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Vinyl- and acetylenic ethers are far less common than alkyl or aryl ethers. Vinylethers, often called enol ethers, are important intermediates in organic synthesis. Acetylenic ethers are especially rare. Di-tert-butoxyacetylene is the most common example of this rare class of compounds. | 0 | Theoretical and Fundamental Chemistry |
The biological monitoring working party (BMWP) is a procedure for measuring water quality using families of macroinvertebrates as biological indicators.
The method is based on the principle that different aquatic invertebrates have different tolerances to pollutants. In the case of BMWP, this is based on the sensitivity/tolerance to organic pollution (i.e. nutrient enrichment that can affect the availability of dissolved oxygen). It is important to recognise that the ranking of sensitivity/tolerance will vary for different kinds of pollution. In the case of BMWP/Organic pollution rankings, the presence of mayflies or stoneflies for instance indicate the cleanest waterways and are given a tolerance score of 10. The lowest scoring invertebrates are worms (Oligochaeta) which score 1. The number of different macroinvertebrates is also an important factor, because a better quality water is assumed to contain fewer pollutants that would exclude "sensitive" species - resulting in a higher diversity.
Kick sampling, where a net is placed downstream from the sampler and the river bed is agitated with the foot for a given period of time (the standard is 3 minutes), is employed. Any macroinvertebrates caught in the net are stored and preserved with an alcohol solution, and identified to the family level, this can be done with the live organisms as well.
The BMWP score equals the sum of the tolerance scores of all macroinvertebrate families in the sample. A higher BMWP score is considered to reflect a better water quality. Alternatively, also the Average Score Per Taxon (ASPT) score is calculated. The ASPT equals the average of the tolerance scores of all macroinvertebrate families found, and ranges from 0 to 10. The main difference between both indices is that ASPT does not depend on the family richness. Once BMWP and ASPT are calculated, the Lincoln Quality Index (LQI) is used to assess the water quality in the Anglian Water Authority area.
Other indices that can be used to assess water quality are the Chandler Score, the Trent Biotic Index and the Rapid Bioassessment Protocols. | 0 | Theoretical and Fundamental Chemistry |
Although the ternary fission process is less common than the binary process, it still produces significant helium-4 and tritium gas buildup in the fuel rods of modern nuclear reactors. This phenomenon was initially detected in 1957, within the environs of the Savannah River National Laboratory. | 0 | Theoretical and Fundamental Chemistry |
A warm body emitting photons has a monochromatic emission coefficient relating to its temperature and total power radiation. This is sometimes called the second Einstein coefficient, and can be deduced from quantum mechanical theory. | 0 | Theoretical and Fundamental Chemistry |
For U.S. food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of daily value (%DV). For magnesium labeling purposes 100% of the daily value was 400 mg, but as of May 27, 2016, it was revised to 420 mg to bring it into agreement with the RDA. A table of the old and new adult Daily Values is provided at Reference Daily Intake. | 1 | Applied and Interdisciplinary Chemistry |
When used as a fully supported roof covering, copper is half the weight (including substrate) of lead and only a quarter of tiled roofs. This generally provides savings in supporting structure and materials costs. Copper cladding offers additional opportunities to reduce the weight of copper structures (For more details, see: Copper cladding and Wall cladding). | 1 | Applied and Interdisciplinary Chemistry |
UFPs are both manufactured and naturally occurring. Hot volcanic lava, ocean spray, and smoke are common natural UFPs sources. UFPs can be intentionally fabricated as fine particles to serve a vast range of applications in both medicine and technology. Other UFPs are byproducts, like emissions, from specific processes, combustion reactions, or equipment such as printer toner and automobile exhaust. Anthropogenic sources of UFPs include combustion of gas, coal or hydrocarbons, biomass burning (i.e. agricultural burning, forest fires and waste disposal), vehicular traffic and industrial emissions, tire wear and tear from car brakes, air traffic, seaport, maritime transportation, construction, demolition, restoration and concrete processing, domestic wood stoves, outdoor burning, kitchen, and cigarette smoke. In 2014, an air quality study found harmful ultrafine particles from the takeoffs and landings at Los Angeles International Airport to be of much greater magnitude than previously thought. There are a multitude of indoor sources that include but are not limited to laser printers, fax machines, photocopiers, the peeling of citrus fruits, cooking, tobacco smoke, penetration of contaminated outdoor air, chimney cracks and vacuum cleaners.
UFPs have a variety of applications in the medical and technology fields. They are used in diagnostic imagining, and novel drug delivery systems that include targeting the circulatory system, and or passage of the blood brain barrier to name just a few. Certain UFPs like silver based nanostructures have antimicrobial properties that are exploited in wound healing and internal instrumental coatings among other uses, in order to prevent infections. In the area of technology, carbon based UFPs have a plethora of applications in computers. This includes the use of graphene and carbon nanotubes in electronic as well as other computer and circuitry components. Some UFPs have characteristics similar to gas or liquid and are useful in powders or lubricants. | 0 | Theoretical and Fundamental Chemistry |
In population dynamics, kinesis is the change of the diffusion coefficient in response to the change of conditions. In models of purposeful kinesis, diffusion coefficient depends on fitness (or reproduction coefficient) r:
where is constant and r depends on population densities and abiotic characteristics of the living conditions. This dependence is a formalisation of the simple rule: Animals stay longer in good conditions and leave quicker bad conditions (the "Let well enough alone" model). | 1 | Applied and Interdisciplinary Chemistry |
A piping and instrumentation diagram (P&ID) is defined as follows:
# A diagram which shows the interconnection of process equipment and the instrumentation used to control the process. In the process industry, a standard set of symbols is used to prepare drawings of processes. The instrument symbols used in these drawings are generally based on International Society of Automation (ISA) Standard S5.1
# The primary schematic drawing used for laying out a process control installation.
They usually contain the following information:
* Mechanical equipment, including:
**Pressure vessels, columns, tanks, pumps, compressors, heat exchangers, furnaces, wellheads, fans, cooling towers, turbo-expanders, pig traps (see symbols below)
**Bursting discs, restriction orifices, strainers and filters, steam traps, moisture traps, sight-glasses, silencers, flares and vents, flame arrestors, vortex breakers, eductors
*Process piping, sizes and identification, including:
**Pipe classes and piping line numbers
**Flow directions
**Interconnections references
**Permanent start-up, flush and bypass lines
**Pipelines and flowlines
**Blinds and spectacle blinds
**Insulation and heat tracing
*Process control instrumentation and designation (names, numbers, unique tag identifiers), including:
**Valves and their types and identifications (e.g. isolation, shutoff, relief and safety valves, valve interlocks)
**Control inputs and outputs (sensors and final elements, interlocks)
**Miscellaneous - vents, drains, flanges, special fittings, sampling lines, reducers and swages
*Interfaces for class changes
*Computer control system
*Identification of components and subsystems delivered by others
P&IDs are originally drawn up at the design stage from a combination of process flow sheet data, the mechanical process equipment design, and the instrumentation engineering design. During the design stage, the diagram also provides the basis for the development of system control schemes, allowing for further safety and operational investigations, such as a Hazard and operability study (HAZOP). To do this, it is critical to demonstrate the physical sequence of equipment and systems, as well as how these systems connect.
P&IDs also play a significant role in the maintenance and modification of the process after initial build. Modifications are red-penned onto the diagrams and are vital records of the current plant design.
They are also vital in enabling development of;
*Control and shutdown schemes
*Safety and regulatory requirements
*Start-up sequences
*Operational understanding.
P&IDs form the basis for the live mimic diagrams displayed on graphical user interfaces of large industrial control systems such as SCADA and distributed control systems. | 1 | Applied and Interdisciplinary Chemistry |
The NCEC was formed in 1973 as a government agency. On 1 March 1979 the Centre launched, in cooperation with the Home Office, its Hazfile computer database, made available to fifteen British fire services, listing over 10,000 chemical compounds; this was later replaced by the Chemdata system. A similar system in the USA is called RTECS (Registry of Toxic Effects of Chemical Substances). | 1 | Applied and Interdisciplinary Chemistry |
Biodegradation of any plastic is a process that happens at solid/liquid interface whereby the enzymes in the liquid phase depolymerize the solid phase. Certain types of bioplastics as well as conventional plastics containing additives are able to biodegrade. Bioplastics are able to biodegrade in different environments hence they are more acceptable than conventional plastics. Biodegradability of bioplastics occurs under various environmental conditions including soil, aquatic environments and compost. Both the structure and composition of biopolymer or bio-composite have an effect on the biodegradation process, hence changing the composition and structure might increase biodegradability. Soil and compost as environment conditions are more efficient in biodegradation due to their high microbial diversity. Composting not only biodegrades bioplastics efficiently but it also significantly reduces the emission of greenhouse gases. Biodegradability of bioplastics in compost environments can be upgraded by adding more soluble sugar and increasing temperature. Soil environments on the other hand have high diversity of microorganisms making it easier for biodegradation of bioplastics to occur. However, bioplastics in soil environments need higher temperatures and a longer time to biodegrade. Some bioplastics biodegrade more efficiently in water bodies and marine systems; however, this causes danger to marine ecosystems and freshwater. Hence it is accurate to conclude that biodegradation of bioplastics in water bodies which leads to the death of aquatic organisms and unhealthy water can be noted as one of the negative environmental impacts of bioplastics. | 0 | Theoretical and Fundamental Chemistry |
Lactoferricin is an amphipathic, cationic peptide with anti-microbial and anti-cancer properties. It can be generated by the pepsin-mediated digestion of lactoferrin.
Lactoferricin is the most studied AMP derived from milk protein. The complete sequence of lactoferricin corresponds to lactoferrin fragment 17-41 (FKCRRWQWRM KKLGAPSITCVRRAF; [http://milkampdb.org/LFB0084 LFB0084] ) and sequences from within this fragment are also antimicrobial. The MilkAMP database contains a total of 111 peptides (natural, synthetic and modified) comprising or derived from the complete lactoferricin. In humans, lactoferricin corresponds to lactoferrin fragment 1-47 but consists of two subunits, namely fragments 1-11 and 12-47 ([http://milkampdb.org/LFH0009 LFH0009] ), connected by a disulfide bridge.
Human Lactoferricin and Bovine Lactoferricin are two greatly studied forms of Lactoferricin. These two forms have great sequence differences. Bovine Lactoferricin contains 25 residues, while Human Lactoferricin contains 49 residues. Also, when placed in solution Bovine Lactoferricin forms a β-pleated sheet, while Human Lactoferricin forms a coiled structure. | 1 | Applied and Interdisciplinary Chemistry |
Many compounds with luster and electrical conductivity maintain a simple stoichiometric formula, such as the golden TiO, blue-black RuO or coppery ReO, all of obvious oxidation state. Ultimately, assigning the free metallic electrons to one of the bonded atoms is not comprehensive and can yield unusual oxidation states. Examples are the LiPb and ordered alloys, the composition and structure of which are largely determined by atomic size and packing factors. Should oxidation state be needed for redox balancing, it is best set to 0 for all atoms of such an alloy. | 0 | Theoretical and Fundamental Chemistry |
The DeMayo reaction is a photochemical reaction in which the enol of a 1,3-diketone reacts with an alkene (or another species with a C=C bond) and the resulting cyclobutane ring undergoes a retro-aldol reaction to yield a 1,5-diketone:
The net effect is to add the two carbon atoms in the C=C double bond between the two carbonyl groups of the diketone. It is thus useful in syntheses both as a relatively selective way to join two parts of a molecule and as a way to apply the more developed chemistry of 1,3-diketone synthesis to 1,5-diketones. The first part is a [2+2] cycloaddition. The ensuing retro-aldol cleavage is favored by the relative instability of the cyclobutane ring. | 0 | Theoretical and Fundamental Chemistry |
The theory behind experimental archaeology comes from the new archaeology technique of the 1950s to use modern day examples in the form of experiments and ethnologies as analogues to past processes. Experimental archaeometallurgy is considered a part of general experimental archaeology and is rarely separated in the literature and as such, many of the principles stay the same while there is a greater focus on a single subject.
Archaeometallurgy works as a good field for experimental reproduction because of the evidence that is provided from excavation is a good starting point for reconstruction. Metallurgical remains provide a durable product that has relatively durable evidence of production methods such as slag and refractory ceramic remains. Experimentation comes in a varied amount of forms including object replication, system replication, behavioral replication, and process replication. | 1 | Applied and Interdisciplinary Chemistry |
The FBP is defined by the ASTM F-316-03 standard as the pressure at which the first continuous gas bubbles are detected. In practice FBP is associated as the largest or maximum pore size.
The calculation of the FBP requires to select a certain minimum flow (e.g. 30, 50, 100 ml/min) and when it is achieved record the pressure. Then this pressure is used to calculate the FBP size. The question is to select the minimum flow through the sample and the major disadvantage is that this minimum flow is different for every sample and it is not easy to determine a priori. If a certain minimum flow is selected for the calculation it is possible that the largest pore in the sample was already open for a while before that particular flow was determined.
With the step/stability method it is possible to measure the true FBP. When applying a constant gas flow, before the opening of the largest flow the pressure increases in a linear way. At the moment that the gas flow passes through the sample via the largest pore the pressure increase drops and it is this particular pressure the one that corresponds to the FBP of the sample. | 1 | Applied and Interdisciplinary Chemistry |
Mitochondria contain their own genome. The human mitochondrial genome is a circular double-stranded DNA molecule of about 16 kilobases. It encodes 37 genes: 13 for subunits of respiratory complexes I, III, IV and V, 22 for mitochondrial tRNA (for the 20 standard amino acids, plus an extra gene for leucine and serine), and 2 for rRNA (12S and 16S rRNA). One mitochondrion can contain two to ten copies of its DNA. One of the two mitochondrial DNA (mtDNA) strands has a disproportionately higher ratio of the heavier nucleotides adenine and guanine, and this is termed the heavy strand (or H strand), whereas the other strand is termed the light strand (or L strand). The weight difference allows the two strands to be separated by centrifugation. mtDNA has one long non-coding stretch known as the non-coding region (NCR), which contains the heavy strand promoter (HSP) and light strand promoter (LSP) for RNA transcription, the origin of replication for the H strand (OriH) localized on the L strand, three conserved sequence boxes (CSBs 1–3), and a termination-associated sequence (TAS). The origin of replication for the L strand (OriL) is localized on the H strand 11,000 bp downstream of OriH, located within a cluster of genes coding for tRNA.
As in prokaryotes, there is a very high proportion of coding DNA and an absence of repeats. Mitochondrial genes are transcribed as multigenic transcripts, which are cleaved and polyadenylated to yield mature mRNAs. Most proteins necessary for mitochondrial function are encoded by genes in the cell nucleus and the corresponding proteins are imported into the mitochondrion. The exact number of genes encoded by the nucleus and the mitochondrial genome differs between species. Most mitochondrial genomes are circular. In general, mitochondrial DNA lacks introns, as is the case in the human mitochondrial genome; however, introns have been observed in some eukaryotic mitochondrial DNA, such as that of yeast and protists, including Dictyostelium discoideum. Between protein-coding regions, tRNAs are present. Mitochondrial tRNA genes have different sequences from the nuclear tRNAs, but lookalikes of mitochondrial tRNAs have been found in the nuclear chromosomes with high sequence similarity.
In animals, the mitochondrial genome is typically a single circular chromosome that is approximately 16 kb long and has 37 genes. The genes, while highly conserved, may vary in location. Curiously, this pattern is not found in the human body louse (Pediculus humanus). Instead, this mitochondrial genome is arranged in 18 minicircular chromosomes, each of which is 3–4 kb long and has one to three genes. This pattern is also found in other sucking lice, but not in chewing lice. Recombination has been shown to occur between the minichromosomes. | 1 | Applied and Interdisciplinary Chemistry |
In practical sense, the most important reaction of metal acyls is their detachment by reductive elimination of aldehydes from acyl metal hydrides:
:LMC(O)R(H) → LM + RCHO
This reaction is the final step of hydroformylation.
Another important reaction is decarbonylation. This reaction requires that the acyl complex be coordinatively unsaturated:
:LMC(O)R → LM(CO)R + L
:LMC(O)R → LM(CO)R
The oxygen center of acyl ligands is basic. This aspect is manifested in O-alkylations, which converts acyl complexes to alkoxycarbene complexes: | 0 | Theoretical and Fundamental Chemistry |
The porous network of clay particles enable nanocomposite hydrogels to swell in the presence of water. Swelling (and de-swelling) distinguishes NC gels from conventionally-made hydrogels (OR gels) as it is a property that OR gels lack. The swelling property of NC gels allows them to collect the surrounding aqueous solution instead of being dissolved by it, which helps make them good candidates for drug delivery carriers. | 0 | Theoretical and Fundamental Chemistry |
Among St Amands many treatises was one on the magnet. His pharmacopoeia was the Commentary on the Antedotary of Nicholas'.
Like Roger Bacon (c. 1219–c. 1292)) after him, St Amand wrote on experimental method. The historian of science Lynn Thorndike explains that St Amand "asserts that experimentum alone is timorous and fallacious, but that fortified by reason it gives experimental knowledge." In his view, what St Amand meant was that experimentation had to be methodical, and used alongside theory. On simples used in herbal medicine, St Amand stated specific rules for practical testing: he advised that the specimen had to be pure; that the test should be on a simple disease; that the test be repeated; and that the dose should depend on the patient. Thorndike notes that both St Amand and Albertus Magnus preceded Bacon in their use of the phrase "experimental knowledge". | 1 | Applied and Interdisciplinary Chemistry |
Lead-Bismuth Eutectic or LBE is a eutectic alloy of lead (44.5 at%) and bismuth (55.5 at%) used as a coolant in some nuclear reactors, and is a proposed coolant for the lead-cooled fast reactor, part of the Generation IV reactor initiative.
It has a melting point of 123.5 °C/254.3 °F (pure lead melts at 327 °C/621 °F, pure bismuth at 271 °C/520 °F) and a boiling point of 1,670 °C/3,038 °F.
Lead-bismuth alloys with between 30% and 75% bismuth all have melting points below 200 °C/392 °F.
Alloys with between 48% and 63% bismuth have melting points below 150 °C/302 °F.
While lead expands slightly on melting and bismuth contracts slightly on melting, LBE has negligible change in volume on melting. | 1 | Applied and Interdisciplinary Chemistry |
Digestive systems take many forms. There is a fundamental distinction between internal and external digestion. External digestion developed earlier in evolutionary history, and most fungi still rely on it. In this process, enzymes are secreted into the environment surrounding the organism, where they break down an organic material, and some of the products diffuse back to the organism. Animals have a tube (gastrointestinal tract) in which internal digestion occurs, which is more efficient because more of the broken down products can be captured, and the internal chemical environment can be more efficiently controlled.
Some organisms, including nearly all spiders, secrete biotoxins and digestive chemicals (e.g., enzymes) into the extracellular environment prior to ingestion of the consequent "soup". In others, once potential nutrients or food is inside the organism, digestion can be conducted to a vesicle or a sac-like structure, through a tube, or through several specialized organs aimed at making the absorption of nutrients more efficient. | 1 | Applied and Interdisciplinary Chemistry |
The phase-down mandated by the AIM Act will lead to R-410A's replacement by other refrigerants beginning in 2022. Alternative refrigerants are available, including hydrofluoroolefins, hydrocarbons (such as propane R-290 and isobutane R-600A), and even carbon dioxide (R-744, GWP = 1). The alternative refrigerants have much lower GWP than R-410A. | 1 | Applied and Interdisciplinary Chemistry |
Some tetrabutylammonium salts of simple anions include:
*tetrabutylammonium fluoride, a desilylation reagent.
*tetrabutylammonium bromide, a precursor to other tetrabutylammonium salts via salt metathesis reactions.
*tetrabutylammonium iodide, a low cost catalyst.
*tetrabutylammonium triiodide, a common carrier of the triiodide anion used in chemical synthesis.
*tetrabutylammonium hydroxide, a precursor to other tetrabutylammonium salts via acid-base reactions.
*tetrabutylammonium hexafluorophosphate, an electrolyte for nonaqueous electrochemistry.
Some tetrabutylammonium salts of more complex examples include:
*polyoxometalates.
*NS.
*metal carbonyl anions.
*Synthetic iron-sulfur clusters such as
*Octachlorodirhenate (). | 0 | Theoretical and Fundamental Chemistry |
The TET enzymes do not specifically bind to 5-methylcytosine except when recruited. Without recruitment or targeting, TET1 predominantly binds to high CG promoters and CpG islands (CGIs) genome-wide by its CXXC domain that can recognize un-methylated CGIs. TET2 does not have an affinity for 5-methylcytosine in DNA. The CXXC domain of the full-length TET3, which is the predominant form expressed in neurons, binds most strongly to CpGs where the C was converted to 5-carboxycytosine (5caC). However, it also binds to un-methylated CpGs.
For a TET enzyme to initiate demethylation it must first be recruited to a methylated CpG site in DNA. Two of the proteins shown to recruit a TET enzyme to a methylated cytosine in DNA are OGG1 (see figure Initiation of DNA demethylation at a CpG site) and EGR1. | 1 | Applied and Interdisciplinary Chemistry |
The Dortmund Data Bank (short DDB) is a factual data bank for thermodynamic and thermophysical data. Its main usage is the data supply for process simulation where experimental data are the basis for the design, analysis, synthesis, and optimization of chemical processes. The DDB is used for fitting parameters for thermodynamic models like NRTL or UNIQUAC and for many different equations describing pure component properties, e.g., the Antoine equation for vapor pressures. The DDB is also used for the development and revision of predictive methods like UNIFAC and PSRK. | 0 | Theoretical and Fundamental Chemistry |
Concrete degradation may have many different causes. Concrete is mostly damaged by the corrosion of reinforcement bars due to the carbonatation of hardened cement paste or chloride attack under wet conditions. Chemical damages are caused by the formation of expansive products produced by various chemical reactions, by aggressive chemical species present in groundwater and seawater (chlorides, sulfates, magnesium ions), or by microorganisms (bacteria, fungi...). Other damaging processes can also involve calcium leaching by water infiltration and different physical phenomena initiating cracks formation and propagation. All these detrimental processes and damaging agents adversely affects the concrete mechanical strength and its durability.
The most destructive agent of concrete structures and components is probably water. Indeed, water often directly participates to chemical reactions as a reagent and is always necessary as a solvent, or a reacting medium, making transport of solutes and reactions possible. Without water, many harmful reactions cannot progress, or are so slow that their harmful consequences become negligible during the planned service life of the construction. Dry concrete has a much longer lifetime than water saturated concrete in contact with circulating water. So, when possible, concrete must first be protected from water infiltrations. | 1 | Applied and Interdisciplinary Chemistry |
Transcription activator-like effector nuclease, TALENs, are a set of restriction enzymes that be created to cut out desired DNA sequences. These enzymes are mostly used in combination with CRISPR-CAS9, Zinc finger nuclease, or HDR. The main reason for this is the ability for these enzymes to have the precision to cut and separate the desired sequence within a gene. | 1 | Applied and Interdisciplinary Chemistry |
A large number of examples of vicinal difunctionalization of unsaturated carbonyl compounds exist in the literature. In one example, the difunctionalization of unsaturated lactone 1 was employed en route to isostegane. This transformation was accomplished in one pot.
Because the reaction creates two new bonds with a moderately high degree of stereocontrol, it represents a highly convergent synthetic method. | 0 | Theoretical and Fundamental Chemistry |
Between 2007 and 2008, the waste commissioner Guido Bertolaso, (the head of the civil protection department), planned to open a landfill but this was opposed by residents of Chiaiano. There was similar resistance in Pianosa to reopening a closed landfill proposed by government commissioner Giovanni De Gennaro. Some of the protests turned violent, and in May 2008, it became a penal felony to protest in the vicinity of landfills, incinerators or any plant related to waste management. It is alleged that there was collusion between local political interests and organised crime over building interests.
By July 17, 2008, Berlusconi declared that the emergency had ended.
The incinerator of Acerra has also received backlash in the local area. In 2009, the Acerra incineration facility was completed at a cost of over €350 million. The incinerator burns 600,000 tons of waste per year to produce refuse-derived fuel. The energy produced from the facility is enough to power 200,000 households per year. | 1 | Applied and Interdisciplinary Chemistry |
Ribosomal RNA, or rRNA, forms the nucleic acid component of ribosomes. rRNA modifications take place in and around the peptidyl transferasecenter, the active site of the ribosome. Some modifications include pseudouridines, 2′-O-methylations on backbone sugars, and methylated bases. It is not well known what the biological effects of these modifications are on the rRNA molecule, but one hypothesis is that they help stabilize the structure and enhance the function of the ribosome, especially during ribosome formation. Moreover, these modifications may alter the chemical properties of the rRNA such that the correct tertiary structure is favored. 2-O-methylation prevents backbone hydrolysis; other noted modifications also seem to help with stabilizing rRNA secondary structures and preventing damage to rRNA strands. 2-O-methylation also helps to increase base stacking forces, stabilizing the secondary and tertiary structure of rRNA even further. Collectively, these modifications in rRNA are indispensable to ribosomal function. | 1 | Applied and Interdisciplinary Chemistry |
Although the Montreal Protocol regulates the phasing out of HCFCs, there was no international agreement on the regulation of HFCs until late 2016 when the Kigali Amendment under the Montreal Protocol was signed, which has put compulsory phase wise phasing out of CFC gases. Efforts are ongoing to develop a global approach for the control of HFCs. Most recently, this has taken the form of a declaration of support for a global phase-down as part of the outcomes of the "Rio+20" United Nations Conference on Sustainable Development. | 1 | Applied and Interdisciplinary Chemistry |
Figure 1 is the phase diagram of He. It is a pressure-temperature (p-T) diagram indicating the solid and liquid regions separated by the melting curve (between the liquid and solid state) and the liquid and gas region, separated by the vapor-pressure line. This latter ends in the critical point where the difference between gas and liquid disappears. The diagram shows the remarkable property that He is liquid even at absolute zero. He is only solid at pressures above 25 bar.
Figure 1 also shows the λ-line. This is the line that separates two fluid regions in the phase diagram indicated by He-I and He-II. In the He-I region the helium behaves like a normal fluid; in the He-II region the helium is superfluid.
The name lambda-line comes from the specific heat – temperature plot which has the shape of the Greek letter λ. See figure 2, which shows a peak at 2.172 K, the so-called λ-point of He.
Below the lambda line the liquid can be described by the so-called two-fluid model. It behaves as if it consists of two components: a normal component, which behaves like a normal fluid, and a superfluid component with zero viscosity and zero entropy. The ratios of the respective densities ρ/ρ and ρ/ρ, with ρ (ρ) the density of the normal (superfluid) component, and ρ (the total density), depends on temperature and is represented in figure 3. By lowering the temperature, the fraction of the superfluid density increases from zero at T to one at zero kelvins. Below 1 K the helium is almost completely superfluid.
It is possible to create density waves of the normal component (and hence of the superfluid component since ρ + ρ = constant) which are similar to ordinary sound waves. This effect is called second sound. Due to the temperature dependence of ρ (figure 3) these waves in ρ are also temperature waves. | 1 | Applied and Interdisciplinary Chemistry |
There exist many different conformations for cyclohexane, such as chair, boat, and twist-boat, but the chair conformation is the most commonly observed state for cyclohexanes because it requires the least amount of energy. The chair conformation minimizes both angle strain and torsional strain by having all carbon-carbon bonds at 110.9° and all hydrogens staggered from one another.
The molecular motions involved in a chair flip are detailed in the figure on the right: The half-chair conformation (D, 10.8 kcal/mol, C symmetry) is the energy maximum when proceeding from the chair conformer (A, 0 kcal/mol reference, D symmetry) to the higher energy twist-boat conformer (B, 5.5 kcal/mol, D symmetry). The boat conformation (C, 6.9 kcal/mol, C symmetry) is a local energy maximum for the interconversion of the two mirror image twist-boat conformers, the second of which is converted to the other chair confirmation through another half-chair. At the end of the process, all axial positions have become equatorial and vice versa. The overall barrier of 10.8 kcal/mol corresponds to a rate constant of about 10 s at room temperature.
Note that the twist-boat (D) conformer and the half-chair (C) transition state are in chiral point groups and are therefore chiral molecules. In the figure, the two depictions of B and two depictions of D are pairs of enantiomers.
As a consequence of the chair flip, the axially-substituted and equatorially-substituted conformers of a molecule like chlorocyclohexane cannot be isolated at room temperature. However, in some cases, the isolation of individual conformers of substituted cyclohexane derivatives has been achieved at low temperatures (–150 °C). | 0 | Theoretical and Fundamental Chemistry |
Some plants mimic the presence of insect eggs on their leaves, dissuading insect species from laying their eggs there. Because female butterflies are less likely to lay their eggs on plants that already have butterfly eggs, some species of neotropical vines of the genus Passiflora (Passion flowers) contain physical structures resembling the yellow eggs of Heliconius butterflies on their leaves, which discourage oviposition by butterflies. | 1 | Applied and Interdisciplinary Chemistry |
Gmelins test is a chemical test used for detecting the presence of bile pigments in urine. It is named after Leopold Gmelin, who introduced the test. Five millilitres of urine is slowly added to five millilitres of concentrated nitric acid in a test-tube. Different coloured rings between the two layers are visible if bile pigments are present as they are oxidised to various chemical products. Nitric acid is used as the oxidising agent. Blue, green and violet rings are seen if bilirubin is present. Gmelins test is not sensitive, so a positive result always indicates the presence of bile pigments, but a negative result does not exclude the presence of small quantities of bile pigments. | 0 | Theoretical and Fundamental Chemistry |
The rise in core (RIC) method is an alternate reservoir wettability characterization method described by S. Ghedan and C. H. Canbaz in 2014. The method enables estimation of all wetting regions such as strongly water wet, intermediate water, oil wet and strongly oil wet regions in relatively quick and accurate measurements in terms of Contact angle rather than wettability index.
During the RIC experiments, core samples saturated with selected reservoir fluid were subjected to imbibition from a second reservoir fluid. RIC wettability measurements are compared with and modified – Amott test and USBM measurements using core plug pairs from different heights of a thick carbonate reservoir. Results show good coherence. The RIC method is an alternate method to Amott and USBM methods and that efficiently characterizes Reservoir Wettability. | 1 | Applied and Interdisciplinary Chemistry |
The mechanism of antiporter transport involves several key steps and a series of conformational changes that are dictated by the structural element described above:
# The substrate binds to its specific binding site on the extracellular side of the plasma membrane, forming a temporary substrate-bound open form of the antiporter.
# This becomes an occluded, substrate-bound state that is still facing the extracellular space.
# The antiporter undergoes a conformational change to become an occluded, substrate-bound protein that is now facing the cytosol. As it does so, it passes through a temporary fully-occluded intermediate stage.
# The substrate is released from the antiporter as it takes on an open, inward-facing conformation.
# The antiporter can now bind to its second substrate and transport it in the opposite direction by taking on its transient substrate-bound open state.
# This is followed by an occluded, substrate-bound state that is still facing the cytosol, a conformation change with a temporary fully-occluded intermediate stage, and a return to the antiporter's open, outward-facing conformation.
# The second substrate is released and the antiporter can return to its original conformation state, where it is ready to bind to new molecules or ions and repeat its transport process. | 1 | Applied and Interdisciplinary Chemistry |
As of November 2023, the International Agency for Research on Cancer (IARC) has classified PFOA as carcinogenic to humans (Group 1) based on “sufficient” evidence for cancer in animals and “strong” mechanistic evidence in exposed humans. IARC also classified PFOS as possibly carcinogenic to humans (Group 2b) based on “strong” mechanistic evidence. There is a lack of high-quality epidemiological data on the associations between many specific PFAS chemicals and specific cancer types, and research is ongoing. | 0 | Theoretical and Fundamental Chemistry |
The harmonic trap potential:
is a model system with many applications in modern physics. The density of states (or more accurately, the degree of degeneracy) for a given spin species is:
where is the harmonic oscillation frequency.
The Fermi energy for a given spin species is: | 0 | Theoretical and Fundamental Chemistry |
The detergent effect draws on surfactin's ability to insert its fatty acid chain into the phospholipid layer, disorganizing the cell membrane to increase its permeability. Insertion of several surfactin molecules into the membrane can lead to the formation of mixed micelles by self-association and bilayer influenced by fatty chain hydrophobicity ultimately leading to bilayer solubilization. | 0 | Theoretical and Fundamental Chemistry |
Some methods are based on solutions to the Poisson–Boltzmann equation (PBE), often referred to as FDPB-based methods (FDPB stands for "finite difference Poisson–Boltzmann"). The PBE is a modification of Poisson's equation that incorporates a description of the effect of solvent ions on the electrostatic field around a molecule.
The [http://newbiophysics.cs.vt.edu/H++/ H++ web server], the [https://web.archive.org/web/20070728080556/http://enzyme.ucd.ie/pKD pKD webserver], [https://gunnerlab.github.io/Stable-MCCE/ MCCE2], [http://agknapp.chemie.fu-berlin.de/karlsberg Karlsberg+], [https://www.itqb.unl.pt/labs/molecular-simulation/in-house-software/ PETIT] and [https://rtullmann.de/parts/gmct-gcem.html GMCT] use the FDPB method to compute pK values of amino acid side chains.
FDPB-based methods calculate the change in the pK value of an amino acid side chain when that side chain is moved from a hypothetical fully solvated state to its position in the protein. To perform such a calculation, one needs theoretical methods that can calculate the effect of the protein interior on a pK value, and knowledge of the pKa values of amino acid side chains in their fully solvated states. | 0 | Theoretical and Fundamental Chemistry |
Excess heme is converted in macrophages to Biliverdin and ferrous ions by the enzyme HO-1. Biliverdin formed further gets converted to Bilirubin and carbon monoxide. Biliverdin and Bilirubin are potent anti oxidants and regulate important biological processes like inflammation, apoptosis, cell proliferation, fibrosis and angiogenesis. | 1 | Applied and Interdisciplinary Chemistry |
Power MOSFETs typically increase their on-resistance with temperature. Under some circumstances, power dissipated in this resistance causes more heating of the junction, which further increases the junction temperature, in a positive feedback loop. As a consequence, power MOSFETs have stable and unstable regions of operation. However, the increase of on-resistance with temperature helps balance current across multiple MOSFETs connected in parallel, so current hogging does not occur. If a MOSFET transistor produces more heat than the heatsink can dissipate, then thermal runaway can still destroy the transistors. This problem can be alleviated to a degree by lowering the thermal resistance between the transistor die and the heatsink. See also Thermal Design Power. | 1 | Applied and Interdisciplinary Chemistry |
Modern research topics in solid-state physics include:
*High-temperature superconductivity
*Quasicrystals
*Spin glass
*Strongly correlated materials
*Two-dimensional materials
*Nanomaterials | 1 | Applied and Interdisciplinary Chemistry |
The classical and most reliable method of log P determination is the shake-flask method, which consists of dissolving some of the solute in question in a volume of octanol and water, then measuring the concentration of the solute in each solvent. The most common method of measuring the distribution of the solute is by UV/VIS spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
A subset X of a metric space is relatively dense if there exists a number r such that all points of X are within distance r of X, and it is uniformly discrete if there exists a number ε such that no two points of X are within distance ε of each other. A set that is both relatively dense and uniformly discrete is called a Delone set. When X is a subset of a vector space, its Minkowski difference X − X is the set {x − y | x, y in X} of differences of pairs of elements of X.
With these definitions, a Meyer set may be defined as a relatively dense set X for which X − X is uniformly discrete. Equivalently, it is a Delone set for which X − X is Delone, or a Delone set X for which there exists a finite set F with X − X ⊂ X + F
Some additional equivalent characterizations involve the set
defined for a given X and ε, and approximating (as ε approaches zero) the definition of the reciprocal lattice of a lattice. A relatively dense set X is a Meyer set if and only if
* For all ε > 0, X is relatively dense, or equivalently
* There exists an ε with 0 is relatively dense.
A character of an additively closed subset of a vector space is a function that maps the set to the unit circle in the plane of complex numbers, such that the sum of any two elements is mapped to the product of their images. A set X is a harmonious set if, for every character χ on the additive closure of X and every ε > 0, there exists a continuous character on the whole space that ε-approximates χ. Then a relatively dense set X is a Meyer set if and only if it is harmonious. | 0 | Theoretical and Fundamental Chemistry |
The U.S. Central Intelligence Agency (CIA) became interested in LSD when they read reports alleging that American prisoners during the Korean War were being brainwashed with the use of some sort of drug or "lie serum". LSD was the original centerpiece of the top secret MKULTRA project, an ambitious undertaking conducted from the 1950s through the 70s designed to explore the possibilities of pharmaceutical mind control. Hundreds of participants, including CIA agents, government employees, military personnel, prostitutes, members of the general public, and mental patients were given LSD, many without their knowledge or consent. The experiments often involved severe psychological torture. To guard against outward reactions, doctors conducted experiments in clinics and laboratories where subjects were monitored by EEG machines and had their words recorded. Some studies investigated whether drugs, stress or specific environmental conditions could be used to break prisoners or to induce confessions.
The CIA also created The Society for the Investigation of Human Ecology, which was a CIA funding front which provided grants to social scientists and medical researchers investigating questions of interest related to the MKULTRA program. Between 1960 and 1963, the CIA gave $856,782 worth of grants to different organizations. The researchers eventually concluded that LSD's effects were too varied and uncontrollable to make it of any practical use as a truth drug, and the project moved on to other substances. It would be decades before the U.S. government admitted the existence of the project and offered apologies to the families of those who were forced to participate in the experiments. During this time period, the use of LSD for psychochemical warfare was under consideration and testing, among other substances. Looking to replicate the effects of nerve gas created by the Germans during World War II without the toxicity, LSD was sought for use under the pretense that it could induce hysteria and psychoses, or at least an inability to fight without wholesale destruction of the enemy and their properties. Thousands of tests on willing research subjects took place at the Edgewood Arsenal in Maryland, with the ultimate conclusion being that LSD was too unpredictable and uncontrollable for any tactical use. | 1 | Applied and Interdisciplinary Chemistry |
A nutrient cycle is the movement and exchange of organic and inorganic matter back into the production of matter. The process is regulated by the pathways available in marine food webs, which ultimately decompose organic matter back into inorganic nutrients. Nutrient cycles occur within ecosystems. Energy flow always follows a unidirectional and noncyclic path, whereas the movement of mineral nutrients is cyclic. Mineral cycles include the carbon cycle, oxygen cycle, nitrogen cycle, phosphorus cycle and sulfur cycle among others that continually recycle along with other mineral nutrients into productive ecological nutrition.
There is considerable overlap between the terms for the biogeochemical cycle and nutrient cycle. Some textbooks integrate the two and seem to treat them as synonymous terms. However, the terms often appear independently. Nutrient cycle is more often used in direct reference to the idea of an intra-system cycle, where an ecosystem functions as a unit. From a practical point, it does not make sense to assess a terrestrial ecosystem by considering the full column of air above it as well as the great depths of Earth below it. While an ecosystem often has no clear boundary, as a working model it is practical to consider the functional community where the bulk of matter and energy transfer occurs. Nutrient cycling occurs in ecosystems that participate in the "larger biogeochemical cycles of the earth through a system of inputs and outputs." | 0 | Theoretical and Fundamental Chemistry |
Degenerate matter exhibits quantum mechanical properties when a fermion system temperature approaches absolute zero. These properties result from a combination of the Pauli exclusion principle and quantum confinement. The Pauli principle allows only one fermion in each quantum state and the confinement ensures that energy of these states increases as they are filled. The lowest states fill up and fermions are forced to occupy high energy states even at low temperature.
While the Pauli principle and Fermi-Dirac distribution applies to all matter, the interesting cases for degenerate matter involve systems of many fermions. These cases can be understood with the help of the Fermi gas model. Examples include electrons in metals and in white dwarf stars and neutrons in neutron stars. The electrons are confined by Coulomb attraction to positive ion cores; the neutrons are confined by gravitation attraction. The fermions, forced in to higher levels by the Pauli principle, exert pressure preventing further compression.
The allocation or distribution of fermions into quantum states ranked by energy is called the Fermi-Dirac distribution. Degenerate matter exhibits the results of Fermi-Dirac distribution. | 0 | Theoretical and Fundamental Chemistry |
Plastoglobuli (singular plastoglobulus, sometimes spelled plastoglobule(s)), are spherical bubbles of lipids and proteins about 45–60 nanometers across. They are surrounded by a lipid monolayer. Plastoglobuli are found in all chloroplasts, but become more common when the chloroplast is under oxidative stress, or when it ages and transitions into a gerontoplast. Plastoglobuli also exhibit a greater size variation under these conditions. They are also common in etioplasts, but decrease in number as the etioplasts mature into chloroplasts.
Plastoglobuli contain both structural proteins and enzymes involved in lipid synthesis and metabolism. They contain many types of lipids including plastoquinone, vitamin E, carotenoids and chlorophylls.
Plastoglobuli were once thought to be free-floating in the stroma, but it is now thought that they are permanently attached either to a thylakoid or to another plastoglobulus attached to a thylakoid, a configuration that allows a plastoglobulus to exchange its contents with the thylakoid network. In normal green chloroplasts, the vast majority of plastoglobuli occur singularly, attached directly to their parent thylakoid. In old or stressed chloroplasts, plastoglobuli tend to occur in linked groups or chains, still always anchored to a thylakoid.
Plastoglobuli form when a bubble appears between the layers of the lipid bilayer of the thylakoid membrane, or bud from existing plastoglobuli—though they never detach and float off into the stroma. Practically all plastoglobuli form on or near the highly curved edges of the thylakoid disks or sheets. They are also more common on stromal thylakoids than on granal ones. | 0 | Theoretical and Fundamental Chemistry |
The length of the vectors (or the strength of the field) is usually coded in color; alternatively, animation can be used. | 1 | Applied and Interdisciplinary Chemistry |
The CKLF-like MARVEL transmembrane domain-containing family (CMTM), previously termed the chemokine-like factor superfamily (CKLFSF), consists of 9 proteins, some of which have various isoforms due to alternative splicing of their respective genes. These proteins along with their isoforms are:
*Chemokine-like factor (CKLF), the founding member of this family, has 4 known isoforms, CKLF1 to CKLF4.
*CKLF like MARVEL transmembrane domain-containing 1 (CMTM1) has 23 known isoforms, CMTM1-v1 to CMTM1-v23.
*CKLF like MARVEL transmembrane domain-containing 2 (CMTM2) has no known isoforms.
*CKLF like MARVEL transmembrane domain-containing 3 (CMTM3) has no known isoforms.
*CKLF like MARVEL transmembrane domain-containing 4 (CMTM4) has 3 known isoforms, CMTM4-v1 to CMTM4-v3.
* CKLF-like MARVEL transmembrane domain-containing 5 (CMTM5) has 6 known isoforms, CMTM5-v1 to CMTM5-v6.
* CKLF like MARVEL transmembrane domain containing 6 (CMTM6) has no known isoforms.
* CKLF like MARVEL transmembrane domain containing 7 (CMTM7) has 2 isoforms, CMTM7-v1 and CMTM7-v2.
* CKLF like MARVEL transmembrane domain-containing 8 (CMTM8) has two isoforms, CMTM8 and CMTM8-v2 (Little is known about the CMTM8-v2 isoform and the CMTM8 isoform is referred to as CMTM8 rather than CMTM8-v1.).
All of these proteins have domains (i.e. regions) similar to analogous domains in the chemokine proteins; tetraspanin proteins (also termed transmembrane-4 superfamily proteins); myelin and lymphocyte protein (also termed MAR protein); proteins that direct membrane vesicle trafficking; and other proteins that are embedded in cell membranes. The genes encoding (i.e. directing the production of) these proteins, CKLF, CMTM1, CMTM2, CMTM3, CMTM4, CMTM5, CMTM6, CMTM7, and CMTM8, respectively, also share similar regions that encode the domains just cited for their proteins. (The 8 CMTM genes were formerly termed CKLFSF1, CKLFSF2, CKLFSF3, CKLFSF4, CKLFSF5, CKLFSF6, CKLFSF7, and CKLFSF8.) The CKLF, CMTM1, CMTM2, CTMT3, and CMTM4 genes cluster together in band 22 on the long (i.e. "q") arm of chromosome 16; the CMTM6, CMTM7, and CMTM8 genes form a second cluster in band 22 on the short (i.e. "p") of chromosome 3; and the CMTM5 gene, located in band 11.2 on the q arm of chromosome 14, is not clustered with the other CMTM genes. These structural similarities and clusterings reflect the close relationships of these proteins and genes. Studies suggest that the members of this family may be involved in the development of various cancers autoimmune diseases, cardiovascular diseases, the male reproductive system, and angiogenesis (i.e. development of new blood vessels from pre-existing blood vessels). In most of these cases, however, further studies are needed to determine if these CMTM proteins and/or their corresponding genes and mRNAs will be promising targets to help in the diagnosis, prognosis, and/or treatment of these disorders. | 1 | Applied and Interdisciplinary Chemistry |
Translation starts with a chain-initiation codon or start codon. The start codon alone is not sufficient to begin the process. Nearby sequences such as the Shine-Dalgarno sequence in E. coli and initiation factors are also required to start translation. The most common start codon is AUG, which is read as methionine or as formylmethionine (in bacteria, mitochondria, and plastids). Alternative start codons depending on the organism include "GUG" or "UUG"; these codons normally represent valine and leucine, respectively, but as start codons they are translated as methionine or formylmethionine.
The three stop codons have names: UAG is amber, UGA is opal (sometimes also called umber), and UAA is ochre. Stop codons are also called "termination" or "nonsense" codons. They signal release of the nascent polypeptide from the ribosome because no cognate tRNA has anticodons complementary to these stop signals, allowing a release factor to bind to the ribosome instead. | 1 | Applied and Interdisciplinary Chemistry |
Upon initiation of a pulse-chase experiment the medium is switched from medium(1) to medium(2). The two media must only differ in their isotope content. Thereby it is possible to distinguish between RNA molecules already existent before experiment initiation (= RNA molecules grown in medium(1)) and RNA molecules that are newly transcribed after experiment initiation (= RNA molecules grown in medium(2)). This allows the detailed study of modification dynamics in vivo. The supplementation of labeled methionine in either medium(1) or medium(2) allows the tracing of methylation processes. Other isotopically labeled metabolites potentially allow for further modification analysis.
Altogether NAIL-MS enables the investigation of RNA modification dynamics by mass spectrometry. With this technique, enzymatic demethylation has been observed for several RNA damages inside living bacteria. | 0 | Theoretical and Fundamental Chemistry |
The operating (or Larmor) frequency of a magnet (usually quoted as absolute value in MHz) is calculated from the Larmor equation
where is the induction of the magnet (SI units of Tesla), and is the magnetogyric ratio of the nucleus an empirically measured fundamental constant determined by the details of the structure of each nucleus. For example, the proton operating frequency for a 1 Tesla magnet is calculated as:
MRI scanners are often referred to by their field strengths (e.g. "a 7 T scanner"), whereas NMR spectrometers are commonly referred to by the corresponding proton Larmor frequency (e.g. "a 300 MHz spectrometer", which has a of 7 T ). While chemical shift is referenced in order that the units are equivalent across different field strengths, the actual frequency separation in Hertz scales with field strength (). As a result, the difference of chemical shift between two signals (ppm) represents a larger number of Hertz on machines that have larger and therefore the signals are less likely to be overlapping in the resulting spectrum. This increased resolution is a significant advantage for analysis. (Larger field machines are also favoured on account of having intrinsically higher signal arising from the Boltzmann distribution of magnetic spin states.) | 0 | Theoretical and Fundamental Chemistry |
Glycopeptide antibiotics are a class of drugs of microbial origin that are composed of glycosylated cyclic or polycyclic nonribosomal peptides. Significant glycopeptide antibiotics include the anti-infective antibiotics vancomycin, teicoplanin, telavancin, ramoplanin and decaplanin, corbomycin, complestatin and the antitumor antibiotic bleomycin. Vancomycin is used if infection with methicillin-resistant Staphylococcus aureus (MRSA) is suspected. | 0 | Theoretical and Fundamental Chemistry |
The ocean naturally sequesters carbon through different processes. The solubility pump moves carbon dioxide from the atmosphere into the surface ocean where it reacts with water molecules to form carbonic acid. The solubility of carbon dioxide increases with decreasing water temperatures. Thermohaline circulation moves dissolved carbon dioxide to cooler waters where it is more soluble, increasing carbon concentrations in the ocean interior. The biological pump moves dissolved carbon dioxide from the surface ocean to the ocean's interior through the conversion of inorganic carbon to organic carbon by photosynthesis. Organic matter that survives respiration and remineralization can be transported through sinking particles and organism migration to the deep ocean.
The low temperatures, high pressure, and reduced oxygen levels in the deep sea slow down decomposition processes, preventing the rapid release of carbon back into the atmosphere and acting as a long-term storage reservoir. | 0 | Theoretical and Fundamental Chemistry |
Many columns of limestone rise above the surface of Mono Lake. These limestone towers consist primarily of calcium carbonate minerals such as calcite (CaCO). This type of limestone rock is referred to as tufa, which is a term used for limestone that forms in low to moderate temperatures. | 1 | Applied and Interdisciplinary Chemistry |
In an ecological context, phototrophs are often the food source for neighboring heterotrophic life. In terrestrial environments, plants are the predominant variety, while aquatic environments include a range of phototrophic organisms such as algae (e.g., kelp), other protists (such as euglena), phytoplankton, and bacteria (such as cyanobacteria).
Cyanobacteria, which are prokaryotic organisms which carry out oxygenic photosynthesis, occupy many environmental conditions, including fresh water, seas, soil, and lichen. Cyanobacteria carry out plant-like photosynthesis because the organelle in plants that carries out photosynthesis is derived from an endosymbiotic cyanobacterium. This bacterium can use water as a source of electrons in order to perform CO reduction reactions.
A photolithoautotroph is an autotrophic organism that uses light energy, and an inorganic electron donor (e.g., HO, H, HS), and CO as its carbon source. | 0 | Theoretical and Fundamental Chemistry |
Capping of the pre-mRNA involves the addition of 7-methylguanosine (mG) to the 5 end. To achieve this, the terminal 5 phosphate requires removal, which is done with the aid of enzyme RNA triphosphatase. The enzyme guanosyl transferase then catalyses the reaction, which produces the diphosphate 5 end. The diphosphate 5 end then attacks the alpha phosphorus atom of a GTP molecule in order to add the guanine residue in a 55 triphosphate link. The enzyme (guanine-N-)-methyltransferase ("cap MTase") transfers a methyl group from S-adenosyl methionine to the guanine ring. This type of cap, with just the (mG) in position is called a cap 0 structure. The ribose of the adjacent nucleotide may also be methylated to give a cap 1. Methylation of nucleotides downstream of the RNA molecule produce cap 2, cap 3 structures and so on. In these cases the methyl groups are added to the 2' OH groups of the ribose sugar.
The cap protects the 5 end of the primary RNA transcript from attack by ribonucleases that have specificity to the 35' phosphodiester bonds. | 1 | Applied and Interdisciplinary Chemistry |
Grantham's distance depends on three properties: composition, polarity and molecular volume.
Distance difference D for each pair of amino acid i and j is calculated as:
where c = composition, p = polarity, and v = molecular volume; and are constants of squares of the inverses of the mean distance for each property, respectively equal to 1.833, 0.1018, 0.000399. According to Grantham's distance, most similar amino acids are leucine and isoleucine and the most distant are cysteine and tryptophan. | 1 | Applied and Interdisciplinary Chemistry |
If a differentiable function is one-to-one (injective) for each independent variable, e.g., is one-to-one for at a fixed while it is not necessarily one-to-one for , then the following total differentials exist because each independent variable is a differentiable function for the other variables, e.g., .
Substituting the first equation into the second and rearranging, we obtain
Since and are independent variables, and may be chosen without restriction. For this last equation to generally hold, the bracketed terms must be equal to zero. The left bracket equal to zero leads to the reciprocity relation while the right bracket equal to zero goes to the cyclic relation as shown below. | 0 | Theoretical and Fundamental Chemistry |
As a gasoline (petrol) additive, benzene increases the octane rating and reduces knocking. As a consequence, gasoline often contained several percent benzene before the 1950s, when tetraethyl lead replaced it as the most widely used antiknock additive. With the global phaseout of leaded gasoline, benzene has made a comeback as a gasoline additive in some nations. In the United States, concern over its negative health effects and the possibility of benzene entering the groundwater has led to stringent regulation of gasoline's benzene content, with limits typically around 1%. European petrol specifications now contain the same 1% limit on benzene content. The United States Environmental Protection Agency introduced new regulations in 2011 that lowered the benzene content in gasoline to 0.62%.
In some European languages, the word for petroleum or gasoline is an exact cognate of "benzene". For instance in Catalan the word benzina can be used for gasoline, though now it is relatively rare. | 1 | Applied and Interdisciplinary Chemistry |
The monument has numerous symbols and inscriptions used in alchemy. The inscriptions are hard to read from the monument itself.
Around the circle at top: “The center is in the triangle of the center.” Also: “There are three marvels: God and man, mother and virgin, triune and one.”
The Hebrew inscription, Ruach Elohim, means “Spirit of God.” Beneath it: “The
Hesperius dragon guards the entrance of the magic garden, and, without Alcides, Jason would not have tasted the delights of Colchis.”
There are six sigils on the jambs, each with its phrase.
Saturn/Lead: “When in your house black crows give birth to white doves, then you will be called wise.”
Jupiter/Tin: “The diameter of the sphere, the tau of the circle, the cross of the globe do not benefit the blind.”
Mars/Iron: “He who can burn with water and wash with fire, makes heaven from earth and precious earth from heaven.”
Venus/Bronze: “If you will make the earth fly upon your head, you will convert the waters of torrents to stone by its feathers.”
Mercury: “Azoth and Fire: by whitening Latona, Diana will come without dress.”
Antimony: “Our son lives dead, the king returns from the fire, and enjoys the occult conjunction.”
On the base, Vitriol: “It is occult work of true wise to open the earth, so as he may germinate health/safety for people.”
In another plate, now lost, was the device VILLAE IANUAM TRANANDO RECLUDENS IASON OBTINET LOCUPLES VELLUS MEDEAE 1680 (Passing by opening the door of the villa, Iason obtained the rich fleece of Medea 1680).
And on the doorstep, “SI SEDES NON IS,” a palindrome, meaning both “If you sit, you do not go,” and “If you do not sit, you go.” | 1 | Applied and Interdisciplinary Chemistry |
Faced with competition from cheaper British iron production, the Swedish iron industry needed to find a new cheaper method of making iron. In the 1810s, experiments were made with puddling, but this proved unsatisfactory, as it needed coal of which Sweden had none. After visited Britain, he published a report of his observations. He had seen closed finery hearths in south Wales and near Ulverston, then in Lancashire (now Cumbria). Those in south Wales were similar to puddling furnaces, but in Lancashire, he saw closed furnaces, where the metal was in contact with the fuel. On his return to Sweden, Ekman experimented and built furnaces similar to what he had seen near Ulverston, most probably at Newland ironworks.
In 1829-30, Waern installed a furnace of the south Wales type at Backefors ironworks, while independently Ekman built Lancashire hearths at Dormsjö and Söderfors. From there the process spread to other forges. Charcoal consumption by the metallurgical industry in Sweden peaked about 1885. In 1887, 406 hearths made 210,500 tons of iron. The last Lancashire forge in Sweden was at Ramnäs, closed in 1964.
In Shropshire, charcoal iron production continued on a significant scale, but declined after 1870, rods for wire-drawing being a significant product. However most charcoal forges were probably closed by 1890. | 1 | Applied and Interdisciplinary Chemistry |
A transmissometer or transmissiometer is an instrument for measuring the extinction coefficient of the atmosphere and sea water, and for the determination of visual range. It operates by sending a narrow, collimated beam of energy (usually a laser) through the propagation medium. A narrow field of view receiver at the designated measurement distance determines how much energy is arriving at the detector, and determines the path transmission and/or extinction coefficient. In a transmissometer the extinction coefficient is determined by measuring direct light transmissivity, and the extinction coefficient is then used to calculate visibility range.
Atmospheric extinction is a wavelength dependent phenomenon, but the most common wavelength in use for transmissometers is 550 nm, which is in the middle of the visible waveband, and allows a good approximation of visual range.
Transmissometers are also referred to as telephotometers, transmittance meters, or hazemeters.
Transmissometers are also used by oceanographers and limnologists to measure the optical properties of natural water. In this context, a transmissometer measures the transmittance or attenuation of incident radiation from a light source with a wavelength of around 660 nm, generally through a shorter distance than in air, as water has a smaller maximum visibility distance. | 0 | Theoretical and Fundamental Chemistry |
The phorbol ester tigilanol tiglate reportedly has in vitro anti-cancer, antiviral, and antibacterial activities. The phorbol derivatives in croton oil are used in folk medicine, with purported purgative, counter-irritant, or anthelmintic activities. | 0 | Theoretical and Fundamental Chemistry |
A secondary carbon is a carbon atom bound to two other carbon atoms. For this reason, secondary carbon atoms are found in almost (neopentane, for example, does not have any secondary carbon atoms) all hydrocarbons having at least three carbon atoms. In unbranched alkanes, the inner carbon atoms are always secondary carbon atoms (see figure). | 0 | Theoretical and Fundamental Chemistry |
Kramers' law is a formula for the spectral distribution of X-rays produced by an electron hitting a solid target. The formula concerns only bremsstrahlung radiation, not the element specific characteristic radiation. It is named after its discoverer, the Dutch physicist Hendrik Anthony Kramers.
The formula for Kramers' law is usually given as the distribution of intensity (photon count) against the wavelength of the emitted radiation:
The constant K is proportional to the atomic number of the target element, and is the minimum wavelength given by the Duane–Hunt law. The maximum intensity is at .
The intensity described above is a particle flux and not an energy flux as can be seen by the fact that the integral over values from to is infinite. However, the
integral of the energy flux is finite.
To obtain a simple expression for the energy flux, first change variables from (the wavelength) to (the angular frequency) using and also using . Now is that quantity which is integrated over from 0 to to get the total number (still infinite) of photons, where :
The energy flux, which we will call (but which may also be referred to as the "intensity" in conflict with the above name of ) is obtained by multiplying the above by the energy :
for
for .
It is a linear function that is zero at the maximum energy . | 0 | Theoretical and Fundamental Chemistry |
Chromatography facilitates separation of distinct molecules within a mixture based on their respective chemical properties, and how those properties interact with the substrate coating the chromatographic column. This separation can happen “on-line,” during the measurement itself, or prior to measurements to isolate a pure compound. Gas and liquid chromatography have distinct advantages, based on the molecules of interest. For example, aqueously soluble molecules are more easily separated with liquid chromatography, while volatile, nonpolar molecules like propane or ethane are separated with gas chromatography. | 0 | Theoretical and Fundamental Chemistry |
Hydraulic fluids can contain a wide range of chemical compounds, including: oils, butanol, esters (e.g. phthalates, like DEHP, and adipates, like bis(2-ethylhexyl) adipate), polyalkylene glycols (PAG), organophosphate (e.g. tributylphosphate), silicones, alkylated aromatic hydrocarbons, polyalphaolefins (PAO) (e.g. polyisobutenes), corrosion inhibitors (incl acid scavengers), anti-erosion additives, etc. | 1 | Applied and Interdisciplinary Chemistry |
Product heterogeneity is common in monoclonal antibodies and other recombinant biological products and is typically introduced either upstream during expression or downstream during manufacturing.
These variants are typically aggregates, deamidation products, glycosylation variants, oxidized amino acid side chains, as well as amino and carboxyl terminal amino acid additions. These seemingly minute structural changes can affect preclinical stability and process optimization as well as therapeutic product potency, bioavailability and immunogenicity. The generally accepted purification method of process streams for monoclonal antibodies includes capture of the product target with protein A, elution, acidification to inactivate potential mammalian viruses, followed by ion chromatography, first with anion beads and then with cation beads.
Displacement chromatography has been used to identify and characterize these often unseen variants in quantities that are suitable for subsequent preclinical evaluation regimens such as animal pharmacokinetic studies. Knowledge gained during the preclinical development phase is critical for enhanced product quality understanding and provides a basis for risk management and increased regulatory flexibility. The recent Food and Drug Administration's Quality by Design initiative attempts to provide guidance on development and to facilitate design of products and processes that maximizes efficacy and safety profile while enhancing product manufacturability. | 1 | Applied and Interdisciplinary Chemistry |
In metagenomics, regions of the genomes that are shared between strains are typically longer than the reads. This complicates the assembly process and makes reconstructing individual genomes for a species a daunting task. Chimeric pairs that are mapped far apart in the genome can facilitate the de novo assembly process. By using a longer-jump library, Ribeiro et al. demonstrated that the assemblies of bacterial genomes were of high quality while reducing both cost and time. | 1 | Applied and Interdisciplinary Chemistry |
The CD V-700 also came with a "check source", a bit of a radioactive isotope under a sticker on the side of the unit. The isotope varied with the maker; depleted or natural uranium was common, though the Instruction and Maintenance Manual for the Lionel Model 6B indicates that a "Radium D+E beta source" with an approximate half-life of 22 years is present under the nameplate. This produced, at the time of installation on the machine, about 1–2 mR/hr adjacent to the source, a value which was clearly visible on the analog meter as well as audible via the headphones that accompanied the units. Measured with the probes beta window uncovered and the probe directly in contact with the operational check source, this is about 100 times normal sea-level background levels of radiation, and similar to the near-field from a uranium oxide-glazed red Fiestaware saucer. The level drops back to background levels a few feet from the source. Since the half-life of the different operational check source materials used varied and since all CD V-700s were manufactured prior to 1964 and are now approaching a half-century old, the amount of radiation emitted from the source may be much lower than when the unit was originally issued. Therefore, accurate calibration via the source cannot be assured.
The units were calibrated at the factory, but this may drift over time and need to be recalibrated by means of an adjusting screw inside the case. The procedure for this will vary from model to model and it is best performed by somebody that is familiar with radiation metrology gear and its calibration. US state emergency management agencies usually maintain a calibration lab intended to keep the state's own inventory of such devices calibrated and often offer such services to local first responding agencies statewide but generally do not offer them to the public. | 0 | Theoretical and Fundamental Chemistry |
* Due to the structure, the pressure difference is theoretically limited to atmospheric pressure (1 bar), and in practice somewhat lower.
* Besides the drum, other accessories, for example, agitators and vacuum pump, vacuum receivers, slurry pumps are required.
* The discharge cake contains residual moisture.
* The cake tends to crack due to their air drawn through by the vacuum system, so that washing and drying are not efficient.
* High energy consumption by the vacuum pump. | 0 | Theoretical and Fundamental Chemistry |
In 1975, Mukaiyama reported that N-methyl-2-chloropyridinium iodide (also called 2-chloro-1-methylpyridinium iodide) allowed for a dehydration condensation between a carboxylic acid and an alcohol or similar functional groups to form an ester linkage. In the initial stage of the process, the carboxyl displaces the halogen atom on the reagent in the presence of a base. The resulting pyridyl ester is an activated electrophile and also serves as a good leaving group in a subsequent nucleophilic acyl substitution reaction with the alcohol reactant as nucleophile. Thus, the family of 2-halo-N-alkylpyridinium salts are named the Mukaiyama reagents. The reaction gives low yields if there are sterically large groups adjacent to the site of the reaction, such as tertiary carbons, but can be improved by using bromine as the halogen. In the years since its discovery, a number of different onium salts of aza-arenes have been used to catalyze a number of different dehydration reactions, including a macrolactonization. In 1994, Isamu Shiina developed his namesake macrolactonization in the Mukaiyama lab, making use of an aromatic carboxylic acid anhydride in the presence of a Lewis acid catalyst. | 0 | Theoretical and Fundamental Chemistry |
dPCR measures the actual number of molecules (target DNA) as each molecule is in one droplet, thus making it a discrete “digital” measurement. It provides absolute quantification because dPCR measures the positive fraction of samples, which is the number of droplets that are fluorescing due to proper amplification. This positive fraction accurately indicates the initial amount of template nucleic acid. Similarly, qPCR utilizes fluorescence; however, it measures the intensity of fluorescence at specific times (generally after every amplification cycle) to determine the relative amount of target molecule (DNA), but cannot specify the exact amount without constructing a standard curve using different amounts of a defined standard. It gives the threshold per cycle (CT) and the difference in CT is used to calculate the amount of initial nucleic acid. As such, qPCR is an analog measurement, which may not be as precise due to the extrapolation required to attain a measurement.
dPCR measures the amount of DNA after amplification is complete and then determines the fraction of replicates. This is representative of an endpoint measurement as it requires the observation of the data after the experiment is completed. In contrast, qPCR records the relative fluorescence of the DNA at specific points during the amplification process, which requires stops in the experimental process. This “real-time” aspect of qPCR may theoretically affect results due to the stopping of the experiment. In practice, however, most qPCR thermal cyclers read each sample's fluorescence very quickly at the end of the annealing/extension step before proceeding to the next melting step, meaning this hypothetical concern is not actually relevant or applicable for the vast majority of researchers. dPCR measures the amplification by measuring the products of end point PCR cycling and is therefore less susceptible to the artifacts arising from impaired amplification efficiencies due to the presence of PCR inhibitors or primer template mismatch.
Real-time Digital PCR (rdPCR) combines the methodologies of digital PCR (dPCR) and quantitative PCR (qPCR), integrating the precision of dPCR with the real-time analysis capabilities of qPCR. This integration aims to provide enhanced sensitivity, specificity, and the ability for absolute quantification of nucleic acid sequences, contributing to the quantification of genetic material in scientific and clinical research.
qPCR is unable to distinguish differences in gene expression or copy number variations that are smaller than twofold. On the other hand, dPCR has a higher precision and has been shown to detect differences of less than 30% in gene expression, distinguish between copy number variations that differ by only 1 copy, and identify alleles that occur at frequencies less than 0.1%. | 1 | Applied and Interdisciplinary Chemistry |
Triflic acid, the short name for trifluoromethanesulfonic acid, TFMS, TFSA, HOTf or TfOH, is a sulfonic acid with the chemical formula CFSOH. It is one of the strongest known acids. Triflic acid is mainly used in research as a catalyst for esterification. It is a hygroscopic, colorless, slightly viscous liquid and is soluble in polar solvents. | 0 | Theoretical and Fundamental Chemistry |
In materials science, a grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are two-dimensional defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material. Most grain boundaries are preferred sites for the onset of corrosion and for the precipitation of new phases from the solid. They are also important to many of the mechanisms of creep. On the other hand, grain boundaries disrupt the motion of dislocations through a material, so reducing crystallite size is a common way to improve mechanical strength, as described by the Hall–Petch relationship. | 1 | Applied and Interdisciplinary Chemistry |
The following student chapters have also been granted Charter Status by the Council:
*Obafemi Awolowo University, Ile-Ife
*Chukwuemeka Odumegwu Ojukwu University, uli
*Ahmadu Bello University, Zaria
*University of Lagos, Akoka, Lagos
*University of Port Harcourt, Port Harcourt
*Rivers State University of Science and Technology, Nkpolu, Port Harcourt;
*Lagos State University, Ojo;
*Ladoke Akintola University of Technology, Ogbomoso
*Enugu State University of science and Technology, Enugu
*Federal University of Technology, Owerri;
*Federal University of Technology Yola now known as(Mautech)
*Kaduna Polytechnic, Kaduna
*University of Benin, Benin City
*Petroleum Training Institute, Effurun
*Auchi Polytechnic, Auchi
*Michael Okpara University of Agriculture
Umudike Abia state
* Federal University of Petroleum Resources Effurun (FUPRE) | 1 | Applied and Interdisciplinary Chemistry |
When an electron moves through a gas, its interactions with the gas atoms cause scattering to occur. These interactions are classified as inelastic if they cause excitation or ionization of the atom to occur and elastic if they do not.
The probability of scattering in such a system is defined as the number of electrons scattered, per unit electron current, per unit path length, per unit pressure at 0 °C, per unit solid angle. The number of collisions equals the total number of electrons scattered elastically and inelastically in all angles, and the probability of collision is the total number of collisions, per unit electron current, per unit path length, per unit pressure at 0 °C.
Because noble gas atoms have a relatively high first ionization energy and the electrons do not carry enough energy to cause excited electronic states, ionization and excitation of the atom are unlikely, and the probability of elastic scattering over all angles is approximately equal to the probability of collision. | 0 | Theoretical and Fundamental Chemistry |
The photosynthetic efficiency is the fraction of light energy converted into chemical energy during photosynthesis in green plants and algae. Photosynthesis can be described by the simplified chemical reaction
:6 HO + 6 CO + energy → CHO + 6 O
where CHO is glucose (which is subsequently transformed into other sugars, starches, cellulose, lignin, and so forth). The value of the photosynthetic efficiency is dependent on how light energy is defined – it depends on whether we count only the light that is absorbed, and on what kind of light is used (see Photosynthetically active radiation). It takes eight (or perhaps ten or more) photons to use one molecule of CO. The Gibbs free energy for converting a mole of CO to glucose is 114 kcal, whereas eight moles of photons of wavelength 600 nm contains 381 kcal, giving a nominal efficiency of 30%. However, photosynthesis can occur with light up to wavelength 720 nm so long as there is also light at wavelengths below 680 nm to keep Photosystem II operating (see Chlorophyll). Using longer wavelengths means less light energy is needed for the same number of photons and therefore for the same amount of photosynthesis. For actual sunlight, where only 45% of the light is in the photosynthetically active wavelength range, the theoretical maximum efficiency of solar energy conversion is approximately 11%. In actuality, however, plants do not absorb all incoming sunlight (due to reflection, respiration requirements of photosynthesis and the need for optimal solar radiation levels) and do not convert all harvested energy into biomass, which results in a maximum overall photosynthetic efficiency of 3 to 6% of total solar radiation. If photosynthesis is inefficient, excess light energy must be dissipated to avoid damaging the photosynthetic apparatus. Energy can be dissipated as heat (non-photochemical quenching), or emitted as chlorophyll fluorescence. | 0 | Theoretical and Fundamental Chemistry |
The blowing of air through the molten pig iron introduces oxygen into the melt which results in oxidation, removing impurities found in the pig iron, such as silicon, manganese, and carbon in the form of oxides. These oxides either escape as gas or form a solid slag. The refractory lining of the converter also plays a role in the conversion — clay linings may be used when there is little phosphorus in the raw material, and Bessemer himself used ganister sandstone – this is known as the acid Bessemer process. When the phosphorus content is high, dolomite, or sometimes magnesite, linings are required in the basic Bessemer limestone process, see below. In order to produce steel with desired properties, additives such as spiegeleisen (a ferromanganese alloy), can be added to the molten steel once the impurities have been removed. | 1 | Applied and Interdisciplinary Chemistry |
The three-year WeNMR project started in November 2010 as the natural successor of the eNMR project. Financial support was provided by the European Community grants 213010 (eNMR) and 261572 (WeNMR) in the 7th Framework Programme (e-Infrastructure RI-261571). | 1 | Applied and Interdisciplinary Chemistry |
PCBs originating from Monsanto Chemical Company in Anniston, Alabama, were dumped into Snow Creek, which then spread to Choccolocco Creek, then Logan Martin Lake. In the early 2000s, class action lawsuits were settled by local land owners, including those on Logan Martin Lake, and Lay Reservoir (downstream on the Coosa River), for the PCB pollution. Donald Stewart, former Senator from Alabama, first learned of the concerns of hundreds of west Anniston residents after representing a church which had been approached about selling its property by Monsanto. Stewart went on to be the pioneer and lead attorney in the first and majority of cases against Monsanto and focused on residents in the immediate area known to be most polluted. Other attorneys later joined in to file suits for those outside the main immediate area around the plant; one of these was the late Johnnie Cochran.
In 2007, the highest pollution levels remained concentrated in Snow and Choccolocco Creeks. Concentrations in fish have declined and continue to decline over time; sediment disturbance, however, can resuspend the PCBs from the sediment back into the water column and food web. | 1 | Applied and Interdisciplinary Chemistry |
Heterodimeric diatomic complexes involving a noble gas and a halide, such as xenon chloride, are common in the construction of excimer lasers, which are excimers' most common application. These lasers take advantage of the fact that excimer components have attractive interactions in the excited state and repulsive interactions in the ground state. Emission of excimer molecules is also used as a source of spontaneous ultraviolet light (excimer lamps).
The molecule pyrene is another canonical example of an excimer that has found applications in biophysics to evaluate the distance between biomolecules.
In organic chemistry, many reactions occur through an exciplex, for example, those of simple arene compounds with alkenes. The reactions of benzene and their products depicted are a [2+2]cycloaddition to the ortho product (A), a [2+3]cycloaddition to the meta product (B) and the [2+4]cycloaddition to the para product (C) with simple alkenes such as the isomers of 2-butene. In these reactions, it is the arene that is excited.
As a general rule, the regioselectivity is in favor of the ortho adduct at the expense of the meta adduct when the amount of charge transfer taking place in the exciplex increases. | 0 | Theoretical and Fundamental Chemistry |
The Froude number may be used to study trends in animal gait patterns. In analyses of the dynamics of legged locomotion, a walking limb is often modeled as an inverted pendulum, where the center of mass goes through a circular arc centered at the foot. The Froude number is the ratio of the centripetal force around the center of motion, the foot, and the weight of the animal walking:
where is the mass, is the characteristic length, is the acceleration due to gravity and is the velocity. The characteristic length may be chosen to suit the study at hand. For instance, some studies have used the vertical distance of the hip joint from the ground, while others have used total leg length.
The Froude number may also be calculated from the stride frequency as follows:
If total leg length is used as the characteristic length, then the theoretical maximum speed of walking has a Froude number of 1.0 since any higher value would result in takeoff and the foot missing the ground. The typical transition speed from bipedal walking to running occurs with . R. M. Alexander found that animals of different sizes and masses travelling at different speeds, but with the same Froude number, consistently exhibit similar gaits. This study found that animals typically switch from an amble to a symmetric running gait (e.g., a trot or pace) around a Froude number of 1.0. A preference for asymmetric gaits (e.g., a canter, transverse gallop, rotary gallop, bound, or pronk) was observed at Froude numbers between 2.0 and 3.0. | 1 | Applied and Interdisciplinary Chemistry |
Through the early development of the hybrid concept the question of overall economics appeared difficult to handle. A series of studies starting in the late 1970s provided a much clearer picture of the hybrid in a complete fuel cycle, and allowed the economics to be better understood. These studies appeared to indicate there was no reason to build a hybrid.
One of the most detailed of these studies was published in 1980 by Los Alamos National Laboratory (LANL). Their study noted that the hybrid would produce most of its energy indirectly, both through the fission events in its own reactor, and much more by providing Pu-239 to fuel conventional fission reactors. In this overall picture, the hybrid is essentially identical to the breeder reactor, which uses fast neutrons from plutonium fission to breed more fuel in a fission blanket in largely the same fashion as the hybrid. Both require chemical processing to remove the bred Pu-239, both presented the same proliferation and safety risks as a result, and both produced about the same amount of fuel. Since that fuel is the primary source of energy in the overall cycle, the two systems were almost identical in the end.
What was not identical, however, was the technical maturity of the two designs. The hybrid would require considerable additional research and development before it would be known if it could even work, and even if that were demonstrated, the result would be a system essentially identical to breeders which were already being built at that time. The report concluded: | 0 | Theoretical and Fundamental Chemistry |
Heinz Falk was born April 29, 1939, in Sankt Pölten, Austria, went to elementary school in Statzendorf and completed middle school in Krems an der Donau. After moving to Vienna in 1953 he completed a three-year program at HBLVA for Chemical Industry, Rosensteingasse and completed his high-school diploma in 1959 through classes at an evening school, where he met his future wife, Rotraud Falk (née Strohbach). | 0 | Theoretical and Fundamental Chemistry |
Chain scission is a term used in polymer chemistry describing the degradation of a polymer main chain. It is often caused by thermal stress (heat) or ionizing radiation (e.g. light, UV radiation or gamma radiation), often involving oxygen. During chain cleavage, the polymer chain is broken at a random point in the backbone to form two - mostly still highly molecular - fragments.
Depolymerization, on the other hand, is the elimination of low molecular weight substances (monomers, dimers and suchlike) from a polymer. | 1 | Applied and Interdisciplinary Chemistry |
Many if not most of the common resolving agents are natural products or derivatives thereof. Illustrative is l-malic acid, a dicarboxylic acid that is found in apples. It is used to resolve α-phenylethylamine, a versatile resolving agent in its own right. | 0 | Theoretical and Fundamental Chemistry |
Except their abilities in catalyzing organic reactions, palladacycles have also shown their potential in medicinal and biological chemistry after the success of cis-Pt(NH)Cl as an anticancer agent. Additionally, they can also be used in CO/SCN- sensing. | 0 | Theoretical and Fundamental Chemistry |
Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom . It is a highly flammable, weakly alkaline, water-miscible liquid with a distinctive, unpleasant fish-like smell. Pyridine is colorless, but older or impure samples can appear yellow. due to the formation of extended, unsaturated polymeric chains, which show significant electrical conductivity. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Historically, pyridine was produced from coal tar. As of 2016, it is synthesized on the scale of about 20,000 tons per year worldwide. | 0 | Theoretical and Fundamental Chemistry |
RNA-Seq refers to the combination of a high-throughput sequencing methodology with computational methods to capture and quantify transcripts present in an RNA extract. The nucleotide sequences generated are typically around 100 bp in length, but can range from 30 bp to over 10,000 bp depending on the sequencing method used. RNA-Seq leverages deep sampling of the transcriptome with many short fragments from a transcriptome to allow computational reconstruction of the original RNA transcript by aligning reads to a reference genome or to each other (de novo assembly). Both low-abundance and high-abundance RNAs can be quantified in an RNA-Seq experiment (dynamic range of 5 orders of magnitude)—a key advantage over microarray transcriptomes. In addition, input RNA amounts are much lower for RNA-Seq (nanogram quantity) compared to microarrays (microgram quantity), which allow examination of the transcriptome even at a single-cell resolution when combined with amplification of cDNA. Theoretically, there is no upper limit of quantification in RNA-Seq, and background noise is very low for 100 bp reads in non-repetitive regions.
RNA-Seq may be used to identify genes within a genome, or identify which genes are active at a particular point in time, and read counts can be used to accurately model the relative gene expression level. RNA-Seq methodology has constantly improved, primarily through the development of DNA sequencing technologies to increase throughput, accuracy, and read length. Since the first descriptions in 2006 and 2008, RNA-Seq has been rapidly adopted and overtook microarrays as the dominant transcriptomics technique in 2015.
The quest for transcriptome data at the level of individual cells has driven advances in RNA-Seq library preparation methods, resulting in dramatic advances in sensitivity. Single-cell transcriptomes are now well described and have even been extended to in situ RNA-Seq where transcriptomes of individual cells are directly interrogated in fixed tissues. | 1 | Applied and Interdisciplinary Chemistry |
It is possible to store energy and produce electrical power at a later time as in pumped-storage hydroelectricity, thermal energy storage, flywheel energy storage, battery storage power station and so on. | 1 | Applied and Interdisciplinary Chemistry |
Steam cracking is a petrochemical process in which saturated hydrocarbons are broken down into smaller, often unsaturated, hydrocarbons. It is the principal industrial method for producing the lighter alkenes (or commonly olefins), including ethene (or ethylene) and propene (or propylene). Steam cracker units are facilities in which a feedstock such as naphtha, liquefied petroleum gas (LPG), ethane, propane or butane is thermally cracked through the use of steam in a bank of pyrolysis furnaces to produce lighter hydrocarbons.
In steam cracking, a gaseous or liquid hydrocarbon feed like naphtha, LPG or ethane is diluted with steam and briefly heated in a furnace without the presence of oxygen. Typically, the reaction temperature is very high, at around 850 °C, but the reaction is only allowed to take place very briefly. In modern cracking furnaces, the residence time is reduced to milliseconds to improve yield, resulting in gas velocities up to the speed of sound. After the cracking temperature has been reached, the gas is quickly quenched to stop the reaction in a transfer line heat exchanger or inside a quenching header using quench oil.
The products produced in the reaction depend on the composition of the feed, the hydrocarbon-to-steam ratio, and on the cracking temperature and furnace residence time. Light hydrocarbon feeds such as ethane, LPGs or light naphtha give product streams rich in the lighter alkenes, including ethylene, propylene, and butadiene. Heavier hydrocarbon (full range and heavy naphthas as well as other refinery products) feeds give some of these, but also give products rich in aromatic hydrocarbons and hydrocarbons suitable for inclusion in gasoline or fuel oil. Typical product streams include pyrolysis gasoline (pygas) and BTX.
A higher cracking temperature (also referred to as severity) favors the production of ethylene and benzene, whereas lower severity produces higher amounts of propylene, C4-hydrocarbons and liquid products. The process also results in the slow deposition of coke, a form of carbon, on the reactor walls. Since coke degrades the efficiency of the reactor, great care is taken to design reaction conditions to minimize its formation. Nonetheless, a steam cracking furnace can usually only run for a few months between de-cokings. "Decokes" require the furnace to be isolated from the process and then a flow of steam or a steam/air mixture is passed through the furnace coils. This decoking is essentially combustion of the carbons, converting the hard solid carbon layer to carbon monoxide and carbon dioxide. | 0 | Theoretical and Fundamental Chemistry |
There are no known contraindication to the use of dexmedetomidine. It has a biphasic effect on blood pressure with lower readings at lower drug concentrations and higher readings at higher concentrations. Common side effects include: hypotension, hypertension, with slight decreases in heart rate, arrhythmias, and hypoxia. Toxic doses may cause first-degree or second-degree atrioventricular block. These adverse events usually occur briefly after administering a loading dose of the drug. Thus, adverse effects may be reduced by omitting a loading dose. | 0 | Theoretical and Fundamental Chemistry |
The process is more environmentally friendly than traditional extraction methods. For the company this can translate into profit, since the necessary limiting of sulfur dioxide emissions during smelting is expensive. Less landscape damage occurs, since the bacteria involved grow naturally, and the mine and surrounding area can be left relatively untouched. As the bacteria breed in the conditions of the mine, they are easily cultivated and recycled.
Toxic chemicals are sometimes produced in the process. Sulfuric acid and H ions that have been formed can leak into the ground and surface water turning it acidic, causing environmental damage. Heavy ions such as iron, zinc, and arsenic leak during acid mine drainage. When the pH of this solution rises, as a result of dilution by fresh water, these ions precipitate, forming "Yellow Boy" pollution. For these reasons, a setup of bioleaching must be carefully planned, since the process can lead to a biosafety failure. Unlike other methods, once started, bioheap leaching cannot be quickly stopped, because leaching would still continue with rainwater and natural bacteria. Projects like Finnish Talvivaara proved to be environmentally and economically disastrous. | 1 | Applied and Interdisciplinary Chemistry |
Blood coagulation is a complex process by which the blood forms clots. It is an essential part of hemostasis and works by stopping blood loss from damaged blood vessels. At the site of injury, where there is an exposure of blood under the endothelium, the platelets gather and immediately form a plug. That process is called primary hemostasis. Simultaneously, a secondary hemostasis occurs. It is defined as the formation of insoluble fibrin by activated coagulation factors, specifically thrombin. These factors activate each other in a blood coagulation cascade that occurs through two separate pathways that interact, the intrinsic and extrinsic pathway. After activating various proenzymes, thrombin is formed in the last steps of the cascade, it then converts fibrinogen to fibrin which leads to clot formation. Factor Xa is an activated serine protease that occupies a key role in the blood coagulation pathway by converting prothrombin to thrombin. Inhibition of factor Xa leads to antithrombotic effects by decreasing the amount of thrombin. Directly targeting factor Xa is suggested to be an effective approach to anticoagulation. | 1 | Applied and Interdisciplinary Chemistry |
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