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There are five types of air pollution dispersion models, as well as some hybrids of the five types:
* Box model – The box model is the simplest of the model types. It assumes the airshed (i.e., a given volume of atmospheric air in a geographical region) is in the shape of a box. It also assumes that the air pollutants inside the box are homogeneously distributed and uses that assumption to estimate the average pollutant concentrations anywhere within the airshed. Although useful, this model is very limited in its ability to accurately predict dispersion of air pollutants over an airshed because the assumption of homogeneous pollutant distribution is much too simple.
*Gaussian model – The Gaussian model is perhaps the oldest (circa 1936) and perhaps the most commonly used model type. It assumes that the air pollutant dispersion has a Gaussian distribution, meaning that the pollutant distribution has a normal probability distribution. Gaussian models are most often used for predicting the dispersion of continuous, buoyant air pollution plumes originating from ground-level or elevated sources. Gaussian models may also be used for predicting the dispersion of non-continuous air pollution plumes (called puff models). The primary algorithm used in Gaussian modeling is the Generalized Dispersion Equation For A Continuous Point-Source Plume.
*Lagrangian model – a Lagrangian dispersion model mathematically follows pollution plume parcels (also called particles) as the parcels move in the atmosphere and they model the motion of the parcels as a random walk process. The Lagrangian model then calculates the air pollution dispersion by computing the statistics of the trajectories of a large number of the pollution plume parcels. A Lagrangian model uses a moving frame of reference as the parcels move from their initial location. It is said that an observer of a Lagrangian model follows along with the plume.
*Eulerian model – an Eulerian dispersion model is similar to a Lagrangian model in that it also tracks the movement of a large number of pollution plume parcels as they move from their initial location. The most important difference between the two models is that the Eulerian model uses a fixed three-dimensional Cartesian grid as a frame of reference rather than a moving frame of reference. It is said that an observer of an Eulerian model watches the plume go by.
*Dense gas model – Dense gas models are models that simulate the dispersion of dense gas pollution plumes (i.e., pollution plumes that are heavier than air). The three most commonly used dense gas models are:
**The DEGADIS model developed by Dr. Jerry Havens and Dr. Tom Spicer at the University of Arkansas under commission by the US Coast Guard and US EPA.
** The SLAB model developed by the Lawrence Livermore National Laboratory funded by the US Department of Energy, the US Air Force and the American Petroleum Institute.
** The HEGADAS model developed by Shell Oil's research division. | 1 | Applied and Interdisciplinary Chemistry |
The turbulent Prandtl number (Pr) is a non-dimensional term defined as the ratio between the momentum eddy diffusivity and the heat transfer eddy diffusivity. It is useful for solving the heat transfer problem of turbulent boundary layer flows. The simplest model for Pr is the Reynolds analogy, which yields a turbulent Prandtl number of 1. From experimental data, Pr has an average value of 0.85, but ranges from 0.7 to 0.9 depending on the Prandtl number of the fluid in question. | 1 | Applied and Interdisciplinary Chemistry |
The water balances are calculated for each reservoir separately as shown in the article Hydrology (agriculture). The excess water leaving one reservoir is converted into incoming water for the next reservoir.<br>
The three soil reservoirs can be assigned a different thickness and storage coefficients, to be given as input data.<br>
In a particular situation, the transition zone or the aquifer need not be present. Then, it must be given a minimum thickness of 0.1 m.<br>
The depth of the water table, calculated from the water balances, is assumed to be the same for the whole area. If this assumption is not acceptable, the area must be divided into separate units.<br>
Under certain conditions, the height of the water table influences the water balance components. For example, a rise of the water table towards the soil surface may lead to an increase of evaporation, surface runoff, and subsurface drainage, or a decrease of percolation losses from canals. This, in turn, leads to a change of the water balance, which again influences the height of the water table, etc.<br>
This chain of reactions is one of the reasons why Saltmod has been developed into a computer program. It takes a number of repeated calculations (iterations) to find the correct equilibrium of the water balance, which would be a tedious job if done by hand. Other reasons are that a computer program facilitates the computations for different water management options over long periods of time (with the aim to simulate their long-term effects) and for trial runs with varying parameters. | 0 | Theoretical and Fundamental Chemistry |
* RRS effect (Resonance Raman Scaterring)
The Raman resonance effect produces an increase in Raman intensity up to 10 times. In this phenomenon, the monochromatic light interaction with the sample produces the transition of the molecules from the fundamental state to an excited electronic state, instead of a virtual state as in normal Raman spectroscopy. This phenomenon of increased intensity could be observed in materials such as carbon nanotubes.
* SERS (Surface-Enhanced Raman Scattering)
Surface-Enhanced Raman Scattering (SERS) is a technique capable of increasing Raman signal intensity up to 10 times. This phenomenon is based on the interaction of monochromatic light with materials that exhibit plasmonic properties. The most common metals used in SERS are nanostructured metals with plasmonic band (gold, silver or copper). Nanostructured electrode surfaces can be generated by depositing metallic nanostructures of these materials. A disadvantage of this phenomenon is, sometimes, the lack of reproducibility of the spectra due to the difficulty of obtaining identical nanostructured surfaces in each experiment.
* SOERS (Surface-Oxidation-Enhanced Raman Scattering)
Surface-oxidation enhanced Raman scattering (SOERS) is a process similar to SERS, which allows the Raman signal to be enhanced when a silver electrode is oxidized in a particular electrolyte composition. This process is carried out at sufficiently positive potentials to ensure the oxidation of the electrode surface. There are significant differences with the SERS effect, but it is a phenomenon that also enhances the Raman signal.
* SHINERS (Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy)
In SHINERS, metallic nanoparticles with plasmonic properties are coated with ultra-thin homogeneous silica or alumina layers, forming isolated nanoparticles. The metallic nucleus (Au or Ag) is responsible of the enhancement of the Raman signals of the nearby molecules, while the coating layers eliminate the influence of the metallic nucleus on the Raman and electrochemical signals by preventing the molecules from being directly adsorbed onto them. Silica and alumina coating can improve the chemical and thermal stability of nanoparticles. This fact has great importance in the in-situ study of catalytic reactions. The high sensitivity of the SHINERS surfaces makes these nanostructures a promising tool for the study of liquid-solid interfaces, especially in spectroelectrochemistry.
* TERS (Tip-Enhanced Raman Scattering)
Tip-enhanced Raman scattering (TERS) is a technique that provides molecular information at nanoscale. In these experiments, metal nanostructures are replaced by a sharp metal tip of nanometric size, concentrating the roughness directly on a small region that improves the spatial resolution of scanning techniques in Raman spectroscopy.
<br /> | 0 | Theoretical and Fundamental Chemistry |
Williams commenced lecturing at McGill University in 1960, and was selected to be the Chairman of the Department of Mining and Metallurgy in 1966. As Chairman, he was instrumental in expanding the department at a time when only six degree programs in Metallurgical Engineering were being offered in Canadian universities, among which McGill's department was the oldest. During his tenure, seven new faculty members were added to the department, with the new faculty primarily focusing its research on extractive (hydro and pyro), process and physical metallurgy. Ties between the department and Canadian industries were also strengthened during this time. Throughout his career, Williams conducted research on a variety of topics ranging from esoteric studies of grain shape to the practical aspects of abrasion resistant cast irons for mineral comminution. Williams held the position of Chairman until 1980, and retired from teaching in 1992. From 1972 to 1973, he was President of the Metallurgical Society of CIM.
As a specialist in failure analysis, Williams was consulted to investigate numerous engineering failures including such notable events as the 1965 LaSalle Heights disaster, the Mississauga train derailment of 1979, and the crash of Quebecair Flight 255. From 1990 to 2000, he was a consultant metallurgist for Via Rail. Williams also served as an expert witness in about 40 court cases in Canada and the United States, and was twice appointed Judge's Expert by justices James K. Hugessen and Antonio Lamar respectively. | 1 | Applied and Interdisciplinary Chemistry |
Genome-wide SNP data can be used for homozygosity mapping. Homozygosity mapping is a method used to identify homozygous autosomal recessive loci, which can be a powerful tool to map genomic regions or genes that are involved in disease pathogenesis. | 1 | Applied and Interdisciplinary Chemistry |
The broadest definition of natural product is anything that is produced by life, and includes the likes of biotic materials (e.g. wood, silk), bio-based materials (e.g. bioplastics, cornstarch), bodily fluids (e.g. milk, plant exudates), and other natural materials (e.g. soil, coal).
Natural products may be classified according to their biological function, biosynthetic pathway, or source. Depending on the sources, the number of known natural product molecules ranges between 300,000 and 400,000. | 1 | Applied and Interdisciplinary Chemistry |
Serotonin syndrome may result from the combined use of dextromethorphan and serotonergic antidepressants such as selective serotonin reuptake inhibitor (SSRIs) or monoamine oxidase inhibitor (MAOIs). Further research is needed to determine whether doses of dextromethorphan beyond those normally used therapeutically are needed to produce this effect. In any case, dextromethorphan should not be taken with MAOIs due to the possibility of this complication. Serotonin syndrome is a potentially life-threatening condition that can occur rapidly, due to a buildup of an excessive amount of serotonin in the body.
Patients who are taking dextromethorphan should exercise caution when drinking grapefruit juice or eating grapefruit, as compounds in grapefruit affect a number of drugs, including dextromethorphan, through the inhibition of the cytochrome P450 system in the liver, and can lead to excessive accumulation of the drug which both increases and prolongs effects. Grapefruit and grapefruit juices (especially white grapefruit juice, but also including other citrus fruits such as bergamot and lime, as well as a number of noncitrus fruits) generally are recommended to be avoided while using dextromethorphan and numerous other medications. | 0 | Theoretical and Fundamental Chemistry |
Zinc finger nucleases are genetically engineered enzymes that combine fusing a zinc finger DNA-binding domain on a DNA-cleavage domain. These are also combined with CRISPR-CAS9 or TALENs to gain a sequence-specific addition, or deletion, within the genome of more complex cells and organisms. | 1 | Applied and Interdisciplinary Chemistry |
Phosphate groups can exist in three different forms depending on a solution's pH. Phosphorus atoms can bind three oxygen atoms with single bonds and a fourth oxygen atom using a double/dative bond. The pH of the solution, and thus the form of the phosphate group determines its ability to bind to other molecules. The binding of phosphate groups to the inositol ring is accomplished by phosphor-ester binding (see phosphoric acids and phosphates). This bond involves combining a hydroxyl group from the inositol ring and a free phosphate group through a dehydration reaction. Considering that the average physiological pH is approximately 7.4, the main form of the phosphate groups bound to the inositol ring in vivo is PO. This gives IP a net negative charge, which is important in allowing it to dock to its receptor, through binding of the phosphate groups to positively charged residues on the receptor. IP has three hydrogen bond donors in the form of its three hydroxyl groups. The hydroxyl group on the 6th carbon atom in the inositol ring is also involved in IP docking. | 1 | Applied and Interdisciplinary Chemistry |
Interest in elixirs of immortality increased during the Han dynasty (206 BC–220 AD). Emperor Wu (156–87 BCE) employed many fangshi alchemists who claimed they could produce the legendary substance. The Book of Han says that around 133 BCE the fangshi Li Shaojun said to Emperor Wu, "Sacrifice to the stove [zao 竈] and you will be able to summon things [i.e. spirits]. Summon spirits and you will be able to change cinnabar powder into yellow gold. With this yellow gold you may make vessels to eat and drink out of. You will then increase your span of life. Having increased your span of life, you will be able to see the [xian 仙] of [Penglai] that is in the midst of the sea. Then you may perform the sacrifices feng [封] and shan [禅], and escape death".
Wei Boyangs c. 142 Cantong qi', which is regarded as the oldest complete alchemical book extant in any culture, influenced developments in elixir alchemy. It listed mercury and lead as the prime ingredients for elixirs, which limited later potential experiments and resulted in numerous cases of poisoning. It is quite possible that "many of the most brilliant and creative alchemists fell victim to their own experiments by taking dangerous elixirs". There is a famous story about animal testing of elixirs by Wei Boyang. Wei entered the mountains to prepare the elixir of immortality, accompanied by three disciples, two of whom were skeptical. When the alchemy was completed he said, "Although the gold elixir is now accomplished we ought first to test it by feeding it to a white dog. If the dog can fly after taking it then it is edible for man; if the dog dies then it is not." The dog fell over and died, but Wei and his disciple Yu took the medicine and immediately died, after which the two cautious disciples fled. Wei and Yu later revived, rejoiced in their faith, took more of the elixir and became immortals.
Elixir ingestion is first mentioned in the c. 81 BCE Discourses on Salt and Iron. | 1 | Applied and Interdisciplinary Chemistry |
Much of the work behind production of monoclonal antibodies is rooted in the production of hybridomas, which involves identifying antigen-specific plasma/plasmablast cells that produce antibodies specific to an antigen of interest and fusing these cells with myeloma cells. Rabbit B-cells can be used to form a rabbit hybridoma. Polyethylene glycol is used to fuse adjacent plasma membranes, but the success rate is low, so a selective medium in which only fused cells can grow is used. This is possible because myeloma cells have lost the ability to synthesize hypoxanthine-guanine-phosphoribosyl transferase (HGPRT), an enzyme necessary for the salvage synthesis of nucleic acids. The absence of HGPRT is not a problem for these cells unless the de novo purine synthesis pathway is also disrupted. Exposing cells to aminopterin (a folic acid analogue, which inhibits dihydrofolate reductase, DHFR), makes them unable to use the de novo pathway and become fully auxotrophic for nucleic acids, thus requiring supplementation to survive.
The selective culture medium is called HAT medium because it contains hypoxanthine, aminopterin and thymidine. This medium is selective for fused (hybridoma) cells. Unfused myeloma cells cannot grow because they lack HGPRT and thus cannot replicate their DNA. Unfused spleen cells cannot grow indefinitely because of their limited life span. Only fused hybrid cells referred to as hybridomas, are able to grow indefinitely in the medium because the spleen cell partner supplies HGPRT and the myeloma partner has traits that make it immortal (similar to a cancer cell).
This mixture of cells is then diluted and clones are grown from single parent cells on microtitre wells. The antibodies secreted by the different clones are then assayed for their ability to bind to the antigen (with a test such as ELISA or antigen microarray assay) or immuno-dot blot. The most productive and stable clone is then selected for future use.
The hybridomas can be grown indefinitely in a suitable cell culture medium. They can also be injected into mice (in the peritoneal cavity, surrounding the gut). There, they produce tumors secreting an antibody-rich fluid called ascites fluid.
The medium must be enriched during in vitro selection to further favour hybridoma growth. This can be achieved by the use of a layer of feeder fibrocyte cells or supplement medium such as briclone. Culture-media conditioned by macrophages can be used. Production in cell culture is usually preferred as the ascites technique is painful to the animal. Where alternate techniques exist, ascites is considered unethical. | 1 | Applied and Interdisciplinary Chemistry |
A solution containing the analyte, A, in the presence of some conductive buffer. If an electrolytic potential is applied to the solution through a working electrode, then the measured current depends (in part) on the concentration of the analyte. Measurement of this current can be used to determine the concentration of the analyte directly; this is a form of amperometry. However, the difficulty is that the measured current depends on several other variables, and it is not always possible to control all of them adequately. This limits the precision of direct amperometry.
If the potential applied to the working electrode is sufficient to reduce the analyte, then the concentration of analyte close to the working electrode will decrease. More of the analyte will slowly diffuse into the volume of solution close to the working electrode, restoring the concentration. If the potential applied to the working electrode is great enough (an overpotential), then the concentration of analyte next to the working electrode will depend entirely on the rate of diffusion. In such a case, the current is said to be diffusion limited. As the analyte is reduced at the working electrode, the concentration of the analyte in the whole solution will very slowly decrease; this depends on the size of the working electrode compared to the volume of the solution.
What happens if some other species which reacts with the analyte (the titrant) is added? (For instance, chromate ions can be added to oxidize lead ions.) After a small quantity of the titrant (chromate) is added, the concentration of the analyte (lead) has decreased due to the reaction with chromate. The current from the reduction of lead ion at the working electrode will decrease. The addition is repeated, and the current decreases again. A plot of the current against volume of added titrant will be a straight line.
After enough titrant has been added to react completely with the analyte, the excess titrant may itself be reduced at the working electrode. Since this is a different species with different diffusion characteristics (and different half-reaction), the slope of current versus added titrant will have a different slope after the equivalence point. This change in slope marks the equivalence point, in the same way that, for instance, the sudden change in pH marks the equivalence point in an acid–base titration.
The electrode potential may also be chosen such that the titrant is reduced, but the analyte is not. In this case, the presence of excess titrant is easily detected by the increase in current above background (charging) current. | 0 | Theoretical and Fundamental Chemistry |
In terms of flowering time in long day conditions, all mutants made the observed flowering late, with PRR7 significantly more late in comparison to the other mutants. All double mutants with PRR7 saw much later flowering time than the PRR5/PRR9 mutant. | 1 | Applied and Interdisciplinary Chemistry |
Industrial product applications include, sealants, adhesives, extenders for putties used for sealing roofs and windows, coatings, polymer modification, tackified polyethylene films, personal care, polybutene emulsions. Hydrogenated polybutenes are used in a wide variety of cosmetic preparations, such as lipstick and lip gloss. It is used in adhesives owing to its tackiness. Polybutene finds a niche use in bird and squirrel repellents and is ubiquitous as the active agent in mouse and insect "sticky traps".
An important physical property is that higher molecular weight grades thermally degrade to lower-molecular weight polybutenes; those evaporate as well as degrade to butene monomers which can also evaporate. This depolymerization mechanism which allows clean and complete volatization is in contrast to mineral oils which leave gum and sludge or thermoplastics which melt and spread. The property is very valuable for a variety of applications. For smoke inhibition in two stroke engine fuels, the lubricant can degrade at temperatures below the combustion temperature. For electrical lubricants and carriers which might be subject to overheating or fires, polybutene does not result in increased insulation (accelerating the overheating) or conductive carbon deposits. | 0 | Theoretical and Fundamental Chemistry |
The equilibrium constant for the protonation of a base, B,
: + H
is an association constant, K, which is simply related to the dissociation constant of the conjugate acid, BH.
The value of is ca. 14 at 25°C. This approximation can be used when the correct value is not known. Thus, the Henderson–Hasselbalch equation can be used, without modification, for bases. | 0 | Theoretical and Fundamental Chemistry |
Even though it is convention to use gauge pressure in the calculation of hydraulic head, it is more correct to use absolute pressure (gauge pressure + atmospheric pressure), since this is truly what drives groundwater flow. Often detailed observations of barometric pressure are not available at each well through time, so this is often disregarded (contributing to large errors at locations where hydraulic gradients are low or the angle between wells is acute.)
The effects of changes in atmospheric pressure upon water levels observed in wells has been known for many years. The effect is a direct one, an increase in atmospheric pressure is an increase in load on the water in the aquifer, which increases the depth to water (lowers the water level elevation). Pascal first qualitatively observed these effects in the 17th century, and they were more rigorously described by the soil physicist Edgar Buckingham (working for the United States Department of Agriculture (USDA)) using air flow models in 1907. | 1 | Applied and Interdisciplinary Chemistry |
Greenhouse gas monitoring involves the direct measurement of atmospheric concentrations and direct and indirect measurement of greenhouse gas emissions. Indirect methods calculate emissions of greenhouse gases based on related metrics such as fossil fuel extraction.
There are several different methods of measuring carbon dioxide concentrations in the atmosphere, including infrared analyzing and manometry. Methane and nitrous oxide are measured by other instruments, such as the range-resolved infrared differential absorption lidar (DIAL). Greenhouse gases are measured from space such as by the Orbiting Carbon Observatory and through networks of ground stations such as the Integrated Carbon Observation System.
The Annual Greenhouse Gas Index (AGGI) is defined by atmospheric scientists at NOAA as the ratio of total direct radiative forcing due to long-lived and well-mixed greenhouse gases for any year for which adequate global measurements exist, to that present in year 1990. These radiative forcing levels are relative to those present in year 1750 (i.e. prior to the start of the industrial era). 1990 is chosen because it is the baseline year for the Kyoto Protocol, and is the publication year of the first IPCC Scientific Assessment of Climate Change. As such, NOAA states that the AGGI "measures the commitment that (global) society has already made to living in a changing climate. It is based on the highest quality atmospheric observations from sites around the world. Its uncertainty is very low." | 1 | Applied and Interdisciplinary Chemistry |
The calculation of the pressure drop along the individual pipes of a gas network requires use of the flow equations. Many gas flow equations have been developed and a number have been used by the gas industry. Most are based on
the result of gas flow experiments. The result of the particular formula normally varies because these
experiments were conducted over different range of flow conditions, and on varying internal surface
roughness. Instead, each formula is applicable to a limited range of flow and pipe surface conditions. | 1 | Applied and Interdisciplinary Chemistry |
Fluorinated gases (F-gases) are a group of gases containing fluorine. They are divided into several types, the main of those are hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulphur hexafluoride (SF6). They are used in refrigeration, air conditioning, heat pumps, fire suppression, electronics, aerospace, magnesium industry, foam and high voltage switchgear. As they are greenhouse gases with a strong global warming potential, their use is regulated. | 1 | Applied and Interdisciplinary Chemistry |
Besides setups in multi-purpose facilities, the first dedicated end-station has been built at the PETRA-III storage ring, where this technique is routinely applied. | 0 | Theoretical and Fundamental Chemistry |
Albert Hofmann, born in Switzerland, joined the pharmaceutical-chemical department of Sandoz Laboratories, located in Basel, as a co-worker with professor Arthur Stoll, founder and director of the pharmaceutical department. He began studying the medicinal plant squill and the fungus ergot as part of a program to purify and synthesize active constituents for use as pharmaceuticals. His main contribution was to elucidate the chemical structure of the common nucleus of Scilla glycosides (an active principle of Mediterranean squill). While researching lysergic acid derivatives, Hofmann first synthesized LSD on November 16, 1938. The main intention of the synthesis was to obtain a respiratory and circulatory stimulant (an analeptic). It was set aside for five years, until April 16, 1943, when Hofmann decided to take a second look at it. While re-synthesizing LSD, he accidentally absorbed a small amount of the drug and discovered its powerful effects. He described what he felt as being: | 1 | Applied and Interdisciplinary Chemistry |
Complexes with three bidentate ligands or two cis bidentate ligands can exist as enantiomeric pairs. Examples are shown below. | 0 | Theoretical and Fundamental Chemistry |
A fitting or adapter is used in pipe systems to connect sections of pipe (designated by nominal size, with greater tolerances of variance) or tube (designated by actual size, with lower tolerance for variance), adapt to different sizes or shapes, and for other purposes such as regulating (or measuring) fluid flow. These fittings are used in plumbing to manipulate the conveyance of fluids such as water for potatory, irrigational, sanitary, and refrigerative purposes, gas, petroleum, liquid waste , or any other liquid or gaseous substances required in domestic or commercial environments, within a system of pipes or tubes, connected by various methods, as dictated by the material of which these are made, the material being conveyed, and the particular environmental context in which they will be used, such as soldering, mortaring, caulking, Plastic welding, welding, friction fittings, threaded fittings, and compression fittings.
Fittings allow multiple pipes to be connected to cover longer distances, increase or decrease the size of the pipe or tube, or extend a network by branching, and make possible more complex systems than could be achieved with only individual pipes. Valves are specialized fittings that permit regulating the flow of fluid within a plumbing system. | 1 | Applied and Interdisciplinary Chemistry |
A set of structure utilities has been included for various applications such as: the transformation of unit cells ([http://www.cryst.ehu.es/cryst/celltran.html CELLTRAN]) or complete structures ([http://www.cryst.ehu.es/cryst/transtru.html TRANSTRU]); strain tensor calculation ([http://www.cryst.ehu.es/cryst/strain.html STRAIN]); assignment of Wyckoff Positions ([http://www.cryst.ehu.es/cryst/wpassign.html WPASSIGN]); equivalent descriptions of a given structure ([http://www.cryst.ehu.es/cryst/equivstru.html EQUIVSTRU]); comparison of different structures with support for the affine normalizers of monoclinic space groups. [http://www.cryst.ehu.es/cryst/rel.html STRUCTURE RELATIONS] calculates the possible transformation matrices for a given pair of group-subgroup related structures. | 0 | Theoretical and Fundamental Chemistry |
The homing endonucleases are a collection of endonucleases encoded either as freestanding genes within introns, as fusions with host proteins, or as self-splicing inteins. They catalyze the hydrolysis of genomic DNA within the cells that synthesize them, but do so at very few, or even singular, locations. Repair of the hydrolyzed DNA by the host cell frequently results in the gene encoding the homing endonuclease having been copied into the cleavage site, hence the term homing to describe the movement of these genes. Homing endonucleases can thereby transmit their genes horizontally within a host population, increasing their allele frequency at greater than Mendelian rates. | 1 | Applied and Interdisciplinary Chemistry |
Many universities offer environmental engineering programs through either the department of civil engineering or chemical engineering and also including electronic projects to develop and balance the environmental
conditions. Environmental engineers in a civil engineering program often focus on hydrology, water resources management, bioremediation, and water and wastewater treatment plant design. Environmental engineers in a chemical engineering program tend to focus on environmental chemistry, advanced air and water treatment technologies, and separation processes. Some subdivisions of environmental engineering include natural resources engineering and agricultural engineering.
Courses for students fall into a few broad classes:
*Mechanical engineering courses oriented towards designing machines and mechanical systems for environmental use such as water and wastewater treatment facilities, pumping stations, garbage segregation plants, and other mechanical facilities.
*Environmental engineering or environmental systems courses oriented towards a civil engineering approach in which structures and the landscape are constructed to blend with or protect the environment.
*Environmental chemistry, sustainable chemistry or environmental chemical engineering courses oriented towards understanding the effects of chemicals in the environment, including any mining processes, pollutants, and also biochemical processes.
*Environmental technology courses oriented towards producing electronic or electrical graduates capable of developing devices and artifacts able to monitor, measure, model and control environmental impact, including monitoring and managing energy generation from renewable sources. | 1 | Applied and Interdisciplinary Chemistry |
Organolithium reagents are sensitive to moisture and thus should be handled under inert atmosphere in anhydrous conditions. Tetrahydrofuran is the most common solvent employed for lateral lithiation reactions. Measurement of the concentration of commercial or prepared alkyllithium solutions may be accomplished using well-established titration methods.
A useful indicator for the progress of lateral lithiations is the color of the reaction mixture. Benzyllithium compounds range in color from red to deep purple, and in many cases the lack of a color change upon addition of an organolithium reagent to the substrate may indicate the presence of an undesired proton source in solution. | 0 | Theoretical and Fundamental Chemistry |
Gel electrophoresis is a method for separation and analysis of biomacromolecules (DNA, RNA, proteins, etc.) and their fragments, based on their size and charge. It is used in clinical chemistry to separate proteins by charge or size (IEF agarose, essentially size independent) and in biochemistry and molecular biology to separate a mixed population of DNA and RNA fragments by length, to estimate the size of DNA and RNA fragments or to separate proteins by charge.
Nucleic acid molecules are separated by applying an electric field to move the negatively charged molecules through a matrix of agarose or other substances. Shorter molecules move faster and migrate farther than longer ones because shorter molecules migrate more easily through the pores of the gel. This phenomenon is called sieving. Proteins are separated by the charge in agarose because the pores of the gel are too large to sieve proteins. Gel electrophoresis can also be used for the separation of nanoparticles.
Gel electrophoresis uses a gel as an anticonvective medium or sieving medium during electrophoresis, the movement of a charged particle in an electric current. Gels suppress the thermal convection caused by the application of the electric field, and can also act as a sieving medium, slowing the passage of molecules; gels can also simply serve to maintain the finished separation so that a post electrophoresis stain can be applied. DNA gel electrophoresis is usually performed for analytical purposes, often after amplification of DNA via polymerase chain reaction (PCR), but may be used as a preparative technique prior to use of other methods such as mass spectrometry, RFLP, PCR, cloning, DNA sequencing, or Southern blotting for further characterization. | 1 | Applied and Interdisciplinary Chemistry |
Epoxides can be deoxygenated using oxophilic reagents. This reaction can proceed with loss or retention of configuration. The combination of tungsten hexachloride and n-butyllithium gives the alkene. | 0 | Theoretical and Fundamental Chemistry |
Conventional dielectrometry is carried out typically in a parallel plate configuration of the dielectric sensor (capacitance probe) and has the capability of monitoring the resin cure throughout the entire cycle, from the liquid to the rubber to the solid state. It is capable of monitoring phase separation in complex resin blends curing also within a fibrous perform. The same attributes belong to the more recent development of the dielectric technique, namely microdielectrometry.
Several versions of dielectric sensors are available commercially. The most suitable format for use in cure monitoring applications are the flat interdigital capacitive structures bearing a sensing grid on their surface. Depending on their design (specifically those on durable substrates) they have some reusability, while flexible substrate sensors can be used also in the bulk of the resin systems as embedded sensors. | 0 | Theoretical and Fundamental Chemistry |
The series above are often truncated at in the study of far field flow, . Within that approximation, , with squirmer parameter . The first mode characterizes a hydrodynamic source dipole with decay (and with that the swimming speed ). The second mode corresponds to a hydrodynamic stresslet or force dipole with decay . Thus, gives the ratio of both contributions and the direction of the force dipole. is used to categorize microswimmers into pushers, pullers and neutral swimmers.
The above figures show the velocity field in the lab frame and in the particle-fixed frame. The hydrodynamic dipole and quadrupole fields of the squirmer model result from surface stresses, due to beating cilia on bacteria, or chemical reactions or thermal non-equilibrium on Janus particles. The squirmer is force-free. On the contrary, the velocity field of the passive particle results from an external force, its far-field corresponds to a "stokeslet" or hydrodynamic monopole. A force-free passive particle doesnt move and doesnt create any flow field. | 1 | Applied and Interdisciplinary Chemistry |
The C metabolic pathway is a valuable recent evolutionary innovation in plants, involving a complex set of adaptive changes to physiology and gene expression patterns. About 7600 species of plants use carbon fixation, which represents about 3% of all terrestrial species of plants. All these 7600 species are angiosperms.
C plants evolved carbon concentrating mechanisms. These work by increasing the concentration of around RuBisCO, thereby facilitating photosynthesis and decreasing photorespiration. The process of concentrating around RuBisCO requires more energy than allowing gases to diffuse, but under certain conditions – i.e. warm temperatures (>25 °C), low concentrations, or high oxygen concentrations – pays off in terms of the decreased loss of sugars through photorespiration.
One type of C metabolism employs a so-called Kranz anatomy. This transports through an outer mesophyll layer, via a range of organic molecules, to the central bundle sheath cells, where the is released. In this way, is concentrated near the site of RuBisCO operation. Because RuBisCO is operating in an environment with much more than it otherwise would be, it performs more efficiently. In C photosynthesis, carbon is fixed by an enzyme called PEP carboxylase, which, like all enzymes involved in C photosynthesis, originated from non-photosynthetic ancestral enzymes.
A second mechanism, CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. The most important benefit of CAM to the plant is the ability to leave most leaf stomata closed during the day. This reduces water loss due to evapotranspiration. The stomata open at night to collect , which is stored as the four-carbon acid malate, and then used during photosynthesis during the day. The pre-collected is concentrated around the enzyme RuBisCO, increasing photosynthetic efficiency. More is then harvested from the atmosphere when stomata open, during the cool, moist nights, reducing water loss.
CAM has evolved convergently many times. It occurs in 16,000 species (about 7% of plants), belonging to over 300 genera and around 40 families, but this is thought to be a considerable underestimate. It is found in quillworts (relatives of club mosses), in ferns, and in gymnosperms, but the great majority of plants using CAM are angiosperms (flowering plants). | 0 | Theoretical and Fundamental Chemistry |
The Womersley number ( or ) is a dimensionless number in biofluid mechanics and biofluid dynamics. It is a dimensionless expression of the pulsatile flow frequency in relation to viscous effects. It is named after John R. Womersley (1907–1958) for his work with blood flow in arteries. The Womersley number is important in keeping dynamic similarity when scaling an experiment. An example of this is scaling up the vascular system for experimental study. The Womersley number is also important in determining the thickness of the boundary layer to see if entrance effects can be ignored.
The square root of this number is also referred to as Stokes number, , due to the pioneering work done by Sir George Stokes on the Stokes second problem. | 1 | Applied and Interdisciplinary Chemistry |
In this article, the following conventions and definitions are to be understood:
* The Reynolds number Re is taken to be Re = V D / ν, where V is the mean velocity of fluid flow, D is the pipe diameter, and where ν is the kinematic viscosity μ / ρ, with μ the fluids Dynamic viscosity, and ρ the fluids density.
* The pipes relative roughness ε / D, where ε is the pipes effective roughness height and D the pipe (inside) diameter.
* f stands for the Darcy friction factor. Its value depends on the flows Reynolds number Re and on the pipes relative roughness ε / D.
* The log function is understood to be base-10 (as is customary in engineering fields): if x = log(y), then y = 10.
* The ln function is understood to be base-e: if x = ln(y), then y = e. | 1 | Applied and Interdisciplinary Chemistry |
A general second messenger system mechanism can be broken down into four steps. First, the agonist activates a membrane-bound receptor. Second, the activated G-protein produces a primary effector. Third, the primary effect stimulates the second messenger synthesis. Fourth, the second messenger activates a certain cellular process.
The G-protein coupled receptors for the PIP messenger system produces two effectors, phospholipase C (PLC) and phosphoinositide 3-kinase (PI3K). PLC as an effector produces two different second messengers, inositol triphosphate (IP) and Diacylglycerol (DAG).
IP is soluble and diffuses freely into the cytoplasm. As a second messenger, it is recognized by the inositol triphosphate receptor (IP3R), a Ca channel in the endoplasmic reticulum (ER) membrane, which stores intracellular Ca. The binding of IP to IP3R releases Ca from the ER into the normally Ca-poor cytoplasm, which then triggers various events of Ca signaling. Specifically in blood vessels, the increase in Ca concentration from IP releases nitric oxide, which then diffuses into the smooth muscle tissue and causes relaxation.
DAG remains bound to the membrane by its fatty acid "tails" where it recruits and activates both conventional and novel members of the protein kinase C family. Thus, both IP and DAG contribute to activation of PKCs.
Phosphoinositide 3-kinase (PI3K) as an effector phosphorylates phosphatidylinositol bisphosphate (PIP) to produce phosphatidylinositol (3,4,5)-trisphosphate (PIP). PIP has been shown to activate protein kinase B, increase binding to extracellular proteins and ultimately enhance cell survival. | 1 | Applied and Interdisciplinary Chemistry |
* Sir Joseph Swan: 1903–1904
* Lord Kelvin: 1905–1907
* Sir William Henry Perkin: 1907
* Sir Oliver Lodge: 1908–1909
* Sir James Swinburne: 1909–1911
* Sir Richard T. Glazebrook: 1911–1913
* Sir Robert Abbott Hadfield: 1913–1920
* Professor Alfred W Porter: 1920–1922
* Sir Robert Robertson: 1922–1924
* Sir Frederick George Donnan: 1924–1926
* Professor Cecil Henry Desch: 1926–1928
* Professor Thomas Martin Lowry: 1928–1930
* Sir Robert Mond: 1930–1932
* Professor Nevil Vincent Sidgwick: 1932–1934
* William Rintoul: 1934–1936
* Professor Morris William Travers: 1936–1938
* Sir Eric Keightley Rideal: 1938–1945
* Professor William Edward Garner: 1945–1947
* Professor Arthur John Allmand: 1947–1948
* Sir John Lennard-Jones: 1948–1950
* Sir Charles Goodeve: 1950–1952
* Sir Hugh Taylor: 1952–1953
* Professor Ronald George Wreyford Norrish: 1953–1955
* Ronald Percy Bell: 1956–1957
* Sir Harry Work Melville: 1958
* Dr Edgar William Steacie: 1959
* Sir Harry Work Melville: 1960
* Sir Cyril Norman Hinshelwood: 1961–1962
* Professor Alfred Rene Ubbelhode: 1963–1964
* Sir Frederick Sydney Dainton: 1965–1966
* Professor Cecil Bawn: 1967–1968
* Professor Geoffrey Gee: 1969–1970
* Professor John Wilfrid Linnett: 1971–1972 | 1 | Applied and Interdisciplinary Chemistry |
A colloidal gel consists of a percolated network of particles in a fluid medium, providing mechanical properties in particular the rise of elastic behaviour. The particles can show attractive interactions through osmotic depletion or through polymeric links.
Colloidal gels have three phases in their lifespan: gelation, aging and collapse. The gel is initially formed by the assembly of particles into a space-spanning network, leading to a phase arrest. In the aging phase, the particles slowly rearrange to form thicker strands, increasing the elasticity of the material. Gels can also be collapsed and separated by external fields such as gravity. Colloidal gels show linear response rheology at low amplitudes. These materials have been explored as candidates for a drug release matrix. | 0 | Theoretical and Fundamental Chemistry |
The material was described in NACA-TN-259 of August 1927, as "a new corrosion resistant aluminium product which is markedly superior to the present strong alloys. Its use should result in greatly increased life of a structural part. Alclad is a heat-treated aluminium, copper, manganese, magnesium alloy that has the corrosion resistance of pure metal at the surface and the strength of the strong alloy underneath. Of particular importance is the thorough character of the union between the alloy and the pure aluminium. Preliminary results of salt spray tests (24 weeks of exposure) show changes in tensile strength and elongation of Alclad 17ST, when any occurred, to be so small as to be well within the limits of experimental error." In applications involving aircraft construction, Alclad has proven to have increased resistance to corrosion at the expense of increased weight when compared to sheet aluminium.
As pure aluminium possesses a relatively greater resistance to corrosion over the majority of aluminium alloys, it was soon recognised that a thin coating of pure aluminium over the exterior surface of those alloys would take advantage of the superior qualities of both materials. Thus, a key advantage of Alclad over most aluminium alloys is its high corrosion resistance. However, considerable care must be taken while working on an Alclad-covered exterior surface, such as while cleaning the skin of an aircraft, to avoid scarring the surface to expose the vulnerable alloy underneath and prematurely age those elements.
Due to its relatively shiny natural finish, it is often considered to be cosmetically pleasing when used for external elements, particularly during restoration efforts. It has been observed that some fabrication techniques, such as welding, are not suitable when used in conjunction with Alclad. Mild cleaners with a neutral pH value and finer abrasives are recommended for cleaning and polishing Alclad surfaces. It is common for waterproof wax and other inhibitive coverings to be applied to further reduce corrosion. In the twenty-first century, research and evaluation was underway into new coatings and application techniques. | 1 | Applied and Interdisciplinary Chemistry |
In size-exclusion chromatography, such as gel permeation chromatography, the intrinsic viscosity of a polymer is directly related to the elution volume of the polymer. Therefore, by running several monodisperse samples of polymer in a gel permeation chromatograph (GPC), the values of and can be determined graphically using a line of best fit. Then the molecular weight and intrinsic viscosity relationship is defined.
Also, the molecular weights of two different polymers in a particular solvent can be related using the Mark–Houwink equation when the polymer-solvent systems have the same intrinsic viscosity:
Knowing the Mark–Houwink parameters and the molecular weight of one of the polymers allows one to find the molecular weight of the other polymer using a GPC. The GPC sorts the polymer chains by volume and as intrinsic viscosity is related to the volume of the polymer chain, the GPC data is the same for the two different polymers. For example, if the GPC calibration curve is known for polystyrene in toluene, polyethylene in toluene can be run in a GPC and the molecular weight of polyethylene can be found according to the polystyrene calibration curve via the above equation. | 0 | Theoretical and Fundamental Chemistry |
A well studied complex is tris(glycinato)cobalt(III). It is produced by the reaction of glycine with sodium tris(carbonato)cobalt(III). Similar synthetic methods apply to the preparation of tris(chelates) of other amino acids.
Commonly amino acid complexes are prepared by ligand displacement reactions of metal aquo complexes and the conjugate bases of amino acids:
:[PtCl] + 2HNCH(R)CO → [Pt(HNCH(R)CO)] + 4 Cl
Relevant to bioinorganic chemistry, amino acid complexes can be generated by the hydrolysis of amino acid esters and amides (en = ethylenediamine):
:[(en)CoOH(κ-HNCH(R)COEt)] → [(en)CoOH(κ-HNCH(R)CO)] + EtOH
Because their 5-membered MNCO chelate ring is rather stable, amino acid complexes represent protecting groups for amino acids, allowing diverse reactions of the side chains. | 0 | Theoretical and Fundamental Chemistry |
Chemical oxidative polymerization is a traditional and commonly used method for the polymerization of aniline in large quantities. When aniline is mixed with an oxidant in an acidic solution, polymerization will occur. The most important parameter to be controlled in this method for the synthesis of polyaniline nanofibers is the domination of homogeneous nucleation over heterogeneous nucleation. Homogeneous nucleation describes when the nuclei are formed spontaneously in solution while heterogeneous nucleation describes when the nuclei are grown on other species. In the early stages of this polymerization, only nanofibers are formed since there are no heteronuclei available for heterogeneous nucleation. However, if the reaction is left uncontrolled, heterogeneous nucleation will begin to dominate as the polyaniline will preferentially grow on existing particles, leading to irreversible agglomeration. The reaction can be made to favor homogeneous nucleation throughout by increasing reaction speed, temperature of the reaction, and allowing the reaction to proceed without stirring.
The diameter of the polyaniline nanofibers can be controlled with this method through choice of acid. Hydrochloric acid produces nanofibers with a diameter of about 30 nm, while camphorsulfonic acid and perchloric acid produce a diameter of 50 nm and 120 nm respectively. Under normal synthetic methods polyaniline derivatives, such as ones that are alkyl and fluoro substituted, do not exhibit a well-defined fibrous shape, however, in the presence of an aniline oligomer nanofibers of certain derivatives can be synthesized. While the most common oxidant is ammonium peroxydisulfate (APS), various others can be used. One study shows the use of potassium biiodate (KH(IO)) as an oxidant, claiming it to lead to polyaniline nanofibers that are longer, have higher crystallinity, and have higher electrical conductivity. | 0 | Theoretical and Fundamental Chemistry |
Liver of sulfur is mainly used in metalworking to form a brown or black patina on copper and silver as well as many (though not all) copper alloys and silver alloys (brass, for example— a copper alloy— does not react with sulfur compounds). It is sold as a yellow brittle solid (a "lump" which must be mixed with water before use) as well as a pre-mixed liquid and a gel form. The solid is believed to have the longest shelf life, though all liver of sulfur tends to decompose with time. Modern gel forms contain stabilizers that allow the reactivity to last much longer. Liver of sulfur that is kept dry, sealed from air, out of the light, and in a freezer will last many times longer than that kept in any other condition.
The highest quality liver of sulfur in solid form is a dark yellow, almost "liver" colored substance. As it ages and is exposed to air, its potency decreases, it will turn lighter yellow and finally white, at which point its reactivity is negligible. Liver of sulfur decomposes to sulfate of potash and carbonate of potash, neither of which has any value as an oxidizer of metal.
The reactivity of liver of sulfur with silver and copper quickly creates a dark or colored patina on the metal. This is done by immersing the metal object in a solution of liver of sulfur and water. When treating silver, the solution must be hot, though if the bath is brought to its boiling point the liver of sulfur will quickly decompose and become ineffective. Also, if the concentration of the solution is too strong, the oxidation process will proceed too quickly and the layer of patina thus created will tend to flake away. The best results are usually obtained by using more dilute solutions and allowing the patina to build more slowly but more securely, and, for silver, keeping the solution just under its boiling point. Lastly, it is critical that the metal surface be extremely clean, as clean as would be necessary to electroplate the same surface. Even small amounts of oil on the metal such as that produced by handling without gloves will be sufficient to protect the metal surface from oxidation. | 0 | Theoretical and Fundamental Chemistry |
In E for Ecstasy (a book examining the uses of the street drug ecstasy in the UK) the writer, activist and ecstasy advocate Nicholas Saunders highlighted test results showing that certain consignments of the drug also contained selegiline. Consignments of ecstasy known as "Strawberry" contained what Saunders described as a "potentially dangerous combination of ketamine, ephedrine and selegiline," as did a consignment of "Sitting Duck" Ecstasy tablets.
David Pearce wrote The Hedonistic Imperative six weeks after starting taking selegiline.
In Gregg Hurwitzs novel Out of the Dark, selegiline (Emsam') and tyramine-containing food were used to assassinate the president of the United States. | 0 | Theoretical and Fundamental Chemistry |
* [http://www.piercenet.com/method/desalting-gel-filtration#gelfiltration Animation of desalting using gel filtration chromatography] | 0 | Theoretical and Fundamental Chemistry |
Cluster decay, also named heavy particle radioactivity, heavy ion radioactivity or heavy cluster decay, is a rare type of nuclear decay in which an atomic nucleus emits a small "cluster" of neutrons and protons, more than in an alpha particle, but less than a typical binary fission fragment. Ternary fission into three fragments also produces products in the cluster size. The loss of protons from the parent nucleus changes it to the nucleus of a different element, the daughter, with a mass number A = A − A and atomic number Z = Z − Z, where A = N + Z.
For example:
This type of rare decay mode was observed in radioisotopes that decay predominantly by alpha emission, and it occurs only in a small percentage of the decays for all such isotopes.
The branching ratio with respect to alpha decay is rather small (see the Table below).
T and T are the half-lives of the parent nucleus relative to alpha decay and cluster radioactivity, respectively.
Cluster decay, like alpha decay, is a quantum tunneling process: in order to be emitted, the cluster must penetrate a potential barrier. This is a different process than the more random nuclear disintegration that precedes light fragment emission in ternary fission, which may be a result of a nuclear reaction, but can also be a type of spontaneous radioactive decay in certain nuclides, demonstrating that input energy is not necessarily needed for fission, which remains a fundamentally different process mechanistically.
In the absence of any energy loss for fragment deformation and excitation, as in cold fission phenomena or in alpha decay, the total kinetic energy is equal to the Q-value and is divided between the particles in inverse proportion with their masses, as required by conservation of linear momentum
where A is the mass number of the daughter, A = A − A.
Cluster decay exists in an intermediate position between alpha decay (in which a nucleus spits out a He nucleus), and spontaneous fission, in which a heavy nucleus splits into two (or more) large fragments and an assorted number of neutrons. Spontaneous fission ends up with a probabilistic distribution of daughter products, which sets it apart from cluster decay. In cluster decay for a given radioisotope, the emitted particle is a light nucleus and the decay method always emits this same particle. For heavier emitted clusters, there is otherwise practically no qualitative difference between cluster decay and spontaneous cold fission. | 0 | Theoretical and Fundamental Chemistry |
The Wikipedia page Metabolic pathway defines a pathway as "a metabolic pathway is a linked series of chemical reactions occurring within a cell". This means that any sequence of reactions can be labeled a metabolic pathway. However, as metabolism was being uncovered, groups of reactions were assigned specific labels, such as glycolysis, Krebs Cycle, or Serine biosynthesis. Often the categorization was based on common chemistry or identification of an input and output. For example, serine biosynthesis starts at 3-phosphoglycerate and ends at serine. This is a somewhat ad hoc means for defining pathways, particularly when pathways are dynamic structures, changing as environmental result in changes in gene expression. For example, the Kreb Cycle is often not cyclic as depicted in textbooks. In E. coli and other bacteria, it is only cyclic during aerobic growth on acetate or fatty acids. Instead, under anaerobiosis, its enzymes function as two distinct biosynthetic pathways producing succinyl-CoA and α-ketoglutarate.
It has therefore been proposed to define a pathway as either a single elementary mode or some combination of elementary modes. The added advantage is that the set of elementary modes is unique and non-decomposable to simpler pathways. A single elementary mode can therefore be thought of as an elementary pathway. Note that the set of elementary modes will change as the set of expressed enzymes change during transitions from one cell state to another.
Elementary modes, therefore, provide an unambiguous definition of a pathway. | 1 | Applied and Interdisciplinary Chemistry |
Immunogold labeling can be used to visualize more than one target simultaneously. This can be achieved in electron microscopy by using two different-sized gold particles. An extension of this method used three different sized gold particles to track the localisation of regulatory peptides. A more complex method of multi-site labeling involves labeling opposite sides of an antigenic site separately, the immunogold particles attached to both sides can then be viewed simultaneously. | 1 | Applied and Interdisciplinary Chemistry |
For a spheroid with equatorial semi-major axis and polar semi-minor axis , the angular velocity about is given by Maclaurin's formula
where is the eccentricity of meridional cross-sections of the spheroid, is the density and is the gravitational constant. The formula predicts two possible equilibrium figures, one which approaches a sphere () when and the other which approaches a very flattened spheroid () when . The maximum angular velocity occurs at eccentricity and its value is , so that above this speed, no equilibrium figures exist. The angular momentum is
where is the mass of the spheroid and is the mean radius, the radius of a sphere of the same volume as the spheroid. | 1 | Applied and Interdisciplinary Chemistry |
The SPC file format is a file format for storing spectroscopic data.
The SPC file format is a file format in which all kinds of spectroscopic data, including among others infrared spectra, Raman spectra and UV/VIS spectra. The format can be regarded as a database with records of variable length and each record stores a different kind of data (instrumental information, information on one spectrum of a dataset, the spectrum itself or extra logs). It was invented by Galactic Industries as generic file format for its programs. Their original specification was implemented in 1986, but a more versatile format was created in 1996.
Galactic Industries was purchased by Thermo Fisher Scientific who now maintain and develop the GRAMS Software Suite for which the format was defined. They provide free tools and libraries to allow developers to create and maintain SPC files consistently.
This file format is not in plaintext, such as XML or CSV, but is a binary format and is therefore not readable with a standard text editor but requires a special reader or software to interpret the file data. The Environmental Protection Agency publishes a free spectra reader called ShowSPC that is open to the public for reading spectra data. Additionally, a company AnalyzeIQ produces a free SPC to CSV converter aptly titled SPC2CSV, an open-source project OpenSpectralWorks is an alternative free reader, as well as SpectraGryph which has analytic and display capabilities for reading SPC files. The Essential FTIR software offers a file reader that can read, display, analyze and export .spc files as well as many other spectroscopy file formats. | 0 | Theoretical and Fundamental Chemistry |
Many phenols of commercial interest are prepared by elaboration of phenol or cresols. They are typically produced by the alkylation of benzene/toluene with propylene to form cumene then is added with to form phenol (Hock process). In addition to the reactions above, many other more specialized reactions produce phenols:
* rearrangement of esters in the Fries rearrangement
* rearrangement of N-phenylhydroxylamines in the Bamberger rearrangement
* dealkylation of phenolic ethers
* reduction of quinones
* replacement of an aromatic amine by an hydroxyl group with water and sodium bisulfide in the Bucherer reaction
*thermal decomposition of aryl diazonium salts, the salts are converted to phenol
* by the oxidation of aryl silanes—an aromatic variation of the Fleming-Tamao oxidation
*catalytic synthesis from aryl bromides and iodides using nitrous oxide | 0 | Theoretical and Fundamental Chemistry |
Though microorganisms are often responsible for corrosion, they can also protect surfaces from corrosion. For example, oxidization is a common cause of corrosion. If a susceptible surface has a biofilm covering it that takes in and uses oxygen, then that surface will be protected from corrosion due to oxidization. Biofilms can also release antimicrobial compounds, which is helpful if the biofilm is not corrosive and can deter microbes that would be. Biofilms provide a barrier between a surface and the ecosystem surrounding it, so as long as the biofilm has no adverse effects, it can serve as protection from corrosion as well. Because biofilms don’t negatively impact the ecosystem, they are potentially one of the best mechanisms for corrosion inhibition. They can also alter the conditions on the surface of a metal so that the metal is less likely to be damaged, preventing corrosion. | 1 | Applied and Interdisciplinary Chemistry |
Polyprotic acids are acids that can lose more than one proton. The constant for dissociation of the first proton may be denoted as K, and the constants for dissociation of successive protons as K, etc. Citric acid is an example of a polyprotic acid HA, as it can lose three protons.
When the difference between successive pK values is less than about 3, there is overlap between the pH range of existence of the species in equilibrium. The smaller the difference, the more the overlap. In the case of citric acid, the overlap is extensive and solutions of citric acid are buffered over the whole range of pH 2.5 to 7.5.
Calculation of the pH with a polyprotic acid requires a speciation calculation to be performed. In the case of citric acid, this entails the solution of the two equations of mass balance:
C is the analytical concentration of the acid, C is the analytical concentration of added hydrogen ions, β are the cumulative association constants. K is the constant for self-ionization of water. There are two non-linear simultaneous equations in two unknown quantities [A] and [H]. Many computer programs are available to do this calculation. The speciation diagram for citric acid was produced with the program HySS.
N.B. The numbering of cumulative, overall constants is the reverse of the numbering of the stepwise, dissociation constants.
Cumulative association constants are used in general-purpose computer programs such as the one used to obtain the speciation diagram above. | 0 | Theoretical and Fundamental Chemistry |
As described above, contact angle is used to characterize surface wettability. A droplet of solvent, typically water for hydrophobic surfaces, is placed perpendicular to the surface. The droplet is imaged and the angle between the solid/liquid and liquid/vapor interfaces is measured. Samples are considered to be superhydrophobic when the contact angle is greater than 150 degrees. Refer to section on Wenzel and Cassie-Baxter models for information on the different behaviors of droplets on topographical surfaces. For drops to roll effectively on a superhydrophobic surface, Contact angle hysteresis is an important consideration. Low levels of contact angle hysteresis will enhance the self-cleaning effect of a superhydrophobic surface. | 0 | Theoretical and Fundamental Chemistry |
R. D. Richtmyer provided a theoretical prediction, and E. E. Meshkov (Евгений Евграфович Мешков) provided experimental verification. Materials in the cores of stars, like Cobalt-56 from Supernova 1987A were observed earlier than expected. This was evidence of mixing due to Richtmyer–Meshkov and Rayleigh–Taylor instabilities. | 1 | Applied and Interdisciplinary Chemistry |
In order to get a meaningful sulfur signal from the analysis, the buffer should not contain sulfur (i.e. no BES, DDT, HEPES, MES, MOPSO or PIPES compounds). Excessive amounts of chlorine in the buffer should also be avoided, since this will overlap with the sulfur peak; KBr and NaBr are suitable alternatives. | 0 | Theoretical and Fundamental Chemistry |
As further discussed, orlistat is a pancreatic and gastric lipase inhibitor. Orlistat is also a potent thioesterase inhibitor and therefore inhibits fatty acid synthase (FAS). Since FAS is essential for tumor cells, for its growth and survival, and is upregulated and overexpressed in variety of tumors, scientists have high expectations for FAS as an oncology drug target. Orlistat inhibits FAS with the same mechanism as it does with pancreatic lipase, that is by binding covalently to the active serine site.
This effect of orlistat as a FAS-inhibitor was first identified in a high throughput screening for enzymes with prostate cancer inhibition activity. However FAS is resistant to many cancer medicines. Orlistat sensitizes these FAS resistance cancer drugs, by inhibiting FAS. There is a low FAS expression in normal tissues so the activity of orlistat on normal cells is limited.
Because of the difference in FAS expression between normal cells and cancer cells, orlistat selectively targets tumor cells. Due to this FAS is a potential drug target in cancer therapy.
Orlistat works locally in the intestines as a lipase inhibitor, and therefore suffers from several limitations in its development as a systemic drug. Its poor bioavailability and solubility are the main reasons to develop a new anticancer analogue to overcome these limitations. | 1 | Applied and Interdisciplinary Chemistry |
Although Hügelkultur beds can safely retain water in light-duty applications (for example, conserving the moisture of rain that falls on the bed), creating heavy-duty rainwater retention areas behind Hügelkultur beds on contour, to catch surface runoff from surrounding areas, can be dangerous. Some designers conflate the Hügelkultur bed's appearance with that of solid earthworks, but Hügelkultur beds cannot predictably control large amounts of stormwater in the way that solid earthworks can. Whereas embankment dams or the hillsides of swales can be relied on to hold back many thousands of gallons of water for weeks to allow it to seep into the ground, and berms can slow runoff, Hügelkultur beds are different in two ways: earthworks have no buoyant core (whereas Hügelkultur mounds contain logs), and the soil that they are made of is compacted. If fresh or dried timber is used in the bed, it may become buoyant in the water-saturated substrate, bursting from the soil covering and releasing all the sitting water through a breach. This can be an issue for years, until the wood is sufficiently rotten and infused with water. Another consideration is that Hügelkultur beds will degrade, shrinking over time into much lower mounds of soft, rich soil. This means that the retention area will have less depth as time goes on, but it also means that the uncompacted soil will remain a threat to breaching even if the logs become saturated.
Some permaculturists have taken mild positions against the "hügel swales" still being promoted by other permaculturists, citing the danger and cross-purposes of Hügelkultur beds and swales. Swales are for long-term installations where perennials - like fruit trees - are grown. Hügelkultur is used for shorter term, more annual crops, as the soil settling that occurs with hugel decomposition is bad for the root system of fruit trees. A common practice is to plant fruit trees beside a hugelkultur mound where some nutrient runoff can feed the tree without the tree’s support collapsing under it, while also allowing the tree to extend its roots laterally under or upward into the hugelkultur mound as far as it “needs.”
There is a recorded instance of a breach occurring in a new project. Upon the first rainstorm, the retention areas behind the Hügelkultur beds filled with water and broke through. The released water carried the freshly-buried logs and dirt downhill, smashing a hole in a building being used as a church and filling the space with mud. No injuries were reported. | 1 | Applied and Interdisciplinary Chemistry |
Phytoplankton supports all life in the ocean as it converts inorganic compounds into organic constituents. This autotrophically produced biomass presents the foundation of the marine food web. In the diagram immediately below, the arrows indicate the various production (arrowhead pointing toward DOM pool) and removal processes of DOM (arrowhead pointing away), while the dashed arrows represent dominant biological processes involved in the transfer of DOM. Due to these processes, the fraction of labile DOM decreases rapidly with depth, whereas the refractory character of the DOM pool considerably increases during its export to the deep ocean. DOM, dissolved organic matter. | 0 | Theoretical and Fundamental Chemistry |
Nests are used as nurseries, resting areas, and as protection against weather. They are constructed of woven grass; they are usually subterranean or are constructed under boards, rocks, logs, brush piles, hay bales, fenceposts, or in grassy tussocks. Eastern meadow voles dig shallow burrows, and in burrows, nests are constructed in enlarged chambers. In winter, nests are often constructed on the ground surface under a covering of snow, usually against some natural formation such as a rock or log.
Eastern meadow voles form runways or paths in dense grasses. | 1 | Applied and Interdisciplinary Chemistry |
Formula for vorticity can give another explanation of the Stokes Paradox. The functions belong to the kernel of and generate the stationary solutions of the vorticity equation with Robin-type boundary condition. From the arguments above any Stokes vorticity flow with no-slip boundary condition must be orthogonal to the obtained stationary solutions. That is only possible for . | 1 | Applied and Interdisciplinary Chemistry |
Cobalt chloride is a common visual moisture indicator due to its distinct colour change when hydrated. The colour change is from some shade of blue when dry, to a pink when hydrated, although the shade of colour depends on the substrate and concentration. It is impregnated into paper to make test strips for detecting moisture in solutions, or more slowly, in air/gas. Desiccants such as silica gel can incorporate cobalt chloride to indicate when it is "spent" (i.e. hydrated). | 0 | Theoretical and Fundamental Chemistry |
The merger of microfluidics and optics is typical known as optofluidics. Examples of optofluidic devices are tunable microlens arrays and optofluidic microscopes.
Microfluidic flow enables fast sample throughput, automated imaging of large sample populations, as well as 3D capabilities. or superresolution. | 1 | Applied and Interdisciplinary Chemistry |
In 1954 and 1958 Krishna Bahadur and co-workers published the successful synthesis of amino acids from a mixture of paraformaldehyde, colloidal molybdenum oxide or potassium nitrate and ferric chloride under sunlight. It appears that this experimental approach was seminal for the assays to produce Jeewanu, which he first reported in 1963 in an obscure Indian journal, Vijnana Parishad Anusandhan Patrika. His detailed syntheses were published in Germany in 1964 in a series of articles.
Their initial experiment consisted of a sterilised apparatus in which inorganic nitrogenous compounds (such as ammonium phosphate and ammonium molybdate) and organic compounds such as citric acid (CHO), paraformaldehyde (OH(CHO)H) and formaldehyde (CHO) for carbon sources were mixed with minerals commonly found in living cells. Inorganic substances such as colloidal ferric chloride or molybdenum compounds supposedly acted as cofactors and catalysts.
When the apparatus was exposed to sunlight for several days and constantly shaken, microscopic spherical particles were formed. The interesting features of these particles were that they were enclosed in a semipermeable membrane, like the typical cell membrane. Like living cells, they were reported to contain amino acids, phospholipid membrane and carbohydrates. In addition, they were claimed to have reproductive capability by budding, much like unicellular organisms, but did not grow on any bacterial culture medium. Bahadur reported that the Jeewanu exhibited various catalytic properties and produced their own peptides by metabolic reactions. Bahadur's later work on the Jeewanu also detected the presence of amino acids in peptide form and sugars in the form of ribose, deoxyribose, fructose and glucose, as well as nucleic acid bases (DNA and RNA building blocks) including adenine, guanine, cytosine, thymine and uracil. Bahadur also reported having detected ATPase-like and peroxidase-like activity. Bahadur stated that by using molybdenum as a cofactor, the Jeewanu showed capability of reversible photochemical electron transfer, and released a gas mixture of oxygen and hydrogen at a 1:2 ratio. | 0 | Theoretical and Fundamental Chemistry |
Initially these were described as ternary RE-B-Si compounds, but later carbon was included to improve the structure description that resulted in a quaternary RE-B-C-Si composition. REBCSi (RE=Y and Gd–Lu) have a unique crystal structure with two units – a cluster of B icosahedra and a Si ethane-like complex – and one bonding configuration (B)≡Si-C≡(B). A representative compound of this group is YBCSi (x=0.68). It has a trigonal crystal structure with space group Rm (No. 166) and lattice constants a = b = 1.00841(4) nm, c = 1.64714(5) nm, α = β = 90° and γ = 120°.
The crystal has layered structure. Figure 15 shows a network of boron icosahedra that spreads parallel to the (001) plane, connecting with four neighbors through B1–B1 bonds. The C3 and Si3 site atoms strengthen the network by bridging the boron icosahedra. Contrary to other boron-rich icosahedral compounds, the boron icosahedra from different layers are not directly bonded. The icosahedra within one layer are linked through Si ethane-like clusters with (B)≡Si-C≡(B) bonds, as shown in figures 16a and b.
There are eight atomic sites in the unit cell: one yttrium Y, four boron B1–B4, one carbon C3 and three silicon sites Si1–Si3. Atomic coordinates, site occupancy and isotropic displacement factors are listed in table Va; 68% of the Y sites are randomly occupied and remaining Y sites are vacant. All boron sites and Si1 and Si2 sites are fully occupied. The C3 and Si3 sites can be occupied by either carbon or silicon atoms (mixed occupancy) with a probability of about 50%. Their separation is only 0.413 Å, and thus either the C3 or Si3 sites, but not both, are occupied. These sites form Si-C pairs, but not Si-Si or C-C pairs. The distances between the C3 and Si3 sites and the surrounding sites for YBCSi are summarized in table Vb and the overall crystal structure is shown in figure 14.
Salvador et al. reported an isotypic terbium compound
TbCSi(B). Most parts of the crystal structure are the same as those described above; however, its bonding configuration is deduced as (B)≡C-C≡(B) instead of (B)≡Si-C≡(B). The authors intentionally added carbon to grow single crystals whereas the previous crystals were accidentally contaminated by carbon during their growth. Thus, higher carbon concentration was achieved. Existence of both bonding schemes of (B)≡Si-C≡(B) and (B)≡C-C≡(B) suggests the occupancy of the carbon sites of 50–100%. On the other hand, (B)≡Si-Si≡(B) bonding scheme is unlikely because of too short Si-Si distance, suggesting that the minimum carbon occupancy at the site is 50%. Some B atoms may replace C atoms at the C3 site, as previously assigned to the B site. However, the carbon occupation is more likely because the site is tetrahedrally coordinated whereas the B occupation of the site needs an extra electron to complete tetrahedral bonding. Thus, carbon is indispensable for this group of compounds. | 0 | Theoretical and Fundamental Chemistry |
Ultraviolet rays are usually invisible to most humans. The lens of the human eye blocks most radiation in the wavelength range of 300–400 nm; shorter wavelengths are blocked by the cornea. Humans also lack color receptor adaptations for ultraviolet rays. Nevertheless, the photoreceptors of the retina are sensitive to near-UV, and people lacking a lens (a condition known as aphakia) perceive near-UV as whitish-blue or whitish-violet. Under some conditions, children and young adults can see ultraviolet down to wavelengths around 310 nm. Near-UV radiation is visible to insects, some mammals, and some birds. Birds have a fourth color receptor for ultraviolet rays; this, coupled with eye structures that transmit more UV gives smaller birds "true" UV vision. | 0 | Theoretical and Fundamental Chemistry |
Naming alkanes per standards listed in the IUPAC Gold Book is done according to the Klyne–Prelog system for specifying angles (called either torsional or dihedral angles) between substituents around a single bond:
* a torsion angle between 0° and ±90° is called syn (s)
* a torsion angle between ±90° and 180° is called anti (a)
* a torsion angle between 30° and 150° or between −30° and −150° is called clinal (c)
* a torsion angle between 0° and ±30° or ±150° and 180° is called periplanar (p)
* a torsion angle between 0° and ±30° is called synperiplanar (sp), also called syn- or cis- conformation
* a torsion angle between 30° to 90° and −30° to −90° is called synclinal (sc), also called gauche or skew
* a torsion angle between 90° and 150° or −90° and −150° is called anticlinal (ac)
* a torsion angle between ±150° and 180° is called antiperiplanar (ap), also called anti- or trans- conformation
Torsional strain or "Pitzer strain" refers to resistance to twisting about a bond. | 0 | Theoretical and Fundamental Chemistry |
The representation of reaction mechanisms using curved arrows to indicate electron flow was developed by Sir Robert Robinson in 1922. Organic chemists use two types of arrows within molecular structures to describe electron movements. Single electrons trajectories are designated with single barbed arrows, whereas double-barbed arrows show movement of electron pairs. The arrows tail is drawn at either a lone pair of electrons on an atom or a bond between atoms, an electron source or area where there is relatively high electron density. Its head points towards electron sinks, or areas of relatively low electron density.
When a bond is broken, electrons leave where the bond was; this is represented by a curved arrow pointing away from the bond and ending with the arrow pointing towards the next unoccupied molecular orbital. The electrons can be transferred to a specific atom or can be transferred to a single (sigma) bond, thus making it a double (pi) bond, but the arrow is always pointing towards a specific atom, because electrons always move to a new atom whenever they are "pushed". Organic chemists represent the formation of a bond by a curved arrow pointing between two species.
For clarity, when pushing arrows, it is best to draw the arrows starting from a lone pair of electrons or a σ or π bond and ending in a position that can accept a pair of electrons, allowing the reader to know exactly which electrons are moving and where they are ending. Bonds are broken in places where a corresponding antibonding orbital is filled. Some authorities allow the simplification that an arrow can originate at a formal negative charge that corresponds to a lone pair. However, not all formal negative charges correspond to the presence of a lone pair (e.g., the B in FB), and care needs to be taken with this usage. | 0 | Theoretical and Fundamental Chemistry |
In October 1955 Geoffrey Wilkinson appointed him as a lecturer in inorganic chemistry at Imperial College London. He was subsequently promoted to Senior Lecturer in 1963, Reader in 1964 and Professor in 1981. He was awarded an FRS in 1981.
His research interests ranged widely over a number of topics in inorganic, organic and physical chemistry. Here we select just three areas which made a lasting contribution to chemistry.
I. Measurement of magnetic susceptibility. For paramagnetic inorganic materials in particular, such measurements are often useful. In 1959, he devised a procedure, now called the Evans Method, in which an NMR tube containing the paramagnetic species is dissolved in water-tert-butanol in the presence of a capillary of pure tert-butanol. From the difference in positions of the H NMR peak of the hydroxyl peak of pure butanol and the same peak shifted by the paramagnetic substrate the susceptibility of the sample can be calculated. In 1967 he devised an ingenious modification of the classical Gouy balance in which, instead of weighing the sample in a magnetic field, a small but powerful magnet was weighed against the static sample. This was further refined in 1974 by using two 6 g. strong magnets, each mounted on a torsion strip. The force that the static paramagnetic sample exerted on one magnet was balanced out by a current passed through a coil placed between the poles of the second magnet; by measurement of this current the magnetic susceptibility of the sample can be calculated.
II Nuclear magnetic resonance spectroscopy (NMR). In addition to his use of NMR to determine magnetic susceptibilities of species in solution (see above) he made wide use of the technique in the study of organometallic and coordination complexes. He also used the technique of double irradiation of organic compounds to establish the relative signs of coupling constants.
III Inorganic chemistry. He made a number of studies on organometallic and coordination complexes. An example of his ingenuity in this area is to show that divalent lanthanides might show Grignard-like behaviour, and to this end he found that samarium, europium and ytterbium formed such species and that they showed Grignard-type reactions. | 0 | Theoretical and Fundamental Chemistry |
Another measure of human faecal contamination is the proportion of the two 3β-ol isomers of the saturated sterol form. 5α-cholestanol is formed naturally in the environment by bacteria and generally does not have a faecal origin. Samples with ratios greater than 0.7 may be contaminated with human faecal matter; samples with values less than 0.3 may be considered uncontaminated. Samples with ratios between these two cut-offs can not readily be categorised on the basis of this ratio alone.<br />
Sediments falling in the red region are classed as “contaminated” by both of the two ratios and those in the green region are classified as “uncontaminated” by the same measures. Those in the blue region are “uncontaminated” according to the 5β-coprostanol / cholesterol ratio and “uncertain” in the 5β-coprostanol / (5β-coprostanol + 5α-cholestanol) ratio. The majority of the samples between the 0.3 and 0.7 cut-offs are considered as “uncontaminated” according to the 5β-coprostanol / cholesterol ratio and so the 0.3 value must be considered as somewhat conservative. | 1 | Applied and Interdisciplinary Chemistry |
The ability to control the electrode potential for electro-switchable biosurfaces facilitates several different applications. One example is the field of molecular electronics, for instance the investigation of DNA-mediated charge transfer.
Another application is the analysis of molecular interactions. To that end, the DNA strand is labeled with a fluorescent dye. Excited fluorescent dyes can transfer energy to metal. Consequently, the fluorescence is quenched in proximity to the metal electrode. To measure interactions, a ligand is additionally attached at the head of the DNA molecule and the interacting analyte is flushed across the biosensor. Two different measurement modes can be performed with the biosensor, a static mode and a dynamic mode. In static mode, the potential applied to the electrode is fixed, keeping the DNA molecule in an upright position. Binding of the analyte to the ligand will change the local environment of the fluorescent dye and thereby quench its fluorescence. The static mode can also be used to measure the activity of enzymes like polymerases that influence the structure of the DNA molecule. In dynamic mode, the potential applied to the electrode is oscillating, thus the DNA molecule switches between the upright and the horizontal position. Binding of an analyte will change the size of the attached complex. Consequently, the hydrodynamic friction will change and the DNA molecule will move through the buffer with a different speed. This speed change can be used to investigate size changes or conformational changes induced by the binding of the analyte. The application of electro-switchable biosurfaces as a sensor for molecular interactions is also known as switchSENSE technology. It belongs to the category of microfluidic surface-bound methods to measure molecular interactions.
A similar application in this category is surface plasmon resonance (SPR), where a thin gold film on top of a glass slide is the sensor surface. In SPR, the gold film can additionally be modified with SAM or other specific layers. One difference to electro-switchable biosurfaces is that no potential is applied to the SPR surface. In contrast to surface-bound methods, there are also in-solution methods to measure molecule interactions, for example isothermal titration calorimetry (ITC).
The electric potential cannot only be used to control the movement of the DNA strands, but also to control the release of the molecules into solution. This has possible applications in the field of gene therapy since it might enable the delivery of genetic material to specific locations. | 1 | Applied and Interdisciplinary Chemistry |
During his lifetime Hahn was awarded orders, medals, scientific prizes, and fellowships of Academies, Societies, and Institutions from all over the world. At the end of 1999, the German news magazine Focus published an inquiry of 500 leading natural scientists, engineers, and physicians about the most important scientists of the 20th century. In this poll Hahn was elected third (with 81 points), after the theoretical physicists Albert Einstein and Max Planck, and thus the most significant chemist of his time.
As well as the Nobel Prize in Chemistry (1944), Hahn was awarded:
* the Emil Fischer Medal of the Society of German Chemists (1922),
* the Cannizaro Prize of the Royal Academy of Science in Rome (1938),
* the Copernicus Prize of the University of Konigsberg (1941),
* the Gothenius Medal of the Akademie der Naturforscher (1943),
* the Max Planck Medal of the German Physical Society, with Lise Meitner (1949),
* the Goethe Medal of the city of Frankfurt-on-the-Main (1949),
* the Golden Paracelsus Medal of the Swiss Chemical Society (1953),
* the Faraday Lectureship Prize with Medal from the Royal Society of Chemistry (1956),
* the Grotius Medal of the Hugo Grotius Foundation (1956),
* Wilhelm Exner Medal of the Austrian Industry Association (1958),
* the Helmholtz Medal of the Berlin-Brandenburg Academy of Sciences and Humanities (1959),
* and the Harnack medal in Gold from the Max Planck Society (1959).
Hahn became the honorary president of the Max Planck Society in 1962.
* He was elected a Foreign Member of the Royal Society (1957).
*His honorary memberships of foreign academies and scientific societies included:
** the Romanian Physical Society in Bucharest,
** the Royal Spanish Society for Chemistry and Physics and the Spanish National Research Council,
** and the Academies in Allahabad, Bangalore, Berlin, Boston, Bucharest, Copenhagen, Göttingen, Halle, Helsinki, Lisbon, Madrid, Mainz, Munich, Rome, Stockholm, Vatican, and Vienna.
He was an honorary fellow of University College London,
* and an honorary citizen of the cities of Frankfurt am Main and Göttingen in 1959,
* and of Berlin (1968).
* Hahn was made an Officer of the Ordre National de la Légion dHonneur' of France (1959),
* and was awarded the Grand Cross First Class of the Order of Merit of the Federal Republic of Germany (1959).
* In 1966, US President Lyndon B. Johnson and the United States Atomic Energy Commission (AEC) awarded Hahn, Lise Meitner and Fritz Strassmann the Enrico Fermi Award. The diploma for Hahn bore the words: "For pioneering research in the naturally occurring radioactivities and extensive experimental studies culminating in the discovery of fission."
* He received honorary doctorates from
** the University of Gottingen,
** the Technische Universität Darmstadt,
** the University of Frankfurt in 1949,
** and the University of Cambridge in 1957.
Objects named after Hahn include:
* NS Otto Hahn, the only European nuclear-powered civilian ship (1964),
* a crater on the Moon (shared with his namesake Friedrich von Hahn),
* and the asteroid 19126 Ottohahn,
* the Otto Hahn Prize of both the German Chemical and Physical Societies and the city of Frankfurt/Main,
* the Otto Hahn Medal and the Otto Hahn Award of the Max Planck Society,
* and the Otto Hahn Peace Medal in Gold of the United Nations Association of Germany (DGVN) in Berlin (1988).
Proposals were made at various times, first in 1971 by American chemists, that the newly synthesised element 105 should be named hahnium in Hahns honour, but in 1997 the IUPAC named it dubnium, after the Russian research centre in Dubna. In 1992 element 108 was discovered by a German research team, and they proposed the name hassium (after Hesse). In spite of the long-standing convention to give the discoverer the right to suggest a name, a 1994 IUPAC committee recommended that it be named hahnium'. After protests from the German discoverers, the name hassium (Hs) was adopted internationally in 1997. | 0 | Theoretical and Fundamental Chemistry |
Automated mineralogy analytical solutions are characterised by integrating largely automated measurement techniques based on Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS). Commercially available lab-based solutions include QEMSCAN and Mineral Liberation Analyzer (MLA) from FEI Company, Mineralogic from Zeiss, AZtecMineral from Oxford Instruments, the TIMA (Tescan integrated mineral analyzer) from TESCAN, AMICS from Bruker, and MaipSCAN from Rock Scientific. The first oil & gas wellsite solution was launched jointly by Zeiss and CGG Veritas in 2011 called RoqSCAN. This was followed approximately 6 months later by the release of QEMSCAN Wellsite by FEI Company. More recently in 2016, a ruggedized mine site solution for mining and mineral processing was launched by Zeiss called MinSCAN. | 0 | Theoretical and Fundamental Chemistry |
T1 rho (T1ρ) is an experimental MRI sequence that may be used in musculoskeletal imaging. It does not yet have widespread use.
Molecules have a kinetic energy that is a function of the temperature and is expressed as translational and rotational motions, and by collisions between molecules. The moving dipoles disturb the magnetic field but are often extremely rapid so that the average effect over a long time-scale may be zero. However, depending on the time-scale, the interactions between the dipoles do not always average away. At the slowest extreme the interaction time is effectively infinite and occurs where there are large, stationary field disturbances (e.g., a metallic implant). In this case the loss of coherence is described as a "static dephasing". T2* is a measure of the loss of coherence in an ensemble of spins that includes all interactions (including static dephasing). T2 is a measure of the loss of coherence that excludes static dephasing, using an RF pulse to reverse the slowest types of dipolar interaction. There is in fact a continuum of interaction time-scales in a given biological sample, and the properties of the refocusing RF pulse can be tuned to refocus more than just static dephasing. In general, the rate of decay of an ensemble of spins is a function of the interaction times and also the power of the RF pulse. This type of decay, occurring under the influence of RF, is known as T1ρ. It is similar to T2 decay but with some slower dipolar interactions refocused, as well as static interactions, hence T1ρ≥T2. | 0 | Theoretical and Fundamental Chemistry |
Benzyne complexes react with a variety of electrophiles, resulting in insertion into one M-C bond. With trifluoroacetic acid, benzene is lost to give the trifluoroacetate Ni(OCF)(dcpe). | 0 | Theoretical and Fundamental Chemistry |
Many of the more popular terms used in discussing the compensation effect are specific to their field or phenomena. In these contexts, the unambiguous terms are preferred. The misapplication of and frequent crosstalk between fields on this matter has, however, often led to the use of inappropriate terms and a confusing picture. For the purposes of this entry different terms may refer to what may seem to be the same effect, but that either a term is being used as a shorthand (isokinetic and isoequilibrium relationships are different, yet are often grouped together synecdochically as isokinetic relationships for the sake of brevity) or is the correct term in context. This section should aid in resolving any uncertainties. (see Criticism section for more on the variety of terms)
compensation effect/rule : umbrella term for the observed linear relationship between: (i) the logarithm of the preexponential factors and the activation energies, (ii) enthalpies and entropies of activation, or (iii) between the enthalpy and entropy changes of a series of similar reactions.
enthalpy-entropy compensation : the linear relationship between either the enthalpies and entropies of activation or the enthalpy and entropy changes of a series of similar reactions.
isoequilibrium relation (IER), isoequilibrium effect : On a Van 't Hoff plot, there exists a common intersection point describing the thermodynamics of the reactions. At the isoequilibrium temperature , all the reactions in the series should have the same equilibrium constant ()
isokinetic relation (IKR), isokinetic effect : On an Arrhenius plot, there exists a common intersection point describing the kinetics of the reactions. At the isokinetic temperature , all the reactions in the series should have the same rate constant ()
isoequilibrium temperature : used for thermodynamic LFERs; refers to in the equations where it possesses dimensions of temperature
isokinetic temperature : used for kinetic LFERs; refers to in the equations where it possesses dimensions of temperature
kinetic compensation : an increase in the preexponential factors tends to compensate for the increase in activation energy:
Meyer-Neldel rule (MNR) : primarily used in materials science and condensed matter physics; the MNR is often stated as the plot of the logarithm of the preexponential factor against activation energy is linear:
where is the preexponential factor, is the activation energy, σ is the conductivity, and is Boltzmann's constant, and is temperature. | 0 | Theoretical and Fundamental Chemistry |
Environmental analysis is the use of examination and statistical methods to study the chemical and biological factors that determine the quality of an environment. The purpose of this is commonly to monitor and study levels of pollutants in the atmosphere, rivers and other specific settings. Also, to monitor amounts of natural and chemical components. Other environmental analysis techniques include biological surveys or biosurvey<nowiki/>s, soil analysis or soil tests, vegetation surveys, tree identification, and remote sensing which uses satellite imagery to assess the environment on different spatial scales. | 0 | Theoretical and Fundamental Chemistry |
Commercially available laboratory-based chemical imaging systems emerged in the early 1990s (ref. 1-5). In addition to economic factors, such as the need for sophisticated electronics and extremely high-end computers, a significant barrier to commercialization of infrared imaging was that the focal plane array (FPA) needed to read IR images were not readily available as commercial items. As high-speed electronics and sophisticated computers became more commonplace, and infrared cameras became readily commercially available, laboratory chemical imaging systems were introduced.
Initially used for novel research in specialized laboratories, chemical imaging became a more commonplace analytical technique used for general R&D, quality assurance (QA) and quality control (QC) in less than a decade. The rapid acceptance of the technology in a variety of industries (pharmaceutical, polymers, semiconductors, security, forensics and agriculture) rests in the wealth of information characterizing both chemical composition and morphology. The parallel nature of chemical imaging data makes it possible to analyze multiple samples simultaneously for applications that require high throughput analysis in addition to characterizing a single sample. | 0 | Theoretical and Fundamental Chemistry |
Radioactive decay results in a reduction of summed rest mass, once the released energy (the disintegration energy) has escaped in some way. Although decay energy is sometimes defined as associated with the difference between the mass of the parent nuclide products and the mass of the decay products, this is true only of rest mass measurements, where some energy has been removed from the product system. This is true because the decay energy must always carry mass with it, wherever it appears (see mass in special relativity) according to the formula E = mc. The decay energy is initially released as the energy of emitted photons plus the kinetic energy of massive emitted particles (that is, particles that have rest mass). If these particles come to thermal equilibrium with their surroundings and photons are absorbed, then the decay energy is transformed to thermal energy, which retains its mass.
Decay energy, therefore, remains associated with a certain measure of the mass of the decay system, called invariant mass, which does not change during the decay, even though the energy of decay is distributed among decay particles. The energy of photons, the kinetic energy of emitted particles, and, later, the thermal energy of the surrounding matter, all contribute to the invariant mass of the system. Thus, while the sum of the rest masses of the particles is not conserved in radioactive decay, the system mass and system invariant mass (and also the system total energy) is conserved throughout any decay process. This is a restatement of the equivalent laws of conservation of energy and conservation of mass. | 0 | Theoretical and Fundamental Chemistry |
Polysialic acid (polySia) is polymer of linearly repeating monomer units of α2,8- and α2,9-glycosidic linked sialic acid residues. Sialic acid refers to carboxylated 9-carbon sugars, 2-keto-3-dexoxy-D-glycero-nononic acids. An unusual property of this sugar is that it often polymerizes into polySia. This is accomplished by attaching the monomers to the nonreducing end of the glycan. This mostly consists of Neu5Ac subunits. It is polyanionic and bulky, meaning there is little ability to reach its central molecules. polySia is useful in signaling in vertebrates and on the cell surface of few glycoproteins and glycolipids causing modifications, and it has been recently found that the function of polySia relates almost directly to its degree of polymerization. The number of units can range from 8 to greater than 400. This vast range causes differences in the polySias ability to adhere different cells, assist in cellular migration, synapse formation, and regulate adhesion in nerve cells by modeling and formating them. polySias most prominent role is in post-translational modifications in a few proteins, with the main one being NCAM. polySia links to adhesion molecules causing their adhesive properties to be subdued allowing for the detailed control of cell migration and cell to cell relations. This is caused by polySia's bulky and polyanionic properties.
The human body produces polySia naturally and attaches it to a various number of proteins. This is done by linking polySia on the α2,3- or α2,6- terminal of the glycoprotein. O-linked glycosylation through threonine or N-linked glycosylation through asparagine is employed. This polySia linkage is found in proteins such as NCAM, E-selectin ligand 1 (ESL-1), C–C chemokine receptor type 7 (CCR7), synaptic cell adhesion molecule-1 (SynCAM-1), neuropilin-2 (NRP-2), the CD36 scavenger receptor found in the milk of humans, and the α-subunit of the voltage-sensitive sodium channel. The synthesis of polySia is enzymatically formed by α2,8-sialyltransferase (ST8Sia) in a Type II transmembrane protein located on the Golgi Apparatus membrane. ST8Sia does this by adding sialic acids to the terminal end of the glycan through the CMP-sialic acid donor at various lengths depending on necessity. The length is controlled extensively by the expression of polysialyltransferase enzymes, once again controlling the function of polySia. | 1 | Applied and Interdisciplinary Chemistry |
The first evidence of presence of a neutralizing substance in the blood that could counter infections came when Emil von Behring along with Kitasato Shibasaburō in 1890 developed effective serum against diphtheria. This they did by transferring serum produced from animals immunized against diphtheria to animals suffering from it. Transferring the serum thus could cure the infected animals. Behring was awarded the Nobel Prize for this work in 1901.
At this time though the chemical nature of what exactly in the blood conferred this protection was not known. In a few decades to follow, it was shown that the protective serum could neutralize and precipitate toxins, and clump bacteria. All these functions were attributed to different substances in the serum, and named accordingly as antitoxin, precipitin and agglutinin. That all the three substances were one entity (gamma globulins) was demonstrated by Elvin A. Kabat in 1939. In the preceding year Kabat had demonstrated the heterogeneity of antibodies through ultracentrifugation studies of horses' sera.
Until this time, cell-mediated immunity and humoral immunity were considered to be contending theories to explain effective immune response, but the former lagged behind owing to lack of advanced techniques. Cell-mediated immunity got an impetus in its recognition and study when in 1942, Merrill Chase successfully transferred immunity against tuberculosis between pigs by transferring white blood cells.
It was later shown in 1948 by Astrid Fagraeus in her doctoral thesis that the plasma B cells are specifically involved in antibody production. The role of lymphocytes in mediating both cell-mediated and humoral responses was demonstrated by James Gowans in 1959.
In order to account for the wide range of antigens the immune system can recognize, Paul Ehrlich in 1900 had hypothesized that preexisting "side chain receptors" bind a given pathogen, and that this interaction induces the cell exhibiting the receptor to multiply and produce more copies of the same receptor. This theory, called the selective theory was not proven for next five decades, and had been challenged by several instructional theories which were based on the notion that an antibody would assume its effective structure by folding around the antigen. In the late 1950s however, the works of three scientists—Jerne, Talmage and Burnet (who largely modified the theory)—gave rise to the clonal selection theory, which proved all the elements of Ehrlich's hypothesis except that the specific receptors that could neutralize the agent were soluble and not membrane-bound.
The clonal selection theory was proved correct when Sir Gustav Nossal showed that each B cell always produces only one antibody.
In 1974, the role of MHC in antigen presentation was demonstrated by Rolf Zinkernagel and Peter C. Doherty. | 1 | Applied and Interdisciplinary Chemistry |
Reducing the surface tension of a body of liquid makes possible to reduce or prevent noise due to droplets falling into it. This would involve adding soap, detergent or a similar substance to water. The reduced surface tension reduces the noise from dripping. | 1 | Applied and Interdisciplinary Chemistry |
Volumetric water content, θ, is defined mathematically as:
where is the volume of water and is equal to the total volume of the wet material, i.e. of the sum of the volume of solid host material (e.g., soil particles, vegetation tissue) , of water , and of air .
Gravimetric water content is expressed by mass (weight) as follows:
where is the mass of water and is the mass of the solids.
For materials that change in volume with water content, such as coal, the gravimetric water content, u, is expressed in terms of the mass of water per unit mass of the moist specimen (before drying):
However, woodworking, geotechnics and soil science require the gravimetric moisture content to be expressed with respect to the sample's dry weight:
And in food science, both and are used and called respectively moisture content wet basis (MC) and moisture content dry basis (MC).
Values are often expressed as a percentage, i.e. u×100%.
To convert gravimetric water content to volumetric water content, multiply the gravimetric water content by the bulk specific gravity of the material: | 0 | Theoretical and Fundamental Chemistry |
* Meier, S. M.; Novak, M. S.; Kandioller, W.; Jakupec, M. A.; Roller, A.; Keppler, B. K.; Hartinger, C. G., Aqueous chemistry and antiproliferative activity of a pyrone-based phosphoramidate Ru(arene) anticancer agent. Dalton Trans, 2014, 43 (26), 9851–9855
* Meier, S. M.; Babak, M. V.; Keppler, B. K.; Hartinger, C. G., Efficiently detecting metallodrug-protein adducts: ion trap versus time-of-flight mass analyzers. ChemMedChem, 2014, 9 (7), 1351–1355
* Hartinger, C. G.; Groessl, M.; Meier, S. M.; Casini, A.; Dyson, P. J., Application of mass spectrometric techniques to delineate the modes-of-action of anticancer metallodrugs. Chem Soc Rev, 2013, 42 (14), 6186–6199
* Meier, S. M.; Novak, M.; Kandioller, W.; Jakupec, M. A.; Arion, V. B.; Metzler-Nolte, N.; Keppler, B. K.; Hartinger, C. G., Identification of the structural determinants for anticancer activity of a ruthenium arene peptide conjugate. Chem Eur J, 2013, 19 (28), 9297–9307
* Kandioller, W.; Balsano, E.; Meier, S. M.; Jungwirth, U.; Göschl S.; Roller, A.; Jakupec, M. A.; Berger, W.; Keppler, B. K.; Hartinger, C. G., Organometallic anticancer complexes of lapachol: metal centre-dependent formation of reactive oxygen species and correlation with cytotoxicity. Chem Commun, 2013, 49 (32), 3348–3350
* Meier, S. M.; Hanif, M.; Pichler, V.; Novak, M.; Jirkovsky, E.; Jakupec, M. A.; Davey, C. A.; Keppler, B. K.; Hartinger, C. G., Novel metal(II) arene 2-pyridinecarbothioamides: A rationale to orally active organometallic anticancer agents. Chem Sci, 2013, 4 (4), 1837–1846
* Babak, M. V.; Meier, S. M.; Legin, A. A.; Adib Razavi, M. S.; Roller, A.; Jakupec, M. A.; Keppler, B. K.; Hartinger, C. G., Am(m)ines make the difference: organoruthenium am(m)ine complexes and their chemistry in anticancer drug development. Chemistry, 2013, 19 (13), 4308–4318
*Kurzwernhart, A.; Kandioller, W.; Bächler S.; Bartel, C.; Martic, S.; Buczkowska, M.; Mühlgassner, G.; Jakupec, M. A.; Kraatz, H.; Berdnarski, P. J.; Arion, V. B.; Markos, D.; Keppler, B. K.; Hartinger, C. G., Structure-activity relationships of targeted Ru(η-p-cymene) anticancer complexes with flavonol-derived ligands. J Med Chem, 2012, 55 (23), 10512-10522 | 0 | Theoretical and Fundamental Chemistry |
Usually, as a plume moves away from its source, it widens because of entrainment of the surrounding fluid at its edges. Plume shapes can be influenced by flow in the ambient fluid (for example, if local wind blowing in the same direction as the plume results in a co-flowing jet). This usually causes a plume which has initially been buoyancy-dominated to become momentum-dominated (this transition is usually predicted by a dimensionless number called the Richardson number). | 1 | Applied and Interdisciplinary Chemistry |
If a magnetic field is oriented along the defect axis it leads to Zeeman splitting separating the m = +1 from the m = -1 states. This technique is used to lift the degeneracy and use only two of the spin states (usually the ground states with m = -1 and m = 0) as a qubit. Population can then be transferred between them using a microwave field. In the specific instance that the magnetic field reaches 1027 G (or 508 G) then the m = –1 and m = 0 states in the ground (or excited) state become equal in energy (Ground/Excited State Level Anticrossing). The following strong interaction results in so-called spin polarization, which strongly affects the intensity of optical absorption and luminescence transitions involving those states.
Importantly, this splitting can be modulated by applying an external electric field, in a similar fashion to the magnetic field mechanism outlined above, though the physics of the splitting is somewhat more complex. Nevertheless, an important practical outcome is that the intensity and position of the luminescence lines is modulated. Strain has a similar effect on the NV center as electric fields.
There is an additional splitting of the m = ±1 energy levels, which originates from the hyperfine interaction between surrounding nuclear spins and the NV center. These nuclear spins create magnetic and electric fields of their own leading to further distortions of the NV spectrum (see nuclear Zeeman and quadrupole interaction). Also the NV center's own spin–orbit interaction and orbital degeneracy leads to additional level splitting in the excited E state.
Temperature and pressure directly influence the zero-field term of the NV center leading to a shift between the ground and excited state levels.
The Hamiltonian, a quantum mechanical equation describing the dynamics of a system, which shows the influence of different factors on the NV center can be found below.
Although it can be challenging, all of these effects are measurable, making the NV center a perfect candidate for a quantum sensor. | 0 | Theoretical and Fundamental Chemistry |
The mechanism of the blue bottle experiment requires an understanding of rates and mechanisms of complex interacting chemical reactions. In complex chemical reactions, individual sub-reactions can occur simultaneously but at significantly different rates. These, in turn, can be affected by reagent concentration and temperature. In most cases, the overall reaction rate is determined by the fastest single component reaction. However, when some processes form intermediate molecules which then react in other processes to form the end product, the rate of the overall reaction is determined by the rate of the slowest reaction. In such circumstances the intermediate products are usually in a steady state at low concentrations because they are highly reactive. Equilibrium state requires that all reaction forward and backward mechanism happens at the same rate. Thus, the overall net reaction is determined by the sum of all the mechanism steps where the rate depends on the concentration and temperature. The blue bottle experiment illustrates this principle of interacting reactions with different rates.
The blue bottle experiment requires only three reagents: potassium hydroxide solution, dextrose solution, and dilute methylene blue solution. These reagents are added to a flask, mixed, and the flask is stoppered. The initial color of the solution is blue, but upon standing for a short interval it spontaneously fades to colorless, as the alkaline dextrose solution reduces the methylene blue to colorless leuco-methylene blue. Shaking the flask causes oxygen present in the head space air to dissolve in the solution and oxidize the leuco-methylene blue back to its colored form again. Another variation uses methylene blue in water, glucose, and caustic soda (NaOH). There are many versions of the experiment, however, unlike the classical version where dye is necessary to use as a catalyst for the reaction, the green and rapid versions undergo autoxidation even in the absence of the dye.
In the past, it was thought that the reaction occurred by the oxidation of an aldehyde group to a carboxylic acid under alkaline conditions. For instance, glucose would be oxidized to gluconate by oxygen. However, the experiment also works with compounds such as vitamin C and benzoin, which do not contain an aldehyde group. Thus, the reaction is actually the oxidation of an acyloin or related α-hydroxycarbonyl group, which is a structural feature of glucose, to a 1,2-diketone. The reduced redox dye (colorless state) is formed from oxidized redox dye (blue). The color-change that occurs in the blue bottle experiment has features of a clock reaction, in which a visible change in the concentration of one or more reagents suddenly occurs upon the exhaustion of a limiting reagent. For example, the limiting reactant, oxygen, is consumed by another reactant, benzoin, with the help of safranin as a catalyst. Once the limited amount of oxygen has been used up, the catalyst is unable to change forms, and as a result, the solution changes color. | 1 | Applied and Interdisciplinary Chemistry |
Studies of retroviruses led to the first demonstrated synthesis of DNA from RNA templates, a fundamental mode for transferring genetic material that occurs in both eukaryotes and prokaryotes. It has been speculated that the RNA to DNA transcription processes used by retroviruses may have first caused DNA to be used as genetic material. In this model, the RNA world hypothesis, cellular organisms adopted the more chemically stable DNA when retroviruses evolved to create DNA from the RNA templates.
An estimate of the date of evolution of the foamy-like endogenous retroviruses placed the time of the most recent common ancestor at > . | 1 | Applied and Interdisciplinary Chemistry |
The Weissenberg number (Wi) is a dimensionless number used in the study of viscoelastic flows. It is named after Karl Weissenberg. The dimensionless number compares the elastic forces to the viscous forces. It can be variously defined, but it is usually given by the relation of stress relaxation time of the fluid and a specific process time. For instance, in simple steady shear, the Weissenberg number, often abbreviated as Wi or We, is defined as the shear rate times the relaxation time . Using the Maxwell model and the Oldroyd-B model, the elastic forces can be written as the first Normal force (N).
Since this number is obtained from scaling the evolution of the stress, it contains choices for the shear or elongation rate, and the length-scale. Therefore the exact definition of all non dimensional numbers should be given as well as the number itself.
While Wi is similar to the Deborah number and is often confused with it in technical literature, they have different physical interpretations. The Weissenberg number indicates the degree of anisotropy or orientation generated by the deformation, and is appropriate to describe flows with a constant stretch history, such as simple shear. In contrast, the Deborah number should be used to describe flows with a non-constant stretch history, and physically represents the rate at which elastic energy is stored or released. | 1 | Applied and Interdisciplinary Chemistry |
The paradigm of toxicological assessment of benzene is shifting towards the domain of molecular toxicology as it allows understanding of fundamental biological mechanisms in a better way. Glutathione seems to play an important role by protecting against benzene-induced DNA breaks and it is being identified as a new biomarker for exposure and effect. Benzene causes chromosomal aberrations in the peripheral blood leukocytes and bone marrow explaining the higher incidence of leukemia and multiple myeloma caused by chronic exposure. These aberrations can be monitored using fluorescent in situ hybridization (FISH) with DNA probes to assess the effects of benzene along with the hematological tests as markers of hematotoxicity. Benzene metabolism involves enzymes coded for by polymorphic genes. Studies have shown that genotype at these loci may influence susceptibility to the toxic effects of benzene exposure. Individuals carrying variant of NAD(P)H:quinone oxidoreductase 1 (NQO1), microsomal epoxide hydrolase (EPHX) and deletion of the glutathione S-transferase T1 (GSTT1) showed a greater frequency of DNA single-stranded breaks. | 1 | Applied and Interdisciplinary Chemistry |
Jiao et al. enabled the formation of a C–N bond via cross-coupling using air as an oxidant and a copper catalyst. No conditions are known for a C–N cross-coupling that breaks a sp or sp C–COOH bond. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, hemithioacetals (or thiohemiacetals) are organosulfur compounds with the general formula . They are the sulfur analogues of the acetals, , with an oxygen atom replaced by sulfur (as implied by the thio- prefix). Because they consist of four differing substituents on a single carbon, hemithioacetals are chiral. A related family of compounds are the dithiohemiacetals, with the formula . Although they can be important intermediates, hemithioacetals are usually not isolated, since they exist in equilibrium with thiols () and aldehydes (). | 0 | Theoretical and Fundamental Chemistry |
ZMPSTE24 is a human gene. The protein encoded by this gene is a metallopeptidase. It is involved in the processing of lamin A. Defects in the ZMPSTE24 gene lead to similar laminopathies as defects in lamin A, because the latter is a substrate for the former. In humans, a mutation abolishing the ZMPSTE24 cleavage site in prelamin A causes a progeroid disorder. Failure to correctly process prelamin A leads to deficient ability to repair DNA double-strand breaks.
As shown by Liu et al., lack of Zmpste24 prevents lamin A formation from its precursor farnesyl-prelamin A. Lack of ZMPSTE24 causes progeroid phenotypes in mice and humans. This lack increases DNA damage and chromosome aberrations and sensitivity to DNA-damaging agents that cause double-strand breaks. Also, lack of ZMPSTE24 allows an increase in non-homologous end joining, but a deficiency in steps leading to homologous recombinational DNA repair. | 1 | Applied and Interdisciplinary Chemistry |
Radioactive contamination is a potential danger for living organisms and results in external hazards, concerning radiation sources outside the body, and internal dangers, as a result of the incorporation of radionuclides inside the body (often by inhalation of particles or ingestion of contaminated food).
In humans, single doses from 0.25 Sv produce first anomalies in the amount of leukocytes. This effect is accentuated if the absorbed dose is between 0.5 and 2 Sv, in whose first damage, nausea and hair loss are suffered. The strip ranging between 2 and 5 Sv is considered the most serious and include bleeding, ulcers and risk of death; values exceeding 5 Sv involve immediate death. If radiation, likewise, is received in small doses over long periods of time, the consequences can be equally severe. It is difficult to quantify the health effects for doses below 10 mSv, but it has been shown that there is a direct relationship between prolonged exposure and cancer risk (although there is not a very clear dose-response relationship to establish clear limits of exposure).
The information available on the effect of natural background radiation with respect anthropogenic pollution on wildlife is scarce and refers to very few species. It is very difficult to estimate from the available data the total doses that can accumulate during specific stages of the life cycle (embryonic development or reproductive age), in changes in behavior or depending on environmental factors such as seasonality. The phenomena of radioactive bioaccumulation, bioconcentration and biomagnification, however, are especially known to sea level. They are caused by the recruitment and retention of radioisotopes by bivalves, crustaceans, corals and phytoplankton, which then amounted to the rest of the food chain at low concentration factors.
Radiobiological literature and IAEA establish a safe limit of absorbed dose of 0.001 Gy/d for terrestrial animals and 0.01 Gy/d for plants and marine biota, although this limit should be reconsidered for long-lived species with low reproductive capacity.
Radiation tests in model organisms that determine the effects of high radiation on animals and plants are:
*Chromosomal aberrations.
*DNA damage.
*Cancer, particularly leukemia.
*Leukopenia.
*Growth reduction.
*Reproductive deficiencies: sterility, reduction in fecundity, and occurrence of developmental abnormalities or reduction in viability of offspring
*Reduced seed germination.
*Burned tissues exposed to radiation.
*Mortality, including both acute lethality and long-term reduction in life span.
The effects of radioactivity on bacteria are given, as in eukaryotes, by ionization of water and production of reactive oxygen species. These compounds mutate DNA strands and produce genetic damage, inducing newly lysis and subsequent cell death.
Its action on viruses, on the other hand, results in damaged nucleic acids and viral inactivation. They have a sensory threshold ranging between 1000 and 10,000 Gy (range occupying most biological organisms) which decreases with increasing genome size. | 1 | Applied and Interdisciplinary Chemistry |
Ben Feringa has served as an editorial board member for several journals published by the Royal Society of Chemistry, including Chemical Communications (until 2012), the Faraday Transactions of the Royal Society, and as Chair of the Editorial Board of Chemistry World. He is the founding Scientific Editor (2002–2006) of the Royal Society of Chemistry journal Organic & Biomolecular Chemistry. In addition, he is an editorial (advisory) board member for the journals Advanced Synthesis and Catalysis, Adv. Phys. Org. Chem., Topics in Stereochemistry, Chemistry: An Asian Journal published by Wiley, and advisory board member for the Journal of Organic Chemistry, Journal of the American Chemical Society published by the American Chemical Society.
On 26 November 2017, Feringa, on a visit to South China Normal University in Guangzhou was appointed honorary Professor of South China Normal University. From December 2017, he holds a "green card" in China, and will lead a team researching “self-healing materials” at Shanghai’s East China University of Science and Technology.
Feringa is a co-founder of the contract research company Selact (now a part of Kiadis), which was originally established to provide services in the area of organic synthesis but later developed high throughput screening methods. | 0 | Theoretical and Fundamental Chemistry |
The dangerous goods definition of an oxidizing agent is a substance that can cause or contribute to the combustion of other material. By this definition some materials that are classified as oxidizing agents by analytical chemists are not classified as oxidizing agents in a dangerous materials sense. An example is potassium dichromate, which does not pass the dangerous goods test of an oxidizing agent.
The U.S. Department of Transportation defines oxidizing agents specifically. There are two definitions for oxidizing agents governed under DOT regulations. These two are Class 5; Division 5.1(a)1 and Class 5; Division 5.1(a)2. Division 5.1 "means a material that may, generally by yielding oxygen, cause or enhance the combustion of other materials." Division 5.(a)1 of the DOT code applies to solid oxidizers "if, when tested in accordance with the UN Manual of Tests and Criteria (IBR, see § 171.7 of this subchapter), its mean burning time is less than or equal to the burning time of a 3:7 potassium bromate/cellulose mixture." 5.1(a)2 of the DOT code applies to liquid oxidizers "if, when tested in accordance with the UN Manual of Tests and Criteria, it spontaneously ignites or its mean time for a pressure rise from 690 kPa to 2070 kPa gauge is less than the time of a 1:1 nitric acid (65 percent)/cellulose mixture." | 0 | Theoretical and Fundamental Chemistry |
CrysTBox (Crystallographic Tool Box) is a suite of computer tools designed to accelerate material research based on transmission electron microscope images via highly accurate automated analysis and interactive visualization. Relying on artificial intelligence and computer vision, CrysTBox makes routine crystallographic analyses simpler, faster and more accurate compared to human evaluators. The high level of automation together with sub-pixel precision and interactive visualization makes the quantitative crystallographic analysis accessible even for non-crystallographers allowing for an interdisciplinary research. Simultaneously, experienced material scientists can take advantage of advanced functionalities for comprehensive analyses.
CrysTBox is being developed in the Laboratory of electron microscopy at the Institute of Physics of the Czech Academy of Sciences. For academic purposes, it is available for free. As of 2022, the suite has been deployed at research and educational facilities in more than 90 countries supporting research of ETH Zurich, Lawrence Berkeley National Laboratory, Max Planck Institutes, Chinese Academy of Sciences, Fraunhofer Institutes or Oxford University. | 0 | Theoretical and Fundamental Chemistry |
In late 2013, new results were published by a research team at Durham University which suggested progress. The scientists tried a new method for multiplying, cloning the original cells not in a 2D but in a 3D system.
A team took healthy dermal papillae from hair transplants and dissected them, then cultured them in a petri dish. In 30 hours they were able to produce 3000 dermal papilla cells. The goal was to create dermal papillae that when injected would reprogram cells around it to produce healthy hair. They chose to try the method by injecting the cloned cells in foreskin samples to "challenge" the cells, as the cells in the foreskin normally don't grow hair. The human skin samples were grafted on rats. After six weeks the cloned papillae cells formed brand-new hair follicles which were able to grow hair.
These are early results and as it is a new approach to hair cloning, several more studies and tests have to be conducted before they can move on to human testing. They also encountered new problems, such as that some of the newly grown hair appeared without pigmentation. | 1 | Applied and Interdisciplinary Chemistry |
Frederick Mason Brewer CBE FRIC (1903 – 11 February 1963) was an English chemist. He was Head of the Inorganic Chemistry Laboratory at the University of Oxford and Mayor of Oxford during 1959–60.
Frederick Brewer was born in Kensal Rise (aka Kensal Green), Middlesex, England. He was the son of Frederick Charles Brewer and Ellen Maria Owen, both school teachers.
Brewer studied chemistry at Lincoln College, Oxford, from 1920, having received an open scholarship, and subsequently gained a first class degree.
After his undergraduate studies, Brewer undertook research with Prof. Frederick Soddy.
Between 1925–7, Brewer was a Commonwealth Fund Fellow at Cornell University in the United States. During 1927–8, he was a lecturer in physical chemistry at the University of Reading. In 1928, he became a demonstrator and lecturer at the University of Oxford Inorganic Chemistry Laboratory. He stayed in Oxford for the remainder of his life. He became attached to St Catherines Society in the 1930s. In 1955, he was appointed Reader in Inorganic Chemistry. When St Catherines Society became St Catherine's College in 1962, he was appointed a Fellow of the College.
In 1944, Brewer was elected as a university member on Oxford City Council. In 1959, he was elected Mayor of Oxford for 1959–60. In 1961, he was appointed an Alderman of the council.
Brewer lived at 6 Moreton Road in North Oxford. He was a Fellow of the Royal Institute of Chemistry and was awarded the honour of Commander of the Order of the British Empire (CBE) in 1963. However, a week after collecting his CBE at Buckingham Palace, at the age of 60, he died at the Radcliffe Infirmary in Oxford. He was married with a son and a daughter. | 0 | Theoretical and Fundamental Chemistry |
The nucleotide sequence of a gene's DNA specifies the amino acid sequence of a protein through the genetic code. Sets of three nucleotides, known as codons, each correspond to a specific amino acid. The principle that three sequential bases of DNA code for each amino acid was demonstrated in 1961 using frameshift mutations in the rIIB gene of bacteriophage T4 (see Crick, Brenner et al. experiment).
Additionally, a "start codon", and three "stop codons" indicate the beginning and end of the protein coding region. There are 64 possible codons (four possible nucleotides at each of three positions, hence 4 possible codons) and only 20 standard amino acids; hence the code is redundant and multiple codons can specify the same amino acid. The correspondence between codons and amino acids is nearly universal among all known living organisms. | 1 | Applied and Interdisciplinary Chemistry |
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