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Katsonis was born in Vienna. She grew up in Orsay, in Paris Region. She is half French and half Greek. She studied chemical engineering at the Chimie ParisTech, before moving to Ecole Normal Superieure for her graduate studies with Ludovic Jullien. Katsonis earned her doctoral degree at the Pierre and Marie Curie University. She worked on nanoscale probes of two dimensional molecular self-assemblies with Denis Fichou. She joined the research group of Ben Feringa at the University of Groningen, where she worked on self-assembly of motors and switches. Whilst at Groningen Katsonis developed scanning probe microscopy for the determination of molecular chirality. | 0 | Theoretical and Fundamental Chemistry |
Technicon published method sheets for a wide range of analyses and a few of these are listed below. These methods and later methods are available from SEAL Analytical. Method lists for manufacturers instruments are readily available on their websites. | 0 | Theoretical and Fundamental Chemistry |
The Kochi reaction is an organic reaction for the decarboxylation of carboxylic acids to alkyl halides with lead(IV) acetate and a lithium halide.
The reaction is a variation of the Hunsdiecker reaction. | 0 | Theoretical and Fundamental Chemistry |
The Hofmeister series or lyotropic series is a classification of ions in order of their lyotrophic properties, which is the ability to salt out or salt in proteins. The effects of these changes were first worked out by Franz Hofmeister, who studied the effects of cations and anions on the solubility of proteins. | 0 | Theoretical and Fundamental Chemistry |
Flammable substances include, but are not limited to:
* Gasoline - Petrol / a complicated mixture of hydrocarbons that includes isomers of octane, CH
* Ethanol / CHCHOH
* Rubber
* Isopropyl alcohol / CHCH(OH)CH
* Methanol / CHOH
* Wood
* Acetone / CHCOCH
* Paper
* Nitromethane / CHNO | 0 | Theoretical and Fundamental Chemistry |
Scotophobin (from ancient Greek σκότος skótos "darkness" and φόβος phóbos "fear") is a peptide discovered by neuroscientist Georges Ungar in 1965 and reported in 1968. The results of Ungar and his collaborators seemed to show that scotophobin induces fear of the dark in various mammals and fish. It was discovered in the brain of laboratory rats conditioned to have a fear of darkness. Moreover, it was claimed that its injection could transfer fear to unconditioned rats. It was the core argument for the hypothesis about memory transfer: that memories are molecularly stored in the brain. Chemical memory transfer was a subject of conferences and books. According to the current knowledge, scotophobin cannot have the effect attributed to it.
The history of scotophobin is covered in the 2006 book Scotophobin: Darkness at the Dawn of the Search for Memory Molecules, a personal account of Louis Neal Irwin, who participated in this research. | 1 | Applied and Interdisciplinary Chemistry |
In the world of performance-enhancing drugs, HCG is increasingly used in combination with various anabolic-androgenic steroid (AAS) cycles. As a result, HCG is included in some sports' illegal drug lists.
When exogenous AAS are put into the male body, natural negative-feedback loops cause the body to shut down its own production of testosterone via shutdown of the hypothalamic-pituitary-gonadal axis (HPGA). This causes testicular atrophy, among other things. HCG is commonly used during and after steroid cycles to maintain and restore testicular size as well as normal testosterone production.
High levels of AASs, that mimic the body's natural testosterone, trigger the hypothalamus to shut down its production of gonadotropin-releasing hormone (GnRH) from the hypothalamus. Without GnRH, the pituitary gland stops releasing luteinizing hormone (LH). LH normally travels from the pituitary via the blood stream to the testes, where it triggers the production and release of testosterone. Without LH, the testes shut down their production of testosterone. In males, HCG helps restore and maintain testosterone production in the testes by mimicking LH and triggering the production and release of testosterone.
Professional athletes who have tested positive for HCG have been temporarily banned from their sport, including a 50-game ban from MLB for Manny Ramirez in 2009 and a 4-game ban from the NFL for Brian Cushing for a positive urine test for HCG. Mixed Martial Arts fighter Dennis Siver was fined $19,800 and suspended 9 months for being tested positive after his bout at UFC 168. | 1 | Applied and Interdisciplinary Chemistry |
Akkermansia muciniphila can reside in the human intestinal tract and is currently being studied for its effects on human metabolism and health. | 1 | Applied and Interdisciplinary Chemistry |
The fuel is first dissolved in nitric acid at a concentration around 7 M. Solids are removed by filtration to avoid the formation of emulsions, referred to as third phases in the solvent extraction community.
The organic solvent consists of 30% tributyl phosphate (TBP) in a hydrocarbon such as kerosene. Uranyl(VI) ions are extracted in the organic phase as UO(NO)·2TBP complexes; plutonium is extracted as similar complexes. The heavier actinides, primarily americium and curium, and the fission products remain in the aqueous phase. The nature of uranyl nitrate complexes with trialkyl phosphates has been characterized.
Plutonium is separated from uranium by treating the TBP-kerosene solution with reducing agents to convert the plutonium to its +3 oxidation state, which will pass into the aqueous phase. Typical reducing agents include N,N-diethyl-hydroxylamine, ferrous sulphamate, and hydrazine. Uranium is then stripped from the kerosene solution by back-extraction into nitric acid at a concentration around 0.2 M. | 0 | Theoretical and Fundamental Chemistry |
RTP was developed in the early 1990s by Wavin Repox, Akzo Nobel and by Tubes d'Aquitaine from France. They developed the first pipes reinforced with synthetic fibre to replace medium pressure steel pipes in response to growing demand for non-corrosive conduits for application in the onshore oil and gas industry, particularly from Shell in the Middle East. Because of its expertise in producing pipes, Pipelife Netherlands was involved in the project to develop long length RTP in 1998. The resulting system is marketed today under the name SoluForce.
SoluForce was the first ever RTP to be installed and used in the year 2000. | 1 | Applied and Interdisciplinary Chemistry |
The discovery of the Nef reaction and the papers about divalent carbon (carbenes) were his major achievements. | 0 | Theoretical and Fundamental Chemistry |
A group of researchers at the École Polytechnique Fédérale de Lausanne (EPFL) has reportedly increased the thermostability of DSC by using amphiphilic ruthenium sensitizer in conjunction with quasi-solid-state gel electrolyte. The stability of the device matches that of a conventional inorganic silicon-based solar cell. The cell sustained heating for 1,000 h at 80 °C.
The group has previously prepared a ruthenium amphiphilic dye Z-907 (cis-Ru(Hdcbpy)(dnbpy)(NCS), where the ligand Hdcbpy is 4,4′-dicarboxylic acid-2,2′-bipyridine and dnbpy is 4,4′-dinonyl-2,2′-bipyridine) to increase dye tolerance to water in the electrolytes. In addition, the group also prepared a quasi-solid-state gel electrolyte with a 3-methoxypropionitrile (MPN)-based liquid electrolyte that was solidified by a photochemically stable fluorine polymer, polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP).
The use of the amphiphilic Z-907 dye in conjunction with the polymer gel electrolyte in DSC achieved an energy conversion efficiency of 6.1%. More importantly, the device was stable under thermal stress and soaking with light. The high conversion efficiency of the cell was sustained after heating for 1,000 h at 80 °C, maintaining 94% of its initial value. After
accelerated testing in a solar simulator for 1,000 h of light-soaking at 55 °C (100 mW cm) the efficiency had decreased by less than 5% for cells covered with an ultraviolet absorbing polymer film. These results are well within the limit for that of traditional inorganic silicon solar cells.
The enhanced performance may arise from a decrease in solvent permeation across the sealant due to the application of the polymer gel electrolyte. The polymer gel electrolyte is quasi-solid at room temperature, and becomes a viscous liquid (viscosity: 4.34 mPa·s) at 80 °C compared with the traditional liquid electrolyte (viscosity: 0.91 mPa·s). The much improved stabilities of the device under both thermal stress and soaking with light has never before been seen in DSCs, and they match the durability criteria applied to solar cells for outdoor use, which makes these devices viable for practical application. | 0 | Theoretical and Fundamental Chemistry |
Temperature programmed desorption (TPD) is one of the most widely used surface analysis techniques available for materials research science. It has several applications such as knowing the desorption rates and binding energies of chemical compounds and elements, evaluation of active sites on catalyst surfaces and the understanding of the mechanisms of catalytic reactions including adsorption, surface reaction and desorption, analysing material compositions, surface interactions and surface contaminates. Therefore, TPD is increasingly important in many industries including, but not limited to, quality control and industrial research on products such as polymers, pharmaceuticals, clays and minerals, food packaging, and metals and alloys.
When TPD is used with the aim of knowing desorption rates of products that were previously adsorbed on a surface, it consists of heating a cold crystal surface that adsorbed a gas or a mixture of gases at a controlled rate. Then, the adsorbates will react as they are heated and then they will desorb from the surface. The results of applying TPD are the desorption rates of each of the product species that have been desorbed as a function of the temperature of the surface, this is called the TPD spectrum of the product. Also, as the temperature at which each of the surface compounds has been desorbed is known, it is possible to compute the energy that bounded the desorbed compound to the surface, the activation energy. | 0 | Theoretical and Fundamental Chemistry |
Some publications use a simpler form of this equation that doesn't correct for the reference range of free T4. It is calculated with
The disadvantage of this uncorrected version is that its numeric results are highly dependent on the used assays and their units of measurement. | 1 | Applied and Interdisciplinary Chemistry |
Slip ratio (or velocity ratio) in gas–liquid (two-phase) flow, is defined as the ratio of the velocity of the gas phase to the velocity of the liquid phase.
In the homogeneous model of two-phase flow, the slip ratio is by definition assumed to be unity (no slip). It is however experimentally observed that the velocity of the gas and liquid phases can be significantly different, depending on the flow pattern (e.g. plug flow, annular flow, bubble flow, stratified flow, slug flow, churn flow). The models that account for the existence of the slip are called "separated flow models".
The following identities can be written using the interrelated definitions:
where:
* S – slip ratio, dimensionless
* indices G and L refer to the gas and the liquid phase, respectively
* u – velocity, m/s
* U – superficial velocity, m/s
* – void fraction, dimensionless
* ρ – density of a phase, kg/m
* x – steam quality, dimensionless. | 1 | Applied and Interdisciplinary Chemistry |
The depth–slope product is used to calculate the shear stress at the bed of an open channel containing fluid that is undergoing steady, uniform flow. It is widely used in river engineering, stream restoration, sedimentology, and fluvial geomorphology. It is the product of the water depth and the mean bed slope, along with the acceleration due to gravity and density of the fluid. | 1 | Applied and Interdisciplinary Chemistry |
Patchoulene oxide (1) could be accessed from terpene patchoulol (52) through a series of acid-catalyzed carbocation rearrangements proceeded by an elimination following Zaitzev's rule to give pathoulene (53). The driving force for the rearrangement is relief of ring strain. Epoxidation of 53 with peracetic acid gave patchoulene oxide 1. | 0 | Theoretical and Fundamental Chemistry |
Although water quality is usually sampled and analyzed at laboratories, since the late 20th century there has been increasing public interest in the quality of drinking water provided by municipal systems. Many water utilities have developed systems to collect real-time data about source water quality. In the early 21st century, a variety of sensors and remote monitoring systems have been deployed for measuring water pH, turbidity, dissolved oxygen and other parameters. Some remote sensing systems have also been developed for monitoring ambient water quality in riverine, estuarine and coastal water bodies.
The following is a list of indicators often measured by situational category:
* Alkalinity
* Color of water
* pH
* Taste and odor (geosmin, 2-Methylisoborneol (MIB), etc.)
* Dissolved metals and salts (sodium, chloride, potassium, calcium, manganese, magnesium)
* Microorganisms such as fecal coliform bacteria (Escherichia coli), Cryptosporidium, and Giardia lamblia; see Bacteriological water analysis
* Dissolved metals and metalloids (lead, mercury, arsenic, etc.)
* Dissolved organics: colored dissolved organic matter (CDOM), dissolved organic carbon (DOC)
* Radon
* Heavy metals
* Pharmaceuticals
* Hormone analogs | 0 | Theoretical and Fundamental Chemistry |
Valentin Rose the Elder (16 August 1736 – 28 April 1771) was a German pharmacist and chemist born in Neuruppin. He is remembered for creation of a fusible alloy known as Rose metal, which is composed of lead, bismuth and tin.
Beginning in 1761, he was owner and manager of a laboratory and pharmacy in Berlin known as Zum Weißen Schwan (At the White Swan). After his death in 1771, famed chemist Martin Heinrich Klaproth (1743–1817) became manager of the establishment.
His son, also named Valentin Rose, was a noted pharmacist. Mineralogists Heinrich Rose and Gustav Rose were his grandsons; the classicist Valentin Rose and the surgeon Edmund Rose were his great-grandsons. | 1 | Applied and Interdisciplinary Chemistry |
Based on the method developed by Poliak and Jonas, a few models are developed in order to describe the critical strain for the onset of DRX as a function of the peak strain of the stress–strain curve. The models are derived for the systems with single peak, i.e. for the materials with medium to low stacking fault energy values. The models can be found in the following papers:
* [https://arxiv.org/abs/1405.0196 Determination of flow stress and the critical strain for the onset of dynamic recrystallization using a sine function]
* [https://dx.doi.org/10.1016/j.matdes.2013.08.055 Determination of flow stress and the critical strain for the onset of dynamic recrystallization using a hyperbolic tangent function]
* [https://dx.doi.org/10.1016/j.matdes.2009.09.001 Determination of critical strain for initiation of dynamic recrystallization]
* [https://www.researchgate.net/publication/260337084_Characteristic_points_of_stressstrain_curve_at_high_temperature Characteristic points of stress–strain curve at high temperature]
The DRX behavior for systems with multiple peaks (and single peak as well) can be modeled considering the interaction of multiple grains during deformation. I. e. the ensemble model describes the transition between single and multi peak behavior based on the initial grain size. It can also describe the effect of transient changes of the strain rate on the shape of the flow curve. The model can be found in the following paper:
* [https://doi.org/10.1016/j.msea.2015.08.085 A new unified approach for modeling recrystallization during hot rolling of steel] | 1 | Applied and Interdisciplinary Chemistry |
Nucleosomes are the basic packing unit of genomic DNA built from histone proteins around which DNA is coiled. They serve as a scaffold for formation of higher order chromatin structure as well as for a layer of regulatory control of gene expression. Nucleosomes are quickly assembled onto newly synthesized DNA behind the replication fork. | 1 | Applied and Interdisciplinary Chemistry |
In E. coli, it has been shown that an inducible, periplasmic TMAO reductase is responsible for almost all TMAO reduction (with the rest being DMSO reduction). While no structural analysis of this E. coli enzyme has been reported, TMAO reductase from Shewanella massilia has been isolated and characterized at a resolution of 2.5 Å.
TMAO reductases have been studied in several organisms, and a common feature is the presence of a molybdenum cofactor in all the known terminal enzymes. The common form of the molybdopterin molecule is a tricyclic ring system comprising a pterin group fused to a pyran ring. The role of this pyran ring could be a way of controlling the oxidation state of the molybdenum cofactor and/or facilitating proton diffusion. Furthermore, the arrangement of aromatic residues in the funnel-like entrance leading to the active center is closely related to that of DMSO reductase structures. A hydrophobic pocket, formed by two tryptophan and two tyrosine residues, is also present in the TMAO reductase and contains highly conserved residues.
When comparing TMAO reductase of S. massilia to DMSO reductase from R. Sphaeroides and R. capsulatus, the overall structure is strikingly similar. However, one major difference in TMAO reductase is a missing tyrosine (Tyr114), in DMSO reductase of R. capsulatus. It is replaced by a threonine (Thr116) in the TMAO reductase, and the backbone stretch around this residue, from residue 100 to 116, is not identical to that in the DMSO reductases. A direct consequence of the missing residue is a wider accessible space, adjacent to the molybdenum active center, which potentially exists to accommodates the somewhat bulkier trimethylamine-oxide molecules more easily than the dimethylsulfoxide molecules. This different demonstrates how an enzyme's form is almost always directly tied to its function.
However, recent discrepancies have risen regarding the structure of the TMAO reductase active site. The proposed active site contains several anomalous bond lengths; one Mo-O bond length is too short for a Mo-O single-bond coordination, and the four Mo-S bond lengths are all considerably longer than expected. Moreover, the proposed molybdenum coordination of the active site is extremely crowded, with the distances between several supposedly nonbonding atoms being significantly shorter than the sum of their van der Waals radii and some bond angles being unreasonably small. Now, it is being hypothesized that this overcrowding is due to the cocrystallization of multiple forms of the enzyme. | 1 | Applied and Interdisciplinary Chemistry |
UIT was originally developed in 1972 and has since been perfected by a team of Russian scientists under the leadership of Dr. Efim Statnikov. Originally developed and utilized to enhance the fatigue and corrosion attributes of ship and submarine structures, UIT has been utilized in aerospace, mining, offshore drilling, shipbuilding, infrastructure, automotive, energy production and other industries.
Different industrial solutions exist nowadays and are commercialized by a limited number of Original Equipment Manufacturers worldwide. | 1 | Applied and Interdisciplinary Chemistry |
This method mainly identifies variant function based on the information whether the variant loci are in the known functional region that harbor genomic or epigenomic signals. The function of non-coding variants are extensive in terms of the affected genomic region and they involve in almost all processes of gene regulation from transcriptional to post translational level | 1 | Applied and Interdisciplinary Chemistry |
In some metal-ammine complexes, the ammonia ligand can be oxidized to nitrosyl:
:HO + [Ru(terpy)(bipy)(NH)] → [Ru(terpy)(bipy)(NO)] + 5H + 6e | 0 | Theoretical and Fundamental Chemistry |
Metabolic ecology is a field of ecology aiming to understand constraints on metabolic organization as important for understanding almost all life processes. Main focus is on the metabolism of individuals, emerging intra- and inter-specific patterns, and the evolutionary perspective.
Two main metabolic theories that have been applied in ecology are Kooijman's Dynamic energy budget (DEB) theory and the West, Brown, and Enquist (WBE) theory of ecology. Both theories have an individual-based metabolic underpinning, but have fundamentally different assumptions.
Models of individual's metabolism follow the energy uptake and allocation, and can focus on mechanisms and constraints of energy transport (transport models), or on dynamic use of stored metabolites (energy budget models). | 1 | Applied and Interdisciplinary Chemistry |
GLD-2, as a poly(A) polymerase (PAP) acts incorporating ATP at the 3' end of mRNAs in a template-independent manner. | 1 | Applied and Interdisciplinary Chemistry |
In biology, the biological cost or metabolic price is a measure of the increased energy metabolism that is required to achieve a function. Drug resistance in microbiology, for instance, has a very high metabolic price, especially for antibiotic resistance. | 1 | Applied and Interdisciplinary Chemistry |
In modern English clinamen is defined as an inclination or a bias. The OED gives its first recorded use in English by Jonathan Swift in his 1704 Tale of a Tub ix.166, satirizing the atomistic theory of Epicurus:
The term was taken up by Harold Bloom to describe the inclinations of writers to "swerve" from the influence of their predecessors; it is the first of his "Ratios of Revision" as described in The Anxiety of Influence.
In Difference and Repetition, Gilles Deleuze employs the term in his description of "multiplicities". In addition, other French writers such as Simone de Beauvoir, Jacques Lacan, Jacques Derrida, Jean-Luc Nancy, Alain Badiou, Louis Althusser, and Michel Serres have made extensive use of the word clinamen in their writings, albeit with very different meanings.
Lucretius concept is central to the book The Swerve: How the World Became Modern', written by Stephen Greenblatt.
"Clinamen" is defined by Alfred Jarry in Chapter 33 of his Exploits and Opinions of Dr. Faustroll, Pataphysician. The notion later figured in the imaginary science of the Jarry-inspired College of Pataphysics, notably in the pataphysical calendar and the experimental literature of OuLiPo. The clinamen figures as a motif in the artistic practice of Rodney Graham – who has said it informs his work in general.
Clinamen is also a term used in systems theory applied to biology. | 1 | Applied and Interdisciplinary Chemistry |
An interesting phenomenon called self-lubricate spinning can facilitate the demolding of the fiber and enables the continuous production of hydrogel fiber from tubular mold. During the polymerization process, if an inert second polymer is present, it will be particularly expelled from the formed network and being able to move with relative ease. The linear polymer on the surface of the crosslinked network also contains water solvent due to the osmic pressure, thus, a lubrication layer is formed. Therefore, the solidified polymer fiber can exit the tube with decreased friction force and continuous production can be achieved.
An example would be the production the PAAM/PAMPS semi-interpenetration network hydrogel fiber reported by Zhao et al. The pregel solution was the mixture of PAMPS, AAM, PEGDA (crosslinker), and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (photoinitiator). The pregel solution was fed into a PTFE tube at a constant speed, with UV light being used to initiate the reaction. | 0 | Theoretical and Fundamental Chemistry |
Cohort studies are impractical for the study of domestic radon exposure. With the expected effect of small exposures being very small, the direct observation of this effect would require huge cohorts: the populations of whole countries.
Several ecological studies have been performed to assess possible relationships between selected cancers and estimated radon levels within particular geographic regions where environmental radon levels appear to be higher than other geographic regions.
Results of such ecological studies are mixed; both positive and negative associations, as well as no significant associations, have been suggested.
The most direct way to assess the risks posed by radon in homes is through case-control studies.
The studies have not produced a definitive answer, primarily because the risk is likely to be very small at the low exposure encountered from most homes and because it is difficult to estimate radon exposures that people have received over their lifetimes. In addition, it is clear that far more lung cancers are caused by smoking than are caused by radon.
Epidemiologic radon studies have found trends to increased lung cancer risk from radon with a no evidence of a threshold, and evidence against a threshold above high as 150 Bq/m (almost exactly the EPA's action level of 4 pCi/L). Another study similarly found that there is no evidence of a threshold but lacked the statistical power to clearly identify the threshold at this low level. Notably, the latter deviance from zero at low level convinced the World Health Organization that, "The dose-response relation seems to be linear without evidence of a threshold, meaning that the lung cancer risk increases proportionally with increasing radon exposure."
The most elaborate case-control epidemiologic radon study performed by R. William Field and colleagues identified a 50% increased lung cancer risk with prolonged radon exposure at the EPA's action level of 4 pCi/L. Iowa has the highest average radon concentrations in the United States and a very stable population which added to the strength of the study. For that study, the odds ratio was found to be increased slightly above the confidence interval (95% CI) for cumulative radon exposures above 17 WLM (6.2 pC/L=230 Bq/m and above).
The results of a methodical ten-year-long, case-controlled study of residential radon exposure in Worcester County, Massachusetts, found an apparent 60% reduction in lung cancer risk amongst people exposed to low levels (0–150 Bq/m) of radon gas; levels typically encountered in 90% of American homes—an apparent support for the idea of radiation hormesis. In that study, a significant result (95% CI) was obtained for the 75–150 Bq/m category.
The study paid close attention to the cohort's levels of smoking, occupational exposure to carcinogens and education attainment. However, unlike the majority of the residential radon studies, the study was not population-based. Errors in retrospective exposure assessment could not be ruled out in the finding at low levels. Other studies into the effects of domestic radon exposure have not reported a hormetic effect; including for example the respected "Iowa Radon Lung Cancer Study" of Field et al. (2000), which also used sophisticated radon exposure dosimetry. | 1 | Applied and Interdisciplinary Chemistry |
Radicals formed on the polymer backbone by either hydrogen abstraction side-group elimination can cause the chain to break by beta scission. As a result the molecular weight decreases rapidly. As new free radicals with high reactivity are formed, monomers cannot be a product of this reaction, also intermolecular chain transfer and disproportion termination reactions can occur.
CH-CH-CH-CH-CH-CH-CH’→
CH-CH-CH=CH + CH-CH-CH’ or
CH’+CH=CH-CH-CH-CH-CH
As polymers approach their ceiling temperature scission starts to take place randomly on the backbone. | 0 | Theoretical and Fundamental Chemistry |
Triglycerides are formed from the esterification of 3 molecules of fatty acids with one molecule of trihydric alcohol, glycerol (glycerine or trihydroxy propane). In the process, 3 molecules of water are eliminated. The word "triglyceride" refers to the number of fatty acids esterified to one molecule of glycerol.
In triglycerides, the three fatty acids are rarely similar and are thus called pure fats. For example, tripalmitin, tristearin, etc. | 1 | Applied and Interdisciplinary Chemistry |
The filtering operation in large eddy simulation can be implicit or explicit. Implicit filtering recognizes that the subfilter scale model will dissipate in the same manner as many numerical schemes. In this way, the grid, or the numerical discretization scheme, can be assumed to be the LES low-pass filter. While this takes full advantage of the grid resolution, and eliminates the computational cost of calculating a subfilter scale model term, it is difficult to determine the shape of the LES filter that is associated with some numerical issues. Additionally, truncation error can also become an issue.
In explicit filtering, an LES filter is applied to the discretized Navier–Stokes equations, providing a well-defined filter shape and reducing the truncation error. However, explicit filtering requires a finer grid than implicit filtering, and the computational cost increases with . Chapter 8 of Sagaut (2006) covers LES numerics in greater detail. | 1 | Applied and Interdisciplinary Chemistry |
Under basic, protic conditions, 2,3-epoxy alcohols undergo a rearrangement in which the alcohol oxygen opens the epoxide with inversion of configuration, forming an isomeric 1,2-epoxy alcohol. Overall, the Payne rearrangement represents a migration of the epoxide. Although the migration itself is fully reversible, nucleophilic opening under Curtin–Hammett conditions provides good yields of functionalized diols derived from a single epoxy alcohol isomer. Intramolecular electrophilic trapping of the new alkoxide generated upon rearrangement may also be used to drive the reaction to completion. In some cases, the thermodynamic difference between epoxide isomers is large enough to obtain a single isomer in synthetically useful yield without relying on kinetic differences associated with trapping.
Strongly basic conditions are required to induce equilibration, which limits the synthetic utility of the transformation to substrates lacking base-labile functionality. Many epoxy alcohol equilibria are very finely balanced; however, taking advantage of the trapping strategies described above may lead to high yields of single isomers. | 0 | Theoretical and Fundamental Chemistry |
For Regime I, the growth rate on the front laterally, referred to as g, is the rate-determining step (RDS) and exceeds the secondary nucleation rate, i. In this instance of g >> i, monolayers are formed one at a time so that if the substrate has a length of L and thickness, b, the overall linear growth can be described through the equation
and the rate of nucleation in specific can further be described by
with K equal to
where
This shows that in Region I, lateral nucleation along the front successfully dominates at temperatures close to the melting temperature, however at more extreme temperatures other forces such as diffusion can impact nucleation rates.
In Regime II, the lateral growth rate is either comparable or smaller than the nucleation rate g ≤ i, which causes secondary (or more) layers to form before the initial layer has been covered. This allows the linear growth rate to be modeled by
Using the assumption that g and i are independent of time, the rate at which new layers are formed can be approximated and the rate of nucleation in regime II can be expressed as
with K equal to about 1/2 of the K from Regime I,
Lastly, Regime III in the L-H model depicts the scenario where lateral growth is inconsequential to the overall rate, since the nucleation of multiple sites causes i >> g. This means that the growth rate can be modeled by the same equation as Regime I,
where G is the prefactor for Regime III and can be experimentally determined through applying the Lauritzen–Hoffman Plot. | 0 | Theoretical and Fundamental Chemistry |
The vanishing valentine experiment is another chemical reaction related to the blue bottle experiment. This reaction occurs when water, glucose, sodium hydroxide, and resazurin is mixed in a flask. When the solution is shaken, it turns from light blue to a reddish color. The solution turns back to a light blue after being left to stand for a while. This reaction can be repeated several times.
After mixing all the components, shake the bottle and the color will turn to red or pink depend on the amount of resazurin in the solution. More resazurin will result in more time needed for the solution to turn back the color and the intensity of the red color.
The chemical reaction stimulates glucose to reduce resazurin to resorufin. It would then be reduced again into a colorless compound called dihydroresorufin. When dihydroresorufin is shaken, it is oxidized back to resorufin. This is due to the fact that shaking it results oxygen in the bottle to oxidized dihydroresorufin back into resorufin. | 1 | Applied and Interdisciplinary Chemistry |
Under certain circumstances, flows of granular materials can be modelled as a continuum, for example using the μ(I) rheology. Such continuum models tend to be non-Newtonian, since the apparent viscosity of granular flows increases with pressure and decreases with shear rate. The main difference is the shearing stress and rate of shear. | 1 | Applied and Interdisciplinary Chemistry |
Tetrafluoroethane is typically made by reacting trichloroethylene with hydrogen fluoride:
:CHCl=CCl + 4 HF → CFCHF + 3 HCl
It reacts with butyllithium to give trifluorovinyl lithium:
:CFCHF + 2 BuLi → CF=CFLi + LiF + 2 BuH | 1 | Applied and Interdisciplinary Chemistry |
In pharmacology, an endogenous agonist for a particular receptor is a compound naturally produced by the body which binds to and activates that receptor. For example, the primary endogenous agonist for serotonin receptors is serotonin, and the primary endogenous agonist for dopamine receptors is dopamine.
In general, receptors for small molecule neurotransmitters such as serotonin will have only one endogenous agonist, but often have many different receptor subtypes (e.g. 13 different receptors for serotonin). On the other hand, neuropeptide receptors tend to have fewer subtypes, but may have several different endogenous agonists. This allows for a high degree of complexity in the body's signalling system, with different tissues often showing quite distinct responses to a particular ligand. Some endogenous antagonists and inverse agonists are also known (e.g., kynurenic acid at the NMDA receptor), but these are much less common. | 1 | Applied and Interdisciplinary Chemistry |
An entrepreneurial-minded Ted Ellis has marketed and sold his art throughout his career. He was already monetizing his creative talents in high school when his classmates and he sold their custom designed T-shirts, first to their school's juniors and seniors, and then throughout the school district.
In building his art business over two decades, Ellis engaged in fact-finding missions in search of financial patrons and customers at art festivals, conventions, reunions and libraries, as well as local businesses. Ellis incorporated his business in 1991. He credits his time at Rollins for teaching him that "if you have a quality product and a good form of distribution, you'll succeed".
When he first got started, Ellis quickly realized that talent was not alone enough after he had to approach 30–40 galleries until he was picked up by two, one of which closed down. He says that "it's a lot of marketing, planning, exhibiting and a lot of rejection".
Ted's wife Erenia, a loan officer, manages his business, "T. Ellis Art, Incorporated", out of a League City, Texas studio. Ellis has sold more than 1.75 million fine art products across the country through direct sales, art galleries, catalog outlets, fine art dealers, and licensing, and has marketed community partnership opportunities meant to educate and empower communities by offering maximum returns on minimal investments. In 2005 he signed for representation with art licensing agency "Alaska Momma" with the intent of opening new merchandising avenues in home décor, furnishings, calendars, apparel and stationery.
Ellis has affiliated with and had art commissioned by corporations like Walt Disney Studios, Minute Maid, Coca-Cola, Marathon Oil, ExxonMobil, State Farm Insurance, Merck Pharmaceutical, J. C. Penney, Southland Corporation, and Avon Products, Philip Morris USA and Integrity Music.
Ellis works have been sold through Army and Air Force Exchange Service catalogs and were available exclusively both through Avons African American Boutique as well as their core brochures.
One of his first major sales was of an original depicting a God-like surgeon in an operating-room, sold to the surgeon. Ellis' art has sold for prices ranging from $750 to $30,000.
Despite his success, while Ellis initially had hoped to build his business up to Fortune 500 stature, he now finds satisfaction in "helping others through art". | 0 | Theoretical and Fundamental Chemistry |
5-Methoxyhydnocarpin (5′-MHC) is a chemical compound that has been isolated from Berberis and Hydnocarpus wightianus'.
5′-MHC potentiates the antimicrobial effect of berberine in vitro. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, the Fischer projection, devised by Emil Fischer in 1891, is a two-dimensional representation of a three-dimensional organic molecule by projection. Fischer projections were originally proposed for the depiction of carbohydrates and used by chemists, particularly in organic chemistry and biochemistry. The use of Fischer projections in non-carbohydrates is discouraged, as such drawings are ambiguous and easily confused with other types of drawing. The main purpose of Fischer projections is to show the chirality of a molecule and to distinguish between a pair of enantiomers. Some notable uses include drawing sugars and depicting isomers. | 0 | Theoretical and Fundamental Chemistry |
A classical event is the retroposition of a spliced pre-mRNA molecule of the c-Src gene into the proviral ancestor of the Rous sarcoma virus (RSV). The retroposed c-src pre-mRNA still contained a single intron and within RSV is now referred to as v-Src gene. | 1 | Applied and Interdisciplinary Chemistry |
In the 1960s, Liu and his colleagues were tasked with recycling nuclear fuels from China's nuclear reactors. He worked under primitive conditions and was exposed to radiation for more than a decade, which caused his hair to turn gray before he was 40.
Starting in 1974, Liu focused on the application of nuclear science in medical fields and the research and development of radiopharmaceuticals. He became a professor at Beijing Normal University and served as deputy chair of its chemistry department and director of its Institute of Applied Chemistry. He made important discoveries in the properties of technetium-99m (99mTc), a radioactive isotope of technetium, and developed several medicines using 99mTc. He also researched radioactive isotopes of halogens, including bromine-82, iodine-131, and astatine-211.
Liu's research won many awards, including the National Science and Technology Conference Award (1979), the State Education Commission Science and Technology Progress Award, Second Class (1993 and 1998), and the State Science and Technology Progress Award, Second Class (1999). He was elected as an academician of the Chinese Academy of Engineering in 1997. | 0 | Theoretical and Fundamental Chemistry |
The word "viscosity" is derived from the Latin ("mistletoe"). also referred to a viscous glue derived from mistletoe berries. | 1 | Applied and Interdisciplinary Chemistry |
An electro-switchable biosurface is a biosensor that is based on an electrode (often gold) to which a layer of biomolecules (often DNA molecules) has been tethered. An alternating or fixed electrical potential is applied to the electrode which causes changes in the structure and position (movement) of the charged biomolecules. The biosensor is used in science, e.g. biomedical and biophysical research or drug discovery, to assess interactions between biomolecules and binding kinetics as well as changes in size or conformation of biomolecules. | 1 | Applied and Interdisciplinary Chemistry |
Fused quartz, fused silica or quartz glass is a glass consisting of almost pure silica (silicon dioxide, SiO) in amorphous (non-crystalline) form. This differs from all other commercial glasses in which other ingredients are added which change the glasses' optical and physical properties, such as lowering the melt temperature. Fused quartz, therefore, has high working and melting temperatures, making it less desirable for most common applications.
The terms fused quartz and fused silica are used interchangeably but can refer to different manufacturing techniques, as noted below, resulting in different trace impurities. However fused quartz, being in the glassy state, has quite different physical properties compared to crystalline quartz. Due to its physical properties it finds specialty uses in semiconductor fabrication and laboratory equipment, for instance.
Compared to other common glasses, the optical transmission of pure silica extends well into the ultraviolet and infrared wavelengths, so is used to make lenses and other optics for these wavelengths. Depending on manufacturing processes, impurities will restrict the optical transmission, resulting in commercial grades of fused quartz optimized for use in the infrared, or (then more often referred to as fused silica) in the ultraviolet. The low coefficient of thermal expansion of fused quartz makes it a useful material for precision mirror substrates. | 1 | Applied and Interdisciplinary Chemistry |
Blue flower colour was always associated with something unusual and desired. Blue roses especially were assumed to be a dream that cannot be realised. Blue colour in flower petals is caused by anthocyanins, which are members of flavonoid class metabolites. We can diversify three main classes of anthocyanin pigments: cyaniding type (two hydroxyl groups in the B-ring) responsible for red coloration, pelargonidin type (one hydroxyl group in the B-ring) responsible for orange colour and delphinidin type (three hydroxyl groups in the B-ring) responsible for violet/blue flower and fruits coloration. The main difference in the structure of listed anthocyanins type is the number of hydroxyl groups in the B-ring of the anthocyanin. Nevertheless, in the monomeric state anthocyanins never show blue colour in the weak acidic and neutral pH. The mechanism of blue colour formation are very complicated in most cases, presence of delphinidin type pigments is not sufficient, great role play also the pH and the formation of complexes of anthocyanins with flavones and metal ions. | 1 | Applied and Interdisciplinary Chemistry |
Bromotrifluoromethane is commercially synthesized in a two-step process from chloroform. Chloroform is fluorinated with hydrogen fluoride.
CHCl3 + 3 HF → CHF3 + 3 HCl
The resulting Fluoroform is then reacted with elemental bromine.
CHF3 + Br2 → CF3Br + HBr | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, neighbouring group participation (NGP, also known as anchimeric assistance) has been defined by the International Union of Pure and Applied Chemistry (IUPAC) as the interaction of a reaction centre with a lone pair of electrons in an atom or the electrons present in a sigma or pi bond contained within the parent molecule but not conjugated with the reaction centre. When NGP is in operation it is normal for the reaction rate to be increased. It is also possible for the stereochemistry of the reaction to be abnormal (or unexpected) when compared with a normal reaction. While it is possible for neighbouring groups to influence many reactions in organic chemistry (e.g. the reaction of a diene such as 1,3-cyclohexadiene with maleic anhydride normally gives the endo isomer because of a secondary effect {overlap of the carbonyl group π orbitals with the transition state in the Diels-Alder reaction}) this page is limited to neighbouring group effects seen with carbocations and S2 reactions. | 0 | Theoretical and Fundamental Chemistry |
Some viruses (e.g. tobacco mosaic virus (TMV)) have RNA sequences that contain a "leaky" stop codon. In TMV 95% of the time the host ribosome will terminate the synthesis of the polypeptide at this codon but the rest of the time it continues past it. This means that 5% of the proteins produced are larger than and different from the others normally produced, which is a form of translational regulation. In TMV, this extra sequence of polypeptide is an RNA polymerase that replicates its genome. | 1 | Applied and Interdisciplinary Chemistry |
The formal definition of the Gibbs free energy for a parcel of volume , pressure and temperature is given by:
where is the internal energy and is the entropy. The differential form of the Gibbs free energy can be given as
where is the chemical potential and is the number of moles. Suppose we have a substance which contains no impurities. Let's consider the formation of a single drop of with radius containing molecules from its pure vapor. The change in the Gibbs free energy due to this process is
where and are the Gibbs energies of the drop and vapor respectively. Suppose we have molecules in the vapor phase initially. After the formation of the drop, this number decreases to , where
Let and represent the Gibbs free energy of a molecule in the vapor and liquid phase respectively. The change in the Gibbs free energy is then:
where is the Gibbs free energy associated with an interface with radius of curvature and surface tension . The equation can be rearranged to give
Let and be the volume occupied by one molecule in the liquid phase and vapor phase respectively. If the drop is considered to be spherical, then
The number of molecules in the drop is then given by
The change in Gibbs energy is then
The differential form of the Gibbs free energy of one molecule at constant temperature and constant number of molecules can be given by:
If we assume that then
The vapor phase is also assumed to behave like an ideal gas, so
where is the Boltzmann constant. Thus, the change in the Gibbs free energy for one molecule is
where is the saturated vapor pressure of over a flat surface and is the actual vapor pressure over the liquid. Solving the integral, we have
The change in the Gibbs free energy following the formation of the drop is then
The derivative of this equation with respect to is
The maximum value occurs when the derivative equals zero. The radius corresponding to this value is:
Rearranging this equation gives the Ostwald–Freundlich form of the Kelvin equation: | 0 | Theoretical and Fundamental Chemistry |
The methods used for small parts and jewellery vary somewhat from those used for sculpture. A wax model is obtained either from injection into a rubber mould or by being custom-made by carving. The wax or waxes are sprued and fused onto a rubber base, called a "sprue base". Then a metal flask, which resembles a short length of steel pipe that ranges roughly from 3.5 to 15 centimeters tall and wide, is put over the sprue base and the waxes. Most sprue bases have a circular rim which grips the standard-sized flask, holding it in place. Investment (refractory plaster) is mixed and poured into the flask, filling it. It hardens, then is burned out as outlined above. Casting is usually done straight from the kiln either by centrifugal casting or vacuum casting.
The lost-wax process can be used with any material that can burn, melt, or evaporate to leave a mould cavity. Some automobile manufacturers use a lost-foam technique to make engine blocks. The model is made of polystyrene foam, which is placed into a casting flask, consisting of a cope and drag, which is then filled with casting sand. The foam supports the sand, allowing shapes that would be impossible if the process had to rely on the sand alone. The metal is poured in, vaporizing the foam with its heat.
In dentistry, gold crowns, inlays and onlays are made by the lost-wax technique. Application of Lost Wax technique for the fabrication of cast inlay was first reported by Taggart. A typical gold alloy is about 60% gold and 28% silver with copper and other metals making up the rest. Careful attention to tooth preparation, impression taking and laboratory technique are required to make this type of restoration a success. Dental laboratories make other items this way as well. | 1 | Applied and Interdisciplinary Chemistry |
For liquids, various units are used depending upon the application and industry, but might include gallons (U.S. or imperial) per minute, liters per second, liters per m per hour, bushels per minute or, when describing river flows, cumecs (cubic meters per second) or acre-feet per day. In oceanography a common unit to measure volume transport (volume of water transported by a current for example) is a sverdrup (Sv) equivalent to 10 m/s. | 1 | Applied and Interdisciplinary Chemistry |
Drugs affecting the central nervous system include psychedelics, hypnotics, anaesthetics, antipsychotics, eugeroics, antidepressants (including tricyclic antidepressants, monoamine oxidase inhibitors, lithium salts, and selective serotonin reuptake inhibitors (SSRIs)), antiemetics, anticonvulsants/antiepileptics, anxiolytics, barbiturates, movement disorder (e.g., Parkinson's disease) drugs, nootropics, stimulants (including amphetamines), benzodiazepines, cyclopyrrolones, dopamine antagonists, antihistamines, cholinergics, anticholinergics, emetics, cannabinoids, and 5-HT (serotonin) antagonists. | 1 | Applied and Interdisciplinary Chemistry |
Acetate esters and acetamides are generally prepared by acetylations. Acetylations are often used in making C-acetyl bonds in Friedel-Crafts reactions. Carbanions and their equivalents are susceptible to acetylations. | 0 | Theoretical and Fundamental Chemistry |
After completing his PhD, Fuchter moved to Australia, for postdoctoral research at CSIRO and the University of Melbourne, where he worked with Andrew Bruce Holmes.
In 2007 Fuchter returned to the United Kingdom, where he began his independent academic career at the School of Pharmacy, University of London (now UCL School of Pharmacy). Less than one year later he was appointed a Lecturer at Imperial College London, where he was promoted to Reader (Associate Professor) in 2015 and Professor in 2019.
Fuchter is interested in how considerations of chirality can be applied to the development of novel approaches in chiral optoelectronic materials and devices. In particular, he focusses on the introduction of chiral-optical (so-called chiroptical) properties into optoelectronic materials. Amongst these materials, Fuchter has extensively evaluated the use of chiral small molecule additives (helicenes) to induce chiroptical properties into light emitting polymers for the realisation of chiral (circularly polarised, CP) OLEDs. He has also investigated the application of such materials in circularly polarised photodetectors, which are devices that are capable of detecting circularly polarised light. As well as using chiral functional materials for light emission and detection, Fuchter has investigated the charge transport properties of enantiopure and racemic chiral functional materials.
Fuchter has also developed novel molecular photoswitches – molecules that can be cleanly and reversibly interconverted between two states using light – with a focus on heteroaromatic versions of azobenzene. The arylazopyrazole switches developed by Fuchter out perform the ubiquitous azobenzene switches, demonstrating complete photoswitching in both directions and thermal half-lives of the Z isomer of up to 46 years. Fuchter continues to apply these switches to a range of photoaddressable applications from photopharmacology to energy storage.
Alongside his work on functional material discovery, Fuchter works in medicinal chemistry and develops small molecule ligands that can either inhibit or stimulate the activity of disease relevant proteins. While he has worked on many drug targets, he has specialised in proteins involved in the transcriptional and epigenetic processes of disease. A particular interest has been the development of inhibitors for the histone-lysine methyltransferase enzymes in the Plasmodium parasite that causes human malaria.
In 2018 one of the cancer drugs developed by Fuchter, together with Anthony Barrett, Simak Ali and Charles Coombes entered a phase 1 clinical trial, and as of 2020, it is in phase 2. The drug, which was designed using computational chemistry, inhibits the cyclin-dependent kinase 7 (CDK7), a transcriptional regulatory protein that also regulates the cell cycle. Certain cancers rely on CDK7, so inhibition of this enzyme has potential to have a significant impact on cancer pathogenesis. | 1 | Applied and Interdisciplinary Chemistry |
The isotropy of the cellular structure and the absorption of fluids can also have an impact on the mechanical properties of a foam. If there is anisotropy present, then the materials response to stress will be directionally dependent, and thus the stress-strain curve, modulus, and energy absorption will vary depending on the direction of applied force. Also, open-cell structures which have connected pores can allow water or other liquids to flow through the structure, which can also affect the rigidity and energy absorption capabilities. | 0 | Theoretical and Fundamental Chemistry |
The linearity of the Stokes equations in the case of an incompressible Newtonian fluid means that a Greens function, , exists. The Greens function is found by solving the Stokes equations with the forcing term replaced by a point force acting at the origin, and boundary conditions vanishing at infinity:
where is the Dirac delta function, and represents a point force acting at the origin. The solution for the pressure p and velocity u with |u| and p vanishing at infinity is given by
where
is a second-rank tensor (or more accurately tensor field) known as the Oseen tensor (after Carl Wilhelm Oseen). Here, r r is a quantity such that .
The terms Stokeslet and point-force solution are used to describe . Analogous to the point charge in electrostatics, the Stokeslet is force-free everywhere except at the origin, where it contains a force of strength .
For a continuous-force distribution (density) the solution (again vanishing at infinity) can then be constructed by superposition:
This integral representation of the velocity can be viewed as a reduction in dimensionality: from the three-dimensional partial differential equation to a two-dimensional integral equation for unknown densities. | 1 | Applied and Interdisciplinary Chemistry |
As the mandelic acid salt (methenamine mandelate) or the hippuric acid salt (methenamine hippurate), it is used for the treatment of urinary tract infections. In an acidic environment, methenamine is believed to act as an antimicrobial by converting to formaldehyde. A systematic review of its use for this purpose in adult women found there was insufficient evidence of benefit and further research was needed. A UK study showed that methenamine is as effective as daily low-dose antibiotics at preventing UTIs among women who experience recurrent UTIs. As methenamine is an antiseptic, it may avoid the issue of antibiotic resistance.
Methenamine acts as an over-the-counter antiperspirant due to the astringent property of formaldehyde. Specifically, methenamine is used to minimize perspiration in the sockets of prosthetic devices. | 0 | Theoretical and Fundamental Chemistry |
The Kesternich test is a common name for the corrosion test with sulfur dioxide (SO) under general moisture condensation. This test was developed in 1951 by Wilhelm Kesternich to simulate the damaging effects of acid rain.
Acid rain and acidic industrial pollutants are corrosive and can degrade coatings and plated surfaces. Kesternich testing, or sulfur dioxide testing, simulates acid rain or industrial chemical exposure to evaluate the relative corrosion resistance of the coating, substrate, or part itself. The test can be used for coatings or for base materials.
The test method is defined by various standards, DIN EN ISO 6988, DIN 50018, ASTM G87, ISO 3231, ISO 22479 are the most common. The parts to be tested are placed in a test chamber with a capacity of 300L and exposed to warm, moist air in combination with a certain amount of sulfur dioxide
Note: Sulfur is interchangeable with Sulphur and SO2 is the abbreviation for Sulfur/Sulphur Dioxide | 1 | Applied and Interdisciplinary Chemistry |
The glycosidic bond can be formed between any hydroxy group on the component monosaccharide. So, even if both component sugars are the same (e.g., glucose), different bond combinations (regiochemistry) and stereochemistry (alpha- or beta-) result in disaccharides that are diastereoisomers with different chemical and physical properties. Depending on the monosaccharide constituents, disaccharides are sometimes crystalline, sometimes water-soluble, and sometimes sweet-tasting and sticky-feeling. Disaccharides can serve as functional groups by forming glycosidic bonds with other organic compounds, forming glycosides. | 0 | Theoretical and Fundamental Chemistry |
The increase in intensity of the Raman signal for adsorbates on particular surfaces occurs because of an enhancement in the electric field provided by the surface. When the incident light in the experiment strikes the surface, localized surface plasmons are excited. The field enhancement is greatest when the plasmon frequency, ω, is in resonance with the radiation ( for spherical particles). In order for scattering to occur, the plasmon oscillations must be perpendicular to the surface; if they are in-plane with the surface, no scattering will occur. It is because of this requirement that roughened surfaces or arrangements of nanoparticles are typically employed in SERS experiments as these surfaces provide an area on which these localized collective oscillations can occur. SERS enhancement can occur even when an excited molecule is relatively far apart from the surface which hosts metallic nanoparticles enabling surface plasmon phenomena.
The light incident on the surface can excite a variety of phenomena in the surface, yet the complexity of this situation can be minimized by surfaces with features much smaller than the wavelength of the light, as only the dipolar contribution will be recognized by the system. The dipolar term contributes to the plasmon oscillations, which leads to the enhancement. The SERS effect is so pronounced because the field enhancement occurs twice. First, the field enhancement magnifies the intensity of incident light, which will excite the Raman modes of the molecule being studied, therefore increasing the signal of the Raman scattering. The Raman signal is then further magnified by the surface due to the same mechanism that excited the incident light, resulting in a greater increase in the total output. At each stage the electric field is enhanced as E, for a total enhancement of E.
The enhancement is not equal for all frequencies. For those frequencies for which the Raman signal is only slightly shifted from the incident light, both the incident laser light and the Raman signal can be near resonance with the plasmon frequency, leading to the E enhancement. When the frequency shift is large, the incident light and the Raman signal cannot both be on resonance with ω, thus the enhancement at both stages cannot be maximal.
The choice of surface metal is also dictated by the plasmon resonance frequency. Visible and near-infrared radiation (NIR) are used to excite Raman modes. Silver and gold are typical metals for SERS experiments because their plasmon resonance frequencies fall within these wavelength ranges, providing maximal enhancement for visible and NIR light. Copper's absorption spectrum also falls within the range acceptable for SERS experiments. Platinum and palladium nanostructures also display plasmon resonance within visible and NIR frequencies. | 0 | Theoretical and Fundamental Chemistry |
Most surfactants are organic compounds with hydrophilic "heads" and hydrophobic "tails." The "heads" of surfactants are polar and may or may not carry an electrical charge. The "tails" of most surfactants are fairly similar, consisting of a hydrocarbon chain, which can be branched, linear, or aromatic. Fluorosurfactants have fluorocarbon chains. Siloxane surfactants have siloxane chains.
Many important surfactants include a polyether chain terminating in a highly polar anionic group. The polyether groups often comprise ethoxylated (polyethylene oxide-like) sequences inserted to increase the hydrophilic character of a surfactant. Polypropylene oxides conversely, may be inserted to increase the lipophilic character of a surfactant.
Surfactant molecules have either one tail or two; those with two tails are said to be double-chained.
Most commonly, surfactants are classified according to polar head group. A non-ionic surfactant has no charged groups in its head. The head of an ionic surfactant carries a net positive, or negative, charge. If the charge is negative, the surfactant is more specifically called anionic; if the charge is positive, it is called cationic. If a surfactant contains a head with two oppositely charged groups, it is termed zwitterionic, or amphoteric. Commonly encountered surfactants of each type include: | 0 | Theoretical and Fundamental Chemistry |
Medical uses include:
* High blood pressure
* Congestive heart failure
* Following heart attack in people with evidence of heart failure
* People over 55 years at high risk: prevention of heart attack, stroke, cardiovascular death, or in need of revascularization procedures
* Prevent the onset and/or delay the progression of diabetic kidney disease, with or without proteinuria. Randomized trial evidence suggests that a maximum tolerable dose prevents cardiovascular events and death in patients with diabetic kidney disease. | 0 | Theoretical and Fundamental Chemistry |
Reciprocal space (also called -space) provides a way to visualize the results of the Fourier transform of a spatial function. It is similar in role to the frequency domain arising from the Fourier transform of a time dependent function; reciprocal space is a space over which the Fourier transform of a spatial function is represented at spatial frequencies or wavevectors of plane waves of the Fourier transform. The domain of the spatial function itself is often referred to as real space. In physical applications, such as crystallography, both real and reciprocal space will often each be two or three dimensional. Whereas the number of spatial dimensions of these two associated spaces will be the same, the spaces will differ in their quantity dimension, so that when the real space has the dimension length (L), its reciprocal space will of inverse length, so L (the reciprocal of length).
Reciprocal space comes into play regarding waves, both classical and quantum mechanical. Because a sinusoidal plane wave with unit amplitude can be written as an oscillatory term , with initial phase , angular wavenumber and angular frequency , it can be regarded as a function of both and (and the time-varying part as a function of both and ). This complementary role of and leads to their visualization within complementary spaces (the real space and the reciprocal space). The spatial periodicity of this wave is defined by its wavelength , where ; hence the corresponding wavenumber in reciprocal space will be .
In three dimensions, the corresponding plane wave term becomes , which simplifies to at a fixed time , where is the position vector of a point in real space and now is the wavevector in the three dimensional reciprocal space. (The magnitude of a wavevector is called wavenumber.) The constant is the phase of the wavefront (a plane of a constant phase) through the origin at time , and is a unit vector perpendicular to this wavefront. The wavefronts with phases , where represents any integer, comprise a set of parallel planes, equally spaced by the wavelength . | 0 | Theoretical and Fundamental Chemistry |
In the Yājñavalkya Smṛti, Nyāya is mentioned as one of the fourteen principal branches of learning. The Matsya-Purāṇa states that knowledge of Nyāya came from the mouth of Brahmā. The Mahābhārata also mentions principles of Nyāya.
The earliest text of the Nyāya School is the of Akṣapāda Gautama|. The text is divided into five books, each having two sections. Vātsāyana|s is a classic commentary on the . Udyotakaras (6th century CE) is written to defend against the attacks made by Dignāga. Vacaspati Misra|s (9th century CE) is the next major exposition of this school. Two other texts, and are also attributed to him. Udayanas (984 CE) is an important commentary on s treatise. His is the first systematic account of theistic . His other works include , and . Jayanta Bhattas (10th century CE) is basically an independent work. s (10th century CE) is a survey of ' philosophy.
The later works on accepted the Vaisheshika| categories and s (12th century CE) is a notable treatise of this syncretist school. s (13th century CE) is another important work of this school.
s (14th century CE) is the first major treatise of the new school of . His son, s , though a commentary on Udayanas , incorporated his fathers views. Jayadeva wrote a commentary on Tattvacintāmaṇi| known as (14th century CE). s (16th century CE) is first great work of Navadvipa school of . Raghunatha Siromani|s and are the next important works of this school. Visvanatha Panchanana Bhattacharya|s (17th century CE) is also a notable work. The Commentaries on ' by Jagadish Tarkalankar (17th century CE) and Gadadhar Bhattacharya (17th century CE) are the last two notable works of this school.
Annambhatta| (17th century CE) tried to develop a consistent system by combining the ancient and the new schools, and and to develop the school. His and are the popular manuals of this school. | 1 | Applied and Interdisciplinary Chemistry |
The Scenedesmus obliquus mitochondrial code (translation table 22) is a genetic code found in the mitochondria of Scenedesmus obliquus, a species of green algae. | 1 | Applied and Interdisciplinary Chemistry |
The low-flow-rate method is based on the fact that the extraction efficiency is dependent on the flow-rate. At high flow-rates, the amount of drug diffusing from the sampling site into the dialysate per unit time is smaller (low extraction efficiency) than at lower flow-rates (high extraction efficiency). At a flow-rate of zero, a total equilibrium between these two sites is established (C = C). This concept is applied for the (low-)flow-rate method, where the probe is perfused with blank perfusate at different flow-rates. Concentration at the sampling site can be determined by plotting the extraction ratios against the corresponding flow-rates and extrapolating to zero-flow. The low-flow-rate method is limited by the fact that calibration times may be rather long before a sufficient sample volume has been collected. | 1 | Applied and Interdisciplinary Chemistry |
The receptor has a broad tissue distribution but is especially abundant in the cerebellum. Most of the InsP3Rs are found integrated into the endoplasmic reticulum. | 1 | Applied and Interdisciplinary Chemistry |
A new synthetic approach, called nanofiber seeding, was developed to control the bulk morphology of chemically synthesized electronic organic polymers. Bulk quantities of nanofibers of conducting polymers such as polyaniline, can be synthesized in one step without the need for conventional templates, surfactants, polymers, or organic solvents.
Conventional oxidative polymerization approaches to nanostructured conducting polymers include the use of hard template zeolites, opals, and controlled pore-size membranes, or soft template such as polymers and surfactants. A “template-free” approach has also been described in which the use of large organic anions results in polyaniline nanofibers and nanotubes having average diameters in the 650-80 nm range.
Standard synthesis of polyaniline yields granular morphology. However, if the conventional reaction is seeded by 1-4 mg (seed quantities) of added pre-synthesized polyaniline nanofibers, (nanofiber seeds could be prepared from interfacial polymerization) the bulk morphology changes dramatically from granular to nano-fibrillar. Furthermore, increased capacitance values were observed in polyaniline nanofibers synthesized by the nanofiber seeding approach. Oxidative polymerization can be also seeded by other nanostructure materials such as vanadium pentoxide nanofibers, where V2O5 nanofibers (i) Rapidly initiate fibrillar polymer growth (ii) Slowly dissolve in aq. 1.0 M HCl, which eliminates template removal steps. Hence only catalytic amounts (4mg) V2O5 nanofibers are needed prior to onset of polymerization, which significantly change the bulk morphology of the polymer precipitate. Moreover, single-walled carbon nanotube and nano fibrous hexapeptide can be also used as templating seeds. This method can be extended to all major classes of conducting polymers, including polypyrrole, PEDOT and other polythiophenes etc.
Nanofiber seeding is a convenient approach to obtain thin, substrate-supported, transparent films of nanofibers of conducting polymers without requiring any bulk processing steps. | 0 | Theoretical and Fundamental Chemistry |
The x-axis is usually some function of compressor entry mass flow, usually corrected flow or non-dimensional flow, as opposed to real flow. This axis can be considered a rough measure of the axial Mach number of the flow through the device. | 0 | Theoretical and Fundamental Chemistry |
Architects often look to architectural copper for continuity in design elements. For example, a copper roofing system may be designed with copper flashings, weatherings, vents, gutters, and downpipes. Cover details may include cornices, moldings, finials and sculptures.
With the growing use of vertical cladding, vertical and roofing surfaces can run into each other so that complete continuity of material and performance is maintained. Rain screens and curtain walling (often linked with transoms and mullions) are also gaining popularity in modern architectural design. | 1 | Applied and Interdisciplinary Chemistry |
For doubly bridging (μ-) ligands, two limiting representation are 4-electron and 2-electron bonding interactions. These cases are illustrated in main group chemistry by and . Complicating this analysis is the possibility of metal–metal bonding. Computational studies suggest that metal-metal bonding is absent in many compounds where the metals are separated by bridging ligands. For example, calculations suggest that lacks an iron–iron bond by virtue of a 3-center 2-electron bond involving one of three bridging CO ligands. | 0 | Theoretical and Fundamental Chemistry |
"Overcooling" is cited as a side effect of PDRCs that may be problematic, especially when PDRCs are applied in high-population areas with hot summers and cool winters, characteristic of temperate zones. While PDRC application in these areas can be useful in summer, in winter it can result in an increase in energy consumption for heating and thus may reduce the benefits of PDRCs on energy savings and emissions. As per Chen et al., "to overcome this issue, dynamically switchable coatings have been developed to prevent overcooling in winter or cold environments."
The detriments of overcooling can be reduced by modulation of PDRCs, harnessing their passive cooling abilities during summer, while modifying them to passively heat during winter. Modulation can involve "switching the emissivity or reflectance to low values during the winter and high values during the warm period." In 2022, Khan et al. concluded that "low-cost optically modulated" PDRCs are "under development" and "are expected to be commercially available on the market soon with high future potential to reduce urban heat in cities without leading to an overcooling penalty during cold periods."
There are various methods of making PDRCs switchable to mitigate overcooling. Most research has used vanadium dioxide (VO2), an inorganic compound, to achieve temperature-based switchable cooling and heating effects. While, as per Khan et al., developing VO2 is difficult, their review found that "recent research has focused on simplifying and improving the expansion of techniques for different types of applications." Chen et al. found that "much effort has been devoted to VO2 coatings in the switching of the mid-infrared spectrum, and only a few studies have reported the switchable ability of temperature-dependent coatings in the solar spectrum." Temperature-dependent switching requires no extra energy input to achieve both cooling and heating.
Other methods of PDRC switching require extra energy input to achieve desired effects. One such method involves changing the dielectric environment. This can be done through "reversible wetting" and drying of the PDRC surface with common liquids such as water and alcohol. However, for this to be implemented on a mass scale, "the recycling, and utilization of working liquids and the tightness of the circulation loop should be considered in realistic applications."
Another method involves switching through mechanical force, which may be useful and has been "widely investigated in [PDRC] polymer coatings owing to their stretchability." For this method, "to achieve a switchable coating in εLWIR, mechanical stress/strain can be applied in a thin PDMS film, consisting of a PDMS grating and embedded nanoparticles." One study estimated, with the use of this method, that "19.2% of the energy used for heating and cooling can be saved in the US, which is 1.7 times higher than the only cooling mode and 2.2 times higher than the only heating mode," which may inspire additional research and development. | 0 | Theoretical and Fundamental Chemistry |
Fuzzy regions modulate the conformational equilibrium or flexibility of the binding interface via transient interactions. Dynamic regions can also compete with binding sites or tether them to the target. Modifications of fuzzy regions by further interactions, or posttranslational modifications impact binding affinity or specificity. Alternative splicing can modulate the length of fuzzy regions resulting in context-dependent binding (e.g. tissue-specificity) on the complex. EGF/MAPK, TGF-β and WNT/Wingless signaling pathways employ tissue-specific fuzzy regions. | 0 | Theoretical and Fundamental Chemistry |
Inversion recovery is an MRI sequence that provides high contrast between tissue and lesion. It can be used to provide high T1 weighted image, high T2 weighted image, and to suppress the signals from fat, blood, or cerebrospinal fluid (CSF). | 0 | Theoretical and Fundamental Chemistry |
Mollapour is widely recognized for his research on post-translation regulation of the molecular chaperone Heat shock protein-90 (Hsp90) and co-chaperones in cancer. His work demonstrated how reversible biochemical reactions can become directional and ordered, and in general, how a house-keeping machine (Hsp90) can be modulated through signaling inputs. Mollapour’s finding on post-translational modifications of the Hsp90 chaperone machinery has also explained the reasons for tumors sensitivity and selectivity towards the Hsp90 inhibitors. | 1 | Applied and Interdisciplinary Chemistry |
In D. melanogaster, FDL-deficient mutants showed paucimannose-deficiency and, notably, caused locomotion defects in fruit flies, indicating that Hex and/or paucimannosidic proteins are involved, via elusive pathways, in essential fruit fly processes. As expected, the less-consequential monoallelic fdl mutation was shown to result in reduced paucimannosidic protein formation and caused a non-lethal, but still severe phenotype, by halting the generation of peripheral long-term memory neurons. Impaired generation of peripheral long-term memory neurons was also observed for fruit fly fdl and MgatI null mutations, which, in turn, resulted in infertility and locomotion defects. The lack of fucosylated paucimannosidic glycans was proposed to contribute to neuronal impairment in both fdl and Mgat1 mutants. The importance of fucosylated paucimannosidic glycans was supported by a study reporting that mutations in the FucT6 gene encoding the D. melanogaster α1,6-fucosyltransferase resulted in an impaired fruit fly immune response towards parasitic infections. Taken together, these phenotypic observations suggest that the fruit fly paucimannosidic glycans, some of which overlap with the human repertoire, are pivotal in the development, immune function and survival processes of D. melanogaster. It was reported that T. castaneum abundantly expresses paucimannosidic proteins during its post-larval stages, recapitulating findings from other studies proposing that paucimannosidic proteins are strongly regulated during early development. Thus, it is likely that paucimannosidic glycans conjugated to still unknown flour beetle carrier proteins, similar to those in nematodes and fruit flies, are vital for growth and survival processes of the flour beetle. | 1 | Applied and Interdisciplinary Chemistry |
The point groups are named according to their component symmetries. There are several standard notations used by crystallographers, mineralogists, and physicists.
For the correspondence of the two systems below, see crystal system. | 0 | Theoretical and Fundamental Chemistry |
Malcolm Leslie Hodder Green (16 April 1936 – 24 July 2020) was Professor of Inorganic Chemistry at the University of Oxford. He made many contributions to organometallic chemistry. | 0 | Theoretical and Fundamental Chemistry |
The integrated stress response can be triggered within a cell due to either extrinsic or intrinsic conditions. Extrinsic factors include hypoxia, amino acid deprivation, glucose deprivation, viral infection and presence of oxidants. The main intrinsic factor is endoplasmic reticulum stress due to the accumulation of unfolded proteins. It has also been observed that the integrated stress response may trigger due to oncogene activation. The integrated stress response will either cause the expression of genes that fix the damage in the cell due to the stressful conditions, or it will cause a cascade of events leading to apoptosis, which occurs when the cell cannot be brought back into homeostasis. | 1 | Applied and Interdisciplinary Chemistry |
Instruments accept small (mm range) and large samples (cm range), e.g. wafers. The limiting factor is the design of the sample holder, the sample transfer, and the size of the vacuum chamber. Large samples are laterally moved in x and y direction to analyze a larger area. | 0 | Theoretical and Fundamental Chemistry |
In 1845, Joule studied the free expansion of a gas into a larger volume. This became known as Joule expansion. The cooling of a gas by allowing it to expand freely is occasionally referred to as the Joule effect. | 0 | Theoretical and Fundamental Chemistry |
Starting with simple linear and branched alkanes and alkenes the method works by collecting a large number of experimental heat of formation data (see: Heat of Formation table) and then divide each molecule up into distinct groups each consisting of a central atom with multiple ligands:
: X-(A)i(B)j(C)k(D)l
To each group is then assigned an empirical incremental value which is independent on its position inside the molecule and independent of the nature of its neighbors:
* P primary C-(C)(H)3 -10.00
* S secondary C-(C)2(H)2 -5.00
* T tertiary C-(C)3(H) -2.40
* Q quaternary C-(C)4 -0.10
* gauche correction +0.80
* 1,5 pentane interference correction +1.60
: in kcal/mol and 298 K
The following example illustrates how these values can be derived.
The experimental heat of formation of ethane is -20.03 kcal/mol and ethane consists of 2 P groups. Likewise propane (-25.02 kcal/mol) can be written as 2P+S, isobutane (-32.07) as 3P+T and neopentane (-40.18 kcal/mol) as 4P+Q. These four equations and 4 unknowns work out to estimations for P (-10.01 kcal/mol), S (-4.99 kcal/mol), T (-2.03 kcal/mol) and Q (-0.12 kcal/mol). Of course the accuracy will increase when the dataset increases.
the data allow the calculation of heat of formation for isomers. For example, the pentanes:
* n-pentane = 2P + 3S = -35 (exp. -35 kcal/mol)
* isopentane = 3P + S + T + 1 gauche correction = -36.6 (exp. -36.7 kcal/mol)
* neopentane = 4P + Q = 40.1 (exp. 40.1 kcal/mol)
The group additivities for alkenes are:
* Cd-(H2) +6.27
* Cd-(C)(D) +8.55
* Cd-(C)2 +10.19
* Cd-(Cd)(H) +6.78
* Cd-(Cd)(C) +8.76
* C-(Cd)(H)3 -10.00
* C-(Cd)(C)(H)2 -4.80
* C-(Cd)(C)2(H) -1.67
* C-(Cd)(C)3 +1.77
* C-(Cd)2(H)2 -4.30
* cis correction +1.10
* alkene gauche correction +0.80
In alkenes the cis isomer is always less stable than the trans isomer by 1.10 kcal/mol.
More group additivity tables exist for a wide range of functional groups. | 0 | Theoretical and Fundamental Chemistry |
The University of Greifswald and Belarusian State University are researching reed beds in Naroch National Park as filters to reduce nitrogen and phosphorus run-off from degraded peatlands agriculture into the Baltic. With research scheduled from January 2019 to September 2021, they aim to investigate the potential for harvesting reeds in the area to incentivise reed bed management. | 1 | Applied and Interdisciplinary Chemistry |
Di-tert-butyl dicarbonate is inexpensive, so it is usually purchased. Classically, this compound is prepared from tert-butanol, carbon dioxide, and phosgene, using DABCO as a base:
This route is currently employed commercially by manufacturers in China and India. European and Japanese companies use the reaction of sodium tert-butoxide with carbon dioxide, catalysed by p-toluenesulfonic acid or methanesulfonic acid. This process involves a distillation of the crude material yielding a very pure grade.
Boc anhydride is also available as a 70% solution in toluene or THF. As boc anhydride may melt at ambient temperatures, its storage and handling is sometimes simplified by using a solution. | 0 | Theoretical and Fundamental Chemistry |
The enzymes trypsin and chymotrypsin were first purified in the 1930s. A serine in each of trypsin and chymotrypsin was identified as the catalytic nucleophile (by diisopropyl fluorophosphate modification) in the 1950s. The structure of chymotrypsin was solved by X-ray crystallography in the 1960s, showing the orientation of the catalytic triad in the active site. Other proteases were sequenced and aligned to reveal a family of related proteases, now called the S1 family. Simultaneously, the structures of the evolutionarily unrelated papain and subtilisin proteases were found to contain analogous triads. The charge-relay mechanism for the activation of the nucleophile by the other triad members was proposed in the late 1960s. As more protease structures were solved by X-ray crystallography in the 1970s and 80s, homologous (such as TEV protease) and analogous (such as papain) triads were found. The MEROPS classification system in the 1990s and 2000s began classing proteases into structurally related enzyme superfamilies and so acts as a database of the convergent evolution of triads in over 20 superfamilies. Understanding how chemical constraints on evolution led to the convergence of so many enzyme families on the same triad geometries has developed in the 2010s.
Since their initial discovery, there have been increasingly detailed investigations of their exact catalytic mechanism. Of particular contention in the 1990s and 2000s was whether low-barrier hydrogen bonding contributed to catalysis, or whether ordinary hydrogen bonding is sufficient to explain the mechanism. The massive body of work on the charge-relay, covalent catalysis used by catalytic triads has led to the mechanism being the best characterised in all of biochemistry. | 1 | Applied and Interdisciplinary Chemistry |
In biotechnology, polymersomes are a class of artificial vesicles, tiny hollow spheres that enclose a solution. Polymersomes are made using amphiphilic synthetic block copolymers to form the vesicle membrane, and have radii ranging from 50 nm to 5 µm or more. Most reported polymersomes contain an aqueous solution in their core and are useful for encapsulating and protecting sensitive molecules, such as drugs, enzymes, other proteins and peptides, and DNA and RNA fragments. The polymersome membrane provides a physical barrier that isolates the encapsulated material from external materials, such as those found in biological systems.
Synthosomes are polymersomes engineered to contain channels (transmembrane proteins) that allow certain chemicals to pass through the membrane, into or out of the vesicle. This allows for the collection or enzymatic modification of these substances.
The term "polymersome" for vesicles made from block copolymers was coined in 1999. Polymersomes are similar to liposomes, which are vesicles formed from naturally occurring lipids. While having many of the properties of natural liposomes, polymersomes exhibit increased stability and reduced permeability. Furthermore, the use of synthetic polymers enables designers to manipulate the characteristics of the membrane and thus control permeability, release rates, stability and other properties of the polymersome. | 1 | Applied and Interdisciplinary Chemistry |
Diazomethane is prepared by hydrolysis of an ethereal solution of an N-methyl nitrosamide with aqueous base. The traditional precursor is N-nitroso-N-methylurea, but this compound is itself somewhat unstable, and nowadays compounds such as N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and N-methyl-N-nitroso-p'-toluenesulfonamide (Diazald) are preferred.
CHN reacts with basic solutions of DO to give the deuterated derivative CDN.
The concentration of CHN can be determined in either of two convenient ways. It can be treated with an excess of benzoic acid in cold EtO. Unreacted benzoic acid is then back-titrated with standard NaOH. Alternatively, the concentration of CHN in EtO can be determined spectrophotometrically at 410 nm where its extinction coefficient, ε, is 7.2.
The gas-phase concentration of diazomethane can be determined using photoacoustic spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
More useful generally than the Gilman reagents are the so-called mixed cuprates with the formula [RCuX] and [RCuX]. Such compounds are often prepared by the addition of the organolithium reagent to copper(I) halides and cyanide. These mixed cuprates are more stable and more readily purified. One problem addressed by mixed cuprates is the economical use of the alkyl group. Thus, in some applications, the mixed cuprate has the formula is prepared by combining thienyllithium and cuprous cyanide followed by the organic group to be transferred. In this higher order mixed cuprate, both the cyanide and thienyl groups do not transfer, only the R group does. | 0 | Theoretical and Fundamental Chemistry |
Gelatin is the denatured form of collagen. Gelatin possesses several advantages for tissue-engineering application: they attract fibroblasts, are non-immunogenic, easy to manipulate and boost the formation of epithelium. There are three types of gelatin-based scaffolds:
* Gelatin-oxidized dextran matrix
* Gelatin-chitosan-oxidized dextran matrix
* Gelatin-glucan matrix
* Gelatin-hyaluronate matrix
* Gelatin-chitosan hyaluronic acid matrix.
Glucan is a polysaccharide with antibacterial, antiviral and anticoagulant properties. Hyaluronic acid is added to improve the biological and mechanical properties of the matrix. | 1 | Applied and Interdisciplinary Chemistry |
Dihalophospaalkenes of the general form R-P=CX, where X is Cl, Br, or I, undergo lithium-halogen exchange with organolithium reagents to yield intermediates of the form R-P=CXLi. These species then eject the corresponding lithium halide salt, LiX, to putatively give a phospha-isocyanide, which can rearrange, much in the same way as an isocyanide, to yield the corresponding phosphaalkyne. This rearrangement has been evaluated using the tools of computational chemistry, which has shown that this isomerization process should proceed very rapidly, in line with current experimental evidence showing that phosphaisonitriles are unobservable intermediates, even at –85 °C (–121 °C). | 0 | Theoretical and Fundamental Chemistry |
Meyer was born on May 17, 1968, in Herne, Germany. He studied chemistry at the Ruhr University Bochum, receiving his diploma (in chemistry) in May 1995. In summer 1995, Meyer then joined the laboratory of Professor Karl Wieghardt at the Max Planck Institute for Radiation Chemistry, where he worked on the synthesis of novel high-valent nitrido complexes of manganese, chromium and iron. These nitrido complexes were generated by the photolysis of the corresponding azido complexes. Meyer graduated in January 1998 with his Ph.D. He then moved to the Massachusetts Institute of Technology as a DFG Postdoctoral Fellow in 1998 to conduct research in the laboratory of Professor Christopher Cummins. AT MIT, Meyer worked on amido complexes of uranium with novel amido ligands and dinitrogen cleavage with heterobimetallic complexes of niobium and molybdenum. | 0 | Theoretical and Fundamental Chemistry |
The formation of humic substances in nature is one of the least understood aspects of humus chemistry and one of the most intriguing. There are three main theories to explain it: the lignin theory of Waksman (1932), the polyphenol theory, and the sugar-amine condensation theory of Maillard (1911). Those theories are insufficient to account for observations in soil research.
Humic substances are formed by the microbial degradation of dead plant matter, such as lignin, cellulose and charcoal. Humic substances in the lab are very resistant to further biodegradation. The structure, elemental composition and content of functional groups of a given sample depend on the water or soil source and the specific conditions of extraction. Nevertheless, the average properties of lab produced humic substances from different sources are remarkably similar. | 0 | Theoretical and Fundamental Chemistry |
In atmospheric dynamics, oceanography, asteroseismology and geophysics, the Brunt–Väisälä frequency, or buoyancy frequency, is a measure of the stability of a fluid to vertical displacements such as those caused by convection. More precisely it is the frequency at which a vertically displaced parcel will oscillate within a statically stable environment. It is named after David Brunt and Vilho Väisälä. It can be used as a measure of atmospheric stratification. | 1 | Applied and Interdisciplinary Chemistry |
Understanding the behavior of nanoparticles at liquid interfaces is essential for integrating them into electronics, optics, sensing, and catalysis devices. Molecular arrangements at liquid/liquid interfaces are uniform. Often, they also provide a defect-correcting platform and thus, liquid/liquid interfaces are ideal for self-assembly. Upon self-assembly, the structural and spatial arrangements can be determined via X-ray diffraction and optical reflectance. The number of nanoparticles involved in self-assembly can be controlled by manipulating the concentration of the electrolyte, which can be in the aqueous or the organic phase. Higher electrolyte concentrations correspond to decreased spacing between the nanoparticles.
Pickering and Ramsden worked with oil/water (O/W) interfaces to portray this idea. Pickering and Ramsden explained the idea of pickering emulsions when experimenting with paraffin-water emulsions with solid particles like iron oxide and silicon dioxide. They observed that the micron-sized colloids generated a resistant film at the interface between the two immiscible phases, inhibiting the coalescence of the emulsion drops. These Pickering emulsions are formed from the self-assembly of colloidal particles in two-part liquid systems, such as oil-water systems. The desorption energy, which is directly related to the stability of emulsions depends on the particle size, particles interacting with each other, and particles interacting with oil and water molecules.
A decrease in total free energy was observed to be a result of the assembly of nanoparticles at an oil/water interface. When moving to the interface, particles reduce the unfavorable contact between the immiscible fluids and decrease the interfacial energy. The decrease in total free energy for microscopic particles is much larger than that of thermal energy, resulting in an effective confinement of large colloids to the interface. Nanoparticles are restricted to the interface by an energy reduction comparable to thermal energy. Thus, nanoparticles are easily displaced from the interface. A constant particle exchange then occurs at the interface at rates dependent on particle size.
For the equilibrium state of assembly, the total gain in free energy is smaller for smaller particles. Thus, large nanoparticle assemblies are more stable. The size dependence allows nanoparticles to self-assemble at the interface to attain its equilibrium structure. Micrometer- size colloids, on the other hand, may be confined in a non-equilibrium state. | 0 | Theoretical and Fundamental Chemistry |
There are multiple different coating methods available to deposit nanoparticles. The methods differ by their ability to control particle packing density and layer thickness, ability to use different particles and the complexity of the method and the instrumentation needed. | 0 | Theoretical and Fundamental Chemistry |
The first EGR systems were crude; some were as simple as an orifice jet between the exhaust and intake tracts which admitted exhaust to the intake tract whenever the engine was running. Difficult starting, rough idling, reduced performance and lost fuel economy inevitably resulted. By 1973, an EGR valve controlled by manifold vacuum opened or closed to admit exhaust to the intake tract only under certain conditions. Control systems grew more sophisticated as automakers gained experience; Volkswagens "Coolant Controlled Exhaust Gas Recirculation" system of 1973 exemplified this evolution: a coolant temperature sensor blocked vacuum to the EGR valve until the engine reached normal operating temperature. This prevented driveability problems due to unnecessary exhaust induction; forms under elevated temperature conditions generally not present with a cold engine. Moreover, the EGR valve was controlled, in part, by vacuum drawn from the carburetors venturi, which allowed more precise constraint of EGR flow to only those engine load conditions under which is likely to form. Later, backpressure transducers were added to the EGR valve control to further tailor EGR flow to engine load conditions. Most modern engines now need exhaust gas recirculation to meet emissions standards. However, recent innovations have led to the development of engines that do not require them. The 3.6 Chrysler Pentastar engine is one example that does not require EGR. | 1 | Applied and Interdisciplinary Chemistry |
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