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The glycosyl donor is protected at C-2 by OAll group. The allyl group is then isomerized to a prop-1-enyl ether using a rhodium hydride generated from Wilkinsons catalyst ((PPh)RhCl) and butyllithium (BuLi). The resulting enol ether is then treated with NIS and the glycosyl acceptor to generate a mixed acetal. The 1,2-cis' (e.g. β-mannosyl) product is formed in a final step through activation of the anomeric leaving group, delivery of the aglycon from the mixed acetal and finally hydrolytic work-up to remove the remains of the propenyl ether from O-2. | 0 | Theoretical and Fundamental Chemistry |
The basic principle of the phenol-chloroform extraction is that DNA and RNA are relatively insoluble in phenol and chloroform, while other cellular components are relatively soluble in these solvents. The addition of a phenol/chloroform mixture will dissolve protein and lipid contaminants, leaving the nucleic acids in the aqueous phase. It also denatures proteins, like DNase, which is especially important if the plasmids are to be used for enzyme digestion. Otherwise, smearing may occur in enzyme restricted form of plasmid DNA. | 1 | Applied and Interdisciplinary Chemistry |
In September 2020, the European Medicines Agency recommended that the use of trabectedin in treating ovarian cancer remain unchanged. | 0 | Theoretical and Fundamental Chemistry |
Work on aequorin began with E. Newton Harvey in 1921. Though Harvey was unable to demonstrate a classical luciferase-luciferin reaction, he showed that water could produce light from dried photocytes and that light could be produced even in the absence of oxygen. Later, Osamu Shimomura began work into the bioluminescence of Aequorea in 1961. This involved tedious harvesting of tens of thousands of jellyfish from the docks in Friday Harbor, Washington. It was determined that light could be produced from extracts with seawater, and more specifically, with calcium. It was also noted during the extraction the animal creates green light due to the presence of the green fluorescent protein, which changes the native blue light of aequorin to green.
While the main focus of his work was on the bioluminescence, Shimomura and two others, Martin Chalfie and Roger Tsien, were awarded the Nobel Prize in 2008 for their work on green fluorescent proteins. | 1 | Applied and Interdisciplinary Chemistry |
Sodium hydrogen selenite is an inorganic chemical consisting of a ratio of one hydrogen, one sodium, three oxygen, and one selenium atom.
It is the sodium salt of the conjugate base of selenous acid. This compound finds therapeutic application for providing the essential trace element selenium. Its preparation involves reacting sodium hydroxide with selenium dioxide. | 0 | Theoretical and Fundamental Chemistry |
Powder defoamers are in principle oil-based defoamers on a particulate carrier like silica. These are added to powdered products like cement, plaster and detergents. | 0 | Theoretical and Fundamental Chemistry |
A volute is a curved funnel that increases in area as it approaches the discharge port. The volute of a centrifugal pump is the casing that receives the fluid being pumped by the impeller, maintaining the velocity of the fluid through to the diffuser. As liquid exits the impeller it has high kinetic energy and the volute directs this flow through to the discharge. As the fluid travels along the volute it is joined by more and more fluid exiting the impeller but, as the cross sectional area of the volute increases, the velocity is maintained if the pump is running close to the design point. If the pump has a low flow rate then the velocity will decrease across the volute leading to a pressure rise causing a cross thrust across the impeller that we see as vibration. If the pump flow is higher than design the velocity will increase across the volute and the pressure will decrease according to the first law of thermodynamics. This will cause a side thrust in the opposite direction to that caused by low flow but the result is the samevibration with resultant short bearing and seal life.
The volute does not convert kinetic energy into pressurethat is done at the diffuser by reducing liquid velocity while increasing pressure.
The name "volute" is inspired by the resemblance of this kind of casing to the scroll-like part near the top of an ionic order column in classical architecture, called a volute. | 1 | Applied and Interdisciplinary Chemistry |
The product, delivered to the point of consumption, is called potable water if it meets the water quality standards required for human consumption.
The water in the supply network is maintained at positive pressure to ensure that water reaches all parts of the network, that a sufficient flow is available at every take-off point and to ensure that untreated water in the ground cannot enter the network. The water is typically pressurised by pumping the water into storage tanks constructed at the highest local point in the network. One network may have several such service reservoirs.
In small domestic systems, the water may be pressurised by a pressure vessel or even by an underground cistern (the latter however does need additional pressurizing). This eliminates the need of a water tower or any other heightened water reserve to supply the water pressure.
These systems are usually owned and maintained by local governments such as cities or other public entities, but are occasionally operated by a commercial enterprise (see water privatization). Water supply networks are part of the master planning of communities, counties, and municipalities. Their planning and design requires the expertise of city planners and civil engineers, who must consider many factors, such as location, current demand, future growth, leakage, pressure, pipe size, pressure loss, fire fighting flows, etc.—using pipe network analysis and other tools.
As water passes through the distribution system, the water quality can degrade by chemical reactions and biological processes. Corrosion of metal pipe materials in the distribution system can cause the release of metals into the water with undesirable aesthetic and health effects. Release of iron from unlined iron pipes can result in customer reports of "red water" at the tap. Release of copper from copper pipes can result in customer reports of "blue water" and/or a metallic taste. Release of lead can occur from the solder used to join copper pipe together or from brass fixtures. Copper and lead levels at the consumer's tap are regulated to protect consumer health.
Utilities will often adjust the chemistry of the water before distribution to minimize its corrosiveness. The simplest adjustment involves control of pH and alkalinity to produce a water that tends to passivate corrosion by depositing a layer of calcium carbonate. Corrosion inhibitors are often added to reduce release of metals into the water. Common corrosion inhibitors added to the water are phosphates and silicates.
Maintenance of a biologically safe drinking water is another goal in water distribution. Typically, a chlorine based disinfectant, such as sodium hypochlorite or monochloramine is added to the water as it leaves the treatment plant. Booster stations can be placed within the distribution system to ensure that all areas of the distribution system have adequate sustained levels of disinfection. | 1 | Applied and Interdisciplinary Chemistry |
In another setting, the chambers are connected side by side horizontally (Zigmond chamber) or as concentric rings on a slide (Dunn chamber) Concentration gradient develops on a narrow connecting bridge between the chambers and the number of migrating cells is also counted on the surface of the bridge by light microscope. In some cases the bridge between the two chambers is filled with agar and cells have to "glide" in this semisolid layer. | 1 | Applied and Interdisciplinary Chemistry |
The Max Planck Institute for Biogeochemistry is located in Jena, Germany. It was created in 1997, and moved into new buildings 2002. It is one of 80 institutes in the Max Planck Society (Max Planck Gesellschaft). | 0 | Theoretical and Fundamental Chemistry |
The most well-known example of a coarctate transition state is that of the epoxidation of an olefin by dimethyldioxirane. In this transition state, the oxygen atom transferred to the olefin forms a cycle with the acetone leaving group and a cycle with the olefin undergoing epoxidation. Another well-studied reaction is the fragmentation of spirocyclic ozonides into formaldehyde, CO, and an olefin.
Selection rules, resembling the Woodward-Hoffmann rules, have been proposed to explain patterns in reaction activation energy related to transition state topology or orbital symmetry. | 0 | Theoretical and Fundamental Chemistry |
Photocurable adhesives are also used in the production of catheters, hearing aids, surgical masks, medical filters, and blood analysis sensors. Photopolymers have also been explored for uses in drug delivery, tissue engineering and cell encapsulation systems. Photopolymerization processes for these applications are being developed to be carried out in vivo or ex vivo. In vivo photopolymerization would provide the advantages of production and implantation with minimal invasive surgery. Ex vivo photopolymerization would allow for fabrication of complex matrices and versatility of formulation. Although photopolymers show promise for a wide range of new biomedical applications, biocompatibility with photopolymeric materials must still be addressed and developed. | 0 | Theoretical and Fundamental Chemistry |
The transition dipole moment is useful for determining if transitions are allowed under the electric dipole interaction. For example, the transition from a bonding orbital to an antibonding orbital is allowed because the integral defining the transition dipole moment is nonzero. Such a transition occurs between an even and an odd orbital; the dipole operator, , is an odd function of , hence the integrand is an even function. The integral of an odd function over symmetric limits returns a value of zero, while for an even function this is not necessarily the case. This result is reflected in the parity selection rule for electric dipole transitions. The transition moment integral
of an electronic transition within similar atomic orbitals, such as s-s or p-p, is forbidden due to the triple integral returning an ungerade (odd) product. Such transitions only redistribute electrons within the same orbital and will return a zero product. If the triple integral returns a gerade (even) product, the transition is allowed. | 0 | Theoretical and Fundamental Chemistry |
In physics, the plane-wave expansion expresses a plane wave as a linear combination of spherical waves:
where
* is the imaginary unit,
* is a wave vector of length ,
* is a position vector of length ,
* are spherical Bessel functions,
* are Legendre polynomials, and
* the hat denotes the unit vector.
In the special case where is aligned with the z axis,
where is the spherical polar angle of . | 0 | Theoretical and Fundamental Chemistry |
FuseNet is a nuclear fusion focused educational organization. Between 2008 and 2013 it was funded by a European Union grant under EURATOM: Fusion Energy Research. | 0 | Theoretical and Fundamental Chemistry |
An inspirator is a device, similar to a venturi tube and an orifice plate, which mixes a fuel gas with atmospheric air in a precise ratio to regulate burn characteristics. Only the pressure of the fuel gas is used to draw in and mix the air. They are the most simple and common type of mixing device for gas stoves and furnaces. Burners using an inspirator are considered to be naturally aspirated.
In an inspirator there are two tubes. The first is a fuel gas pipe with an orifice at the end where the gas comes out. Then in front of this there is another section of tubing with a larger diameter that the gas blows into. Usually (but not always) this second piece of tubing is tapered so that it starts getting narrower downstream from the orifice. Then, at a certain point, it stops getting narrower and either straightens out or starts getting larger again. This gives the fuel and air time to mix. The fuel/air ratio is determined by the ratio of the diameter of the orifice to the diameter of the mixing tube.
The US Government Technological Paper no. 193 describes "inspirators" as "Injecting tubes" when used for "injecting" air into the gas stream for pre-mixing the air and fuel for domestic and industrial gas burners. The experimental evidence provides an optimised "venturi" for developing the low-pressure zone to suck-in the maximum amount of air for a particular gas supply from a jet. The Venturi CSA is optimally 43% of the Burner CSA, and positions and lengths of tubes are described in the document. The "optimum" expansion beyond the venturi is at 2 degrees taper (4 degrees included angle).
This design of "Inspirator" can be seen in many domestic and industrial gas burners in use today. | 1 | Applied and Interdisciplinary Chemistry |
The kappa convention is used to specify which ligand atoms are bonding to the central atom and in polynuclear species which atoms, both bridged and unbridged, link to which central atom. For monodentate ligands there is no ambiguity as to which atom is forming the bond to the central atom. However when a ligand has more than one atom that can link to a central atom the kappa convention is used to specify which atoms in a ligand are forming a bond. The element atomic symbol is italicised and preceded by kappa, κ. These symbols are placed after the portion of the ligand name that represents the ring, chain etc where the ligand is located. For example:
*pentaamminenitrito-κO-cobalt(III) specifies that the nitrite ligand is linking via the oxygen atom
Where there is more than one bond formed from a ligand by a particular element a numerical superscript gives the count. For example:
* aqua[(ethane-1,2-diyldinitrilo-κN,)tris(acetato-κO)acetato]cobaltate(1-), the cobalt anion formed with water and pentadentate edta, which links via two nitrogen atoms and three oxygen atoms. There are two bonds from nitrogen atoms in edta which is specified by -κN,. The three bonds from oxygen are specified by tris(acetato-κO), where there is one ligation per acetate.
In polynuclear complexes the use of the kappa symbol is extended in two related ways. Firstly to specify which ligating atoms bind to which central atom and secondly to specify for a bridging ligand which central atoms are involved. The central atoms must be identified, i.e. by assigning numbers to them. (This is formally dealt with in the recommendations). To specify which ligating atoms in a ligand link to which central atom, the central atom numbers precede the kappa symbol, and numerical superscript specifies the number of ligations and this is followed by the atomic symbol. Multiple occurrences are separated by commas.
Examples:
: di-μ-chlorido-tetrachlorido-1κCl,2κCl-dialuminium, (aluminium trichloride).
:: tetrachlorido-1κCl,2κCl specifies that there are two chloride ligands on each aluminium atom.
:decacarbonyl-1κC,2κC,3κC-di-μ-hydrido-1:2κH;1:2κH-triangulo-(3 Os—Os), (Decacarbonyldihydridotriosmium).
::decacarbonyl-1κC,2κC,3κC shows that there are three carbonyl groups on two osmium atoms and four on the third.
::di-μ-hydrido-1:2κH;1:2κH specifies that the two hydride bridge between the osmium atom 1 and osmium atom 2. | 0 | Theoretical and Fundamental Chemistry |
In 2021, Schröder sent an email to Christopher Jackson in his capacity as a Vice President of the University of Manchester, linking to a right wing website GB News and disputing the presence of institutional racism at the University of Manchester. Jackson has subsequently left the institution, and Schröder has declined to apologise. | 0 | Theoretical and Fundamental Chemistry |
Patents have been criticized in the developing world, as they are thought to reduce access to existing medicines. Reconciling patents and universal access to medicine would require an efficient international policy of price discrimination. Moreover, under the TRIPS agreement of the World Trade Organization, countries must allow pharmaceutical products to be patented. In 2001, the WTO adopted the Doha Declaration, which indicates that the TRIPS agreement should be read with the goals of public health in mind, and allows some methods for circumventing pharmaceutical monopolies: via compulsory licensing or parallel imports, even before patent expiration.
In March 2001, 40 multi-national pharmaceutical companies brought litigation against South Africa for its Medicines Act, which allowed the generic production of antiretroviral drugs (ARVs) for treating HIV, despite the fact that these drugs were on-patent. HIV was and is an epidemic in South Africa, and ARVs at the time cost between US$10,000 and US$15,000 per patient per year. This was unaffordable for most South African citizens, and so the South African government committed to providing ARVs at prices closer to what people could afford. To do so, they would need to ignore the patents on drugs and produce generics within the country (using a compulsory license), or import them from abroad. After international protest in favour of public health rights (including the collection of 250,000 signatures by Médecins Sans Frontières), the governments of several developed countries (including The Netherlands, Germany, France, and later the US) backed the South African government, and the case was dropped in April of that year.
In 2016, GlaxoSmithKline (the world's sixth largest pharmaceutical company) announced that it would be dropping its patents in poor countries so as to allow independent companies to make and sell versions of its drugs in those areas, thereby widening the public access to them. GlaxoSmithKline published a list of 50 countries they would no longer hold patents in, affecting one billion people worldwide. | 1 | Applied and Interdisciplinary Chemistry |
The C NMR spectra were recorded at several spectrometers with resonance frequencies ranging from 15 MHz to 100 MHz and a resolution ranging from 0.025 to 0.045 ppm. Spectra were acquired using a pulse flip angle of 22.5 – 45 degrees and a pulse repetition time of 4 – 7 seconds. Samples were prepared by dissolution in CDCl, DO, or DMSO-d. Each spectrum is accompanied by a list of the observed peaks with their respective chemical shifts in ppm and their intensities. Most spectra show the peak assignment. This collection contains ca 14,200 spectra and is being updated. | 0 | Theoretical and Fundamental Chemistry |
The and distances are 117 and 158 pm. By contrast, in methyl thiocyanate, and distances are 116 and 176 pm.
Typical bond angles for in aryl isothiocyanates are near 165°. Again, the thiocyanate isomers are quite different with angle near 100°. In both isomers the angle approaches 180°. | 0 | Theoretical and Fundamental Chemistry |
This method is mostly used for corrosion monitoring in water industry. These probes are suitable for monitoring fluctuations that may occur in a fluid inside the system. These probes are mostly used for conductive fluids such as water or any similar else. | 1 | Applied and Interdisciplinary Chemistry |
This salt is used as a flotation agent in the purification of molybdenite (MoS) from other components of the ores, where it is usually known as "Nokes reagent" (after Charles M. Nokes, who patented it in 1948). The salt is generated by the reaction of phosphorus pentasulfide with sodium hydroxide, often using impure reagents to obtain a mixture of the desired salt and related thiophosphates and oxidized species. Molybdenite particles, which are normally hydrophobic, become hydrophilic in the presence of this salt. In this context, the Nokes reagent is called a "depressant," because it suppresses the flotation tendency of the solids other than molybdenite. | 1 | Applied and Interdisciplinary Chemistry |
Esters () are named as alkyl derivatives of carboxylic acids. The alkyl (R') group is named first. The part is then named as a separate word based on the carboxylic acid name, with the ending changed from "-oic acid" to "-oate" or "-carboxylate" For example, is methyl pentanoate, and is ethyl 4-methylpentanoate. For esters such as ethyl acetate (), ethyl formate () or dimethyl phthalate that are based on common acids, IUPAC recommends use of these established names, called [http://www.acdlabs.com/iupac/nomenclature/93/r93_511.htm retained names]. The "-oate" changes to "-ate." Some simple examples, named both ways, are shown in the figure above.
If the alkyl group is not attached at the end of the chain, the bond position to the ester group is suffixed before "-yl": may be called butan-2-yl propanoate or butan-2-yl propionate.. The prefix form is "oxycabonyl-" with the (R') group preceding. | 0 | Theoretical and Fundamental Chemistry |
Using vibrational perturbation theory, effects such as tunnelling and variational effects can be accounted for within the SCTST formalism. | 0 | Theoretical and Fundamental Chemistry |
The Crabtree effect, named after the English biochemist Herbert Grace Crabtree, describes the phenomenon whereby the yeast, Saccharomyces cerevisiae, produces ethanol (alcohol) in aerobic conditions at high external glucose concentrations rather than producing biomass via the tricarboxylic acid (TCA) cycle, the usual process occurring aerobically in most yeasts e.g. Kluyveromyces spp. This phenomenon is observed in most species of the Saccharomyces, Schizosaccharomyces, Debaryomyces, Brettanomyces, Torulopsis, Nematospora, and Nadsonia genera. Increasing concentrations of glucose accelerates glycolysis (the breakdown of glucose) which results in the production of appreciable amounts of ATP through substrate-level phosphorylation. This reduces the need of oxidative phosphorylation done by the TCA cycle via the electron transport chain and therefore decreases oxygen consumption. The phenomenon is believed to have evolved as a competition mechanism (due to the antiseptic nature of ethanol) around the time when the first fruits on Earth fell from the trees. The Crabtree effect works by repressing respiration by the fermentation pathway, dependent on the substrate.
Ethanol formation in Crabtree-positive yeasts under strictly aerobic conditions was firstly thought to be caused by the inability of these organisms to increase the rate of respiration above a certain value. This critical value, above which alcoholic fermentation occurs, is dependent on the strain and the culture conditions. More recent evidences demonstrated that the occurrence of alcoholic fermentation might not be primarily due to a limited respiratory capacity, but could be caused by a limit in the cellular Gibbs energy dissipation rate.
For S. cerevisiae in aerobic conditions, glucose concentrations below 150 mg/L did not result in ethanol production. Above this value, ethanol was formed with rates increasing up to a glucose concentration of 1000 mg/L. Thus, above 150 mg/L glucose the organism exhibited a Crabtree effect.
It was the study of tumor cells that led to the discovery of the Crabtree effect. Tumor cells have a similar metabolism, the Warburg effect, in which they favor glycolysis over the oxidative phosphorylation pathway. | 1 | Applied and Interdisciplinary Chemistry |
It is common to treat the principle as a more general observation of systems, such as
or, "roughly stated":
The concept of systemic maintenance of a stable steady state despite perturbations has a variety of names, and has been studied in a variety of contexts, chiefly in the natural sciences. In chemistry, the principle is used to manipulate the outcomes of reversible reactions, often to increase their yield. In pharmacology, the binding of ligands to receptors may shift the equilibrium according to Le Chateliers principle, thereby explaining the diverse phenomena of receptor activation and desensitization. In biology, the concept of homeostasis is different from Le Chateliers principle, in that homoeostasis is generally maintained by processes of active character, as distinct from the passive or dissipative character of the processes described by Le Chatelier's principle in thermodynamics. In economics, even further from thermodynamics, allusion to the principle is sometimes regarded as helping explain the price equilibrium of efficient economic systems. In some dynamic systems, the end-state cannot be determined from the shock or perturbation. | 0 | Theoretical and Fundamental Chemistry |
Friedrich Oskar Giesel (20 May 1852 – 13 November 1927, known as Fritz) was a German organic chemist. During his work in a quinine factory in the late 1890s, he started to work on the at-that-time-new field of radiochemistry and started the production of radium. In the period between 1902 and 1904, he was able to isolate a new element emanium. In a now controversially reviewed process, it was stated that emanium is identical to actinium, which was discovered by André-Louis Debierne in 1899. | 1 | Applied and Interdisciplinary Chemistry |
Thermal radiation is characteristically different from conduction and convection in that it does not require a medium and, in fact it reaches maximum efficiency in a vacuum. Thermal radiation is a type of electromagnetic radiation which is often modeled by the propagation of waves. These waves have the standard wave properties of frequency, and wavelength, which are related by the equationwhere is the speed of light in the medium. | 0 | Theoretical and Fundamental Chemistry |
Several homoleptic (complexes with only one kind of ligand) complexes have been characterized by X-ray crystallography. The inventory includes octahedral complexes (M = Co, Rh). Square-planar homoleptic complexes are also known for Pt(II) and Pd(II). The potassium salts of (M = Zn, Cd) feature homoleptic complexes with four O,O-bidentate nitrite ligands. | 0 | Theoretical and Fundamental Chemistry |
The canonical partition function Z of an ideal gas consisting of N = nN identical (non-interacting) particles, is:
where is the thermal de Broglie wavelength:
with the usual definitions: h is the Planck constant, m the mass of a particle, k the Boltzmann constant and T the absolute temperature. In an ideal gas z is the partition function of a single particle in a container of volume V. In order to derive the Van der Waals equation we assume now that each particle moves independently in an average potential field offered by the other particles. The averaging over the particles is easy because we will assume that the particle density of the Van der Waals fluid is homogeneous.
The interaction between a pair of particles, which are hard spheres, is taken to be:
r is the distance between the centers of the spheres and d is the distance where the hard spheres touch each other (twice the Van der Waals radius). The depth of the Van der Waals well is .
Because the particles are not coupled under the mean field Hamiltonian, the mean field approximation of the total partition function still factorizes:
but the intermolecular potential necessitates two modifications to z. First, because of the finite size of the particles, not all of V is available, but only V − Nb′, where (just as in the conventional derivation above):
Second, we insert a Boltzmann factor
exp[−Φ/2kT] to take care of the average intermolecular potential. We divide here the potential by two because this interaction energy is shared between two particles. Thus:
The total attraction felt by a single particle is:
where we assumed that in a shell of thickness dr there are particles. This is a mean field approximation; the position of the particles is averaged. In reality the density close to the particle is different than far away as can be described by a pair correlation function. Furthermore, it is neglected that the fluid is enclosed between walls. Performing the integral we get:
Hence, we obtain:
From statistical thermodynamics we know that:
so that we only have to differentiate the terms containing . We get: | 0 | Theoretical and Fundamental Chemistry |
MST is based on the quantifiable detection of a fluorescence change in a sample when a temperature change is applied. The fluorescence of a target molecule can be extrinsic or intrinsic (aromatic amino acids) and is altered in temperature gradients due to two distinct effects. On the one hand temperature related intensity change (TRIC), which describes the intrinsic property of fluorophores to change their fluorescence intensity as a function of temperature. The extent of the change in fluorescence intensity is affected by the chemical environment of the fluorescent probe, which can be altered in binding events due to conformational changes or proximity of ligands. On the other hand, MST is also based on the directed movement of molecules along temperature gradients, an effect termed thermophoresis. A spatial temperature difference ΔT leads to a change in molecule concentration in the region of elevated temperature, quantified by the Soret coefficient S:c/c = exp(-S ΔT). Both, TRIC and thermophoresis contribute to the recorded signal in MST measurements in the following way: ∂/∂T(cF)=c∂F/∂T+F∂c/∂T. The first term in this equation c∂F/∂T describes TRIC as a change in fluorescence intensity (F) as a function of temperature (T), whereas the second term F∂c/∂T describes thermophoresis as the change in particle concentration (c) as a function of temperature. Thermophoresis depends on the interface between molecule and solvent. Under constant buffer conditions, thermophoresis probes the size, charge and solvation entropy of the molecules. The thermophoresis of a fluorescently labeled molecule A typically differs significantly from the thermophoresis of a molecule-target complex AT due to size, charge and solvation entropy differences. This difference in the molecule's thermophoresis is used to quantify the binding in titration experiments under constant buffer conditions.
The thermophoretic movement of the fluorescently labelled molecule is measured by monitoring the fluorescence distribution F inside a capillary. The microscopic temperature gradient is generated by an IR-Laser, which is focused into the capillary and is strongly absorbed by water. The temperature of the aqueous solution in the laser spot is raised by ΔT=1-10 K. Before the IR-Laser is switched on a homogeneous fluorescence distribution F is observed inside the capillary. When the IR-Laser is switched on, two effects, occur on the same time-scale, contributing to the new fluorescence distribution F. The thermal relaxation induces a binding-dependent drop in the fluorescence of the dye due to its local environmental-dependent response to the temperature jump (TRIC). At the same time molecules typically move from the locally heated region to the outer cold regions. The local concentration of molecules decreases in the heated region until it reaches a steady-state distribution.
While the mass diffusion D dictates the kinetics of depletion, S determines the steady-state concentration ratio c/c=exp(-S ΔT) ≈ 1-S ΔT under a temperature increase ΔT. The normalized fluorescence F=F/F measures mainly this concentration ratio, in addition to TRIC ∂F/∂T. In the linear approximation we find: F=1+(∂F/∂T-S)ΔT. Due to the linearity of the fluorescence intensity and the thermophoretic depletion, the normalized fluorescence from the unbound molecule F(A) and the bound complex F(AT) superpose linearly. By denoting x the fraction of molecules bound to targets, the changing fluorescence signal during the titration of target T is given by: F=(1-x) F(A)+x F(AT).
Quantitative binding parameters are obtained by using a serial dilution of the binding substrate. By plotting F against the logarithm of the different concentrations of the dilution series, a sigmoidal binding curve is obtained. This binding curve can directly be fitted with the nonlinear solution of the law of mass action, with the dissociation constant K as result. | 1 | Applied and Interdisciplinary Chemistry |
Bisphosphonates were originally synthesized in the 19th century and used in industry for their antiscaling and anticorrosive properties. In the late 1960s their potential to treat diseases related to the metabolism of the bones became evident. The first generation of bisphosphonates included etidronic acid and clodronic acid which were introduced in the 1970s and 1980s. They were the first bisphosphonate drugs to be used successfully in the clinic. They have since then been developed further with the intention to make them more potent, enhance their distribution inside the bone and extend the duration of action. This has made it possible to give zoledronate, the most recent bisphosphonate drug to be placed on the market, in a single annual dose by intravenous infusion. | 1 | Applied and Interdisciplinary Chemistry |
Micro-organisms are utilized in biological remediation to control industrial and commercial vapor effluents. When utilizing biological oxidation systems for the remediation emissions, the off gases or vapors are passed through a packed bed having a thin biological film at the surface. The micro-organisms are immobilized into the thin biological film, as the vapor passes over the film they become attached and are oxidized or stabilized.
The biological film accomplishes the degradation process, as the biological sump water is reprocessed over the biomedia it creates additional biological growth and as the film increases so does the biological oxidizers efficiency.
Large surface area and footprint were once required to treat waste water vapor and industrial plant emissions, with the advent of advanced biological oxidation equipment a smaller footprint is required. The footprint will typically occupy the same space as conventional thermal oxidizers. | 1 | Applied and Interdisciplinary Chemistry |
Titanium foams exhibit high specific strength, high energy absorption, excellent corrosion resistance and biocompatibility. These materials are ideally suited for applications within the aerospace industry. An inherent resistance to corrosion allows the foam to be a desirable candidate for various filtering applications. Further, titanium's physiological inertness makes its porous form a promising candidate for biomedical implantation devices. The largest advantage in fabricating titanium foams is that the mechanical and functional properties can be adjusted through manufacturing manipulations that vary porosity and cell morphology. The high appeal of titanium foams is directly correlated to a multi-industry demand for advancement in this technology. | 0 | Theoretical and Fundamental Chemistry |
Many applications have been considered, but few have been commercialized. ILs are used in the production of gasoline by catalyzing alkylation.
An IL based on tetraalkylphosphonium iodide is a solvent for tributyltin iodide, which functions as a catalyst to rearrange the monoepoxide of butadiene. This process was commercialized as a route to 2,5-dihydrofuran, but later discontinued. | 0 | Theoretical and Fundamental Chemistry |
The process began to be used in residential and commercial applications in Japan and Europe in the 1970s and for residential application in the United States in the 1980s. | 1 | Applied and Interdisciplinary Chemistry |
The principal technology is the cyanide process, in which gold is leached from the ore by treatment with a solution of cyanide. The first step is comminution (grinding) to increase surface area and expose the gold to the extracting solution. The extraction is conducted by dump leaching or heap leaching processes. Sodium cyanide is produced on a billion-ton/year scale mainly for this purpose. "Black cyanide", a carbon-contaminated form of calcium cyanide (Ca(CN)) is often used because it is cheap. The crude ore is washed with a c. 0.3% solution of cyanide in air, often repeatedly, and the aqueous extract is collected and refined further. Recovery from solution typically involves adsorption on activated carbon, the carbon in pulp process.
Thiosulfate leaching has been proven to be effective on ores with high soluble copper values or ores which experience preg-robbing.
Leaching through bulk leach extractable gold, or BLEG, is also a process that is used to test an area for gold concentrations where gold may not be immediately visible. | 1 | Applied and Interdisciplinary Chemistry |
Levorphanol is the INN, BAN, and DCF. As the medically used tartrate salt, the drug is also known as levorphanol tartrate (USAN, BANM). The former developmental code name of levorphanol at Roche was Ro 1-5431. | 0 | Theoretical and Fundamental Chemistry |
Drugs can profoundly affect thyroid function tests. Listed below is a selection of important effects.
↓: reduced serum concentration or structure parameter; ↑: increased serum concentration or structure parameter; ↔: no change; TSH: Thyroid-stimulating hormone; T: Total triiodothyronine; T: Total thyroxine; fT: Free thyroxine; fT: Free triiodothyronine; rT: Reverse triiodothyronine | 1 | Applied and Interdisciplinary Chemistry |
In binary (two component) mixtures, the binodal can be determined at a given temperature by drawing a tangent line to the free energy. | 0 | Theoretical and Fundamental Chemistry |
Crystal violet or gentian violet, also known as methyl violet 10B or hexamethyl pararosaniline chloride, is a triarylmethane dye used as a histological stain and in Gram's method of classifying bacteria. Crystal violet has antibacterial, antifungal, and anthelmintic (vermicide) properties and was formerly important as a topical antiseptic. The medical use of the dye has been largely superseded by more modern drugs, although it is still listed by the World Health Organization.
The name gentian violet was originally used for a mixture of methyl pararosaniline dyes (methyl violet), but is now often considered a synonym for crystal violet. The name refers to its colour, being like that of the petals of certain gentian flowers; it is not made from gentians or violets. | 0 | Theoretical and Fundamental Chemistry |
The EPOC effect can be observed in a wide range of catalytic reactions with several kinds of metal or metal oxide catalysts mostly coupled with solid electrolytes. Versatile catalytic reactions including hydrogenations, dehydrogenations, oxidations, reductions, isomerizations, and chemical decompositions have been known to be promoted electrochemically on various transition metal and oxide catalysts (e.g., Pt, Pd, Rh, Ag, Au, Ni, Cu, Fe, IrO, RuO) deposited on O (YSZ), Na or K, H, F, aqueous, CeO conductors, and molten salts. The main focus and purpose of numerous studies regarding the EPOC effect have been reported so far can be classified as follows: 1) the elucidation of examples for the EPOC effects on specific catalytic reactions with environmental or industrial interest (ex. NOx reduction and hydrocarbons oxidations), 2) the mechanistic investigation of the origin of the EPOC effects (mainly focusing on the system with oxygen-ion conducting electrolytes), 3) the large-scale application and commercialization of the chemical reactions promoted by the EPOC effects along with development of novel compact monolithic reactors and 4) the utilization and incorporation of the EPOC effect in high or low-temperature fuel cell systems. | 0 | Theoretical and Fundamental Chemistry |
SUMO enzymatic cascade catalyzes the dynamic posttranslational modification process of sumoylation (i.e. transfer of SUMO protein to other proteins). The Small Ubiquitin-related Modifier, SUMO-1, is a ubiquitin-like family member that is conjugated to its substrates through three discrete enzymatic steps (see the figure on the right): activation, involving the E1 enzyme (SAE1/SAE2); conjugation, involving the E2 enzyme (UBE2I); substrate modification, through the cooperation of the E2 and E3 protein ligases.
SUMO pathway modifies hundreds of proteins that participate in diverse cellular processes. SUMO pathway is the most studied ubiquitin-like pathway that regulates a wide range of cellular events, evidenced by a large number of sumoylated proteins identified in more than ten large-scale studies. | 1 | Applied and Interdisciplinary Chemistry |
FDA launched HIVE Open Source as a platform to support end to end needs for NGS analytics.
https://github.com/FDA/fda-hive
HIVE biocompute harmonization platform is at the core of High-throughput Sequencing Computational Standards for Regulatory Sciences (HTS-CSRS) project. Its mission is to provide the scientific community with a framework to harmonize biocomputing, promote interoperability, and verify bioinformatics protocols (https://hive.biochemistry.gwu.edu/htscsrs). For more information, see the project description on the FDA Extramural Research page (https://www.fda.gov/ScienceResearch/SpecialTopics/RegulatoryScience/ucm491893.htm | 1 | Applied and Interdisciplinary Chemistry |
When the characteristic plate length is much smaller than the characteristic plate edge depth, the effects of gravity, surface tension, and spring energy become dominant. In this limiting case, it turns out that flexibility does not improve load-bearing capabilities of the plates; indeed, the optimal configuration is a flat plate. Since the plate length is so much smaller than the displacement from the undisturbed water line, the extra fluid displaced by bending a rigid plate is outweighed by the loss of fluid in the column above the plate. | 1 | Applied and Interdisciplinary Chemistry |
Al-Kindi took his view of the solar system from Ptolemy, who placed the Earth at the centre of a series of concentric spheres, in which the known heavenly bodies (the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and the stars) are embedded. In one of his treatises on the subject, he says that these bodies are rational entities, whose circular motion is in obedience to and worship of God. Their role, al-Kindi believes, is to act as instruments for divine providence. He furnishes empirical evidence as proof for this assertion; different seasons are marked by particular arrangements of the planets and stars (most notably the sun); the appearance and manner of people varies according to the arrangement of heavenly bodies situated above their homeland.
However, he is ambiguous when it comes to the actual process by which the heavenly bodies affect the material world. One theory he posits in his works is from Aristotle, who conceived that the movement of these bodies causes friction in the sub-lunar region, which stirs up the primary elements of earth, fire, air and water, and these combine to produce everything in the material world. An alternative view found in the treatise On Rays (De radiis) is that the planets exercise their influence in straight lines; but this treatise, written by a Latin author, probably around the middle of the 13th century, is apocryphal. In each of these, two fundamentally different views of physical interaction are presented; action by contact and action at a distance. This dichotomy is duplicated in his writings on optics.
Some of the notable astrological works by al-Kindi include:
*The Book of the Judgement of the Stars, including The Forty Chapters, on questions and elections.
*On the Stellar Rays (spurious)
*Several epistles on weather and meteorology, including De mutatione temporum, ("On the Changing of the Weather").
*Treatise on the Judgement of Eclipses.
*Treatise on the Dominion of the Arabs and its Duration (used to predict the end of Arab rule).
*The Choices of Days (on elections).
*On the Revolutions of the Years (on mundane astrology and natal revolutions).
*De Signis Astronomiae Applicitis as Mediciam On the Signs of Astronomy as applied to Medicine
*Treatise on the Spirituality of the Planets. | 1 | Applied and Interdisciplinary Chemistry |
More recently, slightly elevated serum GGT has also been found to correlate with cardiovascular diseases and is under active investigation as a cardiovascular risk marker. GGT in fact accumulates in atherosclerotic plaques, suggesting a potential role in pathogenesis of cardiovascular diseases, and circulates in blood in the form of distinct protein aggregates, some of which appear to be related to specific pathologies such as metabolic syndrome, alcohol addiction and chronic liver disease.
Elevated levels of GGT can also be due to congestive heart failure. | 1 | Applied and Interdisciplinary Chemistry |
This form of corrosion occurs principally in metal alloys. The less noble metal of the alloy, is selectively leached from the alloy. Removal of zinc from brass is a more common example. | 1 | Applied and Interdisciplinary Chemistry |
Ocean acidification has occurred previously in Earth's history. It happened during the Capitanian mass extinction, at the end-Permian extinction, during the end-Triassic extinction, and during the Cretaceous–Palaeogene extinction event.
Three of the big five mass extinction events in the geologic past were associated with a rapid increase in atmospheric carbon dioxide, probably due to volcanism and/or thermal dissociation of marine gas hydrates. Elevated CO levels impacted biodiversity. Decreased saturation due to seawater uptake of volcanogenic CO has been suggested as a possible kill mechanism during the marine mass extinction at the end of the Triassic. The end-Triassic biotic crisis is still the most well-established example of a marine mass extinction due to ocean acidification, because (a) carbon isotope records suggest enhanced volcanic activity that decreased the carbonate sedimentation which reduced the carbonate compensation depth and the carbonate saturation state, and a marine extinction coincided precisely in the stratigraphic record, and (b) there was pronounced selectivity of the extinction against organisms with thick aragonitic skeletons, which is predicted from experimental studies. Ocean acidification has also been suggested as a one cause of the end-Permian mass extinction and the end-Cretaceous crisis. Overall, multiple climatic stressors, including ocean acidification, was likely the cause of geologic extinction events.
The most notable example of ocean acidification is the Paleocene-Eocene Thermal Maximum (PETM), which occurred approximately 56 million years ago when massive amounts of carbon entered the ocean and atmosphere, and led to the dissolution of carbonate sediments across many ocean basins. Relatively new geochemical methods of testing for pH in the past indicate the pH dropped 0.3 units across the PETM. One study that solves the marine carbonate system for saturation state shows that it may not change much over the PETM, suggesting the rate of carbon release at our best geological analogy was much slower than human-induced carbon emissions. However, stronger proxy methods to test for saturation state are needed to assess how much this pH change may have affected calcifying organisms. | 0 | Theoretical and Fundamental Chemistry |
Quorum sensing can be a useful tool for improving the function of self-organizing networks such as the SECOAS (Self-Organizing Collegiate Sensor) environmental monitoring system. In this system, individual nodes sense that there is a population of other nodes with similar data to report. The population then nominates just one node to report the data, resulting in power savings. Ad hoc wireless networks can also benefit from quorum sensing, by allowing the system to detect and respond to network conditions.
Quorum sensing can also be used to coordinate the behavior of autonomous robot swarms. Using a process similar to that used by Temnothorax ants, robots can make rapid group decisions without the direction of a controller. | 1 | Applied and Interdisciplinary Chemistry |
The mineralization of copper is restricted to a few areas in western, central and southern Africa, and some have the richest deposits of copper in the world. In the west, copper has only been found in the arid regions of the Sahel and southern Sahara. The main sources of copper are:
# Akjoujt in Mauritania
# Nioro du Sahel to Sirakoro in Northern Mali
# The Aïr Massif near Azelik and Agadez in Niger
There are not any known mines in tropical West Africa, however copper and lead workings have been in the Benue Trough in southeastern Nigeria. With the exception of a few areas near Kilembe in Uganda and Rwanda, there are no sources of copper in East Africa. The largest concentration of copper found in Africa is the Lufilian Arc. It is an eight hundred kilometer crescent shaped belt, which extends from the Copperbelt in Zambia to the southern Shaba Province in Congo. | 1 | Applied and Interdisciplinary Chemistry |
Twin helical strands form the DNA backbone. Another double helix may be found by tracing the spaces, or grooves, between the strands. These voids are adjacent to the base pairs and may provide a binding site. As the strands are not directly opposite each other, the grooves are unequally sized. One groove, the major groove, is 22 Å wide and the other, the minor groove, is 12 Å wide. The narrowness of the minor groove means that the edges of the bases are more accessible in the major groove. As a result, proteins like transcription factors that can bind to specific sequences in double-stranded DNA usually make contacts to the sides of the bases exposed in the major groove. This situation varies in unusual conformations of DNA within the cell (see below), but the major and minor grooves are always named to reflect the differences in size that would be seen if the DNA is twisted back into the ordinary B form. | 0 | Theoretical and Fundamental Chemistry |
Dynamic recrystallization (DRX) is a type of recrystallization process, found within the fields of metallurgy and geology. In dynamic recrystallization, as opposed to static recrystallization, the nucleation and growth of new grains occurs during deformation rather than afterwards as part of a separate heat treatment. The reduction of grain size increases the risk of grain boundary sliding at elevated temperatures, while also decreasing dislocation mobility within the material. The new grains are less strained, causing a decrease in the hardening of a material. Dynamic recrystallization allows for new grain sizes and orientation, which can prevent crack propagation. Rather than strain causing the material to fracture, strain can initiate the growth of a new grain, consuming atoms from neighboring pre-existing grains. After dynamic recrystallization, the ductility of the material increases.
In a stress–strain curve, the onset of dynamic recrystallization can be recognized by a distinct peak in the flow stress in hot working data, due to the softening effect of recrystallization. However, not all materials display well-defined peaks when tested under hot working conditions. The onset of DRX can also be detected from inflection point in plots of the strain hardening rate against stress. It has been shown that this technique can be used to establish the occurrence of DRX when this cannot be determined unambiguously from the shape of the flow curve.
If stress oscillations appear before reaching the steady state, then several recrystallization and grain growth cycles occur and the stress behavior is said to be of the cyclic or multiple peak type. The particular stress behavior before reaching the steady state depends on the initial grain size, temperature, and strain rate.
DRX can occur in various forms, including:
* Geometric dynamic recrystallization
* Discontinuous dynamic recrystallization
* Continuous dynamic recrystallization
Dynamic recrystallization is dependent on the rate of dislocation creation and movement. It is also dependent on the recovery rate (the rate at which dislocations annihilate). The interplay between work hardening and dynamic recovery determines grain structure. It also determines the susceptibility of grains to various types of dynamic recrystallization. Regardless of the mechanism, for dynamic crystallization to occur, the material must have experienced a critical deformation. The final grain size increases with increased stress. To achieve very fine-grained structures the stresses have to be high.
Some authors have used the term postdynamic or metadynamic to describe recrystallization that occurs during the cooling phase of a hot-working process or between successive passes. This emphasises the fact that the recrystallization is directly linked to the process in question, while acknowledging that there is no concurrent deformation. | 1 | Applied and Interdisciplinary Chemistry |
Fusion reactors typically burn a mixture of deuterium (D) and tritium (T). When heated to millions of degrees, the kinetic energy in the fuel begins to overcome the natural electrostatic repulsion between nuclei, the so-called coulomb barrier, and the fuel begins to undergo fusion. This reaction gives off an alpha particle and a high energy neutron of 14 MeV. A key requirement to the economic operation of a fusion reactor is that the alphas deposit their energy back into the fuel mix, heating it so that additional fusion reactions take place. This leads to a condition not unlike the chain reaction in the fission case, known as ignition.
Deuterium can be obtained by the separation of hydrogen isotopes in sea water (see heavy water production). Tritium has a short half life of just over a decade, so only trace amounts are found in nature. To fuel the reactor, the neutrons from the reaction are used to breed more tritium through a reaction in a blanket of lithium surrounding the reaction chamber. Tritium breeding is key to the success of a D-T fusion cycle, and to date this technique has not been demonstrated. Predictions based on computer modeling suggests that the breeding ratios are quite small and a fusion plant would barely be able to cover its own use. Many years would be needed to breed enough surplus to start another reactor. | 0 | Theoretical and Fundamental Chemistry |
If the desired glass property is not related to crystallization (e.g., liquidus temperature) or phase separation, linear regression can be applied using common polynomial functions up to the third degree. Below is an example equation of the second degree. The C-values are the glass component concentrations like NaO or CaO in percent or other fractions, the b-values are coefficients, and n is the total number of glass components. The glass main component silica (SiO) is excluded in the equation below because of over-parametrization due to the constraint that all components sum up to 100%. Many terms in the equation below can be neglected based on correlation and significance analysis. Systematic errors such as seen in the picture are quantified by dummy variables. Further details and examples are available in an online tutorial by Fluegel. | 0 | Theoretical and Fundamental Chemistry |
Motivated by the above discussion, the simplest way to define an attracting LCS is by requiring it to be a locally strongest attracting material surface in the extended phase space (see. Fig. 4) . Similarly, a repelling LCS can be defined as a locally strongest repelling material surface. Attracting and repelling LCSs together are usually referred to as hyperbolic LCSs, as they provide a finite-time generalization of the classic concept of normally hyperbolic invariant manifolds in dynamical systems. | 1 | Applied and Interdisciplinary Chemistry |
Since the first publication by Kansy and coworkers, several companies developed their own versions of the assay. Early models incorporated iso-pH conditions in the compartments separated by a simple lipid membrane; subsequently, commercial products were introduced which incorporated more sophisticated lipid membranes. The commercial products helped ensure that medicinal chemists across different corporate labs within a worldwide organization used the same standardized methodology, reagents and obtained equivalent system performance as demonstrated with a set of test compounds. This has proved very useful as various operational activities have been outsourced to other countries. | 1 | Applied and Interdisciplinary Chemistry |
The heat causing the melting of a reactor may originate from the nuclear chain reaction, but more commonly decay heat of the fission products contained in the fuel rods is the primary heat source. The heat production from radioactive decay drops quickly, as the short half-life isotopes provide most of the heat and radioactive decay, with the curve of decay heat being a sum of the decay curves of numerous isotopes of elements decaying at different exponential half-life rates. A significant additional heat source can be the chemical reaction of hot metals with oxygen or steam.
Hypothetically, the temperature of corium depends on its internal heat generation dynamics: the quantities and types of isotopes producing decay heat, dilution by other molten materials, heat losses modified by the corium physical configuration, and heat losses to the environment. An accumulated mass of corium will lose less heat than a thinly spread layer. Corium of sufficient temperature can melt concrete. A solidified mass of corium can remelt if its heat losses drop, by being covered with heat insulating debris, or if water that is cooling the corium evaporates.
Crust can form on the corium mass, acting as a thermal insulator and hindering thermal losses. Heat distribution throughout the corium mass is influenced by different thermal conductivity between the molten oxides and metals. Convection in the liquid phase significantly increases heat transfer.
The molten reactor core releases volatile elements and compounds. These may be gas phase, such as molecular iodine or noble gases, or condensed aerosol particles after leaving the high temperature region. A high proportion of aerosol particles originates from the reactor control rod materials. The gaseous compounds may be adsorbed on the surface of the aerosol particles. | 0 | Theoretical and Fundamental Chemistry |
The visual cycle can be regulated by the retinal G-protein-coupled Receptor (RGR-opsin) system. When light activates the RGR-opsin, the recycling of chromophore in the RPE is accelerated. This mechanism provides additional chromophore after intense bleaches, and can be seen as an important mechanism in the early phases of dark adaptation and chromophore replenishment. | 1 | Applied and Interdisciplinary Chemistry |
The reason that Pseudomonas aeruginosa produces rhamnolipids is the subject of much speculation. They have been shown to have several properties, and investigations in a rhlA mutant that does not make HAAs nor rhamnolipids have attributed many functions to rhamnolipids which may in fact be due to HAAs. These functions fall broadly into five categories, described below. | 0 | Theoretical and Fundamental Chemistry |
The Faraday generator is named for Michael Faraday's experiments on moving charged particles in the Thames River.
A simple Faraday generator would consist of a wedge-shaped pipe or tube of some non-conductive material. When an electrically conductive fluid flows through the tube, in the presence of a significant perpendicular magnetic field, a voltage is induced in the fluid, which can be drawn off as electrical power by placing the electrodes on the sides at 90-degree angles to the magnetic field.
There are limitations on the density and type of field used. The amount of power that can be extracted is proportional to the cross-sectional area of the tube and the speed of the conductive flow. The conductive substance is also cooled and slowed by this process. MHD generators typically reduce the temperature of the conductive substance from plasma temperatures to just over 1000 °C.
The main practical problem of a Faraday generator is that differential voltages and currents in the fluid short through the electrodes on the sides of the duct. The most powerful waste is from the Hall effect current. This makes the Faraday duct very inefficient. Most further refinements of MHD generators have tried to solve this problem. The optimal magnetic field on duct-shaped MHD generators is a sort of saddle shape. To get this field, a large generator requires an extremely powerful magnet. Many research groups have tried to adapt superconducting magnets to this purpose, with varying success. (For references, please see the discussion of generator efficiency, below.) | 1 | Applied and Interdisciplinary Chemistry |
Bacteriorhodopsin is a light-driven proton pump. It is the retinal molecule that changes its isomerization state from all-trans to 13-cis when it absorbs a photon. The surrounding protein responds to the change in the chromophore shape, by undergoing an ordered sequence of conformational changes (collectively known as the photocycle). The conformational changes alter the pK values of conserved amino acids in the core of the protein, including Asp85, Asp96 and the Schiff base N atom (Lys216). These sequential changes in acid dissociation constant, result in the transfer of one proton from the intracellular side to the extracellular side of the membrane for each photon absorbed by the chromophore.
The bacteriorhodopsin photocycle consists of nine distinct stages, starting from the ground or resting state, which is denoted bR. The intermediates are identified by single letters and may be distinguished by their absorption spectra. The nine stages are:
: bR + photon → K L M M M N N O bR | 0 | Theoretical and Fundamental Chemistry |
The SSA can be simply calculated from a particle size distribution, making some assumption about the particle shape. This method, however, fails to account for surface associated with the surface texture of the particles. | 0 | Theoretical and Fundamental Chemistry |
The settlement was mediated by retired judge Sir Henry Brooke. Before settlement had been reached, Chris Mallender explained: "We have reached a view that there are going to be no outright winners in this. In the circumstances we feel that its better that we try and find a middle ground, we settle in a way thats fair to the families, but is also fair in terms of the residual burden on the council tax payer."
On 16 April 2010 the council released a joint statement with the families solicitors announcing it was dropping its appeal and had agreed a financial settlement with 19 families. Chris Mallender said: "The council recognises that it made mistakes in its clean-up of the former British Steel site years ago and extends its deepest sympathy to the children and their families. Although I accept that money cannot properly compensate these young people for their disabilities and for all that they have suffered to date and their problems in the future, the council sincerely hopes that this apology coupled with todays agreement will mean that they can now put their legal battle behind them and proceed with their lives with a greater degree of financial certainty." The financial terms of the settlement remained confidential, and the agreement forbids disclosure of the financial arrangements. On the subject of cost, Mallender said: "Every £1m of cost involves a payment £5 per household in Corby on average, per year, for the next 20 years. So, simple maths: if the overall bill is £5m, it's £25 per household for 20 years."
The settlement also encompassed three children not covered by the original ruling, including India Harrison and Ashleigh Custance. | 1 | Applied and Interdisciplinary Chemistry |
Some dinophytes, like Kryptoperidinium and Durinskia, have a diatom (heterokontophyte)-derived chloroplast. These chloroplasts are bounded by up to five membranes, (depending on whether the entire diatom endosymbiont is counted as the chloroplast, or just the red algal derived chloroplast inside it). The diatom endosymbiont has been reduced relatively little—it still retains its original mitochondria, and has endoplasmic reticulum, ribosomes, a nucleus, and of course, red algal derived chloroplasts—practically a complete cell, all inside the hosts endoplasmic reticulum lumen. However the diatom endosymbiont cant store its own food—its storage polysaccharide is found in granules in the dinophyte hosts cytoplasm instead. The diatom endosymbionts nucleus is present, but it probably cant be called a nucleomorph because it shows no sign of genome reduction, and might have even been expanded'. Diatoms have been engulfed by dinoflagellates at least three times.
The diatom endosymbiont is bounded by a single membrane, inside it are chloroplasts with four membranes. Like the diatom endosymbiont's diatom ancestor, the chloroplasts have triplet thylakoids and pyrenoids.
In some of these genera, the diatom endosymbionts chloroplasts arent the only chloroplasts in the dinophyte. The original three-membraned peridinin chloroplast is still around, converted to an eyespot. | 0 | Theoretical and Fundamental Chemistry |
Judith Klein-Seetharaman (born May 30, 1971) is an American-German biochemist who is a professor at the Arizona State University. Her research considers the structure-function properties of proteins using computational bio-linguistics. She was supported by the Bill & Melinda Gates Foundation to identify novel therapies to tackle HIV. | 1 | Applied and Interdisciplinary Chemistry |
After the detonation of a weapon at or above the fallout-free altitude (an air burst), fission products, un-fissioned nuclear material, and weapon residues vaporized by the heat of the fireball condense into a suspension of particles 10 nm to 20 µm in diameter. This size of particulate matter, lifted to the stratosphere, may take months or years to settle, and may do so anywhere in the world. Its radioactive characteristics increase the statistical cancer risk. Elevated atmospheric radioactivity remains measurable after the widespread nuclear testing of the 1950s.
Radioactive fallout has occurred around the world; for example, people have been exposed to iodine-131 from atmospheric nuclear testing. Fallout accumulates on vegetation, including fruits and vegetables. Starting from 1951 people may have gotten exposure, depending on whether they were outside, the weather, and whether they consumed contaminated milk, vegetables or fruit. Exposure can be on an intermediate time scale or long term. The intermediate time scale results from fallout that has been put into the troposphere and ejected by precipitation during the first month. Long-term fallout can sometimes occur from deposition of tiny particles carried in the stratosphere. By the time that stratospheric fallout has begun to reach the earth, the radioactivity is very much decreased. Also, after a year it is estimated that a sizable quantity of fission products move from the northern to the southern stratosphere. The intermediate time scale is between 1 and 30 days, with long term fallout occurring after that.
Examples of both intermediate and long term fallout occurred after the 1986 Chernobyl accident, which contaminated over of land in Ukraine and Belarus. The main fuel of the reactor was uranium, and surrounding this was graphite, both of which were vaporized by the hydrogen explosion that destroyed the reactor and breached its containment. An estimated 31 people died within a few weeks after this happened, including two plant workers killed at the scene. Although residents were evacuated within 36 hours, people started to complain of vomiting, migraines and other major signs of radiation sickness. The officials of Ukraine had to close off an area. Long term effects included at least 6,000 cases of thyroid cancer, mainly among children. Fallout spread throughout Western Europe, with Northern Scandinavia receiving a heavy dose, contaminating reindeer herds in Lapland, and salad greens becoming almost unavailable in France. Some sheep farms in North Wales and the North Of England were required to monitor radioactivity levels in their flocks until the control was lifted in 2012. | 0 | Theoretical and Fundamental Chemistry |
The arrangement of the continents has changed over time due to plate tectonics, resulting in the bathymetry of ocean basins also changing over time. The shape and size of the basins influences the circulation patterns and concentration of nutrients within them. Numerical models simulating past arrangements of continents have shown that nutrient traps can form in certain scenarios, increasing local concentrations of phosphate and setting up potential euxinic conditions. On a smaller scale, silled basins often act as nutrient traps due to their estuarine circulation. Estuarine circulation occurs where surface water is replenished from river input and precipitation, causing an outflow of surface waters from the basin, while deep water flows into the basin over the sill. This type of circulation allows for anoxic, high nutrient bottom water to develop within the basin. | 0 | Theoretical and Fundamental Chemistry |
Under these criteria, we can propose a model for the fractions of incident light that are absorbed (), remitted (), and transmitted () by one representative layer.
in which:
• is the fraction of cross-sectional surface area that is occupied by particles of type .
• is the effective absorption coefficient for particles of type .
• is the remission coefficient for particles of type .
• is the thickness of a particle of type in the direction of the incident beam.
• The summation is carried out over all of the distinct “types” of particle.
In effect, represents the fraction of light that will interact with a particle of type , and and quantify the likelihood of that interaction resulting in absorption and remission, respectively.
Surface area fractions and volume fractions for each type of particle can be defined as follows:
in which:
• is the mass fraction of particles of type i in the sample.
• is the fraction of occupied volume composed of particles of type i.
• is the fraction of particle surface area that is composed of particles of type i.
• is the fraction of total volume composed of particles of type i.
• is the fraction of cross-sectional surface area that is composed of particles of type i.
• is the density of particles of type i.
• is the void fraction of the sample.
This is a logical way of relating the spectroscopic behavior of a “representative layer” to the properties of the individual particles that make up the layer. The values of the absorption and remission coefficients represent a challenge in this modeling approach. Absorption is calculated from the fraction of light striking each type of particle and a “Beer’s law”-type calculation of the absorption by each type of particle, so the values of used should ideally model the ability of the particle to absorb light, independent of other processes (scattering, remission) that also occur. We referred to this as the absorbing power in the section above. | 0 | Theoretical and Fundamental Chemistry |
The Poiseuille flow theorem is a consequence of the Helmholtz theorem states that The steady laminar flow of an incompressible viscous fluid down a straight pipe of arbitrary cross-section is characterized by the property that its energy dissipation is least among all laminar (or spatially periodic) flows down the pipe which have the same total flux. | 1 | Applied and Interdisciplinary Chemistry |
* Antirrhinin (cyanidin-3-rutinoside or 3-C-R), found in black raspberry
* Cyanidin-3-xylosylrutinoside, found in black raspberry
* Cyanidin-3,4′-di-O-β-glucopyranoside, found in red onion
* Cyanidin-4′-O-β-glucoside, found in red onion
* Chrysanthemin (cyanidin-3-O-glucoside), found in blackcurrant pomace
* Ideain (cyanidin 3-O-galactoside), found in Vaccinium species
* Cyanin (cyanidin-3,5-O-diglucoside), found in red wine | 0 | Theoretical and Fundamental Chemistry |
Adenylate kinase is present in mitochondrial and myofibrillar compartments in the cell, and it makes two high-energy phosphoryls (β and γ) of ATP available to be transferred between adenine nucleotide molecules. In essence, adenylate kinase shuttles ATP to sites of high energy consumption and removes the AMP generated over the course of those reactions. These sequential phosphotransfer relays ultimately result in propagation of the phosphoryl groups along collections of ADK molecules. This process can be thought of as a bucket brigade of ADK molecules that results in changes in local intracellular metabolic flux without apparent global changes in metabolite concentrations. This process is extremely important for overall homeostasis of the cell. | 1 | Applied and Interdisciplinary Chemistry |
Deuterium is used in heavy water moderated fission reactors, usually as liquid HO, to slow neutrons without the high neutron absorption of ordinary hydrogen. This is a common commercial use for larger amounts of deuterium.
In research reactors, liquid H is used in cold sources to moderate neutrons to very low energies and wavelengths appropriate for scattering experiments.
Experimentally, deuterium is the most common nuclide used in fusion reactor designs, especially in combination with tritium, because of the large reaction rate (or nuclear cross section) and high energy yield of the deuterium–tritium (DT) reaction. There is an even higher-yield H–He fusion reaction, though the breakeven point of H–He is higher than that of most other fusion reactions; together with the scarcity of He, this makes it implausible as a practical power source, at least until DT and deuterium–deuterium (DD) fusion have been performed on a commercial scale. Commercial nuclear fusion is not yet an accomplished technology. | 0 | Theoretical and Fundamental Chemistry |
In E-AB sensors, the signal between electrochemical response and absence of target is small. The aptamer can be reengineered to a large-scale, conformational change. Long flexible loops or complementary strands can also force a change in the aptamers conformation. These techniques to modify aptamers increase the signal ratio, but does not guarantee that it is sufficient enough to be measured.
E-AB sensors are only as sensitive as the aptamer deployed. The selectivity of the aptamer can be a concern when there are similar compounds in the blood or other bodily fluids. cross-reactivity causes interference in in-vivo monitoring and requires understanding of how the aptamer reacts with similar compounds that may be in the sample. | 0 | Theoretical and Fundamental Chemistry |
To demonstrate the lability of drug binding, drug specific T cell lines, T cell clones and TCR hybridoma cells were required. Washing of the cell mix of drug, APC and T cells abrogated p-i reactivity, while T cell reaction to haptens persisted. The presentation of peptides by HLA on APC takes > 4hr pulsing (uptake of hapten modified protein, processing and presentation), and may also require metabolism, if the stimulating drug was chemically inert and not a hapten. Therefore, an immediate reactivity of T cells (e.g. measured by rapid Ca influx) as well as reactivity to the drug in the presence of protein and metabolism inhibitors or by using glutaraldehyde-fixed antigen presenting cells was interpreted as p-i reaction. P-i reactivity was demonstrated for a number of drugs (SMX, lidocain, lamotrigine, carbamazepine, various radio contrast media, quinolones, vancomycin, dapsone, etc.), including some drugs which can act via p-i or as hapten (piperacillin, flucloxacillin, amoxicillin, cephalosporins, monobactams). In these cases the p-i reactivity was responsible for more severe reactions like hepatitis in flucloxacillin/B*57:01 carriers or DRESS with amoxicillin and piperacillin | 1 | Applied and Interdisciplinary Chemistry |
Diphenylphosphoryl azide (DPPA) is an organic compound. It is widely used as a reagent in the synthesis of other organic compounds. | 0 | Theoretical and Fundamental Chemistry |
In order to achieve linear motion from compressed air, a system of pistons is most commonly used. The compressed air is fed into an air-tight chamber that houses the shaft of the piston. Also inside this chamber a spring is coiled around the shaft of the piston in order to hold the chamber completely open when air is not being pumped into the chamber. As air is fed into the chamber the force on the piston shaft begins to overcome the force being exerted on the spring. As more air is fed into the chamber, the pressure increases and the piston begins to move down the chamber. When it reaches its maximum length the air pressure is released from the chamber and the spring completes the cycle by closing off the chamber to return to its original position.
Piston motors are the most commonly used in hydraulic systems. Essentially, piston motors are the same as hydraulic motors except they are used to convert hydraulic energy into mechanical energy.
Piston motors are often used in series of two, three, four, five, or six cylinders that are enclosed in a housing. This allows for more power to be delivered by the pistons because several motors are in sync with each other at certain times of their cycle.
The practical mechanical efficiencies attained by a piston air motor are between 40–50%. | 1 | Applied and Interdisciplinary Chemistry |
When applied to air filtration and purification, biofilters use microorganisms to remove air pollution.
The air flows through a packed bed and the pollutant transfers into a thin biofilm on the surface of the packing material. Microorganisms, including bacteria and fungi are immobilized in the biofilm and degrade the pollutant. Trickling filters and bioscrubbers rely on a biofilm and the bacterial action in their recirculating waters.
The technology finds the greatest application in treating malodorous compounds and volatile organic compounds (VOCs). Industries employing the technology include food and animal products, off-gas from wastewater treatment facilities, pharmaceuticals, wood products manufacturing, paint and coatings application and manufacturing and resin manufacturing and application, etc. Compounds treated are typically mixed VOCs and various sulfur compounds, including hydrogen sulfide. Very large airflows may be treated and although a large area (footprint) has typically been required—a large biofilter (>200,000 acfm) may occupy as much or more land than a football field—this has been one of the principal drawbacks of the technology. Since the early 1990s, engineered biofilters have provided significant footprint reductions over the conventional flat-bed, organic media type.
One of the main challenges to optimum biofilter operation is maintaining proper moisture throughout the system. The air is normally humidified before it enters the bed with a watering (spray) system, humidification chamber, bio scrubber, or bio trickling filter. Properly maintained, a natural, organic packing media like peat, vegetable mulch, bark or wood chips may last for several years but engineered, combined natural organic, and synthetic component packing materials will generally last much longer, up to 10 years. Several companies offer these types of proprietary packing materials and multi-year guarantees, not usually provided with a conventional compost or wood chip bed biofilter.
Although widely employed, the scientific community is still unsure of the physical phenomena underpinning biofilter operation, and information about the microorganisms involved continues to be developed. A biofilter/bio-oxidation system is a fairly simple device to construct and operate and offers a cost-effective solution provided the pollutant is biodegradable within a moderate time frame (increasing residence time = increased size and capital costs), at reasonable concentrations (and lb/hr loading rates) and that the airstream is at an organism-viable temperature. For large volumes of air, a biofilter may be the only cost-effective solution. There is no secondary pollution (unlike the case of incineration where additional CO and NO are produced from burning fuels) and degradation products form additional biomass, carbon dioxide and water. Media irrigation water, although many systems recycle part of it to reduce operating costs, has a moderately high biochemical oxygen demand (BOD) and may require treatment before disposal. However, this "blowdown water", necessary for proper maintenance of any bio-oxidation system, is generally accepted by municipal publicly owned treatment works without any pretreatment.
Biofilters are being utilized in Columbia Falls, Montana at Plum Creek Timber Company's fiberboard plant. The biofilters decrease the pollution emitted by the manufacturing process and the exhaust emitted is 98% clean. The newest, and largest, biofilter addition to Plum Creek cost $9.5 million, yet even though this new technology is expensive, in the long run it will cost less overtime than the alternative exhaust-cleaning incinerators fueled by natural gas (which are not as environmentally friendly). | 1 | Applied and Interdisciplinary Chemistry |
The flow in many fluids varies with density and depends upon the gravity. Due to which the fluid with lower density is always above the fluid with higher density. Stratified flows are very common such as the Earth's ocean and its atmosphere. | 1 | Applied and Interdisciplinary Chemistry |
Advantages of electrofusion welding:
* Simple process capable of producing consistent joints
* Process is entirely contained, reducing the risk of joint contamination
* Process allows repair without the need to remove pipes
Disadvantages of electrofusion welding:
* A special sleeve is required, so it is more expensive than other pipe joining methods such as hot plate joining
* Implanted coils make recycling of parts more difficult | 0 | Theoretical and Fundamental Chemistry |
Glass-ceramics are polycrystalline materials produced through controlled crystallization of base glass, producing a fine uniform dispersion of crystals throughout the bulk material. Crystallization is accomplished by subjecting suitable glasses to a carefully regulated heat treatment schedule, resulting in the nucleation and growth of crystal phases. In many cases, the crystallization process can proceed to near completion, but in a small proportion of processes, the residual glass phase often remains.
Glass-ceramic materials share many properties with both glasses and ceramics. Glass-ceramics have an amorphous phase and one or more crystalline phases and are produced by a so-called "controlled crystallization" in contrast to a spontaneous crystallization, which is usually not wanted in glass manufacturing. Glass-ceramics have the fabrication advantage of glass, as well as special properties of ceramics. When used for sealing, some glass-ceramics do not require brazing but can withstand brazing temperatures up to 700 °C.
Glass-ceramics usually have between 30% [m/m] and 90% [m/m] crystallinity and yield an array of materials with interesting properties like zero porosity, high strength, toughness, translucency or opacity, pigmentation, opalescence, low or even negative thermal expansion, high temperature stability, fluorescence, machinability, ferromagnetism, resorbability or high chemical durability, biocompatibility, bioactivity, ion conductivity, superconductivity, isolation capabilities, low dielectric constant and loss, corrosion resistance, high resistivity and break-down voltage. These properties can be tailored by controlling the base-glass composition and by controlled heat treatment/crystallization of base glass. In manufacturing, glass-ceramics are valued for having the strength of ceramic but the hermetic sealing properties of glass.
Glass-ceramics are mostly produced in two steps: First, a glass is formed by a glass-manufacturing process, after which the glass is cooled down. Second, the glass is put through a controlled heat treatment schedule. In this heat treatment the glass partly crystallizes. In most cases nucleation agents are added to the base composition of the glass-ceramic. These nucleation agents aid and control the crystallization process. Because there is usually no pressing and sintering, glass-ceramics have no pores, unlike sintered ceramics.
A wide variety of glass-ceramic systems exist, e.g., the LiO × AlO × nSiO system (LAS system), the MgO × AlO × nSiO system (MAS system), and the ZnO × AlO × nSiO system (ZAS system). | 0 | Theoretical and Fundamental Chemistry |
The chelation of lithium cation with the methoxy group is one of the most important features of the transition state for Enders hydrazone alkylation reaction. It is necessary to have this chelation effect to achieve high stereoselectivity. The development and modification of Enders hydrazone alkylation reaction mainly focus on the addition of more steric hindrance on the pyrrolidine rings of both SAMP and RAMP, while preserving the methoxy group for lithium chelation.
The most famous four variants of SAMP and RAMP are SADP, SAEP, SAPP and RAMBO, whose structures are shown below.
In 2011, several N-amino cyclic carbamates were synthesized and studied for asymmetric hydrazone alkylation reactions. Both the stereochemistry and regioselectivity of the reactions turned out to be very promising. These new compounds consist of a new class of chiral auxiliary based on the carbamate structure and, therefore, no longer belong to the family of SAMP and RAMP. But they do provide very powerful alternatives to the traditional pyrrolidine systems. | 0 | Theoretical and Fundamental Chemistry |
In the United States Code of Federal Regulations (CFR), Title 40, Part 503 governs the management of biosolids. Within that federal regulation biosolids are generally classified differently depending upon the quantity of pollutants they contain and the level of treatment they have been subjected to (the latter of which determines both the level of vector attraction reduction and the level of pathogen reduction). These factors also affect how they may be disseminated (bulk or bagged) and the level of monitoring oversight which, in turn determines where and in what quantity they may be applied. The National Organic Program prohibits the use of biosolids in farming certified organic crops. | 1 | Applied and Interdisciplinary Chemistry |
In response to iron limitation in their environment, genes involved in microbe siderophore production and uptake are derepressed, leading to manufacture of siderophores and the appropriate uptake proteins. In bacteria, Fe-dependent repressors bind to DNA upstream to genes involved in siderophore production at high intracellular iron concentrations. At low concentrations, Fe dissociates from the repressor, which in turn dissociates from the DNA, leading to transcription of the genes. In gram-negative and AT-rich gram-positive bacteria, this is usually regulated by the Fur (ferric uptake regulator) repressor, whilst in GC-rich gram-positive bacteria (e.g. Actinomycetota) it is DtxR (diphtheria toxin repressor), so-called as the production of the dangerous diphtheria toxin by Corynebacterium diphtheriae is also regulated by this system.
This is followed by excretion of the siderophore into the extracellular environment, where the siderophore acts to sequester and solubilize the iron. Siderophores are then recognized by cell specific receptors on the outer membrane of the cell. In fungi and other eukaryotes, the Fe-siderophore complex may be extracellularly reduced to Fe, while in many cases the whole Fe-siderophore complex is actively transported across the cell membrane. In gram-negative bacteria, these are transported into the periplasm via TonB-dependent receptors, and are transferred into the cytoplasm by ABC transporters.
Once in the cytoplasm of the cell, the Fe-siderophore complex is usually reduced to Fe to release the iron, especially in the case of "weaker" siderophore ligands such as hydroxamates and carboxylates. Siderophore decomposition or other biological mechanisms can also release iron, especially in the case of catecholates such as ferric-enterobactin, whose reduction potential is too low for reducing agents such as flavin adenine dinucleotide, hence enzymatic degradation is needed to release the iron. | 1 | Applied and Interdisciplinary Chemistry |
DNA denaturation, also called DNA melting, is the process by which double-stranded deoxyribonucleic acid unwinds and separates into single-stranded strands through the breaking of hydrophobic stacking attractions between the bases. See Hydrophobic effect. Both terms are used to refer to the process as it occurs when a mixture is heated, although "denaturation" can also refer to the separation of DNA strands induced by chemicals like formamide or urea.
The process of DNA denaturation can be used to analyze some aspects of DNA. Because cytosine / guanine base-pairing is generally stronger than adenine / thymine base-pairing, the amount of cytosine and guanine in a genome is called its GC-content and can be estimated by measuring the temperature at which the genomic DNA melts. Higher temperatures are associated with high GC content.
DNA denaturation can also be used to detect sequence differences between two different DNA sequences. DNA is heated and denatured into single-stranded state, and the mixture is cooled to allow strands to rehybridize. Hybrid molecules are formed between similar sequences and any differences between those sequences will result in a disruption of the base-pairing. On a genomic scale, the method has been used by researchers to estimate the genetic distance between two species, a process known as DNA-DNA hybridization. In the context of a single isolated region of DNA, denaturing gradient gels and temperature gradient gels can be used to detect the presence of small mismatches between two sequences, a process known as temperature gradient gel electrophoresis.
Methods of DNA analysis based on melting temperature have the disadvantage of being proxies for studying the underlying sequence; DNA sequencing is generally considered a more accurate method.
The process of DNA melting is also used in molecular biology techniques, notably in the polymerase chain reaction. Although the temperature of DNA melting is not diagnostic in the technique, methods for estimating T are important for determining the appropriate temperatures to use in a protocol. DNA melting temperatures can also be used as a proxy for equalizing the hybridization strengths of a set of molecules, e.g. the oligonucleotide probes of DNA microarrays. | 1 | Applied and Interdisciplinary Chemistry |
Continuous flow photochemistry offers multiple advantages over batch photochemistry. Photochemical reactions are driven by the number of photons that are able to activate molecules causing the desired reaction. The large surface area to volume ratio of a microreactor maximizes the illumination, and at the same time allows for efficient cooling, which decreases the thermal side products. | 1 | Applied and Interdisciplinary Chemistry |
Imines may be reduced enantioselectively using stoichiometric amounts of chiral metal hydrides. Such methods have the advantage that they are easy to implement. Reduction with hydrosilanes is a second alternative to transition-metal catalyzed hydrogenation. | 0 | Theoretical and Fundamental Chemistry |
Tetrakis(triphenylphosphine)palladium(0) (sometimes called quatrotriphenylphosphine palladium) is the chemical compound [Pd(P(CH))], often abbreviated Pd(PPh), or rarely PdP. It is a bright yellow crystalline solid that becomes brown upon decomposition in air. | 0 | Theoretical and Fundamental Chemistry |
The main areas of use are the conversion of ketones to esters (Baeyer-Villiger oxidation), epoxidation of alkenes (Prilezhaev reaction), conversion of silyl enol ethers to silyl α-hydroxy ketones (Rubottom oxidation), oxidation of sulfides to sulfoxides and sulfones, and oxidation of amines to produce amine oxides. The following scheme shows the epoxidation of cyclohexene with mCPBA.
The epoxidation mechanism is concerted: the cis or trans geometry of the alkene starting material is retained in the epoxide ring of the product. The transition state of the Prilezhaev reaction is given below:
The geometry of the transition state, with the peracid bisecting the C-C double bond, allows the two primary frontier orbital interactions to occur: π (HOMO) to σ* (LUMO) and n (HOMO, regarded as a filled p orbital on a sp hybridized oxygen) to π* (LUMO), corresponding, in arrow-pushing terms, to formation of one C-O bond and cleavage of the O-O bond and formation of the other C-O bond and cleavage of the C=C π bond. | 0 | Theoretical and Fundamental Chemistry |
Bimodal Atomic Force Microscopy (bimodal AFM) is an advanced atomic force microscopy technique characterized by generating high-spatial resolution maps of material properties. Topography, deformation, elastic modulus, viscosity coefficient or magnetic field maps might be generated. Bimodal AFM is based on the simultaneous excitation and detection of two eigenmodes (resonances) of a force microscope microcantilever. | 0 | Theoretical and Fundamental Chemistry |
An extinct radionuclide is a radionuclide that was formed by nucleosynthesis before the formation of the Solar System, about 4.6 billion years ago, but has since decayed to virtually zero abundance and is no longer detectable as a primordial nuclide. Extinct radionuclides were generated by various processes in the early Solar system, and became part of the composition of meteorites and protoplanets. All widely documented extinct radionuclides have half-lives shorter than 100 million years.
Short-lived radioisotopes that are found in nature are continuously generated or replenished by natural processes, such as cosmic rays (cosmogenic nuclides), background radiation, or the decay chain or spontaneous fission of other radionuclides.
Short-lived isotopes that are not generated or replenished by natural processes are not found in nature, so they are known as extinct radionuclides. Their former existence is inferred from a superabundance of their stable or nearly stable decay products.
Examples of extinct radionuclides include iodine-129 (the first to be noted in 1960, inferred from excess xenon-129 concentrations in meteorites, in the xenon-iodine dating system), aluminium-26 (inferred from extra magnesium-26 found in meteorites), and iron-60.
The Solar System and Earth are formed from primordial nuclides and extinct nuclides. Extinct nuclides have decayed away, but primordial nuclides still exist in their original state (undecayed). There are 251 stable primordial nuclides, and remainders of 35 primordial radionuclides that have very long half-lives. | 0 | Theoretical and Fundamental Chemistry |
* Coordinates in square brackets such as denote a direction vector (in real space).
* Coordinates in angle brackets or chevrons such as <100> denote a family of directions which are related by symmetry operations. In the cubic crystal system for example, or the negative of any of those directions.
* Miller indices in parentheses such as (100) denote a plane of the crystal structure, and regular repetitions of that plane with a particular spacing. In the cubic system, the normal to the (hkl) plane is the direction [hkl], but in lower-symmetry cases, the normal to (hkl) is not parallel to [hkl].
* Indices in curly brackets or braces such as denote a family of planes and their normals. In cubic materials the symmetry makes them equivalent, just as the way angle brackets denote a family of directions. In non-cubic materials, <hkl> is not necessarily perpendicular to {hkl}. | 0 | Theoretical and Fundamental Chemistry |
The Schöllkopf method or Schöllkopf Bis-Lactim Amino Acid Synthesis is a method in organic chemistry for the asymmetric synthesis of chiral amino acids. The method was established in 1981 by Ulrich Schöllkopf. In it glycine is a substrate, valine a chiral auxiliary and the reaction taking place an alkylation. | 0 | Theoretical and Fundamental Chemistry |
Hydrogen embrittlement is a volume effect: it affects the volume of the material. Environmental embrittlement is a surface effect where molecules from the atmosphere surrounding the material under test are adsorbed onto the fresh crack surface. This is most clearly seen from fatigue measurements where the measured crack growth rates can be an order of magnitude higher in hydrogen than in air. That this effect is due to adsorption, which saturates when the crack surface is completely covered, is understood from the weak dependence of the effect on the pressure of hydrogen.
Environmental embrittlement is also observed to reduce fracture toughness in fast fracture tests, but the severity is much reduced compared with the same effect in fatigue
Hydrogen embrittlement is the effect where a previously embrittled material has low fracture toughness whatever atmosphere it is tested in. Environmental embrittlement is the effect when the low fracture toughness is only observed when the testing happens in that atmosphere. | 0 | Theoretical and Fundamental Chemistry |
LISICON is an acronym for LIthium Super Ionic CONductor, which refers to a family of solids with the chemical formula LiZnGeO.
The first example of this structure was discovered in 1977 with , providing a chemical formula of LiZn(GeO). The crystal structure of LISICON consists of a network of [LiZn(GeO)] as well as 3 loosely bonded Li. The weaker bonds allow for the lithium ions to easily move from site to site, not needing to break strong bonds to do so. Also, this structure forms large “bottlenecks” between the interstitial positions which these ions occupy, additionally lowering the energy required to move from site to site. These two factors allow for the lithium ions to diffuse quickly and easily through the structure. However, because of the shape of the channels through which these lithium ions can diffuse, they are limited to 2 dimensional diffusion. LISICON compounds have relatively high ionic conductivity, on the order of 10 S/cm at 25 °C. LISICONs readily react with lithium metal and atmospheric gases such as CO; as a result, their conductivity decreases with time. | 0 | Theoretical and Fundamental Chemistry |
The oxygen-evolving complex (OEC), also known as the water-splitting complex, is a water-oxidizing enzyme involved in the photo-oxidation of water during the light reactions of photosynthesis. OEC is surrounded by 4 core proteins of photosystem II at the membrane-lumen interface. The mechanism for splitting water involves absorption of three photons before the fourth provides sufficient energy for water oxidation. Based on a widely accepted theory from 1970 by Kok, the complex can exist in 5 states, denoted S to S, with S the most reduced and S the most oxidized. Photons trapped by photosystem II move the system from state S to S. S is unstable and reacts with water producing free oxygen. For the complex to reset to the lowest state, S, it uses 2 water molecules to pull out 4 electrons.
The OEC active site contains a cluster of manganese and calcium, with the formula MnCaOCl(HCO). This cluster is coordinated by D and CP subunits and stabilized by peripheral membrane proteins. Other characteristics of it have been reviewed.
Currently, the mechanism of the complex is not completely understood, along with the role of Ca+2, Cl−1, and the membrane proteins surrounding the metal cluster. Much of what is known has been collected from flash photolysis experiments, electron paramagnetic resonance (EPR), and X-ray spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
*PLC-ε (230-260kDa ) is activated by Ras and Rho GTPases.
*PLC-ζ (75kDa) is thought to play an important role in vertebrate fertilization by producing intracellular calcium oscillations important for the start of embryonic development. However, the mechanism of activation still remains unclear. This isoform is also capable of entering the early-formed pronucleus after fertilization, which seems to coincide with the cessation of calcium mobilization. It, like PLC-δ1 and PLC-β, possesses nuclear export and localization sequences.
*PLC-η has been implicated in neuronal functioning. | 1 | Applied and Interdisciplinary Chemistry |
Schoell received the 1995 AAPG Best Paper Award and was recognized by the American Association of Petroleum Geologists as authoring one of the top twenty most notable geology-related papers of the 1980s. Specifically, the AAPG recognized Schoell for his paper "Genetic Characterization of Natural Gasses" which describes how the correlation between C concentration, the variation of carbon and hydrogen isotopes in methane, and carbon isotope variation in ethane can be used to qualitatively characterize the composition of natural gasses.
In 2008, Schoell received the annual Alfred Treibs Award. This award is given on a yearly basis by the Geochemical Society in recognition of scientists whose research has made significant contributions to the understanding of geochemical processes. Schoell received this honour in response to his work with stable isotope analyses which revolutionized fossil fuel research and greenhouse gas tracing. | 0 | Theoretical and Fundamental Chemistry |
Mycofactocin is thought to play a role in redox pathways involving nicotinoproteins, enzymes with non-exchangeable bound nicotinamide adenine dinucleotide (NAD). This notion comes largely from comparative genomics work that highlighted the many parallels between mycofactocin and pyrroloquinoline quinone (PQQ). In both cases, maturation of the RiPP requires post-translational modification of a precursor peptide by a radical SAM enzyme, the system appears in very similar form in large numbers of species, the product appears to be used within the cell rather than exported, and several families of enzymes occur exclusively in bacteria with those systems. The number of putatively mycofactocin-dependent oxidoreductases encoded by a single genome can be quite large: at least 19 for Rhodococcus jostii RHA1, and 26 for the short chain dehydrogenase/reductase (SDR) family alone in Mycobacterium avium.
The enzyme LimC (), a nicotinoprotein carveol dehydrogenase (EC 1.1.1.n4), is shown to use both MFT and PMFT in vitro. | 1 | Applied and Interdisciplinary Chemistry |
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