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Many water balance factors depend on the level of the water table, which again depends on some of the water-balance factors. Due to these mutual influences there can be non-linear changes throughout the season. Therefore, the computer program performs daily calculations. For this purpose, the seasonal water-balance factors given with the inpu] are reduced automatically to daily values. The calculated seasonal water-balance factors, as given in the output, are obtained by summations of the daily calculated values. Groundwater levels and soil salinity (the state variables) at the end of the season are found by accumulating the daily changes of water and salt storage.
In some cases the program may detect that the time step must be taken less than 1 day for better accuracy. The necessary adjustments are made automatically. | 9 | Geochemistry |
Due to the presence of two types of oxygen atoms in the PPA backbone, in addition to the fact that H tends to protonate oxygen atoms easily, depolymerization can occur through both endcap cleavage and protonation of oxygen atoms present in the backbone. For this reason, polymer chemists tend to use endcaps rich in oxygen atoms to accelerate depolymerization rate. For example, Moore and co-workers reported the use of a specific ion coactivation (SICA) effect that allowed the ion and acid coactivated-triggered depolymerization of a cyclic PPA microcapsules at the solid/liquid interface of the polymer and solution. | 7 | Physical Chemistry |
In organic chemistry, phosphonium coupling is a cross-coupling reaction for organic synthesis. It is a mild, efficient, chemoselective and versatile methodology for the formation of C–C, C–N, C–O, and C–S bond of unactivated and unprotected tautomerizable heterocycles. The method was originally reported in 2004. The C–OH bond of a tautomerizable heterocycle is activated with a phosphonium salt (PyBroP, PyBOP, BroP, or BOP), and subsequent functionalization with either a nucleophile through SNAr displacement or an organometallic through transition metal catalyzed cross coupling reaction. The in situ activation of the C-OH bond in phosphonium coupling has been applied to cross coupling reactions of tautomerizable heterocycles and arenols using other types of activating reagents.
Phosphonium coupling generates in situ a pseudo aryl or heteroaryl halide (the intermediate phosphonium species), which subsequently reacts with its coupling partner. | 0 | Organic Chemistry |
ATSDR prides itself on using "the best science." And in 2003, BBC News described ATSDR as "widely regarded as the world's leading agency on public health and the environment."
However, ATSDR has also been the focus of scrutiny from Congress and other groups. Much of the criticism is due to the fact that the agency has been overtasked yet understaffed and underfunded for much of its history.
* In August 1991, the General Accounting Office (now the Government Accountability Office) published a report that faulted the quality of ATSDR's original public health assessments and questioned their usefulness. It also placed part of the blame on the deadlines and requirements that Congress imposed with SARA: "SARA’s requirement that ATSDR quickly assess 951 Superfund sites came at a time when the agency was still relatively new and ... not staffed or organized for the job." The report also noted that after meeting the SARA deadline, ATSDR was able to increase the rigor of its public health assessments.
* In May 1992, the Environmental Health Network and the National Toxics Campaign Fund published "Inconclusive by Design," a report which noted structural limitations to the work of CDC and ATSDR.
* In April 2008, the United States House of Representatives Committee on Science and Technology Subcommittee on Investigations and Oversight held a hearing on formaldehyde exposures in trailers that the Federal Emergency Management Agency (FEMA) provided as temporary housing to people displaced by Hurricane Katrina. A report based on the hearing, issued by the subcommittee's Democratic majority staff in September 2008, noted shortcomings in the agency’s original health consultation that examined the health risks of formaldehyde in the FEMA trailers.
* In March 2009, the Democratic majority staff of the Subcommittee on Investigations and Oversight issued another report on ATSDR, which called for leadership changes within the agency. The report stated: "Time and time again ATSDR appears to avoid clearly and directly confronting the most obvious toxic culprits that harm the health of local communities throughout the nation. Instead, they deny, delay, minimize, trivialize or ignore legitimate concerns and health considerations of local communities and well respected scientists and medical professionals."
In the March 12, 2009, congressional hearing, the subcommittee chairman, Congressman Brad Miller, characterized ATSDR as keen to "please industries and government agencies" and referred to ATSDRs reports as "jackleg assessments saying not to worry." In defense of ATSDRs work, director Howard Frumkin noted that ATSDR's staff has declined from 500 to about 300, and that often communities expect "definitive answers about the links between exposures and illnesses," but expectations can be unmet due to scientific uncertainty. However, Dr. Frumkin also acknowledged the possibility that some assessments did not use the best data or monitoring techniques. | 1 | Biochemistry |
Sodium amide can be prepared by the reaction of sodium with ammonia gas, but it is usually prepared by the reaction in liquid ammonia using iron(III) nitrate as a catalyst. The reaction is fastest at the boiling point of the ammonia, c. −33 °C. An electride, , is formed as a reaction intermediate.
is a salt-like material and as such, crystallizes as an infinite polymer. The geometry about sodium is tetrahedral. In ammonia, forms conductive solutions, consistent with the presence of and ions. | 0 | Organic Chemistry |
Unlike its human ortholog, murine perilipin is composed of 517 amino acids in the primary structure of which several regions can be identified. Three moderately hydrophobic sequences (H1, H2, H3) of 18 rem (243-260 aa), 23 rem (320-332 aa) and 16 rem (349-364 aa) can be identified in the centre of the protein, as well as an acidic region of 28 residues where both glutamic and aspartic acids add up to 19 of them. Five sequences 18 residues long that could form amphipathic β-pleated sheets—according to a prediction made through LOCATE program—are found between aa 111 and 182. Serines occupying positions 81, 222, 276, 433, 492 and 517 act as phosphorylation sites -numbered from 1 to 6- for PKA, as well as several other threonines and serines which add up to 27 phosphorylation sites. | 1 | Biochemistry |
Population genetics is essentially a study of the causes and effects of genetic variation within and between populations, and in the past, isozymes have been amongst the most widely used molecular markers for this purpose. Although they have now been largely superseded by more informative DNA-based approaches (such as direct DNA sequencing, single nucleotide polymorphisms and microsatellites), they are still among the quickest and cheapest marker systems to develop, and remain () an excellent choice for projects that only need to identify low levels of genetic variation, e.g. quantifying mating systems. | 1 | Biochemistry |
In chemistry, ethenium, protonated ethylene or ethyl cation is a positive ion with the formula . It can be viewed as a molecule of ethylene () with one added proton (), or a molecule of ethane () minus one hydride ion (). It is a carbocation; more specifically, a nonclassical carbocation. | 7 | Physical Chemistry |
The genus Cronobacter is composed of 7 species. Before 2007, the single species name Enterobacter sakazakii was applied to these organisms. The Cronobacter MLST was initially applied to distinguish between C. sakazakii and C. malonaticus because 16S rDNA sequencing is not always accurate enough, and biotyping is too subjective. The Cronobacter MLST scheme uses 7 alleles; atpD, fusA, glnS, gltB, gyrB, infB and ppsA giving a concatenated sequence of 3036 bp for phylogenetic analysis (MLSA) and comparative genomics. MLST has also been used in the formal recognition of new Cronobacter species. The method has revealed a strong association between one genetic lineage, sequence type 4 (ST4), and cases of neonatal meningitis., The Cronobacter MLST site is at http://www.pubMLST.org/cronobacter. | 1 | Biochemistry |
The FDA issued the approval of escitalopram for major depression in August 2002, and for generalized anxiety disorder in December 2003. In May 2006, the FDA approved a generic version of escitalopram by Teva. In July 2006, the U.S. District Court of Delaware decided in favor of Lundbeck regarding a patent infringement dispute and ruled the patent on escitalopram valid.
In 2006, Forest Laboratories was granted an 828-day (2 years and 3 months) extension on its US patent for escitalopram. This pushed the patent expiration date from 7 December 2009, to 14 September 2011. Together with the 6-month pediatric exclusivity, the final expiration date was 14 March 2012. | 4 | Stereochemistry |
*2001 – Chester F. Carlson Award, American Society for Engineering Education
*2006 – Distinguished Alumni Award, University of Minnesota
*2006 – Distinguished Service Award, American Society for Engineering Education
*2014 – Honorary Doctorate, University of Technology Malaysia
*2015 – Lifetime Achievement Award, American Society for Engineering Education
*2023 – Hall of Fame, American Society for Engineering Education | 8 | Metallurgy |
Primary chloroplasts are cell organelles found in some eukaryotic lineages, where they are specialized in performing photosynthesis. They are considered to have evolved from endosymbiotic cyanobacteria. After some years of debate, it is now generally accepted that the three major groups of primary endosymbiotic eukaryotes (i.e. green plants, red algae and glaucophytes) form one large monophyletic group called Archaeplastida, which evolved after one unique endosymbiotic event.
The morphological similarity between chloroplasts and cyanobacteria was first reported by German botanist Andreas Franz Wilhelm Schimper in the 19th century Chloroplasts are only found in plants and algae, thus paving the way for Russian biologist Konstantin Mereschkowski to suggest in 1905 the symbiogenic origin of the plastid. Lynn Margulis brought this hypothesis back to attention more than 60 years later but the idea did not become fully accepted until supplementary data started to accumulate. The cyanobacterial origin of plastids is now supported by various pieces of phylogenetic, genomic, biochemical and structural evidence. The description of another independent and more recent primary endosymbiosis event between a cyanobacterium and a separate eukaryote lineage (the rhizarian Paulinella chromatophora) also gives credibility to the endosymbiotic origin of the plastids.
In addition to this primary endosymbiosis, many eukaryotic lineages have been subject to secondary or even tertiary endosymbiotic events, that is the "Matryoshka-like" engulfment by a eukaryote of another plastid-bearing eukaryote.
Chloroplasts have many similarities with cyanobacteria, including a circular chromosome, prokaryotic-type ribosomes, and similar proteins in the photosynthetic reaction center. The endosymbiotic theory suggests that photosynthetic bacteria were acquired (by endocytosis) by early eukaryotic cells to form the first plant cells. Therefore, chloroplasts may be photosynthetic bacteria that adapted to life inside plant cells. Like mitochondria, chloroplasts still possess their own DNA, separate from the nuclear DNA of their plant host cells and the genes in this chloroplast DNA resemble those in cyanobacteria. DNA in chloroplasts codes for redox proteins such as photosynthetic reaction centers. The CoRR hypothesis proposes this co-location is required for redox regulation. | 5 | Photochemistry |
The retroviral genome is packaged as viral particles. These viral particles are dimers of single-stranded, positive-sense, linear RNA molecules.
Retroviruses (and orterviruses in general) follow a layout of 5–gag–pro–pol–env–3 in the RNA genome. gag and pol encode polyproteins, each managing the capsid and replication. The pol region encodes enzymes necessary for viral replication, such as reverse transcriptase, protease and integrase. Depending on the virus, the genes may overlap or fuse into larger polyprotein chains. Some viruses contain additional genes. The lentivirus genus, the spumavirus genus, the HTLV / bovine leukemia virus (BLV) genus, and a newly introduced fish virus genus are retroviruses classified as complex. These viruses have genes called accessory genes, in addition to gag, pro, pol and env genes. Accessory genes are located between pol and env, downstream from the env, including the U3 region of LTR, or in the env and overlapping portions. While accessory genes have auxiliary roles, they also coordinate and regulate viral gene expression.
In addition, some retroviruses may carry genes called oncogenes or onc genes from another class. Retroviruses with these genes (also called transforming viruses) are known for their ability to quickly cause tumors in animals and transform cells in culture into an oncogenic state.
The polyproteins are cleaved into smaller proteins each with their own function. The nucleotides encoding them are known as subgenes. | 1 | Biochemistry |
In the 1990s, paroxysmal depolarizing shift-type interictal epileptiform discharges has been suggested to be primarily dependent on autaptic activity for solitary excitatory hippocampal rat neurons grown in microculture.
More recently, in human neocortical tissues of patients with intractable epilepsy, the GABAergic output autapses of fast-spiking (FS) neurons have been shown to have stronger asynchronous release (AR) compared to both non-epileptic tissue and other types of synapses involving FS neurons. The study found similar results using a rat model as well. An increase in residual Ca2+ concentration in addition to the action potential amplitude in FS neurons was suggested to cause this increase in AR of epileptic tissue. Anti-epileptic drugs could potentially target this AR of GABA that seems to rampantly occur at FS neuron autapses. | 1 | Biochemistry |
Published books by Moureu include:
* (doctoral thesis, Contribution to the study of acrylic acid and its derivatives)
* (The azoles, lecture delivered at the laboratory of Charles Friedel)
* (Theoretical study of pyridine compounds and hydropyridines)
* Translated into English as
* (Chemistry and war: science and the future)
* (Speeches and lectures on science and its applications)
Published papers include: | 0 | Organic Chemistry |
Haworth is commemorated at the University of Birmingham in the Haworth Building, which houses most of the University of Birmingham School of Chemistry. The School has a Haworth Chair of Chemistry, held by Professor Nigel Simpkins from 2007 until his retirement in 2017, and by [https://www.birmingham.ac.uk/staff/profiles/chemistry/professor-neil-champness.aspx Professor Neil Champness] since 2021.
In 1977 the Royal Mail issued a postage stamp (one of a series of four) featuring Haworth's achievement in synthesising vitamin C and his Nobel prize.
He also developed a simple method of representing on paper the three-dimensional structure of sugars. The representation, using perspective, now known as a Haworth projection, is still widely used in biochemistry. | 4 | Stereochemistry |
A microfibril is a very fine fibril, or fiber-like strand, consisting of glycoproteins and cellulose. It is usually, but not always, used as a general term in describing the structure of protein fiber, e.g. hair and sperm tail. Its most frequently observed structural pattern is the 9+2 pattern in which two central protofibrils are surrounded by nine other pairs. Cellulose inside plants is one of the examples of non-protein compounds that are using this term with the same purpose. Cellulose microfibrils are laid down in the inner surface of the primary cell wall. As the cell absorbs water, its volume increases and the existing microfibrils separate and new ones are formed to help increase cell strength. | 1 | Biochemistry |
Patients also on diuretics may experience an excessive reduction of blood pressure after initiation of therapy with trandolapril. It can reduce potassium loss caused by thiazide diuretics and increase serum potassium when used alone. Therefore, hyperkalemia is a possible risk. Increased serum lithium levels can occur in patients who are also on lithium. | 4 | Stereochemistry |
Shodex is the brand name of HPLC columns and is best known for polymer-based columns. The product range covers aqueous and organic Size Exclusion Chromatography columns for large (bio-)molecules, columns for the routine analysis of sugars and organic acids, and a variety of Reversed Phase and HILIC columns. Additionally they offer Ion Chromatography (IC) and Ion Exchange columns.
Shodex HPLC Columns are manufactured in Japan by Resonac (formerly known as Showa Denko), one of the largest Japanese chemical companies and listed in the Nikkei 225 index. They produce around 260 different columns, most packed with polymer-based particles, and have been doing so since 1974.
The portfolio includes standard analytical columns, semi-micro columns, and preparative columns. Also size exclusion chromatography calibration standards are available (Pullulan, Polystyrene, Polymethylmethacrylate)
Shodex is distributed worldwide by the different sales offices and by a range of local distributors. | 3 | Analytical Chemistry |
The efficiency of the blast furnace was improved by the change to hot blast, patented by James Beaumont Neilson in Scotland in 1828. This further reduced production costs. Within a few decades, the practice was to have a stove as large as the furnace next to it into which the waste gas (containing CO) from the furnace was directed and burnt. The resultant heat was used to preheat the air blown into the furnace. | 8 | Metallurgy |
Victoria F. Samanidou is a Greek analytical chemist. She is a professor at Aristotle University of Thessaloniki in Thessaloniki, Greece. | 3 | Analytical Chemistry |
The common names of acyl groups are derived typically by replacing the -ic acid suffix of the corresponding carboxylic acid's common name with -yl (or -oyl), as shown in the table below.
In the IUPAC nomenclature of organic chemistry, the systematic names of acyl groups are derived exactly by replacing the -yl suffix of the corresponding hydrocarbyl groups systemic name (or the -oic acid suffix of the corresponding carboxylic acids systemic name) with -oyl, as shown in the table below.
The acyls are between the hydrocarbyls and the carboxylic acids.
The hydrocarbyl group names that end in -yl are not acyl groups, but alkyl groups derived from alkanes (methyl, ethyl, propyl, butyl), alkenyl groups derived from alkenes (propenyl, butenyl), or aryl groups (benzyl). | 0 | Organic Chemistry |
(AD 800/900–1450)
Utilitarian and ceremonial objects; objects of personal adornment
#Amapa, Nayarit
#Apatzingán, Michoacán
#Atoyac, Jalisco
#Cojumatlán, Michoacán
#Coyuca de Catalán, Guerrero
#Culiacán, Sinaloa
#Jiquilpan, Michoacán
#Peñitas, Nayarit
#Río Balsas, Guerrero
#Tancitaro, Michoacán
#Telpalcátepec, Michoacán
#Tepic, Nayarit
#Texmelincan, Guerrero
#Tuxcacuesco, Jalisco
#Tzintzuntzan, Michoacán
#Yestla, Guerrero
#Zacpu, Michoacán
#Zamora, Michoacán | 8 | Metallurgy |
As of September 2018, sixty percent of the worlds solar photovoltaic modules were made in China. As of May 2018, the largest photovoltaic plant in the world is located in the Tengger desert in China. In 2018, China added more photovoltaic installed capacity (in GW) than the next 9 countries combined. In 2021, Chinas share of solar PV module production reached approximately 70%.
In the first half of 2023, Chinas production of PV modules exceeded 220 GW, marking an increase of over 62% compared to the same period in 2022. In 2022, China maintained its position as the worlds largest PV module producer, holding a dominant market share of 77.8%. | 7 | Physical Chemistry |
The transparent wood, tightly packed and perpendicularly aligned cellulose fibers operate as wideband wave-guides with high transmission scattering losses for light. This unique light management capacity results in a light propagation effect. By measuring its optical properties with an integrated sphere, Li and her colleagues found that transparent wood exhibits a high transmittance of 90% (lower than for pure PMMA) and a high optical haze of 95%. As a result, transparent wood as an energy efficient material could be used to decrease the daytime lighting energy usage by efficiently guiding the sunlight into the house while providing uniform and consistent illumination throughout the day.
Similarly, the transparent woods thermal conductivity is attributed to the alignment of the wood cellulose fibers, which has been preserved after lignin removal and polymer infiltration. Transparent wood has a thermal conductivity of 0.32 W⋅m⋅K in the axial direction and 0.15 W⋅m⋅K in the radial direction respectably. Based on the study done by Céline Montanari of the KTH Royal Institute of Technology in Stockholm, the transparent woods thermal conductivity, which transforms from semi-transparent to transparent when heated, could be used to make buildings more energy-efficient by capturing the sun's energy during the day and releasing it later at night into the interior. | 7 | Physical Chemistry |
Stratified waters, in combination with slow vertical mixing, are essential to maintaining euxinic conditions. Stratification occurs when two or more water masses with different densities occupy the same basin. While the less dense surface water can exchange gas with the oxygen-rich atmosphere, the denser bottom waters maintain low oxygen content. In the modern oceans, thermohaline circulation and upwelling prevent the oceans from maintaining anoxic bottom waters. In a silled basin, the stable stratified layers only allow surface water to flow out of the basin while the deep water remains anoxic and relatively unmixed. During an intrusion of dense saltwater however, the nutrient-rich bottom water upwells, causing increased productivity in the surface, further enhancing the nutrient trap due to biological pumping. Rising sea level can exacerbate this process by increasing the amount of deep water entering a silled basin and enhancing estuarine circulation. | 9 | Geochemistry |
*, where k is the Boltzmann constant, and Ω denotes the volume of macrostate in the phase space or otherwise called thermodynamic probability.
*, for reversible processes only | 7 | Physical Chemistry |
1. Bandla, M, D., Chambers, M, R., Sutula, C. L., Immunoassay and method of use, U.S. Patent Number: 7,585,641
2. Roe, R. M., Bailey, W. D., Gould, F., Kennedy, G. G., Sutula, C. L., Insecticide Resistance Assay. U.S. Patent Number: 6,517,856. (2003)
3. Geister, R. L., Bandla, M. D., Sutula, C. L., Multiplex enzyme-linked immunosorbent assay for detecting multiple analytes, U.S. Patent Appl. Number: 20040231776
4. Stiso, S. N., Sutula, C. L., Method, composition and device for determining the specific gravity or osmolality of a liquid, U.S. Patent Number: 4,108,727
5. Sena, E. A., Tolbert, B. M., Sutula, C. L., Liquid scintillation, counting and compositions, U.S. Patent Number: 3,928,227
6. Sutula, C. L., Wilson, J. E., Cleaning porous solids, U.S. Patent Number: 3,325,309 | 3 | Analytical Chemistry |
These phosphoric acids series are generally water-soluble considering the polarity of the molecules. Ammonium and alkali phosphates are also quite soluble in water. The alkaline earth salts start becoming less soluble and phosphate salts of various other metals are even less soluble. | 0 | Organic Chemistry |
Plastids are thought to be descended from endosymbiotic cyanobacteria. The primary endosymbiotic event of the Archaeplastida is hypothesized to have occurred around 1.5 billion years ago and enabled eukaryotes to carry out oxygenic photosynthesis. Three evolutionary lineages in the Archaeplastida have since emerged in which the plastids are named differently: chloroplasts in green algae and/or plants, rhodoplasts in red algae, and muroplasts in the glaucophytes. The plastids differ both in their pigmentation and in their ultrastructure. For example, chloroplasts in plants and green algae have lost all phycobilisomes, the light harvesting complexes found in cyanobacteria, red algae and glaucophytes, but instead contain stroma and grana thylakoids. The glaucocystophycean plastid—in contrast to chloroplasts and rhodoplasts—is still surrounded by the remains of the cyanobacterial cell wall. All these primary plastids are surrounded by two membranes.
The plastid of photosynthetic Paulinella species is often referred to as the cyanelle or chromatophore, and had a much more recent endosymbiotic event about 90–140 million years ago; it is the only known primary endosymbiosis event of cyanobacteria outside of the Archaeplastida. The plastid belongs to the "PS-clade" (of the cyanobacteria genera Prochlorococcus and Synechococcus), which is a different sister clade to the plastids belonging to the Archaeplastida.
In contrast to primary plastids derived from primary endosymbiosis of a prokaryoctyic cyanobacteria, complex plastids originated by secondary endosymbiosis in which a eukaryotic organism engulfed another eukaryotic organism that contained a primary plastid. When a eukaryote engulfs a red or a green alga and retains the algal plastid, that plastid is typically surrounded by more than two membranes. In some cases these plastids may be reduced in their metabolic and/or photosynthetic capacity. Algae with complex plastids derived by secondary endosymbiosis of a red alga include the heterokonts, haptophytes, cryptomonads, and most dinoflagellates (= rhodoplasts). Those that endosymbiosed a green alga include the euglenids and chlorarachniophytes (= chloroplasts). The Apicomplexa, a phylum of obligate parasitic alveolates including the causative agents of malaria (Plasmodium spp.), toxoplasmosis (Toxoplasma gondii), and many other human or animal diseases also harbor a complex plastid (although this organelle has been lost in some apicomplexans, such as Cryptosporidium parvum, which causes cryptosporidiosis). The apicoplast is no longer capable of photosynthesis, but is an essential organelle, and a promising target for antiparasitic drug development.
Some dinoflagellates and sea slugs, in particular of the genus Elysia, take up algae as food and keep the plastid of the digested alga to profit from the photosynthesis; after a while, the plastids are also digested. This process is known as kleptoplasty, from the Greek, kleptes (), thief. | 5 | Photochemistry |
Wootz steel, also known as Seric steel, is a crucible steel characterized by a pattern of bands and high carbon content. These bands are formed by sheets of microscopic carbides within a tempered martensite or pearlite matrix in higher-carbon steel, or by ferrite and pearlite banding in lower-carbon steels. It was a pioneering steel alloy developed in southern India in the mid-1st millennium BC and exported globally. | 8 | Metallurgy |
Like all phyllosilicates, clay minerals are characterised by two-dimensional sheets of corner-sharing tetrahedra or octahedra. The sheet units have the chemical composition . Each silica tetrahedron shares three of its vertex oxygen ions with other tetrahedra, forming a hexagonal array in two dimensions. The fourth oxygen ion is not shared with another tetrahedron and all of the tetrahedra "point" in the same direction; i.e. all of the unshared oxygen ions are on the same side of the sheet. These unshared oxygen ions are called apical oxygen ions.
In clays, the tetrahedral sheets are always bonded to octahedral sheets formed from small cations, such as aluminum or magnesium, and coordinated by six oxygen atoms. The unshared vertex from the tetrahedral sheet also forms part of one side of the octahedral sheet, but an additional oxygen atom is located above the gap in the tetrahedral sheet at the center of the six tetrahedra. This oxygen atom is bonded to a hydrogen atom forming an OH group in the clay structure. Clays can be categorized depending on the way that tetrahedral and octahedral sheets are packaged into layers. If there is only one tetrahedral and one octahedral group in each layer the clay is known as a 1:1 clay. The alternative, known as a 2:1 clay, has two tetrahedral sheets with the unshared vertex of each sheet pointing towards each other and forming each side of the octahedral sheet.
Bonding between the tetrahedral and octahedral sheets requires that the tetrahedral sheet becomes corrugated or twisted, causing ditrigonal distortion to the hexagonal array, and the octahedral sheet is flattened. This minimizes the overall bond-valence distortions of the crystallite.
Depending on the composition of the tetrahedral and octahedral sheets, the layer will have no charge or will have a net negative charge. If the layers are charged this charge is balanced by interlayer cations such as Na or K or by a lone octahedral sheet. The interlayer may also contain water. The crystal structure is formed from a stack of layers interspaced with the interlayers. | 9 | Geochemistry |
In 1998, he founded the journal Accountability in Research, and has served as its editor-in-chief since its inception. He is on the editorial boards of several other journals, including the Drug Information Journal. From 2000 to 2002, he served on the advisory committee for National Human Research Protections. Although he has an extensive list of publications in the fields of biochemistry and microbiology, he is currently busied by his work as an analyst for Foreign Policy In Focus, a project of the Institute for Policy Studies, a think tank, to which he has been contributing since 2005. Shamoo has also authored and co-authored many op-eds on U.S. foreign policy that have been published in newspapers across the country.
Shamoo is also currently occupied with his work in the field of ethics. Since 1991, he has taught a graduate course at the University of Maryland entitled "Responsible Conduct of Research". In 1995, he co-founded the human rights organization, Citizens for Responsible Care and Research (CIRCARE). In 2003, he chaired a Special Issue GlaxoSmithKline Pharmaceuticals Ethics Advisory Group. Shamoo was then appointed to the Armed Forces Epidemiological Board (AFEB) of the United States Department of Defense as ethics consultant (2003–2004). Because he served as chairman on nine international conferences in ethics in research and human research protection, he was asked to testify before a congressional committee and the National Bioethics Advisory Commission. Since 2006, he has served on the Defense Health Board. And from 2006 to 2007,Shamoo was a member of the new Maryland Governors Higher Education Transition Working Group. He was an invited participant and presenter in the 2007 New Year Renaissance Weekend.
Shamoo has held visiting professorships at the Institute for Political Studies in Paris, France and at East Carolina University.
Shamoo has been cited and/or appeared frequently in local and national media both print and television. He has published numerous articles and books. | 1 | Biochemistry |
The use of pesticides inherently entails the risk of resistance developing. Various techniques and procedures of pesticide application can slow the development of resistance, as can some natural features of the target population and surrounding environment. | 2 | Environmental Chemistry |
NAD is synthesized through two metabolic pathways. It is produced either in a de novo pathway from amino acids or in salvage pathways by recycling preformed components such as nicotinamide back to NAD. Although most tissues synthesize NAD by the salvage pathway in mammals, much more de novo synthesis occurs in the liver from tryptophan, and in the kidney and macrophages from nicotinic acid. | 5 | Photochemistry |
After water infiltrates the soil on an up-slope portion of a hill, the water may flow laterally through the soil, and exfiltrate (flow out of the soil) closer to a channel. This is called subsurface return flow or throughflow.
As it flows, the amount of runoff may be reduced in a number of possible ways: a small portion of it may evapotranspire; water may become temporarily stored in microtopographic depressions; and a portion of it may infiltrate as it flows overland. Any remaining surface water eventually flows into a receiving water body such as a river, lake, estuary or ocean. | 2 | Environmental Chemistry |
The highly reducing ferredoxins are reduced either by using another strong reducing agent, or by using some source of energy to "boost" electrons from less reducing sources to the ferredoxin. | 5 | Photochemistry |
Copper chromite is an inorganic compound with the formula CuCrO. It is a black solid that is used to catalyze reactions in organic synthesis. | 0 | Organic Chemistry |
Analysis of a photochemical electrocyclic reaction involves the HOMO, the LUMO, and correlations diagrams.
An electron is promoted into the LUMO changing the frontier molecular orbital involved in the reaction. | 7 | Physical Chemistry |
Maximum entropy methods are at the core of a new view of scientific inference, allowing analysis and interpretation of large and sometimes noisy data. Surprisal analysis extends principles of maximal entropy and of thermodynamics, where both equilibrium thermodynamics and statistical mechanics are assumed to be inferential processes. This enables surprisal analysis to be an effective method of information quantification and compaction and of providing an unbiased characterization of systems. Surprisal analysis is particularly useful to characterize and understand dynamics in small systems, where energy fluxes that are otherwise negligible in large systems heavily influence system behavior.
Foremost, surprisal analysis identifies the state of a system when it reaches its maximal entropy, or thermodynamic equilibrium. This is known as balance state of the system because once a system reaches its maximal entropy, it can no longer initiate or participate in spontaneous processes. Following the determination of the balanced state, surprisal analysis then characterizes all the states in which the system deviates away from the balance state. These deviations are caused by constraints; these constraints on the system prevent the system from reaching its maximal entropy. Surprisal analysis is applied to both identify and characterize these constraints. In terms of the constraints, the probability of an event is quantified by
Here is the probability of the event in the balanced state. It is usually called the “prior probability” because it is the probability of an event prior to any constraints. The surprisal itself is defined as
The surprisal equals the sum over the constraints and is a measure of the deviation from the balanced state. These deviations are ranked on the degree of deviation from the balance state and ordered on the most to least influential to the system. This ranking is provided through the use of Lagrange multipliers. The most important constraint and usually the constraint sufficient to characterize a system exhibit the largest Lagrange multiplier. The multiplier for constraint is denoted above as ; larger multipliers identify more influential constraints. The event variable is the value of the constraint for the event . Using the method of Lagrange multipliers requires that the prior probability and the nature of the constraints be experimentally identified. A numerical algorithm for determining Lagrange multipliers has been introduced by Agmon et al. Recently, singular value decomposition and principal component analysis of the surprisal was utilized to identify constraints on biological systems, extending surprisal analysis to better understanding biological dynamics as shown in the figure. | 7 | Physical Chemistry |
Solutes can have different effects on surface tension depending on the nature of the surface and the solute:
* Little or no effect, for example sugar at water|air, most organic compounds at oil/air
* Increase surface tension, most inorganic salts at water|air
* Non-monotonic change, most inorganic acids at water|air
* Decrease surface tension progressively, as with most amphiphiles, e.g., alcohols at water|air
* Decrease surface tension until certain critical concentration, and no effect afterwards: surfactants that form micelles
What complicates the effect is that a solute can exist in a different concentration at the surface of a solvent than in its bulk. This difference varies from one solute–solvent combination to another.
Gibbs isotherm states that:
* is known as surface concentration, it represents excess of solute per unit area of the surface over what would be present if the bulk concentration prevailed all the way to the surface. It has units of mol/m
* is the concentration of the substance in the bulk solution.
* is the gas constant and the temperature
Certain assumptions are taken in its deduction, therefore Gibbs isotherm can only be applied to ideal (very dilute) solutions with two components. | 6 | Supramolecular Chemistry |
Atomic emission spectroscopy (AES) is a method of chemical analysis that uses the intensity of light emitted from a flame, plasma, arc, or spark at a particular wavelength to determine the quantity of an element in a sample. The wavelength of the atomic spectral line in the emission spectrum gives the identity of the element while the intensity of the emitted light is proportional to the number of atoms of the element. The sample may be excited by various methods. | 3 | Analytical Chemistry |
In planetary science, volatiles are the group of chemical elements and chemical compounds with low boiling points that are associated with a planets or a moons crust or atmosphere.
Very low boiling temperature examples include nitrogen, water, carbon dioxide, ammonia, hydrogen, methane and sulfur dioxide.
In contrast with volatiles, elements and compounds with high boiling points are known as refractory substances.
On the basis of available data, which is sparse for Mars and very uncertain for Venus, the three inner planets then become progressively more depleted in K passing from Mars to Earth to Venus. | 9 | Geochemistry |
The catalytic cycle of galactose oxidase (GOase) illustrates the involvement of non-innocent ligands. GOase oxidizes primary alcohols into aldehydes using O and releasing HO. The active site of the enzyme GOase features a tyrosyl coordinated to a Cu ion. In the key steps of the catalytic cycle, a cooperative Brønsted-basic ligand-site deprotonates the alcohol, and subsequently the oxygen atom of the tyrosinyl radical abstracts a hydrogen atom from the alpha-CH functionality of the coordinated alkoxide substrate. The tyrosinyl radical participates in the catalytic cycle: 1e-oxidation is effected by the Cu(II/I) couple and the 1e oxidation is effected by the tyrosyl radical, giving an overall 2e change. The radical abstraction is fast. Anti-ferromagnetic coupling between the unpaired spins of the tyrosine radical ligand and the d Cu center gives rise to the diamagnetic ground state, consistent with synthetic models. | 0 | Organic Chemistry |
Mitogens are important in cancer research due to their effects on the cell cycle. Cancer is in part defined by a lack of, or failure of, control in the cell cycle. This is usually a combination of two abnormalities: first, cancer cells lose their dependence on mitogens. Second, cancer cells are resistant to anti-mitogens. | 1 | Biochemistry |
Signs and symptoms vary depending on the degree of hypothermia, and may be divided by the three stages of severity. People with hypothermia may appear pale and feel cold to touch.
Infants with hypothermia may feel cold when touched, with bright red skin and an unusual lack of energy.
Behavioural changes such as impaired judgement, impaired sense of time and place, unusual aggression and numbness can be observed in individuals with hypothermia, they can also deny their condition and refuse any help. A hypothermic person can be euphoric and hallucinating.
Cold stress refers to a near-normal body temperature with low skin temperature, signs include shivering. Cold stress is caused by cold exposure and it can lead to hypothermia and frostbite if not treated. | 1 | Biochemistry |
Physical properties of interest to materials science among perovskites include superconductivity, magnetoresistance, ionic conductivity, and a multitude of dielectric properties, which are of great importance in microelectronics and telecommunication. They are also some interests for scintillator as they have large light yield for radiation conversion. Because of the flexibility of bond angles inherent in the perovskite structure there are many different types of distortions which can occur from the ideal structure. These include tilting of the octahedra, displacements of the cations out of the centers of their coordination polyhedra, and distortions of the octahedra driven by electronic factors (Jahn-Teller distortions). The financially biggest application of perovskites is in ceramic capacitors, in which BaTiO is used because of its high dielectric constant. | 3 | Analytical Chemistry |
Tetra-n-butylammonium fluoride, commonly abbreviated to TBAF and n-BuNF, is a quaternary ammonium salt with the chemical formula (CHCHCHCH)NF. It is commercially available as the white solid trihydrate and as a solution in tetrahydrofuran. TBAF is used as a source of fluoride ion in organic solvents. | 0 | Organic Chemistry |
The report commissioned from Atkins Global by Rochdale council, at a cost of £80,000, was published in July 2006 and claimed that previous tests on the land, carried out on behalf of the developers, were not thorough enough, and that extensive work would be required before councillors should even consider the controversial planning application. Atkins Global also claimed that the majority of the developers tests did not detect the true levels of asbestos in the soil. The report concluded that "the presence of asbestos cannot be ruled out across much of the site." In June 2007, Countryside Properties withdrew from the joint planning application. MMC released a statement saying: "Countryside Properties Ltd has withdrawn from the planning application for a mixed use scheme on the former Turner Brothers site because they became disillusioned with the apparent unwillingness of the town planning department to deal with the application as a result of the ill-founded and negative publicity generated by Jason Addys campaign. The people of Rochdale should keep in mind that the site owners have not caused the contamination problems on the site. This was inherited from Federal Mogul... If we were to cave in to Jason Addys uninformed scaremongering and let him have his way, which we most certainly wont, the site would remain a contaminated eyesore on the face of Rochdale in eternity, and all the surrounding houses and properties will be devalued by his badly thought out obsession."
As of 2010, the site remains undeveloped and no significant remediation or decontamination work has been undertaken. | 2 | Environmental Chemistry |
Surveyor nuclease is a mismatch endonuclease enzyme that recognizes all base substitutions and small insertions/deletions (indels), and cleaves the 3′ side of mismatched sites in both DNA strands. | 1 | Biochemistry |
The first DNA-based genome ever fully sequenced was achieved by two-time Nobel Prize winner, Frederick Sanger, in 1977. Sanger and his team of scientists created a library of the bacteriophage, phi X 174, for use in DNA sequencing. The importance of this success contributed to the ever-increasing demand for sequencing genomes to research gene therapy. Teams are now able to catalog polymorphisms in genomes and investigate those candidate genes contributing to maladies such as Parkinsons disease, Alzheimers disease, multiple sclerosis, rheumatoid arthritis, and Type 1 diabetes. These are due to the advance of genome-wide association studies from the ability to create and sequence genomic libraries. Prior, linkage and candidate-gene studies were some of the only approaches. | 1 | Biochemistry |
Atomic spectral lines are due to transitions of electrons between different atomic energy levels E, followed by emission of photons. Atomic levels are a manifestation of the electromagnetic interaction between electrons and nuclei. The energy levels of two atoms, the nuclei of which are different isotopes of the same element, are shifted one with respect to the other, despite the fact that the electric charges Z of the two isotopes are identical. This is so because isotopes differ by the number of neutrons, and therefore the masses and volumes of two isotopes are different; these differences give rise to the isotopic shift on atomic spectral lines.
In the case of two nuclear isomers, the number of protons and the number of neutrons are identical, but the quantum states and in particular the energy levels of the two nuclear isomers differ. This difference induces a difference in the electric charge distributions of two isomers and thus a difference δφ in the corresponding electrostatic nuclear potentials φ, which ultimately leads to a difference ΔE in the atomic energy levels. The isomeric shift on atomic spectral lines is then given by
where ψ is the wave function of the electron involved in the transition, e its electric charge, and the integration is performed over the electron coordinates.
The isotopic and the isomeric shift are similar in the sense that both are effects in which the finite size of the nucleus manifests itself and both are due to a difference in the electromagnetic interaction energy between the electrons and the nucleus of the atom. The isotopic shift had been known decades before the isomeric shift and provided useful but limited information about atomic nuclei. Unlike the isomeric shift, the isotopic shift was at first discovered in experiment and then interpreted theoretically (see also ). While in the case of the isotopic shift the determination of the interaction energy between electrons and nuclei is a relatively simple electromagnetic problem, for isomers the problem is more involved, since it is the strong interaction, which accounts for the isomeric excitation of the nucleus and thus for the difference of charge distributions of the two isomeric states. This circumstance explains in part why the nuclear isomeric shift was not discovered earlier: the appropriate nuclear theory and in particular the nuclear shell model were developed only in the late 1940s and early 1950s. As to the experimental observation of this shift, it also had to await the development of a new technique, that permitted spectroscopy with isomers, which are metastable nuclei. This too happened only in the 1950s.
While the isomeric shift is sensitive to the internal structure of the nucleus, the isotopic shift is (in a good approximation) not. Therefore, the nuclear physics information that can be obtained from the investigation of the isomeric shift, is superior to what can be obtained from isotopic-shift studies. The measurements through the isomeric shift of e.g. the difference of nuclear radii of the excited and ground state constitute one of the most sensitive tests of nuclear models. Moreover, combined with the Mössbauer effect, the isomeric shift constitutes at present a unique tool in many other fields besides physics. | 7 | Physical Chemistry |
In chemistry and physics, cohesion (), also called cohesive attraction or cohesive force, is the action or property of like molecules sticking together, being mutually attractive. It is an intrinsic property of a substance that is caused by the shape and structure of its molecules, which makes the distribution of surrounding electrons irregular when molecules get close to one another, creating electrical attraction that can maintain a macroscopic structure such as a water drop. Cohesion allows for surface tension, creating a "solid-like" state upon which light-weight or low-density materials can be placed.
Water, for example, is strongly cohesive as each molecule may make four hydrogen bonds to other water molecules in a tetrahedral configuration. This results in a relatively strong Coulomb force between molecules. In simple terms, the polarity (a state in which a molecule is oppositely charged on its poles) of water molecules allows them to be attracted to each other. The polarity is due to the electronegativity of the atom of oxygen: oxygen is more electronegative than the atoms of hydrogen, so the electrons they share through the covalent bonds are more often close to oxygen rather than hydrogen. These are called polar covalent bonds, covalent bonds between atoms that thus become oppositely charged. In the case of a water molecule, the hydrogen atoms carry positive charges while the oxygen atom has a negative charge. This charge polarization within the molecule allows it to align with adjacent molecules through strong intermolecular hydrogen bonding, rendering the bulk liquid cohesive. Van der Waals gases such as methane, however, have weak cohesion due only to van der Waals forces that operate by induced polarity in non-polar molecules.
Cohesion, along with adhesion (attraction between unlike molecules), helps explain phenomena such as meniscus, surface tension and capillary action.
Mercury in a glass flask is a good example of the effects of the ratio between cohesive and adhesive forces. Because of its high cohesion and low adhesion to the glass, mercury does not spread out to cover the bottom of the flask, and if enough is placed in the flask to cover the bottom, it exhibits a strongly convex meniscus, whereas the meniscus of water is concave. Mercury will not wet the glass, unlike water and many other liquids, and if the glass is tipped, it will roll around inside. | 6 | Supramolecular Chemistry |
In molecular biology, a scissile bond is a covalent chemical bond that can be broken by an enzyme. Examples would be the cleaved bond in the self-cleaving hammerhead ribozyme or the peptide bond of a substrate cleaved by a peptidase. | 1 | Biochemistry |
Alkalinity (from ) is the capacity of water to resist acidification. It should not be confused with basicity, which is an absolute measurement on the pH scale. Alkalinity is the strength of a buffer solution composed of weak acids and their conjugate bases. It is measured by titrating the solution with an acid such as HCl until its pH changes abruptly, or it reaches a known endpoint where that happens. Alkalinity is expressed in units of concentration, such as meq/L (milliequivalents per liter), μeq/kg (microequivalents per kilogram), or mg/L CaCO (milligrams per liter of calcium carbonate). Each of these measurements corresponds to an amount of acid added as a titrant.
In freshwater, particularly those on non-limestone terrains, alkalinities are low and involve a lot of ions. In the ocean, on the other hand, alkalinity is completely dominated by carbonate and bicarbonate plus a small contribution from borate.
Although alkalinity is primarily a term used by limnologists and oceanographers, it is also used by hydrologists to describe temporary hardness. Moreover, measuring alkalinity is important in determining a streams ability to neutralize acidic pollution from rainfall or wastewater. It is one of the best measures of the sensitivity of the stream to acid inputs. There can be long-term changes in the alkalinity of streams and rivers in response to human disturbances such as acid rain generated by SO and NO emissions. | 9 | Geochemistry |
In radical trifluoromethylation the active species is the trifluoromethyl free radical. Reagents such as bromotrifluoromethane and haloform have been used for this purpose but in response to the Montreal Protocol alternatives such as trifluoroiodomethane have been developed as replacement. One particular combination is CFI / triethylborane
Other reagents that generate the CF radical are sodium trifluoromethanesulfinate and bis(trifluoroacetyl) peroxide.
In the CF radical the fluorine atom is an electron-withdrawing group via the inductive effect but also a weak pi donor through interaction of the fluorine lone pair with the radical center's SOMO. Compared to the methyl radical the CF radical is pyramidal (angle 107.8 °C ) with a large inversion barrier, electrophilic and also more reactive. In reaction with styrene it is 440 times more reactive. An early report (1949) describes the photochemical reaction of iodotrifluoromethane with ethylene to 3-iodo-1,1,1-trifluoropropane. Reagents that have been reported for the direct trifluoromethylation of arenes are CFI, CFBr (thermal or photochemical), silver trifluoroacetate/TiO (photochemical) and sodium trifluoromethanesulfinate/Cu(OSOCF)/tBuOOH. | 0 | Organic Chemistry |
Considering the photothermal mechanism alone, the photoacoustic signal is useful in measuring the light absorption spectrum, particularly for transparent samples where the light absorption is very small. In this case the ordinary method of absorption spectroscopy, based on difference of the intensities of a light beam before and after its passage through the sample, is not practical. In photoacoustic spectroscopy there is no such limitation. the signal is directly related to the light absorption and the light intensity. Dividing the signal spectrum by the light intensity spectrum can give a relative percent absorption spectrum, which can be calibrated to yield absolute values. This is very useful to detect very small concentrations of various materials. Photoacoustic spectroscopy is also useful for the opposite case of opaque samples, where the absorption is essentially complete. In an arrangement where a sensor is placed in a gaseous phase above the sample and the light impinges the sample from above, the photoacoustic signal results from an absorption zone close to the surface. A typical parameter which governs the signal in this case is the "thermal diffusion length", which depends on the material and the modulation frequency and ordinarily is in the order of several micrometers. The signal is related to the light absorbed in the small distance of the thermal diffusion length, allowing the determination of the absorption spectrum. This allows also to separately analyze a surface that is distinct from the bulk. By varying the modulation frequency and wavelength of the probing radiation one essentially varies the probed depth, which results in the possibility of depth profiling and photoacoustic imaging, which discloses inhomogeneities within the sample. This analysis includes also the possibility to determine the thermal properties from the photoacoustic signal.
Recently, the photoacoustic approach has been utilized to quantitatively measure macromolecules, such as proteins. The photoacoustic immunoassay labels and detects target proteins using nanoparticles that can generate strong acoustic signals. The photoacoustics-based protein analysis has also been applied for point-of-care testings.
Another application of the photoacoustic effect is its ability to estimate the chemical energies stored in various steps of a photochemical reaction. Following light absorption photophysical and photochemical conversions occur, which store part of the light energy as chemical energy. Energy storage leads to less heat evolution. The resulting smaller photoacoustic signal thus gives a quantitative estimate of the extent of the energy storage. For transient species this requires the measurement of the signal in the relevant time scale and the capability to extract from the temporal part of the signal the time-dependent heat evolution, by proper deconvolution. There are numerous examples for this application. A similar application is the study of the conversion of light energy to electrical energy in solar cells. A special example is the application of the photoacoustic effect in photosynthesis research. | 7 | Physical Chemistry |
Heavy liquids such as tetrabromoethane can be used to separate ores from supporting rocks by preferential flotation. The rocks are crushed, and while sand, limestone, dolomite, and other types of rock material will float on TBE, ores such as sphalerite, galena and pyrite will sink. | 3 | Analytical Chemistry |
A dicarbonate, also known as a pyrocarbonate, is a chemical containing the divalent or functional group, which consists of two carbonate groups sharing an oxygen atom. These compounds can be viewed as derivatives of the hypothetical compound dicarbonic acid, or . Two important organic compounds containing this group are dimethyl dicarbonate and di-tert-butyl dicarbonate .
It is one of the oxocarbon anions, consisting solely of oxygen and carbon. The anion has the formula or . Dicarbonate salts are apparently unstable at ambient conditions, but can be made under pressure and may have a fleeting existence in carbonate solutions.
The term dicarbonate is sometimes used erroneously to refer to bicarbonate, the common name of the hydrogencarbonate anion or esters of the hydrogencarbonate functional group . It is also sometimes used for chemicals that contain two carbonate units in their covalent structure or stoichiometric formula. | 0 | Organic Chemistry |
Lipidomics is the complete profile of all lipids in a biological system at a given time. This is used to identify and quantify the lipids that can be detected. Since lipids have a variety of functions in the body, being able to understand which specific types are present in the body and at what levels is crucial to understand the diseases that result due to lipids. Methods of lipidomic analysis include mass spectrometry and chromatography. Monitoring lipid concentration can reveal much about an organism's health. | 1 | Biochemistry |
In eukaryotic cells, in general, stable disulfide bonds are formed in the lumen of the RER (rough endoplasmic reticulum) and the mitochondrial intermembrane space but not in the cytosol. This is due to the more oxidizing environment of the aforementioned compartments and more reducing environment of the cytosol (see glutathione). Thus disulfide bonds are mostly found in secretory proteins, lysosomal proteins, and the exoplasmic domains of membrane proteins.
There are notable exceptions to this rule. For example, many nuclear and cytosolic proteins can become disulfide-crosslinked during necrotic cell death. Similarly, a number of cytosolic proteins which have cysteine residues in proximity to each other that function as oxidation sensors or redox catalysts; when the reductive potential of the cell fails, they oxidize and trigger cellular response mechanisms. The virus Vaccinia also produces cytosolic proteins and peptides that have many disulfide bonds; although the reason for this is unknown presumably they have protective effects against intracellular proteolysis machinery.
Disulfide bonds are also formed within and between protamines in the sperm chromatin of many mammalian species. | 0 | Organic Chemistry |
Sweet crude oil has lower sulphur content - lower than 0.5%. It can be refined into kerosene, high-quality diesel, and gasoline. | 9 | Geochemistry |
A number of processes of surface growth in areas ranging from mechanics of growing gravitational bodies through propagating fronts of phase transitions, epitaxial growth of nanostructures and 3D printing, growth of plants, and cell mobility require non-Euclidean description because of incompatibility of boundary conditions and different mechanisms of developing stresses at interfaces. Indeed, these mechanisms result in the curving of initially flat elements of the body and changing separation between different elements of it (especially in the soft matter). Gradual accumulation of deformations under the influx of accumulating mass results in the memory-conscious grows of the body and makes strains the subject of long-range forces. As a result of all above factors, generic non-Euclidean growth is described in terms of Riemannian geometry with a space- and time-dependent curvature. | 7 | Physical Chemistry |
The configuration index has two digits which are the priority numbers of the ligands separated by the largest angle. The lowest priority number of the pair is quoted first. | 4 | Stereochemistry |
The Van Slyke determination is a chemical test for the determination of amino acids containing a primary amine group. It is named after the biochemist Donald Dexter Van Slyke (1883-1971).
One of Van Slyke's first professional achievements was the quantification of amino acids by the Van Slyke determination reaction. To quantify aliphatic amino acids, the sample is diluted in glycerol and then treated with a solution of sodium nitrite, water and acetic acid. The resulting diazotisation reaction produces nitrogen gas which can be observed qualitatively or measured quantitatively.
Van Slyke Reaction:
In addition, Van Slyke developed the so-called Van Slyke apparatus, which can be used to determine the concentration of respiratory gases in the blood, especially the concentration of sodium bicarbonate. This was of high importance to be able to recognize a beginning acidosis in diabetic patients as early as possible, in order to start alkali treatment. The Van Slyke apparatus became a standard equipment in clinical laboratories around the world and the results of Van Slyke's research are still used today to determine abnormalities in the acid-base homeostasis. Later on, Van Slyke further improved his apparatus, increasing its accuracy and sensitivity. Using the new method, he was able to further investigate the role of gas and electrolyte equilibria in the blood and how they change in response to respiration. | 3 | Analytical Chemistry |
An interstitial defect refers to additional atoms occupying some interstitial sites at random as crystallographic defects in a crystal which normally has empty interstitial sites by default. | 3 | Analytical Chemistry |
Ultrasensitive behavior is typically represented by a sigmoidal curve, as small alterations in the stimulus can trigger large changes in the response . One such relation is the Hill equation:
where is the Hill coefficient which quantifies the steepness of the sigmoidal stimulus-response curve and it is therefore a sensitivity parameter. It is often used to assess the cooperativity of a system. A Hill coefficient greater than one is indicative of positive cooperativity and thus, the system exhibits ultrasensitivity.
Systems with a Hill coefficient of 1 are noncooperative and follow the classical Michaelis-Menten kinetics. Enzymes exhibiting noncooperative activity are represented by hyperbolic stimulus/response curves, compared to sigmoidal curves for cooperative (ultrasensitive) enzymes.
In mitogen-activated protein kinase (MAPK) signaling (see example below), the ultrasensitivity of the signaling is supported by the sigmoidal stimulus/response curve that is comparable to an enzyme with a Hill coefficient of 4.0-5.0. This is even more ultrasensitive to the cooperative binding activity of hemoglobin, which has a Hill coefficient of 2.8. | 1 | Biochemistry |
In this case, an extra freedom degree is added via a relatively small work input W (maximum work consumption, Eq.(9) with ΔG ≤ W), and Eq.(10) becomes,
If W is expressed as a fraction f of the process heat Q (Eq.(14)), Eq.(15) becomes after reorganization,
Using a work input equals to a fraction f of the heat input is equivalent relative to the choice of the reactions to operate a pure similar thermochemical cycle but with a hot source with a temperature increased by the same proportion f.
Naturally, this decreases the heat-to-work efficiency in the same proportion f. Consequently, if one want a process similar to a thermochemical cycle operating with a 2000K heat source (instead of 1000K), the maximum heat-to-work efficiency is twice lower. As real efficiencies are often significantly lower than ideal one, such a process is thus strongly limited.
Practically, use of work is restricted to key steps such as product separations, where techniques relying on work (e.g. electrolysis) might sometimes have fewer issues than those using only heat (e.g. distillations) | 7 | Physical Chemistry |
The P1 plasmid has a separate origin of replication (oriL) that is activated during the lytic cycle. Replication begins by a regular bidirectional theta replication at oriL but later in the lytic phase, it switches to a rolling circle method of replication using the host recombination machinery. This results in numerous copies of the genome being present on a single linear DNA molecule called a concatemer. The end of the concatemer is cut a specific site called the pac site or packaging site. This is followed by the packing of the DNA into the heads till they are full. The rest of the concatemer that does not fit into one head is separated and the machinery begins packing this into a new head. The location of the cut is not sequence specific. Each head holds around 110kbp of DNA so there is a little more than one complete copy of the genome (~90kbp) in each head, with the ends of the strand in each head being identical. After infecting a new cell this terminal redundancy is used by the host recombination machinery to cyclize the genome if it lacks two copies of the lox locus. If two lox sites are present (one in each terminally redundant end) the cyclization is carried out by the Cre recombinase.
Once the complete virions are assembled, the host cell is lysed, releasing the viral particles. | 1 | Biochemistry |
In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two organyl groups (e.g., alkyl or aryl). They have the general formula , where R and R′ represent organyl groups (e.g., alkyl or aryl). Ethers can again be classified into two varieties: if the organyl groups are the same on both sides of the oxygen atom, then it is a simple or symmetrical ether, whereas if they are different, the ethers are called mixed or unsymmetrical ethers. A typical example of the first group is the solvent and anaesthetic diethyl ether, commonly referred to simply as "ether" (). Ethers are common in organic chemistry and even more prevalent in biochemistry, as they are common linkages in carbohydrates and lignin. | 0 | Organic Chemistry |
SELDI technology can potentially be used in any application by modifying the SELDI surface. SELDI-TOF-MS is optimal for analyzing low molecular weight proteins (<20 kDa) in a variety of biological materials, such as tissue samples, blood, urine, and serum. This technique is often used in combination with immunoblotting and immunohistochemistry as a diagnostic tool to aid in the detection of biomarkers for diseases, and has also been applied to the diagnosis of cancer and neurological disorders. SELDI-TOF-MS has been used in biomarker discovery for lung, breast, liver, colon, pancreatic, bladder, kidney, cervical, ovarian, and prostate cancers. SELDI technology is most widely used in biomarker discovery to compare protein levels in serum samples from healthy and diseased patients. Serum studies allow for a minimally invasive approach to disease monitoring in patients and are useful in the early detection and diagnosis of diseases and neurological disorders, such as amyotrophic lateral sclerosis (ALS) and Alzheimer's.
SELDI-TOF-MS can also be used in biological applications to detect post-translationally modified proteins and to study phosphorylation states of proteins. | 1 | Biochemistry |
The macadamia (genus Macadamia) nut was discovered by the European settlers, and subsequently the tree was named after him by his friend and colleague, Ferdinand von Mueller (1825-1896), Director of the Royal Botanic Gardens, Melbourne. The tree gave his name to macadamia nuts. The genus Macadamia was first described scientifically in 1857 by Dr. Mueller and he named the new genus in honour of his friend Dr John Macadam. Mueller had done a great deal of taxonomy of the flora, naming innumerable genera but chose this "...a beautiful genus dedicated to John Macadam, M.D. the talented and deserving secretary of our institute." | 3 | Analytical Chemistry |
In the Bodroux–Chichibabin aldehyde synthesis an ortho ester reacts with a Grignard reagent to form an aldehyde; this is an example of a formylation reaction. | 0 | Organic Chemistry |
Soil chemistry is the study of the chemical characteristics of soil. Soil chemistry is affected by mineral composition, organic matter and environmental factors. In the early 1870s a consulting chemist to the Royal Agricultural Society in England, named J. Thomas Way, performed many experiments on how soils exchange ions, and is considered the father of soil chemistry. Other scientists who contributed to this branch of ecology include Edmund Ruffin, and Linus Pauling. | 9 | Geochemistry |
Conventional air conditioning systems are a source of waste heat by releasing waste heat into the outdoor ambient air whilst cooling indoor spaces. This expelling of waste heat from air conditioning can worsen the urban heat island effect. Waste heat from air conditioning can be reduced through the use of passive cooling building design and zero-energy methods like evaporative cooling and passive daytime radiative cooling, the latter of which sends waste heat directly to outer space through the infrared window. | 7 | Physical Chemistry |
The Zeeman effect (; ) is the effect of splitting of a spectral line into several components in the presence of a static magnetic field. It is named after the Dutch physicist Pieter Zeeman, who discovered it in 1896 and received a Nobel prize for this discovery. It is analogous to the Stark effect, the splitting of a spectral line into several components in the presence of an electric field. Also similar to the Stark effect, transitions between different components have, in general, different intensities, with some being entirely forbidden (in the dipole approximation), as governed by the selection rules.
Since the distance between the Zeeman sub-levels is a function of magnetic field strength, this effect can be used to measure magnetic field strength, e.g. that of the Sun and other stars or in laboratory plasmas. | 7 | Physical Chemistry |
Ketenes were first studied as a class by Hermann Staudinger before 1905.
Ketenes were systematically investigated by Hermann Staudinger in 1905 in the form of diphenylketene (conversion of -chlorodiphenyl acetyl chloride with zinc). Staudinger was inspired by the first examples of reactive organic intermediates and stable radicals discovered by Moses Gomberg in 1900 (compounds with triphenylmethyl group). | 0 | Organic Chemistry |
Stakeholder Program on Infant Formula and Adult Nutritionals program (SPIFAN) develops consensus-based standards and methods to make infant formula and adult nutritionals safer for babies and adults to consume. | 3 | Analytical Chemistry |
Entropy of activation determines the preexponential factor of the Arrhenius equation for temperature dependence of reaction rates. The relationship depends on the molecularity of the reaction:
* for reactions in solution and unimolecular gas reactions
* while for bimolecular gas reactions
In these equations is the base of natural logarithms, is the Planck constant, is the Boltzmann constant and the absolute temperature. ' is the ideal gas constant in units of (bar·L)/(mol·K). The factor is needed because of the pressure dependence of the reaction rate. (bar·L)/(mol·K).
The value of provides clues about the molecularity of the rate determining step in a reaction, i.e. the number of molecules that enter this step. Positive values suggest that entropy increases upon achieving the transition state, which often indicates a dissociative mechanism in which the activated complex is loosely bound and about to dissociate. Negative values for indicate that entropy decreases on forming the transition state, which often indicates an associative mechanism in which two reaction partners form a single activated complex. | 7 | Physical Chemistry |
Sensor-based ore sorting is the terminology used in the mining industry. It is a coarse physical coarse particle separation technology usually applied in the size range for . Aim is either to create a lumpy product in ferrous metals, coal or industrial minerals applications or to reject waste before it enters production bottlenecks and more expensive comminution and concentration steps in the process.
In the majority of all mining processes, particles of sub-economic grade enter the traditional comminution, classification and concentration steps. If the amount of sub-economic material in the above-mentioned fraction is roughly 25% or more, there is good potential that sensor-based ore sorting is a technically and financially viable option. High added value can be achieved with relatively low capital expenditure, especially when increasing the productivity through downstream processing of higher grade feed and through increased overall recovery when rejecting deleterious waste. | 3 | Analytical Chemistry |
Asymmetric induction by the molecular framework of an acyclic substrate is the idea that asymmetric steric and electronic properties of a molecule may determine the chirality of subsequent chemical reactions on that molecule. This principal is used to design chemical syntheses where one stereocentre is in place and additional stereocentres are required.
When considering how two functional groups or species react, the precise 3D configurations of the chemical entities involved will determine how they may approach one another. Any restrictions as to how these species may approach each other will determine the configuration of the product of the reaction. In the case of asymmetric induction, we are considering the effects of one asymmetric centre on a molecule on the reactivity of other functional groups on that molecule. The closer together these two sites are, the larger an influence is expected to be observed. A more holistic approach to evaluating these factors is by computational modelling, however, simple qualitative factors may also be used to explain the predominant trends seen for some synthetic steps. The ease and accuracy of this qualitative approach means it is more commonly applied in synthesis and substrate design. Examples of appropriate molecular frameworks are alpha chiral aldehydes and the use of chiral auxiliaries. | 4 | Stereochemistry |
When laser cooling was proposed in 1975, a theoretical limit on the lowest possible temperature was predicted. Known as the Doppler limit, , this was given by the lowest possible temperature attainable considering the cooling of two-level atoms by Doppler cooling and the heating of atoms due to momentum diffusion from the scattering of laser photons. Here, , is the natural line-width of the atomic transition, , is the reduced Planck constant and, , is the Boltzmann constant.
Experiments at the National Institute of Standards and Technology, Gaithersburg, found the temperature of cooled atoms to be well below the theoretical limit.In 1988, Lett et al. directed Sodium atoms through an optical molasses and found the temperatures to be as low as ~40μk; 6 times lower than the expected 240μk doppler cooling limit. Other unexpected properties found in other experimentsincluded significant unexpected insensitivity to laser alignment of the counter-propagating beams. | 7 | Physical Chemistry |
Cast iron, carbon steel, stainless steel and cast aluminium cookware may be seasoned before cooking by applying a fat to the surface and heating it to polymerize it. This produces a dry, hard, smooth, hydrophobic coating, which is non-stick when food is cooked with a small amount of cooking oil or fat. | 7 | Physical Chemistry |
Already now large quantities of water undersaturated in aragonite are upwelling close to the Pacific continental shelf area of North America, from Vancouver to Northern California. These continental shelves play an important role in marine ecosystems, since most marine organisms live or are spawned there. Other shelf areas may be experiencing similar effects.
At depths of 1000s of meters in the ocean, calcium carbonate shells begin to dissolve as increasing pressure and decreasing temperature shift the chemical equilibria controlling calcium carbonate precipitation. The depth at which this occurs is known as the carbonate compensation depth. Ocean acidification will increase such dissolution and shallow the carbonate compensation depth on timescales of tens to hundreds of years. Zones of downwelling are being affected first.
In the North Pacific and North Atlantic, saturation states are also decreasing (the depth of saturation is getting more shallow). Ocean acidification is progressing in the open ocean as the CO travels to deeper depth as a result of ocean mixing. In the open ocean, this causes carbonate compensation depths to become more shallow, meaning that dissolution of calcium carbonate will occur below those depths. In the North Pacific these carbonate saturations depths are shallowing at a rate of 1–2 m per year.
It is expected that ocean acidification in the future will lead to a significant decrease in the burial of carbonate sediments for several centuries, and even the dissolution of existing carbonate sediments. | 9 | Geochemistry |
Prime editing involves three major components:
* A prime editing guide RNA (pegRNA), capable of (i) identifying the target nucleotide sequence to be edited, and (ii) encoding new genetic information that replaces the targeted sequence. The pegRNA consists of an extended single guide RNA (sgRNA) containing a primer binding site (PBS) and a reverse transcriptase (RT) template sequence. During genome editing, the primer binding site allows the 3’ end of the nicked DNA strand to hybridize to the pegRNA, while the RT template serves as a template for the synthesis of edited genetic information.
* A fusion protein consisting of a Cas9 H840A nickase fused to a Moloney Murine Leukemia Virus (M-MLV) reverse transcriptase.
**Cas9 H840A nickase: the Cas9 enzyme contains two nuclease domains that can cleave DNA sequences, a RuvC domain that cleaves the non-target strand and a HNH domain that cleaves the target strand. The introduction of a H840A substitution in Cas9, through which the 840th amino acid histidine is replaced by an alanine, inactivates the HNH domain. With only the RuvC functioning domain, the catalytically impaired Cas9 introduces a single strand nick, hence the name nickase.
**M-MLV reverse transcriptase: an enzyme that synthesizes DNA from a single-stranded RNA template.
* A single guide RNA (sgRNA) that directs the Cas9 H840A nickase portion of the fusion protein to nick the non-edited DNA strand. | 1 | Biochemistry |
Embrittlement is a significant decrease of ductility of a material, which makes the material brittle. Embrittlement is used to describe any phenomena where the environment compromises a stressed material's mechanical performance, such as temperature or environmental composition. This is oftentimes undesirable as brittle fracture occurs quicker and can much more easily propagate than ductile fracture, leading to complete failure of the equipment. Various materials have different mechanisms of embrittlement, therefore it can manifest in a variety of ways, from slow crack growth to a reduction of tensile ductility and toughness. | 8 | Metallurgy |
The majority of prostaglandin signaling occurs via GPCRs (see above) although certain prostaglandins activate nuclear receptors in the PPAR family. (See article eicosanoid receptors for more information). | 1 | Biochemistry |
The eutectoid composition of austenite is approximately 0.8% carbon; steel with less carbon content (hypoeutectoid steel) will contain a corresponding proportion of relatively pure ferrite crystallites that do not participate in the eutectoid reaction and cannot transform into pearlite. Likewise steels with higher carbon content (hypereutectoid steels) will form cementite before reaching the eutectoid point. The proportion of ferrite and cementite forming above the eutectoid point can be calculated from the iron/iron—carbide equilibrium phase diagram using the lever rule.
Steels with pearlitic (eutectoid composition) or near-pearlitic microstructure (near-eutectoid composition) can be drawn into thin wires. Such wires, often bundled into ropes, are commercially used as piano wires, ropes for suspension bridges, and as steel cord for tire reinforcement. High degrees of wire drawing (logarithmic strain above 3) leads to pearlitic wires with yield strengths of several gigapascals. It makes pearlite one of the strongest structural bulk materials on earth.
Some hypereutectoid pearlitic steel wires, when cold wire drawn to true (logarithmic) strains above 5, can even show a maximal tensile strength above . Although pearlite is used in many engineering applications, the origin of its extreme strength is not well understood. It has been recently shown that cold wire drawing not only strengthens pearlite by refining the lamellae structure, but also simultaneously causes partial chemical decomposition of cementite, associated with an increased carbon content of the ferrite phase, deformation induced lattice defects in ferrite lamellae, and even a structural transition from crystalline to amorphous cementite. The deformation-induced decomposition and microstructural change of cementite is closely related to several other phenomena such as a strong redistribution of carbon and other alloy elements like silicon and manganese in both the cementite and the ferrite phase; a variation of the deformation accommodation at the phase interfaces due to a change in the carbon concentration gradient at the interfaces; and mechanical alloying.
Pearlite was first identified by Henry Clifton Sorby and initially named sorbite, however the similarity of microstructure to nacre and especially the optical effect caused by the scale of the structure made the alternative name more popular.
Bainite is a similar structure with lamellae much smaller than the wavelength of visible light and thus lacks this pearlescent appearance. It is prepared by more rapid cooling. Unlike pearlite, whose formation involves the diffusion of all atoms, bainite grows by a displacive transformation mechanism.
The transformation of pearlite to austenite takes place at lower critical temperature of . At this temperature pearlite changes to austenite because of nucleation process. | 8 | Metallurgy |
The hydrophobic effect is the desire for non-polar molecules to aggregate in aqueous solutions in order to separate from water. This phenomenon leads to minimum exposed surface area of non-polar molecules to the polar water molecules (typically spherical droplets), and is commonly used in biochemistry to study protein folding and other various biological phenomenon. The effect is also commonly seen when mixing various oils (including cooking oil) and water. Over time, oil sitting on top of water will begin to aggregate into large flattened spheres from smaller droplets, eventually leading to a film of all oil sitting atop a pool of water. However the hydrophobic effect is not considered a non-covalent interaction as it is a function of entropy and not a specific interaction between two molecules, usually characterized by entropy.enthalpy compensation. An essentially enthalpic hydrophobic effect materializes if a limited number of water molecules are restricted within a cavity; displacement of such water molecules by a ligand frees the water molecules which then in the bulk water enjoy a maximum of hydrogen bonds close to four. | 6 | Supramolecular Chemistry |
Desnitro-imidacloprid is a metabolite of the insecticide imidacloprid, a very common insecticide and the most important member of the class of insecticides called neonicotinoids, the only significant new class of insecticides to be developed between 1970 and 2000. While imidacloprid has proved highly selective against insects, the desnitro- version is highly toxic to mammals, due to its agonist action at the alpha4beta2 nicotinic acetylcholine receptor (nAChR) in the mammalian brain, at least as demonstrated in experiments involving mice. | 1 | Biochemistry |
He turned himself in to coalition forces on April 12, 2003, with the help of ZDF journalists who he asked to monitor and document his surrender. He was detained in Baghdad International Airport as a "High Value Detainee". As such he has been subjected to solitary confinement for 23 hours a day. The International Committee of the Red Cross stated in its confidential report to the coalition authority that this constituted a "serious violation of the Third and Fourth Geneva Conventions". He was both the first person on the most wanted list to turn himself in, and the first to be detained by the U.S.
According to a written Parliamentary answer by Dennis Mcshane MP to Angus Robertson MP, Amer Al Saadi was released by the US on 18 January 2005. However, as detailed here, this claim is highly dubious. A June 20, 2005 Newsweek article reported that a "State Department official...denied al-Sadi had been freed from custody." | 7 | Physical Chemistry |
Lichens demonstrate chemical defenses similar to those mentioned above. Their defenses act against herbivores and pathogens including bacterial, viral, and fungal varieties. To that end, a variety of chemicals are produced by the lichens mycobiont via hydrocarbons produced by the lichens photobiont. However, a single defensive chemical may serve multiple purposes. Usnic acid, for example, is implicated across anti-bacterial, -viral, and -fungal actions. Such defensive chemicals may be stored in various tissue types of the lichen thallus, or they may accumulate on the mycobiont hyphae as extracellular crystals.
Mycobiont-produced acids, including but not limited to, evernic, stictic, and squamatic acids exhibit allelopathy, more specifically, lichen defensive chemicals may inhibit a primary metabolic pathway within competing lichens, mosses, microorganisms, and vascular plants. Documented allelopathic targets include jack pine, white spruce, and garden variety tomato, cabbage, lettuce, and pepper plants. Antimicrobial efforts of lichen are also mediated by various mycobiont-produced acids such as lecanoric and gyrophoric. Similar defensive chemicals were found to inhibit herbivores and insects. Some of these lichen defensive compounds show pharmaceutical potential, too.
In 2004 the death of hundreds of elk near Rawlins, Wyoming was linked to consumption of tumbleweed shield lichen (Xanthoparmelia chlorochroa). This strangely powerful chemical defense is irregular given that such poisoning is very rare while the consumption of this lichen is fairly regular. | 1 | Biochemistry |
Elly Agallidis was born in 1914 to a middle class family of Athens; she was the first child of Ioannis Agallidis and Maria-Edith Agallidis (née Zannou). She graduated with a degree in Physics from the University of Athens in 1934 and continued with postgraduate studies in the Physical Chemistry Laboratory of the University of Munich, then under the direction of Heinrich Otto Wieland. It was there that she met Georg-Maria Schwab, her future husband, who suggested that she examine parahydrogen and supervised her experimental work.
Schwab was banned from teaching in Nazi Germany due to his half-Jewish origin. With the increasing fear of prosecution, he decided in 1930 to emigrate to Elly's homeland, Greece. Agallidis and Schwab married in Athens the same year. Schwab-Agallidis was able to find work for both in the chemical laboratory of the Kanellopoulos Institute of Chemistry and Agriculture, where the couple collaborated on various topics of physico-chemical research for the next ten years (1939–1949). Among those topics Schwab-Agallidis continued her work on the properties of parahydrogen, for which she received her PhD by the Department of Physics of the University of Athens in 1939 and published multiple relevant papers in the following years. At the same period she also delivered lectures on Physical Chemistry at the University of Athens.
After a difficult period for the couple during the Axis occupation of Greece and the resumption of their research after the liberation of Greece, the two scientists eventually returned to West Germany when Schwab was offered the Professorship of Physical Chemistry at the University of Munich in 1951.
Elly Schwab-Agallidis died in Essen at the age of 92 in 2006. | 7 | Physical Chemistry |
Industrial nitric acid production uses the Ostwald process. The combined Ostwald and Haber processes are extremely efficient, requiring only air and natural gas feedstocks.
The Ostwald process' technical innovation is the proper conditions under which anhydrous ammonia burns to nitric oxide (NO) instead of dinitrogen (). The nitric oxide is then oxidized, often with atmospheric oxygen, to nitrogen dioxide ():
The dioxide then disproportionates in water to nitric acid and the nitric oxide feedstock:
The net reaction is maximal oxidation of ammonia:
Dissolved nitrogen oxides are either stripped (in the case of white fuming nitric acid) or remain in solution to form red fuming nitric acid.
Commercial grade nitric acid solutions are usually between 52% and 68% nitric acid by mass, the maximum distillable concentration. Further dehydration to 98% can be achieved with concentrated sulfuric acid|. Historically, higher acid concentrations were also produced by dissolving additional nitrogen dioxide in the acid, but the last plant in the United States ceased using that process in 2012.
More recently, electrochemical means have been developed to produce anhydrous acid from concentrated nitric acid feedstock. | 3 | Analytical Chemistry |
During the 1950s and 1960s, the National Cancer Institute carried out a wide-ranging program of screening plant and marine organism material. As part of that program, extract from the sea squirt Ecteinascidia turbinata was found to have anticancer activity in 1969.
Separation and characterization of the active molecules had to wait many years for the development of sufficiently sensitive techniques, and the structure of one of them, Ecteinascidin 743, was determined by KL Rinehart at the University of Illinois in 1984. Rinehart had collected his sea squirts by scuba diving in the reefs of the West Indies. The biosynthetic pathway responsible for producing the drug has been determined to come from Candidatus Endoecteinascidia frumentensis, a microbial symbiont of the tunicate.
The Spanish company PharmaMar licensed the compound from the University of Illinois before 1994 and attempted to farm the sea squirt with limited success. Yields from the sea squirt are extremely low - 1 tonne of animals is needed to isolate 1 gram of trabectedin - and about 5 grams were believed to be needed for a clinical trial so Rinehart asked the Harvard chemist E. J. Corey to search for a synthetic method of preparation. His group developed such a method and published it in 1996. This was later followed by a simpler and more tractable method which was patented by Harvard and subsequently licensed to PharmaMar. The current supply is based on a semisynthetic process developed by PharmaMar starting from safracin B, an antibiotic obtained by fermentation of the bacterium Pseudomonas fluorescens. PharmaMar entered into an agreement with Johnson & Johnson to market the compound outside Europe. | 0 | Organic Chemistry |
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V). | 1 | Biochemistry |
There are two types of pumps available for uniform delivery of relatively small liquid volumes for GPC: piston or peristaltic pumps. The delivery of a constant flow free of fluctuations is especially important to the precision of the GPC analysis, as the flow-rate is used for the calibration of the molecular weight, or diameter. | 3 | Analytical Chemistry |
Although not as toxic as many similar compounds, inhaled or ingested 1,1,1-trichloroethane does act as a central nervous system depressant and can cause effects similar to those of ethanol intoxication, including dizziness, confusion, and, in sufficiently high concentrations, unconsciousness and death. Fatal poisonings and illnesses linked to intentional inhalation of trichloroethane have been reported. The removal of the chemical from correction fluid commenced due to Proposition 65 declaring it hazardous and toxic.
Prolonged skin contact with the liquid can result in the removal of fats from the skin, resulting in skin irritation.
The International Agency for Research on Cancer places 1,1,1-trichloroethane in Group 2A as a probable carcinogen. | 2 | Environmental Chemistry |
The classical and most reliable method of log P determination is the shake-flask method, which consists of dissolving some of the solute in question in a volume of octanol and water, then measuring the concentration of the solute in each solvent. The most common method of measuring the distribution of the solute is by UV/VIS spectroscopy. | 7 | Physical Chemistry |
Cancer biomarkers have an extremely high upside for therapeutic interventions in cancer patients. Most cancer biomarkers consist of proteins or altered segments of DNA, and are expressed in all cells, just at higher rates in cancer cells. There has not yet been one, universal tumor biomarker, but there is a biomarker for every type of cancer. These tumor biomarkers are used to track the health of tumors, but cannot serve as the sole diagnostic for specific cancers. Examples of tumoral markers used to follow up cancer treatment are the Carcinoembryonic Antigen (CEA) for colorectal cancer and the Prostate Specific Antigen (PSA) for prostate cancer. In 2014, Cancer research identified Circulating Tumor Cells (CTCs) and Circulating Tumor DNA (ctDNA) as metastasizing tumor biomarkers with special cellular differentiation and prognostic skills. Innovative technology needs to be harnessed to determine the full capabilities of CTCs and ctDNA, but insight into their roles has potential for new understanding of cancer evolution, invasion and metastasis. | 1 | Biochemistry |
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