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Plasmalysis is a electrochemical process that requires a voltage source. On the one hand, it describes the plasma-chemical dissociation of organic and inorganic compounds (e.g. C-H and N-H compounds) in interaction with a thermal/non-thermal plasma between two electrodes. On the other hand, it describes the synthesis, i.e. the combination of two or more elements to form a new molecule (e.g. methane synthesis/methanation). Plasmalysis is an artificial word made of plasma and lysis (Greek λύσις, "[dissolution]"). | 0 | Theoretical and Fundamental Chemistry |
Many other industries take into account distribution coefficients, for example in the formulation of make-up, topical ointments, dyes, hair colors and many other consumer products. | 0 | Theoretical and Fundamental Chemistry |
In type II reactions, the Sens* transfers its energy directly with O via a radiation-less transition to create O. O then adds to the substrate in a variety of ways including: cycloadditions (most commonly [4+2]), addition to double bonds to yield 1,2-dioxetanes, and ene reactions with olefins. | 0 | Theoretical and Fundamental Chemistry |
Metachirality is a stronger form of chirality.
It applies to objects or systems that are chiral (not identical to their mirror image) and where, in addition, their mirror image has a symmetry group that differs from the symmetry group of the original object or system.
Many familiar chiral objects, like the capital letter Z embedded in the plane, are not metachiral.
The symmetry group of the capital letter Z embedded in the plane consists of the identity transformation and a rotation over 180˚ (a half turn).
In this case, the mirror image has the same symmetry group.
In particular, asymmetric objects (that only have the identity transformation as symmetry, like a human hand) are not metachiral,
since the mirror image is also asymmetric.
In general, two-dimensional objects and bounded three-dimensional objects are not metachiral.
An example of a metachiral object is an infinite helical staircase.
A helix in 3D has a handedness (either left or right, like screw thread), whereby it differs from its mirror image.
An infinite helical staircase, however, does have symmetries:
screw operations, that is, a combination of a translation and a rotation.
The symmetry group of the mirror image of an infinite helical staircase also contains screw operations.
But they are of the opposite handedness and, hence,
the symmetry groups differ.
Note, however, that these symmetry groups are isomorphic.
Of the 219 space groups, 11 are metachiral.
A nice example of a metachiral spatial structure is the K crystal, also known as Triamond,
and featured in the Bamboozle mathematical artwork. | 0 | Theoretical and Fundamental Chemistry |
SELDM is a stochastic model because it uses Monte Carlo methods to produce the random combinations of input variable values needed to generate the stochastic population of values for each component variable. SELDM calculates the dilution of runoff in the receiving waters and the resulting downstream event mean concentrations and annual average lake concentrations. Results are ranked, and plotting positions are calculated, to indicate the level of risk of adverse effects caused by runoff concentrations, flows, and loads on receiving waters by storm and by year. Unlike deterministic hydrologic models, SELDM is not calibrated by changing values of input variables to match a historical record of values. Instead, input values for SELDM are based on site characteristics and representative statistics for each hydrologic variable. Thus, SELDM is an empirical model based on data and statistics rather than theoretical physicochemical equations.
SELDM is a lumped parameter model because the highway site, the upstream basin, and the lake basin each are represented as a single homogeneous unit. Each of these source areas is represented by average basin properties, and results from SELDM are calculated as point estimates for the site of interest. Use of the lumped parameter approach facilitates rapid specification of model parameters to develop planning-level estimates with available data. The approach allows for parsimony in the required inputs to and outputs from the model and flexibility in the use of the model. For example, SELDM can be used to model runoff from various land covers or land uses by using the highway-site definition as long as representative water quality and impervious-fraction data are available.
SELDM is easy to use because it has a simple graphical user interface and because much of the information and data needed to run SELDM are embedded in the model. SELDM provides input statistics for precipitation, prestorm flow, runoff coefficients, and concentrations of selected water-quality constituents from National datasets. Input statistics may be selected on the basis of the latitude, longitude, and physical characteristics of the site of interest and the upstream basin. The user also may derive and input statistics for each variable that are specific to a given site of interest or a given area. Information and data from hundreds to thousands of sites across the country were compiled to facilitate use of SELDM. Most of the necessary input data are obtained by defining the location of the site of interest and five simple basin properties. These basin properties are the drainage area, the basin length, the basin slope, the impervious fraction, and the basin development factor
SELDM models the potential effect of mitigation measures by using Monte Carlo methods with statistics that approximate the net effects of structural and nonstructural best management practices (BMPs).. Structural BMPs are defined as the components of the drainage pathway between the source of runoff and a stormwater discharge location that affect the volume, timing, or quality of runoff. SELDM uses a simple stochastic statistical model of BMP performance to develop planning-level estimates of runoff-event characteristics. This statistical approach can be used to represent a single BMP or an assemblage of BMPs. The SELDM BMP-treatment module has provisions for stochastic modeling of three stormwater treatments: volume reduction, hydrograph extension, and water-quality treatment. In SELDM, these three treatment variables are modeled by using the trapezoidal distribution and the rank correlation with the associated highway-runoff variables. This report describes methods for calculating the trapezoidal-distribution statistics and rank correlation coefficients for stochastic modeling of volume reduction, hydrograph extension, and water-quality treatment by structural stormwater BMPs and provides the calculated values for these variables. These statistics are different from the statistics commonly used to characterize or compare BMPs. They are designed to provide a stochastic transfer function to approximate the quantity, duration, and quality of BMP effluent given the associated inflow values for a population of storm events. | 1 | Applied and Interdisciplinary Chemistry |
The rotation of plane polarized light by chiral substances was first observed by Jean-Baptiste Biot in 1812, and gained considerable importance in the sugar industry, analytical chemistry, and pharmaceuticals. Louis Pasteur deduced in 1848 that this phenomenon has a molecular basis. The term chirality itself was coined by Lord Kelvin in 1894. Different enantiomers or diastereomers of a compound were formerly called optical isomers due to their different optical properties. At one time, chirality was thought to be restricted to organic chemistry, but this misconception was overthrown by the resolution of a purely inorganic compound, a cobalt complex called hexol, by Alfred Werner in 1911.
In the early 1970s, various groups established that the human olfactory organ is capable of distinguishing chiral compounds. | 0 | Theoretical and Fundamental Chemistry |
Levomilnacipran (brand name Fetzima) is an antidepressant which was approved in the United States in 2013 for the treatment of major depressive disorder (MDD) in adults. It is the levorotatory enantiomer of milnacipran, and has similar effects and pharmacology, acting as a serotonin–norepinephrine reuptake inhibitor (SNRI). | 0 | Theoretical and Fundamental Chemistry |
In crystallography, a lattice plane of a given Bravais lattice is any plane containing at least three noncollinear Bravais lattice points. Equivalently, a lattice plane is a plane whose intersections with the lattice (or any crystalline structure of that lattice) are periodic (i.e. are described by 2d Bravais lattices). A family of lattice planes is a collection of equally spaced parallel lattice planes that, taken together, intersect all lattice points. Every family of lattice planes can be described by a set of integer Miller indices that have no common divisors (i.e. are relative prime). Conversely, every set of Miller indices without common divisors defines a family of lattice planes. If, on the other hand, the Miller indices are not relative prime, the family of planes defined by them is not a family of lattice planes, because not every plane of the family then intersects lattice points.
Conversely, planes that are not lattice planes have aperiodic intersections with the lattice called quasicrystals; this is known as a "cut-and-project" construction of a quasicrystal (and is typically also generalized to higher dimensions). | 0 | Theoretical and Fundamental Chemistry |
While NMR is primarily used for structural determination, it can also be used for purity determination, provided that the structure and molecular weight of the compound is known. This technique requires the use of an internal standard of known purity. Typically this standard will have a high molecular weight to facilitate accurate weighing, but relatively few protons so as to give a clear peak for later integration e.g. 1,2,4,5-tetrachloro-3-nitrobenzene. Accurately weighed portions of the standard and sample are combined and analysed by NMR. Suitable peaks from both compounds are selected and the purity of the sample is determined via the following equation.
Where:
* w: weight of internal standard
* w: weight of sample
* n[H]: the integrated area of the peak selected for comparison in the standard, corrected for the number of protons in that functional group
* n[H]: the integrated area of the peak selected for comparison in the sample, corrected for the number of protons in that functional group
* MW: molecular weight of standard
* MW: molecular weight of sample
* P: purity of internal standard | 0 | Theoretical and Fundamental Chemistry |
The following description of glass beads from an object in the collection of the British Museum, effectively illustrates the range of symptoms that can occur with glass disease: | 0 | Theoretical and Fundamental Chemistry |
In many cases, the splicing process can create a range of unique proteins by varying the exon composition of the same mRNA. This phenomenon is then called alternative splicing. Alternative splicing can occur in many ways. Exons can be extended or skipped, or introns can be retained. It is estimated that 95% of transcripts from multiexon genes undergo alternative splicing, some instances of which occur in a tissue-specific manner and/or under specific cellular conditions. Development of high throughput mRNA sequencing technology can help quantify the expression levels of alternatively spliced isoforms. Differential expression levels across tissues and cell lineages allowed computational approaches to be developed to predict the functions of these isoforms.
Given this complexity, alternative splicing of pre-mRNA transcripts is regulated by a system of trans-acting proteins (activators and repressors) that bind to cis-acting sites or "elements" (enhancers and silencers) on the pre-mRNA transcript itself. These proteins and their respective binding elements promote or reduce the usage of a particular splice site. The binding specificity comes from the sequence and structure of the cis-elements, e.g. in HIV-1 there are many donor and acceptor splice sites. Among the various splice sites, ssA7, which is 3' acceptor site, folds into three stem loop structures, i.e. Intronic splicing silencer (ISS), Exonic splicing enhancer (ESE), and Exonic splicing silencer (ESSE3). Solution structure of Intronic splicing silencer and its interaction to host protein hnRNPA1 give insight into specific recognition. However, adding to the complexity of alternative splicing, it is noted that the effects of regulatory factors are many times position-dependent. For example, a splicing factor that serves as a splicing activator when bound to an intronic enhancer element may serve as a repressor when bound to its splicing element in the context of an exon, and vice versa. In addition to the position-dependent effects of enhancer and silencer elements, the location of the branchpoint (i.e., distance upstream of the nearest 3’ acceptor site) also affects splicing. The secondary structure of the pre-mRNA transcript also plays a role in regulating splicing, such as by bringing together splicing elements or by masking a sequence that would otherwise serve as a binding element for a splicing factor. | 1 | Applied and Interdisciplinary Chemistry |
It is common for nucleic acid samples to be contaminated with other molecules (i.e. proteins, organic compounds, other). The secondary benefit of using spectrophotometric analysis for nucleic acid quantitation is the ability to determine sample purity using the 260 nm:280 nm calculation. The ratio of the absorbance at 260 and 280 nm (A) is used to assess the purity of nucleic acids. For pure DNA, A is widely considered ~1.8 but has been argued to translate - due to numeric errors in the original Warburg paper - into a mix of 60% protein and 40% DNA. The ratio for pure RNA A is ~2.0. These ratios are commonly used to assess the amount of protein contamination that is left from the nucleic acid isolation process since proteins absorb at 280 nm.
The ratio of absorbance at 260 nm vs 280 nm is commonly used to assess DNA contamination of protein solutions, since proteins (in particular, the aromatic amino acids) absorb light at 280 nm. The reverse, however, is not true — it takes a relatively large amount of protein contamination to significantly affect the 260:280 ratio in a nucleic acid solution.
260:280 ratio has high sensitivity for nucleic acid contamination in protein:
260:280 ratio lacks sensitivity for protein contamination in nucleic acids (table shown for RNA, 100% DNA is approximately 1.8):
This difference is due to the much higher mass attenuation coefficient nucleic acids have at 260 nm and 280 nm, compared to that of proteins. Because of this, even for relatively high concentrations of protein, the protein contributes relatively little to the 260 and 280 absorbance. While the protein contamination cannot be reliably assessed with a 260:280 ratio, this also means that it contributes little error to DNA quantity estimation. | 0 | Theoretical and Fundamental Chemistry |
Caesium carbonate or cesium carbonate is a chemical compound with the chemical formula . It is white crystalline solid. Caesium carbonate has a high solubility in polar solvents such as water, ethanol and DMF. Its solubility is higher in organic solvents compared to other carbonates like potassium carbonate and sodium carbonate, although it remains quite insoluble in other organic solvents such as toluene, p-xylene, and chlorobenzene. This compound is used in organic synthesis as a base. It also appears to have applications in energy conversion. | 0 | Theoretical and Fundamental Chemistry |
Target-enrichment methods allow one to selectively capture genomic regions of interest from a DNA sample prior to sequencing. Several target-enrichment strategies have been developed since the original description of the direct genomic selection (DGS) method in 2005.
Though many techniques have been described for targeted capture, only a few of these have been extended to capture entire exomes. The first target enrichment strategy to be applied to whole exome sequencing was the array-based hybrid capture method in 2007, but in-solution capture has gained popularity in recent years. | 1 | Applied and Interdisciplinary Chemistry |
Vortex structures are defined by their vorticity, the local rotation rate of fluid particles. They can be formed via the phenomenon known as boundary layer separation which can occur when a fluid moves over a surface and experiences a rapid acceleration from the fluid velocity to zero due to the no-slip condition. This rapid negative acceleration creates a boundary layer which causes a local rotation of fluid at the wall (i.e. vorticity) which is referred to as the wall shear rate. The thickness of this boundary layer is proportional to (where v is the free stream fluid velocity and t is time).
If the diameter or thickness of the vessel or fluid is less than the boundary layer thickness then the boundary layer will not separate and vortices will not form. However, when the boundary layer does grow beyond this critical boundary layer thickness then separation will occur which will generate vortices.
This boundary layer separation can also occur in the presence of combatting pressure gradients (i.e. a pressure that develops downstream). This is present in curved surfaces and general geometry changes like a convex surface. A unique example of severe geometric changes is at the trailing edge of a bluff body where the fluid flow deceleration, and therefore boundary layer and vortex formation, is located.
Another form of vortex formation on a boundary is when fluid flows perpendicularly into a wall and creates a splash effect. The velocity streamlines are immediately deflected and decelerated so that the boundary layer separates and forms a toroidal vortex ring. | 1 | Applied and Interdisciplinary Chemistry |
It can be prepared by the reaction of allyl magnesium bromide with anhydrous nickel chloride. It was first prepared similarly by Gunther Wilke et al. The same group reported that the complex react with carbon monoxide to give nickel tetracarbonyl and 1,5-hexadiene. It catalyzes the trimerization of butadiene. With tertiary phosphines, the complex gives the tetrakis derivative. Such reactions to proceed via the intermediacy of the 18-electron adduct. | 0 | Theoretical and Fundamental Chemistry |
Trimethylsilyl chloride, also known as chlorotrimethylsilane is an organosilicon compound (silyl halide), with the formula , often abbreviated or TMSCl. It is a colourless volatile liquid that is stable in the absence of water. It is widely used in organic chemistry. | 0 | Theoretical and Fundamental Chemistry |
The interest of growing a smooth and defect-free surface requires a combination set of physical conditions throughout the process. Such conditions are bond strength, temperature, surface-diffusion limited and supersaturation (or impingement) rate. Using KMC surface growth method, following pictures describe final surface structure at different conditions. | 0 | Theoretical and Fundamental Chemistry |
Fluorination with aminosulfuranes is a chemical reaction that transforms oxidized organic compounds into organofluorine compounds. Aminosulfuranes selectively exchange hydroxyl groups for fluorine, but are also capable of converting carbonyl groups, halides, silyl ethers, and other functionality into organofluorides. | 0 | Theoretical and Fundamental Chemistry |
Meropenem is bactericidal except against Listeria monocytogenes, where it is bacteriostatic. It inhibits bacterial cell wall synthesis like other β-lactam antibiotics. In contrast to other beta-lactams, it is highly resistant to degradation by β-lactamases or cephalosporinases. In general, resistance arises due to mutations in penicillin-binding proteins, production of metallo-β-lactamases, or resistance to diffusion across the bacterial outer membrane. Unlike imipenem, it is stable to dehydropeptidase-1, so can be given without cilastatin.
In 2016, a synthetic peptide-conjugated PMO (PPMO) was found to inhibit the expression of New Delhi metallo-beta-lactamase, an enzyme that many drug-resistant bacteria use to destroy carbapenems.
While β-lactam ring in meropenem is more accessible to water molecules than in the other β-lactam antibiotics, that facilitates the hydrolysis process and faster degradation of meropenem's antibacterial properties in aqueous solutions, it is more resistant to degradation by β-lactamase enzymes produced by bacteria than the other β-lactam antibiotics. | 0 | Theoretical and Fundamental Chemistry |
Mass spectrometry (MS) is an analytical technique that measures the mass-to-charge ratio (m/z) of charged particles (ions). Although there are many different kinds of mass spectrometers, all of them make use of electric or magnetic fields to manipulate the motion of ions produced from an analyte of interest and determine their m/z. The basic components of a mass spectrometer are the ion source, the mass analyzer, the detector, and the data and vacuum systems. The ion source is where the components of a sample introduced in a MS system are ionized by means of electron beams, photon beams (UV lights), laser beams or corona discharge. In the case of electrospray ionization, the ion source moves ions that exist in liquid solution into the gas phase. The ion source converts and fragments the neutral sample molecules into gas-phase ions that are sent to the mass analyzer. While the mass analyzer applies the electric and magnetic fields to sort the ions by their masses, the detector measures and amplifies the ion current to calculate the abundances of each mass-resolved ion. In order to generate a mass spectrum that a human eye can easily recognize, the data system records, processes, stores, and displays data in a computer.
The mass spectrum can be used to determine the mass of the analytes, their elemental and isotopic composition, or to elucidate the chemical structure of the sample. MS is an experiment that must take place in gas phase and under vacuum (1.33 * 10 to 1.33 * 10 pascal). Therefore, the development of devices facilitating the transition from samples at higher pressure and in condensed phase (solid or liquid) into a vacuum system has been essential to develop MS as a potent tool for identification and quantification of organic compounds like peptides. MS is now in very common use in analytical laboratories that study physical, chemical, or biological properties of a great variety of compounds. Among the many different kinds of mass analyzers, the ones that find application in LC–MS systems are the quadrupole, time-of-flight (TOF), ion traps, and hybrid quadrupole-TOF (QTOF) analyzers. | 0 | Theoretical and Fundamental Chemistry |
The Debye–Waller factor (DWF), named after Peter Debye and Ivar Waller, is used in condensed matter physics to describe the attenuation of x-ray scattering or coherent neutron scattering caused by thermal motion. It is also called the B factor, atomic B factor, or temperature factor. Often, "Debye–Waller factor" is used as a generic term that comprises the Lamb–Mössbauer factor of incoherent neutron scattering and Mössbauer spectroscopy.
The DWF depends on the scattering vector q. For a given q, DWF(q) gives the fraction of elastic scattering; 1 – DWF(q) correspondingly gives the fraction of inelastic scattering (strictly speaking, this probability interpretation is not true in general). In diffraction studies, only the elastic scattering is useful; in crystals, it gives rise to distinct Bragg reflection peaks. Inelastic scattering events are undesirable as they cause a diffuse background — unless the energies of scattered particles are analysed, in which case they carry valuable information (for instance in inelastic neutron scattering or electron energy loss spectroscopy).
The basic expression for the DWF is given by
where u is the displacement of a scattering center,
and denotes either thermal or time averaging.
Assuming harmonicity of the scattering centers in the material under study, the Boltzmann distribution implies that is normally distributed with zero mean. Then, using for example the expression of the corresponding characteristic function, the DWF takes the form
Note that although the above reasoning is classical, the same holds in quantum mechanics.
Assuming also isotropy of the harmonic potential, one may write
where q, u are the magnitudes (or absolute values) of the vectors q, u respectively, and is the mean squared displacement. In crystallographic publications, values of are often given where . Note that if the incident wave has wavelength , and it is elastically scattered by an angle of , then
In the context of protein structures, the term B-factor is used. The B-factor is defined as
It is measured in units of Å.
The B-factors can be taken as indicating the relative vibrational motion of different parts of the structure. Atoms with low B-factors belong to a part of the structure that is well ordered. Atoms with large B-factors generally belong to part of the structure that is very flexible. Each ATOM record (PDB file format) of a crystal structure deposited with the Protein Data Bank contains a B-factor for that atom. | 0 | Theoretical and Fundamental Chemistry |
Plasmids are the most-commonly used bacterial cloning vectors. These cloning vectors contain a site that allows DNA fragments to be inserted, for example a multiple cloning site or polylinker which has several commonly used restriction sites to which DNA fragments may be ligated. After the gene of interest is inserted, the plasmids are introduced into bacteria by a process called transformation. These plasmids contain a selectable marker, usually an antibiotic resistance gene, which confers on the bacteria an ability to survive and proliferate in a selective growth medium containing the particular antibiotics. The cells after transformation are exposed to the selective media, and only cells containing the plasmid may survive. In this way, the antibiotics act as a filter to select only the bacteria containing the plasmid DNA. The vector may also contain other marker genes or reporter genes to facilitate selection of plasmids with cloned inserts. Bacteria containing the plasmid can then be grown in large amounts, harvested, and the plasmid of interest may then be isolated using various methods of plasmid preparation.
A plasmid cloning vector is typically used to clone DNA fragments of up to 15 kbp. To clone longer lengths of DNA, lambda phage with lysogeny genes deleted, cosmids, bacterial artificial chromosomes, or yeast artificial chromosomes are used. | 1 | Applied and Interdisciplinary Chemistry |
The extraction is performed in water with the addition of potassium hydroxide (KOH), sequestering agents, and hydrotropic surfactants. Heat is used to increase the solubility of humic acids and hence more potassium humate can be extracted. The resulting liquid is dried to produce the amorphous crystalline like product which can then be added as a granule to fertilizer. The potassium humate granules by way of chemical extraction lose their hydrophobic properties and are now soluble. | 0 | Theoretical and Fundamental Chemistry |
Recently, Gregory Fu and colleagues reported a modification of their earlier kinetic resolution work to produce an effective dynamic kinetic resolution. Using the ruthenium racemization catalyst shown to the right, and his planar chiral DMAP catalyst, Fu has demonstrated the dynamic kinetic resolution of secondary alcohols yielding up to 99% and 93% ee, as shown below. Work is ongoing to further develop the applications of the widely used DMAP catalyst to dynamic kinetic resolution. | 0 | Theoretical and Fundamental Chemistry |
The first recorded use of the term automated mineralogy in technical journals can be traced back to seminal papers in the late eighties early nineties describing QEMSCAN technology and applications. The term gained significant popularity after it was used to name a new international conference in July 2006. | 0 | Theoretical and Fundamental Chemistry |
Surfactants are used with quantum dots in order to manipulate their growth, assembly, and electrical properties, in addition to mediating reactions on their surfaces. Research is ongoing in how surfactants arrange themselves on the surface of the quantum dots. | 0 | Theoretical and Fundamental Chemistry |
Quantities of liquids are measured in units of volume. These include the SI unit cubic metre (m) and its divisions, in particular the cubic decimeter, more commonly called the litre (1 dm = 1 L = 0.001 m), and the cubic centimetre, also called millilitre (1 cm = 1 mL = 0.001 L = 10 m).
The volume of a quantity of liquid is fixed by its temperature and pressure. Liquids generally expand when heated, and contract when cooled. Water between 0 °C and 4 °C is a notable exception.
On the other hand, liquids have little compressibility. Water, for example, will compress by only 46.4 parts per million for every unit increase in atmospheric pressure (bar). At around 4000 bar (400 megapascals or 58,000 psi) of pressure at room temperature water experiences only an 11% decrease in volume. Incompressibility makes liquids suitable for transmitting hydraulic power, because a change in pressure at one point in a liquid is transmitted undiminished to every other part of the liquid and very little energy is lost in the form of compression.
However, the negligible compressibility does lead to other phenomena. The banging of pipes, called water hammer, occurs when a valve is suddenly closed, creating a huge pressure-spike at the valve that travels backward through the system at just under the speed of sound. Another phenomenon caused by liquid's incompressibility is cavitation. Because liquids have little elasticity they can literally be pulled apart in areas of high turbulence or dramatic change in direction, such as the trailing edge of a boat propeller or a sharp corner in a pipe. A liquid in an area of low pressure (vacuum) vaporizes and forms bubbles, which then collapse as they enter high pressure areas. This causes liquid to fill the cavities left by the bubbles with tremendous localized force, eroding any adjacent solid surface. | 0 | Theoretical and Fundamental Chemistry |
Although beneficial for the effectiveness of the reaction, the use of copper salts in "classical" Sonogashira reaction is accompanied with several drawbacks, such as the application of environmentally unfriendly reagents, the formation of undesirable alkyne homocoupling (Glaser side products), and the necessity of strict oxygen exclusion in the reaction mixture. Thus, with the aim of excluding copper from the reaction, a lot of effort was undertaken in the developments of Cu-free Sonogashira reaction. Along the development of new reaction conditions, many experimental and computational studies focused on elucidation of reaction mechanism. Until recently, the exact mechanism by which the Cu-free reaction occurs was under debate, with critical mechanistic questions unanswered. It was shown in 2018 by Košmrlj et al. that the reaction proceeds along the two interconnected Pd/Pd catalytic cycles.
* Similar to the original mechanism, the Pd cycle begins with the oxidative addition of the aryl halide or triflate to the Pd catalyst, forming complex B and activating aryl halide substrate for the reaction.
* Acetylene is activated in the second, Pd mediated cycle. Phenylacetylene was proven to form Pd monoacetylide complex D as well as Pd bisacetylide complex F under mild reaction conditions.
* Both activated species, namely complexes B and F, are involved in the transmetallation step, forming complex C and regenerating D.
* The resulting products of reductive elimination, disubstituted alkyne product as well as regenerated Pd catalytic species, complete the Pd catalytic cycle.
It was demonstrated that amines are competitive to the phosphines and can also participate as ligands L in the described reaction species. Depending on the rate of the competition between amine and phosphines, a dynamic and complex interplay is expected when using different coordinative bases. | 0 | Theoretical and Fundamental Chemistry |
Full spectral imaging, along with empirical reflectance retrieval and autonomous remote sensing are the components of the new systems for remote sensing and the successor to the Landsat series of satellites of the Landsat program. | 0 | Theoretical and Fundamental Chemistry |
Blood alcohol content (BAC), also called blood alcohol concentration or blood alcohol level, is a measurement of alcohol intoxication used for legal or medical purposes.
BAC is expressed as mass of alcohol per volume of blood. In the US and many international publications, BAC levels are written as a percentage such as 0.08%, meaning that there is 0.08 g of alcohol for every 100 of blood. In different countries, the maximum permitted BAC when driving ranges from the limit of detection (zero tolerance) to 0.08%. BAC levels above 0.40% are potentially fatal. | 1 | Applied and Interdisciplinary Chemistry |
In 1995 the Fraunhofer Institute for Industrial Mathematics started a research project in order to simulate the paper transport in a printing machine. The transport of papers in printing machines can be modelled as two-dimensional fluid-structure interaction problem. The equations describing the dynamics of the paper transport are derived from shell models based on continuum mechanics that are equivalent to rod models for fiber dynamics. In order to simulate nonwoven production processes the Fraunhofer Institute for Industrial Mathematics extended the Cosserat rod models by a stochastic drag model for fibers in turbulent flows. FIDYST demonstrated its proof of concept 2007. At the EDANA Symposium 2007 the industrial company Oerlikon Neumag presented a new pilot plant where FIDYST had successfully been applied to increase the tenacity of the produced nonwoven. In 2012 the software code was ported from C to C++. 2014 the interaction of fibers with machinery parts was introduced in FIDYST. The latest release of FIDYST can simulate staple fibers. | 1 | Applied and Interdisciplinary Chemistry |
Thyroid hormone increases the number of beta-adrenergic receptors available for epinephrine at the latters target cell, thereby increasing epinephrines effect on that cell. Specially in cardiac cell. Without the thyroid hormone, epinephrine would have only a weak effect.
Cortisol is required for the response of vascular and bronchial smooth muscle to catecholamines. Cortisol is also required for the lipolytic effect of catecholamines, ACTH, and growth hormone on fat cells. Cortisol is also required for the calorigenic effects of glucagon and catecholamines.
The effects of a hormone in the body depend on its concentration. Permissive actions of glucocorticoids like cortisol generally occur at low concentrations. Abnormally high amounts of a hormone can result in atypical effects. Glucocorticoids function by attaching to cytoplasmic receptors to either enhance or suppress changes in the transcription of DNA and thus the synthesis of proteins. Glucocorticoids also inhibit the secretion of cytokines via post-translational modification effects. | 1 | Applied and Interdisciplinary Chemistry |
To function, a modern computer needs three different capabilities: It must be able to store information, transmit information between components, and possess a basic system of logic. Prior to March 2013, scientists had successfully demonstrated the ability to store and transmit data using biological components made of proteins and DNA. Simple two-terminal logic gates had been demonstrated, but required multiple layers of inputs and thus were impractical due to scaling difficulties. | 1 | Applied and Interdisciplinary Chemistry |
There are two rotational friction factors for a general spheroid, one for a rotation about the axial semiaxis (denoted ) and other for a rotation about one of the equatorial semiaxes (denoted ).
Perrin showed that
for both prolate and oblate spheroids. For spheres, , as may be seen by taking the limit .
These formulae may be numerically unstable when , since the numerator and denominator both go to zero into the limit. In such cases, it may be better to expand in a series, e.g.,
for oblate spheroids. | 1 | Applied and Interdisciplinary Chemistry |
DNA sequencing is the process of determining the nucleotide order of a given DNA fragment. So far, most DNA sequencing has been performed using the chain termination method developed by Frederick Sanger. This technique uses sequence-specific termination of a DNA synthesis reaction using modified nucleotide substrates. However, new sequencing technologies such as pyrosequencing are gaining an increasing share of the sequencing market. More genome data are now being produced by pyrosequencing than Sanger DNA sequencing. Pyrosequencing has enabled rapid genome sequencing. Bacterial genomes can be sequenced in a single run with several times coverage with this technique. This technique was also used to sequence the genome of James Watson recently.
The sequence of DNA encodes the necessary information for living things to survive and reproduce. Determining the sequence is therefore useful in fundamental research into why and how organisms live, as well as in applied subjects. Because of the key importance DNA has to living things, knowledge of DNA sequences is useful in practically any area of biological research. For example, in medicine it can be used to identify, diagnose, and potentially develop treatments for genetic diseases. Similarly, research into pathogens may lead to treatments for contagious diseases. Biotechnology is a burgeoning discipline, with the potential for many useful products and services.
The Carlson curve is a term coined by The Economist to describe the biotechnological equivalent of Moores law, and is named after author Rob Carlson. Carlson accurately predicted the doubling time of DNA sequencing technologies (measured by cost and performance) would be at least as fast as Moores law. Carlson curves illustrate the rapid (in some cases hyperexponential) decreases in cost, and increases in performance, of a variety of technologies, including DNA sequencing, DNA synthesis, and a range of physical and computational tools used in protein expression and in determining protein structures. | 1 | Applied and Interdisciplinary Chemistry |
The inductive effect can be used to determine the stability of a molecule depending on the charge present on the atom and the groups bonded to the atom. For example, if an atom has a positive charge and is attached to a -I group its charge becomes amplified and the molecule becomes more unstable. Similarly, if an atom has a negative charge and is attached to a +I group its charge becomes amplified and the molecule becomes more unstable. In contrast, if an atom has a negative charge and is attached to a -I group its charge becomes de-amplified and the molecule becomes more stable than if the I-effect was not taken into consideration. Similarly, if an atom has a positive charge and is attached to a +I group its charge becomes de-amplified and the molecule becomes more stable than if the I-effect was not taken into consideration. The explanation for the above is given by the fact that more charge on an atom decreases stability and less charge on an atom increases stability. | 0 | Theoretical and Fundamental Chemistry |
Sulfone is a relatively inert functional group, typically less oxidizing and 4 bel more acidic than sulfoxides. In the Ramberg–Bäcklund reaction and the Julia olefination, sulfones are converted to alkenes by the elimination of sulfur dioxide. However, sulfones are unstable to bases, eliminating to give an alkene.
Sulfones can also undergo desulfonylation. | 0 | Theoretical and Fundamental Chemistry |
Thomas Henry Haines (born August 9, 1933) was an American author, social activist, biochemist and academic. He was a professor of chemistry at City College of New York and of Biochemistry at the Sophie Davis School of Biomedical Education. He was a visiting professor in the Laboratory of Thomas Sakmar at Rockefeller University. He also served on the board of the Graham School, a social services and foster care agency in New York City. His scientific research focused on the structure and function of the living cell membrane. He is the father of Avril Haines, the seventh Director of National Intelligence. | 1 | Applied and Interdisciplinary Chemistry |
Armodafinil is readily absorbed after oral administration. The absolute oral bioavailability was not determined due to the aqueous insolubility of armodafinil, which precluded intravenous administration. Peak plasma concentrations are attained at approximately 2 hours in the fasted state. Food effect on the overall bioavailability of armodafinil is considered minimal; however, time to reach peak concentration may be delayed 2–4 hours in the fed state. Since the delay in T is also associated with elevated plasma concentration later in time, food can potentially affect the onset and time course of pharmacologic action of armodafinil. | 0 | Theoretical and Fundamental Chemistry |
For laboratory use, the N-alkylation reaction is often unselective. A variety of alternative methods have been developed, such as the Delépine reaction, which uses hexamine. The Gabriel synthesis, involving the use of an equivalent to NH, only applies to primary alkyl halides. | 0 | Theoretical and Fundamental Chemistry |
Oxaloacetic acid (also known as oxalacetic acid or OAA) is a crystalline organic compound with the chemical formula HOCC(O)CHCOH. Oxaloacetic acid, in the form of its conjugate base oxaloacetate, is a metabolic intermediate in many processes that occur in animals. It takes part in gluconeogenesis, the urea cycle, the glyoxylate cycle, amino acid synthesis, fatty acid synthesis and the citric acid cycle. | 1 | Applied and Interdisciplinary Chemistry |
An autapse is a chemical or electrical synapse from a neuron onto itself. It can also be described as a synapse formed by the axon of a neuron on its own dendrites, in vivo or in vitro. | 1 | Applied and Interdisciplinary Chemistry |
The field of surface chemistry started with heterogeneous catalysis pioneered by Paul Sabatier on hydrogenation and Fritz Haber on the Haber process. Irving Langmuir was also one of the founders of this field, and the scientific journal on surface science, Langmuir, bears his name. The Langmuir adsorption equation is used to model monolayer adsorption where all surface adsorption sites have the same affinity for the adsorbing species and do not interact with each other. Gerhard Ertl in 1974 described for the first time the adsorption of hydrogen on a palladium surface using a novel technique called LEED. Similar studies with platinum, nickel, and iron followed. Most recent developments in surface sciences include the 2007 Nobel prize of Chemistry winner Gerhard Ertl's advancements in surface chemistry, specifically
his investigation of the interaction between carbon monoxide molecules and platinum surfaces. | 0 | Theoretical and Fundamental Chemistry |
In presence of molecular orientation anisotropy in the sample, CARS images often display artefacts due to polarization-dependent selection rules that affects the measured intensity with respect of the alignment between the polarization plane of the incident light and the main orientation plane of the molecular bonds.
This is due because the four-wave mixing process is more efficient when the polarization plane of the incident light is aligned with the main orientation plane of the molecular vibrations. | 0 | Theoretical and Fundamental Chemistry |
Pharmacophore<br />
There are three functional groups that are the most important parts for the bioactivity of ARBs, see figure 1 for details.<br />
The first one is the imidazole ring that binds to amino acids in helix 7 (Asn). The second group is the biphenyl-methyl group that binds to amino acids in both helices 6 and 7 (Phe, Phe, Trp and His). The third one is the tetrazole group that interacts with amino acids in helices 4 and 5 (Arg and Lys). <br />
The tetrazole group has been successfully replaced by a carboxylic acid group as is the case with telmisartan.
Structure-activity relationship (SAR)<br />
Most of the ARBs have the same pharmacophore so the difference in their biochemical and physiological effects is mostly due to different substituents. Activity of a drug is dependent of its affinity for the substrate site and the length of time it binds to the site.
Lipophilic substituents like the linear alkyl group at the 2-position on the imidazole ring together with the biphenyl-methyl group, associate with hydrophobic pockets of the receptor. An acidic group like tetrazole, COH or NHSOCF at the 1-position of the biphenyl-methyl group will bind to a basic position in the receptor and are required for potent antagonistic activity. <br />
In valsartan, the imidazole ring of losartan has been replaced with an acylated amino acid.<br />
Several substituents have been tried at the 4- and 5- positions on the imidazole ring. The chloro and hydroxymethyl groups connected to these positions in losartan are probably not of much importance in receptor binding since the other ARBs do not possess these functional groups and have comparable or better binding affinities than losartan. Irbesartan has a carbonyl group at the 5-position, functioning as a hydrogen bond acceptor in place of the hydroxymethyl group of losartan, resulting in a longer binding to the receptor. <br />
The structure of eprosartan is the one that differs most from the other ARBs, the usual biphenyl-methyl group has been replaced by a carboxy benzyl group that mimics more closely the phenolic moiety of Tyr group of Ang II. This change results in a stronger binding to the receptor but the biochemical and physiological effects are not significantly improved. <br />
Telmisartan has a carboxylic acid at the 2-position of the biphenyl-methyl group and is more potent than the tetrazole analogue. <br />
It has been reported that imidazoles that have hydroxymethyl and carboxy groups at the 4- and 5 position, possessed potent antagonistic activity, caused by the hydrogen bonding and hydrophilicity of the hydroxymethyl group.<br />
It has also been reported that an hydroxy group in the 4-position on the imidazole ring, plays an important role in the binding affinity and compensates for the disadvantage of lipophilicity of the bulky alkyl group.<br />
These results show that a medium-sized hydroxy alkyl group, such as CHMeOH and CMeOH, is favorable for the substituent of the 4-position on the imidazole ring. Furthermore, the ionizable group is favorable for the binding affinity.
Candesartan and olmesartan have the highest affinity for the AT receptors, followed by irbesartan and eprosartan. Valsartan, telmisartan and EXP 3174 have similar affinities that are about ten-fold less than that of candesartan. Losartan has the least affinity. ARBs' affinity for the AT receptor is generally much lower (or around 10,000 times less) than for the AT subtype. Therefore, they allow unhindered stimulation of the AT receptor. | 1 | Applied and Interdisciplinary Chemistry |
Younes and Loveland define fission as, "...a collective motion of the protons and neutrons that make up the nucleus, and as such it is distinguishable from other phenomena that break up the nucleus. Nuclear fission is an extreme example of large-amplitude collective motion that results in the division of a parent nucleus into two or more fragment nuclei. The fission process can occur spontaneously, or it can be induced by an incident particle." The energy from a fission reaction is produced by its fission products, though a large majority of it, about 85 percent, is found in fragment kinetic energy, while about 6 percent each comes from initial neutrons and gamma rays and those emitted after beta decay, plus about 3 percent from neutrinos as the product of such decay. | 0 | Theoretical and Fundamental Chemistry |
A deep property of capillary surfaces is the surface energy that is imparted by surface tension:
where is the area of the surface being considered, and the total energy is the summation of all energies. Note that every interface imparts energy. For example, if there are two different fluids (say liquid and gas) inside a solid container with gravity and other energy potentials absent, the energy of the system is
where the subscripts , , and respectively indicate the liquid–gas, solid–gas, and solid–liquid interfaces. Note that inclusion of gravity would require consideration of the volume enclosed by the capillary surface and the solid walls.
Typically the surface tension values between the solid–gas and solid–liquid interfaces are not known. This does not pose a problem; since only changes in energy are of primary interest. If the net solid area is a constant, and the contact angle is known, it may be shown that (again, for two different fluids in a solid container)
so that
where is the contact angle and the capital delta indicates the change from one configuration to another. To obtain this result, it's necessary to sum (distributed) forces at the contact line (where solid, gas, and liquid meet) in a direction tangent to the solid interface and perpendicular to the contact line:
where the sum is zero because of the static state. When solutions to the Young-Laplace equation aren't unique, the most physically favorable solution is the one of minimum energy, though experiments (especially low gravity) show that metastable surfaces can be surprisingly persistent, and that the most stable configuration can become metastable through mechanical jarring without too much difficulty. On the other hand, a metastable surface can sometimes spontaneously achieve lower energy without any input (seemingly at least) given enough time. | 1 | Applied and Interdisciplinary Chemistry |
Shrimp trawlers first reported a dead zone in the Gulf of Mexico in 1950, but it was not until 1970 when the size of the hypoxic zone had increased that scientists began to investigate.
After 1950, the conversion of forests and wetlands for agricultural and urban developments accelerated. "Missouri River Basin has had hundreds of thousands of acres of forests and wetlands (66,000,000 acres) replaced with agriculture activity [. . .] In the Lower Mississippi one-third of the valley's forests were converted to agriculture between 1950 and 1976."
In July 2007, a dead zone was discovered off the coast of Texas where the Brazos River empties into the Gulf. | 0 | Theoretical and Fundamental Chemistry |
Sulfato complexes are commonly produced by reaction of metal sulfates with other ligands.
In some cases, sulfato complexes are produced from sulfur dioxide:
: (PPh = triphenylphosphine)
Sulfato complexes also arise by air-oxidation of metal sulfides. | 0 | Theoretical and Fundamental Chemistry |
A proof-of-concept in-vivo direct DNA data recording system was demonstrated through incorporation of optogenetically regulated recombinases as part of an engineered "molecular recorder" allows for direct encoding of light-based stimuli into engineered E.coli cells. This approach can also be parallelized to store and write text or data in 8-bit form through the use of physically separated individual cell cultures in cell-culture plates.
This approach leverages the editing of a "recorder plasmid" by the light-regulated recombinases, allowing for identification of cell populations exposed to different stimuli. This approach allows for the physical stimulus to be directly encoded into the "recorder plasmid" through recombinase action. Unlike other approaches, this approach does not require manual design, insertion and cloning of artificial sequences to record the data into the genetic code. In this recording process, each individual cell population in each cell-culture plate culture well can be treated as a digital "bit", functioning as a biological transistor capable of recording a single bit of data. | 1 | Applied and Interdisciplinary Chemistry |
October 23, denoted 10/23 in the US, is recognized by some as Mole Day. It is an informal holiday in honor of the unit among chemists. The date is derived from the Avogadro number, which is approximately . It starts at 6:02 a.m. and ends at 6:02 p.m. Alternatively, some chemists celebrate June 2 (), June 22 (), or 6 February (), a reference to the 6.02 or 6.022 part of the constant. | 0 | Theoretical and Fundamental Chemistry |
The duration of action of a drug is the length of time that particular drug is effective. Duration of action is a function of several parameters including plasma half-life, the time to equilibrate between plasma and target compartments, and the off rate of the drug from its biological target. | 1 | Applied and Interdisciplinary Chemistry |
Phillips was born 3 December 1939 in Kendal, lived in South Shields and attended the Grammar School. He studied at the University of Birmingham attaining a BSc and PhD. | 0 | Theoretical and Fundamental Chemistry |
Described below are schemes for synthesizing thalidomide, lenalidomide, and pomalidomide, as reported from prominent primary literature. Note that these synthesis schemes do not necessarily reflect the organic synthesis strategies used to synthesize these single chemical entities. | 1 | Applied and Interdisciplinary Chemistry |
* SS Kronprinz Wilhelm, September 18, 1901 – The most modern German ocean liner of its time (winner of the Blue Riband) was damaged on its maiden voyage from Cherbourg to New York by a huge wave. The wave struck the ship head-on.
* RMS Lusitania (1910) – On the night of 10 January 1910, a wave struck the ship over the bow, damaging the forecastle deck and smashing the bridge windows.
* Voyage of the James Caird (1916) – Sir Ernest Shackleton encountered a wave he termed "gigantic" while piloting a lifeboat from Elephant Island to South Georgia.
* USS Memphis, August 29, 1916 – An armored cruiser, formerly known as the USS Tennessee, wrecked while stationed in the harbor of Santo Domingo, with 43 men killed or lost, by a succession of three waves, the largest estimated at 70 feet.
* RMS Homeric (1924) – Hit by a wave while sailing through a hurricane off the East Coast of the United States, injuring seven people, smashing numerous windows and portholes, carrying away one of the lifeboats, and snapping chairs and other fittings from their fastenings.
* USS Ramapo (1933) – Triangulated at .
* (1942) – Broadsided by a wave and listed briefly about 52° before slowly righting.
* SS Michelangelo (1966) – Hole torn in superstructure, heavy glass smashed above the waterline, and three deaths
* (1975) – Lost on Lake Superior, a Coast Guard report blamed water entry to the hatches, which gradually filled the hold, or errors in navigation or charting causing damage from running onto shoals. However, another nearby ship, the , was hit at a similar time by two rogue waves and possibly a third, and this appeared to coincide with the sinking around 10 minutes later.
* (1978) – Lost at sea, leaving only scattered wreckage and signs of sudden damage including extreme forces above the water line. Although more than one wave was probably involved, this remains the most likely sinking due to a freak wave.
* Esso Languedoc (1980) – A wave washed across the deck from the stern of the French supertanker near Durban, South Africa, and was photographed by the first mate, Philippe Lijour.
* Fastnet Lighthouse – Struck by a wave in 1985
* Draupner wave (North Sea, 1995) – The first rogue wave confirmed with scientific evidence, it had a maximum height of .
* Queen Elizabeth 2 (1995) – Encountered a wave in the North Atlantic, during Hurricane Luis. The master said it "came out of the darkness" and "looked like the White Cliffs of Dover." Newspaper reports at the time described the cruise liner as attempting to "surf" the near-vertical wave in order not to be sunk. | 1 | Applied and Interdisciplinary Chemistry |
It was introduced by Lyklema in “Fundamentals of Interface and Colloid Science”. A recent IUPAC Technical Report used this term explicitly and detailed several means of measurement in physical systems.
The Dukhin number is a ratio of the surface conductivity multiplied by particle size a:
There is another expression of this number that is valid when the surface conductivity is associated only with ions motion above the slipping plane in the double layer. In this case, the value of the surface conductivity depends on ζ-potential, which leads to the following expression for the Dukhin number for symmetrical electrolyte with equal ions diffusion coefficient:
where the parameter m characterizes the contribution of electro-osmosis into motion of ions within the double layer
* F is Faraday constant
* T is absolute temperature
* R is gas constant
* C is ions concentration in bulk
* z is ion valency
* ζ is electrokinetic potential
* ε is vacuum dielectric permittivity
* ε is fluid dielectric permittivity
* η is dynamic viscosity
* D is diffusion coefficient | 0 | Theoretical and Fundamental Chemistry |
A spectral line corresponds to an electron transition in an atom, molecule or ion, which is associated with a specific amount of energy, E. When this energy is measured by means of some spectroscopic technique, the line is not infinitely sharp, but has a particular shape. Numerous factors can contribute to the broadening of spectral lines. Broadening can only be mitigated by the use of specialized techniques, such as Lamb dip spectroscopy. The principal sources of broadening are:
* Lifetime broadening. According to the uncertainty principle the uncertainty in energy, ΔE and the lifetime, Δt, of the excited state are related by
:This determines the minimum possible line width. As the excited state decays exponentially in time this effect produces a line with Lorentzian shape in terms of frequency (or wavenumber).
* Doppler broadening. This is caused by the fact that the velocity of atoms or molecules relative to the observer follows a Maxwell distribution, so the effect is dependent on temperature. If this were the only effect the line shape would be Gaussian.
* Pressure broadening (Collision broadening). Collisions between atoms or molecules reduce the lifetime of the upper state, Δt, increasing the uncertainty ΔE. This effect depends on both the density (that is, pressure for a gas) and the temperature, which affects the rate of collisions. The broadening effect is described by a Lorentzian profile in most cases.
* Proximity broadening. The presence of other molecules close to the molecule involved affects both line width and line position. It is the dominant process for liquids and solids. An extreme example of this effect is the influence of hydrogen bonding on the spectra of protic liquids.
Observed spectral line shape and line width are also affected by instrumental factors. The observed line shape is a convolution of the intrinsic line shape with the instrument transfer function.
Each of these mechanisms, and others, can act in isolation or in combination. If each effect is independent of the other, the observed line profile is a convolution of the line profiles of each mechanism. Thus, a combination of Doppler and pressure broadening effects yields a Voigt profile. | 0 | Theoretical and Fundamental Chemistry |
Radioactivity or radionuclide fixatives are specialized polymer coatings used to “fix” radioactive isotopes or radioactive material to surfaces. These fixatives, also known as permanent coatings in the radioactive contamination control field, have been used for many decades in facilities processing radioactive material to control radioactive contamination. There has been increased interest in these fixatives or coatings recently due to the growing concern of contamination from a radioactivity dispersal device (RDD also known as a dirty bomb) and because radioactivity fixatives in use today lose the ability to contain the radioactivity to the surface during a fire.
Radioactivity fixatives reduce or eliminate the movement of radionuclides from surfaces thereby lowering the health risk of inhalation or other exposure to radioactive isotopes. There are many articles on the use of radioactive fixatives with a review article from 1983 often used as a reference. A more recent review article looks at the use of these radioactive fixatives for use after the detonation of a RDD. Current research is investigating new coatings that are effective at containing radioactive material to the surface during and after fires. | 0 | Theoretical and Fundamental Chemistry |
Veterinary schools, veterinary hospitals, and bovine farming operations in North America often keep a healthy fistulated cow as a microbiota donor. Large animal veterinarians will pull the contents by hand from the healthy cows rumen system to help repopulate the fauna in a sick cows rumen. This process is called transfaunation, or a microbiota transplant.
In Europe, the fistulation of cows to provide rumen contents for transfaunation is considered unethical, and is not practised. Instead, rumen liquor is aspirated through a rumen-fluid collector, consisting of a Frick gag and a flexible hose with a perforated metal tip which serves as a filter. The hose and tip is passed through the gag and down the oesophagus to the rumen. It is normally possible to aspirate five litres of rumen liquor using this device.
Rumen contents from a fistulated cow can also help sheep and goats, which have similar digestive systems.
A 2014 review of rumen transfaunation research indicated that the procedure has been demonstrated to help correct indigestion resulting from illness, surgical correction of displaced abomasum, and ingestion of toxic plants. | 1 | Applied and Interdisciplinary Chemistry |
Gamma-glutamyltransferase (also γ-glutamyltransferase, GGT, gamma-GT, gamma-glutamyl transpeptidase; ) is a transferase (a type of enzyme) that catalyzes the transfer of gamma-glutamyl functional groups from molecules such as glutathione to an acceptor that may be an amino acid, a peptide or water (forming glutamate). GGT plays a key role in the gamma-glutamyl cycle, a pathway for the synthesis and degradation of glutathione as well as drug and xenobiotic detoxification. Other lines of evidence indicate that GGT can also exert a pro-oxidant role, with regulatory effects at various levels in cellular signal transduction and cellular pathophysiology. This transferase is found in many tissues, the most notable one being the liver, and has significance in medicine as a diagnostic marker. | 1 | Applied and Interdisciplinary Chemistry |
Inspired by enzymes with deep active site pocket, List and coworkers designed and constructed a set of confined Bronsted acids with an extremely sterically demanding chiral pocket based on a C-symmetric bis(binapthyl) imidodiphosphoric acid. Within the chiral microenvironment, the catalysts has a geometrically fixed bifunctional active site that activates both an electrophilic part and a nucleophilic part of a substrate. This catalyst enables stereoselective spiroacetal formation with high enantiomeric excess for a variety of substrates. | 0 | Theoretical and Fundamental Chemistry |
Consider a slender body with pointed edges at the front and back. The supersonic flow past this body will be nearly parallel to the -axis everywhere since the shock waves formed (one at the leading edege and one at the trailign edge) will be weak; as a consequence, the flow will be potential everywhere, which can be described using the velocity potential , where is the incoming uniform velocity and characteising the small deviation from the uniform flow. In the linearized theory, satisfies
where , is the sound speed in the incoming flow and is the Mach number of the incoming flow. This is just the two-dimensional wave equation and is a disturbance propagated with an apparent time and with an apparent velocity .
Let the origin be located at the leading end of the pointed body. Further, let be the cross-sectional area (perpendicular to the -axis) and be the length of the slender body, so that for and for . Of course, in supersonic flows, disturbances (i.e., ) can be propagated only into the region behind the Mach cone. The weak Mach cone for the leading-edge is given by , whereas the weak Mach cone for the trailing edge is given by , where is the squared radial distance from the -axis.
The disturbance far away from the body is just like a cylindrical wave propagation. In front of the cone , the solution is simply given by . Between the cones and , the solution is given by
whereas the behind the cone , the solution is given by
The solution described above is exact for all when the slender body is a solid of revolution. If this is not the case, the solution is valid at large distances will have correction associated with the non-linear distortion of the shock profile, whose strength is proportional to and a fcator depending on the shape function .
The drag force is just the -component of the momentum per unti time. To calculate this, consider a cylindircal surface with a large radius and with an axis along the -axis. The momentum flux density crossing through this surface is simply given by . Integrating over the cylindrical surface gives the drag force. Due to symmetry, the first term in upon integration gives zero since the net mass flux is zero on the cylindrical surface considered. The second term gives the non-zero contribution,
At large distances, the values (the wave region) are the most important in the solution for ; this is because, as mentioned earlier, is a like disturbance propating with a speed with an apparent time . This means that we can approximate the expression in the denominator as Then we can write, for example,
From this expression, we can calculate , which is also equal to since we are in the wave region. The factor appearing in front of the integral need not to be differentiated since this gives rise to the small correction proportional to . Effecting the differentiation and returning to the original variables, we find
Substituting this in the drag force formula gives us
This can be simplified by carrying out the integration over . When the integration order is changed, the limit for ranges from the to . Upon integration, we have
The integral containing the term is zero because (of course, in addition to ).
The final formula for the wave drag force may be written as
or
The drag coefficient is then given by
Since that follows from the formula derived above, , indicating that the drag coefficient is proportional to the square of the cross-sectional area and inversely proportional to the fourth power of the body length.
The shape with smallest wave drag for agiven volume and length can be obtained from the wave drag force formula. This shape is known as the Sears–Haack body. | 1 | Applied and Interdisciplinary Chemistry |
Photosensitive glass, also known as photostructurable glass (PSG) or photomachinable glass, is a glass in the lithium-silicate family of glasses onto which images can be etched using short wave radiations such as ultraviolet light. Photosensitive glass was first discovered by S. Donald Stookey in 1937. | 0 | Theoretical and Fundamental Chemistry |
Lord Kelvin devised the thermodynamic scale based on the efficiency of heat engines as shown below:
The efficiency of an engine is the work divided by the heat introduced to the system or
where w is the work done per cycle. Thus, the efficiency depends only on q/q.
Because of Carnot theorem, any reversible heat engine operating between temperatures T and T must have the same efficiency, meaning, the efficiency is the function of the temperatures only:
In addition, a reversible heat engine operating between temperatures T and T must have the same efficiency as one consisting of two cycles, one between T and another (intermediate) temperature T, and the second between T and T. This can only be the case if
Specializing to the case that is a fixed reference temperature: the temperature of the triple point of water. Then for any T and T,
Therefore, if thermodynamic temperature is defined by
then the function f, viewed as a function of thermodynamic temperature, is
and the reference temperature T has the value 273.16. (Of course any reference temperature and any positive numerical value could be used—the choice here corresponds to the Kelvin scale.) | 0 | Theoretical and Fundamental Chemistry |
Another agent involved in autocrine cancer signaling is vascular endothelial growth factor (VEGF). VEGF, produced by carcinoma cells, acts through paracrine signaling on endothelial cells and through autocrine signaling on carcinoma cells. Evidence shows that autocrine VEGF is involved in two major aspects of invasive carcinoma: survival and migration. Moreover, it was shown that tumor progression selects for cells that are VEGF-dependent, challenging the belief that VEGF's role in cancer is limited to angiogenesis. Instead, this research suggests that VEGF receptor-targeted therapeutics may impair cancer survival and invasion as well as angiogenesis. | 1 | Applied and Interdisciplinary Chemistry |
Several factors effect the assay outcome and a recent review summarizes the various parameters that needs to be monitored to keep an assay up and running. | 1 | Applied and Interdisciplinary Chemistry |
In genetics, a promoter is a sequence of DNA to which proteins bind to initiate transcription of a single RNA transcript from the DNA downstream of the promoter. The RNA transcript may encode a protein (mRNA), or can have a function in and of itself, such as tRNA or rRNA. Promoters are located near the transcription start sites of genes, upstream on the DNA (towards the 5' region of the sense strand).
Promoters can be about 100–1000 base pairs long, the sequence of which is highly dependent on the gene and product of transcription, type or class of RNA polymerase recruited to the site, and species of organism.
Promoters control gene expression in bacteria and eukaryotes. RNA polymerase must attach to DNA near a gene for transcription to occur. Promoter DNA sequences provide an enzyme binding site. The -10 sequence is TATAAT. -35 sequences are conserved on average, but not in most promoters.
Artificial promoters with conserved -10 and -35 elements transcribe more slowly. All DNAs have "Closely spaced promoters". Divergent, tandem, and convergent orientations are possible. Two closely spaced promoters will likely interfere. Regulatory elements can be several kilobases away from the transcriptional start site in gene promoters (enhancers).
In eukaryotes, the transcriptional complex can bend DNA, allowing regulatory sequences to be placed far from the transcription site. The distal promoter is upstream of the gene and may contain additional regulatory elements with a weaker influence. RNA polymerase II (RNAP II) bound to the transcription start site promoter can start mRNA synthesis. It also typically contains CpG islands, a TATA box, and TFIIB recognition elements.
Hypermethylation downregulates both genes, while demethylation upregulates them. Non-coding RNAs are linked to mRNA promoter regions. Subgenomic promoters range from 24 to 100 nucleotides (Beet necrotic yellow vein virus). Gene expression depends on promoter binding. Unwanted gene changes can increase a cell's cancer risk.
MicroRNA promoters often contain CpG islands. DNA methylation forms 5-methylcytosines at the 5' pyrimidine ring of CpG cytosine residues. Some cancer genes are silenced by mutation, but most are silenced by DNA methylation. Others are regulated promoters. Selection may favor less energetic transcriptional binding.
Variations in promoters or transcription factors cause some diseases. Misunderstandings can result from using a canonical sequence to describe a promoter. | 1 | Applied and Interdisciplinary Chemistry |
As mentioned previously, Pseudomonas aeruginosa produces a host of virulence factors in concert, under the control of the quorum sensing system. Many studies show that inhibiting quorum sensing down-regulates the pathogenicity of Pseudomonas aeruginosa. However, it has been shown that rhamnolipids specifically are a key virulence determinant in Pseudomonas aeruginosa. A variety of virulence factors were analysed in Pseudomonas aeruginosa strains isolated from pneumonia patients. Rhamnolipids were found to be the only virulence factor that was associated with the deterioration of the patients to ventilator-associated pneumonia. Several other reports also support the role of rhamnolipids in lung infections. The effect of rhamnolipids in Pseudomonas aeruginosa virulence has been further noted in corneal infections (Alarcon et al., 2009; Zhu et al., 2004). It has been shown that rhamnolipids are able to integrate into the epithelial cell membrane and disrupt tight-junctions. This study used reconstituted epithelial membranes and purified rhamnolipids to demonstrate this mechanism. In addition to inhibition and killing of epithelial cells, rhamnolipids are able to kill polymorphonuclear (PMN) leukocytes and macrophages and inhibit phagocytosis. In summary, rhamnolipids have been shown unequivocally to be a potent virulence factor in the human host, however, they are also produced outside of the host, for example in a soil environment.
Rhamnolipids contribute to the establishment and maintenance of infection in cystic fibrosis patients in a number of ways, they disrupt the bronchial epithelium by disrupting the cell membranes, which promotes paracellular invasion of Pseudomonas aeruginosa and causes ciliostasis, further preventing the clearing of mucus. They also solubilise lung surfactant, allowing phospholipase C access to cell membranes and are necessary for correct biofilm formation. | 0 | Theoretical and Fundamental Chemistry |
Polymer-bonded explosives, also called PBX or plastic-bonded explosives, are explosive materials in which explosive powder is bound together in a matrix using small quantities (typically 5–10% by weight) of a synthetic polymer. PBXs are normally used for explosive materials that are not easily melted into a casting, or are otherwise difficult to form.
PBX was first developed in 1952 at Los Alamos National Laboratory, as RDX embedded in polystyrene with dioctyl phthalate plasticizer. HMX compositions with teflon-based binders were developed in 1960s and 1970s for gun shells and for Apollo Lunar Surface Experiments Package (ALSEP) seismic experiments, although the latter experiments are usually cited as using hexanitrostilbene (HNS). | 0 | Theoretical and Fundamental Chemistry |
Zwolinski and Wilhoit defined, in 1972, "gross" and "net" values for heats of combustion. In the gross definition the products are the most stable compounds, e.g. (l), (l), (s) and (l). In the net definition the products are the gases produced when the compound is burned in an open flame, e.g. (g), (g), (g) and (g). In both definitions the products for C, F, Cl and N are (g), (g), (g) and (g), respectively.
The heating value of a fuel can be calculated with the results of ultimate analysis of fuel. From analysis, percentages of the combustibles in the fuel (carbon, hydrogen, sulfur) are known. Since the heat of combustion of these elements is known, the heating value can be calculated using Dulong's Formula:
HHV [kJ/g]= 33.87m + 122.3(m - m ÷ 8) + 9.4m
where m, m, m, m, and m are the contents of carbon, hydrogen, oxygen, nitrogen, and sulfur on any (wet, dry or ash free) basis, respectively. | 0 | Theoretical and Fundamental Chemistry |
PECO has shown promise for water treatment of both stormwater and wastewater. Currently, water treatment methods like the use of biofiltration technologies are widely used. These technologies are effective at filtering out pollutants like suspended solids, nutrients, and heavy metals, but struggle to remove herbicides. Herbicides like diuron and atrazine are commonly used, and often end up in stormwater, posing potential health risks if they are not treated before reuse.
PECO is a useful solution to treating stormwater because of its strong oxidation capacity. Investigating different mechanisms for herbicide degradation in stormwater, like PECO, photocatalytic oxidation (PCO), and electro-catalytic oxidation (ECO), researchers determined that PECO was the best option, demonstrating complete mineralization of diuron in one hour. Further research into this use for PECO is needed, as it was only able to degrade 35% of atrazine in that time, however it is a promising solution moving forward. | 0 | Theoretical and Fundamental Chemistry |
Metallacycles often arise by cyclization of arene-containing donor ligands, e.g. aryl phosphines and amines. An early example is the cyclization of IrCl(PPh) to give the corresponding Ir(III) hydride containing a four-membered IrPCC ring. Palladium(II) and platinum(II) have long been known to ortho-metalate aromatic ligands such as azobenzene, benzylamines, and 2-phenylpyridines. These reactions are strongly influenced by substituent effects, including the Thorpe-Ingold effect. Ligands that lack aryl substituents will sometimes cyclometalate via activation of methyl groups, an early example being the internal oxidative addition of methylphosphine ligands. Metallacycle formation interferes with intermolecular C-H activation processes. For this reason, specialized "pincer ligands" ligands have been developed that resist ortho-metalation. | 0 | Theoretical and Fundamental Chemistry |
RPA is one of several isothermal nucleic acid amplification techniques to be developed as a molecular diagnostic technique, frequently with the objective of simplifying the laboratory instrumentation required relative to PCR. A partial list of other isothermal amplification techniques include LAMP, NASBA, helicase-dependent amplification (HDA), and nicking enzyme amplification reaction (NEAR). The techniques differ in the specifics of primer design and reaction mechanism, and in some cases (like RPA) make use of cocktails of two or more enzymes. Like RPA, many of these techniques offer rapid amplification times with the potential for simplified instrumentation, and reported resistance to substances in unpurified samples that are known to inhibit PCR. With respect to amplification time, modern thermocyclers with rapid temperature ramps can reduce PCR amplification times to less than 30 minutes, particularly for short amplicons using dual-temperature cycling rather than the conventional three-temperature protocols. In addition, the demands of sample prep (including lysis and extraction of DNA or RNA, if necessary) should be considered as part of the overall time and complexity inherent to the technique. These requirements vary according to the technique as well as to the specific target and sample type.
Compared to PCR, the guidelines for primer and probe design for RPA are less established, and may take a certain degree of trial and error, although recent results indicate that standard PCR primers can work as well. The general principle of a discrete amplicon bounded by a forward and reverse primer with an (optional) internal fluorogenic probe is similar to PCR. PCR primers may be used directly in RPA, but their short length means that recombination rates are low and RPA will not be especially sensitive or fast. Typically 30–38 base primers are needed for efficient recombinase filament formation and RPA performance. This is in contrast to some other techniques such as LAMP which use a larger number of primers subject to additional design constraints. Although the original 2006 report of RPA describes a functional set of reaction components, the current (proprietary) formulation of the TwistAmp kit is "substantially different" and is available only from the TwistDx supplier. This is in comparison to reaction mixtures for PCR which are available from many suppliers, or LAMP or NASBA for which the composition of the reaction mixture is freely published, allowing researchers to create their own customized "kits" from inexpensive ingredients.
Published scientific literature generally lacks detailed comparison of the performance of isothermal amplification techniques such as RPA, HDA, and LAMP relative to each other, often rather comparing a single isothermal technique to a "gold standard" PCR assay. This makes it difficult to judge the merits of these techniques independently from the claims of the manufacturers, inventors, or proponents. Furthermore, performance characteristics of any amplification technique are difficult to decouple from primer design: a "good" primer set for one target for RPA may give faster amplification or more sensitive detection than a "poor" LAMP primer set for the same target, but the converse may be true for different primer sets for a different target. An exception is a recent study comparing RT-qPCR, RT-LAMP, and RPA for detection of Schmallenberg virus and bovine viral diarrhea virus, which effectively makes the point that each amplification technique has strengths and weaknesses, which may vary by the target, and that the properties of the available amplification techniques need to be evaluated in combination with the requirements for each application. As with PCR and any other amplification technique, there is obviously a publication bias, with poorly performing primer sets rarely deemed worthy of reporting. | 1 | Applied and Interdisciplinary Chemistry |
From the mathematical point of view the Lippmann–Schwinger equation in coordinate representation is an integral equation of Fredholm type. It can be solved by discretization. Since it is equivalent to the differential time-independent Schrödinger equation with appropriate boundary conditions, it can also be solved by numerical methods for differential equations. In the case of the spherically symmetric potential it is usually solved by partial wave analysis. For high energies and/or weak potential it can also be solved perturbatively by means of Born series. The method convenient also in the case of many-body physics, like in description of atomic, nuclear or molecular collisions is the method of R-matrix of Wigner and Eisenbud. Another class of methods is based on separable expansion of the potential or Green's operator like the method of continued fractions of Horáček and Sasakawa. Very important class of methods is based on variational principles, for example the Schwinger-Lanczos method combining the variational principle of Schwinger with Lanczos algorithm. | 0 | Theoretical and Fundamental Chemistry |
Earlier serological typing approaches had been established for differentiating bacterial isolates, but immunological typing has drawbacks such as reliance on few antigenic loci and unpredictable reactivities of antibodies with different antigenic variants. Several molecular typing schemes have been proposed to determine the relatedness of pathogens such as pulsed-field gel electrophoresis (PFGE), ribotyping, and PCR-based fingerprinting. But these DNA banding-based subtyping methods do not provide meaningful evolutionary analyses. Despite PFGE being considered by many researchers as the “gold standard”, many strains are not typable by this technique due to the degradation of the DNA during the process (gel smears).
The approach of MLST is distinct from Multi locus enzyme electrophoresis (MLEE), which is based on different electrophoretic mobilities (EM) of multiple core metabolic enzymes. The alleles at each locus define the EM of their products, as different amino acid sequences between enzymes result in different mobilities and distinct bands when run on a gel. The relatedness of isolates can then be visualized with a dendrogram generated from the matrix of pairwise differences between the electrophoretic types. This method has a lower resolution than MLST for several reasons, all arising from the fact that enzymatic phenotype diversity is merely a proxy for DNA sequence diversity. First, enzymes may have different amino acid sequences without having sufficiently different EM to give distinct bands. Second, "silent mutations" may alter the DNA sequence of a gene without altering the encoded amino acids. Thirdly, the phenotype of the enzyme can easily be altered in response to environmental conditions and badly affect the reproducibility of MLEE results - common modifications of enzymes are phosphorylation, cofactor binding and cleavage of transport sequences. This also limits comparability of MLEE data obtained by different laboratories, whereas MLST provides portable and comparable DNA sequence data and has great potential for automation and standardization.
MLST should not be confused with DNA barcoding. The latter is a taxonomic method that uses short genetic markers to recognize particular species of eukaryotes. It is based on the fact that mitochondrial DNA (mtDNA) or some parts of the ribosomal DNA cistron have relatively fast mutation rates, which give significant variation in sequences between species. mtDNA methods are only possible in eukaryotes (as prokaryotes lack mitochondria), whereas MLST, although initially developed for prokaryotes, is now finding application in eukaryotes and in principle could be applied to any kingdom. | 1 | Applied and Interdisciplinary Chemistry |
Most elements have more than one possible oxidation state. For example, carbon has nine possible integer oxidation states from −4 to +4: | 0 | Theoretical and Fundamental Chemistry |
Hydrocarbons, primarily paraffins (CH) and lipids but also sugar alcohols.
* Advantages
** Freeze without much supercooling
** Ability to melt congruently
** Self nucleating properties
** Compatibility with conventional material of construction
** No segregation
** Chemically stable
** Safe and non-reactive
* Disadvantages
** Low thermal conductivity in their solid state. High heat transfer rates are required during the freezing cycle. Nano composites were found to yield an effective thermal conductivity increase up to 216%.
** Volumetric latent heat storage capacity can be low
** Flammable. This can be partially alleviated by specialised containment. | 0 | Theoretical and Fundamental Chemistry |
Siwy joined the faculty at the University of California, Irvine in 2005. In 2012 she was made Professor of Chemical Physics. She studies synthetic nanopores, which she looks to use as templates for biomimetic channels as well as ionic diodes and transistors. | 0 | Theoretical and Fundamental Chemistry |
Peters served as the chemistry departments graduate student advisor from 1969 to 1971 where he recruited the departments largest incoming class. His research has focused on the mechanistic and synthetic properties of the oxidation and reduction of halogenated organic compounds and electrocatalysis in organic synthesis. Peters was still actively teaching up to the time he suffered a fall during spring break 2020 and was taken to a hospital. | 0 | Theoretical and Fundamental Chemistry |
The study by Nesmeyanov of the products of the addition of mercuric chloride to ethylene, acetylene and their derivatives led to the concept of the “dual reactivity” of a substance and the “transfer of the reaction center” along the chain π, π-, σ, π-, σ, σ- and p,π-conjugations in a molecule. Further research showed that these phenomena are fundamentally different from tautomerism. With the participation of his colleague A.E. Borisov, Nesmeyanov formulated the rule according to which electrophilic and homolytic substitution at the olefin carbon atom occurs with the preservation of the geometric configuration (Nesmeyanov – Borisov rule). Thanks to his research, which showed the enolate structure of ketone derivatives with alkali metals and magnesium, that is, the existence of O-derivatives of ketones, Nesmeyanov refuted Knorr 's concept of "pseudomerism ". | 0 | Theoretical and Fundamental Chemistry |
Śabda (शब्द) means relying on word, testimony of past or present reliable experts. Hiriyanna explains Sabda-pramana as a concept which means testimony of a reliable and trustworthy person (āptavākya). The schools of Hinduism which consider it epistemically valid suggest that a human being needs to know numerous facts, and with the limited time and energy available, he can learn only a fraction of those facts and truths directly. He must rely on others, his parent, family, friends, teachers, ancestors and kindred members of society to rapidly acquire and share knowledge and thereby enrich each others lives. This means of gaining proper knowledge is either spoken or written, but through Sabda (words). The reliability of the source is important, and legitimate knowledge can only come from the Sabda of reliable sources. The disagreement between the schools of Hinduism has been on how to establish reliability. Some schools, such as Carvaka, state that this is never possible, and therefore Sabda is not a proper pramana'. Other schools debate means to establish reliability.
Testimony can be of two types, Vaidika (Vedic), which are the words of the four sacred Vedas, and Laukika, or words and writings of trustworthy human beings. Vaidika testimony is preferred over Laukika testimony. Laukika-sourced knowledge must be questioned and revised as more trustworthy knowledge becomes available. | 1 | Applied and Interdisciplinary Chemistry |
Deoxyribonucleic acid (DNA) is a nucleic acid containing the genetic instructions used in the development and functioning of all known living organisms. The chemical DNA was discovered in 1869, but its role in genetic inheritance was not demonstrated until 1943. The DNA segments that carry this genetic information are called genes. Other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information. Along with RNA and proteins, DNA is one of the three major macromolecules that are essential for all known forms of life.
DNA consists of two long polymers of monomer units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands are oriented in opposite directions to each other and are, therefore, antiparallel. Attached to each sugar is one of four types of molecules called nucleobases (informally, bases). It is the sequence of these four nucleobases along the backbone that encodes genetic information. This information specifies the sequence of the amino acids within proteins according to the genetic code. The code is read by copying stretches of DNA into the related nucleic acid RNA in a process called transcription.
Within cells, DNA is organized into long sequences called chromosomes. During cell division these chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts. In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed. | 1 | Applied and Interdisciplinary Chemistry |
A coupling connects two pipes. The fitting is known as a reducing coupling, reducer, or adapter if their sizes differ. There are two types of collars: "regular" and "slip". A regular coupling has a small ridge or stops internally to prevent the over-insertion of a pipe and, thus, under-insertion of the other pipe segment (which would result in an unreliable connection).
A slip coupling (sometimes also called a repair coupling) is deliberately made without this internal stop to allow it to be slipped into place in tight locations, such as the repair of a pipe that has a small leak due to corrosion or freeze bursting, or which had to be cut temporarily for some reason. Since the alignment stop is missing, it is up to the installer to carefully measure the final location of the slip coupling to ensure that it is located correctly. | 1 | Applied and Interdisciplinary Chemistry |
For all intents and purposes, each enantiomer in a pair has the same energy. However, theoretical physics predicts that due to parity violation of the weak nuclear force (the only force in nature that can "tell left from right"), there is actually a minute difference in energy between enantiomers (on the order of 10 eV or 10 kJ/mol or less) due to the weak neutral current mechanism. This difference in energy is far smaller than energy changes caused by even small changes in molecular conformation, and far too small to measure by current technology, and is therefore chemically inconsequential. In the sense used by particle physicists, the "true" enantiomer of a molecule, which has exactly the same mass-energy content as the original molecule, is a mirror-image that is also built from antimatter (antiprotons, antineutrons, and positrons). Throughout this article, "enantiomer" is used only in the chemical sense of compounds of ordinary matter that are not superposable on their mirror image. | 0 | Theoretical and Fundamental Chemistry |
A bioprocess is composed mainly of three stages—upstream processing, bioreaction, and downstream processing—to convert raw material to finished product.
The raw material can be of biological or non-biological origin. It is first converted to a more suitable form for processing. This is done in an upstream processing step which involves chemical hydrolysis, preparation of liquid medium, separation of particulate, air purification and many other preparatory operations.
After the upstream processing step, the resulting feed is transferred to one or more bioreaction stages. The biochemical reactors or bioreactors form the base of the bioreaction step. This step mainly consists of three operations, namely, production of biomass, metabolite biosynthesis and biotransformation.
Finally, the material produced in the bioreactor must be further processed in the downstream section to convert it into a more useful form. The downstream process mainly consists of physical separation operations which include solid liquid separation, adsorption, liquid-liquid extraction, distillation, drying etc. | 1 | Applied and Interdisciplinary Chemistry |
* Encyclopaedia of Islam
* al-Muqtabis by Ibn Hayyan
* The Muqaddima of Ibn Khaldoun, [http://www.muslimphilosophy.com/ik/Muqaddimah/Chapter5/Ch_5_31.htm Chapter V, part 31, "The craft of singing."]
* Ta'rikh fath al-Andalus by Ibn al-Qutiyya
* al-Iqd al-farid by Ibn Abd Rabbih
* Ta'rikh Baghdad by Ibn Tayfur
* Kitab al-Aghani by Abu l-Faraj al-Isfahani
* Tawq al-hamama by Ibn Hazm
* Jawdhat al-Muqtabis by Al-Humaydī
* Mughrib fi hula l-Maghrib by Ibn Sa'id | 1 | Applied and Interdisciplinary Chemistry |
It is a potent anesthetic with a minimum alveolar concentration (MAC) of 0.74%. Its blood/gas partition coefficient of 2.4 makes it an agent with moderate induction and recovery time. It is not a good analgesic and its muscle relaxation effect is moderate. | 0 | Theoretical and Fundamental Chemistry |
Binding to the solid phase may be achieved by column chromatography whereby the solid medium is packed onto a column, the initial mixture run through the column to allow settling, a wash buffer run through the column and the elution buffer subsequently applied to the column and collected. These steps are usually done at ambient pressure. Alternatively, binding may be achieved using a batch treatment, for example, by adding the initial mixture to the solid phase in a vessel, mixing, separating the solid phase, removing the liquid phase, washing, re-centrifuging, adding the elution buffer, re-centrifuging and removing the elute.
Sometimes a hybrid method is employed such that the binding is done by the batch method, but the solid phase with the target molecule bound is packed onto a column and washing and elution are done on the column.
The ligands used in affinity chromatography are obtained from both organic and inorganic sources. Examples of biological sources are serum proteins, lectins and antibodies. Inorganic sources are moronic acid, metal chelates and triazine dyes.
A third method, expanded bed absorption, which combines the advantages of the two methods mentioned above, has also been developed. The solid phase particles are placed in a column where liquid phase is pumped in from the bottom and exits at the top. The gravity of the particles ensure that the solid phase does not exit the column with the liquid phase.
Affinity columns can be eluted by changing salt concentrations, pH, pI, charge and ionic strength directly or through a gradient to resolve the particles of interest.
More recently, setups employing more than one column in series have been developed. The advantage compared to single column setups is that the resin material can be fully loaded since non-binding product is directly passed on to a consecutive column with fresh column material. These chromatographic processes are known as periodic counter-current chromatography (PCC). The resin costs per amount of produced product can thus be drastically reduced. Since one column can always be eluted and regenerated while the other column is loaded, already two columns are sufficient to make full use of the advantages. Additional columns can give additional flexibility for elution and regeneration times, at the cost of additional equipment and resin costs. | 0 | Theoretical and Fundamental Chemistry |
By the late Uruk period development had grown to include a large temple/palace complex.
Culturally, Melid was part of the "Northern regions of Greater Mesopotamia" functioning as a trade colony along the Euphrates River bringing raw materials to Sumer (Lower Mesopotamia).
Numerous similarities have been found between these early layers at Arslantepe, and the somewhat later site of Birecik (Birecik Dam Cemetery), also in Turkey, to the southwest of Melid.
Around 3000 BCE, the transitional EBI-EBII, there was widespread burning and destruction, after which Kura–Araxes pottery appeared in the area. This was a mainly pastoralist culture connected with the Caucasus mountains. | 1 | Applied and Interdisciplinary Chemistry |
This pathway has a significant effect in the way genes are translated, restricting the amount of gene expression. It is still a new field in genetics, but its role in research has already led scientists to uncover numerous explanations for gene regulation. Studying nonsense-mediated decay has allowed scientists to determine the causes for certain heritable diseases and dosage compensation in mammals. | 1 | Applied and Interdisciplinary Chemistry |
Like all metals, gold is insoluble in a water. Gold does however exhibit the distinctive properties that in the presence of cyanide ions, it dissolves in the presence of oxygen (or air). This transformation was reported in 1783 by Carl Wilhelm Scheele, but it was not until the late 19th century, that the reactions were exploited commercially. The expansion of gold mining in the Rand of South Africa began to slow down in the 1880s, as the new deposits being found tended to be pyritic ore. The gold was difficult to extract from such ores.
In 1887, John Stewart MacArthur, working in collaboration with brothers Dr Robert and Dr William Forrest for the Tennant Company in Glasgow, Scotland, developed the MacArthur-Forrest Process for the extraction of gold ores. By suspending the crushed ore in a cyanide solution, up to 96 percent gold was extracted.
The process was first used on a large scale at the Witwatersrand in 1890, leading to a boom of investment as larger gold mines were opened up. In 1896, Bodländer confirmed that oxygen was necessary for the process, something that had been doubted by MacArthur, and discovered that hydrogen peroxide was formed as an intermediate.
The method known as heap leaching was first proposed in 1969 by the United States Bureau of Mines, and was in use by the 1970s. | 1 | Applied and Interdisciplinary Chemistry |
The original Asakura–Oosawa model considered only hard-core interactions. In such an athermal mixture the origin of depletion forces is necessarily entropic. If the intermolecular potentials also include repulsive and/or attractive terms, and if the solvent is considered explicitly, the depletion interaction can have additional thermodynamic contributions.
The notion that depletion forces can also be enthalpically driven has surfaced due to recent experiments regarding protein stabilization induced by compatible osmolytes, such as trehalose, glycerol, and sorbitol. These osmolytes are preferentially excluded from protein surfaces, forming a layer of preferential hydration around the proteins. When the protein folds - this exclusion volume diminishes, making the folded state lower in free energy. Hence the excluded osmolytes shift the folding equilibrium towards the folded state. This effect was generally thought to be an entropic force, in the spirit of the original Asakura–Oosawa model and of macromolecular crowding. However, thermodynamic breakdown of the free-energy gain due to osmolyte addition showed the effect is in fact enthalpically driven, whereas entropy can even be disfavorable.
For many cases, the molecular origin of this enthalpically driven depletion force can be traced to an effective "soft" repulsion in the potential of mean force between macromolecule and cosolute. Both Monte-Carlo simulations and a simple analytic model demonstrate that when the hard-core potential (as in Asakura and Oosawa's model) is supplemented with an additional repulsive "softer" interaction, the depletion force can become enthalpically dominated. | 0 | Theoretical and Fundamental Chemistry |
Tetraoxidane is an inorganic compound of hydrogen and oxygen with the chemical formula . This is one of the unstable hydrogen polyoxides. | 0 | Theoretical and Fundamental Chemistry |
NAD kinase (EC 2.7.1.23, NADK) is an enzyme that converts nicotinamide adenine dinucleotide (NAD) into NADP through phosphorylating the NAD coenzyme. NADP is an essential coenzyme that is reduced to NADPH primarily by the pentose phosphate pathway to provide reducing power in biosynthetic processes such as fatty acid biosynthesis and nucleotide synthesis. The structure of the NADK from the archaean Archaeoglobus fulgidus has been determined.
In humans, the genes NADK and MNADK encode NAD kinases localized in cytosol and mitochondria, respectively. Similarly, yeast have both cytosolic and mitochondrial isoforms, and the yeast mitochondrial isoform accepts both NAD and NADH as substrates for phosphorylation. | 1 | Applied and Interdisciplinary Chemistry |
Several capsaicin analogs of the urea type were developed by acylation of homovanillylamine and related amines with different 4-(α-pyridyl)piperidine-1-acyl chlorides. The presence of a polar amino moiety in the hydrophobic C region of capsacinoids was crucial to couple potency and hydrophilicity, mimicking similar observations that led to the discovery of phenylacetylrinvanil (fig. 3b) from olvanil (fig. 3a). Phenylacetylrinvanil is the most potent capsaicinoid reported to date, ~500-fold more potent than capsaicin. Several other ureas emerged as remarkably active TRPV1 antagonists. Compared with capsazepine, the piperazinyl urea (fig. 5a and 5b) showed a higher selectivity profile against a wide variety of enzymes and channels whereas the related very potent and specific TRPV1 antagonist A-425619 (fig. 5c) could reduce pain associated with inflammation and tissue injury in rats. Further research has led to a variety of small-molecule antagonists of TRPV1, including the ureas SB-705498 (fig. 5d), SB-452533 (fig. 5e)[16,17] and ABT-102(fig. 5f), compounds that have entered clinical trials. | 1 | Applied and Interdisciplinary Chemistry |
Six affiliate societies focused on specific areas of materials science also fall under the ASM umbrella:
* The Heat Treating Society (HTS),
* The Thermal Spray Society (TSS),
* The International Metallographic Society (IMS),
* The Electronic Device Failure Analysis Society (EDFAS),
* The Failure Analysis Society (FAS), and
* The International Organization on Shape Memory and Superelastic Technology (SMST).
Each society is led by volunteers, produces specific technical content for members, and holds its own international event. | 1 | Applied and Interdisciplinary Chemistry |
Source:
* Otto Hahn Medal of the Max Planck Society (1979)
* Dreyfus Teacher Scholar Award (1987)
* ACS Arthur C. Cope Scholar Award (1992)
* Otto Bayer Award (1993)
* Janssen Prize for Creativity in Organic Synthesis (2000)
* Havinga Medal (2000)
* Myron L. Bender & Muriel S. Bender Distinguished Summer Lecturer at Northwestern University (2004)
* Humboldt Prize (2005)
* Burckhardt Helferich Prize (2005)
* August Wilhelm von Hofmann-Denkmünze of the German Chemical Society (2006)
* ACS Ronald Breslow Award for Achievements in Biomimetic Chemistry (2007)
* of the German Chemical Society (2011)
* Honorary Doctoral Degree, Technion, Haifa (2012)
* Ernst Hellmut Vits-Preis (2014)
* Prix Paul Metz by the Institut Grand Ducal, Luxembourg (2014)
* EFMC Nauta Award for Pharmacochemistry and for outstanding results of scientific research in the field of Medicinal Chemistry (2016)
* Honorary Membership of the German Chemical Society (Gesellschaft Deutscher Chemiker, GDCh) (2019) | 0 | Theoretical and Fundamental Chemistry |
There are a number of chemical reagents that are available for treating turbidity. Reagents that are available for treating turbidity include aluminium sulfate or alum (Al(SO)·nHO), ferric chloride (FeCl), gypsum (CaSO·2HO), poly-aluminium chloride, long chain acrylamide-based polymers and numerous proprietary reagents. The water chemistry must be carefully considered when chemical dosing as some reagents, such as alum, will alter the pH of the water.
The dosing process must also be considered when using reagents as the flocs may be broken apart by excessive mixing. | 0 | Theoretical and Fundamental Chemistry |
Raindrop sizes typically range from 0.5 mm to 4 mm, with size distributions quickly decreasing past diameters larger than 2-2.5 mm.
Scientists traditionally thought that the variation in the size of raindrops was due to collisions on the way down to the ground. In 2009, French researchers succeeded in showing that the distribution of sizes is due to the drops' interaction with air, which deforms larger drops and causes them to fragment into smaller drops, effectively limiting the largest raindrops to about 6 mm diameter. However, drops up to 10 mm (equivalent in volume to a sphere of radius 4.5 mm) are theoretically stable and could be levitated in a wind tunnel.
The largest recorded raindrop was 8.8 mm in diameter, located at the base of a cumulus congestus cloud in the vicinity of Kwajalein Atoll in July 1999. A raindrop of identical size was detected over northern Brazil in September 1995. | 1 | Applied and Interdisciplinary Chemistry |
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