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Early examples of different solutions to alleviate rotating stall in the front stages include the Rolls-Royce Avon with variable inlet guide vanes and interstage bleed, the General Electric J79 with variable inlet guide vanes and variable stators, the Bristol Olympus with split compressor and the Pratt & Whitney J57 with split compressor and intercompressor bleed. Compressor bleed up to this point had been only necessary for starting and accelerating beyond low corrected speeds where its loss to thrust production, from dumping overboard, was not important.
A further development was permanent compressor bleed routed back into the engine where it contributed to thrust. The Rolls-Royce Conway had a split compressor with intercompressor bleed to the jetpipe. A split compressor with this bypass arrangement allowed the highest pressure ratio of any Rolls-Royce engine, at that time, without the need for variable inlet guide vanes or interstage bleed. It was better known as an arrangement for better propulsive efficiency, a bypass engine. The Pratt & Whitney J58 used interstage overboard bleed for starting and accelerating through low corrected speeds but since it returned to these speeds at high mach numbers the bleed was opened again but this time routed to the jetpipe where it cooled the afterburner and nozzle. This cooling contributed indirectly to thrust in allowing more fuel to be burned in the afterburner. A similar arrangement, but using a split compressor with intercompressor bleed to the jetpipe, was later known as a leaky turbojet, a bypass engine with only enough bypass for cooling the afterburner and nozzle. | 7 | Physical Chemistry |
Since TPD observes the mass of desorbed molecules, it shows what molecules are adsorbed on the surface. Moreover, TPD recognizes the different adsorption conditions of the same molecule from the differences between the desorption temperatures of molecules desorbing different sites at the surface, e.g. terraces vs. steps. TPD also obtains the amounts of adsorbed molecules on the surface from the intensity of the peaks of the TPD spectrum, and the total amount of adsorbed species is shown by the integral of the spectrum.
To measure TPD, one needs a mass spectrometer, such as a quadrupole mass spectrometer or a time-of-flight (TOF) mass spectrometer, under ultrahigh vacuum (UHV) conditions. The amount of adsorbed molecules is measured by increasing the temperature at a heating rate of typically 2 K/s to 10 K/s. Several masses may be simultaneously measured by the mass spectrometer, and the intensity of each mass as a function of temperature is obtained as a TDS spectrum.
The heating procedure is often controlled by the PID control algorithm, with the controller being either a computer or specialised equipment such as a Eurotherm.
Other methods of measuring desorption are Thermal Gravimetric Analysis (TGA) or using infrared detectors, thermal conductivity detectors etc. | 7 | Physical Chemistry |
12-Crown-4, also called 1,4,7,10-tetraoxacyclododecane and lithium ionophore V, is a crown ether with the formula CHO. It is a cyclic tetramer of ethylene oxide which is specific for the lithium cation. | 6 | Supramolecular Chemistry |
Its principal utility is that it provides simple predictions of phase equilibrium based on a single parameter that is readily obtained for most materials. These predictions are often useful for nonpolar and slightly polar (dipole moment < 2 debyes) systems without hydrogen bonding. It has found particular use in predicting solubility and swelling of polymers by solvents. More complicated three-dimensional solubility parameters, such as Hansen solubility parameters, have been proposed for polar molecules.
The principal limitation of the solubility parameter approach is that it applies only to associated solutions ("like dissolves like" or, technically speaking, positive deviations from Raoults law): it cannot account for negative deviations from Raoults law that result from effects such as solvation or the formation of electron donor–acceptor complexes. Like any simple predictive theory, it can inspire overconfidence: it is best used for screening with data used to verify the predictions. | 7 | Physical Chemistry |
Although an attenuation mechanism that involves translation while transcription is ongoing, like to the mechanism for the trp operon (and some other amino acid biosynthetic operons), would not work in eukaryotes, there is evidence for attenuation in Eukaryotes. Research conducted on microRNA processing provides evidence of eukaryotic attenuation; after co-transcriptional endonucleolitical cleavage by Drosha 5->3 exonuclease XRN2 may terminate further transcription by torpedo mechanism. | 1 | Biochemistry |
The known cases up to 2015 are discussed in a review article by Bučar, Lancaster, and Bernstein.
Dibenzoxazepines
Multidisciplinary studies involving experimental and computational approaches were applied to pharmaceutical molecules to facilitate the comparison of their solid-state structures. Specifically, this study has focused on exploring how changes in molecular structure affect the molecular conformation, packing motifs, interactions in the resultant crystal lattices and the extent of solid-state diversity of these compounds. The results highlight the value of crystal structure prediction studies and PIXEL calculations in the interpretation of the observed solid-state behaviour and quantifying the intermolecular interactions in the packed structures and identifying the key stabilising interactions. An experimental screen yielded 4 physical forms for clozapine as compared to 60 distinct physical forms for olanzapine. The experimental screening results of clozapine are consistent with its crystal energy landscape which confirms that no alternate packing arrangement is thermodynamically competitive to the experimentally obtained structure. Whilst in case of olanzapine, crystal energy landscape highlights that the extensive experimental screening has probably not found all possible polymorphs of olanzapine, and further solid form diversity could be targeted with a better understanding of the role of kinetics in its crystallisation. CSP studies were able to offer an explanation for the absence of the centrosymmetric dimer in anhydrous clozapine. PIXEL calculations on all the crystal structures of clozapine revealed that similar to olanzapine, the intermolecular interaction energy in each structure is also dominated by the Ed. Despite the molecular structure similarity between amoxapine and loxapine (molecules in group 2), the crystal packing observed in polymorphs of loxa differs significantly from the amoxapine. A combined experimental and computational study demonstrated that the methyl group in loxapine has a significant influence in increasing the range of accessible solid forms and favouring various alternate packing arrangements. CSP studies have again helped in explaining the observed solid-state diversity of loxapine and amoxapine. PIXEL calculations showed that in absence of strong H-bonds, weak H-bonds such as C–H...O, C–H...N and dispersion interactions play a key role in stabilising the crystal lattice of both the molecules. Efficient crystal packing of amoxapine seems to be contributing towards its monomorphic behaviour as compared to the comparatively less efficient packing of loxapine molecules in both polymorphs. The combination of experimental and computational approaches has provided a deeper understanding of the factors influencing the solid-state structure and diversity in these compounds. Hirshfeld surfaces using Crystal Explorer represent another way of exploring packing modes and intermolecular interactions in molecular crystals. The influence of changes in the small substituents on shape and electron distribution can also be investigated by mapping the total electron density on the electrostatic potential for molecules in the gas phase. This allows straightforward visualisation and comparison of overall shape, electron-rich and electron-deficient regions within molecules. The shape of these molecules can be further investigated to study its influence on diverse solid-state diversity.
Posaconazole
The original formulations of posaconazole on the market licensed as Noxafil were formulated utilising form I of posaconazole. The discovery of polymorphs of posaconazole increased rapidly and resulted in much research in crystallography of posaconazole. A methanol solvate and a 1,4-dioxane co-crystal were added to the Cambridge Structural Database (CSD). | 3 | Analytical Chemistry |
The nuclear genetic code is flexible as illustrated by variant genetic codes that reassign standard stop codons to amino acids. | 1 | Biochemistry |
The ores used in ancient smelting processes were rarely pure metal compounds. Impurities were removed from the ore through the process of slagging, which involves adding heat and chemicals. Slag is the material in which the impurities from ores (known as gangue), as well as furnace lining and charcoal ash, collect. The study of slag can reveal information about the smelting process used at the time of its formation.
The finding of slag is direct evidence of smelting having occurred in that place as slag was not removed from the smelting site. Through slag analysis, archaeologists can reconstruct ancient human activities concerned with metal work such as its organization and specialization.
The contemporary knowledge of slagging gives insights into ancient iron production. In a smelting furnace, up to four different phases might co-exist. From the top of the furnace to the bottom, the phases are slag, matte, speiss, and liquid metal.
Slag can be classified as furnace slag, tapping slag or crucible slag depending on the mechanism of production. The slag has three functions. The first is to protect the melt from contamination. The second is to accept unwanted liquid and solid impurities. Finally, slag can help to control the supply of refining media to the melt.
These functions are achieved if the slag has a low melting temperature, low density and high viscosity which ensure a liquid slag that separates well from the melting metal. Slag should also maintain its correct composition so that it can collect more impurities and be immiscible in the melt.
Through chemical and mineralogical analysis of slag, factors such as the identity of the smelted metal, the types of ore used and technical parameters such as working temperature, gas atmosphere and slag viscosity can be learned. | 8 | Metallurgy |
In recent publications, prof. Sindo Kou has proposed an approach to evaluate susceptibility to solidification cracking; this approach is based on a similar approach where a quantity, , which has the dimensions of a temperature is proposed as an index of the cracking susceptibility. Again one could exploit Scheil based solidification curves to link this index to the slope of the (Scheil) solidification curve:
∂T/(∂(fS)^1/2)=
∂T/(∂(fS)*(∂(fS)^1/2)/∂(fS))=
(1/2)∂T/∂(fS)*(fS)^1/2= | 8 | Metallurgy |
In 1837, Draper accepted an appointment to be head of chemistry in a proposed medical school at New York University, but sufficient funds were not available to go ahead with the project. In 1839, Draper was elected undergraduate professor of chemistry and botany at the university, and moved with his family to New York City . Once there he helped to found the New York University Medical School, acting as a professor there from 1840 to 1850, president of the school from 1850 to 1873, and as a professor of chemistry until 1881. | 5 | Photochemistry |
The human endoglin gene is located on human chromosome 9 with location of the cytogenic band at 9q34.11. Endoglin glycoprotein is encoded by 39,757 bp and translates into 658 amino acids.
The expression of the endoglin gene is usually low in resting endothelial cells. This, however, changes once neoangiogenesis begins and endothelial cells become active in places like tumor vessels, inflamed tissues, skin with psoriasis, vascular injury and during embryogenesis. The expression of the vascular system begins at about 4 weeks and continues after that. Other cells in which endoglin is expressed consist of monocytes, especially those transitioning into macrophages, low expression in normal smooth muscle cells, high expression vascular smooth muscle cells and in kidney and liver tissues undergoing fibrosis. | 1 | Biochemistry |
Yusif Haydar oglu Mammadaliyev (; December 31, 1905 – December 15, 1961) was an Azerbaijani and Soviet chemist. He was a Doctor of Chemistry, academician of the National Academy of Sciences of the Azerbaijan SSR, and was the president of the National Academy of Sciences of the Azerbaijan SSR.
According to the statement of the 4th President of Azerbaijan, Ilham Aliyev , he is the inventor of the incendiary mixture that became known as the “Molotov cocktail”. | 0 | Organic Chemistry |
As in Lewis structures, covalent bonds are indicated by line segments, with a doubled or tripled line segment indicating double or triple bonding, respectively. Likewise, skeletal formulae indicate formal charges associated with each atom (although lone pairs are usually optional, see below). In fact, skeletal formulae can be thought of as abbreviated Lewis structures that observe the following simplifications:
*Carbon atoms are represented by the vertices (intersections or termini) of line segments. For clarity, methyl groups are often explicitly written out as Me or CH, while (hetero)cumulene carbons are frequently represented by a heavy center dot.
* Hydrogen atoms attached to carbon are implied. An unlabeled vertex is understood to represent a carbon attached to the number of hydrogens required to satisfy the octet rule, while a vertex labeled with a formal charge and/or nonbonding electron(s) is understood to have the number of hydrogen atoms required to give the carbon atom these indicated properties. Optionally, acetylenic and formyl hydrogens can be shown explicitly for the sake of clarity.
* Hydrogen atoms attached to a heteroatom are shown explicitly. The heteroatom and hydrogen atoms attached thereto are usually shown as a single group (e.g., OH, NH) without explicitly showing the hydrogen–heteroatom bond. Heteroatoms with simple alkyl or aryl substituents, like methoxy (OMe) or dimethylamino (NMe), are sometimes shown in the same way, by analogy.
* Lone pairs on carbene carbons must be indicated explicitly while lone pairs in other cases are optional and are shown only for emphasis. In contrast, formal charges and unpaired electrons on main-group elements are always explicitly shown.
In the standard depiction of a molecule, the canonical form (resonance structure) with the greatest contribution is drawn. However, the skeletal formula is understood to represent the "real molecule" that is, the weighted average of all contributing canonical forms. Thus, in cases where two or more canonical forms contribute with equal weight (e.g., in benzene, or a carboxylate anion) and one of the canonical forms is selected arbitrarily, the skeletal formula is understood to depict the true structure, containing equivalent bonds of fractional order, even though the delocalized bonds are depicted as nonequivalent single and double bonds. | 0 | Organic Chemistry |
Isocyanides have diverse reactivity.
Isocyanides are stable to strong base (they are often made under strongly basic conditions), but they are sensitive to acid. In the presence of aqueous acid, isocyanides hydrolyse to the corresponding formamides:
This reaction is used to destroy odorous isocyanide mixtures. Some isocyanides can polymerize in the presence of Lewis and Bronsted acids.
Isocyanides participate in many multicomponent reactions of interest in organic synthesis, two of which are: the Ugi reaction and the Passerini reaction.
Isocyanides also participate in cycloaddition reactions, such as the [4+1] cycloaddition with tetrazines. Depending on the degree of substitution of the isocyanide, this reaction converts isocyanides into carbonyls or gives stable cycloadducts. They also undergo insertion into the C–Cl bonds of acyl chlorides in the Nef isocyanide reaction, a process that is believed to be concerted and illustrates their carbene character.
Isocyanides have also been shown to be a useful reagent in palladium catalysed reactions with a wide variety of compounds being formed using this method.
The α position of isocyanides have substantial acidity. For example, benzyl isocyanide has a pK of 27.4. In comparison, benzyl cyanide has a pK of 21.9. In the gas phase, is 1.8 kcal/mol less acidic than .
Chlorination of isocyanides gives isocyanide dichlorides. | 0 | Organic Chemistry |
In natural optical activity, the difference between the LCP light and the RCP light is caused by the asymmetry of the molecules (i.e. chiral molecules). Because of the handedness of the molecule, the absorption of the LCP light would be different from the RCP light. However, in MCD in the presence of a magnetic field, LCP and RCP no longer interact equivalently with the absorbing medium. Thus, there is not the same direct relation between magnetic optical activity and molecular stereochemistry which would be expected, because it is found in natural optical activity. So, natural CD is much more rare than MCD which does not strictly require the target molecule to be chiral.
Although there is much overlap in the requirements and use of instruments, ordinary CD instruments are usually optimized for operation in the ultraviolet, approximately 170–300 nm, while MCD instruments are typically required to operate in the visible to near infrared, approximately 300–2000 nm. The physical processes that lead to MCD are substantively different from those of CD. However, like CD, it is dependent on the differential absorption of left and right hand circularly polarized light. MCD will only exist at a given wavelength if the studied sample has an optical absorption at that wavelength. This is distinctly different from the related phenomenon of optical rotatory dispersion (ORD), which can be observed at wavelengths far from any absorption band. | 7 | Physical Chemistry |
In general, cis–trans stereoisomers contain double bonds or ring structures. In both cases the rotation of bonds is restricted or prevented. When the substituent groups are oriented in the same direction, the diastereomer is referred to as cis, whereas when the substituents are oriented in opposing directions, the diastereomer is referred to as trans. An example of a small hydrocarbon displaying cis–trans isomerism is but-2-ene. 1,2-Dichlorocyclohexane is another example. | 4 | Stereochemistry |
SBTi developed separate sector-specific methodologies, frameworks and requirements for different industries. As of December 2021, guidance is available for:
* Aviation
* Apparel and footwear
* Financial institutions
* Information and Communication Technology | 2 | Environmental Chemistry |
Solvation significantly affects the basicity of amines. N-H groups strongly interact with water, especially in ammonium ions. Consequently, the basicity of ammonia is enhanced by 10 by solvation. The intrinsic basicity of amines, i.e. the situation where solvation is unimportant, has been evaluated in the gas phase. In the gas phase, amines exhibit the basicities predicted from the electron-releasing effects of the organic substituents. Thus tertiary amines are more basic than secondary amines, which are more basic than primary amines, and finally ammonia is least basic. The order of pK's (basicities in water) does not follow this order. Similarly aniline is more basic than ammonia in the gas phase, but ten thousand times less so in aqueous solution.
In aprotic polar solvents such as DMSO, DMF, and acetonitrile the energy of solvation is not as high as in protic polar solvents like water and methanol. For this reason, the basicity of amines in these aprotic solvents is almost solely governed by the electronic effects. | 0 | Organic Chemistry |
For a targeted treatment, the visibility and accessibility of the transition in the welded areas are required.
Existing structures typically are prepared at the transition for surface finishing. The parts must be free of loose rust and old paint. If necessary, previous sandblasting is required.
The device operates with a compressed air supply of 6–8 bar. | 8 | Metallurgy |
Laboratories have developed grading methods to judge oocyte and embryo quality. In order to optimise pregnancy rates, there is significant evidence that a morphological scoring system is the best strategy for the selection of embryos. Since 2009 where the first time-lapse microscopy system for IVF was approved for clinical use, morphokinetic scoring systems has shown to improve to pregnancy rates further. However, when all different types of time-lapse embryo imaging devices, with or without morphokinetic scoring systems, are compared against conventional embryo assessment for IVF, there is insufficient evidence of a difference in live-birth, pregnancy, stillbirth or miscarriage to choose between them. A small prospectively randomized study in 2016 reported poorer embryo quality and more staff time in an automated time-lapse embryo imaging device compared to conventional embryology. Active efforts to develop a more accurate embryo selection analysis based on Artificial Intelligence and Deep Learning are underway. Embryo Ranking Intelligent Classification Algorithm (ERICA), is a clear example. This Deep Learning software substitutes manual classifications with a ranking system based on an individual embryo's predicted genetic status in a non-invasive fashion. Studies on this area are still pending and current feasibility studies support its potential. | 1 | Biochemistry |
Homogeneous broadening is a type of emission spectrum broadening in which all atoms radiating from a specific level under consideration radiate with equal opportunity. If an optical emitter (e.g. an atom) shows homogeneous broadening, its spectral linewidth is its natural linewidth, with a Lorentzian profile. | 7 | Physical Chemistry |
In superalloys strengthened by metal carbides, increasingly large carbide particles form preferentially at grain boundaries, preventing grain boundary sliding at high temperatures. This leads to an increase in the yield strength, and thus a yield strength anomaly. | 8 | Metallurgy |
The Boltzmann constant k (alternatively k) may be used in place of the molar gas constant by working in pure particle count, N, rather than amount of substance, n, since:
where N is the Avogadro constant.
For example, the ideal gas law in terms of the Boltzmann constant is:
where N is the number of particles (molecules in this case), or to generalize to an inhomogeneous system the local form holds:
where ρ = N/V is the number density. | 7 | Physical Chemistry |
Many model organism, such as plants (Arabidopsis thaliana), yeast (Saccharomyces cerevisiae ), flies (Drosophila melanogaster) and worms (C. elegans), have been used to study small non coding RNA-directed Transcriptional gene silencing. In human cell, RNA-directed transcriptional gene silencing was observed a decade ago when exogenous siRNAs silenced a transgenic elongation factor 1 α promoter driving a Green Fluorescent Protein (GFP) reporter gene.
The main mechanisms of transcriptional gene silencing (TGS) involving the RNAi machinery include DNA methylation, histone post-translational modifications, and subsequent chromatin remodeling around the target gene into a heterochromatic state.
SiRNAs can be incorporated into a RNA-induced transcriptional silencing (RITS) complex. An active RITS complex will trigger the formation of heterochromatin around DNA matching the siRNA, effectively silencing the genes in that region of the DNA. | 1 | Biochemistry |
Pyruvate kinase type M2 or PKM2 is present in embryonic, adult stem cells. It is also expressed by many tumor cells. The alterations to metabolism by PKM2 increases ATP resources, stimulates macromolecular biosynthesis and redox control. Pyruvate kinase catalyses the ATP-generating step of glycolysis in which phosphoenolpyruvate (PEP) is converted to pyruvate. This is a rate-limiting step. It decreases the glycolysis activity and allows carbohydrate metabolites to enter other pathways, like hexosamine pathway, Uridine diphosphate glucose–glucose synthesis, glycerol synthesis and Pentose phosphate pathway or PPP. It helps in generating macromolecule precursors, that are necessary to support cell proliferation, and reducing equivalents such as NADPH. It has been observed in some studies that MYC promotes expression of PKM2 over PKM1 by modulating exon splicing.
A key molecule produced as a result of the oxidative PPP by PKM2 is NADPH. NADPH functions as a cofactor and provides reducing power in many enzymatic reactions that are crucial for macromolecular biosynthesis. Another mechanism by which NADPH is produced in mammalian cells is the reaction converting isocitrate to α-ketoglutarate (αKG), which is catalysed by NADP-dependent isocitrate dehydrogenase 1 (IDH1) and IDH2 and have been found linked to tumorigenesis in glioblastoma and acute myeloid leukemia. They are also found to interact with arginine residues required for isocitrate binding in the active site of the proteins of IDH1 and IDH2. | 1 | Biochemistry |
Xylene is flammable but of modest acute toxicity, with ranges from 200 to 5000 mg/kg for animals. Oral for rats is 4300 mg/kg. The principal mechanism of detoxification is oxidation to methylbenzoic acid and hydroxylation to hydroxylene.
The main effect of inhaling xylene vapor is depression of the central nervous system (CNS), with symptoms such as headache, dizziness, nausea and vomiting. At an exposure of 100 ppm, one may experience nausea or a headache. At an exposure between 200 and 500 ppm, symptoms can include feeling "high", dizziness, weakness, irritability, vomiting, and slowed reaction time.
The side effects of exposure to low concentrations of xylene () are reversible and do not cause permanent damage. Long-term exposure may lead to headaches, irritability, depression, insomnia, agitation, extreme tiredness, tremors, hearing loss, impaired concentration and short-term memory loss. A condition called chronic solvent-induced encephalopathy, commonly known as "organic-solvent syndrome" has been associated with xylene exposure. There is very little information available that isolates xylene from other solvent exposures in the examination of these effects.
Hearing disorders have been also linked to xylene exposure, both from studies with experimental animals, as well as clinical studies.
Xylene is also a skin irritant and strips the skin of its oils, making it more permeable to other chemicals. The use of impervious gloves and masks, along with respirators where appropriate, is recommended to avoid occupational health issues from xylene exposure.
Xylenes are metabolized to methylhippuric acids. The presence of methylhippuric acid can be used as a biomarker to determine exposure to xylene. | 2 | Environmental Chemistry |
The types and sizes of bioaerosols vary in marine environments and occur largely because of wet-discharges caused by changes in osmotic pressure or surface tension. Some types of marine originated bioaerosols excrete dry-discharges of fungal spores that are transported by the wind.
One instance of impact on marine species was the 1983 die off of Caribbean sea fans and sea urchins that correlated with dust storms originating in Africa. This correlation was determined by the work of microbiologists and a Total Ozone Mapping Spectrometer, which identified bacteria, viral, and fungal bioaerosols in the dust clouds that were tracked over the Atlantic Ocean. Another instance in of this occurred in 1997 when El Niño possibly impacted seasonal trade wind patterns from Africa to Barbados, resulting in similar die offs. Modeling instances like these can contribute to more accurate predictions of future events. | 7 | Physical Chemistry |
Alclad sheeting has become a widely used material within the aviation industry for the construction of aircraft due to its favourable qualities, such as a high fatigue resistance and its strength. During the first half of the twentieth century, substantial studies were conducted into the corrosion qualities of various lightweight aluminium alloys for aviation purposes. The first aircraft to be constructed from Alclad was the all-metal US Navy airship ZMC-2, which was constructed in 1927 at Naval Air Station Grosse Ile. Prior to this, aluminium had been used on the pioneering zeppelins constructed by Ferdinand Zeppelin.
Alclad has been most commonly present in certain elements of an aircraft, including the fuselage, structural members, skin, and cowls. The aluminium alloy that Alclad is derived from has become one of the most commonly used of all aluminium-based alloys. While unclad aluminium has also continued to be extensively used on modern aircraft, which has a lower weight than Alclad, it is more prone to corrosion; the alternating use of the two materials is often defined by the specific components or elements that are composed of them. In aviation-grade Alclad, the thickness of the outer cladding layer typically varies between 1% and 15% of the total thickness. | 8 | Metallurgy |
* 2014 Outstanding Early Career Award recipient, American Heart Association, BCVS Council
* 2016 Honorary Citizen, Eastern Mani Municipality, Greece
* 2016 Visiting Professorship, UCLA Center for Systems Biomedicine
* 2017 Early Research Investigator Award, Lewis Katz School of Medicine at Temple University
* 2017 Elected Fellow (FAHA), American Heart Association
* 2019 Elected Full Member, Sigma Xi, The Scientific Research Honor Society
* 2022 Visiting Professorship, School of Medicine, Aristotle University of Thessaloniki, Greece
* 2022 Top-Reviewer 2022 for JACC: Basic to Translational Science
* 2023 Honorary Membership at the Biology Society of Cyprus
* 2023 Adjunct Professorship, European University of Cyprus
* 2023 Keynote Speaker, Trinity Translational Medicine Institute, Trinity College Dublin, Ireland
* 2023 Keynote Speaker, Vascular and Heart Research Symposium, The Fralin Biomedical Research Institute, Virginia Tech at Roanoke
* 2024 Elected Fellow of the Graduate College of the University of Cincinnati | 1 | Biochemistry |
The word "nitinol" is derived from its composition and its place of discovery: (Nickel Titanium-Naval Ordnance Laboratory). William J. Buehler along with Frederick E. Wang, discovered its properties during research at the Naval Ordnance Laboratory in 1959. Buehler was attempting to make a better missile nose cone, which could resist fatigue, heat and the force of impact. Having found that a 1:1 alloy of nickel and titanium could do the job, in 1961 he presented a sample at a laboratory management meeting. The sample, folded up like an accordion, was passed around and flexed by the participants. One of them applied heat from his pipe lighter to the sample and, to everyone's surprise, the accordion-shaped strip contracted and took its previous shape.
While the potential applications for nitinol were realized immediately, practical efforts to commercialize the alloy did not take place until a decade later. This delay was largely because of the extraordinary difficulty of melting, processing and machining the alloy. Even these efforts encountered financial challenges that were not readily overcome until the 1980s, when these practical difficulties finally began to be resolved.
The discovery of the shape-memory effect in general dates back to 1932, when Swedish chemist Arne Ölander first observed the property in gold–cadmium alloys. The same effect was observed in Cu-Zn (brass) in the early 1950s. | 8 | Metallurgy |
Benzeneselenol was first reported in 1888 by the reaction of benzene with selenium tetrachloride () in the presence of aluminium trichloride (). | 0 | Organic Chemistry |
When a solution of a substance in one solvent is brought into equilibrium with a second solvent that is immiscible with the first solvent, the dissolved substance may be partitioned between the two solvents. The ratio of concentrations in the two solvents is known as a partition coefficient or distribution coefficient. The partition coefficient is defined as the ratio of the analytical concentrations of the solute in the two phases. By convention the value is reported in logarithmic form.
The partition coefficient is defined at a specified temperature and, if applicable, pH of the aqueous phase. Partition coefficients are very important in pharmacology because they determine the extent to which a substance can pass from the blood (an aqueous solution) through a cell wall which is like an organic solvent. They are usually measured using water and octanol as the two solvents, yielding the so-called octanol-water partition coefficient. Many pharmaceutical compounds are weak acids or weak bases. Such a compound may exist with a different extent of protonation depending on pH and the acid dissociation constant. Because the organic phase has a low dielectric constant the species with no electrical charge will be the most likely one to pass from the aqueous phase to the organic phase. Even at pH 7–7.2, the range of biological pH values, the aqueous phase may support an equilibrium between more than one protonated form. log p is determined from the analytical concentration of the substance in the aqueous phase, that is, the sum of the concentration of the different species in equilibrium.
Solvent extraction is used extensively in separation and purification processes. In its simplest form a reaction is performed in an organic solvent and unwanted by-products are removed by extraction into water at a particular pH.
A metal ion may be extracted from an aqueous phase into an organic phase in which the salt is not soluble, by adding a ligand. The ligand, L, forms a complex with the metal ion, M, [ML] which has a strongly hydrophobic outer surface. If the complex has no electrical charge it will be extracted relatively easily into the organic phase. If the complex is charged, it is extracted as an ion pair. The additional ligand is not always required. For example, uranyl nitrate, UO(NO), is soluble in diethyl ether because the solvent itself acts as a ligand. This property was used in the past for separating uranium from other metals whose salts are not soluble in ether. Currently extraction into kerosene is preferred, using a ligand such as tri-n-butyl phosphate, TBP. In the PUREX process, which is commonly used in nuclear reprocessing, uranium(VI) is extracted from strong nitric acid as the electrically neutral complex [UO(TBP)(NO)]. The strong nitric acid provides a high concentration of nitrate ions which pushes the equilibrium in favour of the weak nitrato complex. Uranium is recovered by back-extraction (stripping) into weak nitric acid. Plutonium(IV) forms a similar complex, [PuO(TBP)(NO)] and the plutonium in this complex can be reduced to separate it from uranium.
Another important application of solvent extraction is in the separation of the lanthanoids. This process also uses TBP and the complexes are extracted into kerosene. Separation is achieved because the stability constant for the formation of the TBP complex increases as the size of the lanthanoid ion decreases.
An instance of ion-pair extraction is in the use of a ligand to enable oxidation by potassium permanganate, KMnO, in an organic solvent. KMnO is not soluble in organic solvents. When a ligand, such as a crown ether is added to an aqueous solution of KMnO, it forms a hydrophobic complex with the potassium cation which allows the uncharged ion pair [KL][MnO] to be extracted into the organic solvent. See also: phase-transfer catalysis.
More complex partitioning problems (i.e. 3 or more phases present) can sometimes be handled with a fugacity capacity approach. | 7 | Physical Chemistry |
Sternhell was born in Lwow, then in Poland but now in western Ukraine. His father was Samson Sternhell, a lawyer. Before the war he attended a Zionist Hebrew language primary school for five years. Having survived the Bergen-Belsen concentration camp, he emigrated to Australia with his parents to join members of the Sternhell family who had left Europe prior to World War II. Arriving in Sydney in February 1947, he enrolled as a boarder at Newington College a few days after the commencement of the first term. Having had no formal education since primary school, and only learnt English recently in Palestine, he spent the next nine months studying for the Leaving Certificate. He sat for his exams and received four A's and a B in English. Following Newington, he attended the University of Sydney and graduated with a BSc (hons) in 1951 and a MSc in 1953. In 1961, he was awarded a PhD and DIC from the University of London. After further study in London, he received a DSc from Imperial College. | 0 | Organic Chemistry |
Numerous reports show a link between age-related diseases, birth defects, and several types of cancer with disruption of certain histone post translational modifications. Studies have identified that N- and C-terminal tails are main targets for acetylation, methylation, ubiquitination and phosphorylation. New evidence is pointing to several modifications within the histone core. Research is turning towards deciphering the role of these histone core modifications at the histone-DNA interface in the chromatin. p300 and cAMP response element-binding protein (CBP) possess histone acetyltransferase activity. p300 and CBP are the most promiscuous histone acetyltransferase enzymes acetylating all four core histones on multiple residues. Lysine 18 and Lysine 27 on H3 were the only histone acetylation sites reduced upon CBP and p300 depletion in mouse embryonic fibroblasts. Also, CBP and p300 knockout mice have an open neural tube defect and therefore die before birth. p300−/− embryos exhibit defective development of the heart. CBP+/− mice display growth retardation, craniofacial abnormalities, hematological malignancies, which are not observed in mice with p300+/−. Mutations of both p300 have been reported in human tumors such as colorectal, gastric, breast, ovarian, lung, and pancreatic carcinomas. Also, activation or localization of two histone acetyltransferases can be oncogenic. | 1 | Biochemistry |
As in most PCR reactions, two primers—one for each end—are used per sequence. To splice two DNA molecules, special primers are used at the ends that are to be joined. For each molecule, the primer at the end to be joined is constructed such that it has a 5' overhang complementary to the end of the other molecule. Following annealing when replication occurs, the DNA is extended by a new sequence that is complementary to the molecule it is to be joined to. Once both DNA molecules are extended in such a manner, they are mixed and a PCR is carried out with only the primers for the far ends. The overlapping complementary sequences introduced will serve as primers and the two sequences will be fused. This method has an advantage over other gene splicing techniques in not requiring restriction sites.
To get higher yields, some primers are used in excess as in asymmetric PCR. | 1 | Biochemistry |
Individual transmembrane adenylyl cyclase isoforms have been linked to numerous physiological functions. Soluble adenylyl cyclase (sAC, AC10) has a critical role in sperm motility. Adenylyl cyclase has been implicated in memory formation, functioning as a coincidence detector. | 1 | Biochemistry |
Perilipin, also known as lipid droplet-associated protein, perilipin 1, or PLIN, is a protein that, in humans, is encoded by the PLIN gene. The perilipins are a family of proteins that associate with the surface of lipid droplets. Phosphorylation of perilipin is essential for the mobilization of fats in adipose tissue. | 1 | Biochemistry |
The resonance condition of any -type Raman process requires that the difference in the two photon energies match the difference in energy between the states at the "legs" of the , here the ground states identified above. In experimental settings, this condition is realized when the detunings of the cycling and repumper frequencies in respect to the and transition frequencies, respectively, are equal.
Unlike most Doppler cooling techniques, light in the gray molasses must be blue-detuned from its resonant transition; the resulting Doppler heating is offset by polarization-gradient cooling. Qualitatively, this is because the choice of means that the AC Stark shifts of the three levels are the same sign at any given position. Selecting the potential energy maxima as the sites of optical pumping to the dark state requires the overall light to be blue-detuned; in doing so, the atoms in the bright state traverse the maximum potential energy difference and thus dissipate the most kinetic energy. A full quantitative explanation of the molasses force with respect to detuning can be found in Hänschs paper. | 7 | Physical Chemistry |
According to the FDA, the stereoisomeric composition of a chiral drug should be known, and its effects should be well-characterized from pharmacologic, toxicologic, and clinical standpoints. In order to profile the different stereoisomers of enantiopure drugs, manufacturers are urged to develop quantitative assays for individual enantiomers in in vivo samples early in the development stage.
Ideally, the main pharmacologic activities of the isomers should be compared in in vitro systems in animals. During instances when toxic findings are present beyond the natural extensions of the pharmacologic effects of the drug, toxicologic evaluation of the individual isomers in question must be completed. | 4 | Stereochemistry |
Domestic combustion pollution is mainly composed of burning fuel including wood, gas, and charcoal in activities of heating, cooking, agriculture, and wildfires. Major domestic pollutants contain 17% of carbon dioxide, 13% of carbon monoxide, 6% of nitrogen monoxide, polycyclic aromatic hydrocarbons, and fine and ultrafine particles.
In the United Kingdom domestic combustion is the largest single source of PM2.5 annually. In some towns and cities in New South Wales wood smoke may be responsible for 60% of fine particle air pollution in the winter. Research conducted about biomass burning in 2015, estimated that 38% of European total particulate pollution emissions are composed of domestic wood burning.
The particulate pollutant is often in microscopic size that enables it to infiltrate into interior space even if windows and doors are closed. The main component of woodsmoke, black carbon significantly appears in the indoor environment compared to other ambient pollutants. If the room is sealed tight enough to prevent woodsmoke transmission, it will also prevent oxygen exchange from indoors to outdoor. The regular dusk mask also can help little with particulate pollutants since they are designed to filter out larger particles. Musk with HEPA filter can filter out microscopic pollutants but cause difficulty of breathing to the population with lung disease.
Living under high concentrations of pollutants can lead to headaches, fatigue, lung disease, asthma, and throat and eye irritation. One of the most common diseases among those living among pollutants is chronic obstructive pulmonary disease (COPD). Exposure to wood and charcoal smoke is significantly associated with COPD diagnoses among those living in developing and developed countries. Exposure to woodsmoke intensifies the respiratory systems and increases the risk of hospital admissions. | 2 | Environmental Chemistry |
Topoisomers or topological isomers are molecules with the same chemical formula and stereochemical bond connectivities but different topologies. Examples of molecules for which there exist topoisomers include DNA, which can form knots, and catenanes. Each topoisomer of a given DNA molecule possesses a different linking number associated with it. DNA topoisomers can be interchanged by enzymes called topoisomerases. Using a topoisomerase along with an intercalator, topoisomers with different linking number may be separated on an agarose gel via gel electrophoresis. | 6 | Supramolecular Chemistry |
Active mTORC1 is positioned on lysosomes. mTOR is inhibited when lysosomal membrane is damaged by various exogenous or endogenous agents, such as invading bacteria, membrane-permeant chemicals yielding osmotically active products (this type of injury can be modeled using membrane-permeant dipeptide precursors that polymerize in lysosomes), amyloid protein aggregates (see above section on Alzheimers disease) and cytoplasmic organic or inorganic inclusions including urate crystals and crystalline silica. The process of mTOR inactivation following lysosomal/endomembrane is mediated by the protein complex termed GALTOR. At the heart of GALTOR is galectin-8, a member of β-galactoside binding superfamily of cytosolic lectins termed galectins, which recognizes lysosomal membrane damage by binding to the exposed glycans on the lumenal side of the delimiting endomembrane. Following membrane damage, galectin-8, which normally associates with mTOR under homeostatic conditions, no longer interacts with mTOR but now instead binds to SLC38A9, RRAGA/RRAGB, and LAMTOR1, inhibiting Ragulators (LAMTOR1-5 complex) guanine nucleotide exchange function-
TOR is a negative regulator of autophagy in general, best studied during response to starvation, which is a metabolic response. During lysosomal damage however, mTOR inhibition activates autophagy response in its quality control function, leading to the process termed lysophagy that removes damaged lysosomes. At this stage another galectin, galectin-3, interacts with TRIM16 to guide selective autophagy of damaged lysosomes. TRIM16 gathers ULK1 and principal components (Beclin 1 and ATG16L1) of other complexes (Beclin 1-VPS34-ATG14 and ATG16L1-ATG5-ATG12) initiating autophagy, many of them being under negative control of mTOR directly such as the ULK1-ATG13 complex, or indirectly, such as components of the class III PI3K (Beclin 1, ATG14 and VPS34) since they depend on activating phosphorylations by ULK1 when it is not inhibited by mTOR. These autophagy-driving components physically and functionally link up with each other integrating all processes necessary for autophagosomal formation: (i) the ULK1-ATG13-FIP200/RB1CC1 complex associates with the LC3B/GABARAP conjugation machinery through direct interactions between FIP200/RB1CC1 and ATG16L1, (ii) ULK1-ATG13-FIP200/RB1CC1 complex associates with the Beclin 1-VPS34-ATG14 via direct interactions between ATG13's HORMA domain and ATG14, (iii) ATG16L1 interacts with WIPI2, which binds to PI3P, the enzymatic product of the class III PI3K Beclin 1-VPS34-ATG14. Thus, mTOR inactivation, initiated through GALTOR upon lysosomal damage, plus a simultaneous activation via galectin-9 (which also recognizes lysosomal membrane breach) of AMPK that directly phosphorylates and activates key components (ULK1, Beclin 1) of the autophagy systems listed above and further inactivates mTORC1, allows for strong autophagy induction and autophagic removal of damaged lysosomes.
Additionally, several types of ubiquitination events parallel and complement the galectin-driven processes: Ubiquitination of TRIM16-ULK1-Beclin-1 stabilizes these complexes to promote autophagy activation as described above. ATG16L1 has an intrinsic binding affinity for ubiquitin); whereas ubiquitination by a glycoprotein-specific FBXO27-endowed ubiquitin ligase of several damage-exposed glycosylated lysosomal membrane proteins such as LAMP1, LAMP2, GNS/N-acetylglucosamine-6-sulfatase, TSPAN6/tetraspanin-6, PSAP/prosaposin, and TMEM192/transmembrane protein 192 may contribute to the execution of lysophagy via autophagic receptors such as p62/SQSTM1, which is recruited during lysophagy, or other to be determined functions. | 1 | Biochemistry |
These experiments address various important questions in evolutionary biology: does evolution proceed in small steps or in large leaps; is evolution reversible; how does complexity evolve? It has been shown that slight mutations in the amino acid sequence of hormone receptors determine an important change in their preferences for hormones. These changes mean huge steps in the evolution of the endocrine system. Thus very small changes at the molecular level may have enormous consequences. The Thornton lab has also been able to show that evolution is irreversible studying the glucocorticoid receptor. This receptor was changed by seven mutations in a cortisol receptor, but reversing these mutations didn't give the original receptor back. Indicating that epistasis plays a major role in protein evolution – an observation that in combination with the observations of several examples of parallel evolution, support the neutral network model mentioned above. Other earlier neutral mutations acted as a ratchet and made the changes to the receptor irreversible. These different experiments on receptors show that, during their evolution, proteins are greatly differentiated and this explains how complexity may evolve. A closer look at the different ancestral hormone receptors and the various hormones shows that at the level of interaction between single amino acid residues and chemical groups of the hormones arise by very small but specific changes. Knowledge about these changes may for example lead to the synthesis of hormonal equivalents capable of mimicking or inhibiting the action of a hormone, which might open possibilities for new therapies.
Given that ASR has revealed a tendency towards ancient thermostability and enzymatic promiscuity, ASR poses as a valuable tool for protein engineers who often desire these traits (producing effects sometimes greater than current, rationally lead tools). ASR also promises to resurrect phenotypically similar ancient organisms which in turn would allow evolutionary biochemists to probe the story of life. Proponents of ASR such as Benner state that through these and other experiments, the end of the current century will see a level of understanding in biology analogous to the one that arose in classical chemistry in the last century. | 1 | Biochemistry |
The cation [((CH)N)S] is a sulfonium ion. The S-N distances are 1.612 and 1.675 pm. The N-S-N angles are 99.6°. The anion is [FSi(CH)]. It is trigonal bipyramidal with mutually trans fluorides. The Si-F distances are 176 picometers. The Si-C distances are 188 pm. | 0 | Organic Chemistry |
In addition to the factors affecting monosaccharide residues, conformational analysis of oligosaccharides and polysaccharides requires consideration additional factors. | 0 | Organic Chemistry |
The catalytically active species is the anions cis-[Rh(CO)I] (top of scheme). The first organometallic step is the oxidative addition of methyl iodide to cis-[Rh(CO)I] to form the hexacoordinate species [(CH)Rh(CO)I]. This anion rapidly transforms, via the migration of a methyl group to an adjacent carbonyl ligand, affording the pentacoordinate acetyl complex [(CHCO)Rh(CO)I]. This five-coordinate complex then reacts with carbon monoxide to form the six-coordinate dicarbonyl complex, which undergoes reductive elimination to release acetyl iodide (CHC(O)I). The catalytic cycle involves two non-organometallic steps: conversion of methanol to methyl iodide and the hydrolysis of the acetyl iodide to acetic acid and hydrogen iodide.
The reaction has been shown to be first-order with respect to methyl iodide and [Rh(CO)I]. Hence the oxidative addition of methyl iodide is proposed as the rate-determining step. | 0 | Organic Chemistry |
Several cetacean species have very high mean blubber PCB concentrations likely to cause population declines and suppress population recovery. Striped dolphins, bottlenose dolphins and orcas were found to have mean levels that markedly exceeded all known marine mammal PCB toxicity thresholds. The western Mediterranean Sea and the south-west Iberian Peninsula were identified as "hotspots". | 2 | Environmental Chemistry |
The combination medicine dextromethorphan/bupropion is approved for major depressive disorder under the brand name Auvelity. | 4 | Stereochemistry |
Hemithioacetals are formed by the reaction of a thiol () and an aldehyde ():
Hemithioacetals usually arise via acid catalysis. They typically are intermediates in the formation of dithioacetals (): | 0 | Organic Chemistry |
An expressed sequence tag (EST) is a short nucleotide sequence generated from a single RNA transcript. RNA is first copied as complementary DNA (cDNA) by a reverse transcriptase enzyme before the resultant cDNA is sequenced. Because ESTs can be collected without prior knowledge of the organism from which they come, they can be made from mixtures of organisms or environmental samples. Although higher-throughput methods are now used, EST libraries commonly provided sequence information for early microarray designs; for example, a barley microarray was designed from 350,000 previously sequenced ESTs. | 1 | Biochemistry |
He was born in the family of an electrician and a land development specialist. Lukinavičius finished secondary school in Jurbarkas. | 1 | Biochemistry |
Fluorophores are essential to our measurement of the metal binding event, and indirectly, metal concentration. There are many types, all with different properties that make them advantageous for different applications. Some work as small metal sensors completely on their own while others must be complexed with a subunit that can chelate or bind a metal ion. Rhodamine for example undergoes a conformation change upon the binding of a metal ion. In so doing it switches between a colorless, non-fluorescent spirocyclic form to a fluorescent, pink open cyclic form. Quinoline based sensors have been developed that form luminescent complexes with Cd(II) and fluorescent ones with Zn(II). It is hypothesized to function by changing its lowest luminescent state from n–* to –* when coordinating to a metal.
When the Dansyl group DNS binds to a metal, it loses a sulfonamide hydrogen, causing fluorescence quenching via a PET or reverse PET mechanism in which an electron is transferred either to or from the metal that is bound. | 5 | Photochemistry |
Sulfur in natural materials can vary widely in isotopic composition: compilations of the δS values of natural sulfur-containing materials include values ranging from −55‰ to 135‰ VCDT. The ranges of δS values vary across sulfur-containing materials: for example, the sulfur in animal tissue ranges from ~ −10 to +20‰ VCDT, while the sulfate in natural waters ranges from ~ −20 to +135‰ VCDT. The range of sulfur isotope abundances in different natural materials results from the isotope fractionation associated with natural processes like the formation and modification of those materials, discussed in the next section. | 9 | Geochemistry |
It is worthy to note that due to the multiple reactive sites of the multivinyl monomers, plenty of unreacted pendent vinyl groups are introduced to linear primary polymer chains. These pendent vinyl groups have the potential to react with propagating active centres either from their own polymer chain or others. Therefore, both of the intramolecular cyclization and intermolecular crosslinking might occur in this process.
Using the deactivation enhanced strategy, a relatively small instantaneous kinetic chain length limits the number of vinyl groups that can be added to a propagating chain end during each activation/deactivation cycles and thus keeps the polymer chains growing in a limited space. In this way, unlike what happens in free radical polymerization (FRP), the formation of huge polymer chains and large-scale combinations at early reaction stages is avoided. Therefore, a small instantaneous kinetic chain length is the prerequisite for further manipulation of intramolecular cyclization or intermolecular crosslinking. Based on the small instantaneous kinetic chain length, regulation of different chain dimensions and concentrations would lead to distinct reaction types. A low ratio of initiator to monomer would result in the formation of longer chains but of a lower chain concentration, This scenario would no doubt increases the chances of intramolecular cyclization due to the high local/spatial vinyl concentration within the growth boundary. Although the opportunity for intermolecular reactions can increase as the polymer chains grow, the likelihood of this occurring at the early stage of reactions is minimal due to the low chain concentration, which is why single chain cyclized/knotted polymers can form. However, in contrast, a high initiator concentration not only diminishes the chain dimension during the linear-growth phase thus suppressing the intramolecular cyclization, but it also increases the chain concentration within the system so that pendent vinyl groups in one chain are more likely to fall into the growth boundary of another chain. Once the monomers are converted to short chains, the intermolecular combination increases and allows the formation of hyperbranched structures with a high density of branching and vinyl functional groups. | 7 | Physical Chemistry |
Between 1978 and 1986, the Congress authorized the Department of Energy (DoE) and NASA to jointly investigate the concept. They organized the Satellite Power System Concept Development and Evaluation Program. The study remains the most extensive performed to date (budget $50 million). Several reports were published investigating the engineering feasibility of such a project. They include:
* Resource Requirements (Critical Materials, Energy, and Land)
* Financial/Management Scenarios
* Public Acceptance
* State and Local Regulations as Applied to Satellite Power System Microwave Receiving Antenna Facilities
* Student Participation
* Potential of Laser for SBSP Power Transmission
* International Agreements
* Centralization/Decentralization
* Mapping of Exclusion Areas For Rectenna Sites
* Economic and Demographic Issues Related to Deployment
* Some Questions and Answers
* Meteorological Effects on Laser Beam Propagation and Direct Solar Pumped Lasers
* Public Outreach Experiment
* Power Transmission and Reception Technical Summary and Assessment
* Space Transportation | 7 | Physical Chemistry |
Though the cyclic forms of sugars are usually heavily favoured, hemiacetals in aqueous solution are in equilibrium with their open-chain forms. In aldohexoses this equilibrium is established as the hemiacetal bond between C-1 (the carbon bound to two oxygens) and C-5 oxygen is cleaved (forming the open-chain compound) and reformed (forming the cyclic compound). When the hemiacetal group is reformed, the OH group on C-5 may attack either of the two stereochemically distinct sides of the aldehyde group on C-1. Which side it attacks on determines whether the α- or β-anomer is formed.
Anomerization of glycosides typically occurs under acidic conditions. Typically, anomerization occurs through protonation of the exocyclic acetal oxygen, ionization to form an oxocarbenium ion with release of an alcohol, and nucleophilic attack by an alcohol on the reverse face of the oxocarbenium ion, followed by deprotonation. | 4 | Stereochemistry |
2-Oxoadipic acid, also known as α-ketoadipic acid, is an intermediate in the metabolism of lysine and tryptophan. The conjugate base and carboxylate is 2-oxoadipate or α-ketoadipate, which is the biochemically relevant form. | 1 | Biochemistry |
In 2018, deulinoleate ethyl was given to a patient with amyotrophic lateral sclerosis (ALS) under a "compassionate use scheme". | 1 | Biochemistry |
Moexipril is available as a prodrug moexipril hydrochloride, and is metabolized in the liver to form the pharmacologically active compound moexiprilat. Formation of moexiprilat is caused by hydrolysis of an ethyl ester group. Moexipril is incompletely absorbed after oral administration, and its bioavailability is low. The long pharmacokinetic half-life and persistent ACE inhibition of moexipril allows once-daily administration.
Moexipril is highly lipophilic, and is in the same hydrophobic range as quinapril, benazepril, and ramipril. Lipophilic ACE inhibitors are able to penetrate membranes more readily, thus tissue ACE may be a target in addition to plasma ACE. A significant reduction in tissue ACE (lung, myocardium, aorta, and kidney) activity has been shown after moexipril use.
It has additional PDE4-inhibiting effects. | 4 | Stereochemistry |
The AFM has been applied to problems in a wide range of disciplines of the natural sciences, including solid-state physics, semiconductor science and technology, molecular engineering, polymer chemistry and physics, surface chemistry, molecular biology, cell biology, and medicine.
Applications in the field of solid state physics include (a) the identification of atoms at a surface, (b) the evaluation of interactions between a specific atom and its neighboring atoms, and (c) the study of changes in physical properties arising from changes in an atomic arrangement through atomic manipulation.
In molecular biology, AFM can be used to study the structure and mechanical properties of protein complexes and assemblies. For example, AFM has been used to image microtubules and measure their stiffness.
In cellular biology, AFM can be used to attempt to distinguish cancer cells and normal cells based on a hardness of cells, and to evaluate interactions between a specific cell and its neighboring cells in a competitive culture system. AFM can also be used to indent cells, to study how they regulate the stiffness or shape of the cell membrane or wall.
In some variations, electric potentials can also be scanned using conducting cantilevers. In more advanced versions, currents can be passed through the tip to probe the electrical conductivity or transport of the underlying surface, but this is a challenging task with few research groups reporting consistent data (as of 2004). | 6 | Supramolecular Chemistry |
The following table shows the characteristics of various HIV-1 bNAbs
In addition to targeting conserved epitopes, bNAbs are known to have long variable regions on their immunoglobulin (Ig) isotypes and subclasses. When compared to non-bNAbs, sequence variability from the germline immunoglobulin isotype is 7 fold. This implies that bNAbs develop from intense affinity maturation in the germinal centers hence the reason for high sequence variability on the variable Ig domain. Indeed HIV-1 patients who develop bNAbs have been shown to have high germinal center activity as exhibited by their comparatively higher levels of plasma CXCL13, which is a biomarker of germinal center activity.
Online databases like bNAber and LANL constantly report and update the discovery of new HIV bNAbs. | 1 | Biochemistry |
The French chemist Louis Pasteur founded zymology, when in 1856 he connected yeast to fermentation.
When studying the fermentation of sugar to alcohol by yeast, Pasteur concluded that the fermentation was catalyzed by a vital force, called "ferments", within the yeast cells. The "ferments" were thought to function only within living organisms. Pasteur wrote that "Alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells." | 1 | Biochemistry |
Particle physics codified the basic laws of dynamics into the standard model. This is formulated as a quantum field theory that has CPT symmetry, i.e., the laws are invariant under simultaneous operation of time reversal, parity and charge conjugation. However, time reversal itself is seen not to be a symmetry (this is usually called CP violation). There are two possible origins of this asymmetry, one through the mixing of different flavours of quarks in their weak decays, the second through a direct CP violation in strong interactions. The first is seen in experiments, the second is strongly constrained by the non-observation of the EDM of a neutron.
Time reversal violation is unrelated to the second law of thermodynamics, because due to the conservation of the CPT symmetry, the effect of time reversal is to rename particles as antiparticles and vice versa. Thus the second law of thermodynamics is thought to originate in the initial conditions in the universe. | 7 | Physical Chemistry |
Hydrogen embrittles a variety of metals including steel, aluminium (at high temperatures only), and titanium. Austempered iron is also susceptible, though austempered steel (and possibly other austempered metals) displays increased resistance to hydrogen embrittlement. NASA has reviewed which metals are susceptible to embrittlement and which only prone to hot hydrogen attack: nickel alloys, austenitic stainless steels, aluminium and alloys, copper (including alloys, e.g. beryllium copper). Sandia has also produced a comprehensive guide. | 7 | Physical Chemistry |
In chemistry, a compartment is a part of a protein that serves a specific function. They are essentially protein subunits with the added condition that a compartment has distinct functionality, rather than being just a structural component.
There may be multiple compartments on one and the same protein. One example is the case of pyruvate dehydrogenase complex. This is the enzyme which catalyses pyruvate decarboxylation, the reaction of pyruvate with coenzyme A and the major entry point into the TCA cycle:
:Pyruvate + Coenzyme A + NAD ⇒ acetyl-CoA + NADH + H + CO
Pyruvate dehydrogenase has three chemical compartments; E1 (pyruvate decarboxylase), E2 (dihydrolipoyl transacetylase) and E3 (dihydrolipoyl dehydrogenase). Each one of the compartments has its own specific function. | 1 | Biochemistry |
Fast parallel proteolysis (FASTpp) is a method to determine the thermostability of proteins by measuring which fraction of protein resists rapid proteolytic digestion. | 1 | Biochemistry |
In case (e), we first form and then form by coupling and . This case is rare but has been observed. Rydberg states which converge to ionic states with spin–orbit coupling (such as Π) are best described as case (e).
The good quantum numbers in case (e) are , , and . Because is once again a good quantum number, the rotational energy is . | 7 | Physical Chemistry |
Measuring the size of a protein molecule is useful as an overall quality indicator, since misfolding, unfolding, oligomerization, aggregation or degradation can all affect size.
The literature specifically demonstrates the use of MDS in sizing protein-nanobody complexes, monitoring the formation of α-synuclein amyloid fibrils. and in observing protein assembly into oligomers
MDS can also be used to size membrane proteins, as the use of a protein specific labelling and detection system allows other species present in the solution (such as free lipid micelles or detergents) to be ignored. | 1 | Biochemistry |
Since many sources of human food are ultimately derived from terrestrial plants, the relative concentration of carbon-14 in human bodies is nearly identical to the relative concentration in the atmosphere. The rates of disintegration of potassium-40 and carbon-14 in the normal adult body are comparable (a few thousand disintegrated nuclei per second). The beta decays from external (environmental) radiocarbon contribute approximately 0.01 mSv/year (1 mrem/year) to each person's dose of ionizing radiation. This is small compared to the doses from potassium-40 (0.39 mSv/year) and radon (variable).
Carbon-14 can be used as a radioactive tracer in medicine. In the initial variant of the urea breath test, a diagnostic test for Helicobacter pylori, urea labeled with approximately carbon-14 is fed to a patient (i.e., 37,000 decays per second). In the event of a H. pylori infection, the bacterial urease enzyme breaks down the urea into ammonia and radioactively-labeled carbon dioxide, which can be detected by low-level counting of the patient's breath. | 9 | Geochemistry |
* 2023: Arthur C. Cope Scholar Award (American Chemical Society)
* 2018: University of California, Irvine Physical Science Outstanding Contributions to the Undergraduate Education
* 2017: Fellow of the AAAS
* 2013-2016: Humboldt Fellowship
* 2013: Japan Society for the Promotion of Science Fellowship
* 2008: NSF CAREER Award
* 2005-2006: National Institutes of Health Postdoctoral Fellow | 0 | Organic Chemistry |
Staphylococcus aureus is a type of pathogen that causes infection to the skin and soft tissue and can lead to a variety of more severe diseases such as osteomyelitis, pneumonia, and endocarditis. Staphylococcus aureus uses biofilms in order to increase its chances of survival by becoming resistant to antibiotics. Biofilms help Staphylococcus aureus become up to 1500 times more resistant to antibiofilm agents which try to break down biofilms formed by Staphylococcus aureus. | 1 | Biochemistry |
Elementary mode analysis closely matches the approach used by extreme pathways. Similar to extreme pathways, there is always a unique set of elementary modes available for a particular metabolic network. These are the smallest sub-networks that allow a metabolic reconstruction network to function in steady state. According to Stelling (2002), elementary modes can be used to understand cellular objectives for the overall metabolic network. Furthermore, elementary mode analysis takes into account stoichiometrics and thermodynamics when evaluating whether a particular metabolic route or network is feasible and likely for a set of proteins/enzymes. | 1 | Biochemistry |
Rett syndrome is a neurodevelopmental disorder involving deterioration of learned language and motor skills, autism, and seizures starting in infancy. Many cases of Rett syndrome are associated with mutations in MECP2, a gene encoding a transcriptional repressor. Mutations in this gene decrease the levels of MeCP2 binding to different promoter sequences, resulting in their overall derepression. The increased expression of these MeCP2 regulated genes in neurons contribute to the Rett syndrome phenotype. | 1 | Biochemistry |
https://web.archive.org/web/20160325004825/https://www.colorado.edu/physics/phys7550/phys7550_sp07/extras/Ramsey90_RMP.pdf | 7 | Physical Chemistry |
The journal is abstracted and indexed in:
*Aquatic Sciences & Fisheries Abstracts
*Chemical Abstracts Service
*Current Contents/Physical, Chemical & Earth Sciences
*Ei-Compendex
*Science Citation Index Expanded
*Scopus
According to the Journal Citation Reports, the journal has a 2022 impact factor of 0.7. | 7 | Physical Chemistry |
Glucose is an energy source in most life forms. For instance, polysaccharides are broken down into their monomers by enzymes (glycogen phosphorylase removes glucose residues from glycogen, a polysaccharide). Disaccharides like lactose or sucrose are cleaved into their two component monosaccharides. | 1 | Biochemistry |
We thus have two new kinds of isometry subgroups: all translations, and rotations sharing a fixed point. Both are subgroups of the even subgroup, within which translations are normal. Because translations are a normal subgroup, we can factor them out leaving the subgroup of isometries with a fixed point, the orthogonal group. | 3 | Analytical Chemistry |
In some very economically important flowers like roses, carnations and chrysanthemums despite a lot of efforts was not possible to breed the flowers with blue petals coloration. The lack of F35H enzyme and hence delphinidin type anthocyanin is the reason why blue flower colour was not possible to obtain. | 1 | Biochemistry |
Ionic transfer is the transfer of ions from one liquid phase to another. This is related to the phase transfer catalysts which are a special type of liquid-liquid extraction which is used in synthetic chemistry.
For instance nitrate anions can be transferred between water and nitrobenzene. One way to observe this is to use a cyclic voltammetry experiment where the liquid-liquid interface is the working electrode. This can be done by placing secondary electrodes in each phase and close to interface each phase has a reference electrode. One phase is attached to a potentiostat which is set to zero volts, while the other potentiostat is driven with a triangular wave. This experiment is known as a polarised Interface between Two Immiscible Electrolyte Solutions (ITIES) experiment. | 7 | Physical Chemistry |
The Abel test is a method developed by the British chemist Frederick Abel (1827–1902) to determine the flash point of a given sample of petroleum in order to ascertain the temperature at which it could safely be stored or used.
The test was mandated by the British Petroleum Act 1879, which fixed the minimum flash point for general and commercial use at . | 3 | Analytical Chemistry |
Xylenes are an important petrochemical produced by catalytic reforming and also by coal carbonisation in the manufacture of coke fuel. They also occur in crude oil in concentrations of about 0.5–1%, depending on the source. Small quantities occur in gasoline and aircraft fuels.
Xylenes are produced mainly as part of the BTX aromatics (benzene, toluene, and xylenes) extracted from the product of catalytic reforming known as reformate.
Several million tons are produced annually. In 2011, a global consortium began construction of one of the world's largest xylene plants in Singapore. | 2 | Environmental Chemistry |
Organic selenocyanates are organoselenium compounds with the general formula RSeCN. They are generally colorless, air-stable solids or liquids with repulsive odors. In terms of structure, synthesis, and reactivity, selenocyanates and thiocyanates behave similarly. | 0 | Organic Chemistry |
The Fürst-Plattner rule (also known as the trans-diaxial effect) describes the stereoselective addition of nucleophiles to cyclohexene derivatives. | 4 | Stereochemistry |
*GB772534A Improvements in or relating to titanium base alloys
*CH457874A Verfahren zur Wärmebehandlung einer Titanlegierung
*GB929931A Titanium-base alloys and their heat treatment
*US3007824A Method of heat treating a ti-be alloy
*US3118828A Electrode structure with titanium alloy base
*FI35168A Sätt att framställa en elektrod
*DE1112838B Verfahren zum Oberflaechenhaerten von (ª‡ú½ª‰) Ti-Legierungen | 8 | Metallurgy |
The response to stimulation of chemoreceptors on the heart rate is complicated. Chemoreceptors in the heart or nearby large arteries, as well as chemoreceptors in the lungs, can affect heart rate. Activation of these peripheral chemoreceptors from sensing decreased O, increased CO and a decreased pH is relayed to cardiac centers by the vagus and glossopharyngeal nerves to the medulla of the brainstem. This increases the sympathetic nervous stimulation on the heart and a corresponding increase in heart rate and contractility in most cases. These factors include activation of stretch receptors due to increased ventilation and the release of circulating catecholamines.
However, if respiratory activity is arrested (e.g. in a patient with a high cervical spinal cord injury), then the primary cardiac reflex to transient hypercapnia and hypoxia is a profound bradycardia and coronary vasodilation through vagal stimulation and systemic vasoconstriction by sympathetic stimulation. In normal cases, if there is reflexive increase in respiratory activity in response to chemoreceptor activation, the increased sympathetic activity on the cardiovascular system would act to increase heart rate and contractility. | 3 | Analytical Chemistry |
The Embeden–Meyerhof pathway and the Krebs cycle are the centre of metabolism in nearly all bacteria and eukaryotes. They provide not only energy but also precursors for biosynthesis of macromolecules that make up living systems. | 1 | Biochemistry |
A special type of hypervalent molecules is hypervalent hydrides. Most known hypervalent molecules contain substituents more electronegative than their central atoms. Hypervalent hydrides are of special interest because hydrogen is usually less electronegative than the central atom. A number of computational studies have been performed on chalcogen hydrides and pnictogen hydrides. Recently, a new computational study has showed that most hypervalent halogen hydrides XH can exist. It is suggested that IH and IH are stable enough to be observable or, possibly, even isolable. | 4 | Stereochemistry |
The reserve pool is not directly connected to the active zone. The increase in presynaptic calcium concentration activates calcium–calmodulin-dependent protein kinase (CaMK). CaMK phosphorylates a protein, synapsin, that mediates the clustering of the reserve pool vesicles and attachment to the cytoskeleton. Phosphorylation of synapsin mobilizes vesicles in the reserve pool and allows them to migrate to the active zone and replenish the readily releasable pool. | 1 | Biochemistry |
James Murray (1923–1961) was an organic chemist at the University of Otago. He was the first twentieth-century lichenologist in New Zealand. | 0 | Organic Chemistry |
It is still unclear the ecological effects of lactonase but it has been proposed that since bacteria mostly coexist with other microorganisms in the environment, some bacteria strains could have evolved its feeding strategies and utilize AHLs as their main resource for energy and nitrogen. | 1 | Biochemistry |
Calmagite is a complexometric indicator used in analytical chemistry to identify the presence of metal ions in solution. As with other metal ion indicators calmagite will change color when it is bound to an ion. Calmagite will be wine red when it is bound to a metal ion and may be blue, red, or orange when it is not bound to a metal ion. Calmagite is often used in conjunction with EDTA, a stronger metal binding agent. This chemical is also used in the quantitation of magnesium in the clinical laboratory. | 3 | Analytical Chemistry |
Bismuth polycations are polyatomic ions of the formula . They were originally observed in solutions of bismuth metal in molten bismuth chloride. It has since been found that these clusters are present in the solid state, particularly in salts where germanium tetrachloride or tetrachloroaluminate serve as the counteranions, but also in amorphous phases such as glasses and gels. Bismuth endows materials with a variety of interesting optical properties that can be tuned by changing the supporting material. Commonly-reported structures include the trigonal bipyramidal cluster, the octahedral cluster, the square antiprismatic cluster, and the tricapped trigonal prismatic cluster. | 7 | Physical Chemistry |
The x-axis of a Tanabe–Sugano diagram is expressed in terms of the ligand field splitting parameter, Δ, or Dq (for "differential of quanta"), divided by the Racah parameter B. The y-axis is in terms of energy, E, also scaled by B. Three Racah parameters exist, A, B, and C, which describe various aspects of interelectronic repulsion. A is an average total interelectron repulsion. B and C correspond with individual d-electron repulsions. A is constant among d-electron configuration, and it is not necessary for calculating relative energies, hence its absence from Tanabe and Suganos studies of complex ions. C is necessary only in certain cases. B is the most important of Racahs parameters in this case. One line corresponds to each electronic state. The bending of certain lines is due to the mixing of terms with the same symmetry. , T, etc.), but "g" and "u" subscripts are usually left off because it is understood that all the states are gerade.) labels may be written in other locations for clarity. Term symbols (e.g. P, S, etc.) for a specific d free ion are listed, in order of increasing energy, on the y-axis of the diagram. The relative order of energies is determined using Hund's rules. For an octahedral complex, the spherical, free ion term symbols split accordingly:
Certain Tanabe–Sugano diagrams (d, d, d, and d) also have a vertical line drawn at a specific Dq/B value, which is accompanied by a discontinuity in the slopes of the excited states energy levels. This pucker in the lines occurs when the identity of the ground state changes, shown in the diagram below. The left depicts the relative energies of the d ion states as functions of crystal field strength (Dq), showing an intersection of the T and the E states near Dq/B' ~ 2.1. Subtracting the ground state energy produces the standard Tanabe–Sugano diagram shown on the right.
This change in identity generally happens when the spin pairing energy, P, is equal to the ligand field splitting energy, Dq. Complexes to the left of this line (lower Dq/B values) are high-spin, while complexes to the right (higher Dq/B values) are low-spin. There is no low-spin or high-spin designation for d, d, or d because none of the states cross at reasonable crystal field energies. | 7 | Physical Chemistry |
Sulfur from meteorites was determined in the early 1950s to be an adequate reference standard because it exhibited a small variability in isotopic ratios. It was also believed that because of their extraterrestrial provenances, meteors represented primordial terrestrial isotopic conditions. During a meeting of the National Science Foundation in April 1962, troilite from the Canyon Diablo meteorite found in Arizona, US, was established as the standard with which δS values (and other sulfur stable isotopic ratios) could be calculated. Known as Canyon Diablo Troilite (CDT), the standard was established as having a S:S ratio of 22.220 and was used for around three decades. In 1993, the International Atomic Energy Agency (IAEA) established a new standard, Vienna-CDT (VCDT), based on artificially prepared silver sulfide (IAEA-S-1) that was defined to have a δS value of −0.3‰. In 1994, the original CDT material was found not to be isotopically homogeneous, with internal variations as great as 0.4‰, confirming its unsuitability as a reference standard. | 9 | Geochemistry |
Plants growing at high light invest less of their biomass in leaves and stems, and more in roots. They grow faster, per unit leaf area (ULR) and per unit total plant mass (RGR), and therefore high-light grown plants generally have more biomass. They have shorter internodes, with more stem biomass per unit stem length, but plant height is often not strongly affected. High-light plants do show more branches or tillers. | 5 | Photochemistry |
A first ChIP-on-chip experiment was performed in 1999 to analyze the distribution of cohesin along budding yeast chromosome III. Although the genome was not completely represented, the protocol in this study remains equivalent as those used in later studies. The ChIP-on-chip technique using all of the ORFs of the genome (that nevertheless remains incomplete, missing intergenic regions) was then applied successfully in three papers published in 2000 and 2001. The authors identified binding sites for individual transcription factors in the budding yeast Saccharomyces cerevisiae. In 2002, Richard Youngs group determined the genome-wide positions of 106 transcription factors using a c-Myc tagging system in yeast. The first demonstration of the mammalian ChIp-on-chip technique reported the isolation of nine chromatin fragments containing weak and strong E2F binding site was done by Peggy Farnhams lab in collaboration with Michael Zhang's lab and published in 2001. This study was followed several months later in a collaboration between the Young lab with the laboratory of Brian Dynlacht which used the ChIP-on-chip technique to show for the first time that E2F targets encode components of the DNA damage checkpoint and repair pathways, as well as factors involved in chromatin assembly/condensation, chromosome segregation, and the mitotic spindle checkpoint Other applications for ChIP-on-chip include DNA replication, recombination, and chromatin structure. Since then, ChIP-on-chip has become a powerful tool in determining genome-wide maps of histone modifications and many more transcription factors. ChIP-on-chip in mammalian systems has been difficult due to the large and repetitive genomes. Thus, many studies in mammalian cells have focused on select promoter regions that are predicted to bind transcription factors and have not analyzed the entire genome. However, whole mammalian genome arrays have recently become commercially available from companies like Nimblegen. In the future, as ChIP-on-chip arrays become more and more advanced, high resolution whole genome maps of DNA-binding proteins and chromatin components for mammals will be analyzed in more detail. | 1 | Biochemistry |
Vitamin A toxicity (hypervitaminosis A) occurs when too much vitamin A accumulates in the body. It comes from consumption of preformed vitamin A but not of carotenoids, as conversion of the latter to retinol is suppressed by the presence of adequate retinol. | 1 | Biochemistry |
Tengiz Beridze (Georgian: თენგიზ გიორგის ძე ბერიძე) is a Georgian biochemist. He was born on 26 October 1939 in Tbilisi, Georgian SSR, USSR. | 1 | Biochemistry |
After securing the fellowship of the Pakistan Academy of Sciences, Rahman had been affiliated with the Pakistan government regarding education and science affairs. From 1996 until 2012, Rahman served in the board of directors of the Committee on Scientific and Technological Cooperation, representing Pakistans delegation. In 1997, Rahman served as the Coordinator General of the Organisation of Islamic Cooperations (OIC) Committee on Scientific and Technological Cooperation (COMSTECH) that comprised 57 Ministers of Science and Technology from 57 OIC member countries. In recognition of his scientific transformation of Pakistan and building a large number of Centers of Excellence in the country as well as promoting scientific research, Rahman was conferred the TWAS Prize in Institution Building, in Durban, South Africa in 2009. Atta-ur-Rahman has seved as the co-chairman of UN ESCAP.
In 1999, he joined the Ministry of Science and Technology (MoSci) as its minister, assisting in drafting the official science policy of the country. In 2002, he was appointed as minister of the Ministry of Education (MoEd) as well as becoming the chairman of the Higher Education Commission (HEC) until resigning in 2008. Atta-ur-Rahman has also served as Chairman of the Prime Ministers National Task Force on Science and Technology, Co Chairman of Prime Ministers National Task Force on Information Technology and Telecommunications, and Vice Chairman of the Prime Ministers Task Force on Technology Driven Knowledge Economy during the years 2019 to 2022. He is the President of the Network of Science of Organisation of Islamic Countries (NASIC) | 0 | Organic Chemistry |
Non-destructive detectors in liquid chromatography:
*Ultraviolet light detectors, fixed or variable wavelength, which includes diode array detectors. The ultraviolet light absorption of the effluent is continuously measured at single or multiple wavelengths. These are by far most popular detectors for liquid chromatography.
* Fluorescence detector. Irradiates the effluent with a light of set wavelength and measure the fluorescence of the effluent at a single or multiple wavelength.
* Refractive index detector. Continuously measures the refractive index of the effluent. The lowest sensitivity of all detectors. Often used in size exclusion chromatography for polymer analysis.
* Radio flow detector. Measures radioactivity of the effluent. This detector can be destructive if a scintillation cocktail is continuously added to the effluent.
* Chiral detector continuously measures the optical angle of rotation of the effluent. It is used only when chiral compounds are being analyzed.
* Conductivity monitor. Continuously measures the conductivity of the effluent. Used only when conductive eluents (water or alcohols) are used.
Non-destructive detectors in gas chromatography:
* Thermal conductivity detector: measures the thermal conductivity of the eluent.
* Electron capture detector: the most sensitive detector known. Allows for the detection of organic molecules containing halogen, nitro groups etc.
* Photoionization detector measures the increase in conductivity achieved by ionizing the effluent gas with ultraviolet light radiation.
* Olfactometric detector: assesses the odor activity of the eluent using human assessors.
* Electronic nose detector which mimics human nose is emerging as a modern and advanced version of the olfactory detection is the electronic nose detector. | 3 | Analytical Chemistry |
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