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Karl Samuel Leberecht Hermann (20 January 1765 – 1 September 1846) was a German chemist who helped discover cadmium in 1817.
Cadmium was discovered in 1817 by a physician, Friedrich Stromeyer (1776–1835). The element was first found in the condensation of vapors (mixed with soot and zinc oxide) that rose out of a furnace in which zinc oxide was being roasted. Cadmium’s discovery is also loosely attributed to K.S.L. Hermann and J.C.H. Roloff who may have found cadmium in zinc oxide during the same year. A historical debate still remains as to who actually discovered the pure form of the element first.
The phase of scientific history in which Stromeyer was active was one in which chemical discovery was being accomplished primarily by pharmacists, apothecaries and physicians. The practice of alchemy was dying out, and chemistry was just beginning to emerge as a separate science. Stromeyer, a professor at the University of Göttingen, was testing zinc oxide, a medicine in those days, for purity.
The name of the element was derived from the Latin “cadmia” and the Greek “kadmeia,” both ancient names for calamine (zinc carbonate). | 1 | Applied and Interdisciplinary Chemistry |
A scleroscope is a device used to measure rebound hardness. It consists of a steel ball dropped from a fixed height. The device was invented in 1907. As an improvement on this rough method, the Leeb Rebound Hardness Test, invented in the 1970s, uses the ratio of impact and rebound velocities (as measured by a magnetic inducer) to determine hardness. | 1 | Applied and Interdisciplinary Chemistry |
Although geopolymerization does not rely on toxic organic solvents but only on water, it needs chemical ingredients that may be dangerous and therefore requires some safety procedures. Material Safety rules classify the alkaline products in two categories: corrosive products (named here: hostile) and irritant products (named here: friendly). The two classes are recognizable through their respective logos.
The table lists some alkaline chemicals and their corresponding safety label. The corrosive products must be handled with gloves, glasses and masks. They are user-hostile and cannot be implemented in mass applications without the appropriate safety procedures. In the second category one finds Portland cement or hydrated lime, typical mass products. Geopolymeric alkaline reagents belonging to this class may also be termed as User-friendly, although the irritant nature of the alkaline component and the potential inhalation risk of powders still require the selection and use of appropriate personal protective equipment, as in any situation where chemicals or powders are handled.
The development of so-called alkali-activated-cements or alkali-activated geopolymers (the latter considered by some to be incorrect terminology), as well as several recipes found in the literature and on the Internet, especially those based on fly ashes, use alkali silicates with molar ratios SiO:MO below 1.20, or systems based on pure NaOH (8M or 12M). These conditions are not user-friendly for the ordinary labor force, and require careful consideration of personal protective equipment if employed in the field. Indeed, laws, regulations, and state directives push to enforce for more health protections and security protocols for workers’ safety.
Conversely, Geopolymer cement recipes employed in the field generally involve alkaline soluble silicates with starting molar ratios ranging from 1.45 to 1.95, particularly 1.60 to 1.85, i.e. user-friendly conditions. It may happen that for research, some laboratory recipes have molar ratios in the 1.20 to 1.45 range. | 0 | Theoretical and Fundamental Chemistry |
The Z-factor (Z-prime factor) is defined in terms of four parameters: the means () and standard deviations () of both the positive (p) and negative (n) controls (, , and , ). Given these values, the Z-factor is defined as:
The Z'-factor is a characteristic parameter of the assay itself, without intervention of samples. | 1 | Applied and Interdisciplinary Chemistry |
In terms of its coordination properties, phenanthroline is similar to 2,2'-bipyridine (bipy) with the advantage that the two nitrogen donors are preorganized for chelation. Phenanthroline is a stronger base than bipy. According to one ligand ranking scale, phen is a weaker donor than bipy.
Several homoleptic complexes are known of the type [M(phen)]. Particularly well studied is [Fe(phen)], called "ferroin." It can be used for the photometric determination of Fe(II). It is used as a redox indicator with standard potential +1.06 V. The reduced ferrous form has a deep red colour and the oxidised form is light-blue. The pink complex [Ni(phen)] has been resolved into its Δ and Λ isomers. The complex [Ru(phen)] is bioactive.
Copper(I) forms [Cu(phen)], which is luminescent. | 0 | Theoretical and Fundamental Chemistry |
On 2 October 1798, Davy joined the Pneumatic Institution at Bristol. It had been established to investigate the medical powers of factitious airs and gases (gases produced experimentally or artificially), and Davy was to superintend the various experiments. The arrangement agreed between Dr Beddoes and Davy was generous, and enabled Davy to give up all claims on his paternal property in favour of his mother. He did not intend to abandon the medical profession and was determined to study and graduate at Edinburgh, but he soon began to fill parts of the institution with voltaic batteries. While living in Bristol, Davy met the Earl of Durham, who was a resident in the institution for his health. | 1 | Applied and Interdisciplinary Chemistry |
The Kinetic PreProcessor (KPP) is an open-source software tool used in atmospheric chemistry. Taking a set of chemical reactions and their rate coefficients as input, KPP generates Fortran 90, FORTRAN 77, C, or Matlab code
of the resulting ordinary differential equations (ODEs). Solving the ODEs allows the temporal integration of the kinetic system. Efficiency is obtained by exploiting the sparsity structures of the Jacobian and of the Hessian. A comprehensive suite of stiff numerical integrators is also provided. Moreover, KPP can be used to generate the tangent linear model, as well as the continuous and discrete adjoint models of the chemical system. | 0 | Theoretical and Fundamental Chemistry |
In the end of Feynmans paper, he states that, "Van der Waals forces can also be interpreted as arising from charge distributions with higher concentration between the nuclei. The Schrödinger perturbation theory for two interacting atoms at a separation , large compared to the radii of the atoms, leads to the result that the charge distribution of each is distorted from central symmetry, a dipole moment of order being induced in each atom. The negative charge distribution of each atom has its center of gravity moved slightly toward the other. It is not the interaction of these dipoles which leads to van der Waalss force, but rather the attraction of each nucleus for the distorted charge distribution of its own' electrons that gives the attractive force." | 0 | Theoretical and Fundamental Chemistry |
It once was a popular solvent in organic chemistry, but because of its adverse health effects, it is rarely used today. It is sometimes useful as a solvent for infrared spectroscopy, because there are no significant absorption bands above 1600 cm. Because carbon tetrachloride does not have any hydrogen atoms, it was historically used in proton NMR spectroscopy. In addition to being toxic, its dissolving power is low. Its use in NMR spectroscopy has been largely superseded by deuterated solvents (mainly deuterochloroform). The use of carbon tetrachloride in the determination of oil has been replaced by various other solvents, such as tetrachloroethylene. Because it has no C–H bonds, carbon tetrachloride does not easily undergo free-radical reactions. It is a useful solvent for halogenations either by the elemental halogen or by a halogenation reagent such as N-bromosuccinimide (these conditions are known as Wohl–Ziegler bromination). | 1 | Applied and Interdisciplinary Chemistry |
A thermometric titration is one of a number of instrumental titration techniques where endpoints can be located accurately and precisely without a subjective interpretation on the part of the analyst as to their location. Enthalpy change is arguably the most fundamental and universal property of chemical reactions, so the observation of temperature change is a natural choice in monitoring their progress. It is not a new technique, with possibly the first recognizable thermometric titration method reported early in the 20th century (Bell and Cowell, 1913). In spite of its attractive features, and in spite of the considerable research that has been conducted in the field and a large body of applications that have been developed; it has been until now an under-utilized technique in the critical area of industrial process and quality control. Automated potentiometric titration systems have pre-dominated in this area since the 1970s. With the advent of cheap computers able to handle the powerful thermometric titration software, development has now reached the stage where easy to use automated thermometric titration systems can in many cases offer a superior alternative to potentiometric titrimetry. | 0 | Theoretical and Fundamental Chemistry |
* hydrocarbonate
**Water gas prepared by passing steam over charcoal/coke. Alternatively prepared from unspecified alcohol and sulphuric acid.
**Hydrocarbonate was recognized to brighten venous blood and compete with oxygen around 1796, although credit is widely awarded to Claude Bernard's work in the mid-1850s.
*hydrocarbonous acid
* heavy inflammable air
*carbonated hydrogene
* carbonic oxide / protoxide
**William Cruickshank discovered the composition of carbon monoxide and named it gaseous oxide of carbon. Cruickshank recognized water and hydrogen were not a constituent of the combustible base which contained the same ingredients as carbonic acid, although containing less oxygen.
**Carbonic oxide was identified in the intestine of cattle in the 1800s, marking a trace origin for endogenous carbon monoxide.
*carbonous oxyd
**The name carbonous oxyd relative to carbonic acid was once considered analogous to nitrous oxide to nitric acid based on the oxide not having sufficient oxygen to form the acid. | 1 | Applied and Interdisciplinary Chemistry |
A typical amount of 32 ng of cfDNA was utilized for library preparation. DNA input was adjusted to mitigate the effects of high molecular-weight DNA contamination. The library preparation process encompassed end repair, A-tailing, and adapter ligation, which also incorporated molecular barcodes into each read. These procedures were conducted according to ligation based library preparation standardized protocols, with overnight ligation performed at 4 °C. Following this, shotgun cfDNA libraries underwent hybrid capture targeting specific genomic regions, as detailed below. | 1 | Applied and Interdisciplinary Chemistry |
The Union Carbide (UCC) process, also known as low-pressure oxo process (LPO), relies on a rhodium catalyst dissolved in high-boiling thick oil, a higher molecular weight condensation product of the primary aldehydes, for the hydroformylation of propene. The reaction mixture is separated in a falling film evaporator from volatile components. The liquid phase is distilled and butyraldehyde is removed as head product while the catalyst containing bottom product is recycled to the process. The process is carried out at about 1.8 MPa and 95–100 °C. | 0 | Theoretical and Fundamental Chemistry |
Multiomics, multi-omics, integrative omics, "panomics" or "pan-omics" is a biological analysis approach in which the data sets are multiple "omes", such as the genome, proteome, transcriptome, epigenome, metabolome, and microbiome (i.e., a meta-genome and/or meta-transcriptome, depending upon how it is sequenced); in other words, the use of multiple omics technologies to study life in a concerted way. By combining these "omes", scientists can analyze complex biological big data to find novel associations between biological entities, pinpoint relevant biomarkers and build elaborate markers of disease and physiology. In doing so, multiomics integrates diverse omics data to find a coherently matching geno-pheno-envirotype relationship or association. The OmicTools service lists more than 99 softwares related to multiomic data analysis, as well as more than 99 databases on the topic.
Systems biology approaches are often based upon the use of panomic analysis data. The American Society of Clinical Oncology (ASCO) defines panomics as referring to "the interaction of all biological
functions within a cell and with other body functions, combining data collected by targeted tests ... and global assays (such as genome sequencing) with other patient-specific information." | 1 | Applied and Interdisciplinary Chemistry |
Photoreceptor proteins typically consist of a protein attached to a non-protein chromophore (sometimes referred as photopigment, even so photopigment may also refer to the photoreceptor as a whole). The chromophore reacts to light via photoisomerization or photoreduction, thus initiating a change of the receptor protein which triggers a signal transduction cascade. Chromophores found in photoreceptors include retinal (retinylidene proteins, for example rhodopsin in animals), flavin (flavoproteins, for example cryptochrome in plants and animals) and bilin (biliproteins, for example phytochrome in plants). The plant protein UVR8 is exceptional amongst photoreceptors in that it contains no external chromophore. Instead, UVR8 absorbs light through tryptophan residues within its protein coding sequence. | 1 | Applied and Interdisciplinary Chemistry |
Drospirenone has been found to stimulate the proliferation and migration of breast cancer cells in preclinical research, similarly to certain other progestins. However, some evidence suggests that drospirenone may do this more weakly than certain other progestins, like medroxyprogesterone acetate. The combination of estradiol and drospirenone has been found to increase breast density, an established risk factor for breast cancer, in postmenopausal women.
Data on risk of breast cancer in women with newer progestins like drospirenone are lacking at present. Progestogen-only birth control is not generally associated with a higher risk of breast cancer. Conversely, combined birth control and menopausal hormone therapy with an estrogen and a progestogen are associated with higher risks of breast cancer. | 0 | Theoretical and Fundamental Chemistry |
Because cycling probe technology does not involve the amplification of target DNA, CPT has a lower risk of cross contamination than PCR. In addition, CPT is faster than PCR and doesn't require a specialized thermocycler. CPT also does not require running CPT products on a gel. | 1 | Applied and Interdisciplinary Chemistry |
As stated previously, two diastereomers will not have identical chemical properties. This knowledge is harnessed in chiral synthesis to separate a mixture of enantiomers. This is the principle behind chiral resolution. After preparing the diastereomers, they are separated by chromatography or recrystallization. Note also the example of the stereochemistry of ketonization of enols and enolates. | 0 | Theoretical and Fundamental Chemistry |
The most important reaction types involving free radicals are:
* Free-radical substitution, for instance free-radical halogenation and autoxidation.
* Free-radical addition reactions
* Intramolecular free radical reactions (substitution or addition) such as the Hofmann–Löffler reaction or the Barton reaction
* Free radical rearrangement reactions are rare compared to rearrangements involving carbocations and restricted to aryl migrations.
* Fragmentation reactions or homolysis, for instance the Norrish reaction, the Hunsdiecker reaction and certain decarboxylations. For fragmentations taking place in mass spectrometry see mass spectrum analysis.
* Electron transfer. An example is the decomposition of certain peresters by Cu(I) which is a one-electron reduction reaction forming Cu(II), an alkoxy oxygen radical and a carboxylate. Another example is Kolbe electrolysis.
* Radical-nucleophilic aromatic substitution is a special case of nucleophilic aromatic substitution.
* Carbon–carbon coupling reactions, for example manganese-mediated coupling reactions.
* Elimination reactions
Free radicals can be formed by photochemical reaction and thermal fission reaction or by oxidation reduction reaction. Specific reactions involving free radicals are combustion, pyrolysis and cracking. Free radical reactions also occur within and outside of cells, are injurious, and have been implicated in a wide range of human diseases (see 13-Hydroxyoctadecadienoic acid, 9-hydroxyoctadecadienoic acid, reactive oxygen species, and Oxidative stress) as well as many of the maladies associated with ageing (see ageing). | 0 | Theoretical and Fundamental Chemistry |
The Gaussian line shape has the standardized form,
The subsidiary variable, x, is defined in the same way as for a Lorentzian shape. Both this function and the Lorentzian have a maximum value of 1 at x = 0 and a value of 1/2 at x=±1. | 0 | Theoretical and Fundamental Chemistry |
Robinson, an African American, started his college education at LeMoyne-Owen College and graduated from Memphis State University now the University of Memphis, in 1979 with summa cum laude honors and a B.S. degree in chemistry. He received a Ph.D. in nuclear chemistry from Washington University in St. Louis in 1984. In that same year, he joined the research staff of Oak Ridge National Laboratory (ORNL), where he was a research scientist and served as a group leader, of the neutron activation analysis facility. He accepted a position as a visiting professor at FAMU in January 1995, and left ORNL two years later to accept a permanent faculty position at FAMU.
At FAMU, Robinson became director of the universitys Environmental Sciences Institute. In addition to conducting research on environmental chemistry of coastal ecosystems, he had a leadership role in establishing new B.S. and Ph.D. degree programs. In 2003, he became FAMU provost and vice president for academic affairs, serving until 2005. In 2007 he became the universitys chief operating officer and vice president for research, and served for several weeks as the school's interim president. In May 2010, he left that position to become Assistant Secretary for Conservation and Management in the National Oceanic and Atmospheric Administration. In November 2011 he returned to FAMU as a professor and special assistant, and in March 2012 he was named provost and vice president for academic affairs.
In July 2012, the FAMU Board of Trustees appointed Robinson to serve as the university's interim president, replacing James H. Ammons. On September 15, 2016, he was named to a third stint as interim university president following the approval of a separation agreement with the 11th president, Elmira Mangum. On November 30, 2017, Robinson was named the 12th President of Florida A&M University. | 0 | Theoretical and Fundamental Chemistry |
Glycomics is the study of the carbohydrate components of cells. Though not exclusive to glycoproteins, it can reveal more information about different glycoproteins and their structure. One of the purposes of this field of study is to determine which proteins are glycosylated and where in the amino acid sequence the glycosylation occurs. Historically, mass spectrometry has been used to identify the structure of glycoproteins and characterize the carbohydrate chains attached. | 0 | Theoretical and Fundamental Chemistry |
In 2009, Zurek et al. predicted that the alloy would be a stable metal at only one quarter of the pressure required to metallize hydrogen, and that similar effects should hold for alloys of type LiH and possibly "other alkali high-hydride systems", i.e. alloys of type XH, where X is an alkali metal. This was later verified in AcH and LaH with T approaching 270 K leading to speculation that other compounds may even be stable at mere MPa pressures with room-temperature superconductivity. | 0 | Theoretical and Fundamental Chemistry |
Infrared radiation can pass through dry, clear air in the wavelength range of 8–13 µm. Materials that can absorb energy and radiate it in those wavelengths exhibit a strong cooling effect. Materials that can also reflect 95% or more of sunlight in the 200 nanometres to 2.5 µm range can exhibit cooling even in direct sunlight. | 0 | Theoretical and Fundamental Chemistry |
If the particle in question is not spherical, the rotational motion must be considered as well because the scattering of the light will be different depending on orientation. According to Pecora, rotational Brownian motion will affect the scattering when a particle fulfills two conditions; they must be both optically and geometrically anisotropic. Rod-shaped molecules fulfill these requirements, so a rotational diffusion coefficient must be considered in addition to a translational diffusion coefficient. In its most succinct form, the equation appears as
Where is the ratio of the two relaxation modes (translational and rotational), contains information about the axis perpendicular to the central axis of the particle, and contains information about the axis parallel to the central axis.
In 2007, Peter R. Lang and his team decided to use dynamic light scattering to determine the particle length and aspect ratio of short gold nanorods. They chose this method since it does not destroy the sample and it has a relatively easy setup. Both relaxation states were observed in VV geometry and the diffusion coefficients of both motions were used to calculate the aspect ratios of the gold nanoparticles. | 0 | Theoretical and Fundamental Chemistry |
The objectives of the European Coil Coating Association are described in the association's statutes and rules of procedure:
* Setting quality performance standards and developing test methods
* Spreading the benefits of coil and/or sheet coated metal with particular emphasis on environmental, cost and quality benefits
* Stimulating product, process, application and market developments
* Increasing the awareness of coil and/or sheet-coated metal through professional marketing and by organising educational training programmes for non-users
* Creating an industry network and forum for the development and exchange of ideas
* Representation of the Industry in its contacts with Public Officials and Public Authorities
* Providing liaison with other Trade Associations and Professional Bodies. | 1 | Applied and Interdisciplinary Chemistry |
A geoporphyrin, also known as a petroporphyrin, is a porphyrin of geologic origin. They can occur in crude oil, oil shale, coal, or sedimentary rocks. Abelsonite is possibly the only geoporphyrin mineral, as it is rare for porphyrins to occur in isolation and form crystals.
The field of organic geochemistry had its origins in the isolation of porphyrins from petroleum. This finding helped establish the biological origins of petroleum. Petroleum is sometimes "fingerprinted" by analysis of trace amounts of nickel and vanadyl porphyrins. | 1 | Applied and Interdisciplinary Chemistry |
Because the ligaments of these materials are essentially small metallic samples, they are themselves expected to be quite ductile; although, the entire nano-porous material is often observed to be brittle in tension. Dislocation behavior is extensive within the ligaments (just as would be expected in a metal): a high density. of partial dislocations, stacking faults and twins have been observed both in simulation and in TEM. However, the morphology of the ligaments makes bulk dislocation motion very difficult; the limited size of each ligament and complex connectivity within the nano-porous structure means that a dislocation cannot freely travel long distances and thus induce large-scale plasticity. | 1 | Applied and Interdisciplinary Chemistry |
Dispersants can be delivered in aerosolized form by an aircraft or boat. Sufficient dispersant with droplets in the proper size are necessary; this can be achieved with an appropriate pumping rate. Droplets larger than 1,000 µm are preferred, to ensure they are not blown away by the wind. The ratio of dispersant to oil is typically 1:20. | 1 | Applied and Interdisciplinary Chemistry |
During the development of B cells, the immunoglobulin gene undergoes sequences of rearrangements that lead to formation of the antibody repertoire. For example, in the lymphoid cell, a partial rearrangement of the heavy-chain gene occurs which is followed by complete rearrangement of heavy-chain gene. Here at this stage, Pre-B cell, mμ heavy chain and surrogate light chain are formed. The final rearrangement of the light chain gene generates immature B cell and mIgM. The process explained here occurs only in the absence of the antigen. The mature B cell formed as RNA processing changes leaves the bone marrow and is stimulated by the antigen then differentiated into IgM -secreted plasma cells. Also at first, the mature B cell expresses membrane-bound IgD and IgM. These two classes could switch to secretory IgD and IgM during the processing of mRNAs.
Finally, further class switching follows as the cell keep dividing and differentiating. For instance, IgM switches to IgG which switches to IgA that eventually switches to IgE | 1 | Applied and Interdisciplinary Chemistry |
The process of depolarization is entirely dependent upon the intrinsic electrical nature of most cells. When a cell is at rest, the cell maintains what is known as a resting potential. The resting potential generated by nearly all cells results in the interior of the cell having a negative charge compared to the exterior of the cell. To maintain this electrical imbalance, ions are transported across the cells plasma membrane. The transport of the ions across the plasma membrane is accomplished through several different types of transmembrane proteins embedded in the cells plasma membrane that function as pathways for ions both into and out of the cell, such as ion channels, sodium potassium pumps, and voltage-gated ion channels. | 0 | Theoretical and Fundamental Chemistry |
Since wave-making resistance is based on the energy required to push the water out of the way of the hull, there are a number of ways that this can be minimized. | 1 | Applied and Interdisciplinary Chemistry |
Acid rain can damage buildings, historic monuments, and statues, especially those made of rocks, such as limestone and marble, that contain large amounts of calcium carbonate. Acids in the rain react with the calcium compounds in the stones to create gypsum, which then flakes off.
:CaCO (s) + HSO (aq) CaSO (s) + CO (g) + HO (l)
The effects of this are commonly seen on old gravestones, where acid rain can cause the inscriptions to become completely illegible. Acid rain also increases the corrosion rate of metals, in particular iron, steel, copper and bronze. | 1 | Applied and Interdisciplinary Chemistry |
Within a homogeneous medium such as a solution, there is no scattering. For this case, researched extensively by August Beer, the concentration of the absorbing species follows the same linear contribution to absorbance as the path-length. Additionally, the contributions of individual absorbing species are additive. This is a very favorable situation, and made absorbance an absorption metric far preferable to absorption fraction (absorptance). This is the case for which the term "absorbance" was first used.
A common expression of the Beer's law relates the attenuation of light in a material as: where is the absorbance; is the molar attenuation coefficient or absorptivity of the attenuating species; is the optical path length; and is the concentration of the attenuating species. | 0 | Theoretical and Fundamental Chemistry |
Arginylation is a post-translational modification in which proteins are modified by the addition of arginine (Arg) at the N-terminal amino group or side chains of reactive amino acids by the enzyme, arginyltransferase (ATE1). Recent studies have also revealed that hundreds of proteins in vivo are arginylated, proteins which are essential for many biological pathways. While still poorly understood in a biological setting, the ATE1 enzyme is highly conserved which suggests that arginylation is an important biological post-translational modification.
Examples of ATE1 targets which have been identified include ornithine decarboxylase., thyroglobulin, insulin, and neurotensin. | 1 | Applied and Interdisciplinary Chemistry |
The IL-10 family is a family of interleukins.
In addition to IL-10, it includes IL-19, IL-20, IL-22, IL-24 and IL-26.
Some sources also include the interferons IL-28 and IL-29.
The IL-10 family are helical cytokines categorized based on their specific similarities and can be classified as class 2 cytokines. | 1 | Applied and Interdisciplinary Chemistry |
Field effects can arise from the electric dipole field of a bond containing an electronegative atom or electron-withdrawing substituent, as well as from an atom or substituent bearing a formal charge. The directionality of a dipole, and concentration of charge, can both define the shape of a molecule's electric field which will manipulate the localization of electron density toward or away from sites of interest, such as an acidic hydrogen. Field effects are typically associated with the alignment of a dipole field with respect to a reaction center. Since these are through space effects, the 3D structure of a molecule is an important consideration. A field may be interrupted by other bonds or atoms before propagating to a reactive site of interest. Atoms of differing electronegativities can move closer together resulting in bond polarization through space that mimics the inductive effect through bonds. Bicycloheptane and bicyclooctane (seen left) are two compounds in which the change in acidity with substitution was attributed to the field effect. The C-X dipole is oriented away from the carboxylic acid group, and can draw electron density away because the molecule center is empty, with a low dielectric constant, so the electric field is able to propagate with minimal resistance. | 0 | Theoretical and Fundamental Chemistry |
Essential genes are the set of genes thought to be critical for an organisms survival. This definition assumes the abundant availability of all relevant nutrients and the absence of environmental stress. Only a small portion of an organisms genes are essential. In bacteria, an estimated 250–400 genes are essential for Escherichia coli and Bacillus subtilis, which is less than 10% of their genes. Half of these genes are orthologs in both organisms and are largely involved in protein synthesis. In the budding yeast Saccharomyces cerevisiae the number of essential genes is slightly higher, at 1000 genes (~20% of their genes). Although the number is more difficult to measure in higher eukaryotes, mice and humans are estimated to have around 2000 essential genes (~10% of their genes). The synthetic organism, Syn 3, has a minimal genome of 473 essential genes and quasi-essential genes (necessary for fast growth), although 149 have unknown function.
Essential genes include housekeeping genes (critical for basic cell functions) as well as genes that are expressed at different times in the organisms development or life cycle. Housekeeping genes are used as experimental controls when analysing gene expression, since they are constitutively expressed at a relatively constant level. | 1 | Applied and Interdisciplinary Chemistry |
If we deal with a non-peptide organic libraries library it is not as simple to determine the identity of the content of a bead as in the case of a peptide one. In order to circumvent this difficulty methods had been developed to attach to the beads, in parallel with the synthesis of the library, molecules that encode the structure of the compound formed in the bead.
Ohlmeyer and his colleagues published a binary encoding method They used mixtures of 18 tagging molecules that after cleaving them from the beads could be identified by Electron Capture Gas Chromatography. Sarkar et al. described chiral oligomers of pentenoic amides (COPAs) that can be used to construct mass encoded OBOC libraries.
Kerr et al. introduced an innovative encoding method An orthogonally protected removable bifunctional linker was attached to the beads. One end of the linker was used to attach the non-natural building blocks of the library while to the other end encoding amino acid triplets were linked. The building blocks were non-natural amino acids and the series of their encoding amino acid triplets could be determined by Edman degradation. The important aspect of this kind of encoding was the possibility to cleave down from the beads the library members together with their attached encoding tags forming a soluble library. The same approach was used by Nikolajev et al. for encoding with peptides.
In 1992 by Brenner and Lerner introduced DNA sequences to encode the beads of the solid support that proved to be the most successful encoding method. Nielsen, Brenner and Janda also used the Kerr approach for implementing the DNA encoding
In the latest period of time there were important advancements in DNA sequencing. The next generation techniques make it possible to sequence large number of samples in parallel that is very important in screening of DNA encoded libraries. There was another innovation that contributed to the success of DNA encoding. In 2000 Halpin and Harbury omitted the solid support in the split-mix synthesis of the DNA encoded combinatorial libraries and replaced it by the encoding DNA oligomers. In solid phase split and pool synthesis the number of components of libraries can't exceed the number of the beads of the support. By the novel approach of the authors, this restraint was eliminated and made it possible to prepare new compounds in practically unlimited number. The Danish company Nuevolution for example synthesized a DNA encoded library containing 40 trillion! components
The DNA encoded libraries are soluble that makes possible to apply the efficient affinity binding in screening. Some authors apply the DEL for acromim of DNA encoded combinatorial libraries others are using DECL. The latter seems better since in this name the combinatorial nature of these libraries is clearly expressed.
Several types of DNA encoded combinatorial libraries had been introduced and described in the first decade of the present millennium. These libraries are very successfully applied in drug research.
* DNA templated synthesis of combinatorial libraries described in 2001 by Gartner et al.
* Dual pharmacophore DNA encoded combinatorial libraries invented in 2004 by Mlecco et al.
* Sequence encoded routing published by Harbury Halpin and Harbury in 2004.
* Single pharmacophore DNA encoded combinatorial libraries introduced in 2008 by Manocci et al.
* DNA encoded combinatorial libraries formed by using yoctoliter-scale reactor published by Hansen et al. in 2009
Details are found about their synthesis and application in the page DNA-encoded chemical library.
The DNA encoded soluble combinatorial libraries have drawbacks, too. First of all the advantage coming from the use of solid support is completely lost. In addition, the polyionic character of DNA encoding chains limits the utility of non-aqueous solvents in the synthesis. For this reason many laboratories choose to develop DNA compatible reactions for use in the synthesis of DECLs. Quite a few of available ones are already described | 1 | Applied and Interdisciplinary Chemistry |
Planck held that all "natural processes" (meaning, in present-day terminology, a thermodynamic operation followed by a thermodynamic process) are irreversible and proceed in the sense of increase of entropy sum. In these terms, it would be by thermodynamic operations that, if he could exist, Maxwells demon would conduct unnatural affairs, which include transitions in the sense away from thermodynamic equilibrium. They are physically theoretically conceivable up to a point, but are not natural processes in Plancks sense. The reason is that ordinary thermodynamic operations are conducted in total ignorance of the very kinds of microscopic information that is essential to the efforts of Maxwell's demon. | 0 | Theoretical and Fundamental Chemistry |
The first contribution to van der Waals forces is due to electrostatic interactions between rotating permanent dipoles, quadrupoles (all molecules with symmetry lower than cubic), and multipoles. It is termed the Keesom interaction, named after Willem Hendrik Keesom. These forces originate from the attraction between permanent dipoles (dipolar molecules) and are temperature dependent.
They consist of attractive interactions between dipoles that are ensemble averaged over different rotational orientations of the dipoles. It is assumed that the molecules are constantly rotating and never get locked into place. This is a good assumption, but at some point molecules do get locked into place. The energy of a Keesom interaction depends on the inverse sixth power of the distance, unlike the interaction energy of two spatially fixed dipoles, which depends on the inverse third power of the distance. The Keesom interaction can only occur among molecules that possess permanent dipole moments, i.e., two polar molecules. Also Keesom interactions are very weak van der Waals interactions and do not occur in aqueous solutions that contain electrolytes. The angle averaged interaction is given by the following equation:
where d = electric dipole moment, = permitivity of free space, = dielectric constant of surrounding material, T = temperature, = Boltzmann constant, and r = distance between molecules. | 0 | Theoretical and Fundamental Chemistry |
For this purpose an optical fiber tip of an optical fiber temperature sensor is equipped with a gallium arsenide crystal. Starting at a light wavelength of 850 nm GaAs becomes optically translucent. Since the spectral position of the band gap is temperature dependent, it shifts about 0.4 nm/K. The measurement device contains a light source and a device for the spectral detection of the band gap. With the changing of the band gap, (0.4 nm/K) an algorithm calculates the temperature (all 250 ms). | 0 | Theoretical and Fundamental Chemistry |
The exact origin of the term cantarella is unknown. It may have been derived from kantharos (), a type of ancient Greek cup used for drinking, or the Neo-Latin word ("small cup"), in reference to the cups in which the poison would have been served. The word may also be related to kantharis (), referring to the Spanish fly and other blister beetles that secrete cantharidin, a substance that is poisonous in large doses. | 1 | Applied and Interdisciplinary Chemistry |
The Hall–Petch relation predicts that as the grain size decreases the yield strength increases. The Hall–Petch relation was experimentally found to be an effective model for materials with grain sizes ranging from 1 millimeter to 1 micrometer. Consequently, it was believed that if average grain size could be decreased even further to the nanometer length scale the yield strength would increase as well. However, experiments on many nanocrystalline materials demonstrated that if the grains reached a small enough size, the critical grain size which is typically around , the yield strength would either remain constant or decrease with decreasing grains size. This phenomenon has been termed the reverse or inverse Hall–Petch relation. A number of different mechanisms have been proposed for this relation. As suggested by Carlton et al., they fall into four categories: (1) dislocation-based, (2) diffusion-based, (3) grain-boundary shearing-based, (4) two-phase-based.
There have been several works done to investigate the mechanism behind the inverse Hall–Petch relationship on numerous materials. In Han’s work, a series of molecular dynamics simulations were done to investigate the effect of grain size on the mechanical properties of nanocrystalline graphene under uniaxial tensile loading, with random shapes and random orientations of graphene rings. The simulation was run at grain sizes of nm and at room temperature. It was found that in the grain size of range 3.1 nm to 40 nm, inverse Hall–Petch relationship was observed. This is because when the grain size decreases at nm scale, there is an increase in the density of grain boundary junctions which serves as a source of crack growth or weak bonding. However, it was also observed that at grain size below 3.1 nm, a pseudo Hall–Petch relationship was observed, which results an increase in strength. This is due to a decrease in stress concentration of grain boundary junctions and also due to the stress distribution of 5-7 defects along the grain boundary where the compressive and tensile stress are produced by the pentagon and heptagon rings, etc. Chen at al. have done research on the inverse HallPetch relations of high-entropy CoNiFeAlCu alloys. In the work, polycrystalline models of FCC structured CoNiFeAlCu with grain sizes ranging from 7.2 nm to 18.8 nm were constructed to perform uniaxial compression using molecular dynamic simulations. All compression simulations were done after setting the periodic boundary conditions across the three orthogonal directions. It was found that when the grain size is below 12.1 nm the inverse Hall–Petch relation was observed. This is because as the grain size decreases partial dislocations become less prominent and so as deformation twinning. Instead, it was observed that there is a change in the grain orientation and migration of grain boundaries and thus cause the growth and shrinkage of neighboring grains. These are the mechanisms for inverse Hall–Petch relations. Sheinerman et al. also studied inverse Hall–Petch relation for nanocrystalline ceramics. It was found that the critical grain size for the transition from direct Hall–Petch to inverse Hall–Petch fundamentally depends on the activation energy of grain boundary sliding. This is because in direct Hall–Petch the dominant deformation mechanism is intragrain dislocation motion while in inverse Hall–Petch the dominant mechanism is grain boundary sliding. It was concluded that by plotting both the volume fraction of grain boundary sliding and volume fraction of intragrain dislocation motion as a function of grain size, the critical grain size could be found where the two curves cross.
Other explanations that have been proposed to rationalize the apparent softening of metals with nanosized grains include poor sample quality and the suppression of dislocation pileups.
The pileup of dislocations at grain boundaries is a hallmark mechanism of the Hall–Petch relationship. Once grain sizes drop below the equilibrium distance between dislocations, though, this relationship should no longer be valid. Nevertheless, it is not entirely clear what exactly the dependency of yield stress should be on grain sizes below this point. | 1 | Applied and Interdisciplinary Chemistry |
Marrow's research focuses on the degradation of structural materials, the role of microstructure, and the mechanisms of materials ageing. A key aspect is the investigation of fundamental mechanisms of damage accumulation - including irradiation - using novel materials characterisation techniques. This has concentrated recently on computed X-ray tomography and strain mapping by digital image correlation and digital volume correlation, together with X-ray and neutron diffraction. He applies these techniques to study the degradation of Generation IV nuclear materials such as graphite and silicon carbide composites, as well as new materials for electrical energy storage. | 1 | Applied and Interdisciplinary Chemistry |
According to the FDA, the stereoisomeric composition of a chiral drug should be known, and its effects should be well-characterized from pharmacologic, toxicologic, and clinical standpoints. In order to profile the different stereoisomers of enantiopure drugs, manufacturers are urged to develop quantitative assays for individual enantiomers in in vivo samples early in the development stage.
Ideally, the main pharmacologic activities of the isomers should be compared in in vitro systems in animals. During instances when toxic findings are present beyond the natural extensions of the pharmacologic effects of the drug, toxicologic evaluation of the individual isomers in question must be completed. | 0 | Theoretical and Fundamental Chemistry |
Milos Vratislav Novotny (born 19 April 1942) is an American chemist, currently the Distinguished Professor Emeritus and Director of the Novotny Glycoscience Laboratory and the Institute for Pheromone Research at Indiana University, and also a published author. Milos Novotny received his Bachelor of Science from the University of Brno, Czechoslovakia in 1962. In 1965, Novotny received his Ph.D. at the University of Brno. Novotny also holds honorary doctorates from Uppsala University, Masaryk University and Charles University, and he has been a major figure in analytical separation methods. Novotny was recognized for the development of PAGE Polyacrylamide Gel-filled Capillaries for Capillary Electrophoresis in 1993. In his years of work dedicated to analytical chemistry he has earned a reputation for being especially innovative in the field and has contributed a great deal to several analytical separation methods. Most notably, Milos has worked a great deal with microcolumn separation techniques of liquid chromatography, supercritical fluid chromatography, and capillary electrophoresis. Additionally, he is highly acclaimed for his research in proteomics and glycoanalysis and for identifying the first mammalian pheromones. | 0 | Theoretical and Fundamental Chemistry |
*Olfaction: In terrestrial vertebrates, olfaction occurs in the nose. Volatile chemical stimuli enter the nose and eventually reach the olfactory epithelium which houses the chemoreceptor cells known as olfactory sensory neurons often referred to as OSNs. Embedded in the olfactory epithelium are three types of cells: supporting cells, basal cells, and OSNs. While all three types of cells are integral to normal function of the epithelium, only OSN serve as receptor cells, i.e. responding to the chemicals and generating an action potential that travels down the olfactory nerve to reach the brain. In insects, antennae act as distance chemoreceptors. For example, antennae on moths are made up of long feathery hairs that increase sensory surface area. Each long hair from the main antenna also has smaller sensilla that are used for volatile olfaction. Since moths are mainly nocturnal animals, the development of greater olfaction aids them in navigating the night.
*Gustation: In many terrestrial vertebrates, the tongue serves as the primary gustatory sensory organ. As a muscle located in the mouth, it acts to manipulate and discern the composition of food in the initial stages of digestion. The tongue is rich in vasculature, allowing the chemoreceptors located on the top surface of the organ to transmit sensory information to the brain. Salivary glands in the mouth allow for molecules to reach chemoreceptors in an aqueous solution. The chemoreceptors of the tongue fall into two distinct superfamilies of G protein-coupled receptors. GPCRs are intramembrane proteins than bind to an extracellular ligand- in this case chemicals from food- and begin a diverse array of signaling cascades that can result in an action potential registering as input in an organisms brain. Large quantities of chemoreceptors with discrete ligand-binding domains provide for the five basic tastes: sour, salty, bitter, sweet, and savory. The salty and sour tastes work directly through the ion channels, the sweet and bitter taste work through G protein-coupled receptors, and the savory sensation is activated by glutamate.Gustatory chemosensors are not just present on the tongue but also on different cells of the gut epithelium where they communicates the sensory information to several effector systems involved in the regulation of appetite, immune responses, and gastrointestinal motility.
*Contact Chemoreception: Contact chemoreception is dependent on the physical contact of the receptor with the stimulus. The receptors are short hairs or cones that have a single pore at, or close to the tip of the projection. They are known as uniporous receptors. Some receptors are flexible, while others are rigid and do not bend with contact. They are mostly found in the mouthparts, but can also occur on the antennae or legs of some insects. There is a collection of dendrites located near the pores of the receptors, yet the distribution of these dendrites changes depending on the organism being examined. The method of transduction of the signal from the dendrites differs depending on the organism and the chemical it is responding to.
When inputs from the environment are significant to the survival of the organism, the input must be detected. As all life processes are ultimately based on chemistry it is natural that detection and passing on of the external input will involve chemical events. The chemistry of the environment is, of course, relevant to survival, and detection of chemical input from the outside may well articulate directly with cell chemicals.
Chemoreception is important for the detection of food, habitat, conspecifics including mates, and predators. For example, the emissions of a predator's food source, such as odors or pheromones, may be in the air or on a surface where the food source has been. Cells in the head, usually the air passages or mouth, have chemical receptors on their surface that change when in contact with the emissions. It passes in either chemical or electrochemical form to the central processor, the brain or spinal cord. The resulting output from the CNS (central nervous system) makes body actions that will engage the food and enhance survival. | 0 | Theoretical and Fundamental Chemistry |
Both free and protein-bound flavins are photoreducible, that is, able to be reduced by light, in a mechanism mediated by several organic compounds, such as some amino acids, carboxylic acids and amines. This property of flavins is exploited by various light-sensitive proteins. For example, the LOV domain, found in many species of plant, fungi and bacteria, undergoes a reversible, light-dependent structural change which involves the formation of a bond between a cysteine residue in its peptide sequence and a bound FMN. | 1 | Applied and Interdisciplinary Chemistry |
Each chloroplast contains around 100 copies of its DNA in young leaves, declining to 15–20 copies in older leaves. They are usually packed into nucleoids which can contain several identical chloroplast DNA rings. Many nucleoids can be found in each chloroplast.
Though chloroplast DNA is not associated with true histones, in red algae, a histone-like chloroplast protein (HC) coded by the chloroplast DNA that tightly packs each chloroplast DNA ring into a nucleoid has been found.
In primitive red algae, the chloroplast DNA nucleoids are clustered in the center of a chloroplast, while in green plants and green algae, the nucleoids are dispersed throughout the stroma. | 0 | Theoretical and Fundamental Chemistry |
Looking back to the beginning of the CERN heavy ion program one sees de facto announcements of quark–gluon plasma discoveries. The CERN-NA35 and CERN-WA85 experimental collaborations announced formation in heavy ion reactions in May 1990 at the Quark Matter Conference, Menton, France. The data indicates a significant enhancement of the production of this antimatter particle comprising one antistrange quark as well as antiup and antidown quarks. All three constituents of the particle are newly produced in the reaction. The WA85 results were in agreement with theoretical predictions. In the published report, WA85 interpreted their results as QGP. NA35 had large systematic errors in its data, which were improved in the following years. Moreover, the collaboration needed to evaluate the pp-background. These results are presented as function of the variable called rapidity which characterizes the speed of the source. The peak of emission indicates that the additionally formed antimatter particles do not originate from the colliding nuclei themselves, but from a source that moves at a speed corresponding to one-half of the rapidity of the incident nucleus that is a common center of momentum frame of reference source formed when both nuclei collide, that is, the hot quark–gluon plasma fireball. | 0 | Theoretical and Fundamental Chemistry |
Elementoid clusters are ligand-stabilized clusters of metal atoms that possess more direct element-element than element-ligand contacts. Examples of structurally characterized clusters feature ligand stabilized cores of Al, Ga, and Pd. | 0 | Theoretical and Fundamental Chemistry |
Ceramography is the art and science of preparation, examination and evaluation of ceramic microstructures. Ceramography can be thought of as the metallography of ceramics. The microstructure is the structure level of approximately 0.1 to 100 µm, between the minimum wavelength of visible light and the resolution limit of the naked eye. The microstructure includes most grains, secondary phases, grain boundaries, pores, micro-cracks and hardness microindentations. Most bulk mechanical, optical, thermal, electrical and magnetic properties are significantly affected by the microstructure. The fabrication method and process conditions are generally indicated by the microstructure. The root cause of many ceramic failures is evident in the microstructure. Ceramography is part of the broader field of materialography, which includes all the microscopic techniques of material analysis, such as metallography, petrography and plastography. Ceramography is usually reserved for high-performance ceramics for industrial applications, such as 85–99.9% alumina (AlO) in Fig. 1, zirconia (ZrO), silicon carbide (SiC), silicon nitride (SiN), and ceramic-matrix composites. It is seldom used on whiteware ceramics such as sanitaryware, wall tiles and dishware. | 1 | Applied and Interdisciplinary Chemistry |
Most settlements in human history were placed along rivers, developing into riverine cities and traceable by their considerable environmental footprint. The human influence on rivers can be divided into six chronological stages: | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used as a placeholder for the aryl group in chemical structure diagrams, analogous to “R” used for any organic substituent. “Ar” is not to be confused with the elemental symbol for argon.
A simple aryl group is phenyl (), a group derived from benzene. Examples of other aryl groups consist of:
* The tolyl group () which is derived from toluene (methylbenzene)
* The xylyl group (), which is derived from xylene (dimethylbenzene)
* The naphthyl group (), which is derived from naphthalene
Arylation is the process in which an aryl group is attached to a substituent. It is typically achieved by cross-coupling reactions. | 0 | Theoretical and Fundamental Chemistry |
Biosolids are solid organic matter recovered from a sewage treatment process and used as fertilizer. In the past, it was common for farmers to use animal manure to improve their soil fertility. In the 1920s, the farming community began also to use sewage sludge from local wastewater treatment plants. Scientific research over many years has confirmed that these biosolids contain similar nutrients to those in animal manures. Biosolids that are used as fertilizer in farming are usually treated to help to prevent disease-causing pathogens from spreading to the public. Some sewage sludge can not qualify as biosolids due to persistent, bioaccumulative and toxic chemicals, radionuclides, and heavy metals at levels sufficient to contaminate soil and water when applied to land. | 1 | Applied and Interdisciplinary Chemistry |
The majority of third generation cephalosporins have the aminothiazole group at position C-7. Different groups are found at the 7-α-position like 7-α-iminohydroxy and 7-α-iminomethoxy groups. Ceftibuten however possesses a 7-α-ethylidene group. This group gives ceftibuten higher resistance to enhanced spectrum β-lactamases. Many of the oral third generation cephalosporins are esters of parenteral forms and are hydrolysed by esterases in the digestive tract (cefteram pivoxil). Some of the third generation drugs can be absorbed orally without the need of esterification. This is for example done with cefixime and cefdinir by putting a vinyl group in the C-3 position. | 1 | Applied and Interdisciplinary Chemistry |
The first frozen zoo was established at the San Diego Zoo by pathologist Kurt Benirschke in 1972. At the time there was no technology available to make use of the collection, but Benirschke believed such technology would be developed in the future. The frozen zoo idea was later supported in Gregory Benford's 1992 paper proposing a Library of Life. Zoos such as the San Diego Zoo and research programs such as the Audubon Center for Research of Endangered Species cryopreserve genetic material in order to protect the diversity of the gene pool of endangered species, or to provide for a prospective reintroduction of such extinct species as the Tasmanian tiger and the mammoth.
Gathering material for a frozen zoo is rendered simple by the abundance of sperm in males. Sperm can be taken from an animal following death. The production of eggs, which in females is usually low, can be increased through hormone treatment to obtain 10–20 oocytes, dependent on the species. Some frozen zoos prefer to fertilize eggs and freeze the resulting embryo, as embryos are more resilient under the cryopreservation process. Some centers also collect skin cell samples of endangered animals or extinct species. The Scripps Research Institute has successfully made skin cells into cultures of special cells called induced pluripotent stem cells (IPS cells). It is theoretically possible to make sperm and egg cells from these IPS cells.
Several animals whose cells were preserved in frozen zoos have been cloned to increase the genetic diversity of endangered species, . One attempt to clone an extinct species was made in 2003; the newborn Pyrenean ibex died of a development disorder which may have been linked to the cloning, and there are not enough genetic samples in frozen zoos to re-create a breeding Pyrenean ibex population. | 1 | Applied and Interdisciplinary Chemistry |
The key outputs of the marine carbon system are particulate organic matter (POC) and calcium carbonate (PIC) preservation as well as reverse weathering. While there are regions with local loss of CO to the atmosphere and hydrothermal processes, a net loss in the cycle does not occur. | 0 | Theoretical and Fundamental Chemistry |
Standard codes are followed when designing (or manufacturing) a piping system. Organizations which promulgate piping standards include:
* ASME: American Society of Mechanical Engineers
** A112.19.1 Enameled cast-iron and steel plumbing fixtures standards
** A112.19.2 Ceramic plumbing fixtures standard
* ASTM International: American Society for Testing and Materials
* API: American Petroleum Institute
* AWS: American Welding Society
* AWWA: American Water Works Association
* MSS: Manufacturers Standardization Society
* ANSI: American National Standards Institute
* NFPA: National Fire Protection Association
* EJMA: Expansion Joint Manufacturers Association
* CGA: Compressed Gas Association
*PCA: [https://ablis.business.gov.au/service/ag/the-plumbing-code-of-australia-pca-/31066 Plumbing Code of Australia]
Pipes must conform to the dimensional requirements of:
* ASME B36.10M: Welded and seamless wrought-steel pipe
* ASME B36.19M: Stainless-steel pipe
* ASME B31.3 2008: Process piping
* ASME B31.4 XXXX: Power piping | 1 | Applied and Interdisciplinary Chemistry |
Cobalt is essential to the metabolism of all animals. It is a key constituent of cobalamin, also known as vitamin B, the primary biological reservoir of cobalt as an ultratrace element. Bacteria in the stomachs of ruminant animals convert cobalt salts into vitamin B, a compound which can only be produced by bacteria or archaea. A minimal presence of cobalt in soils therefore markedly improves the health of grazing animals, and an uptake of 0.20 mg/kg a day is recommended because they have no other source of vitamin B.
Proteins based on cobalamin use corrin to hold the cobalt. Coenzyme B features a reactive C-Co bond that participates in the reactions. In humans, B has two types of alkyl ligand: methyl and adenosyl. MeB promotes methyl (−CH) group transfers. The adenosyl version of B catalyzes rearrangements in which a hydrogen atom is directly transferred between two adjacent atoms with concomitant exchange of the second substituent, X, which may be a carbon atom with substituents, an oxygen atom of an alcohol, or an amine. Methylmalonyl coenzyme A mutase (MUT) converts MMl-CoA to Su-CoA, an important step in the extraction of energy from proteins and fats.
Although far less common than other metalloproteins (e.g. those of zinc and iron), other cobaltoproteins are known besides B. These proteins include methionine aminopeptidase 2, an enzyme that occurs in humans and other mammals that does not use the corrin ring of B, but binds cobalt directly. Another non-corrin cobalt enzyme is nitrile hydratase, an enzyme in bacteria that metabolizes nitriles. | 1 | Applied and Interdisciplinary Chemistry |
The main durations of embryo culture are until cleavage stage (day two to four after co-incubation) or the blastocyst stage (day five or six after co-incubation). Embryo culture until the blastocyst stage confers a significant increase in live birth rate per embryo transfer, but also confers a decreased number of embryos available for transfer and embryo cryopreservation, so the cumulative clinical pregnancy rates are increased with cleavage stage transfer. Transfer day two instead of day three after fertilisation has no differences in live birth rate. There are significantly higher odds of preterm birth (odds ratio 1.3) and congenital anomalies (odds ratio 1.3) among births having from embryos cultured until the blastocyst stage compared with cleavage stage. | 1 | Applied and Interdisciplinary Chemistry |
Ioliomics (from a portmanteau of ions and liquids) is the study of ions in liquids (or liquid phases) and stipulated with fundamental differences of ionic interactions. Ioliomics covers a broad research area concerning structure, properties and applications of ions involved in various biological and chemical systems. The concept of this research discipline is related to other comprehensive research fields, such as genomics, proteomics, glycomics, petroleomics, etc., where the suffix -omics is used for describing the comprehensiveness of data. | 1 | Applied and Interdisciplinary Chemistry |
The term macrocycle is used for compounds having a rings of 8 or more atoms. Macrocycles may be fully carbocyclic (rings containing only carbon atoms, e.g. cyclooctane), heterocyclic containing both carbon and non-carbon atoms (e.g. lactones and lactams containing rings of 8 or more atoms), or non-carbon (containing only non-carbon atoms in the rings, e.g. diselenium hexasulfide). Heterocycles with carbon in the rings may have limited non-carbon atoms in their rings (e.g., in lactones and lactams whose rings are rich in carbon but have limited number of non-carbon atoms), or be rich in non-carbon atoms and displaying significant symmetry (e.g., in the case of chelating macrocycles). Macrocycles can access a number of stable conformations, with preference to reside in conformations that minimize transannular nonbonded interactions within the ring (e.g., with the chair and chair-boat being more stable than the boat-boat conformation for cyclooctane, because of the interactions depicted by the arcs shown). Medium rings (8-11 atoms) are the most strained, with between 9-13 (kcal/mol) strain energy, and analysis of factors important in the conformations of larger macrocycles can be modeled using medium ring conformations. Conformational analysis of odd-membered rings suggests they tend to reside in less symmetrical forms with smaller energy differences between stable conformations. | 0 | Theoretical and Fundamental Chemistry |
Liebig–Pasteur dispute is the dispute between Justus von Liebig and Louis Pasteur on the processes and causes of fermentation. | 1 | Applied and Interdisciplinary Chemistry |
* 1900 – Max Planck suggests that light may be emitted in discrete frequencies, giving his law of black-body radiation
* 1905 – Albert Einstein, in the first of his miracle year papers, argues that the reality of quanta would explain the photoelectric effect
* 1905 – Einstein mathematically analyzes Brownian motion as a result of random molecular motion in his paper On the movement of small particles suspended in a stationary liquid demanded by the molecular-kinetic theory of heat
* 1906 – Nernst presents a formulation of the third law of thermodynamics
* 1907 – Einstein uses quantum theory to estimate the heat capacity of an Einstein solid
* 1909 – Constantin Carathéodory develops an axiomatic system of thermodynamics
* 1910 – Einstein and Marian Smoluchowski find the Einstein–Smoluchowski formula for the attenuation coefficient due to density fluctuations in a gas
* 1911 – Paul Ehrenfest and Tatjana Ehrenfest–Afanassjewa publish their classical review on the statistical mechanics of Boltzmann, Begriffliche Grundlagen der statistischen Auffassung in der Mechanik
* 1912 – Peter Debye gives an improved heat capacity estimate by allowing low-frequency phonons
* 1916 – Sydney Chapman and David Enskog systematically develop the kinetic theory of gases
* 1916 – Einstein considers the thermodynamics of atomic spectral lines and predicts stimulated emission
* 1919 – James Jeans discovers that the dynamical constants of motion determine the distribution function for a system of particles
* 1920 – Meghnad Saha states his ionization equation
* 1923 – Debye and Erich Hückel publish a statistical treatment of the dissociation of electrolytes
* 1924 – Satyendra Nath Bose introduces Bose–Einstein statistics, in a paper translated by Einstein
* 1926 – Enrico Fermi and Paul Dirac introduce Fermi–Dirac statistics
* 1927 – John von Neumann introduces the density matrix representation, establishing quantum statistical mechanics
* 1928 – John B. Johnson discovers Johnson noise in a resistor
* 1928 – Harry Nyquist derives the fluctuation-dissipation theorem, a relationship to explain Johnson noise in a resistor
* 1931 – Lars Onsager publishes his groundbreaking paper deriving the Onsager reciprocal relations
* 1935 – Ralph H. Fowler invents the title the zeroth law of thermodynamics to summarise postulates made by earlier physicists that thermal equilibrium between systems is a transitive relation
* 1938 – Anatoly Vlasov proposes the Vlasov equation for a correct dynamical description of ensembles of particles with collective long range interaction
* 1939 – Nikolay Krylov and Nikolay Bogolyubov give the first consistent microscopic derivation of the Fokker–Planck equation in the single scheme of classical and quantum mechanics
* 1942 – Joseph L. Doob states his theorem on Gauss–Markov processes
* 1944 – Lars Onsager gives an analytic solution to the 2-dimensional Ising model, including its phase transition | 0 | Theoretical and Fundamental Chemistry |
The purpose of both the (primary) bioluminescence (from aequorins action on luciferin) and the (secondary) fluorescence of GFP in jellyfish is unknown. GFP is co-expressed with aequorin in small granules around the rim of the jellyfish bell. The secondary excitation peak (480 nm) of GFP does absorb some of the blue emission of aequorin, giving the bioluminescence a more green hue. The serine 65 residue of the GFP chromophore is responsible for the dual-peaked excitation spectra of wild-type GFP. It is conserved in all three GFP isoforms originally cloned by Prasher. Nearly all mutations of this residue consolidate the excitation spectra to a single peak at either 395 nm or 480 nm. The precise mechanism of this sensitivity is complex, but, it seems, involves donation of a hydrogen from serine 65 to glutamate 222, which influences chromophore ionization. Since a single mutation can dramatically enhance the 480 nm excitation peak, making GFP a much more efficient partner of aequorin, A. victoria appears to evolutionarily prefer the less-efficient, dual-peaked excitation spectrum. Roger Tsien has speculated that varying hydrostatic pressure with depth may affect serine 65s ability to donate a hydrogen to the chromophore and shift the ratio of the two excitation peaks. Thus, the jellyfish may change the color of its bioluminescence with depth. However, a collapse in the population of jellyfish in Friday Harbor, where GFP was originally discovered, has hampered further study of the role of GFP in the jellyfish's natural environment.
Most species of lancelet are known to produce GFP in various regions of their body. Unlike A. victoria, lancelets do not produce their own blue light, and the origin of their endogenous GFP is still unknown. Some speculate that it attracts plankton towards the mouth of the lancelet, serving as a passive hunting mechanism. It may also serve as a photoprotective agent in the larvae, preventing damage caused by high-intensity blue light by converting it into lower-intensity green light. However, these theories have not been tested.
GFP-like proteins have been found in multiple species of marine copepods, particularly from the Pontellidae and Aetideidae families. GFP isolated from Pontella mimocerami has shown high levels of brightness with a quantum yield of 0.92, making them nearly two-fold brighter than the commonly used EGFP isolated from A. victoria. | 1 | Applied and Interdisciplinary Chemistry |
Reflections, or mirror isometries, can be combined to produce any isometry. Thus isometries are an example of a reflection group. | 0 | Theoretical and Fundamental Chemistry |
The working principle involves the acceleration of an electrically conductive fluid (which can be a liquid or an ionized gas called a plasma) by the Lorentz force, resulting from the cross product of an electric current (motion of charge carriers accelerated by an electric field applied between two electrodes) with a perpendicular magnetic field. The Lorentz force accelerates all charged particles, positive and negative species (in opposite directions). If either positive or negative species dominate the vehicle is put in motion in the opposite direction from the net charge.
This is the same working principle as an electric motor (more exactly a linear motor) except that in an MHD drive, the solid moving rotor is replaced by the fluid acting directly as the propellant. As with all electromagnetic devices, an MHD accelerator is reversible: if the ambient working fluid is moving relatively to the magnetic field, charge separation induces an electric potential difference that can be harnessed with electrodes: the device then acts as a power source with no moving parts, transforming the kinetic energy of the incoming fluid into electricity, called an MHD generator.
As the Lorentz force in an MHD converter does not act on a single isolated charged particle nor on electrons in a solid electrical wire, but on a continuous charge distribution in motion, it is a "volumetric" (body) force, a force per unit volume:
where f is the force density (force per unit volume), ρ the charge density (charge per unit volume), E the electric field, J the current density (current per unit area) and B the magnetic field. | 1 | Applied and Interdisciplinary Chemistry |
The MOSE project is estimated to cost €5.496 billion, up €1.3 billion from initial cost projections. On 30 January 2019, the last of the 78 gates was put in place. In November 2019, the project was 94% completed and was expected to be ready by the end of 2021, and later moved to 2025. | 1 | Applied and Interdisciplinary Chemistry |
Sealants are an alternative to solder where additional strength is not required. In most cases, sealants should not be necessary with a properly designed copper installation. They are at best a relatively short-term solution requiring frequent maintenance. Regardless, sealant-filled joints have been used successfully as a secondary waterproofing measure for standing seam and batten seam roofing applications where low-sloped roofs are less than . Sealants can also be used in joints that are primarily designed to accommodate thermal movement of the copper.
The sealants used should be tested by the manufacturer and designated as compatible for use with copper.
In general, butyl, polysulfide, polyurethane, and other inorganic or rubber-based sealants are reasonably compatible with copper. Acrylic, neoprene, and nitrile-based sealants actively corrode copper. Silicone sealants are somewhat successful with copper but their suitability should be verified before application. | 1 | Applied and Interdisciplinary Chemistry |
The BCA assay is largely incompatible with reducing agents and metal chelators, although trace quantities may be tolerated. The BCA assay also reportedly responds to common membrane lipids and phospholipids. | 1 | Applied and Interdisciplinary Chemistry |
Similar to natural bases, x-nucleotides selectively assemble into a duplex-structure resembling B-DNA. xDNA was originally synthesized by incorporating a benzene ring into the nitrogenous base. However, other expanded bases have been able to incorporate thiophene and [[Benzothiophene|benzo[b]thiophene]] as well. xDNA and yDNA use benzene rings to widen the bases and are thus termed "benzo-homologated". Another form of expanded nucleobases known as yyDNA incorporate naphthalene into the base and are "naptho-homologated". xDNA has a rise of 3.2Å and a twist of 32°, significantly smaller than B-DNA, which has a rise of 3.3Å and a twist of 34.2° xDNA nucleotides can occur on both strands—either alone (known as "doubly expanded DNA") or mixed with natural bases—or exclusively on one strand or the other. Similar to B-DNA, xDNA can recognize and bind complementary single-stranded DNA or RNA sequences.
Duplexes formed from xDNA are similar to natural duplexes aside from the distance between the two sugar-phosphate backbones. xDNA helices have a greater number of base pairs per turn of the helix as a result of a reduced distance between neighbour nucleotides. NMR spectra report that xDNA helices are anti-parallel, right-handed and take an anti conformation around the glycosidic bond, with a C2-endo sugar pucker. Helices created from xDNA are more likely to take a B-helix over an A-helix conformation, and have an increased major groove width by 6.5Å (where the backbones are farthest apart) and decreased minor groove width by 5.5Å (where the backbones are closest together) compared to B-DNA. Altering groove width affects the xDNAs ability to associate with DNA-binding proteins, but as long as the expanded nucleotides are exclusive to one strand, recognition sites are sufficiently similar to B-DNA to allow bonding of transcription factors and small polyamide molecules. Mixed helices present the possibility of recognizing the four expanded bases using other DNA-binding molecules. | 1 | Applied and Interdisciplinary Chemistry |
The mitochondrial shuttles are biochemical transport systems used to transport reducing agents across the inner mitochondrial membrane. NADH as well as NAD+ cannot cross the membrane, but it can reduce another molecule like FAD and [QH] that can cross the membrane, so that its electrons can reach the electron transport chain.
The two main systems in humans are the glycerol phosphate shuttle and the malate-aspartate shuttle. The malate/a-ketoglutarate antiporter functions move electrons while the aspartate/glutamate antiporter moves amino groups. This allows the mitochondria to receive the substrates that it needs for its functionality in an efficient manner. | 1 | Applied and Interdisciplinary Chemistry |
SSCP used to be a way to discover new DNA polymorphisms apart from DNA sequencing but is now being supplanted by sequencing techniques on account of efficiency and accuracy. These days, SSCP is most applicable as a diagnostic tool in molecular biology. It can be used in genotyping to detect homozygous individuals of different allelic states, as well as heterozygous individuals that should each demonstrate distinct patterns in an electrophoresis experiment. SSCP is also widely used in virology to detect variations in different strains of a virus, the idea being that a particular virus particle present in both strains will have undergone changes due to mutation, and that these changes will cause the two particles to assume different conformations and, thus, be differentiable on an SSCP gel. | 1 | Applied and Interdisciplinary Chemistry |
Jorge Eduardo Allende Rivera, (born 11 November 1934) is a Chilean biochemist and biophysicist known for his contributions to the understanding of proteic biosynthesis and how transfer RNA is generated, and the regulation of maturation of amphibian eggs. He has been a foreign associate of the United States National Academy of Sciences since 2001, and was awarded the Chilean National Prize for Nature Sciences (Chile) in 1992. | 1 | Applied and Interdisciplinary Chemistry |
Flap endonuclease (FEN) is an endonuclease that catalyzes structure-specific cleavage. This cleavage is highly sensitive to mismatches and can be used to interrogate SNPs with a high degree of specificity
In the basic Invader assay, a FEN called cleavase is combined with two specific oligonucleotide probes, that together with the target DNA, can form a tripartite structure recognized by cleavase. The first probe, called the Invader oligonucleotide is complementary to the 3’ end of the target DNA. The last base of the Invader oligonucleotide is a non-matching base that overlaps the SNP nucleotide in the target DNA. The second probe is an allele-specific probe which is complementary to the 5’ end of the target DNA, but also extends past the 3’ side of the SNP nucleotide. The allele-specific probe will contain a base complementary to the SNP nucleotide. If the target DNA contains the desired allele, the Invader and allele-specific probes will bind to the target DNA forming the tripartite structure. This structure is recognized by cleavase, which will cleave and release the 3’ end of the allele-specific probe. If the SNP nucleotide in the target DNA is not complementary to the allele-specific probe, the correct tripartite structure is not formed and no cleavage occurs. The Invader assay is usually coupled with fluorescence resonance energy transfer (FRET) system to detect the cleavage event. In this setup, a quencher molecule is attached to the 3’ end and a fluorophore is attached to the 5’ end of the allele-specific probe. If cleavage occurs, the fluorophore will be separated from the quencher molecule generating a detectable signal.
Only minimal cleavage occurs with mismatched probes making the Invader assay highly specific. However, in its original format, only one SNP allele could be interrogated per reaction sample and it required a large amount of target DNA to generate a detectable signal in a reasonable time frame. Several developments have extended the original Invader assay. By carrying out secondary FEN cleavage reactions, the Serial Invasive Signal Amplification Reaction (SISAR) allows both SNP alleles to be interrogated in a single reaction. SISAR Invader assay also requires less target DNA, improving the sensitivity of the original Invader assay. The assay has also been adapted in several ways for use in a high-throughput format. In one platform, the allele-specific probes are anchored to microspheres. When cleavage by FEN generates a detectable fluorescent signal, the signal is measured using flow-cytometry. The sensitivity of flow-cytometry, eliminates the need for PCR amplification of the target DNA (Rao et al. 2003). These high-throughput platforms have not progressed beyond the proof-of-principle stage and so far the Invader system has not been used in any large scale SNP genotyping projects. | 1 | Applied and Interdisciplinary Chemistry |
Most aliphatic compounds are flammable, allowing the use of hydrocarbons as fuel, such as methane in natural gas for stoves or heating; butane in torches and lighters; various aliphatic (as well as aromatic) hydrocarbons in liquid transportation fuels like petrol/gasoline, diesel, and jet fuel; and other uses such as ethyne (acetylene) in welding. | 0 | Theoretical and Fundamental Chemistry |
The compound is used in high-end electric and semiconductor products, and as a raw material to produce phosphor. Also it is used as a magnetic material and sputtering target material. | 0 | Theoretical and Fundamental Chemistry |
After cycling several times and being removed from the calcium loop, the waste sorbent will have attrited, sulfated and become mixed with the ash from any fuel used. The amount of ash in the waste sorbent will depend on the fraction of the sorbent being removed and the ash and calorific content of the fuel. The size fraction of the sorbent is dependent on the original size fraction but also the number of cycles used and the type of limestone used. | 1 | Applied and Interdisciplinary Chemistry |
A monolithic HPLC column, or monolithic column, is a column used in high-performance liquid chromatography (HPLC). The internal structure of the monolithic column is created in such a way that many channels form inside the column. The material inside the column which separates the channels can be porous and functionalized. In contrast, most HPLC configurations use particulate packed columns; in these configurations, tiny beads of an inert substance, typically a modified silica, are used inside the column. Monolithic columns can be broken down into two categories, silica-based and polymer-based monoliths. Silica-based monoliths are known for their efficiency in separating smaller molecules while, polymer-based are known for separating large protein molecules. | 0 | Theoretical and Fundamental Chemistry |
There are other omega-3 fish-oil based drugs on the market that have similar uses and mechanisms of action:
* Omega-3-acid ethyl esters (brand names Omacor [renamed Lovaza in the U.S. to avoid confusion with Amicar and Omtryg]), and as of March 2016, four generic versions
* Omega-3 carboxylic acids (Epanova); the Epanova brand name was discontinued in the United States. | 1 | Applied and Interdisciplinary Chemistry |
By modeling reactions as Langevin motion along a one dimensional reaction coordinate, Hendrik Kramers was able to derive a relationship between the shape of the potential energy surface along the reaction coordinate and the transition rates of the system. The formulation relies on approximating the potential energy landscape as a series of harmonic wells. In a two state system, there will be three wells; a well for state A, an upside-down well representing the potential energy barrier, and a well for state B.
In the overdamped (or "diffusive") regime, the transition rate from state A to B is related to the resonant frequency of the wells via
where is the frequency of the well for state A, is the frequency of the barrier well, is the viscous damping, is the energy of the top of the barrier, is the energy of bottom of the well for state A, and is the temperature of the system times the Boltzmann constant.
For general damping (overdamped or underdamped), there is a similar formula. | 0 | Theoretical and Fundamental Chemistry |
The friction head can be related to the pressure loss due to friction by dividing the pressure loss by the product of the acceleration due to gravity and the density of the fluid. Accordingly, the relationship between the friction head and the Fanning friction factor is:
where:
* is the friction loss (in head) of the pipe.
* is the Fanning friction factor of the pipe.
* is the flow velocity in the pipe.
* is the length of pipe.
* is the local acceleration of gravity.
* is the pipe diameter. | 1 | Applied and Interdisciplinary Chemistry |
N-Oleoylsarcosine is a mild surfactant which irritates skin and eyes comparatively little and is therefore used in personal care products such as skin cleansing agents because of its antimicrobial and virucidal properties.
The sarcosine head group of the long-chain amphiphilic N-acylamino acid is responsible for the formation of chelate-like structures in the adsorption on polar and charged surfaces, e.g. on metals.
The molecules form oriented monomolecular films that protect the metal surface from corrosive attack.
N-Oleoylsarcosine possesses already at low concentrations very good rust protection properties (in particularly in combination with the imidazoline derivative 2-(2-heptadec-8-enyl-2-imidazolin-1-yl)ethanol which also acts emulsifying and anticorrosive), also against non-ferrous metals such as aluminum and copper. Therefore, N-oleoylsarcosine is added as a corrosion inhibitor and emulsifier to rust protection fluids and lubricating greases, fuels and lubricants and refrigerating lubricants such as drilling and cutting oils. | 0 | Theoretical and Fundamental Chemistry |
In 1989 and 1993, Yamada and co-workers reported the first enantioselective total synthesis of both the enantiomers of ptaquilosin, the aglycone of ptaquiloside. In the first step, the menthyl ester of cyclopentane-1,2-dicarboxylic acid 1 was partially hydrolyzed to afford the monomenthyl ester, which was later alkylated with methallyl bromide in the presence of HMPA to selectively produce 2. The product 2 was then converted to the acid chloride and treated with stannic chloride to effect Friedel-Crafts acylation to give enone 3. Hydride reduction, selective oxidation of the allylic alcohol, and silylation were then performed to provide compound 4. On treatment with base and a chloroethyl sulfonium salt, a mixture of spirocyclopropanes was obtained. The minor product 5a can be isomerized with p-toluenesulfonic acid to 5b with 81% yield. Desaturation by selenylation/dehydroselenation and basic peroxide oxidation afforded epoxide 6. Mild reduction, methyl Grignard addition, and oxidation gave compound 7. Methylation of the cyclopentanone under Noyoris condition using the TASF enolate produced a mixture of isomers. The undesired isomer 8a can be equilibriumed with potassium tert-butoxide in 81% yield to exclusively generate 8b. Reduction, deprotection, and oxidation afforded 9. On treatment with oxygen in warm ethyl acetate, the aldehyde on 9 was oxidized to the acyl radical for decarbonylation. Stereoselective trapping of the tertiary radical by oxygen gave the hydroperoxide 10. Under mild reduction, the naturally occurred (-)-ptaquilosin 11 was obtained. The Yamadas synthesis proceeded in 20 steps with an overall yield of 2.9%. Similarly, the unnatural (+)-enantiomer of ptaquilosin was synthesized from the diastereomer of 2.
Multiple synthetic studies directed towards ptaquilosin 11 have been reported since 1989. In 1994, Padwa and co-workers described the synthesis of the core skeleton of ptaquilosin by a highly convergent approach. In 1995, Cossy and co-workers reported novel routes to the racemic and optically active ptaquilosin skeleton. Their properly functionalized tricyclic compound would be of great utility for the synthesis of 11. | 0 | Theoretical and Fundamental Chemistry |
The dosage form for a pharmaceutical contains the active pharmaceutical ingredient, which is the drug substance itself, and excipients, which are the ingredients of the tablet, or the liquid in which the active agent is suspended, or other material that is pharmaceutically inert. Drugs are chosen primarily for their active ingredients. During formulation development, the excipients are chosen carefully so that the active ingredient can reach the target site in the body at the desired rate and extent.
Patients often have difficulty identifying the active ingredients in their medication, as well as being unaware of the notion of an active ingredient. When patients are on multiple medications, active ingredients can interfere with each other, often resulting in severe or life-threatening complications.
Many online services can help identify the active ingredient of most medications, such as the Medicines Database providing information on medications available in Australia. | 1 | Applied and Interdisciplinary Chemistry |
Nitrification is the biological oxidation of ammonia to nitrate via the intermediary nitrite. Nitrification is an important step in the nitrogen cycle in soil. The process of complete nitrification may occur through separate organisms or entirely within one organism, as in comammox bacteria. The transformation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an aerobic process performed by small groups of autotrophic bacteria and archaea. | 1 | Applied and Interdisciplinary Chemistry |
Cationic detergents are similar to anionic ones, but quaternary ammonium replaces the hydrophilic anionic sulfonate group. The ammonium sulfate center is positively charged. Cationic surfactants generally have poor detergency. | 0 | Theoretical and Fundamental Chemistry |
A flow process is a type of thermodynamic process, where matter flows in and out of an open system called the control volume. Such a process may be steady, meaning that the matter and energy flowing into and out of the system are constant through time. It can also be unsteady, or transient, meaning that the flows may change and differ at different times.
Many proofs of the theorem demonstrate it specifically for flow systems. Thus, the theorem is particularly useful in performing exergy analysis on such systems. | 0 | Theoretical and Fundamental Chemistry |
A novel input representation has been developed consisting of a combination of sparse encoding, Blosum encoding, and input derived from hidden Markov models. this method predicts T-cell epitopes for the genome of hepatitis C virus and discuss possible applications of the prediction method to guide the process of rational vaccine design. | 1 | Applied and Interdisciplinary Chemistry |
William Christopher Zeise (15 October 1789 – 12 November 1847) was a Danish organic chemist. He is best known for synthesising one of the first organometallic compounds, named Zeise's salt in his honour. He also performed pioneering studies in organosulfur chemistry, discovering the xanthates in 1823. | 0 | Theoretical and Fundamental Chemistry |
As of March 2024, 11 U.S. states and two territories have passed statewide legislation to explicitly ban polystyrene foam:
* In 2019, Maryland was the first state to enact a ban, which went into effect on October 1, 2020. Bans were also passed that year in Maine and Vermont, with both states' laws taking effect on July 1, 2021.
* In 2020, New York passed a ban that took effect on January 1, 2022, while New Jersey passed a ban that took effect on May 4, 2022.
* In 2021, Colorado passed a ban that took effect on January 1, 2024. Virginia passed a ban on polystyrene foam takeout containers that will come into force for large businesses by July 2028 and for small businesses by July 2030. Washington also passed a polystyrene ban, effective starting in June 2023, with food serviceware prohibited starting June 1, 2024.
* In 2023, Delaware, Oregon and Rhode Island all signed bans into law, with provisions set to take effect in each state in 2025.
* Washington, D.C. banned polystyrene foam takeout containers on January 1, 2016. The ban was expanded on January 1, 2021, to include the retail sale of polystyrene foam.
* American Samoa banned the import, sale, and distribution of polystyrene foam containers on February 6, 2024, taking effect 60 days later.
In Hawaii, a de facto ban is in effect after every county enacted polystyrene bans except state-administered Kalawao County. Bans in Hawaii County took effect July 2019, followed by Kauai County, Maui County, and Honolulu County in 2022. Maui separately banned polystyrene foam coolers, and the sale or rental of disposable bodyboards in 2022.
In California, the legislature passed SB54 in June 2022 as the Plastic Pollution Prevention and Packaging Producer Responsibility Act. The law codifies extended producer responsibility (EPR) requirements for plastics, including a requirement that polystyrene be banned if recycling rates do not reach 25% by 2025. Recycling rates averaged 6% at passage, leading some to call the law a de facto ban, anticipating an inability to comply within three years. | 0 | Theoretical and Fundamental Chemistry |
Process analytical chemistry involves the following sub-disciplines of analytical chemistry: microanalytical systems, nanotechnology, chemical detection, electrochemistry or electrophoresis, chromatography, spectroscopy, mass spectrometry, process chemometrics, process control, flow injection analysis, ultrasound, and handheld sensors. | 0 | Theoretical and Fundamental Chemistry |
The FRET efficiency () is the quantum yield of the energy-transfer transition, i.e. the probability of energy-transfer event occurring per donor excitation event:
where the radiative decay rate of the donor, is the rate of energy transfer, and the rates of any other de-excitation pathways excluding energy transfers to other acceptors.
The FRET efficiency depends on many physical parameters that can be grouped as: 1) the distance between the donor and the acceptor (typically in the range of 1–10 nm), 2) the spectral overlap of the donor emission spectrum and the acceptor absorption spectrum, and 3) the relative orientation of the donor emission dipole moment and the acceptor absorption dipole moment.
depends on the donor-to-acceptor separation distance with an inverse 6th-power law due to the dipole–dipole coupling mechanism:
with being the Förster distance of this pair of donor and acceptor, i.e. the distance at which the energy transfer efficiency is 50%.
The Förster distance depends on the overlap integral of the donor emission spectrum with the acceptor absorption spectrum and their mutual molecular orientation as expressed by the following equation all in SI units:
where is the fluorescence quantum yield of the donor in the absence of the acceptor, is the dipole orientation factor, is the refractive index of the medium, is the Avogadro constant, and is the spectral overlap integral calculated as
where is the donor emission spectrum, is the donor emission spectrum normalized to an area of 1, and is the acceptor molar extinction coefficient, normally obtained from an absorption spectrum.
The orientation factor is given by
where denotes the normalized transition dipole moment of the respective fluorophore, and denotes the normalized inter-fluorophore displacement.
= 2/3 is often assumed. This value is obtained when both dyes are freely rotating and can be considered to be isotropically oriented during the excited-state lifetime. If either dye is fixed or not free to rotate, then = 2/3 will not be a valid assumption. In most cases, however, even modest reorientation of the dyes results in enough orientational averaging that = 2/3 does not result in a large error in the estimated energy-transfer distance due to the sixth-power dependence of on . Even when is quite different from 2/3, the error can be associated with a shift in , and thus determinations of changes in relative distance for a particular system are still valid. Fluorescent proteins do not reorient on a timescale that is faster than their fluorescence lifetime. In this case 0 ≤ ≤ 4.
The units of the data are usually not in SI units. Using the original units to calculate the Förster distance is often more convenient. For example, the wavelength is often in unit nm and the extinction coefficient is often in unit , where is concentration . obtained from these units will have unit . To use unit Å () for the , the equation is adjusted to
: (Å)
For time-dependent analyses of FRET, the rate of energy transfer () can be used directly instead:
where is the donor's fluorescence lifetime in the absence of the acceptor.
The FRET efficiency relates to the quantum yield and the fluorescence lifetime of the donor molecule as follows:
where and are the donor fluorescence lifetimes in the presence and absence of an acceptor respectively, or as
where and are the donor fluorescence intensities with and without an acceptor respectively. | 1 | Applied and Interdisciplinary Chemistry |
Normal phase elution is achieved by pumping the non-aqueous or phase of a biphasic solvent system through the column as the mobile phase, with a more polar stationary phase being retained in the column. The cause of original nomenclature of is relevant. As original stationary phases of paper chromatography were superseded by more efficient materials such as diatomaceous earths (natural micro-porous silica) and followed by modern silica gel, the thin-layer chromatography stationary phase was polar (hydroxy groups attached to silica) and maximum retention was achieved with non-polar solvents such as n-hexane. Progressively more polar eluents were then used to move polar compounds up the plate. Various alkane bonded phases were tried with C18 becoming the most popular. Alkane chains were chemically bonded to the silica, and a reversal of the elution trend occurred. Thus a polar stationary became "normal" phase chromatography, and the non-polar stationary phase chromatography became "reversed" phase chromatography. | 0 | Theoretical and Fundamental Chemistry |
Many analogues have been prepared from primary, secondary, and even tertiary amines:
* Borane tert-butylamine ()
* Borane trimethylamine ()
* Borane isopropylamine ()
The first amine adduct of borane was derived from trimethylamine. Borane tert-butylamine complex is prepared by the reaction of sodium borohydride with t-butylammonium chloride. Generally adduct are more robust with more basic amines. Variations are also possible for the boron component, although primary and secondary boranes are less common. | 0 | Theoretical and Fundamental Chemistry |
Viscosity is measured with various types of viscometers and rheometers. Close temperature control of the fluid is essential to obtain accurate measurements, particularly in materials like lubricants, whose viscosity can double with a change of only 5 °C. A rheometer is used for fluids that cannot be defined by a single value of viscosity and therefore require more parameters to be set and measured than is the case for a viscometer.
For some fluids, the viscosity is constant over a wide range of shear rates (Newtonian fluids). The fluids without a constant viscosity (non-Newtonian fluids) cannot be described by a single number. Non-Newtonian fluids exhibit a variety of different correlations between shear stress and shear rate.
One of the most common instruments for measuring kinematic viscosity is the glass capillary viscometer.
In coating industries, viscosity may be measured with a cup in which the efflux time is measured. There are several sorts of cup—such as the Zahn cup and the Ford viscosity cup—with the usage of each type varying mainly according to the industry.
Also used in coatings, a Stormer viscometer employs load-based rotation to determine viscosity. The viscosity is reported in Krebs units (KU), which are unique to Stormer viscometers.
Vibrating viscometers can also be used to measure viscosity. Resonant, or vibrational viscometers work by creating shear waves within the liquid. In this method, the sensor is submerged in the fluid and is made to resonate at a specific frequency. As the surface of the sensor shears through the liquid, energy is lost due to its viscosity. This dissipated energy is then measured and converted into a viscosity reading. A higher viscosity causes a greater loss of energy.
Extensional viscosity can be measured with various rheometers that apply extensional stress.
Volume viscosity can be measured with an acoustic rheometer.
Apparent viscosity is a calculation derived from tests performed on drilling fluid used in oil or gas well development. These calculations and tests help engineers develop and maintain the properties of the drilling fluid to the specifications required.
Nanoviscosity (viscosity sensed by nanoprobes) can be measured by fluorescence correlation spectroscopy. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, Lamb vector is the cross product of vorticity vector and velocity vector of the flow field, named after the physicist Horace Lamb. The Lamb vector is defined as
where is the velocity field and is the vorticity field of the flow. It appears in the Navier–Stokes equations through the material derivative term, specifically via convective acceleration term,
In irrotational flows, the Lamb vector is zero, so does in Beltrami flows. The concept of Lamb vector is widely used in turbulent flows. The Lamb vector is analogous to electric field, when the Navier–Stokes equation is compared with Maxwell's equations. | 1 | Applied and Interdisciplinary Chemistry |
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