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[https://www.breastcancer.org/symptoms/types/idc ] is one of the common types of breast cancer which accounts for 8 out of 10 of all invasive breast cancers. According to the American Cancer Society, more than 180,000 women in the United States find out that they have breast cancers each year, and most are diagnosed with this specific type of cancer. While it is essential to detect breast cancer early to reduce the death rate there may be already more than 10,000,000 cells in breast cancer when it can be observed by [https://www.cdc.gov/cancer/breast/basic_info/mammograms.htm#:~:text=A%20mammogram%20is%20an%20X,before%20it%20can%20be%20felt. ]. however, the IR Spectrum proposed by Szu et al seems to be more promising in detecting breast cancer cells several months ahead of a mammogram. Clinical tests have been carried out with approval of Institutional Review Board of National Taiwan University Hospital. So from August 2007 to June 2008 35 patients aged between (30-66) with an average age of 49 were enlisted in this project. the results established that about 63% of the success rate could be achieved with the cross-sectional data. Therefore the results concluded that breast cancers may be detected more accurately by maps]</u> of multiple three-points. | 0 | Theoretical and Fundamental Chemistry |
Nucleosomes can be assembled in vitro by either using purified native or recombinant histones. One standard technique of loading the DNA around the histones involves the use of salt dialysis. A reaction consisting of the histone octamers and a naked DNA template can be incubated together at a salt concentration of 2 M. By steadily decreasing the salt concentration, the DNA will equilibrate to a position where it is wrapped around the histone octamers, forming nucleosomes. In appropriate conditions, this reconstitution process allows for the nucleosome positioning affinity of a given sequence to be mapped experimentally. | 1 | Applied and Interdisciplinary Chemistry |
A polytropic process is a thermodynamic process that obeys the relation:
where P is the pressure, V is volume, n is any real number (the "polytropic index"), and C is a constant. This equation can be used to accurately characterize processes of certain systems, notably the compression or expansion of a gas, but in some cases, liquids and solids. | 0 | Theoretical and Fundamental Chemistry |
2α-Mannobiose is a disaccharide. It is formed by a condensation reaction, when two mannose molecules react together, in the formation of a glycosidic bond. | 1 | Applied and Interdisciplinary Chemistry |
To carry out metal cation titrations using EDTA, it is almost always necessary to use a complexometric indicator to determine when the end point has been reached. Common indicators are organic dyes such as Fast Sulphon Black, Eriochrome Black T, Eriochrome Red B, Patton Reeder, or Murexide. Color change shows that the indicator has been displaced (usually by EDTA) from the metal cations in solution when the end point has been reached. Thus, the free indicator (rather than the metal complex) serves as the endpoint indicator. | 0 | Theoretical and Fundamental Chemistry |
DNA molecules were fixed on molten agarose developed between a cover slip and a microscope slide. Restriction enzyme was pre-mixed with the molten agarose before DNA placement and cleavage was triggered by addition of magnesium. | 1 | Applied and Interdisciplinary Chemistry |
The use of RNA-dependent RNA polymerase plays a major role in RNA interference in eukaryotes, a process used to silence gene expression via small interfering RNAs (siRNAs) binding to mRNA rendering them inactive. Eukaryotic RdRp becomes active in the presence of dsRNA, and is a less widely distributed compared to other RNAi components as it lost in some animals, though still found in C. elegans and P. tetraurelia and plants. This presence of dsRNA triggers the activation of RdRp and RNAi processes by priming the initiation of RNA transcription through the introduction of siRNAs into the system. In C. elegans, siRNAs are integrated into the RNA-induced silencing complex, RISC, which works alongside mRNAs targeted for interference to recruit more RdRps to synthesize more secondary siRNAs and repress gene expression. | 1 | Applied and Interdisciplinary Chemistry |
A black light may also be formed by simply using a UV filter coating such as Wood's glass on the envelope of a common incandescent bulb. This was the method that was used to create the very first black light sources. Although incandescent black light bulbs are a cheaper alternative to fluorescent tubes, they are exceptionally inefficient at producing UV light since most of the light emitted by the filament is visible light which must be blocked. Due to its black body spectrum, an incandescent light radiates less than 0.1% of its energy as UV light. Incandescent UV bulbs, due to the necessary absorption of the visible light, become very hot during use. This heat is, in fact, encouraged in such bulbs, since a hotter filament increases the proportion of UVA in the black-body radiation emitted. This high running-temperature drastically reduces the life of the lamp, however, from a typical 1,000 hours to around 100 hours. | 0 | Theoretical and Fundamental Chemistry |
A normal ferritin blood level, referred to as the reference interval is determined by many testing laboratories. The ranges for ferritin can vary between laboratories but typical ranges would be between 40 and 300 ng/mL (=μg/L) for males, and 20–200 ng/mL (=μg/L) for females. | 1 | Applied and Interdisciplinary Chemistry |
A typical CO absorption process consists of a feed gas, an absorption column, a stripper column, and output streams of CO-rich gas to be sequestered, and CO-poor gas to be released to the atmosphere. Ionic liquids could follow a similar process to amine gas treating, where the CO is regenerated in the stripper using higher temperature. However, ionic liquids can also be stripped using pressure swings or inert gases, reducing the process energy requirement. A current issue with ionic liquids for carbon capture is that they have a lower working capacity than amines. Task-specific ionic liquids that employ chemisorption and physisorption are being developed in an attempt to increase the working capacity. 1-butyl-3-propylamineimidazolium tetrafluoroborate is one example of a TSIL. | 0 | Theoretical and Fundamental Chemistry |
HPLC in the field of microfluidics comes in two different forms. Early designs included running liquid through the HPLC column then transferring the eluted liquid to microfluidic chips and attaching HPLC columns to the microfluidic chip directly. The early methods had the advantage of easier detection from certain machines like those that measure fluorescence. More recent designs have fully integrated HPLC columns into microfluidic chips. The main advantage of integrating HPLC columns into microfluidic devices is the smaller form factor that can be achieved, which allows for additional features to be combined within one microfluidic chip. Integrated chips can also be fabricated from multiple different materials, including glass and polyimide which are quite different from the standard material of PDMS used in many different droplet-based microfluidic devices. This is an important feature because different applications of HPLC microfluidic chips may call for different pressures. PDMS fails in comparison for high-pressure uses compared to glass and polyimide. High versatility of HPLC integration ensures robustness by avoiding connections and fittings between the column and chip. The ability to build off said designs in the future allows the field of microfluidics to continue expanding its potential applications.
The potential applications surrounding integrated HPLC columns within microfluidic devices have proven expansive over the last 10–15 years. The integration of such columns allows for experiments to be run where materials were in low availability or very expensive, like in biological analysis of proteins. This reduction in reagent volumes allows for new experiments like single-cell protein analysis, which due to size limitations of prior devices, previously came with great difficulty. The coupling of HPLC-chip devices with other spectrometry methods like mass-spectrometry allow for enhanced confidence in identification of desired species, like proteins. Microfluidic chips have also been created with internal delay-lines that allow for gradient generation to further improve HPLC, which can reduce the need for further separations. Some other practical applications of integrated HPLC chips include the determination of drug presence in a person through their hair and the labeling of peptides through reverse phase liquid chromatography. | 1 | Applied and Interdisciplinary Chemistry |
For organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such as aldehydes, ketones and carboxylic acids), as part of many larger functional groups. A compound containing a carbonyl group is often referred to as a carbonyl compound.
The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e.g. nickel carbonyl).
The remainder of this article concerns itself with the organic chemistry definition of carbonyl, such that carbon and oxygen share a double bond. | 0 | Theoretical and Fundamental Chemistry |
The Dyson Perrins Laboratory is in the science area of the University of Oxford and was the main centre for research into organic chemistry of the University from its foundation in 1916 until its closure as a research laboratory in 2003. Until 2018, parts of the building were used as teaching laboratories in which undergraduate students were trained in practical organic chemistry.
It was founded with an endowment from Charles Dyson Perrins, heir to the Lea & Perrins Worcestershire sauce company, and stands on the north side of South Parks Road in Oxford. | 1 | Applied and Interdisciplinary Chemistry |
Narendra Nayak (born 5 February 1951) is a rationalist, sceptic, and godman debunker from Mangalore, Karnataka, India. Nayak is the current president of the Federation of Indian Rationalist Associations (FIRA). He founded the Dakshina Kannada Rationalist Association in 1976 and has been its secretary since then. He also founded an NGO called Aid Without Religion in July 2011. He tours the country conducting workshops to promote scientific temper and showing people how to debunk godmen and frauds. He has conducted over 2000 such demonstrations in India, including some in Australia, Greece, England, Norway, Denmark, Sri Lanka and Nepal. He is also a polyglot who speaks 9 languages fluently, which helps him when he is giving talks in various parts of the country. | 1 | Applied and Interdisciplinary Chemistry |
Compounds that were historically given the formulae REAlB and REB have the MgAlB structure with an orthorhombic symmetry and space group Imma (No. 74). In this structure, rare-earth atoms enter the Mg site. Aluminium sites are empty for REB. Both metal sites of REAlB structure have partial occupancies of about 60–70%, which shows that the compounds are actually non-stoichiometric. The REB formula merely reflects the average atomic ratio [B]/[RE] = 25. Yttrium borides form both YAlB and YB structures. Experiments have confirmed that the borides based on rare-earth elements from Tb to Lu can have the REAlB structure. A subset of these borides, which contains rare-earth elements from Gd to Er, can also crystallize in the REB structure.
Korsukova et al. analyzed the YAlB crystal structure using a single crystal grown by the high-temperature solution-growth method. The lattice constants were deduced as a = 0.58212(3), b = 1.04130(8) and c = 0.81947(6) nm, and the atomic coordinates and site occupancies are summarized in table I.
Figure 3 shows the crystal structure of YAlB viewed along the x-axis. The large black spheres are Y atoms, the small blue spheres are Al atoms and the small green spheres are the bridging boron sites; B clusters are depicted as the green icosahedra. Boron framework of YAlB is one of the simplest among icosahedron-based borides – it consists of only one kind of icosahedra and one bridging boron site. The bridging boron site is tetrahedrally coordinated by four boron atoms. Those atoms are another boron atom in the counter bridge site and three equatorial boron atoms of one of three B icosahedra. Aluminium atoms are separated by 0.2911 nm and are arranged in lines parallel to the x-axis, whereas yttrium atoms are separated by 0.3405 nm. Both the Y atoms and B icosahedra form zigzags along the x-axis. The bridging boron atoms connect three equatorial boron atoms of three icosahedra and those icosahedra make up a network parallel to the (101) crystal plane (x-z plane in the figure). The bonding distance between the bridging boron and the equatorial boron atoms is 0.1755 nm, which is typical for the strong covalent B-B bond (bond length 0.17–0.18 nm); thus, the bridging boron atoms strengthen the individual network planes. On the other hand, the large distance between the boron atoms within the bridge (0.2041 nm) suggests weaker interaction, and thus the bridging sites contribute little to the bonding between the network planes.
The boron framework of YAlB needs donation of four electrons from metal elements: two electrons for a B icosahedron and one electron for each of the two bridging boron atoms – to support their tetrahedral coordination. The actual chemical composition of YAlB, determined by the structure analysis, is YAlB as described in table I. If both metal elements are trivalent ions then 3.99 electrons can be transferred to the boron framework, which is very close to the required value of 4. However, because the bonding between the bridging boron atoms is weaker than in a typical B-B covalent bond, less than 2 electrons are donated to this bond, and metal atoms need not be trivalent. On the other hand, the electron transfer from metal atoms to the boron framework implies that not only strong covalent B-B bonding within the framework but also ionic interaction between metal atoms and the framework contribute to the YAlB phase stabilization. | 0 | Theoretical and Fundamental Chemistry |
Asp85 accepts a proton from the Schiff base N atom. In the M intermediate, neither the Schiff base nor Asp85 are charged. | 0 | Theoretical and Fundamental Chemistry |
In cyanobacteria, inorganic phosphate (P) also participates in the co-ordinated regulation of photosynthesis: P binds to the RuBisCO active site and to another site on the large chain where it can influence transitions between activated and less active conformations of the enzyme. In this way, activation of bacterial RuBisCO might be particularly sensitive to P levels, which might cause it to act in a similar way to how RuBisCO activase functions in higher plants. | 0 | Theoretical and Fundamental Chemistry |
In analytical chemistry, Karl Fischer titration is a classic titration method that uses coulometric or volumetric titration to determine trace amounts of water in a sample. It was invented in 1935 by the German chemist Karl Fischer. Today, the titration is done with an automated Karl Fischer titrator. | 0 | Theoretical and Fundamental Chemistry |
Animals and plants have evolved to synthesise a vast array of poisonous products including secondary metabolites, peptides and proteins that can act as inhibitors. Natural toxins are usually small organic molecules and are so diverse that there are probably natural inhibitors for most metabolic processes. The metabolic processes targeted by natural poisons encompass more than enzymes in metabolic pathways and can also include the inhibition of receptor, channel and structural protein functions in a cell. For example, paclitaxel (taxol), an organic molecule found in the Pacific yew tree, binds tightly to tubulin dimers and inhibits their assembly into microtubules in the cytoskeleton.
Many natural poisons act as neurotoxins that can cause paralysis leading to death and function for defence against predators or in hunting and capturing prey. Some of these natural inhibitors, despite their toxic attributes, are valuable for therapeutic uses at lower doses. An example of a neurotoxin are the glycoalkaloids, from the plant species in the family Solanaceae (includes potato, tomato and eggplant), that are acetylcholinesterase inhibitors. Inhibition of this enzyme causes an uncontrolled increase in the acetylcholine neurotransmitter, muscular paralysis and then death. Neurotoxicity can also result from the inhibition of receptors; for example, atropine from deadly nightshade (Atropa belladonna) that functions as a competitive antagonist of the muscarinic acetylcholine receptors.
Although many natural toxins are secondary metabolites, these poisons also include peptides and proteins. An example of a toxic peptide is alpha-amanitin, which is found in relatives of the death cap mushroom. This is a potent enzyme inhibitor, in this case preventing the RNA polymerase II enzyme from transcribing DNA. The algal toxin microcystin is also a peptide and is an inhibitor of protein phosphatases. This toxin can contaminate water supplies after algal blooms and is a known carcinogen that can also cause acute liver haemorrhage and death at higher doses.
Proteins can also be natural poisons or antinutrients, such as the trypsin inhibitors (discussed in the "metabolic regulation" section above) that are found in some legumes. A less common class of toxins are toxic enzymes: these act as irreversible inhibitors of their target enzymes and work by chemically modifying their substrate enzymes. An example is ricin, an extremely potent protein toxin found in castor oil beans. This enzyme is a glycosidase that inactivates ribosomes. Since ricin is a catalytic irreversible inhibitor, this allows just a single molecule of ricin to kill a cell. | 1 | Applied and Interdisciplinary Chemistry |
Auger therapy (AT) makes use of a very high dose of ionizing radiation in situ that provides molecular modifications at an atomic scale. AT differs from conventional radiation therapy in several aspects; it neither relies upon radioactive nuclei to cause cellular radiation damage at a cellular dimension, nor engages multiple external pencil-beams from different directions to zero-in to deliver a dose to the targeted area with reduced dose outside the targeted tissue/organ locations. Instead, the in situ delivery of a very high dose at the molecular level using AT aims for in situ molecular modifications involving molecular breakages and molecular re-arrangements such as a change of stacking structures as well as cellular metabolic functions related to the said molecule structures. | 0 | Theoretical and Fundamental Chemistry |
Fluoride volatility is the tendency of highly fluorinated molecules to vaporize at comparatively low temperatures. Heptafluorides, hexafluorides and pentafluorides have much lower boiling points than the lower-valence fluorides. Most difluorides and trifluorides have high boiling points, while most tetrafluorides and monofluorides fall in between. The term "fluoride volatility" is jargon used particularly in the context of separation of radionuclides. | 0 | Theoretical and Fundamental Chemistry |
For a fluid moving between two plane parallel surfaces—where the width is much greater than the space between the plates—then the characteristic dimension is equal to the distance between the plates. This is consistent with the annular duct and rectangular duct cases above, taken to a limiting aspect ratio. | 1 | Applied and Interdisciplinary Chemistry |
The ratio of O to O in ice and deep sea cores is temperature dependent, and can be used as a proxy measure for reconstructing climate change. During colder periods of the Earth's history (glacials) such as during the ice ages, O is preferentially evaporated from the colder oceans, leaving the slightly heavier and more sluggish O behind. Organisms such as foraminifera which combine oxygen dissolved in the surrounding water with carbon and calcium to build their shells therefore incorporate the temperature-dependent O to O ratio. When these organisms die, they settle out on the sea bed, preserving a long and invaluable record of global climate change through much of the Quaternary. Similarly, ice cores on land are enriched in the heavier O relative to O during warmer climatic phases (interglacials) as more energy is available for the evaporation of the heavier O isotope. The oxygen isotope record preserved in the ice cores is therefore a "mirror" of the record contained in ocean sediments.
Oxygen isotopes preserve a record of the effects of the Milankovitch cycles on climate change during the Quaternary, revealing an approximately 100,000-year cyclicity in the Earth's climate. | 0 | Theoretical and Fundamental Chemistry |
Analogously to the in situ IR experiments described above, in situ UV-visible absorbance spectroscopy may be used to monitor the course of a reaction, provided a reagent or product shows distinctive absorbance in the UV spectral region. The rate of reactant consumption and/or product formation may be abstracted from the change of absorbance over time (by application of Beer's Law), again leading to classification as an integral technique. Due to the spectral region utilized, UV-vis techniques are more commonly utilized on inorganic or organometallic systems than on purely organic reactions, and examples include exploration of the samarium Barbier reaction. | 0 | Theoretical and Fundamental Chemistry |
Milk is a commonly cited example of an emulsion, a specific type of dispersion of one liquid into another liquid where the two liquids are immiscible. The fat molecules suspended in milk provide a mode of delivery of important fat-soluble vitamins and nutrients from the mother to newborn. The mechanical, thermal, or enzymatic treatment of milk manipulates the integrity of these fat globules and results in a wide variety of dairy products.
Oxide dispersion-strengthened alloy (ODS) is an example of oxide particle dispersion into a metal medium, which improves the high temperature tolerance of the material. Therefore these alloys have several applications in the nuclear energy industry, where materials must withstand extremely high temperatures to maintain operation.
The degradation of coastal aquifers is a direct result of seawater intrusion into the and dispersion into the aquifer following excessive use of the aquifer. When an aquifer is depleted for human use, it is naturally replenished by groundwater moving in from other areas. In the case of coastal aquifers, the water supply is replenished both from the land boundary on one side and the sea boundary on the other side. After excessive discharge, saline water from the sea boundary will enter the aquifer and disperse in the freshwater medium, threatening the viability of the aquifer for human use. Several different solutions to seawater intrusion in coastal aquifers have been proposed, including engineering methods of artificial recharge and implementing physical barriers at the sea boundary.
Chemical dispersants are used in oil spills to mitigate the effects of the spill and promote the degradation of oil particles. The dispersants effectively isolate pools on oil sitting on the surface of the water into smaller droplets that disperse into the water, which lowers the overall concentration of oil in the water to prevent any further contamination or impact on marine biology and coastal wildlife. | 0 | Theoretical and Fundamental Chemistry |
In nucleotide sugar metabolism a group of biochemicals known as nucleotide sugars act as donors for sugar residues in the glycosylation reactions that produce polysaccharides. They are substrates for glycosyltransferases. The nucleotide sugars are also intermediates in nucleotide sugar interconversions that produce some of the activated sugars needed for glycosylation reactions. Since most glycosylation takes place in the endoplasmic reticulum and golgi apparatus, there are a large family of nucleotide sugar transporters that allow nucleotide sugars to move from the cytoplasm, where they are produced, into the organelles where they are consumed.
Nucleotide sugar metabolism is particularly well-studied in yeast, fungal pathogens, and bacterial pathogens, such as E. coli and Mycobacterium tuberculosis, since these molecules are required for the synthesis of glycoconjugates on the surfaces of these organisms. These glycoconjugates are virulence factors and components of the fungal and bacterial cell wall. These pathways are also studied in plants, but here the enzymes involved are less well understood. | 1 | Applied and Interdisciplinary Chemistry |
Pre-implantation genetic diagnosis (PGD) is criticised for giving select demographic groups disproportionate access to a means of creating a child possessing characteristics that they consider "ideal". Many fertile couples now demand equal access to embryonic screening so that their child can be just as healthy as one created through IVF. Mass use of PGD, especially as a means of population control or in the presence of legal measures related to population or demographic control, can lead to intentional or unintentional demographic effects such as the skewed live-birth sex ratios seen in China following implementation of its one-child policy.
While PGD was originally designed to screen for embryos carrying hereditary genetic diseases, the method has been applied to select features that are unrelated to diseases, thus raising ethical questions. Examples of such cases include the selection of embryos based on histocompatibility (HLA) for the donation of tissues to a sick family member, the diagnosis of genetic susceptibility to disease, and sex selection.
These examples raise ethical issues because of the morality of eugenics. It becomes frowned upon because of the advantage of being able to eliminate unwanted traits and selecting desired traits. By using PGD, individuals are given the opportunity to create a human life unethically and rely on science and not by natural selection.
For example, a deaf British couple, Tom and Paula Lichy, have petitioned to create a deaf baby using IVF. Some medical ethicists have been very critical of this approach. Jacob M. Appel wrote that "intentionally culling out blind or deaf embryos might prevent considerable future suffering, while a policy that allowed deaf or blind parents to select for such traits intentionally would be far more troublesome." | 1 | Applied and Interdisciplinary Chemistry |
The many different software packages available to the NMR spectroscopy community have traditionally employed a number of different data formats and standards to represent computational information. The inception of CCPN was partly to look at this situation and to develop a more unified approach. It was deemed that multiple, informally connected data standards not only made it more difficult for a user to move from one program to the next, but also adversely affected data fidelity, harvesting and database deposition. To this end CCPN has developed a common data standard for NMR, referred to as the CCPN data model, as well as software routines and libraries that allow access, manipulation and storage of the data. The CCPN system works alongside the Bio Mag Res Bank which continues to handle archiving NMR database depositions; the CCPN standard is for active data exchange and in-program manipulation.
Although NMR spectroscopy remains at the core of the data standard it naturally expands into other related areas of science that support and complement NMR. These include molecular and macromolecular description, three-dimensional biological structures, sample preparation, workflow management and software setup. The CCPN libraries are created using the principles of model-driven architecture and automatic code generation; the CCPN data model provides a specification for the automatic generation of APIs in multiple languages. To date CCPN provides APIs to its data model in Python, Java and C programming languages. Through its collaborations, CCPN continues to link new and existing software via its data standards. To enable interaction with as much external software as possible, CCPN has created a format conversion program. This allows data to enter from outside the CCPN scheme and provides a mechanism to translate between existing data formats. The open-source CcpNmr FormatConverter software was first released in 2005 and is available for download (from CCPN and SourceForge) but is also recently accessible as a web application. | 0 | Theoretical and Fundamental Chemistry |
Non-competitive inhibition models a system where the inhibitor and the substrate may both be bound to the enzyme at any given time. When both the substrate and the inhibitor are bound, the enzyme-substrate-inhibitor complex cannot form product and can only be converted back to the enzyme-substrate complex or the enzyme-inhibitor complex. Non-competitive inhibition is distinguished from general mixed inhibition in that the inhibitor has an equal affinity for the enzyme and the enzyme-substrate complex.
For example, in the enzyme-catalyzed reactions of glycolysis, accumulation phosphoenol is catalyzed by pyruvate kinase into pyruvate. Alanine is an amino acid which is synthesized from pyruvate also inhibits the enzyme pyruvate kinase during glycolysis. Alanine is a non-competitive inhibitor, therefore it binds away from the active site to the substrate in order for it to still be the final product.
Another example of non-competitive inhibition is given by glucose-6-phosphate inhibiting hexokinase in the brain. Carbons 2 and 4 on glucose-6-phosphate contain hydroxyl groups that attach along with the phosphate at carbon 6 to the enzyme-inhibitor complex. The substrate and enzyme are different in their group combinations that an inhibitor attaches to. The ability of glucose-6-phosphate to bind at different places at the same time makes it a non-competitive inhibitor.
The most common mechanism of non-competitive inhibition involves reversible binding of the inhibitor to an allosteric site, but it is possible for the inhibitor to operate via other means including direct binding to the active site. It differs from competitive inhibition in that the binding of the inhibitor does not prevent binding of substrate, and vice versa, but simply prevents product formation for a limited time.
This type of inhibition reduces the maximum rate of a chemical reaction without changing the apparent binding affinity of the catalyst for the substrate (K – see Michaelis-Menten kinetics). When a non-competitive inhibitor is added the Vmax is changed, while the Km remains unchanged. According to the Lineweaver-Burk plot the Vmax is reduced during the addition of a non-competitive inhibitor, which is shown in the plot by a change in both the slope and y-intercept when a non-competitive inhibitor is added.
The primary difference between competitive and non-competitive is that competitive inhibition affects the substrate's ability to bind by binding an inhibitor in place of a substrate, which lowers the affinity of the enzyme for the substrate. In non-competitive inhibition, the inhibitor binds to an allosteric site and prevents the enzyme-substrate complex from performing a chemical reaction. This does not affect the Km (affinity) of the enzyme (for the substrate). Non-competitive inhibition differs from uncompetitive inhibition in that it still allows the substrate to bind to the enzyme-inhibitor complex and form an enzyme-substrate-inhibitor complex, this is not true in uncompetitive inhibition, it prevents the substrate from binding to the enzyme inhibitor through conformational change upon allosteric binding. | 1 | Applied and Interdisciplinary Chemistry |
Solomon's considerable contributions to science have been recognised by his peers through election to the following Academies:
* Fellow of the Institution of Chemical Engineers (FIChemE, 2007)
* Fellow of the Royal Society (FRS, 2004).
* Foundation Fellow of the Australian Academy of Technological Sciences and Engineering (FTSE, 1976).
* Fellow of the Australian Academy of Science (FAA, 1975).
* Fellow of the Royal Australian Chemical Institute (FRACI, 1966)
Solomon has always been active in these societies, in particular the Royal Australian Chemical Institute (RACI). In 2001 the RACI established the Solomon Lecture Series in recognition of his contribution to the field and to the RACI. A biennial series presented by an invited leading international polymer researcher, this Lecture Series recognizes the importance of promoting the exchange of ideas and expertise and to expose young scientists to the best in their field internationally. | 0 | Theoretical and Fundamental Chemistry |
The density of surface seawater ranges from about 1020 to 1029 kg/m, depending on the temperature and salinity. At a temperature of 25 °C, the salinity of 35 g/kg and 1 atm pressure, the density of seawater is 1023.6 kg/m. Deep in the ocean, under high pressure, seawater can reach a density of 1050 kg/m or higher. The density of seawater also changes with salinity. Brines generated by seawater desalination plants can have salinities up to 120 g/kg. The density of typical seawater brine of 120 g/kg salinity at 25 °C and atmospheric pressure is 1088 kg/m. | 0 | Theoretical and Fundamental Chemistry |
* 2,2,2-Trichloroethyl chloroformate, pyridine or aqueous sodium hydroxide at ambient temperature
* Electrolysis
* Deprotection using zinc metal | 0 | Theoretical and Fundamental Chemistry |
The following is an example of the algorithm for determining the axis/angle representation of misorientation between two texture components given as Euler angles:
:Copper [90,35,45]
:S3 [59,37,63]
The first step is converting the Euler angle representation, to an orientation matrix by:
where and represent and of the respective Euler component. This yields the following orientation matrices:
The misorientation is then:
The axis/angle description (with the axis as a unit vector) is related to the misorientation matrix by:
(There are errors in the similar formulae for the components of r given in the book by Randle and Engler (see refs.), which will be corrected in the next edition of their book. The above are the correct versions, note a different form for these equations has to be used if Θ = 180 degrees.)
For the copper—S misorientation given by , the axis/angle description is 19.5° about [0.689,0.623,0.369], which is only 2.3° from <221>. This result is only one of the 1152 symmetrically related possibilities but does specify the misorientation. This can be verified by considering all possible combinations of orientation symmetry (including switching symmetry). | 0 | Theoretical and Fundamental Chemistry |
Consider a growth-optimizing investor in a fair game with mutually exclusive outcomes
(e.g. a “horse race” in which the official odds add up to one).
The rate of return expected by such an investor is equal to the relative entropy
between the investor's believed probabilities and the official odds.
This is a special case of a much more general connection between financial returns and divergence measures.
Financial risks are connected to via information geometry. Investors views, the prevailing market view, and risky scenarios form triangles on the relevant manifold of probability distributions. The shape of the triangles determines key financial risks (both qualitatively and quantitatively). For instance, obtuse triangles in which investors views and risk scenarios appear on “opposite sides” relative to the market describe negative risks, acute triangles describe positive exposure, and the right-angled situation in the middle corresponds to zero risk. | 0 | Theoretical and Fundamental Chemistry |
The remediation, or removal, of PCBs from estuarian and coastal river sediments is quite difficult due to the overlying water column and the potential for resuspension of contaminants during the removal process. The most common method of PCB extraction from sediments is to dredge an area and dispose of the sediments in a landfill. This method is troubling for a number of reasons, namely that it has a risk of resuspension of the chemicals as the sediments are disturbed, and this method can be very damaging to ecosystems.
A potential cost effective, low risk remediation technique is bioremediation. Bioremediation involves the use of biota to remediate sediments. Phytoremediation, the use of plants to remediate soils, has been found to be effective for a broad range of contaminants such as mercury PCB and PAHs in terrestrial soils. A promising study conducted in New Bedford Harbor found that Ulva rigida, a type of seaweed common throughout the world, is effective at removing PCB from sediments. During a typical bloom in New Bedford Harbor, U. rigida forms a thick mat that lies on top of and in contact with the sediment. This allows for U. rigida to uptake large amounts of PCB from the sediment with concentrations of PCB in U. rigida reaching 1580 μg kg within 24 hours of the bloom. Live tissue tended to take up higher concentrations of PCB than dead tissue, but this is not to say that dead tissue did not still take up large amounts of PCB as well. | 1 | Applied and Interdisciplinary Chemistry |
Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atoms electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus. The higher the associated electronegativity, the more an atom or a substituent group attracts electrons. Electronegativity serves as a simple way to quantitatively estimate the bond energy, and the sign and magnitude of a bonds chemical polarity, which characterizes a bond along the continuous scale from covalent to ionic bonding. The loosely defined term electropositivity is the opposite of electronegativity: it characterizes an element's tendency to donate valence electrons.
On the most basic level, electronegativity is determined by factors like the nuclear charge (the more protons an atom has, the more "pull" it will have on electrons) and the number and location of other electrons in the atomic shells (the more electrons an atom has, the farther from the nucleus the valence electrons will be, and as a result, the less positive charge they will experience—both because of their increased distance from the nucleus and because the other electrons in the lower energy core orbitals will act to shield the valence electrons from the positively charged nucleus).
The term "electronegativity" was introduced by Jöns Jacob Berzelius in 1811,
though the concept was known before that and was studied by many chemists including Avogadro.
In spite of its long history, an accurate scale of electronegativity was not developed until 1932, when Linus Pauling proposed an electronegativity scale which depends on bond energies, as a development of valence bond theory. It has been shown to correlate with a number of other chemical properties. Electronegativity cannot be directly measured and must be calculated from other atomic or molecular properties. Several methods of calculation have been proposed, and although there may be small differences in the numerical values of the electronegativity, all methods show the same periodic trends between elements.
The most commonly used method of calculation is that originally proposed by Linus Pauling. This gives a dimensionless quantity, commonly referred to as the Pauling scale (χ), on a relative scale running from 0.79 to 3.98 (hydrogen = 2.20). When other methods of calculation are used, it is conventional (although not obligatory) to quote the results on a scale that covers the same range of numerical values: this is known as an electronegativity in Pauling units.
As it is usually calculated, electronegativity is not a property of an atom alone, but rather a property of an atom in a molecule. Even so, the electronegativity of an atom is strongly correlated with the first ionization energy. The electronegativity is slightly negatively correlated (for smaller electronegativity values) and rather strongly positively correlated (for most and larger electronegativity values) with the electron affinity. It is to be expected that the electronegativity of an element will vary with its chemical environment, but it is usually considered to be a transferable property, that is to say that similar values will be valid in a variety of situations.
Caesium is the least electronegative element (0.79); fluorine is the most (3.98). | 0 | Theoretical and Fundamental Chemistry |
In 2014 SaskPower a provincial-owned electric utility finished renovations on Boundary Dams boiler number 3 making it the worlds first post-combustion carbon capture storage facility. The renovation project ended up costing a little over $1.2 billion and can scrub out and toxins from up to 90 percent of the flue gas that it emits. | 1 | Applied and Interdisciplinary Chemistry |
Glycogen is a branched biopolymer consisting of linear chains of glucose residues with an average chain length of approximately 8–12 glucose units and 2,000-60,000 residues per one molecule of glycogen.
Like amylopectin, glucose units are linked together linearly by α(1→4) glycosidic bonds from one glucose to the next. Branches are linked to the chains from which they are branching off by α(1→6) glycosidic bonds between the first glucose of the new branch and a glucose on the stem chain.
Each glycogen is essentially a ball of glucose trees, with around 12 layers, centered on a glycogenin protein, with three kinds of glucose chains: A, B, and C. There is only one C-chain, attached to the glycogenin. This C-chain is formed by the self-glucosylation of the glycogenin, forming a short primer chain. From the C-chain grows out B-chains, and from B-chains branch out B- and A-chains. The B-chains have on average 2 branch points, while the A-chains are terminal, thus unbranched. On average, each chain has length 12, tightly constrained to be between 11 and 15. All A-chains reach the spherical surface of the glycogen.
Glycogen in muscle, liver, and fat cells is stored in a hydrated form, composed of three or four parts of water per part of glycogen associated with 0.45 millimoles (18 mg) of potassium per gram of glycogen.
Glucose is an osmotic molecule, and can have profound effects on osmotic pressure in high concentrations possibly leading to cell damage or death if stored in the cell without being modified. Glycogen is a non-osmotic molecule, so it can be used as a solution to storing glucose in the cell without disrupting osmotic pressure. | 1 | Applied and Interdisciplinary Chemistry |
As early as the late 18th century and early 19th century, the digestion of meat by stomach secretions and the conversion of starch to sugars by plant extracts and saliva were known. However, the mechanism by which this occurred had not been identified.
In the 19th century, when studying the fermentation of sugar to alcohol by yeast, Louis Pasteur concluded that this fermentation was catalyzed by a vital force contained within the yeast cells called ferments, which he thought functioned only within living organisms. He wrote that "alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells."
In 1833 Anselme Payen discovered the first enzyme, diastase, and in 1878 German physiologist Wilhelm Kühne (1837–1900) coined the term enzyme, which comes from Greek in leaven, to describe this process. The word enzyme was used later to refer to nonliving substances such as pepsin, and the word ferment was used to refer to chemical activity produced by living organisms.
In 1897 Eduard Buchner began to study the ability of yeast extracts to ferment sugar despite the absence of living yeast cells. In a series of experiments at the University of Berlin, he found that the sugar was fermented even when there were no living yeast cells in the mixture. He named the enzyme that brought about the fermentation of sucrose zymase. In 1907 he received the Nobel Prize in Chemistry "for his biochemical research and his discovery of cell-free fermentation". Following Buchners example; enzymes are usually named according to the reaction they carry out. Typically the suffix -ase is added to the name of the substrate (e.g., lactase is the enzyme that cleaves lactose) or the type of reaction (e.g.', DNA polymerase forms DNA polymers).
Having shown that enzymes could function outside a living cell, the next step was to determine their biochemical nature. Many early workers noted that enzymatic activity was associated with proteins, but several scientists (such as Nobel laureate Richard Willstätter) argued that proteins were merely carriers for the true enzymes and that proteins per se were incapable of catalysis. However, in 1926, James B. Sumner showed that the enzyme urease was a pure protein and crystallized it; Sumner did likewise for the enzyme catalase in 1937. The conclusion that pure proteins can be enzymes was definitively proved by Northrop and Stanley, who worked on the digestive enzymes pepsin (1930), trypsin, and chymotrypsin. These three scientists were awarded the 1946 Nobel Prize in Chemistry.
This discovery, that enzymes could be crystallized, meant that scientists eventually could solve their structures by x-ray crystallography. This was first done for lysozyme, an enzyme found in tears, saliva, and egg whites that digests the coating of some bacteria; the structure was solved by a group led by David Chilton Phillips and published in 1965. This high-resolution structure of lysozyme marked the beginning of the field of structural biology and the effort to understand how enzymes work at an atomic level of detail. | 1 | Applied and Interdisciplinary Chemistry |
For gene knockout investigations, RNA interference (RNAi), a more recent method, also known as gene silencing, has gained popularity. In RNA interference (RNAi), messenger RNA for a particular gene is inactivated using small interfering RNA (siRNA) or short hairpin RNA (shRNA). This effectively stops the gene from being expressed. Oncogenes like Bcl-2 and p53, as well as genes linked to neurological disease, genetic disorders, and viral infections, have all been targeted for gene silencing utilizing RNA interference (RNAi). | 1 | Applied and Interdisciplinary Chemistry |
Bioluminescence imaging (BLI) is a technology developed over the past decades (1990's and onward). that allows for the noninvasive study of ongoing biological processes Recently, bioluminescence tomography (BLT) has become possible and several systems have become commercially available. In 2011, PerkinElmer acquired one of the most popular lines of optical imaging systems with bioluminescence from Caliper Life Sciences. | 1 | Applied and Interdisciplinary Chemistry |
The exponential amplification via reverse transcription polymerase chain reaction provides for a highly sensitive technique in which a very low copy number of RNA molecules can be detected. RT-PCR is widely used in the diagnosis of genetic diseases and, semiquantitatively, in the determination of the abundance of specific different RNA molecules within a cell or tissue as a measure of gene expression. | 1 | Applied and Interdisciplinary Chemistry |
Alexis Constantin Georg Pappas (16 October 1915 – 12 February 2010) was a Norwegian chemist. Born in London to Greek expatriates in 1915, he moved to Norway a few years later together with his parents. He specialized in nuclear chemistry, and was a professor from 1957 to 1985.
His family used to live in Belgium, but sought refuge in England during World War I, the family then moved to Norway after the war. Pappas finished his secondary education at Frogner School in 1934 and enrolled at the Royal Frederick University. His masters advisor (in radiation chemistry) was Ellen Gleditsch, and he graduated with the cand.real. degree in 1940. He started working in the private business, but was also a research assistant for Gleditsch. From 1947 to 1952, he was a research fellow, with included studies at the Institut du Radium and the Collège de France, and from 1949 to 1951 at the Massachusetts Institute of Technology. In 1952, he returned to Norway, where he worked at the University of Oslos quarters for the research council NTNF. In 1954, he took the Dr. Philos degree on the thesis A Radiochemical Study of Fission Yields. From 1954 to 1957, he worked in Uppsala.
With funding from the Norwegian Cancer Society Pappas was given a professorship in radioisotope studies in 1957. The professorship was changed to nuclear chemistry in 1962, still at the University of Oslo. He retired in 1985. An adviser and sporadic guest scholar at CERN from 1957 to 1967, he served as the Norwegian delegate to CERN Council between 1968 and 1983, and vice president from 1976 to 1978. He was also deputy chairman of the Norwegian Nuclear Energy Safety Authority from 1973 to 1993, during its entire existence, and also the president of the Norwegian Chemical Society from 1966 to 1970. He was a member of the Norwegian Academy of Science and Letters from 1959 to his death, honorary member of the Norwegian Chemical Society from 1993, and in 1979 he was made a Knight 1st Class of the Royal Norwegian Order of St. Olav in 1979.
He married Ela Mjøset (1917–2000) in 1942. He died in February 2010 in Oslo. | 0 | Theoretical and Fundamental Chemistry |
Bismuth polycations form despite the fact that they possess fewer total valence electrons than would seem necessary for the number of sigma bonds. The shapes of these clusters are generally dictated by Wade's rules, which are based on the treatment of the electronic structure as delocalized molecular orbitals. The bonding can also be described with three-center two-electron bonds in some cases, such as the cluster.
Bismuth clusters have been observed to act as ligands for copper and ruthenium ions. This behavior is possible due to the otherwise fairly inert lone pairs on each of the bismuth that arise primarily from the s-orbitals left out of Bi–Bi bonding. | 0 | Theoretical and Fundamental Chemistry |
It is a common observation that when oil and water are poured into the same container, they separate into two phases or layers, because they are immiscible. In general, aqueous (or water-based) solutions, being polar, are immiscible with non-polar organic solvents (cooking oil, chloroform, toluene, hexane etc.) and form a two-phase system. However, in an ABS, both immiscible components are water-based.
The formation of the distinct phases is affected by the pH, temperature and ionic strength of the two components, and separation occurs when the amount of a polymer present exceeds a certain limiting concentration (which is determined by the above factors). | 0 | Theoretical and Fundamental Chemistry |
A restriction enzyme, restriction endonuclease, REase, ENase or restrictase is an enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites. Restriction enzymes are one class of the broader endonuclease group of enzymes. Restriction enzymes are commonly classified into five types, which differ in their structure and whether they cut their DNA substrate at their recognition site, or if the recognition and cleavage sites are separate from one another. To cut DNA, all restriction enzymes make two incisions, once through each sugar-phosphate backbone (i.e. each strand) of the DNA double helix.
These enzymes are found in bacteria and archaea and provide a defense mechanism against invading viruses. Inside a prokaryote, the restriction enzymes selectively cut up foreign DNA in a process called restriction digestion; meanwhile, host DNA is protected by a modification enzyme (a methyltransferase) that modifies the prokaryotic DNA and blocks cleavage. Together, these two processes form the restriction modification system.
More than 3,600 restriction endonucleases are known which represent over 250 different specificities. Over 3,000 of these have been studied in detail, and more than 800 of these are available commercially. These enzymes are routinely used for DNA modification in laboratories, and they are a vital tool in molecular cloning. | 1 | Applied and Interdisciplinary Chemistry |
In Type I photosensitized reactions, the photosensitizer is excited by a light source into a triplet state. The excited, triplet state photosensitizer then reacts with a substrate molecule which is not molecular oxygen to both form a product and reform the photosensitizer. Type I photosensitized reactions result in the photosensitizer being quenched by a different chemical substrate than molecular oxygen. | 0 | Theoretical and Fundamental Chemistry |
Increased risk might be posed by the expected rise in total sulphur emissions from 4,400 kilotonnes (kt) in 1990 to 6,500 kt in 2000, 10,900 kt in 2010 and 18,500 in 2020. | 1 | Applied and Interdisciplinary Chemistry |
In 1927, Nikolai Koltsov proposed that inherited traits would be inherited via a "giant hereditary molecule" which would be made up of "two mirror strands that would replicate in a semi-conservative fashion using each strand as a template". Max Delbrück, Nikolay Timofeev-Ressovsky, and Karl G. Zimmer published results in 1935 suggesting that chromosomes are very large molecules the structure of which can be changed by treatment with X-rays, and that by so changing their structure it was possible to change the heritable characteristics governed by those chromosomes. In 1937 William Astbury produced the first X-ray diffraction patterns from DNA. He was not able to propose the correct structure but the patterns showed that DNA had a regular structure and therefore it might be possible to deduce what this structure was.
In 1943, Oswald Theodore Avery and a team of scientists discovered that traits proper to the "smooth" form of the Pneumococcus could be transferred to the "rough" form of the same bacteria merely by making the killed "smooth" (S) form available to the live "rough" (R) form. Quite unexpectedly, the living R Pneumococcus bacteria were transformed into a new strain of the S form, and the transferred S characteristics turned out to be heritable. Avery called the medium of transfer of traits the transforming principle; he identified DNA as the transforming principle, and not protein as previously thought. He essentially redid Frederick Griffith's experiment. In 1953, Alfred Hershey and Martha Chase did an experiment (Hershey–Chase experiment) that showed, in T2 phage, that DNA is the genetic material (Hershey shared the Nobel prize with Luria). | 1 | Applied and Interdisciplinary Chemistry |
The basic requirements for the formation of euxinic conditions are the absence of oxygen (O), and the presence of sulfate ions (SO), organic matter (CHO), and bacteria capable of reducing sulfate to hydrogen sulfide (HS). The bacteria utilize the redox potential of sulfate as an oxidant and organic matter as a reductant to generate chemical energy through cellular respiration. The chemical species of interest can be represented via the reaction:
2CHO + SO → HS + 2HCO
In the reaction above, the sulfur has been reduced to form the byproduct hydrogen sulfide, the characteristic compound present in water under euxinic conditions. Although sulfate reduction occurs in waters throughout the world, most modern-day aquatic habitats are oxygenated due to photosynthetic production of oxygen and gas exchange between the atmosphere and surface water. Sulfate reduction in these environments is often limited to occurring in seabed sediments that have a strong redox gradient and become anoxic at some depth below the sediment-water interface. In the ocean the rate of these reactions is not [https://online.science.psu.edu/biol011_active002/node/4343 limited] by sulfate, which has been present in large quantities throughout the oceans for the past 2.1 billion years. The Great Oxygenation Event increased atmospheric oxygen concentrations such that oxidative weathering of sulfides became a major source of sulfate to the ocean. Despite plentiful sulfate ions being present in solution, they are not preferentially used by most bacteria. The reduction of sulfate does not give as much energy to an organism as reduction of oxygen or nitrate, so the concentrations of these other elements must be nearly zero for sulfate-reducing bacteria to out-compete aerobic and denitrifying bacteria. In most modern settings these conditions only occur in a small portion of sediments, resulting in insufficient concentrations of hydrogen sulfide to form euxinic waters.
Conditions required for the formation of persistent euxinia include anoxic waters, high nutrient levels, and a stratified water column. These conditions are not all-inclusive and are based largely on modern observations of euxinia. Conditions leading up to and triggering large-scale euxinic events, such as the Canfield ocean, are likely the result of multiple interlinking factors, many of which have been inferred through studies of the geologic record at relevant locations. The formation of stratified anoxic waters with high nutrient levels is influenced by a variety of global and local-scale phenomena such as the presence of nutrient traps and a warming climate. | 0 | Theoretical and Fundamental Chemistry |
Wetland restoration involves restoring a wetlands natural biological, geological, and chemical functions through re-establishment or rehabilitation. It has also been proposed as a potential climate change mitigation strategy. Wetland soil, particularly in coastal wetlands such as mangroves, sea grasses, and salt marshes, is an important carbon reservoir; 20–30% of the worlds soil carbon is found in wetlands, while only 5–8% of the world's land is composed of wetlands. Studies have shown that restored wetlands can become productive sinks and many restoration projects have been enacted in the US and around the world. Aside from climate benefits, wetland restoration and conservation can help preserve biodiversity, improve water quality, and aid with flood control.
The plants that make up wetlands absorb carbon dioxide (CO) from the atmosphere and convert it into organic matter. The waterlogged nature of the soil slows down the decomposition of organic material, leading to the accumulation of carbon-rich peat, acting as a long-term carbon sink. Additionally, anaerobic conditions in waterlogged soils hinder the complete breakdown of organic matter, promoting the conversion of carbon into more stable forms.
As with forests, for the sequestration process to succeed, the wetland must remain undisturbed. If it is disturbed somehow, the carbon stored in the plants and sediments will be released back into the atmosphere and the ecosystem will no longer function as a carbon sink. Additionally, some wetlands can release non- greenhouse gases, such as methane and nitrous oxide which could offset potential climate benefits. The amounts of carbon sequestered via blue carbon by wetlands can also be difficult to measure.
Wetlands are created when water overflows into heavily vegetated soil causing plants to adapt to a flooded ecosystem. Wetlands can occur in three different regions. Marine wetlands are found in shallow coastal areas, tidal wetlands are also coastal but are found farther inland, and non-tidal wetlands are found inland and have no effects from tides. Wetland soil is an important carbon sink; 14.5% of the worlds soil carbon is found in wetlands, while only 5.5% of the worlds land is composed of wetlands. Not only are wetlands a great carbon sink, they have many other benefits like collecting floodwater, filtering air and water pollutants, and creating a home for numerous birds, fish, insects, and plants.
Climate change could alter soil carbon storage changing it from a sink to a source. With rising temperatures comes an increase in greenhouse gasses from wetlands especially locations with permafrost. When this permafrost melts it increases the available oxygen and water in the soil. Because of this, bacteria in the soil would create large amounts of carbon dioxide and methane to be released into the atmosphere.
The link between climate change and wetlands is still not fully known. It is also not clear how restored wetlands manage carbon while still being a contributing source of methane. However, preserving these areas would help prevent further release of carbon into the atmosphere. | 0 | Theoretical and Fundamental Chemistry |
In optics, two non-Lambertian sources that emit beamed energy can interact in a way that causes a shift in the spectral lines. It is analogous to a pair of tuning forks with similar frequencies (pitches), connected together mechanically with a sounding board; there is a strong coupling that results in the resonant frequencies getting "dragged down" in pitch. The Wolf Effect requires that the waves from the sources are partially coherent - the wavefronts being partially in phase. Laser light is coherent while candlelight is incoherent, each photon having random phase. It can produce either redshifts or blueshifts, depending on the observer's point of view, but is redshifted when the observer is head-on.
For two sources interacting while separated by a vacuum, the Wolf effect cannot produce shifts greater than the linewidth of the source spectral line, since it is a position-dependent change in the distribution of the source spectrum, not a method by which new frequencies may be generated. However, when interacting with a medium, in combination with effects such as Brillouin scattering it may produce distorted shifts greater than the linewidth of the source. | 0 | Theoretical and Fundamental Chemistry |
There are several researchers in nanochemistry that have been credited with the development of the field. Geoffrey A. Ozin, from the University of Toronto, is known as one of the "founding fathers of Nanochemistry" due to his four and a half decades of research on this subject. This research includes the study of matrix isolation laser Raman spectroscopy, naked metal clusters chemistry and photochemistry, nanoporous materials, hybrid nanomaterials, mesoscopic materials, and ultrathin inorganic nanowires.
Another chemist who is also viewed as one of the nanochemistry's pioneers is Charles M. Lieber at Harvard University. He is known for his contributions to the development of nano-scale technologies, particularly in the field of biology and medicine. The technologies include nanowires, a new class of quasi-one-dimensional materials that have demonstrated superior electrical, optical, mechanical, and thermal properties and can be used potentially as biological sensors. Research under Lieber has delved into the use of nanowires mapping brain activity.
Shimon Weiss, a professor at the University of California, Los Angeles, is known for his research of fluorescent semiconductor nanocrystals, a subclass of quantum dots, for biological labeling.
Paul Alivisatos, from the University of California, Berkeley, is also notable for his research on the fabrication and use of nanocrystals. This research has the potential to develop insight into the mechanisms of small-scale particles such as the process of nucleation, cation exchange, and branching. A notable application of these crystals is the development of quantum dots.
Peidong Yang, another researcher from the University of California, Berkeley, is also notable for his contributions to the development of 1-dimensional nanostructures. The Yang group has active research projects in the areas of nanowire photonics, nanowire-based solar cells, nanowires for solar to fuel conversion, nanowire thermoelectrics, nanowire-cell interface, nanocrystal catalysis, nanotube nanofluidics, and plasmonics. | 0 | Theoretical and Fundamental Chemistry |
The total acid number (TAN) is a measurement of acidity that is determined by the amount of potassium hydroxide in milligrams that is needed to neutralize the acids in one gram of oil. It is an important quality measurement of crude oil.
The TAN value indicates to the crude oil refinery the potential of corrosion problems. It is usually the naphthenic acids in the crude oil that cause corrosion problems. This type of corrosion is referred to as naphthenic acid corrosion (NAC).
TAN values may also be useful in other industries where oils are used as lubricants to determine oxidation and the subsequent corrosion risk to machinery.
TAN value can be deduced by various methods, including
* Potentiometric titration: The sample is normally dissolved in toluene and propanol with a little water and titrated with alcoholic potassium hydroxide (if sample is acidic). A glass electrode and reference electrode is immersed in the sample and connected to a voltmeter/potentiometer. The meter reading (in millivolts) is plotted against the volume of titrant. The end point is taken at the distinct inflection of the resulting titration curve corresponding to the basic buffer solution.
* Color indicating titration: An appropriate pH color indicator e.g. phenolphthalein, is used. Titrant is added to the sample by means of a burette. The volume of titrant used to cause a permanent color change in the sample is recorded and used to calculate the TAN value.
* Spectroscopic methods: as with many chemical parameters, spectroscopy can be used to make fast, accurate measurements once calibrated by a reference method. Mid and near infrared spectroscopy are most commonly used for this purpose. Spectroscopic methods are valuable as they can also be used to simultaneously measure a number of other parameters and do away with the need for wet chemistry. | 0 | Theoretical and Fundamental Chemistry |
The current editor in chief of JBIC is Nils Metzler-Nolte (Ruhr University Bochum). He followed Lawrence Que (University of Minnesota) who led the journal from 1999 to 2020 and succeeded Ivano Bertini (University of Florence) who was the founding editor of JBIC. | 0 | Theoretical and Fundamental Chemistry |
FSIS is a subsection of the United States Department of Agriculture (USDA), which is tasked with the responsibility of "ensuring that the nation's commercial supply of meat, poultry, and egg products is safe, wholesome, and correctly labeled and packaged." The USDA partnered with the Food and Drug Administration (FDA) to develop and issue regulations against the inappropriate usage of "natural" labels; yet, the FDA does not have specific rules for "natural" labeling. It advised on their website "the agency has not objected to the use of the term if the food does not contain added color, artificial flavors, or synthetic substances."
Furthermore, the FDA has not developed any rules or regulations on the defining features of what qualifies a product as "natural". The FDA does reference a definition of "natural" in their informal policy (Ref. 53) that defines "natural" as "nothing artificial or synthetic (including colors regardless of source) is included in, or has been added to, the product that would not normally be expected to be there."
The Food, Drug, and Cosmetic Act prohibits labeling that is false or misleading. The USDA has a standard for organic food called the National Organic Program. As of August 2005, the USDA had a section governing "natural claims" in its Food Standards and Labeling Policy Book.
The poultry industry has been criticized by the Center for Science in the Public Interest for labeling chicken meat "all-natural" after it has been injected with saline solution up to 25% of its weight. There is no legal recourse to prevent this labeling. | 1 | Applied and Interdisciplinary Chemistry |
Supercritical hydrolysis is a method of converting all biomass polysaccharides as well the associated lignin into low molecular compounds by contacting with water alone under supercritical conditions. The supercritical water, acts as a solvent, a supplier of bond-breaking thermal energy, a heat transfer agent and as a source of hydrogen atoms. All polysaccharides are converted into simple sugars in near-quantitative yield in a second or less. The aliphatic inter-ring linkages of lignin are also readily cleaved into free radicals that are stabilized by hydrogen originating from the water. The aromatic rings of the lignin are unaffected under short reaction times so that the lignin-derived products are low molecular weight mixed phenols. To take advantage of the very short reaction times needed for cleavage a continuous reaction system must be devised. The amount of water heated to a supercritical state is thereby minimized. | 0 | Theoretical and Fundamental Chemistry |
The expression of VMAT1 in healthy endocrine cells was compared to VMAT1 expression in infants with hyperinsulinemic hypoglycemia and adults with pancreatic endocrine tumors. Through immunohistochemistry (IHC) and in situ hybridization (ISH), they found VMAT1 and VMAT2 were located in mutually exclusive cell types, and that in insulinomas VMAT2 activity disappeared, suggesting that if only VMAT1 activity is present in the endocrine system, this type of cancer is likely. | 1 | Applied and Interdisciplinary Chemistry |
Coagulation, the formation of a blood clot or thrombus, occurs when the proteins of the coagulation cascade are activated, either by contact with a damaged blood vessel wall and exposure to collagen in the tissue space (intrinsic pathway) or by activation of factor VII by tissue activating factors (extrinsic pathway). Both pathways lead to the generation of thrombin, an enzyme that turns the soluble blood protein fibrinogen into fibrin, which aggregates into protofibrils. Another thrombin-generated enzyme, factor XIII, then crosslinks the fibrin protofibrils at the D fragment site, leading to the formation of an insoluble gel that serves as a scaffold for blood clot formation.
The circulating enzyme plasmin, the main enzyme of fibrinolysis, cleaves the fibrin gel in a number of places. The resultant fragments, "high molecular weight polymers", are digested several times more by plasmin to lead to intermediate and then to small polymers (fibrin degradation products or FDPs). The cross-link between two D fragments remains intact, however, and these are exposed on the surface when the fibrin fragments are sufficiently digested. The structure of D-dimer is either a 180 kDa or 195 kDa molecule of two D domains, or a 340 kDa molecule of two D domains and one E domain of the original fibrinogen molecule. The half-life of D-dimer in blood is approximately 6 to 8 hours.
D-dimers are not normally present in human blood plasma, except when the coagulation system has been activated, for instance, because of the presence of thrombosis or disseminated intravascular coagulation. The D-dimer assay depends on the binding of a monoclonal antibody to a particular epitope on the D-dimer fragment. Several detection kits are commercially available; all of them rely on a different monoclonal antibody against D-dimer. For some of these, the area of the D-dimer to which the antibody binds is known. The binding of the antibody is then measured quantitatively by one of various laboratory methods. | 1 | Applied and Interdisciplinary Chemistry |
in sodium hydroxide at 50–70 °C followed by crystallizing the filtered product. If crystallized below 10 °C, the decahydrate forms. Above 10 °C, the dihydate crystallizes. The anhydrous salt is obtained by heating this product at 100 °C. | 0 | Theoretical and Fundamental Chemistry |
The first mention of any research or study of the gold halides dates back to the early-to-mid-19th century, and there are three primary researchers associated with the extensive investigation of this particular area of chemistry: Thomsen, Schottländer, and Krüss. | 0 | Theoretical and Fundamental Chemistry |
Oxyntomodulin could be a potential candidate for treating obesity because of its ability to suppress appetite. In a 4 week study, healthy overweight and obese volunteers were given either saline or oxyntomodulin injections. Their body weight, energy intake, and the levels of adipose hormones were taken prior to the treatment. The volunteers maintained their usual diets and daily activities and self-administered the injections three times daily, 30 minutes before their meals. In the course of 4 weeks, volunteers treated with oxyntomodulin injections had an average weight loss of 2.3±0.4 kg compared to those treated with saline who had an average of 0.5±0.5 kg, indicating oxyntomodulin was successful in weight loss. | 1 | Applied and Interdisciplinary Chemistry |
In 2021, Abouzar Mirzaei-Paiaman investigated the validity of Craigs rules of thumb and showed that while the third rule is generally unreliable, the first rule is suitable. Moreover, he showed that the second rule needed a modification. He pointed out that using 50% water saturation as a reference value in the Craigs second rule is unrealistic. That author defined a reference crossover saturation (RCS). According to the modified Craig's second rule, the crossover point of relative permeability curves lies to the right of RCS in water-wet rocks, whereas for oil-wet systems, the crossover point is expected to be located at the left of the RCS. | 0 | Theoretical and Fundamental Chemistry |
As public concern arose about the disposal of increased volumes of solids in the United States being removed from sewage during sewage treatment mandated by the Clean Water Act. The Water Environment Federation (WEF) sought a new name to distinguish the clean, agriculturally viable product generated by modern wastewater treatment from earlier forms of sewage sludge widely remembered for causing offensive or dangerous conditions. Of 300 suggestions, biosolids was attributed to Dr. Bruce Logan of the University of Arizona, and recognized by WEF in 1991. | 1 | Applied and Interdisciplinary Chemistry |
The genome size, and the number of genes it encodes varies widely between organisms. The smallest genomes occur in viruses, and viroids (which act as a single non-coding RNA gene). Conversely, plants can have extremely large genomes, with rice containing >46,000 protein-coding genes. The total number of protein-coding genes (the Earth's proteome) is estimated to be 5 million sequences.
Although the number of base-pairs of DNA in the human genome has been known since the 1950s, the estimated number of genes has changed over time as definitions of genes, and methods of detecting them have been refined. Initial theoretical predictions of the number of human genes in the 1960s and 1970s were based on mutation load estimates and the numbers of mRNAs and these estimates tended to be about 30,000 protein-coding genes. During the 1990s there were guesstimates of up to 100,000 genes and early data on detection of mRNAs (expressed sequence tags) suggested more than the traditional value of 30,000 genes that had been reported in the textbooks during the 1980s.
The initial draft sequences of the human genome confirmed the earlier predictions of about 30,000 protein-coding genes however that estimate has fallen to about 19,000 with the ongoing GENCODE annotation project . The number of noncoding genes is not known with certainty but the latest estimates from Ensembl suggest 26,000 noncoding genes. | 1 | Applied and Interdisciplinary Chemistry |
The surface-area-to-volume ratio or surface-to-volume ratio (denoted as SA:V, SA/V, or sa/vol) is the ratio between surface area and volume of an object or collection of objects.
SA:V is an important concept in science and engineering. It is used to explain the relation between structure and function in processes occurring through the surface the volume. Good examples for such processes are processes governed by the heat equation, that is, diffusion and heat transfer by thermal conduction. SA:V is used to explain the diffusion of small molecules, like oxygen and carbon dioxide between air, blood and cells, water loss by animals, bacterial morphogenesis, organism's thermoregulation, design of artificial bone tissue, artificial lungs and many more biological and biotechnological structures. For more examples see Glazier.
The relation between SA:V and diffusion or heat conduction rate is explained from flux and surface perspective, focusing on the surface of a body as the place where diffusion, or heat conduction, takes place, i.e., the larger the SA:V there is more surface area per unit volume through which material can diffuse, therefore, the diffusion or heat conduction, will be faster. Similar explanation appears in the literature: "Small size implies a large ratio of surface area to volume, thereby helping to maximize the uptake of nutrients across the plasma membrane", and elsewhere.
For a given volume, the object with the smallest surface area (and therefore with the smallest SA:V) is a ball, a consequence of the isoperimetric inequality in 3 dimensions. By contrast, objects with acute-angled spikes will have very large surface area for a given volume. | 0 | Theoretical and Fundamental Chemistry |
Cobalt(III) chloride or cobaltic chloride is an unstable and elusive compound of cobalt and chlorine with formula . In this compound, the cobalt atoms have a formal charge of +3.
The compound has been reported to exist in the gas phase at high temperatures, in equilibrium with cobalt(II) chloride and chlorine gas. It has also been found to be stable at very low temperatures, dispersed in a frozen argon matrix.
Some articles from the 1920s and 1930s claim the synthesis of bulk amounts of this compound in pure form; however, those results do not seem to have been reproduced, or have been attributed to other substances like the hexachlorocobaltate(III) anion . Those earlier reports claim that it gives green solutions in anhydrous solvents such as ethanol and diethyl ether, and that it is stable only a very low temperatures (below −60 °C). | 0 | Theoretical and Fundamental Chemistry |
The synthesis of isocyanates from amines illustrates the electrophilic character of this reagent and its use in introducing the equivalent synthon "CO":
:, where R = alkyl, aryl
Such reactions are conducted on laboratory scale in the presence of a base such as pyridine that neutralizes the hydrogen chloride side-product.
Phosgene is used to produce chloroformates such as benzyl chloroformate:
In these syntheses, phosgene is used in excess to prevent formation of the corresponding carbonate ester.
With amino acids, phosgene (or its trimer) reacts to give amino acid N-carboxyanhydrides. More generally, phosgene acts to link two nucleophiles by a carbonyl group. For this purpose, alternatives to phosgene such as carbonyldiimidazole (CDI) are safer, albeit expensive. CDI itself is prepared by reacting phosgene with imidazole.
Phosgene is stored in metal cylinders. In the US, the cylinder valve outlet is a tapered thread known as "CGA 160" that is used only for phosgene. | 0 | Theoretical and Fundamental Chemistry |
Susceptibility to photo-oxidation varies depending on the chemical structure of the polymer. Some materials have excellent stability, such as fluoropolymers, polyimides, silicones and certain acrylate polymers. However, global polymer production is dominated by a range of commodity plastics which account for the majority of plastic waste. Of these polyethylene terephthalate (PET) has only moderate UV resistance and the others, which include polystyrene, polyvinyl chloride (PVC) and polyolefins like polypropylene (PP) and polyethylene (PE) are all highly susceptible.
Photo-oxidation is a form of photodegradation and begins with formation of free radicals on the polymer chain, which then react with oxygen in chain reactions. For many polymers the general autoxidation mechanism is a reasonable approximation of the underlying chemistry. The process is autocatalytic, generating increasing numbers of radicals and reactive oxygen species. These reactions result in changes to the molecular weight (and molecular weight distribution) of the polymer and as a consequence the material becomes more brittle. The process can be divided into four stages:
:Initiation the process of generating the initial free radical.
:Propagation the conversion of one active species to another
:Chain branching steps which end with more than one active species being produced. The photolysis of hydroperoxides is the main example.
:Termination steps in which active species are removed, for instance by radical disproportionation
Photo-oxidation can occur simultaneously with other processes like thermal degradation, and each of these can accelerate the other. | 0 | Theoretical and Fundamental Chemistry |
In inlet boundary conditions, the distribution of all flow variables needs to be specified at inlet boundaries mainly flow velocity. This type of boundary conditions are common and specified mostly where inlet flow velocity is known. | 1 | Applied and Interdisciplinary Chemistry |
The joule per mole (symbol: J·mol or J/mol) is the unit of energy per amount of substance in the International System of Units (SI), such that energy is measured in joules, and the amount of substance is measured in moles.
It is also an SI derived unit of molar thermodynamic energy defined as the energy equal to one joule in one mole of substance. For example, the Gibbs free energy of a compound in the area of thermochemistry is often quantified in units of kilojoules per mole (symbol: kJ·mol or kJ/mol), with 1 kilojoule = 1000 joules.
Physical quantities measured in J·mol usually describe quantities of energy transferred during phase transformations or chemical reactions. Division by the number of moles facilitates comparison between processes involving different quantities of material and between similar processes involving different types of materials. The precise meaning of such a quantity is dependent on the context (what substances are involved, circumstances, etc.), but the unit of measurement is used specifically to describe certain existing phenomena, such as in thermodynamics it is the unit of measurement that describes molar energy.
Since 1 mole = 6.02214076 particles (atoms, molecules, ions etc.), 1 joule per mole is equal to 1 joule divided by 6.02214076 particles, ≈1.660539 joule per particle. This very small amount of energy is often expressed in terms of an even smaller unit such as the kJ·mol, because of the typical order of magnitude for energy changes in chemical processes. For example, heats of fusion and vaporization are usually of the order of 10 kJ·mol, bond energies are of the order of 100 kJ·mol, and ionization energies of the order of 1000 kJ·mol. For this reason, it is common within the field of chemistry to quantify the enthalpy of reaction in units of kJ·mol.
Other units sometimes used to describe reaction energetics are kilocalories per mole (kcal·mol), electron volts per particle (eV), and wavenumbers in inverse centimeters (cm). 1 kJ·mol is approximately equal to 1.04 eV per particle, 0.239 kcal·mol, or 83.6 cm. At room temperature (25 °C, or 298.15 K) 1 kJ·mol is approximately equal to 0.4034 . | 0 | Theoretical and Fundamental Chemistry |
Xing Qiyi () was a Chinese organic chemist who contributed to the total synthesis of bovine insulin, Xing is still well-known nowadays in China as the main editor of a highly-influential organic chemistry textbook. He was a member of China Democratic League since 1952. | 0 | Theoretical and Fundamental Chemistry |
Evans and his co-workers has developed a strategy that relies heavily on asymmetric aldol methodology for the production of the polypropionate backbone. They used a Claisen condensation reaction to construct the C(13)–C(14) trisubstituted Z-olefin. The Evans synthesis of (+)-discodermolide has an overall yield of 6.4% with a longest linear sequence of 31 steps and 49 total steps. | 0 | Theoretical and Fundamental Chemistry |
Shikimic acid, more commonly known as its anionic form shikimate, is a cyclohexene, a cyclitol and a cyclohexanecarboxylic acid. It is an important biochemical metabolite in plants and microorganisms. Its name comes from the Japanese flower shikimi (, the Japanese star anise, Illicium anisatum), from which it was first isolated in 1885 by Johan Fredrik Eykman. The elucidation of its structure was made nearly 50 years later. | 1 | Applied and Interdisciplinary Chemistry |
Endonucleases are enzymes that recognise and cleave nucleic acid segments and they can be used to direct DNA assembly. Of the different types of restriction enzymes, the type II restriction enzymes are the most commonly available and used because their cleavage sites are located near or in their recognition sites. Hence, endonuclease-mediated assembly methods make use of this property to define DNA parts and assembly protocols. | 1 | Applied and Interdisciplinary Chemistry |
In the field of molecular biology, trans-acting (trans-regulatory, trans-regulation), in general, means "acting from a different molecule" (i.e., intermolecular). It may be considered the opposite of cis-acting (cis-regulatory, cis-regulation), which, in general, means "acting from the same molecule" (i.e., intramolecular).
In the context of transcription regulation, a trans-acting factor is usually a regulatory protein that binds to DNA. The binding of a trans-acting factor to a cis-regulatory element in DNA can cause changes in transcriptional expression levels. microRNAs or other diffusible molecules are also examples of trans-acting factors that can regulate target sequences.
The trans-acting gene may be on a different chromosome to the target gene, but the activity is via the intermediary protein or RNA that it encodes. Cis-acting elements, on the other hand, do not code for protein or RNA. Both the trans-acting gene and the protein/RNA that it encodes are said to "act in trans" on the target gene. | 1 | Applied and Interdisciplinary Chemistry |
Halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) is a dense, highly volatile, clear, colourless, nonflammable liquid with a chloroform-like sweet odour. It is very slightly soluble in water and miscible with various organic solvents. Halothane can decompose to hydrogen fluoride, hydrogen chloride and hydrogen bromide in the presence of light and heat.
Chemically, halothane is an alkyl halide (not an ether like many other anesthetics). The structure has one stereocenter, so (R)- and (S)-optical isomers occur. | 0 | Theoretical and Fundamental Chemistry |
Based on characteristic that molecules usually have extraordinarily larger Stokes shift when ESIPT occurs, various applications have been developed using red-shifted fluorescence. Applications include turn-on photoluminescence sensor, photochromic, non-destructive optical memory, and white-light emitting materials.
Because phenol does not form a ketal under normal conditions because it does not tautomerize to any useful extent; however under ESIPT in the presence of an alcohol, e.g. ethylene glycol, it became possible to trap 1,4-Dioxaspiro[4.5]deca-6,8-diene [23783-59-7]. | 0 | Theoretical and Fundamental Chemistry |
fMRS has been used in migraine and pain research. It has supported the important hypothesis of mitochondria dysfunction in migraine with aura (MwA) patients. Here the ability of fMRS to measure chemical processes in the brain over time proved crucial for confirming that repetitive photic stimulation causes higher increase of the lactate level and higher decrease of the N-acetylaspartate (NAA) level in the visual cortex of MwA patients compared to migraine without aura (MwoA) patients and healthy individuals.
In pain research fMRS complements fMRI and PET techniques. Although fMRI and PET are continuously used to localize pain processing areas in the brain, they can not provide direct information about changes in metabolites during pain processing that could help to understand physiological processes behind pain perception and potentially lead to novel treatments for pain. fMRS overcomes this limitation and has been used to study pain-induced (cold-pressure, heat, dental pain) neurotransmitter level changes in the anterior cingulate cortex, anterior insular cortex and left insular cortex. These fMRS studies are valuable because they show that some or all Glx compounds (glutamate, GABA and glutamine) increase during painful stimuli in the studied brain regions. | 0 | Theoretical and Fundamental Chemistry |
Gram-positive bacteria that participate in quorum sensing typically use secreted oligopeptides as autoinducers. Peptide autoinducers usually result from posttranslational modification of a larger precursor molecule. In many Gram-positive bacteria, secretion of peptides requires specialized export mechanisms. For example, some peptide autoinducers are secreted by ATP-binding cassette transporters that couple proteolytic processing and cellular export. Following secretion, peptide autoinducers accumulate in extracellular environments. Once a threshold level of signal is reached, a histidine sensor kinase protein of a two-component regulatory system detects it and a signal is relayed into the cell. As with AHLs, the signal ultimately ends up altering gene expression. Unlike some AHLs, however, most oligopeptides do not act as transcription factors themselves. | 1 | Applied and Interdisciplinary Chemistry |
The Journal of Physical Chemistry A is a scientific journal which reports research on the chemistry of molecules - including their dynamics, spectroscopy, kinetics, structure, bonding, and quantum chemistry. It is published weekly by the American Chemical Society.
Before 1997 the title was simply Journal of Physical Chemistry. Owing to the ever-growing amount of research in the area, in 1997 the journal was split into Journal of Physical Chemistry A (molecular theoretical and experimental physical chemistry) and The Journal of Physical Chemistry B (solid state, soft matter, liquids, etc.). Beginning in 2007, the latter underwent a further split, with The Journal of Physical Chemistry C now being dedicated to nanotechnology, molecular electronics, and related subjects.
According to the Journal Citation Reports, the journal had an impact factor of 2.944 for 2021. | 0 | Theoretical and Fundamental Chemistry |
In 1974 Bryan Research and Engineering (BR&E) began developing simulation software for sulfur recovery units with a command-line interface. In 1976 this program was released under the name SULFUR. Amine sweetening, for which BR&E is most well known, was added in 1978 and the simulation package was renamed TSWEET. A second product, DEHY, was released in 1980 for modeling glycol dehydration units. Natural gas processing was added to the DEHY program in 1983 and the package was renamed PROSIM. In 1988 BR&E introduced a graphical user interface to both programs, a novelty for chemical process simulators at the time.
TSWEET and PROSIM were both MS-DOS based programs and were both incorporated into ProMax. ProMax is a late generation Windows application which uses Microsoft Visio as the graphical user interface. Other capabilities were included in ProMax besides those already available in TSWEET and PROSIM enabling it to model almost any process in the oil and gas industry. | 1 | Applied and Interdisciplinary Chemistry |
Common side effects associated with oral vancomycin administration (used to treat intestinal infections) include:
* gastrointestinal adverse effects (such as abdominal pain and nausea);
* dysgeusia (distorted sense of taste), in case of administration of vancomycin oral solution, but not in case of vancomycin capsules. | 0 | Theoretical and Fundamental Chemistry |
Magnetometers are used to measure or monitor mechanical stress in ferromagnetic materials. Mechanical stress will improve alignment of magnetic domains in microscopic scale that will raise the magnetic field measured close to the material by magnetometers. There are different hypothesis about stress-magnetisation relationship. However the effect of mechanical stress on measured magnetic field near the specimen is claimed to be proven in many scientific publications. There have been efforts to solve the inverse problem of magnetisation-stress resolution in order to quantify the stress based on measured magnetic field. | 0 | Theoretical and Fundamental Chemistry |
* 2011 Royal Society of Chemistry Harrison-Meldola Award
* 2015 Royal Society of Chemistry Marlow Award
* 2017 EBSA Young Investigator Award and Medal
* 2018 Klung Wilhelmy Science Award (Chemistry)
* 2019 Blavatnik Awards for Young Scientists UK (Chemistry) Laureate
* 2021 [https://www.rms.org.uk/opportunities/competitions-awards/rms-section-awards/award-for-light-microscopy.html RMS Medal for Light Microscopy]
*2022 [https://www.eurekalert.org/news-releases/948615 Emil Thomas Kaiser Award]
*2022 [https://britishbiophysics.org/posts/2022/2022-05-01-kukuraheptares/ Sosei Heptares Prize For Biophysics of the British Biophysical Society] | 0 | Theoretical and Fundamental Chemistry |
Diagnostic qualitative PCR is applied to rapidly detect nucleic acids that are diagnostic of, for example, infectious diseases, cancer and genetic abnormalities. The introduction of qualitative PCR assays to the clinical microbiology laboratory has significantly improved the diagnosis of infectious diseases, and is deployed as a tool to detect newly emerging diseases, such as new strains of flu and coronavirus, in diagnostic tests. | 1 | Applied and Interdisciplinary Chemistry |
For a considerable time following the first tRNA structures, the field of RNA structure did not dramatically advance. The ability to study an RNA structure depended upon the potential to isolate the RNA target. This proved limiting to the field for many years, in part because other known targets—i.e., the ribosome—were significantly more difficult to isolate and crystallize. Further, because other interesting RNA targets had simply not been identified, or were not sufficiently understood to be deemed interesting, there was simply a lack of things to study structurally. As such, for some twenty years following the original publication of the tRNA structure, the structures of only a handful of other RNA targets were solved, with almost all of these belonging to the transfer RNA family. This unfortunate lack of scope would eventually be overcome largely because of two major advancements in nucleic acid research: the identification of ribozymes, and the ability to produce them via in vitro transcription.
Subsequent to Tom Cechs publication implicating the Tetrahymena group I intron as an autocatalytic ribozyme, and Sidney Altmans report of catalysis by ribonuclease P RNA, several other catalytic RNAs were identified in the late 1980s, including the hammerhead ribozyme. In 1994, McKay et al. published the structure of a hammerhead RNA-DNA ribozyme-inhibitor complex at 2.6 Ångström resolution, in which the autocatalytic activity of the ribozyme was disrupted via binding to a DNA substrate. The conformation of the ribozyme published in this paper was eventually shown to be one of several possible states, and although this particular sample was catalytically inactive, subsequent structures have revealed its active-state architecture. This structure was followed by Jennifer Doudnas publication of the structure of the P4-P6 domains of the Tetrahymena group I intron, a fragment of the ribozyme originally made famous by Cech. The second clause in the title of this publication—Principles of RNA Packing—concisely evinces the value of these two structures: for the first time, comparisons could be made between well described tRNA structures and those of globular RNAs outside the transfer family. This allowed the framework of categorization to be built for RNA tertiary structure. It was now possible to propose the conservation of motifs, folds, and various local stabilizing interactions. For an early review of these structures and their implications, see RNA FOLDS: Insights from recent crystal structures, by Doudna and Ferre-DAmare.
In addition to the advances being made in global structure determination via crystallography, the early 1990s also saw the implementation of NMR as a powerful technique in RNA structural biology. Coincident with the large-scale ribozyme structures being solved crystallographically, a number of structures of small RNAs and RNAs complexed with drugs and peptides were solved using NMR. In addition, NMR was now being used to investigate and supplement crystal structures, as exemplified by the determination of an isolated tetraloop-receptor motif structure published in 1997. Investigations such as this enabled a more precise characterization of the base pairing and base stacking interactions which stabilized the global folds of large RNA molecules. The importance of understanding RNA tertiary structural motifs was prophetically well described by Michel and Costa in their publication identifying the tetraloop motif: "...it should not come as a surprise if self-folding RNA molecules were to make intensive use of only a relatively small set of tertiary motifs. Identifying these motifs would greatly aid modeling enterprises, which will remain essential as long as the crystallization of large RNAs remains a difficult task". | 1 | Applied and Interdisciplinary Chemistry |
In the ultrasonic reactor method, the ultrasonic waves cause the reaction mixture to produce and collapse bubbles constantly; this cavitation simultaneously provides the mixing and heating required to carry out the transesterification process. Use of an ultrasonic reactor for biodiesel production can drastically reduce reaction time and temperatures, and energy input. Using such reactors, the process of transesterification can run inline rather than using the time-consuming batch processing. Industrial scale ultrasonic devices allow for processing of several thousand barrels per day. | 0 | Theoretical and Fundamental Chemistry |
The five āstikāya mentioned in the text are :—
#Jīva (soul),
# Pudgala (matter),
#Dharma (medium of motion),
#Adharma (medium of rest), and
#Akasa (space) | 1 | Applied and Interdisciplinary Chemistry |
Fixed aRME are established either by silencing of one allele that previously has been biallelically expressed, or by activation of a single allele from previously silent gene. Expression activation of the silent allele is coupled with a feedback mechanism that prevents expression of the second allele. Another scenario is also possible due to limited time-window of low-probability initiation, that could lead to high frequencies of cells with single-allele expression. It is estimated that 2-10% of all genes are fixed aRME. Studies
of fixed aRME require either expansion of monoclonal cultures or lineage-traced in vivo or in vitro cells that are mitotically.
Dynamic aRME occurs as a consequence of stochastic allelic expression. Transcription happens in bursts, which results in RNA molecules being synthesized from each allele separately. So over time, both alleles have a probability to initiate transcription. Transcriptional bursts are allelically stochastic, and lead to either maternal or paternal allele being accumulated in the cell. The gene transcription burst frequency and intensity combined with RNA-degradation rate form the shape of RNA distribution at the moment of observation and thus whether the gene is bi- or monoallelic. Studies that distinguish fixed and dynamic aRME require single-cell analyses of clonally related cells. | 1 | Applied and Interdisciplinary Chemistry |
In mass spectrometry, matrix-assisted laser desorption/ionization (MALDI) is an ionization technique that uses a laser energy-absorbing matrix to create ions from large molecules with minimal fragmentation. It has been applied to the analysis of biomolecules (biopolymers such as DNA, proteins, peptides and carbohydrates) and various organic molecules (such as polymers, dendrimers and other macromolecules), which tend to be fragile and fragment when ionized by more conventional ionization methods. It is similar in character to electrospray ionization (ESI) in that both techniques are relatively soft (low fragmentation) ways of obtaining ions of large molecules in the gas phase, though MALDI typically produces far fewer multi-charged ions.
MALDI methodology is a three-step process. First, the sample is mixed with a suitable matrix material and applied to a metal plate. Second, a pulsed laser irradiates the sample, triggering ablation and desorption of the sample and matrix material. Finally, the analyte molecules are ionized by being protonated or deprotonated in the hot plume of ablated gases, and then they can be accelerated into whichever mass spectrometer is used to analyse them. | 1 | Applied and Interdisciplinary Chemistry |
* Invisible ink: when suspended in solution, cobalt(II) chloride can be made to appear invisible on a surface; when that same surface is subsequently exposed to significant heat (such as from a handheld heat gun or lighter) the ink reversibly changes to blue.
* Cobalt chloride is an established chemical inducer of hypoxia-like responses such as erythropoiesis. Cobalt supplementation is not banned and therefore would not be detected by current anti-doping testing. Cobalt chloride is a banned substance under the Australian Thoroughbred Racing Board.
* Cobalt chloride is one method used to induce pulmonary arterial hypertension in animals for research and evaluation of treatment efficacy. | 0 | Theoretical and Fundamental Chemistry |
A solution of 13.0 g (0.1 mol) of 1-octanol in 25 mL of dichloromethane was added dropwise to a solution of 16.1 g (0.1 mol) of diethylaminosulfur trifluoride in 60 mL of dichloromethane cooled to –70° to –65°. The reaction mixture was warmed to 25°, 50 mL of water was added, and the lower organic layer was separated and dried with anhydrous magnesium sulfate and distilled to give 12.0 g (90%) of 1-fluorooctane as a colorless liquid, bp 42–43° (20 mm). F NMR (CClF): -218.8 ppm (tt, J = 49 Hz, J = 25 Hz). | 0 | Theoretical and Fundamental Chemistry |
Biomaterial surfaces are often modified using light-activated mechanisms (such as photografting) to functionalize the surface without compromising bulk mechanical properties.
The modification of surfaces to keep polymers biologically inert has found wide uses in biomedical applications such as cardiovascular stents and in many skeletal prostheses. Functionalizing polymer surfaces can inhibit protein adsorption, which may otherwise initiate cellular interrogation upon the implant, a predominant failure mode of medical prostheses.
Narrow biocompatibility requirements within the medical industry have over the past ten years driven surface modification techniques to reach an unprecedented level of accuracy. | 0 | Theoretical and Fundamental Chemistry |
In a centrosymmetric ligand field, such as in octahedral complexes of transition metals, the arrangement of electrons in the d-orbital is not only limited by electron repulsion energy, but it is also related to the splitting of the orbitals due to the ligand field. This leads to many more electron configuration states than is the case for the free ion. The relative energy of the repulsion energy and splitting energy defines the high-spin and low-spin states.
Considering both weak and strong ligand fields, a Tanabe–Sugano diagram shows the energy splitting of the spectral terms with the increase of the ligand field strength. It is possible for us to understand how the energy of the different configuration states is distributed at certain ligand strengths. The restriction of the spin selection rule makes it even easier to predict the possible transitions and their relative intensity. Although they are qualitative, Tanabe–Sugano diagrams are very useful tools for analyzing UV-vis spectra: they are used to assign bands and calculate Dq values for ligand field splitting. | 0 | Theoretical and Fundamental Chemistry |
Using the definition above for and , the first and second derivatives can be expressed in terms of the Faddeeva function as
and
respectively.
Often, one or multiple Voigt profiles and/or their respective derivatives need to be fitted to a measured signal by means of non-linear least squares, e.g., in spectroscopy. Then, further partial derivatives can be utilised to accelerate computations. Instead of approximating the Jacobian matrix with respect to the parameters , , and with the aid of finite differences, the corresponding analytical expressions can be applied. With and , these are given by:
for the original voigt profile ;
for the first order partial derivative ; and
for the second order partial derivative . Since and play a relatively similar role in the calculation of , their respective partial derivatives also look quite similar in terms of their structure, although they result in totally different derivative profiles. Indeed, the partial derivatives with respect to and show more similarity since both are width parameters. All these derivatives involve only simple operations (multiplications and additions) because the computationally expensive and are readily obtained when computing . Such a reuse of previous calculations allows for a derivation at minimum costs. This is not the case for finite difference gradient approximation as it requires the evaluation of for each gradient respectively. | 0 | Theoretical and Fundamental Chemistry |
Prototropy is the most common form of tautomerism and refers to the relocation of a hydrogen atom. Prototropic tautomerism may be considered a subset of acid-base behavior. Prototropic tautomers are sets of isomeric protonation states with the same empirical formula and total charge. Tautomerizations are catalyzed by:
* bases, involving a series of steps: deprotonation, formation of a delocalized anion (e.g., an enolate), and protonation at a different position of the anion; and
* acids, involving a series of steps: protonation, formation of a delocalized cation, and deprotonation at a different position adjacent to the cation).
Two specific further subcategories of tautomerizations:
*Annular tautomerism is a type of prototropic tautomerism wherein a proton can occupy two or more positions of the heterocyclic systems found in many drugs, for example, 1H- and 3H-imidazole; 1H-, 2H- and 4H- 1,2,4-triazole; 1H- and 2H- isoindole.
*Ring–chain tautomers occur when the movement of the proton is accompanied by a change from an open structure to a ring, such as the open chain and cyclic hemiacetal (typically pyranose or furanose forms) of many sugars. (See .) The tautomeric shift can be described as H−O ⋅ C=O ⇌ O−C−O−H, where the "⋅" indicates the initial absence of a bond. | 0 | Theoretical and Fundamental Chemistry |
* During Underway replenishment the helmsman of each ship must constantly steer away from the other ship due to the Venturi effect, otherwise they will collide.
* Cargo eductors on oil product and chemical ship tankers
* Inspirators mix air and flammable gas in grills, gas stoves, Bunsen burners and airbrushes
* Water aspirators produce a partial vacuum using the kinetic energy from the faucet water pressure
* Steam siphons use the kinetic energy from the steam pressure to create a partial vacuum
* Atomizers disperse perfume or spray paint (i.e. from a spray gun)
* Carburetors use the effect to suck gasoline into an engine's intake air stream
* Cylinder heads in piston engines have multiple Venturi areas like the valve seat and the port entrance, although these are not part of the design intent, merely a byproduct and any venturi effect is without specific function.
* Wine aerators infuse air into wine as it is poured into a glass
* Protein skimmers filter saltwater aquaria
* Automated pool cleaners use pressure-side water flow to collect sediment and debris
* Clarinets use a reverse taper to speed the air down the tube, enabling better tone, response and intonation
* The leadpipe of a trombone, affecting the timbre
* Industrial vacuum cleaners use compressed air
* Venturi scrubbers are used to clean flue gas emissions
* Injectors (also called ejectors) are used to add chlorine gas to water treatment chlorination systems
* Steam injectors use the Venturi effect and the latent heat of evaporation to deliver feed water to a steam locomotive boiler.
* Sandblasting nozzles accelerate and air and media mixture
* Bilge water can be emptied from a moving boat through a small waste gate in the hull. The air pressure inside the moving boat is greater than the water sliding by beneath.
* A scuba diving regulator uses the Venturi effect to assist maintaining the flow of gas once it starts flowing
* In recoilless rifles to decrease the recoil of firing
* The diffuser on an automobile
* Race cars utilising ground effect to increase downforce and thus become capable of higher cornering speeds
* Foam proportioners used to induct fire fighting foam concentrate into fire protection systems
* Trompe air compressors entrain air into a falling column of water
* The bolts in some brands of paintball markers
* Low-speed wind tunnels can be considered very large Venturi because they take advantage of the Venturi effect to increase velocity and decrease pressure to simulate expected flight conditions. | 1 | Applied and Interdisciplinary Chemistry |
It is typical that the lasing properties of a medium are determined by the temperature and the population at the excited laser level, and are not sensitive to the method of excitation used to achieve it. In this case, the absorption cross-section
and the emission cross-section
at frequency can be related to the lasers gain in such a way, that the gain at this frequency can be determined as follows:
D.E.McCumber had postulated these properties and found that the emission and absorption cross-sections are not independent; they are related with Equation (1). | 0 | Theoretical and Fundamental Chemistry |
Merely giving a treatment can have nonspecific effects. These are controlled for by the inclusion of patients who receive only a placebo. Subjects are assigned randomly without informing them to which group they belonged. Many trials are doubled-blinded so that researchers do not know to which group a subject is assigned.
Assigning a subject to a placebo group can pose an ethical problem if it violates his or her right to receive the best available treatment. The Declaration of Helsinki provides guidelines on this issue. | 1 | Applied and Interdisciplinary Chemistry |
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