www.studioars.com/en/urbano_9_hydra/145/2 Urbano Hydra], AutoCAD/Map3D/Civil3D application software used for the hydraulic calculation, analysis, design and operation of water distribution networks. Integrated with GIS system and ready for BIM workflows developed by StudioARS Company
*[https://softwarepublico.gov.br/gitlab/gsan/geosan/wikis/home GeoSan], open source GIS software to manage water pipes and consumers, developed by [https://www.nexusbr.com/en/ NEXUS GeoEngenharia] available at [https://softwarepublico.gov.br/social/gsan www.softwarepublico.gov.br].
*WateNET-CAD developed by Diolkos3D.
*Esurvey Water - developed by {https://www.esurveying.net], The output Files from EPANET can be used to generate LS and presentable Final Drawings
Most of these applications allow for multiple demand conditions, planning scenarios, and various methods of integrating with other data sources an agency may already have in place not supported in EPANET, such as GIS, and support additional types of analyses not found in EPANET.
ESurvey Water is developed to create Auto Designed Longitudinal Profiles, and auto generation of the final outputs after the hydraulic design is completed in EPANET and other software. | 1 | Applied and Interdisciplinary Chemistry |
Operation of the modified Q cycle in Complex III results in the reduction of Cytochrome c, oxidation of ubiquinol to ubiquinone, and the transfer of four protons into the intermembrane space, per two-cycle process.
Ubiquinol (QH) binds to the Q site of complex III via hydrogen bonding to His182 of the Rieske iron-sulfur protein and Glu272 of Cytochrome b. Ubiquinone (Q), in turn, binds the Q site of complex III. Ubiquinol is divergently oxidized (gives up one electron each) to the Rieske iron-sulfur (FeS) protein and to the b heme. This oxidation reaction produces a transient semiquinone before complete oxidation to ubiquinone, which then leaves the Q site of complex III.
Having acquired one electron from ubiquinol, the FeS protein is freed from its electron donor and is able to migrate to the Cytochrome c subunit. FeS protein then donates its electron to Cytochrome c, reducing its bound heme group. The electron is from there transferred to an oxidized molecule of Cytochrome c externally bound to complex III, which then dissociates from the complex. In addition, the reoxidation of the FeS protein releases the proton bound to His181 into the intermembrane space.
The other electron, which was transferred to the b heme, is used to reduce the b heme, which in turn transfers the electron to the ubiquinone bound at the Q site. The movement of this electron is energetically unfavourable, as the electron is moving towards the negatively charged side of the membrane. This is offset by a favourable change in E from −100 mV in B to +50mV in the B heme. The attached ubiquinone is thus reduced to a semiquinone radical. The proton taken up by Glu272 is subsequently transferred to a hydrogen-bonded water chain as Glu272 rotates 170° to hydrogen bond a water molecule, in turn hydrogen-bonded to a propionate of the b heme.
Because the last step leaves an unstable semiquinone at the Q site, the reaction is not yet fully completed. A second Q cycle is necessary, with the second electron transfer from cytochrome b reducing the semiquinone to ubiquinol. The ultimate products of the Q cycle are four protons entering the intermembrane space, two from the matrix and two from the reduction of two molecules of cytochrome c. The reduced cytochrome c is eventually reoxidized by complex IV. The process is cyclic as the ubiquinol created at the Q site can be reused by binding to the Q site of complex III. | 1 | Applied and Interdisciplinary Chemistry |
* In windy mountain passes, resulting in erroneous pressure altimeter readings
*The mistral wind in southern France increases in speed through the Rhone valley. | 1 | Applied and Interdisciplinary Chemistry |
Describing the ratio of gravitational to capillary forces, the Eötvös or Bond number is given by the equation:
* : difference in density of the two phases, (SI units: kg/m)
* g: gravitational acceleration, (SI units : m/s)
* L: characteristic length, (SI units : m) (for example the radii of curvature for a drop)
* : surface tension, (SI units : N/m)
The Bond number can also be written as
where is the capillary length.
A high value of the Eötvös or Bond number indicates that the system is relatively unaffected by surface tension effects; a low value (typically less than one) indicates that surface tension dominates. Intermediate numbers indicate a non-trivial balance between the two effects. It may be derived in a number of ways, such as scaling the pressure of a drop of liquid on a solid surface. It is usually important, however, to find the right length scale specific to a problem by doing a ground-up scale analysis. Other similar dimensionless numbers are:
where Go and De are the Goucher and Deryagin numbers, which are identical: the Goucher number arises in wire coating problems and hence uses a radius as a typical length scale while the Deryagin number arises in plate film thickness problems and hence uses a Cartesian length.
In order to consider all three of the forces that act on a moving fluid front in the presence of a gas (or other fluid) phase, namely viscous, capillary and gravitational forces, the generalized Bond number, which is denoted commonly as Bo, can be used. This is defined as: | 1 | Applied and Interdisciplinary Chemistry |
After a brief interval at Bratton Clovelly, in 1793
William and his family moved permanently to the rectory of Creed in Cornwall. Here he continued his remarkably accurate chemical analysis of minerals, most of which came from Cornwall, such as the zeolites found in gabbro on The Lizard. He also analysed wavellite, tourmaline, and the uranium minerals torbernite and autunite, the arsenate scorodite, the lead mineral mimetite and the nickel mineral niccolite, and others. But he is best known for one of his earliest discoveries: in 1791, while analysing the minerals in a black sand he had discovered in the Manaccan valley, he isolated the calx of an unknown metal which he named manaccanite. Later in 1791, Martin Heinrich Klaproth discovered what is now known as titanium in the mineral rutile. Believing this to be a new discovery, Klaproth named it titanium after the Titans of Greek Mythology, but eventually it was clarified that Gregor made the discovery first. Gregor was credited with the discovery, but the element kept the name chosen by Klaproth. Gregor later found titanium in corundum from Tibet, and in a tourmaline from a local tin mine. See the main article on titanium for information on its many uses. Titanium is a transition metal with the atomic number of 22 and atomic mass 47.867. | 1 | Applied and Interdisciplinary Chemistry |
Pyridine supports a series of radical reactions, which is used in its dimerization to bipyridines. Radical dimerization of pyridine with elemental sodium or Raney nickel selectively yields 4,4-bipyridine, or 2,2-bipyridine, which are important precursor reagents in the chemical industry. One of the name reactions involving free radicals is the Minisci reaction. It can produce 2-tert-butylpyridine upon reacting pyridine with pivalic acid, silver nitrate and ammonium in sulfuric acid with a yield of 97%. | 0 | Theoretical and Fundamental Chemistry |
In size-exclusion chromatography, the residence time of a molecule is related to its volume, which is roughly proportional to its molecular weight. Residence times also affect the performance of continuous fermentors.
Biofuel cells utilize the metabolic processes of anodophiles (electronegative bacteria) to convert chemical energy from organic matter into electricity. A biofuel cell mechanism consists of an anode and a cathode that are separated by an internal proton exchange membrane (PEM) and connected in an external circuit with an external load. Anodophiles grow on the anode and consume biodegradable organic molecules to produce electrons, protons, and carbon dioxide gas, and as the electrons travel through the circuit they feed the external load. The HRT for this application is the rate at which the feed molecules are passed through the anodic chamber. This can be quantified by dividing the volume of the anodic chamber by the rate at which the feed solution is passed into the chamber. The hydraulic residence time (HRT) affects the substrate loading rate of the microorganisms that the anodophiles consume, which affects the electrical output. Longer HRTs reduce substrate loading in the anodic chamber which can lead to reduced anodophile population and performance when there is a deficiency of nutrients. Shorter HRTs support the development of non-exoelectrogenous bacteria which can reduce the Coulombic efficiency electrochemical performance of the fuel cell if the anodophiles must compete for resources or if they do not have ample time to effectively degrade nutrients. | 0 | Theoretical and Fundamental Chemistry |
Air pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m, μg/m, etc.) at sea level will decrease with increasing altitude. The concentration decrease is directly proportional to the pressure decrease with increasing altitude. Some governmental regulatory jurisdictions require industrial sources of air pollution to comply with sea level standards corrected for altitude. In other words, industrial air pollution sources located at altitudes well above sea level must comply with significantly more stringent air quality standards than sources located at sea level (since it is more difficult to comply with lower standards). For example, New Mexico's Department of the Environment has a regulation with such a requirement.
The change of atmospheric pressure with altitude (<20 km) can be obtained from this equation:
Given an air pollutant concentration at sea-level atmospheric pressure, the concentration at higher altitudes can be obtained from this equation:
As an example, given an air pollutant concentration of 260 mg/m at sea level, calculate the equivalent pollutant concentration at an altitude of 2800 meters:
:C = 260 × [ { 288 - (6.5)(2.8) } / 288] = 260 × 0.71 = 185 mg/m
Note:
* The above equation for the decrease of air pollution concentrations with increasing altitude is applicable only for about the first 10 km of altitude in the troposphere (the lowest atmospheric layer) and is estimated to have a maximum error of about 3 percent. However, 10 km of altitude is sufficient for most purposes involving air pollutant concentrations. | 1 | Applied and Interdisciplinary Chemistry |
Molten plutonium, alloyed with other metals to lower its melting point and encapsulated in tantalum, was tested in two experimental reactors, LAMPRE I and LAMPRE II, at Los Alamos National Laboratory in the 1960s. "LAMPRE experienced three separate fuel failures during operation." | 0 | Theoretical and Fundamental Chemistry |
Very little is known about the initiation of epigenetic silencing of transposable elements, and aside from the rare exception to this rule, as in the gene Muk, present as an initiator of regulatory epigenetic modification in maize, there are many other unclear aspects of how transposons are regulated in plant genomes. Might they be a first step in evolution that we never knew about? [1] Might they be, simply, a kink in the chain of genetic coding, one that will eventually be worked out? Again, given the lack of information it is hard to say. Future research into this field will see the changing of our conceptions of transposons and their role in eukaryote development, one way or another. | 1 | Applied and Interdisciplinary Chemistry |
The possibility of using photochromic compounds for data storage was first suggested in 1956 by Yehuda Hirshberg. Since that time, there have been many investigations by various academic and commercial groups, particularly in the area of 3D optical data storage which promises discs that can hold a terabyte of data. Initially, issues with thermal back-reactions and destructive reading dogged these studies, but more recently more stable systems have been developed. | 0 | Theoretical and Fundamental Chemistry |
Pipelines for major energy resources (petroleum and natural gas) are not merely an element of trade. They connect to issues of geopolitics and international security as well, and the construction, placement, and control of oil and gas pipelines often figure prominently in state interests and actions. A notable example of pipeline politics occurred at the beginning of the year 2009, wherein a dispute between Russia and Ukraine ostensibly over pricing led to a major political crisis. Russian state-owned gas company Gazprom cut off natural gas supplies to Ukraine after talks between it and the Ukrainian government fell through. In addition to cutting off supplies to Ukraine, Russian gas flowing through Ukraine—which included nearly all supplies to Southeastern Europe and some supplies to Central and Western Europe—was cut off, creating a major crisis in several countries heavily dependent on Russian gas as fuel. Russia was accused of using the dispute as leverage in its attempt to keep other powers, and particularly the European Union, from interfering in its "near abroad".
Oil and gas pipelines also figure prominently in the politics of Central Asia and the Caucasus. | 1 | Applied and Interdisciplinary Chemistry |
Cellular noise is often investigated in the framework of intrinsic and extrinsic noise. Intrinsic noise refers to variation in identically regulated quantities within a single cell: for example, the intra-cell variation in expression levels of two identically controlled genes. Extrinsic noise refers to variation in identically regulated quantities between different cells: for example, the cell-to-cell variation in expression of a given gene.
Intrinsic and extrinsic noise levels are often compared in dual reporter studies, in which the expression levels of two identically regulated genes (often fluorescent reporters like GFP and YFP) are plotted for each cell in a population.
An issue with the general depiction of extrinsic noise as a spread along the main diagonal in dual-reporter studies is the assumption that extrinsic factors cause positive expression correlations between the two reporters. In fact, when the two reporters compete for binding of a low-copy regulator, the two reporters become anomalously anticorrelated, and the spread is perpendicular to the main diagonal. In fact, any deviation of the dual-reporter scatter plot from circular symmetry indicates extrinsic noise. Information theory offers a way to avoid this anomaly. | 1 | Applied and Interdisciplinary Chemistry |
XPS detects only electrons that have actually escaped from the sample into the vacuum of the instrument. In order to escape from the sample, a photoelectron must travel through the sample. Photo-emitted electrons can undergo inelastic collisions, recombination, excitation of the sample, recapture or trapping in various excited states within the material, all of which can reduce the number of escaping photoelectrons. These effects appear as an exponential attenuation function as the depth increases, making the signals detected from analytes at the surface much stronger than the signals detected from analytes deeper below the sample surface. Thus, the signal measured by XPS is an exponentially surface-weighted signal, and this fact can be used to estimate analyte depths in layered materials. | 0 | Theoretical and Fundamental Chemistry |
The same technique has been used to construct process maps for sintering, diffusion bonding, hot isostatic pressing, and indentation. | 1 | Applied and Interdisciplinary Chemistry |
It is important to note, that negligible viscosity can no longer be assumed near solid boundaries, such as the case of the airplane wing. In turbulent flow regimes (Re >> 1), viscosity can typically be neglected, however this is only valid at distances far from solid interfaces. When considering flow in the vicinity of a solid surface, such as flow through a pipe or around a wing, it is convenient to categorize four distinct regions of flow near the surface:
* Main turbulent stream: Furthest from the surface, viscosity can be neglected.
* Inertial sub-layer: The start of the main turbulent stream, viscosity has only minor importance.
* Buffer layer: The transformation between inertial and viscous layers.
* Viscous sub-layer: Closest to the surface, here viscosity is important.
Although these distinctions can be a useful tool in illustrating the significance of viscous forces near solid interfaces, it is important to note that these regions are fairly arbitrary. Assuming inviscid flow can be a useful tool in solving many fluid dynamics problems, however, this assumption requires careful consideration of the fluid sub layers when solid boundaries are involved. | 1 | Applied and Interdisciplinary Chemistry |
One challenge when synthesising a metallic glass is that the techniques often only produce very small samples, due to the need for high cooling rates. 3D-printing methods have been suggested as a method to create larger bulk samples. Selective laser melting (SLM) is one example of an additive manufacturing method that has been used to make iron based metallic glasses. Laser foil printing (LFP) is another method where foils of the amorphous metals are stacked and welded together, layer by layer. | 1 | Applied and Interdisciplinary Chemistry |
Marion McQuillan (30 October 1921 – 24 June 1998) was a British metallurgist who specialised in the engineering uses for titanium and its alloys. She researched jet engine metals and was on the first team to research titanium for the Royal Aircraft Establishment Farnborough (RAE). | 1 | Applied and Interdisciplinary Chemistry |
Nitrilimines or nitrile amides are a class of organic compounds sharing a common functional group with the general structure R-CN-NR corresponding to the conjugate base of an amine bonded to the N-terminus of a nitrile. The dominant structure for the parent compound nitrilimine is that of the propargyl-like in scheme 1 with a C-N triple bond and with a formal positive charge on nitrogen and two lone pairs and a formal negative charge on the terminal nitrogen. Other structures such as hypervalent , allene-like , allylic and carbene are of lesser relevance.
Nitrilimines were first observed in the thermal decomposition of 2-tetrazoles releasing nitrogen:
Nitrilimines are linear 1,3-dipoles represented by structures and . A major use is in heterocyclic synthesis. E.g. with alkynes they generate pyrazoles in a 1,3-dipolar cycloaddition. Due to their high energy, they are usually generated in situ as a reactive intermediate. | 0 | Theoretical and Fundamental Chemistry |
tert-Butyl hydroperoxide (tBuOOH) is the organic compound with the formula (CH)COOH. It is one of the most widely used hydroperoxides in a variety of oxidation processes, like the Halcon process. It is normally supplied as a 69–70% aqueous solution. Compared to hydrogen peroxide and organic peracids, tert-butyl hydroperoxide is less reactive and more soluble in organic solvents. Overall, it is renowned for the convenient handling properties of its solutions. Its solutions in organic solvents are highly stable. | 0 | Theoretical and Fundamental Chemistry |
The number to be transferred depends on the number available, the age of the patient and other health and diagnostic factors. In countries such as Canada, the UK, Australia and New Zealand, a maximum of two embryos are transferred except in unusual circumstances. In the UK and according to HFEA regulations, a woman over 40 may have up to three embryos transferred, whereas in the US, there is no legal limit on the number of embryos which may be transferred, although medical associations have provided practice guidelines. Most clinics and country regulatory bodies seek to minimise the risk of multiple pregnancy, as it is not uncommon for multiple embryos to implant if multiple embryos are transferred. Embryos are transferred to the patient's uterus through a thin, plastic catheter, which goes through their vagina and cervix. Several embryos may be passed into the uterus to improve chances of implantation and pregnancy. | 1 | Applied and Interdisciplinary Chemistry |
Numerous viruses exploit lipid rafts and endocytosis as entry pathways. Notably, SARS-CoV-2 has been demonstrated to leverage heightened cholesterol levels stemming from an immune response, thereby amplifying endocytosis and infectivity. Moreover, tissue cholesterol levels tend to rise with age. This augmented cholesterol presence provides insight into the greater severity of COVID-19 in elderly and chronically ill patients. | 1 | Applied and Interdisciplinary Chemistry |
Ligand can bind into an active site within a protein by using a docking search algorithm, and scoring function in order to identify the most likely cause for an individual ligand while assigning a priority order. | 1 | Applied and Interdisciplinary Chemistry |
The Oxford Chemistry Primers are a series of short texts providing accounts of a range of essential topics in chemistry and chemical engineering written for undergraduate study. The first primer Organic Synthesis: The Roles of Boron and Silicon was published by Oxford University Press in 1991. As of 2017 there are 100 titles in the series, written by a wide range of authors. The editors are Steve G. Davies (Organic Chemistry), Richard G. Compton (Physical Chemistry), John Evans (Inorganic Chemistry) and Lynn Gladden (Chemical Engineering). | 1 | Applied and Interdisciplinary Chemistry |
Process simulation is used for the design, development, analysis, and optimization of technical process of simulation of processes such as: chemical plant s, chemical processes, environmental systems, power stations, complex manufacturing operations, biological processes, and similar technical functions. | 1 | Applied and Interdisciplinary Chemistry |
As cyclamin is not yet used as pharmaceutical drug such as for chemotherapy, no side effects were yet determined. | 0 | Theoretical and Fundamental Chemistry |
Ligand exchange involves replacement of a water ligand ("coordinated water") with water in solution ("bulk water"). Often the process is represented using labeled water :
In the absence of isotopic labeling, the reaction is degenerate, meaning that the free energy change is zero.
Rates vary over many orders of magnitude. The main factor affecting rates is charge: highly charged metal aquo cations exchange their water more slowly than singly charged cations. Thus, the exchange rates for and differ by a factor of 10. Electron configuration is also a major factor, illustrated by the fact that the rates of water exchange for and differ by a factor of 10 also. Water exchange usually follows a dissociative substitution pathway, so the rate constants indicate first order reactions. | 0 | Theoretical and Fundamental Chemistry |
An explicit scheme of FDM has been considered and stability criteria are formulated. In this scheme, temperature is totally dependent on the old temperature (the initial conditions) and , a weighting parameter between 0 and 1. Substitution of gives the explicit discretization of the unsteady conductive heat transfer equation.
where
* is the uniform grid spacing (mesh step) | 1 | Applied and Interdisciplinary Chemistry |
Neil Vasdev is a Canadian and American radiochemist and expert in nuclear medicine and molecular imaging, particularly in the application of PET. Radiotracers developed by the Vasdev Lab are in preclinical use worldwide, and many have been translated for first-in-human neuroimaging studies. He is the director and chief radiochemist of the Brain Health Imaging Centre and director of the Azrieli Centre for Neuro-Radiochemistry at the Centre for Addiction and Mental Health (CAMH). He is the Tier 1 Canada Research Chair in Radiochemistry and Nuclear Medicine, the endowed Azrieli Chair in Brain and Behaviour and Professor of Psychiatry at the University of Toronto. Vasdev has been featured on Global News, CTV, CNN, New York Times, Toronto Star and the Globe and Mail for his innovative research program.
Vasdev began his independent faculty career at CAMH/University of Toronto in 2004. From 2011–2017 he served as the director of radiochemistry and an associate centre director at the Massachusetts General Hospital and served as an associate professor in the department of radiology at Harvard Medical School from 2012–2022. He was recruited back to CAMH and the University of Toronto in November 2017. | 0 | Theoretical and Fundamental Chemistry |
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V) | 1 | Applied and Interdisciplinary Chemistry |
Gold(III) bromide is used as a catalyst in a variety of reactions, but one of its most interesting uses is found in the Diels-Alder reaction. Specifically, the compound catalyzes the reaction between an enynal unit and carbonyl compounds to form a six-membered cyclic compound.
Another catalytic use of gold tribromide is in the nucleophilic substitution reaction of propargylic alcohols. In this reaction, the gold complex acts as an alcohol-activating agent to facilitate the substitution. | 0 | Theoretical and Fundamental Chemistry |
Calcium looping (CaL), or the regenerative calcium cycle (RCC), is a second-generation carbon capture technology. It is the most developed form of carbonate looping, where a metal (M) is reversibly reacted between its carbonate form (MCO) and its oxide form (MO) to separate carbon dioxide from other gases coming from either power generation or an industrial plant. In the calcium looping process, the two species are calcium carbonate (CaCO) and calcium oxide (CaO). The captured carbon dioxide can then be transported to a storage site, used in enhanced oil recovery or used as a chemical feedstock. Calcium oxide is often referred to as the sorbent.
Calcium looping is being developed as it is a more efficient, less toxic alternative to current post-combustion capture processes such as amine scrubbing. It also has interesting potential for integration with the cement industry. | 1 | Applied and Interdisciplinary Chemistry |
Tube cleaning describes the activity of, or device for, the cleaning and maintenance of fouled tubes.
The need for cleaning arises because the medium that is transported through the tubes may cause deposits and finally even obstructions. In system engineering and in industry, particular demands are placed upon surface roughness or heat transfer. In the food and pharmaceutical industries as well as in medical technology, the requirements are germproofness, and that the tubes are free from foreign matter, for example after the installation of the tube or after a change of product. Another trouble source may be corrosion due to deposits which may also cause tube failure. | 1 | Applied and Interdisciplinary Chemistry |
*Furnace Type (spray roaster, fluidised bed or combined furnace)
*Physical Properties of Iron Oxide By-Product (ferric oxide powder or pellets)
*Purity and commercial value of Iron Oxide By-Product
**Cl content
**SiO content (typically 40 to 1000 ppm)
**other impurities
**specific weight (typically 0.3 to 4 kg per litre)
**specific surface (typically 0.01 to 8 m2/g)
*Energy Consumption (between 600 and 1200 kcal/L)
*Fuel type
*Concentration of regenerated acid (typically approx. 18% wt/wt)
*Purity of regenerated acid (remaining Fe content, Cl content)
*Recovery efficiency (typically 99%)
*Rinse water utilization
*Stack emissions (HCl, Cl, Dust, CO, NOx)
*Liquid effluents (composition, amount) | 0 | Theoretical and Fundamental Chemistry |
The PMF can be obtained in Monte Carlo or molecular dynamics simulations to examine how a systems energy changes as a function of some specific reaction coordinate parameter. For example, it may examine how the systems energy changes as a function of the distance between two residues, or as a protein is pulled through a lipid bilayer. It can be a geometrical coordinate or a more general energetic (solvent) coordinate. Often PMF simulations are used in conjunction with umbrella sampling, because typically the PMF simulation will fail to adequately sample the system space as it proceeds. | 0 | Theoretical and Fundamental Chemistry |
A column is prepared by packing a solid adsorbent into a cylindrical glass or plastic tube. The size will depend on the amount of compound being isolated. The base of the tube contains a filter, either a cotton or glass wool plug, or glass frit to hold the solid phase in place. A solvent reservoir may be attached at the top of the column.
Two methods are generally used to prepare a column: the dry method and the wet method. For the dry method, the column is first filled with dry stationary phase powder, followed by the addition of mobile phase, which is flushed through the column until it is completely wet, and from this point is never allowed to run dry. For the wet method, a slurry is prepared of the eluent with the stationary phase powder and then carefully poured into the column. The top of the silica should be flat, and the top of the silica can be protected by a layer of sand. Eluent is slowly passed through the column to advance the organic material.
The individual components are retained by the stationary phase differently and separate from each other while they are running at different speeds through the column with the eluent. At the end of the column they elute one at a time. During the entire chromatography process the eluent is collected in a series of fractions. Fractions can be collected automatically by means of fraction collectors. The productivity of chromatography can be increased by running several columns at a time. In this case multi stream collectors are used. The composition of the eluent flow can be monitored and each fraction is analyzed for dissolved compounds, e.g. by analytical chromatography, UV absorption spectra, or fluorescence. Colored compounds (or fluorescent compounds with the aid of a UV lamp) can be seen through the glass wall as moving bands. | 0 | Theoretical and Fundamental Chemistry |
Despite being a powerful model organism for biology and the study of transcriptional enhancers, the tissue specific activity of less than 5% of the estimated 50,000 transcriptional enhancers in Drosophila melanogaster have been discovered. Over the past decade, the main method for detection of tissue- or cell-type specific activities of enhancers in Drosophila melanogaster was to test candidate enhancers by traditional reporter assays, which are low-throughput and costly. Over the past few years, even though enhancer discovery has been improved and other parallel reporter assays have been developed, none so far allowed the direct identification of enhancer activity in a genomic context in cell types of interest in a whole embryo. | 1 | Applied and Interdisciplinary Chemistry |
Reaction of diborane with ammonia mainly gives the diammoniate salt (diammoniodihydroboronium tetrahydroborate). Ammonia borane is the main product when an adduct of borane is employed in place of diborane:
It can also be synthesized from sodium borohydride. | 0 | Theoretical and Fundamental Chemistry |
Some atmospheric effects on the functionality of adhesive devices can be characterized by following the theory of surface energy and interfacial tension. It is known that γ = (1/2)W = (1/2)W. If γ is high, then each species finds it favorable to cohere while in contact with a foreign species, rather than dissociate and mix with the other. If this is true, then it follows that when the interfacial tension is high, the force of adhesion is weak, since each species does not find it favorable to bond to the other. The interfacial tension of a liquid and a solid is directly related to the liquid's wettability (relative to the solid), and thus one can extrapolate that cohesion increases in non-wetting liquids and decreases in wetting liquids. One example that verifies this is polydimethyl siloxane rubber, which has a work of self-adhesion of 43.6 mJ/m in air, 74 mJ/m in water (a nonwetting liquid) and 6 mJ/m in methanol (a wetting liquid).
This argument can be extended to the idea that when a surface is in a medium with which binding is favorable, it will be less likely to adhere to another surface, since the medium is taking up the potential sites on the surface that would otherwise be available to adhere to another surface. Naturally this applies very strongly to wetting liquids, but also to gas molecules that could adsorb onto the surface in question, thereby occupying potential adhesion sites. This last point is actually fairly intuitive: Leaving an adhesive exposed to air too long gets it dirty, and its adhesive strength will decrease. This is observed in the experiment: when mica is cleaved in air, its cleavage energy, W or W, is smaller than the cleavage energy in vacuum, W, by a factor of 13. | 0 | Theoretical and Fundamental Chemistry |
The prefix "S" indicates that the NO group is attached to sulfur. The angle is near 114°, reflecting the influence of the lone pair of electrons on nitrogen.
S-Nitrosothiols may arise from condensation from nitrous acid and a thiol:
Other methods for their synthesis. They can be synthesized from and tert-butyl nitrite (tBuONO) are commonly used.
Once formed, these deeply colored compounds are often thermally unstable with respect to formation of the disulfide and nitric oxide:
S-Nitrosothiols release nitrosonium ions () upon treatment with acids:
and they can transfer nitroso groups to other thiols: | 0 | Theoretical and Fundamental Chemistry |
The viscous forces that arise during fluid flow are distinct from the elastic forces that occur in a solid in response to shear, compression, or extension stresses. While in the latter the stress is proportional to the amount of shear deformation, in a fluid it is proportional to the rate of deformation over time. For this reason, James Clerk Maxwell used the term fugitive elasticity for fluid viscosity.
However, many liquids (including water) will briefly react like elastic solids when subjected to sudden stress. Conversely, many "solids" (even granite) will flow like liquids, albeit very slowly, even under arbitrarily small stress. Such materials are best described as viscoelastic—that is, possessing both elasticity (reaction to deformation) and viscosity (reaction to rate of deformation).
Viscoelastic solids may exhibit both shear viscosity and bulk viscosity. The extensional viscosity is a linear combination of the shear and bulk viscosities that describes the reaction of a solid elastic material to elongation. It is widely used for characterizing polymers.
In geology, earth materials that exhibit viscous deformation at least three orders of magnitude greater than their elastic deformation are sometimes called rheids. | 1 | Applied and Interdisciplinary Chemistry |
Liquid drugs are stored in vials, IV bags, ampoules, cartridges, and prefilled syringes.
As with solid formulations, liquid formulations combine the drug product with a variety of compounds to ensure a stable active medication following storage. These include solubilizers, stabilizers, buffers, tonicity modifiers, bulking agents, viscosity enhancers/reducers, surfactants, chelating agents, and adjuvants.
If concentrated by evaporation, the drug may be diluted before administration. For IV administration, the drug may be transferred from a vial to an IV bag and mixed with other materials. | 1 | Applied and Interdisciplinary Chemistry |
Calcium is the most abundant metal in the eukaryotes and by extension humans. The body is made up of approximate 1.5% calcium and this abundance is reflected in its lack of redox toxicity and its participation in the structure stability of membranes and other biomolecules. Calcium plays a part in fertilization of an egg, controls several developmental process and may regulate cellular processes like metabolism or learning. Calcium also plays a part in bone structure as the rigidity of vertebrae bone matrices are akin to the nature of the calcium hydroxyapatite. Calcium usually binds with other proteins and molecules in order to perform other functions in the body. The calcium bound proteins usually play an important role in cell-cell adhesion, hydrolytic processes (such as hydrolytic enzymes like glycosidases and sulfatases) and protein folding and sorting. These processes play into the larger part of cell structure and metabolism. | 1 | Applied and Interdisciplinary Chemistry |
For a molecule with atoms, the positions of all nuclei depend on a total of 3 coordinates, so that the molecule has 3 degrees of freedom including translation, rotation and vibration. Translation corresponds to movement of the center of mass whose position can be described by 3 cartesian coordinates.
A nonlinear molecule can rotate about any of three mutually perpendicular axes and therefore has 3 rotational degrees of freedom. For a linear molecule, rotation about the molecular axis does not involve movement of any atomic nucleus, so there are only 2 rotational degrees of freedom which can vary the atomic coordinates.
An equivalent argument is that the rotation of a linear molecule changes the direction of the molecular axis in space, which can be described by 2 coordinates corresponding to latitude and longitude. For a nonlinear molecule, the direction of one axis is described by these two coordinates, and the orientation of the molecule about this axis provides a third rotational coordinate.
The number of vibrational modes is therefore 3 minus the number of translational and rotational degrees of freedom, or 3–5 for linear and 3–6 for nonlinear molecules. | 0 | Theoretical and Fundamental Chemistry |
Gražvydas Lukinavičius is a Lithuanian biochemist. His scientific interest and main area of research is focused on labeling of biomolecules and visualization using super-resolution microscopy. He is co-invertor of DNA labeling technology known as Methyltransferase-Directed Transfer of Activated Groups (mTAG) and biocompatible and cell permeable fluorophore – silicon-rhodamine (SiR). Both inventions were commercialized. He is studying labeling methods and apply them for chromatin dynamics visualization in living cells. | 1 | Applied and Interdisciplinary Chemistry |
Organisms in all three domains of life, eukaryotes, bacteria and archaea, are able to carry out de novo biosynthesis of purines. This ability reflects the essentiality of purines for life. The biochemical pathway of synthesis is very similar in eukaryotes and bacterial species, but is more variable among archaeal species. A nearly complete, or complete, set of genes required for purine biosynthesis was determined to be present in 58 of the 65 archaeal species studied. However, also identified were seven archaeal species with entirely, or nearly entirely, absent purine encoding genes. Apparently the archaeal species unable to synthesize purines are able to acquire exogenous purines for growth., and are thus similar to purine mutants of eukaryotes, e.g. purine mutants of the Ascomycete fungus Neurospora crassa, that also require exogenous purines for growth. | 1 | Applied and Interdisciplinary Chemistry |
More accurately, a single formula that describes the titration of a weak acid with a strong base from start to finish is given below:
where
" φ = fraction of completion of the titration (φ < 1 is before the equivalence point, φ = 1 is the equivalence point, and φ > 1 is after the equivalence point)
: = the concentrations of the acid and base respectively
: = the volumes of the acid and base respectively | 0 | Theoretical and Fundamental Chemistry |
Consider two equal bodies (not affected by gravity), each of mass m, attached to three springs, each with spring constant k. They are attached in the following manner, forming a system that is physically symmetric:
where the edge points are fixed and cannot move. Well use x(t) to denote the horizontal displacement of the left mass, and x(t') to denote the displacement of the right mass.
If one denotes acceleration (the second derivative of x(t) with respect to time) as , the equations of motion are:
Since we expect oscillatory motion of a normal mode (where ω is the same for both masses), we try:
Substituting these into the equations of motion gives us:
Since the exponential factor is common to all terms, we omit it and simplify:
And in matrix representation:
If the matrix on the left is invertible, the unique solution is the trivial solution (A, A) = (x, x) = (0,0). The non trivial solutions are to be found for those values of ω whereby the matrix on the left is singular i.e. is not invertible. It follows that the determinant of the matrix must be equal to 0, so:
Solving for , we have two positive solutions:
If we substitute ω into the matrix and solve for (A, A), we get (1, 1). If we substitute ω, we get (1, −1). (These vectors are eigenvectors, and the frequencies are eigenvalues.)
The first normal mode is:
Which corresponds to both masses moving in the same direction at the same time. This mode is called antisymmetric.
The second normal mode is:
This corresponds to the masses moving in the opposite directions, while the center of mass remains stationary. This mode is called symmetric.
The general solution is a superposition of the normal modes where c, c, φ, and φ, are determined by the initial conditions of the problem.
The process demonstrated here can be generalized and formulated using the formalism of Lagrangian mechanics or Hamiltonian mechanics. | 0 | Theoretical and Fundamental Chemistry |
A dyotropic reaction (from the Greek dyo, meaning two) in organic chemistry is a type of organic reaction and more specifically a pericyclic valence isomerization in which two sigma bonds simultaneously migrate intramolecularly. The reaction type is of some relevance to organic chemistry because it can explain how certain reactions occur and because it is a synthetic tool in the synthesis of organic molecules for example in total synthesis. It was first described by Manfred T. Reetz in 1971
In a type I reaction two migrating groups interchange their relative positions and a type II reaction involves migration to new bonding sites without positional interchange. | 0 | Theoretical and Fundamental Chemistry |
The Centers for Disease Control and Prevention has published the following laboratory procedure manuals for measuring thyroid-stimulating hormone:
* [https://www.cdc.gov/NCHS/data/nhanes/nhanes_09_10/THYROD_F_met_TSH.pdf Thyroid Stimulating Hormone (TSH) (University of Washington Medical Center)]. September 2011. Method: Access 2 (Beckman Coulter).
* [https://www.cdc.gov/NCHS/data/nhanes/nhanes_09_10/THYROD_F_met_TSH_CLS.pdf Thyroid Stimulating Hormone (TSH) (Collaborative Laboratory Services)]. September 2011. Method: Access 2 (Beckman Coulter).
* [https://www.cdc.gov/nchs/data/nhanes/nhanes_07_08/THYROD_e_met_Thyroid_Stimulating_Hormone.pdf Thyroid Stimulating Hormone (TSH)]. September 2009. Method: Access 2 (Beckman Coulter).
* [https://www.cdc.gov/nchs/data/nhanes/nhanes_01_02/l18t4_b_met_b_tsh.pdf Lab 18 Thyroid Stimulating Hormone]. 2001-2002. Method: Microparticle Enzyme Immunoassay.
* [https://www.cdc.gov/nchs/data/nhanes/nhanes_99_00/lab18_met_tsh.pdf Lab 18 TSH - Thyroid Stimulating Hormone]. 1999-2000. Method: Microparticle Enzyme Immunoassay. | 1 | Applied and Interdisciplinary Chemistry |
The discovery of mineral acids such as nitric acid is generally believed to go back to 13th-century European alchemy. The conventional view is that nitric acid was first described in pseudo-Gebers De inventione veritatis' ("On the Discovery of Truth", after ).
However, according to Eric John Holmyard and Ahmad Y. al-Hassan, the nitric acid also occurs in various earlier Arabic works such as the ("Chest of Wisdom") attributed to Jabir ibn Hayyan (8th century) or the attributed to the Fatimid caliph al-Hakim bi-Amr Allah (985–1021).
The recipe in the attributed to Jabir has been translated as follows:
Nitric acid is also found in post-1300 works falsely attributed to Albert the Great and Ramon Llull (both 13th century). These works describe the distillation of a mixture containing niter and green vitriol, which they call "eau forte" (aqua fortis). | 0 | Theoretical and Fundamental Chemistry |
Harford County, Maryland, found MTBE in wells near several of its filling stations beginning in 2004. This led the state of Maryland to make moves to ban MTBE.
In 2005, an Exxon-Mobil station in Fallston, Maryland, was found to be leaking MTBE into the local wells. The discovery resulted in the station being abruptly closed. Exxon-Mobil referred to the closure as a "business decision". Following the closure, MTBE levels in the area dropped.
In September 2004, Harford County placed a six-month moratorium on construction of filling stations. | 1 | Applied and Interdisciplinary Chemistry |
Temperature affects the elasticity of elastomers in an unusual way. When the elastomer is assumed to be in a stretched state, heating causes them to contract. Vice versa, cooling can cause expansion.
This can be observed with an ordinary rubber band. Stretching a rubber band will cause it to release heat (press it against your lips), while releasing it after it has been stretched will lead it to absorb heat, causing its surroundings to become cooler. This phenomenon can be explained with the Gibbs free energy. Rearranging ΔG=ΔH−TΔS, where G is the free energy, H is the enthalpy, and S is the entropy, we get . Since stretching is nonspontaneous, as it requires external work, TΔS must be negative. Since T is always positive (it can never reach absolute zero), the ΔS must be negative, implying that the rubber in its natural state is more entangled (with more microstates) than when it is under tension. Thus, when the tension is removed, the reaction is spontaneous, leading ΔG to be negative. Consequently, the cooling effect must result in a positive ΔH, so ΔS will be positive there.
The result is that an elastomer behaves somewhat like an ideal monatomic gas, inasmuch as (to good approximation) elastic polymers do not store any potential energy in stretched chemical bonds or elastic work done in stretching molecules, when work is done upon them. Instead, all work done on the rubber is "released" (not stored) and appears immediately in the polymer as thermal energy. In the same way, all work that the elastic does on the surroundings results in the disappearance of thermal energy in order to do the work (the elastic band grows cooler, like an expanding gas). This last phenomenon is the critical clue that the ability of an elastomer to do work depends (as with an ideal gas) only on entropy-change considerations, and not on any stored (i.e., potential) energy within the polymer bonds. Instead, the energy to do work comes entirely from thermal energy, and (as in the case of an expanding ideal gas) only the positive entropy change of the polymer allows its internal thermal energy to be converted efficiently (100% in theory) into work. | 0 | Theoretical and Fundamental Chemistry |
Beginning in 1994, the lab practical was added to the National Exam. It contains two tasks to be performed by each student with only the specified materials, and students are expected to describe their procedures and organize their findings. Past tasks have included chromatography, titration and qualitative analysis, and 90 minutes are allotted to complete the two experiments. | 1 | Applied and Interdisciplinary Chemistry |
The mechanism of fluorination by DAST parallels that of sulfur tetrafluoride. Attack of the hydroxyl group of the substrate on sulfur and elimination of hydrogen fluoride lead to an alkoxyaminosulfur difluoride intermediate. Nucleophilic attack by fluoride, either by an S1 or S2 pathway, leads to the product. Although clean configurational inversion has been observed in a number of chiral alcohols, carbocationic rearrangements have also been observed in some cases. The operative pathway depends on the structure of the substrate.
Conversion of aldehydes and ketones to the corresponding geminal difluorides proceeds by a similar mechanism, with addition of hydrogen fluoride preceding the hydroxyl replacement mechanism described above. An important side product in fluorinations of enolizable ketones is the corresponding vinyl fluoride, which results from deprotonation of intermediate fluoro carbocations.
Halides react by an essentially metathetical exchange of the halide for fluoride. Byproducts containing the exchanged halide have been isolated. | 0 | Theoretical and Fundamental Chemistry |
Temperature has an effect on both, the equilibrium state and kinetics of protein adsorption. The amount of protein adsorbed at high temperature is usually higher than that at room temperature. Temperature variation causes conformational changes in protein influencing adsorption. These conformational rearrangements in proteins results in an entropy gain which acts as a major driving force for protein adsorption. The temperature effect on protein adsorption can be seen in food manufacturing processes, especially liquid foods such as, milk which causes severe fouling on the wall surfaces of equipment where thermal treatment is carried out. | 1 | Applied and Interdisciplinary Chemistry |
River linking is a project of linking two or more rivers by creating a network of manually created reservoirs and canals, and providing land areas that otherwise does not have river water access and reducing the flow of water to sea using this means. It is based on the assumptions that surplus water in some rivers can be diverted to deficit rivers by creating a network of canals to interconnect the rivers. | 1 | Applied and Interdisciplinary Chemistry |
Plastarch Material (PSM) is a biodegradable, thermoplastic resin. It is composed of starch combined with several other biodegradable materials. The starch is modified in order to obtain heat-resistant properties, making PSM one of few bioplastics capable of withstanding high temperatures. PSM began to be commercially available in 2005.
PSM is stable in the atmosphere, but biodegradable in compost, wet soil, fresh water, seawater, and activated sludge where microorganisms exist. It has a softening temperature of 257 °F (125 °C) and a melting temperature of 313 °F (156 °C).
It is also hygroscopic. The material has to be dried in a material dryer at 150 °F (66 °C) for five hours or 180 °F (82 °C) for three hours. For injection molding and extrusion the barrel temperatures should be at 340° +/- 10 °F (171 °C) with the nozzle/die at 360 °F (182 °C).
Due to how similar PSM is to other plastics (such as polypropylene and CPET), PSM can run on many existing thermoforming and injection molding lines. PSM is currently used for a wide variety of applications in the plastic market, such as food packaging and utensils, personal care items, plastic bags, temporary construction tubing, industrial foam packaging, industrial and agricultural film, window insulation, construction stakes, and horticulture planters.
Since PSM is derived from a renewable resource (corn starch), it has become an attractive alternative to petrochemical-derived products. Unlike plastic, PSM can also be disposed of through incineration, resulting in non-toxic smoke and a white residue which can be used as fertilizer. However, concerns have been expressed about the impact of such technologies on food prices. | 0 | Theoretical and Fundamental Chemistry |
Organometallic compounds find wide use in commercial reactions, both as homogenous catalysts and as stoichiometric reagents. For instance, organolithium, organomagnesium, and organoaluminium compounds, examples of which are highly basic and highly reducing, are useful stoichiometrically but also catalyze many polymerization reactions.
Almost all processes involving carbon monoxide rely on catalysts, notable examples being described as carbonylations. The production of acetic acid from methanol and carbon monoxide is catalyzed via metal carbonyl complexes in the Monsanto process and Cativa process. Most synthetic aldehydes are produced via hydroformylation. The bulk of the synthetic alcohols, at least those larger than ethanol, are produced by hydrogenation of hydroformylation-derived aldehydes. Similarly, the Wacker process is used in the oxidation of ethylene to acetaldehyde.
Almost all industrial processes involving alkene-derived polymers rely on organometallic catalysts. The world's polyethylene and polypropylene are produced via both heterogeneously via Ziegler–Natta catalysis and homogeneously, e.g., via constrained geometry catalysts.
Most processes involving hydrogen rely on metal-based catalysts. Whereas bulk hydrogenations (e.g., margarine production) rely on heterogeneous catalysts, for the production of fine chemicals such hydrogenations rely on soluble (homogenous) organometallic complexes or involve organometallic intermediates. Organometallic complexes allow these hydrogenations to be effected asymmetrically.
Many semiconductors are produced from trimethylgallium, trimethylindium, trimethylaluminium, and trimethylantimony. These volatile compounds are decomposed along with ammonia, arsine, phosphine and related hydrides on a heated substrate via metalorganic vapor phase epitaxy (MOVPE) process in the production of light-emitting diodes (LEDs). | 0 | Theoretical and Fundamental Chemistry |
Examples of tetrazol-5-ylidenes based on tetrazole have been prepared by Araki. The N1 and N3 positions are substituted with alkyl or aryl groups. Transition metal complexes of these carbenes have been generated in situ. Mesoionic carbenes based on isoxazole and thiazole have been reported by Albrecht and Bertrand respectively. The isoxazol-4-ylidenes are trisubstituted in the N2, C3, and C5 positions with alkyl groups. The thiazol-5-ylidenes are trisubstituted in the C2, N3, and C4 positions with aryl groups. Transition metal complexes of both types of carbenes have been generated in situ. Bertrand also reported a 1,3-dithiol-5-ylidene based on 1,3-dithiolane, but it can only be isolated as a transition metal complex. | 0 | Theoretical and Fundamental Chemistry |
Sulfones with a good leaving group in the β position may undergo reductive elimination under desulfonylation conditions to afford alkenes. This process is a key step of the Julia olefination, which yields alkenes via addition of an α-sulfonyl carbanion to an aldehyde followed by reductive elimination. Sodium amalgam or samarium(II) iodide/HMPA may be used to convert β-sulfonyloxy or β-acyloxy sulfones to the corresponding alkenes. The key mechanistic step of this process is elimination of an anionic or organometallic intermediate to generate the alkene.
The use of sodium amalgam, which promotes the formation of essentially free alkyl anions, leads to (E) alkenes with extremely high selectivity. Samarium(II) iodide also produces the (E) alkene predominantly, but with lower selectivity. | 0 | Theoretical and Fundamental Chemistry |
This set of methods include number and brightness (N&B), photon counting histogram (PCH), fluorescence intensity distribution analysis (FIDA), and Cumulant Analysis. and Spatial Intensity Distribution Analysis. Combination of multiple methods is also reported.
Fluorescence cross correlation spectroscopy overcomes the weak dependence of diffusion rate on molecular mass by looking at multicolor coincidence. What about homo-interactions? The solution lies in brightness analysis. These methods use the heterogeneity in the intensity distribution of fluorescence to measure the molecular brightness of different species in a sample. Since dimers will contain twice the number of fluorescent labels as monomers, their molecular brightness will be approximately double that of monomers. As a result, the relative brightness is sensitive a measure of oligomerization. The average molecular brightness () is related to the variance () and the average intensity () as follows:
Here and are the fractional intensity and molecular brightness, respectively, of species . | 0 | Theoretical and Fundamental Chemistry |
Adrenodoxin (adrenal ferredoxin; ), putidaredoxin, and terpredoxin make up a family of soluble FeS proteins that act as single electron carriers, mainly found in eukaryotic mitochondria and Pseudomonadota. The human variant of adrenodoxin is referred to as ferredoxin-1 and ferredoxin-2. In mitochondrial monooxygenase systems, adrenodoxin transfers an electron from NADPH:adrenodoxin reductase to membrane-bound cytochrome P450. In bacteria, putidaredoxin and terpredoxin transfer electrons between corresponding NADH-dependent ferredoxin reductases and soluble P450s. The exact functions of other members of this family are not known, although Escherichia coli Fdx is shown to be involved in biogenesis of Fe–S clusters. Despite low sequence similarity between adrenodoxin-type and plant-type ferredoxins, the two classes have a similar folding topology.
Ferredoxin-1 in humans participates in the synthesis of thyroid hormones. It also transfers electrons from adrenodoxin reductase to CYP11A1, a CYP450 enzyme responsible for cholesterol side chain cleavage. FDX-1 has the capability to bind to metals and proteins. Ferredoxin-2 participates in heme A and iron–sulphur protein synthesis. | 0 | Theoretical and Fundamental Chemistry |
A boronic acid is an organic compound related to boric acid () in which one of the three hydroxyl groups () is replaced by an alkyl or aryl group (represented by R in the general formula ). As a compound containing a carbon–boron bond, members of this class thus belong to the larger class of organoboranes.
Boronic acids act as Lewis acids. Their unique feature is that they are capable of forming reversible covalent complexes with sugars, amino acids, hydroxamic acids, etc. (molecules with vicinal, (1,2) or occasionally (1,3) substituted Lewis base donors (alcohol, amine, carboxylate)). The pK of a boronic acid is ~9, but they can form tetrahedral boronate complexes with pK ~7. They are occasionally used in the area of molecular recognition to bind to saccharides for fluorescent detection or selective transport of saccharides across membranes.
Boronic acids are used extensively in organic chemistry as chemical building blocks and intermediates predominantly in the Suzuki coupling. A key concept in its chemistry is transmetallation of its organic residue to a transition metal.
The compound bortezomib with a boronic acid group is a drug used in chemotherapy. The boron atom in this molecule is a key substructure because through it certain proteasomes are blocked that would otherwise degrade proteins. Boronic acids are known to bind to active site serines and are part of inhibitors for porcine pancreatic lipase, subtilisin and the protease Kex2. Furthermore, boronic acid derivatives constitute a class of inhibitors for human acyl-protein thioesterase 1 and 2, which are cancer drug targets within the Ras cycle.
The boronic acid functional group is reputed to have low inherent toxicity. This is one of the reasons for the popularity of the Suzuki coupling in the development and synthesis of pharmaceutical agents. However, a significant fraction of commonly used boronic acids and their derivatives were recently found to gives a positive Ames test and act as chemical mutagens. The mechanism of mutagenicity is thought to involve the generation of organic radicals via oxidation of the boronic acid by atmospheric oxygen. | 0 | Theoretical and Fundamental Chemistry |
In the electron transport chain, complex I (CI) catalyzes the reduction of ubiquinone (UQ) to ubiquinol (UQH) by the transfer of two electrons from reduced nicotinamide adenine dinucleotide (NADH) which translocates four protons from the mitochondrial matrix to the IMS:
Complex III (CIII) catalyzes the Q-cycle. The first step involving the transfer of two electrons from the UQH reduced by CI to two molecules of oxidized cytochrome c at the Q site. In the second step, two more electrons reduce UQ to UQH at the Q site. The total reaction is:
Complex IV (CIV) catalyzes the transfer of two electrons from the cytochrome c reduced by CIII to one half of a full oxygen. Utilizing one full oxygen in oxidative phosphorylation requires the transfer of four electrons. The oxygen will then consume four protons from the matrix to form water while another four protons are pumped into the IMS, to give a total reaction | 0 | Theoretical and Fundamental Chemistry |
During the implosion of an inertial confinement fusion target, the hot shell material surrounding the cold D–T fuel layer is shock-accelerated. This instability is also seen in magnetized target fusion (MTF). Mixing of the shell material and fuel is not desired and efforts are made to minimize any tiny imperfections or irregularities which will be magnified by RMI.
Supersonic combustion in a scramjet may benefit from RMI as the fuel-oxidants interface is enhanced by the breakup of the fuel into finer droplets. Also in studies of deflagration to detonation transition (DDT) processes show that RMI-induced flame acceleration can result in detonation. | 1 | Applied and Interdisciplinary Chemistry |
RuBP acts as an enzyme inhibitor for the enzyme rubisco, which regulates the net activity of carbon fixation. When RuBP is bound to an active site of rubisco, the ability to activate via carbamylation with and is blocked. The functionality of rubisco activase involves removing RuBP and other inhibitory bonded molecules to re-enable carbamylation on the active site. | 0 | Theoretical and Fundamental Chemistry |
The fundamental law of extinction states that the extinction process is linear in the intensity of radiation and amount of radiatively active matter, provided that the physical state is held constant. (Neither concentration or length are fundamental parameters.) There are two factors that determine the degree to which a medium containing particles will attenuate a light beam: the number of particles encountered by the light beam, and the degree to which each particle extinguishes the light.
For the case of absorption (Beer), this later quantity is called the absorptivity [], which is defined as "the property of a body that determines the fraction of incident radiation absorbed by the body". The Beer-Lambert law uses concentration and length in order to determine the number of particles the beam encounters. If we know the area of a collimated beam (directed radiation), we can get the number of particles in a distance. The number of particles encountered can be calculated from Avogadro's number, the molar concentration, the cross-sectional area of the incident beam .
There must be a large number of particles that are uniformly distributed for this relationship to hold. In practice, the beam area is thought of as a constant, and since the fraction [] has the area in both the numerator and denominator, the beam area cancels in the calculation of the absorbance. The units of the absorptivity must match the units in which the sample is described. For example, if the sample is described by mass concentration (g/L) and length (cm), then the units on the absorptivity would be [ L g cm], so that the absorbance has no units.
For the case of "extinction" (Bouguer), the sum of absorption and scatter, the terms absorption, scattering, and extinction cross-sections are often used. The fraction of light extinguished by the sample may be described by the extinction cross section (fraction extinguished per particle). the number of particles in a unit distance and the distance in those units. For example: [ (fraction extinguished / particle) (# particles / meter) (# meters / sample) = fraction extinguished / sample ] | 0 | Theoretical and Fundamental Chemistry |
Benzyl and allyl ligands often exhibit similar chemical properties. Benzyl ligands commonly adopt either η or η bonding modes. The interconversion reactions parallel those of η- or η-allyl ligands:
:CpFe(CO)(η-CHPh) → CpFe(CO)(η-CHPh) + CO
In all bonding modes, the benzylic carbon atom is more strongly attached to the metal as indicated by M-C bond distances, which differ by ca. 0.2 Å in η-bonded complexes. X-ray crystallography demonstrate that the benzyl ligands in tetrabenzylzirconium are highly flexible. One polymorph features four η-benzyl ligands, whereas another polymorph has two η- and two η-benzyl ligands. | 0 | Theoretical and Fundamental Chemistry |
Formation with mineral bridges occur with the formation of nanocrystals. Growth is quenched at this stage by the absorption of a polymer into the nanoparticle surface. Now mineral bridges can nucleate at the defect site, within the growing inhibition layer on the nanocrystal. Through this, a new nanocrystal grows on the mineral bridge, and the growth is again stopped by the polymer. This process is repeated until the crystal builds up. | 0 | Theoretical and Fundamental Chemistry |
Size-exclusion chromatography (SEC) separates polymer molecules and biomolecules based on differences in their molecular size (actually by a particle's Stokes radius). The separation process is based on the ability of sample molecules to permeate through the pores of gel spheres, packed inside the column, and is dependent on the relative size of analyte molecules and the respective pore size of the absorbent. The process also relies on the absence of any interactions with the packing material surface.
Two types of SEC are usually termed:
# Gel permeation chromatography (GPC)—separation of synthetic polymers (aqueous or organic soluble). GPC is a powerful technique for polymer characterization using primarily organic solvents.
# Gel filtration chromatography (GFC)—separation of water-soluble biopolymers. GFC uses primarily aqueous solvents (typically for aqueous soluble biopolymers, such as proteins, etc.).
The separation principle in SEC is based on the fully, or partially penetrating of the high molecular weight substances of the sample into the porous stationary-phase particles during their transport through column. The mobile-phase eluent is selected in such a way that it totally prevents interactions with the stationary phase's surface. Under these conditions, the smaller the size of the molecule, the more it is able to penetrate inside the pore space and the movement through the column takes longer. On the other hand, the bigger the molecular size, the higher the probability the molecule will not fully penetrate the pores of the stationary phase, and even travel around them, thus, will be eluted earlier. The molecules are separated in order of decreasing molecular weight, with the largest molecules eluting from the column first and smaller molecules eluting later. Molecules larger than the pore size do not enter the pores at all, and elute together as the first peak in the chromatogram and this is called total exclusion volume which defines the exclusion limit for a particular column. Small molecules will permeate fully through the pores of the stationary phase particles and will be eluted last, marking the end of the chromatogram, and may appear as a total penetration marker.
In biomedical sciences it is generally considered as a low resolution chromatography and thus it is often reserved for the final, "polishing" step of the purification. It is also useful for determining the tertiary structure and quaternary structure of purified proteins. SEC is used primarily for the analysis of large molecules such as proteins or polymers. SEC works also in a preparative way by trapping the smaller molecules in the pores of a particles. The larger molecules simply pass by the pores as they are too large to enter the pores. Larger molecules therefore flow through the column quicker than smaller molecules: that is, the smaller the molecule, the longer the retention time.
This technique is widely used for the molecular weight determination of polysaccharides. SEC is the official technique (suggested by European pharmacopeia) for the molecular weight comparison of different commercially available low-molecular weight heparins. | 0 | Theoretical and Fundamental Chemistry |
The colloidal probes are normally fabricated by gluing a colloidal particle to a tip-less cantilever with a micromanipulator in air. The subsequent rewetting of the probe may lead to the formation of nanosized bubbles on the probe surface. This problem can be avoided by attaching the colloidal particles under wet conditions in AFM fluid cell to appropriately functionalized cantilevers. While the colloidal probe technique is mostly used in the sphere-plane geometry, it can be also used in the sphere-sphere geometry. The latter geometry further requires a lateral centering of the two particles, which can be either achieved with an optical microscope or an AFM scan. The results obtained in these two different geometries can be related with the Derjaguin approximation.
The force measurements rely on an accurate value of the spring constant of the cantilever. This spring constant can be measured by different techniques. The thermal noise method is the simplest to use, as it is implemented on most AFMs. This approach relies on the determination of the mean square amplitude of the cantilever displacement due to spontaneous thermal fluctuations. This quantity is related to the spring constant by means of the equipartition theorem. In the added mass method one attaches a series of metal beads to the cantilever and each case one determines the resonance frequency. By exploiting the relation for a harmonic oscillator between the resonance frequency and the mass added one can evaluate the spring constant as well. The frictional force method relies on measurement of the approach and retract curves of the cantilever through a viscous fluid. Since the hydrodynamic drag of a sphere close to a planar substrate is known theoretically, the spring constant of the cantilever can be deduced. The geometrical method exploits relations between the geometry of the cantilever and its elastic properties.
The separation is normally measured from the onset of the constant compliance region. While the relative surface separation can be determined with a resolution of 0.1 nm or better, the absolute surface separation is obtained from the onset of the constant compliance region. While this onset can be determined for solid samples with a precision between 0.5–2 nm, the location of this onset can be problematic for soft repulsive interactions and for deformable surfaces. For this reason, techniques have been developed to measure the surface separation independently (e.g., total internal reflection microscopy, reflection interference contrast microscopy).
By scanning the sample with the colloidal probe laterally permits to exploit friction forces between the probe and the substrate. Since this technique exploits the torsion of the cantilever, to obtain quantitative data the torsional spring constant of the cantilever must be determined.
A related technique involving similar type of force measurements with the AFM is the single molecular force spectroscopy. However, this technique uses a regular AFM tip to which a single polymer molecule is attached. From the retraction part of the force curve, one can obtain information about stretching of the polymer or its peeling from the surface. | 0 | Theoretical and Fundamental Chemistry |
The presence of atmospheric methane has a role in the scientific search for extra-terrestrial life. The justification is that on an astronomical timescale, methane in the atmosphere of an Earth-like celestial body will quickly dissipate, and that its presence on such a planet or moon therefore indicates that something is replenishing it. If methane is detected (by using a spectrometer for example) this may indicate that life is, or recently was, present.
This was debated when methane was discovered in the Martian atmosphere by M.J. Mumma of NASAs Goddard Flight Center, and verified by the Mars Express Orbiter (2004) and in Titans atmosphere by the Huygens probe (2005). This debate was furthered with the discovery of transient, spikes of methane on Mars by the Curiosity Rover.
It is argued that atmospheric methane can come from volcanoes or other fissures in the planet's crust and that without an isotopic signature, the origin or source may be difficult to identify.
On 13 April 2017, NASA confirmed that the dive of the Cassini orbiter spacecraft on 28 October 2015 discovered an Enceladus plume which has all the ingredients for methanogenesis-based life forms to feed on. Previous results, published in March 2015, suggested hot water is interacting with rock beneath the sea of Enceladus; the new finding supported that conclusion, and add that the rock appears to be reacting chemically. From these observations scientists have determined that nearly 98 percent of the gas in the plume is water, about 1 percent is hydrogen, and the rest is a mixture of other molecules including carbon dioxide, methane and ammonia. | 1 | Applied and Interdisciplinary Chemistry |
The tentative rate equation determined by the method of initial rates is therefore normally verified by comparing the concentrations measured over a longer time (several half-lives) with the integrated form of the rate equation; this assumes that the reaction goes to completion.
For example, the integrated rate law for a first-order reaction is
where is the concentration at time and is the initial concentration at zero time. The first-order rate law is confirmed if is in fact a linear function of time. In this case the rate constant is equal to the slope with sign reversed. | 0 | Theoretical and Fundamental Chemistry |
As defined above, the light compensation point I is when no net carbon assimilation occurs. At this point, the organism is neither consuming nor building biomass. The net gaseous exchange is also zero at this point.
I is a practical value that can be reached during early mornings and early evenings. Respiration is relatively constant with regard to light, whereas photosynthesis depends on the intensity of sunlight. | 0 | Theoretical and Fundamental Chemistry |
Carborane acid was first discovered and synthesized by Professor Christopher Reed and his colleagues in 2004 at the University of California, Riverside. The parent molecule from which carborane acid is derived, an icosahedral carboranate anion, , was first synthesized at DuPont in 1967 by Walter Knoth. Research into this molecule's properties was put on hiatus until the mid 1980s when the Czech group of boron scientists, Plešek, Štíbr, and Heřmánek improved the process for halogenation of carborane molecules. These findings were instrumental in developing the current procedure for carborane acid synthesis. The process consists of treating Cs[HCBH] with , refluxing under dry argon to fully chlorinate the molecule yielding carborane acid, but this has been shown to fully chlorinate only under select conditions.
In 2010, Reed published a guide giving detailed procedures for the synthesis of carborane acids and their derivatives. Nevertheless, the synthesis of carborane acids remains lengthy and difficult and requires a well-maintained glovebox and some specialized equipment. The starting material is commercially available decaborane(14), a highly toxic substance. The most well-studied carborane acid is prepared in 13 steps. The last few steps are especially sensitive and require a glovebox at O without any weakly basic solvent vapors, since bases as weak as benzene or dichloromethane will react with carborane-based electrophiles and Brønsted acids. The final step of the synthesis is the metathesis of the μ-hydridodisilylium carboranate salt with excess liquid, anhydrous hydrogen chloride, presumably driven by the formation of strong Si–Cl and H–H bonds in the volatile byproducts:
::[EtSi–H–SiEt][HCBCl] + 2HCl → + 2EtSiCl + H
The product was isolated by evaporation of the byproducts and was characterized by its infrared (ν = 3023 cm) and nuclear magnetic resonance (δ 4.55 (s, 1H, CH), 20.4 (s, 1H, H) in liquid SO) spectra (note the extremely downfield chemical shift of the acidic proton). Although the reactions used in the synthesis are analogous, obtaining a pure sample of the more acidic turned out to be even more difficult, requiring extremely rigorous procedures to exclude traces of weakly basic impurities. | 0 | Theoretical and Fundamental Chemistry |
The removal of the inhibitory RuBP, CA1P, and the other inhibitory substrate analogs by activase requires the consumption of ATP. This reaction is inhibited by the presence of ADP, and, thus, activase activity depends on the ratio of these compounds in the chloroplast stroma. Furthermore, in most plants, the sensitivity of activase to the ratio of ATP/ADP is modified by the stromal reduction/oxidation (redox) state through another small regulatory protein, thioredoxin. In this manner, the activity of activase and the activation state of RuBisCO can be modulated in response to light intensity and, thus, the rate of formation of the ribulose 1,5-bisphosphate substrate. | 0 | Theoretical and Fundamental Chemistry |
After initial reports of a "homoaromatic" structure for the tris-homocyclopropenyl cation were published by Winstein, many groups began to report observations of similar compounds. One of the best studied of these molecules is the homotropylium cation, the parent compound of which was first isolated as a stable salt by Pettit, et al. in 1962, when the group reacted cyclooctatraene with strong acids. Much of the early evidence for homoaromaticity comes from observations of unusual NMR properties associated with this molecule. | 0 | Theoretical and Fundamental Chemistry |
During the 1960s and early 1970s, the drug culture adopted LSD as the psychedelic drug of choice, particularly amongst the hippie community. However, LSD dramatically decreased in popularity in the mid-1970s (see above graph which covers the period 2008). This decline was due to negative publicity centred on side-effects of LSD use, its criminalization, and the increasing effectiveness of drug law enforcement efforts, rather than new medical information. The last country to produce LSD legally (until 1975) was Czechoslovakia; during the 1960s, high-quality LSD was imported from the communist country to California, a fact appreciated by Leary in The Politics of Ecstasy.
Victor James Kapur had the first known home grown UK acid lab. Up to then, all LSD had been imported from the U.S. or was remnant produce of Sandoz before it stopped producing LSD. In 1967, Kapur was caught distributing 19 grams of crystalline LSD and subsequently the police raided both of his laboratories. One was in the back room of Kapur's chemist shop and another, larger one, was in a garage he rented from a friend of his brother-in-law.
A second group was busted in 1969. A lab in Kent, and a flat in London were raided simultaneously and quantities of equipment and LSD seized along with the two men who had been making the LSD, Quentin Theobald and Peter Simmons.
The availability of LSD had been drastically reduced by the late 1970s due to a combination of governmental controls and law enforcement. The supply of constituent chemicals including lysergic acid, which was used for production of LSD in the 1960s, and ergotamine tartrate, which was used for production in the 1970s, were placed under tight surveillance and government funding for LSD research was almost eliminated. These efforts were augmented by a series of major busts in England and Europe. One of the most famous was "Operation Julie" in Britain in 1978, named after the first name of the female drug squad officer involved; it broke up one of the largest LSD manufacturing and distribution operations in the world at that time, headed by chemist Richard Kemp. The group targeted by the Julie task force were reputed to have had links to the mysterious The Brotherhood of Eternal Love and to Ronald Stark. | 1 | Applied and Interdisciplinary Chemistry |
As of late 2009, available public information suggests that quite a few are in clinical trials. Several biotechnology and pharmaceutical companies are developing TRPV1 ligands and the emphasis seems to be on both agonists and antagonists. Although the agonists appear to be further along in clinical development. | 1 | Applied and Interdisciplinary Chemistry |
Particles of refractory material in contact with aluminium can detach and become inclusions. We can find graphite inclusions (C), alumina inclusions (alpha-AlO), CaO, SiO, …
After some time, graphite refractory in contact with aluminium will react to create aluminum carbides (harder and more detrimental inclusions).
In aluminium alloy containing magnesium, the magnesium reacts with some refractories to create rather big and hard inclusions similar to spinels.
Unreacted refractory particles can originate from the degradation of refractory materials which comes in contact with the melt. | 1 | Applied and Interdisciplinary Chemistry |
Histone Acetyltransferases, also known as HATs, are a family of enzymes that acetylate the histone tails of the nucleosome. This, and other modifications, are expressed based on the varying states of the cellular environment. Many proteins with acetylating abilities have been documented and, after a time, were categorized based on sequence similarities between them. These similarities are high among members of a family, but members from different families show very little resemblance. Some of the major families identified so far are as follows. | 0 | Theoretical and Fundamental Chemistry |
In coordination chemistry, a structure is first described by its coordination number, the number of ligands attached to the metal (more specifically, the number of donor atoms). Usually one can count the ligands attached, but sometimes even the counting can become ambiguous. Coordination numbers are normally between two and nine, but large numbers of ligands are not uncommon for the lanthanides and actinides. The number of bonds depends on the size, charge, and electron configuration of the metal ion and the ligands. Metal ions may have more than one coordination number.
Typically the chemistry of transition metal complexes is dominated by interactions between s and p molecular orbitals of the donor-atoms in the ligands and the d orbitals of the metal ions. The s, p, and d orbitals of the metal can accommodate 18 electrons (see 18-Electron rule). The maximum coordination number for a certain metal is thus related to the electronic configuration of the metal ion (to be more specific, the number of empty orbitals) and to the ratio of the size of the ligands and the metal ion. Large metals and small ligands lead to high coordination numbers, e.g. . Small metals with large ligands lead to low coordination numbers, e.g. . Due to their large size, lanthanides, actinides, and early transition metals tend to have high coordination numbers.
Most structures follow the points-on-a-sphere pattern (or, as if the central atom were in the middle of a polyhedron where the corners of that shape are the locations of the ligands), where orbital overlap (between ligand and metal orbitals) and ligand-ligand repulsions tend to lead to certain regular geometries. The most observed geometries are listed below, but there are many cases that deviate from a regular geometry, e.g. due to the use of ligands of diverse types (which results in irregular bond lengths; the coordination atoms do not follow a points-on-a-sphere pattern), due to the size of ligands, or due to electronic effects (see, e.g., Jahn–Teller distortion):
*Linear for two-coordination
*Trigonal planar for three-coordination
*Tetrahedral or square planar for four-coordination
*Trigonal bipyramidal for five-coordination
*Octahedral for six-coordination
*Pentagonal bipyramidal for seven-coordination
*Square antiprismatic for eight-coordination
*Tricapped trigonal prismatic for nine-coordination
The idealized descriptions of 5-, 7-, 8-, and 9- coordination are often indistinct geometrically from alternative structures with slightly differing L-M-L (ligand-metal-ligand) angles, e.g. the difference between square pyramidal and trigonal bipyramidal structures.
*Square pyramidal for five-coordination
* Capped octahedral or capped trigonal prismatic for seven-coordination
* Dodecahedral or bicapped trigonal prismatic for eight-coordination
*Capped square antiprismatic for nine-coordination
To distinguish between the alternative coordinations for five-coordinated complexes, the τ geometry index was invented by Addison et al. This index depends on angles by the coordination center and changes between 0 for the square pyramidal to 1 for trigonal bipyramidal structures, allowing to classify the cases in between. This system was later extended to four-coordinated complexes by Houser et al. and also Okuniewski et al.
In systems with low d electron count, due to special electronic effects such as (second-order) Jahn–Teller stabilization, certain geometries (in which the coordination atoms do not follow a points-on-a-sphere pattern) are stabilized relative to the other possibilities, e.g. for some compounds the trigonal prismatic geometry is stabilized relative to octahedral structures for six-coordination.
*Bent for two-coordination
*Trigonal pyramidal for three-coordination
*Trigonal prismatic for six-coordination | 0 | Theoretical and Fundamental Chemistry |
NADPH plays an important role as an antioxidant by decreasing the reactive oxygen produced during rapid cell proliferation. It has been shown that attenuation of the PPP would dampen NADPH production in cancer cells, leading to the decrease in macromolecular biosynthesis and rendering the transformed cells that are vulnerable free radical-mediated damage. In this way, the advantage conferred by PKM2 expression would be eliminated. In preclinical studies, drugs such as 6-amino-nicotinamide (6-AN), which inhibits G6P dehydrogenase, the enzyme that initiates the PPP have shown anti-tumorigenic effects in leukemia, glioblastoma and lung cancer cell lines.
Cyclosporine inhibits TOR and is used as an effective immunosuppressant. Mycophenolic acid inhibits of IMPDH and pyrimidine biosynthesis and is clinically used as immunosuppressant. Both agents also display anti-tumor effects in animal studies. Metabolites such as Alanine, Saturated lipids, Glycine, Lactate, Myo-Inositol, Nucleotides, Polyunsaturated fatty acids and Taurine are considered as the potential biomarkers in various studies. | 1 | Applied and Interdisciplinary Chemistry |
Spirapril, sold under the brand name Renormax among others, is an ACE inhibitor antihypertensive drug used to treat hypertension. It belongs to dicarboxy group of ACE inhibitors.
It was patented in 1980 and approved for medical use in 1995. | 0 | Theoretical and Fundamental Chemistry |
Efforts to understand how proteins are encoded began after DNA's structure was discovered in 1953. The key discoverers, English biophysicist Francis Crick and American biologist James Watson, working together at the Cavendish Laboratory of the University of Cambridge, hypothesied that information flows from DNA and that there is a link between DNA and proteins. Soviet-American physicist George Gamow was the first to give a workable scheme for protein synthesis from DNA. He postulated that sets of three bases (triplets) must be employed to encode the 20 standard amino acids used by living cells to build proteins, which would allow a maximum of amino acids. He named this DNA–protein interaction (the original genetic code) as the "diamond code".
In 1954, Gamow created an informal scientific organisation the RNA Tie Club, as suggested by Watson, for scientists of different persuasions who were interested in how proteins were synthesised from genes. However, the club could have only 20 permanent members to represent each of the 20 amino acids; and four additional honorary members to represent the four nucleotides of DNA.
The first scientific contribution of the club, later recorded as "one of the most important unpublished articles in the history of science" and "the most famous unpublished paper in the annals of molecular biology", was made by Crick. Crick presented a type-written paper titled "On Degenerate Templates and the Adaptor Hypothesis: A Note for the RNA Tie Club" to the members of the club in January 1955, which "totally changed the way we thought about protein synthesis", as Watson recalled. The hypothesis states that the triplet code was not passed on to amino acids as Gamow thought, but carried by a different molecule, an adaptor, that interacts with amino acids. The adaptor was later identified as tRNA. | 1 | Applied and Interdisciplinary Chemistry |
This is also known as the P test. It uses a 1–5% ethanolic solution of para-phenylenediamine (PD), made by placing a drop of ethanol (70–95%) over a few crystals of the chemical; this yields an unstable, light sensitive solution that lasts for about a day. An alternative form of this solution, called Steiners solution, is much longer lasting although it produces less intense colour reactions. It is typically prepared by dissolving 1 gram of PD, 10 grams of sodium sulfite, and 0.5 millilitres of detergent in 100 millilitres of water; initially pink in colour, the solution becomes purple with age. Steiners solution will last for months. The phenylenediamine reacts with aldehydes to yield Schiff bases according to the following reaction:
Products of this reaction are yellow to red in colour. Most β-orcinol depsidones and some β-orcinol depsides will react positively. The PD test, known for its high specificity towards substances that yield K+ yellow or red reactions, has largely replaced the simpler yet less conclusive K test. PD is poisonous both as a powder and a solution, and surfaces that come in contact with it (including skin) will discolour.
Some common and widely distributed lichens that have lichen products with a positive reaction to P include Parmelia subrudecta, which is PD+ (yellow) because of the didepside atranorin, and Hypogymnia physodes, which is PD+ (orange) because of the depsidone physodalic acid. | 0 | Theoretical and Fundamental Chemistry |
In radical disproportionation reactions one molecule acts as an acceptor while the other molecule acts as a donor. In the most common disproportionation reactions, a hydrogen atom is taken, or abstracted by the acceptor as the donor molecule undergoes an elimination reaction to form a double bond. Other atoms such as halogens may also be abstracted during a disproportionation reaction. Abstraction occurs as a head to tail reaction with the atom that is being abstracted facing the radical atom on the other molecule. | 0 | Theoretical and Fundamental Chemistry |
Measured area depends on instrument design. The minimum analysis area ranges from 10 to 200 micrometres. Largest size for a monochromatic beam of X-rays is 1–5 mm. Non-monochromatic beams are 10–50 mm in diameter. Spectroscopic image resolution levels of 200 nm or below has been achieved on latest imaging XPS instruments using synchrotron radiation as X-ray source. | 0 | Theoretical and Fundamental Chemistry |
During neurotransmission, the pre-synaptic neuron releases neurotransmitters into the synaptic cleft which bind to cognate receptors expressed on the post-synaptic neuron. Based upon the interaction between the transmitter and receptor, neurotransmitters may trigger a variety of effects in the post-synaptic cell, such as excitation, inhibition, or the initiation of second messenger cascades. Based on the cell, these effects may result in the on-site synthesis of endogenous cannabinoids anandamide or 2-AG by a process that is not entirely clear, but results from an elevation in intracellular calcium. Expression appears to be exclusive, so that both types of endocannabinoids are not co-synthesized. This exclusion is based on synthesis-specific channel activation: a recent study found that in the bed nucleus of the stria terminalis, calcium entry through voltage-sensitive calcium channels produced an L-type current resulting in 2-AG production, while activation of mGluR1/5 receptors triggered the synthesis of anandamide.
Evidence suggests that the depolarization-induced influx of calcium into the post-synaptic neuron causes the activation of an enzyme called transacylase. This enzyme is suggested to catalyze the first step of endocannabinoid biosynthesis by converting phosphatidylethanolamine, a membrane-resident phospholipid, into N-acyl-phosphatidylethanolamine (NAPE). Experiments have shown that phospholipase D cleaves NAPE to yield anandamide. This process is mediated by bile acids.
In NAPE-phospholipase D (NAPEPLD)-knockout mice, cleavage of NAPE is reduced in low calcium concentrations, but not abolished, suggesting multiple, distinct pathways are involved in anandamide synthesis. The synthesis of 2-AG is less established and warrants further research.
Once released into the extracellular space by a putative endocannabinoid transporter, messengers are vulnerable to glial cell inactivation. Endocannabinoids are taken up by a transporter on the glial cell and degraded by fatty acid amide hydrolase (FAAH), which cleaves anandamide into arachidonic acid and ethanolamine or monoacylglycerol lipase (MAGL), and 2-AG into arachidonic acid and glycerol. While arachidonic acid is a substrate for leukotriene and prostaglandin synthesis, it is unclear whether this degradative byproduct has unique functions in the central nervous system. Emerging data in the field also points to FAAH being expressed in postsynaptic neurons complementary to presynaptic neurons expressing cannabinoid receptors, supporting the conclusion that it is major contributor to the clearance and inactivation of anandamide and 2-AG after endocannabinoid reuptake. A neuropharmacological study demonstrated that an inhibitor of FAAH (URB597) selectively increases anandamide levels in the brain of rodents and primates. Such approaches could lead to the development of new drugs with analgesic, anxiolytic-like and antidepressant-like effects, which are not accompanied by overt signs of abuse liability. | 1 | Applied and Interdisciplinary Chemistry |
Receptor-activated G proteins are bound to the inner surface of the cell membrane. They consist of the G and the tightly associated G subunits.
There are four main families of G subunits: Gα (G stimulatory), Gα (G inhibitory), Gα, and Gα. They behave differently in the recognition of the effector molecule, but share a similar mechanism of activation. | 1 | Applied and Interdisciplinary Chemistry |
Hydrophilic solids, which include many solids of biological origin, can readily absorb water. Polar interactions between water and the molecules of the solid favor partition of the water into the solid, which can allow significant absorption of water vapor even in relatively low humidity. | 0 | Theoretical and Fundamental Chemistry |
In a split volute or double volute pump, the path along the volute is partitioned, providing two distinct discharge paths. The streams start out 180 degrees from each other, and merge by the time they reach the discharge port. This arrangement helps to balance the radial force on the bearings. | 1 | Applied and Interdisciplinary Chemistry |
Strong evidence of metallurgical activities has been revealed in levels 9 to 6, dating to the Ubaid period, and especially in level 7 (4166 +/- 170 cal BC). Hearths or natural draft furnaces, slag, ore, and pigment had been recovered throughout the site. This was in the context of architectural complexes typical of southern Mesopotamian architecture.
Unusually, the metallurgical activities at the site appear to have been limited to the melting and casting of copper objects. Arsenical copper objects were clearly manufactured on site, yet the technological aspects of this productions remain unclear. This is because the primary smelting of ore seems to have been undertaken elsewhere, perhaps already at the mining sites. So questions remain as to whether or not arsenic was already present in the ores, or added later.
In contrast, the related Norşuntepe site provides a better context of production, and demonstrates that some form of arsenic alloying was indeed taking place by the 4th millennium BC. Since the slag identified at Norşuntepe contains no arsenic, this means that arsenic was added separately. | 1 | Applied and Interdisciplinary Chemistry |
Amphiphiles are molecules that have both hydrophobic and hydrophilic domains. Detergents are composed of amphiphiles that allow hydrophobic molecules to be solubilized in water by forming micelles and bilayers (as in soap bubbles). They are also important to cell membranes composed of amphiphilic phospholipids that prevent the internal aqueous environment of a cell from mixing with external water. | 0 | Theoretical and Fundamental Chemistry |
The N terminal domain is well conserved across different species. This may be due to its important function in substrate and cation binding. The residues involved in methionine binding are found in the N-terminal domain. | 1 | Applied and Interdisciplinary Chemistry |
Signs Of LIfe Detector (SOLID) is an analytical instrument under development to detect extraterrestrial life in the form of organic biosignatures obtained from a core drill during planetary exploration.
The instrument is based on fluorescent immunoassays and it is being developed by the Spanish Astrobiology Center (CAB) in collaboration with the NASA Astrobiology Institute. SOLID is currently undergoing testing for use in astrobiology space missions that search for common biomolecules that may indicate the presence of extraterrestrial life, past or present. The system was validated in field tests and engineers are looking into ways to refine the method and miniaturize the instrument further. | 1 | Applied and Interdisciplinary Chemistry |
Macromolecular Chemistry and Physics is a biweekly peer-reviewed scientific journal covering polymer science. It publishes full papers, talents, trends, and highlights in all areas of polymer science, from chemistry to physical chemistry, physics, and materials science. | 0 | Theoretical and Fundamental Chemistry |
This method cannot be applied if Mantoux test (tuberculin skin test) has been done within the last 40 days, because it can hamper the results of the ALS test. This test is used as a complementary test to other tests, e.g. chest X-ray, ESR, CRP, history of contact with active TB case, failure with conventional antibiotic treatment etc.; anti-TB therapy is not provided if only ALS test is positive. The reason is that this method is potentially an early biomarker of active infection. However, if a subject does not show any physical symptoms, the doctors cannot prescribe anti-TB treatment. | 1 | Applied and Interdisciplinary Chemistry |
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