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A further step beyond superstructures and aperiodic materials is what is called diffuse scattering in electron diffraction patterns due to disorder, which is also known for x-ray or neutron scattering. This can occur from inelastic processes, for instance, in bulk silicon the atomic vibrations (phonons) are more prevalent along specific directions, which leads to streaks in diffraction patterns. Sometimes it is due to arrangements of point defects. Completely disordered substitutional point defects lead to a general background which is called Laue monotonic scattering. Often there is a probability distribution for the distances between point defects or what type of substitutional atom there is, which leads to distinct three-dimensional intensity features in diffraction patterns. An example of this is for a NbCoSb sample, with the diffraction pattern shown in Figure 16. Because of the vacancies at the niobium sites, there is diffuse intensity with snake-like structure due to correlations of the distances between vacancies and also the relaxation of Co and Sb atoms around these vacancies. | 0 | Theoretical and Fundamental Chemistry |
The polymolybdates and polytungstates are derived, formally at least, from the dianionic [MO] precursors. The most common units for polymolybdates and polyoxotungstates are the octahedral {MO} centers, sometimes slightly distorted. Some polymolybdates contain pentagonal bipyramidal units. These building blocks are found in the molybdenum blues, which are mixed valence compounds. | 0 | Theoretical and Fundamental Chemistry |
In the case of a translating ribosome, a frameshift can either result in Nonsense mutation, a premature stop codon after the frameshift, or the creation of a completely new protein after the frameshift. In the case where a frameshift results in nonsense, the nonsense-mediated mRNA decay (NMD) pathway may destroy the mRNA transcript, so frameshifting would serve as a method of regulating the expression level of the associated gene.
If a novel or off-target protein is produced, it can trigger other unknown consequences. | 1 | Applied and Interdisciplinary Chemistry |
The glutathione peroxidase family of enzymes (abbreviated GSH-Px) catalyze reduction of hydrogen peroxide and organic hydroperoxides:
:2GSH + HO → GSSG + 2 HO
The two H atoms are donated by thiols in a process that begins with oxidation of a selenol side chain in GSH-Px. The organoselenium compound ebselen is a drug used to supplement the action of GSH-Px. It functions as a catalyst for the destruction of hydrogen peroxide.
A related selenium-containing enzyme in some plants and in animals (thioredoxin reductase) generates reduced thioredoxin, a dithiol that serves as an electron source for peroxidases and also the important reducing enzyme ribonucleotide reductase that makes DNA precursors from RNA precursors. | 1 | Applied and Interdisciplinary Chemistry |
Letting , the mass of the particle, the integrated Boltzmann equation becomes the conservation of mass equation:
where is the mass density, and is the average fluid velocity. | 1 | Applied and Interdisciplinary Chemistry |
All diatomic molecules are linear and characterized by a single parameter which is the bond length or distance between the two atoms. Diatomic nitrogen has a triple bond, diatomic oxygen has a double bond, and diatomic hydrogen, fluorine, chlorine, iodine, and bromine all have single bonds. | 0 | Theoretical and Fundamental Chemistry |
Another type of motion of a diatomic molecule is for each atom to oscillate—or vibrate—along the line connecting the two atoms. The vibrational energy is approximately that of a quantum harmonic oscillator:
:where
:: is an integer
:: is the reduced Planck constant and
:: is the angular frequency of the vibration. | 0 | Theoretical and Fundamental Chemistry |
De Silva and McClenaghan designed a proof-of-principle arithmetic device based on molecular logic gates. As depicted in Figure 10 A, Compound A is a push-pull olefin with the top receptor containing four carboxylic acid anion groups (and non-disclosed counter cations) capable of binding to calcium. The bottom part is a quinoline molecule which is a receptor for hydrogen ions. The logic gate operates as follows. Without any chemical input of Ca or H, the chromophore shows a maximum absorbance in UV/VIS spectroscopy at 390 nm. When calcium is introduced a hypsochromic shift (blue shift) takes place and the absorbance at 390 nm decreases. Likewise, addition of protons causes a bathochromic shift (red shift), and when both cations are in the water, the net result is absorption at the original 390 nm wavelength. This system represents an XNOR logic gate in absorption and an XOR logic gate in transmittance.
In another XOR logic gate system, the chemistry is based on the pseudorotaxane depicted in Figure 11. In organic solution the electron-deficient diazapyrenium salt (rod) and the electron-rich 2,3-dioxynaphthalene units of the crown ether (ring) self-assemble by formation of a charge transfer complex. An added tertiary amine like tributylamine forms a 1:2 adduct with the diazapyrene and the complex gets dethreaded. This process is accompanied by an increase in emission intensity at 343 nm resulting from freed crown ether. Added trifluoromethanesulfonic acid reacts with the amine and the process is reverted. Excess acid locks the crown ether by protonation and again the complex is de-threaded. | 0 | Theoretical and Fundamental Chemistry |
Diffusion-trapping methods utilizes diffusion techniques to get the substrates into the crystal and thereafter different trapping techniques are applied to get the intermediate of interest to accumulate in the crystal prior to collection of the diffraction pattern. These trapping methods could involve changes in pH, use of inhibitor or lowering the temperature in order to slow down the turnover rate or maybe even stop the reaction completely at a specific step. Just starting the reaction and then flash-freeze it, thereby quenching it at a specific time step, is also a possible method. One drawback with diffusion-trapping methods is that they can only be used to study intermediates that can be trapped, thereby limiting the time resolution one can obtain through the methods as compared to the pump-probe method. | 0 | Theoretical and Fundamental Chemistry |
John Alexander Reina Newlands (26 November 1837 – 29 July 1898) was a British chemist who worked concerning the periodicity of elements. | 0 | Theoretical and Fundamental Chemistry |
For a mixture of chemical species labelled by indices the equation for species is
where , and the collision term is
where , the magnitude of the relative momenta is
and is the differential cross-section, as before, between particles i and j. The integration is over the momentum components in the integrand (which are labelled i and j). The sum of integrals describes the entry and exit of particles of species i in or out of the phase-space element. | 1 | Applied and Interdisciplinary Chemistry |
Starpharma, an Australian pharmaceutical company, has multiple products that have either already been approved for use or are in the clinical trial phase. SPL7013, also known as astodrimer sodium, is a hyperbranched polymer used in Starpharma’s VivaGel line of pharmaceuticals that is currently approved to treat bacterial vaginosis and prevent the spread of HIV, HPV, and HSV in Europe, Southeast Asia, Japan, Canada, and Australia. Due to SPL7013’s broad antiviral action, it has recently been tested by the company as a potential drug to treat SARS-CoV-2. The company states preliminary in-vitro studies show high efficacy in preventing SARS-CoV-2 infection in cells. | 0 | Theoretical and Fundamental Chemistry |
As the name suggests, the prerequisite of a successful RDRP is fast and reversible activation/deactivation of propagating chains. There are three types of RDRP; namely deactivation by catalyzed reversible coupling, deactivation by spontaneous reversible coupling and deactivation by degenerative transfer (DT). A mixture of different mechanisms is possible; e.g. a transition metal mediated RDRP could switch among ATRP, OMRP and DT mechanisms depending on the reaction conditions and reagents used.
In any RDRP processes, the radicals can propagate with the rate coefficient k by addition of a few monomer units before the deactivation reaction occurs to regenerate the dormant species. Concurrently, two radicals may react with each other to form dead chains with the rate coefficient k. The rates of propagation and termination between two radicals are not influenced by the mechanism of deactivation or the catalyst used in the system. Thus it is possible to estimate how fast a RDRP can be conducted with preserved chain end functionality?
In addition, other chain breaking reactions such as irreversible chain transfer/termination reactions of the propagating radicals with solvent, monomer, polymer, catalyst, additives, etc. would introduce additional loss of chain end functionality (CEF). The overall rate coefficient of chain breaking reactions besides the direct termination between two radicals is represented as k.
In all RDRP methods, the theoretical number average molecular weight of obtained polymers, M, can be defined by following equation:
where M is the molecular weight of monomer; [M] and [M] are the monomer concentrations at time 0 and time t; [R-X] is the initial concentration of the initiator.
Besides the designed molecular weight, a well controlled RDRP should give polymers with narrow molecular distributions, which can be quantified by M/M values, and well preserved chain end functionalities.
A well controlled RDRP process requires: 1) the reversible deactivation process should be sufficiently fast; 2) the chain breaking reactions which cause the loss of chain end functionalities should be limited; 3) properly maintained radical concentration; 4) the initiator should have proper activity. | 0 | Theoretical and Fundamental Chemistry |
Early research in the 19th and 20th centuries on osmosis and diffusion provided the foundation for understanding the passive movement of molecules across cell membranes.
In 1855, the physiologist Adolf Fick was the first to define osmosis and simple diffusion as the tendency for solutes to move from a region of higher concentration to a lower concentration, also very well-known as Fick's Laws of Diffusion. Through the work of Charles Overton in the 1890s, the concept that the biological membrane is semipermeable became important to understanding the regulation of substances in and out of the cells. The discovery of facilitated diffusion by Wittenberg and Scholander suggested that proteins in the cell membrane aid in the transport of molecules. In the 1960s - 1970s, studies on the transport of glucose and other nutrients highlighted the specificity and selectivity of membrane transport proteins.
Technological advancements in biochemistry helped isolate and characterize these proteins from cell membranes. Genetic studies on bacteria and yeast identified genes responsible for encoding transporters. This led to the discovery of glucose transporters (GLUT proteins), with GLUT1 being the first to be characterized. Identification of gene families encoding various transporters, such as solute carrier (SLC) families, also advanced knowledge on uniporters and its functions.
Newer research is focusing on techniques using recombinant DNA technology, electrophysiology and advanced imaging to understand uniporter functions. These experiments are designed to clone and express transporter genes in host cells to further analyze the three-dimensional structure of uniporters, as well as directly observe the movement of ions through proteins in real-time. The discovery of mutations in uniporters has been linked to diseases such as GLUT1 deficiency syndrome, cystic fibrosis, Hartnup disease, primary hyperoxaluria and hypokalemic periodic paralysis. | 1 | Applied and Interdisciplinary Chemistry |
Historically, in traditional medicine of Europe, Lobaria pulmonaria was collected in large quantities as "lungwort", due to its lung-like appearance (the "doctrine of signatures" suggesting that herbs can treat body parts that they physically resemble). Similarly, Peltigera leucophlebia ("ruffled freckled pelt") was used as a supposed cure for thrush, due to the resemblance of its cephalodia to the appearance of the disease.
Lichens produce metabolites being researched for their potential therapeutic or diagnostic value. Some metabolites produced by lichens are structurally and functionally similar to broad-spectrum antibiotics while few are associated respectively to antiseptic similarities. Usnic acid is the most commonly studied metabolite produced by lichens. It is also under research as a bactericidal agent against Escherichia coli and Staphylococcus aureus. | 1 | Applied and Interdisciplinary Chemistry |
Hubel majored in mechanical engineering at Iowa State University, graduating in 1983. She continued her studies at the Massachusetts Institute of Technology (MIT), where she earned a master's degree in 1989 and completed her Ph.D. in the same year.
She worked as a research fellow at Massachusetts General Hospital from 1989 to 1990, and as an instructor at MIT from 1990 to 1993, before moving to the University of Minnesota in 1993 as a research associate in the Department of Laboratory Medicine and Pathology. In 1996 she became an assistant professor in that department, and in 2002 she moved to the Department of Mechanical Engineering as an associate professor. She was promoted to full professor in 2009, and became director of the Biopreservation Core Resource in 2010.
With two of her students, she founded a spinoff company, BlueCube Bio (later renamed Evia Bio) to commercialize their technology for preserving cells in cell therapy. She continues to serve as chief scientific officer for Evia Bio.
She became president-elect of the Society for Cryobiology for the 2022–2023 term, and will become president in the subsequent term. | 1 | Applied and Interdisciplinary Chemistry |
Two promising methods for the description of the acid–base properties of metal oxides are Calorimetric measurements of adsorption enthalpies and Temperature Programmed desorption. The measurement of the heat of adsorption of basic or acidic probe molecules can give a description of acidic and basic sites on metal oxide surfaces. Temperature programmed desorption provides information about acid–base properties by saturating the surface with a probe molecule and measuring the amount that desorbs from the surface as a function of temperature. The calorimetric method provides a quantitative thermodynamic scale of acetate properties by measuring the heat of adsorption. Calorimetric methods can be considered to give a measure of the total acidity or basicity as it is not discriminate to either Lewis or Brønsted sites. However, when differential heats of adsorption are combined with other techniques, such as IR spectroscopy, the nature and distribution of acid–base adsorption sites can be obtained. | 0 | Theoretical and Fundamental Chemistry |
Grain growth has long been studied primarily by the examination of sectioned, polished and etched samples under the optical microscope. Although such methods enabled the collection of a great deal of empirical evidence, particularly with regard to factors such as temperature or composition, the lack of crystallographic information limited the development of an understanding of the fundamental physics. Nevertheless, the following became well-established features of grain growth:
# Grain growth occurs by the movement of grain boundaries and also by coalescence (i.e. like water droplets)
#Grain growth competition between Ordered coalescence and the movement of grain boundaries
# Boundary movement may be discontinuous and the direction of motion may change suddenly during abnormal grain growth.
# One grain may grow into another grain whilst being consumed from the other side
# The rate of consumption often increases when the grain is nearly consumed
# A curved boundary typically migrates towards its centre of curvature | 1 | Applied and Interdisciplinary Chemistry |
After receiving his PhD in 1942, Smith began teaching in the Chemistry Department at the Missouri School of Mines in Rolla. While teaching at Missouri, Smith became a mentor to a brilliant 15-year old high student and future National Medal of Science winner named M. Frederick Hawthorne who would eventually follow him to Pomona.
During World War II, Smith worked on the Manhattan Project at the Hanford Site in Richland, Washington. During the 1951–1952 academic year, he did a Guggenheim Fellowship in England on surface chemistry.
Smith joined the faculty at Pomona in 1945. His research focus was colloids. In 1956, he was promoted to the rank of full professor, and he later became the chair of the colleges chemistry department. During the 1958–1959 academic year, he did another fellowship in England sponsored by the American Chemical Societys Petroleum Research Fund.
In 1958, he co-authored with colleague W. Conway Pierce the textbook General Chemistry Problems. He and Pierce published several later editions of the book under the title Solving General Chemistry Problems.
Smith was an early adopter of computer technology, which he used in his courses. | 0 | Theoretical and Fundamental Chemistry |
Inert-gas condensation is frequently used to produce metallic nanoparticles. The metal is evaporated in a vacuum chamber containing a reduced atmosphere of an inert gas. Condensation of the supersaturated metal vapor results in creation of nanometer-size particles, which can be entrained in the inert gas stream and deposited on a substrate or studied in situ. Early studies were based on thermal evaporation. Using magnetron sputtering to create the metal vapor allows to achieve higher yields. The method can easily be generalized to alloy nanoparticles by choosing appropriate metallic targets. The use of sequential growth schemes, where the particles travel through a second metallic vapor, results in growth of core-shell (CS) structures. | 0 | Theoretical and Fundamental Chemistry |
The search for new ways to improve treatment of patients infected with HIV is constant. Considering the experience that has been gathered since the 1980s of ARV drug development arrival of INSTIs as a new potent class of ARV signals a new era in the treatment of HIV. Development of a successful INSTI treatment was accomplished when raltegravir was discovered by Merck Sharp & Dohme Limited. A conditional marketing authorization was licensed in December 2007 by the European Commission which was valid throughout the European Union. In 2009 this authorization was converted to a full marketing authorization and in the same year the FDA changed the approval from accelerated to traditional approval and listed the drug as a first line ARV treatment agent. The second INSTI drug, elvitegravir, was identified by Japan Tobacco and clinical trials began in 2005. In 2011 the drug was still in phase three clinical trials, where it is being compared to raltegravir, in treatment experienced subjects and is also in phase two development in naïve subjects as a part of a multidrug treatment. S/GSK1349572 is an integrase inhibitor discovered by ViiV/Shinongi which was entering phase three in clinical trials in 2011. This new drug is promising and seems to be well tolerated and so far shows better results than both raltegravir and elvitegravir.
Since there have been problems with resistance to raltegravir and elvitegravir, scientists have started to work on new second generation integrase inhibitors, such as MK-2048 which in 2009 was developed by Merck. It's a prototype second generation INSTI that remains potent against viruses containing mutations against raltegravir and elvitegravir. The mechanism of action and SAR of MK-2048 is the same as of the other INSTIs, the structure of MK-2048 shown in figure 6 with essential pharmacophore highlighted.
Even though drugs discussed above are promising the development has a long way to go and many things are still unknown about the efficacy, safety and mechanism of action of these drugs. | 1 | Applied and Interdisciplinary Chemistry |
Protein Data Bank in Europe – Knowledge Base (PDBe-KB) is a community-driven, open-access, integrated resource whose mission is to place macromolecular structure data in their biological context and to make them accessible to the scientific community in order to support fundamental and translational research and education. It is part of the European Bioinformatics Institute (EMBL-EBI), based at the Wellcome Genome Campus, Hinxton, Cambridgeshire, England. | 1 | Applied and Interdisciplinary Chemistry |
John Garton and his two brothers, Robert and Thomas, were in business with their father, Peter, in Golborne and Newton-le-Willows in Lancashire, England, as corn and agricultural merchants.
As a young man, John Garton (1863–1922), was the first to understand that whilst some agricultural plants were self-pollinating, others were cross-pollinating. He began experimenting with the artificial cross pollination firstly of cereal plants, then herbage species and root crops.
He attracted the friendship and encouragement of a young Scottish seedsman, George Peddie Miln (1861–1928) who had trained in Dundee and was seed manager of Dicksons Limited of Chester.
Knowing he had developed a far reaching new technique in plant breeding John Garton began to carry out many thousands of controlled crosses on fields at the family farm in Newton-le-Willows. He and his colleagues tried in 1889 to interest the UK Government’s new Board of Agriculture in the invention they called Scientific Farm Plant Breeding. But this was to no avail. | 1 | Applied and Interdisciplinary Chemistry |
A Coulomb crystal (also Ion Coulomb crystal) is a collection of trapped ions confined in a crystal-like structure at low temperature. The structures represent an equilibrium between the repulsive Coulomb interaction between ions and the electric and magnetic fields used to confine the ions. Depending on the confinement techniques and parameters, as well as the number of ions in the trap, these can be 1-, 2- or 3-dimensional, with typical spacing between ions of ~10μm, which is significantly larger than typical solid-state crystal structures. Outside of ion traps, Coulomb crystals also occur naturally in celestial objects such as neutron stars. | 0 | Theoretical and Fundamental Chemistry |
Using the dynamic partitioning capabilities employed in dPCR, improved NGS sequencing can be achieved by partitioning of complex PCR reactions prior to amplification to give more uniform amplification across many distinct amplicons for NGS analysis. Additionally, the improved specificity of complex PCR amplification reactions in droplets has been shown to greatly reduce the number of iterations required to select for high affinity aptamers in the SELEX method. Partitioning can also allow for more robust measurements of telomerase activity from cell lysates. dPCR’s dynamic partitioning capabilities can also be used to partition thousands of nuclei or whole cells into individual droplets to facilitate library preparation for a single cell assay for transposase-accessible chromatin using sequencing (scATAC-seq). | 1 | Applied and Interdisciplinary Chemistry |
To compare the shape of the velocity profile, it can be assumed that
where
is the shape function.
It is important to notice that this formulation ignores the inertial effects. The velocity profile approximates a parabolic profile or a plug profile, for low or high Womersley numbers, respectively. | 1 | Applied and Interdisciplinary Chemistry |
SH3BP2 (SH3 domain-binding protein 2) is a protein that comes from a gene located on Chromosome 4. SH3BP2 binds differentially to the SH3 domains of certain proteins of signal transduction pathways. It binds to phosphatidylinositols linking the hemopoietic tyrosine kinase fes to the cytoplasmic membrane in a phosphorylation dependent mechanism. It is also associated with cherubism. | 1 | Applied and Interdisciplinary Chemistry |
In metallurgy, the Bower–Barff process is a method of coating iron or steel with magnetic iron oxide, such as FeO, in order to minimize atmospheric corrosion.
The articles to be treated are put into a closed retort and a current of superheated steam passed through for twenty minutes followed by a current of producer gas (carbon monoxide), to reduce any higher oxides that may have been formed. | 1 | Applied and Interdisciplinary Chemistry |
Several TILLING centers exist over the world that focus on agriculturally important species:
*Rice – UC Davis (USA)
*Maize – Purdue University (USA)
*Brassica napus – University of British Columbia (CA)
*Brassica rapa – John Innes Centre (UK)
*Arabidopsis – Fred Hutchinson Cancer Research
*Soybean – Southern Illinois University (USA)
*Lotus and Medicago – John Innes Centre (UK)]
*Wheat – UC Davis (USA)
*Pea, Tomato - INRA (France)
*Tomato - RTGR, University of Hyderabad (India) | 1 | Applied and Interdisciplinary Chemistry |
Karrer was married to Helena Froelich in 1914 and had three sons, one of whom died in infancy. He died on 18 June 1971, at the age of 82 in Zürich. His wife died in 1972. | 0 | Theoretical and Fundamental Chemistry |
The ionic mechanism of oxidative addition is similar to the S2 type in that it involves the stepwise addition of two distinct ligand fragments. The key difference being that ionic mechanisms involve substrates which are dissociated in solution prior to any interactions with the metal center. An example of ionic oxidative addition is the addition of hydrogen chloride. | 0 | Theoretical and Fundamental Chemistry |
Fission chain reactions occur because of interactions between neutrons and fissile isotopes (such as U). The chain reaction requires both the release of neutrons from fissile isotopes undergoing nuclear fission and the subsequent absorption of some of these neutrons in fissile isotopes. When an atom undergoes nuclear fission, a few neutrons (the exact number depends on uncontrollable and unmeasurable factors; the expected number depends on several factors, usually between 2.5 and 3.0) are ejected from the reaction. These free neutrons will then interact with the surrounding medium, and if more fissile fuel is present, some may be absorbed and cause more fissions. Thus, the cycle repeats to give a reaction that is self-sustaining.
Nuclear power plants operate by precisely controlling the rate at which nuclear reactions occur. Nuclear weapons, on the other hand, are specifically engineered to produce a reaction that is so fast and intense it cannot be controlled after it has started. When properly designed, this uncontrolled reaction will lead to an explosive energy release. | 0 | Theoretical and Fundamental Chemistry |
The Koschevnikov gland is a gland of the honeybee located near the sting shaft. The gland produces an alarm pheromone that is released when a bee stings. The pheromone contains more than 40 different compounds, including pentylacetate, butyl acetate, 1-hexanol, n-butanol, 1-octanol, hexylacetate, octylacetate, and 2-nonanol. These components have a low molar mass and evaporate quickly. This collection of compounds is the least specific of all pheromones. The alarm pheromone is released when a honey bee stings another animal to attract other bees to attack, as well. The release of the alarm pheromone may entice more bees to sting at the same location. Smoking the bees can reduce the pheromone's efficacy. | 1 | Applied and Interdisciplinary Chemistry |
This approach is based on first-principles physics alone and is not limited to vortex tubes only, but applies to moving gas in general. It shows that temperature separation in a moving gas is due only to enthalpy conservation in a moving frame of reference.
The thermal process in the vortex tube can be estimated in the following way:
The main physical phenomenon of the vortex tube is the temperature separation between the cold vortex core and the warm vortex periphery. The "vortex tube effect" is fully explained with the work equation of Euler, also known as Euler's turbine equation, which can be written in its most general vectorial form as:
where is the total, or stagnation temperature of the rotating gas at radial position , the absolute gas velocity as observed from the stationary frame of reference is denoted with ; the angular velocity of the system is and is the isobaric heat capacity of the gas. This equation was published in 2012; it explains the fundamental operating principle of vortex tubes (Here's a video with animated demonstration of how this works). The search for this explanation began in 1933 when the vortex tube was discovered and continued for more than 80 years.
The above equation is valid for an adiabatic turbine passage; it clearly shows that while gas moving towards the center is getting colder, the peripheral gas in the passage is "getting faster". Therefore, vortex cooling is due to angular propulsion. The more the gas cools by reaching the center, the more rotational energy it delivers to the vortex and thus the vortex rotates even faster. This explanation stems directly from the law of energy conservation. Compressed gas at room temperature is expanded in order to gain speed through a nozzle; it then climbs the centrifugal barrier of rotation during which energy is also lost. The lost energy is delivered to the vortex, which speeds its rotation. In a vortex tube, the cylindrical surrounding wall confines the flow at periphery and thus forces conversion of kinetic into internal energy, which produces hot air at the hot exit.
Therefore, the vortex tube is a rotorless turboexpander. It consists of a rotorless radial inflow turbine (cold end, center) and a rotorless centrifugal compressor (hot end, periphery). The work output of the turbine is converted into heat by the compressor at the hot end. | 0 | Theoretical and Fundamental Chemistry |
Acetogenesis is a process through which acetate is produced by prokaryote microorganisms either by the reduction of CO or by the reduction of organic acids, rather than by the oxidative breakdown of carbohydrates or ethanol, as with acetic acid bacteria.
The different bacterial species capable of acetogenesis are collectively termed acetogens. Reduction of CO to acetate by anaerobic bacteria occurs via the Wood–Ljungdahl pathway and requires an electron source (e.g., H, CO, formate, etc.). Some acetogens can synthesize acetate autotrophically from carbon dioxide and hydrogen gas. Reduction of organic acids to acetate by anaerobic bacteria occurs via fermentation. | 1 | Applied and Interdisciplinary Chemistry |
A plain tube can be used as a siphon. An external pump has to be applied to start the liquid flowing and prime the siphon (in home use this is often done by a person inhaling through the tube until enough of it has filled with liquid; this may pose danger to the user, depending on the liquid that is being siphoned). This is sometimes done with any leak-free hose to siphon gasoline from a motor vehicles gasoline tank to an external tank. (Siphoning gasoline by mouth often results in the accidental swallowing of gasoline, or aspirating it into the lungs, which can cause death or lung damage.) If the tube is flooded with liquid before part of the tube is raised over the intermediate high point and care is taken to keep the tube flooded while it is being raised, no pump is required. Devices sold as siphons often come with a siphon pump' to start the siphon process.
In some applications it can be helpful to use siphon tubing that is not much larger than necessary. Using piping of too great a diameter and then throttling the flow using valves or constrictive piping appears to increase the effect of previously cited concerns over gases or vapor collecting in the crest which serve to break the vacuum. If the vacuum is reduced too much, the siphon effect can be lost. Reducing the size of pipe used closer to requirements appears to reduce this effect and creates a more functional siphon that does not require constant re-priming and restarting. In this respect, where the requirement is to match a flow into a container with a flow out of said container (to maintain a constant level in a pond fed by a stream, for example) it would be preferable to utilize two or three smaller separate parallel pipes that can be started as required rather than attempting to use a single large pipe and attempting to throttle it. | 1 | Applied and Interdisciplinary Chemistry |
The Tulkun is a whale-like creature native to Pandoras ocean. They are similar to Earths whales and possess a form of sentience with their own language, laws, and philosophy which makes them capable of bonding with Navi in a more spiritual way than other animals. Each member of the Metkayina Clan forms a life-long bond with a tulkun as a spirit brother/sister. Once violent creatures who continually warred with one another, they are now completely pacifistic, refusing to kill even to defend themselves. As such they banish those who commit violence. They are introduced in Avatar: The Way of Water, in which humans have begun hunting them to harvest their brain enzymes for creating anti-aging remedies called amrita. Jake Sullys son, Lo'ak, bonds with an outcast tulkun named Payakan after he is banished for killing the whalers who killed his mother. | 1 | Applied and Interdisciplinary Chemistry |
Polyatomic and molecular ions are often formed by the gaining or losing of elemental ions such as a proton, , in neutral molecules. For example, when ammonia, , accepts a proton, —a process called protonation—it forms the ammonium ion, . Ammonia and ammonium have the same number of electrons in essentially the same electronic configuration, but ammonium has an extra proton that gives it a net positive charge.
Ammonia can also lose an electron to gain a positive charge, forming the ion . However, this ion is unstable, because it has an incomplete valence shell around the nitrogen atom, making it a very reactive radical ion.
Due to the instability of radical ions, polyatomic and molecular ions are usually formed by gaining or losing elemental ions such as , rather than gaining or losing electrons. This allows the molecule to preserve its stable electronic configuration while acquiring an electrical charge. | 0 | Theoretical and Fundamental Chemistry |
In pharmaceutics, hairstyling, personal hygiene, and cosmetics, emulsions are frequently used. These are usually oil and water emulsions but dispersed, and which is continuous depends in many cases on the pharmaceutical formulation. These emulsions may be called creams, ointments, liniments (balms), pastes, films, or liquids, depending mostly on their oil-to-water ratios, other additives, and their intended route of administration. The first 5 are topical dosage forms, and may be used on the surface of the skin, transdermally, ophthalmically, rectally, or vaginally. A highly liquid emulsion may also be used orally, or may be injected in some cases.
Microemulsions are used to deliver vaccines and kill microbes. Typical emulsions used in these techniques are nanoemulsions of soybean oil, with particles that are 400–600 nm in diameter. The process is not chemical, as with other types of antimicrobial treatments, but mechanical. The smaller the droplet the greater the surface tension and thus the greater the force required to merge with other lipids. The oil is emulsified with detergents using a high-shear mixer to stabilize the emulsion so, when they encounter the lipids in the cell membrane or envelope of bacteria or viruses, they force the lipids to merge with themselves. On a mass scale, in effect this disintegrates the membrane and kills the pathogen. The soybean oil emulsion does not harm normal human cells, or the cells of most other higher organisms, with the exceptions of sperm cells and blood cells, which are vulnerable to nanoemulsions due to the peculiarities of their membrane structures. For this reason, these nanoemulsions are not currently used intravenously (IV). The most effective application of this type of nanoemulsion is for the disinfection of surfaces. Some types of nanoemulsions have been shown to effectively destroy HIV-1 and tuberculosis pathogens on non-porous surfaces. | 0 | Theoretical and Fundamental Chemistry |
For black body emitters or imperfect selective emitters, filters reflect non-ideal wavelengths back to the emitter. These filters are imperfect. Any light that is absorbed or scattered and not redirected to the emitter or the converter is lost, generally as heat. Conversely, practical filters often reflect a small percentage of light in desired wavelength ranges. Both are inefficiencies. The absorption of suboptimal wavelengths by the photovoltaic device also contributes inefficiency and has the added effect of heating it, which also decreases efficiency. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, polyvalency (or polyvalence, multivalency) is the property of chemical species (generally atoms or molecules) that exhibit more than one valence by forming multiple chemical bonds (Fig. 1). A bivalent species can form two bonds; a trivalent species can form three bonds; and so on.
The principle of polyvalency also applies to larger species, such as antibodies, medical drugs, and even nanoparticles surface-functionalized with ligands, like spherical nucleic acids, which can show enhanced or cooperative binding compared to their monovalent counterparts. Nanoparticles with multiple nucleic acid strands on their surfaces (e.g., DNA) can form multiple bonds with one another by DNA hybridization to form hierarchical assemblies, some of which are highly crystalline in nature. | 0 | Theoretical and Fundamental Chemistry |
When the first law of thermodynamics emerges:
where power is interpreted as
and the heat current .
Additional conditions have to be imposed on the dissipator to be consistent with thermodynamics.
First the invariant should become an equilibrium Gibbs state.
This implies that the dissipator should commute with the unitary part generated by .
In addition an equilibrium state is stationary and stable. This assumption is used to derive
the Kubo-Martin-Schwinger stability criterion for thermal equilibrium i.e. KMS state.
A unique and consistent approach is obtained by deriving the generator, , in the weak system bath
coupling limit.
In this limit, the interaction energy can be neglected. This approach represents a thermodynamic idealization: it allows energy transfer, while keeping a tensor product separation
between the system and bath, i.e., a quantum version of an isothermal partition.
Markovian behavior involves a rather complicated cooperation between system and bath dynamics. This means that in
phenomenological treatments, one cannot combine arbitrary system Hamiltonians, , with a given L-GKS generator. This observation is particularly important in the context of quantum thermodynamics,
where it is tempting to study Markovian dynamics with an arbitrary control Hamiltonian. Erroneous derivations of the quantum master equation can easily lead to a violation of the laws of thermodynamics.
An external perturbation modifying the Hamiltonian of the system will also modify the heat flow. As a result, the L-GKS generator has to be renormalized. For a slow change, one can adopt the adiabatic approach and use the instantaneous system’s Hamiltonian to derive . An important class of problems in quantum thermodynamics is periodically driven systems. Periodic quantum heat engines and power-driven refrigerators fall into this class.
A reexamination of the time-dependent heat current expression using quantum transport techniques has been proposed.
A derivation of consistent dynamics beyond the weak coupling limit has been suggested.
Phenomenological formulations of irreversible quantum dynamics consistent with the second law and implementing the geometric idea of "steepest entropy ascent" or "gradient flow" have been suggested to model relaxation and strong coupling. | 0 | Theoretical and Fundamental Chemistry |
A human artificial chromosome (HAC) is a microchromosome that can act as a new chromosome in a population of human cells. That is, instead of 46 chromosomes, the cell could have 47 with the 47th being very small, roughly 6–10megabases (Mb) in size instead of 50–250Mb for natural chromosomes, and able to carry new genes introduced by human researchers. Ideally, researchers could integrate different genes that perform a variety of functions, including [http://io9.com/how-artificial-chromosomes-could-transform-humanity-754993569 disease defense].
Alternative methods of creating transgenes, such as utilizing yeast artificial chromosomes and bacterial artificial chromosomes, lead to unpredictable problems. The genetic material introduced by these vectors not only leads to different expression levels, but the inserts also disrupt the original genome. HACs differ in this regard, as they are entirely separate chromosomes. This separation from existing genetic material assumes that no insertional mutants would arise. This stability and accuracy makes HACs preferable to other methods such as viral vectors, YACs, and BACs. HACs allow for delivery of more DNA (including promoters and copy-number variation) than is possible with viral vectors.
Yeast artificial chromosomes and bacterial artificial chromosomes were created before human artificial chromosomes, which were first developed in 1997. HACs are useful in expression studies as gene transfer vectors, as a tool for elucidating human chromosome function, and as a method for actively annotating the human genome. | 1 | Applied and Interdisciplinary Chemistry |
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 | Applied and Interdisciplinary Chemistry |
The absorbance pattern responsible for the red color of anthocyanins may be complementary to that of green chlorophyll in photosynthetically active tissues such as young Quercus coccifera leaves. It may protect the leaves from attacks by herbivores that may be attracted by green color. | 0 | Theoretical and Fundamental Chemistry |
In metallurgy, the Darken equations are used to describe the solid-state diffusion of materials in binary solutions. They were first described by Lawrence Stamper Darken in 1948. The equations apply to cases where a solid solution's two components do not have the same coefficient of diffusion. | 0 | Theoretical and Fundamental Chemistry |
The cyclopentadienyl cation is another textbook example of an antiaromatic compound. It is conventionally understood to be planar, cyclic, and have 4 π electrons (4n for n=1) in a conjugated system.
However, it has long been questioned if the cyclopentadienyl cation is genuinely antiaromatic and recent discoveries have suggested that it may not be. The lowest-energy singlet state is antiaromatic, but the lowest-energy triplet state is aromatic due to Baird's rule, and research in 2007 showed the triplet state to be the ground state. | 0 | Theoretical and Fundamental Chemistry |
The River Restoration Centre, based at Cranfield University, is responsible for the National River Restoration Inventory, which is used to document best practice in river watercourse and floodplain restoration, enhancement and management efforts in the United Kingdom. Other established sources for information on stream restoration include the NRRSS in the U.S. and the European Centre for River Restoration (ECRR), which holds details of projects across Europe. ECRR and the LIFE+ RESTORE project have developed a wiki-based inventory of river restoration case studies. | 1 | Applied and Interdisciplinary Chemistry |
C and C plants have different signatures, allowing the abundance of C grasses to be detected through time in the δC record. Whereas plants have a δC of −16 to −10‰, plants have a δC of −33 to −24‰.
Mass extinctions are often marked by a negative δC anomaly thought to represent a decrease in primary productivity and release of plant-based carbon.
Positive δC excursions are interpreted as an increase in burial of organic carbon in sedimentary rocks following either a spike in primary productivity, a drop in decomposition under anoxic ocean conditions or both.
The evolution of large land plants in the late Devonian led to increased organic carbon burial and consequently a rise in δC.
Other important applications of δC involves understanding its signatures from soft sediments especially in lacustrine environments. This depends on the system from which it is extracted (open system, closed system, etc.). Temporal variations in δ13C in organic matter are influenced by diverse internal and external processes:
# Changes in the Dominant Source of Dissolved Inorganic Carbon: In stratified lakes, the accumulation of 13C-depleted carbon in deep water is common as sinking and degrading phytoplankton cells contribute to this pool. Recirculating this water to the surface can lead to a significant decrease in δ13C. Prolonged stratification enriches the dissolved inorganic carbon (DIC) pool in the epilimnion with 13C. Long-term variations in factors affecting upwelling intensity or depth, such as windiness, water temperature, or salinity-related stratification, manifest as shifts between more negative and positive δ13C values.
# Changes in Productivity/Eutrophication: Increased productivity accelerates the transfer of organic matter with negative δ13C values to the hypolimnion, affecting the δ13C of residual epilimnetic DIC. This impact, combined with mixing effects, results in variations in the δ13C signal.
# Changes in Metabolic Pathways for Carbon Fixation: Major changes in lake alkalinity influence benthic and planktonic primary production. Shifts in the dominant source of DIC for photosynthesis, driven by pH changes, can lead to trends toward more positive δ13C, particularly in lakes dominated by autochthonous organic matter and exhibiting evidence of high alkalinity.
# Changes in Availability of Dissolved CO2: Cool water can dissolve higher concentrations of CO2 than warmer water, affecting δ13C in organic matter during cooling events. Changes in atmospheric CO2 concentrations also influence δ13C, with lower pCO2 during glacial periods causing isotopic discrimination in plants using dissolved CO2.
# Changes in Dominant Vegetation Within the Watershed: Shifts in watershed vegetation, especially transitions between C3 and C4 photosynthetic pathways, significantly alter the carbon isotopic composition in lake sediments. These changes can be indicative of broader paleoclimatic shifts.
# Diagenetic Trends: Diagenetic processes, such as the loss of reactive components like amino acids, result in sustained shifts in δ13C in organic matter. Marsh sediments, rich in carbon, exhibit shifts towards more negative bulk organic matter. These diagenetic trends should be considered when interpreting isotopic changes accompanying major Total Organic Carbon (TOC) changes or methanogenesis.
Understanding these processes is crucial for interpreting δ13C variations in lake sediments and reconstructing paleoenvironmental conditions. | 0 | Theoretical and Fundamental Chemistry |
Many lichens produce secondary compounds, including pigments that reduce harmful amounts of sunlight and powerful toxins that deter herbivores or kill bacteria. These compounds are very useful for lichen identification, and have had economic importance as dyes such as cudbear or primitive antibiotics.
A pH indicator (which can indicate acidic or basic substances) called litmus is a dye extracted from the lichen Roccella tinctoria ("dyer's weed") by boiling. It gives its name to the well-known litmus test.
Traditional dyes of the Scottish Highlands for Harris tweed and other traditional cloths were made from lichens, including the orange Xanthoria parietina ("common orange lichen") and the grey foliaceous Parmelia saxatilis common on rocks and known colloquially as "crottle".
There are reports dating almost 2,000 years old of lichens being used to make purple and red dyes. Of great historical and commercial significance are lichens belonging to the family Roccellaceae, commonly called orchella weed or orchil. Orcein and other lichen dyes have largely been replaced by synthetic versions. | 1 | Applied and Interdisciplinary Chemistry |
Atmospheric nitrogen is inaccessible to most organisms, because its triple covalent bond is very strong. Most take up fixed nitrogen from various sources. For every 100 atoms of carbon, roughly 2 to 20 atoms of nitrogen are assimilated. The atomic ratio of carbon (C) : nitrogen (N) : phosphorus (P) observed on average in planktonic biomass was originally described by Alfred Redfield, who determined the stoichiometric relationship between C:N:P atoms, The Redfield Ratio, to be 106:16:1. | 1 | Applied and Interdisciplinary Chemistry |
Although ISO 13943 defines flashover as "transition to a state of total surface involvement in a fire of combustible materials within an enclosure", a broad definition that embraces several different scenarios, including backdrafts, there is nevertheless considerable disagreement regarding whether or not backdrafts should be properly considered flashovers. The most common use of the term flashover is to describe the near-simultaneous ignition of material caused by heat attaining the autoignition temperature of the combustible material and gases in an enclosure. Flashovers of this type are not backdrafts as they are caused by thermal change. Backdrafts are caused by the introduction of oxygen into an enclosed space with conditions already suitable for ignition, and are thus caused by chemical change. | 0 | Theoretical and Fundamental Chemistry |
The primary fire code writing organization is the private National Fire Protection Association or NFPA. NFPA sets the standards for technical aspects of sprinklers installed in the USA. Building codes, which specify which buildings require sprinklers are generally left to local jurisdictions. However, there are some exceptions:
In 1990 the US passed PL-101-391, better known as the Hotel and Motel Fire Safety Act of 1990. This law requires that any hotel, meeting hall, or similar institution that receives federal funds (i.e. for overnight stay, or a conference, etc.), must meet fire and other safety requirements. The most visible of these conditions is the implementation of sprinklers. As more and more hotels and other public accommodations upgraded their facilities to enable business with government visitors, this type of construction became the de facto industry norm – even when not directly mandated by any local building codes.
If building codes do not explicitly mandate the use of fire sprinklers, the code often makes it highly advantageous to install them as an optional system. Most US building codes allow for less-expensive construction materials, larger floor area limitations, longer egress paths, and fewer requirements for fire-rated construction in structures which are protected by fire sprinklers. Consequently, the total building cost is often decreased by installing a sprinkler system and saving money in the other aspects of the project, as compared to building a non-sprinklered structure.
In 2011, Pennsylvania and California became the first US states to require sprinkler systems in all new residential construction. However, Pennsylvania repealed the law later that same year. Many municipalities now require residential sprinklers, even if they are not required at the state level. | 1 | Applied and Interdisciplinary Chemistry |
The probe to be detected is labeled with some biotin-molecules. After incubation with a gold-coupled anti-biotin conjugate, silver nitrate and a reducing agent are added. The reaction starts whereas the gold particle serves as a starting point for the silver precipitation.
The reaction needs to be stopped after a specific time. The constant reaction time is essential to obtain comparable results. | 1 | Applied and Interdisciplinary Chemistry |
Before Frank-Kamenetskii, his doctoral advisor Nikolay Semyonov (or Semenov) proposed a thermal explosion theory with a simpler model with which he assumed a linear function for the heat conduction process instead of the Laplacian operator. Semenov's equation reads as
in which the exponential term will tend to increase as time proceeds whereas the linear term will tend to decrease . The relevant importance between the two terms are determined by the Damköhler number . The numerical solution of the above equation for different values of is shown in the figure. | 1 | Applied and Interdisciplinary Chemistry |
Photoluminescence excitation (abbreviated PLE) is a specific type of photoluminescence and concerns the interaction between electromagnetic radiation and matter. It is used in spectroscopic measurements where the frequency of the excitation light is varied, and the luminescence is monitored at the typical emission frequency of the material being studied. Peaks in the PLE spectra often represent absorption lines of the material. PLE spectroscopy is a useful method to investigate the electronic level structure of materials with low absorption due to the superior signal-to-noise ratio of the method compared to absorption measurements. | 0 | Theoretical and Fundamental Chemistry |
In 1831, British vinegar merchant Peregrine Phillips patented the contact process, which was a far more economical process for producing sulfur trioxide and concentrated sulfuric acid. Today, nearly all of the world's sulfuric acid is produced using this method. | 0 | Theoretical and Fundamental Chemistry |
The northern blot is used to study the presence of specific RNA molecules as relative comparison among a set of different samples of RNA. It is essentially a combination of denaturing RNA gel electrophoresis, and a blot. In this process RNA is separated based on size and is then transferred to a membrane that is then probed with a labeled complement of a sequence of interest. The results may be visualized through a variety of ways depending on the label used; however, most result in the revelation of bands representing the sizes of the RNA detected in sample. The intensity of these bands is related to the amount of the target RNA in the samples analyzed. The procedure is commonly used to study when and how much gene expression is occurring by measuring how much of that RNA is present in different samples, assuming that no post-transcriptional regulation occurs and that the levels of mRNA reflect proportional levels of the corresponding protein being produced. It is one of the most basic tools for determining at what time, and under what conditions, certain genes are expressed in living tissues. | 1 | Applied and Interdisciplinary Chemistry |
Second sound has been observed in solid He and He,
and in some dielectric solids such as Bi in the temperature
range of 1.2 to 4.0 K with a velocity of 780 ± 50 m/s,
or solid sodium fluoride (NaF) around 10 to 20 K. In 2021 this effect was observed in a BKT superfluid as well as in a germanium semiconductor | 0 | Theoretical and Fundamental Chemistry |
In surface chemistry, disjoining pressure (symbol ) according to an IUPAC definition arises from an attractive interaction between two surfaces. For two flat and parallel surfaces, the value of the disjoining pressure (i.e., the force per unit area) can be calculated as the derivative of the Gibbs energy of interaction per unit area in respect to distance (in the direction normal to that of the interacting surfaces). There is also a related concept of disjoining force, which can be viewed as disjoining pressure times the surface area of the interacting surfaces.
The concept of disjoining pressure was introduced by Derjaguin (1936) as the difference between the pressure in a region of a phase adjacent to a surface confining it, and the pressure in the bulk of this phase. | 0 | Theoretical and Fundamental Chemistry |
Bis(pyridine)iodonium(I) tetrafluoroborate or Barluenga's reagent, named after José Barluenga, is a mild iodinating reagent. Commercially available, it may be prepared by reacting iodine with pyridine in the presence of silver tetrafluoroborate supported on silica gel. | 0 | Theoretical and Fundamental Chemistry |
Pan evaporation is used to estimate the evaporation from lakes. There is a correlation between lake evaporation and pan evaporation. Evaporation from a natural body of water is usually at a lower rate because the body of water does not have metal sides that get hot with the sun, and while light penetration in a pan is essentially uniform, light penetration in natural bodies of water will decrease as depth increases. Most textbooks suggest multiplying the pan evaporation by 0.75 to correct for this. | 1 | Applied and Interdisciplinary Chemistry |
In the kinetic theory of gases, kinetic energy is assumed to purely consist of linear translations according to a speed distribution of particles in the system. However, in real gases and other real substances, the motions which define the kinetic energy of a system (which collectively determine the temperature), are much more complex than simple linear translation due to the more complex structure of molecules, compared to single atoms which act similarly to point-masses. In real thermodynamic systems, quantum phenomena play a large role in determining thermal motions. The random, thermal motions (kinetic energy) in molecules is a combination of a finite set of possible motions including translation, rotation, and vibration. This finite range of possible motions, along with the finite set of molecules in the system, leads to a finite number of microstates within the system; we call the set of all microstates an ensemble. Specific to atomic or molecular systems, we could potentially have three different kinds of ensemble, depending on the situation: microcanonical ensemble, canonical ensemble, or grand canonical ensemble. Specific combinations of microstates within an ensemble are how we truly define macrostate of the system (temperature, pressure, energy, etc.). In order to do that, we must first count all microstates though use of a partition function. The use of statistical mechanics and the partition function is an important tool throughout all of physical chemistry, because it is the key to connection between the microscopic states of a system and the macroscopic variables which we can measure, such as temperature, pressure, heat capacity, internal energy, enthalpy, and entropy, just to name a few. (Read: Partition function Meaning and significance)
Using the partition function to find the energy of a molecule, or system of molecules, can sometimes be approximated by the Equipartition theorem, which greatly-simplifies calculation. However, this method assumes all molecular degrees of freedom are equally populated, and therefore equally utilized for storing energy within the molecule. It would imply that internal energy changes linearly with temperature, which is not the case. This ignores the fact that heat capacity changes with temperature, due to certain degrees of freedom being unreachable (a.k.a. "frozen out") at lower temperatures. As internal energy of molecules increases, so does the ability to store energy within additional degrees of freedom. As more degrees of freedom become available to hold energy, this causes the molar heat capacity of the substance to increase. | 0 | Theoretical and Fundamental Chemistry |
The prevailing view that single ion activities are unmeasurable, or perhaps even physically meaningless, has its roots in the work of Edward A. Guggenheim in the late 1920s. However, chemists have not given up the idea of single ion activities. For example, pH is defined as the negative logarithm of the hydrogen ion activity. By implication, if the prevailing view on the physical meaning and measurability of single ion activities is correct it relegates pH to the category of thermodynamically unmeasurable quantities. For this reason the International Union of Pure and Applied Chemistry (IUPAC) states that the activity-based definition of pH is a notional definition only and further states that the establishment of primary pH standards requires the application of the concept of primary method of measurement tied to the Harned cell. Nevertheless, the concept of single ion activities continues to be discussed in the literature, and at least one author purports to define single ion activities in terms of purely thermodynamic quantities. The same author also proposes a method of measuring single ion activity coefficients based on purely thermodynamic processes. | 0 | Theoretical and Fundamental Chemistry |
The second strategy attempts to deploy multiple NLR genes simultaneously, a breeding strategy known as stacking. Cultivars generated by either DNA-assisted molecular breeding or gene transfer will likely display more durable resistance, because pathogens would have to mutate multiple effector genes. DNA sequencing allows researchers to functionally “mine” NLR genes from multiple species/strains.
The avrBs2 effector gene from Xanthomona perforans is the causal agent of bacterial spot disease of pepper and tomato. The first “effector-rationalized” search for a potentially durable R gene followed the finding that avrBs2 is found in most disease-causing Xanthomonas species and is required for pathogen fitness. The Bs2 NLR gene from the wild pepper, Capsicum chacoense, was moved into tomato, where it inhibited pathogen growth. Field trials demonstrated robust resistance without bactericidal chemicals. However, rare strains of Xanthomonas overcame Bs2-mediated resistance in pepper by acquisition of avrBs2 mutations that avoid recognition but retain virulence. Stacking R genes that each recognize a different core effector could delay or prevent adaptation.
More than 50 loci in wheat strains confer disease resistance against wheat stem, leaf and yellow stripe rust pathogens. The Stem rust 35 (Sr35) NLR gene, cloned from a diploid relative of cultivated wheat, Triticum monococcum, provides resistance to wheat rust isolate Ug99. Similarly, Sr33, from the wheat relative Aegilops tauschii, encodes a wheat ortholog to barley Mla powdery mildew–resistance genes. Both genes are unusual in wheat and its relatives. Combined with the Sr2 gene that acts additively with at least Sr33, they could provide durable disease resistance to Ug99 and its derivatives. | 1 | Applied and Interdisciplinary Chemistry |
A cloning vector need not contain suitable elements for the expression of a cloned target gene, such as a promoter and ribosomal binding site (RBS), many however do, and may then work as an expression vector. The target DNA may be inserted into a site that is under the control of a particular promoter necessary for the expression of the target gene in the chosen host. Where the promoter is present, the expression of the gene is preferably tightly controlled and inducible so that proteins are only produced when required. Some commonly used promoters are the T7 and lac promoters. The presence of a promoter is necessary when screening techniques such as blue-white selection are used.
Cloning vectors without promoter and RBS for the cloned DNA sequence are sometimes used, for example when cloning genes whose products are toxic to E. coli cells. Promoter and RBS for the cloned DNA sequence are also unnecessary when first making a genomic or cDNA library of clones since the cloned genes are normally subcloned into a more appropriate expression vector if their expression is required.
Some vectors are designed for transcription only with no heterologous protein expressed, for example for in vitro mRNA production. These vectors are called transcription vectors. They may lack the sequences necessary for polyadenylation and termination, therefore may not be used for protein production. | 1 | Applied and Interdisciplinary Chemistry |
In the United Kingdom, Green Infrastructure planning is increasingly recognised as a valuable approach for spatial planning and is now seen in national, regional and local planning and policy documents and strategies, for example in the Milton Keynes and South Midlands Growth area.
In 2009, guidance on green infrastructure planning was published by Natural England. This guidance promotes the importance of green infrastructure in place-making, i.e. in recognizing and maintaining the character of a particular location, especially where new developments are planned.
In North West England the former Regional Spatial Strategy had a specific Green Infrastructure Policy (EM3 – Green Infrastructure) as well as other references to the concept in other land use development policies (e.g. DP6). The policy was supported by the North West Green Infrastructure Guide. The Green Infrastructure Think Tank (GrITT) provides the support for policy development in the region and manages the web site that acts as a repository for information on Green Infrastructure.
The Natural Economy Northwest programme has supported a number of projects, commissioned by The Mersey Forest to develop the evidence base for green infrastructure in the region. In particular work has been undertaken to look at the economic value of green infrastructure, the linkage between grey and green infrastructure and also to identify areas where green infrastructure may play critical role in helping to overcome issues such as risks of flood or poor air quality.
In March 2011, a prototype Green Infrastructure Valuation Toolkit was launched. The Toolkit is available under a Creative Commons license, and provides a range of tools that provide economic valuation of green infrastructure interventions. The toolkit has been trialled in a number of areas and strategies, including the Liverpool Green Infrastructure Strategy.
In 2012, the Greater London Authority published the All London Green Grid Supplementary Planning Guidance (ALGG SPG) which proposes an integrated network of green and open spaces together with the Blue Ribbon Network of rivers and waterways. The ALGG SPG aims to promote the concept of green infrastructure, and increase its delivery by boroughs, developers, and communities, to benefit areas such as sustainable travel, flood management, healthy living and the economic and social uplift these support.
Green Infrastructure is being promoted as an effective and efficient response to projected climate change.
Green Infrastructure may include geodiversity objectives. | 1 | Applied and Interdisciplinary Chemistry |
Numerous desorber types are available today. Some of the more common types are listed below.
* Indirect fired rotary
* Direct fired rotary
* Heated screw (hot oil, molten salt, electric)
* Infrared
* Microwave
Most indirect fired rotary systems use an inclined rotating metallic cylinder to heat the feed material. The heat transfer mechanism is usually conduction through the cylinder wall. In this type of system neither the flame nor the products of combustion can contact the feed solids or the offgas. Think of it as a rotating pipe inside a furnace with both ends sticking outside of the furnace. The cylinder for full-scale transportable systems is typically five to eight feet in diameter with heated lengths ranging from twenty to fifty feet. With a carbon steel shell, the maximum solids temperature is around 1,000 °F, while temperatures of 1,800 °F with special alloy cylinders are attainable. Total residence time in this type of desorber normally ranges from 30 to 120 minutes. Treatment capacities can range from 2 to 30 tons per hour for transportable units.
Direct-fired rotary desorbers have been used extensively over the years for petroleum contaminated soils and soils contaminated with Resource Conservation and Recovery Act hazardous wastes as defined by the United States Environmental Protection Agency. A 1992 paper on treating petroleum contaminated soils estimated that between 20 and 30 contractors have 40 to 60 rotary dryer systems available. Today, it is probably closer to 6 to 10 contractors with 15 to 20 portable systems commercially available. The majority of these systems utilize a secondary combustion chamber (afterburner) or catalytic oxidizer to thermally destroy the volatilized organics. A few of these systems also have a quench and scrubber after the oxidizer which allows them to treat soils containing chlorinated organics such as solvents and pesticides. The desorbing cylinder for full-scale transportable systems is typically four to ten feet in diameter with heated lengths ranging from twenty to fifty feet. The maximum practical solids temperature for these systems is around 750 to 900 °F depending on the material of construction of the cylinder. Total residence time in this type of desorber normally ranges from 3 to 15 minutes. Treatment capacities can range from 6 to over 100 tons per hour for transportable units.
Heated screw systems are also an indirect heated system. Typically they use a jacketed trough with a double auger that intermeshes. The augers themselves frequently contain passages for the heating medium to increase the heat transfer surface area. Some systems use electric resistance heaters instead of a heat transfer media and may employ a single auger in each housing. The augers can range from 12 to 36 inches in diameter for full-scale systems, with lengths up to 20 feet. The auger/trough assemblies can be connected in parallel and/or series to increase throughput. Full scale capabilities up to 4 tons per hour have been demonstrated. This type of system has been most successful treating refinery wastes.
In the early days, there was a continuous infrared system that is no longer in common use. In theory, microwaves would be an excellent technical choice since uniform and accurately controlled heating can be achieved with no heat transfer surface fouling problems. One can only guess that capital and/or energy costs have prevented the development of a microwave thermal desorber at the commercial scale. | 1 | Applied and Interdisciplinary Chemistry |
Iodobenzene dichloride is hydrolyzed by basic solutions to give iodosobenzene (PhIO) and is oxidized by sodium hypochlorite to give iodoxybenzene (PhIO).
In organic synthesis, iodobenzene dichloride is used as a reagent for the selective chlorination of alkenes. and alkynes. | 0 | Theoretical and Fundamental Chemistry |
Monomeric aquo complexes of Nb, Ta, Mo, W, Mn, Tc, Re, and Os in oxidation states +4 to +7 have not been reported. For example, is unknown: the hydrolyzed species is the principal species in dilute solutions. With the higher oxidation states the effective electrical charge on the cation is further reduced by the formation of oxo-complexes. | 0 | Theoretical and Fundamental Chemistry |
* The pump is very reliable. The very simple principle is a clear advantage. Only air with a higher pressure than the liquid is required.
* The liquid is not in contact with any mechanical elements. Therefore, neither the pump can be abraded (which is important for sandwater wells), nor the contents in the pipe (which is important for archeological research in the sea).
* Act as a water aerator and can in some configurations lift stagnant bottom water to the surface (of water tanks).
* Since there are no restrictive pump parts, solids up to 70% of the pipe diameter can be reliably pumped. | 1 | Applied and Interdisciplinary Chemistry |
Few episodes of euxinia are evident in the sedimentary record during the Cenozoic. Since the end of the Cretaceous OAEs, it is most likely that the oceanic bottom waters have stayed oxic. | 0 | Theoretical and Fundamental Chemistry |
Legislation has been implemented by Japan, Singapore, and Australia that offers subsidies and other incentives to encourage the development of drugs that treat orphan diseases. | 1 | Applied and Interdisciplinary Chemistry |
Photoprotection of the human skin is achieved by extremely efficient internal conversion of DNA, proteins and melanin. Internal conversion is a photochemical process that converts the energy of the UV photon into small, harmless amounts of heat. If the energy of the UV photon were not transformed into heat, then it would lead to the generation of free radicals or other harmful reactive chemical species (e.g. singlet oxygen, or hydroxyl radical).
In DNA this photoprotective mechanism evolved four billion years ago at the dawn of life. The purpose of this extremely efficient photoprotective mechanism is to prevent direct DNA damage and indirect DNA damage. The ultrafast internal conversion of DNA reduces the excited state lifetime of DNA to only a few femtoseconds (10s)—this way the excited DNA does not have enough time to react with other molecules.
For melanin this mechanism has developed later in the course of evolution. Melanin is such an efficient photoprotective substance that it dissipates more than 99.9% of the absorbed UV radiation as heat.
This means that less than 0.1% of the excited melanin molecules will undergo harmful chemical reactions or produce free radicals. | 0 | Theoretical and Fundamental Chemistry |
ASBMB has hosted a yearly meeting each year since 1956. It has also coordinated the joint ComBio meeting with societies in related research fields since 1999. It also supports smaller special interest group meetings, symposia, workshops, conferences, and school science competitions. | 1 | Applied and Interdisciplinary Chemistry |
Metals can also be affixed with bioactive glass using a Sol-Gel Process, in which the bioactive glass is sintered onto metals at a controlled temperature that is high enough to perform the sintering, but low enough to avoid phase-shifts and other unwanted side effects. Experimentation has been done with sintering double layered, silica-based bioactive glass onto stainless steel substrates at 600 °C for 5 hours. This method has proven to maintain largely amorphous structure while containing key crystalline elements, and also achieves a remarkably similar level of bioactivity to bioactive glass. | 0 | Theoretical and Fundamental Chemistry |
Originally discovered by Frost and co-workers, the meta selective sulfonation of 2-phenylpyridine using a sulfonyl chloride coupling partner, utilising a ruthenium(II) catalyst. This reaction has been proposed to proceed via a similar method to that of the meta alkylation reported by Frost and Ackermann which involves a meta-selective C-H bond alkylation reaction with secondary and tertiary alkyl halides catalyzed by ruthenium(II) carboxylate catalysts. The directing group first coordinate to the ruthenium catalyst. A reversible metalation takes place to generate the cycloruthenated complex as the key intermediates. The cycloruthenation activates the aromatic ring to undergo SAr type alkylation at the position para to the C–Ru bond. | 0 | Theoretical and Fundamental Chemistry |
The core of an aquasome can be made from either ceramic or polymeric materials. Examples of such polymers include acrylates and gelatin. However, because ceramic materials are more ordered due to their naturally occurring crystalline structure, they are more often preferred as the material type for the core. Some of the most common ceramic materials used in the formation of an aquasome core include tin oxide, calcium phosphate, and even diamond. Another characteristic that ceramic materials provide is enhanced binding of the carbohydrate layer due to the high surface energy present on the orderly surface. The binding affinity of the carbohydrate layer also reduces surface tension for its bond to the ceramic core. The first aquasomes fabricated with a nanocrystalline core using ceramic material are detailed in Kossovsky et al. in 1996. Calcium phosphate ceramic nanoparticles (brushite) were first prepared via the method of solution precipitation and sonication. Precipitation methods are the most common techniques employed when synthesizing the core of an aquasome as they offer control over the homogeneity and purity of the precipitated products, which are important design features in the core structure. Once the cores are prepared, they are separated by centrifugation and then washed to remove any salt byproducts from the solution precipitation process. Finally, the washed cores are passed through a Millipore filter to selectively isolate core particles of a certain size. | 0 | Theoretical and Fundamental Chemistry |
Sodium hydroxide was first prepared by soap makers. A procedure for making sodium hydroxide appeared as part of a recipe for making soap in an Arab book of the late 13th century: (Inventions from the Various Industrial Arts), which was compiled by al-Muzaffar Yusuf ibn Umar ibn Ali ibn Rasul (d. 1295), a king of Yemen. The recipe called for passing water repeatedly through a mixture of alkali (Arabic: , where is ash from saltwort plants, which are rich in sodium; hence alkali was impure sodium carbonate) and quicklime (calcium oxide, CaO), whereby a solution of sodium hydroxide was obtained. European soap makers also followed this recipe. When in 1791 the French chemist and surgeon Nicolas Leblanc (1742–1806) patented a process for mass-producing sodium carbonate, natural "soda ash" (impure sodium carbonate that was obtained from the ashes of plants that are rich in sodium) was replaced by this artificial version. However, by the 20th century, the electrolysis of sodium chloride had become the primary method for producing sodium hydroxide. | 0 | Theoretical and Fundamental Chemistry |
The prototypical super leaving group is triflate, and the term has come to mean any leaving group of comparable ability. Compounds where loss of a super leaving group can generate a stable carbocation are usually highly reactive and unstable. Thus, the most commonly encountered organic triflates are methyl triflate and alkenyl or aryl triflates, all of which cannot form stable carbocations on ionization, rendering them relatively stable. It has been noted that steroidal alkyl nonaflates (another super leaving group) generated from alcohols and perfluorobutanesulfonyl fluoride were not isolable as such but immediately formed the products of either elimination or substitution by fluoride generated by the reagent. Mixed acyl-trifluoromethanesulfonyl anhydrides smoothly undergo Friedel-Crafts acylation without a catalyst, unlike the corresponding acyl halides, which require a strong Lewis acid. Methyl triflate, however, does not participate in Friedel-Crafts alkylation reactions with electron-neutral aromatic rings.
Beyond super leaving groups in reactivity lie the "hyper" leaving groups. Prominent among these are λ-iodanes, which include diaryl iodonium salts, and other halonium ions. In one study, a quantitative comparison of these and other leaving groups was conducted. Relative to chloride (k = 1), reactivities increased in the order bromide (k = 14), iodide (k = 91), tosylate (k = 3.7), triflate (k = 1.4), phenyliodonium tetrafluoroborate (, k = 1.2). Along with the criterion that a hyper leaving group be a stronger leaving group than triflate is the necessity that the leaving group undergo reductive elimination. In the case of halonium ions this involves reduction from a trivalent halonium to a monovalent halide coupled with the release of an anionic fragment. Part of the exceptional reactivity of compounds of hyper leaving groups has been ascribed to the entropic favorability of having one molecule split into three.
Dialkyl halonium ions have also been isolated and characterized for simple alkyl groups. These compounds, despite their extreme reactivity towards nucleophiles, can be obtained pure in the solid state with very weakly nucleophilic counterions such as and . The strongly electrophilic nature of these compounds engendered by their attachment to extremely labile (R = alkyl, X = Cl, Br, I) leaving groups is illustrated by their propensity to alkylate very weak nucleophiles. Heating neat samples of under reduced pressure resulted in methylation of the very poorly nucleophilic carborane anion with concomitant expulsion of the leaving group. Dialkyl halonium hexafluoroantimonate salts alkylate excess alkyl halides to give exchanged products. Their strongly electrophilic nature, along with the instability of primary carbocations generated from ionization of their alkyl groups, points to their possible involvement in Friedel-Crafts alkylation chemistry. The order of increasing lability of these leaving groups is . | 0 | Theoretical and Fundamental Chemistry |
Sir William Crookes (; 17 June 1832 – 4 April 1919) was a British chemist and physicist who attended the Royal College of Chemistry, now part of Imperial College London, and worked on spectroscopy. He was a pioneer of vacuum tubes, inventing the Crookes tube which was made in 1875. This was a foundational discovery that eventually changed the whole of chemistry and physics.
He is credited with discovering the element thallium, announced in 1861, with the help of spectroscopy. He was also the first to describe the spectrum of terrestrial helium, in 1865.
Crookes was the inventor of the Crookes radiometer but did not discern the true explanation of the phenomenon he detected. Crookes also invented a 100% ultraviolet blocking sunglass lens.
For a time, he was interested in spiritualism and became president of the Society for Psychical Research. | 1 | Applied and Interdisciplinary Chemistry |
In order for seawater mineral and element extractions to take place while taking close consideration of sustainable practices, it is necessary for monitored management systems to be put in place. This requires management of ocean areas and their conditions, environmental planning, structured guidelines to ensure that extractions are controlled, regular assessments of the condition of the sea post-extraction, and constant monitoring. The use of technology, such as underwater drones, can facilitate sustainable extractions. The use of low-carbon infrastructure would also allow for more sustainable extraction processes while reducing the carbon footprint from mineral extractions.
Another practice that is being considered closely is the process of desalination in order to achieve a more sustainable water supply from seawater. Although desalination also comes with environmental concerns, such as costs and resources, researchers are working closely to determine more sustainable practices, such as creating more productive water plants that can deal with larger water supplies in areas where these plans weren't always available. Although seawater extractions can benefit society greatly, it is crucial to consider the environmental impact and to ensure that all extractions are conducted in a way that acknowledges and considers the associated risks to the sustainability of seawater ecosystems. | 0 | Theoretical and Fundamental Chemistry |
Oxidative phosphorylation works by using energy-releasing chemical reactions to drive energy-requiring reactions. The two sets of reactions are said to be coupled. This means one cannot occur without the other. The chain of redox reactions driving the flow of electrons through the electron transport chain, from electron donors such as NADH to electron acceptors such as oxygen and hydrogen (protons), is an exergonic process – it releases energy, whereas the synthesis of ATP is an endergonic process, which requires an input of energy. Both the electron transport chain and the ATP synthase are embedded in a membrane, and energy is transferred from the electron transport chain to the ATP synthase by movements of protons across this membrane, in a process called chemiosmosis. A current of protons is driven from the negative N-side of the membrane to the positive P-side through the proton-pumping enzymes of the electron transport chain. The movement of protons creates an electrochemical gradient across the membrane, is called the proton-motive force. It has two components: a difference in proton concentration (a H gradient, ΔpH) and a difference in electric potential, with the N-side having a negative charge.
ATP synthase releases this stored energy by completing the circuit and allowing protons to flow down the electrochemical gradient, back to the N-side of the membrane. The electrochemical gradient drives the rotation of part of the enzyme's structure and couples this motion to the synthesis of ATP.
The two components of the proton-motive force are thermodynamically equivalent: In mitochondria, the largest part of energy is provided by the potential; in alkaliphile bacteria the electrical energy even has to compensate for a counteracting inverse pH difference. Inversely, chloroplasts operate mainly on ΔpH. However, they also require a small membrane potential for the kinetics of ATP synthesis. In the case of the fusobacterium Propionigenium modestum it drives the counter-rotation of subunits a and c of the F motor of ATP synthase.
The amount of energy released by oxidative phosphorylation is high, compared with the amount produced by anaerobic fermentation. Glycolysis produces only 2 ATP molecules, but somewhere between 30 and 36 ATPs are produced by the oxidative phosphorylation of the 10 NADH and 2 succinate molecules made by converting one molecule of glucose to carbon dioxide and water, while each cycle of beta oxidation of a fatty acid yields about 14 ATPs. These ATP yields are theoretical maximum values; in practice, some protons leak across the membrane, lowering the yield of ATP. | 1 | Applied and Interdisciplinary Chemistry |
The influence of dead zones on fisheries and other marine commercial activities varies by the length of occurrence and location. Dead zones are often accompanied by a decrease in biodiversity and collapse in benthic populations, lowering the diversity of yield in commercial fishing operations, but in cases of eutrophication-related dead zone formations, the increase in nutrient availability can lead to temporary rises in select yields among pelagic populations, such as anchovies. However, studies estimate that the increased production in the surrounding areas do not offset the net decrease in productivity resulting from the dead zone. For instance, an estimated 17,000 MT of carbon in the form of prey for fisheries has been lost as a result of dead zones in the Gulf of Mexico. Additionally, many stressors in fisheries are worsened by hypoxic conditions. Indirect factors such as increased success by invasive species and increased pandemic intensity in stressed species such as oysters both lead to losses in revenue and ecological stability in affected regions. | 0 | Theoretical and Fundamental Chemistry |
The society holds an annual meeting in March, every year.
* The 102nd CSJ Annual Meeting is held on March 23 to March 26, 2022 at the Nishinomiya Uegahara campus of Kwansei Gakuin University.
* The 101st CSJ Annual Meeting was virtually held on March 19 to March 21, 2021. | 1 | Applied and Interdisciplinary Chemistry |
In molecular biology, complementarity describes a relationship between two structures each following the lock-and-key principle. In nature complementarity is the base principle of DNA replication and transcription as it is a property shared between two DNA or RNA sequences, such that when they are aligned antiparallel to each other, the nucleotide bases at each position in the sequences will be complementary, much like looking in the mirror and seeing the reverse of things. This complementary base pairing allows cells to copy information from one generation to another and even find and repair damage to the information stored in the sequences.
The degree of complementarity between two nucleic acid strands may vary, from complete complementarity (each nucleotide is across from its opposite) to no complementarity (each nucleotide is not across from its opposite) and determines the stability of the sequences to be together. Furthermore, various DNA repair functions as well as regulatory functions are based on base pair complementarity. In biotechnology, the principle of base pair complementarity allows the generation of DNA hybrids between RNA and DNA, and opens the door to modern tools such as cDNA libraries.
While most complementarity is seen between two separate strings of DNA or RNA, it is also possible for a sequence to have internal complementarity resulting in the sequence binding to itself in a folded configuration. | 1 | Applied and Interdisciplinary Chemistry |
Cells were first seen in 17th-century Europe with the invention of the compound microscope. In 1665, Robert Hooke referred to the building blocks of all living organisms as "cells" (published in Micrographia) after looking at a piece of cork and observing a cell-like structure; however, the cells were dead. They gave no indication to the actual overall components of a cell. A few years later, in 1674, Anton Van Leeuwenhoek was the first to analyze live cells in his examination of algae. Many years later, in 1831, Robert Brown discovered the nucleus. All of this preceded the cell theory which states that all living things are made up of cells and that cells are organisms' functional and structural units. This was ultimately concluded by plant scientist Matthias Schleiden and animal scientist Theodor Schwann in 1838, who viewed live cells in plant and animal tissue, respectively. 19 years later, Rudolf Virchow further contributed to the cell theory, adding that all cells come from the division of pre-existing cells. Viruses are not considered in cell biology – they lack the characteristics of a living cell and instead are studied in the microbiology subclass of virology. | 1 | Applied and Interdisciplinary Chemistry |
Freshwater environmental quality parameters are those chemical, physical or biological parameters that can be used to characterise a freshwater body. Because almost all water bodies are dynamic in their composition, the relevant quality parameters are typically expressed as a range of expected concentrations.
They include the natural and man-made chemical, biological and microbiological characteristics of rivers, lakes and ground-waters, the ways they are measured and the ways that they change. The values or concentrations attributed to such parameters can be used to describe the pollution status of an environment, its biotic status or to predict the likelihood or otherwise of a particular organisms being present. Monitoring of environmental quality parameters is a key activity in managing the environment, restoring polluted environments and anticipating the effects of man-made changes on the environment. | 1 | Applied and Interdisciplinary Chemistry |
In bipolar disorder, one commonly identified endophenotype is a deficit in face emotion labeling, which is found in both individuals with bipolar disorder and in individuals who are "at risk" (i.e., have a first degree relative with bipolar disorder). Using fMRI, this endophenotype has been linked to dysfunction in the dorsolateral and ventrolateral prefrontal cortex, anterior cingulate cortex, striatum, and amygdala. A polymorphism in the CACNA1C gene coding for the voltage-dependent calcium channel Ca1.2 has been found to be associated with deficits in facial emotion recognition. | 1 | Applied and Interdisciplinary Chemistry |
*O'Callaghan, Amy; van Sinderen, Douwe (2016). Bifidobacteria and Their Role as Members of the Human Gut Microbiota. Frontiers in Microbiology, 7,
*Paul György; Robert F. Norris; Catharine S. Rose (1954). Bifidus factor. I. A variant of Lactobacillus bifidus requiring a special growth factor, 48 (1), 193–201. | 1 | Applied and Interdisciplinary Chemistry |
The Wenzel model (Robert N. Wenzel, 1936) describes the homogeneous wetting regime, as seen in Figure 7, and is defined by the following equation for the contact angle on a rough surface:
where is the apparent contact angle which corresponds to the stable equilibrium state (i.e. minimum free energy state for the system). The roughness ratio, r, is a measure of how surface roughness affects a homogeneous surface. The roughness ratio is defined as the ratio of true area of the solid surface to the apparent area.
θ is the Young contact angle as defined for an ideal surface. Although Wenzel's equation demonstrates the contact angle of a rough surface is different from the intrinsic contact angle, it does not describe contact angle hysteresis. | 0 | Theoretical and Fundamental Chemistry |
In speleology, a siphon or a sump is that part of a cave passage that lies under water and through which cavers have to dive to progress further into the cave system, but it is not an actual siphon. | 1 | Applied and Interdisciplinary Chemistry |
Diethanolamides are common ingredients used in cosmetics to act as a foaming agents or as emulsifiers. Chemically, they are amides formed from diethanolamine and carboxylic acids, typically fatty acids.
Examples include:
* Cocamide diethanolamine
* Lauramide diethanolamine
* Oleamide diethanolamine | 0 | Theoretical and Fundamental Chemistry |
For ammonia, NH, the symmetric bending vibration is observed as two branches near 930 cm and 965 cm. This so-called inversion doubling arises because the symmetric bending vibration is actually a large-amplitude motion known as inversion, in which the nitrogen atom passes through the plane of the three hydrogen atoms, similar to the inversion of an umbrella. The potential energy curve for such a vibration has a double minimum for the two pyramidal geometries, so that the vibrational energy levels occur in pairs which correspond to combinations of the vibrational states in the two potential minima. The two v = 1 states combine to form a symmetric state (1) at 932.5 cm above the ground (0) state and an antisymmetric state (1) at 968.3 cm.
The vibrational ground state (v = 0) is also doubled although the energy difference is much smaller, and the transition between the two levels can be measured directly in the microwave region, at ca. 24 Ghz (0.8 cm). This transition is historically significant and was used in the ammonia maser, the fore-runner of the laser. | 0 | Theoretical and Fundamental Chemistry |
In the ecosystem, different substrates are attacked at different rates by consortia of organisms from different kingdoms. Aspergillus and other moulds play an important role in these consortia because they are adept at recycling starches, hemicelluloses, celluloses, pectins and other sugar polymers. Some aspergilli are capable of degrading more refractory compounds such as fats, oils, chitin, and keratin. Maximum decomposition occurs when there is sufficient nitrogen, phosphorus and other essential inorganic nutrients. Fungi also provide food for many soil organisms.
For Aspergillus the process of degradation is the means of obtaining nutrients. When these moulds degrade human-made substrates, the process usually is called biodeterioration. Both paper and textiles (cotton, jute, and linen) are particularly vulnerable to Aspergillus degradation. Our artistic heritage is also subject to Aspergillus assault. To give but one example, after Florence in Italy flooded in 1969, 74% of the isolates from a damaged Ghirlandaio fresco in the Ognissanti church were Aspergillus versicolor. | 1 | Applied and Interdisciplinary Chemistry |
Assay offices did and do exist in the U.S., but they are affiliated with the governments coinage mints and serve only the governments purposes in that field. They are not involved in hallmarking, as there has never been a hallmarking scheme in the U.S.
In the 1800s, the functions of assay offices in the U.S. included receiving bullion deposits from the public and from mining prospectors in the various American territories. The assay offices that still operate today function solely within national coining system (including bullion coinage for sales to investors). | 0 | Theoretical and Fundamental Chemistry |
The conjugate base of hydroxamic acids forms is called a hydroxamate. Deprotonation occurs at the group, with the hydrogen atom being removed, resulting in a hydroxamate anion . The resulting conjugate base presents the metal with an anionic, conjugated O,O chelating ligand. Many hydroxamic acids and many iron hydroxamates have been isolated from natural sources.
They function as ligands, usually for iron. Nature has evolved families of hydroxamic acids to function as iron-binding compounds (siderophores) in bacteria. They extract iron(III) from otherwise insoluble sources (rust, minerals, etc.). The resulting complexes are transported into the cell, where the iron is extracted and utilized metabolically.
Ligands derived from hydroxamic acid and thiohydroxamic acid (a hydroxamic acid where one or both oxygens in the functional group are replaced by sulfur) also form strong complexes with lead(II). | 0 | Theoretical and Fundamental Chemistry |
Energetic polymers (e.g. nitro or azido derivates of polymers) can be used as a binder to increase the explosive power in comparison with inert binders. Energetic plasticizers can be also used. The addition of a plasticizer lowers the sensitivity of the explosive and improves its processibility. | 0 | Theoretical and Fundamental Chemistry |
Light crude oils have higher API gravity figures, due to having fewer impurities. It is more commonly used to produce diesel and gasoline than heavier oils are. Due to its lower viscosity, it is easier to extract and to transport. | 0 | Theoretical and Fundamental Chemistry |
Bromatometry is a titration process in which the bromination of a chemical indicator is observed.
Potassium bromate alone can be used for the analysis of organoarsenicals. | 0 | Theoretical and Fundamental Chemistry |
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