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The Applied Inorganic Chemistry Award, established in 2008, is conferred biennially by the Dalton division of the Royal Society of Chemistry for "outstanding contributions to the development of any branch of inorganic chemistry which has an application in industry." The winner gives a lecture tour in the UK, and receives a medal and £2000. The award was discontinued in 2020. | 0 | Theoretical and Fundamental Chemistry |
Some radionuclides, such as cobalt-60 and iridium-192, are made by the neutron irradiation of normal non-radioactive cobalt and iridium metal in a nuclear reactor, creating radioactive nuclides of these elements which contain extra neutrons, compared to the original stable nuclides.
In addition to their uses in radiography, both cobalt-60 () and iridium-192 () are used in the radiotherapy of cancer. Cobalt-60 tends to be used in teletherapy units as a higher photon energy alternative to caesium-137, while iridium-192 tends to be used in a different mode of therapy, internal radiotherapy or brachytherapy. The iridium wires for brachytherapy are a palladium-coated iridium/palladium alloy wire made radioactive by neutron activation. This wire is then inserted into a tumor such as a breast tumor, and the tumor is irradiated by gamma ray photons from the wire. At the end of the treatment the wire is removed.
A rare but notable gamma source is sodium-24; this has a fairly short half-life of 15 hours, but it emits photons with very high energies (>2 MeV). It could be used for radiography of thick steel objects if the radiography occurred close to the point of production. Similarly to and , it is formed by the neutron activation of the commonly found stable isotope. | 0 | Theoretical and Fundamental Chemistry |
Pets, especially dogs, can contribute to fecal contamination of surface waters. Runoff from roads, parking lots, and yards can carry animal wastes to streams through storm sewers. Birds can be a significant source of fecal coliform bacteria. Swans, geese, seagulls, and other waterfowl can all elevate bacterial counts, especially in wetlands, lakes, ponds, and rivers. | 0 | Theoretical and Fundamental Chemistry |
Aside from ethylene oxide, most epoxides are generated by treating alkenes with peroxide-containing reagents, which donate a single oxygen atom. Safety considerations weigh on these reactions because organic peroxides are prone to spontaneous decomposition or even combustion.
Metal complexes are useful catalysts for epoxidations involving hydrogen peroxide and alkyl hydroperoxides. Peroxycarboxylic acids, which are more electrophilic, convert alkenes to epoxides without the intervention of metal catalysts. In specialized applications, other peroxide-containing reagents are employed, such as dimethyldioxirane. Depending on the mechanism of the reaction and the geometry of the alkene starting material, cis and/or trans epoxide diastereomers may be formed. In addition, if there are other stereocenters present in the starting material, they can influence the stereochemistry of the epoxidation. Metal-catalyzed epoxidations were first explored using tert-butyl hydroperoxide (TBHP). Association of TBHP with the metal (M) generates the active metal peroxy complex containing the MOOR group, which then transfers an O center to the alkene.
Organic peroxides are used for the production of propylene oxide from propylene. Catalysts are required as well. Both t-butyl hydroperoxide and ethylbenzene hydroperoxide can be used as oxygen sources. | 0 | Theoretical and Fundamental Chemistry |
UV is an investigative tool at the crime scene helpful in locating and identifying bodily fluids such as semen, blood, and saliva. For example, ejaculated fluids or saliva can be detected by high-power UV sources, irrespective of the structure or colour of the surface the fluid is deposited upon. UV–vis microspectroscopy is also used to analyze trace evidence, such as textile fibers and paint chips, as well as questioned documents.
Other applications include the authentication of various collectibles and art, and detecting counterfeit currency. Even materials not specially marked with UV sensitive dyes may have distinctive fluorescence under UV exposure or may fluoresce differently under short-wave versus long-wave ultraviolet. | 0 | Theoretical and Fundamental Chemistry |
In some literature articles, the terms "mechanism of action" and "mode of action" are used interchangeably, typically referring to the way in which the drug interacts and produces a medical effect. However, in actuality, a mode of action describes functional or anatomical changes, at the cellular level, resulting from the exposure of a living organism to a substance. This differs from a mechanism of action since it is a more specific term that focuses on the interaction between the drug itself and an enzyme or receptor and its particular form of interaction, whether through inhibition, activation, agonism, or antagonism. Furthermore, the term "mechanism of action" is the main term that is primarily used in pharmacology, whereas "mode of action" will more often appear in the field of microbiology or certain aspects of biology. | 1 | Applied and Interdisciplinary Chemistry |
Nitrates do not affect infants and pregnant women. Blue baby syndrome is caused by a number of other factors such as gastric upset, such as diarrheal infection, protein intolerance, heavy metal toxicity etc., with nitrates playing a minor role. | 0 | Theoretical and Fundamental Chemistry |
The dipolar powder pattern (also Pake pattern) has a very characteristic shape that arises when two nuclear spins are coupled together within a crystallite. The splitting between the maxima (the "horns") of the pattern is equal to the dipolar coupling constant .:
where γ and γ are the gyromagnetic ratios of the dipolar-coupled nuclei, is the internuclear distance, is the reduced Planck's constant, and is the vacuum permeability. | 0 | Theoretical and Fundamental Chemistry |
was a Japanese medical doctor working as a medical scientist who discovered tranexamic acid in the 1950s in her quest to find a drug that would treat bleeding after childbirth (post-partum haemorrhage). After publishing results in 1962 she became a chair at Kobe Gakuin University, where she worked from 1966 until her retirement in 1990. Okamoto's career was hampered by a very male dominated environment.
During her lifetime she was unable to persuade obstetricians at Kobe to trial the antifibrinolytic agent, which had become a drug on the WHO list of essential medicines in 2009. She lived to see the 2010 beginning of the study of tranexamic acid in 20 000 women with post-partum haemorrhage, but died before its completion in 2016 and the publication of tranexamic acids fatality preventing results in 2017, that she had predicted. | 1 | Applied and Interdisciplinary Chemistry |
Pyrometallurgy involves high temperature processes where chemical reactions take place among gases, solids, and molten materials. Solids containing valuable metals are treated to form intermediate compounds for further processing or converted into their elemental or metallic state. Pyrometallurgical processes that involve gases and solids are typified by calcining and roasting operations. Processes that produce molten products are collectively referred to as smelting operations. The energy required to sustain the high temperature pyrometallurgical processes may derive from the exothermic nature of the chemical reactions taking place. Typically, these reactions are oxidation, e.g. of sulfide to sulfur dioxide . Often, however, energy must be added to the process by combustion of fuel or, in the case of some smelting processes, by the direct application of electrical energy.
Ellingham diagrams are a useful way of analysing the possible reactions, and so predicting their outcome. | 1 | Applied and Interdisciplinary Chemistry |
An open reading frame (ORF) is a reading frame that has the potential to be transcribed into RNA and translated into protein. It requires a continuous sequence of DNA which may include a start codon, through a subsequent region which has a length that is a multiple of 3 nucleotides, to a stop codon in the same reading frame.
When a putative amino acid sequence resulting from the translation of an ORF remained unknown in mitochondrial and chloroplast genomes, the corresponding open reading frame was called an unidentified reading frame (URF). For example, the MT-ATP8 gene was first described as URF A6L when the complete human mitochondrial genome was sequenced. | 1 | Applied and Interdisciplinary Chemistry |
TLRs are a type of pattern recognition receptor (PRR) and recognize molecules that are broadly shared by pathogens but distinguishable from host molecules, collectively referred to as pathogen-associated molecular patterns (PAMPs). In addition to the recognition of exogenous PAMPs, TLRs can also bind to endogenous damage-associated molecular patterns (DAMPs) such as heat shock proteins (HSPs) or plasma membrane constituents. TLRs together with the Interleukin-1 receptors form a receptor superfamily, known as the "interleukin-1 receptor / toll-like receptor superfamily"; all members of this family have in common a so-called TIR (toll-IL-1 receptor) domain.
Three subgroups of TIR domains exist. Proteins with subgroup 1 TIR domains are receptors for interleukins that are produced by macrophages, monocytes, and dendritic cells and all have extracellular Immunoglobulin (Ig) domains. Proteins with subgroup 2 TIR domains are classical TLRs, and bind directly or indirectly to molecules of microbial origin. A third subgroup of proteins containing TIR domains consists of adaptor proteins that are exclusively cytosolic and mediate signaling from proteins of subgroups 1 and 2. | 1 | Applied and Interdisciplinary Chemistry |
Increased blood CRP levels were higher in people with avian flu H7N9 compared to those with H1N1 (more common) influenza, with a review reporting that severe H1N1 influenza had elevated CRP. In 2020, people infected with COVID-19 in Wuhan, China, had elevated CRP. | 1 | Applied and Interdisciplinary Chemistry |
SREBPs have been found to play a role with the nutritional or hormonal effects on the lipogenic gene expression.
Overexpression of SREBP-1a or SREBP-1c in mouse liver cells results in the build-up of hepatic triglycerides and higher expression levels of lipogenic genes.
Lipogenic gene expression in the liver via glucose and insulin is moderated by SREBP-1. The effect of glucose and insulin on the transcriptional factor can occur through various pathways; there is evidence suggesting that insulin promotes SREBP-1 mRNA expression in adipocytes and hepatocytes. It has also been suggested that the hormone increases transcriptional activation by SREBP-1 through MAP-kinase-dependent phosphorylation regardless of changes in the mRNA levels. Along with insulin glucose also have been shown to promote SREBP-1 activity and mRNA expression. | 1 | Applied and Interdisciplinary Chemistry |
DNA sequences distal to a protein binding site may be brought into physical proximity through looping of chromosomes. For example, such interactions mediate enhancer and promoter function. These interactions can be detected through the action of Dam methylation. If Dam is targeted to a specific known DNA locus, distal sites brought into proximity due to the 3D configuration of the DNA will also be methylated and can be detected as in conventional DamID. | 1 | Applied and Interdisciplinary Chemistry |
Some chiral three-dimensional objects, such as the helix, can be assigned a right or left handedness, according to the right-hand rule.
Many other familiar objects exhibit the same chiral symmetry of the human body, such as gloves and shoes. Right shoes differ from left shoes only by being mirror images of each other. In contrast thin gloves may not be considered chiral if you can wear them inside-out.
The J-, L-, S- and Z-shaped tetrominoes of the popular video game Tetris also exhibit chirality, but only in a two-dimensional space. Individually they contain no mirror symmetry in the plane. | 0 | Theoretical and Fundamental Chemistry |
Structurally, the lac repressor protein is a homotetramer. More precisely, the tetramer contains two DNA-binding subunits composed of two monomers each (a dimer of dimers). Each monomer consists of four distinct regions:
*An N-terminal DNA-binding domain (in which two LacI proteins bind a single operator site)
*A regulatory domain (sometimes called the core domain, which binds allolactose, an allosteric effector molecule)
*A linker that connects the DNA-binding domain with the core domain (sometimes called the hinge helix, which is important for allosteric communication)
*A C-terminal tetramerization region (which joins four monomers in an alpha-helix bundle)
DNA binding occurs via an N-terminal helix-turn-helix structural motif and is targeted to one of several operator DNA sequences (known as O, O and O). The O operator sequence slightly overlaps with the promoter, which increases the affinity of RNA polymerase for the promoter sequence such that it cannot enter elongation and remains in abortive initiation. Additionally, because each tetramer contains two DNA-binding subunits, binding of multiple operator sequences by a single tetramer induces DNA looping. | 1 | Applied and Interdisciplinary Chemistry |
Apart from the very bulky substituents, a η-coordination of diphosphene to a metal is also possible to stabilize the P-P double bond. In 1982, K. R. Dixon et al. synthesized platinum and palladium complexes (with M=Pt or Pd and L=(PPh3) or ), which contained side-on coordination. Different from η coordination complex, where P-P still kept the double bond nature, P-P distance in side-on coordination complexes (2.121Å in ) was significantly longer than that in non-coordinated bis(2,4,6-tri-tert-butylphenyl)diphosphene. | 0 | Theoretical and Fundamental Chemistry |
Kanu was the first member of his family to attend university. He attended University of Sierra Leone, where he studied chemistry in Fourah Bay College. He was involved with track and field as an undergraduate student. Kanu was awarded a Commonwealth Scholarship, and moved from Sierra Leone to Manchester for his graduate studies. When he arrived at the University of Manchester Kanu started to work on gas chromatography–mass spectrometry. For his doctoral degree he developed miniaturised systems for environmental monitoring. His doctoral research formed the basis of two patents focussing on membrane sampling, which reduced sampling time by 60%. | 0 | Theoretical and Fundamental Chemistry |
The figure illustrates a two-component medium. Consider the cross-hatched volume of conductivity , take it as a sphere of volume and assume it is embedded in a uniform medium with an effective conductivity . If the electric field far from the inclusion is then elementary considerations lead to a dipole moment associated with the volume
This polarization produces a deviation from . If the average deviation is to vanish, the total polarization summed over the two types of inclusion must vanish. Thus
where and are respectively the volume fraction of material 1 and 2. This can be easily extended to a system of dimension that has an arbitrary number of components. All cases can be combined to yield Eq. (1).
Eq. (1) can also be obtained by requiring the deviation in current to vanish.
It has been derived here from the assumption that the inclusions are spherical and it can be modified for shapes with other depolarization factors; leading to Eq. (2).
A more general derivation applicable to bianisotropic materials is also available. | 0 | Theoretical and Fundamental Chemistry |
Firefly luciferase bioluminescence color can vary between yellow-green (λ = 550 nm) to red (λ = 620). There are currently several different mechanisms describing how the structure of luciferase affects the emission spectrum of the photon and effectively the color of light emitted.
One mechanism proposes that the color of the emitted light depends on whether the product is in the keto or enol form. The mechanism suggests that red light is emitted from the keto form of oxyluciferin, while green light is emitted from the enol form of oxyluciferin. However, 5,5-dimethyloxyluciferin emits green light even though it is constricted to the keto form because it cannot tautomerize.
Another mechanism proposes that twisting the angle between benzothiazole and thiazole rings in oxyluciferin determines the color of bioluminescence. This explanation proposes that a planar form with an angle of 0° between the two rings corresponds to a higher energy state and emits a higher-energy green light, whereas an angle of 90° puts the structure in a lower energy state and emits a lower-energy red light.
The most recent explanation for the bioluminescence color examines the microenvironment of the excited oxyluciferin. Studies suggest that the interactions between the excited state product and nearby residues can force the oxyluciferin into an even higher energy form, which results in the emission of green light. For example, Arg 218 has electrostatic interactions with other nearby residues, restricting oxyluciferin from tautomerizing to the enol form. Similarly, other results have indicated that the microenvironment of luciferase can force oxyluciferin into a more rigid, high-energy structure, forcing it to emit a high-energy green light. | 1 | Applied and Interdisciplinary Chemistry |
A Type V-K system was originally characterized from a cyanobacteria, Scytonema hofmanni, and contains a single Cas effector, Cas12k, that functions with a tracrRNA. This system functions similarly to Tn7 but does not have a TnsA protein which can result in off-targeting and chimera formation during over-expression. The Cas12k and tracrRNA complex bind to the target site and TnsC is polymerized directly adjacent prior to TniQ attachment and TnsB recognition and integration. While these systems use traditional tracrRNA characteristic of Type II CRISPR systems, they can also target with short crRNA located adjacent to the transposon end. Type V-K spacers preferentially target locations near tRNA genes, but other sites have been observed in these short crRNA guides which have been acquired by non-traditional means. | 1 | Applied and Interdisciplinary Chemistry |
The Kidd Process development team modified its cathode plates to cope with high-corrosion environments, such as the liberator cells used to remove contaminants in refineries and some high-corrosion environments in electrowinning plants.
The design of the plate features a stainless-steel jacket that surrounds a solid-copper hanger bar, protecting it from corrosion. A corrosion-resistant resin inside the stainless steel jacket protects the conductive interior weld between the header bar and the plate. The hanger bar is then finished with high-quality sealing to prevent ingress of electrolytes into the conductive interior weld.
This corrosion resistance electrode is marketed as the HP cathode plate. | 1 | Applied and Interdisciplinary Chemistry |
Health Canada published recommended dietary intakes (DRIs) and tolerable upper intake levels (ULs) for vitamin D based on the jointly commissioned and funded Institute of Medicine 2010 report. | 1 | Applied and Interdisciplinary Chemistry |
There are several possible potential benefits to chiral switching or chiral specific drugs. These include:
#An improved (less complex, more selective) pharmacodynamic profile
#A higher therapeutic index (improved safety margin)
#Less complex pharmacokinetic profile, less complex drug interactions
#Less complex relationship between plasma concentration and effect
#More rational therapeutic drug monitoring
#Expose the patient to less body load and thus reduce metabolic/renal/hepatic drug load
The chiral switching approach has sometimes resulted in failures and disappointments. | 0 | Theoretical and Fundamental Chemistry |
The capnellane group became a focal point for synthesis in the 1970s and 80’s. Scientists believed that these compounds had antimicrobial properties, based on an earlier discovery of antimicrobial activity in gorgonian soft corals and a later study of antimicrobial terpenoid compounds in alcyonarians. It was also postulated that capnellenes also protect the soft coral by preventing larval settlement.
Capnella imbricata is a rich source of many non-isoprenoid sesquiterpenes, which all share the ring system. Consequently, the first known isolation of a capnellane derivative was not capnellene but a capnellanol. As part of an ongoing search for terpenoids from marine sources, Kaisin et al. (1974) characterized the most abundant terpenoid, Δ-capnellene-3β,8β,10α-triol, from colonies of Capnella imbricata. The structure and absolute configuration of the triol were determined by nuclear magnetic resonance (NMR) spectroscopy and later confirmed by x-ray crystallography.
Kaisin et al. (1974) coined the name “capnellane” for the hydrocarbon skeleton on which the molecule was based. However, Shiekh et al. (1976) also claim to have originated the name. The first isolation of the hydrocarbon form, Δ9-capnellene, was achieved in 1978. Since then, numerous groups have isolated both Δ-capnellene and its alcohol derivatives. | 0 | Theoretical and Fundamental Chemistry |
There are significant advantages to using MAS NMR in structural biology. Magic angle spinning can be used to characterize large insoluble systems, including biological assemblies and intact viruses, that cannot be studied with other methods. | 0 | Theoretical and Fundamental Chemistry |
Fluorine is estimated to be the 13th-most abundant element in Earth's crust and is widely dispersed in nature, entirely in the form of fluorides. The vast majority is held in mineral deposits, the most commercially important of which is fluorite (CaF). Natural weathering of some kinds of rocks, as well as human activities, releases fluorides into the biosphere through what is sometimes called the fluorine cycle. | 1 | Applied and Interdisciplinary Chemistry |
All nucleons, that is neutrons and protons, composing any atomic nucleus, have the intrinsic quantum property of spin, an intrinsic angular momentum analogous to the classical angular momentum of a spinning sphere. The overall spin of the nucleus is determined by the spin quantum number S. If the numbers of both the protons and neutrons in a given nuclide are even then , i.e. there is no overall spin. Then, just as electrons pair up in nondegenerate atomic orbitals, so do even numbers of protons or even numbers of neutrons (both of which are also spin- particles and hence fermions), giving zero overall spin.
However, a proton and neutron spin vector that aligns itself opposite to the external magnetic field vector will have a lower energy when their spins are parallel, not anti-parallel. This parallel spin alignment of distinguishable particles does not violate the Pauli exclusion principle. The lowering of energy for parallel spins has to do with the quark structure of these two nucleons. As a result, the spin ground state for the deuteron (the nucleus of deuterium, the H isotope of hydrogen), which has only a proton and a neutron, corresponds to a spin value of 1, not of zero. On the other hand, because of the Pauli exclusion principle, the tritium isotope of hydrogen must have a pair of anti-parallel spin neutrons (of total spin zero for the neutron-spin pair), plus a proton of spin . Therefore, the tritium total nuclear spin value is again , just like for the simpler, abundant hydrogen isotope, H nucleus (the proton). The NMR absorption frequency for tritium is also similar to that of H. In many other cases of non-radioactive nuclei, the overall spin is also non-zero. For example, the nucleus has an overall spin value .
A non-zero spin is always associated with a non-zero magnetic dipole moment, , via the relation where γ is the gyromagnetic ratio. Classically, this corresponds to the proportionality between the angular momentum and the magnetic dipole moment of a spinning charged sphere, both of which are vectors parallel to the rotation axis whose length increases proportional to the spinning frequency. It is the magnetic moment and its interaction with magnetic fields that allows the observation of NMR signal associated with transitions between nuclear spin levels during resonant RF irradiation or caused by Larmor precession of the average magnetic moment after resonant irradiation. Nuclides with even numbers of both protons and neutrons have zero nuclear magnetic dipole moment and hence do not exhibit NMR signal. For instance, is an example of a nuclide that produces no NMR signal, whereas , , and are nuclides that do exhibit NMR spectra. The last two nuclei have spin S > and are therefore quadrupolar nuclei.
Electron spin resonance (ESR) is a related technique in which transitions between electronic rather than nuclear spin levels are detected. The basic principles are similar but the instrumentation, data analysis, and detailed theory are significantly different. Moreover, there is a much smaller number of molecules and materials with unpaired electron spins that exhibit ESR (or electron paramagnetic resonance (EPR)) absorption than those that have NMR absorption spectra. On the other hand, ESR has much higher signal per spin than NMR does. | 0 | Theoretical and Fundamental Chemistry |
In any solid at any temperature, the primary particles (e.g. atoms or molecules) are not stationary, but rather vibrate about mean positions. In insulators the capacity of the solid to store thermal energy is due almost entirely to these vibrations. Many physical properties of the solid (e.g. modulus of elasticity) can be predicted given knowledge of the frequencies with which the particles vibrate. The simplest assumption (by Einstein) is that all the particles oscillate about their mean positions with the same natural frequency ν. This is equivalent to the assumption that all atoms vibrate independently with a frequency ν. Einstein also assumed that the allowed energy states of these oscillations are harmonics, or integral multiples of hν. The spectrum of waveforms can be described mathematically using a Fourier series of sinusoidal density fluctuations (or thermal phonons).
Debye subsequently recognized that each oscillator is intimately coupled to its neighboring oscillators at all times. Thus, by replacing Einstein's identical uncoupled oscillators with the same number of coupled oscillators, Debye correlated the elastic vibrations of a one-dimensional solid with the number of mathematically special modes of vibration of a stretched string (see figure). The pure tone of lowest pitch or frequency is referred to as the fundamental and the multiples of that frequency are called its harmonic overtones. He assigned to one of the oscillators the frequency of the fundamental vibration of the whole block of solid. He assigned to the remaining oscillators the frequencies of the harmonics of that fundamental, with the highest of all these frequencies being limited by the motion of the smallest primary unit.
The normal modes of vibration of a crystal are in general superpositions of many overtones, each with an appropriate amplitude and phase. Longer wavelength (low frequency) phonons are exactly those acoustical vibrations which are considered in the theory of sound. Both longitudinal and transverse waves can be propagated through a solid, while, in general, only longitudinal waves are supported by fluids.
In the longitudinal mode, the displacement of particles from their positions of equilibrium coincides with the propagation direction of the wave. Mechanical longitudinal waves have been also referred to as compression waves. For transverse modes, individual particles move perpendicular to the propagation of the wave.
According to quantum theory, the mean energy of a normal vibrational mode of a crystalline solid with characteristic frequency ν is:
The term (1/2)hν represents the "zero-point energy", or the energy which an oscillator will have at absolute zero. E(ν) tends to the classic value kT at high temperatures
By knowing the thermodynamic formula,
the entropy per normal mode is:
The free energy is:
which, for kT >> hν, tends to:
In order to calculate the internal energy and the specific heat, we must know the number of normal vibrational modes a frequency between the values ν and ν + dν. Allow this number to be f(ν)dν. Since the total number of normal modes is 3N, the function f(ν) is given by:
The integration is performed over all frequencies of the crystal. Then the internal energy U will be given by: | 0 | Theoretical and Fundamental Chemistry |
John Walshe first described the use of penicillamine in Wilsons disease in 1956. He had discovered the compound in the urine of patients (including himself) who had taken penicillin, and experimentally confirmed that it increased urinary copper excretion by chelation. He had initial difficulty convincing several world experts of the time (Denny Brown and Cumings) of its efficacy, as they held that Wilsons disease was not primarily a problem of copper homeostasis but of amino acid metabolism, and that dimercaprol should be used as a chelator. Later studies confirmed both the copper-centered theory and the efficacy of -penicillamine. Walshe also pioneered other chelators in Wilson's such as triethylene tetramine and tetrathiomolybdate.
Penicillamine was first synthesized by John Cornforth under supervision of Robert Robinson.
Penicillamine has been used in rheumatoid arthritis since the first successful case in 1964. | 0 | Theoretical and Fundamental Chemistry |
SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, structural, and evolutionary units that form proteins. Domains of common Ancestry are grouped into superfamilies. The domains and domain superfamilies are defined and described in SCOP. Superfamilies are groups of proteins which have structural evidence to support a common evolutionary ancestor but may not have detectable sequence homology. | 1 | Applied and Interdisciplinary Chemistry |
In December 2008, a number of Irish news sources reported testing had revealed "extremely high" levels of dioxins, by toxic equivalent, in pork products, ranging from 80 to 200 times the EU's upper safe limit of 1.5 pg WHO-TEQ/μg i.e. 0.12 to 0.3 parts per billion.
Brendan Smith, the Minister for Agriculture, Fisheries and Food, stated the pork contamination was caused by PCB-contaminated feed that was used on 9 of Ireland's 400 pig farms, and only one feed supplier was involved. Smith added that 38 beef farms also used the same contaminated feed, but those farms were quickly isolated and no contaminated beef entered the food chain. While the contamination was limited to just 9 pig farms, the Irish government requested the immediate withdrawal and disposal of all pork-containing products produced in Ireland and purchased since September 1, 2008. This request for withdrawal of pork products was confirmed in a press release by the Food Safety Authority of Ireland on December 6.
It is thought that the incident resulted from the contamination of fuel oil used in a drying burner at a single feed processor, with PCBs. The resulting combustion produced a highly toxic mixture of PCBs, dioxins and furans, which was included in the feed produced and subsequently fed to a large number of pigs. | 1 | Applied and Interdisciplinary Chemistry |
Zirconium tungstate () is the zirconium salt of tungstic acid and has unusual properties. The phase formed at ambient pressure by reaction of ZrO and WO is a metastable cubic phase, which has negative thermal expansion characteristics, namely it shrinks over a wide range of temperatures when heated. In contrast to most other ceramics exhibiting negative CTE (coefficient of thermal expansion), the CTE of ZrWO is isotropic and has a large negative magnitude (average CTE of -7.2x10K) over a wide range of temperature (-273 °C to 777 °C). A number of other phases are formed at high pressures. | 0 | Theoretical and Fundamental Chemistry |
A number of microbial metabolisms fractionate sulfur isotopes in distinctive ways, and the sulfur isotopic fingerprints of these metabolisms can be preserved in minerals and ancient organic matter. By measuring the sulfur isotopic composition of these preserved materials, scientists can reconstruct ancient biological processes and the environments where they occurred. δS values in the geologic record have been inferred to reveal the history of microbial sulfate reduction and sulfide oxidation. Paired δS and ΔS records have also been used to show ancient microbial sulfur disproportionation.
Microbial dissimilatory sulfate reduction (MSR), an energy-yielding metabolism performed by bacteria in anoxic environments, is associated with an especially large fractionation factor. The observed ε values range from 0 to −65.6‰. Many factors influence the size of this fractionation, including sulfate reduction rate, sulfate concentration and transport, availability of electron donors and other nutrients, and physiological differences like protein expression. Sulfide produced through MSR may then go on to form the mineral pyrite, preserving the S-depleted fingerprint of MSR in sedimentary rocks. Many studies have investigated the δS values of ancient pyrite in order to understand past biological and environmental conditions. For example, pyrite δS records have been used to reconstruct shifts in primary productivity levels, changing ocean oxygen content, and glacial-interglacial changes in sea level and weathering. Some studies compare sulfur isotopes in pyrite to a second sulfur-containing material, like dissolved sulfate or preserved organic matter. Comparing pyrite to another material gives a fuller picture of how sulfur moved through ancient environments: it provides clues about the size of ancient ε values and the environmental conditions controlling MSR fractionation of sulfur isotopes. | 0 | Theoretical and Fundamental Chemistry |
Charles William Shoppee FAA FRS (1904–1994) was a British-born organic chemist who performed major research into steroids. He was Professor of Chemistry at the University College of Swansea (1946–1956) and Professor of Organic Chemistry at the University of Sydney (1956–1969).
The short citation on his election as Fellow of the Australian Academy of Science (in 1958) reads: [Shoppee] "is distinguished for his contributions to organic chemistry, with special reference to the investigation of problems of reaction mechanism, the establishment of the structures of the adreno-cortical hormones, and the elucidation of stereochemical relationships in the steroid field."
Born on 24 February 1904 at Crouch End, (London, UK), to Joseph William and Emma Elizabeth Shoppee (née Hawkswell of York), he was educated at the Stationers Companys School and Imperial College (Royal College of Science). Early positions were at the University of Leeds (1924-1938), Basel (1938-1945) and the University of London (1945-1948). He married Eileen West on 18 July 1929 and completed a D.Sc. from the University of London in 1931.
From 1948 to 1956 he was Professor of Chemistry at the University College, Swansea, of the University of Wales, and from 1956 until his compulsory retirement he was Professor of Organic Chemistry at the University of Sydney. He was elected Fellow of the Royal Society (1956) and Fellow of the Australian Academy of Science (1958).
On his retirement in 1969, aged 65, he accepted the position of Foundation Welch Professorship of Chemistry at Texas Technological University (1970–1974). He returned to Australia in 1975, where he served as an honorary professorial fellow at Macquarie University (1976–1979) and was honorary visiting professor at La Trobe University from 1980 where he was still active in the laboratory in 1991. He died on . | 0 | Theoretical and Fundamental Chemistry |
The Schikorr reaction formally describes the conversion of the iron(II) hydroxide (Fe(OH)) into iron(II,III) oxide (FeO). This transformation reaction was first studied by Gerhard Schikorr. The global reaction follows:
It is of special interest in the context of the serpentinization, the formation of hydrogen by the action of water on a common mineral. | 1 | Applied and Interdisciplinary Chemistry |
Advertising is common in healthcare journals as well as through more mainstream media routes. In some countries, notably the US, they are allowed to advertise directly to the general public. Pharmaceutical companies generally employ salespeople (often called drug reps or, an older term, detail men) to market directly and personally to physicians and other healthcare providers. In some countries, notably the US, pharmaceutical companies also employ lobbyists to influence politicians. Marketing of prescription drugs in the US is regulated by the federal Prescription Drug Marketing Act of 1987. The pharmaceutical marketing plan incorporates the spending plans, channels, and thoughts which will take the drug association, and its items and administrations, forward in the current scene. | 1 | Applied and Interdisciplinary Chemistry |
Pollution from metals is very common, as they are used in many industrial processes such as electroplating, textiles, paint and leather. The wastewater from these industries is often used for agricultural purposes, so besides the immediate damage to the ecosystem it is spilled into, the metals can enter creatures and humans far away through the food chain. Mycoremediation is one of the cheapest, most effective and environmental-friendly solutions to this problem.
Many fungi are hyperaccumulators, therefore they are able to concentrate toxins in their fruiting bodies for later removal. This is usually true for populations that have been exposed to contaminants for a long time, and have developed a high tolerance. Hyperaccumulation occurs via biosorption on the cellular surface, where the metals enter the mycelium passively with very little intracellular uptake.
A variety of fungi, such as Pleurotus, Aspergillus, Trichoderma has proven to be effective in the removal of lead, cadmium, nickel, chromium, mercury, arsenic, copper, boron, iron and zinc in marine environments, wastewater and on land.
Not all the individuals of a species are effective in the same way in the accumulation of toxins. The single individuals are usually selected from an older polluted environment, such as sludge or wastewater, where they had time to adapt to the circumstances, and the selection is carried on in the laboratory. A dilution of the water can drastically improve the ability of biosorption of the fungi.
The capacity of certain fungi to extract metals from the ground also can be useful for bioindicator purposes, and can be a problem when the mushroom is of an edible variety. For example, the shaggy ink cap (Coprinus comatus), a common edible mushroom found in the Northern Hemisphere, can be a very good bioindicator of mercury. However, as the shaggy ink cap accumulates mercury in its body, it can be toxic to the consumer.
The capacity of metals uptake of mushroom has also been used to recover precious metals from medium. For example, VTT Technical Research Centre of Finland reported an 80% recovery of gold from electronic waste using mycofiltration techniques. | 1 | Applied and Interdisciplinary Chemistry |
Systems that admit a treatment with the system size expansion may be described by a probability distribution , giving the probability of observing the system in state at time . may be, for example, a vector with elements corresponding to the number of molecules of different chemical species in a system. In a system of size (intuitively interpreted as the volume), we will adopt the following nomenclature: is a vector of macroscopic copy numbers, is a vector of concentrations, and is a vector of deterministic concentrations, as they would appear according to the rate equation in an infinite system. and are thus quantities subject to stochastic effects.
A master equation describes the time evolution of this probability. Henceforth, a system of chemical reactions will be discussed to provide a concrete example, although the nomenclature of "species" and "reactions" is generalisable. A system involving species and reactions can be described with the master equation:
Here, is the system size, is an operator which will be addressed later, is the stoichiometric matrix for the system (in which element gives the stoichiometric coefficient for species in reaction ), and is the rate of reaction given a state and system size .
is a step operator, removing from the th element of its argument. For example, . This formalism will be useful later.
The above equation can be interpreted as follows. The initial sum on the RHS is over all reactions. For each reaction , the brackets immediately following the sum give two terms. The term with the simple coefficient −1 gives the probability flux away from a given state due to reaction changing the state. The term preceded by the product of step operators gives the probability flux due to reaction changing a different state into state . The product of step operators constructs this state . | 0 | Theoretical and Fundamental Chemistry |
The inherent properties and the incorporation of wood fiber and particles in this composite, has made it possible to produce GWC building materials that are light weight and has a variety of uses due to its heat storage capacity, for example in areas of thermal insulation, fire and noise protection.
The wood-geopolymer composite material in the building walls can serve as a microclimate regulator absorbing the moisture when the air humidity is high and returning the moisture when there is a low air humidity period, thus improving the hygrothermal comfort in the building. | 0 | Theoretical and Fundamental Chemistry |
Most of the calculations above are exact at zero temperature, yet remain as good approximations for temperatures lower than the Fermi temperature. For other thermodynamics variables it is necessary to write a thermodynamic potential. For an ensemble of identical fermions, the best way to derive a potential is from the grand canonical ensemble with fixed temperature, volume and chemical potential µ. The reason is due to Pauli exclusion principle, as the occupation numbers of each quantum state are given by either 1 or 0 (either there is an electron occupying the state or not), so the (grand) partition function can be written as
where , indexes the ensembles of all possible microstates that give the same total energy and number of particles , is the single particle energy of the state (it counts twice if the energy of the state is degenerate) and , its occupancy. Thus the grand potential is written as
The same result can be obtained in the canonical and microcanonical ensemble, as the result of every ensemble must give the same value at thermodynamic limit . The grand canonical ensemble is recommended here as it avoids the use of combinatorics and factorials.
As explored in previous sections, in the macroscopic limit we may use a continuous approximation (Thomas–Fermi approximation) to convert this sum to an integral:
where is the total density of states. | 0 | Theoretical and Fundamental Chemistry |
Another role for these receptors is at the junction of the innervated tissues and the postganglionic neurons in the parasympathetic division of the autonomic nervous system. Here acetylcholine is again used as a neurotransmitter, and muscarinic receptors form the principal receptors on the innervated tissue. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, hydrocyanation is a process for conversion of alkenes to nitriles. The reaction involves the addition of hydrogen cyanide and requires a catalyst. This conversion is conducted on an industrial scale for the production of precursors to nylon. | 0 | Theoretical and Fundamental Chemistry |
Thylakoids can be purified from plant cells using a combination of differential and gradient centrifugation. Disruption of isolated thylakoids, for example by mechanical shearing, releases the lumenal fraction. Peripheral and integral membrane fractions can be extracted from the remaining membrane fraction. Treatment with sodium carbonate (NaCO) detaches peripheral membrane proteins, whereas treatment with detergents and organic solvents solubilizes integral membrane proteins. | 0 | Theoretical and Fundamental Chemistry |
Cryptands and crown ethers typically do not form inclusion complexes since the guest is bound by forces stronger than van der Waals bonding. If the guest is enclosed on all sides so that it is trapped, the compound is known as a clathrate, not an inclusion complex. In molecular encapsulation, a guest molecule is trapped inside another molecule. | 0 | Theoretical and Fundamental Chemistry |
ortho-Carborane undergoes 2e- reduction when treated with a solution of lithium in ammonia. The result is the nido cluster 7,9-[CBH]. In the dianion, the carbon vertices are not adjacent. The same cluster is produced by reduction of meta-carborane. Oxidation of the resulting 7,9-[CBH] gives ortho-carborane. | 0 | Theoretical and Fundamental Chemistry |
Milling is the complex shaping of metal or other materials by removing material to form the final shape. It is generally done on a milling machine, a power-driven machine that in its basic form consists of a milling cutter that rotates about the spindle axis (like a drill), and a worktable that can move in multiple directions (usually two dimensions [x and y axis] relative to the workpiece). The spindle usually moves in the z axis. It is possible to raise the table (where the workpiece rests). Milling machines may be operated manually or under computer numerical control (CNC), and can perform a vast number of complex operations, such as slot cutting, planing, drilling and threading, rabbeting, routing, etc. Two common types of mills are the horizontal mill and vertical mill.
The pieces produced are usually complex 3D objects that are converted into x, y, and z coordinates that are then fed into the CNC machine and allow it to complete the tasks required. The milling machine can produce most parts in 3D, but some require the objects to be rotated around the x, y, or z coordinate axis (depending on the need). Tolerances come in a variety of standards, depending on the locale. In countries still using the imperial system, this is usually in the thousandths of an inch (unit known as thou), depending on the specific machine. In many other European countries, standards following the ISO are used instead.
In order to keep both the bit and material cool, a high temperature coolant is used. In most cases the coolant is sprayed from a hose directly onto the bit and material. This coolant can either be machine or user controlled, depending on the machine.
Materials that can be milled range from aluminum to stainless steel and almost everything in between. Each material requires a different speed on the milling tool and varies in the amount of material that can be removed in one pass of the tool. Harder materials are usually milled at slower speeds with small amounts of material removed. Softer materials vary, but usually are milled with a high bit speed.
The use of a milling machine adds costs that are factored into the manufacturing process. Each time the machine is used coolant is also used, which must be periodically added in order to prevent breaking bits. A milling bit must also be changed as needed in order to prevent damage to the material. Time is the biggest factor for costs. Complex parts can require hours to complete, while very simple parts take only minutes. This in turn varies the production time as well, as each part will require different amounts of time.
Safety is key with these machines. The bits are traveling at high speeds and removing pieces of usually scalding hot metal. The advantage of having a CNC milling machine is that it protects the machine operator. | 1 | Applied and Interdisciplinary Chemistry |
Methods of nuclear spectroscopy use properties of a nucleus to probe a materials properties, especially the materials local structure. Common methods include nuclear magnetic resonance spectroscopy (NMR), Mössbauer spectroscopy (MBS), and perturbed angular correlation (PAC). | 0 | Theoretical and Fundamental Chemistry |
The aims of Statistical hydrology is to provide appropriate statistical methods for analyzing and modeling various parts of the hydrological cycle. By analyzing the statistical properties of hydrologic records, such as rainfall or river flow, hydrologists can estimate future hydrologic phenomena. When making assessments of how often relatively rare events will occur, analyses are made in terms of the return period of such events. Other quantities of interest include the average flow in a river, in a year or by season.
These estimates are important for engineers and economists so that proper risk analysis can be performed to influence investment decisions in future infrastructure and to determine the yield reliability characteristics of water supply systems. Statistical information is utilized to formulate operating rules for large dams forming part of systems which include agricultural, industrial and residential demands. | 1 | Applied and Interdisciplinary Chemistry |
Autoclave reactors are used for reactions at higher temperatures, which can enhance the rate of the reaction. Similarly, autoclaves enable the use of gaseous reagents in the system. | 1 | Applied and Interdisciplinary Chemistry |
In high-temperature metal joining processes (welding, brazing and soldering), fluxes are nearly inert at room temperature, but become strongly reducing at elevated temperatures, preventing oxidation of the base and filler materials. The role of flux is typically dual: dissolving the oxides already present on the metal surface to facilitate wetting by molten metal, and acting as an oxygen barrier by coating the hot surface, preventing oxidation.
For example, tin-lead solder attaches very well to copper metal, but poorly to its oxides, which form quickly at soldering temperatures. By preventing the formation of metal oxides, flux enables the solder to adhere to the clean metal surface, rather than forming beads, as it would on an oxidized surface. | 1 | Applied and Interdisciplinary Chemistry |
Under normal physiological conditions, inflammatory cells protect the body from foreign objects, and the body undergoes a foreign body reaction based on the adsorption of blood and proteins on the biomaterial surface. In the first two to four weeks post implant, there is an association between biomaterial adherent macrophages and cytokine expression near the foreign implant site, which can be explored using semi-quantitative RT-PCR. Macrophages fuse together to form foreign body giant cells (FBGCs), which similarly express cytokine receptors on their cell membranes and actively participate in the inflammatory response. Device failure in organic polyether polyurethane (PEU) pacemakers compared to silicone rubber showcases that the foreign body response may indeed lead to degradation of biomaterials, causing subsequent device failures. The utilization of to prevent functionality and durability compromise is proposed to minimize and slow the rate of biomaterial degradation. | 1 | Applied and Interdisciplinary Chemistry |
UV degradation is one form of polymer degradation that affects plastics exposed to sunlight. The problem appears as discoloration or fading, cracking, loss of strength or disintegration. The effects of attack increase with exposure time and sunlight intensity. The addition of UV absorbers inhibits the effect.
Sensitive polymers include thermoplastics and speciality fibers like aramids. UV absorption leads to chain degradation and loss of strength at sensitive points in the chain structure. Aramid rope must be shielded with a sheath of thermoplastic if it is to retain its strength.
Many pigments and dyes absorb UV and change colour, so paintings and textiles may need extra protection both from sunlight and fluorescent lamps, two common sources of UV radiation. Window glass absorbs some harmful UV, but valuable artifacts need extra shielding. Many museums place black curtains over watercolour paintings and ancient textiles, for example. Since watercolours can have very low pigment levels, they need extra protection from UV. Various forms of picture framing glass, including acrylics (plexiglass), laminates, and coatings, offer different degrees of UV (and visible light) protection. | 0 | Theoretical and Fundamental Chemistry |
Sodium hydroxide reacts with protic acids to produce water and the corresponding salts. For example, when sodium hydroxide reacts with hydrochloric acid, sodium chloride is formed:
In general, such neutralization reactions are represented by one simple net ionic equation:
This type of reaction with a strong acid releases heat, and hence is exothermic. Such acid–base reactions can also be used for titrations. However, sodium hydroxide is not used as a primary standard because it is hygroscopic and absorbs carbon dioxide from air. | 0 | Theoretical and Fundamental Chemistry |
Polymers, which are not fully saturated, are vulnerable to attack by ozone. This gas exists naturally in the atmosphere but is also formed by nitrogen oxides released in vehicle exhaust pollution. Many common elastomers (rubbers) are affected, with natural rubber, polybutadiene, styrene-butadiene rubber and NBR being most sensitive to degradation. The ozonolysis reaction results in immediate chain scission. Ozone cracks in products under tension are always oriented at right angles to the strain axis, so will form around the circumference in a rubber tube bent over. Such cracks are dangerous when they occur in fuel pipes because the cracks will grow from the outside exposed surfaces into the bore of the pipe, and fuel leakage and fire may follow. The problem of ozone cracking can be prevented by adding antiozonants. | 0 | Theoretical and Fundamental Chemistry |
Sewer network structures are prone to biodeterioration of materials due to the action of some microorganisms associated to the sulfur cycle. It can be a severely damaging phenomenon which was firstly described by Olmstead and Hamlin in 1900 for a brick sewer located in Los Angeles. Jointed mortar between the bricks disintegrated and ironwork was heavily rusted. The mortar joint had ballooned to two to three times its original volume, leading to the destruction or the loosening of some bricks.
Around 9% of damages described in sewer networks can be ascribed to the successive action of two kinds of microorganisms. Sulfate-reducing bacteria (SRB) can grow in relatively thick layers of sedimentary sludge and sand (typically 1 mm thick) accumulating at the bottom of the pipes and characterized by anoxic conditions. They can grow using oxidized sulfur compounds present in the effluent as electron acceptor and excrete hydrogen sulfide (HS). This gas is then emitted in the aerial part of the pipe and can impact the structure in two ways: either directly by reacting with the material and leading to a decrease in pH, or indirectly through its use as a nutrient by sulfur-oxidizing bacteria (SOB), growing in oxic conditions, which produce biogenic sulfuric acid. The structure is then submitted to a biogenic sulfuric acid attack. Materials like calcium aluminate cements, PVC or vitrified clay pipe may be substituted for ordinary concrete or steel sewers that are not resistant in these environments.
Mild steel corrosion reduction in water by uptake of dissolved oxygen is carried out by Rhodotorula mucilaginosa(7). | 1 | Applied and Interdisciplinary Chemistry |
Hyperspectral surveillance is the implementation of hyperspectral scanning technology for surveillance purposes. Hyperspectral imaging is particularly useful in military surveillance because of countermeasures that military entities now take to avoid airborne surveillance. The idea that drives hyperspectral surveillance is that hyperspectral scanning draws information from such a large portion of the light spectrum that any given object should have a unique spectral signature in at least a few of the many bands that are scanned. Hyperspectral imaging has also shown potential to be used in facial recognition purposes. Facial recognition algorithms using hyperspectral imaging have been shown to perform better than algorithms using traditional imaging.
Traditionally, commercially available thermal infrared hyperspectral imaging systems have needed liquid nitrogen or helium cooling, which has made them impractical for most surveillance applications. In 2010, Specim introduced a thermal infrared hyperspectral camera that can be used for outdoor surveillance and UAV applications without an external light source such as the sun or the moon. | 0 | Theoretical and Fundamental Chemistry |
Catalysts also have a role in the unblocking of blocked isocyanates. As with regular isocyanates organometallic compounds and tertiary amines may lower the unblocking temperature. Tin compounds, such as dibutyltin dilaurate, dibutyltin diacetate and other metal compounds are effective deblocking catalysts. | 0 | Theoretical and Fundamental Chemistry |
Through the process of saponification, fats (like tallow, pig, and bone fats) or vegetable oils react with sodium hydroxide to form the sodium salts of fatty acids and glycerin. The resulting mixture is known as soft soap, which serves as a precursor for hard soap production. After adding sodium chloride (a process known as salting out), the soap nucleus rises and separates. The water-soluble glycerin and unwanted fat residues remain in the solution (see also soap). | 0 | Theoretical and Fundamental Chemistry |
A Bjerrum defect is a crystallographic defect which is specific to ice, and which is partly responsible for the electrical properties of ice. It was first proposed by Niels Bjerrum in 1952 in order to explain the electrical polarization of ice in an electric field. A hydrogen bond normally has one proton, but a hydrogen bond with a Bjerrum defect will have either two protons (D defect, from "doppel" in German, meaning "double") or no proton (L defect, from "leer" in German, meaning "empty"). D-defects are more energetically favorable than L-defects. The unfavorable defect strain is resolved when a water molecule pivots about an oxygen atom to produce hydrogen bonds with single protons. Dislocations of ice Ih along a slip plane create pairs of Bjerrum defects, one D defect and one L defect.
Nonpolar molecules such as methane can form clathrate hydrates with water, especially under high pressure. Although there is no hydrogen bonding of water molecules when methane is the guest molecule of the clathrate, guest-host hydrogen bonding often forms with guest molecules in clathrates of many larger organic molecules, such as pinacolone and tetrahydrofuran. In such cases the guest-host hydrogen bonds result in the formation of L-type Bjerrum defect in the clathrate lattice. Oxygen atoms (in alcohol or carbonyl functional groups) and nitrogen atoms (in amine functional groups) in the guest molecules lead to transient hydrogen bonds and misoriented water molecules in the hydrate lattice. | 0 | Theoretical and Fundamental Chemistry |
Small, electronegative molecules such as nitrogen and oxygen, which are the primary gases in air, significantly impact the ability of surrounding molecules to participate in hydrogen bonding. These molecules compete with surrounding hydrogen bond acceptors for hydrogen bond donors, therefore acting as "hydrogen bond breakers" and weakening interactions between surrounding molecules in the environment. Antiparellel strands in DNA double helices are non-covalently bound by hydrogen bonding between base pairs; nitrogen and oxygen therefore maintain the potential to weaken the integrity of DNA when exposed to air. As a result, DNA strands exposed to air require less force to separate and exemplify lower melting temperatures. | 1 | Applied and Interdisciplinary Chemistry |
Illicit diversion of pseudoephedrine in Australia has caused significant changes to the way the products are regulated. , all products containing pseudoephedrine have been rescheduled as either "Pharmacist Only Medicines" (Schedule 3) or "Prescription Only Medicines" (Schedule 4), depending on the amount of pseudoephedrine in the product. A Pharmacist Only Medicine may only be sold to the public if a pharmacist is directly involved in the transaction. These medicines must be kept behind the counter, away from public access.
Pharmacists are also encouraged (and in some states required) to log purchases with the online database Project STOP.
As a result, some pharmacies no longer stock Sudafed, the common brand of pseudoephedrine cold/sinus tablets, opting instead to sell Sudafed PE, a phenylephrine product that has not been proven effective in clinical trials. | 0 | Theoretical and Fundamental Chemistry |
Caking mechanisms depend on the nature of the material. Caking is a consequence of chemical reactions of grain surfaces. Often these reactions involve adsorption of water vapor or other gases. Crystalline solids often cake by formation of liquid bridge between microcrystals and subsequent fusion of a solid bridge. Amorphous materials can cake by glass transitions and changes in viscosity. Polymorphic phase transitions can also induce caking. The caking process can involve electrostatic attractions or the formation of weak chemical bonds between particles. | 1 | Applied and Interdisciplinary Chemistry |
The Randle cycle, also known as the glucose fatty-acid cycle, is a metabolic process involving the competition of glucose and fatty acids for substrates. It is theorized to play a role in explaining type 2 diabetes and insulin resistance.
It was named for Philip Randle, who described it in 1963. | 1 | Applied and Interdisciplinary Chemistry |
Source:
* University of Fribourg (Switzerland, 1966)
* University of Chicago (US, 1966)
* University of Edinburgh (United Kingdom, 1979)
* University of Bologna (Italy, 1989)
* Goethe University Frankfurt (Germany, 1990)
* Louis Pasteur University (France, 1991)
* Harvard University (US, 1993)
* Scripps Research Institute (US, 2000)
* University of Innsbruck (Austria, 2010) | 0 | Theoretical and Fundamental Chemistry |
Examples of lyotropic liquid crystals can also be generated using 2D nanosheets. The most striking example of a true nematic phase has been demonstrated for many smectite clays. The issue of the existence of such a lyotropic phase was raised by Langmuir in 1938, but remained an open question for a very long time and was only confirmed recently. With the rapid development of nanosciences, and the synthesis of many new anisotropic 2D nanoparticles, the number of such Nematic mesophase based on 2D nanosheet has increased quickly, with, for example graphene oxide colloidal suspensions.
Noteworhty, a lamellar phase was even discovered, HSbPO, which exhibits hyperswelling up to ~250 nm for the interlamellar distance. | 0 | Theoretical and Fundamental Chemistry |
Expansion joints are often included in industrial piping systems to accommodate movement due to thermal and mechanical changes in the system. When the process requires large changes in temperature, metal components change size. Expansion joints with metal bellows are designed to accommodate certain movements while minimizing the transfer of forces to sensitive components in the system.
Pressure created by pumps or gravity is used to move fluids through the piping system. Fluids under pressure occupy the volume of their container. The unique concept of pressure balanced expansion joints is they are designed to maintain a constant volume by having balancing bellows compensate for volume changes in the bellows (line bellows) which is moved by the pipe. An early name for these devices was “pressure-volumetric compensator”. | 1 | Applied and Interdisciplinary Chemistry |
In normal usage, the rate-limiting step or rate-determining step is defined as the slowest step of a chemical reaction that determines the speed (rate) at which the overall reaction proceeds. The flux control coefficients do not measure this kind of rate-limitingness. For example, in a linear chain of reactions at steady-state, all steps carry the same flux. That is, there is no slow or fast step with respect to the rate or speed of a reaction. The flux control coefficient, instead, measures how much influence a given step has on the steady-state flux. A step with a high flux control coefficient means that changing the activity of the step (by changing the expression level of the enzyme) will have a large effect on the steady-state flux through the pathway and vice versa.
Historically the concept of the rate-limiting steps was also related to the notion of the master step. However, this drew much criticism due to a misunderstanding of the concept of the steady-state. | 1 | Applied and Interdisciplinary Chemistry |
Through the Partnership for Safe Water AWWA also works with the United States Environmental Protection Agency and other water organizations to help water providers optimize system performance beyond existing regulatory levels.
AWWA offers opportunities for people to meet, learn, and network at the international, national, and section levels. In addition to publications and conferences for water professionals, AWWA hosts a variety of workshops, symposia, teleconferences, and programs focused on specific aspects of water stewardship. In cooperation with other professional associations, AWWA is a resource for water professionals’ continuing education and development. | 1 | Applied and Interdisciplinary Chemistry |
A screw axis (helical axis or twist axis) is a line that is simultaneously the axis of rotation and the line along which translation of a body occurs. Chasles' theorem shows that each Euclidean displacement in three-dimensional space has a screw axis, and the displacement can be decomposed into a rotation about and a slide along this screw axis.
Plücker coordinates are used to locate a screw axis in space, and consist of a pair of three-dimensional vectors. The first vector identifies the direction of the axis, and the second locates its position. The special case when the first vector is zero is interpreted as a pure translation in the direction of the second vector. A screw axis is associated with each pair of vectors in the algebra of screws, also known as screw theory.
The spatial movement of a body can be represented by a continuous set of displacements. Because each of these displacements has a screw axis, the movement has an associated ruled surface known as a screw surface. This surface is not the same as the axode, which is traced by the instantaneous screw axes of the movement of a body. The instantaneous screw axis, or instantaneous helical axis (IHA), is the axis of the helicoidal field generated by the velocities of every point in a moving body.
When a spatial displacement specializes to a planar displacement, the screw axis becomes the displacement pole, and the instantaneous screw axis becomes the velocity pole, or instantaneous center of rotation, also called an instant center. The term centro is also used for a velocity pole, and the locus of these points for a planar movement is called a centrode. | 0 | Theoretical and Fundamental Chemistry |
Before atomic orbitals were understood, spectroscopists discovered various distinctive series of spectral lines in atomic spectra, which they identified by letters. These letters were later associated with the azimuthal quantum number, ℓ. The letters, "s", "p", "d", and "f", for the first four values of ℓ were chosen to be the first letters of properties of the spectral series observed in alkali metals. Other letters for subsequent values of ℓ were assigned in alphabetical order, omitting the letter "j" because some languages do not distinguish between the letters "i" and "j":
This notation is used to specify electron configurations and to create the term symbol for the electron states in a multi-electron atom. When writing a term symbol, the above scheme for a single electron's orbital quantum number is applied to the total orbital angular momentum associated to an electron state. | 0 | Theoretical and Fundamental Chemistry |
* Centrifugation and cyclonic separation, separates based on density differences
* Chelation
* Chromatography separates dissolved substances by different interaction with (i.e., travel through) a material.
** High-performance liquid chromatography (HPLC)
** Thin-layer chromatography (TLC)
** Countercurrent chromatography (CCC)
** Droplet countercurrent chromatography (DCC)
** Paper chromatography
** Ion chromatography
** Size-exclusion chromatography (SEC)
** Affinity chromatography
** Centrifugal partition chromatography
** Gas chromatography and Inverse gas chromatography
* Crystallization
* Decantation
* Demister (vapor), removes liquid droplets from gas streams
* Distillation, used for mixtures of liquids with different boiling points
* Drying, removes liquid from a solid by vaporization or evaporation
* Electrophoresis, separates organic molecules based on their different interaction with a gel under an electric potential (i.e., different travel)
** Capillary electrophoresis
* Electrostatic separation, works on the principle of corona discharge, where two plates are placed close together and high voltage is applied. This high voltage is used to separate the ionized particles.
* Elutriation
* Evaporation
* Extraction
** Leaching
** Liquid–liquid extraction
** Solid phase extraction
** Supercritical fluid extraction
** Subcritical fluid extraction
* Field flow fractionation
* Filtration – Mesh, bag and paper filters are used to remove large particulates suspended in fluids (e.g., fly ash) while membrane processes including microfiltration, ultrafiltration, nanofiltration, reverse osmosis, dialysis (biochemistry) utilising synthetic membranes, separates micrometre-sized or smaller species
* Flocculation, separates a solid from a liquid in a colloid, by use of a flocculant, which promotes the solid clumping into flocs
* Fractional distillation
* Fractional freezing
* Magnetic separation
* Oil-water separation, gravimetrically separates suspended oil droplets from waste water in oil refineries, petrochemical and chemical plants, natural gas processing plants and similar industries
* Precipitation
* Recrystallization
* Scrubbing, separation of particulates (solids) or gases from a gas stream using liquid.
* Sedimentation, separates using vocal density pressure differences
** Gravity separation
* Sieving
* Sponge, adhesion of atoms, ions or molecules of gas, liquid, or dissolved solids to a surface
* Stripping
* Sublimation
* Vapor–liquid separation, separates by gravity, based on the Souders–Brown equation
* Winnowing
* Zone refining | 0 | Theoretical and Fundamental Chemistry |
C-Path programs are focused on reducing the time, cost, and risk of drug development and regulatory review. Where appropriate, C-Path forms consortia to improve the drug development process.
* The Predictive Safety Testing Consortium (PSTC) works to find improved safety biomarkers to detect drug induced toxicity.
* The Patient-Reported Outcome (PRO) Consortium develops, evaluates, and qualifies PRO instruments (e.g., questionnaires) for use in clinical trials designed to assess the safety and effectiveness of medical products.
* The Critical Path to TB Drug Regimens (CPTR) aims to accelerate the development of new, safe, and highly effective tuberculosis treatment regimens with shortened durations of therapy.
*The Polycystic Kidney Disease (PKD) Consortium evaluates the evidence supporting total kidney volume (TKV) as a biomarker for assessing the progression of autosomal dominant PKD.
*The Critical Path for Alzheimer's Disease (CPAD) aims to increase the efficiency of the development process of new treatments for Alzheimer disease (AD) and related neurodegenerative disorders with impaired cognition and function.
*The Critical Path for Parkinson's (CPP) works to improve the clinical trial process.
*The Data Collaboration Center (DCC) develops data solutions for scientific research.
*The Duchenne Regulatory Science Consortium (D-RSC) supports collaborative research through shared data access and drug development tools.
*The Electronic Patient-Reported Outcome Consortium (e-PRO) supports the collection of patient-focused outcomes data in clinical trials.
*The Huntingtons Disease Regulatory Science Consortium (HD-RSC) aims to accelerate the regulatory approval of Huntingtons disease therapies.
*The International Neonatal Consortium (INC) seeks to forge a predictable regulatory path for evaluating the safety and effectiveness of therapies for neonates.
*The Multiple Sclerosis Outcome Assessments Consortium (MSOAC) works to qualify a new measure of disability as a primary or secondary endpoint for future trials of MS therapies.
*The Type 1 Diabetes Consortium (T1D) works to qualify islet autoimmunity antibodies as prognostic biomarkers.
*The goal of the Transplant Therapeutics Consortium (TTC) is to accelerate the medical product development process for transplantation.
*The TB-Platform for Aggregation of Clinical TB Studies (TB-PACTS) curates and standardizes Phase III tuberculosis (TB) clinical trial data.
*The successfully completed Pediatric Trials Consortium worked toward the efficient evaluation of innovative drugs, biologics, and devices for children. | 1 | Applied and Interdisciplinary Chemistry |
Proteins are translated by reading tri-nucleotides on the mRNA strand, also known as codons, from one end of the mRNA to the other (from the 5 to the 3 end) starting with the amino acid methionine as the start (initiation) codon AUG. Each codon is translated into a single amino acid. The code itself is considered degenerate, meaning that a particular amino acid can be specified by more than one codon. However, a shift of any number of nucleotides that is not divisible by 3 in the reading frame will cause subsequent codons to be read differently. This effectively changes the ribosomal reading frame. | 1 | Applied and Interdisciplinary Chemistry |
Vildagliptin (Galvus)(Figure 6) was first synthesized in May 1998 and was named after Edwin B. Villhauer. It was discovered when researchers at Novartis examined adamantyl derivatives that had proven to be very potent. The adamantyl group worked as a steric bulk and slowed intramolecular cyclization while increasing chemical stability. Furthermore, the primary metabolites were highly active. To avoid additional chiral center a hydroxylation at the adamantyl ring was carried out (Figure 6). The product, vildagliptin, was even more stable, undergoing intramolecular cyclization 30-times slower, and having high DPP-4 inhibitory activity and longer-lasting pharmacodynamic effect. | 1 | Applied and Interdisciplinary Chemistry |
Currently, appearance of drug resistant viruses is an inevitable consequence of prolonged exposure of HIV-1 to antiretroviral therapy. Drug resistance is a serious clinical concern in treatment of viral infection, and it is a particularly difficult problem in treatment of HIV. Resistance mutations are known for all approved NRTIs.
Two main mechanisms are known that cause NRTI drug resistance: Interference with the incorporation of NRTIs and excision of incorporated NRTIs. Interference with the incorporated NRTIs involves a mutation in the p66 subdomain of the RT. The mutation causes a steric hindrance that can exclude certain drugs, for example lamivudine, from being incorporated during reverse transcription. In case of excision of incorporated NRTIs the resistant enzymes readily accept the inhibitor as a substrate for incorporation into the DNA chain. Subsequently, the RT enzyme can remove the incorporated NRTI by reversing the polymerization step. The excision reaction requires a pyrophosphate donor which RT joins to the NRTI at the 3´primer terminus, excising it from the primer DNA.
To achieve efficient inhibition of HIV-1 replication in patients, and to delay or prevent appearance of drug resistant viruses, drug combinations are used. HAART, also known as highly active antiretroviral therapy consists of combinations of antiviral drugs which include NRTIs, NtRTI, non-nucleoside reverse-transcriptase inhibitors and protease inhibitors. | 1 | Applied and Interdisciplinary Chemistry |
From 1955 until 1977, the Sangamo Weston plant in Pickens, South Carolina, used PCBs to manufacture capacitors, and dumped 400,000 pounds of PCB contaminated wastewater into the Twelve Mile Creek. In 1990, the EPA declared the site of the capacitor plant, its landfills and the polluted watershed, which stretches nearly downstream to Lake Hartwell as a Superfund site. Two dams on the Twelve Mile Creek are to be removed and on Feb. 22, 2011 the first of two dams began to be dismantled. Some contaminated sediment is being removed from the site and hauled away, while other sediment is pumped into a series of settling ponds.
In 2013, the state environmental regulators issued a rare emergency order, banning all sewage sludge from being land applied or deposited on landfills, as it contained very high levels of PCBs. The problem had not been discovered until thousands of acres of farm land in the state had been contaminated by the hazardous sludge. A criminal investigation to determine the perpetrator of this crime was launched. | 1 | Applied and Interdisciplinary Chemistry |
Here, the aglycone is a simple phenolic structure. An example is arbutin found in the Common Bearberry Arctostaphylos uva-ursi. It has a urinary antiseptic effect. | 0 | Theoretical and Fundamental Chemistry |
There have been attempts to treat cancer using gene therapy. As of 2017, 65% of gene therapy trials were for cancer treatment.
Adenovirus vectors are useful for some cancer gene therapies because adenovirus can transiently insert genetic material into a cell without permanently altering the cell's nuclear genome. These vectors can be used to cause antigens to be added to cancers causing an immune response, or hinder angiogenesis by expressing certain proteins. An Adenovirus vector is used in the commercial products Gendicine and Oncorine. Another commercial product, Rexin G, uses a retrovirus-based vector and selectively binds to receptors that are more expressed in tumors.
One approach, suicide gene therapy, works by introducing genes encoding enzymes that will cause a cancer cell to die. Another approach is the use oncolytic viruses, such as Oncorine, which are viruses that selectively reproduce in cancerous cells leaving other cells unaffected.
mRNA has been suggested as a non-viral vector for cancer gene therapy that would temporarily change a cancerous cell's function to create antigens or kill the cancerous cells and there have been several trials. | 1 | Applied and Interdisciplinary Chemistry |
Non-metallic inclusions arise because of many physical-chemical effects that occur in molten and consolidated metal during production.
Non-metallic inclusions that arise because of different reactions during metal production are called natural or indigenous. They include oxides, sulfides, nitrides and phosphides.
Apart from natural inclusions there are also parts of slag, refractories, material of a casting mould (the material the metal contacts during production) in the metal. Such non-metallic inclusions are called foreign, accidental or exogenous.
Most inclusions in the reduction smelting of metal formed because of admixture dissolubility decreasing during cooling and consolidation.
The present-day level of steel production technology allows the elimination of most natural and foreign inclusions from the metal. However its general content in different steels can vary between wide limits and has a big influence on the metal properties. | 1 | Applied and Interdisciplinary Chemistry |
One of the important capabilities of using FTIR photoacoustic spectroscopy has been the ability to evaluate samples in their in situ state by infrared spectroscopy, which can be used to detect and quantify chemical functional groups and thus chemical substances. This is particularly useful for biological samples that can be evaluated without crushing to powder or subjecting to chemical treatments. Seashells, bone and such samples have been investigated. Using photoacoustic spectroscopy has helped evaluate molecular interactions in bone with osteogenesis imperfecta.
While most academic research has concentrated on high resolution instruments, some work has gone in the opposite direction. In the last twenty years, very low cost instruments for applications such as leakage detection and for the control of carbon dioxide concentration have been developed and commercialized. Typically, low cost thermal sources are used which are modulated electronically. Diffusion through semi-permeable disks instead of valves for gas exchange, low-cost microphones, and proprietary signal processing with digital signal processors have brought down the costs of these systems. The future of low-cost applications of photoacoustic spectroscopy may be the realization of fully integrated micromachined photoacoustic instruments.
The photoacoustic approach has been utilized to quantitatively measure macromolecules, such as proteins. The photoacoustic immunoassay labels and detects target proteins using nanoparticles that can generate strong acoustic signals. The photoacoustics-based protein analysis has also been applied for point-of-care testings.
Photoacoustic spectroscopy also has many military applications. One such application is the detection toxic chemical agents. The sensitivity of photoacoustic spectroscopy makes it an ideal analysis technique for detecting trace chemicals associated with chemical attacks.
LPAS sensors may be applied in industry, security (nerve agent and explosives detection), and medicine (breath analysis). | 0 | Theoretical and Fundamental Chemistry |
Cascade process is any process that takes place in a number of steps, usually because the single step is too inefficient to produce the desired result. For example, in some uranium-enrichment processes the separation of the desired isotope is only poorly achieved in a single stage; to achieve better separation the process has to be repeated a number of times, in a series, with the enriched fraction of one stage being fed to the succeeding stage for further enrichment. Another example of cascade process is that operating in a cascade liquefier. | 1 | Applied and Interdisciplinary Chemistry |
The last decade has seen a proliferation of information technology use in the planning and conduct of clinical trials. Clinical trial management systems are often used by research sponsors or CROs to help plan and manage the operational aspects of a clinical trial, particularly with respect to investigational sites. Advanced analytics for identifying researchers and research sites with expertise in a given area utilize public and private information about ongoing research. Web-based electronic data capture (EDC) and clinical data management systems are used in a majority of clinical trials to collect case report data from sites, manage its quality and prepare it for analysis. Interactive voice response systems are used by sites to register the enrollment of patients using a phone and to allocate patients to a particular treatment arm (although phones are being increasingly replaced with web-based (IWRS) tools which are sometimes part of the EDC system). While patient-reported outcome were often paper based in the past, measurements are increasingly being collected using web portals or hand-held ePRO (or ) devices, sometimes wireless. Statistical software is used to analyze the collected data and prepare them for regulatory submission. Access to many of these applications are increasingly aggregated in web-based clinical trial portals. In 2011, the FDA approved a PhaseI trial that used telemonitoring, also known as remote patient monitoring, to collect biometric data in patients' homes and transmit it electronically to the trial database. This technology provides many more data points and is far more convenient for patients, because they have fewer visits to trial sites. | 1 | Applied and Interdisciplinary Chemistry |
Because uranium minerals emit radon gas, and their harmful and highly radioactive decay products, uranium mining is considerably more dangerous than other (already dangerous) hard rock mining, requiring adequate ventilation systems if the mines are not open pit. In the 1950s, a significant number of American uranium miners were Navajo, as many uranium deposits were discovered on Navajo reservations. A statistically significant subset of these miners later developed small-cell lung cancer, a type of cancer usually not associated with smoking, after exposure to uranium ore and radon-222, a natural decay product of uranium. The radon, which is produced by the uranium, and not the uranium itself has been shown to be the cancer causing agent. Some survivors and their descendants received compensation under the Radiation Exposure Compensation Act in 1990.
Currently the level of radon in the air of mines is normally controlled by law. In a working mine, the radon level can be controlled by ventilation, sealing off old workings and controlling the water in the mine. The level in a mine can go up when a mine is abandoned, it can reach a level which is able to cause the skin to become red (a mild radiation burn). The radon levels in some of the mines can reach 400 to 700 kBq m.
A common unit of exposure of lung tissue to alpha emitters is the working level month (WLM), this is where the human lungs have been exposed for 170 hours (a typical month worth of work for a miner) to air which has 3.7 kBq of Rn (in equilibrium with its decay products). This is air which has the alpha dose rate of 1 working level (WL). It is estimated that the average person (general public) is subject to 0.2 WLM per year, which works out at about 15 to 20 WLM in a lifetime. According to the NRC 1 WLM is a 5 to 10 mSv lung dose (0.5 to 1.0 rem), while the Organisation for Economic Co-operation and Development (OECD) consider that 1 WLM is equal to a lung dose of 5.5 mSv, the International Commission on Radiological Protection (ICRP) consider 1 WLM to be a 5 mSv lung dose for professional workers (and 4 mSv lung dose for the general public). Lastly the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) consider that the exposure of the lungs to 1 Bq of Rn (in equilibrium with its decay products) for one year will cause a dose of 61 μSv. | 0 | Theoretical and Fundamental Chemistry |
A natural neuroactive substance (NAS) is a chemical synthesized by neurons that affects the actions of other neurons or muscle cells. Natural neuroactive substances include neurotransmitters, neurohormones, and neuromodulators. Neurotransmitters work only between adjacent neurons through synapses. Neurohormones are released into the blood and work at a distance. Some natural neuroactive substances act as both transmitters and as hormones. | 1 | Applied and Interdisciplinary Chemistry |
In fresh water, sound travels at about at (see the External Links section below for online calculators). Applications of underwater sound can be found in sonar, acoustic communication and acoustical oceanography. | 1 | Applied and Interdisciplinary Chemistry |
Herbicide volatilisation refers to evaporation or sublimation of a volatile herbicide. The effect of gaseous chemical is lost at its intended place of application and may move downwind and affect other plants not intended to be affected causing crop damage. Herbicides vary in their susceptibility to volatilisation. Prompt incorporation of the herbicide into the soil may reduce or prevent volatilisation. Wind, temperature, and humidity also affect the rate of volatilisation with humidity reducing in. 2,4-D and dicamba are commonly used chemicals that are known to be subject to volatilisation but there are many others. Application of herbicides later in the season to protect herbicide-resistant genetically modified plants increases the risk of volatilisation as the temperature is higher and incorporation into the soil impractical. | 1 | Applied and Interdisciplinary Chemistry |
Dry agglomeration is agglomeration performed without water or binding liquids, instead using compression only. | 1 | Applied and Interdisciplinary Chemistry |
Directional freezing freezes from only one direction.
Directional freezing can freeze water, from only one direction or side of a container, into clear ice.
Directional freezing in a domestic freezer can be done by putting water in a insulated container so that the water freezes from the top down, and removing before fully frozen, so that the minerals in the water are not frozen.
F Hoffmann La Roche AG, Roche Diagnostics GmbH has a 2017 directional freezing patent for drying solid material. | 0 | Theoretical and Fundamental Chemistry |
The same sensor film can also be used as an actuator. Changes in thickness can be induced by applying a voltage on the film; compression and expansion of the film depends on the polarity of the voltage, and it occurs when both the outer surfaces of the film either attract or repel from each other. The attractive force between the surfaces while the film is uncharged is given by the equation:
x</big>
where C is the capacitance of the film and x is the film's thickness. | 1 | Applied and Interdisciplinary Chemistry |
Heavy crude oils have lower API gravity figures, and a larger percentage of impurities. It is used in the making of heavier outputs - e.g., asphalt - and has a higher viscosity, making it more difficult to transport and extract. | 0 | Theoretical and Fundamental Chemistry |
This pathway does not produce any ATP, this pathway does not replace glycolysis, it runs simultaneously to glycolysis and is only initiated with an increased concentration of sugar phosphates. One believed purpose of the methylglyoxal pathway is to help release the stress of elevated sugar phosphate concentration. Also when methylglyoxal is formed from DHAP, an inorganic phosphate is given off which can be used to replenish a low concentration of needed inorganic phosphate. The methylglyoxal pathway is a rather dangerous tactic, both because less energy is produced and a toxic compound, methylglyoxal is formed. ([http://mic.sgmjournals.org/cgi/reprint/151/3/707 Weber] 715). | 1 | Applied and Interdisciplinary Chemistry |
[F]FDG was first synthesized via electrophilic fluorination with [F]F. Subsequently, a "nucleophilic synthesis" was devised with the same radioisotope.
As with all radioactive F-labeled radioligands, the fluorine-18 must be made initially as the fluoride anion in a cyclotron. Synthesis of complete [F]FDG radioactive tracer begins with synthesis of the unattached fluoride radiotracer, since cyclotron bombardment destroys organic molecules of the type usually used for ligands, and in particular, would destroy glucose.
Cyclotron production of fluorine-18 may be accomplished by bombardment of neon-20 with deuterons, but usually is done by proton bombardment of O-enriched water, causing a (p-n) reaction (sometimes called a "knockout reaction"a common type of nuclear reaction with high probability where an incoming proton "knocks out" a neutron) in the O. This produces "carrier-free" dissolved [F]fluoride ([F]F) ions in the water. The 109.8-minute half-life of fluorine-18 makes rapid and automated chemistry necessary after this point.
Anhydrous fluoride salts, which are easier to handle than fluorine gas, can be produced in a cyclotron. To achieve this chemistry, the [F]F is separated from the aqueous solvent by trapping it on an ion-exchange column, and eluted with an acetonitrile solution of 2,2,2-cryptand and potassium carbonate. Evaporation of the eluate gives [(crypt-222)K] [F]F (2) .
The fluoride anion is nucleophilic but its anhydrous conditions are required to avoid competing reactions involving hydroxide, which is also a good nucleophile. The use of the cryptand to sequester the potassium ions avoids ion-pairing between free potassium and fluoride ions, rendering the fluoride anion more reactive.
Intermediate 2 is treated with the protected mannose triflate (1); the fluoride anion displaces the triflate leaving group in an S2 reaction, giving the protected fluorinated deoxyglucose (3). Base hydrolysis removes the acetyl protecting groups, giving the desired product (4) after removing the cryptand via ion-exchange: | 1 | Applied and Interdisciplinary Chemistry |
The sensing of bacterial signals is performed by peptidoglycan recognition protein LC (PGRP-LC), a transmembrane protein with an intracellular domain. Binding of bacterial peptidoglycan leads to dimerization of PGRP-LC which generates the conformation needed to bind and activate the Imd protein. However alternate isoforms of PGRP-LC can also be expressed with different functions: PGRP-LCx recognizes polymeric peptidoglycan, while PGRP-LCa does not bind peptidoglycan directly but acts alongside PGRP-LCx to bind monomeric peptidoglycan fragments (called tracheal cytotoxin or "TCT"). Another PGRP (PGRP-LE) also acts intracellularly to bind TCT that has crossed the cell membrane or is derived from an intracellular infection. PGRP-LA promotes the activation of Imd signalling in epithelial cells, but the mechanism is still unknown.
Other PGRPs can inhibit the activation of Imd signalling by binding bacterial signals or inhibiting host signalling proteins: PGRP-LF is a transmembrane PGRP that lacks an intracellular domain and does not bind peptidoglycan. Instead PGRP-LF forms dimers with PGRP-LC preventing PGRP-LC dimerization and consequently activation of Imd signalling. A number of secreted PGRPs have amidase activity that downregulate the Imd pathway by digesting peptidoglycan into short, non-immunogenic fragments. These include PGRP-LB, PGRP-SC1A, PGRP-SC1B, and PGRP-SC2. Additionally, PGRP-LB is the major regulator in the gut. | 1 | Applied and Interdisciplinary Chemistry |
An exergonic process is one which there is a positive flow of energy from the system to the surroundings. This is in contrast with an endergonic process. Constant pressure, constant temperature reactions are exergonic if and only if the Gibbs free energy change is negative (∆G < 0). "Exergonic" (from the prefix exo-, derived for the Greek word ἔξω exō, "outside" and the suffix -ergonic, derived from the Greek word ἔργον ergon, "work") means "releasing energy in the form of work". In thermodynamics, work is defined as the energy moving from the system (the internal region) to the surroundings (the external region) during a given process.
All physical and chemical systems in the universe follow the second law of thermodynamics and proceed in a downhill, i.e., exergonic, direction. Thus, left to itself, any physical or chemical system will proceed, according to the second law of thermodynamics, in a direction that tends to lower the free energy of the system, and thus to expend energy in the form of work. These reactions occur spontaneously.
A chemical reaction is also exergonic when spontaneous. Thus in this type of reactions the Gibbs free energy decreases. The entropy is included in any change of the Gibbs free energy. This differs from an exothermic reaction or an endothermic reaction where the entropy is not included. The Gibbs free energy is calculated with the Gibbs–Helmholtz equation:
where:
: T = temperature in kelvins (K)
: ΔG = change in the Gibbs free energy
: ΔS = change in entropy (at 298 K) as ΔS = ΣS(Product) − ΣS(Reagent)
: ΔH = change in enthalpy (at 298 K) as ΔH = ΣH(Product) − ΣH(Reagent)
A chemical reaction progresses spontaneously only when the Gibbs free energy decreases, in that case the ΔG is negative. In exergonic reactions the ΔG is negative and in endergonic reactions the ΔG is positive:
: exergon
: endergon
where:
: equals the change in the Gibbs free energy after completion of a chemical reaction. | 0 | Theoretical and Fundamental Chemistry |
For turbidity measurement, a formazine suspension is prepared by mixing solutions of 10 g/L hydrazine sulfate and 100 g/L hexamethylenetetramine with ultrapure water. The resulting solution is left for 24 hours, at 25 °C ±3 °C, for the suspension to develop. This produces a suspension with a turbidity value of 4000 NTU/FAU/FTU/FNU. This is then diluted to a value to suit the instrument range. There is no straightforward relationship between FTU/FAU and NTU/FNU because it depends on the optical characteristics of the particular matter in the sample. A general difficulty encountered for preparing formazine standards is to obtain sufficiently reproducible and accurate results. The preparation temperature is essential because it affects the size of the formazine particles. Uncertainties related to temperature fluctuations are of the order of 1.2% per °C.
The purity of the water used in the preparation of the formazine dispersion is also important as it cannot initially contain colloidal particles. Experience shows that water filtered as required has a residual scatter of about 0.02 FTU = 20 mFTU (inherent brightening effect). This has to be taken into account during calibration and for the detection of very low turbidity levels. The commercially available aqueous dispersions of formazine standard are often traceable according to the EN ISO 7027 norm. The shelf life of formazine dispersions does not exceed a few months (a few weeks if the bottle has been opened) as their characteristics evolve with time due to the ageing of the colloidal particles (Ostwald ripening: change in their size distribution and in their number due to their coalescence/aggregation) and the possible development of micro-organisms such bacteria, microscopic fungi, and yeast. | 0 | Theoretical and Fundamental Chemistry |
The nucleus was discovered in 1911, as a result of Ernest Rutherfords efforts to test Thomsons "plum pudding model" of the atom. The electron had already been discovered by J. J. Thomson. Knowing that atoms are electrically neutral, J. J. Thomson postulated that there must be a positive charge as well. In his plum pudding model, Thomson suggested that an atom consisted of negative electrons randomly scattered within a sphere of positive charge. Ernest Rutherford later devised an experiment with his research partner Hans Geiger and with help of Ernest Marsden, that involved the deflection of alpha particles (helium nuclei) directed at a thin sheet of metal foil. He reasoned that if J. J. Thomson's model were correct, the positively charged alpha particles would easily pass through the foil with very little deviation in their paths, as the foil should act as electrically neutral if the negative and positive charges are so intimately mixed as to make it appear neutral. To his surprise, many of the particles were deflected at very large angles. Because the mass of an alpha particle is about 8000 times that of an electron, it became apparent that a very strong force must be present if it could deflect the massive and fast moving alpha particles. He realized that the plum pudding model could not be accurate and that the deflections of the alpha particles could only be explained if the positive and negative charges were separated from each other and that the mass of the atom was a concentrated point of positive charge. This justified the idea of a nuclear atom with a dense center of positive charge and mass. | 0 | Theoretical and Fundamental Chemistry |
In geometry, a sphere packing is an arrangement of non-overlapping spheres within a containing space. The spheres considered are usually all of identical size, and the space is usually three-dimensional Euclidean space. However, sphere packing problems can be generalised to consider unequal spheres, spaces of other dimensions (where the problem becomes circle packing in two dimensions, or hypersphere packing in higher dimensions) or to non-Euclidean spaces such as hyperbolic space.
A typical sphere packing problem is to find an arrangement in which the spheres fill as much of the space as possible. The proportion of space filled by the spheres is called the packing density of the arrangement. As the local density of a packing in an infinite space can vary depending on the volume over which it is measured, the problem is usually to maximise the average or asymptotic density, measured over a large enough volume.
For equal spheres in three dimensions, the densest packing uses approximately 74% of the volume. A random packing of equal spheres generally has a density around 63.5%. | 0 | Theoretical and Fundamental Chemistry |
Although perhaps less efficient than desulfurization, SCR, and electrostatic precipitation, wet scrubbers can remove both gases and particulates. | 1 | Applied and Interdisciplinary Chemistry |
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