text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
TALEN can be used to edit genomes by inducing double-strand breaks (DSB), which cells respond to with repair mechanisms.
Non-homologous end joining (NHEJ) directly ligates DNA from either side of a double-strand break where there is very little or no sequence overlap for annealing. This repair mechanism induces errors in the genome via indels (insertion or deletion), or chromosomal rearrangement; any such errors may render the gene products coded at that location non-functional. Because this activity can vary depending on the species, cell type, target gene, and nuclease used, it should be monitored when designing new systems. A simple heteroduplex cleavage assay can be run which detects any difference between two alleles amplified by PCR. Cleavage products can be visualized on simple agarose gels or slab gel systems.
Alternatively, DNA can be introduced into a genome through NHEJ in the presence of exogenous double-stranded DNA fragments.
Homology directed repair can also introduce foreign DNA at the DSB as the transfected double-stranded sequences are used as templates for the repair enzymes. | 1 | Applied and Interdisciplinary Chemistry |
* Amino acid-based surfactants are surfactants derived from an amino acid. Their properties vary and can be either anionic, cationic, or zwitterionic, depending on the amino acid used and which part of the amino acid is condensed with the alkyl/aryl chain.
* Gemini surfactants consist of two surfactant molecules linked together at or near their head groups. Compared to monomeric surfactants, they have much lower critical micelle concentrations. | 0 | Theoretical and Fundamental Chemistry |
Eco pickled surface technology has been tested and approved for use as a replacement for acid pickled steel by automotive manufacturers General Motors and Chrysler. The Eco Pickled Surface process was a finalist in the 2013 American Metal Market (AMM) Awards for Steel Excellence. | 1 | Applied and Interdisciplinary Chemistry |
Coral is a calcifying organism, putting it at high risk for decay and slow growth rates as ocean acidification increases. Aragonite assists the coral as they build their skeletons because it is another form of calcium carbonate (CaCO) that is more soluble. When the pH of the water decreases, aragonite decreases as well, leading to the loss of calcium carbonate uptake in corals. Levels of aragonite have decreased by 16% since industrialization and could be lower in some portions of the Great Barrier Reef due to the current, which allows northern corals to take up more aragonite than southern corals. Aragonite is predicted to reduce by 0.1 by 2100 which could greatly hinder coral growth. Since 1990, calcification rates of Porites, a common large reef-building coral in the Great Barrier Reef, have decreased by 14.2% annually. Aragonite levels across the Great Barrier Reef itself are not equal; due to currents and circulation, some portions of the Great Barrier Reef can have half as much aragonite as others. Levels of aragonite are also affected by calcification and production, which can vary from reef to reef.If atmospheric carbon dioxide reaches 560 ppm, most ocean surface waters will be adversely undersaturated with respect to aragonite, and the pH will have reduced by about 0.24 units, from almost 8.2 today to just over 7.9. At this point (sometime in the third quarter of this century, at current rates of carbon dioxide increase), only a few parts of the Pacific will have levels of aragonite saturation adequate for coral growth. Additionally, if atmospheric carbon dioxide reaches 800 ppm, the ocean surface water pH decrease will be 0.4 units, and the total dissolved carbonate ion concentration will have decreased by at least 60%. Recent estimates state that with business-as-usual emission levels, the atmospheric carbon dioxide could reach 800 ppm by the year 2100. At this point, it is almost certain that all the reefs in the world will be in erosional states. Increasing the pH and replicating pre-industrialization ocean chemistry conditions in the Great Barrier Reef, however, led to an increase in coral growth rates of 7%. | 0 | Theoretical and Fundamental Chemistry |
Magnetorheological dampers of various applications have been and continue to be developed. These dampers are mainly used in heavy industry with applications such as heavy motor damping, operator seat/cab damping in construction vehicles, and more.
As of 2006, materials scientists and mechanical engineers are collaborating to develop stand-alone seismic dampers which, when positioned anywhere within a building, will operate within the building's resonance frequency, absorbing detrimental shock waves and oscillations within the structure, giving these dampers the ability to make any building earthquake-proof, or at least earthquake-resistant. | 1 | Applied and Interdisciplinary Chemistry |
The gag-onc fusion protein is a general term for a fusion protein formed from a group-specific antigen (gag) gene and that of an oncogene (onc), a gene that plays a role in the development of a cancer. The name is also written as Gag-v-Onc, with "v" indicating that the Onc sequence resides in a viral genome. Onc is a generic placeholder for a given specific oncogene, such as C-jun. (In the case of a fusion with C-jun, the resulting "gag-jun" protein is known alternatively as p65). | 1 | Applied and Interdisciplinary Chemistry |
The ambush hypothesis is a hypothesis in the field of molecular genetics that suggests that the prevalence of “hidden” or off-frame stop codons in DNA selectively deters off-frame translation of mRNA to save energy, molecular resources, and to reduce strain on biosynthetic machinery by truncating the production of non-functional, potentially cytotoxic protein products. Typical coding sequences of DNA lack in-frame internal stop codons to avoid the premature reduction of protein products when translation proceeds normally. The ambush hypothesis suggests that kinetic, cis-acting mechanisms are responsible for the productive frameshifting of translational units so that the degeneracy of the genetic code can be used to prevent deleterious translation. Ribosomal slippage is the most well described mechanism of translational frameshifting where the ribosome moves one codon position either forward (+1) or backward (-1) to translate the mRNA sequence in a different reading frame and thus produce different protein products.
In respect to codon usage, the ambush hypothesis theorizes that there is a positive correlation between the use of a codon and the amount a codon contributes to hidden stops. Phylogenetic analyses of both the nuclear and mitochondrial genomes of all major taxonomic kingdoms suggests ubiquitous off-frame stop codon existence and a positive correlation between the usage frequency of a codon and the number of ways a codon can contribute to hidden stop codons in different translational reading frames.
Combinatorics have been used across genetic codes to determine how each in-frame codon can potentially contribute to stop codons in off-frame contexts. The standard genetic code only contains 20 codons that cannot become stop codons in a frameshifted ribosomal environment (-1 frameshift: 42, +1 frameshift: 28) and 127 out of the 400 (31.75%) possible adjacent amino acid combinations in the vertebrate mitochondrial code creates an off-frame stop codon. This suggests that substitutions and synonymous codon usage are not neutral and that selective pressures might have readjusted codon assignments to increase the frequencies of those that can be used as hidden stops.
Observations that the number of off-frame stop codons is positively correlated with the expression level of a gene support the ambush hypothesis by increasing translational regulation (hidden stop frequency) to discourage off-frame reading in genes that are expressed at a high level. The positive correlation indicates that the off-frame translation of larger genes with higher expression levels likely costs a cell more energy, resources, and pathway efficiency than translating smaller, more rare genes in a shifted reading frame. Off-frame stop codon frequency is negatively correlated with gestation time in primates and though there are many factors that link molecular translational efficiency to the rate of morphogenesis, these findings suggests that not only individual cells but entire organisms may benefit from the development of hidden stop codons to effectively halt off-frame synthesis.
The ambush hypothesis is challenged by recent observations that off-frame stop codons are directly correlated with the GC content in the genome because stop codons are GC-poor. [http://www.biomedcentral.com/1471-2164/14/418 Morgens et al. 2013] argues that previous research concerning the ambush hypothesis has relied on codon usage data which is representative of the GC content of an organism and thus not appropriate to evaluate the selective effect of off-frame stop codons. | 1 | Applied and Interdisciplinary Chemistry |
Branched chain fatty acids are usually saturated and are found in two distinct families: the iso-series and anteiso-series. It has been found that Actinomycetales contain unique branch-chain fatty acid synthesis mechanisms, including that which forms tuberculosteric acid. | 1 | Applied and Interdisciplinary Chemistry |
PDRCs can be broadband in their thermal emittance capacity, meaning they possess high emittance in both the solar spectrum and atmospheric LWIR window (8 to 14 μm), or selective emitters, meaning they narrowband emit longwave infrared radiation only in the infrared window.
In theory, selective thermal emitters can achieve higher cooling power. However, selective emitters also face additional challenges in real-world applications that can weaken their performance, such as from dropwise condensation, which is common even in semi-arid environments, that can accumulate on the PDRC surface even when it has been made hydrophobic and alter the narrowband emission. Broadband emitters also outperform selective materials when "the material is warmer than the ambient air, or when its sub-ambient surface temperature is within the range of several degrees."
Both emitters can be advantageous for different types of applications. Broadband emitters may be less problematic for horizontal applications, such as on roofs, whereas selective emitters may be more useful if implemented on vertical surfaces like building facades, where dropwise condensation is inconsequential and their stronger cooling power can be actualized.
Broadband emitters can be made angle-dependent to potentially enhance their cooling performance. Polydimethylsiloxane (PDMS) is a common broadband emitter used for PDRC. Most PDRC materials are broadband primarily credited to their lower cost and higher performance at above-ambient temperatures. | 0 | Theoretical and Fundamental Chemistry |
A deformation mechanism map is a way of representing the dominant deformation mechanism in a material loaded under a given set of conditions. The technique is applicable to all crystalline materials, metallurgical as well as geological. Additionally, work has been conducted regarding the use of deformation maps to nanostructured or very fine grain materials. Deformation mechanism maps usually consist of some kind of stress plotted against some kind of temperature axis, typically stress normalized using the shear modulus versus homologous temperature with contours of strain rate. The normalized shear stress is plotted on a log scale. While plots of normalized shear stress vs. homologous temperature are most common, other forms of deformation mechanism maps include shear strain rate vs. normalized shear stress and shear strain rate vs. homologous temperature. Thus deformation maps can be constructed using any two of stress (normalized), temperature (normalized), and strain rate, with contours of the third variable. A stress/strain rate plot is useful because power-law mechanisms then have contours of temperature which are straight lines.
For a given set of operating conditions, calculations are conducted and experiments performed to determine the predominant mechanism operative for a given material. Constitutive equations for the type of mechanism have been developed for each deformation mechanism and are used in the construction of the maps. The theoretical shear strength of the material is independent of temperature and located along the top of the map, with the regimes of plastic deformation mechanisms below it. Constant strain rate contours can be constructed on the maps using the constitutive equations of the deformation mechanisms which makes the maps extremely useful. | 1 | Applied and Interdisciplinary Chemistry |
Thymidine diphosphate (TDP) or deoxythymidine diphosphate (dTDP) (also thymidine pyrophosphate, dTPP) is a nucleotide diphosphate. It is an ester of pyrophosphoric acid with the nucleoside thymidine. dTDP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase thymine. Unlike the other deoxyribonucleotides, thymidine diphosphate does not always contain the "deoxy" prefix in its name. | 1 | Applied and Interdisciplinary Chemistry |
The signal generated by probe modulation is much smaller than the original pump beam, so the two are spectrally separated within the detection path using a dichroic mirror. The probe signal can be collected with many different types of photodetectors, typically a photodiode. Then, the modulated signal is amplified using a lock-in amplifier tuned to the pump modulation frequency. | 0 | Theoretical and Fundamental Chemistry |
This area of study has recently gained more importance due to the increasing evidence that post-transcriptional regulation plays a larger role than previously expected. Even though protein with DNA binding domains are more abundant than protein with RNA binding domains, a recent study by Cheadle et al. (2005) showed that during T-cell activation 55% of significant changes at the steady-state level had no corresponding changes at the transcriptional level, meaning they were a result of stability regulation alone.
Furthermore, RNA found in the nucleus is more complex than that found in the cytoplasm: more than 95% (bases) of the RNA synthesized by RNA polymerase II never reaches the cytoplasm. The main reason for this is due to the removal of introns which account for 80% of the total bases. Some studies have shown that even after processing the levels of mRNA between the cytoplasm and the nucleus differ greatly.
Developmental biology is a good source of models of regulation, but due to the technical difficulties it was easier to determine the transcription factor cascades than regulation at the RNA level. In fact several key genes such as nanos are known to bind RNA but often their targets are unknown. Although RNA binding proteins may regulate post transcriptionally large amount of the transcriptome, the targeting of a single gene is of interest to the scientific community for medical reasons, this is RNA interference and microRNAs which are both examples of posttranscriptional regulation, which regulate the destruction of RNA and change the chromatin structure. To study post-transcriptional regulation several techniques are used, such as RIP-Chip (RNA immunoprecipitation on chip). | 1 | Applied and Interdisciplinary Chemistry |
Several studies have suggested that vanillin can affect the performance of antibiotics in laboratory conditions. | 0 | Theoretical and Fundamental Chemistry |
Carbonic anhydrase-related protein is a protein that in humans is encoded by the CA8 gene. The CA8 protein lacks the catalytic activity of other carbonic anhydrase enzymes. A rare, autosomal recessive form of cerebellar ataxia known as "cerebellar ataxia, mental retardation, and dysequilibrium syndrome 3" (CAMRQ3) is caused by mutations in the CA8 gene. | 1 | Applied and Interdisciplinary Chemistry |
A solar fuel is a synthetic chemical fuel produced from solar energy.
Solar fuels can be produced through photochemical (i.e. activation of certain chemical reactions by photons), photobiological (i.e., artificial photosynthesis), and electrochemical reactions (i.e. using the electricity from solar panels to drive a chemical reaction).
Solar fuels can also be produced by thermochemical reactions (i.e., through the use of solar heat supplied by concentrated solar thermal energy to drive a chemical reaction).
Light is used as an energy source, with solar energy being transduced to chemical energy, typically by reducing protons to hydrogen, or carbon dioxide to organic compounds.
A solar fuel can be produced and stored for later use, when sunlight is not available, making it an alternative to fossil fuels and batteries. Examples of such fuels are hydrogen, ammonia, and hydrazine.
Diverse photocatalysts are being developed to carry these reactions in a sustainable, environmentally friendly way. | 0 | Theoretical and Fundamental Chemistry |
Although not usually isolated as such, the salt ammonium carbamate is produced on a large scale as an intermediate in the production of the commodity chemical urea from ammonia and carbon dioxide. | 0 | Theoretical and Fundamental Chemistry |
Giuseppe Resnati (born 26 August 1955) is an Italian chemist with interests in supramolecular chemistry and fluorine chemistry. He has a particular focus on self-assembly processes driven by halogen bonds and chalcogen bonds. | 0 | Theoretical and Fundamental Chemistry |
Fast hole drilling EDM was designed for producing fast, accurate, small, deep holes. It is conceptually akin to sinker EDM but the electrode is a rotating tube conveying a pressurized jet of dielectric fluid. It can make a hole an inch deep in about a minute and is a good way to machine holes in materials too hard for twist-drill machining. This EDM drilling type is used largely in the aerospace industry, producing cooling holes into aero blades and other components. It is also used to drill holes in industrial gas turbine blades, in molds and dies, and in bearings. | 1 | Applied and Interdisciplinary Chemistry |
Low-impact development (LID) is a term used in Canada and the United States to describe a land planning and engineering design approach to manage stormwater runoff as part of green infrastructure. LID emphasizes conservation and use of on-site natural features to protect water quality. This approach implements engineered small-scale hydrologic controls to replicate the pre-development hydrologic regime of watersheds through infiltrating, filtering, storing, evaporating, and detaining runoff close to its source. Green infrastructure investments are one approach that often yields multiple benefits and builds city resilience.
Broadly equivalent terms used elsewhere include Sustainable drainage systems (SuDS) in the United Kingdom (where LID has a different meaning), water-sensitive urban design (WSUD) in Australia, natural drainage systems in Seattle, Washington, "Environmental Site Design" as used by the Maryland Department of the Environment, and "Onsite Stormwater Management", as used by the Washington State Department of Ecology. | 1 | Applied and Interdisciplinary Chemistry |
The Society has hosted scientific technical meetings since 1902 including its biannual meetings in the spring and fall of each year. The ECS biannual meetings bring together the most active researchers in academia, government, and industry—both professionals and students—to engage, discuss, and innovate in the areas of electrochemistry solid-state science, and related technology. They are a premier destination—in person or online—for industry professionals to experience five days of learning, technical presentations, business development, and networking. ECS also sponsors meetings for other renowned scientific organizations including the Storage X International Symposium Series, the International Meeting on Chemical Sensors, and the International Symposium on Solid Oxide Fuel Cells. | 0 | Theoretical and Fundamental Chemistry |
Once a theory is formulated, its validity must be tested, that is, compare its predictions with the results of the experiments.
When the expression form of the rate constant is compared with the rate equation for an elementary bimolecular reaction, , it is noticed that
unit M⋅s (= dm⋅mol⋅s), with all dimension unit dm including k.
This expression is similar to the Arrhenius equation and gives the first theoretical explanation for the Arrhenius equation on a molecular basis. The weak temperature dependence of the preexponential factor is so small compared to the exponential factor that it cannot be measured experimentally, that is, "it is not feasible to establish, on the basis of temperature studies of the rate constant, whether the predicted T dependence of the preexponential factor is observed experimentally". | 0 | Theoretical and Fundamental Chemistry |
In the next phase (Scheme 2), starting from ketal 12, the cyclohexane ring was cleaved to provide two anchoring points for fusion with the A ring. Alcohol 12 was protected by a benzyl group. The acetonide protecting group was removed from the ketone. Ketone 14 was converted to silyl enol ether 15 by reaction with trimethylsilyl triflate, and a modified Rubottom oxidation using 3,3-dimethyldioxirane followed by a treatment with camphorsulfonic acid introduced a hydroxyl group alpha to the ketone. Ring opening by oxidative cleavage with lead tetraacetate in methanol gave compound 17. In the next step, the aldehyde was protected as a dimethyl acetal, and the ester was reduced to give primary alcohol 18. The hydroxyl group was converted in a Grieco elimination to the selenide (19), which on oxidation with hydrogen peroxide gave alkene 20. Ozonolysis with ozone and triphenylphosphine provided aldehyde 21. | 0 | Theoretical and Fundamental Chemistry |
The final section of the guidelines involves information on how the analysis of the qPCR data was done. The essential parts of that include the program and program version used for the analysis, the method for how the Cq was determined, figuring out the outlier points in the data and how they are used or excluded and why, what results were found for the controls with no template genetic material, an explanation for why the reference genes used were chosen and why the number of them was chosen, the method used to normalize the data, how many technical replicates were included, how repeatable was the data within the assays, what methods were used to determine significance of the results, and what software was used for this part of the qualitative analysis.
It is also desired to include information on the number of biological replicates and whether they matched the results from the technical replicates, the reproducibility data for the concentration variants, data on the power analysis, and lastly for the researchers to submit the raw data in the RDML file format. | 1 | Applied and Interdisciplinary Chemistry |
In uncompetitive inhibition the inhibitor binds only to the enzyme-substrate complex. This type of inhibition causes V to decrease (maximum velocity decreases as a result of removing activated complex) and K to decrease (due to better binding efficiency as a result of Le Chateliers principle and the effective elimination of the ES complex thus decreasing the K' which indicates a higher binding affinity). Uncompetitive inhibition is rare. | 1 | Applied and Interdisciplinary Chemistry |
Additive effect in pharmacology describes the situation when the combining effects of two drugs equal the sum of the effects of the two drugs acting independently. The concept of additive effect is derived from the concept of synergy. It was introduced by the scientists in pharmacology and biochemistry fields in the process of understanding the synergistic interaction between drugs and chemicals over the century.
Additive effect often occurs when two similar drugs are taken together to achieve the same degree of therapeutic effect while reducing the specific adverse effect of one particular drug. For example, aspirin, paracetamol, and caffeine are formulated together to treat pain caused by tension headaches and migraine.
Additive effect can be used to detect synergy as it can be considered as the baseline effect in methods determining whether drugs have synergistic effect. Synergistic effect is similar to additive effect, having a combination effect greater than additive effect. It can produce an effect of 2+2 > 4 when two drugs are used together. Additive effect can also be found in a majority of combination therapies, although synergistic effect is more common. If the combination of two drugs in combination therapy has an effect lower than the sum of the effects of the two drugs acting independently, also known as antagonistic effect, the drugs will seldom be prescribed together in the same therapy.
Drug or chemical combinations with additive effects can cause adverse effects. For example, co-administration of non-steroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids increases the risk of gastric bleeding. | 1 | Applied and Interdisciplinary Chemistry |
Space stations transmitting solar power have appeared in science-fiction works like Isaac Asimovs "Reason" (1941), that centers around the troubles caused by the robots operating the station. Asimovs short story "The Last Question" also features the use of SBSP to provide limitless energy for use on Earth.
Erc Kotani and John Maddox Robertss 2000 novel The Legacy of Prometheus' posits a race between several conglomerates to be
the first to beam down a gigawatt of energy from a solar satellite in geosynchronous orbit.
In Ben Bovas novel PowerSat (2005), an entrepreneur strives to prove that his companys nearly completed power satellite and spaceplane (a means of getting maintenance crews to the satellite efficiently) are both safe and economically viable, while terrorists with ties to oil producing nations attempt to derail these attempts through subterfuge and sabotage.
Various aerospace companies have also showcased imaginative future solar power satellites in their corporate vision videos, including Boeing, Lockheed Martin, and United Launch Alliance.
The solar satellite is one of three means of producing energy in the browser-based game OGame. The city building game SimCity 2000 also features a Microwave Power Plant.
In the 1978 anime TV series Future Boy Conan, SBSP enables the country of Industria to develop geomagnetic weapons, more powerful than nuclear weapons, that destroy entire continents. | 0 | Theoretical and Fundamental Chemistry |
Capillary action (sometimes called capillarity, capillary motion, capillary rise, capillary effect, or wicking) is the process of a liquid flowing in a narrow space in opposition to or at least without the assistance of any external forces like gravity.
The effect can be seen in the drawing up of liquids between the hairs of a paint-brush, in a thin tube such as a straw, in porous materials such as paper and plaster, in some non-porous materials such as sand and liquefied carbon fiber, or in a biological cell.
It occurs because of intermolecular forces between the liquid and surrounding solid surfaces. If the diameter of the tube is sufficiently small, then the combination of surface tension (which is caused by cohesion within the liquid) and adhesive forces between the liquid and container wall act to propel the liquid. | 0 | Theoretical and Fundamental Chemistry |
Lotka underscored the centrality of available energy in the struggle for survival and evolution. By asserting that organisms with more efficient energy-capturing mechanisms gain an advantage, Lotka essentially aligned with the MPP. The MPP posits that biological systems, like any other complex systems, tend to evolve in ways that maximize their power intake or energy flux. In this context, organisms that effectively capture and utilize energy resources are more likely to thrive and propagate, driving evolutionary processes. Lotkas observation provides an early theoretical foundation for understanding the role of energy dynamics in biological evolution.Odums proposition of linking Darwinian natural selection with the fourth law of thermodynamics is significant. It suggests that the principles governing biological evolution are intimately connected with those of thermodynamics, particularly the concepts of energy flow and entropy production. By considering natural selection as a thermodynamic process, Odum implies that organisms evolve traits and behaviors that enhance their energy capture and utilization, consistent with the MPP. Furthermore, by emphasizing the regulation of heat generation and efficiency in biological processes, Odum highlights the importance of optimizing energy utilization for survival and reproduction, echoing the principles of the MPP.Odum's advocacy for recognizing the MPP as the fourth thermodynamic law represents a culmination of earlier insights into the relationship between thermodynamics and biology. By elevating the MPP to the status of a fundamental thermodynamic law, Odum underscores its universal applicability across various complex systems, including biological ones. This perspective emphasizes that biological systems, driven by the imperatives of survival and reproduction, tend to evolve in ways that maximize their power output, thereby enhancing their capacity to exploit available energy resources. By acknowledging the MPP as a governing principle, Odum highlights its explanatory power in understanding ecosystem dynamics, population interactions, and evolutionary trajectories. | 0 | Theoretical and Fundamental Chemistry |
The Thai Institute of Chemical Engineering and Applied Chemistry (TIChE) () is a professional organization for chemical engineers. TIChE was established in 1996 to distinguish chemical engineers as a profession independent of chemists and mechanical engineers. | 1 | Applied and Interdisciplinary Chemistry |
Needham and Lus first explanation is that many alchemical mineral preparations were capable of giving an "initial exhilaration" or transient sense of well-being, usually involving weight loss and increased libido. These preliminary tonic effects could have acted as a kind of "bait" inveigling an elixir-taker deeper into substance intoxication, even to the point of death. Chinese medical texts recorded that realgar (arsenic disulphide) and orpiment (arsenic trisulphide) were aphrodisiacs and stimulated fertility, while cinnabar and sulphur elixirs increased longevity, averted hunger, and "lightened the body" (namely, qīngshēn' 輕身, which is a common description of elixir effects).
Wine, as mentioned above, was both prescribed to be drunk when taking elixir pills and to relieve the unpleasant side-effects of elixir poisoning. Needham and Lu further suggest the possibility that elixir alchemy included hallucinogenic drugs, tentatively identifying the busi zhi yao 不死之藥 "drug of deathlessness" as fly-agaric and busi zhi shu 不死之樹 "tree of deathlessness" as birch. The elixir that Tao Hongjing's disciple Zhou Ziliang took to commit suicide "probably had hallucinogenic and toxic mushrooms". In the present day, realgar wine is traditionally consumed as part of the Dragon Boat Festival. | 1 | Applied and Interdisciplinary Chemistry |
Gradation is usually specified for each engineering application it is used for. For example, foundations might only call for coarse aggregates, and therefore an open gradation is needed.
Sieve analysis determines the particle size distribution of a given soil sample and hence helps in easy identification of a soil's mechanical properties. These mechanical properties determine whether a given soil can support the proposed engineering structure. It also helps determine what modifications can be applied to the soil and the best way to achieve maximum soil strength. | 1 | Applied and Interdisciplinary Chemistry |
Enantioselective catalysis (known traditionally as "asymmetric catalysis") is performed using chiral catalysts, which are typically chiral coordination complexes. Catalysis is effective for a broader range of transformations than any other method of enantioselective synthesis. The chiral metal catalysts are almost invariably rendered chiral by using chiral ligands, but it is possible to generate chiral-at-metal complexes composed entirely of achiral ligands.
Most enantioselective catalysts are effective at low substrate/catalyst ratios. Given their high efficiencies, they are often suitable for industrial scale synthesis, even with expensive catalysts. A versatile example of enantioselective synthesis is asymmetric hydrogenation, which is used to reduce a wide variety of functional groups.
The design of new catalysts is dominated by the development of new classes of ligands. Certain ligands, often referred to as "privileged ligands", are effective in a wide range of reactions; examples include BINOL, Salen, and BOX. Most catalysts are effective for only one type of asymmetric reaction. For example, Noyori asymmetric hydrogenation with BINAP/Ru requires a β-ketone, although another catalyst, BINAP/diamine-Ru, widens the scope to α,β-alkenes and aromatic chemicals. | 0 | Theoretical and Fundamental Chemistry |
Fluorescent reporter probes detect only the DNA containing the sequence complementary to the probe; therefore, use of the reporter probe significantly increases specificity, and enables performing the technique even in the presence of other dsDNA. Using different-coloured labels, fluorescent probes can be used in multiplex assays for monitoring several target sequences in the same tube. The specificity of fluorescent reporter probes also prevents interference of measurements caused by primer dimers, which are undesirable potential by-products in PCR. However, fluorescent reporter probes do not prevent the inhibitory effect of the primer dimers, which may depress accumulation of the desired products in the reaction.
The method relies on a DNA-based probe with a fluorescent reporter at one end and a quencher of fluorescence at the opposite end of the probe. The close proximity of the reporter to the quencher prevents detection of its fluorescence; breakdown of the probe by the 5 to 3 exonuclease activity of the Taq polymerase breaks the reporter-quencher proximity and thus allows unquenched emission of fluorescence, which can be detected after excitation with a laser. An increase in the product targeted by the reporter probe at each PCR cycle therefore causes a proportional increase in fluorescence due to the breakdown of the probe and release of the reporter.
# The PCR is prepared as usual (see PCR), and the reporter probe is added.
# As the reaction commences, during the annealing stage of the PCR both probe and primers anneal to the DNA target.
# Polymerisation of a new DNA strand is initiated from the primers, and once the polymerase reaches the probe, its 5-3-exonuclease degrades the probe, physically separating the fluorescent reporter from the quencher, resulting in an increase in fluorescence.
# Fluorescence is detected and measured in a real-time PCR machine, and its geometric increase corresponding to exponential increase of the product is used to determine the quantification cycle (C) in each reaction. | 1 | Applied and Interdisciplinary Chemistry |
Most equilibrium fractionations are thought to result from the reduction in vibrational energy (especially zero-point energy) when a more massive isotope is substituted for a less massive one. This leads to higher concentrations of the massive isotopes in substances where the vibrational energy is most sensitive to isotope substitution, i.e., those with the highest bond force constants.
In a reaction involving the exchange of two isotopes, X and X, of element "X" in molecules AX and BX,
each reactant molecule is identical to a product except for the distribution of isotopes (i.e., they are isotopologues). The amount of isotopic fractionation in an exchange reaction can be expressed as a fractionation factor:
indicates that the isotopes are distributed evenly between AX and BX, with no isotopic fractionation. indicates that X is concentrated in substance AX, and indicates X is concentrated in substance BX. is closely related to the equilibrium constant (K):
where is the product of the rotational symmetry numbers of the products (right side of the exchange reaction), is the product of the rotational symmetry numbers of the reactants (left side of the exchange reaction), and is the number of atoms exchanged.
An example of equilibrium isotope fractionation is the concentration of heavy isotopes of oxygen in liquid water, relative to water vapor,
At 20 °C, the equilibrium fractionation factor for this reaction is
Equilibrium fractionation is a type of mass-dependent isotope fractionation, while mass-independent fractionation is usually assumed to be a non-equilibrium process.
For non-equilibrium reactions, isotopic effects are better described by the GEBIK and GEBIF equations for transient kinetic isotope fractionation, which generalize non-steady isotopic effects in any chemical and biochemical reactions. | 0 | Theoretical and Fundamental Chemistry |
Relative to other SNRIs, levomilnacipran, as well as milnacipran, differ in that they are much more balanced reuptake inhibitors of serotonin and norepinephrine. To demonstrate, the serotonin:norepinephrine ratios of SNRIs are as follows: venlafaxine = 30:1, duloxetine = 10:1, desvenlafaxine = 14:1, milnacipran = 1.6:1, and levomilnacipran = 1:2. The clinical implications of more balanced elevations of serotonin and norepinephrine are unclear, but may include improved effectiveness, though also increased side effects.
Levomilnacipran is selective for the serotonin and norepinephrine transporters, lacking significant affinity for over 23 off-target sites. However, it does show some affinity for the dizocilpine (MK-801/) site of the NMDA receptor (K = 1.7 μM), and has been found to inhibit NR2A and NR2B subunit-containing NMDA receptors with respective IC values of 5.62 and 4.57 μM. As such, levomilnacipran is an NMDA receptor antagonist at high concentrations.
Levomilnacipran has recently been found to act as an inhibitor of beta-site amyloid precursor protein cleaving enzyme-1 (BACE-1), which is responsible for β-amyloid plaque formation, and hence may be a potentially useful drug in the treatment of Alzheimer's disease. | 0 | Theoretical and Fundamental Chemistry |
Common names for ketones can be derived by naming the two alkyl or aryl groups bonded to the carbonyl group as separate words followed by the word ketone.
*Acetone
*Acetophenone
*Benzophenone
*Ethyl isopropyl ketone
*Diethyl ketone
The first three of the names shown above are still considered to be [http://www.acdlabs.com/iupac/nomenclature/93/r93_701.htm acceptable IUPAC names]. | 0 | Theoretical and Fundamental Chemistry |
The Kuwajima Taxol total synthesis by the group of Isao Kuwajima of the Tokyo Institute of Technology is one of several efforts in taxol total synthesis published in the 1990s. The total synthesis of Taxol is considered a landmark in organic synthesis.
This synthesis is truly synthetic without any help from small biomolecule precursors and also a linear synthesis with molecule ring construction in the order of A, B, C, D. At some point chirality is locked into the molecule via an asymmetric synthesis step which is unique compared to the other efforts. In common with the other efforts the tail addition is based on the Ojima lactam.
The 20 carbon frame is constructed from several pieces: propargyl alcohol (C1, C2, C14), propionaldehyde (C13, C12, C18), isobutyric acid (C15, C16, C17, C11), Trimethyl(phenylthiomethyl)silane (C10), 2-bromobenzaldehyde (C3 to C9), diethylaluminum cyanide (C19) and trimethylsilylmethyl bromide (C20) | 0 | Theoretical and Fundamental Chemistry |
*1983, 1984 NASA Lewis Research Center Summer Faculty Fellow
*1985, 1986, 1987: Senior Visiting Scientist, Burroughs Wellcome Co.
*1987: East Carolina University Sigma XI Helms Award for outstanding Research
*1999: East Carolina University 5-Year Achievement Research/Creative Activity Award
*2001: East Carolina University College of Arts and Sciences Distinguished Professor of Chemistry, Lifetime Achievement Award
*2003: Eastern Analytical Symposium Award for Achievement in Chemometrics.
*2010: Applied Spectroscopy William F. Meggers Award for outstanding paper appearing in Applied Spectroscopy
*2014: Distinguished Alumni Award, Cleveland State University | 0 | Theoretical and Fundamental Chemistry |
A cumomer is a set of isotopomer sharing similar properties and is a concept that relates to metabolic flux analysis. The concept was developed in 1999. In a metabolic cascade, many molecules will contain the same pattern of isotope labelling. In order to simplify the analysis of such cascades, molecules with identically labelled atoms are aggregated into a virtual molecular called a cumomer (a conflation of cumulative and isotopomer). | 0 | Theoretical and Fundamental Chemistry |
Soil biology and chemistry can be seriously damaged by acid rain. Some microbes are unable to tolerate changes to low pH and are killed. The enzymes of these microbes are denatured (changed in shape so they no longer function) by the acid. The hydronium ions of acid rain also mobilize toxins, such as aluminium, and leach away essential nutrients and minerals such as magnesium.
:2 H (aq) + Mg (clay) 2 H (clay) + Mg (aq)
Soil chemistry can be dramatically changed when base cations, such as calcium and magnesium, are leached by acid rain, thereby affecting sensitive species, such as sugar maple (Acer saccharum).
Impacts of acidic water and soil acidification on plants could be minor or in most cases major. Most minor cases which do not result in fatality of plant life can be attributed to the plants being less susceptible to acidic conditions and/or the acid rain being less potent. However, even in minor cases, the plant will eventually die due to the acidic water lowering the plants natural pH. Acidic water enters the plant and causes important plant minerals to dissolve and get carried away; which ultimately causes the plant to die of lack of minerals for nutrition. In major cases, which are more extreme, the same process of damage occurs as in minor cases, which is removal of essential minerals, but at a much quicker rate. Likewise, acid rain that falls on soil and on plant leaves causes drying of the waxy leaf cuticle, which ultimately causes rapid water loss from the plant to the outside atmosphere and eventually results in death of the plant. Soil acidification can lead to a decline in soil microbes as a result of a change in pH, which would have an adverse effect on plants due to their dependence on soil microbes to access nutrients. To see if a plant is being affected by soil acidification, one can closely observe the plant leaves. If the leaves are green and look healthy, the soil pH is normal and acceptable for plant life. But if the plant leaves have yellowing between the veins on their leaves, that means the plant is suffering from acidification and is unhealthy. Moreover, a plant suffering from soil acidification cannot photosynthesize; the acid-water-induced process of drying out of the plant can destroy chloroplast organelles. Without being able to photosynthesize, a plant cannot create nutrients for its own survival or oxygen for the survival of aerobic organisms, which affects most species on Earth and ultimately ends the purpose of the plants existence. | 1 | Applied and Interdisciplinary Chemistry |
Like Ohta, H.T.Odum also sought to order energy form conversions according to their quality, however his hierarchical scale for ranking was based on extending ecological system food chain concepts to thermodynamics rather than simply relative ease of transformation . For H.T.Odum energy quality rank is based on the amount of energy of one form required to generate a unit of another energy form. The ratio of one energy form input to a different energy form output was what H.T.Odum and colleagues called transformity: "the EMERGY per unit energy in units of emjoules per joule" (H.T.Odum 1988, p. 1135). | 0 | Theoretical and Fundamental Chemistry |
The use of ionic liquids in carbon capture is a potential application of ionic liquids as absorbents for use in carbon capture and sequestration. Ionic liquids, which are salts that exist as liquids near room temperature, are polar, nonvolatile materials that have been considered for many applications. The urgency of climate change has spurred research into their use in energy-related applications such as carbon capture and storage. | 0 | Theoretical and Fundamental Chemistry |
Courtois was acknowledged by Humphry Davy and Joseph Louis Gay-Lussac as the true discoverer of iodine. He went into manufacturing high-quality iodine and its salts in 1822. In 1831 he was awarded 6,000 francs as part of the Montyon Prize by LAcademie royale des sciences for the medicinal value of this element. He struggled financially for the rest of his life and died 27 September 1838. He was 61 years old and had no assets left for his widow or son. In the year of his death, the Journal de chimie médicale' drily noted his passing under the heading Obituary as: | 1 | Applied and Interdisciplinary Chemistry |
In order to excite surface plasmon polaritons in a resonant manner, one can use electron bombardment or incident light beam (visible and infrared are typical). The incoming beam has to match its momentum to that of the plasmon. In the case of p-polarized light (polarization occurs parallel to the plane of incidence), this is possible by passing the light through a block of glass to increase the wavenumber (and the momentum), and achieve the resonance at a given wavelength and angle. S-polarized light (polarization occurs perpendicular to the plane of incidence) cannot excite electronic surface plasmons.
Electronic and magnetic surface plasmons obey the following dispersion relation:
where k() is the wave vector, is the relative permittivity, and is the relative permeability of the material (1: the glass block, 2: the metal film), while is angular frequency and is the speed of light in vacuum.
Typical metals that support surface plasmons are silver and gold, but metals such as copper, titanium or chromium have also been used.
When using light to excite SP waves, there are two configurations which are well known. In the Otto configuration, the light illuminates the wall of a glass block, typically a prism, and is totally internally reflected. A thin metal film (for example gold) is positioned close enough to the prism wall so that an evanescent wave can interact with the plasma waves on the surface and hence excite the plasmons.
In the Kretschmann configuration (also known as Kretschmann–Raether configuration), the metal film is evaporated onto the glass block. The light again illuminates the glass block, and an evanescent wave penetrates through the metal film. The plasmons are excited at the outer side of the film. This configuration is used in most practical applications. | 0 | Theoretical and Fundamental Chemistry |
For a given Mach number, M, and corner angle, θ, the oblique shock angle, β, and the downstream Mach number, M, can be calculated. Unlike after a normal shock where M must always be less than 1, in oblique shock M can be supersonic (weak shock wave) or subsonic (strong shock wave). Weak solutions are often observed in flow geometries open to atmosphere (such as on the outside of a flight vehicle). Strong solutions may be observed in confined geometries (such as inside a nozzle intake). Strong solutions are required when the flow needs to match the downstream high pressure condition. Discontinuous changes also occur in the pressure, density and temperature, which all rise downstream of the oblique shock wave. | 1 | Applied and Interdisciplinary Chemistry |
Cavitation in fluid mechanics and engineering normally refers to the phenomenon in which the static pressure of a liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, called "bubbles" or "voids", collapse and can generate shock waves that may damage machinery. These shock waves are strong when they are very close to the imploded bubble, but rapidly weaken as they propagate away from the implosion. Cavitation is a significant cause of wear in some engineering contexts. Collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion. This results in surface fatigue of the metal, causing a type of wear also called "cavitation". The most common examples of this kind of wear are to pump impellers, and bends where a sudden change in the direction of liquid occurs. Cavitation is usually divided into two classes of behavior: inertial (or transient) cavitation and non-inertial cavitation.
The process in which a void or bubble in a liquid rapidly collapses, producing a shock wave, is called inertial cavitation. Inertial cavitation occurs in nature in the strikes of mantis shrimp and pistol shrimp, as well as in the vascular tissues of plants. In manufactured objects, it can occur in control valves, pumps, propellers and impellers.
Non-inertial cavitation is the process in which a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as an acoustic field. The gas in the bubble may contain a portion of a different gas than the vapor phase of the liquid. Such cavitation is often employed in ultrasonic cleaning baths and can also be observed in pumps, propellers, etc.
Since the shock waves formed by collapse of the voids are strong enough to cause significant damage to parts, cavitation is typically an undesirable phenomenon in machinery (although desirable if intentionally used, for example, to sterilize contaminated surgical instruments, break down pollutants in water purification systems, emulsify tissue for cataract surgery or kidney stone lithotripsy, or homogenize fluids). It is very often specifically prevented in the design of machines such as turbines or propellers, and eliminating cavitation is a major field in the study of fluid dynamics. However, it is sometimes useful and does not cause damage when the bubbles collapse away from machinery, such as in supercavitation. | 1 | Applied and Interdisciplinary Chemistry |
A backdraft can occur when a compartment fire has little or no ventilation. Due to this, little or no oxygen can flow into the compartment. Then, because fires reduce oxygen, the oxygen concentration decreases. When the oxygen concentration becomes too low to support combustion, some or all of the combustion switches to pyrolysis. However, the hydrocarbons and smoke (primarily particulate matter) remain at a temperature hot enough to auto-ignite. If oxygen is then re-introduced to the compartment, e.g. by opening a door or window to a closed room, while the gasses are still hot enough to auto-ignite, combustion will restart, often abruptly or even explosively, as the gasses are heated by the combustion and expand rapidly because of the rapidly increasing temperature, combined with the energy released from combustion.
The colour and movement of smoke is used by firefighters to infer fire conditions, including the risk of backdraft. Characteristic warning signs of a backdraft include yellow or brown smoke, smoke which exits small holes in puffs (a sort of breathing effect) and is often found around the edges of doors and windows, and windows which appear brown or black when viewed from the exterior due to soot from incomplete combustion. This is an indication that the room lacks enough oxygen to permit oxidation of the soot particles. Firefighters often look to see if there is soot on the inside of windows and in any cracks in the window (caused e.g. by the heat). The windows may also have a slight vibration due to varying pressure within the compartment due to intermittent combustion.
If firefighters discover a room sucking air into itself, for example through a crack, they generally evacuate immediately, because this is a strong indication that a backdraft is imminent. Due to pressure differences, puffs of smoke are sometimes drawn back into the enclosed space from which they emanated, which is how the term backdraft originated.
Backdrafts are very dangerous, often surprising even experienced firefighters. The most common tactic used by firefighters to defuse a potential backdraft is to ventilate a room from its highest point, allowing the heat and smoke to escape without igniting.
Common signs of imminent backdraft include a sudden inrush of air upon an opening into a compartment being created, lack of visible signs of flame (fire above its upper flammability limit), "pulsing" smoke plumes from openings and auto-ignition of hot gases at openings where they mix with oxygen in the surrounding air. | 0 | Theoretical and Fundamental Chemistry |
In addition to treating the liquid waste excreted by fish the solid waste must also be treated, this is done by concentrating and flushing the solids out of the system. Removing solids reduces bacteria growth, oxygen demand, and the proliferation of disease. The simplest method for removing solids is the creation of settling basin where the relative velocity of the water is slow and particles can settle at the bottom of the tank where they are either flushed out or vacuumed out manually using a siphon. However, this method is not viable for RAS operations where a small footprint is desired. Typical RAS solids removal involves a sand filter or particle filter where solids become lodged and can be periodically backflushed out of the filter. Another common method is the use of a mechanical drum filter where water is run over a rotating drum screen that is periodically cleaned by pressurized spray nozzles, and the resulting slurry is treated or sent down the drain. In order to remove extremely fine particles or colloidal solids a protein fractionator may be used with or without the addition of ozone (O). | 1 | Applied and Interdisciplinary Chemistry |
In 1999, NASA initiated its Space Solar Power Exploratory Research and Technology program (SERT) for the following purposes:
* Perform design studies of selected flight demonstration concepts.
* Evaluate studies of the general feasibility, design, and requirements.
* Create conceptual designs of subsystems that make use of advanced SSP technologies to benefit future space or terrestrial applications.
* Formulate a preliminary plan of action for the U.S. (working with international partners) to undertake an aggressive technology initiative.
* Construct technology development and demonstration roadmaps for critical space solar power (SSP) elements.
SERT went about developing a solar power satellite (SPS) concept for a future gigawatt space power system, to provide electrical power by converting the Suns energy and beaming it to Earths surface, and provided a conceptual development path that would utilize current technologies. SERT proposed an inflatable photovoltaic gossamer structure with concentrator lenses or solar heat engines to convert sunlight into electricity. The program looked both at systems in Sun-synchronous orbit and geosynchronous orbit. Some of SERT's conclusions:
* The increasing global energy demand is likely to continue for many decades resulting in new power plants of all sizes being built.
* The environmental impact of those plants and their impact on world energy supplies and geopolitical relationships can be problematic.
* Renewable energy is a compelling approach, both philosophically and in engineering terms.
* Many renewable energy sources are limited in their ability to affordably provide the base load power required for global industrial development and prosperity, because of inherent land and water requirements.
* Based on their Concept Definition Study, space solar power concepts may be ready to reenter the discussion.
* Solar power satellites should no longer be envisioned as requiring unimaginably large initial investments in fixed infrastructure before the emplacement of productive power plants can begin.
* Space solar power systems appear to possess many significant environmental advantages when compared to alternative approaches.
* The economic viability of space solar power systems depends on many factors and the successful development of various new technologies (not least of which is the availability of much lower cost access to space than has been available); however, the same can be said of many other advanced power technologies options.
* Space solar power may well emerge as a serious candidate among the options for meeting the energy demands of the 21st century.
* Launch costs in the range of $100–$200 per kilogram of payload from low Earth orbit to Geosynchronous orbit are needed if SPS is to be economically viable. | 0 | Theoretical and Fundamental Chemistry |
Minimum solid area models assume that the load bearing area (cross-sectional area normal to the stress) is the logical basis for modeling mechanical behavior. MSA models assume pore interaction results in reduction of stress. Therefore, the minimum solid areas are the carriers of stress. As a result, predicted mechanical properties fluctuate based on the quantification of the solid area of the foam. For titanium foams consisting of partially sintered powders, the minimum solid area consists of the neck area between powders through the cross-section of cell walls between macropores.
The mathematical relationships in MSA models
are relatively consistent with the Gibson & Ashby model.
However, the MSA models are designed to predict mechanical property parameters over a broader range of porosity levels. Like the Gibson & Ashby models, MSA models were derived assuming idealized (defect-free) structures containing uniform pore shapes, size and distribution. | 0 | Theoretical and Fundamental Chemistry |
The high error rate (0.01-0.001) of standard NGS platforms introduced during sample preparation or sequencing is a major limitation for the detection of variants present in a small fraction of cells. Due to the duplex tagging system and use of information in both strands of DNA, duplex sequencing has significantly decreased the error rate of sequencing about 10 million fold using both SSCS and DCS method. | 1 | Applied and Interdisciplinary Chemistry |
Calling it "The Crime of Falsification", the Pope specified that any person who either produced, successfully ordered the production of, assisted in the production of or knowingly sold false alchemic metals in attempt to pay off debt should be sentenced to pay a fine; the fine was to be calculated by weighing the alchemic metal and then charging however much that weight of real silver or gold would cost. Provisions were also made for those who could not afford to pay, the decree stated that other forms of punishment were allowed to be used, such as imprisonment, but that the precise sentence depended on the surrounding factors of the case. Those who went on to use alchemic metals for the forging of coins were also condemned (one possible motivating factor for this inclusion being that the papacy was located in the French commune of Avignon, which had a lot of counterfeit currency in circulation), but the harshest punishment was reserved for clerics, who if found guilty, were to be subjected to the loss of all their clerical benefices and denied the chance to regain them in the future, in addition to the normal punishment detailed above. As a result of the decree, alchemists were forced to conduct their practice in secret.
The decretal is frequently misunderstood to have been an anti-science (specifically an anti-chemistry) edict, but this is false – it was specifically against fraudulent alchemy. Pope John XXII had himself studied chemistry before entering the clergy, and his papacy was marked by events that led one historian to remark that he was "one of the most liberal patrons of education and of science in history."
Spondent Pariter is sometimes referred to as a papal bull, though canonically it is not a bull but a less important document termed a decretal, specifically an Extravagantes. It is listed in Corpus Juris Canonici Tome II (published in Lyons, 1799), but not in the ordinary list of Pope John XXII's bulls. | 1 | Applied and Interdisciplinary Chemistry |
MDL Chime was a free plugin used by web browsers to display the three-dimensional structures of molecules. and was based on the RasMol code. | 0 | Theoretical and Fundamental Chemistry |
Solomons ground-breaking work on free radical polymerization was initiated through observations made in industry. For example, anomalies that were not explained by polymerization theory at the time, and the observation that during the production of polymer/mineral composites some batches underwent spontaneous combustion. This led to discoveries that had significant influence on the future directions of radical chemistry. It led to the development of Nitroxide Mediated Polymerization (NMP), the first example of a controlled, or living, radical polymerization technique. This research also produced early examples of what was to become known as RAFT, or Reversible addition−fragmentation chain-transfer polymerization. Solomons work rewrote the theory on free radical polymerization, and he was co-author with Graeme Moad on the definitive reference book: The Chemistry of Radical Polymerization (Moad & Solomon, 2006). Previous theories attempted to explain radical polymerization on the basis of thermodynamic stability controlling structure. Solomon's work showed that kinetics was the major factor in controlling the way polymer chains formed. | 0 | Theoretical and Fundamental Chemistry |
The point of zero charge (pzc) is generally described as the pH at which the net charge of total particle surface (i.e. absorbent's surface) is equal to zero, which concept has been introduced in the studies dealt with colloidal flocculation to explain pH affecting the phenomenon.
A related concept in electrochemistry is the electrode potential at the point of zero charge. Generally, the pzc in electrochemistry is the value of the negative decimal logarithm of the activity of the potential-determining ion in the bulk fluid. The pzc is of fundamental importance in surface science. For example, in the field of environmental science, it determines how easily a substrate is able to adsorb potentially harmful ions. It also has countless applications in technology of colloids, e.g., flotation of minerals. Therefore, the pzc value has been examined in many application of adsorption to the environmental science. The pzc value is typically obtained by titrations and several titration method has been developed. Related values associated with the soil characteristics exist along with the pzc value, including zero point of charge (zpc), point of zero net charge (pznc), etc. | 0 | Theoretical and Fundamental Chemistry |
Diffraction patterns depend on whether the beam is diffracted by one single crystal or by a number of differently oriented crystallites, for instance in a polycrystalline material. If there are many contributing crystallites, the diffraction image is a superposition of individual crystal patterns, see Figure 12. With a large number of grains this superposition yields diffraction spots of all possible reciprocal lattice vectors. This results in a pattern of concentric rings as shown in Figure 12 and 13.
Textured materials yield a non-uniform distribution of intensity around the ring, which can be used to discriminate between nanocrystalline and amorphous phases. However, diffraction often cannot differentiate between very small grain polycrystalline materials and truly random order amorphous. Here high-resolution transmission electron microscopy and fluctuation electron microscopy can be more powerful, although this is still a topic of continuing development. | 0 | Theoretical and Fundamental Chemistry |
In orthodox two-component signaling, a histidine kinase protein autophosphorylates on a histidine residue in response to an extracellular signal, and the phosphoryl group is subsequently transferred to an aspartate residue on the receiver domain of a response regulator. In phosphorelays, the "hybrid" histidine kinase contains an internal aspartate-containing receiver domain to which the phosphoryl group is transferred, after which an HPt protein containing a phosphorylatable histidine receives the phosphoryl group and finally transfers it to the response regulator. The relay system thus progresses in the order His-Asp-His-Asp, with the second His contributed by Hpt. In some cases, a phosphorelay system is constructed from four separate proteins rather than a hybrid histidine kinase with an internal receiver domain, and in other examples both the receiver and the HPt domains are present in the histidine kinase polypeptide chain. A census of two-component system domain architecture found that HPt domains in bacteria are more common as domains of larger proteins than they are as individual proteins. | 1 | Applied and Interdisciplinary Chemistry |
Ralph Edward Oesper (14 June 1886 – 10 December 1977) was an American chemist and historian of chemistry. He is noted for his biographies of scientists, emphasizing their personal lives in addition to their scientific contributions. Oesper translated significant works in the field of chemistry to various languages especially English. As an independent investigator, he developed improved analytical methods. These contributions included new reagents for certain types of titrations. One such new reagent, Oesper's Salt, is named for him. | 1 | Applied and Interdisciplinary Chemistry |
First discovered and named by E. Rink and H. Böhm in 1974 they were isolated in cell suspension cultures of the Papaveraceae Macleaya microcarpa.
Since then, many minor advancements have been made in this particular topic, but BBE-like enzymes, either for their lack of study, or the lack of clear indications that it might contain useful information for other scientific research, have yet to be fully worked on, and subsequently known at their full complexity. | 1 | Applied and Interdisciplinary Chemistry |
When a septic tank is used in combination with a biofilter, the height and catabolic area of the drain field may be reduced. Biofilter technology may allow higher density residential construction, minimal site disturbance and more usable land for trees, swimming pools, or gardens. With adequate routine maintenance it may reduce the chances of the drain field plugging up. The biofilter will not reduce the volume of liquid that must percolate into soil, but it may reduce the oxygen demand of organic materials in that liquid. | 1 | Applied and Interdisciplinary Chemistry |
Coating components are subject to particle-particle, particle-solvent, and particle-polymer interactions. Van der Waals forces, electrostatic repulsions, and steric stabilization are the reasons for these interactions. Importantly, the characteristics of adhesion and cohesion between the components form the base coating structure. Calcium carbonate and kaolin are commonly used pigments. Pigments support a structure of fine porosity and form a light scattering surface. The surface charge of the pigment plays an important role in dispersion consistency. The surface charge of calcium carbonate is negative and not dependent on pH, however it can decompose under acidic conditions. Kaolin has negatively charged faces while the charge of its laterals depend on pH, being positive in acidic conditions and negative in basic conditions with an isoelectric point at 7.5. The equation for determining the isoelectric point is as follows:
In the papermaking process, the pigment dispersions are generally kept at a pH above 8.0. | 0 | Theoretical and Fundamental Chemistry |
A set of empirical rules relating the protein structure to the pK values of ionizable residues have been developed by Li, Robertson, and Jensen. These rules form the basis for the [https://biolib.com/bio-utils/propka/ web-accessible] program called PROPKA for rapid predictions of pK values. A recent empirical pK prediction program was released by Tan KP et.al. with the online server [http://mspc.bii.a-star.edu.sg/tankp/ DEPTH web server]. | 0 | Theoretical and Fundamental Chemistry |
The Bay is well-known for its seafood, especially blue crabs, clams, and oysters. In the middle of the 20th century, the Bay supported 9,000 full-time watermen, according to one account. Today, the body of water is less productive than it used to be because of runoff from urban areas (mostly on the Western Shore) and farms (especially on the Eastern Shore and in the Susquehanna River watershed), over-harvesting, and invasion of foreign species.
The plentiful oyster harvests led to the development of the skipjack, the state boat of Maryland, which is the only remaining working boat type in the United States still under sail power. Other characteristic bay-area workboats include sail-powered boats such as the log canoe, the pungy, the bugeye, and the motorized Chesapeake Bay deadrise, the state boat of Virginia.
In addition to harvesting wild oysters, oyster farming is a growing industry in the Bay. Oyster aquaculture is passive in that the Bay provides all the natural oyster food needed, making it an environmentally friendly practice in contrast to other kinds of fish farming. Oyster farms provide jobs as well as a natural effort for filtering excess nutrients from the water in an effort to reduce the effects of eutrophication pollution (too much algae). The Chesapeake Bay Program promotes oyster restoration projects to reduce the amount of nitrogen compounds entering the bay.
The Bay is famous for its rockfish, a regional name for striped bass. Once on the verge of extinction, rockfish have made a significant comeback because of legislative action that put a moratorium on rockfishing, which allowed the species to re-populate. Rockfish can now be fished in strictly controlled and limited quantities.
Other popular recreational fisheries in the Chesapeake Bay include shad, cobia, croaker, and redfish, winter flounder, and summer flounder. Recently, non-native blue catfish have proliferated in tributaries like the James River and may be moving to other areas of the Bay. A commercial fishery exists for menhaden, too oily for human consumption but instead used for bait, fish oil, and livestock feed. | 1 | Applied and Interdisciplinary Chemistry |
Radionuclides which emit gamma radiation are valuable in a range of different industrial, scientific and medical technologies. This article lists some common gamma-emitting radionuclides of technological importance, and their properties. | 0 | Theoretical and Fundamental Chemistry |
1,3-Propanedithiol reacts with metal ions to form chelate rings. Illustrative is the synthesis of the derivative diiron propanedithiolate hexacarbonyl upon reaction with triiron dodecacarbonyl:
:Fe(CO) + CH(SH) → Fe(SCH)(CO) + H + Fe(CO) + CO | 0 | Theoretical and Fundamental Chemistry |
Starting in the 1980s, scientific advances allowed the use of DNA as a material for the identification of an individual. The first patent covering the direct use of DNA variation for forensics ([https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US5593832.pdf US5593832A]) was filed by Jeffrey Glassberg in 1983, based upon work he had done while at Rockefeller University in the United States in 1981.
British geneticist Sir Alec Jeffreys independently developed a process for DNA profiling in 1985 while working in the Department of Genetics at the University of Leicester. Jeffreys discovered that a DNA examiner could establish patterns in unknown DNA. These patterns were a part of inherited traits that could be used to advance the field of relationship analysis. These discoveries lead to the first use of DNA profiling in a criminal case.
The process, developed by Jeffreys in conjunction with Peter Gill and Dave Werrett of the Forensic Science Service (FSS), was first used forensically in the solving of the murder of two teenagers who had been raped and murdered in Narborough, Leicestershire in 1983 and 1986. In the murder inquiry, led by Detective David Baker, the DNA contained within blood samples obtained voluntarily from around 5,000 local men who willingly assisted Leicestershire Constabulary with the investigation, resulted in the exoneration of Richard Buckland, an initial suspect who had confessed to one of the crimes, and the subsequent conviction of Colin Pitchfork on January 2, 1988. Pitchfork, a local bakery employee, had coerced his coworker Ian Kelly to stand in for him when providing a blood sample—Kelly then used a forged passport to impersonate Pitchfork. Another coworker reported the deception to the police. Pitchfork was arrested, and his blood was sent to Jeffreys lab for processing and profile development. Pitchforks profile matched that of DNA left by the murderer which confirmed Pitchfork's presence at both crime scenes; he pleaded guilty to both murders. After some years, a chemical company named Imperial Chemical Industries (ICI) introduced the first ever commercially available kit to the world. Despite being a relatively recent field, it had a significant global influence on both criminal justice system and society.
Although 99.9% of human DNA sequences are the same in every person, enough of the DNA is different that it is possible to distinguish one individual from another, unless they are monozygotic (identical) twins. DNA profiling uses repetitive sequences that are highly variable, called variable number tandem repeats (VNTRs), in particular short tandem repeats (STRs), also known as microsatellites, and minisatellites. VNTR loci are similar between closely related individuals, but are so variable that unrelated individuals are unlikely to have the same VNTRs.
Before VNTRs and STRs, people like Jeffreys used a process called Restriction Fragment Length Polymorphism (RFLP). This process regularly used large portions of DNA to analyze the differences between two DNA samples. RFLP was among the first technologies used in DNA profiling and analysis. However, as technology has evolved, new technologies, like STR, emerged and took the place of older technology like RFLP.
The admissibility of DNA evidence in courts was disputed in the United States in the 1980s and 1990s, but has since become more universally accepted due to improved techniques. | 1 | Applied and Interdisciplinary Chemistry |
In October 2006, Taiwan banned ractopamine along with other beta-adrenergic agonists. In a 2012 climb-down, its legislature passed amendments to its Act Governing Food Sanitation, authorising government agencies to set safety standards for ractopamine. The Taiwanese Department of Health ultimately established an MRL of 10 ppb for ractopamine in beef on 31 July 2012.
The American Institute in Taiwan, which represents US interests in Taiwan, states that these "and many other countries have determined that meat from animals fed ractopamine is safe for human consumption"; this is in the context of an ongoing trade dispute between Taiwan and the US on this subject, which threatened to prevent Taiwan's entry to the Trans-Pacific Partnership trade pact.
In 2020, restrictions on imports of US pork with ractopamine were relaxed, leading to protests. A referendum took place on December 18, 2021 , deciding whether to ban the import of pork with ractopamine, and the ban was rejected. | 0 | Theoretical and Fundamental Chemistry |
Leukotriene D (LTD) is one of the leukotrienes. Its main function in the body is to induce the contraction of smooth muscle, resulting in bronchoconstriction and vasoconstriction. It also increases vascular permeability. LTD is released by basophils. Other leukotrienes that function in a similar manner are leukotrienes C and E. Pharmacological agents that inhibit the function of these leukotrienes are leukotriene receptor antagonists (e.g., zafirlukast, montelukast) and are useful for asthmatic individuals. | 1 | Applied and Interdisciplinary Chemistry |
The kiln connects with a material exit hood at the lower end and ducts for waste gases. This requires gas-tight seals at either end of the kiln. The exhaust gas may go to waste, or may enter a preheater, which further exchanges heat with the entering feed. The gases must be drawn through the kiln, and the preheater if fitted, by a fan situated at the exhaust end. In preheater installations which may have a high pressure-drop, considerable fan power may be needed, and the fan drive is often the largest drive in the kiln system. Exhaust gases contain dust, and there may be undesirable constituents, such as sulfur dioxide or hydrogen chloride. Equipment is installed to scrub these from the gas stream before passing to the atmosphere. | 1 | Applied and Interdisciplinary Chemistry |
Quantum mechanics effects become noticeable for nanoscale objects. They include quantum confinement in semiconductor particles, localized surface plasmons in some metal particles, and superparamagnetism in magnetic materials. Quantum dots are nanoparticles of semiconducting material that are small enough (typically sub 10 nm or less) to have quantized electronic energy levels.
Quantum effects are responsible for the deep-red to black color of gold or silicon nanopowders and nanoparticle suspensions. Absorption of solar radiation is much higher in materials composed of nanoparticles than in thin films of continuous sheets of material. In both solar PV and solar thermal applications, by controlling the size, shape, and material of the particles, it is possible to control solar absorption.
Core-shell nanoparticles can support simultaneously both electric and magnetic resonances, demonstrating entirely new properties when compared with bare metallic nanoparticles if the resonances are properly engineered. The formation of the core-shell structure from two different metals enables an energy exchange between the core and the shell, typically found in upconverting nanoparticles and downconverting nanoparticles, and causes a shift in the emission wavelength spectrum.
By introducing a dielectric layer, plasmonic core (metal)-shell (dielectric) nanoparticles enhance light absorption by increasing scattering. Recently, the metal core-dielectric shell nanoparticle has demonstrated a zero backward scattering with enhanced forward scattering on a silicon substrate when surface plasmon is located in front of a solar cell. | 0 | Theoretical and Fundamental Chemistry |
Tetra-primer amplification refractory mutation system PCR, or ARMS-PCR, employs two pairs of primers to amplify two alleles in one PCR reaction. The primers are designed such that the two primer pairs overlap at a SNP location but each match perfectly to only one of the possible SNPs. The basis of the invention is that unexpectedly, oligonucleotides with a mismatched 3'-residue will not function as primers in the PCR under appropriate conditions. As a result, if a given allele is present in the PCR reaction, the primer pair specific to that allele will produce product but not to the alternative allele with a different SNP. The two primer pairs are also designed such that their PCR products are of a significantly different length allowing for easily distinguishable bands by gel electrophoresis or melt temperature analysis. In examining the results, if a genomic sample is homozygous, then the PCR products that result will be from the primer that matches the SNP location and the outer opposite-strand primer, as well from the two outer primers. If the genomic sample is heterozygous, then products will result from the primer of each allele and their respective outer primer counterparts as well as the outer primers.
An alternative strategy is to run multiple qPCR reactions with different primer sets that target each allele separately. Well-designed primers will amplify their target SNP at a much earlier cycle than the other SNPs. This allows more than two alleles to be distinguished, although an individual qPCR reaction is required for each SNP. To achieve high enough specificity, the primer sequence may require placement of an artificial mismatch near its 3'-end, which is an approach generally known as Taq-MAMA. | 1 | Applied and Interdisciplinary Chemistry |
Thiols are easily deprotonated. Relative to the alcohols, thiols are more acidic. The conjugate base of a thiol is called a thiolate. Butanethiol has a pK of 10.5 vs 15 for butanol. Thiophenol has a pK of 6, versus 10 for phenol. A highly acidic thiol is pentafluorothiophenol (CFSH) with a pK of 2.68. Thus, thiolates can be obtained from thiols by treatment with alkali metal hydroxides. | 0 | Theoretical and Fundamental Chemistry |
Depending on the application, various types of working fluids are used. In a thermodynamic cycle it may be the case that the working fluid changes state from gas to liquid or vice versa. Certain gases such as helium can be treated as ideal gases. This is not generally the case for superheated steam and the ideal gas equation does not really hold. At much higher temperatures however it still yields relatively accurate results. The physical and chemical properties of the working fluid are extremely important when designing thermodynamic systems. For instance, in a refrigeration unit, the working fluid is called the refrigerant. Ammonia is a typical refrigerant and may be used as the primary working fluid. Compared with water (which can also be used as a refrigerant), ammonia makes use of relatively high pressures requiring more robust and expensive equipment.
In air standard cycles as in gas turbine cycles, the working fluid is air. In the open cycle gas turbine, air enters a compressor where its pressure is increased. The compressor therefore inputs work to the working fluid (positive work). The fluid is then transferred to a combustion chamber where this time heat energy is input by means of the burning of a fuel. The air then expands in a turbine thus doing work against the surroundings (negative work).
Different working fluids have different properties and in choosing one in particular the designer must identify the major requirements. In refrigeration units, high latent heats are required to provide large refrigeration capacities. | 0 | Theoretical and Fundamental Chemistry |
The derivative of an activity coefficient with respect to temperature is related to excess molar enthalpy by
Similarly, the derivative of an activity coefficient with respect to pressure can be related to excess molar volume. | 0 | Theoretical and Fundamental Chemistry |
A spot test in lichenology is a spot analysis used to help identify lichens. It is performed by placing a drop of a chemical reagent on different parts of the lichen and noting the colour change (or lack thereof) associated with application of the chemical. The tests are routinely encountered in dichotomous keys for lichen species, and they take advantage of the wide array of lichen products (secondary metabolites) produced by lichens and their uniqueness among taxa. As such, spot tests reveal the presence or absence of chemicals in various parts of a lichen. They were first proposed as a method to help identify species by the Finnish lichenologist William Nylander in 1866.
Three common spot tests use either 10% aqueous KOH solution (K test), saturated aqueous solution of bleaching powder or calcium hypochlorite (C test), or 5% alcoholic p-phenylenediamine solution (P test). The colour changes occur due to presence of particular secondary metabolites in the lichen. In identification key reference literature, the outcome of chemical spot tests serves as a primary characteristic for determining the species of lichens. There are several other less frequently used spot tests of more limited use that are employed in specific situations, such as to distinguish between certain species. Variations of the technique, including using filter paper to enhance visibility of reactions or examining under a microscope, accommodate different lichen types and pigmentations, with results typically summarised by a short code indicating the substance and reaction observed. Other diagnostic methods like ultraviolet (UV) light exposure can help identify lichen metabolites and distinguish between species, as some substances fluoresce under UV, aiding in the differentiation of closely related species. | 0 | Theoretical and Fundamental Chemistry |
Diels-Alder reaction between cyclopentadiene and chlorosulfonyl isocyanate (CSI) can be utilized to obtain both β- as well as γ-lactam. At lower temp (−78 °C), β-lactam is the preferred product. At optimum temperatures, a highly useful γ-lactam known as Vince Lactam is obtained. | 0 | Theoretical and Fundamental Chemistry |
The system is the part of the universe being studied, while the surroundings is the remainder of the universe that lies outside the boundaries of the system. It is also known as the environment or the reservoir. Depending on the type of system, it may interact with the system by exchanging mass, energy (including heat and work), momentum, electric charge, or other conserved properties. The environment is ignored in the analysis of the system, except in regards to these interactions. | 0 | Theoretical and Fundamental Chemistry |
In spectroscopy, spectral flux density is the quantity that describes the rate at which energy is transferred by electromagnetic radiation through a real or virtual surface, per unit surface area and per unit wavelength (or, equivalently, per unit frequency). It is a radiometric rather than a photometric measure. In SI units it is measured in W m, although it can be more practical to use W m nm (1 W m nm = 1 GW m = 1 W mm) or W m μm (1 W m μm = 1 MW m), and respectively by W·m·Hz, Jansky or solar flux units. The terms irradiance, radiant exitance, radiant emittance, and radiosity are closely related to spectral flux density.
The terms used to describe spectral flux density vary between fields, sometimes including adjectives such as "electromagnetic" or "radiative", and sometimes dropping the word "density". Applications include:
*Characterizing remote telescopically unresolved sources such as stars, observed from a specified observation point such as an observatory on earth.
*Characterizing a natural electromagnetic radiative field at a point, measured there with an instrument that collects radiation from a whole sphere or hemisphere of remote sources.
*Characterizing an artificial collimated electromagnetic radiative beam. | 0 | Theoretical and Fundamental Chemistry |
Lanthanum(III) iodide adopts the same crystal structure as plutonium(III) bromide, with 8-coordinate metal centres arranged in layers. This orthorhombic structure is typical of the triiodides of the lighter lanthanides (La–Nd), whereas heavier lanthanides tend to adopt the hexagonal bismuth(III) iodide structure. | 0 | Theoretical and Fundamental Chemistry |
Active metabolism of glucose with production of bicarbonate has been demonstrated by Pettersson and Cohen.
Pettersson studies were on the metabolism of glucose and fatty acids by kidneys during 6 day hypothermic perfusion storage and he found that the kidneys consumed glucose at 4.4 μmol/g/day and fatty acids at 5.8 μmol/g/day. In Cohens study the best 8 day stored kidneys consumed glucose at the rate of 2.3 μmol/g/day and 4.9 μmol/g/day respectively which made it likely that they were using fatty acids at similar rates to Petterssons dogs' kidneys. The constancy of both the glucose consumption rate and the rate of bicarbonate production implied that no injury was affecting the glycolytic enzyme or carbonic anhydrase enzyme systems.
Lee showed that fatty acids were the preferred substrate of the rabbits kidney cortex at normothermic temperatures, and glucose the preferred substrate for the medullary cells which normally metabolise anaerobically. Abodeely showed that both fatty acids and glucose could be utilised by the outer medulla of the rabbits kidney but that glucose was used preferentially. At hypothermia the metabolic needs of the kidney are much reduced but measurable consumption of glucose, fatty acids and ketone bodies occurs. Horsburgh showed that lipid is utilised by hypothermic kidneys, with palmitate consumption being 0-15% of normal in the rat kidney cortex at 15 °C. Pettersson showed that, on a molar basis, glucose and fatty acids were metabolised by hypothermically perfused kidneys at about the same rates. The cortex of the hypothermic dog kidney was shown by Huang to lose lipid (35% loss of total lipid after 24 hours) unless oleate was added to the kidney perfusate. Huang commented that this loss could affect the structure of the cell and that the loss also suggested that the kidney was utilising fatty acid. In a later publication Huang showed that dog kidney cortex slices metabolised fatty acids, but not glucose, at 10 °C.
Even if the correct nutrients are provided, they may be lost by absorption into the tubing of the preservation system. Lee demonstrated that silicone rubber (a material used extensively in kidney preservation systems) absorbed 46% of a perfusate's oleic acid after 4 hours of perfusion. | 1 | Applied and Interdisciplinary Chemistry |
*He was awarded a Tilden Prize of the Royal Society of Chemistry in 1974
*He was elected a Fellow of the Royal Society in 1978. | 0 | Theoretical and Fundamental Chemistry |
The strength of non-covalent interactions in a mechanically interlocked molecular architecture increases as compared to the non-mechanically bonded analogues. This increased strength is demonstrated by the necessity of harsher conditions to remove a metal template ion from catenanes as opposed to their non-mechanically bonded analogues. This effect is referred to as the "catenand effect". The augmented non-covalent interactions in interlocked systems compared to non-interlocked systems has found utility in the strong and selective binding of a range of charged species, enabling the development of interlocked systems for the extraction of a range of salts. This increase in strength of non-covalent interactions is attributed to the loss of degrees of freedom upon the formation of a mechanical bond. The increase in strength of non-covalent interactions is more pronounced on smaller interlocked systems, where more degrees of freedom are lost, as compared to larger mechanically interlocked systems where the change in degrees of freedom is lower. Therefore, if the ring in a rotaxane is made smaller the strength of non-covalent interactions increases, the same effect is observed if the thread is made smaller as well. | 0 | Theoretical and Fundamental Chemistry |
The bond length in peroxides is about 1.45 Å, and the angles (R = H, C) are about 110° (water-like). Characteristically, the dihedral angles are about 120°. The bond is relatively weak, with a bond dissociation energy of , less than half the strengths of , , and bonds.
Hydroperoxides are typically more volatile than the corresponding alcohols:
* tert-BuOOH (b.p. 36°C) vs tert-BuOH (b.p. 82-83°C)
* Methyl hydroperoxide| (b.p. 46°C) vs Methanol| (b.p. 65°C)
* cumene hydroperoxide (b.p. 153°C) vs cumyl alcohol (b.p. 202°C) | 0 | Theoretical and Fundamental Chemistry |
In addition to the above-mentioned classification based on energy, muon beams are also divided according to the time structure of the particle accelerator, i.e. continuous or pulsed.
For continuous muon sources no dominating time structure is present. By selecting an appropriate incoming muon rate, muons are implanted into the sample one-by-one. The main advantage is that the time resolution is solely determined by the detector construction and the read-out electronics. There are two main limitations for this type of source, however: (i) unrejected charged particles accidentally hitting the detectors produce non-negligible random background counts; this compromises measurements after a few muon lifetimes, when the random background exceeds the true decay events; and (ii) the requirement to detect muons one at a time sets a maximum event rate. The background problem can be reduced by the use of electrostatic deflectors to ensure that no muons enter the sample before the decay of the previous muon. PSI and TRIUMF host the two continuous muon sources available for µSR experiments.
At pulsed muon sources protons hitting the production target are bunched into short, intense, and widely separated pulses that provide a similar time structure in the secondary muon beam. An advantage of pulsed muon sources is that the event rate is only limited by detector construction. Furthermore, detectors are active only after the incoming muon pulse, strongly reducing the accidental background counts. The virtual absence of background allows the extension of the time window for measurements up to about ten times the muon mean lifetime. The principal downside is that the width of the muon pulse limits the time resolution. ISIS Neutron and Muon Source and J-PARC are the two pulsed muon sources available for µSR experiments. | 0 | Theoretical and Fundamental Chemistry |
The strip consists of two strips of different metals which expand at different rates as they are heated, usually steel and copper, or in some cases steel and brass. The strips are joined together throughout their length by riveting, brazing or welding. The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial temperature. The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled. The sideways displacement of the strip is much larger than the small lengthways expansion in either of the two metals.
In some applications, the bimetal strip is used in the flat form. In others, it is wrapped into a coil for compactness. The greater length of the coiled version gives improved sensitivity.
The radius of curvature of a bimetallic strip depends on temperature according the formula derived by French physicist Yvon Villarceau in 1863 in his research for improving the precision of clocks:
where is the total thickness of the bimetal and is the coefficient of thermal expansion and is the thickness. The formula can also be rewritten as a function of the thermal misfit strain . And if the modulus and height are similar, we simply have .
An equivalent formula can be derived from the beam theory. | 1 | Applied and Interdisciplinary Chemistry |
In order to perform geometric phase analysis, a computer tool is needed. Firstly, because manual evaluation of transforms between spatial and frequential domain would be highly impractical. Secondly, a vector of crystallographic plane is an important input parameter and the analysis is sensitive to the accuracy of its localization. Therefore, the accuracy and repeatability of the analysis can be increased by an automated localization of diffraction spots.
The required functionalities are available in crystallographic suite CrysTBox. It offers an interactive implementation geometric phase analysis called gpaGUI. Within gpaGUI, it is possible to index the diffraction spots and localize them with sub-pixel precision using an automated tool diffractGUI. | 0 | Theoretical and Fundamental Chemistry |
Barbara Grzybowska-Świerkosz (born 1937), is a Polish chemist. She graduated from the Faculty of Mathematics, Physics and Chemistry of the Jagiellonian University in Kraków in 1959, and received a PhD from the Department of Chemistry at the University of Edinburgh in 1963. After completing a post-doctoral degree at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw in 1974, she researched and taught at that institution, where she has been a professor of chemical sciences since 1990. She has authored more than 140 publications, including articles, monographs and teaching documents.
Her scientific achievements have been recognized with multiple awards, and she has been a member or leader of professional groups including the Academy of Sciences of the Comecon Countries, the Coordinating Committee of Research on Catalysis of the Polish Academy of Sciences, EUROCAT-oxides, and the European Commission Action COST-15 "Interfacial Chemistry and Catalysis". She also served on the editorial boards of the journals Applied Catalysis (1991-1993) and the Polish Journal of Chemistry (1997-). | 0 | Theoretical and Fundamental Chemistry |
In geophysics the anisotropy in elastic properties is usually weak, in which case . When the exact expressions for the wave velocities above are linearized in these small quantities, they simplify to
where
are the P and S wave velocities in the direction of the axis of symmetry () (in geophysics, this is usually, but not always, the vertical direction). Note that may be further linearized, but this does not lead to further simplification.
The approximate expressions for the wave velocities are simple enough to be physically interpreted, and sufficiently accurate for most geophysical applications. These expressions are also useful in some contexts where the anisotropy is not weak. | 0 | Theoretical and Fundamental Chemistry |
A bimolecular elimination reaction will occur in a molecule where the breaking carbon-hydrogen bond and the leaving group are anti-periplanar (Figure 8). This geometry is preferred because it aligns σ and σ* orbitals. Figure 9 shows the σ orbital and the σ* orbital parallel to each other, allowing the σ orbital to donate into the σ* anti-bonding orbital through hyperconjugation. This serves to weaken C-H and C-X bond, both of which are broken in an E reaction. It also sets up the molecule to more easily move its σ electrons into a π orbital (Figure 10). | 0 | Theoretical and Fundamental Chemistry |
The first study reporting molecular delivery using ultrasound was a 1987 in vitro study attempting to transfer plasmid DNA to cultured mouse fibroblast cells using sonoporation. This successful plasmid DNA transfection conferring G418 antibiotic resistance ultimately led to further in vitro studies that hinted at the potential for sonoporation transfection of plasmid DNA and siRNA in vivo. | 1 | Applied and Interdisciplinary Chemistry |
Trace amounts of benzene are found in petroleum and coal. It is a byproduct of the incomplete combustion of many materials. For commercial use, until World War II, much of benzene was obtained as a by-product of coke production (or "coke-oven light oil") for the steel industry. However, in the 1950s, increased demand for benzene, especially from the growing polymers industry, necessitated the production of benzene from petroleum. Today, most benzene comes from the petrochemical industry, with only a small fraction being produced from coal. Benzene has been detected on Mars. | 1 | Applied and Interdisciplinary Chemistry |
Many compounds from first row of transition metal monoxides (MO), from TiO to NiO, have a rocksalt structure. The rock salt structure is generated by filling all octahedral sites with cations in an oxygen anion fcc array. | 0 | Theoretical and Fundamental Chemistry |
Chemical structure of the herbicide is of primary affecting efficacy. 2,4-D, mecoprop, and dicamba control many broadleaf weeds but remain ineffective against turf grasses.
Chemical additives influence selectivity. Surfactants alter the physical properties of the spray solution and the overall phytotoxicity of the herbicide, increasing translocation. Herbicide safeners enhance the selectivity by boosting herbicide resistance by the crop but allowing the herbicide to damage the weed.
Selectivity is determined by the circumstances and technique of application. Climatic factors affect absorption including humidity, light, precipitation, and temperature. Foliage-applied herbicides will enter the leaf more readily at high humidity by lengthening the drying time of the spray droplet and increasing cuticle hydration. Light of high intensity may break down some herbicides and cause the leaf cuticle to thicken, which can interfere with absorption. Precipitation may wash away or remove some foliage-applied herbicides, but it will increase root absorption of soil-applied herbicides. Drought-stressed plants are less likely to translocate herbicides. As temperature increases, herbicides' performance may decrease. Absorption and translocation may be reduced in very cold weather. | 1 | Applied and Interdisciplinary Chemistry |
Acyl complexes are usually low-spin and spin-paired.
Monometallic acyl complexes adopt one of two related structures, C-bonded and η-C-O-bonded. These forms sometimes interconvert. For the purpose of electron-counting, C-bonded acyl ligands count as 1-electron ligands, akin to pseudohalides. η-Acyl ligands count as 3-electron "L-X" ligands.
bridging acyl ligands are also well known, where the carbon bonds to one metal and the oxygen bonds to a second metal. One example is the bis(μ-acetyl) complex [(CO)Fe(C(O)CH)Fe(CO)]. | 0 | Theoretical and Fundamental Chemistry |
An electron microprobe (EMP), also known as an electron probe microanalyzer (EPMA) or electron micro probe analyzer (EMPA), is an analytical tool used to non-destructively determine the chemical composition of small volumes of solid materials. It works similarly to a scanning electron microscope: the sample is bombarded with an electron beam, emitting x-rays at wavelengths characteristic to the elements being analyzed. This enables the abundances of elements present within small sample volumes (typically 10-30 cubic micrometers or less) to be determined, when a conventional accelerating voltage of 15-20 kV is used. The concentrations of elements from lithium to plutonium may be measured at levels as low as 100 parts per million (ppm), material dependent, although with care, levels below 10 ppm are possible. The ability to quantify lithium by EPMA became a reality in 2008. | 0 | Theoretical and Fundamental Chemistry |
Levopropylhexedrine (Eventin) is an adrenergic alkylamine used as an anorectic in Germany and patented by Smith Kline & French in 1947. It has also been used in the anticonvulsant preparation barbexaclone in combination with phenobarbital to offset sedation. Levopropylhexedrine is the levorotatory S-enantiomer of propylhexedrine. The dextrorotatory counterpart is known as dextropropylhexedrine. | 0 | Theoretical and Fundamental Chemistry |
The United States National Chemistry Olympiad (or USNCO) is a contest held by the American Chemical Society (ACS) used to select the four-student team that represents the United States at the International Chemistry Olympiad (IChO).
Each local ACS section selects eight students (or more for larger ACS sections) to take the USNCO National Exam. To qualify for the national exam, students must first take the local exam. Approximately 16,000 U.S. students sit for the local exam each year. More than 1000 students qualify to take the National Exam annually. | 1 | Applied and Interdisciplinary Chemistry |
Pyranose and furanose forms can exist in different conformers and one can interconvert between the different conformations if an energy requirement is met. For the furanose system there are two possible conformers: twist (T) and envelope (E). In the pyranose system five conformers are possible: chair (C), boat (B), skew (S), half-chair (H) or envelope (E). In all cases there are four or more atoms that make up a plane. In order to define which atoms are above and below the plane one must orient the molecule so that the atoms are numbered clockwise when looking from the top. Atoms above the plane are prefixed as a superscript and atoms below the plane are suffixed as a subscript. If the ring oxygen is above or below the plane it must be prefixed or suffixed appropriately. | 0 | Theoretical and Fundamental Chemistry |
Its membership in the amphetamine class has made pseudoephedrine a sought-after chemical precursor in the illicit manufacture of methamphetamine and methcathinone. As a result of the increasing regulatory restrictions on the sale and distribution of pseudoephedrine, pharmaceutical firms have reformulated medications to use alternative compounds, particularly phenylephrine, even though its efficacy as an oral decongestant has been demonstrated to be indistinguishable from placebo.
In the United States, federal laws control the sale of pseudoephedrine-containing products. Retailers in the US have created corporate policies restricting the sale of pseudoephedrine-containing products. Their policies restrict sales by limiting purchase quantities and requiring a minimum age and government issued photographic identification. These requirements are similar to and sometimes more stringent than existing law. Internationally, pseudoephedrine is listed as a Table I precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances. | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.