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Cram was born and raised in Chester, Vermont, to a Scottish immigrant father, and a German immigrant mother. His father died before Cram turned four, leaving him the only male in a family of five. He grew up on Aid to Dependent Children, and learned to work at an early age, doing jobs such as picking fruit, tossing newspapers, and painting houses, while bartering for piano lessons. By the time he turned eighteen, he had worked at least eighteen different jobs.
Cram attended the Winwood High School in Long Island, N.Y.
From 1938 to 1941, he attended Rollins College in Winter Park, Florida on a national honorary scholarship, where he worked as an assistant in the chemistry department, and was active in theater, chapel choir, Lambda Chi Alpha, Phi Society, and Zeta Alpha Epsilon. It was at Rollins that he became known for building his own chemistry equipment. In 1941, he graduated from Rollins College with a BS in chemistry.
In 1942, he graduated from the University of Nebraska–Lincoln with a MS in organic chemistry, with Norman O. Cromwell serving as his thesis adviser. His subject was "Amino ketones, mechanism studies of the reactions of heterocyclic secondary amines with -bromo-, -unsaturated ketones."
In 1947, Cram graduated from Harvard University with a PhD in organic chemistry, with Louis Fieser serving as the adviser on his dissertation on "Syntheses and reactions of 2-(ketoalkyl)-3-hydroxy-1,4-naphthoquinones" | 0 | Theoretical and Fundamental Chemistry |
The concept of homoaromaticity has its origins in the debate over the non-classical carbonium ions that occurred in the 1950s. Saul Winstein, a famous proponent of the non-classical ion model, first described homoaromaticity while studying the 3-bicyclo[3.1.0]hexyl cation.
In a series of acetolysis experiments, Winstein et al. observed that the solvolysis reaction occurred empirically faster when the tosyl leaving group was in the equatorial position. The group ascribed this difference in reaction rates to the anchimeric assistance invoked by the "cis" isomer. This result thus supported a non-classical structure for the cation.
Winstein subsequently observed that this non-classical model of the 3-bicyclo[3.1.0]hexyl cation is analogous to the previously well-studied aromatic cyclopropenyl cation. Like the cyclopropenyl cation, positive charge is delocalized over three equivalent carbons containing two π electrons. This electronic configuration thus satisfies Huckel's rule (requiring 4n+2 π electrons) for aromaticity. Indeed, Winstein noticed that the only fundamental difference between this aromatic propenyl cation and his non-classical hexyl cation was the fact that, in the latter ion, conjugation is interrupted by three -- units. The group thus proposed the name "tris-homocyclopropenyl"—the tris-homo counterpart to the cyclopropenyl cation. | 0 | Theoretical and Fundamental Chemistry |
* The main room for gender studies at the National University of Cuyo was named after Rietti in October 2010, to pay tribute to Argentine women scientists.
* On 4 November 2011, the National University of Rosario awarded her an honorary doctorate.
* In 2022, Rietti was one of eleven women scientists honored in the renamed Hall of Argentine Science, which is located in the Government House, first floor. | 0 | Theoretical and Fundamental Chemistry |
In the study of conformational isomerism, the gauche effect is an atypical situation where a gauche conformation (groups separated by a torsion angle of approximately 60°) is more stable than the anti conformation (180°).
There are both steric and electronic effects that affect the relative stability of conformers. Ordinarily, steric effects predominate to place large substituents far from each other. However, this is not the case for certain substituents, typically those that are highly electronegative. Instead, there is an electronic preference for these groups to be gauche. Typically studied examples include 1,2-difluoroethane (HFCCFH), ethylene glycol, and vicinal-difluoroalkyl structures.
There are two main explanations for the gauche effect: hyperconjugation and bent bonds. In the hyperconjugation model, the donation of electron density from the C−H σ bonding orbital to the C−F σ antibonding orbital is considered the source of stabilization in the gauche isomer. Due to the greater electronegativity of fluorine, the C−H σ orbital is a better electron donor than the C−F σ orbital, while the C−F σ orbital is a better electron acceptor than the C−H σ orbital. Only the gauche conformation allows good overlap between the better donor and the better acceptor.
Key in the bent bond explanation of the gauche effect in difluoroethane is the increased p orbital character of both C−F bonds due to the large electronegativity of fluorine. As a result, electron density builds up above and below to the left and right of the central C−C bond. The resulting reduced orbital overlap can be partially compensated when a gauche conformation is assumed, forming a bent bond. Of these two models, hyperconjugation is generally considered the principal cause behind the gauche effect in difluoroethane.
The molecular geometry of both rotamers can be obtained experimentally by high-resolution infrared spectroscopy augmented with in silico work. In accordance with the model described above, the carbon–carbon bond length is higher for the anti-rotamer (151.4 pm vs. 150 pm). The steric repulsion between the fluorine atoms in the gauche rotamer causes increased CCF bond angles (by 3.2°) and increased FCCF dihedral angles (from the default 60° to 71°).
In the related compound 1,2-difluoro-1,2-diphenylethane, the threo isomer is found (by X-ray diffraction and from NMR coupling constants) to have an anti conformation between the two phenyl groups and the two fluorine groups and a gauche conformation is found for both groups for the erythro isomer. According to in silico results, this conformation is more stable by 0.21 kcal/mol (880 J/mol).
A gauche effect has also been reported for a molecule featuring an all-syn array of four consecutive fluoro substituents. The reaction to install the fourth one is stereoselective:
The gauche effect is also seen in 1,2-dimethoxyethane and some vicinal-dinitroalkyl compounds.
The alkene cis effect is an analogous atypical stabilizing of certain alkenes. | 0 | Theoretical and Fundamental Chemistry |
Example: A porcine ERV (PERV) Chinese-born minipig isolate, PERV-A-BM, was sequenced completely and along with different breeds and cell lines in order to understand its genetic variation and evolution. The observed number of nucleotide substitutions and among the different genome sequences helped researchers determine an estimate age that PERV-A-BM was integrated into its host genome, which was found to be of an evolutionary age earlier than the European-born pigs isolates. | 1 | Applied and Interdisciplinary Chemistry |
Methanogenesis, the process that generates methane from CO, involves a series of methylation reactions. These reactions are caused by a set of enzymes harbored by a family of anaerobic microbes.
In reverse methanogenesis, methane is the methylating agent. | 0 | Theoretical and Fundamental Chemistry |
There are four different types of cross ventilation:
*Single-sided ventilation: This method depends on the pressure contrasts between different openings within the occupied space. For rooms that only feature a single opening, the ventilation is impelled by turbulence, thereby creating a pumping activity on that lone opening, causing small inflows and outflows. It is worth noting that single-sided ventilation has a weak effect. It is preferable when cross ventilation is not achievable, where it uses windows or vents at the other side of the space to control air pressure.
*Cross ventilation (single spaces): Being unsophisticated and efficacious, this type of ventilation is a horizontal process that is driven by pressure differences between the windward and leeward sides of the occupied indoor environment. Ventilation here is generally provided using windows and vents at either side of a building where the variation in pressure draw air in and out.
*Cross ventilation (double-banked spaces): Involving banked rooms, this method features openings in the hallway structure. The openings allow a way for noise to move between spaces. It can provide a much higher air-exchange rate in comparison with single-sided ventilation.
*Stack ventilation: This ventilation is a vertical process and it's beneficiary for taller buildings with central atriums. It draws cooler air in at a lower level, whereby the air rises thereafter due to heat exposure before it is ventilated out at a higher level. Benefits from temperature compartmentalization and related pressure quality of the air, whereby warm air loses density when it rises and the cooler air supplants it. | 1 | Applied and Interdisciplinary Chemistry |
In 2018, OpenCFD Ltd. and some of its industrial, academic, and community partners established an administrative body, i.e. OpenFOAM Governance, to allow the OpenFOAM's user community to decide/contribute the future development and direction of their variant of the software.
The structure of OpenFOAM Governance consisted of a Steering Committee and various Technical Committees. The Steering Committee comprised representatives from the main sponsors of OpenFOAM in industry, academia, release authorities and consultant organisations. The organisation composition of the initial committee involved members from OpenCFD Ltd., ESI Group, Volkswagen, General Motors, FM Global, TotalSim Ltd., TU Darmstadt, and Wikki Ltd.
In addition, nine technical committees were established in the following areas: Documentation, high performance computing, meshing, multiphase, numerics, optimisation, turbulence, marine applications, and nuclear applications with the members from the organisations of OpenCFD Ltd., CINECA, University of Zagreb, TU Darmstadt, National Technical University of Athens, Upstream CFD GmbH, University of Michigan, and EPFL. | 1 | Applied and Interdisciplinary Chemistry |
Systematic surveys can be used to in searching for mineral deposits or locating lost objects. Such surveys are divided into:
*Aeromagnetic survey
*Borehole
*Ground
*Marine
Aeromag datasets for Australia can be downloaded from the [https://web.archive.org/web/20110601172707/http://www.geoscience.gov.au/bin/mapserv36?map=%2Fpublic%2Fhttp%2Fwww%2Fgeoportal%2Fgadds%2Fgadds.map&mode=browse GADDS database].
Data can be divided in point located and image data, the latter of which is in ERMapper format. | 0 | Theoretical and Fundamental Chemistry |
Adrenal androgen stimulating hormone (AASH), also known as cortical androgen stimulating hormone (CASH), is a hypothetical hormone which has been proposed to stimulate the adrenal glands to produce adrenal androgens such as dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), and androstenedione (A4). It is hypothesized to be involved in adrenarche and adrenopause. The existence of this hormone is controversial and disputed and it has not been identified to date. A number of other mechanisms and/or hormones may instead play the functional role of the so-called AASH. | 1 | Applied and Interdisciplinary Chemistry |
Other salts of the dimethylaminomethylene cation:
*Dimethyl(methylidene)ammonium trifluoroacetate.
*Dimethyl(methylidene)ammonium chloride (Böhmes salt', after Horst Böhme) | 0 | Theoretical and Fundamental Chemistry |
Superhydrophilicity refers to the phenomenon of excess hydrophilicity, or attraction to water; in superhydrophilic materials, the contact angle of water is equal to zero degrees. This effect was discovered in 1995 by the Research Institute of Toto Ltd. for titanium dioxide irradiated by sunlight. Under light irradiation, water dropped onto titanium dioxide forms no contact angle (almost 0 degrees).
Superhydrophilic material has various advantages. For example, it can defog glass, and it can also enable oil spots to be swept away easily with water. Such materials are already commercialized as door mirrors for cars, coatings for buildings, self-cleaning glass, etc.
Several mechanisms of this superhydrophilicity have been proposed by researchers. One is the change of the surface structure to a metastable structure, and another is cleaning the surface by the photodecomposition of dirt such as organic compounds adsorbed on the surface, after either of which water molecules can adsorb to the surface. The mechanism is still controversial, and it is too soon to decide which suggestion is correct. To decide, atomic scale measurements and other studies will be necessary. | 0 | Theoretical and Fundamental Chemistry |
Druggability is a term used in drug discovery to describe a biological target (such as a protein) that is known to or is predicted to bind with high affinity to a drug. Furthermore, by definition, the binding of the drug to a druggable target must alter the function of the target with a therapeutic benefit to the patient. The concept of druggability is most often restricted to small molecules (low molecular weight organic substances) but also has been extended to include biologic medical products such as therapeutic monoclonal antibodies.
Drug discovery comprises a number of stages that lead from a biological hypothesis to an approved drug. Target identification is typically the starting point of the modern drug discovery process. Candidate targets may be selected based on a variety of experimental criteria. These criteria may include disease linkage (mutations in the protein are known to cause a disease), mechanistic rationale (for example, the protein is part of a regulatory pathway that is involved in the disease process), or genetic screens in model organisms. Disease relevance alone however is insufficient for a protein to become a drug target. In addition, the target must be druggable. | 1 | Applied and Interdisciplinary Chemistry |
The broad scope of the Kröhnke pyridine synthesis has made it particularly useful for the synthesis of poly aryl systems including pyridyl, thienyl, and furanyl moieties as well. The method tolerates a broad array of aryl substitiuents on both the α-pyridinium methyl ketone fragment and the α, β-unsaturated carbonyl compounds and can thus be used to generate a wide catalog of poly-aryl systems. Additionally, electron-withdrawing groups and electron-donating groups on the incoming aryl substituents are both well tolerated. The Kröhnke synthesis can also employ alkyl and vinyl substituents giving moderated to good yields as well. Due to its broad scope, the Kröhnke method has seen wide applicability to for the synthesis of bipyridines (16), terpyridines (17), quaterpyridines (18) and even up to septipyridines (19) as shown below. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, the pressure coefficient is a dimensionless number which describes the relative pressures throughout a flow field. The pressure coefficient is used in aerodynamics and hydrodynamics. Every point in a fluid flow field has its own unique pressure coefficient, .
In many situations in aerodynamics and hydrodynamics, the pressure coefficient at a point near a body is independent of body size. Consequently, an engineering model can be tested in a wind tunnel or water tunnel, pressure coefficients can be determined at critical locations around the model, and these pressure coefficients can be used with confidence to predict the fluid pressure at those critical locations around a full-size aircraft or boat. | 1 | Applied and Interdisciplinary Chemistry |
The phage particle adsorbs onto the surface of the bacterium using the tail fibers for specificity. The tail sheath contracts and the DNA of the phage is injected into the host cell. The host DNA recombination machinery or the cre enzyme translated from the viral DNA recombine the terminally redundant ends and circularize the genome. Depending on various physiological cues, the phage may immediately proceed to the lytic phase or it may enter a lysogenic state.
The gene that encodes the tail fibers have a set of sequences that can be targeted by a site specific recombinase Cin. This causes the C terminal end of the protein to switch between two alternate forms at a low frequency. The viral tail fibers are responsible for the specificity of binding to the host receptor. The targets of the viral tail fibers are under a constant pressure to evolve and evade binding. This method of recombinational diversity of the tail allows the virus to keep up with the bacterium. This system has close sequence homologies to recombinational systems in the tail fibers of unrelated phages like the mu phage and the lambda phage. | 1 | Applied and Interdisciplinary Chemistry |
In the hybridization-ligation assay a template probe replaces the capture probe in the sandwich assay for immobilization to the solid support. The template probe is fully complementary to the oligonucleotide analyte and is intended to serve as a substrate for T4 DNA ligase-mediated ligation. The template probe has in addition an additional stretch complementary to a ligation probe so that the ligation probe will ligate onto the 3'-end of the analyte. Albeit generic, the ligation probe is similar to a detection probe in that it is labelled with, for example, digoxigenin for downstream signalling. Stringent, low/no salt wash will remove un-ligated products.
The ligation of the analyte to the ligation probe makes the method specific for the 3-end of the analyte, ligation by T4 DNA ligase being much less efficient over a bulge loop, which would happen for a 3 metabolite N-1 version of the analyte, for example. The specificity of the hybridization-ligation assay for ligation at the 3-end is particularly relevant because the predominant nucleases in blood are 3 to 5' exonucleases.
One limitation of the method is that it requires a free 3-end hydroxyl which may not be available when targeting moieties are attached to the 3-end, for example. Further, more exotic nucleic acid chemistries with oligonucleotide drugs may impact upon the activity of the ligase, which needs to be determined on a case-by-case basis. | 1 | Applied and Interdisciplinary Chemistry |
Volkensin is a eukaryotic ribosome-inactivating protein found in the Adenia volkensii plant. It is a glycoprotein with two subunits A and B. A subunit is linked to B subunit with disulfide bridges and non-covalent bonds. B subunit is responsible for binding to the galactosyl-terminated receptors on the cell membrane that allows the entry the A subunit of the toxin into the cell, which performs the inhibitory function. Volkensin is a galactose specific lectin that can inhibit protein synthesis in whole cells and in cell-free lysates. This protein can be included into the category of risin like toxins and it resembles modeccin, the toxin of Adenia digitata. Although very similar in composition, volkensin contains more cysteine residues and more than twice as much sugar than modeccin, due to high content of galactose and mannose. In addition, volkensin is able to inhibit protein synthesis at concentrations 10 times lower than required for modeccin. From gene sequencing analysis, volkensin was found to be coded by 1569-bp ORF, that is 523 amino acid residues without introns. The internal linker sequence is 45 bp. The active site of the A subunit contains Ser203, a novel residue that is conserved in all ribosome inactivating proteins.
The toxin can be isolated via affinity chromatography, using acid-treated Sepharose 6B.
Volkensin, and toxins alike are studied to understand protein entry into the cell and many have been found to have antitumor applicability. Rats that have been administered a high dose of volkensin died between 7 and 12 hours. For 1–2 hours after poisoning, rats behaved normally and then became sedated until death with short-lasting seizures. Rats that have been administered lower doses died within several days and showed wax-like peritoneal fat, which indicated the formation of a pancreatic lesion.
In addition, volkensin has been also found to agglutinate red blood cells without any specificity for a particular blood group. This is likely due to its affinity for galactose residues, which are in common with all three blood groups.
Volkensin is a potent neurotoxin that can kill neurons. It is able to bind to the axon terminal of neurons, where it is internalized and transported to the cell body and inactivates ribosomes, thereby killing the neuron. Experiments performed in vitro showed increased toxicity of volkensin to microglia and astrocytes. | 1 | Applied and Interdisciplinary Chemistry |
A magnetohydrodynamic accelerator is an MHD converter that imparts motion to an electrically conductive fluid initially at rest, using cross electric current and magnetic field both applied within the fluid. MHD propulsion has been mostly tested with models of ships and submarines in seawater. Studies are also ongoing since the early 1960s about aerospace applications of MHD to aircraft propulsion and flow control to enable hypersonic flight: action on the boundary layer to prevent laminar flow from becoming turbulent, shock wave mitigation or cancellation for thermal control and reduction of the wave drag and form drag, inlet flow control and airflow velocity reduction with an MHD generator section ahead of a scramjet or turbojet to extend their regimes at higher Mach numbers, combined to an MHD accelerator in the exhaust nozzle fed by the MHD generator through a bypass system. Research on various designs are also conducted on electromagnetic plasma propulsion for space exploration.
In an MHD accelerator, the Lorentz force accelerates all charge carriers in the same direction whatever their sign, as well as neutral atoms and molecules of the fluid through collisions. The fluid is ejected toward the rear and as a reaction, the vehicle accelerates forward. | 1 | Applied and Interdisciplinary Chemistry |
For a reaction to be considered a click reaction, it must satisfy certain characteristics:
* modularity
* insensitivity to solvent parameters
* high chemical yields
* insensitivity towards oxygen and water
* regiospecificity and stereospecificity
* a large thermodynamic driving force (>20 kcal/mol) to favor a reaction with a single reaction product. A distinct exothermic reaction makes a reactant "spring-loaded".
The process would preferably:
* have simple reaction conditions
* use readily available starting materials and reagents
* use no solvent or use a solvent that is benign or easily removed (preferably water)
* provide simple product isolation by non-chromatographic methods (crystallisation or distillation)
* have high atom economy.
Many of the click chemistry criteria are subjective, and even if measurable and objective criteria could be agreed upon, it is unlikely that any reaction will be perfect for every situation and application. However, several reactions have been identified that fit the concept better than others:
* [3+2] cycloadditions, such as the Huisgen 1,3-dipolar cycloaddition, in particular the Cu(I)-catalyzed stepwise variant, are often referred to simply as Click reactions
* Thiol-ene reaction
* Diels-Alder reaction and inverse electron demand Diels-Alder reaction
* [4+1] cycloadditions between isonitriles (isocyanides) and tetrazines
* nucleophilic substitution especially to small strained rings like epoxy and aziridines
* carbonyl-chemistry-like formation of ureas but not reactions of the aldol type due to low thermodynamic driving force.
* addition reactions to carbon-carbon double bonds like dihydroxylation or the alkynes in the thiol-yne reaction.
* Sulfur (VI) Fluoride exchange | 0 | Theoretical and Fundamental Chemistry |
ortho-Substituted aryl aldehyde complexes undergo diastereoselective nucleophilic addition with organometallic reagents and other nucleophiles. Equation (8) is an example of a diastereoselective Morita-Baylis-Hillman reaction.
Pinacol coupling and the corresponding diamine coupling are possible in the presence of a one-electron reducing agent such as samarium(II) iodide.
Benzylic cations of chromium arene complexes are conformationally stable, and undergo only exo attack to afford S1 products stereospecifically, with retention of configuration. Propargyl and oxonium cations undergo retentive substitution reactions, and even β carbocations react with a significant degree of retention.
Benzylic anions of chromium arene complexes exhibit similar reactivity to cations. They are also conformationally restricted and undergo substitution reactions with retention of stereochemistry at the benzylic carbon. In the example below, complexation of the pyridine nitrogen to lithium is essential for high stereoselectivity.
Nucleophilic addition to styrenes followed by quenching with an electrophile leads to cis products with essentially complete stereoselectivity.
Diastereoselective reduction of styrenes is possible with samarium(II) iodide. A distant alkene is untouched during this reaction, which provides the reduced alkylarene product in high yield.
Complexation of a haloarene to chromium increases its propensity to undergo oxidative addition. Suzuki cross coupling of a planar chiral chromium haloarene complex with an aryl boronic acid is thus a viable method for the synthesis of axially chiral biaryls. In the example below, the syn isomer is formed in preference to the anti isomer; when R is the formyl group, the selectivity reverses.
Tetralones complexed to chromium may be deprotonated without side reactions. Alkylation of the resulting enolate proceeds with complete diastereoselectivity to afford the exo product. | 0 | Theoretical and Fundamental Chemistry |
The Puckorius scaling index (PSI) uses slightly different parameters to quantify the relationship between the saturation state of the water and the amount of limescale deposited. | 0 | Theoretical and Fundamental Chemistry |
Most chemical safety legislation in the UK covers the transport of hazardous chemicals by road. Companies carrying dangerous substances must comply with the legislation. The NCEC worked with the European Chemical Industry Council (CEFIC) to develop a set of safety codes for carrying dangerous chemicals for National Intervention in Chemical Transport Emergencies Centres across Europe. | 1 | Applied and Interdisciplinary Chemistry |
The plasma concentration of levobupivacaine is influenced by both the dosage and the method of administration. Additionally, absorption depends on the vascularity of the tissue. Maximum plasma concentration of 1.2 µg/mL is reached approximately 30 minutes post epidural injection.
Levobupivacaine undergoes biotransformation in the liver by the cytochrome P450 enzyme, specifically CYP1A2 and CYP3A isoforms as part of phase one biotransformation, thereby producing inactive metabolites. The major metabolite produced is 3-hydroxy-levobupivacaine and the minor one is desbutyl-levobupivacaine. Subsequently, levobupivacaine metabolites are further converted into glucuronic acid and sulphate ester conjugates as a part of phase two. Metabolic inversion of levobupivacaine is not observed. The extensive metabolism of levobupivacaine by the liver ensures that no unchanged drug is excreted via urine. As a result, in patients with renal dysfunction, only the inactive metabolites accumulate instead of the drug itself.
Research tracing radiolabelled levobupivacaine showed that 71% was recovered in urine and 24% was recovered in faecesl After the intravenous administration of 40 mg of levobupivacaine, the half-life was approximately 80 minutes and the rate of clearance was 651 ± 221.5 mL/min. | 0 | Theoretical and Fundamental Chemistry |
As a strategy to stabilize mountain streams, the construction of check dams has a long tradition in many mountainous regions dating back to the 19th century in Europe. Steep slopes impede access by heavy construction machinery to mountain streams, so check dams have been built in place of larger dams. Because the typical high slope causes high flow velocity, a terraced system of multiple closely spaced check dams is typically necessary to reduce velocity and thereby counteract erosion. Such consolidation check dams, built in terraces, attempt to prevent both headward and downward cutting into channel beds while also stabilizing adjacent hill slopes. They are further used to mitigate flood and debris flow hazards. | 1 | Applied and Interdisciplinary Chemistry |
A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. According to the Organisation for the Prohibition of Chemical Weapons (OPCW), this can be any chemical compound intended as a weapon "or its precursor that can cause death, injury, temporary incapacitation or sensory irritation through its chemical action. Munitions or other delivery devices designed to deliver chemical weapons, whether filled or unfilled, are also considered weapons themselves."
Chemical weapons are classified as weapons of mass destruction (WMD), though they are distinct from nuclear weapons, biological weapons, and radiological weapons. All may be used in warfare and are known by the military acronym NBC (for nuclear, biological, and chemical warfare). Weapons of mass destruction are distinct from conventional weapons, which are primarily effective due to their explosive, kinetic, or incendiary potential. Chemical weapons can be widely dispersed in gas, liquid and solid forms, and may easily afflict others than the intended targets. Nerve gas, tear gas, and pepper spray are three modern examples of chemical weapons.
Lethal unitary chemical agents and munitions are extremely volatile and they constitute a class of hazardous chemical weapons that have been stockpiled by many nations. Unitary agents are effective on their own and do not require mixing with other agents. The most dangerous of these are nerve agents (GA, GB, GD, and VX) and vesicant (blister) agents, which include formulations of sulfur mustard such as H, HT, and HD. They all are liquids at normal room temperature, but become gaseous when released. Widely used during the World War I, the effects of so-called mustard gas, phosgene gas, and others caused lung searing, blindness, death and maiming.
During World War II the Nazi regime used a commercial hydrogen cyanide blood agent trade-named Zyklon B to commit industrialised genocide against Jews and other targeted populations in large gas chambers. The Holocaust resulted in the largest death toll to chemical weapons in history.
, CS gas and pepper spray remain in common use for policing and riot control; CS and pepper spray are considered non-lethal weapons. Under the Chemical Weapons Convention (1993), there is a legally binding, worldwide ban on the production, stockpiling, and use of chemical weapons and their precursors. However, large stockpiles of chemical weapons continue to exist, usually justified as a precaution against possible use by an aggressor. Continued storage of these chemical weapons is a hazard, as many of the weapons are now more than 50 years old, raising risks significantly. The United States is now undergoing measures to dispose of their chemical weapons in a safe manner. | 1 | Applied and Interdisciplinary Chemistry |
The dose of the coagulant to be used can be determined via the jar test. The jar test involves exposing same volume samples of the water to be treated to different doses of the coagulant and then simultaneously mixing the samples at a constant rapid mixing time. The microfloc formed after coagulation further undergoes flocculation and is allowed to settle. Then the turbidity of the samples is measured and the dose with the lowest turbidity can be said to be optimum. | 1 | Applied and Interdisciplinary Chemistry |
When a virus transforms a cell it often causes cancer by either altering the cells' existing genome or introducing additional genetic material which causes cells to uncontrollably replicate. It is rarely considered that what causes so much harm also has the capability of reversing the process and slowing the cancer growth or even leading to remission. Viruses transform host cells in order to survive and replicate; however, the immune responses of the host cell are typically compromised during transformation making transformed cells more susceptible to other viruses.
The idea of using viruses to treat cancers was first introduced in 1951 when a 4-year-old boy suddenly went into a temporary remission from leukemia while he had chickenpox. This led to research in the 1990s where scientists worked to create a strain of the herpes simplex virus strong enough to infect and transform tumor cells but weak enough to leave healthy cells unharmed. Treating patients with viral transformation has the possibility of treating patients more safely and more effectively than using traditional methods, such as chemotherapy. Viruses used in the treatment of cancer gain strength and increase their effectiveness as the multiply in the body while causing only minor side effects, such as nausea, fatigue, and aches. | 1 | Applied and Interdisciplinary Chemistry |
The limit of detection (LOD or LoD) is the lowest signal, or the lowest corresponding quantity to be determined (or extracted) from the signal, that can be observed with a sufficient degree of confidence or statistical significance. However, the exact threshold (level of decision) used to decide when a signal significantly emerges above the continuously fluctuating background noise remains arbitrary and is a matter of policy and often of debate among scientists, statisticians and regulators depending on the stakes in different fields. | 0 | Theoretical and Fundamental Chemistry |
2-Iodoxybenzoic acid (IBX) is an organic compound used in organic synthesis as an oxidizing agent. This periodinane is especially suited to oxidize alcohols to aldehydes. IBX is prepared from 2-iodobenzoic acid, potassium bromate, and sulfuric acid. Frigerio and co-workers have also demonstrated, in 1999 that potassium bromate may be replaced by commercially available Oxone. One of the main drawbacks of IBX is its limited solubility; IBX is insoluble in many common organic solvents. In the past, it was believed that IBX was shock sensitive, but it was later proposed that samples of IBX were shock sensitive due to the residual potassium bromate left from its preparation. Commercial IBX is stabilized by carboxylic acids such as benzoic acid and isophthalic acid. | 0 | Theoretical and Fundamental Chemistry |
# Wash pipe ends to create clean surfaces for joining
# Square pipe ends to facilitate optimal fit-up
# Clean area where coupler will be placed with isopropyl alcohol
# Mark the pipes slightly beyond half the length of the coupler, to indicate where scraping will take place in later steps
# Mark the area to be scraped
# Scrape pipe in marked areas to remove surface layer, allowing clean pipe material to contact the coupler
# Examine scraped area thoroughly, making sure that fresh pipe material is exposed throughout area
# Insert pipe ends into coupling to appropriate depth
# Secure coupler using clamp
# Connect fitting to control box using electrical leads
# Apply fusion cycle
# Allow joint to be undisturbed for the entire prescribed cooling time
# Pressure test pipe
# Back fill pipe with appropriate contents
# Begin service | 0 | Theoretical and Fundamental Chemistry |
Enyne cycloisomerization, an alkyne variant of the Alder-ene reaction (figure 5), is an intramolecular rearrangement of 1,n–enynes to give the corresponding cyclic isomer.
Although the rearrangement may occur under thermal conditions, the scope of the thermal rearrangement is limited due to the requirement of high temperatures, thus transition metals such as Au, Pd, Pt, Rh and Ir are often employed as catalysts. As synthesis quarrels to build complex structural motifs in the presence of inductive, stereoelectronic and steric demands this rearrangement has recently been developed as a robust method for constructing carbo– and heterocyclic scaffolds with excellent chemo–, regio– and diastereoselective outcomes.
There is not a single mechanism that can be used to describe enyne cycloisomerizations as the mechanism depends on reaction conditions and catalyst selection. Intermediates of the metal catalyzed cycloisomerization in which the metal coordinates the alkyne or alkene activating either or both are possible and are shown in figure 6.
Activation of the alkyne by complexation with the metal leading to an η–metal intermediate such as 18 opens up the alkyne to nucleophilic attack and engenders carbocation intermediates. This Pull–push reactivity is important for understanding reactions mediated by π–acids. Complexation of the alkyne to the metal fragment depletes electron density in the bond (‘pull’), in concert with the ability of the metal to back donate (“push”) arouses the observed consecutive electrophilic and nucleophilic character to the vicinal carbon atoms of the alkyne (figure 7).
Metallacycle intermediates (19) are the result of the simultaneous complexation and activation of both partners. Hydrometallation of the alkyne giving a vinyl metal species that may in turn carbometalate the olefin is also possible (20). An example of a 1,6–enyne cycloisomerization proceeding through an η–activated metal intermediate is given in figure 8, which is common for enyne cycloisomerizations mediated by Pt or Au due to their π–acidic nature. Notably, in this example chirality transfer takes place in which the absolute stereochemistry of the enyne (26) controls stereochemistry of the product (27). | 0 | Theoretical and Fundamental Chemistry |
Ferhan Çeçen was born on June 15, 1961, in Istanbul, Turkey. She graduated from the Deutsche Schule Istanbul in 1980 and speaks fluent English and German in addition to her native Turkish. Çeçen completed a B.S. in chemical engineering at Boğaziçi University in 1984.
In 1986, she completed a M.S. in environmental engineering at the Istanbul Technical University (ITU). Her Masters thesis was titled Metal Complexation and its Implications on related Technologies'. Her graduate advisor was .
Çeçen earned a Ph.D. in environmental engineering at ITU in 1990. Her dissertation was titled Nitrogen Removal from High-strength Wastewaters by Upflow Submerged Nitrification and Denitrification Filters. Her doctoral advisor was . | 1 | Applied and Interdisciplinary Chemistry |
Disorders in mtFASII lead to the following metabolic diseases:
* ACSF3: Combined malonic and methylmalonic aciduria (CMAMMA)
* MCAT: Medium-chain acyl-CoA dehydrogenase deficiency (MCAD)
* MECR: Mitochondrial enoyl-CoA reductase protein-associated neurodegeneration (MEPAN) | 1 | Applied and Interdisciplinary Chemistry |
In early 1871 Belgian inventor Zénobe Gramme invented a generator powerful enough to produce power on a commercial scale for industry.
In 1878, a hydroelectric power station was designed and built by William, Lord Armstrong at Cragside, England. It used water from lakes on his estate to power Siemens dynamos. The electricity supplied power to lights, heating, produced hot water, ran an elevator as well as labor-saving devices and farm buildings.
In January 1882 the world's first public coal-fired power station, the Edison Electric Light Station, was built in London, a project of Thomas Edison organized by Edward Johnson. A Babcock & Wilcox boiler powered a steam engine that drove a generator. This supplied electricity to premises in the area that could be reached through the culverts of the viaduct without digging up the road, which was the monopoly of the gas companies. The customers included the City Temple and the Old Bailey. Another important customer was the Telegraph Office of the General Post Office, but this could not be reached through the culverts. Johnson arranged for the supply cable to be run overhead, via Holborn Tavern and Newgate.
In September 1882 in New York, the Pearl Street Station was established by Edison to provide electric lighting in the lower Manhattan Island area. The station ran until destroyed by fire in 1890. The station used reciprocating steam engines to turn direct-current generators. Because of the DC distribution, the service area was small, limited by voltage drop in the feeders. In 1886 George Westinghouse began building an alternating current system that used a transformer to step up voltage for long-distance transmission and then stepped it back down for indoor lighting, a more efficient and less expensive system which is similar to modern systems. The war of the currents eventually resolved in favor of AC distribution and utilization, although some DC systems persisted to the end of the 20th century. DC systems with a service radius of a mile (kilometer) or so were necessarily smaller, less efficient of fuel consumption, and more labor-intensive to operate than much larger central AC generating stations.
AC systems used a wide range of frequencies depending on the type of load; lighting load using higher frequencies, and traction systems and heavy motor load systems preferring lower frequencies. The economics of central station generation improved greatly when unified light and power systems, operating at a common frequency, were developed. The same generating plant that fed large industrial loads during the day, could feed commuter railway systems during rush hour and then serve lighting load in the evening, thus improving the system load factor and reducing the cost of electrical energy overall. Many exceptions existed, generating stations were dedicated to power or light by the choice of frequency, and rotating frequency changers and rotating converters were particularly common to feed electric railway systems from the general lighting and power network.
Throughout the first few decades of the 20th century central stations became larger, using higher steam pressures to provide greater efficiency, and relying on interconnections of multiple generating stations to improve reliability and cost. High-voltage AC transmission allowed hydroelectric power to be conveniently moved from distant waterfalls to city markets. The advent of the steam turbine in central station service, around 1906, allowed great expansion of generating capacity. Generators were no longer limited by the power transmission of belts or the relatively slow speed of reciprocating engines, and could grow to enormous sizes. For example, Sebastian Ziani de Ferranti planned what would have reciprocating steam engine ever built for a proposed new central station, but scrapped the plans when turbines became available in the necessary size. Building power systems out of central stations required combinations of engineering skill and financial acumen in equal measure. Pioneers of central station generation include George Westinghouse and Samuel Insull in the United States, Ferranti and Charles Hesterman Merz in UK, and many others. | 1 | Applied and Interdisciplinary Chemistry |
The Italian program began in 1989 with a budget of about 20 million $US, and had three main development areas:
# MHD Modelling.
# Superconducting magnet development. The goal in 1994 was a prototype 2m long, storing 66MJ, for an MHD demonstration 8m long. The field was to be 5teslas, with a taper of 0.15T/m. The geometry was to resemble a saddle shape, with cylindrical and rectangular windings of niobium-titanium copper.
# Retrofits to natural gas powerplants. One was to be at the Enichem-Anic factor in Ravenna. In this plant, the combustion gases from the MHD would pass to the boiler. The other was a 230MW (thermal) installation for a power station in Brindisi, that would pass steam to the main power plant. | 1 | Applied and Interdisciplinary Chemistry |
Amorphous materials in soil strongly influence bulk density, aggregate stability, plasticity, and water holding capacity of soils. The low bulk density and high void ratios are mostly due to glass shards and other porous minerals not becoming compacted. Andisol soils contain the highest amounts of amorphous materials. | 0 | Theoretical and Fundamental Chemistry |
The pressure inside an ideal spherical bubble can be derived from thermodynamic free energy considerations. The above free energy can be written as:
where is the pressure difference between the inside (A) and outside (B) of the bubble, and is the bubble volume. In equilibrium, , and so,
For a spherical bubble, the volume and surface area are given simply by
and
Substituting these relations into the previous expression, we find
which is equivalent to the Young–Laplace equation when . | 0 | Theoretical and Fundamental Chemistry |
Solvent effects on colors and stability are often attributable to changes in the second coordination sphere. Such effects can be pronounced in complexes where the ligands in the first coordination sphere are strong hydrogen-bond donors and acceptors, e.g. respectively [Co(NH)] and [[Ferricyanide|[Fe(CN)]]]. Crown-ethers bind to polyamine complexes through their second coordination sphere. Polyammonium cations bind to the nitrogen centres of cyanometallates. | 0 | Theoretical and Fundamental Chemistry |
Photoelectrochemical processes are processes in photoelectrochemistry; they usually involve transforming light into other forms of energy. These processes apply to photochemistry, optically pumped lasers, sensitized solar cells, luminescence, and photochromism. | 0 | Theoretical and Fundamental Chemistry |
Boric acid is used in some nuclear power plants as a neutron poison. The boron in boric acid reduces the probability of thermal fission by absorbing some thermal neutrons. Fission chain reactions are generally driven by the probability that free neutrons will result in fission and is determined by the material and geometric properties of the reactor. Natural boron consists of approximately 20% boron-10 and 80% boron-11 isotopes. Boron-10 has a high cross-section for absorption of low energy (thermal) neutrons. By increasing boric acid concentration in the reactor coolant, the probability that a neutron will cause fission is reduced. Changes in boric acid concentration can effectively regulate the rate of fission taking place in the reactor. During normal at power operation, boric acid is used only in pressurized water reactors (PWRs), whereas boiling water reactors (BWRs) employ control rod pattern and coolant flow for power control, although BWRs can use an aqueous solution of boric acid and borax or sodium pentaborate for an emergency shutdown system if the control rods fail to insert. Boric acid may be dissolved in spent fuel pools used to store spent fuel elements. The concentration is high enough to keep neutron multiplication at a minimum. Boric acid was dumped over Reactor 4 of the Chernobyl nuclear power plant after its meltdown to prevent another reaction from occurring. | 0 | Theoretical and Fundamental Chemistry |
Gases are compressible and change volume when placed under pressure, are heated or are cooled. A volume of gas under one set of pressure and temperature conditions is not equivalent to the same gas under different conditions. References will be made to "actual" flow rate through a meter and "standard" or "base" flow rate through a meter with units such as acm/h (actual cubic meters per hour), sm/sec (standard cubic meters per second), kscm/h (thousand standard cubic meters per hour), LFM (linear feet per minute), or MMSCFD (million standard cubic feet per day).
Gas mass flow rate can be directly measured, independent of pressure and temperature effects, with ultrasonic flow meters, thermal mass flowmeters, Coriolis mass flowmeters, or mass flow controllers. | 1 | Applied and Interdisciplinary Chemistry |
The metal-dependent Fdh's feature Mo or W at their active sites. These active sites resemble the motif seen in DMSO reductase, with two molybdopterin cofactors bound to Mo/W in a bidentate fashion. The fifth and sixth ligands are sulfide and either cysteinate or selenocysteinate.
The mechanism of action appears to involve 2e redox of the metal centers, induced by hydride transfer from formate and release of carbon dioxide:
In this scheme, represents the four thiolate-like ligands provided by the two dithiolene cofactors, the molybdopterins. The dithiolene and cysteinyl/selenocysteinyl ligands are redox-innocent. In terms of the molecular details, the mechanism remains uncertain, despite numerous investigations. Most mechanisms assume that formate does not coordinate to Mo/W, in contrast to typical Mo/W oxo-transferases (e.g., DMSO reductase). A popular mechanistic proposal entails transfer of H from formate to the Mo/W=S group. | 1 | Applied and Interdisciplinary Chemistry |
Once Boltwood was offered a full professorship and chair of radiochemistry position at Yale in 1910, his career became more academic and he no longer actively pursued research. He was elected to both the United States National Academy of Sciences and the American Philosophical Society in 1911. He was elected to the American Academy of Arts and Sciences in 1913. In 1918, Boltwood became the director of Yale College chemical laboratory. As he took on more responsibilities at the college, he began overseeing the setup of two laboratories – Sloane Physics and Sterling Chemistry. During this time of added stress, he experienced bouts of depression and was forced to take time off to recover from a mental breakdown in 1924. He returned with renewed zeal and continued his work, but fell into periods of depression over the following years. On August 15, 1927, he took his own life in Hancock Point, Maine at the age of 57. | 0 | Theoretical and Fundamental Chemistry |
Chinese descriptions of alchemical laboratory equipment vary among texts and traditions, but share some common terminology. The following outline concerns alchemical hardware rather than liturgical or magical artifacts such as the sword, sun and moon mirrors, and peach-wood talismans.
The alchemy laboratory was called the Chamber of Elixirs ( , , or ). Sources differ about how to construct one. One text says the Chamber is ideally built near a mountain stream on in a secluded place (compare a clandestine drug lab), and has two doors, facing east and south; another says it should never be built over an old well or tomb, and has doors facing in all directions except north.
A layered "laboratory bench" called "altar; platform" was placed either in the center or along a wall of the Chamber. It was commonly depicted as a three-tiered clay stove platform, with eight ventilating openings on each tier—8 numerologically signifying (lit. eight directions) "eight points of the compass; all directions". The alchemists heating apparatus, interchangeably called stove; furnace or (kitchen) stove, was placed on the highest tier of the platform. Owing to inconsistent textual terminology, it translates as stove or furnace in some sources and as oven or combustion chamber' in others. Depending upon the alchemical formula, rice hulls, charcoal, or horse manure served as fuel.
A alchemical crucible; cauldron was placed over the stove or sometimes inside it. The double crucible was commonly made of red clay and had two halves joined to each other by their mouths. Another type of crucible had an iron lower half and clay upper one. After placing the ingredients in a crucible, the alchemist would hermetically seal it by applying several layers of a lute clay preparation inside and outside. The classic alchemical luting mixture was Six-and-One Mud with seven ingredients, typically alum, Turkestan rock salt ( ), lake salt, arsenolite, oyster shells, red clay, and talc.
Two common types of open alchemical reaction vessels were called tripod; container; cauldron and box; casing; container; aludel. Ding originally named a "tripod cauldron" Chinese ritual bronze, but alchemists used the term (and ) in reference to numerous metal or clay instruments with different shapes and functions. generally named both pots and various other reaction vessels to which fire was applied externally—as distinguished from that contained fire within. (an old character for cupboard; cabinet) was an alchemical name for a reaction vessel casing that was placed within a reaction chamber. Broadly speaking, had lids while were open at the top.
Besides the more open bowl-like or crucible forms of reaction vessels, whether lidded or not, many kinds of sealed containers were employed. Two common ones were the (lit. divine chamber) corresponding to the aludel subliming pot used in Arabic alchemy, and the pyx; bomb vessel composed of two roughly hemispherical crucible-like bowls with flanges placed mouth to mouth.
In addition to these basic tools, the alchemical apparatus also includes both common utensils (like mortars and pestles) and various specialized laboratory instruments for steaming, condensation, sublimation, distillation, and extraction. | 1 | Applied and Interdisciplinary Chemistry |
In April 1989, MIM Holdings Limited acquired the world rights to the Jameson Cell from TUNRA, with TUNRA retaining the rights to use the Cell for waste water treatment.
After the initial applications within the MIM Holdings group of companies, the years to 1994 saw Jameson Cells installed by various base and precious metals companies in Asia, South Africa, Canada and the United States, mainly in concentrate cleaning duties, but also in SX–EW electrolyte cleaning duties. The installation by Phelps Dodge (now Freeport-McMoRan) for electrolyte cleaning at its Morenci operation in Arizona was notable for having a large cell 6.5 m in diameter with 30 downcomers. The Morenci Jameson Cell consistently recovered over 82% of the organic extractant.
Toward the end of the period, Cells were installed in coal preparation plants operated by the BHP Mitsubishi Alliance and by Peabody for fines recovery. | 1 | Applied and Interdisciplinary Chemistry |
An electrode electrolyte interface behaves like a capacitance called electrochemical double-layer capacitance . The equivalent circuit for the redox reaction in Fig. 2 includes the double-layer capacitance as well as the charge transfer resistance . Another analog circuit commonly used to model the electrochemical double-layer is called a constant phase element.
The electrical impedance of this circuit is easily obtained remembering the impedance of a capacitance which is given by:
where is the angular frequency of a sinusoidal signal (rad/s), and .
It is obtained:
Nyquist diagram of the impedance of the circuit shown in Fig. 3 is a semicircle with a diameter and an angular frequency at the apex equal to (Fig. 3). Other representations, Bode plots, or Black plans can be used. | 0 | Theoretical and Fundamental Chemistry |
The EPS process (see Figure 2) begins with hot rolled strip steel in coil form. This steel pays off of an uncoiler, then passes through a machine which serves the purpose of "scale breaker", "leveler" or both. This machine (see Figure 2) works the material between sets of hardened rollers. This has the effect of removing the curvature of the strip ("coil set") and breaking loose the outer layers of mill scale which encase the steel strip.
After passing through the "scale breaker/leveler" machine, the steel strip enters the first "EPS slurry blasting cell". Slurry blasting is a wet abrasive blasting process that combines a fine-particle metallic abrasive with a "carrier liquid" (the most common one being water). This abrasive + water slurry mixture is fed into a rotating impeller which propels it at high velocity across the object to be cleaned (see Figure 3). Slurry blasting is a method for removing rust/scale, for blast cleaning and shot peening. Cleaning agents can be introduced into the carrier liquid to reduce smut and aid in rust prevention.
An EPS slurry blasting cell is composed of eight of the slurry discharge heads shown in Figure 3 – four for the top surface and four for the bottom surface of the strip. Inside the slurry blasting cell, jets of water cleanse the steel strip of both the abrasive particles and the dislodged mill scale. An EPS production system may use multiple EPS slurry blasting cells arranged in tandem, so the steel strip passes from one cell into the next, then into the next, and so on. Multiple cells increase the exposure of the steel strip to the slurry blast streams, thereby allowing the strip to move faster, yet still achieve the necessary level of scale removal. The strip speed and, therefore, system output increases in rough proportion to the number of EPS slurry blasting cells used.
The strip emerges from the final blasting cell and is dried using high-velocity air blowers. At this point the strip passes beneath a real-time oxide detector camera, which provides feedback to the line control to assure full oxide removal is accomplished.
To conclude the process, the strip may, optionally, have an oil film or lubricant applied, then it is recoiled. Of note is that tension created by the force of the recoiler pulling the strip through the scale breaker/leveler serves to flatten the strip, removing bow, edge wave and minor coil breaks. Also, not shown in Figure 2 is the slurry delivery/recirculation/filtering system. This closed-loop system collects the carrier liquid, abrasive and removed scale, filters out the removed scale, other contaminants and "undersized" abrasive particles, and returns a cleansed slurry mixture back to the blasting cells. | 1 | Applied and Interdisciplinary Chemistry |
Rotational–vibrational spectroscopy is a branch of molecular spectroscopy that is concerned with infrared and Raman spectra of molecules in the gas phase. Transitions involving changes in both vibrational and rotational states can be abbreviated as rovibrational (or ro-vibrational) transitions. When such transitions emit or absorb photons (electromagnetic radiation), the frequency is proportional to the difference in energy levels and can be detected by certain kinds of spectroscopy. Since changes in rotational energy levels are typically much smaller than changes in vibrational energy levels, changes in rotational state are said to give fine structure to the vibrational spectrum. For a given vibrational transition, the same theoretical treatment as for pure rotational spectroscopy gives the rotational quantum numbers, energy levels, and selection rules. In linear and spherical top molecules, rotational lines are found as simple progressions at both higher and lower frequencies relative to the pure vibration frequency. In symmetric top molecules the transitions are classified as parallel when the dipole moment change is parallel to the principal axis of rotation, and perpendicular when the change is perpendicular to that axis. The ro-vibrational spectrum of the asymmetric rotor water is important because of the presence of water vapor in the atmosphere. | 0 | Theoretical and Fundamental Chemistry |
Cram once admitted that his career wasnt without sacrifice. His first wife was Rollins classmate, Jean Turner, who also graduated in 1941, and went on to receive a masters degree in social work from Columbia University. His second wife, Jane, is a former chemistry professor at Mount Holyoke College. Cram chose not to have any children, "because I would either be a bad father or a bad scientist."
Cram died of cancer in 2001, at the age of 82. | 0 | Theoretical and Fundamental Chemistry |
Bond length is related to bond order: when more electrons participate in bond formation the bond is shorter. Bond length is also inversely related to bond strength and the bond dissociation energy: all other factors being equal, a stronger bond will be shorter. In a bond between two identical atoms, half the bond distance is equal to the covalent radius.
Bond lengths are measured in the solid phase by means of X-ray diffraction, or approximated in the gas phase by microwave spectroscopy. A bond between a given pair of atoms may vary between different molecules. For example, the carbon to hydrogen bonds in methane are different from those in methyl chloride. It is however possible to make generalizations when the general structure is the same. | 0 | Theoretical and Fundamental Chemistry |
A combination of radiochemistry and radiation chemistry is used to study nuclear reactions such as fission and fusion. Some early evidence for nuclear fission was the formation of a short-lived radioisotope of barium which was isolated from neutron irradiated uranium (Ba, with a half-life of 83 minutes and Ba, with a half-life of 12.8 days, are major fission products of uranium). At the time, it was thought that this was a new radium isotope, as it was then standard radiochemical practice to use a barium sulfate carrier precipitate to assist in the isolation of radium. More recently, a combination of radiochemical methods and nuclear physics has been used to try to make new superheavy elements; it is thought that islands of relative stability exist where the nuclides have half-lives of years, thus enabling weighable amounts of the new elements to be isolated. For more details of the original discovery of nuclear fission see the work of Otto Hahn. | 0 | Theoretical and Fundamental Chemistry |
Surprisal (a term coined in this context by Myron Tribus) was first introduced to better understand the specificity of energy release and selectivity of energy requirements of elementary chemical reactions. This gave rise to a series of new experiments which demonstrated that in elementary reactions, the nascent products could be probed and that the energy is preferentially released and not statistically distributed. Surprisal analysis was initially applied to characterize a small three molecule system that did not seemingly conform to principles of thermodynamics and a single dominant constraint was identified that was sufficient to describe the dynamic behavior of the three molecule system. Similar results were then observed in nuclear reactions, where differential states with varying energy partitioning are possible. Often chemical reactions require energy to overcome an activation barrier. Surprisal analysis is applicable to such applications as well. Later, surprisal analysis was extended to mesoscopic systems, bulk systems and to dynamical processes. | 0 | Theoretical and Fundamental Chemistry |
* Faculty of Humanities
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* Faculty of Chemistry and Technology of Rare Elements and electronic materials
* Faculty of Biotechnology and Organic synthesis
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* Institute of Polymer Technologies and Materials
* The State Institute of Professional Development and Retraining chemical, microbiological and medical industry
* Institute of Distance Education | 1 | Applied and Interdisciplinary Chemistry |
When comparing a polar and nonpolar molecule with similar molar masses, the polar molecule in general has a higher boiling point, because the dipole–dipole interaction between polar molecules results in stronger intermolecular attractions. One common form of polar interaction is the hydrogen bond, which is also known as the H-bond. For example, water forms H-bonds and has a molar mass M = 18 and a boiling point of +100 °C, compared to nonpolar methane with M = 16 and a boiling point of –161 °C. | 0 | Theoretical and Fundamental Chemistry |
One application of molecular imprinting technology is in affinity-based separations for biomedical, environmental, and food analysis. Sample preconcentration and treatment can be carried out by removing targeted trace amounts of analytes in samples using MIPs. The feasibility of MIPs in solid-phase extraction, solid-phase microextraction, and stir bar sorption extraction has been studied in several publications. Moreover, chromatography techniques such as HPLC and TLC can make use of MIPs as packing materials and stationary phases for the separation of template analytes. The kinetics of noncovalently imprinted materials were observed to be faster than materials prepared by the covalent approach, so noncovalent MIPs are more commonly used in chromatography.
Another application is the use of molecularly imprinted materials as chemical and biological sensors. They have been developed to target herbicides, sugars, drugs, toxins, and vapors. MIP-based sensors not only have high selectivity and high sensitivity, but they can also generate output signals (electrochemical, optical, or piezoelectric) for detection. This allows them to be utilized in fluorescence sensing, electrochemical sensing, chemiluminescence sensing, and UV-Vis sensing. Forensic applications that delve into detections of illicit drugs, banned sport drugs, toxins, and chemical warfare agents are also an area of growing interest.
Molecular imprinting has steadily been emerging in fields like drug delivery and biotechnology. The selective interaction between template and polymer matrix can be utilized in preparation of artificial antibodies. In the biopharmaceutical market, separation of amino acids, chiral compounds, hemoglobin, and hormones can be achieved with MIP adsorbents. Methods to utilize molecular imprinting techniques for mimicking linear and polyanionic molecules, such as DNA, proteins, and carbohydrates have been researched. An area of challenges is protein imprinting. Large, water-soluble biological macromolecules have posed a difficulty for molecular imprinting because their conformational integrity cannot be ensured in synthetic environments. Current methods to navigate this include immobilizing template molecules at the surface of solid substrates, thereby minimizing aggregation and controlling the template molecules to locate at the surface of imprinted materials. However, a critical review of molecular imprinting of proteins by scientists from Utrecht University found that further testing is required.
Pharmaceutical applications include selective drug delivery and control drug release systems, which make use of MIPs’ stable conformations, fast equilibrium release, and resistance to enzymatic and chemical stress. Intelligent drug release, the release of a therapeutic agent as a result of a specific stimuli, has also been explored. Molecularly imprinted materials of insulin and other drugs at the nanoscale were shown to exhibit high adsorption capacity for their respective targets, showing huge potential for newfound drug delivery systems. In comparison with natural receptors, MIPs also have higher chemical and physical stability, easier availability, and lower cost. MIPs could especially be used for stabilization of proteins, particularly selective protection of proteins against denaturation from heat. | 0 | Theoretical and Fundamental Chemistry |
The entropy due to a set of states that can be either occupied with probability or empty with probability can be written as:
where is Boltzmann constant.
For a continuously distributed set of states as a function of energy, such as the eigenstates in an electronic band structure, the above sum can be written as an integral over the possible energy values, rather than a sum. Switching from summing over individual states to integrating over energy levels, the entropy can be written as:
where is the density of states of the solid. The probability of occupation of each eigenstate is given by the Fermi function, :
where is the Fermi energy and is the absolute temperature. One can then re-write the entropy as:
This is the general formulation of the density-of-states based electronic entropy. | 0 | Theoretical and Fundamental Chemistry |
Norsteroids (nor-, L. norma, from "normal" in chemistry, indicating carbon removal) are a structural class of steroids that have had an atom or atoms (typically carbon) removed, biosynthetically or synthetically, from positions of branching off of rings or side chains (e.g., removal of methyl groups), or from within rings of the steroid ring system. For instance, 19-norsteroids (e.g., 19-norprogesterone) constitute an important class of natural and synthetic steroids derived by removal of the methyl group of the natural product progesterone; the equivalent change between testosterone and 19-nortestosterone (nandrolone) is illustrated below. | 1 | Applied and Interdisciplinary Chemistry |
The concept of shear flow is particularly useful when analyzing semi-monocoque structures, which can be idealized using the skin-stringer model. In this model, the longitudinal members, or stringers, carry only axial stress, while the skin or web resists the externally applied torsion and shear force. In this case, since the skin is a thin-walled structure, the internal shear stresses in the skin can be represented as shear flow. In design, the shear flow is sometimes known before the skin thickness is determined, in which case the skin thickness can simply be sized according to allowable shear stress. | 1 | Applied and Interdisciplinary Chemistry |
Deoxyguanosine monophosphate (dGMP), also known as deoxyguanylic acid or deoxyguanylate in its conjugate acid and conjugate base forms, respectively, is a derivative of the common nucleic acid guanosine triphosphate (GTP), in which the –OH (hydroxyl) group on the 2 carbon on the nucleotides pentose has been reduced to just a hydrogen atom (hence the "deoxy-" part of the name). It is used as a monomer in DNA. | 1 | Applied and Interdisciplinary Chemistry |
Electro-electrodialysis is an electromembrane process utilizing three compartments, which combines electrodialysis and electrolysis. It is commonly used to recover acid from a solution using AEM, CEM and electrolysis. The three compartments are separated by two barriers, which are the ion exchange membranes. The compartment in the middle has the water to be treated. The compartments located on the sides contain clean water. The anions pass through the AEM, while the cations pass through the CEM. The electricity creates H in the anions side and OH in the cations side, which react with the respective ions. | 1 | Applied and Interdisciplinary Chemistry |
Pulsed sources allow for the utilization of Fourier-transform spectroscopy principles in scanning near-field optical microscopy techniques. Particularly in nano-FTIR, where the scattering from a sharp probe-tip is used to perform spectroscopy of samples with nanoscale spatial resolution, a high-power illumination from pulsed infrared lasers makes up for a relatively small scattering efficiency (often < 1%) of the probe. | 0 | Theoretical and Fundamental Chemistry |
The Eschenmoser sulfide contraction is an organic reaction first described by Albert Eschenmoser for the synthesis of 1,3-dicarbonyl compounds from a thioester. The method requires a base and a tertiary phosphine. The method is of some relevance to organic chemistry and has been notably applied in the vitamin B total synthesis.
A base abstracts the labile hydrogen atom in the thioester, a sulfide anion is formed through an episulfide intermediate which is removed by the phosphine. | 0 | Theoretical and Fundamental Chemistry |
* [https://sosradon.org/devices National radon program services]. Kansas State University. Accessed 17 October 2017. | 1 | Applied and Interdisciplinary Chemistry |
Because of the ambiguity of the term valence, other notations are currently preferred. Beside the lambda notation, as used in the IUPAC nomenclature of inorganic chemistry, oxidation state is a more clear indication of the electronic state of atoms in a molecule.
The oxidation state of an atom in a molecule gives the number of valence electrons it has gained or lost. In contrast to the valency number, the oxidation state can be positive (for an electropositive atom) or negative (for an electronegative atom).
Elements in a high oxidation state have an oxidation state higher than +4, and also, elements in a high valence state (hypervalent elements) have a valence higher than 4. For example, in perchlorates , chlorine has 7 valence bonds (thus, it is heptavalent, in other words, it has valence 7), and it has oxidation state +7; in ruthenium tetroxide , ruthenium has 8 valence bonds (thus, it is octavalent, in other words, it has valence 8), and it has oxidation state +8.
In some molecules, there is a difference between valence and oxidation state for a given atom. For example, in disulfur decafluoride molecule , each sulfur atom has 6 valence bonds (5 single bonds with fluorine atoms and 1 single bond with the other sulfur atom). Thus, each sulfur atom is hexavalent or has valence 6, but has oxidation state +5. In the dioxygen molecule , each oxygen atom has 2 valence bonds and so is divalent (valence 2), but has oxidation state 0. In acetylene , each carbon atom has 4 valence bonds (1 single bond with hydrogen atom and a triple bond with the other carbon atom). Each carbon atom is tetravalent (valence 4), but has oxidation state −1. | 0 | Theoretical and Fundamental Chemistry |
GaN is another option, because metal nitrides usually have a narrow band gap that could encompass almost the entire solar spectrum. GaN has a narrower band gap than but is still large enough to allow water splitting to occur at the surface. GaN nanowires exhibited better performance than GaN thin films, because they have a larger surface area and have a high single crystallinity which allows longer electron-hole pair lifetimes. Meanwhile, other non-oxide semiconductors such as GaAs, Molybdenum disulfide|, and are used as n-type electrode, due to their stability in chemical and electrochemical steps in the photocorrosion reactions. | 0 | Theoretical and Fundamental Chemistry |
Absolute size-exclusion chromatography (ASEC) is a technique that couples a light scattering instrument, most commonly multi-angle light scattering (MALS) or another form of static light scattering (SLS), but possibly a dynamic light scattering (DLS) instrument, to a size-exclusion chromatography system for absolute molar mass and/or size measurements of proteins and macromolecules as they elute from the chromatography system.
The definition of “absolute” in this case is that calibration of retention time on the column with a set of reference standards is not required to obtain molar mass or the hydrodynamic size, often referred to as hydrodynamic diameter (D in units of nm). Non-ideal column interactions, such as electrostatic or hydrophobic surface interactions that modulate retention time relative to standards, do not impact the final result. Likewise, differences between conformation of the analyte and the standard have no effect on an absolute measurement; for example, with MALS analysis, the molar mass of inherently disordered proteins are characterized accurately even though they elute at much earlier times than globular proteins with the same molar mass, and the same is true of branched polymers which elute late compared to linear reference standards with the same molar mass. Another benefit of ASEC is that the molar mass and/or size is determined at each point in an eluting peak, and therefore indicates homogeneity or polydispersity within the peak. For example, SEC-MALS analysis of a monodisperse protein will show that the entire peak consists of molecules with the same molar mass, something that is not possible with standard SEC analysis.
Determination of molar mass with SLS requires combining the light scattering measurements with concentration measurements. Therefore SEC-MALS typically includes the light scattering detector and either a differential refractometer or UV/Vis absorbance detector. In addition, MALS determines the rms radius R of molecules above a certain size limit, typically 10 nm. SEC-MALS can therefore analyze the conformation of polymers via the relationship of molar mass to R. For smaller molecules, either DLS or, more commonly, a differential viscometer is added to determine hydrodynamic radius and evaluate molecular conformation in the same manner.
In SEC-DLS, the sizes of the macromolecules are measured as they elute into the flow cell of the DLS instrument from the size exclusion column set. The hydrodynamic size of the molecules or particles are measured and not their molecular weights. For proteins a Mark-Houwink type of calculation can be used to estimate the molecular weight from the hydrodynamic size.
A major advantage of DLS coupled with SEC is the ability to obtain enhanced DLS resolution. Batch DLS is quick and simple and provides a direct measure of the average size, but the baseline resolution of DLS is a ratio of 3:1 in diameter. Using SEC, the proteins and protein oligomers are separated, allowing oligomeric resolution. Aggregation studies can also be done using ASEC. Though the aggregate concentration may not be calculated with light scattering (an online concentration detector such as that used in SEC-MALS for molar mass measurement also determines aggregate concentration), the size of the aggregate can be measured, only limited by the maximum size eluting from the SEC columns.
Limitations of ASEC with DLS detection include flow-rate, concentration, and precision. Because a correlation function requires anywhere from 3–7 seconds to properly build, a limited number of data points can be collected across the peak. ASEC with SLS detection is not limited by flow rate and measurement time is essentially instantaneous, and the range of concentration is several orders of magnitude larger than for DLS. However, molar mass analysis with SEC-MALS does require accurate concentration measurements. MALS and DLS detectors are often combined in a single instrument for more comprehensive absolute analysis following separation by SEC. | 1 | Applied and Interdisciplinary Chemistry |
In a manuscript from 1704, Newton describes his attempts to extract scientific information from the Bible and estimates that the world would end no earlier than 2060. In predicting this, he said, "This I mention not to assert when the time of the end shall be, but to put a stop to the rash conjectures of fanciful men who are frequently predicting the time of the end, and by doing so bring the sacred prophesies into discredit as often as their predictions fail." | 1 | Applied and Interdisciplinary Chemistry |
This equipment is a spectroscopic (light gathering) apparatus and corresponding method for rapidly detecting and analyzing analytes in a sample. The sample is irradiated by an excitation source in optical communication with the sample. The excitation source may include, but is not limited to, a laser, a flash lamp, an arc lamp, a light-emitting diode, or the like.
Figure 1 depicts the current version of the SOFIA system. Four linear arrays (101) extend from a sample holder (102), which houses an elongated, transparent sample container which is open at both ends, to an end port (103). The distal end of the endport (104) is inserted into an end port assembly (200). The linear arrays (101) comprise a plurality of optical fibers having a first end and a second end, the plurality of optical fibers optionally surrounded by a protective and/or insulating sheath. The optical fibers are linearly arranged, meaning that they are substantially coplanar with respect to one another so as to form an elongated row of fibers. | 1 | Applied and Interdisciplinary Chemistry |
When the receptor is inactive, the GEF domain may be bound to an also inactive α-subunit of a heterotrimeric G-protein. These "G-proteins" are a trimer of α, β, and γ subunits (known as Gα, Gβ, and Gγ, respectively) that is rendered inactive when reversibly bound to Guanosine diphosphate (GDP) (or, alternatively, no guanine nucleotide) but active when bound to guanosine triphosphate (GTP). Upon receptor activation, the GEF domain, in turn, allosterically activates the G-protein by facilitating the exchange of a molecule of GDP for GTP at the G-protein's α-subunit. The cell maintains a 10:1 ratio of cytosolic GTP:GDP so exchange for GTP is ensured. At this point, the subunits of the G-protein dissociate from the receptor, as well as each other, to yield a Gα-GTP monomer and a tightly interacting Gβγ dimer, which are now free to modulate the activity of other intracellular proteins. The extent to which they may diffuse, however, is limited due to the palmitoylation of Gα and the presence of an isoprenoid moiety that has been covalently added to the C-termini of Gγ.
Because Gα also has slow GTP→GDP hydrolysis capability, the inactive form of the α-subunit (Gα-GDP) is eventually regenerated, thus allowing reassociation with a Gβγ dimer to form the "resting" G-protein, which can again bind to a GPCR and await activation. The rate of GTP hydrolysis is often accelerated due to the actions of another family of allosteric modulating proteins called regulators of G-protein signaling, or RGS proteins, which are a type of GTPase-activating protein, or GAP. In fact, many of the primary effector proteins (e.g., adenylate cyclases) that become activated/inactivated upon interaction with Gα-GTP also have GAP activity. Thus, even at this early stage in the process, GPCR-initiated signaling has the capacity for self-termination. | 1 | Applied and Interdisciplinary Chemistry |
The glucose transporter (GLUTs) is a type of uniporter responsible for the facilitated diffusion of glucose molecules across cell membranes.Glucose is a vital energy source for most living cells, however, due to its large size, it cannot freely move through the cell membrane. The glucose transporter is specialized in transporting glucose specifically across the membrane. The GLUT proteins have several types of isoforms, each distributed in different tissues and exhibiting different kinetic properties.
GLUTs are integral membrane proteins composed of 12 α-helix membrane spanning regions. The GLUT proteins are encoded by the SLC2 genes and categorized into three classes based on amino acid sequence similarity. Humans have been found to express fourteen GLUT proteins. Class I GLUTs include GLUT1, one of the most studied isoforms, and GLUT2. GLUT1 is found in various tissues like the red blood cells, brain, and blood-brain barrier and is responsible for basal glucose uptake. GLUT2 is predominantly found in the liver, pancreas, and small intestines. It plays an important role in insulin secretion from pancreatic beta cells. Class II includes the GLUT3 and GLUT4. GLUT3, primarily found in the brain, neurons and placenta, has a high affinity for glucose in facilitating glucose uptake into neurons. GLUT4 plays a role in insulin-regulated glucose uptake and is mainly found in insulin-sensitive tissues such as muscle and adipose tissue. Class III includes GLUT5, found in the small intestine, kidney, testes, and skeletal muscle. Unlike the other GLUTs, GLUT5 specifically transports fructose rather than glucose.
Glucose transporters allow glucose molecules to move down their concentration gradient from areas of high glucose concentration to areas of low concentration. This process often involves bringing glucose from the extracellular space or blood into the cell. The concentration gradient set up by glucose concentrations fuels the process without the need for ATP.
When glucose binds to the glucose transporter, the protein channels change shape and undergo a conformational change to transport the glucose across the membrane. Once the glucose unbinds, the protein returns to its original shape. The glucose transporter is essential for carrying out physiological processes that require high energy demands in the brain, muscles, and kidneys by providing an adequate amount of energy substrate for metabolism. Diabetes, an example of a condition that involves glucose metabolism, highlights the importance of the regulation of glucose uptake in disease management. | 1 | Applied and Interdisciplinary Chemistry |
Biotechnology,
Bioluminescence,
Molecular chemistry,
Enzymatic chemistry,
Genetic engineering,
Pharmaceuticals,
Endocrinology,
Neurochemistry,
Hematology,
Nutrition,
Photosynthesis,
Environmental,
Toxicology | 1 | Applied and Interdisciplinary Chemistry |
The 17-bp transcriptional complex has an 8-bp DNA-RNA hybrid, that is, 8 base-pairs involve the RNA transcript bound to the DNA template strand. As transcription progresses, ribonucleotides are added to the 3′ end of the RNA transcript and the RNAP complex moves along the DNA. The characteristic elongation rates in prokaryotes and eukaryotes are about 10–100 nts/sec.
Aspartyl (asp) residues in the RNAP will hold on to Mg ions, which will, in turn, coordinate the phosphates of the ribonucleotides. The first Mg will hold on to the α-phosphate of the NTP to be added. This allows the nucleophilic attack of the 3′-OH from the RNA transcript, adding another NTP to the chain. The second Mg will hold on to the pyrophosphate of the NTP. The overall reaction equation is:
:(NMP) + NTP → (NMP) + PP | 1 | Applied and Interdisciplinary Chemistry |
Subsequent research on DNA computing has produced [https://ieeexplore.ieee.org/document/8642913 reversible DNA computing], bringing the technology one step closer to the silicon-based computing used in (for example) PCs. In particular, [https://web.archive.org/web/20190201104419/https://users.cs.duke.edu/~reif/index.htm John Reif] and his group at Duke University have proposed two different techniques to reuse the computing DNA complexes. The first design uses dsDNA gates, while the second design uses DNA hairpin complexes.
While both the designs face some issues (such as reaction leaks), this appears to represent a significant breakthrough in the field of DNA computing. Some other groups have also attempted to address the gate reusability problem.
Using strand displacement reactions (SRDs), reversible proposals are presented in the [https://www.mdpi.com/2073-8994/13/7/1242 "Synthesis Strategy of Reversible Circuits on DNA Computers" paper] for implementing reversible gates and circuits on DNA computers by combining DNA computing and reversible computing techniques. This paper also proposes a universal reversible gate library (URGL) for synthesizing n-bit reversible circuits on DNA computers with an average length and cost of the constructed circuits better than the previous methods. | 1 | Applied and Interdisciplinary Chemistry |
The cross-over temperature from the normal hadronic to the QGP phase is about . This "crossover" may actually not be only a qualitative feature, but instead one may have to do with a true (second order) phase transition, e.g. of the universality class of the three-dimensional Ising model. The phenomena involved correspond to an energy density of a little less than . For relativistic matter, pressure and temperature are not independent variables, so the equation of state is a relation between the energy density and the pressure. This has been found through lattice computations, and compared to both perturbation theory and string theory. This is still a matter of active research. Response functions such as the specific heat and various quark number susceptibilities are currently being computed. | 0 | Theoretical and Fundamental Chemistry |
Photophoresis denotes the phenomenon that small particles suspended in gas (aerosols) or liquids (hydrocolloids) start to migrate when illuminated by a sufficiently intense beam of light. The existence of this phenomenon is owed to a non-uniform distribution of temperature of an illuminated particle in a fluid medium. Separately from photophoresis, in a fluid mixture of different kinds of particles, the migration of some kinds of particles may be due to differences in their absorptions of thermal radiation and other thermal effects collectively known as thermophoresis. In laser photophoresis, particles migrate once they have a refractive index different from their surrounding medium. The migration of particles is usually possible when the laser is slightly or not focused. A particle with a higher refractive index compared to its surrounding molecule moves away from the light source due to momentum transfer from absorbed and scattered light photons. This is referred to as a radiation pressure force. This force depends on light intensity and particle size but has nothing to do with the surrounding medium. Just like in Crookes radiometer, light can heat up one side and gas molecules bounce from that surface with greater velocity, hence push the particle to the other side. Under certain conditions, with particles of diameter comparable to the wavelength of light, the phenomenon of a negative indirect photophoresis occurs, due to the unequal heat generation on the laser irradiation between the back and front sides of particles, this produces a temperature gradient in the medium around the particle such that molecules at the far side of the particle from the light source may get to heat up more, causing the particle to move towards the light source.
If the suspended particle is rotating, it will also experience the Yarkovsky effect.
Discovery of photophoresis is usually attributed to Felix Ehrenhaft in the 1920s, though earlier observations were made by others including Augustin-Jean Fresnel. | 0 | Theoretical and Fundamental Chemistry |
Barbas has a Ph.D. from Complutense University of Madrid. From 2005 until 2006 she was a Marie Curie fellow at King's College London. As of 2022 she is a professor of analytical chemistry at the Universidad CEU San Pablo and is the president of the Madrid section of the Spanish Royal Society of Chemistry. | 0 | Theoretical and Fundamental Chemistry |
The corrosive effects of nitric acid are exploited for some specialty applications, such as etching in printmaking, pickling stainless steel or cleaning silicon wafers in electronics.
A solution of nitric acid, water and alcohol, nital, is used for etching metals to reveal the microstructure. ISO 14104 is one of the standards detailing this well known procedure.
Nitric acid is used either in combination with hydrochloric acid or alone to clean glass cover slips and glass slides for high-end microscopy applications. It is also used to clean glass before silvering when making silver mirrors.
Commercially available aqueous blends of 5–30% nitric acid and 15–40% phosphoric acid are commonly used for cleaning food and dairy equipment primarily to remove precipitated calcium and magnesium compounds (either deposited from the process stream or resulting from the use of hard water during production and cleaning). The phosphoric acid content helps to passivate ferrous alloys against corrosion by the dilute nitric acid.
Nitric acid can be used as a spot test for alkaloids like LSD, giving a variety of colours depending on the alkaloid. | 0 | Theoretical and Fundamental Chemistry |
Excessive doses of escitalopram usually cause relatively minor untoward effects, such as agitation and tachycardia. However, dyskinesia, hypertonia, and clonus may occur in some cases. Therapeutic blood levels of escitalopram are usually in the range of 20–80 μg/L but may reach 80–200 μg/L in the elderly, patients with hepatic dysfunction, those who are poor CYP2C19 metabolizers or following acute overdose. Monitoring of the drug in plasma or serum is generally accomplished using chromatographic methods. Chiral techniques are available to distinguish escitalopram from its racemate, citalopram. | 0 | Theoretical and Fundamental Chemistry |
A large group of organocatalysts incorporate the urea or the thiourea moiety. These catalytically effective (thio)urea derivatives termed (thio)urea organocatalysts provide explicit double hydrogen-bonding interactions to coordinate and activate H-bond accepting substrates.
Their current uses are restricted to asymmetric multicomponent reactions, including those involving Michael addition, asymmetric multicomponent reactions for the synthesis of spirocycles, asymmetric multicomponent reactions involving acyl Strecker reactions, asymmetric Petasis reactions, asymmetric Biginelli reactions, asymmetric Mannich reactions, asymmetric aza-Henry reactions, and asymmetric reductive coupling reactions. | 0 | Theoretical and Fundamental Chemistry |
Before gunpowder was applied to civil engineering, there were two ways to break up large rocks, by hard labor or by heating with large fires followed by rapid quenching. The earliest record for the use of gunpowder in mines comes from Hungary in 1627. It was introduced to Britain in 1638 by German miners, after which records are numerous. Until the invention of the safety fuse by William Bickford in 1831, the practice was extremely dangerous. Another reason for danger were the dense fumes given off and the risk of igniting flammable gas when used in coal mines. | 1 | Applied and Interdisciplinary Chemistry |
The monocyte activation test (MAT) is another proposed method to test for endotoxins based on monocytes in human blood. It measures the release of cytokines from these due to the presence of pyrogens, basically mirroring the process by which these toxins cause fever in humans (and rabbits, as in the original pyrogen test). A protocol for the MAT test, using cultured cells, is described in the European Pharmacopoeia.
A recent study employing genetically engineered monocytes was able to significantly enhance the sensitivity of monocyte-based detection assays by bringing down the assay-completion time from more than 20 hours to 2–3 hours. | 0 | Theoretical and Fundamental Chemistry |
Oseltamivir total synthesis concerns the total synthesis of the antiinfluenza drug oseltamivir marketed by Hoffmann-La Roche under the trade name Tamiflu. Its commercial production starts from the biomolecule shikimic acid harvested from Chinese star anise and from recombinant E. coli. Control of stereochemistry is important: the molecule has three stereocenters and the sought-after isomer is only 1 of 8 stereoisomers. | 0 | Theoretical and Fundamental Chemistry |
The following table lists some of the most important radiogenic isotope systems used in geology, in order of decreasing half-life of the radioactive parent isotope. The values given for half-life and decay constant are the current consensus values in the Isotope Geology community.
</big> indicates ultimate decay product of a series.
Units used in this table years years years | 0 | Theoretical and Fundamental Chemistry |
* Lauro Magnani, Chiesa di Sant’Anna Guide di Genova, 90, Genova, SAGEP Edizioni, 1979,
* Antonio Corvi ed Ernesto Riva, La farmacia monastica e conventuale, Pacini Editore, 1996.
* Antonio Corvi, "La Medicina curativa di Le Roy", in Atti e Memorie dell'Associazione Italiana Storia Della Farmacia, XIV n. 2 1997 p. 137
* Osservatorio Civis, Genova, guida alle botteghe storiche, De Ferrari & Devega Editori, Genova, 2002.
* Paolo Oliveri, La Farmacia di SantAnna dei Padri Carmelitani Scalzi in Genova, in Rivista di Storia della Farmacia', XXV, n. 1., Aprile 2008.
* Corinna Praga, Andar per creuse oltre il centro storico 2, Itinerari dal Portello, dal Vico della Croce Bianca e da via Balbi verso la Porta delle Chiappe, Italia Nostra, Genova, ERGA, 2016.
* Ezio Battaglia e Silvia Piacentini, Il Convento di SantAnna e la sua Antica Farmacia a Genova', SAGEP Editori, Genova 2020.
* Catalogo Generale dei Beni Culturali, Bottega storica, Farmacia, Antica Farmacia SantAnna.' | 1 | Applied and Interdisciplinary Chemistry |
The chloroplast gene rbcL, which codes for the large subunit of RuBisCO has been widely used as an appropriate locus for analysis of phylogenetics in plant taxonomy. | 0 | Theoretical and Fundamental Chemistry |
* 1801 - René Just Haüy published his multi-volume Traité de Minéralogie in Paris. A second edition under the title Traité de Cristallographie was published in 1822.
* 1801 - Déodat de Dolomieu published his Sur la philosophie minéralogique et sur lespèce minéralogique' in Paris.
* 1815 - René Just Haüy published his Law of Symmetry.
* 1815 - Christian Samuel Weiss, founder of the dynamist school of crystallography, developed a geometric treatment of crystals in which crystallographic axes are the basis for classification of crystals rather than Haüy’s polyhedral molecules.
* 1819 - Eilhard Mitscherlich discovered crystallographic isomorphism.
* 1822 - Friedrich Mohs attempted to bring the molecular approach of Haüy and the geometric approach of Weiss into agreement.
* 1823 - Franz Ernst Neumann invented a system of crystal face notation, by using the reciprocals of the intercepts with crystal axes, which becomes the standard for the next 60 years.
* 1824 - Ludwig August Seeber conceived of the concept of using an array of discrete (molecular) points to represent a crystal.
* 1826 - Moritz Ludwig Frankenheim deriveed the 32 crystal classes by using the crystallographic restriction, consistent with Haüy’s laws, that only 2, 3, 4 and 6-fold rotational axes are permitted.
* 1830 - Johann F. C. Hessel publishes an independent geometrical derivation of the 32 point groups (crystal classes).
* 1832 - Friedrich Wöhler and Justus von Liebig discovered polymorphism in molecular crystals, using the example of benzamide.
* 1839 - William Hallowes Miller invented zonal relations by projecting the faces of a crystal upon the surface of a circumscribed sphere. Miller indices are defined which form a notation system in crystallography for planes in crystal (Bravais) lattices.
* 1840 - Gabriel Delafosse, independently of Seeber, represented crystal structure as an array of discrete points generated by defined translations.
* 1842 - Moritz Frankenheim derived 15 different theoretical networks of points in space not dependent on molecular shape.
* 1848 - Louis Pasteur discovered that sodium ammonium tartrate can crystallize in left- and right-handed forms and showed that the two forms can rotate polarized light in opposite directions. This was the first demonstration of molecular chirality, and also the first explanation of isomerism.
* 1850 - Auguste Bravais derived the 14 space lattices.
* 1869 - Axel Gadolin, independently of Hessel, derived the 32 crystal classes using stereographic projection.
* 1877 - Paul Heinrich von Groth founded the journal Zeitschrift für Krystallographie und Mineralogie, and served as its editor for 44 years.
* 1877 - Ernest-François Mallard, building on the work of Auguste Bravais, published a memoir on optically “anomalous” crystals (that is, those crystals the morphology of which seems to be of greater symmetry than their optics), in which the importance of crystal twinning and "pseudosymmetry" were used as explanatory concepts.
* 1879 - Leonhard Sohncke listed the 65 crystallographic point systems using rotations and reflections in addition to translations.
* 1880 - Pierre Curie and Paul-Jacques Curie discovered piezoelectricity in crystals. In 1881 they demonstrated the reverse effect: that crystals could be made to deform when subject to an electric field.
* 1888 - Friedrich Reinitzer discovered the existence of liquid crystals during investigations of cholesteryl benzoate.
* 1889 - Otto Lehmann, after receiving a letter from Friedrich Reinitzer, used polarizing light to explain the phenomenon of liquid crystals.
* 1891 - Derivation of the 230 space groups (by adding mirror-image symmetry to Sohncke’s work) by a collaborative effort of Evgraf Fedorov and Arthur Schoenflies.
* 1894 - William Barlow, using a sphere packing approach, independently derived the 230 space groups.
* 1894 - Pierre Curie described the now called Curie's principle for the symmetry properties of crystals.
* 1895 - Wilhelm Conrad Röntgen on 8 November 1895 produced and detected electromagnetic radiation in a wavelength range now known as X-rays or Röntgen rays, an achievement that earned him the first Nobel Prize in Physics in 1901. X-rays became the major mode of crystallographic research in the 20th century. | 1 | Applied and Interdisciplinary Chemistry |
Reef Ball Development Group was founded in 1993 by Todd Barber, with the goal of helping to preserve and protect coral reefs for the benefit of future generations. Barber witnessed his favorite coral reef on Grand Cayman destroyed by Hurricane Gilbert, and wanted to do something to help increase the resiliency of eroding coral reefs. Barber and his father patented the idea of building reef substrate modules with a central inflatable bladder, so that the modules would be buoyant, making them easy to deploy by hand or with a small boat, rather than requiring heavy machinery.
Over the next few years, with the help of research colleagues at University of Georgia, Nationwide Artificial Reef Coordinators and the Florida Institute of Technology (FIT), Barber, his colleagues, and business partners worked to perfect the design. In 1997, Kathy Kirbo established The Reef Ball Foundation, Inc as a non-profit organization with original founders being Todd Barber as chairman and charter member, Kathy Kirbo founding executive director, board secretary, and charter member, Larry Beggs as vice president and a charter member and Eric Krasle as treasurer and a charter member, Jay Jorgensen as a charter member. Reef balls can be found in almost every coastal state in the United States, and on every continent including Antarctica. The foundation has expanded the scope of its projects to include coral rescue, propagation and transplant operations, beach restorations, mangrove restorations and nursery development. Reef Ball also participates in education and outreach regarding environmental stewardship and coral reefs.
In 2001, Reef Ball Foundation took control of the Reef Ball Development Group, and operates all aspects of the business as a non-profit organization. By 2007, the foundation has deployed 550,000 reef balls worldwide.
In 2019, Reef Ball Foundation deployed 1,400 reef balls in the shores of Progreso, Yucatán in Mexico. Artificial reefs were also built in Quintana Roo, Baja California, Colima, Veracruz, and Campache. Almost 25,000 reef balls have been established in the surrounding seas of Mexico. | 1 | Applied and Interdisciplinary Chemistry |
Gas chromatography (GC) coupled to mass spectrometry (MS) is one of the most widespread routine technologies applied to the large scale screening and discovery of novel biomarkers in metabolomics. However, the majority of MSTs currently measured in plant metabolomic profiling experiments remains unidentified due to the lack of authenticated pure reference substances and the expensive and time-consuming effort to maintain mass spectral RI libraries required for compound identification by GC-MS.
As the communication of analytical results and other approach-related details such as mass spectral and RI reference information within the scientific community is becoming increasingly popular, open access platforms for information exchange, such as the GMD, are obligatory.
Due to the lack of mandatory standards it remains difficult to compare individual mass spectrums.
While the different mass detector technologies, namely
quadrupole, ion trap and time of flight, can be deemed irrelevant, the chromatography settings such as temperature programming, type of capillary column and choice of column manufacturer heavily affect the empirically determined RI properties. Procedures for the transfer of RI properties between chromatography variants are, therefore, highly relevant for a shared library use. The GMD assesses the accuracy of RI transfer between chromatography variants and implements means to transfer empirically determined RI properties.
Aiming at the classification and identification of un-identified MSTs, the GMD accesses the information on available reference compounds. These compounds serve as training set of data to apply decision trees (DT) as a supervised machine learning approach. Structural feature extraction was applied to classify the metabolite space of the GMD prior to DT training. DT-based predictions of the most frequent substructures classify low resolution GC-MS mass spectra of the linked (potentially unknown) metabolite with respect to the presence or absence of the chemical moieties.
The web-based frontend supports conventional mass spectral and RI comparison by ranked hit lists as well as advanced DT supported substructure prediction. Batch processing is enabled via Simple Object Access Protocol (SOAP)-based web services while web-based data access services expose particular data base entities adapting Representational State Transfer (ReST) principles and mass spectral standards such as NIST-MSP and JCAMP-DX.
The GMD visualise quantitative metabolite pool size changes data. | 0 | Theoretical and Fundamental Chemistry |
The relative motion between a droplet and the gas results in an increase of the heat and mass transfer rates in the gas film surrounding the droplet. A convective boundary layer and a wake can surround the droplet. Furthermore, the shear force on the liquid surface causes an internal circulation that enhances the heating of the liquid. As a consequence, the vaporization rate increases with the droplet Reynolds number. Many different models exist for the single convective droplet vaporization case. Vaporizing droplet models can be seen to belong to six different classes:
# Constant droplet temperature model (d-law)
# Infinite liquid conductivity model
# Spherically symmetric transient droplet heating model
# Effective conductivity model
# Vortex model of droplet heating
# Navier-Stokes solution
The main difference between all these models is the treatment of the heating of the liquid phase which is usually the rate controlling phenomenon in droplet vaporization. The first three models do not consider internal liquid circulation. The effective conductivity model (4) and the vortex model of droplet heating (5) account for internal circulation and internal convective heating. The direct resolution of the Navier-Stokes equations provide, in principle, exact solutions both for the gas phase and the liquid phase.
Model (1) is a simplification of model (2) which is in turn a simplification of model (3). The spherically symmetric transient droplet heating model (3) solves the equation for heat diffusion through the liquid phase. A droplet heating time τ can be defined as the time required for a thermal diffusion wave to penetrate from the droplet surface to its center. The droplet heating time is compared to the droplet lifetime, τ. If the droplet heating time is short compared to the droplet lifetime we can assume that the temperature field inside the droplet is uniform and model (2) is obtained. In the infinite liquid conductivity model (2) the temperature of the droplet is uniform but varies with time. It is possible to go one step further and find the conditions for which we can neglect the temporal variation of the droplet temperature. The liquid temperature varies in time until the wet-bulb temperature is reached. If the wet-bulb temperature is reached in a time of the same order of magnitude as the droplet heating time, then the liquid temperature can be considered to be constant with regard to time; model (1), the d-law, is obtained.
The infinite liquid conductivity model is widely used in industrial spray calculations: for its balance between computational costs and accuracy. To account for the convective effects which enhanced the heat and mass transfer rates around the droplet, a correction is applied to the spherically symmetric expressions of the Sherwood and Nusselt numbers
Abramzon and Sirignano suggest the following formulation for the modified Sherwood and Nusselt numbers:
where and account for surface blowing which results in a thickening of the boundary layer surrounding the droplet.
and can be found from the well-known Frössling, or Ranz-Marshall, correlation:
where
* is the Schmidt number,
* is the Prandtl number,
* is the Reynolds number.
The expressions above show that the heat and mass transfer rates increase with increasing Reynolds number. | 1 | Applied and Interdisciplinary Chemistry |
The woodsprite (Atokirina in Navi) is an animal, also called seed, of the "holy tree", appearing similar to airborne jellyfish. Neytiri describes them as very pure spirits, and slaps Jake for shooing two of them away. The Omaticaya Clan plants one of these seeds on the body of a deceased Navi, so the Navis consciousness will become part of Eywa. | 1 | Applied and Interdisciplinary Chemistry |
The Colebrook equation is usually solved numerically due to its implicit nature. Recently, the Lambert W function has been employed to obtain explicit reformulation of the Colebrook equation.
or
will get:
then: | 1 | Applied and Interdisciplinary Chemistry |
Arsenic exposure in small children distorts the ratio of T helper cells (CD4) to cytotoxic T cells (CD8), which are responsible for immunodepression. In addition, arsenic also increases the number of inflammatory molecules being secreted through macrophages. The excess amount of granulocytes and monocytes lead to a chronic state of inflammation, which might result in cancer development. | 1 | Applied and Interdisciplinary Chemistry |
The Westinghouse Lamp Plant was constructed on Arlington Avenue in 1920 near the Watsessing Station of the rail line in the Watsessing neighborhood that connected Montclair, Glen Ridge and Bloomfield. The population in the area had grown since the time that the Township of Bloomfield was incorporated as a township from portions of Newark Township by an act of the New Jersey Legislature on March 23, 1812 until World War II. The population boom was contributed by the manufacturing jobs at the Westinghouse Lamp Plant along with other manufacturing plants such as General Electric, Lehn and Fink and Schering during the war time.
The Westinghouse Lamp Plant was devoted to lamp manufacturing in its early years. The plant had a research department to find a new suitable material for a light bulb filament. After World War I, the department led by Harvey C. Rentschler, and his deputy, John W. Marden, started looking into uranium to discover whether there was any similarity with tungsten to be used as a filament. The problem at the time was to make uranium into a metal form so that researchers could work with it. Westinghouse failed to establish uranium as a viable filament material, however, the research department continued to experiment with it until they found an electrolysis method to use a fused uranium salt to produce a metal. The metal was pure enough for nuclear research in many university laboratories during the 1930s. By 1941, Westinghouse Lamp Plant had the only practical process for producing pure uranium metal. | 1 | Applied and Interdisciplinary Chemistry |
* The mass-market application of microchannel plates is in image intensifier tubes of night vision goggles, which amplify visible and invisible light to make dark surroundings visible to the human eye.
* A 1 GHz real-time display CRT for an analog oscilloscope (the Tektronix 7104) used a microchannel plate placed behind the phosphor screen to intensify the image. Without the plate, the image would be excessively dim, because of the electron-optical design.
* MCP detectors are often employed in instrumentation for physical research, and they can be found in devices such as electron and mass spectrometers. | 0 | Theoretical and Fundamental Chemistry |
According to momentum theory, a velocity is imparted to the air passing through the propeller, and half of this velocity is given the air by the time it reaches the propeller plane. This increase of velocity of the air as it passes into the propeller disc is called the inflow velocity. It is always found where there is pressure discontinuity in a fluid. In the case of a wing moving horizontally, the air is given a downward velocity, as shown in Fig. 4., and theoretically half of this velocity is imparted in front of and above the wing, and the other half below and behind.
This induced downflow is present in the model wing tests from which the airfoil coefficients used in the blade-element theory are obtained; the inflow indicated by the momentum theory is therefore automatically taken into account in the simple blade-element theory. However, the induced downflow is widely different for different aspect ratios, being zero for infinite aspect ratio. Most model airfoil tests are made with rectangular wings having an arbitrarily chosen aspect ratio of 6, and there is no reason to suppose that the downflow in such a test corresponds to the inflow for each element of a propeller blade. In fact, the general conclusion drawn from an exhaustive series of tests, in which the pressure distribution was measured over 12 sections of a model propeller running in a wind tunnel, is that the lift coefficient of the propeller blade element differs considerably from that measured at the same angle of attack on an airfoil of aspect ratio 6. This is one of the greatest weaknesses of the simple blade-element theory.
Another weakness is that the interference between the propeller blades is not considered. The elements of the blades at any particular radius form a cascade similar to a multiplane with negative stagger, as shown in Fig. 4. Near the tips where the gap is large the interference is very small, but in toward the blade roots it is quite large.
In actual propellers there is a tip loss which the blade-element theory does not take into consideration. The thrust and torque forces as computed by means of the theory are therefore greater for the elements near the tip than those found by experiment.
In order to eliminate scale effect, the wind tunnel tests on model wings should be run at the same value of Reynolds number (scale) as the corresponding elements in the propeller blades. Airfoil characteristics measured at such a low scale as, for example, an air velocity of 30 m.p.h. with a 3-in. chord airfoil, show peculiarities not found when the tests are run at a scale comparable with that of propeller elements. The standard propeller section characteristics given in Figs. 11, 12, 13, and 14 were obtained from high Reynolds-number tests in the Variable Density Tunnel of the N.A.C.A., and, fortunately, for all excepting the thickest of these sections there is very little difference in characteristics at high and low Reynolds numbers. These values may be used with reasonable accuracy as to scale for propellers operating at tip speeds well below the speed of sound in air, and therefore relatively free from any effects of compressibility.
The poor accuracy of the simple blade-element theory is very well shown in a report by Durand and Lesley, in which they have computed the performance of a large number of model propellers (80) and compared the computed values with the actual performances obtained from tests on the model propellers themselves. In the words of the authors: The airfoils were tested in two different wind tunnels and in one of the tunnels at two different air velocities, and the propeller characteristics computed from the three sets of airfoil data differ by as much as 28%, illustrating quite forcibly the necessity for having the airfoil tests made at the correct scale.
In spite of all its inaccuracies the simple blade-element theory has been a useful tool in the hands of experienced propeller designers. With it a skilful designer having a knowledge of suitable empirical factors can design propellers which usually fit the main conditions imposed upon them fairly well in that they absorb the engine power at very nearly the proper revolution speed. They are not, however, necessarily the most efficient propellers for their purpose, for the simple theory is not sufficiently accurate to show slight differences in efficiency due to changes in pitch distribution, plan forms, etc. | 1 | Applied and Interdisciplinary Chemistry |
Though many people conceptualize images and diffraction patterns separately, they contain principally the same information. In the simplest approximation, the two are simply Fourier transforms of one another. Thus, the effects of beam precession on diffraction patterns also have significant effects on the corresponding images in the TEM. Specifically, the reduced dynamical intensity transfer between beams that is associated with PED results in reduced dynamical contrast in images collected during precession of the beam. This includes a reduction in thickness fringes, bend contours, and strain fields. While these features can often provide useful information, their suppression enables a more straightforward interpretation of diffraction contrast and mass contrast in images. | 0 | Theoretical and Fundamental Chemistry |
:For a synthetic analogue see also 3,5-Difluoro-4-hydroxybenzylidene imidazolinone.
Mechanistically, the process involves base-mediated cyclization followed by dehydration and oxidation. In the reaction of 7a to 8 involves the formation of an enamine from the imine, while in the reaction of 7b to 9 a proton is abstracted. The formed HBI fluorophore is highlighted in green.
The reactions are catalyzed by residues Glu222 and Arg96. An analogous mechanism is also possible with threonine in place of Ser65. | 1 | Applied and Interdisciplinary Chemistry |
The Lydersen method is a group contribution method for the estimation of critical properties temperature (T), pressure (P) and volume (V). The Lydersen method is the prototype for and ancestor of many new models like Joback, Klincewicz,
Ambrose,
Gani-Constantinou and others.
The Lydersen method is based in case of the critical temperature on the Guldberg rule which establishes a relation between the normal boiling point and the critical temperature. | 0 | Theoretical and Fundamental Chemistry |
Clean up efforts have led to a reconstructed Hazeltine Creek, although the contaminated slurry that made its way into Polley Lake and Quesnel Lake remains in the waterways. A drinking water ban was lifted within weeks of the spill and regular water testing is being conducted by the B.C. government, the Mount Polley mine, the University of Northern British Columbia and local residents.
Other remediation and reconstruction efforts have included investigation on impacts to human health and safety and affected ecosystems while removing the tailings spill, reconstructing creek shorelines, installing fish habitats, and replanting trees and other local vegetation. Investigation by the remediation team showed elevated levels of selenium, arsenic and other metals. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits