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Williams was born in Tonypandy, Wales, the son of a coal miner. In 1944, he won a scholarship to study at the University of Bristol, where he earned a bachelors degree in 1948 and later a Master of Science in physics. In working to earn his masters degree, he studied stereo micro-radiography at the University of Chicago, under the direction of Cyril Stanley Smith. Around the same time, he also took up a position as a metallurgist with the Revere Copper Company in Rome, New York.
In 1960, Williams earned his doctorate from the University of Toronto. | 1 | Applied and Interdisciplinary Chemistry |
Groups that are attached to the side of the backbone are held by bonds which are weaker than the bonds connecting the chain. When the polymer is heated, the side groups are stripped off from the chain before it is broken into smaller pieces.
For example, the PVC eliminates HCl, under 100–120 °C.
CH(Cl)CHCHCH(Cl)→CH=CH-CH=CH+2HCl
Side group elimination can also proceed in a radical manner. For instance, methyl groups in polypropylene are susceptible to homolysis at high temperatures, leaving radicals on the polymer backbone. | 0 | Theoretical and Fundamental Chemistry |
Early studies showed that individuals who swam in waters with geometric mean coliform densities above 2300/100 mL for three days had higher illness rates. In the 1960s, these numbers were converted to fecal coliform concentrations assuming 18 percent of total coliforms were fecal. Consequently, the National Technical Advisory Committee in the US recommended the following standard for recreational waters in 1968: 10 percent of total samples during any 30-day period should not exceed 400 fecal coliforms/100 mL or a log mean of 200/100 mL (based on a minimum of 5 samples taken over not more than a 30-day period).
Despite criticism, EPA recommended this criterion again in 1976, however, the Agency initiated numerous studies in the 1970s and 1980s to overcome the weaknesses of the earlier studies. In 1986, EPA revised its bacteriological ambient water quality criteria recommendations to include E. coli and enterococci.
Canadas National Agri-Environmental Standards Initiatives approach to characterizing risks associated with fecal water pollution bacterial water quality at agricultural sites is to compare these sites with those at reference sites away from human or livestock sources. This approach generally results in lower levels if E. coli being used as a standard or “benchmark” based on a study that indicated pathogens were detected in 80% of water samples with less than 100 cfu E. coli per 100 mL. | 0 | Theoretical and Fundamental Chemistry |
Flortaucipir (F) is a radioactive diagnostic agent for adults with cognitive impairment who are being evaluated for Alzheimers disease. It is indicated for positron emission tomography (PET) imaging of the brain to estimate the density and distribution of aggregated tau neurofibrillary tangles (NFTs), a primary marker of Alzheimers disease.
Flortaucipir (F) is not indicated for use in the evaluation of people for chronic traumatic encephalopathy (CTE). | 1 | Applied and Interdisciplinary Chemistry |
Embryos can be either "fresh" from fertilized egg cells of the same menstrual cycle, or "frozen", that is they have been generated in a preceding cycle and undergone embryo cryopreservation, and are thawed just prior to the transfer, which is then termed "frozen embryo transfer" (FET). The outcome from using cryopreserved embryos has uniformly been positive with no increase in birth defects or development abnormalities, also between fresh versus frozen eggs used for intracytoplasmic sperm injection (ICSI). In fact, pregnancy rates are increased following FET, and perinatal outcomes are less affected, compared to embryo transfer in the same cycle as ovarian hyperstimulation was performed. The endometrium is believed to not be optimally prepared for implantation following ovarian hyperstimulation, and therefore frozen embryo transfer avails for a separate cycle to focus on optimizing the chances of successful implantation. Children born from vitrified blastocysts have significantly higher birthweight than those born from non-frozen blastocysts. When transferring a frozen-thawed oocyte, the chance of pregnancy is essentially the same whether it is transferred in a natural cycle or one with ovulation induction.
There is probably little or no difference between FET and fresh embryo transfers in terms of live birth rate and ongoing pregnancy rate and the risk of ovarian hyperstimulation syndrome may be less using the "freeze all" strategy. The risk of having a large-for-gestational-age baby and higher birth rate, in addition to maternal hypertensive disorders of pregnancy may be increased using a "freeze all" strategy. | 1 | Applied and Interdisciplinary Chemistry |
One of the first common applications of surface plasmon resonance spectroscopy was the measurement of the thickness (and refractive index) of adsorbed self-assembled nanofilms on gold substrates. The resonance curves shift to higher angles as the thickness of the adsorbed film increases. This example is a static SPR measurement.
When higher speed observation is desired, one can select an angle right below
the resonance point (the angle of minimum reflectance), and measure the reflectivity changes at that point.
This is the so-called dynamic SPR measurement. The interpretation of the data assumes that the structure of the film does not change significantly during the measurement. | 0 | Theoretical and Fundamental Chemistry |
An anodyne is a drug used to lessen pain through reducing the sensitivity of the brain or nervous system. The term was common in medicine before the 20th century, but such drugs are now more often known as analgesics or painkillers.
The term anodyne derives from Greek anōdynos (), from an- (, "without") and odynē (, "pain"). Etymologically, the word covers any substance that reduces pain, but doctors used it more narrowly. Some definitions restrict the term to topical medications, including herbal simples such as onion, lily, root of mallows, leaves of violet, and elderberry. Other definitions include ingested narcotics, hypnotics, and opioids. In the 19th century, the primary anodynes were opium, henbane, hemlock, tobacco, nightshade (stramonium), and chloroform.
Certain compound medicines were also called by this name, such as anodyne balsam, made of castile soap, camphor, saffron, and spirit of wine, and digested in a sand heat. It was recommended not only for easing extreme pain, but also for assisting in discharging the diseased tissue that caused or occurred with the pain.
In literary usage, the word has escaped its strictly medical meaning to convey anything "soothing or relaxing" (since the 18th century) or even anything "non-contentious", "blandly agreeable", or unlikely to cause offence or debate. | 1 | Applied and Interdisciplinary Chemistry |
Distribution of STAT4 is restricted to myeloid cells, thymus and testis. In resting human T cells it is expressed at very low levels, but its production is amplified by PHA stimulation. | 1 | Applied and Interdisciplinary Chemistry |
Particulate matter (PM), particularly PM2.5, was found to be harmful to aquatic invertebrates. These aquatic invertebrates include fish, crustaceans, and Mollusca. In a study by Han et al, the effects of PM<2.5 micrometers on life history traits and oxidative stress were observed in Tigriopus japonicus. Exposure to particulate matter of less than 2.5 micrometers in diameter led to significant changes in ROS levels, indicating that particulate matter exposure was a causative agent of oxidative stress in Tigriopus japonicus. In addition to aquatic invertebrates, negative effects of particulate matter have been noted in mammals as well. Following acute exposure to ambient particulate matter, rats showed a significant increase in neutrophils and a significant decrease in lymphocytes, indicating that particulate matter exposure can result in activation of the sympathetic stress response. | 1 | Applied and Interdisciplinary Chemistry |
Vitamin D is produced when the skin is exposed to UVB, whether from sunlight or an artificial source. It is needed for mineralization of bone and bone growth. Areas in which vitamin D's role is being investigated include reducing the risk of cancer, heart disease, multiple sclerosis and glucose dysregulation. Exposing arms and legs to a minimal 0.5 erythemal (mild sunburn) UVB dose is equal to consuming about 3000 IU of vitamin D3. In a study in Boston, MA, researchers found that adults who used tanning beds had "robust" levels of 25(OH)D (46 ng/mL on average), along with higher hip bone density, compared to adults who did not use them.
Obtaining vitamin D from indoor tanning has to be weighed against the risk of developing skin cancer. The indoor-tanning industry has stressed the relationship between tanning and the production of vitamin D. According to the US National Institutes of Health, some researchers have suggested that "5–30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen usually lead to sufficient vitamin D synthesis and that the moderate use of commercial tanning beds that emit 2%–6% UVB radiation is also effective". Most researchers say the health risks outweigh the benefits, that the UVB doses produced by tanning beds exceed what is needed for adequate vitamin D production, and that adequate vitamin D levels can be achieved by taking supplements and eating fortified foods. | 0 | Theoretical and Fundamental Chemistry |
Detected as enhanced absorptive or emissive signals in the NMR spectra of the reaction products, CIDNP has been exploited for the last 30 years to characterise transient free radicals and their reaction mechanisms. In certain cases, CIDNP also offers the possibility of large improvements in NMR sensitivity. The principal application of this photo-CIDNP technique, as devised by Kaptein in 1978, has been to proteins in which the aromatic amino acid residues histidine, tryptophan and tyrosine can be polarized using flavins or other aza-aromatics as photosensitisers. The key feature of the method is that only solvent accessible histidine, tryptophan and tyrosine residues can undergo the radical pair reactions that result in nuclear polarization. Photo-CIDNP has thus been used to probe the surface structure of proteins, both in native and partially folded states, and their interactions with molecules that modify the accessibility of the reactive side chains.
Although usually observed in liquids, the photo-CIDNP effect has also been detected in solid state, for example on C and N nuclei in photosynthetic reaction centres, where significant nuclear polarization can accumulate as a result of spin selection processes in the electron transfer reactions. | 0 | Theoretical and Fundamental Chemistry |
AR-TP009 is expressed by Halorubrum sp. TP009. Its ability to act as a neural silencer has been investigated in mouse cortical pyramidal neurons. | 0 | Theoretical and Fundamental Chemistry |
Certain kinds of IVF have been shown to lead to distortions in the sex ratio at birth. Intracytoplasmic sperm injection (ICSI), which was first applied in 1991, leads to slightly more female births (51.3% female). Blastocyst transfer, which was first applied in 1984, leads to significantly more male births (56.1% male). Standard IVF done at the second or third day leads to a normal sex ratio.
Epigenetic modifications caused by extended culture leading to the death of more female embryos has been theorised as the reason why blastocyst transfer leads to a higher male sex ratio; however, adding retinoic acid to the culture can bring this ratio back to normal. A second theory is that the male-biased sex ratio may due to a higher rate of selection of male embryos. Male embryos develop faster in vitro, and thus may appear more viable for transfer. | 1 | Applied and Interdisciplinary Chemistry |
A membrane osmometer is a device used to indirectly measure the number average molecular weight () of a polymer sample. One chamber contains pure solvent and the other chamber contains a solution in which the solute is a polymer with an unknown . The osmotic pressure of the solvent across the semipermeable membrane is measured by the membrane osmometer. This osmotic pressure measurement is used to calculate for the sample. | 0 | Theoretical and Fundamental Chemistry |
Source: [https://scheringstiftung.de/en/programm/lebenswissenschaften/ernst-schering-preis/ Schering Foundation]
*1992 , (Center for Molecular Biology, University of Heidelberg, Germany)
*1993 Christiane Nüsslein-Volhard, (Max Planck Institute for Developmental Biology in Tübingen, Germany)
*1994 Bert Vogelstein, (Oncology Center, Johns Hopkins University, Baltimore, Maryland, US)
*1995 Yasutomi Nishizuka, (Kobe University, Japan)
*1996 Judah Folkman, (Harvard Medical School, Harvard University, Boston, US)
*1997 Johann Mulzer, (Institute for Organic Chemistry, University of Vienna, Austria)
*1998 Ilme Schlichting, (Max Planck Institute for Molecular Physiology in Dortmund, Germany)
*1999 Michael Berridge, (Babraham Institute in Cambridge, UK)
*2000 , (University of Tokyo, Japan)
*2001 Kyriacos Nicolaou, (University of California, San Diego, California, and The Scripps Research Institute, La Jolla, California, US)
*2002 Ian Wilmut, (The Roslin Institute in Edinburgh, UK)
*2003 Svante Pääbo, (Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany)
*2004 , (National Institute of Neurological Disorders and Stroke (NINDS), Bethesda, Maryland, US)
*2005 Thomas Tuschl, (Laboratory of RNA Molecular Biology, Rockefeller University, New York)
*2006 Wolfgang Baumeister, (Max Planck Institute of Biochemistry in Martinsried, Germany)
*2007 Carolyn Bertozzi, (University of California, Berkeley, US)
*2008 Klaus Rajewsky, (Harvard Medical School, Boston, US)
*2009 Rudolf Jaenisch, (Whitehead Institute, Cambridge, Massachusetts, US)
*2010 Marc Feldmann and Sir Ravinder Maini, (Kennedy Institute of Rheumatology at Imperial College London, UK)
*2011 Bert W. O'Malley, (Tom Thompson Distinguished Service Professor and Chair of Molecular and Cellular Biology at Baylor College of Medicine in Houston, Texas)
*2012 Matthias Mann, (Max Planck Institute of Biochemistry in Martinsried, Germany)
*2013 , (Institute of Molecular Virology at the Ulm University Medical Center in Ulm, Germany)
*2014 Magdalena Götz, (Director of the Institute of Stem Cell Research at the Helmholtz Zentrum München and chair of Physiological Genomics at the University of Munich (LMU) in Munich, Germany)
*2015 David MacMillan, (Professor of Chemistry at Princeton University, US).
*2016 Franz-Ulrich Hartl, (Max Planck Institute of Biochemistry in Martinsried, Germany).
*2017 Elly Tanaka, (Senior Scientist at Research Institute of Molecular Pathology in Vienna, Austria)
*2018 Bonnie L. Bassler, (Princeton University, New Jersey)
*2019 Patrick Cramer, (Director at the Max Planck Institute for Biophysical Chemistry in Göttingen)
*2020 , (Director at the ( in Cologne)
*2021 Aviv Regev, (Head of Genentech Research and Early Development in South San Francisco, US)
*2022 (Professor of Computer-Assisted Drug Design at the Institute of Pharmaceutical Sciences at ETH Zurich and director of the Singapore-ETH Center)
*2023 Matthias Tschöp (CEO and scientific director at Helmholtz Zentrum München, Germany. Alexander von Humboldt Professor at the Technical University of Munich (TUM), and Helmholtz Vice President of Health Research | 1 | Applied and Interdisciplinary Chemistry |
The minimization of radiation dose to the subject is an attractive feature of the use of short-lived radionuclides. Besides its established role as a diagnostic technique, PET has an expanding role as a method to assess the response to therapy, in particular, cancer therapy, where the risk to the patient from lack of knowledge about disease progress is much greater than the risk from the test radiation. Since the tracers are radioactive, the elderly and pregnant are unable to use it due to risks posed by radiation.
Limitations to the widespread use of PET arise from the high costs of cyclotrons needed to produce the short-lived radionuclides for PET scanning and the need for specially adapted on-site chemical synthesis apparatus to produce the radiopharmaceuticals after radioisotope preparation. Organic radiotracer molecules that will contain a positron-emitting radioisotope cannot be synthesized first and then the radioisotope prepared within them, because bombardment with a cyclotron to prepare the radioisotope destroys any organic carrier for it. Instead, the isotope must be prepared first, then the chemistry to prepare any organic radiotracer (such as FDG) accomplished very quickly, in the short time before the isotope decays. Few hospitals and universities are capable of maintaining such systems, and most clinical PET is supported by third-party suppliers of radiotracers that can supply many sites simultaneously. This limitation restricts clinical PET primarily to the use of tracers labelled with fluorine-18, which has a half-life of 110 minutes and can be transported a reasonable distance before use, or to rubidium-82 (used as rubidium-82 chloride) with a half-life of 1.27 minutes, which is created in a portable generator and is used for myocardial perfusion studies. In recent years a few on-site cyclotrons with integrated shielding and "hot labs" (automated chemistry labs that are able to work with radioisotopes) have begun to accompany PET units to remote hospitals. The presence of the small on-site cyclotron promises to expand in the future as the cyclotrons shrink in response to the high cost of isotope transportation to remote PET machines. In recent years the shortage of PET scans has been alleviated in the US, as rollout of radiopharmacies to supply radioisotopes has grown 30%/year.
Because the half-life of fluorine-18 is about two hours, the prepared dose of a radiopharmaceutical bearing this radionuclide will undergo multiple half-lives of decay during the working day. This necessitates frequent recalibration of the remaining dose (determination of activity per unit volume) and careful planning with respect to patient scheduling. | 1 | Applied and Interdisciplinary Chemistry |
Acoustic foam is an open celled foam used for acoustic treatment. It attenuates airbone sound waves, reducing their amplitude, for the purposes of noise reduction or noise control. The energy is dissipated as heat. Acoustic foam can be made in several different colors, sizes and thickness.
Acoustic foam can be attached to walls, ceilings, doors, and other features of a room to control noise levels, vibration, and echoes.
Many acoustic foam products are treated with dyes and/or fire retardants. | 0 | Theoretical and Fundamental Chemistry |
Biocatalysis refers to the use of living (biological) systems or their parts to speed up (catalyze) chemical reactions. In biocatalytic processes, natural catalysts, such as enzymes, perform chemical transformations on organic compounds. Both enzymes that have been more or less isolated and enzymes still residing inside living cells are employed for this task. Modern biotechnology, specifically directed evolution, has made the production of modified or non-natural enzymes possible. This has enabled the development of enzymes that can catalyze novel small molecule transformations that may be difficult or impossible using classical synthetic organic chemistry. Utilizing natural or modified enzymes to perform organic synthesis is termed chemoenzymatic synthesis; the reactions performed by the enzyme are classified as chemoenzymatic reactions. | 0 | Theoretical and Fundamental Chemistry |
Unsaturated polyesters are condensation polymers formed by the reaction of polyols (also known as polyhydric alcohols), organic compounds with multiple alcohol or hydroxy functional groups, with unsaturated and in some cases saturated dibasic acids. Typical polyols used are glycols including ethylene glycol, propylene glycol, and diethylene glycol; typical acids used are phthalic acid, isophthalic acid, terephthalic acid, and maleic anhydride. Water, a condensation by-product of esterification reactions, is continuously removed by distillation, driving the reaction to completion via Le Chateliers principle. Unsaturated polyesters are generally sold to parts manufacturers as a solution of resin in reactive diluent; styrene is the most common diluent and the industry standard. The diluent allows control over the viscosity of the resin, and is also a participant in the curing reaction. The initially liquid resin is converted to a solid by cross-linking chains. This is done by creating free radicals at unsaturated bonds, which propagate in a chain reaction to other unsaturated bonds in adjacent molecules, linking them in the process. Unsaturation is generally in the form of maleate and fumarate species along the polymer chain. Maleate/fumarate generally does not self-polymerize via radical reactions, but readily reacts with styrene. Maleic anhydride and styrene are known to form alternating copolymers, and are in fact the textbook case of this phenomenon. This is one reason that styrene has been so hard to displace in the market as the industry standard reactive diluent for unsaturated polyester resins, despite increasing efforts to displace the material such as Californias Proposition 65. The initial free radicals are induced by adding a compound that easily decomposes into free radicals. This compound is known as the catalyst within the industry, but initiator is a more appropriate term. Transition metal salts are usually added as a catalyst for the chain-growth crosslinking reaction, and in the industry this type of additive is known as a promoter; the promoter is generally understood to lower the bond dissociation energy of the radical initiator. Cobalt salts are the most common type of promoter used. Common radical initiators used are organic peroxides such as benzoyl peroxide or methyl ethyl ketone peroxide.
Polyester resins are thermosetting and, as with other resins, cure exothermically. The use of excessive initiator especially with a catalyst present can, therefore, cause charring or even ignition during the curing process. Excessive catalyst may also cause the product to fracture or form a rubbery material.
Unsaturated polyesters (UPR) are utilized in many different industrially relevant markets, but in general are used as the matrix material for various types of composites. Glass fiber-reinforced composites comprise the largest segment into which UPRs are used and can be processed via SMC, BMC, pultrusion, cured-in-place pipe (known as relining in Europe), filament winding, vacuum molding, spray-up molding, resin transfer molding (RTM). Wind turbine blades also use them as well as many more processes. UPRs are also used in non-reinforced applications with common examples being gel coats, shirt buttons, mine-bolts, , polymer concrete, and engineered stone/cultured marble. | 0 | Theoretical and Fundamental Chemistry |
The widespread application of passive daytime radiative cooling (PDRC) technologies that use the infrared window (8–13 µm) to dissipate heat through longwave infrared (LWIR) thermal radiation heat transfer with outer space, has been proposed as a method of reducing temperature increases caused by climate change. The installation of passive radiative heat emission technologies has been proposed as necessary to lower the temperature of Earth at a fast enough rate for human survivability. Munday summarized the global implementation of such technologies: more than it is emitting, which leads to an overall warming of the climate. By covering the Earth with a small fraction of thermally emitting materials, the heat flow away from the Earth can be increased, and the net radiative flux can be reduced to zero (or even made negative), thus stabilizing (or cooling) the Earth (...) If only 1%–2% of the Earth’s surface were instead made to radiate at this rate rather than its current average value, the total heat fluxes into and away from the entire Earth would be balanced and warming would cease. with a diffuse component between 50-100 W/m. The average PDRC has an estimated cooling power of ~100-150 W/m. The cooling power of PDRCs is proportional to the exposed surface area of the installation. | 0 | Theoretical and Fundamental Chemistry |
In geometry and crystallography, the Laves graph is an infinite and highly symmetric system of points and line segments in three-dimensional Euclidean space, forming a periodic graph. Three equal-length segments meet at 120° angles at each point, and all cycles use ten or more segments. It is the shortest possible triply periodic graph, relative to the volume of its fundamental domain. One arrangement of the Laves graph uses one out of every eight of the points in the integer lattice as its points, and connects all pairs of these points that are nearest neighbors, at distance . It can also be defined, divorced from its geometry, as an abstract undirected graph, a covering graph of the complete graph on four vertices.
named this graph after Fritz Laves, who first wrote about it as a crystal structure in 1932. It has also been called the K crystal, (10,3)-a network, diamond twin, triamond, and the srs net. The regions of space nearest each vertex of the graph are congruent 17-sided polyhedra that tile space. Its edges lie on diagonals of the regular skew polyhedron, a surface with six squares meeting at each integer point of space.
Several crystalline chemicals have known or predicted structures in the form of the Laves graph. Thickening the edges of the Laves graph to cylinders produces a related minimal surface, the gyroid, which appears physically in certain soap film structures and in the wings of butterflies. | 0 | Theoretical and Fundamental Chemistry |
Marcus' theory of outer sphere electron transfer predicts that such a tunneling process will occur most quickly in systems where the electron transfer is thermodynamically favorable (i.e. between strong reductants and oxidants) and where the electron transfer has a low intrinsic barrier.
The intrinsic barrier of electron transfer derives from the Franck–Condon principle, stating that electronic transition takes place more quickly given greater overlap between the initial and final electronic states. Interpreted loosely, this principle suggests that the barrier of an electronic transition is related to the degree to which the system seeks to reorganize. For an electronic transition with a system, the barrier is related to the "overlap" between the initial and final wave functions of the excited electron–i.e. the degree to which the electron needs to "move" in the transition.
In an intermolecular electron transfer, a similar role is played by the degree to which the nuclei seek to move in response to the change in their new electronic environment. Immediately after electron transfer, the nuclear arrangement of the molecule, previously an equilibrium, now represents a vibrationally excited state and must relax to its new equilibrium geometry. Rigid systems, whose geometry is not greatly dependent on oxidation state, therefore experience less vibrational excitation during electron transfer, and have a lower intrinsic barrier. Photocatalysts such as [Ru(bipy)], are held in a rigid arrangement by flat, bidentate ligands arranged in an octahedral geometry around the metal center. Therefore, the complex does not undergo much reorganization during electron transfer. Since electron transfer of these complexes is fast, it is likely to take place within the duration of the catalyst's active state, i.e. during the lifetime of the triplet excited state. | 0 | Theoretical and Fundamental Chemistry |
Total suspended solids (TSS) concentration is the concentration (dry weight mass per unit volume of water) of all the material in water that is caught on a filter, usually a filter with about a 0.7 micrometer pore size. This includes all the particles suspended in water, such as mineral particles (silt, clay), organic detritus, and phytoplankton cells. Clear water bodies have low TSS concentrations. Other names for TSS include total suspended matter (TSM) and suspended particulate matter (SPM). The term suspended sediment concentration (SSC) refers to the mineral component of TSS but is sometimes used interchangeably with TSS. If desired, the concentrations of volatile (organic) and fixed (inorganic) suspended solids can be separated out using the loss-on-ignition method by burning the filter in a muffle furnace to burn off organic matter, leaving behind ash including mineral particles and inorganic components of phytoplankton cells, with TSS = volatile suspended solids + fixed suspended solids. | 0 | Theoretical and Fundamental Chemistry |
Calcite rafts were first observed by Allison in 1923 on solution drops attached to concrete derived straw stalactites, and later by Ver Steeg. When the drip rate is ≥5 minutes between drops, calcium carbonate will have precipitated on the solution drop surface (at the end of a stalactite) to form calcite rafts visible to the naked eye (up to 0.5 mm across). If the drip rate is greater than ≈12 minutes between drops, and there is very little air movement, these rafts may join up and become a latticework of calcite rafts covering the drop surface. Significant air movement will cause the rafts to become scattered and spin turbulently around the drops surface. This turbulent movement of calcite rafts can cause some to shear off the drops surface tension and be pushed onto the outside of the straw stalactite, thus increasing the outside diameter and creating minute irregularities. | 1 | Applied and Interdisciplinary Chemistry |
Capsular exopolysaccharides can protect pathogenic bacteria against desiccation and predation, and contribute to their pathogenicity. Sessile bacteria fixed and aggregated in biofilms are less vulnerable compared to drifting planktonic bacteria, as the EPS matrix is able to act as a protective diffusion barrier. The physical and chemical characteristics of bacterial cells can be affected by EPS composition, influencing factors such as cellular recognition, aggregation, and adhesion in their natural environments. Furthermore, the EPS layer acts as a nutrient trap, facilitating bacterial growth. The exopolysaccharides of some strains of lactic acid bacteria, e.g., Lactococcus lactis subsp. cremoris, contribute a gelatinous texture to fermented milk products (e.g., Viili), and these polysaccharides are also digestible. An example of the industrial use of exopolysaccharides is the application of dextran in panettone and other breads in the bakery industry.
Apart from negative contributions of EPS in biofilms, EPS can also contribute to some beneficial functions. For example, B. subtilis has gained interest for its probiotic properties due to its biofilm which allows it to effectively maintain a favorable microenvironment in the gastrointestinal tract. In order to survive the passage through the upper gastrointestinal tract, B. subtilis produces an extracellular matrix that protects it from stressful environments such as the highly acidic environment in the stomach. In B. subtilis, the protein matrix component, TasA, and the exopolysaccharide have both been shown to be essential for effective plant-root colonization in Arabidopsis and tomato plants. It was also suggested that TasA plays an important role in mediating interspecies aggregation with streptococci. | 1 | Applied and Interdisciplinary Chemistry |
Molecular medicine is a broad field, where physical, chemical, biological, bioinformatics and medical techniques are used to describe molecular structures and mechanisms, identify fundamental molecular and genetic errors of disease, and to develop molecular interventions to correct them. The molecular medicine perspective emphasizes cellular and molecular phenomena and interventions rather than the previous conceptual and observational focus on patients and their organs. | 1 | Applied and Interdisciplinary Chemistry |
Azlocillin is considered a broad spectrum antibiotic and can be used against a number of Gram positive and Gram negative bacteria. The following represents MIC susceptibility data for a few medically significant organisms.
* Escherichia coli 1 μg/mL – 32 μg/mL
* Haemophilus spp. 0.03 μg/mL – 2 μg/mL
* Pseudomonas aeruginosa 4 μg/mL – 6.25 μg/mL | 0 | Theoretical and Fundamental Chemistry |
In continuum mechanics, this theorem is often used for material elements. These are parcels of fluids or solids which no material enters or leaves. If is a material element then there is a velocity function , and the boundary elements obey
This condition may be substituted to obtain: | 1 | Applied and Interdisciplinary Chemistry |
Different countries around the world maintain regulatory frameworks that are responsible for the management and use of radionuclides in different medical settings. For example, in the US, the Nuclear Regulatory Commission (NRC) and the Food and Drug Administration (FDA) have guidelines in place for hospitals to follow. With the NRC, if radioactive materials arent involved, like X-rays for example, they are not regulated by the agency and instead are regulated by the individual states. International organizations, such as the International Atomic Energy Agency (IAEA), have regularly published different articles and guidelines for best practices in nuclear medicine as well as reporting on emerging technologies in nuclear medicine. Other factors that are considered in nuclear medicine include a patients medical history as well as post-treatment management. Groups like International Commission on Radiological Protection have published information on how to manage the release of patients from a hospital with unsealed radionuclides. | 1 | Applied and Interdisciplinary Chemistry |
Sensory and neurological implants are used for disorders affecting the major senses and the brain, as well as other neurological disorders. They are predominately used in the treatment of conditions such as cataract, glaucoma, keratoconus, and other visual impairments; otosclerosis and other hearing loss issues, as well as middle ear diseases such as otitis media; and neurological diseases such as epilepsy, Parkinson's disease, and treatment-resistant depression. Examples include the intraocular lens, intrastromal corneal ring segment, cochlear implant, tympanostomy tube, and neurostimulator. | 1 | Applied and Interdisciplinary Chemistry |
Sumerians from 4500 years ago have said to use insecticides in the form of sulfur compounds. Additionally, the Chinese from about 3200 years ago used mercury and arsenic compounds to control the body lice.
Agrochemicals were introduced to protect crops from pests and enhance crop yields. The most common agrochemicals include pesticides and fertilizers. Chemical fertilizers in the 1960s were responsible for the beginning of the "Green Revolution", where using the same surface of land using intensive irrigation and mineral fertilizers such as nitrogen, phosphorus, and potassium has greatly increased food production. Throughout the 1970s through 1980s, pesticide research continued into producing more selective agrochemicals. Due to the adaptation of pests to these chemicals, more and new agrochemicals were being used, causing side effects in the environment. | 1 | Applied and Interdisciplinary Chemistry |
High-level waste (HLW) is produced by nuclear reactors and the reprocessing of nuclear fuel. The exact definition of HLW differs internationally. After a nuclear fuel rod serves one fuel cycle and is removed from the core, it is considered HLW. Spent fuel rods contain mostly uranium with fission products and transuranic elements generated in the reactor core. Spent fuel is highly radioactive and often hot. HLW accounts for over 95% of the total radioactivity produced in the process of nuclear electricity generation but it contributes to less than 1% of volume of all radioactive waste produced in the UK. Overall, the 60-year-long nuclear program in the UK up until 2019 produced 2150 m of HLW.
The radioactive waste from spent fuel rods consists primarily of cesium-137 and strontium-90, but it may also include plutonium, which can be considered transuranic waste. The half-lives of these radioactive elements can differ quite extremely. Some elements, such as cesium-137 and strontium-90 have half-lives of approximately 30 years. Meanwhile, plutonium has a half-life that can stretch to as long as 24,000 years.
The amount of HLW worldwide is currently increasing by about 12,000 tonnes every year. A 1000-megawatt nuclear power plant produces about 27 t of spent nuclear fuel (unreprocessed) every year. For comparison, the amount of ash produced by coal power plants in the United States alone is estimated at 130,000,000 t per year and fly ash is estimated to release 100 times more radiation than an equivalent nuclear power plant.
In 2010, it was estimated that about 250,000 t of nuclear HLW were stored globally. This does not include amounts that have escaped into the environment from accidents or tests. Japan is estimated to hold 17,000 t of HLW in storage in 2015. As of 2019, the United States has over 90,000 t of HLW. HLW have been shipped to other countries to be stored or reprocessed and, in some cases, shipped back as active fuel.
The ongoing controversy over high-level radioactive waste disposal is a major constraint on the nuclear power's global expansion. Most scientists agree that the main proposed long-term solution is deep geological burial, either in a mine or a deep borehole. As of 2019 no dedicated civilian high-level nuclear waste site is operational as small amounts of HLW did not justify the investment before. Finland is in the advanced stage of the construction of the Onkalo spent nuclear fuel repository, which is planned to open in 2025 at 400–450 m depth. France is in the planning phase for a 500 m deep Cigeo facility in Bure. Sweden is planning a site in Forsmark. Canada plans a 680 m deep facility near Lake Huron in Ontario. The Republic of Korea plans to open a site around 2028. The site in Sweden enjoys 80% support from local residents as of 2020.
The Morris Operation in Grundy County, Illinois, is currently the only de facto high-level radioactive waste storage site in the United States. | 0 | Theoretical and Fundamental Chemistry |
Activation of β adrenergic receptors on airway smooth muscle leads to the activation of adenylate cyclase and to an increase in the intracellular concentration of 3,5-cyclic adenosine monophosphate (cyclic AMP). The increase in cyclic AMP is associated with the activation of protein kinase A, which in turn, inhibits the phosphorylation of myosin and lowers intracellular ionic calcium concentrations, resulting in muscle relaxation.
Levosalbutamol relaxes the smooth muscles of all airways, from the trachea to the terminal bronchioles. Increased cyclic AMP concentrations are also associated with the inhibition of the release of mediators from mast cells in the airways. Levosalbutamol acts as a functional agonist that relaxes the airway irrespective of the spasmogen involved, thereby protecting against all bronchoconstrictor challenges.
While it is recognized that β adrenergic receptors are the predominant receptors on bronchial smooth muscle, data indicate that there are beta receptors in the human heart, 10–50% of which are β adrenergic receptors. The precise function of these receptors has not been established. However, all β adrenergic agonist drugs can produce a significant cardiovascular effect in some patients, as measured by pulse rate, blood pressure, and restlessness symptoms, and/or electrocardiographic (ECG). | 0 | Theoretical and Fundamental Chemistry |
An interesting property of Stokes flow is known as the Stokes' paradox: that there can be no Stokes flow of a fluid around a disk in two dimensions; or, equivalently, the fact there is no non-trivial solution for the Stokes equations around an infinitely long cylinder. | 1 | Applied and Interdisciplinary Chemistry |
Transcription can be measured and detected in a variety of ways:
* G-Less Cassette transcription assay: measures promoter strength
* Run-off transcription assay: identifies transcription start sites (TSS)
* Nuclear run-on assay: measures the relative abundance of newly formed transcripts
* KAS-seq: measures single-stranded DNA generated by RNA polymerases; can work with 1,000 cells.
* RNase protection assay and ChIP-Chip of RNAP: detect active transcription sites
* RT-PCR: measures the absolute abundance of total or nuclear RNA levels, which may however differ from transcription rates
* DNA microarrays: measures the relative abundance of the global total or nuclear RNA levels; however, these may differ from transcription rates
* In situ hybridization: detects the presence of a transcript
* MS2 tagging: by incorporating RNA stem loops, such as MS2, into a gene, these become incorporated into newly synthesized RNA. The stem loops can then be detected using a fusion of GFP and the MS2 coat protein, which has a high affinity, sequence-specific interaction with the MS2 stem loops. The recruitment of GFP to the site of transcription is visualized as a single fluorescent spot. This new approach has revealed that transcription occurs in discontinuous bursts, or pulses (see Transcriptional bursting). With the notable exception of in situ techniques, most other methods provide cell population averages, and are not capable of detecting this fundamental property of genes.
* Northern blot: the traditional method, and until the advent of RNA-Seq, the most quantitative
* RNA-Seq: applies next-generation sequencing techniques to sequence whole transcriptomes, which allows the measurement of relative abundance of RNA, as well as the detection of additional variations such as fusion genes, post-transcriptional edits and novel splice sites
* Single cell RNA-Seq: amplifies and reads partial transcriptomes from isolated cells, allowing for detailed analyses of RNA in tissues, embryos, and cancers | 1 | Applied and Interdisciplinary Chemistry |
In transient equilibrium, the daughter activity increases and eventually reaches a maximum value that can exceed the parent activity. The time of maximum activity is given by:
where and are the half-lives of the parent and daughter, respectively. In the case of generator, the time of maximum activity () is approximately 24 hours which makes it convenient for medical use. | 0 | Theoretical and Fundamental Chemistry |
The oxygen effect is quantified by measuring the radiation sensitivity or Oxygen Enhancement Ratio (OER) of a particular biological effect (e.g., cell death or DNA damage), which is the ratio of doses under pure oxygen and anoxic conditions. Consequently, OER varies from unity in anoxia to a maximum value for 100% oxygen of typically up to three for low ionizing-density-radiation (beta-, gamma-, or x-rays), or so-called low linear energy transfer (LET) radiations.
Radiosensitivity varies most rapidly for oxygen partial pressures below ~1% atmospheric (Fig. 1). Howard-Flanders and Alper (1957) developed a formula for the hyperbolic function of OER and its variation with oxygen concentration, or oxygen pressure in air.
Radiobiologists identified additional characteristics of the oxygen effect that influence radiotherapy practices. They found that the maximum OER value diminishes as the ionizing-density of the radiation increases (Fig. 2), from low-LET to high-LET radiations. The OER is unity irrespective of the oxygen tension for alpha-particles of high-LET around 200 keV/μm. The OER is reduced for low doses as evaluated for cultured mammalian cells exposed to x-rays under aerobic (21% O2, 159 mmHg) and anoxic (nitrogen) conditions. Typical fractionation treatments are daily 2 Gy exposures, as below this dose the so-called shoulder or repair region of the cell survival curve is encroached upon reducing the OER (Fig. 3). | 1 | Applied and Interdisciplinary Chemistry |
Essential medicines, as defined by the World Health Organization (WHO), are "those drugs that satisfy the health care needs of the majority of the population; they should therefore be available at all times in adequate amounts and in appropriate dosage forms, at a price the community can afford." Recent studies have found that most of the medicines on the WHO essential medicines list, outside of the field of HIV drugs, are not patented in the developing world, and that lack of widespread access to these medicines arise from issues fundamental to economic development – lack of infrastructure and poverty. Médecins Sans Frontières also runs a Campaign for Access to Essential Medicines campaign, which includes advocacy for greater resources to be devoted to currently untreatable diseases that primarily occur in the developing world. The Access to Medicine Index tracks how well pharmaceutical companies make their products available in the developing world.
World Trade Organization negotiations in the 1990s, including the TRIPS Agreement and the Doha Declaration, have centered on issues at the intersection of international trade in pharmaceuticals and intellectual property rights, with developed world nations seeking strong intellectual property rights to protect investments made to develop new drugs, and developing world nations seeking to promote their generic pharmaceuticals industries and their ability to make medicine available to their people via compulsory licenses.
Some have raised ethical objections specifically with respect to pharmaceutical patents and the high prices for drugs that they enable their proprietors to charge, which poor people around the world, cannot afford. Critics also question the rationale that exclusive patent rights and the resulting high prices are required for pharmaceutical companies to recoup the large investments needed for research and development. One study concluded that marketing expenditures for new drugs often doubled the amount that was allocated for research and development. Other critics claim that patent settlements would be costly for consumers, the health care system, and state and federal governments because it would result in delaying access to lower cost generic medicines.
Novartis fought a protracted battle with the government of India over the patenting of its drug, Gleevec, in India, which ended up in a Supreme Court in a case known as Novartis v. Union of India & Others. The Supreme Court ruled narrowly against Novartis, but opponents of patenting drugs claimed it as a major victory. | 1 | Applied and Interdisciplinary Chemistry |
Isomers are types of molecules that share a chemical formula but have difference geometries, resulting in different properties:
* A pure substance is composed of only one type of isomer of a molecule (all have the same geometrical structure).
* Structural isomers have the same chemical formula but different physical arrangements, often forming alternate molecular geometries with very different properties. The atoms are not bonded (connected) together in the same orders.
** Functional isomers are special kinds of structural isomers, where certain groups of atoms exhibit a special kind of behavior, such as an ether or an alcohol.
* Stereoisomers may have many similar physicochemical properties (melting point, boiling point) and at the same time very different biochemical activities. This is because they exhibit a handedness that is commonly found in living systems. One manifestation of this chirality or handedness is that they have the ability to rotate polarized light in different directions.
* Protein folding concerns the complex geometries and different isomers that proteins can take. | 0 | Theoretical and Fundamental Chemistry |
Many laboratory techniques rely on the ability of nucleic acid strands to separate. By understanding the properties of nucleic acid denaturation, the following methods were created:
* PCR
* Southern blot
* Northern blot
* DNA sequencing | 1 | Applied and Interdisciplinary Chemistry |
The water enters the boiler through a section in the convection pass called the economizer. From the economizer it passes to the steam drum and from there it goes through downcomers to inlet headers at the bottom of the water walls. From these headers the water rises through the water walls of the furnace where some of it is turned into steam and the mixture of water and steam then re-enters the steam drum. This process may be driven purely by natural circulation (because the water is the downcomers is denser than the water/steam mixture in the water walls) or assisted by pumps. In the steam drum, the water is returned to the downcomers and the steam is passed through a series of steam separators and dryers that remove water droplets from the steam. The dry steam then flows into the superheater coils.
The boiler furnace auxiliary equipment includes coal feed nozzles and igniter guns, soot blowers, water lancing, and observation ports (in the furnace walls) for observation of the furnace interior. Furnace explosions due to any accumulation of combustible gases after a trip-out are avoided by flushing out such gases from the combustion zone before igniting the coal.
The steam drum (as well as the superheater coils and headers) have air vents and drains needed for initial start up. | 1 | Applied and Interdisciplinary Chemistry |
There is no specific antidote to common tear gases. At the first sign of exposure or potential exposure, masks are applied when available. People are removed from the affected area when possible. Immediate removal of contact lenses has also been recommended, as they can retain particles.
Decontamination is by physical or mechanical removal (brushing, washing, rinsing) of solid or liquid agents. Water may transiently exacerbate the pain caused by CS gas and pepper spray but is still effective, although fat-containing oils or soaps may be more effective against pepper spray. Eyes are decontaminated by copious flushing with sterile water or saline or (with OC) open-eye exposure to wind from a fan. Referral to an ophthalmologist is needed if slit-lamp examination shows impaction of solid particles of agent. Blowing the nose to get rid of the chemicals is recommended, as is avoiding rubbing of the eyes. There are reports that water may increase pain from CS gas, but the balance of limited evidence currently suggests water or saline are the best options. Some evidence suggests that Diphoterine, a hypertonic amphoteric salt solution, a first aid product for chemical splashes, may help with ocular burns or chemicals in the eye.
Bathing and washing the body vigorously with soap and water can remove particles that adhere to the skin. Clothes, shoes and accessories that come into contact with vapors must be washed well since all untreated particles can remain active for up to a week. Some advocate using fans or hair dryers to evaporate the spray, but this has not been shown to be better than washing out the eyes and it may spread contamination.
Anticholinergics can work like some antihistamines as they reduce lacrymation and decrease salivation, acting as an antisialagogue, and for overall nose discomfort as they are used to treat allergic reactions in the nose (e.g., itching, runny nose, and sneezing).
Oral analgesics may help relieve eye pain.
Most effects resulting from riot-control agents are transient and do not require treatment beyond decontamination, and most patients do not need observation beyond 4 hours. However, patients should be instructed to return if they develop effects such as blistering or delayed-onset shortness of breath. | 1 | Applied and Interdisciplinary Chemistry |
Scientific publications of the society include , Angewandte Chemie, Chemistry: A European Journal, European Journal of Inorganic Chemistry, European Journal of Organic Chemistry, ChemPhysChem, ChemSusChem, ChemBioChem, ChemMedChem, ChemCatChem, ChemistryViews, Chemie Ingenieur Technik and Chemie in unserer Zeit.
In the 21st century, the society has become a member of ChemPubSoc Europe, which is an organization of 16 European chemical societies. This European consortium was established in the late 1990s as many chemical journals owned by national chemical societies were amalgamated. | 1 | Applied and Interdisciplinary Chemistry |
3D cell culturing by magnetic levitation method (MLM) was developed from collaboration between scientists at Rice University and University of Texas MD Anderson Cancer Center in 2008. Since then, this technology has been licensed and commercialized by Nano3D Biosciences. | 0 | Theoretical and Fundamental Chemistry |
The RNA Characterization of Secondary Structure Motifs database (RNA CoSSMos) is a repository of three-dimensional nucleic acid PDB structures containing secondary structure motifs ( loops, hairpin loops ...). | 0 | Theoretical and Fundamental Chemistry |
The formation of an amide using a carbodiimide is a common reaction, but carries the risk of several side reactions. The acid 1 will react with the carbodiimide to produce the key intermediate: the O-acylisourea 2, which can be viewed as a carboxylic ester with an activated leaving group. The O-acylisourea will react with amines to give the desired amide 3 and urea 4.
The possible reactions of the O-acylisourea 2 produce both desired and undesired products. The O-acylisourea 2 can react with an additional carboxylic acid 1 to give an acid anhydride 5, which can react further to give the amide 3. The main undesired reaction pathway involves the rearrangement of the O-acylisourea 2 to the stable N-acylurea 6. The use of solvents with low dielectric constants such as dichloromethane or chloroform can minimize this side reaction. | 0 | Theoretical and Fundamental Chemistry |
A direct indicating dial thermometer, common in household devices (such as a patio thermometer or a meat thermometer), uses a bimetallic strip wrapped into a coil in its most common design. The coil changes the linear movement of the metal expansion into a circular movement thanks to the helicoidal shape it draws. One end of the coil is fixed to the housing of the device as a fix point and the other drives an indicating needle inside a circular indicator. A bimetallic strip is also used in a recording thermometer. Breguet's thermometer consists of a tri-metallic helix in order to have a more accurate result. | 1 | Applied and Interdisciplinary Chemistry |
The process flow diagram below depicts a single chemical engineering unit process known as an amine treating plant: | 1 | Applied and Interdisciplinary Chemistry |
Principal component analysis (PCA) was one of the earliest methods used for pump–probe data analysis, as it is commonly used for hyperspectral data analysis. PCA decomposes the data into orthogonal components. In melanoma studies, the principal components have shown good agreement with the signals obtained from the different forms of melanin. An advantage of PCA is that noise can be reduced by keeping only the principal components that account for majority of the variance in the data. However, the principal components do not necessarily reflect actual properties of the underlying chemical species, which are typically non-orthogonal. Therefore, a limitation is that the number of unique chemical species cannot be inferred using PCA. | 0 | Theoretical and Fundamental Chemistry |
Given an incompressible two-dimensional flow which is also irrotational we have:
Which is in cylindrical coordinates
We look for a solution with separated variables:
which gives
Given the left part depends only on r and the right parts depends only on , the two parts must be equal to a constant independent from r and . The constant shall be positive.
Therefore,
The solution to the second equation is a linear combination of and
In order to have a single-valued velocity (and also a single-valued stream function) m shall be a positive integer.
therefore the most generic solution is given by
The potential is instead given by | 1 | Applied and Interdisciplinary Chemistry |
Although the concept of circles and spheres can be extended to hyperbolic space, finding the densest packing becomes much more difficult. In a hyperbolic space there is no limit to the number of spheres that can surround another sphere (for example, Ford circles can be thought of as an arrangement of identical hyperbolic circles in which each circle is surrounded by an infinite number of other circles). The concept of average density also becomes much more difficult to define accurately. The densest packings in any hyperbolic space are almost always irregular.
Despite this difficulty, K. Böröczky gives a universal upper bound for the density of sphere packings of hyperbolic n-space where n ≥ 2. In three dimensions the Böröczky bound is approximately 85.327613%, and is realized by the horosphere packing of the order-6 tetrahedral honeycomb with Schläfli symbol {3,3,6}. In addition to this configuration at least three other horosphere packings are known to exist in hyperbolic 3-space that realize the density upper bound. | 0 | Theoretical and Fundamental Chemistry |
Several definitions describe a "molecular machine" as a class of molecules typically described as an assembly of a discrete number of molecular components intended to produce mechanical movements in response to specific stimuli. The expression is often more generally applied to molecules that simply mimic functions that occur at the macroscopic level. A few prime requirements for a molecule to be considered a "molecular machine" are: the presence of moving parts, the ability to consume energy, and the ability to perform a task. Molecular machines differ from other stimuli-responsive compounds that can produce motion (such as cis-trans isomers) in their relatively larger amplitude of movement (potentially due to chemical reactions) and the presence of a clear external stimulus to regulate the movements (as compared to random thermal motion). Piezoelectric, magnetostrictive, and other materials that produce a movement due to external stimuli on a macro-scale are generally not included, since despite the molecular origin of the motion the effects are not useable on the molecular scale.
This definition generally applies to synthetic molecular machines, which have historically gained inspiration from the naturally occurring biological molecular machines (also referred to as "nanomachines"). Biological machines are considered to be nanoscale devices (such as molecular proteins) in a living system that convert various forms of energy to mechanical work in order to drive crucial biological processes such as intracellular transport, muscle contractions, ATP generation and cell division. | 0 | Theoretical and Fundamental Chemistry |
Because of the complex inter-relationship between analytical method, sample concentration, limits of detection and method precision, the management of Analytical Quality Control is undertaken using a statistical approach to determine whether the results obtained lie within an acceptable statistical envelope. | 1 | Applied and Interdisciplinary Chemistry |
The Maximum entropy method is an analysis method that has great developmental potential. The method is also used for the quantification of sedimentation velocity data from analytical ultracentrifugation. The maximum entropy method involves several iterative steps to minimize the deviation of the fitted data from the experimental data and subsequently reduce the χ of the fitted data. | 0 | Theoretical and Fundamental Chemistry |
Multiple classical translation factor family GTPases play important roles in initiation, elongation and termination of protein biosynthesis. Sharing a similar mode of ribosome binding due to the β-EI domain following the GTPase, the most well-known members of the family are EF-1A/EF-Tu, EF-2/EF-G, and class 2 release factors. Other members include EF-4 (LepA), BipA (TypA), SelB (bacterial selenocysteinyl-tRNA EF-Tu paralog), Tet (tetracycline resistance by ribosomal protection), and HBS1L (eukaryotic ribosome rescue protein similar to release factors).
The superfamily also includes the Bms1 family from yeast. | 1 | Applied and Interdisciplinary Chemistry |
11β-hydroxylase is a steroidogenic enzyme, i.e. the enzyme involved in the metabolism of steroids. The enzyme is primarily localized in the zona glomerulosa and zona fasciculata of the adrenal cortex. The enzyme functions by introducing a hydroxyl group at carbon position 11β on the steroid nucleus, thereby facilitating the conversion of certain steroids.
Humans have two isozymes with 11β-hydroxylase activity: CYP11B1 and CYP11B2.
CYP11B1 (11β-hydroxylase) is expressed at high levels and is regulated by ACTH, while CYP11B2 (aldosterone synthase) is usually expressed at low levels and is regulated by angiotensin II. In addition to the 11β-hydroxylase activity, both isozymes have 18-hydroxylase activity. The CYP11B1 isozyme has strong 11β-hydroxylase activity, but the activity of 18-hydroxylase is only one-tenth of CYP11B2. The weak 18-hydroxylase activity of CYP11B1 explains why an adrenal with suppressed CYP11B2 expression continues to synthesize 18-hydroxycorticosterone.
Here are some of the steroids, grouped by catalytic activity of the CYP11B1 isozyme:
* strong activity:
** 11-deoxycortisol to cortisol,
** 11-deoxycorticosterone to corticosterone;
* medium activity:
** progesterone to 11β-hydroxyprogesterone,
** 17α-hydroxyprogesterone to 21-deoxycortisol,
** androstenedione to 11β-hydroxyandrostenedione;
** testosterone to 11β-hydroxytestosterone,
* weak activity:
** corticosterone to 18-hydroxycorticosterone,
** cortisol to 18-hydroxycortisol. | 1 | Applied and Interdisciplinary Chemistry |
Variant annotation tools use machine learning algorithms to predict variant annotations. Different annotation tools use different algorithms. Common algorithms include:
* Interval/Random forest-eg.MutPred, SNPeff
* Neural networks-eg.SNAP
* Support Vector Machines-e.g. PhD-SNP, SNPs&GO
* Bayesian classification-eg.PolyPhen-2 | 1 | Applied and Interdisciplinary Chemistry |
A thermocouple can produce current to drive some processes directly, without the need for extra circuitry and power sources. For example, the power from a thermocouple can activate a valve when a temperature difference arises. The electrical energy generated by a thermocouple is converted from the heat which must be supplied to the hot side to maintain the electric potential. A continuous transfer of heat is necessary because the current flowing through the thermocouple tends to cause the hot side to cool down and the cold side to heat up (the Peltier effect).
Thermocouples can be connected in series to form a thermopile, where all the hot junctions are exposed to a higher temperature and all the cold junctions to a lower temperature. The output is the sum of the voltages across the individual junctions, giving larger voltage and power output. In a radioisotope thermoelectric generator, the radioactive decay of transuranic elements as a heat source has been used to power spacecraft on missions too far from the Sun to use solar power.
Thermopiles heated by kerosene lamps were used to run batteryless radio receivers in isolated areas. There are commercially produced lanterns that use the heat from a candle to run several light-emitting diodes, and thermoelectrically powered fans to improve air circulation and heat distribution in wood stoves. | 1 | Applied and Interdisciplinary Chemistry |
It is free to become a member of BOGS. To join the mailing list for BOGS, an email is sent to the BOGS webmaster at calewis@plymouth.ac.uk. | 0 | Theoretical and Fundamental Chemistry |
In the United States, it is normal to use fuel once in a power reactor before placing it in a waste store. The long-term plan is currently to place the used civilian reactor fuel in a deep store. This non-reprocessing policy was started in March 1977 because of concerns about nuclear weapons proliferation. President Jimmy Carter issued a Presidential directive which indefinitely suspended the commercial reprocessing and recycling of plutonium in the United States. This directive was likely an attempt by the United States to lead other countries by example, but many other nations continue to reprocess spent nuclear fuels. The Russian government under President Vladimir Putin repealed a law which had banned the import of used nuclear fuel, which makes it possible for Russians to offer a reprocessing service for clients outside Russia (similar to that offered by BNFL). | 0 | Theoretical and Fundamental Chemistry |
A semi-closed impeller has an additional back wall, giving it more strength. These impellers can pass mixed solid-liquid mixtures at the cost of reduced efficiency. | 1 | Applied and Interdisciplinary Chemistry |
Numerous reports show a link between age-related diseases, birth defects, and several types of cancer with disruption of certain histone post translational modifications. Studies have identified that N- and C-terminal tails are main targets for acetylation, methylation, ubiquitination and phosphorylation. New evidence is pointing to several modifications within the histone core. Research is turning towards deciphering the role of these histone core modifications at the histone-DNA interface in the chromatin. p300 and cAMP response element-binding protein (CBP) possess histone acetyltransferase activity. p300 and CBP are the most promiscuous histone acetyltransferase enzymes acetylating all four core histones on multiple residues. Lysine 18 and Lysine 27 on H3 were the only histone acetylation sites reduced upon CBP and p300 depletion in mouse embryonic fibroblasts. Also, CBP and p300 knockout mice have an open neural tube defect and therefore die before birth. p300−/− embryos exhibit defective development of the heart. CBP+/− mice display growth retardation, craniofacial abnormalities, hematological malignancies, which are not observed in mice with p300+/−. Mutations of both p300 have been reported in human tumors such as colorectal, gastric, breast, ovarian, lung, and pancreatic carcinomas. Also, activation or localization of two histone acetyltransferases can be oncogenic. | 1 | Applied and Interdisciplinary Chemistry |
In a 1987 article in New Scientist, Jack Harris reported that oxide jacking has caused significant damage to many historic structures in the United Kingdom, including St Pauls Cathedral, the British Museum and the Albert Memorial in London, Gloucester Cathedral, St. Margarets Church in King's Lynn, Winchester Cathedral, and Blackburn Cathedral.
Harris also wrote that oxide jacking also damaged the ancient Horses of Saint Mark on the exterior of St. Mark's Basilica in Venice. Expansive rusting of iron and steel bolts and reinforcements affected the structural integrity of the copper horse sculptures, which were relocated indoors and replaced with replicas. Poorly-designed early 20th-century renovations also led to oxide jacking damage to the Acropolis of Athens.
In the United States, rusting of iron pegs inserted into holes in the stone entrance stair in order to support handrails resulted in cracking of the steps at the Basilica of the Sacred Heart in Notre Dame, Indiana.
Oxide jacking damaged the terra cotta cornice on the Land Title Building in Philadelphia, designed in 1897 and expanded in 1902 by pioneer skyscraper architect Daniel Burnham. The Land Title complex, with its two interconnected towers, is on the National Register of Historic Places. By 1922, experts on architectural terra cotta were warning that the rusting of embedded iron fasteners could cause decorative building components to fail. This 1902 cornice is nearly high, projects from the facade of the building and is long. The cornice was stabilized, steel anchors subject to rusting were replaced with new stainless steel anchors, and the cornice was completely renovated. The project was completed in 1991.
Flooding in 2007 damaged the modernist Farnsworth House in Plano, Illinois, designed in 1945 by Ludwig Mies van der Rohe, and now owned by the National Trust for Historic Preservation. Among the damage discovered by an architect inspecting the house in 2007 was oxide jacking at the corners of the house's steel framework. The house flooded again in 2008. | 1 | Applied and Interdisciplinary Chemistry |
Pervious concrete consists of cement, coarse aggregate (size should be 9.5 mm to 12.5 mm) and water with little to no fine aggregates. The addition of a small amount of sand will increase the strength. The mixture has a water-to-cement ratio of 0.28 to 0.40 with a void content of 15 to 25 percent.
The correct quantity of water in the concrete is critical. A low water to cement ratio will increase the strength of the concrete, but too little water may cause surface failure. A proper water content gives the mixture a wet-metallic appearance. As this concrete is sensitive to water content, the mixture should be field checked. Entrained air may be measured by a Rapid Air system, where the concrete is stained black and sections are analyzed under a microscope.
A common flatwork form has riser strips on top such that the screed is 3/8-1/2 inches (9 to 12 mm) above final pavement elevation. Mechanical screeds are preferable to manual. The riser strips are removed to guide compaction. Immediately after screeding, the concrete is compacted to improve the bond and smooth the surface. Excessive compaction of pervious concrete results in higher compressive strength, but lower porosity (and thus lower permeability).
Jointing varies little from other concrete slabs. Joints are tooled with a rolling jointing tool prior to curing or saw cut after curing. Curing consists of covering concrete with 6 mil plastic sheeting within 20 minutes of concrete discharge. However, this contributes to a substantial amount of waste sent to landfills. Alternatively, preconditioned absorptive lightweight aggregate as well as internal curing admixture (ICA) have been used to effectively cure pervious concrete without waste generation. | 1 | Applied and Interdisciplinary Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2021 impact factor of 4.755. | 0 | Theoretical and Fundamental Chemistry |
As EPIC-seq studies epigenetic markers to infer gene expression, one can study epigenetic sequencing methods like ChIP-seq, ATAC-seq, MeDIP-seq, and Bisulfite-Free DNA Methylation sequencing in combination with methods for profiling RNA expression such as RNA-seq and scRNA-seq.
Considering the method is mainly developed for early cancer detection or subgrouping, liquid biopsy methods, such as [https://www.twistbioscience.com/resources/technical-document/twist-cfdna-pan-cancer-reference-standard-variant-list Twist cfDNA Pan-Cancer Reference Standard], can be used as an alternative. Different liquid biopsy methods focus on cell-free tumour markers, tumour methylation markers, exomes, proteins, lipids, carbohydrates, electrolytes, metabolites, RNA, extracellular vesicles, circulating tumour cells, and tumour-educated platelets for early identification of cancer non-invasively. Some of the proposed liquid biopsy methods provide a comprehensive detection of cancer types, such as ATR-FTIR spectroscopy and CancerSEEK, while others, like Dxcover and SelectMdx operate on more specific (even single) cancer targets.
EPIC-seq utilizes fragmentomic features to infer expression levels of genes. Several studies also employ fragmentomic features to infer cancer existence, infer cell death, and detect other clinical conditions such as transplant failure. | 1 | Applied and Interdisciplinary Chemistry |
FSL constructs, when in solution (saline) and in contact, will spontaneously incorporate into cell and virus membranes. The methodology involves simply preparing a solution of FSL constructs in the range of 1–1000 μg/mL. The actual concentration will depend on the construct and the quantity of construct required in the membrane. One part of FSL solution is added to one part of cells (up to 100% suspension) and they are incubated at a set temperature within the range of 4–37 °C (39–99 °F) depending on temperature compatibility of the cells being modified. The higher the temperature, the faster the rate of FSL insertion into the membrane. For red blood cells, at 37 °C incubation for 2 hours achieves >95% insertion with at least 50% insertion being achieved within 20 minutes. In general, FSL insertion time of 4 hours at room temperature or 20 hours at 4 °C gives results similar to 1 hour at 37 °C for carbohydrate based FSLs inserting into red blood cells. The resultant kodecytes or kodevirions do not required to be washed, however this option should be considered if an excess of FSL construct is used in the koding process. | 1 | Applied and Interdisciplinary Chemistry |
In his 1891 novel The Doings of Raffles Haw, Arthur Conan Doyle talks about turning elements into other elements of decreasing atomic number, until a gray matter is reached.
In his 1959 novel Life and Fate, Vasily Grossmans principal character, the physicist Viktor Shtrum, reflects on Prouts hypothesis about hydrogen being the origin of other elements (and the felicitous fact that Prout's incorrect data led to an essentially correct conclusion), as he worries about his inability to formulate his own thesis. | 1 | Applied and Interdisciplinary Chemistry |
Glycine encephalopathy, also known as non-ketotic hyperglycinemia (NKH), is a primary disorder of the glycine cleavage system, resulting from lowered function of the glycine cleavage system causing increased levels of glycine in body fluids. The disease was first clinically linked to the glycine cleavage system in 1969. Early studies showed high levels of glycine in blood, urine and cerebrospinal fluid. Initial research using carbon labeling showed decreased levels of CO and serine production in the liver, pointing directly to deficiencies glycine cleavage reaction. Further research has shown that deletions and mutations in the 5' region of the P-protein are the major genetic causes of nonketotic hyperglycinemia. . In more rare cases, a missense mutation in the genetic code of the T-protein, causing the histidine in position 42 to be mutated to arginine, was also found to result in nonketotic hypergycinemia. This specific mutation directly affected the active site of the T-protein, causing lowered efficiency of the glycine cleavage system. | 1 | Applied and Interdisciplinary Chemistry |
A fallout shelter is an enclosed space specially designated to protect occupants from radioactive debris or fallout resulting from a nuclear explosion. Many such shelters were constructed as civil defense measures during the Cold War.
During a nuclear explosion, matter vaporized in the resulting fireball is exposed to neutrons from the explosion, absorbs them, and becomes radioactive. When this material condenses in the rain, it forms dust and light sandy materials that resemble ground pumice. The fallout emits alpha and beta particles, as well as gamma rays.
Much of this highly radioactive material falls to Earth, subjecting anything within the line of sight to radiation, becoming a significant hazard. A fallout shelter is designed to allow its occupants to minimize exposure to harmful fallout until radioactivity has decayed to a safer level, over a few weeks or months. | 0 | Theoretical and Fundamental Chemistry |
The most common application of passive daytime radiative cooling currently is on building envelopes, including PDRC cool roofs, which can significantly lower indoor space temperatures within buildings. A PDRC roof application can double the energy savings of a white roof. This makes PDRCs a sustainable and low-cost alternative or supplement to air conditioning by decreasing energy demand, alleviating energy grids in peak periods, and reducing emissions caused by air conditioning's release of hydrofluorocarbons into the atmosphere which can be thousands of times more potent that .
Air conditioning alone accounts for 12%-15% of global energy usage, while emissions from air conditioning account for "13.7% of energy-related emissions, approximately 52.3 EJ yearly" or 10% of emissions total. Air conditioning applications are expected to rise, despite their negative impacts on energy sectors, costs, and global warming, which has been described as a "vicious cycle." However, this can be significantly reduced with the mass production of low-cost PDRCs for indoor space cooling. A multilayer PDRC surface covering 10% of a building's roof can replace 35% of air conditioning used during the hottest hours of daytime.
In suburban single-family residential areas, PDRCs can lower energy costs by 26% to 46% in the United States and lower temperatures on average by 5.1ᵒC. With the addition of "cold storage to utilize the excess cooling energy of water generated during off-peak hours, the cooling effects for indoor air during the peak-cooling-load times can be significantly enhanced" and air temperatures may be reduced by 6.6–12.7 °C.
In cities, PDRCs can result in significant energy and cost savings. In a study on US cities, Zhou et al. found that "cities in hot and arid regions can achieve high annual electricity consumption savings of >2200 kWh, while <400 kWh is attainable in colder and more humid cities," being ranked from highest to lowest by electricity consumption savings as follows: Phoenix (~2500 kWh), Las Vegas (~2250 kWh), Austin (~2100 kWh), Honolulu (~2050 kWh), Atlanta (~1500 kWh), Indianapolis (~1200 kWh), Chicago (~1150 kWh), New York City (~900 kWh), Minneapolis (~850 kWh), Boston (~750 kWh), Seattle (~350 kWh). In a study projecting energy savings for Indian cities in 2030, Mumbai and Kolkata had a lower energy savings potential, Jaisalmer, Varansai, and Delhi had a higher potential, although with significant variations from April to August dependent on humidity and wind cover.
The growing interest and rise in PDRC application to buildings has been attributed to cost savings related to "the sheer magnitude of the global building surface area, with a market size of ~$27 billion in 2025," as estimated in a 2020 study. | 0 | Theoretical and Fundamental Chemistry |
The units of the structure-factor amplitude depend on the incident radiation. For X-ray crystallography they are multiples of the unit of scattering by a single electron (2.82 m); for neutron scattering by atomic nuclei the unit of scattering length of m is commonly used.
The above discussion uses the wave vectors and . However, crystallography often uses wave vectors and . Therefore, when comparing equations from different sources, the factor may appear and disappear, and care to maintain consistent quantities is required to get correct numerical results. | 0 | Theoretical and Fundamental Chemistry |
A variety of defense mechanisms can lead to ecological escape from predators. Plants use chemical defenses in the form of secondary metabolites or allelochemicals. These allelochemicals inhibit the growth, behavior, and health of herbivores, allowing plants to escape. An example of a plant allelochemical are alkaloids that can inhibit protein synthesis in herbivores. Other forms of plant defense include mechanical defenses such as thigmonasty movements which have the plant leaves close in response to tactile stimulation. Indirect mechanisms plant include shedding of plant leaves so less leaves are available which deters herbivores, growth in locations in that are difficult to reach, and even mimicry. For organisms other than plants, examples of defense mechanisms allowing for escape include camouflage, aposematism, heightened senses and physical capabilities, and even defensive behaviors such as feigning death. An example of an organism using one of these defense mechanisms is the granular poison frog which defends itself through aposematism. It is important to understand that in order for escape and radiate coevolution to occur, it is necessary that the developed defense is novel rather than previously established.
Induced defense stemming from adaptive phenotypic plasticity may help a plant defend itself against multiple enemies. Phenotypic plasticity occurs when an organism undergoes an environmental change forcing a change altering its behavior, physiology, etc. These induced defenses allow for an organism to escape. | 1 | Applied and Interdisciplinary Chemistry |
Besides the amount of radiation reaching a plant in the PAR region of the spectrum, it is also important to consider the quality of such radiation. Radiation reaching a plant contains entropy as well as energy, and combining those two concepts the exergy can be determined. This sort of analysis is known as exergy analysis or second law analysis, and the exergy represents a measure of the useful work, i.e., the useful part of radiation which can be transformed into other forms of energy.
The spectral distribution of the exergy of radiation is defined as:
One of the advantages of working with the exergy is that it depends not only on the temperature of the emitter (the Sun), , but also on the temperature of the receiving body (the plant), , i.e., it includes the fact that the plant is emitting radiation. Naming and , the exergy emissive power of radiation in a region is determined as:
Where is a special function called the polylogarithm.
By definition, the exergy obtained by the receiving body is always lower than the energy radiated by the emitting blackbody, as a consequence of the entropy content in radiation.
Thus, as a consequence of the entropy content, not all the radiation reaching the Earth's surface is "useful" to produce work. Therefore, the efficiency of a process involving radiation should be measured against its exergy, not its energy.
Using the expression above, the optimal efficiency or second law efficiency for the conversion of radiation to work in the PAR region (from 400 nm to 700 nm), for a blackbody at = 5800 K and an organism at = 300 K is determined as:
about 8.3% lower than the value considered until now, as a direct consequence of the fact that the organisms which are using solar radiation are also emitting radiation as a consequence of their own temperature. Therefore, the conversion factor of the organism will be different depending on its temperature, and the exergy concept is more suitable than the energy one. | 0 | Theoretical and Fundamental Chemistry |
Halon 1301 was developed in a joint venture between the U.S. Army and Purdue University in the late 1940's, and became a DuPont product in 1954. It was introduced as an effective gaseous fire suppression fixed systems agent in the 1960s, and was used around valuable materials, such as aircraft, mainframe computers, and telecommunication switching centers, usually in total flooding systems. It was also widely used in the maritime industry to add a third level of protection should the main and emergency fire pumps become inoperable or ineffective. Halon 1301 was never widely used in portables outside marine, military and spacecraft applications, due to its limited range, and invisible discharge. It does not produce the characteristic white cloud like CO and is difficult to direct when fighting large fires. Halon 1301 is ideal for armored vehicles and spacecraft, because it produces fewer toxic by-products than does Halon 1211, which is critical for combat or space conditions where a compartment may not be able to be ventilated immediately. Halon 1301 is widely used by the U.S. Military and NASA in a 2-3/4 lb portable extinguisher with a sealed, disposable cylinder for quick recharging. Other agents such as CO and FE-36 (HFC-236fa) wet chemical are largely replacing halon 1301 for environmental concerns. Civilian models in 2-3/4, 3, and 4 lb sizes were also made.
It is considered good practice to avoid all unnecessary exposure to Halon 1301, and to limit exposures to concentrations of 7% and below to 15 minutes. Exposure to Halon 1301 in the 5% to 7% range produces little, if any, noticeable effect. At levels between 7% and 10%, mild central nervous system effects such as dizziness and tingling in the extremities have been reported. In practice, the operators of many Halon 1301 total flooding systems evacuate the space on impending agent discharge.
Halon systems are among the most effective and commonly used fire protection systems used on commercial aircraft. Halon 1301 is the primary agent used in commercial aviation engine, cargo compartments, and auxiliary power unit fire zones. Efforts to find a suitable replacement for Halon 1301 have not produced a widely accepted replacement.
Bromotrifluoromethane was also used as a filling of the bubble chamber in the neutrino detector Gargamelle.
Before the dangers of Halon 1301 as an ozone depleter were known, many industrial chillers used it as an efficient refrigerant gas. | 1 | Applied and Interdisciplinary Chemistry |
In 1993 the silicon carbide was considered a semiconductor in both research and early mass production providing advantages for fast, high-temperature and/or high-voltage devices. The first devices available were Schottky diodes, followed by junction-gate FETs and MOSFETs for high-power switching. Bipolar transistors and thyristors were described.
A major problem for SiC commercialization has been the elimination of defects: edge dislocations, screw dislocations (both hollow and closed core), triangular defects and basal plane dislocations. As a result, devices made of SiC crystals initially displayed poor reverse blocking performance, though researchers have been tentatively finding solutions to improve the breakdown performance.
Apart from crystal quality, problems with the interface of SiC with silicon dioxide have hampered the development of SiC-based power MOSFETs and insulated-gate bipolar transistors. Although the mechanism is still unclear, nitriding has dramatically reduced the defects causing the interface problems.
In 2008, the first commercial JFETs rated at 1200 V were introduced to the market, followed in 2011 by the first commercial MOSFETs rated at 1200 V. JFETs are now available rated 650 V to 1700 V with resistance as low as 25 mΩ. Beside SiC switches and SiC Schottky diodes (also Schottky barrier diode, SBD) in the popular TO-247 and TO-220 packages, companies started even earlier to implement the bare chips into their power electronic modules.
SiC SBD diodes found wide market spread being used in PFC circuits and IGBT power modules.
Conferences such as the International Conference on Integrated Power Electronics Systems (CIPS) report regularly about the technological progress of SiC power devices.
Major challenges for fully unleashing the capabilities of SiC power devices are:
* Gate drive: SiC devices often require gate drive voltage levels that are different from their silicon counterparts and may be even unsymmetric, for example, +20 V and −5 V.
* Packaging: SiC chips may have a higher power density than silicon power devices and are able to handle higher temperatures exceeding the silicon limit of 150 °C. New die attach technologies such as sintering are required to efficiently get the heat out of the devices and ensure a reliable interconnection.
Beginning with Tesla Model 3 the inverters in the drive unit use 24 pairs of silicon carbide (SiC) MOSFET chips rated for 650 volts each. Silicon carbide in this instance gave Tesla a significant advantage over chips made of silicon in terms of size and weight. A number of automobile manufacturers are planning to incorporate silicon carbide into power electronic devices in their products. A significant increase in production of silicon carbide is projected, beginning with a large plant opened 2022 by Wolfspeed in upstate New York. | 1 | Applied and Interdisciplinary Chemistry |
The following, exact equation can be derived from an advection-diffusion equation (see below), with a diffusion term (D=0) of zero:
In parallel with the definition of the Lyapunov exponent, we define the matrix
, as follows:
It is easy to show that:
If we define as the squared lengths of the principal components of the tracer
gradient matrix, , then:
where the 's are arranged, as before, from largest to smallest.
Therefore,
growth in the error vector will cause a corresponding decrease in the tracer
gradient and vice versa. This can be understood very simply and intuitively by
considering two nearby points: since the difference in tracer concentration will
be fixed, the only source of variation in the gradients between them will be their
separation. | 1 | Applied and Interdisciplinary Chemistry |
Suppose that we have a sample consisting of 14 sheets described above, each one of which has an absorbance of 0.0222. If we are able to estimate the absorbing power (the absorbance of a sample of the same thickness, but having no scatter) from the sample without knowing how many sheets are in the sample (as would be the general case), it would have the desirable property of being proportional to the thickness. In this case, we know that the absorbing power (scatter corrected absorbance) should be: {14 x the absorbance of a single sheet} . This is the value we should have for the sample if the absorbance is to follow the law of Bouguer (often referred to as Beer's law).
In the Table below, we see that the sample has the A,R,T values for the case of 14 sheets in the Table above. Because of the presence of scatter, the measured absorbance of the sample would be: . Then we calculate this for the half sample thickness using another of Benford's equations. If , and are known for a layer with thickness , the ART fractions for a layer with thickness of are:
In the line for half sample [S/2], we see the values which are the same as those for 7 layers in the Table above, as we expect. Note that . We desire to have the absorbance be linear with sample thickness, but we find when we multiply this value by 2, we get , which is a significant departure from the previous estimate for the absorbing power.
The next iteration of the formula produces the estimate for A,R,T for a quarter sample: . Note that this time the calculation corresponds to three and a half layers, a thickness of sample that cannot exist physically.
Continuing for the sequentially higher powers of two, we see a monotonically increasing estimate. Eventually the numbers will start jumping with round off error, but one can stop when getting a constant value to a specified number of significant figures. In this case, we become constant to 4 significant figures at 0.3105, which is our estimate for the absorbing power of the sample. This corresponds to our target value of 0.312 determined above. | 0 | Theoretical and Fundamental Chemistry |
The number of workers in the United States exposed to beryllium vary but has been estimated to be as high as 800,000 during the 1960s and 1970s. A more recent study from 2004 estimated the number of exposed workers in the United States to be around 134,000.
The rate of workers becoming sensitized to beryllium varies based on genetics and exposure levels. In one study researchers found the prevalence of beryllium sensitization to range from 9–19% depending on the industry. Many workers who are found to be sensitive to beryllium also meet the diagnostic criteria for chronic beryllium disease. In one study of nuclear workers, among those who were sensitized to beryllium, 66% were found to have chronic beryllium disease as well. The rate of progression from beryllium sensitization to chronic beryllium disease has been estimated to be approximately 6–8% per year. Stopping exposure to beryllium in those sensitized has not been definitively shown to stop the progression to chronic beryllium disease.
The overall prevalence of chronic beryllium disease among workers exposed to beryllium has ranged from 1–5% depending on industry and time period of study.
The general population is unlikely to develop acute or chronic beryllium disease because ambient air levels of beryllium are normally very low (). However, a study found 1% of people living within 3/4 of a mile of a beryllium plant in Lorain, Ohio, had berylliosis after exposure to concentrations estimated to be less than 1 milligram per cubic metre of air. In the United States the Beryllium Case Registry contained 900 records, early cases relating to extraction and fluorescent lamp manufacture, later ones coming from the aerospace, ceramics and metallurgical industries. | 1 | Applied and Interdisciplinary Chemistry |
In terms of structure, GPCRs are characterized by an extracellular N-terminus, followed by seven transmembrane (7-TM) α-helices (TM-1 to TM-7) connected by three intracellular (IL-1 to IL-3) and three extracellular loops (EL-1 to EL-3), and finally an intracellular C-terminus. The GPCR arranges itself into a tertiary structure resembling a barrel, with the seven transmembrane helices forming a cavity within the plasma membrane that serves a ligand-binding domain that is often covered by EL-2. Ligands may also bind elsewhere, however, as is the case for bulkier ligands (e.g., proteins or large peptides), which instead interact with the extracellular loops, or, as illustrated by the class C metabotropic glutamate receptors (mGluRs), the N-terminal tail. The class C GPCRs are distinguished by their large N-terminal tail, which also contains a ligand-binding domain. Upon glutamate-binding to an mGluR, the N-terminal tail undergoes a conformational change that leads to its interaction with the residues of the extracellular loops and TM domains. The eventual effect of all three types of agonist-induced activation is a change in the relative orientations of the TM helices (likened to a twisting motion) leading to a wider intracellular surface and "revelation" of residues of the intracellular helices and TM domains crucial to signal transduction function (i.e., G-protein coupling). Inverse agonists and antagonists may also bind to a number of different sites, but the eventual effect must be prevention of this TM helix reorientation.
The structure of the N- and C-terminal tails of GPCRs may also serve important functions beyond ligand-binding. For example, The C-terminus of M muscarinic receptors is sufficient, and the six-amino-acid polybasic (KKKRRK) domain in the C-terminus is necessary for its preassembly with G proteins. In particular, the C-terminus often contains serine (Ser) or threonine (Thr) residues that, when phosphorylated, increase the affinity of the intracellular surface for the binding of scaffolding proteins called β-arrestins (β-arr). Once bound, β-arrestins both sterically prevent G-protein coupling and may recruit other proteins, leading to the creation of signaling complexes involved in extracellular-signal regulated kinase (ERK) pathway activation or receptor endocytosis (internalization). As the phosphorylation of these Ser and Thr residues often occurs as a result of GPCR activation, the β-arr-mediated G-protein-decoupling and internalization of GPCRs are important mechanisms of desensitization. In addition, internalized "mega-complexes" consisting of a single GPCR, β-arr(in the tail conformation), and heterotrimeric G protein exist and may account for protein signaling from endosomes.
A final common structural theme among GPCRs is palmitoylation of one or more sites of the C-terminal tail or the intracellular loops. Palmitoylation is the covalent modification of cysteine (Cys) residues via addition of hydrophobic acyl groups, and has the effect of targeting the receptor to cholesterol- and sphingolipid-rich microdomains of the plasma membrane called lipid rafts. As many of the downstream transducer and effector molecules of GPCRs (including those involved in negative feedback pathways) are also targeted to lipid rafts, this has the effect of facilitating rapid receptor signaling.
GPCRs respond to extracellular signals mediated by a huge diversity of agonists, ranging from proteins to biogenic amines to protons, but all transduce this signal via a mechanism of G-protein coupling. This is made possible by a guanine-nucleotide exchange factor (GEF) domain primarily formed by a combination of IL-2 and IL-3 along with adjacent residues of the associated TM helices. | 1 | Applied and Interdisciplinary Chemistry |
Control equations can also be derived by considering the effect of perturbations on the system. Consider that reaction rates and are determined by two enzymes and respectively. Changing either enzyme will result in a change to the steady state level of and the steady state reaction rates . Consider a small change in of magnitude . This will have a number of effects, it will increase which in turn will increase which in turn will increase . Eventually the system will settle to a new steady state. We can describe these changes by focusing on the change in and . The change in , which we designate , came about as a result of the change . Because we are only considering small changes we can express the change in terms of using the relation
where the derivative measures how responsive is to changes in . The derivative can be computed if we know the rate law for . For example, if we assume that the rate law is then the derivative is . We can also use a similar strategy to compute the change in as a result of the change . This time the change in is a result of two changes, the change in itself and the change in . We can express these changes by summing the two individual contributions:
We have two equations, one describing the change in and the other in . Because we allowed the system to settle to a new steady state we can also state that the change in reaction rates must be the same (otherwise it wouldn't be at steady state). That is we can assert that . With this in mind we equate the two equations and write
Solving for the ratio we obtain:
In the limit, as we make the change smaller and smaller, the left-hand side converges to the derivative :
We can go one step further and scale the derivatives to eliminate units. Multiplying both sides by and dividing both sides by yields the scaled derivatives:
The scaled derivatives on the right-hand side are the elasticities, and the scaled left-hand term is the scaled sensitivity coefficient or concentration control coefficient,
We can simplify this expression further. The reaction rate is usually a linear function of . For example, in the Briggs–Haldane equation, the reaction rate is given by . Differentiating this rate law with respect to and scaling yields .
Using this result gives:
A similar analysis can be done where is perturbed. In this case we obtain the sensitivity of with respect to :
The above expressions measure how much enzymes and control the steady state concentration of intermediate . We can also consider how the steady state reaction rates and are affected by perturbations in and . This is often of importance to metabolic engineers who are interested in increasing rates of production. At steady state the reaction rates are often called the fluxes and abbreviated to and . For a linear pathway such as this example, both fluxes are equal at steady-state so that the flux through the pathway is simply referred to as . Expressing the change in flux as a result of a perturbation in and taking the limit as before we obtain
The above expressions tell us how much enzymes and control the steady state flux. The key point here is that changes in enzyme concentration, or equivalently the enzyme activity, must be brought about by an external action. | 1 | Applied and Interdisciplinary Chemistry |
The presence or absence of certain plant or other vegetative life in an ecosystem can provide important clues about the health of the environment: environmental preservation. There are several types of plant biomonitors, including mosses, lichens, tree bark, bark pockets, tree rings, and leaves. As an example, environmental pollutants can be absorbed and incorporated into tree bark, which can then be analyzed to pollutant presence and concentration in the surrounding environment. The leaves of certain vascular plants experience harmful effects in the presence of ozone, particularly tissue damage, making them useful in detecting the pollutant. These plants are observed abundantly in Atlantic islands in the Northern Hemisphere, the Mediterranean Basin, equatorial Africa, Ethiopia, the Indian coastline, the Himalayan region, southern Asia, and Japan. These regions with high endemic richness are particularly vulnerable to ozone pollution, emphasizing the importance of certain vascular plant species as valuable indicators of environmental health in terrestrial ecosystems. Conservationists use such plant bioindicators as tools, allowing them to ascertain potential changes and damages to the environment.
As an example, Lobaria pulmonaria has been identified as an indicator species for assessing stand age and macrolichen diversity in Interior Cedar–Hemlock forests of east-central British Columbia, highlighting its ecological significance as a bioindicator. The abundance of Lobaria pulmonaria was strongly correlated with this increase in diversity, suggesting its potential as an indicator of stand age in the ICH. Another Lichen species, Xanthoria parietina, serves as a reliable indicator of air quality, effectively accumulating pollutants like heavy metals and organic compounds. Studies have shown that X. parietina samples collected from industrial areas exhibit significantly higher concentrations of these pollutants compared to those from greener, less urbanized environments. This highlights the lichen's valuable role in assessing environmental health and identifying areas with elevated pollution levels, aiding in targeted mitigation efforts and environmental management strategies.
Fungi is also useful as bioindicators, as they are found throughout the globe and undergo noticeable changes in different environments.
Lichens are organisms comprising both fungi and algae. They are found on rocks and tree trunks, and they respond to environmental changes in forests, including changes in forest structure – conservation biology, air quality, and climate. The disappearance of lichens in a forest may indicate environmental stresses, such as high levels of sulfur dioxide, sulfur-based pollutants, and nitrogen oxides.
The composition and total biomass of algal species in aquatic systems serve as an important metric for organic water pollution and nutrient loading such as nitrogen and phosphorus.
There are genetically engineered organisms that can respond to toxicity levels in the environment; e.g., a type of genetically engineered grass that grows a different colour if there are toxins in the soil. | 1 | Applied and Interdisciplinary Chemistry |
Angela Casini is a medicinal and inorganic chemist who works on metal-based compounds as therapeutic agents. She was awarded the 2012 European Medal for Bio-Inorganic Chemistry and made the 2019 American Chemical Society Inorganic Lecturer. | 0 | Theoretical and Fundamental Chemistry |
There are also several pyrometallurgical processes that reduce zinc oxide using carbon, then distil the metallic zinc from the resulting mix in an atmosphere of carbon monoxide. The major downfall of any of the pyrometallurgical process is that it is only 98% pure; a standard composition is 1.3% lead, 0.2% cadmium, 0.03% iron, and 98.5% zinc. This may be pure enough for galvanization, but not enough for die casting alloys, which requires special high-grade zinc (99.995% pure). In order to reach this purity the zinc must be refined.
The four types of commercial pyrometallurgical processes are the St. Joseph Minerals Corporations (electrothermic) process, the blast furnace process, the New Jersey Zinc continuous vertical-retort process, and the Belgian-type horizontal retort' process. | 1 | Applied and Interdisciplinary Chemistry |
The endocannabinoid system, broadly speaking, includes:
* The endogenous arachidonate-based lipids, anandamide (N-arachidonoylethanolamide) and 2-AG, besides other N-acylethanolamines (NAEs); these are known as "endocannabinoids" and are physiological ligands for the cannabinoid receptors. Endocannabinoids are all eicosanoids.
* The enzymes that synthesize and degrade the endocannabinoids, such as fatty acid amide hydrolase or monoacylglycerol lipase.
* The cannabinoid receptors CB and CB, two G protein-coupled receptors that are located in the central and peripheral nervous systems.
The neurons, neural pathways, and other cells where these molecules, enzymes, and one or both cannabinoid receptor types are all colocalized collectively comprise the endocannabinoid system.
The endocannabinoid system has been studied using genetic and pharmacological methods. These studies have revealed that cannabinoids act as neuromodulators for a variety of processes, including motor learning, appetite, and pain sensation, among other cognitive and physical processes. The localization of the CB1 receptor in the endocannabinoid system has a very large degree of overlap with the orexinergic projection system, which mediates many of the same functions, both physical and cognitive. Moreover, CB1 is colocalized on orexin projection neurons in the lateral hypothalamus and many output structures of the orexin system, where the CB1 and orexin receptor 1 (OX1) receptors physically and functionally join to form the CB1–OX1 receptor heterodimer. | 1 | Applied and Interdisciplinary Chemistry |
Many alcohols are produced by hydroxylation, i.e., the installation of a hydroxy group using oxygen or a related oxidant. Hydroxylation is the means by which the body processes many poisons, converting lipophilic compounds into hydrophilic derivatives that are more readily excreted. Enzymes called hydroxylases and oxidases facilitate these conversions.
Many industrial alcohols, such as cyclohexanol for the production of nylon, are produced by hydroxylation. | 0 | Theoretical and Fundamental Chemistry |
Mesocrystal is an abbreviation for mesoscopically structured crystal, where individual subunits often form a perfect 3D order, as in a traditional crystal where the subunits are individual atoms. | 0 | Theoretical and Fundamental Chemistry |
Amalgamated zinc is zinc that has been surface treated with mercury to form a surface amalgam containing little contamination from other elements. It is typically used for reduction, and is written as Zn(Hg) in reactions. | 0 | Theoretical and Fundamental Chemistry |
Some of the simplest reactive transport problems can be solved analytically. Where equilibrium sorption is described by a linear distribution coefficient, for example, the sorbing solute's velocity is retarded relative to that of a nonreactive tracer; the relative velocities can be described with a retardation factor. Analytical solutions are exact solutions of the governing equations.
Complex reactive transport problems are more commonly solved numerically. In this case, the governing equations are approximated so that they can be solved by computer algorithms. The governing equations, including both reaction and transport terms, can be solved simultaneously using a one-step or global implicit simulator. This technique is straightforward conceptually, but computationally very difficult.
Instead of solving all the relevant equations together, the transport and chemical reaction equations can be solved separately. Operator splitting, as this technique is known, uses appropriate numerical techniques to solve the reaction and transport equations at each time step. Various methods exist, including the sequential non-iterative approach (SNIA), Strang splitting, and sequential iterative approach (SIA). Since the reaction and transport terms are handled separately, separate programs for batch reaction and transport can be linked together. Cross-linkable re-entrant software objects designed for this purpose readily enable construction of reactive transport models of any flow configuration. | 0 | Theoretical and Fundamental Chemistry |
Prior to Kaminsky, titanium chlorides supported on various materials were widely used (and still are) as heterogeneous catalysts for alkene polymerization. These halides are typically activated by treatment with trimethylaluminium. Kaminsky discovered that titanocene and related complexes emulated some aspects of these Ziegler–Natta catalysts but with low activity. He subsequently found that high activity could be achieved upon activation of these metallocenes with methylaluminoxane (MAO). The MAO serves two roles: (i) alkylation of the metallocene halide and (ii) abstraction of an anionic ligand (chloride or methyl) to give an electrophilic catalyst with a labile coordination site. | 0 | Theoretical and Fundamental Chemistry |
Zanamivir can be found under tradenames such as Relenza™, Verenza and Z-Flu DPI.
Zanamivir is used for patients 5 years and older. It is given as one 10 mg dose, twice a day for the treatment of influenza. In the prevention of influenza, zanamivir is given as one 10 mg dose, once a day for 10 days after contacting with an infected person or up the 28 days (during influenza epidemic). The most common side effect of Zanamivir is reported to be rash. | 1 | Applied and Interdisciplinary Chemistry |
Consider the set of active centers (fig.1.). Assume fast transition between sublevels within each level, and slow transition between levels.
According to the McCumber hypothesis, the cross-sections and do not depend on the populations and .
Therefore, we can deduce the relation, assuming the thermal state.
Let be group velocity of light in the medium, the product is spectral rate of
stimulated emission, and is that of absorption; is spectral rate of spontaneous emission. (Note that in this approximation, there is no such thing as a spontaneous absorption)
The balance of photons gives:
Which can be rewritten as
The thermal distribution of density of photons follows from blackbody radiation
Both (4) and (5) hold for all frequencies . For the case of idealized two-level active centers, , and , which leads to the relation between the spectral rate of spontaneous emission and the emission cross-section . (We keep the term probability of emission for the quantity , which is probability of emission of a photon within small spectral interval during a short time interval , assuming that at time the atom is excited.) The relation (D2) is a fundamental property of spontaneous and stimulated emission, and perhaps the only way to prohibit a spontaneous break of the thermal equilibrium in the thermal state of excitations and photons.
For each site number , for each sublevel number , the partial spectral emission probability can be expressed from consideration of idealized two-level atoms:
Neglecting the cooperative coherent effects, the emission is additive: for any concentration of sites and for any partial population of sublevels, the same proportionality between and holds for the effective cross-sections:
Then, the comparison of (D1) and (D2) gives the relation
This relation is equivalent of the McCumber relation (mc), if we define the zero-line frequency as solution of equation
the subscript indicates that the ratio of populations in evaluated in the thermal state. The zero-line frequency can be expressed as
Then (n1n2) becomes equivalent of the McCumber relation (mc).
No specific property of sublevels of active medium is required to keep the McCumber relation. It follows from the assumption about quick transfer of energy among excited laser levels and among lower laser levels. The McCumber relation (mc) has the same range of validity as the concept of the emission cross-section
itself. | 0 | Theoretical and Fundamental Chemistry |
Silver being in the same group as copper, Pd–Ag(I) bimetallic systems are inherently similar to Pd–Cu catalytic systems. However, silver salts are better suited for protodecarboxylation of carboxylic acids than their copper equivalents, allowing milder reaction conditions in Pd–Ag cycles relative to Pd–Cu cycles.
Ag(I) catalyzed monometallic systems have also been reported. Their proficiency (relative to copper) is likely attributed to lower electronegativity and greater expansion of d-orbitals, which promote decarboxylation of the substrate.
One limitation of this catalyst combination is that the silver salts will form insoluble silver halides, forcing the reaction to require a stoichiometric amount of Ag if halides are present. This obstacle was overcome by Goossen et al. in 2010 by using aryl triflates, and catalytic reaction with aryl sulfonates has also been reported. | 0 | Theoretical and Fundamental Chemistry |
#Anthocyanin pigments are assembled like all other flavonoids from two different streams of chemical raw materials in the cell:
#* One stream involves the shikimate pathway to produce the amino acid phenylalanine, (see phenylpropanoids)
#* The other stream produces three molecules of malonyl-CoA, a C unit from a C unit (acetyl-CoA),
#These streams meet and are coupled together by the enzyme chalcone synthase, which forms an intermediate chalcone-like compound via a polyketide folding mechanism that is commonly found in plants,
#The chalcone is subsequently isomerized by the enzyme chalcone isomerase to the prototype pigment naringenin,
#Naringenin is subsequently oxidized by enzymes such as flavanone hydroxylase, flavonoid 3-hydroxylase, and flavonoid 3,5'-hydroxylase,
#These oxidation products are further reduced by the enzyme dihydroflavonol 4-reductase to the corresponding colorless leucoanthocyanidins,
#Leucoanthocyanidins once were believed to be the immediate precursors of the next enzyme, a dioxygenase referred to as anthocyanidin synthase, or, leucoanthocyanidin dioxygenase. Flavan-3-ols, the products of leucoanthocyanidin reductase (LAR), recently have been shown to be their true substrates,
#The resulting unstable anthocyanidins are further coupled to sugar molecules by enzymes such as UDP-3-O-glucosyltransferase, to yield the final relatively-stable anthocyanins.
Thus, more than five enzymes are required to synthesize these pigments, each working in concert. Even a minor disruption in any of the mechanisms of these enzymes by either genetic or environmental factors, would halt anthocyanin production. While the biological burden of producing anthocyanins is relatively high, plants benefit significantly from the environmental adaptation, disease tolerance, and pest tolerance provided by anthocyanins.
In anthocyanin biosynthetic pathway, -phenylalanine is converted to naringenin by phenylalanine ammonialyase, cinnamate 4-hydroxylase, 4-coumarate CoA ligase, chalcone synthase, and chalcone isomerase. Then, the next pathway is catalyzed, resulting in the formation of complex aglycone and anthocyanin through composition by flavanone 3-hydroxylase, flavonoid 3'-hydroxylase, dihydroflavonol 4-reductase, anthocyanidin synthase, UDP-glucoside: flavonoid glucosyltransferase, and methyl transferase. | 0 | Theoretical and Fundamental Chemistry |
Oceanic and atmospheric currents transfer particles, debris, and organisms all across the globe. While the transport of organisms, such as phytoplankton, are essential for the preservation of ecosystems, oil and other pollutants are also mixed in the current flow and can carry pollution far from its origin. Eddy formations circulate trash and other pollutants into concentrated areas which researchers are tracking to improve clean-up and pollution prevention. The distribution and motion of plastics caused by eddy formations in natural water bodies can be predicted using Lagrangian transport models. Mesoscale ocean eddies play crucial roles in transferring heat poleward, as well as maintaining heat gradients at different depths. | 1 | Applied and Interdisciplinary Chemistry |
Another commonly considered model is the heat pump or refrigerator. Again there are four bodies: the working body, the hot reservoir, the cold reservoir, and the work reservoir. A single cycle starts with the working body colder than the cold reservoir, and then energy is taken in as heat by the working body from the cold reservoir. Then the work reservoir does work on the working body, adding more to its internal energy, making it hotter than the hot reservoir. The hot working body passes heat to the hot reservoir, but still remains hotter than the cold reservoir. Then, by allowing it to expand without passing heat to another body, the working body is made colder than the cold reservoir. It can now accept heat transfer from the cold reservoir to start another cycle.
The device has transported energy from a colder to a hotter reservoir, but this is not regarded as by an inanimate agency; rather, it is regarded as by the harnessing of work . This is because work is supplied from the work reservoir, not just by a simple thermodynamic process, but by a cycle of thermodynamic operations and processes, which may be regarded as directed by an animate or harnessing agency. Accordingly, the cycle is still in accord with the second law of thermodynamics. The efficiency of a heat pump (which exceeds unity) is best when the temperature difference between the hot and cold reservoirs is least.
Functionally, such engines are used in two ways, distinguishing a target reservoir and a resource or surrounding reservoir. A heat pump transfers heat to the hot reservoir as the target from the resource or surrounding reservoir. A refrigerator transfers heat, from the cold reservoir as the target, to the resource or surrounding reservoir. The target reservoir may be regarded as leaking: when the target leaks heat to the surroundings, heat pumping is used; when the target leaks coldness to the surroundings, refrigeration is used. The engines harness work to overcome the leaks. | 0 | Theoretical and Fundamental Chemistry |
The van Deemter equation relates height equivalent to a theoretical plate (HETP) of a chromatographic column to the various flow and kinetic parameters which cause peak broadening, as follows:
Where
* HETP = a measure of the resolving power of the column [m]
* A = Eddy-diffusion parameter, related to channeling through a non-ideal packing [m]
* B = diffusion coefficient of the eluting particles in the longitudinal direction, resulting in dispersion [m s]
* C = Resistance to mass transfer coefficient of the analyte between mobile and stationary phase [s]
* u = speed [m s]
In open tubular capillaries, the A term will be zero as the lack of packing means channeling does not occur. In packed columns, however, multiple distinct routes ("channels") exist through the column packing, which results in band spreading. In the latter case, A will not be zero.
The form of the Van Deemter equation is such that HETP achieves a minimum value at a particular flow velocity. At this flow rate, the resolving power of the column is maximized, although in practice, the elution time is likely to be impractical. Differentiating the van Deemter equation with respect to velocity, setting the resulting expression equal to zero, and solving for the optimum velocity yields the following: | 0 | Theoretical and Fundamental Chemistry |
The quantum fluctuations of the electromagnetic field have important physical consequences. In addition to the Casimir effect, they also lead to a splitting between the two energy levels and (in term symbol notation) of the hydrogen atom which was not predicted by the Dirac equation, according to which these states should have the same energy. Charged particles can interact with the fluctuations of the quantized vacuum field, leading to slight shifts in energy; this effect is called the Lamb shift. The shift of about is roughly of the difference between the energies of the 1s and 2s levels, and amounts to 1,058 MHz in frequency units. A small part of this shift (27 MHz ≈ 3%) arises not from fluctuations of the electromagnetic field, but from fluctuations of the electron–positron field. The creation of (virtual) electron–positron pairs has the effect of screening the Coulomb field and acts as a vacuum dielectric constant. This effect is much more important in muonic atoms. | 0 | Theoretical and Fundamental Chemistry |
*Missing top fluorides:
**PrF (because it decomposes at 90 °C)
**TbF (because it decomposes at 300 °C)
**CeF (because it decomposes at 600 °C)
*Without stable fluorides: Kr | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, stagnation pressure is the static pressure at a stagnation point in a fluid flow. At a stagnation point the fluid velocity is zero. In an incompressible flow, stagnation pressure is equal to the sum of the free-stream static pressure and the free-stream dynamic pressure.
Stagnation pressure is sometimes referred to as pitot pressure because the two pressures are numerically equal. | 1 | Applied and Interdisciplinary Chemistry |
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