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Modulating the pyrimidine metabolism pharmacologically has therapeutical uses, and could implement in cancer treatment.
Pyrimidine synthesis inhibitors are used in active moderate to severe rheumatoid arthritis and psoriatic arthritis, as well as in multiple sclerosis. Examples include Leflunomide and Teriflunomide (the active metabolite of leflunomide). | 1 | Applied and Interdisciplinary Chemistry |
Polyadenylation is the covalent linkage of a polyadenylyl moiety to a messenger RNA molecule. In eukaryotic organisms most messenger RNA (mRNA) molecules are polyadenylated at the 3' end, but recent studies have shown that short stretches of uridine (oligouridylation) are also common. The poly(A) tail and the protein bound to it aid in protecting mRNA from degradation by exonucleases. Polyadenylation is also important for transcription termination, export of the mRNA from the nucleus, and translation. mRNA can also be polyadenylated in prokaryotic organisms, where poly(A) tails act to facilitate, rather than impede, exonucleolytic degradation.
Polyadenylation occurs during and/or immediately after transcription of DNA into RNA. After transcription has been terminated, the mRNA chain is cleaved through the action of an endonuclease complex associated with RNA polymerase. After the mRNA has been cleaved, around 250 adenosine residues are added to the free 3' end at the cleavage site. This reaction is catalyzed by polyadenylate polymerase. Just as in alternative splicing, there can be more than one polyadenylation variant of an mRNA.
Polyadenylation site mutations also occur. The primary RNA transcript of a gene is cleaved at the poly-A addition site, and 100–200 As are added to the 3 end of the RNA. If this site is altered, an abnormally long and unstable mRNA construct will be formed. | 1 | Applied and Interdisciplinary Chemistry |
When compounded with fibers, thermosetting resins form fiber-reinforced polymer composites, which are used in the fabrication of factory-finished structural composite OEM or replacement parts, and as site-applied, cured and finished composite repair and protection materials. When used as the binder for aggregates and other solid fillers, they form particulate-reinforced polymer composites, which are used for factory-applied protective coating or component manufacture, and for site-applied and cured construction, or maintenance purposes. | 0 | Theoretical and Fundamental Chemistry |
Dioxiranes are derivatives of this parent in which the hydrogens are replaced by other groups. Difluorodioxirane, which boils at about –80 to –90 °C, is one of the very few dioxirane derivatives that is stable in pure form at room temperature and is thermodynamically stable (ΔH° = –104 kcal/mol). Dimesityldioxirane is another relatively stable derivative which has been characterized by X-ray crystallography.
Dimethyldioxirane (DMDO) and the still more reactive methyl(trifluoromethyl)dioxirane have seen some use in organic synthesis, Dioxiranes are intermediate in the Shi epoxidation reaction. | 0 | Theoretical and Fundamental Chemistry |
The discovery that the β chemokines RANTES, MIP (macrophage inflammatory proteins) 1α and 1β (now known as CCL5, CCL3 and CCL4 respectively) suppress HIV-1 provided the initial connection and indicated that these molecules might control infection as part of immune responses in vivo, and that sustained delivery of such inhibitors have the capacity of long-term infection control. The association of chemokine production with antigen-induced proliferative responses, more favorable clinical status in HIV infection, as well as with an uninfected status in subjects at risk for infection suggests a positive role for these molecules in controlling the natural course of HIV infection. | 1 | Applied and Interdisciplinary Chemistry |
Micromatabilin, the green pigment of the spider species Micrommata virescens, is characterized as a mixture of biliverdin conjugates. The two isolated fractions have identical absorption bands (free base: 620–630 μm, hydrochloride: 690 μm, zinc complex: 685–690 μm). Chromic acid degradation yields imides I, II, IIIa, and IIIb. Differences in the non-hydrolytic degradation and in polarity lead to the conclusion that fraction 1 is a monoconjugate and fraction 2a diconjugate of biliverdin. | 1 | Applied and Interdisciplinary Chemistry |
An expanded granular sludge bed (EGSB) reactor is a variant of the upflow anaerobic sludge blanket digestion (UASB) concept for anaerobic wastewater treatment. The distinguishing feature is that a faster rate of upward-flow velocity is designed for the wastewater passing through the sludge bed. The increased flux permits partial expansion (fluidisation) of the granular sludge bed, improving wastewater-sludge contact as well as enhancing segregation of small inactive suspended particle from the sludge bed. The increased flow velocity is either accomplished by utilizing tall reactors, or by incorporating an effluent recycle (or both). A scheme depicting the EGSB design concept is shown in this EGSB diagram.
The EGSB design is appropriate for low strength soluble wastewaters (less than 1 to 2 g soluble COD/l) or for wastewaters that contain inert or poorly biodegradable suspended particles which should not be allowed to accumulate in the sludge bed. | 1 | Applied and Interdisciplinary Chemistry |
Supercritical carbon dioxide is also emerging as a useful high-temperature refrigerant, being used in new, CFC/HFC-free domestic heat pumps making use of the transcritical cycle. These systems are undergoing continuous development with supercritical carbon dioxide heat pumps already being successfully marketed in Asia. The EcoCute systems from Japan are some of the first commercially successful high-temperature domestic water heat pumps. | 0 | Theoretical and Fundamental Chemistry |
When the adhesion is stronger than the cohesion, fewer liquid particles turn into vapor thereby lowering the vapor pressure and leading to negative deviation in the graph.
For example, the system of chloroform (CHCl) and acetone (CHCOCH) has a negative deviation from Raoults law, indicating an attractive interaction between the two components that have been described as a hydrogen bond. The system HCl–water has a large enough negative deviation to form a minimum in the vapor pressure curve known as a (negative) azeotrope, corresponding to a mixture that evaporates without change of composition. When these two components are mixed, the reaction is exothermic as ion-dipole intermolecular forces of attraction are formed between the resulting ions (HO and Cl) and the polar water molecules so that ΔH' is negative. | 0 | Theoretical and Fundamental Chemistry |
In the mid-1960s, the role of tRNA in protein synthesis was being intensively studied. At this point, ribosomes had been implicated in protein synthesis, and it had been shown that an mRNA strand was necessary for the formation of these structures. In a 1964 publication, Warner and Rich showed that ribosomes active in protein synthesis contained tRNA molecules bound at the A and P sites, and discussed the notion that these molecules aided in the peptidyl transferase reaction. However, despite considerable biochemical characterization, the structural basis of tRNA function remained a mystery. In 1965, Holley et al. purified and sequenced the first tRNA molecule, initially proposing that it adopted a cloverleaf structure, based largely on the ability of certain regions of the molecule to form stem loop structures. The isolation of tRNA proved to be the first major windfall in RNA structural biology. Following Robert W. Holleys publication, numerous investigators began work on isolation tRNA for crystallographic study, developing improved methods for isolating the molecule as they worked. By 1968 several groups had produced tRNA crystals, but these proved to be of limited quality and did not yield data at the resolutions necessary to determine structure. In 1971, Kim et al. achieved another breakthrough, producing crystals of yeast tRNA that diffracted to 2–3 Ångström resolutions by using spermine, a naturally occurring polyamine, which bound to and stabilized the tRNA. Despite having suitable crystals, however, the structure of tRNA was not immediately solved at high resolution; rather it took pioneering work in the use of heavy metal derivatives and a good deal more time to produce a high-quality density map of the entire molecule. In 1973, Kim et al.' produced a 4 Ångström map of the tRNA molecule in which they could unambiguously trace the entire backbone. This solution would be followed by many more, as various investigators worked to refine the structure and thereby more thoroughly elucidate the details of base pairing and stacking interactions, and validate the published architecture of the molecule.
The tRNA structure is notable in the field of nucleic acid structure in general, as it represented the first solution of a long-chain nucleic acid structure of any kind—RNA or DNA—preceding Richard E. Dickerson's solution of a B-form dodecamer by nearly a decade. Also, tRNA demonstrated many of the tertiary interactions observed in RNA architecture which would not be categorized and more thoroughly understood for years to come, providing a foundation for all future RNA structural research. | 1 | Applied and Interdisciplinary Chemistry |
Bisphosphonates are an important class of drugs originally commercialised in the mid to late 20th century. They are used for the treatment of osteoporosis and other bone disorders that cause bone fragility and diseases where bone resorption is excessive. Osteoporosis is common in post-menopausal women and patients in corticosteroid treatment where biphosphonates have been proven a valuable treatment and also used successfully against Paget's disease, myeloma, bone metastases and hypercalcemia. Bisphosphonates reduce breakdown of bones by inhibiting osteoclasts, they have a long history of use and today there are a few different types of bisphosphonate drugs on the market around the world. | 1 | Applied and Interdisciplinary Chemistry |
Surface diffusion is a general process involving the motion of adatoms, molecules, and atomic clusters (adparticles) at solid material surfaces. The process can generally be thought of in terms of particles jumping between adjacent adsorption sites on a surface, as in figure 1. Just as in bulk diffusion, this motion is typically a thermally promoted process with rates increasing with increasing temperature. Many systems display diffusion behavior that deviates from the conventional model of nearest-neighbor jumps. Tunneling diffusion is a particularly interesting example of an unconventional mechanism wherein hydrogen has been shown to diffuse on clean metal surfaces via the quantum tunneling effect.
Various analytical tools may be used to elucidate surface diffusion mechanisms and rates, the most important of which are field ion microscopy and scanning tunneling microscopy. While in principle the process can occur on a variety of materials, most experiments are performed on crystalline metal surfaces. Due to experimental constraints most studies of surface diffusion are limited to well below the melting point of the substrate, and much has yet to be discovered regarding how these processes take place at higher temperatures.
Surface diffusion rates and mechanisms are affected by a variety of factors including the strength of the surface-adparticle bond, orientation of the surface lattice, attraction and repulsion between surface species and chemical potential gradients. It is an important concept in surface phase formation, epitaxial growth, heterogeneous catalysis, and other topics in surface science. As such, the principles of surface diffusion are critical for the chemical production and semiconductor industries. Real-world applications relying heavily on these phenomena include catalytic converters, integrated circuits used in electronic devices, and silver halide salts used in photographic film. | 0 | Theoretical and Fundamental Chemistry |
;Aldehydes and ketones
Polymeric hydrosilanes, such as polymethylhydrosiloxane (PHMS), may be employed to facilitate separation of the reduced products from silicon-containing byproducts.
Enantioselective reductions of ketones may be accomplished through the use of catalytic amounts of chiral transition metal complexes. In some cases, the transition metal simply serves as a Lewis acid that coordinates to the ketone oxygen; however, some metals (most notably copper) react with hydrosilanes to afford metal hydride intermediates, which act as the active reducing agent.
In the presence of rhodium catalyst 1 and rhodium trichloride, 2-phenylcyclohexanone is reduced with no diastereoselectivity but high enantioselectivity.
;Esters
Esters may be reduced to alcohols under conditions of nucleophilic activation with caesium or potassium fluoride.
Aldehydes undergo hydrosilylation in the presence of hydrosilanes and fluoride. The resulting silyl ethers can be hydrolyzed with 1 M hydrochloric acid. Optimal yields of the hydrosilylation are obtained when the reaction is carried out in very polar solvents. | 0 | Theoretical and Fundamental Chemistry |
* Spinal neurons that pass over to the opposite side of the spinal cord.
* A protein complex that contains two or more different polypeptides. | 1 | Applied and Interdisciplinary Chemistry |
Ann E. McDermott is an American biophysicist who uses nuclear magnetic resonance to study the structure, function, and dynamics of proteins in native-like environments. She is currently the Esther Breslow Professor of Biological Chemistry and Chair of the Educational Policy and Planning Committee of the Arts and Sciences at Columbia University. She has also previously served as Columbia's Associate Vice President for Academic Advising and Science Initiatives in the Arts and Sciences. She is an elected member of both the American Academy of Arts and Sciences and the National Academy of Sciences. | 0 | Theoretical and Fundamental Chemistry |
Most imaging tests have not been able to localize recurrent prostate cancer when the PSA is mildly increased. Axumin scans were compared to [C]-tagged choline PET scans, another FDA approved PET scan that can assist in this situation, and to biopsy results. Fluciclovine tagged PET scans appear to more sensitive than CT scans and to [C]-tagged choline PET scans. | 1 | Applied and Interdisciplinary Chemistry |
The Japanese program in the late 1980s concentrated on closed-cycle MHD. The belief was that it would have higher efficiencies, and smaller equipment, especially in the clean, small, economical plant capacities near 100 megawatts (electrical) which are suited to Japanese conditions. Open-cycle coal-powered plants are generally thought to become economical above 200 megawatts.
The first major series of experiments was FUJI-1, a blow-down system powered from a shock tube at the Tokyo Institute of Technology. These experiments extracted up to 30.2% of enthalpy, and achieved power densities near 100 megawatts per cubic meter. This facility was funded by Tokyo Electric Power, other Japanese utilities, and the Department of Education. Some authorities believe this system was a disc generator with a helium and argon carrier gas and potassium ionization seed.
In 1994, there were detailed plans for FUJI-2, a 5 MWe continuous closed-cycle facility, powered by natural gas, to be built using the experience of FUJI-1. The basic MHD design was to be a system with inert gases using a disk generator. The aim was an enthalpy extraction of 30% and an MHD thermal efficiency of 60%. FUJI-2 was to be followed by a retrofit to a 300MWe natural gas plant. | 1 | Applied and Interdisciplinary Chemistry |
The ISASMELT process began with the invention in 1973 of the Sirosmelt lance by Drs Bill Denholm and John Floyd at the CSIRO. The lance was developed as a result of investigations into improved tin-smelting processes, in which it was found that the use of a top-entry submerged lance would result in greater heat transfer and mass transfer efficiencies.
The idea of top-entry submerged lances goes back to at least 1902, when such a system was attempted in Clichy, France. However, early attempts failed because of the short lives of the lances on submersion in the bath. The Mitsubishi copper smelting process is one alternative approach, wherein lances are used in a furnace, but they are not submerged into the bath. Instead, they blow oxygen-enriched air onto the surface of the slag (top jetting). Similarly, a water-cooled, top-jetting lance was the basis of the LD (Linz-Donawitz) steelmaking process. This does not produce the same intensity of mixing in the bath as a submerged lance.
The CSIRO scientists first tried developing a submerged lance system using a water-cooled lance, but moved to an air-cooled system because "scale up of the water-cooled lance would have been problematic". Introducing any water to a system involving molten metals and slags can result in catastrophic explosions, such as that in the Scunthorpe Steelworks in November 1975 in which 11 men lost their lives.
The inclusion of the swirlers in the Sirosmelt lance and forming a splash coating of slag on the lance were the major innovations that led to the successful development of submerged lance smelting.
From 1973, the CSIRO scientists began a series of trials using the Sirosmelt lance to recover metals from industrial slags in Australia, including lead softener slag at the Broken Hill Associated Smelters in Port Pirie (1973), tin slag from Associated Tin Smelters in Sydney (1974), copper converter slag at the Electrolytic Refining and Smelting ("ER&S") Port Kembla plant (1975) and copper anode furnace slag at Copper Refineries Limited (another subsidiary of MIM Holdings) in Townsville (1976) and of copper converter slag in Mount Isa (1977). The work then proceeded to smelting tin concentrates (1975) and then sulfidic tin concentrates (1977).
MIM and ER&S jointly funded the 1975 Port Kembla converter slag treatment trials and MIM's involvement continued with the slag treatment work in Townsville and Mount Isa.
In parallel with the copper slag treatment work, the CSIRO was continuing to work in tin smelting. Projects included a five tonne ("t") plant for recovering tin from slag being installed at Associated Tin Smelters in 1978, and the first sulfidic smelting test work being done in collaboration with Aberfoyle Limited, in which tin was fumed from pyritic tin ore and from mixed tin and copper concentrates. Aberfoyle was investigating the possibility of using the Sirosmelt lance approach to improve the recovery of tin from complex ores, such as its mine at Cleveland, Tasmania, and the Queen Hill ore zone near Zeehan in Tasmania.
The Aberfoyle work led to the construction and operation in late 1980 of a four t/h tin matte fuming pilot plant at the Western Mining Corporation's Kalgoorlie Nickel Smelter, located to the south of Kalgoorlie, Western Australia. | 1 | Applied and Interdisciplinary Chemistry |
Oct-2 (octamer-binding protein 2) also known as POU domain, class 2, transcription factor 2 is a protein that in humans is encoded by the POU2F2 gene.
Oct-2 is an octamer transcription factor which is a member of the POU family. | 1 | Applied and Interdisciplinary Chemistry |
Ankaramite is volcanic rock type of mafic composition. It is a dark porphyritic variety of basanite containing abundant pyroxene and olivine phenocrysts. It contains minor amounts of plagioclase and accessory biotite, apatite, and iron oxides.
Its type locality is Ankaramy in Madagascar. It was first described in 1916. It is also found in the Sierra de Guanajuato of Central Mexico, the South Pacific on islands such as Tahiti, Rarotonga, Samoa and in the Zealandia, Alexandra Volcanic Group. | 0 | Theoretical and Fundamental Chemistry |
Mechanical lysis involves the use of physical force, such as grinding or sonication, to break down bacterial cells and release the plasmid DNA. There are several different mechanical lysis methods that can be used, including French press, bead-beating, and ultrasonication. | 1 | Applied and Interdisciplinary Chemistry |
In the panel it is shown an example of the working principle of a Mott detector, supposing a value for . If an electron beam with a 3:1 ratio of spin-up over spin-down electrons collide with the target, it will be splitted with a ratio 5:3, according to previous equation, with an asymmetry of 25%. | 0 | Theoretical and Fundamental Chemistry |
Some companion plants help prevent pest insects or pathogenic fungi from damaging the crop, through their production of aromatic volatile chemicals, another type of allelopathy. For example, the smell of the foliage of marigolds is claimed to deter aphids from feeding on neighbouring plants. A 2005 study found that oil volatiles extracted from Mexican marigold could suppress the reproduction of three aphid species (pea aphid, green peach aphid and glasshouse and potato aphid) by up to 100% after 5 days from exposure. Another example familiar to gardeners is the interaction of onions and carrots with each other's pests: it is popularly believed that the onion smell puts off carrot root fly, while the smell of carrots puts off onion fly.
Some studies have demonstrated beneficial effects. For instance, cabbage crops can be seriously damaged by the cabbage moth. It has a natural enemy, the parasitoid wasp Microplitis mediator. Companion planting of cornflowers among cabbages enables the wasp to increase sufficiently in number to control the moth. This implies the possibility of natural control, with reduced use of insecticides, benefiting the farmer and local biodiversity. In horticulture, marigolds provide good protection to tomato plants against the greenhouse whitefly (an aphid), via the aromatic limonene that they produce. Not all combinations of target and companion are effective; for instance, clover, a useful companion to many crop plants, does not mask Brassica crops.
However, effects on multi-species systems are complex and may not increase crop yields. Thus, French marigold inhibits codling moth, a serious pest whose larva destroys apples, but it also inhibits the moths insect enemies, such as the parasitoid wasp Ascogaster quadridentata', an ichneumonid. The result is that the companion planting fails to reduce damage to apples. | 1 | Applied and Interdisciplinary Chemistry |
Transmission of electric discharge through a glass tube with quartz windows containing a mixture of nitrogen and sulfur vapor (rigorously free of oxygen) results in the spectrum of emitted light gaining bands consistent with the formation of NS.
Passing a mixture of gaseous N and SCl through the side arm of an absorption cell undergoing microwave discharge produces NS. Infrared diode laser spectroscopy taken using this method allowed for derivation of the equilibrium rotational constant, and therefore calculation of the equilibrium bond length as 1.4940 Å.
With low pressure microwave discharge of elemental nitrogen and sulfur, followed by low temperature trapping in argon matrices, one obtains a mixture of products including NS, NNS, SNS, and NSS. By adding excess sulfur, SSNS is also produced. | 0 | Theoretical and Fundamental Chemistry |
Leonard P. Guarente is recognized as the leading proponent of the hypothesis that caloric restriction slows aging by activation of Sirtuins.
STACs have been discovered by Konrad Howitz of Biomol Inc and biologist David Sinclair. In September 2003, Howitz and Sinclair et al. published a highly cited paper reporting that polyphenols such as resveratrol activate human SIRT1 and extend the lifespan of budding yeast (Howitz et al., Nature, 2003). Other examples of such products are butein, piceatannol, isoliquiritigenin, fisetin, and quercetin.
Sirtuins depend on the crucial cellular molecule called nicotinamide adenine dinucleotide (NAD+) for their function. Falling NAD+ levels during aging may adversely impact sirtuin maintenance of DNA integrity and ability to combat oxidative stress-induced cell damage. Increasing cellular NAD+ levels with supplements like nicotinamide mononucleotide (NMN) during aging may slow or reverse certain aging processes with sirtuin function enhancement.
Some STACs can cause artificial effects in the assay initially used for their identification, but it has been shown that STACs also activate SIRT1 against regular polypeptide substrates, with an influence of the substrate sequence.
Sirtris Pharmaceuticals, Sinclair's company, was purchased by GlaxoSmithKline (GSK) in 2008, and subsequently shut down as a separate entity within GSK. | 1 | Applied and Interdisciplinary Chemistry |
The biosynthesis of asparagine originates with aspartate using a transaminase enzyme. The enzyme asparagine synthetase produces asparagine, AMP, glutamate, and pyrophosphate from aspartate, glutamine, and ATP. In the asparagine synthetase reaction, ATP is used to activate aspartate, forming β-aspartyl-AMP. Glutamine donates an ammonium group, which reacts with β-aspartyl-AMP to form asparagine and free AMP.
Two asparagine synthetases are found in bacteria. Both are referred to as the AsnC protein. They are coded for by the genes AsnA and AsnB. AsnC is autogenously regulated, which is where the product of a structural gene regulates the expression of the operon in which the genes reside. The stimulating effect of AsnC on AsnA transcription is downregulated by asparagine. However, the autoregulation of AsnC is not affected by asparagine. | 1 | Applied and Interdisciplinary Chemistry |
Mass spectrometry measures mass-to-charge ratio of molecules using electric and magnetic fields. There are several ionization methods: electron ionization, chemical ionization, electrospray, fast atom bombardment, matrix-assisted laser desorption/ionization, and others. Also, mass spectrometry is categorized by approaches of mass analyzers: magnetic-sector, quadrupole mass analyzer, quadrupole ion trap, time-of-flight, Fourier transform ion cyclotron resonance, and so on. | 0 | Theoretical and Fundamental Chemistry |
*Go Down Old Hannah: the Living History of African American Texans Naomi Mitchell Carrier
*They Dance Alone Christine LeVeaux (2005)
*Harlem Renaissance by Ella O. Williams
*National Medical Association journal covers
**Summer 2007, Volume 99, Number 12
**December 2008, Volume 100, Number 12
**January 2010, Volume 102, Number 1
*National Directory of African American Organizations 2001–2003 Philip Morris Co. (Keep the Dream Alive)
*Worship in the House was commissioned by Integrity Music to be used as a CD cover.
*Beyond the Blues: Reflections of African America in the Fine Arts Collection of the Amistad Research Center (The Struggle Continues)
*2006 South Central Region Jack and Jill of America cookbook
*The Ensemble Theatre's 2008 production of Radio Golf playbill cover. | 0 | Theoretical and Fundamental Chemistry |
* Edward Harrison Memorial Prize (1932)
* Tilden Lecture to the Chemical Society (1942)
* Fellow of the Royal Society (1946)
* Liversidge Award (1954)
* Alfred Stock Memorial Prize and medal of the Gesellschaft Deutscher Chemiker (1954)
* Commander of the Order of the British Empire (1958)
* Davy Medal of the Royal Society (1962)
* Henri Moissan prize for fluorine chemistry, Germany (1991)
* Lavoisier Medal of the Société Chimique de France (French Chemical Society) | 0 | Theoretical and Fundamental Chemistry |
The hydrogenation of alkenes to alkanes is exothermic. The amount of energy released during a hydrogenation reaction, known as the heat of hydrogenation, is inversely related to the stability of the starting alkene: the more stable the alkene, the lower its heat of hydrogenation. Examining the heats of hydrogenation for various alkenes reveals that stability increases with the amount of substitution.
The increase in stability associated with additional substitutions is the result of several factors. Alkyl groups are electron donating by inductive effect, and increase the electron density on the sigma bond of the alkene. Also, alkyl groups are sterically large, and are most stable when they are far away from each other. In an alkane, the maximum separation is that of the tetrahedral bond angle, 109.5°. In an alkene, the bond angle increases to near 120°. As a result, the separation between alkyl groups is greatest in the most substituted alkene.
Hyperconjugation, which describes the stabilizing interaction between the HOMO of the alkyl group and the LUMO of the double bond, also helps explain the influence of alkyl substitutions on the stability of alkenes. In regards to orbital hybridization, a bond between an sp carbon and an sp carbon is stronger than a bond between two sp-hybridized carbons. Computations reveal a dominant stabilizing hyperconjugation effect of 6 kcal/mol per alkyl group. | 0 | Theoretical and Fundamental Chemistry |
The earliest sources of tin in the Early Bronze Age in the Near East are still unknown and the subject of much debate in archaeology.) Possibilities include minor now-depleted sources in the Near East, trade from Central Asia, Sub-Saharan Africa, Europe, or elsewhere.
It is possible that as early as 2500 BC, the Ore Mountains had begun exporting tin, using the well established Baltic amber trade route to supply Scandinavia as well as the Mediterranean with tin. By 2000 BC, the extraction of tin in Britain, France, Spain, and Portugal had begun and tin was traded to the Mediterranean sporadically from all these sources. Evidence of tin trade in the Mediterranean can be seen in a number of Bronze Age shipwrecks containing tin ingots such as the Uluburun off the coast of Turkey dated 1300 BC which carried over 300 copper bars weighing 10 tons, and approximately 40 tin bars weighing 1 ton. Evidence of direct tin trade between Europe and the Eastern Mediterranean has been demonstrated through the analysis of tin ingots dated to the 13th-12th centuries BC from sites in Israel, Turkey and modern-day Greece; tin ingots from Israel, for example, have been found to share chemical composition with tin from Cornwall and Devon (Great Britain).
While Sardinia does not appear to have much in terms of significant sources of tin, it does have rich copper and other mineral wealth and served as a centre for metals trade during the Bronze Age and likely actively imported tin from the Iberian Peninsula for export to the rest of the Mediterranean.
By classical Greek times, the tin sources were well established. Greece and the Western Mediterranean appear to have traded their tin from European sources, while the Middle East acquired their tin from Central Asian sources through the Silk Road. For example, Iron Age Greece had access to tin from Iberia by way of the Phoenicians who traded extensively there, from the Erzgebirge by way of the Baltic Amber Road overland route, or from Brittany and Cornwall through overland routes from their colony at Massalia (modern day Marseilles) established in the 6th century BC. In 450 BC, Herodotus described tin as coming from Northern European islands named the Cassiterides along the extreme borders of the world, suggesting very long-distance trade, likely from Britain, northwestern Iberia, or Brittany, supplying tin to Greece and other Mediterranean cultures. The idea that the Phoenicians went to Cornwall for its tin and supplied it to the whole of the Mediterranean has no archaeological basis and is largely considered a myth.
The early Roman world was mainly supplied with tin from its Iberian provinces of Gallaecia and Lusitania and to a lesser extent Tuscany. Pliny mentions that in 80 BC, a senatorial decree halted all mining on the Italian Peninsula, stopping any tin mining activity in Tuscany and increasing Roman dependence on tin from Brittany, Iberia, and Cornwall. After the Roman conquest of Gaul, Brittany's tin deposits saw intensified exploitation after the first century BC. With the exhaustion of the Iberian tin mines, Cornwall became a major supplier of tin for the Romans after the 3rd century AD.
Throughout the medieval period, demand for tin increased as pewter gained popularity. Brittany and Cornwall remained the major producers and exporters of tin throughout the Mediterranean through to modern times. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, the Darcy–Weisbach equation is an empirical equation that relates the head loss, or pressure loss, due to friction along a given length of pipe to the average velocity of the fluid flow for an incompressible fluid. The equation is named after Henry Darcy and Julius Weisbach. Currently, there is no formula more accurate or universally applicable than the Darcy-Weisbach supplemented by the Moody diagram or Colebrook equation.
The Darcy–Weisbach equation contains a dimensionless friction factor, known as the Darcy friction factor. This is also variously called the Darcy–Weisbach friction factor, friction factor, resistance coefficient, or flow coefficient. | 1 | Applied and Interdisciplinary Chemistry |
Cefuroxime is generally well tolerated, and its side effects are usually transient. If ingested after food, this antibiotic is both better absorbed and less likely to cause its most common side effects of diarrhea, nausea, vomiting, headaches/migraines, dizziness, and abdominal pain compared to most antibiotics in its class.
Although a widely stated cross-allergic risk of about 10% exists between cephalosporins and penicillin, an assessment in 2006 have shown no increased risk for a cross-allergic reaction for cefuroxime and several other second-generation or later cephalosporins. | 0 | Theoretical and Fundamental Chemistry |
Levonorgestrel is marketed alone or in combination with an estrogen (specifically ethinylestradiol, estradiol, or estradiol valerate) under a multitude of brand names throughout the world, including Alesse, Altavera, Alysena, Amethia, Amethyst, Ashlyna, Aviane, Camrese, Chateal, Climara Pro, Cycle 21, Daysee, Emerres, Enpresse, Erlibelle, Escapelle, Falmina, Introvale, Isteranda, Jadelle, Jaydess, Jolessa, Klimonorm, Kurvelo, Kyleena, Lessina, Levlen, Levodonna, Levonelle, Levonest, Levosert, Levora, Liletta, Loette, Logynon, LoSeasonique, Lutera, Lybrel, Marlissa, Microgynon, Microlut, Microvlar, Min-Ovral, Miranova, Mirena, My Way, Myzilra, Next Choice, Nordette, Norgeston, NorLevo, Norplant, One Pill, Option 2, Orsythia, Ovima, Ovranette, Plan B, Plan B One-Step, Portia, Postinor, Postinor-2, Preventeza, Ramonna, Rigevidon, Quartette, Quasense, Seasonale, Seasonique, Skyla, Sronyx, Tri-Levlen, Trinordiol, Triphasil, Triquilar, Tri-Regol, Trivora, and Upostelle, among many others. These formulations are used as emergency contraceptives, normal contraceptives, or in menopausal hormone therapy for the treatment of menopausal symptoms.
As an emergency contraceptive, levonorgestrel is often referred to colloquially as the "morning-after pill". | 0 | Theoretical and Fundamental Chemistry |
The most important aliphatic compounds are:
* n-, iso- and cyclo-alkanes (saturated hydrocarbons)
* n-, iso- and cyclo-alkenes and -alkynes (unsaturated hydrocarbons).
Important examples of low-molecular aliphatic compounds can be found in the list below (sorted by the number of carbon-atoms): | 0 | Theoretical and Fundamental Chemistry |
Transfer RNA (tRNA) helps decode a messenger RNA sequence into a protein. They function at specific sites within the ribosome during translation (the process going from code to protein). Within the mRNA molecule we have three nucleotides in length codons. These codons all have a unique universal code which represents a particular amino acid. tRNAs can be classified as an adaptor molecule, being typically 76 to 90 nucleotides in length. | 1 | Applied and Interdisciplinary Chemistry |
The Germanium Detector Array (GERDA) collaboration's result of phase I of the detector was a limit of years (90% C.L.). It used germanium both as source and detector material. Liquid argon was used for muon vetoing and as a shielding from background radiation. The -value of for 0νββ decay is 2039 keV, but no excess of events in this region was found. Phase II of the experiment started data-taking in 2015, and it used around 36 kg of germanium for the detectors. The exposure analyzed until July 2020 was 10.8 kg yr. Again, no signal was found and thus a new limit was set to years (90% C.L.). The detector has stopped working and published its final results in December 2020. No neutrinoless double beta decay was observed. | 0 | Theoretical and Fundamental Chemistry |
One of Robinsons primary research interests is environmental chemistry, including the detection of trace elements in environmental matrices by nuclear methods. In 1991, while at ORNL, Robinson was a participant in a well-publicized investigation into the cause of the death of 19th-century U.S. President Zachary Taylor. When Taylor died rather suddenly in 1850, the cause of his death was listed as gastroenteritis, but some historians thought he might have been poisoned with arsenic. His descendants gave permission for his remains to be exhumed in order to allow analysis of tiny samples of his hair and fingernails. With ORNLs High Flux Isotope Reactor as a neutron source, Robinson and colleagues used neutron activation analysis to measure arsenic levels in the samples.
The analysis led to a finding that Taylor did not die from arsenic poisoning, as arsenic was not detected in the samples, indicating that arsenic concentrations were many times lower than would be expected in arsenic poisoning. | 0 | Theoretical and Fundamental Chemistry |
High-spin metal complexes have singly occupied orbitals and may not have any empty orbitals into which ligands could donate electron density. In general, there are few or no π-acidic ligands in the complex. These singly occupied orbitals can combine with the singly occupied orbitals of radical ligands (e.g., oxygen), or addition of a strong field ligand can cause electron-pairing, thus creating a vacant orbital that it can donate into.
Examples:
*CrCl(THF) (15 e)
*[Mn(HO)] (17 e)
*[Cu(HO)] (21 e, see comments below)
Complexes containing strongly π-donating ligands often violate the 18-electron rule. These ligands include fluoride (F), oxide (O), nitride (N), alkoxides (RO), and imides (RN). Examples:
*[CrO] (16 e)
*Mo(=NR)Cl (12 e)
In the latter case, there is substantial donation of the nitrogen lone pairs to the Mo (so the compound could also be described as a 16 e compound). This can be seen from the short Mo–N bond length, and from the angle Mo–N–C(R), which is nearly 180°.
Counter-examples:
*trans-WO(MePCHCHPMe) (18 e)
*Cp*ReO (18 e)
In these cases, the M=O bonds are "pure" double bonds (i.e., no donation of the lone pairs of the oxygen to the metal), as reflected in the relatively long bond distances. | 0 | Theoretical and Fundamental Chemistry |
FIA is an automated method of chemical analysis in which a sample is injected into a flowing carrier solution that mixes with reagents before reaching a detector. Over past 30 years, FIA techniques developed into a wide array of applications using spectrophotometry, fluorescence spectroscopy, atomic absorption spectroscopy, mass spectrometry, and other methods of instrumental analysis for detection.
Automated sample processing, high repeatability, adaptability to micro-miniaturization, containment of chemicals, waste reduction, and reagent economy in a system that operates at microliter levels are all valuable assets that contribute to the application of flow injection to real-world assays. The main assets of flow injection are the well defined concentration gradient that forms when an analyte is injected into the reagent stream (which offers an infinite number of well-reproduced analyte/reagent ratios) and the exact timing of fluidic manipulations (which provide exquisite control over the reaction conditions).
Based on computer control, FIA evolved into Sequential Injection and Bead Injection which are novel techniques based on flow programming. FIA literature comprises over 22,000 scientific papers and 22 monographs. | 0 | Theoretical and Fundamental Chemistry |
The additional radioactivity in the biosphere caused by human activity due to the releases of man-made radioactivity and of Naturally Occurring Radioactive Materials (NORM) can be divided into several classes.
# Normal licensed releases which occur during the regular operation of a plant or process handling man-made radioactive materials.
#* For instance the release of Tc from a nuclear medicine department of a hospital which occurs when a person given a Tc imaging agent expels the agent.
# Releases of man-made radioactive materials which occur during an industrial or research accident.
#* For instance the Chernobyl accident.
# Releases which occur as a result of military activity.
#* For example, a nuclear weapons test.
# Releases which occur as a result of a crime.
#* For example, the Goiânia accident where thieves, unaware of its radioactive content, stole some medical equipment and as a result a number of people were exposed to radiation.
# Releases of naturally occurring radioactive materials (NORM) as a result of mining etc.
#* For example, the release of the trace quantities of uranium and thorium in coal, when it is burned in power stations. | 0 | Theoretical and Fundamental Chemistry |
A reactive center, also called a propagating center, in chemistry is a particular location, usually an atom, within a chemical compound that is the likely center of a reaction in which the chemical is involved. In chain-growth polymer chemistry, this is also the point of propagation for a growing chain. The reactive center is commonly radical, anionic, or cationic, but can also take other forms. | 0 | Theoretical and Fundamental Chemistry |
In polymer chemistry, reversible-deactivation radical polymerizations (RDRPs) are members of the class of reversible-deactivation polymerizations which exhibit much of the character of living polymerizations, but cannot be categorized as such as they are not without chain transfer or chain termination reactions.
Several different names have been used in literature, which are:
*Living radical polymerization
*Living free radical polymerization
*Controlled/"living" radical polymerization
*Controlled radical polymerization
*Reversible deactivation radical polymerization
Though the term "living" radical polymerization was used in early days, it has been discouraged by IUPAC, because radical polymerization cannot be a truly living process due to unavoidable termination reactions between two radicals. The commonly-used term controlled radical polymerization is permitted, but reversible-deactivation radical polymerization or controlled reversible-deactivation radical polymerization (RDRP) is recommended. | 0 | Theoretical and Fundamental Chemistry |
Dialysis tubing, also known as Visking tubing, is an artificial semi-permeable membrane tubing used in separation techniques, that facilitates the flow of tiny molecules in solution based on differential diffusion.
In the context of life science research, dialysis tubing is typically used in the sample clean-up and processing of proteins and DNA samples or complex biological samples such as blood or serums. Dialysis tubing is also frequently used as a teaching aid to demonstrate the principles of diffusion, osmosis, Brownian motion and the movement of molecules across a restrictive membrane.
For the principles and usage of dialysis in a research setting, see Dialysis (biochemistry). | 1 | Applied and Interdisciplinary Chemistry |
Atta-ur-Rahman has been selected as one of the 500 most influential personalities of the Islamic World. Institutions have been named after Rahman in China, the Atta-ur-Rahman Institute for Natural Product Discovery (AuRIns) in Malaysia and the Academician Professor Atta-ur-Rahman One Belt and One Road TCM Research Center were named after Rahman, as well as the Atta-ur-Rahman School of Applied Biosciences at the National University of Sciences & Technology (Islamabad, Pakistan) and the Atta-ur-Rahman Laboratories, International Center for Chemical and Biological Sciences at the University of Karachi (Karachi, Pakistan). The US Publisher ARKAT USA has published a special issue of the journal Arkivoc, Vol 2007, in honour of Atta-ur-Rahman FRS which had contributions from top scientists in the field of natural product chemistry. Similarly, the international journal Molecules published by the Swiss publisher MDPI published a special issue of the journal in honour of Atta-ur-Rahman. The World Academy of Science, Italy has introduced a special Prize in his honour (TWAS-Atta-ur-Rahman Award in Chemistry) for young scientists which is awarded once every two years. In recognition of his eminent contributions, Prof. Atta-ur-Rahman has received honorary doctorate degrees from many universities including the University of Cambridge (UK), Coventry University (UK), Bradford University (UK), Universiti Teknologi Mara (Malaysia), Asian Institute of Teknologi (Thailand), University of Karachi (Pakistan), Gomal University (Pakistan), and several other universities | 0 | Theoretical and Fundamental Chemistry |
The types of spectroscopy are distinguished by the type of radiative energy involved in the interaction. In many applications, the spectrum is determined by measuring changes in the intensity or frequency of this energy. The types of radiative energy studied include:
* Electromagnetic radiation was the first source of energy used for spectroscopic studies. Techniques that employ electromagnetic radiation are typically classified by the wavelength region of the spectrum and include microwave, terahertz, infrared, near-infrared, ultraviolet-visible, x-ray, and gamma spectroscopy.
* Particles, because of their de Broglie waves, can also be a source of radiative energy. Both electron and neutron spectroscopy are commonly used. For a particle, its kinetic energy determines its wavelength.
* Acoustic spectroscopy involves radiated pressure waves.
* Dynamic mechanical analysis can be employed to impart radiating energy, similar to acoustic waves, to solid materials. | 0 | Theoretical and Fundamental Chemistry |
* The trace of the correlation tensor reduces to
* The homogeneity condition implies that both and are even functions of and . | 1 | Applied and Interdisciplinary Chemistry |
Alternative protein assays include:
* Ultraviolet–visible spectroscopy
* RGBradford
* Biuret protein assay
* Lowry protein assay
* BCA protein assay
* Amido black protein assay
* Colloidal gold protein assay | 0 | Theoretical and Fundamental Chemistry |
In scientific visualization, image-based flow visualization (or visualisation) is a computer modelling technique developed by Jarke van Wijk to visualize two dimensional flows of liquids such as water and air, like the wind movement of a tornado. Compared with integration techniques it has the advantage of producing a whole image at every step, as the technique relies upon graphical computing methods for frame-by-frame capture of the model of advective transport of a decaying dye. It is a method from the texture advection family. | 1 | Applied and Interdisciplinary Chemistry |
Sewage treatment is less effective when sanitary waste is diluted with stormwater, and combined sewer overflows occur when runoff from heavy rainfall or snowmelt exceeds the hydraulic capacity of sewage treatment plants. To overcome these disadvantages, some cities built separate sanitary sewers to collect only municipal wastewater and exclude stormwater runoff, which is collected in separate storm drains. The decision to build a combined sewer system or two separate systems is mainly based on the need for sewage treatment and the cost of providing treatment during heavy rain events. Many cities with combined sewer systems built their systems prior to installing sewage treatment plants, and have not subsequently replaced those sewer systems. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, a benzylidene acetal is the functional group with the structural formula CHCH(OR) (R = alkyl, aryl). Benzylidene acetals are used as protecting groups in glycochemistry. These compounds can also be oxidized to carboxylic acids in order to open important biological molecules, such as glycosaminoglycans, to other routes of synthesis. They arise from the reaction of a 1,2- or 1,3-diols with benzaldehyde. Other aromatic aldehydes are also used. | 0 | Theoretical and Fundamental Chemistry |
The use of monoclonal antibodies for therapy is now widespread for treatment of cancers and inflammatory diseases. Using cellulose sulphate technology, scientists have successfully encapsulated antibody producing hybridoma cells and demonstrated subsequent release of the therapeutic antibody from the capsules. The capsules containing the hybridoma cells were used in pre-clinical studies to deliver neutralising antibodies to the mouse retrovirus FrCasE, successfully preventing disease. | 1 | Applied and Interdisciplinary Chemistry |
Pioneer factors are transcription factors that can directly bind condensed chromatin. They can have positive and negative effects on transcription and are important in recruiting other transcription factors and histone modification enzymes as well as controlling DNA methylation. They were first discovered in 2002 as factors capable of binding to target sites on nucleosomal DNA in compacted chromatin and endowing competency for gene activity during hepatogenesis. Pioneer factors are involved in initiating cell differentiation and activation of cell-specific genes. This property is observed in histone fold-domain containing transcription factors (fork head box (FOX) and NF-Y) and other transcription factors that use zinc finger(s) for DNA binding (Groucho TLE, Gal4, and GATA).
The eukaryotic cell condenses its genome into tightly packed chromatin and nucleosomes. This ability saves space in the nucleus for only actively transcribed genes and hides unnecessary or detrimental genes from being transcribed. Access to these condensed regions is done by chromatin remodelling by either balancing histone modifications or directly with pioneer factors that can loosen the chromatin themselves or as a flag recruiting other factors. Pioneer factors are not necessarily required for assembly of the transcription apparatus and may dissociate after being replaced by other factors. | 1 | Applied and Interdisciplinary Chemistry |
Guha Research Conference (GRC) is a professional society set up by Indian scholars to develop the field of Biochemistry. It was established in 1960, and is named after Biresh Chandra Guha (1904-1962).
The first four GRC meetings were held alongside the annual conference of the Indian Science Congress. Subsequently, under the guidance of Pushpa Mittra Bhargava, it was registered as a society with a convener elected annually, to organize the annual conference. According to Parthasarathi Benerjee, affiliation to GRC, "acts as the token, assuring easier access to prizes of several sorts."
During its formative years (1960–65), GRC had 33 professionals from major national institutes such as AIIMS, CMC Vellore, IISc, Tata Memorial Centre, Indian Institute of Chemical Biology, Banaras Hindu University, Bhabha Atomic Research Centre, and TIFR. By 2004, the membership had grown to 114 members. | 1 | Applied and Interdisciplinary Chemistry |
Snf3 is a protein which regulates glucose uptake in yeast. It senses glucose in the environment with high affinity. | 1 | Applied and Interdisciplinary Chemistry |
Cefamandole (INN, also known as cephamandole) is a second-generation broad-spectrum cephalosporin antibiotic. The clinically used form of cefamandole is the formate ester cefamandole nafate, a prodrug which is administered parenterally. Cefamandole is no longer available in the United States.
The chemical structure of cefamandole, like that of several other cephalosporins, contains an N-methylthiotetrazole (NMTT or 1-MTT) side chain. As the antibiotic is broken down in the body, it releases free NMTT, which can cause hypoprothrombinemia (likely due to inhibition of the enzyme vitamin K epoxide reductase)(vitamin K supplement is recommended during therapy) and a reaction with ethanol similar to that produced by disulfiram (Antabuse), due to inhibition of aldehyde dehydrogenase.
Cefamandole has a broad spectrum of activity and can be used to treat bacterial infections of the skin, bones and joints, urinary tract, and lower respiratory tract. The following represents cefamandole MIC susceptibility data for a few medically significant microorganisms.
* Escherichia coli: 0.12 - 400 μg/ml
* Haemophilus influenzae: 0.06 - >16 μg/ml
* Staphylococcus aureus: 0.1 - 12.5 μg/ml
CO is generated during the normal constitution of cefamandole and ceftazidime, potentially resulting in an explosive-like reaction in syringes. | 0 | Theoretical and Fundamental Chemistry |
Biosurvey protocols have been published for use in different waterbody types and ecoregions. One such publication is the Rapid Bioassessment Protocol for streams and rivers, issued by the U.S. Environmental Protection Agency (EPA). Such protocols provide a structure for developing an IBI, which may include measures such as richness of taxa (species, genera, etc.) and proportion of pollution-tolerant or intolerant taxa. | 1 | Applied and Interdisciplinary Chemistry |
In general, polymeric mixtures are far less miscible than mixtures of small molecule materials. This effect results from the fact that the driving force for mixing is usually entropy, not interaction energy. In other words, miscible materials usually form a solution not because their interaction with each other is more favorable than their self-interaction, but because of an increase in entropy and hence free energy associated with increasing the amount of volume available to each component. This increase in entropy scales with the number of particles (or moles) being mixed. Since polymeric molecules are much larger and hence generally have much higher specific volumes than small molecules, the number of molecules involved in a polymeric mixture is far smaller than the number in a small molecule mixture of equal volume. The energetics of mixing, on the other hand, is comparable on a per volume basis for polymeric and small molecule mixtures. This tends to increase the free energy of mixing for polymer solutions and thereby making solvation less favorable, and thereby making the availability of concentrated solutions of polymers far rarer than those of small molecules.
Furthermore, the phase behavior of polymer solutions and mixtures is more complex than that of small molecule mixtures. Whereas most small molecule solutions exhibit only an upper critical solution temperature phase transition (UCST), at which phase separation occurs with cooling, polymer mixtures commonly exhibit a lower critical solution temperature phase transition (LCST), at which phase separation occurs with heating.
In dilute solutions, the properties of the polymer are characterized by the interaction between the solvent and the polymer. In a good solvent, the polymer appears swollen and occupies a large volume. In this scenario, intermolecular forces between the solvent and monomer subunits dominate over intramolecular interactions. In a bad solvent or poor solvent, intramolecular forces dominate and the chain contracts. In the theta solvent, or the state of the polymer solution where the value of the second virial coefficient becomes 0, the intermolecular polymer-solvent repulsion balances exactly the intramolecular monomer-monomer attraction. Under the theta condition (also called the Flory condition), the polymer behaves like an ideal random coil. The transition between the states is known as a coil–globule transition. | 0 | Theoretical and Fundamental Chemistry |
Some complexes have more than 18 electrons. Examples:
* Cobaltocene (19 e)
* Nickelocene (20 e)
* The hexaaquacopper(II) ion [Cu(HO)] (21 e)
*TM(CO) (TM = Sc, Y) (20 e)
Often, cases where complexes have more than 18 valence electrons are attributed to electrostatic forces – the metal attracts ligands to itself to try to counterbalance its positive charge, and the number of electrons it ends up with is unimportant. In the case of the metallocenes, the chelating nature of the cyclopentadienyl ligand stabilizes its bonding to the metal. Somewhat satisfying are the two following observations: cobaltocene is a strong electron donor, readily forming the 18-electron cobaltocenium cation; and nickelocene tends to react with substrates to give 18-electron complexes, e.g. CpNiCl(PR) and free CpH.
In the case of nickelocene, the extra two electrons are in orbitals which are weakly metal-carbon antibonding; this is why it often participates in reactions where the M–C bonds are broken and the electron count of the metal changes to 18.
The 20-electron systems TM(CO) (TM = Sc, Y) have a cubic (O) equilibrium geometry and a singlet (A) electronic ground state. There is one occupied valence MO with a symmetry, which is formed only by ligand orbitals without a contribution from the metal AOs. But the adducts TM(CO) (TM=Sc, Y) fulfill the 18-electron rule when one considers only those valence electrons, which occupy metal–ligand bonding orbitals. | 0 | Theoretical and Fundamental Chemistry |
Gadolin made contributions in a variety of areas.
Although he never visited France, he became a proponent of Antoine Lavoisiers theory of combustion. Gadolins Inledning till Chemien (1798) was the first chemistry textbook in the Nordic countries that questioned the theory of phlogiston and discussed the role of oxygen in combustion in a modern way. | 1 | Applied and Interdisciplinary Chemistry |
In coordination chemistry, anation is the "replacement of the ligand water by an anion in a coordination entity." The term is however used more loosely to include displacement of any neutral ligand by an anion. The reaction is pervasive in coordination chemistry. The reverse reaction, displacement of an anionic ligand by water, is called aquation. | 0 | Theoretical and Fundamental Chemistry |
Thomas Matthias Klapötke (born 24 February 1961 in Göttingen) is a German inorganic chemist at Ludwig Maximilian University of Munich, studying explosives.
Klapötke grew up in Berlin and studied at the Technical University of Berlin (TU Berlin), completing his undergraduate degree in 1982, his PhD in 1986, and his habilitation in 1990. Klapötke worked as a lecturer at TU Berlin until 1995, when the University of Glasgow hired him for the Ramsay professorship. Since 1997, Klapötke has worked at the Ludwig Maximilian University of Munich (LMU) as a professor of Inorganic Chemistry.
Klapötkes lab at the University of Munich is a group of about 30 employees, mainly studying explosives. Klapötkes goal is to generate "green" explosives, that either burn to completion or leave few toxic residues. Die Zeit called it "the only university laboratory in Germany investigating implements of war". For this reason, the Federal Office for the Protection of the Constitution watches Klapötke's lab quite closely. Klapötke is funded both by the German federal government and the US military and has won a number of awards, including the 1986 Schering Prize. | 0 | Theoretical and Fundamental Chemistry |
Peroxisome proliferator activated receptor gamma 1-alpha coactivator (PGC-1 alpha) is a specific myokine since it stimulates satellite cells, but stimulates M1 and M2 macrophages; M1 macrophages release interleukin 6 (IL-6), Insulin growth factor type 1 (IGF-1) and vascular endothelial growth factor (VEGF), while M2 macrophages mainly secrete IGF-1, VEGF and monocyte chemoattractant protein 1 (MCP-1)) and all this process the muscle becomes muscle hypertrophy.
Macrophages M2 stimulate satellite cells for proliferation and growth but M1 stimulates blood vessels and produces pro-inflammatory cytokines only M2 produces anti-inflammatory in muscles. | 1 | Applied and Interdisciplinary Chemistry |
As a RDC provides spatially and temporally averaged information about an angle between the external magnetic field and a bond vector in a molecule, it may provide rich geometrical information about dynamics on a slow timescale (>10 s) in proteins. In particular, due to its radial dependence the RDC is in particular sensitive to large-amplitude angular processes An early example by Tolman et al. found previously published structures of myoglobin insufficient to explain measured RDC data, and devised a simple model of slow dynamics to remedy this. However, for many classes of proteins, including intrinsically disordered proteins, analysis of RDCs becomes more involved, as defining an alignment frame is not trivial. The problem can be addressed by circumventing the necessity of explicitly defining the alignment frame. | 0 | Theoretical and Fundamental Chemistry |
* [http://www.maizegdb.org/cgi-bin/displaylocusrecord.cgi?id=12097 MaizeGDB]
* [https://www.ncbi.nlm.nih.gov/gene?cmd=search&term=542117 NCBI]
* [https://www.uniprot.org/uniprot/P42390 Uniprot] | 1 | Applied and Interdisciplinary Chemistry |
*1967 Luis Leloir (1970 Chemistry)
*1968 Har Gobind Khorana (1968 Physiology or Medicine), Marshall Warren Nirenberg (1968 Physiology or Medicine)
*1969 Max Delbrück (1969 Physiology or Medicine), Salvador E. Luria (1969 Physiology or Medicine)
*1970 Albert Claude (1974 Physiology or Medicine), George E. Palade (1974 Physiology or Medicine), Keith R. Porter
*1971 Hugh E. Huxley
*1972 Stephen W. Kuffler
*1973 Renato Dulbecco (1975 Physiology or Medicine), Harry Eagle, Theodore T. Puck
*1974 Boris Ephrussi
*1975 K. Sune D. Bergstrom (1982 Physiology or Medicine), Bengt Samuelsson (1982 Physiology or Medicine)
*1976 Seymour Benzer, Charles Yanofsky
*1977 Michael Heidelberger, Elvin A. Kabat, Henry G. Kunkel
*1978 David Hubel (1981 Physiology of Medicine), Vernon Mountcastle, Torsten Wiesel (1981 Physiology or Medicine)
*1979 Walter Gilbert (1980 Chemistry), Frederick Sanger (1980 Chemistry)
*1980 César Milstein (1984 Physiology or Medicine)
*1981 Aaron Klug (1982 Chemistry)
*1982 Barbara McClintock (1983 Physiology or Medicine), Susumu Tonegawa (1987 Physiology or Medicine)
*1983 Stanley Cohen (1986 Physiology or Medicine), Viktor Hamburger, Rita Levi-Montalcini (1986 Physiology or Medicine)
*1984 Michael S. Brown (1985 Physiology or Medicine), Joseph L. Goldstein (1985 Physiology or Medicine)
*1985 Donald D. Brown, Mark Ptashne
*1986 Erwin Neher (1991 Physiology or Medicine), Bert Sakmann (1991 Physiology or Medicine)
*1987 Günter Blobel (1999 Physiology or Medicine)
*1988 Thomas R. Cech (1989 Chemistry), Philip A. Sharp (1993 Physiology or Medicine)
*1989 Alfred G. Gilman (1994 Physiology or Medicine), Edwin G. Krebs (1994 Physiology or Medicine)
*1990 Stephen C. Harrison, Michael G. Rossmann, Don C. Wiley
*1991 Richard R. Ernst (1991 Chemistry), Kurt Wüthrich (2001 Chemistry)
*1992 Christiane Nüsslein-Volhard (1995 Physiology or Medicine), Edward B. Lewis (1995 Physiology or Medicine)
*1993 Nicole Marthe Le Douarin, Donald Metcalf
*1994 Philippa Marrack, John W. Kappler
*1995 Leland H. Hartwell (2001 Physiology or Medicine)
*1996 Clay M. Armstrong, Bertil Hille
*1997 Stanley B. Prusiner (1997 Physiology or Medicine)
*1998 Arnold J. Levine, Bert Vogelstein
*1999 Pierre Chambon, Robert Roeder, Robert Tjian
*2000 H. Robert Horvitz (2002 Physiology or Medicine), Stanley J. Korsmeyer
*2001 Avram Hershko (2004 Chemistry), Alexander Varshavsky
*2002 James E. Rothman (2013 Physiology or Medicine), Randy W. Schekman (2013 Physiology or Medicine)
*2003 Roderick MacKinnon (2003 Chemistry)
*2004 Tony Hunter, Tony Pawson
*2005 Ada Yonath (2009 Chemistry)
*2006 Roger D. Kornberg (2006 Chemistry)
*2007 Joseph G. Gall, Elizabeth H. Blackburn (2009 Physiology or Medicine), Carol W. Greider (2009 Physiology or Medicine)
*2008 F. Ulrich Hartl, Arthur Horwich and Honorary Horwitz Prize to Rosalind Franklin
*2009 Victor R. Ambros, Gary Ruvkun
*2010 Thomas J. Kelly, Bruce Stillman
*2011 Jeffrey C. Hall (2017 Physiology or Medicine), Michael Rosbash (2017 Physiology or Medicine), Michael W. Young (2017 Physiology or Medicine)
*2012 Richard Losick, Joe Lutkenhaus, Lucy Shapiro
*2013 Edvard I. Moser (2014 Physiology or Medicine), May-Britt Moser (2014 Physiology or Medicine), John O’Keefe (2014 Physiology or Medicine)
*2014 James P. Allison (2018 Physiology or Medicine)
*2015 S. Lawrence Zipursky
*2016 Howard Cedar, Aharon Razin,
*2017 Jeffrey I. Gordon
*2018 Pierre Chambon, Ronald M. Evans, Bert O’Malley
*2019 Lewis C. Cantley, David M. Sabatini, Peter K. Vogt
*2020 Robert Fettiplace, James Hudspeth, Christine Petit
*2021 Katalin Karikó (2023 Physiology or Medicine), Drew Weissman (2023 Physiology or Medicine)
*2022 Karl Deisseroth, Peter Hegemann, Gero Miesenböck
*2023 Zhijian Chen, Glen Barber | 1 | Applied and Interdisciplinary Chemistry |
Unprotected exposure to Ca(OH), as with any strong base, can cause severe skin irritation, chemical burns, blindness, lung damage or rashes. | 0 | Theoretical and Fundamental Chemistry |
TLR3 does not use the MyD88 dependent pathway. Its ligand is retroviral double-stranded RNA (dsRNA), which activates the TRIF dependent signalling pathway. To explore the role of this pathway in retroviral reprograming, knock down techniques of TLR3 or TRIF were prepared, and results showed that only the TLR3 pathway is required for full induction of target gene expression by the retrovirus expression vector. This retroviral expression of four transcriptional factors (Oct4, Sox2, Klf4 and c-Myc; OSKM) induces pluripotency in somatic cells. This is supported by study, which shows, that efficiency and amount of human iPSC generation, using retroviral vectors, is reduced by knockdown of the pathway with peptide inhibitors or shRNA knockdown of TLR3 or its adaptor protein TRIF. Taken together, stimulation of TLR3 causes great changes in chromatin remodeling and nuclear reprogramming, and activation of inflammatory pathways is required for these changes, induction of pluripotency genes and generation of human induced pluripotent stem cells (iPSC) colonies. | 1 | Applied and Interdisciplinary Chemistry |
Mathematically, the stress at some point in the material is a plane stress if one of the three principal stresses (the eigenvalues of the Cauchy stress tensor) is zero. That is, there is Cartesian coordinate system in which the stress tensor has the form
For example, consider a rectangular block of material measuring 10, 40 and 5 cm along the , , and , that is being stretched in the direction and compressed in the direction, by pairs of opposite forces with magnitudes 10 N and 20 N, respectively, uniformly distributed over the corresponding faces. The stress tensor inside the block will be
More generally, if one chooses the first two coordinate axes arbitrarily but perpendicular to the direction of zero stress, the stress tensor will have the form
and can therefore be represented by a 2 × 2 matrix, | 1 | Applied and Interdisciplinary Chemistry |
When designing distillation processes for separating zeotropic mixtures, the sequencing of distillation columns is vital to saving energy and costs. In addition, other methods can be used to lower the energy or equipment costs required to distill zeotropic mixtures. This includes combining distillation columns, using side columns, combining main columns with side columns, and re-using waste heat for the system. After combining distillation columns, the amount of energy used is only that of one separated column rather than both columns combined. In addition, using side columns saves energy by preventing different columns from carrying out the same separation of mixtures. Combining main and side columns saves equipment costs by reducing the number of heat exchangers in the system. Re-using waste heat requires the amount of heat and temperature levels of the waste to match that of the heat needed. Thus, using waste heat requires changing the pressure inside evaporators and condensers of the distillation system in order to control the temperatures needed. Controlling the temperature levels in a part of a system is possible with Pinch Technology. These energy-saving techniques have a wide application in industrial distillation of zeotropic mixtures: side columns have been used to refine crude oil, and combining main and side columns is increasingly used. | 1 | Applied and Interdisciplinary Chemistry |
Walsh diagrams in conjunction with molecular orbital theory can also be used as a tool to predict reactivity. By generating a Walsh Diagram and then determining the HOMO/LUMO of that molecule, it can be determined how the molecule is likely to react. In the following example, the Lewis acidity of AH molecules such as BH and CH is predicted.
Six electron AH molecules should have a planar conformation. It can be seen that the HOMO, 1e’, of planar AH is destabilized upon bending of the A-H bonds to form a pyramid shape, due to disruption of bonding. The LUMO, which is concentrated on one atomic center, is a good electron acceptor and explains the Lewis acid character of BH and CH.
Walsh correlation diagrams can also be used to predict relative molecular orbital energy levels. The distortion of the hydrogen atoms from the planar CH to the tetrahedral CH-Nu causes a stabilization of the C-Nu bonding orbital, σ. | 0 | Theoretical and Fundamental Chemistry |
For cases where the molecule is un-ionized:
For other cases, estimation of log D at a given pH, from log P and the known mole fraction of the un-ionized form, , in the case where partition of ionized forms into non-polar phase can be neglected, can be formulated as
The following approximate expressions are valid only for monoprotic acids and bases:
Further approximations for when the compound is largely ionized:
* for acids with , ,
* for bases with , .
For prediction of pK, which in turn can be used to estimate log D, Hammett type equations have frequently been applied. | 0 | Theoretical and Fundamental Chemistry |
In countercurrent flow, the two flows move in opposite directions.
Two tubes have a liquid flowing in opposite directions, transferring a property from one tube to the other. For example, this could be transferring heat from a hot flow of liquid to a cold one, or transferring the concentration of a dissolved solute from a high concentration flow of liquid to a low concentration flow.
The counter-current exchange system can maintain a nearly constant gradient between the two flows over their entire length of contact. With a sufficiently long length and a sufficiently low flow rate this can result in almost all of the property transferred. So, for example, in the case of heat exchange, the exiting liquid will be almost as hot as the original incoming liquid's heat. | 1 | Applied and Interdisciplinary Chemistry |
In radiobiology a broad or focused ion beam is used to study mechanisms of inter- and intra- cellular communication, signal transduction and DNA damage and repair. | 0 | Theoretical and Fundamental Chemistry |
Elizabeth MacGregor Hardy was born in Ottawa, Ontario, Canada to parents Thomas Woodburne Hardy and Margaret Ada (Graham) Hardy. Hardy attended McGill University and graduated with a Bachelor in Science in 1938. In 1939, Hardy obtained a Master of Arts degree from Bryn Mawr College. She went on to earn a Ph.D. in organic chemistry in 1942 at Bryn Mawr College, working in the labs of Arthur C. Cope.
Hardy and Evelyn Hancock, another graduate student, coauthored nearly half of Cope's papers from Bryn Mawr.
Hardy went on to work for American Cyanamid. | 0 | Theoretical and Fundamental Chemistry |
In most cases mesocrystals form nanoparticles in solution. These nanoparticles aggregate and arrange in crystallographic formation, without any additives. The main causes of this ordering are tensorial polarization forces and dipole fields. | 0 | Theoretical and Fundamental Chemistry |
The spectral shape and intensity of the optical signals from the NV centers are sensitive to external perturbation, such as temperature, strain, electric and magnetic field. However, the use of spectral shape for sensing those perturbation is impractical, as the diamond would have to be cooled to cryogenic temperatures to sharpen the NV signals. A more realistic approach is to use luminescence intensity (rather than lineshape), which exhibits a sharp resonance when a microwave frequency is applied to diamond that matches the splitting of the ground-state levels. The resulting optically detected magnetic resonance signals are sharp even at room temperature, and can be used in miniature sensors. Such sensors can detect magnetic fields of a few nanotesla or electric fields of about 10 V/cm at kilohertz frequencies after 100 seconds of averaging. This sensitivity allows detecting a magnetic or electric field produced by a single electron located tens of nanometers away from an NV center.
Using the same mechanism, the NV centers were employed in scanning thermal microscopy to measure high-resolution spatial maps of temperature and thermal conductivity (see image).
Because the NV center is sensitive to magnetic fields, it is being actively used in scanning probe measurements to study myriad condensed matter phenomena both through measuring a spatially varying magnetic field or inferring local currents in a device.
Another possible use of the NV centers is as a detector to measure the full mechanical stress tensor in the bulk of the crystal. For this application, the stress-induced splitting of the zero-phonon-line is exploited, and its polarization properties. A robust frequency-modulated radio receiver using the electron-spin-dependent photoluminescence that operated up to 350 °C demonstrates the possibility for use in extreme conditions.
In addition to the quantum optical applications, luminescence from the NV centers can be applied for imaging biological processes, such as fluid flow in living cells. This application relies on good compatibility of diamond nano-particles with the living cells and on favorable properties of photoluminescence from the NV centers (strong intensity, easy excitation and detection, temporal stability, etc.). Compared with large single-crystal diamonds, nanodiamonds are cheap (about 1 USD per gram) and available from various suppliers. NV centers are produced in diamond powders with sub-micrometre particle size using the standard process of irradiation and annealing described above. Due to the relatively small size of nanodiamond, NV centers can be produced by irradiating nanodiamond of 100 nm or less with medium energy H+ beam. This method reduces the required ion dose and reaction, making it possible to mass produce fluorescent nanodiamonds in ordinary laboratory. Fluorescent nanodiamond produced with such method is bright and photostable, making it excellent for long-term, three dimensional tracking of single particle in living cell. Those nanodiamonds are introduced in a cell, and their luminescence is monitored using a standard fluorescence microscope.
Stimulated emission from the NV center has been demonstrated, though it could be achieved only from the phonon side-band (i.e. broadband light) and not from the ZPL. For this purpose, the center has to be excited at a wavelength longer than ~650 nm, as higher-energy excitation ionizes the center.
The first continuous-wave room-temperature maser has been demonstrated. It used 532-nm pumped NV centers held within a high Purcell factor microwave cavity and an external magnetic field of 4300 G. Continuous maser oscillation generated a coherent signal at ~9.2 GHz.
The NV center can have a very long spin coherence time approaching the second regime. This is advantageous for applications in quantum sensing and quantum communication. Disadvantageous for these applications is the long radiative lifetime (~12 ns
) of the NV center and the strong phonon sideband in its emission spectrum. Both issues can be addressed by putting the NV center in an optical cavity. | 0 | Theoretical and Fundamental Chemistry |
In modern everyday life there are many observations that can be successfully explained by application of Bernoulli's principle, even though no real fluid is entirely inviscid, and a small viscosity often has a large effect on the flow.
*Bernoullis principle can be used to calculate the lift force on an airfoil, if the behaviour of the fluid flow in the vicinity of the foil is known. For example, if the air flowing past the top surface of an aircraft wing is moving faster than the air flowing past the bottom surface, then Bernoullis principle implies that the pressure on the surfaces of the wing will be lower above than below. This pressure difference results in an upwards lifting force. Whenever the distribution of speed past the top and bottom surfaces of a wing is known, the lift forces can be calculated (to a good approximation) using Bernoulli's equations, which were established by Bernoulli over a century before the first man-made wings were used for the purpose of flight.
*The carburetor used in many reciprocating engines contains a venturi to create a region of low pressure to draw fuel into the carburetor and mix it thoroughly with the incoming air. The low pressure in the throat of a venturi can be explained by Bernoulli's principle; in the narrow throat, the air is moving at its fastest speed and therefore it is at its lowest pressure.
*An injector on a steam locomotive or a static boiler.
*The pitot tube and static port on an aircraft are used to determine the airspeed of the aircraft. These two devices are connected to the airspeed indicator, which determines the dynamic pressure of the airflow past the aircraft. Bernoulli's principle is used to calibrate the airspeed indicator so that it displays the indicated airspeed appropriate to the dynamic pressure.
*A De Laval nozzle utilizes Bernoullis principle to create a force by turning pressure energy generated by the combustion of propellants into velocity. This then generates thrust by way of Newtons third law of motion.
*The flow speed of a fluid can be measured using a device such as a Venturi meter or an orifice plate, which can be placed into a pipeline to reduce the diameter of the flow. For a horizontal device, the continuity equation shows that for an incompressible fluid, the reduction in diameter will cause an increase in the fluid flow speed. Subsequently, Bernoulli's principle then shows that there must be a decrease in the pressure in the reduced diameter region. This phenomenon is known as the Venturi effect.
*The maximum possible drain rate for a tank with a hole or tap at the base can be calculated directly from Bernoullis equation and is found to be proportional to the square root of the height of the fluid in the tank. This is Torricellis law, which is compatible with Bernoulli's principle. Increased viscosity lowers this drain rate; this is reflected in the discharge coefficient, which is a function of the Reynolds number and the shape of the orifice.
*The Bernoulli grip relies on this principle to create a non-contact adhesive force between a surface and the gripper.
*During a cricket match, bowlers continually polish one side of the ball. After some time, one side is quite rough and the other is still smooth. Hence, when the ball is bowled and passes through air, the speed on one side of the ball is faster than on the other, and this results in a pressure difference between the sides; this leads to the ball rotating ("swinging") while travelling through the air, giving advantage to the bowlers. | 1 | Applied and Interdisciplinary Chemistry |
*Group 3 elements scandium and yttrium form monoanions, [M(CO)] (M = Sc, Y) which are 20-electron carbonyls, as does the lanthanide lanthanum.
*Group 4 elements as dianions resemble neutral group 6 derivatives: [Ti(CO)].
*Group 5 elements as monoanions resemble again neutral group 6 derivatives: [V(CO)].
*Group 7 elements as monoanions resemble neutral group 8 derivatives: [M(CO)] (M = Mn, Tc, Re).
*Group 8 elements as dianaions resemble neutral group 10 derivatives: [[disodium tetracarbonylferrate|[M(CO)] (M = Fe, Ru, Os)]]. Condensed derivatives are also known.
*Group 9 elements as monoanions resemble neutral group 10 metal carbonyl. [Co(CO)] is the best studied member.
Large anionic clusters of nickel, palladium, and platinum are also well known. Many metal carbonyl anions can be protonated to give metal carbonyl hydrides. | 0 | Theoretical and Fundamental Chemistry |
Neutron backscattering is one of several inelastic neutron scattering techniques. Backscattering from monochromator and analyzer crystals is used to achieve an energy resolution on the order of a microelectronvolt (μeV). Neutron backscattering experiments are performed to study atomic or molecular motion on a nanosecond time scale. | 0 | Theoretical and Fundamental Chemistry |
When a substance undergoes a phase transition (changes from one state of matter to another) it usually either takes up or releases energy. For example, when water evaporates, the increase in kinetic energy as the evaporating molecules escape the attractive forces of the liquid is reflected in a decrease in temperature. The energy required to induce the phase transition is taken from the internal thermal energy of the water, which cools the liquid to a lower temperature; hence evaporation is useful for cooling. See Enthalpy of vaporization. The reverse process, condensation, releases heat. The heat energy, or enthalpy, associated with a solid to liquid transition is the enthalpy of fusion and that associated with a solid to gas transition is the enthalpy of sublimation. | 0 | Theoretical and Fundamental Chemistry |
The concept of green engineering began between 1966 and 1970 during the Organization for Economic Cooperation and Development under the name: "The Ten Ecological Commandments for Earth Citizens". The idea was expressed visually as the following cycle starting with the first commandment and ending with the tenth:
# Respect the laws of nature
# Learn as responsible earth citizens from the wisdom of nature
# Do not reduce plurality richness, abundance of living species
# Do not pollute
# Face earth-responsibility every day for our children and our children's children
# Follow the principle of nature precaution/sustainability in all economic activities!
# Act as you speak!
# Prefer small clever and intelligent problem solutions, including rational and emotional intelligence factors
# Information about environmental damage belongs to mankind - not (only) to privilieged big business
# Listen carefully [to] what your own body tells you about [the] impact of your very personal social and natural environment upon your wellbeing
The idea was then presented by Peter Menke-Glückert at the United Nations Educational, Scientific, and Cultural Conference at Paris in 1968. These principles are similar to the Principles of Green Engineering in that each individual has an intrinsic responsibility to uphold these values. The Ten Ecological Commandments for Earth Citizens is thought by Dr. Płotka-Wasylka to have influenced The Principles of Green Engineering, which has been said to imply that all engineers have a duty to uphold sustainable values and practices when creating new processes.
Green engineering is a part of a larger push for sustainable practices in the creation of products such as chemical compounds. This movement is more widely known as green chemistry, and has been headed since 1991 by Paul Anastas and John C. Warner. Green chemistry, being older than green engineering, is a more researched field of study and began in 1991 with the creation of the 12 Principles of Green Chemistry. | 1 | Applied and Interdisciplinary Chemistry |
Brown was born Herbert Brovarnik in London, to Ukrainian Jewish immigrants from Zhitomir, Pearl (née Gorinstein) and Charles Brovarnik, a hardware store manager and carpenter. His family moved to Chicago in June 1914, when he was two years old. Brown attended Crane Junior College in Chicago, where he met Sarah Baylen, whom he would later marry. The college was under threat of closing, and Brown and Baylen transferred to Wright Junior College. In 1935 he left Wright Junior College and that autumn entered the University of Chicago, completed two years of studies in three quarters, and earned a B.S. in 1936. That same year, he became a naturalized United States citizen. On February 6, 1937, Brown married Baylen, the person he credits with making him interested in hydrides of boron, a topic related to the work in which he, together with Georg Wittig, won the Nobel prize in Chemistry in 1979. Two years after starting graduate studies, he earned a Ph.D. in 1938, also from the University of Chicago.
Unable to find a position in industry, he decided to accept a postdoctoral position. This became the beginning of his academic career. He became an instructor at the University of Chicago in 1939, and held the position for four years before moving to Wayne University in Detroit as an assistant professor. In 1946, he was promoted to associate professor. He became a professor of inorganic chemistry at Purdue University in 1947 and joined the Beta Nu chapter of Alpha Chi Sigma there in 1960. He held the position of Professor Emeritus from 1978 until his death in 2004. The Herbert C. Brown Laboratory of Chemistry was named after him on Purdue University's campus. He was an honorary member of the International Academy of Science, Munich.
During World War II, while working with Hermann Irving Schlesinger, Brown discovered a method for producing sodium borohydride (NaBH), which can be used to produce boranes, compounds of boron and hydrogen. His work led to the discovery of the first general method for producing asymmetric pure enantiomers. The elements found as initials of his name H, C and B were his working field.
In 1969, he was awarded the National Medal of Science.
Brown was quick to credit his wife Sarah with supporting him and allowing him to focus on creative efforts by handling finances, maintaining the house and yard, etc. According to Brown, after receiving the Nobel prize in Stockholm, he carried the medal and she carried the US$100,000 award.
In 1971, he received the Golden Plate Award of the American Academy of Achievement.
He was inducted into the Alpha Chi Sigma Hall of Fame in 2000.
He died December 19, 2004, at a hospital in Lafayette, Indiana after a heart attack. His wife died May 29, 2005, aged 89. | 0 | Theoretical and Fundamental Chemistry |
As a result of the Manhattan Project, the United States government needed ready access to uranium. Many different techniques in leaching were quickly employed at a large scale. Both synthetic resins and organic solvents were used early on to extract uranium. Ultimately, the use of organic solvents was less tedious compared to ion exchange through synthetic resins, and further production of uranium and other rare earth metals moved towards solvent extraction. | 1 | Applied and Interdisciplinary Chemistry |
According to Beer–Lambert law, the intensity of an electromagnetic wave inside a material falls off exponentially from the surface as
If denotes the penetration depth, we have
Penetration depth is one term that describes the decay of electromagnetic waves inside of a material. The above definition refers to the depth at which the intensity or power of the field decays to 1/e of its surface value. In many contexts one is concentrating on the field quantities themselves: the electric and magnetic fields in the case of electromagnetic waves. Since the power of a wave in a particular medium is proportional to the square of a field quantity, one may speak of a penetration depth at which the magnitude of the electric (or magnetic) field has decayed to 1/e of its surface value, and at which point the power of the wave has thereby decreased to or about 13% of its surface value:
Note that is identical to the skin depth, the latter term usually applying to metals in reference to the decay of electrical currents (which follow the decay in the electric or magnetic field due to a plane wave incident on a bulk conductor). The attenuation constant is also identical to the (negative) real part of the propagation constant, which may also be referred to as using a notation inconsistent with the above use. When referencing a source one must always be careful to note whether a number such as or refers to the decay of the field itself, or of the intensity (power) associated with that field. It can also be ambiguous as to whether a positive number describes attenuation (reduction of the field) or gain; this is usually obvious from the context. | 0 | Theoretical and Fundamental Chemistry |
Droplet countercurrent chromatography (DCCC or DCC) was introduced in 1970 by Tanimura, Pisano, Ito, and Bowman. DCCC is considered to be a form of liquid-liquid separation, which includes countercurrent distribution and countercurrent chromatography, that employs a liquid stationary phase held in a collection of vertical glass columns connected in series. The mobile phase passes through the columns in the form of droplets. The DCCC apparatus may be run with the lower phase stationary and the upper phase being introduced to the bottom of each column. Or it may be run with the upper phase stationary and the lower phase being introduced from the top of the column. In both cases, the work of gravity is allowed influence the two immiscible liquids of different densities to form the signature droplets that rise or descend through the column. The mobile phase is pumped at a rate that will allow droplets to form that maximize the mass transfer of a compound between the upper and lower phases. Compounds that are more soluble in the upper phase will travel quickly through the column, while compounds that are more soluble in the stationary phase will linger. Separation occurs because different compounds distribute differently, in a ratio called the partition coefficient, between the two phases.
The biphasic solvent system must be carefully formulated so that it will perform appropriately in the DCCC column. The solvent system must form two phases without excess emulsification in order to form droplets. The densities of the two phases must also be sufficiently different so that the phases will move past each other in the column. Many DCCC solvent systems contain both chloroform and water. The solvent system used in the seminal publication was made from chloroform, acetic acid, and aqueous 0.1 M hydrochloric acid. Many subsequent solvents systems were made with chloroform, methanol, and water which is sometimes represented as a ChMWat solvent system. Solvent systems formulated with n-butanol, water and a modifier such as acetic acid, pyridine or n-propanol have also enjoyed some success in DCCC. In some cases, non-aqueous biphasic solvent systems such as acetonitrile and methanol have been utilized.
The main difference between DCCC and other types of countercurrent chromatography techniques is that there is no vigorous mixing of phases to enhance the mass transfer of compounds that allows them to distribute between the two phases. In 1951 Kies and Davis described an apparatus similar to the DCCC. They created a series of open tubes that were arranged in a cascade to either drip a more dense phase through a less dense stationary phase or, conversely, a less dense phase could be introduced into the bottom of the tube to dribble through the more dense phase. In 1954, a fractionation column was introduced by Kepes the resembled a CCC column divided into chambers with perforated plastic disks. Similar DCCC-type instruments have been created by A. E. Kostanyan and collaborators which employ vertical columns that are divided into partitions with porous disks. Once the columns are filled with stationary phase, the mobile phase is pumped through, not continuously but, in pulses. The solvent motion created by a pulsed pumping action creates the mixing and settling that is common to most all forms of countercurrent chromatography. | 0 | Theoretical and Fundamental Chemistry |
Airless spray equipment used for Dimetcote should have a fluid tip with orifice no smaller than 0.019 inch (0.48), and the minimum level of pump ratio is 28:1. Some standard airless sprays such as Spee-Flo, Graco, Nordson-Bede, and DeVilbiss meet these requirements. | 1 | Applied and Interdisciplinary Chemistry |
Vertical manipulation is a process of transferring an atom from substrate to STM tip, repositioning the STM tip and transferring the atom back on a desired position. Transferring an atom from substrate to STM tip is done by placing the tip above the atom in a constant current mode, turning off the feedback loop and applying high bias for a few seconds. In some cases it is also required to slowly approach the tip while applying high bias. Sudden spikes or drops in current during this process correspond to either transfer or to the atom being pushed away from the given spot. As such, there is always some level of randomness in this process. Transferring an atom from STM tip to substrate is done the same way but by applying opposite bias. | 0 | Theoretical and Fundamental Chemistry |
Oxacillin is a penicillinase-resistant β-lactam. It is similar to methicillin, and has replaced methicillin in clinical use. Other related compounds are nafcillin, cloxacillin, dicloxacillin, and flucloxacillin. Since it is resistant to penicillinase enzymes, such as that produced by Staphylococcus aureus, it is widely used clinically in the US to treat penicillin-resistant Staphylococcus aureus. However, with the introduction and widespread use of both oxacillin and methicillin, antibiotic-resistant strains called methicillin-resistant and oxacillin-resistant Staphylococcus aureus (MRSA/ORSA) have become increasingly prevalent worldwide. MRSA/ORSA can be treated with vancomycin or other new antibiotics. | 0 | Theoretical and Fundamental Chemistry |
The Peregrine soliton can also be seen as the limiting case of the space-periodic Akhmediev breather when the period tends to infinity. | 1 | Applied and Interdisciplinary Chemistry |
One of the important functions of an FSL construct is that it can optimise the presentation of antigens, both on cell surfaces and solid-phase membranes. This optimisation is achieved primarily by the spacer, and secondarily by the lipid tail. In a typical immunoassay, the antigen is deposited directly onto the microplate surface and binds to the surface either in a random fashion, or in a preferred orientation depending on the residues present on the surface of this antigen. Usually this deposition process is uncontrolled. In contrast, the FSL Kode construct bound to a microplate presents the antigen away from the surface in an orientation with a high level of exposure to the environment. Furthermore, typical immunoassays use recombinant peptides rather than discrete peptide antigens. As the recombinant peptide is many times bigger than the epitope of interest, a lot of undesired and unwanted peptide sequences are also represented on the microplate. These additional sequences may include unwanted microbial related sequences (as determined by a BLAST analysis) that can cause issues of low level cross-reactivity. Often the mechanism by which an immunoassay is able to overcome this low level activity is to dilute the serum so that the low level microbial reactive antibodies are not seen, and only high-level specific antibodies result in an interpretable result. In contrast, FSL Kode constructs usually use specifically selected peptide fragments (up to 40 amino acids), thereby overcoming cross-reactivity with microbial sequences, and allowing for the use of undiluted serum (which increases sensitivity).
The F component can be further enhanced by presentation of it in multimeric formats and with specific spacing. The four types of multimeric format include linear repeating units, linear repeating units with spacing, clusters, and branching (Fig. 4). | 1 | Applied and Interdisciplinary Chemistry |
The bottom part of ring B was constructed by nucleophilic addition to the aldehyde of 2.1 (scheme 2) with dibenzyl acetal of 2-bromobenzaldehyde 2.2 as its aryllithium. This step is much in common with the B ring synthesis in the Nicolaou Taxol total synthesis except that the aldehyde group is located at ring A and not ring B. The diol in 2.3 was protected as the boronic ester 2.4 preparing the molecule for upper part ring closure with tin tetrachloride to tricycle 2.5 in a Grob fragmentation-like reaction.
After deprotection (pinacol) to diol 2.6, DIBAL reduction to triol 2.7 and TBS reprotection (TBSOtf, lutidine) to alcohol 2.8 it was possible to remove the phenylsulfide group in with a tributyltin hydride and AIBN(see Barton-McCombie deoxygenation) to alcohol 2.9. Palladium on carbon hydrogenation removed the benzyl protecting group allowing the Swern oxidation of 2.10 to ketone 2.11 | 0 | Theoretical and Fundamental Chemistry |
The most important of these techniques would prove to be Brills pioneering application of lead isotope analysis, hitherto used only in geology, to archaeological objects. Brill first presented this idea at the 1965 Seminar in Examination of Works of Art, held at the Museum of Fine Arts Boston, but the first widely published account of the method seems to be Brill and Wamplers 1967 article in the American Journal of Archaeology. Here, Brill and Wampler outlined how the technique could be used to provenance the lead contents of archaeological objects to lead ore sources around the world, based on the isotopic signature of various leads, which relates them to ‘ores occurring in different geographical areas’ (1967, 63). These different areas have different signatures because they are of varying geological age, something reflected by the individual lead isotopes which form only after the radioactive decay of uranium and thorium (Brill et al. 1965, Brill and Wampler 1967). While the lead isotope ratios used for provenancing are different, they are not unique: areas geologically similar will yield similar lead isotope signatures (Brill 1970). Furthermore, if leads were salvaged and mixed in ancient times, the isotope ratio will be compromised (Brill 1970). Aside from these two limitations, there is little else that could affect the lead isotope reading an object would yield. As such, Brill's method was greeted enthusiastically and he went on to develop the technique, as well as oxygen isotope analysis, in his 1970 publication. Here he demonstrated how the technique could be used both to classify early glasses and to a certain extent characterize the ingredients from which they were made (1970, 143). | 0 | Theoretical and Fundamental Chemistry |
Let be the gas density, the velocity, the pressure and the speed of sound. In isentropic flows, entropy is constant and if the initial state of the gas is homogenous, then entropy is a constant everywhere at all times and therefore the pressure is a function only of , i.e., In simple waves, all dependent variables are just function of any one of the dependent variables (this is certainly the case in one-dimensional sound waves) and therefore we can assume the velocity to be also a function only of . i.e., This latter property is the cause of origin of the name simple wave, although the wave is nonlinear.
From the one-dimensional Euler equations, we have
which, because , can be written as
Further, since (remember that the time derivative of a function integrated along a curve is given by )
the two equations lead to
However, since determines and therefore the above derivatives must be equal so that . Thus, we obtain , whence
This equation provides the required relation or, or, etc. The above equation is just a statement that either the or the Riemann invariant is constant.
Thus, we obtain
which upon integration becomes
where is an arbitrary function. This equation indicates that the characteristics in the - plane are just straight lines. When and when consequently length scale and time scale associated with the initial function disappears, the problem is self-similar and the solution depends only on the ratio . This particular case is referred as the centred simple wave. | 1 | Applied and Interdisciplinary Chemistry |
AVIRIS has been flown on four aircraft platforms: the NASA ER-2 jet, Twin Otter Internationals turboprop, Scaled Composites Proteus, and NASAs WB-57. The ER-2 flies at approximately 20 km above sea level, at about 730 km/h. The Twin Otter aircraft flies at 4 km above ground level at 130 km/h. AVIRIS has flown North America, Europe, portions of South America, and Argentina. | 0 | Theoretical and Fundamental Chemistry |
Once a refinement has been completed the results should be checked to verify that the chosen model is acceptable. generally speaking, a model is acceptable when the data are fitted within experimental error, but there is no single criterion to use to make the judgement. The following should be considered. | 0 | Theoretical and Fundamental Chemistry |
There are 35 naturally occurring isotopes capable of double beta decay. In practice, the decay can be observed when the single beta decay is forbidden by energy conservation. This happens for elements with an even atomic number and even neutron number, which are more stable due to spin-coupling. When single beta decay or alpha decay also occur, the double beta decay rate is generally too low to observe. However, the double beta decay of (also an alpha emitter) has been measured radiochemically. Two other nuclides in which double beta decay has been observed, and , can also theoretically single beta decay, but this decay is extremely suppressed and has never been observed. Similar suppression of energetically barely possible single beta decay occurs for Gd and Rn, but both these nuclides are rather short-lived alpha emitters.
Fourteen isotopes have been experimentally observed undergoing two-neutrino double beta decay (ββ) or double electron capture (εε). The table below contains nuclides with the latest experimentally measured half-lives, as of December 2016, except for Xe (for which double electron capture was first observed in 2019). Where two uncertainties are specified, the first one is statistical uncertainty and the second is systematic.
Searches for double beta decay in isotopes that present significantly greater experimental challenges are ongoing. One such isotope is .
The following known beta-stable (or almost beta-stable in the cases Ca, Zr, and Rn) nuclides with A ≤ 260 are theoretically capable of double beta decay, where red are isotopes that have a double-beta rate measured experimentally and black have yet to be measured experimentally: Ca, , Zn, , Se, , Kr, Zr, , Mo, , Ru, Pd, Cd, , Sn, Sn, , , Xe, , Ce, Nd, Nd, , Sm, Gd, Er, Yb, W, Os, Pt, Hg, Po, Rn, Rn, Ra, Th, , Pu, Cm, Cf, Cf, and Fm.
The following known beta-stable (or almost beta-stable in the case Gd) nuclides with A ≤ 260 are theoretically capable of double electron capture, where red are isotopes that have a double-electron capture rate measured and black have yet to be measured experimentally: Ar, Ca, Cr, Fe, Ni, Zn, Se, , Sr, Mo, Ru, Pd, Cd, Cd, Sn, Te, , Xe, , Ba, Ce, Ce, Sm, Gd, Gd, Gd, Dy, Dy, Dy, Er, Er, Yb, Hf, W, Os, Pt, Hg, Rn, Rn, Ra, Th, U, Pu, Cm, Fm, and No.
In particular, Ar is the lightest observationally stable nuclide whose decay is energetically possible. | 0 | Theoretical and Fundamental Chemistry |
The company's formulation plant in Waltham Abbey was alleged to be at the centre and therefore the cause of a cancer hotspot. This was highlighted by Storyline, an investigative television programme by Carlton Television, in early 1993. Reports of an unusual occurrence of cancer around the plant and subsequent legal action taken by the residents were the basis for this programme. | 1 | Applied and Interdisciplinary Chemistry |
δ-Carotene (delta-carotene) or ε,ψ-carotene is a form of carotene with an ε-ring at one end, and the other uncyclized, labelled ψ (psi). It is an intermediate synthesis product in some photosynthetic plants between lycopene and α-carotene (β,ε-carotene) or ε-carotene (ε,ε-carotene). δ-Carotene is fat soluble. Delta-carotene contains an alpha-ionone instead of a beta-ionone ring; this conversion is carried out by the gene Del which shifts the position of the double bond in the ring structure. The formation delta-carotene under the presence of the Del gene is sensitive to high temperatures. | 1 | Applied and Interdisciplinary Chemistry |
Researchers have extensively investigated the use of hematite (α-FeO) in PEC water-splitting devices due to its low cost, ability to be n-type doped, and band gap (2.2eV). However, performance is plagued by poor conductivity and crystal anisotropy. Some researchers have enhanced catalytic activity by forming a layer of co-catalysts on the surface. Co-catalysts include cobalt-phosphate and iridium oxide, which is known to be a highly active catalyst for the oxygen evolution reaction. | 0 | Theoretical and Fundamental Chemistry |
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