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Iodobenzene dichloride is hydrolyzed by basic solutions to give iodosobenzene (PhIO) and is oxidized by sodium hypochlorite to give iodoxybenzene (PhIO).
In organic synthesis, iodobenzene dichloride is used as a reagent for the selective chlorination of alkenes. and alkynes. | 0 | Organic Chemistry |
Biological cells which form bonds with a substrate and are at the same time subject to a flow can form long thin membrane cylinders called tethers. These tethers connect the adherent area of the substrate to the main body of the cell. Under physiological conditions, neutrophil tethers can extend to several micrometers.
In biochemistry, a tether is a molecule that carries one or two carbon intermediates from one active site to another. They are commonly used in lipid synthesis, gluconeogenesis, and the conversion of pyruvate into Acetyl CoA via PDH complex. Common tethers are lipoate -lysine residue complex associated with dihydrolipoyl transacetylase, which is used for carrying hydroxyethyl from hydroxyethyl TPP. This compound forms Acetyl- CoA, a convergent molecule in metabolic pathways.
Another tether is biotin-lysine residue complex associated with pyruvate carboxylase, an enzyme which plays an important role in gluconeogenesis. It is involved in the production of oxaloacetate from pyruvate.
One of the biological tethers used in the synthesis of fats is a β- mercaptoethylamine-pantothenate complex associated with an acyl carrier protein. | 1 | Biochemistry |
The table, like most shaking tables, consists of a riffled deck with a gentle tilt on a stable support to counteract the tables oscillation. A motor, usually mounted to the side, drives a small arm that shakes the table along its length. The riffles are typically less than high and cover more than half the tables surface. Varied riffle designs are available for specific applications. The riffles run longitudinally, parallel to the long dimension of the table. The table's shaking motion is parallel to the riffle pattern.
Deck construction varies from wood to hard-wearing fiberglass where the riffles are formed as part of the mold. The decks are lined with high coefficient-of-friction materials (linoleum, rubber or plastic), which assists in the mineral recovery process.
During operation, a slurry of < sample material consisting of about 25% solids by weight is fed with wash water along the top of the table, perpendicular to the direction of table motion. The table is shaken longitudinally, using a slow forward stroke and a rapid return strike that causes particles to migrate or crawl along the deck parallel to the direction of motion. Particles move diagonally across the deck from the feed end and separate on the table according to size and density. Water flow rate, table tilt angle and intensity of the shaking motion must be properly adjusted for effective mineral recovery.
The riffles cause mineral particles to stratify in the protected inter-riffle regions. The finest and heaviest particles are forced to the bottom and the coarsest and lightest particles remain at the top. Particle layers migrate across the riffles with addition of new slurry feed and continued water wash. The riffles are tapered and flatten (disappear) towards the concentrate end of the table. The taper of the riffles causes migrating particles of progressively finer size and higher density to be brought into contact with the flowing film of water that tops the riffles; lighter material is washed away as tailings and middlings. Final concentration takes place in the unriffled region at the end of the deck where the layer of material at this stage is usually only a few particles deep. | 8 | Metallurgy |
It is possible to work out the equilibrium constant for a chemical reaction involving a mixture of gases given the partial pressure of each gas and the overall reaction formula. For a reversible reaction involving gas reactants and gas products, such as:
the equilibrium constant of the reaction would be:
For reversible reactions, changes in the total pressure, temperature or reactant concentrations will shift the equilibrium so as to favor either the right or left side of the reaction in accordance with Le Chatelier's Principle. However, the reaction kinetics may either oppose or enhance the equilibrium shift. In some cases, the reaction kinetics may be the overriding factor to consider. | 7 | Physical Chemistry |
Triethyloxonium tetrafluoroborate is a very strong alkylating agent, although the hazards are diminished because it is non-volatile. It releases strong acid upon contact with water. The properties of the methyl derivative are similar. | 0 | Organic Chemistry |
For cellular processes that are not directly related to pathogen resistance or defense, BIK1 does not utilize traditional defense-mediating hormones such as SA, JA, or ACC, but instead utilizes an herbicide, known as paraquat which produces ROIs. It is believed that SA, JA, and ACC have no effect on BIK1 induction because they are likely located downstream from the BIK1 gene, or it is possible that BIK1 operates completely independently. However, it is believed that BIK1 does play a vital role in the ET signaling pathway. Based on the signaling function of BIK1 in ET responses, it is believed that Botrytis-induced kinase1 accumulates response signals that it receives from upstream regulators and then integrates them into its own resistance mechanism.
BIK1 is a receptor-like cytoplasmic kinase (RLCK) that associates with a cell-surface receptor, FLS2, and a co-receptor kinase, BAK1 to transduce signals when a PAMP is detected. In order for BIK1 to be activated, site-specific phosphorylation must occur. | 1 | Biochemistry |
The evidence suggests that there is a general interdependence between base composition patterns and coding region availability. The coding region is thought to contain a higher GC-content than non-coding regions. There is further research that discovered that the longer the coding strand, the higher the GC-content. Short coding strands are comparatively still GC-poor, similar to the low GC-content of the base composition translational stop codons like TAG, TAA, and TGA.
GC-rich areas are also where the ratio point mutation type is altered slightly: there are more transitions, which are changes from purine to purine or pyrimidine to pyrimidine, compared to transversions, which are changes from purine to pyrimidine or pyrimidine to purine. The transitions are less likely to change the encoded amino acid and remain a silent mutation (especially if they occur in the third nucleotide of a codon) which is usually beneficial to the organism during translation and protein formation.
This indicates that essential coding regions (gene-rich) are higher in GC-content and more stable and resistant to mutation compared to accessory and non-essential regions (gene-poor). However, it is still unclear whether this came about through neutral and random mutation or through a pattern of selection. There is also debate on whether the methods used, such as gene windows, to ascertain the relationship between GC-content and coding region are accurate and unbiased. | 1 | Biochemistry |
The 2013 ILCOR and 2010 American Heart Association guidelines support the use of cooling following resuscitation from cardiac arrest. These recommendations were largely based on two trials from 2002 which showed improved survival and brain function when cooled to after cardiac arrest.
However, more recent research suggests that there is no benefit to cooling to when compared with less aggressive cooling only to a near-normal temperature of ; it appears cooling is effective because it prevents fever, a common complication seen after cardiac arrest. There is no difference in long term quality of life following mild compared to more severe cooling.
In children, following cardiac arrest, cooling does not appear useful as of 2018. | 1 | Biochemistry |
Yuri Zhdanov was born on August 20, 1919, in Tver. He graduated from Moscow State University in 1941 with a degree in organic chemistry and served with the Red Army during World War II. He received a Ph.D. in 1948.
In 1947, he was appointed head of the Central Committees Science Department. As head of the department, he publicly criticized the scientific theories of Trofim Lysenko at a meeting with party propagandists and was subsequently rebuked by Joseph Stalin at a Politburo meeting ("Dont you know that our entire agriculture depends on Lysenko?").
He married Svetlana Alliluyeva in the spring of 1949 "as a matter of hard common sense but without any special love or affection". Joseph Stalin respected the Zhdanov family and had always hoped the two families would be linked in marriage. They soon divorced in 1952. They had a daughter Yekaterina in 1950.
He joined Rostov State University in 1953, becoming a member of the Soviet Academy of Sciences and eventually Rector of the University. He was the author of numerous papers on organic chemistry.
In 1950 as the member of Soviet political leadership Zhdanov took active role in the implementation of the national policy of antisemitism. In his later year while being the Rector of Rostov State University and the Chair of the North-Caucasian Scientific Center of Higher Education he established the atmosphere of ethnic and religious tolerance. At that time most Soviet colleges and universities had severe quota on Jewish students and faculty. Many Jewish students from different regions of the Soviet Union were coming to Rostov-on-Don knowing that they would be admitted to local colleges and university. Most colleges and universities of the Rostov-on-Don region under the leadership of Zhdanov employed Jewish faculty and staff. Three out of five scientific research institutes of Rostov State University were headed by Jews.
He died on 19 December 2006 in Rostov-on-Don. | 0 | Organic Chemistry |
Knowledge of charge carrier mobility in semiconductors is important for understanding the electronic and materials properties of a system. It is also valuable in device design and optimization. This is particularly true for thin film solar cells and thin film transistors, where charge extraction and amplification, respectively, are highly dependent upon mobility. TRMC has been used to study electron and hole dynamics in hydrogenated amorphous silicon, organic semiconductors, metal halide perovskites, metal oxides, dye sensitized systems, quantum dots, carbon nanotubes, chalcogenides, metal organic frameworks, and the interfaces between various systems.
Because charges are normally generated using a green (~2.3 eV) or ultraviolet (~3 eV) laser, this restricts materials to those with comparable or smaller bandgaps. The technique is hence well suited to the study of solar absorbers, but not to wide bandgap semiconductors such as metal oxides.
While it is very similar, and has the same dimensions, the parameter is not the same a charge carrier mobility. contains contributions from both holes and electrons, which cannot conventionally be resolved using TRMC. This is in contrast to Hall Measurements or transistor measurements, where hole and electron mobility can easily be separated. Additionally, the mobility is not directly extracted from the measurements, it is measured multiplied by the carrier generation yield, . The carrier generation yield is the number of electron hole pairs generated per absorbed photon. Because some absorbed photons can lead to bound neutral excitons, not all absorbed photons will lead to detectable free carriers. This can make interpretation of more complicated than mobility. However, generally both mobility and are parameters which one wishes to maximize when developing solar cells.
As a time-resolved technique, TRMC also provides information on the timescale of carrier recombination in solar cells. Unlike time resolved photoluminescence measurements, TRMC is not sensitive to the lifetime of excitons. | 7 | Physical Chemistry |
Brenna visited the FDA infant formula team in late 2001 to encourage omega-3 DHA to be included in infant formula. A few weeks later the FDA issued its “no questions” letter accepting this suggestion and citing his work. | 3 | Analytical Chemistry |
Generating data on RNA transcripts can be achieved via either of two main principles: sequencing of individual transcripts (ESTs, or RNA-Seq) or hybridisation of transcripts to an ordered array of nucleotide probes (microarrays). | 1 | Biochemistry |
Hypothermia has been applied therapeutically since antiquity. The Greek physician Hippocrates, the namesake of the Hippocratic Oath, advocated the packing of wounded soldiers in snow and ice. Napoleonic surgeon Baron Dominique Jean Larrey recorded that officers who were kept closer to the fire survived less often than the minimally pampered infantrymen. In modern times, the first medical article concerning hypothermia was published in 1945. This study focused on the effects of hypothermia on patients with severe head injury. In the 1950s, hypothermia received its first medical application, being used in intracerebral aneurysm surgery to create a bloodless field. Most of the early research focused on the applications of deep hypothermia, defined as a body temperature of . Such an extreme drop in body temperature brings with it a whole host of side effects, which made the use of deep hypothermia impractical in most clinical situations.
This period also saw sporadic investigation of more mild forms of hypothermia, with mild hypothermia being defined as a body temperature of . In the 1950s, Doctor Rosomoff demonstrated in dogs the positive effects of mild hypothermia after brain ischemia and traumatic brain injury. In the 1980s further animal studies indicated the ability of mild hypothermia to act as a general neuroprotectant following a blockage of blood flow to the brain. This animal data was supported by two landmark human studies that were published simultaneously in 2002 by the New England Journal of Medicine. Both studies, one occurring in Europe and the other in Australia, demonstrated the positive effects of mild hypothermia applied following cardiac arrest. Responding to this research, in 2003 the American Heart Association (AHA) and the International Liaison Committee on Resuscitation (ILCOR) endorsed the use of targeted temperature management following cardiac arrest. Currently, a growing percentage of hospitals around the world incorporate the AHA/ILCOR guidelines and include hypothermic therapies in their standard package of care for patients with cardiac arrest. Some researchers go so far as to contend that hypothermia represents a better neuroprotectant following a blockage of blood to the brain than any known drug. Over this same period a particularly successful research effort showed that hypothermia is a highly effective treatment when applied to newborn infants following birth asphyxia. Meta-analysis of a number of large randomised controlled trials showed that hypothermia for 72 hours started within 6 hours of birth significantly increased the chance of survival without brain damage. | 1 | Biochemistry |
Pipe materials with higher molecular weights (MW), or densities, will have slower material flow rates when in the molten state during fusion. Despite the differences in flow rates, the final joint strength is generally consistent over a fairly wide range of pipe molecular weights. | 7 | Physical Chemistry |
Cornforth was the focus of a skit on an episode of Comedy Inc., whereby a fictional Who Wants to Be A Millionaire? contestant (played by Genevieve Morris) is asked "Which Australian scientist won the Nobel Prize for Chemistry in 1975?" for the million-dollar question. As it happens, the contest gleefully claims they are second cousins with Conforth (despite being nearly 50 years his junior) and knows Cornforth is the answer, confidently rattling off a bunch of highly specific and esoteric facts about Cornforths life and achievements, all the while the host (a satirical portrayal of Eddie McGuire) stubbornly and continuously stalls her for dramatic effect, asking her for several minutes if shed like to think about it more to an absurd degree.
On September 7, 2017, Google celebrated his 100th birthday with a Google Doodle. | 0 | Organic Chemistry |
Fiber-reinforced polymers (FRP) are commonly used by civil engineers in their structures. FRPs respond linear-elastically to axial stress, making them a great material to hold a load. FRPs are usually in a laminate formation with each lamina having unidirectional fibers, typically carbon or glass, embedded within a layer of light polymer matrix material. FRPs have great resistance against environmental exposure and great durability. | 7 | Physical Chemistry |
The trihexagonal tiling can be geometrically distorted into topologically equivalent tilings of lower symmetry. In these variants of the tiling, the edges do not necessarily line up to form straight lines. | 3 | Analytical Chemistry |
Some nitrones oligimerize: Syntheses with nitrone precursors obviate the issue with increased temperature, to exaggerate entropic factors; or with a nitrone excess. | 0 | Organic Chemistry |
There are many types of passive samplers used that specialize in absorbing different classes of aquatic contaminants found in the environment. Chemcatcher and SMPD are two types of passive samplers that are also commonly used. Monitoring programs use SMPDs to measure to hydrophobic organic contaminants. SPMDs are designed to mimic the bioconcentration of contaminants in fatty tissues (ITRC, 2006). Contaminants applicable to the use of an SPMD include, but are not limited to, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides, dioxins, and furans.
The SPMD consist of a thin-walled, nonporous, polyethylene membrane tube that is filled with high molecular weight lipid. These tubes are approximately 90 cm long and wrap around the inside of a stainless steel deployment canister. SMPDs are efficient at absorbing pollutants with a log Kow of 4-8. This slightly overlaps with the range of contaminants absorbed by POCIS. Because of this, SMPDs and POCIS devices are often used together in monitoring studies to achieve a more representative understanding of contamination. | 3 | Analytical Chemistry |
Many experiments are continuing in the production of metallic hydrogen in laboratory conditions at static compression and low temperature. Arthur Ruoff and Chandrabhas Narayana from Cornell University in 1998, and later Paul Loubeyre and René LeToullec from Commissariat à l'Énergie Atomique, France in 2002, have shown that at pressures close to those at the center of the Earth () and temperatures of , hydrogen is still not a true alkali metal, because of the non-zero band gap. The quest to see metallic hydrogen in laboratory at low temperature and static compression continues. Studies are also ongoing on deuterium. Shahriar Badiei and Leif Holmlid from the University of Gothenburg have shown in 2004 that condensed metallic states made of excited hydrogen atoms (Rydberg matter) are effective promoters to metallic hydrogen, however these results are disputed. | 7 | Physical Chemistry |
Smelting has serious effects on the environment, producing wastewater and slag and releasing such toxic metals as copper, silver, iron, cobalt, and selenium into the atmosphere. Smelters also release gaseous sulfur dioxide, contributing to acid rain, which acidifies soil and water.
The smelter in Flin Flon, Canada was one of the largest point sources of mercury in North America in the 20th century. Even after smelter releases were drastically reduced, landscape re-emission continued to be a major regional source of mercury. Lakes will likely receive mercury contamination from the smelter for decades, from both re-emissions returning as rainwater and leaching of metals from the soil. | 8 | Metallurgy |
In the following years, polymer chemists started studying the characteristics of this polymer and worked on enhancing its thermal stability and mechanical properties. In particular, Moore and coworkers conducted rigorous mechanistic studies on poly(phthalaldehyde) by modifying the type of catalyst used, as well as the starting monomer concentration in an effort to control the molar mass, decrease the polydispersity index, and increase the polymer's purity. Among the catalysts used were triethyloxonium borofluoride, tin chloride, and triphenylmethylium tetrafluoroborate. | 7 | Physical Chemistry |
Glyceraldehyde 3-phosphate occurs as a byproduct in the biosynthesis pathway of tryptophan, an essential amino acid that cannot be produced by the human body. | 5 | Photochemistry |
Because of the importance of end groups, there have been many analytical techniques developed for the identification of the groups. The three main methods for analyzing the identity of the end group are by NMR, mass spectrometry (MS) or vibrational spectroscopy (IR or Raman). Each technique has its advantages and disadvantages, which are details below. | 7 | Physical Chemistry |
In materials science, Ostwalds rule or Ostwalds step rule, conceived by Wilhelm Ostwald, describes the formation of polymorphs. The rule states that usually the less stable polymorph crystallizes first. Ostwald's rule is not a universal law but a common tendency observed in nature.
This can be explained on the basis of irreversible thermodynamics, structural relationships, or a combined consideration of statistical thermodynamics and structural variation with temperature. Unstable polymorphs more closely resemble the state in solution, and thus are kinetically advantaged.
For example, out of hot water, metastable, fibrous crystals of benzamide appear first, only later to spontaneously convert to the more stable rhombic polymorph. Another example is magnesium carbonate, which more readily forms dolomite. A dramatic example is phosphorus, which upon sublimation first forms the less stable white phosphorus, which only slowly polymerizes to the red allotrope. This is notably the case for the anatase polymorph of titanium dioxide, which having a lower surface energy is commonly the first phase to form by crystallisation from amorphous precursors or solutions despite being metastable, with rutile being the equilibrium phase at all temperatures and pressures. | 3 | Analytical Chemistry |
Position isomers (also positional isomers or regioisomers) are structural isomers that can be viewed as differing only on the position of a functional group, substituent, or some other feature on the same "parent" structure.
For example, replacing one of the 12 hydrogen atoms –H by a hydroxyl group –OH on the n-pentane parent molecule can give any of three different position isomers:
Another example of regioisomers are α-linolenic and γ-linolenic acids, both octadecatrienoic acids, each of which has three double bonds, but on different positions along the chain. | 4 | Stereochemistry |
Apoptotic DNA fragmentation is a natural fragmentation that cells perform in apoptosis (programmed cell death). DNA fragmentation is a biochemical hallmark of apoptosis. In dying cells, DNA is cleaved by an endonuclease that fragments the chromatin into nucleosomal units, which are multiples of about 180-bp oligomers and appear as a DNA ladder when run on an agarose gel. The enzyme responsible for apoptotic DNA fragmentation is the Caspase-activated DNase. CAD is normally inhibited by another protein, the Inhibitor of Caspase Activated DNase (ICAD). During apoptosis, the apoptotic effector caspase, caspase 3, cleaves ICAD and thus causes CAD to become activated.
CAD cleaves the DNA at the internucleosomal linker sites between the nucleosomes, protein-containing structures that occur in chromatin at ~180-bp intervals. This is because the DNA is normally tightly wrapped around histones, the core proteins of the nucleosomes. The linker sites are the only parts of the DNA strand that are exposed and thus accessible to CAD.
Men with sperm motility defects often have high levels of sperm DNA fragmentation.
The degree of DNA fragmentation in sperm cells can predict outcomes for in vitro fertilization (IVF) and its expansion intracytoplasmic sperm injection (ICSI). The sperm chromatin dispersion test (SCD) and TUNEL assay are both effective in detecting sperm DNA damage. Using bright-field microscopy, the SCD test appears to be more sensitive than the TUNEL assay. | 1 | Biochemistry |
Tungsten is the most common refractory metal that can be used as a selective emitter. It has higher emissivity in the visible and near-IR range of 0.45 to 0.47 and a low emissivity of 0.1 to 0.2 in the IR region. The emitter is usually in the shape of a cylinder with a sealed bottom, which can be considered a cavity. The emitter is attached to the back of a thermal absorber such as SiC and maintains the same temperature. Emission occurs in the visible and near IR range, which can be readily converted by the PV to electrical energy. However, compared to other metals, tungsten oxidizes more easily. | 7 | Physical Chemistry |
Hydrogen is the simplest solar fuel. Its formation involves only the transference of two electrons to two protons:
The hydrogenase enzymes effect this conversion
Dirhodium photocatalyst and cobalt catalysts. | 5 | Photochemistry |
In condensed matter physics, a quantum spin liquid is a phase of matter that can be formed by interacting quantum spins in certain magnetic materials. Quantum spin liquids (QSL) are generally characterized by their long-range quantum entanglement, fractionalized excitations, and absence of ordinary magnetic order.
The quantum spin liquid state was first proposed by physicist Phil Anderson in 1973 as the ground state for a system of spins on a triangular lattice that interact antiferromagnetically with their nearest neighbors, i.e. neighboring spins seek to be aligned in opposite directions. Quantum spin liquids generated further interest when in 1987 Anderson proposed a theory that described high-temperature superconductivity in terms of a disordered spin-liquid state. | 7 | Physical Chemistry |
The carbonate pump is sometimes referred to as the “hard tissue” component of the biological pump. Some surface marine organisms, like Coccolithophores, produce hard structures out of calcium carbonate, a form of particulate inorganic carbon, by fixing bicarbonate. This fixation of DIC is an important part of the oceanic carbon cycle.
:Ca + 2 → CaCO + CO + HO
While the biological carbon pump fixes inorganic carbon (CO) into particulate organic carbon in the form of sugar (CHO), the carbonate pump fixes inorganic bicarbonate and causes a net release of CO. In this way, the carbonate pump could be termed the carbonate counter pump. It works counter to the biological pump by counteracting the CO flux from the biological pump. | 9 | Geochemistry |
In simple manual columns, the eluent is collected in constant volumes, known as fractions. The more similar the particles are in size the more likely they are in the same fraction and not detected separately. More advanced columns overcome this problem by constantly monitoring the eluent.
The collected fractions are often examined by spectroscopic techniques to determine the concentration of the particles eluted. Common spectroscopy detection techniques are refractive index (RI) and ultraviolet (UV). When eluting spectroscopically similar species (such as during biological purification), other techniques may be necessary to identify the contents of each fraction. It is also possible to analyze the eluent flow continuously with RI, LALLS, Multi-Angle Laser Light Scattering MALS, UV, and/or viscosity measurements.
The elution volume (Ve) decreases roughly linear with the logarithm of the molecular hydrodynamic volume. Columns are often calibrated using 4-5 standard samples (e.g., folded proteins of known molecular weight), and a sample containing a very large molecule such as thyroglobulin to determine the void volume. (Blue dextran is not recommended for Vo determination because it is heterogeneous and may give variable results) The elution volumes of the standards are divided by the elution volume of the thyroglobulin (Ve/Vo) and plotted against the log of the standards' molecular weights. | 1 | Biochemistry |
PubMeth is a database that contains information about DNA hypermethylation in cancer. It can be queried either by searching a list of genes, or cancer (sub)types.
It was created at the lab for bioinformatics and computational genomics in the Department of Molecular Biotechnology, Faculty of Bioscience Engineering at Ghent University, Belgium.
It was published in Nucleic Acids Research | 1 | Biochemistry |
These angles are best construed to mean the angles observed (measured) for a given system, and not an historically observed range in values (e.g., as in the range of the original Bürgi–Dunitz aminoketones), or an idealized value computed for a particular system (such as the = 0° for hydride addition to formaldehyde). That is, the and angles of the hydride-formadehyde system have one pair of values, while the angles observed for other systems—combinations of nucelophile and electrophile, in combination with catalyst and other variables that define the experimental condition, including whether the reaction is in solutio or otherwise—are fully expected (and are reported) to vary, at least somewhat, from the theoretical, symmetric hydride-formaldehyde case.
A stated convention for is that it is positive (>0°) when it deviates in direction:
* away from the larger substituent attached to the electrophilic center,
* away from the more electron-rich substituent (where these two and other factors can be in a complex competition, see below);
hence, as noted, for reaction of a simple nucleophile with a symmetrically substituted carbonyl (R = R, or other symmetric planar electrophile) is expected to be 0° in vacuo or in solutio', e.g., as in the case of the computed and experimental addition of hydride (H) to formaldehyde (HC=O). | 7 | Physical Chemistry |
During the Mississippian period (800–1600 CE, varying locally), elites at major political and religious centers throughout the midwestern and southeastern United States used copper ornamentation as a sign of their status by crafting the sacred material into representations connected with the Chiefly Warrior cult of the Southeastern Ceremonial Complex (S.E.C.C.).
This ornamentation includes Mississippian copper plates, repousséd plates of beaten copper now found as far afield as Alabama, Florida, Georgia, Illinois, Mississippi, Oklahoma, and Tennessee. Some of the more famous of the plates are of raptorial birds and avian-themed dancing warriors. These plates, such as the Rogan plates from Etowah, the Spiro plates from the Spiro in Oklahoma, and the Wulfing cache from southeast Missouri, were instrumental in the development of the archaeological concept known as the S.E.C.C.
The only Mississippian culture site where a copper workshop has been located by archaeologists is Cahokia in western Illinois, where a copper workshop dating to the Moorehead Phase () was identified at Mound 34. Gregory Perino identified the site in 1956 and archaeologists subsequently excavated it.
Numerous copper fragments were found at the site; metallographic analysis indicated that Mississippian copper workers worked copper into thin sheet through repeated hammering and annealing, a process that could be successful over open-pit wood fires.
After the collapse of the Mississippian way of life in the 1500s with the advent of European colonization, copper still retained a place in Native American religious life as a special material. Copper was traditionally regarded as sacred by many historic period Eastern tribes. Copper nuggets are included in medicine bundles among Great Lakes tribes. Among 19th century Muscogee Creeks, a group of copper plates carried along the Trail of Tears are regarded as some of the tribe's most sacred items. | 8 | Metallurgy |
From the table, poly(ethylene) has a solubility parameter of 7.9 cal cm. Good solvents are likely to be diethyl ether and hexane. (However, PE only dissolves at temperatures well above 100 °C.) Poly(styrene) has a solubility parameter of 9.1 cal cm, and thus ethyl acetate is likely to be a good solvent. Nylon 6,6 has a solubility parameter of 13.7 cal cm, and ethanol is likely to be the best solvent of those tabulated. However, the latter is polar, and thus we should be very cautions about using just the Hildebrand solubility parameter to make predictions. | 7 | Physical Chemistry |
The Emerson effect is the increase in the rate of photosynthesis after chloroplasts are exposed to light of wavelength 680 nm (deep red spectrum) and more than 680 nm (far red spectrum). When simultaneously exposed to light of both wavelengths, the rate of photosynthesis is far higher than the sum of the red light and far red light photosynthesis rates. The effect was early evidence that two photosystems, processing different wavelengths, cooperate in photosynthesis. | 5 | Photochemistry |
Marrow's research focuses on the degradation of structural materials, the role of microstructure, and the mechanisms of materials ageing. A key aspect is the investigation of fundamental mechanisms of damage accumulation - including irradiation - using novel materials characterisation techniques. This has concentrated recently on computed X-ray tomography and strain mapping by digital image correlation and digital volume correlation, together with X-ray and neutron diffraction. He applies these techniques to study the degradation of Generation IV nuclear materials such as graphite and silicon carbide composites, as well as new materials for electrical energy storage. | 8 | Metallurgy |
A second metabolite of C. raciborskii was identified from extracts of the cyanobacteria after the observation of a frequently occurring peak accompanying that of CYN during UV and MS experiments. Analysis by MS and NMR methods concluded that this new compound was missing the oxygen adjacent to the uracil ring, and was named deoxycylindrospermopsin (Figure 3).
In 1999, an epimer of CYN, named 7-epicyclindrospermopsin (epiCYN), was also identified as a minor metabolite from Aphanizomenon ovalisporum. This occurred whilst isolating CYN from cyanobacteria taken from Lake Kinneret in Israel. The proposed structure of this molecule differed from CYN only in the orientation of the hydroxyl group adjacent to the uracil ring (Figure 4). | 0 | Organic Chemistry |
Improvements were gradual over the 1960s. This was also the reason that costs remained high, because space users were willing to pay for the best possible cells, leaving no reason to invest in lower-cost, less-efficient solutions. The price was determined largely by the semiconductor industry; their move to integrated circuits in the 1960s led to the availability of larger boules at lower relative prices. As their price fell, the price of the resulting cells did as well. These effects lowered 1971 cell costs to some $100 per watt.
In late 1969 Elliot Berman joined Exxon's task force which was looking for projects 30 years in the future and in April 1973 he founded Solar Power Corporation (SPC), a wholly owned subsidiary of Exxon at that time. The group had concluded that electrical power would be much more expensive by 2000, and felt that this increase in price would make alternative energy sources more attractive. He conducted a market study and concluded that a price per watt of about $20/watt would create significant demand. The team eliminated the steps of polishing the wafers and coating them with an anti-reflective layer, relying on the rough-sawn wafer surface. The team also replaced the expensive materials and hand wiring used in space applications with a printed circuit board on the back, acrylic plastic on the front, and silicone glue between the two, "potting" the cells. Solar cells could be made using cast-off material from the electronics market. By 1973 they announced a product, and SPC convinced Tideland Signal to use its panels to power navigational buoys, initially for the U.S. Coast Guard. | 7 | Physical Chemistry |
β-Catenin was initially discovered in the early 1990s as a component of a mammalian cell adhesion complex: a protein responsible for cytoplasmatic anchoring of cadherins. But very soon, it was realized that the Drosophila protein armadillo – implicated in mediating the morphogenic effects of Wingless/Wnt – is homologous to the mammalian β-catenin, not just in structure but also in function. Thus, β-catenin became one of the first examples of moonlighting: a protein performing more than one radically different cellular function. | 1 | Biochemistry |
In the Boord olefin synthesis, the addition of magnesium to certain β-haloethers results in an elimination reaction to the alkene. This reaction can limit the utility of Grignard reactions. | 0 | Organic Chemistry |
Many experiments that suggest the possible sequence of steps in a reaction mechanism have been designed, including:
* measurement of the effect of temperature (Arrhenius equation) to determine the activation energy
* spectroscopic observation of reaction intermediates
* determination of the stereochemistry of products, for example in nucleophilic substitution reactions
* measurement of the effect of isotopic substitution on the reaction rate
* for reactions in solution, measurement of the effect of pressure on the reaction rate to determine the volume change on formation of the activated complex
* for reactions of ions in solution, measurement of the effect of ionic strength on the reaction rate
* direct observation of the activated complex by pump-probe spectroscopy
* infrared chemiluminescence to detect vibrational excitation in the products
* electrospray ionization mass spectrometry.
* crossover experiments. | 7 | Physical Chemistry |
In the case of female patients who want to be treated with HCG Pubergen, Pregnyl:
a) Since infertile female patients who undergo medically assisted reproduction (especially those who need in vitro fertilization), are known to often be suffering from tubal abnormalities, after a treatment with this drug they might experience many more ectopic pregnancies. This is why early ultrasound confirmation at the beginning of a pregnancy (to see whether the pregnancy is intrauterine or not) is crucial. Pregnancies that have occurred after a treatment with this drug have a higher risk of multiple pregnancy. Female patients who have thrombosis, severe obesity, or thrombophilia should not be prescribed this medicine as they have a higher risk of arterial or venous thromboembolic events after or during a treatment with HCG Pubergen, Pregnyl. b)Female patients who have been treated with this medicine are usually more prone to pregnancy losses.
In the case of male patients: A prolonged treatment with HCG Pubergen, Pregnyl is known to regularly lead to increased production of androgen. Therefore: Patients who have overt or latent cardiac failure, hypertension, renal dysfunction, migraines, or epilepsy might not be allowed to start using this medicine or may require a lower dose of HCG Pubergen, Pregnyl. This drug should be used with extreme caution in the treatment of prepubescent teenagers in order to reduce the risk of precocious sexual development or premature epiphyseal closure. This type of patients' skeletal maturation should be closely and regularly monitored.
Both male and female patients who have the following medical conditions must not start a treatment with HCG Pubergen, Pregnyl: (1) Hypersensitivity to this drug or to any of its main ingredients. (2) Known or possible androgen-dependent tumors for example male breast carcinoma or prostatic carcinoma. | 1 | Biochemistry |
Either the enantiomer of the substrate is derivatized with two enantiomers of the CDA or both enantiomers of the substrate are derivatized with one enantiomer of the CDA. Two diastereomers form in both cases and the chemical shifts of their nuclei are evaluated to assign the configuration of the substrate. | 4 | Stereochemistry |
West Mexican smiths worked primarily in copper during the initial period, with some low-arsenic alloys, as well as occasional employment of silver and gold. Lost-wax cast bells were introduced from lower Central America and Colombia during this phase, along with several classes of cold-worked ornaments and hand tools, such as needles and tweezers. The prototypes for these small, often utilitarian items appear rooted in southern Ecuador and northern Peru. Small copper rings, generally found in burial contexts, are also common to Ecuador and Western Mexico and are abundant during this phase.
Excavated assemblages from the initial phase indicate that lost-wax cast bells also occupied a substantial portion of West Mexican artisans' efforts. Unlike similar bells recovered from coastal Ecuador, West Mexican bells were cast, rather than worked, metal. Typically composed of a smooth, suspended metal shell encasing an interior clapper, the West Mexican bells were generally fashioned from copper alloys and bore particular resemblance to bells made in Colombia, Panama and Costa Rica. | 8 | Metallurgy |
Le Chateliers principle (pronounced or ), also called Chateliers principle (or the Equilibrium Law), is a principle of chemistry used to predict the effect of a change in conditions on chemical equilibrium. The principle is named after French chemist Henry Louis Le Chatelier, and sometimes also credited to Karl Ferdinand Braun, who discovered it independently. It can be defined as:
In scenarios outside thermodynamic equilibrium, there can arise phenomena in contradiction to an over-general statement of Le Chatelier's principle.
Le Chatelier's principle is sometimes alluded to in discussions of topics other than thermodynamics. | 7 | Physical Chemistry |
The White catalyst has been found to be an effective catalyst for an oxidative version of the classic Heck reaction. Rather than performing allylic C-H cleavage—a relatively slow process—the catalyst quickly transmetallates with a boronic acid. This aryl palladium intermediate undergoes a 1,2-addition across the alkene double bond. β-Hydride elimination releases the product. The oxidative Heck was originally reported as a sequential process following allylic C-H esterification. It was subsequently demonstrated as a stand-alone method for a broad range of α-olefin substrates. The regioselectivity of the reaction is controlled by directing groups such as carbonyls, alcohols and amines. | 0 | Organic Chemistry |
An RNA sequence that is complementary to an endogenous mRNA transcript is sometimes called "antisense RNA". In other words, it is a non-coding strand complementary to the coding sequence of RNA; this is similar to negative-sense viral RNA. When mRNA forms a duplex with a complementary antisense RNA sequence, translation is blocked. This process is related to RNA interference. Cells can produce antisense RNA molecules naturally, called microRNAs, which interact with complementary mRNA molecules and inhibit their expression. The concept has also been exploited as a molecular biology technique, by artificially introducing a transgene coding for antisense RNA in order to block the expression of a gene of interest. Radioactively or fluorescently labelled antisense RNA can be used to show the level of transcription of genes in various cell types.
Some alternative antisense structural types have been experimentally applied as antisense therapy. In the United States, the Food and Drug Administration (FDA) has approved the phosphorothioate antisense oligonucleotides fomivirsen (Vitravene) and mipomersen (Kynamro) for human therapeutic use. | 1 | Biochemistry |
Hyperspectral imaging can provide information about the chemical constituents of materials which makes it useful for waste sorting and recycling. It has been applied to distinguish between substances with different fabrics and to identify natural, animal and synthetic fibers. HSI cameras can be integrated with machine vision systems and, via simplifying platforms, allow end-customers to create new waste sorting applications and other sorting/identification applications. A system of machine learning and hyperspectral camera can distinguish between 12 different types of plastics such as PET and PP for automated separation of waste of, as of 2020, highly unstandardized plastics products and packaging. | 7 | Physical Chemistry |
Copper has earned a respected place in the related fields of architecture, building construction, and interior design. From cathedrals to castles and from homes to offices, copper is used for a variety of architectural elements, including roofs, flashings, gutters, downspouts, domes, spires, vaults, wall cladding, and building expansion joints.
The history of copper in architecture can be linked to its durability, corrosion resistance, prestigious appearance, and ability to form complex shapes. For centuries, craftsmen and designers utilized these attributes to build aesthetically pleasing and long-lasting building systems.
For the past quarter century, copper has been designed into a much wider range of buildings, incorporating new styles, varieties of colors, and different shapes and textures. Copper clad walls are a modern design element in both indoor and outdoor environments.
Some of the worlds most distinguished modern architects have relied on copper. Examples include Frank Lloyd Wright, who specified copper materials in all of his building projects; Michael Graves, an AIA Gold Medalist who designed over 350 buildings worldwide; Renzo Piano, who designed pre-patinated clad copper for the NEMO-Metropolis Museum of Science in Amsterdam; Malcolm Holzman, whose patinated copper shingles at the WCCO Television Communications Centre made the facility an architectural standout in Minneaoplis; and Marianne Dahlbäck and Göran Månsson, who designed the Vasa Museum, a prominent feature of Stockholms skyline, with copper cladding. Architect Frank O. Gehry's enormous copper fish sculpture atop the Vila Olimpica in Barcelona is an example of the artistic use of copper.
Coppers most noteworthy aesthetic trait is its range of hues, from a bright metallic colour to iridescent brown to near black and, finally, to a greenish verdigris patina. Architects describe the array of browns as russet, chocolate, plum, mahogany, and ebony. The metals distinctive green patina has long been coveted by architects and designers.
This article describes practical and aesthetic benefits of copper in architecture as well as its use in exterior applications, interior design elements, and green buildings. | 8 | Metallurgy |
Nicolas Dauphas married a fellow planetary scientist, Reika Yokochi. The couple had two children. In February 2024, Dauphas posted to his Twitter (X) account that Yokochi had died from EGFR-positive lung cancer.
Dauphas states that he is of "French-American citizenship". | 9 | Geochemistry |
Atomic hydrogen diffusing through metals may collect at internal defects like inclusions and laminations and form molecular hydrogen. High pressures may be built up at such locations due to continued absorption of hydrogen leading to blister formation, growth and eventual bursting of the blister. Such hydrogen induced blister cracking has been observed in steels, aluminium alloys, titanium alloys and nuclear structural materials. Metals with low hydrogen solubility (such as tungsten) are more susceptible to blister formation. While in metals with high hydrogen solubility like vanadium, hydrogen prefers to induce stable metal-hydrides instead of bubbles or blisters. | 8 | Metallurgy |
During springtime in the polar regions of Earth, unique photochemistry converts inert halide salt ions (e.g. Br) into reactive halogen species (e.g. Br atoms and BrO) that episodically deplete ozone in the atmospheric boundary layer to near zero levels. These processes are favored by light and low temperature conditions. Since their discovery in the late 1980s, research on these ozone depletion events has shown the central role of
bromine photochemistry. The exact sourcs and mechanisms that release bromine are still not fully understood, but the combination of concentrated sea salt in a condensed phase substrate appears to be a pre-requisite. Shallow boundary layers are also likely to be beneficial since they enhance the speed of autocatalytic bromine release by confining the released bromine to a smaller space. Under these conditions, and with sufficient acidity, gaseous hypobromous acid (HOBr) can react with condensed sea salt bromide and produce bromine that is then released to the atmosphere. Subsequent photolysis of this bromine generates bromine radicals that can react with and destroy ozone. Due to the autocatalytic nature of the reaction mechanism, it has been called bromine explosion. | 2 | Environmental Chemistry |
Sodium nitrate is used to remove air bubbles from molten glass and some ceramics. Mixtures of the molten salt are used to harden some metals. | 0 | Organic Chemistry |
The apparent (molal) volume of a solute can be expressed as a function of the molality b of that solute (and of the densities of the solution and solvent). The volume of solution per mole of solute is
Subtracting the volume of pure solvent per mole of solute gives the apparent molal volume:
For more solutes the above equality is modified with the mean molar mass of the solutes as if they were a single solute with molality b:
The sum of products molalities – apparent molar volumes of solutes in their binary solutions equals the product between the sum of molalities of solutes and apparent molar volume in ternary of multicomponent solution mentioned above. | 7 | Physical Chemistry |
Protein acylation is the post-translational modification of proteins via the attachment of functional groups through acyl linkages. Protein acylation has been observed as a mechanism controlling biological signaling. One prominent type is fatty acylation, the addition of fatty acids to particular amino acids (e.g. myristoylation, palmitoylation or palmitoleoylation). Different types of fatty acids engage in global protein acylation. Palmitoleoylation is an acylation type where the monounsaturated fatty acid palmitoleic acid is covalently attached to serine or threonine residues of proteins. Palmitoleoylation appears to play a significant role in the trafficking, targeting, and function of Wnt proteins. | 0 | Organic Chemistry |
It has been shown that endoglin expression and TGF-beta secretion are attenuated in bone marrow stromal cells when they are cocultured with prostate cancer cells. Also, the downstream TGF-beta/bone morphogenic protein (BMP) signaling pathway, which includes Smad1 and Smad2/3, were attenuated along with Smad-dependent gene transcription. Another result in this study was that both Smad1/5/8-dependent inhibitor of DNA binding 1 expression and Smad2/3-dependent plasminogen activator inhibitor I had a reduction in expression and cell proliferation. Ultimately, the cocultured prostate cancer cells altered the TGF-beta signaling in the bone stromal cells, which suggests this modulation is a mechanism of prostate cancer metastases facilitating their growth and survival in the reactive bone stroma. This study emphasizes the importance of endoglin in TGF-beta signaling pathways in other cell types other than endothelial cells. | 1 | Biochemistry |
Chlorophenol red is an indicator dye that changes color from yellow to violet in the pH range 5.4 to 6.8. The pH of a substance is determined by taking the negative logarithm of the Hydronium ion concentration and the indictor changes color due to the dissociation of H ions. The lambda max is at 572 nm. | 3 | Analytical Chemistry |
It is produced by thermal reactions of compounds of the type HNCHCHX (X = OH, NH, or NHR) in the presence of zeolitic catalysts. An idealized conversion is shown for the conversion from ethanolamine:
:3 HNCHCHOH → N(CHCH)N + NH + 3 HO | 0 | Organic Chemistry |
Magnet-assisted transfection is a relatively new and time-saving method to introduce nucleic acids into a target cell with increased efficiency. In particular, adherent mammalian cell lines and primary cell cultures show very high transfection rates. Suspension cells and cells from other organisms can also be successfully transfected. A major advantage of the method is the mild treatment of the cells in comparison to liposome-based transfection reagents (lipofection) and electroporation, which may result in the death of 20-50% of cells. In addition, the transfection efficiency is increased in numerous cases by the directed transport in a magnetic field, especially for low amounts of nucleic acids. In contrast, methods like lipofection offer only statistical hits between cargo and cells, because of the three-dimensional motion of cells and transfection aggregates in a liquid suspension. Magnet-assisted transfection can also be performed in the presence of serum, which is a further benefit. Currently, there are over 150 cells known to be successfully transfected. Additionally, synergistic effects in transfection efficiency can arise from the possible combination of lipofection and magnet-assisted transfection.
In future, this technology might be also an alternative strategy to the currently used viral and non-viral vectors in gene-therapy and gene transfer. | 1 | Biochemistry |
After lysis of the cells (typically 1 to 2 hours at 4 °C) the slides are washed in distilled water to remove all salts and immersed in a second solution – an electrophoresis solution. Again this solution can have its pH adjusted depending upon the type of damage that is being investigated.
The slides are left for ~20 minutes in the electrophoresis solution prior to an electric field being applied. In alkaline conditions the DNA double helix is denatured and the nucleoid becomes single stranded.
An electric field is applied (typically 1 V/cm) for ~20 minutes. The slides are then neutralised to pH 7, stained with a DNA-specific fluorescent stain and analysed using a microscope with an attached CCD (charge-coupled device – essentially a digital camera) that is connected to a computer with image analysis software. | 1 | Biochemistry |
Note: The table only lists a few examples, there are many more crosses. The possibilities of this technology are great; however, not all species are easily put into protoplast culture. | 1 | Biochemistry |
Mixed-anion compounds, heteroanionic materials or mixed-anion materials are chemical compounds containing cations and more than one kind of anion. The compounds contain a single phase, rather than just a mixture. | 7 | Physical Chemistry |
During recent decades, many thermometric techniques have been developed.
The most promising and widespread non-invasive thermometric techniques in a biotech context are based on the analysis of magnetic resonance images, computerized tomography images and echotomography. These techniques allow monitoring temperature within tissues without introducing a sensing element. In the field of reactive flows (e.g., combustion, plasmas), laser induced fluorescence (LIF), CARS, and laser absorption spectroscopy have been exploited to measure temperature inside engines, gas-turbines, shock-tubes, synthesis reactors etc. The capability of such optical-based techniques include rapid measurement (down to nanosecond timescales), notwithstanding the ability to not perturb the subject of measurement (e.g., the flame, shock-heated gases). | 7 | Physical Chemistry |
The applications of RNA-Seq are growing day by day. Other new application of RNA-Seq includes detection of microbial contaminants, determining cell type abundance (cell type deconvolution), measuring the expression of TEs and Neoantigen prediction etc. | 1 | Biochemistry |
*[[9-Borabicyclo(3.3.1)nonane|9-Borabicyclo[3.3.1]nonane]] (9-BBN).
* Thexylborane ((1,1,2-trimethylpropyl)borane, ThxBH), a primary borane obtained by hydroboration of tetramethylethylene. | 0 | Organic Chemistry |
Much gold jewelry is produced by casting, with little or no cold working; which, depending on the alloy grade, may leave the metal relatively soft and bendable. However, a jeweler may intentionally use work hardening to strengthen wearable objects that are exposed to stress, such as rings. | 8 | Metallurgy |
Digital PCR has many applications in basic research, clinical diagnostics and environmental testing. Its uses include pathogen detection and digestive health analysis; liquid biopsy for cancer monitoring, organ transplant rejection monitoring and non-invasive prenatal testing for serious genetic abnormalities; copy number variation analysis, single gene expression analysis, rare sequence detection, gene expression profiling and single-cell analysis; the detection of DNA contaminants in bioprocessing, the validation of gene edits and detection of specific methylation changes in DNA as biomarkers of cancer. dPCR is also frequently used as an orthogonal method to confirm rare mutations detected through next-generation sequencing (NGS) and to validate NGS libraries. | 1 | Biochemistry |
The physicochemical profiling of poorly soluble drug candidates performed using a HTS surface tension device. Allowed prediction of penetration through the blood–brain barrier. | 7 | Physical Chemistry |
This disorder occurs through a mutation in the SPR gene, which is responsible for encoding the sepiapterin reductase enzyme. The enzyme is involved in the last step of producing tetrahydrobiopterin, better known as BH. BH is involved in the processing of amino acids and the production of neurotransmitters, specifically that of dopamine and serotonin which are primarily used in transmission of signals between nerve cells in the brain. The mutation in the SPR gene interferes with the production of the enzyme by producing enzymes with little or no function at all. This interference results in a lack of BH specifically in the brain. The lack of BH only occurs in the brain because other parts of the body adapt and utilize alternate pathways for the production of BH. The mutation in the SPR gene leads to nonfunctional sepiapterin reductase enzymes, which results in a lack of BH and ultimately disrupts the production of dopamine and serotonin in the brain. The disruption of dopamine and serotonin production leads to the visible symptoms present in patients suffering from sepiapterin reductase deficiency. SR deficiency is considered an inherited autosomal recessive condition disorder because each parent carries one copy of the mutated gene, but typically do not show any signs or symptoms of the condition. | 1 | Biochemistry |
Due to their extensive use, non-ferrous scrap metals are usually recycled. The secondary materials in scrap are vital to the metallurgy industry, as the production of new metals often needs them. Some recycling facilities re-smelt and recast non-ferrous materials; the dross is collected and stored onsite while the metal fumes are filtered and collected. Non-ferrous scrap metals are sourced from industrial scrap materials, particle emissions and obsolete technology (for example, copper cables) scrap. | 8 | Metallurgy |
Reactivity of sterically demanding lithium (fluorosilyl)silylphosphanides with GeI yields green, cubic crystals in moderate yield. The identity of this species was investigated using only multinuclear NMR, elemental analysis, and UV-vis. Computational calculations (at the CIS level with the ab initio Los Alamos pseudopotential method (LAN L 1 DZ)) of the diphosphagermylene electronic structure was in agreement experimentally-derived electronic transition values. Due to disorder, the crystal structure of the diphosphagermylene could not be investigated. | 0 | Organic Chemistry |
As T-RFLP is a fingerprinting technique its advantages and drawbacks are often discussed in comparison with other similar techniques, mostly DGGE. | 1 | Biochemistry |
Chemists have long been interested in mimicking chemical processes in nature. Coordination cages quickly became a hot topic as they can be made by self-assembly, a tool of chemistry in nature. The conceptualization of a closed-surface molecule capable of incorporating a guest was described by Donald Cram in 1985. Early cages were synthesized from bottom-up. Makoto Fujita introduced self-assembling cages, which are less tedious to prepare. These cages arise from the condensation of square planar complexes using polypodal ligands. | 6 | Supramolecular Chemistry |
N-X-L nomenclature, introduced collaboratively by the research groups of Martin, Arduengo, and Kochi in 1980, is often used to classify hypervalent compounds of main group elements, where:
* N represents the number of valence electrons
* X is the chemical symbol of the central atom
* L the number of ligands to the central atom
Examples of N-X-L nomenclature include:
* XeF, 10-Xe-2
* PCl, 10-P-5
* SF, 12-S-6
* IF, 14-I-7 | 4 | Stereochemistry |
The P700 reaction center is composed of modified chlorophyll a that best absorbs light at a wavelength of 700 nm. P700 receives energy from antenna molecules and uses the energy from each photon to raise an electron to a higher energy level (P700*). These electrons are moved in pairs in an oxidation/reduction process from P700* to electron acceptors, leaving behind P700. The pair of P700* - P700 has an electric potential of about −1.2 volts. The reaction center is made of two chlorophyll molecules and is therefore referred to as a dimer. The dimer is thought to be composed of one chlorophyll a molecule and one chlorophyll a′ molecule. However, if P700 forms a complex with other antenna molecules, it can no longer be a dimer. | 5 | Photochemistry |
Alkenes that are particularly amenable to asymmetric hydrogenation often feature a polar functional group adjacent to the site to be hydrogenated. In the absence of this functional group, catalysis often results in low ees. For some unfunctionalized olefins, iridium with P,N'-based ligands) have proven effective, however. Alkene substrates are often classified according to their substituents, e.g., 1,1-disubstituted, 1,2-diaryl trisubstituted, 1,1,2-trialkyl and tetrasubstituted olefins. and even within these classes variations may exist that make different solutions optimal.
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Conversely to the case of olefins, asymmetric hydrogenation of enamines has favoured diphosphine-type ligands; excellent results have been achieved with both iridium- and rhodium-based systems. However, even the best systems often suffer from low ee's and a lack of generality. Certain pyrrolidine-derived enamines of aromatic ketones are amenable to asymmetrically hydrogenation with cationic rhodium(I) phosphonite systems, and I and acetic acid system with ee values usually above 90% and potentially as high as 99.9%. A similar system using iridium(I) and a very closely related phosphoramidite ligand is effective for the asymmetric hydrogenation of pyrrolidine-type enamines where the double bond was inside the ring: in other words, of dihydropyrroles. In both cases, the enantioselectivity dropped substantially when the ring size was increased from five to six. | 0 | Organic Chemistry |
Due to the ability of Ang to protect motoneurons (MNs), causal links between Ang mutations and amyotrophic lateral sclerosis (ALS) are likely. The angiogenic factors associated with Ang may protect the central nervous system and MNs directly. Experiments with wild type Ang found that it slows MN degeneration in mice that had developed ALS, providing evidence for further development of Ang protein therapy in ALS treatment. Angiogenin expression in Parkinsons disease is dramatically decreased in the presence of alpha-synuclein (α-syn) aggregations. Exogenous angiogenin applied to dopamine-producing cells leads to the phosphorylation of PKB/AKT and the activation of this complex inhibits cleavage of caspase 3 and apoptosis when cells are exposed to a Parkinsons-like inducing substance. | 1 | Biochemistry |
To date, OTTR has been used for quantifying tRNA species. This method provides a reliable and precise quantification of tRNAs and allows for the detection of changes in tRNA levels under different physiological conditions. Therefore, this method is useful for a variety of research applications in the field of molecular biology and genetics.
As tRNAs are essential components of translation, the ability to quantify tRNA levels accurately is crucial for understanding how the translation machinery is regulated. Using OTTR, researchers can determine changes in tRNA levels in response to different growth conditions, environmental stress, or genetic modifications. This information can help to identify factors that affect tRNA abundance and their potential roles in modulating translation.
In particular, the OTTR protocol has been used to characterize the small RNA composition of mammalian sperm populations. This work revealed that sperm small RNA pools are composed largely of rRNA fragments and both 5 and 3 tRNA halves from the majority of tRNAs. This improved understanding of sperm payload composition has implications for our understanding of the biogenesis of structural RNA fragments in the male germline, as well as the biochemical nature of the RNAs delivered to the zygote upon fertilization.
The OTTR protocol could also be used in the study of piwi-interacting RNAs (piRNAs), which is another important classes of small RNAs. While the applications of OTTR have mainly been focused on tRNA fragment detection, OTTR has also been shown to perform well in the capture of miRNAs which could be useful for the study of miRNA expression patterns in different cell types or under different conditions.
Future applications of protocols similar to OTTR are also being considered in the development of diagnostic assays for small RNAs. The high fidelity of the OTTR protocol in capturing small RNAs could make it an attractive option when paired with liquid biopsy assays, where circulating small RNAs are analyzed as biomarkers for various diseases. | 1 | Biochemistry |
Unit conversion is a notorious source of errors. Many people apply individual rules, e.g. "to obtain length in centimeters multiply the length in inches by 2.54", but combining several such conversions is laborious and prone to mistakes. A better way is to use the factor-label method, which is closely related to dimensional analysis, and quantity calculus explained in sections 1.1 and 7.1 of this compilation. | 3 | Analytical Chemistry |
The cyclic enones include cyclopropenone, cyclobutenone, cyclopentenone, cyclohexenone, and cycloheptenone. | 0 | Organic Chemistry |
The esperamicins are a sub-family of enediynes that are considered among the most potent antitumor antibiotics discovered. First isolated in Actinomadura verrucosospora, members of the esperamicin family include esperamicin A1, A1b, A2, A3, A4, B1, B2, and X. Esperamicin X is an inactive esperamicin naturally produced by A. verrucosospora. Compounds with thiol groups induce triggering among the esperamicins. | 0 | Organic Chemistry |
Reticular synthesis was used by Yaghi and coworkers in 2005 to construct the first two COFs reported in the literature: COF-1, using a dehydration reaction of benzenediboronic acid (BDBA), and COF-5, via a condensation reaction between hexahydroxytriphenylene (HHTP) and BDBA. These framework scaffolds were interconnected through the formation of boroxine and boronate linkages, respectively, using solvothermal synthetic methods. | 6 | Supramolecular Chemistry |
Persons with certain genetic variations in human leukocyte antigens (HLAs) are under increased risk of developing skin reactions such as acute generalized exanthematous pustulosis (AGEP), but also severe ones such as Stevens–Johnson and DRESS syndrome, under treatment with carbamazepine and drugs with related chemical structures. This is true for the HLA-A*3101 allele, which occurs in 2 to 5% of Europeans and 10% of Japanese people, and the HLA-B*1502 allele, which is mainly found in people of Asian descent. Theoretically, this may also apply to ESL. | 4 | Stereochemistry |
Chloridizing roasting transforms certain metal compounds to chlorides through oxidation or reduction. Some metals such as uranium, titanium, beryllium and some rare earths are processed in their chloride form. Certain forms of chloridizing roasting may be represented by the overall reactions:
:2NaCl + MS + 2O -> NaSO + MCl,
:4NaCl + 2MO + S + 3O -> 2NaSO + 2MCl
The first reaction represents the chlorination of a sulfide ore involving an exothermic reaction. The second reaction involving an oxide ore is facilitated by addition of elemental sulfur. Carbonate ores react in a similar manner as the oxide ore, after decomposing to their oxide form at high temperatures. | 8 | Metallurgy |
Scientists performing biomonitoring testing are able to detect and measure concentrations of natural and manmade chemicals in human blood and urine samples at parts-per-billion to parts-per-quadrillion levels. A 2006 U.S. National Research Council report found that while scientists were capable of detecting the chemicals at these levels, methods for interpreting and communicating what their presence meant regarding potential health risks to an individual or population were still lacking. The report recommended that scientific research be done to improve the interpretation and communication of biomonitoring results through the use of existing risk assessments of specific chemicals.
To address this situation, several groups recognized that exposure guidance values, such as reference dose and tolerable daily intake, could, with sufficient data, be translated into corresponding estimates of biomarker concentrations for use in the interpretation of biomonitoring data. In 2007, the initial methodology for the systematic translation of exposure guidance values into corresponding screening values for biomonitoring data, dubbed Biomonitoring Equivalents, was published by scientists from Summit Toxicology. Subsequently, an expert panel from government, industry and academia, convened to develop detailed guidelines for deriving and communicating these Biomonitoring Equivalents.
Biomonitoring Equivalents can be used for evaluation of biomonitoring data in a risk assessment context. Comparing biomonitoring data for a chemical with its Biomonitoring Equivalent provides a means for assessing whether population exposures to chemicals are within or above the levels considered safe by regulatory agencies. Biomonitoring Equivalents can thus assist scientists and risk managers in the prioritization of chemicals for follow-up or risk management activities.
Since 2007, scientists have derived and published Biomonitoring Equivalents for more than 110 chemicals, including cadmium, benzene, chloroform, arsenic, toluene, methylene chloride, triclosan, dioxins, volatile organic compounds, and others. Several have been developed through collaborations of scientists from the U.S. Environmental Protection Agency, CDC and Health Canada. Researchers from the German Human Biomonitoring Commission have also proposed a concept for deriving screening values similar to Biomonitoring Equivalents. | 2 | Environmental Chemistry |
Pathways utilizing nutrients found in low concentrations in the local environment are generally found in higher abundance in the virus. In marine environments, AMGs can confer fitness advantages for both host and viruses under relatively nutrient-limited conditions compared to sediment and strong ultraviolet stress of water. In sunlit versus dark ocean waters, AMGs in distinct pathways are unequally distributed to reprogram host energy production and viral replication based on available nutrients. In sedimentary environments, carbon and sulfur metabolism AMGs are typically more prevalent to outcompete other organisms for the abundant resources. | 1 | Biochemistry |
The two enantiomers of a molecule possess many of the same physical properties (e.g. melting point, boiling point, polarity etc.) and so behave identically to each other. As a result, they will migrate with an identical R in thin layer chromatography and have identical retention times in HPLC and GC. Their NMR and IR spectra are identical.
This can make it very difficult to determine whether a process has produced a single enantiomer (and crucially which enantiomer it is) as well as making it hard to separate enantiomers from a reaction which has not been 100% enantioselective. Fortunately, enantiomers behave differently in the presence of other chiral materials and this can be exploited to allow their separation and analysis.
Enantiomers do not migrate identically on chiral chromatographic media, such as quartz or standard media that has been chirally modified. This forms the basis of chiral column chromatography, which can be used on a small scale to allow analysis via GC and HPLC, or on a large scale to separate chirally impure materials. However this process can require large amount of chiral packing material which can be expensive. A common alternative is to use a chiral derivatizing agent to convert the enantiomers into a diastereomers, in much the same way as chiral auxiliaries. These have different physical properties and hence can be separated and analysed using conventional methods. Special chiral derivitizing agents known as chiral resolution agents are used in the NMR spectroscopy of stereoisomers, these typically involve coordination to chiral europium complexes such as Eu(fod) and Eu(hfc).
The separation and analysis of component enantiomers of a racemic drugs or pharmaceutical substances are referred to as chiral analysis. or enantioselective analysis. The most frequently employed technique to carry out chiral analysis involves separation science procedures, specifically chiral chromatographic methods.
The enantiomeric excess of a substance can also be determined using certain optical methods. The oldest method for doing this is to use a polarimeter to compare the level of optical rotation in the product against a standard of known composition. It is also possible to perform ultraviolet-visible spectroscopy of stereoisomers by exploiting the Cotton effect.
One of the most accurate ways of determining the chirality of compound is to determine its absolute configuration by X-ray crystallography. However this is a labour-intensive process which requires that a suitable single crystal be grown. | 4 | Stereochemistry |
Several quasi-2-D systems, including layered transition metal dichalcogenides, undergo Peierls transitions to form quasi-2-D CDWs. These result from multiple nesting wavevectors coupling different flat regions of the Fermi surface. The charge modulation can either form a honeycomb lattice with hexagonal symmetry or a checkerboard pattern. A concomitant periodic lattice displacement accompanies the CDW and has been directly observed in 1T-TaS using cryogenic electron microscopy. In 2012, evidence for competing, incipient CDW phases were reported for layered cuprate high-temperature superconductors such as YBCO. | 7 | Physical Chemistry |
Recombinases have a central role in homologous recombination in a wide range of organisms. Such recombinases have been described in archaea, bacteria, eukaryotes and viruses. | 1 | Biochemistry |
Antibody-vaccine engineered construct abbreviated AVEC is an anti cancer drug in clinical trials that enables the immune system to detect and naturally eliminate malignant cells. It is a biomolecularly engineered molecule consisting of the two main components: (1) antibody; (2) vaccine. (1) The antibody component binds AVEC to the targeted molecule, e.g., to epidermal growth factor receptor 2 (HER2) on breast cancer cells. (2) The vaccine component elicits an immune response, directed against the cancer cells bound by the antibody component, e.g., immune response to the HBV vaccine mounted by the prophylactic immunity gained by vaccination.
It has the potential to be used to treat a variety of types of cancer, including breast cancer, ovarian cancer, colorectal cancer and leukemias. | 1 | Biochemistry |
S-Methylcysteine is the amino acid with the nominal formula CHSCHCH(NH)COH. It is the S-methylated derivative of cysteine. This amino acid occurs widely in plants, including many edible vegetables. | 1 | Biochemistry |
Solid materials typically come in two main types: crystalline and amorphous. In either case, a lattice or network of atoms and molecules form. In crystals, the lattice is a very neat, uniform assembly. However, nearly all crystals have defects in the stacking sequence of these molecules and atoms. A vacancy defect, where an atom is simply missing from its place, leaving an empty "hole", is one type of defect. Sometimes atoms can move from place to place within the lattice, creating Schottky defects or Frenkel defects. Other defects can occur from impurities in the lattice. For example, when a normal atom is substituted by a different atom of much larger or smaller size, a substitutional defect occurs, while an interstitial defect occurs when a much smaller atom gets trapped in the "interstices", or the spaces between atoms. In contrast, amorphous materials have no "long-range order" (beyond the space of a few atoms in any direction), thus by definition are filled with defects.
When a defect occurs, depending on the type and material, it can create a hole, or a "trap". For example, a missing oxygen atom from a zinc oxide compound creates a hole in the lattice, surrounded by unbound zinc-atoms. This creates a net force or attraction that can be measured in electron-volts. When a high-energy photon strikes one of the zinc atoms, its electron absorbs the photon and is thrown out into a higher orbit. The electron may then enter the trap and be held in place (out of its normal orbit) by the attraction. To trigger the release of the energy, a random spike in thermal energy is needed of sufficient magnitude to boost the electron out of the trap and back into its normal orbit. Once in orbit, the electron's energy can drop back to normal (ground state) resulting in the release of a photon.
The release of energy in this way is a completely random process, governed mostly by the average temperature of the material versus the "depth" of the trap, or how many electron-volts it exerts. A trap that has a depth of 2.0 electron-volts would require a great amount of thermal energy (very high temperatures) to overcome the attraction, while at a depth of 0.1 electron-volts very little heat (very cold temperatures) are needed for the trap to even hold an electron. Higher temperatures may cause the faster release of energy, resulting in a brighter yet short-lived emission, while lower temperatures may produce dimmer but longer-lasting glows. Temperatures that are too hot or cold, depending on the substance, may not allow the accumulation or release of energy at all. The ideal depth of trap for persistent phosphorescence at room temperature is typically between 0.6 and 0.7 electron-volts. If the phosphorescent quantum yield is high, that is, if the substance has a large number of traps of the correct depth, these substances will release significant amounts of light over long time scales, creating so-called "glow in the dark" materials.
Persistent phosphorescence is the mechanism of most anything commonly referred to as glow in the dark. Typical uses include toys, frisbees and balls, safety signs, paints and markings, make-ups, art and décor, and a variety of other uses. | 7 | Physical Chemistry |
In superconducting materials, the characteristics of superconductivity appear when the temperature T is lowered below a critical temperature T. The value of this critical temperature varies from material to material. Conventional superconductors usually have critical temperatures ranging from around 20 K to less than 1 K. Solid mercury, for example, has a critical temperature of 4.2 K. As of 2015, the highest critical temperature found for a conventional superconductor is 203 K for HS, although high pressures of approximately 90 gigapascals were required. Cuprate superconductors can have much higher critical temperatures: YBaCuO, one of the first cuprate superconductors to be discovered, has a critical temperature above 90 K, and mercury-based cuprates have been found with critical temperatures in excess of 130 K. The basic physical mechanism responsible for the high critical temperature is not yet clear. However, it is clear that a two-electron pairing is involved, although the nature of the pairing ( wave vs. wave) remains controversial.
Similarly, at a fixed temperature below the critical temperature, superconducting materials cease to superconduct when an external magnetic field is applied which is greater than the critical magnetic field. This is because the Gibbs free energy of the superconducting phase increases quadratically with the magnetic field while the free energy of the normal phase is roughly independent of the magnetic field. If the material superconducts in the absence of a field, then the superconducting phase free energy is lower than that of the normal phase and so for some finite value of the magnetic field (proportional to the square root of the difference of the free energies at zero magnetic field) the two free energies will be equal and a phase transition to the normal phase will occur. More generally, a higher temperature and a stronger magnetic field lead to a smaller fraction of electrons that are superconducting and consequently to a longer London penetration depth of external magnetic fields and currents. The penetration depth becomes infinite at the phase transition.
The onset of superconductivity is accompanied by abrupt changes in various physical properties, which is the hallmark of a phase transition. For example, the electronic heat capacity is proportional to the temperature in the normal (non-superconducting) regime. At the superconducting transition, it suffers a discontinuous jump and thereafter ceases to be linear. At low temperatures, it varies instead as e for some constant, α. This exponential behavior is one of the pieces of evidence for the existence of the energy gap.
The order of the superconducting phase transition was long a matter of debate. Experiments indicate that the transition is second-order, meaning there is no latent heat. However, in the presence of an external magnetic field there is latent heat, because the superconducting phase has a lower entropy below the critical temperature than the normal phase. It has been experimentally demonstrated that, as a consequence, when the magnetic field is increased beyond the critical field, the resulting phase transition leads to a decrease in the temperature of the superconducting material.
Calculations in the 1970s suggested that it may actually be weakly first-order due to the effect of long-range fluctuations in the electromagnetic field. In the 1980s it was shown theoretically with the help of a disorder field theory, in which the vortex lines of the superconductor play a major role, that the transition is of second order within the type II regime and of first order (i.e., latent heat) within the type I regime, and that the two regions are separated by a tricritical point. The results were strongly supported by Monte Carlo computer simulations. | 7 | Physical Chemistry |
In most cases, unidirectional transcription of enhancer regions generates long (>4kb) and polyadenylated eRNAs. Enhancers that generate polyA+ eRNAs have a lower H3K4me1/me3 ratio in their chromatin signature than 2D-eRNAs. PolyA+ eRNAs are distinct from long multiexonic poly transcripts (meRNAs) that are generated by transcription initiation at intragenic enhancers. These long non-coding RNAs, which accurately reflect the host gene's structure except for the alternative first exon, display poor coding potential. As a result, polyA+ 1D-eRNAs may represent a mixed group of true enhancer-templated RNAs and multiexonic RNAs. | 1 | Biochemistry |
PT is released from B. pertussis in an inactive form. Following PT binding to a cell membrane receptor, it is taken up in an endosome, after which it undergoes retrograde transport to the trans-Golgi network and endoplasmic reticulum. At some point during this transport, the A subunit (or protomer) becomes activated, perhaps through the action of glutathione and ATP. PT catalyzes the ADP-ribosylation of the α subunits of the heterotrimeric G protein. This prevents the G proteins from interacting with G protein-coupled receptors on the cell membrane, thus interfering with intracellular communication. The Gi subunits remain locked in their GDP-bound, inactive state, thus unable to inhibit adenylate cyclase activity, leading to increased cellular concentrations of cAMP.
Increased intracellular cAMP affects normal biological signaling. The toxin causes several systemic effects, among which is an increased release of insulin, causing hypoglycemia. Whether the effects of pertussis toxin are responsible for the paroxysmal cough remains unknown.
As a result of this unique mechanism, PT has also become widely used as a biochemical tool to ADP-ribosylate GTP-binding proteins in the study of signal transduction. It has also become an essential component of new acellular vaccines. | 1 | Biochemistry |
The lost-wax technique came to be known in the Mediterranean during the Bronze Age. It was a major metalworking technique utilized in the ancient Mediterranean world, notably during the Classical period of Greece for large-scale bronze statuary and in the Roman world.
Direct imitations and local derivations of Oriental, Syro-Palestinian and Cypriot figurines are found in Late Bronze Age Sardinia, with a local production of figurines from the 11th to 10th century BC. The cremation graves (mainly 8th-7th centuries BC, but continuing until the beginning of the 4th century) from the necropolis of Paularo (Italian Oriental Alps) contained fibulae, pendants and other copper-based objects that were made by the lost-wax process. Etruscan examples, such as the bronze anthropomorphic handle from the Bocchi collection (National Archaeological Museum of Adria), dating back to the 6th to 5th centuries BC, were made by cire perdue. Most of the handles in the Bocchi collection, as well as some bronze vessels found in Adria (Rovigo, Italy) were made using the lost-wax technique. The better known lost-wax produced items from the classical world include the "Praying Boy" (in the Berlin Museum), the statue of Hera from Vulci (Etruria), which, like most statues, was cast in several parts which were then joined. Geometric bronzes such as the four copper horses of San Marco (Venice, probably 2nd century) are other prime examples of statues cast in many parts.
Examples of works made using the lost-wax casting process in Ancient Greece largely are unavailable due to the common practice in later periods of melting down pieces to reuse their materials. Much of the evidence for these products come from shipwrecks. As underwater archaeology became feasible, artifacts lost to the sea became more accessible. Statues like the Artemision Bronze Zeus or Poseidon (found near Cape Artemision), as well as the Victorious Youth (found near Fano), are two such examples of Greek lost-wax bronze statuary that were discovered underwater.
Some Late Bronze Age sites in Cyprus have produced cast bronze figures of humans and animals. One example is the male figure found at Enkomi. Three objects from Cyprus (held in the Metropolitan Museum of Art in New York) were cast by the lost-wax technique from the 13th and 12th centuries BC, namely, the amphorae rim, the rod tripod, and the cast tripod.
Other, earlier examples that show this assembly of lost-wax cast pieces include the bronze head of the Chatsworth Apollo and the bronze head of Aphrodite from Satala (Turkey) from the British Museum. | 8 | Metallurgy |
TRH may cause nausea, vomiting and some patients experience an urge to urinate.
Rarely, TRH may cause blood vessel constriction leading to hemorrhage in patients with pre-existing pituitary tumors. Accordingly, patients should be advised about the risks, albeit rare, of TRH testing. | 1 | Biochemistry |
Trifluoroperacetic acid (trifluoroperoxyacetic acid, TFPAA) is an organofluorine compound, the peroxy acid analog of trifluoroacetic acid, with the condensed structural formula . It is a strong oxidizing agent for organic oxidation reactions, such as in Baeyer–Villiger oxidations of ketones. It is the most reactive of the organic peroxy acids, allowing it to successfully oxidise relatively unreactive alkenes to epoxides where other peroxy acids are ineffective. It can also oxidise the chalcogens in some functional groups, such as by transforming selenoethers to selones. It is a potentially explosive material and is not commercially available, but it can be quickly prepared as needed. Its use as a laboratory reagent was pioneered and developed by William D. Emmons. | 0 | Organic Chemistry |
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