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A plasmid partition system is a mechanism that ensures the stable inheritance of plasmids during bacterial cell division. Each plasmid has its independent replication system which controls the number of copies of the plasmid in a cell. The higher the copy number, the more likely the two daughter cells will contain the plasmid. Generally, each molecule of plasmid diffuses randomly, so the probability of having a plasmid-less daughter cell is 2, where N is the number of copies. For instance, if there are 2 copies of a plasmid in a cell, there is 50% chance of having one plasmid-less daughter cell. However, high-copy number plasmids have a cost for the hosting cell. This metabolic burden is lower for low-copy plasmids, but those have a higher probability of plasmid loss after a few generations. To control vertical transmission of plasmids, in addition to controlled-replication systems, bacterial plasmids use different maintenance strategies, such as multimer resolution systems, post-segregational killing systems (addiction modules), and partition systems. | 1 | Applied and Interdisciplinary Chemistry |
Over the life of Fulmer about 500 people were members of staff. Among these, because of the wide range of projects that Fulmer undertook, investigators and other technical staff had to be able to adapt their specialist skills and to innovate. They were also expected to play a part in attracting the necessary funding from business or Government. | 1 | Applied and Interdisciplinary Chemistry |
There have been palytoxin poisonings through skin absorption e.g. in people who handled corals without gloves in their home aquariums in Germany and the USA. | 0 | Theoretical and Fundamental Chemistry |
Hitchins worked with Soddy over a period of 15 years, which included his most productive periods of achievement. She was his primary research assistant, and the only person to work with him for a long period of time. Her careful preparation of radioactive materials, and her painstaking experimental work with uranium, protactinium, and lead isotopes, made crucial contributions to the research for which Soddy received the Nobel Prize. | 0 | Theoretical and Fundamental Chemistry |
George Gabriel Stokes (not to neglect the later work of Gustav Kirchhoff) is often given credit for having first enunciated the fundamental principles of spectroscopy. In 1862, Stokes published formulas for determining the quantities of light remitted and transmitted from "a pile of plates". He described his work as addressing a "mathematical problem of some interest". He solved the problem using summations of geometric series, but the results are expressed as continuous functions. This means that the results can be applied to fractional numbers of plates, though they have the intended meaning only for an integral number. The results below are presented in a form compatible with discontinuous functions.
Stokes used the term "reflexion", not "remission", specifically referring to what is often called regular or specular reflection. In regular reflection, the Fresnel equations describe the physics, which includes both reflection and refraction, at the optical boundary of a plate. A "pile of plates" is still a term of art used to describe a polarizer in which a polarized beam is obtained by tilting a pile of plates at an angle to an unpolarized incident beam. The area of polarization was specifically what interested Stokes in this mathematical problem. | 0 | Theoretical and Fundamental Chemistry |
Nephelometers are also used in global warming studies, specifically measuring the global radiation balance. Three wavelength nephelometers fitted with a backscatter shutter can determine the amount of solar radiation that is reflected back into space by dust and particulate matter. This reflected light influences the amount of radiation reaching the earth's lower atmosphere and warming the planet. | 0 | Theoretical and Fundamental Chemistry |
The symmetry of this ideal solution has a stagnation point on the rear side of the cylinder, as well as on the front side. The pressure distribution over the front and rear sides are identical, leading to the peculiar property of having zero drag on the cylinder, a property known as dAlemberts paradox. Unlike an ideal inviscid fluid, a viscous flow past a cylinder, no matter how small the viscosity, will acquire a thin boundary layer adjacent to the surface of the cylinder. Boundary layer separation will occur, and a trailing wake will exist in the flow behind the cylinder. The pressure at each point on the wake side of the cylinder will be lower than on the upstream side, resulting in a drag force in the downstream direction. | 1 | Applied and Interdisciplinary Chemistry |
The Zeeman effect is utilized in many laser cooling applications such as a magneto-optical trap and the Zeeman slower. | 0 | Theoretical and Fundamental Chemistry |
This is the simplest method of non-viral transfection. Clinical trials carried out of intramuscular injection of a naked DNA plasmid have occurred with some success; however, the expression has been very low in comparison to other methods of transfection. In addition to trials with plasmids, there have been trials with naked PCR product, which have had similar or greater success. Cellular uptake of naked DNA is generally inefficient. Research efforts focusing on improving the efficiency of naked DNA uptake have yielded several novel methods, such as electroporation, sonoporation, and the use of a "gene gun", which shoots DNA coated gold particles into the cell using high pressure gas. | 1 | Applied and Interdisciplinary Chemistry |
The techniques observed in all of them are quite similar. Basically they used the thermic alteration or firesetting (Mohen 1992, Craddock 1995, Eiroa et al. 1996, Timberlake 2003). This consists of applying fire to the rock and then pouring water over it: the rapid changes of temperature will cause cracks within the rocks that can be totally broken with the help of mauls and picks. Then the useful masses were selected, crushed and transported to the production centre that could be in the surrounding area (Mitterberg) or far away (Rudna Glava).
The mines were exploited in extremely efficient and clever ways, according to the technology available (Jovanovic 1980, Craddock 1995, Timberlake 2003). The entire convenient mineral was collected and the abandoned shafts carefully refilled with gangue and rocks (Mohen 1992; 85). For example, at Mount Gabriel, it was estimated that they extracted the astonishing number of of rock, gangue and ore. The usable amount of copper was 162.85 tonnes and the final smelting finished metal was 146.56 tonnes (Jackson 1980; 24). The entire process was thoroughly described in 1744 by Lewis Morris, Crown Mineral Agent for Cardiganshire, and, incidentally, antiquarian.
The tools employed are mainly presented in Lewis' observations, but other ones have been recovered in archaeological context:
*Stone tools: The most frequent find are the stone hammers, normally made of hard rocks accessible to the mine, beach or river pebbles. There is no standardization of these mauls but is common a system of hafting, usually a groove carved in the middle for where a rope was tied to the handle, like the twisted hazel recovered in Copa Hill.
* Antler and bone tools: Picks and scrapes made of bone and antlers have been found in the majority of the mines.
* Wood: Evidence of wooden tools are more infrequent. Nevertheless in places like Ai Bunar or Mount Gabriel were recovered shovels and wedges. A rudimentary system of stairs or scaffoldings can be supposed (Mohen 1992).
* Metal: The use of any metallic tool is rather strange and extraordinary. It seems that the copper was not used for the miners' tools. However copper chisels and discarded axes could be utilized as wedges.
* Other evidence: The presence of coal and charcoal, crucial for the firing (fire-setting) and furnace (fuel), is habitual. Leather sacks (at Ai Bunar) and shoulder baskets (at Copa Hill) were used to transport the crushed mineral. | 1 | Applied and Interdisciplinary Chemistry |
Since there is a frequent large pharmacokinetic and pharmacodynamic differences between enantiomers of a chiral drug it is not surprising that enantiomers may result in stereoselective toxicity. They can reside in the pharmacologically active enantiomer (eutomer) or in the inactive one (distomer). The toxicologic differences between enantiomers of have also been demonstrated. The following are examples of some of the chiral drugs where their toxic/undesirable side-effects dwell almost in the distomer. This would seem to be a clear cut case of going for a chiral switch. | 0 | Theoretical and Fundamental Chemistry |
S. S. Goldich derived this series in 1938 after studying soil profiles and their parent rocks. Based on sample analysis from a series of weathered localities, Goldich determined that the weathering rate of minerals is controlled at least in part by the order in which they crystallize from a melt. This order meant that the minerals that crystallized first from the melt were the least stable under earth surface conditions, while the minerals that crystallized last were the most stable. This is not the only control on weathering rate; this rate is dependent on both intrinsic (qualities specific to the minerals) and extrinsic (qualities specific to the environment) variables. Climate is a key extrinsic variable, controlling the water to rock ratio, pH, and alkalinity, all of which impact the rate of weathering. The Goldich dissolution series concerns intrinsic mineral qualities, which were proven both by Goldich as well as preceding scientists to also be important for constraining weathering rates.
Earlier work by Steidtmann demonstrated that the order of ionic loss of a rock as it weathers is: CO, Mg, Na, K, SiO, Fe, and finally Al. Goldich furthered this analysis by noting the relative mineral stability order, which is related to the relative resistance of these ions to leaching. Goldich notes that overall, mafic (rich in iron and magnesium) minerals are less stable than felsic (rich in silica) minerals. The order of stability in the series echoes Bowen's reaction series very well, leading Goldich to suggest that the relative stability at the surface is controlled by crystallization order.
While Goldich’s original order of mineral weathering potential was qualitative, later work by Michal Kowalski and J. Donald Rimstidt placed in the series in quantitative terms. Kowalski and Rimstidt performed an analysis of mechanical and chemical grain weathering, and demonstrated that the average lifetime of chemically weathered detrital grains quantitatively fit the Goldich sequence extremely well. This helped to supplement the real-world applicability of the dissolution series. The difference in chemical weathering time can span millions of years. For example, quickest to weather of the common igneous minerals is apatite, which reaches complete weathering in an average of 10 years, and slowest to weather is quartz, which weathers fully in 10 years. | 0 | Theoretical and Fundamental Chemistry |
Type I restriction enzymes were the first to be identified and were first identified in two different strains (K-12 and B) of E. coli. These enzymes cut at a site that differs, and is a random distance (at least 1000 bp) away, from their recognition site. Cleavage at these random sites follows a process of DNA translocation, which shows that these enzymes are also molecular motors. The recognition site is asymmetrical and is composed of two specific portions—one containing 3–4 nucleotides, and another containing 4–5 nucleotides—separated by a non-specific spacer of about 6–8 nucleotides. These enzymes are multifunctional and are capable of both restriction digestion and modification activities, depending upon the methylation status of the target DNA. The cofactors S-Adenosyl methionine (AdoMet), hydrolyzed adenosine triphosphate (ATP), and magnesium (Mg) ions, are required for their full activity. Type I restriction enzymes possess three subunits called HsdR, HsdM, and HsdS; HsdR is required for restriction digestion; HsdM is necessary for adding methyl groups to host DNA (methyltransferase activity), and HsdS is important for specificity of the recognition (DNA-binding) site in addition to both restriction digestion (DNA cleavage) and modification (DNA methyltransferase) activity. | 1 | Applied and Interdisciplinary Chemistry |
Calcium oxide is friable, that is, quite brittle. In fluidised beds, the calcium oxide particles can break apart upon collision with the other particles in the fluidised bed or the vessel containing it. The problem seems to be greater in pilot plant tests than at a bench scale. | 1 | Applied and Interdisciplinary Chemistry |
Ferrier proposed the following reaction mechanism:
In this mechanism, the terminal olefin undergoes hydroxymercuration to produce the first intermediate, compound 2, a hemiacetal. Next, methanol is lost and the dicarbonyl compound cyclizes through an attack on the electrophilic aldehyde to form the carbocycle as the product. A downside to this reaction is that the loss of CHOH at the anomeric position (carbon-1) results in a mixture of α- and β-anomers. The reaction also works for substituted alkenes (e. g. having an -OAc group on the terminal alkene).
Ferrier also reported that the final product, compound 5, could be converted into a conjugated ketone (compound 6) by reaction with acetic anhydride (AcO) and pyridine, as shown below. | 0 | Theoretical and Fundamental Chemistry |
The Nernst heat theorem was formulated by Walther Nernst early in the twentieth century and was used in the development of the third law of thermodynamics. | 0 | Theoretical and Fundamental Chemistry |
With termination collisions restricted, the concentration of active polymerizing chains and simultaneously the consumption of monomer rises rapidly. Assuming abundant unreacted monomer, viscosity changes affect the macromolecules but do not prove high enough to prevent smaller molecules – such as the monomer – from moving relatively freely. Therefore, the propagation reaction of the free-radical polymerization process is relatively insensitive to changes in viscosity. This also implies that at the onset of autoacceleration the overall rate of reaction increases relative to the rate of unautoaccelerated reaction given by the overall rate of reaction equation for free-radical polymerization:
Approximately, as the termination decreases by a factor of 4, the overall rate of reaction will double. The decrease of termination reactions also allows radical chains to add monomer for longer time periods, raising the mass-average molecular mass dramatically. However, the number-average molecular mass only increases slightly, leading to broadening of the molecular mass distribution (high dispersity, very polydispersed product). | 0 | Theoretical and Fundamental Chemistry |
Electrokinetic phenomena are a family of several different effects that occur in heterogeneous fluids or in porous bodies filled with fluid. The sum of these phenomena deals with the effect on a particle from some outside resulting in a net electrokinetic effect.
The common source of all these effects stems from the interfacial double layer of charges. Particles influenced by an external force generate tangential motion of a fluid with respect to an adjacent charged surface. This force may consist of electric, pressure gradient, concentration gradient, gravity. In addition, the moving phase might be either the continuous fluid or dispersed phase.
Sedimentation potential is the field of electrokinetic phenomena dealing with the generation of an electric field by sedimenting colloid particles. | 0 | Theoretical and Fundamental Chemistry |
Silyl ethers are a group of chemical compounds which contain a silicon atom covalently bonded to an alkoxy group. The general structure is RRRSi−O−R where R is an alkyl group or an aryl group. Silyl ethers are usually used as protecting groups for alcohols in organic synthesis. Since RRR can be combinations of differing groups which can be varied in order to provide a number of silyl ethers, this group of chemical compounds provides a wide spectrum of selectivity for protecting group chemistry. Common silyl ethers are: trimethylsilyl (TMS), tert-butyldiphenylsilyl (TBDPS), tert-butyldimethylsilyl (TBS/TBDMS) and triisopropylsilyl (TIPS). They are particularly useful because they can be installed and removed very selectively under mild conditions. | 0 | Theoretical and Fundamental Chemistry |
Due to the versatility of SPR instrumentation, this technique pairs well with other approaches, leading to novel applications in various fields, such as biomedical and environmental studies.
When coupled with nanotechnology, SPR biosensors can use nanoparticles as carriers for therapeutic implants. For instance, in the treatment of Alzheimer's disease, nanoparticles can be used to deliver therapeutic molecules in targeted ways. In general, SPR biosensing is demonstrating advantages over other approaches in the biomedical field due to this technique being label-free, lower in costs, applicable in point-of-care settings, and capable of producing faster results for smaller research cohorts.
In the study of environmental pollutants, SPR instrumentation can be used as a replacement for former chromatography-based techniques. Current pollution research relies on chromatography to monitor increases in pollution in an ecosystem over time. When SPR instrumentation with a Kretschmann prism configuration was used in the detection of chlorophene, an emerging pollutant, it was demonstrated that SPR has similar precision and accuracy levels as chromatography techniques. Furthermore, SPR sensing surpasses chromatography techniques through its high-speed, straightforward analysis. | 0 | Theoretical and Fundamental Chemistry |
Smith continued his academic career as an assistant professor at the University of Minnesota in 1980, later becoming associate professor in 1986 and Professor in 2004. In 2011 he served as Distinguished Engineering Education Innovation (EI) Fellow at the Hong Kong University of Science and Technology. He retired from the University of Minnesota in 2011 and between 2006 and 2022 he served as Cooperative Learning Professor of Engineering Education at Purdue University's School of Engineering Education. Also since 2011, he has held positions as an emeritus Professor of Civil, Environmental, and Geo-Engineering, Morse-Alumni Distinguished University Teaching Professor, and Faculty Member at the Technological Leadership Institute at the University of Minnesota. Additionally, in collaboration with Tony Starfield, Alan Wassyng, Sam Sharp, and others, he developed the civil engineering systems and "How to model it" courses for upper division and first-year students, respectively, which, alongside his work in cooperative learning and teamwork with David W. and Roger T. Johnson, led to the creation of the Civil Engineering Project Management course and the Management of Technology Project and Knowledge Management course.
Between 1999 and 2004, he had a split appointment with Michigan State University where he served as a Senior Consultant to the Provost for Faculty Development. At the University of Minnesota, he was the Co-coordinator of the Bush Faculty Development Program for Excellence and Diversity in Teaching from 1996 to 1997, Director of undergraduate studies in the Department of Civil Engineering from 1999 to 2004, and executive co-director and researcher in the STEM Education Research Center from 2012 to 2018. He was inducted into the Michigan Technological University Academy for Engineering Education Leadership in 2018. | 1 | Applied and Interdisciplinary Chemistry |
There are several other reliable tests and V̇O max calculators to estimate V̇O max, most notably the multi-stage fitness test (or beep test). | 1 | Applied and Interdisciplinary Chemistry |
Androstenediol sulfate, also known as androst-5-ene-3β,17β-diol 3β-sulfate, is an endogenous, naturally occurring steroid and a urinary metabolites of androstenediol. It is a steroid sulfate which is formed from sulfation of androstenediol by steroid sulfotransferase and can be desulfated back into androstenediol by steroid sulfatase. | 1 | Applied and Interdisciplinary Chemistry |
Defects involving genetic mutations altering cytochrome c oxidase (COX) functionality or structure can result in severe, often fatal metabolic disorders. Such disorders usually manifest in early childhood and affect predominantly tissues with high energy demands (brain, heart, muscle). Among the many classified mitochondrial diseases, those involving dysfunctional COX assembly are thought to be the most severe.
The vast majority of COX disorders are linked to mutations in nuclear-encoded proteins referred to as assembly factors, or assembly proteins. These assembly factors contribute to COX structure and functionality, and are involved in several essential processes, including transcription and translation of mitochondrion-encoded subunits, processing of preproteins and membrane insertion, and cofactor biosynthesis and incorporation.
Currently, mutations have been identified in seven COX assembly factors: SURF1, SCO1, SCO2, COX10, COX15, COX20, COA5 and LRPPRC. Mutations in these proteins can result in altered functionality of sub-complex assembly, copper transport, or translational regulation. Each gene mutation is associated with the etiology of a specific disease, with some having implications in multiple disorders. Disorders involving dysfunctional COX assembly via gene mutations include Leigh syndrome, cardiomyopathy, leukodystrophy, anemia, and sensorineural deafness. | 1 | Applied and Interdisciplinary Chemistry |
Aqueous normal-phase chromatography (ANP) is also called hydrophilic interaction liquid chromatography (HILIC). This is a chromatographic technique which encompasses the mobile phase region between reversed-phase chromatography (RP) and organic normal phase chromatography (ONP). HILIC is used to achieve unique selectivity for hydrophilic compounds, showing normal phase elution order, using "reversed-phase solvents", i.e., relatively polar mostly non-aqueous solvents in the mobile phase. Many biological molecules, especially those found in biological fluids, are small polar compounds that do not retain well by reversed phase-HPLC. This has made hydrophilic interaction LC (HILIC) an attractive alternative and useful approach for analysis of polar molecules. Additionally, because HILIC is routinely used with traditional aqueous mixtures with polar organic solvents such as ACN and methanol, it can be easily coupled to MS. | 0 | Theoretical and Fundamental Chemistry |
Introns are the parts of a gene that are transcribed into the precursor RNA sequence, but ultimately removed by RNA splicing during the processing to mature RNA. Introns are found in both types of genes: protein-coding genes and noncoding genes. They are present in prokaryotes but they are much more common in eukaryotic genomes.
Group I and group II introns take up only a small percentage of the genome when they are present. Spliceosomal introns (see Figure) are only found in eukaryotes and they can represent a substantial proportion of the genome. In humans, for example, introns in protein-coding genes cover 37% of the genome. Combining that with about 1% coding sequences means that protein-coding genes occupy about 38% of the human genome. The calculations for noncoding genes are more complicated because there is considerable dispute over the total number of noncoding genes but taking only the well-defined examples means that noncoding genes occupy at least 6% of the genome. | 1 | Applied and Interdisciplinary Chemistry |
Cram expanded upon Charles Pedersens ground-breaking synthesis of crown ethers, two-dimensional organic compounds that are able to recognize and selectively combine with the ions of certain metal elements. He synthesized molecules that took this chemistry into three dimensions, creating an array of differently shaped molecules that could interact selectively with other chemicals because of their complementary three-dimensional structures. Crams work represented a large step toward the synthesis of functional laboratory-made mimics of enzymes and other natural molecules whose special chemical behavior is due to their characteristic structure. He also did work in stereochemistry and Cram's rule of asymmetric induction is named after him.
In 1973, Cram collaborated on research with Irish chemist Francis Leslie Scott. | 0 | Theoretical and Fundamental Chemistry |
In modern computational chemistry, pharmacophores are used to define the essential features of one or more molecules with the same biological activity. A database of diverse chemical compounds can then be searched for more molecules which share the same features arranged in the same relative orientation. Pharmacophores are also used as the starting point for developing 3D-QSAR models. Such tools and a related concept of "privileged structures", which are "defined as molecular frameworks which are able of providing useful ligands for more than one type of receptor or enzyme target by judicious structural modifications", aid in drug discovery. | 1 | Applied and Interdisciplinary Chemistry |
In some cases, equations are unsolvable analytically, but can be solved using numerical methods if data values are given. There are two different ways to do this, by either using software programmes or mathematical methods such as the Euler method. Examples of software for chemical kinetics are i) Tenua, a Java app which simulates chemical reactions numerically and allows comparison of the simulation to real data, ii) Python coding for calculations and estimates and iii) the Kintecus software compiler to model, regress, fit and optimize reactions.
-Numerical integration: for a 1st order reaction A → B
The differential equation of the reactant A is:
It can also be expressed as
which is the same as
To solve the differential equations with Euler and Runge-Kutta methods we need to have the initial values. | 0 | Theoretical and Fundamental Chemistry |
A rule-of-thumb is that any molecule that will dissolve in methanol or a less polar solvent is compatible with SFC, including non-volatile polar solutes. CO has polarity similar to n-heptane at its critical point. The solvent's elution strength can be increased just by increasing density or alternatively, using a polar co-solvent. In practice, when the fraction of the co-solvent is high, the mobile phase might not be truly at supercritical fluid state, but this terminology is used regardless, and the chromatograms show better elution and higher efficiency nevertheless. | 0 | Theoretical and Fundamental Chemistry |
Carl Auer von Welsbach (1 September 1858 – 4 August 1929), who received the Austrian noble title of Freiherr Auer von Welsbach in 1901, was an Austrian scientist and inventor, who separated didymium into the elements neodymium and praseodymium in 1885. He was also one of three scientists to independently discover the element lutetium (which he named cassiopeium), separating it from ytterbium in 1907, setting off the longest priority dispute in the history of chemistry.
He had a talent not only for making scientific advances, but also for turning them into commercially successful products. His work on rare-earth elements led to the development of the ferrocerium "flints" used in modern lighters, the gas mantle that brought light to the streets of Europe in the late 19th century, and the metal-filament light bulb. He took the phrase plus lucis, meaning "more light", as his motto. | 1 | Applied and Interdisciplinary Chemistry |
Some cyanobacteria are sold as food, notably Arthrospira platensis (Spirulina) and others (Aphanizomenon flos-aquae).
Some microalgae contain substances of high biological value, such as polyunsaturated fatty acids, amino acids, proteins, pigments, antioxidants, vitamins, and minerals. Edible blue-green algae reduce the production of pro-inflammatory cytokines by inhibiting NF-κB pathway in macrophages and splenocytes. Sulfate polysaccharides exhibit immunomodulatory, antitumor, antithrombotic, anticoagulant, anti-mutagenic, anti-inflammatory, antimicrobial, and even antiviral activity against HIV, herpes, and hepatitis. | 0 | Theoretical and Fundamental Chemistry |
The Comparative Toxicogenomics Database (CTD) is a public website and research tool that curates scientific data describing relationships between chemicals, genes/proteins, diseases, taxa, phenotypes, GO annotations, pathways, and interaction modules, launched on November 12, 2004.
The database is maintained by the Department of Biological Sciences at North Carolina State University. | 1 | Applied and Interdisciplinary Chemistry |
In many cases, giving a placebo to a person suffering from a disease may be unethical. To address this, it has become a common practice to conduct "active comparator" (also known as "active control") trials. In trials with an active control group, subjects are given either the experimental treatment or a previously approved treatment with known effectiveness. | 1 | Applied and Interdisciplinary Chemistry |
Andrew Bruce Holmes (born 5 September 1943) is an Australian and British senior research chemist and professor at the Bio21 Institute, Melbourne, Australia, and the past President of the Australian Academy of Science. His research interests lie in the synthesis of biologically-active natural products (spanning therapeutic materials to new biotechnological probes) and optoelectronic polymers (with applications to electroluminescent flexible displays and organic solar cells). | 0 | Theoretical and Fundamental Chemistry |
The interaction of the tip with the sample modifies the amplitudes, phase shifts and frequency resonances of the excited modes. Those changes are detected and processed by the feedback of the instrument. Several features make bimodal AFM a very powerful surface characterization method at the nanoscale. (i) Resolution. Atomic, molecular or nanoscale spatial resolution was demonstrated. (ii) Simultaneity. Maps of different properties are generated at the same time. (iii) Efficiency. A maximum number of four data points per pixel are needed to generate material property maps. (iv) Speed. Analytical solutions link observables with material properties. | 0 | Theoretical and Fundamental Chemistry |
Lectin is a kind of protein that can bind to carbohydrate with their carbohydrate recognition domains (CRDs). We could use different CRD to classify them. | 0 | Theoretical and Fundamental Chemistry |
Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric (enantiomeric or diastereomeric) products in unequal amounts."
Put more simply: it is the synthesis of a compound by a method that favors the formation of a specific enantiomer or diastereomer. Enantiomers are stereoisomers that have opposite configurations at every chiral center. Diastereomers are stereoisomers that differ at one or more chiral centers.
Enantioselective synthesis is a key process in modern chemistry and is particularly important in the field of pharmaceuticals, as the different enantiomers or diastereomers of a molecule often have different biological activity. | 0 | Theoretical and Fundamental Chemistry |
As polymers approach their ceiling temperature, thermal degradation gives way to complete decomposition. Certain polymers like PTFE, polystyrene and PMMA undergo depolymerization to give their starting monomers, whereas others like polyethylene undergo pyrolysis, with random chain scission giving a mixture of volatile products. Where monomers are obtained, they can be converted back into new plastic (chemical or feedstock recycling), whereas pyrolysis products are used as a type of synthetic fuel (energy recycling). In practice, even very efficient depolymerisation to monomers tends to see some competitive pyrolysis. Thermoset polymers may also be converted in this way, for instance, in tyre recycling. | 0 | Theoretical and Fundamental Chemistry |
The thermodynamic square can also be used to find the first-order derivatives in the common Maxwell relations. The following procedure should be considered:
# Looking at the four corners of the square and make a shape with the quantities of interest.
# Read the shape in two different ways by seeing it as L and ⅃. The L will give one side of the relation and the ⅃ will give the other. Note that the partial derivative is taken along the vertical stem of L (and ⅃) while the last corner is held constant.
# Use L to find .
# Similarly, use ⅃ to find . Again, notice that the sign convention affects only the variable held constant in the partial derivative, not the differentials.
# Finally, use above equations to get the Maxwell relation: .
By rotating the shape (randomly, for example by 90 degrees counterclockwise into a shape) other relations such as:
can be found. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group (these may respectively be called alkylamines and arylamines; amines in which both types of substituent are attached to one nitrogen atom may be called alkylarylamines). Important amines include amino acids, biogenic amines, trimethylamine, and aniline. Inorganic derivatives of ammonia are also called amines, such as monochloramine ().
The substituent is called an amino group.
Compounds with a nitrogen atom attached to a carbonyl group, thus having the structure , are called amides and have different chemical properties from amines. | 0 | Theoretical and Fundamental Chemistry |
By the 1980s, CCF Xe actually being the product of fission was doubtful, and the alternate theory that it had arisen from r-process (neutron capture) nucleosynthesis gained more ground. Researchers looked at the isotopic anomalies in nearby elements samarium, neodymium, and barium, and compared to the amount of xenon. Whether CCF Xe was produced by nucleosynthesis or fission, comparable amounts of barium-135 should be produced. When researchers compared the experimental data to predicted amounts of Barium following each model, neither model came close to predicting the anomalies correctly, leading to Lewis et al. calling the experiment an "embarrassment" for both models. However, in the case of nucleosynthesis, it is possible that samarium, neodymium, and barium were separated from Xe by prior condensation in the supernova shell or plasma processes. Based on this data it was deemed unlikely that CCF Xe had actually arose from fission. | 0 | Theoretical and Fundamental Chemistry |
In a fluidized-bed roaster, finely ground sulfide concentrates are suspended and oxidized in feedstock bed supported on an air column. As in the suspension roaster, the reaction rates for desulfurization are more rapid than in the older multiple-hearth processes. Fluidized-bed roasters operate under a pressure slightly lower than atmospheric and at temperatures averaging . In the fluidized-bed process, no additional fuel is required after ignition has been achieved. The major advantages of this roaster are greater throughput capacities, greater sulfur removal capabilities, and lower maintenance. | 1 | Applied and Interdisciplinary Chemistry |
C-terminus - C4 photosynthesis - cadherin - calbindin -calcitonin - calcitonin gene-related peptide - calcitonin gene-related peptide receptor - calcitonin receptor - calcitriol receptor - calcium channel - calcium signaling - calcium-binding protein - calmodulin - calmodulin-binding protein - Calvin cycle - CAM photosynthesis - CAM plants - cancer - capsid - carbohydrate - carbon - carbon fixation - carboxylic acid - carcinoembryonic antigen - carrier - carrier protein - CAS registry number - casein - catabolism - catalyst - catalytic domain - CCR5 receptor - CD4 antigen - CD45 antigen - CD95 antigen - CDC28 protein kinase - cell - cell adhesion molecule - cell biology - cell cycle protein - cell membrane - cell membrane transport - cell nucleus - cell surface receptor - cellular respiration - cellulose - centriole - centromere - centrosome - chaperone - chelation - chemical biology - chemical bond - chemical compound - conformation - chemical element - chemical equilibrium - chemical formula - chemical nomenclature - chemical property - chemical reaction - chemical series - chemical thermodynamics - cheminformatics - chemiosmosis - chemiosmotic hypothesis - chemiosmotic potential - chemist - chemistry - chemistry basic topics - chemotroph - chemokine receptor - chemoreceptor - chiasma - chimera (protein) - chimeric protein - chirality - chloride channel - chlorophyll - chloroplast - chloroplast membrane - cholecystokinin receptor - cholesterine - cholinergic receptor - chorionic gonadotropin - chromatid - chromatin - ciclosporin - chromatography - chromosomal crossover - chromosome - chromosome walking - cilium - circular dichroism - cis face - citric acid - citric acid cycle - cladistics - cloning - coenzyme - cofactor (biochemistry) - colchicine - collagen - colloid - colony-stimulating factor - colony stimulating factor 1 receptor - colorimeter - comparative biochemistry - competitive inhibition - complement 3A - complement 5A - complement factor B - complement membrane attack complex - complement receptor - complex - computational biology - computational chemistry - computational genomics - concanavalin A - concentration - concentration gradient - consensus sequence - conserved sequence - cooperative - cooperative binding - cooperativity - cooperativity cellular respiration - corticotropin - corticotropin receptor - corticotropin-releasing hormone - corticotropin-releasing hormone receptor - cotransport metabolism - covalent bond - covalent radius - CpG island - cristae - cryptobiology - crystal structure - crystallography - cuticula - CXCR4 receptor - cyclic AMP receptor - cyclic AMP receptor protein - cyclic AMP-responsive DNA-binding protein - cyclic electron flow - cyclic nucleotide - cyclic peptide - cyclin - cyclin A - cyclin B - cyclin E - cyclin-dependent kinase - cycloleucine - cyclosporin - cyclosporine - cystatin - cysteine - cystic fibrosis transmembrane conductance regulator - cytochrome B - cytochrome C - cytochrome P-450 - cytochrome P-450 CYP1A1 - cytochrome C oxidase - cytokine receptor - cytoplasm - cytoplasmic and nuclear receptor - cytosine - cytoskeletal protein - cytoskeleton - cytosol - cytotoxic T cell | 1 | Applied and Interdisciplinary Chemistry |
Cannon has conducted research in the field of mammalian thermogenesis. Her research portfolio includes 185 original articles, as well as 125 invited review articles and book chapters. Notably, she authored a fundamental review on brown adipose tissue function in Physiological Reviews and a paradigm-changing review article for the American Journal of Physiology where she presented findings from radiology literature suggesting the existence of brown adipose tissue in adult humans. | 1 | Applied and Interdisciplinary Chemistry |
After a chloroplast polypeptide is synthesized on a ribosome in the cytosol, ATP energy can be used to phosphorylate, or add a phosphate group to many (but not all) of them in their transit sequences. Serine and threonine (both very common in chloroplast transit sequences—making up 20–30% of the sequence) are often the amino acids that accept the phosphate group. The enzyme that carries out the phosphorylation is specific for chloroplast polypeptides, and ignores ones meant for mitochondria or peroxisomes.
Phosphorylation changes the polypeptide's shape, making it easier for 14-3-3 proteins to attach to the polypeptide. In plants, 14-3-3 proteins only bind to chloroplast preproteins. It is also bound by the heat shock protein Hsp70 that keeps the polypeptide from folding prematurely. This is important because it prevents chloroplast proteins from assuming their active form and carrying out their chloroplast functions in the wrong place—the cytosol. At the same time, they have to keep just enough shape so that they can be recognized and imported into the chloroplast.
The heat shock protein and the 14-3-3 proteins together form a cytosolic guidance complex that makes it easier for the chloroplast polypeptide to get imported into the chloroplast.
Alternatively, if a chloroplast preprotein's transit peptide is not phosphorylated, a chloroplast preprotein can still attach to a heat shock protein or Toc159. These complexes can bind to the TOC complex on the outer chloroplast membrane using GTP energy. | 0 | Theoretical and Fundamental Chemistry |
Carbon dioxide, a greenhouse gas, traps heat in the atmosphere, the bionic leaf can potentially be used to reduce the carbon dioxide within the atmosphere. While the bionic leaf is running mimics photosynthesis by converting the carbon dioxide in air into fuels. The bionic leaf can eliminate 180 grams of carbon dioxide out of 230,000 liters of air for each kilowatt hour of energy it consumes. While removing large amounts of carbon dioxide from the atmosphere not possible yet on a large scale, this technology is useful in areas where carbon dioxide is produced such as power plants. It can also be implemented within urban areas, providing clean air to the area. The technology may also be used on a smaller scale, helping communities produce, harness, and consume the require energy they need. | 0 | Theoretical and Fundamental Chemistry |
The chemical composition of slag can reveal much about the smelting process. XRF is the most commonly used tool in analysing the chemical composition of slag. Through chemical analysis, the composition of the charge, the firing temperature, the gas atmosphere and the reaction kinetics can be determined.
Ancient slag composition is usually a quaternary eutectic system CaO-SiO-FeO-AlO simplified to CaO-SiO-FeO, giving a low and uniform melting point. In some circumstances, the eutectic system was created according to the proportion of silicates to metal oxides in the gangue, together with the type of ore and the furnace lining. In other instances, a flux was required to achieve the correct system.
The melting temperature of slag can be determined by plotting its chemical composition in a ternary plot.
The viscosity of slag can be calculated through its chemical composition with equation:
where is the index of viscosity.
With recent advances in rotational viscometry techniques, viscosities of iron oxide slags are also widely undertaken. Coupled with phase equilibria studies, these analysis provide a better understanding of physico-chemical behaviour of slags at high temperatures.
In the early stages of smelting, the separation between melting metal and slag is not complete. Hence, the main, minor and trace elements of metal in the slag can be indicators of the type of ore used in the smelting process. | 1 | Applied and Interdisciplinary Chemistry |
The reactive enodiolate species is also sensitive to oxygen (O), which results in the dual carboxylase / oxygenase activity of RuBisCO. This reaction is considered wasteful as it produces products (3-phosphoglycerate and 2-phosphoglycolate) that must be catabolized through photorespiration. This process requires energy and is a missed-opportunity for CO fixation, which results in the net loss of carbon fixation efficiency for the organism. The dual carboxylase / oxygenase activity of RuBisCO is exacerbated by the fact that O and CO are small, relatively indistinguishable molecules that can bind only weakly, if at all, in Michaelis-Menten complexes. There are four forms of RuBisCO (Form I, II, III, and IV), with Form I being the most abundantly used form. Form I is used extensively by higher plants, eukaryotic algae, cyanobacteria, and Pseudomonadota (formerly proteobacteria). Form II is also used but much less widespread, and can be found in some species of Pseudomonadota and in dinoflagellates. RuBisCOs from different photosynthetic organisms display varying abilities to distinguish between CO and O. This property can be quantified and is termed "specificity" (S). A higher value of S means that a RuBisCO's carboxylase activity is greater than its oxygenase activity. | 0 | Theoretical and Fundamental Chemistry |
Dipalmitoylphosphatidylcholine (DPPC) is a phospholipid with two 16-carbon saturated chains and a phosphate group with quaternary amine group attached. The DPPC is the strongest surfactant molecule in the pulmonary surfactant mixture. It also has a higher compaction capacity than the other phospholipids, because the apolar tail is less bent. Nevertheless, without the other substances of the pulmonary surfactant mixture, the DPPCs adsorption kinetics is very slow. This happens primarily because the phase transition temperature between gel to liquid crystal of pure DPPC is 41.5 °C, which is higher than the human bodys temperature of 37 °C. | 0 | Theoretical and Fundamental Chemistry |
Scheme 3: The scheme illustrates the first displacement, the rate determining step and slowest step, where the starting material is converted to the iodo-intermediate. The intermediate is not detectable as it is rapidly converted to the unsaturated sugar. Experiments with azide instead of the iodide confirmed attack occurs at the C-3 as nitrogen-intermediates were isolated. The order of reactivity from most reactive to least reactive is: β-glucopyranosides > β-mannopyranosides > α-glucopyranosides> α-mannopyranosides.
The reaction of β–mannopyranosides gives low yields and required longer reaction times than with β-glucopyranosides due to the presence of a neighboring axial substituent (sulfonyloxy) relative to C-3 sulfonyloxy group in the starting material. The axial substituent increases the steric interactions in the transition state, causing unfavorable eclipsing of the two sulfonyloxy groups. α-Glucopyranosides possess a β-trans-axial substituent relative to C-3 sulfonyloxy (anomeric OCH group) in the starting material. The β-trans-axial substituent influences the transition state by also causing an unfavorable steric interaction between the two groups. In the case of α-mannopyranosides, both a neighboring axial substituent (2-sulfonyloxy group) and a β-trans-axial substituent (anomeric OCH group) are present, therefore significantly increasing the reaction time and decreasing the yield. | 0 | Theoretical and Fundamental Chemistry |
Froth flotation is a process for separating minerals from gangue by exploiting differences in their hydrophobicity. Hydrophobicity differences between valuable minerals and waste gangue are increased through the use of surfactants and wetting agents. The flotation process is used for the separation of a large range of sulfides, carbonates and oxides prior to further refinement. Phosphates and coal are also upgraded (purified) by flotation technology. "Grade-recovery curves" are tools for weighing the trade-off of producing a high grade of concentrate vs cost. These curves only compare the grade-recovery relations of a specific feed grade and feed rate. | 1 | Applied and Interdisciplinary Chemistry |
Last but not least prof. E.J.Zoqui has summarized in his work the approach proposed by several researchers in the criteria for semi-solid processing, which involves the stability of the solid phase fs with the temperature; to process semisolid alloys the sensitivity to variation of solid fraction with temperature should be minimal: in one direction it could evolve to a difficult to deform solid, on the other to a liquid which may be difficult to shape without proper moulding. It turns out that we can express this criterion again by evaluating the slope of the solidification curve, in fact ∂(fS)/∂T should be less than a certain threshold, which is commonly accepted in the scientific and technical literature to be below 0.03 1/K. Mathematically this may be expressed by an inequation, ∂(fS)/∂T < 0.03 (1/K) - where K stands for Kelvin degrees - could be equally assumed for a rough estimate of the two main semi-solid casting processing: both rheocasting ( 0.3<fs<0.4 ) and thixoforming (0.6<fs<0.7). If one would go back just to the (numerical) and functional approaches above, one should consider the reciprocal value i.e. ∂T/∂(fS)> 33 (K) | 1 | Applied and Interdisciplinary Chemistry |
The sigma (σ) phase is an intermetallic compound known as the one without definite stoichiometric composition and formed at the electron/atom ratio range of 6.2 to 7. It has a primitive tetragonal unit cell with 30 atoms. CrFe is a typical alloy crystallizing in the σ phase at the equiatomic composition. With physical properties adjustable based on its structural components, or its chemical composition provided a given structure.
The μ phase has an ideal AB stoichiometry, with its prototype WFe, containing rhombohedral cell with 13 atoms. While many other Frank-Kasper alloy types have been identified, more continue to be found. The alloy NbNiAl is the prototype for the M phase. It has orthorhombic space group with 52 atoms per unit cell. The alloy CrMoNi is the prototype for the P-phase. It has a primitive orthorhombic cell with 56 atoms. The alloy CoCrMo is the prototype for the R-phase which belongs to the rhombohedral space group with 53 atoms per cell. | 1 | Applied and Interdisciplinary Chemistry |
Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible (400–750 nm), or infrared radiation (750–2500 nm).
In nature, photochemistry is of immense importance as it is the basis of photosynthesis, vision, and the formation of vitamin D with sunlight. It is also responsible for the appearance of DNA mutations leading to skin cancers.
Photochemical reactions proceed differently than temperature-driven reactions. Photochemical paths access high-energy intermediates that cannot be generated thermally, thereby overcoming large activation barriers in a short period of time, and allowing reactions otherwise inaccessible by thermal processes. Photochemistry can also be destructive, as illustrated by the photodegradation of plastics. | 0 | Theoretical and Fundamental Chemistry |
*Hilal-i-Imtiaz (2003)
*Sitara-e-Imtiaz (1999)
* President, Pakistan Materials Research Society
*Fellow, Pakistan Institute of Metallurgical Engineers
*Fellow of Pakistan Nuclear Society | 0 | Theoretical and Fundamental Chemistry |
A later paper by Edwards and Pearson, following research done by Jencks and Carriuolo in 1960 led to the discovery of an additional factor in nucleophilic reactivity, which Edwards and Pearson called the alpha effect, where nucleophiles with a lone pair of electrons on an atom adjacent to the nucleophilic center have enhanced reactivity. The alpha effect, basicity, and polarizability are still accepted as the main factors in determining nucleophilic reactivity. As such, the Edwards equation is applied in a qualitative sense much more frequently than in a quantitative one.
In studying nucleophilic reactions, Edwards and Pearson noticed that for certain classes of nucleophiles most of the contribution of nucleophilic character originated from their basicity, resulting in large β values. For other nucleophiles, most of the nucleophilic character came from their high polarizability, with little contribution from basicity, resulting in large α values. This observation led Pearson to develop his hard-soft acid-base theory, which is arguably the most important contribution that the Edwards equation has made to current understanding of organic and inorganic chemistry. Nucleophiles, or bases, that were polarizable, with large α values, were categorized as “soft”, and nucleophiles that were non-polarizable, with large β and small α values, were categorized as “hard”.
The Edwards equation parameters have since been used to help categorize acids and bases as hard or soft, due to the approach's simplicity. | 0 | Theoretical and Fundamental Chemistry |
It was not until 1666 that Isaac Newton showed that white lights from the sun could be dissipated into a continuous series of colors. So Newton introduced the concept which he called spectrum to describe this phenomenon. He used a small aperture to define the beam of light, a lens to collimate it, a glass prism to disperse it, and a screen to display the resulting spectrum. Newtons analysis of light was the beginning of the science of Later, It became clear that the Suns radiation might have components outside the visible portion of the spectrum. In 1800 William Hershel showed that the suns radiation extended into [https://www.livescience.com/50260-infrared-radiation.html ], and in 1801 John Wilhelm Ritter also made a similar observation in the . Joseph Von Fraunhofer extended Newtons discovery by observing the suns spectrum when sufficiently dispersed was blocked by a fine dark lines now known as Fraunhofer also developed which disperses the lights in much the same way as does a glass prism but with some advantages. the grating applied interference of lights to produce provides a direct measuring of wavelengths of diffracted beams. So by extending Thomas Youngs study which demonstrated that a light beam passes slit emerges in patterns of light and dark edges Fraunhofer was able to directly measure the wavelengths of spectral lines. However, despite his enormous achievements, Fraunhofer was unable to understand the origins of the special line in which he observed. It was not until 33 years after his passing that Gustav Kirchhoff established that each element and compound has its unique spectrum and that by studying the spectrum of an unknown source, one could determine its chemical compositions, and with these advancements, spectroscopy became a truly scientific method of analyzing the structures of chemical compounds. Therefore, by recognizing that each atom and molecule has its spectrum Kirchhoff and Robert Bunsen established spectroscopy as a scientific tool for probing atomic and molecular structures and founded the field of spectrochemical analysis for analyzing the composition of materials. | 0 | Theoretical and Fundamental Chemistry |
Nonidet P-40 is a nonionic, non-denaturing detergent. Its official IUPAC name is octylphenoxypolyethoxyethanol.
Nonidet P-40 is sometimes abbreviated as NP-40, but should not be confused with a different detergent by the same name NP-40, nonylphenoxypolyethoxyethanol of the Tergitol NP series of Dow Chemicals.
Nonidet was a trademark of Shell Chemical Co. from 1956 to the early 2000s, but they no longer make it.
Nonidet P-40 is no longer sold by the chemical company Sigma-Aldrich. Sigma-Aldrich has replaced Nonidet P-40 with IGEPAL CA-630, which is described as a "nonionic, non-denaturing detergent". Sigma-Aldrich claims that IGEPAL CA-630 is "chemically indistinguishable from Nonidet P-40".
IGEPAL consists of octyl-phenoxy(polyoxyethylene)ethanol. Tergitol and the Sigma and BioChemica Nonidet P40 substitute detergents consist of nonyl-phenyl-polyethylene glycol. The original Shell Nonidet P-40 consisted of octyl-phenoxy(polyoxyethylene)ethanol, making IGEPAL the most comparable of the four substitutes. | 1 | Applied and Interdisciplinary Chemistry |
A pitot tube is used to measure fluid flow velocity. The tube is pointed into the flow and the difference between the stagnation pressure at the tip of the probe and the static pressure at its side is measured, yielding the dynamic pressure from which the fluid velocity is calculated using Bernoulli's equation. A volumetric rate of flow may be determined by measuring the velocity at different points in the flow and generating the velocity profile. | 1 | Applied and Interdisciplinary Chemistry |
Born in the city of Ipoh on 22 March 1973, she is the youngest of four children of William Stanley Walker Davidson (Salim Davidson), an Englishman and his ethnic Malay wife of mixed Arab and Thai descent, Sharifah Azaliah binti Syed Omar Shahabudin who is from Alor Setar, Kedah. She is also an extended member of Kedah Royal Family on her maternal side and has three elder brothers. Her father is a prominent lawyer in Perak and Kuala Lumpur.
Zara, who has a strong interest in foreign languages, studied at SMK Convent Ipoh and represented her school in squash and tennis from 1988 to 1990. She also represented Perak in swimming between 1981 and 1987.
After completing her A-Levels at Prime College in 1992, she left for the United Kingdom to study chemical engineering at the University of Nottingham and graduated with first class honours in July 1995. She also won the top student award for her final-year project.
Coincidentally her father-in-law, the late Sultan Azlan Shah, read law at the same university and was conferred the Bachelor of Laws degree in 1953 before being admitted to the English Bar in 1954. | 1 | Applied and Interdisciplinary Chemistry |
Growing crystals for X-ray crystallography can be quite difficult. For X-ray analysis, single perfect crystals are required. Typically a small amount (5–100 mg) of a pure compound is used, and crystals are allowed to grow very slowly. Several techniques can be used to grow these perfect crystals:
* Slow evaporation of a single solvent - typically the compound is dissolved in a suitable solvent and the solvent is allowed to slowly evaporate. Once the solution is saturated crystals can be formed.
* Slow evaporation of a multi-solvent system - the same as above, however as the solvent composition changes due to evaporation of the more volatile solvent. The compound is more soluble in the volatile solvent, and so the compound becomes increasingly insoluble in solution and crystallizes.
* Slow diffusion - similar to the above. However, a second solvent is allowed to evaporate from one container into a container holding the compound solution (gas diffusion). As the solvent composition changes due to an increase in the solvent that has gas diffused into the solution, the compound becomes increasingly insoluble in the solution and crystallizes.
* Interface/slow mixing (often performed in an NMR tube). Similar to the above, but instead of one solvent gas-diffusing into another, the two solvents mix (diffuse) by liquid-liquid diffusion. Typically a second solvent is "layered" carefully on top of the solution containing the compound. Over time the two solution mix. As the solvent composition changes due to diffusion, the compound becomes increasingly insoluble in solution and crystallizes, usually at the interface. Additionally, it is better to use a denser solvent as the lower layer, and/or a hotter solvent as the upper layer because this results in the slower mixing of the solvents.
* Specialized equipment can be used in the shape of an "H" to perform the above, where one of the vertical lines of the "H" is a tube containing a solution of the compound, and the other vertical line of the "H" is a tube containing a solvent which the compound is not soluble in, and the horizontal line of the "H" is a tube which joins the two vertical tubes, which also has a fine glass sinter that restricts the mixing of the two solvents.
* Once single perfect crystals have been obtained, it is recommended that the crystals are kept in a sealed vessel with some of the liquid of crystallization to prevent the crystal from drying out. Single perfect crystals may contain solvent of crystallization in the crystal lattice. Loss of this internal solvent from the crystals can result in the crystal lattice breaking down, and the crystals turning to powder. | 0 | Theoretical and Fundamental Chemistry |
Fluorescent black light tubes are typically made in the same fashion as normal fluorescent tubes except that a phosphor that emits UVA light instead of visible white light is used on the inside of the tube. The type most commonly used for black lights, designated blacklight blue or "BLB" by the industry, has a dark blue filter coating on the tube, which filters out most visible light, so that fluorescence effects can be observed. These tubes have a dim violet glow when operating. They should not be confused with "blacklight" or "BL" tubes, which have no filter coating, and have a brighter blue color. These are made for use in "bug zapper" insect traps where the emission of visible light does not interfere with the performance of the product. The phosphor typically used for a near 368 to 371 nanometer emission peak is either europium-doped strontium fluoroborate (:) or europium-doped strontium borate (:) while the phosphor used to produce a peak around 350 to 353 nanometres is lead-doped barium silicate (:). "Blacklight blue" lamps peak at 365 nm.
Manufacturers use different numbering systems for black light tubes. Philips uses one system which is becoming outdated (2010), while the (German) Osram system is becoming dominant outside North America. The following table lists the tubes generating blue, UVA and UVB, in order of decreasing wavelength of the most intense peak. Approximate phosphor compositions, major manufacturer's type numbers and some uses are given as an overview of the types available. "Peak" position is approximated to the nearest 10 nm. "Width" is the measure between points on the shoulders of the peak that represent 50% intensity. | 0 | Theoretical and Fundamental Chemistry |
Many invasive plant species interfere with native plants through allelopathy. A famous case of purported allelopathy is in desert shrubs. One of the most widely known early examples was Salvia leucophylla, because it was on the cover of the journal Science in 1964. Bare zones around the shrubs were hypothesized to be caused by volatile terpenes emitted by the shrubs. However, like many allelopathy studies, it was based on artificial lab experiments and unwarranted extrapolations to natural ecosystems. In 1970, Science published a study where caging the shrubs to exclude rodents and birds allowed grass to grow in the bare zones.
A detailed history of this story can be found in Halsey 2004.
Garlic mustard is another invasive plant species that may owe its success partly to allelopathy. Its success in North American temperate forests may be partly due to its excretion of glucosinolates like sinigrin that can interfere with mutualisms between native tree roots and their mycorrhizal fungi.
Allelopathy has been shown to play a crucial role in forests, influencing the composition of the vegetation growth, and also provides an explanation for the patterns of forest regeneration. The black walnut (Juglans nigra) produces the allelochemical juglone, which affects some species greatly while others not at all. However, most of the evidence for allelopathic effects of juglone come from laboratory assays and it thus remains controversial to what extent juglone affects the growth of competitors under field conditions. The leaf litter and root exudates of some Eucalyptus species are allelopathic for certain soil microbes and plant species. The tree of heaven, Ailanthus altissima, produces allelochemicals in its roots that inhibit the growth of many plants. Spotted knapweed (Centaurea) is considered an invasive plant that also utilizes allelopathy.
Another example of allelopathy is seen in Leucaena leucocephala, known as the miracle tree. This plant contains toxic amino acids that inhibit other plants’ growth but not its own species growth. Different crops react differently to these allelochemicals, so wheat yield decreases, while rice increases in the presence of L. leucocephala.
Capsaicin is an allelochemical found in many peppers that are cultivated by humans as a spice/food source. It is considered an allelochemical because it is not required for plant growth and survival, but instead deters herbivores and prevents other plants from sprouting in its immediate vicinity. Among the plants it has been studied on are grasses, lettuce, and alfalfa, and on average, it will inhibit the growth of these plants by about 50%. Capsaicin has been shown to deter both herbivores and certain parasites’ performance. Herbivores such as caterpillars show decreased development when fed a diet high in capsaicin. | 1 | Applied and Interdisciplinary Chemistry |
Following application of the patch to humans, an average of 25% to 30% of the selegiline content is delivered systemically over 24 hours. Transdermal dosing results in significantly higher exposure to selegiline and lower exposure to all metabolites when compared to oral dosing; this is due to the extensive first-pass metabolism of the pill form and low first-pass metabolism of the patch form. The site of application is not a significant factor in how the drug is distributed. In humans, selegiline does not accumulate in the skin, nor is it metabolized there. | 0 | Theoretical and Fundamental Chemistry |
The metabolism of xenobiotics is often divided into three phases: modification, conjugation, and excretion. These reactions act in concert to detoxify xenobiotics and remove them from cells. | 1 | Applied and Interdisciplinary Chemistry |
Fiona C. Meldrum is a British scientist who is a Professor of Inorganic Chemistry at the University of Leeds where she works on bio-inspired materials and crystallisation processes. She won the 2017 Royal Society of Chemistry Interdisciplinary Prize. | 0 | Theoretical and Fundamental Chemistry |
The Central Interstate Low Level Radioactive Waste Compact is made up of the states of Louisiana, Arkansas, Oklahoma, and Kansas. The compact was established by the "Compact Law" and the "Low-Level Radioactive Waste Policy Amendments of the 1985."
The Central Interstate Low Level Radioactive Waste Compact and US Ecology purchased land 2 miles west of Butte, Nebraska in the early 1990s with the intention of placing a dump site there. There was extensive controversy and the dump site was eventually removed from consideration.
Citizens and factions throughout Boyd County, where Butte is located, fought for over 15 years over the placement of a disposal site in this area. Nebraska governors Kay Orr and Ben Nelson were heavily involved on different sides of the issue.
Nebraska was officially removed from the compact after a series of long court battles that ended in 2004. The state of Nebraska had to pay a settlement and there have been attempts made to sell the compact's land just outside Butte. | 0 | Theoretical and Fundamental Chemistry |
Osmotic concentration, formerly known as osmolarity, is the measure of solute concentration, defined as the number of osmoles (Osm) of solute per litre (L) of solution (osmol/L or Osm/L). The osmolarity of a solution is usually expressed as Osm/L (pronounced "osmolar"), in the same way that the molarity of a solution is expressed as "M" (pronounced "molar"). Whereas molarity measures the number of moles of solute per unit volume of solution, osmolarity measures the number of osmoles of solute particles per unit volume of solution. This value allows the measurement of the osmotic pressure of a solution and the determination of how the solvent will diffuse across a semipermeable membrane (osmosis) separating two solutions of different osmotic concentration. | 0 | Theoretical and Fundamental Chemistry |
Huntingtons disease (HD) is an inherited neurodegenerative disorder, with symptoms emerging during an individuals mid-adulthood. The most noticeable symptoms of this progressive disease are cognitive and motor impairments, as well as behavioral alterations. These impairments can develop into dementia, chorea, and eventually death. At the molecular level, HD results from a mutation in the huntingtin protein (Htt). More specifically, there is an abnormal repetition of a CAG sequence towards the 5’-end of the gene, which then leads to the development of a toxic polyglutamine (polyQ) stretch in the protein. The mutated Htt protein affects an individual's proper neural functions by inhibiting the action of REST/NRSF.
REST/NRSF is an important silencer element that binds to regulatory regions to control the expression of certain proteins involved in neural functions. The mechanistic actions of huntingtin are still not fully understood, but a correlation between Htt and REST/NRSF exists in HD development. By attaching to the REST/NRSF, the mutated huntingtin protein inhibits the action of the silencer element, and retains it in the cytosol. Thus, REST/NRSF cannot enter the nucleus and bind to the 21 base-pair RE-1/NRSE regulatory element. An adequate repression of specific target genes are of fundamental importance, as many are involved in the proper development of neuronal receptors, neurotransmitters, synaptic vesicle proteins, and channel proteins. A deficiency in the proper development of these proteins can cause the neural dysfunctions seen in Huntingtons disease. In addition to the lack of repression due to the inactive REST/NRSF, mutated huntingtin protein can also decrease the transcription of the brain-derived neurotropic factor (BDNF) gene. BDNF influences the survival and development of neurons in the central nervous system as well as the peripheral nervous system. This abnormal repression occurs when the RE1/NRSE region within the BDNF promoter region is activated by the binding of REST/NRSF, which leads to the lack of transcription of the BDNF gene. Hence, the anomalous repression of the BDNF protein suggests a significant impact in Huntingtons disease. | 1 | Applied and Interdisciplinary Chemistry |
Pharmacodynamic (PD) biomarkers can measure the direct interaction between a drug and its receptor. Pharmacodynamic biomarkers reveal drug mechanisms, if the drug has its intended effect on the biology of the disease, ideal biological dosing concentrations, and physiologic response/resistance mechanisms. Pharmacodynamic biomarkers are particularly relevant in drug mechanisms of tumor cells, where pharmacodynamic endpoints for drug interventions can be assessed directly on tumor tissues. For example, protein phosphorylation biomarkers indicate alterations in target protein kinases and activation of downstream signaling molecules. | 1 | Applied and Interdisciplinary Chemistry |
The term "oxidation state" in English chemical literature was popularized by Wendell Mitchell Latimer in his 1938 book about electrochemical potentials. He used it for the value (synonymous with the German term Wertigkeit) previously termed "valence", "polar valence" or "polar number" in English, or "oxidation stage" or indeed the "state of oxidation". Since 1938, the term "oxidation state" has been connected with electrochemical potentials and electrons exchanged in redox couples participating in redox reactions. By 1948, IUPAC used the 1940 nomenclature rules with the term "oxidation state", instead of the original valency. In 1948 Linus Pauling proposed that oxidation number could be determined by extrapolating bonds to being completely ionic in the direction of electronegativity. A full acceptance of this suggestion was complicated by the fact that the Pauling electronegativities as such depend on the oxidation state and that they may lead to unusual values of oxidation states for some transition metals. In 1990 IUPAC resorted to a postulatory (rule-based) method to determine the oxidation state. This was complemented by the synonymous term oxidation number as a descendant of the Stock number introduced in 1940 into the nomenclature. However, the terminology using "ligands" gave the impression that oxidation number might be something specific to coordination complexes. This situation and the lack of a real single definition generated numerous debates about the meaning of oxidation state, suggestions about methods to obtain it and definitions of it. To resolve the issue, an IUPAC project (2008-040-1-200) was started in 2008 on the "Comprehensive Definition of Oxidation State", and was concluded by two reports and by the revised entries "Oxidation State" and "Oxidation Number" in the IUPAC Gold Book. The outcomes were a single definition of oxidation state and two algorithms to calculate it in molecular and extended-solid compounds, guided by Allen electronegativities that are independent of oxidation state. | 0 | Theoretical and Fundamental Chemistry |
A subclass of acylureas known as benzoylureas are insecticides. They act as insect growth regulators by inhibiting the synthesis of chitin resulting in weakened cuticles and preventing molting. Members of this class include diflubenzuron, flufenoxuron, hexaflumuron, lufenuron, and teflubenzuron. | 0 | Theoretical and Fundamental Chemistry |
Similar to Pourbaix diagrams for the speciation of redox species as a function of the redox potential and the pH, ionic partition diagrams indicate in which phase an acid or a base is predominantly present in a biphasic system as a function of the Galvani potential difference
between the two phases and the pH of the aqueous solution | 0 | Theoretical and Fundamental Chemistry |
The data analysis becomes more demanding if there are competing parallel dissociation channels or if the dissociation at threshold is too slow to be observed on the time scale (several μs) of the experiment. In the first case, the slower dissociation channel will appear only at higher energies, an effect called competitive shift, whereas in the second, the resulting kinetic shift means that the fragmentation will only be observed at some excess energy, i.e. only when it is fast enough to take place on the experimental time scale. When several dissociation steps follow sequentially, the second step typically occurs at high excess energies: the system has much more internal energy than needed for breaking the weakest bond in the parent ion. Some of this excess energy is retained as internal energy of the fragment ion, some may be converted into the internal energy of the leaving neutral fragment (invisible to mass spectrometry) and the rest is released as kinetic energy, in that the fragments fly apart at some non-zero velocity.
More often than not, dissociative photoionization processes can be described within a statistical framework, similarly to the approach used in collision-induced dissociation experiments. If the ergodic hypothesis holds, the system will explore each region of the phase space with a probability according to its volume. A transition state (TS) can then be defined in the phase space, which connects the dissociating ion with the dissociation products, and the dissociation rates for the slow or competing dissociations can be expressed in terms of the TS phase space volume vs. the total phase space volume. The total phase space volume is calculated in a microcanonical ensemble using the known energy and the density of states of the dissociating ion. There are several approaches how to define the transition state, the most widely used being RRKM theory. The unimolecular dissociation rate curve as a function of energy, k(E), vanishes below the dissociative photoionization energy, E.
Statistical theory can also be used in the microcanonical formalism to describe the excess energy partitioning in sequential dissociation steps, as proposed by Klots for a canonical ensemble. Such a statistical approach was used for more than a hundred systems to determine accurate dissociative photoionization onsets, and derive thermochemical information from them.
Furthermore, algorithms based on probabilistic Bayesian analyses are known to considerably reduce systematic biases induced by false coincidences. The intensity of these false coincidences can big strong enough to appear as a separate peaks in the signal and complicate the analysis of the spectra. | 0 | Theoretical and Fundamental Chemistry |
Von Kármán swirling flow is a flow created by a uniformly rotating infinitely long plane disk, named after Theodore von Kármán who solved the problem in 1921. The rotating disk acts as a fluid pump and is used as a model for centrifugal fans or compressors. This flow is classified under the category of steady flows in which vorticity generated at a solid surface is prevented from diffusing far away by an opposing convection, the other examples being the Blasius boundary layer with suction, stagnation point flow etc. | 1 | Applied and Interdisciplinary Chemistry |
Capsazepine (fig. 4a), the first competitive vanilloid antagonist, reported by Novartis group, was aimed at assessing the effect of conformational constraint on the lipophilic C-region of capsaicin. In capsazepine the amide bond of the capsaicin is replaced by a thiourea moiety and a propylidene linker between the aromatic vanillyl 2-carbon A ring and the B-linker amide nitrogen forces the aromatic ring in an orthogonal orientation with respect to the thiourea bond. This constraint has long been considered as the distinctive characteristic of vanilloid antagonism. Capsazepine competes for the capsaicin-binding site on TRPV1 however, due to low metabolic stability and poor pharmacokinetic properties the compound did not reach into clinical development. It was observed later on that this tether was not critical for activity as powerful antagonists free from this structural feature were developed, with 1,3-di(arylalkyl)thioureas emerging as one of the most promising non-vanilloid class of TRPV1 antagonist showing excellent therapeutical potential in pain regulation. Within these compounds, the replacement of the guaiacyl moiety of capsaicinoids with a 3-fluoro-4-sulfonylamido group found critical to revert activity. This led to the design of C-region moiety mimicked on RTX, led to compound seen in figure 4b, that showed excellent analgesic activity in mice. An alternative optimization of the lipophilic C region led to JYL1421 (fig. 4c), another promising clinical candidate. | 1 | Applied and Interdisciplinary Chemistry |
Bands of alternating light and dark in the positive column are called striations. There is no universal mechanism explaining the striations for all conditions of gas and pressure producing them, but recent theoretical and modelling studies, supported with experimental results, mention the importance of the Dufour effect. | 0 | Theoretical and Fundamental Chemistry |
The concept of replacing hydrogen with deuterium is an example of bioisosterism, whereby similar biological effects to a known drug are produced in an analog designed to confer superior properties. The first patent in the US granted for deuterated molecules was in the 1970s. Since then patents on deuterated drugs have become more common.
The applications of the deuterium isotope effect has increased over time, and it is now applied extensively in mechanistic studies of the metabolism of drugs as well as other studies focused on pharmacokinetics (PK), efficacy, tolerability, bioavailability, and safety. The introduction of deuterated drug candidates that began in the 1970s evolved from earlier work with deuterated metabolites. However, it took more than 40 years for the first deuterated drug, Austedo® (deutetrabenazine), to be approved by the FDA. Numerous publications have discussed the advantages and disadvantages of deuterated drugs.
A number of publications have discussed aspects of intellectual property of deuterated versions of drugs. | 1 | Applied and Interdisciplinary Chemistry |
Alfred Burger served as its first editor-in-chief before passing on the mantle to Richard Glennon (Virginia Commonwealth University). Stephen J. Cutler (University of South Carolina) then took over and served between 2002 and 2019. Longqin Hu (Rutgers University–New Brunswick) became editor in 2020. | 1 | Applied and Interdisciplinary Chemistry |
The use of radioactive tracer elements in ion uptake assays allows the calculation of km, Ki and Vmax and determines the initial change in the ion content of the cells. Mg decays by the emission of a high-energy beta or gamma particle, which can be measured using a scintillation counter. However, the radioactive half-life of Mg, the most stable of the radioactive magnesium isotopes, is only 21 hours. This severely restricts the experiments involving the nuclide. Also, since 1990, no facility has routinely produced Mg, and the price per mCi is now predicted to be approximately US$30,000. The chemical nature of Mg is such that it is closely approximated by few other cations. However, Co, Mn and Ni have been used successfully to mimic the properties of Mg in some enzyme reactions, and radioactive forms of these elements have been employed successfully in cation transport studies. The difficulty of using metal ion replacement in the study of enzyme function is that the relationship between the enzyme activities with the replacement ion compared to the original is very difficult to ascertain. | 1 | Applied and Interdisciplinary Chemistry |
Foods and beverages contain numerous aromatic compounds, some naturally present in the raw materials and some forming during processing. GC–MS is extensively used for the analysis of these compounds which include esters, fatty acids, alcohols, aldehydes, terpenes etc. It is also used to detect and measure contaminants from spoilage or adulteration which may be harmful and which is often controlled by governmental agencies, for example pesticides. | 0 | Theoretical and Fundamental Chemistry |
RNA molecules that do not code for any proteins still maintain a function in the cell. The function of the RNA depends on its classification. These roles include:
* aiding protein synthesis
* catalyzing reactions
* regulating various processes.
Protein synthesis is aided by functional RNA molecules such as tRNA, which helps add the correct amino acid to a polypeptide chain during translation, rRNA, a major component of ribosomes (which guide protein synthesis), as well as mRNA which carry the instructions for creating the protein product.
One type of functional RNA involved in regulation are microRNA (miRNA), which works by repressing translation. These miRNAs work by binding to a complementary target mRNA sequence to prevent translation from occurring. Short-interfering RNA (siRNA) also work by negative regulation of transcription. These siRNA molecules work in RNA-induced silencing complex (RISC) during RNA interference by binding to a target DNA sequence to prevent transcription of a specific mRNA. | 1 | Applied and Interdisciplinary Chemistry |
VIPA devices have been commercialized by LightMachinery as spectral disperser devices or components with various customized design parameters. | 0 | Theoretical and Fundamental Chemistry |
The micro-atmosphere method is an antimicrobial testing method involving the use of potentially bacteriostatic or fungicidal compounds which are obtained from the volatile oils of plants, such as citronella grass. This method involves the use of essential oils, a growth medium, a selection of bacterial or cultures and an incubator. | 1 | Applied and Interdisciplinary Chemistry |
The source of adhesive forces, according to the dispersive adhesion mechanism, is the weak interactions that occur between molecules close together. These interactions include London dispersion forces, Keesom forces, Debye forces and hydrogen bonds. Individually, these attractions are not very strong, but when summed over the bulk of a material, they can become significant. | 0 | Theoretical and Fundamental Chemistry |
In biological systems, methylation is accomplished by enzymes. Methylation can modify heavy metals and can regulate gene expression, RNA processing, and protein function. It is a key process underlying epigenetics. Sources of methyl groups include S-methylmethionine, methyl folate, methyl B12. | 0 | Theoretical and Fundamental Chemistry |
The AFM was invented by IBM scientists in 1985. The precursor to the AFM, the scanning tunneling microscope (STM), was developed by Gerd Binnig and Heinrich Rohrer in the early 1980s at IBM Research – Zurich, a development that earned them the 1986 Nobel Prize for Physics. Binnig invented the atomic force microscope and the first experimental implementation was made by Binnig, Quate and Gerber in 1986.
The first commercially available atomic force microscope was introduced in 1989. The AFM is one of the foremost tools for imaging, measuring, and manipulating matter at the nanoscale. | 0 | Theoretical and Fundamental Chemistry |
All biologically active elements exist in a number of different isotopic forms, of which two or more are stable. For example, most carbon is present as C, with approximately 1% being C. The ratio of the two isotopes may be altered by biological and geophysical processes, and these differences can be utilized in a number of ways by ecologists.
The main elements used in isotope ecology are carbon, nitrogen, oxygen, hydrogen and sulfur, but also include silicon, iron, and strontium. | 0 | Theoretical and Fundamental Chemistry |
There is an additional multiplex advantage for emission lines of atomic and molecular spectra. At the peak of the emission line, a monochromator measurement will be noisy, since the noise is proportional to the square root of the signal. For the same reason, the measurement will be less noisy at the baseline of the spectrum. In a multiplexed measurement, however, the noise in a given measurement is spread more or less evenly across the spectrum, regardless of the local signal intensity. Thus, multiplexed measurements can achieve higher SNR at the emission line peaks. There is a corresponding multiplex disadvantage, however. When the signals of interest are absorption lines in the spectrum, then the same principle will produce increased noise at the valleys of the absorption lines relative to the noise of a scanning monochromator. | 0 | Theoretical and Fundamental Chemistry |
The first use of epitope tagging was described by Munro and Pelham in 1984. The FLAG-tag was the second example of a fully functional, improved epitope tag, published in the scientific literature. and was the only epitope tag to be patented. It has since become one of the most commonly used protein tags in laboratories worldwide. Unlike some other tags (e.g. myc, HA), where a monoclonal antibody was first isolated against an existing protein, then the epitope was characterized and used as a tag, the FLAG epitope was an idealized, artificial design, to which monoclonal antibodies were raised. The FLAG-tag's sequence was optimized for compatibility with proteins it is attached to, in that FLAG-tag is more hydrophilic than other common epitope tags and therefore less likely to reduce the activity of proteins to which FLAG-tag is appended. In addition, N-terminal FLAG tags can be removed readily from proteins once they have been isolated, by treatment with the specific protease, enterokinase (enteropeptidase).
The third report of epitope tagging, (HA-tag), appeared about one year after the Flag system had been first shipped. | 1 | Applied and Interdisciplinary Chemistry |
:V09EA01 Technetium (Tc) pentetic acid
:V09EA02 Technetium (Tc) technegas
:V09EA03 Technetium (Tc) nanocolloid | 1 | Applied and Interdisciplinary Chemistry |
After clearing and labeling, tissues are typically imaged using confocal microscopy, two-photon microscopy, or one of the many variants of light-sheet fluorescence microscopy. Other less commonly used methods include optical projection tomography and stimulated Raman scattering. | 1 | Applied and Interdisciplinary Chemistry |
The Froude–Krylov force can be calculated from:
where
* is the Froude–Krylov force,
* is the wetted surface of the floating body,
* is the pressure in the undisturbed waves and
* the body's normal vector pointing into the water.
In the simplest case the formula may be expressed as the product of the wetted surface area (A) of the floating body, and the dynamic pressure acting from the waves on the body:
The dynamic pressure, , close to the surface, is given by:
where
* is the sea water density (approx. 1030 kg/m)
* is the acceleration due to the earth's gravity (9.81 m/s)
* is the wave height from crest to trough. | 1 | Applied and Interdisciplinary Chemistry |
In analytical chemistry, the detection limit, lower limit of detection, also termed LOD for limit of detection or analytical sensitivity (not to be confused with statistical sensitivity), is the lowest quantity of a substance that can be distinguished from the absence of that substance (a blank value) with a stated confidence level (generally 99%). The detection limit is estimated from the mean of the blank, the standard deviation of the blank, the slope (analytical sensitivity) of the calibration plot and a defined confidence factor (e.g. 3.2 being the most accepted value for this arbitrary value). Another consideration that affects the detection limit is the adequacy and the accuracy of the model used to predict concentration from the raw analytical signal.
As a typical example, from a calibration plot following a linear equation taken here as the simplest possible model:
where, corresponds to the signal measured (e.g. voltage, luminescence, energy, etc.), "" the value in which the straight line cuts the ordinates axis, "" the sensitivity of the system (i.e., the slope of the line, or the function relating the measured signal to the quantity to be determined) and "" the value of the quantity (e.g. temperature, concentration, pH, etc.) to be determined from the signal , the LOD for "" is calculated as the "" value in which equals to the average value of blanks "" plus "" times its standard deviation "" (or, if zero, the standard deviation corresponding to the lowest value measured) where "" is the chosen confidence value (e.g. for a confidence of 95% it can be considered = 3.2, determined from the limit of blank).
Thus, in this didactic example:
There are a number of concepts derived from the detection limit that are commonly used. These include the instrument detection limit (IDL), the method detection limit (MDL), the practical quantitation limit (PQL), and the limit of quantitation (LOQ). Even when the same terminology is used, there can be differences in the LOD according to nuances of what definition is used and what type of noise contributes to the measurement and calibration.
The figure below illustrates the relationship between the blank, the limit of detection (LOD), and the limit of quantitation (LOQ) by showing the probability density function for normally distributed measurements at the blank, at the LOD defined as 3 × standard deviation of the blank, and at the LOQ defined as 10 × standard deviation of the blank. (The identical spread along Abscissa of these two functions is problematic.) For a signal at the LOD, the alpha error (probability of false positive) is small (1%). However, the beta error (probability of a false negative) is 50% for a sample that has a concentration at the LOD (red line). This means a sample could contain an impurity at the LOD, but there is a 50% chance that a measurement would give a result less than the LOD. At the LOQ (blue line), there is minimal chance of a false negative. | 0 | Theoretical and Fundamental Chemistry |
In photo reduction the promoted electron of the metal oxide is accepted by an acceptor species. In the case of CO reduction, shown in the table below, the absence of dissolved oxygen in the aqueous system favors reduction of protons to form hydrogen radicals which then go on to reduce CO to HCOOH. HCOOH can then be further reduced to HCOH and water. Further reduction leads to the production of CH that can combine in a number of ways to produce CH or CH, etc. | 0 | Theoretical and Fundamental Chemistry |
A simple modification to atom transfer radical polymerization (ATRP) was introduced in 2007 to kinetically control the polymerization by increasing the ratio of inactive copper(II) catalyst to active copper(I) catalyst. The modification to this strategy is termed deactivation enhanced ATRP, whereby different ratios of copper(II)/copper(I) are added. Alternatively a copper(II) catalyst may be used in the presence of small amounts of a reducing agent such as ascorbic acid to produce low percentages of copper(I) in situ and to control the ratio of copper (II)/copper (I). Deactivation enhanced ATRP features the decrease of the instantaneous kinetic chain length ν as defined by:,
<br />
meaning an average number of monomer units are added to a propagating chain end during each activation/deactivation cycle, The resulting chain growth rate is slowed down to allow sufficient control over the reaction thus greatly increasing the percentage of multi-vinyl monomers in the reaction system (even up to 100 percent (homopolymerization)). | 0 | Theoretical and Fundamental Chemistry |
In Canada, modafinil is not specifically included in the lists of controlled drugs and substances specified within the Controlled Drugs and Substances Act. However, it is classified as a Schedule F prescription drug. This means that modafinil can only be obtained legally with a valid prescription from a licensed health care practitioner in Canada, and the import of modafinil to Canada from other countries is subject to restrictions: importing prescription drugs without an import permit may result in the seizure of the drugs at the border, the refusal of entry of the drugs into Canada, or prosecution. | 0 | Theoretical and Fundamental Chemistry |
This method involves using time-dependent Navier-Stokes equation which is advantageous because of its inherent ability to evolve to the correct steady state solution.
The continuity, momentum and energy equations and some other situational equations are needed to solve the problem. MacCormack's time marching technique is applied and then using Taylor series expansion the flow field variables are advanced at each grid point. Then, initial boundary conditions are applied and solving equations will converge to approximated results.
These equations can be solved by using different algorithms to get better and efficient results with minimum errors. | 1 | Applied and Interdisciplinary Chemistry |
In organosulfur chemistry, a sulfonyl group can refer either to a functional group found primarily in sulfones, or to a substituent obtained from a sulfonic acid by the removal of the hydroxyl group, similarly to acyl groups. Sulfonyl groups can be written as having the general formula , where there are two double bonds between the sulfur and oxygen.
Sulfonyl groups can be reduced to the sulfide with DIBALH. Lithium aluminium hydride () reduces some but not all sulfones to sulfides.
In inorganic chemistry, when the group is not connected to any carbon atoms, it is referred to as sulfuryl. | 0 | Theoretical and Fundamental Chemistry |
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