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A quantum jump is the abrupt transition of a quantum system (atom, molecule, atomic nucleus) from one quantum state to another, from one energy level to another. When the system absorbs energy, there is a transition to a higher energy level (excitation); when the system loses energy, there is a transition to a lower energy level.
The concept was introduced by Niels Bohr, in his 1913 Bohr model.
A quantum jump is a phenomenon that is peculiar to quantum systems and distinguishes them from classical systems, where any transitions are performed gradually. In quantum mechanics, such jumps are associated with the non-unitary evolution of a quantum-mechanical system during measurement.
A quantum jump can be accompanied by the emission or absorption of photons; energy transfer during a quantum jump can also occur by non-radiative resonant energy transfer or in collisions with other particles.
In modern physics, the concept of a quantum jump is rarely used; as a rule scientists speak of transitions between quantum states or energy levels. | 7 | Physical Chemistry |
Adenylosuccinate is an intermediate in the interconversion of purine nucleotides inosine monophosphate (IMP) and adenosine monophosphate (AMP). The enzyme adenylosuccinate synthase carries out the reaction by the addition of aspartate to IMP and requires the input of energy from a phosphoanhydride bond in the form of guanosine triphosphate (GTP). GTP is used instead of adenosine triphosphate (ATP), so the reaction is not dependent on its products. | 1 | Biochemistry |
The saprobic system is a tool to measure water quality, and specifically it deals with the capacity of a water body to self-regulate and degrade organic matter. The saprobic system derives from so-called saprobes — organisms that thrive through degradation of organic matter, which is called saprotrophic nutrition.
The saprobic system is based on a survey of indicator organisms. For example, the abundance of Lymnaea stagnalis water snails and other organisms is estimated, and using a formula, the listed saprobic and tolerance values of the organisms allow the water quality grade — the saprobic index — to be computed.
Saprobic water quality is expressed in four classes ranging from I to IV; and with three intermediate grades (I-II, II-III and III-IV). Water bodies of class I are the cleanest and of the highest quality. The inherent drawback of the saprobic systems as a water quality measure is that it only regards biodegradable organic material, and so ignores other factors like heavy metal pollution. Though the presence of certain organisms can rule out the presence of toxic substances, the incorporation of such organisms would deviate from the saprobic system's concept. | 2 | Environmental Chemistry |
As alkylating agents, haloalkanes are potential carcinogens. The more reactive members of this large class of compounds generally pose greater risk, e.g. carbon tetrachloride. | 0 | Organic Chemistry |
The Chesapeake Bay is home to numerous fauna that either migrate to the Bay at some point during the year or live there year-round. There are over 300 species of fish and numerous shellfish and crab species. Some of these include the Atlantic menhaden, striped bass, American eel, eastern oyster, Atlantic horseshoe crab, and the blue crab.
Birds include ospreys, great blue herons, bald eagles, and peregrine falcons, the last two of which were threatened by DDT; their numbers plummeted but have risen in recent years. The piping plover is a near threatened species that inhabits the wetlands.
Larger fish such as Atlantic sturgeon, varieties of sharks, and stingrays visit the Chesapeake Bay. The waters of the Chesapeake Bay have been regarded as one of the most important nursery areas for sharks along the east coast. Megafaunas such as bull sharks, tiger sharks, scalloped hammerhead sharks, and basking sharks and manta rays are also known to visit. Smaller species of sharks and stingrays that are known to be regular to occasional residents in the bay include the smooth dogfish, spiny dogfish, cownose ray, and bonnethead.
Bottlenose dolphins are known to live seasonally/yearly in the Bay. There have been unconfirmed sightings of humpback whales in recent years. Endangered North Atlantic right whale and fin, and minke and sei whales have also been sighted within and in the vicinity of the Bay.
A male manatee visited the Bay several times between 1994 and 2011, even though the area is north of the species normal range. The manatee, recognizable due to distinct markings on its body, was nicknamed "Chessie" after a legendary sea monster that was allegedly sighted in the Bay during the 20th century. The same manatee has been spotted as far north as Rhode Island, and was the first manatee known to travel so far north. Other manatees are occasionally seen in the Bay and its tributaries, which contain sea grasses that are part of the manatees diet.
Loggerhead turtles are known to visit the Bay.
The Chesapeake Bay is also home to a diverse flora, both land and aquatic. Common submerged aquatic vegetation includes eelgrass and widgeon grass. A report in 2011 suggested that information on underwater grasses would be released, because "submerged grasses provide food and habitat for a number of species, adding oxygen to the water and improving water clarity." Other vegetation that makes its home in other parts of the Bay are wild rice, various trees like the red maple, loblolly pine and bald cypress, and spartina grass and phragmites. Invasive plants have taken a significant foothold in the Bay. Plants such as Phragmites, Purple loosestrife and Japanese stiltgrass have established high levels of permanency in Chesapeake wetlands. Additionally, plants such as Brazilian waterweed, native to South America, have spread to most continents with the help of aquarium owners, who often dump the contents of their aquariums into nearby lakes and streams. It is highly invasive and has the potential to flourish in the low-salinity tidal waters of the Chesapeake Bay. Dense stands of Brazilian waterweed can restrict water movement, trap sediment and affect water quality. Various local K-12 schools in the Maryland and Virginia region often have programs that cultivate native bay grasses and plant them in the Bay. | 2 | Environmental Chemistry |
The liquid junction potential cannot be measured directly but calculated. The electromotive force (EMF) of a concentration cell with transference includes the liquid junction potential.
The EMF of a concentration cell without transport is:
where and are activities of HCl in the two solutions, is the universal gas constant, is the temperature and is the Faraday constant.
The EMF of a concentration cell with transport (including the ion transport number) is:
where and are activities of HCl solutions of right and left hand electrodes, respectively, and is the transport number of Cl.
Liquid junction potential is the difference between the two EMFs of the two concentration cells, with and without ionic transport: | 7 | Physical Chemistry |
Many systems use ventilation holes or slits kept on the box of equipment to dissipate heat. Heat sinks are often attached to portions of the circuit that produce most heat or are vulnerable to heat. Fans are also often used. Some high-voltage instruments are kept immersed in oil. In some cases, to remove unwanted heat, a cooling system like air conditioning or refrigerating heat-pumps may be required. | 7 | Physical Chemistry |
In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are substituted determines which of three structural isomers results. It is a colorless, flammable, slightly greasy liquid of great industrial value.
The mixture is referred to as both xylene and, more precisely, xylenes. Mixed xylenes refers to a mixture of the xylenes plus ethylbenzene. The four compounds have identical empirical formulas . Typically the four compounds are produced together by various catalytic reforming and pyrolysis methods. | 2 | Environmental Chemistry |
This particular function is considered a scaffold's most basic function. Scaffolds assemble signaling components of a cascade into complexes. This assembly may be able to enhance signaling specificity by preventing unnecessary interactions between signaling proteins, and enhance signaling efficiency by increasing the proximity and effective concentration of components in the scaffold complex. A common example of how scaffolds enhance specificity is a scaffold that binds a protein kinase and its substrate, thereby ensuring specific kinase phosphorylation. Additionally, some signaling proteins require multiple interactions for activation and scaffold tethering may be able to convert these interactions into one interaction that results in multiple modifications. Scaffolds may also be catalytic as interaction with signaling proteins may result in allosteric changes of these signaling components. Such changes may be able to enhance or inhibit the activation of these signaling proteins. An example is the Ste5 scaffold in the mitogen-activated protein kinase (MAPK) pathway. Ste5 has been proposed to direct mating signaling through the Fus3 MAPK by catalytically unlocking this particular kinase for activation by its MAPKK Ste7. | 1 | Biochemistry |
The First Asian Conference on Electrochemical Power Sources (ACEPS-1) was held November 15–17, 2006, in Kyoto, Japan, with the aim of strengthening regional research potential and improving infrastructures in the Asian region. ACEPS promotes collaboration and co-operation between Asian scientists in the fields of fuel cells, storage batteries, super capacitors and electrochemical science. | 7 | Physical Chemistry |
After a conflict with that university, Markovnikov was appointed professor at the University of Odesa in 1871 and, two years later, at the University of Moscow, where he stayed the rest of his career. He was elected as a member to the American Philosophical Society in 1901. | 0 | Organic Chemistry |
Through her experiences carrying out domestic chores, especially dishwashing, Pockels became interested in the effect of soaps on water and more generally on the effect of impurities on water and soapy water. By age 18, she began conducting experiments in her home to understand the physical properties of water and impurities, as an amateur chemist.
As a result of her interests, by age 20, Pockels devised a slide trough for making quantitative measurements on the surface properties of soapy water and related substances. Specifically, this consisted of a trough, made of metal and rectangular in shape, roughly 70 centimeters (cm) long, 5 cm wide, and 2 cm deep. The trough was filled with water. A metal strip of about 1.5 cm width was laid on top of the water across the width of the trough so as to divide the surface of the water in two parts. There was a ruler along the length of the trough so that the position of the metal strip, and therefore the surface area of each of the two parts of the trough, could be determined as the strip was moved along the length of the trough.
Pockels further developed her apparatus by placing a small disk (typically 6 millimeters in diameter), such as a button, on the surface of the water in the trough. She then used a weighing scale (typically an apothecary's balance) to determine the force (weight) necessary to lift the disk from the water. By comparing the forces required to lift the disk from pure water to water containing impurities, she devised a direct measure of surface tension. This apparatus enabled her to investigate the surface forces of mono-molecular films, the surface tension of emulsions and solutions, the effect of impurities on the physical properties of water, and providing an understanding of surfactancy.
Pockels sliding trough design built on the prior findings of Ludwig Wilhelmys plate method of measuring surface tension. Pockels' design influenced later investigators who improved on the method, leading to the modern Langmuir-Blodgett trough which is in extensive use in colloid and surface science in contemporary times. | 7 | Physical Chemistry |
Soil acidification is the buildup of hydrogen cations, which reduces the soil pH. Chemically, this happens when a proton donor gets added to the soil. The donor can be an acid, such as nitric acid, sulfuric acid, or carbonic acid. It can also be a compound such as aluminium sulfate, which reacts in the soil to release protons. Acidification also occurs when base cations such as calcium, magnesium, potassium and sodium are leached from the soil.
Soil acidification naturally occurs as lichens and algae begin to break down rock surfaces. Acids continue with this dissolution as soil develops. With time and weathering, soils become more acidic in natural ecosystems. Soil acidification rates can vary, and increase with certain factors such as acid rain, agriculture, and pollution. | 9 | Geochemistry |
The M muscarinic receptors are located in the heart and lungs. In the heart, they act to slow the heart rate down below the normal baseline sinus rhythm, by slowing the speed of depolarization. In humans, under resting conditions, vagal activity dominates over sympathetic activity. Hence, inhibition of M receptors (e.g. by atropine) will cause a raise in heart rate. They also moderately reduce contractile forces of the atrial cardiac muscle, and reduce conduction velocity of the atrioventricular node (AV node). It also serves to slightly decrease the contractile forces of the ventricular muscle.
M muscarinic receptors act via a G type receptor, which causes a decrease in cAMP in the cell, inhibition of voltage-gated Ca channels, and increasing efflux of K, in general, leading to inhibitory-type effects. | 1 | Biochemistry |
Chemosphere is a biweekly peer-reviewed scientific journal published since 1972 by Elsevier and covering environmental chemistry. Its co-editors-in-chief are Jacob de Boer (Vrije Universiteit Amsterdam) and Shane Snyder (University of Arizona). The journal has a 2020 impact factor of 7.086, and is ranked 30th out of 274 journals in the category "Environmental Sciences." | 2 | Environmental Chemistry |
The method was invented by Joseph Louis Gay-Lussac. Justus von Liebig studied the method while working with
Gay-Lussac between 1822 and 1824 and improved the method in the following years to a level that it could be used as standard procedure for organic analysis. | 0 | Organic Chemistry |
Construction is underway for Velocys commercial reference plant incorporating its microchannel Fischer–Tropsch technology; ENVIA Energys Oklahoma City GTL project being built adjacent to Waste Management's East Oak landfill site. The project is being financed by a joint venture between Waste Management, NRG Energy, Ventech and Velocys. The feedstock for this plant will be a combination of landfill gas and pipeline natural gas. | 0 | Organic Chemistry |
* 2011 Royal Society of Chemistry Harrison-Meldola Award
* 2015 Royal Society of Chemistry Marlow Award
* 2017 EBSA Young Investigator Award and Medal
* 2018 Klung Wilhelmy Science Award (Chemistry)
* 2019 Blavatnik Awards for Young Scientists UK (Chemistry) Laureate
* 2021 [https://www.rms.org.uk/opportunities/competitions-awards/rms-section-awards/award-for-light-microscopy.html RMS Medal for Light Microscopy]
*2022 [https://www.eurekalert.org/news-releases/948615 Emil Thomas Kaiser Award]
*2022 [https://britishbiophysics.org/posts/2022/2022-05-01-kukuraheptares/ Sosei Heptares Prize For Biophysics of the British Biophysical Society] | 7 | Physical Chemistry |
The dominant type in Sweden was the German forge, which had a single hearth that was used for all processes. | 8 | Metallurgy |
Retroviruses that cause tumor growth include Rous sarcoma virus and mouse mammary tumor virus. Cancer can be triggered by proto-oncogenes that were mistakenly incorporated into proviral DNA or by the disruption of cellular proto-oncogenes. Rous sarcoma virus contains the src gene that triggers tumor formation. Later it was found that a similar gene in cells is involved in cell signaling, which was most likely excised with the proviral DNA. Nontransforming viruses can randomly insert their DNA into proto-oncogenes, disrupting the expression of proteins that regulate the cell cycle. The promoter of the provirus DNA can also cause over expression of regulatory genes.
Retroviruses can cause diseases such as cancer and immunodeficiency. If viral DNA is integrated into host chromosomes, it can lead to permanent infections. It is therefore important to discover the body's response to retroviruses. Exogenous retroviruses are especially associated with pathogenic diseases. For example, mice have mouse mammary tumor virus (MMTV), which is a retrovirus. This virus passes to newborn mice through mammary milk. When they are 6 months old, the mice carrying the virus get mammary cancer because of the retrovirus. In addition, leukemia virus I (HTLV-1), found in human T cell, has been found in humans for many years. It is estimated that this retrovirus causes leukemia in the ages of 40 and 50. It has a replicable structure that can induce cancer. In addition to the usual gene sequence of retroviruses, HTLV-1 contains a fourth region, PX. This region encodes Tax, Rex, p12, p13 and p30 regulatory proteins. The Tax protein initiates the leukemic process and organizes the transcription of all viral genes in the integrated HTLV proviral DNA. | 1 | Biochemistry |
Coenzyme F is a family of coenzymes involved in redox reactions in a number of bacteria and archaea. It is derived from coenzyme F (7,8-didemethyl-8-hydroxy-5-deazariboflavin) and differs by having a oligoglutamyl tail attached via a 2-phospho-L-lactate bridge. F is so named because it is a flavin derivative with an absorption maximum at 420 nm.
F was originally discovered in methanogenic archaea and in Actinomycetota (especially in Mycobacterium). It is now known to be used also by Cyanobacteria and by soil Proteobacteria, Chloroflexi and Firmicutes. Eukaryotes including the fruit fly Drosophila melanogaster and the algae Ostreococcus tauri also use Coenzyme F.
F is structurally similar to FMN, but catalytically it is similar to NAD and NADP: it has low redox potential and always transfer a hydride. As a result, it is not only a versatile cofactor in biochemical reactions, but also being eyed for potential as an industrial catalyst. Similar to FMN, it has two states: one reduced state, notated as F-H, and one oxidized state, written as just F. F has largely similar redox properties, but cannot carry an electric charge and as a result probably slowly leaks out of the cellular membrane.
A number of F molecules, differing by the length of the oligoglutamyl tail, are possible; F-2, for example, refers to the version with two glutamyl units attached. Lengths from 4 to 9 are typical. | 1 | Biochemistry |
An on-line method of measuring hydrogen in aluminum is then required to characterize and optimize the process, which helps ensure the quality of outgoing products and monitors the performance of these degassing processes. Traditional laboratory methods, such as hot extraction, are too expensive for routine quality assurance, and too slow for effective process control. The Reduced Pressure Test (RPT) is often used on the foundry floor. The RPT is a semi-quantitative method with limited accuracy that provides an indication of the hydrogen level. | 8 | Metallurgy |
MTBE is manufactured via the chemical reaction of methanol and isobutylene. Methanol is primarily derived from natural gas, where steam reforming converts the various light hydrocarbons in natural gas (primarily methane) into carbon monoxide and hydrogen. The resulting gases then further react in the presence of a catalyst to form methanol. Isobutylene can be produced through a variety of methods. n-butane can be isomerized into isobutane which can be dehydrogenated to isobutylene. In the Halcon process, t-Butyl hydroperoxide derived from isobutane oxygenation is reacted with propylene to produce propylene oxide and t-butanol. The t-butanol can be dehydrated to isobutylene.
MTBE production in the U.S. peaked in 1999 at 260,000 barrels per day before dropping down to about 50,000 barrels per day and holding steady, mostly for the export market. After the purchase of SABIC, oil giant Saudi Aramco is now considered to be the world's largest producer with an estimated production capacity of 2.37 million metric tons per year (mt/yr). Worldwide production capacity of MTBE in 2018 was estimated to be 35 million metric tons. | 2 | Environmental Chemistry |
It has also been used in septic shock and anaphylaxis.
Methylene blue consistently increases blood pressure in people with vasoplegic syndrome (redistributive shock), but has not been shown to improve delivery of oxygen to tissues or to decrease mortality.
Methylene blue has been used in calcium channel blocker toxicity as a rescue therapy for distributive shock unresponsive to first line agents. Evidence for its use in this circumstance is very poor and limited to a handful of case reports. | 3 | Analytical Chemistry |
Genomic biomarkers analyze DNA by identifying irregular sequences in the genome, typically a single nucleotide polymorphism. Genetic biomarkers are particularly significant in cancer because most cancer cell lines carry somatic mutations. Somatic mutations are distinguishable from hereditary mutations because the mutation is not in every cell; just the tumor cells, making them easy targets. | 1 | Biochemistry |
Changes in promoter sequences are critical in evolution as indicated by the relatively stable number of genes in many lineages. For instance, most vertebrates have roughly the same number of protein-coding genes (about 20,000) which are often highly conserved in sequence, hence much of evolutionary change must come from changes in gene expression. | 1 | Biochemistry |
Since the EPA methods are created by different regulatory departments within the EPA, finding methods on the EPA website itself can be challenging. To make finding methods easier, some organizations have created method search databases that organize all the methods into one place and link to actual test methods. Some allow searching by method number, analyte, or other keywords in the method. | 3 | Analytical Chemistry |
A phenomenon that is commonly presented as evidence for the existence of zero-point energy in vacuum is the Casimir effect, proposed in 1948 by Dutch physicist Hendrik Casimir, who considered the quantized electromagnetic field between a pair of grounded, neutral metal plates. The vacuum energy contains contributions from all wavelengths, except those excluded by the spacing between plates. As the plates draw together, more wavelengths are excluded and the vacuum energy decreases. The decrease in energy means there must be a force doing work on the plates as they move.
Early experimental tests from the 1950s onwards gave positive results showing the force was real, but other external factors could not be ruled out as the primary cause, with the range of experimental error sometimes being nearly 100%. That changed in 1997 with Lamoreaux conclusively showing that the Casimir force was real. Results have been repeatedly replicated since then.
In 2009, Munday et al. published experimental proof that (as predicted in 1961) the Casimir force could also be repulsive as well as being attractive. Repulsive Casimir forces could allow quantum levitation of objects in a fluid and lead to a new class of switchable nanoscale devices with ultra-low static friction.
An interesting hypothetical side effect of the Casimir effect is the Scharnhorst effect, a hypothetical phenomenon in which light signals travel slightly faster than between two closely spaced conducting plates. | 7 | Physical Chemistry |
The MCD signal ΔA is derived via the absorption of the LCP and RCP light as
This signal is often presented as a function of wavelength λ, temperature T or magnetic field H. MCD spectrometers can simultaneously measure absorbance and ΔA along the same light path. This eliminates error introduced through multiple measurements or different instruments that previously occurred before this advent.
The MCD spectrometer example shown below begins with a light source that emits a monochromatic wave of light. This wave is passed through a Rochon prism linear polarizer, which separates the incident wave into two beams that are linearly polarized by 90 degrees. The two beams follow different paths- one beam (the extraordinary beam) traveling directly to a photomultiplier (PMT), and the other beam (the ordinary beam) passing through a photoelastic modulator (PEM) oriented at 45 degrees to the direction of the ordinary ray polarization. The PMT for the extraordinary beam detects the light intensity of the input beam. The PEM is adjusted to cause an alternating plus and minus 1/4 wavelength shift of one of the two orthogonal components of the ordinary beam. This modulation converts the linearly polarized light into circularly polarized light at the peaks of the modulation cycle. Linearly polarized light can be decomposed into two circular components with intensity represented as
The PEM will delay one component of linearly polarized light with a time dependence that advances the other component by 1/4 λ (hence, quarter-wave shift). The departing circularly polarized light oscillates between RCP and LCP in a sinusoidal time-dependence as depicted below:
The light finally travels through a magnet containing the sample, and the transmittance is recorded by another PMT. The schematic is given below:
The intensity of light from the ordinary wave that reaches the PMT is governed by the equation:
Here A and A are the absorbances of LCP or RCP, respectively; ω is the modulator frequency – usually a high acoustic frequency such as 50 kHz; t is time; and δ is the time-dependent wavelength shift.
This intensity of light passing through the sample is converted into a two-component voltage via a current/voltage amplifier. A DC voltage will emerge corresponding to the intensity of light passed through the sample. If there is a ΔA, then a small AC voltage will be present that corresponds to the modulation frequency, ω. This voltage is detected by the lock in amplifier, which receives its reference frequency, ω, directly from the PEM. From such voltage, ΔA and A can be derived using the following relations:
where V is the (DC) voltage measured by the PMT from the extraordinary wave, and V is the DC component of the voltage measured by the PMT for the ordinary wave (measurement path not shown in the diagram).
Some superconducting magnets have a small sample chamber, far too small to contain the entire optical system. Instead, the magnet sample chamber has windows on two opposite sides. Light from the source enters one side, interacts with the sample (usually also temperature controlled) in the magnetic field, and exits through the opposite window to the detector. Optical relay systems that allow the source and detector each to be about a meter from the sample are typically employed. This arrangement avoids many of the difficulties that would be encountered if the optical apparatus had to operate in the high magnetic field, and also allows for a much less expensive magnet. | 7 | Physical Chemistry |
Metabolic network modelling aims at reproducing cellular metabolism in silico. Metabolite damage and repair create cellular energy costs, and consequently need to be incorporated into genome-scale metabolic models so that these models can more effectively guide metabolic engineering design.
In addition, genes encoding so-far unrecognized metabolite damage-control systems may constitute a significant fraction of the many conserved genes of unknown function found in the genomes of all organisms. | 1 | Biochemistry |
Nickel has a wide utility of application in manufactured metals because it is both strong and malleable, leading to ubiquitous presence and the potential for consumers to be in contact with it daily. However, for those who have the rash of allergic contact dermatitis (ACD) due to a nickel allergy, it can be a challenge to avoid. Foods, common kitchen utensils, cell phones, jewelry, and many other items may contain nickel and be a source of irritation due to the allergic reaction caused by the absorption of free released nickel through direct and prolonged contact. The most appropriate measure for nickel-allergic persons is to prevent contact with the allergen.
In 2011, researchers showed that applying a thin layer of glycerine emollient containing nanoparticles of either calcium carbonate or calcium phosphate on an isolated piece of pig skin (in vitro) and on the skin of mice (in vivo) prevents the penetration of nickel ions into the skin. The nanoparticles capture nickel ions by cation exchange, and remain on the surface of the skin, allowing them to be removed by simple washing with water. Approximately 11-fold fewer nanoparticles by mass are required to achieve the same efficacy as the chelating agent ethylenediamine tetraacetic acid. Using nanoparticles with diameters smaller than 500 nm in topical creams may be an effective way to limit the exposure to metal ions that can cause skin irritation'.
Pre-emptive avoidance strategies (PEAS) might ultimately lower the sensitization rates of children who would develop ACD It is theorized that prevention of exposure to nickel early on could reduce the number of those that are sensitive to nickel by one-quarter to one-third. Identification of the many sources of nickel is vital to understanding the nickel sensitization story, food like chocolate and fish, zippers, buttons, cell phones and even orthodontic braces and eyeglass frames might contain nickel. Items that contain sentimental value (heirlooms, wedding rings) could be treated with an enamel or rhodium plating.
The Dermatitis Academy has created an educational website to provide more information about nickel, including information about prevention, exposure, sources, and general information about nickel allergy. These resources provide guidance in a prevention initiative for children worldwide.
Prevention of SNAS includes modifying dietary choices to avoid certain foods that are higher in nickel than others. | 1 | Biochemistry |
Levacetylmethadol (INN), levomethadyl acetate (USAN), OrLAAM (trade name) or levo-α-acetylmethadol (LAAM) is a synthetic opioid similar in structure to methadone. It has a long duration of action due to its active metabolites. | 4 | Stereochemistry |
Typically, absorbance of a dissolved substance is measured using absorption spectroscopy. This involves shining a light through a solution and recording how much light and what wavelengths were transmitted onto a detector. Using this information, the wavelengths that were absorbed can be determined. First, measurements on a "blank" are taken using just the solvent for reference purposes. This is so that the absorbance of the solvent is known, and then any change in absorbance when measuring the whole solution is made by just the solute of interest. Then measurements of the solution are taken. The transmitted spectral radiant flux that makes it through the solution sample is measured and compared to the incident spectral radiant flux. As stated above, the spectral absorbance at a given wavelength is
The absorbance spectrum is plotted on a graph of absorbance vs. wavelength.
An Ultraviolet-visible spectroscopy#Ultraviolet–visible spectrophotometer will do all this automatically. To use this machine, solutions are placed in a small cuvette and inserted into the holder. The machine is controlled through a computer and, once it has been "blanked", automatically displays the absorbance plotted against wavelength. Getting the absorbance spectrum of a solution is useful for determining the concentration of that solution using the Beer–Lambert law and is used in HPLC. | 7 | Physical Chemistry |
The Science Based Targets initiative (SBTi) is a collaboration between the CDP (it was the Carbon Disclosure Project), the United Nations Global Compact, World Resources Institute (WRI) and the World Wide Fund for Nature (WWF). Since 2015, more than 1,000 companies have joined the initiative to set a science-based climate target. | 2 | Environmental Chemistry |
Biosynthesis of coelenterazine in Metridia starts from two molecules of tyrosine and one molecule of phenylalanine, and some researchers believe this comes in the form of a cyclized "Phe-Tyr-Tyr" (FYY) peptide.
Many members of the genus Metridia also produce luciferases that use this compound, some of which are secreted into extracellular space, an unusual property for luciferases. | 1 | Biochemistry |
* Tribology Gold Medal, Institution of Mechanical Engineers (2013)
*ACS National Award in Colloid and Surface Chemistry (2009)
* Named by the AICHE as one of the “One Hundred Chemical Engineers of the Modern Era (2008)
* Honorary Degree of Doctor of Engineering – University of South Florida (2007)
* Honorary Degree of Doctor sc. h.c. - ETH Zurich (2006)
* Schlumberger Visiting Professor – University of Oxford, UK (2005)
* MRS Medal, awarded for recent work on adhesion and friction (2004)
* Elected to the US National Academy of Sciences in the area of Engineering Science (2004)
* Elected Fellow of the American Physical Society in the area of Biological Physics (2004)
* Adhesion Society Award for “excellence in adhesion science (2003)
* Fellow of the Royal Society (1988)
* Matthew Flinders Medal and Lecture (1986)
* David Syme Research Prize (1983)
* (FAA) (Elected a fellow of the Australian Academy of Science (1982)
* Pawsey Medal (1977) | 6 | Supramolecular Chemistry |
During the synthesis of eukaryotic ribosomes, four mature ribosomal RNAs (the 5S, 5.8S, 18S, and 25S) must be synthesized. Three of these rRNAs (5.8S, 18S, and 25S) come from a single pre-rRNA known as the 35S. Although many of the intermediates in this rRNA processing pathway have been identified in the last thirty years, there are still a number of proteins involved in this process whose specific function is unknown. | 1 | Biochemistry |
Electrolysers require high currents produced by very low voltages. A homopolar generator has the ability to do this, so in Bockris and Ghoroghchians original experiment in 1985, they followed Faradays idea. Using a magnetic field of 0.86T produced by permanent magnets, they placed a stainless-steel disc in between. The disc needed a rotation speed of 2000 rpm to reach the correct electrical potential for electrolysis. The difference between Faradays original model and Bockris and Ghorogchians is that their disc will only rotate when it is in contact with an electrolyte.
They encountered one large problem, a viscous force created by the electrolyte, that slowed down the motion of the disc. The two ways they could fix this is to rotate the disc and solution together or increase the magnetic field used. The latter being most practicable, the required magnetic field was calculated according to the power consumption rate or producing a cubic meter of hydrogen. It was discovered a magnetic field of 11T was needed for effective electrolysis, more than 16 times greater than what was originally used. Since superconducting magnets would be required, and they can become too expensive to justify their use, ruling this out as a possible method.
Their final decision was to use a homopolar generator as an external source of power. This follows Faraday's method more closely.
In this method, a pulse potential was created to take advantage of previous studies that give an effectiveness factor of 2 when either a nickel electrode or a Teflon-bonded platinum electrode was used.
The generator was constructed with a magnetic flux density of 0.6T, a propeller radius of 30 cm and a loop coated with copper strips. To increase the output potential, and reducing the rotation speed required, these were connected in series. Pulses of 2-3V that were sustained for 1ms were achieved.
This was the first instance of a successful application of pulse electrolysis for the production of hydrogen. However, it still presents its own limitations in the possibility for it to be used in industry. | 7 | Physical Chemistry |
The visualization of single molecules, single biological cells, biological tissues and nanomaterials is very important and attractive approach in analytical science. Also, hybridization with other traditional analytical tools is revolutionizing analytical science. Microscopy can be categorized into three different fields: optical microscopy, electron microscopy, and scanning probe microscopy. Recently, this field has been rapidly progressing because of the rapid development of the computer and camera industries. | 3 | Analytical Chemistry |
A typical pressure injection cell holds a micro-tube or a vial in its central chamber. A small magnetic stir bar can be used to keep the particles in suspension. | 3 | Analytical Chemistry |
Methylations are epigenetic modification that, in eukaryotes, regulates processes as cell differentiation, and embryogenesis, while in prokaryotes can have a role in self recognition, protecting the DNA from being cleaved by the restriction endonuclease system, or for gene regulation. The first function is controlled by the restriction methylation system while the second by Orphan MTases as Dam and CcrM.
CcrM role have been characterized in the marine model organism Caulobacter crescentus, which is suitable for the study of cell cycle and epigenetics as it asymmetrically divides generating different progeny, a stalked and a swarmer cell, with different phenotypes and gene regulation. The swarmer cell has a single flagellum and polar pili and is characterized by its mobility, while the stacked cell has a stalk and is fixed to the substrate. The stacked cell enters immediately in S-phase, while the swarmer cell stays in G1-phase and will differentiate to a stacked cell before entering the S-phase again.
The stacked cell in S phase will replicate its DNA in a semiconservative manner producing two hemimethylated DNA double strands that will be rapidly methylated by the Methyltransferase CcrM, which is only produced at the end of the S phase. The enzyme will methylate more than 4 thousand 5-GANTC-3 sites in around 20 minutes, and then it will be degraded by the LON protease. This fast methylation plays an important role in the transcriptional control of several genes and controls the cell differentiation. CcrM expression is regulated by the CtrA master regulator, and in addition various 5-GANTC-3 sites methylation sites regulate CcrM expression, which will only occur at the end of the S phase when this sites are hemimethylated. In this process CtrA regulates the expression of CcrM and more than 1000 genes in the pre-divisional state, and SciP prevents the activation of CcrM transcription in non replicative cells. | 1 | Biochemistry |
When surfactants are present in a liquid, they tend to adsorb in the liquid-air or liquid-liquid interface. Interfacial rheology deals with the response of the adsorbed interfacial layer on the deformation. The response depends on the layer composition, and thus interfacial rheology is relevant in many applications in which adsorbed layer play a crucial role, for example in development surfactants, foams and emulsions. Many biological systems like pulmonary surfactant and meibum are dependent on interfacial viscoelasticity for their functionality. Interfacial rheology has been employed to understand the structure-function relationship of these physiological interfaces, how compositional deviations cause diseases such as infant respiratory distress syndrome or dry eye syndrome, and has helped to develop therapies like artificial pulmonary surfactant replacements and eye drops.
Interfacial rheology enables the study of surfactant kinetics, and the viscoelastic properties of the adsorbed interfacial layer correlate well with emulsion and foam stability. Surfactants and surface active polymers used are for stabilising emulsions and foams in food and cosmetic industries. Proteins are surface active and tend to adsorb at the interface, where they can change conformation and influence the interfacial properties. Natural surfactants like asphaltenes and resins stabilize water-oil emulsions in crude oil applications, and by understanding their behavior the crude oil separation process can be enhanced. Also enhanced oil recovery efficiency can be optimized.
Specialized setups that allow bulk exchange during interfacial rheology measurements are used to investigate the response of adsorbed proteins or surfactants upon changes in pH or salinity. These setups can also be used to mimic more complex conditions like the gastric environment to investigate the in vitro displacement or enzymatic hydrolysis of polymers adsorbed at oil-water interfaces to understand how respective emulsion are digested the stomach.
Interfacial rheology allows the probation of bacteria adsorption and biofilm formation at liquid-air or liquid-liquid interfaces.
In food science, interfacial rheology was used to understand the stability of emulsions like mayonnaise, the stability of espresso foam, the film formed on black tea, or the formation of kombucha biofilms. | 7 | Physical Chemistry |
Chloromethyl methyl ether (CMME) is a compound with formula CHOCHCl. A colorless liquid, it is a chloroalkyl ether. It is used as an alkylating agent. In organic synthesis, it is used for introducing the methoxymethyl ether (MOM) protecting group, and is thus often called MOM-Cl or MOM chloride. It also finds application as a chloromethylating agent in some variants of the Blanc chloromethylation. | 0 | Organic Chemistry |
In the 16th century, heap leaching became commonly used to extract copper as well as saltpeter, from organic matter. Primarily used in Germany and Spain, pyrite would be brought to the surface and left out in the open. The pyrite would be set outside for months at a time, where rain and air exposure would lead to chemical weathering. A solution containing copper sulfide would be collected in a basin, then precipitated in a process called cementation, resulting in metallic copper. Heap leaching, in this natural chemical-free form, was further developed to obtain different, more economically viable, types of ore. This was done by incorporating chemical lixiviation, which applies more chemical manipulation and technique to heap leaching.
From 1767-1867, the production of potash in Quebec became an important industry to supply France's glass and soap manufacturers. Potash was most frequently made from the ash remains of wood-burning stoves and fireplaces, which were agitated with water and filtered. Once evaporated, the remains would be potash. 400 tons of hardwood would be required to burn to yield one ton of potash.
In 1858, Adolf von Patera, an Austrian metallurgist, utilized lixiviation to separate soluble and insoluble compounds from silver in an aqueous solution.The technique of Patera's lixiviation was further developed by American E. H. Russell around 1884, creating the "Russell Process". In 1887, when the cyanidation process was patented in England, it began to be incorporated into the existing leaching process, creating the more specific cyanide leaching.
In 1887, when the cyanidation process was patented in England, it began to phase out the existing Russell Process. Cyanidation was much more efficient and had a recovery rate of up to 90%.
Leading up to World War I, many new ideas for leaching processes were experimented. This included using ammonia solutions for copper sulfides, and nitric acid for leaching sulfide ores. Most of these ideas were phased out into obscurity due to the high cost of the leaching agents required. | 8 | Metallurgy |
In the United States and India, some coal-producing states have invested in Fischer–Tropsch plants. In Pennsylvania, Waste Management and Processors, Inc. was funded by the state to implement FT technology licensed from Shell and Sasol to convert so-called waste coal (leftovers from the mining process) into low-sulfur diesel fuel. | 0 | Organic Chemistry |
Support for this theory has been bolstered by studies linking a lower basal metabolic rate (evident with a lowered heartbeat) to increased life expectancy. This has been proposed by some to be the key to why animals like the giant tortoise can live over 150 years.
However, the ratio of resting metabolic rate to total daily energy expenditure can vary between 1.6 and 8.0 between species of mammals. Animals also vary in the degree of coupling between oxidative phosphorylation and ATP production, the amount of saturated fat in mitochondrial membranes, the amount of DNA repair, and many other factors that affect maximum life span. Furthermore, a number of species with high metabolic rate, like bats and birds, are long-lived. In a 2007 analysis it was shown that, when modern statistical methods for correcting for the effects of body size and phylogeny are employed, metabolic rate does not correlate with longevity in mammals or birds. | 1 | Biochemistry |
By February 1994, several regional landfills in Campania had become overfilled, and Prime Minister Carlo Azeglio Ciampi declared a state of emergency and created the Committee for the Waste Emergency in Campania (Commissariato di Governo per lemergenza rifiuti in Campania').
By December 1999, all regional landfills had reached capacity. Reports in 2008 stated that the crisis was caused at least in part by the Camorra, the powerful Campania-based mafia, which created a lucrative business in the municipal waste disposal sector, mostly in the triangle of death. With the complicity of industrial companies, the illegal dumpers frequently mix heavy metals, industrial waste, and chemicals and household waste together, and then dump them near roads and burn them to avoid detection, leading to severe soil and air pollution.
According to Giacomo D'Alisa et al., "the situation worsened during this period as the Camorra diversified their illegal waste disposal strategy: 1) transporting and dumping hazardous waste in the countryside by truck; 2) dumping waste in illegal caves or holes; 3) mixing toxic waste with textiles to avoid explosions and then burning it; and 4) mixing toxic with urban waste for disposal in landfills and incinerators."
A Camorra member, Nunzio Perella was arrested in 1992, and began collaborating with authorities; he had stated "the rubbish is gold." The boss of the Casalesi clan, Gaetano Vassallo, admitted to systematically working for 20 years to bribe local politicians and officials to gain their acquiescence to dumping toxic waste. Giorgio Napolitano, then President of Italian Republic, said in June 2008: | 2 | Environmental Chemistry |
Theresa M. Reineke (born January 1, 1972) is an American chemist and Distinguished McKnight University Professor at the University of Minnesota. She designs sustainable, environmentally friendly polymer-based delivery systems for targeted therapeutics. She is the associate editor of ACS Macro Letters. | 1 | Biochemistry |
Mutations in the STAT1 molecule can be gain of function (GOF) or loss of function (LOF). Both of them can cause different phenotypes and symptoms. Recurring common infections are frequent in both GOF and LOF mutations. In humans STAT1 has been particularly under strong purifying selection when populations shifted from hunting and gathering to farming, because this went along with a change in the pathogen spectrum. | 1 | Biochemistry |
In molecular genetics, the three prime untranslated region (3′-UTR) is the section of messenger RNA (mRNA) that immediately follows the translation termination codon. The 3′-UTR often contains regulatory regions that post-transcriptionally influence gene expression.
During gene expression, an mRNA molecule is transcribed from the DNA sequence and is later translated into a protein. Several regions of the mRNA molecule are not translated into a protein including the 5 cap, 5 untranslated region, 3′ untranslated region and poly(A) tail. Regulatory regions within the 3′-untranslated region can influence polyadenylation, translation efficiency, localization, and stability of the mRNA. The 3′-UTR contains binding sites for both regulatory proteins and microRNAs (miRNAs). By binding to specific sites within the 3′-UTR, miRNAs can decrease gene expression of various mRNAs by either inhibiting translation or directly causing degradation of the transcript. The 3′-UTR also has silencer regions which bind to repressor proteins and will inhibit the expression of the mRNA.
Many 3′-UTRs also contain AU-rich elements (AREs). Proteins bind AREs to affect the stability or decay rate of transcripts in a localized manner or affect translation initiation. Furthermore, the 3′-UTR contains the sequence AAUAAA that directs addition of several hundred adenine residues called the poly(A) tail to the end of the mRNA transcript. Poly(A) binding protein (PABP) binds to this tail, contributing to regulation of mRNA translation, stability, and export. For example, poly(A) tail bound PABP interacts with proteins associated with the 5' end of the transcript, causing a circularization of the mRNA that promotes translation.
The 3′-UTR can also contain sequences that attract proteins to associate the mRNA with the cytoskeleton, transport it to or from the cell nucleus, or perform other types of localization. In addition to sequences within the 3′-UTR, the physical characteristics of the region, including its length and secondary structure, contribute to translation regulation. These diverse mechanisms of gene regulation ensure that the correct genes are expressed in the correct cells at the appropriate times. | 1 | Biochemistry |
It is likely that most externally fertilizing species (e.g. marine worms, sea urchins) coordinate their sexual behaviour (release of sperm and eggs) using pheromones. This coordination is very important because sperm are diluted easily, and are short-lived. Coordination therefore provides a selective advantage to both males and females: individuals that do not coordinate are unlikely to achieve fertilisation and hence to leave offspring.
The main selective advantage of outcrossing is that it promotes the masking of deleterious recessive alleles, while inbreeding promotes their harmful expression. | 1 | Biochemistry |
FAIRE-extracted DNA fragments can be analyzed in a high-throughput way using next-generation sequencing techniques. In general, libraries are made by ligating specific adapters to the DNA fragments that allow them to cluster on a platform and be amplified resulting in the DNA sequences being read/determined, and this in parallel for millions of the DNA fragments.
Depending on the size of the genome FAIRE-seq is performed on, a minimum of reads is required to create an appropriate coverage of the data, ensuring a proper signal can be determined. In addition, a reference or input genome, which has not been cross-linked, is often sequenced alongside to determine the level of background noise.
Note that the extracted FAIRE-fragments can be quantified in an alternative method by using quantitative PCR. However, this method does not allow a genome wide / high-throughput quantification of the extracted fragments. | 1 | Biochemistry |
The lower critical solution temperature (LCST) or lower consolute temperature is the critical temperature below which the components of a mixture are miscible in all proportions. The word lower indicates that the LCST is a lower bound to a temperature interval of partial miscibility, or miscibility for certain compositions only.
The phase behavior of polymer solutions is an important property involved in the development and design of most polymer-related processes. Partially miscible polymer solutions often exhibit two solubility boundaries, the upper critical solution temperature (UCST) and the LCST, both of which depend on the molar mass and the pressure. At temperatures below LCST, the system is completely miscible in all proportions, whereas above LCST partial liquid miscibility occurs.
In the phase diagram of the mixture components, the LCST is the shared minimum of the concave up spinodal and binodal (or coexistence) curves. It is in general pressure dependent, increasing as a function of increased pressure.
For small molecules, the existence of an LCST is much less common than the existence of an upper critical solution temperature (UCST), but some cases do exist. For example, the system triethylamine-water has an LCST of 19 °C, so that these two substances are miscible in all proportions below 19 °C but not at higher temperatures. The nicotine-water system has an LCST of 61 °C, and also a UCST of 210 °C at pressures high enough for liquid water to exist at that temperature. The components are therefore miscible in all proportions below 61 °C and above 210 °C (at high pressure), and partially miscible in the interval from 61 to 210 °C. | 7 | Physical Chemistry |
All crystal structures belong to one of thirty-two crystal classes based on the number of rotational axes and reflection planes they possess that leave the crystal structure unchanged (point groups). Of the thirty-two crystal classes, twenty-one are non-centrosymmetric (not having a centre of symmetry). Of these twenty-one, twenty exhibit direct piezoelectricity, the remaining one being the cubic class 432. Ten of these twenty piezoelectric classes are polar, i.e., they possess a spontaneous polarization, having a dipole in their unit cell, and exhibit pyroelectricity. If this dipole can be reversed by the application of an electric field, the material is said to be ferroelectric. Any dielectric material develops a dielectric polarization (electrostatics) when an electric field is applied, but a substance which has such a natural charge separation even in the absence of a field is called a polar material. Whether or not a material is polar is determined solely by its crystal structure. Only 10 of the 32 point groups are polar. All polar crystals are pyroelectric, so the ten polar crystal classes are sometimes referred to as the pyroelectric classes.
Piezoelectric crystal classes: 1, 2, m, 222, mm2, 4, -4, 422, 4mm, -42m, 3, 32, 3m, 6, -6, 622, 6mm, -62m, 23, -43m
Pyroelectric: 1, 2, m, mm2, 3, 3m, 4, 4mm, 6, 6mm | 7 | Physical Chemistry |
The amount of useful work which may be extracted from a thermodynamic system is determined by the second law of thermodynamics. Under many practical situations this can be represented by the thermodynamic availability, or Exergy, function. Two important cases are: in thermodynamic systems where the temperature and volume are held constant, the measure of useful work attainable is the Helmholtz free energy function; and in systems where the temperature and pressure are held constant, the measure of useful work attainable is the Gibbs free energy. | 7 | Physical Chemistry |
Alkaline cleaners are classified as compounds with pH 7-14. Proteins are most effectively removed from surfaces by cleaners with a pH of 11 or higher. An example of a strong alkaline cleaning agent is sodium hydroxide, also called caustic soda. Although sodium hydroxide (NaOH) can cause corrosion on food contact surfaces such as stainless steel, it is the preferred cleaning agent for protein removal due to its efficacy in dissolving proteins and dispersing/emulsifying food soils. Silicates are often added to these cleaners to reduce corrosion on metal surfaces. The mechanism of alkaline cleaning action in proteins follows a three-step process:
# Gel formation: Upon contact with the alkaline solution, the protein soil swells and forms a removable gel.
# Protein removal: The protein gel is removed through mass transfer, while the cleaning agent continues to diffuse through the soil, increasing gel formation.
# Decay stage: The protein gel has been eroded to the point where it is a thin deposit. Removal at this stage is governed by shear stress forces and mass transfer of the gel.
Hypochlorite is often added to alkaline cleaners to peptize proteins. Chlorinated cleansers work by oxidizing sulfide crosslinks in proteins. Cleaning speed and efficiency is improved due to increased diffusion of the cleaner into the soil matrix, now composed of smaller, more soluble proteins. | 1 | Biochemistry |
Janus interphase catalyst is a new generation of heterogeneous catalysts, which is capable to do organic reactions on the interface of two phases via the formation of Pickering emulsion. | 7 | Physical Chemistry |
The reverse Krebs cycle is proposed to be a major role in the pathophysiology of melanoma. Melanoma tumors are known to alter normal metabolic pathways in order to utilize waste products. These metabolic adaptations help the tumor adapt to its metabolic needs. The most well known adaptation is the Warburg effect where tumors increase their uptake and utilization of glucose. Glutamine is one of the known substances to be utilized in the reverse Krebs cycle in order to produce acetyl-CoA. This type of mitochondrial activity could provide a new way to identify and target cancer causing cells. | 1 | Biochemistry |
A wide variety of agroindustrial waste products can be fermented to use as food for animals, especially ruminants. Fungi have been employed to break down cellulosic wastes to increase protein content and improve in vitro digestibility. | 1 | Biochemistry |
It was envisaged that Taxol (51) could be accessed through tail addition of the Ojima lactam 48 to alcohol 47. Of the four rings of Taxol, the D ring was formed last, the result of a simple intramolecular S2 reaction of hydroxytosylate 38, which could be synthesized from hydroxyketone 27. Formation of the six-membered C ring took place through a Dieckmann condensation of lactone 23, which could be obtained through a Chan rearrangement of carbonate ester 15. Substrate 15 could be derived from ketone 6, which, after several oxidations and rearrangements, could be furnished from commercially available patchoulene oxide 1. | 0 | Organic Chemistry |
The CompTox Chemicals Dashboard is a freely accessible online database created and maintained by the U.S. Environmental Protection Agency (EPA). The database provides access to multiple types of data including physicochemical properties, environmental fate and transport, exposure, usage, in vivo toxicity, and in vitro bioassay. EPA and other scientists use the data and models contained within the dashboard to help identify chemicals that require further testing and reduce the use of animals in chemical testing. The Dashboard is also used to provide public access to information from EPA Action Plans, e.g. around perfluorinated alkylated substances.
Originally titled the Chemistry Dashboard, the first version was released in 2016. The latest release of the database (version 3.0.5) contains manually curated data for over 875,000 chemicals and incorporates the latest data generated from the EPA's Toxicity Forecaster (ToxCast) high-throughput screening program. The Chemicals Dashboard incorporates data from several previous EPA databases into one package including the ToxCast Dashboard, the Endocrine Disruption Screening Program (EDSP) Dashboard and the Chemical and Products Database (CPDat). | 2 | Environmental Chemistry |
Baku has the main moorings of all large vessels, such as oil tankers, in Azerbaijan. It is the largest port of the Caspian Sea. The port (and tankers) have access to the oceans along the Caspian Sea–Volga–Don Canal, and the Don–Sea of Azov. A northern alternate is the Volga–Baltic (a sea which has a connection to the North Sea of the Atlantic, as the White Sea does via the White Sea-Baltic canal). Baku Sea Trade Port and Caspian Shipping Company CJSC, have a big role in the sea transportation of Azerbaijan. The Caspian Sea Shipping Company CJSC has two fleets plus shipyards. Its transport fleet has 51 vessels: 20 tankers, 13 ferries, 15 universal dry cargo vessels, 2 Ro-Ro vessels, as well as 1 technical vessel and 1 floating workshop. Its specialized fleet has 210 vessels: 20 cranes, 25 towing and supplying vehicles, 26 passenger, two pipe-laying, six fire-fighting, seven engineering-geological, two diving and 88 auxiliary vessels.
The Caspian Sea Shipping Company of Azerbaijan, which acts as a liaison in the Transport Corridor Europe-Caucasus-Asia (TRACECA), simultaneously with the transportation of cargo and passengers in the Trans-Caspian direction, also performs work to fully ensure the processes of oil and gas production at sea. In the 19th century, the sharp increase in oil production in Baku gave a huge impetus to the development of shipping in the Caspian Sea, and as a result, there was a need to create fundamentally new floating facilities for the transportation of oil and oil products. | 2 | Environmental Chemistry |
Zero-point energy (ZPE) is the lowest possible energy that a quantum mechanical system may have. Unlike in classical mechanics, quantum systems constantly fluctuate in their lowest energy state as described by the Heisenberg uncertainty principle. Therefore, even at absolute zero, atoms and molecules retain some vibrational motion. Apart from atoms and molecules, the empty space of the vacuum also has these properties. According to quantum field theory, the universe can be thought of not as isolated particles but continuous fluctuating fields: matter fields, whose quanta are fermions (i.e., leptons and quarks), and force fields, whose quanta are bosons (e.g., photons and gluons). All these fields have zero-point energy. These fluctuating zero-point fields lead to a kind of reintroduction of an aether in physics since some systems can detect the existence of this energy. However, this aether cannot be thought of as a physical medium if it is to be Lorentz invariant such that there is no contradiction with Einstein's theory of special relativity.
The notion of a zero-point energy is also important for cosmology, and physics currently lacks a full theoretical model for understanding zero-point energy in this context; in particular, the discrepancy between theorized and observed vacuum energy in the universe is a source of major contention. Yet according to Einstein's theory of general relativity, any such energy would gravitate, and the experimental evidence from the expansion of the universe, dark energy and the Casimir effect shows any such energy to be exceptionally weak. One proposal that attempts to address this issue is to say that the fermion field has a negative zero-point energy, while the boson field has positive zero-point energy and thus these energies somehow cancel each other out. This idea would be true if supersymmetry were an exact symmetry of nature; however, the LHC at CERN has so far found no evidence to support it. Moreover, it is known that if supersymmetry is valid at all, it is at most a broken symmetry, only true at very high energies, and no one has been able to show a theory where zero-point cancellations occur in the low-energy universe we observe today. This discrepancy is known as the cosmological constant problem and it is one of the greatest unsolved mysteries in physics. Many physicists believe that "the vacuum holds the key to a full understanding of nature". | 7 | Physical Chemistry |
The narrowness of the band of colors that a monochromator can generate is related to the focal length of the monochromator collimators. Using a longer focal length optical system also unfortunately decreases the amount of light that can be accepted from the source. Very high resolution monochromators might have a focal length of 2 meters. Building such monochromators requires exceptional attention to mechanical and thermal stability. For many applications a monochromator of about 0.4 meter focal length is considered to have excellent resolution. Many monochromators have a focal length less than 0.1 meter. | 7 | Physical Chemistry |
* Photo-reflectance measures differential reflectivities as small as one part per million, whereas ellipsometry and/or standard reflectance measure differential reflectivities on the order of one part per thousand.
* Photo-reflectance spectra exhibits sharp derivative-like structures localized at interband transition energies, whereas ellipsometry and/or standard reflectance exhibit broad slowly varying spectra.
* The photo-reflectance response at a particular wavelength typically arises from specific interband transitions confined to specific materials within the sample.
* By using phase-locked detection methods, ambient (nonsynchronous) light does not influence photo-reflectance measurements.
* By using a laser probe beam, the refractive part of the photo-reflectance response can be isolated without the necessity to take spectroscopic data or perform a fit procedure.
* Laser photo-reflectance has been proven in statistical process control for microelectronics manufacturing for over three decades. | 7 | Physical Chemistry |
Thiosulfate is an acceptable common name (but used almost always); functional replacement IUPAC name is sulfurothioate; the systematic additive IUPAC name is trioxidosulfidosulfate(2−) or trioxido-1κO-disulfate(S—S)(2−). The external sulfur atom has a valence of 2 while the central sulfur atom has a valence of 6. The oxygen atoms have a valence of 2.
Thiosulfate also refers to the esters of thiosulfuric acid, e.g. O,S-dimethyl thiosulfate . Such species are rare. | 8 | Metallurgy |
By introducing an asymmetric field effect along the nanochannel, a field-effect reconfigurable nanofluidic diode is feasible, which features post-fabrication reconfiguration of the diode functions, such as the forward/reverse directions and the rectification degrees. Unlike the nanofluidic field-effect transistor, where only the amount of ions/molecules is regulated by an electrostatic potential, the field-effect reconfigurable diode can be used to control both directions and magnitudes of ion/molecule transport. This device could be deemed as the building blocks for ionic counterpart of the electronic field-programmable gate array. | 7 | Physical Chemistry |
Water striders (Gerris remigis), most commonly called Jesus bugs, have an extraordinary ability that lets them walk on the water. In a fashion similar to superhydrophobic plants, their legs are highly water repellent due to their hierarchical morphology. They are built up with hydrophobic waxy microhairs, microsetae, and each hair is covered with nanogrooves. As a result, air is entrapped between micro- and nanohairs, which repels water. Feng et al. measured how deep the leg can dip into water and the contact angle of the leg. They found the contact angle at least 168° and the maximum depth reported 4.38 ± 0.02 mm. | 7 | Physical Chemistry |
Viral (as well as some eukaryotic) 5′ UTRs contain internal ribosome entry sites, which is a cap-independent method of translational activation. Instead of building up a complex at the 5′ cap, the IRES allows for direct binding of the ribosomal complexes to the transcript to begin translation. The IRES enables the viral transcript to translate more efficiently due to the lack of needing a preinitation complex, allowing the virus to replicate quickly. | 1 | Biochemistry |
Fumarylacetoacetic acid (fumarylacetoacetate) is an intermediate in the metabolism of tyrosine. It is formed through the conversion of maleylacetoacetate into fumarylacetoacetate by the enzyme maleylacetoacetate isomerase. | 1 | Biochemistry |
The redox potentials of photoredox catalysts must be matched to the reaction's other components. While ground state redox potentials are easily measured by cyclic voltammetry or other electrochemical methods, measuring the redox potential of an electronically excited state cannot be accomplished directly by these methods. However, two methods exist that allow estimation of the excited-state redox potentials and one method exists for the direct measurement of these potentials. To estimate the excited-state redox potentials, one method is to compare the rates of electron transfer from the excited state to a series of ground-state reactants whose redox potentials are known. A more common method to estimate these potentials is to use an equation developed by Rehm and Weller that describes the excited-state potentials as a correction of the ground-state potentials:
In these formulas, E* represents the reduction or oxidation potential of the excited state, E represents the reduction or oxidation potential of the ground state, E represents the difference in energy between the zeroth vibrational states of the ground and excited states and w represents the work function, an electrostatic interaction that arises due to the separation of charges that occurs during electron-transfer between two chemical species. The zero-zero excitation energy, E is usually approximated by the corresponding transition in the fluorescence spectrum. This method allows calculation of approximate excited-state redox potentials from more easily measured ground-state redox potentials and spectroscopic data.
Direct measurement of the excited-state redox potentials is possible by applying a method known as phase-modulated voltammetry. This method works by shining light onto an electrochemical cell in order to generate the desired excited-state species, but to modulate the intensity of the light sinusoidally, so that the concentration of the excited-state species is not constant. In fact, the concentration of excited-state species in the cell should change exactly in phase with the intensity of light incident on the electrochemical cell. If the potential applied to the cell is strong enough for electron transfer to occur, the change in concentration of the redox-competent excited state can be measured as an alternating current (AC). Furthermore, the phase shift of the AC current relative to the intensity of the incident light corresponds to the average lifetime of an excited-state species before it engages in electron transfer.
Charts of redox potentials for the most common photoredox catalysts are available for quick access. | 5 | Photochemistry |
Metal spraying equipment uses compressed gases which create noise. Sound levels vary with the type of spraying equipment, the material being sprayed, and the operating parameters. Typical sound pressure levels are measured at 1 meter behind the arc. | 8 | Metallurgy |
Arformoterol, sold under the brand name Brovana among others, is a medication used for the treatment of chronic obstructive pulmonary disease (COPD).
It is a long-acting β adrenoreceptor agonist (LABA) and it is the active (R,R)-(−)-enantiomer of formoterol. It was approved for medical use in the United States in October 2006. It is available as a generic medication. | 4 | Stereochemistry |
Microsegregation is a non-uniform chemical separation and concentration of elements or impurities in alloys after they have solidified. | 7 | Physical Chemistry |
As powerful nucleophiles, enolates react readily with a variety of electrophiles. These reactions generate new C-C bonds and often new stereocenters. The stereoselectivity and regioselectivity is influenced by additives, solvent, counterions, etc. One important class of electrophiles are alkyl halides, and in this case a classic problem arises: O-alkylation vs C-alkylation. Controlling this selectivity has drawn much attention. The negative charge in enolates is concentrated on the oxygen, but that center is also highly solvated, which leads to C-alkylation.
Other important electrophiles are aldehydes/ketones and Michael acceptors. | 0 | Organic Chemistry |
Maxwell Garnett Equation describes optical properties of nanocomposites which consist in a collection of perfectly spherical nanoparticles. All these nanoparticles must have the same size. However, due to confinement effect, the optical properties can be influenced by the nanoparticles size distribution. As shown by Battie et al., the Maxwell Garnett equation can be generalized to take into account this distribution.
and are the nanoparticle radius and size distribution, respectively. and are the mean radius and the volume fraction of the nanoparticles, respectively. is the first electric Mie coefficient.
This equation reveals that the classical Maxwell Garnett equation gives a false estimation of the volume fraction nanoparticles when the size distribution cannot be neglected. | 7 | Physical Chemistry |
Foams can form following the degradation of harmful algal blooms (HABs). These are primarily composed of algal species, but can also consist of dinoflagellates and cyanobacteria. Biomass from algae in the bloom is integrated into sea foam in the sea surface microlayer. When the impacted sea foam breaks down, toxins from the algae are released into the air causing respiratory issues and occasionally initiating asthma attacks. Phaeocystis globosa is one algal species that is considered problematic, as observed in a study in the Netherlands. Its high biomass accumulation allows it to create large quantities of toxic foam that often wash onto beaches. P. globosa blooms are initiated in areas of high nutrient availability, often affiliated with coastal locations with a lot of stormwater runoff and eutrophication. Studies suggest that the development of foam is directly correlated to blooms caused by P. globosa, despite that foam formation typically occurs approximately two weeks after the appearance of an algal bloom offshore. Organic material from P. globosa was observed decomposing while suspended at the sea surface, but was not observed lower in the water column. P. globosa is also considered a nuisance species because its large foam formations impair the public's ability to enjoy the beach. | 9 | Geochemistry |
Ferromagnetic resonance, or FMR, is coupling between an electromagnetic wave and the magnetization of a medium through which it passes. This coupling induces a significant loss of power of the wave. The power is absorbed by the precessing magnetization (Larmor precession) of the material and lost as heat. For this coupling to occur, the frequency of the incident wave must be equal to the precession frequency of the magnetization (Larmor frequency) and the polarization of the wave must match the orientation of the magnetization.
This effect can be used for various applications such as spectroscopic techniques or conception of microwave devices.
The FMR spectroscopic technique is used to probe the magnetization of ferromagnetic materials. It is a standard tool for probing spin waves and spin dynamics. FMR is very broadly similar to electron paramagnetic resonance (EPR), and also somewhat similar to nuclear magnetic resonance (NMR), except that FMR probes the sample magnetization resulting from the magnetic moments of dipolar-coupled but unpaired electrons, while NMR probes the magnetic moment of atomic nuclei that are screened by the atomic or molecular orbitals surrounding such nuclei of non-zero nuclear spin.
The FMR resonance is also the basis of various high-frequency electronic devices, such as resonance isolators or circulators. | 7 | Physical Chemistry |
Transparent hydrogel fibers can be used as optical fiber, and stimuli-responsive functional groups can be grafted on to create optical sensors. For example, in the research done by Yun et al. the glucose-sensitive phenylboronic acid was grafted onto the polymer network. When the glucose concentration changes, the adsorption of the phenylboronic acid will change accordingly and can be recorded with the light intensity at a certain wavelength. | 7 | Physical Chemistry |
In thermodynamics, entropy is related to the amount of energy of a system that can be converted into mechanical work in a concrete process. In quantum mechanics, this translates to the ability to measure and manipulate the system based on the information gathered by measurement. An example is the case of Maxwell’s demon, which has been resolved by Leó Szilárd.
The entropy of an observable is associated with the complete projective measurement of an observable, where the operator has a spectral decomposition:
: where are the projection operators of the eigenvalue
The probability of outcome is The entropy associated with the observable is the Shannon entropy with respect to the possible outcomes:
The most significant observable in thermodynamics is the energy represented by the Hamiltonian operator and its associated energy entropy,
John von Neumann suggested to single out the most informative observable to characterize the entropy of the system. This invariant is obtained by minimizing the entropy with respect to all possible observables. The most informative observable operator commutes with the state of the system. The
entropy of this observable is termed the Von Neumann entropy and is equal to
As a consequence, for all observables. At thermal equilibrium the energy entropy is equal to the von Neumann entropy:
is invariant to a unitary transformation changing the state. The Von Neumann entropy is additive only for a system state that is composed of a tensor product of its subsystems: | 7 | Physical Chemistry |
A chlorosome is a photosynthetic antenna complex found in green sulfur bacteria (GSB) and many green non-sulfur bacteria (GNsB), together known as green bacteria. They differ from other antenna complexes by their large size and lack of protein matrix supporting the photosynthetic pigments. Green sulfur bacteria are a group of organisms that generally live in extremely low-light environments, such as at depths of 100 metres in the Black Sea. The ability to capture light energy and rapidly deliver it to where it needs to go is essential to these bacteria, some of which see only a few photons of light per chlorophyll per day. To achieve this, the bacteria contain chlorosome structures, which contain up to 250,000 chlorophyll molecules. Chlorosomes are ellipsoidal bodies, in GSB their length varies from 100 to 200 nm, width of 50-100 nm and height of 15 – 30 nm, in GNsB the chlorosomes are somewhat smaller.
Chlorosomes are a type of chromatophores that are found in photosynthetic bacteria (e.g. purple bacteria). | 5 | Photochemistry |
In 1932, organisms were discovered that could convert hydrogen gas and carbon dioxide into acetic acid. The first acetogenic bacterium species, Clostridium aceticum, was discovered in 1936 by Klaas Tammo Wieringa. A second species, Moorella thermoacetica, attracted wide interest because of its ability, reported in 1942, to convert glucose into three moles of acetic acid. | 1 | Biochemistry |
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid, phosphoric acid .
The phosphate or orthophosphate ion is derived from phosphoric acid by the removal of three protons . Removal of one proton gives the dihydrogen phosphate ion while removal of two protons gives the hydrogen phosphate ion . These names are also used for salts of those anions, such as ammonium dihydrogen phosphate and trisodium phosphate.
In organic chemistry, phosphate or orthophosphate is an organophosphate, an ester of orthophosphoric acid of the form where one or more hydrogen atoms are replaced by organic groups. An example is trimethyl phosphate, . The term also refers to the trivalent functional group in such esters. Phosphates may contain sulfur in place of one or more oxygen atoms (thiophosphates and organothiophosphates).
Orthophosphates are especially important among the various phosphates because of their key roles in biochemistry, biogeochemistry, and ecology, and their economic importance for agriculture and industry. The addition and removal of phosphate groups (phosphorylation and dephosphorylation) are key steps in cell metabolism.
Orthophosphates can condense to form pyrophosphates. | 0 | Organic Chemistry |
Several metal objects similar to those in the Kfar Monash hoard were found in this general area of the Levant. They were subject to metallurgical analysis, and generally dated to the Early Bronze Age. For example, objects from Ashkelon-Afridar, and from Tell esh-Shuna (the Jordan Valley) were seen as similar. Also the axes from early EB I Yiftah’el are seen as relevant.
Kfar Monash objects were also dated, based on typological considerations, to EB IB, similarly to the axes from Tel Beth Shean.
The study of Kfar Monash hoard indicated that some of them were made of unalloyed copper. The source of this unalloyed copper was found likely to be in Wadi Feynan, in southern Jordan. Such unalloyed copper was apparently mainly used for the production of tools.
Other objects were made using a CuAsNi alloy. This is the copper-arsenic-nickel alloy that is especially characteristic of Chalcolithic period Arslantepe in Eastern Anatolia (the upper Euphrates region). Nevertheless, the adzes that were made of this alloy were determined to be of "an Egyptian type".
Objects from Arslantepe using such polymetallic ores are mainly ascribed to Level VIA (3400–3000 BCE), dating to the Uruk period. | 8 | Metallurgy |
Again, define and to be conjugate pairs, and the to be the natural variables of some potential . We may take the "cross differentials" of the state equations, which obey the following relationship:
From these we get the Maxwell relations. There will be of them for each potential giving a total of equations in all. If we restrict ourselves the , , ,
Using the equations of state involving the chemical potential we get equations such as:
and using the other potentials we can get equations such as: | 7 | Physical Chemistry |
The simplest approach is to connect two commercial columns in series, which is termed a “tandem column”. Another approach is “biphasic column”, by packing two stationary phases separately in two ends of the same column. The third approach is to homogenize two or more different types of stationary phases in a single column, which is termed a “hybrid column” or “mixed-bed column”. | 3 | Analytical Chemistry |
Many tools and concepts have been developed to exploit the advantages of intramolecular cyclizations. For example, installing large substituents exploits the Thorpe-Ingold effect. High dilution reactions suppress intermolecular processes. One set of tools involves tethering as discussed below. | 0 | Organic Chemistry |
In other cases, comonomers are used to introduce crosslinking. Divinylbenzene, for example, when copolymerized with styrene, gives a crosslinked polystyrene. | 7 | Physical Chemistry |
Cefuroxime is active against many bacteria including susceptible strains of Staphylococci and Streptococci, as well as a range of gram negative organisms. As with the other cephalosporins, it is susceptible to beta-lactamase, although as a second-generation variety, it is less so. Hence, it may have greater activity against Haemophilus influenzae, Neisseria gonorrhoeae, and Lyme disease. Unlike other second-generation cephalosporins, cefuroxime can cross the blood–brain barrier.
A systematic review found high quality evidence that injecting the eye with cefuroxime after cataract surgery will lower the chance of developing endophthalmitis after surgery. | 4 | Stereochemistry |
The first pathogenic mutation in mitochondrial DNA was identified in 1988; from that time to 2016, around 275 other disease-causing mutations were identified. | 1 | Biochemistry |
* John Shorter, 2000, "The prehistory of the Hammett equation," Chem. Listy, 94:210-214.
* Frank Westheimer, 1997, "Louis Plack Hammett, 1894—1987: A Biographical Memoir," pp. 136–149, in Biographical Memoirs, Washington, DC, US: National Academies Press, see [http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hammett-louis-p.pdf], accessed 22 June 2015. | 7 | Physical Chemistry |
Gas chromatography (GC) is ideal to separate volatilized VOCs due to their low molecular weight. VOCs are carried by a gas vector (helium) through a chromatographic column (the solid phase) on which they have different affinities, which allows to separate them.
Liquid chromatography may be used for liquid extractions of floral tissue. | 1 | Biochemistry |
Pseudoephedrine may be quantified in blood, plasma, or urine to monitor any possible performance-enhancing use by athletes, confirm a diagnosis of poisoning, or to assist in a medicolegal death investigation. Some commercial immunoassay screening tests directed at the amphetamines cross-react appreciably with pseudoephedrine, but chromatographic techniques can easily distinguish pseudoephedrine from other phenethylamine derivatives. Blood or plasma pseudoephedrine concentrations are typically in the 50–300 µg/L range in persons taking the drug therapeutically, 500–3000 µg/L in people with substance use disorder involving pseudoephedrine, or poisoned patients and 10–70 mg/L in cases of acute fatal overdose. | 4 | Stereochemistry |
* Beta carbon nitride - a solid with a formula β-, which is predicted to be harder than diamond.
* Graphitic carbon nitride - g-, with important catalytic and sensor properties.
* - a combined triazole and triazine framework.
* MCN-12 () and MCN-13 (). | 0 | Organic Chemistry |
It can occur because of a change in environmental conditions: for example, a change in solvent polarity will result in solvatochromism.
A series of structurally-related molecules in a substitution series can also show a bathochromic shift. Bathochromic shift is a phenomenon seen in molecular spectra, not atomic spectra; it is thus more common to speak of the movement of the peaks in the spectrum rather than lines.
where is the wavelength of the spectral peak of interest and | 7 | Physical Chemistry |
Dextrorphan (DXO) is a psychoactive drug of the morphinan class which acts as an antitussive or cough suppressant and in high doses a dissociative hallucinogen. It is the dextrorotatory enantiomer of racemorphan; the levorotatory enantiomer is levorphanol. Dextrorphan is produced by O-demethylation of dextromethorphan by CYP2D6. Dextrorphan is an NMDA antagonist and contributes to the psychoactive effects of dextromethorphan. | 4 | Stereochemistry |
The STRENDA Guidelines propose those minimum information that is needed to comprehensively report kinetic and equilibrium data from investigations of enzyme activities including corresponding experimental conditions.
This minimum information is suggested to be addressed in a scientific publication when enzymology research data is reported to ensure that data sets are comprehensively described. This allows scientists not only to review, interpret and corroborate the data but also to reuse the data for modelling and simulation of biocatalytic pathways. In addition, the guidelines support researchers making their experimental data reproducible and transparent.
As of March 2020, more than 55 international biochemistry journal included the STRENDA Guidelines in their authors' instructions as recommendations when reporting enzymology data.
The STRENDA project is registered with FAIRsharing.org and the Guidelines are part of the FAIRDOM Community standards for Systems Biology. | 1 | Biochemistry |
; Note
* There is no difference between the lower and higher heating values for the combustion of carbon, carbon monoxide and sulfur since no water is formed during the combustion of those substances.
* BTU/lb values are calculated from MJ/kg (1 MJ/kg = 430 BTU/lb). | 7 | Physical Chemistry |
Figure 3 shows an impedance spectrum of a measurement series of a painted steel sample during water uptake (upper part in Figure 3). The symbols in the diagram represent the interpolation points (nodes) of the measurement, while the solid lines represent the theoretical values simulated according to an appropriate model. The interpolation points for the impedance were obtained by the Z-HIT reconstruction of the phase shift.
The bottom part of Figure 3 depicts the normalized error (Z − Z)/Z·100 of the impedance. For the error calculation, two different procedures are used to determine the "extrapolated impedance values":
* the "extrapolated impedance values" can be calculated from the "splined (=Z)" data of the impedance (magenta)
* the impedance values (blue) can be reconstructed by the Z-HIT (= Z) using the spline of the phase shift
The simulation according to the appropriate model is performed using the two different impedance curves. The corresponding residuals are calculated and depicted in the bottom part of the diagram in Figure (3).
Note: Error patterns as shown in the magenta bottom diagram in Figure (3) may be the motivation to extend an existing model by additional elements to minimize the fitting error. However, this is not possible in every case. The drift in the impedance spectrum mainly influences the low-frequency part by means of a changing system during the measurement. The spectrum in Figure 3 is caused by water penetrating into the pores of the lacquer, which reduces the impedance (resistance) of the coating. Therefore, the system behaves as if at each low-frequency measurement point the resistance of the coating was replaced by a further, smaller resistance due to the water uptake. However, there is no impedance element that exhibits such behavior. Therefore, any extension of the model would only result in a "smearing" of the error over a wider frequency range without reducing the error itself. Only the removal of the drift by reconstructing the impedance using Z-HIT leads to a significantly better compatibility between measurement and model.
Figure 4 shows a Bode plot of an impedance series measurement, performed on a fuel cell where the hydrogen of the fuel gas was deliberately poisoned by the addition of carbon monoxide. Due to the poisoning, active centers of the platinum catalyst are blocked, which severely impairs the performance of the fuel cell. Thereby, the blocking of the catalyst is depending on the potential, resulting in an alternating sorption and desorption of the carbon monoxide on the catalyst surface within the cell. This cyclical change of the active catalyst surface translates to pseudo-inductive behavior, which can be observed in the impedance spectrum of Figure 4 at low frequencies (< 3 Hz). The impedance curve was reconstructed by Z-HIT and is represented by the purple line, while the originally measured values are represented by the blue circles. The deviation in the low frequency part of the measurement can be clearly observed. Evaluation of the spectra shows significantly better agreement between model and measurement if the reconstructed Z-HIT impedances are used instead of the original data. | 7 | Physical Chemistry |
* F: Formylation (optional)
* A: Adenylation (required in a module)
* PCP: Thiolation and peptide carrier protein with attached 4'-phospho-pantetheine (required in a module)
* C: Condensation forming the amide bond (required in a module)
* Cy: Cyclization into thiazoline or oxazolines (optional)
* Ox: Oxidation of thiazolines or oxazolines to thiazoles or oxazoles (optional)
* Red: Reduction of thiazolines or oxazolines to thiazolidines or oxazolidines (optional)
* E: Epimerization into D-amino acids (optional)
* NMT: N-methylation (optional)
* TE: Termination by a thio-esterase (only found once in a NRPS)
* R: Reduction to terminal aldehyde or alcohol (optional)
* X: Recruits cytochrome P450 enzymes (optional) | 1 | Biochemistry |
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